FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
& The Patent Rules, 2003
COMPLETE SPECIFICATION
1.TITLE OF THE INVENTION:
DISPLAY BODY, ARTICLE, ORIGINAL PLATE, AND METHOD FOR PRODUCING
ORIGINAL PLATE
2. APPLICANT:
Name: TOPPAN PRINTING CO., LTD.
Nationality: Japan
Address: 5-1, Taito 1-chome, Taito-ku, Tokyo 1100016, Japan.
3. PREAMBLE TO THE DESCRIPTION:
The following specification particularly describes the invention and the manner in which it is
to be performed:
2
DESCRIPTION
TECHNICAL FIELD
[0001] The present invention relates to a display that
may be used as a structure for preventing counterfeiting, an
article including a display, an original plate for producing a
display, and a method for producing an original plate.
BACKGROUND ART
[0002] Securities, such as banknotes, gift certificates,
and checks, cards, such as credit cards, bank cards, and ID
cards, and identity documents, such as passports and driver's
licenses, have display bodies affixed to prevent
counterfeiting of these articles by providing visual effects
different from those of printed articles formed by dyes or
pigments.
[0003] A known display that provides visual effects
different from those of printed articles has a plurality of
relief diffraction gratings. The relief diffraction gratings
differ from one another in the extending direction of grooves
or the grating constant, allowing the display to display an
iridescent image (see Patent Document 1, for example).
[0004] Such display bodies are widely used to prevent
counterfeiting of articles, so the techniques used for the
display bodies are widely known. Accordingly, the possibility
of counterfeiting of the display bodies has been increased,
resulting in the need for display bodies that are more
effective in preventing counterfeiting than the display bodies
that display iridescent images.
[0005] In recent years, for the purpose of preventing
counterfeiting more effectively, a display has been proposed
that provides visual effects that differ from those of display
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bodies having relief diffraction gratings. The proposed
display includes a reflection surface having an relief
structure, which is formed by a plurality of first surfaces
and a second surface. The display emits light of a mixed
color produced by a plurality of wavelengths of light (see
Patent Document 2, for example).
PRIOR ART DOCUMENTS
Patent Documents
[0006] Patent Document 1: U.S. Patent No. 5058992
Patent Document 2: Japanese Patent No. 4983899
SUMMARY OF THE INVENTION
Problems that the Invention is to Solve
[0007] When the display of Patent Document 2 is
illuminated with light, the display emits light of a specific
color toward a wide area in the space above the reflection
surface. The display emits the light whose color remains
substantially the same regardless of any change in the
observation conditions, such as the position of the
illumination source relative to the display and the position
of the observer relative to the display. The display
therefore displays substantially the same image regardless of
any change in the observation conditions. However, to enhance
the visual effects of display bodies, there has been a demand
for display bodies that display images that change as the
observation conditions change.
[0008] Such a demand applies not only to a display used
to prevent counterfeiting but also to a display for decorating
an article and a display that is observed for its own quality.
[0009] It is an objective of the present invention to
provide a display, an article, an original plate for producing
a display, and a method for producing an original plate that
emit colored light to display an image that changes
dynamically.
4
Means for Solving the Problems
[0010] To achieve the foregoing objective, a display is
provided that includes a substrate including a covered surface
and a reflection layer covering at least part of the covered
surface. The reflection layer has an obverse surface
including a plurality of first reflection surfaces and a
second reflection surface. In a plan view facing the obverse
surface of the reflection layer, the first reflection surfaces
are substantially square in shape, and the second reflection
surface occupies gaps between adjacent ones of the first
reflection surfaces. A distance between the first reflection
surfaces and the second reflection surface in a thickness
direction of the substrate has an extent that the obverse
surface of the reflection layer emit colored light by
interference between light reflected from the first reflection
surfaces and light reflected from the second reflection
surface. In a plan view facing the obverse surface of the
reflection layer, more than one of the first reflection
surfaces are located on each of a plurality of imaginary lines.
On a straight line intersecting more than one of the imaginary
lines, distances between adjacent ones of the imaginary lines
have different extents.
To achieve the foregoing objective, an article is
provided that includes a display and a support portion that
supports the display. The display is the above described
display.
[0011] To achieve the foregoing objective, an original
plate for producing a display is provided that includes a
covered surface, which includes first covered surfaces and a
second covered surface, and a reflection layer, which covers
the covered surface. The original plate includes a substrate
including a surface and a resist layer that is located on the
surface of the substrate and includes a transfer surface,
which is opposite to a surface that is in contact with the
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substrate. The transfer surface includes a plurality of first
transfer surfaces for forming the first covered surfaces and a
second transfer surface for forming the second covered surface.
In a plan view facing the transfer surface, the first transfer
surfaces are substantially square in shape, and the second
transfer surface occupies gaps between adjacent ones of the
first transfer surfaces. A distance between the first
transfer surfaces and the second transfer surface in a
thickness direction of the substrate is set to an extent that
an obverse surface of the reflection layer emit colored light
by interference between light reflected from sections of the
obverse surface of the reflection layer that are located on
the first covered surfaces and light reflected from a section
of the obverse surface of the reflection layer that is located
on the second covered surface. In a plan view facing the
transfer surface, more than one of the first transfer surfaces
are located on each of a plurality of imaginary lines. On a
straight line intersecting more than one of the imaginary
lines, distances between adjacent ones of the imaginary lines
have different extents.
[0012] To achieve the foregoing objective, a method for
producing an original plate is provided. The original plate
is used to produce a display including a covered surface,
which includes first covered surfaces and a second covered
surface, and a reflection layer, which covers the covered
surface. The method comprising: forming a resist layer on a
surface of a substrate; exposing the resist layer to light;
and developing the exposed resist layer to form a transfer
surface in the resist layer. The exposing includes exposing
the resist layer such that: the transfer surface after
developing includes a plurality of first transfer surfaces for
forming the first covered surfaces and a second transfer
surface for forming the second covered surface, in a plan view
facing the transfer surface, the first transfer surfaces are
substantially square in shape, and the second transfer surface
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occupies gaps between adjacent ones of the first transfer
surfaces; a distance between the first transfer surfaces and
the second transfer surface in a thickness direction of the
substrate is set to an extent that an obverse surface of the
reflection layer emit colored light by interference between
light reflected from sections of the obverse surface of the
reflection layer that are located on the first covered
surfaces and light reflected from a section of the obverse
surface of the reflection layer that is located on the second
covered surface; and in a plan view facing the transfer
surface, more than one of the first transfer surfaces are
located on each of a plurality of imaginary lines, and, on a
straight line intersecting more than one of the imaginary
lines, distances between adjacent ones of the imaginary lines
have different extents.
[0013] The above described configurations is able the
display to emit light having a color that is determined by the
distance between the first reflection surfaces and the second
reflection surface. Since a plurality of first reflection
surfaces is arranged on each imaginary line, the first
reflection surfaces and the second reflection surface located
between the first reflection surfaces on each imaginary line
may be considered as forming one pseudo surface. Thus, the
interference between the reflection light from the first
reflection surfaces arranged on the imaginary lines and the
reflection light from the second reflection surface located
between the imaginary lines produces colored light. The
colored light has directivity and is emitted in the direction
substantially perpendicular to the extending direction of the
imaginary lines in a plan view facing the obverse surface of
the reflection layer. As such, the display emits colored
light and displays an image that changes dynamically as
compared to a structure that emits light isotropically.
EFFECTS OF THE INVENTION
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[0014] The present invention displays an image that is
formed by colored light and changes dynamically.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] Fig. 1 is a plan view showing the planar structure
of a display of one embodiment according to the present
invention.
Fig. 2 is a cross-sectional view taken along line I-I in
Fig. 1, showing a part of the cross-sectional structure of the
display.
Fig. 3 is an enlarged cross-sectional view showing a
part of the cross-sectional structure of the display.
Fig. 4 is a plan view showing the planar structure of a
display portion as viewed facing the reflection surface.
Fig. 5 is a plan view showing an example of structures
formed by hairline finish.
Fig. 6 is a plan view showing the planar structures of
display portions as viewed facing the reflection surface.
Fig. 7 is a plan view showing the planar structures of a
display portion of the first display region, a display portion
of the second display region, and a display portion of the
third display region, which are arranged side by side.
Fig. 8 is a cross-sectional view showing the crosssectional
structures of a display portion of the first display
region, a display portion of the second display region, and a
display portion of the third display region, which are
arranged side by side.
Fig. 9 is a schematic view of the state in which a
diffraction grating having a relatively small grating constant
emits positive first-order diffracted light.
Fig. 10 is a schematic view of the state in which a
diffraction grating having a relatively large grating constant
emits positive first-order diffracted light.
Fig. 11 is a perspective view showing the structure of
an example of a display portion.
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Fig. 12 is a diagram for illustrating the operation of
the display portion.
Fig. 13 is a diagram for illustrating the operation of a
diffraction grating.
Fig. 14 is a plan view showing the planar structure of
an IC card of one embodiment in which the article of the
present invention is embodied as an IC card.
Fig. 15 is a cross-sectional view taken along line II-II
in Fig. 14, showing the cross-sectional structure of the IC
card.
Fig. 16 is a flowchart for illustrating the sequence in
the method for producing an original plate.
Fig. 17 is a perspective view showing the structure of
an original plate.
Fig. 18 is a perspective view showing the structure of
an example of an anti-reflection portion of a display of a
modification.
Fig. 19 is a perspective view showing the structure of
an example of a light scattering portion of a display of a
modification.
Fig. 20 is a plan view for illustrating the state of the
imaginary lines in a display of a modification.
Fig. 21 is a diagram for illustrating the operation of
the display of the modification.
Fig. 22 is a diagram for illustrating the operation of
the display of the modification.
Fig. 23 is a diagram for illustrating the operation of
the display of the modification.
Fig. 24 is a diagram for illustrating the operation of
the display of the modification.
Fig. 25 is a diagram for illustrating the operation of
the display of the modification.
Fig. 26 is a diagram for illustrating the operation of
the display of the modification.
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MODES FOR CARRYING OUT THE INVENTION
[0016] Referring to Figs. 1 to 17, one embodiment of a
display, an article, an original plate, and a method for
producing an original plate according to the present invention
is now described. In the following descriptions, the
structure of the display, the operation of the display, the
structure of the article, a method for producing the display,
and a method for producing an original plate are described in
this order.
[0017] [Structure of Display]
Referring to Figs. 1 to 8, the structure of the display
is now described. For purpose of illustration, the reflection
layer of the display is not shown in Fig. 1.
As shown in Fig. 1, a display 10 includes a planar
substrate 11. A first display region 12, a second display
region 13, and a third display region 14 are defined in the
display 10. Each display region includes a plurality of
display portions. The first display region 12 displays letter
A, the second display region 13 displays letter B, and the
third display region 14 displays letter C. The display 10
displays character string ABC formed by the first display
region 12, the second display region 13, and the third display
region 14.
[0018] The display 10 may include two or less display
regions or four or more display regions. The display regions
may display images other than characters, such as numbers,
symbols, and pictures.
[0019] Fig. 2 shows the cross-sectional structure taken
along line I-I in Fig. 1. As shown in Fig. 2, the display 10
includes a light transmissive substrate 11 and a reflection
layer 21. The substrate 11 includes a support layer 22 and an
relief layer 23. The relief layer 23 has a covered surface
23s, which is an relief surface and opposite to the support
layer 22. Although the substrate 11 of the present embodiment
includes the support layer 22 and the relief layer 23, the
10
substrate 11 may include only one layer having the covered
surface 23s.
[0020] The covered surface 23s includes a plurality of
first covered surfaces 23a and a second covered surface 23b.
The first covered surfaces 23a differ from the second covered
surface 23b in position in the thickness direction of the
substrate 11.
[0021] Although the reflection layer 21 covers the entire
covered surface 23s, it is sufficient that the reflection
layer 21 cover the first covered surfaces 23a and the second
covered surface 23b, which form at least part of the covered
surface 23s. The surface of the reflection layer 21 that is
in contact with the covered surface 23s of the relief layer 23
is a reflection surface 21s, which is an example of the
obverse surface of the reflection layer 21. In the present
embodiment, light enter from the side on the support layer 22
of the display 10. Thus, surface of the reflection layer 21
that is in contact with the covered surface 23s of the
substrate 11 is the reflection surface 21s, which reflects the
light incident on the display 10.
[0022] The reflection layer 21 increases reflection
efficiency of incident light on the display 10, thus emit
light intensity of the display 10 is higher than a display
that does not employ a reflection layer. The reflection layer
21 increases visibility of the display 10 accordingly.
[0023] Light may be incident on the reflection layer 21
from opposite side to the substrate 11 with respect to the
reflection layer 21. In this case, surface of the reflection
layer 21 that is opposite to surface in contact with the
covered surface 23s serves as reflection surface.
[0024] The reflection surface 21s includes a plurality of
first reflection surfaces 21a and a second reflection surface
21b. In the thickness direction of the substrate 11, the
first reflection surfaces 21a differ from the second
reflection surface 21b in position, but each first reflection
11
surface 21a is identical to the other first reflection
surfaces 21a in position. The first and second reflection
surfaces 21a and 21b are flat surfaces, and the first
reflection surfaces 21a are substantially parallel to the
second reflection surface 21b.
[0025] That is, the sections of the reflection surface
21s that are in contact with the first covered surfaces 23a of
the relief layer 23 are the first reflection surfaces 21a, and
the section that is in contact with the second covered surface
23b of the relief layer 23 is the second reflection surface
21b.
[0026] The thickness of the reflection layer 21 in the
thickness direction of the substrate 11 is between 30 nm and
150 nm inclusive, for example. In the reflection layer 21,
the sections corresponding to the first reflection surfaces
21a and the section corresponding to the second reflection
surface 21b have the same thickness.
[0027] Referring to Fig. 3, the distance between the
first reflection surfaces 21a and the second reflection
surface 21b in the thickness direction of the substrate 11 is
referred to as an inter-reflection-surface distance D1. The
inter-reflection-surface distance D1 has an extent that the
reflection surface 21s emit colored light by the interference
between first reflection light RL1 reflected from the first
reflection surfaces 21a and second reflection light RL2
reflected from the second reflection surface 21b.
[0028] When white light enter on the reflection surface
21s, the first reflection light RL1 reflected from the first
reflection surfaces 21a differs from the second reflection
light RL2 reflected from the second reflection surface 21b in
optical path length, which is the value obtained by
multiplying geometric distance by refractive index. The
interference of light according to the difference in optical
path lengths reduces the diffraction efficiency of the
diffracted light of a certain wavelength at the reflection
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surface 21s, whereas the diffraction efficiency of the light
of the other wavelengths is not reduced. The reflection
surface 21s thus emits light of a predetermined color, that is,
a specific color determined by the inter-reflection-surface
distance D1.
[0029] The distance between the first covered surfaces
23a, which are in contact with the first reflection surfaces
21a, and the second covered surface 23b, which is in contact
with the second reflection surface 21b, is referred to as an
inter-covered-surface distance D2. The inter-covered-surface
distance D2 is preferably between 0.05 μm and 0.5 μm inclusive,
more preferably between 0.15 μm and 0.4 μm inclusive, for
example.
[0030] The inter-covered-surface distance D2 that is
greater than or equal to 0.05 μm reduces intensity of light in
the visible wavelength range, allowing the reflection surface
21s to emit light of a color having a higher chroma than white.
When the inter-covered-surface distance D2 is greater than or
equal to 0.05 μm, external factors in manufacturing of the
display 10, such as the condition of manufacturing apparatus,
a change in manufacturing environment of the display 10, and a
change in the composition of the material of the display 10,
are less likely to affect optical properties of the display 10.
Further, the inter-covered-surface distance D2 that is less
than or equal to 0.5 μm allows the covered surface 23s to be
formed with a higher accuracy in shape and size than a
structure having a greater inter-covered-surface distance D2.
[0031] In the structure in which light enter on the
reflection layer 21 from opposite side to the substrate 11
with respect to the reflection layer 21, the surface of the
reflection layer 21 that is opposite to the surface in contact
with the relief layer 23 serves as the reflection layer. Thus,
premising that the sections of the reflection layer 21
corresponding to the first reflection surfaces 21a and the
section corresponding to the second reflection surface are
13
equal in thickness, the inter-covered-surface distance D2 that
is within the range described above results in the interreflection-
surface distance D1 having an extent that
reflection surface emit light of the specific color.
[0032] The sections of the reflection layer 21
corresponding to the first reflection surfaces 21a may differ
from the section corresponding to the second reflection
surface 21b in thickness, as long as the inter-reflectionsurface
distance D1, which is the distance between the first
reflection surfaces 21a and the second reflection surface 21b,
is within the range described above for the inter-coveredsurface
distance D2.
[0033] The side surfaces 23c connecting the first covered
surfaces 23a to the second covered surface 23b are
substantially perpendicular to the second covered surface 23b.
However, the side surfaces 23c may be inclined with respect to
the direction normal to the second covered surface 23b.
Nevertheless, the angle formed by the side surfaces 23c and
the second covered surface 23b is preferably closer to a right
angle. The angle between the side surfaces 23c and the second
covered surface 23b that is closer to right angle increases
chroma of the color of light emitted by the reflection surface
21s.
[0034] The sections of the reflection layer 21 covering
the side surfaces 23c have a thickness in the direction
perpendicular to the thickness direction of the substrate 11.
The thickness is less than the thickness of the sections of
the reflection layer 21 corresponding to the first reflection
surfaces 21a and the second reflection surface 21b in the
thickness direction of the substrate 11.
[0035] Fig. 4 is an enlarged view showing one of display
portions forming the first display region 12. The display
portion is a part of the first display region 12. Fig. 4
shows the planar structure as viewed facing the reflection
surface 21s.
14
[0036] The display portion shown in Fig. 4 is square in
shape, but the display portion may have other shape, such as
the shape of a rectangle, a triangle, a circle, or an ellipse.
When the display portion has a polygonal shape, the length of
one side of outer edge of the display portion is preferably
less than or equal to 300 μm. Each display portion serves as
one pixel with which the first display region 12 displays one
image.
[0037] As shown in Fig. 4, in a plan view facing the
reflection surface 21s, the first reflection surfaces 21a in
one display portion 12p of the first display region 12 are
substantially square in shape, and the second reflection
surface 21b occupies gaps between adjacent ones of the first
reflection surfaces 21a.
[0038] In a plan view facing the reflection surface 21s,
a plurality of first reflection surfaces 21a is located on
each imaginary line Lv. That is, a plurality of first
reflection surfaces 21a is arranged on each imaginary line Lv.
The imaginary lines Lv extend in X direction, which is one
direction, and the imaginary lines Lv are arranged in Y
direction, which is perpendicular to the X direction. The
imaginary lines Lv are arranged in the Y direction so as to
reduce emission of diffracted light that is perceivable by the
naked eye.
[0039] Distance between two imaginary lines Lv, which are
adjacent to each other in the Y direction, is referred to as
an inter-imaginary-line distance D3. The inter-imaginary-line
distance D3 varies irregularly with respect to the order of
arrangement of the imaginary lines Lv. In other words, the
imaginary lines Lv are arranged in the Y direction in a random
manner, and each imaginary line Lv is parallel to the other
imaginary lines Lv. That is, in a plan view facing the
reflection surface 21s, the inter-imaginary-line distances D3
have different extents and vary irregularly with respect to
the order of arrangement of the imaginary lines Lv on a
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straight line intersecting imaginary lines Lv, for example a
straight line extending in the Y direction.
[0040] The inter-imaginary-line distances D3 of the
imaginary lines Lv are preferably between 0.3 μm and 2 μm
inclusive, for example. A smaller inter-imaginary-line
distance D3 increases the range of angles at which light beams
are emitted in the direction perpendicular to the extending
direction of the imaginary lines Lv. This enlarges region
from which the observer of the display 10 can see emitted
light. In contrast, a larger inter-imaginary-line distance D3
reduces the range of angles at which light beams are emitted
in the direction perpendicular to extending direction of the
imaginary lines Lv. This reduces size of the region from
which the observer of the display 10 can see the emitted light.
[0041] On each imaginary line Lv, a plurality of first
reflection surfaces 21a is arranged in a random manner. Thus,
for the first reflection surfaces 21a arranged along one
imaginary line Lv, the distances between adjacent ones of the
first reflection surfaces 21a are not uniform values and vary
irregularly with respect to the order of arrangement of the
first reflection surfaces 21a. The structure in which a
plurality of first reflection surfaces 21a is arranged in a
random manner on each imaginary line Lv is advantageous in
that the structure limits emission of diffracted light in the
extending direction of the imaginary lines Lv, which would
otherwise occur according to the periodicity of the first
reflection surfaces 21a.
[0042] In the present embodiment, each imaginary line Lv
differs from the other imaginary lines Lv in positions of the
first reflection surfaces 21a on the imaginary line Lv.
However, as long as first reflection surfaces 21a are arranged
in a random manner on each imaginary line Lv, each imaginary
line Lv may be identical to the other imaginary lines Lv in
the positions of the first reflection surfaces 21a on the
imaginary line Lv.
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[0043] In addition, first reflection surfaces 21a may be
arranged regularly on each imaginary line Lv. That is, first
reflection surfaces 21a may be arranged with a fixed
periodicity. Such a structure still allows the display
portion 12p to emit colored light by the interference between
the light reflected from the first reflection surfaces 21a and
the light reflected from the second reflection surface 21b.
[0044] Since a plurality of first reflection surfaces 21a
is arranged on each imaginary line Lv, the plurality of first
reflection surfaces 21a arranged along one imaginary line Lv
functions like a structure formed by hairline finish on a
surface of a metal layer, for example. Thus, the display
portion 12p emits light in the direction perpendicular to the
extending direction of the imaginary lines Lv but hardly emits
colored light in the extending direction of the imaginary
lines Lv.
[0045] The first reflection surfaces 21a that are
arranged along one imaginary line Lv and the second reflection
surface 21b that occupies the gaps between adjacent ones of
the first reflection surfaces 21a on that imaginary line Lv
function as a pseudo surface 21d extending along the imaginary
line Lv. Consequently, the colored light that is produced by
the pseudo surfaces 21d and the second reflection surface 21b
located between adjacent pseudo surfaces 21d is emitted in
direction perpendicular to the imaginary lines Lv.
[0046] In other words, among the directions in which
light is emitted from the display portion 12p, the direction
that is perpendicular to the direction in which the intensity
of the emitting light is maximized is the extending direction
of the imaginary lines Lv in the display portion 12p.
Therefore, the extending direction of the imaginary lines Lv
in the display portion 12p can be identified by the direction
in which light is emitted from the display portion 12p.
[0047] Fig. 5 shows structures HL that are formed in a
surface of a metal layer by typical hairline finish. As shown
17
in Fig. 5, the metal layer after hairline finish includes a
plurality of linear structures extending in the Y direction.
The structures are arranged at irregular intervals in a
direction that intersects the Y direction. The heights of the
structures have different extents. Thus, the structures
formed by hairline finish do not function to reduce the
diffraction efficiency of light of a specific wavelength.
When white light enter on the metal layer having hairline
finish, the metal layer emits white scattered light in the X
direction, which is perpendicular to the Y direction.
[0048] As viewed facing the reflection surface 21s, the
length of one side of each first reflection surface 21a is
preferably between 0.3 μm and 2 μm inclusive. When the first
reflection surfaces 21a having such dimensions are arranged in
the display portion 12p, the distances between adjacent first
reflection surfaces 21a may be between 0.3 μm and 2 μm
inclusive, for example.
[0049] When the length of one side of the first
reflection surface 21a and the distances between first
reflection surfaces 21a are between 0.3 μm and 2 μm inclusive,
the emission angle of the diffracted light is greater than
that in a structure in which length of one side of the first
reflection surface 21a and the distances between first
reflection surfaces 21a are greater. This enlarges the region
in which the colored light that consists of a plurality of
light can be observed.
[0050] In a plan view facing the reflection surface 21s,
the length of one side of each first reflection surface 21a of
the display portion 12p is preferably about same as the length
of one side of the other first reflection surfaces 21a. That
is, the first reflection surfaces 21a are substantially square
in shape and preferably have substantially same area.
[0051] When length of one side of each first reflection
surface 21a is between 0.3 μm and 2 μm inclusive as described
above, the first reflection surfaces 21a are extremely minute
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structures. Such a first reflection surface 21a is difficult
to form as compared to a first reflection surface 21a having a
longer side. To form each first reflection surface 21a with
high accuracy, the first reflection surfaces 21a are
preferably substantially identical to one another in shape and
area.
[0052] The first reflection surfaces 21a that are
substantially identical in shape and area reduce process
defects, such as variance in flatness of the first reflection
surfaces 21a or variance in the inter-reflection-surface
distance D1 of the first reflection surfaces 21a, as compared
to a structure in which the first reflection surfaces 21a have
different shapes. Thus, the color of light emitted from the
display portion 12p is less likely to be changed from designed
color to an unintentional color, which would otherwise occur
if the display portion 12p has process defects.
[0053] In a plan view facing the reflection surface 21s
of the display portion 12p, the sum of area of the second
reflection surface 21b and the areas of all first reflection
surfaces 21a is an area S of the display portion 12p, and the
sum of areas of all first reflection surfaces 21a is the area
S1. Proportion of the area S1 to the area S (S1/S) in
percentage is the occupancy ratio of the first reflection
surfaces 21a in the display portion 12p.
[0054] In a plan view facing the reflection surface 21s,
the occupancy ratio of the first reflection surfaces 21a are
preferably substantially equal to one another the display
portions 12p.. In other words, it is preferable that each
display portion 12p be substantially equal to the other
display portions 12p in the area occupied by all the first
reflection surfaces 21a in the display portion 12p. In each
display portion 12p, the occupancy ratio of the first
reflection surfaces 21a determines the intensity of colored
light emitted from the display portion 12p.
[0055] Thus, when each display portion 12p is
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substantially equal to the other display portions 12p in the
occupancy ratio of the first reflection surfaces 21a, the
difference among the display portions 12p in the intensity of
light emitted from each display portions 12p is reduced. This
limits relief distribution of the intensity of light emitted
from the first display region 12, increasing the quality of
the image displayed by the display 10.
[0056] In each display portion 12p, the occupancy ratio
of the first reflection surfaces 21a is preferably between 15%
and 50% inclusive, for example. That is, in the display
portion 12p, the area occupied by all first reflection
surfaces 21a is preferably between 15% and 50% inclusive of
the total area of the display portion 12p.
[0057] The first reflection surfaces 21a in each display
portion 12p are substantially square in shape, and each first
reflection surface 21a is arranged separate from the other
first reflection surfaces 21a. Therefore, the occupancy ratio
is 50% at maximum. A higher occupancy ratio in a display
portion 12p increases the intensity of light emitted from the
display portion 12p and is therefore preferred to brighten the
image displayed by the first display region 12. When the
occupancy ratio is greater than or equal to 15%, intensity of
light emitted from the display portion 12p will be high enough
for the observer to perceive the image displayed by the first
display region 12.
[0058] That is, in order for the display portion 12p to
emit light having a color determined by the inter-reflectionsurface
distance D1 and to emit such light in a sufficient
intensity, the occupancy ratio of the first reflection
surfaces 21a is preferably between 15% and 50% inclusive.
[0059] As viewed facing the first reflection surfaces 21a,
the sides defining each first reflection surface 21a include
the sides extending in X direction and the sides extending in
Y direction. However, the sides defining each first
reflection surface 21a may include the sides inclined with
20
respect to the X direction and the sides inclined with respect
to the Y direction. A plurality of first reflection surfaces
21a arranged on one imaginary line Lv may include a first
reflection surface 21a that is defined by the sides extending
in the X direction and the sides extending in the Y direction,
and a first reflection surface 21a that is defined by the
sides inclined with respect to the X direction and the sides
inclined with respect to the Y direction.
[0060] As shown in Fig. 6, in each display portion 12p
forming the first display region 12, all first reflection
surfaces 21a are separated from outer edge of the display
portion 12p. At the boundaries between the display portions
12p, there are gaps between the first reflection surfaces 21a
of one display portion 12p and the first reflection surfaces
21a of another display portion 12p. One display portion 12p
is an example of the first display portion, and another
display portion 12p is an example of second display portion.
[0061] As long as there are gaps between the first
reflection surfaces 21a of one display portion 12p and the
first reflection surfaces 21a of another display portion 12p
at the boundary between the display portions 12p, each display
portion 12p may include a first reflection surface 21a that is
in contact with the outer edge of the display portion 12p.
[0062] Fig. 7 shows one display portion of each of the
first display region 12, the second display region 13, and the
third display region 14. These portions are parts of the
display regions. In Fig. 7, for purpose of illustration, the
display portions of the display regions are arranged in one
direction. Fig. 7 shows planar structures as viewed facing
the reflection surface 21s.
[0063] As shown in Fig. 7, in a plan view facing the
reflection surface 21s, the display portion 13p of the second
display region 13 includes a plurality of imaginary lines Lv
in a similar manner as the display portion 12p of the first
display region 12. In the display portion 13p, the imaginary
21
lines Lv extend in second extending direction which intersects
the X direction, and the direction of orientation which is the
extending direction of the imaginary lines Lv differs from
that in the display portion 12p of the first display region 12.
The imaginary lines Lv are arranged in the direction
perpendicular to the second extending direction in a random
manner.
[0064] On each imaginary line Lv, a plurality of first
reflection surfaces 21a is arranged in a random manner.
However, the first reflection surfaces 21a may be arranged on
the imaginary line Lv with a fixed periodicity.
[0065] In a plan view facing the reflection surface 21s,
the display portion 14p of the third display region 14
includes a plurality of imaginary lines Lv in a similar manner
as the display portion 12p of the first display region 12.
The imaginary lines Lv extend in third extending direction,
which intersects the X direction, and the angle formed by the
X direction and the third extending direction is greater than
the angle formed by the X direction and the second extending
direction. In the display portion 14p, the direction of
orientation, which is the extending direction of the imaginary
lines Lv, differs from both of the direction of orientation in
the first display region 12 and the direction of orientation
in the second display region 13. The angle formed by the X
direction and the third extending direction may be smaller
than the angle formed by the X direction and the second
extending direction. The imaginary lines Lv are arranged in
the direction perpendicular to the third extending direction
in a random manner.
[0066] On each imaginary line Lv, a plurality of first
reflection surfaces 21a is arranged in a random manner.
However, the first reflection surfaces 21a may be arranged on
the imaginary line Lv with a fixed periodicity.
[0067] The first display region 12, the second display
region 13, and the third display region 14 differ from one
22
another in the extending direction of the imaginary lines Lv.
Accordingly, directivity of emitted light of the first display
region 12, the second display region 13, and the third display
region 14 differ from one another .
[0068] The first display region 12, the second display
region 13, and the third display region 14 differ from one
another in the extending direction of the imaginary lines Lv.
However, at least two of the three display regions may be
identical in the extending direction of the imaginary lines Lv.
[0069] The inter-reflection-surface distance D1 of the
first display region 12, the inter-reflection-surface distance
D1 of the second display region 13, and the inter-reflectionsurface
distance D1 of the third display region 14 are equal.
Accordingly, the first display region 12, the second display
region 13, and the third display region 14 emit light of same
color.
[0070] Alternatively, as shown in Fig. 8, the first
display region 12, the second display region 13, and the third
display region 14 may differ from one another in the interreflection-
surface distance D1. For example, the interreflection-
surface distance D1 of the first display region 12
is smallest, the inter-reflection-surface distance D1 of the
second display region 13 is second smallest, and the interreflection-
surface distance D1 of the third display region 14
is largest.
[0071] Since the first display region 12, the second
display region 13, and the third display region 14 differ from
one another in the inter-reflection-surface distance D1, the
first display region 12, the second display region 13, and the
third display region 14 emit light of mutually different
colors.
[0072] Further, in each of the first display region 12,
the second display region 13, and the third display region 14,
each display portion may differ from the other display
portions in the inter-reflection-surface distance D1. By
23
this ,each the first display region 12, the second display
region 13, and the third display region 14 display a mixed
color of multiple colors.
[0073]
[Operation of Display] Referring to Figs. 9 to 13, the
operation of the display 10 is now described. Before the
description of the operation of the display 10, the
relationship among the grating constant of the diffraction
grating, which is the pitch of the grooves in the diffraction
grating, the wavelengths of illumination light, the incident
angle of illumination light, and the emission angle of
diffracted light is described.
[0074] [Diffraction Grating]
When the diffraction grating is illuminated with
illumination light from a light source, the diffraction
grating emits strong diffracted light in a specific direction
according to the traveling direction and the wavelength of the
illumination light, which is the incident light.
The emission angle β of the mth-order diffracted light
(m = 0, ±1, ±2,...) is calculated from Equation (1) below when
the light travels in a plane that is perpendicular to the
extending direction of the grooves of the diffraction grating.
[0075]
[Math.1]
[0076] In Equation (1), d is the grating constant of the
diffraction grating, m is the diffraction order, and λ is the
wavelength of the incident light and the diffracted light.
Further, α is the emission angle of the zeroth-order
diffracted light, which is the regular reflection light. The
absolute value of α is equal to the incident angle of the
illumination light. When the diffraction grating is a
reflective diffraction grating, the incident direction of the
24
illumination light and the emission direction of the regular
reflection light are symmetrical with respect to the direction
normal to the surface including the diffraction grating.
[0077] When the diffraction grating is a reflective
diffraction grating, the angle α is greater than or equal to
0° and less than 90° inclusive. Further, when illumination
light is inclined with respect to the surface including the
diffraction grating and two angular ranges bounded by angle of
the direction normal to the surface, which is 0°, are set,
angle β is a positive value if the emission direction of the
diffracted light and the emission direction of the regular
reflection light are within the same angular range, and the
angle β is a negative value if the emission direction of the
diffracted light and the incident direction of the
illumination light are within same angular range.
[0078] Fig. 9 schematically shows state in which a
diffraction grating having a relatively small grating constant
emits first-order diffracted light. Fig. 10 schematically
shows the state in which a diffraction grating having a
relatively large grating constant emits first-order diffracted
light.
[0079] As shown in Figs. 9 and 10, a point light source
LS emits white illumination light IL. The illumination light
IL contains a red light component, which has wavelengths in
the red wavelength region, a green light component, which has
wavelengths in the green wavelength region, and a blue light
component, which has wavelengths in the blue wavelength region.
The green light component, the blue light component, and the
red light component emitted by the point light source LS are
incident on a diffraction grating GR at an incident angle α
with respect to the normal direction CD. The diffraction
grating GR emits part of the green light component as
diffracted light DLg at an emission angle βg, emits part of
the blue light component as diffracted light DLb at an
emission angle βb, and emits part of the red light component
25
as diffracted light DLr at an emission angle βr.
[0080] As clearly shown by the comparison between the
emission angles β shown in Fig. 9 and the emission angles β
shown in Fig. 10, the diffraction grating GR having a greater
grating constant d emits diffracted light beams in directions
closer to the direction in which the regular reflection light
RL is emitted. In addition, the greater the grating constant
d of the diffraction grating GR, the smaller the differences
among the emission angle βg, the emission angle βb, and the
emission angle βr.
[0081] For purpose of illustration, of the diffracted
light beams emitted by the diffraction grating GR, the
diffracted light of other orders that are obtained by Equation
(1) are not shown in Figs. 9 and 10.
[0082] Under specific illumination conditions, the
diffraction grating GR emits diffracted light beams at
different emission angles depending on wavelengths of
diffracted light. When light source is a white light source,
such as sun or a fluorescent lamp, the diffraction grating GR
emits light beams of different wavelengths at different
emission angles. Thus, the image displayed by the diffraction
grating GR is iridescent and changes its color in response to
change in observation angle of the observer of the diffraction
grating GR, which is the viewing direction of the observer
relative to the surface including the diffraction grating GR.
With reference to Equation (2), the relationship among
grating constant of diffraction grating, wavelength of the
illumination light, and intensity of diffracted light in an
emission direction of diffracted light, i.e., diffraction
efficiency, is now described.
[0083] According to Equation (1), when illumination light
enter at an incident angle α on a diffraction grating GR of a
grating constant d, diffraction grating emits diffracted light
at an emission angle β. Diffraction efficiency of light of a
wavelength λ varies depending on factors such as grating
26
constant of diffraction grating and the depth of grooves. The
diffraction efficiency may be obtained by Equation (2) below.
[0084]
[Math.2]
[0085] In Equation (2), η is diffraction efficiency (η is
a value between 0 and 1 inclusive), r is depth of grooves in
diffraction grating, L is width of the grooves in diffraction
grating, d is grating constant, θ is incident angle of
illumination light, and λ is wavelength of illumination light
and diffracted light. Equation (2) holds true for diffraction
grating that has shape of a rectangular wave in a crosssection
taken in a plane perpendicular to longitudinal
direction of grooves and in which grooves have a relatively
small depth.
[0086] As is evident from Equation (2), the diffraction
efficiency η varies depending on depth r of grooves, grating
constant d, incident angle θ, and wavelength λ. In addition,
the diffraction efficiency η tends to decrease gradually as
diffraction order m increases.
[0087] [Display]
Referring to Figs. 11 to 13, optical characteristics of
the display 10 is now described. Figs. 11 and 12 show an
example of structure of a display portion in the display 10 in
which first reflection surfaces 21a are arranged on imaginary
lines Lv that are inclined with respect to the X direction.
[0088] In Figs. 11 and 12, for the purpose of
illustration, the reflection layer 21 of the display portion
is shown as a structure formed by a plurality of protrusions,
each having a first reflection surface 21a as the top surface,
and a layer including the second reflection surface 21b as one
surface on which the protrusions are located.
27
[0089] As shown in Fig. 11, the reflection layer 21 of
the display portion includes a reflection surface 21s that in
contact with the covered surface 23s of a substrate 11. The
reflection surface 21s includes the first reflection surfaces
21a and the second reflection surface 21b. The first
reflection surfaces 21a are substantially square in shape and
arranged on the corresponding one of the imaginary lines Lv of
the display portion. The imaginary lines Lv are parallel to
one another and extended in a direction that intersects the X
direction. The imaginary lines Lv are arranged random in the
direction perpendicular to the extending direction of the
imaginary lines Lv.
[0090] As shown in Fig. 12, when white illumination light
IL emitted by a light source LS enter on the reflection
surface 21s, relief structure which is formed by the first
reflection surfaces 21a and the second reflection surface 21b
in the reflection surface 21s emits diffracted light. Since
more than one of the first reflection surfaces 21a are
arranged along each of the imaginary lines Lv, the reflection
surface 21s emits diffracted light in the direction
perpendicular to the extending direction of the imaginary
lines Lv. When the direction that is perpendicular to the X
direction and the Y direction and is parallel to the thickness
direction of the substrate 11 is the Z direction, and the
direction in which the imaginary lines Lv are arranged is the
arrangement direction, the reflection surface 21s emits
diffracted light in a plane extending in the arrangement
direction and the Z direction.
[0091] The imaginary lines Lv are arranged at random
intervals, and a plurality of first reflection surfaces 21a
arranged along one imaginary line Lv and the second reflection
surface 21b that is located between adjacent ones of the first
reflection surfaces 21a on the imaginary line Lv are
considered as forming one pseudo surface. The first
reflection surfaces 21a may be considered as a structure in
28
which multiple pseudo surfaces are arranged in different
intervals, that is a structure having different grating
constants d. In such a structure, relief structures of
different grating constants d overlap with one another in one
display portion. Accordingly, the reflection surface 21s does
not emit diffracted light at different emission angles
according to the wavelengths of the diffracted light. Instead,
diffracted light of each wavelength are emitted at multiple
angles so that diffracted light beams of different wavelengths
are superimposed.
[0092] Although the illumination light IL enter on a
point in display portion in Fig. 12, the light source LS
actually emits the illumination light IL toward an area. The
illumination light IL enter on certain area, rather than a
point, in display portion. Thus, the light perceived by the
observer at a fixed point is mixed of multiple lights of
different wavelengths had a cetain range wavelength. As a
result, the observer perceives light having a color produced
by multiple light beams of different wavelengths.
[0093] As shown in Equation (2), the light intensity,
i.e., the diffraction efficiency η, of a diffracted light beam
emitted from diffraction grating varies depending on
wavelength of the diffracted light. Assuming that the width
of grating lines of diffraction grating, that is, width L of
grooves and grating constant d are uniform, the depth r of
grooves in diffraction grating and wavelength λ of
illumination light determine the diffraction efficiency η.
[0094] Thus, in display portion, the diffraction
efficiency η of a diffracted light beam of each wavelength
depends on the inter-reflection-surface distance D1 between
the first reflection surfaces 21a and the second reflection
surface 21b of the display portion and wavelength λ of
illumination light. The light that reaches eyes of the
observer is the colored light in which the intensity of the
light of a certain wavelength has been lowered in the white
29
illumination light incident on the reflection surface 21s.
[0095] For example, when the inter-reflection-surface
distance D1 of a display is set to a specific value, the
diffraction efficiency of blue light having a wavelength of
460 nm is reduced, so that the diffracted light that reaches
the eyes of the observer mainly consists of red light of a
wavelength of 630 nm and green light of a wavelength of 540 nm.
Accordingly, the observer perceives yellow light.
[0096] In contrast, with a display portion in which the
inter-reflection-surface distance D1 is set to a value that
differs from the value of the example described above, the
diffraction efficiency of red light, for example, is reduced,
so that the diffracted light that reaches eyes of the observer
mainly consists of green light and blue light. Accordingly,
the observer perceives cyan colored light, that is, light blue
colored light.
[0097] Fig. 12 shows an example of display portion. Of
the illumination light IL from the light source LS, which
emits white light, the display portion dimming the intensity
of red diffracted light DLr and emits green diffracted light
DLg and blue diffracted light DLb are higher than that of the
red diffracted light DLr. The light beams of different
wavelengths are emitted at various emission angles as compared
to the light diffracted by a diffraction grating. Thus, the
light emitted from the display portion is less likely to be
iridescent and change its color as the viewing point changes.
As a result, light having a color that is produced by light
beams of certain wavelengths is perceived.
[0098] The displayed color, which is the color of light
emitted by the display portion, is not perceived by the
observer who is in a position where the diffracted light
emitted by the display portion does not reach. Thus, unlike a
printed article formed by dyes or pigments, the display
portion provides two states, a state in which the observer
perceives the displayed color and a state in which the
30
observer does not perceive the displayed color, depending on
the position of light source or the observer.
That is, the conditions for observing the display
portion includes conditions under which light emitted by
display portion can be perceived, and conditions under which
light emitted by display portion cannot be perceived.
[0099] The conditions under which light can be perceived
may include an indoor situation in which light from the light
source LS, such as a fluorescent lamp, enter on the reflection
surface 21s of the display 10 in the direction substantially
perpendicular to the reflection surface 21s and the observer
can visually perceive the light emitted from the display
portion of the display 10. Further, the conditions under
which the light can be perceived may include an outdoor
situation in which light, such as sunlight, enter on the
reflection surface 21s in the direction substantially
perpendicular to the reflection surface 21s and the observer
can visually perceive light emitted by display portion.
[0100] The condition under which the light cannot be
perceived may include a situation in which the light from the
light source LS enter on the reflection surface 21s from the
substantially horizontal direction, so that the display
portion hardly emits light. Further, the conditions under
which the light cannot be perceived may include a situation in
which the observer looks at the display 10 from a direction
that differs from the direction perpendicular to the extending
direction of the imaginary lines Lv of the display 10 and,
even though the reflection surface 21s emits diffracted light,
the observer looks at the display 10 at such an angle that the
diffracted light does not reach the observer.
[0101] In the display portion of the display 10, a
plurality of first reflection surfaces 21a is arranged along
each imaginary line Lv. This gives the directivity to the
emission direction of the light emitted by the display portion.
Thus, unlike a structure in which the display portions emit
31
light isotropically, the display 10 emits colored light, and
the image displayed by the display 10 changes dynamically.
[0102] Fig. 13 shows a diffraction grating GR having a
plurality of grating lines GL extending in the Y direction.
The grating lines GL are arranged regularly in the X direction.
This diffraction grating GR emits diffracted light as follows.
When the illumination light IL emitted by the light source LS
enter on the diffraction grating GR, the diffraction grating
GR emits red diffracted light DLr, green diffracted light DLg,
and blue diffracted light DLb in the XZ plane at mutually
different emission angles in the X direction. The X direction
is perpendicular to the Y direction, in which the grating
lines GL extend.
[0103] When light enter on each of the display 10 and the
diffraction grating GR, diffracted light is emitted in
predetermined directions as emission light. In addition,
regular reflection light, or specular reflection light, is
emitted in the direction of regular reflection relative to the
incident direction of incident light. Regular reflection
light is emitted by the display 10 and the diffraction
gratings GR regardless of the shapes of the minute structures
of the display 10 and the diffraction gratings GR. When the
observer looks at the display 10 having the reflection layer
21, the observer typically finds regular reflection light too
bright due to high intensity of regular reflection light. The
observer thus looks at the display 10 such that regular
reflection light does not reach eyes. As such, for purpose of
illustration, regular reflection light is not shown in Figs.
11 to 13.
[0104] [Structure of Article]
Referring to Figs. 14 and 15, structure of an IC card
that is an example of an article including the display 10 is
now described. The display portions of the display 10
described above are capable of displaying an image having a
specific color that cannot be displayed by printing using inks
32
or the like, or by structures other than the reflection
surface 21s described above. The image displayed by the
display 10 is therefore difficult to reproduce with high
accuracy, increasing difficulty of counterfeiting the display
10. Accordingly, any article that includes the display 10 is
difficult to counterfeit, so the display 10 may be used to
limit counterfeiting of articles.
[0105] As shown in Fig. 14, an integrated circuit (IC)
card 30 includes a planar card substrate 31, which may be a
plastic card substrate 31, a print layer 32 on which an image
is printed, an IC chip 33, and a display 10.
[0106] As shown in Fig. 15, the print layer 32 is formed
on the card substrate 31. The display 10 described above is
fixed to the display surface, which is the surface of the
print layer 32 that is opposite to the surface in contact with
the card substrate 31. The display 10 is fixed using an
adhesive layer, for example. The display 10 may be prepared
as transfer foil or a sticker having an adhesive layer and
affixed to the print layer 32, which is an example of the
support portion.
[0107] The print layer 32 may have information including
at least one of a character, a number, a symbol, and the like
and a picture having aesthetic appearance. In addition to the
upper side of the card substrate 31, the print layer 32 may be
formed on the obverse surface of the display 10, which is
opposite to the surface in contact with the print layer 32.
[0108] Alternatively, the display 10 may be affixed to
the card substrate 31. In this case, the print layer 32 may
be formed on the section of the card substrate 31 that is not
covered by the display 10 and the obverse surface of the
display 10, which is opposite to the surface in contact with
the card substrate 31. In this structure, the card substrate
31 is an example of the support portion.
[0109] The print layer 32 is made of inks, which may
include pigments or dyes, or toner. The inks and toner that
33
may be used for the print layer 32 do not provide the optical
effects of the display portions of the display 10. That is,
the color and the brightness of the printed article formed by
inks or toner remain substantially the same regardless of any
change in the observation conditions of the printed article.
In other words, the image displayed by the printed article
remains substantially same even when observation conditions of
the printed article are changed.
[0110] When the IC card 30 including the display 10 is
observed under different observation conditions, image
displayed by the print layer 32 remains substantially same
regardless of the observation conditions, while the image
displayed by the display 10 vary under different observation
conditions. Accordingly, when the IC card 30 is observed
under different observation conditions, comparison between the
print layer 32 and the display 10 clarifies the difference
between the optical effect of the display 10 and that of the
print layer 32. This allows for accurate authentication of
the IC card 30 using the display 10.
[0111] Specifically, brightness of the color of the image
displayed by the print layer 32 is preferably equivalent to
the brightness of the image displayed by the display 10 under
certain observation conditions. Such a structure facilitates
visual perception of the difference between a change in the
brightness of the image displayed by the display 10 and a
change in the brightness of image displayed by the print layer
32 when the IC card 30 is observed under different observation
conditions. The print layer 32 and the display 10 thus formed
increases effects of preventing counterfeiting.
[0112] The print layer 32 may be made of a functional ink
that changes the visual effect of the print layer 32 when the
observation conditions of the print layer 32 are changed. The
functional ink may change image displayed by the print layer
32 when observation conditions of the print layer 32 are
changed. The functional ink may be a phosphorescent ink,
34
liquid crystal, or an ink that is invisible when illuminated
with visible light and becomes visible when illuminated with
ultraviolet rays or infrared rays. When ink that is visible
when illuminated with ultraviolet rays or infrared rays is
used, the information formed by the ink is hidden from the
observer when the ink is illuminated with visible light. When
the information is illuminated with ultraviolet rays or
infrared rays, the information is reproduced for the observer.
[0113] In addition to providing visual effect that
changes when observation conditions of the print layer 32 are
changed, the print layer 32 formed by functional ink provides
a visual effect that differs from that of display portion.
Thus, combining the display 10 and the print layer 32 formed
by functional ink further increases anti-counterfeiting effect.
[0114] Further, the print layer 32 may be a layer whose
color changes when energy, such as a laser beam, an
ultraviolet ray, heat, or pressure, is applied.
[0115] The surface of the card substrate 31 that is in
contact with the print layer 32 has a depression 31a, which
extends toward the surface that is opposite to the surface in
contact with the print layer 32. The print layer 32 includes
a through hole 32a in the position aligned with the depression
31a as viewed in the thickness direction of the IC card 30.
The IC chip 33 is fitted into the depression 31a and the
through hole 32a. The IC chip 33 has an obverse surface,
which is surrounded by the print layer 32 and includes a
plurality of electrodes. Information is written into and read
from the IC chip 33 through electrodes.
[0116] The IC card 30 is difficult to counterfeit since
the IC card 30 has the display 10 that is difficult to
counterfeit. Moreover, the IC card 30 has the IC chip 33 and
the print layer 32 in addition to the display 10. The
electronic data of the IC chip 33 and the visual effects of
the display 10 and the print layer 32 facilitate prevention of
counterfeiting.
35
[0117] [Method for Producing Display]
A method for producing the display 10 is now described.
To produce the display 10, a light transmissive plastic
sheet or film is prepared as the support layer 22. The
support layer 22 may be made of polyethylene terephthalate
(PET) or polycarbonate (PC), for example. Light transmissive
synthetic resin, such as thermoplastic resin, thermosetting
resin, or light curing resin, is applied to one surface of the
support layer 22 to form a coating. The formed coating is
kept in close contact with a metal stamper while the resin is
cured. When the coating is made of a thermosetting resin,
heat is applied to the coating to cure the resin. When the
coating is made of a light curing resin, light is applied to
the coating to cure the resin.
[0118] The metal stamper is removed from the cured
coating so that an relief layer 23 having a covered surface
23s is formed. The support layer 22 is in close contact with
the relief layer 23. Thus, when the support layer 22 and the
relief layer 23 are made of the same material, there is no
boundary between the support layer 22 and the relief layer 23.
As such, the support layer 22 and the relief layer 23 may be
considered as a substrate 11 that is formed by a single layer.
[0119] Then, a reflection layer 21 is formed on the
covered surface 23s of the substrate 11 so as to conform to
shape of the covered surface 23s. The reflection layer 21 may
be formed by vapor-phase deposition, such as vacuum deposition
or sputtering.
[0120] In the reflection layer 21, the following
situations reduce effect of light canceling each other by
interference. The situations include a situation in which the
sections of the reflection layer 21 located on the first
covered surfaces 23a and the section located on the second
covered surface 23b have low flatness, and a situation in
which the thickness of the sections located on the first
covered surfaces 23a and the thickness of the section located
36
on the second covered surface 23b are not uniform.
[0121] Such situations lower diffraction efficiency for a
wider range of light wavelengths, reducing the difference
between the distribution of wavelengths in the light emitted
by the display 10 and the distribution of wavelengths in the
white incident light. This lowers the chroma of the color of
the light emitted by the display 10, causing the color of the
emitted light to resemble white.
[0122] Thus, the reflection layer 21 is preferably formed
such that the first reflection surfaces 21a are substantially
parallel to the second reflection surface 21b, conforming to
the flatness of the first covered surfaces 23a and the second
covered surface 23b.
[0123] The reflection layer 21 may be either of a metal
layer and a dielectric layer. When the reflection layer 21 is
a metal layer, the reflection layer 21 may be made of aluminum,
silver, gold, or an alloy of these metals. When the
reflection layer 21 is a dielectric layer, the reflection
layer 21 may be made of zinc sulfide (ZnS) or titanium oxide
(TiO2).
[0124] Further, when the reflection layer 21 is a
dielectric layer, the reflection layer 21 may be of a singlelayer
structure or a multilayer structure. Adjacent ones of
the layers forming the multilayer structure may have different
refractive indices.
[0125] Thickness of the reflection layer 21 is preferably
between 30 nm and 150 nm inclusive, more preferably between 30
nm and 70 nm inclusive, and yet more preferably 50 nm. The
reflection layer 21 may be formed as a thin film by vaporphase
deposition. However, when the reflection layer 21 is
made of one of the metals described above, granular structures
tend to form on the obverse surface of the reflection layer 21.
Greater thickness of the reflection layer 21, larger granular
structures become. For this reason, the reflection layer 21
preferably has a small thickness to increase flatness of the
37
reflection layer 21. However, if thickness of the reflection
layer 21 is too small, the reflection layer 21 fails to
sufficiently reflect light.
[0126] Through a thorough study of the relationship
between the thickness of the reflection layer 21 and the
function of the reflection layer 21, the inventor of the
present application has discovered that the thickness of the
reflection layer 21 is preferably between 30 nm and 150 nm
inclusive in order for the reflection layer 21 to have a
desirable flatness and to fully function to reflect light.
[0127] As described above, the reflection layer 21 may
cover the entire covered surface 23s of the substrate 11, or
may cover a part of the covered surface 23s. That is, the
reflection layer 21 may partially cover the covered surface
23s. When the reflection layer 21 partially covers the
covered surface 23s, the reflection layer 21 may form an image,
such as a picture, a character, or a symbol, using the section
of the covered surface 23s on which the reflection layer 21 is
formed and the section of that on which the reflection layer
21 is not formed.
[0128] The reflection layer 21 that partially covers the
covered surface 23s may be formed by first forming the
reflection layer 21 over the entire covered surface 23s by
vapor-phase deposition and then dissolving part of the
reflection layer 21 using an agent. Alternatively, the
reflection layer 21 that partially covers the covered surface
23s may be formed by first forming the reflection layer 21
over the entire covered surface 23s and then peeling a part of
the reflection layer 21 from the relief layer 23 using an
adhesive material having a higher adhesiveness to the
reflection layer 21 than the relief layer 23. The reflection
layer 21 that partially covers the covered surface 23s may
also be formed by vapor-phase deposition using a mask, or a
lift-off method.
[0129] The display 10 may include other functional layers,
38
such as a protection layer for protecting the obverse surface
of the display 10 or an antibacterial coating layer that
covers the obverse surface of the display 10 to inhibit growth
of bacteria on the obverse surface of the display 10.
[0130] [Method for Producing Original plate]
Referring to Figs. 16 and 17, a method for producing an
original plate for producing a display 10 is now described.
The original plate is used to produce a display 10 that
includes a covered surface 23s, which includes first covered
surfaces 23a and a second covered surface 23b, and a
reflection layer 21, which covers the covered surface 23s.
Original plate is used as the die for the metal stamper
described above.
[0131] As shown in Fig. 16, the method for producing an
original plate includes a step of forming a resist layer on a
surface of a substrate (Step S11), a step of exposing the
resist layer to light (Step S12), and a step of developing the
exposed resist layer to form a transfer surface in the resist
layer (Step S13). That is, the method for producing the
original plate includes a resist layer formation step, an
exposure step, and a developing step.
[0132] The resist layer formation step may include
preparing a planar glass substrate and applying a resist on a
surface of the glass substrate to form a resist layer. The
resist may be an electron-beam resist or a photoresist. The
resist is a positive resist, and the exposed portion of the
resist is more soluble to developer than the unexposed portion.
In the developing step, the exposed portion of the resist is
removed from the unexposed portion.
[0133] The exposure step includes exposing the resist
layer as follows. The exposure step exposes the resist layer
to light such that the transfer surface after developing
includes a plurality of first transfer surfaces for forming
first covered surfaces 23a and a second transfer surface for
forming a second covered surface 23b. In addition, the
39
exposure step exposes the resist layer such that the first
transfer surfaces are substantially square in shape and the
second transfer surface occupies gaps between adjacent ones of
the first transfer surfaces in a plan view facing the transfer
surface.
[0134] Furthermore, the exposure step exposes the resist
layer such that the distance between the first transfer
surfaces and the second transfer surface in the thickness
direction of the glass substrate is set to an extent that the
reflection surface 21s of the reflection layer 21 emit colored
light by the interference between the light reflected from the
sections of the reflection surface 21s of the reflection layer
21 that are located on the first covered surfaces 23a and the
light reflected from the section located on the second covered
surface 23b.
[0135] In addition, in a plan view facing the transfer
surface, the exposure step exposes the resist layer such that
more than one of the first transfer surfaces are located on
each of imaginary lines and, on a straight line intersecting
more than one of the imaginary lines, the distances between
adjacent ones of the imaginary lines have different extents.
[0136] Specifically, exposure step apply to divide the
sections of the original plate that correspond to the first
reflection surfaces 21a of the display 10 and the section that
corresponds to the second reflection surface 21b. When the
resist layer is made of an electron-beam resist, the exposure
of the resist layer is performed by irradiating the resist
layer with electron beams. When the resist layer is made of a
photoresist, the exposure of the resist layer is performed by
irradiating the resist layer with laser beams of ultraviolet
wavelengths.
[0137] In exposure step, glass substrate is placed on an
XY stage, which can move two-dimensionally in the X direction,
which is one direction, and the Y direction perpendicular to
the X direction. The resist layer is patterning by exposed
40
with electron beams or laser beams irradiation and moving of
the XY stage using a controller that controls the movement of
the XY stage.
[0138] When the resist is an electron-beam resist,
variable-shaped beam exposure method, or rectangular beam
exposure method, is preferably used to irradiate the electronbeam
resist with electron beams. In the variable-shaped beam
exposure method, the electron beam from an electron gun passes
through shaping apertures, which are rectangular openings as
viewed in the irradiation direction of electron beam, so that
the shape of the electron beam in a cross-section
perpendicular to the irradiation direction of the electron
beam changes to a rectangular shape before the electron beam
strikes the obverse surface of the resist layer.
[0139] In the spot beam exposure method, the electron
beam strikes the resist layer without passing through shaping
apertures, and the flexibility of exposure pattern is greater
than that of the variable-shaped beam exposure method.
However, the spot beam exposure method provides a smaller
irradiation area in one exposure and therefore takes more time
for pattering than the variable-shaped beam exposure method.
The variable-shaped beam exposure method provides a larger
irradiation area in one exposure than the spot beam exposure
method. In addition, because of the irradiation area of each
exposure is variable, required the patterning time can be
short.
[0140] In the variable-shaped beam exposure method, the
section of the resist layer corresponding to each first
covered surface 23a of the display portion is preferably
pattered in one exposure. This allows the entire of one first
covered surface 23a is exposed under the same conditions,
increasing flatness of the first covered surface 23a as
compared to when the section of one first covered surface 23a
is written in multiple exposures.
[0141] In addition, when each section corresponding to
41
one first covered surface 23a is written in one exposure, the
sections corresponding to first covered surfaces 23a are
exposed under substantially same conditions. Consequently,
the sections corresponding to the first covered surfaces 23a
are substantially equal to one another in the distance in
which the energy for dissolving the resist is obtained from
the electron beam. This distance is measured in the thickness
direction of the resist layer.
[0142] In the step of exposing the resist layer, electron
beams or laser beams not only strike the irradiation section
of the resist layer, which is irradiated with electron beams
or laser beams, but also scatters to an area near the
irradiation section. Accordingly, the energy of electron
beams or laser beams is applied to the irradiation section and
also to the area near the irradiation section. Thus, the
pattering of the resist layer may not satisfy the requirements
set to the irradiation apparatus of electron beams or laser
beams.
[0143] In this respect, when the display portions in one
display region are substantially equal to one another in the
occupancy ratio of the first covered surfaces 23a, the
sections of the resist layer corresponding to the display
portions receive substantially the same amount of electron
beams or laser beams. Thus, the scattering of electron beams
or laser beams affects the display portions substantially
equally. Consequently, even if the scattering of electron
beams or laser beams affects the resist layer, the color of
light emitted by the display portions is less likely to be
relief or shifted.
[0144] Further, in exposure process of the resist layer
using electron beams, the larger the area irradiated with
electron beams, the greater the distance in which the energy
for dissolving the resist is obtained from the electron beam
in the thickness direction of the resist layer, even when the
amounts of energy provided by the electron beams are the same.
42
Thus, in order to reduce variant in the distances between the
first covered surfaces 23a and the second covered surface 23b
in the display portions, all the first covered surfaces 23a in
the display portions are preferably substantially equal in the
length of one side of the first reflection surface 21a in a
plan view facing the reflection surface 21s.
[0145] In a structure in which a first reflection surface
21a of the display 10 is in contact with another first
reflection surface 21a, an irradiated region and another
irradiated region that is in contact with the first
irradiated region are irradiated with electron beams in the
exposure process of the resist layer. Consequently, the
electron beam that strikes one of the two irradiated region
scatters to the other, and the amount of energy given by
electron beams becomes excessive at the boundary between the
two irradiated regions. This lowers the accuracy of the shape
at the boundary between the two irradiated regions after the
developing process.
[0146] For this reason, in the display 10, each first
covered surface 23a in each display portion is preferably
separated from the other first covered surfaces 23a. In
addition, in a plurality of display portions, the first
covered surfaces 23a in a display portion are preferably
separated by gaps from the first covered surfaces 23a of the
other display portions adjacent to the display portion.
[0147] In the developing step, the resist layer
irradiated with electron beams or laser beams is developed.
This process removes the section of the resist layer
irradiated with electron beams or laser beams from the section
that is not irradiated with electron beams or laser beams,
forming the transfer surface, which is an relief surface, in
the obverse surface of the resist layer.
[0148] That is, as shown in Fig. 17, an original plate 40
includes a glass substrate 41 and a resist layer 42. The
resist layer 42 includes a transfer surface 42s, which is
43
opposite to the surface that is in contact with the glass
substrate 41. The transfer surface 42s includes a plurality
of first transfer surfaces 42a for forming first covered
surfaces 23a and a second transfer surface 42b for forming a
second covered surface 23b. The positions of the first
transfer surfaces 42a differ from the position of the second
transfer surface 42b in the thickness direction of the
transfer surface 42s. The second transfer surface 42b
occupies gaps between adjacent ones of the first transfer
surfaces 42a as viewed facing the transfer surface 42s.
[0149] The first transfer surfaces 42a of the transfer
surface 42s are transferred to form the first covered surfaces
23a of the covered surface 23s of the display 10, and the
second transfer surface 42b is transferred to form the second
covered surface 23b of the covered surface 23s.
[0150] In the original plate 40, the distance between the
first transfer surfaces 42a and the second transfer surface
42b is equal to the inter-covered-surface distance D2. That
is, the distance between the first transfer surfaces 42a and
the second transfer surface 42b is set to an extent that the
interference between the light reflected from the first
reflection surfaces 21a located on the first covered surfaces
23a of the display 10 and the light reflected from the second
reflection surface 21b located on the second covered surface
23b for emit color light.
[0151] In a plan view facing the transfer surface 42s of
the resist layer 42, the first transfer surfaces 42a are
substantially square in shape, and a plurality of first
transfer surfaces 42a is arranged on each of the imaginary
lines Lv. On a straight line intersecting imaginary lines Lv,
the distances between adjacent ones of the imaginary lines Lv
have different extents.
[0152] The original plate 40 produced as described above
is subjected to electroforming and plating to form a metal
stamper having the relief surface to which the transfer
44
surface 42s of the original plate 40 has been transferred.
[0153] The advantages of the display, the article, the
original plate, and the method for producing an original plate
described above are now described.
(1) The display 10 emits light having a color determined
by the inter-reflection-surface distance D1. Since a
plurality of first reflection surfaces 21a is arranged on each
imaginary line Lv, the first reflection surfaces 21a on each
imaginary line Lv may be considered as forming one pseudo
surface 21d. The interference between the reflection light
from the first reflection surfaces 21a arranged on the
imaginary lines Lv and the reflection light from the second
reflection surface 21b located between the imaginary lines Lv
produces colored light. The colored light has directivity and
is emitted in the direction substantially perpendicular to the
imaginary lines Lv as viewed in the thickness direction of the
substrate 11. Consequently, the display 10 emits colored
light and displays an image that changes dynamically as
compared to a structure that emits light isotropically.
[0154] (2) On each imaginary line Lv, first reflection
surfaces 21a are not arranged with a fixed periodicity,
reducing the likelihood that the structure including the first
reflection surfaces 21a emits diffracted light in the
extending direction of the imaginary lines Lv.
[0155] (3) The irradiation sections irradiated with light
in the exposure step, which are the sections of the original
plate 40 corresponding to the first reflection surfaces 21a,
are substantially equal in size. Therefore, each irradiation
section receives substantially the same amount of energy from
the light, limiting reduction in the accuracy of the shape of
the original plate 40, which would otherwise occur if the
amount of energy applied to the irradiation sections is not
uniform. This limits reduction in the accuracy of the shape
of the display 10.
[0156] (4) In the exposure step, an irradiation section
45
of the original plate 40 corresponding to one of the first
reflection surfaces 21a is not in contact with the other
irradiation sections corresponding to other first reflection
surfaces 21a. This avoids a situation in which an excessive
amount of energy is given to the boundary between two
irradiation sections. As a result, the accuracy of shape of
the original plate 40 and thus the accuracy of shape of the
display 10 are unlikely to be lowered.
[0157] (5) When the display portions are substantially
equal to one another in area occupied by the first reflection
surfaces 21a, the display portions emit light of substantially
same intensity.
(6) When the occupancy ratio of the first reflection
surfaces 21a in each display portion is between 15% and 50%
inclusive, the intensity of light emitted by the display
portion is high enough to be perceived.
[0158] [Modifications]
The above-described embodiment may be modified as
follows.
The article is not limited to an IC card and may be
other cards, such as a magnetic card, a wireless card, and an
identification (ID) card. Alternatively, the article may be
securities, such as banknotes or gift certificates, or a
luxury product, such as an art object. Further, the article
may be a tag to be attached to a product that should be
authenticated, or may be a package enclosing a product that
should be authenticated, or a part of the package.
[0159] In addition to the display portion described above,
the reflection surface 21s of the reflection layer 21 of the
display may include a portion of different functionality,
which is a region having an optical effect that differs from
that of the display portion. The portion of different
functionality includes at least one of a diffraction portion
that diffracts the light incident on the reflection surface
21s, an anti-reflection portion that prevents reflection of
46
the light incident on the reflection surface 21s, and a light
scattering portion that scatters the light incident on the
reflection surface 21s.
[0160] The diffraction portion may be the diffraction
grating that is described above with reference to Fig. 13 and
diffracts the light incident on the reflection surface 21s to
emit light of iridescent colors that change depending on the
conditions under which the observer looks at the display.
[0161] As shown in Fig. 18, an anti-reflection portion 50
includes a plurality of minute protrusions 51 arranged at a
pitch that is shorter than or equal to visible wavelengths.
The protrusions 51 limit reflection of the light incident on
the protrusions 51. The anti-reflection portion 50 displays a
black color accordingly.
[0162] As shown in Fig. 19, a light scattering portion 60
includes a plurality of protrusions 61 that differ from one
another in at least one of the size as viewed facing the
reflection surface 21s of the display and the dimension in the
thickness direction of the display. The dimension of each
protrusion 61 in the thickness direction of the display is a
few μm or greater, for example. The light scattering portion
60 diffusely reflects the light incident on the light
scattering portion 60 and emits white light.
[0163] This configuration has the following advantages.
(7) The reflection surface 21s includes at least one of
the diffraction portion, the anti-reflection portion 50, and
the light scattering portion 60. Accordingly, the display has
an additional optical effect that differs from the optical
effect of emitting colored light. The display thus provides
complex optical effects as compared to a structure in which
the reflection surface 21s includes only the display portion.
This increases the difficulties in counterfeiting the display.
[0164] In each of the first display region 12, the second
display region 13, and the third display region 14, the
display portions do not have to be identical to each other in
47
the extending direction of the imaginary lines Lv. The
structure described above with reference to Fig. 7 has the
first display region 12, the second display region 13, and the
third display region 14, which differ from one another in the
extending direction of the imaginary lines Lv. In addition,
each display region may include display portions that differ
from one another in the extending direction of the imaginary
lines Lv.
[0165] Specifically, in each of the display portions
included in each display region, the imaginary lines Lv are
parallel to each other within the display portion. In
addition, for two display portions adjacent to each other, the
angle between imaginary lines, which is the angle formed by
the extending direction of the imaginary lines Lv in one of
the display portions and the extending direction of the
imaginary lines Lv in the other display portion, is preferably
less than or equal to 10°. One of the display portions is an
example of the third display portion, and the other display
portion is an example of the fourth display portion.
[0166] This configuration has the following advantages.
(8) The angle between imaginary lines for two display
portions adjacent to each other is less than or equal to 10°.
Therefore, the brightness of the two adjacent display portions
change successively as the angle formed by the extending
direction of the imaginary lines and the viewing direction of
the observer changes.
[0167] In each display portion, occupancy ratio of the
first reflection surfaces 21a may be less than 15%. Such a
structure still has an advantage equivalent to advantage (1)
since the display portion emits light having a color
determined by the inter-reflection-surface distance D1 to some
extent.
[0168] In a plurality of display portions, it is
sufficient that at least two display portions have the same
occupancy ratio of the first reflection surfaces 21a. Such a
48
structure still provides an advantage equivalent to advantage
(5) by the display portions that have same occupancy ratio of
the first reflection surfaces 21a.
[0169] Each display portion may have a different
occupancy ratio of the first reflection surfaces 21a. Such a
structure still has an advantage equivalent to advantage (1)
since the reflection surface 21s emits light having a color
determined by the inter-reflection-surface distance D1.
[0170] In a plurality of display portions, it is
sufficient that at least two display portions adjacent to each
other are formed such that there are gaps between the first
reflection surfaces 21a of one of the display portions and the
first reflection surfaces 21a of the other. Such a structure
still provides an advantage equivalent to advantage (4) by the
display portions that have gaps between the first reflection
surfaces 21a.
[0171] Two display portions adjacent to each other may be
formed so as not to have gaps between first reflection
surfaces 21a of one of the display portions and first
reflection surfaces 21a of the other. Such a structure still
provides an advantage equivalent to advantage (4) in each
display portion, since each of the first reflection surfaces
21a in each display portion is separated from the other first
reflection surfaces 21a in the display portion as viewed
facing the first reflection surfaces 21a.
[0172] The lengths of sides of the first reflection
surfaces 21a may have different extents. Such a structure
still has an advantage equivalent to advantage (1) since the
reflection surface 21s emits light having a color determined
by the inter-reflection-surface distance D1.
[0173] As shown in Fig. 20, in a display 70, a plurality
of imaginary lines Lv may extend radially from a starting
portion St in the reflection surface 21s of the display 70.
Fig. 20 shows the planar structure as viewed facing the
reflection surface 21s of the display 70. For the purpose of
49
illustration, Fig. 20 does not show the first reflection
surfaces 21a arranged on the imaginary lines Lv.
[0174] As shown in Fig. 20, the display 70 has a
rectangular shape extending in the X direction. The starting
portion St is located on one of two sides of outer edge of the
display 70 that extend in the X direction. The starting
portion St includes the center in the X direction of the side.
The display 70 includes a plurality of imaginary lines Lv,
which extends radially from one starting portion St in the
reflection surface 21s in shape of a circular sector. The
imaginary lines Lv extend from same starting point. On a
straight line Ls intersecting imaginary lines Lv, the interimaginary-
line distances D3 have different extents. The angle
formed by two adjacent ones of the imaginary lines Lv is set
to be less than or equal to 10°, for example, and is
preferably a few degrees.
[0175] In the reflection surface 21s, the distance
between the first reflection surfaces 21a arranged along each
imaginary line Lv and the second reflection surface 21b is
substantially uniform over the entire display 70. Thus, the
display 70 emits light having a fixed color that is the same
over the entire display 70.
[0176] Referring to Figs. 21 to 26, the operation of the
display 70 is now described. In Figs. 21 to 26, the viewing
direction, which is the viewing direction of the observer of
the display 70, extends in the Y direction as viewed facing
the display 70. Figs. 21 to 26 show the images perceived by
the observer while the display 70 is rotated gradually from
the initial state, in which the side in outer edges of the
display 70 that includes the starting portion St extends in
the X direction. The display 70 is rotated counterclockwise
as viewed in Figs. 21 to 26 about the rotation axis, which
passes through the starting portion St and extends
perpendicularly to the drawing sheet. In Figs. 21 to 26, the
region of the display 70 that is perceived by the observer as
50
having a high brightness is shown in white, and the region
that is perceived by the observer as having a low brightness
is shaded with dots.
[0177] Referring to Fig. 21, the section of the display
70 that is on the left side of the center line C, which passes
through the starting portion St and extends in the Y direction,
is a left section 70L, and the section on the right side of
the center line C is a right section 70R. In the initial
state, the entire left section 70L and part of the right
section 70R form a high-brightness region 71 having a high
brightness in the display 70, and the part of the right
section 70R that is not included in the high-brightness region
71 forms a low-brightness region 72.
[0178] As shown in Fig. 22, when the display 70 rotates
counterclockwise about rotation axis, the entire left section
70L of the display 70 is the high-brightness region 71 as with
the initial state, while the part of the right section 70R
that is included in the high-brightness region 71 expands as
compared to the initial state.
[0179] As shown in Figs. 23 and 24, as the display 70
further rotates counterclockwise increasing the rotation angle,
the part of the left section 70L that is included in the lowbrightness
region 72 expands, while the part of the right
section 70R that is included in the low-brightness region 72
becomes narrower. In other words, the part of the left
section 70L that is included in the high-brightness region 71
becomes narrower, and the part of the right section 70R that
is included in the high-brightness region 71 expands.
[0180] As shown in Figs. 25 and 26, as the display 70
further rotates counterclockwise increasing the rotation angle,
the part of the left section 70L that is included in the lowbrightness
region 72 expands, while the entire right section
70R remains as the high-brightness region 71.
[0181] The display 70 described above has the following
advantage.
51
(9) As the angle formed by the extending direction of
the imaginary lines Lv and the viewing direction of the
observer changes, the part of the display 70 that is perceived
as the high-brightness region 71, which has a relatively high
brightness, and the part that is perceived as the lowbrightness
region 72, which has a relatively low brightness,
change continuously.
[0182] In a structure in which a plurality of imaginary
lines Lv extends radially from one starting portion St, the
plurality of imaginary lines Lv may form a circular shape in
one display.
In a structure in which a plurality of imaginary lines
Lv extends radially from the starting portion St, the starting
portion St may be a region having a certain area. In this
case, the imaginary lines Lv share the starting portion St,
but do not have to extend from the same starting point. In
such a structure, the plurality of imaginary lines Lv may form
a ring shape or an arcuate shape in one display.
[0183] In a structure in which one display includes a
plurality of display portions, the plurality of display
portions may include at least one of the display portions
described below, in addition to the display portions that are
identical to one another in the extending direction of the
imaginary lines Lv. That is, the plurality of display
portions may include at least one of a set of two display
portions that are adjacent to each other and have an angle
between imaginary lines of less than or equal to 10° and a
display portion including a plurality of imaginary lines Lv
extending radially from one starting portion St.
[0184] The lengths of sides of the first reflection
surfaces 21a may have different extents. Such a structure
still is able the reflection surface 21s to emit light having
a color determined by the inter-reflection-surface distance D1,
as long as each first reflection surface 21a is substantially
identical to the other first reflection surfaces 21a in the
52
inter-reflection-surface distance D1.
[0185] The purpose of the display is not limited to
preventing counterfeiting. The display may be used to
decorate an article. Further, the display may be a display
that is observed for its own quality. The display that is
observed for its own quality may be used as an item such as a
toy or a learning material.
53
WE CLAIM:
1. A display comprising:
a substrate including a covered surface; and
a reflection layer covering at least part of the covered
surface, wherein
the reflection layer has an obverse surface including a
plurality of first reflection surfaces and a second reflection
surface,
in a plan view facing the obverse surface of the
reflection layer, the first reflection surfaces are
substantially square in shape, and the second reflection
surface occupies gaps between adjacent ones of the first
reflection surfaces,
a distance between the first reflection surfaces and the
second reflection surface in a thickness direction of the
substrate has an extent that the obverse surface of the
reflection layer emit colored light by interference between
light reflected from the first reflection surfaces and light
reflected from the second reflection surface,
in a plan view facing the obverse surface of the
reflection layer, more than one of the first reflection
surfaces are located on each of a plurality of imaginary lines,
and
on a straight line intersecting more than one of the
imaginary lines, distances between adjacent ones of the
imaginary lines have different extents.
2. The display according to claim 1, wherein, on each
of the imaginary lines, distances between adjacent ones of the
first reflection surfaces vary irregularly with respect to an
order of arrangement of the first reflection surfaces.
3. The display according to claim 1 or 2, wherein the
imaginary lines extend radially.
54
4. The display according to any one of claims 1 to 3,
wherein, in a plan view facing the obverse surface of the
reflection layer, a length of one side of each first
reflection surface is substantially equal to a length of one
side of other first reflection surfaces.
5. The display according to any one of claims 1 to 4,
wherein
the obverse surface of the reflection layer includes a
plurality of first display portions and a plurality of second
display portions,
the first display portions each include more than one of
the first reflection surfaces,
the second display portions each include more than one
of the first reflection surfaces, and
at boundaries between the first display portions and the
second display portions adjacent to the first display portions,
there are gaps between the first reflection surfaces in the
first display portions and the first reflection surfaces in
the second display portions.
6. The display according to claim 5, wherein, in a
plan view facing the obverse surface of the reflection layer,
an area of each first display portion that is occupied by all
the first reflection surfaces is substantially equal to an
area of each second display portion that is occupied by all
the first reflection surfaces.
7. The display according to claim 5 or 6, wherein an
area of each first display portion that is occupied by all the
first reflection surfaces is between 15% and 50% inclusive of
a total area of each first display portion.
8. The display according to any one of claims 1 to 7,
wherein
55
the obverse surface of the reflection layer includes a
third display portion and a fourth display portion,
the third display portion includes more than one of the
first reflection surfaces,
the fourth display portion includes more than one of the
first reflection surfaces,
more than one of the imaginary lines are set in each of
the third display portion and the fourth display portion, each
imaginary line is parallel to the other imaginary lines in
each of the third display portion and the fourth display
portion,
a direction in which the imaginary lines extend in the
third display portion is a third direction,
a direction in which the imaginary lines extend in the
fourth display portion is a fourth direction, which differs
from the third direction, and
the third direction and the fourth direction form an
angle of less than or equal to 10°.
9. The display according to any one of claims 1 to 8,
wherein the obverse surface of the reflection layer includes
at least one of a diffraction portion that diffracts light
incident on the obverse surface of the reflection layer, an
anti-reflection portion that limits reflection of light
incident on the obverse surface of the reflection layer, and a
light scattering portion that scatters light incident on the
obverse surface of the reflection layer.
10. An article comprising:
a display; and
a support portion that supports the display,
wherein the display is the display according to any one
of claims 1 to 9.
11. An original plate for producing a display
56
including a covered surface, which includes first covered
surfaces and a second covered surface, and a reflection layer,
which covers the covered surface, the original plate
comprising:
a substrate including a surface; and
a resist layer that is located on the surface of the
substrate and includes a transfer surface, which is opposite
to a surface that is in contact with the substrate, wherein
the transfer surface includes a plurality of first
transfer surfaces for forming the first covered surfaces and a
second transfer surface for forming the second covered surface,
in a plan view facing the transfer surface, the first
transfer surfaces are substantially square in shape, and the
second transfer surface occupies gaps between adjacent ones of
the first transfer surfaces,
a distance between the first transfer surfaces and the
second transfer surface in a thickness direction of the
substrate is set to an extent that an obverse surface of the
reflection layer emit colored light by interference between
light reflected from sections of the obverse surface of the
reflection layer that are located on the first covered
surfaces and light reflected from a section of the obverse
surface of the reflection layer that is located on the second
covered surface,
in a plan view facing the transfer surface, more than
one of the first transfer surfaces are located on each of a
plurality of imaginary lines, and
on a straight line intersecting more than one of the
imaginary lines, distances between adjacent ones of the
imaginary lines have different extents.
12． A method for producing an original plate for
producing a display including a covered surface, which
includes first covered surfaces and a second covered surface,
and a reflection layer, which covers the covered surface, the
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method comprising:
forming a resist layer on a surface of a substrate;
exposing the resist layer to light; and
developing the exposed resist layer to form a transfer
surface in the resist layer, wherein
the exposing includes exposing the resist layer such
that:
the transfer surface after developing includes a
plurality of first transfer surfaces for forming the first
covered surfaces and a second transfer surface for forming the
second covered surface, in a plan view facing the transfer
surface, the first transfer surfaces are substantially square
in shape, and the second transfer surface occupies gaps
between adjacent ones of the first transfer surfaces;
a distance between the first transfer surfaces and
the second transfer surface in a thickness direction of the
substrate is set to an extent that an obverse surface of the
reflection layer emit colored light by interference between
light reflected from sections of the obverse surface of the
reflection layer that are located on the first covered
surfaces and light reflected from a section of the obverse
surface of the reflection layer that is located on the second
covered surface; and
in a plan view facing the transfer surface, more
than one of the first transfer surfaces are located on each of
a plurality of imaginary lines, and, on a straight line
intersecting more than one of the imaginary lines, distances
between adjacent ones of the imaginary lines have different
extents.