具体实施方式：
[0051]Hereinafter, an embodiment of a three-dimensional structure according to the present embodiment will be described. FIG. 1 is a perspective view of a three-dimensional structure, FIG. 2 is a front view of FIG. 1, and FIG. 3 is a cross-sectional view taken along the line A-A in FIG. 2. The three-dimensional structure is formed by a rubber composition. Note that the three-dimensional structure and so forth will be described in accordance with the up, down, front, rear, left, and right directions shown in FIG. 1 and so forth. The X direction, the Y direction, and the Z direction in the present invention correspond respectively to the front-rear direction, the left-right direction, and the up-down direction in the present embodiment, although the three-dimensional structure according to the present invention is not limited to this. In the following, the three-dimensional structure will be described first, and then a method for producing a rubber composition and the three-dimensional structure will be described.
[0052]<1. Three-Dimensional Structure>
[0053]As shown in FIGS. 1 to 3, the three-dimensional structure according to the present embodiment is composed of a body portion 10, which is a combination of three triangular prisms having a triangular cross-sectional shape and five quadrangular prisms having a square cross-sectional shape, and two plate-shaped partition bodies 4, 5. In the following, the triangular prisms in the lowermost layer will be referred to as first, second, and third triangular prisms 11 to 13 in order from left in FIG. 2, the two quadrangular prisms in the second layer will be referred to as first and second middle-layer quadrangular prisms 21, 22 in order from left in the drawing, and the quadrangular prisms in the third layer will be referred to as first, second, and third upper-layer quadrangular prisms 31 to 33 in order from left in the drawing.
[0054]The triangular prisms 11 to 13 are composed of their respective plate-shaped bottom surface portion 111, 121, 131, their respective left inclined surface portion 112, 122, 132, and their respective right inclined surface portion 113, 123, 133. The quadrangular prisms are composed of their respective plate-shaped lower-left inclined surface portions 211, 221, 311, 321, 331, their respective lower-right inclined surface portions 212, 222, 312, 322, 332, their respective upper-left inclined surface portions 213, 223, 313, 323, 333, and their respective upper-right inclined surface portions 214, 224, 314, 324, 334. Note, however, that adjacent triangular prisms or quadrangular prisms share the surfaces constituting the triangular prisms or quadrangular prisms. For example, the right inclined surface portion 113 of the first triangular prism 11 and the lower-left inclined surface portion 211 of the first middle-layer quadrangular prism 21 are constituted by the same member. The detailed description will be given below.
[0055]As described above, the three-dimensional structure according to the present embodiment is composed of the body portion 10, which is a combination of the plurality of triangular prisms 11 to 13 and the plurality of quadrangular prisms 21, 22, 31 to 33, and the two partition bodies 4, 5. The triangular prisms 11 to 13 and the quadrangular prisms 21, 22, 31 to 33 are all formed by a hollow having an internal space, and each internal space is formed so as to extend in the front-rear direction. Then, the triangular prisms 11 to 13 are disposed such that the bottom surface portions 111, 121, 131 extend horizontally. The left inclined surface portions 112, 122, 132 and the right inclined surface portions 113, 123,133 are respectively coupled at right angles at the upper ends thereof.
[0056]The quadrangular prisms 21, 22, 31 to 33 are disposed such that the lower-left inclined surface portions 211, 221, 311, 321, 331 and the lower-right inclined surface portions 212, 222, 312, 322, 332 are each inclined at an angle of 45 degrees relative to a horizontal plane and are respectively coupled at an angle of 90 degrees. This also applies to the upper-left inclined surface portions 213, 223, 313, 323, 333, and the upper-right inclined surface portions 214, 224, 314, 324, 334. The first middle-layer quadrangular prism 21 is disposed between the first triangular prism. 11 and the second triangular prism 12, and the second middle-layer quadrangular prism 22 is disposed between the second triangular prism 12 and the third triangular prism 13. As described above, the lower-left inclined surface portions 211, 221 and the lower-right inclined surface portions 212, 222 of the middle-layer quadrangular prisms 21, 22 are shared by the triangular prisms 11 to 13.
[0057]The first upper-layer quadrangular prism 31 is coupled to the upper-left inclined surface portion 213 of the first middle-layer quadrangular prism. 21, and the second upper-layer quadrangular prism 32 is disposed between the first middle-layer quadrangular prism. 21 and the second middle-layer quadrangular prism 22. The third upper-layer quadrangular prism 33 is coupled to the upper-right inclined surface portion 224 of the second middle-layer quadrangular prism 22. Then, as described above, in the upper-layer quadrangular prisms 31 to 33, at least one of the lower-left inclined surface portions 321, 331 and at least one of the lower-right inclined surface portions 312, 322 are also used as one of the upper-left inclined surface portions 213, 223 of the middle-layer quadrangular prism 21 to 23 and the lower-right inclined surface portions 214, 224.
[0058]Note that the internal spaces formed in the above-described triangular prisms 11 to 13 and quadrangular prisms 21, 22, 31 to 33 correspond to the through holes of the present invention. In the following, each of the triangular prisms and the quadrangular prisms that are to be combined may be occasionally referred to as a unit structure.
[0059]Next, the partition bodies 4, 5 will be described. As described above, the body portion 10 is provided with the two partition bodies 4, 5 that are formed in a plate shape. Each of the partition bodies 4, 5 is disposed such that the plane direction thereof extends in the up-down direction and the left-right direction. The two partition bodies 4, 5 are disposed at a predetermined interval in the front-rear direction. In the following, the partition body disposed on the front side will be referred to as a first partition body 4, and the partition body disposed on the rear side will be referred to as a second partition body 5.
[0060]The partition bodies 4, 5 are disposed at positions at which the body portion 10 is divided into three substantially equal portions in the front-rear direction. Then, the partition bodies 4, 5 are disposed so as to extend through all of the triangular prisms 11 to 13 and the quadrangular prisms 21, 22, 31 to 33 in the up-down direction and the left-right direction. That is, the partition bodies 4, 5 extend through the internal spaces of all of the triangular prisms 11 to 13 and the quadrangular prisms 21, 22, 31 to 33 in the up-down direction, and partition each internal space into three spaces in the front-rear direction. Of the three spaces, the space disposed at the center in the front-rear direction is defined as a closed space by the two partition bodies 4, 5, as shown in FIG. 3. Here, in the partition bodies 4, 5, portions partitioning the internal spaces of the triangular prisms 11 to 13 and the quadrangular prisms 21, 22, 31 to 33 will be referred to as partition portions 41, 51.
[0061]The partition bodies 4, 5 form protruding portions 42, 52 having a triangular shape as seen in front view and protruding between the upper-right inclined surface portion 314 of the first upper-layer quadrangular prism 31 and the left inclined surface portion 323 of the second upper-layer quadrangular prism 32. Similarly, protruding portions 42, 52 having a triangular shape as seen in front view are formed between the upper-right inclined surface portion 324 of the second upper-layer quadrangular prism 32 and the left inclined surface portion 333 of the third upper-layer quadrangular prism 33.
[0062]<2. Rubber Composition>
[0063]Next, a rubber composition for forming the above-described three-dimensional structure will be described. The rubber composition includes a liquid rubber. A known liquid rubber can be used as the liquid rubber without any particular limitation. Specific examples of the liquid rubber include a liquid butadiene rubber, a liquid styrene-butadiene copolymer rubber, a liquid isoprene-butadiene copolymer rubber, a liquid isoprene rubber, a liquid hydrogenated isoprene rubber, and a liquid isoprene-styrene copolymer rubber. Among them, from the viewpoint of providing a viscosity suitable for three-dimensional additive manufacturing, while achieving excellent rubber characteristics (e.g., Shore hardness, elongation at break, breaking stress, and compression permanent strain, which will be described later) for a three-dimensional structural body, which is a rubber molded body obtained by curing, it is preferable to use a liquid rubber including an unsaturated bond of a (meth)acryloyl group, a vinyl group or the like that is cross-linked by heat, light, electron beams or the like, and a liquid rubber including a cyclic ether such as an epoxy compound or an oxetane compound, and it is particularly preferable to use a liquid rubber including a (meth)acryloyl group. One of the liquid rubbers may be included alone, or two or more of them may be included. Note that in the present invention “(meth)acryloyl group” means “acryloyl group or methacryloyl group”, and the same applies to similar expressions.
[0064]From the viewpoint of providing a viscosity suitable for three-dimensional additive manufacturing, while achieving excellent rubber characteristics for a three-dimensional structural body obtained by curing, the liquid rubber content in the rubber composition may be, but is not particularly limited to, preferably 40 mass % or more, more preferably about 45 to 90 mass %, further preferably about 50 to 70 mass %.
[0065]From a similar viewpoint, the number-average mean molecular weight (Mn) of the liquid rubber may be, but is not particularly limited to, preferably 500 or more, more preferably about 5,000 to 60,000, further preferably about 5,000 to 40,000.
[0066]Note that the number-average mean molecular weight (Mn) of the liquid rubber is a value measured using a gel permeation chromatograph, and converted by standard polystyrene.
[0067]Furthermore, from the viewpoint of providing a viscosity suitable for three-dimensional structure, while achieving excellent rubber characteristics for a three-dimensional structural body obtained by curing, the rubber composition may include a co-cross-linking agent. As the co-cross-linking agent, a known co-cross-linking agent such as a photoreactive resin can be used. Specific examples of the co-cross-linking agent include zinc acrylate, magnesium acrylate, zinc methacrylate, magnesium methacrylate; co-cross-linking agents including an unsaturated bond such as a styrene monomer, a (meth)acrylate monomer, and a (meth)acrylamide monomer, and oligomers thereof. One of the co-cross-linking agents may be included alone, or two or more of them may be included.
[0068]From the viewpoint of providing a viscosity suitable for three-dimensional additive manufacturing, while achieving excellent rubber characteristics for a three-dimensional structural body obtained by curing, the co-cross-linking agent content in the rubber composition may be, but is not particularly limited to, preferably 1 mass % or more, more preferably about 5 to 50 mass %, further preferably about 10 to 30 mass %.
[0069]From the viewpoint of providing a viscosity suitable for a three-dimensional structure, while achieving excellent rubber characteristics for a three-dimensional structural body obtained by curing, the rubber composition may include a vulcanized rubber. A known vulcanized rubber obtained by vulcanizing a natural rubber or a synthetic rubber can be used as the vulcanized rubber without any particular limitation. Examples of the rubber component constituting the vulcanized rubber include a natural rubber, an isoprene rubber, a butadiene rubber, a styrene butadiene rubber, a butyl rubber, an ethylene propylene diene rubber, an ethylene propylene rubber, a chloroprene rubber, an acrylonitrile-butadiene rubber, chlorosulfonated polyethylene, an epichlorohydrine rubber, chlorinated polyethylene, a silicone rubber, a fluorine rubber, and a urethane rubber. Among them, from the viewpoint of providing a viscosity suitable for three-dimensional additive manufacturing, while achieving excellent rubber characteristics for a three-dimensional structural body obtained by curing, a vulcanized rubber obtained by vulcanizing a natural rubber is preferable. One of the vulcanized rubbers may be included alone, or two or more of them may be included.
[0070]From the viewpoint of providing a viscosity suitable for a three-dimensional structure, while achieving excellent rubber characteristics for a three-dimensional structural body obtained by curing, the vulcanized rubber is preferably in the form of fine particles. The particle diameter of the vulcanized rubber is not particularly limited, but, from a similar viewpoint, the central particle diameter is preferably about 200 μm or less, more preferably about 100 μm or less, further preferably about 50 μm or less.
[0071]Note that the central particle diameter of the vulcanized rubber in the present invention is a median diameter (cumulative 50% particle diameter) obtained using a laser diffraction/scattering particle diameter measurement device.
[0072]From the viewpoint of providing a viscosity suitable for three-dimensional additive manufacturing, while achieving excellent rubber characteristics for a three-dimensional structural body obtained by curing, the vulcanized rubber content in the rubber composition may be, but is not particularly limited to, preferably 10 mass % or more, more preferably about 20 to 80 mass %, further preferably about 30 to 50 mass %.
[0073]The rubber composition preferably includes a radical initiator. The inclusion of a radical initiator can accelerate the curing of the above-described liquid rubber. A known radical initiator that generates radicals by heating, light irradiation, electron beam irradiation, or the like can be used as the radical initiator without any particular limitation. Examples of a preferable radical initiator include acetophenone, 4,4′-dimethoxy benzyl, dibenzoyl, 2-hydroxy-2-phenylacetophenone, benzophenone, benzophenone-2-carboxylic acid, benzophenone-4-carboxylic acid, methyl benzophenone-2-carboxylate, N, N, N′,N′-tetraethyl-4,4′-diaminobenzophenone, 2-methoxy-2-phenylacetophenone, 2-isopropoxy-2-phenylacetophenone, 2-isobutoxy-2-phenylacetophenone, 2-ethoxy-2-phenylacetophenone, 2,2′-bis(2-chlorophenyl)-4,4′,5,5′-tetraphenyl-1,2′-biimidazole, 2-(1,3-benzodioxole-5-yl)-4,6-bis(trichloromethyl)-1,3,5-triazine, 2-benzyl-2-(dimethylamino)-1-[4-(morpholino)phenyl]-1-butanone, 4,4′-dichlorobenzophenone, 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,4-diethyl thioxanthene-9-one, diphenyl(2,4,6-trimethyl benzoyl)phosphine oxide, phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide, 1,4-dibenzoylbenzene, 2-ethylanthraquinone, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl propiophenone, 2-hydroxy-4′-(2-hydroxy ethoxy)-2-methylpropiophenone, 2-methyl-4′-(methylthio)-2-morpholinopropiophenone, 2-isonitrosopropiophenone, 2-phenyl-2-(p-toluenesulfonyloxy)acetophenone, phenylglyoxylic acid methyl ester, 1,2-octanedione,1-[4-(phenyl thio)-,2-(O-benzoyloxime)], and ethanone,1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazole-3-yl]-,1-(O-acetyloxime). The radical initiator may be used alone or in combination of two or more.
[0074]The radical initiator content may be preferably about 0.5 to 10 parts by mass, more preferably about 1 to 7 parts by mass, per 100 parts by mass of the liquid rubber.
[0075]The rubber composition may further include a filler. The inclusion of a filler makes it possible to adjust the viscosity of a rubber composition for three-dimensional additive manufacturing, and the rubber characteristics for a three-dimensional structural body obtained by curing.
[0076]The filler is not particularly limited, and examples thereof include carbon black, silica, calcium carbonate, clay, and talc. In the case of using silica as the filler, a silica that has not been surface-modified may be used. By using a surface-modified silica that has been surface-modified with a silane coupling agent or the like, or a mixture of silica and a silane coupling agent as the filler, it is possible to further increase the mechanical strength of a three-dimensional structural body obtained by curing. The filler may be used alone or in combination of two or more.
[0077]When the rubber composition includes a filler, it may further include a silane coupling agent. In particular, when a filler that has not been surface-modified is formulated, the inclusion of a silane coupling agent enables the liquid rubber and the filler to be firmly bonded, making it possible to achieve excellent rubber characteristics for a three-dimensional structural body obtained by curing.
[0078]From the viewpoint of providing a viscosity suitable for three-dimensional additive manufacturing, while achieving excellent rubber characteristics for a three-dimensional structural body obtained by curing, the filler content may be, but is not particularly limited to, preferably 5 mass % or more, more preferably about 5 to 70 mass %, further preferably about 10 to 50 mass %.
[0079]From the viewpoint of providing a viscosity suitable for three-dimensional additive manufacturing, while achieving excellent rubber characteristics for a rubber molded body obtained by curing, the rubber composition may include a polyrotaxane capable of being chemically bonded to the liquid rubber. A polyrotaxane is a compound in which capping groups are disposed at both ends of a pseudopolyrotaxane (both ends of a linear molecule) in which the opening part of a cyclic molecule is included in a linear molecule in a skewed manner, and a known polyrotaxane may be used.
[0080]Examples of the linear molecule constituting the polyrotaxane include polycaprolactone, a styrene-butadiene copolymer, an isobutene-isoprene copolymer, polyisoprene, a natural rubber (NR), polyethylene glycol, polyisobutylene, polybutadiene, polypropylene glycol, polytetrahydrofuran, polydimethylsiloxane, polyethylene, polypropylene, and an ethylene-polypropylene copolymer.
[0081]The linear molecule may be, for example, a polymer of one or more aromatic vinyl compounds such as styrene, α-methylstyrene, 1-vinylnaphthalene, 3-vinyltoluene, ethylvinylbenzene, divinylbenzene, 4-cyclohexylstyrene, and 2,4,6-trimethylstyrene; a polymer of one or more conjugated diene compounds such as 1,3-butadiene, isoprene, 1,3-pentadiene, 2,3-dimethylbutadiene, 2-phenyl-1,3-butadiene, and 1,3-hexadiene; or a copolymer or the like of the aromatic vinyl compound and the conjugated diene compound.
[0082]Any of these linear molecules may be used alone or in combination of two or more. The linear molecule preferably has a weight-average molecular weight of about 10000 or more and 1000000 or less. Examples of the capping groups that cap both ends of the linear molecule include a dinitrophenyl group, an adamantyl group, a trityl group, fluoresceine, pyrene, or one or more derivatives thereof.
[0083]Examples of the cyclic molecule include cyclodextrin, crown ether, benzocrown, dibenzocrown, dicyclohexanocrown, or one or more derivatives thereof. As the cyclic molecule, α-, β-, or γ-cyclodextrin or one or more derivatives thereof are particularly preferable.
[0084]The polyrotaxane is capable of being chemically bonded to the liquid rubber. More specifically, the polyrotaxane includes a functional group capable of being chemically bonded to the liquid rubber. The functional group is preferably present at side chains of the cyclic molecule.
[0085]In the polyrotaxane, the functional group capable of being chemically bonded to the liquid rubber is not particularly limited, but is preferably an unsaturated bond such as a (meth)acryloyl group or vinyl group that is cross-linked by heat, light, electron beams, and is particularly preferably a (meth)acryloyl group. When the above-described liquid rubber includes the above-described unsaturated bond, which is cross-linked by heat, light, electron beams, or the like, the unsaturated bond of the liquid rubber and the functional group of the polyrotaxane can be chemically bonded.
[0086]As the polyrotaxane, a commercially available product can also be used. Examples of a commercially available product of an ultraviolet-curable polyrotaxane include SeRM (registered trademark) super polymers SM3403P, SA3403P, SA2403P, SM1313P, and SA1313P manufactured by Advanced Softmaterials Inc. Each of these products is supplied as a 50 mass % MEK solution, and SM3405P, SA3405P, SA2405P, etc., are each supplied as a 70 mass % ethyl acetate solution. Further, as the ultraviolet-curable polyrotaxane, a polyrotaxane in which a reactive diluent such as an acrylic oligomer is formulated is also supplied. Examples of such a product include SeRM (registered trademark) Key-Mixture SM3400C, SA3400C, SA2400C, etc., manufactured by Advanced Softmaterials Inc.
[0087]The polyrotaxane may be used alone or in combination of two or more.
[0088]From the viewpoint of providing a viscosity suitable for three-dimensional additive manufacturing, while achieving excellent rubber characteristics for a rubber molded body obtained by curing, the polyrotaxane content contained in the rubber composition may be, but is not particularly limited to, preferably approximately 1 mass % or more, more preferably about 1 to 20 mass %, further preferably about 2 to 10 mass %, particularly preferably about 3 to 10 mass %.
[0089]Furthermore, the rubber composition may further include various additives within the range that does not impair the effects of the present invention. The additives are not particularly limited, and examples thereof include a polymer, a dye, a pigment, a leveling agent, a fluidity adjustor, an antifoaming agent, a plasticizer, a polymerization inhibitor, a flame retardant, a dispersion stabilizer, a storage stabilizer, an antioxidant, a metal, a metal oxide, a metal salt, and a ceramic. The rubber composition may include one additive, or two or more additives.
[0090]The viscosity of the rubber composition for a three-dimensional structure is not particularly limited as long as the viscosity allows rendering and lamination to be performed by a production apparatus of the three-dimensional structure. From the viewpoint of being suitable for a three-dimensional structure and achieving excellent rubber characteristics for a three-dimensional structural body obtained by curing, the viscosity measured using an E-type viscometer under an environment at a temperature of 60° C. (with an error of ±2° C.) and a relative humidity of 50% may be preferably 1500 Pa·s or less, more preferably about 0.1 to 1500 Pa·s, further preferably about 1 to 1000 Pa·s. More specifically, this viscosity is a viscosity measured using an E-type viscometer (MCR301 manufactured by Anton-Paar) with an amplitude of 1% and a frequency of 1 Hz.
[0091]As described above, the rubber composition for a three-dimensional structure according to the present embodiment can be easily produced by mixing a liquid rubber with a co-cross-linking agent, a vulcanized rubber, an initiator, a filler, a polyrotaxane, various additives and the like that are included as needed.
[0092]Note that when the above-described rubber composition including a polyrotaxane capable of being chemically bonded to to a liquid rubber is used for producing a rubber molded body, the liquid rubber and the polyrotaxane form a chemical bond in a cured material constituting the rubber molded body.
[0093]As a result of a three-dimensional structure being produced by the rubber composition described above, the three-dimensional structure preferably has physical properties such as those shown below. That is, the Shore A hardness of the three-dimensional structure may be appropriately set in accordance with the hardness required for the product, but may be in the range of preferably 25 to 90, from the viewpoint of achieving excellent rubber characteristics. Note that the Shore A hardness is a value measured in accordance with the method prescribed in JIS K6253.
[0094]The elongation at break of the three-dimensional structure may be appropriately set in accordance with the elongation at break required for the product, but may be preferably 50% or more, more preferably 90% or more, from the viewpoint of achieving excellent rubber characteristics. The upper limit of the elongation at break is usually about 500%. Note that this elongation is a value measured in accordance with the method prescribed in JIS K6251.
[0095]The breaking stress of the three-dimensional structure may be appropriately set in accordance with the breaking stress required for the product, but may be preferably 0.7 MPa or more, from the viewpoint of achieving excellent rubber characteristics. The upper limit of the breaking stress is usually about 30 MPa. Note that this breaking stress is a value measured in accordance with the method prescribed in JIS K6251.
[0096]Furthermore, the compression permanent strain (after 24 hours) of the three-dimensional structure may be appropriately set in accordance with the compression permanent strain required for the product, but may be in the range of preferably 10% or less, more preferably 7% or less, from the viewpoint of achieving excellent rubber characteristics. The compression permanent strain (after 0.5 hours) may be appropriately set in accordance with the compression permanent strain required for the product, but may be in the range of preferably 20% or less, more preferably 15% or less, from the viewpoint of achieving excellent rubber characteristics. Note that this compression permanent strain is a value measured in accordance with the method prescribed in JIS K6262.
[0097]<3. Method for Producing Three-Dimensional Structural Body>
[0098]Next, a method for producing a three-dimensional structure configured in the above-described manner will be described. In this production method, the viscosity of the rubber composition is reduced by heating as needed, and the rubber composition is dropped from a nozzle, thereby forming a thin film having a predetermined shape and pattern. Then, the dropped thin-film rubber composition is subjected to heating, light irradiation, or electron beam irradiation, thereby curing the rubber composition. Thereafter, the rubber composition is laminated while repeating the dropping and the curing of the rubber composition, to form a three-dimensional structure. Accordingly, when the viscosity of the rubber composition is not high, the rubber composition can be dropped without being heated. Even when the viscosity of the rubber composition is somewhat high, the rubber composition can be dropped without being heated, depending on the apparatus. Therefore, the heating of the rubber composition may not be necessarily performed.
[0099]Specifically, a production apparatus as shown in FIG. 4 is provided, for example. The production apparatus includes a horizontal table 81 and a nozzle 82 capable of moving upward and downward, forward and rearward, and leftward and rightward, above the table 81. The nozzle 82 is configured such that a heated rubber composition is dropped therefrom. The heating temperature of the rubber composition is not particularly limited, but is set to be preferably about 15 to 170° C., more preferably about 30 to 160° C. The heating time is set to be preferably about 1 to 60 minutes, more preferably about 5 to 30 minutes. Note that the diameter of the discharge outlet of the nozzle 82 is not particularly limited, but is set to be, for example, preferably about 0.001 to 1 mm, more preferably about 0.01 to 0.5 mm. Consequently, when the rubber composition is dropped, a line having a line width and a thickness that are comparable to the diameter of the discharge outlet is formed as will be described next.
[0100]Furthermore, in the production apparatus 8, a light irradiation device 83 is attached to the nozzle 82, and the light irradiation device is configured to be movable together with the nozzle 82. Then, the dropped rubber composition is cured by the light emitted from the light irradiation device 83. For example, ultraviolet irradiation is preferable as such light irradiation, and it is preferable that the rubber composition is cured at a wavelength of about 365 nm under conditions of an ultraviolet intensity of about 1 mW/cm2 to 10 W/cm2 and an accumulated light amount of about 1 mJ/cm2 to 100 J/cm2.
[0101]Next, a specific method for producing the above-described three-dimensional structure will be described. As shown in FIG. 5, first, the rubber composition is dropped while moving the nozzle 82 in the front-rear direction, to form a first line 91 extending in the front-rear direction. In the following, linear rubber compositions extending in the front-rear direction will be all referred to as a first line 91. At this time, the rubber composition dropped from the nozzle 82 is cured by light, such as ultraviolet light, emitted from the light irradiation device 83 that moves together with the nozzle 82. Consequently, a cured first line 91 is formed on the table 81. Then, as shown in FIG. 6, a first line 91 extending in the front-rear direction is formed in the same manner so as to be in contact with the cured first line 91. Thus, while repeating the movement of the nozzle 91 in the front-rear direction, first lines 91 are aligned in the left-right direction, to form a plate-shaped portion. This will serve as the bottom surface portions 111, 121, 131 of the three triangular prisms 11 to 13 of the three-dimensional structure.
[0102]Next, while stacking the first lines 91 on the bottom surface portions 111, 121, 131, the left inclined surface portions 112, 122, 132 and the right inclined surface portions 113, 123, 133 of the three triangular prisms 11 to 13 are formed. At this time, the left inclined surface portions 112, 122, 132 and the right inclined surface portions 113, 123, 133 are inclined, and therefore the first lines 91 are stacked while being shifted in the left-right direction. For example, as shown in FIG. 7, in order to form the left inclined surface portions 112, 122, 132, the first lines 91 are stacked so as to be gradually shifted to the right side. At this time, the rubber composition has a certain degree of viscosity, and is cured. Accordingly, even when the first lines 91 are obliquely stacked, the inclined surface portions can be formed without collapsing. This also applied to the quadrangular prisms 21, 22, 31 to 33.
[0103]The partition bodies 4, 5 are also formed in the same manner. First, as shown in FIG. 8, while moving the nozzle 82 in the left-right direction, the rubber composition is dropped, to forma second line 92 extending in the left-right direction. In the following, linear rubber compositions extending in the left-right direction will be all referred to as a second line. Then, the second lines 92 are stacked, thereby forming the partition bodies 4, 5.
[0104]Meanwhile, since the second line 92 is stacked so as to intersect the first line 91, two layers are stacked at the portion at which the first line 91 and the second line 92 intersect, as shown in FIG. 9. Accordingly, this portion has an increased thickness as compared with a portion at which only the first line 91 or the second line 92 is stacked. As a result, only the thickness of the intersection portion is increased. Therefore, in the present embodiment, the discharge outlet of the nozzle 82 is brought into proximity to the already stacked first line 91 (e.g., the distance between the first line 91 and the discharge outlet is made as close to 0 mm as possible), and the rubber composition is dropped while compressing the first line 91, as shown in FIG. 10. Accordingly, as shown in FIG. 11, a layer having a thickness substantially corresponding to one layer can be also formed at the intersection portion of the first line 91 and the second line 92. In addition, as shown in FIG. 12A,