Patent Publication Number: US-2020298606-A1

Title: Medium including thermally expansive layer and production method for medium including thermally expansive layer

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of Japanese Patent Application No. 2019-052917, filed on Mar. 20, 2019, the entire disclosure of which is incorporated by reference herein. 
     FIELD 
     This application relates to a medium including a thermally expansive layer that uses a thermally expandable material that foams and expands in accordance with an amount of heat absorbed and relates to a production method for the medium including the thermally expansive layer. 
     BACKGROUND 
     A thermally expandable sheet that has a thermally expansive layer, which includes a thermally expandable material that foams and expands in accordance with an absorbed heat amount, formed on one side of a base sheet is conventionally known. Due to formation of a layer that converts light to heat on this thermally expandable sheet and irradiation this thermal conversion layer with light, the thermally expansive layer can be expanded in part or on the whole. Moreover, methods are known for formation of a shaped object having three-dimensional unevenness on a thermally expandable sheet causing a change of shape of the thermal conversion layer (for example, see Unexamined Japanese Patent Application Kokai Publication No. S64-28660 and Unexamined Japanese Patent Application Kokai Publication No. 2001-150812. 
     In conventional thermally expandable sheets, since heat from the layer for converting light to heat transfers to the surrounding area, this surrounding area may also expand. As a result, the outer edge portions (edges) of the portion caused to rise (convexity), due to the foaming of the thermally expandable material, becomes round which is problematic in that the outline of the convexity rises. For example, in the case where a protrusion is formed into a shape of a character, there is a problem in that the character becomes rather illegible due to, for example, the outline of the character becoming deformed or the entirety of the character becoming swollen. 
     In consideration of the aforementioned circumstances, an objective of the present disclosure is to provide a medium that includes a thermally expansive layer that can sharply form outer edge portions (edges) of convexities of the thermally expansive layer and to provide a method of producing the medium that includes the thermally expansive layer. 
     SUMMARY 
     A medium including: 
     a base; and 
     a thermally expansive layer provided on the base, the thermally expansive layer including thermally expandable material, 
     wherein the thermally expansive layer further includes a porous material. 
     A method of producing a medium including a thermally expansive layer, the method including: 
     forming a thermally expansive layer including thermally expandable material on a base, 
     wherein porous material is added to the thermally expansive layer. 
     The present disclosure can provide a medium including a thermally expansive layer enabling outer edge portions of convexities of the thermally expansive layer to be sharply formed and provide a method for producing the medium including the thermally expansive layer. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more complete understanding of this application can be obtained when the following detailed description is considered in conjunction with the following drawings, in which: 
         FIG. 1  is a cross-sectional view illustrating an overview of a thermally expandable sheet according to an embodiment; 
         FIG. 2A  is a diagram demonstrating a production method of the thermally expandable sheet according to the embodiment; 
         FIG. 2B  is another diagram demonstrating the production method of the thermally expandable sheet according to the embodiment; 
         FIG. 2C  is yet another diagram demonstrating the production method of the thermally expandable sheet according to the embodiment; 
         FIG. 3  is a flowchart demonstrating a production method of a shaped object according to the embodiment; 
         FIG. 4A  is a cross-sectional view demonstrating the production method of the shaped object according to the embodiment; 
         FIG. 4B  is another cross-sectional view demonstrating the production method of the shaped object according to the embodiment; 
         FIG. 5  is a diagram illustrating an overview of an expansion device; 
         FIG. 6A  is a diagram demonstrating a convexity of a thermally expansive layer of a conventional example; 
         FIG. 6B  is a diagram demonstrating a convexity of a thermally expansive layer according to the embodiment; 
         FIG. 7  is a diagram illustrating a portion for which the height of the convexity of the thermally expandable sheet according to an implemented example is measured; 
         FIG. 8A  is diagram illustrating the height of the convexity of the thermally expandable sheet according to the implemented example; and 
         FIG. 8B  is a diagram illustrating the height of a thermally expandable sheet according to a comparison example. 
     
    
    
     DETAILED DESCRIPTION 
     A medium including a thermally expansive layer and method for producing the medium including the thermally expansive layer according to the present embodiment are described in detail below with reference to the drawings. 
     In the present embodiment, a thermally expandable sheet  20  having a base  21  that is a sheet-type is described as an example of a medium  10  that includes a thermally expansive layer. 
     In the embodiment, a shaped object is expressed on a surface by the rising of a thermally expansive layer  22  on a top surface of the medium  10 . Also, in the present disclosure, the term “shaped object” broadly includes shapes such as simple shapes, geometrical shapes, characters, decorations, or the like. The term “decorations” refers to objects that appeal to the aesthetic sense through visual and/or tactile sensation. The term “shaping” (or forming) is not limited to the simple formation of the shaped object but rather is to be construed to also include concepts such as decorating and ornamenting. Further, the term “decorative shaped object” indicates a shaped object formed as a result of decoration or ornamentation. 
     The shaped object of the present embodiment has unevenness in a direction, such as the Z-axis direction, perpendicular to a standard surface taken to be a two-dimensional surface, such as the XY plane, within a three-dimensional space. Although such a shaped object is one example of a three-dimensional (3D) image, to distinguish this three-dimensional image from three-dimensional images formed using so-called 3D printer technology, the shaped object is called a 2.5-dimensional (2.5D) image or a pseudo-three-dimensional (pseudo-3D) image. 
     Thermally Expandable Sheet  20   
     The thermally expandable sheet  20 , as illustrated in  FIG. 1 , includes the base  21 , the thermally expansive layer  22 , and an ink receiving layer  23 . 
     The base (base body)  21  is a sheet-like member for support of the thermally expansive layer  22  and the like. The thermally expansive layer  22  is provided on a surface (the front surface; the top surface in  FIG. 1 ) of the base  21 . Paper such as high-quality paper, or a sheet (including films) made from a resin such as polyethylene terephthalate (PET) is used as the base  21 . The paper is not limited to a sheet made from PET, and any known sheet can be used. Additionally, the resin is not limited to PET, and any resin can be used. Without particular limitation, examples of the resins include materials selected from polyolefin resins such as polyethylene (PE) and polypropylene (PP), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), and polybutylene terephthalate (PBT), polyester resins, polyamide resins such as nylon, polyvinyl chloride (PVC) resins, polystyrene (PS), polyimide resins, silicone resins, and the like. 
     The base  21  is provided with sufficient strength such that, when the thermally expansive layer  22  distends in part or on the whole due to foaming, the opposite side of the base  21  (the underside illustrated in  FIG. 1 ) does not rise. Moreover, the base  21  is provided with sufficient strength such that, during expansion of the thermally expansive layer  22 , shape as a sheet is not lost by generation of winkles, formation of large undulations, or the like. In addition, the base  21  has sufficient heat resistance so as to withstand heat during foaming of the thermally expansive layer  22 . The base  21  may further have elasticity and the base  21  may deform in accordance with the distension of the thermally expansive layer  22 , and the deformed shape of the base  21  may be maintained after the distension of the thermally expansive layer  22 . 
     The thermally expansive layer  22  is provided on a first side (the top surface in  FIG. 1 ) of the base  21 . The thermally expansive layer  22  is a layer that distends in size in accordance with a degree of heating (such as a heating temperature or a heating period). The thermally expansive layer  22  includes binder  31 , thermally expandable material (thermally-expandable microcapsules, micropowder)  32 , and porous material  33 . The thermally expandable material  32  and the porous material  33  are dispersed in the binder  31 . The thermally expansive layer  22  is not limited to a single layer. The thermally expansive layer  22  may include multiple layers that contain the thermally expandable material  32 . Moreover, the thermally expansive layer  22  may be formed by staking these layers. The thermally expansive layer  22  is provided with a thickness of, for example, 50 μm to 500 μm. Preferably, the thermally expansive layer  22  is provided with a thickness of 80 μm to 200 μm. 
     Any thermoplastic resin, such as an ethylene-vinyl acetate polymer or an acrylic polymer, may be used as the binder  31  of the thermally expansive layer  22 . Also, the thermally expandable material  32  encapsulates propane, butane, or another low boiling point substance inside shells of the thermoplastic resin. The shells are formed from a thermoplastic resin such as, for example, polystyrene, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, polyacrylic acid ester, polyacrylonitrile, polybutadiene, and copolymers thereof. Average particle size of the thermally expandable material  32  is about 5 μm to 50 μm, for example. When the thermally expandable material is heated to at least the temperature at which expansion begins, the shells made of resin soften, and the encapsulated low-boiling point volatile substance volatilizes, causing the shells to expand due to pressure in a balloon-like manner. Although dependent on characteristics of the used thermally expandable material  32 , the particle size of the thermally expandable material  32  after expansion increases to about five times the size prior to expansion. Further, variance exists in the particle size of the thermally expandable material  32 . Note that, while diagrams such as  FIG. 1  illustrate the particle size of the thermally expandable material  32  as being substantially uniform, not all particles have the same size. That is, there is variation in the particle size of the thermally expandable material  32 . 
     The porous material  33  is a material that includes fine pores. The material includes porous silica, porous ceramic (porous alumina, for example), and the like. One type or multiple types may be used as the porous material  33 . In the present embodiment, with the inclusion of the porous material  33  in the thermally expansive layer  22 , as described in detail further below, the edges of the swollen portions (convexity  22   a ) of the thermally expansive layer  22  can be sharpened. 
     In the thermally expansive layer  22 , although not limiting, it is preferable that the weight of the thermally expandable material  32  with respect to the total weight of the binder  31 , the thermally expandable material  32 , and the porous material  33  is 20 wt % to 60 wt %. Moreover, it is preferable that the weight of the porous material  33  with respect to the total weight of the binder  31 , thermally expandable material  32  and the porous material  33  is no less than 15 wt %, and that the weight of the porous material  33  is no greater than the binder  31  is wt % total weight of the binder  31 , the thermally expandable material  32 , and the porous material  33 . For example, the weight ratio of the binder  31  to the thermally expandable material  32  to the porous material  33  is 1:3:1. 
     The ink receiving layer  23  can be provided on the thermally expansive layer  22 . The ink receiving layer  23  is a for layer receiving and holding ink used in a printing step such as water-based ink of an inkjet printer. The ink receiving layer  23  is formed using a known material according to the type of ink to be used in the printing step. In a case where voids are to be used to receive ink, the ink receiving layer  23  includes porous silica, for example. In a case where the ink receiving layer  23  is to receive ink while being swollen, the ink receiving layer  23 , the ink receiving layer  23  includes a resin selected from, for example, polyvinyl alcohol (PVA) resin, a polyester resin, a polyurethane resin, an acrylic resin, and the like. 
     The ink receiving layer  23  may be omitted. For example, in a case where printing is to be performed with use of, for example, ultraviolet curable ink, the ink receiving layer  23  may be omitted. Additionally, since the thermally expansive layer  22  of the present embodiment includes the porous material  33  as described above, the thermally expansive layer  22  can be made to serve as an ink receiving layer. In this case as well, the ink receiving layer  23  may be omitted. 
     In the present embodiment, an electromagnetic wave thermal conversion layer (hereinafter also referred to simply as “thermal conversion layer” or “conversion layer”) for converting that converts electromagnetic waves into heat is provided on the top surface (front surface) of the thermally expandable sheet  20 , and is irradiated with electromagnetic waves to cause the thermal conversion layer to generate heat. The thermal conversion layer is heated due to being irradiated with electromagnetic waves and, as such, is also called a “heated layer.” The heat generated by the thermal conversion layer provided on the front surface of the thermally expandable sheet  20  is transmitted to the thermally expansive layer  22 . As a result, the thermally expandable material in the thermally expansive layer  22  foams and distends. The electromagnetic waves are converted to heat more quickly where the thermal conversion layer is provided than in other regions where the thermal conversion layer is not provided. As such, the regions in close proximity to the thermal conversion layer can be exclusively and selectively heated, and specific regions of the thermally expansive layer  22  can be exclusively and selectively caused to distend. The thermal conversion layer may be provided on the bottom surface (back surface) or may be provided on the top surface and the bottom surface. 
     Production Method of Thermally Expandable Sheet 
     Next, a production method of the thermally expandable sheet  20  is described with reference to  FIG. 2A  to  FIG. 2C . 
     First, the base (base body)  21  is prepared ( FIG. 2A ). For example, a roll of paper is used as the base  21 . However, the manufacturing method described further below is not limited to a roll, and an individual sheet may be used. 
     Next, the aforementioned binder  31 , the thermally expandable material  32 , and the porous material  33  are used in a known dispersion device or the like to prepare a coating liquid for forming the thermally expansive layer  22 . Subsequently, the coating liquid is applied on one of the surfaces of the base  21  using a known coating device such as a bar coater, roller coater, or a spray coater. Subsequently, the coating is dried, thereby forming the thermally expansive layer  22  as illustrated in  FIG. 2B . Both the application and the drying of the coating liquid may be repeated multiple times in order to obtain a target thickness of the thermally expansive layer  22 . Moreover, the thermally expansive layer  22  may be formed by use of a printing device or the like. 
     Next, a coating liquid is prepared using the material of the aforementioned ink receiving layer  23 . Subsequently, the liquid is applied on the thermally expansive layer  22  using a known application device such as the bar coater, the roller coater, or the spray coater. Both the application and the drying of the coating liquid may be repeated multiple times in order to obtain a target thickness of the ink receiving layer  23 . Subsequently, the coating is dried, thereby forming the ink receiving layer  23  as illustrated in  FIG. 2C . Moreover, the ink receiving layer  23  may be formed by use of a printing device or the like. 
     In a case where the base  21  is in roll-form, cutting is performed as necessary to obtain the thermally expandable sheet  20 . 
     The thermally expandable sheet  20  is produced by the steps described above. 
     Production Method of Shaped Object 
     Next, the flow of the process for producing the shaped object  40  using the thermally expandable sheet  20  is described with reference to the flowchart illustrated in  FIG. 3 , the cross-sectional views of the thermally expandable sheet  20  illustrated in  FIG. 4A  and  FIG. 4B . 
     First, the thermally expandable sheet  20  is prepared. Foaming data (data corresponding thermal conversion layer  81 ) indicating the portion to be foamed in the front surface of the thermally expandable sheet  20  and caused to distend is determined in advance. Next, the printing device is used to print a thermal conversion layer  81  onto the front surface of the thermally expandable sheet  20  (step S 1 ). The thermal conversion layer  81  is a layer formed by foamable ink that includes the electromagnetic wave thermal conversion material. The layer is formed by a foamable ink that includes carbon black, cesium tungsten oxide, or LaB 6 . The printing device prints on the front surface of the thermally expandable sheet  20  using the foamable ink. The printing is performed in accordance with the designated foaming data. As a result, the thermal conversion layer  81  is formed on the front surface of the thermally expandable sheet  20  as illustrated in  FIG. 4A . When the thermal conversion layer  81  is printed darkly, the amount of heat generated increases and, as a result, the thermally expansive layer  22  rises higher. Accordingly, the deformation height of the thermally expansive layer  22  can be controlled by controlling the density of the thermal conversion layer  81 . 
     Second, the thermally expandable sheet  20  onto which the thermal conversion layer  81  is printed is transported to the expansion device an expansion device  50  such that the front surface of the thermally expandable sheet  20  faces upward and then the thermal conversion layer  81  is irradiated with electromagnetic waves causing the thermally expansive layer  22  to distend (step S 2 ). 
     Specifically, the expansion device  50 , as illustrated in  FIG. 5 , includes a lamp heater, a reflection plate  52  that reflects the electromagnetic waves emitted from the irradiation unit  51  toward the thermally expandable sheet  20 , a temperature sensor  53  that measures the temperature of the reflection plate  52 , and a cooler  54  that cools the interior of the expansion device  50 , a pair of conveying rollers that hold therebetween the thermally expandable sheet  20  for conveyance along a conveyance guide, and a conveying motor for rotating the pair of conveying rollers. Also, the irradiation unit  51 , the reflection plate  52 , the temperature sensor  53 , and the cooler  54  are housed within a housing  55 . The pair of conveying rollers conveys the thermally expandable sheet  20  to underneath the irradiation unit  51 . 
     The lamp heater, for example, includes a halogen lamp, and the lamp heater irradiates the thermally expandable sheet  20  with the electromagnetic waves (light) in the near-infrared region (750 to 1,400 nm wavelength range), the visible light region (380 to 750 nm wavelength range), or the intermediate infrared region (1,400 to 4,000 nm wavelength range). The irradiation unit  51  is not limited to a halogen lamp, and a different configuration may be used as long as irradiation with the electromagnetic waves can be performed. Moreover, the wavelength of the electromagnetic waves is not limited to the aforementioned ranges. 
     The thermally expandable sheet  20  printed with the thermal conversion layers  81  illustrated in  FIG. 4A  is conveyed toward the expansion device  50  with the front surface face upward. At the expansion device  50 , the front surface of the thermally expandable sheet  20  is irradiated with the electromagnetic waves by the irradiation unit  51 . In the parts where the thermal conversion layers  81  are formed, the electromagnetic waves are converted to heat with greater efficiency in comparison to the parts where the thermal conversion layers  81  are not provided. Thus within the thermally expandable sheet  20 , parts where the thermal conversion layers  81  are formed are mainly heated, and, when the temperature at which expansion begins is reached, the thermally expandable material expands. As a result, the thermally expansive layer  22  in the regions where the thermal conversion layers  81  are formed expand and convexities  22   a  are formed as illustrated in  FIG. 4B . 
     The shaped object  40  is produced using the thermally expandable sheet  20  as a result of execution of the procedure described above. 
     Since the thermally expansive layer does not include porous material in the conventional example, the heat from the thermal conversion layer also transfers to the area surrounding the thermal conversion layer. As a consequence of this, the thermally expandable material in the area surrounding the thermal conversion layer also expands. As a result, the region (portion of  90  illustrated in  FIG. 6A ) in close proximity to the thermal conversion layer extensively expands, and portions in contact with the outer edge portions, not forming as corners, also become rounded in shape instead. Also, the angle of inclination of the side surfaces of the convexity have is smooth in comparison with that of the embodiment. Additionally, the portion near the bottom end of the convexity (portion of  91  illustrated in  FIG. 6A ) also gently rises. Therefore, the convexity in the conventional example becomes swollen in shape extending outwards into the surrounding area. Thus, the outline becomes blurred. This is especially problematic in a case where the convexity is formed into the shape of a character because the resolution decreases. 
     In contrast to this, according to the present embodiment, the inclusion of the porous material  33  in the thermally expansive layer  22  enables the outer edge portions (edges) of the portion that were caused to distend (convexity  22   a ) to be sharply formed. Specifically, air can be easily contained within the porous material  33  included in the thermally expansive layer  22 . Therefore, it is assumedly easier to suppress or prevent heat, generated by the thermal conversion layer  81 , from transferring in the direction outward from the thermal conversion layer  81 . As a result, the transfer of heat to region surrounding the thermal conversion layer  81  is suppressed or prevented and as illustrated in  FIG. 6B , the area directly underneath the thermal conversion layer  81  and the region in close proximity to the thermal conversion layer  81  distends on the thermally expansive layer  22 , thereby forming the convexity  22   a . At this point in time, the angle of inclination of the side surface  22   c  of the convexity  22   a  is more vertical than that in the conventional example illustrated in  FIG. 6A . Therefore, a top end (outer edge portion)  22   d  is formed when an upper surface  22   b  and the side surface  22   c  of the convexity  22   a , easily coming in contact with each other, together form a corner. Also, since the angle of inclination of the side surface  22   c  of the convexity  22   a  is more vertical than that in the conventional example, a bottom end  22   e  illustrated in  FIG. 6B  clearly is more distinctly formed. Since the shape of the convexity  22   a  is generated by the distension of the thermally expandable material  32 , the corners generated by the upper surface  22   b  and the side surface  22   c  of the convexity  22   a  also include round corners. 
     With the convexity  22   a  of the present embodiment being provided with this top end  22   d  which has a corner, the outer edge portion (top end  22   d ) of the convexity  22   a  can be sharply formed. Also, the outline of the convexity  22   a  becomes distinctly recognizable. Moreover, the resolution of the shaped object  40  can be enhanced. 
     Implemented Example 
     With paper being used as the base, a sheet including a thermally expansive layer on the paper was prepared as the thermally expandable sheet according to the implemented example. Binder, thermally expandable material, and porous material, in a 1:3:1 weight ratio, were included in the thermally expansive layer. Wet silica (porous silica) was used as the porous material. Also, as a comparison example, a thermally expandable sheet including a thermally expansive layer not having porous material was prepared. Binder and thermally expandable material, in a 1:1 weight ratio, were included in the thermally expansive layer. In both the embodiment and the implemented example, the same material is used for the binder and the thickness of the base and the thickness of the thermally expansive layer are the same. 
     An inkjet printer and ink including carbon black were used to print a rectangular-shaped thermal conversion layer onto a thermally expandable sheet of the implemented example. Next, the thermal conversion layer was irradiated with electromagnetic waves. This caused the thermally expansive layer to distend, thereby forming a convexity. Under the same conditions, a convexity was also formed on the thermally expandable sheet of the comparison example by causing the thermally expansive layer to distend. Also, the height of the end of the convexity of the thermally expandable sheet of the comparison example and the height of area in close proximity to the convexity were measured using a laser scan. The measurement portion is illustrated in  FIG. 7 . The measurement portion is the X-Y line illustrated in  FIG. 7 . The left end X is referred to as the reference point. For the comparison example, the height of the same portion as that in the implemented example was also measured. In the comparison example, the measurement was performed up to the position where the height is greatest since the swelling is gradual as described further below. 
     The measurement result of the height of the convexity of the thermal expandable sheet according to the implemented example is illustrated in  FIG. 8A . The horizontal axis in  FIG. 8A  represents distance (mm) from a reference point disposed in a region where the thermally expandable sheet is not distended and the vertical axis represents height (mm). As illustrated in  FIG. 8A , at the thermally expandable sheet of the implemented example, the end of the thermal conversion layer is at a position of 2.4 mm from the reference point and the portion indicated by the arrow in  FIG. 8A  is where the thermal conversion layer is formed. The convexity begins to rise from a position of 1.5 mm from the reference point, gradually increasing in height up to the end portion of the thermal conversion layer. The distension height of the region where the thermal conversion layer is formed is highest in height and the end portion of the thermal conversion layer is where the corner is created (portion of the top end of the thermal conversion layer illustrated in  FIG. 8A ). Additionally, no rising occurs in the area in close proximity to the reference point and height from the reference point up to the position 1.5 mm from the reference point is substantially the same. Therefore, there is a distinct demarcation between the region where no rising occurs and the portion where rising begins, and thus a shape having a corner, such as the portion near the bottom end illustrated in  FIG. 8A , is formed. 
     In contrast to this, in the comparison example, as illustrated in  FIG. 8B , bulging also occurs in the area in close proximity to the reference point, and this bulging around the entirety of the thermal expansion layer gradually increases toward the thermal expansion layer. Moreover, since end portions of the thermal conversion layer are not formed into distinct corners or the like, and instead the shape is such that there is curving all the way around. 
     It was confirmed that the angle of inclination of a side of a convexity with the configuration of the implemented example illustrated in  FIG. 8A  is more vertical than that in the comparison example illustrated in  FIG. 8B . It was also confirmed that the angled upper-end (outer edge portion) was formed with the configuration of the implemented example. 
     This application is not limited to the embodiments described above and various modifications and uses are possible. For example, although a medium provided with a thermally expansive layer in the embodiment described above is described as being a sheet-type, this is not limiting. For example, the thermally expansive layer  22  may be provided on, for example, a base whose surface has a convexity and/or a concavity. The base  21  is not limited to the sheet-type, and it may be more thickly formed. Additionally, the base  21  may have a curved surface and the front surface of the base  21  may have unevenness. In such a case, the step of forming the thermally expansive layer  22  may be modifying in accordance with the shape of the base  21 . 
     A shaped object  40  may be provided with color ink layer (not illustrated) on at least one of the surfaces (the front surface or the back surface illustrated in  FIG. 4A ). The color ink layer is a layer formed from ink using a freely selected printing device such as an offset printing device or a flexographic printing device. The color ink layer may be formed from a water-based ink, an oil-based ink, an ultraviolet-curing type ink, or the like. Moreover, the color ink layer expresses a desired image such as characters, numbers, photographs, patterns, or the like. When the color ink layer is to be formed using a water-based ink jet printer, preferably, an ink receiving layer (non-illustrated) is provided that receives the ink on the surface where the color ink layer is to be formed, and then the color ink layer is formed. 
     Also, the thermal conversion layer  81  may be formed on the back-side surface of the thermally expandable sheet  20  or may be formed on the front side and the back side. Moreover, the case in which the surface on which the thermal conversion layer  81  is formed is irradiated with the electromagnetic waves is not limiting, and the side opposite to the surface on which the thermal conversion layer  81  is formed may be irradiated with the electromagnetic waves. 
     Also, the direct formation of the thermal conversion layer  81  on the thermally expandable sheet  20  is not limiting, and such formation may be performed with an intermediary such as a film provided therebetween. 
     Also, the expansion device  50  is not limited to a stand-alone configuration as illustrated in  FIG. 5 . For example, a forming system equipped with a control unit, a printing unit, a display unit, and the like in addition to the expansion device  50  can also be used. The control unit is equipped with parts such as a controller that has components such as a central processing unit (CPU), and controls the expansion device  50 , the printing unit, the display unit, or the like. The printing unit is a known printing apparatus such as an inkjet printer. The display unit is a liquid crystal panel, a touch panel, or the like. 
     In the above described embodiments, although an example is given where the step of forming the thermal conversion layer  81  is performed when the shaped object  40  is to be produced but this, this is not limiting. The thermal conversion layer  81  maybe formed when the thermally expandable sheet  20  is to be produced, and during the method for production of the shaped object, and a single step of expanding with use of the expansion device may be performed. Furthermore, the production of the thermally expandable sheet  20  illustrated in  FIG. 2A  to  FIG. 2C  and the production of the shaped object  40  illustrated in  FIG. 4A  and  FIG. 4B  may be combined and performed together. 
     Although the thermal conversion layer or the color ink layer, depending on factors such as the type of the image to be printed or the method of printing, might not form a distinct layer, the expression “layer” as in “thermal conversion layer” and “color ink layer” is used in the present description for each of description. 
     Moreover, the drawings used in the various embodiments are each used for description of the embodiments. Thus there is no intent for ratios of thicknesses of the various formed layers of the thermally expandable sheet to be construed as being limited to the ratios illustrated in the drawings. Moreover, in the drawings used in the various embodiments, thickness of the thermal conversion layer or the like that is provided on the thermally expandable sheet is emphasized for the sake of description. Accordingly, the ratios of the thicknesses at which the heat conversion layer or the like is formed are not intended to be construed as limiting. 
     The foregoing describes some example embodiment for explanatory purposes. Although the foregoing discussion has presented specific embodiment, persons skilled in the art will recognize that changes may be made in form and detail without departing from the broader spirit and scope of the invention. Accordingly, the specification and drawings are to be regarded in an illustrative rather than a restrictive sense. This detailed description, therefore, is not to be taken in a limiting sense, and the scope of the invention is defined only by the included claims, along with the full range of equivalents to which such claims are entitled.