JPH08118780A - Manufacture of sheet with stereoscopic image, image forming device, and stereoscopic image forming sheet - Google Patents

Abstract

PURPOSE: To make degrees of expansion of figures of which sizes are different equlized and flat when the figure is formed on a thermally expansible sheet, irradiated with light to be made three-dimensional, and a stereoscopic image is formed. CONSTITUTION: Regular squares 10, 11 are different in size. They are divided into regions 12, 12' which are a specific distance apart from respective outer peripheries or the like, and a light absorber is transferred so that optical densities of respective regions become nonuniform. Specifically, the light absorber is transferred so that the optical density decreases gradually from an outside region. When that is irradiated with light, each absorbs light to be heated. Since each region is so formed as to have an appropriate optical density, each figure is made three-dimensional in a flat state of a specific height.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a sheet with a stereoscopic image, an apparatus used for the method, and other objects.

[0002]

2. Description of the Related Art Conventionally, a method of manufacturing a three-dimensional image forming sheet has been proposed. For example, in the method described in Japanese Examined Patent Publication No. 59-35359, a desired image is formed on the surface of the heat-expandable sheet with a material having a higher light absorption property than the sheet, and then the surface of the sheet is irradiated with light to absorb light. The image portion is selectively heated and raised due to the difference of

Further, according to the image forming method described in JP-A-61-72589, an image having a high light absorption property is formed by a thermal transfer method, and the image is irradiated with light to form a foamed recording material. An uneven pattern corresponding to the image signal is formed on the top. According to these methods, with simple operation,
An uneven pattern can be formed on the sheet.

[0004]

However, when a pattern having a large area is formed on the heat-expandable sheet by this method and light irradiation is performed, a thermal interaction occurs in the pattern, resulting in a uniform pattern. There is a problem that a three-dimensional image of height cannot be formed.

That is, as an example, consider a case where two similar patterns 50 and 51 having a similarity ratio of 2 and uniform density are formed on a thermal expansion sheet as shown in FIG. The amount of heat generated by absorbing light is almost proportional to the area of the figure. Since the area of the graphic 50 is four times the area of the graphic 51, the heat generation amount from the graphic 50 is about four times the heat generation amount from the graphic 51.

On the other hand, the perimeter of the graphic 50 is twice the perimeter of the graphic a. The cooling process of the generated figure is performed by dissipating the generated heat to the low temperature portion around the figure. It is known that the heat dissipation rate is inversely proportional to the area of the heat passage that contributes to heat dissipation, and in the case of cooling a figure as shown in FIG. It corresponds to the area of the passage. From the above, the dissipation of heat from the graphic 50 is performed at a speed approximately twice that of the dissipation from 51.

Therefore, when the figures 50 and 51 are irradiated with uniform light, the figure 50 generates four times as much heat as the figure 51, and heats at a rate twice as high. Is dissipated. Therefore, to cool the figure 50 after light irradiation,
As compared with the cooling of the graphic 51, about twice as much time is required, and the heat of the graphic 50 is maintained for a longer time than the graphic 51. As a result, the thermal expansion layer below the figure expands more.

That is, the degree of three-dimensionalization varies depending on the size of the figure, and the larger the figure, the larger the expansion. A cross-sectional view of the figure after three-dimensionalization is shown in the lower part of FIG. The three-dimensional shape of the figure 50 as described above is higher than the three-dimensional shape of the figure 51. Further, both of the figures 50 and 51 are raised so that the center of the figure is high and the height is low toward the edge.

Therefore, when an uneven image made up of figures as shown in FIG. 9 is manufactured using a conventional sheet with a stereoscopic image and used as a stamp, the lower 51 is not shown, or the square 51 is supposed to be 50. There is also a problem that the part is only visible in a circle. Therefore, it is an object of the present invention to make it possible to adjust the height of each part in an image when manufacturing a sheet with a stereoscopic image. In particular, the second purpose is to make the top surface flat by aligning the ridge height of the center part and the ridge height of the edge part of a large area graphic, and the ridge between two or more shapes of different areas. The third purpose is to make the heights uniform.

[0010]

Means, Actions and Effects for Solving the Problems In the method for producing a sheet with a stereoscopic image of the present invention, a material having higher light absorption than the sheet is attached to the surface of the heat-expandable sheet to form a desired image. In the method for producing a sheet with a three-dimensional image by forming the image, and then subjecting the thermally expandable sheet to irradiation with light containing infrared rays to form selective ridges based on the difference in light absorption, thereby forming the image. At this time, the material having a high light absorbing property is attached onto the heat-expandable sheet so that the optical density changes depending on the position in the image.

According to this method for producing a sheet with a stereoscopic image, the optical density of a material having a high light absorption is changed in the image. The amount of heat generation is large in the portion with high optical density, and the amount of heat generation is small in the portion with low optical density. As a result, the relationship between the heat generation amount and the heat dissipation amount can be adjusted for each part. Therefore, for example, if it is desired to indent only a certain portion of the figure, a method of making the optical density of that portion extremely lower than the surroundings may be adopted. On the contrary, if you want to raise only a certain portion higher, you can take a method of making the optical density of that portion extremely higher than the surroundings. Further, if there are two figures having the same area and only one of them is desired to be raised, a method of increasing only the optical density of that one may be adopted.

[0012] In achieving the second object, in particular, for each figure included in the image, the optical density is reduced so that the optical density decreases as the distance from the edge of the figure increases. A material having a high heat resistance may be attached to the heat-expandable sheet. With such a configuration, it is possible to eliminate the difference in the amount of heat between the edge of the figure and the inside and to raise the figure to a uniform height.

In achieving the third object, two or more figures having different areas are included as the image, and the light absorption property is set so that the figure having a larger area has a smaller average optical density. A material having a high heat resistance may be attached to the heat-expandable sheet. With this configuration, it is possible to eliminate the difference in the amount of heat between the figures and to raise the patterns to a uniform height.

In order to realize such a method for producing a sheet with a three-dimensional image, the surface of the heat-expandable sheet is
An image forming apparatus for forming an image by adhering a material having higher light absorption than the sheet, the image information acquiring unit acquiring information of an image to be formed, and the image information acquiring unit acquired. Based on the image information, each figure included in the image information is divided into areas by extracting an area at a constant width from the edge of each figure, and a figure dividing unit, and a figure dividing unit that divides the extracted areas. An optical density setting unit that sets the optical density to a smaller value in a region farther from the edge, and an attaching unit that attaches a material having a high light absorbing property onto the heat-expandable sheet based on the setting content of the optical density setting unit. It is good to use one.

According to this image forming apparatus, the figure dividing means sets the optical density for each area extracted from the outermost edge portion of the image at a constant width. Then, when only one figure is viewed, the optical density is reduced from the edge of the figure toward the inside, so that this device can be used in realizing the method for achieving the second object. Also, 2 with different areas
Looking at the above figures, the larger the figure is, the larger the number of divided areas becomes, and the area having a lower optical density is provided. Therefore, the average optical densities of these figures are brought close to each other, and it is possible to suppress the overprotrusion of the figures having a large area.

In carrying out the method of the present invention, a sheet for stereoscopic image formation, in which a material having a higher light absorbing property than the sheet is attached to the surface of the heat-expandable sheet to transfer an image, Each figure has a sheet for stereoscopic image formation characterized in that the material having high light absorption is attached so that the optical density becomes smaller as the distance from each edge becomes larger, and the thermal expansion property. A three-dimensional image forming sheet in which a material having a higher light absorbing property than that of the sheet is attached to the surface of the sheet to transfer an image, and the image includes two or more figures having different areas and has a larger area. If a sheet for stereoscopic image formation is prepared in which the material having high light absorbing property is adhered so that the average optical density of the figure becomes smaller, all that is required is to irradiate light. Desired three-dimensional It is possible to produce an image sheet with.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. A cross-sectional view of a heat-expandable sheet used for the three-dimensional image forming sheet of the present invention is shown in FIG. The heat-expandable sheet 60 is formed by forming a heat-expansion layer 61 on a base material 62.

The thermal expansion layer 61 is formed by dispersing a foaming agent 63 in a thermoplastic resin. A non-toxic gas is generated in the foaming agent 63 by thermal decomposition of bicarbonate such as sodium hydrogen carbonate, various peroxides, azo compounds such as diazoaminobenzene, aluminum paradicarboxylate, and azobisisobutyronitrile. Those that do are preferably used.

Further, a shell material made of polystyrene, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, polyacrylic acid ester, polyacrylonitrile, polybutadiene, or a copolymer thereof is used in the interior of a shell material containing propane, butane, propane, or the like. Encapsulating a vaporizable substance with a boiling point,
Micro-encapsulated heat-expandable capsules having a diameter of 10 to 20 μm may be used as a foaming agent.

These foaming agents are placed in a solution or emulsion of a resin used as a binder in a roll mill,
Dispersion is performed using a known dispersing device such as a sand mill. The dispersion liquid is applied onto the base material 62 using a known application device and further dried to form the thermal expansion layer 61.

In the resin for the binder, when the foaming agent is heated and thermally decomposed to generate a gas, or when the thermally expandable capsule thermally expands, it is simultaneously softened to form a stable foamed layer. As possible, a thermoplastic resin such as a vinyl acetate polymer or an acrylic polymer is preferably used.

The characteristics required of the base material 62 are smoothness, water resistance, and tensile strength, as well as the opposite side of the thermal expansion layer 61 when the foaming agent foams. It can be said that it has rigidity so that it does not rise. As those having these characteristics, for example, besides paper, synthetic paper such as polypropylene, polyethylene terephthalate (PET), polybutylene terephthalate (P
Various plastic films such as BT) are preferably used. Above all, PET that has been foamed and has many bubbles inside
When a film is used, the heat insulating effect is high, so that an image can be three-dimensionalized with low energy.

A method of creating a three-dimensional image using the heat-expandable sheet having the above structure will be described with reference to FIGS.
First, as shown in FIG. 2, a thermal transfer ribbon 72 is overlaid on the thermal expansion layer 61, and a thermal head 71 as a heating unit is pressed against the back surface of the thermal transfer ribbon 72. The thermal head 71 is controlled by a control circuit (not shown) based on the image signal to generate heat. This heat melts the ink layer at the corresponding location on the thermal transfer ribbon 72 and fuses to the surface of the thermal expansion layer 61. After the ink is cooled, the thermal transfer ribbon 7
When 2 is peeled off, only the image portion of the ink layer of the thermal transfer ribbon 72 is transferred to the thermal expansion layer 61, and an image is formed on the thermal expansion layer 61.

In the present embodiment, the thermal expansion layer 61
Although the thermal head 71 is used to form an image on the above, it is also possible to use a heating means other than the thermal head 71. For example, the back surface of the thermal transfer ribbon 72 is scanned and heated with laser light whose intensity is modulated based on an image signal to melt the ink layer at a location corresponding to the thermal transfer ribbon 72 irradiated with the laser light of high intensity. It may be fused to the surface of the thermal expansion layer 61.

Here, the ink of the thermal transfer ribbon 72 includes
A material that absorbs light and generates heat is used. For example, when a black printed image is desired, carbon black may be used. Carbon black absorbs light from visible light to near infrared, and its light energy is converted into heat.

On the other hand, when a printed image other than black is required, known dyes / pigments such as red, blue and yellow are used. However, since these dyes and pigments have little light absorption in the infrared region, sufficient light energy cannot be converted into heat. Therefore, it is desirable to increase the light absorption in the infrared region by appropriately mixing a composite oxide containing an oxide of tin, antimony, or indium as a main component.

Through the above steps, an image is formed on the thermal expansion layer 61 with the light absorbing ink. Next, as shown in FIG. 3, the stereoscopic image forming sheet 60 carrying the light absorbing image is irradiated with light from the lamp 73. As the lamp 73, a lamp capable of emitting visible light to near infrared light such as a tungsten lamp, a halogen lamp, or a xenon lamp is used.

When the light absorptive image 64 on the thermal expansion layer 61 is illuminated by the lamp 23, the light is emitted to the image 64.
Is absorbed by and converted into heat energy. Therefore, the thermal expansion layer 61 under the image 64 is heated.
When a foaming agent is used as the thermal expansion layer 61, the surface of the thermal expansion layer 61 rises due to foaming due to thermal decomposition of the foaming agent. When a thermally expandable capsule is used, the expansion of the capsule causes the surface of the thermally expandable layer 61 to rise.

At this time, if the fan 73 blows light near the surface of the thermal expansion layer 61 while irradiating the lamp 73 with light, it is possible to prevent the ambient temperature near the thermal expansion layer 61 from rising. This makes it possible to increase the temperature difference between the portion where light is absorbed and the temperature is raised and the portion where light is reflected and the temperature is not raised. Therefore, it is possible to firmly raise only the portion of the heat-expandable layer 61 desired to be raised,
The resolution of a stereoscopic image can be improved.

Through the steps as described above, the image on the heat-expandable sheet can be irradiated with light to make the figure three-dimensional. Next, a processing procedure for creating a stereoscopic image having a uniform height, which is a feature of this embodiment, will be described. FIG. 4 shows a square 10 having a side length L _{1 and} a square 1 having a side length L ₂ .
FIG. 2 is a cross-sectional view of a figure before light irradiation and a three-dimensional image after three-dimensionalization by irradiating light when 1 and 2 are formed by a thermal transfer method and these figures are three-dimensionalized. As shown
In this embodiment, the optical density of the figure is not a constant value,
Ink is transferred so as to have a distribution. For example, the distribution of optical density in a figure is determined by the following procedure.

First, a figure of interest is selected, and the figure is sequentially divided into a constant width from the periphery in contact with a white background. At this time,
The width of the divided region is preferably 0.5 mm to 3 mm, more preferably 1 mm to 2 mm.
The optical density of each of the divided parts is changed by various dither methods such as an error dispersion type and a spiral type. The three-dimensional image-forming sheet thus obtained has the highest optical density in the part in contact with the white background, the optical density is gradually decreased toward the inside of the figure, and the ink is transferred so that the center part of the figure has the lowest density. To be done.

This procedure can be easily realized by using a known graphic processing procedure using a computer. This will be described with reference to the flowchart shown in FIG. When there are a large number of figures, the figures are first separated into ones according to a known image processing procedure (S10). In addition,
As a premise for this, image information is input to a computer. As a method thereof, the image itself may be drawn on paper or the like and read by an image scanner or the like.

Next, for each of the separated figures,
The outer periphery of the figure is detected (S20). Next, it is determined whether or not the figure whose outer shape is detected has a size capable of cutting out a region having a constant width from the outer circumference (S30). Then, when cutting out from the outer circumference is possible, an area at a constant distance from the outer circumference is cut out (S40). Then, the density for the cut out portion is determined (S50). At this time, the density is programmed so that the maximum density value is set when S50 is executed for the first time, and the density value is reduced according to a predetermined condition each time S50 is executed.

In the example of FIG. 4, by the processing of S40 and S50, the area 12 is cut out from the larger square 10 and the area 12 'is cut out from the smaller square 11, and the maximum is cut out respectively. The density value will be set. When the cutting out of the fixed width portion and the determination of the density are completed in this way, it is determined whether or not the remaining portion remains one (S6).
0). For example, as shown in FIG. 7, in a shape in which two circles are attached to each other, when the regions 31 and 32 are cut out, the remaining portion of the figure is a region including the regions 33 and 34 and a region 33′34 ′. It is divided into a part consisting of. In such a case, it is determined that the number of remaining areas is not one.

When it is determined in S60 that there is one remaining area, the process returns to S20 again, and the outer circumference of the remaining area is detected for the currently recognized number of figures, and the cutout with a constant width is performed. Repeat the determination of the concentration. On the other hand, if it is determined in S60 that the number of remaining areas is not one, the process returns to S10 and starts from the processing of separating the figures that are not one.

In this way, the process of cutting out the first figure by a certain width and determining the density of the cut-out portion is repeatedly executed, and when it becomes impossible to cut out (S30 = NO), that is the case for all figures. (S70).

If it is for all figures, the density is determined for the last area and the routine exits (S8).
0). On the other hand, when only some of the figures cannot be cut out, the density of the figure that cannot be cut out is determined and the figure is excluded from the processing target (S90, S
100), and the process returns to S40 again. Then, an area having a constant width is cut out from the graphic to be processed (S40), and its density is determined (S50). At this time, S80 and S9
The determination values of the density at 0 and S50 are the same density value.

In this way, when all the figures to be processed are reduced to the uncuttable state, this routine is exited. By executing the above processing, for example,
In the example of FIG. 4, the areas 12 and 12 ′ having a constant width from the outermost circumference of the squares 10 and 11 are both determined to be areas of maximum density,
The next regions 13 and 13 'are determined as regions having a slightly lighter density than that, and thereafter, the regions are sequentially cut out by a constant width to determine the density.

This density can be expressed as a dot density when the ink is transferred by the thermal head 71.
When this density is expressed by the optical density DL, when the optical density DL of the outermost peripheral portion is DL = DL0,
It may be determined from the smaller constant constant K as in the following equation.

[0040]

## EQU1 ## DL = K ^n-1 · DL0 Here, n is a natural number in which the outermost circumference is 1, the inner circumference is 2, the inner circumference is 3, and so on.

For example, the outermost peripheral portions 12, 12 'having the highest concentration
Assuming that the optical density DL0 of 1. is 1.60 and the constant K is 0.9, the optical density of the regions 13 and 13 ′ located one layer inside from the outer periphery is 1.44 and the regions 14 and 14 ′ located inside thereof are 1 The density of each area can be determined in a manner such as .30.

This constant K is generally 0.95 to 0.
A value between 6 and 6 is preferable, but in practice, the optimum value varies from system to system due to differences in the lamp output during light irradiation, and so it is advisable to experimentally determine and use this. The constant K is not necessarily constant, and may be different for each layer, such as 0.90 for the first layer and 0.95 for the second and subsequent layers.

Furthermore, it is not always necessary to use a constant number, and the optimum value of the density of each layer may be obtained in advance by an experiment, and this density may be used as the density of each region. In this way, after cutting out the area and determining the density of each area, determine the dot density according to this information,
The thermal head 71 is driven and controlled. As a result, as is the case with the image in FIG. 4, it is possible to obtain a sheet on which ink has been transferred in such a manner that each figure has the highest dot density in a certain width and the dot density gradually decreases from the outer circumference. it can.

Therefore, when this sheet is irradiated with light as shown in FIG. 3, in the case of the figure shown in FIG. 4, the outermost regions 12, 1 are formed.
The maximum amount of heat generated per unit area is 2 ', and the amount of heat generated per unit area decreases toward the inner area. Since the outermost circumference is located at the edge of the figure, the heat dissipation from it is the fastest, but the original amount of heat generation is suppressed toward the inside, so when you look at the process from heat generation to cooling, the entire figure is almost uniform It will be in a state of heat generation and heat dissipation. As a result, it is possible to form a stereoscopic image having a flat top surface, as shown in the lower part of FIG.

Also, a large square 10 and a small square 1
In the case of 1, the process from the start of heat generation to the cooling is substantially the same, and heat does not remain only in the larger square 10, so that the heights of both figures are uniform. This is because the average optical density of the large square 10 as a whole is smaller than that of the smaller square 11.

As a result of the above, according to this embodiment, it is possible to form a stereoscopic image in which square figures of different sizes are raised at the same height and the top surface is flat. Next, an example of how to set the optical density when another figure is formed by the same method will be described.

FIG. 6 is a cross-sectional view of a figure before light irradiation and a three-dimensional image after thermal expansion is completed after light irradiation when two large and small circles are irradiated with light for three-dimensionalization. According to the method of the embodiment, the circle 20 having a large area and the circle 21 having a small area both have substantially the same height, and can be three-dimensionally flat.

FIG. 7 is a figure in which two circles overlap.
Even in the case of such a figure 30, by dividing the figure according to the processing procedure shown in FIG. 5, the entire figure can be made into a uniform three-dimensional shape. FIG. 8 shows a donut-shaped figure 40 having a white background in the center. Even in the case of such a figure, the figure can be sequentially divided from the portion in contact with the white background by the above-described procedure to achieve a good three-dimensional shape. That is, in the detection of the outer circumference in FIG. 5, in such a donut-shaped figure, both the outer diameter circle and the inner diameter circle are detected as the outer circumference, and the areas 41 and 47, 42 and 46, 43 and 44 are detected.
Are determined to have the same concentration. As a result, even a donut-shaped figure can form a flat stereoscopic image.

Although the embodiments have been described above, if a figure having a fixed shape and size is to be three-dimensionalized,
A pattern with the optimum optical density should be stored together with the shape in the storage device in advance so that the optical density gradually decreases from the part near the edge in one figure, and the pattern with the larger area in two or more figures Printing may be performed so that the average of the optical densities is lower than that of a figure having a smaller area, and a stereoscopic image having a constant height may be obtained by a simple printing device.

In this case, instead of changing the optical density of each area by changing the dot density using the same ink, a method of changing the optical density of each area using inks of different darkness may be used. . Further, it is also possible to perform printing in a state in which the optical density is changed by using a blurring technique, instead of performing clear area division.

Further, instead of the thermal transfer method as in the embodiment, the optical density can be measured by various methods such as an electrophotographic method, drawing by a pen plotter, and a method of handwriting by preparing a plurality of pens having different darkness. A changing figure may be formed. As described above, according to the embodiment, it is possible to form a stereoscopic image in which the height of each figure is constant. Therefore, for example, when manufacturing a stamp composed of a complicated figure, it is possible to finish the whole to the same height, and to provide a stamp capable of accurately transferring such a complicated figure. It also has a great effect on the application.

Although the embodiment has been described above, the present invention is not limited to this embodiment. In addition, as long as it does not deviate from the gist of the present invention, a method different from the embodiment is used. Of course, you can. For example,
Instead of forming a flat three-dimensional image as a whole, a light absorber may be transferred so that the optical densities of the respective portions are made different in order to intentionally form a three-dimensional image having different heights.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a heat-expandable sheet used in Examples.

FIG. 2 is an explanatory diagram showing a process of thermally transferring an image of a light absorbing material onto a thermally expandable sheet in an example.

FIG. 3 is an explanatory diagram showing a step of three-dimensionalizing a heat-expandable sheet in an example.

FIG. 4 is an explanatory view showing a method of adhering a light absorber when forming a stereoscopic image of two large and small squares and a sectional shape of a completed three-dimensional figure as an example.

FIG. 5 is a flowchart of a process for obtaining conditions for forming an image on the heat-expandable sheet with the light absorbing agent in the example.

FIG. 6 is an explanatory diagram showing a method of attaching a light absorbing agent when two large and small circles are three-dimensionalized by the method of the embodiment and a sectional shape of a finished three-dimensional figure.

FIG. 7 is an explanatory diagram showing a method of adhering a light absorber when a figure formed by overlapping two circles is three-dimensionally formed by the method of the example, and a sectional shape of a finished three-dimensional figure.

FIG. 8 is an explanatory diagram showing a method of adhering a light absorber when a donut-shaped figure is three-dimensionally formed by the method of the example, and a sectional shape of a finished three-dimensional figure.

FIG. 9 is an explanatory diagram showing a method of adhering a light absorber and a sectional shape of a finished three-dimensional figure in the case of forming a three-dimensional image of two large and small squares by a conventional technique. FIG. 3 is a cross-sectional view of a stereoscopic image after thermal expansion.

[Explanation of symbols]

60 ... Thermally expandable sheet, 61 ... Thermal expansion layer, 62
... Base material, 63 ... Foaming agent, 64 ... Light absorbing image, 71 ... Thermal head, 72 ... Thermal transfer ribbon, 73 ... Lamp, 74 ... Fan.

Claims (6)

[Claims] 1. A desired image is formed by adhering a material having higher light absorption than the heat-expandable sheet to the surface of the sheet,
Then, in the method for producing a sheet with a three-dimensional image by forming a selective ridge based on the difference in light absorption by irradiating the heat-expandable sheet with light containing infrared rays, when forming the image, the image A method for producing a sheet with a three-dimensional image, characterized in that the material having a high light absorbing property is adhered onto a heat-expandable sheet so that the optical density changes depending on the position inside. 2. The method for manufacturing a sheet with a stereoscopic image according to claim 1, wherein for each figure included in the image,
A method for producing a sheet with a three-dimensional image, characterized in that the material having a high light-absorbing property is adhered onto a heat-expandable sheet so that the optical density becomes smaller as the distance from the edge of the figure becomes larger. 3. The method for producing a sheet with a stereoscopic image according to claim 1, wherein the image includes two or more figures having different areas, and the figure having a larger area has a smaller average optical density. A method for producing a sheet with a three-dimensional image, characterized in that the material having a high light absorbing property is attached onto a heat-expandable sheet. 4. An image forming apparatus for forming an image by adhering a material having a higher light-absorbing property to the surface of a heat-expandable sheet, the image acquiring information of an image to be formed. Information acquisition means, and figure dividing means for dividing each figure included in the image information based on the image information acquired by the image information acquisition means by extracting a region at a constant width from the edge of each figure. And an optical density setting unit that sets the optical density to a smaller value in a region farther from the edge of the figure with the extracted region as a unit, and based on the setting content of the optical density setting unit, the An image forming apparatus comprising: an attaching unit that attaches a highly absorbent material. 5. A three-dimensional image forming sheet in which an image is transferred by adhering a material having a higher light absorption property to the surface of the heat-expandable sheet, and each figure in the image has a respective edge. A sheet for three-dimensional image formation, wherein the material having high light absorption is attached so that the optical density becomes smaller as the distance from the sheet becomes larger. 6. A three-dimensional image forming sheet in which an image is transferred by adhering a material having a higher light absorbing property to the surface of the heat-expandable sheet, the sheet having a different area in the image.
A stereoscopic image forming sheet comprising the above-mentioned figures, wherein the material having a high light-absorbing property is attached so that the figure having a larger area has a smaller average optical density.