TW202103949A - Surface protective film - Google Patents

Abstract

Provided is a surface protective film including a hard coat layer, a substrate layer, an adhesive layer in this order, wherein the surface protective film can sufficiently follow repeated curves. This surface protective film according to the present invention includes a hard coat layer, a substrate layer, and an adhesive layer in this order, wherein the Young's modulus of a laminate of the hard coat layer and the substrate layer is 5 MPa to 1,800 MPa at 23 DEG C, and Tg measured by the DSC of an adhesive constituting the adhesive layer is no greater than 0 DEG C.

Description

Surface protective film

The present invention relates to a surface protective film.

Surface protection film is used for surface protection of various shapes of components. However, if a surface protection film is to be attached to a corner (for example, a corner of a wall, etc.) or a curved part (for example, a movable bending part of a folding member, etc.), the following problems occur, for example.

When the surface protection film is bent at an angle, a compressive force acts on the inner diameter side of the curve, so that the force is relieved, and the surface protection film itself is deformed. Specifically, for example, wrinkles become easy to appear.

When the surface protection film is bent at an angle, the tensile stress acts on the outer diameter side of the bending. Therefore, when the stress is relieved, the swelling occurs from the adherend.

When the surface protective film is bent at an angle, the thickness of the bent or stretched portion of the surface protective film changes greatly. In this state, it becomes prone to wrinkles or bulges. For example, when the surface protection film is stretched, the thickness of the surface protection film is greatly reduced, and it becomes easy to bulge from the adherend.

In this way, the conventional surface protection film cannot sufficiently follow the unevenness of the corner or the curved portion.

In recent years, on the display surface of various display devices, surface protection films for protecting transparent plates such as glass used for the display surface have been used. As such a surface protective film, a hard coat layer having scratch resistance has been put into practical use (Patent Document 1).

As various display devices, the development of display devices with movable bending parts, such as a foldable display device and a roll-up display device, is currently underway. When the previous surface protection film is applied to this type of display device, the repeated bending cannot be fully followed, and it becomes a state where creases (so-called "marks") are left on the movable bending portion. Moreover, the conventional surface protection film with a hard coat layer has the following problems: the hard coat layer cannot fully follow the repeated bending, is difficult to adhere along the curved surface, or cannot fully follow the repeated bending, and peels off from the display surface. Prior art literature Patent literature

Patent Document 1: Japanese Patent Laid-Open No. 2016-208138

[The problem to be solved by the invention]

The subject of the present invention is to provide a surface protection film which includes a hard coat layer, a base layer and an adhesive layer in this order, and can sufficiently follow repeated bending. [Technical means to solve the problem]

The surface protective film of the present invention Including a hard coat layer, a substrate layer and an adhesive layer in this order, and The Young's modulus at 23°C of the laminate of the hard coat layer and the substrate layer is 5 MPa to 1800 MPa, The Tg measured by DSC of the adhesive constituting the adhesive layer is below 0°C.

In one embodiment, the hardness of the hard coat layer is H or higher.

In one embodiment, the tensile deformation rate when cracks occur in the hard coat rupture test of the surface protective film of the present invention is 15% or more.

In one embodiment, the thickness of the hard coat layer is 1 μm-50 μm.

In one embodiment, the adhesive layer has a peeling angle of 180 degrees at 23° C. and a peeling speed of 300 mm/min. The adhesion to the PET film is 0.1 N/20 mm or more.

In one embodiment, the thickness of the substrate layer is 1 μm to 500 μm.

In one embodiment, the thickness of the adhesive layer is 0.1 μm-50 μm.

In one embodiment, the total light transmittance of the surface protective film is 85% or more. [Effects of Invention]

According to the present invention, it is possible to provide a surface protection film which includes a hard coat layer, a substrate layer and an adhesive layer in this order, and can sufficiently follow repeated bending.

≪≪Surface protection film≫≫ The surface protection film of the present invention sequentially includes a hard coat layer, a substrate layer and an adhesive layer. That is, if the surface protection film of the present invention includes a hard coat layer, a base layer, and an adhesive layer in this order, it may have any suitable other layers within a range that does not impair the effects of the present invention.

Fig. 1 is a schematic cross-sectional view showing an embodiment of the surface protection film of the present invention. In FIG. 1, the surface protection film 1000 of the present invention has a hard coat layer 100, a base layer 200, and an adhesive layer 300 in sequence, which are directly laminated.

The hard coat layer may be one layer or two or more layers. In terms of further expressing the effect of the present invention, the hard coat layer is preferably one layer.

The thickness of the hard coat layer is preferably 0.5 μm-50 μm, more preferably 0.5 μm-40 μm, still more preferably 0.5 μm-30 μm, particularly preferably 0.5 μm-20 μm. If the thickness of the hard coat layer is within the above range, the effect of the present invention can be further exhibited.

The base material layer may be one layer, or two or more layers. In terms of further exhibiting the effects of the present invention, the base material layer is preferably one layer.

The thickness of the substrate layer is preferably 1 μm to 500 μm, more preferably 3 μm to 400 μm, further preferably 5 μm to 300 μm, and particularly preferably 10 μm to 200 μm. If the thickness of the substrate layer is within the above range, the effect of the present invention can be further exhibited.

The adhesive layer may be one layer, or two or more layers. In terms of further exhibiting the effects of the present invention, the adhesive layer is preferably one layer.

The thickness of the adhesive layer is preferably 1 μm to 100 μm, more preferably 1 μm to 80 μm, still more preferably 1 μm to 70 μm, and particularly preferably 1 μm to 60 μm. If the thickness of the adhesive layer is within the above range, the effect of the present invention can be further exhibited.

For protection before use, the surface protection film of the present invention may be provided with any suitable release liner on the surface of the adhesive layer on the opposite side to the base layer.

As a release liner, for example, a release liner in which the surface of a substrate (liner substrate) such as paper or plastic film is treated with polysiloxane, and the surface of a substrate (liner substrate) such as paper or plastic film is used. Polyolefin resin laminated release liner, etc. Examples of the plastic film as the backing substrate include polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, vinyl chloride copolymer film, poly Ethylene terephthalate film, polybutylene terephthalate film, polyurethane film, ethylene-vinyl acetate copolymer film, etc.

The thickness of the release liner is preferably 1 μm to 500 μm, more preferably 3 μm to 450 μm, still more preferably 5 μm to 400 μm, and particularly preferably 10 μm to 300 μm.

The total thickness of the surface protection film of the present invention is preferably 3 μm to 1000 μm, more preferably 5 μm to 650 μm, further preferably 7 μm to 500 μm, and particularly preferably 10 μm to 400 μm. If the total thickness of the surface protection film of the present invention is within the above range, the effects of the present invention can be further exhibited.

The ratio of the thickness of the substrate layer of the surface protection film of the present invention to the total thickness (thickness of the substrate layer/total thickness) is preferably 90% or less, more preferably 20% to 90%, and still more preferably 25% ～90%, particularly preferably 30%～85%. If the ratio of the thickness of the substrate layer of the surface protection film of the present invention to the total thickness (the thickness of the substrate layer/total thickness) is within the above range, the effects of the present invention can be further exhibited.

The laminated body of the hard coat layer and the substrate layer of the surface protective film of the present invention has a Young's modulus at 23°C of 5 MPa to 1800 MPa, preferably 10 MPa to 1500 MPa, more preferably 20 MPa to 1200 MPa , More preferably 30 MPa to 1100 MPa, particularly preferably 50 MPa to 1000 MPa. If the Young's modulus at 23° C. of the laminate of the hard coat layer and the substrate layer is within the above range, the effect of the present invention can be further exhibited. The method for measuring the Young's modulus at 23°C of the laminate of the hard coat layer and the substrate layer is described in detail below.

The Tg of the adhesive constituting the adhesive layer of the surface protective film of the present invention measured by DSC is below 0°C, preferably -100°C to 0°C, more preferably -90°C to 0°C, and more preferably -80℃～0℃, particularly preferably -70℃～0℃. If the Tg measured by DSC of the adhesive constituting the adhesive layer is within the above range, the effect of the present invention can be further exhibited. The measurement of Tg by DSC of the adhesive constituting the adhesive layer will be described in detail below.

The total light transmittance of the surface protective film of the present invention is preferably 85% or more, more preferably 88% or more, still more preferably 90% or more, and particularly preferably 92% or more. If the total light transmittance of the surface protective film of the present invention is within the above range, the surface protective film of the present invention can be used for applications requiring high transparency.

≪Hard coating≫ The hardness of the hard coat layer is preferably H or more, more preferably 2H or more. The method for measuring the hardness of the hard coating is described in detail below.

The tensile deformation rate when the cracks occur in the hard coat rupture test of the surface protective film of the present invention is preferably 15% or more, more preferably 15% to 1000%, and still more preferably 20% to 800%, especially Preferably, it is 25% to 500%. If the tensile deformation rate when the crack occurs in the hard coat rupture test is within the above range, the effect of the present invention can be further exhibited. Regarding the hard coat rupture test, the details are described below.

As the hard coat layer, any suitable hard coat layer can be used within a range that does not impair the effects of the present invention.

Typically, the hard-coat layer can be formed from the composition for hard-coat layer formation. Specifically, for example, the composition for forming a hard coat layer may be applied to one surface of the substrate layer, and a hard coat layer may be formed if necessary (for example, ultraviolet irradiation or heat treatment). Furthermore, after the hard coat layer is formed, surface treatments such as corona treatment and plasma treatment may be applied to the hard coat layer.

As the coating method of the composition for forming a hard coat layer, any suitable method can be adopted within a range that does not impair the effects of the present invention. As such a coating method, for example, bar coating method, gravure roll coating method, die nozzle coating method, rod coating method, slot coating method, curtain coating method, spray Injection coating method, missing corner wheel coating method, etc.

The heating temperature of the coating layer formed by coating the composition for forming a hard coat layer can be set to any suitable temperature according to the composition of the composition for forming a hard coat layer. Such heating temperature is preferably set to be equal to or lower than the glass transition temperature of the resin contained in the base layer. If heating is performed at a temperature lower than the glass transition temperature of the resin contained in the substrate layer, a surface protective film with a hard coat layer with suppressed deformation due to heating can be obtained. The heating temperature is preferably 60°C to 140°C, more preferably 60°C to 100°C. By heating in such a range, a hard coat layer with excellent adhesion to the substrate layer can be formed.

As the hardening treatment, any suitable hardening treatment can be adopted within a range that does not impair the effects of the present invention. As the hardening treatment, typically, ultraviolet irradiation, heat treatment, and the like can be cited. The cumulative light intensity of ultraviolet irradiation is preferably 200 mJ to 400 mJ.

The composition for forming a hard coat layer may contain any suitable monomer or resin (at least one selected from the group consisting of oligomers, prepolymers, and polymers) within a range that does not impair the effects of the present invention. . In one embodiment, the composition for forming a hard coat layer contains a thermosetting type or a photocuring type curable compound. The curable compound is, for example, at least one selected from the group consisting of monomers and resins (at least one selected from the group consisting of oligomers, prepolymers, and polymers).

As the curable compound, it is preferable to use at least one selected from the group consisting of polyfunctional monomers and oligomers. Examples of such curable compounds include monomers or oligomers having two or more (meth)acrylic groups, (meth)acrylate urethane or (meth)acrylate urethane Among the oligomers, epoxy-based monomers or oligomers, silicone-based monomers or oligomers, etc., in terms of further exhibiting the effects of the present invention, as curable compounds, Preferably, it is an oligomer of (meth)acrylate urethane or (meth)acrylate urethane.

The composition for forming a hard coat layer may contain any suitable additives within a range that does not impair the effects of the present invention. Examples of such additives include: polymerization initiators, leveling agents, anti-blocking agents, dispersion stabilizers, thixotropic agents, antioxidants, ultraviolet absorbers, defoamers, thickeners, dispersants, interface Active agents, catalysts, fillers, lubricants, antistatic agents, etc. Such additives may be only one type or two or more types. The type, combination, content, etc. of additives that can be included in the composition for forming a hard coat layer can be appropriately set according to the purpose or required characteristics.

The composition for forming a hard coat layer may contain fine particles as an additive. If a composition for forming a hard coat layer containing fine particles is used, an anti-glare function can be imparted. The fine particles may be inorganic fine particles or organic fine particles. Examples of inorganic fine particles include silica fine particles, titanium oxide fine particles, alumina fine particles, zinc oxide fine particles, tin oxide fine particles, calcium carbonate fine particles, barium sulfate fine particles, talc fine particles, kaolin fine particles, calcium sulfate fine particles, and the like. Examples of organic fine particles include: polymethyl methacrylate resin powder (PMMA fine particles), silicone resin powder, polystyrene resin powder, polycarbonate resin powder, acrylic styrene resin powder, benzoguanamine resin Powder, melamine resin powder, polyolefin resin powder, polyester resin powder, polyamide resin powder, polyimide resin powder, polyvinyl fluoride resin powder, etc. The fine particles that can be contained in the composition for forming a hard coat layer may be only one type or two or more types. The type, combination, content, etc. of the fine particles that can be contained in the composition for forming a hard coat layer can be appropriately set according to the purpose or required characteristics.

The composition for forming a hard coat layer may also contain a solvent. Examples of solvents include dibutyl ether, dimethoxymethane, dimethoxyethane, diethoxyethane, propylene oxide, 1,4-dioxane, and 1,3-dioxane Cyclopentane, 1,3,5-trioxane, tetrahydrofuran, acetone, methyl ethyl ketone (MEK), diethyl ketone, dipropyl ketone, diisobutyl ketone, cyclopentanone (CPN), Cyclohexanone, methylcyclohexanone, ethyl formate, propyl formate, n-pentyl formate, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, n-pentyl acetate, acetone, Diacetone alcohol, methyl acetylacetate, ethyl acetylacetate, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 1-pentanol, 2-methyl- 2-butanol, cyclohexanol, isopropanol (IPA), isobutyl acetate, methyl isobutyl ketone (MIBK), 2-octanone, 2-pentanone, 2-hexanone, 2-heptanone , 3-Heptanone, ethylene glycol monoethyl ether acetate, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, etc. The solvent which can be contained in the composition for hard-coat layer formation may only be 1 type, and may be 2 or more types. The type, combination, content, etc. of the solvent that can be contained in the composition for forming a hard coat layer can be appropriately set according to the purpose or required characteristics.

≪Substrate layer≫ The Young's modulus of the substrate layer at 23° C. is preferably 0.5 MPa to 4000 MPa, more preferably 10 MPa to 3500 MPa, further preferably 20 MPa to 3000 MPa, particularly preferably 30 MPa to 2500 MPa. If the Young's modulus at 23°C of the substrate layer is within the above range, the effect of the present invention can be further exhibited. The measurement of the Young's modulus at 23°C of the substrate layer will be described in detail below.

As the material of the substrate layer, any suitable material can be used within a range that does not impair the effect of the present invention. As such a material, it is preferable to cite at least one selected from the group consisting of urethane-based resins and polyester-based resins. The material of the substrate layer may be only one type or two or more types.

Examples of urethane resins include ether-based polyurethane resins and ester-based polyurethane resins.

Examples of polyester resins include soft PET (polyethylene terephthalate) resins and rigid PET (polyethylene terephthalate) resins. In terms of further expressing the effects of the present invention, the polyester resin is preferably a soft PET (polyethylene terephthalate) resin.

≪Adhesive layer≫ The adhesive layer contains an adhesive.

The adhesion of the adhesive layer to the PET film at a peeling angle of 180 degrees at 23°C and a peeling speed of 300 mm/min is 0.1 N/20 mm or more, more preferably 0.1 N/20 mm～30 N/20 mm, and then It is preferably 0.1 N/20 mm to 25 N/20 mm, and particularly preferably 0.5 N/20 mm to 20 N/20 mm. If the peeling angle of the adhesive layer at 23° C. is 90 degrees and the peeling speed is 300 mm/min, the adhesion to the PET film is within the above range, the effect of the present invention can be further exhibited. The method for measuring the adhesion of the adhesive layer to the PET film at a peeling angle of 180 degrees at 23°C and a peeling speed of 300 mm/min will be described in detail below.

The adhesive contains a base polymer. The base polymer may be only one type or two or more types. In terms of further exhibiting the effects of the present invention, the content ratio of the base polymer in the adhesive is preferably 30% by weight to 99.9% by weight, more preferably 40% by weight to 99% by weight, and still more preferably 50% by weight. Weight %～99% by weight.

As the base polymer, any suitable polymer can be used within a range that does not impair the effects of the present invention. In terms of further exhibiting the effects of the present invention, the base polymer is preferably selected from acrylic polymers, rubber polymers, silicone polymers, and urethane polymers. At least one of them. That is, the adhesive layer is preferably selected from acrylic adhesives containing acrylic polymers, rubber-based adhesives containing rubber-based polymers, silicone-based adhesives containing silicone-based polymers, and amines. At least one of the urethane-based adhesives of the carbamate-based polymer.

In terms of further exhibiting the effects of the present invention, the base polymer is preferably an acrylic polymer. That is, the adhesive layer preferably contains an acrylic adhesive containing an acrylic polymer.

In terms of further exhibiting the effects of the present invention, among all the monomer components used to constitute the acrylic polymer, the monomer having a Tg of 0°C or higher for the corresponding homopolymer is preferably 25% by weight or less, and more It is preferably 23% by weight or less, more preferably 20% by weight or less, and particularly preferably 18% by weight or less.

As Tg of the corresponding homopolymer, specifically, the following values can be used, for example. 2-Ethylhexyl acrylate -70°C N-Butyl Acrylate -55°C Acrylic 106°C 2-Hydroxyethyl acrylate -15°C 4-Hydroxybutyl acrylate -40°C

Regarding the Tg of homopolymers other than those exemplified above, the value described in "Polymer Handbook" (3rd edition, John Wiley & Sons, Inc., 1989) can be used. When multiple values are recorded in the above "Polymer Handbook", conventional values are used. Regarding the monomers not listed in the above "Polymer Handbook", the catalog value of the monomer manufacturer is used. As the Tg of the homopolymer of the monomer which is not described in the above-mentioned "Polymer Handbook" and does not provide the catalog value of the monomer manufacturer, it is obtained by the measurement method described in Japanese Patent Laid-Open No. 2007-51271 value.

In terms of further exhibiting the effects of the present invention, as the acrylic polymer, it is preferable to include an alkyl (meth)acrylate as a main monomer, and further may include a side monomer copolymerizable with the main monomer. The monomer component of the polymer.

As the alkyl (meth)acrylate, for example, a compound represented by the following formula (1) can be preferably used. CH ₂ =C(R ¹ )COOR ² (1)

^{Here, R 1} in the above formula (1) is a hydrogen atom or a methyl group, and R ² is a chain alkyl group having 1 to 20 carbon atoms (hereinafter, such a range of carbon atoms is expressed as "C1- 20”). From the viewpoint of the storage modulus of the adhesive layer, R ^{2 is} preferably a C1-14 chain alkyl group, more preferably a C2-10 chain alkyl group, and even more preferably a C4-8 chain alkyl group. alkyl. Here, the term "chain shape" includes linear and branched chain shapes.

Examples of alkyl (meth)acrylates in which R ² is a C1-20 chain alkyl group include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, Isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, second butyl (meth)acrylate, amyl (meth)acrylate, (meth)acrylic acid Isoamyl ester, hexyl (meth)acrylate, heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, ( Nonyl meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, laurel (meth)acrylate Ester, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, cetyl (meth)acrylate, (meth) Heptadecyl acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, nonadecyl (meth)acrylate, eicosyl (meth)acrylate, etc. . These alkyl (meth)acrylates may be only one type or two or more types.

In terms of further exhibiting the effect of the present invention, the content ratio of the alkyl (meth)acrylate in all monomer components used in the synthesis of acrylic polymer is preferably 60% by weight to 100% by weight , More preferably 65% by weight to 99.5% by weight, still more preferably 70% by weight to 99% by weight, and particularly preferably 80% by weight to 98% by weight.

As an embodiment of the acrylic polymer, an acrylic polymer in which less than 60% by weight of all monomer components is 2-ethylhexyl acrylate (2EHA) can be cited. In this case, the content ratio of 2-ethylhexyl acrylate (2EHA) in all monomer components is preferably more than 0% by weight and 55% by weight or less in terms of further exhibiting the effects of the present invention , More preferably 5% to 53% by weight, still more preferably 10% to 50% by weight, particularly preferably 15% to 48% by weight, most preferably 20% to 45% by weight. In this embodiment, furthermore, the ratio of the total monomer components may not reach 60% by weight of the total monomer components (preferably more than 0% by weight and 55% by weight or less, more preferably 5% by weight to 53% by weight %, more preferably 10% to 50% by weight, particularly preferably 15% to 48% by weight, and most preferably 20% to 45% by weight) contains isostearyl acrylate (ISTA).

As an embodiment of the acrylic polymer, an acrylic polymer in which 50% by weight or more of all monomer components is n-butyl acrylate (BA) can be mentioned. In this case, in terms of further exhibiting the effects of the present invention, the content ratio of n-butyl acrylate (BA) in all monomer components is preferably more than 50% by weight and 100% by weight or less, more preferably It is 55% by weight to 95% by weight, more preferably 60% by weight to 90% by weight, particularly preferably 63% by weight to 85% by weight, and most preferably 65% by weight to 80% by weight. In this embodiment, all the monomer components may be less than the ratio of n-butyl acrylate (BA), and further include 2-ethylhexyl acrylate (2EHA).

In all the monomer components used to constitute the acrylic polymer, other monomers may be included in the range that does not impair the effect of the present invention. There may be only one type of other monomers, or two or more types. The content ratio of other monomers in all monomer components is preferably 0.001% by weight to 40% by weight, more preferably 0.01% by weight to 40% by weight, still more preferably 0.1% by weight to 10% by weight, and particularly preferably 0.5 Weight% to 5% by weight, preferably 1% to 3% by weight.

Examples of other monomers that can be introduced into the acrylic polymer that can become a cross-linking group point or can contribute to improving adhesion include: hydroxyl group (OH group)-containing monomers, carboxyl group-containing monomers, Acid anhydride group-containing monomers, amine group-containing monomers, amine group-containing monomers, imine group-containing monomers, epoxy group-containing monomers, (meth)acrylic acid, sulfonic acid Monomers, monomers containing phosphoric acid groups, monomers containing cyano groups, vinyl acetate (VAc), vinyl propionate, vinyl laurate, aromatic vinyl compounds, vinyl ethers, etc.

As an embodiment of the acrylic polymer, an acrylic polymer in which a carboxyl group-containing monomer is copolymerized as another monomer can be cited. Examples of carboxyl group-containing monomers include acrylic acid (AA), methacrylic acid (MAA), carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, and Maleic acid, crotonic acid, methacrylic acid, etc. Among them, in terms of further exhibiting the effect of the present invention, the carboxyl group-containing monomer preferably includes acrylic acid (AA) and methacrylic acid (MAA), and more preferably acrylic acid (AA).

When a carboxyl group-containing monomer is used as the other monomer, the content ratio of the other monomer in all monomer components is preferably 0.1% by weight to 10% by weight in terms of further exhibiting the effect of the present invention , More preferably 0.2% by weight to 8% by weight, still more preferably 0.5% by weight to 5% by weight, particularly preferably 0.7% by weight to 4% by weight, most preferably 1% by weight to 3% by weight.

As an embodiment of the acrylic polymer, an acrylic polymer in which a hydroxyl group-containing monomer is copolymerized as another monomer can be cited. Examples of hydroxyl-containing monomers include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and (meth)acrylic acid 2 -Hydroxyalkyl (meth)acrylates such as hydroxybutyl, 4-hydroxybutyl (meth)acrylate, etc.; polypropylene glycol mono(meth)acrylate; N-hydroxyethyl(meth)acrylamide, etc. Among them, as a hydroxyl group-containing monomer, in terms of further exhibiting the effect of the present invention, preferably, the alkyl group is a linear (meth)acrylic hydroxyl group having 2 to 4 carbon atoms. Specific examples of the alkyl ester include 2-hydroxyethyl acrylate (HEA) and 4-hydroxybutyl acrylate (4HBA), and more preferably 4-hydroxybutyl acrylate (4HBA).

When a hydroxyl-containing monomer is used as the other monomer, the content ratio of the other monomer in all monomer components is preferably 0.001% by weight to 10% by weight in terms of further exhibiting the effect of the present invention. , More preferably 0.01% by weight to 5% by weight, still more preferably 0.02% by weight to 2% by weight, particularly preferably 0.03% by weight to 1% by weight, most preferably 0.05% by weight to 0.5% by weight.

As a method of obtaining an acrylic polymer, for example, various polymerization methods known as acrylic polymer synthesis methods, such as a solution polymerization method, an emulsion polymerization method, a bulk polymerization method, and a suspension polymerization method, can be suitably adopted. Among these polymerization methods, the solution polymerization method can be preferably used. As a method of supplying monomers when performing solution polymerization, a batch addition method in which the entire amount of monomer components are supplied at once, a continuous supply (dropping) method, a batch supply (dropping) method, etc. can be suitably adopted. The polymerization temperature can be appropriately selected according to the types of monomers and solvents used, the types of polymerization initiators, etc., and is preferably 20°C or higher, more preferably 30°C or higher, still more preferably 40°C or higher, and more preferably 170°C or lower, more preferably 160°C or lower, and still more preferably 140°C or lower. As a method of obtaining acrylic polymer, photopolymerization by irradiating light such as UV (typically, in the presence of a photopolymerization initiator) or irradiating radiation such as β-rays and γ-rays can also be used. Active energy ray irradiation polymerization such as radiation polymerization.

As the solvent (polymerization solvent) used for solution polymerization, it can be appropriately selected from any suitable organic solvents. For example, aromatic compounds (typically aromatic hydrocarbons) such as toluene, acetates such as ethyl acetate, aliphatic or alicyclic hydrocarbons such as hexane or cyclohexane, and the like can be cited.

The initiator (polymerization initiator) used for the polymerization can be appropriately selected from any suitable polymerization initiators according to the type of polymerization method. The polymerization initiator may be only one type or two or more types. Examples of such polymerization initiators include azo polymerization initiators such as 2,2'-azobisisobutyronitrile (AIBN); persulfates such as potassium persulfate; benzyl peroxide, peroxy Peroxide-based initiators such as hydrogen oxide; substituted ethane-based initiators such as phenyl-substituted ethane; aromatic carbonyl compounds, etc. As another example of the polymerization initiator, a redox initiator obtained by using a combination of a peroxide and a reducing agent can be cited.

The amount of the polymerization initiator used is preferably 0.005 part by weight to 1 part by weight, and more preferably 0.01 part by weight to 1 part by weight relative to 100 parts by weight of all monomer components.

The Mw of the acrylic polymer is preferably 10×10 ⁴ to 500×10 ⁴ , more preferably 10×10 ⁴ to 150×10 ⁴ , still more preferably 20×10 ⁴ to 75×10 ⁴ , particularly preferably 35 ×10 ⁴ ～65×10 ⁴ . Here, Mw means a standard polystyrene conversion value obtained by GPC (Gel Permeation Chromatography). As the GPC device, for example, the model name "HLC-8320GPC" (column: TSKgel GMH-H(S), manufactured by Tosoh) can be used.

In terms of further exhibiting the effect of the present invention, the acrylic adhesive may include an adhesion-imparting resin. Examples of adhesion-imparting resins include rosin-based adhesion-imparting resins, terpene-based adhesion-imparting resins, hydrocarbon-based adhesion-imparting resins, epoxy-based adhesion-imparting resins, polyamide-based adhesion-imparting resins, elastic system adhesion-imparting resins, and phenol-based adhesion-imparting resins. Adhesion imparting resin, ketone-based adhesiveness imparting resin, etc. There may be only one type of adhesion-imparting resin, or two or more types.

In terms of further exhibiting the effects of the present invention, the amount of the adhesion-imparting resin used relative to 100 parts by weight of the base polymer is preferably 5 parts by weight to 70 parts by weight, more preferably 10 parts by weight to 60 parts by weight, It is more preferably 15 parts by weight to 50 parts by weight, still more preferably 20 parts by weight to 45 parts by weight, particularly preferably 25 parts by weight to 40 parts by weight, and most preferably 25 parts by weight to 35 parts by weight.

In terms of further exhibiting the effects of the present invention, the adhesion-imparting resin preferably includes adhesion-imparting resin TL having a softening point of less than 105°C. The adhesion-imparting resin TL can effectively contribute to improving the deformability of the adhesive layer in the plane direction (shear direction). From the viewpoint of obtaining a higher deformability improvement effect, the softening point of the adhesion-imparting resin used as the adhesion-imparting resin TL is preferably 50°C to 103°C, more preferably 60°C to 100°C, and even more preferably 65 ℃～95℃, particularly preferably 70℃～90℃, most preferably 75℃～85℃.

The softening point of the adhesion imparting resin is defined as the value measured based on the softening point test method (Ring and Ball method) specified in JIS K5902 and JIS K2207. Specifically, quickly melt the sample at the lowest possible temperature and fill it up in a ring placed on a flat metal plate, taking care not to generate foam. After cooling, use a slightly heated knife to cut off the raised part from the plane of the upper end of the containing ring. Then, put the holder (ring table) in a glass container (heating bath) with a diameter of 85 mm or more and a height of 127 mm or more, and inject glycerin until the depth becomes 90 mm or more. Then, the steel ball (diameter 9.5 mm, weight 3.5 g) and the ring filled with the sample were immersed in glycerin without contacting each other, and the temperature of the glycerin was kept at 20°C±5°C for 15 minutes. Then, place a steel ball in the center of the surface of the sample in the ring, and place it in a fixed position on the holder. Then, keep the distance from the upper end of the ring to the glycerin surface at 50 mm, place a thermometer, set the center of the mercury ball of the thermometer to the same height as the center of the ring, and heat the container. The flame of the Bunsen burner used for heating is located between the center and the edge of the bottom of the container, so that the heating becomes uniform. Furthermore, after heating is started, the rate of increase in bath temperature after reaching 40°C must be 5.0±0.5°C per minute. The sample slowly softens and flows down from the circulation. Read the temperature when it finally contacts the bottom plate and set it as the softening point. The softening point can be measured at more than two at the same time, and the average value is used.

As the usage amount of the adhesion imparting resin TL, in terms of further showing the effect of the present invention, relative to 100 parts by weight of the base polymer, it is preferably 5 parts by weight to 50 parts by weight, more preferably 10 parts by weight to 45 parts by weight. Parts by weight, more preferably 15 parts by weight to 40 parts by weight, particularly preferably 20 parts by weight to 35 parts by weight, most preferably 25 parts by weight to 32 parts by weight.

As the adhesion-imparting resin TL, one or two or more suitably selected from the above-exemplified adhesion-imparting resins whose softening point is less than 105°C can be used. The adhesion-imparting resin TL preferably contains a rosin-based resin.

As rosin-based resins that can be preferably used as the adhesion-imparting resin TL, for example, rosin esters such as unmodified rosin ester or modified rosin ester, etc. Examples of modified rosin esters include hydrogenated rosin esters.

In terms of further exhibiting the effect of the present invention, the adhesion-imparting resin TL preferably contains hydrogenated rosin ester. As the hydrogenated rosin ester, in terms of further exhibiting the effects of the present invention, the softening point is preferably less than 105°C, more preferably 50°C to 100°C, still more preferably 60°C to 90°C, and particularly preferably 70℃～85℃, preferably 75℃～85℃.

The adhesion-imparting resin TL may also contain non-hydrogenated rosin ester. Here, the so-called non-hydrogenated rosin ester refers to a concept other than the hydrogenated rosin ester among the above-mentioned rosin esters broadly. Examples of non-hydrogenated rosin esters include unmodified rosin esters, disproportionated rosin esters, and polymerized rosin esters.

As the non-hydrogenated rosin ester, in terms of further exhibiting the effects of the present invention, the softening point is preferably less than 105°C, more preferably 50°C to 100°C, and still more preferably 60°C to 90°C, especially It is 70°C to 85°C, preferably 75°C to 85°C.

In addition to the rosin-based resin, the adhesion-imparting resin TL may also include other adhesion-imparting resins. As other adhesion-imparting resins, one or two or more suitably selected from the above-exemplified adhesion-imparting resins whose softening point is less than 105°C can be used. The adhesion-imparting resin TL may include, for example, a rosin-based resin and a terpene resin.

In terms of further exhibiting the effects of the present invention, the content ratio of the rosin-based resin in the total adhesion-imparting resin TL is preferably more than 50% by weight, more preferably 55% to 100% by weight, and still more preferably 60% to 99% by weight, particularly preferably 65% to 97% by weight, most preferably 75% to 97% by weight.

In terms of further exhibiting the effects of the present invention, the adhesion-imparting resin may also include the adhesion-imparting resin TL and the adhesion-imparting resin TH having a softening point of 105° C. or higher (preferably 105° C. to 170° C.).

As the adhesion-imparting resin TH, one or 2 or more kinds appropriately selected from those having a softening point of 105° C. or higher among the adhesion-imparting resins exemplified above can be used. The adhesion-imparting resin TH may include at least one selected from the group consisting of rosin-based adhesion-imparting resins (for example, rosin esters) and terpene-based adhesion-imparting resins (for example, terpene phenol resin).

The acrylic adhesive can contain a crosslinking agent. There may be only one type of crosslinking agent, or two or more types. Through the use of crosslinking agent, it can impart a moderate cohesive force to the acrylic adhesive. The cross-linking agent can also help to adjust the offset distance and return distance in the retention test. The acrylic adhesive containing a crosslinking agent can be obtained, for example, by forming an adhesive layer using an adhesive composition containing the crosslinking agent. The cross-linking agent may be included in the acrylic adhesive in the form after the cross-linking reaction, the form before the cross-linking reaction, the form in which the cross-linking reaction partially undergoes the cross-linking reaction, and the intermediate or composite form of these. Typically, the crosslinking agent is mainly contained in the acrylic adhesive in the form after the crosslinking reaction.

In terms of further exhibiting the effects of the present invention, the amount of the crosslinking agent used is preferably 0.005 parts by weight to 10 parts by weight, more preferably 0.01 parts by weight to 7 parts by weight, relative to 100 parts by weight of the base polymer. It is more preferably 0.05 parts by weight to 5 parts by weight, particularly preferably 0.1 parts by weight to 4 parts by weight, and most preferably 1 part by weight to 3 parts by weight.

Examples of crosslinking agents include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, silicone-based crosslinking agents, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, and silane-based crosslinking agents. Crosslinking agent, alkyl etherified melamine-based crosslinking agent, metal chelate-based crosslinking agent, peroxide and other crosslinking agents, etc., in terms of further exhibiting the effects of the present invention, isocyanate-based crosslinking agents are preferred The linking agent, epoxy-based crosslinking agent, more preferably an isocyanate-based crosslinking agent.

As the isocyanate-based crosslinking agent, a compound having two or more isocyanate groups (including isocyanate regeneration type functional groups that temporarily protect the isocyanate groups by a blocking agent or quantitative integration) can be used in one molecule. Examples of the isocyanate-based crosslinking agent include aromatic isocyanates such as toluene diisocyanate and xylene diisocyanate; alicyclic isocyanates such as isophorone diisocyanate; and aliphatic isocyanates such as hexamethylene diisocyanate.

As the isocyanate-based crosslinking agent, more specifically, for example, lower aliphatic polyisocyanates such as butylene diisocyanate and hexamethylene diisocyanate; cyclopentyl diisocyanate, cyclohexyl diisocyanate, isocyanate, etc. Alicyclic isocyanates such as phorone diisocyanate; aromatics such as 2,4-toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, xylylene diisocyanate, polymethylene polyphenyl isocyanate, etc. Diisocyanates; Trimethylolpropane/toluene diisocyanate trimer adduct (for example, Tosoh Corporation, trade name Corona L), trimethylolpropane/hexamethylene diisocyanate trimer adduct ( For example, Tosoh company, trade name: Coronate HL), hexamethylene diisocyanate isocyanurate body (for example, Tosoh company, trade name: Coronaate HX) and other isocyanate adducts; xylylene diisocyanate Trimethylolpropane adduct (for example, manufactured by Mitsui Chemicals, trade name: Takenate D110N), trimethylolpropane adduct of xylylene diisocyanate (for example, manufactured by Mitsui Chemicals, trade name: Takenate D120N) , Trimethylolpropane adduct of isophorone diisocyanate (for example, manufactured by Mitsui Chemicals, trade name: Takenate D140N), trimethylolpropane adduct of hexamethylene diisocyanate (for example, Mitsui Chemicals Manufacturing, trade name: Takenate D160N); polyether polyisocyanate, polyester polyisocyanate, and their adducts with various polyols; using isocyanurate bond, biuret bond, allophanate bond And other multifunctional polyisocyanates. Among these, the aromatic isocyanate and the alicyclic isocyanate are preferable in terms of achieving a balance between deformability and cohesive force.

In terms of further exhibiting the effects of the present invention, the amount of the isocyanate-based crosslinking agent used relative to 100 parts by weight of the base polymer is preferably 0.005 parts by weight to 10 parts by weight, more preferably 0.01 parts by weight to 7 parts by weight Parts, more preferably 0.05 parts by weight to 5 parts by weight, particularly preferably 0.1 parts by weight to 4 parts by weight, most preferably 1 part by weight to 3 parts by weight.

As the epoxy-based crosslinking agent, a multifunctional epoxy compound having two or more epoxy groups in one molecule can be used. Examples of epoxy-based crosslinking agents include: N,N,N',N'-tetraglycidyl-m-xylylenediamine, diglycidylaniline, 1,3-bis(N,N-di Glycidyl amino methyl) cyclohexane, 1,6-hexanediol diglycidyl ether, neopentyl glycol diglycidyl ether, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polyethylene two Alcohol diglycidyl ether, polypropylene glycol diglycidyl ether, sorbitol polyglycidyl ether, glycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, polyglycerol polyglycidyl ether, sorbitan polyglycidyl ether, trimethylol Propane polyglycidyl ether, diglycidyl adipate, diglycidyl phthalate, triglycidyl tris (2-hydroxyethyl) isocyanurate, resorcinol diglycidyl ether, double Phenol-S-diglycidyl ether, epoxy resin having two or more epoxy groups in the molecule, etc. As a commercially available product of an epoxy-based crosslinking agent, for example, trade names "Tetrad C" and "Tetrad X" manufactured by Mitsubishi Gas Chemical Co., Ltd. can be cited.

In terms of further exhibiting the effects of the present invention, the amount of epoxy-based crosslinking agent used relative to 100 parts by weight of the base polymer is preferably 0.005 parts by weight to 10 parts by weight, more preferably 0.01 parts by weight to 5 parts by weight. Parts by weight, more preferably 0.015 parts by weight to 1 part by weight, particularly preferably 0.015 parts by weight to 0.5 parts by weight, most preferably 0.015 parts by weight to 0.3 parts by weight.

Acrylic adhesives can also contain levelling agents, crosslinking aids, plasticizers, softeners, fillers, antistatic agents, anti-aging agents, ultraviolet absorbers, antioxidants, light stabilizers and other adhesives as needed. Among the usual additives. Regarding such various additives, conventionally known ones can be used. [Example]

Examples and comparative examples are listed below to explain the present invention more specifically. However, the present invention is not subject to any such restrictions. Furthermore, in the following description, as long as there is no special description, "parts" and "%" are based on weight.

＜Measurement method of Young's modulus at 23℃ of laminate of hard coat layer and substrate layer＞ Young's modulus is calculated based on the results of a 20% expansion test conducted under the following conditions. Regarding the following Examples and Comparative Examples, the same method was also used. [20% extended test] Sample shape: strip with a width of 10 mm Distance between initial chucks: 20 mm Stretching speed: 300 mm/min Tensile deformation: 20% Procedure: Under a measurement environment of 23°C and 50%RH, clamp the sample to the chuck of the tensile testing machine so that the distance between the initial chuck becomes 20 mm. Then, stretch the sample (20% expansion) at the above-mentioned stretching speed until the distance between the chucks becomes 24 mm, and calculate the Young's modulus based on the obtained displacement and stress results. Furthermore, the stretching direction in the above test is not particularly limited, but it is preferably the same as the length direction of the surface protection film. As the tensile tester, for example, the product name "Autograph AG-10G Tensile Tester" manufactured by Shimadzu Corporation can be used.

＜Method for measuring the Young’s modulus at 23℃ of the substrate layer＞ Young's modulus is calculated based on the results of a 20% expansion test conducted under the following conditions. Regarding the following Examples and Comparative Examples, the same method was also used. [20% extended test] Sample shape: strip with a width of 10 mm Distance between initial chucks: 20 mm Stretching speed: 300 mm/min Tensile deformation: 20% Procedure: Under a measurement environment of 23°C and 50%RH, clamp the sample to the chuck of the tensile testing machine so that the distance between the initial chuck becomes 20 mm. Then, stretch the sample (20% expansion) at the above-mentioned stretching speed until the distance between the chucks becomes 24 mm, and calculate the Young's modulus based on the obtained displacement and stress results. Furthermore, the stretching direction in the above test is not particularly limited, but it is preferably the same as the length direction of the surface protection film. As the tensile tester, for example, the product name "Autograph AG-10G Tensile Tester" manufactured by Shimadzu Corporation can be used.

＜Measurement method of Tg by DSC of the adhesive constituting the adhesive layer＞ Using the adhesive layer obtained in the Examples and Comparative Examples as samples, weigh about 5 mg of the sample in an aluminum cylindrical tank with a diameter of 5 mm and a depth of 2 mm, and seal the sample after closing the lid. As a reference sample, an empty aluminum cylindrical tank was prepared, and a differential scanning calorimeter (DSC: manufactured by TA Instruments, Q2000) was used to measure under a nitrogen atmosphere (nitrogen flow rate: 50 ml/min) at a rate of 10°C/min. After the speed is raised from -80°C to 80°C, it is quickly cooled to -80°C, and the endothermic curve when the temperature is raised in the range of -80°C to 80°C at a rate of 10°C/min again. Set the middle point of the two critical points before and after Tg as Tg.

＜Method for measuring the adhesion of the adhesive layer to the PET film at a peeling angle of 180 degrees at 23°C and a peeling speed of 300 mm/min＞ Adhesion refers to the 180-degree peel strength (180-degree peel adhesion) to the PET film. For 180 degree peel strength, the surface protection film is applied to a measurement sample cut into a size of 20 mm in width and 100 mm in length, and a 2 kg roller is reciprocated once at 23°C and 50% RH, and the above measurement sample The adhesive layer is pressed on the surface of the PET film. After placing it in the same environment for 30 minutes, use a universal tensile and compression testing machine to measure the peel strength (N/20) at a tensile speed of 300 mm/min and a peel angle of 180 degrees in accordance with JIS Z 0237: 2000. mm). As a universal tensile and compression testing machine, for example, "Tensile Compression Testing Machine, TG-1kN" manufactured by Minebea Corporation can be used.

×30 cm，合計90 cm ・溶離液：四氫呋喃(濃度0.1重量%) ・流量：0.8 ml/min ・入口壓力：1.6 MPa ・檢測器：示差折射計(RI) ・管柱溫度：40℃ ・注入量：100 μl ・溶離液：四氫呋喃 ・檢測器：示差折射計 ・標準試樣：聚苯乙烯<Method for measuring weight average molecular weight Mw> The weight average molecular weight of the obtained acrylic polymer was measured by GPC (Gel Permeation Chromatography). The sample uses the filtrate obtained by dissolving the sample in tetrahydrofuran to make a 0.1% by weight solution, leaving it to stand overnight, and filtering it with a 0.45 μm membrane filter.・Analytical device: HLC-8120GPC manufactured by Tosoh Corporation ・Column: (meth)acrylic polymer manufactured by Tosoh Corporation: GM7000HXL＋GMHXL＋GMHXL Aromatic polymer: G3000HXL＋2000HXL＋G1000HXL ・Column size: 7.8 mm each

×30 cm, 90 cm in total ・Eluent: Tetrahydrofuran (concentration 0.1% by weight) ・Flow rate: 0.8 ml/min ・Inlet pressure: 1.6 MPa ・Detector: Differential refractometer (RI) ・Column temperature: 40℃ ・Injection Quantity: 100 μl ・Lluent: Tetrahydrofuran ・Detector: Differential Refractometer ・Standard sample: Polystyrene

＜Measurement method of total light transmittance＞ On one side of a glass slide (manufactured by Songnang Glass Industry Co., Ltd., trade name "S-1111") with total light transmittance = 91.8% and haze = 0.4%, the surface protective film obtained in the examples and comparative examples is attached , Measure the total light transmittance with a haze meter (manufactured by Murakami Color Research Institute, HM-150). When measuring with a haze meter, the surface protective film is arranged so as to be the light source side. The total light transmittance (%) adopts the measured value.

＜Measurement method of hardness of hard coating＞ A PET film (thickness = 100 μm) is applied with a hard coat film, which is attached to a glass plate via an adhesive with a thickness of 50 μm, according to the scratch hardness (pencil method) described in JIS K 5600, Part 5, Section 4 ) Perform the measurement.

＜Tensile test (hard coating rupture test)＞ The tensile test (hard coat rupture test) was carried out under the following conditions. Regarding the following Examples and Comparative Examples, the same method was also used. Sample shape: strip with a width of 10 mm Distance between initial chucks: 20 mm Stretching speed: 5 mm/min Procedure: Apply a black spray to the whole under the measuring environment of 23℃ and 50%RH in order to easily observe the rupture on the adhesive layer of the sample. Clamp the sample to the chuck of the tensile testing machine in such a way that the initial distance between the chucks becomes 20 mm. Then, at the above-mentioned stretching speed, the amount of stretching deformation was increased by 1% successively, and it was visually confirmed whether or not cracks appeared on the hard coat surface perpendicular to the stretching direction. In the case of cracks, the tensile deformation rate at that point in time is recorded as the measured value, and the test is terminated. If there are no cracks, increase the tensile deformation rate by 1% successively, visually confirm, and repeat until cracks appear or the tensile deformation rate reaches 100%. Furthermore, the stretching direction in the above test is not particularly limited, but it is preferably the same as the length direction of the surface protection film. As the tensile tester, the product name "Autograph AG-10G Tensile Tester" manufactured by Shimadzu Corporation can be used.

<Bending test (hard coat side and adhesive layer side)> Under a measurement environment of 23°C and 50%RH, peel off the release film on the adhesive side of the sample, and bond the exposed adhesive layer to the PET film with a pressure of 0.3 MPa and a speed of 2 m/min (thickness = 100 μm, one side of Lumirror S10) of Toray Co., Ltd. The laminate thus obtained was cut into short strips with a width of 20 mm × a length of 200 mm, and this was used as a sample for bending evaluation. For the obtained samples, using a desktop endurance testing machine "Planar Unloaded U-shaped Stretch Test DLD-FS" manufactured by Yuasa System Co., Ltd., the bending evaluation was repeated under the following conditions. In addition, the sample was set in the bending tester so that the hard coat surface became the inner side of the curve, and the PET film became the outer side of the curve. Bending radius: 1 mm Bending times: 30000 times Environment: 23℃, 50%RH Visually confirm the bent portion of the sample after the above-mentioned bending evaluation is completed, and judge it according to the following criteria. [Hard coating side] ○: No fold lines are seen at all in the hard coat layer, or fold lines are slightly seen. ×: Cracks are seen in the hard coat layer. [Adhesive layer side] ⊚: Between PET and the adhesive layer, no swelling is seen at all in the bent part. ○: Between the PET and the adhesive layer, swelling is seen in a part of the bent part, but the width of the sample is 50% or less. ×: Between the PET and the adhesive layer, the bent portion is completely peeled off.

[Manufacturing Example 1] Acrylic urethane resin (manufactured by DIC Corporation, product name "UNIDIC 17-806"): 100 parts and leveling agent (manufactured by DIC Corporation, product name "GRANDIC PC4100"): 1 part, photopolymerization initiator (Manufactured by Ciba Japan, trade name: Irgacure907): 3 parts are mixed and diluted with cyclopentanone so that the solid content concentration becomes 40%, to prepare a composition for forming a hard coat layer.

[Example 1] 2-ethylhexyl acrylate (2EHA): 50 parts, isostearyl acrylate (ISTA): 50 parts, 4-hydroxybutyl acrylate (HBA): 1 part, 1-vinyl- 2-Pyrrolidone (NVP): 20 parts, photopolymerization initiator (trade name: Irgacure184, manufactured by BASF company): 0.05 parts, and photopolymerization initiator (trade name: Irgacure651, manufactured by BASF company): 0.05 parts Into the four-necked flask, prepare the monomer mixture. Then, the prepared monomer mixture is exposed to ultraviolet rays under a nitrogen atmosphere to partially perform photopolymerization, thereby obtaining a partial polymer (acrylic polymer slurry) with a polymerization rate of about 10% by weight. To 100 parts of the obtained acrylic polymer slurry, add trimethylolpropane triacrylate (TMPTA): 0.1 part, α-glycidoxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.) , KBM-403): After 0.3 parts, these are uniformly mixed to prepare monomer components. Then, the prepared monomer components were applied to a polyester film with a thickness of 38 μm (trade name: DIAFOIL MRF, Mitsubishi Plastics Co., Ltd.), which was peeled off on one side with polysiloxane, so that the final thickness became 50 μm. Company manufacture) peeled off the treated surface to form a coating layer. Next, a polyester film with a thickness of 38 μm (trade name: DIAFOIL MRF, manufactured by Mitsubishi Plastics Co., Ltd.), which has been peeled off on one side with silicone, is changed to the side of the coating layer. The method is coated on the surface of the coated monomer component. Thereby, the coating layer of the monomer component is blocked from oxygen. For the sheet with the coating layer obtained in this way, use a chemical lamp (manufactured by Toshiba Co., Ltd.) with an illuminance of 5 mW/cm ² (measured by TOPCON UVR-T1 with maximum sensitivity at about 350 nm). Ultraviolet rays for 360 seconds harden the coating layer to form the adhesive layer (1). The polyester film coated on both sides of the adhesive layer (1) functions as a release liner. The release liner on one of the two sides of the adhesive layer (1) covered with the release liner obtained in the above is peeled off to expose the adhesive layer (1). As the base layer (1), a polyurethane resin film with a thickness of 100 μm was prepared. On one surface of the substrate layer (1), the exposed adhesive layer (1) formed on the release liner is attached. The release liner is directly left on the adhesive layer (1) to protect the surface (adhesive layer) of the adhesive layer (1). After passing the obtained structure through a laminating machine at 80°C (0.3 MPa, speed 0.5 m/min) once, it was cured in an oven at 50°C for 1 day. In this way, a laminate (1) of "base material layer (1)/adhesive layer (1)/release liner" was obtained. Then, the laminate was transported, and the hard coat layer forming composition prepared in Production Example 1 was applied to the surface of the laminate on the substrate layer (1) side, and heated at 80°C. After heating the coated layer, use a high-pressure mercury lamp to irradiate ^{ultraviolet light with a cumulative amount of 300 mJ/cm 2 to} harden the coated layer to form a hard coat layer (1) (thickness: 3 μm). In this way, a surface protective film (1) with a configuration of "hard coat layer (1)/base material layer (1)/adhesive layer (1)/release liner" is obtained. The results are shown in Table 1.

[Example 2] In place of the base layer (1), a soft PET resin film with a thickness of 38 μm was used as the base layer (2), except that in the same manner as in Example 1, a "hard coat layer (1)/base layer (2)/Adhesive layer (1)/Release liner" composed of surface protective film (2). The results are shown in Table 1.

[Example 3] Add 2-ethylhexyl acrylate (2EHA): 30 parts, n-butyl acrylate (BA): 70 parts, acrylic acid ( AA): 2 parts, and 4-hydroxybutyl acrylate (4HBA): 0.1 part, 2,2'-azobisisobutyronitrile (AIBN) as polymerization initiator: 0.08 part, and acetic acid as polymerization solvent Ethyl ester: 150 parts, solution polymerization was performed at 65°C for 8 hours to obtain an ethyl acetate solution of acrylic polymer (A). The weight average molecular weight of this acrylic polymer (A) was 440,000. With respect to the acrylic polymer (A) contained in the ethyl acetate solution: 100 parts, adhesion-imparting resin TA (manufactured by Harima Chemicals, hydrogenated rosin glyceride, trade name "HARITACK SE10", softening point 75-85 °C): 30 parts, and 2.7 parts of an isocyanate-based crosslinking agent (manufactured by Tosoh, trade name "Coronate L") to prepare an adhesive composition (3). In place of the acrylic adhesive composition (1), the acrylic adhesive composition (3) was used, except that the same method as in Example 1 was used to obtain "hard coat layer (1)/substrate layer (1) /Adhesive layer (3)/Release liner" composed of surface protective film (3). The results are shown in Table 1.

[Comparative Example 1] Instead of the base material layer (1), a rigid PET resin film (manufactured by Toray, trade name "Lumirror S10") with a thickness of 100 μm was used as the base material layer (C1), except that it was obtained in the same manner as in Example 1 Surface protective film (C1) composed of "hard coat layer (1)/base material layer (C1)/adhesive layer (1)/release liner". The results are shown in Table 1.

[Comparative Example 2] Put 2,2'-azobis{2-[1-(2-hydroxyethyl)-2-imidazolin-2-yl]propane into a reactor equipped with a cooling tube, a nitrogen introduction tube, a thermometer and a stirrer }Dihydrochloride (trade name "VA-060", manufactured by Wako Pure Chemical Industries, Ltd.) (starting agent): 0.279 g and ion exchange water: 100 g, and stirring for 1 hour while introducing nitrogen. Keep it at 60°C, and slowly dropwise add butyl acrylate: 72 parts, acrylonitrile: 27 parts, acrylic acid: 1 part, dodecyl mercaptan (chain transfer agent): 0.04 part, and poly Sodium oxyethylene lauryl ether sulfate (emulsifier): 2 parts are added to ion exchange water: 41 parts and emulsifier (emulsion of monomer raw material): 400 g, and the emulsion polymerization reaction is carried out. After the dropwise addition of the monomer raw material emulsion is completed, the temperature is further maintained at the same temperature for 3 hours to mature. The aqueous dispersion (emulsion) of the acrylic polymer polymerized in this manner is dried to obtain the acrylic polymer (X). The weight average molecular weight of the acrylic polymer (X) is 700,000. Dissolved acrylic polymer (X) [copolymer obtained by blending (monomer composition) 72 parts of butyl acrylate (BA), 27 parts of acrylonitrile (AN), and 1 part of acrylic acid (AA)] : To 100 parts of ethyl acetate solution, add adhesion-imparting resin TA (manufactured by Harima Chemicals, hydrogenated rosin glyceride, trade name "HARITACK SE10", softening point 75-85°C): 30 parts, isocyanate-based crosslinking agent ( Tosoh, trade name "Coronate L"): 2.7 parts, and an adhesive composition (C2) was prepared. In place of the acrylic adhesive composition (1), the acrylic adhesive composition (C2) was used, except that the same method as in Example 1 was used to obtain "hard coat layer (1)/substrate layer (1) /Adhesive layer (C2)/Release liner" composed of surface protective film (C2). The results are shown in Table 1.

[Table 1] Example 1 Example 2 Example 3 Comparative example 1 Comparative example 2 Hard coating Hard coating (1) Hard coating (1) Hard coating (1) Hard coating (1) Hard coating (1) Substrate layer Substrate layer (1) Substrate layer (2) Substrate layer (1) Substrate layer (C1) Substrate layer (1) Adhesive layer Adhesive layer (1) Adhesive layer (1) Adhesive layer (3) Adhesive layer (1) Adhesive layer (C2) Total thickness (μm) 153 91 153 153 153 Hard coating thickness (μm) 3 3 3 3 3 Substrate layer thickness (μm) 100 38 100 100 100 Adhesive layer thickness (μm) 50 50 50 50 50 Thickness ratio (base material layer thickness/total thickness) 65% 42% 65% 65% 65% Young's modulus of the laminate of the hard coat layer and the substrate layer (MPa) 92 814 72 2061 72 Tg of adhesive layer (DSC) -17.0 -17.0 -36.9 -17.0 6.7 HC hardness (using PET100) 2H 2H 2H 2H 2H Adhesion (N/20 mm) 15.0 15.0 11.3 15.0 0.5 Total light transmittance (%) 91.7 89.1 91.5 88.3 85.0 Young's modulus of substrate layer (MPa) 50 601 50 1642 50 Tensile test Hard coat rupture test ○(40%) △(27%) ◎(＞100%) ×(10%) ◎(＞100%) Bend evaluation (hard coat side) ○ ○ ○ X ○ Bend evaluation (adhesive side) ○ ○ ◎ ○ X [Industrial availability]

The surface protection film of the present invention is excellent in flexibility, and therefore can be preferably used in, for example, a state of being attached to a member having a movable bending portion.

100: Hard coating 200: substrate layer 300: Adhesive layer 1000: Surface protective film

Fig. 1 is a schematic cross-sectional view showing an embodiment of the surface protection film of the present invention.

100: Hard coating

200: substrate layer

300: Adhesive layer

1000: Surface protective film

Claims (8)

A surface protective film, which It includes a hard coat layer, a substrate layer and an adhesive layer in sequence, and The Young's modulus at 23°C of the laminate of the hard coat layer and the substrate layer is 5 MPa to 1800 MPa, The Tg measured by DSC of the adhesive constituting the adhesive layer is below 0°C. The surface protection film of claim 1, wherein the hardness of the hard coat layer is H or higher. Such as the surface protection film of claim 1 or 2, in which the tensile deformation rate when the cracks in the hard coat rupture test occurs is 15% or more. The surface protection film of any one of claims 1 to 3, wherein the thickness of the hard coat layer is 1 μm-50 μm. The surface protection film of any one of claims 1 to 4, wherein the adhesive layer has a peeling angle of 180 degrees at 23°C and a peeling speed of 300 mm/min. The adhesion to the PET film is 0.1 N/20 mm or more . The surface protection film of any one of claims 1 to 5, wherein the thickness of the substrate layer is 1 μm to 500 μm. The surface protection film according to any one of claims 1 to 6, wherein the thickness of the adhesive layer is 0.1 μm-50 μm. For example, the surface protective film of any one of claims 1 to 7 has a total light transmittance of 85% or more.

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