Surface protective film, hard coat film with surface protective film, and method for manufacturing resin molding

Abstract

To provide an adhesive which prevents generation of streaks on a hard coat layer when a resin molded article is manufactured using a hard coat film for resin molding having a surface protective film provided on a semi-cured hard coat layer, the hard coat layer is completely cured after molding, and a protective layer is peeled off, and a surface protective film of the hard coat layer using the adhesive.SOLUTION: A surface protective film for protecting a hard coat layer of a film having the hard coat layer on the outermost layer has an adhesive layer formed on one outermost surface of a base material, the base material contains a thermoplastic resin, and the adhesive layer contains an elastomer, a thermoplastic resin, and a tackifier.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a surface protective film, a hard coat film with a surface protective film, and a method for producing a resin molded product. [Background technology]

[0002] Resin molded products are widely used in portable information terminal devices such as mobile phones, notebook computers, home appliances, and automobile interior and exterior parts. These resin molded products are usually decorated on their surfaces to enhance their design after molding the plastic resin. A known decoration method is to provide a decorative film with a pattern or hard coat layer by printing or coating on the film, and then apply the film to the surface of the resin molded product using the in-mold molding method.

[0003] The in-mold lamination method (hereinafter sometimes abbreviated as the "IML method" in this specification), which is one of the in-mold molding methods, is a technology in which a decorative film, which has a hard coat layer on one side of a base film and a pattern layer or adhesive layer on the other side, is held inside an injection molding die, and the decorative film is bonded to the surface of a resin molded product at the same time as injection molding.

[0004] A known laminated hard-coated film for molding used in the IML method includes a hard-coat layer containing an active energy ray-curable resin provided on a substrate film, the hard-coat layer containing a hindered phenol-based antioxidant in an amount of 1 to 10 parts by weight relative to 100 parts by weight of the active energy ray-curable resin, and the laminated hard-coated film has an elongation of 30% or more in an atmosphere of 23°C and 50% RH after heat treatment at 150°C or higher (see Patent Document 1).

[0005] The laminated hard coat film for molding is produced by coating one side of a substrate film with a coating composition containing at least an active energy ray curable resin, a polymerization initiator, and a hindered phenol-based antioxidant, drying the coating composition to form a hard coat layer, irradiating the hard coat layer with active energy rays as necessary, and then laminating a protective film on the side of the hard coat layer opposite to the substrate film. In this case, the hard coat layer is not completely cured but is in a semi-cured state.

[0006] In addition, a resin molded product using the laminated hard-coated film for molding is produced by forming a decorative layer on the laminated hard-coated film for molding by printing or the like as necessary, preheating the laminated hard-coated film for molding, and then forming the laminated hard-coated film for molding into a resin molded product by simultaneously molding and integrating it with a resin material by an IML method, and then post-exposing the laminated hard-coated film for molding integrated with the resin molded product to active energy rays to completely cure it.

[0007] In addition, as the protective film for the laminated hard coat film for molding, a polyethylene terephthalate (PET) film, a polyolefin film (e.g., polyethylene, polypropylene, etc.), etc. can be preferably used, and as the material for the adhesive layer for providing the protective film on the hard coat layer, acrylic, urethane, polyester, rubber, silicone-based adhesives, etc. can be mentioned. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] JP 2012-210755 A Summary of the Invention [Problem to be solved by the invention]

[0009] However, when a resin molded product is produced using the laminated hard coat film for molding in which a protective layer is provided on a semi-cured hard coat layer using the adhesive, there is a problem that streaks are generated on the hard coat layer when the hard coat layer is completely cured after molding and the protective layer is peeled off. An object of the present invention is to provide a pressure-sensitive adhesive that does not cause streaks on a hard coat layer as described above, and a surface protection film for a hard coat layer that uses such a pressure-sensitive adhesive. [Means for solving the problem]

[0010] As a result of intensive research into solving the above-mentioned problems, the present inventors discovered that the above-mentioned problems can be solved by forming an adhesive layer of a surface protection film for protecting a hard coat layer of a film having a hard coat layer as its outermost layer from a composition containing an elastomer, a thermoplastic resin, and a tackifier, and thus completed the present invention.

[0011] In other words, the present invention relates to a surface protection film for protecting a hard coat layer of a film having a hard coat layer as an outermost layer, the surface protection film comprising an adhesive layer formed on one outermost surface of a substrate, the substrate containing a thermoplastic resin, and the adhesive layer containing an elastomer, a thermoplastic resin, and a tackifier.

[0012] The elastomer is preferably a styrene-based elastomer. The thermoplastic resin is preferably a polyolefin resin.

[0013] The surface protection film is cut to a width of 25 mm and a length of 200 mm, and is attached to a hard coat layer using a 2 kg roller to obtain a test piece. After leaving the test piece at 23°C for one day, the adhesion strength of the surface protection film to the hard coat layer (peel speed 0.3 m / min, 180° peel) is in the range of 0.01 to 0.5 N / 25 mm, and it is preferable that the surface protection film is cut to a width of 25 mm and a length of 200 mm, and is attached to a hard coat layer using a 2 kg roller to obtain a test piece. After leaving the test piece at 100°C for two hours, the adhesion strength of the surface protection film to the hard coat layer (peel speed 0.3 m / min, 180° peel) is 0.5 N / 25 mm or less.

[0014] Furthermore, the surface protection film is cut to a width of 25 mm and a length of 200 mm, and the surface protection film is attached to a hard coat layer using a 2 kg roller to obtain a test piece. After leaving the test piece at 100°C for 2 hours, it is preferable that the adhesive strength of the surface protection film to the hard coat layer (peel speed 0.3 m / min, 180° peel) is 0.1 N / 25 mm or less.

[0015] The surface roughness of the adhesive layer is preferably in the range of 0.01 to 0.30 μm. Furthermore, the surface roughness of the adhesive layer is preferably in the range of 0.01 to 0.10 μm.

[0016] The adhesive layer preferably contains 40 to 70% by mass of elastomer, 20 to 40% by mass of polyolefin resin, and 10 to 20% by mass of tackifier based on the entirety of the adhesive layer.

[0017] The present invention further relates to a hard coat film with a surface protective film, which is obtained by laminating an adhesive layer of any one of the above surface protective films and a hard coat layer of a film having the above hard coat layer as the outermost layer.

[0018] The hard coat film with a surface protective film is preferably a film with a surface protective film for resin molding. The resin molding is preferably in-mold molding.

[0019] Furthermore, the present invention relates to a method for producing a resin molded product, comprising applying a composition for forming a hard coat to one of the outermost layers of a film to form a hard coat layer, laminating an adhesive layer of any one of the surface protection films to the hard coat layer while the hard coat layer is in a semi-cured state to form a hard coat film with a surface protection film, performing resin molding using the hard coat film with the surface protection film and a resin, and then curing the hard coat layer. The resin molding is preferably in-mold molding. Effect of the Invention

[0020] By using the surface protective film of the present invention, even if the surface protective film is attached and resin molding is performed before the hard coat layer is completely cured, the effect of preventing streaks from occurring on the surface of the hard coat layer after the surface protective film is peeled off is achieved. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] The surface protection film of the present invention is a surface protection film for protecting a hard coat layer of a film having a hard coat layer as an outermost layer, and comprises an adhesive layer formed on one outermost surface of a substrate, the substrate containing a thermoplastic resin, and the adhesive layer containing an elastomer, a thermoplastic resin, and a tackifier.

[0022] The thermoplastic resin contained in the substrate constituting the surface protection film of the present invention is not particularly limited, and specific examples thereof include polycarbonate resin, an alloy of polyphenylene ether resin and polystyrene resin, an alloy of polyphenylene ether resin and polyamide resin, a thermoplastic polyester resin, a methyl methacrylate / acrylonitrile / butadiene / styrene copolymer resin, a methyl methacrylate / styrene copolymer resin, a methyl methacrylate resin, a rubber-reinforced methyl methacrylate resin, a polyamide resin, a polyacetal resin, a polylactic acid resin, a polyolefin resin, and a polyphenylene sulfide resin.

[0023] Among them, polyolefin resins or polyester resins are preferred. Specific examples of polyolefin resins include low-density polyethylene, medium-density polyethylene, high-density polyethylene, linear low-density polyethylene, low-crystalline or non-crystalline ethylene-α-olefin copolymers, polypropylene, propylene-ethylene copolymers (random copolymers or block copolymers), propylene-α-olefin copolymers, propylene-ethylene-α-olefin copolymers, ethylene-ethyl (meth)acrylate copolymers, ethylene-methyl (meth)acrylate copolymers, ethylene-n-butyl (meth)acrylate copolymers, and ethylene-vinyl acetate copolymers. The α-olefins are not particularly limited as long as they are copolymerizable with propylene or ethylene, and specific examples include 1-butene, 1-hexene, 4-methyl-1-pentene, 1-octene, 1-pentene, and 1-heptene.

[0024] Specific examples of polyester resins include polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polybutylene naphthalate (PBN), etc. Among these, polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), or polyethylene terephthalate (PET) are preferred because of their high elastic modulus and low-temperature moldability.

[0025] The thermoplastic resin may be used alone or in combination of two or more. In addition, the thermoplastic resin preferably has a melting point at a heating temperature when resin molding is performed using a hard coat film (described later) to which the surface protection film is attached.

[0026] The shape of the substrate may be a film, a sheet, or the like, with a film being preferred. The thickness of the substrate is not particularly limited, but is preferably in the range of 2 to 100 μm, more preferably in the range of 10 to 90 μm, even more preferably in the range of 20 to 80 μm, and further preferably in the range of 30 to 60 μm.

[0027] The base layer may contain additives as necessary. Specific examples of the additives include antioxidants, ultraviolet absorbers, antiaging agents, light stabilizers, antistatic agents, surface lubricants, plasticizers, low molecular weight polymers, corrosion inhibitors, polymerization inhibitors, silane coupling agents, inorganic and organic fillers (e.g., calcium oxide, magnesium oxide, silica, zinc oxide, titanium oxide, etc.), metal powders, colorants, pigments, heat stabilizers, eye plug inhibitors, lubricants, and antiblocking agents.

[0028] Specific examples of the elastomer contained in the adhesive layer constituting the surface protective film of the present invention include urethane-based elastomers, olefin-based elastomers, vinyl chloride-based elastomers, polyester-based elastomers, styrene-based elastomers, acrylic elastomers, amide-based elastomers, etc. Among these, styrene-based elastomers are preferred as the elastomer contained in the adhesive layer constituting the surface protective film of the present invention.

[0029] More specifically, styrene-based elastomers include ABA type block polymers such as styrene-butadiene-styrene (SBS), styrene-isobutylene-styrene (SIBS), styrene-isoprene-styrene (SIS), styrene-ethylene-butylene copolymer-styrene (SEBS), and styrene-ethylene-propylene copolymer-styrene (SEPS); AB type block polymers such as styrene-butadiene (SB), styrene-isobutylene (SIB), styrene-isoprene (SI), styrene-ethylene-butylene copolymer (SEB), and styrene-ethylene-propylene copolymer (SEP); styrene-based random copolymers such as styrene-butadiene rubber (SBR); ABC type styrene-olefin crystalline block polymers such as styrene-ethylene-butylene copolymer-olefin crystalline (SEBC); CBC type olefin crystalline block polymers such as olefin crystalline-ethylene-butylene copolymer-olefin crystalline (CEBC), and hydrogenated versions of these. Among them, hydrogenated styrene-butadiene copolymer (HSBR), styrene-ethylene-butylene-styrene copolymer (SEBS), and styrene-isobutylene copolymer (SIB) are preferably used, and more preferably styrene-isobutylene copolymer (SIB). The above styrene-based elastomers can be used alone or in combination of two or more.

[0030] The weight-average molecular weight of the styrene-based elastomer is preferably in the range of 50,000 to 400,000, and more preferably 50,000 to 200,000. If the weight-average molecular weight is less than 50,000, the cohesive strength of the adhesive layer may decrease, causing adhesive residue when peeled off from the adherend, whereas if it exceeds 400,000, the viscosity may increase, causing productivity to decrease.

[0031] The styrene content in the styrene-based elastomer is preferably in the range of 5 to 50% by mass, more preferably in the range of 8 to 40% by mass. If the styrene content is less than 5% by mass, the cohesive strength of the adhesive layer decreases, and adhesive residue may occur when peeled off from the adherend, while if it exceeds 50% by mass, the adhesion to the adherend decreases, and the adhesiveness may be insufficient.

[0032] Specific examples of polyolefin resins contained in the adhesive layer constituting the surface protection film of the present invention include low-density polyethylene, medium-density polyethylene, high-density polyethylene, linear low-density polyethylene, low-crystalline or amorphous ethylene-α-olefin copolymers, crystalline polypropylene, low-crystalline polypropylene, amorphous polypropylene, propylene-ethylene copolymers (random copolymers or block copolymers), propylene-α-olefin copolymers, propylene-ethylene-α-olefin copolymers, polybutene, 4-methyl-1-pentene-α-olefin copolymers, ethylene-ethyl (meth)acrylate copolymers, ethylene-methyl (meth)acrylate copolymers, ethylene-n-butyl (meth)acrylate copolymers, and ethylene-vinyl acetate copolymers. Among these, low-density polyethylene, linear low-density polyethylene, ethylene-α-olefin copolymer, polypropylene, propylene-α-olefin copolymer, polybutene, low-crystalline polypropylene, amorphous polypropylene, and 4-methyl-1-pentene-α-olefin copolymer are preferred as polyolefin resins contained in the adhesive layer constituting the surface protection film of the present invention. The α-olefin is not particularly limited as long as it is copolymerizable with ethylene, propylene, and 4-methyl-1-pentene, and examples thereof include ethylene, propylene, 1-butene, 1-hexene, 4-methyl-1-pentene, 1-octene, 1-pentene, and 1-heptene. These may be used alone or in combination of two or more.

[0033] As defined in JIS Z 0109 (1992), a tackifier is a material that is blended to adjust the adhesiveness of the adhesive layer, and one having a softening point of 80 to 150°C can be used. The tackifier contained in the adhesive layer constituting the surface protective film of the present invention is not particularly limited as long as it can adjust the adhesiveness of the adhesive layer, and specific examples thereof include petroleum resins such as aliphatic copolymers, aromatic copolymers, aliphatic-aromatic copolymers, and alicyclic copolymers, terpene resins, terpene phenol resins, rosin resins, alkylphenol resins, xylene resins, and hydrogenated versions of these. Among these, petroleum resins are preferred. The tackifiers can be used alone or in combination of two or more.

[0034] The adhesive layer may contain, as required, a softener, a silicone polymer, a liquid acrylic copolymer, a phosphate compound, an antiaging agent, a hindered amine light stabilizer, an ultraviolet absorbing agent, and the like.

[0035] The elastomer is contained in the entire pressure-sensitive adhesive layer in a range of preferably 40 to 70% by mass, more preferably 45 to 65% by mass, and even more preferably 50 to 60% by mass.

[0036] The polyolefin resin is preferably contained in the adhesive layer in an amount of 20 to 40% by mass, more preferably 25 to 35% by mass, and even more preferably 27 to 33% by mass.

[0037] The tackifier is preferably contained in the adhesive layer in an amount of 10 to 20% by mass, more preferably 12 to 18% by mass, and even more preferably 13 to 17% by mass, based on the total mass of the adhesive layer.

[0038] The thickness of the adhesive layer is preferably in the range of 5 to 20 μm. If the thickness of the adhesive layer is less than 5 μm, there is a risk of insufficient adhesion and compatibility with the adherend, whereas if the thickness of the adhesive layer exceeds 20 μm, the adhesive strength is too strong, and the peeling workability may be poor.

[0039] The surface roughness of the adhesive layer is preferably in the range of 0.01 to 0.30 μm, more preferably in the range of 0.01 to 0.10 μm. By smoothing the surface of the adhesive layer and forming it into the composition of the adhesive layer of the present invention, the hard coat layer has a good appearance without streaks even when the surface protection film is peeled off after resin molding. The surface roughness can be measured by a scanning white light interference microscope.

[0040] The method for producing the surface protection film of the present invention is not particularly limited. Specifically, the following methods include a method in which the components constituting the adhesive layer (hereinafter also referred to as "adhesive layer components") are supplied to an extruder for producing an adhesive layer, the components constituting the base layer (hereinafter also referred to as "base layer components") are supplied to an extruder for producing a base layer, and the materials are co-extruded from one die from two extruders to be integrally molded by a two-layer co-extrusion method, a method in which a base layer previously molded by a known inflation method, T-die method, calendar method, etc. is subjected to a surface treatment such as corona treatment, and then a composition for forming an adhesive layer in which the adhesive components are dissolved or dispersed in a solvent is applied and dried, a method in which an adhesive material is applied to a release sheet and dried, and then the adhesive layer is pressed against a previously molded base layer, or a method in which an adhesive layer is melt-extruded and laminated on a previously molded base layer, etc.

[0041] The base material layer component may be a mixture of the thermoplastic resin and the additive, or a master batch in which the additive is kneaded in advance into the thermoplastic resin may be supplied to the extruder. The adhesive layer component may be a mixture of the elastomer and the other components, or a master batch in which the other components are kneaded in advance into the elastomer may be supplied to the extruder.

[0042] The surface protection film is cut into a piece having a width of 25 mm and a length of 200 mm, and is attached to a hard coat layer using a 2 kg roller to obtain a test piece. After leaving the test piece at rest for one day at 23° C., the adhesive strength of the surface protection film to the hard coat layer (peel speed 0.3 m / min, 180° peel) is preferably in the range of 0.01 to 0.5 N / 25 mm. If it is less than 0.01 N / 25 mm, the adhesion to the hard coat layer is insufficient, and if it is 0.5 N / 25 mm or more, it may be difficult to peel the surface protection film from the hard coat layer after heating.

[0043] The surface protection film is cut into a size of 25 mm wide x 200 mm long, and is attached to a hard coat layer using a 2 kg roller to obtain a test piece. The adhesive strength of the surface protection film to the hard coat layer after leaving the test piece at 100°C for 2 hours (peel speed 0.3 m / min, 180° peel) is preferably 0.5 N / 25 mm or less, more preferably 0.1 N / 25 mm or less. If it is more than 0.5 N / 25 mm, it may be difficult to peel the surface protection film from the hard coat layer. Even when resin molding is performed using the surface protection film of the present invention, the adhesive layer of the present invention is suppressed from increasing in adhesive strength due to heat during resin molding, and the surface protection film is easily peeled from the hard coat layer even after resin molding.

[0044] In addition, when the surface protective film is used in a molding process of a resin molded product, the surface protective film preferably has extensibility capable of following the elongation of the hard coat layer during molding. In addition, the surface protective film preferably has ultraviolet light transmittance so as to be compatible with an exposure process (described in detail below) in the production of the hard coat film with the surface protective film and a post-exposure process (described in detail below) in the production of a resin molded product.

[0045] The hard coat film with a surface protective film of the present invention has a structure in which an adhesive layer of a surface protective film and a hard coat layer of a film having a hard coat layer as an outermost layer are laminated together. The film having the hard coat layer as the outermost layer (hereinafter, sometimes referred to as "hard coat film A") has a structure in which a hard coat layer is provided on a substrate film.

[0046] The material constituting the base film (hereinafter, sometimes referred to as "base film A") constituting the hard coat film A is not particularly limited, but is preferably a thermoformable material that has low stress when stretched and can be stretched with a small force. Specific examples include polyethylene terephthalate (PET) film, acrylic film, polycarbonate (PC) film, etc. When the base film A is composed of a PET film, the PET film is preferably a general-purpose biaxially stretched PET film, but in order to obtain better formability, an easily formable biaxially stretched PET film is more preferable. In addition, when the base film A is composed of an acrylic film or a polycarbonate (PC) film, they can be suitably used even if they are both unstretched films.

[0047] The thickness of the base film A is not particularly limited, but can be specifically set to a range of 25 μm to 150 μm. Specifically, when used for resin molding by the IML method or vacuum molding method, the base film A is preferably thick, 100 μm or more.

[0048] As a material constituting the hard coat layer, an active energy ray curable resin can be preferably used, since it can impart hardness (pencil hardness, scratch resistance) to the surface of the hard coat layer, and it is possible to adjust the degree of crosslinking by the amount of exposure to active energy rays, thereby making it possible to adjust both the extensibility and hardness of the hard coat layer.

[0049] The active energy ray curable resin is not particularly limited as long as it is a transparent resin that is cured by irradiation with active energy rays (e.g., ultraviolet rays, electron beams, etc.), and specific examples thereof include urethane acrylate resins, polyester acrylate resins, etc. More specific examples of the active energy ray curable resin include ultraviolet ray curable polyfunctional acrylates having two or more (meth)acryloyl groups in the molecule.

[0050] Specific examples of ultraviolet-curable polyfunctional acrylates having two or more (meth)acryloyl groups in the molecule include polyol polyacrylates such as neopentyl glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, pentaerythritol tri(meth)acrylate, and dipentaerythritol hexa(meth)acrylate, and bisphenol A diglycidyl ether. diacrylate of neopentyl glycol diglycidyl ether, di(meth)acrylate of 1,6-hexanediol diglycidyl ether, and other epoxy (meth)acrylates; polyester (meth)acrylates obtainable by esterifying a polyhydric alcohol, a polycarboxylic acid and / or anhydride thereof, and acrylic acid; urethane (meth)acrylates obtainable by reacting a polyhydric alcohol, a polyisocyanate, and a hydroxyl group-containing (meth)acrylate; and polysiloxane poly(meth)acrylates.

[0051] The ultraviolet-curable polyfunctional acrylates can be used alone or in combination of two or more, and the content is preferably in the range of 50 to 95% by mass based on the total resin solid content of the hard coat layer-forming composition. In addition to the polyfunctional (meth)acrylates, monofunctional acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and glycidyl (meth)acrylate can also be added in an amount of 10% by weight or less based on the total resin solid content of the hard coat layer-forming composition.

[0052] In addition to the active energy ray curable resin, the hard coat layer may contain thermoplastic resins such as polyethylene, polypropylene, polystyrene, polycarbonate, and polyester, and thermosetting resins such as phenol resin, urea resin, unsaturated polyester, epoxy, and silicone resin, within a range that does not impair the extensibility and hardness of the hard coat layer.

[0053] The hard coat layer may contain a heat resistance stabilizer (antioxidant) for suppressing thermal curing due to preheating (described later) during molding. In particular, when high-temperature preheating (about 150 to 200°C) is performed during molding in a vacuum molding method, even if the hard coat layer has good extensibility before heating, the hard coat layer may be thermally cured by preheating, and the extensibility may be significantly deteriorated. Specific examples of the heat resistance stabilizer include hindered phenol-based antioxidants. The hindered phenol-based antioxidant is preferably contained in an amount of 1 to 10 parts by weight relative to 100 parts by weight of the active energy ray-curable resin.

[0054] When the hard coat layer is cured with ultraviolet light, the hard coat layer preferably contains a photopolymerization initiator. Specific examples of the photopolymerization initiator include carbonyl compounds such as acetophenone, 2,2-diethoxyacetophenone, p-dimethylacetophenone, p-dimethylaminopropiophenone, benzophenone, 2-chlorobenzophenone, 4,4'-dichlorobenzophenone, 4,4'-bisdiethylaminobenzophenone, Michler's ketone, benzil, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, methylbenzoyl formate, p-isopropyl-α-hydroxyisobutylphenone, α-hydroxyisobutylphenone, 2,2-dimethoxy-2-phenylacetophenone, and 1-hydroxycyclohexylphenyl ketone, sulfur compounds such as tetramethylthiuram monosulfide, tetramethylthiuram disulfide, thioxanthone, 2-chlorothioxanthone, and 2-methylthioxanthone, and peroxide compounds such as benzoyl peroxide and di-t-butyl peroxide. These photopolymerization initiators can be used alone or in combination of two or more. The amount of the photopolymerization initiator added is preferably in the range of 0.01 to 15 parts by mass relative to 100 parts by mass of the active energy ray curable resin. If the amount is less than 0.01 parts by mass, the reaction is slow, and sufficient surface hardness and scratch resistance may not be obtained due to remaining unreacted materials. If the amount is more than 15 parts by mass, the hard coat layer may turn yellow.

[0055] In addition to the hindered phenol-based antioxidant, the hard coat layer may contain hindered amine-based light stabilizers (such as HALS), benzotriazole-based ultraviolet absorbers, defoamers, leveling agents, surface tension regulators, antifouling agents, nano-fine particle dispersions such as silica and alumina for preventing surface scratches, and antistatic agents. Furthermore, it is preferable to add a thermal polymerization inhibitor such as hydroquinone, hydroquinone monomethyl ether, or 2,5-t-butylhydroquinone to the composition for forming a hard coat layer in order to prevent thermal polymerization during production and dark reactions during storage. The amount of the thermal polymerization inhibitor added is preferably in the range of 0.005 to 0.05 parts by mass relative to 100 parts by mass of the active energy ray-curable resin contained in the composition for forming a hard coat layer.

[0056] The thickness of the hard coat layer is not particularly limited, but is preferably in the range of 3.0 to 30 μm. If the thickness of the hard coat layer is less than 3.0 μm, the required hardness may not be obtained, and if the thickness of the hard coat layer is more than 30 μm, good extensibility may not be obtained.

[0057] In addition, a urethane resin or the like may be provided between the hard coat layer and the base film in order to enhance adhesion therebetween, and the base film may be subjected to a corona treatment or plasma treatment to facilitate adhesion.

[0058] The hard coat film with a surface protective film of the present invention is prepared by applying a composition for forming a hard coat containing at least an active energy ray curable resin and a polymerization initiator to one surface of the base film A, drying the composition to form the hard coat layer (step 1), and irradiating the hard coat layer with active energy rays of 50 mJ / cm as necessary. 2 The hard coat layer is semi-cured by irradiation with the following cumulative exposure amount (step 2), and the adhesive layer of the surface protection film is attached to the side of the hard coat layer opposite to the base film A (step 3).

[0059] In the above (Step 1), a hard coat layer-forming composition in which an active energy ray curable resin, a polymerization initiator, and other additives are dissolved or dispersed in a suitable solvent is applied onto the substrate film A and dried to form the hard coat layer. The solvent can be appropriately selected depending on the solubility of the active energy ray curable resin, and may be any solvent that can uniformly dissolve or disperse at least solid contents. Specific examples of such solvents include ketones (acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, etc.), ethers (dioxane, tetrahydrofuran, etc.), aliphatic hydrocarbons (hexane, etc.), alicyclic hydrocarbons (cyclohexane, etc.), aromatic hydrocarbons (toluene, xylene, etc.), halogenated carbons (dichloromethane, dichloroethane, etc.), esters (methyl acetate, ethyl acetate, butyl acetate, etc.), alcohols (methanol, ethanol, isopropanol, butanol, cyclohexanol, etc.), cellosolves (methyl cellosolve, ethyl cellosolve, etc.), cellosolve acetates, sulfoxides, amides, etc. The solvents can be used alone or in combination of two or more.

[0060] The coating method is not particularly limited, but examples thereof include gravure coating, microgravure coating, fountain bar coating, slide die coating, slot die coating, and other methods that allow easy adjustment of the coating thickness.

[0061] In the step 2, the hard coat layer is irradiated with active energy rays at a rate of 50 mJ / cm 2 The irradiation is performed with the following cumulative exposure dose. This allows the crosslinking of the active energy ray curable resin contained in the hard coat layer to proceed to a certain degree, resulting in a semi-cured state. When the solvent in the coating film is evaporated or the thermal crosslinking proceeds to a certain degree by hot air drying or the like after the application of the hard coat layer, so that the holding power of the hard coat layer can be obtained to a certain degree, the irradiation of active energy rays is not necessarily performed, but in order to adjust both the properties of the extensibility and holding power of the hard coat layer in a well-balanced manner, it is preferable to irradiate with active energy rays.

[0062] The active energy rays may be ultraviolet rays, electron beams, or the like, depending on the type of resin. Specific examples of sources of ultraviolet rays include high-pressure mercury lamps, metal halide lamps, and electrodeless lamps. The integrated exposure dose of the active energy rays can be specifically determined in consideration of matching with the absorption wavelength of the polymerization initiator used, but is preferably 50 mJ / cm. 2 The following cumulative exposure dose is preferred: 2 If it exceeds this range, the degree of crosslinking of the active energy ray curable resin contained in the hard coat layer becomes too high, and the extensibility of the hard coat layer deteriorates, so that the hard coat film with the surface protective film may not be able to obtain an elongation of 10% or more under an atmosphere of 23°C and 50% RH.

[0063] In the above (Step 3), the surface protective film is attached and laminated to the surface of the hard coat layer, that is, the surface opposite to the base film A, via the adhesive layer.

[0064] The hard coat film with a surface protective film of the present invention is preferably used for resin molding, particularly for resin molding. The resin molding method is not particularly limited, but is preferably an in-mold molding method, and more preferably an IML method.

[0065] The resin molded body of the present invention can be produced by applying a hard coat forming composition to one of the outermost layers of the base film A to form a hard coat layer, bonding the adhesive layer of the surface protective film to the hard coat forming composition layer while the hard coat layer is in a semi-cured state to form a hard coat film with the surface protective film, performing resin molding using the hard coat film with the surface protective film and a resin, and then curing the hard coat layer.

[0066] In more detail, the resin molded body of the present invention is produced by forming a decorative layer by printing or the like on the hard coat film with the surface protective film as necessary (step A), preheating the hard coat film with the surface protective film (step B), and then forming a resin molded body by simultaneously molding and integrating the hard coat film with the surface protective film with a resin material (step C), and then post-exposing the hard coat film with the surface protective film integrated with the resin molded body to active energy rays (step D).

[0067] In the above (step A), a decorative layer (design layer) is formed by printing, deposition, etc., on the base film A side of the hard coat film with the surface protective film to provide a desired design. Specific examples of the printing method include gravure printing, offset printing, screen printing, flexographic printing, inkjet printing, etc.

[0068] In the above (step B), the hard coat film with the surface protective film or the decorative film in which a decorative layer is formed on the hard coat film with the surface protective film (hereinafter, collectively referred to as "the hard coat film with the surface protective film, etc.") is preheated in order to soften it before molding. The preheating temperature is basically determined by the type of film used. For example, PET film requires preheating at a higher temperature than other types of film. The thermal softening temperature of the easily molded PET film is lower than that of a general-purpose PET film. The required preheating temperature also varies depending on the molding method, and a particularly high temperature is required in the vacuum molding method. When an elongation rate of 30% or more is required in the vacuum molding method, and particularly moldability of 100 to 300% or more is required, it is difficult to mold the easily molded PET film unless the temperature is high, such as about 180 to 200°C. As described above, by incorporating a heat resistance stabilizer (antioxidant) in the hard coat layer, it is possible to suppress the deterioration of the extensibility of the film due to the progress of heat curing caused by high-temperature preheating during molding.

[0069] Specific examples of the above-mentioned (Step C) include a case in which the hard coat film with the surface protective film or the like is molded and integrated with a resin material by an IML molding method to produce a resin molded body, and a case in which the hard coat film with the surface protective film or the like that has been preheated is brought into contact with a resin molded product prepared in advance by a vacuum molding method, and the film is stretched and bonded to the surface of the resin molded product to integrate them.

[0070] In the above (Step D), post-exposure is performed by irradiating the hard coat film with the surface protective film, etc., integrated with the resin molded body, with active energy rays. This post-exposure completely cures the hard coat layer. The active energy ray source can be the same as that used in the manufacturing process of the hard coat film with the surface protective film (Step 2). The exposure dose of the post-exposure is the exposure dose required to completely cure the hard coat layer, and can be appropriately set. The resin molded product that has undergone the above post-exposure is completed by appropriately performing finishing processing such as trimming.

[0071] The resin molded article obtained as described above has a good surface appearance with no streaks remaining on the surface of the hard coat layer even when the surface protective film is peeled off. EXAMPLES

[0072] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples in any way. EXAMPLES

[0073] 55 parts by mass of styrene-based elastomer, 30 parts by mass of polypropylene, and 15 parts by mass of tackifier were melt-mixed at 200°C to prepare adhesive layer-forming composition 1. The adhesive layer-forming composition 1 prepared using a T-die was extruded onto a polypropylene film at a molding temperature of 200°C to obtain surface protection film 1. The obtained surface protection film 1 was evaluated as follows. The results are shown in Table 1.

[0074] <Adhesive strength> The obtained surface protection film 1 was cut to a width of 25 mm and a length of 200 mm, and was attached to a hard coat film using a 2 kg roller to obtain a test piece 1. Test piece 1 was left to stand at 23°C for one day or at 100°C for two hours, and then peeled using a tensile tester at a peel speed of 0.3 m / min and a peel angle of 180° to measure the peel strength.

[0075] <Surface roughness> The surface of the adhesive layer of the surface protection film was measured using a scanning white light interference microscope.

[0076] <Feeling> The obtained surface protection film 1 was cut to a width of 25 mm and a length of 200 mm, and was attached to a hard coat film in a semi-cured state with a 2 kg roller to obtain a test piece 2. The obtained test piece 2 was heated at 200°C for 10 seconds, and then further irradiated with ultraviolet light to cure the hard coat layer. Thereafter, the surface protection film was peeled off, and the appearance of the hard coat layer was visually observed. The hard coat layer was marked with × when abnormalities such as streaks were observed, and marked with ◯ when no abnormalities were observed.

[0077] [Comparative Example 1] Except for preparing a composition 2 for forming an adhesive layer by melt-mixing 85 parts by mass of a styrene-based elastomer and 15 parts by mass of a tackifier, a surface protective film 2 was produced in the same manner as in Example 1, and the surface protective film 2 was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0078] [Comparative Example 2] Except for preparing the adhesive layer-forming composition 3 by melt-mixing 70 parts by mass of a styrene-based elastomer and 30 parts by mass of polypropylene, the surface protective film 3 was produced in the same manner as in Example 1, and the surface protective film 3 was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0079] [Comparative Example 3] Except for preparing the adhesive layer-forming composition 4 by melt-mixing 100 parts by mass of an ethylene-vinyl acetate copolymer resin, the same procedure as in Example 1 was carried out to prepare a surface protective film 4, and the surface protective film 4 was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0080] [Table 1]

[0081] The surface protection film 1 obtained in Example 1, in which the adhesive strength to the hard coat layer is 0.01 N / 25 mm or more at 23° C. and the surface roughness of the adhesive layer is 0.3 μm or less, has an excellent surface feel.

[0082] On the other hand, in Comparative Example 1, in which the adhesive strength after heating to the hard coat layer exceeds 0.5 N / 25 mm, when used in thermoforming that requires heating, the adhesive layer hardens and becomes difficult to peel off. In Comparative Example 2, in which the surface roughness of the adhesive layer exceeds 0.30 μm, the shape of the adhesive layer is transferred to the hard coat layer, resulting in poor surface feel. In addition, Comparative Example 4 did not stick to the hard coat film. [Industrial Applicability]

[0083] The surface protective film of the present invention is useful as a surface protective film for protecting a hard coat layer, and can be used in the field of producing a resin molded article having a hard coat layer on its surface by resin molding by an in-mold lamination method.

Claims

1. A surface protective film for protecting a hard coat layer of a film having a hard coat layer as an outermost layer, comprising: The surface protection film has an adhesive layer formed on one outermost surface of a substrate, The substrate contains a thermoplastic resin, The surface protection film, wherein the adhesive layer contains an elastomer, a thermoplastic resin, and a tackifier.

2. 2. The surface protection film according to claim 1, wherein the elastomer is a styrene-based elastomer.

3. The surface protective film according to claim 1 , wherein the thermoplastic resin is a polyolefin resin.

4. The surface protective film according to claim 1 or 2, wherein a test piece obtained by cutting the surface protective film to a width of 25 mm and a length of 200 mm and laminating the film to a hard coat layer using a 2 kg roller is left standing at 23° C. for one day, and the adhesive strength of the surface protective film to the hard coat layer (peel speed 0.3 m / min, 180° peel) is in the range of 0.01 to 0.5 N / 25 mm; and a test piece obtained by cutting the surface protective film to a width of 25 mm and a length of 200 mm and laminating the film to a hard coat layer using a 2 kg roller is left standing at 100° C. for two hours, and the adhesive strength of the surface protective film to the hard coat layer (peel speed 0.3 m / min, 180° peel) is 0.5 N / 25 mm or less.

5. 3. The surface protection film according to claim 1 or 2, wherein the surface protection film is cut to a width of 25 mm and a length of 200 mm, and the surface protection film is attached to a hard coat layer using a 2 kg roller to obtain a test piece, and the test piece is allowed to stand at 100° C. for 2 hours. After this, the adhesive strength of the surface protection film to the hard coat layer (peel speed 0.3 m / min, 180° peel) is 0.1 N / 25 mm or less.

6. The surface protective film according to any one of claims 1 to 3, wherein the surface roughness of the adhesive layer is in the range of 0.01 to 0.30 µm.

7. The surface protective film according to any one of claims 1 to 3, wherein the surface roughness of the adhesive layer is in the range of 0.01 to 0.10 µm.

8. The surface protection film according to any one of claims 1 to 3, wherein the adhesive layer contains 40 to 70% by mass of the elastomer, 20 to 40% by mass of the polyolefin resin, and 10 to 20% by mass of the tackifier.

9. A hard coat film with a surface protective film, comprising the adhesive layer of the surface protective film according to any one of claims 1 to 3 and a hard coat layer of a film having a hard coat layer as an outermost layer, the hard coat layer being laminated together with the adhesive layer.

10. 10. The hard coat film with a surface protective film according to claim 9, which is a hard coat film with a surface protective film for resin molding.

11. The hard coat film with a surface protective film according to claim 10, wherein the resin molding is in-mold molding.

12. A method for producing a resin molded product, comprising the steps of: applying a composition for forming a hard coat to one outermost layer of a film to form a hard coat layer; laminating an adhesive layer of the surface protective film according to any one of claims 1 to 3 to the composition layer for forming a hard coat while the hard coat layer is in a semi-cured state to form a hard coat film with a surface protective film; performing resin molding using the hard coat film with the surface protective film and a resin; and then curing the hard coat layer.

13. The method for producing a resin molded product according to claim 12, wherein the resin molding is in-mold molding.

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