Inkjet ink for injection molding resin molds, laminates, and methods for manufacturing molded products

Abstract

To provide inkjet ink capable of forming a resin mold for injection molding having high durability.SOLUTION: Inkjet ink contains a photo-polymerizable compound containing a monofunctional monomer and (meth)acrylate oligomer. The monofunctional monomer contains (meth)acrylamide compound. A content of the (meth)acrylamide compound accounts for 75 mass% or higher based on the whole content of the monofunctional monomer. A content of the (meth)acrylamide compound accounts for 50 mass% or higher with respect to the whole content of the photo-polymerizable compound.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an inkjet ink, a laminate, and a method for manufacturing a molded article.

Background Art

[0002] Conventionally, a method has been proposed in which an inkjet ink containing a radiation-curable composition is printed on a substrate and cured to produce a laminate, and the laminate is processed. In Patent Document 1, a radiation-curable composition for obtaining a cured product having punching processability, stretchability, and strength up to a certain temperature range is disclosed.

[0003] The radiation-curable composition of Patent Document 1 contains a monofunctional polymerizable monomer in an amount of 50% by mass or more based on the total amount of the polymerizable compounds, and a polyfunctional monomer in an amount of 10% by mass or more and 20% by mass or less based on the total amount of the polymerizable compounds. The monofunctional polymerizable monomer contains a monofunctional monomer having a polar group and a monofunctional monomer having no polar group. The ratio of the monofunctional monomer having a polar group to the monofunctional monomer having no polar group is 0.33 to 3.0.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Incidentally, from the perspective of reducing the processing time and cost of injection molding molds, resin molds that can be formed by inkjet methods instead of conventional molds are attracting attention. However, if a resin mold is made by inkjet methods and resin is injection molded using that resin mold, there is a risk that the resin mold will deform due to heat. In such cases, it becomes impossible to form multiple injection molded products, so there is a need for inkjet inks that can form highly durable injection molding resin molds.

[0006] This invention has been made in view of the problems of the prior art. The object of this invention is to provide an inkjet ink capable of forming highly durable resin molds for injection molding. Furthermore, the object of this invention is to provide a method for manufacturing laminates and molded articles using the inkjet ink. [Means for solving the problem]

[0007] To solve the above problems, an inkjet ink according to an embodiment of the present invention contains a photopolymerizable compound comprising a monofunctional monomer and a (meth)acrylate oligomer. The monofunctional monomer comprises a (meth)acrylamide compound. The content of the (meth)acrylamide compound is 75% by mass or more of the total content of the monofunctional monomer. The content of the (meth)acrylamide compound is 50% by mass or more of the total content of the photopolymerizable compound.

[0008] An embodiment of the present invention comprises a polycarbonate substrate and a cured product of inkjet ink disposed on the polycarbonate substrate.

[0009] In a method for manufacturing a molded product according to an aspect of the present invention, a laminate is used as a resin mold for injection molding, and a molded product is obtained by injection molding. [Effects of the Invention]

[0010] This disclosure provides an inkjet ink capable of forming highly durable injection molding resin molds, and a method for manufacturing laminates and molded products using the inkjet ink. [Brief explanation of the drawing]

[0011] [Figure 1] This is a schematic cross-sectional view showing an example of a laminate according to this embodiment. [Figure 2] This is a schematic diagram illustrating the manufacturing method of the laminate according to this embodiment. [Figure 3] This is a schematic diagram illustrating the heating of the laminate according to this embodiment. [Figure 4] This is a schematic cross-sectional view showing the vacuum forming process of a heated laminate. [Figure 5] This is a schematic cross-sectional view showing a state in which thermoplastic resin is poured into a mold on which a laminate is placed. [Figure 6] This is a schematic cross-sectional view showing a molded product made of thermoplastic resin that has been removed from the mold. [Modes for carrying out the invention]

[0012] The manufacturing methods for the inkjet ink, laminate, and molded product according to this embodiment will be described in detail below with reference to the drawings. Note that the dimensional ratios in the drawings are exaggerated for illustrative purposes and may differ from the actual ratios.

[0013] [Inkjet ink] The inkjet ink according to this embodiment contains a photopolymerizable compound. The photopolymerizable compound contains a monofunctional monomer and a (meth)acrylate oligomer.

[0014] Monofunctional monomers include (meth)acrylamide compounds. Note that (meth)acrylamide compounds are a concept that encompasses methacrylamide compounds and acrylamide compounds. (Meth)acrylamide compounds include (meth)acrylamide, N-methyl(meth)acrylamide, N-ethyl(meth)acrylamide, N-isopropyl(meth)acrylamide, Nt-butyl(meth)acrylamide, N-hexyl(meth)acrylamide, N-cyclohexyl(meth)acrylamide, N-dodecyl(meth)acrylamide, N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N,N-dipropyl(meth)acrylamide, N,N-dibutyl(meth)acrylamide, N,N-dihexyl(meth)acrylamide, (meth)acryloylmorpholine, N-(hydroxymethyl)(meth)acrylamide, N-(2-hydroxyethyl)(meth)acrylamide, and N-isobutoxymethyl(meth)acrylamide. The material may contain at least one selected from the group consisting of mid, N-(3-dimethylaminopropyl)(meth)acrylamide, N-(1,1-dimethyl-3-oxobutyl)(meth)acrylamide, diacetone(meth)acrylamide, N,N-butoxymethyl(meth)acrylamide, N,N-dimethylaminomethyl(meth)acrylamide, N,N-dimethylaminoethyl(meth)acrylamide, N,N-dimethylaminopropyl(meth)acrylamide, N,N-dimethylaminohexyl(meth)acrylamide, N,N-diethylaminomethyl(meth)acrylamide, N,N-diethylaminoethyl(meth)acrylamide, N,N-diethylaminopropyl(meth)acrylamide, N,N-diethylaminohexyl(meth)acrylamide, etc. The monofunctional monomer may contain, for example, at least one selected from the group consisting of acryloylmorpholine, N,N-diethylacrylamide, and N,N-dimethylacrylamide.

[0015] The content of the (meth)acrylamide compound is 75% by mass or more based on the total content of the monofunctional monomers. When the content of the (meth)acrylamide compound is 75% by mass or more based on the total content of the monofunctional monomers, an inkjet ink capable of forming an injection molding resin mold with high durability can be obtained. The content of the (meth)acrylamide compound may be 80% by mass or more, 85% by mass or more, 90% by mass or more, or 95% by mass or more based on the total content of the monofunctional monomers. The content of the (meth)acrylamide compound may be 100% by mass or less based on the total content of the monofunctional monomers.

[0016] The content of the (meth)acrylamide compound is 50% by mass or more based on the total content of the photopolymerizable compounds. When the content of the (meth)acrylamide compound is 50% by mass or more based on the total content of the photopolymerizable compounds, the adhesion to the substrate can be improved. The content of the (meth)acrylamide compound may be 60% by mass or more, 70% by mass or more, 80% by mass or more, or 90% by mass or more based on the total content of the photopolymerizable compounds. The content of the (meth)acrylamide compound may be 90% by mass or less, 80% by mass or less, 70% by mass or less, or 60% by mass or less based on the total content of the photopolymerizable compounds.

[0017] When the (meth)acrylamide compound contains acryloylmorpholine, the content of acryloylmorpholine based on the total content of the (meth)acrylamide compound may be 50% by mass or more, 70% by mass or more, or 80% by mass or more. The content of the acryloylmorpholine may be 100% by mass or less.

[0018] When the (meth)acrylamide compound contains N,N - diethylacrylamide or N,N - dimethylacrylamide, the total content of N,N - diethylacrylamide and N,N - dimethylacrylamide relative to the total content of the (meth)acrylamide compound may be 5% by mass or more and 45% by mass or less. The above total content may be 10% by mass or more, may be 15% by mass or more, may be 20% by mass or more. Also, the above total content may be 40% by mass or less, may be 35% by mass or less, may be 30% by mass or less, may be 25% by mass or less, may be 20% by mass or less.

[0019] The monofunctional monomer may contain monomers other than the (meth)acrylamide compound. As the photopolymerizable monomer, for example, it may contain (meth)acrylate. Here, (meth)acrylate is a concept that includes methacrylate and acrylate. (meth)acrylate may contain at least one selected from the group consisting of monofunctional (meth)acrylate, difunctional (meth)acrylate, and polyfunctional (meth)acrylate having three or more functional groups. The polymerizable compound may be used alone or in combination of two or more kinds.

[0020] Examples of monofunctional (meth)acrylates include isoamyl (meth)acrylate, stearyl (meth)acrylate, lauryl (meth)acrylate, octyl (meth)acrylate, decyl (meth)acrylate, isomiristyl (meth)acrylate, isostearyl (meth)acrylate, 2-ethylhexyl-diglycol (meth)acrylate, 2-hydroxybutyl (meth)acrylate, butoxyethyl (meth)acrylate, ethoxydiethylene glycol (meth)acrylate, methoxydiethylene glycol (meth)acrylate, and methoxypolyethylene glycol. Examples include methyl(meth)acrylate, methoxypropylene glycol (meth)acrylate, phenoxyethyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, isobornyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, lactone-modified flexible (meth)acrylate, t-butylcyclohexyl (meth)acrylate, dicyclopentanyl (meth)acrylate, and dicyclopentenyloxyethyl (meth)acrylate. Specifically, monofunctional (meth)acrylate may contain isobornyl acrylate.

[0021] Examples of difunctional (meth)acrylates include triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, dimethylol-tricyclodecane di(meth)acrylate, bisphenol A EO (ethylene oxide) adduct di(meth)acrylate, bisphenol A PO (propylene oxide) adduct di(meth)acrylate, hydroxypivalate neopentyl glycol di(meth)acrylate, polytetramethylene glycol di(meth)acrylate, and 2-(allyloxymethyl)acrylate methyl acrylate.

[0022] The content of the difunctional photopolymerizable monomer may be 5% by mass or more, or 10% by mass or more, relative to the total content of the photopolymerizable compound. Furthermore, the content of the difunctional photopolymerizable monomer may be 40% by mass or less, 30% by mass or less, or 20% by mass or less, relative to the total content of the photopolymerizable compound.

[0023] The photopolymerizable compound may contain at least one of the bifunctional monomers dimethylol-tricyclodecanediaacrylate and methyl 2-(allyloxymethyl)acrylate. When the photopolymerizable compound contains these monomers, the durability of the laminate formed, as described later, can be further improved. Furthermore, when the photopolymerizable compound contains these monomers, the stretchability can be improved.

[0024] The amount of at least one of the difunctional monomers, dimethylol-tricyclodecanediaacrylate and methyl 2-(allyloxymethyl)acrylate, is preferably 35% by mass or less of the total content of the photopolymerizable compound. By limiting the content of these difunctional monomers to 35% by mass or less, the stretchability can be further improved. The amount of at least one of the difunctional monomers, dimethylol-tricyclodecanediaacrylate and methyl 2-(allyloxymethyl)acrylate, is more preferably 30% by mass or less, and even more preferably 25% by mass or less. The amount of at least one of the difunctional monomers, dimethylol-tricyclodecanediaacrylate and methyl 2-(allyloxymethyl)acrylate, may be 5% by mass or more, or 10% by mass or more, of the total content of the photopolymerizable compound.

[0025] Examples of polyfunctional (meth)acrylates with three or more functions include trimethylolpropane tri(meth)acrylate, EO-modified trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, ethoxylated trimethylolpropane tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, glycerin propoxytri(meth)acrylate, cauprolactone-modified trimethylolpropane tri(meth)acrylate, pentaerythritol ethoxytetra(meth)acrylate, ethoxylated pentaerythritol tetra(meth)acrylate, and caprolactam-modified dipentaerythritol hexa(meth)acrylate.

[0026] (Meth)acrylate oligomers are a concept that encompasses methacrylate oligomers and acrylate oligomers. Examples of (meth)acrylate oligomers include (meth)acrylate oligomers obtained by polymerization of the above (meth)acrylate monomers, epoxy (meth)acrylates, urethane (meth)acrylates such as aliphatic urethane (meth)acrylates and aromatic urethane (meth)acrylates, polyether (meth)acrylates, and polyester (meth)acrylates. Among these, the photopolymerizable oligomer is preferably a urethane (meth)acrylate oligomer. The (meth)acrylate oligomer may contain at least one of a difunctional (meth)acrylate oligomer and a polyfunctional (meth)acrylate oligomer with three or more functions. However, from the viewpoint of stretchability, the (meth)acrylate oligomer is preferably a difunctional (meth)acrylate oligomer.

[0027] The content of (meth)acrylate oligomers may be 5% by mass or more and 20% by mass or less relative to the total content of photopolymerizable compounds. Furthermore, the content of difunctional (meth)acrylate oligomers may be 80% by mass or more, 90% by mass or more, or 95% by mass or more relative to the total content of (meth)acrylate oligomers. The content of difunctional (meth)acrylate oligomers may also be 100% by mass or less relative to the total content of (meth)acrylate oligomers.

[0028] The glass transition temperature (Tg) of the (meth)acrylate oligomer is preferably greater than 20°C. When the glass transition temperature of the (meth)acrylate oligomer is greater than 20°C, the heat resistance can be improved. The glass transition temperature of the (meth)acrylate oligomer may be 25°C or higher, or 30°C or higher. Furthermore, the glass transition temperature of the (meth)acrylate oligomer may be 80°C or lower, 60°C or lower, or 40°C or lower. The glass transition temperature of the (meth)acrylate oligomer can be measured using a viscoelasticity measuring device after the (meth)acrylate oligomer has been cured. Examples of (meth)acrylate oligomers with a glass transition temperature greater than 20°C include EBECRYL® 8807 (Tg 32°C) and EBECRYL 8191 (Tg 70°C) manufactured by Daicel Ornex Co., Ltd. However, a highly durable cured product can also be formed using the (meth)acrylate oligomer EBECRYL8402 (Tg 14℃).

[0029] The content of the photopolymerizable compound may be 90% by mass or more, or 95% by mass or more, relative to the total content of the inkjet ink. The inkjet ink may also further contain a photopolymerization initiator and a surfactant as a surface modifier.

[0030] Examples of photopolymerization initiators included in inkjet inks include aromatic ketones, acylphosphine oxide compounds, aromatic onium salt compounds, organic peroxides, thio compounds (such as thioxanthone compounds and thiophenyl group-containing compounds), hexaarylbiimidazole compounds, ketoxime ester compounds, borate compounds, azinium compounds, metallocene compounds, active ester compounds, compounds having carbon-halogen bonds, and alkylamine compounds.

[0031] Specific examples of photopolymerization initiators include acetophenone, acetophenone benzyl ketal, 1-hydroxycyclohexyl phenyl ketone, 2,2-dimethoxy-2-phenylacetophenone, xanthones, fluorenone, benzaldehyde, fluorene, anthraquinone, triphenylamine, carbazole, 3-methylacetophenone, 4-chlorobenzophenone, 4,4'-dimethoxybenzophenone, 4,4'-diaminobenzophenone, Michler ketone, benzoin propyl ether, benzoin ethyl ether, benzyldimethyl ketal, 1-(4-isopropylphenyl)-2-hydroxy-2- Examples include methylpropan-1-one, 2-hydroxy-2-methyl-1-phenylpropan-1-one, thioxanthone, diethylthioxanthone, 2-isopropylthioxanthone, 2-chlorothioxanthone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-propan-1-one, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, 2,4-diethylthioxanthone, and bis-(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide.

[0032] Examples of commercially available photopolymerization initiators include IRGACURE® 651 (2,2-dimethoxy-1,2-diphenylethane-1-one), IRGACURE 184 (1-hydroxycyclohexylphenyl ketone), DAROCUR® 1173 (2-hydroxy-2-methyl-1-phenylpropane-1-one), IRGACURE 2959 (1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propane-1-one), IRGACURE 127 (2-hydroxy-1-{4-[4-(2-hydroxy-2-methylpropionyl)-benzyl]phenyl}-2-methylpropane-1-one), IRGACURE 907 (2-methyl-1-(4-methylthiophenyl)-2-morpholinopropane-1-one), and IRGACURE 369 (2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1), IRGACURE 379 (2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-(4-morpholinyl)phenyl]-1-butanone), DAROCURE TPO (2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide), IRGACURE 819 (bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide), IRGACURE 784 (bis(cyclopenta-2,4-dien-1-yl)bis[2,6-difluoro-3-(1H-pyrrole-1-yl)phenyl]titanium), IRGACURE OXE01 (1,2-octanedione,1-[4-(phenylthio)phenyl]-,2-(O-benzoyl oxime)), IRGACURE Examples include OXE02 (ethanone, 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazole-3-yl]-,1-(O-acetyloxime)) and IRGACURE 754 (a mixture of oxyphenylacetic acid, 2-[2-oxo-2-phenylacetoxyethoxy]ethyl ester and oxyphenylacetic acid, 2-(2-hydroxyethoxy)ethyl ester) (both manufactured by BASF).Furthermore, commercially available photopolymerization initiators include Speedcure® TPO, Speedcure DETX (2,4-diethylthioxanthone), and Speedcure ITX (2-isopropylthioxanthone) (all manufactured by Lambson). Commercially available photopolymerization initiators include KAYACURE® DETX-S (2,4-diethylthioxanthone) (manufactured by Nippon Kayaku Co., Ltd.), Lucirin® TPO, LR8893, and LR8970 (all manufactured by BASF). Commercially available photopolymerization initiators include Omnirad® 127, Omnirad 184, Omnirad 819, and Omnirad TPOH (all manufactured by Toyotsu Chemiplus Co., Ltd.), and Yubecryl P36 (manufactured by UCB).

[0033] Among these, Omnirad 127 and Omnirad 184, which have the characteristic of hypoxia inhibition, are preferred as photopolymerization initiators. Also, Omnirad 819 and Omnirad TPOH, which have the characteristic of long-wavelength absorption, are preferred as photopolymerization initiators. Such photopolymerization initiators may be used individually or in combination of two or more.

[0034] Examples of surfactants include silicone-based surfactants, acrylic-based surfactants, cationic surfactants, anionic surfactants, nonionic surfactants, amphoteric surfactants, and fluorine-based surfactants. Among these, silicone-based surfactants are preferred because they can significantly reduce the surface tension of inkjet ink and prevent damage to components that come into contact with the ink, such as the print head and ink supply device.

[0035] As silicone-based surfactants, modified silicones such as polyester-modified silicones and polyether-modified silicones can be used. Among these, polyether-modified silicones are preferred from the viewpoint of significantly reducing surface tension and providing even better wettability and spreadability of the ink on the substrate. Polyether-modified polydimethylsiloxane is preferably used as the polyether-modified silicone. Polyester-modified polydimethylsiloxane is also preferably used as the polyester-modified silicone.

[0036] Examples of commercially available silicone-based surfactants include BYK-347, BYK-348, BYK-UV3500, BYK-UV3510, BYK-UV3530, and BYK-UV3570 (all manufactured by BYK). Among these, BYK-UV3500 can significantly reduce the surface tension of inkjet inks. Furthermore, because BYK-UV3500 has an acrylic group and can chemically bond with photopolymerizable compounds, it is less likely to wear off and separate during molding, making it preferable in terms of durability.

[0037] When using a silicone-based surfactant as the surfactant, the content of the silicone-based surfactant in the inkjet ink is not particularly limited, but is preferably 0.01% to 1% by mass, and more preferably 0.05% to 0.2% by mass.

[0038] The viscosity of the inkjet ink is not particularly limited and should be any viscosity that allows it to be ejected from the inkjet nozzle. From the viewpoint of ejection stability, the viscosity of the inkjet ink is preferably 1 mPa·s to 50 mPa·s at 25°C. Viscosity can be measured using a rheometer manufactured by TA Instruments (model number: AR2000ex) in rotation mode.

[0039] The surface tension of inkjet ink at 25°C is preferably between 20 mN / m and 50 mN / m, from the viewpoint of balancing ejection stability and the reliability of dot formation after impact. A surface tension of 25 mN / m or higher is more preferable. Furthermore, a surface tension of 40 mN / m or lower is even more preferable. The surface tension can be measured by the droplet method at 25°C using a contact angle meter (FAMAS DM500, manufactured by Kyowa Interface Chemical Co., Ltd.).

[0040] As described above, the inkjet ink according to this embodiment contains a photopolymerizable compound comprising a monofunctional monomer and a (meth)acrylate oligomer. The monofunctional monomer includes a (meth)acrylamide compound. The content of the (meth)acrylamide compound is 75% by mass or more of the total content of the monofunctional monomer. The content of the (meth)acrylamide compound is 50% by mass or more of the total content of the photopolymerizable compound. According to the inkjet ink according to this embodiment, it is possible to form a resin mold for injection molding with high durability.

[0041] [Laminated structure] Next, the laminate 1 according to this embodiment will be described with reference to Figure 1. As shown in Figure 1, the laminate 1 according to this embodiment comprises a polycarbonate substrate 2 and a cured inkjet ink 3 disposed on the polycarbonate substrate 2. The cured ink 3 is provided on the outermost surface of the laminate 1, and the surface 3a of the cured ink 3 is exposed.

[0042] The polycarbonate substrate 2 supports the cured product 3. Because the polycarbonate substrate 2 and the cured product 3 of the inkjet ink have high adhesion, providing the cured product 3 to the polycarbonate substrate 2 makes handling easier. Furthermore, the glass transition temperature of the polycarbonate substrate 2 is high, for example, 160°C, and it has high heat resistance, allowing it to be repeatedly used as a resin mold for injection molding. However, if the injection molding temperature is low, the polycarbonate substrate 2 may be made of a resin such as polyethylene terephthalate, ABS resin, or acrylic resin. Also, the shape of the polycarbonate substrate 2 is not particularly limited and can be, for example, flat. The surface 3a of the cured product 3 may have irregularities formed to create a decorative surface (texture, pattern).

[0043] The glass transition temperature Tg of the cured product 3 is preferably 110°C or higher. A high glass transition temperature Tg of the cured product 3 can suppress deformation and fracture of the cured product 3 after molding the thermoplastic resin, thereby improving the durability of the laminate 1. It is more preferable that the glass transition temperature of the cured product 3 is 130°C or higher. However, even if the glass transition temperature Tg of the cured product 3 is not 110°C or higher, a molded product of thermoplastic resin can be formed if the cured product 3 has a glass transition temperature higher than the temperature at which the molded product of thermoplastic resin is released from the mold. The glass transition temperature of the cured product 3 may be 250°C or lower. The glass transition temperature Tg of the cured product 3 can be measured using a viscoelasticity measuring device.

[0044] The storage modulus of cured product 3 at 160°C is 1 × 10⁻⁶ 7 It is preferable that the storage modulus is Pa or higher. When the storage modulus of the cured product 3 is high, deformation and fracture of the cured product 3 after molding the thermoplastic resin can be suppressed, thereby improving the durability of the laminate 1. The storage modulus is 1 × 10⁻⁶. 10 It may be less than or equal to Pa. The storage modulus of the cured product 3 can be measured using a viscoelasticity measuring device.

[0045] The laminate 1 may be stretched. The laminate 1 can be stretched by a stretching process such as vacuum forming to obtain a desired shape. That is, the polycarbonate substrate 2 and the cured product 3 of the laminate 1 are stretched. When such a laminate 1 is used, for example, as a resin mold for injection molding, a wide variety of molded products can be obtained.

[0046] The laminate 1 may be an injection molding resin mold. Such a laminate 1 can be used, for example, as a transfer decoration mold. Because the laminate 1 according to this embodiment has high durability, when used as an injection molding resin mold, it can be repeatedly subjected to injection molding.

[0047] The laminate 1 may be constructed such that the polycarbonate substrate 2 is covered with a cured material 3 so that the molten thermoplastic resin used to form the injection-molded product during injection molding does not come into contact with the surface of the polycarbonate substrate 2. This helps maintain the durability of the laminate 1. The cured material 3 may cover one entire surface of the polycarbonate substrate 2, or it may cover the entire surface.

[0048] [Method for manufacturing laminates] Next, the manufacturing method of the laminate 1 according to this embodiment will be described with reference to Figure 2. The laminate 1 can be manufactured by an inkjet method. Specifically, first, as shown in Figure 2, inkjet ink 3b is applied to the surface of the polycarbonate substrate 2 using an inkjet device 10. As mentioned above, the substrate is not limited to the polycarbonate substrate 2, but may be a substrate made of other resins. The inkjet device 10 includes an inkjet head 11 that ejects the inkjet ink 3b from a nozzle and an ultraviolet lamp 12 that irradiates ultraviolet light. The inkjet ink 3b ejected from the inkjet head 11 adheres to the surface of the polycarbonate substrate 2, and then hardens when irradiated with ultraviolet light emitted from the ultraviolet lamp 12. By repeating the ejection of inkjet ink 3b and ultraviolet irradiation in this manner, a cured product 3 having a predetermined shape can be formed.

[0049] When ejecting inkjet ink 3b from the inkjet head 11, it is preferable to heat the inkjet ink 3b to 30-80°C to reduce its viscosity to 3-15 mPa·s. It is even more preferable to heat the inkjet ink 3b to 32-50°C to reduce its viscosity to 3-13 mPa·s. In particular, it is preferable to use an inkjet ink 3b with a viscosity of 50 mPa·s or less at 25°C, as this allows for good ejection. By using an inkjet ink 3b with such viscosity, high ejection stability can be achieved.

[0050] The cured product 3 may be subjected to additional ultraviolet irradiation or heat treatment. Such additional ultraviolet irradiation and heat treatment may be performed multiple times. In this embodiment, the inkjet ink 3b was cured using ultraviolet light, but active energy rays such as visible light may also be used.

[0051] Thus, the laminate 1 of this embodiment can be manufactured by the inkjet method. Therefore, compared to the case where the mold is manufactured by cutting, the processing time can be reduced and the processing cost can be lowered.

[0052] [Method for manufacturing stretched laminates] Next, the method for manufacturing the stretched laminate 1 according to this embodiment will be described with reference to Figures 3 and 4. The method for manufacturing the laminate 1 according to this embodiment includes a step of stretching the laminate 1.

[0053] The process of stretching the laminate 1 may include at least one stretching step selected from the group consisting of a uniaxial stretching step for stretching the laminate 1 in one direction, a biaxial stretching step for stretching the laminate 1 in two directions, and a multiaxial stretching step for stretching the laminate 1 in three or more directions. These stretching steps may allow for the formation of various patterns on the surface of the laminate 1. The stretching step may involve stretching the laminate 1 in multiple stages. For example, the laminate 1 may be uniaxially stretched followed by biaxial stretching.

[0054] The process of stretching the laminate 1 may include a vacuum forming process, a pressure forming process, or a combination thereof. The vacuum forming process may include a heating process, a vacuum process, and a cooling process. The pressure forming process may include a heating process, a pressure forming process, and a cooling process.

[0055] As shown in Figure 3, in the heating step, the laminate 1 is heated to a temperature that allows for thermal deformation, such as 60°C to 200°C. Next, as shown in Figure 4, in the vacuum step, air is sucked between the laminate 1 and the mold 21 through an air channel 22 provided in the mold 21 so that the heated laminate 1 deforms along the mold 21. As the laminate 1 deforms to conform to the mold 21, at least a portion of the heated laminate 1 is stretched by the vacuum step. In the cooling step, the laminate 1, which has been stretched in at least a portion, is cooled to, for example, 0°C to 50°C. Once the laminate 1 solidifies in the cooling step, the laminate 1 can be removed from the mold 21 while maintaining its stretched shape.

[0056] The pressure forming process differs from the vacuum forming process in that the vacuum process is replaced by the pressure forming process. Other aspects are the same as the vacuum forming process and will not be explained further. In the pressure forming process, compressed air is used to pressurize the space opposite the mold to the laminate 1 so that the laminate 1, heated in the heating process, deforms along the mold. Because the pressurization causes the laminate 1 to deform along the mold, at least a portion of the laminate 1 heated by the pressure forming process is stretched. The stretched laminate 1 can then be cooled by the cooling process described above.

[0057] The laminate 1 formed by at least one of the pressure forming process and the vacuum forming process may be used as an injection molding resin mold while still attached to the mold after the cooling process. For example, the laminate 1 may be used as an injection molding resin mold while still attached to the mold. Alternatively, the laminate 1 formed by at least one of the pressure forming process and the vacuum forming process may be removed from the mold after the cooling process. For example, the laminate 1 removed from the mold may be reattached to another mold and used as an injection molding resin mold.

[0058] As described above, the manufacturing method of the laminate 1 according to this embodiment includes a step of stretching the laminate 1. By stretching and processing the laminate 1, a desired shape can be obtained. When such a laminate 1 is used, for example, as a resin mold for injection molding, a wide variety of molded products can be obtained. Specifically, an inkjet head enables sharp planar printing by aligning the nozzles on a plane so that the distance between the workpiece and each nozzle is constant. On the other hand, when printing directly onto a curved member using an inkjet head, it is not easy to form a sharp printed product because the distance between the curved workpiece and each nozzle aligned on a plane is not constant. However, the laminate 1 according to this embodiment can be stretched and processed. Therefore, for example, by applying inkjet printing to a flat part of a polycarbonate substrate 2 and stretching the flat part so that it has a curved shape, a resin mold can be formed that can transfer a decorative surface to a curved part.

[0059] [Method of manufacturing molded products] Next, the method for manufacturing the molded product according to this embodiment will be described with reference to Figures 5 and 6. In the method for manufacturing the molded product according to this embodiment, the laminate 1 is used as a resin mold for injection molding, and the molded product is obtained by injection molding.

[0060] Specifically, the method for manufacturing a molded product according to this embodiment includes an injection step of injecting a thermoplastic resin 40 into a mold containing a laminate 1, and a release step of releasing the product from the mold at a temperature lower than the glass transition temperature Tg of the cured product 3 to obtain a molded product 40A.

[0061] First, as shown in Figures 5 and 6, a master mold (molding mold) 30 is prepared, which includes a fixed metal mold 31 consisting of a box-shaped cavity with a recess 31a in the center, and a movable metal mold 32 having an injection hole 32a for press-injecting thermoplastic resin 40. By clamping the fixed mold 31 and the movable mold 32 together, a cavity is defined inside the master mold 30.

[0062] Then, the laminate 1 is fixed in the recess 31a of the fixed mold 31 so that the surface 3a of the hardened material 3 faces the cavity. Since the laminate 1 is used as a nest, various shapes and patterns of decorative surfaces can be formed on the molded product 40A by replacing the laminate 1.

[0063] Next, if necessary, the fixed mold 31, the movable mold 32, and the laminate 1 are heated to a predetermined temperature, and then the molten thermoplastic resin 40 is injected into the cavity through the injection hole 32a of the movable mold 32. At this time, the thermoplastic resin 40 comes into direct contact with the surface 3a of the cured product 3 of the laminate 1.

[0064] Next, the fixed mold 31 and the movable mold 32 are cooled to lower the temperature of the thermoplastic resin 40 and allow it to solidify. When releasing the solidified thermoplastic resin 40 from the fixed mold 31 and the laminate 1, the temperature of the thermoplastic resin 40 is lowered to a temperature lower than the glass transition temperature Tg of the cured product 3. This suppresses deformation and breakage of the cured product 3. Then, as shown in Figure 6, the molded product 40A, which has solidified due to the lowered temperature, is removed from the master mold 30. In this way, a molded product 40A having a decorative surface corresponding to the surface shape of the cured product 3 can be obtained.

[0065] The thermoplastic resin 40 formed by the laminate 1 is not particularly limited, but may include polyethylene, polypropylene, polystyrene, polyethylene terephthalate, vinyl chloride resin, ABS resin, polycarbonate, acrylic resin such as polymethyl methacrylate resin (PMMA), polybutylene terephthalate, polyacetal, polyamide, polyvinylidene chloride, or polyvinylidene fluoride. The thermoplastic resin 40 may also contain additives such as inorganic fillers as needed.

[0066] In this embodiment, the laminate 1 is fixed to the fixed mold 31, but the laminate 1 may also be fixed to the movable mold 32, or to both the fixed mold 31 and the movable mold 32. In other words, the laminate 1 may be fixed to the mold, or to at least one of the fixed mold 31 and the movable mold 32. [Examples]

[0067] The embodiment will be described in more detail below with reference to examples and comparative examples, but the embodiment is not limited to these examples.

[0068] [Preparation of inkjet ink] First, inkjet inks according to Examples 1 to 7 and Comparative Examples 1 to 2 were prepared. The raw materials used for the inkjet inks in each example were as follows. (1) Photopolymerizable monomers (1-1) Monofunctional monomers • 4-Acryloylmorpholin; Product name ACMO (registered trademark), manufactured by KJ Chemicals Co., Ltd., glass transition temperature 145℃ • N,N-diethylacrylamide; product name DEAA (registered trademark), manufactured by KJ Chemicals Co., Ltd., glass transition temperature 81℃ • N,N-dimethylacrylamide; product name DMAA (registered trademark), manufactured by KJ Chemicals Co., Ltd., glass transition temperature 119℃ • Isobornyl acrylate; Product name: Light Acrylate (registered trademark) IB-XA, manufactured by Kyoeisha Chemical Co., Ltd. (1-2) Difunctional monomers • Dimethylol-tricyclodecanediaacrylate; Product name: Light Acrylate (registered trademark) DCP-A, manufactured by Kyoeisha Chemical Co., Ltd. • 2-(allyloxymethyl)methyl acrylate; product name AOMA (registered trademark), manufactured by Nippon Shokubai Co., Ltd. Triethylene glycol diacrylate; product name Light Acrylate (registered trademark) 3EG-A, manufactured by Kyoeisha Chemical Co., Ltd. (2) Photopolymerizable oligomers • Aliphatic urethane acrylate; Product name EBECRYL (registered trademark) 8807, manufactured by Daicel Ornex Corporation, glass transition temperature 32℃ • Aliphatic urethane acrylate; Product name EBECRYL (registered trademark) 8402, manufactured by Daicel Ornex Corporation, glass transition temperature 14℃ (3) Photopolymerization initiator Phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide; product name Omnirad 819, manufactured by Toyotsu Chemiplus Co., Ltd. 2,2'-Dihydroxy-2,2'-dimethyl-1,1'-[methylenebis(4,1-phenylene)]bis(propan-1-one); Product name Omnirad 127, manufactured by Toyotsu Chemiplus Co., Ltd. (4) Additives • Polyether-modified polydimethylsiloxane; Product name BYK-UV3500, manufactured by Bic Chemie Japan Co., Ltd., silicone-based surface modifier.

[0069] The photopolymerizable monomer, photopolymerizable oligomer, photopolymerization initiator, and additives were mixed according to the formulations shown in Table 1, and then completely dissolved using a mixer. In this way, inkjet inks for each example were obtained.

[0070] [Table 1]

[0071] [Fabrication of laminates] For each example, the inkjet ink was sprayed onto the central part of the surface of a polycarbonate substrate measuring 80 mm in length, 50 mm in width, and 0.5 mm in thickness using an inkjet device, and the laminate was fabricated by curing with ultraviolet light. The inkjet device used was the Stage JET manufactured by Trytech Co., Ltd. The ultraviolet light source for the inkjet device was a metal halide lamp, with an irradiation intensity of 170 mW / cm². 2 , cumulative light intensity 600 mJ / cm 2 The inkjet-cured material was 50 mm long, 30 mm wide, and 0.3 mm thick.

[0072] [evaluation] (Glass transition temperature Tg) The glass transition temperature (Tg) of the inkjet-cured material in each example's laminate was measured using a viscoelasticity analyzer (EXSTAR6000, manufactured by SII Nanotechnology Co., Ltd.). The measurement conditions for the glass transition temperature (Tg) of the inkjet-cured material are shown below. Measurement mode: Tensile Temperature: 0℃~200℃ Heating rate: 5°C / min. Frequency: 10Hz

[0073] (Storage modulus) The storage modulus at 160°C of the inkjet-cured laminates in each example was measured using a viscoelasticity analyzer (EXSTAR6000, manufactured by SII Nanotechnology Co., Ltd.). The measurement conditions for the storage modulus of the inkjet-cured materials are shown below. Measurement mode: Tensile Temperature: 0℃~200℃ Heating rate: 5°C / min. Frequency: 10Hz

[0074] (Stretch test) The substrate, with 10 mm sections from both ends that were not coated with inkjet ink curing, was clamped in the chuck of a tensile testing machine and heated in a 160°C chamber for 15 minutes. Next, the substrate was pulled at a speed of 50 mm / min by a tensile testing machine in the chamber maintained at 160°C. Each example of the substrate was pulled to achieve elongation ratios of 35%, 25%, and 15%, respectively. The elongation ratio was calculated using the following formula. Elongation = {(Length of substrate after tensile test - Length of substrate before tensile test) / Length of substrate before tensile test} × 100 In this example, the length of the substrate (distance between chucks) before the tensile test was 60 mm. Therefore, when the length of the substrate (distance between chucks) after the tensile test was 69 mm, 75 mm, and 81 mm, the elongation rates were 15%, 25%, and 35%, respectively. The inkjet-cured materials were then observed for cracks and delamination after stretching at each elongation rate.

[0075] (injection molding) Laminates from each example were vacuum-formed to obtain a corrugated resin mold. In Examples 1-2, Examples 4-7, and Comparative Examples 1-2, the elongation ratio was 25%, while in Example 3, the elongation ratio was 15% for vacuum forming. Then, polypropylene (PP) and ABS resin were injection-molded using the resin mold. The resin temperature during injection molding was 220°C for PP and 240°C for ABS resin. Injection molding was stopped when the substrate and the inkjet-cured product separated, and the number of shots that yielded a good molded product was counted.

[0076] [Table 2]

[0077] As shown in Table 2, at an elongation rate of 15%, the polycarbonate substrates and cured products of Examples 1 to 7 did not delaminate, and no cracks occurred in the cured products. On the other hand, in the laminate of Comparative Example 1, the polycarbonate substrate and cured product delaminated at the periphery at all elongation rates. From these results, it is considered that increasing the content of the (meth)acrylamide compound relative to the total content of the photopolymerizable compound improved the adhesion between the polycarbonate substrate and the cured product.

[0078] Furthermore, when PP was injection molded using the resin molds of Examples 1 to 7, good molded products of 50 shots or more were obtained. Also, when ABS was injection molded using the resin molds of Examples 1 to 7, good molded products of 28 shots were obtained. This is thought to be because the inkjet ink cured product of the resin mold did not deform during injection molding, and the penetration of the PP or ABS resin into the polycarbonate substrate was suppressed.

[0079] On the other hand, when the laminate of Comparative Example 1 was vacuum-formed, the inkjet ink cured material peeled off from the polycarbonate substrate, making it impossible to create a resin mold. Furthermore, when PP was injection-molded using the resin mold of Comparative Example 2, only 22 shots yielded good molded products. It is thought that in the resin mold of Comparative Example 2, the PP embedded itself in the cured material, causing stress and resulting in delamination. Additionally, when ABS was injected using the resin mold of Comparative Example 2, good molded products could not be obtained.

[0080] These results indicate that increasing the content of (meth)acrylamide compounds relative to the total content of monofunctional monomers, and the content of (meth)acrylamide compounds relative to the total content of photopolymerizable compounds, to above predetermined levels improves the durability of injection molding resin molds.

[0081] Furthermore, as shown in Table 2, at a stretch ratio of 25%, the polycarbonate substrates and cured products of Examples 1-2 and 4-7 did not delaminate, and no cracks occurred in the cured products. Also, at a stretch ratio of 25%, although cracks occurred in the cured product of Example 3, the polycarbonate substrate and cured product did not delaminate. In addition, when using the resin mold of Example 3, good molded products were obtained in 35 shots by ABS injection molding. Furthermore, when using the resin molds of Examples 4-7, good molded products were obtained in 42 shots or more by ABS injection molding. From these results, it is considered that dimethylol-tricyclodecanediaacrylate and 2-(allyloxymethyl)methyl acrylate contribute to the stretchability and durability of the laminate.

[0082] Furthermore, as shown in Table 2, at an elongation rate of 35%, the polycarbonate substrates and cured products in Examples 1-2 and 7 did not delaminate, and no cracks occurred in the cured products. Also, at an elongation rate of 35%, although cracks occurred in the cured products in Examples 3-6, the polycarbonate substrates and cured products did not delaminate. In addition, when using the resin mold of Example 4, good molded products were obtained in 42 shots by ABS injection molding. On the other hand, when using the resin molds of Examples 5-7, good molded products were obtained in 50 or more shots by ABS injection molding. From these results, it can be seen that the stretchability and durability of the laminate can be further improved when the content of at least one of dimethylol-tricyclodecanediaacrylate and 2-(allyloxymethyl)methyl acrylate is within a predetermined range.

[0083] Although this embodiment has been described above, this embodiment is not limited to these, and various modifications are possible within the scope of the gist of this embodiment. [Explanation of symbols]

[0084] 1. Laminate 2. Polycarbonate substrate 3 Cured product 40A molded product

Claims

1. The compound comprises a photopolymerizable compound containing a monofunctional monomer and a (meth)acrylate oligomer, The aforementioned monofunctional monomer comprises a (meth)acrylamide compound. The content of the (meth)acrylamide compound is 75% by mass or more relative to the total content of the monofunctional monomer. The content of the (meth)acrylamide compound is 50% by mass or more relative to the total content of the photopolymerizable compound. The glass transition temperature of the (meth)acrylamide compound is 81°C or higher. The glass transition temperature of the (meth)acrylate oligomer is 14°C or higher, and this is an inkjet ink for injection molding resin molds.

2. The inkjet ink for injection molding resin molds according to claim 1, wherein the glass transition temperature of the (meth)acrylate oligomer is greater than 20°C.

3. The photopolymerizable compound comprises at least one of the bifunctional monomers dimethylol-tricyclodecanediaacrylate and methyl 2-(allyloxymethyl)acrylate, wherein the inkjet ink for injection molding resin molds is as described in claim 1 or 2.

4. Polycarbonate base material, A cured product of the inkjet ink for injection molding resin molds according to claim 1, disposed on the polycarbonate substrate, A laminate comprising the above.

5. The laminate according to claim 4, which is stretched.

6. A method for manufacturing a molded product, comprising using the laminate described in claim 4 or 5 as a resin mold for injection molding, and obtaining a molded product by injection molding.

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