Resin composition for film formation, inkjet printing film, decorative sheet, and license plate

Abstract

To provide a resin composition for film formation that can form an inkjet printing film having superior inkjet printability and causing no appearance defects even when subjected to heat treatment at high temperature.SOLUTION: The resin composition for film formation comprises a polyurethane resin, a (meth)acrylic resin, an isocyanate crosslinking agent, and a pigment, wherein the content of the (meth)acrylic resin is 15 pts.mass or more based on 100 pts.mass of the polyurethane resin, and the content of the isocyanate crosslinking agent is 5 pts.mass to 20 pts.mass based on 100 pts.mass of the polyurethane resin.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a film-forming resin composition, an inkjet printing film, a decorative sheet, and a license plate. [Background technology]

[0002] Films with design layers formed by inkjet printing are used to decorate vehicles and buildings. These films are sometimes provided with a surface protective layer to protect the design layer (see, for example, Patent Documents 1 to 3). It is also known that an inkjet printing film with a design layer protected by a surface protective layer is laminated to a substrate (such as a metal plate, resin plate, or resin film), three-dimensionally molded, and used as a number plate (also called a "license plate") (see, for example, Patent Document 4). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2016-078301 [Patent Document 2] Japanese Patent Application Publication No. 2020-131589 [Patent Document 3] Japanese Patent Publication No. 2022-146027 [Patent Document 4] Japanese Patent Application Publication No. 2017-177481 Summary of the Invention [Problem to be solved by the invention]

[0004] Inkjet printing films (hereinafter also referred to as decorative sheets) with a surface protective layer attached may be used in high-temperature environments (for example, 200°C or higher). For example, when using a decorative sheet as a license plate, the sheet is exposed to a high-temperature environment when the characters (kanji characters and numbers) are formed by baking printing with resin ink. In addition, when using a decorative sheet as a heat-resistant film or a molded film, it is expected that it will also be exposed to the above-mentioned high-temperature environment. When conventional decorative sheets are used in such high-temperature environments, the inkjet printing film may blister, resulting in poor appearance. Furthermore, increasing the cohesive strength of the film to suppress blistering may result in a decrease in inkjet printability. As described above, it may be difficult to simultaneously prevent poor appearance and ensure inkjet printability in a decorative sheet. The present disclosure has been made in consideration of the above-mentioned conventional circumstances, and aims to provide a film-forming resin composition capable of forming an inkjet printing film suitable for use in decorative sheets, which has excellent inkjet printability and does not suffer from poor appearance even when subjected to heat treatment at high temperatures (e.g., 200°C or higher); an inkjet printing film formed using this film-forming resin composition; and a decorative sheet and license plate using this inkjet printing film. [Means for solving the problem]

[0005] Specific means for achieving the above object are as follows. <1> The composition includes a polyurethane resin, a (meth)acrylic resin, an isocyanate crosslinking agent, and a pigment, the content of the (meth)acrylic resin relative to 100 parts by mass of the polyurethane resin is 15 parts by mass or more; The film-forming resin composition has a content of the isocyanate-based crosslinking agent of 5 to 20 parts by mass relative to 100 parts by mass of the polyurethane-based resin. <2> The pigment is at least one white pigment selected from the group consisting of titanium oxide, zinc oxide, zirconium oxide, aluminum hydroxide, zinc sulfide, and barium sulfate. <1> The film-forming resin composition according to claim 1. <3> The polyurethane resin includes at least one selected from the group consisting of polycarbonate polyurethane resins, polyester polyurethane resins, and polyether polyurethane resins. <1> or <2> The film-forming resin composition according to claim 1. <4> The polyurethane resin has an acid value of 0.1 mgKOH / g to 1.0 mgKOH / g, and a hydroxyl value of 0.1 mgKOH / g to 30 mgKOH / g. <1> ~ <3> The film-forming resin composition according to any one of the preceding claims. <5> <1> ~ <4> 1. A film for inkjet printing formed from the resin composition for film formation according to any one of claims 1 to 9. <6> The gel fraction is 20% by mass to 80% by mass. <5> 10. The inkjet printing film according to claim 19. <7> <5> or <6> a decorative sheet comprising the inkjet printing film described in 1), a pressure-sensitive adhesive layer provided on one side of the inkjet printing film, and a surface protection layer provided on the side of the inkjet printing film opposite to the side on which the pressure-sensitive adhesive layer is provided. <8> a plate substrate and a <7> A license plate comprising the decorative sheet according to claim 1. [Effects of the Invention]

[0006] According to the present disclosure, it is possible to provide a film-forming resin composition capable of forming an inkjet printing film suitable for use in a decorative sheet, which has excellent inkjet printability and does not suffer from poor appearance even when subjected to heat treatment at high temperatures (e.g., 200°C or higher); an inkjet printing film formed using this film-forming resin composition; and a decorative sheet and license plate using this inkjet printing film. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a cross-sectional view of an embodiment of a decorative sheet according to the present disclosure. [Figure 2] FIG. 1 is a cross-sectional view of one embodiment of a license plate of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments of the present disclosure will be described in detail. However, the present disclosure is not limited to the following embodiments. In the following embodiments, components (including element steps, etc.) are not essential unless otherwise specified. The same applies to numerical values ​​and their ranges, and do not limit the present disclosure. When embodiments of the present disclosure are described with reference to the drawings, the configuration of the embodiment is not limited to the configuration shown in the drawings. Furthermore, the size of components in each drawing is conceptual, and the relative size relationships between components are not limited to this. Furthermore, in each drawing, components having substantially the same function are assigned the same reference numerals, and redundant descriptions may be omitted.

[0009] In the present disclosure, numerical ranges indicated using "to" include the numerical values ​​before and after "to" as the minimum and maximum values, respectively. In the numerical ranges described in stages in this disclosure, the upper or lower limit value described in one numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. Furthermore, in the numerical ranges described in this disclosure, the upper or lower limit value of that numerical range may be replaced with a value shown in the examples. In the present disclosure, each component may contain multiple substances corresponding to the component. When multiple substances corresponding to each component are present in the composition, the content or amount of each component means the total content or amount of the multiple substances present in the composition, unless otherwise specified. In the present disclosure, the terms "layer" and "film" include cases where the layer or film is formed over the entire area when the area in which the layer or film is present is observed, as well as cases where the layer or film is formed over only a portion of the area. In this disclosure, the term "lamination" refers to stacking layers, and two or more layers may be bonded together, or two or more layers may be detachable. In the present disclosure, "(meth)acrylic" means at least one of acrylic and methacrylic.

[0010] In the present disclosure, the average thickness of a layer or film is a value calculated as the arithmetic mean value of thickness measurements made at five points on the target layer or film. The thickness of the layer or film is the value measured using a constant pressure thickness gauge (measuring probe diameter 5 mm). In the present disclosure, the term "polyurethane resin" refers to a resin obtained as a reaction product of a polyol, an organic polyisocyanate, and an optional chain extender. In the present disclosure, "(meth)acrylic resin" means a resin that contains structural units derived from (meth)acrylic monomers, and in which the proportion of structural units derived from (meth)acrylic monomers in all structural units of the (meth)acrylic resin is 50 mass % or more. In the present disclosure, "methacrylic resin" refers to a resin in which the proportion of structural units derived from methacrylic monomers in all structural units of the (meth)acrylic resin is 50% by mass or more. Also, in the present disclosure, "acrylic resin" refers to a resin in which the proportion of structural units derived from acrylic monomers in all structural units of the (meth)acrylic resin is 50% by mass or more. Note that when the proportions of structural units derived from methacrylic monomers and structural units derived from acrylic monomers in all structural units of the (meth)acrylic resin are both 50% by mass, the (meth)acrylic resin will be referred to as a methacrylic resin in the present disclosure. In the present disclosure, the term "solid content" refers to components other than the solvent contained in the composition. In this disclosure, "solvent" means water and / or organic solvents.

[0011] <Film-forming resin composition> The film-forming resin composition of the present disclosure comprises a polyurethane resin, a (meth)acrylic resin, an isocyanate-based crosslinking agent, and a pigment, wherein the content of the (meth)acrylic resin relative to 100 parts by mass of the polyurethane resin is 15 parts by mass or more, and the content of the isocyanate-based crosslinking agent relative to 100 parts by mass of the polyurethane resin is 5 parts by mass to 20 parts by mass. The film-forming resin composition of the present disclosure makes it possible to form a film for inkjet printing that has excellent inkjet printability and does not suffer from poor appearance even when subjected to heat treatment at high temperatures. The reason for this is not clear, but is presumed to be as follows. The film-forming resin composition contains 5 to 20 parts by mass of an isocyanate-based crosslinking agent per 100 parts by mass of polyurethane-based resin, which improves the cohesive strength of the film and makes it possible to suppress deformation of the film in a high-temperature environment. As a result, it is presumed that it is possible to suppress the occurrence of poor appearance when subjected to heat treatment at high temperatures. Furthermore, by making the content of (meth)acrylic resin in the film-forming resin composition 15 parts by mass or more per 100 parts by mass of polyurethane resin, the urethane phase and the (meth)acrylic phase are appropriately separated in the inkjet printing film, and the solvent of the inkjet ink is easily absorbed by the (meth)acrylic phase present between the urethane phases. As a result, it is presumed that the inkjet printing film formed from the film-forming resin composition of the present disclosure exhibits moderate phase separation between the urethane phase and the (meth)acrylic phase while maintaining the cohesive strength of the film, thereby suppressing poor appearance caused by swelling when heat-treated at high temperatures and improving inkjet printability. The film-forming resin composition of the present disclosure is suitable for use in forming an inkjet printing film that constitutes a decorative sheet having a surface protective layer. Even when a decorative sheet is heated in a state in which a surface protective layer is provided on an inkjet printing film formed using the film-forming resin composition of the present disclosure, the occurrence of blistering of the inkjet printing film tends to be easily suppressed.

[0012] Each component constituting the film-forming resin composition of the present disclosure will be described in detail below. The film-forming resin composition of the present disclosure contains a polyurethane resin, a (meth)acrylic resin, an isocyanate crosslinking agent, and a pigment, and may contain other components such as organic solvents, plasticizers, softeners, dyes, UV absorbers, light stabilizers, antioxidants, antifoaming agents, surfactants, etc. as needed.

[0013] (Polyurethane resin) The film-forming resin composition of the present disclosure contains a polyurethane-based resin. The type of polyurethane-based resin is not particularly limited, and conventionally known polyurethane-based resins such as polycarbonate-based polyurethane resins, polyester-based polyurethane resins, and polyether-based polyurethane resins can be used. The polyurethane-based resins may be used alone or in combination of two or more. The polyurethane-based resin preferably includes at least one selected from the group consisting of polycarbonate-based polyurethane resins, polyester-based polyurethane resins, and polyether-based polyurethane resins, and from the viewpoint of improving the weather resistance of the inkjet printing film, polycarbonate-based polyurethane resins are more preferred.

[0014] The elongation of the polyurethane resin at 23°C is preferably 50% GL to 1000% GL, more preferably 75% GL to 750% GL, and even more preferably 100% GL to 500% GL, from the viewpoint of preventing cracking of the film when three-dimensionally molding the film for inkjet printing.

[0015] The yield point of the polyurethane resin at 23°C is preferably 0.5N to 20N, more preferably 0.8 to 15N, and even more preferably 1.0N to 10N, from the viewpoint of preventing cracking of the film when three-dimensionally molding the film for inkjet printing.

[0016] The Young's modulus of the polyurethane resin at 23°C is preferably 10 MPa to 2000 MPa, more preferably 15 MPa to 1500 MPa, and even more preferably 20 MPa to 1000 MPa, from the viewpoint of preventing cracking of the film when three-dimensionally molding the film for inkjet printing.

[0017] In this disclosure, the elongation, yield point, and Young's modulus of a polyurethane-based resin at 23°C refer to values ​​determined by conducting a tensile test on a polyurethane-based resin test piece having an average thickness of 35 μm, a length of 150 mm, and a width of 10 mm using a tensile tester in a test environment of 23°C, with a gripping distance of 100 mm and a tensile speed of 300 mm / min.

[0018] When the acid value and hydroxyl value of a polyurethane resin are low, the proportion of urethane bonds among the reactive groups in the polyurethane resin is relatively high, making it easier for the urethane bonds to react with the isocyanate groups of the isocyanate crosslinking agent to form allophanate bonds. Furthermore, when the acid value and hydroxyl value of a polyurethane resin are low, more of the isocyanate crosslinking agent remains unreacted with the polyurethane resin, making it easier for the remaining isocyanate crosslinking agent to form polymers or react with water in the environment to form urea. Furthermore, the polyurethane resin branched by the isocyanate crosslinking agent becomes entangled with the isocyanate polymer and urea, making it easier to form a pseudo-IPN structure (physical crosslinking). Therefore, the solvent resistance and low-temperature impact resistance of inkjet printing films formed from the film-forming resin composition of the present disclosure tend to be improved. From this viewpoint, the polyurethane resin preferably has an acid value of 1.0 mgKOH / g or less and a hydroxyl value of 30 mgKOH / g or less, more preferably an acid value of 0.7 mgKOH / g or less and a hydroxyl value of 27 mgKOH / g or less, and even more preferably an acid value of 0.5 mgKOH / g or less and a hydroxyl value of 25 mgKOH / g or less. The polyurethane resin may have an acid value of 0.1 mgKOH / g or more, 0.2 mgKOH / g or more, or 0.3 mgKOH / g or more. When the polyurethane resin has an acid value of 0.1 mgKOH / g or more, the carboxyl groups in the polyurethane resin react with the isocyanate groups in the isocyanate crosslinking agent, resulting in stronger bonding between the polyurethane resins. As a result, the solvent resistance of the inkjet printing film formed from the film-forming resin composition of the present disclosure is more likely to be improved. The polyurethane resin may have a hydroxyl value of 0.1 mgKOH / g or more, 1 mgKOH / g or more, or even 10 mgKOH / g or more. When the polyurethane resin has a hydroxyl value of 0.1 mgKOH / g or more, the hydroxyl groups in the polyurethane resin react with the isocyanate groups in the isocyanate crosslinking agent, resulting in stronger bonding between the polyurethane resins. As a result, the solvent resistance of the inkjet printing film formed from the film-forming resin composition of the present disclosure is more likely to be improved. The polyurethane resin may have an acid value of 0.1 mgKOH / g to 1.0 mgKOH / g and a hydroxyl value of 0.1 mgKOH / g to 30 mgKOH / g.

[0019] In this disclosure, the acid value of the polyurethane resin is determined in accordance with JIS K0070:1992 This refers to the value measured by the method described above.

[0020] In the present disclosure, the hydroxyl value of a polyurethane resin refers to a value measured by a method in accordance with JIS K0070:1992.

[0021] The proportion of polyurethane resin in the solid content of the film-forming resin composition is not particularly limited, but from the viewpoint of improving the low-temperature impact resistance of the inkjet printing film, it is preferably 40% by mass to 75% by mass, more preferably 45% by mass to 70% by mass, and even more preferably 50% by mass to 65% by mass.

[0022] As the polyurethane resin, commercially available products can be used. Examples of commercially available polyurethane resins include "Rezamin NE-8836 (polycarbonate-based)," "Rezamin NE-8811 (polycarbonate-based)," and "Rezamin NE-8850 (polycarbonate-based)" (all manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd.), as well as "Superflex 420 (polycarbonate-based)," "Superflex 460 (polycarbonate-based)," and "Superflex 210 (polyester-based)" (all manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), and "Pandex T-9280 (polycarbonate-based)," "Pandex T-9290 (polycarbonate-based)," "Pandex T-1190 (polyester-based)," and "Pandex T-8190 (polyether-based)" (all manufactured by DIC Covestro Polymer Co., Ltd.).

[0023] The polyurethane resin in the present disclosure also includes the urethane resin contained in the pigment dispersion liquid described below.

[0024] ((Meth)acrylic resin) The film-forming resin composition of the present disclosure contains a (meth)acrylic resin. The type of (meth)acrylic resin is not particularly limited, and conventionally known (meth)acrylic resins can be used. The (meth)acrylic resins may be used alone or in combination of two or more.

[0025] The (meth)acrylic resin may be a homopolymer consisting of structural units derived from a single (meth)acrylic monomer, or a copolymer consisting of structural units derived from two or more types of (meth)acrylic monomers. Here, the (meth)acrylic monomer refers to at least one of acrylic acid, derivatives of acrylic acid such as alkyl acrylate esters, and derivatives of methacrylic acid such as alkyl methacrylate esters. The derivatives of acrylic acid and the derivatives of methacrylic acid may have a substituent such as a hydroxyl group, an amino group, a carboxyl group, or a glycidyl group.

[0026] The (meth)acrylic resin may be either a solventless type or a solvent type, and from the viewpoint of ease of handling, it is preferable to use a solventless (meth)acrylic resin.

[0027] Examples of solvent-free (meth)acrylic resins include powder, pellet, and bead-shaped (meth)acrylic resins. Powdered (meth)acrylic resins may also be used that have a core-shell structure, in which the core and shell have different monomer compositions.

[0028] As the solvent-free (meth)acrylic resin, commercially available products may be used as they are, but when the (meth)acrylic resin is purchased in a solvent-type state as described below, it may be used after being made solvent-free by distilling off the solvent. For example, a powdered (meth)acrylic resin obtained by distilling off the solvent from an emulsion type (aqueous dispersion of a (meth)acrylic resin) can be used.

[0029] Commercially available solvent-free (meth)acrylic resins include "Dianal MB-2593" (manufactured by Mitsubishi Chemical Corporation), "Parapet GR-F" (manufactured by Kuraray Co., Ltd.), as well as "Dianal BR-50," "Dianal BR-73," "Dianal BR-83," "Dianal BR-101," "Dianal BR-105," "Dianal BR-106," "Dianal BR-113," "Dianal BR-115," "Dianal BR-116," "Dianal BR-117," "Dianal BR-119," "Dianal BR-605," and "Dianal MB-2660." ", "Dianal MB-2952", "Dianal MB-7922", "Dianal LP-3104", "Dianal LP-3106", "Dianal LP-3109", "Dianal LP-3121", "Dianal LP-3130", "Dianal LP-3202", "Dianal LP-3207", "Dianal LP-4100", "Dianal LP-4200", "Dianal LP-5013" (all manufactured by Mitsubishi Chemical Corporation), "Parapet SA-FP", "Parapet SA-NP", "Parapet SA-CP" (all manufactured by Kuraray Co., Ltd.), and the like.

[0030] The solvent used in the solvent-type (meth)acrylic resin may be an organic solvent or water, and the solvent-type (meth)acrylic resin may be an emulsion type (aqueous dispersion of the (meth)acrylic resin).

[0031] Commercially available solvent-based (meth)acrylic resins may be used. Commercially available solvent-based (meth)acrylic resins include "Dianal SE-5437", "Dianal SE-5102", "Dianal SE-5377", "Dianal SE-5649", "Dianal SE-5466", "Dianal SE-5482", "Dianal HR-169", "Dianal HR-124", "Dianal HR-1127", "Dianal HR-116", "Dianal HR-113", "Dianal HR-1148", "Dianal HR-131", "Dianal HR-470", "Dianal HR-634", and "Dianal H". Examples of suitable acrylic resins include "Dianal R-606," "Dianal HR-607," "Dianal LR-1065," "Dianal LR-574," "Dianal LR-143," "Dianal LR-396," "Dianal LR-637," "Dianal LR-162," "Dianal LR-469," "Dianal LR-216," "Dianal LX-1010," and "Dianal LX-2011" (all manufactured by Mitsubishi Chemical Corporation), "Nikasol TS-620," "Nissetsu KP-1876E" (both manufactured by Nippon Carbide Industries Co., Ltd.), and "H-4002" (manufactured by Negami Chemical Industries Co., Ltd.).

[0032] The (meth)acrylic resin in the present disclosure also includes the acrylic resin contained in the pigment dispersion liquid described below.

[0033] The (meth)acrylic resin is preferably a methacrylic resin from the viewpoint of further improving the inkjet printability of the inkjet printing film. When a methacrylic resin and an acrylic resin are used in combination as the (meth)acrylic resin, the proportion of structural units derived from methacrylic monomers in the entire methacrylic resin and acrylic resin is preferably 60% by mass or more, more preferably 70% by mass or more, and even more preferably 80% by mass or more.

[0034] The content of the (meth)acrylic resin relative to 100 parts by mass of the polyurethane resin is 15 parts by mass or more. When the content of the (meth)acrylic resin relative to 100 parts by mass of the polyurethane resin is 15 parts by mass or more, the inkjet printing performance of the inkjet printing film is improved. The content of the (meth)acrylic resin relative to 100 parts by mass of the polyurethane resin is preferably 60 parts by mass or less, from the viewpoint of improving the impact resistance of the inkjet printing film. The content of the (meth)acrylic resin relative to 100 parts by mass of the polyurethane resin is preferably 15 parts by mass to 60 parts by mass, more preferably 15 parts by mass to 56 parts by mass, even more preferably 20 parts by mass to 54 parts by mass, and particularly preferably 25 parts by mass to 52 parts by mass.

[0035] (Isocyanate-based crosslinking agent) The film-forming resin composition of the present disclosure contains an isocyanate-based crosslinking agent. The type of isocyanate-based crosslinking agent is not particularly limited, and conventionally known isocyanate-based crosslinking agents can be used. The isocyanate-based crosslinking agents may be used alone or in combination of two or more. In the present disclosure, the term "isocyanate-based crosslinking agent" refers to a compound having two or more isocyanate groups in one molecule (so-called polyisocyanate compound).

[0036] Examples of the isocyanate crosslinking agent include aromatic polyisocyanate compounds such as xylylene diisocyanate (XDI), diphenylmethane diisocyanate, triphenylmethane triisocyanate, and tolylene diisocyanate (TDI), and aliphatic polyisocyanate compounds or alicyclic polyisocyanate compounds such as hexamethylene diisocyanate (HMDI), pentamethylene diisocyanate (PDI), isophorone diisocyanate, and hydrogenated aromatic polyisocyanate compounds. Further, examples of the isocyanate-based crosslinking agent include dimers, trimers, and pentamers of the above polyisocyanate compounds, adducts of the above polyisocyanate compounds with polyol compounds such as trimethylolpropane, and biuret forms of the above polyisocyanate compounds.

[0037] As the isocyanate-based crosslinking agent, commercially available products can be used. Examples of commercially available isocyanate crosslinking agents include "Coronate HX," "Coronate HL-S," "Coronate L," "Coronate L-45E," "Coronate 2031," "Coronate 2037," "Coronate 2234," "Coronate 2785," "Aquanate 200," and "Aquanate 210" (all manufactured by Tosoh Corporation), "Sumidur N3300," "Desmodur N3400," and "Sumidur N75" (all manufactured by Sumika Covestro Urethane Co., Ltd.), Examples include "Duranate E-405-80T," "Duranate AE700-100," "Duranate 24A-100," and "Duranate TSE-100" (all manufactured by Asahi Kasei Corporation), "Takenate D-110N," "Takenate D-120N," "Takenate M-631N," "MT-Olestar NP1200," "Stabio D-370N," ​​and "Stabio XD-340N" (all manufactured by Mitsui Chemicals, Inc.), and "Rezamin X-100" (manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd.).

[0038] The content of the isocyanate-based crosslinking agent is 5 to 20 parts by mass per 100 parts by mass of the polyurethane-based resin. If the content of the isocyanate-based resin is 5 parts by mass or more per 100 parts by mass of the polyurethane-based resin, the occurrence of defective appearance when the inkjet printing film is heat-treated at high temperatures is suppressed. Furthermore, if the content of the isocyanate-based resin is 20 parts by mass or less per 100 parts by mass of the polyurethane-based resin, the inkjet printing performance of the inkjet printing film is improved. The content of the isocyanate-based crosslinking agent is preferably 6 parts by mass to 15 parts by mass, more preferably 7 parts by mass to 12 parts by mass, relative to 100 parts by mass of the polyurethane-based resin.

[0039] (pigment) The film-forming resin composition of the present disclosure contains a pigment. The type of pigment is not particularly limited, and conventionally known pigments can be used. The pigments may be used alone or in combination of two or more. Examples of pigments include white pigments such as titanium oxide, zinc oxide, zirconium oxide, aluminum hydroxide, zinc sulfide, and barium sulfate, color pigments such as iron oxide, chromium oxide, carbon black, and ultramarine, and extender pigments such as kaolin, talc, mica, and sericite. The pigment preferably contains a color pigment because it enables the inkjet printing film to be colored in a predetermined color, and more preferably a white pigment from the viewpoint of further improving the whiteness of the inkjet printing film, and even more preferably at least one white pigment selected from the group consisting of titanium oxide, zinc oxide, zirconium oxide, aluminum hydroxide, zinc sulfide, and barium sulfate.

[0040] The pigment may be used in the form of a pigment dispersion in which the pigment is dispersed in a dispersion medium. Examples of the dispersion medium include a resin component such as a urethane resin or an acrylic resin, and a solvent component such as butyl acetate or N,N-dimethylformamide. By using such a pigment dispersion, the pigment can be dispersed more uniformly in the film-forming resin composition of the present disclosure without aggregation.

[0041] When the dispersion medium is a urethane-based resin or an acrylic-based resin, these resin components are classified as "polyurethane-based resin" and "(meth)acrylic resin" respectively in the present disclosure. For example, when "NX-501 White" (manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd., 58% by mass of pigment, 21% by mass of acrylic resin, 21% by mass of butyl acetate) is used as the pigment dispersion, the 58% by mass of pigment is classified as a "pigment" in the present disclosure, while the 21% by mass of acrylic resin is classified as a "(meth)acrylic resin" in the present disclosure.

[0042] The content of the pigment relative to 100 parts by mass of the polyurethane resin may be 10 parts by mass to 70 parts by mass. As mentioned above, when a pigment dispersion is used, the content refers to the content of only the pigment, excluding dispersion media such as resin components and solvent components.

[0043] When a white pigment is used as the pigment, the content of the white pigment relative to 100 parts by mass of the polyurethane-based resin is preferably 10 to 70 parts by mass. When the content of the white pigment relative to 100 parts by mass of the polyurethane-based resin is 10 parts by mass or more, good whiteness can be obtained. When the content of the white pigment relative to 100 parts by mass of the polyurethane-based resin is 70 parts by mass or less, a film with excellent low-temperature impact resistance and a smooth and good appearance can be obtained. The content of the white pigment relative to 100 parts by mass of the polyurethane resin is more preferably 15 parts by mass to 65 parts by mass, and even more preferably 20 parts by mass to 60 parts by mass.

[0044] (organic solvent) The film-forming resin composition of the present disclosure may contain an organic solvent from the viewpoint of obtaining a smooth coating appearance. The type of organic solvent is not particularly limited, and is not particularly limited as long as it dissolves or disperses the various components contained in the film-forming resin composition. Examples of organic solvents include ketone-based organic solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; ester-based organic solvents such as methyl acetate, ethyl acetate, propyl acetate, and butyl acetate; aliphatic hydrocarbon-based organic solvents such as n-hexane, n-heptane, and n-octane; alicyclic hydrocarbon-based organic solvents such as cyclohexane, methylcyclohexane, ethylcyclohexane, cycloheptane, and cyclooctane; aromatic hydrocarbon-based organic solvents such as toluene and xylene; and amide-based organic solvents such as N,N-dimethylformamide. The organic solvents may be used alone or in combination of two or more. The content of the organic solvent is appropriately set in consideration of the coating method of the film-forming resin composition of the present disclosure, drying conditions, the types of components contained in the composition, and the like.

[0045] (Other ingredients) The film-forming resin composition of the present disclosure may contain other components such as plasticizers, softeners, dyes, ultraviolet absorbers, light stabilizers, antioxidants, antifoaming agents, and surfactants, as needed. When the film-forming resin composition of the present disclosure contains other components, the content thereof is not particularly limited and may be appropriately set within a range that does not affect the effects of the film-forming resin composition of the present disclosure.

[0046] <Inkjet printing film> The inkjet printing film of the present disclosure is formed from the film-forming resin composition of the present disclosure. Examples of methods for forming the inkjet printing film of the present disclosure using the film-forming resin composition of the present disclosure include known methods using a single-layer T-die extruder, a multi-layer T-die extruder, a calendar molding machine, etc. Alternatively, a film for inkjet printing can be formed by applying a film-forming resin composition containing an organic solvent to one side of a release-treated temporary support such as a polyethylene terephthalate film, a polypropylene film, or paper, and then drying the composition. Examples of such application methods include screen printing, gravure printing, bar coating, knife coating, roll coating, comma coating, blade coating, die coating, spray coating, and methods using an applicator. The crosslinking reaction may be accelerated by heating the inkjet printing film, for example, by drying with hot air or by heating with a heating device such as an oven or a hot plate.

[0047] (average thickness) The average thickness of the inkjet printing film of the present disclosure is appropriately set depending on the application, and is, for example, preferably 20 μm to 120 μm, more preferably 25 μm to 110 μm, and even more preferably 30 μm to 105 μm.

[0048] (gel fraction) The gel fraction of the film for inkjet printing of the present disclosure is preferably 20% by mass or more, more preferably 25% by mass or more, and even more preferably 40% by mass or more, from the viewpoint of improving solvent resistance. The gel fraction of the inkjet printing film of the present disclosure is preferably 80% by mass or less, more preferably 75% by mass or less, and even more preferably 70% by mass or less, from the viewpoint of improving the flexibility of the film. The gel fraction of the inkjet printing film of the present disclosure is preferably 20% by mass to 80% by mass, more preferably 25% by mass to 75% by mass, and even more preferably 40% by mass to 70% by mass, from the viewpoint of achieving both solvent resistance and flexibility of the film. In the present disclosure, the gel fraction refers to a value determined by the method described in the Examples.

[0049] <Decorative sheet> The decorative sheet of the present disclosure comprises the inkjet printing film of the present disclosure, a pressure-sensitive adhesive layer provided on one side of the inkjet printing film, and a surface protective layer provided on the side of the inkjet printing film opposite the side on which the pressure-sensitive adhesive layer is provided. Because the decorative sheet of the present disclosure comprises the inkjet printing film of the present disclosure, it has excellent inkjet printability and is less likely to suffer from poor appearance. The decorative sheet of the present disclosure may have layers other than the pressure-sensitive adhesive layer and the surface protective layer (intermediate layer, design layer, etc.).

[0050] (Adhesive layer) The adhesive layer constituting the decorative sheet is not particularly limited in terms of its components as long as it can adhere to an adherend such as a resin plate, a metal plate, or a glass plate, and can be formed using a (meth)acrylic adhesive, a silicone adhesive, a synthetic rubber adhesive, or the like. The pressure-sensitive adhesive layer preferably contains a (meth)acrylic resin and a crosslinking agent from the viewpoint of improving the adhesion and durability of the decorative sheet to the adherend. Furthermore, the pressure-sensitive adhesive layer preferably further contains a pigment from the viewpoint of improving the concealing properties of the adherend. The pressure-sensitive adhesive layer may contain other components as necessary.

[0051] -(Meth)acrylic resin- The (meth)acrylic resin contained in the pressure-sensitive adhesive layer is preferably an acrylic resin, from the viewpoint of further improving the adhesion and durability of the decorative sheet to an adherend. When an acrylic resin and a methacrylic resin are used in combination as the (meth)acrylic resin contained in the pressure-sensitive adhesive layer, the proportion of structural units derived from acrylic monomers in the entire acrylic resin and methacrylic resin is preferably 70% by mass or more, more preferably 75% by mass or more, and even more preferably 80% by mass or more.

[0052] Furthermore, the total proportion of structural units derived from monomers containing a carboxy group in the molecule, such as acrylic acid, methacrylic acid, and other monomers containing a carboxy group, in all structural units of the (meth)acrylic resin contained in the pressure-sensitive adhesive layer is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and even more preferably 1.0% by mass or more, from the viewpoint of improving the adhesion of the decorative sheet to an adherend and shrinkage resistance. The total proportion of structural units derived from monomers containing a carboxy group in the molecule in all structural units of the (meth)acrylic resin contained in the pressure-sensitive adhesive layer is preferably 20% by mass or less, more preferably 15% by mass or less, and even more preferably 12.5% ​​by mass or less, from the viewpoint of obtaining a good coating appearance of the pressure-sensitive adhesive layer. The total proportion of structural units derived from monomers containing a carboxy group in the molecule in all structural units of the (meth)acrylic resin contained in the pressure-sensitive adhesive layer is preferably 0.1% by mass to 20% by mass.

[0053] The proportion of the (meth)acrylic resin in the solid content of the adhesive layer is not particularly limited, but from the viewpoint of improving the adhesion of the decorative sheet to the substrate, it is preferably 70% by mass to 95% by mass, more preferably 75% by mass to 92% by mass, and even more preferably 80% by mass to 90% by mass.

[0054] -Crosslinking agent- The type of crosslinking agent contained in the pressure-sensitive adhesive layer is not particularly limited, and conventionally known isocyanate-based crosslinking agents, epoxy-based crosslinking agents, etc. The crosslinking agents may be used alone or in combination of two or more. The content of the crosslinking agent is preferably 1 to 10 parts by mass, more preferably 2 to 9 parts by mass, and even more preferably 3 to 8 parts by mass per 100 parts by mass of the (meth)acrylic resin (100 parts by mass of the (meth)acrylic resins in total when two or more types of (meth)acrylic resins are used in combination).

[0055] -Pigments- The type of pigment contained in the pressure-sensitive adhesive layer is not particularly limited, and any conventionally known pigment can be used. The pigments may be used alone or in combination of two or more. The pigment contained in the pressure-sensitive adhesive layer may be the same as or different from the pigment contained in the film for inkjet printing. The pigment contained in the adhesive layer is preferably a white pigment from the viewpoint of improving the whiteness of the decorative sheet, and more preferably contains at least one selected from the group consisting of titanium oxide, zinc oxide, zirconium oxide, aluminum hydroxide, zinc sulfide, and barium sulfate.

[0056] The content of the pigment relative to 100 parts by mass of the (meth)acrylic resin (when two or more types of (meth)acrylic resins are used in combination, 100 parts by mass of the (meth)acrylic resins in total) is preferably 3 parts by mass to 15 parts by mass, more preferably 5 parts by mass to 12 parts by mass, and even more preferably 7 parts by mass to 10 parts by mass.

[0057] -Other ingredients- The pressure-sensitive adhesive layer may contain other components such as a plasticizer, a softener, a light stabilizer, a heat stabilizer, and a tackifier, if necessary. When the pressure-sensitive adhesive layer contains other components, the content of the other components is not particularly limited and may be appropriately set within a range that does not affect the function of the pressure-sensitive adhesive layer.

[0058] -Average thickness- The average thickness of the pressure-sensitive adhesive layer is not particularly limited, and is, for example, preferably 10 μm to 70 μm, more preferably 20 μm to 60 μm, and even more preferably 30 μm to 50 μm.

[0059] (middle class) The decorative sheet of the present disclosure may have an intermediate layer between the inkjet printing film and the pressure-sensitive adhesive layer from the viewpoint of imparting rigidity to improve the handleability of the sheet and from the viewpoint of suppressing migration of inkjet ink solvent to the pressure-sensitive adhesive layer. The intermediate layer preferably contains a polyurethane resin and a pigment from the viewpoints of improving the low-temperature impact resistance of the decorative sheet and suppressing color unevenness. The intermediate layer may contain other components as necessary.

[0060] (Design layer) The decorative sheet of the present disclosure may have a design layer. The design layer is formed on the surface of the inkjet printing film constituting the decorative sheet opposite to the side on which the pressure-sensitive adhesive layer is provided. The design layer may be formed on at least a portion of the inkjet printing film when the inkjet printing film is viewed in plan. In this case, the design layer is a layer provided to impart design to the decorative sheet described below, and is a layer that expresses a pattern, picture, etc. The design layer is formed by known inkjet printing.

[0061] (Surface protective layer) The material of the surface protection layer is not particularly limited. Examples of the surface protective layer include layers made of films containing resins such as polyolefin resins (e.g., polyethylene (PE) and polypropylene (PP)), polyester resins (e.g., polyethylene terephthalate (PET)), acetate resins (e.g., triacetyl cellulose), polyethersulfone resins, polycarbonate resins, polyamide resins, polyimide resins, polyurethane resins, (meth)acrylic resins, vinyl chloride resins, ABS (Acrylonitrile Butadiene Styrene) resins, and fluorine-based resins. The surface protective layer preferably contains a polyurethane resin from the viewpoint of improving the low-temperature impact resistance and the processability during three-dimensional molding of the decorative sheet, and more preferably contains a cured polyurethane resin crosslinked with a crosslinking agent from the viewpoint of improving the low-temperature impact resistance, the processability during three-dimensional molding, and the solvent resistance. The surface protective layer may contain various additives such as a plasticizer, a heat stabilizer, an ultraviolet absorber, a light stabilizer, an antistatic agent, a flame retardant, an antioxidant, a filler, an antifoaming agent, and a surfactant.

[0062] -Average thickness- The average thickness of the surface protective layer is not particularly limited and is, for example, preferably 20 μm to 100 μm, more preferably 20 μm to 90 μm, and even more preferably 30 μm to 70 μm.

[0063] The surface protection layer may be laminated directly onto the surface opposite to the adhesive layer provided on one surface of the inkjet printing film, or may be laminated via an additional adhesive layer. When the surface protective layer is laminated via an additional pressure-sensitive adhesive layer, the types of resin and crosslinking agent contained in the pressure-sensitive adhesive layer are not particularly limited, and conventionally known materials can be used. The resin and crosslinking agent contained in the pressure-sensitive adhesive layer may be the same material as or different from the pressure-sensitive adhesive layer formed on the side of the inkjet printing film opposite to the side on which the surface protective layer is provided.

[0064] The decorative sheet of the present disclosure can be used as a component of the license plate of the present disclosure, which will be described later. In addition to license plates, the decorative sheet of the present disclosure can also be used for the interior or exterior of vehicles such as automobiles, the interior of buildings such as walls, floors, and ceilings, heat-resistant films, molded films, and the like.

[0065] 1 is a cross-sectional view of one embodiment of the decorative sheet of the present disclosure. Hereinafter, in the decorative sheet of the present disclosure, the pressure-sensitive adhesive layer provided on one surface of the inkjet printing film will also be referred to as the "first pressure-sensitive adhesive layer." The decorative sheet 10 in Figure 1 has an inkjet printing film 20, a first adhesive layer 30 provided on one side of the inkjet printing film 20, and a surface protection layer 40 provided on the side of the inkjet printing film 20 opposite to the side on which the first adhesive layer 30 is provided. Between the inkjet printing film 20 and the surface protection layer 40, a second adhesive layer 50 is disposed, which adheres the surface protection layer 40 onto the surface of the inkjet printing film 20. A design layer 60 is provided on the surface of the inkjet printing film 20 opposite to the surface on which the first pressure-sensitive adhesive layer 30 is provided. The first pressure-sensitive adhesive layer 30 and the second pressure-sensitive adhesive layer 50 may have the same configuration or different configurations. The inkjet printing film 20, the first adhesive layer 30, the surface protection layer 40, the second adhesive layer 50, and the design layer 60 are as described above in detail. By providing the surface protection layer 40 on the design layer 60, the durability of the design layer 60 is improved.

[0066] The decorative sheet of the present disclosure may be produced through any process. For example, a pressure-sensitive adhesive film for inkjet printing may be formed by providing a pressure-sensitive adhesive layer on one side of a film for inkjet printing. Separately, a pressure-sensitive adhesive layer may be provided on one side of a surface protection film to form a surface-protecting pressure-sensitive adhesive film. Next, a surface-protecting pressure-sensitive adhesive film may be attached to the side of the film for inkjet printing opposite to the side on which the pressure-sensitive adhesive layer is provided, thereby obtaining a decorative sheet. Alternatively, the above-mentioned inkjet printing adhesive film may be attached to a substrate such as a plate substrate constituting a license plate as described below, and then the above-mentioned surface protective adhesive film may be attached to the inkjet printing adhesive film, thereby forming a decorative sheet on the substrate.

[0067] <License plate> The license plate of the present disclosure comprises a plate substrate and a decorative sheet of the present disclosure provided on one side of the plate substrate. The license plate of the present disclosure may be configured, for example, by adhering an adhesive layer of the decorative sheet of the present disclosure to one side of the plate substrate, and a design layer (e.g., license plate characters) may be provided on the surface of the surface protection layer constituting the decorative sheet opposite the side on which the inkjet printing film is placed. The method for forming the design layer on the surface of the surface protection layer opposite the side on which the inkjet printing film is provided is not particularly limited, and the design layer can be formed by known printing methods such as inkjet printing, screen printing, gravure printing, hot stamp printing, letterpress printing, etc. In particular, when forming the characters on the license plate, it is preferable to form the characters by printing a heat-curable ink using a known printing method and then baking it (so-called baked coating).

[0068] 2 is a cross-sectional view of one embodiment of the license plate of the present disclosure. Hereinafter, in the license plate of the present disclosure, the adhesive layer provided on one side of the inkjet printing film will also be referred to as the "first adhesive layer." License plate 70 in FIG. 2 has plate substrate 80, first adhesive layer 30, inkjet printing film 20, second adhesive layer 50, and surface protection layer 40, in this order. In license plate 70, second design layer 90 is provided on surface protective layer 40. In addition, design layer 60 is provided on the surface of inkjet printing film 20 opposite to the surface on which first adhesive layer 30 is provided. The details of the plate substrate 80 will be described later. The details of the decorative sheet 10 and the second design layer 90 are as described above.

[0069] The plate substrate can be a metal plate or a resin plate. Examples of metal plates include aluminum plates, stainless steel plates, and iron plates. Examples of resin plates include polycarbonate plates, polyester plates, vinyl chloride plates, acrylic plates, ABS plates, and PP plates. If necessary, these plate materials can be molded into the shape of a frame or the like. [Example]

[0070] The present disclosure will be described in more detail below based on examples, but the present disclosure is not limited to these examples.

[0071] <Preparation of film-forming resin composition> The film-forming resin compositions of each Example and Comparative Example were prepared by mixing the polyurethane resin, (meth)acrylic resin, isocyanate crosslinker, and pigment (white pigment) in the amounts listed in Table 1 with a 1:1 (by weight) mixed solvent of N,N-dimethylformamide and toluene as the organic solvent using a disper mixer at 23°C for 1 hour. The organic solvent was added so that the solids content of the film-forming composition was 23% by weight. The polyurethane resin, (meth)acrylic resin, isocyanate crosslinker, and pigment (white pigment) listed in Table 1 all represent the amount (parts by weight) of the solids. Regarding the pigment (white pigment) contained in NX-501 White (described below), the pigment (titanium oxide) content is listed in the "White Pigment" column, and the acrylic resin content is listed in the "(meth)acrylic Resin" column.

[0072] <Preparation of film for inkjet printing> The obtained film-forming resin composition was applied using an applicator to a polyethylene terephthalate film (manufactured by Lintec Corporation, thickness: 75 μm, product name P756050) that had been subjected to a release treatment so that the average thickness after drying would be 30 μm, and the film was dried by heating in an atmosphere of 100°C for 3 minutes and in an atmosphere of 160°C for 3 minutes to obtain inkjet printing films of Examples 1-10 and Comparative Examples 1-3. In Table 1, the details of each component contained in the film-forming resin composition are as follows.

[0073] NE-8836: "Rezamin NE-8836" [Dainichiseika Color & Chemicals Mfg. Co., Ltd., one-component non-yellowing polycarbonate-based urethane resin], elongation at 23°C: 166% GL, yield point at 23°C: 8.7 N, Young's modulus at 23°C: 431.7 MPa, acid value: 0.3 mg KOH / g, hydroxyl value: 15 mg KOH / g NE-8811: "Rezamin NE-8811" [Dainichiseika Color & Chemicals Mfg. Co., Ltd., one-component non-yellowing polycarbonate-based urethane resin], elongation at 23°C: 278% GL, yield point at 23°C: 1.7 N, Young's modulus at 23°C: 65.0 MPa, acid value: 0.3 mg KOH / g, hydroxyl value: 17 mg KOH / g MB-2593: "Dianal MB-2593" (Mitsubishi Chemical Corporation, methacrylic resin, solvent-free (powder)) GR-F: "Parapet GR-F" (Kuraray Co., Ltd., methacrylic resin, solvent-free type (powder, core-shell type)) X-100: "Rezamin X-100" (Dainichiseika Color & Chemicals Mfg. Co., Ltd., isocyanate-based crosslinking agent) N3300: "Sumidur N3300" (manufactured by Sumika Covestro Urethane Co., Ltd., hexamethylene diisocyanate trimer) D-370N: "STABIO D-370N" (manufactured by Mitsui Chemicals, Inc., pentamethylene diisocyanate-based polyisocyanate) NX-501: "NX-501 White" [Dainichiseika Color & Chemicals Mfg. Co., Ltd., titanium dioxide dispersion (pigment 58% by mass, acrylic resin 21% by mass, butyl acetate 21% by mass (solids content 79% by mass)]

[0074] The elongation, yield point and Young's modulus at 23° C. for each polyurethane resin (NE-8836 and NE-8811) were measured as follows. A polyurethane resin and N,N-dimethylformamide as a diluent were mixed and stirred using a disper at 23°C for 10 minutes, and the resulting solution was applied to an untreated polyethylene terephthalate film (manufactured by Lintec Corporation, thickness: 75µm, product name P756050) using an applicator to an average thickness of 35µm, and then heated and dried at 100°C for 3 minutes and then at 160°C for 3 minutes to form a film. The diluent was blended so that the solid content in the solution was 23% by mass. The film thus obtained was cut into a length of 150 mm and a width of 10 mm, and a tensile test was performed using a tensile tester (manufactured by A&D Co., Ltd., product name RTG-1310) at a grip distance of 100 mm and a pulling speed of 300 mm / min to determine the elongation, yield point, and Young's modulus. The measurement temperature was 23°C.

[0075] [Preparation of adhesive film for inkjet printing] -Synthesis of acrylic copolymer- A reactor equipped with a stirrer, a reflux condenser, a successive dropping device, and a thermometer was charged with 25 mass% of a monomer mixture consisting of 90 parts by mass of n-butyl acrylate and 10 parts by mass of acrylic acid, 45.0 parts by mass of ethyl acetate (organic solvent), and 0.015 parts by mass of 2,2'-azobisisobutyronitrile (AIBN; polymerization initiator), and the mixture was heated to carry out polymerization at the reflux temperature for 20 minutes. Next, to the polymerization reactant in the reactor maintained at reflux temperature, the remaining 75% by mass of the monomer mixture and a polymerization initiator solution consisting of 30.0 parts by mass of ethyl acetate and 0.15 parts by mass of 2,2'-azobisisobutyronitrile were successively added dropwise over 1.5 hours, and the mixture was maintained for 1 hour to carry out a polymerization reaction. Thereafter, a polymerization initiator solution consisting of 25.0 parts by mass of ethyl acetate and 0.30 parts by mass of 2,2'-azobisisobutyronitrile was successively added dropwise over 1 hour, and the polymerization reaction was further carried out for 2 hours to obtain an acrylic copolymer solution.

[0076] A mixture of 100 parts by weight (solids equivalent) of the acrylic copolymer obtained as described above, 8.34 parts by weight (solids equivalent) of the white pigment DAD-100 (DIC Corporation, titanium oxide pigment), 5.0 parts by weight (solids equivalent) of the isocyanate crosslinking agent Coronate L-45E (Mitsubishi Gas Chemical Company, Inc.), and ethyl acetate was applied to a release-treated polyethylene terephthalate film (Lintec Corporation, thickness: 75 μm, PET75GS (product name)) to a dry thickness of 40 μm, and then heated and dried at 100 ° C. for 1 minute to obtain a pressure-sensitive adhesive layer. The resulting pressure-sensitive adhesive layer was attached to one side of the inkjet printing film prepared as described above to prepare an evaluation sheet (inkjet printing pressure-sensitive adhesive film).

[0077] [Preparation of surface protection film (surface protection layer)] In a reactor equipped with a stirrer, 90 parts by weight of polyurethane resin 1 (trade name: Resamine NE-8836), 10 parts by weight of polyurethane resin 2 (trade name: Resamine NE-8811), 20 parts by weight of crosslinker (trade name: Resamine X-100), 0.1 parts by weight of crosslinking catalyst (trade name: UA-38, tin 2-ethylhexylate, manufactured by Tokushiki Co., Ltd.), and diluent (N,N-dimethylformamide) were mixed and stirred using a disper at an ambient temperature of 23°C for 10 minutes to obtain a composition for forming a surface protective film. The diluent was added so that the solids content of the composition for forming a surface protective film was 25% by weight. Next, the composition for forming a surface protective film was applied to the easily peelable surface of a release film (trade name: P756050, polyethylene terephthalate (PET), thickness: 75 μm, manufactured by Lintec Corporation) that had been surface-treated with a silicone-based release treatment agent (so-called easy-peeling treatment) so that the coating film would have a thickness of 35 μm after drying, forming a coating film. The formed coating film was then heated at 100°C for 3 minutes, and then further heated at 160°C for 3 minutes to dry, thereby producing a surface protective film (surface protective layer).

[0078] [Preparation of adhesive film for surface protection] -Synthesis of Resin A- A reactor equipped with a stirrer, a reflux condenser, a successive dropping device, and a thermometer was charged with 25 mass% of a monomer mixture consisting of 53 parts by mass of n-butyl acrylate, 43 parts by mass of methyl acrylate, and 4 parts by mass of acrylic acid, 45.0 parts by mass of ethyl acetate (organic solvent), and 0.015 parts by mass of 2,2'-azobisisobutyronitrile (AIBN; polymerization initiator), and the mixture was heated to carry out polymerization at the reflux temperature for 20 minutes. Next, the remaining 75% by weight of the monomer mixture and a polymerization initiator solution consisting of 30.0 parts by weight of ethyl acetate and 0.15 parts by weight of 2,2'-azobisisobutyronitrile were added dropwise over 1.5 hours to the polymerization reaction mixture in the reactor maintained at reflux temperature. The polymerization reaction was continued for 1 hour, and then a polymerization initiator solution consisting of 25.0 parts by weight of ethyl acetate and 0.30 parts by weight of 2,2'-azobisisobutyronitrile was added dropwise over 1 hour. The polymerization reaction was continued for another 2 hours to obtain a polymerization reaction mixture. The resulting polymerization reaction mixture was diluted with methyl ethyl ketone (MEK) to a solids concentration of 35% by weight and then cooled to obtain a solution of resin A. Note that "solids concentration" here refers to the mass proportion of resin A in the resin A solution. -Synthesis of Resin B- A reactor equipped with a stirrer, a reflux condenser, a successive dropping device, and a thermometer was charged with 20 mass% of a monomer mixture consisting of 80 parts by mass of methyl methacrylate, 14 parts by mass of ethyl acrylate, and 6 parts by mass of 2-dimethylaminoethyl methacrylate, 45.0 parts by mass of ethyl acetate (organic solvent), and 0.15 parts by mass of 2,2'-azobisisobutyronitrile (AIBN; polymerization initiator), and the mixture was heated to carry out polymerization at the reflux temperature for 20 minutes. To the polymerization reaction mixture in the reactor, which was maintained at reflux temperature, the remaining 80% by weight of the monomer mixture and a polymerization initiator solution consisting of 30.0 parts by weight of ethyl acetate and 0.15 parts by weight of 2,2'-azobisisobutyronitrile were added dropwise over 1.5 hours. The mixture was maintained for 1 hour to allow the polymerization reaction to proceed. Then, a polymerization initiator solution consisting of 25.0 parts by weight of ethyl acetate and 0.30 parts by weight of 2,2'-azobisisobutyronitrile was added dropwise over 1 hour. The polymerization reaction was continued for another 2 hours to obtain a polymerization reaction mixture. The resulting polymerization reaction mixture was diluted with methyl ethyl ketone (MEK) to a solids concentration of 36% by weight and then cooled to obtain a solution of resin B. Note that "solids concentration" here refers to the mass proportion of resin B in the resin B solution.

[0079] -Preparation of adhesive film for surface protection- A surface protective adhesive film was prepared as follows using a surface protective film and an adhesive composition obtained by mixing 100 parts by mass of Resin A, 15 parts by mass of Resin B, and 0.1 parts by mass of Tetrad C (trade name, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, epoxy equivalent: 100, solids content 100% by mass, manufactured by Mitsubishi Gas Chemical Company, Inc.) with respect to each of 100 parts by mass of Resin A. A pressure-sensitive adhesive composition was applied to the easily peelable surface of a release film (trade name: PET75GS, material: polyethylene terephthalate (PET), thickness: 75 μm, manufactured by Lintec Corporation) that had been surface-treated with a silicone-based release agent (so-called easy-release treatment) to form a coating film with a dry thickness of 25 μm. The formed coating film was then dried by heating at 100°C for 1 minute to form a pressure-sensitive adhesive layer on the release film. A surface protection film was then attached to the exposed surface of the pressure-sensitive adhesive layer, and the resulting film was aged at 23°C for 1 week to produce a surface-protective pressure-sensitive adhesive film having a surface protection film (surface protection layer) / pressure-sensitive adhesive layer / release film configuration.

[0080] [Appearance (swelling) evaluation] -Preparation of evaluation plates- The evaluation sheet was attached to an aluminum plate, and then a surface-protecting adhesive film was attached on top of that. The evaluation sheet and the surface-protecting adhesive film constituted a decorative sheet. After attachment, the sheet was heated at 120°C for 1 hour to produce an evaluation plate. The evaluation plates were heated at 250°C for 3 minutes using a hot air dryer. After heating, the appearance of the samples was visually evaluated. The evaluation criteria are as follows: "A" and "B" are practically acceptable levels, with "A" being the most preferable. The results are shown in Table 1. A: No swelling B: Slight swelling is observed C: Numerous blisters have occurred

[0081] [Inkjet (IJ) printability evaluation] Using an inkjet printer JV-300 (manufactured by MIMAKI), a 100% M (magenta) solid print was printed in a size of 150 mm x 150 mm on the side of the evaluation sheet where the inkjet printing film was exposed, and the appearance of the printed area was visually evaluated. The evaluation criteria for printability are as follows: "A" and "B" are practical levels, with "A" being the most preferable. The results are shown in Table 1. A: There are no uneven shades and it looks uniform. B: Slight unevenness in shading is visible C: Print bleeding and unevenness in density are clearly visible

[0082] [Solvent resistance evaluation] The gel fraction of the prepared inkjet printing film was measured. The "gel fraction of the film" refers to the proportion of solvent-insoluble matter measured using a 1:1 (by mass) mixture of toluene and isopropyl alcohol as an extraction solvent. Specifically, the gel fraction of the film was measured according to the following (1) to (4). (1) Approximately 0.15 g of inkjet printing film was attached to a 250-mesh wire mesh (100 mm x 100 mm) whose mass was accurately measured using a precision balance, and the wire mesh was folded five times with the inkjet printing film facing inward to prevent leakage of the gel. The mass was then accurately measured using a precision balance. (2) The obtained sample was immersed in 80 mL of a solvent in which toluene and isopropyl alcohol were mixed in a 1:1 ratio (by mass) at 23°C for 3 days. (3) The sample was taken out, washed with a small amount of the mixed solvent, and dried for 24 hours at 120° C. Thereafter, the mass was accurately measured using a precision balance. (4) The gel fraction was calculated using the following formula: Gel fraction (unit: mass%) = (ZX) / (YX) × ​​100 where X is the mass of the wire mesh (unit: g), Y is the mass of the wire mesh with the film attached before immersion (unit: g), and Z is the mass of the wire mesh with the film attached after immersion and drying (unit: g). The evaluation criteria were as follows: "A" and "B" are practically acceptable levels, with "A" being the most preferable. The results are shown in Table 1. A: 40% by mass or more B: 20% by mass or more and less than 40% by mass C: Less than 20% by mass

[0083] [Table 1]

[0084] The evaluation results shown in Table 1 reveal the following: The inkjet printing film formed from the film-forming resin composition of Comparative Example 1, in which the content of (meth)acrylic resin was less than 15 parts by mass per 100 parts by mass of polyurethane resin, had poor inkjet printability. The inkjet printing film formed from the film-forming resin composition of Comparative Example 2, which did not contain an isocyanate-based crosslinking agent, suffered from poor appearance when subjected to heat treatment at high temperature. The inkjet printing film formed from the film-forming resin composition of Comparative Example 3, in which the content of the isocyanate-based crosslinking agent exceeded 20 parts by mass per 100 parts by mass of the polyurethane-based resin, had poor inkjet printability. On the other hand, the inkjet printing films formed from the film-forming resin compositions of Examples 1-10 had excellent inkjet printability and were less likely to suffer from poor appearance even when subjected to heat treatment at high temperatures. [Explanation of symbols]

[0085] 10 Decorative sheet 20 Inkjet printing film 30 Adhesive layer (first adhesive layer) 40 Surface protective layer 50 Second adhesive layer 60 Design Layer 70 license plate 80 Plate substrate 90 Second Design Layer

Claims

1. The composition includes a polyurethane resin, a (meth)acrylic resin, an isocyanate crosslinking agent, and a pigment, the content of the (meth)acrylic resin relative to 100 parts by mass of the polyurethane resin is 15 parts by mass or more; The film-forming resin composition has a content of the isocyanate-based crosslinking agent of 5 to 20 parts by mass relative to 100 parts by mass of the polyurethane-based resin.

2. 2. The film-forming resin composition according to claim 1, wherein the pigment is at least one white pigment selected from the group consisting of titanium oxide, zinc oxide, zirconium oxide, aluminum hydroxide, zinc sulfide, and barium sulfate.

3. 2. The film-forming resin composition according to claim 1, wherein the polyurethane resin comprises at least one selected from the group consisting of polycarbonate-based polyurethane resins, polyester-based polyurethane resins, and polyether-based polyurethane resins.

4. 2. The film-forming resin composition according to claim 1, wherein the polyurethane resin has an acid value of 0.1 mgKOH / g to 1.0 mgKOH / g and a hydroxyl value of 0.1 mgKOH / g to 30 mgKOH / g.

5. A film for inkjet printing formed from the film-forming resin composition according to any one of claims 1 to 4.

6. 6. The film for inkjet printing according to claim 5, wherein the gel fraction is 20% by mass to 80% by mass.

7. A decorative sheet comprising: the inkjet printing film according to claim 5; an adhesive layer provided on one side of the inkjet printing film; and a surface protection layer provided on the side of the inkjet printing film opposite to the side on which the adhesive layer is provided.

8. A license plate comprising a plate substrate and the decorative sheet according to claim 7 provided on one surface of the plate substrate.

Images