U.S. patent application number 13/302461 was filed with the patent office on 2012-03-15 for optical device and method of manufacturing the same.
This patent application is currently assigned to TOPPAN PRINTING CO., LTD. Invention is credited to Akira Kubo, Chikara Sawamura, Koji Umezaki, Kazuhiro YASHIKI.
Application Number | 20120064303 13/302461 |
Document ID | / |
Family ID | 43356502 |
Filed Date | 2012-03-15 |
United States Patent
Application |
20120064303 |
Kind Code |
A1 |
YASHIKI; Kazuhiro ; et
al. |
March 15, 2012 |
OPTICAL DEVICE AND METHOD OF MANUFACTURING THE SAME
Abstract
An optical device includes a relief structure formation layer, a
first layer made of a first material having a refractive index
different from that of a material of the relief structure formation
layer, and a second layer made of a second material different from
the first material and covering the first layer. A ratio of an
amount of the second material at a position of the second region to
an apparatus area of the second region is zero or smaller than a
ratio of an amount of the second material at the position of the
second sub-region to an apparatus area of the second
sub-region.
Inventors: |
YASHIKI; Kazuhiro; (Tokyo,
JP) ; Sawamura; Chikara; (Tokyo, JP) ;
Umezaki; Koji; (Tokyo, JP) ; Kubo; Akira;
(Tokyo, JP) |
Assignee: |
TOPPAN PRINTING CO., LTD
Tokyo
JP
|
Family ID: |
43356502 |
Appl. No.: |
13/302461 |
Filed: |
November 22, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/JP2010/060306 |
Jun 17, 2010 |
|
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13302461 |
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Current U.S.
Class: |
428/172 ;
427/162 |
Current CPC
Class: |
B42D 25/324 20141001;
B42D 25/29 20141001; B42D 25/328 20141001; B05D 5/063 20130101;
G02B 5/32 20130101; B42D 2033/18 20130101; B42D 2033/24 20130101;
G02B 5/1842 20130101; Y10T 428/24612 20150115 |
Class at
Publication: |
428/172 ;
427/162 |
International
Class: |
B32B 3/30 20060101
B32B003/30; B05D 5/06 20060101 B05D005/06 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 18, 2009 |
JP |
2009-145532 |
Apr 13, 2010 |
JP |
2010-092079 |
Claims
1. An optical device comprising: a relief structure formation layer
including first and second regions adjacent to each other, the
first region including first and second sub-regions, the first
sub-region being adjacent to the second region and extending along
a boundary between the first and second regions, the second
sub-region being adjacent to the second region with the first
sub-region interposed therebetween, the second region being
provided with recesses or protrusions and having a ratio of surface
area to apparent area greater than that of the first region; a
first layer made of a first material having a refractive index
different from that of a material of the relief structure formation
layer and covering at least the second sub-region, a portion of the
first layer corresponding to the second sub-region having a surface
profile corresponding to a surface profile of the second
sub-region, a ratio of an amount of the first material at a
position of the second region to an apparatus area of the second
region being zero or smaller than a ratio of an amount of the first
material at a position of the second sub-region to an apparatus
area of the second sub-region; and a second layer made of a second
material different from the first material and covering the first
layer, a ratio of an amount of the second material at a position of
the second region to the apparatus area of the second region being
zero or smaller than a ratio of an amount of the second material at
the position of the second sub-region to the apparatus area of the
second sub-region.
2. The optical device according to claim 1, wherein the first
region is provided with recesses or protrusions, the recesses or
protrusions of the second region have an average values of ratios
of depth to diameter or width of openings of the recesses or an
average value of ratios of height to diameter or width of bottoms
of the protrusions greater than that of the recesses or protrusions
of the first region.
3. The optical device according to claim 2, wherein the recesses or
protrusions of the first region have the average value of the
ratios of depth to diameter or width of the openings of the
recesses or the average value of the ratios of height to diameter
or width of the bottoms of the protrusions of 0.5 or less, and the
recesses or protrusions of the second region have the average value
of the ratios of depth to diameter or width of the openings of the
recesses or the average value of the ratios of height to diameter
or width of the bottoms of the protrusions falling within a range
of 0.8 to 2.0.
4. The optical device according to claim 1, wherein the recesses or
protrusions of the second region are arranged
two-dimensionally.
5. The optical device according to claim 1, wherein a portion of
the second layer corresponding to the second sub-region has an
average thickness falling within a range of 0.3 nm to 200 nm.
6. The optical device according to claim 1, wherein the second
layer is a layer formed by a vapor deposition method.
7. The optical device according to claim 1, wherein the first layer
is provided only at a position corresponding to the second
sub-region or a position corresponding to the first region.
8. The optical device according to claim 1, wherein a first
orthogonal projection of a contour of the first layer on the main
surface entirely overlaps a second orthogonal projection of a
contour of the second layer on the main surface, the first
orthogonal projection has a shape similar to the second orthogonal
projection and is surrounded by the second orthogonal projection,
or a part of the first orthogonal projection overlaps a part of the
second orthogonal projection and the remainder of the first
orthogonal projection has a shape similar to the remainder of the
second orthogonal projection and is surrounded by the second
orthogonal projection.
9. The optical device according to claim 1, wherein a maximum value
of a shortest distance from a boundary between the first and second
regions to the contour of the first layer is 20 .mu.m or less.
10. A method of manufacturing an optical device, comprising:
forming a relief structure formation layer including first and
second regions adjacent to each other, the second region being
provided with recesses or protrusions and having a ratio of surface
area to apparent area greater than that of the first region;
vapor-depositing a first material having a refractive index
different from that of a material of the relief structure formation
layer entirely on the first and second regions to form a reflective
material layer, the reflective material layer having a surface
profile corresponding to surface profiles of the first and second
regions, or the reflective material layer having a surface profile
corresponding to the surface profile of the first region at a
portion corresponding to the first region and being partially
opened correspondingly to an arrangement of the recesses or
protrusions at a portion corresponding to the second region;
vapor-depositing a second material different from the first
material on the reflective material layer to form a mask layer, the
mask layer having a surface profile corresponding to the surface
profiles of the first and second regions, or the mask layer having
a surface profile corresponding to the surface profile of the first
region at a portion corresponding to the first region and being
partially opened correspondingly to the arrangement of the recesses
or protrusions at a portion corresponding to the second region; and
exposing the mask layer to a reactive gas or liquid capable of
causing a reaction with the first material to cause the reaction at
least at a position of the second region, thereby obtaining a first
layer made of the first material and a second layer made of the
second material.
11. The method according to claim 10, wherein the reflective
material layer is partially removed by the reaction.
12. The method according to claim 11, wherein the partial removal
of the reflective material layer obtains the first layer as a layer
covering only the first region of the first and second regions.
13. The method according to claim 10, wherein the reaction changes
a part of the reflective material layer into a layer made of a
material different from the first material.
14. The method according to claim 10, wherein the reflective
material layer is formed to have an average thickness falling
within a range of 5 nm to 500 nm at a portion corresponding to the
first region, and the mask layer is formed to have an average
thickness falling within a range of 0.3 nm to 200 nm at a portion
corresponding to the first region.
15. The method according to claim 10, wherein the main surface of
the relief structure formation layer further includes a third
region, the third region being provided with recesses or
protrusions and having a ratio of surface area to apparent area
greater than that of the first region, the reflective material
layer is formed by vapor-depositing the first material entirely on
the first to third regions, and the method further comprises
forming a cover layer facing only the third region of the second
and third regions prior to causing the reaction.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a Continuation application of PCT
Application No. PCT/JP2010/060306, filed Jun. 17, 2010 and based
upon and claiming the benefit of priority from prior Japanese
Patent Applications No. 2009-145532, filed Jun. 18, 2009; and No.
2010-092079, filed Apr. 13, 2010, the entire contents of all of
which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to an optical technique that
offers, for example, forgery prevention effect, decorative effect
and/or aesthetic effect.
[0004] 2. Description of the Related Art
[0005] Securities, certificates, brands, media for personal
authentication, etc. are required to be difficult to forge. Thus,
in some cases, an optical device excellent in forgery prevention
performance is provided on such articles.
[0006] Most of the optical devices include a microstructure such as
diffraction grating, hologram, lens array, etc. The microstructures
are hard to analyze. Further, in order to manufacture an optical
device including the microstructure, an expensive manufacturing
apparatus such as electron beam writer is necessary. For these
reasons, the above optical devices achieve an excellent performance
in forgery prevention.
[0007] Normally, the optical devices include a relief structure
formation layer with a main surface having the microstructure and a
reflective layer provided thereon. In this case, the reflective
layer may be formed in a pattern on a part of the main surface in
order to further enhance the forgery prevention effect. For
example, when the reflective layer is provided on the main surface
to have contours corresponding to micro-characters, a pattern that
emits diffracted light and has a shape corresponding to the
micro-characters can be obtained.
[0008] As the method of forming a patterned reflective layer, for
example, photolithography can be used (for example, refer to Patent
Document 1). This method allows forming a patterned reflective
layer with high definition.
[0009] This method requires alignment of the relief structure
formation layer with respect to a mask. Simultaneously achieving a
high producibility and a high positional accuracy is, however,
impossible or very difficult. For example, according to this
method, a displacement of 100 .mu.m or more may be produced between
the target position and the contour of the reflective layer.
[0010] On the other hand, in Patent Document 2, employed are the
following methods in order to form a reflective layer with a high
positional accuracy.
[0011] In the first method, prepared first is a relief structure
formation layer that includes a "first region" having a relief
structure with a greater depth-to-width ratio and a "second region"
as a flat region or a region having a relief structure with a
smaller depth-to-width ratio. Subsequently, a metal reflective
layer is formed on the relief structure formation layer to have a
uniform surface density. Then, the stacked body thus obtained is
subjected to an etching treatment.
[0012] The portion of the metal reflective layer corresponding to
the "first region" is lower in etching resistance than the portion
corresponding to the "second region". Therefore, the portion
corresponding to the "first region" can be removed before the
portion of the metal reflective layer corresponding to the "second
region" is removed completely. That is, the metal reflective layer
can be formed only on the "second region".
[0013] According to this method, however, the portion of the metal
reflective layer corresponding to the "second region" is partially
removed by the etching treatment. For this reason, there is a
possibility that the portion of the metal reflective layer
corresponding to the "second region" has an excessively small
thickness and thus has an insufficient reflectance. Alternatively,
there is a possibility that the thickness of the metal reflective
layer greatly varies at the portion corresponding to the "second
region". That is, according to this method, it is difficult to
stably form the metal reflective layer.
[0014] In the second method, utilized is a difference between the
transmittance of the portions of the above-described stacked body
corresponding to the "first region" and the "second region".
Specifically, utilized is the fact that the stacked body has a
higher transmittance at the portion corresponding to the "first
region" than at the portion corresponding to the "second
region".
[0015] That is, prepared first is a stacked body of a relief
structure formation layer and a metal reflective layer. A
photosensitive layer is formed on the metal reflective layer. Then,
the stacked body is entirely irradiated with light from the relief
structure formation layer's side. This makes it possible to cause a
photoreaction at a higher efficiency in the portion of the
photosensitive layer corresponding to the "first region". Then,
either one of the regions of the photosensitive layer corresponding
to the "first region" and the "second region" is removed by
treating it with a suitable solvent, etc.
[0016] Then, the metal reflective layer is subjected to an etching
treatment using the partially removed photosensitive layer as a
mask. Thus, either of the portions of the metal reflective layer
corresponding to the "first region" and the "second region" is
removed.
[0017] Since the difference between the above reflectances is
generally small, the photoreaction also occurs in the portion of
the photosensitive layer corresponding to the "second region".
Thus, it is in reality impossible or difficult to cause the
above-described reaction in only one of the portions of the
photosensitive layer corresponding to the "first region" and the
"second region". Therefore, when using this method, it is also in
fact impossible or difficult to form a metal reflective layer with
a high positional accuracy.
[0018] Further, this method requires an exposure process for the
photosensitive layer. Therefore, this method is disadvantageous in
cost and producibility.
PRIOR ART DOCUMENTS
[0019] Patent Document 1: Japanese Patent Application Publication
No. 2003-255115 [0020] Patent Document 2: Japanese Patent
Application Publication No. 2008-530600
BRIEF SUMMARY OF THE INVENTION
[0021] An object of the present invention is to provide an optical
technique that makes it possible to stably form a reflective layer
with a high positional accuracy.
[0022] According to a first aspect of the present invention, there
is provided an optical device comprising a relief structure
formation layer including first and second regions adjacent to each
other, the first region including first and second sub-regions, the
first sub-region being adjacent to the second region and extending
along a boundary between the first and second regions, the second
sub-region being adjacent to the second region with the first
sub-region interposed therebetween, the second region being
provided with recesses or protrusions and having a ratio of surface
area to apparent area greater than that of the first region; a
first layer made of a first material having a refractive index
different from that of a material of the relief structure formation
layer and covering at least the second sub-region, a portion of the
first layer corresponding to the second sub-region having a surface
profile corresponding to a surface profile of the second
sub-region, a ratio of an amount of the first material at a
position of the second region to an apparatus area of the second
region being zero or smaller than a ratio of an amount of the first
material at a position of the second sub-region to an apparatus
area of the second sub-region; and a second layer made of a second
material different from the first material and covering the first
layer, a ratio of an amount of the second material at a position of
the second region to the apparatus area of the second region being
zero or smaller than a ratio of an amount of the second material at
the position of the second sub-region to the apparatus area of the
second sub-region.
[0023] According to a second aspect of the present invention, there
is provided a method of manufacturing an optical device, comprising
forming a relief structure formation layer including first and
second regions adjacent to each other, the second region being
provided with recesses or protrusions and having a ratio of surface
area to apparent area greater than that of the first region;
vapor-depositing a first material having a refractive index
different from that of a material of the relief structure formation
layer entirely on the first and second regions to form a reflective
material layer, the reflective material layer having a surface
profile corresponding to surface profiles of the first and second
regions, or the reflective material layer having a surface profile
corresponding to the surface profile of the first region at a
portion corresponding to the first region and being partially
opened correspondingly to an arrangement of the recesses or
protrusions at a portion corresponding to the second region;
vapor-depositing a second material different from the first
material on the reflective material layer to form a mask layer, the
mask layer having a surface profile corresponding to the surface
profiles of the first and second regions, or the mask layer having
a surface profile corresponding to the surface profile of the first
region at a portion corresponding to the first region and being
partially opened correspondingly to the arrangement of the recesses
or protrusions at a portion corresponding to the second region; and
exposing the mask layer to a reactive gas or liquid capable of
causing a reaction with the first material to cause the reaction at
least at a position of the second region, thereby obtaining a first
layer made of the first material and a second layer made of the
second material.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
[0024] FIG. 1 is a plan view schematically showing an example of an
optical device according to an embodiment of the present
invention;
[0025] FIG. 2 is a sectional view of the optical device taken along
a line II-II shown in FIG. 1;
[0026] FIG. 3 is a sectional view schematically showing a method of
manufacturing the optical device shown in FIGS. 1 and 2;
[0027] FIG. 4 is a sectional view schematically showing the method
of manufacturing the optical device shown in FIGS. 1 and 2;
[0028] FIG. 5 is a sectional view schematically showing the method
of manufacturing the optical device shown in FIGS. 1 and 2;
[0029] FIG. 6 is a sectional view schematically showing the method
of manufacturing the optical device shown in FIGS. 1 and 2;
[0030] FIG. 7 is a plan view schematically showing an optical
device according to a modified example;
[0031] FIG. 8 is a sectional view of the optical device taken along
a line VIII-VIII shown in FIG. 7;
[0032] FIG. 9 is a plan view schematically showing an optical
device according to another modified example;
[0033] FIG. 10 is a sectional view of the optical device taken
along a line X-X shown in FIG. 9;
[0034] FIG. 11 is a plan view schematically showing an optical
device according to another embodiment of the present
invention;
[0035] FIG. 12 is a sectional view of the optical device taken
along a line XII-XII shown in FIG. 11;
[0036] FIG. 13 is a sectional view schematically showing a method
of manufacturing the optical device shown in FIGS. 11 and 12;
[0037] FIG. 14 is a sectional view schematically showing the method
of manufacturing the optical device shown in FIGS. 11 and 12;
[0038] FIG. 15 is a sectional view schematically showing the method
of manufacturing the optical device shown in FIGS. 11 and 12;
[0039] FIG. 16 is a sectional view schematically showing the method
of manufacturing the optical device shown in FIGS. 11 and 12;
[0040] FIG. 17 is a sectional view schematically showing the method
of manufacturing the optical device shown in FIGS. 11 and 12;
and
[0041] FIG. 18 is a graph showing an example of a relationship
between presence or absence of the mask layer and the etching
rate.
DETAILED DESCRIPTION OF THE INVENTION
[0042] Embodiments of the present invention will be described below
with reference to drawings. In the drawings, the same reference
symbols denote components having the same or similar functions and
duplicate descriptions will be omitted.
[0043] FIG. 1 is a plan view schematically showing an example of an
optical device according to an embodiment of the present invention.
FIG. 2 is a sectional view of the optical device taken along a line
II-II shown in FIG. 1. In FIGS. 1 and 2, the X and Y directions are
parallel with a main surface of the optical device 10 and
perpendicular to each other, while the Z direction is perpendicular
to the main surface of the optical device 10. Further, in FIG. 1,
the display portion DP1 is the portion of the optical device 10
that corresponds to the first region R1 described later, while the
display portion DP2 is the portion of the optical device 10 that
corresponds to the second region R2 described later.
[0044] The optical device 10 shown in FIGS. 1 and 2 includes a
relief structure formation layer 110, a first layer 120' and a
second layer 130'.
[0045] On one main surface of the relief structure formation layer
110, relief structures are provided. The first layer 120' partially
covers the main surface of the relief structure formation layer
110. The second layer 130' covers the first layer 120'. The
structure of the optical device 10, etc. will be described later in
more detail.
[0046] A method of manufacturing the optical device 10 shown in
FIGS. 1 and 2 will be described with reference to FIGS. 3 to 6.
[0047] FIGS. 3 to 6 are sectional views schematically showing a
method of manufacturing the optical device shown in FIGS. 1 and
2.
[0048] In this method, prepared first is a relief structure
formation layer 110 that has a main surface including a first
region R1 and a second region R2 as shown in FIG. 3.
[0049] The first region R1 is flat or provided with a recessed
structure and/or a protruding structure. Recesses and protrusions
constitute the recessed structure and the protruding structure,
respectively. In the case where the first region R1 is provided
with the recesses or protrusions, the recesses or protrusions may
be arranged one-dimensionally or two-dimensionally. Also, in this
case, the recesses or protrusions may be arranged regularly or
randomly. FIG. 3 shows the case where the first region R1 is
provided with grooves as the recesses that are arranged
one-dimensionally and regularly. Typically, the grooves form a
diffraction grating or hologram that emits a diffracted light when
illuminated with a white light.
[0050] The cross sections of the grooves that are perpendicular to
the lengthwise directions thereof have, for example, tapered shapes
such as shapes of letters V and U or rectangular shapes. FIG. 3
shows the case where the cross sections are V-shaped as an
example.
[0051] The widths of the openings of the grooves provided to the
first region R1 are set within, for example, a range of 100 to
3,000 nm. The depths of the grooves are set within, for example, a
range of 20 to 1,500 nm. The mean value of ratios of the depths to
the widths of the openings of the grooves is set, for example, at
0.5 or less, and typically within a range of 0.05 to 0.3.
[0052] The second region R2 is provided with a recessed structure
and/or a protruding structure. Recesses and protrusions constitute
the recessed structure and the protruding structure, respectively.
The recesses or protrusions may be arranged one-dimensionally or
two-dimensionally. Also, the recesses or protrusions may be
arranged regularly or randomly. FIG. 3 shows the case where the
second region R2 is provided with grooves as the recesses that are
arranged one-dimensionally and regularly.
[0053] The cross sections of the grooves that are perpendicular to
the lengthwise directions thereof have, for example, tapered shapes
such as shapes of letters V and U or rectangular shapes. FIG. 3
shows the case where the cross sections are V-shaped as an
example.
[0054] The second region R2 has a ratio of a surface area to an
apparent area greater than that of the first region R1. Here, an
"apparent area" of a region means an area of an orthogonal
projection of the region on a plane parallel with the region, that
is, an area of the region from which the recessed structure and the
protruding structure are omitted. On the other hand, a "surface
area" of a region means an area of the region in consideration of
the recessed structure and the protruding structure.
[0055] In the case where the first region R1 is provided with the
recesses or protrusions, the recesses or protrusions on the second
region R2 typically have a mean value of ratios of the depths to
the diameters or widths of the openings of the recesses or a mean
value of ratios of the heights to the diameters or widths of the
bottoms of the protrusions greater than that of the recesses or
protrusions on the first region R1. In the example shown in FIG. 3,
the groves on the second region R2 have a ratio of the depth to the
width of the opening of the groove greater than that of the grooves
on the first region R1.
[0056] The widths of the grooves on the second region R2 are set
within, for example, a range of 100 to 3,000 nm. The depths of the
grooves are set within, for example, a range of 80 to 6,000 nm. In
the case where both the regions R1 and R2 are provided with the
grooves, the mean value of the ratios of the depths to the widths
of the openings of the grooves on the second region R2 is set
greater than the mean value of the ratios of the depths to the
widths of the openings of the grooves on the first region R1. The
mean value of the ratios of the depths to the widths of the
openings of the grooves on the second region R2 is set within, for
example, a range of 0.8 to 2.0, and typically a range of 0.8 to
1.2. When the value is excessively large, there is a possibility
that the producibility of the relief structure formation layer 110
is degraded.
[0057] The relief structure formation layer 110 can be formed by,
for example, pressing a stamping die provided with fine protrusions
against a resin. The protrusions have shapes that correspond to the
shapes of the recesses on the region R2 or the recesses on the
regions R1 and R2.
[0058] The relief structure formation layer 110 is formed by, for
example, a method in which a substrate is coated with a
thermoplastic resin and then a plate having the above-described
protrusions thereon is pressed against the resin while applying
heat thereto. In this case, as the thermoplastic resin, for
example, acrylic resin, epoxy resin, cellulosic resin, vinyl resin,
mixtures thereof or copolymers thereof is used.
[0059] Alternatively, the relief structure formation layer 110 may
be formed by a method in which a substrate is coated with a
thermosetting resin, a plate having the above-described protrusions
thereon is pressed against the resin while applying heat thereto,
and then the plate is removed therefrom. In this case, as the
thermosetting resin, for example, urethane resin, melamine resin,
epoxy resin, phenol resin, mixtures thereof or copolymers thereof
is used. Note that the urethane resin can be obtained by, for
example, adding polyisocyanate as a crosslinking agent to acrylic
polyol or polyester polyol having a reactive hydroxyl group and
causing crosslinking reaction thereof.
[0060] Alternatively, the relief structure formation layer may be
formed by a method in which a substrate is coated with a
radiation-curing resin, the rein is irradiated with radiation such
as ultraviolet ray while pressing the late against the resin, and
then the plate is removed therefrom. Alternatively, the relief
structure formation layer may be formed by a method in which the
composition is injected between a substrate and the plate, this
material is cured by a radiation exposure, and then the plate is
removed therefrom.
[0061] The radiation-curing resin typically contains a
polymerizable compound and an initiator.
[0062] As the polymerizable compound, for example, a compound
capable of causing a photo-induced radical polymerization is used.
As the compound capable of causing a photo-induced radical
polymerization, for example a monomer, oligomer or polymer having
an ethylenic unsaturated bond or ethylenic unsaturated group is
used. Alternatively, as the compound capable of causing a
photo-induced radical polymerization, a monomer such as
1,6-hexanediol, neopentyl glycol diacrylate, trimethylol propane
triacrylate, pentaerythritol triacrylate, pentaerythritol
tetraacrylate, pentaerythritol pentaacrylate and dipentaerythritol
hexaacrylate; an oligomer such as epoxy acrylate, urethane acrylate
and polyester acrylate; or a polymer such as urethane-modified
acrylic resin and epoxy-modified acrylic resin may be used.
[0063] In the case where the compound capable of causing a
photo-induced radical polymerization is used as the polymerizable
compound, a photo-induced radical polymerization initiator is used
as the initiator. As the photo-induced radical polymerization
initiator, for example, benzoin-based compound such as benzoin,
benzoin methyl ether and benzoin ethyl ether; anthraquinone-based
compound such as anthraquinone and methyl anthraquinone; phenyl
ketone-based compound such as acetophenone, diethoxy acetophenone,
benzophenone, hydroxy acetophenone, 1-hydroxycyclohexyl phenyl
ketone, .alpha.-aminoacetophenone and 2-methyl-1-(4-methyl
thiophenyl)-2-morpholinopropane-1-one; benzyldimethyl ketal;
thioxanthone; acylphosphine oxide; or Michler's ketone is used.
[0064] Alternatively, a compound capable of causing photo-induced
cationic polymerization may be used as the polymerizable compound.
As the compound capable of causing photo-induced cationic
polymerization, for example, a monomer, oligomer or polymer having
an epoxy group; a compound having an oxetane skeleton; or vinyl
ether is used.
[0065] In the case where the compound capable of causing
photo-induced cationic polymerization is used as the polymerizable
compound, a photo-induced cationic polymerization initiator is uses
as the initiator. As the photo-induced cationic polymerization
initiator, for example, aromatic diazonium salt, aromatic iodonium
salt, aromatic sulfonium salt, aromatic sulfonium salt, aromatic
phosphonium salt or a metal salt with mixed ligands is used.
[0066] Alternatively, a mixture of the compound capable of causing
a photo-induced radical polymerization and the compound capable of
causing a photo-induced cationic polymerization may be used as the
polymerizable compound. In this case, as the initiator, for
example, a mixture of the photo-induced radical polymerization
initiator and the photo-induced cationic polymerization initiator
is used as the initiator. Alternatively, in this case, an initiator
that can function as both the photo-induced radical polymerization
initiator and the photo-induced cationic polymerization initiator
may be used. As such an initiator, for example, aromatic iodonium
salt or aromatic sulfonium salt is used.
[0067] Note that a proportion of the initiator in the
radiation-curing resin is set within, for example, a range of 0.1%
to 15% by mass.
[0068] The radiation-curing resin may further contain sensitizing
dye, dye, pigment, polymerization inhibitor, leveling agent,
antifoaming agent, anti-sagging agent, adhesion promoter, coating
surface-modifying agent, plasticizer, nitrogen-containing compound,
crosslinking agent such as epoxy resin, release agent or a
combination thereof. The radiation-curing resin may further contain
non-reactive resin in order to improve the moldability. As the
non-reactive resin, for example, the above-described thermoplastic
resin and/or thermosetting resin can be used.
[0069] The above-described plate used for forming the relief
structure formation layer 110 is manufactured, for example, using
an electron beam writer or nanoimprinting apparatus. In this case,
the above-described recesses or protrusions can be formed with a
high degree of accuracy. Note that in normal cases, a reversal
plate is manufactured first by transferring the relief structure of
the original plate thereon, and replicated plates are manufactured
by transferring the relief structure of the reversal plate thereon.
Further, reversal plate is manufactured using the replicated plate
as an original plate and replicated plates are manufactured by
transferring the relief structure of the reversal plate thereon, if
necessary. In actual manufacturing processes, the replicated plate
thus obtained is used in normal cases.
[0070] The relief structure formation layer 110 typically includes
a substrate and a resin layer formed thereon. As the substrate, a
film substrate is used typically. As the film substrate, for
example, a plastic film such as polyethylene terephthalate (PET)
film, polyethylene naphthalate (PEN) film and polypropylene (PP)
film is used. Alternatively, paper, synthetic paper, multilayer
plastic paper or resin-impregnated paper may be used as the
substrate. The substrate may be omitted.
[0071] The resin layer is formed by, for example, the
above-described method. The thickness of the resin layer is set
within, for example, a range of 0.1 to 10 .mu.m. When the thickness
is excessively large, squeeze-out and/or wrinkling of the resin due
to the pressure induced on the processing are prone to occur. When
the thickness is excessively small, there is a possibility that
formation of the recessed structure and/or protruding structure is
difficult. The thickness of the resin layer is set equal to or
greater than the depth or height of the recesses or protrusions
provided on the main surface thereof. The thickness is set at a
value, for example, 1 to 10 times, typically a value 3 to 5 times
the depth of height of the recesses or protrusions.
[0072] Formation of the relief structure formation layer 110 may be
performed by the "press method" described in Japanese Patent No.
4194073, the "casting method" described in Japanese Utility Model
No. 2524092, or the "photopolymer method" described in Japanese
Patent Application Publication No. 2007-118563.
[0073] Next, a first material having a refractive index different
from that of the material of the relief structure formation layer
110 is vapor-deposited on the regions R1 and R2. Thus, a reflective
layer 120 is formed on the main surface of the relief structure
formation layer 110 that includes the regions R1 and R2.
[0074] As the first material, for example, a material having a
refractive index different from that of the material of the relief
structure formation layer 110 by 0.2 or more is used. When this
difference is small, there is a possibility that a reflection by
the interface between the relief structure formation layer 110 and
the first layer 120' described later is less prone to occur.
[0075] As the first material, used typically is at least one metal
material selected from the group consisting of Al, Sn, Cr, Ni, Cu,
Au, Ag and alloys thereof.
[0076] Alternatively, as the first material with a relatively high
transparency, the ceramic material or the organic polymer material
listed below may be used. Note that the parenthesized numerical
value following the chemical formula or compound name indicates the
refractive index of the corresponding material.
[0077] That is, as the ceramic material, for example,
Sb.sub.2O.sub.3 (3.0), Fe.sub.2O.sub.3 (2.7), TiO.sub.2 (2.6), CdS
(2.6), CeO.sub.2 (2.3), ZnS (2.3), PbCl.sub.2 (2.3), CdO (2.2),
Sb.sub.2O.sub.3 (5), WO.sub.3 (5), SiO (5), Si.sub.2O.sub.3 (2.5),
In.sub.2O.sub.3 (2.0), PbO (2.6), Ta.sub.2O.sub.3 (2.4), ZnO (2.1),
ZrO.sub.2 (5), MgO (1), SiO.sub.2 (1.45), Si.sub.2O.sub.2 (10),
MgF.sub.2 (4), CeF.sub.3 (1), CaF.sub.2 (1.3-1.4), AlF.sub.3 (1),
Al.sub.2O.sub.3 (1) or GaO (2) can be used.
[0078] As the organic polymer material, for example, polyethylene
(1.51), polypropylene (1.49), polytetrafluoroethylene (1.35),
polymethylmethacrylate (1.49) or polystyrene (1.60) can be
used.
[0079] The vapor deposition of the first material is performed
using, for example, vacuum evaporation, sputtering, or chemical
vapor deposition (CVD).
[0080] The vapor deposition is performed with uniform density
in-plane directions parallel with the main surface of the relief
structure formation layer 110. Specifically, the vapor deposition
is performed such that a ratio of the amount of the first material
at the position of the first region R1 to the apparent area of the
first region R1 and a ratio of the amount of the first material at
the position of the second region R2 to the apparent area of the
second region R2 are equal to each other.
[0081] Regarding to the vapor deposition, the thickness in the case
of supposing the main surface of the relief structure formation
layer 110 is constituted entirely by a flat surface (hereinafter
referred to as target thickness) is typically determined as
follows. That is, the target thickness is determined such that the
reflective material layer 120 satisfies the following
conditions.
[0082] Firstly, the portion of the reflective material layer 120
corresponding to the first region R1 has a surface configuration
that corresponds to the surface configuration of the first region
R1. In the example shown in FIG. 4, this portion forms a continuous
film having a surface configuration that corresponds to the grooves
on the first region R1.
[0083] Secondly, the portion of the reflective material layer 120
corresponding to the second region R2 has a surface configuration
that corresponds to the surface configuration of the second region
R2 or partially opens correspondingly to the arrangement of the
recesses or protrusions on the second region R2. FIG. 4 shows the
former case as an example. That is, in the example shown in FIG. 4,
this portion forms a continuous film having a surface configuration
that corresponds to the grooves on the second region R2.
[0084] As described above, the second region R2 has a ratio of the
surface area to the apparent area greater than that of the second
region R2. Thus, in the case where the target thickness is
determined such that the reflective material layer 120 has a
surface configuration corresponding to the surface configurations
of the regions R1 and R2, the portion of the reflective material
layer 120 corresponding to the second region R2 has a smaller mean
thickness as compared with the portion of the reflective material
layer 120 corresponding to the first region R1.
[0085] Here a "mean thickness" of a layer means a mean value of
distances between points on a main surface of the layer and
corresponding foots of perpendicular lines that extend from the
points to the other main surface of the layer.
[0086] When the target thickness is set at a smaller value, the
reflective material layer 120 can be formed to have a surface
configuration corresponding to the surface configuration of the
first region R1 at the portion corresponding to the first region R1
and partially open correspondingly to the arrangement of the
recesses and protrusions at the portion corresponding to the second
region R2.
[0087] The target thickness of the reflective material layer 120 is
typically set smaller than the depth or height of the recesses or
protrusions on the second region R2. In the case where the first
region R1 is provided with the recesses or protrusions, the target
thickness is typically set smaller than the depth or height
thereof.
[0088] Specifically, the target thickness of the reflective
material layer 120 is set within, for example, a range of 5 to 500
nm, and typically a range of 30 to 300 nm. When the target
thickness is excessively small, there is a possibility that a
reflection by an interface between the relief structure formation
layer 110 and the first layer 120' described later is less prone to
occur. When the target thickness is excessively large, there is a
possibility that the reflective material layer 120 is difficult to
form to satisfy the above-described conditions.
[0089] The mean thickness of the portion of the reflective material
layer 120 corresponding to the first region R1 is set within, for
example a range of 5 to 500 nm, and typically a range of 30 to 300
nm. When the mean thickness is excessively small, there is a
possibility that a reflection by an interface between the relief
structure formation layer 110 and the first layer 120' described
later is less prone to occur. When the mean thickness is
excessively large, there is a possibility that the producibility of
the optical device 10 is degraded.
[0090] Subsequently, a second material different from the material
of the reflective material layer 120 is vapor-deposited on the
reflective material layer 120 as shown in FIG. 5. Thus, formed is a
mask layer 130 that faces the relief structure formation layer 110
with the reflective material layer 120 interposed therebetween.
[0091] As the second material, an inorganic material is typically
used. Examples of the inorganic material include MgF.sub.2, Sn, Cr,
ZnS, ZnO, Ni, Cu, Au, Ag, TiO.sub.2, MgO, SiO.sub.2 and
Al.sub.2O.sub.3. In particular, in the case where MgF.sub.2 is used
as the second material, the mask layer 130 and the second layer
130' can deliver a higher performance in the conformability and
abrasion resistance when the substrate is bent or an impact is
applied thereto.
[0092] Alternatively, an organic material may be used as the second
material. As the organic material, for example, an organic material
having a weight-average molecular weight of 1,500 or less is used.
Examples of such an organic material include a polymerizable
compound such as acrylate, urethaneacrylate and epoxyacrylate.
Alternatively, as the organic material, it is possible to use a
substance obtained by mixing the polymerizable compound and an
initiator together, vapor-depositing the radiation-curing resin
thus obtained, and irradiating it with radiation to cause
polymerization.
[0093] Alternatively, metal alkoxide may be used as the second
material. Alternatively, as the second material, it is possible to
use a substance obtained by vapor-depositing the metal alkoxide and
causing polymerization thereof. In this case, a dry treatment may
be performed between the vapor deposition and the
polymerization.
[0094] The vapor deposition of the second material is performed
using, for example, vacuum evaporation, sputtering or CVD.
[0095] The vapor deposition is performed with uniform density
in-plane directions parallel with the main surface of the relief
structure formation layer 110. Specifically, the vapor deposition
is performed such that a ratio of the amount of the second material
at the position of the first region R1 to the apparent area of the
first region R1 and a ratio of the amount of the second material at
the position of the second region R2 to the apparent area of the
second region R2 are equal to each other.
[0096] Regarding to the vapor deposition, the target thickness of
the mask layer 130 is determined as follows. That is, the target
thickness is determined such that the mask layer 130 satisfies the
following conditions.
[0097] Firstly, the portion of the mask layer 130 corresponding to
the first region R1 has a surface configuration that corresponds to
the surface configuration of the first region R1. In the example
shown in FIG. 5, this portion forms a continuous film having a
surface configuration that corresponds to the grooves on the first
region R1.
[0098] Secondly, the portion of the mask layer 130 corresponding to
the second region R2 has a surface configuration that corresponds
to the surface configuration of the second region R2 or partially
opens correspondingly to the arrangement of the recesses or
protrusions on the second region R2. FIG. 5 shows the latter case
as an example. That is, in the example shown in FIG. 5, this
portion forms a discontinuous film on the reflective material layer
120 that partially opens correspondingly to the arrangement of the
grooves on the second region R2.
[0099] As described above, the second region R2 has a ratio of the
surface area to the apparent area greater than that of the second
region R2. Thus, in the case where the target thickness is
determined such that the mask layer 130 has a surface configuration
corresponding to the surface configurations of the regions R1 and
R2, the portion of the mask layer 130 corresponding to the second
region R2 has a smaller mean thickness as compared with the portion
of the mask layer 130 corresponding to the first region R1.
[0100] When the target thickness is set at a smaller value, the
mask layer 130 can be formed to have a surface configuration
corresponding to the surface configuration of the first region R1
at the portion corresponding to the first region R1 and partially
open correspondingly to the arrangement of the recesses and
protrusions at the portion corresponding to the second region
R2.
[0101] The target thickness of the mask layer 130 is typically set
smaller than the depth or height of the recesses or protrusions on
the second region R2. In the case where the first region R1 is
provided with the recesses or protrusions, the target thickness is
typically set smaller than the depth or height thereof. Further,
the target thickness of the mask layer 130 is typically set smaller
than the target thickness of the reflective material layer 120.
[0102] Specifically, the target thickness of the mask layer 130 is
set within, for example, a range of 0.3 to 200 nm, and typically a
range of 3 to 80 nm. When the target thickness is excessively
small, there is a possibility that the mean thickness of the
portion of the mask layer 130 corresponding to the first region R1
is excessively small, and thus the protection of the portion of the
reflective material layer 120 corresponding to the first region R1
by the mask layer 130 is insufficient. When the target thickness is
excessively large, there is a possibility that the protection of
the portion of the reflective material layer 120 corresponding to
the second region R2 by the mask layer 130 is excessive.
[0103] The mean thickness of the portion of the mask layer 130
corresponding to the first region R1 is typically set smaller than
the mean thickness of the portion of the reflective material layer
120 corresponding to the first region R1.
[0104] The mean thickness of the portion of the mask layer 130
corresponding to the first region R1 is set within, for example a
range of 0.3 to 200 nm, and typically a range of 3 to 80 nm. When
the mean thickness is excessively small, there is a possibility
that the mean thickness of the portion of the mask layer 130
corresponding to the first region R1 is excessively small, and thus
the mean thickness of the portion of the first layer 120' described
later corresponding to the first region R1 is excessively small.
When the target thickness is excessively large, there is a
possibility that the protection of the portion of the reflective
material layer 120 corresponding to the second region R2 by the
mask layer 130 is excessive.
[0105] Subsequently, the mask layer 130 is exposed to a reactive
gas or liquid that can react with the material of the reflective
material layer 120. This allows the material of the reflective
material layer 120 to cause the above-described reaction at least
at a position of the second region R2.
[0106] Here, described is the case where an etching liquid capable
of dissolving the material of the reflective material layer 120 is
used as the reactive gas or liquid. An alkaline solution such as
sodium hydroxide solution, sodium carbonate solution and potassium
hydroxide solution is typically used as the etching liquid.
Alternatively, an acidic solution such as hydrochloric acid, nitric
acid, sulfuric acid and acetic acid may be used as the etching
liquid.
[0107] As shown in FIG. 5, the portion of the mask layer 130
corresponding to the first region R1 forms a continuous film, while
the portion corresponding to the second region R2 forms a
discontinuous film that opens partially. The reactive gas or liquid
can easily come in contact with the portion of the reflective
material layer 120 that is not covered by the mask layer 130 as
compared with the portion of the reflective material layer 120 that
is covered by the mask layer 130. Thus, the former is easily etched
than the latter.
[0108] When the portion of the reflective material layer 120 that
is not covered by the mask layer 130 is removed, openings
corresponding to the openings of the mask layer 130 are produced in
the reflective material layer 120. When the etching treatment is
further continued, the etching of the reflective material layer 120
proceeds in the in-plane directions at the positions of the
openings. As a result, above the second region R2, the portion of
the reflective material layer that supports the mask layer 130 is
removed together with the mask layer 130 thereon.
[0109] Therefore, by adjusting the concentration and temperature of
the etching liquid and the duration of etching, etc., only the
portion of the reflective material layer 120 that corresponds to
the second region R2 can be removed as shown in FIG. 6. Thus,
obtained is the first layer 120' that covers only the first region
R1 of the regions R1 and R2.
[0110] The optical device 10 shown in FIGS. 1 and 2 is thus
obtained.
[0111] The optical device 10 obtained by the above-described method
has the following characteristics.
[0112] The first layer 120' is a reflective layer and typically
made of the above-described first material. The first layer 120'
covers only the first region R1 of the regions R1 and R2. That is,
the first layer 120' is provided only at a position corresponding
to the first region R1. A ratio of the amount of the first material
at the position of the second region R2 to the apparent area of the
second region R2 is zero.
[0113] The first layer 120' has a surface configuration that
corresponds to the surface configuration of the first region R1. In
the example shown in FIGS. 1 and 2, the first layer 120' has a
surface configuration that corresponds to the grooves on the first
region R1. The grooves on the first region R1 typically form on the
surface of the first layer 120' a diffraction grating or hologram
that emits a diffracted light when illuminated with a white light.
In this case, the display portion DP1 of the optical device 10 can
display a color corresponding to the diffracted light. Therefore,
in this case, a higher forgery prevention effect and a higher
decorative effect can be achieved.
[0114] An orthogonal projection of the contour of the first layer
120' on the main surface of the relief structure formation layer
110 entirely overlaps the contour of the first region R1. That is,
the first layer 120' is patterned correspondingly to the shape of
the first region R1. Thus, when the regions R1 and R2 are formed
with a high positional accuracy, the first layer 120' can be formed
with a high positional accuracy.
[0115] Note that in the method described with reference to FIGS. 3
to 6, the portion of the reflective material layer 12 corresponding
to the first region R1 is covered with the mask layer 130. Thus, in
the case where the above-described etching treatment is performed,
the thickness of the portion is scarcely decreased or is not
decreased at all. Therefore, the mean thickness of the portion of
the first layer 120' corresponding to the first region R1 is
typically equal to the mean thickness of the portion of the
reflective material layer 120 corresponding to the first region R1.
That is, the mean thickness falls within, for example, a range of 5
to 500 nm, and typically a range of 30 to 300 nm.
[0116] Note that the maximum value of the shortest distances from
the boundary between the regions R1 and R2 to the contour of the
first layer 120' is set, for example, less than 20 .mu.m,
preferably less than 10 .mu.m, and more preferably less than 3
.mu.m.
[0117] The second layer 130' is, for example, a layer formed by
vapor deposition. The second layer 130' covers the first layer
120'. The second layer 130' faces only the first region R1 of the
regions R1 and R2 with the first layer 120' interposed
therebetween. That is, the orthogonal projection of the contour of
the first layer 120' on the main surface of the relief structure
formation layer 110 entirely overlaps an orthogonal projection of
the contour of the second layer 130' on the main surface. A ratio
of the amount of the second material at the position of the second
region R2 to the apparent area of the second region R2 is zero.
[0118] The mean thickness of the portion of the second layer 130'
corresponding to the first region R1 is equal to or smaller than
the mean thickness of the portion of the mask layer 130
corresponding to the first region R1. The mean thickness falls
within, for example, a range of 0.3 to 200 nm, and typically a
range of 3 to 80 nm.
[0119] The second layer 130' plays, for example, a role of
protecting the first layer 120'. In the case where the second layer
130' is provided, forgery of the optical device 10 is more
difficult as compared with the case where the second layer 130' is
absent.
[0120] In the case where a colored material is used as the second
material and the optical device 10 is observed from the side of the
second layer 130', the second layer 130' makes it possible to
change the color of the portion of the optical device 10 where the
first layer 120' is provided without affecting the color of the
other portion of the optical device 10. For example, in the case
where Al is used as the first material and Sn or Cr is used as the
second material, it is possible to impart a blackish color to the
portion of the optical device 10 where the first layer 120' is
provided. Alternatively, in the case where Al is used as the first
material and ZnS is used as the second material, it is possible to
impart a yellowish color to the portion of the optical device 10
where the first layer 120' is provided. Note that in the case where
the mean thickness of the first layer 120' is small, these effects
can be obtained when the optical device 10 is observed from the
side of the relief structure formation layer 110.
[0121] In the above, described is the case where both the regions
R1 and R2 are provided with grooves arranged regularly. The
structures of the regions R1 and R2 are not limited to this.
[0122] For example, the first region R1 may be flat. In this case,
the display portion D1 is seen, for example, like a specular
surface. Note that in this case, the ratio of the surface area to
the apparent area of the first region R1 is equal to 1.
[0123] Alternatively, the first region R1 may be provided with
recesses or protrusions arranged two-dimensionally. In this case,
the recesses or protrusions are typically tapered. For example, the
recesses or protrusions have a shape of a circular cone, a pyramid,
a circular truncated cone, a truncated pyramid, an elliptic
paraboloid or a paraboloid of revolution. The sidewalls of the
recesses or protrusions may be smooth or stepwise. Alternatively,
the recesses or protrusions may have columnar shapes such as
circular columns or prisms.
[0124] The recesses or protrusions arranged two-dimensionally may
be arranged regularly or randomly. In the former case, the recesses
or protrusions typically form on the surface of the first layer
120' a diffraction grating or hologram that emits a diffracted
light when illuminated with a white light.
[0125] In the case where the first region R1 is provided with the
recesses or protrusions arranged two-dimensionally, the recesses or
protrusions are arranged in a square lattice. Alternatively, the
recesses or protrusions may be arranged in a rectangular or
triangle lattice.
[0126] In the case where the first region R1 is provided the
recesses or protrusions arranged two-dimensionally, the mean value
of the diameters of the openings of the recesses or the mean value
of the diameters of the bottoms of the protrusions is set within,
for example, a range of 100 to 3,000 nm. The mean value of the
depths of the recesses or the mean value of the heights of the
protrusions is set within, for example, a range of 20 to 1,500 nm.
The mean value of ratios of the depths to the diameters of the
recesses or the mean value of the ratios of the heights to
diameters of the bottoms of the protrusions is set, for example, at
0.5 or less, and typically within a range of 0.05 to 0.3.
[0127] The second region R2 may be provided with recesses or
protrusions arranged two-dimensionally. The recesses or protrusions
can employ, for example, the same structure as that described for
the recesses or protrusions of the first region R1 except that the
mean value of the ratios of the depths to the diameters of the
recesses or the mean vale of the ratios of the heights to the
diameters of the bottoms of the protrusions is greater.
[0128] In the case where the second regions R2 is provided with the
recesses or protrusions arranged two-dimensionally, the mean value
of the diameters of the openings of the recesses or the mean value
of the diameters of the bottoms of the protrusions is set within,
for example, a range of 100 to 3,000 nm. The mean value of the
depths of the recesses or the mean value of the heights of the
protrusions is set within, for example, 80 to 6,000 nm. The mean
value of the ratios of the depths to the diameters of the recesses
or the mean value of the ratios of the heights to the diameters of
the bottom of the protrusions is set within, for example, a range
of 0.8 to 2.0, and typically a range of 0.8 to 1.5.
[0129] The recesses or protrusions provided to the regions R1 and
R2 may form a relief hologram, a diffraction grating, a
sub-wavelength grating, micro-lenses, a polarizing element, a
condensing element, a scattering element, a diffusing element or a
combination thereof.
[0130] In the above, described is the case where the reflective
material layer 120 has a surface configuration that corresponds to
the surface configurations of the regions R1 and R2, the portion of
the mask layer 130 corresponding to the first region R1 has a
surface configuration that corresponds to the surface configuration
of the first region R1, and the portion of the mask layer 130
corresponding to the second region R2 partially opens
correspondingly to the arrangement of the recesses or protrusions
on the second region R2. The structures of the layers are not
limited to this.
[0131] For example, it is possible to employ the structure in which
both the reflective material layer 120 and the mask layer have
surface configurations that correspond to the surface
configurations of the regions R1 and R2. In this case, as described
above, portions of the reflective material layer 120 and the mask
layer 130 corresponding to the second region R2 have mean
thicknesses smaller than the mean thicknesses of the portions of
these layers corresponding to the first region R1,
respectively.
[0132] In general, the portion of the mask layer 130 having a
smaller mean thickness is prone to allow the reactive gas or liquid
to permeate as compared with the portion having a larger mean
thickness. In the case where the reactive gas or liquid reacts with
the second material, and the reaction product is readily removed
from the mask layer 130, the mask layer 130 can be opened only
above the second region R2.
[0133] Therefore, also in this case, by adjusting the concentration
and temperature of the etching liquid and the duration of the
etching treatment, etc., the optical device 10 shown in FIGS. 1 and
2 can be manufactured.
[0134] Alternatively, it is possible to employ the structure in
which both the reflective material layer 120 and the mask layer
have surface configurations that correspond to the surface
configurations of the first region R1 at the portions corresponding
to the first region R1 and partially open correspondingly to the
arrangement of the recesses or protrusions on the second region R2
at the portion corresponding to the second region R2. Also, in this
case, by adjusting the concentration and temperature of the etching
liquid and the duration of the etching treatment, etc., the optical
device 10 shown in FIGS. 1 and 2 can be manufactured.
[0135] In the above, described is the case where the portions of
the reflective material layer 120 and the mask layer 130
corresponding to the second region R2 are removed completely. The
removal may be performed such that parts of the portions remain.
For example, it is possible to shorten the duration of the etching
treatment so as to make the ratio of the amount of the first
material at the position of the second region 2 to the apparent
area of the second region R2 greater than zero and smaller than the
ratio of the amount of the first material at the position of the
first region R1 to the apparent area of the first region R1.
Alternatively, in a similar way, the ratio of the amount of the
second material at the position of the second region 2 to the
apparent area of the second region R2 may be made greater than zero
and smaller than the ratio of the amount of the second material at
the position of the first region R1 to the apparent area of the
first region R1.
[0136] Further, in the above, described is the case where each of
the reflective material layer 120 and the first layer 120' has a
single-layer structure. Each of the layers may have a multilayer
structure. By employing this structure, for example, the first
layer 120' of the optical device 10 may form a multilayer
interference film.
[0137] In this case, the first layer 120' includes, for example, a
multilayer film in which a miller layer, a spacer layer and a
half-mirror layer are stacked in this order from the side of the
relief structure formation layer 110.
[0138] The miller layer is a metal layer and typically includes an
elemental metal or an alloy. Examples of the metal included in the
miller layer include aluminum, gold, copper and silver. As the
metal, aluminum is in particular preferable. The thickness of the
miller layer is set, for example, at 300 nm or less, and typically
within a range of 20 to 200 nm.
[0139] The spacer layer typically includes a dielectric material.
Preferably, the refractive index of the dielectric material is 1.65
or less. Further, it is preferable that the dielectric material is
transparent. Examples of the dielectric material include SiO.sub.2
and MgF.sub.2. The thickness of the spacer layer is set within, for
example, a range of 5 to 500 nm.
[0140] The half-miller layer is a reflective layer having a
light-transmitting property and typically includes an elemental
metal, an alloy, a metallic oxide or a metallic sulfide. Examples
of the metal or alloy included in the half-miller layer include
aluminum, nickel, Inocel (registered trademark), titanium oxide
(TiO.sub.2), zinc sulfide (ZnS), molybdenum sulfide (MoS.sub.2) and
ferric oxide (III) (Fe.sub.2O.sub.3). The thickness of the
half-miller layer is set within, for example, a range of 5 to 80
nm. In the case where a metallic oxide such as titanium oxide or a
metallic sulfide such as zinc sulfide, which is a material with a
high transparency and a high refractive index, is used, the
thickness is preferably set within a range of 30 to 80 nm. In the
case where a metal such as aluminum, which is a material with a
high reflectance and a high light-shielding property, is used, the
thickness is preferably set within a range of 5 to 45 nm.
[0141] In the above, described is the case where each of the mask
layer 130 and the second layer 130' has a single-layer structure.
Each of the layers may have a multilayer structure. By employing
this structure, for example, the second layer 130' of the optical
device 10 may form a multilayer interference film.
[0142] Alternatively, the laminated structure of the first layer
120' and the second layer 130' may form a multilayer interference
film.
[0143] In these cases, when the method described with reference to
FIGS. 3 to 6 is employed, it is possible to stably form the
multilayer interference film with a high positional accuracy.
[0144] In the method described with reference to FIGS. 3 to 6, the
steps described with reference to FIGS. 4 and 6 may be repeated
after forming the first layer 120' and the second layer 130'. This
makes it possible to obtain a structure in which the first layer
120' and the second layer 130' are stacked alternately. Thus, it is
possible, for example, to form a multilayer interference film on
the first region R1. Also in this case, the multilayer interference
film can be formed stably with a high positional accuracy.
[0145] In the above, described is the case where an etching liquid
used as the reactive gas or liquid. The reactive gas or liquid is
not limited to this. For example, an etching gas that can vaporize
the material of the reflective material layer 120 may be used as
the reactive gas or liquid.
[0146] Alternatively, a gas or liquid that can react with the first
material to change a portion of the reflective material layer 120
into a layer made of a material different from the first material
may be used as the reactive gas or liquid. In this case, for
example, it is possible to change the portion of the reflective
material layer 120 corresponding to the second region R2 into a
layer made of a material different from the first material instead
of removing this portion.
[0147] As such a reactive gas or liquid, for example, an oxidizer
that can oxidize the first material can be used. Examples of the
oxidizer include oxygen, ozone, or halogen; halides such as
chlorine dioxide, hypohalous acid, subhalogen acid, perhalogen
acid, and salts thereof; inorganic peroxides such as hydrogen
peroxide, persulfates, peroxocarbonates, peroxosulfates, and
peroxophosphates; organic peroxides such as benzoyl peroxide,
t-butylhydroperoxide, cumene hydroperoxide, diisopropylbenzene
hydroperoxide, performic acid, peracetic acid, perbenzoic acid;
metals or metal compounds such as cerium salts, salts of Mn (III),
Mn (IV) and Mn (VI), silver salts, copper salts, chromium salts,
cobalt salts, dichromates, chromates, permanganates, magnesium
perphthalate, ferric chloride, and cupric chloride; or inorganic
acids or inorganic salts such as nitric acid, nitrates, bromates,
periodates, and iodates.
[0148] For example, in the case where Cu is used as the material of
the reflective material layer 120', when the portion of the
reflective material layer 120' corresponding to at least the second
region R2 is reacted with the oxidizer, the portion can be changed
into a layer made of Cu oxide. Alternatively, in the case where Al
is used as the material of the reflective material layer 120', when
the portion of the reflective material layer 120' corresponding to
at least the second region R2 is reacted with the oxidizer, the
portion can be changed into a layer made of Al oxide such as
boehmite.
[0149] Alternatively, a reducer that can reduce the material of the
reactive material layer 120' may be used as the above-described
reactive gas or liquid. As the reducer, for example, hydrogen
sulfide, sulfur dioxide, hydrogen fluoride, alcohols, carboxylic
acids, hydrogen gas, hydrogen plasma, remote hydrogen plasma,
diethylsilane, ethylsilane, dimethylsilane, phenylsilane, silane,
disilane, aminosilane, boranes, diborane, alane, germane,
hydrazine, ammonia, hydrazine, methylhydrazine,
1,1-dimethylhydrazine, 1,2-dimethyldhyrazine, t-butylhydrazine,
benzylhydrazine, 2-hydrazinoethanol, 1-n-butyl-1-phenylhydrazine,
phenylhydrazine, 1-naphthylhydrazine, 4-chlorophenylhydrazine,
1,1-diphenylhydrazine, p-hydrazinobenzenesulfonic acid,
1,2-diphenylhydrazine, acetylhydrazine, or benzoylhydrazine is
used.
[0150] In the method described with reference to FIGS. 3 to 6, the
second layer 130' may be removed after forming the first layer 120'
by etching treatment, etc. The removal of the second layer 130' is
effective, for example, in the case where ionization of the first
material due to the difference between the ionization tendencies of
the first and second materials is concerned.
[0151] FIG. 7 is a plan view schematically showing an optical
device according to a modified example. FIG. 8 is a sectional view
of the optical device taken along a line VIII-VIII shown in FIG. 7.
The optical device 10 shown in FIGS. 7 and 8 can be manufactured by
the same method as that described with reference to FIGS. 3 to 6
except that the structures of the regions R1 and R2 included in the
main surface of the relief structure formation layer 110 are
changed.
[0152] In the optical device 10 shown in FIGS. 7 and 8, the first
region R1 has a contour corresponding to micro-characters "TP".
[0153] The first region R1 includes a flat region FR constituted by
a flat surface and an uneven region UR provided with recesses or
protrusions. The uneven region UR is bordered with the flat region
FR. In FIG. 7, the portion of the optical device 10 corresponding
to the flat region FR is a display portion DPF, while the portion
of the optical device 10 corresponding to the uneven region UR is a
display portion DPU.
[0154] The width of the display portion DPF bordering the display
portion DPU falls within, for example, a range of 10 to 2,000
.mu.m, and typically a range of 50 to 1,000 .mu.m. In order to form
such a display portion DPF, the first layer 120' need to be formed
with an extremely high positional accuracy. Therefore, formation of
such an optical device 10 using a conventional patterning method is
impossible or very difficult.
[0155] On the other hand, when using the method described with
reference to FIGS. 3 to 6, the first layer 120' can be formed with
a high positional accuracy as described above. Therefore, when
using this method, even a fine image such as the above-described
micro-characters can be displayed with a high definition.
[0156] FIG. 9 is a plan view schematically showing an optical
device according to another modified example. FIG. 10 is a
sectional view of the optical device taken along a line X-X shown
in FIG. 9. In FIG. 9, the portion of the optical device
corresponding to the first sub-region SR1, which will be described
later, is a display portion DSP1, while the portion of the optical
device corresponding to the second sub-region SR1 is a display
portion DSP2.
[0157] The optical device 10 shown in FIGS. 9 and 10 has the same
structure as that of the optical device shown in FIGS. 1 and 2
except for the followings.
[0158] That is, in the optical device 10 shown in FIGS. 9 and 10,
the first region R1 includes a first sub-region SR1 and a second
sub-region SR2. The first sub-region SR1 is adjacent to the second
region R2 and extends along the boundary between the regions R1 and
R2. The second sub-region SR2 is adjacent to the second region R2
with the first sub-region SR1 interposed therebetween. The contour
of the second sub-region SR2 typically has a shape similar to the
contour of the first region R1.
[0159] The first layer 120' is provided only at the position
corresponding to the second sub-region SR2. That is, only the
second sub-region SR2 of the regions R1 and R2 is covered with the
first layer 120'. Further, the portion of the first layer 120'
corresponding to the second sub-region SR2 has a surface
configuration that corresponds to the surface configuration of the
second sub-region SR2.
[0160] The mean thickness of the portion of the first layer 120'
corresponding to the second sub-region SR2 falls within, for
example, a range of 5 to 500 nm, and typically a range of 5 to 300
nm. When the mean thickness is excessively small, there is a
possibility that the reflection by the interface between the relief
structure formation layer 110 and the first layer 120' is less
prone to occur. When the mean thickness is excessively large, there
is a possibility that the producibility of the optical device 10 is
degraded.
[0161] Typically, the second layer 130' faces the entire surface of
the first region R1. That is, the second layer 130' typically
includes a first portion P1 covering the first layer 120' and a
second portion P2 outwardly protruding from the first portion P1.
Typically, a first orthogonal projection of the contour of the
first layer 120' on the main surface of the relief structure
formation layer 110 has a shape similar to a second orthogonal
projection of a contour of the vapor-deposited layer on the main
surface and is surrounded by the second orthogonal projection.
[0162] Therefore, for example, in the case where the second
material is colored, it is possible to display different colors at
the portion DSR1 of the optical device 10 corresponding to the
first sub-region SR1 and the portion DSR2 of the optical device 10
corresponding to the second sub-region SR2. The difference between
the colors can be perceived, for example, by the observation of the
optical device 10 using a microscope. Alternatively, in the case
where the area occupied by the first sub-region SR1 is large, the
difference between the colors can be perceived with unaided eyes.
As above, the optical device 10 described with reference to FIGS. 9
and 10 can achieve a special optical effect.
[0163] The mean thickness of the portion of the second layer 130'
corresponding to the second sub-region SR2 falls within, for
example, a range of 0.3 to 200 nm, and typically a range of 3 to 80
nm.
[0164] The optical device 10 shown in FIGS. 9 and 10 is
manufactured by, for example, the following method. That is, by
adjusting the concentration and temperature of the etching liquid
and the duration of the etching treatment, a side-etching is caused
at a portion of the reflective material layer 120 corresponding to
the first region R1 after the steps described with reference to
FIGS. 3 to 5. This removes the portion of the reflective material
layer 120 corresponding to the first sub-region SR1 together with
the portions of the reflective material layer 120 and the mask
layer 130 corresponding to the second region R2. Thus, the optical
device 10 shown in FIGS. 9 and 10 is obtained.
[0165] The above-described side-etching starts at the contour of
the portion of the reflective material layer 120 corresponding to
the first region R1 and progresses toward the inside at a
substantially constant rate. Thus, the variations of the width of
the portion removed by this side-etching, i.e., the variations of
the distance from the contour of the first sub-region SR1 to the
contour of the first region is relatively small. Thus, the contour
of the second sub-region SR2 typically has a shape similar to the
contour of the first region R1. Therefore, even in the case of
employing such a method, the first layer 120' can be formed with a
high positional accuracy.
[0166] Since the portion of the reflective material layer 120
corresponding to the first region R1 is covered with the mask layer
130, no etching or almost no etching occurs at the main surface
under the condition that the side-etching occurs at the side
surface. Therefore, even in the case of employing such a method,
the first layer 120' can be formed stably.
[0167] In the above, described is the structure in which the first
orthogonal projection of the contour of the first layer 120' on the
relief structure formation layer 110 has a shape similar to the
second orthogonal projection of the contour of the vapor-deposited
layer on the main surface and is surrounded by the second
orthogonal projection. The structures of the first layer 120' and
the second layer 130' are not limited to this. For example, in the
case where the structure after the etching treatment is cut across
the first region R1, a part of the first orthogonal projection
overlaps a part of the second orthogonal projection, while the
remainder of the first orthogonal projection has a shape similar to
the remainder of the second projection and is surrounded by the
second projection.
[0168] FIG. 11 is a plan view schematically showing an optical
device according to another embodiment of the present invention.
FIG. 12 is a sectional view of the optical device taken along a
line XII-XII shown in FIG. 11. FIGS. 13 to 17 are sectional views
schematically showing a method of manufacturing the optical device
shown in FIGS. 11 and 12. Note that in FIG. 11, the portion of the
optical device 10 corresponding to the third region R3, which will
be described later, is indicated as a display portion DP3.
[0169] A method of manufacturing the optical device 10 shown in
FIGS. 11 and 12 will be described below with reference to FIGS. 13
to 17.
[0170] First, prepared is a relief structure formation layer 110
having a main surface that includes a first region R1, a second
region R2 and a third region R3 as shown in FIG. 13. The relief
structure formation layer 110 has the same structure as that of the
relies structure formation layer described with reference to FIG. 3
except that this relief structure formation layer 110 further
includes the third region R3.
[0171] The third region R3 is provided with recesses or
protrusions. The third region R3 has a ratio of the specific
surface area to the apparent area greater than that of the first
region R1. Typically, the third region R3 has the same structure as
that of the second region R2.
[0172] Next, a first material is vapor-deposited on the regions R1
to R3 as shown in FIG. 14. This obtains a reflective material layer
120. Formation of the reflective material layer 120 is performed by
the same method as that described with reference to FIG. 4. In the
example shown in FIG. 14, the portion of the reflective material
layer 120 corresponding to the first region R1 forms a continuous
film having a surface configuration that corresponds to the grooves
on the first region R1. The portions of the reflective material
layer 120 corresponding to the regions R2 and R3 form discontinuous
films that partially open correspondingly to the arrangements of
the groove on the regions R2 and R3.
[0173] Subsequently, formed is a cover layer 140 that faces only
the third region R3 of the regions R2 and R3. The cover layer 140
may further face at least a portion of the first region R1. FIG. 16
shows the case where the cover layer 140 faces the entire third
region R3 and a part of the first region R1.
[0174] Formation of the cover layer 140 can be performed using a
known pattern formation method. As the pattern formation method,
for example, flexographic printing, gravure printing, inkjet
printing, offset printing or security intaglio printing is used. As
the material of the cover layer 140, for example, the
above-described thermoplastic resin, thermosetting resin or
radiation-curing resin is used. Alternatively, as the material of
the cover layer 140, a high-temperature resin such as
polycarbonate, polyamide and polyimide, a mixture thereof or a
copolymer thereof may be used. In order use the material as paint
for printing, the resin may be dissolved in a solvent such as water
or organic solvent and added with dye, pigment, leveling agent,
antifoaming agent, anti-sagging agent, adhesion promoter, coating
surface-modifying agent, plasticizer, nitrogen-containing compound,
crosslinking agent such as epoxy resin or a combination thereof, if
necessary.
[0175] Then, the mask layer 130 and the cover layer 140 are exposed
to a reactive gas or liquid that can react with the material of the
reflective material layer 120. This allows the material of the
reflective material layer 120 to cause the reaction with the
material of the reflective material layer 120 at least at a
position of the second region R2. Here, described is the case where
an etching liquid capable of dissolving the material of the
reflective material layer 120 is used as an example of the reactive
gas or liquid.
[0176] As shown in FIG. 16, the portion of the mask layer 130
corresponding to the first region R1 forms a continuous film, while
the portion corresponding to the second region R2 forms a
discontinuous film that opens partially. Thus, the portion of the
mask layer 130 corresponding to the second region R2 is easily
etched than the portion corresponding to the first region R1.
[0177] As shown in FIG. 16, the cover layer 140 is formed on the
portion of the mask layer 130 corresponding to the third region R3.
On the other hand, the cover layer 140 is not formed on the portion
of the mask layer 130 corresponding to the second region R2. Thus,
the portion of the mask layer 130 corresponding to the second
region R2 is easily etched than the portion corresponding to the
third region R3.
[0178] Therefore, by adjusting the concentration and temperature of
the etching liquid and the duration of etching, etc., only the
portion of the reflective material layer 120 that corresponds to
the second region R2 can be removed as shown in FIG. 17. Note that
when the portion of the reflective layer 120 corresponding to the
second region R2 is removed, the portion of the mask layer 130
corresponding to the second region R2 is also removed.
[0179] The optical device 10 shown in FIGS. 11 and 12 is thus
obtained.
[0180] The optical device 10 includes the relief structure
formation layer 110, the first layer 120', the second layer 130'
and the cover layer 140. In the optical device 10, the first layer
120' is also present on the region other than the first region R1,
i.e., the third region R3. Therefore, for example, when the third
region R3 is provided with recesses or protrusions that offers an
optical effect of hologram, diffraction grating, sub-wavelength
grating, zero-order diffraction filter, polarized light separation
filter, etc., an optical device 10 offering a further special
visual effect can be obtained.
[0181] The optical device 10 may further include a protective film.
The optical device 10 may have antireflection treatment on the
surface thereof. In the manufacture of the optical device 10, at
least one surface of the layers included in the optical device 10
may be subjected to corona treatment, flame treatment or plasma
treatment.
[0182] Two or more of the embodiments and modifications described
above may be combined with each other.
[0183] The above-described techniques may be combined with a known
process for partially forming a reflective layer. As the known
process, for example, used is a laser method in which a part of a
reflective is removed using a laser to form a pattern.
Alternatively, as this process, it is possible to use a method in
which forming a patterned mask on a reflective layer and removing
the portion of the mask not covered by the mask. Alternatively, as
this process, it is possible to use a method in which a patterned
mask is formed on a main surface of a layer or substrate, forming a
reflective layer on the entire main surface, and then the portion
of the reflective layer on the mask is removed together with the
mask. Note that formation of the mask is performed, for example,
using printing method or photoresist method.
[0184] The optical device 10 may be uses as a part of an adhesive
label. The adhesive label includes the optical device 10 and an
adhesive layer provided on the back surface of the optical device
10.
[0185] Alternatively, the optical layer 10 may be used as a part of
a transfer foil. The transfer foil includes the optical device 10
and a support layer releasably supporting the optical device
10.
[0186] The optical device 10 may be supported by an article. For
example, the optical device 10 may be supported by a plastic card,
etc. Alternatively, the optical device 10 may be embedded in a
paper. The optical device 10 may be broken into flakes and used as
a component of pigment.
[0187] The optical device 10 may be used for purposes other than
forgery prevention. For example, the optical device can be used as
a toy, educational material, or decoration.
EXAMPLES
Relationship Between Presence or Absence of Mask Layer and Etching
Rate
[0188] Studied first was a relationship between the presence or
absence of the mask layer 130 and the etching rate of the portions
of the reflective material layer 120 corresponding to the regions
R1 and R2.
[0189] (Manufacture of Laminated Body LB1)
[0190] A laminated body of the relief structure formation layer
110, the reflective material layer 120 and the mask layer 130 was
manufactured by the following method.
[0191] First, a composition containing 50.0 parts by mass of
urethane (meta)acrylate, 30.0 parts by mass of methyl ethyl ketone,
20.0 parts by mass of ethyl acetate and 1.5 parts by mass of
photoinitiator was prepared as the material of an
ultraviolet-curing resin. As the urethane (meta)acrylate, used was
a multi-functional substance having a molecular weight of 6,000. As
the photoinitiator, "Irgacure 184" manufactured by CIBA SPECIALTY
CORP. was used.
[0192] Next, the above-described composition was applied to a
transparent PET film with a thickness of 23 .mu.m by gravure
printing such that the coated film thus obtained had a thickness of
1 .mu.m in a dried state.
[0193] Then, an original plate provided with protrusions was fixed
on a cylindrical surface of a printing cylinder, and the coated
film was irradiated with ultraviolet ray from the PET film's side
while pressing the original plate against the coated film so as to
cure the ultraviolet-curing resin. Here, the pressing was performed
under the conditions that the pressure was 2 kgf/cm.sup.2, the
temperature was 80.degree. C., and the speed was 10 m/minute. The
ultraviolet irradiation was performed using a high-pressure
mercury-vapor lamp at an intensity of 300 mJ/cm.sup.2.
[0194] Thus, obtained was the relief structure 110 having a main
surface including the regions R1 and R2.
[0195] The relief structure formation layer 110 had grooves
arranged regularly on the entire first region R1. The cross
sections of the grooves were V-shaped. The pitch of the grooves was
1,000 nm. The width of the opening of each groove was 1,000 nm,
while the depth of each groove was 100 nm. That is, on the first
region R1, formed were grooves each having a ratio of the depth to
the width of the opening of the groove of 100 nm/1,000 nm=0.1.
[0196] The relief structure formation layer 110 further had
recesses arranged in a square lattice on the entire second region
R2. The recesses were pyramidal. The minimum center-to-center
distance of the recesses was 333 nm. The width of the opening of
each recess was 333 nm, while the depth thereof was 333 nm. That
is, on the second region R2, formed were recesses each having a
ratio of the depth to the width of the opening of the groove of 333
nm/333 nm=1.0.
[0197] Subsequently, Al as the first material was deposited on the
above-described main surface of the relief structure formation
layer by vacuum evaporation. Thus, the reflective material layer
120 was formed. Here, the target thickness of the reflective
material layer 120 was set at 50 nm.
[0198] Then, MgF.sub.2 as the second material was deposited on the
main surface of the reflective material layer 120 opposite to the
relief structure formation layer 110 by vacuum evaporation. Thus,
the mask layer 130 was formed. Here, the target thickness of
MgF.sub.2 was set at 20 nm.
[0199] As above, the laminated body including the relief structure
formation layer 110, the reflective material layer 120 and the mask
layer 130 was obtained. Hereinafter, the laminated body thus
manufactured is referred to as a "laminated body LB1".
[0200] (Manufacture of Laminated Body LB2; Comparative Example)
[0201] A laminated body of the relief structure formation layer 110
and the reflective material layer 120 was manufactured by the
method as that described for the laminated body LB1 except that
formation of the mask layer 130 was omitted. Hereinafter, the
laminated body is referred to as a "laminated body LB2".
[0202] (Evaluation)
[0203] The laminated bodies LB1 and LB2 were subjected to an
etching treatment using aqueous sodium hydroxide. Here, the
temperature of the aqueous sodium hydroxide was changed, and the
following evaluation was performed in each case. That is, measured
were the time T1 for the transmittance of the portion of the
laminated body corresponding to the first region R1 to reach 20%
and the time T2 for the transmittance of the portion of the
laminated body corresponding to the second region R2 to reach 80%.
FIG. 18 shows the results. Note that the concentration of the
aqueous sodium hydroxide was 0.1 mol/L, and the temperatures of the
solution were 60.degree. C., 50.degree. C., 40.degree. C.,
30.degree. C. and 25.degree. C. in decreasing order of
temperature.
[0204] FIG. 18 is a graph showing an example of a relationship
between presence or absence of the mask layer and the etching rate.
FIG. 18 shows the measurement results of the time T1 and T2 for
each of the laminated bodies LB1 and LB2 and a linear line
represented by a formula: T1=T2. Note that the data on each curve
are arranged in decreasing order of temperature of the aqueous
sodium hydroxide toward in a direction away from the origin.
[0205] According to the measurements, the greater the value of T1
is, the smaller the etching rate at the portion of the reflective
material layer 120 corresponding to the second region RG2. Thus,
The greater the value of the ratio T1/T2 is, the higher the etching
selectivity.
[0206] As shown in FIG. 18, for the laminated body LB2, the ratio
T1/T2 was almost equal to 1 in the case where the temperature of
the aqueous sodium hydroxide was high. That is, in this temperature
range, the etching selectivity was low. In the case where the
temperature of the aqueous sodium hydroxide was low, when the
temperature was lowered, the ratio T1/T2 gradually increased. That
is, in this temperature range, the etching selectivity was improved
by lowering the temperature of the aqueous sodium hydroxide.
Therefore, in the case of using the laminated body LB2, it is
necessary to set the temperature of the aqueous sodium hydroxide
low in order to manufacture the optical devices with a high
stability. In this case, however, the time for the etching
treatment should be prolonged inadmissibly. Therefore, in this
case, it is impossible or very difficult to simultaneously achieve
the producibility and stability in the manufacture of the optical
devices.
[0207] On the other hand, for the laminated body LB1, the ratio
T1/T2 was high regardless of the temperature of the aqueous sodium
hydroxide. That is, the laminated body LB1 achieved a high etching
selectivity regardless of the temperature of the aqueous sodium
hydroxide. Therefore, in the case of using the laminated body LB1,
the optical devices can be stably manufactured with a short etching
time. That is, in this case, it is possible to simultaneously
achieve the producibility and stability in the manufacture of the
optical devices.
[0208] <Evaluations of Selectivity for Removal of Reflective
Material Layer and Positional Accuracy of Reflective Layer>
[0209] First, the optical devices OD1 to OD9 were manufactured as
follows.
Example 1
Manufacture of Optical Device OD1
[0210] The above-described laminated body LB1 was subjected to an
etching treatment. Specifically, the laminated body LB1 was exposed
to 0.1 mol/L aqueous sodium hydroxide at 60.degree. C. for 7
seconds. Thus, the portions of the reflective material layer 120
and the mask layer 130 corresponding to the second region R2 were
removed.
[0211] As above, the optical device 10 was manufactured.
Hereinafter, the optical device 10 is referred to as an "optical
device OD1". The optical device OD1 had a laminated structure
including the relief structure formation layer 110, the first layer
120' covering only the entire first region R1 of the regions R1 and
R2, and the second layer 130' covering the entire first layer
120'.
[0212] In the optical device OD1, the mean thickness of the first
layer 120' was 50 nm. The mean diameter of the second layer 130'
was 20 nm.
Example 2
Manufacture of Optical Device OD2
[0213] An optical device was manufactured by the same method as
that for the optical device OD1 except that the minimum
center-to-center distance of the recesses on the second region R2
was set at 200 nm, and the width of the opening and the depth of
each recess were set at 200 nm and 160 nm, respectively.
Hereinafter, the optical device is referred to as an "optical
device OD2".
[0214] In the optical device OD2, a ratio of the depth to the width
of the opening of each groove on the first region R1 was 100
nm/1,000 nm=0.1. A ratio of the depth to the width of the opening
of each groove on the second region R2 was 160 nm/200 nm=0.8.
[0215] In the optical device OD2, the mean thickness of the first
layer 120' was 50 nm. The mean diameter of the second layer 130'
was 20 nm.
Example 3
Manufacture of Optical Device OD3
[0216] An optical device was manufactured by the same method as
that for the optical device OD1 except that the pitch of the
grooves on the first region R1 was set at 300 nm, the width of the
opening and the depth of each groove were set at 300 nm and 100 nm,
respectively, the minimum center-to-center distance of the recesses
on the second region R2 was set at 375 nm, and the width of the
opening and the depth of each recess were set at 375 nm and 300 nm,
respectively. Hereinafter, the optical device is referred to as an
"optical device OD3".
[0217] In the optical device OD3, a ratio of the depth to the width
of the opening of each groove on the first region R1 was 100 nm/300
nm=0.33. A ratio of the depth to the width of the opening of each
groove on the second region R2 was 300 nm/375 nm=0.8.
[0218] In the optical device OD3, the mean thickness of the first
layer 120' was 50 nm. The mean diameter of the second layer 130'
was 20 nm.
Example 4
Manufacture of Optical Device OD4
[0219] An optical device was manufactured by the same method as
that for the optical device OD3 except that the minimum
center-to-center distance of the recesses on the second region R2
was set at 300 nm, and the width of the opening and the depth of
each recess were set at 300 nm and 300 nm, respectively.
Hereinafter, the optical device is referred to as an "optical
device OD4".
[0220] In the optical device OD4, a ratio of the depth to the width
of the opening of each groove on the first region R1 was 100 nm/300
nm=0.33. A ratio of the depth to the width of the opening of each
groove on the second region R2 was 300 nm/300 nm=1.0.
[0221] In the optical device OD4, the mean thickness of the first
layer 120' was 50 nm. The mean diameter of the second layer 130'
was 20 nm.
Example 5
Manufacture of Optical Device OD5
[0222] First, the relief structure formation layer 110 whose main
surface included the third region R3 in addition to the regions R1
and R2 was formed by the same method as that described for the
laminated body LB1. In the regions R1 and R2 of the relief
structure formation layer 110, the same structures as those of the
laminated body LB1 were employed. In the third region R3, the same
structure as that in the second region R2 was employed.
[0223] Next, the reflective material layer 120 and the mask layer
130 were formed by the same method as that described for the
laminated body LB1.
[0224] Then, using gravure printing, the cover layer 140 was formed
to face only the entire third region R3 and a part of the first
region R1 of the regions R1 to R3.
[0225] Subsequently, an etching treatment was performed by the same
method as that described for the optical device OD1. Thus, only the
portions of the reflective material layer 120 and the mask layer
130 corresponding to the second region R2 were removed to form the
reflective layer 120 and the vapor-deposited layer 130.
Hereinafter, the optical device thus obtained is referred to as an
"optical device OD5".
[0226] In the optical device OD5, a ratio of the depth to the width
of the opening of each groove on the first region R1 was 100
nm/1,000 nm=0.1. A ratio of the depth to the width of the opening
of each groove on the second region R2 was 333 nm/333 nm=1.0.
[0227] In the optical device OD5, the mean thickness of the first
layer 120' was 50 nm. The mean diameter of the second layer 130'
was 20 nm.
Example 6
Manufacture of Optical Device OD6; Comparative Example
[0228] An optical device was manufactured by the same method as
that described for the optical device OD1 except that the laminated
body LB2 was used instead of the laminated body LB1 and was exposed
to 0.1 mol/L aqueous sodium hydroxide at 30.degree. C. for 60
seconds instead of exposing it to 0.1 mol/L aqueous sodium
hydroxide at 60.degree. C. for 7 seconds. Hereinafter, the optical
device is referred to as an "optical device OD6".
Example 7
Manufacture of Optical Device OD7; Comparative Example
[0229] An optical device was manufactured by the same method as
that described for the optical device OD6 except that the target
thickness of the reflective material layer 120 was set at 20 nm.
Hereinafter, the optical device is referred to as an "optical
device OD7".
Example 8
Manufacture of Optical Device OD8; Comparative Example
[0230] An optical device was manufactured by the same method as
that described for the optical device OD6 except that the target
thickness of the reflective material layer 120 was set at 80 nm.
Hereinafter, the optical device is referred to as an "optical
device OD8".
Example 9
Manufacture of Optical Device OD9; Comparative Example
[0231] In this example, an optical device was manufactured by the
same method as that described for the optical device OD1 except
that the mask layer 130 was formed as follows.
[0232] That is, in this example, the mask layer 130 was formed
using gravure printing instead of forming it on the entire
reflective material layer 120 by vapor deposition. Specifically,
prepared first was a composition containing 50.0 parts by mass of
vinyl chloride-vinyl acetate copolymer resin, 30.0 parts by mass of
methyl ethyl ketone, and 20.0 parts by mass of ethyl acetate. Then,
the composition was gravure-printed on the pattern formed by the
portion of the reflective material layer 120 corresponding to the
first region R1. This printing was performed such that the mask
layer 130 had a mean thickness of 1.0 .mu.m. Hereinafter, the
optical device is referred to as an "optical device OD9".
[0233] (Evaluation)
[0234] The selectivity for removal of the reflective material layer
120 was evaluated on each of the optical devices OD1 to OD9.
Specifically, for each of the optical devices OD1 to OD9, the
transmittances for visible light were measured at portions
corresponding to the regions R1 and R2. The optical devices were
evaluated as "OK" in the case where the transmittance for visible
light at the portion corresponding to the first region R1 was 20%
or less and the transmittance for visible light at the portion
corresponding to the second region R2 was 90% or more. The other
optical devices were evaluated as "NG". The results are summarized
in TABLE 1 below.
TABLE-US-00001 TABLE 1 Target thickness Selectivity Posi- of Target
for tional Aspect Aspect reflective thickness removal of accuracy
ratio in ratio in material of mask reflective of Optical 1st 2nd
layer layer material reflective device region region (nm) (nm)
layer layer OD1 0.1 1.0 50 20 OK OK OD2 0.1 0.8 50 20 OK OK OD3
0.33 0.8 50 20 OK OK OD4 0.33 1.0 50 20 OK OK OD5 0.1 1.0 50 20 OK
OK OD6 0.1 1.0 50 0 NG OK OD7 0.1 1.0 20 0 NG OK OD8 0.1 1.0 80 0
NG OK OD9 0.1 1.0 50 1,000 OK NG
[0235] In TABLE 1, the "aspect ratio" means a mean value of the
ratios of the depths to the widths of the openings of the
grooves.
[0236] As shown in TABLE 1, in the optical devices OD6 to OD8, the
selectivity for removal of the reflective material layer 120 was
insufficient. That is, in the optical devices OD6 to OD8, the
transmittance for visible light at the portion corresponding to the
first region R1 was greater than 20% or the transmittance for
visible light at the portion corresponding to the second region R2
was less than 90%. On the other hand, in the optical devices OD1 to
OD5 and OD9, the selectivity for removal of the reflective material
layer 120 was high.
[0237] Next, the positional accuracy of the reflective layer 120
was evaluated on each of the optical devices OD1 to OD9.
Specifically, for each optical device, the maximum value of the
shortest distances from the boundary between the regions R1 and R2
to the contour of the first layer 120' was measured. The optical
devices were evaluated as "OK" in the case where this value was
less than 20 .mu.m, while the optical devices were evaluated as
"NG" in the case where this value was 20 .mu.m or more. The results
are summarized in TABLE 1.
[0238] As shown in TABLE 1, in the optical device OD9, the
positional accuracy of the reflective layer 120 was insufficient.
That is, in the optical device OD9, the maximum value of the
shortest distances from the boundary between the regions R1 and R2
to the contour of the first layer 120' was 20 .mu.m or more. On the
other hand, in the optical devices OD1 to OD8, the positional
accuracy of the reflective layer 120 was high.
[0239] As above, the optical devices OD1 to OD5 were excellent in
both the selectivity for removal of the reflective material layer
120 and the positional accuracy of the first layer 120'.
[0240] Additional advantages and modifications will readily occur
to those skilled in the art. Therefore, the invention in its
broader aspects is not limited to the specific details and
representative embodiments shown and described herein. Accordingly,
various modifications may be made without departing from the spirit
or scope of the general inventive concept as defined by the
appended claims and their equivalents.
REFERENCE TO SYMBOLS
[0241] 10 . . . Optical device [0242] 110 . . . Relief structure
formation layer [0243] 120 . . . Reflective material layer [0244]
120' . . . First layer [0245] 130 . . . Mask layer [0246] 130' . .
. Second layer [0247] 140 . . . Cover layer [0248] DP1 . . .
Display portion [0249] DP2 . . . Display portion [0250] DP3 . . .
Display portion [0251] DPF . . . Display portion [0252] DPU . . .
Display portion [0253] DSP1 . . . Display portion [0254] DSP2 . . .
Display portion [0255] P1 . . . First portion [0256] P2 . . .
Second portion [0257] R1 . . . First region [0258] R2 . . . Second
region [0259] R3 . . . Third region [0260] SR1 . . . First
sub-region [0261] SR2 . . . Second sub-region
* * * * *