WO2014002506A1 - (meth)acrylic resin composition, method for producing same, and optical member - Google Patents

Abstract

A (meth)acrylic resin composition is obtained by means of a method which involves: obtaining a polymerization reaction solution by dissolving a block copolymer (B), which has a polymer block (a) comprising an alkyl ester (meth)acrylate unit and a polymer block (b) comprising a conjugated diene compound unit, in a monomer mixture (a') containing 50 to 100 mass% of a methyl methacrylate; and polymerizing the monomer mixture (a') once the moisture content within the polymerization reaction solution reaches 1000 ppm or less.

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 includes a (meth) acrylic resin composition, a method for producing the same, and a (meth) acrylic resin composition that have excellent toughness, high heat resistance, and hardly generate optical defects when formed into a molded product. It is related with the optical member formed.

The polarizing plate usually has a polarizing film and a protective film laminated on both sides thereof. The polarizing plate is incorporated in an optical device such as a liquid crystal display device.
A triacetyl cellulose (TAC) film is used as a protective film for a polarizing plate. However, since triacetyl cellulose has high hygroscopicity, a polarizing plate using a protective film made of triacetyl cellulose, when exposed to high-temperature conditions and high-humidity heat conditions, the degree of polarization and hue change, The performance of the optical device may be degraded.

The use of methacrylic resin as a protective film material as an alternative to triacetylcellulose has been studied.
Methacrylic resin is a material excellent in transparency and wet heat resistance, small in birefringence and excellent in optical homogeneity. On the other hand, methacrylic resin is brittle and has a property of being easily broken by fluctuations in tension. In order to impart toughness to such a methacrylic resin, a technique for blending a modifier with the methacrylic resin is known.
The following are known as such modifiers. For example, Patent Document 1 discloses a multilayer structure acrylic rubber produced by an emulsion polymerization method. Patent Document 2 discloses a rubber-like substance made of a butadiene-butyl acrylate copolymer. Patent Document 3 discloses a partially hydrogenated conjugated diene polymer. Patent Document 4 discloses a modified block copolymer comprising a (meth) acrylic acid alkyl ester unit and an aromatic vinyl monomer unit. Patent Document 5 discloses a block copolymer comprising a polymer block A mainly composed of a vinyl aromatic compound and a polymer block B mainly composed of a conjugated diene compound, and a part of the polymer block B is epoxidized. It is disclosed. Patent Document 6 discloses an ethylene-vinyl acetate copolymer and the like. Patent Document 7 discloses a block copolymer comprising a conjugated diene polymer component rich in vinyl bonds and an acrylic ester or methacrylic ester polymer component. Patent Document 8 discloses a star block copolymer having a polymer block (a) composed of (meth) acrylic acid alkyl ester units and a polymer block (b) composed of conjugated diene compound units.

Japanese Examined Patent Publication No.59-36645 Japanese Examined Patent Publication No. 45-26111 WO96 / 032440 JP 2000-313786 A Japanese Unexamined Patent Publication No. 7-207110 JP-A-6-345933 JP 49-45148 WO2008 / 032732

However, the conventional (meth) acrylic resin composition may contain a small amount of a resin having a high molecular weight and difficult to melt by heat, which is unexpectedly generated by the polymerization reaction in the gas phase portion of the polymerization reactor. When a film or the like is molded with the (meth) acrylic resin composition containing a resin that is difficult to melt by heat, an optical defect may occur, and the performance of the optical member may be deteriorated.
An object of the present invention is to provide a (meth) acrylic resin composition having excellent toughness, high heat resistance, and hardly producing optical defects when formed into a molded product, and an optical member comprising the composition. It is.

As means for achieving the above object, the present invention includes the following aspects.
[1] having 65 to 99 parts by mass of methyl methacrylate homopolymer (A), and a polymer block (a) composed of (meth) acrylic acid alkyl ester units and a polymer block (b) composed of conjugated diene compound units 1 to 35 parts by mass of the block copolymer (B)
A (meth) acrylic resin composition containing 100 parts by mass of the total of the methyl methacrylate homopolymer (A) and the block copolymer (B).
[2] The block copolymer (B) contains a star-shaped block copolymer,
The star-shaped block copolymer contains an arm polymer block having at least a polymer block (a) and / or a polymer block (b), and is obtained by gel permeation chromatography (GPC). The (meth) acrylic resin composition according to [1], wherein the calculated number average molecular weight in terms of polystyrene satisfies [number average molecular weight of star block copolymer] / [number average molecular weight of arm polymer block]> 2. .
[3] The star block copolymer (B) has the 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 [2].
[4] The (meth) acrylic resin composition according to any one of [1] to [3], further containing 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 subjected to an antiglare treatment and / or an antireflection treatment.
[8] A polarizing plate having a polarizing film and the film according to any one of [6] and [7] bonded to at least one surface thereof.
[9] A block copolymer (B) having a polymer block (a) composed of (meth) acrylic acid alkyl ester units and a polymer block (b) composed of conjugated diene compound units is prepared by using 50% by mass of methyl methacrylate. Dissolved in the monomer mixture (a ′) containing 100% by mass or less to obtain a polymerization reaction solution,
Subsequently, the manufacturing method of the (meth) acrylic resin composition including superposing | polymerizing a monomer mixture (a ') by making the moisture content in a polymerization reaction liquid into 1000 ppm or less.
[10] The (meth) acrylic resin composition according to [9], wherein the monomer mixture (a ′) comprises 100% by mass of methyl methacrylate (which may contain inevitable impurities). Production method.

The (meth) acrylic resin composition according to the present invention has excellent toughness, high heat resistance, and hardly generates optical defects when formed into a molded product. By molding the (meth) acrylic resin composition according to the present invention, an optical member such as a protective film for a polarizing plate having almost no optical defect can be obtained.

According to the production method of the present invention, when the monomer mixture (a ′) containing 50% by mass or more and 100% by mass or less of methyl methacrylate with a water content in the polymerization reaction solution of 1000 ppm or less is excellent in toughness, A (meth) acrylic resin composition having high heat resistance and very few gel colonies and resin foreign matters can be easily obtained. The (meth) acrylic resin composition obtained by the production method according to the present invention is excellent in toughness and hardly generates crater-like optical defects. By molding the methacrylic resin composition obtained by the production method according to 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 an embodiment of the present invention comprises a methyl methacrylate homopolymer (A), a polymer block (a) composed of (meth) acrylic acid alkyl ester units, and a conjugated diene compound unit. It contains a block copolymer (B) having a polymer block (b).
The amount of the methyl methacrylate homopolymer (A) is 65 to 99 parts by mass, preferably 77 to 99 parts by mass with respect to 100 parts by mass in total of the methyl methacrylate homopolymer (A) and the block copolymer (B). Part, more preferably 80 to 98 parts by weight, still more preferably 83 to 97 parts by weight.
The amount of the block copolymer (B) is 1 to 35 parts by mass, preferably 1 to 23 parts by mass with respect to 100 parts by mass in total of the methyl methacrylate homopolymer (A) and the block copolymer (B). More preferably, it is 2 to 20 parts by mass, and still 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 (meth) acrylic acid alkyl ester units and a polymer block (b) composed of conjugated diene compound units. “(Meth) acryl” is an abbreviation of “methacryl or acrylic”. In the block copolymer (B), the glass transition temperature of the 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) composed of (meth) acrylic acid alkyl ester units can be formed by polymerizing (meth) acrylic acid alkyl ester. Such alkyl (meth) acrylates include methyl methacrylate, ethyl methacrylate, butyl methacrylate, cyclohexyl methacrylate; methyl acrylate, ethyl acrylate, n-butyl acrylate, i-butyl acrylate, acrylic acid 2 -Ethylhexyl and the like. These can be used alone or in combination of two or more. Among these, a (meth) acrylic acid alkyl ester which gives a polymer block (a) having a glass transition temperature (Tg) of 0 ° C. or less or a combination thereof is preferable, and a polymer block (a) having a Tg of −10 ° C. or less. More preferred are (meth) acrylic acid alkyl esters or combinations thereof. As such (meth) acrylic acid alkyl ester, n-butyl acrylate and / or 2-ethylhexyl acrylate are preferable, and n-butyl acrylate is more preferable.

The polymer block (b) composed of a conjugated diene compound unit can be formed by polymerizing a conjugated diene. Such conjugated dienes include 1,3-butadiene, isoprene, pentadiene, 2,3-dimethylbutadiene and the like. These can be used alone or in combination of two or more. Among these, a conjugated diene that gives a polymer block (b) having a glass transition temperature (Tg) of 0 ° C. or lower or a combination thereof is preferable, and a conjugated diene that gives a polymer block (b) having a Tg of −10 ° C. or lower A combination thereof is more preferred. As such a conjugated diene, 1,3-butadiene and / or isoprene are preferable, and 1,3-butadiene is more preferable from the viewpoints of versatility, economy, and handleability.

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

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

The mass ratio of the polymer block (a) and 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, The combined 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 by its refractive index, but when the (meth) acrylic resin composition of the present invention requires transparency, the refractive index of the block copolymer (B) is methacrylic. It is preferable to match the refractive index of the acid methyl homopolymer (A). Specifically, the refractive index of the block copolymer (B) is preferably 1.48 to 1.50, more preferably 1.485 to 1.495.

The block copolymer (B) preferably contains a star block copolymer. The star-shaped block copolymer has a structure in which a plurality of arm polymer blocks are connected and spread radially. The connecting part of the arm polymer block is usually constituted by a group (coupling agent residue) derived from a polyfunctional monomer, a polyfunctional coupling agent or the like.
The star block copolymer has, for example, a 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 includes a polymer block (a) (hereinafter sometimes simply referred to as (a)) and a polymer block (b) (hereinafter sometimes simply referred to as (b)). It is preferable to have at least. The structure of the arm polymer block is not particularly limited. For example, (a)-(b) type block copolymerized structure, (a)-(b)-(a) type block copolymerized structure, (b)-(a)-(b) type blocked Examples include a copolymerized structure, a structure (a)-(b)-(a)-(b) type block copolymerized, and a structure (a) and (b) block copolymerized in total of 5 or more. . The plurality of arm polymer blocks constituting the star block copolymer (B) may all have the same block copolymerized structure, or may have different block copolymerized structures. Of these, the arm polymer block preferably has the (a)-(b) type block copolymerized structure. That is, the block copolymer (B) used in the present invention has a 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, and n represents a number exceeding 2), and preferably contains a star block copolymer represented by:
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), and more preferably contains a star block copolymer.

The star-shaped block copolymer suitable as the block copolymer (B) has a polystyrene-equivalent number average molecular weight calculated by gel permeation chromatography (GPC).
[Number average molecular weight of star block copolymer] / [Number average molecular weight of arm polymer block]> 2.
The ratio of [number average molecular weight of star block copolymer] / [number average molecular weight of arm polymer block] is sometimes referred to as the number of arms.
By making the number average molecular weight of the star block copolymer more than twice the number average molecular weight of the arm polymer block, the shear of the particles of the star block copolymer (B) dispersed in the methacrylic resin As a result, the desired mechanical strength can be obtained. The number average molecular weight of the star block copolymer is more than 100 times the number average molecular weight of the arm polymer block, because synthesis is difficult. Therefore, the number average of the industrially preferred star block copolymer (B) The molecular weight is more than 2 times and less than 100 times the number average molecular weight of the arm polymer block, more preferably 2.5 to 50 times, still more preferably 3 to 10 times.
The block copolymer (B) used in the present invention is not limited to the star block copolymer as described above, but the arm polymer block that is a constituent material of the star block copolymer is a coupling agent residue. It may be left as it is without being connected.

The method for producing the block copolymer (B) used in the present invention is not particularly limited, and a method according to a known method can be employed. In general, as a method of obtaining a block copolymer, a method of living polymerizing a monomer that is a structural unit is employed. Examples of such living polymerization methods include a method of polymerizing using an organic rare earth metal complex as a polymerization initiator, an alkali metal or alkaline earth metal mineral salt using an organic alkali metal compound as a polymerization initiator, and the like. And a method of anionic polymerization in the presence of an organic alkali metal compound as a polymerization initiator, an anion polymerization in the presence of an organoaluminum compound, an atom transfer radical polymerization (ATRP) method, and the like.

Among the above production methods, the method of using an organic alkali metal compound as a polymerization initiator and anionic polymerization in the presence of an organoaluminum compound can produce a block copolymer having a narrower molecular weight distribution and less residual monomer. It can be carried out under relatively mild temperature conditions, and is preferable in that the environmental load in industrial production (mainly the power consumption of the refrigerator necessary for controlling the polymerization temperature) is small.

An organic alkali metal compound is usually used as the polymerization initiator for the anionic polymerization. Examples of the organic alkali metal compound include methyl lithium, ethyl lithium, n-propyl lithium, isopropyl lithium, n-butyl lithium, sec-butyl lithium, isobutyl lithium, tert-butyl lithium, n-pentyl lithium, n-hexyl lithium, tetra Alkyllithium and alkyldilithium such as methylenedilithium, pentamethylenedilithium, hexamethylenedilithium; aryllithium and aryldilithium such as phenyllithium, m-tolyllithium, p-tolyllithium, xylyllithium, lithium naphthalene; Benzyllithium, diphenylmethyllithium, trityllithium, 1,1-diphenyl-3-methylpentyllithium, α-methylstyryllithium, diisopropenylbenzene Aralkyllithium and aralkyldilithium such as dilithium produced by the reaction of butyllithium; lithium amides such as lithium dimethylamide, lithium diethylamide and lithium diisopropylamide; methoxylithium, ethoxylithium, n-propoxylithium, isopropoxylithium, n-butoxy Lithium, sec-butoxylithium, tert-butoxylithium, pentyloxylithium, hexyloxylithium, heptyloxylithium, octyloxylithium, phenoxylithium, 4-methylphenoxylithium, benzyloxylithium, 4-methylbenzyloxylithium, etc. Organic lithium compounds such as alkoxides can be mentioned. These can be used alone or in combination of two or more.

As an organoaluminum compound used in the above anionic polymerization, for example,
General formula: AlR ¹ R ² R ³
Wherein R ¹ , R ² and R ³ are each independently an alkyl group which may have a substituent, a cycloalkyl group which may have a substituent, or an aryl group which may have a substituent. Represents an aralkyl group which may have a substituent, an alkoxyl group which may have a substituent, an aryloxy group which may have a substituent or an N, N-disubstituted amino group, or R ¹ Represents any of the groups described above, and R ² and R ³ together represent an aryleneoxy group which may have a substituent.

Specific examples of the organoaluminum compound represented by the above general formula include trimethylaluminum, triethylaluminum, tri-n-butylaluminum, tris-butylaluminum, tri-t-butylaluminum, triisobutylaluminum, tri-n-hexylaluminum, Trialkylaluminum such as tri-n-octylaluminum, tri-2-ethylhexylaluminum, triphenylaluminum, dimethyl (2,6-di-tert-butyl-4-methylphenoxy) aluminum, dimethyl (2,6-di-tert- Butylphenoxy) aluminum, diethyl (2,6-di-tert-butyl-4-methylphenoxy) aluminum, diethyl (2,6-di-tert-butylphenoxy) aluminum, diisobutyl ( , 6-Di-tert-butyl-4-methylphenoxy) aluminum, diisobutyl (2,6-di-tert-butylphenoxy) aluminum, di-n-octyl (2,6-di-tert-butyl-4-methyl) Phenoxy) aluminum, dialkylphenoxyaluminum such as di-n-octyl (2,6-di-tert-butylphenoxy) aluminum, methylbis (2,6-di-tert-butyl-4-methylphenoxy) aluminum, methylbis (2 , 6-Di-tert-butylphenoxy) aluminum, ethyl [2,2'-methylenebis (4-methyl-6-tert-butylphenoxy)] aluminum, ethylbis (2,6-di-tert-butyl-4-methyl) Phenoxy) aluminum, ethyl bis (2,6-di-t rt- butyl phenoxy) aluminum, ethyl [2,2'-methylenebis (4-methyl -6-tert-butyl phenoxy)] aluminum,

Isobutylbis (2,6-di-tert-butyl-4-methylphenoxy) aluminum, isobutylbis (2,6-di-tert-butylphenoxy) aluminum, isobutyl [2,2′-methylenebis (4-methyl-6) -Tert-butylphenoxy)] aluminum, n-octylbis (2,6-di-tert-butyl-4-methylphenoxy) aluminum, n-octylbis (2,6-di-tert-butylphenoxy) aluminum, n-octyl [2,2′-methylenebis (4-methyl-6-tert-butylphenoxy)] alkyldiphenoxyaluminum such as aluminum, methoxybis (2,6-di-tert-butyl-4-methylphenoxy) aluminum, methoxybis (2 , 6-Di-tert-butylfe Xy) aluminum, methoxy [2,2′-methylenebis (4-methyl-6-tert-butylphenoxy)] aluminum, ethoxybis (2,6-di-tert-butyl-4-methylphenoxy) aluminum, ethoxybis (2, 6-di-tert-butylphenoxy) aluminum, ethoxy [2,2′-methylenebis (4-methyl-6-tert-butylphenoxy)] aluminum, isopropoxybis (2,6-di-tert-butyl-4-) Methylphenoxy) aluminum, isopropoxybis (2,6-di-tert-butylphenoxy) aluminum, isopropoxy [2,2′-methylenebis (4-methyl-6-tert-butylphenoxy)] aluminum, tert-butoxybis ( 2,6-di-tert-bu Ru-4-methylphenoxy) aluminum, tert-butoxybis (2,6-di-tert-butylphenoxy) aluminum, tert-butoxy [2,2'-methylenebis (4-methyl-6-tert-butylphenoxy)] aluminum And triphenoxyaluminum such as tris (2,6-di-tert-butyl-4-methylphenoxy) aluminum and tris (2,6-diphenylphenoxy) aluminum.

These can be used alone or in combination of two or more. Among these organoaluminum compounds, isobutylbis (2,6-di-tert-butyl-4-methylphenoxy) aluminum, isobutylbis (2,6-di-tert-butylphenoxy) aluminum, isobutyl [2,2 ′ -Methylenebis (4-methyl-6-tert-butylphenoxy)] aluminum is preferred because it is easy to handle and allows the anionic polymerization reaction to proceed without deactivation under relatively mild temperature conditions.

In the anionic polymerization reaction system, if necessary, ethers such as dimethyl ether, dimethoxyethane, diethoxyethane, 12-crown-4; triethylamine, N, N, N ′, N′-tetramethylethylenediamine, Nitrogen-containing compounds such as N, N, N ′, N ″, N ″ -pentamethyldiethylenetriamine, 1,1,4,7,10,10-hexamethyltriethylenetetramine, pyridine, 2,2′-dipyridyl, It can coexist for stabilization of a polymerization reaction.

Examples of a method for obtaining a block copolymer used in the present invention include a method in which a small amount of a polyfunctional monomer, a polyfunctional coupling agent, or the like is added to an anionic polymerization reaction system for polymerization. The polyfunctional monomer is a compound having two or more ethylenically unsaturated groups, and specifically includes allyl methacrylate, ethylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, divinylbenzene, 1 , 6-hexanediol diacrylate and the like.

The polyfunctional coupling agent is a compound having 3 or more reactive groups, specifically, trichloromethylsilane, tetrachlorosilane, butyltrichlorosilane, bis (trichlorosilyl) ethane, tetrachlorotin, butyltrichlorotin, Examples include tetrachlorogermanium.

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

(Methyl methacrylate homopolymer (A))
The methyl methacrylate homopolymer (A) used in the present invention is a resin obtained by polymerizing only methyl metallate. Since methyl methacrylate homopolymer tends to cause depolymerization, methacrylic resin is usually copolymerized with methyl methacrylate and methyl acrylate. When methyl methacrylate and methyl acrylate are copolymerized, the heat resistance of the (meth) acrylic resin composition decreases, and the composition ratio of the monomer units varies, resulting in optical characteristics such as refractive index. The reproduction accuracy of is reduced.

The methyl methacrylate homopolymer has a weight average molecular weight of preferably 40,000 to 200,000, more preferably 50,000 to 180,000, still more preferably 60,000 to 160,000. If the weight average molecular weight is too small, the impact resistance and toughness of the molded product obtained from the (meth) acrylic resin composition tend to decrease. On the contrary, 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 methyl methacrylate homopolymer has a molecular weight distribution (weight average molecular weight / number average molecular weight) of preferably 1.9 to 3.0, more preferably 2.1 to 2.8, particularly preferably 2.2 to. 2.7. If the molecular weight distribution is too small, the moldability of the (meth) acrylic resin composition tends to decrease. Conversely, if the molecular weight distribution is too large, the impact resistance of the molded product obtained from the (meth) acrylic resin composition tends to be reduced.
In addition, a weight average molecular weight and a number average molecular weight are molecular weights of standard polystyrene conversion measured by GPC (gel permeation chromatography). The molecular weight and molecular weight distribution of the methacrylic resin can be controlled by adjusting the types and amounts of the polymerization initiator and the chain transfer agent.

The (meth) acrylic resin composition according to the present invention is preferably such that the block copolymer (B) forms a domain in the methyl methacrylate homopolymer (A) and is dispersed.
The size of the domain (domain average diameter) 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 impact resistance tends to decrease, and if the average diameter of the domain is large, the rigidity tends to decrease, and the transparency tends to decrease. The domain structure and average diameter can be confirmed by a transmission electron micrograph of a section cut out by an ultrathin section method.

The (meth) acrylic resin composition according to the present invention has a load deflection temperature of preferably 90 ° C. or higher, more preferably 92 ° C. or higher, and further preferably 94 ° C. or higher. If the temperature is too low, thermal deformation tends to occur at the normal use temperature of the molded product. The load deflection temperature is a value measured under a condition in which a load of 1.82 MPa is applied to a test piece having a thickness of 4 mm.

In the film made of the (meth) acrylic resin composition according to the present invention, defects caused by the unmelted resin are identified with an optical microscope or a laser microscope. Since the resin unmelted material is transparent without being stained with osmium tetroxide, it was determined that the unstained defect by microscopic observation was caused by the resin unmelted material. Optical defects detected in a film formed by molding a resin composition include a defect caused by the resin composition itself and a defect caused by various conditions of the molding process. It is surmised that the defects due to the resin composition itself are mainly due to gel colonies contained in the resin composition and unmelted resin that is difficult to melt.

The (meth) acrylic resin composition of the present invention is not particularly limited by its production method. For example, a method of obtaining a resin composition by melt-kneading a methyl methacrylate homopolymer (A) and a block copolymer (B) in a single-screw or biaxial melt extruder, or a block copolymer A method in which methyl methacrylate is polymerized in the presence of (B) to obtain a resin composition in situ, or a block copolymer (B) is produced in the presence of methyl methacrylate homopolymer, and the resin composition in situ. The method of obtaining a thing etc. are mentioned. Among these, a method of polymerizing methyl methacrylate in the presence of the block copolymer (B) to obtain a resin composition in situ is preferable. As the polymerization method, a solution polymerization method or a bulk polymerization method is preferable, and a bulk polymerization method is more preferable.

The method for producing a (meth) acrylic resin composition according to an embodiment of the present invention comprises a polymer block (a) comprising a (meth) acrylic acid alkyl ester unit and a polymer block (b) comprising a conjugated diene compound unit. The block copolymer (B) having the following formula 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.
This includes polymerizing the monomer mixture (a ′) by setting the water content in the polymerization reaction solution 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) as described above. It can also be used for the production of a (meth) acrylic resin composition containing (A ′) and a block copolymer (B). The methyl methacrylate homopolymer (A) is a resin produced by polymerization of a monomer mixture (a ′) composed of 100% by mass of methyl methacrylate, and the (meth) acrylic resin (A ′) is methyl methacrylate. It is a resin produced by polymerization of a monomer mixture (a ′) comprising less than 100% by mass.

(Monomer mixture (a ′))
In the monomer mixture (a ′) used in the present invention, methyl methacrylate is 50% by mass to 100% by mass, preferably 80% by mass to 100% by mass, more preferably 80% by mass to 96% by mass. Is included. The monomer mixture (a ′) composed of 100% by mass of methyl methacrylate may contain inevitable impurities.

Monomers other than methyl methacrylate include alkyl acrylates such as methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate and 2-ethylhexyl acrylate; aryl acrylates such as phenyl acrylate; acrylic Cycloacrylates such as cyclohexyl and norbornenyl acrylate; alkyl methacrylates other than methyl methacrylate such as ethyl methacrylate and butyl methacrylate; aryl methacrylates such as phenyl methacrylate; cyclohexyl methacrylate and methacrylic acid In one molecule such as cycloalkyl methacrylate such as norbornenyl; other vinyl monomers such as acrylamide, methacrylamide, acrylonitrile, methacrylonitrile, styrene, α-methylstyrene; The non-crosslinkable vinyl monomer having a polymerizable alkenyl group only one can be cited. The amount of monomers other than methyl methacrylate is preferably 0% by mass or more and 50% by mass or less, preferably 0% by mass or more and 20% by mass or less, more preferably 4% by mass or more, based on all monomer units. It is 20 mass% or less. Of the monomers other than methyl methacrylate, alkyl acrylate is preferable, and methyl acrylate is more preferable.

The monomer mixture (a ′) used in the production method of the present invention has a dissolved oxygen content of preferably 10 ppm or less, more preferably 5 ppm or less, further preferably 4 ppm or less, and most preferably 3 ppm or less. When the amount of dissolved oxygen is in such a range, the polymerization reaction proceeds smoothly, and it becomes easy to obtain a molded product without silver or coloring.

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 resulting (meth) acrylic resin composition is molded, a molded product with little coloration is easily obtained with high production efficiency. As will be described later, when the polymerization conversion rate is not so high in the polymerization of the monomer mixture (a ′), unreacted monomers remain in the polymerization reaction solution. Unreacted monomer can be recovered from the polymerization reaction solution and used again for the polymerization reaction. The yellow index of the recovered monomer may increase due to heat applied during recovery. The recovered monomer is preferably purified by an appropriate method to reduce the yellow index. The yellow index is a value measured according to JIS Z-8722 using a colorimetric color difference meter ZE-2000 manufactured by Nippon Denshoku Industries Co., Ltd.

Further, the methyl methacrylate used in the production method of the present invention is preferably b ^* of −1 to 2, more preferably −0.5 to 1.5. When the monomer b ^* is within this range, when the resulting (meth) acrylic resin composition is molded, a molded product with little coloration is easily obtained with high production efficiency. Note that b ^* is a value measured according to the International Commission on Illumination (CIE) standard (1976) or JIS Z-8722.

The mass ratio of the block copolymer (B) to the monomer mixture (a ′) is preferably 1/99 to 35/65, more preferably 1/99 to 23/77, and even more preferably 2/98 to 20 / 80, most preferably 3/97 to 17/83. When the amount of the block copolymer (B) is small, the impact resistance of the (meth) acrylic resin composition tends to decrease, and conversely, when it is large, not only the elastic modulus and rigidity tend to decrease, but also phase inversion hardly occurs. It becomes difficult to uniformly disperse the block copolymer (B) in the (meth) acrylic resin (A ′) or the methyl methacrylate homopolymer (A).

The method for 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 dissolution, it is preferable to remove the unmelted resin from the polymerization reaction solution with a filter or the like.

After the block copolymer (B) is dissolved in the monomer mixture (a ′), the monomer mixture (a ′) is polymerized. In this polymerization, the amount of water in the polymerization reaction solution is 1000 ppm or less, preferably 700 ppm or less, more preferably 280 ppm or less. By reducing the amount of water in the polymerization system, it is possible to suppress the formation of resin foreign matter of several μm to several tens of μm generated during the polymerization reaction. The occurrence of defects of several tens of μm can be greatly reduced, and an optical member having high optical homogeneity can be obtained. The method for adjusting the amount of water in the polymerization reaction solution is not particularly limited. For example, a method of dehydrating the block copolymer (B), monomer mixture (a ′) and other polymerization auxiliary materials used as raw materials by adsorption, or introducing an inert gas into the gas phase part of the tank reactor For example, a method may be used in which a part of the monomer vapor is accompanied by an inert gas, condensed by a brine-cooled condenser, and extracted out of the system.

Polymerization is preferably performed while applying shear to the polymerization reaction solution. 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 solution) containing the block copolymer (B). When the polymerization reaction proceeds while adding, the phase containing the (meth) acrylic resin (A ′) or methyl methacrylate homopolymer (A) and the phase containing the block copolymer (B) are reversed, and (meth) The phase containing the block copolymer (B) is dispersed in the phase containing the acrylic resin (A ′) or the methyl methacrylate homopolymer (A). The polymerization conversion rate of the monomer when this phase inversion occurs is the volume ratio of block copolymer (B) to (meth) acrylic resin (A ′) or methyl methacrylate homopolymer (A), block The molecular weight of the copolymer (B), the graft ratio to the block copolymer (B), and when a solvent is added, can be adjusted according to the amount of solvent and the type of solvent.

In the period from the initial stage of polymerization until the phase inversion occurs, the polymerization is preferably carried out by a bulk polymerization method or a solution polymerization method. When the polymerization in the period is performed by a bulk polymerization method or a solution polymerization method, shear due to stirring is more applied to the phase containing the block copolymer (B), and phase inversion is likely to occur.
Examples of the apparatus for performing bulk polymerization or solution polymerization include a tank reactor with a stirrer, a tubular reactor with a stirrer, a tubular reactor having a static stirring ability, and the like. One or more of these apparatuses may be used, or two or more reactors of the same type or different types may be connected in parallel or in series. The polymerization may be either batch or continuous. The polymerization conversion rate of bulk polymerization or solution polymerization can be adjusted by the supply amount of the reaction raw material liquid, the withdrawal amount of the reaction product liquid, and the average residence time. The polymerization conversion rate is preferably 70% by mass or more, more preferably 85% by mass or more, and 90% by mass or more from the viewpoint of increasing the toughness of a molded product such as an optical member formed by molding the resulting methacrylic resin composition. Further preferred. In a tank reactor, usually, a stirring means for stirring the liquid in the reaction tank, a supply unit for supplying a monomer mixture or a polymerization auxiliary material to the reaction tank, and a reaction product is extracted from the reaction tank. And an extraction part. In the continuous flow reaction, the amount supplied to the reaction vessel and the amount withdrawn from the reaction vessel are balanced so that the amount of liquid in the reaction vessel becomes substantially constant. The amount of liquid in the reaction tank is preferably ¼ or more, more preferably 1/4 to 3/4, and still more preferably 1/3 to 2/3 with respect to the volume of the reaction tank.

The size of the dispersed phase depends on factors such as the number of revolutions of stirring in the case of a reactor equipped with a stirrer; the linear velocity of the reaction liquid, the viscosity of the polymerization reaction liquid in the case of a static stirring reactor represented by a tower reactor, It can be controlled by various factors such as the graft ratio to the block copolymer (B) before phase inversion. In addition, after the phase inversion has occurred, a bulk polymerization method or a solution polymerization method can be applied, but in addition to these, a suspension polymerization method can also be applied.

The solvent used for the solution polymerization has solubility in the monomer mixture (a ′), the (meth) acrylic resin (A ′) or the methyl methacrylate homopolymer (A), and the block copolymer (B). If it is a solvent, it will not restrict | limit in particular. For example, aromatic hydrocarbons such as benzene, toluene and ethylbenzene can be used. These can be used alone or in combination of two or more. As long as it has a solubility in the monomer mixture (a ′), the (meth) acrylic resin (A ′) or the methyl methacrylate homopolymer (A), and the block copolymer (B), the solvent contains: A solvent that does not have solubility in the monomer mixture (a ′), the (meth) acrylic resin (A ′) or the methyl methacrylate homopolymer (A), and the block copolymer (B) is included. Also good. Examples of the solvent having no solubility include alcohols such as methanol, ethanol and butanol; ketones such as acetone and methyl ethyl ketone; hydrocarbons such as hexane; alicyclic hydrocarbons such as cyclohexane and the like. A preferable amount of the solvent that can be used in the present invention is in the range of 0 to 90% by mass when the monomer mixture (a ′) and the solvent mixture are 100% by mass.

The polymerization initiator used in the production method of the present invention is not particularly limited as long as it generates a reactive radical. For example, azo compounds such as azobisisobutyronitrile and azobiscyclohexylcarbonitrile; benzoyl peroxide; t-butyl peroxybenzoate, di-t-butyl peroxide, dicumyl peroxide, 1,1-bis (t-butylperoxy) 3,3,5-trimethylcyclohexane, t-butyl peroxyisopropyl carbonate, 1 , 1-bis (t-butylperoxy) cyclohexane, di-t-butyl peroxide, and organic peroxides such as t-butylperoxybenzoate. These can be used alone or in combination of two or more. The addition amount and addition method of the polymerization initiator are not particularly limited as long as they are appropriately set according to the purpose.

When the monomer mixture (a ′) is polymerized, a chain transfer agent typified by alkyl mercaptan may be added to the polymerization reaction solution as necessary. Alkyl mercaptans include n-dodecyl mercaptan, t-dodecyl mercaptan, 1,4-butanedithiol, 1,6-hexanedithiol, ethylene glycol bisthiopropionate, butanediol bisthioglycolate, butanediol bisthiopropio Nate, hexanediol bisthioglycolate, hexanediol bisthiopropionate, trimethylolpropane tris- (β-thiopropionate), pentaerythritol tetrakisthiopropionate, and the like.

The temperature in the polymerization of the monomer mixture (a ′) is preferably 100 to 150 ° C., more preferably 110 to 140 ° C. The polymerization reaction time is preferably 0.5 to 4 hours, and more preferably 1 to 3 hours. In the case of a continuous flow reactor, the polymerization reaction time is an average residence time in the reactor. If the polymerization reaction time is too short, the required amount of polymerization initiator increases. Further, increasing the amount of the polymerization initiator makes it difficult to control the polymerization reaction, and tends to make it difficult to control the molecular weight. On the other hand, if the polymerization reaction time is too long, it takes time for the reaction to reach a steady state, and the productivity tends to decrease. The polymerization is preferably performed in an inert gas atmosphere such as nitrogen gas.

After the polymerization is completed, the unreacted monomer and solvent are usually removed. The removal method is not particularly limited, but heating devolatilization is preferable. Examples of the devolatilization method include an equilibrium flash method and an adiabatic flash method. Of these, the adiabatic flash method is preferable. The adiabatic flash type devolatilization is preferably performed at a temperature of 200 to 300 ° C., more preferably 220 to 270 ° C. If it is less than 200 ° C., it takes time for devolatilization, and if the devolatilization is insufficient, the molded product may have poor appearance such as silver. On the other hand, when the temperature exceeds 300 ° C., the (meth) acrylic resin composition may be colored due to oxidation, burn, or the like.

In addition, the (meth) acrylic resin composition of the present invention is a (meth) acrylic resin (by a known method), if necessary, in order to improve heat resistance, optical properties and the like within a range not impairing the effects of the present invention. A ′) or methyl methacrylate homopolymer (A) may be modified. The method for the modification treatment is not particularly limited. For example, in imidization modification, a (meth) acrylic resin composition is dissolved in a solvent, and a monoalkylamine or the like is added to the solution and reacted, or the (meth) acrylic resin composition is melt-kneaded with an extruder or the like. In this case, the reaction can be carried out by adding a monoalkylamine or the like to react.

The (meth) acrylic resin composition of the present invention may contain various additives as necessary. In addition, when there is too much content of an additive, external appearance defects, such as silver, may be produced in a molded article.
Additives include antioxidants, thermal degradation inhibitors, UV absorbers, light stabilizers, lubricants, mold release agents, polymer processing aids, antistatic agents, flame retardants, dyes and pigments, light diffusing agents, organic dyes , Matting agents, impact resistance modifiers, phosphors and the like.

The antioxidant alone has an effect of preventing oxidative deterioration of the resin in the presence of oxygen. Examples thereof include phosphorus antioxidants, hindered phenol antioxidants, and thioether antioxidants. These antioxidants can be used alone or in combination of two or more. Among these, from the viewpoint of preventing the deterioration of optical properties due to coloring, phosphorus-based antioxidants and hindered phenol-based antioxidants are preferable, and the combined use of phosphorus-based antioxidants and hindered phenol-based antioxidants is more preferable. preferable.
In the case where a phosphorus antioxidant and a hindered phenol antioxidant are used in combination, the ratio is not particularly limited, but is preferably a mass ratio of phosphorus antioxidant / hindered phenol antioxidant, preferably 1/5. ˜2 / 1, more preferably ½ to 1/1.

Examples of phosphorus antioxidants include 2,2-methylenebis (4,6-di-t-butylphenyl) octyl phosphite (Asahi Denka Co., Ltd .; trade name: ADK STAB HP-10), Tris (2,4-dit -Butylphenyl) phosphite (manufactured by Ciba Specialty Chemicals; trade name: IRUGAFOS168) is preferred.

As the hindered phenol-based antioxidant, pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] (manufactured by Ciba Specialty Chemicals; trade name IRGANOX 1010), Octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate (manufactured by Ciba Specialty Chemicals; trade name IRGANOX 1076) is preferred.

The thermal degradation inhibitor can prevent thermal degradation of the resin by scavenging polymer radicals generated when exposed to high heat in a substantially oxygen-free state.
Examples of the thermal degradation inhibitor include 2-t-butyl-6- (3′-t-butyl-5′-methyl-hydroxybenzyl) -4-methylphenyl acrylate (manufactured by Sumitomo Chemical Co., Ltd .; trade name Sumilizer GM), 2,4-di-t-amyl-6- (3 ′, 5′-di-t-amyl-2′-hydroxy-α-methylbenzyl) phenyl acrylate (manufactured by Sumitomo Chemical Co., Ltd .; trade name Sumitizer GS) preferable.

The ultraviolet absorber is a compound having an ability to absorb ultraviolet rays. The ultraviolet absorber is a compound that is said to have a function of mainly converting light energy into heat energy.
Examples of the ultraviolet absorber include benzophenones, benzotriazoles, triazines, benzoates, salicylates, cyanoacrylates, succinic anilides, malonic esters, formamidines, acrylonitriles, and the like. These can be used alone or in combination of two or more.

Examples of benzotriazoles include 2- (2H-benzotriazol-2-yl) -4- (1,1,3,3-tetramethylbutyl) phenol (manufactured by Ciba Specialty Chemicals; trade name TINUVIN329), 2 -(2H-benzotriazol-2-yl) -4,6-bis (1-methyl-1-phenylethyl) phenol (manufactured by Ciba Specialty Chemicals; 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'-methylenediphenol (trade name ADEKA, manufactured by ADEKA) Tab LA31) and the like.

Triazines include 2- [4,6-di (2,4-xylyl) -1,3,5-triazin-2-yl] -5-octyloxyphenol (manufactured by Ciba Specialty Chemicals; trade name) TINUVIN 411L), 2- [4-[(2-hydroxy-3-dodecyloxypropyl) oxy] -4,6-bis (2,4-dimethylphenyl) -1,3,5-triazine / 2- [4- [(2-Hydroxy-3-tridodecyloxypropyl) oxy] -2-hydroxyphenyl] -4,6-bis (2,4-dimethylphenyl) -1,3,5-triazine (Ciba Specialty Chemicals) Product name: TINUVIN400), 2- (4,6-diphenyl-1,3,5-triazin-2-yl) -5- (hexyloxy) phenol (Ciba Specialte) Chemicals, Inc .; trade name TINUVIN 1577).
These ultraviolet absorbers can 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 with respect to 100 parts by mass of the (meth) acrylic resin composition. As a method of containing the ultraviolet absorber, the ultraviolet absorber is preliminarily blended in the (meth) acrylic resin composition and pelletized, and this is formed into a film by melt extrusion, directly at the time of melt extrusion molding, Examples include a method of adding an ultraviolet absorber, and any method can be used.

The light stabilizer is a compound that is said to have a function of capturing radicals generated mainly by oxidation by light. Suitable light stabilizers include hindered amines such as compounds having a 2,2,6,6-tetraalkylpiperidine skeleton.

The mold release agent is a compound having a function of facilitating release of the molded product from the mold. Examples of the release agent include higher alcohols such as cetyl alcohol and stearyl alcohol; glycerin higher fatty acid esters such as stearic acid monoglyceride and stearic acid diglyceride. In the present invention, it is preferable to use a higher alcohol and a glycerin fatty acid monoester in combination as a release agent. When higher alcohols and glycerin fatty acid monoester are used in combination, the ratio is not particularly limited, but the mass ratio of higher alcohols / glycerin fatty acid monoester is preferably 2.5 / 1 to 3.5 / 1. The preferred range is 2.8 / 1 to 3.2 / 1.

The polymer processing aid is a compound that exhibits an effect on thickness accuracy and thinning when a (meth) acrylic resin composition is molded. The polymer processing aid is polymer particles having a particle diameter of 0.05 to 0.5 μm, which can be usually produced by an emulsion polymerization method.
The polymer particles may be single layer particles composed of polymers having a single composition ratio and single intrinsic viscosity, or multilayer particles composed of two or more kinds of polymers having different composition ratios or intrinsic viscosities. May be. Among these, particles having a two-layer structure having a polymer layer having a low intrinsic viscosity in the inner layer and a polymer layer having a high intrinsic viscosity of 5 dl / g or more in the outer layer are preferable.

The polymer processing aid preferably has an intrinsic viscosity of 3 to 6 dl / g. If the intrinsic viscosity is too small, the effect of improving moldability tends to be low. If the intrinsic viscosity is too large, the melt fluidity of the (meth) acrylic resin composition tends to be lowered.

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

As the organic dye, a compound having a function of converting ultraviolet rays that are harmful to the resin into visible light is preferably used.
Examples of the light diffusing agent and matting agent include glass fine particles, polysiloxane-based crosslinked fine particles, crosslinked polymer fine particles, talc, calcium carbonate, and barium sulfate.
Examples of the phosphor include a fluorescent pigment, a fluorescent dye, a fluorescent white dye, a fluorescent brightener, and a fluorescent bleach.

Examples of lubricants include stearic acid esters such as stearic acid, behenic acid, methyl stearate, ethyl stearate, monoglyceride stearate; metal salts such as stearamide, zinc stearate, calcium stearate, magnesium stearate, ethylene bis Examples include stearamide. The blending amount of the lubricant is preferably 0.01 to 0.1 parts by mass, more preferably 0.03 to 0.07 parts by mass with respect to 100 parts by mass of the (meth) acrylic resin composition.

Other inorganic fillers such as silicon dioxide, pigment release agents such as iron oxide, paraffinic process oil, naphthenic process oil, aromatic process oil, paraffin, organic polysiloxane, mineral oil, etc. , Flame retardants, antistatic agents, reinforcing agents such as organic fibers, glass fibers, carbon fibers, metal whiskers, colorants, fluorescent brighteners, dispersants, heat stabilizers, light stabilizers, antioxidants and other additives or You may mix | blend these etc.
Furthermore, the (meth) acrylic resin composition of the present invention can be used by mixing with other resins such as high impact polystyrene resin and vinyl chloride resin.

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

Various molded products can be obtained by molding the (meth) acrylic resin composition of the present invention by a conventionally known molding method such as injection molding, compression molding, extrusion molding, vacuum molding, cast molding, or the like. . In particular, the (meth) acrylic resin composition of the present invention can produce a molded product with a thin wall and a large area with little residual distortion and little coloration even when injection molding is performed at a low cylinder temperature and a high injection pressure with high production efficiency. Can be provided.

The (meth) acrylic resin composition of the present invention can be formed into various molded products by a known molding method. Molded products include, for example, billboard parts such as advertising towers, stand signs, sleeve signs, bamboard signs, and rooftop signs; display parts such as showcases, dividers, and store displays; fluorescent lamp covers, mood lighting covers, lamp shades, Lighting parts such as optical ceilings, light walls, chandeliers; interior parts such as pendants and mirrors; building parts such as doors, domes, safety window glass, partitions, staircases, balconies, roofs of leisure buildings; aircraft windshields , Pilot visor, motorcycle, motor boat windshield, bus shading plate, automotive side visor, rear visor, head wing, headlight cover and other transportation equipment related parts; audio visual nameplate, stereo cover, TV protection mask, vending machine Electronic equipment parts such as incubators, X-ray parts, etc. Medical equipment parts; machine-related parts such as machine covers, instrument covers, experimental devices, rulers, dials, observation windows; LCD protective plates, light guide plates, light guide films, Fresnel lenses, lenticular lenses, front plates of various displays, diffusion Optical components such as plates, polarizer protective films, polarizing plate protective films, retardation films, etc .; traffic-related components such as road signs, guide plates, curve mirrors, and sound barriers; surface materials for automobile interiors, surface materials for mobile phones, Film members such as marking films; canopy materials for washing machines, control panels, top panels for rice cookers, etc .; greenhouses, large aquariums, box aquariums, clock panels, bathtubs, sanitary, desk mats, games Examples include parts, toys, and masks for face protection during welding. Among these, the (meth) acrylic resin composition of the present invention is suitable for an optical member, and among the optical members, it is suitable for a film, particularly a protective film for a polarizing plate.

[Optical members, films]
The optical member or film of one embodiment of the present invention contains a (meth) acrylic resin composition. The optical member or film can be obtained by a known molding method such as an extrusion molding method or an injection molding method. Specifically, a (meth) acrylic resin composition is melt kneaded using a melt kneader such as a single screw extruder, a twin screw extruder, a Banbury mixer, a brabender, various kneaders, and then a T die, a circular die, etc. A film or the like can be obtained by molding using an extrusion molding machine or the like equipped with a mold. In addition, the film of the present invention can be obtained by blow molding, injection blow molding, inflation molding, foam molding, cast molding, and the like, and further, secondary processing molding methods such as pressure molding and vacuum molding can be used. The obtained film can be stretched or surface-treated depending on the application.

The film of one embodiment of the present invention has a haze value in a 23 ° C. environment of preferably 2% or less, more preferably 1.2% or less, and further preferably 1.0% or less. When the haze value in a 23 ° C. environment is small, the film is highly transparent and suitable for optics.
The film according to an embodiment of the present invention has an absolute value of a photoelastic coefficient under a 23 ° C. environment of preferably 8.0 × 10 ⁻¹² Pa ⁻¹ or less, more preferably 6.0 × 10 ⁻¹² Pa ^−1. Hereinafter, it is more 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 therefore, when used in a liquid crystal display device or the like, there is a tendency that contrast and screen uniformity are excellent.

Note that the “photoelastic coefficient” is a coefficient C _R [Pa ⁻¹ ] representing the ease with which birefringence changes due to external force, and is defined by the following equation.
C _R = Δn / σ _R
Here, σ _R is extensional stress [Pa], Δn is birefringence when stress is applied, and Δn is defined by the following equation.
Δn = n ₁ −n ₂
(Where n ₁ is the refractive index in the direction parallel to the stretching direction, and n ₂ is the refractive index in the direction perpendicular to the stretching direction.)

The optical film of one embodiment of the present invention has a thickness of preferably 100 μm or less, more preferably 10 μm or more and 90 μm or less, further 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 an optical film used around a liquid crystal display is used, the thickness is preferably 100 μm or less from the viewpoint of bending strength.

The optical film of one embodiment of the present invention is not particularly limited by the values of the in-plane direction retardation (Re), the thickness direction retardation (Rth), and the Nz coefficient. In-plane direction retardation (Re), thickness direction retardation (Rth) and Nz coefficient are the composition ratio of the material constituting the (meth) acrylic resin composition, film thickness, stretching temperature, stretching ratio, stretching speed. These can be controlled by appropriately setting the above.
Here, the in-plane direction retardation (Re), the thickness direction retardation (Rth), and the Nz coefficient are defined by the following equations.
_{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: x-direction of the refractive index in the case where the direction in which the refractive index in the film plane is maximized and the x, n _y: y when a direction perpendicular to the x direction in the film plane is y Refractive index in the direction, _nz : refractive index in the film thickness direction, d: film thickness (nm).)

When the film of one embodiment of the present invention is used as a protective film for a polarizing plate, the absolute value of the thickness direction retardation (Rth) is preferably 20 nm or less, more preferably 15 nm or less, and 5 nm. More preferably, it is as follows. When the absolute value of Rth exceeds 20 nm, the displacement due to the incident angle of retardation becomes large, which may cause problems such as a decrease in contrast in the liquid crystal display device.

The film of one embodiment of the present invention is subjected to surface functionalization treatment such as antiglare treatment, antireflection treatment, transparent conductive treatment, electromagnetic wave shielding treatment, gas barrier treatment, hard coat treatment, antistatic treatment, and antifouling treatment. You may give suitably.
When using the film of one Embodiment of this invention as a protective film for polarizing plates, an antistatic function can be provided by surface treatment. Moreover, you may provide an antistatic function to other members, such as an adhesive layer incorporated in an optical film as needed.

When anti-glare treatment is applied to the film, the effects of improving visibility, preventing reflection of external light, and reducing moire due to light interference are exhibited. By the antiglare treatment, a layer having a fine uneven shape on the film surface, that is, an antiglare layer is formed. A hard coat material is preferably used for forming the antiglare layer. The thickness of the antiglare layer is not particularly limited, but is preferably 2 μm or more and 30 μm or less, more preferably 3 μm or more and 20 μm or less. If the thickness of the antiglare layer is too thin, sufficient hardness cannot be obtained, and the surface tends to be easily damaged. On the other hand, if the antiglare layer is too thick, the film tends to break or the film curls due to cure shrinkage of the antiglare layer, and the productivity tends to decrease.

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

[Polarizer]
The polarizing plate according to the present invention has a polarizing film and a film according to the present invention bonded to at least one surface thereof.
The polarizing film used in the present invention is not particularly limited. The polarizing film can be obtained, for example, by adding iodine, dye, or the like to polyvinyl alcohol, forming the film into a film, stretching the film, and molecularly orienting the film.
If 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, the film should be bonded so that the functional layer is on the surface away from the polarizing film. preferable.
Depending on the characteristics required for the polarizing plate, the film of the present invention may be bonded to both surfaces of the polarizing film, the film of the present invention is bonded to one surface of the polarizing film, and the other surface of the polarizing film is bonded. A film made of another resin may be bonded.

The method for laminating the polarizing film and the film of the present invention is not particularly limited. For example, bonding can be performed using an adhesive containing an epoxy resin, a urethane resin, a cyanoacrylate resin, an acrylamide resin, or the like.

Prior to bonding the polarizing film and the film of the present invention, one or both of the bonded surfaces may be subjected to corona discharge treatment or the like. By performing the corona discharge treatment, the adhesive force between the film of the present invention and the polarizing film can be increased. The corona discharge treatment is a treatment for activating the resin film disposed between the electrodes by discharging by applying a high voltage between the electrodes. The effect of corona discharge treatment varies depending on the type of electrode, electrode spacing, voltage, humidity, type of resin film used, etc. For example, the electrode spacing is set to 1 to 5 mm and the moving speed is set to about 3 to 20 m / min. It is preferable to do this. Next, the adhesive as described above is applied to the corona discharge treated surface, and both films are bonded together.

The present invention will be described more specifically with reference to the following examples. In addition, this invention is not restrict | limited by a following example. In addition, the present invention includes all aspects that are obtained by arbitrarily combining the above-described items representing technical characteristics such as characteristic values, forms, manufacturing methods, and uses.
The measurement of the physical property values in the examples was carried out by the following method.

<Moisture measurement>
Moisture measurement was performed using a Karl Fischer (KMA-210) manufactured by Kyoto Electronics Industry Co., Ltd.

<Polymerization conversion>
Shimadzu Gas Chromatograph GC-14A is connected to GL Sciences Inc. INERT CAP 1 (df = 0.4 μm, 0.25 mm ID × 60 m) as a column, the injection temperature is set to 180 ° C., and the detector temperature is set. The column temperature was set to 180 ° C., 60 ° C. (holding for 5 minutes) → temperature increase rate 10 ° C./min→200° C. (holding for 10 minutes).

<Measurement of load deflection temperature>
Measurement was performed according to JIS-K7191.

<Film appearance>
The resin composition was extruded with an optical control system company counter (model FS-5) at a cylinder and T-die temperature of 260 ° C. and a lip gap of 0.5 mm, adjusted to a film thickness of 75 μm, and defects were detected. Among the detected transparent defects, the defects that were not stained with osmium tetroxide were regarded as unmelted. The relative number of defects was evaluated according to the following criteria.
◯: Number of unmelted bumps is less than 50% of the number of unmelted bumps of Example 1 (Table 2) or Example 12 (Table 3) Δ: Number of unmelted bumps is Example 1 (Table 2) or Example 12 (Table 3) 50% or more and less than 100% of the number of unmelted butts x: 100% or more of the number of unmelted butts of Example 1 (Table 2) or Example 12 (Table 3)

<Measurement of film thickness>
The thickness of the central part of each film was measured using a micrometer (manufactured by Mitutoyo Corporation).

<Measurement of haze>
Measurement was performed according to JIS-K7136. Haze was measured for a film immediately after molding and a film after being left in an environment of a temperature of 85 ° C. and a relative humidity of 85% for 100 hours.

<Trouser tear test>
The measurement was performed according to JIS-K7128.

Synthesis Example 1 Production of Block Copolymer (B-1) (1) 640 ml of toluene and 0.009 ml of 1,2-dimethoxyethane were put into a 1.5 liter autoclave vessel equipped with a stirrer and purged with nitrogen for 20 minutes. Went. Thereto was added 2.86 ml of a cyclohexane solution of 1.3 mol / l sec-butyllithium, then 72.6 ml of 1,3-butadiene, and reacted at 30 ° C. for 1.5 hours. A reaction mixture containing a polymer was obtained. As a result of sampling analysis of a part of the obtained reaction mixture, the 1,3-butadiene polymer in the reaction mixture has a number average molecular weight (Mn) of 24,000 and a molecular weight distribution (Mw / Mn) of 1.06. The amount of side chain vinyl bonds was 30 mol%.

(2) The reaction mixture obtained in (1) above is cooled to −30 ° C., and toluene containing 0.45 mol / l isobutylbis (2,6-di-t-butyl-4-methylphenoxy) aluminum 27.5 ml of the solution and 6.5 ml of 1,2-dimethoxyethane were added and stirred for 10 minutes to obtain 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 polymerized at −30 ° C. for 1 hour. A part of the obtained reaction mixture was sampled and analyzed for molecular weight by GPC (polystyrene conversion). As a result, the butadiene-n-butyl diblock copolymer (arm polymer block) in the reaction mixture had a number average molecular weight. The weight average molecular weight / number average molecular weight ratio (Mw / Mn) was 1.02.

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

(5) A part of the reaction mixture obtained in the above (4) was extracted and precipitated with methanol. The obtained star-shaped block copolymer (B-1) comprises a polymer block (b) comprising 1,3-butadiene units (46) by mass and a polymer block (a) 54 comprising n-butyl acrylate units. A star-shaped block comprising a diblock copolymer consisting of mass% as an arm polymer block, having a number average molecular weight (Mn) of 210,000 (number of arms = 5.1) and Mw / Mn of 1.16 The copolymer contained 56% by mass (a ratio calculated from the area ratio of GPC). Table 1 shows the characteristics of the star block copolymer (B-1). In the table, BA means n-butyl acrylate, and BD means 1,3-butadiene.

(6) To the reaction mixture obtained in (4) above, 1000 g of water was added and shaken to extract impurities contained in the reaction mixture with water. After shaking, the mixture was allowed to stand and separated into a toluene solution of the block copolymer (B-1) and an aqueous phase, and the aqueous phase was removed. This operation was repeated 4 times.

(7) A toluene solution of the block copolymer (B-1) from which impurities have been removed by the extraction is heated to 80 ° C., and a portion of the toluene is distilled off under reduced pressure. The toluene concentration of the block copolymer (B-1) was obtained by adjusting the coalescence concentration to 30% by mass.

<< Synthesis Example 2 >> Production of Block Copolymer (B-2) A 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 had a number average molecular weight (Mn) of 24,000, a molecular weight distribution (Mw / Mn) of 1.06, and a side chain vinyl bond content of 30 mol%. The butadiene-n-butyl acrylate diblock copolymer had a number average molecular weight of 41,000 and a weight average molecular weight / number average molecular weight ratio (Mw / Mn) of 1.02.

Synthesis Example 3 Production of Block Copolymer (B-3) Same as 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. A star block copolymer (B-3) was produced by this method. The obtained star-shaped block copolymer (B-3) comprises 45% by mass of a polymer block (b) composed of 1,3-butadiene units and a polymer block (a) 55 composed of n-butyl acrylate units. A star block copolymer comprising a diblock copolymer consisting of mass% as an arm polymer block, having a number average molecular weight (Mn) of 210,000 (number of arms = 5.1) and Mw / Mn of 1.16. It contained 56% by mass of the polymer (a ratio calculated from the area ratio of GPC).
The 1,3-butadiene polymer produced during the production had a number average molecular weight (Mn) of 23,000, a molecular weight distribution (Mw / Mn) of 1.06, and a side chain vinyl bond content of 30 mol%. . The butadiene-n-butyl acrylate diblock copolymer produced during the production has a number average molecular weight of 41,000, and the weight average molecular weight / number average molecular weight ratio (Mw / Mn) is 1.02. there were.

<< Synthesis Example 4 >> Production of Block Copolymer (B-4) A 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 had a number average molecular weight (Mn) of 23,000, a molecular weight distribution (Mw / Mn) of 1.06, and a side chain vinyl bond content of 30 mol%. The butadiene-n-butyl acrylate diblock copolymer had a number average molecular weight of 41,000 and a weight average molecular weight / number average molecular weight ratio (Mw / Mn) of 1.02.
Table 1 shows properties of the block copolymers (B-1), (B-2), (B-3) and (B-4).

(Example 1)
In an autoclave equipped with a stirrer and a sampling tube, 60 parts by mass of methyl methacrylate, 33 parts by mass of a 30% by mass toluene solution of the star block copolymer (B-1), and 7 parts by mass of toluene were charged and mixed. Thereafter, 0.03 part by mass of 1,1-bis (t-butylperoxy) cyclohexane and 0.2 part by mass of n-dodecyl mercaptan were added and dissolved uniformly to obtain a polymerization reaction solution. Nitrogen expelled oxygen in the reaction system. A portion of this polymerization reaction solution was collected, and the water content measured by Karl Fischer was 1200 ppm.
The polymerization reaction liquid was heated to 115 ° C. and solution polymerization was performed for 2.5 hours. The reaction solution was collected from the collection tube. The reaction solution had a polymerization conversion of 60% by mass as measured by gas chromatography.

Next, 0.08 part by mass of 1,1-bis (t-butylperoxy) cyclohexane was added to the reaction solution, and solution polymerization was performed at 120 ° C. for 2 hours to obtain a reaction solution (d-1). The polymerization conversion rate of the reaction liquid (d-1) measured by gas chromatography was 95% by mass. The reaction solution (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 with a lab plast mill, and a flat plate having a thickness of 4 mm was obtained by hot pressing. A predetermined test piece was cut out from the flat plate, and the load deflection temperature was measured. The evaluation results are shown in Table 2.

The dried (meth) acrylic resin composition was pelletized using a twin-screw extruder KZW20TW-45MG-NH-600 manufactured by Technobel Co., Ltd., and film formation was performed. The evaluation results are shown in Table 2.

(Example 2)
An (meth) acrylic resin composition was obtained in the same manner as in Example 1 except that an adsorbent (Mizusawa Chemical Industry Co., Ltd .: Mizuka Sieves) was added to the polymerization reaction solution to adsorb moisture, and then the adsorbent was removed with a 2 μm filter. . The water content of the polymerization reaction solution as measured by Karl Fischer was 250 ppm. Film forming was performed 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)
An autoclave equipped with a stirrer and a sampling tube was charged with 66.7 parts by weight of methyl methacrylate, 11.1 parts by weight of a 30% by weight toluene solution of the star block copolymer (B-1), and 22.2 parts by weight of toluene. Mixed. Thereafter, 0.03 part by mass of 1,1-bis (t-butylperoxy) cyclohexane and 0.2 part by mass of n-dodecyl mercaptan were added and dissolved uniformly. Oxygen in the reaction system was removed with nitrogen. A portion of this polymerization reaction solution was collected, and the water content measured by Karl Fischer was 500 ppm. The polymerization reaction solution was heated to 115 ° C. and subjected to solution polymerization for 2.5 hours. The reaction solution was collected from the collection tube. The reaction solution had a polymerization conversion of 60% by mass as measured by gas chromatography. Film forming was performed in the same manner as in Example 1 except that the obtained (meth) acrylic resin composition was used.

(Example 4)
Evaluation was performed 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)
An autoclave equipped with a stirrer and a sampling tube was charged with 42.9 parts by mass of methyl methacrylate, 27.1 parts by mass of star-shaped block copolymer (B-1), and 30 parts by mass of toluene. Solution. Thereafter, 0.03 part by mass of 1,1-bis (t-butylperoxy) cyclohexane and 0.2 part by mass of n-dodecyl mercaptan were added and dissolved uniformly. Oxygen in the reaction system was removed with nitrogen. A portion of this polymerization reaction solution was collected, and the water content measured by Karl Fischer was 300 ppm. The polymerization reaction solution was heated to 115 ° C. and subjected to solution polymerization for 2.5 hours. The reaction solution was collected from the collection tube. The reaction solution had a polymerization conversion of 60% by mass as measured by gas chromatography. Thereafter, the same operation as in Example 1 was performed.

(Example 6)
In an autoclave equipped with a stirrer and a sampling tube, 61.7 parts by mass of methyl methacrylate, 5.0 parts by mass of methyl acrylate, a toluene solution of the star-shaped block copolymer (B-3) obtained in Synthesis Example 3 11.1. Part by mass and 22.2 parts by mass of toluene were charged and mixed with stirring. Thereafter, 0.03 part by mass of 1,1-bis (t-butylperoxy) cyclohexane and 0.2 part by mass of n-dodecyl mercaptan were added and dissolved uniformly. Oxygen in the reaction system was removed with nitrogen. A portion of this polymerization reaction solution was collected, and the water content measured by Karl Fischer was 400 ppm. Solution polymerization was performed at 115 ° C. for 2.5 hours. The reaction solution was collected from the collection tube. The reaction solution had a polymerization conversion of 60% by mass as measured by gas chromatography. Thereafter, the same operation as in Example 1 was performed.

As shown in Table 2, Examples 1 to 4 in which the ratio of the methyl methacrylate homopolymer (A) and the block copolymer (B) is within the scope of the present invention have lower haze than Example 5.
In addition, Examples 1 to 4 using methyl methacrylate homopolymer (A) have a higher load deflection temperature, that is, heat-resistant temperature, compared to Example 6 using a copolymer of methyl methacrylate and methyl acrylate. .

(Example 7)
A polarizing film having a thickness of about 30 μm was obtained by adsorbing and orienting iodine on polyvinyl alcohol. The film produced in Example 2 was bonded to both surfaces of the polarizing film via an adhesive to obtain a polarizing plate.

(Example 8) Production of (meth) acrylic resin composition (solution polymerization → solution polymerization)
In an autoclave equipped with a stirrer and a sampling tube, 55.5 parts by mass of methyl methacrylate, 5.0 parts by mass of methyl acrylate, 33 parts by mass of a toluene solution of the star-shaped block copolymer (B-3) obtained in Synthesis Example 3 And 7 parts by mass of toluene were charged and mixed with stirring. Thereafter, 0.03 part by mass of 1,1-bis (t-butylperoxy) cyclohexane and 0.2 part by mass of n-dodecyl mercaptan were added and dissolved uniformly. Nitrogen expelled oxygen in the reaction system. An adsorbent (Mizusawa Chemical Industry Co., Ltd .: Mizuka Sieves) was added to this polymerization reaction solution to adsorb moisture. Thereafter, the adsorbent was removed with a 2 μm filter. This polymerization reaction liquid had a water content of 250 ppm as measured by Karl Fischer.
The polymerization reaction solution was heated to 115 ° C. and solution polymerization was performed for 2.5 hours. The polymerization conversion rate was 60% by mass.

Next, 0.08 part by mass of 1,1-bis (t-butylperoxy) cyclohexane was added to the reaction solution, and solution polymerization was performed at 120 ° C. for 2 hours. The polymerization conversion rate was 95% by mass.
This was vacuum dried to remove unreacted monomers and toluene, and a (meth) acrylic resin composition was obtained. The dried (meth) acrylic resin composition was pelletized using a twin-screw extruder KZW20TW-45MG-NH-600 manufactured by Technobell.
Film formation was performed using the pellets. The evaluation results are shown in Table 3.

(Example 9)
Using 100 parts by weight of the pellets obtained in Example 8 and 200 parts by weight of (meth) acrylic resin (C) (parapet EH-S manufactured by Kuraray Co., Ltd.) using a twin-screw extruder KZW20TW-45MG-NH-600 manufactured by Technobell Co., Ltd. And kneaded into pellets.
Film formation was performed using the pellets. The evaluation results are shown in Table 3.

(Example 10)
In an autoclave equipped with a stirrer and a sampling tube, 61.7 parts by mass of methyl methacrylate, 5.0 parts by mass of methyl acrylate, a toluene solution of the star-shaped block copolymer (B-3) obtained in Synthesis Example 3 11.1. Part by mass and 22.2 parts by mass of toluene were charged and mixed with stirring. Thereafter, 0.03 part by mass of 1,1-bis (t-butylperoxy) cyclohexane and 0.2 part by mass of n-dodecyl mercaptan were added and dissolved uniformly. Nitrogen expelled oxygen in the reaction system. The polymerization reaction solution had a water content of 500 ppm as measured by Karl Fischer. Solution polymerization was performed at 115 ° C. for 2.5 hours. The polymerization conversion rate was 60% by mass.
Next, 0.08 part by mass of 1,1-bis (t-butylperoxy) cyclohexane was added to the reaction solution, and solution polymerization was performed at 120 ° C. for 2 hours. The polymerization conversion rate was 95% by mass.
This was vacuum dried to remove unreacted monomers and toluene, and a (meth) acrylic resin composition was obtained. The dried (meth) acrylic resin composition was pelletized using a twin-screw extruder KZW20TW-45MG-NH-600 manufactured by Technobell.
Film formation was performed using the pellets. The evaluation results are shown in Table 3.

(Example 11)
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. (Meth) acrylic resin composition pellets were obtained in the same manner. The reaction solution had a water content of 690 ppm as measured by Karl Fischer. Film formation was performed using the pellets. 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 no adsorbent was added to the polymerization reaction solution. The reaction solution had a water content of 1500 ppm as measured by Karl Fischer. Film formation was performed using the pellets. The evaluation results are shown in Table 3.

(Example 13)
100 parts by mass of the pellets obtained in Example 12 and 200 parts by mass of (meth) acrylic resin (C) (parapet EH-S manufactured by Kuraray Co., Ltd.) were used using a twin-screw extruder KZW20TW-45MG-NH-600 manufactured by Technobell. And pelletized. Film formation was performed using the pellets. The evaluation results are shown in Table 3.

(Example 14)
A pellet of a (meth) acrylic resin composition was obtained in the same manner as in Example 11 except that no adsorbent was added to the polymerization reaction solution. The reaction solution had a water content of 2100 ppm as measured by Karl Fischer. Film formation was performed using the pellets. The evaluation results are shown in Table 3.

As shown in Table 2 and Table 3, Examples 2 to 6 and Examples 8 to 11 in which the water content when polymerizing the (meth) acrylic resin was 1000 ppm or less were the same as Example 1 and Example in which the water content was more than 1000 ppm. It can be seen that defects due to unmelted bumps are reduced as compared with 12-14.

Claims (10)

1. 65-99 parts by mass of a methyl methacrylate homopolymer (A), and a block copolymer having a polymer block (a) comprising (meth) acrylic acid alkyl ester units and a polymer block (b) comprising conjugated diene compound units 1 to 35 parts by mass of the combined (B)
   A (meth) acrylic resin composition containing 100 parts by mass of the total of the methyl methacrylate homopolymer (A) and the block copolymer (B).
2. The block copolymer (B) contains a star-shaped block copolymer,
   The star block copolymer contains an arm polymer block having at least a polymer block (a) and / or a polymer block (b), and is calculated by gel permeation chromatography (GPC). The number average molecular weight in terms of polystyrene
   The (meth) acrylic resin composition according to claim 1, which satisfies [number average molecular weight of star block copolymer] / [number average molecular weight of arm polymer block]> 2.
3. The star block copolymer (B) has the chemical structural formula:
   (Polymer block (b) -polymer block (a)-) _n X
   The (meth) acrylic resin composition according to claim 2, wherein X is a coupling agent residue, and n is a number exceeding 2.
4. The (meth) acrylic resin composition according to any one of claims 1 to 3, further comprising an ultraviolet absorber.
5. An optical member comprising the (meth) acrylic resin composition according to any one of claims 1 to 4.
6. A film comprising the (meth) acrylic resin composition according to any one of claims 1 to 4.
7. The film according to claim 6, which is subjected to an antiglare treatment and / or an antireflection treatment.
8. A polarizing plate having a polarizing film and the film according to claim 6 bonded to at least one surface thereof.
9. A block copolymer (B) having a polymer block (a) composed of a (meth) acrylic acid alkyl ester unit and a polymer block (b) composed of a conjugated diene compound unit is used in an amount of 50% by mass or more and 100% by mass of methyl methacrylate. % To obtain a polymerization reaction solution by dissolving in a monomer mixture (a ′) containing at most
   Subsequently, the manufacturing method of the (meth) acrylic resin composition including superposing | polymerizing a monomer mixture (a ') by making the moisture content in a polymerization reaction liquid into 1000 ppm or less.
10. The method for producing a (meth) acrylic resin composition according to claim 9, wherein the monomer mixture (a ') is 100% methyl methacrylate (including those containing inevitable impurities).