[Document Type] SPECIFICATION
[Title of the Invention] SURFACE-TREATED METAL AND METHOD FOR
PRODUCING SAME
[Technical Field]
[OOO 11
The present invention relates to a surface-treated metal which includes a film
(hereinafter, referred as "photocatalytic film") showing photocatalytic activity on a
surface thereof and has superior contamination resistance, and to a method of
producing the same. In particular, the present invention relates to a surface-treated
metal in which a photocatalytic film contains a matrix resin having a little amount of
deterioration caused by a photocatalyst and has concave so as to exhibit superior
contamination resistance due to high photocatalytic activity for a long period of time
from the initial stage immediately after usage starts, and to a method of producing the
same.
Priority is claimed on Japanese Patent Application No. 2011-135378, filed on
June 17,201 1 and Japanese Patent Application No. 201 1-25 1698, filed on November
17,2011, the contents of which are incorporated herein by reference.
[Background Art]
[0002]
There are many cases in which a metal (for example, steel) is coated and used
for improving durability or for obtaining a beautiful external appearance, and a coated
metal is widely used in various fields such as home electronics, automobiles, building
materials, and outdoor structures. It is necessary that the metal has superior
contamination resistance in addition to corrosion resistance, because the metal is
exposed to rain, wind, dust, and the like, particularly when being used in outdoors.
[0003]
Photocatalytic technique is a technique of dispersing particles having superior
photocatalytic activity in a coating film of a material surface in order to decompose
and remove contaminants mainly composed of organic materials. In this technique,
the particles having superior photocatalytic activity have a high effect on the
decomposition of contaminants of the surface. But also this technique deteriorates a
coating film by gradually decomposing the resin-based coating film which is an
organic material. Therefore, it is difficult to use the coating film for a long period of
time without any change. Accordingly, in order to minimize deterioration of the
coating film, various proposals have been made.
[0004]
For example, a method of using an inorganic material as a matrix is disclosed
in Patent Documents 1 and 2. In addition, since a fluororesin among organic
materials for coating films is relatively stable to a photocatalyst, a method of using a
fluororesin as a matrix is disclosed (Patent Document 3). In addition, in order to
obtain high stability to a photocatalyst and workability which are required particularly
for a precoated metal, a technique of using a silica-organosilane material as a matrix is
disclosed in Patent Documents 4 and 5 as a method of using an acrylic silicate, which
is obtained by a polymerization reaction of an acrylic resin and an organoalkoxysilane,
as a matrix. In addition, a method using a vinylidene fluoride resin and an acrylic
resin is disclosed in Patent Document 6.
[OOOS]
Meanwhile, since particles (hereinafter, referred as "photocatalytic particles")
having photocatalytic activity are almost uniformly dispersed in a film, the
concentration of the photocatalytic particles in a surface of the film is not necessarily
high. In addition, while the photocatalytic particles are dispersed in the film, surfaces
of the particles are covered with a matrix resin. Therefore, even when the
photocatalytic particles are present near the surface of the film, contaminants on the
surface may not be decomposed immediately after usage starts.
[0006]
In addition, regarding the photocatalytic film, while the film is used for a
certain period under sunlight or ultraviolet light, a resin near a surface of the film is
slightly decomposed and impaired by a photocatalytic effect and thus, surfaces of
photocatalytic particles are exposed to the outside, thereby superior contamination
resistance is exhibited. However, as described above, when a stable resin to a
photocatalyst is used as a matrix resin, it is difficult to advance the decomposition and
deterioration of the resin. Therefore, a long period of time is required in order to
exhibit superior contamination resistance. Accordingly, in a coated metal, it is
difficult to exhibit superior contamination resistance from the initial stage immediately
after usage starts, and to suppress the decomposition and deterioration of a matrix resin
of a film and thus maintain superior contamination resistance for a long period of time.
[Citation List]
[Patent Document]
[0007]
[Patent Document I] Japanese Unexamined Patent Application, First
Publication No. H07-113272
[Patent Document 21 Japanese Unexamined Patent Application, First
Publication No. H08-164334
[Patent Document 31 Japanese Unexamined Patent Application, First
Publication No. H07-17 1408
[Patent Document 41 Japanese Unexamined Patent Application, First
Publication No. H10-225658
[Patent Document 51 Japanese Unexamined Patent Application, First
Publication No. 2000-3 17393
[Patent Document 61 Japanese Unexamined Patent Application, First
Publication No. 2000-63733
[Summary of the Invention]
[Problem to be solved by the Invention]
[0008]
An object of the invention is to provide a surface-treated metal capable of
solving the above-described problems of the related art.
[0009]
Another object of the invention is to provide a surface-treated metal in which
superior contamination resistance can be exhibited by exhibiting a sufficient
photocatalytic effect from the initial stage immediately after usage starts.
[OO 1 01
Still another object of the invention is to provide a surface-treated metal in
which there is almost no deterioration of a matrix resin and an organic resin coating
film. The matrix resin constitutes a part of a photocatalytic film, and the organic
resin coating film is an undercoat of the photocatalytic film.
[Means for Solving the Problems]
[OO 1 11
In order to solve the above-described problems, as a result of thorough
investigation, the present inventors found that the above-described problems could be
solved by using a stable resin to a photocatalyst as a matrix resin and introducing
concave into a photocatalytic film.
[OO 121
The invention may include, for example, the following aspects.
[00 1 31
(1) A surface-treated metal according to an aspect of the invention includes:
a metal, and a coated material that is formed on a surface of the metal, in which an
outermost layer of the coated material is a photocatalytic film that contains particles
showing a photocatalytic activity and an organic-inorganic composite resin, a volume
ratio of the particles showing photocatalytic activity to the photocatalytic film is in a
range fiom 0.5 vol% to 50 vol%, the organic-inorganic composite resin contains a
siloxane bond and at least one group selected from the group consisting of an aryl
group, a carboxyl group, an amino group, a hydroxyl group, and an alkyl group having
1 to 12 carbon atoms, the coated material has a concave on a surface on the outermost
layer side thereof, the concave extends in a direction perpendicular to a thickness
direction of the outermost layer, the concave separates the outermost layer in the
direction perpendicular to the thickness direction when the outermost layer is seen in a
cross-sectional view taken along the thickness direction, an area of the outermost layer
is 50% to 98% of an area of the surface of the metal when the coated material is seen
in a plan view, and a surface area of the outermost layer is 101% to 5000% of the area
of the surface of the metal.
[00 1 41
(2) In the surface-treated metal according to (I), when dimensions of the
concaves in a direction perpendicular to both a direction in which the concave extends
and the thickness direction are represented by widths W and dimensions of the concave
in the direction in which the concave extends are represented by lengths L, a total of
the lengths L of the concave of portions in which the widths W is in a range from 1%
to 1000% of a thickness of the outermost layer may be 90% to 100% of a total of the
lengths L of the concave.
[00 1 51
(3) In the surface-treated metal according to (I) or (2), when the coated
material is seen in a plan view, a plurality of the concaves may be present, the
concaves may form a network shape, and sizes of the outermost layer portions which
are surrounded by the concaves may be different from each other.
[00 1 61
(4) In the surface-treated metal according to any one of (1) to (3), when the
outermost layer is seen in a cross-sectional view taken along the thickness direction, a
surface opposite the metal among two surfaces facing each other in the thickness
direction of the outermost layer may have a plurality of flat areas, and a total length of
the plurality of flat areas may be 70% to 99% of a total length of the surface.
[00 1 71
(5) In the surface-treated metal according to any one of (1) to (4), the
particles showing photocatalytic activity may contain a titanium oxide having an
anatase-type structure.
[00 1 81
(6) In the surface-treated metal according to any one of (I) to (3, the metal
may be any one selected from the group consisting of a steel sheet, a stainless steel
sheet, a titanium sheet, a titanium alloy sheet, an aluminum sheet, an aluminum alloy
sheet, and a plated metal sheet having a plated layer.
[0019]
(7) In the surface-treated metal according to any one of (1) to (6), the coated
material may have a second layer in contact with the outermost layer between the
outermost layer and the metal.
[0020]
(8) In the surface-treated metal according to (7), a ratio of a micro-Vickers
hardness of the second layer to a micro-Vickers hardness of the outermost layer may be
0.20 to 0.95.
[002 11
(9) In the surface-treated metal according to (7) or (8), a water contact angle
of the second layer may be in a range obtained by adding 10" to 80' to a water contact
angle of the outermost layer.
[0022]
(10) In the surface-treated metal according to any one of (I) to (9), a ratio of
the particles showing photocatalytic activity to the photocatalytic film may be in a
range from 0.5 mass% to 50 mass%, a particle size distribution based on the number of
the particles showing photocatalytic activity may have a plurality of maximum values
and minimum values which are present between adjacent maximum values in the
plurality of maximum values, and two or more maximum values in the plurality of
maximum values may have a number frequency which is 1.5 times or greater of a
number frequencies of minimum values adjacent to the maximum values thereof.
[0023]
(1 1) In the surface-treated metal according to (lo), the particle size
distribution may have at least one of the two or more maximum values of a particle
size range of 100 nm or less and may have at least one of the two or more maximum
values of a particle size range of 500 nm or greater.
[0024]
(12) According to another aspect of the invention, there is provided a
method of producing a surface-treated metal by forming a coated material on a surface
of a substrate containing a metal, the method including: mixing particles showing a
photocatalytic activity with a liquid which contains a hydrolysate of an alkoxysilane
having at least one group selected from a group consisting of an aryl group, a carboxyl
group, an amino group, a hydroxyl group, and an alkyl group having 1 to 12 carbon
atoms such that a ratio of the particles showing the photocatalytic activity to the liquid
is in a range from 1 g/l to 50 g/l to prepare a first treatment liquid, coating the first
treatment liquid such that the first treatment liquid covers an outermost layer of the
coated material, and baking the first treatment liquid.
[0025]
(13) In the method of producing the surface-treated metal according to (12),
the liquid or the first treatment liquid may further contain a hydrolysate of at least one
tetraalkoxysilane selected from a group consisting of a tetramethoxysilane and a
tetraethoxysilane.
[0026]
(14) In the method of producing the surface-treated metal according to (12)
or (13), a non-volatile content in the first treatment liquid may be 2.5 mass% to 10
mass%.
[002 71
(15) The method of producing the surface-treated metal according to any
one of (12) to (14) may further include cooling the outermost layer, after baking the
first treatment liquid, such that an average cooling rate in a temperature range from
250°C to 100°C is 100 "Clsec to 1500 "Clsec.
[0028]
(16) In the method of producing the surface-treated metal according to any
one of (12) to (15), the first treatment liquid may be coated using a dip coating method,
a spray coating method, a bar coating method, a roll coating method, a spin coating
method, or a curtain coating method.
[0029]
(1 7) In the method of producing the surface-treated metal according to any
one of (12) to (16), various types of treatment liquids may be coated to form the coated
material having a plurality of layers, and the various types of treatment liquids may
include the first treatment liquid and a second treatment liquid which is a different type
fi-om the first treatment liquid.
[003 01
(18) In the method of producing the surface-treated metal according to (17),
a ratio of a micro-Vickers hardness when the second treatment liquid is cured to a
micro-Vickers hardness when the first treatment liquid is cured may be 0.20 to 0.95.
[003 11
(19) In the method of producing the surface-treated metal according to (17)
or (18), a water contact angle when the second treatment liquid is cured may be in a
range obtained by adding 10" to 80" to a water contact angle when the first treatment
liquid is cured.
[0032]
(20) In the method of producing the surface-treated metal according to any
one of (17) to (19), a lower layer film containing an organic resin may be formed on
the surface of the substrate, the second treatment liquid and the first treatment liquid
may be simultaneously coated on the lower layer film, and the second treatment liquid
and the first treatment liquid may be simultaneously dried and baked to form a multilayer
film including the lower layer film formed on the surface of the substrate, a
second layer film formed by curing the second treatment liquid on the lower layer film,
and an outermost layer film formed by curing the first treatment liquid on the second
layer film.
[0033]
(21) In the method of producing the surface-treated metal according to any
one of (1 7) to (20), a coating liquid used to form a lower layer film containing an
organic resin, the second treatment liquid, and the first treatment liquid may be
simultaneously coated on the surface of the substrate, and the coating liquid, the
second treatment liquid, and the first treatment liquid may be simultaneously dried and
baked to form a multi-layer film including the lower layer film formed on the surface
of the substrate, a second layer film formed by curing the second treatment liquid on
the lower layer film, and an outermost layer film formed by curing the first treatment
liquid on the second layer film.
[0034]
(22) In the method of producing the surface-treated metal according to any
one of (12) to (21), the particles showing photocatalytic activity may contain a titanium
oxide having an anatase-type structure.
[003 51
(23) In the method of producing the surface-treated metal according to any
one of (12) to (22), the substrate containing the metal may be any one selected from
the group consisting of a steel sheet, a stainless steel sheet, a titanium sheet, a titanium
alloy sheet, an aluminum sheet, an aluminum alloy sheet, a plated metal sheet having a
plated layer, and a prepainted steel sheet.
[003 61
(24) In the method of producing the surface-treated metal according to any
one of (12) to (23), a particle size distribution based on a number of the particles
showing photocatalytic activity may have a plurality of maximum values and
minimum values which are present between adjacent maximum values in the plurality
of maximum values, and two or more maximum values in the plurality of maximum
values may have a number frequency which is 1.5 times or greater of number
frequencies of minimum values adjacent to the maximum values thereof.
[003 71
(25) In the method of producing the surface-treated metal according to (24),
the particle size distribution may have at least one of the two or more maximum values
of a particle size range of 100 nm or less and may have at least one of the two or more
maximum values of a particle size range of 500 nm or greater.
[Effects of the Invention]
[003 81
According to the above-described aspects of the invention, it is possible to
provide a surface-treated metal which is capable of exhibiting superior contamination
resistance due to high photocatalytic activity for a long period of time from the initial
stage immediately after usage starts. Therefore, without washing the surface-treated
metal, the user of a product or a structure can maintain an external appearance of the
product or the structure in the clean and the favorable state until a product lifetime or a
service life after usage starts.
[0039]
According to the above-described aspects of the invention, it is possible to
easily obtain a surface-treated metal which has superior contamination resistance due
to a photocatalytic effect from the initial stage immediately after usage starts and in
which there is almost no deterioration of a matrix resin and an organic resin coating
film. The matrix resin constitutes a part of a photocatalytic film, and the organic
resin coating film is an undercoat of the photocatalytic film.
[0040]
In addition, according to the above-described aspect of the method of
producing a surface-treated metal of the invention, a photocatalytic film which is
usually formed by using a post-coating method in the related art can be easily obtained
by using a pre-coating method. That is, according to the above-described aspect of
the invention, a surface-treated metal which has superior weather resistance and
contamination resistance for a long period of time can be easily obtained, and
processes such as bending and drawing can be performed thereto. Therefore, the
surface-treated metal can be more flexibly applied to various products or structures.
[Brief Description of the Drawing]
[004 11
FIG. 1A is a vertical cross-sectional view schematically illustrating a part of
an example of a surface-treated metal according to an embodiment of the invention.
FIG. 1B is a vertical cross-sectional view schematically illustrating a part of
another example of the surface-treated metal according to the embodiment.
FIG. 1C is a vertical cross-sectional view schematically illustrating a part of
still another example of the surface-treated metal according to the embodiment.
FIG. 2 is an enlarged diagram schematically illustrating a part of FIG. 1 A
indicated by a two-dot chain line.
FIG. 3 is a top view schematically illustrating a part of an example of the
surface-treated metal according to the embodiment.
FIG. 4 is a graph illustrating a predetermined maximum value for explanation.
FIG. 5 is a flowchart illustrating an example of a method of producing a
surface-treated metal according to an embodiment of the invention.
[Description of Embodiments]
[0042]
Objects of the invention are as follows.
[0043]
First, by using a resin which is difficult to decompose and deteriorate with
respect to a photocatalyst as a matrix resin of a photocatalytic film, the decomposition
and deterioration of the resin by the photocatalyst is suppressed, and superior
contamination resistance is maintained for a long period of time. As the matrix resin
of the photocatalytic film of the outermost layer, an organic-inorganic composite resin
which has been investigated by the present inventors is mainly used. Thus, the matrix
resin has high resistance to deterioration to a photocatalyst. Therefore, a
contamination resistance effect can be obtained by a photocatalyst such that the
surface-treated metal can maintain its external appearance in the favorable state for a
long period of time.
[0044]
Second, by existing concave (for example, cracks) on the above-described
photocatalytic film, a surface area of the film is increased. Therefore a photocatalytic
reaction can be effectively induced. In addition, contamination resistance caused by
the decomposition of contaminants is an effect obtained by photocatalytic particles
which are present on a film surface. By existing the concave, even photocatalytic
particles which are present inside the film can contribute to contamination resistance.
Furthermore, as described below in detail, in a step of forming a film, particularly in
the case of concave which are physically introduced during heating, cooling, or the like,
photocatalytic particles which are not covered with a resin may be exposed through
side surfaces of the concave. Therefore, the photocatalytic particles can exhibit
contamination resistance due to a photocatalytic effect from the initial stage which is in
contact with contaminants. That is, by introducing concave into a photocatalytic film,
the photocatalytic film can exhibit a high level of contamination resistance fkom the
initial stage immediately after usage starts.
[0045]
Regarding this point, in a general surface-treated steel sheet (of the related art),
by introducing concave (for example, cracks) into a coating layer of a surface, there are
many cases in which the adhesion of the coating layer may deteriorate or in which the
corrosion resistance of the steel sheet may deteriorate. In addition, since there may be
a problem that the design of an external appearance deteriorates, the introduction of
concave into a coating layer of a surface side of the surface-treated steel sheet is a
method which is not usually adopted. However, the present inventors have found that
a significantly high level of contamination resistance can be exhibited by using the
above-described two methods from the initial stage immediately after usage starts. In
addition, by regulating the properties and amount of concave which are introduced into
a photocatalytic film, it is confirmed that the adhesion of a coating layer such as a
photocatalytic film and the external appearance of a steel sheet do not deteriorate.
[0046]
According to the above-described facts, advantageous effects can be applied
to a surface-treated metal, in that a high level of contamination resistance can be
exhibited fiom the initial stage immediately after usage starts, and in that this effect
(contamination resistance) can be maintained for a long period of time.
[0047]
Hereinbelow, a surface-treated metal according to an embodiment of the
invention will be described in detail.
[0048]
FIG. 1A is a vertical cross-sectional view schematically illustrating a part of
an example of a surface-treated metal according to the embodiment, and FIG. 2 is an
enlarged diagram schematically illustrating a part of FIG 1A indicated by a two-dot
chain line.
As illustrated in FIG lA, a surface-treated metal 1 according to the
embodiment includes a metal 2 and a coated material 3 that is formed on a surface of
the metal 2. The coated material 3 includes at least one of coating layers 3a to 3e.
As illustrated in FIG. 2, the outermost layer 3a of the coated material 3 is the
photocatalytic film 3a including particles which are showing photocatalytic activity or
aggregates thereof 5 (hereinafter, also abbreviated as "photocatalytic dispersed phase
5") and an organic-inorganic composite resin 6 (hereinafter, also abbreviated as
"matrix resin 6").
Furthermore, in this specification and the drawings, components having
substantially the same function and composition are represented by the same reference
numerals and a description thereof will not be repeated here.
[0049]
(Presence of Concave)
The surface-treated metal 1 according to the embodiment includes concave 4
(for example, cracks) on a surface of the outermost layer 3a side of the coated material
3 (a side (an environmental side) on which the photocatalytic film 3a is in contact with
gas (for example, the air) or liquid (for example, water)) when seen from the metal 2
side. With these concaves 4, coverage of the photocatalytic film 3a per unit area of
the metal 2 which is a substrate is controlled to be in a range from 98% to 50%. The
above fact has the following meaning. When the outermost layer 3a is seen in a
cross-sectional view (refer to FIGS. 1A and 2) taken along a thickness direction thereof,
a part of the concaves 4 separate the outermost layer 3a in a direction perpendicular to
the thickness direction of the outermost layer 3a. Therefore, when the coated material
3 is seen in a plan view (refer to FIG. 3 described below), an area of the outermost
layer 3a is 50% to 98% of an area of a surface of the metal 2. That is, bottoms 41 of a
part of the concaves 4 reach the surface of the metal 2 which is the substrate (for
example, refer to a concave 4i of FIG. 1B described below and concaves 4k and 4m of
FIG. 1C described below). Alternatively, when other coating layers 3b to 3e are
present below the outermost layer 3a (between the outermost layer 3a and the metal 2),
the bottoms 4 1 of a part of the concaves 4 reach surfaces or insides of the coating
layers 3b to 3e (for example, refer to concaves 4a, 4c, and 4d of FIG. 1A and concaves
4f, 4g, and 4h of FIG. 1B described below). In addition when the other coating layers
3b to 3e are present below the outermost layer 3a, it is not necessary for the concaves 4
to penetrate the other coating layers 3b to 3e so as to expose the surface of the metal 2
which is the substrate.
[OOSO]
Due to the presence of the concaves 4 which is penetrated, the photocatalytic
film (outermost layer) 3a according to the embodiment has coverage in a range from
98% to 50%. When the coverage of the photocatalytic film 3a is excessively large, it
is difficult to sufficiently obtain the effect of the introduction of the concaves 4 into the
coated material 3. Conversely, when the coverage of the photocatalytic film 3a is
excessively small, sufficient contamination resistance cannot be obtained. Regarding
the coverage of the photocatalytic film 3a due to the presence of the concaves 4, the
lower limit thereof is preferably greater than or equal to 55% or 60% and more
preferably greater than or equal to 70%, and the upper limit thereof is preferably less
than or equal to 95%, more preferably less than or equal to 90%, and still more
preferably less than or equal to 85%.
[005 11
FIG. 3 is a top view schematically illustrating a part of an example of the
surface-treated metal 1 according to the embodiment. As illustrated in FIG. 3, in the
outermost layer 3a of the surface-treated metal 1, the concaves 4 extend in an arbitrary
in-plane direction of the outermost layer 3a (direction perpendicular to the thickness
direction of the outermost layer 3a). In addition, in the example of FIG. 3, the
plurality of concaves 4 are present in a network shape. Based on a sum Av of areas of
the network-shaped concaves 4 (however concaves other than the concaves 4 which do
not penetrate the outermost layer 3a are excepted, for example, a concave 4b of FIG
1 A, a concave 4e of FIG. IB, and a concave 4j of FIG. 1C) and a measured area AM,
the coverage ((AM-Av)/AMx1 00%) of the photocatalytic film 3a can be obtained.
[0052]
(Surface Area of Photocatalytic film)
In the surface-treated metal 1 according to the embodiment, by the presence
of concaves 4 in the photocatalytic film 3a, it is preferable that a surface area (rate of
increase of the surface area) of the photocatalytic film 3a be controlled to be 1 .O1
(times) to 50.0 (times) of a surface area per unit area of the metal 2 which is the
substrate. That is, the surface area of the outermost layer 3a is preferably in a range
from 101% to 5000% of the area of the surface of the metal 2. This range represents
that the surface area of the photocatalytic film 3a increases in a range from 1 .O1 times
to 50 times of the surface area of the metal 2 by the concaves 4 (that is, the surface area
of the photocatalytic film 3% when the surface of the photocatalytic film 3a on the
environmental side is completely flat). Due to the introduction of the concaves 4, the
surface in contact with the environment is newly formed, and a photocatalytic effect
can increase along with an increase in surface area.
[0053]
For example, it is assumed that the concaves 4 having the same width W
(wherein W=t) as the thickness (film thickness) t of the photocatalytic film 3a are
introduced. In this example, the surface area of the photocatalytic film 3a is
decreased by the area of "txL (that is, WxL)" by the concaves 4 having the length L,
whereas the surface area of the photocatalytic film 3a is increased by the area of
"2txL" by the concaves 4 having the length L. When there are many concaves 4
having a width W (for example, W<2t) narrower than the film thickness t, the surface
area of the photocatalytic film 3a can be effectively increased by the concaves 4. On
the other hand, when there are concaves 4 having a width W wider than two times (2t)
of the film thickness t, the surface area of the photocatalytic film 3a is decreased by the
introduction of the concaves 4. However, it is difficult to strictly control the widths
W of the concaves 4, and concaves 4 having the width W narrower than or equal to 2t
are also effectively introduced by the concaves 4 having the width W wider than 2t.
Therefore, it is not necessary that concaves 4 having a wide width W are excluded.
[0054]
In addition, in the embodiment, the photocatalytic film 3a contains the
photocatalytic dispersed phase (photocatalytic particles and aggregates thereof) 5.
Therefore, surfaces of fractures (a part of or all of the side surfaces 42 of the concave)
of the photocatalytic film 3a which are generated by the concaves 4 are not smooth,
and small irregularities or pores are present in the photocatalytic film 3a due to the
photocatalytic dispersed phase 5. Accordingly, a surface area of the fractures
generated by the formation of the concaves 4 is usually greater than "2txL", and it can
be expected that the surface area of the photocatalytic film 3a is effectively increased
by the concaves 4.
[005 51
Regarding an increase in the surface area of the photocatalytic film 3a by the
concaves 4, a lower limit of a ratio of the surface area of the photocatalytic film
(outermost layer) 3a to the area of the surface of the metal 2 is preferably greater than
or equal to 1.01 (greater than or equal to 101%), more preferably greater than or equal
to 1.02 (greater than or equal to 102%), still more preferably greater than or equal to
1.05 (greater than or equal to 105%), and particularly preferably greater than or equal
to 1.10 (greater than or equal to 110%). In addition, regarding an increase in the
surface area of the photocatalytic film 3a by the concaves 4, an upper limit of the ratio
of the surface area of the photocatalytic film (outermost layer) 3a to the area of the
surface of the metal 2 is preferably less than or equal to 50.0 (less than or equal to
5000%), more preferably less than or equal to 48.0 (less than or equal to 4800%), still
more preferably less than or equal to 45.0 (less than or equal to 4500%), and
particularly preferably less than or equal to 40.0 (less than or equal to 4000%). When
the rate of increase in the surface area is excessively small, an amount of an increase in
photocatalytic effect by the introduction of the concaves 4 is not large and may be
insufficient. On the other hand, when the rate of increase of the surface area is
excessively large, there are no significant problems. However, such formation of the
concaves 4 is not realistic.
[0056]
(Widths of Concave)
The widths W of the concaves 4 present in the coated material 3 to the film
thickness t are preferably in a range from 0.0 1 to 10 (1% to 1000%) by a ratio thereof
to the film thickness t. In this way, the desired widths W of the concaves 4 are
specified using the ratio thereof to the film thickness t, and the concaves 4 having a
width W in this range are present in the coated material 3. As a result, the
contamination resistance of the surface-treated metal 1 can be more effectively
improved. On the other hand, as described above, when the widths W of the
introduced concaves 4 are excessively wide in relation to the film thickness t, the
surface area of the photocatalytic film 3a cannot be effectively increased. Therefore,
the widths W of the concaves 4 are preferably in a range from 0.01 to 5 (1% to 500%)
and more preferably in a range from 0.01 to 2 (1% to 200%) in terms of the ratio
thereof to the film thickness t.
[0057]
In addition, by providing the concaves 4 having the above-described
properties (for example, the widths W of the concaves 4 are in a range from 0.0 1 to 10
by the ratio thereof to the film thickness t) such that a ratio of the lengths thereof to a
total length Lt of the concaves 4 is 90% or higher, the contamination resistance of the
surface-treated metal 1 can be more effectively improved. When the ratio of the
lengths of the concaves 4 having the above-described width W to the total length L, of
the concaves 4 is small, there are many concaves 4 having an excessively narrow width
W or concave having an excessively wide width W. In order to increase the
contamination resistance effect by a photocatalyst, it is preferable that the concave 4
having a width W in the above-described range be present in 95% or higher and more
preferably in 98% or higher. An upper limit of the ratio of the lengths of the concaves
4 having the above-described width W to the total length Lt of the concaves 4 is not
particularly limited and may be, for example, 100%.
[005S]
Regarding the measurement of the widths W of the concave 4, it is preferable
that as many concaves 4 as possible be measured. However, due to temporal and
economical limitations, the widths W can be represented by the measurement results of
concaves 4 present in a given range.
[0059]
Specifically, when the widths W of the concaves 4 are not large in relation to
the film thickness t, for example, when the film thickness t is 10 pm and the maximum
width W of the concaves 4 is approximately 20 pm to 30 pm, it is only necessary that
concaves 4 present in a 100 pmx100 pm area be measured. On the other hand, when
the film thickness t is 10 pm and the maximum width W of the concaves 4 is
approximately 100 pm, it is preferable that concaves 4 present in a 0.5 mmx0.5 mm
area or a 1 mmx 1 mm area be measured. In addition, when the film thickness t is 10
prn and the maximum width W of the concaves 4 is approximately 1 pm, it is only
necessary that concaves 4 present in a 10 pmxlO pm area or a 20 pnx20 ym area be
measured. That is, the properties of all the concaves 4 can be determined by
appropriately selecting a measurement area from a 10 pmx 10 pm area to a 1 mrnx 1
mm area according to the thickness t of the photocatalytic film 3a and the widths W of
the concaves 4 and measuring concaves 4 present in the selected area. Needless to
say, the selected area (measurement area) is not necessarily quadrangle and may be
appropriately selected from various shapes such as a circular shape, an elliptical shape,
and a polygonal shape.
[0060]
In addition, as illustrated in FIG. 3, when the coated material 3 is seen in a
plan view, the concaves 4 may form a network shape, and sizes of portions of the
outermost layer (photocatalytic film) 3a which are surrounded by the concaves 4 may
be different from each other. In this case, for example, when a liquid containing
organic pollutants is attached on the surface of the photocatalytic film 3% the organic
pollutants are likely to be guided to the concaves 4 having a pattern randomized by
capillarity and the like. As a result, contact efficiency (collision frequency) between
the organic pollutants and the photocatalytic particles 5 can be improved and the
surface-treated metal 1 exhibits high contamination resistance. Furthermore, the
production cost of the surface-treated metal 1 can be suppressed as compared to a case
in which a pattern is uniformly formed to form the film.
Furthermore, it is preferable that, when the outermost layer 3a is seen in a
cross-sectional view taken along the thickness direction thereof using, for example,
SEM, a surface opposite the metal 2 among two surfaces facing each other in the
thickness direction of the outermost layer 3a has plural flat areas. In this case, for
example, when the surface-treated metal 1 is processed using a mold or the like,
surface-contacting portions (flat areas) are increased. Therefore, a local stress applied
to the photocatalytic film 3a can be reduced. Accordingly, as the surface-treated
metal 1, a precoated metal having high workability (for example, bendability and deep
drawability) can be provided at a low cost. In this case, a total length of the plural flat
areas is preferably 70% to 99% of a length (total length) of the entire surface opposite
the metal 2. For example, in a coating process of a production method according to
an embodiment described below, these flat areas can be formed on the photocatalytic
film 3a using a surface tension of a treatment liquid and the like. When the surface of
the metal 2 is set as a reference line (reference surface), surfaces having an angle of
20" or less (which is set in a range (absolute value) from 0" to 90°) from this reference
line are defined as the flat areas, and such surfaces are linearly approximated and
evaluated. In addition, when the side surfaces 42 of the concaves 4 have a steep slope
(for example, when side surfaces 42 of concaves 4 having an angle in a range of 70" to
90" from the reference line are 70% to 100% of all the side surfaces 42 of the concaves
4), a contact efficiency (collision frequency) between contaminants which are
incorporated into grooves of the concaves 4 and the photocatalytic particles 5 can be
improved, and the surface-treated metal 1 can exhibit high contamination resistance.
Recessed portions in a cross-section of the surface-treated metal 1 are defined
as the concaves 4. Therefore, for example, when only the photocatalytic film 3a is
taken into consideration, the concaves 4 may have a hole shape. However, hereinafter,
such a case will be also described as the concaves 4 being formed on the photocatalytic
film 3a.
1006 11
(Photocatalytic Particles)
The surface-treated metal 1 according to the embodiment includes the coated
material 3 having one or more layers of the coating layers 3a to 3e on the surface of the
metal 2. The coated material 3 includes the photocatalytic film 3% which contains at
least one type of photocatalytic particles 5 in a volume ratio range of 0.5% to 50%, as
the outermost layer 3a.
[0062]
Preferable examples of the photocatalytic particles 5 include titanium oxide,
zinc oxide, cerium oxide, tin oxide, bismuth oxide, indium oxide, zirconium oxide,
tungsten oxide, chromium oxide, molybdenum oxide, iron oxide, nickel oxide,
ruthenium oxide, cobalt oxide, copper oxide, manganese oxide, germanium oxide, lead
oxide, cadmium oxide, vanadium oxide, niobium oxide, tantalum oxide, rhodium oxide,
rhenium oxide, barium titanate, strontium titanate, and iron titanate. Among these,
titanium oxide, zinc oxide, tin oxide, zirconium oxide, tungsten oxide, iron oxide, and
niobium oxide are more preferable from the viewpoint of showing high activity even
when a heat treatment is performed at a low temperature of 100°C or lower. Among
these, a titanium oxide having an anatase-type structure is particularly preferable from
the viewpoint of showing high activity as a photocatalyst.
[0063]
The amount of the photocatalytic particles 5 is preferably greater than or equal
to 0.5%, more preferably greater than or equal to 1.0%, and still more preferably
greater than or equal to 2.0% by volume ratio (~01%t)h ereof to the total volume of the
photocatalytic film 3a. In addition, the amount of the photocatalytic particles 5 is
preferably less than or equal to 50%, more preferably less than or equal to 45%, and
still more preferably less than or equal to 40% or 30% by volume ratio (~01%t)h ereof
to the total volume of the photocatalytic film 3a. When the amount of the
photocatalytic particles 5 is less than 0.5% by volume ratio, it is difficult to exhibit a
contamination resistance function by a photocatalytic effect. On the other hand, when
the amount of the photocatalytic particles 5 is greater than 50% by volume ratio, a
sufficient contamination resistance hnction is exhibited, but the decomposition and
deterioration of the organic-inorganic composite resin 6 constituting the photocatalytic
film 3a is promoted. The organic-inorganic composite resin 6 of the photocatalytic
film 3a which is used in the embodiment is difficult to decompose and deteriorate with
a photocatalyst. However, when the amount of the photocatalyst is excessively large,
it is difficult to obtain superior contamination resistance for a long period of time. In
addition, by suppressing an upper limit of the amount of the photocatalyst, the cost can
be suppressed.
[0064]
In addition, as described above, since the cross-sections 42 of the concaves 4
are not smooth, it can be expected that the surface area of the photocatalytic film 3a is
increased by the introduction of the concaves 4. This effect is particularly high when
the photocatalytic film 3a contains a given amount or greater of the photocatalyst.
Accordingly, the amount of the photocatalytic particles 5 in the photocatalytic film 3a
is preferably greater than or equal to 3.0% and most preferably greater than or equal to
5.0% by volume ratio.
[0065]
The particle size of the photocatalytic particles 5 to be used is not particularly
limited, and a photocatalyst having any particle size can be used. However, by using
photocatalytic particles having a small particle size (primary particle size), the
photocatalytic effect of the embodiment can be improved. That is, since
photocatalytic particles having a small average primary particle size have higher
photocatalytic activity than that of photocatalytic particles having a large average
primary particle size, a superior contamination resistance effect can be obtained by the
photocatalytic particles having a small average primary particle size.
[0066]
The average primary particle size of the photocatalytic particles 5 is more
preferably less than or equal to 100 nm, still more preferably less than or equal to 50
nm or 30 nm, and most preferably less than or equal to 20 nm. In addition, it is also
preferable that the average primary particle size of the photocatalytic particles 5 be in
the above-described range from the viewpoint of increasing the surface area by the
introduction of the concave portion 4. In addition, in order to krther increase the
surface area, the above-described small photocatalytic particles 5 may form aggregates
(aggregated particles) having an appropriate size. The size of the aggregates of the
photocatalytic particles 5 is not particularly limited, but a lower limit thereof is
preferably greater than or equal to 0.5 pn and more preferably greater than or equal to
1.0 p~In. a ddition, an upper limit of the size of the aggregates of the photocatalytic
particles 5 is preferably less than or equal to 5.0 pm. When the size of the aggregates
is greater than or equal to 0.5 pm or greater than or equal to 1.0 pm, there is a
sufficient or significant difference between the size of the aggregates and the size of
the primary particles. As a result, an effect of increasing the surface area by the
formation of the aggregates can be improved. In addition, when the size of the
aggregates is less than or equal to 5.0 pm, the size of the aggregated particles is
controlled in relation to the thickness of the photocatalytic film, and a favorable
external appearance can be secured.
[0067]
Furthermore, in order to more efficiently utilize the increase in the surface
area of the photocatalytic film 3a by the concaves 4, the photocatalytic dispersed phase
5 containing a photocatalyst of the outermost layer (photocatalytic film) 3a may have
two or more dispersed particle sizes and a particle size distribution thereof may include
two or more maximum values. This characteristic can be achieved by the following
particle size distribution control methods (A) to (D).
(A) Photocatalysts which are the same materials showing photocatalytic
activity and have different particle size distributions of primary particles are mixed
with each other.
(B) A plurality of types of photocatalysts which are all different materials
showing photocatalytic activity and have different particle size distributions of primary
particles are mixed with each other.
(C) By using photocatalysts which are the same materials showing
photocatalytic activity, a particle size distribution of primary particles and a particle
size distribution of secondary particles (aggregates) are controlled.
@) By using a plurality of types of photocatalysts which are all different
materials showing photocatalytic activity, particle size distributions are controlled such
that when one photocatalyst forms a particle size distribution of primary particles, the
other photocatalyst forms a particle size distribution of secondary particles
(aggregates).
As a method other than the methods (A) to (D), by using a plurality of types
of photocatalysts which are all different materials showing photocatalytic activity and
controlling particle size distributions such that particle size distributions of secondary
particles of the respective photocatalysts are different from each other, the
photocatalytic effect can be improved immediately after usage starts. However, it is
difficult to control particle size distributions of secondary particles of different
materials in one coating system. Therefore, when particle size distributions are
controlled, it is preferable that the above-described particle size distribution control
methods (A) to (D) be applied.
[0068]
In the above-described particle size distribution control, when the
photocatalytic film 3a contains secondary particles (aggregates), one type of secondary
particles are used as one type of particles, the photocatalytic particles 5 present in the
photocatalytic film 3a have a particle size distribution from small particles (primary
particles) to large aggregates, and this particle size distribution has two or more
predetermined maximum values. In this case, as illustrated in FIG. 4, the maximum
value refers to a central point (inflection point 1) of particle sizes in the particle size
range, when the number (frequency) of particles belonging to the specific particle size
range (for example, class) is shifted from an increase to a decrease. In this definition,
there is a large variation in the particle size distribution, and there are many maximum
values when an increase and a decrease of the number of particles are repeated in
particle size ranges adjacent to each other. Therefore, by using an inflection point 2
(a central point or minimum value of particle sizes in the particle size range when the
number (frequency) of particles belonging to the specific particle size range is shifted
from a decrease to an increase) in the opposite direction which is present between two
inflection points 1 (when three or more inflection points 1 are present, two arbitrary
inflection points adjacent to each other are selected) as a reference, an inflection point
1 of which the numbers (frequency) of particles is 1.5 times or greater than the number
(frequency) of the inflection point 2 is defined (refer to FIG. 4.) as a maximum value
(predetermined maximum value). In FIG. 4, two inflection points 2 adjacent to
inflection points 1 (l(1) and l(2)) are present (actually, there is also a case where one
inflection point 2 adjacent to the inflection points 1 may be present). An inflection
point 1 which satisfies the above-described relationship with the one or two inflection
points 2 is defined as a predetermined maximum value. For example, when an
example of FIG. 4 is used for description, the inflection point l(1) is a predetermined
maximum value because a1 21 .5xbl and a121.5xb2 are satisfied. On the other hand,
the inflection point l(2) is not a predetermined maximum value because a2 21.5xb2 is
satisfied but a221.5xb3 is not satisfied.
[0069]
That is, when the particle size distribution of the photocatalytic particles 5 is
controlled, it is preferable that the particle size distribution based on the number of the
photocatalytic particles 5 has a plurality of maximum values and minimum values
which are present between adjacent maximum values in the plurality of maximum
values, and that two or more maximum values in the plurality of maximum values has
a number frequency which is 1.5 times or greater of number frequencies of minimum
values adjacent to the maximum values thereof. Hereinafter (the following
embodiment and examples), the maximum value refers to the predetermined maximum
value unless specified otherwise.
[0070]
With the above-described particle size distribution control, photocatalytic
particles having a large particle size or dispersed particle size improves contamination
resistance on the surfaces and fractures (a part of or all of the side surfaces 42 of the
concave) of the photocatalytic film 3a in the initial stage, and photocatalytic particles
having a small particle size and a high dispersion state further improves contamination
resistance for a long period of time. Accordingly, by the particle size distribution
control of photocatalytic particles having two or more dispersion states, superior
contamination resistance can be maintained for a long period of time from the initial
stage.
[007 11
Even when the number of maximum values is large, there are no significant
problems. However, 10 or less maximum values are sufficient. The particle size
(central point in a particle size range, for example, xl in FIG. 4) corresponding to the
maximum values is not particularly limited. When at least one of maximum values is
present in a particle size range of 100 nm or less and one of the other maximum values
is present in a particle size range of 500 nm or greater, more preferable contamination
resistance can be obtained in the initial and intermediate stages. It is still more
preferable that at least one of maximum values is present in a particle size range of 50
nm or less and one of the other maximum values is present in a particle size range of
600 nm or greater. In this way, when the maximum values of the particle size
distribution of the photocatalytic particles 5 are controlled, a more preferable
contamination resistance effect by a photocatalyst can be obtained for a long period of
time from the initial stage. An upper limit of the particle size range of the
photocatalytic particles 5 relating to the maximum values is not particularly limited but,
for example, is preferably 5.0 pm (5000 nm) in consideration of the dispersibility of
the photocatalytic particles 5 and the like.
LO0721
When the photocatalytic particles 5 have two maximum values of particle size,
by volume ratio with respect to the entire photocatalytic particles 5, it is preferable that
photocatalytic particles having a maximum value corresponding to a small particle size
be 5% to 80% and photocatalytic particles having a maximum value corresponding to a
large particle size be 20% to 95%, it is more preferable that photocatalytic particles
having a maximum value corresponding to a small particle size be 10% to 80% and
photocatalytic particles having a maximum value corresponding to a large particle size
be 20% to 90%, and it is still more preferable that photocatalytic particles having a
maximum value corresponding to a small particle size be 20% to 70% and
photocatalytic particles having a maximum value corresponding to a large particle size
be 30% to 80%. When photocatalytic particles having a maximum value
corresponding to a small particle size and photocatalytic particles having a maximum
value corresponding to a large particle size are in the above-described ranges, a
preferable contamination resistance effect by a photocatalyst can be obtained for a long
period of time from the initial stage, and deterioration in the film by a photocatalyst
can be suppressed to the minimum. In addition, when the photocatalytic particles 5
have three or more maximum values of particle size, a total volume ratio of
photocatalytic particles having a maximum value in a particle size range of 100 nm or
less and photocatalytic particles having a maximum value in a particle size range of
500 nrn or greater to all the photocatalytic particles 5 is preferably greater than or equal
to 50%, more preferably greater than or equal to 60%, and still more preferably greater
than or equal to 70%. In this case, as in the case in which the photocatalytic particles
5 have two maximum values of particle size, a preferable contamination resistance
effect by a photocatalyst can be obtained for a long period of time from the initial stage,
and deterioration in the film by a photocatalyst can be suppressed to the minimum.
[0073]
Here, a method of measuring a particle size distribution of the photocatalytic
particles 5 in the photocatalytic film 3a will be described.
In order to measure the particle size distribution, a cross-section of the
photocatalytic film 3a is observed using a microscope, and the size of particles to be
observed is directly measured. It is preferable that a microscope to be used be
selected according to the particle size distribution of particles to be observed. That is,
when particles having a relatively large size of pm order are observed, a scanning
electron microscope (SEM) is used, and when particles having a relatively small size
of nm level are observed, a transmission electron microscope (TEM) is used. By
using these microscopes together, the photocatalytic particles 5 can be effectively
observed. A cutting direction of observation particles is not particularly limited and
can be determined according to the thickness of the photocatalytic film 3a and the
particle size distribution of the photocatalytic particles 5 in a range in which there is no
variation in the measurement. In addition, the rate (mass% and ~01%o)f the
photocatalytic particles 5 (including aggregates) in the photocatalytic film 3a can be
simultaneously measured along with the above-described measurement of the particles
size distribution. That is, the volume ratio (~01%o) f the photocatalytic particles 5 can
be calculated from an area ratio of the photocatalytic particles 5 in the cross-section of
the photocatalytic film 3a. From this volume ratio and the true density of the
photocatalytic particles 5, the mass ratio (mass%) of the photocatalytic particles 5 can
be calculated. In consideration of the resolution of the measurement method and @e
like, a lower limit of the average primary particle size of the photocatalytic particles 5,
and a lower limit of the particle size range of the photocatalytic particles 5 relating to
the above-described maximum values may be 0.5 nm.
[0074]
In this method, in order to obtain the particle size distribution of the
photocatalytic particles 5 in the photocatalytic film 3a, it is preferable that the particle
sizes of all the photocatalytic particles 5 be measured from the viewpoint of obtaining
the particle size distribution with high precision. However, since there are significant
problems in such a method, it is impossible to conduct the method. Therefore, all the
particle sizes (particle size distribution) can be represented by measuring the particle
sizes of a part of particles which are extracted with a random method. As a result of
investigating particles having an already-known average particle size, the present
inventors found that the average particle size can be obtained almost without error by
measuring particle sizes of 500 or more, preferably, 1000 or more particles. However,
since it is considerably difficult to measure 500 to 1000 particles, the particle size may
be automatically measured with a method such as image processing. In this method,
when particles form moderate aggregates, aggregated particles may be determined as
primary particles. Therefore, even when a resin or the like is contained in an
aggregate, image processing or the like is set such that an outline of the aggregate on
the outermost side is determined as a particle surface.
[0075]
As the methods for making two or more maximum values present in the
particle size distribution, the above-described four methods (A) to (D) are usually used.
[0076]
First, cases in which photocatalysts having different primary particle sizes are
used in combination as in the cases of the above methods (A) and (B) will be described.
[0077]
Examples of a case in which two or more maximum values (the abovedescribed
predetermined maximum values) are formed in a particle size distribution by
primary particles of the same material showing photocatalytic activity include a case in
which the photocatalytic film 3a contains mixed particles prepared by mixing Ti02
having an average primary particle size of 10 nm with Ti02 having an average primary
particle size of 800 nm. In this case, the material showing photocatalytic activity is
titanium oxide. In addition, when primary particles of a photocatalyst are small, in
order to realize the above-described particle size distribution, the photocatalyst may be
supported by a carrier such as an inorganic porous material having the desired particle
size distribution. Even in this case, when at least one of maximum values of a
particle size distribution of primary particles is present in a particle size range of 100
nm or less and at least one of the other maximum values is present in a particle size
range of 500 nm or greater, more preferable contamination resistance can be obtained
in the initial and intermediate stages. In addition, it is still more preferable that at
least one of maximum values of a particle size distribution of primary particles is
present in a particle size range of 50 nm or less and at least one of the other maximum
values is present in a particle size range of 600 nm or greater. When the abovedescribed
supported photocatalyst is used, it is preferable that a particle size
distribution of the photocatalyst including the carrier satisfy the above-described
particle size distribution. In addition, examples of a case in which two or more
maximum values (the above-described predetermined maximum values) are formed in
a particle size distribution by primary particles of different materials showing
photocatalytic activity include a case in which the photocatalytic film 3a contains
mixed particles prepared by mixing Ti02 having an average primary particle size of 10
nm with ZnO having an average primary particle size of 1000 nm.
[0078]
Next, cases in which a particle size distribution of primary particles and a
particle size distribution of secondary particles (aggregates) are combined as in the
cases of the above methods (C) and (D) will be described. In such a method, a
particle size distribution having 2 to 10 maximum values can be obtained.
[0079]
Since the particle size distribution of secondary particles changes depending
on the types of dispersed particles and a matrix, a dispersing method, dispersing
conditions, and the like, the particle size distribution of secondary particles is generally
difficult to control. Therefore, in the cases of the methods (C) and (D), photocatalysts
having different dispersion states, particularly, different positions of maximum values
of the particle size distributions are mixed with each other in advance, and the
photocatalytic film 3a is formed while maintaining the dispersion states and the
particle size distributions as they are as much as possible.
[OOSO]
For example, by using powdered photocatalytic particles as one material
showing photocatalfic activity and using particles (material) in the sol state as the
other material showing photocatalytic activity, a particle size distribution having the
two or more predetermined maximum values can be obtained. In this case, one
material showing photocatalytic activity may be different from the other material
showing photocatalytic activity.
[008 11
In addition, when the above-described particle size distribution control is
performed, the amount of the photocatalytic particles 5 in the photocatalytic film 3a on
the surface of the surface-treated metal 1 may be 0.5% to 50% by mass ratio. By
controlling the amount of the photocatalytic particles 5 in the photocatalytic film 3a to
be 0.5 mass% to 50 mass%, good cost balance and long lifetime of the film can be
obtained while securing sufficient contamination resistance. The amount of the
photocatalytic particles 5 is preferably greater than or equal to 1.0 mass% and more
preferably greater than or equal to 2.5 mass%. In addition, the amount of the
photocatalytic particles 5 is more preferably less than or equal to 40 mass% and still
more preferably less than or equal to 35 mass%. In addition, in consideration of a
difference in specific gravity (difference in density) between the photocatalytic
particles 5 and the matrix resin 6 in the photocatalytic film 3a, it is preferable that the
content of the photocatalytic particles 5 be, for example, greater than or equal to 0.5
vol%, greater than or equal to 1.0 vol%, or greater than or equal to 2.5 vol% and be,
for example, less than or equal to 45 vol%, less than or equal to 35 vol%, or less than
or equal to 30 vol%
[0082]
(Matrix Resin of Photocatalytic film)
In the surface-treated metal 1 according to the embodiment, the matrix resin 6
constituting the photocatalytic film 3a also has a significant characteristic. That is,
even when the matrix resin 6 is used in combination with a photocatalyst, the
decomposition and deterioration of the matrix resin 6 by the photocatalyst is extremely
small. Hereinafter, the matrix resin 6 will be described in detail.
[0083]
First, the matrix resin 6 includes an inorganic skeleton, which is developed in
a three-dimensional network structure, as a main structure and contains an inorganic
siloxane bond represented by =Si-O-Si= as a main bond of the main skeleton. The
structure containing this siloxane bond as a major component contains at least one
selected fiom the group consisting of an alkyl group having 1 to 12 carbon atoms, an
aryl group, a carboxyl group, an amino group, and a hydroxyl group. As a result, the
surface-treated metal 1 also has, for example, workability which is required for a
precoated film in addition to superior stability to a photocatalyst and weather resistance.
The present inventors presume the reason for this to be that stability to a photocatalyst
and weather resistance of the photocatalytic film 3a are secured by the structure
containing the inorganic siloxane bond as a major component, and flexibility is given
to the film and superior workability is secured by the above-described functional group
controlling the crosslinking density of the resin and by the organic group.
[0084]
Examples of the alkyl group having 1 to 12 carbon atoms include a methyl
group, an ethyl group, a propyl group, a butyl group, a hexyl group, a 2-ethylhexyl
group, and a dodecyl group, and examples of the aryl group include a phenyl group, a
tolyl group, a xylyl group, and a naphthyl group. In addition, the carboxyl group
represents -COOH, the amino group represents -NH2, and the hydroxyl group
represents -OH.
[OOSS]
(Organic Components in Matrix Resin)
In the embodiment, the matrix resin 6 may contain two or more types of
organic components as an organic component. Among these, a major organic group,
that is, an organic group having the greatest content in the matrix resin 6 is preferably
an alkyl group or an aryl group. In this case, the number of carbon atoms in the alkyl
group is preferably more than or equal to 1. In addition, the number of carbon atoms
in the alkyl group is preferably less than or equal to 12, more preferably less than or
equal to 10, and still more preferably less than or equal to 8 or 6. In this way, as the
number of carbon atoms in the alkyl group is smaller, the alkyl group is more easily
used as an organic group. Likewise, the number of carbon atoms in the aryl group is
greater than or equal to 6, but is preferably less than or equal to 12, more preferably
less than or equal to 11, and still more preferably less than or equal to 10 or 8. In this
way, as the number of carbon atoms in the aryl group is smaller, the aryl group is more
easily used as an organic group. Among these, the most preferable organic group is a
phenyl group. By using only a phenyl group as an organic group in combination with
the siloxane bond forming the main skeleton, the photocatalytic film 3a having
superior stability to a photocatalyst, weather resistance, workability, and adhesion
during a process can be obtained. These organic components may be present in the
main skeleton of the matrix resin 6 or may be present in a side chain of the matrix resin
6. When these components are present in the photocatalytic film 3% the abovedescribed
various properties of the photocatalytic film 3a can be further improved.
[0086]
(Bond Other Than Siloxane Bond)
Examples of a bond other than the siloxane bond include an ether bond such
as -CH2-CH(CH2)-O-CH2-, and an amino bond such as secondary or tertiary amine.
Among these, when the photocatalytic film 3a contains either or both of an ether bond
and an amino bond in either or both of the main structure and a side chain of the film
structure, the film having particularly stability to a photocatalyst and workability can
be obtained.
[0087]
(Thickness of Photocatalytic film)
The thickness t of the photocatalytic film 3a varies depending on required
properties or the use, and a lower limit thereof is preferably greater than or equal to
0.01 pm, more preferably greater than or equal to 0.05 pm and still more preferably
greater than or equal to 0.1 p.m. Likewise, an upper limit of the thickness t of the
photocatalytic film 3a is preferably less than or equal to 25 pm, more preferably less
than or equal to 20 pm, and still more preferably less than or equal to 10 pm. When
the film thickness t is 0.01 pm to 25 pm, the controllability in the coverage of the
photocatalytic film 3a is improved, higher photocatalytic performance can be obtained,
and higher moldability and higher adhesion during a process can be obtained. In
addition, when a thick film is formed due to the properties of the film which forms a
matrix, the film may be formed through multiple operations in order to suppress
cracking, peeling, and the like. For example, when a film having a predetermined
thickness or larger is formed, it is preferable that coating and drying (solidifying)
described below be repeated.
[OOS 81
(Metal Elements in Photocatalytic film Other Than Si)
In the embodiment, the matrix resin 6 contains Si as a metal element, but may
further contain, as an element other than Si, one or more metal elements selected from
B, Al, Ge, Ti, Y, Zr, Nb, Ta, and the like. Among these metal elements, Al, Ti, Nb,
and Ta function as a catalyst for completing the solidification of a film at a low
temperature or within a short period of time when an acid is added to a system (for
example, a photocatalytic film-forming treatment liquid described below) as a catalyst.
When a metalalkoxide is added to the system using an acid as a catalyst, the ringopening
rate of an epoxy increases, and a film can be cured at a low temperature within
a short period of time. In particular, an alkoxide of Ti such as Ti-ethoxide or Tiisopropoxide
is frequently used as a material. In addition, in a system containing Zr,
since alkali resistance of a film is improved, a matrix resin containing Zr is preferably
used particularly when alkali resistance is required.
[0089]
In the photocatalytic film 3a, it is preferable that the dispersed phase (the
photocatalytic particles 5 and the other particles) be uniformly dispersed. However, it
is not necessary that the dispersed phase be uniformly dispersed. For example, the
dispersed phase may form aggregates, the concentrations of the dispersed phase
between the outermost portion and the inside of the photocatalytic film 3a may be
different from each other, and the concentration of the dispersed phase may have a
gradient. In such cases, since superior contamination resistance effect and superior
other properties may be obtained, it is not necessary that the dispersed phase be
uniformly dispersed.
[0090]
(Substrate)
The metal 2 which is the substrate of the surface-treated metal 1 according to
the embodiment is not limited in characteristics thereof (including material, shape,
whether being treated or not, and whether being a final product (shape) or not), and
any metals can be desirably used as the metal 2. For example, as the metal 2
~ (material), various metals such as steel, stainless steel, titanium, aluminum, and
i
aluminum alloys, and plated metal sheets having a plated layer which is obtained by
plating the above-described metals can be preferably used. In addition, as the metal 2
(shape), molded materials such as steel sections, steel plates, steel sheets, pipes and
tubes, bars, and wire rods can be preferably used.
[009 11
Among these, particularly preferable examples of the metal include a steel
sheet, a stainless steel sheet, a titanium sheet, a titanium alloy sheet, an aluminum sheet,
an aluminum alloy sheet, a plated metal sheet obtained by plating the above-described
metal sheets, and a prepainted steel sheet obtained by forming an organic coating film
on the above-described metal sheets. Examples of the coated steel plates and sheets
include a galvanized steel sheet, a zinc-iron alloy coated steel sheet, a zinc-nickel alloy
coated steel sheet, a zinc-chromium alloy coated steel sheet, a zinc-aluminum alloy
coated steel sheet, an aluminized steel sheet, a zinc-aluminum-magnesium alloy coated
steel sheet, a zinc-aluminum-magnesium-silicon alloy coated steel sheet, an aluminumsilicon
alloy coated steel sheet, a galvanized stainless steel sheet, and an aluminized
stainless steel sheet.
[0092]
Examples of the stainless steel sheet include an austenitic stainless steel sheet,
a ferritic stainless steel sheet, and a martensitic stainless steel sheet. Regarding the
thickness of the stainless steel sheet, stainless steel sheets having various thicknesses
from a thick stainless steel sheet having a thickness of about several tens of mm to a
so-called stainless steel foil of which the thickness is reduced to about 10 pm by
rolling can be used. The surfaces of the stainless steel sheet and the stainless steel
- - foil may be subjected to a surface treatment such as bright-annealing or buffing.
- 40 -
[0093]
Examples of the aluminum alloy sheet include JIS 1000 series (pure Al series),
JIS 2000 series (Al-Cu series), JIS 3000 series (Al-Mn series), JIS 4000 series (Al-Si
series), JIS 5000 series (Al-Mg series), JIS 6000 series (Al-Mg-Si series), and JIS 7000
series (Al-Zn series).
[0094]
In addition, when the photocatalytic film 3a is formed on a metal other than
prepainted steel sheet, the photocatalytic film 3a may be formed directly on the metal 2
or may be formed on the metal 2 on which another coating layer (including a pretreatment
film) is formed. For example, the photocatalytic film 3a may be formed on
a surface of a metal on which a chromate conversion coating is formed by chromating
or on a surface of a metal which is subjected to a surface treatment (for example,
phosphating) other than chromating.
[0095]
The above-described photocatalytic film 3a can also be formed directly on, for
example, a surface of an organic coating film of resin-based. As described above
repeatedly, this is because the organic-inorganic composite resin 6 which is the matrix
of the photocatalytic film 3a does not substantially deteriorate due to a photocatalyst
and thus, even when photocatalytic particles are present in the interface between the
photocatalytic film 3a and an organic coating film, the deterioration of the organic
coating film can be suppressed. On the other hand, when it is desired that the
deterioration of a lower layer film by a photocatalyst is completely suppressed, an
intermediate layer (protective layer) may be provided between the lower layer film and
the photocatalytic film 3a. When a film not containing the photocatalytic particles 5
is used as this intermediate layer, this film does not substantially deteriorate.
Therefore, most of compositions can be used as a film of the intermediate layer. In
particular, the above-described organic-inorganic composite resin 6, that is, the matrix
resin which is used on the photocatalytic film 3a of the outermost surface may be used
without being mixed with a photocatalyst.
[0096]
(Configuration of Coating Layer of Coated Material)
FIGS. 1B and 1C are vertical cross-sectional view illustrating a part of other
examples of the surface-treated metal according to the embodiment. The coating
layer (number of layers) of the coated material 3 may include a single layer as
illustrated in FIG. 1C or may include two or more layers as illustrated in FIGS. 1A and
1B. For example, when one type of treatment liquid is coated in multiple layers, the
same type of continuous layers is considered as one layer.
[0097]
Furthermore, in order to further increase an effect of improving contamination
resistance using the above-described concaves 4 or to further increase the
deformability (workability) of the coated material 3, the coated material 3 may include
a second layer 3b in contact with the outermost layer 3a between the outermost layer
(photocatalytic film) 3a and the metal 2.
In this case, for example, in order to further improve the deformability of the
coated material 3, a ratio of a micro-Vickers hardness of the second layer 3b to a
micro-Vickers hardness of the outermost layer 3a may be 0.20 to 0.95. In this way,
by controlling the hardness ratio of the outermost layer 3a and the second layer 3b, the
workability of the coated material 3 can be increased while relaxing stress
concentration in the coated material 3 during processing, and the sound surface-treated
metal 1 can be obtained. In order to further increase the workability of the coated
material 4, regarding the above-described micro-Vickers hardness ratio, the lower limit
thereof is more preferably greater than or equal to 0.30 and still more preferably
greater than or equal to 0.50, and the upper limit thereof is more preferably less than or
equal to 0.90 and still more preferably less than or equal to 0.85. The micro-Vickers
hardnesses of the outermost layer 3a and the second layer 3b can be obtained by
measuring (measuring at least 10 points which are statistically sufficient) a crosssection
(cross-section illustrated in FIGS. lA to 1C) of the surface-treated metal 1.
Regarding the outermost layer 3a, the surface (surface illustrated in FIG. 3) of the
surface-treated metal may be measured.
In addition, for example, in order to further increase the effect of improving
contamination resistance using the above-described concaves 4, a water contact angle
of the second layer 3b may be in a range obtained by adding 10" to 80" to a water
contact angle of the outermost layer 3a. The upper limit of this range is more
preferably less than or equal to 70" and still more preferably less than or equal to 60".
In this way, by controlling a relationship regarding hydrophilicity between the
outermost layer 3a and the second layer 3b, the adhesion of organic pollutants on the
bottoms 41 of the concave can be suppressed. Examples of a method of obtaining
such a second layer 3b include a method of increasing organic components (organic
groups) of the second layer 3b to be more than that of the outermost layer 3a, a method
of decreasing the amount of a photocatalyst added to the second layer 3b to be less
than that added to the outermost layer 3% and a method of controlling the
hydrophilicity of the second layer 3b due to dispersing a hydrophilic dispersoid and a
hydrophobic dispersoid in the second layer 3b. Regarding the water contact angle, a
measurement portion is irradiated with ultraviolet rays, and a contact angle of water on
each layer is measured in a room having a illuminance of about 300 lux using a sessile
drop method (for example, refer to JIS R3257 (1999)). The water contact angle of the
second layer 3b can be determined by using a sample in which a photocatalytic film is
not formed or by using a sample in which a photocatalytic film is removed with a
physical or chemical method.
[0098]
The surface-treated metal 1 according to the embodiment can be provided as a
material before a processing (materials for various processing) or can be provided as a
component after a processing. A provided component is not particularly limited and
can be desirably used for building materials such as an outer wall of a house or a sizing
material, outdoor home electric appliances such as an outdoor unit of an air conditioner
or a housing (outer plate) of a water heater, and outdoor machines such as automobiles.
[0099]
Hereinafter, a method of producing a surface-treated metal according to an
embodiment of the invention will be described in detail.
[O 1001
FIG. 5 is a flowchart illustrating an example of the method of producing a
surface-treated metal according to the embodiment. In the method of producing a
surface-treated metal according to the embodiment, by using various materials (a
substrate containing a metal and raw materials for a treatment liquid) with a method
illustrated in FIG. 5, a coated material including a photocatalytic film on the outermost
layer thereof is formed on a surface of a substrate containing a metal. That is, the
method of producing a surface-treated metal according to the embodiment includes a
process (treatment liquid preparing process: S1) of mixing particles showing
photocatalytic activity with a liquid which contains a hydrolysate of an alkoxysilane to
prepare a photocatalytic film-forming treatment liquid (first treatment liquid), a
process (coating process: S2) of coating the photocatalytic film-forming treatment
liquid such that the photocatalytic film-forming treatment liquid covers an outermost
layer of the coated material, and a process (baking process: S3) of baking the coated
photocatalytic film-forming treatment liquid. In addition, the method of producing a
surface-treated metal according to the embodiment may further include a process
(rapid cooling process: S4) of rapidly cooling the film obtained after the baking
process.
First, a treatment liquid used in the treatment liquid preparing process (S 1)
will be described.
[ O l O l ]
(Photocatalytic film-Forming Treatment Liquid)
The photocatalytic film-forming treatment liquid (first treatment liquid) used
in the method of producing a surface-treated metal according to the embodiment
contains a liquid, which contains a composition (hydrolysate) of an alkoxysilane
having at least one group selected from the group consisting of an aryl group, a
carboxyl group, an amino group, a hydroxyl goup, and an alkyl group having 1 to 12
carbon atoms, and photocatalytic particles (particles showing photocatalytic activity).
In particular, a preferable treatment liquid contains, as a major component, a
composition (including a hydrolysate) derived from tetraalkoxysilane, and at least one
alkoxysilane selected from the group consisting of an alkoxysilane which contains an
alkyl group having 1 to 12 carbon atoms and an alkoxysilane which contains an aryl
group, and the preferable treatment liquid contains photocatalytic particles as a
dispersoid. Examples of the tetraalkoxysilane include tetramethoxysilane,
tetraethoxysilane, tetrapropoxysilane, and tetrabutoxysilane. In addition, examples of
the alkoxysilane which contains an alkyl group having 1 to-12 carbon atoms include
methyltrimethoxysilane, dimethyldimethoxysilane, methyltriethoxysilane,
dimethyldiethoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane,
decyltrimethoxysilane, and decyltriethoxysilane. Examples of the alkoxysilane which
contains an aryl group include phenyltrimethoxysilane, diphenyldimethoxysilane,
phenyltriethoxysilane, and diphenyldiethoxysilane. In addition, a part or all of the
photocatalytic particles may form aggregates.
[O 1021
The photocatalytic film-forming treatment liquid contains, as a major
component, the above-described silane compounds, hydrolysates thereof, and a
composition derived from silane compounds such as polymers (polycondensates), and
condensates. By using the above-described components, an organic-inorganic
composite resin, which contains a siloxane bond as a main bond of a main skeleton
thereof and contains at least one group selected from the group consisting of an alkyl
group having 1 to 12 carbon atoms, an aryl group, a carboxyl group, an amino group,
and a hydroxyl group, can be easily obtained. In addition, by using the abovedescribed
components, a ratio of organic components to inorganic components in the
composite resin can be easily changed. In addition, the type and amount of organic
components introduced into the resin can be easily controlled. That is, according to
properties required for the photocatalytic film, inorganic components in the organicinorganic
composite resin can increase or, conversely, organic components can
increase. Furthermore, the type of organic components to be added can be
appropriately selected according to properties required for the photocatalytic film. In
addition, as a mere example, when a thin film is formed using the above-described
resin, it is substantially unnecessary that the workability of the film be considered.
, . . Therefore, the photocatalytic film can be used as a film mainly composed of inorganic
components having smaller deterioration by a photocatalyst. On the other hand, when
organic components are added to the treatment liquid to some extent, resin components
can be designed in consideration of balance between workability and flexibility, and
resistance to the deterioration of the film by a photocatalyst.
[0 1031
The photocatalytic film-forming treatment liquid used in the method of
producing a surface-treated metal steel sheet according to the embodiment may fbrther
contain an alkoxysilane having an epoxy group and an alkoxysilane having an amino
group. Preferable examples of the alkoxysilane having an epoxy group include yglycidoxypropyltrimethoxysilane,
y-glycidoxypropyltriethoxysilane, yglycidoxypropyltripropoxysilane,
y-glycidoxypropyltributoxysilane, 3,4-
epoxycyclohexylmethyltrimethoxysialne, 3,4-epoxycyclohexylmethyltriethoxysialne,
p-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, and 8-(3,4-
epoxycyclohexyl)ethyltriethoxysilane. In particular, among these alkoxysilanes
having an epoxy group, y-glycidoxypropyltriethoxysilane is preferably used from the
viewpoints of easy handleability, reactivity, and the like.
[0 1041
In addition, preferable examples of the alkoxysilane having an amino group
include aminopropyltrimethoxysilane, aminopropyltriethoxysilane, (P-aminoethy1)-Pamionpropyltrimethoxysilane,
(P-aminoethy1)-a- aminopropylmethyldimethoxysilane,
and (p-aminoethy1)-y- aminopropyltrimethoxysilane. Among these alkoxysilanes
having an amino group, aminopropyltriethoxysialne is particularly preferable from the
viewpoints of easy handleability and the likes.
[0105]
Regarding these alkoxysilanes, similar to the above-described alkoxysilanes,
there is no problem that a part or all of the alkoxy groups may be hydrolyzed in the
treatment liquid, or a hydrolyzed product may be converted into a high-molecularweight
compound by a polymerization or condensation reaction. When the
alkoxysilane having an epoxy group is mixed with the alkoxysilane having an amino
group in the treatment liquid, there is an advantageous effect in that the adhesion of the
photocatalytic film with the metal or the lower layer film, and the stability of the
organic-inorganic composite resin to a photocatalyst are improved. Regarding the
reason for this, the details are not clear. However, the present inventors presume the
reason to be that, by adding an epoxy group and an amino group, a strong bond which
contributes to the adhesion of the photocatalytic film with the metal or the lower layer
film is formed.
[0 1061
In addition, the treatment liquid may optionally further contain an alkoxide
containing a metal element other than Si as an additive. In particular, when an
alkoxide of one metal selected from Ti, Al, Ta, and Nb is added to the treatment liquid
and acetic acid is used as an acid catalyst, the ring-opening rate of an epoxy group
increases, and the treatment liquid can be cured at a low temperature within a short
period of time. In the metal alkoxides other than alkoxysilane, a part or all of the
alkoxy groups may be hydrolyzed.
[0107]
In addition, the treatment liquid may optionally further contain at least one of,
for example, zirconium alkoxide, hydrolysates thereof, and zirconium oxide (zirconia)
sols as a compound of zirconia. This component containing zirconium improves the
alkali chemical resistance of the treatment liquid containing silica as a major
component and the film formed by this treatment liquid. A mechanism with which
and the baking process, an operation of changing the dispersed particle size of the
particles in the treatment liquid is not performed. Therefore, in many cases, the
particle size distribution of the photocatalytic particles in the treatment liquid is
approximately the same as the particle size distribution of the photocatalytic particles
in the photocatalytic film. Furthermore, in this method, the particle size distribution
of the dispersoid can be directly measured while maintaining the state of the dispersion
system. Therefore, aggregates in the treatment liquid can be measured not as primary
particles but as aggregated particles.
[0 1 091
(Additives in Photocatalytic film-Forming Treatment Liquid)
In order to improve the design characteristics, corrosion resistance, wear
resistance, catalytic function, and the like of the photocatalytic film, the abovedescribed
treatment liquid may further contain a color pigment, a moisture-resistant
pigment, a catalyst, a rust preventive pigment, metal powder, a high-frequency loss
agent, and an aggregate as additives. Examples of the pigment include the abovedescribed
compounds, oxides and composite oxides of Ti, Al and the like and metal
powders such as Zn powder and Al powder. Preferable examples of the rust
preventive pigment include pigments such as calcium molybdate, calcium
phosphomolybdate, and aluminum phosphomolybdate which do not contain
environmental pollutants such as chromic acid. In addition, examples of the highfrequency
loss agent include Zn-Ni ferrite, and examples of the aggregate include
potassium titanate fiber.
[OllO]
In addition, the treatment liquid may optionally contain an acid catalyst.
Examples of the acid catalyst include organic acids such as formic acid, maleic acid,
and benzoic acid, and inorganic acids such as hydrochloric acid and nitric acid.
Particularly, acetic acid is preferably used. By using an acid as a catalyst,
alkoxysilane which is used as a raw material is likely in the polymerization state
suitable for film formation. In addition, when acetic acid is used as a catalyst, the
ring opening of an epoxy group is promoted, and the treatment liquid can be cured at a
low temperature within a short period of time.
[Olll]
In addition, as an additive, a leveling effect agent, an antioxidant, an
ultraviolet absorber, a stabilizer, a plasticizer, a wax, an addition type ultraviolet
stabilizer or the like may be mixed with the treatment liquid. In addition, optionally,
the treatment liquid may contain an organic resin such as a fluororesin, a polyester
resin, or a urethane resin in a range not departing the heat resistance of the film or in a
range in which there is no deterioration by a photocatalyst. As the additive, only one
type of additive may be used, or two types of additives may be approximately mixed
and used.
[0112]
(Method of Forming Coating Layer of Surface-Treated Metal)
In the method of producing a surface-treated metal according to the
embodiment, in the coating process (S2), the above-described treatment liquid is
coated on a surface of a metal which is a substrate or on a surface of a metal which is
undercoated. In this process, the treatment liquid can be coated using a dip coating
method, a spray coating method, a bar coating method, a roll coating method, or a spin
coating method. Next, in the baking process (S3), a surface-treated metal can be
obtained by baking the coated treatment liquid and drying and curing the treatment
liquid. Depending on the thickness of a photocatalytic film to be formed, the coating
process (S2) and the baking process (S3) may be repeated multiple times.
When a two-layer coating including the lower layer film (for example, the
coating layers 3b to 3e in FIG. 1A) such as the intermediate layer is formed, the abovedescribed
processes (processes corresponding to S2 and S3) are repeated twice. In
addition, when a three-layer or multi-layer coating is formed, the above-described
processes are repeated three or more times.
Conditions (type, shape, and whether being processed or not) of the metal on
which the treatment liquid is coated are the same as the conditions of the metal
described in the above-described embodiment. In addition, a surface of the substrate
to be coated with the treatment liquid may be a part (for example, a single surface of
the sheet) of the substrate or may be the entire surface of the substrate.
[0113]
In addition, when a plurality of coating layers are formed, a plurality of types
of treatment liquid for forming the plurality of coating layers are simultaneously coated
on a surface of the substrate, and these treatment liquids are simultaneously dried and
baked. In this case, for example, the treatment liquid may be appropriately selected
such that two coating layers having different amounts of photocatalytic particles are
formed. In this way, when a plurality of types of treatment liquids are simultaneously
coated on the surface of the substrate (multilayer simultaneous coating), a method
using a multilayer curtain coater or the like is preferably used.
[0114]
As described above, a coated material having a plurality of coating layers may
be formed by coating a plurality of types of treatment liquids on a surface of a
substrate containing a metal. For example, a second layer-forming treatment liquid
(second treatment liquid) different from theqhotocatalytic film-forming treatment
liquid is used as one of the plurality of types of treatment liquids other than the
photocatalytic film-forming treatment, and the second layer-forming treatment liquid
may be coated such that a second layer formed between the metal and the
photocatalytic film-forming treatment liquid may be in contact with the photocatalytic
film-forming treatment liquid. In this case, as mentioned above, the photocatalytic
film-forming treatment liquid and the second layer-forming treatment liquid may be
selected such that a ratio of a micro-Vickers hardness when the second layer-forming
treatment liquid is cured to a micro-Vickers hardness when the photocatalytic filmforming
treatment liquid is cured is 0.20 to 0.95. In addition, the photocatalytic filmforming
treatment liquid and the second layer-forming treatment liquid may be
selected such that a water contact angle when the second layer-forming treatment
liquid is cured is in a range obtained by adding 10" to 80" to a water contact angle
when the photocatalytic film-forming treatment liquid is cured. Furthermore, the
lower layer film containing an organic resin may be formed on a surface of the
substrate containing a metal.
[0115]
In such a case, as the above-described multilayer simultaneous coating
method, for example, a method may be adopted in which the lower layer film (one
layer or multiple layers) containing an organic resin is formed on the surface of the
substrate, next, the second treatment liquid and the first treatment liquid are
simultaneously coated on the lower layer film, and the second treatment liquid and the
first treatment liquid are simultaneously dried and baked. In addition, for example, a
method may be adopted in which at least one coating liquid (for example, liquid
containing an organic monomer and an organic polymer) for forming the lower layer
coating containing an organic resin, the second treatment liquid, and the first treatment
liquid are simultaneously coated on the surface of the substrate, and these liquid are
simultaneously dried and baked. With these methods, it is possible to form a multilayer
film (film on which a plurality of layers are laminated) including the lower layer
film (one layer or multiple layers) formed on the surface of the substrate, a second
layer film (second layer) formed by curing the second treatment liquid on the lower
layer film, and an outermost layer film (photocatalytic film) formed by curing the first
treatment liquid on the second layer film.
[0116]
In the baking process (S3), usually, the coating layer is cured by heating. As
standard heating conditions, it is preferable that a heating treatment be performed for 1
hour to several seconds in a temperature range from 150°C to 400°C. When the
coating layer is cured at a temperature of 150°C or higher, the heating time can be
reduced, and the productivity can be sufficiently secured. On the other hand, when
the coating layer is cured at a temperature of 400°C or lower, the baking process
becomes more economical. In general, when the heat treatment temperature is high,
the coating layer can be cured within a short period of time, and when the heat
treatment temperature is low, a long period of time of heat treatment is necessary. In
addition, when there are no sufficient temperature and time for drying or the heat
treatment, the coating layer can be temporarily dried and baked to be cured and
optionally can be left to stand at room temperature for 1 day to 5 days. Through these
processes, the hardness of the coating layer can be increased as compared to that
immediately before coating.
[0117]
(Introduction of Concave)
Here, examples of "a preferable method" for introducing concave into the
coated material (photocatalytic film) will be described. Of course, even when a
coated material having concave is formed without using the following methods, as
long as such a coated material having concave satisfies the conditions according to the
above-described embodiment, the coated material is the target of the surface-treated
metal according to the above-described embodiment. In addition, a plurality of a
combination method of the following examples may be used. Furthermore, with such
a concave introducing method, the surface area (surface area of photocatalytic particles
which contribute to contamination resistance) of the outermost layer per unit area of
the surface-treated metal (metal) can be effectively increased.
[0118]
(First Concave Introducing Method)
A first method of effectively introducing concave will be described. When
the photocatalytic film is formed, as described above, the hydrolysis and
polycondensation of chemical components such as a silane coupling agent, silicon
alkoxide, and an alkoxide of a metal other than silicon are used. Therefore, by
selecting the types and amounts of a silane coupling agent and alkoxides which are
used, concave can be introduced into the film.
[0119]
In a silane coupling agent and alkoxides, when the number of organic groups
which are directly bonded to a metal element such as silicon is small, concave are
likely to be introduced into the photocatalytic film. Therefore, a silane coupling
agent and alkoxides which have many inorganic components and many functional
groups contributing to a siloxane bond may be used. For example, in the case of
silicon, in tetramethoxysilane, tetraethoxysilane, and the like, a methoxy group and an
ethoxy group bonded to silicon are hydrolyzed to form hydroxyl groups, and a silicon
compound having these hydroxyl groups is further polycondensed to form siloxane.
Therefore, during the hydrolysis and polycondensation, a large shrinkage occurs, and
thus concave are likely to be introduced into the photocatalytic film. In addition, in
this case, since the amount of organic components is small, the rigidity of the film after
the polycondensation is high. For example, during a heat treatment for forming a film,
concave are likely to be introduced into the photocatalytic film. Accordingly, it is
preferable that the treatment liquid further contain a composition (for example,
hydrolysate) derived from at least one tetraalkoxysilane selected from the group
consisting of tetramethoxysilane and tetraethoxysilane.
[0120]
(Second Concave Introducing Method)
A second method of effectively introducing concave is to appropriately reduce
a coating amount of the treatment liquid for forming the film or reduce a concentration
of a non-volatile content (solid content) in the treatment liquid. In this case, along
with the volatilization of a solvent during the drying process or the baking process after
coating, a large shrinkage of the film occurs, and thus concave are likely to be
introduced. However, when the concentration of the non-volatile content in the
treatment liquid is reduced more than necessary, there is a possibility that the desired
film thickness may not be secured. Therefore, it is preferable that the concentration
of the non-volatile content in the treatment liquid be controlled to be in a
predetermined range. For example, in order to flexibly control the film thickness, it is
preferable that this concentration of the non-volatile content be controlled to be 2.5
mass% to 5.0 mass%. In addition, in order to form concave in the photocatalytic film,
under general conditions, it is preferable that the concentration of the non-volatile
content in the treatment liquid be set to be less than or equal to approximately 5 mass%, - . .
However, under conditions for the system in which the above-described
tetramethoxysilane and tetraethoxysilane are used, it is preferable that the
concentration of the non-volatile content be set to be less than or equal to
approximately 10 mass%.
[0121]
(Third Concave Introducing Method)
A third method of effectively introducing concave is to rapidly cool the film
after drying and baking. This method is particularly effective for a hard film having
many inorganic components or for a film having a large film thickness. In this
method, a sound film is formed first, and then concave are physically introduced into
the film. Therefore, a film containing a large amount of photocatalysts, in which the
surface area is significantly large and a surface is not covered with a resin and is
exposed, can be formed. For example, an average cooling rate in a temperature range
from the baking temperature (for example, around 250°C which is a general baking
temperature) to 100°C is higher than or equal to 100 "Clsec, preferably, higher than or
equal to 200 "Clsec. This average cooling rate can be obtained by, for example,
cooling the coating layer in water after baking. An upper limit of the average cooling
rate is not particularly limited but, for example, may be 1500 "Clsec for convenience
of measurement.
[Examples]
[O 1221
The invention will be described in more detail using the following examples.
[0123]
(Example 1)
110 parts by mass of y-glycidoxypropyltriethoxysilane (GPTES), 9.0 parts by
mass of titanium tetraethoxide (TE), and 192.5 parts by mass of tetraethoxysilane
(TEOS) were sufficiently stirred, followed by hydrolysis under acidic conditions using
distilled water diluted with ethanol. 44 parts by mass of arninopropyltriethoxysilane
(APTES) was added to this solution, followed by hydrolysis using a mixed solution of
distilled water and ethanol. As a result, a treatment liquid containing an organicinorganic
complex as a major component was prepared. A sufficient amount of water
was used for hydrolysis, and the amount of water was adjusted such that a
concentration of an non-volatile content in the treatment liquid (when being dried at
150°C) was 8 mass%. Anatase-type Ti02 particles (manufactured by Ishihara Sangyo
Kaisha, LTD., ST series, average particle size ~PAaVpp:r oximately 10 nm) showing
photocatalytic activity, ZnO particles (manufactured by Hakusuitech Co., Ltd., Zincox
Super F series, average particle size dPAVa:p proximately 60 nm), and Nb205 particles
(laboratory-synthesized product, average particle size ~PAaVpp:r oximately 100 nm)
were added to the treatment liquid as level shown in Table 1 to prepare a coating liquid.
Furthermore, in this coating liquid, as clearly seen from the mixing ratios of the abovedescribed
respective raw materials, a ratio of the particles showing photocatalytic
activity to the treatment liquid containing the above-described organic-inorganic
complex as a major component was in a range from 2.5 g/l to 50 g/l.
[0 1241
(Steel Sheets for Contamination Resistance Test)
In a contamination resistance test, a steel sheet, which was obtained by
treating a surface of a hot-dip galvanized steel sheet with an organic silicate, was used
as a substrate. This steel sheet was coated with the above-described coating liquid
using a bar coater and was dried and baked at a maximum temperature of 250°C under
temperature rise conditions which the sheet temperature reached the maximum
temperature after 50 seconds. Next, the steel sheet in which the coating liquid was
baked was rapidly cooled in water. In this way, surface-treated steel sheets (surfacetreated
metals) which included a photocatalytic film containing photocatalytic particles
on a surface thereof were obtained (Nos. 1 to 12). The average cooling rates of the
surfaces of the surface-treated steel sheets, that is, the average cooling rates of the
photocatalytic films were approximately 1000 "Clsec, and a plurality of concave were
present in the formed photocatalytic films. These concaves formed a network shape,
and the sizes of outermost layer portions surrounded by the concave were different
fiom each other. The properties of the concave are shown in Table 1. All the
thicknesses t of the formed films (Nos. 1 to 12 in Table 1) were approximately 2 ym.
[0125]
In order to obtain the properties (fw and rs) of the concave in Table 1, the
dimensions (the widths W of the concave and the total length Lt of the concave) of the
concave present in a 100 pmx100 pm arbitrary area were measured using a scanning
electron microscope (SEM). In this measurement, values measured at three different
areas are averaged to calculate the widths W of the concave. At the same time, the
lengths of all the concave present in the same three areas were measured, and the
obtained values were averaged to calculate the total length L, of the concave.
Furthermore, with the same method, the lengths of concave in which "Wlt" was
satisfied in a range from 0.01 to 1.0 were measured, and the obtained value L, (the
average value of the three areas) was divided by the total length L, of the concave.
As a result, a ratio fw of the concave in which "Wlt" was 0.01 to 10 to all the concave
was calculated. In addition, the surface area of the photocatalytic film was measured
with a gas absorption method using Nz, and the unit area (the area of the surfhce) of the
metal which was substrate was calculated from the size of a sample used in the gas
absorption method. In the gas absorption method, the surface area of an exposed
portion of a lower layer film which was present below the photocatalytic film was also
measured at the same time. Previously, using a sample in which the photocatalytic
film was not coated, the surface area of the entire lower layer film was measured using
the same gas absorption method, and the surface area of the lower layer film per unit
area of the metal was calculated. The surface area of the lower layer film per unit
area of the metal, and the surface area of the exposed portion of the lower film
calculated by the following coverage were subtracted from the surface area of the
surface-treated steel sheet including the photocatalytic film. As a result, the surface
area of the photocatalytic film was calculated in anticipation of an increase in surface
area by the introduction of the concave. By dividing the obtained surface area of the
photocatalytic film by the unit area of the metal, a ratio rs of the surface area of the
photocatalytic film to the surface area of the metal was calculated. In order to obtain
the coverage fc of the photocatalytic film, using the same measurement method as that
of the dimensions of the concave, arbitrary three 100 pmx 100 pm areas were observed
using SEM to perform image processing. As a result, the surface area where the
photocatalytic films were not coated was calculated. The coverage fc of the
photocatalytic film was calculated from the obtained surface area where the
photocatalytic films were not coated, and the surface area of the observed areas. In
addition, the ratio of the concave in which "Wlt" was 0.01 to 10 was calculated in
0.5% increments in consideration of the measurement precision of the widths W of the
concave and the thickness t of the photocatalytic film.
[0126]
In addition, the following steel sheets were prepared as comparative examples.
First, through the same processes (except the concentration of a non-volatile content
and the conditions shown in Table 1) as those of Nos. 1 to 12, a treatment liquid having
a concentration of a non-volatile content of 20 mass% was prepared, and
photocatalytic particles shown in Table 1 were added to the treatment liquid, thereby
obtaining a coating liquid. As a substrate of a photocatalytic film, a steel sheet, which
was obtained by treating a surface of a hot-dip galvanized steel sheet with an organic
silicate, was used. This steel sheet was coated with the above-described coating
liquid using a bar coater and was dried and baked at a maximum temperature of 250°C
under temperature rise conditions which the sheet temperature reached the maximum
temperature after 50 seconds. Next, the steel sheet in which the coating liquid was
baked was rapidly cooled in water. In this way, surface-treated steel sheets which
included a photocatalytic film containing photocatalytic particles on a surface thereof
were obtained (Nos. 101 to 108). In Nos. 101 to 108, concaves were not observed.
[0 1271
[Table I]
[0 1281
A photocatalytic effect of the surface-treated steel sheet was verified with the
following methods.
[0 1291
(i) First, in order to evaluate contamination resistance, an exposure test of the
surface-treated steel sheet was performed outdoors. Contamination by raindrops and
contamination by dust and the like after 2 weeks as an index immediately after usage
starts, and contamination by raindrops and contamination by dust and the like after 6
months as an index for a long period of time, were evaluated by visual inspection.
(ii) Particularly, as a method of easily evaluating contamination resistance
within a short period of time, pollutants (a black marker and a red marker) were coated
on the surface of the surface-treated steel sheet, and the irradiation time of ultraviolet
rays and the removal state of the pollutants were measured. The removal state of the
pollutants was evaluated by measuring the color of the surface of the surface-treated
steel sheet using a color-difference meter.
(iii) The state of deterioration (damage) of the photocatalytic film was
evaluated by measuring the color and gloss of the surface of the surface-treated steel
sheet before and after the outdoor exposure test using a color-difference meter and a
glossmeter.
In addition, when a polyester film was formed immediately below the
photocatalytic film, the state of deterioration of the polyester film was also evaluated
by observing the state of an interface (cut surface) between the photocatalytic film and
the polyester film.
The state of deterioration (damage) of the photocatalytic film and the state of
deterioration of the polyester film were evaluated as the resistance to deterioration of
the film.
For the evaluation of the test results, a part or all of 5 grades of A, B, C, D,
and E were used. Furthermore in order to clearly distinguish the grades from each
other, 5 grades of A to E were used for the state of deterioration of the film and the
comprehensive evaluation. Evaluation criteria for the respective items in Table 3
were shown in Table 2.
[0130]
[Table 21
[0131]
The results were shown in Table 3. Since the concaves were present in the
- film, the surface-treated steel sheets of Nos. 1 to 12 had superior contamination -
resistance to the contamination in the initial stage 2 weeks after the outdoor exposure
test and the marker contamination. In addition, the surface-treated steel sheets also
had superior contamination resistance to the contamination 6 months afier the outdoor
exposure test (after a certain period of time). Furthermore, in the surface-treated steel
sheets of Nos. 1 to 12, no deterioration of the photocatalytic film was observed 6
months after the outdoor exposure test, and the photocatalytic film was in the
extremely favorable state. It was found from these results that, in the surface-treated
steel sheets of Nos. 1 to12, the photocatalytic film was difficult to deteriorate and
contamination resistance was superior for a long period of time from the initial stage.
On the other hand, in the surface-treated steel sheets of Nos. 101 to 108, since
concaves were not present in the film, a long period of time was required for
decomposing the markers which were the pollutants and contamination resistance to
the markers were low. In these surface-treated steel sheets, no deterioration of the
photocatalytic film was observed, and the photocatalytic film was in the extremely
favorable state.
[0 1321
It was found from the above results that, in the surface-treated steel sheet of
Nos. 1 to 12, contamination resistance was superior from the initial stage and the
contamination resistance was maintained for a long period of time, whereas in the
surface-treated steel sheets of Nos. 101 to 108, there were problems regarding the
contamination resistance of the initial stage.
In addition, when measured using both SEM and TEM, the particle size
distribution of a photocatalytic material in the photocatalytic film of the outermost
layer of the surface-treated steel sheet was almost the same as the particle size
distribution measured in the coating liquid.
[0133]
[Table 31
[0 1341
(Example 2)
100 parts by mass of y-glycidoxypropyltriethoxysilane (GPTES), 8.2 parts by
mass of titanium tetraethoxide (TE), 144 parts by mass of phenyltriethoxysilane
(PhTES), and 36 parts by mass of dimethyldiethoxysilane (DMDES) were sufficiently
stirred, followed by hydrolysis under acidic conditions using distilled water diluted
with ethanol. 40 parts by mass of aminopropyltriethoxysilane (APTES) was added to
this solution, further followed by hydrolysis using a mixed solution of distilled water
and ethanol. As a result, a treatment liquid containing an organic-inorganic complex
as a major component was prepared. A sufficient amount of water was used for
hydrolysis. Then, in order to change the properties of the concave when the
photocatalytic film was formed, the amount of water was adjusted such that a
concentration of an non-volatile content in the treatment liquid when being dried at
150°C was 15 mass%. Anatase-type TiOz particles (average particle size dpAV:
approximately 10 nm) showing photocatalytic activity were added to the treatment
liquid such that a volume ratio thereof to the total volume of the photocatalytic film
was lo%, to prepare a coating liquid. Furthermore, in this coating liquid, as clearly
seen from the mixing ratios of the above-described respective raw materials, a ratio of
the particles showing photocatalytic activity to the treatment liquid containing the
above-described organic-inorganic complex as a major component was in a range from
2.5 g/l to 50 dl.
[0135]
In a contamination resistance test, a precoated steel sheet, which was obtained
by coating the outermost surface of a galvanized steel sheet with a polyester film
having a melamine crosslinking agent at a thickness of about 15 pm, was used as a
substrate. This precoated steel sheet was coated with the above-described coating
liquid using a bar coater and was dried and baked at a maximum temperature of 250°C
under temperature rise conditions which the sheet temperature reached the maximum
temperature after 50 seconds. Next, the precoated steel sheet in which the coating
liquid was baked was rapidly cooled in water. In this way, surface-treated steel sheets
were obtained. The average cooling rates of the surfaces of the surface-treated steel
sheets, that is, the average cooling rates of the photocatalytic films were 1000 "Clsec.
All the thicknesses t of the formed films was approximately 5 pm (Nos. 13 to 20 in
Table 4). A plurality of concave was present in the formed photocatalytic films on the
surfaces of the obtained steel sheets. Due to these concaves, the coverage values and
surface areas of the films were different from each other. These concaves formed a
network shape, and the sizes of outermost layer portions surrounded by the concave
were different from each other. Methods of measuring the properties (abovedescribed
fw and rs) of the concave, the coverage fc of the photocatalytic film, and the
like were the same as those of Example 1. In addition, in Table 4, a ratio rf of the
total length of flat areas of the outermost layer to the length of the entire surface of the
outermost layer which was obtained by observing a cross-section of the outermost
layer using SEM is also shown.
[0136]
In addition, as a comparative example, a treatment liquid having a
concentration of a non-volatile content of 20% was prepared through the same
processes as above. The same Ti02 particles (average particle size dpAv:
approximately 10 nm) showing photocatalytic activity as those of Nos. 13 to 20 were
added to the treatment liquid such that a volume ratio of the TiOz particles to the total
volume of the photocatalytic film was lo%, to prepare a coating liquid. The obtained
coating liquid was coated with the same precoated steel sheet as above and was dried
and baked. Next, the precoated steel sheet in which the coating liquid was baked was
cooled by blowing mist thereto. In this way, a surface-treated steel sheet which
included a photocatalytic film not having concave and having the same thickness as
that of Nos. 13 to 20 was obtained (No. 109). In No. 109, the average cooling rate of
the photocatalytic film was approximately 50 "C/sec.
[0137]
[Table 41
[0138]
Similar to Example 1, a photocatalytic effect of the surface-treated steel sheet
was verified by (i) the evaluation of raindrop contamination and dust contamination
after 2 weeks and after 6 months in the outdoor exposure test, (ii) the evaluation of the
removal amount of marker contamination, and (iii) the evaluation of the deterioration
amount of the coating film. Similar to Example 1, for the evaluation of the test
results, a part or all (the resistance to deterioration of the film and the comprehensive
evaluation) of 5 grades ofA to E were used to evaluate the respective items regarding
the contamination resistance of the film and the resistance to deterioration.
Evaluation criteria were as shown above in Table 2.
[0139]
The results were shown in Table 5. Since the concaves were present in the
film, the surface-treated steel sheets of Nos. 13 to 20 had superior contamination
resistance to the contamination in the initial stage 2 weeks after the outdoor exposure
test and the marker contamination. In addition, the surface-treated steel sheets also
had superior contamination resistance to the contamination 6 months after the outdoor
exposure test (after a certain period of time). Furthermore, in the surface-treated steel
sheets of Nos. 13 to 20, no deterioration of the photocatalytic film was observed 6
months after the outdoor exposure test, and the photocatalytic film was in the
extremely favorable state. It was found from the results of Nos. 13 to 20 that, when
the coverage of the photocatalytic film was less than 98%, contamination resistance to
the raindrop contamination in the initial stage and the marker contamination could be
improved. In addition, it was found from the results of Nos. 13 to 20 that, when the
coverage of the photocatalytic film was greater than 50%, contamination resistance to
the raindrop contamination in the initial stage, the marker contamination, and the
raindrop contamination and dust contamination after 6 months could be improved. It
was found from these results that, in the surface-treated steel sheets of Nos. 13 to 20,
the photocatalytic film was difficult to deteriorate and contamination resistance was
superior for a long period of time from the initial stage.
[0 1401
On the other hand, in the surface-treated steel sheet of No. 109, since
concaves were not present in the film, a long period of time was required for
decomposing the markers which were the pollutants and contamination resistance to
the markers were low. In No. 109, no deterioration of the photocatalytic film was
observed, and the photocatalytic film was in the extremely favorable state.
[0141]
It was found from the above results that, in the surface-treated steel sheet of
Nos. 13 to 20, contamination resistance was superior substantially fiom the initial stage
and the contamination resistance was maintained for a long period of time, whereas in
the surface-treated steel sheet of No. 109, there were problems regarding the
contamination resistance of the initial stage.
In addition, when measured using both SEM and TEM, the particle size
distribution of a photocatalytic material in the photocatalytic film of the outermost
layer of the surface-treated steel sheet was almost the same as the particle size
distribution measured in the coating liquid.
[0 1421
[Table 51
[0 1431
(Example 3)
A first treatment liquid was prepared with the following method. 117 parts
by mass of y-glycidoxypropyltriethoxysilane (GPTES), 9.6 parts by mass of titanium
tetraethoxide (TE), 67 parts by mass of phenyltriethoxysilane (PhTES), and 146 parts
by mass of tetraethoxysilane (TEOS) were sufficiently stirred, followed by hydrolysis
under acidic conditions using distilled water diluted with ethanol. 46 parts by mass of
aminopropyltriethoxysilane (APTES) was added to this solution, hrther followed by
hydrolysis using a mixed solution of distilled water and ethanol. As a result, a
treatment liquid containing an organic-inorganic complex as a major component was
prepared. A sufficient amount of water was used for hydrolysis, and the amount of
water was adjusted such that a concentration of an non-volatile content in the treatment
liquid when being dried at 150°C was 20 mass%. Anatase-type Ti02 particles
(average particle size dPAVa:p proximately 10 nm) showing photocatalytic activity were
added to the treatment liquid such that a volume ratio of the Ti02 particles to the total
volume of the photocatalytic film was 20%, to prepare the first treatment liquid. In
addition, in this first treatment liquid, as clearly seen from the mixing ratios of the
above-described respective raw materials, a ratio of the particles showing
photocatalytic activity to the treatment liquid containing the above-described organicinorganic
complex as a major component was in a range from 2.5 g/l to 50 g/l.
A second treatment liquid was prepared with the following method. 100
parts by mass of y-glycidoxypropyltriethoxysilane (GPTES), 8.2 parts by mass of
titanium tetraethoxide (TE), 144 parts by mass of phenyltriethoxysilane (PhTES), and
71 parts by mass of dimethyldiethoxysilane (DMDES) were sufficiently stirred,
followed by hydrolysis under acidic conditions using distilled water diluted with
ethanol. 40 parts by mass of aminopropyltriethoxysilane (APTES) was added to this
solution, further followed by hydrolysis using a mixed solution of distilled water and
ethanol. As a result, a treatment liquid containing an organic-inorganic complex as a
major component was prepared. A sufficient amount of water was used for
hydrolysis, and the amount of water was adjusted such that a concentration of an nonvolatile
content in the treatment liquid when being dried at 150°C was 15 mass%.
Anatase-type TiOz particles (average particle size ~PAVap:p roximately 10 nrn) showing
photocatalytic activity were added to the treatment liquid such that a volume ratio of
the TiOz particles to the total volume of the photocatalytic film was 2%, to prepare the
second treatment liquid.
[0 1441
In a contamination resistance test, a precoated steel sheet, which was obtained
by coating the outermost surface of a galvanized steel sheet with a polyester film
having a melamine crosslinking agent at a thickness of about 15 pm, was used as a
substrate. This precoated steel sheet was coated with the above-described second
coating liquid using a bar coater and was dried and baked at a maximum temperature
of 2 10°C under temperature rise conditions which the sheet temperature reached the
maximum temperature afier 50 seconds. The precoated steel sheet was allowed to
cool naturally, and a second layer was formed. The thickness of the second layer was
about 3 pm, and concaves were not observed on the surface of the second layer. The
surface on which the second layer was formed was further coated with the first
treatment liquid using a bar coater and was dried and baked at a maximum temperature
of 250°C under temperature rise conditions which the sheet temperature reached the
maximum temperature after 50 seconds. Next, the precoated steel sheet in which the
respective treatment liquids were baked was cooled at various average cooling rates
under various conditions from rapid cooling in water to slow cooling by the blowing of
mist containing a large amount of water. In this way, surface-treated steel sheets were
prepared. The average cooling rate was changed in a range from 1000 "Clsec (No.
21), which was the highest rate, to 250 "Clsec (No. 25). All the thicknesses t of the
formed films was approximately 10 pm (Nos. 21 to 25 in Table 6). Aplurality of
concave having different widths was introduced into the obtained steel sheets.
Methods of measuring the properties (above- described fw and rs) of the concave, the
coverage fc of the photocatalytic film, and the like were the same as those of Example
1 (Nos. 21 to 25 in Table 6). These concaves formed a network shape, and the sizes
of outermost layer portions surrounded by the concave were different from each other.
After the outermost layer was formed, concaves were not observed in the second layer.
[0145]
In addition, as a comparative example, the first treatment liquid and the
second treatment liquid to which photocatalytic particles were added with the same
mixing ratios as those of Nos. 21 to 25 were prepared through the same processes as
those of Nos. 21 to 25. The obtained two types of treatment liquids were coated on
the same precoated steel sheet as that of Nos. 21 to 25 and was dried and baked. In
this way a surface-treated steel sheet was prepared (No. 11 0). In, No. 1 10, similar to
No. 109, the surface-treated steel sheet was cooled by blowing mist thereto. In this
way, a surface-treated steel sheet which included a photocatalytic film not having
concave and having the same thickness as that of Nos. 21 to 25 was obtained (No. 110).
[0 1461
[Table 61
[0147]
Similar to Example 1, a photocatalytic effect of the surface-treated steel sheet
was verified by the above-described items (i) to (iii). In addition, the micro-Vickers
hardnesses and water contact angles of the outermost layer and the second layer were
measured using the following methods.
In order to obtain a measurement surface for measuring the micro-Vickers
hardnesses, a cross-section of the surface-treated steel sheet on which the outermost
layer and the second layer were formed was grinded and was finally finished with a 1
lm diamond paste to form a smooth surface. The hardnesses were measured at a load
of 25 gf. The water contact angle of the outermost layer of the surface-treated steel
sheet was measured using a sessile drop method after being irradiated with ultraviolet
rays for 8 hours. The water contact angle of the second layer was measured after
removing the outermost layer of the surface-treated steel sheet by dissolving it in 20%
aqueous NaOH solution to expose the second layer and irradiating the second layer
with ultraviolet rays for 8 hours.
Similar to Example 1, for the evaluation of the test results, a part or all (the
resistance to deterioration of the film and the comprehensive evaluation) of 5 grades of
A to E were used to evaluate the respective items regarding the contamination
resistance of the film and the resistance to deterioration. Evaluation criteria were as
shown above in Table 2. The micro-Vickers hardnesses were represented by a ratio
(H2lH1) of a measured value H2 of the second layer to a measured value H1 of the
outermost layer. The water contact angle was represented by a value (82-81) of a
measured value 02 of the second layer relative to a measured value 81 of the outermost
layer.
[0148]
The results were shown in Table 7. Since the concaves were present in the
film, the surface-treated steel sheets of Nos. 21 to 25 had superior contamination
resistance to the contamination in the initial stage 2 weeks after the outdoor exposure
test and the marker contamination. In addition, the surface-treated steel sheets also
had superior contamination resistance to the contamination 6 months after the outdoor
exposure test (after a certain period of time). Furthermore, in the surface-treated steel
sheets of Nos. 21 to 25, no deterioration of the photocatalytic film was observed 6
months after the outdoor exposure test, and the photocatalytic film was in the
extremely favorable state. It was found from the results of Nos. 21 to 25 that the
contamination resistance (for example, contamination resistance to raindrop
contamination and marker contamination) in the initial stage could be further improved
when the total of the lengths of concave in which the ratio "Wlt" of the width W of the
concave portion to the thickness t of the concave portion was in a range of 0.01 to 10
were greater than 90.4%, particularly, greater than 95.6% of the total length of all the
concaves. In addition, the ratio (H2/H1) of the micro-Vickers hardness H2 of the
second layer to the micro-Vickers hardness HI of the outermost layer was in a range
from 0.7 to 0.75, and the water contact angle 82 of the second layer was greater than
the water contact angle 81 of the outermost layer by 15' to 20'. It was found from
these results that, in the surface-treated steel sheets of Nos. 21 to 25, the photocatalytic
film was difficult to deteriorate and contamination resistance was superior for a long
period of time from the initial stage.
[0149]
On the other hand, in the surface-treated steel sheet of No. 11 0, since
concaves were not present in the film, a long period of time was required for
decomposing the markers which were the pollutants and contamination resistance to
the markers were low. In No. 110, no deterioration of the photocatalytic film was
observed, and the photocatalytic film was in the extremely favorable state.
[0150]
It was found from the above results that, in the surface-treated steel sheet of
Nos. 21 to 25, contamination resistance was superior substantially from the initial stage
and the contamination resistance was maintained for a long period of time, whereas in
the surface-treated steel sheet of No. 11 0, there were problems regarding the
contamination resistance of the initial stage.
In addition, when measured using both SEM and TEM, the particle size
distribution of a photocatalytic material in the photocatalytic film of the outermost
layer of the surface-treated steel sheet was almost the same as the particle size
distribution measured in the coating liquid.
[0151]
[Table 71
[0152]
(Example 4)
25 parts by mass of y-glycidoxypropyltriethoxysilane (GPTES), 8.2 parts by
mass of titanium tetraethoxide (TE), and 174.6 parts by mass of tetraethoxysilane
(TEOS) were sufficiently stirred, followed by hydrolysis under acidic conditions using
distilled water diluted with ethanol. 39.7.parts by mass of
aminopropyltriethoxysilane (APTES) was added to this solution, hrther followed by
hydrolysis using a mixed solution of distilled water and ethanol. As a result, a
treatment liquid containing an organic-inorganic complex as a major component was
prepared. A sufficient amount of water was used for hydrolysis, and the amount of
water was adjusted such that a concentration of an non-volatile content in the treatment
liquid (when being dried at 150°C) was 12.5 mass%. Anatase-type Ti02 particles
(average particle size ~PAaVpp:r oximately 10 nm) showing photocatalytic activity were
added to the treatment liquid as level shown in Table 8 to prepare a coating liquid (Nos.
26 to 30).
In addition, 35 parts by mass of y-glycidoxypropyltriethoxysilane (GPTES),
8.2 parts by mass of titanium tetraethoxide (TE), 87.3 parts by mass of
tetraethoxysilane (TEOS), and 63.8 parts by mass of tetramethoxysilane (TMOS) were
sufficiently stirred, followed by hydrolysis under acidic conditions using distilled
water diluted with ethanol. 39.7 parts by mass of aminopropyltriethoxysilane
(APTES) was added to this solution, hrther followed by hydrolysis using a mixed
solution of distilled water and ethanol. As a result, a treatment liquid containing an
organic-inorganic complex as a major component was prepared. A sufficient amount
of water was used for hydrolysis, and the amount of water was adjusted such that a
concentration of an non-volatile content in the treatment liquid (when being dried at
150°C) was 12.5 mass%. Anatase-type Ti02 particles (average particle size dpAv:
approximately 10 nm) showing photocatalytic activity were added to the treatment
liquid as level shown in Table 8 to prepare a coating liquid (Nos. 3 1 to 35).
Furthermore, in this coating liquid, as clearly seen from the mixing ratios of
the above-described respective raw materials, a ratio of the particles showing
photocatalytic activity to the treatment liquid containing the above-described organicinorganic
complex as a major component was in a range from 2.5 g/l to 50 dl.
[0153]
In a contamination resistance test, a precoated steel sheet having a thickness
of 0.35 rnm, which was obtained by coating the outermost surface of a zinc-aluminum
alloy coated steel sheet with a polyester film having a melamine crosslinking agent at a
thickness of about 15 pm, was used as a substrate. This precoated steel sheet was
coated with the above-described coating liquid using a bar coater and was dried and
baked at a maximum temperature of 250°C under temperature rise conditions which
the sheet temperature reached the maximum temperature after 50 seconds. In this
way, surface-treated steel sheets including a photocatalytic film on the outermost layer
were obtained. A plurality of concave was present in the formed photocatalytic films.
The properties of the concave were also shown in Table 8. These concaves formed a
network shape, and the sizes of outermost layer portions surrounded by the concave
were different from each other. The thicknesses t of the formed films were
approximately 3 pm in Nos. 26 to 30 and were approximately 3.5 pm in Nos. 3 1 to 35.
[O 1541
Concaves were present in the photocatalytic films which were the outermost
layers of the surface-treated steel sheets. Methods of measuring the properties
(above-described fw and rs) of the concave, the coverage fc of the photocatalytic film,
and the like were the same as those of Example 1.
[0155]
[Table 81
[0156]
Similar to Examples 1 to 3, a photocatalytic effect of the surface-treated steel
sheet was verified by the above-described items (i) to (iii). Similar to Examples 1 to
3, for the evaluation of the test results, a part or all (the resistance to deterioration of
the film and the comprehensive evaluation) of 5 grades of A to E were used to evaluate
the respective items regarding the contamination resistance of the film and the
resistance to deterioration. Evaluation criteria were as shown above in Table 2.
[0157]
The results were shown in Table 9. Since the concaves were present in the
film, the surface-treated steel sheets of Nos. 26 to 30 and Nos. 3 1 to 35 had superior
contamination resistance to the contamination in the initial stage 2 weeks after the
outdoor exposure test and the marker contamination. In addition, the surface-treated
steel sheets also had superior contamination resistance to the contamination 6 months
after the outdoor exposure test (after a certain period of time). Furthermore, in the
surface-treated steel sheets of Nos. 26 to 30 and Nos. 3 1 to 35, no deterioration of the
photocatalytic film was observed 6 months after the outdoor exposure test, and the
photocatalytic film was in the extremely favorable state.
It was found from these results that, in the surface-treated steel sheets of Nos.
26 to 30 and Nos. 3 1 to 35, the photocatalytic film was difficult to deteriorate and
contamination resistance was superior for a long period of time from the initial stage.
In addition, when measured using both SEM and TEM, the particle size
distribution of a photocatalytic material in the photocatalytic film of the outermost
layer of the surface-treated steel sheet was almost the same as the particle size
distribution measured in the coating liquid.
[0158]
[Table 91
[0159]
(Example 5)
component was prepared with the same formulation as that of the first treatment liquid
of Example 3. The amount of water was adjusted such that a concentration (C, in
Table 10) of an non-volatile content in the treatment liquid was 2.5, 5.0,7.5, or 10
mass% when being dried at 150°C. Matase-type Ti02 particles (average particle
size: about 10 nm) showing photocatalytic activity were added to the treatment liquid
such that a mass ratio thereof to the total mass of the photocatalytic film was lo%, to
prepare a coating liquid (Nos. 36 to 39). Furthermore, in this coating liquid, a ratio of
the particles showing photocatalytic activity to the treatment liquid containing the
above-described organic-inorganic complex as a major component was in a range from
2.5 g/l to 50 g/l.
[O 1601
As a comparative example, a coating liquid having the same composition as
I that of Nos. 36 to 39 was prepared, except that a concentration of an non-volatile
content (other than photocatalytic particles) in the treatment liquid when being dried at
150°C was 25 mass% (No. 11 1).
[0 16 11
In a contamination resistance test, a steel sheet, which was obtained by
treating a surface of a hot-dip galvanized steel sheet having a thickness of 0.4mrn with
an organic silicate, was used as a substrate. This steel sheet was coated with the
above-described coating liquid using a bar coater and was dried and baked at a
maximum temperature of 250°C under temperature rise conditions which the sheet
temperature reached the maximum temperature after 50 seconds. In this way,
surface-treated steel sheets including a photocatalytic film on the outermost layer were
- . obtained. The thicknesses t of the formed films were approximately 1 pm to 1.5 pm
in Nos. 36 to 39 and approximately 2 pm in No. 11 1. A plurality of concave was
present in the photocatalytic films of Nos. 36 to 39. Methods of measuring the
properties (above-described fw and rs) of the concave, the coverage fc of the
photocatalytic film, and the like were the same as those of Example 1. The results
thereof are shown in Table 10. These concaves formed a network shape, and the sizes
of outermost layer portions surrounded by the concave were different from each other.
No concaves were present in the photocatalytic film of No. 11 1.
[0 1 621
[Table 101
[0 1631
Similar to Examples 1 to 4, a photocatalytic effect of the surface-treated steel
sheet was verified by the above-described items (i) to (iii). Similar to Examples 1 to
4, for the evaluation of the test results, a part or all (the resistance to deterioration of
the film and the comprehensive evaluation) of 5 grades of A to E were used to evaluate
the respective items regarding the contamination resistance of the film and the
resistance to deterioration. Evaluation criteria were as shown above in Table 2.
[0 1641
The results were shown in Table 11. Since the concaves were present in the
film, the surface-treated steel sheets of Nos. 36 to 39 had superior contamination
resistance to the contamination in the initial stage 2 weeks after the outdoor exposure
test and the marker contamination. In addition, the surface-treated steel sheets also
had superior contamination resistance to the contamination 6 months after the outdoor
exposure test (after a certain period of time). Furthermore, in the surface-treated steel
sheets of Nos. 36 to 39, no deterioration of the photocatalytic film was observed 6
months after the outdoor exposure test, and the photocatalytic film was in the
extremely favorable state. It was found fiom these results that, in the surface-treated
steel sheets of Nos. 36 to 39, the photocatalytic film was difficult to deteriorate and
contamination resistance was superior for a long period of time from the initial stage.
[0165]
On the other hand, in the surface-treated steel sheet of No. 111, since
concaves were not present in the film, a long period of time was required for
decomposing the markers which were the pollutants and contamination resistance to
the markers were low. In No. 11 1, no deterioration of the photocatalytic film was
observed, and the photocatalytic film was in the extremely favorable state.
[0 1661
It was found from the above results that, in the surface-treated steel sheet of
Nos. 36 to 39, contamination resistance was superior substantially fiom the initial stage
and the contamination resistance was maintained for a long period of time, whereas in
the surface-treated steel sheet of No. 11 I, there were problems regarding the
contamination resistance of the initial stage.
In addition, when measured using both SEM and TEM, the particle size
distribution of a photocatalytic material in the photocatalytic film of the outermost
layer of the surface-treated steel sheet was almost the same as the particle size
distribution measured in the coating liquid.
[0167]
[Table 1 I]
[O 1681
(Example 6)
100 parts by mass of y-glycidoxypropyltriethoxysilane (GPTES), 8.2 parts by
mass of titanium tetraethoxide (TE), 144 parts by mass of phenyltriethoxysilane
(PhTES), and 87 parts by mass of tetraethoxysilane (TEOS) were sufficiently stirred,
followed by hydrolysis under acidic conditions using distilled water diluted with
ethanol. 39.7 parts by mass of aminopropyltriethoxysilane (APTES) was added to
this solution, fbrther followed by hydrolysis using a mixed solution of distilled water
and ethanol. As a result, a treatment liquid containing an organic-inorganic complex
as a major component was prepared. A sufficient amount of water was used for
hydrolysis, and the amount of water was adjusted such that a concentration of a nonvolatile
content in the treatment liquid was 15 mass% when being dried at 150°C.
Ti02 particles (anatase-type, average primary particle size: about 10 nrn) showing
photocatalytic activity were added to the treatment liquid, followed by dispersion using
a paint shaker. Furthermore, Ti02 sol (anatase-type, average crystallite diameter: 15
nm) was added to the treatment liquid to prepare a coating liquid. When Ti02
particles and Ti02 sol were used in combination, a ratio (mass ratio) of a concentration
of each solid content thereof was 112. In addition, in this coating liquid, as clearly
seen from the mixing ratios of the above-described respective raw materials, a ratio of
the particles showing photocatalytic activity to the treatment liquid containing the
above-described organic-inorganic complex as a major component was in a range from
2.5 gll to 50 gll.
[0 1691
In a contamination resistance test, a precoated steel sheet, which was obtained
by coating the outermost surface of a zinc-aluminum alloy coated steel sheet having a
thickness of 0.35 mm with a polyester film having a melamine crosslinking agent at a
thickness of about 15 pm, was used as a substrate. This precoated steel sheet was
coated with the above-described coating liquid using a bar coater and was dried and
baked at a maximum temperature of 250°C under temperature rise conditions which
the sheet temperature reached the maximum temperature after 50 seconds. Next, the
precoated steel sheet in which the coating liquid was baked was rapidly cooled in water.
In this way, surface-treated steel sheets including a photocatalytic film on the
outermost layer were obtained. The average cooling rates of the photocatalytic films
of the outermost layers were approximately 1000 "Clsec. All the thicknesses t of the
formed films were approximately 5 pm (Nos. 40 to 52).
[0 1701
The particle size distribution of a photocatalyst present in the coating liquid
was measured with a light scattering method using laser light. The results thereof
were shown in Table 12. In Nos. 40 to 48, the particle size distribution had two
maximum values (the above-described predetermined maximum values), one
maximum value was present in a particle size range of 15 nm to 25 nm, and the other
maximum value was present in a particle size range of 685 nm to 795 nm. In addition,
a plurality of concave was present in the films, these concaves formed a network shape,
and the sizes of outermost layer portions surrounded by the concave were different
from each other. Methods of measuring the properties (above-described fw and rs) of
the concave, the coverage fc of the photocatalytic film, and the like were the same as
those of Example 1. The results thereof were shown in Table 12.
[0171]
[Table 121
[0 1 721
Similar to Examples 1 to 5, a photocatalytic effect of the surface-treated steel
sheet was verified by the above-described items (i) to (iii). Similar to Examples 1 to
5, for the evaluation of the test results, a part or all (the resistance to deterioration of
the film and the comprehensive evaluation) of 5 grades of A to E were used to evaluate
the respective items regarding the contamination resistance of the film and the
resistance to deterioration. Evaluation criteria were as shown above in Table 2.
[0 1 731
[Table 131
[0174]
The results were shown in Table 13. Since the concaves were present in the
photocatalytic film of the outermost layer and the photocatalytic particles in the film
had a particle size distribution having two or more maximum values, the surfacetreated
steel sheets of Nos. 40 to 48 had superior contamination resistance to the
contamination in the initial stage 2 weeks after the outdoor exposure test and the
marker contamination. In addition, the surface-treated steel sheets also had superior
contamination resistance to the contamination 6 months after the outdoor exposure test
(after a certain period of time). Furthermore, in the surface-treated steel sheets of Nos.
40 to 48, no deterioration of the photocatalytic film was observed 6 months after the
outdoor exposure test, and the photocatalytic film was in the extremely favorable state.
[0175]
In the surface-treated steel sheets of Nos. 49 to 52, concaves were present in
the photocatalyst of the outermost layer, and the photocatalytic particles had a particle
size distribution having one maximum value. Therefore, in the surface-treated steel
steels of Nos. 49 to 52, the photocatalytic film had sufficient contamination resistance
and resistance to deterioration.
In addition, it was found that, due to a difference in particle size distribution,
when the surface-treated steel sheets of Nos. 40 to 48 were compared to the surfacetreated
steel sheets of Nos. 49 to 52, contamination resistance to the contamination 2
weeks after the outdoor exposure test and the marker contamination was further
improved.
In addition, when measured using both SEM and TEM, the particle size
distribution of a photocatalytic material in the photocatalytic film of the outermost
layer of the surface-treated steel sheet was almost the same as the particle size
distribution measured in the coating liquid.
[0 1761
It was found from the above results that, in all the surface-treated steel sheets
of Nos. 40 to 52, contamination resistance was superior from the initial stage and the
contamination resistance was maintained for a long period of time. In particular, in
the surface-treated steel sheet of Nos. 40 to 48, concave were present in the
photocatalytic film of the outermost layer, the particle size distribution of
photocatalytic particles in the film had a plurality of maximum values, one of the
maximum values was present in a range of 100 nm or less, and another one of the
maximum values was present in 500 nm or less. It was found that such surfacetreated
steel sheets had particularly superior contamination resistance in the initial
stage.
[0 1771
Hereinabove, the preferable examples of the invention have been described.
However, the invention is not limited to these examples. Various configuration
additions, omissions, substitutions, and other modifications can be made within a range
not departing from the concepts of the invention. The invention is not limited to the
above descriptions and is only limited to the accompanying claims.
[Industrial Applicability]
[0178]
According to the invention, it is possible to provide a surface-treated metal
which includes a photocatalytic film having superior resistance to deterioration and can
maintain superior contamination resistance for a long period of time .from the initial
. -
stage immediately after usage starts.
[Reference Sign List]
[0179]
1 : SURFACE-TREATED METAL
2: METAL
.. -
3: COATED MATERIAL
3a: OUTERMOST LAYER (PHOTOCATALYTIC FILM)
3b to 3e: COATING LAYERS
4: CONCAVES
4a to 4k, 4m: CONCAVES
5: PHOTOCATALYTIC DISPERSED PHASE (PARTICLES SHOWING
PHOTOCATALYTIC ACTIVITY OR AGGREGATES THEREOF,
PHOTOCATALYTIC PARTICLES)
6: MATRIX RESIN (ORGANIC-INORGANIC COMPOSITE RESIN)
4 1 : BOTTOM OF CONCAVE : '
42: SIDE SURFACE OF CONCAVE
TABLE. 1
108 Nb205 100 10.0 No concave
' '
loo
Comparative
Example
+
TABLE.
Orades
A
B
C
D
E
2
Contamination
Resistance to
Raindrop
contamination
and Dust Pollution
(After 2 Weeks)
-
Contaminants
were
Unremarkable
Contaminants
were Slightly
Attached
Attachment of
Contaminants
Was Remarkable
-
Contamination
Resistance to
Raindrop
Contamination
. and Dust Pollution
(After 6 Months)
-
Contaminants
were
Unremarkable
Contaminants
were Slightly
Attached
Attachment of
Contaminanls
Was Remarkable
-
Contamination
Resistance to
Markers
-
Fading was Clearly
Observed after 0.5
hours from
Ultraviolet
Irradiation
Fading was
Observed
hour from
Ultraviolet
Irradiation
Fading was 'lightly
Observed after
hours from
Ultraviolet
Irradiation
No Fading was
Observed after 2
hours from
Ultraviolet
Irradiation
Resistance to
Deterioration of
Film
No Deterioration
after Exposure
during 6 months
(Gloss Retention:
95% or Higher)
No Deterioration
after Exposure
during 6 months
(Gloss Retention:
90% or Higher)
Small
Deterioration after
Exposure during
- 6 months (Gloss
Retention: 60% to
Lower Than 90%)
Small
Deterioration after
Exposure during
6 months (Gloss
Retention: Lower
Than 60%)
Small
Deterioration after
Exposure during
3 months (Gloss
Retention: Lower
Than 50%)
TABLE. 3
No.
1
2
3'
4
5
6
7
8
9
10
11
12
101
102
103
104
105
106
107
108
Contamination Resistance
(After 2
Raindrop
Contamination
C
C
B
' B
B
B
B
B
B
B
C
B
C
C
C
C
C
C
C
C
Weeks)
Dust
Pollution
B
B
B
B
B
B
B -
B
B
B
B
B
C
C
B
B
B
B
B
B
Contamination Resistance
Contamination
Resistance to
Markers
B
B
B
B
B
B
B
B
B
B
B
B
E
D
c D
, D
- - -D -
D
D
E
(After 6
Raindrop
Contamination
C
B
B
B
B
B
B c .
B
B
B
B
B
C
B
B
B
B
B
B
B
Months)
Dust
Pollution
B
B
B
B
B
B
B
B
B
B
B
B
B
B
B
B
B
B
B
B
Resistance to
Deterioration
of Film
A
A
A
A
A
A
A
B
A
A
A
A
A
A
A
A
A
A
A
A
Comprehensive
Evaluation
C
B
A
A
A
' A
I A
' B
A
A
C
A
E
D
D
D
D
D
D
D
Note
Example
Example
Example
Example
Example
Example
Example
Example
Example
Example
Example
Example
Comparative Example
Comparative Example
Comparative Example
Comparative Example
Comparative Example
Comparative Example
Comparative Example
Comparative Example
TABLE. 4
TABLE. 5
No.
13
14
15
16
17
18
19
20
109
Contamination Resistance '
(After 2 Weeks)
Raindrop
Contamination
C
B
B
B
B
Dust
Pollution
B
B
B'
B
B
Contamination Resistance
(After 6 Months)
B
Contamination
Resistance
to Markers
C
B
B
B
B
Raindrop
Contamination
B
B
B .
B
B
B
. C
C
Dust
Pollution
B
B
B
B
B
Resistance to
Deterioration
of Film
A
A
A
A
A
B
B
B
Comprehensive
Evaluation
B
. , A
A
A
A
B
C
B
Note
Example
Example
Example
Example
Example
B
C
B
B
C
D
A
A
A
A
C
D
Example
Example
Comparative
Example
:' TABLE. 6
Photocatalytic Particles in Primary
No. Treatment Liquid
Properties of
Concave .
No Concave
Note
Example
Example
Comparative
* TiO, represents an anatase-type TiO,
TABLE. 7
I' 1 Contamination Resistance 1 Contamination Resistance I
No.
2 1
22
23
24
25
Resistance to
Deterioration of Film
- (After 2 Weeks)
Raindrop Dust
Contamination Pollution
B B -
B B
B B
B B
C C
A ,
A
A
A
A
comprehensive
Evaluation
A
Note
.
A
A
A
B
C
Contamination
Resistance to Markers
B
B
B
C
C
(After 6 Months)
- Example
Example
Example
Example
Example
D
Raindrop
Contamination '
B
B
B.
B
B
~~~t
Pollution
B
B
B
B
B
Comparative
Example ,
TABLE. 8
. * Ti02 represents an anatase-type TiOz
TABLE. 9

TABLE. 11
No.
3 6
3 7
3 8
3 9
111
Contamination Resistance
(. After 2 Weeks)
Raindrop
Contamination
C
B
B
B
C
Dust
Pollution
B .
B
B
B
B
Contamination Resistance
(After 6 Months) Contamination
Resistance
to Markers
C
B
B
B
D
Raindrop
Contamination
B
B -
' B
B
B
Dust
Pollution
B
B
B
B
B
Resistance to
Deterioration
of Film
A '
A
A
A
A
Comprehensive
Evaluation
B -
A
A
A
D
Note
Example
Example
Example
Example
CoEmxapmarpalteiv e
- d
'1
W

TABLE. 13
No.
40
41
42
43
44
45
46
47
48
49
50 -
5 1
52
Contaminatjon Resistance
(After 2 Weeks)
Raindrop
Contamination
B
B
B
B
B
B
B
B
B
---C
C - -- - -
C
C
Dust
Pollution
B
B
B
. B
B
B
B
B
B
B
B - -
C
C
Contamination Resistance
(After 6 Months)
-7- ---. --- -B- C -Example
B B C A C Example
B B C A C Example
Contamination
Resistance
to Markers
B
B
B
B
B
B
B
B
B
C
Raindrop
Contamination
B
B
B
B
B
B
B
B
B
B
-
Dust
Pollution
B
B
B
B
B
B
B
B
B
B
Resistance to
Deterioration
of Film
A
A
A
A '
A
A
A
A
A
A
Comprehensive
Evaluation
A
A
A
A -
A
A
A
A
A
B
Note
Example
Example
Example
Example
Example
Example
Example
Example
Example
-Example

[Document type] ' CLAIMS
[Claim 11
A surface-treated metal comprising:
a metal; and
a coated material that is formed on a surface of the metal,
wherein an outermost layer of the coated material is a photocatalytic film that
contains particles showing a photocatalytic activity and an organic-inorganic
composite resin,
a volume ratio of the particles showing the photocatalytic activity to the
photocatalytic film is in a range from 0.5 vol% to 50 vol%,
the organic-inorganic composite resin contains a siloxane bond and at least
one group selected from a group consisting of an aryl group, a carboxyl group, an
amino group, a hydroxyl group, and an alkyl group having 1 to 12 carbon atoms,
the coated material has a concave on a surface on the outermost layer side
thereof,
the concave extends in a direction perpendicular to a thickness direction of the
outermost layer,
the concave separates the outermost layer in the direction perpendicular to the
thickness direction when the outermost layer is seen in a cross-sectional view taken
along the thickness direction,
an area of the outermost layer is 50% to 98% of an area of the surface of the
metal when the coated material is seen in a plan view, and
I a surface area of the outermost layer is 101 % to 5000% of the area of the
I
1
I surface of the metal.
1 [Claim 21
The surface-treated metal according to Claim 1,
wherein, when dimensions of the concave in a direction perpendicular to both
a direction in which the concave extends and the thickness direction are represented by
widths W and dimensions of the concave in the direction in which the concave extends
are represented by lengths L, a total of the lengths L of the concave of portions in
which the widths W are in a range from 1% to 1000?/o of a thickness of the outermost
layer is 90% to 100% of a total of the lengths L of the concave.
,. -
[Claim 31
The surface-treated metal according to Claim 1,
wherein, when the coated material is seen in the plan view, a plurality of the
concaves is present,
the concaves form a network shape, and
sizes of portions of the outermost layer which are syrrounded by the concaves
are different from each other.
- -
[Claim 41
The surface-treated metal according to Claim 1,
wherein, when the outermost layer is.. seen in the crass-sectional view taken
along the thickness direction, among two surfaces facing.each other in the thickness
direction of the outermost layer, a surface opposite the metal has a plurality of flat
areas, and a total length of the plurality of flat areas is 70% to 99% of a total length of
the surface.
[Claim 51
The surface-treated metal according to Claim 1,
I I wherein the particles showing the photocatalytic activity contain a titanium
I
I
I oxide having an anatase-type structure. I
[Claim 61
The surface-treated metal according to Claim 1,
wherein the metal is any one selected from a group consisting of a steel sheet,
a stainless steel sheet, a titanium sheet, a titanium alloy sheet, an aluminum sheet, an
aluminum alloy sheet, and a plated metal sheet having a plated layer.
[Claim 71
The surface-treated metal according to Claim 1,
.. -
wherein the coated material has a second layer in contact with the outermost
layer between the outermost layer and the metal.
[Claim 81
The surface-treated metal according to Claim 7,
wherein a ratio of a micro-Vickers hardness of the second layer to a micro-
Vickers hardness of the outermost layer is 0.20 to 0.95.
[Claim 91
The surface-treated metal according to Claim 7,
wherein a water contact angle of the second layer is in a range obtained by
adding 10" to 80" to a water contact angle of the outermost layer.
[Claim lo]
The surface-treated metal according to Claim 1,
wherein a ratio of the particles showing the photocatalytic activity to the
photocatalytic film is in a range from 0.5 mass% to 50 mass%,
a particle size distribution based on a number of the particles showing the
photocatalytic activity has a plurality of maximum values and minimum values which
are present between adjacent maximum values in the plurality of maximum values, and
two or more maximum values in the plurality of maximum values have a
values adjacent to the maximum values thereof.
[Claim 111
The surface-treated metal according to Claim 10,
whereiri the particle size distribution has at least one of the two or more
maximum values of a particle size range of 100 nm or less and has at least one of the
two or more maximum values of a particle size range of 500 n.q or greater.
,. -
[Claim 121
A method of producing a surface-treated metal by forming a coated material
on a surface of a substrate containing a metal, the method comprising:
mixing particles showing a photocatalytic activity with a liquid which
contains a hydrolysate of an alkoxysilane having at least one group selected fiom a
group consisting of an aryl group, a carboxyl group, an amino group, a hydroxyl group,
and an alkyl group having 1 to 12 carbon atoms such that a ratio of the particles
showing the photocatalytic activity to the liquid is in a range fiom 1.0 g/l to 50 g/l to
prepare a first treatment liquid;
coating the first treatment liquid suck that the first treatment liquid covers an
outermost layer of the coated material; and
baking the first treatment liquid.
[Claim 131
The method of producing the surface-treated metal according to Claim 12,
wherein the liquid or the first treatment liquid further contains a hydrolysate
of at least one tetraalkoxysilane selected fiom a group consisting of a
tetramethoxysilane and a tetraethoxysilane.
[Claim 141
wherein a non-volatile content in the first treatment liquid is 2.5 mass% to 10
mass%. . -
[Claim 151
The method of producing the surface-treated metal according to Claim 12,
M e r comprising:
cooling the outermost layer, after baking the first treatment liquid, such that
an.average cooling rate in a temperature range from 250°C to 1 00°C is 100 "Clsec to
[Claim 161
The method of producing the surface-treated metal according to Claim 12,
wherein the first treatment liquid is coated using a dip coating method, a spray
coating method, a bar coating method, a roll coating method, a spin coating method, or
a curtain coating method.
[Claim 171
The method of producing the surface-treated metal according to Claim 12,
wherein various types of treatment liquids are coatsd to form the coated
material having a plurality of layers, and
the various types of treatment liquids include the first treatment liquid and a
second treatment liquid which is a different type from the first treatment liquid.
[Claim 181
-. .
The method of producing the surface-treated metal according to Claim 17,
wherein a ratio of a micro-Vickers hardness when the second treatment liquid
is cured to a micro-Vickers hardness when the first treatment liquid is cured is 0.20 to
[Claim 191
The method of producing the surface-treated metal according to Claim 17,
wherein a .water contact angle when the second treatment liquid is cured is in
a range obtained by adding 10" to 80" to a water contact angle when the first treatment
liquid is cured.
[Claim 201
The method of producing the surface-treated metal according to Claim 17,
,. -
wherein a lower layer film containing an organic resin is formed on the
surface of the substrate, secondly, the second treatment liquid and the first treatment
liquid are simultaneously coated on the lower layer film, and the second treatment
liquid and the first treatment liquid are simultaneously dried &d baked to form a multilayer
film including the lower layer film formed on the surface of the substrate, a
second layer film formed by curing the second treatment liq+d on the lower layer film,
and an outermost layer film formed by curing the first treatment liquid as like as the
second layer film.
[Claim 2 11
The method of producing the surface-treated metal according to Claim 17,
wherein a coating liquid used to form a lower layer film containing an organic
resin, the second treatment liquid, and the first treatment liquid are simultaneously
coated on the surface of the substrate, and the coating liquid, the second treatment
liquid, and the first treatment liquid are simultaneously dried and baked to form a
multi-layer film including the lower layer film formed on the surface of the substrate, a
second layer film formed by curing the second treatment liquid on the lower layer film,
and an outermost layer film formed by curing the first treatment liquid on the second
layer film.
The method ofproducing the surface-treated metal according to Claim 12,
wherein the particles showing the photocatalytic activity contain a titanium
oxide having & anat'ase-type structure.
[Cl* 231 .
The mehod of producing the sdace-treated metal according to Claim 12,
wherein the substrate containing the metal is any one selected fiom a group
copsisting of a steel sheet, a stainless steei--sheet, a titanium sheet, a .-- titkurn alloy
sheet, an aluminum sheet, an aluminum alloy sheet, a plated metal sheet having.a
plated laye-r., an- d a. prepainted steel sheet.
[Claim 241
The method of producing the sdace-treated metal according to Claim 12,
wherein a particle size distribution based on a number of the particles showing
the phptocatalytic activity has a plurality of maximum values and min. im&. values . .
. -. . ...- . .
which are present between adjacent maximum values in the plurality of maximum
values, and
- - -- - - . . . -
two or more maximum values in theplurality of maximum values have
. ..
number frequencies which is 1.5 times or greater of number frequencies of minimum
I values adjacent to the maximum values thereof .
[Claim 251
I The method of producing the surfack-treated metal according to Claim 24,
-. -
wherein the particle size distribution has at least one of the two or more I I maximum values of a particle size range of 100 nm or less and has at least one of the
two or more maximum values of a particle size range of 500 nni or greater.

Dated this 16/12/2013 .

NEHA SRIVASTAVA
I OF REMFRY & SAGAR
ATTORNEY FOR THE APPLICANT