FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
& The Patent Rules, 2003
COMPLETE SPECIFICATION
1. TITLE OF THE INVENTION:
DISPLAY BODYAND ARTICLE
2. APPLICANT:
Name: TOPPAN PRINTING CO., LTD.
Nationality: Japan
Address: 5-1, Taito 1-chome, Taito-ku, Tokyo 110-0016 Japan
3. PREAMBLE TO THE DESCRIPTION:
The following specification particularly describes the invention and the manner in
which it is to be performed:
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DESCRIPTION
TECHNICAL FIELD
[0001] The present invention relates to, for example, a
display body for preventing counterfeiting of an article and
an article with such a display body.
BACKGROUND ART
[0002] A display body having visual effects different from
those of normal printed objects printed using inks containing
dyes or pigments is attached to valuable stock certificates
such as gift tickets and checks, cards such as credit cards,
cash cards, and ID cards, and certificates such as passports
and driver’s licenses, for the purpose of preventing
counterfeiting of these articles. In recent years,
counterfeit articles besides these articles have been widely
distributed, and thus the display body is also attached to
such articles.
[0003] A display body including a diffraction grating
constituted by a plurality of grooves in a substrate, that is,
a relief diffraction grating is known as the display body
having visual effects different from those of normal printed
objects. This display body can display, for example, an
image that changes depending on observation conditions or a
stereoscopic image. Moreover, conventional printing
techniques using the inks mentioned above cannot achieve an
iridescent spectrum represented by the diffraction grating.
Consequently, the display body including the diffraction
grating has been widely used for the purpose of preventing
counterfeiting of the articles described above (for example,
see Patent Document 1).
[0004] A display body that can display an iridescent color
and a black color has been proposed as the display body
including the relief diffraction grating. Such a display
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body has a fine structure formed by protrusions or recesses
regularly arranged in an X-direction that is one direction
and a Y-direction perpendicular to the X-direction at
intervals less than or equal to the shortest wavelength of
visible light. The protrusions or recesses constituting the
fine structure suppress the reflection of light that is
incident on the fine structure and display the black color in
a front view in which the protrusions or recesses are
observed from the front. Moreover, the protrusions or
recesses constituting the fine structure function as a
diffraction grating that diffracts light that is incident on
the fine structure and display the iridescent color in an
oblique view in which the protrusions or recesses are
observed obliquely (for example, see Patent Documents 2 and
3).
PRIOR ART DOCUMENTS
Patent Documents
[0005] Patent Document 1: U.S. Patent No. 5058992
Patent Document 2: Japanese Patent No. 4420138
Patent Document 3: Japanese Patent No. 4315334
SUMMARY OF THE INVENTION
Problems that the Invention is to Solve
[0006] As described above, a fine structure displays black
in a front view even if a reduced amount of light is incident
on the fine structure. However, as the amount of light
incident on the fine structure is reduced, it is more
difficult for the fine structure to display an iridescent
color in an oblique view. To prevent counterfeiting of
articles more reliably, a display body preferably has a front
view and an oblique view that are clearly different from each
other even if a reduced amount of light is incident on the
fine structure. Consequently, it is necessary to increase
the brightness of diffracted light. Such a need arises not
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only in a display body for anti-counterfeiting but also in a
display body for decorating articles or a display body that
by itself is an observation target.
An object of the present invention is to provide a
display body that, when displaying a dark image in a front
view and a bright image in an oblique view, displays the
bright image with increased brightness, and an article.
Means for Solving the Problems
[0007] To achieve the foregoing objective and in
accordance with one aspect of the present invention, a
display body including a plurality of lattice lines that are
arranged along a plane of incidence on which light is
incident is provided. The lattice lines have properties for
forming a bright image with diffracted light of the incident
light in an oblique view in which the plane of incidence is
viewed obliquely and absorbing some of the incident light. A
surface of each of the lattice lines includes a plurality of
dispersed fine steps that are repetitive in a direction in
which the lattice lines extend. The steps have an
antireflection function and form a dark image in a front view
directly facing the plane of incidence.
[0008] To achieve the foregoing objective, an article is
provided that includes the above described display body.
[0009] With this aspect, the display body forms a bright
image by light diffracted by the lattice lines, and thus the
brightness of the bright image is increased.
[0010] In accordance with another aspect of the above
described display body, an interval between the lattice lines
that are adjacent to each other may be a lattice line pitch,
and the lattice line pitch may include a value less than or
equal to a shortest wavelength of visible light. Also, an
interval between the steps that are adjacent to each other on
each of the lattice lines may be a step pitch, and the step
pitch may include a value less than or equal to the shortest
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wavelength of visible light.
[0011] With this aspect of the display body, the lattice
lines and the steps form a dark image in a front view. Thus,
the brightness of the dark image is further reduced as
compared to a case where only the steps form a dark image.
[0012] In accordance with another aspect of the above
described display body, an interval between the lattice lines
that are adjacent to each other may be a lattice pitch, and
the lattice line pitch may include a value less than or equal
to a shortest wavelength of visible light. Also, an interval
between the steps that are adjacent to each other on each of
the lattice lines may be a step pitch, and the step pitch may
include a value greater than the shortest wavelength of
visible light.
[0013] With this aspect of the display body, the number of
the steps per unit area is less than that in a case where the
step pitch is less than or equal to the shortest wavelength
of visible light. Thus, the brightness of a dark image is
reduced by the lattice lines and the steps. Also, the
accuracy of the shape of the display body is improved as
compared to the case where the step pitch is less than or
equal to the shortest wavelength of visible light.
[0014] In accordance with another aspect of the above
described display body, an interval between the lattice lines
that are adjacent to each other may be a lattice line pitch,
and the lattice line pitch may include a value greater than a
shortest wavelength of visible light. Also, an interval
between the steps that are adjacent to each other on each of
the lattice lines may be a step pitch, and the step pitch may
include a value less than or equal to the shortest wavelength
of visible light.
[0015] With this aspect of the display body, the angle
formed by the direction in which diffracted light is emitted,
that is, the direction in which a plane of incidence is
viewed obliquely and the direction in which the plane of
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incidence is viewed from the front is small as compared to
the case where the interval between the lattice lines is less
than or equal to the shortest wavelength of visible light.
It is thus easy to observe diffracted light emitted by the
display body.
[0016] In accordance with another aspect of the above
described display body, the steps may be aperiodically
arranged in the direction in which the lattice lines extend.
With this aspect of the display body, the steps are
aperiodically arranged in the display body. It is thus
possible to prevent the steps from emitting part of incident
light as diffracted light.
[0017] In accordance with another aspect of the above
described display body, the steps may be periodically
arranged in the direction in which the lattice lines extend.
With this aspect of the display body, the steps are
periodically arranged. The steps not only form a dark image
but also have an optical effect according to the step pitch.
[0018] In accordance with another aspect of the above
described display body, at least a part of the plane of
incidence may be made of metal.
With this aspect of the display body, a part of the
plane of incidence that is formed of metal has a relatively
high light reflectance.
[0019] In accordance with another aspect of the above
described display body, the display body may include a
plurality of display parts each including the lattice lines,
and the display parts may include a display part in which at
least either an interval between the lattice lines that are
adjacent to each other and a direction in which the lattice
lines extend varies.
[0020] With this aspect of the display body, the display
parts may include display parts in which at least either the
wavelength of diffracted light or the directions in which
diffracted light is emitted vary. The display body thus
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displays a more complicated bright image as compared to a
case where the display parts include only display parts with
the same interval between the lattice lines that are adjacent
to each other and the same direction in which the lattice
lines extend.
[0021] In accordance with another aspect of the above
described display body, the display body may include a
plurality of display parts each including the lattice lines,
and the display parts may include a display part in which at
least either a rule for arranging the steps and an arranged
density of the steps varies.
[0022] With this aspect of the display body, the display
parts include display parts in which at least one of the type
of light emitted from the steps and the brightness of a dark
image formed by the steps varies. The display body thus
displays a bright image and a dark image in a complicated
manner as compared to a case where the display parts include
only display parts with the same rule for arranging the steps
and the same density of the steps.
EFFECTS OF THE INVENTION
[0023] According to the present invention, when a dark
image is displayed in a front view and a bright image is
displayed in an oblique view, the bright image is displayed
with increased brightness.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] Fig. 1 is a plan view showing the planar structure
of a display body according to an embodiment that embodies a
display body according to the present invention.
Fig. 2 is a partially enlarged perspective view of an
obliquely viewed structure of the display body.
Fig. 3 is a partially enlarged plan view of a planar
structure of the display body.
Fig. 4 is a schematic view of positive first-order
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diffracted light emitted by a diffraction grating with a
relatively large lattice constant.
Fig. 5 is a schematic view of positive first-order
diffracted light emitted by a diffraction grating with a
relatively small lattice constant.
Fig. 6 is a perspective view of an obliquely viewed
structure of a conventional display body in which its relief
part includes only a plurality of protrusions.
Fig. 7 is a partial cross-sectional view showing a
cross-sectional structure of an example of the display body.
Fig. 8 is a partial cross-sectional view showing a
cross-sectional structure of an example of the display body.
Fig. 9 is a plan view of a schematic structure of an IC
card according to an embodiment of one of articles with the
display body.
Fig. 10 is a cross-sectional view showing a crosssectional
structure taken along line X-X in Fig. 9.
Fig. 11 is a plan view showing a planar structure of a
display body according to another embodiment.
Fig. 12 is a plan view showing a planar structure of a
display body according to still another embodiment.
Fig. 13 is a plan view showing a planar structure of a
display body according to still another embodiment.
MODES FOR CARRYING OUT THE INVENTION
[0025] One embodiment that embodies a display body and an
article according to the present invention is described with
reference to Figs. 1 to 10. Hereinafter, the overall
structure of the display body, a relief part of the display
body, a display area of the display body, an effect of the
display body, a laminated structure of the display body, and
the structure of the article are described in this order.
[0026]
[Overall Structure of Display Body] The overall structure of
the display body is described with reference to Fig. 1.
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As shown in Fig. 1, a display body 10 is formed in a
rectangular plate shape and includes a display area 11. The
display area 11 is divided into a plurality of display parts
12. The display body 10 may be formed in a polygonal plate
shape other than the rectangular plate shape or in a disk
plate shape. The display body 10 may include a plurality of
display areas 11.
[0027] The display area 11 is divided into a plurality of
display parts 12 arranged regularly. A Z-direction is a
thickness direction of the display body 10, that is, a
direction in which a front surface 10f, which is one of
surfaces included in the display body 10, is viewed from the
front. Each display part 12 has a square shape as viewed
from the Z-direction. The display parts 12 are arranged in
an X-direction that is one direction and a Y-direction
perpendicular to the X-direction. That is, the display parts
12 are arranged in a square lattice.
[0028] The display part 12 may have a circular shape or a
polygonal shape other than the square shape, for example, a
triangle shape, or a quadrilateral shape such as a
rectangular shape or a diamond shape, as viewed from the Zdirection.
Moreover, the display parts 12 may be arranged in,
other than the square lattice, for example, a rectangular
lattice, or a triangular lattice.
[0029] The display parts 12 include at least some relief
parts 21 each having a relief structure that includes a
plurality of lattice lines. Each relief part 21 may include
the relief structure on its entire square structure, or may
include a relief structure and a flat surface without a
relief structure. The display area 11 includes flat parts 22,
which are a part of the display parts 12. Each flat part 22
includes a flat surface without the relief structure. The
flat parts 22 indicated by broken lines in Fig. 1 are
imaginarily divided in the same size as the relief part 21.
[0030] The display area 11 includes an area where the
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relief parts 21 are arranged in the X-direction and the Ydirection
and an area where the flat parts 22 are arranged in
the X-direction and the Y-direction. In the display area 11,
the relief parts 21 and the flat parts 22 may be alternately
arranged in the X-direction and the Y-direction.
Alternatively, the relief parts 21 may be arranged
aperiodically in the display area 11 and the flat parts 22
may be disposed in portions other than the relief parts 21.
[0031] Each relief part 21 is so small that it is
impossible or difficult to distinguish the relief part 21
from other adjacent relief parts 21 with the naked eye.
[0032] For example, the X-direction length of the relief
part 21 is within the range of 3 μm to 300 μm, inclusive,
whereas the Y-direction length of the relief part 21 is also
within the range of 3 μm to 300 μm, inclusive, as viewed from
the Z-direction.
[0033] The X-direction and Y-direction lengths of the
relief part 21 are less than or equal to 300 μm.
Consequently, when observing the display body 10 with the
naked eye, the observer hardly recognizes the shape of each
relief part 21. The X-direction and Y-direction lengths of
the relief part 21 are greater than or equal to 3 μm.
Consequently, the relief part 21 is sufficiently large for
having an optical effect. The accuracy of the shape of the
relief part 21 with respect to the shape of the original
plate of the relief part 21 is sufficiently high for the
relief part 21 to have an optical effect.
[0034]
[Structure of Relief Part] The structure of a relief part
is described with reference to Figs. 2 and 3. Fig. 2 shows
an obliquely viewed structure of a part of the relief part.
As shown in Fig. 2, the relief part 21 includes a
plurality of lattice lines 51 as viewed from the front
surface 10f of the display body 10. Each lattice line 51 is
linear and extends in the X-direction. The lattice lines 51
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are arranged in the Y-direction at equal intervals.
[0035] A plurality of dispersed fine protrusions 51a is
formed on a surface 51s of each of the lattice lines 51. The
protrusions 51a are repeatedly formed in the X-direction, in
which the lattice lines 51 extend at equal intervals, that is,
periodically arranged. The protrusion 51a is an example of a
step. The step is a protrusion that projects from the
surface 51s of the lattice line 51 or a recess that is
recessed from the surface 51s of the lattice line 51 in the
Z-direction. The step is embodied as the protrusion 51a in
the present embodiment.
[0036] Two lattice lines 51 in the relief part 21 that are
adjacent to each other in the Y-direction form a recess 52.
In the relief part 21, the surface 51s of each lattice line
51 and a surface 52s of each recess 52 form a plane of
incidence 21s on which light is incident. That is, each of
the lattice lines 51 is arranged along the plane of incidence
21s.
[0037] The protrusions 51a function to prevent the
reflection of light that is incident on the plane of
incidence 21s, thus forming a dark image in a front view in
which the plane of incidence 21s is viewed from the front.
[0038] It is only necessary that the protrusions 51a are
periodically arranged in the relief part 21 so as to enable
the protrusions 51a to transmit part of light that is
incident on the plane of incidence 21s. Additionally, it is
only necessary that the relief part 21 includes a part that
absorbs light having been transmitted through the plane of
incidence 21s, and has transmittance that enables light to be
transmitted to the absorbing part. Moreover, it is only
necessary that at least the lattice line 51 in the relief
part 21 functions to absorb part of light that is incident on
the plane of incidence 21s.
[0039] In other words, it is only necessary that the
relief part 21 includes, at its inner side, a part that
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converts light having been transmitted through the plane of
incidence 21s into thermal energy, and has transmittance that
enables light to be transmitted to the part that converts
light into thermal energy.
[0040] The light absorbing part of the relief part 21 may
function to reflect light. It is only necessary that light
that is incident on the light absorbing part is absorbed by
multi-reflection of the relief part 21.
[0041] The interval between two adjacent lattice lines 51
in the relief part 21 is referred to as a lattice line pitch
P1. The lattice line pitch P1 is less than or equal to 500
nm. The lattice line pitch P1 is preferably less than or
equal to 400 nm, which is the shortest wavelength of visible
light. The lattice line pitch P1 is preferably greater than
or equal to a half of the shortest wavelength of visible
light, that is, 200 nm. The Y-direction width of the lattice
line 51 in the relief part 21 is referred to as a lattice
line width LW. The lattice line width LW is, for example,
less than a half of the lattice line pitch P1.
[0042] In the relief part 21, the interval between two
adjacent protrusions 51a in the X-direction is referred to as
a step pitch P2. The step pitch P2 is within the range of
200 nm to 500 nm, inclusive. The step pitch P2 is the Xdirection
distance between surfaces of the protrusions 51a at
relatively higher positions in the Z-direction than any other
surfaces. In other words, the step pitch P2 is the distance
between the tops of the protrusions 51a that are adjacent to
each other in the X-direction.
[0043] The protrusion 51a is formed in a truncated
quadrangular pyramid shape, which is an example of a tapered
shape, which diminishes along the Z-direction. The
protrusion 51a preferably has a tapered shape and may have,
for example, a half-spindle shape, a cone shape such as a
circular cone shape or a pyramid shape, or a truncated cone
shape such as a truncated circular cone shape or a truncated
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pyramid shape. While all side surfaces of the protrusion 51a
are inclined surfaces, the side surfaces may include a
stepped surface.
[0044] When the display body 10 is formed of various
resins, the display body 10 is formed using a stamper. In
this case, the tapered shape of the protrusion 51a enables
the stamper to be easily removed from a cured resin, thus
improving the productivity of the display body 10. The
protrusion 51a does not need to have a tapered shape, and may
have a shape other than the tapered shape, for example, a
pillar shape including a cylindrical shape and a prism shape.
[0045] To reduce the brightness of a dark image, the
maximum value HM of the height H of the lattice line 51 in
the Z-direction is preferably large. As the maximum value HM
of the height H of the lattice line 51 is reduced, the
brightness of the dark image is increased. The maximum value
HM of the height of the lattice line 51 is preferably greater
than or equal to a half of the lattice line pitch P1 of the
lattice line 51 or a half of the step pitch P2 of the
protrusion 51a.
[0046] In a case where the lattice line pitch P1 and the
step pitch P2 of the lattice line 51 are 500 nm, if the
maximum value HM of the height of the lattice line 51 is
greater than or equal to 250 nm, the protrusions 51a can form
a grayish dark image. As the maximum value HM of the height
of the lattice line 51 is greater than 250 nm, the
protrusions 51a can display a dark image with reduced
brightness, that is, a dark image that is blackish gray or
black.
[0047] The black is displayed under conditions in which,
for example, when white light is irradiated onto the relief
part 21 in a front view direction and the intensity of
specularly reflected light is measured, all optical
components within the wavelength of visible light, that is,
in the range of 400 nm to 700 nm have a reflectance of 10% or
14
less.
[0048] The gray is displayed under conditions in which,
for example, when white light is irradiated onto the relief
part 21 in the front view direction and the intensity of
specularly reflected light is measured, all optical
components within the wavelength of visible light, that is,
within the range of 400 nm to 700 nm have a reflectance of
approximately 25% or less.
[0049] When the maximum value HM of the height of the
lattice line 51 is greater than the lattice line pitch P1 and
the step pitch P2, that is, 500 nm, the protrusions 51a can
display a dark image that is black. If the maximum value HM
of the height of the lattice line 51 is further increased,
the brightness of the dark image is further reduced.
[0050] However, even if the aspect ratio, that is, the
ratio of the step pitch P2 to the maximum value HM of the
height of the lattice line 51 is greater than 1.5 and the
maximum value HM of the height of the lattice line 51 is
greater than 750 nm, the brightness of the dark image is kept
at the substantially same value. When the aspect ratio is
greater than or equal to 1.5, this complicates the
manufacturing of the display body 10 because, for example, it
is difficult to manufacture an original plate or to keep high
accuracy of the shape of the display body 10 with respect to
the shape of the original shape.
[0051] The aspect ratio is thus preferably less than or
equal to 1.5. Since the aspect ratio is less than or equal
to 1.5, the brightness of a dark image formed by the
protrusions 51a can be sufficiently reduced, and it is
possible to prevent complicated manufacturing of the display
body 10.
[0052] The aspect ratio is preferably greater than or
equal to 0.5. When the aspect ratio is greater than or equal
to 0.5, the reflectance on the lattice line 51 is reduced
sufficiently for a dark image that is black or gray to be
15
displayed.
[0053] While the maximum value HM of the height of the
lattice line 51 is the same for all the protrusions 51a, the
maximum value HM may be different for each of the lattice
lines 51 or each of the protrusions 51a. When the maximum
value HM of the height of the lattice line 51 is different
for each of the lattice lines 51 or the protrusions 51a, a
dark image includes portions with different brightness. The
brightness of the dark image may be uneven. Consequently,
when the maximum value HM is the same for all the protrusions
51a, uneven brightness hardly occurs in the dark image.
[0054] As shown in Fig. 3, the lattice lines 51 are
regularly arranged in the relief part 21 in the Y-direction
with the lattice line pitch P1. As described above, the
lattice line pitch P1 is less than or equal to 500 nm, and is
preferably less than or equal to the shortest wavelength of
visible light, that is, 400 nm. The lattice line pitch P1 is
preferably greater than or equal to a half of the shortest
wavelength of visible light, that is, 200 nm.
[0055] When the lattice line pitch P1 is less than or
equal to the shortest wavelength of visible light, it is
determined that the relief part 21 has a refractive index
that changes continuously in the Z-direction.
[0056] The protrusions 51a are arranged in the relief part
21 in the X-direction at equal intervals, that is, with the
step pitch P2. The step pitch P2 is within the range of 200
nm to 500 nm, inclusive, as described above. The step pitch
P2 is the X-direction distance between surfaces of the
protrusions 51a at relatively higher positions in the Zdirection
than any other surfaces, that is, the distance
between the tops of the protrusions 51a that are adjacent to
each other in the X-direction.
[0057] In the lattice line 51, when the step pitch P2 is
less than or equal to the shortest wavelength of visible
light, that is, 400 nm, the reflectance of specularly
16
reflected light can be reliably reduced. The protrusions 51a
thus form a dark image in a front view of the display body 10.
[0058] In a part of the lattice line 51 in which the step
pitch P2 is consecutively greater than or equal to a half of
the shortest wavelength of visible light, that is, 200 nm,
the protrusions 51a emit first-order diffracted light. The
observer views first-order diffracted light when observing
the display body 10 in the X-direction. In diffracted light
emitted by the display body 10, the amount of diffracted
light originating from the protrusions 51a is smaller than
the amount of diffracted light originating from the lattice
lines 51. Diffracted light originating from the protrusions
51a is used as a criterion for determining the authenticity
of the display body 10. That is, if the display body 10
emits diffracted light originating from the protrusions 51a,
it is determined that the display body 10 is authentic.
[0059] In a part of the lattice line 51 in which the step
pitches P2 is consecutively less than 200 nm, first-order
diffracted light originating from the protrusions 51a is not
emitted and the protrusions 51a have an effect of reducing
the reflectance of specularly reflected light.
[0060] When the protrusions 51a are regularly arranged,
the protrusions 51a are arranged in the relief part 21 more
densely than in a case where the protrusions 51a are randomly
arranged. The regular arrangement of the protrusions 51a
enables the density of the protrusions 51a per unit area to
be increased, thus further reducing the reflection of light.
The lattice line pitch P1 and the step pitch P2 may be
less than or equal to the shortest wavelength of visible
light or may exceed the shortest wavelength of visible light.
[0061] The bottom surface of the protrusion 51a at a
position in the Z-direction that is the same as that of a
surface between the protrusions 51a that are adjacent to each
other in the X-direction has a square shape as viewed from
the Z-direction. When the bottom surface of the protrusion
17
51a has a square shape, patterning is easily performed to
arrange the protrusions 51a at predetermined intervals on a
reference surface of the surface 51s of the lattice line 51,
where the protrusions 51a are formed. When the bottom
surface of the protrusion 51a has a rectangular shape other
than the square shape, patterning is performed more easily to
arrange the protrusions 51a at predetermined intervals, as
compared to a case where the bottom surface has a circular
shape or an elliptical shape.
[0062] The width of the bottom surface of the protrusion
51a in the Y-direction that is perpendicular to the direction
in which the lattice lines 51 extend is substantially equal
to the lattice line width LW. The protrusion 51a is formed
as a part of the surface of the lattice line 51 to enable the
lattice lines 51 to emit an increased amount of diffracted
light.
[0063] That is, the protrusions 51a that form a dark image
are not disposed in the recess 52 between two lattice lines
51 that are adjacent to each other in the Y-direction as
structures separate from the lattice line 51. The recess 52
between two adjacent lattice lines 51 thus has a flat surface.
The relief part 21 includes the lattice lines 51 and the
recesses 52 each having a flat surface, and the lattice lines
51 and the recesses 52 are consecutively arranged in the Ydirection.
The display body 10 can thus emit diffracted
light originating from the lattice lines 51 and the recesses
52 with increased brightness.
[0064] The Y-direction width of the protrusion 51a is
equal to the lattice line width LW in such a structure, and
thus it is possible to maximize the effect of the protrusion
51a to suppress light reflection.
[0065] In case that the area of one divided relief part 21
formed in a square shape is a unit area, the density of the
protrusions 51a per unit area is preferably within the range
of 30% to 70%, inclusive. The density of the protrusions 51a
18
is the ratio of the total area of bottom surfaces of the
protrusions 51a arranged in the relief part 21 to the unit
area.
[0066] When the density of the protrusions 51a is 50%, it
is possible to maximize the effect of the protrusion 51a to
suppress the reflection of light that is incident on the
relief part 21. In such a state, a dark image formed by the
protrusions 51a has the lowest brightness. When the density
of the protrusions 51a is 50%, the protrusions 51a form, for
example, a dark image that is black.
[0067] As the density of the protrusions 51a is reduced
from 50% to 30%, the effect of the protrusion 51a to suppress
the reflection of light that is incident on the relief part
21 is reduced. The brightness of the dark image formed by
the protrusions 51a is increased and thus the protrusions 51a
form a dark image that is gray. When the density of the
protrusions 51a is less than 50%, the brightness of the dark
image is increased as the density of the protrusions 51a is
reduced.
[0068] As the density of the protrusions 51a is increased
from 50% to 70%, the effect of the protrusion 51a to suppress
the reflection of light that is incident on the relief part
21 is reduced. The brightness of the dark image formed by
the protrusions 51a is increased and thus the protrusions 51a
form a dark image that is gray. When the density of the
protrusions 51a is greater than 50%, the brightness of the
dark image is increased as the density of the protrusions 51a
is increased.
[0069] When the density of the protrusions 51a is within
the range of 30% to 70%, inclusive, the reflectance is kept
to be less than or equal to 25% in all optical components
within the wavelength of visible light, that is, in the range
of 400 nm to 700 nm.
[0070] When a plurality of recesses is formed in each
lattice line 51 as a plurality of steps arranged in the X19
direction, the density of the recesses is the ratio of the
total area of the open recesses arranged in the relief part
21 to the unit area described above.
[0071]
[Display area of Display Body] The display area 11 of the
display body 10 is described.
The display body 10 includes the relief parts 21 as
described above. An azimuth angle corresponds to the
direction in which the lattice lines 51 extend. The relief
parts 21 may have the same azimuth angle, or may have
different azimuth angles. Alternatively, the azimuth angle
may be different for each group of several relief parts 21 in
the display area 11.
[0072] Since the display body 10 includes the relief parts
21 with different azimuth angles, the emission direction of
diffracted light differs between the relief parts 21 with
different azimuth angles. When the observer obliquely views
the display body 10 at a fixed point on a light incident side
at which the observer faces the front surface 10f of the
display body 10, the relief part 21 in which diffracted light
is observed and the relief part 21 in which diffracted light
is not observed are included in the display area 11. Since
the azimuth angle differs between the relief parts 21, it is
possible to display a predetermined image on the display body
10 by using the relief part 21 in which diffracted light is
observed and the relief part 21 in which diffracted light is
not observed.
[0073] All the relief parts 21 may have the same lattice
line pitch P1 of the lattice line 51, or may have different
lattice line pitches P1. Alternatively, the lattice line
pitch P1 may be different for each group of several relief
parts 21 in the display area 11.
[0074] The display body 10 includes the relief parts 21
with different lattice line pitches P1. The wavelength of
diffracted light that is emitted from the lattice line 51 and
20
reaches the observer thus differs between the relief parts 21
with different lattice line pitches P1 under predetermined
illumination conditions. That is, the color of a bright
image formed by diffracted light differs between the relief
parts 21 with different lattice line pitches P1.
Consequently, since the lattice line pitch P1 differs between
the relief parts 21, it is possible to display an image
including a plurality of colors on the display body 10 by
using colors of diffracted light emitted from the relief
parts 21.
[0075] All the relief parts 21 may have the same step
pitch P2 and the same density of protrusions 51a, or may have
different step pitches P2 and different densities of the
protrusions 51a. Alternatively, the step pitch P2 and the
density of the protrusions 51a may be different for each
group of several relief parts 21.
[0076] Since the display body 10 includes the relief parts
21 with different step pitches P2, the degree to which the
reflection of incident light is suppressed thus differs
between the relief parts 21 with different step pitches P2.
Consequently, since the density of the protrusions 51a
differs between the relief parts 21, it is possible to
display a dark image including a plurality of rays of light
with different brightness on the display body 10 by using
reflected light emitted from the relief parts 21.
[0077] Since the display body 10 includes the relief parts
21 with different step pitches P2, the wavelength of
diffracted light that is emitted from the protrusions 51a and
reaches the observer thus differs between the relief parts 21
with different step pitches P2 under predetermined
illumination conditions. That is, the color of a bright
image formed by diffracted light emitted from the protrusions
51a differs between the relief parts 21 with different step
pitches P2.
[0078] Since the display body 10 includes the relief parts
21
21 with different densities of the protrusions 51a, the
degree to which the reflection of incident light is
suppressed thus differs between the relief parts 21 with
different densities of the protrusions 51a. Consequently,
since the density of the protrusions 51a differs between the
relief parts 21, it is possible to display a dark image
including a plurality of rays of light with different
brightness on the display body 10 by using reflected light
emitted from the relief parts 21.
[0079] [Effect of Display Body]
An effect of a display body is described with reference
to Figs. 4 and 5. Prior to description of the effect of the
display body 10, an effect of a diffraction grating included
in the display body 10 is described.
The diffraction grating emits diffracted light with high
intensity in a predetermined direction with respect to the
direction in which light that is incident on the diffraction
grating travels.
[0080] An emission angle β of m-th order diffracted light
(m = 0, ±1, ±2…) is calculated using the following formula
(1), which is an equation, when light travels through a plane
that is vertical to the lengthwise direction of a groove of
the diffraction grating, that is, the lengthwise direction of
a recess of the diffraction grating.
d = mλ/(sin- sinβ) … formula (1)
[0081] In the formula (1), d indicates the lattice
constant of the diffraction grating, m indicates the order of
diffraction, and λ indicates the wavelength of incident light
and diffracted light. α indicates the emission angle of
transmitted light or specularly reflected light, which is 0-
th order diffracted light. That is, the absolute value of
the emission angle α is equal to the incident angle of
irradiated light. In a reflection diffraction grating, the
incident direction of irradiated light is symmetrical to the
emission direction of specularly reflected light with respect
22
to a front view direction in which the diffraction grating is
observed the from the front.
[0082] The emission angle α is 0° or more and less than
90° in the reflection diffraction grating. Light is
irradiated in a direction in which a plane of incidence of
the diffraction grating with recesses and protrusions is
inclined at a predetermined angle to the front view direction.
Two angle ranges are then defined across the front view
direction, that is, with a boundary value of 0°. The angle
range that includes the emission direction of specularly
reflected light is a positive angle range, whereas the angle
range that includes the incident direction of irradiated
light is a negative angle range.
[0083] When the emission direction of diffracted light and
the emission direction of specularly reflected light are
included in the same angle range, the emission angle β has a
positive value. Meanwhile, when the emission direction of
diffracted light and the incident direction of irradiated
light are included in the same angle range, the emission
angle β has a negative value.
[0084] When the diffraction grating is viewed in a front
view, only diffracted light with an emission angle β of 0°
contributes to displaying by the display body. When the
lattice constant d is greater than the wavelength λ, it is
possible to obtain the wavelength λ and the incident angle α
that satisfy the formula (1). The observer can thus observe
diffracted light with the wavelength λ that satisfies the
formula (1).
[0085] In contrast, when the lattice constant d is less
than the wavelength λ, it is impossible to obtain the
incident angle α that satisfy the formula (1). Therefore,
the observer cannot observe diffracted light emitted by the
display body.
[0086] Fig. 4 schematically shows a state where a
diffraction grating with a relatively large lattice constant
23
emits first-order diffracted light. Meanwhile, Fig. 5
schematically shows a state where a diffraction grating with
a relatively small lattice constant emits first-order
diffracted light. In Fig. 5, components corresponding to
those of Fig. 4 are denoted by the same reference numerals.
[0087] As shown in Fig. 4, a diffraction grating DG
includes an interface IF that has a projecting and recessed
surface, which is a surface of the diffraction grating DG.
The front view direction of the interface IF is denoted by NL.
The lattice constant d of the diffraction grating DG is
greater than 400 nm, which is the shortest wavelength of
visible light.
[0088] When white irradiated light IL including a
plurality of rays of light with different wavelengths is
irradiated from a light source LS onto the interface IF, the
diffraction grating DG emits reflected light RL as specularly
reflected light or 0-th order diffracted light. The
diffraction grating DG also emits first-order diffracted
light DLr having a wavelength corresponding to red, firstorder
diffracted light DLg having a wavelength corresponding
to green, and first-order diffracted light DLb having a
wavelength corresponding to blue. These rays of diffracted
light are diffracted from the white irradiated light IL.
[0089] As can be seen from the formula (1), in a case
where the lattice constant d of the diffraction grating DG is
greater than the shortest wavelength of visible light, that
is, 400 nm, when irradiated light IL is obliquely irradiated
onto the interface IF, the diffraction grating DG emits
first-order diffracted light DLr, DLg, DLb within the
positive angle range. The emission angle β of first-order
diffracted light DLr having a wavelength corresponding to red
is denoted by βr, the emission angle β of first-order
diffracted light DLg having a wavelength corresponding to
green is denoted by βg, and the emission angle β of firstorder
diffracted light DLb having a wavelength corresponding
24
to blue is denoted by βb. The diffraction grating DG also
emits first-order diffracted light having a wavelength
different from those of rays of diffracted light described
above.
[0090] The lattice constant d of the diffraction grating
DG shown in Fig. 5 is smaller than the lattice constant d of
the diffraction grating DG shown in Fig. 4, and is less than
or equal to the shortest wavelength of visible light, that is,
400 nm. When white irradiated light is obliquely irradiated
onto the interface IF under conditions in which the lattice
constant d of the diffraction grating DG is greater than a
half of the shortest wavelength of visible light and less
than the shortest wavelength of visible light, the
diffraction grating DG emits first-order diffracted light DLr,
DLg, DLb within the negative angle range. For example, when
the emission angle α is 50° and the lattice constant d is 330
nm, the diffraction grating DG emits first-order diffracted
light DLg of white irradiated light IL, which is green and
has a wavelength λ of 540 nm, at an emission angle βg of
approximately -60°.
[0091] Each of the relief parts 21 included in the display
body 10 includes the lattice lines 51 that extend in the Xdirection
and are arranged in the Y-direction at equal
intervals as described above, and thus each relief part 21
functions as a diffraction grating. The lattice line pitch
P1 of the lattice line 51 in the relief part 21 is within the
range of 200 nm to 500 nm, inclusive.
[0092] In the relief part 21, when the lattice line pitch
P1 is less than or equal to the shortest wavelength of
visible light, that is, when the lattice line pitch P1 is
within the range of 200 nm to 400 nm, inclusive, the relief
part 21 emits diffracted light not within the positive angle
range but within the negative angle range, as described above.
[0093] In contrast, in the relief part 21, when the
lattice line pitch P1 exceeds the shortest wavelength of
25
visible light, that is, when the lattice line pitch P1 is
greater than 400 nm and less than or equal to 500 nm, the
relief part 21 emits diffracted light within the positive
angle range.
[0094] When the observer typically observes an article, in
particular, an article that has small light reflectivity and
small light scattering property but has high light
absorbability, the observer adjusts the relative position
between a light source and the article so that the observer’s
eye can view specularly reflected light. When the lattice
line pitch P1 is less than or equal to the shortest
wavelength of visible light, the observer who does not know
that the display body 10 emits diffracted light within the
negative angle range usually cannot view diffracted light.
The observer thus hardly finds that the display body 10 is
capable of emitting diffracted light.
[0095] In contrast, when the lattice line pitch P1 exceeds
the shortest wavelength of visible light, the display body 10
emits diffracted light within the positive angle range.
Consequently, if the observer does not know that the display
body 10 emits diffracted light within the positive angle
range, the observer is highly likely to view diffracted light.
In the case where the lattice line pitch P1 exceeds the
shortest wavelength of visible light, the angle formed by the
front view direction and the direction in which diffracted
light is emitted is smaller than that in the case where the
lattice line pitch P1 is less than or equal to the shortest
wavelength of visible light. The observer thus easily views
diffracted light emitted by the display body 10 in which the
lattice line pitch P1 exceeds the shortest wavelength of
visible light.
[0096] As described above, if the protrusion 51a is formed
in a tapered shape, and the lattice line pitch P1 and the
step pitch P2, that is, the distance between the protrusions
51a that are adjacent to each other in the X-direction, are
26
sufficiently small, it is determined that the relief part 21
has a refractive index that continuously changes in the Zdirection.
If the plane of incidence 21s of the display body
10 is viewed at any angle on the light incident side, the
reflectance of specularly reflected light is low in the
relief part 21.
[0097] To reduce the reflectance of specularly reflected
light in the relief part 21, one of the lattice line pitch P1
and the step pitch P2 is preferably less than or equal to the
shortest wavelength of visible light, and more preferably,
both the lattice line pitch P1 and the step pitch P2 are less
than or equal to the shortest wavelength of visible light.
[0098] When the lattice line pitch P1 is less than or
equal to the shortest wavelength of visible light and the
step pitch P2 is also less than or equal to the shortest
wavelength of visible light in the relief part 21 described
above, the relief part 21 does not emit diffracted light in
the front view direction of the relief part 21, and has low
reflectance of specularly reflected light in the front view
direction. The relief part 21 thus displays a dark image
that has a color between black and gray in a front view.
When the observer observes the relief part 21 in a front view,
it seems to the observer that the relief part 21 is a print
layer that has a color between black and gray.
[0099] When conditions for irradiating light onto the
display body 10 include a condition in which the angle at
which the observer observes the display body 10 is within the
negative angle range, the relief part 21 emits diffracted
light that has a predetermined color. That is, the relief
part 21 forms a bright image that has a predetermined color
in an oblique view.
[0100] When the lattice line pitch P1 exceeds the shortest
wavelength of visible light and the step pitch P2 is less
than or equal to the shortest wavelength of visible light in
the relief part 21 described above, the relief part 21 has
27
the similar effect as the relief part 21 described above.
That is, the relief part 21 does not emit diffracted light in
the front view direction of the relief part 21, and has low
reflectance of specularly reflected light in the front view
direction.
[0101] When the conditions for irradiating light onto the
display body 10 include a condition in which the angle at
which the observer observes the display body 10 is within the
positive angle range, the relief part 21 emits diffracted
light that has a predetermined color.
[0102] When the lattice line pitch P1 is less than or
equal to the shortest wavelength of visible light and the
step pitch P2 exceeds the shortest wavelength of visible
light in the relief part 21 described above, the reflectance
of light specularly reflected by the protrusions 51a is
higher than that in the case where the step pitch P2 is less
than or equal to the shortest wavelength of visible light.
However, the lattice line pitch P1 is less than or equal to
the shortest wavelength of visible light and thus the lattice
lines 51 can suppress the reflection of light in the front
view direction. Consequently, the relief part 21 can form a
dark image.
[0103] In contrast, a conventional relief part 100 that
includes only a plurality of protrusions 101 emits diffracted
light originating from a periodic arrangement of the
protrusions 101, as shown in Fig. 6. The relief part 100
does not include the lattice lines 51 unlike the relief part
21 according to the present embodiment. The area of a
portion of the relief part 100 that emits diffracted light in
the X-direction is thus reduced. Consequently, the amount of
diffracted light emitted by the relief part 100 is smaller
than that of the relief part 21 according to the present
embodiment, and thus the brightness of light that is observed
by the observer is reduced.
[0104] According to the relief part 21 of the present
28
embodiment, the relief part 21 includes the lattice lines 51
and thus the amount of diffracted light emitted by the relief
part 21 is increased. Consequently, when a dark image is
displayed in a front view and a bright image is displayed in
an oblique view, the bright image is displayed with increased
brightness.
[0105] The display body 10 according to the present
embodiment forms a dark image in a front view and a bright
image in an oblique view. Consequently, to counterfeit the
display body 10, it is necessary to configure the display
body 10 so that both the dark image and the bright image are
formed. Counterfeiting of a display body is thus more
difficult compared to a display body that forms only one of a
dark image and a bright image.
[0106]
[Laminated Structure of Display Body] A structure that can
be used as the display body 10 described above is described
with reference to Figs. 7 and 8. In the display body 10, the
flat part 22 is different from the relief part 21 in that the
flat part 22 does not include a relief structure. However,
materials for layers of the display body 10 and the laminated
structure in the relief part 21 are common to those in the
flat part 22. Descriptions of the structure of the relief
part 21 in the display body 10 are given below and
descriptions of the structure of the flat part 22 are omitted.
[0107] As shown in Fig. 7, an example of the display body
10 includes a relief layer 71 and a covering layer 72 that
covers, among surfaces included in the relief layer 71, a
surface having the lattice lines 51 disposed thereon. The
plane of incidence 21s of the display body 10 is a surface of
the relief layer 71 that is in contact with the covering
layer 72. The plane of incidence 21s includes the lattice
lines 51 arranged in a direction perpendicular to the plane
of drawing at equal intervals. The protrusions 51a are
formed on each lattice line 51 in the direction in which the
29
lattice lines 51 extend.
[0108] Among surfaces included in the covering layer 72,
the front surface of the display body 10 is a flat surface,
which is opposite to a surface in contact with the relief
layer 71. The rear surface of the display body 10 is a
surface of the relief layer 71 that is opposite to a surface
in contact with the covering layer 72.
[0109] Examples of materials for forming the relief layer
71 include aluminum, silver, gold, and alloys of such metals.
The plane of incidence 21s of the relief layer 71 is formed
of metal, in other words, the plane of incidence 21s is made
of metal, and thus the reflectance of light on the plane of
incidence 21s is increased.
[0110] Light is incident on the display body 10 from its
front surface. At least one of the group of the lattice
lines 51 and group of the protrusions 51a is periodically
arranged on the plane of incidence 21s so as to enable light
reflection to be suppressed. The reflection of light on the
plane of incidence 21s is thus suppressed and part of light
that is incident on the plane of incidence 21s is transmitted
through the relief layer 71. Light that travels inside of
the relief layer 71 is then absorbed by the relief layer 71,
that is, then converted into thermal energy within the relief
layer 71.
[0111] Part of light that is incident on the plane of
incidence 21s is reflected by the plane of incidence 21s and
part of light that is reflected by the plane of incidence 21s
is incident on the plane of incidence 21s again, and part of
incident light is absorbed by the relief layer 71. Since
light is absorbed by the relief layer 71 multiple times, it
is possible to suppress the reflection of light on the plane
of incidence 21s and the transmission of light through a
surface of the relief layer 71 that is opposite to the plane
of incidence 21s.
[0112] The covering layer 72 has a light transmission
30
property, and is made of, for example, a thermoplastic resin,
a thermosetting resin, or a photosetting resin.
[0113] If the display body 10 includes the relief layer 71
and the covering layer 72, the plane of incidence 21s of the
relief layer 71 is not exposed to the outside of the display
body 10. The plane of incidence 21s is thus less damaged
compared to a case where the display body 10 does not include
the covering layer 72. Consequently, the display body 10 can
display an image with improved visibility.
[0114] The display body 10 may be formed by coating a
resin for forming the covering layer 72 on the relief layer
71 formed by physically or chemically etching a metal layer.
Alternatively, the display body 10 may be formed as follows.
That is, the covering layer 72 that functions as a recessed
plate for forming the relief layer 71 is formed, and a metal
layer is then formed on the covering layer 72.
[0115] As shown in Fig. 8, an example of the display body
10 is a laminate of the relief layer 71 and a light
transmitting layer 81. The front surface of the display body
10 is a surface of the light transmitting layer 81 that is
opposite to a surface that is in contact with the relief
layer 71. The rear surface of the display body 10 is a
surface of the relief layer 71 that is opposite to the light
transmitting layer 81. The rear surface may be a surface
constituted by the light transmitting layer 81. In this case,
the front surface may be a surface constituted by the relief
layer 71.
[0116] The light transmitting layer 81 is a laminate
constituted by a support layer 73 and the covering layer 72,
and the covering layer 72 is interposed between the support
layer 73 and the relief layer 71. When the front surface is
a surface of the light transmitting layer 81 that is opposite
to the surface in contact with the relief layer 71, the plane
of incidence 21s is a surface of the relief layer 71 in
contact with the covering layer 72. When the front surface
31
is a surface of the relief layer 71 that is opposite to the
surface in contact with the light transmitting layer 81, the
front surface is also a plane of incidence.
[0117] The light transmitting layer 81 may have a multilayered
structure of three or more layers including the
support layer 73, the covering layer 72, and other layers.
In this case, other layers may be disposed, for example,
between the support layer 73 and the covering layer 72 or on
a surface of the support layer 73 that is opposite to the
covering layer 72.
[0118] The support layer 73 is a film or a sheet that can
be handled alone. Materials for forming the support layer 73
include a resin having a light transmission property such as
polycarbonate and polyester.
[0119] For example, the covering layer 72 is formed by a
step of coating a resin on the support layer 73 to form a
coating and a step of pressing a stamper against the coating
to cure the resin that forms the coating. Materials for
forming the covering layer 72 include, for example, a
thermoplastic resin, a thermosetting resin, and a
photosetting resin.
[0120] While the relief layer 71 is formed on the overall
surface of the covering layer 72 that is in contact with the
relief layer 71, the relief layer 71 may be formed on only a
part of the surface of the covering layer 72 that is in
contact with the relief layer 71. That is, the relief layer
71 may include only the lattice lines 51 and does not need to
include the recess 52 between two lattice lines 51 that are
adjacent to each other in a direction perpendicular to the
plane of drawing. In this case, the recess 52 is formed by
the covering layer 72.
[0121] The relief layer 71 is formed with any of the
metals and alloys described above. The plane of incidence
21s of the relief layer 71 is made of metal and thus the
plane of incidence 21s has relatively high light reflectance.
32
[0122] Like the display body 10 described with reference
to Fig. 7, the reflection of light on the plane of incidence
21s is suppressed and part of light that is incident on the
plane of incidence 21s is transmitted through the relief
layer 71. A light that travels inside of the relief layer 71
is absorbed by the relief layer 71. Since part of light that
is incident on the plane of incidence 21s is absorbed by the
relief layer 71 multiple times, it is possible to suppress
the reflection of light on the plane of incidence 21s and the
transmission of light through a surface of the relief layer
71 that is opposite to the plane of incidence 21s.
[0123] For example, the relief layer 71 is formed by
vapor-phase deposition such as vacuum deposition or
sputtering. When the relief layer 71 is formed on a part of
the surface of the covering layer 72 that is in contact with
the relief layer 71, the relief layer 71 is formed as follows.
That is, the relief layer 71 is formed by a step of forming a
metal thin layer on portions of the surface covering layer 72
with recesses and protrusions by vapor-phase deposition and a
step of patterning the thin film.
[0124] At the step of patterning the thin layer, a part of
the thin layer may be dissolved using alkaline or acid
chemicals. Alternatively, a part of the thin layer may be
peeled off using an adhesive material that has adhesive
strength greater than that of the thin layer and the covering
layer 72.
[0125] The relief layer 71 that is disposed on a part of a
surface of the covering layer 72 that is in contact with the
relief layer 71 may be formed by vapor-phase deposition using
a mask.
[0126] The display body 10 may include, in addition to the
light transmitting layer 81 and the relief layer 71 described
above, other layers including an adhesion layer, a sticking
layer, and a resin layer.
[0127] When the display body 10 includes at least one of
33
the adhesion layer and the sticking layer, it is only
necessary that the adhesion layer or the sticking layer
covers a surface of the relief layer 71 that is opposite to
the covering layer 72, and functions as the rear surface of
the display body 10. When the display body 10 includes both
the light transmitting layer 81 and the relief layer 71, the
shape of the rear surface constituted by the relief layer 71
is usually the same as the shape of the interface of the
light transmitting layer 81 and the relief layer 71. If at
least one of the adhesion layer and the sticking layer
constitutes the rear surface of the display body 10, it is
possible to prevent the surface of the relief layer 71 from
being exposed to the outside of the display body 10.
[0128] The shape of the rear surface of the display body
10 that is included in at least one of the adhesion layer and
the sticking layer is obtained by smoothening the shapes of
the structures on the surface of the relief layer 71, and
thus is different from the shape of the surface of the relief
layer 71. Consequently, it is difficult to duplicate the
display body 10 for the purpose of counterfeiting.
[0129] The relief layer 71 of the display body 10 does not
need to be made of metal, and may be embodied as the
following layer. That is, the relief layer 71 may be an
adhesion layer or a sticking layer that covers a recessed and
projecting structure formed on the covering layer 72 so as to
correspond to the lattice lines 51. In such a case, the
adhesion layer or the sticking layer has a light reflecting
property and a light absorbing property.
[0130] When the rear surface of the display body 10 is a
surface of the light transmitting layer 81 that is opposite
to the relief layer 71 and the front surface thereof is a
surface of the relief layer 71 that is opposite to the lighttransmitting
layer 81, it is only necessary that at least one
of the adhesion layer and the sticking layer is formed on the
surface of the light transmitting layer 81 that is opposite
34
to the surface in contact with the relief layer 71. When the
front surface of the display body 10 is the surface of the
relief layer 71 that is opposite to the light-transmitting
layer 81 and is also a plane of incidence, a light blocking
layer, in addition to the light transmitting layer 81 or
instead of the light transmitting layer 81, may be disposed
behind the relief layer 71.
[0131] It is only necessary that a resin layer included in
the display body 10 is disposed on a laminate of the light
transmitting layer 81 and the relief layer 71 as a layer that
constitutes the front surface of the display body 10. For
example, when the relief layer 71 is disposed on the front
surface side of the light transmitting layer 81 and covered
by the resin layer, it is possible to prevent the relief
layer 71 from being damaged. Additionally, since the relief
layer 71 is covered by the resin layer, it is difficult to
duplicate the relief part 21 for the purpose of
counterfeiting.
[0132] Examples of the resin layer include a hard coat
layer for preventing the front surface of the display body 10
from being scratched, an antifouling layer for preventing the
display body 10 from being contaminated, an antireflection
layer for preventing light reflection on the front surface of
the display body 10, and an antistatic layer for preventing
charging on the display body 10.
[0133] The display body 10 may further include a print
layer. It is only necessary that the print layer is disposed
on a side of the relief layer 71 at which the light
transmitting layer 81 is disposed. That is, the print layer
may be disposed on a surface of the support layer 73 that is
opposite to a surface in contact with the covering layer 72,
may be interposed between the support layer 73 and the
covering layer 72, or may be interposed between the covering
layer 72 and the relief layer 71. When the display body 10
includes the print layer, the information that can be
35
displayed by the display body 10 is added using the print
layer, and thus the display body 10 can display a more
complicated image. The print layer also enables the
information to be added to the display body 10 more easily
than in a case where the information is added using the
relief structure.
[0134] [Structure of Article]
An example in which an article is embodied as an IC card
is described as an embodiment of an article with the display
body 10, with reference to Figs. 9 and 10.
As shown in Fig. 9, an IC (integrated circuit) card 60
includes a base 61 that has a plate shape and is made of, for
example, plastic, a print layer 62 having a predetermined
image printed thereon, an IC chip 63, and the display body 10.
[0135] As shown in Fig. 10, the print layer 62 is formed
on the base 61, and the display body 10 described above is
fixed on a display surface of the print layer 62 that is
opposite to a surface in contact with the base 61 by using,
for example, a sticking layer. For example, the display body
10 is prepared as a sticker with a sticking layer or a
transfer foil, and adhered to the print layer 62.
[0136] A recess 61a is formed in the base 61. The recess
61a is recessed from a part of the surface of the base 61 in
contact with the print layer 62 toward a surface of the base
61 that is opposite to the surface in contact with the print
layer 62. A through-hole 62a is formed at a position on the
print layer 62 that matches the recess 61a in a thickness
direction of the IC card 60. The IC chip 63 is fitted into
the recess 61a and the through-hole 62a. The IC chip 63
includes a plurality of electrodes on its surface surrounded
by the print layer 62. Information is written in the IC chip
63 through the electrodes, and information recorded in the IC
chip 63 is read from the IC chip 63 through the electrodes.
[0137] The IC card 60 includes the display body 10 that is
difficult to counterfeit, and thus the IC card 60 itself is
36
also difficult to counterfeit. The IC card 60 includes, in
addition to the display body 10, the IC chip 63 and the print
layer 62, and thus it is possible to prevent counterfeiting
by using the IC chip 63 and the print layer 62.
[0138] As described above, the embodiment of a display
body and an article has the following advantages.
(1) The display body 10 forms a bright image by light
diffracted by the lattice lines 51, and thus the brightness
of the bright image is increased.
[0139] (2) When both the lattice line pitch P1 and the
step pitch P2 are less than or equal to the shortest
wavelength of visible light, the lattice lines 51 and the
protrusions 51a form a dark image in a front view. The
brightness of the dark image is further reduced as compared
to a case where only the protrusions 51a form a dark image.
[0140] (3) When the lattice line pitch P1 is less than or
equal to the shortest wavelength of visible light and the
step pitch P2 exceeds the shortest wavelength of visible
light, the number of the protrusions 51a per unit area is
less than that in a case where the step pitch P2 is less than
or equal to the shortest wavelength of visible light. Thus,
the brightness of a dark image is reduced by the lattice
lines 51 and the protrusions 51a, and simultaneously, the
accuracy of the shape of the display body 10 is improved as
compared to the case where the step pitch P2 is less than or
equal to the shortest wavelength of visible light.
[0141] (4) When the lattice line pitch P1 exceeds the
shortest wavelength of visible light and the step pitch P2 is
less than or equal to the shortest wavelength of visible
light, the angle formed by the direction in which diffracted
light is emitted, that is, the direction in which a plane of
incidence is viewed obliquely and the front view direction in
which the plane of incidence is viewed from the front is
small. It is thus easy to observe diffracted light emitted
by the display body 10.
37
[0142] (5) The protrusions 51a are periodically arranged.
Thus, the protrusions 51a not only form a dark image but also
have an optical effect according to the step pitch P2.
[0143] (6) At least a part of the plane of incidence 21s
is formed of the relief layer 71 made of metal. Thus, the
part of the plane of incidence 21s that is formed of the
relief layer 71 has relatively high light reflectance.
[0144] (7) The relief parts 21 may include relief parts 21
in which at least one of the lattice line pitch P1 of the
lattice lines 51 and the direction in which the lattice lines
51 extend is different from each other. In this case, the
relief parts 21 include the relief parts 21 in which at least
one of the wavelength of diffracted light and the direction
in which diffracted light is emitted is different from each
other, and thus the display body 10 displays a more
complicated bright image.
[0145] (8) The relief parts 21 may include relief parts 21
having different rules for arranging at least either the
protrusions 51a or the density of the protrusions 51a. In
this case, the relief parts 21 include display parts in which
at least one of the type of light emitted from the
protrusions 51a and the brightness of a dark image formed by
the protrusions 51a is different from each other, and thus
the display body 10 displays a bright image and a dark image
in a complicated manner.
[0146] [Other Embodiments]
Other embodiments are described with reference to Figs.
11 to 13. Three embodiments that are different from the
embodiment described above are described below in order. In
Figs. 11 to 13, the same structures as in the embodiment
described above are denoted by the same reference numerals,
and descriptions thereof are omitted.
[0147] As shown in Fig. 11, protrusions 51a included in a
lattice line 51 are arranged aperiodically in an X-direction.
When the protrusions 51a are arranged aperiodically, a step
38
pitch P2 is within the range of 200 nm to 500 nm, inclusive.
The step pitch P2 is preferably less than or equal to 500 nm,
and is more preferably less than or equal to 400 nm, that is,
the shortest wavelength of visible light. The step pitch P2
is preferably greater than or equal to 200 nm.
[0148] The average value calculated by dividing the total
of the step pitches P2 by the number of the step pitches P2
is preferably within the range of 200 nm to 500 nm, inclusive.
The most frequent value, which is a value obtained most
frequently among values of the step pitch P2, is more
preferably within the range of 200 nm to 500 nm, inclusive.
All the values of the step pitch P2 are more preferably
within the range of 200 nm to 500 nm, inclusive.
[0149] The maximum value P2M among the values of the step
pitch P2 is preferably 500 nm, whereas the minimum value P2m
is preferably 200 nm.
[0150] This configuration has the following advantages.
(9) It is possible to reduce the emission of diffracted
light due to arrangement in the X-direction of the
protrusions 51a in the display body 10 at equal intervals.
[0151] When the relief part 21 is viewed in the Xdirection,
that is, the direction in which the lattice lines
51 extend under certain illumination conditions, white
scattering light emitted from the protrusions 51a
aperiodically arranged in the X-direction is observed. When
the relief part 21 of the display body 10 is viewed in a Ydirection,
diffracted light is observed. Meanwhile, when the
relief part 21 is viewed in the X-direction that is rotated
from the Y-direction by 90°, white scattering light that has
a different hue from that of diffracted light is observed.
[0152] One way to determine whether the display body 10 is
genuine or counterfeit is to check that the hue of light
viewed in the Y-direction is different from the hue of light
viewed in the X-direction.
[0153] As shown in Fig. 12, protrusions 51a included in
39
one lattice line 51 are arranged in the X-direction at equal
intervals. Meanwhile, the protrusions 51a are arranged in
one relief part 21 in an arrangement direction AD crossing
the Y-direction at equal intervals. The color of diffracted
light that reaches a fixed point is thus different from that
in a case where the protrusions 51a are arranged in one
relief part 21 in the Y-direction at equal intervals. Since
the protrusions 51a are arranged in the arrangement direction
AD crossing the Y-direction, it is possible to emit
diffracted light originating from the protrusions 51a to the
relief part 21 in a direction crossing the X-direction.
[0154] As shown in Fig. 13, the lattice line width LW of
each lattice line 51 is greater than or equal to a half of a
lattice line pitch P1. The amount of diffracted light
emitted by the lattice line 51 is not greatly affected by the
lattice line width LW of the lattice line 51. On the other
hand, when the lattice line width LW of the lattice line 51
is increased, that is, when the area of a recess 52 between
two adjacent lattice lines 51 in the Y-direction is reduced,
the area of the relief part 21 occupied by the lattice lines
51 is increased. That is, such a structure is preferable in
order to reduce the brightness of a dark image formed by the
relief part 21.
[0155] The lattice line pitch P1 may be less than or equal
to the shortest wavelength of visible light or may exceed the
shortest wavelength of visible light in the three relief
parts 21 described in other embodiments. The step pitch P2
may be less than or equal to the shortest wavelength of
visible light or may exceed the shortest wavelength of
visible light. Since the lattice line pitch P1 and the step
pitch P2 are within the ranges described above in other
embodiments, advantages that are equivalent to those of the
embodiment described above can be obtained in other
embodiments.
[0156] The relief parts 21 that constitute the display
40
area 11 may include relief part 21 according to the
embodiment described above and three types of the relief
parts 21 according to other embodiments in any combination
thereof. When the relief parts 21 include the relief parts
21 in which at least one of a rule for arranging the
protrusions 51a, that is, the step pitch P2 and the
arrangement periodicity of the protrusions 51a is different
from each other, an advantage that is similar to (8)
described above can be obtained.
[0157] [Modifications]
The above-described embodiments may be modified as
follows.
The article may be other cards such as magnetic cards,
wireless cards, and ID (identification) cards. Alternatively,
the article may be valuable stock certificates such as gift
tickets and stock certificates, articles that needs be
confirmed as being genuine such as brand-name products and
works of art, or packages or a part of packages that
accommodate an article that needs to be confirmed as being
genuine.
[0158] When the base of the article is made of paper, the
display body 10 may be supported by the article as follows.
That is, the base is watermarked with the display body 10,
and an opening is formed at a position on the base that
overlaps the display body 10 in a thickness direction of the
base. In this way, the display body 10 is supported by the
article.
[0159] When the base is made of a light transmitting
material, the display body 10 may be embedded in the base, or
may be fixed on the rear surface of the base, that is, a
surface of the base that is the farthest from a display
surface of the display body 10.
[0160] In case that a surface that forms the surface 51s
of the lattice line 51 is set as a reference surface, the
surface 51s of the lattice line 51 may include both a
41
protrusion that projects from the reference surface in a Zdirection
and a recess that is recessed from the reference
surface in the Z-direction.
[0161] When the display body 10 includes a plurality of
display areas 11, each display area 11 may be provided with a
part having an optical effect different from the display part
12 described above. In such a case, it is only necessary
that the display body 10 includes, for example, a light
scattering pattern, a light collection pattern, or a
diffraction grating that constitutes a part of the display
area 11.
[0162] For example, the light scattering pattern is a
surface on which steps are irregularly formed. The steps
have different sizes in its width direction, different shapes,
and different height differences from the reference surface.
Light that is incident on the light scattering pattern
reflects diffusely in all directions, and thus is observed by
the observer as white or white cloudy light. The step of the
light scattering pattern has, for example, a width of 3 μm or
more and a height difference of 1 μm or more. The width and
the height difference of the step in the light scattering
pattern are greater than the width and the height difference
of a recessed and projecting structure included in the relief
part 21. If the interval between the steps and the shape of
the step are determined according to a predetermined rule,
the light scattering pattern can have directive light
scattering characteristics.
[0163] The light collection pattern is a lens pattern for
a microlens or a Fresnel lens. The light collection pattern
can be formed if the thickness of the display body 10 is
relatively smaller than that in a case where other lenses are
used. It seems to the observer that incident light that is
incident on these lens patterns is collected on a light
incident side or a rear surface side with respect to a
surface of the display body 10, and thus special visual
42
effects are added to the display body 10.
[0164] Unlike the relief part 21 described above, the
diffraction grating does not form a dark image in a front
view and forms a bright image by diffracted light in an
oblique view. The lattice line pitch of the diffraction
grating is preferably 0.5 μm or more and 3 μm or less.
[0165] The structure of the plane of incidence 21s of the
display body 10 described above enables the display body 10
to have a more complicated optical effect, and thus it is
more difficult to counterfeit the display body 10.
[0166] The display body 10 does not need to be a display
body used for the purpose of preventing counterfeiting of an
article. The display body 10 may be, for example, a display
body for decorating an article or a toy or a learning
material in which a display body by itself is an observation
target.
DESCRIPTION OF THE REFERENCE NUMERALS
[0167] 10: Display body
10f: Front surface
11: Display area
12: Display part
21, 100: Relief part
21s: Plane of incidence
22: Flat part
51: Lattice line
51a, 101: Protrusion
51s, 52s: Surface
52, 61a: Recess
60: IC card
61: Base
62: Print layer
62a: Through-hole
63: IC chip
71: Relief layer
43
72: Covering layer
73: Support layer
81: Light transmitting layer
DG: Diffraction grating
IF: Interface
44
We claim:
1. A display body comprising a plurality of lattice lines
that are arranged along a plane of incidence on which light
is incident, wherein
the lattice lines have properties for forming a bright
image with diffracted light of the incident light in an
oblique view in which the plane of incidence is viewed
obliquely and absorbing some of the incident light,
a surface of each of the lattice lines includes a
plurality of dispersed fine steps that are repetitive in a
direction in which the lattice lines extend, and
the steps have an antireflection function and form a
dark image in a front view directly facing the plane of
incidence.
2. The display body according to claim 1, wherein
an interval between the lattice lines that are adjacent
to each other is a lattice line pitch,
the lattice line pitch includes a value less than or
equal to a shortest wavelength of visible light,
an interval between the steps that are adjacent to each
other on each of the lattice lines is a step pitch, and
the step pitch includes a value less than or equal to
the shortest wavelength of visible light.
3. The display body according to claim 1, wherein
an interval between the lattice lines that are adjacent
to each other is a lattice pitch,
the lattice line pitch includes a value less than or
equal to a shortest wavelength of visible light,
an interval between the steps that are adjacent to each
other on each of the lattice lines is a step pitch, and
the step pitch includes a value greater than the
shortest wavelength of visible light.
45
4. The display body according to claim 1, wherein
an interval between the lattice lines that are adjacent
to each other is a lattice line pitch,
the lattice line pitch includes a value greater than a
shortest wavelength of visible light,
an interval between the steps that are adjacent to each
other on each of the lattice lines is a step pitch, and
the step pitch includes a value less than or equal to
the shortest wavelength of visible light.
5. The display body according to any one of claims 1 to 4,
wherein the steps are aperiodically arranged in the direction
in which the lattice lines extend.
6. The display body according to any one of claims 1 to 4,
wherein the steps are periodically arranged in the direction
in which the lattice lines extend.
7. The display body according to any one of claims 1 to 6,
wherein at least a part of the plane of incidence is made of
metal.
8. The display body according to any one of claims 1 to 7,
further comprising a plurality of display parts each
including the lattice lines,
wherein the display parts include a display part in
which at least either an interval between the lattice lines
that are adjacent to each other and a direction in which the
lattice lines extend varies.
9. The display body according to any one of claims 1 to 8,
further comprising a plurality of display parts each
including the lattice lines,
wherein the display parts include a display part in
46
which at least either a rule for arranging the steps and an
arranged density of the steps varies.
10. An article with a display body, wherein the display body
is the display body according to any one of claims 1 to 9.