U.S. patent application number 12/792170 was filed with the patent office on 2010-09-23 for image display body and image formation method.
This patent application is currently assigned to DAI NIPPON PRINTING CO., LTD.. Invention is credited to Hiroshi FUNADA.
Application Number | 20100238553 12/792170 |
Document ID | / |
Family ID | 36991606 |
Filed Date | 2010-09-23 |
United States Patent
Application |
20100238553 |
Kind Code |
A1 |
FUNADA; Hiroshi |
September 23, 2010 |
IMAGE DISPLAY BODY AND IMAGE FORMATION METHOD
Abstract
An image display body in which a decorative effect is obtained
more effectively by an optical diffraction structure. In an image
display body, an optical diffraction structure portion constituted
by the optical diffraction structure in a halftone dot state is
provided in a colored region on a base material. In the image
display body, a dot area percent of a halftone dot a constituting
the optical diffraction structure portion to the colored region
ranges from 15% to 60%, an area of each halftone dot is smaller
than 0.25 mm.sup.2. The halftone dots are diffused by an error
diffusion method.
Inventors: |
FUNADA; Hiroshi; (Tokyo-to,
JP) |
Correspondence
Address: |
LADAS & PARRY LLP
224 SOUTH MICHIGAN AVENUE, SUITE 1600
CHICAGO
IL
60604
US
|
Assignee: |
DAI NIPPON PRINTING CO.,
LTD.
Tokyo-to
JP
|
Family ID: |
36991606 |
Appl. No.: |
12/792170 |
Filed: |
June 2, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11908520 |
Sep 13, 2007 |
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PCT/JP2006/304882 |
Mar 13, 2006 |
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12792170 |
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Current U.S.
Class: |
359/558 ;
156/230 |
Current CPC
Class: |
B44C 1/1704 20130101;
G02B 5/1842 20130101; B44F 1/08 20130101 |
Class at
Publication: |
359/558 ;
156/230 |
International
Class: |
G02B 27/42 20060101
G02B027/42; B32B 37/14 20060101 B32B037/14 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 14, 2005 |
JP |
2005-070567 |
Mar 14, 2005 |
JP |
2005-070993 |
Claims
1. An image display body in which an optical diffraction structure
portion constituted by optical diffraction structure in a halftone
dot state is formed on an image on a base material, wherein, each
of a plurality of halftone dots constituting the optical
diffraction structure portion is formed such that each of the
halftone dots is enclosed in each of same size square regions a
side of which is 400 .mu.m or less, and when each of the halftone
dots is enclosed in each of the square regions, the plurality of
square regions are arranged at equal intervals in a diagonal
direction, and in the diagonal direction a distance between a
corner of one of adjacent square regions and a corner of another of
the adjacent square regions is 220 .mu.m or less.
2. The image display body according to claim 1, wherein a dot area
percent of the optical diffraction structure portion is 40% or
less.
3. The image display body according to claim 1, wherein a length of
one side of the square region ranges from 100 .mu.m to 200
.mu.m.
4. The image display body according to claim 1, wherein a distance
between the adjacent square regions ranges from 50 .mu.m to 150
.mu.m.
5. An image formation method in which an optical diffraction
structure portion constituted by optical diffraction structure is
formed in a halftone dot state on a predetermined image by using a
transfer sheet where the optical diffraction structure is laminated
on a base material sheet thereof, wherein each of a plurality of
halftone dots constituting the optical diffraction structure
portion is formed such that each the plurality of halftone dots is
enclosed in each of same size square regions a side of which is 400
.mu.m or less, and when each of the halftone dots is enclosed in
each of the square regions, the plurality of square regions are
arranged at equal intervals in a diagonal direction, and in the
diagonal direction a distance between a corner of one of adjacent
square regions and a corner of another of the adjacent square
regions is 220 .mu.m or less.
Description
TECHNICAL FIELD
[0001] The present invention relates to an image display body in
which an optical diffraction structure is formed in a halftone dot
sate and an image information method for the image display
body.
BACKGROUND ART
[0002] A transfer foil having an optical diffraction structure
forming layer is utilized for the purposes of improving design
performance and security performance. The optical diffraction
structure having a fine concavo-convex relief structure such as a
hologram and a diffraction grating is formed in the optical
diffraction structure forming layer. There is a known method of
coloring the optical diffraction structure in order to improve the
design performance and the security performance. For example, there
is a known colored layer transfer material having a fine relief
structure and a reflecting layer made of a metal colored a unique
color (For example, see Patent Documents 1 and 2), as a colored
layer transfer material to obtain an effect of looking like a
colored optical diffraction structure (hereinafter sometimes
referred to as "colored hologram"). The inventor also discloses a
layer configuration, in which the optical diffraction structure
forming layer and the reflecting layer are laminated and a colored
layer is added to an observation side to the reflecting layer in
order to obtain the effect of looking like the colored hologram
(For example, see Patent Documents 3 and 4).
[0003] There is a known colored layer transfer material having the
colored layer and the metal layer (the reflecting layer) and
sensuously looking like, for example, gold (For example, see Patent
Documents 5 to 7), as the colored layer transfer material which can
be transferred onto a transfer body to obtain a colored-metal
glossy color. However, in the above colored layer transfer
materials, because the fine concavo-convex relief structure such as
a hologram and a diffraction grating which exerts the optical
diffraction effect is not provided, the particular design or the
optical effect cannot be obtained.
[0004] On the other hand, there is also a known method of forming
an optical diffraction structure portion having optical diffraction
structure in a halftone dot sate to add a decorative effect by
diffracted light to an image, by transferring the optical
diffraction structure in a halftone dot state onto a base material
having a predetermined image (For example, see Patent Documents 8
to 10).
[0005] Patent Document 1: Japanese Patent Laid-Open No.
09-160475
[0006] Patent Document 2: Japanese Patent Laid-Open No.
08-328456
[0007] Patent Document 3: Japanese Patent Laid-Open No.
61-238079
[0008] Patent Document 4: Japanese Patent Laid-Open No.
62-17784
[0009] Patent Document 5: Japanese Patent Laid-Open No.
63-30288
[0010] Patent Document 6: Japanese Patent Laid-Open No.
63-230389
[0011] Patent Document 7: Japanese Patent Laid-Open No.
09-11638
[0012] Patent Document 8: Japanese Patent Laid-Open No.
08-123299
[0013] Patent Document 9: Japanese Patent Laid-Open N 11-227368
[0014] Patent Document 10: Japanese Patent Laid-Open No.
2004-101834
DISCLOSURE OF THE INVENTION
Problems to be Solved by the Invention
[0015] However, in the method of configuring the reflecting layer
by using the metal colored the unique color, due to the use of an
alloy having its unique color, it is very difficult that continuous
deposition is performed while a desired compound ratio of the alloy
is stably kept. It takes a lot of time to provide an exchange a
predetermined alloy material during the deposition, that could
cause a risk of contamination (pollution with the material used
before and after) is generated, and thereby the method of forming
the reflecting layer with the metal colored the intrinsic color has
a cost disadvantage.
[0016] In the method of adding and providing the colored layer,
basically the colored layer transfer material has a single color,
and it is impossible to color the optical diffraction structure
plural desired colors. For example, it is difficult to color plural
portions of the optical diffraction structure different colors such
as gold, a sapphire tone, an emerald tone, and a ruby tone.
Accordingly, there is no colored layer transfer material having a
low cost, good productivity, good storage stability of a color
tone, and the optical diffraction effect by the optical diffraction
structure.
[0017] Additionally, in the conventional method of transferring the
optical diffraction structure in the halftone dot state, a visual
synergic effect obtained by the diffracted light of the optical
diffraction structure portion and the color of a region located
below the optical diffraction structure portion is hardly
considered. Accordingly, it sometimes happens that almost of the
colored region is covered with the transferred optical diffraction
structure.
[0018] Even if the case where the above synergic effect is
considered, in the conventional transfer method, brightness by the
diffracted light of the optical diffraction structure portion
frequently becomes unnatural, and the synergic effect is not
sufficiently exerted.
[0019] In view of the foregoing, an object of the invention is to
provide an image display body in which the optical diffraction
structure appears to be colored a desired color and whereby the
decoration effect is obtained more effectively, and an image
formation method for the image display body. Another object of the
invention is to provide an image display body in which the
decoration effect is provided more effectively in the image by the
optical diffraction structure and an image formation method for the
image display body.
Means for Solving the Problems
[0020] A first image display body of the present invention solves
the above problems as an image display body in which an optical
diffraction structure portion constituted by optical diffraction
structure in a halftone dot state is provided in a colored region
on a base material, wherein a dot area percent of the halftone dots
constituting the optical diffraction structure portion to the
colored region ranges from 15% to 60%, an area of each halftone dot
is smaller than 0.25 mm.sup.2, and the halftone dots are diffused
to be provided by an error diffusion method.
[0021] The inventor has discovered that natural brightness based on
diffracted light can be given evenly to the colored region by
providing the halftone dots constituting the optical diffraction
structure portion on the colored region in the state where the
halftone dots are diffused by an error diffusion method under
conditions of the above dot area and the above dot area percent. By
the present invention, as the brightness can be given evenly to the
colored region, the colored region where the optical diffraction
structure portion of the present invention is formed can be used
such as a colored optical diffraction structure.
[0022] In the present invention, the optical diffraction structure
includes a diffraction grating having a constant concavo-convex
pattern and a hologram where a fringe pattern generating a
predetermined hologram image is formed. It doesn't matter which
error diffusion method is employed to the present invention, such
as a random dithering method, Floyd&Steinberg type, and
Judice&Ninke type. Also, it doesn't matter which printing
method is taken for the colored region of the present invention.
Moreover, the colored region may be colored a single color.
Thereby, the colored region where the optical diffraction structure
is formed can be used as a single-colored optical diffraction
structure colored the color of the colored region.
[0023] A first image formation method of the present invention
solves the above problems as an image formation method in which an
optical diffraction structure forming layer is transferred in a
halftone dot state to a colored region on a transfer body to form
an optical diffraction structure portion by using a transfer sheet
where the optical diffraction structure forming layer in which an
optical diffraction structure is formed is laminated on a base
material sheet thereof, wherein the halftone dots constituting the
optical diffraction structure portion are transferred to the
colored region in a diffused state by an error diffusion method so
that an area of the halftone dot is smaller than 0.25 mm.sup.2 and
a dot area percent to the colored region ranges from 15% to
60%.
[0024] By the above formation method, the first image display body
of the present invention can be obtained. The conceptions of the
optical diffraction structure and the error diffusion method are
the same as the above mentioned conceptions.
[0025] The optical diffraction structure forming layer may be
thermally transferred from the transfer sheet to the colored region
by using a thermal head, and each of the halftone dots may be
transferred based on printing energy applied to the thermal head so
that the halftone dots are diffused in a state of the area and the
dot area percent by the error diffusion method. Thereby, the
printing energy of the thermal head can be optimized based on
materials of the optical diffraction structure and the transfer
body. As each halftone dot is transferred based on the optimized
printing energy, the image display body having more natural
brightness can be obtained.
[0026] the colored region of the transfer body may be colored a
single color. Thereby, by the present invention, the colored region
where the optical diffraction structure is formed can be used as a
single-colored optical diffraction structure colored the color of
the colored region.
[0027] A second image display body of the present invention solves
the above problems as an image display body in which an optical
diffraction structure portion constituted by optical diffraction
structure in a halftone dot state is formed on an image on a base
material, wherein, each of a plurality of halftone dots
constituting the optical diffraction structure portion is formed
such that each of the halftone dots is enclosed in each of same
size square regions a side of which is 400 .mu.m or less, and when
each of the halftone dots is enclosed in each of the square
regions, the plurality of square regions are arranged at equal
intervals in a diagonal direction, and in the diagonal direction a
distance between a corner of one of adjacent square regions and a
corner of another of the adjacent square regions is 220 .mu.m or
less.
[0028] the inventor finds out the fact that optical diffraction
structure can be provided to an image as more naturally decorative
effect as a lame when the halftone dots constituting the optical
diffraction structure portion are formed such that the halftone
dots are arranged regularly. Thereby, such the effect as a glittery
lame can be easily given to the image printed with natural ink.
[0029] It is not necessary that the shape of the halftone dot is a
square as long as the halftone dot can be enclosed in the square
region the side of which is 400 .mu.m or less. For example, a
circle shape, an ellipse shape, a polygon shape or an irregular
shape can be employed as the halftone dot. The optical diffraction
structure includes a diffraction grating having a constant pattern
and a hologram having a fringe pattern forming a predetermined
image.
[0030] Moreover, in the second image display body of the present
invention, a dot area percent of the optical diffraction structure
portion may be 40% or less. In a case of this halftone dot area
percent, such the effect as a more natural glitter lame can be
given to the image. When a length of one side of the square region
ranges from 100 .mu.m to 200 .mu.m, and/or a distance between the
adjacent square regions ranges from 50 .mu.m to 150 .mu.m, a
furthermore decorative effect can be performed.
[0031] A second image formation method solves the above problems as
an image formation method in which an optical diffraction structure
portion constituted by optical diffraction structure is formed in a
halftone dot state on a predetermined image by using a transfer
sheet where the optical diffraction structure is laminated on a
base material sheet thereof, wherein each of a plurality of
halftone dots constituting the optical diffraction structure
portion is formed such that each the plurality of halftone dots is
enclosed in each of same size square regions a side of which is 400
.mu.m or less, and when each of the halftone dots is enclosed in
each of the square regions, the plurality of square regions are
arranged at equal intervals in a diagonal direction, and in the
diagonal direction a distance between a corner of one of adjacent
square regions and a corner of another of the adjacent square
regions is 220 .mu.m or less.
EFFECTS OF THE INVENTION
[0032] As described above, according to the invention, the
diffraction structure in a halftone dot sate is provided to the
colored region under the conditions that the area of each halftone
dot is smaller than 0.25 mm.sup.2, the dot area percent ranges from
15% to 60%, and the halftone dots are diffused by the error
diffusion method. Thereby, the image display body and the like in
which the optical diffraction structure appeared to be colored the
desired color, and the decorative effect is obtained more
effectively can be provided. Moreover, by specifying the mode where
halftone dots are arranged on an image in a size and a distance,
the image display body and the like where more decorative effect by
an optical diffraction structure is given to the image can be
provided
BRIEF DESCRIPTION OF THE DRAWINGS
[0033] FIG. 1 is a view showing an example of the first image
display body of the present invention;
[0034] FIG. 2 is a sectional view taken along a line V-V of FIG.
1;
[0035] FIG. 3 is an enlarged view of a colored hologram portion
which is formed with dot area percent of 15%;
[0036] FIG. 4 is an enlarged view of a colored hologram portion
which is formed with dot area percent of 35%;
[0037] FIG. 5 is an enlarged view of a colored hologram portion
which is formed with dot area percent of 60%;
[0038] FIG. 6 is a view showing an image producing apparatus of the
present mode;
[0039] FIG. 7 is a sectional view of a hologram transfer sheet used
in the image producing apparatus of FIG. 6;
[0040] FIG. 8 is a view showing a state in which a colored portion
is provided in a base material;
[0041] FIG. 9 is a flowchart showing a flow of processes for
producing an image display body;
[0042] FIG. 10 is a flowchart showing a flow of a hologram transfer
process;
[0043] FIG. 11 is a view showing a state in which halftone dot
information is obtained from gray-scale information;
[0044] FIG. 12 is a view showing an example of the second image
display body in the present invention;
[0045] FIG. 13 is a partially enlarged view of an optical
diffraction structure portion shown in FIG. 12;
[0046] FIG. 14 is a view showing a section of an example of a
transfer sheet in the present invention;
[0047] FIG. 15A is a view showing a transfer body in which the
image display body shown in FIG. 12 is formed; and
[0048] FIG. 15B is a partially enlarged sectional view of the image
display body shown in FIG. 12, in which the optical diffraction
structure portion is formed.
BEST MODE FOR CARRYING OUT THE INVENTION
[0049] FIG. 1 is a view showing an example of the first image
display body 1 of the present invention. The image display body 1
includes plural colored portions 20, 30, and 40 on a base material
10. The colored portions 20, 30, and 40 are colored the different
colors respectively. In the whole of the colored portion 20, an
optical diffraction structure in a halftone dot state is provided
as an optical diffraction structure portion 21. Therefore, a visual
effect by diffracted light is given to the colored portion 20 in
addition to the coloring. Hereinafter the colored portion 20 in the
state in which the optical diffraction structure portion 21 is
provided is referred to as colored hologram portion 22. Although
the colored portions 20, 30, and 40 are colored by a dye
sublimation printing in the present embodiment, any printing method
may be employed to color the colored portions 20, 30, and 40.
[0050] In the present embodiment, a diffraction grating is used as
the optical diffraction structure constituting the optical
diffraction structure portion 21. The optical diffraction structure
includes the diffraction grating and a hologram, and the
diffraction grating constituted by a constant concavo-convex
pattern is strictly distinguished from the hologram constituted by
a fringe pattern generating a predetermined hologram image.
However, hereinafter the hologram is used in the same meaning of
the optical diffraction structure. Materials respectively used for
the base material 10 and colored portion 20 may be appropriately
determined according to a use purpose of the image display body 1.
Any type of hologram may be used in the optical diffraction
structure portion 21 as long as a hologram is a diffraction grating
which can be formed as a hologram forming layer onto a
later-mentioned hologram transfer sheet.
[0051] As shown in FIG. 2, the colored portion 20 constituted with
ink is laminated on the base material 10 in the colored hologram
portion 22 of the image display body 1, and plural halftone dots
21a, . . . , 21a constituting the optical diffraction structure
portion 21 are provided all over the colored portion 20. An area of
each halftone dot 21a is smaller than 0.25 mm.sup.2, and a halftone
dot area percent to the colored hologram portion 22 ranges from 15%
to 60%. The halftone dots 21a are provided while diffused by an
error diffusion method, namely, the halftone dots 21a are provided
not in a state where the halftone dots having a constant shape are
regularly arranged at equal intervals, but in a sate where the
uneven halftone dots are unevenly disposed.
[0052] The plural halftone dots 21a, . . . , 21a constituting the
optical diffraction structure portion 21 are provided in the
colored portion 20 under the above conditions, whereby natural
brightness by the diffracted light is represented in all over the
colored hologram portion 22, and the colored hologram portion 22
looks like a hologram colored the color of the colored portion 20.
For example, in the case where the colored portion 20 is colored
red, the colored hologram portion 22 looks like the hologram
colored red. FIGS. 3 to 5 show the states in which the plural
halftone dots 21a are provided in the colored portion 20 with dot
area percents of 15%, 35%, and 60% respectively. In each drawing, a
whitish portion is a port ion where the halftone dot 21a is
provided.
[0053] Then, a method of producing the image display body 1 will be
described. In the present embodiment, the image display body 1 is
produced with an image producing apparatus 50 shown in FIG. 6. The
image producing apparatus 50 includes an input unit 51, a display
unit 52, a hologram transfer unit 53, a storage unit 54, a body
where to be transferred supply unit 55, a discharge unit 56, and a
control unit 57. The input unit 51 accepts various kinds of setting
operations of a user. The display unit 52 displays an image
corresponding to the setting by the user or various messages to the
user. The hologram transfer unit 53 transfers the hologram. Various
kinds of drawing patterns and various kinds of information to be
provided on the base material 10 are stored in the storage unit 54.
The transfer body supply unit 55 supplies a transfer body. The
discharge unit 56 discharges the produced image display body 1. The
control unit 57 controls operations of the units 51, . . . ,
56.
[0054] The hologram transfer unit 53 of the present embodiment
prints the hologram by using a hologram transfer sheet 60 shown in
FIG. 7 by a thermal transfer method. In the hologram transfer sheet
60, a peel layer 62, a hologram forming layer 63 in which the
hologram is formed, a reflecting layer 64, and a bonding layer 65
are laminated on one side of a base material sheet 61, while a
heat-resistant layer 66 is provided on the other side of the base
material sheet 61. The hologram transfer sheet 60 of the present
embodiment is a transfer foil in which the diffraction grating is
formed as the hologram of the hologram forming layer 63.
[0055] The bonding layer 65 is bonded to the transfer body, and a
thermal head is pressed against the hologram transfer sheet 60 from
the side of the heat-resistant layer 66, which peels off the side
of the base material sheet 61 from the side of the hologram forming
layer 63 to transfer the hologram forming layer 63 onto the
transfer body. Each of the layers 61, . . . , 66 may be made of
well-known materials. An aspect in which the hologram forming layer
63 is transferred onto the transfer body includes an aspect in
which the hologram transfer sheet 60 is peeled off between the base
material sheet 61 and the peel layer 62 to transfer the layers 62
to 65 including the hologram forming layer 63 onto the transfer
body, an aspect in which the hologram transfer sheet 60 is peeled
off between the peel layer 62 and the hologram forming layer 63 to
transfer the layers 63 to 65 including the hologram forming layer
63 onto the transfer body, and an aspect in which the hologram
transfer sheet 60 is peeled off at the peel layer 62 into the side
of the hologram forming layer 63 and the side of the base material
sheet 61 to transfer the hologram forming layer 63 onto the
transfer body.
[0056] A relief diffraction effect can be enhanced by providing the
reflecting layer 64 to a relief surface of the hologram forming
layer 63. Desirably, the reflecting layer 64 is made of a metal
having a high light reflectance. The higher light reflectance of
the metal constituting the reflecting layer 64 is, the brighter
diffracted light is obtained. Specifically, the reflecting layer 64
may be formed by a single thin film made of a metal such as Cr, Ni,
Ag, Au, and Al, an oxide, a sulfide, and a nitride thereof, and a
combination thereof. The metal thin film having the high light
reflectance has a thickness ranging from around 10 to 2000 nm,
preferably from 20 to 1000 nm so as to obtain a sufficient
reflecting effect.
[0057] In the present embodiment, an image display body 1' shown in
FIG. 8 is used as the transfer body. In the image display body 1',
the plural colored portions 20, 30, and 40 are provided on the base
material 10. Although the coloring of the colored portions 20, 30,
and 40 is printed by the dye sublimation method, the colored
portions 20, 30, and 40 may be colored by other printing methods.
In the transfer body supply unit 55, plural variations colored
different colors are prepared as the colored portions 20, 30, and
40.
[0058] The flow of whole processes for producing the image display
body 1 with the image producing apparatus 50 will be described with
reference to a flowchart of FIG. 9. Each process in the flowchart
of FIG. 9 is performed by the control unit 57 according to a
predetermined program. First a drawing pattern select ion process
is performed (Step S70). In the drawing pattern selection process,
the process lets the user select his/her desiring colored
drawing-pattern to be provided on the base material 10. For
example, the plural selectable colored drawing-patterns are
displayed on the display unit 52, and the input unit 51 accepts the
user selection operation.
[0059] The image display body 1' is displayed on the display unit
52 according to the user selection operation during the drawing
pattern selection process. At this point, sizes and positions of
the colored portions 20, 30, and 40 may be appropriately changed by
the input operation of the user. When the drawing pattern selection
process is finished, the process lets the user specify a region
where the hologram is transferred in the image display body 1'
(Step S72). In the present embodiment, the process lets the user
select the drawing pattern onto which the hologram is transferred
in the image display body 1'. The case in which the colored portion
20 of the image display body 1' is selected will be described
below. When the colored portion 20 is specified as the region to
which the hologram is transferred, a hologram transfer process is
performed (Step S74). In the hologram transfer process, the optical
diffraction structure portion 21 is formed in the colored portion
20 to produce the image display body 1. The specific process of the
hologram transfer process is described later. Finally the produced
image display body 1 is discharged from the discharge unit 56 (Step
S76), and the processes concerning producing of the image display
body 1 finishes.
[0060] The hologram transfer process will be specifically described
with reference to a flowchart shown in FIG. 10. When the colored
portion 20 is specified as the region where the hologram is
transferred, gray-scale information is read from the storage unit
54 (Step S80). The gray-scale information means a proportion of an
area which the hologram occupies to a predetermined region, e.g.
one dot, when the hologram is transferred. The gray-scale
information is set as a value of printing energy given to the
thermal head. The optimum value of the gray-scale information is
previously set according to the material constituting the hologram
of the hologram forming layer 63 and the image display body 1', and
the use application of the image display body 1. The optimum value
of the gray-scale information is stored in the storage unit 54.
[0061] Then, a diffusion process is performed based on the
gray-scale information (Step S82). In the diffusion process, on the
basis of the gray-scale information, the position and size of the
halftone dot 21a provided as the optical diffraction structure
portion 21 on the colored portion 20 so that the predetermined
conditions are satisfied. Hereinafter the information on the
halftone dot 21a determined in the diffusion process is referred to
as halftone dot information. The predetermined conditions mean the
area of the halftone dot, the dot area percent to the colored
portion 20, and the process performed by the error diffusion
method. In the present embodiment, the halftone dot information on
each halftone dot 21a is computed such that the halftone dot 21a
has the area of 0.04 mm.sup.2, the dot area percent is 30%, and the
halftone dots 21a are arranged in a state of being diffused by a
random dithering method which is one of the error diffusion
methods.
[0062] The area of the halftone dot 21a may be smaller than 0.25
mm.sup.2, and the dot area percent may range from 15% to 60%. The
error diffusion method is not limited to the random dithering
method, but any method may be employed. Appropriate values of the
area and dot area percent are previously set according to the use
purpose of the image display body 1.
[0063] A method of obtaining the halftone dot information using the
gray-scale information will be described with reference to FIG. 11.
As described above, the gray-scale information is the proportion of
the area which the hologram can occupy to the predetermined region.
For example, when the case of the gray-scale information of 35%
about the colored portion 20 is conceptually shown, as a
pre-diffusion process state A, a white region 90 where to transfer
the hologram occupies 35% of the whole of the colored portion 20,
and a black region 91 where not to transfer the hologram occupies
the other 65%. By diffusing the white region 90 where to transfer
the hologram in the uneven halftone dot state by the error
diffusion method while satisfying the above conditions, the
halftone dot information on each halftone dot 21a is computed. A
post-diffusion process state B of FIG. 11 shows a state where the
diffusion is performed at the dot area percent of 35% in the
colored portion 20 which is a rectangular shape.
[0064] Returning to FIG. 10, when the halftone dot information is
obtained through the diffusion process, the thermal head operation
is controlled based on the halftone dot information, and the
hologram forming layer 63 is thermally transferred from the
hologram transfer sheet 60 onto the colored portion 20 in the
halftone dot state in the above-described manner (Step S84).
Thereby the optical diffraction structure portion 21 can be
provided on the colored portion 20.
[0065] FIG. 12 is a view showing an example of a second image
display body 100 of the present invention. In the image display
body 100, an optical diffraction structure portion 103 constituted
by optical diffraction structure is formed in a halftone dot state
on an image 102 provided to a predetermined base material 101. As
shown in FIG. 13, each of plural halftone dots 110, . . . , 110
constituting the optical diffraction structure portion 103 can be
enclosed by each of square regions 111, . . . , 111 whose sizes are
equal to one another, and the plural square regions 111, . . . ,
111 are formed so as to be arranged at equal intervals in diagonal
directions 112, . . . , 112.
[0066] A length of one side of the square region 111 may be 400
.mu.m or less, and preferably the length ranges from 100 to 200
.mu.m. In the adjacent square regions 11 and 11, all distances d
between a corner 11a of one of the square region 11 and a corner
11b of the other square region 11 are equal to one another and
should be 220 .mu.m or less. Preferably the distance d ranges from
50 to 150 .mu.m. Moreover, Preferably the dot area percent of the
halftone dots 110, . . . , 110 to the area of the image 102 is 40%
or less.
[0067] The material for the base material 101 and the method of
forming the image 102 may be appropriately determined according to
the use application of the image display body 100. Examples of the
image display body 100 include cards such as a credit card, an ID
card, and a prepaid card and paper tickets such as an exchange
coupon, a check, paper money, a stock certificate, an entrance
ticket, and various certificates. Any card or paper ticket can be
used as the image display body 100 as long as the card or paper
ticket has the image 102 on the base material 101. The image 102
also includes a substance formed by various kinds of printing
methods and a photograph.
[0068] Then, a method of forming the optical diffraction structure
portion 103 in the image 102 by using a transfer sheet 120 shown in
FIG. 14 will be described. In the transfer sheet 120, a peel layer
122, an optical diffraction structure layer 123, a reflecting layer
124, and a bonding layer 125 are laminated on a base material sheet
121, and a heat-resistant protective layer 126 is formed on the
backside of the base material sheet 121. In the optical diffraction
structure layer 123, the concavo-convex pattern of the diffraction
grating is formed as the optical diffraction structure. The relief
diffraction effect can be enhanced by providing the reflecting
layer 124 on the relief surface of the optical diffraction
structure layer 123. Desirably the reflecting layer 124 is made of
a metal having the high light reflectance. The higher light
reflectance of the metal constituting the reflecting layer 124 is,
the brighter diffracted light is obtained. Specifically, the
reflecting layer 124 may be formed by a single thin film made of a
metal such as Cr, Ni, Ag, Au, and Al, an oxide, a sulfide, or a
nitride thereof, or a combination thereof. The metal thin film
having the high light reflectance has a thickness ranging from
around 10 to 2000 nm, preferably from 20 to 1000 nm so as to obtain
the sufficient reflecting effect.
[0069] The thermal transfer printer transfers the optical
diffraction structure layer 123 of the transfer sheet 120 to a
transfer body 130 in which the image 102 is provided to the base
material 101 as shown in FIG. 15A. By controlling the thermal head
operation of the thermal transfer printer, the halftone dots 110, .
. . , 110 can be formed on the image 102 in the above mentioned
sate by the optical diffraction structure layer 123.
[0070] The conventional method in which the optical diffraction
structure is transferred in a halftone dot state from the transfer
sheet with the thermal transfer printer may be employed as the
method of controlling the thermal head operation. FIG. 15B is a
view showing the state in which the optical diffraction structure
portion 103 is formed by transferring the optical diffraction
structure layer 123 as the halftone dots 110, . . . , 110 onto the
image 102 provided to the base material 101. Through the above
forming method, the optical diffraction structure portion 103 is
formed on the image 102, and a natural lame effect can be given to
the image 102 by the diffracted light.
[0071] The present invention relating to the first image display
body 1 is not limited to the above-described embodiment, and the
present invention can be realized in various embodiments. At least
one colored portion of the image display body 1 may be required,
and the whole of the image display body 1 may be colored. The
colors of the plural colored portions may be different from one
another or identical to one another. The shape of the colored
portion 20 of the image display body 1 is not limited to the star
shape.
[0072] In the image producing apparatus 50, plural kinds of
transferable holograms may be prepared and the user may be allowed
to select the desired hologram. In this case, the optimum
gray-scale information may be previously set to each hologram and
correlated with the hologram. The region to which the hologram is
transferred may be previously determined. A printing unit which
colors the base material 10 may be provided in the image producing
apparatus 50.
[0073] In the hologram transfer sheet 60, it is hot necessary to
provide the peel layer 62 and the bonding layer 65 when the other
layers have the sufficient peel properties or bonding properties.
Other layers such as a surface lubricant layer may be provided if
needed.
[0074] The invention relating to the second image display body 100
is not also limited to the above-described embodiment, and the
second image display body 100 of the invention can be realized in
various embodiments. For example, although the halftone dot 110
shown in FIG. 13 has the circular shape, the halftone dot 110 may
have any shape such as an ellipse, a polygon, and an irregular
shape. The image 102 is not limited to the star shape shown in FIG.
12 and may have any shape. The image 102 may be colored not a
single color but plural colors. The image 102 may be provided in
not apart of the base material 101 but the whole of the base
material 101.
[0075] In the transfer sheet 120, the peel layer 122 is not
required depending on the function of the base material sheet 121
or the optical diffraction structure layer 123. A layer except for
the peel layer 122 may be laminated depending on the use
application of the image display body 100. For example, a
particular-color layer constituted by coloring ink such as gold is
provided to the transfer sheet 120 to form the optical diffraction
structure portion together with the optical diffraction structure
layer 123.
[0076] Moreover, the transfer sheet 120 is designed such that the
transfer sheet 120 is peeled off between the base material sheet
121 and the peel layer 122 to transfer the layers 122 to 125
including the optical diffraction structure layer 123 onto the
transfer body 130. In some cases, the transfer sheet 120 may be
designed such that the transfer sheet 120 is peeled off between the
peel layer 122 and the optical diffraction structure layer 123 to
transfer the layers 123 to 125 except for the peel layer 122 onto
the transfer body 130. Additionally, the transfer sheet 120 may be
designed such that the transfer sheet 120 is peeled off at the peel
layer 122 into the side of the optical diffraction structure layer
123 and the side of the base material sheet 121.
* * * * *