TW201410772A - (Meth) acrylic resin composition, production method thereof, and optical element - Google Patents

Abstract

A method comprising the steps of dissolving a block copolymer (B) comprising polymer block (a) comprising (meth)acrylic acid alkyl ester unit and polymer block (b) comprising conjugated diene compound unit in monomer mixture (a') comprising not less than 50 % by mass and not more than 100 % by mass of methyl methacrylate to obtain polymerization solution, and polymerizing the monomer mixture (a') under the condition that the polymerization solution has the content of water of not more than 1000 ppm to produce a (meth)acrylic resin composition.

Description

(Meth)acrylic resin composition, method for producing the same, and optical member

The present invention relates to a (meth)acrylic resin composition, a method for producing the same, and an optical member. More specifically, the present invention relates to a (meth)acrylic resin composition which is excellent in toughness and high in heat resistance and which does not cause optical defects as a molded article, a method for producing the same, and a composition containing a (meth)acrylic resin composition. Optical components.

The polarizing plate usually has a polarizing film and a protective film in its two-layer layer. This polarizing plate is incorporated in an optical device such as a liquid crystal display device.

As a protective film for a polarizing plate, a triacetyl cellulose (TAC) film is used. However, due to the high hygroscopicity of triacetyl cellulose, the polarizing plate using a protective film made of triacetyl cellulose can be changed in polarization or color when exposed to high temperature and high humidity. The performance of the device is reduced.

As a substitute for triethylenesulfide cellulose, a material for using a methacrylic resin for a protective film was reviewed.

The methacrylic resin is excellent in transparency and heat and humidity resistance, and is excellent in optical homogeneity with small birefringence. On the other hand, methacryl Acid resins are also fragile and easily broken due to changes in tension. In order to impart toughness to such a methacrylic resin, a technique of blending a modifier in a methacrylic resin is known.

As such a modifier, the following are known. For example, Patent Document 1 discloses a multilayer structure acrylic rubber produced by an emulsion polymerization method. Patent Document 2 discloses a rubbery substance composed of a butadiene-butyl acrylate copolymer. Patent Document 3 discloses a partially hydrogenated conjugated diene polymer. Patent Document 4 discloses a modified block copolymer composed of an alkyl (meth)acrylate unit and an aromatic vinyl monomer unit. Patent Document 5 discloses that a polymer block A mainly composed of a vinyl aromatic compound and a polymer block B mainly composed of a conjugated diene compound are epoxidized and a part of the polymer block B is epoxidized. A block copolymer. Patent Document 6 discloses an ethylene-vinyl acetate copolymer or the like. Patent Document 7 discloses a block copolymer composed of a conjugated diene polymer component rich in a vinyl bond and an acrylate or methacrylate polymer component. Patent Document 8 discloses a star block copolymer having a polymer block (a) composed of an alkyl (meth) acrylate unit and a polymer block (b) composed of a conjugated diene compound unit. .

Prior technical literature Patent literature

Patent Document 1 Japanese Patent Publication No. 59-36645

Patent Document 2 Japanese Patent Publication No. 45-26111

Patent Document 3 WO96/032440

Patent Document 4 Japanese Patent Laid-Open Publication No. 2000-313786

Patent Document 5 Japanese Patent Laid-Open No. Hei 7-207110

Patent Document 6 Japanese Patent Laid-Open No. Hei 6-345933

Patent Document 7 Japanese Patent Laid-Open Publication No. SHO 49-45148

Patent Document 8 WO2008/032732

However, in the conventional (meth)acrylic resin composition, a resin having a high molecular weight which is unexpectedly formed by a polymerization reaction in a gas phase portion of a polymerization reactor and which is difficult to be thermally melted is slightly contained. Since the (meth)acrylic resin composition of the resin which is difficult to thermally melt is contained, an optical defect occurs when a film or the like is formed, and the performance of the optical member is lowered.

An object of the present invention is to provide a (meth)acrylic resin composition which is excellent in toughness and has high heat resistance and which does not cause optical defects as a molded article, and an optical member containing the composition.

As means for achieving the above object, the present invention encompasses the following aspects.

[1] A (meth)acrylic resin composition containing 65 to 99 parts by mass in a total of 100 parts by mass of the total of the methyl methacrylate homopolymer (A) and the block copolymer (B) a methyl methacrylate homopolymer (A), and 1 to 35 parts by mass of a polymer block (a) having a (meth)acrylic acid alkyl ester unit and a conjugated diene compound unit The block copolymer (B) of the polymer block (b).

[2] The (meth)acrylic resin composition according to [1], wherein the block copolymer (B) contains a star block copolymer containing at least a polymer block ( a) and/or the arm polymer block of the polymer block (b), and the polystyrene-converted number average molecular weight calculated by gel permeation chromatography (GPC) satisfies [star embedded The number average molecular weight of the segment copolymer] / [the number average molecular weight of the arm polymer block] is >2.

[3] The (meth)acrylic resin composition as described in [2], wherein the star block copolymer (B) is represented by a chemical structural formula: (polymer block (b) - polymer block ( a)-) _n X

(wherein X represents a coupling agent residue, and n represents a number exceeding 2).

[4] The (meth)acrylic resin composition according to any one of [1] to [3] which further contains an ultraviolet absorber.

[5] An optical member comprising the (meth)acrylic resin composition according to any one of [1] to [4].

[6] A film comprising the (meth)acrylic resin composition according to any one of [1] to [4].

[7] The film according to [6], which is obtained by applying an antiglare treatment and/or an antireflection treatment.

[8] A polarizing plate comprising a film according to any one of [6] or [7], wherein the polarizing film is bonded to at least one side of the surface.

[9] A method for producing a (meth)acrylic resin composition, comprising: forming a polymer block (a) composed of an alkyl (meth) acrylate unit and a conjugated diene compound unit Incorporation of polymer block (b) The segment copolymer (B) is dissolved in a monomer mixture (a') containing 50% by mass or more and 100% by mass or less of methyl methacrylate to obtain a polymerization reaction liquid, and then the amount of water in the polymerization reaction liquid is 1000 ppm. Hereinafter, the monomer mixture (a') is polymerized.

[10] The method for producing a (meth)acrylic resin composition according to [9], wherein the monomer mixture (a') is 100% by mass of methyl methacrylate (which may contain inevitable impurities) The constituents.

The (meth)acrylic resin composition of the present invention has excellent toughness and high heat resistance, and almost no optical defects occur as a molded article. By molding the (meth)acrylic resin composition of the present invention, an optical member such as a protective film for a polarizing plate having almost no optical defects can be obtained.

According to the production method of the present invention, when the amount of water in the polymerization reaction liquid is 1000 ppm or less, and the monomer mixture (a') containing 50% by mass or more and 100% by mass or less of methyl methacrylate is polymerized, it is easily obtained. A (meth)acrylic resin composition which is excellent in toughness, high in heat resistance, and extremely small in a gel cluster or a resin foreign matter. The (meth)acrylic resin composition obtained by the production method of the present invention is excellent in toughness and hardly causes pit-shaped optical defects. By molding the methacrylic resin composition obtained by the production method of the present invention, an optical member such as a protective film for a polarizing plate having almost no optical defects can be obtained.

The (meth)acrylic resin composition according to one embodiment of the present invention contains: a methyl methacrylate homopolymer (A); and a polymer block formed of an alkyl (meth)acrylate unit ( a) a block copolymer (B) of a polymer block (b) formed from a conjugated diene compound unit.

The amount of the methyl methacrylate homopolymer (A) is 65 to 99 parts by mass, preferably 65 parts by mass, based on 100 parts by mass of the total of the methyl methacrylate homopolymer (A) and the block copolymer (B). 77 to 99 parts by mass, more preferably 80 to 98 parts by mass, and particularly preferably 83 to 97 parts by mass.

The amount of the block copolymer (B) is 1 to 35 parts by mass, preferably 1 to 23 mass, based on 100 parts by mass of the total of the methyl methacrylate homopolymer (A) and the block copolymer (B). It is preferably 2 to 20 parts by mass, more preferably 3 to 17 parts by mass.

(block copolymer (B))

The block copolymer (B) used in the present invention has a polymer block (a) composed of an alkyl (meth) acrylate unit and a polymer block formed from a conjugated diene compound unit (b) )By. In addition, "(meth)acrylic acid" omits "methacrylic acid or acrylic acid". The glass transition temperature of the block copolymer (B)-based polymer block (a) and/or the polymer block (b) is preferably 0 ° C or lower, more preferably -10 ° C or lower.

The polymer block (a) made of an alkyl (meth) acrylate unit can be formed by polymerizing an alkyl (meth) acrylate. Examples of the (meth)acrylic acid alkyl ester include methyl methacrylate and ethyl methacrylate. Butyl methacrylate, cyclohexyl methacrylate; methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate, and the like. These may be used alone or in combination of two or more. Among these, it is preferred to give a (meth)acrylic acid alkyl ester of a polymer block (a) having a glass transition temperature (Tg) of 0 ° C or less or a combination thereof, and more preferably a Tg of -10. The alkyl (meth) acrylate of the polymer block (a) below °C or a combination thereof. As such an alkyl (meth)acrylate, n-butyl acrylate and/or 2-ethylhexyl acrylate are preferred, and n-butyl acrylate is more preferred.

The polymer block (b) composed of the conjugated diene compound unit can be formed by polymerizing a conjugated diene. Examples of the conjugated diene include 1,3-butadiene, isoprene, pentadiene, and 2,3-dimethylbutadiene. These may be used alone or in combination of two or more. Among these, it is preferred to give a conjugated diene of the polymer block (b) having a glass transition temperature (Tg) of 0 ° C or less or a combination thereof, and more preferably a Tg of -10 ° C or less. a conjugated diene of polymer block (b) or a combination thereof. As such a conjugated diene, from the viewpoints of general versatility, economy, and workability, 1,3-butadiene and/or isoprene is preferred, and 1,3-butadiene is more preferred. Alkene.

The conjugated diene has a case of 1,4-addition polymerization and a 1,2- or 3,4-addition polymerization. When the conjugated diene is 1,4-addition polymerized, it has a carbon-carbon double bond in the main chain of the molecule. When the conjugated diene is subjected to 1,2- or 3,4-addition polymerization, it has a vinyl group (carbon-carbon double bond) bonded as a side chain in the main chain of the molecule. The carbon-carbon double bond in the main chain of the molecule and/or the carbon-carbon double bond which is a molecular side chain bond is the starting point of the graft reaction or the crosslinking reaction. The ratio of the carbon-carbon double bond in the molecular side chain to the carbon-carbon double bond in the molecular backbone, It can be increased by adding a polar compound such as an ether to the polymerization reaction system.

The polymer block (b) may also be a hydrogenated carbon-carbon double bond in the main chain of the molecule and/or all or a part of the carbon-carbon double bond bonded as a molecular side chain. The hydrogenation rate of the polymer block (b) is preferably less than 70 mol%, more preferably less than 50 mol%, from the viewpoint of maintaining the efficacy of the present invention. The method of hydrogenation is not particularly limited, and can be achieved, for example, by the method disclosed in Japanese Patent Publication No. 5-20442.

The mass ratio of the polymer block (a) to the polymer block (b) is not particularly limited, but when the total of the polymer block (a) and the polymer block (b) is 100% by mass, polymerization is carried out. The block (a) is usually 45 to 75% by mass, preferably 50 to 70% by mass. The polymer block (b) is usually 25 to 55% by mass, preferably 30 to 50% by mass.

The block copolymer (B) is not particularly limited in its refractive index, but when transparency is required in the (meth)acrylic resin composition of the present invention, the refractive index of the block copolymer (B) is preferably It is consistent with the refractive index of the methyl methacrylate homopolymer (A). Specifically, the refractive index of the block copolymer (B) is preferably from 1.48 to 1.50, more preferably from 1.485 to 1.495.

The block copolymer (B) is preferably one containing a star block copolymer. The star block copolymer is a block of a plurality of arm polymer blocks having a structure that expands into a radial shape. The linking portion of the arm polymer block is usually composed of a group (coupler residue) derived from a polyfunctional monomer or a polyfunctional coupling agent.

The star block copolymer can be expressed, for example, by the following chemical structural formula: (arm polymer block -) _n X

(wherein X represents a coupling agent residue, and n represents a number exceeding 2).

The arm polymer block preferably has at least a polymer block (a) (hereinafter also referred to as (a)) and a polymer block (b) (hereinafter also referred to simply as (b)). The structure of the arm polymer block is not particularly limited. For example, a structure in which (a)-(b) type block is copolymerized, a structure in which (a)-(b)-(a) type block is copolymerized, and (b)-(a)- The structure of the (b) type block copolymerization, the structure of the (a)-(b)-(a)-(b) type block copolymerization, and the total of (a) and (b) are 5 or more blocks. The structure of the polymerization, etc. The plurality of arm polymer block systems constituting the star block copolymer (B) may be a structure in which all of the same block copolymerization is carried out, or a structure in which mutually different blocks are copolymerized. Among these, the arm polymer block is preferably a structure in which the (a)-(b) type block is copolymerized. That is, the block copolymer (B) used in the present invention is preferably one containing a star block copolymer represented by the following chemical structural formula: (polymer block (b) - polymer block (a) - _n X, or (polymer block (a) - polymer block (b) -) _n X

(wherein, X represents a coupling agent residue, n represents a number exceeding 2), more preferably a star-shaped block copolymer represented by the following chemical structural formula: (polymer block (b)-polymer embedded Segment (a)-) _n X

(wherein X represents a coupling agent residue, and n represents a number exceeding 2).

A star-shaped block copolymer suitable as the block copolymer (B), the polystyrene-converted number average molecular weight calculated by gel permeation chromatography (GPC) satisfies [the number average of the star block copolymer) Molecular weight] / [number average molecular weight of the arm polymer block] > 2.

Further, the ratio of [the number average molecular weight of the star block copolymer] / [the number average molecular weight of the arm polymer block] is also referred to as the number of arms.

Since the number average molecular weight of the star block copolymer is more than twice the number average molecular weight of the arm polymer block, the particles of the star block copolymer (B) dispersed in the methacrylic resin are sheared The mechanical strength is increased to obtain the desired impact resistance. Furthermore, since the number average molecular weight of the star block copolymer is larger than 100 times the number average molecular weight of the arm polymer block, the industrially preferred star block copolymer (B) is averaged in number. The molecular weight is greater than twice the number average molecular weight of the arm polymer block and is 100 times or less, more preferably 2.5 to 50 times, and particularly preferably 3 to 10 times.

Further, the block copolymer (B) used in the present invention may be an arm polymer block which is a constituent material of the star block copolymer, other than the star block copolymer as described above. The residue of the mixture is linked and remains in its original state.

The method for producing the block copolymer (B) used in the present invention is not particularly limited, and a method based on a well-known method can be employed. In general, as a method of obtaining a block copolymer, a method of livingly polymerizing a monomer constituting a unit is employed. As such a method of living polymerization, for example, a method of performing polymerization using an organic rare earth metal complex as a polymerization initiator; an organic alkali metal compound as a polymerization initiator, and a mineral acid of an alkali metal or alkaline earth metal can be mentioned. A method of performing anionic polymerization in the presence of the like; a method of performing anionic polymerization in the presence of an organoaluminum compound using an organic alkali metal compound as a polymerization initiator; an atomic mobile radical polymerization (ATRP) method, and the like.

Among the above production methods, an anionic polymerization method is carried out using an organic alkali metal compound as a polymerization initiator in the presence of an organoaluminum compound, whereby a block copolymer having a narrow molecular weight distribution can be produced, and the residual monomer is small. It is preferably carried out under relatively mild temperature conditions, and the environmental load in industrial production (mainly the power consumption of the refrigerator required to control the polymerization temperature) is small.

As the polymerization initiator for the anionic polymerization, an organic alkali metal compound is usually used. As the organic alkali metal compound, methyl lithium, ethyl lithium, n-propyl lithium, isopropyl lithium, n-butyl lithium, second butyl lithium, isobutyl lithium, t-butyl lithium, and a positive combination may be used. Alkyl lithium and alkyl dilithium such as pentyl lithium, n-hexyl lithium, tetramethylene dilithium, pentamethylene dilithium, hexamethylene dilithium; phenyl lithium, m-tolyl lithium, p-toluene Lithium aryl and aryl dilithium; lithium benzyl, diphenylmethyllithium, trityllithium, 1,1-diphenyl-3-methyl Aralkyl lithium and aralkyl dilithium such as dilithium formed by reaction of pentyl lithium, α-methylstyryl lithium, diisopropenylbenzene and butyllithium; lithium dimethyl decylamine, lithium Lithium decylamine such as diethyl decylamine or lithium diisopropyl decylamine; lithium methoxide, lithium ethoxide, lithium n-propoxide, lithium isopropoxide, lithium n-butoxide, second butyl Lithium oxyhydride, lithium hexoxide, lithium pentoxide, lithium hexoxide, lithium heptoxide, lithium octyl oxide, lithium phenoxide, lithium 4-methylphenoxy, lithium benzyloxide, An organic lithium compound such as lithium alkoxide such as 4-methylbenzyloxylithium. These may be used alone or in combination of two or more.

The organoaluminum compound used in the above anionic polymerization may, for example, be a formula: AlR ¹ R ² R ³

(wherein R ¹ , R ² and R ³ each independently represent an alkyl group which may have a substituent, a cycloalkyl group which may have a substituent, an aryl group which may have a substituent, an aralkyl group which may have a substituent, An alkoxy group which may have a substituent, an aryloxy group which may have a substituent or an N,N-disubstituted amine group, or R ¹ represents any of the above groups, and R ² and R ³ together represent a stretch which may have a substituent Illustrated by aryldioxy).

Specific examples of the organoaluminum compound represented by the above formula include trimethyl aluminum, triethyl aluminum, tri-n-butyl aluminum, three second butyl aluminum, tri-tert-butyl aluminum, and triiso Trialkyl aluminum, dimethyl (2,6-di-t-butyl-4-), such as butyl aluminum, tri-n-hexyl aluminum, tri-n-octyl aluminum, tri-ethyl 2-ethylhexyl aluminum, triphenyl aluminum Methylphenoxy)aluminum, dimethyl(2,6-di-t-butylphenoxy)aluminum, diethyl(2,6-di-t-butyl-4-methylphenoxy)aluminum , diethyl (2,6-di-t-butylphenoxy)aluminum, diisobutyl (2,6-di-t-butyl-4-methylphenoxy)aluminum, diisobutyl ( 2,6-di-t-butylphenoxy)aluminum, di-n-octyl (2,6-di-t-butyl-4-methylphenoxy)aluminum, di-n-octyl (2,6-di Dialkylphenoxy aluminum such as tert-butylphenoxy)aluminum, methylbis(2,6-di-t-butyl-4-methylphenoxy)aluminum, methyl-bis(2,6) -di-t-butylphenoxy)aluminum, ethyl[2,2'-methylenebis(4-methyl-6-t-butylphenoxy)]aluminum, ethyl bis (2,6 -di-tert-butyl-4-methylphenoxy)aluminum, ethylbis(2,6-di-t-butylphenoxy)aluminum, ethyl[2,2'-methylenebis(4) -Methyl-6-t-butylphenoxy)]aluminum, isobutylbis(2,6-di-t-butyl-4-methylphenoxy)aluminum, isobutyl bis (2,6 -di-t-butylphenoxy)aluminum, isobutyl[2,2'-methylenebis(4-methyl-6-t-butylphenoxy)]aluminum, n-octyl bis (2 ,6-di-t-butyl-4-methylphenoxy)aluminum, n-octyl bis(2,6-di-third butyl Alkyl phenoxy aluminum, methoxy group such as n-phenoxy)aluminum, n-octyl[2,2'-methylenebis(4-methyl-6-t-butylphenoxy)]aluminum Bis(2,6-di-t-butyl-4-methylphenoxy)aluminum, methoxybis(2,6-di-t-butylphenoxy)aluminum, methoxy[2,2 '-Methylene bis(4-methyl-6-t-butylphenoxy)]aluminum, ethoxybis(2,6-di-t-butyl-4-methylphenoxy)aluminum, Ethoxybis(2,6-di-t-butylphenoxy)aluminum, ethoxy[2,2'-methylenebis(4-methyl-6-t-butylphenoxy)] Aluminum, isopropoxy bis(2,6-di-t-butyl-4-methylphenoxy)aluminum, isopropoxy bis(2,6-di-t-butylphenoxy)aluminum, different Propoxy[2,2'-methylenebis(4-methyl-6-t-butylphenoxy)]aluminum, tert-butoxybis(2,6-di-t-butyl-4 -Methylphenoxy)aluminum, tert-butoxybis(2,6-di-t-butylphenoxy)aluminum, tert-butoxy[2,2'-methylenebis(4-methyl) Alkoxydiphenoxyaluminum, ginseng (2,6-di-t-butyl-4-methylphenoxy)aluminum, ginseng (2,6-t-butylphenoxy)] , triphenylphenoxy aluminum or the like such as 6-diphenylphenoxy)aluminum.

These may be used alone or in combination of two or more. Among these organoaluminum compounds, isobutylbis(2,6-di-t-butyl-4-methylphenoxy)aluminum, isobutylbis(2,6-di-t-butylbenzene) Aluminium, isobutyl [2,2'-methylenebis(4-methyl-6-t-butylphenoxy)]aluminum is easy to handle and does not lose activity under relatively mild temperature conditions. The point at which anionic polymerization can be carried out is preferred.

In the above anionic polymerization reaction system, if necessary, for the stability of the polymerization reaction, an ether such as dimethyl ether, dimethoxyethane, diethoxyethane or 12-crown-4 may be used. Ethylamine, N,N,N',N'-tetramethylethylenediamine, N,N,N',N",N"-pentamethyldiethylenetriamine, 1,1,4, A nitrogen-containing compound such as 7,10,10-hexamethyltris-ethylenetetramine, pyridine or 2,2'-bipyridine is coexistent.

The method of obtaining the block copolymer used in the present invention includes a method in which a polyfunctional monomer or a polyfunctional coupling agent is added in a small amount in an anionic polymerization reaction system to carry out polymerization. The polyfunctional single system has two or more ethylenically unsaturated groups, and specific examples thereof include allyl methacrylate, ethylene glycol dimethacrylate, and 1,3-butyl methacrylate. A glycol ester, divinylbenzene, 1,6-hexanediol diacrylate, or the like.

The polyfunctional coupling agent is a compound having three or more reactive groups, and specific examples thereof include trichloromethyl nonane, tetrachlorodecane, butyl trichlorodecane, bis(trichlorodecanealkyl)ethane, and tetra Chloro tin, butyl trichlorotin, tetrachloroguanidine, and the like.

The number average molecular weight (Mn) of the entire block copolymer (B) used in the present invention is preferably from 5,000 to 1,000,000, from the viewpoint of improving the impact resistance of the obtained (meth)acrylic resin composition. Good is 10,000~800,000, especially 10,000~500,000.

(methyl methacrylate homopolymer (A))

The methyl methacrylate homopolymer (A) used in the present invention is a resin obtained by polymerizing only methyl methacrylate. Since the methyl methacrylate homopolymer is easily depolymerized, a methacrylic resin usually copolymerizes methyl methacrylate and methyl acrylate. When methyl methacrylate and methyl acrylate are copolymerized, the heat resistance of the (meth)acrylic resin composition is lowered, and the composition ratio of the monomer unit varies, and the reproduction accuracy of the optical characteristics such as the refractive index is lowered.

The methyl methacrylate homopolymer has a weight average molecular weight of preferably 40,000 to 200,000, more preferably 50,000 to 180,000, particularly preferably It is 60,000~160,000. When the weight average molecular weight is too small, the impact resistance or toughness of the molded article obtained from the (meth)acrylic resin composition tends to be lowered. On the other hand, when the weight average molecular weight is too large, the fluidity of the (meth)acrylic resin composition is lowered, and the moldability tends to be lowered.

Further, the molecular weight distribution (weight average molecular weight / number average molecular weight) of the methyl methacrylate homopolymer is preferably from 1.9 to 3.0, more preferably from 2.1 to 2.8, particularly preferably from 2.2 to 2.7. When the molecular weight distribution is too small, the moldability of the (meth)acrylic resin composition tends to be lowered. On the other hand, when the molecular weight distribution is too large, the impact resistance of the molded article obtained from the (meth)acrylic resin composition tends to be lowered.

Further, the weight average molecular weight and the number average molecular weight are molecular weights in terms of standard polystyrene measured by GPC (gel permeation chromatography). The molecular weight or molecular weight distribution of the methacrylic resin can be controlled by adjusting the type or amount of the polymerization initiator and the chain transfer agent.

The (meth)acrylic resin composition of the present invention preferably disperses the block copolymer (B) in a domain formed by forming a domain in the methyl methacrylate homopolymer (A).

The size of the domain (the average diameter of the domain) is not particularly limited, but is preferably 0.05 to 2.0 μm, more preferably 0.1 to 1.0 μm. If the average diameter of the domain is small, the punching resistance tends to be lowered, and if the average diameter of the domain is large, the rigidity tends to decrease, and the transparency tends to be lowered. Furthermore, the structure and average diameter of the domain can be confirmed by a transmission electron micrograph of a slice cut by ultrathin sectioning.

The (meth)acrylic resin composition of the present invention has a load deflection temperature of preferably 90 ° C or higher, more preferably 92 ° C or higher, and particularly preferably 94 ° C or higher. When the temperature is too low, the molded article is liable to be thermally deformed at a normal use temperature. Further, the load deflection temperature was a value measured under a condition of applying a load of 1.82 MPa to a test piece having a thickness of 4 mm.

In the film composed of the (meth)acrylic resin composition of the present invention, defects caused by the resin unmelted material can be recognized by an optical microscope or a laser microscope. Since the resin unmelted material is transparent because it is not dyed by osmium tetroxide, the undyed defects are judged to be defects caused by the resin unmelted material by microscopic observation. Among the optical defects detected in the film formed by molding the resin composition, there are defects caused by the resin composition itself and defects caused by the conditions of the forming step. The defects caused by the resin composition itself are presumably caused mainly by defects caused by the gel plexes contained in the resin composition or the unmelted resin which is difficult to thermally melt.

The (meth)acrylic resin composition of the present invention is not particularly limited by the production method thereof. For example, a method of obtaining a resin composition by melt-kneading a methyl methacrylate homopolymer (A) and a block copolymer (B) in a uniaxial or biaxial melt extruder or the like can be mentioned. Or a method of polymerizing methyl methacrylate in the presence of a block copolymer (B) to obtain a resin composition in-situ; or manufacturing in the presence of a methyl methacrylate homopolymer; The segment copolymer (B), a method of obtaining a resin composition in situ, and the like. Among these, a method of obtaining a resin composition in situ by polymerizing methyl methacrylate in the presence of the block copolymer (B) is preferred. As the polymerization method, a solution polymerization method or a bulk polymerization method is preferred, and a bulk polymerization method is more preferred.

A method for producing a (meth)acrylic resin composition according to an embodiment of the present invention comprises a polymer block (a) having a (meth)acrylic acid alkyl ester unit and a conjugated diene compound unit The block copolymer (B) of the polymer block (b) is dissolved in a monomer mixture (a') containing 50% by mass or more and 100% by mass or less of methyl methacrylate to obtain a polymerization reaction solution. The monomer mixture (a') was polymerized by setting the amount of water in the polymerization reaction liquid to 1000 ppm or less. This production method can be used for the production of the (meth)acrylic resin composition containing the methyl methacrylate homopolymer (A) and the block copolymer (B) described above, and can also be used for the inclusion ( The (meth)acrylic resin composition of the (meth)acrylic resin (A') and the block copolymer (B) is produced. Further, the methyl methacrylate homopolymer (A) is a resin produced by polymerization of a monomer mixture (a') composed of 100% by mass of methyl methacrylate, (meth)acrylic resin (A') is a resin produced by polymerization of a monomer mixture (a') composed of less than 100% by mass of methyl methacrylate.

(monomer mixture (a'))

The monomer mixture (a') used in the present invention contains 50% by mass or more and 100% by mass or less, preferably 80% by mass or more and 100% by mass or less, more preferably 80% by mass or more and 96% by mass or less of methacrylic acid. Methyl ester. Further, the monomer mixture (a') composed of 100% by mass of methyl methacrylate may contain unavoidable impurities.

Examples of the monomer other than methyl methacrylate include alkyl acrylates such as methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, and 2-ethylhexyl acrylate; An aryl acrylate; a cycloalkyl acrylate such as cyclohexyl acrylate or a norbornene acrylate; an alkyl methacrylate other than methyl methacrylate such as ethyl methacrylate or butyl methacrylate; An aryl methacrylate such as phenyl acrylate; a cycloalkyl methacrylate such as cyclohexyl methacrylate or norbornene methacrylate; acrylamide, methacrylamide, acrylonitrile, methacryl A non-crosslinkable vinyl monomer having only one polymerizable alkenyl group in one molecule, such as a nitrile, styrene or α-methylstyrene. The amount of the monomer other than methyl methacrylate is preferably 0% by mass or more and 50% by mass or less, more preferably 0% by mass or more and 20% by mass or less, and particularly preferably 4% by mass or more, based on all the monomer units. 20% by mass or less. Among the monomers other than methyl methacrylate, an alkyl acrylate is preferred, and methyl acrylate is more preferred.

The amount of dissolved oxygen in the monomer mixture (a') used in the production method of the present invention is preferably 10 ppm or less, more preferably 5 ppm or less, still more preferably 4 ppm or less, and most preferably 3 ppm or less. When the amount of dissolved oxygen in such a range is reached, the polymerization reaction proceeds smoothly, and a molded article free from silver streaks or coloring can be easily obtained.

The monomer mixture (a') used in the production method of the present invention preferably has a yellow index of 2 or less, more preferably 1 or less. When the yellow index of the monomer mixture (a') is small, when the obtained (meth)acrylic resin composition is molded, it is easy to obtain a molded article having almost no coloration with high production efficiency. In the polymerization of the monomer mixture (a') to be described later, when the polymerization conversion ratio is not too high, the unreacted single system remains in the polymerization reaction liquid. The unreacted single system can be recovered from the polymerization reaction liquid and reused in the polymerization reaction. The yellow index of the recovered monomer will be due to the heat applied during recovery. And become higher. The recovered monomer is preferably purified by a suitable method to reduce the yellowness index. Further, the yellow index is a value measured by JIS Z-8722 using a colorimeter ZE-2000 manufactured by Nippon Denshoku Industries Co., Ltd.

Further, the methyl methacrylate-based b ^* used in the production method of the present invention is preferably -1 to 2, more preferably -0.5 to 1.5. When b ^{* of the} monomer is in this range, when the obtained (meth)acrylic resin composition is molded, it is easy to obtain a molded article having almost no coloration with high production efficiency. Further, b ^* is a value measured according to the International Commission on Illumination (CIE) specification (1976) or JIS Z-8722.

The mass of the block copolymer (B) relative to the monomer mixture (a') is preferably from 1/99 to 35/65, more preferably from 1/99 to 23/77, and particularly preferably from 2/98 to 20/80. The best is 3/97~17/83. When the amount of the block copolymer (B) is small, the impact resistance of the (meth)acrylic resin composition tends to be lowered. On the other hand, if the amount is large, the elastic modulus and the rigidity tend to be lowered, and the reverse rotation is less likely to occur. The block copolymer (B) is difficult to uniformly disperse in the (meth)acrylic resin (A') or the methyl methacrylate homopolymer (A).

The method of dissolving the block copolymer (B) in the monomer mixture (a') is not particularly limited. For example, the block copolymer (B) can be dissolved in the monomer mixture (a') by heating to about 30 to 60 ° C and stirring. After the dissolution, it is preferred to remove the unmelted resin from the polymerization reaction liquid by a filter or the like.

After the block copolymer (B) is dissolved in the monomer mixture (a'), the monomer mixture (a') is polymerized. In the polymerization, it is preferred that the amount of water in the polymerization reaction liquid be 1000 ppm or less, more preferably 700 ppm. In the following, it is particularly preferable to be 280 ppm or less. By reducing the amount of water in the polymerization system, it is possible to suppress the formation of a resin foreign matter of several μm to several tens of μm which is generated in the polymerization reaction, thereby greatly reducing the resin foreign matter as a core when formed into a film or a sheet. With the occurrence of defects of several tens of μm, an optical member having high optical homogeneity can be obtained. The method of adjusting the amount of water in the polymerization reaction liquid is not particularly limited. For example, a method of dehydrating a block copolymer (B), a monomer mixture (a'), and other polymerization auxiliary materials used as a raw material by adsorption or the like may be mentioned in the gas phase portion of the tank reactor. An inert gas is introduced to cause a part of the monomer vapor to be condensed with an inert gas, a condenser cooled by brine, and extracted to the outside of the system.

The polymerization is preferably carried out while applying shear to the polymerization reaction liquid. In the initial stage of the polymerization reaction, the (meth)acrylic resin (A') or the methyl methacrylate homopolymer (A) is dispersed in the continuous phase (polymerization reaction liquid) containing the block copolymer (B). However, if the polymerization is carried out while applying shear, the phase containing the (meth)acrylic resin (A') or the methyl methacrylate homopolymer (A) is opposite to the phase containing the block copolymer (B). The mixture is in a state in which the phase containing the block copolymer (B) is dispersed in the phase containing the (meth)acrylic resin (A') or the methyl methacrylate homopolymer (A). Furthermore, the polymerization conversion rate of the monomer at the time of the reverse rotation can be achieved by the block copolymer (B) and the (meth)acrylic resin (A') or the methyl methacrylate homopolymer (A). The volume ratio, the molecular weight of the block copolymer (B), the graft ratio to the block copolymer (B), and the amount of the solvent or the type of the solvent are added when the solvent is added.

It is preferred to carry out the polymerization by a bulk polymerization method or a solution polymerization method from the initial stage of the polymerization to the time of the reverse rotation. When the polymerization in this period is carried out by a bulk polymerization method or a solution polymerization method, shearing due to stirring is more applied to the phase containing the block copolymer (B), and the reverse rotation is liable to occur.

Examples of the apparatus for performing bulk polymerization or solution polymerization include a tank reactor equipped with a stirrer, a tubular reactor equipped with a stirrer, and a tubular reactor having static stirring ability. These devices may be one or more, and two or more reactors of the same or different types may be connected in parallel or in series. Further, the polymerization system may be either a batch type or a continuous type. The polymerization conversion ratio of the bulk polymerization or the solution polymerization can be adjusted by the supply amount of the reaction raw material liquid, the extraction amount of the reaction production liquid, and the average residence time. The polymerization conversion ratio is preferably 70% by mass or more, and more preferably 85% by mass or more, from the viewpoint of improving the toughness of a molded article such as an optical member obtained by molding the obtained methacrylic resin composition. It is 90% by mass or more. In the tank reactor, generally, a stirring means for stirring the liquid in the reaction tank, a supply portion for supplying a monomer mixture or a polymerization auxiliary material to the reaction tank, and a reaction product for extracting the reaction product from the reaction tank are provided. The extraction department. In the continuous flow type reaction, in order to balance the amount supplied to the reaction tank with the amount extracted from the reaction tank, the amount of liquid in the reaction tank is made substantially constant. The amount of liquid in the reaction tank is preferably 1/4 or more, more preferably 1/4 to 3/4, and particularly preferably 1/3 to 2/3, with respect to the volume of the reaction tank.

The size of the dispersed phase, if it is a reactor with a stirrer, can be controlled by a factor of stirring the number of rotations, etc., if it is a tower type reactor The representative static stirring reactor can be controlled by various factors such as the linear velocity of the reaction liquid, the viscosity of the polymerization reaction liquid, and the graft ratio to the block copolymer (B) up to the reverse rotation. Further, after the reverse rotation, a bulk polymerization method or a solution polymerization method may be employed, and in addition to this, a suspension polymerization method may also be employed.

A solvent used for solution polymerization as long as it is soluble for the monomer mixture (a'), the (meth)acrylic resin (A') or the methyl methacrylate homopolymer (A) and the block copolymer (B) There is no particular limitation on the solvent of ability. For example, aromatic hydrocarbons, such as benzene, toluene, and ethylbenzene, etc. are mentioned. These may be used alone or in combination of two or more. In the solvent having a dissolving ability to the monomer mixture (a'), the (meth)acrylic resin (A') or the methyl methacrylate homopolymer (A) and the block copolymer (B), A solvent having no dissolving power for the monomer mixture (a'), the (meth)acrylic resin (A') or the methyl methacrylate homopolymer (A) and the block copolymer (B). Examples of the solvent having no dissolving ability include alcohols such as methanol, ethanol, and butanol; ketones such as acetone and methyl ethyl ketone; hydrocarbons such as hexane; and alicyclic hydrocarbons such as cyclohexane. Wait. When the mixture of the monomer mixture (a') and the solvent is 100% by mass, the amount of the preferable solvent which can be used in the present invention is in the range of 0 to 90% by mass.

The polymerization initiator to be used in the production method of the present invention is not particularly limited as long as it generates reactive radicals, and examples thereof include azo compounds such as azobisisobutyronitrile and azobiscyclohexylcarbonitrile; Benzoyl sulfonium oxide, tert-butyl peroxybenzoate, di-tert-butyl peroxide, diisopropylbenzene peroxide, 1,1-bis(t-butylperoxy) 3,3, 5-trimethylcyclohexane, tert-butylperoxyisopropyl carbonate, An organic peroxide such as 1,1-bis(t-butylperoxy)cyclohexane, di-tert-butyl peroxide or t-butylperoxybenzoate. These may be used alone or in combination of two or more. Moreover, the amount of addition or the addition method of the polymerization initiator can be appropriately set depending on the purpose, and is not particularly limited.

When the monomer mixture (a') is polymerized, a chain transfer agent typified by an alkyl mercaptan or the like may be added to the polymerization reaction liquid as needed. Examples of the alkyl mercaptan include n-dodecyl mercaptan, tridecyl mercaptan, 1,4-butanedithiol, 1,6-hexanedithiol, and ethylene glycol dithiopropionic acid. Ester, butanediol dithioglycolate, butanediol dithiopropionate, hexanediol dithioglycolate, hexanediol dithiopropionate, trimethylolpropane ginseng- --thiopropionate), pentaerythritol thiopropionate, and the like.

The temperature at which the monomer mixture (a') is polymerized is preferably from 100 to 150 ° C, more preferably from 110 to 140 ° C. The polymerization time is preferably from 0.5 to 4 hours, more preferably from 1 to 3 hours. Furthermore, in the case of a continuous flow reactor, the polymerization time is the average residence time in the reactor. If the polymerization reaction time is too short, the amount of the polymerization initiator required increases. Further, the control of the polymerization reaction is difficult due to the increase in the polymerization initiator, and the control of the molecular weight tends to be difficult. On the other hand, if the polymerization reaction time is too long, it takes time until the reaction becomes stable, and the productivity tends to be lowered. Further, the polymerization is preferably carried out under an inert gas atmosphere such as nitrogen.

After the end of the polymerization, unreacted monomers and solvents are usually removed. The removal method is not particularly limited, but is preferably a heating devolatilization. As the devolatilization method, a balanced flash method or a heat-insulating flash method can be mentioned. to Among these, a heat-insulating flashing method is preferred. The deflation of the heat-insulating flashing method is preferably carried out at a temperature of 200 to 300 ° C, more preferably 220 to 270 ° C. When the temperature is lower than 200 ° C, it takes time to devolatilize, and when the devolatilization is insufficient, it is easy to cause appearance defects such as silver streaks in the molded body. On the other hand, when it exceeds 300 ° C, the (meth)acrylic resin composition may be colored by oxidation, scorching or the like.

Further, in the (meth)acrylic resin composition of the present invention, in order to improve heat resistance, optical properties, and the like, the (meth)acrylic acid may be used by a well-known method, as long as the effects of the present invention are not impaired. The resin (A') or methyl methacrylate homopolymer (A) is subjected to a modification treatment. The method of the modification treatment is not particularly limited. For example, the oxime imidization modification can be carried out by dissolving a (meth)acrylic resin composition in a solvent, adding a monoalkylamine or the like to the solution, or reacting it with an extruder or the like ( When the methyl group-acrylic resin composition is melt-kneaded, a monoalkylamine or the like is added and reacted.

The (meth)acrylic resin composition of the present invention may additionally contain various additives as needed. In addition, when the content of the additive is too large, appearance defects such as silver streaks are likely to occur in the molded article.

Examples of the additive include an antioxidant, a heat deterioration inhibitor, an ultraviolet absorber, a light stabilizer, a slip agent, a mold release agent, a polymer processing aid, an antistatic agent, a flame retardant, a dye pigment, a light diffusing agent, and an organic solvent. Pigments, matting agents, impact-resistant modifiers, phosphors, etc.

The antioxidant has an effect of preventing oxidative degradation of the resin with a monomer in the presence of oxygen. For example, a phosphorus-based antioxidant, a hindered phenol-based antioxidant, a thioether-based antioxidant, or the like can be given. These antioxidants may be used alone or in combination of two or more. Such Among them, from the viewpoint of preventing the effect of deterioration of optical characteristics due to coloring, a phosphorus-based antioxidant or a hindered phenol-based antioxidant is preferable, and a phosphorus-based antioxidant and a hindered phenol-based antioxidant are more preferably used in combination.

When a phosphorus-based antioxidant and a hindered phenol-based antioxidant are used in combination, the ratio thereof is not particularly limited, but the quality of the phosphorus-based antioxidant/hindered phenol-based antioxidant is preferably 1/5 to 2/1, more preferably 1 /2~1/1.

As the phosphorus-based antioxidant, 2,2-methylenebis(4,6-di-t-butylphenyl)octylphosphite (manufactured by Asahi Kasei Co., Ltd.; trade name: ADEKA STAB HP-10) is preferred. , ginseng (2,4-di-t-butylphenyl) phosphite (manufactured by CIBA Specialty Chemicals Co., Ltd.; trade name: IRUGAFOS 168).

As the hindered phenol-based antioxidant, pentaerythritol 肆 [3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate] (manufactured by CIBA Specialty Chemicals Co., Ltd.; trade name IRGANOX 1010), ten Octa-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate (manufactured by CIBA Specialty Chemicals, trade name: IRGANOX 1076).

The heat deterioration preventing agent can prevent thermal deterioration of the resin by capturing polymer radicals generated when exposed to high heat in a substantially oxygen-free state.

As the heat-resistant deterioration agent, 2-t-butyl-6-(3'-tert-butyl-5'-methyl-hydroxybenzyl)-4-methylphenyl acrylate (Sumitomo Chemical Co., Ltd.) is preferred. Manufactured under the trade name Sumilizer GM), 2,4-di-p-pentyl-6-(3',5'-di-t-pentyl-2'-hydroxy-α-methylbenzyl)phenyl acrylate ( Sumitomo Chemical Co., Ltd.; trade name Sumilizer GS).

The ultraviolet absorber is a compound having an ability to absorb ultraviolet rays. The ultraviolet absorber mainly refers to a compound having a function of converting light energy into heat energy.

Examples of the ultraviolet absorber include diphenyl ketones, benzotriazoles, and trisole. Classes, benzoates, salicylates, cyanoacrylates, oxalic anilides, malonic esters, formazan, and the like. These may be used alone or in combination of two or more.

As the benzotriazole, 2-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol (manufactured by CIBA Specialty Chemicals Co., Ltd.) is preferred. ; trade name TINUVIN329), 2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol (manufactured by CIBA Specialty Chemicals Co., Ltd.; trade name TINUVIN234), 2,2'-methylenebis[4-(1,1,3,3-tetramethylbutyl)-6-(2H-benzotriazol-2-yl)phenol], 6, 6'-bis(2H-benzotriazol-2-yl)-4,4'-bis(2,4,4-trimethylpentan-2-yl)-2,2'-methylene diphenol (made by Adeka Co., Ltd.; trade name ADEKA STAB LA31).

As three Class, which can be exemplified by 2-[4,6-di(2,4-dimethylphenyl)-1,3,5-three -2-yl]-5-octyloxyphenol (manufactured by CIBA Specialty Chemicals, trade name TINUVIN411L), 2-[4-[(2-hydroxy-3-dodecyloxy)oxy)-4 ,6-bis(2,4-dimethylphenyl)-1,3,5-three /2-[4-[(2-Hydroxy-3-n-dodecyloxy)oxy]-2-hydroxyphenyl]-4,6-bis(2,4-dimethylphenyl)- 1,3,5-three (manufactured by CIBA Specialty Chemicals; trade name TINUVIN400), 2-(4,6-diphenyl-1,3,5-three -2-yl)-5-(hexyloxy)phenol (manufactured by CIBA Specialty Chemicals Co., Ltd.; trade name TINUVIN 1577).

These ultraviolet absorbers may be used alone or in combination of two or more.

The blending amount of the ultraviolet absorber is preferably 0.1 to 5 parts by mass, more preferably 0.5 to 3 parts by mass, per 100 parts by mass of the (meth)acrylic resin composition. The method of containing a UV absorber is a method in which a UV absorber is previously blended in a (meth)acrylic resin composition to be pelletized, and this film is melt-extruded or the like to form a film; Any method such as a method of directly adding a UV absorber can be used.

The light stabilizer is mainly a compound having a function of capturing radicals generated by oxidation due to light. As a suitable light stabilizer, a hindered amine such as a compound having a 2,2,6,6-tetraalkylpiperidine skeleton can be mentioned.

The release agent is a compound having a function of easily releasing a molded article from a mold. Examples of the release agent include higher alcohols such as cetyl alcohol and stearyl alcohol, and glycerin higher fatty acid esters such as stearic acid monoglyceride and stearic acid diglyceride. In the present invention, as the release agent, a higher alcohol and a glycerin fatty acid monoester are preferably used in combination. When a higher alcohol and a glycerin fatty acid monoester are used together, the ratio thereof is not particularly limited, but the quality of the higher alcohol/glycerol fatty acid monoester is preferably from 2.5/1 to 3.5/1, more preferably from 2.8/1 to 3.2/. 1.

The polymer processing aid is a compound which exhibits thickness precision and thin film when the (meth)acrylic resin composition is molded. The polymer processing aid is usually a polymer particle having a particle diameter of 0.05 to 0.5 μm which can be produced by an emulsion polymerization method.

The polymer particles may be a single layer particle composed of a polymer having a single composition ratio and a single ultimate viscosity, or may be a multilayer particle composed of two or more kinds of polymers having different composition ratios or ultimate viscosity. Among them, a polymer layer having a low ultimate viscosity in the inner layer and a two-layer structure having a polymer layer having a high ultimate viscosity of 5 dl/g or more in the outer layer are preferable.

The ultimate viscosity of the polymer processing aid is preferably from 3 to 6 dl/g. If the ultimate viscosity is too small, the effect of improving the formability tends to be lowered. If the ultimate viscosity is too large, the melt fluidity of the (meth)acrylic resin composition tends to decrease.

In the (meth)acrylic resin composition of the present invention, a wash-resistant modifier can also be used. Examples of the impact-resistant modifier include a core-shell type modifier containing an acrylic rubber or a diene rubber as a core component, and a modifier containing a plurality of rubber particles.

As the organic dye, a compound having a function of converting ultraviolet rays harmful to the resin into visible light is preferably used.

Examples of the light diffusing agent or the matting agent include glass fine particles, polyoxyalkylene crosslinked fine particles, crosslinked polymer fine particles, talc, calcium carbonate, barium sulfate, and the like.

Examples of the phosphor include a fluorescent pigment, a fluorescent dye, a fluorescent white dye, a fluorescent whitening agent, and a fluorescent bleaching agent.

Examples of the slip agent include stearic acid such as stearic acid, eucalyptus acid, methyl stearate, ethyl stearate, and stearic acid monoglyceride; decyl stearate and stearic acid; A metal salt such as zinc acid, calcium stearate or magnesium stearate; and ethyl bis-stearylamine. Relative to 100 parts by mass of (methyl) The blending amount of the acrylic resin composition and the slip agent is preferably 0.01 to 0.1 part by mass, more preferably 0.03 to 0.07 part by mass.

Further, an inorganic filler such as cerium oxide, a pigment release agent such as iron oxide, a paraffin-based processing oil, a naphthenic processing oil, an aromatic processing oil, a paraffin, an organic polyoxane, or a mineral may be blended. Softeners such as oil ‧ plasticizers, flame retardants, antistatic agents, organic fibers, glass fibers, carbon fibers, metal whiskers, etc., reinforcing agents, coloring agents, fluorescent whitening agents, dispersing agents, thermal stabilizers, Light stabilizers, antioxidants and other additives or mixtures of such.

Further, the (meth)acrylic resin composition of the present invention can be used in combination with other resins such as impact-resistant polystyrene resin or vinyl chloride resin.

These additives may be added to the polymerization reaction liquid when the monomer mixture (a') is polymerized, or may be added to the produced (meth)acrylic resin composition.

The (meth)acrylic resin composition of the present invention is molded by a conventional molding method such as injection molding, compression molding, extrusion molding, vacuum molding, or casting molding to obtain various molded articles. In particular, when the (meth)acrylic resin composition of the present invention is injection-molded at a high discharge temperature at a low cylinder temperature, it is possible to provide a thin wall having a small residual strain and almost no coloration and a wide area formation with high production efficiency. Product.

The (meth)acrylic resin composition of the present invention can be obtained into various molded articles by a well-known molding method. Examples of the molded article include an advertising tower, a vertical signboard, a side signboard, and an inter-column stroke. Signboard parts such as cards, roof signs, etc.; display parts such as window, partition, shop display, etc.; lighting parts such as fluorescent lamp covers, atmosphere lighting covers, lampshades, ceiling lights, wall lamps, chandeliers, etc.; Decorative parts; construction parts for doors, domes, safety windows, room partitions, stair panels, balcony panels, roofs for leisure buildings, aircraft windshields, pilot masks, motorcycles, motorboat windshields Transporter-related parts such as bus visors, side visors for vehicles, rear visors, head blades, headlight covers, etc.; electronic machine parts for audio image signs, stereo speakers, TV shields, vending machines, etc.; Medical equipment parts such as instruments and X-ray machine parts; machine-related parts such as mechanical covers, measuring instrument covers, experimental devices, rulers, dials, observation windows, etc.; liquid crystal protective plates, light guide plates, light guiding films, Fresnel Optically related parts such as lenses, lenticular lenses, front panels of various displays, diffusers, etc.; traffic-related zeros for road signs, guide plates, curved mirrors, soundproof walls, etc. a polarizing mirror protective film, a polarizing plate protective film, a retardation film, a surface material for an automobile interior, a surface material of a mobile phone, a film member such as a marking film, a top cover material of a washing machine or a control panel, and a top surface of the electric cooker Components for home appliances such as panels; greenhouses, large sinks, box sinks, clock panels, bathtubs, sanitary facilities, table mats, game parts, toys, face protection covers for welding, etc. Among these, the (meth)acrylic resin composition of the present invention is suitable for an optical member, and is also suitable for a film among optical members, and is particularly suitable for a protective film for a polarizing plate.

[Optical member, film]

An optical member or a film according to an embodiment of the present invention contains a (meth)acrylic resin composition. Optical member or film system can be A well-known molding method is obtained, for example, by an extrusion molding method, an injection molding method, or the like. Specifically, a (meth)acrylic resin composition is used in a melt kneader such as a uniaxial extruder, a biaxial extruder, a Banbury mixer, a Brabender, and various kneaders. The melt-kneading is followed by molding using an extrusion molding machine or the like using a mold to which a T die or a circular die is attached, and a film or the like can be obtained. Further, the film of the present invention can be obtained by blow molding, injection blow molding, inflation molding, foam molding, casting molding, or the like, and a secondary molding method such as air pressure molding or vacuum molding can also be used. . The resulting film can be subjected to elongation treatment or surface treatment depending on the application.

The film of the embodiment of the present invention has a haze value of preferably 2% or less, more preferably 1.2% or less, and particularly preferably 1.0% or less in a 23 ° C environment. If the haze value in the 23 ° C environment is small, the film is given a high degree of transparency and is suitable for optics.

The absolute value of the photoelastic coefficient of the film of one embodiment of the present invention in an environment of 23 ° C is preferably 8.0 × 10 ^-12 Pa ^-1 or less, more preferably 6.0 × 10 ^-12 Pa ^-1 or less, and particularly preferably 5.0. ×10 ^-12 Pa ^-1 or less. When the photoelastic coefficient is within the above range, the change in birefringence due to stress is small, and when used in a liquid crystal display device or the like, the contrast or the uniformity of the screen tends to be excellent.

In addition, the "photoelastic coefficient" is a coefficient C _R [Pa ^-1 ] indicating the easiness of occurrence of a change in birefringence due to an external force, and is defined by the following formula.

C _R =Δn/σ _R

Here, σ _R is a tensile stress [Pa], and Δn is a birefringence when stress is applied, and Δn is defined by the following formula.

Δn=n ₁ -n ₂

(wherein n ₁ is a refractive index in a direction parallel to the stretching direction, and n ₂ is a refractive index in a direction perpendicular to the stretching direction).

The thickness of the optical film according to the embodiment of the present invention is preferably 100 μm or less, more preferably 10 μm or more and 90 μm or less, still more preferably 20 μm or more and 80 μm or less, and particularly preferably 30 μm or more and 60 μm or less. In particular, when it is used as an optical film used for a liquid crystal display, it is preferably a thickness of 100 μm or less from the viewpoint of the folding strength.

The optical film according to an embodiment of the present invention is not particularly limited by the values of the in-plane retardation value (Re) and the thickness direction hysteresis value (Rth) and the Nz coefficient. The in-plane retardation value (Re) and the thickness direction hysteresis value (Rth) and the Nz coefficient can be obtained by the composition ratio of the material constituting the (meth)acrylic resin composition, the thickness of the film, the extension temperature, the stretching ratio, and the elongation. The speed and the like are appropriately set and controlled.

Here, the in-plane retardation value (Re) and the thickness direction hysteresis value (Rth) and the Nz coefficient are defined by the following formula.

Re=(n _x -n _y )×d

Rth=((n _x +n _y )/2)-n _z )×d

Nz=(n _x -n _z )/∣(n _x -n _y )∣

(wherein n _x : the refractive index in the x direction when the refractive index in the plane of the film is maximized is x, and n _y : when y is perpendicular to the x direction in the plane of the film; The refractive index of the direction, n _z : refractive index in the thickness direction of the film, d: thickness (nm) of the film).

When the film of the embodiment of the present invention is used as a protective film for a polarizing plate, the absolute value of the retardation value (Rth) in the thickness direction is preferably 20 nm or less, more preferably 15 nm or less, and still more preferably 5 nm or less. When the absolute value of Rth exceeds 20 nm, the variation of the hysteresis value due to the incident angle is large, and there is a problem that a contrast reduction occurs in the liquid crystal display device.

The film of one embodiment of the present invention can be suitably subjected to surface functionalization such as antiglare treatment, antireflection treatment, transparent conductive treatment, electromagnetic wave shielding treatment, gas barrier treatment, hard coating treatment, antistatic treatment, and antifouling treatment. deal with.

When the film of one embodiment of the present invention is used as a protective film for a polarizing plate, the antistatic function can be imparted by surface treatment. Further, an antistatic function can be imparted to other members such as an adhesive layer incorporated into the optical film as needed.

When the film is subjected to an anti-glare treatment, effects such as improvement in visibility, prevention of external light, and reduction of moiré due to drying of the light are achieved. By the anti-glare treatment, a layer having a fine uneven shape is formed on the surface of the film, that is, an anti-glare layer is formed. It is preferred to form a hard coat material using an anti-glare layer. The thickness of the antiglare layer is not particularly limited, but is preferably 2 μm or more and 30 μm or less, and more preferably 3 μm or more and 20 μm or less. If the thickness of the antiglare layer is too small, sufficient hardness cannot be obtained, and the surface tends to be easily damaged. Further, when the thickness of the antiglare layer is too large, the film is easily broken, or the film is curled due to the hardening and shrinkage of the antiglare layer, and the productivity tends to be lowered.

The antireflection treatment is carried out by providing a layer having a refractive index lower than the refractive index of the film on the surface of the film, or by laminating a layer having a high refractive index and a layer having a low refractive index. The low refractive index layer or the high refractive index layer can be formed by coating or by physical or chemical vapor deposition.

[Polarizer]

The polarizing plate of the present invention has a polarizing film and a film of the present invention bonded to at least one side thereof.

The polarizing film used in the present invention is not particularly limited. The polarizing film can be formed, for example, by adding iodine or a dye to polyvinyl alcohol, forming a film, and stretching the film to align the molecules.

When the film to be bonded to the polarizing film has a functional layer such as an antireflection layer or an antiglare layer on the surface, it is preferable to bond the film so that the functional layer or the like faces away from the surface of the polarizing film.

The film of the present invention may be attached to both sides of the polarizing film in accordance with characteristics required for the polarizing plate, and the film of the present invention may be attached to one side of the polarizing film, and on the other side of the polarizing film. A film made of other resin is bonded to the surface.

The bonding method of the polarizing film and the film of the present invention is not particularly limited. For example, an adhesive such as an epoxy resin, an urethane resin, a cyanoacrylate resin, or a acrylamide resin can be used for bonding.

Before the polarizing film and the film of the present invention are bonded, one or both sides of the bonded surface may be subjected to corona discharge treatment or the like. By applying a corona discharge treatment, the adhesion between the film of the present invention and the polarizing film can be improved. The so-called corona discharge treatment is to apply between the electrodes The voltage is increased and discharged, and the resin film disposed between the electrodes is activated. The effect of the corona discharge treatment differs depending on the type of the electrode, the electrode interval, the voltage, the humidity, the type of the resin film to be used, and the like. For example, it is preferable to set the electrode interval to 1 to 5 mm and set the moving speed. It is around 3~20m/min. Next, an adhesive such as the above was applied to the corona discharge treated surface to bond the two films.

[Examples]

The embodiments are shown below to more specifically illustrate the invention. Further, the present invention is not limited by the following examples. Further, the present invention includes all of the aspects in which the above-described technical characteristics such as characteristic values, forms, preparation methods, and uses are arbitrarily combined.

The measurement of the physical property values of the examples and the like are carried out by the following methods.

<Moisture measurement>

Moisture measurement was carried out using Karl Fischer (KMA-210) manufactured by Kyoto Electronics Industry Co., Ltd.

<Polymerization conversion rate>

INERT CAP 1 (df=0.4 μm, 0.25 mm I.D.×60 m) manufactured by GL Sciences Inc. as a column was connected to Gas Chromatograph GC-14A manufactured by Shimadzu Corporation, and the injection temperature was set at 180 °C. The temperature of the column was set to 180 ° C, and the column temperature was set to 60 ° C (for 5 minutes) → the temperature increase rate was 10 ° C / min → 200 ° C (for 10 minutes), and analysis was performed based on this.

<Measurement of deflection temperature of load>

The measurement was carried out in accordance with JIS-K7191.

<film appearance>

Using a puncture counter (type FS-5) manufactured by Optical Control Systems, the resin composition was extruded at a temperature of 260 ° C and a lip gap of 0.5 mm in a cylinder and a T die, and adjusted to a film thickness of 75 μm to detect defects. Defects not stained with osmium tetroxide were treated as unmelted pitting within the transparent defects detected. The relative number of defects was evaluated using the following criteria.

○: 50% of the number of unmelted pittings of less than Example 1 (Table 2) or Example 12 (Table 3)

△: 50% or more and less than 100% of the number of unmelted pittings of Example 1 (Table 2) or Example 12 (Table 3)

×: 100% or more of the number of unmelted pittings of Example 1 (Table 2) or Example 12 (Table 3)

<Measurement of film thickness>

The thickness of the central portion of each film was measured using a micrometer (manufactured by MITUTOYO Co., Ltd.).

<Measurement of fog value>

The measurement was carried out in accordance with JIS-K7136. The haze value was measured for a film which was placed immediately after molding and placed in an environment of a temperature of 85 ° C and a relative humidity of 85% for 100 hours.

<Pants tear test>

The measurement was carried out in accordance with JIS-K7128.

Production of Synthesis Example 1 Block Copolymer (B-1)

(1) In a 1.5-liter autoclave vessel equipped with a stirrer, 640 ml of toluene and 0.009 ml of 1,2-dimethoxyethane were placed, and nitrogen purge was performed for 20 minutes. A second butyl group having a concentration of 1.3 mol/l was added thereto. 2.86 ml of a lithium cyclohexane solution was added, followed by addition of 72.6 ml of 1,3-butadiene, and the mixture was reacted at 30 ° C for 1.5 hours to obtain a reaction mixture containing a 1,3-butadiene polymer. A part of the obtained reaction mixture was sampled and analyzed, and as a result, the 1,3-butadiene polymer coefficient in the reaction mixture had an average molecular weight (Mn) of 24,000 and a molecular weight distribution (Mw/Mn) of 1.06, a side chain vinyl bond. The amount of the precipitate was 30 mol%.

(2) The reaction mixture obtained in the above (1) is cooled to -30 ° C, and 27.5 ml of isobutyl bis(2,6-di-t-butyl-4-methylphenoxy) containing 0.45 mol/l is added. A solution of aluminum in toluene and 6.5 ml of 1,2-dimethoxyethane were stirred for 10 minutes to form a homogeneous solution.

(3) Next, while vigorously stirring the solution obtained in the above (2), 60.0 ml of n-butyl acrylate was added, and polymerization was carried out at -30 ° C for 1 hour. A part of the obtained reaction mixture was sampled, and the molecular weight was analyzed by GPC (polystyrene conversion), and as a result, the amount of butadiene-n-butyl acrylate diblock copolymer (arm polymer block) in the reaction mixture was averaged. The molecular weight was 41,000, and the ratio of the weight average molecular weight / number average molecular weight (Mw / Mn) was 1.02.

(4) The reaction mixture obtained in the above (3) was kept at -30 ° C, and 3.2 ml of 1,6-hexanediol diacrylate was added under vigorous stirring, and polymerization was carried out for 0.5 hour. Next, about 1 ml of methanol was added to stop the polymerization.

(5) A part of the reaction mixture obtained in the above (4) was taken out and precipitated with methanol. The obtained star block copolymer (B-1) contains a polymer block (b) composed of 46% by mass of 1,3-butadiene units and 54% by mass of n-butyl acrylate unit. The diblock copolymer composed of the formed polymer block (a) is an arm polymer block and contains 56 masses. The amount % (the ratio calculated from the area ratio of GPC) was such that the number average molecular weight (Mn) was 210,000 (arm number = 5.1) and the Mw/Mn was 1.16 star block copolymer. The characteristics of the star block copolymer (B-1) are shown in Table 1. Further, in the table, BA means n-butyl acrylate, and BD means 1,3-butadiene.

(6) 1000 g of water was added to the reaction mixture obtained in the above (4), and impurities contained in the reaction mixture were extracted with water by shaking. After shaking, it was allowed to stand, and the toluene solution of the block copolymer (B-1) was separated from the aqueous phase to remove the aqueous phase. Repeat this operation 4 times.

(7) The toluene solution of the block copolymer (B-1) obtained by removing the impurities by the above extraction is heated to 80 ° C, and a part of the toluene is distilled off under reduced pressure to adjust the block copolymer in the toluene solution. The concentration was 30% by mass, and a toluene solution of the block copolymer (B-1) was obtained.

Production of Synthesis Example 2 Block Copolymer (B-2)

The block copolymer (B-2) was produced in the same manner as in Synthesis Example 1, except that 1,6-hexanediol diacrylate was not added. The 1,3-butadiene polymer coefficient had an average molecular weight (Mn) of 24,000, a molecular weight distribution (Mw/Mn) of 1.06, and a side chain vinyl bond amount of 30 mol%. Further, the butadiene-n-butyl acrylate diblock copolymer had a coefficient average molecular weight of 41,000 and a weight average molecular weight/number average molecular weight ratio (Mw/Mn) of 1.02.

Production of Synthesis Example 3 Block Copolymer (B-3)

The star block copolymer (B-3) was produced in the same manner as in Synthesis Example 1, except that the amount of 1,3-butadiene was changed to 71.1 ml, and the amount of n-butyl acrylate was changed to 61.1 ml. The obtained star block copolymer (B-3) contains a polymer block (b) composed of 45% by mass of 1,3-butadiene units and 55 mass% of n-butyl acrylate units. Made polymer The diblock copolymer composed of the block (a) as the arm polymer block has a number average molecular weight (Mn) of 210,000 (the number of arms = 5.1) containing 56% by mass (the ratio calculated from the area ratio of GPC). ), Mw / Mn is 1.16 star block copolymer.

Further, the 1,3-butadiene polymer coefficient produced during the production had an average molecular weight (Mn) of 23,000, a molecular weight distribution (Mw/Mn) of 1.06, and a side chain vinyl bond amount of 30 mol%. Further, the butadiene-n-butyl acrylate diblock copolymer coefficient average molecular weight was 41,000, and the weight average molecular weight/number average molecular weight ratio (Mw/Mn) was 1.02.

Production of Synthesis Example 4 Block Copolymer (B-4)

The block copolymer (B-4) was produced in the same manner as in Synthesis Example 3 except that 1,6-hexanediol diacrylate was not added. The 1,3-butadiene polymer coefficient had an average molecular weight (Mn) of 23,000, a molecular weight distribution (Mw/Mn) of 1.06, and a side chain vinyl bond amount of 30 mol%. Further, the butadiene-n-butyl acrylate diblock copolymer had a coefficient average molecular weight of 41,000 and a weight average molecular weight/number average molecular weight ratio (Mw/Mn) of 1.02.

The properties of the block copolymers (B-1), (B-2), (B-3) and (B-4) are shown in Table 1.

(example 1)

60 parts by mass of methyl methacrylate, 33 parts by mass of a 30% by mass toluene solution of a star block copolymer (B-1), and 7 parts by mass of toluene were placed in an autoclave equipped with a stirrer and a collecting tube. Stir and mix. Then, 0.03 parts by mass of 1,1-bis(t-butylperoxy)cyclohexane and 0.2 parts by mass of n-dodecylmercaptan were added and uniformly dissolved to obtain a polymerization reaction liquid. The oxygen in the reaction system is driven out by nitrogen. A part of this polymerization liquid was collected, and the moisture measured by Karl Fischer was 1200 ppm.

The polymerization reaction solution was warmed to 115 ° C, and solution polymerization was carried out for 2.5 hours. The reaction liquid was separated by a collection tube. The polymerization conversion rate of the reaction liquid was 60% by mass as determined by gas chromatography.

Next, 0.08 parts by mass of 1,1-bis(t-butylperoxy)cyclohexane was added to the reaction liquid, and solution polymerization was carried out at 120 ° C for 2 hours to obtain a reaction liquid (d-1). The polymerization conversion ratio by gas chromatography of the reaction liquid (d-1) was 95% by mass. The reaction liquid (d-1) was vacuum dried to remove unreacted monomers and toluene to obtain a (meth)acrylic resin composition (e-1).

The dried (meth)acrylic resin composition was kneaded by an experimental refiner and hot pressed to obtain a flat plate having a thickness of 4 mm. The designated test piece was cut out from the plate, and the deflection temperature of the load was measured. The evaluation results are shown in Table 2.

The dried (meth)acrylic resin composition was pelletized using a biaxial extruder KZW20TW-45MG-NH-600 manufactured by TECHNOVEL Co., Ltd. to form a film. The evaluation results are shown in Table 2.

(Example 2)

A (meth)acrylic resin composition was obtained in the same manner as in Example 1 except that an adsorbent (Mizukasieves, manufactured by Mizusawa Chemical Co., Ltd.) was added to the polymerization reaction solution to adsorb moisture, and then the adsorbent was removed by using a 2 μm filter. . The amount of water measured by Karl Fischer of the polymerization reaction liquid was 250 ppm. Film formation was carried out in the same manner as in Example 1 except that the obtained (meth)acrylic resin composition was used. The evaluation results are shown in Table 2.

(Example 3)

66.7 parts by mass of methyl methacrylate, 11.1 parts by mass of a 30% by mass toluene solution of a star block copolymer (B-1), and 22.2 parts by mass of toluene were placed in an autoclave equipped with a stirrer and a collecting tube. Stir and mix. Then, 0.03 parts by mass of 1,1-bis(t-butylperoxy)cyclohexane and 0.2 parts by mass of n-dodecylmercaptan were added to uniformly dissolve them. The oxygen in the reaction system is driven out by nitrogen. A part of this polymerization reaction liquid was collected, and the moisture measured by Karl Fischer was 500 ppm. The polymerization reaction solution was warmed to 115 ° C, and solution polymerization was carried out for 2.5 hours. The reaction liquid was separated by a collecting tube. The polymerization conversion rate of the reaction liquid was 60% by mass as determined by gas chromatography. Film formation was carried out in the same manner as in Example 1 except that the obtained (meth)acrylic resin composition was used.

(Example 4)

Evaluation was carried out in the same manner as in Example 3 except that the block copolymer (B-1) was changed to the block copolymer (B-2).

(Example 5)

42.9 parts by mass of methyl methacrylate, 27.1 parts by mass of a star block copolymer (B-1) and 30 parts by mass of toluene were added to an autoclave equipped with a stirrer and a collecting tube, and the mixture was stirred and mixed at 60 ° C. And become a homogeneous solution. Then, 0.03 parts by mass of 1,1-bis(t-butylperoxy)cyclohexane and 0.2 parts by mass of n-dodecylmercaptan were added to uniformly dissolve them. The oxygen in the reaction system is driven out by nitrogen. A part of this polymerization liquid was collected, and the moisture measured by Karl Fischer was 300 ppm. The polymerization reaction solution was warmed to 115 ° C, and solution polymerization was carried out for 2.5 hours. The reaction liquid was separated by a collection tube. The polymerization conversion rate of the reaction liquid was 60% by mass as determined by gas chromatography. Then, the same operation as in Example 1 was carried out.

(Example 6)

61.7 parts by mass of methyl methacrylate, 5.0 parts by mass of methyl acrylate, and 11.1 parts by mass of the star block copolymer (B-3) obtained in Synthesis Example 3 were placed in an autoclave equipped with a stirrer and a collecting tube. The toluene solution and 22.2 parts by mass of toluene were stirred and mixed. Then, 0.03 parts by mass of 1,1-bis(t-butylperoxy)cyclohexane and 0.2 parts by mass of n-dodecylmercaptan were added to uniformly dissolve them. The oxygen in the reaction system is driven out by nitrogen. A part of this polymerization liquid was collected, and the moisture measured by Karl Fischer was 400 ppm. The solution polymerization was carried out at 115 ° C for 2.5 hours. The reaction liquid was separated by a collecting tube. The polymerization conversion rate of the reaction liquid was 60% by mass as determined by gas chromatography. Then, the same operation as in Example 1 was carried out.

As shown in Table 2, the ratio of the methyl methacrylate homopolymer (A) to the block copolymer (B) was low in the range of the haze value of Examples 1 to 4 in the range of the present invention.

Further, in Examples 1 to 4 using methyl methacrylate homopolymer (A), compared with Example 6 using a copolymer of methyl methacrylate and methyl acrylate, the load deflection temperature, that is, the heat resistance temperature high.

(Example 7)

The iodine was adsorbed to polyvinyl alcohol to obtain a polarizing film having a thickness of about 30 μm. The film prepared in Example 2 was bonded to both faces of the polarizing film via an adhesive to obtain a polarizing plate.

(Example 8) Production of (meth)acrylic resin composition (solution polymerization → solution polymerization)

55.5 parts by mass of methyl methacrylate, 5.0 parts by mass of methyl acrylate, 33 mass in an autoclave equipped with a stirrer and a collecting tube The toluene solution of the star block copolymer (B-3) obtained in Synthesis Example 3 and 7 parts by mass of toluene were stirred and mixed. Then, 0.03 parts by mass of 1,1-bis(t-butylperoxy)cyclohexane and 0.2 parts by mass of n-dodecylmercaptan were added to uniformly dissolve them. The oxygen in the reaction system is driven out by nitrogen. An adsorbent (Mizukasieves, manufactured by Mizusawa Chemical Co., Ltd.) was added to the polymerization reaction solution to adsorb water. Then, the adsorbent was removed with a 2 μm filter. The polymerization liquid was measured by Karl Fischer to have a water content of 250 ppm.

The polymerization reaction solution was warmed to 115 ° C, and the solution was polymerized for 2.5 hours. The polymerization conversion ratio was 60% by mass.

Next, 0.08 parts by mass of 1,1-bis(t-butylperoxy)cyclohexane was added to the reaction liquid, and the solution was polymerized at 120 ° C for 2 hours. The polymerization conversion ratio was 95% by mass.

This vacuum was dried to remove unreacted monomers and toluene to obtain a (meth)acrylic resin composition. The dried (meth)acrylic resin composition was pelletized using a biaxial extruder KZW20TW-45MG-NH-600 manufactured by TECHNOVEL Co., Ltd.

The pellets were used for film formation. The evaluation results are shown in Table 3.

(Example 9)

100 parts by mass of the pellet obtained in Example 8 and 200 parts by mass of (meth)acrylic resin (C) (Parapet EH-made by KURARAY Co., Ltd.) using a biaxial extruder KZW20TW-45MG-NH-600 manufactured by TECHNOVEL Co., Ltd. S) is mixed and pelletized.

The pellets were used for film formation. The evaluation results are shown in Table 3.

(Example 10)

61.7 parts by mass of methyl methacrylate, 5.0 parts by mass of methyl acrylate, and 11.1 parts by mass of the star block copolymer (B-3) obtained in Synthesis Example 3 were placed in an autoclave equipped with a stirrer and a collecting tube. The toluene solution and 22.2 parts by mass of toluene were stirred and mixed. Then, 0.03 parts by mass of 1,1-bis(t-butylperoxy)cyclohexane and 0.2 parts by mass of n-dodecylmercaptan were added to uniformly dissolve them. The oxygen in the reaction system is driven out by nitrogen. The polymerization liquid was measured by Karl Fischer to have a water content of 500 ppm. The solution was polymerized at 115 ° C for 2.5 hours. The polymerization conversion ratio was 60% by mass.

Next, 0.08 parts by mass of 1,1-bis(t-butylperoxy)cyclohexane was added to the reaction liquid, and the solution was polymerized at 120 ° C for 2 hours. The polymerization conversion ratio was 95% by mass.

This vacuum was dried to remove unreacted monomers and toluene to obtain a (meth)acrylic resin composition. The dried (meth)acrylic resin composition was pelletized using a biaxial extruder KZW20TW-45MG-NH-600 manufactured by TECHNOVEL Co., Ltd.

The pellets were used for film formation. The evaluation results are shown in Table 3.

(Example 11)

The same procedure as in Example 8 except that the toluene solution of the star block copolymer (B-3) obtained in Synthesis Example 3 was changed to the toluene solution of the star block copolymer (B-4) obtained in Synthesis Example 4. The particles of the (meth)acrylic resin composition are obtained by a method. The amount of water in the reaction solution measured by Karl Fischer was 690 ppm. The pellets were used for film formation. The evaluation results are shown in Table 3.

(Example 12)

A pellet of a (meth)acrylic resin composition was obtained in the same manner as in Example 8 except that the adsorbent was not added to the polymerization reaction solution. The amount of water in the reaction solution measured by Karl Fischer was 1500 ppm. The pellets were used for film formation. The evaluation results are shown in Table 3.

(Example 13)

Using 100 parts by mass of the pellet obtained in Example 12 and 200 parts by mass of (meth)acrylic resin (C) (Parapet EH-made by KURARAY Co., Ltd.) using a biaxial extruder KZW20TW-45MG-NH-600 manufactured by TECHNOVEL Co., Ltd. S) granulate. The pellets were used for film formation. The evaluation results are shown in Table 3.

(Example 14)

Particles of the (meth)acrylic resin composition were obtained in the same manner as in Example 11 except that the adsorbent was not added to the polymerization reaction liquid. The amount of water in the reaction solution measured by Karl Fischer was 2,100 ppm. The pellets were used for film formation. The evaluation results are shown in Table 3.

As shown in Table 2 and Table 3, it is understood that Examples 2 to 6 and examples in which the amount of water in the polymerization of the (meth)acrylic resin is 1000 ppm or less, compared with Example 1 and Examples 12 to 14 in which the amount of water exceeds 1000 ppm. 8~Example 11 is a reduction in defects caused by unmelted pitting.

Claims (10)

A (meth)acrylic resin composition containing 65 to 99 parts by mass of a methyl group in a total amount of 100 parts by mass of the total of the methyl methacrylate homopolymer (A) and the block copolymer (B) a methyl acrylate homopolymer (A), and 1 to 35 parts by mass of a polymer block (a) composed of an alkyl (meth) acrylate unit and a polymer formed from a conjugated diene compound unit Block copolymer (B) of block (b). The (meth)acrylic resin composition of claim 1, wherein the block copolymer (B) contains a star block copolymer containing at least a polymer block (a) and/or Or the polymer block of the polymer block (b), and the polystyrene-converted number average molecular weight calculated by gel permeation chromatography (GPC) satisfies [star block copolymer The number average molecular weight] / [the number average molecular weight of the arm polymer block] is >2. The (meth)acrylic resin composition of claim 2, wherein the star block copolymer (B) is represented by the following chemical structural formula: (polymer block (b) - polymer block (a) - _n X (wherein X represents a coupling agent residue, and n represents a number exceeding 2). The (meth)acrylic resin composition according to any one of claims 1 to 3, which further contains an ultraviolet absorber. An optical member comprising the (meth)acrylic resin composition according to any one of claims 1 to 4. A film comprising the (meth)acrylic resin composition according to any one of claims 1 to 4. The film of claim 6 which is subjected to an anti-glare treatment and/or an anti-reflection treatment. A polarizing plate having a polarizing film and a film according to claim 6 attached to at least one side thereof. A method for producing a (meth)acrylic resin composition, comprising: a polymer block (a) having a (meth)acrylic acid alkyl ester unit and a polymer formed from a conjugated diene compound unit The block copolymer (B) of the block (b) is dissolved in a monomer mixture (a') containing 50% by mass or more and 100% by mass or less of methyl methacrylate to obtain a polymerization reaction liquid, followed by polymerization. The amount of water in the liquid is 1000 ppm or less, and the monomer mixture (a') is polymerized. The process for producing a (meth)acrylic resin composition according to claim 9, wherein the monomer mixture (a') is 100% methyl methacrylate (containing unavoidable impurities).