Method for manufacturing surface protective film, hard coat film with surface protective film, and resin molded product

Abstract

The present invention aims to provide a surface protective film for a hard coat layer that, even when a protective layer is applied to a semi-cured hard coat layer, does not cause streaks on the hard coat layer when the protective layer is peeled off, and also has good adhesion to the hard coat layer after it has hardened. [Solution] A surface protection film for protecting the hard coat layer of a film having a hard coat layer as its outermost layer, wherein the surface protection film has an adhesive layer formed on one outermost surface of a substrate, the substrate contains a thermoplastic resin, and the adhesive layer contains, with respect to the entire adhesive layer, elastomer in an amount greater than 70% by mass and 95% by mass or less, thermoplastic resin in an amount of 3 to 25% by mass, and tackifier in an amount of 2 to 25% by mass.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a surface protection film, a hard coat film with a surface protection film, and a resin molded body.

Background Art

[0002] Resin molded products are widely used in portable information terminal devices such as mobile phones, notebook personal computers, household electrical appliances, and interior and exterior automotive parts. In order to enhance the design of these resin molded products after molding plastic resins, their surfaces are usually decorated. As a decoration method, there is known a method of providing a decorative film provided with a pattern or a hard coat layer by printing or coating on a film on the surface of a resin molded product by an in-mold molding method, an in-mold lamination molding method, or the like.

[0003] For example, there is known a protective layer-added decorative film provided with a protective film composed of an adhesive layer made of an acrylic elastomer and at least one base material layer on a thermally cured hard coat layer composed of an acrylic acid copolymer and an isocyanate curing agent (see Patent Document 1).

[0004] On the other hand, an in-mold lamination molding method, which is one method of the in-mold molding method (hereinafter sometimes abbreviated as "IML method" in this specification), is a technique in which a decorative film having a hard coat layer formed on one side of a base material film and a pattern layer, an adhesive layer, or the like formed on the other side is held inside an injection molding die, and the decorative film is adhered to the surface of a resin molded product simultaneously with injection molding.

[0005] A moldable laminated hard coat film is known for use in the IML method, which has a hard coat layer containing an active energy ray curable resin provided on a base film, wherein the hard coat layer contains a hindered phenol-based antioxidant in an amount of 1 to 10 parts by weight per 100 parts by weight of the active energy ray curable resin, and the laminated hard coat film has an elongation rate of 30% or more at 23°C and 50% RH after heat treatment at 150°C or higher (see Patent Document 2).

[0006] The moldable laminated hard coat film described in Patent Document 2 is manufactured by coating one side of a base film with a coating composition containing at least an active energy ray-curable resin, a polymerization initiator, and a hindered phenol-based antioxidant, drying it to form a hard coat layer, irradiating the hard coat layer with active energy rays as needed, and then laminating a protective film on the side of the hard coat layer opposite to the base film. In this case, the hard coat layer is not completely cured but is in a semi-cured state.

[0007] Furthermore, the resin molded product using the moldable laminated hard coat film described in Patent Document 2 is manufactured by first forming a decorative layer on the moldable laminated hard coat film by printing or the like as necessary, then preheating the moldable laminated hard coat film, and then producing a resin molded body in which the moldable laminated hard coat film is simultaneously molded and integrated with a resin material by IML molding, and thereafter, performing post-exposure with active energy rays on the moldable laminated hard coat film integrated with the resin molded body to achieve complete curing.

[0008] Furthermore, as the protective film for the molded laminated hard coat film of Patent Document 2, polyethylene terephthalate (PET) film, polyolefin-based film (e.g., polyethylene, polypropylene, 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, and silicone adhesives can be cited. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Japanese Patent Publication No. 2018-171708 [Patent Document 2] Japanese Patent Publication No. 2012-210755 [Overview of the project] [Problems that the invention aims to solve]

[0010] However, except in cases where the same type of resin is used for both the adhesive layer and the hard coat layer, as in Patent Document 1, when a protective layer having an adhesive layer is provided on the hard coat layer after curing, there is a problem that the adhesive strength of the adhesive layer to the hard coat layer is low. Furthermore, when a resin molded product is manufactured using a moldable laminated hard coat film in which a protective layer is applied to a semi-cured hard coat layer using an adhesive, as described in Patent Document 2, there is a problem in that streaks appear on the hard coat layer when the hard coat layer is fully cured after molding and the protective layer is peeled off. The present invention aims to provide a surface protective film for a hard coat layer that, even when the protective layer is applied to a semi-cured hard coat layer, does not leave streaks on the hard coat layer when the protective layer is peeled off, and when the protective layer is applied to a cured hard coat layer, exhibits good adhesion of the protective layer to the hard coat layer. [Means for solving the problem]

[0011] As a result of diligent research to solve the above problems, the inventors of the present invention have found that the above problems can be solved by configuring the adhesive layer of a surface protective film for protecting the hard coat layer of a film having a hard coat layer as its outermost layer with an elastomer, thermoplastic resin, and tackifier in specific proportions relative to the entire adhesive layer, and have completed the present invention.

[0012] In other words, the present invention relates to a surface protection film for protecting the hard coat layer of a film having a hard coat layer as its outermost layer, wherein the surface protection film has an adhesive layer formed on one outermost surface of a substrate, the substrate contains a thermoplastic resin, and the adhesive layer contains, with respect to the entire adhesive layer, an elastomer in an amount of 65% to 95% by mass, a thermoplastic resin in an amount of 3% to 25% by mass, and a tackifier in an amount of 2% to 25% by mass.

[0013] The elastomer is preferably a styrene-based elastomer. The thermoplastic resin is preferably a polyolefin-based resin. The surface protective film is cut to a width of 25 mm and a length of 200 mm, and the test piece obtained by laminating it to the hard coat layer using a 2 kg roller is left standing at 23°C for one day. The adhesive strength of the surface protective film to the hard coat layer (peeling speed 0.3 m / min, 180° peel) is preferably in the range of 0.01 N / 25 mm to 0.5 N / 25 mm, and more preferably in the range of 0.01 N / 25 mm to 0.3 N / 25 mm.

[0014] The surface roughness of the adhesive layer is preferably in the range of 0.01 μm to 0.30 μm, and more preferably in the range of 0.01 μm to 0.10 μm. Furthermore, the present invention relates to a hard-coat film with a surface protective film, wherein the adhesive layer of the surface protective film is bonded to the hard-coat layer of a film having the hard-coat layer as its outermost layer.

[0015] It is preferable that the hard coat film with surface protection film is a film with a surface protection film for resin molding. Furthermore, the present invention relates to a method for manufacturing a resin molded body, which comprises applying a hard coat-forming composition to one outermost layer of a film to form a hard coat layer, laminating an adhesive layer of the surface protection film 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 a surface protection film and a resin, and then curing the hard coat layer.

[0016] Furthermore, the present invention relates to a method for manufacturing a resin molded body, which comprises applying a hard coat-forming composition to one outermost layer of a film to form a hard coat layer, curing the hard coat layer, laminating an adhesive layer of the surface protection film to the hard coat layer to form a hard coat film with a surface protection film, and performing resin molding using the hard coat film with a surface protection film and a resin. Preferably, the resin molding is in-mold molding or in-mold lamination molding.

Advantages of the Invention

[0017] By using the surface protection film of the present invention, resin molding can be performed by laminating the surface protection film before the hard coat layer is completely cured, and even after the hard coat layer is cured, the surface protection film can be peeled off while preventing a part of the surface protection film from remaining on the hard coat layer, and moreover, streaks can be prevented from occurring on the surface of the hard coat layer. Also, by using the surface protection film of the present invention, even when resin molding is performed by laminating the surface protection film after curing the hard coat layer, the surface protection film can be prevented from peeling off or the edges from curling, and can adhere well. Further, the present invention has the effect that the surface protection film can be peeled off without leaving a part of the surface protection film on the hard coat layer.

Embodiments for Carrying Out the Invention

[0018] The surface protection film of the present invention is a surface protection film for protecting the hard coat layer of a film having a hard coat layer on the outermost layer. In the surface protection film, an adhesive layer is 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 an adhesion promoter.

[0019] The thermoplastic resin contained in the base material constituting the surface protection film of the present invention is not particularly limited. Specifically, examples include polycarbonate resin, an alloy of polyphenylene ether resin and polystyrene resin, an alloy of polyphenylene ether resin and polyamide resin, thermoplastic polyester resin, methyl methacrylate / acrylonitrile / butadiene / styrene copolymer resin, methyl methacrylate / styrene copolymer resin, methyl methacrylate resin, rubber-reinforced methyl methacrylate resin, polyamide resin, polyacetal resin, polylactic acid resin, polyolefin resin, polyphenylene sulfide resin, and the like.

[0020] Among the thermoplastic resins contained in the base material constituting the surface protection film of the present invention, polyolefin resins or polyester resins are preferably mentioned. Specific examples of the polyolefin resins include low-density polyethylene, medium-density polyethylene, high-density polyethylene, linear low-density polyethylene, low-crystalline or amorphous 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, ethylene / vinyl acetate copolymers, and the like. The α-olefin is not particularly limited as long as it can copolymerize with propylene or ethylene. Specific examples include 1-butene, 1-hexene, 4-methyl-1-pentene, 1-octene, 1-pentene, 1-heptene, and the like.

[0021] Examples of the polyester resins mentioned above include polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), and polybutylene naphthalate (PBN). Among these, polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), or polyethylene terephthalate (PET) are preferred due to their high elastic modulus and low-temperature moldability.

[0022] The thermoplastic resin may be used alone or in combination of two or more types. Furthermore, a thermoplastic resin having a melting point that does not melt even at the heating temperature when performing resin molding using a hard coat film (described later) to which the surface protective film is attached is preferred.

[0023] The shape of the substrate can be a film, a sheet, or the like, but it is preferably a film. 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 particularly preferably in the range of 30 to 60 μm.

[0024] The substrate layer may contain additives as needed. Specifically, examples of such additives include antioxidants, ultraviolet absorbers, anti-aging 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 discharge inhibitors, lubricants, antiblocking agents, and the like.

[0025] Examples of elastomers contained in the adhesive layer constituting the surface protective film of the present invention include urethane elastomers, olefin elastomers, vinyl chloride elastomers, polyester elastomers, styrene elastomers, acrylic elastomers, amide elastomers, and the like. Among these, styrene elastomers are preferred as the elastomer contained in the adhesive layer.

[0026] More specifically, the 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 crystals (SEBC); CBC-type olefin crystalline block polymers such as olefin crystals-ethylene-butylene copolymer-olefin crystals (CEBC); and hydrogenated versions thereof. Among the styrene-based elastomers, hydrogenated styrene-butadiene copolymer (HSBR), styrene-ethylene-butylene-styrene copolymer (SEBS), and styrene-isobutylene copolymer (SIB) are preferred, with styrene-isobutylene copolymer (SIB) being more preferred. The styrene-based elastomers can be used individually or in combination of two or more.

[0027] The weight-average molecular weight of the styrene-based elastomer is preferably in the range of 50,000 to 400,000, and more preferably in the range of 50,000 to 200,000. If the weight-average molecular weight is less than 50,000, the cohesive force of the adhesive layer decreases, which may result in adhesive residue when peeled off from the adherend, and if it exceeds 400,000, the viscosity increases, which may reduce productivity.

[0028] The styrene content in the styrene-based elastomer is preferably in the range of 5 to 50% by mass, and more preferably in the range of 8 to 40% by mass. If the styrene content is less than 5% by mass, the cohesive force of the adhesive layer decreases, which may result in adhesive residue when peeled off from the adherend. If it exceeds 50% by mass, the adhesion to the adherend decreases, which may result in insufficient tackiness.

[0029] Specific examples of polyolefin resins contained in the adhesive layer constituting the surface protective 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 copolymer, crystalline polypropylene, low-crystalline polypropylene, amorphous polypropylene, propylene-ethylene copolymer (random copolymer or block copolymer), propylene-α-olefin copolymer, propylene-ethylene-α-olefin copolymer, polybutene, 4-methyl-1-pentene-α-olefin copolymer, ethylene-ethyl (meth)acrylate copolymer, ethylene-methyl (meth)acrylate copolymer, ethylene-n-butyl (meth)acrylate copolymer, and ethylene-vinyl acetate copolymer.

[0030] Among the polyolefin resins contained in the adhesive layer, 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 particularly preferred.

[0031] The α-olefin is not particularly limited as long as it can copolymerize with ethylene, propylene, and 4-methyl-1-pentene. Examples include ethylene, propylene, 1-butene, 1-hexene, 4-methyl-1-pentene, 1-octene, 1-pentene, and 1-heptene. These can be used individually or in combination of two or more types.

[0032] A tackifier, as defined in JIS Z 0109 (1992), is a material added to adjust the tackiness of an adhesive layer. For example, a tackifier with a softening point of 80 to 150°C can be used.

[0033] 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 tackiness of the adhesive layer. Specifically, examples include aliphatic copolymers, aromatic copolymers, aliphatic-aromatic copolymers, alicyclic copolymers, and other petroleum resins, terpene resins, terpene phenol resins, rosin resins, alkylphenol resins, xylene resins, or hydrogenated versions thereof. Among the tackifiers, petroleum resins are preferred. The tackifiers can be used individually or in combination of two or more.

[0034] The adhesive layer may contain, as needed, softening agents, silicone polymers, liquid acrylic copolymers, phosphate ester compounds, antioxidants, hindered amine light stabilizers, ultraviolet absorbers, and the like.

[0035] The adhesive layer contains the elastomer in an amount of 60% by mass or more, preferably 65% ​​by mass or more, more preferably 70% by mass or more, and particularly preferably 75% by mass or more. The adhesive layer contains the elastomer in an amount of 95% by mass or less, more preferably 90% by mass or less, and even more preferably 85% by mass or less.

[0036] The adhesive layer contains the polyolefin resin in an amount of 3% by mass or more, more preferably 5% by mass or more, and even more preferably 8% by mass or more. The adhesive layer contains the polyolefin resin in an amount of 35% by mass or less, more preferably 30% by mass or less, even more preferably 25% by mass or less, particularly preferably in the range of 20% by mass or more, and especially preferably 15% by mass or less.

[0037] The adhesive layer contains the tackifier in an amount of 2% by mass or more, more preferably 5% by mass or more, and even more preferably 8% by mass or more. The adhesive layer contains the tackifier in an amount of 25% by mass or less, more preferably 20% by mass or less, and even more preferably 15% by mass or less.

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

[0039] The surface roughness of the adhesive layer is preferably in the range of 0.01 μm to 0.30 μm, and more preferably in the range of 0.01 μm to 0.10 μm. By using the composition of the adhesive layer of the present invention, the surface of the adhesive layer is smoothed, and even if the surface protective film of the present invention is applied when the hard coat layer is semi-cured, and the hard coat layer is cured after resin molding and the surface protective film is peeled off, the hard coat layer will have a good appearance with no streaks or with very few streaks. The surface roughness can be measured using a scanning white light interference microscope.

[0040] The method for manufacturing the surface protective film of the present invention is not particularly limited. Specifically, examples include a method of integrally forming the film by a two-layer co-extrusion method in which components constituting the adhesive layer (hereinafter sometimes referred to as "adhesive layer components" in this specification) are supplied to an extrusion molding machine for producing the adhesive layer, and components constituting the base layer (hereinafter sometimes referred to as "base layer components" in this specification) are supplied to an extrusion molding machine for producing the base layer, and the materials from each machine are co-extruded from a single die; a method of applying and drying an adhesive layer forming composition obtained by dissolving or dispersing the adhesive components in a solvent after the base layer has been pre-formed by a known inflation method, T-die method, calendering method, etc., has been surface-treated such as corona treatment; a method of applying and drying the adhesive layer forming composition to a release sheet and then pressing it with the pre-formed base layer; or a method of melt-extruding and laminating the adhesive layer components to the pre-formed base layer.

[0041] The base layer component may be supplied to the extruder by mixing the thermoplastic resin with the additive as needed, or a masterbatch in which the additive has been kneaded into the thermoplastic resin in advance may be supplied to the extruder. The adhesive layer component may be supplied to the extruder by mixing the elastomer, the polyolefin resin, the tackifier, and other components as needed, or a masterbatch in which the other components have been kneaded into the elastomer in advance may be supplied to the extruder.

[0042] The surface protective film is cut to a width of 25 mm and a length of 200 mm, and a test piece is obtained by laminating it to the hard coat layer using a 2 kg roller. After leaving the test piece standing at 23°C for one day, the adhesive strength of the surface protective film to the hard coat layer (peeling speed of 0.3 m / min, peeling at 180°) is preferably 0.01 N / 25 mm or more, and more preferably 0.015 N / 25 mm or more. The surface protective film is cut to a width of 25 mm and a length of 200 mm, and a test piece is obtained by laminating it to the hard coat layer using a 2 kg roller. After leaving the test piece standing at 23°C for one day, the adhesive strength of the surface protective film to the hard coat layer (peeling speed of 0.3 m / min, peeling at 180°) is preferably 0.5 N / 25 mm or less, more preferably 0.1 N / 25 mm or less, even more preferably 0.05 N / 25 mm or less, and particularly preferably 0.03 N / 25 mm or less. If the N / 25mm value is less than 0.01N, the adhesion to the hard coat layer is insufficient, and if it is 0.5N / 25mm or more, it may be difficult to peel the surface protective film from the hard coat layer after heating.

[0043] The surface protective film is cut to a width of 25 mm and a length of 200 mm, and the test piece obtained by laminating it to the hard coat layer using a 2 kg roller is left to stand at 100°C for 2 hours. The adhesive strength of the surface protective film to the hard coat layer (peeling speed of 0.3 m / min, 180° peel) is preferably 0.01 / 25 mm or more, and more preferably 0.015 / 25 mm or more.

[0044] When the surface protective film is cut to a width of 25 mm and a length of 200 mm, and a test piece is obtained by laminating it to the hard coat layer using a 2 kg roller, and after standing the test piece at 100°C for 2 hours, the adhesive strength of the surface protective film to the hard coat layer (peeling speed 0.3 m / min, 180° peeling) is preferably 0.5 N / 25 mm or less, more preferably 0.2 N / 25 mm or less, even more preferably 0.1 N / 25 mm or less, and particularly preferably 0.05 N / 25 mm or less. If the adhesive strength of the surface protective film to the hard coat layer (peeling speed 0.3 m / min, 180° peeling) after the test piece is obtained by cutting the surface protective film to a width of 25 mm and a length of 200 mm, and laminating it to the hard coat layer using a 2 kg roller, and after standing the test piece at 100°C for 2 hours is greater than 0.5 N / 25 mm, it may become difficult to peel the surface protective film from the hard coat layer. Even when resin molding is performed using the surface protective film of the present invention, the adhesive layer of the present invention suppresses the increase in adhesive strength due to the heat generated during resin molding, and peeling from the hard coat layer of the surface protective film is easy even after resin molding.

[0045] If the adhesive strength of the surface protective film to the hard coat layer (peeling speed 0.3 m / min, 180° peel) after cutting the surface protective film to a length of 25 mm and laminating it to the hard coat layer using a 2 kg roller and leaving the test piece to stand at 100°C for 2 hours is less than 0.01, the surface protective film of the present invention may peel off or its edges may curl up during resin molding.

[0046] Furthermore, when the surface protective film is used in the molding process of a resin molded product, it is preferable that the surface protective film has elongation properties that can follow the elongation of the hard coat layer during molding. In addition, in the hard coat film with the surface protective film, if the hard coat film is composed of an active energy ray curable resin, it is preferable that the surface protective film has active energy ray (e.g., ultraviolet) transmittance so that it can accommodate the exposure process in the manufacture of the hard coat film (details described later) and the exposure process in the manufacture of the resin molded product (details described later).

[0047] The hard coat film with a surface protective film of the present invention has a structure in which the adhesive layer of the surface protective film is bonded to the hard coat layer of a film having the hard coat layer as its outermost layer. The film having the hard coat layer as its outermost layer (hereinafter referred to as "hard coat film A" in this specification) has a structure in which a hard coat layer is provided on a base film.

[0048] The material constituting the base film (hereinafter sometimes referred to as "base film A" in this specification) that constitutes the hard coat film A is not particularly limited, but it is preferably a thermoformable material that has low stress during elongation and can be stretched with a weak force. Specifically, examples of materials constituting the base film A include polyethylene terephthalate (PET) film, acrylic film, and polycarbonate (PC) film. When the base film A is composed of a PET film, a general-purpose biaxially oriented PET film is preferred, but an easily moldable biaxially oriented PET film is more preferred to obtain better moldability. Furthermore, when the base film A is composed of an acrylic film or a polycarbonate (PC) film, both can be suitably used even if they are unoriented films.

[0049] The thickness of the base film A is not particularly limited, but as a specific example, it can be in the range of 25 μm to 150 μm. When the hard coat film with surface protective film is used in resin molding by IML or in-mold molding, the thickness of the base film A is preferably 100 μm or more.

[0050] As the material constituting the hard coat layer, a thermosetting urethane acrylic resin can be used when the primary purpose is to impart scratch resistance. However, an active energy ray curable resin is preferable because it can impart hardness (pencil hardness, scratch resistance) to the surface of the hard coat layer and allows for adjustment of the degree of crosslinking by the amount of exposure to active energy rays, thus enabling adjustment of both the elongation and hardness of the hard coat layer.

[0051] The active energy ray curable resin is not particularly limited as long as it is a transparent resin that hardens when irradiated with active energy rays (e.g., ultraviolet rays, electron beams, etc.), and specifically, examples include urethane acrylate resins and polyester acrylate resins. More specifically, examples of the active energy ray curable resin include UV-curable polyfunctional acrylates having two or more (meth)acryloyl groups in the molecule.

[0052] The UV-curable polyfunctional acrylate having two or more (meth)acryloyl groups in the molecule includes, specifically, 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, as well as bisphenol A diglycidyl ether. Examples include epoxy (meth)acrylates such as diacrylate of acrylic acid, diacrylate of neopentyl glycol diglycidyl ether, and di(meth)acrylate of 1,6-hexanediol diglycidyl ether; polyester (meth)acrylates that can be obtained by esterifying a polyhydric alcohol with a polyhydric carboxylic acid and / or its anhydride with acrylic acid; urethane (meth)acrylates obtained by reacting a polyhydric alcohol with a polyhydric isocyanate and a hydroxyl group-containing (meth)acrylate; and polysiloxane poly(meth)acrylates.

[0053] The UV-curable polyfunctional acrylate can be used alone or in combination of two or more types, and its content is preferably in the range of 50 to 95% by mass relative to the total resin solids of the hard coat layer forming composition. In addition to the polyfunctional (meth)acrylate, 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 mass or less relative to the total resin solids of the hard coat layer forming composition.

[0054] Furthermore, in addition to the active energy ray curable resin, the hard coat layer may also contain thermoplastic resins such as polyethylene, polypropylene, polystyrene, polycarbonate, and polyester, as well as thermosetting resins such as phenolic resins, urea resins, unsaturated polyesters, epoxy, and silicon resins, within a range that does not impair the elongation and hardness of the hard coat layer.

[0055] The hard coat layer may contain a heat-resistant stabilizer (antioxidant) to suppress thermal hardening caused by preheating during molding (described later). In particular, when high-temperature preheating (around 150-200°C) is performed during molding in the in-mold molding method, even if the material has good extensibility before heating, the thermal hardening of the hard coat layer may progress due to preheating, potentially causing a significant deterioration in extensibility. Specifically, a hindered phenol-based antioxidant is a suitable example of the heat-resistant stabilizer. The hindered phenol-based antioxidant is preferably contained in an amount of 1 to 10 parts by mass per 100 parts by mass of the active energy ray-curable resin.

[0056] When the hard coat layer is cured by active energy rays such as ultraviolet light, it is preferable that the hard coat layer contains a polymerization initiator. Examples of polymerization initiators include carbonyl compounds such as acetophenone, 2,2-diethoxyacetophenone, p-dimethylacetophenone, p-dimethylaminopropiophenone, benzophenone, 2-chlorobenzophenone, 4,4'-dichlorobenzophenone, 4,4'-bisdiethylaminobenzophenone, Michler ketone, benzyl, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, methylbenzoyl phosphate, 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 polymerization initiators can be used alone or in combination of two or more.

[0057] The amount of the photopolymerization initiator added is preferably in the range of 0.01 parts by mass or more and 15 parts by mass or less per 100 parts by mass of the active energy ray curable resin. If the amount of the polymerization initiator added 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 residual unreacted material. If the amount of the photopolymerization initiator added is greater than 15 parts by mass, the hard coat layer may yellow.

[0058] Furthermore, the hard coat layer may contain, in addition to the hindered phenol antioxidant, a hindered amine light stabilizer (such as HALS), a benzotriazole ultraviolet absorber, an antifoaming agent, a leveling agent, a surface tension modifier, an antifouling agent, a nanoparticle dispersion such as silica or alumina to prevent surface scratching, an antistatic agent, and the like. In addition, it is preferable to add a thermal polymerization inhibitor such as hydroquinone, hydroquinone monomethyl ether, or 2,5-t-butylhydroquinone to the composition that forms the hard coat layer (hereinafter referred to as "hard coat layer forming composition" in this specification) in order to prevent thermal polymerization during manufacturing and dark reactions during storage. The amount of thermal polymerization inhibitor added is preferably in the range of 0.005 parts by mass or more and 0.05 parts by mass or less per 100 parts by mass of the active energy ray curable resin contained in the hard coat layer forming composition.

[0059] The thickness of the hard coat layer is not particularly limited, but is preferably in the range of 3.0 μm 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 greater than 30 μm, good elongation may not be obtained.

[0060] Furthermore, a urethane resin or the like can be provided between the hard coat layer and the base film to enhance their adhesion, or the base film can be treated for easy adhesion by corona treatment or plasma treatment.

[0061] The hard coat film with a surface protective film of the present invention is formed by coating one side of the base film A with the hard coat forming composition containing at least the active energy ray curable resin and the polymerization initiator, drying it to form the hard coat layer (Step 1), and optionally applying an active energy ray of 50 mJ / cm to the hard coat layer. 2 The hard coat layer is semi-cured by irradiating it with the following cumulative exposure amount (step 2), and the adhesive layer of the surface protective film is attached to the side of the hard coat layer opposite to the base film A (step 3) to manufacture the product.

[0062] Furthermore, the hard coat film with a surface protective film of the present invention is formed by coating one side of the base film A with the hard coat forming composition containing at least the active energy ray curable resin and the polymerization initiator, drying it, and then applying an active energy ray of 50 mJ / cm to the hard coat layer (step 1'), and then applying an active energy ray of 50 mJ / cm to the hard coat layer. 2 The hard coat layer is cured by irradiating it with the above cumulative exposure amount (step 2'), and the adhesive layer of the surface protective film is attached to the side of the hard coat layer opposite to the base film A (step 3') to manufacture the product.

[0063] In steps (1) and (1') described above, the hard coat layer forming composition, which is obtained by dissolving and dispersing the active energy ray curable resin, the polymerization initiator, and other additives in a suitable solvent, is coated onto the substrate film A and dried to form the hard coat layer. The solvent can be appropriately selected according to the solubility of the active energy ray curable resin, and any solvent that can uniformly dissolve or disperse at least the solid content is acceptable.

[0064] 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, and the like. Furthermore, these solvents can be used individually or in combination of two or more.

[0065] The coating method is not particularly limited, but examples include gravure coating, microgravure coating, fountain bar coating, slide die coating, and slot die coating, which allow for easy adjustment of the coating thickness.

[0066] In step 2, an active energy ray of 50 mJ / cm was applied to the hard coat layer. 2 The material is irradiated with the following cumulative exposure dose. This causes the crosslinking of the active energy ray-curable resin contained in the hard coat layer to progress to a certain extent, resulting in a semi-cured state.

[0067] If the solvent in the coating film evaporates or thermal crosslinking progresses to some extent by hot air drying after coating the hard coat layer, and a certain degree of retention force is obtained in the hard coat layer, then irradiation with active energy rays is not necessarily required. However, in order to adjust both the elongation and retention force characteristics of the hard coat layer in a balanced manner, it is preferable to irradiate with active energy rays.

[0068] In the above (step 2'), an active energy ray of 50 mJ / cm was applied to the hard coat layer. 2 The material is irradiated with the above cumulative exposure dose. This causes the crosslinking of the active energy ray-curable resin contained in the hard coat layer to proceed, resulting in a cured state.

[0069] The activated energy beam used may be ultraviolet light, an electron beam, or the like, depending on the type of resin. Specific examples of ultraviolet light sources include high-pressure mercury lamps, metal halide lamps, and electrodeless lamps. Furthermore, the cumulative exposure dose of the activated energy beam in step (2) can be specifically determined by considering its matching with the absorption wavelength of the polymerization initiator used, but is generally set at 50 mJ / cm². 2 The following cumulative exposure amounts are preferred.

[0070] The cumulative exposure dose was 50 mJ / cm². 2 If the value exceeds a certain limit, the degree of crosslinking of the active energy ray curable resin contained in the hard coat layer becomes too high, degrading the elongation of the hard coat layer. As a result, it may not be possible to obtain an elongation of 10% or more for the hard coat film with the surface protective film in an atmosphere of 23°C and 50% RH.

[0071] The cumulative exposure dose of the active energy rays in step (2') can be specifically determined by considering the matching with the absorption wavelength of the polymerization initiator used, but is 50 mJ / cm 2 The above cumulative exposure amounts are preferred.

[0072] In steps (3) and (3') described above, the surface protective film is attached to the surface of the hard coat layer, that is, the side opposite to the base film A, via the adhesive layer, and laminated.

[0073] The hard coat film with surface protection film of the present invention is particularly preferable for use in resin molding. The resin molding method is not particularly limited, but an in-mold molding method or an IML molding method is preferred.

[0074] The resin molded body of the present invention can be manufactured by applying a hard coat forming composition to one of the outermost layers of the base film A to form a hard coat layer, laminating the adhesive layer of the surface protective film to the hard coat forming composition layer when the hard coat layer is in a semi-cured or 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 resin, and then curing the hard coat layer if it is in a semi-cured state.

[0075] More specifically, the resin molded body of the present invention is manufactured by first forming a decorative layer on the hard coat film with a surface protective film by printing or the like as necessary (Step A), then preheating the hard coat film with a surface protective film (Step B), then molding the hard coat film with a surface protective film and simultaneously integrating it with the resin material to produce a resin molded body (Step C), and if the hard coat layer of the hard coat film is in a semi-cured state, performing post-exposure with active energy rays on the hard coat film with a surface protective film integrated with the resin molded body (Step D).

[0076] In step A, a decorative layer (pattern layer) is formed by printing, vapor deposition, or the like to give the base film A of the hard coat film with surface protective film the necessary design properties. Specific printing methods include gravure printing, offset printing, screen printing, flexographic printing, and inkjet printing.

[0077] In step B described above, preheating is performed for the purpose of softening the hard coat film with a surface protective film or the decorative film in which a decorative layer is formed on the hard coat film with a surface protective film (hereinafter collectively referred to as "the hard coat film with a surface protective film, etc." in this specification) before molding.

[0078] The preheating temperature is basically determined by the type of film being used. For example, PET film requires higher preheating temperatures than other types of film. Easy-to-form PET film has a lower heat softening temperature than general-purpose PET film. The required preheating temperature also varies depending on the molding method, with in-mold molding requiring particularly high temperatures. When easy-to-form PET film requires an elongation rate of 30% or more, or even 100-300% or more, in in-mold molding, molding is difficult unless the temperature is around 180-200°C.

[0079] As mentioned above, by including a heat-resistant stabilizer (antioxidant) in the hard coat layer, it is possible to suppress the deterioration of the film's stretchability due to thermal curing caused by high-temperature preheating during molding.

[0080] Specifically, in step C, a resin molded body is produced by simultaneously molding and integrating the hard coat film with the surface protective film with a resin material using an in-mold molding method, IML molding method, or the like. More specifically, step C may include a step in which the preheated hard coat film with surface protection film is molded using a mold for the resin molded body, the molded hard coat film with surface protection film is brought into contact with the mold for the resin molded body, or a step in which the preheated hard coat film with surface protection film is brought into contact with the mold for the resin molded body, and then the resin constituting the resin molded body is injected into the mold.

[0081] In step D, the hard coat film with surface protective film, which is integrated with the resin molded body, is subjected to post-exposure by irradiation with active energy rays. This post-exposure further hardens the hard coat layer. The active energy source can be the same as that used in the manufacturing process of the hard coat film with surface protective film (step 2). The exposure amount for the post-exposure described above is the amount of exposure necessary to completely cure the hard coat layer and can be set as appropriate. The resin molded product after completing (step C) or (step D) is completed by performing finishing processes such as trimming as appropriate.

[0082] The resin molded body after completing step D has a good surface texture in which no streaks remain on the surface of the hard coat layer even after the surface protective film is peeled off. The resin molded body after completing step (C) can adequately protect the surface of the hard coat layer without the surface protective film peeling off or its edges curling up during step (C). [Examples]

[0083] The present invention will be specifically described below with reference to examples, but the present invention is not limited in any way to these examples. [Examples]

[0084] Composition 1 for forming an adhesive layer was prepared by melt-mixing 80 parts by mass of styrene elastomer, 10 parts by mass of polypropylene, and 10 parts by mass of a tackifier at 200°C. The prepared adhesive layer forming composition 1 was extruded onto a polypropylene film using a T-die at a molding temperature of 200°C to obtain a surface protective film 1. The obtained surface protection film 1 was evaluated as follows. The results are shown in Table 1. [Examples]

[0085] Composition 2 for forming an adhesive layer was prepared by melt-mixing 65 parts by mass of styrene elastomer, 20 parts by mass of polypropylene, and 15 parts by mass of tackifier at 200°C. The prepared adhesive layer forming composition 2 was extruded onto a polypropylene film using a T-die at a molding temperature of 200°C to obtain a surface protective film 2. The obtained surface protection film 2 was evaluated as follows. The results are shown in Table 1.

[0086] [Comparative Example 1] A surface protective film 3 was prepared in the same manner as in Example 1, except that a composition 3 for forming an adhesive layer was prepared by melt-mixing 55 parts by mass of styrene elastomer, 30 parts by mass of polypropylene, and 15 parts by mass of a tackifier. The fabricated surface protection film 3 was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0087] [Comparative Example 2] A surface protective film 4 was prepared in the same manner as in Example 1, except that 85 parts by mass of styrene-based elastomer and 15 parts by mass of tackifier were melt-mixed to prepare a composition 4 for forming an adhesive layer. The fabricated surface protective film 4 was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0088] [Comparative Example 3] A surface protective film 5 was prepared in the same manner as in Example 1, except that 70 parts by mass of styrene-based elastomer and 30 parts by mass of polypropylene were melt-mixed to prepare a composition 5 for forming an adhesive layer. The fabricated surface protective film 5 was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0089] <Adhesive strength 1> The obtained surface protection films 1 to 5 were cut to a width of 25 mm and a length of 200 mm, and test specimen 1 was obtained by laminating them onto a hard coat film with a semi-cured hard coat layer using a 2 kg roller. Test specimen 1 was left to stand at 23°C for one day or at 100°C for two hours, and then peeled using a tensile testing machine under conditions of a peeling speed of 0.3 m / min and a peeling angle of 180°, and the peel strength was measured.

[0090] <Adhesive strength 2> The obtained surface protection films 1 to 5 were cut to a width of 25 mm and a length of 200 mm, and test specimen 2 was obtained by laminating them onto a hard coat film with a hard coat layer that had hardened using a 2 kg roller. Test specimen 1 was left to stand at 23°C for one day or at 100°C for two hours, and then peeled using a tensile testing machine under conditions of a peeling speed of 0.3 m / min and a peeling angle of 180°, and the peel strength was measured.

[0091] <Surface roughness> The adhesive layer surface of surface protection films 1-5 was measured using a scanning white light interference microscope.

[0092] <Face 1> The obtained surface protection films 1-5 were cut to a width of 25 mm and a length of 200 mm, and test specimen 3 was obtained by laminating them onto a hard coat film with a semi-cured hard coat layer using a 2 kg roller. The obtained test specimen 3 was heated at 200°C for 10 seconds, and then irradiated with ultraviolet light to cure the hard coat layer. After that, the surface protection film was peeled off, and the appearance of the hard coat layer was observed visually. We marked the hard court layer with × if any abnormalities such as streaks were observed, and with ○ if no abnormalities were observed.

[0093] <Face 2> The obtained surface protection films 1 to 5 were cut to a width of 25 mm and a length of 200 mm, and test specimen 3 was obtained by laminating them onto a hard coat film with a hard coat layer that had hardened using a 2 kg roller. After heating the obtained test specimen 3 at 200°C for 10 seconds, the surface protection film was peeled off, and the appearance of the hard coat layer was visually observed. We marked the hard court layer with × if any abnormalities such as streaks were observed, and with ○ if no abnormalities were observed.

[0094] [Table 1] *1: Not measured.

[0095] The surface protective films 1 and 2 obtained in Examples 1 and 2, which have adhesive layers formed from adhesive layer-forming compositions 1 and 2, exhibit an adhesive strength 1 to the hard coat layer of 0.01 N / 25 mm or more at 23°C, an adhesive strength 2 to the hard coat layer of 0.5 N / 25 mm or less, a surface roughness of 0.3 μm or less, and excellent surface feel 1 and 2, regardless of whether they are applied to a hard coat layer in a cured state or a hard coat layer in a semi-cured state.

[0096] On the other hand, Comparative Example 1, which contains 55 parts by mass of styrene-based elastomer in the adhesive layer-forming composition, exhibits insufficient adhesive strength 2 to the hard coat layer when applied to a hard coat layer in a cured state. Comparative Example 2, which does not contain polypropylene in the adhesive layer-forming composition, is difficult to peel off from the hard coat layer after heating when applied to a semi-cured hard coat layer. Furthermore, in Comparative Example 3, which did not contain a tackifier in the adhesive layer-forming composition, an abnormality was observed in the hard coat layer. [Industrial applicability]

[0097] The surface protection film of the present invention is useful as a surface protection film for protecting the hard coat layer regardless of the hardening state of the hard coat layer, and can be used in fields where resin molded products with a hard coat layer on the surface are manufactured by resin molding using methods such as in-mold molding and in-mold lamination molding.

Claims

1. In a surface protective film for protecting the hard coat layer of a film having a hard coat layer as its outermost layer, The aforementioned surface protection film has an adhesive layer formed on one of its outermost surfaces, The aforementioned substrate contains a thermoplastic resin, The adhesive layer is a surface protective film containing, with respect to the entire adhesive layer, 65% to 95% by mass of elastomer, 3% to 25% by mass of thermoplastic resin, and 2% to 25% by mass of tackifier.

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

3. The surface protective film according to claim 1 or 2, wherein the thermoplastic resin is a polyolefin resin.

4. The surface protective film according to claim 1 or 2, wherein the surface protective film is cut to a width of 25 mm x length of 200 mm, and a test piece obtained by laminating it 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 (peeling speed 0.3 m / min, 180° peel) is in the range of 0.01 N / 25 mm or more and 0.5 N / 25 mm or less.

5. The surface protective film according to claim 1 or 2, wherein the surface protective film is cut to a width of 25 mm x a length of 200 mm, and a test piece obtained by laminating it 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 (peeling speed 0.3 m / min, 180° peel) is in the range of 0.01 N / 25 mm or more and 0.30 N / 25 mm or less.

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

7. The surface protective film according to claim 1 or 2, wherein the surface roughness of the adhesive layer is in the range of 0.01 μm or more and 0.30 μm or less.

8. The surface protective film according to claim 1 or 2, wherein the surface roughness of the adhesive layer is in the range of 0.01 μm or more and 0.10 μm or less.

9. A hard coat film with a surface protective film, wherein the adhesive layer of the surface protective film described in claim 1 or 2 is bonded to the hard coat layer of a film having a hard coat layer as its outermost layer.

10. The hard coat film with a surface protective film according to claim 9, wherein the hard coat film with a surface protective film 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 or in-mold lamination molding.

12. A method for manufacturing a resin molded body, comprising: applying a hard coat forming composition to one outermost layer of a film to form a hard coat layer; laminating the adhesive layer of the surface protection film described in claim 1 or 2 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 a surface protection film; performing resin molding using the hard coat film with a surface protection film and a resin; and then curing the hard coat layer.

13. A method for manufacturing a resin molded body, comprising applying a hard coat forming composition to one outermost layer of a film to form a hard coat layer, curing the hard coat layer, then laminating the adhesive layer of the surface protection film described in claim 1 or 2 to the hard coat layer to form a hard coat film with a surface protection film, and performing resin molding using the hard coat film with a surface protection film and a resin.

14. A method for manufacturing a resin molded article according to claim 12, wherein the resin molding is performed by in-mold molding or in-mold lamination molding.

15. A method for manufacturing a resin molded article according to claim 13, wherein the resin molding is performed by in-mold molding or in-mold lamination molding.

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