具体实施方式：
[0058]Hereinafter, embodiments of the present disclosure are described in detail while referencing the drawings. In the following embodiments, a three-dimensionally shaped object is described as an embodiment of the technical idea of the present disclosure, but the present disclosure is not limited thereto. To elucidate the description, some of the sizes, positional relationships, and the like of the constituents illustrated in the drawings have been exaggerated and some of the shapes have been simplified. In addition, in the following description, constituents and steps that are identical or substantially identical are assigned the same reference numerals and descriptions are appropriately foregone.
Embodiment 1: Three-Dimensionally Shaped Object
[0059]The configuration of a three-dimensionally shaped object 1 according to Embodiment 1 of the present disclosure is described while referencing FIG. 1 to FIG. 3B. FIG. 1 is an appearance view of the three-dimensionally shaped object 1. FIG. 2A is a plan view schematically illustrating the configuration of the three-dimensionally shaped object 1. FIG. 2B is a cross-sectional view schematically illustrating the configuration of the three-dimensionally shaped object 1. FIGS. 3A and 3B are drawings explaining use examples of the three-dimensionally shaped object 1, and are appearance view of decorated three-dimensional objects 8 and 8A. In this application, “three-dimensionally shaped object” means a sheet-like printed object having unevennesses on the surface of one side due to being thicker in some portions than others. Particularly, a three-dimensionally shaped object that has color on the surface of a side that has unevennesses is appropriately referred to as “2.5D image.” Moreover, in this application, unless otherwise noted, “top” and “bottom” in FIG. 2B and the other cross-sectional drawings describe the same “top” and “bottom.”
[0060]As illustrated in FIG. 1, a 2.5D image (the three-dimensionally shaped object) 1 according to Embodiment 1 of the present disclosure is a sheet-like flexible member in which an image and unevennesses accompanying the image are formed on one surface. In the following, the surface of the 2.5D image 1 on which the unevennesses or the unevennesses and the image is formed is referred to as the “front side” of the 2.5D image 1, and the surface of the side opposite the front side of the 2.5D image 1 is referred to as the “back side” of the 2.5D image 1. In the present embodiment, as illustrated in FIG. 2A and FIG. 2B, a design of grapes is drawn in the 2.5D image 1. In this design, the globes of the bunch of grapes are raised high (the thickness is great), the leaves of the bunch of grapes are raised lower than the globes of the bunch of grapes, and the background is the lowest and flat. The overall shape of the 2.5D image 1 is square, but the shape, the size, and the like of the 2.5D image 1 is appropriately selected depending on purpose. Furthermore, the 2.5D image 1 has elasticity and, as illustrated in FIG. 1, deforms into three-dimensional curved shapes such as spherical surfaces and hyperbolic paraboloidal surfaces. For example, the 2.5D image 1 can be affixed to an article B having a three-dimensional curved surface such as that illustrated in FIG. 3A to produce a decorated three-dimensional object 8. The 2.5D image 1 can be affixed to the surface of an article of any shape without slack, tears, or the like (details are given later in the description of the production method). Examples of the article include household items such as furniture, containers such as beverage bottles, and packaging materials, but are not limited thereto.
[0061]As illustrated in FIG. 2B, the 2.5D image 1 according to the present embodiment includes a first base 21, a thermally expansive layer 3 provided on the first base 21 and having unevennesses in the top surface, an ink receiving layer 4 provided with substantially uniform thickness on the entire surface of the thermally expansive layer 3, and a color layer 6 that is formed on a surface of the ink receiving layer 4, namely the front side of the 2.5D image 1, to form an image. In the following, the surface of the first base 21 on which the thermally expansive layer 3 is provided is referred to as the “front side” of the first base 21, and the surface of the side opposite the front side of the first base 21 is referred to as the “back side” of the first base 21. The surface of the thermally expansive layer 3 on which the ink receiving layer 4 is provided (also, in the 2.5D image 1, the top surface having the unevennesses) is referred to as the “front side” of the thermally expansive layer 3, and the surface of the side opposite the front side of the thermally expansive layer 3 is referred to as the “back side” of the thermally expansive layer 3. The surface of the ink receiving layer 4 on the thermally expansive layer 3 side is referred to as the “back side” of the ink receiving layer 4, and the surface of the side opposite the back side of the ink receiving layer 4 is referred to as the “front side” of the ink receiving layer 4. The 2.5D image 1 includes an adhesive layer 23 on the entire back side, that is, on the entire back side of the first base 21. The 2.5D image 1 is produced using a three-dimensionally shaped object forming sheet 10 illustrated in FIG. 4. Note that the unevennesses of the 2.5D image 1 can also be expressed by being formed in the surface of the thermally expansive layer 3 side of the 2.5D image 1. The three-dimensionally shaped object forming sheet 10 is also referred to as a “thermally expandable sheet 10.”
Embodiment 1: Thermally Expandable Sheet
[0062]The configuration of the thermally expandable sheet 10 used in the formation of the 2.5D image 1 is described below while referencing FIG. 4. FIG. 4 is a cross-sectional view schematically illustrating the configuration of the three-dimensionally shaped object forming sheet (the thermally expandable sheet) 10 according to Embodiment 1 of the present disclosure. As illustrated in FIG. 4, the thermally expandable sheet 10 according to the present embodiment includes a base 2 obtained by laminating a second base 22 on the first base 21, the thermally expansive layer 3 provided having a uniform thickness on the entire surface of the first base 21 side of the base 2, and the ink receiving layer 4 provided having a uniform thickness on the entire surface of the thermally expansive layer 3. In the following, the top surface of the thermally expandable sheet 10 is referred to as the “front side” of the thermally expandable sheet 10, and the surface of the side opposite the front side of the thermally expandable sheet 10 is referred to as the “back side” (or the “bottom surface”) of the thermally expandable sheet 10. The front sides and the back sides of the first base 21, the thermally expansive layer 3, and the ink receiving layer 4 are the same as described for the 2.5D image 1. Note that, in some cases, the front side of the first base 21 is referred to as the front side of the base 2. The base 2 includes the adhesive layer 23 between the first base 21 and the second base 22. The thermally expandable sheet 10 is an object to be printed (or object to be processed) in which color inks that form the color layer 6 are printed on the front side (top surface) and black ink that forms a photothermal conversion layer 5 (see FIG. 6C) is printed on the back side (bottom surface). It is sufficient that the dimensions of the thermally expandable sheet 10 are greater than or equal to the dimensions of the 2.5D image 1. Moreover, the dimensions of the thermally expandable sheet 10 correspond to the printer used to form the photothermal conversion layer 5 and the color layer 6. For example, the thermally expandable sheet 10 is an A3 paper size.
[0063]Base
[0064]The base 2 supports the soft thermally expansive layer 3. The base 2 imparts enough strength (rigidity) for the thermally expandable sheet 10 to function as an object to be printed. The base 2 has strength sufficient to prevent wrinkles, undulations, and the like from forming in the thermally expandable sheet 10 when the thermally expansive layer 3 distends in part. Furthermore, the base 2 has flexibility and heat resistance corresponding to the transport mechanism of the coating device, the printer, and the like used when forming the thermally expansive layer 3. In this application, the term “heat resistance” refers to resistance to the heat applied to the constituents of the thermally expandable sheet 10 and the 2.5D image 1 during the production of the thermally expandable sheet 10 and the 2.5D image 1, and particularly to resistance to the heat that causes the thermally expansive layer 3 to distend. The base 2 has a laminated structure obtained by laminating the second base 22 on the first base 21, on which the thermally expansive layer 3 is provided. Furthermore, the base 2 includes the adhesive layer 23 between the first base 21 and the second base 22. As such, with the base 2, the first base 21 and the second base 22 can be peeled from each other. In the following, the surface of the second base 22 on the first base 21 side is referred to as the “front side” of the second base 22, and the surface of the side opposite the front side of the second base 22 is referred to as the “back side” of the second base 22. Note that, in some cases, the back side of the second base 22 is referred to as the back side of the base 2. The first base 21, the second base 22, and the adhesive layer 23 individually have heat resistance. It is sufficient that the first base 21, the second base 22, and the adhesive layer 23 have the strength described above while laminated (that is, while configured as the base 2). Moreover, as described later, the photothermal conversion layer 5, which releases heat that causes the thermally expansive layer 3 to distend, is printed on the back side of the thermally expandable sheet 10 (that is, on the back side of the second base 22). Accordingly, it is preferable that the thickness of the base 2 be small while maintaining strength so as to facilitate the propagation of the heat released by the photothermal conversion layer 5 to the thermally expansive layer 3. Additionally, it is preferable that the first base 21, the second base 22, and the adhesive layer 23 individually have high thermal conductivity.
[0065]The elasticity of the first base 21, on which the thermally expansive layer 3 is provided, is greater than the elasticity of the second base 22. In the 2.5D image 1, the first base 21 can stretch together with the thermally expansive layer 3 due to external forces while reinforcing the soft thermally expansive layer 3. Accordingly, it is preferable that the coefficient of extension of the first base 21 is substantially equivalent to the coefficient of extension of the thermally expansive layer 3 prior to thermal expansion, or is lower than the coefficient of expansion of the thermally expansive layer 3 prior to thermal expansion. Moreover, it is preferable that the coefficient of extension of the first base 21 is greater than or equal to the coefficient of extension of the region in the 2.5D image 1 where the coefficient of extension is lowest (the region where the thickness is greatest). Furthermore, it is preferable that the first base 21 can stretch and contract together with the thermally expansive layer 3 in the 2.5D image 1. As a result of the first base 21 stretching and contracting, not only does the 2.5D image 1 stretch due to external forces, but also contracts to return to the shape prior to stretching. As such, it is easier to affix the 2.5D image 1 to an article. Moreover, the 2.5D image 1 can be affixed to an article having cushioning properties such as the seat of a chair. It is preferable that the first base 21 has durability greater than or equal to that of the thermally expansive layer 3. Furthermore, depending on the use of the 2.5D image 1, it is preferable that the first base 21 has water resistance. The front side of the first base 21 has high adhesiveness to the thermally expansive layer 3, and the back side of the first base 21 has high adhesiveness to the adhesive layer 23. In one example, the first base 21 is a resin film and is formed from a resin selected from polyethylene, polypropylene, polyvinyl alcohol, polyvinyl chloride, and polyurethane resins, copolymers thereof, and the like. The first base 21 is formed having a thickness whereby the required strength, the required coefficient of extension, and the like can be obtained.
[0066]The second base 22 is a member that primarily ensures the strength (rigidity) of the base 2. The second base 22 suppresses the elasticity of the base 2 and the thermally expandable sheet 10 and maintains the shape of the thermally expandable sheet 10 when the thermally expandable sheet 10 is transported by the transport mechanisms (transport rollers, for example) of the printer, the light irradiation device, and the like. Accordingly, it is preferable that the second base 22 be substantially non-elastic. Moreover, it is preferable that the second base 22 is formed from a material that allows ink to be printed on the back side. In cases where it is difficult to print ink on the back side of the second base 22, an ink receiving layer (not illustrated in the drawings) similar to the ink receiving layer 4 (described later) is provided on the back side of the second base 22. While configured as the thermally expandable sheet 10, the second base 22 is laminated on the first base 21 with the adhesive layer 23 disposed therebetween, but the second base 22 is removed when producing the 2.5D image 1. The adhesive layer 23 remains on the back side of the 2.5D image 1 (see FIG. 2B). Accordingly, the front side of the second base 22 peels from the adhesive layer 23 easier than the back side of the first base 21. Specifically, as the second base 22, it is possible to use a non-elastic resin film or the like made from high-quality paper that has been subjected to silicone resin processing, kraft paper that has been subjected to silicone resin processing, polyethylene terephthalate (PET), or the like.
[0067]In the base 2, the adhesive layer 23 functions as an adhesive that bonds the first base 21 to the second base 22. The adhesive layer 23 also functions as an adhesive that bonds the 2.5D image 1 to the article. Accordingly, it is preferable that the adhesive layer 23 is formed from a known adhesive that has characteristics such as adhesive strength and water resistance that correspond to the first base 21, the article, and the uses thereof. Furthermore, it is preferable that the adhesive layer 23 has strong adhesiveness that prevents the first base 21 from peeling from the second base 22 due to the first base 21 conforming to the thermally expansive layer 3 and trying to deform when the thermally expansive layer 3 distends in part. Additionally, it is preferable that the adhesive layer 23 has sufficient heat resistance.
[0068]Note that tack paper can be used as the base 2 that includes the first base 21, the second base 22, and the adhesive layer 23. Tack paper is commercially available and is used for seals that can be stretched by peeling off the release paper.
[0069]Thermally Expansive Layer
[0070]The thermally expansive layer 3 forms unevennesses on the front side of the 2.5D image 1 by distending in part. For example, the thermally expansive layer 3 is a film that is used in known thermally expandable sheets that contains thermally expandable microcapsules and a thermoplastic resin as a binder. The thermally expansive layer 3 is formed having a uniform thickness t0 on the base 2. The thermally expandable microcapsules are formed from a thermoplastic resin and contain a volatile solvent. While dependent on the type of the thermoplastic resin and the type of the volatile solvent, the volatile solvent vaporizes when the thermally expandable microcapsules are heated to about 80° C. or higher and, as a result, distend to a size in accordance with the heating temperature and the heating time. Therefore, the distension of the thermally expandable microcapsules is limited to the region of the thermally expandable sheet 10 where the thermally expansive layer 3 was heated. As a result, the front side of the thermally expansive layer 3, which is not fixed to the base 2, rises, and unevennesses are formed in the front side of the thermally expansive layer 3, which is not fixed. This partial heating of the thermally expansive layer 3 is performed by the photothermal conversion layer 5 (see FIG. 6C), which is made from black ink and is formed on the back side of the thermally expandable sheet 10, converting light and releasing heat. Moreover, as described in the modified examples later, the partial heating of may be performed by a photothermal conversion layer 5A (see FIG. 2C), which is made from black ink and is formed on the front side of a thermally expandable sheet 10A, converting light and releasing heat. The thermally expansive layer 3 may contain a white pigment such as titanium oxide. By including a white pigment in the thermally expansive layer 3, the base color of the thermally expansive layer 3 can be made white so that the color layer 6 formed on the front side of the thermally expansive layer 3 will exhibit a clear appearance. Depending on the appearance of the 2.5D image 1, the thermally expansive layer 3 may be colored to a desired color by a (carbon black-free) pigment other than black. Furthermore, depending on the use of the 2.5D image 1, the thermally expansive layer 3 has water resistance.
[0071]The thermally expansive layer 3 distends, for example, to a thickness that is, at maximum, about 10-times the thickness prior to distending. The thickness t0 of the thermally expandable sheet 10 prior to distending, that is, the thickness t0 in the region (the background or the like of the design) that does not distend is set in accordance with the desired height of the highest convexity. The thermally expansive layer 3 has elasticity prior to distending. Moreover, the thermally expansive layer 3 has elasticity in at least the thickness t0 portion after distending as the 2.5D image 1. Note that in the distended thermally expansive layer 3, elasticity tends to be lower in the regions that are thicker than the thickness t0, that is, in the regions where the amount of distension is greater.
[0072]Ink Receiving Layer
[0073]The thermally expansive layer 3 generally is hydrophobic, and ink does not readily adhere thereto. As such, the ink receiving layer 4 is provided to cause the ink of the color layer 6 to adhere. The ink receiving layer 4 includes porous silica or alumina that absorbs ink into gaps, a super absorbent polymer that swells to absorb ink, or the like, and is formed having a thickness of 10 to tens of μm depending on the material. Moreover, a receiving layer used in typical inkjet printer printing paper can be used as the ink receiving layer 4.
[0074]Photothermal Conversion Layer
[0075]As illustrated in FIG. 6C, in the production of the 2.5D image 1, the photothermal conversion layer 5 is formed as a black pattern on the back side of the thermally expandable sheet 10 except for in the region where the thickness of the 2.5D image 1 is the smallest (the thickness t0 region illustrated in FIG. 2B). After the unevennesses have been formed in the front side of the thermally expansive layer 3, the photothermal conversion layer 5 is removed from the thermally expandable sheet 10 together with the second base 22 of the base 2. Accordingly, the photothermal conversion layer 5 is not present in the 2.5D image 1. The photothermal conversion layer 5 is a layer that absorbs light of a specific wavelength region such as near infrared light (wavelength: 780 nm to 2.5 μm), converts the absorbed light to heat, and releases the converted heat. Specifically, the photothermal conversion layer 5 is made from, for example, typical carbon black-containing black (K) ink used for printing. The temperature of the photothermal conversion layer 5 reached due to the released heat depends on the gradation, that is, the density of the carbon black. The thermally expansive layer 3 distends in accordance with the temperature of the photothermal conversion layer 5 and forms the unevennesses in the front side. Accordingly, the photothermal conversion layer 5 is printed by gray scale printing and, when viewed from the front side, is printed at higher densities in regions where higher convexities are to be formed. Moreover, the pattern of the photothermal conversion layer 5 is printed on the back side of the thermally expandable sheet 10 and, as such, is a mirror image of the unevenness pattern of the 2.5D image 1. Note that the photothermal conversion layer 5 is not limited to absorbing light and may absorb electromagnetic waves containing radio waves, convert the absorbed electromagnetic waves to heat, and release the converted heat. Accordingly, the photothermal conversion layer 5 can also be described as an electromagnetic wave heat conversion layer 5. In this application, unless otherwise noted, the term “light” means near-infrared light that is converted to heat by the carbon black of the photothermal conversion layer 5.
[0076]Returning to the description of the 2.5D image 1, next, the elements of the 2.5D image 1 not included in the thermally expandable sheet 10, and the elements of the 2.5D image 1 that differ from the thermally expandable sheet 10 will be described. With the exception of the planar shape, the first base 21 is the same as the thermally expandable sheet 10. The ink receiving layer 4 conforms to the deformation of the top surface of the thermally expansive layer 3 and covers the thermally expansive layer 3.
[0077]Thermally Expansive Layer
[0078]The thermally expansive layer 3 of the 2.5D image 1 is a main element of the 2.5D image 1 and is a film in which the thickness differs by region so as to form the unevennesses on one side (the front side). In the thermally expansive layer 3 of the 2.5D image 1, the thickness of the region where the unevennesses are smallest, that is, the thinnest region, is the thickness t0. The thermally expansive layer 3 has flexibility and elasticity in the 2.5D image 1 as well. As described above, in the thermally expansive layer 3 of the 2.5D image 1, flexibility and elasticity tend to be lower in the regions having greater thickness. Accordingly, when producing a decorated three-dimensional object 8, it is preferable that the unevenness shapes, the heights of the convexities, the maximum length, and the like be designed such that the 2.5D image 1 deforms in accordance with the surface shape of the article B to which the 2.5D image 1 is to be affixed.
[0079]Color Layer
[0080]The color layer 6 is made from typical cyan (C), magenta (M), and yellow (Y) printing-use color inks. The color layer 6 is formed in a desired image pattern on the front side of the 2.5D image 1, that is, on the ink receiving layer 4, by full-color printing, for example. The color layer 6 may further contain white ink. Note that black in the color layer 6 is expressed by blending the three CMY colors, and carbon black-containing black ink is not used in the color layer 6. Depending on the use of the 2.5D image 1, a pigment-based ink, for example, is used to provide the color layer 6 with water resistance.
[0081]Decorated Three-Dimensional Object
[0082]Configurations of decorated three-dimensional objects according to the embodiments of the present disclosure are described while referencing FIG. 3A and FIG. 3B. As illustrated in FIG. 3A, the article B is a wine bottle having a typical shape. The 2.5D image 1 is affixed from the spherical shoulder portion onto the cylindrical body portion of the article B. The 2.5D image 1 is used as a label for decorating the article B. Note that the size of the 2.5D image 1 is not limited to sizes that can be affixed to a portion of the surface of a small article. For example, as illustrated in FIG. 3B, the size of a 2.5D image 1C (the shaded region in the drawing) may be a size that can be affixed to the entire front side (the front sides of the seat and the backrest) of an article C, which is a backrest-seat integrated chair wherein the seat has a gentle hyperbolic paraboloidal surface.
[0083]Production Method for 2.5D Image and Decorated Three-Dimensional Object Production Device for 2.5D Image
[0084]Next, a simple description is given of the devices used in the production of the thermally expandable sheet and the 2.5D image according to the present disclosure. A coating device that forms the thermally expansive layer 3, prior to distending, on the base 2 is used in the production of the thermally expandable sheet 10. Furthermore, as necessary, a known cutting machine is used to cut the thermally expandable sheet 10 to desired dimensions. A printer and a light irradiation device are also used in the production of the 2.5D image 1. The printer prints the photothermal conversion layer 5 and the color layer 6 on the thermally expandable sheet 10. The light irradiation device irradiates the thermally expandable sheet 10 with near-infrared light and causes the photothermal conversion layer 5 to release heat, thereby causing the thermally expansive layer 3 to distend.
[0085]The coating device is a device that applies coating material to the sheet-like base to form a coating film having a uniform thickness. A known device using a bar coater system, a roll coater system, a spray system, or the like can be used for the coating device. It is preferable that the coating device uses a bar coater system suitable for coating at a uniform thickness.
[0086]The printer prints the photothermal conversion layer 5 and the color layer 6. An off-set printer, an inkjet printer, or other known printer is used depending on the print quality, production model (mass production, small quantity production), and the like. Moreover, the printer satisfies specifications corresponding to the dimensions and the thickness of the object to be printed, namely the thermally expandable sheet 10. The printer prints the photothermal conversion layer 5 and the color layer 6 by a method in which the thermally expansive layer 3 is not heated to, or higher than, the expansion starting temperature of the thermally expansive layer 3 (for example, 80° or higher). The printer may be a printer that can separate the inks by use and print the photothermal conversion layer 5 and the color layer 6 by the same system. Moreover, the printing system of the printer that prints the photothermal conversion layer 5 and the printing system of the printer that prints the color layer 6 may be different from each other.
[0087]The light irradiation device is a device that irradiates the photothermal conversion layer 5 of the thermally expandable sheet 10 with light and causes the photothermal conversion layer 5 to heat the thermally expansive layer 3, thereby causing the thermally expansive layer 3 to distend. A known device for forming a conventional three-dimensionally shaped object using a conventional thermally expandable sheet can be used as the light irradiation device. The light irradiation device satisfies specifications corresponding to the thickness of the object to be irradiated, namely the 2.5D image 1. Specifically, the light irradiation device includes a transport mechanism that transports the sheet-like object to be irradiated, a light source that irradiates light including near-infrared light that is converted to heat by the photothermal conversion layer 5, a reflection plate that reflects the light irradiated from the light source, and a cooler that cools the device. In one example, the light source is a halogen lamp. The light source is provided across the entire width of the object to be irradiated. In order to efficiently irradiate the object to be irradiated with the light irradiated from the light source, the reflection plate is formed as a substantially semi-cylindrical cylindrical curved surface and has a mirror face on the inner surface. The reflection plate covers the side opposite to the side of the light source facing the object to be irradiated. The cooler is an air cooling-type fan, a water cooling-type radiator, or the like. In one example, the cooler is provided in the vicinity of the reflection plate.
[0088]Production Method for 2.5D Image
[0089]Next, the production method for the 2.5D image 1 according to Embodiment 1 will be described while referencing FIG. 5, FIGS. 6A to 6D and, as appropriate, FIGS. 2A to 2C and FIG. 4. FIG. 5 is a flowchart illustrating the flow of the production method for the three-dimensionally shaped object 1. FIG. 6A is a schematic view (cross-sectional view) for explaining a base laminating step in the production method for the three-dimensionally shaped object 1. FIG. 6B is a schematic view (cross-sectional view) for explaining a thermally expansive layer forming step and a ink receiving layer forming step in the production method for the three-dimensionally shaped object 1. FIG. 6C is a schematic view (cross-sectional view) for explaining a photothermal conversion layer printing step and an image printing step in the production method for the three-dimensionally shaped object 1. FIG. 6D is a schematic view (cross-sectional view) for explaining a light irradiation step in the production method for the three-dimensionally shaped object 1. As illustrated in FIG. 5, in the production method for the 2.5D image 1 according to the present embodiment, a thermally expandable sheet production step S10 for producing the thermally expandable sheet 10, a photothermal conversion layer printing step S20, an image printing step S30, and a light irradiation step S40 are sequentially performed. Thereafter, a base peeling step S52 and an affixing step S53 are sequentially performed. Thus, the decorated three-dimensional object 8 is produced. As necessary, a cutting step S51 is performed prior to the affixing step S53. In the thermally expandable sheet production step S10, a base laminating step S11, a thermally expansive layer forming step S12, and an ink receiving layer forming step S13 are sequentially performed. Furthermore, as necessary, a cutting step S14 is performed.
[0090]In the base laminating step S11, as illustrated in FIG. 6A, a base paper 20 of the base 2 is produced. The base paper 20 is the base 2 prior to being cut, and, for example, is rolled paper having a size corresponding to the coating device used in the thermally expansive layer forming step S12 and the ink receiving layer forming step S13. In the base laminating step S11, the first base 21 and the second base 22 having the dimensions of the base paper 20 are bonded to each other using the adhesive layer 23.
[0091]In the thermally expansive layer forming step S12, the thermally expansive layer 3 is formed on the surface of the first base 21 side (the front side of the first base 21) of the base paper 20 (see FIG. 6B). First, a slurry is prepared by blending the thermally expandable microcapsules, a white pigment, and a thermoplastic resin solution. Next, the prepared slurry is coated on the base paper 20 by the coating device. The coated slurry is dried and, thus, a thermally expansive layer 3 having the desired thickness t0 is formed. Note that multiple coatings are performed as necessary.
[0092]In the ink receiving layer forming step S13, as illustrated in FIG. 6B, the ink receiving layer 4 is formed on the thermally expansive layer 3. First, as in the thermally expansive layer forming step S12, a slurry of the ingredients of the ink receiving layer 4 is prepared. Next, the prepared slurry is coated on the thermally expansive layer 3 on the base paper 20 by the coating device. Then, the coated slurry is dried and, thus, an ink receiving layer 4 having a predetermined thickness is formed.
[0093]In the cutting step S14, the base paper 20 and the thermally expansive layer 3 and the ink receiving layer 4 formed on the base paper 20 are cut, thereby obtaining a thermally expandable sheet 10 having dimensions corresponding to the printer to be used in the photothermal conversion layer printing step S20 and the image printing step S30 (see FIG. 4).
[0094]In the photothermal conversion layer printing step S20, as illustrated in FIG. 6C, the photothermal conversion layer 5 is printed using black ink on the back side (the surface of the base 2 side) of the thermally expandable sheet