Method for manufacturing (meth)acrylic resin film, method for manufacturing adhesive sheet, and method for manufacturing polarizing film

Abstract

The present invention provides a method for manufacturing (meth)acrylic resin films, adhesive sheets, and polarizing films that can be used in a solution casting method to obtain thin resin films and exhibit excellent folding resistance, cut resistance, elongation, and solvent resistance. [Solution] A method for producing a (meth)acrylic resin film, comprising the steps of applying a solution of a (meth)acrylic resin composition containing a (meth)acrylic polymer, a rubber compound, and a crosslinking agent onto a substrate using a solution casting method and heating to crosslink, wherein the (meth)acrylic polymer contains (A) methyl methacrylate and alkyl (meth)acrylate other than methyl methacrylate, the homopolymer having a Tg of 0°C or higher and the number of carbon atoms in the alkyl group being C1 to C14, and (B) a monomer having a functional group that can react with the crosslinking agent, selected from the group consisting of monomers having a hydroxyl group and monomers having a carboxyl group.

Description

Technical Field

[0001] The present invention relates to a (meth)acrylic resin composition suitably used for forming a (meth)acrylic resin film or the like, and a (meth)acrylic resin film using the same.

Background Art

[0002] Conventionally, (meth)acrylic resin films have been used as resin films for surface coating of various equipment parts such as electronic devices, household appliances, interior and exterior automotive parts, and building members because they are excellent in high transparency, heat processability, weather resistance, and chemical resistance. In recent years, (meth)acrylic resin films have been used as optical films because they are excellent in high transparency, weather resistance, etc.

[0003] 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 by melt extrusion of PMMA resin has been adopted because of its high productivity.

[0004] For example, Patent Document 1 discloses an acrylic resin film suitably used for a member that integrates an acrylic resin film and a molding resin, and particularly a coating alternative acrylic resin film suitable for forming a protective layer on the surface. The acrylic resin film according to the invention described in Patent Document 1 combines a specific type of ultraviolet absorber and lubricant added to the acrylic resin film, and moreover, these components are in specific contents. Therefore, Patent Document 1 states that it can be suitably used as a coating alternative acrylic resin film used for forming a protective layer on the surface.

[0005] Furthermore, Patent Document 2 discloses a method for improving the impact resistance, which is an inherent drawback of acrylic resins, without including rubber-containing graft copolymers, which would impair the unique, beautiful color tone and transparency that are advantages of acrylic resins. The acrylic resin composition according to the invention described in Patent Document 2 solves the problem that when the melt extrusion temperature is increased when the resin composition is made into a film by melt extrusion, cooling rolls such as cast rolls are contaminated by decomposition gases or bleed-out materials generated by the thermal decomposition of the graft copolymer, resulting in reduced productivity. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2009-286960 [Patent Document 2] International Publication No. 2016 / 139927 [Overview of the project] [Problems that the invention aims to solve]

[0007] Incidentally, the acrylic resin film according to the invention described in Patent Document 1 is produced by a melt extrusion method, in which a mixture of an acrylic resin composition containing a thermoplastic polymer is kneaded in a degassing twin-screw extruder to obtain pellets of the acrylic resin composition, and then the molten resin composition is extruded through a T-die in a melt extruder to produce an acrylic resin film. Furthermore, in Examples 1 to 6 described in Patent Document 1, acrylic resin films with a film thickness of 50 to 125 μm were obtained. However, since the acrylic resin film according to the invention described in Patent Document 1 is a resin film produced by the melt extrusion method, it had the problem that it was difficult to obtain a thin resin film with a film thickness of 40 μm or less.

[0008] Furthermore, the acrylic resin composition described in Patent Document 2 had the problem that it required a long time to obtain the graft copolymer because it involved a 3-4 step graft polymerization reaction to gradually complete the graft copolymer. In addition, in Examples 6-8 of Patent Document 2, in which acrylic resin films were produced by melt extrusion, the thickness of the acrylic resin film obtained without stretching was 80 μm, and a thin resin film with a thickness of 40 μm or less without stretching could not be obtained.

[0009] In this context, there was a need for a method of producing PMMA resin films using the solution casting method, which is simpler than the melt extrusion method and has the advantage of being able to produce thin films. The inventors of the present invention diligently investigated a method of producing PMMA resin films using the solution casting method. As a result, they discovered that by using a specific PMMA resin composition, it is possible to obtain a PMMA resin film with excellent physical properties equivalent to or better than those produced by the melt extrusion method, even when produced by the solution casting method, and thus completed the present invention.

[0010] Conventional methods for producing (meth)acrylic resin films using melt extrusion have made it difficult to thin them to a thickness of 40 μm or less. On the other hand, while solution casting allows for thinning to a thickness of 40 μm or less, it presents the problem of difficulty in improving the solvent resistance of the resulting (meth)acrylic resin film. Furthermore, 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 million or more, resulting in a highly viscous solution for the (meth)acrylic resin composition, which hinders workability during the film-forming process.

[0011] The present invention aims to provide a (meth)acrylic resin composition and a (meth)acrylic resin film that can be used in a solution casting method for obtaining thin resin films, wherein the molded articles such as the resin films produced exhibit excellent fold resistance, cut resistance, elongation, and solvent resistance. Furthermore, the various physical properties of the manufactured (meth)acrylic resin film can be determined by, for example, measuring the number of folds for "fold resistance," measuring the tensile breaking strength for "cut resistance," measuring the elongation at break for "elongation," and measuring the gel fraction for "solvent resistance." [Means for solving the problem]

[0012] The present inventors, through diligent research to solve the above problems, have found that a (meth)acrylic resin composition containing a (meth)acrylic polymer, a rubber compound, and a crosslinking agent, wherein the (meth)acrylic polymer is a copolymer obtained by copolymerizing MMA (methyl methacrylate), an alkyl (meth)acrylate other than MMA, having a homopolymer Tg of 0°C or higher and an alkyl group with C1 to C14 carbon atoms, and at least one copolymerizable monomer having a functional group, in a specific proportion, results in a (meth)acrylic resin film obtained by the solution casting method using such a (meth)acrylic resin composition exhibits excellent fold resistance, cut resistance, elongation, and solvent resistance, with particularly significant improvements in fold resistance and elongation, thus completing the present invention. In other words, the technical concept of the present invention is to obtain a (meth)acrylic resin film consisting of a resin layer crosslinked with a (meth)acrylic resin composition containing a specific (meth)acrylic polymer, a rubber compound, and a crosslinking agent, by the solution casting method.

[0013] To solve the aforementioned problems, the present invention provides a (meth)acrylic resin composition containing a (meth)acrylic polymer, a rubber compound, and a crosslinking agent, wherein the (meth)acrylic polymer is a copolymer with a weight-average molecular weight of over 100,000 and up to 1,000,000, obtained by copolymerizing (A) 100 parts by weight of a total of 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 at least one alkyl group having C1 to C14 carbon atoms, and (B) 1.0 to 20.0 parts by weight of a total of at least one copolymerizable monomer having a functional group that can react with the crosslinking agent, and the rubber compound is contained in a ratio of 1.0 to 25.0 parts by weight per 100 parts by weight of the total of (A).

[0014] Preferably, the (meth)acrylic polymer is a copolymer with a weight-average molecular weight of over 100,000 and up to 1,000,000, obtained by copolymerizing (A) 100 parts by weight of 80 to 99 parts by weight of methyl methacrylate and 1 to 20 parts by weight of at least one alkyl (meth)acrylate other than methyl methacrylate, wherein the homopolymer Tg is 0°C or higher and the number of carbon atoms in the alkyl group is C1 to C14, and (B) 1.0 to 20.0 parts by weight of at least one copolymerizable monomer selected from the group consisting of copolymerizable monomers having a hydroxyl group and copolymerizable monomers having a carboxyl group, which have a functional group that can react with the crosslinking agent.

[0015] Preferably, the crosslinking agent is one or more compounds selected from the group consisting of epoxy compounds, aziridine compounds, and isocyanate compounds.

[0016] The rubber compound is preferably 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, with a volume-based average particle diameter of 0.05 to 2.0 μm.

[0017] Preferably, the copolymerizable monomer having a hydroxyl group is at least one selected from the group of compounds consisting of 8-hydroxyoctyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, N-hydroxy(meth)acrylamide, N-hydroxymethyl (meth)acrylamide, and N-hydroxyethyl (meth)acrylamide, and also contains at least one selected from the group of compounds consisting of 8-hydroxyoctyl methacrylate, 6-hydroxyhexyl methacrylate, 4-hydroxybutyl methacrylate, 2-hydroxyethyl methacrylate, and 2-hydroxyethyl acrylate.

[0018] Furthermore, the present invention provides a (meth)acrylic resin film having a thickness of 10 to 50 μm, which is a resin layer obtained by crosslinking the (meth)acrylic resin composition, characterized in that the in-plane phase difference Re of the (meth)acrylic resin film is 1.0 nm or less and the haze value is 3.0% or less.

[0019] Furthermore, the present invention provides a (meth)acrylic resin film which is a resin layer formed by crosslinking the (meth)acrylic resin composition, characterized in that the gel fraction as a measure of solvent resistance of the (meth)acrylic resin film is 90% or more, the number of folds (JIS P8115) as a measure of folding resistance is 100 times or more, and the elongation at break as a measure of elongation is 10% or more.

[0020] The present invention also provides an adhesive sheet characterized in that an adhesive layer is formed on one or both sides of a (meth)acrylic resin film which is a resin layer formed by crosslinking the (meth)acrylic resin composition.

[0021] The present invention also provides a polarizing film characterized in that a (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.

Advantages of the Invention

[0022] According to the present invention, there can be provided a (meth)acrylic resin composition that can be used in a solution casting method for obtaining a resin film with a thin film thickness, and a molded article such as the formed resin film is excellent in fold resistance, cut resistance, stretchability, and solvent resistance, and a (meth)acrylic resin film. 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 the ratio of the (meth)acrylic resin film remaining as an insoluble component (residue) without eluting into the solvent (so-called gel fraction) is measured to test the solvent resistance. In addition, when producing a (meth)acrylic resin film by the melt extrusion method of the prior art, the film thickness could not be made 40 μm or less unless uniaxial or biaxial stretching was performed after forming the resin film. On the other hand, by using the (meth)acrylic resin composition of the present invention, a thin (meth)acrylic resin film with a film thickness of 40 μm or less can be produced only by using the solution casting method, the manufacturing process becomes simpler, and the cost of the manufacturing equipment can be reduced.

Embodiments for Carrying Out the Invention

[0023] Hereinafter, the present invention will be described based on preferred embodiments.

[0024] The (meth)acrylic resin composition of this embodiment is a (meth)acrylic resin composition containing a (meth)acrylic polymer, a rubber compound, and a crosslinking agent, wherein the (meth)acrylic polymer is a (meth)acrylic polymer consisting of a copolymer with a weight-average molecular weight of over 100,000 and up to 1,000,000, obtained by copolymerizing (A) 100 parts by weight of a total of 80 parts by weight or more of methyl methacrylate and at least one alkyl (meth)acrylate other than the methyl methacrylate, the homopolymer Tg being 0°C or higher and the number of carbon atoms in the alkyl group being C1 to C14, and (B) 1.0 to 20.0 parts by weight of a total of at least one copolymerizable monomer having a functional group that can react with the crosslinking agent, and the rubber compound is contained in a ratio of 1.0 to 25.0 parts by weight per 100 parts by weight of the total of (A).

[0025] The (meth)acrylic polymer used in the (meth)acrylic resin composition of this embodiment is preferably a (meth)acrylic polymer mainly composed of alkyl (meth)acrylate having C1 to C14 carbon atoms in the alkyl group, and particularly preferably methyl methacrylate (MMA) as the main component. The alkyl group of the alkyl (meth)acrylate may be acyclic (linear, branched) or cyclic (monocyclic, polycyclic). The (meth)acrylic polymer is preferably a copolymer containing at least two types of alkyl (meth)acrylate having C1 to C14 carbon atoms in the alkyl group. The (meth)acrylic polymer is preferably a copolymer obtained by copolymerizing at least one type of alkyl (meth)acrylate having a Tg of 0°C or higher and having C1 to C14 carbon atoms in the alkyl group. Here, the main component of the (meth)acrylic polymer means a compound that accounts for 50% by weight or more of the (meth)acrylic polymer by a single type, or a group of compounds that account for 50% by weight or more of the (meth)acrylic polymer in total by two or more types. In other words, this refers to a case where the main component accounts for 50 parts by weight or more of 100 parts by weight of the (meth)acrylic polymer. Note that in the following explanation, when referring to a monomer simply as Tg, it may refer to the Tg of the homopolymer.

[0026] In the (meth)acrylic polymer described above, the alkyl (meth)acrylate, in which the Tg of the homopolymer is 0°C or higher and the number of carbon atoms in the alkyl group is C1 to C14, is one or more selected from the group of compounds consisting of 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)acrylate, isobornyl (meth)acrylate, and dicyclopentanyl (meth)acrylate. Here, (meth)acrylate means at least one of acrylate or methacrylate.

[0027] In the (meth)acrylic polymer described above, the alkyl (meth)acrylate having a homopolymer Tg of 0°C or higher and an alkyl group with C1 to C14 carbon atoms is preferably an alkyl (meth)acrylate with an alkyl group with C1 to C6 carbon atoms, and more preferably an alkyl (meth)acrylate with an alkyl group with C1 to C4 carbon atoms. Furthermore, among alkyl (meth)acrylates other than methyl methacrylate that have an alkyl group with C1 to C4 carbon atoms, it is particularly preferable that one or more compounds selected from the group consisting of methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, s-butyl methacrylate, t-butyl acrylate, and t-butyl methacrylate are used.

[0028] Furthermore, in the (meth)acrylic polymer, it is preferable that the (A) methyl methacrylate and at least one alkyl (meth)acrylate other than the methyl methacrylate, in a ratio of 80 parts by weight or more and 20 parts by weight or less of the total of at least one alkyl (meth)acrylate other than the methyl methacrylate, in a ratio of 80 to 99 parts by weight and 1 to 20 parts by weight of the total of the homopolymer Tg of the homopolymer and at least one alkyl (meth)acrylate other than the methyl methacrylate, in a ratio of 1 to 20 parts by weight.

[0029] The (meth)acrylic polymer preferably contains, in proportion to 100 parts by weight of the total of (A) methyl methacrylate and at least one alkyl (meth)acrylate other than methyl methacrylate, having a homopolymer Tg of 0°C or higher and an alkyl group with C1 to C14 carbon atoms, at least one copolymerizable monomer having a functional group that can react with (B) a crosslinking agent, in proportion to at least 1.0 to 20.0 parts by weight, more preferably 1.0 to 12.0 parts by weight, and particularly preferably 1.0 to 9.0 parts by weight.

[0030] The copolymerizable monomer having a functional group that can react with the crosslinking agent (B) can be any monomer selected from the group of monomers consisting of copolymerizable monomers having a hydroxyl group and copolymerizable monomers having a carboxyl group. The copolymerizable monomer having a functional group that can react with the crosslinking agent (B) may consist only of copolymerizable monomers having a hydroxyl group, only of copolymerizable monomers having a carboxyl group, or a combination of copolymerizable monomers having a hydroxyl group and copolymerizable monomers having a carboxyl group.

[0031] The copolymerizable monomer having a hydroxyl group is preferably at least one selected from the group of compounds consisting of hydroxyalkyl (meth)acrylates and hydroxyl group-containing (meth)acrylamides. Furthermore, the copolymerizable monomer having a hydroxyl group is preferably at least one selected from the group of compounds consisting of 8-hydroxyoctyl(meth)acrylate, 6-hydroxyhexyl(meth)acrylate, 4-hydroxybutyl(meth)acrylate, 2-hydroxyethyl(meth)acrylate, N-hydroxy(meth)acrylamide, N-hydroxymethyl(meth)acrylamide, and N-hydroxyethyl(meth)acrylamide.

[0032] Furthermore, it is preferable that the copolymerizable monomer having a hydroxyl group includes at least one compound selected from the group consisting of 8-hydroxyoctyl methacrylate, 6-hydroxyhexyl methacrylate, 4-hydroxybutyl methacrylate, 2-hydroxyethyl methacrylate, and 2-hydroxyethyl acrylate.

[0033] The copolymerizable monomer having a carboxyl group is preferably at least one selected from the group of compounds consisting of (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, 2-(meth)acryloyloxyethylhexahydrophthalic acid, 2-(meth)acryloyloxypropylhexahydrophthalic acid, 2-(meth)acryloyloxyethyl phthalic acid, 2-(meth)acryloyloxyethyl succinic acid, 2-(meth)acryloyloxyethyl maleic acid, carboxypolycaprolactone mono(meth)acrylate, 2-(meth)acryloyloxyethyl tetrahydrophthalic acid, and the like.

[0034] The acrylic polymer preferably contains, in proportion to 100 parts by weight of the total of (A) methyl methacrylate and at least one alkyl (meth)acrylate other than methyl methacrylate, having a homopolymer Tg of 0°C or higher and an alkyl group with C1 to C14 carbon atoms, at least one monomer selected from the group of monomers consisting of copolymerizable monomers having a hydroxyl group and copolymerizable monomers having a carboxyl group, in proportion to 1.0 to 20.0 parts by weight, more preferably 1.0 to 12.0 parts by weight, and particularly preferably 1.0 to 9.0 parts by weight.

[0035] The method for producing the acrylic polymer is not particularly limited, and any known polymerization method, such as solution polymerization or emulsion polymerization, can be used as appropriate. The acrylic polymer is preferably a copolymer with a weight-average molecular weight of over 100,000 and up to 1,000,000, more preferably a copolymer with a weight-average molecular weight of over 100,000 and up to 950,000, and particularly preferably a copolymer with a weight-average molecular weight of over 100,000 and up to 900,000. If the weight-average molecular weight of the acrylic polymer is 100,000 or less, it becomes difficult to obtain molded articles such as (meth)acrylic resin films with excellent physical properties even when the (meth)acrylic resin composition is crosslinked. If the weight-average molecular weight of the acrylic polymer is greater than 1,000,000, the solution of the (meth)acrylic resin composition becomes highly viscous, resulting in poor workability in the film-forming process.

[0036] Examples of the crosslinking agent include compounds having crosslinkable functional groups that can crosslink with the functional groups of the (meth)acrylic polymer. From the viewpoint of storage stability of the (meth)acrylic resin composition, it is preferable that the crosslinking agent is a compound that does not readily undergo the crosslinking reaction at room temperature (generally 5 to 35°C), but initiates the crosslinking reaction when heated above a predetermined temperature.

[0037] Preferably, the crosslinking agent is one or more compounds selected from the group consisting of epoxy compounds, aziridine compounds, and isocyanate compounds. The (meth)acrylic resin composition of this embodiment preferably contains the crosslinking agent in a ratio of 0.01 to 10 parts by weight per 100 parts by weight of the total of (A) methyl methacrylate and at least one alkyl (meth)acrylate other than methyl methacrylate, wherein the Tg of the homopolymer is 0°C or higher and the number of carbon atoms in the alkyl group is C1 to C14.

[0038] The crosslinking agent (epoxy crosslinking agent) consisting of the epoxy compound is not particularly limited as long as it is a bifunctional or more functional epoxy compound, but examples include at least one selected from the group of compounds consisting of polyglycidyl ethers of polyols (including diols, glycols, and bisphenols), diglycidyl esters of dicarboxylic acids, diglycidyl-substituted amines, tetraglycidyl-substituted diamines, and so on.

[0039] Examples of polyglycidyl ethers of polyols among the epoxy crosslinking agents include ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, polyethylene glycol diglycidyl ether, resorcinol 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 ester and diglycidyl phthalate ester. Examples of diglycidyl-substituted amines include N,N-diglycidylaniline and N,N-diglycidyltoluidine. Examples of tetraglycidyl-substituted diamines include 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane and N,N,N′,N′-tetraglycidyl-m-xylenediamine.

[0040] The crosslinking agent (aziridine crosslinking agent) consisting of the aziridine compound is not particularly limited as long as it is a bifunctional or more functional aziridine compound, a compound having two or more aziridine functional groups in one molecule, etc. Examples of aziridine functional groups include substituted aziridinyl groups having substituents such as 1-aziridinyl group [-N(CH2)2], 2-aziridinyl group, and methyl group. Specific examples of aziridine crosslinking agents include, for example, the addition products of polyisocyanate compounds and aziridine as shown in (1) to (2) below, the addition products of polyol polyacrylate compounds and aziridine as shown in (3) to (4) below, and other polyacridine compounds as shown in (5) to (7) below.

[0041] (1) 4,4′-Bis[(1-aziridinyl)carbonylamino]diphenylmethane (CH2)2NCONH-C6H4CH2C6H4-NHCON(CH2)2 (2) 1,6-Bis[(1-aziridinyl)carbonylamino]hexane (CH2)2NCONH-(CH2)6-NHCON(CH2)2 (3) Trimethylolpropane-Tris[2-(1-aziridinyl)propionate] CH3CH2C[CH2O-COCH2CH2N(CH2)2]3 (4) Tetramethylolmethane-Tris[2-(1-aziridinyl)propionate] HOCH2C[CH2O-COCH2CH2N(CH2)2]3 (5) Tris(1-aziridinyl)phosphine oxide O=P[N(CH2)2]3 (6) Tris(1-aziridinyl)phosphine sulfide S=P[N(CH2)2]3 (7) 2,4,6-Tris(1-aziridinyl)-1,3,5-triazine (C3N3)[N(CH2)2]3

[0042] The crosslinking agent consisting of the isocyanate compound (isocyanate-based crosslinking agent) can be selected from at least one compound from the group consisting of difunctional isocyanates (diisocyanate compounds) such as hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), diphenylmethane diisocyanate (MDI), tolylene diisocyanate (TDI), and xylylene diisocyanate (XDI), or trifunctional or more polyisocyanate compounds such as biuret-modified, isocyanurate-modified, and adduct-modified versions thereof. Here, the trifunctional or more adduct-modified versions can be defined as adduct-modified versions of a diisocyanate compound and a trivalent or higher polyol such as trimethylolpropane or glycerin.

[0043] The (meth)acrylic resin composition contains a rubber compound as an essential component, in addition to a (meth)acrylic polymer and a crosslinking agent for crosslinking the (meth)acrylic polymer. The (meth)acrylic resin composition of this embodiment preferably contains the rubber compound in a ratio of 1.0 to 25.0 parts by weight, and more preferably 3.0 to 20.0 parts by weight, per 100 parts by weight of the total of (A) methyl methacrylate and at least one alkyl (meth)acrylate other than methyl methacrylate, the homopolymer having a Tg of 0°C or higher and the alkyl group having C1 to C14 carbon atoms.

[0044] The rubber compound is not particularly limited as long as it is a polymer exhibiting rubber-like elasticity, but rubber compounds that have excellent dispersibility or miscibility with the (meth)acrylic polymer are preferred. For example, rubber compounds made from vinyl polymers such as olefin elastomers, styrene elastomers, acrylic elastomers, acrylic rubber, nitrile rubber, butadiene rubber, polyisoprene rubber, and natural rubber are preferred. The rubber compound may be a copolymer consisting of hard segments and soft segments, and may be a block copolymer having at least three or more blocks, such as (hard segment)-(soft segment)-(hard segment).

[0045] The rubber compound is preferably crosslinked by physical crosslinking or chemical crosslinking. Physical crosslinking is not limited to hydrogen bonds, hydrophobic bonds, etc., but is not particularly limited as long as it is a crosslinking due to interactions other than covalent bonds. In the case of physical crosslinking, the crosslinking points are fixed at room temperature, and at high temperatures the bonds dissociate, making it possible for the rubber compound to exhibit thermoplasticity. For chemical crosslinking, compounds having functional groups such as vinyl groups, epoxy groups, and isocyanate groups, such as crosslinkable monomers or crosslinking agents, are used. Crosslinked polymers may also be synthesized by copolymerizing crosslinkable monomers with non-crosslinkable monomers. Crosslinked polymers may also be synthesized by reacting a crosslinking agent with a non-crosslinked polymer obtained from non-crosslinkable monomers. Crosslinking of non-crosslinked polymers can also be carried out by introducing covalent bonds into the polymer using radical generators such as peroxides or energy rays such as ultraviolet light.

[0046] Examples of the olefin-based elastomer include copolymers of aliphatic olefins such as propylene-ethylene copolymer, ethylene-1-butene copolymer, ethylene-1-hexene copolymer, ethylene-1-octene copolymer, propylene-ethylene-1-butene copolymer, and propylene-1-butene copolymer. Examples of the styrene-based elastomer include styrene-butadiene copolymers such as styrene-butadiene rubber (SBR), styrene-isoprene copolymers, and aromatic olefin-aliphatic olefin copolymers such as styrene-ethylene copolymers. Examples of the aforementioned acrylic elastomers include (meth)acrylic acid ester-acrylonitrile copolymers, (meth)acrylic acid ester-ethylene copolymers, and acrylic acid ester-methacrylic acid ester block copolymers.

[0047] Examples of the aforementioned acrylic rubber include acrylic acid ester-acrylonitrile copolymers and acrylic acid ester-chloroethyl vinyl ether copolymers. Examples of the nitrile rubber include acrylonitrile-butadiene copolymer and acrylonitrile-isoprene copolymer. Examples of the butadiene-based rubber include polybutadiene, acrylonitrile-butadiene-styrene copolymer, and methyl methacrylate-butadiene-styrene copolymer. As the rubber compound, a crosslinked rubber may be used, which is mainly composed of an acrylic acid ester and copolymerized with a crosslinkable monomer such as alkylene glycol di(meth)acrylate, polyalkylene glycol di(meth)acrylate, or allyl(meth)acrylate.

[0048] The rubber compound is preferably a core-shell particle formed from a rubber layer in the core portion and an acrylic layer in the shell portion. This improves the compatibility and dispersibility of the rubber compound with respect to the (meth)acrylic polymer. Various rubber compounds described above can be used as the material for the rubber layer forming the core portion. The rubber compound may also be a copolymer containing a conjugated diene such as butadiene or isoprene.

[0049] Examples of acrylic materials forming the acrylic layer of the shell include (meth)acrylic polymers containing at least one monomer such as (meth)acrylic acid ester, (meth)acrylic acid, or (meth)acrylonitrile. The acrylic material may also be a methyl methacrylate copolymer or methyl methacrylate homopolymer containing methyl methacrylate (MMA). The (meth)acrylic polymer may also be a (meth)acrylic copolymer obtained by copolymerizing olefins such as ethylene, propylene, butadiene, isoprene, and styrene. The acrylic material may also be a (meth)acrylic copolymer obtained by copolymerizing monomers having functional groups such as hydroxyl groups, carboxyl groups, and vinyl groups.

[0050] The core-shell particle may have a structure in which the shell portion completely covers the core portion, or it may have a structure in which the shell portion covers only a portion of the core portion. The shell portion may be formed around the core portion by coating and curing a resin. The core-shell particles may have an intermediate layer between the core and the shell. The intermediate layer may be omitted, and the shell layer may be formed in contact with the core. The intermediate layer may have a transient composition in which the rubber compound forming the core and the acrylic layer forming the shell layer are mixed. An adhesive layer between the core and the shell may be laminated as the intermediate layer.

[0051] In the aforementioned core-shell particles, the core portion and the shell portion may be bonded together via chemical bonds. For example, the structure may be one in which the resin forming the shell portion is graft polymerized onto the core portion by polymerizing the monomer forming the shell portion in the presence of rubber compound particles forming the core portion. The core portion and the shell portion may form an integrated graft copolymer.

[0052] The method for producing the core-shell particles is not particularly limited, but for example, by allowing the polymerization of the core portion to proceed until it reaches a desired diameter, a particulate core portion with high uniformity in shape and dimensions can be formed. Furthermore, by allowing the polymerization of the shell portion to proceed until it reaches a desired diameter, a particulate shell portion with high uniformity in shape and dimensions 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 via chemical bonding, so peeling of the shell layer can be suppressed.

[0053] The rubber compound is preferably in particulate form in the (meth)acrylic resin composition. When the (meth)acrylic resin composition is heat-molded, the rubber compound may maintain its granular shape, or it may melt and disperse in the (meth)acrylic resin composition. Examples of the particle size of the rubber compound include the volume-based average particle size that can be measured by laser diffraction or the like. The volume-based average particle size of the rubber compound is preferably 0.05 to 2.0 μm, and more preferably 0.05 to 1.0 μm. If the rubber compound is a core-shell particle, the particle size of the core-shell particle also includes the range of the shell portion.

[0054] The rubber compound is preferably 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 particle is preferably 0.05 to 2.0 μm, and more preferably 0.05 to 1.0 μm.

[0055] The (meth)acrylic resin composition may contain, as appropriate, known additives such as surfactants, curing accelerators, curing retarders, plasticizers, fillers, lubricants, processing aids, antioxidants, heat stabilizers, light stabilizers, antioxidants, antistatic agents, colorants, ultraviolet absorbers, and infrared absorbers, in addition to the additives described above. These additives can be used individually or in combination of two or more.

[0056] The (meth)acrylic resin composition can be cured by reacting the (meth)acrylic polymer with the crosslinking agent after being molded or applied to a predetermined shape. The molded articles obtained from the (meth)acrylic resin composition are not particularly limited, but include films, sheets, rods, and fibers. The molding method for the molded articles is not particularly limited, but includes casting, lamination, and extrusion. When the (meth)acrylic resin composition is applied to a substrate, a resin film can be formed on the substrate by, for example, solution coating. The substrate is not particularly limited, but includes resin films, release films, paper substrates, metal foils, and laminates.

[0057] If the crosslinking agent contained in the (meth)acrylic resin composition is a thermal crosslinking agent that initiates a crosslinking reaction upon heating, it is preferable to fluidize the acrylic polymer as a solution of the (meth)acrylic resin composition during molding of the molded article, rather than heating and melting the acrylic polymer to fluidize it. The solvent used to obtain the solution of the (meth)acrylic resin composition is not particularly limited as long as it can dissolve the acrylic polymer without impairing the functional groups of the acrylic polymer and the reactivity of the crosslinking agent. Examples of solvents 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 ester solvents such as ethyl acetate. When the acrylic polymer is produced by solution polymerization, at least a portion of the solvent used for polymerization may become at least a portion of the solvent in the (meth)acrylic resin composition.

[0058] The (meth)acrylic resin film of this embodiment is characterized by being a resin layer formed by crosslinking the (meth)acrylic resin composition. The (meth)acrylic resin film can be manufactured, for example, by using a solution casting method, which involves applying a solution of the (meth)acrylic resin composition onto a predetermined substrate to form a thin film, and then heating and drying the film to evaporate the solvent from the thin film and cause crosslinking. The substrate is not limited to a fixed flat surface, but can also include a resin film unwound from a roll of resin film, a movable belt, a drum, etc. The surface properties of the substrate are preferably smooth, but it is also possible to transfer the irregularities to the surface of the obtained (meth)acrylic resin film by providing predetermined irregularities on the substrate.

[0059] The (meth)acrylic resin film obtained by the solution casting method described above may be stretched in predetermined directions such as the longitudinal direction and the width direction, or it may be left unstretched. When it is necessary to reduce anisotropy in applications as optical films, it is preferable to use an unstretched (meth)acrylic resin film. The (meth)acrylic resin film may also be stretched in the longitudinal and width directions to be processed into a biaxially oriented film. Note that the anisotropy of the film is not limited to anisotropy of mechanical properties such as "elongation at break," but also includes optical anisotropy such as "birefringence."

[0060] The mechanical properties of the (meth)acrylic resin film depend on the application, but when used in adhesive sheets, optical films, surface protection films, process films, etc., or when transported in the longitudinal direction, unwound from rolls, or wound onto rolls, it is preferable that the film has a high number of folding resistance and high tensile breaking strength, as well as an appropriate elongation at break to allow for conformability to the adherend.

[0061] 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, even more preferably 90-100%, and particularly preferably 93-100%. By having such a high gel fraction of the resin layer, the solvent resistance, which is a required physical property of the (meth)acrylic resin film, can be improved.

[0062] The thickness of the (meth)acrylic resin film is not particularly limited, but for example, in the case of an optical film, a thickness of about 10 to 200 μm is preferred, a thickness of 10 to 50 μm is more preferred, a thickness of 10 to 40 μm is particularly preferred, and it is also possible to make a thin film with a thickness of 40 μm or less. When laminating other materials on one or both sides of the (meth)acrylic resin film, easy adhesion treatments such as surface modification by corona discharge or application of an anchor coating agent may be performed as needed.

[0063] The (meth)acrylic resin film can improve bending resistance because it contains a rubber compound in the (meth)acrylic resin composition. When measured in accordance with JIS P8115 (Paper and cardboard - Folding strength test method - MIT testing machine method), the (meth)acrylic resin film preferably has a folding resistance of 100 or more cycles, and more preferably 200 or more cycles. Typical measurement conditions for folding resistance include repeatedly bending a test piece with a width of 15.0 ± 0.1 mm and a length of approximately 110 mm back and forth at a speed of 175 ± 10 times per minute with a load of 9.8 N. The number of back and forth folds until the test piece breaks is measured as the folding resistance.

[0064] The (meth)acrylic resin film can be made more deformable because it contains a rubber compound in the (meth)acrylic resin composition. The elongation at break of the (meth)acrylic resin film is preferably 10% or more, and more preferably 20% or more. The elongation at break of films can be measured in accordance with standards such as JIS K7161 (Plastics - Method for determining tensile properties) and JIS K7127 (Plastics - Test method for tensile properties).

[0065] The (meth)acrylic resin film may also be used as a substrate for optical films. Examples of optical films include polarizing films, phase difference films, anti-reflective films, anti-glare films, ultraviolet absorbing films, infrared absorbing films, optical compensation films, and brightness-enhancing films. Examples of devices to which optical components 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.

[0066] It is preferable that the in-plane phase difference Re of the (meth)acrylic resin film is 1.0 nm or less. The smaller the in-plane phase difference Re, the more optically isotropic the (meth)acrylic resin film becomes, and the more the change in color tone can be suppressed when it is attached to an optical device or used for optical inspection.

[0067] It is preferable that the haze value of the (meth)acrylic resin film is 3.0% or less. The lower the haze value, the less light scattering occurs when light passes through the (meth)acrylic resin film. For example, when the (meth)acrylic resin film is incorporated into an optical device such as a display, light leakage due to scattered light can be suppressed.

[0068] When measuring optical properties such as in-plane phase difference Re and haze value for the purpose of comparing the optical properties of the (meth)acrylic resin composition, the thickness of the (meth)acrylic resin film used for measurement may differ from the thickness of the (meth)acrylic resin film used as the final product. The thickness of the (meth)acrylic resin film used as the standard for optical properties may be, for example, 20 to 30 μm, or more specifically, 25 μm.

[0069] One or more layers, such as a hard coat layer, an antistatic layer, an antireflective layer, an antifouling layer, an anti-glare layer, a low refractive index layer, an adhesive layer, and a release layer, may be laminated on one or both sides of the (meth)acrylic resin film. Examples of fluorine compounds used in the composition for forming the low refractive index layer include fluorine-containing copolymers which are polymers of one or more fluorinated olefins, fluorinated vinyl ethers, fluorinated alkyl (meth)acrylates, and condensates such as fluorinated alkyl group-containing silane compounds. In addition to fluorinated monomers, the fluorine-containing copolymer may also contain unfluorinated monomers such as olefins, vinyl ethers, and (meth)acrylates. The low refractive index layer may be combined with a high refractive index layer or the like to form an antireflective layer.

[0070] The adhesive sheet of this embodiment is characterized by having an adhesive layer formed on one or both sides of the (meth)acrylic resin film, which is a resin layer formed by crosslinking the (meth)acrylic resin composition. The adhesive layer is preferably an adhesive layer made of a (meth)acrylic adhesive. The method for forming the adhesive layer on the (meth)acrylic resin film can be a known method. 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.

[0071] The adhesive sheet may be an optical film with an adhesive layer, wherein an adhesive layer is laminated on at least one surface of an optical film made of the (meth)acrylic resin film as a base material. The optical film with an adhesive layer can be used for laminating optical films in various display devices such as liquid crystal displays, touch panels, electronic paper, and organic EL displays. The adhesive surface of the adhesive layer used for laminating optical films may be protected with a release film. The release film may be treated with a release agent such as a silicone-based or fluorine-based release agent on the side that comes into contact with the adhesive surface of the adhesive layer.

[0072] The adhesive sheet may constitute a surface protection film that is bonded via the adhesive layer to protect the surface of an object such as glass, an optical film, or an optical component. With the surface protection film bonded to the object, the optical properties of the object, the presence or absence of foreign matter, etc., can be optically inspected. Furthermore, when the object is incorporated into a product, the surface protection film can be peeled off and removed from the object.

[0073] The polarizing film of this 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. The surface treatment applied to the surface of the protective layer of the polarizer may be at least one selected from the group consisting of untreated, AG treatment, LR treatment, AR treatment, AG-LR treatment, and AG-AR treatment. Here, AG stands for Anti-Glare, LR stands for Low Reflection, and AR stands for Anti-Reflection.

[0074] Examples of the protective layer for the polarizer include acrylic resins such as triacetylcellulose (TAC) and polymethyl methacrylate (PMMA), polyester resins such as polyethylene terephthalate (PET), cyclic olefin polymers, and polycarbonate. The (meth)acrylic resin film may be laminated to the protective layer for the polarizer via the adhesive layer of the adhesive sheet. Alternatively, the (meth)acrylic resin film, which is a resin layer formed by crosslinking the (meth)acrylic resin composition of this embodiment, can also be used as the protective layer for the polarizer. [Examples]

[0075] The present invention will be specifically described below with reference to examples.

[0076] <Production of (meth)acrylic polymers and (meth)acrylic resin compositions> [Example 1] Nitrogen gas was introduced into a reactor equipped with a stirrer, thermometer, reflux condenser, and nitrogen inlet tube to replace the air in the reactor with nitrogen gas. Then, 95 parts by weight of methyl methacrylate, 5 parts by weight of methyl acrylate, and 3.0 parts by weight of 8-hydroxyoctyl methacrylate were added to the reactor along with a solvent (ethyl acetate). Subsequently, 0.1 parts by weight of azobisisobutyronitrile was added dropwise as a polymerization initiator, and the mixture was heated to 65°C and reacted for a predetermined time to obtain the (meth)acrylic polymer solution of Example 1. The weight-average molecular weight (Mw) of the (meth)acrylic polymer contained in this (meth)acrylic polymer solution was measured to be 200,000. To the (meth)acrylic polymer solution of Example 1, 10 parts by weight of Kaneace® M-230 as a rubber compound and 3.0 parts by weight of Coronate® HX as a crosslinking agent were added and stirred to obtain the (meth)acrylic resin composition of Example 1.

[0077] [Examples 2-7 and Comparative Examples 1-3] Except for the compositions of the (meth)acrylic polymer and (meth)acrylic resin composition of Example 1 being as shown in Table 1, the (meth)acrylic polymers and (meth)acrylic resin compositions of Examples 2-7 and Comparative Examples 1-3 were obtained in the same manner as in Example 1. The weight-average molecular weight (Mw) of the (meth)acrylic polymers of Examples 2-7 and Comparative Examples 1-3 were as shown in Table 1.

[0078] [Comparative Example 4] A commercially available PMMA film (thickness: 80 μm) manufactured by melt extrusion 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.

[0079] [Table 1]

[0080] In Table 1, the values ​​in parts by weight, calculated with the total amount of monomers in group (A) set to 100 parts by weight, are shown along with the abbreviations corresponding to the compound names. The meanings of the abbreviations used in Table 1 (compound names, etc.) are as follows:

[0081] [Monomers of group (A)] "MMA": Methyl methacrylate "MA": Methyl acrylate "TBA": t-butyl acrylate "BMA": n-butyl methacrylate "EMA": Ethyl methacrylate "IBMA": Isobutyl methacrylate

[0082] [Monomers of group (B)] "8HOA": 8-hydroxyoctylacrylate "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

[0083] [Rubber compounds] Note that the particle sizes shown below are all volume-based average particle sizes. "M-230": KaneAce (registered trademark) M-230 (core-shell particle, particle size: 0.1 μm, core: SBR, shell: MMA, product name of Kaneka Corporation) "M-210": KaneAce (registered trademark) M-210 (core-shell particle, particle size: 0.2 μm, core: SBR, shell: MMA, product name of Kaneka Corporation) "B-513": KaneAce (registered trademark) B-513 (core-shell particle, particle size: 0.2 μm, core: butadiene, shell: MMA, product name of Kaneka Corporation) "LP-4100": Metabrene (registered trademark) LP-4100 (acrylic rubber particles, particle size: 1 μm, product name of Mitsubishi Chemical Corporation)

[0084] [Crosslinking agent] "HX": Coronate® HX (HDI isocyanurate, a product name of Tosoh Corporation) "HL": Coronate (registered trademark) HL (HDI adduct body, product name of Tosoh Corporation) "D-140N": Takenate (registered trademark) D-140N (IPDI adduct body, product name of Mitsui Chemicals, Inc.) "TX": TETRAD(registered trademark)-X (a tetrafunctional epoxy compound, a product name of Mitsubishi Gas Chemical Company, Inc.)

[0085] <(Meth)acrylic resin film fabrication> The (meth)acrylic resin compositions of Examples 1-7 and Comparative Examples 1-3 were formed into resin films by solution casting, and then heated and dried under temperature conditions suitable for solvent drying and crosslinking agent curing, and crosslinked to obtain the (meth)acrylic resin films of Examples 1-7 and Comparative Examples 1-3. The thickness (μm) of each film is shown in Table 2. Furthermore, as the (meth)acrylic resin film for Comparative Example 4, a commercially available PMMA film (thickness: 80 μm) manufactured by the melt extrusion method was used, as described above.

[0086] <Test methods and evaluation of (meth)acrylic resin films> The (meth)acrylic resin films of Examples 1-7 and Comparative Examples 1-4 were evaluated using the following test methods.

[0087] <Haze value> Test specimens were prepared from the (meth)acrylic resin films of Examples 1-7 and Comparative Examples 1-4, and the haze value (%) was measured using a haze meter (manufacturer: Nippon Denshoku Co., Ltd., model: Haze Meter, NDH2000).

[0088] <Number of bending cycles as a measure of bending resistance> After preparing test specimens from the (meth)acrylic resin films of Examples 1-7 and Comparative Examples 1-4, the folding resistance was tested using a folding resistance tester (manufacturer: Tester Industries Co., Ltd., model: MIT folding resistance tester BE-201) in accordance with JIS P8115 (Paper and cardboard - Folding strength test method - MIT testing machine method), and the number of back-and-forth folds until the test specimen broke (folding resistance) was measured.

[0089] <Gel fraction as a measure of solvent resistance> As a test method for solvent resistance, a test piece of (meth)acrylic resin film was immersed in a solvent solution for a predetermined time, as described below. Then, the percentage of (meth)acrylic resin film that did not dissolve in the solvent and remained as insoluble material (residue) (so-called gel fraction) was measured to test the solvent resistance. Test specimens were prepared from the (meth)acrylic resin films of Examples 1-7 and Comparative Examples 1-4. The mass of each test specimen was accurately measured, and after immersion in methyl ethyl ketone (MEK) for 24 hours, the specimens were filtered through a 200-mesh wire mesh. The filtrate was then dried at 100°C for 1 hour, and the mass of the resulting residue was accurately measured. The gel fraction (%) obtained by immersion in the solvent was then measured using the following formula as a test method for solvent resistance. Gel fraction (%) = Insoluble matter (residue) mass (g) / Film (test piece) mass (g) × 100

[0090] <Tensile breaking strength as a measure of cut resistance, and elongation rate as a measure of elongation> Test specimens were prepared from the (meth)acrylic resin films of Examples 1-7 and Comparative Examples 1-4. Tensile strength (MPa), which represents the cut resistance until the test specimen breaks, and elongation at break (%), which represents the elongation, were measured using a tensile testing apparatus (manufacturer: Shimadzu Corporation, model: AGS-X).

[0091] <Phase difference (in-plane phase difference Re value)> The in-plane phase difference (Re) values ​​(nm) of the (meth)acrylic resin films of Examples 1-7 and Comparative Examples 1-4 were measured using a phase difference measuring device (Manufacturer: Oji Instruments Co., Ltd., Model: KOBRA-HBPR / SPC). The wavelength for measuring the phase difference can be appropriately selected from the visible region, for example, 450-550 nm. The Re value is calculated by taking the x-axis (slow phase axis) as the direction in which the in-plane refractive index is maximum, and the y-axis (fast phase axis) as the direction perpendicular to it, and the refractive index n in the x-axis direction. x And the refractive index n in the y-axis direction y The thickness d of the film is used to calculate the following formula. In-plane phase difference Re=(n x -n y )×d Here, the film thickness d is in nanometers, just like the in-plane phase difference Re, and is therefore 1000 times the film thickness (μm).

[0092] Table 2 shows the evaluation results for the (meth)acrylic resin films of Examples 1-7 and Comparative Examples 1-4.

[0093] [Table 2]

[0094] The (meth)acrylic resin films of Examples 1 to 5 were formed as thin films with a thickness of 40 μm or less, exhibiting a haze value of 3.0% or less, fold resistance of 200 or more folds, solvent resistance of 90% or more gel fraction, cut resistance of 40 MPa or more (approximately 50 MPa or more) tensile breaking strength, elongation at break of 20% or more, and in-plane phase difference Re of 1.0 nm or less. Thus, the (meth)acrylic resin films of Examples 1 to 5 exhibited excellent physical properties in all aspects.

[0095] The (meth)acrylic resin film of Example 6 was formed as a thin film with a thickness of 40 μm or less. Although it had a slightly high haze value, it exhibited excellent properties in all aspects: fold resistance of 200 or more folds, solvent resistance of 90% or more gel fraction, cut resistance of 50 MPa or more tensile breaking strength, elongation at break of 20% or more, and in-plane phase difference Re of 1.0 nm or less. Thus, the (meth)acrylic resin film of Example 6 showed excellent physical properties in all aspects.

[0096] The (meth)acrylic resin film of Example 7 was formed as a thin film with a thickness of 40 μm or less. Although it had a high haze value, it exhibited excellent properties in all aspects: fold resistance of 100 or more folds, solvent resistance of 90% or more gel fraction, cut resistance of 50 MPa or more tensile breaking strength, elongation at break of 10% or more, and in-plane phase difference Re of 1.0 nm or less. Thus, the (meth)acrylic resin film of Example 7 showed excellent physical properties in all aspects.

[0097] Thus, it has been demonstrated that the (meth)acrylic resin films of Examples 1 to 7 can solve the problems of the present invention.

[0098] The (meth)acrylic resin film of Comparative Example 1 had a low number of folds it could withstand, possibly because the (meth)acrylic resin composition did not contain a rubber compound. Comparing Example 7 and Comparative Example 1 with regard to the presence or absence of a rubber compound, while the elongation at break (stretchability) of Comparative Example 1 and Example 7 were approximately the same, the number of folds it could withstand was more than twice as good for Example 7 than for Comparative Example 1.

[0099] The (meth)acrylic resin film of Comparative Example 2 was copolymerized using only MMA as the (meth)acrylic polymer, with the alkyl (meth)acrylate having C1 to C14 carbon atoms in the alkyl group. Because it did not copolymerize with alkyl (meth)acrylate other than MMA, which has a homopolymer Tg of 0°C or higher and whose alkyl group has C1 to C14 carbon atoms, it exhibited low fold resistance and extremely low elongation at break.

[0100] The (meth)acrylic resin film of Comparative Example 3 had a low number of folds in terms of fold resistance and an extremely low gel fraction in terms of solvent resistance, possibly because the (meth)acrylic resin composition did not contain a rubber compound and a crosslinking agent. The extremely low gel fraction in terms of solvent resistance is thought to be because the (meth)acrylic resin composition was not crosslinked with a crosslinking agent.

[0101] The (meth)acrylic resin film of Comparative Example 4 was a resin film manufactured by the melt extrusion method, but it had a low number of folds in terms of fold resistance, an extremely low gel fraction in terms of solvent resistance, and a large in-plane phase difference Re. The extremely low gel fraction in terms of solvent resistance is thought to be because the resin film manufactured by the melt extrusion method was not crosslinked with a crosslinking agent.

[0102] Furthermore, assuming that the thickness of the (meth)acrylic resin film in Comparative Example 4 is 20 μm, the value of Re will be 1 / 4 of the value corresponding to the thickness ratio (20 / 80), but even then the Re value is large, so the birefringence (n x -n y The value of ) itself is considered to be large.

[0103] As described above, the (meth)acrylic resin films of Comparative Examples 1 to 4 failed to solve the problem of the present invention, which is to provide a (meth)acrylic resin film that is excellent in folding resistance, cut resistance, elongation, and solvent resistance. [Industrial applicability]

[0104] The (meth)acrylic resin composition of the present invention, and the (meth)acrylic resin film using it, have superior physical properties compared to (meth)acrylic resin films obtained by conventional melt extrusion methods, particularly in terms of thinness, fold resistance, and solvent resistance. Therefore, they are expected to be effective in thinning and improving the durability of various optical devices such as displays, and thus have great industrial value.

Claims

1. A method for producing a (meth)acrylic resin film, comprising the steps of applying a solution of a (meth)acrylic resin composition containing a (meth)acrylic polymer, a rubber compound, and a crosslinking agent onto a substrate using a solution casting method, and then heating to crosslink it, The (meth)acrylic polymer mentioned above (A) The monomers of group (A) include methyl methacrylate and alkyl (meth)acrylates other than methyl methacrylate, in which the Tg of the homopolymer is 0°C or higher and the number of carbon atoms in the alkyl group is C1 to C14. (B) A method for producing a (meth)acrylic resin film, characterized in that it contains a copolymer of monomers selected from the group consisting of copolymerizable monomers having hydroxyl groups and copolymerizable monomers having carboxyl groups, as copolymerizable monomers having functional groups that can react with the crosslinking agent.

2. The method for producing a (meth)acrylic resin film according to claim 1, characterized in that the copolymerizable monomer having a hydroxyl group is at least one selected from the group of compounds consisting of 8-hydroxyoctyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, N-hydroxy(meth)acrylamide, N-hydroxymethyl (meth)acrylamide, and N-hydroxyethyl (meth)acrylamide, and also contains at least one selected from the group of compounds consisting of 8-hydroxyoctyl methacrylate, 6-hydroxyhexyl methacrylate, 4-hydroxybutyl methacrylate, 2-hydroxyethyl methacrylate, and 2-hydroxyethyl acrylate.

3. The method for producing a (meth)acrylic resin film according to claim 1 or 2, characterized in that 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.

4. The method for producing a (meth)acrylic resin film according to claim 3, characterized in that the volume-based average particle diameter of the core-shell particles is 0.05 to 2.0 μm.

5. A method for producing a (meth)acrylic resin film according to any one of claims 1 to 4, characterized in that the rubber compound is contained in a proportion of 1.0 to 25.0 parts by weight per 100 parts by weight of the total monomers of group (A).

6. A method for producing a (meth)acrylic resin film according to any one of claims 1 to 5, characterized in that the crosslinking agent is one or more selected from the group of compounds consisting of epoxy compounds, aziridine compounds, and isocyanate compounds, and the crosslinking agent is contained in a ratio of 0.01 to 10 parts by weight per 100 parts by weight of the total monomers of group (A).

7. A method for manufacturing an adhesive sheet, characterized by comprising the step of forming an adhesive layer on one or both sides of a (meth)acrylic resin film obtained by the method for manufacturing a (meth)acrylic resin film according to any one of claims 1 to 6.

8. A method for manufacturing a polarizing film, characterized by comprising the step of laminating a (meth)acrylic resin film obtained by the method for manufacturing a (meth)acrylic resin film according to any one of claims 1 to 6 onto one or both sides of a polarizer.

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