TECHNICAL FIELD
[0001]
The present invention relates to an electroconductive film
used for touch sensors, touch panels, and the like and relates
to a touch panel and a display device which are provided with
the electroconductive film. In particular, the present invention
relates to an electroconductive film in which the occurrence of
moire is reduced regardless of the viewing angle (observation
angle) and relates to a touch panel and a display device which
are provided with the electroconductive film.
BACKGROUND ART
[0002]
Examples of an electroconductive film installed on a
display unit of a display device (hereinafter, also referred to
as a "display") include electroconductive films for
electromagnetic wave shields, electroconductive films for touch
panels, and the like (for example, see Patent Literatures 1 and
2).
[0003]
Patent Literature 1 discloses a technique that provides a
wiring pattern having excellent visibility by controlling moire
frequencies based only on frequency information on a black
matrix pattern and a wiring pattern of a display in forming a
wiring pattern of an electromagnetic wave shielding film.
Specifically, Patent Literature 1 discloses that a second
pattern, which is generated from second pattern data in which
the relative distance between spectrum peaks of two-dimensional
Fourier spectra (2DFFTSp) of the respective pattern data of a
first pattern such as a pixel array pattern (for example, a
black matrix (hereinafter, also referred to as "BM") pattern) of
a display and the second pattern such as an electromagnetic wave
shielding pattern exceeds a predetermined spatial frequency, for
2
2
example, 8 cm-1, is automatically selected. Patent Literature 1
also discloses that when the aforementioned relative distance
does not exceed the predetermined spatial frequency, the
operation of generating new second pattern data by changing one
or more of the rotation angle, the pitch, and the pattern width
of the second pattern data is repeated until the aforementioned
relative distance exceeds the predetermined spatial frequency.
In this way, according to Patent Literature 1, it is
possible to automatically select an electromagnetic wave
shielding pattern that can inhibit the occurrence of moire, and
that can also prevent an increase in surface resistivity and
deterioration of transparency.
[0004]
An electroconductive sheet for a touch panel in Patent
Literature 2 has first electroconductive portions which are
formed on the main surface at one side of a substrate and second
electroconductive portions which are formed on the main surface
at the other side of the substrate. The first electroconductive
portions extend in a first direction, are arrayed in a second
direction orthogonal to the first direction, and have two or
more first transparent electroconductive patterns. The second
electroconductive portions extend in the second direction, are
arrayed in the first direction, and have two or more second
transparent electroconductive patterns. When viewed from above,
the first transparent electroconductive patterns and the second
transparent electroconductive patterns are arranged to cross
each other and deviate in directions different from the first
direction and the second direction. In this way, according to
Patent Literature 2, a plurality of spatial frequencies are
combined with each other. As a result, the interference with the
pixel array of a liquid crystal display device is inhibited, and
the occurrence of moire is effectively reduced.
CITATION LIST
PATENT LITERATURE
[0005]
3
3
Patent Literature 1: JP 2009-117683 A
Patent Literature 2: JP 2011-237839 A
SUMMARY OF INVENTION
TECHNICAL PROBLEMS
[0006]
Patent Literature 1 is for shielding electromagnetic waves,
and in this document, the electromagnetic wave shielding pattern
is formed at only one layer. Meanwhile, if the electromagnetic
wave shielding pattern is formed at two or more layers, both of
the reduction of moire which is visually recognized when the
pattern is observed from the front and the reduction of moire
when the viewing angle is changed need to be considered.
However, because Patent Literature 1 relates to a technique
of optimizing moire for only one layer, this cannot be applied
to a touch panel or the like in which wiring is present at a
plurality of layers.
Moreover, although Patent Literature 2 considers the moire
of a transparent electroconductive pattern having a doublelayered
structure, it does not at all consider the moire
occurring when the viewing angle is changed.
As described above, in the current circumstances, regarding
a touch panel or the like in which a wiring pattern is present
at a plurality of layers, there is no technique that considers
the occurrence of moire caused by change of the viewing angle
and the reduction of the occurrence of moire.
[0007]
An object of the present invention is to provide an
electroconductive film which can reduce the occurrence of moire
regardless of the viewing angle (observation angle) and
particularly, even when being superimposed on a display unit
such as a display panel, can lead to excellent visibility, as
well as a touch panel and a display device provided with the
electroconductive film.
SOLUTION TO PROBLEMS
[0008]
4
4
In order to attain the objects described above, the present
invention provides as its first aspect an electroconductive film
installed on a display unit of a display device, comprising: one
or two or more transparent substrates; and two or more wiring
layers that are formed on both surfaces of the one transparent
substrate or are each formed on one surface of each of the two
or more transparent substrates, are disposed in a form of a
laminate, and are regularly arranged, wherein wiring patterns of
the two or more wiring layers are superimposed on a pixel array
pattern of the display unit, and a wiring pattern of a wiring
layer as a lower layer is disposed at a displaced position in
phase relative to a wiring pattern of a wiring layer as an upper
layer, and wherein the electroconductive film satisfies: fm1 
fm2, provided that among spatial frequencies of moire as
obtained by convolution of spatial frequency characteristics of
the wiring patterns of the two or more wiring layers and spatial
frequency characteristics of the pixel array pattern of the
display unit, a lowest frequency is set to a first lowest
frequency fm1, and among spatial frequencies of moire as
obtained by convolution of spatial frequency characteristics of
a half of the wiring patterns of the two or more wiring layers
and the spatial frequency characteristics of the pixel array
pattern of the display unit, a lowest frequency is set to a
second lowest frequency fm2.
[0009]
Preferably, the spatial frequency characteristics of the
wiring patterns of the two or more wiring layers are spatial
frequency characteristics in a direction perpendicular to the
one or two or more transparent substrates, and the spatial
frequency characteristics of a half of the wiring patterns of
the two or more wiring layers are spatial frequency
characteristics in a direction inclined by a predetermined angle
with respect to the one or two or more transparent substrates.
Preferably, the two or more wiring layers are formed on
both surfaces of the one transparent substrate.
5
5
Preferably, the two or more transparent substrates are
laminated on each other, the two or more wiring layers being
each formed on one surface of each of the two or more
transparent substrates.
Preferably, the two or more wiring layers each have a
wiring pattern in a form of mesh in which a plurality of
openings are arranged.
Preferably, the pixel array pattern is a black matrix
pattern of the display unit.
[0010]
In order to attain the objects described above, the present
invention provides as its second aspect a touch panel,
comprising: the electroconductive film of the first aspect of
the invention; and a detection control portion configured to
detect, within a region where the two or more wiring layers are
formed, a position at which an object makes a contact with the
electroconductive film from outside.
In order to attain the objects described above, the present
invention provides as its third aspect a display device,
comprising: a display unit; and the electroconductive film of
the first aspect of the invention installed on the display unit.
In order to attain the objects described above, the present
invention provides as its fourth aspect a display device,
comprising: a display unit; and the electroconductive film of
the first aspect of the invention installed on the display unit.
ADVANTAGEOUS EFFECTS OF INVENTION
[0011]
According to the present invention, it is possible to
reduce moire not only in the case of observing a display from
the front but also in the case of changing the viewing angle,
regardless of the viewing angle. In particular, according to the
present invention, it is possible to provide an
electroconductive film which can lead to the improvement in
visibility and exhibit excellent visibility even when being
superimposed on a display unit such as a display panel, as well
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6
as a touch panel and a display device provided with the
electroconductive film.
Consequentially, the image quality of the touch panel and
the display device provided with the electroconductive film of
the present invention can be further improved.
BRIEF DESCRIPTION OF DRAWINGS
[0012]
FIG. 1 is a schematic view showing an example of a display
device according to an embodiment of the present invention.
FIG. 2(a) is a schematic cross-sectional view showing an
example of an electroconductive film of the embodiment of the
present invention, and FIG. 2(b) is a schematic view showing an
example of a wiring pattern of the electroconductive film of the
embodiment of the present invention.
FIG. 3 is a schematic cross-sectional view showing another
example of the electroconductive film of the embodiment of the
present invention.
FIG. 4 is a schematic view showing an example of a pixel
array pattern of a part of a liquid crystal display portion for
which the electroconductive film of the present invention is
employed.
FIG. 5 is a schematic view showing wiring pattern images
that are formed in the electroconductive film shown in FIG. 2(a)
with different viewing angles.
FIG. 6 is a graph showing frequency peak positions of
moire.
FIG. 7(a) is a schematic view showing a wiring pattern
formed when a viewing angle is 0, and FIG. 7(b) is a view
showing spatial frequency characteristics of the wiring pattern
shown in FIG. 7(a).
FIG. 8(a) is a schematic view showing a wiring pattern
formed when a viewing angle is not 0, and FIG. 8(b) is a view
showing spatial frequency characteristics of the wiring pattern
shown in FIG. 8(a).
FIG. 9(a) is a schematic view showing a wiring pattern
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7
formed when a viewing angle is 0C, and FIG. 9(b) is a view
showing spatial frequency characteristics of the wiring pattern
shown in FIG. 9(a).
FIG. 10(a) is a schematic view showing a wiring pattern
formed when a viewing angle is not 0, and FIG 10(b) is a view
showing spatial frequency characteristics of the wiring pattern
shown in FIG. 10(a).
FIGS. 11(a) and 11(b) are views respectively showing an
exemplary front observation image and an exemplary oblique
observation image in the invention, with the condition of a
first lowest frequency fm1  a second lowest frequency fm2, which
is a spatial frequency condition of moire of the present
invention, being satisfied.
FIGS. 12(a) and 12(b) are views respectively showing an
exemplary front observation image and an exemplary oblique
observation image in a comparative example, with the condition
of the first lowest frequency fm1  the second lowest frequency
fm2, which is the spatial frequency condition of moire of the
present invention, being not satisfied.
FIG. 13 is a flowchart showing an example of a
determination method of a wiring pattern of the
electroconductive film of the embodiment of the present
invention.
FIG. 14(a) is a schematic view showing an example of a
pixel array pattern of a display unit of the embodiment of the
present invention, FIG. 14(b) is a schematic view showing an
example of a wiring pattern of an electroconductive film to be
superimposed on the pixel array pattern of FIG. 14(a), and FIG.
14(c) is a partially enlarged view of the pixel array pattern of
FIG. 14(a).
FIG. 15 is a schematic view showing spatial frequency
characteristics of a two-dimensional Fourier spectrum of
transmittance image data of a pixel array pattern of a black
matrix.
8
8
DESCRIPTION OF EMBODIMENTS
[0013]
Hereinafter, based on a preferable embodiment shown in the
attached drawings, an electroconductive film of the present
invention as well as a touch panel and a display device provided
with the electroconductive film will be described in detail.
In the following description, regarding the
electroconductive film of the present invention, an
electroconductive film for a touch panel using a liquid crystal
display panel (LCD) as a display panel will be described as a
typical example. However, the present invention is not limited
thereto. The electroconductive film of the present invention is
not limited to the electroconductive film for a touch panel and
may be any type of electroconductive film as long as it is
installed on a display unit of any of various display devices
which will be described later. Needless to say, the
electroconductive film of the present invention may be, for
example, an electroconductive film for an electromagnetic wave
shield.
FIG. 1 is a schematic view showing a display device
according to the embodiment of the present invention. FIG. 2(a)
is a schematic cross-sectional view showing an example of the
electroconductive film of the embodiment of the present
invention, and FIG. 2(b) is a schematic view showing an example
of a wiring pattern of the electroconductive film of the
embodiment of the present invention.
[0014]
As shown in FIG. 1, a display device 10 of the present
embodiment has a touch sensor 12 (touch panel) in the form of a
panel and a display unit 14.
The touch sensor 12 includes a first adhesive layer 16, an
electroconductive film 18 of the present embodiment, a second
adhesive layer 20, and a protective layer 22 that are laminated
on each other in this order, and a detection control portion 23
that is electrically connected to the electroconductive film 18
9
9
through a cable 21. The touch sensor 12 is preferably stuck on
the display unit 14 through the first adhesive layer 16 or a
bonding layer. However, the touch sensor 12 may be simply placed
on the display unit 14.
The display unit 14 includes a backlight unit (BLK) 24 that
emits planar illumination light and a liquid crystal display
cell (LCC) 26 that is illuminated from the rear surface thereof
by the backlight unit 24 and constitutes a display portion.
[0015]
As shown in FIG. 1, the electroconductive film 18 of the
present embodiment is installed on the display unit 14 of the
display device 10. The electroconductive film 18 is an
electroconductive film having a wiring pattern that is excellent
in inhibiting the occurrence of moire with respect to the pixel
array of the liquid crystal display cell 26, which will be
described later, of the display unit 14 and therefore with
respect to a black matrix (hereinafter, also referred to as
"BM"), particularly, having a wiring pattern that leads to the
reduction in occurrence of moire with respect to a black matrix
pattern (hereinafter, also referred to as a "BM pattern")
regardless of the viewing angle when being superimposed on the
BM pattern and that has improved visibility.
As shown in FIG. 2(a), the electroconductive film 18 has a
transparent substrate 30 and wiring layers 34a and 34b that are
formed on a front surface 30a and a rear surface 30b of the
transparent substrate 30, respectively, and are each formed of a
plurality of thin wires 32 made of a metal (hereinafter,
referred to as "thin metal wires").
[0016]
The transparent substrate 30 is formed of a material having
insulating properties and a high degree of translucency.
Examples of the material include a resin, glass, silicon, and
the like. Examples of the resin include PET (polyethylene
terephthalate), PMMA (polymethyl methacrylate), PP
(polypropylene), PS (polystyrene), and the like. The transparent
10
10
substrate 30 has a thickness d of about 100 m to 150 m.
The transparent substrate 30 may be constituted with at
least one layer.
[0017]
The wiring layer 34a and the wiring layer 34b have the same
or similar wiring patterns 35. The wiring layer 34b as a lower
layer is disposed at a displaced position in phase relative to
the wiring layer 34a as an upper layer such that each of the
thin metal wires 32 of the wiring layer 34b as a lower layer is
positioned between two adjacent thin metal wires 32 of the
wiring layer 34a as an upper layer. For example, the wiring
layer 34b as a lower layer is disposed at the position at which
it is displaced in phase by a half (1/2) pitch relative to the
wiring layer 34a as an upper layer. Specifically, as shown in
FIG. 2(a), the wiring layers 34a and 34b are disposed such that
each of the thin metal wires 32 of the wiring layer 34b as a
lower layer is positioned in the middle between two adjacent
thin metal wires 32 of the wiring layer 34a as an upper layer.
In the present Description, such an arrangement of the wiring
layer 34a and the wiring layer 34b is referred to as a nested
arrangement of the wiring layer 34b as a lower layer relative to
the wiring layer 34a as an upper layer. That is, the wiring
pattern 35 of the lower layer is disposed at a displaced
position in phase relative to the wiring pattern 35 of the upper
layer to establish the nested arrangement.
[0018]
The wiring layers 34a and 34b are collectively called a
wiring layer(s) 34. For example, as shown in FIG. 2(b), the
wiring layer 34 has a wiring pattern 35 in the form of mesh
composed of the thin metal wires 32 and having arranged openings
36.
The thin metal wires 32 constituting the wiring layer 34
(34a and 34b) are not particularly limited as long as they are
thin wires made of a metal having a high degree of
electroconductivity. Examples thereof include wires formed of a
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11
wire material such as gold (Au), silver (Ag), or copper (Cu). In
view of visibility, the line width of the thin metal wires 32 is
preferably small and, for example, should be equal to or less
than 30 m. When the thin metal wires 32 are used for a touch
panel, the line width thereof is preferably equal to or greater
than 0.1 m but equal to or less than 15 m, more preferably
equal to or greater than 1 m but equal to or less than 9 m, and
even more preferably equal to or greater than 2 m but equal to
or less than 7 m.
[0019]
In the example shown in FIG. 2(b), the mesh shape of the
openings 36 of the wiring layer 34 is rhombic but the present
invention is not limited thereto. As long as the mesh can
constitute the wiring layer 34 that is optimized in terms of the
moire visibility with respect to a predetermined BM pattern,
which will be described later, and has a polygonal shape having
at least three sides, any mesh shape may be employed.
Furthermore, the wiring layer 34 may be constituted with a
uniform mesh shape or different mesh shapes. Examples of the
uniform or different mesh shapes include polygons such as
triangles including an equilateral triangle and an isosceles
triangle, quadrangles (rectangles) including a square and a
rectangle, pentagons, and hexagons.
[0020]
In the touch sensor 12 shown in FIG. 1, the first adhesive
layer 16 is disposed on the rear surface 30b (see FIG. 2(a)) of
the transparent substrate 30 (see FIG. 2(a)) of the
electroconductive film 18 so as to cover the wiring layer 34b
(see FIG. 2(a)). Instead of the first adhesive layer 16, a resin
film such as a PET film, a glass plate, or the like may be
provided. In such cases, the electroconductive film 18 of the
touch sensor 12 is installed on a display surface of the liquid
crystal display cell 26 of the display unit 14 via the resin
film or the glass plate.
12
12
[0021]
The second adhesive layer 20 (see FIG. 1) is disposed on
the front surface 30a (see FIG. 2(a)) of the transparent
substrate 30 (see FIG. 2(a)) so as to cover the wiring layer 34a
(see FIG. 2(a)).
The material of the first adhesive layer 16 and the second
adhesive layer 20 is not limited as long as it is a resin
material having adhesion or bonding properties. Examples of the
material include a wet lamination adhesive, a dry lamination
adhesive, a hot melt adhesive, and the like.
The first adhesive layer 16 and the second adhesive layer
20 may be formed of the same material or different materials.
[0022]
The protective layer 22 is disposed on the second adhesive
layer 20. The protective layer 22 is for protecting the
electroconductive film 18. Similarly to the transparent
substrate 30, the protective layer 22 is formed of a material
having a high degree of translucency, such as a resin, glass, or
silicon. For example, the protective layer 22 is constituted
with a transparent resin film or a glass plate. A refractive
index n1 of the protective layer 22 is preferably equal to or
close to a refractive index n0 of the transparent substrate 30.
In this case, a relative refractive index nr1 of the transparent
substrate 30 with respect to the protective layer 22 is close to
1.
[0023]
Herein, the refractive index in the present Description
means a refractive index for light having a wavelength of 589.3
nm (sodium D-line). For example, in the case of a resin, the
refractive index is defined by ISO 14782:1999 that is the
international standard (corresponding to JIS K 7105). The
relative refractive index nr1 of the transparent substrate 30
with respect to the protective layer 22 is defined by nr1 =
(n1/n0). Herein, the relative refractive index nr1 is preferably
equal to or greater than 0.86 but equal to or less than 1.15,
13
13
and more preferably equal to or greater than 0.91 but equal to
or less than 1.08.
By limiting the relative refractive index nr1 to the above
range and controlling the light transmittance between the
transparent substrate 30 and the protective layer 22, it is
possible to further improve and ameliorate moire visibility.
[0024]
A refractive index n2 of the second adhesive layer 20 and a
refractive index n3 of the first adhesive layer 16 are both
equal to or close to the refractive index n0 of the transparent
substrate 30. In this case, a relative refractive index nr2 of
the transparent substrate 30 with respect to the second adhesive
layer 20 and a relative refractive index nr3 of the transparent
substrate 30 with respect to the first adhesive layer 16 are
both close to 1. Herein, the refractive indices and the relative
refractive indices are defined in the same manner as described
above. Accordingly, the relative refractive index nr2 of the
transparent substrate 30 with respect to the second adhesive
layer 20 is defined by nr2 = (n2/n0), and the relative
refractive index nr3 of the transparent substrate 30 with
respect to the first adhesive layer 16 is defined by nr3 =
(n3/n0).
Similarly to the relative refractive index nr1, the
relative refractive index nr2 and the relative refractive index
nr3 are preferably equal to or greater than 0.86 but equal to or
less than 1.15, and more preferably equal to or greater than
0.91 but equal to or less than 1.08.
By limiting the relative refractive index nr2 and the
relative refractive index nr3 to the above range, the moire
visibility can be further improved as with the case in which the
relative refractive index nr1 is limited to the aforementioned
range.
[0025]
The wiring layers 34a and 34b of the electroconductive film
18 are electrically connected to the detection control portion
14
14
23, which is constituted with an electronic circuit formed on a
flexible substrate (not shown in the drawing), through the cable
21.
The flexible substrate is an electronic substrate having
flexibility. The detection control portion 23 is disposed under
the backlight unit 24. However, the arrangement is not limited
thereto and can be variously changed with the constitution of
the display device 10.
The detection control portion 23 detects, within the region
where the wiring layers 34a and 34b are formed, the position at
which a contacting body (not shown in the drawing) that is a
conductor comes into contact with the electroconductive film 18
from the outside. For example, when the electroconductive film
18 is a capacitance type, the detection control portion 23 is
constituted with an electronic circuit which senses the change
in capacitance between the contacting body and the
electroconductive film 18 that are making contact with or
approaching each other, and detects the contacting position or
the approaching position.
[0026]
The electroconductive film 18 shown in FIG. 2(a) has the
wiring layers 34a and 34b respectively provided on both surfaces
of the transparent substrate 30, but the present invention is
not limited thereto. For example, as an electroconductive film
18a shown in FIG. 3, the electroconductive film of the present
invention may be constituted with a plurality of
electroconductive film elements 19 (19a and 19b) laminated on
each other, the electroconductive film elements 19 respectively
having the wiring layers 34 (34c and 34d) formed only on the
front surfaces 30a of the transparent substrates 30, that is,
each of the electroconductive film elements 19 having the wiring
layer 34 only on one surface of the transparent substrate 30. In
this way, even when the electroconductive film of the present
invention is the electroconductive film 18a in which a plurality
of the electroconductive film elements 19 are laminated on each
15
15
other, the respective wiring layers 34 (34c and 34d) having the
same or similar wiring patterns 35 are the wiring patterns 35
that are the same as or similar to each other as described
above, and the wiring layer 34 (34c or 34d) as an upper layer is
disposed at a displaced position in phase relative to the wiring
layer 34 (34d or 34c) as a lower layer to establish the nested
arrangement.
Specifically, as shown in FIG. 3, all of the wiring layers
34 of the electroconductive elements 19a each positioned kth
from the top (k is an odd number represented by (2n-1), n =
natural number (1, 2, )) are formed of the wiring layers 34c
having the same constitution, while all of the wiring layers 34
of the electroconductive elements 19b each positioned kth from
the top (k is an even number represented by 2n, n = natural
number (1, 2, )) are formed of the wiring layers 34d having the
same constitution. The wiring layers 34c are disposed at a
displaced position in phase relative to the wiring layers 34d
such that each of the thin metal wires 32 of the even-numbered
wiring layers 34d is positioned between two adjacent thin metal
wires 32 of the odd-numbered wiring layers 34c, preferably
positioned in the middle between two adjacent thin metal wires
32. That is, the wiring layers 34d are disposed at a displaced
position in phase relative to the wiring layers 34c in the same
manner.
[0027]
The wiring layers 34, that is, the wiring layer 34c and the
wiring layer 34d have the same constitution as the wiring layer
34a and the wiring layer 34b, respectively. Therefore, detailed
description thereof will be omitted.
The number of the wiring layers 34 laminated is not
particularly limited regardless of which is used, the
electroconductive film 18 in which the wiring layer 34a and the
wiring layer 34b are formed on both surfaces of the transparent
substrate 30 or the electroconductive film 18a obtained by
laminating the electroconductive film elements 19 (19a and 19b)
16
16
each having the wiring layer 34 formed only on one surface of
the transparent substrate 30. The number of the wiring layers 34
laminated is appropriately selected according to the
specification required for a touch sensor or a touch panel.
The electroconductive films 18 and 18a may be either of a
capacitance type or of a resistive film type. Alternatively, the
combination of a capacitance type and a resistive film type may
be employed.
In the following description, the electroconductive film 18
will be mainly described as a typical example. However, needless
to say, the description can be applied to the electroconductive
film 18a.
[0028]
As described above, the display unit 14 has, for example,
the backlight unit 24 and the liquid crystal display cell 26.
As the backlight unit 24, known backlights compatible with
the liquid crystal display cell 26 can be appropriately used.
Needless to say, the backlight is not limited to an edge light
type (side light type or light guide plate type) ones and may be
of a direct type.
Also as the liquid crystal display cell 26, any of known
liquid crystal display cells can be used as long as it is used
as a display panel of the display unit 14 and includes a
predetermined pixel array pattern. The display panel used in the
present invention is not limited to the liquid crystal display
cell 26, and display panels such as a plasma display panel
(PDP), an organic electroluminescence display panel (OELD), and
an inorganic electroluminescence display panel can be used. As
the backlight unit 24, backlights compatible with the display
panel for use can be appropriately used. Accordingly, depending
on the type of the display panel, the backlight unit 24 may not
be necessarily provided.
[0029]
FIG. 4 is a schematic view showing an example of a pixel
array pattern of a part of a liquid crystal display cell to
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17
which the electroconductive film of the present invention is
applied.
In the liquid crystal display cell 26 partially shown in
FIG. 4, a plurality of pixels 40 are arrayed in the form of
matrix and constitutes a predetermined pixel array pattern. A
single pixel 40 is constituted with three sub-pixels (a red subpixel
40r, a green sub-pixel 40g, and a blue sub-pixel 40b) that
are arrayed in the horizontal direction. A single sub-pixel has
a rectangular shape that is long in the vertical direction. An
array pitch of the horizontal direction (horizontal pixel pitch
Ph) of the pixels 40 is approximately the same as an array pitch
in the vertical direction (vertical pixel pitch Pv) of the
pixels 40. That is, a single pixel 40 and a black matrix (BM) 42
surrounding the single pixel 40 form a square shape (see a
shaded area 44). The aspect ratio of a single pixel 40 is not 1
and satisfies the relation of length in the horizontal
(crosswise) direction > length in the vertical (lengthwise)
direction.
[0030]
As is evident from FIG. 4, the pixel array pattern
constituted with the plurality of pixels 40 each including the
red sub-pixel 40r, the green sub-pixel 40g, and the blue subpixel
40b is defined by a BM pattern 46 of the BM 42 surrounding
each of the red sub-pixel 40r, the green sub-pixel 40g, and the
blue sub-pixel 40b, and the moire occurring when the
electroconductive film 18 is superimposed on the liquid crystal
display cell 26 is caused by the interference between the BM
pattern 46 of the BM 42 of the liquid crystal display cell 26
and the wiring layer 34 of the electroconductive film 18.
Accordingly, although in a strict sense, the BM pattern 46 is an
inverted pattern of the pixel array pattern, in the present
Description, the BM pattern 46 is regarded as representing the
same pattern as the pixel array pattern.
[0031]
For example, when the electroconductive film 18 is disposed
18
18
on the liquid crystal display cell 26 having the BM pattern 46
constituted with the BM 42 of the liquid crystal display cell
26, the wiring layers 34a and 34b of the electroconductive film
18 are optimized in terms of the moire visibility with respect
to the BM pattern 46 such that the moire visibility does not
depend on the change of the viewing angle. Therefore, even when
the viewing angle is changed as described later, there is
practically no interference in the spatial frequency between an
array period of the pixels 40 and a wiring array period of the
thin metal wires 32 of the electroconductive film 18 or 18a, and
thus the occurrence of moire is inhibited.
The aforementioned electroconductive films 18 and 18a of
the present invention are applied to, for example, the touch
sensor 12 of the liquid crystal display cell 26 of the display
unit 14 schematically shown in FIG. 1, and each have the wiring
pattern 35 that has been optimized in terms of the moire
visibility with respect to the pixel array pattern of the
display unit 14, and thus, with respect to the BM (black matrix)
pattern 46 such that the moire visibility does not depend on the
viewing angle (observation angle) with respect to the liquid
crystal display cell 26 of the display unit 14. In the present
invention, the wiring pattern that has been optimized in terms
of the moire visibility with respect to the BM (pixel array)
pattern refers to one, two, or more groups of wiring patterns
with which moire occurring with respect to a predetermined BM
pattern is not visually recognized by a human being even when
the viewing angle is changed.
The display device 10 and the electroconductive films 18
and 18a of the present embodiment are basically constituted as
above.
[0032]
Hereinafter, the evaluation of the moire visibility of the
wiring pattern of the electroconductive film with respect to a
predetermined BM pattern of the display device and the
optimization of the wiring pattern leading to the moire
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visibility which does not depend on the viewing angle
(observation angle) in the present invention will be described.
That is, in the electroconductive film of the present invention,
the wiring pattern optimized such that the moire occurring with
respect to a predetermined BM pattern of a display device is not
visually recognized by a human being even when the viewing angle
is changed and a procedure of determining the optimized wiring
pattern will be described.
Herein, the explanation will be made on the optimization of
the moire visibility of the wiring pattern with respect to a
predetermined BM pattern, the optimization not depending on the
viewing angle; that is, the reduction of the occurrence of moire
caused by the interference between the BM pattern and the wiring
pattern, to be achieved without depending on the viewing angle
(observation angle). Before that, the relationship between the
wiring pattern of the electroconductive film and the viewing
angle will be described first.
[0033]
FIG. 5 is a schematic view showing an example of different
wiring pattern images formed in the electroconductive film shown
in FIG. 2(a) according to different viewing angles.
As shown in the drawing, when the viewing angle  is zero (
= 0), that is, when the wiring pattern is viewed from a
direction perpendicular to the front surface 30a of the
transparent substrate 30, the wiring patterns 35 of the wiring
layers 34a and 34b of the electroconductive film 18 are observed
as a pattern that is projected in the form of a synthetic wiring
pattern image 54 on a plane 50 parallel to the front surface 30a
of the transparent substrate 30.
In contrast, when the viewing angle  is not zero (  0),
that is, when the wiring pattern is viewed from a direction
inclined by a predetermined angle  with respect to the direction
perpendicular to the front surface 30a of the transparent
substrate 30, the wiring layers 34a and 34b of the
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20
electroconductive film 18 are projected in the form of a
synthetic wiring pattern image 56 on a plane 52 inclined by the
angle  with respect to the plane 50.
Herein, in the synthetic wiring pattern image 54 formed on
the plane 50 and the synthetic wiring pattern image 56 formed on
the plane 52, white marks represent projection images resulting
from the thin metal wires 32 forming the wiring pattern 35 of
the wiring layer 34a on the front side, that is, the observing
side, and black marks represent projection images resulting from
the thin metal wires 32 forming the wiring pattern 35 of the
wiring layer 34b on the rear side.
[0034]
In the electroconductive film 18, the wiring layers 34a and
34b have the same wiring pattern 35, and the wiring patterns 35
of the wiring layers 34a and 34b have the same pitch P1.
Consequentially, when the synthetic wiring pattern image 54 is
compared with the synthetic wiring pattern image 56, in the
synthetic wiring pattern image 54, pitches (an interval between
adjacent white marks and an interval between adjacent black
marks) P1a of the projection images of the wiring patterns 35 of
the wiring layers 34a and 34b are the same as the pitch P1 (P1a
= P1) and do not change from the pitch P1, whereas in the
synthetic wiring pattern image 56, because the viewing angle  is
not zero (for example, 0 <  < /2), pitches P1b of the
projection images of the wiring patterns 35 of the wiring layers
34a and 34b are represented by P1cos (P1b = P1cos) with the
relationship of 0 < cos < 1 (0 <  < /2) being established,
whereby the pitches P1b are smaller than P1 (P1b = P1cos < P1).
[0035]
Because the wiring pattern 35 of the wiring layer 34a and
the wiring pattern 35 of the wiring layer 34b are displaced in
phase from each other by 1/2 pitch, a pitch (phase difference)
P2 between the wiring patterns 35 is to be P1/2 (P2 = P1/2).
Accordingly, in the synthetic wiring pattern image 54, pitches
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21
(intervals between adjacent white mark and black mark) P2a of
the projection images of the wiring patterns 35 of the wiring
layers 34a and 34b exhibit the same phase difference F and do
not change from the pitch P2, whereas in the synthetic wiring
pattern image 56, because the viewing angle  is not zero (for
example, 0 <  < /2), the synthetic wiring pattern image is
influenced by the transparent substrate 30 of the
electroconductive film 18 and therefore, a pitch P2b and a pitch
P2c of the projection images of the wiring patterns 35 of the
wiring layers 34a and 34b are represented by P2cos - dsin (P2b
= P2cos - dsin) and P2cos + dsin (P2c = P2cos + dsin)
(absolute value), respectively, with the thickness of the
transparent substrate 30 being d. That is, while the pitch P2b
is smaller than P2 (P2b < P2), the pitch P2c is greater than P2
(P2c > P2). In other words, a phase difference of dsin that
depends on the thickness d of the transparent substrate 30
arises between the projection images of the wiring patterns 35
of the wiring layers 34a and 34b.
[0036]
Consequentially, as described later, in the synthetic
wiring pattern image 54, the wiring pitch is an equal pitch (see
FIG. 7(a)). In contrast, in the synthetic wiring pattern image
56, a wiring pattern in which adjacent wiring pitches are not
equal to each other is repeated (see FIG. 8(a)).
This is because the wiring pattern is observed from the
direction (viewing angle ) inclined from the front (viewing
angle = 0), and thus the synthetic wiring pattern image is
influenced by the thickness d of the transparent substrate 30.
In this way, due to the viewing angle , the synthetic wiring
pattern image 56 of the wiring layers 34a and 34b is influenced
by the thickness d of the transparent substrate 30. Note that in
FIG. 5, in order to clearly show the thin metal wires 32
constituting the wiring pattern 35, the thickness of the thin
metal wires 32 is emphasized relative to the thickness of the
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22
transparent substrate 30. However, because the thickness of the
thin metal wires 32 is negligible compared to the thickness of
the transparent substrate 30, the thickness d of the transparent
substrate 30 is described as including the thickness of the thin
metal wires 32 constituting the wiring pattern 35.
[0037]
The visibility of moire is determined from the frequency
and the intensity of moire occurring due to the interference
between two patterns. Specifically, two dimensional Fourier
spectra (2DFFTSp) of pattern data of two patterns are
calculated; and from each of the two-dimensional Fourier spectra
of two patterns, one spectral peak is selected; and the
visibility of moire is determined based on the frequency of
moire given by a (spatial) frequency difference between the two
spectral peaks, that is, by a relative distance between the
spectral peaks on spatial frequency coordinates, and the
intensity of moire given by a product of peak intensities of the
two spectral peaks.
Meanwhile, in the image (spatial frequency coordinates) of
the two-dimensional Fourier spectrum (2DFFTSp) showing the
spatial frequency characteristics of a pattern, spectral peaks
appear in the form of reciprocals of the pitch of the pattern.
Accordingly, in order to predict visually-recognizable moire
that occurs due to the interference between the BM pattern of
the liquid crystal display cell 26 and the wiring pattern of the
wiring layer 34 of the electroconductive film 18, only the pitch
(m) of the BM pattern and the pitch (m) of the wiring pattern
of the wiring layer are needed.
[0038]
As described above, the visibility of moire is determined
by the frequency and the intensity of the moire. However, even
when the moire has a frequency at the level of visuallyrecognizable
moire, if the intensity of the moire is not at the
level of visually-recognizable moire, the moire is not visually
recognized in practice. Furthermore, even when the intensity is
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23
enough, if the frequency of the moire is not at the level of
visually-recognizable moire, the moire is not visually
recognized.
Therefore, normally, from the viewpoint of optimizing the
visibility of moire, the intensity of moire should be considered
as described above. However, when the visually-recognizable
moire that occurs due to the interference between the BM pattern
and the wiring pattern is considered, and when considered is the
moire that depends on the angle at which the BM pattern, i.e.,
the display screen of the liquid crystal display cell 26 is
observed, that is, depends on the viewing angle, it is difficult
to define the intensity of the moire with the viewing angle. The
reason is as follows. As described above, provided that the
pitch of the projection image of the wiring pattern 35 of each
of the wiring layers 34a and 34b is equal to the pitch P1 of the
wiring pattern 35, if the viewing angle  is changed, the pitch
of the projection image is changed according to P1cos with the
viewing angle  as a parameter. In addition, the phase of the
wiring pattern 35 of one of the wiring layers, e.g., the wiring
layer 34b, with respect to the wiring pattern 35 of the other of
the wiring layers, e.g., the wiring layer 34a, is changed
according to dsin with the thickness d of the transparent
substrate 30 and the viewing angle  as parameters. As a result,
the peak frequency and the peak intensity obtained from the
spectral peaks are changed, and thus the frequency and the
intensity of the moire also varies. Herein,  represents a
viewing angle, and as shown in FIG. 5,  of the front direction
is 0.
For the aforementioned reason, in the present invention,
moire is predicted by using only the frequency.
[0039]
In order to obtain the peak frequencies used for the 2DFFT
(two-dimensional fast Fourier transform) processing, for
calculating peaks, frequency peaks (peak frequencies) are
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24
obtained from the basic frequencies of the BM pattern 46 and the
wiring pattern of the wiring layer 34. This is because the data
used for the 2DFFT processing is in the form of a discrete
value, and thus the peak frequencies (frequencies of spectral
peaks) of the two-dimensional Fourier spectra depend on the
reciprocal of the image size. As shown in FIG. 6, the positions
of the frequency peaks (positions of the spectral peaks) of the
two-dimensional Fourier spectra can be expressed in the form of
a combination of bars a and b which are independent twodimensional
basic frequency vector components. Accordingly,
naturally, the obtained peak positions form a lattice shape.
Although FIG. 6 is a graph showing frequency peak positions of
the wiring layer 34, the frequency peak positions of the BM
pattern 46 can also be determined in the same manner as used for
the wiring layer 34.
[0040]
For example, the synthetic wiring pattern image 54 of the
wiring layers 34a and 34b shown in FIG. 7(a) that was obtained
by front observation (viewing angle = 0) was subjected to twodimensional
Fourier transform, and a two-dimensional Fourier
spectrum was obtained. In this way, the spatial frequency
characteristics (FFT image) of the synthetic wiring pattern
image 54 of the wiring layers 34a and 34b were obtained. The
result is shown in FIG 7(b).
Furthermore, the synthetic wiring pattern image 56 of the
wiring layers 34a and 34b shown in FIG. 8(a) that was obtained
by oblique observation (viewing angle  0) was subjected to twodimensional
Fourier transform, and a two-dimensional Fourier
spectrum was obtained. In this way, the spatial frequency
characteristics (FFT image) of the synthetic wiring pattern
image 56 of the wiring layers 34a and 34b were obtained. The
result is shown in FIG. 8(b).
Herein, as shown in FIG. 5, the pitch P1b of the synthetic
wiring pattern image 56 at the time of oblique observation
(viewing angle  0) is smaller than the pitch P1a of the
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25
synthetic wiring pattern image 54 at the time of front
observation (viewing angle = 0) in accordance with the
observation direction. For obtaining the spatial frequency
characteristics (FFT image) of the synthetic wiring pattern
image 56 at the time of oblique observation (viewing angle  0),
the pitch P1b of the synthetic wiring pattern image 56 at the
time of oblique observation is widened such that the pitch P1b
is the same as the pitch P1a at the time of front observation,
which will be described later in detail.
[0041]
As described above, in the image obtained by oblique
observation (see FIG. 8(a)), the wiring pattern in which
adjacent wiring pitches are not equal to each other is repeated,
unlike in the image obtained by front observation (see FIG.
7(a)) in which the wiring pitch is an equal pitch.
Therefore, the peak interval between spectral peaks is
smaller in the FFT image obtained by oblique observation (see
FIG. 8(b)) than in the FFT image obtained by front observation
(see FIG. 7(b)). Accordingly, when the wiring pattern is
superimposed on the BM pattern, the image quality deteriorates
in accordance with the viewing angle.
[0042]
In the FFT images (on the spatial frequency coordinates)
shown in FIGS. 7(b) and 8(b), the white points and the grey
points in the black ground represent spectral peaks. The
concentrations of the white points and the grey points depend on
the peak intensity of the spectral peaks. However, for
optimization of the visibility of moire in the present
invention, the peak intensity is not considered, and the peak
frequencies of the spectral peaks are used. Accordingly, the
peak positions on the spatial frequency coordinates are
represented by the white points and the grey points.
For obtaining peak frequencies of spectral peaks of the
wiring pattern (synthetic wiring pattern) and the BM pattern,
for example, only the peaks which show the intensity equal to or
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26
greater than a specific degree when the frequency
characteristics (peak frequency and peak intensity) of each of
the patterns are convolved with the standard visual response
characteristics of human beings, may be selected in advance. By
doing so, only the difference between the selected peaks is
obtained, and accordingly, the time taken for calculation can be
shortened.
[0043]
In order to prevent the image quality from deteriorating in
accordance with the viewing angle when the wiring pattern is
superimposed on the BM pattern, the image quality of the wiring
pattern designed for viewing from the front in the wiring layer
needs to avoid deteriorating in accordance with the viewing
angle. In order to satisfy the aforementioned condition, when
the frequency characteristics of the wiring pattern of the
wiring layer designed for viewing from the front (synthetic
wiring pattern image 54 (see FIG. 5)) are compared with the
frequency characteristics of the wiring pattern of the wiring
layer resulting from the phase difference (synthetic wiring
pattern image 56 (see FIG. 5)), the condition needs to be
satisfied, as follows: image quality in front viewing  image
quality depending on the viewing angle. That is, the frequency
of moire observed from the front and the frequency of moire
obliquely observed and varying depending on the viewing angle
needs to be predicted.
When a plurality of layers of wiring patterns of the wiring
layers are laminated on each other as shown in FIG. 3, it is
premised that the wiring layers 34 (34c and 34d) are in the
nested arrangement as described above with k = 1 (the first
layer) and K = 2 (the second layer), and the synthetic wiring
pattern image 54 has a single frequency at the time of front
observation.
Herein, considering the variation in manufacturing, even
when an error of about 5% occurs in wiring patterns of wiring
layers, the wiring patterns are regarded as having a
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27
substantially constant regular pattern.
[0044]
When a plurality of wiring layers having the wiring
patterns are laminated on each other, from the viewpoint of
improving transmittance, the wiring layers 34 (34c and 34d) are
disposed at a displaced position in phase relative to each other
with k = 2n and k = 2n + 1, similarly to the wiring layers 34a
and 34b, and in the nested arrangement as described above.
Herein, all of the wiring patterns of the wiring layers
have an equal pitch. That is, the interval between adjacent thin
metal wires 32 are the same. In the present invention, it is
premised that each of the thin metal wires 32 of the wiring
layer as a lower layer is positioned in the pitch between the
thin metal wires 32 of the wiring layer as an uppermost layer.
In the example illustrated in FIG. 3, a thin metal wire 32 of
the second wiring layer 34 is disposed between two thin metal
wires 32 from the left of the uppermost wiring layer 34.
Likewise, also in the case of the third wiring layer 34 and the
following layers disposed thereunder, a thin metal wire 32 of a
wiring layer 34 is disposed between two thin metal wires 32 from
the left of the uppermost wiring layer 34. Even when the number
of the layers laminated is increased, each of the thin metal
wires 32 of the wiring layers as lower layers is positioned in
the pitch between adjacent two thin metal wires 32 of the wiring
layer as the uppermost layer.
[0045]
In order to predict the frequency characteristics of the
wiring patterns (see the synthetic wiring pattern image 56) of
the wiring layers 34 in consideration of up to kth wiring layer
34 in accordance with the viewing angle based on the
aforementioned premise, provided that a basic frequency (a
frequency of a lowest peak frequency component) of the wiring
pattern (see the synthetic wiring pattern image 54) constituted
with the wiring layers 34 with k = 1 and k = 2 is f1, the wiring
pattern needs to be designed in consideration of f1/2 from the
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28
repeating patterns formed in the wiring layers 34 with k = 1 and
k = 2. For example, when k = 2, the frequency characteristics of
front viewing is f1, and the frequency characteristics depending
on the viewing angle is f1/2. That is, the frequency
characteristics depending on the viewing angle are a half of the
frequency characteristics of front viewing.
[0046]
The moire occurring at the time of front observation can be
represented by convolution of the frequency characteristics f1
at the time of the front observation of the wiring pattern of
the wiring layer with the spatial frequency characteristics of
the BM pattern. The frequency of moire that depends on the
viewing angle, that is, the frequency of moire that occurs at
the time of oblique observation can also be represented by
convolution of the frequency characteristics f1/2 of the wiring
pattern of the wiring layer depending on the viewing angle (in
the oblique observation) with the spatial frequency
characteristics of the BM pattern.
Hereinafter, the present invention will be more
specifically described taking the case of k = 2 as an example.
Herein, when k = 2, examples of the constitution include
the electroconductive film 18 shown in FIG. 2(a) that has the
wiring layers 34a and 34b on both surfaces of the single
transparent substrate 30, and the electroconductive film 18a
shown in FIG. 3 that is a laminate of a transparent substrate 30
having on its front surface 30a the wiring layer 34c and another
transparent substrate 30 having on its front surface 30a the
wiring layer 34d.
[0047]
The wiring pattern shown in FIG. 9(a) that is observed from
the front is subjected to the 2DFFT processing to obtain the
two-dimensional Fourier spectrum, whereby the spatial frequency
characteristics (FFT image) shown in FIG. 9(b) can be obtained.
Meanwhile, the obliquely observed wiring pattern shown in
FIG. 10(a) is subjected to the 2DFFT processing to obtain the
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29
two-dimensional Fourier spectrum, whereby the spatial frequency
characteristics (FFT image) shown in FIG. 10(b) can be obtained.
Similarly to the cases of FIGS. 7(b) and 8(b), in FIGS.
9(b) and 10(b), for obtaining the frequency characteristics (FFT
image) of the wiring pattern image at the time of oblique
observation (viewing angle  0), the pitch P1b of the synthetic
wiring pattern image 56 at the time of oblique observation is
widened such that the pitch P1b is equal to the pitch P1a at the
time of front observation, the details of which will be
described later.
[0048]
In the FFT images (on the spatial frequency coordinates)
shown in FIGS. 9(b) and 10(b), the white points and the grey
points in the black ground represent spectral peaks, and the
concentrations of the white points and the grey points depend on
the peak intensity of the spectral peaks. However, for
optimization of the visibility of moire in the present
invention, the peak intensity is not considered, and the peak
frequencies of the spectral peaks are used. Accordingly, the
peak positions on the spatial frequency coordinates are
represented by the white points and the grey points.
Comparing the spatial frequency characteristics shown in
FIG 9(b) that are obtained through front observation with the
spatial frequency characteristics shown in FIG. 10(b) that are
obtained through oblique observation, the peak interval of the
spectral peaks in the FFT image of oblique observation is a half
of the peak interval of the spectral peaks in the FFT image of
front observation. It means that because the viewing angle is
not zero, one of the wiring patterns is displaced in phase from
the other wiring pattern, and thus the period of the wiring
patterns is doubled. This agrees with the aforementioned fact
that the frequency characteristics depending on the viewing
angle is f1/2.
[0049]
The frequency characteristics of the BM pattern are
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30
determined by the constitution of the liquid crystal display
cell 26 and are constant. Therefore, in order to satisfy the
condition of "quality of image observed from the front  quality
of image observed at a viewing angle of not zero," under the
condition that in the two-dimensional Fourier spectra, the
frequency of the BM pattern and the frequency of the wiring
pattern of the wiring layer are considered up to the tenth
order, provided that the lowest frequency of the moire observed
from the front is a first lowest frequency fm1 and the lowest
frequency of the moire observed at a viewing angle of not zero
is a second lowest frequency fm2, the wiring layer needs to have
a wiring pattern that satisfies fm1  fm2.
[0050]
This is because the frequency of the moire visually
recognized from the oblique direction is to be the value
obtained by adding +, which is the increase in peak of the
wiring pattern caused by observing the moire from the oblique
direction, to the frequency of the moire visually recognized
from the front direction. Consequentially, the image quality is
the best when the image is viewed from the front and is always
poorer when the image is viewed from the oblique direction. In
order to suppress the deterioration of image quality to a
maximum extent, it is necessary to make the first lowest
frequency fm1 equal to or lower than the second lowest frequency
fm2. Accordingly, in the present invention, the wiring layer is
configured to satisfy the condition of fm1  fm2. When fm1 =
fm2, the quality of image observed from the oblique direction
does not deteriorate, and "image quality in front viewing" is
equal to "image quality depending on the viewing angle."
[0051]
As shown in FIG. 5, when the viewing angle is not zero, the
pitch P1b of the wiring pattern is smaller than the pitch P1a of
the wiring pattern observed from the front. In the present
invention, under a precondition that the pitch of the wiring
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31
pattern in the case in which the viewing angle is not zero is
the same as the pitch of the wiring pattern observed from the
front, the spatial frequencies of these wiring patterns are
obtained. Therefore, the pitch of the wiring pattern when the
viewing angle is not zero needs to be widened so as to be the
same as the pitch of the wiring pattern observed from the front.
In the BM pattern, when the viewing angle is not zero, the same
issue as with the pitch of the wiring pattern arises.
Accordingly, also in the BM pattern, the pitch is also widened
so as to be the same as the pitch at the time of front
observation.
Hereinafter, the process of widening the pitch of the
wiring pattern when the viewing angle is not zero such that the
pitch becomes the same as the pitch of the wiring pattern
observed from the front is simply referred to as
"standardization."
[0052]
Regarding the standardization, when the viewing angle  is
known beforehand, the standardization can be performed by using
1/cos as a coefficient of viewing angle dependency for the pitch
of the wiring pattern at the time of oblique observation. In
this case, also for the BM pattern, the use of 1/cos can make
the pitch the same as the pitch at the time of front
observation.
In addition, the standardization can also be performed by
using the BM pattern in the following manner.
For example, when the BM pattern assumes a square when
viewed from the front and assumes a rectangle when viewed from
the oblique direction, a coefficient (enlargement ratio) is
calculated for use in enlarging the rectangle to be the square
at the time of front observation. The standardization can be
performed using the coefficient. Likewise, also for the BM
pattern, the use of the coefficient can make the pitch the same
as the pitch at the time of front observation in the same manner
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32
as used for the pitch of the wiring pattern. The standardization
method is not limited to the aforementioned methods as long as
the standardization is accomplished.
[0053]
In the aforementioned precondition, the spatial frequency
when the viewing angle is not zero includes the spatial
frequency at the time of front observation. This point will be
specifically described below.
When FIG. 7(b) and FIG. 8(b) are superimposed on each
other, the spectral peaks of FIG. 7(b) completely overlap the
spectral peaks of FIG. 8(b). This is because under the
aforementioned precondition, the repetition period of the wiring
pattern observed at a viewing angle of not zero is a twice as
long as the repetition period of the wiring pattern observed
from the front. As a result, the frequency peaks of the wiring
pattern observed at a viewing angle of not zero appear at an
interval which is a half of the interval of the frequency peaks
of the wiring pattern observed from the front, and thus the
spectral peaks completely overlap with each other.
Consequentially, the spectral peaks of FIG. 7(b) includes all of
the positions of the spectral peaks of FIG. 8(b).
As described above, the frequency of moire is given by the
difference in spatial frequency between the peaks of the wiring
pattern and the peaks of the BM pattern (relative distance
between peaks on the spatial frequency coordinates). Therefore,
the frequency of the moire visually recognized from the oblique
direction is to be a value obtained by adding +, which is the
increase in peak of the wiring pattern caused by observing the
moire from the oblique direction, to the frequency of the moire
visually recognized from the front direction.
[0054]
FIGS. 11(a) and 11(b) respectively show an exemplary front
observation image and an exemplary oblique observation image in
the invention, each exhibiting the combination of the wiring
pattern and the BM pattern satisfying a spatial frequency
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33
condition of moire, fm1  fm2, of the invention.
FIGS. 12(a) and 12(b) respectively show an exemplary front
observation image and an exemplary oblique observation image in
a comparative example, with the condition of fm1  fm2, which is
the spatial frequency condition of moire of the present
invention, being not satisfied.
In the examples of the present invention shown in FIGS.
11(a) and 11(b) that satisfy fm1  fm2, even when the observation
direction is changed from the front direction to the oblique
direction, low-frequency moire does not newly occur although in
the figures, the wiring patterns are emphasized for the purpose
of showing the change in the wiring patterns caused with the
change in the observation direction from the front direction to
the oblique direction.
In contrast, as is evident from the comparative examples
shown in FIGS. 12(a) and 12(b) that do not satisfy fm1  fm2,
moire is not visually recognized at all when the observation
direction is the front direction, but when the observation
direction is the oblique direction, low-frequency moire newly
occurs as indicated by arrows in FIG. 12(b).
As described above, it is evident that when the spatial
frequency condition of moire of fm1  fm2 is satisfied in the
present invention, the occurrence of moire can be reduced.
[0055]
In the present invention, in order to calculate the
frequency of moire, for both the BM pattern and the wiring
pattern, the frequencies of two-dimensional Fourier spectra up
to the tenth order (up to the tenth order peak frequency) are
used. This is because the present inventor has a rule of thumb
in which by using the frequencies of two-dimensional Fourier
spectra up to the tenth order, substantially all of visuallyrecognizable
moire is included. That is, the peak intensity of
the two-dimensional Fourier spctra of a term of the eleventh or
higher order is ignorable since it does not lead to visually-
34
34
recognizable moire.
Herein, the visually-recognizable moire refers to the moire
having an intensity of, for example, equal to or greater than -
4.0 in terms of a common logarithm (equal to or greater than 10-4
in terms of an antilogarithm).
[0056]
Accordingly, in the display device 10 and the
electroconductive film 18, when the wiring layers 34a and 34b
laminated on each other satisfy fm1  fm2 as described above,
even in the case in which the electroconductive film 18 is
superimposed on the BM pattern 46 of the liquid crystal display
cell 26, it is possible to reduce the occurrence of moire
resulting from the interference between the wiring pattern 35 of
the electroconductive film 18 and the BM pattern 46 of the
liquid crystal display cell 26, regardless of the viewing angle.
As a result, in the display device 10, the quality of an image
observed from the oblique direction can be improved, and the
overall image quality including the viewing angle and the like
can be further improved.
[0057]
Next, the procedure of determining a wiring pattern, which
can reduce the occurrence of moire regardless of the viewing
angle in the electroconductive film 18 superimposed on the
liquid crystal display cell 26 of the display device 10 will be
described.
FIG. 13 is a flowchart showing an example of a
determination method of the wiring pattern of the wiring layer
of the electroconductive film of the present invention.
[0058]
In the determination method of the wiring pattern of the
wiring layer of the electroconductive film of the present
invention, the BM pattern 46 of the liquid crystal display cell
26 of the display device 10 and the wiring pattern 35 of the
wiring layers 34a and 34b of the electroconductive film 18 are
subjected to frequency analysis by using two-dimensional fast
35
35
Fourier transform (2DFFT); from the moire frequencies given as a
difference between the peak frequencies of both patterns
(relative distance between peak positions) from the spatial
frequency characteristics of the respective patterns obtained by
the frequency analysis, the lowest frequencies of the moire are
calculated; and by using the calculated lowest frequencies of
the moire, the wiring pattern of the wiring layer capable of
reducing the moire occurrence regardless of the viewing angle is
determined. For calculating the frequency of moire, FFT is
generally used. However, because the frequency of an object
greatly varies depending on the usage of the FFT, the procedure
is specified as below.
[0059]
In the determination method, first, as Procedure 1, pieces
of transmittance image data of the BM pattern and the wiring
patterns of the wiring layers are created. That is, as shown in
FIG. 13, in Step S10, a piece of transmittance image data of the
BM pattern 46 (BM 42) (see FIG. 4) of the liquid crystal display
cell 26 of the display device 10 shown in FIG. 5 and pieces of
transmittance image data of the wiring patterns of the wiring
layers 34a and 34b (thin metal wires 32) (see FIG. 14(b)) of the
electroconductive film 18 are created and obtained.
In this case, regarding the wiring layers 34a and 34b, for
the synthetic wiring pattern when the viewing angle is zero,
that is, in the case of front observation, and for the synthetic
wiring pattern when the viewing angle is not zero, that is, in
the case of oblique observation, separate pieces of
transmittance image data are created.
In the present embodiment, a key point is how accurately
the frequency is extracted from the two-dimensional Fourier
spectra. Therefore, the pieces of transmittance image data of
the BM pattern and the wiring patterns of the wiring layers are
created using the periodic boundary condition.
Herein, when the pieces of transmittance image data of the
BM pattern 46 and the wiring patterns of the wiring layers 34a
36
36
and 34b (including both the cases in which the viewing angle is
zero and not zero) are prepared or stored beforehand, the
transmittance image data may be acquired from the prepared or
stored data.
[0060]
As shown in, for example, FIG. 14(a) and FIG. 14(c) which
is a partially enlarged view of the region H of FIG. 14(a), the
BM pattern 46 of the liquid crystal display cell 26 can be in
the form of a pattern in which a single pixel 40 is an RGB color
pixel constituted with the red sub-pixel 40r, the green subpixel
40g, and the blue sub-pixel 40b. However, when a single
color is used, for example, when only the green sub-pixel 40g of
G channel is used, the transmittance image data of R and B
channels is preferably set to be 0. In the present invention,
the image data of the BM 42, that is, the transmittance image
data of the BM pattern 46 is not limited to the pattern shown in
FIG. 14(a) in which the BM 42 has rectangular openings (the red
sub-pixels 40r, the green sub-pixels 40g, and the blue subpixels
40b). A usable BM pattern may not have rectangular
openings, or a BM pattern having BM openings of any shape may be
designated and used. For example, the opening is not limited to
a simple rectangular shape, and may have an intricately
doglegged shape or a hook-like shape.
[0061]
Meanwhile, in the wiring layers 34a and 34b of the
electroconductive film 18, for example, as shown in FIG. 14(b),
the wiring pattern 35 is in a square lattice shape in which the
thin metal wires 32 forming the wiring are inclined by 45. The
wiring layer 34a is disposed on the front surface (not shown in
the drawing) of the transparent substrate 30 (not shown in the
drawing), and the wiring layer 34b is disposed on the rear
surface (not shown in the drawing) of the transparent substrate
30 (not shown in the drawing).
Herein, the size of the transmittance image data of the BM
pattern 46 and the wiring patterns of the wiring layers 34a and
37
37
34b is not particularly limited as long as the transmittance
image data of the BM pattern 46 and the wiring patterns of the
wiring layers 34a and 34b can be taken out based on a certain
period by using the periodic boundary condition. Herein, the
phrase "based on a certain period" refers to the state in which
the image is repeated on a period basis and for example, in the
case of the wiring patterns of the wiring layers 34a and 34b,
refers to the state shown in FIG. 9(a). As described above, when
the transmittance image data can be taken out based on a certain
period by using the periodic boundary condition, the image is
repeated on a period basis, and thus folding processing or
flipping processing is not necessary.
[0062]
Thereafter, as Procedure 2, each piece of the transmittance
image data created in Procedure 1 is subjected to twodimensional
fast Fourier transform (2DFFT (base 2)). That is, as
shown in FIG. 13, in Step S12, the respective pieces of
transmittance image data of the BM pattern 46 and the wiring
layers 34 created in Step S10 are subjected to 2DFFT (base 2).
Then, from the two-dimensional Fourier spectra of the respective
pieces of transmittance image data of the BM pattern 46 and the
wiring layers 34, peak frequencies of a plurality of spectral
peaks are calculated.
[0063]
FIG. 15 is a view showing the spatial frequency
characteristics of the two-dimensional Fourier spectrum of the
transmittance image data of the BM pattern. In FIG. 15, the
white portions represent the spectral peaks of the BM pattern
46. From the results shown in FIG. 15, the peak frequencies of
the spectral peaks are calculated for the BM pattern 46. That
is, the positions of the spectral peaks of the two-dimensional
Fourier spectrum of the BM pattern 46 shown in FIG. 15 on
frequency coordinates, in other words, the peak positions
represent peak frequencies. The intensities of the twodimensional
Fourier spectrum at the peak positions represent the
38
38
peak intensities.
Regarding the wiring layers 34a and 34b, for example, when
the viewing angle is zero, that is, when the wiring pattern is
observed from the front, the spatial frequency characteristics
of the two-dimensional Fourier spectrum shown in FIG. 9(b) are
used. When the viewing angle is not zero, that is, when the
wiring pattern is obliquely observed, the spatial frequency
characteristics of the two-dimensional Fourier spectrum shown in
FIG. 10(b) are used.
[0064]
The frequencies of the respective spectral peaks of the BM
pattern 46 and the wiring layers 34a and 34b are calculated and
obtained in the following manner.
The peak frequencies of the BM pattern 46 and the wiring
patterns of the wiring layers 34a and 34b can be obtained in the
aforementioned manner.
[0065]
Next, as Procedure 3, frequency information on moire is
calculated. That is, as shown in FIG. 13, in Step S14, from the
difference of the peak frequencies of the respective twodimensional
Fourier spectra of the BM pattern 46 and the wiring
layers 34a and 34b as calculated in Step S12, a large number of
moire frequencies are calculated as frequency information on the
moire. In the present invention, for the peak frequencies of the
two-dimensional Fourier spectra, it is preferable to use
frequencies up to the tenth order based on the aforementioned
rule of thumb in which substantially all of visuallyrecognizable
moire can be included by using frequencies up to
the tenth order.
In the real space, the moire originally occurs by the
multiplication of the transmittance image data of the wiring
patterns of the wiring layers 34a and 34b and the transmittance
image data of the BM pattern 46 and accordingly, in the
frequency space, convolution integral of these pieces of
transmittance image data is performed. As a result, the moire
39
39
frequencies between the BM pattern 46 and the wiring layers 34a
and 34b observed from the front are obtained, and the moire
frequencies between the BM pattern 46 and the wiring layers 34a
and 34b when the viewing angle is not zero are obtained.
[0066]
Subsequently, as Procedure 4, viewing angle characteristics
of the moire are determined.
Specifically, first, as shown in FIG. 13, in Step S16, by
using the frequency information on the moire that has been
obtained in Step S14, the lowest frequency is calculated from a
large number of moire frequencies of the BM pattern 46 and the
synthetic wiring pattern of the wiring layers 34a and 34b
observed from the front. This lowest frequency is taken as the
first lowest frequency fm1.
Then, from a large number of moire frequencies of the BM
pattern 46 and the synthetic wiring pattern of the wiring layers
34a and 34b when the viewing angle is not zero, the lowest
frequency is calculated. This lowest frequency is taken as the
second lowest frequency fm2.
[0067]
Thereafter, in Step S18, the first lowest frequency fm1 is
compared with the second lowest frequency fm2.
When the first lowest frequency fm1 is equal to or lower
than the second lowest frequency fm2, that is, the condition of
fm1  fm2 is satisfied, the wiring pattern of the wiring layer is
determined (Step S22).
In contrast, when the first lowest frequency fm1 is not
equal to or lower than the second lowest frequency fm2, that is,
the condition of fm1  fm2 is not satisfied, the transmittance
image data of the wiring pattern of the wiring layer is updated
(Step S20), and then the process returns to Step S12.
Herein, the new wiring pattern of the wiring layer provided
at the update may be prepared beforehand or newly created. In
the case of newly creating the wiring pattern, any one or more
among the rotation angle, the pitch, and the pattern width of
40
40
the transmittance image data of the wiring pattern of the wiring
layer may be changed, or the shape or the size of the openings
of the wiring pattern of the wiring layer may be changed.
Alternatively, these may be combined as appropriate.
[0068]
Then, the Step S12 for calculating peak frequencies, Step
S14 for calculating the frequency information on moire, Step S16
for calculating the first lowest frequency fm1 and the second
lowest frequency fm2, Step S18 for comparing the first lowest
frequency fm1 with the second lowest frequency fm2, and Step S20
for updating the transmittance image data of the wiring pattern
of the wiring layer are repeated until the condition of fm1  fm2
is satisfied.
In this way, the determination method of the wiring pattern
of the wiring layer of the electroconductive film of the present
invention ends. Thus, the determination method makes it possible
to obtain the electroconductive film of the present invention
having a wiring pattern with which the occurrence of moire is
inhibited when the wiring pattern is superimposed on the BM
pattern of a display unit of a display device and even when the
viewing angle is not zero. It is also possible to obtain the
touch sensor 12 (touch panel) and the display device 10 each of
which is provided with the electroconductive film 18 having the
aforementioned wiring pattern.
[0069]
The present invention is basically constituted as above. Up
to now, the electroconductive film of the present invention and
the touch panel and the display device which are provided with
the electroconductive film of the present invention have been
specifically described. However, the present invention is not
limited to the aforementioned embodiments. Needless to say,
within a scope that does not depart from the gist of the present
invention, modification or alteration can be performed in
various ways.
DESCRIPTION OF SYMBOLS
41
41
[0070]
10: DISPLAY DEVICE
12: TOUCH SENSOR
14: DISPLAY UNIT
16: FIRST ADHESIVE LAYER
18: ELECTROCONDUCTIVE FILM
19, 19a, 19b: ELECTROCONDUCTIVE FILM ELEMENT
20: SECOND ADHESIVE LAYER
21: CABLE
22: PROTECTIVE LAYER
23: DETECTION CONTROL PORTION
24: BACKLIGHT UNIT
26: LIQUID CRYSTAL DISPLAY CELL
30: TRANSPARENT SUBSTRATE
34, 34a, 34b, 34c, 34d: WIRING LAYER
35: WIRING PATTERN
40: PIXEL
42: BLACK MATRIX (BM)
46: BM PATTERN
54, 56: SYNTHETIC WIRING PATTERN IMAGE

CLAIMS
An electroconductive film installed on a display unit of a
display device, comprising:
one or two or more transparent substrates; and
two or more wiring layers that are formed on both surfaces
of the one transparent substrate or are each formed on one
surface of each of the two or more transparent substrates, are
disposed in a form of a laminate, and are regularly arranged,
wherein wiring patterns of the two or more wiring layers
are superimposed on a pixel array pattern of the display unit,
and a wiring pattern of a wiring layer as a lower layer is
disposed at a displaced position in phase relative to a wiring
pattern of a wiring layer as an upper layer, and
wherein the electroconductive film satisfies:
fm1 ≤ fm2
provided that among spatial frequencies of moire as
obtained by convolution of spatial frequency characteristics of
the wiring patterns of the two or more wiring layers and spatial
frequency characteristics of the pixel array pattern of the
display unit, a lowest frequency is set to a first lowest
frequency fm1, and among spatial frequencies of moire as
obtained by convolution of spatial frequency characteristics of
a half of the wiring patterns of the two or more wiring layers
and the spatial frequency characteristics of the pixel array
pattern of the display unit, a lowest frequency is set to a
second lowest frequency fm2.
[Claim 2]
The electroconductive film according to Claim 1,
wherein the spatial frequency characteristics of the wiring
patterns of the two or more wiring layers are spatial frequency
characteristics in a direction perpendicular to the one or two
or more transparent substrates, and
wherein the spatial frequency characteristics of a half of
the wiring patterns of the two or more wiring layers are spatial
frequency characteristics in a direction inclined by a
predetermined angle with respect to the one or two or more
transparent substrates.
[Claim 3]
The electroconductive film according to Claim 1 or 2,
wherein the two or more wiring layers are formed on both
surfaces of the one transparent substrate.
[Claim 4]
The electroconductive film according to Claim 1 or 2,
wherein the two or more transparent substrates are
laminated on each other, the two or more wiring layers being
each formed on one surface of each of the two or more
transparent substrates.
[Claim 5]
The electroconductive film according to any one of Claims 1
to 4,
wherein the two or more wiring layers each have a wiring
pattern in a form of mesh in which a plurality of openings are
arranged.
[Claim 6]
The electroconductive film according to any one of Claims 1
to 5,
wherein the pixel array pattern is a black matrix pattern
of the display unit.
[Claim 7]
A touch panel, comprising:
the electroconductive film according to any one of Claims 1
to 6; and
a detection control portion configured to detect, within a
region where the two or more wiring layers are formed, a
position at which an object makes a contact with the
electroconductive film from outside.
[Claim 8]
44
44
A display device, comprising:
a display unit; and
the electroconductive film according to any one of Claims 1
to 6 installed on the display unit.
[Claim 9]
A display device, comprising:
a display unit; and
the touch panel according to Claim 7 installed on the display unit.