JP2020163648A - Surface protective film - Google Patents

Abstract

To provide a surface protective film including a hard coat layer, a substrate layer and an adhesive layer in this order, the surface protective film capable of sufficiently following repeated flexure.SOLUTION: A surface protective film includes a hard coat layer, a substrate layer and an adhesive layer in this order. The laminate of the hard coat layer and the substrate layer at 23°C has a Young's modulus of 5-1800 MPa. An adhesive agent composing the adhesive layer has Tg of 0°C or lower measured by DSC.SELECTED DRAWING: Figure 1

Description

The present invention relates to a surface protective film.

Surface protective films are used to protect the surface of members of various shapes. However, when an attempt is made to attach the surface protective film to a corner portion (for example, a corner portion of a wall) or a bent portion (for example, a movable bent portion of a folding member), the following problems occur, for example.

When the surface protective film is bent at an angle, a compressing force acts on the bent inner diameter side, so that the surface protective film itself is deformed in an attempt to alleviate the force. Specifically, for example, wrinkles are likely to occur.

When the surface protective film is bent at an angle, a tensile stress acts on the bent outer diameter side. Therefore, when the stress is relieved, floating from the adherend occurs.

When the surface protective film is bent at an angle, the thickness of the bent part and the pulled part of the surface protective film changes greatly, and even in such a state, wrinkles are likely to occur and floating occurs. To do. For example, when the surface protective film is pulled, the thickness of the surface protective film is significantly reduced, and the surface protective film is likely to float from the adherend.

As described above, in the conventional surface protective film, the unevenness tracking to the corner portion and the bent portion cannot be sufficiently achieved.

In recent years, a surface protective film for protecting a transparent plate such as glass used for the display surface of various display devices has been widely used. As such a surface protective film, a film provided with a scratch-resistant hard coat layer has been put into practical use (Patent Document 1).

As various display devices, very recently, display devices having a movable bending portion, such as a foldable display device and a retractable display device, have been developed. When a conventional surface protective film is applied to such a display device, it cannot sufficiently follow repeated bending, and a crease mark (so-called "habit") is formed on the movable bending portion. Further, the surface protective film provided with the conventional hard coat layer cannot sufficiently follow the repeated bending of the hard coat layer, and it is difficult to attach the hard coat layer along the curved surface, or the surface protective film is sufficiently resistant to repeated bending. There is a problem that it cannot follow and peels off from the display surface.

Japanese Unexamined Patent Publication No. 2016-208138

An object of the present invention is to provide a surface protective film including a hard coat layer, a base material layer, and an adhesive layer in this order, which can sufficiently follow repeated bending.

The surface protective film of the present invention is
A surface protective film containing a hard coat layer, a base material layer, and an adhesive layer in this order.
The Young's modulus of the laminate of the hard coat layer and the base material layer at 23 ° C. is 5 MPa to 1800 MPa.
The Tg measured by DSC of the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer is 0 ° C. or lower.

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

In one embodiment, the surface protective film of the present invention has a tensile deformation rate of 15% or more at the time of crack occurrence in the hard coat layer cracking test.

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

In one embodiment, the adhesive force of the pressure-sensitive adhesive layer on a PET film at a peeling angle of 180 degrees and a peeling speed of 300 mm / min at 23 ° C. is 0.1 N / 20 mm or more.

In one embodiment, the base material layer has a thickness of 1 μm to 500 μm.

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

In one embodiment, the surface protective film has a total light transmittance of 85% or more.

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

FIG. 1 is a schematic cross-sectional view showing one embodiment of the surface protective film of the present invention.

≪≪Surface protection film≫≫
The surface protective film of the present invention includes a hard coat layer, a base material layer, and an adhesive layer in this order. That is, the surface protective film of the present invention may have any other suitable layer as long as the hard coat layer, the base material layer and the pressure-sensitive adhesive layer are included in this order, as long as the effects of the present invention are not impaired. Good.

FIG. 1 is a schematic cross-sectional view showing one embodiment of the surface protective film of the present invention. In FIG. 1, the surface protective film 1000 of the present invention has a hard coat layer 100, a base material layer 200, and an adhesive layer 300 in this order, and these are directly laminated.

The hard coat layer may be one layer or two or more layers. The hard coat layer is preferably one layer in that the effects of the present invention can be more exhibited.

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

The base material layer may be one layer or two or more layers. The base material layer is preferably one layer in that the effects of the present invention can be more exhibited.

The thickness of the base material 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. When the thickness of the base material layer is within the above range, the effect of the present invention can be more exhibited.

The pressure-sensitive adhesive layer may be one layer or two or more layers. The pressure-sensitive adhesive layer is preferably one layer in that the effects of the present invention can be more exhibited.

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

The surface protective film of the present invention may be provided with an arbitrary suitable release liner on the surface opposite to the base material layer of the pressure-sensitive adhesive layer for protection until use or the like.

Examples of the release liner include a release liner in which the surface of a base material (liner base material) such as paper or plastic film is treated with silicone, and a polyolefin resin on the surface of a base material (liner base material) such as paper or plastic film. Examples include a laminated release liner. Examples of the plastic film as the liner base material include polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, vinyl chloride copolymer film, polyethylene terephthalate film, and polybutylene terephthalate film. Examples thereof include a polyurethane film and an ethylene-vinyl acetate copolymer film.

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

The surface protective film of the present invention has a total thickness of preferably 3 μm to 1000 μm, more preferably 5 μm to 650 μm, still more preferably 7 μm to 500 μm, and particularly preferably 10 μm to 400 μm. When the total thickness of the surface protective film of the present invention is within the above range, the effect of the present invention can be further exhibited.

In the surface protective film of the present invention, the ratio of the thickness of the base material layer to the total thickness (thickness of the base material layer / total thickness) is preferably 90% or less, more preferably 20% to 90%, and further. It is preferably 25% to 90%, and particularly preferably 30% to 85%. When the ratio of the thickness of the base material layer to the total thickness of the surface protective film of the present invention (thickness of the base material layer / total thickness) is within the above range, the effect of the present invention can be further exhibited.

In the surface protective film of the present invention, the Young's modulus of the laminate of the hard coat layer and the base material layer at 23 ° C. is 5 MPa to 1800 MPa, preferably 10 MPa to 1500 MPa, more preferably 20 MPa to 1200 MPa, still more preferable. Is 30 MPa to 1100 MPa, and particularly preferably 50 MPa to 1000 MPa. When the Young's modulus of the laminate of the hard coat layer and the base material layer at 23 ° C. is within the above range, the effect of the present invention can be further exhibited. The measurement of Young's modulus of the laminate of the hard coat layer and the base material layer at 23 ° C. will be described in detail later.

The surface protective film of the present invention has a Tg of 0 ° C. or lower, preferably -100 ° C. to 0 ° C., more preferably −90 ° C. to 0 ° C. as measured by DSC of the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer. Yes, more preferably −80 ° C. to 0 ° C., and particularly preferably −70 ° C. to 0 ° C. If the Tg measured by the DSC of the pressure-sensitive adhesive constituting the pressure-sensitive 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 pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer will be described in detail later.

The surface protective film of the present invention has a total light transmittance of preferably 85% or more, more preferably 88% or more, further 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 in applications requiring high transparency.

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

The surface protective film of the present invention has a tensile deformation rate at the time of crack occurrence in the hard coat layer cracking test, preferably 15% or more, more preferably 15% to 1000%, still more preferably 20% to 800%. It is particularly preferably 25% to 500%. If the tensile deformation rate at the time of crack occurrence in the hard coat layer cracking test is within the above range, the effect of the present invention can be further exhibited. The hard coat cracking test will be described in detail later.

As the hard coat layer, any suitable hard coat layer may be adopted as long as the effects of the present invention are not impaired.

The hard coat layer can typically be formed from a composition for forming a hard coat layer. Specifically, for example, a composition for forming a hard coat layer is applied to one surface of a base material layer, and if necessary, a curing treatment (for example, ultraviolet irradiation, heat treatment, etc.) is performed to form a hard coat layer. Form. After forming the hard coat layer, the hard coat layer may be subjected to surface treatment such as corona treatment and plasma treatment.

As a method for applying the composition for forming a hard coat layer, any appropriate method can be adopted as long as the effects of the present invention are not impaired. Examples of such a coating method include a bar coating method, a gravure roll coating method, a die coating method, a rod coating method, a slot orifice coating method, a curtain coating method, a fountain coating method, and a comma coating method.

The heating temperature of the coating layer formed by coating the composition for forming the hard coat layer can be set to an arbitrary appropriate temperature depending on the composition of the composition for forming the hard coat layer. Such a heating temperature is preferably set to be equal to or lower than the glass transition temperature of the resin contained in the base material layer. By heating at a temperature equal to or lower than the glass transition temperature of the resin contained in the base material layer, it is possible to obtain a surface protective film with a hard coat layer in which deformation due to heating is suppressed. 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 having excellent adhesion to the base material layer can be formed.

As the curing treatment, any appropriate curing treatment can be adopted as long as the effects of the present invention are not impaired. Typical examples of the curing treatment include ultraviolet irradiation and heat treatment. The integrated 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) as long as the effects of the present invention are not impaired. In one embodiment, the hard coat layer forming composition comprises a thermosetting or photocurable 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, at least one selected from the group consisting of polyfunctional monomers and oligomers can be preferably adopted. Such curable compounds include monomers or oligomers having two or more (meth) acryloyl groups, urethane (meth) acrylates or urethane (meth) acrylate oligomers, epoxy monomers or oligomers, silicone monomers or oligomers, Among these, the curable compound is preferably an oligomer of urethane (meth) acrylate or urethane (meth) acrylate in that the effects of the present invention can be more exhibited.

The composition for forming a hard coat layer may contain any suitable additive as long as the effect of the present invention is not impaired. Examples of such additives include polymerization initiators, leveling agents, antiblocking agents, dispersion stabilizers, rocking agents, antioxidants, UV absorbers, defoamers, thickeners, dispersants, and surfactants. Examples include agents, catalysts, fillers, lubricants, antistatic agents and the like. Such an additive may be only one kind or two or more kinds. The types, combinations, contents, and the like of additives that can be contained in the composition for forming a hard coat layer can be appropriately set according to the purpose and desired properties.

The composition for forming a hard coat layer may contain fine particles as an additive. An anti-glare function can be imparted by using a composition for forming a hard coat layer containing fine particles. The fine particles may be inorganic fine particles or organic fine particles. Examples of the inorganic fine particles include silicon oxide fine particles, titanium oxide fine particles, aluminum oxide 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 the 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, and polyester resin powder. , Polylamin resin powder, polyimide resin powder, polyfluorinated ethylene resin powder and the like. The composition for forming a hard coat layer may contain only one type of fine particles, or may contain two or more types of fine particles. The types, combinations, contents, and the like 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 and desired characteristics.

The composition for forming a hard coat layer may contain a solvent. Examples of the solvent include dibutyl ether, dimethoxymethane, dimethoxyethane, diethoxyethane, propylene oxide, 1,4-dioxane, 1,3-dioxolane, 1,3,5-trioxane, tetrahydrofuran, acetone and methyl ethyl ketone (MEK). , Diethylketone, dipropylketone, diisobutylketone, cyclopentanone (CPN), cyclohexanone, methylcyclohexanone, ethyl foretone, propyl forrate, n-pentyl acrylate, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, n acetate -Pentyl, acetylacetone, diacetone alcohol, methyl acetoacetate, ethyl acetoacetate, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 1-pentanol, 2-methyl-2-butanol, Cyclohexanol, isopropyl alcohol (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 Examples thereof include ether, ethylene glycol monobutyl ether, ethylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, and propylene glycol monomethyl ether. The solvent for forming the hard coat layer may contain only one type or two or more types. The types, combinations, contents, and the like of the solvents that can be contained in the composition for forming a hard coat layer can be appropriately set according to the purpose and desired properties.

≪Base material layer≫
The Young's modulus of the base material 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, and particularly preferably 30 MPa to 2500 MPa. When the Young's modulus of the base material layer at 23 ° C. is within the above range, the effect of the present invention can be further exhibited. The measurement of Young's modulus of the base material layer at 23 ° C. will be described in detail later.

As the material of the base material, any suitable material can be adopted as long as the effect of the present invention is not impaired. As such a material, preferably, at least one selected from the group consisting of urethane-based resin and polyester-based resin can be mentioned. The material of the base material layer may be only one kind or two or more kinds.

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

Examples of the polyester-based resin include soft PET (polyethylene terephthalate) resin and hard PET (polyethylene terephthalate) resin. The polyester-based resin is preferably a soft PET (polyethylene terephthalate) resin in that the effects of the present invention can be further exhibited.

≪Adhesive layer≫
The pressure-sensitive adhesive layer is composed of a pressure-sensitive adhesive.

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

The pressure-sensitive adhesive includes a base polymer. The base polymer may be only one kind or two or more kinds. The content ratio of the base polymer in the pressure-sensitive adhesive is preferably 30% by weight to 99.9% by weight, more preferably 40% by weight to 99% by weight, in that the effects of the present invention can be more exhibited. More preferably, it is 50% by weight to 99% by weight.

As the base polymer, any suitable polymer can be adopted as long as the effects of the present invention are not impaired. The base polymer is preferably at least one selected from an acrylic polymer, a rubber polymer, a silicone polymer, and a urethane polymer in that the effects of the present invention can be further exhibited. That is, the pressure-sensitive adhesive layer is preferably composed of an acrylic pressure-sensitive adhesive containing an acrylic polymer, a rubber-based pressure-sensitive adhesive containing a rubber-based polymer, a silicone-based pressure-sensitive adhesive containing a silicone-based polymer, and a urethane-based pressure-sensitive adhesive containing a urethane-based polymer. It consists of at least one selected.

The base polymer is preferably an acrylic polymer in that the effects of the present invention can be more exhibited. That is, the pressure-sensitive adhesive layer is preferably composed of an acrylic pressure-sensitive adhesive containing an acrylic polymer.

Among all the monomer components for forming the acrylic polymer, the monomer having a Tg of 0 ° C. or higher of the corresponding homopolymer is preferably 25% by weight or less, more preferably 25% by weight or less, in that the effect of the present invention can be more exhibited. Is 23% by weight or less, more preferably 20% by weight or less, and particularly preferably 18% by weight or less.

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

For Tg of homopolymers other than those exemplified above, the numerical values described in "Polymer Handbook" (3rd edition, John Wiley & Sons, Inc., 1989) can be used. When a plurality of numerical values are described in the above "Polymer Handbook", the value of conventional is adopted. For the monomers not described in the above "Polymer Handbook", the catalog values of the monomer manufacturing companies are adopted. As the Tg of the homopolymer of the monomer which is not described in the above-mentioned "Polymer Handbook" and the catalog value of the monomer manufacturing company is not provided, the value obtained by the measuring method described in JP-A-2007-51271 is used. To do.

In terms of further exhibiting the effects of the present invention, the acrylic polymer includes a monomer component polymer containing an alkyl (meth) acrylate as a main monomer and further containing a submonomer having copolymerizability with the main monomer. preferable.

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 defined as “C1-”. It may be expressed as "20"). From the viewpoint of storage modulus of the pressure-sensitive adhesive layer, R ² is preferably a chain alkyl group of C1-14, more preferably a chain alkyl group having C2-10, more preferably of C4-8 It is a chain alkyl group. Here, the chain shape means a linear shape and a branched shape.

Examples of the alkyl (meth) acrylate in which R ² is a chain alkyl group of C1-20 include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, and n-butyl. (Meta) acrylate, isobutyl (meth) acrylate, s-butyl (meth) acrylate, pentyl (meth) acrylate, isopentyl (meth) acrylate, 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, Lauryl (meth) acrylate, Tridecyl (Meta) acrylate, tetradecyl (meth) acrylate, pentadecyl (meth) acrylate, hexadecyl (meth) acrylate, heptadecyl (meth) acrylate, octadecyl (meth) acrylate, isostearyl (meth) acrylate, nonadecil (meth) acrylate, ecocil ( Meta) acrylate and the like can be mentioned. These alkyl (meth) acrylates may be only one kind or two or more kinds.

The content ratio of the alkyl (meth) acrylate in all the monomer components used in the synthesis of the acrylic polymer is preferably 60% by weight to 100% by weight, more preferably 100% by weight, in that the effect of the present invention can be more exhibited. It is 65% by weight to 99.5% by weight, more preferably 70% by weight to 99% by weight, and particularly preferably 80% by weight to 98% by weight.

One embodiment of the acrylic polymer is an acrylic polymer in which less than 60% by weight of the total monomer component is 2-ethylhexyl acrylate (2EHA). In this case, the content ratio of 2-ethylhexyl acrylate (2EHA) in all the monomer components is preferably more than 0% by weight and 55% by weight or less, more preferably 5 in that the effect of the present invention can be more exhibited. It is from% 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. In this embodiment, the total monomer component further contains isostearyl acrylate (ISTA) in a proportion of less than 60% by weight (preferably more than 0% by weight and 55% by weight or less, more preferably 5) of the total monomer component. It is contained in an amount of% 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). May be good.

One embodiment of the acrylic polymer is an acrylic polymer in which 50% by weight or more of all the monomer components are n-butyl acrylate (BA). In this case, the content ratio of n-butyl acrylate (BA) in all the monomer components is preferably more than 50% by weight and 100% by weight or less, more preferably 55, in that the effect of the present invention can be more exhibited. It is from% 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, the total monomer component may further contain 2-ethylhexyl acrylate (2EHA) in a smaller proportion than n-butyl acrylate (BA).

Other monomers may be contained in all the monomer components for forming the acrylic polymer as long as the effects of the present invention are not impaired. The other monomer may be only one kind or two or more kinds. The content of the other monomers in the total 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 40% by weight. It is 10% by weight, particularly preferably 0.5% by weight to 5% by weight, and most preferably 1% by weight to 3% by weight.

Other monomers that can introduce a functional group that can serve as a cross-linking base to the acrylic polymer or contribute to the improvement of adhesive strength include, for example, hydroxyl group (OH group) -containing monomer, carboxy group-containing monomer, acid anhydride group-containing monomer, and amide. Group-containing monomer, amino group-containing monomer, imide group-containing monomer, epoxy group-containing monomer, (meth) acryloylmorpholine, sulfonic acid group-containing monomer, phosphate group-containing monomer, cyano group-containing monomer, vinyl acetate (VAc), propionic acid Examples include vinyl, vinyl laurate, aromatic vinyl compounds, vinyl ethers and the like.

One embodiment of the acrylic polymer is an acrylic polymer in which a carboxy group-containing monomer is copolymerized as another monomer. Examples of the carboxy group-containing monomer include acrylic acid (AA), methacrylic acid (MAA), carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, and isocrotonic acid. Can be mentioned. Among these, acrylic acid (AA) and methacrylic acid (MAA) are preferably mentioned as the carboxy group-containing monomer, and acrylic acid (AA) is more preferable, because the effects of the present invention can be more exhibited. is there.

When a carboxy group-containing monomer is used as the other monomer, the content ratio of the other monomer in all the monomer components is preferably 0.1% by weight to 10% by weight in that the effect of the present invention can be more exhibited. It is more preferably 0.2% by weight to 8% by weight, further preferably 0.5% by weight to 5% by weight, particularly preferably 0.7% by weight to 4% by weight, and most preferably 1% by weight. % To 3% by weight.

One embodiment of the acrylic polymer is an acrylic polymer in which a hydroxyl group-containing monomer is copolymerized as another monomer. Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, and 4-hydroxybutyl (meth) acrylate. ) Hydroxyalkyl (meth) acrylates such as acrylates; polypropylene glycol mono (meth) acrylates; N-hydroxyethyl (meth) acrylamides; and the like. Among these, as the hydroxyl group-containing monomer, hydroxyalkyl (meth) acrylate in which the alkyl group is linear with 2 to 4 carbon atoms is preferable because the effect of the present invention can be more exhibited. Specific examples thereof include 2-hydroxyethyl acrylate (HEA) and 4-hydroxybutyl acrylate (4HBA), and more preferably 4-hydroxybutyl acrylate (4HBA).

When a hydroxyl group-containing monomer is used as the other monomer, the content ratio of the other monomer in all the monomer components is preferably 0.001% by weight to 10% by weight, and more, in that the effect of the present invention can be more exhibited. It is preferably 0.01% by weight to 5% by weight, more preferably 0.02% by weight to 2% by weight, particularly preferably 0.03% by weight to 1% by weight, and most preferably 0.05% by weight. It is from% by weight to 0.5% by weight.

As a method for obtaining an acrylic polymer, for example, various polymerization methods known as synthetic methods for acrylic polymers, such as a solution polymerization method, an emulsion polymerization method, a massive polymerization method, and a suspension polymerization method, are appropriately adopted. Can be done. Among these polymerization methods, the solution polymerization method can be preferably used. As a monomer supply method for solution polymerization, a batch charging method, a continuous supply (dropping) method, a divided feeding (dropping) method, or the like in which the entire amount of the monomer components is supplied at one time can be appropriately adopted. The polymerization temperature can be appropriately selected depending on the type of monomer and solvent used, the type of polymerization initiator, etc., and is preferably 20 ° C. or higher, more preferably 30 ° C. or higher, still more preferably 40 ° C. The above is preferably 170 ° C. or lower, more preferably 160 ° C. or lower, and further preferably 140 ° C. or lower. As a method for obtaining an acrylic polymer, photopolymerization performed by irradiating with light such as UV (typically performed in the presence of a photopolymerization initiator) or irradiation with radiation such as β-rays and γ-rays is performed. Active energy ray irradiation polymerization such as radiation polymerization may be adopted.

The solvent (polymerization solvent) used for solution polymerization can be appropriately selected from any suitable organic solvent. Examples thereof include aromatic compounds such as toluene (typically aromatic hydrocarbons), acetate esters such as ethyl acetate, and aliphatic or alicyclic hydrocarbons such as hexane and cyclohexane.

The initiator (polymerization initiator) used for the polymerization can be appropriately selected from any suitable polymerization initiator according to the type of the polymerization method. The polymerization initiator may be only one kind or two or more kinds. Examples of such a polymerization initiator include an azo-based polymerization initiator such as 2,2'-azobisisobutyronitrile (AIBN); a persulfate such as potassium persulfate; a benzoyl peroxide, hydrogen peroxide and the like. Peroxide-based initiators; substituted ethane-based initiators such as phenyl-substituted ethane; aromatic carbonyl compounds; and the like. Another example of the polymerization initiator is a redox-based initiator that is a combination of a peroxide and a reducing agent.

The amount of the polymerization initiator used is preferably 0.005 parts by weight to 1 part by weight, more preferably 0.01 parts by weight to 1 part by weight, based on 100 parts by weight of all the 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 , and even more preferably 20 × 10 ⁴ to 75 × 10 ⁴ . , Particularly preferably 35 × 10 ^{4 to} 65 × 10 ⁴ . Here, Mw refers to a standard polystyrene-equivalent value obtained by GPC (gel permeation chromatography). As the GPC apparatus, for example, a model name "HLC-8320GPC" (column: TSKgel GMH-H (S), manufactured by Tosoh Corporation) can be used.

The acrylic pressure-sensitive adhesive may include a pressure-imparting resin in that the effects of the present invention can be more exhibited. Examples of the tackifier resin include rosin-based tackifier resin, terpene-based tackifier resin, hydrocarbon-based tackifier resin, epoxy-based tackifier resin, polyamide-based tackifier resin, elastomer-based tackifier resin, and phenol-based tackifier resin. , Ketone-based tackifier resin and the like. The tackifier resin may be only one type or two or more types.

The amount of the tackifier resin used is preferably 5 parts by weight to 70 parts by weight, more preferably 10 parts by weight to 60 parts by weight, based on 100 parts by weight of the base polymer, in that the effects of the present invention can be more exhibited. It is, more preferably 15 parts by weight to 50 parts by weight, further 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 parts. It is 35 parts by weight.

The tackifier resin preferably contains a tackifier resin TL having a softening point of less than 105 ° C. in that the effects of the present invention can be more exhibited. The tackifier resin TL can effectively contribute to the improvement of the deformability of the pressure-sensitive adhesive layer in the surface direction (shearing direction). From the viewpoint of obtaining a higher deformability improving effect, the softening point of the tackifier resin used as the tackifier resin TL is preferably 50 ° C. to 103 ° C., more preferably 60 ° C. to 100 ° C., and further preferably. It is 65 ° C. to 95 ° C., particularly preferably 70 ° C. to 90 ° C., and most preferably 75 ° C. to 85 ° C.

The softening point of the tackifier resin is defined as a value measured based on the softening point test method (ring ball method) specified in JIS K5902 and JIS K2207. Specifically, the sample is melted as quickly as possible at the lowest possible temperature, and the ring placed on a flat metal plate is carefully filled to prevent bubbles. After cooling, use a slightly heated knife to cut off the raised part from the flat surface including the upper end of the ring. Next, a support (ring stand) is placed in a glass container (heating bath) having a diameter of 85 mm or more and a height of 127 mm or more, and glycerin is poured until the depth becomes 90 mm or more. Next, the steel ball (diameter 9.5 mm, weight 3.5 g) and the ring filled with the sample are immersed in glycerin without contacting each other, and the temperature of glycerin is kept at 20 ° C. plus or minus 5 ° C. for 15 minutes. .. Next, a steel ball is placed in the center of the surface of the sample in the ring and placed in place on the support. Next, the distance from the upper end of the ring to the glycerin surface is kept at 50 mm, a thermometer is placed, the center of the mercury bulb of the thermometer is set to the same height as the center of the ring, and the container is heated. The Bunsen burner flame used for heating should be between the center and the edge of the bottom of the container to equalize the heating. The rate at which the bath temperature rises after reaching 40 ° C. after the start of heating must be 5.0 plus or minus 0.5 ° C. per minute. The temperature at which the sample gradually softens and flows down from the ring and finally comes into contact with the bottom plate is read, and this is used as the softening point. Two or more softening points are measured at the same time, and the average value is adopted.

The amount of the tackifier resin TL used is preferably 5 parts by weight to 50 parts by weight, more preferably 10 parts by weight, based on 100 parts by weight of the base polymer, in that the effects of the present invention can be more exhibited. It is 45 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, and most preferably 25 parts by weight to 32 parts by weight.

As the tackifier resin TL, one or more of the tackifier resins exemplified above, which are appropriately selected from those having a softening point of less than 105 ° C., can be adopted. The tackifier resin TL preferably contains a rosin-based resin.

Examples of the rosin-based resin that can be preferably used as the tackifier resin TL include rosin esters such as unmodified rosin ester and modified rosin ester. Examples of the modified rosin ester include hydrogenated rosin ester.

The tackifier resin TL preferably contains a hydrogenated rosin ester in that the effects of the present invention can be more exhibited. As the hydrogenated rosin ester, the softening point is preferably less than 105 ° C., more preferably 50 ° C. to 100 ° C., still more preferably 60 ° C. to 90 ° C. in that the effect of the present invention can be more exhibited. It is particularly preferably 70 ° C. to 85 ° C., and most preferably 75 ° C. to 85 ° C.

The tackifier resin TL may contain a non-hydrogenated rosin ester. Here, the non-hydrogenated rosin ester is a concept that comprehensively refers to the above-mentioned rosin esters other than hydrogenated rosin esters. Examples of the non-hydrogenated rosin ester include unmodified rosin ester, disproportionated rosin ester, and polymerized rosin ester.

As the non-hydrogenated rosin ester, the softening point is preferably less than 105 ° C., more preferably 50 ° C. to 100 ° C., still more preferably 60 ° C. to 90 ° C. in that the effect of the present invention can be more exhibited. ° C., particularly preferably 70 ° C. to 85 ° C., and most preferably 75 ° C. to 85 ° C.

The tackifier resin TL may contain other tackifier resins in addition to the rosin-based resin. As the other tackifier resin, one or more of the tackifier resins exemplified above, which are appropriately selected from those having a softening point of less than 105 ° C., may be adopted. The tackifier resin TL may contain, for example, a rosin resin and a terpene resin.

The content ratio of the rosin-based resin in the entire tackifier resin TL is preferably more than 50% by weight, more preferably 55% by weight to 100% by weight, still more preferably, in that the effect of the present invention can be more exhibited. Is 60% by weight to 99% by weight, particularly preferably 65% by weight to 97% by weight, and most preferably 75% by weight to 97% by weight.

The tackifier resin may contain a combination of the tackifier resin TL and the tackifier resin TH having a softening point of 105 ° C. or higher (preferably 105 ° C. to 170 ° C.) in that the effects of the present invention can be more exhibited. Good.

As the tackifier resin TH, one or more of the tackifier resins exemplified above, which are appropriately selected from those having a softening point of 105 ° C. or higher, can be adopted. The tackifier resin TH may include at least one selected from rosin-based tackifier resins (eg, rosin esters) and terpene-based tackifier resins (eg, terpene phenolic resins).

A cross-linking agent can be contained in the acrylic pressure-sensitive adhesive. The cross-linking agent may be only one kind or two or more kinds. By using a cross-linking agent, an appropriate cohesive force can be imparted to the acrylic pressure-sensitive adhesive. Crosslinkers can also help adjust shift and return distances in retention tests. An acrylic pressure-sensitive adhesive containing a cross-linking agent can be obtained, for example, by forming a pressure-sensitive adhesive layer using a pressure-sensitive adhesive composition containing the cross-linking agent. The cross-linking agent may be contained in the acrylic pressure-sensitive adhesive in a form after the cross-linking reaction, a form before the cross-linking reaction, a form partially cross-linked, an intermediate or a composite form thereof, and the like. The cross-linking agent is typically contained in the acrylic pressure-sensitive adhesive exclusively in the form after the cross-linking reaction.

The amount of the cross-linking agent used is preferably 0.005 parts by weight to 10 parts by weight, more preferably 0.01 parts by weight, based on 100 parts by weight of the base polymer, in that the effects of the present invention can be more exhibited. It is ~ 7 parts by weight, 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 the cross-linking agent include isocyanate-based cross-linking agents, epoxy-based cross-linking agents, silicone-based cross-linking agents, oxazoline-based cross-linking agents, aziridine-based cross-linking agents, silane-based cross-linking agents, alkyl etherified melamine-based cross-linking agents, and metal chelate-based cross-linking agents. , Crosslinking agents such as peroxides, etc. are preferable, and isocyanate-based crosslinking agents and epoxy-based crosslinking agents are preferable, and isocyanate-based crosslinking agents are more preferable, in that the effects of the present invention can be more exhibited. ..

As the isocyanate-based cross-linking agent, a compound having two or more isocyanate groups (including an isocyanate regenerated functional group in which the isocyanate group is temporarily protected by a blocking agent or quantification) in one molecule can be used. Examples of the isocyanate-based cross-linking agent include aromatic isocyanates such as tolylene diisocyanate and xylene diisocyanate; aliphatic isocyanates such as isophorone diisocyanate; and aliphatic isocyanates such as hexamethylene diisocyanate.

More specifically, as the isocyanate-based cross-linking agent, for example, lower aliphatic polyisocyanates such as butylene diisocyanate and hexamethylene diisocyanate; alicyclic isocyanates such as cyclopentylene diisocyanate, cyclohexylene diisocyanate and isophorone diisocyanate; 2 , 4-Tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, xylylene diisocyanate, polymethylenepolyphenyl isocyanate and other aromatic diisocyanates; trimethylolpropane / tolylene diisocyanate trimer adduct (eg, manufactured by Toso Co., Ltd., Product name Coronate L), Trimethylol propane / hexamethylene diisocyanate trimeric adduct (for example, manufactured by Toso Co., Ltd., trade name: Coronate HL), isocyanurate of hexamethylene diisocyanate (for example, manufactured by Toso Co., Ltd., trade name: Coronate Isocyanate adduct such as HX); Trimethylol propane adduct of xylylene diisocyanate (for example, manufactured by Mitsui Chemicals, trade name: Takenate D110N), Trimethylol propane adduct of xylylene diisocyanate (eg, manufactured by Mitsui Chemicals Co., Ltd.) Name: Takenate D120N), Trimethylol propane adduct of isophorone diisocyanate (for example, manufactured by Mitsui Chemicals, trade name: Takenate D140N), Trimethylol propane adduct of hexamethylene diisocyanate (eg, manufactured by Mitsui Chemicals, trade name: Takenate) D160N); polyether polyisocyanates, polyester polyisocyanates, and additions of these to various polyols; polyisocyanates polyfunctionalized by isocyanurate bond, burette bond, allophanate bond, etc.; and the like. Among these, aromatic isocyanates and alicyclic isocyanates are preferable because they can achieve both deformability and cohesive force in a well-balanced manner.

The amount of the isocyanate-based cross-linking agent used is preferably 0.005 to 10 parts by weight, more preferably 0.01, based on 100 parts by weight of the base polymer, in that the effects of the present invention can be more exhibited. It is 7 parts by weight to 7 parts by weight, 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 to 3 parts by weight. is there.

As the epoxy-based cross-linking agent, a polyfunctional epoxy compound having two or more epoxy groups in one molecule can be used. Examples of the epoxy-based cross-linking agent include N, N, N', N'-tetraglycidyl-m-xylene diamine, diglycidyl aniline, 1,3-bis (N, N-diglycidyl aminomethyl) cyclohexane, 1, 6-Hexanediol diglycidyl ether, neopentyl glycol diglycidyl ether, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, sorbitol polyglycidyl ether, glycerol polyglycidyl ether, penta Erislithol polyglycidyl ether, polyglycerol polyglycidyl ether, sorbitan polyglycidyl ether, trimethylpropane polyglycidyl ether, diglycidyl adipate, o-phthalic acid diglycidyl ester, triglycidyl-tris (2-hydroxyethyl) isocyanurate, Examples thereof include resorcin diglycidyl ether, bisphenol-S-diglycidyl ether, and epoxy resins having two or more epoxy groups in the molecule. Examples of commercially available epoxy-based cross-linking agents include trade names "Tetrad C" and "Tetrad X" manufactured by Mitsubishi Gas Chemical Company.

The amount of the epoxy-based cross-linking agent used is preferably 0.005 to 10 parts by weight, more preferably 0.01, based on 100 parts by weight of the base polymer, in that the effects of the present invention can be more exhibited. It is 5 parts by weight to 5 parts by weight, more preferably 0.015 parts by weight to 1 part by weight, particularly preferably 0.15 parts by weight to 0.5 parts by weight, and most preferably 0.015 parts by weight to 1 part by weight. It is 0.3 parts by weight.

Acrylic adhesives, if necessary, adhere to leveling agents, cross-linking aids, plasticizers, softeners, fillers, antistatic agents, anti-aging agents, UV absorbers, antioxidants, light stabilizers, etc. It may contain various additives that are common in the field of agents. As for such various additives, conventionally known ones can be used by a conventional method.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. However, the present invention is not limited thereto. In the following description, "part" and "%" are based on weight unless otherwise specified.

<Measurement method of Young's modulus at 23 ° C of the laminate of the hard coat layer and the base material layer>
Young's modulus was calculated based on the results of a 20% stretch test performed under the following conditions. The same method was adopted for Examples and Comparative Examples described later.
[20% stretch test]
Sample shape: Band-shaped initial chuck distance of 10 mm width: 20 mm
Tensile speed: 300 mm / min Tensile deformation amount: 20%
Procedure: In a measurement environment of 23 ° C. and 50% RH, the sample was sandwiched between chucks of a tensile tester so that the initial distance between chucks was 20 mm. Then, the sample was stretched (20% stretch) at the above tensile speed until the distance between the chucks became 24 mm, and the Young's modulus was calculated from the results of the obtained displacement and stress. The tensile direction in the above test is not particularly limited, but it is preferable to match the tensile direction with the longitudinal direction of the surface protective film. As the tensile tester, for example, the product name "Autograph AG-10G type tensile tester" manufactured by Shimadzu Corporation can be used.

<Method of measuring Young's modulus of base material layer at 23 ° C>
Young's modulus was calculated based on the results of a 20% stretch test performed under the following conditions. The same method was adopted for Examples and Comparative Examples described later.
[20% stretch test]
Sample shape: Band-shaped initial chuck distance of 10 mm width: 20 mm
Tensile speed: 300 mm / min Tensile deformation amount: 20%
Procedure: In a measurement environment of 23 ° C. and 50% RH, the sample was sandwiched between chucks of a tensile tester so that the initial distance between chucks was 20 mm. Then, the sample was stretched (20% stretch) at the above tensile speed until the distance between the chucks became 24 mm, and the Young's modulus was calculated from the results of the obtained displacement and stress. The tensile direction in the above test is not particularly limited, but it is preferable to match the tensile direction with the longitudinal direction of the surface protective film. As the tensile tester, for example, the product name "Autograph AG-10G type tensile tester" manufactured by Shimadzu Corporation can be used.

<Method of measuring Tg by DSC of the adhesive constituting the adhesive layer>
Using the pressure-sensitive adhesive layer obtained in Examples and Comparative Examples as a sample, about 5 mg of the sample was weighed into an aluminum cylindrical cell having a diameter of 5 mm and a depth of 2 mm, covered with a lid, and then sealed. An empty aluminum cylindrical cell was prepared as a reference sample, and a differential scanning calorimeter (DSC: TA Instrument Co., Ltd., Q2000) was used in a nitrogen atmosphere (nitrogen flow rate: 50 ml / min) at -80 ° C. After raising the temperature to 80 ° C at a rate of 10 ° C / min, quenching to -80 ° C, and measuring the endothermic curve when the temperature is raised again in the range of -80 ° C to 80 ° C at a rate of 10 ° C / min. did. The midpoint between the two bending points appearing before and after Tg was defined as Tg.

<Method of measuring the adhesive force of the adhesive layer on the PET film at 23 ° C. at a peeling angle of 180 degrees and a peeling speed of 300 mm / min>
Adhesive strength refers to 180 degree peel strength (180 degree peeling adhesive strength) with respect to PET film. The 180-degree peel strength is such that the pressure-sensitive adhesive layer surface of the measurement sample is applied to the surface of the PET film in an environment of 23 ° C. and 50% RH for the measurement sample obtained by cutting the surface protective film into a size of 20 mm in width and 100 mm in length. A 2 kg roll was reciprocated once and crimped. After leaving this in the same environment for 30 minutes, using a universal tensile compression tester, the peel strength (N /) under the conditions of a tensile speed of 300 mm / min and a peel angle of 180 degrees according to JIS Z 0237: 2000. 20 mm) was measured. As the universal tensile compression tester, for example, a "tensile compression tester, TG-1 kN" manufactured by Minebea can be used.

<Measurement method of weight average molecular weight Mw>
The weight average molecular weight of the obtained acrylic polymer was measured by GPC (gel permeation chromatography). As a sample, a filtrate obtained by dissolving the sample in tetrahydrofuran to prepare a 0.1% by weight solution, allowing it to stand overnight, and then filtering it with a 0.45 μm membrane filter was used.
-Analyzer: HLC-8120GPC manufactured by Tosoh Corporation
・ Column: Made by Tosoh
(Meta) Acrylic polymer: GM7000HXL + GMHXL
+ GMHXL
Aromatic polymer: G3000HXL + 2000HXL + G1000HXL
-Column size: 7.8 mmφ x 30 cm each, 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 ° C
・ Injection amount: 100 μl
・ Eluent: tetrahydrofuran ・ Detector: Differential refractometer ・ Standard sample: Polystyrene

<Measurement method of total light transmittance>
Slide glass with total light transmittance = 91.8% and haze = 0.4% (manufactured by Matsunami Glass Industry Co., Ltd., trade name "S-1111", surface protective film obtained in Examples and Comparative Examples on one side. The total light transmittance was measured by pasting and using a haze meter (HM-150, manufactured by Murakami Color Technology Research Institute). In the measurement by the haze meter, the surface protective film was placed so as to be on the light source side. For (%), the measured value was adopted.

<Measuring method of hardness of hard coat layer>
A film having a hard coat layer applied on a PET film (thickness = 100 μm) is attached onto a glass plate via an adhesive having a thickness of 50 μm, and the scratch hardness (pencil) described in JIS K 5600 Part 5, Section 4. Measured according to the method).

<Tensile test (hard coat layer cracking test)>
The tensile test (hard coat layer cracking test) was performed under the following conditions. The same method was adopted for Examples and Comparative Examples described later.
Sample shape: Band-shaped initial chuck distance of 10 mm width: 20 mm
Tensile rate: 5 mm / min Procedure: Under a measurement environment of 23 ° C. and 50% RH, a black spray was applied to the entire surface of the pressure-sensitive adhesive layer of the sample so that cracks could be easily observed. The sample was sandwiched between chucks of a tensile tester so that the initial distance between chucks was 20 mm. Then, the amount of tensile deformation was increased by 1% at the above tensile speed, and it was visually confirmed whether or not cracks were formed on the hard coat layer surface perpendicular to the tensile direction. If cracks were found, the tensile deformation rate at that time was described as the measured value, and the test was completed. If no cracks were formed, the tensile deformation rate was increased by 1%, visual confirmation was performed, and this was repeated until cracks occurred or the tensile deformation rate reached 100%. The tensile direction in the above test is not particularly limited, but it is preferable to match the tensile direction with the longitudinal direction of the surface protective film. As the tensile tester, the product name "Autograph AG-10G type tensile tester" manufactured by Shimadzu Corporation can be used.

<Bending test (hard coat layer side and adhesive layer side)>
In a measurement environment of 23 ° C. and 50% RH, the separator on the adhesive side of the sample was peeled off, and the exposed adhesive layer surface was pressured 0 with a laminator on one surface of a PET film (thickness = 100 μm, Toray Industries, Inc. Lumirror S10). They were bonded at 3 MPa and a speed of 2 m / min. The laminate thus obtained was cut into strips having a width of 20 mm and a length of 200 mm, and this was used as a sample for bending evaluation. The obtained sample was repeatedly evaluated for bending under the following conditions using a desktop durability tester "Spherical body no-load U-shaped expansion / contraction test DLD-FS" manufactured by Yuasa System Co., Ltd. The sample was set in the bending tester so that the hard coat layer surface was inside the bending and the PET film was outside the bending.
Bending radius: 1 mm
Number of bends: 30,000 times Environment: 23 ° C, 50% RH
The bent portion of the sample after the completion of the bending evaluation was visually confirmed, and the judgment was made according to the following criteria.
[Hard coat layer side]
〇: No polygonal lines can be seen in the hard coat layer, or slight polygonal lines can be seen.
X: Cracks are visible in the hard coat layer.
[Adhesive layer side]
⊚: No floating is observed at the bent portion between the PET and the adhesive layer.
◯: A part of the bent portion is floated between the PET and the pressure-sensitive adhesive layer, but it is 50% or less of the sample width.
X: The bent portion is completely peeled off between the PET and the pressure-sensitive adhesive layer.

[Manufacturing Example 1]
Urethane acrylate resin (manufactured by DIC, product name "Unidic 17-806"): 100 parts and leveling agent (manufactured by DIC, product name "GRANDIC PC4100"): 1 part, photopolymerization initiator (manufactured by Ciba Japan) , Trade name: Irgacure 907): Three parts were mixed and diluted with cyclopentanone so that the solid content concentration became 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, 2 types Photopolymerization initiator (trade name: Irgacure 184, manufactured by BASF): 0.05 parts and photopolymerization initiator (trade name: Irgacure 651, manufactured by BASF): 0.05 parts are put into a four-mouth flask. To prepare a monomer mixture.
Then, the prepared monomer mixture was exposed to ultraviolet rays in a nitrogen atmosphere and partially photopolymerized to obtain a partial polymer (acrylic polymer syrup) having a polymerization rate of about 10% by weight. In 100 parts of the obtained acrylic polymer syrup, trimethylolpropane triacrylate (TMPTA): 0.1 part, α-glycidoxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., KBM-403): 0. After adding 3 parts, these were uniformly mixed to prepare a monomer component.
Next, the adjusted monomer component was peeled off on one side of a polyester film (trade name: Diafoil MRF, manufactured by Mitsubishi Plastics Co., Ltd.) having a thickness of 38 μm so that the final thickness was 50 μm. It was applied to form a coating layer. Next, a polyester film (trade name: Diafoil MRF, manufactured by Mitsubishi Plastics Co., Ltd.) having a thickness of 38 μm, one side of which was peeled with silicone, was applied to the surface of the coated monomer component, and the peeled surface of the film was on the coated layer side. It was coated so as to be. As a result, the coating layer of the monomer component was shielded from oxygen. The sheet having the coating layer thus obtained is exposed to ultraviolet rays having an illuminance of 5 mW / cm ² (measured by Topcon UVR-T1 having the maximum sensitivity at about 350 nm) for 360 seconds using a chemical light lamp (manufactured by Toshiba Corporation). The coating layer was irradiated and cured to form the pressure-sensitive adhesive layer (1). The polyester film coated on both sides of the pressure-sensitive adhesive layer (1) functions as a release liner.
The release liner on one side of the pressure-sensitive adhesive layer (1) obtained above, which was coated on both sides with a release liner, was peeled off to expose the pressure-sensitive adhesive layer (1). As the base material layer (1), a polyurethane resin film having a thickness of 100 μm was prepared. The exposed pressure-sensitive adhesive layer (1) formed on the release liner was bonded to one surface of the base material layer (1). The release liner was left as it was on the pressure-sensitive adhesive layer (1) and used to protect the surface (pressure-sensitive adhesive layer surface) of the pressure-sensitive adhesive layer (1). The obtained structure was passed once through a laminator (0.3 MPa, speed 0.5 m / min) at 80 ° C., and then aged 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.
Next, while transporting the laminated body, the composition for forming a hard coat layer prepared in Production Example 1 was applied to the surface of the laminated body on the base material layer (1) side, and heated at 80 ° C. The coated layer after heating was irradiated with ultraviolet rays having an integrated light intensity of 300 mJ / cm ² with a high-pressure mercury lamp to cure the coated layer to form a hard coat layer (1) (thickness: 3 μm).
In this way, a surface protective film (1) having a structure of "hard coat layer (1) / base material layer (1) / adhesive layer (1) / release liner" was obtained. The results are shown in Table 1.

[Example 2]
In the same manner as in Example 1, "hard coat layer (1) / base material layer (1) / base material layer (1), except that a soft PET resin film having a thickness of 38 μm was used as the base material layer (2) instead of the base material layer (1). A surface protective film (2) having the structure of "2) / adhesive layer (1) / release liner" was obtained. The results are shown in Table 1.

[Example 3]
2-Ethylhexyl acrylate (2EHA) as a monomer component: 30 parts, n-butyl acrylate (BA): 70 parts, acrylic acid (AA) in a reaction vessel equipped with a stirrer, a thermometer, a nitrogen gas introduction tube and a cooler. : 2 parts, 4-hydroxybutyl acrylate (4HBA): 0.1 parts, 2,2'-azobisisobutyronitrile (AIBN) as a polymerization initiator: 0.08 parts, as a polymerization solvent Ethyl acetate: 150 parts was charged and solution-polymerized at 65 ° C. for 8 hours to obtain an ethyl acetate solution of the acrylic polymer (A). The weight average molecular weight of this acrylic polymer (A) was 440,000.
Acrylic polymer (A) contained in the above ethyl acetate solution: Adhesive-imparting resin TA (manufactured by Harima Chemicals, hydrogenated rosing lyserin ester, trade name "Haritac SE10", softening point 75 to 85 ° C.) with respect to 100 parts. : 30 parts and 2.7 parts of an isocyanate-based cross-linking agent (manufactured by Tosoh, trade name "Coronate L") were added to prepare a pressure-sensitive adhesive composition (3).
"Hard coat layer (1) / base material layer (1)" in the same manner as in Example 1 except that the acrylic pressure-sensitive adhesive composition (3) was used instead of the acrylic pressure-sensitive adhesive composition (1). A surface protective film (3) having the structure of "/ adhesive layer (3) / release liner" was obtained. The results are shown in Table 1.

[Comparative Example 1]
In the same manner as in Example 1, a hard PET resin film having a thickness of 100 μm (manufactured by Toray Industries, Inc., trade name “Lumilar S10”) was used as the base material layer (C1) instead of the base material layer (1). A surface protective film (C1) having a structure of "hard coat layer (1) / base material layer (C1) / adhesive layer (1) / release liner" was obtained. The results are shown in Table 1.

[Comparative Example 2]
2,2'-azobis {2- [1- (2-hydroxyethyl) -2-imidazolin-2-yl] propane} dihydrochloride in a reactor equipped with a condenser, nitrogen inlet tube, thermometer and stirrer. Trade name "VA-060", manufactured by Wako Pure Chemical Industries, Ltd.) (initiator): 0.279 g and ion-exchanged water: 100 g were added, and the mixture was stirred for 1 hour while introducing nitrogen gas. Keep this at 60 ° C., where butyl acrylate: 72 parts, acrylonitrile: 27 parts, acrylic acid: 1 part, dodecanethiol (chain transfer agent): 0.04 parts, and polyoxyethylene lauryl ether sodium sulfate (emulsifier). ): 2 parts were added to 41 parts of ion-exchanged water and emulsified (emulsion of monomer raw material): 400 g was gradually added dropwise over 3 hours to proceed with the emulsion polymerization reaction. After the completion of dropping the monomer raw material emulsion, the mixture was kept at the same temperature for another 3 hours for aging. The aqueous dispersion (emulsion) of the acrylic polymer polymerized in this manner was dried to obtain an acrylic polymer (X). The weight average molecular weight of the acrylic polymer (X) was 700,000. Acrylic polymer (X) [(monomer composition) Copolymer obtained by polymerizing 72 parts of butyl acrylate (BA), 27 parts of acrylonitrile (AN), and 1 part of acrylic acid (AA)]: Adhesive resin TA (manufactured by Harima Kasei Co., Ltd., hydrogenated rosing lyserine ester, trade name "Haritac SE10", softening point 75 to 85 ° C.): 30 parts, isocyanate-based cross-linking agent (made by Harima Kasei Co., Ltd., in which 100 parts are dissolved Tosoh Co., Ltd., trade name "Coronate L"): 2.7 parts was added to prepare an adhesive composition (C2).
"Hard coat layer (1) / base material layer (1)" in the same manner as in Example 1 except that the acrylic pressure-sensitive adhesive composition (C2) was used instead of the acrylic pressure-sensitive adhesive composition (1). A surface protective film (C2) having the structure of "/ adhesive layer (C2) / release liner" was obtained. The results are shown in Table 1.

Since the surface protective film of the present invention is excellent in flexibility, it can be preferably used, for example, in a mode of being attached to a member having a movable bending portion.

1000 Surface protection film 100 Hard coat layer 200 Base material layer 300 Adhesive layer

Claims (8)

A surface protective film containing a hard coat layer, a base material layer, and an adhesive layer in this order.
The Young's modulus of the laminate of the hard coat layer and the base material layer at 23 ° C. is 5 MPa to 1800 MPa.
The Tg measured by DSC of the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer is 0 ° C. or lower.
Surface protective film. The surface protective film according to claim 1, wherein the hardness of the hard coat layer is H or more. The surface protective film according to claim 1 or 2, wherein the tensile deformation rate at the time of crack occurrence in the hard coat layer cracking test is 15% or more. The surface protective film according to any one of claims 1 to 3, wherein the thickness of the hard coat layer is 1 μm to 50 μm. The method according to any one of claims 1 to 4, wherein the adhesive force of the pressure-sensitive adhesive layer on a PET film at a peeling angle of 180 degrees and a peeling speed of 300 mm / min at 23 ° C. is 0.1 N / 20 mm or more. Surface protective film. The surface protective film according to any one of claims 1 to 5, wherein the base material layer has a thickness of 1 μm to 500 μm. The surface protective film according to any one of claims 1 to 6, wherein the pressure-sensitive adhesive layer has a thickness of 0.1 μm to 50 μm. The surface protective film according to any one of claims 1 to 7, wherein the total light transmittance is 85% or more.

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