JP6025927B2 - Acrylic film and method for producing the same - Google Patents

Description

The present invention relates to an acrylic film having a low coefficient of thermal expansion and having a small color change due to temperature fluctuation when incorporated in a liquid crystal display device, a method for producing the same, a polarizing plate produced using the film, an optical compensation film, and an antireflection film And a liquid crystal display device.

Acrylic resins represented by polymethylmethacrylate (hereinafter referred to as “PMMA”) have high light transmittance, high hardness, excellent surface gloss, excellent weather resistance, and birefringence is difficult to develop. It is characterized by. Because of these characteristics, it has been applied to light guide plates and plastic lenses.

However, because of its poor mechanical strength and various heat resistance (glass transition temperature, thermal expansion coefficient, etc.), it has been actively used in optical film applications used for liquid crystal display devices, plasma displays, organic EL display devices, etc. It wasn't done.

As acrylic resins that solve these conventional problems, in recent years, acrylic resins having heat resistance (hereinafter referred to as “heat-resistant acrylic resins”) include polymers having hydroxyl groups and ester groups in their molecular chains. A lactone ring-containing polymer obtained by cyclization condensation reaction (for example, Patent Document 1), a polymer containing glutaric anhydride units (for example, Patent Document 2), and a polymer containing maleic anhydride units An acrylic resin having a glass transition temperature higher than the conventional one has been invented (for example, Patent Document 3). However, even with these heat-resistant acrylic films, heat resistance (particularly thermal expansion coefficient) and mechanical strength have not been improved until it can be said that they are sufficient for optical film applications. It is desired.
In particular, among these optical film applications, when these conventional heat-resistant acrylic films are used in liquid crystal display devices, there is a problem of large variations in color when the liquid crystal display devices are used under various temperature conditions. .

JP 2007-63541 A JP 2006-241263 A JP 2007-113109 A JP 2007-297615 A JP 2008-50550 A

The inventor of the present invention caused the variation in color when the liquid crystal display device was used under various temperature conditions because of the dimensional variation of the acrylic film derived from the large thermal expansion coefficient of the conventionally known heat-resistant acrylic film. I found out for the first time.

The first object of the present invention is to provide an acrylic film having a low coefficient of thermal expansion in the MD direction and TD direction and having a small color change due to temperature fluctuation when incorporated in a liquid crystal display device, and a method for producing the same. The second object of the present invention is to provide a polarizing plate, an optical compensation film, an antireflection film and a liquid crystal display device using such an acrylic film.

As a result of intensive research, the present inventors reduced the thermal expansion coefficient of the acrylic film by forming the acrylic film by a specific manufacturing method, and incorporated the heat-resistant acrylic film into the liquid crystal display device. It has been found that the above problem can be solved by imparting dimensional stability against temperature fluctuations. Moreover, it discovered that it could apply without a problem also in a heat resistant acrylic film. That is, this invention solves the said subject with the following structures.

[1] An acrylic film having a thermal expansion coefficient of 40 to 100 ppm / ° C in both the film longitudinal direction (MD) and the width direction (TD) at 40 ° C to 90 ° C.
[2] The acrylic film according to [1], wherein the elastic modulus in the film longitudinal direction (MD) and the width direction (TD) at 25 ° C. is 2500 to 4000 MPa.
[3] The acrylic film as described in [1] or [2], wherein the breaking elongation in the film longitudinal direction (MD) and the width direction (TD) at 25 ° C. is 15 to 55%.
[4] Any of [1] to [3], wherein the acrylic film contains an acrylic polymer including at least one unit selected from a lactone ring unit, a maleic anhydride unit, and a glutaric anhydride unit. An acrylic film according to claim 1.
[5] The acrylic film according to any one of [1] to [4], wherein the film thickness is 20 to 80 μm.
[6] The total light transmittance is 91 to 94%, the in-plane direction retardation (Re) is −3 to 3 nm, and the thickness direction retardation (Rth) is 0 to −15 nm. The acrylic film according to any one of [1] to [5], which is characterized.
[7] In the method for producing an acrylic film including a step of stretching an unstretched acrylic film, the stretching is
MD direction stretching step for stretching in the MD direction under conditions satisfying a stretching temperature Tg-5 to Tg + 30 ° C., a stretching ratio 50 to 300% and a stretching speed 1 to 50% / sec;
A TD direction stretching step for stretching in a TD direction under conditions satisfying a stretching temperature Tg-5 to Tg + 30 ° C., a stretching ratio 50 to 300%, and a stretching speed 1 to 50% / sec;
(Wherein Tg is a glass transition temperature (unit: ° C.) of the acrylic film).
[8] The method for producing an acrylic film according to [7], wherein the MD direction stretching step is performed by passing the film between two pairs of nip rolls satisfying the following conditions A to C.
Condition A: The peripheral speed of the downstream nip roll is faster than the peripheral speed of the upstream nip roll.
Condition B: The temperature between the two pairs of nip rolls is Tg-5 to Tg + 30 ° C.
Condition C: The ratio (L / W) between the gap (L) between the nip rolls and the film width (W) before stretching is more than 2 and 50 or less.
[9] In the TD stretching step, the film end in the TD direction is gripped with a clip and stretched in the TD direction, and the temperature at the TD stretching start portion of the clip is set to Tg-30 ° C to Tg + 10 ° C. The method for producing an acrylic film according to [7] or [8].
[10] The acrylic film production according to any one of [7] to [9], wherein a ratio of a draw ratio in the MD direction / a draw ratio in the TD direction is 0.85 to 1.15. Method.
[11] The acrylic film according to any one of [1] to [6], which is produced by the method for producing an acrylic film according to any one of [7] to [10].
[12] A polarizing plate using the acrylic film according to any one of [1] to [6] or [11].
[13] The polarizing plate according to [12], comprising a cellulose acylate film.
[14] An optical compensation film using the acrylic film according to any one of [1] to [6] or [11].
[15] An antireflection film comprising the acrylic film according to any one of [1] to [6] or [11].
[16] A liquid crystal display device using the acrylic film according to any one of [1] to [6] or [11].

According to the acrylic film of the present invention, it is possible to improve the dimensional stability due to temperature fluctuation of the polarizing plate without impairing the advantages of the conventional acrylic film, and it is possible to suppress color temperature fluctuation of the liquid crystal display device. Furthermore, the acrylic film of the present invention has good optical characteristics such as total light transmittance and retardation, and the color temperature change is further improved particularly when used in a liquid crystal display device for IPS. In addition, since the acrylic film of the present invention has a suitable elongation at break, the reworkability at the time of recycling is improved, and the industrial applicability is high. On the other hand, according to the method for producing an acrylic film of the present invention, it is possible to produce the acrylic film of the present invention having low thermal expansion coefficients in the MD direction and the TD direction and having the above-mentioned good properties.

Hereinafter, the acrylic film of the present invention, the production method thereof, the polarizing plate, the optical compensation film, the antireflection film, the liquid crystal display device and the like will be described in detail.
The description of the constituent elements described below may be made based on typical embodiments of the present invention, but the present invention is not limited to such embodiments. In the present specification, a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.

In the present specification, unless otherwise specified, “acrylic film” represents a methacrylic film and an acrylic film. On the other hand, “(meth) acrylate” represents acrylate and methacrylate, and “(meth) acryl” represents acrylic and methacrylic.

[acrylic resin]
The acrylic resin of the present invention is a resin obtained by polymerizing (meth) acrylic acid or a derivative of (meth) acrylic acid as a main component and a resin containing the derivative, as long as the effects of the present invention are not impaired. It does not specifically limit and a well-known (meth) acrylic-acid type thermoplastic resin can be used. Examples of the (meth) acrylic acid derivative include methacrylic acid esters and acrylic acid esters. Examples of the methacrylic acid ester include cyclohexyl methacrylate, t-butyl cyclohexyl methacrylate, methyl methacrylate and the like. Examples of the acrylic ester include methyl acrylate, ethyl acrylate, butyl acrylate, isopropyl acrylate, and 2-ethylhexyl acrylate.
Examples of other acrylic resins that are derivatives of (meth) acrylic acid include those represented by the following general formula (1).

In the general formula (1), R ¹ and R ² each independently represent a hydrogen atom or an organic residue having 1 to 20 carbon atoms. The organic residue specifically represents a linear, branched or cyclic alkyl group having 1 to 20 carbon atoms.
As the acrylic resin of the present invention, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, n-butyl (meth) acrylate, tert-butyl (meth) acrylate, ( N-hexyl (meth) acrylate, 2-chloroethyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2,3,4,5, (meth) acrylic acid 6-Pentahydroxyexyl and 2,3,4,5-tetrahydroxypentyl (meth) acrylate are preferred, and methyl (meth) acrylate (hereinafter also referred to as MMA) is more preferred from the viewpoint of excellent thermal stability. The acrylic resin of the present invention is a copolymer of at least one acrylic resin and another resin, whether it is a single polymer of acrylic resin or a copolymer of two or more acrylic resins. It may be a copolymer of an acrylic resin and a copolymer of other resins from the viewpoint of improving the dimensional stability of the polarizing plate due to temperature fluctuations and reducing the color change of the liquid crystal display device. preferable.

(Copolymerization component)
As monomers other than the acrylic resin copolymerizable with the acrylic resin of the present invention, styrene and o-methylstyrene, p-methylstyrene, 2,4-dimethylstyrene, o-ethylstyrene, p-ethylstyrene, p -Aromatic vinyl compounds such as nuclear alkyl-substituted styrene such as tert-butylstyrene, α-alkyl-substituted styrene such as α-methylstyrene and α-methyl-p-methylstyrene, and vinyl cyanides such as acrylonitrile and methacrylonitrile. , Maleimides such as N-phenylmaleimide and N-cyclohexylmaleimide, lactone ring units, glutaric anhydride units, unsaturated carboxylic anhydrides such as maleic anhydride, unsaturated acids such as maleic acid, glutarimide units, etc. Is mentioned. Among these, N-substitution such as N-phenylmaleimide, N-cyclohexylmaleimide, N-methylmaleimide and the like from the viewpoint of improving the dimensional stability of the polarizing plate due to temperature fluctuation and reducing the color change of the liquid crystal display device. A maleimide, lactone ring unit, glutaric anhydride unit, maleic anhydride unit, glutarimide unit and the like are preferable, and a lactone ring unit, maleic anhydride unit or glutaric anhydride unit is more preferable. That is, the glass transition temperature (hereinafter also referred to as Tg) of the acrylic film of the present invention is a TAC film (triacetyl cellulose film generally used when incorporated in a polarizing plate, for example, Fuji Film T.Fujitac T When the Tg is the same as that of -60, the dimensional stability of the polarizing plate due to temperature fluctuations can be further improved, and the color change start temperature of the liquid crystal display device can be improved.

From the viewpoint of improving the dimensional stability of the polarizing plate due to temperature fluctuation and reducing the color change of the liquid crystal display device, the glass transition temperature is high and the heat resistance is high, the lactone ring unit, maleic anhydride unit or glutaric acid. An anhydride unit is preferably included, and at least one unit of a lactone ring unit, a maleic anhydride unit or a glutaric anhydride unit is more preferably included.

(Lactone ring unit)
By forming a lactone ring structure in the molecular chain of the polymer (also called the main chain in the main skeleton of the polymer), high heat resistance is imparted to the acrylic resin as the copolymer, and Tg is Since it becomes high, it is preferable. Moreover, it is preferable that the reaction rate of the cyclization condensation reaction which introduce | transduces a lactone ring structure is high enough from a viewpoint of heat resistance improvement and the foam at the time of film manufacture, and silver streak suppression.

In the present invention, the lactone ring unit used for copolymerization with the acrylic resin is not particularly limited, but JP-A-2007-297615, JP-A-2007-63541, JP-A-2007-70607, JP-A-2007-. JP, 100044, JP 2007-254726, JP 2007-254727, JP 2007-261265, JP 2007-293272, JP 2007-297619, JP 2007-316366, JP 2008-9378. And JP-A-2008-76764. In addition, these do not limit this invention, These can be used individually or in combination of 2 or more types.

The structure of the lactone ring unit in the main chain is preferably a 4- to 8-membered ring, more preferably a 5- to 6-membered ring, and particularly preferably a 6-membered ring in terms of structural stability. When the structure of the lactone ring unit in the main chain is a 6-membered ring, the structure represented by the following general formula (2), the structure represented by JP 2004-168882 A, and the like can be mentioned. The point of high polymerization yield when synthesizing the polymer before introducing the structure of the lactone ring unit, the point that it is easy to obtain a polymer with a high content ratio of the lactone ring structure at a high polymerization yield, methyl methacrylate, etc. The structure represented by the following general formula (2) is particularly preferred because of good copolymerizability with the (meth) acrylic acid ester.

In said general formula (2), R < ¹¹ > -R < ¹³ > represents a hydrogen atom or a C1-C20 organic residue each independently.
The organic residue is not particularly limited as long as it has 1 to 20 carbon atoms, and examples thereof include a linear or branched alkyl group, a linear or branched alkylene group, an aryl group, and an -OAc group. , -CN group and the like. The organic residue may contain an oxygen atom.
R ^{11 to} R ¹³ preferably have 1 to 10 carbon atoms, and more preferably 1 to 5 carbon atoms.

The method for producing the lactone ring unit-containing acrylic resin is not particularly limited. Preferably, after obtaining a polymer having a hydroxyl group and an ester group in the molecular chain by a polymerization step, the obtained polymer is subjected to a heat treatment. Thus, a lactone ring-containing polymer can be obtained by performing a lactone cyclization condensation step for introducing a lactone ring structure into the polymer.

(Maleic anhydride unit)
By forming the maleic anhydride structure in the molecular chain of the polymer (in the main skeleton of the polymer), it is preferable because the acrylic resin as the copolymer is given high heat resistance and Tg is also increased.

In the present invention, the maleic anhydride unit used for copolymerization with the acrylic resin is not particularly limited, but JP-A No. 2007-113109, JP-A No. 2003-292714, JP-A No. Hei 6-279546, and JP-A No. 2007. JP-A No.-51233, JP-A No. 2001-270905, JP-A No. 2002-167694, JP-A No. 2000-302988, JP-A No. 2007-111110, JP-A No. 2007-11565, and maleic acid modification Resins can be mentioned. In addition, these do not limit this invention. Among these, the resin described in JP-A-2007-113109 and a maleic acid-modified MAS resin (methyl methacrylate-acrylonitrile-styrene copolymer, for example, Delpet 980N manufactured by Asahi Kasei Chemicals Corporation) can be preferably used. . In addition, these do not limit this invention, These can be used individually or in combination of 2 or more types. In addition, a method for producing an acrylic resin containing a maleic anhydride unit is not particularly limited, and a known method can be used.

The maleic acid-modified resin is not limited as long as the resulting polymer contains maleic anhydride units, and examples thereof include (anhydrous) maleic acid-modified MS resin, (anhydrous) maleic acid-modified MAS resin (methacrylic acid). Methyl-acrylonitrile-styrene copolymer), (anhydrous) maleic acid modified MBS resin, (anhydrous) maleic acid modified AS resin, (anhydrous) maleic acid modified AA resin, (anhydrous) maleic acid modified ABS resin, ethylene-maleic anhydride Examples include acid copolymers, ethylene- (meth) acrylic acid-maleic anhydride copolymers, maleic anhydride grafted polypropylene, and the like.

The maleic anhydride unit has a structure represented by the following general formula (3).

前記一般式（３）中、Ｒ²¹およびＲ²²は、それぞれ独立に、水素原子または炭素数１〜２０の有機残基を表す。
前記有機残基は、炭素数が１〜２０の範囲内であれば特には限定されないが、例えば、直鎖若しくは分岐状のアルキル基、直鎖もしくは分岐状のアルキレン基、アリール基、−ＯＡｃ基、−ＣＮ基などなどが挙げられる。また、有機残基は酸素原子を含んでいてもよい。
前記Ｒ²¹およびＲ²²の炭素数は１〜１０であることが好ましく、１〜５であることがより好ましい。

In the general formula (3), R ²¹ and R ²² each independently represent a hydrogen atom or an organic residue having 1 to 20 carbon atoms.
The organic residue is not particularly limited as long as it has 1 to 20 carbon atoms, and examples thereof include a linear or branched alkyl group, a linear or branched alkylene group, an aryl group, and an -OAc group. , -CN group and the like. The organic residue may contain an oxygen atom.
R ²¹ and R ²² preferably have 1 to 10 carbon atoms, and more preferably 1 to 5 carbon atoms.

In the case where each of R ²¹ and R ²² represents a hydrogen atom, it is preferable to further contain other copolymer components from the viewpoint of adjusting intrinsic birefringence. As such a ternary or higher heat-resistant acrylic resin, for example, methyl methacrylate-maleic anhydride-styrene copolymer can be preferably used.

(Glutaric anhydride unit)
It is preferable because the glutaric acid anhydride structure is formed in the molecular chain of the polymer (in the main skeleton of the polymer), thereby giving high heat resistance to the acrylic resin as the copolymer and increasing Tg. .
In the present invention, the maleic anhydride unit used for copolymerization with an acrylic resin is not particularly limited, but JP-A-2006-241263, JP-A-2004-70290, JP-A-2004-70296, and JP-A-2004. -126546, JP-A-2004-163924, JP-A-2004-291302, JP-A-2004-292812, JP-A-2005-314534, JP-A-2005-326613, JP-A-2005-331728, JP-A-2006- 131898, JP2006-134882, JP2006-206881, JP2006-241197, JP2006-283013, JP2007-118266, JP2007-176982, JP2007-178504 No., JP 2007-197703, JP No. 2008-74918, those described in JP-like WO WO2005 / 105 918 can be used. Among these, those described in JP-A-2008-74918 are more preferable. In addition, these do not limit this invention, These can be used individually or in combination of 2 or more types.

The glutaric anhydride unit has a structure represented by the following general formula (4).

In the general formula (4), R ³¹ and R ³² represent the same or different hydrogen atoms or alkyl groups having 1 to 5 carbon atoms.

R ³¹ and R ³² preferably have 1 to 10 carbon atoms, and more preferably 1 to 5 carbon atoms.

An acrylic resin containing such a glutaric anhydride unit is prepared by using an unsaturated carboxylic acid monomer that gives a glutaric anhydride unit and an unsaturated carboxylic acid alkyl ester monomer as a copolymer, The polymer can be produced by heating in the presence or absence of a suitable catalyst to cause an intramolecular cyclization reaction by dealcoholization and / or dehydration.

(Other copolymer components)
The acrylic resin may have a unit obtained by copolymerizing other monomer components that can be copolymerized within a range not impairing heat resistance. Specific examples of other copolymerizable monomer components include styrene, α-methylstyrene, o-methylstyrene, p-methylstyrene, o-ethylstyrene, p-ethylstyrene, and pt-butylstyrene. Aromatic vinyl monomers such as, vinyl cyanide monomers such as acrylonitrile, methacrylonitrile, ethacrylonitrile, allyl glycidyl ether, styrene-p-glycidyl ether, p-glycidyl styrene, itaconic anhydride, N -Methylmaleimide, N-ethylmaleimide, N-cyclohexylmaleimide, N-phenylmaleimide, acrylamide, methacrylamide, N-methylacrylamide, butoxymethylacrylamide, N-propylmethacrylamide, aminoethyl acrylate, propylamino acrylate Chill, dimethylaminoethyl methacrylate, ethylaminopropyl methacrylate, phenylaminoethyl methacrylate, cyclohexylaminoethyl methacrylate, N-vinyldiethylamine, N-acetylvinylamine, allylamine, methallylamine, N-methylallylamine, p-amino Styrene, 2-isopropenyl-oxazoline, 2-vinyl-oxazoline, 2-acryloyl-oxazoline, 2-styryl-oxazoline, nitrile monomers such as acrylonitrile, vinyl esters such as vinyl acetate, glutarimide units, etc. It is done.

The acrylic resin of the present invention is preferably an acrylic resin containing the lactone ring unit, an acrylic resin containing the maleic anhydride unit, and an acrylic resin containing the glutaric anhydride unit, and the acrylic resin containing the lactone ring unit and the anhydrous An acrylic resin containing a maleic acid unit is more preferable.

Acrylic resins are generally known to be easily decomposed by heat. Acrylic resins containing lactone ring units, acrylic resins containing maleic anhydride units, and acrylic resins containing glutaric anhydride units are general acrylic resins. It is easier to pyrolyze than. On the other hand, an acrylic resin containing a lactone ring unit, an acrylic resin containing a maleic anhydride unit, and an acrylic resin containing a glutaric anhydride unit have physical properties that a general acrylic resin has a high Tg and high light transmittance. Therefore, it is preferable as a material for a liquid crystal display device.

For such an acrylic resin that is easily pyrolyzed, especially an acrylic resin that contains a lactone ring unit that is more easily pyrolyzed, an acrylic resin that contains a maleic anhydride unit, and an acrylic resin that contains a glutaric anhydride unit. According to the method for producing an acrylic film of the invention, an acrylic film having Re and Rth within a preferable range of the present invention can be obtained. That is, when forming a film using a resin that is easily pyrolyzed, it is necessary to form a film with a high viscosity because the melting temperature cannot be raised. It is easy to stretch with a large force or to apply a gap between the touch and chill roll with a large force. As a result, the conventional methods for producing an acrylic film exceed the preferable ranges of Re and Rth. On the other hand, by using the method for producing an acrylic film of the present invention, it is possible to obtain the acrylic film of the present invention controlled to a suitable range of Re and Rth from a high viscosity acrylic resin.

As for the acrylic resin of this invention, what contains 30 mol% or more of MMA units (monomer) in all the monomers which comprise an acrylic resin is preferable, and what contains 30-80 mol% is more preferable. In addition to MMA, at least one unit of a lactone ring unit, a maleic anhydride unit or a glutaric anhydride unit is more preferable. The lactone ring unit, maleic anhydride unit and glutaric anhydride unit are preferably contained in 5 mol% to 60 mol% in all monomers constituting the acrylic resin, and may be contained in 10 mol% to 50 mol%. More preferred.

The glass transition temperature (Tg) of the acrylic resin of the present invention is preferably 105 ° C to 170 ° C, more preferably 110 ° C to 160 ° C, and further preferably 115 ° C to 150 ° C. These melt viscosities are preferably 500 Pa · s to 10000 Pa · s, more preferably 800 Pa · s to 7000 Pa · s, and still more preferably 1000 Pa · s to 5000 Pa · s when a 1% strain is applied at 230 ° C. at 1 Hz. It is.

The weight average molecular weight of the acrylic resin of the present invention is preferably in the range of 1,000 to 2,000,000, more preferably in the range of 5,000 to 1,000,000, still more preferably 10,000 to 500. In the range of 50,000, particularly preferably in the range of 50,000 to 500,000.

(Additive)
It is also preferable to use various additives in combination with the acrylic resin of the present invention. Examples of such additives include plasticizers, stabilizers, matting agents, ultraviolet absorbers, infrared absorbers, and retardation adjusting agents.

Examples of the plasticizer include alkyl phthalyl alkyl glycolates, phosphate esters, carboxylic acid esters, and polyhydric alcohols, and among them, phosphate esters from the viewpoint of heat resistance and impact resistance. Carboxylic acid esters are preferred.
The addition amount of the plasticizer is preferably 0 to 20% by mass, more preferably 0 to 15% by mass, and particularly preferably 0 to 10% by mass.

Examples of the stabilizer include phosphite stabilizers (for example, tris (4-methoxy-3,5-diphenyl) phosphite, tris (nonylphenyl) phosphite, tris (2,4-di-tert-butylphenyl) phosphite). Phyto), phenol-based stabilizers (for example, 2,6-di-tert-butyl-4-methylphenol, 2,2-methylenebis (4-ethyl-6-tert-butylphenol), 2,5-di-tert- Butylhydroquinone, pentaerythrityltetrakis [.3- (3,5-di-tert-butyl-4-hydroxyphenyl) propiolate, 4,4-thiobis- (6-tert-butyl-3-methylphenol), 1 , ^1, - bis (4-hydroxyphenyl) cyclohexane, octadecyl-3- (3,5-di -te t- butyl-4-hydroxyphenyl) propiolate], an epoxy compound, may be mentioned thioether compounds, from the viewpoint of heat resistance and thermal coloring Among them, Fenoru based stabilizer is preferred.

The added amount of the stabilizer is preferably 0 to 3% by mass, more preferably 0.1 to 1% by mass, and particularly preferably 0.1 to 0.5% by mass.

Examples of the matting agent include inorganic fine particles such as silica, titania, zirconia, alumina, calcium carbonate, and clay, organic fine particles such as cross-linked acrylic and cross-linked styrene, and Japanese Patent Application Laid-Open Nos. 2008-9378 and 2008-74918. In particular, inorganic fine particles and elastic organic fine particles are preferable from the viewpoint of handling properties.
The addition amount of the matting agent is preferably 0 to 1000 ppm, more preferably 0 to 500 ppm, and particularly preferably 0 to 100 ppm.

As the ultraviolet absorber, a known ultraviolet absorber can be used. For example, 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2,2, -methylenebis [4- (1,1,3 , 3-tetramethylbutyl) -6-[(2H-benzotriazol-2-yl) phenol]] can be preferably used.
The addition amount of the ultraviolet absorber is preferably 0 to 3% by mass, more preferably 0 to 2% by mass, and particularly preferably 0 to 1.5% by mass.

(Other additives)
As other additives, an infrared absorber and a retardation adjusting agent may be added, and these types are not particularly limited. The addition amount of other additives is preferably 0 to 15% by mass, preferably 0 to 10% by mass, and particularly preferably 0 to 8% by mass.

[Acrylic film]
(Retardation)
The birefringence (Re) in the in-plane direction of the acrylic film of the present invention is preferably -3 to 3 nm, more preferably -2 to 2 nm, and particularly preferably -1 to 1 nm. The slow axis of Re may be oriented anywhere, but it is more preferred that it is oriented in the width direction.

The birefringence (Rth) in the thickness direction of the acrylic film of the present invention is preferably 0 to -15 nm, more preferably -1 to -13 nm, and particularly preferably -3 to -10 nm.

Here, Re is measured with KOBRA 21ADH or WR (manufactured by Oji Scientific Instruments Co., Ltd.) by making light having a wavelength of λ nm incident in the normal direction of the film.
When the film to be measured is represented by a uniaxial or biaxial refractive index ellipsoid, Rth is calculated by the following method.
Rth is the Re in-plane slow axis (determined by KOBRA 21ADH or WR) as the tilt axis (rotation axis) (in the absence of the slow axis, any direction in the film plane) The light of wavelength λ nm was incident from each inclined direction in steps of 10 degrees from the normal direction to 50 degrees on one side with respect to the film normal direction of the rotation axis), and a total of 6 points were measured. KOBRA 21ADH or WR is calculated based on the retardation value, the assumed average refractive index, and the input film thickness value.
In the above case, in the case of a film having a direction in which the retardation value is zero at a certain tilt angle with the in-plane slow axis from the normal direction as the rotation axis, retardation at a tilt angle larger than the tilt angle. The value is calculated by KOBRA 21ADH or WR after changing its sign to negative.
The retardation value is measured from two inclined directions with the slow axis as the tilt axis (rotation axis) (if there is no slow axis, the arbitrary direction in the film plane is the rotation axis). Rth can also be calculated from the following formula (A) and formula (B) based on the value, the assumed value of the average refractive index, and the input film thickness value.

なお、上記のＲｅ（θ）は法線方向から角度θ傾斜した方向におけるレターデーション値をあらわす。
また、式（Ａ）におけるｎｘは、面内における遅相軸方向の屈折率を表し、ｎｙは面内においてｎｘに直交する方向の屈折率を表し、ｎｚはｎｘおよびｎｙに直交する方向の屈折率を表す。

Note that Re (θ) represents a retardation value in a direction inclined by an angle θ from the normal direction.
In the formula (A), nx represents the refractive index in the slow axis direction in the plane, ny represents the refractive index in the direction orthogonal to nx in the plane, and nz represents the refraction in the direction orthogonal to nx and ny. Represents a rate.

Rth = ((nx + ny) / 2−nz) × d (Equation (B)
When the film to be measured is a film that cannot be expressed by a uniaxial or biaxial refractive index ellipsoid, that is, a film without a so-called optical axis, Rth is calculated by the following method.
Rth is a step of 10 degrees from −50 degrees to +50 degrees with respect to the normal direction of the film, using Re as an in-plane slow axis (determined by KOBRA 21ADH or WR) as a tilt axis (rotation axis). Then, 11 points of light having a wavelength of λ nm are incident from the inclined direction, and KOBRA 21ADH or WR is calculated based on the measured retardation value, the assumed average refractive index, and the input film thickness value. To do.

In the above measurement, as the assumed value of the average refractive index, values in the polymer handbook (John Wiley & Sons, Inc.) and catalogs of various optical films can be used. If the average refractive index is not known, it can be measured with an Abbe refractometer. The average refractive index values of main optical films are exemplified below: cellulose acylate (1.48), cycloolefin polymer (1.52), polycarbonate (1.59), polymethyl methacrylate (1.49), Polystyrene (1.59). By inputting these assumed values of average refractive index and film thickness, KOBRA 21ADH or WR calculates nx, ny, and nz. From the calculated nx, ny, and nz, Nz = (nx−nz) / (nx−ny) is further calculated.

By setting Re and Rth in the above ranges, the viewing angle dependency of the color is lowered, which is preferable.

(Elastic modulus)
The elastic modulus in the film longitudinal direction (MD) and the width direction (TD) at 25 ° C. of the acrylic film of the present invention is preferably 2500 to 4000 MPa, more preferably 2800 to 3800 MPa in both the MD direction and the TD direction. Preferably, both MD direction and TD direction are 2800-3700 MPa. By setting the elastic modulus in the range of 2500 to 4000 MPa in both the MD direction and the TD direction, the elastic modulus is equivalent to that of TAC, and the balance of the mechanical strength on both sides of the polarizing plate is preferable.

(Elongation at break)
The breaking elongation in the film longitudinal direction (MD) and width direction (TD) at 25 ° C. of the acrylic film of the present invention is preferably 15 to 55%, and both MD and TD directions are 20 to 55%. It is more preferable that both the MD direction and the TD direction be 30 to 55%. A conventional acrylic thermoplastic film has an elongation at break of several percent or only in one direction in a range of 15 to 55%, and an elongation in both MD and TD directions of 15 to 55%. The film has not been known so far. By making the breaking elongation in the MD direction and the TD direction both in the above ranges, it becomes possible for the first time to peel off the acrylic film from the polarizing plate or the like without breaking the acrylic film during recycling. That is, it is preferable that the MD direction and the TD direction be 15 to 55% because reworkability at the time of recycling is greatly improved.

(Coefficient of thermal expansion)
In the acrylic film of the present invention, the thermal expansion coefficient in the longitudinal direction (MD) and the width direction (TD) of the acrylic film at 40 to 90 ° C. is preferably 40 to 100 ppm / ° C., and 50 to 100 ppm / ° C. It is more preferable that it is 60-100 ppm / degreeC. Here, the thermal expansion coefficients of a TAC film and a PVA film for general polarizing plates are 40 to 90 ppm / ° C. and 70 to 120 ppm / ° C., respectively. It is preferable to use the acrylic film of the present invention that thermally expands in the same manner as TAC and PVA because the dimensional stability of the polarizing plate due to temperature fluctuation is improved. That is, the acrylic film of the present invention has a thermal expansion coefficient of 40 to 100 ppm / ° C., so that the acrylic film and a polarizing plate having, for example, a TAC film for polarizing plate and a PVA film for a polarizer member are displayed on a liquid crystal display. When incorporated in the apparatus, the color change start temperature can be increased. In addition, the aspect of the polarizing plate using the acrylic film of this invention is not limited to said aspect.

(Total light transmittance)
The total light transmittance of the acrylic film of the present invention is preferably 91 to 94%, and more preferably 92 to 94%. By setting the total light transmittance of the acrylic film in such a range, it is possible to further improve the color when incorporated in a liquid crystal display device.

(Film thickness)
The thickness of the acrylic film of the present invention is preferably 20 μm to 80 μm, preferably 20 μm to 60 μm from the viewpoint of improving the dimensional stability of the polarizing plate due to temperature fluctuations and reducing the color change of the liquid crystal display device. Is more preferable, and 30 to 60 μm is particularly preferable. When the film thickness is 20 to 80 μm and the thickness is equivalent to that of a TAC film generally used in combination with a polarizing plate, the dimensional stability of the polarizing plate is further improved due to temperature fluctuations, and the color change of the liquid crystal display device Can be suppressed more.
The thickness unevenness is preferably 0% to 3% in both the longitudinal direction and the width direction, more preferably 0% to 2%, and still more preferably 0% to 1%.

(Film forming width)
The film forming width of the acrylic film of the present invention is preferably 1.5 m to 4 m, more preferably 1.7 m to 3.5 m, and particularly preferably 1.8 m to 3 m.

[Acrylic film production method]
The acrylic film of the present invention can be produced by the following method. Further, according to the production method of the present invention, the range of the thermal expansion coefficient in the film longitudinal direction and the width direction of the present invention, the preferable range of the elastic modulus in the film longitudinal direction and the width direction, the elongation at break in the film longitudinal direction and the width direction. A range of degrees, film thickness, Re, Rth, and total light transmittance can be achieved.

The method for producing an acrylic film of the present invention includes a step of making an acrylic resin into pellets, a step of charging the pellets into a kneading extruder to obtain a melt, a step of supplying the melt to a die, A step of extruding the melt, and a step of solidifying the melt extruded from the die to form a film.
Below, the manufacturing method of the acrylic film of this invention is demonstrated in detail.

(Melting method)
The acrylic film of the present invention may be produced using a solution casting method or a melt casting method, but is preferably produced by a melt casting method. In the melt film-forming method, a resin and additives are mixed in advance and pelletized, then charged into a kneading extruder to melt to obtain a molten resin (hereinafter also referred to as melt), and the melt is extruded from a die. Cool and solidify on a casting drum to form a film.
In the melt film forming method preferably used in the present invention, it is known that, unlike the solution film forming method, it is generally not preferable to subject the melt extruded from a die immediately before film formation to filtration. In the melt film forming method, the thermal decomposition proceeds while the melted acrylic resin stays in the filter, and therefore, a foreign substance derived from the pyrolyzate is generated in the filter. That is, there is a tendency that foreign matter tends to increase by filtration, and it is not preferable to subject to filtration. Therefore, in order to prevent foreign matter from being generated so much in the acrylic film, it is necessary to produce the acrylic film by a method that does not fundamentally generate foreign material nuclei that cause foreign matter during film production.

(Pelletized)
The acrylic resin and the additive are preferably mixed and pelletized prior to melt film formation.
The pellet was obtained by drying the acrylic resin and the additive to obtain a mixture having a water content of 0.1% or less, and then introducing the mixture into an extruder and melting at 150 ° C. to 300 ° C. It can be obtained by extruding the mixture into noodles, solidifying in air or water and cutting. Further, after melting by an extruder, pelletization may be performed by an underwater cutting method or the like in which the molten mixture is cut while being directly extruded from a die into water.

As the extruder, it is possible to use a single screw extruder, a non-meshing type different direction rotating twin screw extruder, a meshing type different direction rotating twin screw extruder, a meshing type same direction rotating twin screw extruder, or the like. it can. The number of rotations of the extruder is preferably 10 rpm to 1000 rpm, more preferably 20 rpm to 700 rpm. The extrusion residence time in the extruder is preferably from 10 seconds to 10 minutes, more preferably from 20 seconds to 5 minutes.

Preferably the size of the pellets is 10mm ³ ~1000mm ^2, more preferably 30 mm ³ 500 mm ^3.

(Kneading and melting)
It is preferable to reduce the moisture in the pellets prior to melt film formation. A preferable drying temperature is 40 to 200 ° C, more preferably 60 to 150 ° C, and still more preferably 80 ° C to 130 ° C. The moisture content in the pellets after drying is preferably 0.5% by mass or less, and more preferably 0.1% by mass or less. Drying may be performed in air, nitrogen, or vacuum.

The dried pellets are fed into the cylinder through the feed port of the extruder, and are kneaded and melted. The inside of the cylinder is composed of a supply unit, a compression unit, and a metering unit in order from the supply port side. The screw compression ratio of the extruder is preferably 1.5 to 4.5. The ratio of the cylinder length to the cylinder inner diameter (L / D) is preferably 20 to 70. The inner diameter of the cylinder is preferably 30 mm to 150 mm. Furthermore, in order to prevent the molten resin from being oxidized by residual oxygen, it is also preferable to carry out the inside of the extruder in an inert (nitrogen or the like) air flow or while evacuating using a vented extruder.

(filtration)
It is preferable to provide a filtration apparatus incorporating a breaker plate type filtration or a leaf type disk filter for filtering foreign substances in the resin. Filtration may be performed in one stage or multistage filtration. The filtration accuracy is preferably 2 μm to 15 μm, more preferably 3 μm to 10 μm. It is desirable to use stainless steel as the filter medium. As the configuration of the filter medium, a knitted wire, a sintered metal fiber or metal powder (sintered filter medium) can be used, and among them, a sintered filter medium is preferable.

The filtration in the method for producing an acrylic film of the present invention is preferably performed after the raw material is extruded from the screw and before the melt is extruded from the die. This is because filtration of the melt extruded from the die is generally known to cause foreign substances.

(Gear pump)
In order to reduce the fluctuation of the discharge amount and improve the thickness accuracy, it is preferable to provide a gear pump between the extruder and the die. As a result, the resin pressure fluctuation range in the die can be within ± 1%.
In order to improve the quantitative supply performance by the gear pump, a method of controlling the pressure before the gear pump to be constant by changing the number of rotations of the screw can also be used.

(Static mixer)
In order to suppress melt stagnation at the end of the die, it is preferable to install a static mixer in the melt pipe between the extruder and the die.
The static mixer may be installed anywhere in the melt pipe between the extruder and the die, but is preferably installed between the melt filter and the die, and more preferably just before the entrance of the die.
The static mixer preferably has 4 to 50 elements, more preferably 5 to 40 sheets, and still more preferably 6 to 30 sheets. Compared with the central part of the pipe, the vicinity of the pipe wall has a slower melt flow rate and a longer residence time, and foreign substances derived from pyrolysates are likely to be generated. On the other hand, the use of a static mixer promotes the stirring of the melt in the pipe and suppresses the stay of the melt on the pipe wall.
In the static mixer, a rectangular plate twisted from 30 ° to 360 °, more preferably from 60 ° to 240 °, and even more preferably from 80 ° to 200 ° is mounted within the range of the number of sheets along the melt pipe. It is preferable. By passing the melt through the static mixer configured as described above, the melt is rotated and the stirring in the pipe is promoted. The length of such a static mixer per sheet is not particularly limited, but is preferably 0.5 to 10 times the diameter of the melt pipe, more preferably 0.8 to 6 times, and still more preferably 1. 0 to 3 times.
The material of the static mixer is not particularly limited, but it is preferable to use stainless steel, and it is more preferable to apply plating such as hard chrome or tungsten carbide thereon.

(Die)
The molten resin is melted by the extruder configured as described above, and the molten resin is continuously fed to the die via a filter and a gear pump as necessary. The die may be any of a T die, a fish tail die, and a hanger coat die.
The die is preferably adjustable in thickness at intervals of 5 to 50 mm. An automatic thickness adjustment die that calculates downstream film thickness and thickness deviation and feeds back the results to die thickness adjustment is also effective.
In addition to the single layer film forming apparatus, it is also possible to manufacture using a multilayer film forming apparatus.
Thus, the residence time from when the resin enters the extruder through the supply port until it exits from the die is preferably 3 to 40 minutes, more preferably 4 to 30 minutes.

(Die clearance)
In the method for producing an acrylic film of the present invention, the ratio (C / T) of the die lip clearance (C) and the film thickness (T) after film formation is preferably 5 to 30, and preferably 5 to 25. More preferably, it is 5-22.

Moreover, it can control to Re and Rth of the preferable range of the acrylic film of this invention by extruding a melt from die | dye in the said C / T range. The molten resin (melt) is stretched and thinned at the above-mentioned magnification before being solidified after being extruded from the die, and this becomes a residual strain and expresses Re and Rth. By setting the C / T range, the draw ratio can be suppressed, and Re and Rth can be controlled within a preferable range.

(Die center temperature and die end temperature)
In the present specification, the temperature at the center of the die refers to the average value of three points at the center of the temperature measured at 20 points at equal intervals across the entire width of the die lip and the melt pipe.
Further, in this specification, the temperatures at both ends of the die are two points from the ends of the die (total 4 points) among the temperatures measured at 20 points at equal intervals across the entire width of the die lip and the melt pipe. The average value of points.

In the method for producing an acrylic film of the present invention, the temperature at both ends of the die is preferably 0.1 ° C. to 20 ° C. higher than the temperature at the center of the die. The temperature at both ends of the die is more preferably 0.5 ° C to 15 ° C higher than the temperature at the center of the die, and more preferably 1 ° C to 10 ° C. That is, in the die, the path length through which the melt passes through both ends is longer than the path length through which the melt passes through the central portion. For this reason, by heating both ends of the die and lowering the melt viscosity, the fluidity of the melt is increased and the residence time is shortened, thereby reducing the number of foreign matters resulting from thermal decomposition. If the temperature at both ends of the die is higher by 0.5 ° C or more than the temperature at the center of the die, the viscosity of the melt can be sufficiently lowered, and a sufficient effect is produced. Since the thermal decomposition does not proceed excessively, it is preferable because foreign matters are reduced.

In addition, the temperature of die | dye center part is Tg + 70 degreeC-Tg + 170 degreeC, More preferably, it is Tg + 80 degreeC-Tg + 160 degreeC, More preferably, it is Tg + 90 degreeC-Tg + 150 degreeC.
Such temperature adjustment of the temperature at the center of the die and the temperature at both ends of the die can be achieved by attaching heaters divided in the width direction of the die and adjusting the respective temperatures. The preferred number of divisions is 3-20.

(Die temperature and die lip temperature)
In this specification, the temperature of the die refers to the average value of temperatures measured at 10 points at equal intervals over the entire width of the die, at the intermediate point between the die lip and the melt pipe.
In the present specification, the temperature of the die lip refers to an average value of temperatures obtained by measuring the surface temperature of the die lip at 10 points at equal intervals in the die width direction.

In the method for producing an acrylic film of the present invention, the die lip temperature is preferably 1 ° C to 30 ° C higher than the die temperature, more preferably 2 ° C to 26 ° C higher, and 3 ° C to 22 ° C higher. Particularly preferred.

By making the temperature of the die lip higher than the temperature of the die by the above temperature, the temperature of the melt coming out of the die becomes high, and it becomes easy to perform stretching and thinning after coming out of the die. Furthermore, since the melt reaches the cast roll at a high temperature, the measurement angle dependency (α) of the in-plane retardation formed by the cast roll and the touch roll can be easily expressed, and the preferable α range of the acrylic film This is preferable because it can be controlled.

Further, by making the temperature of the die lip higher than the temperature of the die by the above temperature, the acrylic resin melt is slightly pyrolyzed and yellowed, and the wavelength dispersion can be within the range of the acrylic film of the present invention. .

By making the temperature of the die lip higher than the temperature of the die by the above-mentioned temperature, the viscosity of the melt at the die outlet can be lowered, the increase in internal pressure at the die lip can be suppressed, and the expansion can be suppressed.

By making the temperature of the die lip higher than the temperature of the die by the above-mentioned temperature, it is possible to increase the film forming speed and increase the productivity, which is preferable. The problem with high-speed film formation is that when the melt comes into contact with the cast roll, air is brought in, and the melt cannot adhere to the cast roll, increasing the thickness unevenness. For this reason, the viscosity of the melt can be increased by improving the temperature of the die lip by the above temperature from the temperature of the die as described above, and the adhesion to the cast roll can be improved. Such an effect is particularly remarkable in an acrylic resin.

By making the temperature of the die lip 1 ° C. to 15 ° C. higher than the temperature of the die, the above effect can be sufficiently produced, which is preferable. On the other hand, by making the temperature of the die lip 15 ° C. or less higher than the temperature of the die, the thermal decomposition of the acrylic resin is suppressed to an appropriate range, and the foreign matter of 1 μm to 10 mm due to the thermal decomposition is reduced to 3 / m ² or less. This is preferable.

In order to raise the temperature of the die lip, a bar heater can be installed in the vicinity of the die lip. The width of the lip portion to be heated is preferably 0.5 cm to 20 cm, more preferably 1 cm to 10 cm, and still more preferably 1.5 cm to 5 cm.

By such a method, only the vicinity of the lip can be heated, whereby the heating time of the acrylic resin can be minimized, and the generation of foreign matters due to thermal decomposition can be particularly suppressed.

(cast)
The molten resin (melt) extruded from the die onto the sheet is cooled and solidified on a cast roll (hereinafter also referred to as chill roll) to obtain a film.
At this time, it is preferable to shield between the die and the cast roll to suppress the influence of wind.
When the melt contacts the cast roll, it is preferable to increase the adhesion between the cast roll and the melt using an electrostatic application method, an air knife method, an air chamber method, a vacuum nozzle method, a touch roll method, etc. preferable. Such an adhesion improving method may be performed on the entire surface of the melt or may be performed on a part thereof.

(Touch roll method)
In the present invention, the chill roll refers to a cast roll that is first contacted by the melt extruded from the die, and the touch roll refers to a roll that is installed facing the chill roll. It is more preferable to install, and it is particularly preferable that the melt extruded from the die is passed between the touch roll and the chill roll and cooled and solidified while being molded. By using such a touch roll method, the thermal expansion coefficient can be controlled within the range of the present invention. In the following description, the term “cast roll” includes the chill roll and the second and subsequent cast rolls when there are a plurality of cast rolls.

(Touch pressure)
In the present invention, the touch pressure is a value obtained by dividing the force pressing the touch roll by the contact area between the film and the touch roll. The touch pressure is preferably 0.1 MPa to 10 MPa, more preferably 0.3 MPa to 7 MPa, and particularly preferably 0.5 MPa to 3 MPa. In addition, the surface pressure of the touch roll generally used conventionally is about 30 MPa.

(Touch roll)
In order to realize such a weak touch pressure, the touch roll is preferably not elastic and usually elastic. For this purpose, it is necessary to make the outer cylinder thickness of the roll thinner than that of a normal roll, and the outer wall thickness Z is preferably 0.05 mm to 7.0 mm, more preferably 0.2 mm to 5 mm. 0.0 mm, more preferably 0.3 mm to 3.5 mm.

The surface of the touch roll and the cast roll in the method for producing the acrylic film has an arithmetic average height Ra of 100 nm or less, preferably 50 nm or less, more preferably 25 nm or less. By forming the film using such Ra touch roll and cast roll, the acrylic film having appropriate surface irregularities can be formed.
The material of the touch roll and the cast roll is preferably a metal, more preferably stainless steel. Moreover, the touch roll and cast roll which performed metal plating on the surface of the touch roll and cast roll are also preferable. It is preferable that the surface of the touch roll and the cast roll is metal because Ra of the touch roll and the cast roll can be easily set to 100 nm or less.

The touch roll includes, for example, JP-A-11-314263, JP-A-2002-36332, JP-A-11-235747, WO97 / 28950, JP-A-2004-216717, JP-A-2004-216717. The thing of 2003-145609 gazette can be utilized.

More preferably, a plurality of cast rolls are used for slow cooling (of which the touch roll is used so that the first cast roll on the most upstream side (the one closer to the die), that is, the chill roll, is touched. ). In general, 2 to 6 cooling rolls are used relatively well, but this is not a limitation. The diameter of the roll is preferably 100 mm to 1500 mm, more preferably 150 mm to 1000 mm. The interval between the plurality of rolls is preferably 0.3 mm to 300 mm, more preferably 1 mm to 100 mm, and still more preferably 3 mm to 30 mm.

When the melt extruded from the die is solidified on three or more multi-cast cast rolls, it is preferable that the temperature pattern of the cast roll is 1 to 15 ° C. lower than the upstream roll. More preferably, the temperature is lower by 10 ° C to 10 ° C, particularly preferably lower by 2 ° C to 8 ° C.
As described above, by gradually cooling the acrylic film to be formed by setting the temperature distribution of the multiple cast roll, it is possible to promote the improvement of the packing density. Therefore, the humidity expansion coefficient, thermal expansion coefficient, and Ra of the acrylic film obtained can be easily controlled within the scope of the present invention. In addition, when the acrylic film is used as a protective film of the polarizing plate of the present invention, it is possible to make the physical properties of both surfaces of the obtained acrylic film more uniform and to easily eliminate residual strain in the acrylic film. In addition, the dimensional stability against humidity and heat can be improved.

(Cast roll temperature)
When the melt extruded from the die is solidified on the cast roll, the temperature of the touch roll to be used is preferably Tg-30 ° C to Tg + 10 ° C based on Tg of the acrylic resin, and Tg-20 ° C to Tg + 5 ° C. More preferably, it is particularly preferably Tg-10 ° C to Tg. For example, in the case of an acrylic resin that is preferably used in the present invention, the temperature of the touch roll is preferably 60 ° C to 160 ° C, more preferably 70 ° C to 150 ° C, and 80 ° C to 140 ° C. Although it is particularly preferred to do so, they do not limit the invention.
Such temperature control can be achieved by passing a temperature-controlled liquid or gas through these rolls. Thus, what has a temperature control mechanism inside is more preferable. Examples of the temperature control mechanism include a mode in which a touch roll is installed on a metal shaft and a heat medium (fluid) is passed between them, and an elastic layer is provided between the outer cylinder and the metal shaft. And an embodiment in which a heat medium (fluid) is filled between the outer cylinders. In these embodiments, the temperature of the touch roll can be adjusted by adjusting the temperature of the heating medium.

When the melt extruded from the die is solidified on a cast roll, it is preferable to use a touch roll having a temperature in the above range and sandwich the film with a touch pressure in the above range to form a film.

(Film forming speed)
Such a wide film formation can be achieved by forming a film at the film forming speed as described above. In other words, widening the die increases the flow area in the die and tends to disturb the melt flow, but increasing the film forming speed increases the melt speed in the die and causes the melt to stay in the die. Can eliminate the non-uniformity of the flow.

Such an effect is remarkable when the film forming speed is 12 m / min to 50 m / min, more preferably 14 m / min to 40 m / min, and still more preferably 16 m / min to 35 m / min. Normal acrylic melt film formation is performed at a speed of 10 m / min or less, but by forming the film at a high speed as described above, the effect of slippage at the die lip can be expressed more strongly.
When the film forming speed is less than the above range, the effect of such shift is small, and Re and Rth are less than the range of the present invention, which is not preferable. On the other hand, when the film forming rate exceeds the range of the present invention, Re and Rth exceed the range of the present invention, which is not preferable.

Furthermore, Ra of the said acrylic film can be controlled to a preferable range by setting it as the high film forming speed of 12 m / min-50 m / min. By increasing the film forming speed, the melt is pulled at the die lip outlet, the expansion of the melt is suppressed, and the surface unevenness of the acrylic film is controlled within a preferable range by suppressing the friction between the melt and the lip surface. be able to.

Further, by setting the film forming speed as described above, the residence time in the die can be suppressed, and the number of foreign matters can be reduced. If the film forming speed is less than 12 m / min, the residence time in the die increases, which is not preferable. If the film forming speed exceeds 50 m / min, the flow of melt in the die is disturbed, and the uniformity in the film is reduced. When this is done, image distortion occurs, which is not preferable.

(trimming)
It is also preferable to trim both ends after the film is formed in this way. The portion cut off by trimming may be crushed and used again as a raw material.

(Thickening processing)
Further, it is also preferable to perform a thickness increasing process (knurling process) on one or both ends. The height of the unevenness due to the thickness increasing process is preferably 1 μm to 50 μm, more preferably 3 μm to 20 μm. Thickening processing may be convex on both sides or convex on one side. The width of the thickness increasing process is preferably 1 mm to 50 mm, more preferably 3 mm to 30 mm. Extrusion can be performed at room temperature to 300 ° C.

(Winding)
Then, it peels off from a cast roll, winds up after passing through a nip roll. The winding speed is preferably 10 m / min to 100 m / min, more preferably 15 m / min to 80 m / min, still more preferably 20 m / min to 70 m / min.
A preferable winding tension is 2 kg / m width to 50 kg / width, more preferably 5 kg / m width to 30 kg / width.
It is also preferable to attach a laminated film on one side or both sides before winding. The thickness of the laminated film is preferably 5 μm to 100 μm, more preferably 10 μm to 50 μm. The material is not particularly limited, such as polyethylene, polyester, and polypropylene.

(Stretching)
The melt-formed acrylic film is preferably subjected to longitudinal stretching (hereinafter also referred to as MD stretching) and lateral stretching (hereinafter also referred to as MD stretching), and may further be combined with relaxation shrinkage treatment. Thus, by carrying out MD extending | stretching and / or TD extending | stretching of an acrylic film, it can make it easy to control the thermal expansion coefficient of the short side direction and long side direction of an acrylic film to the range of this invention.

(MD direction stretching process)
In the MD direction stretching step in the method for producing an acrylic film of the present invention, stretching is performed in the MD direction at a stretching temperature Tg-5 to Tg + 30 ° C. If the stretching temperature is Tg−5 ° C. or higher, it is preferable because the film does not break before stretching, and if it is Tg + 30 ° C. or lower, the relaxation of the molecular chain is small and the molecules are easily oriented.
The stretching temperature is preferably Tg to Tg + 30 ° C, and more preferably Tg to Tg + 15 ° C.

In the MD direction stretching step in the method for producing an acrylic film of the present invention, stretching is performed in the MD direction at a stretch ratio of 50 to 300%. When the draw ratio is 50% or more, the molecular orientation is preferably increased, and when it is 300% or less, a film can be formed without breaking, which is preferable.
The draw ratio is preferably 70 to 300%, more preferably 100 to 300%.
In addition, the draw ratio as used in the field of this invention is defined by a following formula.
Stretch ratio (%) = 100 × {(Length after stretching) − (Length before stretching)} / (Length before stretching)

In the MD direction stretching step in the method for producing an acrylic film of the present invention, stretching is performed in the MD direction at a stretching speed of 1 to 50% / sec. When the stretching speed is 1% / sec or more, the molecular orientation is preferably increased, and when it is 30% / sec or less, the film can be formed without breaking, which is preferable.
The stretching speed is preferably 2 to 30% / sec, and more preferably 5 to 30% / sec.

The stretching in the MD direction is preferably performed with the TD direction as a free end. By extending | stretching by such a method, stable MD extending | stretching can be performed and a thermal expansion coefficient can be reduced.

Longitudinal stretching can be achieved by installing two pairs of nip rolls and heating the gap between them so that the peripheral speed of the nip roll on the outlet side is higher than the peripheral speed of the nip roll on the inlet side. Under the present circumstances, the expression of the retardation of the thickness direction can be changed by changing the space | interval (L) between nip rolls, and the film width (W) before extending | stretching. When L / W exceeds 2 and is 50 or less (long span stretching), Rth can be decreased, and when L / W is 0.01 to 0.3 (short span stretching), Rth can be increased. In the method for producing an acrylic film of the present invention, L / W is preferably more than 2 and 50 or less, more preferably 5 to 40, and particularly preferably 5 to 20. By extending | stretching by such a method, it can control to the range of preferable Rth in the acrylic film of this invention. Furthermore, stable MD stretching can also be performed, and the thermal expansion coefficient can be lowered within the range of the acrylic film of the present invention.

(TD direction stretching step)
TD direction stretching The above can be carried out using a known method, preferably using a tenter clip. That is, the film is stretched by holding both ends in the width direction with clips and widening the film in the lateral direction. At this time, the stretching temperature can be controlled by sending wind at a desired temperature into the tenter.

In the TD direction stretching step in the method for producing an acrylic film of the present invention, stretching is performed in the TD direction at a stretching temperature Tg-5 to Tg + 30 ° C. If the stretching temperature is Tg−5 ° C. or higher, it is preferable because the film does not break before stretching, and if it is Tg + 30 ° C. or lower, the relaxation of the molecular chain is small and the molecules are easily oriented.
The stretching temperature is preferably Tg to Tg + 30 ° C, and more preferably Tg to Tg + 15 ° C.

In the TD direction stretching step in the method for producing an acrylic film of the present invention, stretching is performed in the TD direction at a stretching ratio of 50 to 300%. When the draw ratio is 50% or more, the molecular orientation is preferably increased, and when it is 300% or less, a film can be formed without breaking, which is preferable.
The draw ratio is preferably 70 to 300%, more preferably 100 to 300%.

In the TD direction stretching step in the method for producing an acrylic film of the present invention, stretching is performed in the TD direction at a stretching speed of 1 to 50% / sec. When the stretching speed is 1% / sec or more, the molecular orientation is preferably increased, and when it is 30% / sec or less, the film can be formed without breaking, which is preferable.
The stretching speed is preferably 2 to 30% / sec, and more preferably 5 to 30% / sec.

The TD stretching is preferably performed using a clip. By stretching by such a method, stable TD stretching can be performed.
The temperature at the beginning of TD stretching of the clip is preferably Tg-30 ° C to Tg + 10 ° C, more preferably Tg-20 to Tg + 5 ° C, and particularly preferably Tg-20 to Tg ° C. If it is Tg-30 degreeC or more, a film does not crack with a clip and it is preferable, and since it is difficult for a film to adhere to a clip and Tg + 10 degrees C or less, the cause of a film breakage is preferable.

(Heat treatment)
By performing preheating before MD stretching or TD stretching, and post-heat treatment after stretching, Re and Rth distribution after stretching can be reduced, and variations in orientation angles associated with bowing can be reduced. Either pre-heating or post-heating may be performed, but both are more preferable. These preheating and post heat treatment are preferably carried out by holding with a clip, that is, carried out continuously with stretching.
The post heat treatment is preferably performed at a temperature lower than the stretching temperature by 1 ° C to 50 ° C, more preferably 2 ° C to 40 ° C, and further preferably 3 ° C to 30 ° C. More preferably, it is less than the stretching temperature and less than Tg. The preheating time is preferably 1 second to 10 minutes, more preferably 5 seconds to 4 minutes, and even more preferably 10 seconds to 2 minutes. During the heat setting, it is preferable to keep the width of the tenter substantially constant. Here, “substantially” refers to 0% (the same width as the tenter width after stretching) to −10% (shrinking by 10% from the tenter width after stretching = reduced width) of the tenter width after stretching. If the width is wider than the stretched width, residual strain tends to occur in the film, which is not preferable.
Preheating is a stretching temperature ± 50 ° C, more preferably a stretching temperature ± 35 ° C, and still more preferably a stretching temperature ± 20 ° C. When the bowing after the post heat treatment is convex in the traveling direction, it is preferably lower than the stretching temperature, and when the bowing is concave in the traveling direction, it is preferably higher than the stretching temperature. The preheating time is preferably 1 second to 10 minutes, more preferably 5 seconds to 4 minutes, and even more preferably 10 seconds to 2 minutes. During preheating, it is preferable to keep the width of the tenter substantially constant. Here, “substantially” refers to ± 10% of the width of the unstretched film.
Thus, it is more preferable that the heat setting temperature <the stretching temperature <the preheating temperature.

Such MD stretching and TD stretching can reduce variations in Re and Rth in the width direction and longitudinal direction, and deviation of the orientation angle from MD (longitudinal direction) or TD (width direction).

(Biaxial stretching)
In the method for producing an acrylic film of the present invention, biaxial stretching is performed by the MD direction stretching step and the TD direction stretching step under the conditions of the stretching temperature, the stretching ratio, and the stretching speed. Surprisingly, the acrylic film of the present invention having a thermal expansion coefficient of 40 to 90 ppm / ° C. in both the MD direction and the TD direction is produced by biaxial stretching under such conditions. Although not bound by any theory, by performing biaxial stretching under such conditions, molecular chains can be oriented without generating microcracks, and an acrylic film having a low thermal expansion coefficient is produced. It is thought that was made. Further, the biaxial stretching in the method for producing an acrylic film of the present invention may be simultaneous biaxial stretching or sequential biaxial stretching.

In the method for producing an acrylic film of the present invention, the ratio of the draw ratio in the MD direction / the draw ratio in the TD direction is preferably 0.85 to 1.15, more preferably 0.95 to 1.10. 0.97 to 1.07 is particularly preferable. If the ratio of the stretching ratio in the MD direction / the stretching ratio in the TD direction is within the above range, it is preferable because a film having a small Re can be produced.

Furthermore, such stretching can reduce variations in Re and Rth in the width direction and longitudinal direction, and deviation of the orientation angle from MD (longitudinal direction) or TD (width direction).

3) Relaxation treatment It is preferable to perform relaxation treatment after longitudinal and transverse stretching. The relaxation treatment is Tg ± 40 ° C., more preferably Tg ± 30 ° C., further preferably Tg ± 20 ° C., and low tension (0.1-10 kg / m, more preferably 0.2-5 kg / m, more preferably 0.3 to 3 kg / m) is preferably 0.1 to 30 minutes, more preferably 0.3 to 15 minutes, and even more preferably 0.5 to 8 minutes. Thereby, heat shrinkage can be suppressed without changing the birefringence (retardation) developed by stretching.

(Film processing)
The acrylic film of the present invention is combined with a functional layer described in detail on pages 32 to 45 in the Japan Society for Invention and Innovation Technical Report (Public Technical Number 2001-1745, published on March 15, 2001, Japan Society for Invention). It is also preferable. Among them, the polarizing plate of the present invention obtained by providing a polarizing layer, the optical compensation film of the present invention obtained by providing an optically anisotropic layer, and the antireflection film of the present invention obtained by providing an antireflection layer are preferable. is there. Moreover, it is also preferable to use these processed films for the liquid crystal display device of the present invention.

[Polarizer]
The polarizing plate of the present invention can be obtained by laminating at least a polarizer (hereinafter also referred to as a polarizing film) on the acrylic film of the present invention. Hereinafter, the polarizing plate of the present invention will be described.

If the polarizing plate of this invention uses the acrylic film and polarizer of this invention, there will be no restriction | limiting in particular in a structure. For example, when the polarizing plate of the present invention is composed of a polarizer and two polarizing plate protective films (transparent polymer film) protecting both surfaces thereof, the acrylic film of the present invention is used as at least one polarizing plate protective film. Can do. Moreover, the polarizing plate of this invention may have an adhesive layer for sticking with another member in the at least one surface. Moreover, in the polarizing plate of this invention, if the surface of the acrylic film of this invention is an uneven | corrugated structure, it will have an anti-glare (anti-glare) function. Further, the polarizing plate of the present invention includes an antireflection film of the present invention in which an antireflection layer (low refractive index layer) is further laminated on the surface of the acrylic film of the present invention, and an optically different surface on the surface of the acrylic film of the present invention. It is also preferable to use the optical compensation film of the present invention in which an anisotropic layer is laminated.

In general, a liquid crystal display device includes four polarizing plate protective films because a liquid crystal cell is provided between two polarizing plates. The acrylic film of the present invention may be used for any of the four polarizing plate protective films, but the acrylic film of the present invention is a protective film disposed between a liquid crystal cell and a polarizing plate in a liquid crystal display device. It can be used particularly advantageously.

As for the polarizing plate of this invention, it is more preferable that a cellulose acylate film, a polarizer, and the acrylic film of this invention are laminated | stacked in this order. Moreover, the structure which the cellulose acylate film, the polarizer, the acrylic film of this invention, and the adhesive layer are laminated | stacked in this order is also more preferable.

(Acrylic film)
The acrylic film of the present invention is used for the acrylic film of the polarizing plate of the present invention. The acrylic film may be surface treated. Examples of the surface treatment method include methods such as corona discharge, glow discharge, UV irradiation, and flame treatment.

(Cellulose acylate film)
As the cellulose acylate film of the polarizing plate of the present invention, a known cellulose acylate film for a polarizing plate is used. For example, a known triacetyl cellulose (TAC) film (for example, Fujitac T-60 manufactured by Fuji Film Co., Ltd.) can be preferably used. The lurose acylate film may be surface treated. Examples of the surface treatment method include saponification treatment.

(Polarizer)
As the polarizer, for example, a film obtained by immersing and stretching a polyvinyl alcohol film in an iodine solution can be used.

As the polarizer used in the present invention, any appropriate one can be selected as long as the object of the present invention can be achieved. Examples of the polarizer include a uniaxially stretched film obtained by adsorbing a dichroic substance such as iodine or a dichroic dye on a hydrophilic polymer film, a dehydrated polyvinyl alcohol product or a dehydrochlorinated polyvinyl chloride product. And polyene-based oriented films. Examples of the hydrophilic polymer film include a polyvinyl alcohol film, a partially formalized polyvinyl alcohol film, and an ethylene / vinyl acetate copolymer partially saponified film. In the present invention, a polarizer in which iodine is adsorbed on a polyvinyl alcohol film is preferable.

In the case of a polarizer in which iodine is adsorbed on a polyvinyl alcohol film, the content of iodine is, for example, in the range of 2.0% by weight to 5.0% by weight, preferably 2 The range is from 0.0 wt% to 4.0 wt%.

The polarizer preferably further contains at least one of potassium and boron. The potassium content of the polarizer is preferably in the range of 0.2% by weight to 1.0% by weight, and more preferably in the range of 0.3% by weight to 0.9% by weight. The boron content of the polarizer is preferably in the range of 0.5% by weight to 3.0% by weight, and more preferably in the range of 1.0% by weight to 2.8% by weight. When the polarizer contains potassium and boron, a polarizer (polarizing plate) having a composite elastic modulus (Er) in a preferable range and having a high degree of polarization can be obtained. For production of a polarizer containing at least one of potassium and boron, for example, a film which is a material for forming a polarizer may be immersed in a solution of at least one of potassium and boron. The solution may also serve as a solution containing iodine.

Any appropriate molding method can be adopted as a method for obtaining the polyvinyl alcohol film. A conventionally known method can be applied as the molding method. Moreover, a commercially available film can be used as it is for the polyvinyl alcohol film. Examples of commercially available polyvinyl alcohol films include the product name “Kuraray Vinylon Film” manufactured by Kuraray Co., Ltd., the product name “Tosero Vinylon Film” manufactured by Tosero Co., Ltd., and the product manufactured by Nippon Synthetic Chemical Industry Co., Ltd. Names include “Nippon Vinylon Film”.

Regarding an example of a method for producing a polarizer, for example, a polymer film (raw film) mainly composed of a polyvinyl alcohol resin is immersed in a swelling bath containing pure water and a dyeing bath containing an aqueous iodine solution. Swelling treatment and dyeing treatment are performed while applying tension in the film longitudinal direction with different rolls. Next, the film subjected to the swelling treatment and the dyeing treatment is immersed in a crosslinking bath containing potassium iodide, and is subjected to crosslinking treatment and final stretching treatment while tension is applied in the longitudinal direction of the film with rolls having different speed ratios. Is given. The film subjected to crosslinking treatment is immersed in a washing bath containing pure water by a roll and subjected to a washing treatment. The film subjected to the water washing treatment is dried and wound up after adjusting the moisture content. Thus, the polarizer can be obtained by stretching the original film, for example, 5 to 7 times the original length.

The polarizer may be subjected to any surface modification treatment in order to improve the adhesion with the adhesive. Examples of the surface modification treatment include corona treatment, plasma treatment, glow discharge treatment, flame treatment, ozone treatment, UV ozone treatment, and ultraviolet treatment. These treatments may be used alone or in combination of two or more.

(Adhesive layer)
The polarizing plate of the present invention may have an adhesive layer as at least one of the outermost layers (such a polarizing plate may be referred to as an adhesive polarizing plate). As a particularly preferred embodiment, a pressure-sensitive adhesive layer for adhering to other members such as other optical films and liquid crystal cells can be provided on the side of the acrylic film where the polarizer is not adhered.

For the formation of the pressure-sensitive adhesive layer, an appropriate pressure-sensitive adhesive can be used such that the deviation of the creep test in which a load of 1 kg is applied for 1 hour at 25 ° C. and a relative humidity of 60% is 100 μm to 800 μm. There are no particular restrictions on the type. Adhesives include rubber adhesives, acrylic adhesives, silicone adhesives, urethane adhesives, vinyl alkyl ether adhesives, polyvinyl alcohol adhesives, polyvinyl pyrrolidone adhesives, polyacrylamide adhesives, Examples thereof include cellulose-based adhesives.

In order to control the creep amount of the pressure-sensitive adhesive layer, for example, by controlling the type of base monomer, copolymerization monomer, the blending ratio, the type of crosslinking agent, the blending amount, the type of additive, the blending amount, etc. It can be carried out. For example, it is effective to adjust the molecular weight of the pressure-sensitive adhesive base polymer, copolymerize monomers having different glass transition temperatures or cohesiveness, or control the degree of crosslinking depending on the amount of the crosslinking agent added.

Among these pressure-sensitive adhesives, those having excellent optical transparency, suitable wettability, cohesiveness, and adhesive pressure-sensitive adhesive properties, and excellent weather resistance and heat resistance are preferably used. An acrylic pressure-sensitive adhesive is preferably used as one exhibiting such characteristics. In particular, those formed of an adhesive containing an acrylic polymer and a crosslinking agent can be suitably used.

The acrylic pressure-sensitive adhesive is based on an acrylic polymer having a monomer unit of (meth) acrylic acid alkyl ester as a main skeleton. The (meth) acrylic acid alkyl ester refers to an acrylic acid alkyl ester and / or a methacrylic acid alkyl ester, and (meth) in the present invention has the same meaning. Examples of the (meth) acrylic acid alkyl ester constituting the main skeleton of the acrylic polymer include linear or branched alkyl groups having 1 to 20 carbon atoms. For example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, (meth) acrylic Illustrative examples include isononyl acid, isomyristyl (meth) acrylate, and lauryl (meth) acrylate. These can be used alone or in combination. The average carbon number of these alkyl groups is preferably 3-9.

Among the acrylic polymers, it is preferable that an acrylic polymer having a monomer unit of (meth) acrylic acid alkyl ester having high hydrophobicity as a main skeleton is used as a base polymer from the viewpoint of controlling the equilibrium moisture content low. In general, (meth) acrylic acid alkyl ester is a linear or branched alkyl group carbon in terms of optical transparency, moderate wettability and cohesion, adhesion, weather resistance and heat resistance. The thing of several 3-9, Preferably the thing of 4-8 is preferably used practically. Among these alkyl groups, the larger the carbon number of the alkyl group, the higher the hydrophobicity, which is preferable for reducing the equilibrium moisture content. Examples of the alkyl (meth) acrylate include butyl (meth) acrylate and isooctyl (meth) acrylate. Among these, isooctyl (meth) acrylate having high hydrophobicity is preferable.

In the acrylic polymer, one or more kinds of copolymerization monomers can be introduced by copolymerization for the purpose of improving adhesiveness and heat resistance. Specific examples of such a copolymerization monomer include, for example, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, (meth) acrylic acid 6 Hydroxyl group-containing monomers such as hydroxyhexyl, 8-hydroxyoctyl (meth) acrylate, 10-hydroxydecyl (meth) acrylate, 12-hydroxylauryl (meth) acrylate and (4-hydroxymethylcyclohexyl) -methyl acrylate Carboxyl group-containing monomers such as (meth) acrylic acid, carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, itaconic acid, maleic acid, fumaric acid and crotonic acid; acid anhydrides such as maleic anhydride and itaconic anhydride Substance-based materials -; Caprolactone adduct of acrylic acid; styrene sulfonic acid, allyl sulfonic acid, 2- (meth) acrylamide-2-methylpropane sulfonic acid, (meth) acrylamide propane sulfonic acid, sulfopropyl (meth) acrylate, (meth) acryloyl Examples thereof include sulfonic acid group-containing monomers such as oxynaphthalenesulfonic acid; and phosphoric acid group-containing monomers such as 2-hydroxyethylacryloyl phosphate.

In addition, (N-substituted) amides such as (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N-butyl (meth) acrylamide, N-methylol (meth) acrylamide, N-methylolpropane (meth) acrylamide, etc. Monomer; Alkylaminoalkyl (meth) acrylate monomers such as aminoethyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, and tert-butylaminoethyl (meth) acrylate; (meth) acrylic (Meth) acrylic acid alkoxyalkyl monomers such as methoxyethyl acid and ethoxyethyl (meth) acrylate; N- (meth) acryloyloxymethylenesuccinimide, N- (meth) acryloyl-6-oxyhexamethylenesuccinimide, N- ( Meta) Acryl Succinimide monomers such as ru-8-oxyoctamethylene succinimide and N-acryloylmorpholine; maleimide monomers such as N-cyclohexylmaleimide and N-isopropylmaleimide, N-laurylmaleimide and N-phenylmaleimide; N-methylitaconimide; Itaconimide-based monomers such as N-ethylitaconimide, N-butylitaconimide, N-octylitaconimide, N-2-ethylhexylitaconimide, N-cyclohexylitaconimide, N-laurylitaconimide, etc. Take an example.

Further, as modifying monomers, vinyl acetate, vinyl propionate, N-vinyl pyrrolidone, methyl vinyl pyrrolidone, vinyl pyridine, vinyl piperidone, vinyl pyrimidine, vinyl piperazine, vinyl pyrazine, vinyl pyrrole, vinyl imidazole, vinyl oxazole, vinyl morpholine, N- Vinyl monomers such as vinylcarboxylic acid amides, styrene, α-methylstyrene, N-vinylcaprolactam; cyanoacrylate monomers such as acrylonitrile and methacrylonitrile; epoxy group-containing acrylic monomers such as glycidyl (meth) acrylate; (Meth) acrylic acid polyethylene glycol, (meth) acrylic acid polypropylene glycol, (meth) acrylic acid methoxyethylene glycol, (meth) acrylic acid meth Glycol acrylic ester monomers such as polypropylene glycol; acrylic acid ester monomers such as tetrahydrofurfuryl (meth) acrylate, fluorine (meth) acrylate, silicone (meth) acrylate and 2-methoxyethyl acrylate may also be used. it can.

Although the ratio of the copolymerization monomer in the acrylic polymer is not particularly limited, it is preferably about 0 to 30%, more preferably about 0.1 to 15% in the weight ratio of all the constituent monomers.

Among these copolymer monomers, a hydroxyl group-containing monomer, a carboxyl group-containing monomer, and an acid anhydride group-containing monomer are preferably used from the viewpoint of adhesion to a liquid crystal cell and durability for optical film applications. These monomers serve as reaction points with the crosslinking agent. Hydroxyl group-containing monomers, carboxyl group-containing monomers, acid anhydride monomers, and the like are preferably used for improving the cohesiveness and heat resistance of the resulting pressure-sensitive adhesive layer because they are highly reactive with intermolecular crosslinking agents. For example, the hydroxyl group-containing monomer is preferably 4-hydroxybutyl (meth) acrylate, more preferably 6-hydroxyhexyl (meth) acrylate, rather than 2-hydroxyethyl (meth) acrylate. It is preferable to use a hydroxyalkyl group having a large alkyl group. When a hydroxyl group-containing monomer is used as a copolymerization monomer, the proportion is preferably 0.01 to 5%, more preferably 0.01 to 3% in the weight ratio of all constituent monomers. Moreover, when using a carboxyl group-containing monomer as a copolymerization monomer, the ratio is 0.01-10% in the weight ratio of all the constituent monomers, Furthermore, it is preferable that it is 0.01-7%.

The average molecular weight of the acrylic polymer is not particularly limited, but the weight average molecular weight is preferably about 100,000 to 2.5 million. The acrylic polymer can be produced by various known methods. For example, a radical polymerization method such as a bulk polymerization method, a solution polymerization method, or a suspension polymerization method can be appropriately selected. As the radical polymerization initiator, various known azo and peroxide initiators can be used. The reaction temperature is usually about 50 to 80 ° C., and the reaction time is 1 to 8 hours. Among the above production methods, the solution polymerization method is preferable, and ethyl acetate, toluene and the like are generally used as the solvent for the acrylic polymer. The solution concentration is usually about 20 to 80% by weight.

The pressure-sensitive adhesive is preferably a pressure-sensitive adhesive composition containing a crosslinking agent. Examples of the polyfunctional compound that can be blended in the pressure-sensitive adhesive include organic crosslinking agents and polyfunctional metal chelates. Examples of the organic crosslinking agent include an epoxy crosslinking agent, an isocyanate crosslinking agent, an imine crosslinking agent, and a peroxide crosslinking agent. These crosslinking agents can be used alone or in combination of two or more. As the organic crosslinking agent, an isocyanate crosslinking agent is preferable. Moreover, an isocyanate type crosslinking agent is used suitably in combination with a peroxide type crosslinking agent. A polyfunctional metal chelate is one in which a polyvalent metal is covalently or coordinately bonded to an organic compound. Examples of polyvalent metal atoms include Al, Cr, Zr, Co, Cu, Fe, Ni, V, Zn, In, Ca, Mg, Mn, Y, Ce, Sr, Ba, Mo, La, Sn, Ti, and the like. can give. Examples of the atom in the organic compound that is covalently or coordinately bonded include an oxygen atom, and the organic compound includes an alkyl ester, an alcohol compound, a carboxylic acid compound, an ether compound, a ketone compound, and the like.

The blending ratio of the base polymer such as the acrylic polymer and the crosslinking agent is not particularly limited, but is usually preferably about 0.001 to 20 parts by weight of the crosslinking agent (solid content) per 100 parts by weight of the base polymer (solid content). Furthermore, about 0.01-15 weight part is preferable. As said crosslinking agent, an isocyanate type crosslinking agent and a peroxide type crosslinking agent are preferable. The peroxide crosslinking agent is preferably about 0.01 to 3 parts by weight, preferably about 0.02 to 2.5 parts by weight, and more preferably 0.05 to 100 parts by weight of the base polymer (solid content). About 2.0 parts by weight is preferable. The isocyanate-based crosslinking agent is preferably about 0.001 to 2 parts by weight, more preferably about 0.01 to 1.5 parts by weight with respect to 100 parts by weight of the base polymer (solid content). Moreover, an isocyanate type crosslinking agent and a peroxide type crosslinking agent can be used in the said range, and can be preferably used in combination of these.

Furthermore, the pressure-sensitive adhesive includes a silane coupling agent, a tackifier, a plasticizer, glass fiber, glass beads, an antioxidant, an ultraviolet absorber, transparent fine particles, and the like, if necessary, and does not depart from the purpose of the present invention. Various additives can be appropriately used within a range.

As the additive, a silane coupling agent is suitable, and the silane coupling agent (solid content) is preferably about 0.001 to 10 parts by weight with respect to 100 parts by weight of the base polymer (solid content). It is preferable to add about 005 to 5 parts by weight. As the silane coupling agent, those conventionally known can be used without particular limitation. For example, epoxy groups such as γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, 2- (3,4 epoxycyclohexyl) ethyltrimethoxysilane -Containing silane coupling agent, 3-aminopropyltrimethoxysilane, N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, 3-triethoxysilyl-N- (1,3-dimethylbutylidene) propylamine Amino group-containing silane coupling agents such as 3-acryloxypropyltrimethoxysilane, (meth) acrylic group-containing silane coupling agents such as 3-methacryloxypropyltriethoxysilane, and isocyanates such as 3-isocyanatopropyltriethoxysilane Base It can be exemplified a silane coupling agent.

Examples of the base polymer of the rubber adhesive include natural rubber, isoprene rubber, styrene-butadiene rubber, recycled rubber, polyisobutylene rubber, styrene-isoprene-styrene rubber, and styrene-butadiene-styrene rubber. Etc. Examples of the base polymer of the silicone-based pressure-sensitive adhesive include dimethylpolysiloxane and diphenylpolysiloxane, and those base polymers into which a functional group such as a carboxyl group is introduced can also be used.

(Production method of polarizing plate)
The manufacturing method of the polarizing plate of this invention is demonstrated.
The polarizing plate of the present invention can be produced by bonding one side of the acrylic film of the present invention (a surface-treated surface in the case of surface treatment) to at least one side of the polarizer using an adhesive. In addition, when the cellulose acylate film, the polarizer, and the acrylic film of the present invention are bonded together in this order, the polarizing plate of the present invention is manufactured by laminating the polarizer and other films using an adhesive on both sides of the polarizer. it can. In the manufacturing method of the polarizing plate of this invention, it is preferable that the acrylic film of this invention is directly bonded with the polarizer.

As the adhesive, a known polarizing plate production adhesive can be used. Moreover, the aspect which has an adhesive bond layer between the said polarizer and each film is also preferable. Specific examples of the adhesive include an aqueous solution of polyvinyl alcohol or polyvinyl acetal (eg, polyvinyl butyral) and a latex of a vinyl-based polymer (eg, polybutyl acrylate). A particularly preferred adhesive is an aqueous solution of fully saponified polyvinyl alcohol. The polyvinyl alcohol-based adhesive preferably contains a polyvinyl alcohol-based resin and a crosslinking agent.

The manufacturing method of the polarizing plate of this invention is not limited to said method, Another method can also be used. For example, JP 2000-171635, JP 2003-215563, JP 2004-70296, JP 2005-189437, JP 2006-199788, JP 2006-215463, JP 2006-227090. JP, 2006-243216, JP 2006-243681, JP 2006-259313, JP 2006-276574, JP 2006-316181, JP 2007-10756, JP 2007-128025, Use methods described in JP 2007-140092, JP 2007-171943, JP 2007-197703, JP 2007-316366, JP 2007-334307, JP 2008-20891, etc. it can. Among these, the methods described in JP-A-2007-316366 and JP-A-2008-20891 are more preferable.

The polarizing plate of the present invention thus obtained is preferably used in a liquid crystal display device, and may be provided on either the viewing side or the backlight side of the liquid crystal cell, or on both sides. Not. Specific examples of the image display device to which the polarizing plate of the present invention can be applied include a self-luminous display device such as an electroluminescence (EL) display, a plasma display (PD), and a field emission display (FED: Field Emission Display). Can be mentioned. The liquid crystal display device is applied to a transmissive liquid crystal display device, a reflective liquid crystal display device, and the like.

[Optical compensation film]
The optical compensation film of the present invention can be obtained by adding an optically anisotropic layer to the acrylic film of the present invention. Hereinafter, the optical compensation film of the present invention will be described.

(Optically anisotropic layer)
The optically anisotropic layer is preferably designed so as to compensate for the liquid crystalline compound in the liquid crystal cell in the black display of the liquid crystal display device. The alignment state of the liquid crystal compound in the liquid crystal cell in black display varies depending on the mode of the liquid crystal display device. The alignment state of the liquid crystal compound in this liquid crystal cell is described in IDW'00, P411 to 414 of FMC7-2, and the like.
The optically anisotropic layer is formed directly from the liquid crystalline compound on the support or from the liquid crystalline compound via an alignment film. The alignment film preferably has a thickness of 10 μm or less.
The liquid crystalline compound used for the optically anisotropic layer includes a rod-like liquid crystalline compound and a discotic liquid crystalline compound. The rod-like liquid crystal compound and the discotic liquid crystal compound may be a high-molecular liquid crystal or a low-molecular liquid crystal, and further include those in which the low-molecular liquid crystal is cross-linked and no longer exhibits liquid crystallinity. The optically anisotropic layer can be formed by applying a liquid crystal compound and, if necessary, a coating liquid containing a polymerizable initiator and optional components on the alignment film. A preferred example of the alignment film of the present invention is described in JP-A-8-338913.

(Bar-shaped liquid crystalline compound)
Examples of rod-like liquid crystalline compounds include azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, benzoic acid esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines, alkoxy-substituted phenylpyrimidines. , Phenyldioxanes, tolanes and alkenylcyclohexylbenzonitriles are preferably used.
The rod-like liquid crystalline compound includes a metal complex. Moreover, the liquid crystal polymer which contains a rod-shaped liquid crystalline compound in a repeating unit can also be used as a rod-shaped liquid crystalline compound. That is, the rod-like liquid crystalline compound may be bonded to a (liquid crystal) polymer.
Regarding rod-like liquid crystalline compounds, for example, Quarterly Chemical Review Vol. 22, Liquid Crystal Chemistry (1994), Chapter 4, Chapter 7 and Chapter 11 of the Chemical Society of Japan, and Liquid Crystal Device Handbook, Japan Society for the Promotion of Science, 142nd Committee The one described in Chapter 3 of the edition can be adopted.
The birefringence of the rod-like liquid crystalline compound is preferably in the range of 0.001 to 0.7.

The rod-like liquid crystalline compound preferably has a polymerizable group in order to fix its alignment state. The polymerizable group is preferably an unsaturated polymerizable group or an epoxy group, more preferably an unsaturated polymerizable group, and most preferably an ethylenically unsaturated polymerizable group.

(Discotic liquid crystalline compounds)
Examples of discotic liquid crystalline compounds include C.I. Benzene derivatives described in a research report of Destrade et al. (Mol. Cryst. 71, 111 (1981)), C.I. Destrode et al. (Mol. Cryst. 122, 141 (1985), Physics lett, A, 78, 82 (1990)) described in The cyclohexane derivatives described in the research report of Kohne et al. (Angew. Chem. 96, 70 (1984)) and M.M. Lehn et al. (JCS, Chem. Commun., 1794 (1985)), J.C. Azacrown-type and phenylacetylene-type macrocycles described in the research report of Zhang et al. (J. Am. Chem. Soc. 116, 2655 (1994)) are included.

The discotic liquid crystalline compound also includes a compound having a structure in which a linear alkyl group, an alkoxy group, and a substituted benzoyloxy group are radially substituted as a side chain of the mother nucleus with respect to the mother nucleus at the center of the molecule. The molecule or the assembly of molecules is preferably a compound having rotational symmetry and imparting a certain orientation. The optically anisotropic layer formed from the discotic liquid crystalline compound does not necessarily require that the compound finally contained in the optically anisotropic layer is a discotic liquid crystalline compound. Also included are compounds having a group that reacts with heat or light and, as a result, polymerized or cross-linked by reaction with heat or light, resulting in a high molecular weight and loss of liquid crystallinity. Preferred examples of the discotic liquid crystalline compound are described in JP-A-8-50206. Moreover, about superposition | polymerization of a discotic liquid crystalline compound, Unexamined-Japanese-Patent No. 8-27284 has description.

In order to fix the discotic liquid crystalline compound by polymerization, it is necessary to bond a polymerizable group as a substituent to the discotic core of the discotic liquid crystalline compound. However, when the polymerizable group is directly connected to the disc-shaped core, it becomes difficult to maintain the orientation state in the polymerization reaction. Therefore, a linking group is introduced between the discotic core and the polymerizable group. Therefore, the discotic liquid crystalline compound having a polymerizable group is preferably a compound represented by the following formula (5).

General formula (5)
D (-LQ) _r
(In General Formula (5), D is a discotic core, L is a divalent linking group, Q is a polymerizable group, and r is an integer of 4 to 12.)

An example of the disk-shaped core (D) is shown below. In each of the following examples, LQ (or QL) means a combination of a divalent linking group (L) and a polymerizable group (Q).

In the general formula (5), the divalent linking group (L) is selected from the group consisting of an alkylene group, an alkenylene group, an arylene group, —CO—, —NH—, —O—, —S—, and combinations thereof. It is preferable that it is a bivalent coupling group. The divalent linking group (L) is a divalent combination of at least two divalent groups selected from the group consisting of an alkylene group, an arylene group, -CO-, -NH-, -O-, and -S-. More preferably, it is a linking group. The divalent linking group (L) is most preferably a divalent linking group in which at least two divalent groups selected from the group consisting of an alkylene group, an arylene group, -CO- and -O- are combined. . The alkylene group preferably has 1 to 12 carbon atoms. The alkenylene group preferably has 2 to 12 carbon atoms. The number of carbon atoms in the arylene group is preferably 6-10.

Examples of the divalent linking group (L) are shown below. The left side is bonded to the discotic core (D), and the right side is bonded to the polymerizable group (Q). AL represents an alkylene group or an alkenylene group, and AR represents an arylene group. The alkylene group, alkenylene group and arylene group may have a substituent (eg, an alkyl group).
L1: -AL-CO-O-AL-,
L2: -AL-CO-O-AL-O-,
L3: -AL-CO-O-AL-O-AL-,
L4: -AL-CO-O-AL-O-CO-,
L5: -CO-AR-O-AL-,
L6: -CO-AR-O-AL-O-,
L7: -CO-AR-O-AL-O-CO-,
L8: -CO-NH-AL-,
L9: -NH-AL-O-,
L10: -NH-AL-O-CO-,

L11: -O-AL-,
L12: -O-AL-O-,
L13: -O-AL-O-CO-,
L14: -O-AL-O-CO-NH-AL-,
L15: -O-AL-S-AL-,
L16: -O-CO-AL-AR-O-AL-O-CO-,
L17: -O-CO-AR-O-AL-CO-,
L18: -O-CO-AR-O-AL-O-CO-,
L19: -O-CO-AR-O-AL-O-AL-O-CO-,
L20: -O-CO-AR-O-AL-O-AL-O-AL-O-CO-,
L21: -S-AL-,
L22: -S-AL-O-,
L23: -S-AL-O-CO-,
L24: -S-AL-S-AL-,
L25: -S-AR-AL-.

The polymerizable group (Q) of the general formula (5) is determined according to the type of polymerization reaction. Examples of the polymerizable group (Q) are shown below.

The polymerizable group (Q) is preferably an unsaturated polymerizable group (Q1, Q2, Q3, Q7, Q8, Q15, Q16, Q17) or an epoxy group (Q6, Q18). More preferably, it is most preferably an ethylenically unsaturated polymerizable group (Q1, Q7, Q8, Q15, Q16, Q17). A specific value of r is determined according to the type of the disk-shaped core (D). In addition, although the combination of several L and Q may differ, it is preferable that it is the same.

In the hybrid alignment, the angle between the major axis (disk surface) of the discotic liquid crystalline compound and the surface of the support, that is, the inclination angle is in the direction of the depth of the optically anisotropic layer (that is, perpendicular to the transparent support). And it increases or decreases as the distance from the plane of the polarizing film increases. The angle preferably increases with increasing distance. Further, the change in the tilt angle can be continuous increase, continuous decrease, intermittent increase, intermittent decrease, change including continuous increase and continuous decrease, or intermittent change including increase and decrease. . The intermittent change includes a region where the inclination angle does not change in the middle of the thickness direction. Even if a region where the angle does not change is included, it may be increased or decreased as a whole. However, it is preferred that the tilt angle changes continuously.

The average direction of the major axis (disk surface) of the discotic liquid crystalline compound (average of the major axis direction of each molecule) is generally selected by selecting the discotic liquid crystalline compound or the material of the alignment film, or selecting the rubbing treatment method. By doing so, it can be adjusted. The major axis (disk surface) direction of the discotic liquid crystalline compound on the surface side (air side) is generally adjusted by selecting the type of additive used together with the discotic liquid crystalline compound or the discotic liquid crystalline compound. be able to.
Examples of the additive used together with the discotic liquid crystalline compound include a plasticizer, a surfactant, a polymerizable monomer and a polymer. The degree of change in the orientation direction of the major axis can also be adjusted by selecting liquid crystalline molecules and additives as described above.

The plasticizer, surfactant and polymerizable monomer used together with the discotic liquid crystalline compound are compatible with the discotic liquid crystalline compound, and can change the tilt angle of the discotic liquid crystalline compound or change the orientation. It is preferable not to inhibit. Among the additive components, addition of a polymerizable monomer (eg, a compound having a vinyl group, a vinyloxy group, an acryloyl group and a methacryloyl group) is preferable. The amount of the compound added is generally in the range of 1 to 50% by mass and preferably in the range of 5 to 30% by mass with respect to the discotic liquid crystalline compound. In addition, when a monomer having 4 or more polymerizable reactive functional groups is mixed and used, adhesion between the alignment film and the optically anisotropic layer can be improved.

The optically anisotropic layer may contain a polymer together with the discotic liquid crystalline compound. The polymer preferably has a certain degree of compatibility with the discotic liquid crystalline compound and can change the tilt angle of the discotic liquid crystalline compound. A cellulose ester can be mentioned as an example of a polymer. Preferable examples of the cellulose ester include cellulose acetate, cellulose acetate propionate, hydroxypropyl cellulose and cellulose acetate butyrate. The addition amount of the polymer is preferably in the range of 0.1 to 10% by mass with respect to the discotic liquid crystalline compound so as not to inhibit the orientation of the discotic liquid crystalline compound, and 0.1 to 8% by mass. More preferably, it is in the range of 0.1 to 5% by mass.
The discotic nematic liquid crystal phase-solid phase transition temperature of the discotic liquid crystalline compound is preferably 70 to 300 ° C, more preferably 70 to 170 ° C.

(Fixing the alignment state of liquid crystalline molecules)
The aligned liquid crystal molecules can be fixed while maintaining the alignment state. The immobilization is preferably performed by a polymerization reaction. The polymerization reaction includes a thermal polymerization reaction using a thermal polymerization initiator and a photopolymerization reaction using a photopolymerization initiator. A photopolymerization reaction is preferred.

(Photopolymerization initiator)
Examples of photopolymerization initiators include α-carbonyl compounds (described in US Pat. Nos. 2,367,661 and 2,367,670), acyloin ethers (described in US Pat. No. 2,448,828), α-hydrocarbon substituted aromatic acyloin compounds ( US Pat. No. 2,722,512), polynuclear quinone compounds (described in US Pat. Nos. 3,046,127 and 2,951,758), a combination of triarylimidazole dimer and p-aminophenyl ketone (described in US Pat. No. 3,549,367), Phenazine compounds (described in JP-A-60-105667 and US Pat. No. 4,239,850) and oxadiazole compounds (described in US Pat. No. 4,221,970) are included.

The amount of the photopolymerization initiator used is preferably in the range of 0.01 to 20% by mass, more preferably in the range of 0.5 to 5% by mass, based on the solid content of the coating solution.
It is preferable to use ultraviolet rays for light irradiation for polymerization of liquid crystalline molecules.
The irradiation energy is preferably in the range of ^{20mJ / cm 2 ~50J / cm 2} , more preferably in the range of ^{20mJ / cm 2 ~5000mJ / cm 2} , a range of 100mJ / cm ² ~800mJ / cm ² More preferably. In order to accelerate the photopolymerization reaction, light irradiation may be performed under heating conditions.
A protective layer may be provided on the optically anisotropic layer.

The optically anisotropic layer is prepared by preparing a coating solution containing at least one of the liquid crystalline compounds and, optionally, an additive such as a polymerizable initiator and a fluorine-based polymer, and applying the coating solution to the alignment film surface. It can be formed by drying.

(Fluorine compounds)
Examples of the fluorine-based compound include conventionally known compounds. Specific examples include the fluorine-based compounds described in paragraphs [0028] to [0056] of JP-A-2001-330725. It is done.

(solvent)
As a solvent used for preparing the coating solution, an organic solvent is preferably used. Examples of organic solvents include amides (eg, N, N-dimethylformamide), sulfoxides (eg, dimethyl sulfoxide), heterocyclic compounds (eg, pyridine), hydrocarbons (eg, benzene, hexane), alkyl halides (eg, , Chloroform, dichloromethane, tetrachloroethane), esters (eg, methyl acetate, butyl acetate), ketones (eg, acetone, methyl ethyl ketone), ethers (eg, tetrahydrofuran, 1,2-dimethoxyethane). Alkyl halides and ketones are preferred. Two or more organic solvents may be used in combination.
When producing an optical compensation film with high uniformity, the surface tension of the coating solution is preferably 25 mN / m or less, and more preferably 22 mN / m or less.

(Method for producing optical compensation film)
The coating liquid can be applied by a known method (eg, extrusion coating method, direct gravure coating method, reverse gravure coating method, die coating method).

Prior to the application of the liquid crystalline compound, it is preferable to rub the surface of the film to be applied. In the rubbing method, a rubbing treatment method widely adopted as a liquid crystal alignment treatment process of LCD can be applied. That is, orientation is obtained by rubbing the surface of the film in a certain direction using paper, gauze, felt, rubber, nylon, or polyester fiber. In general, it is carried out by rubbing several times using a cloth in which fibers having a uniform length and thickness are planted on average. It is preferable to carry out using a rubbing roll in which the roundness, cylindricity, and deflection (eccentricity) of the roll itself are 30 μm or less. The film wrap angle on the rubbing roll is preferably 0.1 to 90 degrees. However, as described in JP-A-8-160430, a stable rubbing treatment can be obtained by winding 360 degrees or more.
When rubbing a long film, the film is preferably transported at a speed of 1 to 100 m / min in a constant tension state by a transport device. The rubbing roll is preferably rotatable in the horizontal direction with respect to the film traveling direction for setting an arbitrary rubbing angle. It is preferable to select an appropriate rubbing angle in the range of 0 to 60 degrees. When used in a liquid crystal display device, 40 to 50 degrees is preferable. 45 degrees is particularly preferable.

[Antireflection film]
By providing an antireflection layer on the acrylic film of the present invention, the antireflection film of the present invention is obtained. The antireflection film generally includes a low refractive index layer which is also an antifouling layer, and at least one layer having a refractive index higher than that of the low refractive index layer (a high refractive index layer and a medium refractive index in the present specification). Layer) on a (transparent) support.

Colloidal metal by multilayer deposition of transparent thin films of inorganic compounds (metal oxides, etc.) with different refractive indexes by chemical vapor deposition (CVD) method, physical vapor deposition (PVD) method, sol-gel method of metal compounds such as metal alkoxides Examples include a method of forming a thin film by post-processing (ultraviolet irradiation: JP-A-9-157855, plasma processing: JP-A-2002-327310) after forming an oxide particle film.
On the other hand, various antireflection films formed by laminating thin films in which inorganic particles are dispersed in a matrix have been proposed as antireflection films with high productivity.
The antireflection film which consists of the antireflection layer which provided the anti-glare property which the antireflection film by application | coating as mentioned above provided the surface of the uppermost layer with the shape of a fine unevenness | corrugation is also mentioned.
The acrylic film of the present invention can be applied to any of the above-mentioned methods, but a coating method (coating type) is particularly preferable.

(Layer structure)
(Transparent) The antireflection film comprising a layer structure of at least a middle refractive index layer, a high refractive index layer, and a low refractive index layer (outermost layer) on the support has a refractive index satisfying the following relationship: Designed.
Refractive index of high refractive index layer> refractive index of medium refractive index layer> refractive index of transparent support> refractive index of low refractive index layer In addition, a hard coat layer is provided between the transparent support and the intermediate refractive index layer. May be. Furthermore, it may consist of a medium refractive index hard coat layer, a high refractive index layer and a low refractive index layer.
Examples thereof include JP-A-8-122504, JP-A-8-110401, JP-A-10-300902, JP-A-2002-243906, JP-A-2000-11706, and the like.

Other functions may be imparted to each layer, for example, an antifouling low refractive index layer or an antistatic high refractive index layer (eg, JP-A-10-206603, JP-A-2002). -243906 publication etc.) etc. are mentioned.

The haze of the antireflection film is preferably 5% or less, more preferably 3% or less. Further, the strength of the film is preferably H or more, more preferably 2H or more, and most preferably 3H or more in a pencil hardness test according to JIS K5400.

(High refractive index layer and medium refractive index layer)
The layer having a high refractive index of the antireflection film is composed of a curable film containing at least an inorganic compound ultrafine particle having a high refractive index having an average particle size of 100 nm or less and a matrix binder.
Examples of the high refractive index inorganic compound fine particles include inorganic compounds having a refractive index of 1.65 or more, preferably those having a refractive index of 1.9 or more. Examples thereof include oxides such as Ti, Zn, Sb, Sn, Zr, Ce, Ta, La, and In, and composite oxides containing these metal atoms.
In order to obtain such ultrafine particles, the surface of the particles is treated with a surface treatment agent (for example, silane coupling agents, etc .: JP-A-11-295503, JP-A-11-153703, JP-A-2000-9908). No., anionic compound or organometallic coupling agent: Japanese Patent Laid-Open No. 2001-310432, etc., core-shell structure with high refractive index particles as a core (Japanese Patent Laid-Open No. 2001-166104, etc.), specific dispersant Combined use (for example, Unexamined-Japanese-Patent No. 11-153703, patent number US62081058B1, Unexamined-Japanese-Patent No. 2002-27776069 etc.) etc. are mentioned.
Examples of the material forming the matrix include conventionally known thermoplastic resins and curable resin films.
Further, it is selected from a polyfunctional compound-containing composition containing at least two radically polymerizable and / or cationically polymerizable groups, an organometallic compound containing a hydrolyzable group, and a partial condensate composition thereof. At least one composition is preferred. Examples thereof include compounds described in JP-A Nos. 2000-47004, 2001-315242, 2001-31871, and 2001-296401.
A curable film obtained from a colloidal metal oxide obtained from a hydrolyzed condensate of metal alkoxide and a metal alkoxide composition is also preferred. For example, it describes in Unexamined-Japanese-Patent No. 2001-293818.
The refractive index of the high refractive index layer is generally 1.70 to 2.20. The thickness of the high refractive index layer is preferably 5 nm to 10 μm, and more preferably 10 nm to 1 μm.
The refractive index of the middle refractive index layer is adjusted to be a value between the refractive index of the low refractive index layer and the refractive index of the high refractive index layer. The refractive index of the middle refractive index layer is preferably 1.50 to 1.70.

(Low refractive index layer)
The low refractive index layer is formed by sequentially laminating on the high refractive index layer. The refractive index of the low refractive index layer is 1.20 to 1.55. Preferably it is 1.30-1.50.
It is preferable to construct as the outermost layer having scratch resistance and antifouling property. As means for greatly improving the scratch resistance, imparting slipperiness to the surface is effective, and conventionally known thin film layer means such as introduction of silicone or introduction of fluorine can be applied.
The refractive index of the fluorine-containing compound is preferably 1.35 to 1.50. More preferably, it is 1.36-1.47. The fluorine-containing compound is preferably a compound containing a crosslinkable or polymerizable functional group containing fluorine atoms in the range of 35 to 80% by mass.
For example, paragraph numbers [0018] to [0026] of Japanese Patent Application Laid-Open No. 9-222503, paragraph numbers [0019] to [0030] of Japanese Patent Application Laid-Open No. 11-38202, and paragraph numbers of Japanese Patent Application Laid-Open No. 2001-40284. [0027] to [0028], JP-A 2000-284102, and the like.
The silicone compound is a compound having a polysiloxane structure, preferably containing a curable functional group or a polymerizable functional group in the polymer chain and having a crosslinked structure in the film. For example, reactive silicone (eg, Silaplane (manufactured by Chisso Corporation), silanol group-containing polysiloxane (Japanese Patent Laid-Open No. 11-258403, etc.) and the like can be mentioned.

The crosslinking or polymerization reaction of the fluorine-containing and / or siloxane polymer having a crosslinking or polymerizable group is carried out at the same time or after the coating composition for forming the outermost layer containing a polymerization initiator, a sensitizer, etc. It is preferable to carry out by light irradiation or heating.
Also preferred is a sol-gel cured film in which an organometallic compound such as a silane coupling agent and a specific fluorine-containing hydrocarbon group-containing silane coupling agent are cured by a condensation reaction in the presence of a catalyst.

For example, a polyfluoroalkyl group-containing silane compound or a partially hydrolyzed condensate thereof (Japanese Patent Laid-Open Nos. 58-142958, 58-147483, 58-147484, Japanese Patent Laid-Open Nos. 9-157582, 11) -106704), silyl compounds containing a poly "perfluoroalkyl ether" group which is a fluorine-containing long chain group (Japanese Patent Application Laid-Open Nos. 2000-117902, 2001-48590, 2002) 53804), and the like.

The low refractive index layer has an average primary particle diameter of 1 to 150 nm such as a filler (for example, silicon dioxide (silica), fluorine-containing particles (magnesium fluoride, calcium fluoride, barium fluoride)) as an additive other than the above. Low refractive index inorganic compounds, organic fine particles described in paragraphs [0020] to [0038] of JP-A-11-3820, etc.), silane coupling agents, slip agents, surfactants, and the like can be contained.
When the low refractive index layer is located below the outermost layer, the low refractive index layer may be formed by a vapor phase method (vacuum deposition method, sputtering method, ion plating method, plasma CVD method, etc.). The coating method is preferable because it can be manufactured at a low cost.
The film thickness of the low refractive index layer is preferably 30 to 200 nm, more preferably 50 to 150 nm, and most preferably 60 to 120 nm.

(Hard coat layer)
The hard coat layer is provided on the surface of the transparent support in order to impart physical strength to the antireflection film. In particular, it is preferably provided between the transparent support and the high refractive index layer.
The hard coat layer is preferably formed by a crosslinking reaction or a polymerization reaction of a light and / or heat curable compound.
The curable functional group is preferably a photopolymerizable functional group, and the hydrolyzable functional group-containing organometallic compound is preferably an organic alkoxysilyl compound.
Specific examples of these compounds are the same as those exemplified for the high refractive index layer.
Specific examples of the constituent composition of the hard coat layer include those described in JP-A Nos. 2002-144913, 2000-9908, and WO 00/46617.
The high refractive index layer can also serve as a hard coat layer. In such a case, it is preferable to form fine particles dispersed in the hard coat layer using the method described for the high refractive index layer.

The hard coat layer can also serve as an antiglare layer (described later) provided with particles having an average particle size of 0.2 to 10 μm to provide an antiglare function (antiglare function).
The film thickness of the hard coat layer can be appropriately designed depending on the application. The film thickness of the hard coat layer is preferably 0.2 to 10 μm, more preferably 0.5 to 7 μm.
The strength of the hard coat layer is preferably H or higher, more preferably 2H or higher, and most preferably 3H or higher in a pencil hardness test according to JIS K5400. Further, in the Taber test according to JIS K5400, the smaller the wear amount of the test piece before and after the test, the better.

(Forward scattering layer)
The forward scattering layer is provided in order to give a viewing angle improvement effect when the viewing angle is inclined in the vertical and horizontal directions when applied to a liquid crystal display device. By dispersing fine particles having different refractive indexes in the hard coat layer, it can also serve as a hard coat function.
For example, Japanese Patent Laid-Open No. 11-38208 specifying a forward scattering coefficient, Japanese Patent Laid-Open No. 2000-199809 having a relative refractive index of a transparent resin and fine particles in a specific range, and Japanese Patent Laid-Open No. 2002 specifying a haze value of 40% or more. -107512 gazette etc. are mentioned.

(Other layers)
In addition to the above layers, a primer layer, an antistatic layer, an undercoat layer, a protective layer, and the like may be provided.

(Production method of antireflection film)
Each layer of the antireflection film is formed by a dip coating method, an air knife coating method, a curtain coating method, a roller coating method, a wire bar coating method, a gravure coating, a micro gravure method or an extrusion coating method (US Pat. No. 2,681,294). It can be formed by coating.

The antireflection film may have an antiglare function that scatters external light. The antiglare function is obtained by forming irregularities on the surface of the antireflection film. When the antireflection film has an antiglare function, the haze of the antireflection film is preferably 3 to 30%, more preferably 5 to 20%, and most preferably 7 to 20%.

As a method for forming irregularities on the surface of the antireflection film, any method can be applied as long as these surface shapes can be sufficiently maintained. For example, a method of forming irregularities on the film surface using fine particles in the low refractive index layer (for example, JP 2000-271878 A), a lower layer of the low refractive index layer (high refractive index layer, medium refractive index layer) Alternatively, a small amount (0.1 to 50% by mass) of relatively large particles (particle size 0.05 to 2 μm) is added to the hard coat layer to form a surface uneven film, and these shapes are maintained thereon. A method of providing a low refractive index layer (for example, JP 2000-281410 A, JP 2000-95893 A, JP 2001-100004 A, 2001-281407, etc.), an uppermost layer (antifouling layer) A method of physically transferring the uneven shape onto the surface after coating (for example, as an embossing method, Japanese Patent Laid-Open Nos. 63-278839, 11-183710, 2000-275401) It includes equal forth) and the like.

[Liquid Crystal Display]
The optical compensation film and polarizing plate of the present invention can be used in various modes of liquid crystal display devices, and the liquid crystal display devices of the present invention can be obtained. Hereinafter, the liquid crystal display device of the present invention will be described together with preferred forms of the optically anisotropic layer in each liquid crystal mode.

(IPS mode liquid crystal display)
The acrylic film of the present invention is particularly advantageously used as a support for an optical compensation sheet of an IPS type liquid crystal display device having an IPS mode liquid crystal cell, or as a protective film for a polarizing plate. In these modes, the liquid crystal material is aligned substantially in parallel during black display, and black is displayed by aligning liquid crystal molecules in parallel with the substrate surface in the absence of applied voltage. In these embodiments, the polarizing plate using the acrylic film of the present invention contributes to widening the viewing angle and improving the contrast.
Examples of the IPS liquid crystal display device include Japanese Patent Application Laid-Open Nos. 2003-15160, 2003-75850, 2003-295171, 2004-12730, 2004-12731, and 2005-106967. JP 2005-134914, JP 2005-241923, JP 2005-284304, JP 2006-189758, JP 2006-194918, JP 2006-220680, JP 2007-140353, JP 2007-178904, JP 2007-293290, JP 2007-328350, JP 2008-3251, JP 2008-39806, JP 2008-40291, JP 2008-65196, JP 2008 -76849, JP-A-2008-96815, etc. It can be used those described in JP.

(TN mode liquid crystal display)
The TN mode liquid crystal cell is most frequently used as a color TFT liquid crystal display device, and is described in many documents.
The alignment state in the liquid crystal cell in the TN mode black display is an alignment state in which a rod-like liquid crystalline molecule rises at the center of the cell and the rod-like liquid crystalline compound lies in the vicinity of the cell substrate.

The rod-like liquid crystalline compound in the center of the cell is compensated with a discotic liquid crystalline compound of the homeotropic orientation (horizontal orientation in which the disk surface is lying) or a (transparent) support, and the rod-like liquid crystalline property in the vicinity of the cell substrate The compound can be compensated with a discotic liquid crystalline compound having a hybrid alignment (an alignment in which the inclination of the major axis changes with the distance from the polarizing film).
In addition, the rod-like liquid crystalline compound at the center of the cell is compensated with a rod-like liquid crystalline compound having a homogeneous orientation (horizontal orientation in which the major axis lies) or a (transparent) support, and the rod-like liquid crystalline property in the vicinity of the cell substrate is compensated. The compound can be compensated with a discotic liquid crystalline compound having a hybrid alignment.

The homeotropic alignment liquid crystal compound is aligned in a state where the angle between the average alignment direction of the major axis of the liquid crystal compound and the plane of the polarizing film is 85 to 95 degrees.
The liquid crystal compound of homogeneous alignment is aligned with the angle between the average alignment direction of the major axis of the liquid crystal compound and the plane of the polarizing film being less than 5 degrees.
In the hybrid alignment liquid crystalline compound, the angle between the long axis average alignment direction of the liquid crystalline compound and the plane of the polarizing film is preferably 15 degrees or more, and more preferably 15 degrees to 85 degrees.

(Transparent) Optically anisotropic layer in which the support or discotic liquid crystalline compound is homeotropically oriented, optically anisotropic layer in which rod-like liquid crystalline compound is homogeneously oriented, or even homeotropically oriented discotic The optically anisotropic layer composed of a mixture of a liquid crystal compound and a homogeneously aligned rod-like liquid crystal compound preferably has an Rth retardation value of 40 nm to 200 nm and an Re retardation value of 0 to 70 nm.
Regarding the discotic liquid crystal compound layer having homeotropic alignment (horizontal alignment) and the rod-like liquid crystal compound layer having homogeneous alignment (horizontal alignment), Japanese Patent Laid-Open Nos. 12-304931 and 12-304932 describe them. Have been described. The discotic liquid crystal compound layer having a hybrid orientation is described in JP-A-8-50206.

(OCB mode liquid crystal display)
The OCB mode liquid crystal cell is a bend alignment mode liquid crystal cell in which a rod-like liquid crystal compound is aligned in a substantially opposite direction (symmetrically) between an upper portion and a lower portion of the liquid crystal cell. Liquid crystal display devices using a bend alignment mode liquid crystal cell are disclosed in US Pat. Nos. 4,583,825 and 5,410,422. Since the rod-like liquid crystal compounds are symmetrically aligned at the upper and lower portions of the liquid crystal cell, the bend alignment mode liquid crystal cell has a self-optical compensation function. Therefore, this liquid crystal mode is called an OCB (Optically Compensatory Bend) liquid crystal mode.
Similarly to the TN mode, the liquid crystal cell in the OCB mode is in a black display, and the alignment state in the liquid crystal cell is such that the rod-like liquid crystal compound rises at the center of the cell and the rod-like liquid crystal compound lies in the vicinity of the cell substrate. .

Since the TN mode and the alignment of the liquid crystal are the same in black display, the preferred mode is the same for the TN mode. However, since the OCB mode has a larger range in which the liquid crystal compound has risen at the center of the cell than the TN mode, an optically anisotropic layer in which the discotic liquid crystal compound is homeotropically aligned or a rod-like liquid crystal It is necessary to slightly adjust the retardation value of the optically anisotropic layer in which the functional compound is homogeneously oriented. Specifically, the optically anisotropic layer in which the discotic liquid crystalline compound on the (transparent) support is homeotropically aligned, or the optically anisotropic layer in which the rod-like liquid crystalline compound is homogeneously aligned is Rth The retardation value is preferably 150 nm to 500 nm, and the Re retardation value is preferably 20 to 70 nm.

(VA mode liquid crystal display device)
In the VA mode liquid crystal cell, the rod-like liquid crystalline compound is aligned substantially vertically when no voltage is applied.
The VA mode liquid crystal cell includes (1) a narrowly defined VA mode liquid crystal cell in which a rod-like liquid crystal compound is aligned substantially vertically when no voltage is applied, and is substantially horizontally aligned when a voltage is applied (Japanese Patent Laid-Open No. 2). 176625 (in Japanese Patent Publication No. 176625), and (2) a liquid crystal cell (SID97, Digest of tech. Papers (Proceedings) 28 (1997) 845 in which the VA mode is converted into a multi-domain (for MVA mode) in order to enlarge the viewing angle. ), (3) A liquid crystal cell in a mode (n-ASM mode) in which a rod-like liquid crystalline compound is substantially vertically aligned when no voltage is applied and twisted multi-domain alignment is applied when a voltage is applied (Preliminary Collection 58-59 of the Japan Liquid Crystal Society) (1998)) and (4) SURVAVAL mode liquid crystal cells (announced at LCD International 98).

In the black display of the VA mode liquid crystal display device, most of the rod-like liquid crystalline compounds in the liquid crystal cell are in a standing state, so that the optically anisotropic layer in which the discotic liquid crystalline compounds are homeotropically aligned, Alternatively, the liquid crystalline compound is compensated by an optically anisotropic layer in which the rod-like liquid crystalline compound is homogeneously oriented, and separately, the rod-like liquid crystalline compound is homogeneously oriented, and the average orientation direction of the major axis of the rod-like liquid crystalline compound and the polarizing film It is preferable to compensate the viewing angle dependency of the polarizing plate with an optically anisotropic layer having an angle with respect to the transmission axis direction of less than 5 degrees.

(Transparent) The optically anisotropic layer in which the support or the discotic liquid crystalline compound is homeotropically oriented, or the optically anisotropic layer in which the rod-like liquid crystalline compound is homogeneously oriented has an Rth retardation value of 150 nm to It is preferably 500 nm and the Re retardation value is 20 to 70 nm.

(Other liquid crystal display devices)
The ECB mode and STN mode liquid crystal display devices can be optically compensated in the same way as described above.

The features of the present invention will be described more specifically with reference to the following examples.
The materials, amounts used, ratios, processing details, processing procedures, and the like shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below.
Examples 1 and 6 are reference examples.

(Measuring method)
The measurement method used in the present invention is described below.

1. The stretching temperature K thermocouple was attached to the film with heat-resistant tape, and the film temperature in the stretching zone was measured.

2. Clip temperature K thermocouple was attached to the clip with heat resistant tape, and the clip temperature at the tenter entrance was measured.

3. A sample piece having a width of 5 mm and a length of 32 mm is collected from the produced film in the casting direction (MD) and the transverse direction (TD) of the sample film. The average thermal expansion coefficient between 40 ° C. and 90 ° C. was measured with TMA (manufactured by Rigaku Denki Co., Ltd., TMA8310) under the measurement conditions of a load of 40 mN and a heating rate of 5 ° C./min.

4). An elastic modulus and elongation at break were sampled to a width of 10 mm and a length of 150 mm, and measured with Tensilon (manufactured by Toyo Baldwin Co., Ltd., Tensilon RTM-25) at a tensile rate of 10 mm / min and a measurement temperature of 25 ° C. Under the conditions, the elastic modulus and elongation at break were determined. Three samples were measured, and the average value was listed in the examples.

5). Film thickness (thickness)
Ten points were measured at equal intervals in the film width direction with a film thickness measuring machine (manufactured by Ono Sokki, ST-022), and the average value was obtained.

6). Total light transmittance was measured according to ISO 13468-1 using a haze meter manufactured by JASCO.

7). Re, Rth
(1) After slitting 5 cm at both ends of the film-forming film, five points were sampled (3 cm × 3 cm square) at equal intervals over the entire width. At this time, each side of the square was cut out parallel to MD (film forming direction) and TD (width direction).
(2) After conditioning the sample film to 25 ° C. and 60% relative humidity for 5 hours or more, using an automatic birefringence meter (KOBRA-21ADH: manufactured by Oji Scientific Instruments) at 25 ° C. and 60% relative humidity The retardation value at a wavelength of 550 nm was measured from the direction inclining by 10 ° from the normal direction to the sample film surface and ± 50 ° from the normal to the film surface.
(3) In-plane retardation (Re) from the vertical (normal) direction, and retardation in the thickness direction (Rth) were calculated from the measured values in the vertical and ± 10 to 50 ° directions.
(4) The average value of these 5 points was determined and used as Re and Rth.

8). Color change start temperature The liquid crystal display device is placed in a variable room with temperatures of 25 ° C., 40 ° C., 50 ° C., and 60 ° C. for 1 hour or more, and the displayed image changes compared to the color of the image when the temperature is 25 ° C. The temperature was recorded.
It is practically preferable that the color change start temperature is “60 ° C. or higher”. Moreover, if the color change start temperature is “50 to 60 ° C.”, it is within a practically acceptable range. On the other hand, if the color change start temperature is lower than that, it is not practical.

[Example 1]
(Acrylic film formation)
After drying the PMMA resin (Delpet 80N manufactured by Asahi Kasei Chemicals Corporation) with a vacuum dryer at 90 ° C. to reduce the water content to 0.03% or less, a stabilizer (Irganox 1010 (manufactured by Ciba-Gigi Co., Ltd.)) 0 The mixture was extruded into water using a twin-screw kneading extruder with a vent at 230 ° C. in a nitrogen stream at 230 ° C., and then cut into pellets having a diameter of 3 mm and a length of 5 mm.
The pellets were dried with a 90 ° C. vacuum dryer to a water content of 0.03% or less, and then kneaded at a supply unit 210 ° C., a compression unit 230 ° C., and a weighing unit 230 ° C. using a single-screw kneading extruder. . At this time, a 300-mesh screen filter, a gear pump, and a leaf disk filter with a filtration accuracy of 7 μm were arranged in this order between the extruder and the die, and these were connected by a melt pipe. Furthermore, the static mixer described in Table 1 was installed in the melt pipe immediately before the die.
Thereafter, the melt (molten resin) was extruded onto a triple cast roll. At this time, the touch roll was brought into contact with the uppermost cast roll. The touch roll described in Example 1 of Japanese Patent Application Laid-Open No. 11-235747 was used (the one described as a double holding roll, except that the thickness of the thin metal outer cylinder was 2 mm).
Then, after trimming both ends (5 cm each of the total width) immediately before winding, the both ends were subjected to thicknessing processing (knurling) having a width of 10 mm and a height of 20 μm, and wound at 3000 m at 30 m / min.

(Stretching)
The obtained acrylic film was MD stretch ratio 50%, MD stretch temperature Tg, MD stretch speed 10% / sec, TD stretch ratio 50%, TD stretch temperature Tg, TD stretch speed 10% / sec, L / W ratio 5 times. The film was biaxially stretched at a clip temperature Tg-5 ° C. The obtained acrylic film was used as the acrylic film of Example 1.

[Polarizing plate creation]
(Creating a polarizer)
A polyvinyl alcohol film having a thickness of 80 μm was dyed in an aqueous iodine solution of 5% by weight (weight ratio: iodine / potassium iodide = 1/10). Next, after immersing in an aqueous solution containing 3% by weight boric acid and 2% by weight potassium iodide and further stretching to 6.0 times in an aqueous solution containing 4% by weight boric acid and 3% by weight potassium iodide. It was immersed in a 5% by weight aqueous potassium iodide solution. Then, it dried for 3 minutes in 40 degreeC oven, and obtained the 30-micrometer-thick polarizer.

(Preparation of acrylic film with cellulose resin layer)
A solution was prepared by diluting a cellulose-based resin (manufactured by Eastman Chemical Co., cellulose acetate propionate) in butyl acetate (solid content concentration: 7.5% by weight). This solution was applied to one side of the acrylic film of Example 1 and dried in an oven at 100 ° C. for 3 minutes to obtain a polarizer protective film with a cellulose resin layer. The dry thickness of the cellulose resin layer was 0.8 μm.

(Preparation of aqueous solution of polyvinyl alcohol adhesive)
A polyvinyl alcohol adhesive aqueous solution prepared by adjusting an aqueous solution containing 20 parts by weight of methylolmelamine to 100 parts by weight of an acetoacetyl-modified polyvinyl alcohol resin (degree of acetylation 13%) to a concentration of 0.5% by weight Prepared.

(Creation of polarizing plate)
The surface of the cellulose-based resin layer of the polarizer protective film is on one side of the polarizer, and the saponified triacetyl cellulose (TAC) film (Fujitac T-60, manufactured by Fuji Film Co., Ltd., thickness) is provided on the other side. 60 μm) was in contact with each other using the polyvinyl alcohol-based adhesive aqueous solution prepared above. Then, it was made to dry at 70 degreeC for 10 minute (s), and the polarizing plate of Example 1 of this invention was obtained.

[Examples 2 to 12, Comparative Examples 1 to 12]
Example 1 except that the acrylic resin material, MD stretch ratio, MD stretch temperature, MD stretch speed, TD stretch ratio, TD stretch temperature, TD stretch speed, L / W ratio, and clip temperature were as shown in Table 1 below. In the same manner, acrylic films of Examples 2 to 12 and Comparative Examples 1 to 12 and polarizing plates of Examples 2 to 12 and Comparative Examples 1 to 12 were prepared. In Table 1 below, acrylic material Delpet 980N represents an acrylic resin containing maleic anhydride units (trade name Delpet 980N, manufactured by Asahi Kasei Chemicals Corporation), Tg is 117 ° C., and is anhydrous in all monomers. It contains 15 mol% maleic acid, 18 mol% styrene, and 67 mol% methyl methacrylate. The acrylic material lactone ring modification was synthesized from methyl methacrylate = 7500 g and 2- (hydroxymethyl) methyl acrylate 2500 g according to Production Example 1 of JP 2008-9378 A [0222] to [0224]. Represents a resin with 98%, Tg = 134 ° C. Further, the glutaryl modification of the acrylic material was synthesized in accordance with JP-A-2006-241263 [0130] to [0135], glutaric anhydride unit 32% by weight, methyl methacrylate unit 65% by weight, methacrylic acid unit 3% by weight. , Tg = 138 ° C. resin.

4). Various physical properties of the acrylic films of Evaluation Examples 1 to 12 and Comparative Examples 1 to 12 were evaluated according to the evaluation method. The results are shown in Table 2 below. Further, the polarizing plates of Examples 1 to 12 and Comparative Examples 1 to 12 were incorporated instead of the polarizing plates incorporated in the IPS type liquid crystal display device (26 type IPS liquid crystal television monitor (26C3500), manufactured by Toshiba Corporation), The liquid crystal display device of the present invention was manufactured, and the color change start temperature of the liquid crystal display device was evaluated according to the evaluation method. The results are shown in Table 2 below.

In Table 1, since the film of Comparative Example 7 was broken after MD stretching, TD stretching could not be performed and evaluation could not be performed. In Table 2, the films of Comparative Examples 2, 3, 6, 8, and 9 could not be evaluated because the film was broken after TD stretching.
From Table 1 and Table 2, since the thermal expansion coefficients of MD direction and TD direction of Examples 1-12 are both 40-100 ppm / degrees C, the color change start temperature of the liquid crystal display device using an acrylic film is 50 degreeC. It was ˜60 ° C. or 60 ° C. or higher, and showed practically sufficient performance. On the other hand, among the acrylic films of Comparative Examples 1 to 12, the acrylic film that was not broken has a thermal expansion coefficient in the MD direction and the TD direction that exceeds the range of the present invention, and a liquid crystal using the acrylic film of such a comparative example. In the display device, the color change start temperature is 40 ° C. or lower or 40 ° C. to 50 ° C., and the performance is not practical.
In addition, the present invention exhibits the preferable properties as described above when the stretching ratio and stretching temperature in the MD direction and the TD direction, and the ratio of the stretching ratio in the MD direction and the stretching ratio in the TD direction are within the range of the production method of the present invention. It has been found that the acrylic film of the invention can be obtained.

(Production of other liquid crystal display elements)
The polarizing plate of the present invention using the stretched acrylic film is a liquid crystal display device described in Example 1 of JP-A-10-48420, or a discotic liquid crystal molecule described in Example 1 of JP-A-9-26572. An optically anisotropic layer containing an alignment film, an alignment film coated with polyvinyl alcohol, a 20-inch VA liquid crystal display device described in FIGS. 2 to 9 of JP-A-2000-154261, and FIG. 10 of JP-A-2000-154261 When used in the 20-inch OCB type liquid crystal display device described in -15, good characteristics were obtained.

(Creation of optical compensation film)
(1) Surface treatment The stretched acrylic film was subjected to corona discharge treatment under the following conditions.
Electrode: Coron-Plus manufactured by VETAPONE
Generator: CP1C
Output: 900W
Film transport speed: 6m / min

(2) Preparation of alignment film for optically anisotropic layer On these thermoplastic films, the coating liquid of the following composition was apply | coated 28 mL / m < ² > with the wire bar coater of # 16. Drying was performed with warm air of 60 ° C. for 60 seconds, and further with warm air of 90 ° C. for 150 seconds.
(2-1) Alignment film coating solution composition Modified polyvinyl alcohol 20 parts by weight Water 360 parts by weight Methanol 120 parts by weight Glutaraldehyde (crosslinking agent) 1.0 part by weight

(2-2) Preparation of optically anisotropic layer On the alignment film, the following coating solution is conveyed at 30 m / min by rotating # 3.2 wire bar in the same direction as the film conveying direction at 1171 rotations. It was continuously applied to the alignment film surface of the roll film. In the step of continuously heating from room temperature to 100 ° C., the solvent is dried, and then the film surface wind speed corresponding to the discotic liquid crystal compound layer is 1.5 m / sec in parallel with the film conveyance direction in the 135 ° C. drying zone. And heated for about 90 seconds to align the discotic liquid crystal compound. Next, the film is transported to a drying zone at 80 ° C., and an ultraviolet ray with an illuminance of 600 mW is applied by an ultraviolet irradiation device (ultraviolet lamp: output 160 W / cm, emission length 1.6 m) with the film surface temperature being about 100 ° C. Irradiation was carried out for 4 seconds to advance the crosslinking reaction, and the discotic liquid crystal compound was fixed to the orientation. Then, it was allowed to cool to room temperature and wound into a cylindrical shape to form a roll. The thickness of the optically anisotropic layer was 1.3 μm.
Further, the elastic modulus of the obtained optical compensation sheet was measured and found to be 2.4 MPa.

(2-3) Coating liquid composition of optically anisotropic layer The following composition was dissolved in 97 parts by mass of methyl ethyl ketone to prepare a coating liquid.
The following discotic liquid crystalline compound (1) 41.01 parts by mass Ethylene oxide modified trimethylolpropane triacrylate (V # 360, manufactured by Osaka Organic Chemical Co., Ltd. 4.06 parts by mass cellulose acetate butyrate (CAB551-0.2) 0.34 parts by mass cellulose acetate butyrate (CAB531-1, manufactured by Eastman Chemical Co.) 0.11 parts by mass The following fluoroaliphatic group-containing polymer 1 0.56 parts by mass The following fluoroaliphatic groups Containing polymer 2 0.06 parts by mass Photopolymerization initiator (Irgacure 907, manufactured by Ciba Geigy) 1.35 parts by mass sensitizer (Kayacure DETX, manufactured by Nippon Kayaku Co., Ltd.) 0.45 parts by mass

Discotic liquid crystalline compounds (1)

When the polarizing plate was placed in a crossed Nicol arrangement and the unevenness of the obtained optical compensation sheet was observed, no unevenness was detected even when viewed from the front and a direction inclined by 60 degrees from the normal.

(3) Production of Polarizing Plate A polarizing plate was produced from the optical compensation acrylic film in the same manner as in the production method of the polarizing plate.

(4) Evaluation with a TN liquid crystal panel A pair of polarizing plates provided in a liquid crystal display device (MDT-191S, manufactured by Mitsubishi Electric Corporation) using a TN type liquid crystal panel is peeled off, and the polarization produced above is used instead. The plates were attached one by one to the observer side and the backlight side through an adhesive so that the optical compensation film was on the liquid crystal cell side. The transmission axis of the polarizing plate on the viewer side and the transmission axis of the polarizing plate on the backlight side were arranged to be in the O mode. Those of the present invention showed good characteristics without image distortion.

(Preparation of antireflection film)
When the stretched acrylic film of the present invention was produced as a low reflection film in accordance with Example 47 of the Japan Society for Invention and Innovation (public technical number 2001-1745), good optical performance was obtained.

Claims (24)

The thickness is 20-60 μm,
The thermal expansion coefficients of the film longitudinal direction (MD) and the width direction (TD) at 40 ° C. to 90 ° C. are both 50 to 100 ppm / ° C.,
Including acrylic resin,
The thickness direction retardation (Rth) is 0-30 nm,
Does not contain a graft copolymer containing conjugated diene rubber,
An acrylic film characterized by being a single layer.   The acrylic film according to claim 1, wherein the elastic modulus in the film longitudinal direction (MD) and the width direction (TD) at 25 ° C is 2800 to 3800 MPa.   The thickness is 20-60 μm,
  The thermal expansion coefficients of the film longitudinal direction (MD) and the width direction (TD) at 40 ° C. to 90 ° C. are both 50 to 100 ppm / ° C.,
  Including acrylic resin,
  The thickness direction retardation (Rth) is 0-30 nm,
  Both the elastic modulus in the film longitudinal direction (MD) and the width direction (TD) at 25 ° C. is 2800 to 3800 MPa,
  An acrylic film characterized by being a single layer. The acrylic film according to any one of claims 1 to 3, wherein the elastic modulus in the film longitudinal direction (MD) and the width direction (TD) at 25 ° C is 2800 to 3700 MPa. The thickness is 20-60 μm,
The thermal expansion coefficients of the film longitudinal direction (MD) and the width direction (TD) at 40 ° C. to 90 ° C. are both 50 to 100 ppm / ° C.,
The elongation at break in the longitudinal direction of the film (MD) at 25 ° C. is 15 to 38%,
Including acrylic resin,
The thickness direction retardation (Rth) is 0-30 nm,
An acrylic film characterized by being a single layer. The acrylic film according to claim 5 , wherein the elongation at break in the film width direction (TD) at 25 ° C is 15 to 55%. The acrylic film according to claim 5 or 6 , wherein the breaking elongation in the film longitudinal direction (MD) at 25 ° C is 20 to 38%. The acrylic film according to any one of claims 1 to 7 , wherein an optically anisotropic layer is provided. The acrylic film according to any one of claims 1 to 7 , further comprising an antireflection layer. The acrylic film according to any one of claims 1 to 7 , wherein a thermal expansion coefficient in a longitudinal direction (MD) and a width direction (TD) of the acrylic film at 40 ° C to 90 ° C is 60 to 100 ppm / ° C. The acrylic film as described in any one of Claims 1-10 in which the slow axis of retardation (Re) of an in-plane direction has faced the width direction. The acrylic film according to any one of claims 1 to 11 , wherein a retardation (Rth) in a thickness direction is 0 to -15 nm. The styrene acrylic resin is a copolymer component, nuclear alkyl-substituted styrenes, acrylic film according to any one of claims 1 to 12 containing at least one of the group consisting of α- alkyl-substituted styrenes. The acrylic film according to any one of claims 1 to 13 , which has a total light transmittance of 91 to 94%. Acrylic film according to any one of claims 1 to 14 having a primer layer. The acrylic film according to claim 15 , wherein the primer layer contains at least a cellulose resin. The acrylic film according to any one of claims 1 to 16 , comprising a stabilizer. The acrylic film according to claim 17 , wherein the stabilizer is a phenol-based stabilizer. The polarizing plate using the acrylic film according to any one of claims 1 to 18. Having a polyvinyl alcohol film (PVA film),
The polarizing plate according to claim 19 , wherein the PVA film has a thermal expansion coefficient of 40 to 90 ppm / ° C. and 70 to 120 ppm / ° C. in the longitudinal direction (MD) and the width direction (TD), respectively. The polarizing plate according to claim 19 or 20 characterized by having a cellulose acylate film. A liquid crystal display device using the acrylic film according to any one of claims 1 to 18 or the polarizing plate according to any one of claims 19 to 21 . The liquid crystal display device according to claim 22 , comprising an IPS or VA liquid crystal. A method for manufacturing an acrylic film according to any one of claims 1 to 18
A method for producing an acrylic film comprising a step of MD stretching and / or TD stretching of an unstretched acrylic film.