JP2022169104A - (meth)acrylic resin film - Google Patents

Abstract

To provide a (meth)acrylic resin film which is excellent in folding resistance, cutting resistance, extensibility and solvent resistance even if it has thin film thickness.SOLUTION: A (meth)acrylic resin film is obtained by crosslinking a (meth)acrylic resin composition containing a (meth)acrylic polymer, a rubber compound, a crosslinking agent and an antioxidant, wherein the (meth)acrylic polymer is composed of a copolymer which is obtained by copolymerizing (A) 100 pts.wt. of the total of 80 pts.wt. or more of methyl methacrylate, and alkyl (meth)acrylate other than the methyl methacrylate whose Tg of a homopolymer is 0°C or higher and an alkyl group has 1 to 14 carbon atoms, and (B) 1.0-20.0 pts.wt. of a copolymerizable monomer having a functional group reactive with a crosslinking agent, and has a weight average molecular weight of more than 100,000 and 1,000,000 or less, contains 1.0-25.0 pts.wt. of a rubber compound with respect to 100 pts.wt. of the total of (A), and has thickness of 10 μm or less.SELECTED DRAWING: None

Description

The present invention relates to a (meth)acrylic resin film.

It has been used as a resin film for surface coating of various equipment parts such as electronic equipment, home appliances, interior and exterior parts of automobiles, building materials, etc., due to its excellent transparency, heat processability, weather resistance, and chemical resistance. , (meth)acrylic resin films are used.
In recent years, (meth)acrylic resin films have been used as optical films because of their high transparency and excellent weather resistance.

Conventionally, as a method for producing a (meth)acrylic resin film (PMMA film) made of polymethyl methacrylate (PMMA) resin, a method of forming a film from PMMA resin by a melt extrusion method has been adopted because of its high productivity. was

For example, Patent Document 1 describes an acrylic resin film that can be suitably used for a member that integrates an acrylic resin film and a molding resin, and is particularly suitable for forming a surface protective layer. disclosed. The acrylic resin film according to the invention described in Patent Document 1 is a combination of specific types of ultraviolet absorbers and lubricants added to the acrylic resin film, and these components are contained in specific amounts. Therefore, in Patent Document 1, it is stated that it can be suitably used as an acrylic resin film in place of coating for forming a protective layer on the surface.

In addition, in Patent Document 2, it is an essential disadvantage of acrylic resin that it does not contain a rubber-containing graft copolymer that causes deterioration of unique beautiful color tone and transparency, which are advantages of acrylic resin. A method for improving impact resistance is disclosed. In the acrylic resin composition according to the invention described in Patent Document 2, when the melt extrusion temperature is increased when the resin composition is formed into a film by a melt extrusion method, the graft copolymer is thermally decomposed. It is possible to solve the problem that cooling rolls such as cast rolls are contaminated by cracked gas or bleed-out substances, resulting in a decrease in productivity.

JP 2009-286960 A WO2016/139927

By the way, the acrylic resin film according to the invention described in Patent Document 1 is obtained by kneading a mixture of an acrylic resin composition containing a thermoplastic polymer with a degassing twin-screw extruder to obtain pellets of the acrylic resin composition. After that, an acrylic resin film is formed by a melt extrusion method in which the melted resin composition is extruded through a T-die using a melt extruder. Further, in Examples 1 to 6 described in Patent Document 1, acrylic resin films having a film thickness of 50 to 125 μm are obtained. However, since the acrylic resin film according to the invention described in Patent Document 1 is a resin film formed by a melt extrusion method, it has a problem that it is difficult to obtain a thin resin film having a thickness of 10 μm or less. Was.

In addition, the acrylic resin composition according to the invention described in Patent Document 2 undergoes three to four stages of graft polymerization reaction to gradually complete the graft copolymer, so the process of obtaining the graft copolymer takes a long time. had a problem. Further, in Examples 6 to 8 in which the acrylic resin film was produced by the melt extrusion method in Patent Document 2, the thickness of the acrylic resin film obtained without stretching was 80 μm, and the acrylic resin film obtained by stretching was used. was 40 μm, and a thin resin film having a thickness of 10 μm or less was not obtained.

Under these circumstances, there has been a demand for a method of forming a PMMA resin film by a solution casting method, which is a simpler resin film forming method than the melt extrusion method and has the advantage of being able to form a thin film. Furthermore, in optical applications and display applications where PMMA resin is used, the demand for thinner films is increasing day by day, and thin films that satisfy these demands cannot be produced by melt extrusion. ing.

The present inventors have extensively studied a method for forming a PMMA resin film by a solution casting method. As a result, by using the specific PMMA resin composition, even when the film is formed by the solution casting method, it has excellent physical properties equal to or higher than those formed by the melt extrusion method, and the film thickness is 10 μm or less. We have found that it is possible to produce a thin PMMA resin film, and have completed the present invention.

In the case of a method of forming a (meth)acrylic resin film by a conventional melt extrusion method, it was difficult to reduce the thickness to a thickness of 10 μm or less. On the other hand, in the case of a method of forming a (meth)acrylic resin film by a solution casting method, it is possible to reduce the thickness to a thickness of 10 μm or less. There is a problem that it is difficult to improve the performance of solvent resistance as a physical property. Further, in the solution casting method, the weight average molecular weight of the uncrosslinked PMMA resin contained in the (meth)acrylic resin composition must be a large value of 1,000,000 or more. There was a problem that the solution of the substance was highly viscous and the workability in the film forming process was not good.

An object of the present invention is to provide a (meth)acrylic resin film that is excellent in folding resistance, cut resistance, elongation and solvent resistance even if it is thin.
Various physical properties of the formed (meth)acrylic resin film are, for example, measurement of "number of folds" for "folding resistance", measurement of "tensile breaking strength" for "cutting resistance", measurement of "Elongation" can be determined by measuring "elongation at break", and "solvent resistance" can be determined by measuring "gel fraction".

As a result of intensive studies by the present inventors to solve the above problems, the (meth)acrylic polymer containing a (meth)acrylic polymer, a rubber compound, a cross-linking agent, and an antioxidant, is MMA (methyl methacrylate), an alkyl (meth) acrylate having a homopolymer Tg of 0° C. or higher and an alkyl group having a carbon number of C1 to C14 other than MMA, and a functional group-containing copolymer Obtained by a solution casting method using a (meth)acrylic resin composition, which is a (meth)acrylic polymer composed of a copolymer obtained by copolymerizing at least one or more possible monomers in a specific ratio. The resulting (meth)acrylic resin film is excellent in folding resistance, cut resistance, extensibility, and solvent resistance, and in particular, the folding resistance and extensibility are remarkably improved. I was able to That is, the present invention comprises a resin layer obtained by cross-linking a (meth) acrylic resin composition containing a specific (meth) acrylic polymer, a rubber compound, a cross-linking agent, and an antioxidant (meth) The technical idea is to obtain an acrylic resin film by a solution casting method.

In order to solve the above problems, the present invention provides a resin layer obtained by crosslinking a (meth)acrylic resin composition containing a (meth)acrylic polymer, a rubber compound, a crosslinking agent, and an antioxidant. A (meth)acrylic resin film, wherein the (meth)acrylic polymer comprises (A) methyl methacrylate of 80 parts by weight or more, and homopolymers other than methyl methacrylate have a Tg of 0° C. or higher, and 100 parts by weight in total of at least one or more alkyl (meth)acrylates in which the alkyl group has C1 to C14 carbon atoms, and (B) a copolymerizable monomer having a functional group capable of reacting with the cross-linking agent. A (meth)acrylic polymer comprising a copolymer having a weight average molecular weight of more than 100,000 and not more than 1,000,000 obtained by copolymerizing 1.0 to 20.0 parts by weight of at least one or more total, and The meth)acrylic resin composition contains 1.0 to 25.0 parts by weight of the rubber compound with respect to 100 parts by weight of (A) in total, and the thickness of the resin layer is 10 μm or less. Provided is a (meth)acrylic resin film characterized by:

The (meth)acrylic polymer comprises (A) methyl methacrylate of 80 parts by weight or more, a homopolymer other than the methyl methacrylate having a Tg of 0° C. or higher, and an alkyl group having a carbon number of C1 to C14. 100 parts by weight in total with at least one alkyl (meth)acrylate, and (B) a monomer group consisting of a copolymerizable monomer having a hydroxyl group and a copolymerizable monomer having a carboxyl group. A (meth)acrylic polymer comprising a copolymer having a weight average molecular weight of more than 100,000 and not more than 1,000,000 obtained by copolymerizing 1.0 to 20.0 parts by weight of at least one or more monomers in total, The antioxidant is at least one selected from phenolic antioxidants, thioether antioxidants, phosphite antioxidants, and hindered amine antioxidants, and the total weight of (A) is 100. It is preferably contained in a ratio of 0.01 to 0.5 parts by weight per part.

The cross-linking agent is preferably one or more selected from the compound group consisting of epoxy compounds, aziridine compounds, and isocyanate compounds.

The rubber compound is a core-shell particle formed from a rubber layer mainly composed of SBR or butadiene in the core portion and an acrylic layer mainly composed of methyl methacrylate in the shell portion, and the core-shell particle has a volume-based average particle diameter of It is preferably 0.1 to 0.3 μm.

The (B) copolymerizable monomer having a hydroxyl group is at least one selected from 8-hydroxyoctyl methacrylate, 6-hydroxyhexyl methacrylate, 4-hydroxybutyl methacrylate, and 2-hydroxyethyl methacrylate. preferable.

In the (meth)acrylic resin film, the resin layer preferably has a thickness of 0.1 to 9 μm.

The (meth)acrylic resin film preferably has an in-plane retardation Re of 1.0 nm or less and a haze value of 3.0% or less.

The (meth)acrylic resin film has a gel fraction of 90% or more as solvent resistance, a folding endurance (JIS P8115) of 200 times or more, and a breaking elongation of 20%. It is preferable that it is above.

The present invention also provides a pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer formed on one side or both sides of the (meth)acrylic resin film.

Further, the present invention provides a polarizing film comprising the (meth)acrylic resin film formed on one or both sides of a polarizer and having a total thickness of 80 μm or less.

According to the present invention, it is possible to provide a (meth)acrylic resin film that is excellent in folding resistance, cut resistance, elongation and solvent resistance even if it is thin. In the present invention, as a test method for solvent resistance, a test piece of a (meth)acrylic resin film is immersed in a solvent solution for a predetermined time, and then an insoluble portion (residue) is formed without being eluted in the solvent. The ratio of the (meth)acrylic resin film remaining as a (so-called gel fraction) was measured, and the solvent resistance was tested.

In the case of forming a (meth)acrylic resin film by a conventional melt extrusion method, the film thickness shall be 10 μm or less unless the resin film is uniaxially or biaxially stretched. I couldn't. On the other hand, if the (meth)acrylic resin composition of the present invention is used, a thin (meth)acrylic resin film having a thickness of 10 μm or less, or even a thickness of 9 μm or less can be produced only by the solution casting method. As a result, the manufacturing process becomes simpler and the cost of the manufacturing equipment can be reduced.

Further, according to the present invention, by using an antioxidant together with the (meth)acrylic resin composition, the antioxidant can be easily blended even if the thickness of the (meth)acrylic resin film is thin. can be done. By blending an antioxidant, it is possible to suppress changes in the appearance of the (meth)acrylic resin film.

The present invention will be described below based on preferred embodiments.

The (meth)acrylic resin film of the present embodiment is a resin obtained by cross-linking a (meth)acrylic resin composition containing a (meth)acrylic polymer, a rubber compound, a cross-linking agent, and an antioxidant. A (meth)acrylic resin film which is a layer, wherein the (meth)acrylic polymer comprises (A) methyl methacrylate of 80 parts by weight or more, and homopolymers other than methyl methacrylate have a Tg of 0° C. or higher. and at least one alkyl (meth)acrylate having an alkyl group with a carbon number of C1 to C14, and (B) a copolymerizable copolymer having a functional group capable of reacting with the cross-linking agent. A (meth)acrylic polymer comprising a copolymer having a weight average molecular weight of more than 100,000 and not more than 1,000,000 obtained by copolymerizing a total of 1.0 to 20.0 parts by weight of at least one type of monomer, The (meth)acrylic resin composition contains 1.0 to 25.0 parts by weight of the rubber compound with respect to 100 parts by weight of (A) in total, and the thickness of the resin layer is 10 μm. It is characterized by the following.

The (meth)acrylic polymer used in the (meth)acrylic resin film of the present embodiment is mainly composed of an alkyl (meth)acrylate having an alkyl group having C1 to C14 carbon atoms, especially methyl methacrylate (MMA). A (meth)acrylic polymer as a main component is preferred. The alkyl group of the alkyl (meth)acrylate may be either acyclic (linear or branched) or cyclic (monocyclic or polycyclic). The (meth)acrylic polymer is preferably a copolymer containing at least two or more alkyl (meth)acrylates having alkyl groups of C1 to C14 carbon atoms. The (meth)acrylic polymer is a copolymer obtained by copolymerizing at least one alkyl (meth)acrylate having a homopolymer Tg of 0° C. or higher and an alkyl group having a carbon number of C1 to C14. is preferably Here, the main component of the (meth)acrylic polymer is one type of compound that accounts for 50% by weight or more of the (meth)acrylic polymer, or two or more types in total of 50% of the (meth)acrylic polymer. It means a group of compounds occupying % by weight or more. In other words, the main component accounts for 50 parts by weight or more in 100 parts by weight of the (meth)acrylic polymer. In the following description, when a monomer is simply referred to as Tg, it may refer to the Tg of a homopolymer.

In the (meth)acrylic polymer, examples of the alkyl (meth)acrylate having a homopolymer Tg of 0° C. or higher and having an alkyl group having a carbon number of C1 to C14 include methyl (meth)acrylate, ethyl methacrylate, n - propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, s-butyl methacrylate, t-butyl (meth)acrylate, n-pentyl methacrylate, isopentyl methacrylate, n-hexyl methacrylate, isohexyl methacrylate, cyclohexyl (meth) One or more selected from the compound group consisting of acrylate, isobornyl (meth)acrylate, and dicyclopentanyl (meth)acrylate can be mentioned. Here, (meth)acrylate means at least one of acrylate and methacrylate.

In the (meth)acrylic polymer, the alkyl (meth)acrylate having a homopolymer Tg of 0° C. or higher and having an alkyl group having a carbon number of C1 to C14 has an alkyl group having a carbon number of C1 to C6. Certain alkyl (meth)acrylates are preferred, and alkyl (meth)acrylates in which the alkyl group has from C1 to C4 carbon atoms are more preferred. In addition, among alkyl (meth)acrylates other than methyl methacrylate, in which the alkyl group has C1 to C4 carbon atoms, methyl acrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, s One or more selected from the compound group consisting of -butyl methacrylate, t-butyl acrylate, and t-butyl methacrylate is particularly preferred.

Further, in the (meth)acrylic polymer, (A) methyl methacrylate and an alkyl (methyl ) Of the total 100 parts by weight of at least one or more acrylates, 80 parts by weight or more of methyl methacrylate, and the Tg of the homopolymer other than the methyl methacrylate is 0 ° C. or higher, and the number of carbon atoms in the alkyl group is It is preferable to contain a total of at least one or more C1 to C14 alkyl (meth)acrylates in a proportion of 20 parts by weight or less, and 80 to 99 parts by weight of methyl methacrylate and homogenous It is more preferable to contain at least one or more alkyl (meth)acrylates having a polymer Tg of 0° C. or higher and an alkyl group having C1 to C14 carbon atoms in a proportion of 1 to 20 parts by weight. preferable.

The (meth)acrylic polymer is an alkyl (meth)acrylic polymer having a homopolymer Tg of 0° C. or higher and an alkyl group having C1 to C14 carbon atoms other than the (A) methyl methacrylate and the methyl methacrylate. The total amount of at least one copolymerizable monomer having a functional group capable of reacting with the cross-linking agent (B) is 1.0 to 20.0, per 100 parts by weight of the total of at least one acrylate. It is preferably contained in a proportion of 1.0 to 12.0 parts by weight, particularly preferably in a proportion of 1.0 to 9.0 parts by weight.

The (B) copolymerizable monomer having a functional group capable of reacting with the cross-linking agent is at least selected from a monomer group consisting of copolymerizable monomers having hydroxyl groups and copolymerizable monomers having carboxyl groups. One or more monomers are included. The (B) copolymerizable monomer having a functional group capable of reacting with a cross-linking agent may be only a copolymerizable monomer having a hydroxyl group, may be only a copolymerizable monomer having a carboxyl group, or may be a copolymer having a hydroxyl group. Both monomers capable of carrying out polymerization and copolymerizable monomers having a carboxyl group may be used in combination.

The copolymerizable monomer having a hydroxyl group is preferably at least one selected from a group of compounds including hydroxyalkyl (meth)acrylates and hydroxyl group-containing (meth)acrylamides. Further, as the copolymerizable monomer having a hydroxyl group, specifically, 8-hydroxyoctyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 2-hydroxyethyl It is preferably at least one selected from the compound group consisting of (meth)acrylate, N-hydroxy(meth)acrylamide, N-hydroxymethyl(meth)acrylamide, and N-hydroxyethyl(meth)acrylamide.

Further, the copolymerizable monomer having a hydroxyl group is preferably at least one selected from 8-hydroxyoctyl methacrylate, 6-hydroxyhexyl methacrylate, 4-hydroxybutyl methacrylate, and 2-hydroxyethyl methacrylate. .

Examples of copolymerizable monomers having a carboxyl group include (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, 2-(meth)acryloyloxyethylhexahydrophthalic acid, 2-( meth) acryloyloxypropyl hexahydrophthalate, 2-(meth) acryloyloxyethyl phthalate, 2-(meth) acryloyloxyethyl succinate, 2-(meth) acryloyloxyethyl maleate, carboxy polycaprolactone It is preferably at least one selected from the group of compounds consisting of mono(meth)acrylate, 2-(meth)acryloyloxyethyltetrahydrophthalic acid and the like.

The acrylic polymer comprises at least (A) methyl methacrylate and an alkyl (meth) acrylate other than the methyl methacrylate, the Tg of the homopolymer of which is 0° C. or higher, and the number of carbon atoms in the alkyl group is C1 to C14. As the (B) copolymerizable monomer having a functional group capable of reacting with the cross-linking agent, a hydroxyl group-containing copolymerizable monomer and a carboxyl group-containing copolymer It is preferable to contain at least one or more monomers selected from a monomer group consisting of possible monomers in a total amount of 1.0 to 20.0 parts by weight, preferably 1.0 to 12.0 parts by weight. More preferably, it is contained in a proportion of 1.0 to 9.0 parts by weight.

The method for producing the acrylic polymer is not particularly limited, and known polymerization methods such as a solution polymerization method and an emulsion polymerization method can be used as appropriate. The acrylic polymer is preferably a copolymer having a weight average molecular weight of more than 100,000 and not more than 1,000,000, more preferably a copolymer having a weight average molecular weight of more than 100,000 and not more than 950,000. It is particularly preferred that the copolymer is more than 100,000 and 900,000 or less. When the weight average molecular weight of the acrylic polymer is 100,000 or less, it becomes difficult to obtain a molded product such as a (meth)acrylic resin film having excellent physical properties even if the (meth)acrylic resin composition is crosslinked. . When the weight average molecular weight of the acrylic polymer is more than 1,000,000, the solution of the (meth)acrylic resin composition becomes highly viscous, resulting in poor workability in the film-forming process.

Examples of the cross-linking agent include compounds having a cross-linkable functional group capable of cross-linking reaction with the functional group of the (meth)acrylic polymer. From the viewpoint of the storage stability of the (meth)acrylic resin composition, the cross-linking agent hardly causes a cross-linking reaction at room temperature (generally 5 to 35 ° C.), and the cross-linking reaction starts when heated to a predetermined temperature or higher. It is preferably a compound that

The cross-linking agent is preferably one or more selected from the compound group consisting of epoxy compounds, aziridine compounds, and isocyanate compounds. In the (meth)acrylic resin composition, the (A) methyl methacrylate and an alkyl ( It is preferable to contain the cross-linking agent in a proportion of 0.01 to 10 parts by weight with respect to 100 parts by weight of the total of at least one or more meth)acrylates.

The cross-linking agent (epoxy-based cross-linking agent) composed of the epoxy compound is not particularly limited as long as it is a bifunctional or higher functional epoxy compound. At least one selected from the group of compounds consisting of ethers, diglycidyl esters of dicarboxylic acids, diglycidyl-substituted amines, tetraglycidyl-substituted diamines, and the like.

Among the epoxy-based cross-linking agents, polyglycidyl ethers of polyols include, for example, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, and polyethylene glycol. Diglycidyl ether, resorcin diglycidyl ether, glycerol polyglycidyl ether, trimethylolpropane polyglycidyl ether, pentaerythritol polyglycidyl ether, sorbitol polyglycidyl ether and the like.
Examples of diglycidyl esters of dicarboxylic acids include diglycidyl adipic acid and diglycidyl phthalate.
Examples of diglycidyl-substituted amines include N,N-diglycidylaniline and N,N-diglycidyltoluidine.
Tetraglycidyl-substituted diamines include 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane and N,N,N',N'-tetraglycidyl-m-xylenediamine.

The cross-linking agent (aziridine-based cross-linking agent) composed of the aziridine compound is not particularly limited as long as it is a bifunctional or higher aziridine compound, a compound having two or more aziridine-based functional groups in one molecule, and the like. The aziridinyl functional group includes a 1-aziridinyl group [—N(CH ₂ ) ₂ ], a 2-aziridinyl group, and a substituted aziridinyl group having a substituent such as a methyl group. Specific examples of aziridine-based cross-linking agents include addition products of polyisocyanate compounds and aziridine, such as the following (1) to (2), and polyols, such as the following (3) to (4). Addition products of polyacrylate compounds and aziridines, and other polyacridine compounds such as the following (5) to (7) can be mentioned.

(1) 4,4′-bis[(1-aziridinyl)carbonylamino]diphenylmethane (CH ₂ ) ₂ NCONH—C ₆ H ₄ CH ₂ C ₆ H ₄ —NHCON(CH ₂ ) ₂
(2) 1,6-bis[(1-aziridinyl)carbonylamino]hexane (CH ₂ ) ₂ NCONH—(CH ₂ ) ₆ —NHCON(CH ₂ ) ₂
(3) trimethylolpropane-tris[2-(1-aziridinyl)propionate]
_CH3CH2C [ _{CH2O - COCH2CH2N ( CH2} ) ₂ ] ₃
(4) Tetramethylolmethane-tris[2-(1-aziridinyl)propionate]
HOCH ₂ C[CH ₂ O--COCH ₂ CH ₂ N(CH ₂ ) ₂ ] ₃
(5) tris(1-aziridinyl)phosphine oxide O═P[N(CH ₂ ) ₂ ] ₃
(6) tris(1-aziridinyl)phosphine sulfide S=P[N(CH ₂ ) ₂ ] ₃
(7) 2,4,6-tris(1-aziridinyl)-1,3,5-triazine (C ₃ N ₃ )[N(CH ₂ ) ₂ ] ₃

Examples of the crosslinking agent (isocyanate-based crosslinking agent) composed of the isocyanate compound include hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), diphenylmethane diisocyanate (MDI), tolylene diisocyanate (TDI), xylylene diisocyanate (XDI), and the like. Bifunctional isocyanate (diisocyanate compound), and at least one selected from a compound group consisting of polyisocyanate compounds having tri- or higher functionality such as burette-modified products, isocyanurate-modified products, and adducts thereof. Here, examples of tri- or higher functional adducts include adducts of diisocyanate compounds and tri- or higher polyols such as trimethylolpropane and glycerin.

The (meth)acrylic resin composition contains, as essential components, a (meth)acrylic polymer, a cross-linking agent that crosslinks the (meth)acrylic polymer, a rubber compound, and an antioxidant.

In the (meth)acrylic resin composition, the (A) methyl methacrylate and an alkyl ( It is preferable that the rubber compound is contained in a proportion of 1.0 to 25.0 parts by weight, preferably 3.0 to 20.0 parts by weight, based on 100 parts by weight of the total amount of meth)acrylate and at least one type of acrylate. It is more preferable to contain at a ratio of

The rubber compound is not particularly limited as long as it is a polymer that exhibits rubber-like elasticity, but a rubber compound that is excellent in dispersibility or miscibility with the (meth)acrylic polymer is preferable. For example, rubber compounds composed of vinyl polymers such as olefin elastomers, styrene elastomers, acrylic elastomers, acrylic rubbers, nitrile rubbers, butadiene rubbers, polyisoprene rubbers and natural rubbers are preferred. The rubber compound may be a copolymer consisting of a hard segment and a soft segment, for example, a block having at least three blocks such as (hard segment) - (soft segment) - (hard segment) It may be a copolymer.

The rubber compound is preferably crosslinked by physical or chemical crosslinking.
Physical cross-linking is not limited to, for example, hydrogen bonding, hydrophobic bonding, or the like, and is not particularly limited as long as it is cross-linking due to interaction not based on covalent bonding. In the case of physical cross-linking, it is possible that the cross-linking points are fixed at room temperature and the bonds are dissociated at high temperature, so that the rubber compound exhibits thermoplasticity.
For chemical cross-linking, a compound having a functional group such as a vinyl group, an epoxy group, or an isocyanate group is used, like a cross-linkable monomer or cross-linking agent. Crosslinkable monomers may be copolymerized with non-crosslinkable monomers to synthesize crosslinked polymers. A cross-linked polymer may be synthesized by reacting a non-cross-linked polymer obtained from a non-cross-linked monomer with a cross-linking agent. Crosslinking of a non-crosslinked polymer can also be performed by introducing a covalent bond into the polymer using a radical generator such as a peroxide, an energy ray such as an ultraviolet ray, or the like.

Examples of the olefin elastomer include propylene-ethylene copolymer, ethylene-1-butene copolymer, ethylene-1-hexene copolymer, ethylene-1-octene copolymer, and propylene-ethylene-1-butene copolymer. and copolymers of aliphatic olefins such as propylene-1-butene copolymers.
Examples of the styrene elastomer include styrene-butadiene copolymers such as styrene-butadiene rubber (SBR), aromatic olefin-aliphatic olefin copolymers such as styrene-isoprene copolymers and styrene-ethylene copolymers. mentioned.
Examples of the acrylic elastomer include (meth)acrylic acid ester-acrylonitrile copolymer, (meth)acrylic acid ester-ethylene copolymer, acrylic acid ester-methacrylic acid ester block copolymer, and the like.

Examples of the acrylic rubber include acrylate-acrylonitrile copolymers and acrylate-chloroethyl vinyl ether copolymers.
Examples of the nitrile rubber include acrylonitrile-butadiene copolymers and acrylonitrile-isoprene copolymers.
Examples of the butadiene rubber include polybutadiene, acrylonitrile-butadiene-styrene copolymer, and methyl methacrylate-butadiene-styrene copolymer.
As the rubber compound, a crosslinked rubber containing acrylic acid ester as a main component and copolymerized with a crosslinkable monomer such as alkylene glycol di(meth)acrylate, polyalkylene glycol di(meth)acrylate, or allyl (meth)acrylate is used. good too.

The rubber compound is preferably a core-shell particle formed from a rubber layer of the core portion and an acrylic layer of the shell portion. Thereby, compatibility and dispersibility of the rubber compound with the (meth)acrylic polymer can be improved. As a material for the rubber layer forming the core portion, the various rubber compounds described above can be employed. The rubber compound may be a copolymer containing a conjugated diene such as butadiene or isoprene.

As the acrylic material forming the acrylic layer of the shell portion, a (meth)acrylic polymer containing at least one of (meth)acrylic acid ester, (meth)acrylic acid, (meth)acrylonitrile, etc. as a monomer. mentioned. The acrylic material may be a methyl methacrylate copolymer containing methyl methacrylate (MMA) or a methyl methacrylate homopolymer. The (meth)acrylic polymer may be a (meth)acrylic copolymer obtained by copolymerizing olefins such as ethylene, propylene, butadiene, isoprene and styrene. The acrylic material may be a (meth)acrylic copolymer obtained by copolymerizing a monomer having a functional group such as a hydroxyl group, a carboxyl group, or a vinyl group.

The core-shell particles may have a structure in which the core part is completely covered with the shell part, or may have a structure in which the core part is partially covered with the shell part. A shell portion may be formed around the core portion by applying or curing a resin.
The core-shell particles may have an intermediate layer between the core portion and the shell portion. The intermediate layer may be omitted and a shell layer may be formed in contact with the core portion. The intermediate layer may have a transitional composition in which the rubber compound forming the core portion and the acrylic layer forming the shell layer are mixed. As an intermediate layer, an adhesive layer between the core portion and the shell portion may be laminated.

In the core-shell particles, the core portion and the shell portion may be bonded via a chemical bond. For example, it may be a structure in which a monomer forming the shell portion is polymerized in the presence of rubber compound particles forming the core portion, thereby graft-polymerizing the resin forming the shell portion onto the core portion. . The core and shell may form an integral graft copolymer.

Although the method for producing the core-shell particles is not particularly limited, for example, by allowing the core portion to undergo emulsion polymerization or the like until the core portion reaches a desired diameter, the uniformity of the shape, size, etc. is high. A particulate core can be formed. Furthermore, by allowing the shell to polymerize until the desired diameter of the shell is reached by emulsion polymerization or the like, a particulate shell having high uniformity in shape, size, etc. can be formed. When the core portion and the shell portion are bonded by graft polymerization, the core portion and the shell portion are strongly integrated through chemical bonding, so peeling of the shell layer can be suppressed.

The rubber compound is preferably particulate in the (meth)acrylic resin composition. When the (meth)acrylic resin composition is thermally molded, the rubber compound may maintain the shape of the particles, or the rubber compound may be melted into the (meth)acrylic resin composition. May be distributed. Examples of the particle size of the rubber compound include a volume-based average particle size that can be measured by a laser diffraction method or the like. The volume-based average particle size of the rubber compound is, for example, preferably 0.05 to 2.0 μm, more preferably 0.05 to 1.0 μm, even more preferably 0.1 to 0.3 μm. When the rubber compound is the core-shell particles, the particle size of the core-shell particles includes the range of the shell portion.

The rubber compound is a core-shell particle formed from a rubber layer mainly composed of styrene-butadiene rubber (SBR) or butadiene in the core portion and an acrylic layer mainly composed of methyl methacrylate (MMA) in the shell portion. The volume-based average particle diameter of the core-shell particles is preferably 0.05 to 2.0 μm, more preferably 0.05 to 1.0 μm, even more preferably 0.1 to 0.3 μm.

The antioxidant is not particularly limited as long as it is a compound suitable for blending into the (meth)acrylic resin composition and (meth)acrylic resin film, and is appropriately selected from known antioxidants. can be used. As the antioxidant, an organic antioxidant is preferable. Examples thereof include at least one selected from phenolic antioxidants, thioether antioxidants, phosphite antioxidants, and hindered amine antioxidants.

When the (meth)acrylic resin composition and (meth)acrylic resin film are used as a resin material for optical applications, display applications, etc., the antioxidant should not affect the optical properties of the resin material. is preferred. For example, it is preferable to use a material and concentration of antioxidant that allows the (meth)acrylic resin composition or the (meth)acrylic resin film to which an antioxidant is added to maintain colorless transparency.

In the (meth)acrylic resin composition, the (A) methyl methacrylate and an alkyl ( It is preferable to contain the antioxidant in a proportion of 0.01 to 0.5 parts by weight, preferably 0.05 to 0.4 parts by weight, with respect to the total 100 parts by weight of at least one or more meth)acrylates. It is more preferable to contain in the ratio of part.

Phenolic antioxidants are not particularly limited, but specific examples include pentaerythritol-tetrakis (3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate), N,N'-hexane- 1,6-diylbis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionamide), 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl )-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, 2,6-di-tert-butyl-p-cresol, 2,5-di-tert-butylhydroquinone, etc. is mentioned.

The thioether-based antioxidant is not particularly limited, but specific examples include didodecyl-3,3'-thiodipropionate, ditridecyl-3,3'-thiodipropionate, ditetradecyl-3,3'-thiodipropionate, pionate, dioctadecyl-3,3'-thiodipropionate, pentaerythritol-tetrakis (3-dodecylthiopropionate), pentaerythritol-tetrakis (3-tetradecylthiopropionate), pentaerythritol-tetrakis ( 3-octadecylthiopropionate) and the like.

Phosphite-based antioxidants are not particularly limited, but specific examples include tris(2,4-di-tert-butylphenyl) phosphite, bis(2,4-di-tert-butylphenyl) pentaerythritol di phosphite, bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol diphosphite and the like.

The hindered amine antioxidant is not particularly limited, but specific examples include bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, methyl (1,2,2,6,6-pentamethyl -4-piperidinyl) sebacate, bis (2,2,6,6-tetramethyl-1-octyloxy-4-piperidinyl) sebacate, bis (2,2,6,6-tetramethyl-1-octyloxy-4) -piperidinyl) dodecanedioate and the like.

The (meth)acrylic resin composition is not limited to the above additives, surfactants, curing accelerators, curing retarders, plasticizers, fillers, lubricants, processing aids, anti-aging agents, heat stabilizers , a light stabilizer, an antistatic agent, a colorant, an ultraviolet absorber, an infrared absorber, and other known additives may be added as appropriate. These additives can be used alone or in combination of two or more.

The (meth)acrylic resin composition can be cured by reacting the (meth)acrylic polymer with the cross-linking agent after being molded into a predetermined shape or applied.

When the cross-linking agent contained in the (meth)acrylic resin composition is a thermal cross-linking agent that initiates a cross-linking reaction by heating, the acrylic polymer is heated and melted during molding of the molded product to flow. It is preferable to fluidize the (meth)acrylic resin composition as a solution instead of making it fluid. The solvent for obtaining the solution of the (meth)acrylic resin composition is particularly limited as long as it can dissolve the acrylic polymer without impairing the reactivity of the functional groups of the acrylic polymer and the cross-linking agent. not. Examples of the solvent include hydrocarbon solvents such as toluene, alcohol solvents such as ethanol and isopropyl alcohol, ether solvents such as diethyl ether and tetrahydrofuran, ketone solvents such as acetone and methyl ethyl ketone (MEK), and esters such as ethyl acetate. system solvents and the like. When the acrylic polymer is produced by a solution polymerization method, at least part of the solvent used for polymerization may become at least part of the solvent for the (meth)acrylic resin composition.

The (meth)acrylic resin film of the present embodiment is a resin layer formed by cross-linking the (meth)acrylic resin composition, and the thickness of the resin layer is 10 μm or less. The (meth)acrylic resin film is produced, for example, by applying a solution of the (meth)acrylic resin composition onto a predetermined substrate to form a thin film by using a solution casting method, followed by heating and drying. It can be produced by volatilizing the solvent from the thin film and cross-linking it. The substrate is not limited to a fixed flat surface, and may be a resin film unwound from a resin film roll, a movable belt, a drum, or the like. The substrate preferably has a smooth surface, but it is also possible to transfer the unevenness to the surface of the obtained (meth)acrylic resin film by forming predetermined unevenness on the substrate.

The (meth)acrylic resin film obtained by the solution casting method may be stretched in a predetermined direction such as the longitudinal direction or the width direction, or may be left unstretched. When it is necessary to reduce the anisotropy in the application of the optical film, the (meth)acrylic resin film is preferably a non-stretched film. The (meth)acrylic resin film may be processed into a biaxially stretched film by adding an operation of stretching in the longitudinal direction and the width direction. The anisotropy of the film is not limited to the anisotropy of mechanical properties such as "elongation at break", but also optical anisotropy such as "birefringence".

The mechanical properties of the (meth)acrylic resin film depend on the application. When winding on a roll, etc., in addition to having a large number of folding endurances as folding resistance and high tensile breaking strength as cut resistance, followability to adherends etc. It is preferable to have an appropriate elongation at break as elongation.

The gel fraction of the resin layer formed by crosslinking the (meth)acrylic resin composition, which constitutes the (meth)acrylic resin film, is preferably 50% or more, more preferably 70% or more. It is more preferably 90 to 100%, and particularly preferably 93 to 100%. Such a high gel fraction of the resin layer can improve solvent resistance, which is a required physical property of the (meth)acrylic resin film.

The (meth)acrylic resin film preferably has a thickness of 10 μm or less, more preferably less than 10 μm, and particularly preferably 0.1 to 9 μm. When another material is laminated on one or both sides of the (meth)acrylic resin film, if necessary, surface modification by corona discharge, adhesion-facilitating treatment such as application of an anchor coating agent may be performed. .

Since the (meth)acrylic resin film contains a rubber compound in the (meth)acrylic resin composition, the bending resistance can be improved. The (meth)acrylic resin film has a folding endurance of 100 times or more when measured according to JIS P8115 (Paper and paperboard-Folding strength test method-MIT tester method). One is preferable, and 200 times or more is more preferable. As a normal measurement condition for the number of folding endurance, a test piece with a width of 15.0 ± 0.1 mm and a length of about 110 mm is repeatedly bent back and forth at a speed of 175 ± 10 times per minute under a load of 9.8 N. is mentioned. The number of times of reciprocating bending until the test piece breaks is measured as the number of folding endurance.

Since the (meth)acrylic resin film contains a rubber compound in the (meth)acrylic resin composition, the deformability can be improved. The (meth)acrylic resin film preferably has an elongation at break of 10% or more, more preferably 20% or more. The elongation at break of films can be measured according to standards such as JIS K7161 (Plastics-Determination of tensile properties) and JIS K7127 (Plastics-Testing methods for tensile properties).

The (meth)acrylic resin film may be used as a substrate for an optical film. Examples of optical films include polarizing films, retardation films, antireflection films, antiglare films, ultraviolet absorbing films, infrared absorbing films, optical compensation films, and brightness enhancement films. Devices to which optical members are applied include liquid crystal panels, organic EL panels, and touch panels. When the (meth)acrylic resin film is used as an optical film, it is preferably colorless and transparent.

The (meth)acrylic resin film preferably has an in-plane retardation Re of 1.0 nm or less. The smaller the in-plane retardation Re, the more the (meth)acrylic resin film becomes optically isotropic, and the (meth)acrylic resin film can be attached to an optical device or used for optical inspection. change in color tone can be suppressed.

The (meth)acrylic resin film preferably has a haze value of 3.0% or less. The lower the haze value, the less light is scattered when passing through the (meth)acrylic resin film. For example, when the (meth)acrylic resin film is incorporated in an optical device such as a display, light leakage due to scattered light can be suppressed.

For the purpose of comparing the optical properties of the (meth)acrylic resin composition, when measuring optical properties such as in-plane retardation Re and haze value, the thickness of the (meth)acrylic resin film used for measurement is , may be different from the thickness of the (meth)acrylic resin film as a product. The thickness of the (meth)acrylic resin film used as a reference for the in-plane retardation Re and the haze value may be, for example, 20 to 30 μm, more specifically, 25 μm.

It is preferable that the (meth)acrylic resin film contain an antioxidant to suppress changes in appearance such as yellowing. For example, it is preferable that the (meth)acrylic resin film does not change its appearance even after 30 days at 70°C.

On one or both sides of the (meth)acrylic resin film, one of a hard coat layer, an antistatic layer, an antireflection layer, an antifouling layer, an antiglare layer, a low refractive index layer, an adhesive layer, and a release layer. Or you may laminate|stack two or more types. As the fluorine compound used in the composition for forming the low refractive index layer, one or more fluorine-containing copolymers such as fluorinated olefins, fluorinated vinyl ethers, and fluorinated alkyl (meth)acrylates are polymerized. Examples include condensates such as polymers and silane compounds containing fluorinated alkyl groups. In addition to fluorinated monomers, the fluorine-containing copolymer may be copolymerized with non-fluorinated monomers such as olefins, vinyl ethers and (meth)acrylates. The low refractive index layer may constitute an antireflection layer in combination with a high refractive index layer or the like.

The adhesive sheet of the present embodiment is characterized by forming an adhesive layer on one or both sides of the (meth)acrylic resin film, which is a resin layer formed by cross-linking the (meth)acrylic resin composition. and As the adhesive layer, an adhesive layer made of a (meth)acrylic adhesive is preferable. A known method may be used to form the adhesive layer on the (meth)acrylic resin film. Specifically, known coating methods such as reverse coating, comma coating, gravure coating, slot die coating, Meyer bar coating, and air knife coating can be used.

The pressure-sensitive adhesive sheet may be an optical film with a pressure-sensitive adhesive layer, in which a pressure-sensitive adhesive layer is laminated on at least one surface of an optical film having the (meth)acrylic resin film as a base material. The adhesive layer-attached optical film can be used for bonding optical films in various display devices such as liquid crystal display devices, touch panels, electronic paper, and organic EL. The adhesive surface of the adhesive layer used for bonding the optical film may be protected with a release film. The release film may be subjected to release treatment with a silicone-based or fluorine-based release agent or the like on the side of the release film that is to be matched with the adhesive surface of the adhesive layer.

The pressure-sensitive adhesive sheet may constitute a surface protective film bonded via the pressure-sensitive adhesive layer to protect the surface of an adherend such as glass, an optical film, or an optical member. The optical properties of the adherend, the presence or absence of foreign matter, etc. can be optically inspected in a state in which the surface protective film is attached to the adherend. Moreover, at the stage of incorporating the adherend into a product, the surface protection film can be peeled off from the adherend and removed.

Since the (meth)acrylic resin film can be made very thin with a thickness of 10 μm or less, further 0.1 to 9 μm, the total thickness of the adhesive film can be reduced. A double-sided pressure-sensitive adhesive film in which pressure-sensitive adhesive layers are formed on both sides of the (meth)acrylic resin film can also be made as thin as a double-sided pressure-sensitive adhesive film having a single pressure-sensitive adhesive layer.

The polarizing film of the present embodiment is characterized in that the (meth)acrylic resin film, which is a resin layer formed by crosslinking the (meth)acrylic resin composition, is formed on one or both sides of a polarizer. and

Since the (meth)acrylic resin film can be made very thin with a thickness of 10 μm or less, further 0.1 to 9 μm, the total thickness of the polarizing film can be reduced. The total thickness of the polarizing film is preferably 150 μm or less, more preferably 80 μm or less. Polarizers for polarizing films used in liquid crystal displays and the like are not particularly limited, but examples include polyvinyl alcohol (PVA) layers containing iodine molecules (I ₂ ).

The surface treatment applied to the surface of the protective layer of the polarizer is at least one selected from the group consisting of untreated, AG treatment, LR treatment, AR treatment, AG-LR treatment, and AG-AR treatment. There may be. Here, AG is anti-glare, LR is low reflection, and AR is anti-reflection.

Examples of the protective layer of the polarizer include acrylic resins such as triacetyl cellulose (TAC) and polymethyl methacrylate (PMMA), polyester resins such as polyethylene terephthalate (PET), cyclic olefin polymers, and polycarbonate. The (meth)acrylic resin film may be bonded to the protective layer of the polarizer via the adhesive layer of the adhesive sheet. The (meth)acrylic resin film of this embodiment can also be used as the protective layer of the polarizer.

EXAMPLES The present invention will be specifically described below with reference to examples.

<Production of (meth)acrylic polymer and (meth)acrylic resin composition>
[Example 1]
Nitrogen gas was introduced into a reactor equipped with a stirrer, a thermometer, a reflux condenser and a nitrogen inlet tube to replace the air in the reactor with nitrogen gas. A solvent (ethyl acetate) was then added to the reactor along with 95 parts by weight of methyl methacrylate, 5 parts by weight of methyl acrylate, and 3.0 parts by weight of 8-hydroxyoctyl methacrylate. Thereafter, 0.1 part by weight of azobisisobutyronitrile as a polymerization initiator was added dropwise, heated to 65° C. and reacted for a predetermined time to obtain a (meth)acrylic polymer solution of Example 1. When the weight average molecular weight (Mw) of the (meth)acrylic polymer contained in this (meth)acrylic polymer solution was measured, it was 200,000. For the (meth)acrylic polymer solution of Example 1, 10 parts by weight of Kaneace (registered trademark) M-230 as a rubber compound, 3.0 parts by weight of Coronate (registered trademark) HX as a cross-linking agent, 0.1 part by weight of Irganox (registered trademark) 1010 was added as an antioxidant and mixed with stirring to obtain a (meth)acrylic resin composition of Example 1.

[Examples 2 to 6 and Comparative Examples 1 to 4]
Examples 2 to 6 and comparative (Meth)acrylic polymers and (meth)acrylic resin compositions of Examples 1 to 4 were obtained. The weight average molecular weights (Mw) of the (meth)acrylic polymers of Examples 2-6 and Comparative Examples 1-4 were as shown in Table 1.

[Comparative Example 5]
A commercially available PMMA film (thickness: 80 μm) produced by a melt extrusion method was dissolved in methyl ethyl ketone (MEK) as a solvent, and the weight average molecular weight (Mw) of the polymer contained in the PMMA film was measured to be 300,000. rice field.

In Table 1, the values of parts by weight calculated based on 100 parts by weight of the total monomers of group (A) are shown together with abbreviations corresponding to the names of the compounds.
The meanings of the abbreviations (compound names, etc.) used in Table 1 are as follows.

[(A) Group Monomer]
"MMA": methyl methacrylate "MA": methyl acrylate "TBA": t-butyl acrylate "BMA": n-butyl methacrylate "EMA": ethyl methacrylate "IBMA": isobutyl methacrylate

[(B) Group Monomer]
"8HOA": 8-hydroxyoctyl acrylate "8HOMA": 8-hydroxyoctyl methacrylate "6HHA": 6-hydroxyhexyl acrylate "6HHMA": 6-hydroxyhexyl methacrylate "4HBMA": 4-hydroxybutyl methacrylate "HEA": 2 - hydroxyethyl acrylate "HEMA": 2-hydroxyethyl methacrylate "Aac": acrylic acid

[Rubber compound]
In addition, all the particle diameters shown below are volume-based average particle diameters.
"M-230": Kane Ace (registered trademark) M-230 (core-shell particles, particle size: 0.1 μm, core part: SBR, shell part: MMA, trade name of Kaneka Corporation)
"M-210": Kane Ace (registered trademark) M-210 (core-shell particles, particle size: 0.2 μm, core part: SBR, shell part: MMA, trade name of Kaneka Corporation)
"B-513": Kane Ace (registered trademark) B-513 (core-shell particles, particle size: 0.2 μm, core part: butadiene, shell part: MMA, trade name of Kaneka Corporation)
“LP-4100”: Metabrene (registered trademark) LP-4100 (acrylic rubber particles, particle size: 1 μm, trade name of Mitsubishi Chemical Corporation)

[Crosslinking agent]
“HX”: Coronate (registered trademark) HX (HDI isocyanurate, trade name of Tosoh Corporation)
“HL”: Coronate (registered trademark) HL (HDI adduct, trade name of Tosoh Corporation)
“D-140N”: Takenate (registered trademark) D-140N (IPDI adduct, trade name of Mitsui Chemicals, Inc.)
“TX”: TETRAD (registered trademark)-X (tetrafunctional epoxy compound, trade name of Mitsubishi Gas Chemical Company, Inc.)

[Antioxidant]
"E-1": Irganox (registered trademark) 1010 (phenolic antioxidant, trade name of BASF)
"E-2": Tinuvin (registered trademark) 292 (hindered amine antioxidant, trade name of BASF)
"E-3": Irgafos (registered trademark) 168 (phosphite antioxidant, trade name of BASF)
"E-4": Irganox (registered trademark) PS822FL (thioether antioxidant, trade name of BASF)

<Production of (meth)acrylic resin film>
The (meth)acrylic resin compositions of Examples 1 to 6 and Comparative Examples 1 to 4 are formed into resin films by a solution casting method, and heated under temperature conditions suitable for drying the solvent and curing the cross-linking agent. By drying and cross-linking, (meth)acrylic resin films of Examples 1-6 and Comparative Examples 1-4 were obtained. The thickness (μm) of each film is shown in "Thickness" in Table 2.
As the (meth)acrylic resin film of Comparative Example 5, a commercially available PMMA film (thickness: 80 μm) produced by the melt extrusion method was used as described above.

<Preparation of polarizing film>
A polarizing film was produced using a (meth)acrylic resin film having the "thickness" shown in Table 2 as a surface substrate. A polyvinyl alcohol (PVA) layer having a thickness of 30 μm was used as a polarizer. A triacetyl cellulose (TAC) film having a thickness of 30 μm was used as the base material used on the opposite side of the surface base material. The total thickness of the obtained polarizing film is shown in Table 2, "Total thickness".

<Test method and evaluation of (meth)acrylic resin film>
The (meth)acrylic resin films of Examples 1-6 and Comparative Examples 1-5 were evaluated by the following test methods.

<Haze value>
Test pieces were prepared from the (meth)acrylic resin films of Examples 1 to 6 and Comparative Examples 1 to 5, and a haze meter (manufacturer: Nippon Denshoku Co., Ltd., model: Haze Meter, NDH2000) was used to determine the haze value. (%) was measured.

<Appearance change>
Test pieces were prepared from the (meth)acrylic resin films of Examples 1 to 6 and Comparative Examples 1 to 5, and after standing at 70° C. for 30 days, changes in appearance of the films were visually judged. "○" indicates that there is no change in appearance compared to the appearance of the film before being left at 70 ° C. for 30 days (or a film that can be assumed to have no change in appearance after being left at 23 ° C. for the same period). , the case where there was a partial color change in appearance was evaluated as "Δ", and the case where there was a change in appearance and yellowing was evaluated as "x".

<Number of folding endurance as folding endurance>
After preparing test pieces from the (meth)acrylic resin films of Examples 1 to 6 and Comparative Examples 1 to 5, in accordance with JIS P8115 (Paper and paperboard-Folding strength test method-MIT tester method) , A folding endurance test was performed using a folding endurance tester (manufacturer: Tester Sangyo Co., Ltd., model: MIT folding endurance tester BE-201), and the number of reciprocating foldings until the test piece broke (endurance number of folds) was measured.

<Gel fraction as solvent resistance>
As a test method for solvent resistance, a test piece of a (meth)acrylic resin film is immersed in a solvent solution for a predetermined period of time as described below. The ratio of the (meth)acrylic resin film (so-called gel fraction) was measured to test the solvent resistance.
Test pieces were prepared from the (meth)acrylic resin films of Examples 1 to 6 and Comparative Examples 1 to 5, the mass of the test piece was accurately measured, and immersed in methyl ethyl ketone (MEK) for 24 hours. Filtered through wire mesh. After that, the filtrate was dried at a temperature of 100 ° C. for 1 hour, and the mass of the residue obtained was accurately measured, and the gel fraction (% ) was measured.
Gel fraction (%) = insoluble matter (residue) mass (g) / film (test piece) mass (g) × 100

<Tensile breaking strength as cut resistance, elongation at break as elongation>
Test pieces were prepared from the (meth)acrylic resin films of Examples 1 to 6 and Comparative Examples 1 to 5, and measured using a tensile tester (manufacturer: Shimadzu Corporation, model: AGS-X), and tested. The values of tensile strength at break (MPa) as cut resistance until the piece breaks and elongation at break (%) as elongation were determined.

<Phase difference (in-plane phase difference Re value)>
In-plane retardation (Re) values (nm) of the (meth)acrylic resin films of Examples 1 to 6 and Comparative Examples 1 to 5 were measured using a retardation measuring device (manufacturer: Oji Keisokuki Co., Ltd., model: KOBRA- HBPR/SPC). The measurement wavelength of the phase difference can be appropriately selected from the visible region such as 450 to 550 nm. When the direction in which the in-plane refractive index is maximized is the x-axis (slow axis) and the direction orthogonal to this is the y-axis (fast axis), the refractive index n _x in the x-axis direction and It is calculated by the following formula from the refractive index ny in the _y -axis direction and the thickness d of the film.
In-plane retardation Re=(n _x −n _y )×d
Here, the thickness d of the film is in units of nm, like the in-plane retardation Re, and is 1000 times the thickness (μm) of the film.

Table 2 shows the evaluation results of the (meth)acrylic resin films of Examples 1-6 and Comparative Examples 1-5.

The (meth)acrylic resin films of Examples 1 to 5 were formed into thin films with a thickness of 10 μm or less, and could be used to produce polarizing films with a total thickness of 80 μm or less. Further, the (meth)acrylic resin films of Examples 1 to 5 had a haze value of 3.0% or less, a folding endurance of 200 times or more, a solvent resistance of 90% or more, and a gel fraction of 90% or more. The tensile strength at break was 40 MPa or more (about 50 MPa or more) as cut resistance, the elongation at break was 20% or more as elongation, and the in-plane retardation Re was 1.0 nm or less. Thus, the (meth)acrylic resin films of Examples 1 to 5 were excellent in all physical properties. In addition, the (meth)acrylic resin films of Examples 1 to 5 contained an antioxidant and did not change in appearance even after 30 days at 70°C.

The (meth)acrylic resin film of Example 6 was formed into a thin film having a thickness of 10 μm or less, and could be used to produce a polarizing film having a total thickness of 80 μm or less. In addition, although the (meth)acrylic resin film of Example 6 has a slightly high haze value, it has a folding endurance of 200 times or more, a gel fraction of 90% or more as solvent resistance, and a tensile strength as cut resistance. The breaking strength was 50 MPa or more, the elongation at break was 20% or more, and the in-plane retardation Re was 1.0 nm or less. Thus, the (meth)acrylic resin film of Example 6 was excellent in all physical properties. In addition, the (meth)acrylic resin film of Example 6 contained an antioxidant and did not change its appearance even after 30 days at 70°C.

Thus, it was demonstrated that the (meth)acrylic resin films of Examples 1 to 6 can solve the problems of the present invention.

The (meth)acrylic resin film of Comparative Example 1 had a low folding endurance, probably because the (meth)acrylic resin composition did not contain a rubber compound. Moreover, the (meth)acrylic resin film of Comparative Example 1 had a change (yellowing) in appearance after 30 days at 70° C., probably because it did not contain an antioxidant.

The (meth)acrylic resin film of Comparative Example 2 had a high haze value, probably because it was a thick film. In addition, the (meth)acrylic resin film of Comparative Example 2 had a change (precipitation) in appearance after 30 days at 70°C.

In the (meth)acrylic resin film of Comparative Example 3, the (meth)acrylic polymer was obtained by copolymerizing only MMA as an alkyl (meth)acrylate having an alkyl group with a carbon number of C1 to C14, and other than MMA. , the Tg of the homopolymer is 0 ° C. or higher, and the alkyl (meth) acrylate having a carbon number of C1 to C14 in the alkyl group is not copolymerized, and the number of folding endurance is small, and , the breaking elongation rate as elongation was extremely low. In addition, the (meth)acrylic resin film of Comparative Example 3 had a change (yellowing) in appearance after 30 days at 70° C., probably because it did not contain an antioxidant.

The (meth)acrylic resin film of Comparative Example 4 has a low folding endurance and solvent resistance, probably because the (meth)acrylic resin composition does not contain a rubber compound and a cross-linking agent. The gel fraction as was extremely low. The reason why the gel fraction as solvent resistance is extremely low is considered to be that the (meth)acrylic resin composition is not crosslinked with a crosslinking agent.

The (meth)acrylic resin film of Comparative Example 5 is a resin film produced by a melt extrusion method. The internal phase difference Re was large. The reason why the gel fraction as solvent resistance is extremely low is considered to be that the resin film produced by the melt extrusion method is not crosslinked with a crosslinking agent.

As described above, the (meth)acrylic resin films of Comparative Examples 1 to 5 are excellent in folding resistance, cut resistance, elongation, and solvent resistance even with a thin film thickness, which is the problem of the present invention. However, it was not possible to solve the problem of providing a (meth)acrylic resin film.

The (meth)acrylic resin film of the present invention has excellent physical properties, particularly in terms of thinning, folding resistance, and solvent resistance, as compared with (meth)acrylic resin films obtained by conventional melt extrusion methods. Since it can be expected to be effective in reducing the thickness of various optical devices such as displays and improving durability, it has great industrial utility value.

Claims (10)

A (meth)acrylic resin film which is a resin layer obtained by crosslinking a (meth)acrylic resin composition containing a (meth)acrylic polymer, a rubber compound, a crosslinking agent, and an antioxidant, ,
The (meth)acrylic polymer is
(A) 80 parts by weight or more of methyl methacrylate, and at least one alkyl (meth)acrylate other than the methyl methacrylate, having a homopolymer Tg of 0° C. or higher and having an alkyl group with a carbon number of C1 to C14. The sum of the above is 100 parts by weight,
(B) a total of 1.0 to 20.0 parts by weight of at least one copolymerizable monomer having a functional group capable of reacting with the cross-linking agent;
A (meth)acrylic polymer comprising a copolymer having a weight average molecular weight of more than 100,000 and not more than 1,000,000 obtained by copolymerizing
The (meth)acrylic resin composition contains 1.0 to 25.0 parts by weight of the rubber compound with respect to the total 100 parts by weight of (A),
A (meth)acrylic resin film, wherein the resin layer has a thickness of 10 μm or less. The (meth)acrylic polymer is
(A) 80 parts by weight or more of methyl methacrylate, and at least one alkyl (meth)acrylate other than the methyl methacrylate, having a homopolymer Tg of 0° C. or higher and having an alkyl group with a carbon number of C1 to C14. 100 parts by weight of the total of the above,
(B) a total of 1.0 to 20.0 parts by weight of at least one monomer selected from a monomer group consisting of a copolymerizable monomer having a hydroxyl group and a copolymerizable monomer having a carboxyl group; is a (meth)acrylic polymer made of a copolymer having a weight average molecular weight of more than 100,000 and not more than 1,000,000, which is obtained by copolymerizing
The antioxidant is at least one selected from phenolic antioxidants, thioether antioxidants, phosphite antioxidants, and hindered amine antioxidants, and the total weight of (A) is 100. 2. The (meth)acrylic resin film according to claim 1, which is contained in a ratio of 0.01 to 0.5 parts by weight per part. 3. The (meth)acrylic resin film according to claim 1, wherein the cross-linking agent is one or more selected from the compound group consisting of epoxy compounds, aziridine compounds and isocyanate compounds. The rubber compound is a core-shell particle formed from a rubber layer mainly composed of SBR or butadiene in the core portion and an acrylic layer mainly composed of methyl methacrylate in the shell portion, and the core-shell particle has a volume-based average particle diameter of The (meth)acrylic resin film according to any one of claims 1 to 3, which has a thickness of 0.1 to 0.3 µm. The (B) copolymerizable monomer having a hydroxyl group is at least one selected from 8-hydroxyoctyl methacrylate, 6-hydroxyhexyl methacrylate, 4-hydroxybutyl methacrylate, and 2-hydroxyethyl methacrylate. The (meth)acrylic resin film according to claim 2. The (meth)acrylic resin film according to any one of claims 1 to 5, wherein the resin layer has a thickness of 0.1 to 9 µm. The (meth)acrylic resin film according to any one of claims 1 to 6, which has an in-plane retardation Re of 1.0 nm or less and a haze value of 3.0% or less. A gel fraction of 90% or more as solvent resistance, a folding endurance of 200 times or more (JIS P8115) as folding endurance, and a breaking elongation of 20% or more. 8. The (meth)acrylic resin film according to any one of 1 to 7. A pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer formed on one side or both sides of the (meth)acrylic resin film according to any one of claims 1 to 8. A polarizing film comprising the (meth)acrylic resin film according to any one of claims 1 to 8 formed on one or both sides of a polarizer and having a total thickness of 80 µm or less.