JPWO2010100993A1 - Retardation film - Google Patents

Abstract

An object of the present invention is to provide a retardation film having a wide contrast viewing angle and small retardation unevenness. The object of the present invention is an optically biaxial retardation film, and when the X axis, Y axis, Z axis, A, B, C, and β are defined as follows, the following (1) to ( Retardation film characterized by having all the relationship of 6). (1) 0 ≦ β ≦ 50 degrees (2) B = 90 degrees (3) A ≠ 90 degrees (4) C ≠ 90 degrees (5) 80 degrees <A <90 degrees (6) 80 degrees <C <90 degrees X axis: direction of the maximum refractive index in the plane of the refractive index ellipsoid Y axis: direction in the plane of the refractive index ellipsoid of the refractive index ellipsoid and perpendicular to the maximum refractive index in the plane Z axis: refractive index ellipsoid Minimum refractive index direction A: X-axis and Z-axis angle B: X-axis and Y-axis angle C: Y-axis and Z-axis angle β: Achieved by the normal direction of the film and the Z-axis angle It was.

Description

  The present invention relates to a retardation film, and more particularly to a retardation film film excellent in contrast viewing angle and retardation unevenness.

  Cellulose ester films, polycarbonate films, polycycloolefin films and the like are used as retardation films for TN type liquid crystal display devices.

  The TN liquid crystal display device has a problem that the halftone is inverted. For this reason, Patent Document 1 attempts to solve this problem by controlling the tilt angle of the discotic compound, but this method is not sufficient to eliminate halftone inversion, and the practical viewing angle is still very high. Remained narrow.

  On the other hand, with a polycarbonate film, a retardation film (hereinafter referred to as a tilted film) suitable for a TN type liquid crystal display device in which shearing is forcibly applied during film formation and a retardation is developed by tilting the optical axis in the film thickness direction. Has also been proposed (Patent Documents 2 to 3).

  Patent Document 4 discloses a technique using a thermoplastic norbornene resin (a type of polycycloolefin film) instead of polycarbonate, polyester, and triacetylcellulose, which are unstable in developing retardation due to a large photoelastic coefficient. It is disclosed.

  However, since the thermoplastic norbornene resin film has a wide contrast viewing angle, even if the retardation unevenness is almost the same as that of normal stretching, it becomes very conspicuous and the LCD quality is lowered.

  Further, it has been found that the tilt angle of the retardation layer is optically biaxial in order to solve this problem by simply tilting one axis, the contrast viewing angle is not sufficiently widened.

JP 2007-264449 A JP-A-6-222213 JP 2003-25414 A JP 2007-38646 A

  Accordingly, an object of the present invention is to provide a retardation film having a wide contrast viewing angle and small retardation unevenness.

  The above object of the present invention is achieved by the following configurations.

1. When optically a biaxial retardation film and the X-axis, Y-axis, Z-axis, A, B, C, and β are defined as follows, all the following relationships (1) to (6) are satisfied. A retardation film comprising:
(1) 0 ≦ β ≦ 50 degrees (2) B = 90 degrees (3) A ≠ 90 degrees (4) C ≠ 90 degrees (5) 80 degrees <A <90 degrees (6) 80 degrees <C <90 degrees X axis: direction of the in-plane maximum refractive index of the refractive index ellipsoid Y axis: direction in the plane of the refractive index ellipsoid of the refractive index ellipsoid and perpendicular to the in-plane maximum refractive index Z axis: refractive index ellipsoid A: Angle formed by X-axis and Z-axis B: Angle formed by X-axis and Y-axis C: Angle formed by Y-axis and Z-axis β: Angle formed by normal direction of film and Z-axis 2. The retardation film as described in 1 above, wherein the retardation film is a cellulose ester film.

  According to the present invention, it is possible to provide a retardation film having a small variation in inclination angle even when continuously produced for a long period of time.

It is an example of arrangement | positioning of the drive roller and a follower roller in the inclination process of this invention. It is a technical conceptual diagram of the conventional inclination film. It is a technical conceptual diagram of the inclined film of this invention.

  The best mode for carrying out the present invention will be described in detail below, but the present invention is not limited thereto.

  The retardation film of the present invention is a film itself, which is a film provided with a retardation which is an optical function without applying a liquid crystal or an optically anisotropic compound. The film necessary for the phase difference function is a film completed in one film forming process.

  That is, even when layers having different components and compositions in the thickness direction are laminated, any retardation film produced by a single film formation belongs to the retardation film of the present invention.

  For example, what provides the layer which gives a slip product by co-casting, co-extrusion, etc. belongs to the retardation film of this invention.

The retardation film of the present invention is an optically biaxial retardation film. When the X axis, Y axis, Z axis, A, B, C, and β are defined as follows, the following (1): It is characterized by having all the relations (6) to (6).
(1) 0 ≦ β ≦ 50 degrees (2) B = 90 degrees (3) A ≠ 90 degrees (4) C ≠ 90 degrees (5) 80 degrees <A <90 degrees (6) 80 degrees <C <90 degrees X axis: direction of the in-plane maximum refractive index of the refractive index ellipsoid Y axis: direction in the plane of the refractive index ellipsoid of the refractive index ellipsoid and perpendicular to the in-plane maximum refractive index Z axis: refractive index ellipsoid A: Angle between X axis and Z axis B: Angle between X axis and Y axis C: Angle between Y axis and Z axis β: Angle between normal direction of film and Z axis (inclination) angle)
These axes and angles can be measured or calculated using a birefringence meter capable of measuring tilt (for example, KOBRA-31WR manufactured by Oji Scientific Instruments, Axoscan manufactured by Opto Science Co., Ltd., and Spectroscopic Ellipsometer DVA36VW manufactured by Mizoji Optical Co., Ltd.). Can do.

  β can be measured by, for example, KOBRA31WR manufactured by Oji Scientific Instruments. The three axes X, Y, and Z of the refractive index ellipsoid are measured by an ellipsometer (for example, a spectroscopic ellipsometer DVA36VW manufactured by Mizoji Optical Co., Ltd.) and the like, and are angles formed by the respective axes.

  Whether or not the Z direction is inclined from the surface normal direction of the refractive index ellipsoid can be simply confirmed by a birefringence meter. If Z is inclined from the normal, A ≠ 90 degrees and C ≠ 90 degrees. Measurement is performed with the in-plane fast axis of the refractive index ellipsoid as the tilt axis, the angle at which the phase difference becomes zero (that is, the optical axis) is measured, and the center (average) angle is calculated to calculate the Z axis. be able to.

  The biggest difference between the present invention and the techniques described in Patent Documents 2 to 4 is that the conventional inclined film has A = B = C = 90 degrees, whereas the inclined film of the present invention has B = 90 degrees. However, A ≠ 90 degrees and C ≠ 90 degrees.

  This makes the effect of the present invention that the contrast viewing angle is widened while suppressing the reversal of the halftone particularly in the downward direction is remarkable.

  The tilt angle β of the retardation film of the present invention is in the range of 0 ≦ β ≦ 50 degrees, more preferably 15 ≦ β ≦ 45 degrees.

The inclined film of the present invention is preferably a cellulose ester film described below composed of a cellulose ester.
<Cellulose ester film of the present invention>
The optical film of the present invention is preferably a cellulose ester film described below, an aromatic terminal polyester compound represented by the following general formula (I),
General formula (I) B- (GA) n-GB
(In the formula, B is an arylcarboxylic acid residue, G is an alkylene glycol residue having 2 to 12 carbon atoms, an aryl glycol residue having 6 to 12 carbon atoms, or an oxyalkylene glycol residue having 4 to 12 carbon atoms, A Represents an alkylene dicarboxylic acid residue having 4 to 12 carbon atoms or an aryl dicarboxylic acid residue having 6 to 12 carbon atoms, and n represents an integer of 1 or more.)
And at least one compound selected from the group consisting of an ester compound having at least one of the pyranose structure or furanose structure and having all or part of the OH groups of the structure esterified, An ester film is preferred.

<Cellulose ester>
The cellulose ester of the present invention is not particularly limited, but the cellulose ester is a carboxylic acid ester having about 2 to 22 carbon atoms, and may be an aromatic carboxylic acid ester, particularly a lower fatty acid ester having 6 or less carbon atoms. It is preferable.

  The acyl group bonded to the hydroxyl group may be linear or branched or may form a ring. Furthermore, another substituent may be substituted. When the degree of substitution is the same, birefringence decreases when the number of carbon atoms is large, and therefore, the number of carbon atoms is preferably selected from acyl groups having 2 to 6 carbon atoms. The cellulose ester preferably has 2 to 4 carbon atoms, more preferably 2 to 3 carbon atoms.

  Specifically, as the cellulose ester, cellulose acetate, cellulose acetate propionate, cellulose acetate butyrate, or cellulose acetate to which propionate group or butyrate group is bonded in addition to acetyl group such as cellulose acetate propionate butyrate. Mixed fatty acid esters can be used.

  The butyryl group that forms butyrate may be linear or branched. As the cellulose ester preferably used in the present invention, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, and cellulose acetate phthalate are particularly preferably used.

  Preferred cellulose esters other than cellulose acetate phthalate for the present invention preferably satisfy the following formulas (1) and (2).

Formula (1) 2.0 <= X + Y <= 3.0
Formula (2) 0 ≦ Y ≦ 1.5
In the formula, X is the degree of substitution of the acetyl group, and Y is the degree of substitution of the propionyl group or butyryl group, or a mixture thereof.

  Further, in order to obtain optical characteristics that meet the purpose, resins having different degrees of substitution may be mixed and used. The mixing ratio is preferably 10:90 to 90:10 (mass ratio).

  Of these, cellulose acetate propionate is particularly preferably used. In cellulose acetate propionate, 1.0 ≦ X ≦ 2.5, preferably 0.1 ≦ Y ≦ 1.5, and 2.0 ≦ X + Y ≦ 3.0. The measuring method of the substitution degree of an acyl group can be measured according to ASTM-D817-96.

  The number average molecular weight of the cellulose ester used in the present invention is preferably in the range of 60,000 to 300,000 because the mechanical strength of the resulting film is strong. Furthermore, the thing of 70000-200000 is used preferably.

  The weight average molecular weight Mw and number average molecular weight Mn of the cellulose ester were measured using gel permeation chromatography (GPC).

  The measurement conditions are as follows.

Solvent: Methylene chloride Column: Shodex K806, K805, K803G (Used by connecting three Showa Denko Co., Ltd.)
Column temperature: 25 ° C
Sample concentration: 0.1% by mass
Detector: RI Model 504 (manufactured by GL Sciences)
Pump: L6000 (manufactured by Hitachi, Ltd.)
Flow rate: 1.0ml / min
Calibration curve: Standard polystyrene STK standard polystyrene (manufactured by Tosoh Corporation) Mw = 100000 to 500 calibration curves with 13 samples were used. Thirteen samples are used at approximately equal intervals.

  The cellulose used as a raw material of the cellulose ester used in the present invention is not particularly limited, and examples thereof include cotton linter, wood pulp, and kenaf. Moreover, the cellulose ester obtained from them can be mixed and used in arbitrary ratios, respectively.

  The cellulose ester such as cellulose acetate phthalate of the present invention can be produced by a known method. Specifically, it can be synthesized with reference to the method described in JP-A-10-45804.

<Aromatic-terminated polyester compound represented by general formula (I)>
In the present invention, an aromatic terminal polyester compound represented by the following general formula (I) is used.

General formula (I) B- (GA) n-GB
(In the formula, B is an arylcarboxylic acid residue, G is an alkylene glycol residue having 2 to 12 carbon atoms, an aryl glycol residue having 6 to 12 carbon atoms, or an oxyalkylene glycol residue having 4 to 12 carbon atoms, A Represents an alkylene dicarboxylic acid residue having 4 to 12 carbon atoms or an aryl dicarboxylic acid residue having 6 to 12 carbon atoms, and n represents an integer of 1 or more.)
In general formula (I), an arylcarboxylic acid residue represented by B and an alkylene glycol residue or oxyalkylene glycol residue or arylglycol residue represented by G, an alkylenedicarboxylic acid residue or aryldicarboxylic acid represented by A And is obtained by the same reaction as a normal polyester compound.

  Examples of the arylcarboxylic acid component of the aromatic-terminated polyester compound used in the present invention include, for example, benzoic acid, para-tert-butylbenzoic acid, orthotoluic acid, metatoluic acid, p-toluic acid, dimethylbenzoic acid, ethylbenzoic acid, normal There are propylbenzoic acid, aminobenzoic acid, acetoxybenzoic acid and the like, and these can be used as one kind or a mixture of two or more kinds, respectively.

  Examples of the alkylene glycol component having 2 to 12 carbon atoms of the aromatic terminal polyester compound that can be used in the present invention include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1,3-butanediol, 1,2-propanediol, 2-methyl 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 2,2-dimethyl-1,3-propanediol (Neopentyl glycol), 2,2-diethyl-1,3-propanediol (3,3-dimethylolpentane), 2-n-butyl-2-ethyl-1,3-propanediol (3,3-dimethylol) Heptane), 3-methyl-1,5-pentanediol 1,6-hexanediol, 2,2,4-trimethyl 1, -Pentanediol, 2-ethyl 1,3-hexanediol, 2-methyl 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,12-octadecanediol, etc. Glycol is used as one or a mixture of two or more.

  In particular, an alkylene glycol having 2 to 12 carbon atoms is particularly preferable because of excellent compatibility with a cellulose ester.

  In addition, examples of the oxyalkylene glycol component having 4 to 12 carbon atoms of the aromatic terminal polyester compound include diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, and tripropylene glycol. One kind or a mixture of two or more kinds can be used.

  Examples of the alkylene dicarboxylic acid component having 4 to 12 carbon atoms of the aromatic terminal polyester compound include succinic acid, maleic acid, fumaric acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, and dodecanedicarboxylic acid. These are used as one kind or a mixture of two or more kinds, respectively.

  Examples of the arylene dicarboxylic acid component having 6 to 12 carbon atoms include phthalic acid, terephthalic acid, isophthalic acid, 1,5 naphthalene dicarboxylic acid, and 1,4 naphthalene dicarboxylic acid.

  As for the aromatic terminal polyester type compound used by this invention, it is preferable that n is 1 or more and 100 or less, The number average molecular weight becomes like this. Preferably it is 300-1500, More preferably, the range of 400-1000 is suitable.

  The acid value is 0.5 mgKOH / g or less, the hydroxyl value is 25 mgKOH / g or less, more preferably the acid value is 0.3 mgKOH / g or less, and the hydroxyl value is 15 mgKOH / g or less.

  The aromatic terminal polyester compound represented by the general formula (I) of the present invention is preferably contained in an amount of 0.5 to 30% by mass with respect to the cellulose ester.

  Although the specific compound of the aromatic terminal polyester type compound which can be used for this invention below is shown, this invention is not limited to this.

<Ester compound in which at least one of pyranose structure or furanose structure is 1 or more and 12 or less and all or part of OH groups of the structure are esterified>
The cellulose ester film of the present invention is characterized by comprising an ester compound having at least one pyranose structure or at least one furanose structure and having all or part of OH groups in the structure esterified.

  The proportion of esterification is preferably 70% or more of the OH groups present in the pyranose structure or furanose structure.

  In the present invention, ester compounds are collectively referred to as sugar ester compounds.

  Examples of the ester compound of the present invention include the following, but the present invention is not limited thereto.

  Glucose, galactose, mannose, fructose, xylose or arabinose, lactose, sucrose, nystose, 1F-fructosyl nystose, stachyose, maltitol, lactitol, lactulose, cellobiose, maltose, cellotriose, maltotriose, raffinose or kestose .

  In addition, gentiobiose, gentiotriose, gentiotetraose, xylotriose, galactosyl sucrose, and the like are also included.

  Among these compounds, compounds having both a pyranose structure and a furanose structure are particularly preferable.

  Examples include sucrose, kestose, nystose, 1F-fructosyl nystose, stachyose, and more preferably sucrose.

  The monocarboxylic acid used for esterifying all or part of the OH groups in the pyranose structure or furanose structure of the present invention is not particularly limited, and known aliphatic monocarboxylic acids, alicyclic monocarboxylic acids, An aromatic monocarboxylic acid or the like can be used. The carboxylic acid used may be one type or a mixture of two or more types.

  Preferred aliphatic monocarboxylic acids include acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, 2-ethyl-hexanecarboxylic acid, undecylic acid, lauric acid , Saturated fatty acids such as tridecylic acid, myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, lignoceric acid, serotic acid, heptacosanoic acid, montanic acid, melicic acid, and laccelic acid, Examples include unsaturated fatty acids such as undecylenic acid, oleic acid, sorbic acid, linoleic acid, linolenic acid, arachidonic acid and octenoic acid.

  Examples of preferable alicyclic monocarboxylic acids include acetic acid, cyclopentanecarboxylic acid, cyclohexanecarboxylic acid, cyclooctanecarboxylic acid, and derivatives thereof.

  Examples of preferred aromatic monocarboxylic acids include aromatic monocarboxylic acids having an alkyl group or alkoxy group introduced into the benzene ring of benzoic acid such as benzoic acid and toluic acid, cinnamic acid, benzylic acid, biphenylcarboxylic acid, and naphthalene. Examples thereof include aromatic monocarboxylic acids having two or more benzene rings such as carboxylic acid and tetralin carboxylic acid, or derivatives thereof. More specifically, xylyl acid, hemelic acid, mesitylene acid, prenylic acid, γ-isoduric acid, jurylic acid, mesitic acid, α-isoduric acid, cumic acid, α-toluic acid, hydroatropic acid, atropic acid, hydrocinnamic acid, salicylic acid, o-anisic acid, m-anisic acid, p-anisic acid , Creosote acid, o-homosalicylic acid, m-homosalicylic acid, p-homosalicylic acid, o-pyroca Succinic acid, β-resorcylic acid, vanillic acid, isovanillic acid, veratromic acid, o-veratrumic acid, gallic acid, asaronic acid, mandelic acid, homoanisic acid, homovanillic acid, homoveratrumic acid, o-homoveratrumic acid, phthalonic acid, p- Although coumaric acid can be mentioned, benzoic acid is particularly preferable.

  The oligosaccharide ester compound can be applied as a compound having 1 to 12 at least one of the pyranose structure or furanose structure according to the present invention.

  Oligosaccharides are produced by allowing an enzyme such as amylase to act on starch, sucrose, etc. Examples of oligosaccharides that can be applied to the present invention include maltooligosaccharides, isomaltoligosaccharides, fructooligosaccharides, galactooligosaccharides, xylooligos. Sugar.

Moreover, the said ester compound is a compound which condensed 1 or more and 12 or less of at least 1 sort (s) of the pyranose structure or furanose structure represented with the following general formula (A). However, R < ₁₁ > -R < ₁₅ >, R < ₂₁ > -R < ₂₅ > represents a C2-C22 acyl group or a hydrogen atom, m and n represent the integer of 0-12 respectively, and m + n represents the integer of 1-12.

R _{11 to} R ₁₅ and R _{21 to} R ₂₅ are preferably a benzoyl group or a hydrogen atom. Benzoyl group may further have a substituent R _{26 (p} is 0-5), for example, an alkyl group, an alkenyl group, an alkoxyl group and a phenyl group, further the alkyl group, an alkenyl group, a phenyl group May have a substituent. Oligosaccharides can also be produced by the same method as the ester compound of the present invention.

  Although the specific example of the ester compound which concerns on this invention is given to the following, this invention is not limited to this.

  The cellulose ester film of the present invention preferably contains the sugar ester compound of the present invention in an amount of 0.5 to 30% by mass of the cellulose ester film in order to suppress the fluctuation of the retardation value and stabilize the display quality. In particular, the content is preferably 5 to 30% by mass.

  The content of the aromatic terminal polyester compound and the sugar ester compound represented by the general formula (I) of the present invention can be selected in a mass ratio of 99: 1 to 1:99, and the total amount of both compounds is It is preferable that it is 1-40 mass% with respect to a cellulose ester.

<Plasticizer>
The cellulose ester film of the present invention can contain a plasticizer as necessary to obtain the effects of the present invention.

  The plasticizer is not particularly limited, but preferably a (meth) acrylic polymer plasticizer, a polycarboxylic acid ester plasticizer, a glycolate plasticizer, a phthalate ester plasticizer, a fatty acid ester plasticizer, It is selected from polyhydric alcohol ester plasticizers, polyester plasticizers and the like.

  Of these, when two or more plasticizers are used, at least one plasticizer is preferably a polyhydric alcohol ester plasticizer.

<(Meth) acrylic polymer>
The (meth) acrylic polymer used in the present invention preferably exhibits negative birefringence with respect to the stretching direction as a function when contained in an optical compensation film, and the structure is not particularly limited. However, it is preferably a polymer having a weight average molecular weight of 500 or more and 30000 or less obtained by polymerizing an ethylenically unsaturated monomer. In addition, about the birefringence, the presence was confirmed by the following test.

(Test method for birefringence of (meth) acrylic polymers)
A (meth) acrylic polymer was dissolved in a solvent, cast into a film, then dried by heating, and birefringence was evaluated for a film having a transmittance of 80% or more.

  Refractive index measurement was performed using an Abbe refractometer-4T (manufactured by Atago Co., Ltd.) using a multi-wavelength light source. The refractive index ny in the stretching direction and the refractive index in the orthogonal in-plane direction were nx. For a film where (ny−nx) <0 for each refractive index at 550 nm, the (meth) acrylic polymer is judged to be negatively birefringent with respect to the stretching direction.

  The (meth) acrylic polymer having a weight average molecular weight of 500 to 30,000 used in the present invention is a (meth) acrylic polymer having an aromatic ring in the side chain or a (meth) acrylic having a cyclohexyl group in the side chain. A polymer may be used.

  When the polymer has a weight average molecular weight of 500 or more and 30000 or less, and the composition of the polymer is controlled, for example, when the optical compensation film is a cellulose ester film particularly preferable in the present invention, the cellulose ester and the polymer The compatibility with can be improved.

  For a (meth) acrylic polymer having an aromatic ring in the side chain or a (meth) acrylic polymer having a cyclohexyl group in the side chain, preferably if the weight average molecular weight is from 500 to 10,000, The cellulose ester film after film formation is excellent in transparency, has extremely low moisture permeability, and exhibits excellent performance as a protective film for a polarizing plate.

  Since the polymer has a weight average molecular weight of 500 or more and 30000 or less, it is considered to be between the oligomer and the low molecular weight polymer. In order to synthesize such a polymer, it is difficult to control the molecular weight in normal polymerization, and it is desirable to use a method that can align the molecular weight as much as possible by a method that does not increase the molecular weight too much.

  In particular, the (meth) acrylic polymer used in the optical compensation film of the present invention includes an ethylenically unsaturated monomer Xa having no aromatic ring and hydroxyl group in the molecule, and no hydroxyl ring in the molecule. A polymer X having a weight average molecular weight of 2,000 to 30,000 obtained by copolymerization of an ethylenically unsaturated monomer Xb having Xb and a copolymerizable ethylenically unsaturated monomer excluding Xa and Xb, or an aromatic ring The polymer Y is preferably a polymer Y having a weight average molecular weight of 500 or more and 3000 or less, which is obtained by polymerizing a non-ethylenically unsaturated monomer Ya and an ethylenically unsaturated monomer copolymerizable with Ya.

[Polymer X, Polymer Y]
The method for adjusting Ro and Rt of the optical compensation film according to the present invention includes an ethylenically unsaturated monomer Xa having no aromatic ring and a hydroxyl group in the molecule, and ethylene having a hydroxyl group and no aromatic ring in the molecule. High molecular weight polymer X having a weight average molecular weight of 2,000 to 30,000 obtained by copolymerization of the polymerizable unsaturated monomer Xb and a copolymerizable ethylenically unsaturated monomer excluding Xa and Xb, and more preferably, Contains a low molecular weight polymer Y having a weight average molecular weight of 500 to 3,000 obtained by polymerizing an ethylenically unsaturated monomer Ya having no aromatic ring and an ethylenically unsaturated monomer copolymerizable with Ya It is preferable.

  The polymer X used in the present invention includes an ethylenically unsaturated monomer Xa having no aromatic ring and a hydroxyl group in the molecule and an ethylenically unsaturated monomer Xb having no hydroxyl ring in the molecule and having a hydroxyl group, Xa and Xb. Is a polymer having a weight average molecular weight of 2000 or more and 30000 or less obtained by copolymerization with a copolymerizable ethylenically unsaturated monomer other than.

  Preferably, Xa is an acrylic or methacrylic monomer having no aromatic ring and hydroxyl group in the molecule, and Xb is an acrylic or methacrylic monomer having no aromatic ring and having a hydroxyl group in the molecule.

  The polymer X used in the present invention is represented by the following general formula (X).

Formula (X)
-[Xa] m- [Xb] n- [Xc] p-
In the general formula (X), Xa represents an ethylenically unsaturated monomer having no aromatic ring and hydroxyl group in the molecule, and Xb represents an ethylenically unsaturated monomer having no aromatic ring and having a hydroxyl group in the molecule. Xc represents a copolymerizable ethylenically unsaturated monomer excluding Xa and Xb. m, n, and p each represent a molar composition ratio. However, m ≠ 0 and m + n + p = 100.

  Furthermore, the polymer X is preferably a polymer represented by the following general formula (X-1).

Formula (X-1)
_{- [CH 2 -C (-R1)} (- CO 2 R2)] m- [CH 2 -C (-R3) (- CO 2 R4-OH) -] n- [Xc] p-
In the general formula (X-1), R1 and R3 each represent a hydrogen atom or a methyl group. R2 represents an alkyl group having 1 to 12 carbon atoms or a cycloalkyl group.

R4 is _{-CH 2 -, - C 2 H} 4 - or _-C 3 _{H 6} - represents a. Xc _{is, [CH 2 -C (-R1)} (- CO 2 R2)] representing the a polymerizable monomer unit or _{[CH 2 -C (-R3) (} - - CO 2 R4-OH)]. m, n, and p represent a molar composition ratio. However, m ≠ 0 and m + n + p = 100.

  Although the monomer as a monomer unit which comprises the polymer X which concerns on this invention is mentioned below, it is not limited to this.

  In X, the hydroxyl group means not only a hydroxyl group but also a group having an ethylene oxide chain.

  Examples of the ethylenically unsaturated monomer Xa having no aromatic ring and hydroxyl group in the molecule include methyl acrylate, ethyl acrylate, propyl acrylate (i-, n-), and butyl acrylate (n-, i-, s). -, T-), pentyl acrylate (n-, i-, s-), hexyl acrylate (n-, i-), heptyl acrylate (n-, i-), octyl acrylate (n-, i -), Nonyl acrylate (n-, i-), myristyl acrylate (n-, i-), acrylic acid (2-ethylhexyl), acrylic acid (ε-caprolactone), etc. The thing changed into acid ester can be mentioned.

  Among these, methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, and propyl methacrylate (i-, n-) are preferable.

  The ethylenically unsaturated monomer Xb having no hydroxyl ring in the molecule and having a hydroxyl group is preferably acrylic acid or methacrylic acid ester as a monomer unit having a hydroxyl group, such as acrylic acid (2-hydroxyethyl), acrylic acid. (2-hydroxypropyl), acrylic acid (3-hydroxypropyl), acrylic acid (4-hydroxybutyl), acrylic acid (2-hydroxybutyl), or those obtained by replacing these acrylic acids with methacrylic acid. Preferred are acrylic acid (2-hydroxyethyl) and methacrylic acid (2-hydroxyethyl), acrylic acid (2-hydroxypropyl), and acrylic acid (3-hydroxypropyl).

  Xc is not particularly limited as long as it is a monomer other than Xa and Xb and is a copolymerizable ethylenically unsaturated monomer, but preferably has no aromatic ring.

  The molar composition ratio m: n of Xa and Xb is preferably in the range of 99: 1 to 65:35, more preferably in the range of 95: 5 to 75:25. P of Xc is 0-10. Xc may be a plurality of monomer units.

  When the molar composition ratio of Xa is large, the compatibility with the cellulose ester is improved, but the retardation value Rt in the film thickness direction is increased. When the molar composition ratio of Xb is large, the compatibility is deteriorated, but the effect of reducing Rt is high.

  Further, if the molar composition ratio of Xb exceeds the above range, haze tends to occur during film formation, and it is preferable to optimize these and determine the molar composition ratio of Xa and Xb.

  The molecular weight of the high molecular weight polymer X is more preferably 5,000 or more and 30,000 or less, and still more preferably 8,000 or more and 25,000 or less.

  By setting the weight average molecular weight to 5,000 or more, it is preferable because advantages such as little dimensional change of the optical compensation film under high temperature and high humidity and less curling as a polarizing plate protective film can be obtained.

  When the weight average molecular weight is 30000 or less, compatibility with the cellulose ester is further improved, and bleeding out under high temperature and high humidity and further haze generation immediately after film formation are suppressed.

  The weight average molecular weight of the polymer X according to the present invention can be adjusted by a known molecular weight adjusting method. Examples of such a molecular weight adjusting method include a method of adding a chain transfer agent such as carbon tetrachloride, lauryl mercaptan, octyl thioglycolate, and the like.

  The polymerization temperature is usually from room temperature to 130 ° C., preferably from 50 ° C. to 100 ° C., and this temperature or the polymerization reaction time can be adjusted.

  The measuring method of a weight average molecular weight can be calculated | required by the following method.

(Average molecular weight measurement method)
The weight average molecular weight Mw and the number average molecular weight Mn were measured using gel permeation chromatography (GPC).

  The measurement conditions are as follows.

Solvent: Methylene chloride Column: Shodex K806, K805, K803G (Used by connecting three Showa Denko Co., Ltd.)
Column temperature: 25 ° C
Sample concentration: 0.1% by mass
Detector: RI Model 504 (manufactured by GL Sciences)
Pump: L6000 (manufactured by Hitachi, Ltd.)
Flow rate: 1.0ml / min
Calibration curve: Standard polystyrene STK standard polystyrene (manufactured by Tosoh Corporation) Mw = 100000 to 500 calibration curves with 13 samples were used. Thirteen samples are used at approximately equal intervals.

  The low molecular weight polymer Y used in the present invention is a polymer having a weight average molecular weight of 500 or more and 3000 or less obtained by polymerizing an ethylenically unsaturated monomer Ya having no aromatic ring. A weight average molecular weight of 500 or more is preferred because the residual monomer in the polymer is reduced.

  Moreover, it is preferable to set it as 3000 or less in order to maintain retardation value Rt fall performance. Ya is preferably an acrylic or methacrylic monomer having no aromatic ring.

  The polymer Y used in the present invention is represented by the following general formula (Y).

General formula (Y)
-[Ya] k- [Yb] q-
In the general formula (Y), Ya represents an ethylenically unsaturated monomer having no aromatic ring, and Yb represents an ethylenically unsaturated monomer copolymerizable with Ya. k and q each represent a molar composition ratio. However, k ≠ 0 and k + q = 100.

  The polymer Y according to the present invention is more preferably a polymer represented by the following general formula (Y-1).

General formula (Y-1)
_{- [CH 2 -C (-R5)} (- CO 2 R6)] k- [Yb] q-
In the general formula (Y-1), R5 represents a hydrogen atom or a methyl group, respectively. R6 represents an alkyl group having 1 to 12 carbon atoms or a cycloalkyl group. Yb represents a monomer unit copolymerizable with [CH ₂ —C (—R 5) (— CO ₂ R 6)]. k and q each represent a molar composition ratio. However, k ≠ 0 and k + q = 100.

Yb is a _{Ya [CH 2 -C (-R5)} (- CO 2 R6)] and is not particularly limited as long as it is copolymerizable ethylenically unsaturated monomers. Yb may be plural. k + q = 100, q is preferably 1-30.

  The ethylenically unsaturated monomer Ya constituting the polymer Y obtained by polymerizing the ethylenically unsaturated monomer having no aromatic ring is, for example, methyl acrylate, ethyl acrylate, propyl acrylate ( i-, n-), butyl acrylate (n-, i-, s-, t-), pentyl acrylate (n-, i-, s-), hexyl acrylate (n-, i-), acrylic Acid heptyl (n-, i-), octyl acrylate (n-, i-), nonyl acrylate (n-, i-), myristyl acrylate (n-, i-), cyclohexyl acrylate, acrylic acid ( 2-ethylhexyl), acrylic acid (ε-caprolactone), acrylic acid (2-hydroxyethyl), acrylic acid (2-hydroxypropyl), acrylic acid (3-hydroxypropiyl) ), Acrylic acid (4-hydroxybutyl), acrylic acid (2-hydroxybutyl), methacrylic acid ester, the above acrylic acid ester changed to methacrylic acid ester; unsaturated acid, for example, acrylic acid, methacrylic acid And maleic anhydride, crotonic acid, itaconic acid and the like.

  Yb is not particularly limited as long as it is an ethylenically unsaturated monomer copolymerizable with Ya. Examples of vinyl esters include vinyl acetate, vinyl propionate, vinyl butyrate, vinyl valerate, vinyl pivalate, and vinyl caproate. Vinyl caprate, vinyl laurate, vinyl myristate, vinyl palmitate, vinyl stearate, vinyl cyclohexanecarboxylate, vinyl octylate, vinyl methacrylate, vinyl crotonate, vinyl sorbate, vinyl cinnamate and the like are preferred. Yb may be plural.

  In order to synthesize the polymers X and Y, it is difficult to control the molecular weight in normal polymerization, and it is desirable to use a method that can make the molecular weight as uniform as possible by a method that does not increase the molecular weight too much.

  Such polymerization methods include a method using a peroxide polymerization initiator such as cumene peroxide and t-butyl hydroperoxide, a method using a polymerization initiator in a larger amount than normal polymerization, and a mercapto compound in addition to the polymerization initiator. And a method of using a chain transfer agent such as carbon tetrachloride, a method of using a polymerization terminator such as benzoquinone and dinitrobenzene in addition to the polymerization initiator, and further, Japanese Patent Application Laid-Open No. 2000-128911 or 2000-344823. Examples thereof include a compound having one thiol group and a secondary hydroxyl group, or a bulk polymerization method using a polymerization catalyst in which the compound and an organometallic compound are used in combination. Used.

  In particular, the polymer Y is preferably a polymerization method using a compound having a thiol group and a secondary hydroxyl group in the molecule as a chain transfer agent. In this case, the terminal of the polymer Y has a hydroxyl group and a thioether resulting from the polymerization catalyst and the chain transfer agent. The compatibility of Y and cellulose ester can be adjusted by this terminal residue.

  The hydroxyl values of the polymers X and Y are preferably 30 to 150 [mgKOH / g].

(Measurement method of hydroxyl value)
The measurement of the hydroxyl value is based on JIS K 0070 (1992). This hydroxyl value is defined as the number of mg of potassium hydroxide required to neutralize acetic acid bonded to a hydroxyl group when 1 g of a sample is acetylated.

  Specifically, sample Xg (about 1 g) is precisely weighed in a flask, and 20 ml of an acetylating reagent (a solution obtained by adding pyridine to 20 ml of acetic anhydride to 400 ml) is accurately added thereto. An air cooling tube is attached to the mouth of the flask and heated in a glycerin bath at 95-100 ° C. After 1 hour and 30 minutes, the mixture is cooled, 1 ml of purified water is added from an air condenser, and acetic anhydride is decomposed into acetic acid.

  Next, titration is performed with a 0.5 mol / L potassium hydroxide ethanol solution using a potentiometric titrator, and the inflection point of the obtained titration curve is set as the end point.

  Further, as a blank test, titration is performed without a sample, and an inflection point of the titration curve is obtained. The hydroxyl value is calculated by the following formula.

Hydroxyl value = {(BC) × f × 28.05 / X} + D
In the formula, B is the amount (ml) of 0.5 mol / L potassium hydroxide ethanol solution used for the blank test, C is the amount (ml) of 0.5 mol / L potassium hydroxide ethanol solution used for titration, f is a factor of a 0.5 mol / L potassium hydroxide ethanol solution, D is an acid value, and 28.05 is 1/2 of 1 mol amount 56.11 of potassium hydroxide.

  The above-mentioned polymer X and polymer Y are both excellent in compatibility with cellulose ester, excellent in productivity without evaporation and volatilization, good retention as a protective film for polarizing plates, low moisture permeability, and dimension stability. Excellent in properties.

The content of the polymer X and the polymer Y in the optical compensation film is preferably in a range satisfying the following formulas (i) and (ii). When the content of the polymer X is Xg (mass% = (mass of polymer X / mass of cellulose ester) × 100) and the content of the polymer Y is Yg (mass%),
Formula (i) 5 ≦ Xg + Yg ≦ 35 (mass%)
Formula (ii) 0.05 ≦ Yg / (Xg + Yg) ≦ 0.4
A preferable range of (Xg + Yg) in the formula (i) is 10 to 35% by mass. If the polymer X and the polymer Y are 5 mass% or more as a total amount with respect to the total mass of the cellulose ester, the polymer X and the polymer Y have a sufficient effect for adjusting the retardation value Rt. Moreover, if it is 35 mass% or less as a total amount, adhesiveness with polarizer PVA is favorable.

  The polymer X and the polymer Y can be directly added and dissolved as a material constituting the dope solution described later, or can be added to the dope solution after being previously dissolved in an organic solvent for dissolving the cellulose ester.

  The polyhydric alcohol ester plasticizer is a plasticizer comprising an ester of a dihydric or higher aliphatic polyhydric alcohol and a monocarboxylic acid, and preferably has an aromatic ring or a cycloalkyl ring in the molecule. Preferably it is a 2-20 valent aliphatic polyhydric alcohol ester.

  The polyhydric alcohol preferably used in the present invention is represented by the following general formula (a).

Formula (a) R1- (OH) n
However, R1 represents an n-valent organic group, n represents a positive integer of 2 or more, and the OH group represents an alcoholic and / or phenolic hydroxyl group.

  Examples of preferred polyhydric alcohols include the following, but the present invention is not limited to these.

  Adonitol, arabitol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propanediol, 1,3-propanediol, dipropylene glycol, tripropylene glycol, 1,2-butanediol, 1,3- Butanediol, 1,4-butanediol, dibutylene glycol, 1,2,4-butanetriol, 1,5-pentanediol, 1,6-hexanediol, hexanetriol, galactitol, mannitol, 3-methylpentane- Examples include 1,3,5-triol, pinacol, sorbitol, trimethylolpropane, trimethylolethane, xylitol and the like.

  In particular, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, sorbitol, trimethylolpropane, and xylitol are preferable.

  There is no restriction | limiting in particular as monocarboxylic acid used for polyhydric alcohol ester, Well-known aliphatic monocarboxylic acid, alicyclic monocarboxylic acid, aromatic monocarboxylic acid, etc. can be used. Use of an alicyclic monocarboxylic acid or aromatic monocarboxylic acid is preferred in terms of improving moisture permeability and retention.

  Examples of preferred monocarboxylic acids include the following, but the present invention is not limited thereto.

  As the aliphatic monocarboxylic acid, a fatty acid having a straight chain or side chain having 1 to 32 carbon atoms can be preferably used. The number of carbon atoms is more preferably 1-20, and particularly preferably 1-10. When acetic acid is contained, the compatibility with the cellulose ester is increased, and it is also preferable to use a mixture of acetic acid and another monocarboxylic acid.

  Preferred aliphatic monocarboxylic acids include acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, 2-ethyl-hexanoic acid, undecylic acid, lauric acid, tridecylic acid, Saturated fatty acids such as myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, lignoceric acid, serotic acid, heptacosanoic acid, montanic acid, melicic acid, laccelic acid, undecylenic acid, olein Examples thereof include unsaturated fatty acids such as acid, sorbic acid, linoleic acid, linolenic acid, and arachidonic acid.

  Examples of preferred alicyclic monocarboxylic acids include cyclopentane carboxylic acid, cyclohexane carboxylic acid, cyclooctane carboxylic acid, or derivatives thereof.

  Examples of preferred aromatic monocarboxylic acids include those in which 1 to 3 alkoxy groups such as an alkyl group, a methoxy group or an ethoxy group are introduced into the benzene ring of benzoic acid such as benzoic acid or toluic acid, biphenylcarboxylic acid, Examples thereof include aromatic monocarboxylic acids having two or more benzene rings such as naphthalenecarboxylic acid and tetralincarboxylic acid, or derivatives thereof. Benzoic acid is particularly preferable.

  The molecular weight of the polyhydric alcohol ester is not particularly limited, but is preferably 300 to 1500, and more preferably 350 to 750. A higher molecular weight is preferred because it is less likely to volatilize, and a smaller one is preferred in terms of moisture permeability and compatibility with cellulose ester.

  The carboxylic acid used for the polyhydric alcohol ester may be one kind or a mixture of two or more kinds. Moreover, all the OH groups in the polyhydric alcohol may be esterified, or a part of the OH groups may be left as they are.

  Below, the specific compound of a polyhydric alcohol ester is illustrated.

  The glycolate plasticizer is not particularly limited, but alkylphthalylalkyl glycolates can be preferably used.

  Examples of alkyl phthalyl alkyl glycolates include methyl phthalyl methyl glycolate, ethyl phthalyl ethyl glycolate, propyl phthalyl propyl glycolate, butyl phthalyl butyl glycolate, octyl phthalyl octyl glycolate, methyl phthalyl ethyl Glycolate, ethyl phthalyl methyl glycolate, ethyl phthalyl propyl glycolate, methyl phthalyl butyl glycolate, ethyl phthalyl butyl glycolate, butyl phthalyl methyl glycolate, butyl phthalyl ethyl glycolate, propyl phthalyl butyl glycol Butyl phthalyl propyl glycolate, methyl phthalyl octyl glycolate, ethyl phthalyl octyl glycolate, octyl phthalyl methyl glycolate, octyl phthalate Ethyl glycolate, and the like.

  Examples of the phthalate ester plasticizer include diethyl phthalate, dimethoxyethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate, dioctyl phthalate, dicyclohexyl phthalate, and dicyclohexyl terephthalate.

  Examples of the citrate plasticizer include acetyl trimethyl citrate, acetyl triethyl citrate, and acetyl tributyl citrate.

  Examples of fatty acid ester plasticizers include butyl oleate, methylacetyl ricinoleate, and dibutyl sebacate.

  Examples of the phosphate ester plasticizer include triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate, tributyl phosphate and the like.

  The polyvalent carboxylic acid ester compound is composed of an ester of divalent or higher, preferably divalent to 20 valent polyvalent carboxylic acid and alcohol. The aliphatic polyvalent carboxylic acid is preferably 2 to 20 valent, and in the case of an aromatic polyvalent carboxylic acid or an alicyclic polyvalent carboxylic acid, it is preferably 3 to 20 valent.

  The polyvalent carboxylic acid is represented by the following general formula (b).

Formula (b) R2 (COOH) m (OH) n
(Wherein R2 is an (m + n) -valent organic group, m is a positive integer of 2 or more, n is an integer of 0 or more, a COOH group is a carboxyl group, and an OH group is an alcoholic or phenolic hydroxyl group)
Examples of preferred polyvalent carboxylic acids include the following, but the present invention is not limited to these.

  Trivalent or higher aromatic polyvalent carboxylic acids such as trimellitic acid, trimesic acid, pyromellitic acid or derivatives thereof, succinic acid, adipic acid, azelaic acid, sebacic acid, oxalic acid, fumaric acid, maleic acid, tetrahydrophthal An aliphatic polyvalent carboxylic acid such as an acid, an oxypolyvalent carboxylic acid such as tartaric acid, tartronic acid, malic acid and citric acid can be preferably used. In particular, it is preferable to use an oxypolycarboxylic acid from the viewpoint of improving retention.

  There is no restriction | limiting in particular as alcohol used for the polyhydric carboxylic acid ester compound which can be used for this invention, Well-known alcohol and phenols can be used.

  For example, an aliphatic saturated alcohol or aliphatic unsaturated alcohol having a straight chain or a side chain having 1 to 32 carbon atoms can be preferably used. It is more preferable that it is C1-C20, and it is especially preferable that it is C1-C10.

  In addition, alicyclic alcohols such as cyclopentanol and cyclohexanol or derivatives thereof, aromatic alcohols such as benzyl alcohol and cinnamyl alcohol, or derivatives thereof can also be preferably used.

  When an oxypolycarboxylic acid is used as the polycarboxylic acid, the alcoholic or phenolic hydroxyl group of the oxypolycarboxylic acid may be esterified with a monocarboxylic acid. Examples of preferred monocarboxylic acids include the following, but the present invention is not limited thereto.

  As the aliphatic monocarboxylic acid, a fatty acid having a straight chain or a side chain having 1 to 32 carbon atoms can be preferably used. It is more preferable that it is C1-C20, and it is especially preferable that it is C1-C10.

  Preferred aliphatic monocarboxylic acids include acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, 2-ethyl-hexanecarboxylic acid, undecylic acid, lauric acid, tridecylic acid, Saturated fatty acids such as myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, lignoceric acid, serotic acid, heptacosanoic acid, montanic acid, melicic acid, and laccelic acid, undecylenic acid, olein Examples thereof include unsaturated fatty acids such as acid, sorbic acid, linoleic acid, linolenic acid, and arachidonic acid.

  Examples of preferred alicyclic monocarboxylic acids include cyclopentane carboxylic acid, cyclohexane carboxylic acid, cyclooctane carboxylic acid, or derivatives thereof.

  Examples of preferred aromatic monocarboxylic acids include those in which an alkyl group is introduced into the benzene ring of benzoic acid such as benzoic acid and toluic acid, and two or more benzene rings such as biphenyl carboxylic acid, naphthalene carboxylic acid, and tetralin carboxylic acid. The aromatic monocarboxylic acid which has, or those derivatives can be mentioned. Particularly preferred are acetic acid, propionic acid, and benzoic acid.

  The molecular weight of the polyvalent carboxylic acid ester compound is not particularly limited, but is preferably in the range of 300 to 1000, and more preferably in the range of 350 to 750. The larger one is preferable in terms of improvement in retention, and the smaller one is preferable in terms of moisture permeability and compatibility with cellulose ester.

  The alcohol used for the polyvalent carboxylic acid ester that can be used in the present invention may be one kind or a mixture of two or more kinds.

  The acid value of the polyvalent carboxylic acid ester compound that can be used in the present invention is preferably 1 mgKOH / g or less, and more preferably 0.2 mgKOH / g or less. Setting the acid value in the above range is preferable because the environmental fluctuation of retardation is also suppressed.

  In addition, an acid value means the milligram number of potassium hydroxide required in order to neutralize the acid (carboxyl group which exists in a sample) contained in 1g of samples. The acid value is measured according to JIS K0070.

  Examples of particularly preferred polyvalent carboxylic acid ester compounds are shown below, but the present invention is not limited thereto.

  For example, triethyl citrate, tributyl citrate, acetyl triethyl citrate (ATEC), acetyl tributyl citrate (ATBC), benzoyl tributyl citrate, acetyl triphenyl citrate, acetyl tribenzyl citrate, dibutyl tartrate, diacetyl dibutyl tartrate, Examples include tributyl trimellitic acid and tetrabutyl pyromellitic acid.

  The retardation film of the present invention preferably has a Ro range of 10 to 70 nm and a Rt range of 70 to 400 nm.

Ro = (nx−ny) × d
Rt = ((nx + ny) / 2−nz) × d
(Where nx is the refractive index in the slow axis direction in the plane of the cellulose ester film, ny is the refractive index in the direction perpendicular to the slow axis in the plane, nz is the refractive index in the thickness direction, and d is the refractive index in the thickness direction) (Represents the thickness (nm) of the cellulose ester film. The refractive index is measured at 590 nm.)
The refractive index can be obtained at a wavelength of 590 nm under an environment of 23 ° C. and 55% RH using, for example, KOBRA-21ADH (Oji Scientific Instruments).
<Other additives>
Hereinafter, other general additives that can be added to the optical film of the present invention will be described.

(UV absorber)
The cellulose ester film B according to the present invention can also contain an ultraviolet absorber. The ultraviolet absorber is intended to improve durability by absorbing ultraviolet rays of 400 nm or less, and in particular, the transmittance at a wavelength of 370 nm is preferably 10% or less, more preferably 5% or less, and further Preferably it is 2% or less.

  Although the ultraviolet absorber used in the present invention is not particularly limited, for example, oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, triazine compounds, nickel complex compounds, inorganic powders Examples include the body.

  For example, 5-chloro-2- (3,5-di-sec-butyl-2-hydroxylphenyl) -2H-benzotriazole, (2-2H-benzotriazol-2-yl) -6- (linear and side Chain dodecyl) -4-methylphenol, 2-hydroxy-4-benzyloxybenzophenone, 2,4-benzyloxybenzophenone, etc., and tinuvin 109, tinuvin 171, tinuvin 234, tinuvin 326, tinuvin 327, tinuvin 328, etc. These are commercially available products from Ciba Japan and can be preferably used.

  The UV absorbers preferably used in the present invention are benzotriazole UV absorbers, benzophenone UV absorbers, and triazine UV absorbers, particularly preferably benzotriazole UV absorbers and benzophenone UV absorbers. .

  In addition, a discotic compound such as a compound having a 1,3,5 triazine ring is also preferably used as the ultraviolet absorber.

  It is preferable that the polarizing plate protective film concerning this invention contains 2 or more types of ultraviolet absorbers.

  As the UV absorber, a polymer UV absorber can also be preferably used, and in particular, a polymer type UV absorber described in JP-A-6-148430 is preferably used.

  The method of adding the UV absorber can be added to the dope after dissolving the UV absorber in an alcohol such as methanol, ethanol or butanol, an organic solvent such as methylene chloride, methyl acetate, acetone or dioxolane or a mixed solvent thereof. Or you may add directly in dope composition.

  For an inorganic powder that does not dissolve in an organic solvent, a dissolver or a sand mill is used in the organic solvent and cellulose ester to disperse and then added to the dope.

  The amount of the UV absorber used is not uniform depending on the type of UV absorber, the operating conditions, etc., but when the dry film thickness of the polarizing plate protective film is 30 to 200 μm, it is 0.5 with respect to the polarizing plate protective film. -10 mass% is preferable, and 0.6-4 mass% is still more preferable.

(Antioxidant)
Antioxidants are also referred to as deterioration inhibitors. When a liquid crystal image display device or the like is placed in a high humidity and high temperature state, the cellulose ester film may be deteriorated.

  The antioxidant has a role of delaying or preventing the cellulose ester film from being decomposed by, for example, a residual solvent amount of halogen in the cellulose ester film or phosphoric acid of a phosphoric acid plasticizer. It is preferable to make it contain in a film.

  As such an antioxidant, a hindered phenol compound is preferably used. For example, 2,6-di-t-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di- -T-butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate], 1,6-hexanediol-bis [3 -(3,5-di-t-butyl-4-hydroxyphenyl) propionate], 2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-t-butylanilino)- 1,3,5-triazine, 2,2-thio-diethylenebis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], octa Sil-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, N, N'-hexamethylenebis (3,5-di-t-butyl-4-hydroxy-hydrocinnamamide) 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene, tris- (3,5-di-t-butyl-4-hydroxy Benzyl) -isocyanurate and the like.

  In particular, 2,6-di-t-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis [3 -(3-t-butyl-5-methyl-4-hydroxyphenyl) propionate] is preferred. Further, for example, hydrazine-based metal deactivators such as N, N′-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyl] hydrazine and tris (2,4-di- A phosphorus processing stabilizer such as t-butylphenyl) phosphite may be used in combination.

  The addition amount of these compounds is preferably 1 ppm to 1.0%, more preferably 10 to 1000 ppm in terms of mass ratio with respect to the cellulose derivative.

(Fine particles)
The cellulose ester film according to the present invention preferably contains fine particles.

  As fine particles used in the present invention, examples of inorganic compounds include silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, and hydrated silicic acid. Mention may be made of calcium, aluminum silicate, magnesium silicate and calcium phosphate. Further, fine particles of an organic compound can also be preferably used.

  Examples of organic compounds include polytetrafluoroethylene, cellulose acetate, polystyrene, polymethyl methacrylate, polypropyl methacrylate, polymethyl acrylate, polyethylene carbonate, acrylic styrene resin, silicone resin, polycarbonate resin, benzoguanamine resin, melamine resin Also, pulverized and classified products of organic polymer compounds such as polyolefin-based powders, polyester-based resins, polyamide-based resins, polyimide-based resins, polyfluorinated ethylene-based resins, and starches. Alternatively, a polymer compound synthesized by a suspension polymerization method, a polymer compound made spherical by a spray dry method or a dispersion method, or an inorganic compound can be used.

  Fine particles containing silicon are preferable in terms of low turbidity, and silicon dioxide is particularly preferable.

  The average primary particle diameter of the fine particles is preferably 5 to 400 nm, and more preferably 10 to 300 nm.

  These may be mainly contained as secondary aggregates having a particle size of 0.05 to 0.3 μm, and may be contained as primary particles without being aggregated if the particles have an average particle size of 100 to 400 nm. preferable.

  The content of these fine particles in the polarizing plate protective film is preferably 0.01 to 1% by mass, particularly preferably 0.05 to 0.5% by mass. In the case of a polarizing plate protective film having a multilayer structure by the co-casting method, it is preferable to contain fine particles of this addition amount on the surface.

  Silicon dioxide fine particles are commercially available, for example, under the trade names Aerosil R972, R972V, R974, R812, 200, 200V, 300, R202, OX50, TT600 (above Nippon Aerosil Co., Ltd.). it can.

  Zirconium oxide fine particles are commercially available, for example, under the trade names Aerosil R976 and R811 (manufactured by Nippon Aerosil Co., Ltd.), and can be used.

  Examples of the polymer include silicone resin, fluororesin and acrylic resin. Silicone resins are preferable, and those having a three-dimensional network structure are particularly preferable. For example, Tospearl 103, 105, 108, 120, 145, 3120, and 240 (manufactured by Toshiba Silicone Co., Ltd.) It is marketed by name and can be used.

  Among these, Aerosil 200V and Aerosil R972V are particularly preferably used because they have a large effect of reducing the friction coefficient while keeping the turbidity of the polarizing plate protective film low. In the polarizing plate protective film used in the present invention, the dynamic friction coefficient of at least one surface is preferably 0.2 to 1.0.

  Various additives may be batch-added to a dope that is a cellulose ester-containing solution before film formation, or an additive solution may be separately prepared and added in-line. In particular, it is preferable to add a part or all of the fine particles in-line in order to reduce the load on the filter medium.

  When the additive solution is added in-line, it is preferable to dissolve a small amount of cellulose ester in order to improve mixing with the dope. The amount of the cellulose ester is preferably 1 to 10 parts by mass, more preferably 3 to 5 parts by mass with respect to 100 parts by mass of the solvent.

In order to perform in-line addition and mixing in the present invention, for example, an in-line mixer such as a static mixer (manufactured by Toray Engineering) or SWJ (Toray static type in-tube mixer Hi-Mixer) is preferably used.
<The manufacturing method of the cellulose-ester film of this invention-film formation process->
<Method for producing cellulose ester film>
Next, the manufacturing method of the cellulose-ester film of this invention is demonstrated.

  The cellulose ester film according to the present invention can be preferably used regardless of whether it is a film produced by a solution casting method or a film produced by a melt casting method.

  The cellulose ester film of the present invention is prepared by dissolving a cellulose ester and an additive in a solvent to prepare a dope, casting a dope onto an endless metal support that moves infinitely, and casting the dope. It is carried out by a step of drying as a web, a step of peeling from a metal support, a step of stretching or maintaining the width, a step of further drying, and a step of winding up the finished film.

  The process for preparing the dope will be described. The concentration of cellulose ester in the dope is preferably higher because the drying load after casting on the metal support can be reduced. However, if the concentration of cellulose ester is too high, the load during filtration increases and the filtration accuracy is poor. Become. As a density | concentration which makes these compatible, 10-35 mass% is preferable, More preferably, it is 15-25 mass%.

  The solvent used in the dope may be used alone or in combination of two or more, but it is preferable to use a mixture of a good solvent and a poor solvent of cellulose ester in terms of production efficiency, and there are many good solvents. This is preferable from the viewpoint of the solubility of the cellulose ester.

  The preferable range of the mixing ratio of the good solvent and the poor solvent is 70 to 98% by mass for the good solvent and 2 to 30% by mass for the poor solvent. With a good solvent and a poor solvent, what dissolve | melts the cellulose ester to be used independently is defined as a good solvent, and what poorly swells or does not melt | dissolve is defined as a poor solvent.

  Therefore, depending on the average acetylation degree (acetyl group substitution degree) of the cellulose ester, the good solvent and the poor solvent change. For example, when acetone is used as the solvent, the cellulose ester acetate ester (acetyl group substitution degree 2.4), cellulose Acetate propionate is a good solvent, and cellulose acetate (acetyl group substitution degree 2.8) is a poor solvent.

  Although the good solvent used for this invention is not specifically limited, Organic halogen compounds, such as a methylene chloride, dioxolanes, acetone, methyl acetate, methyl acetoacetate, etc. are mentioned. Particularly preferred is methylene chloride or methyl acetate.

  Moreover, although the poor solvent used for this invention is not specifically limited, For example, methanol, ethanol, n-butanol, cyclohexane, cyclohexanone, etc. are used preferably. Moreover, it is preferable that 0.01-2 mass% of water contains in dope.

  Moreover, the solvent used for melt | dissolution of a cellulose ester collect | recovers the solvent removed from the film by drying at the film-forming process, and uses this again.

  The recovery solvent may contain trace amounts of additives added to the cellulose ester, such as plasticizers, UV absorbers, polymers, monomer components, etc., but even if these are included, they are preferably reused. Can be purified and reused if necessary.

  A general method can be used as a dissolution method of the cellulose ester when preparing the dope described above. When heating and pressurization are combined, it is possible to heat above the boiling point at normal pressure.

  It is preferable to stir and dissolve while heating at a temperature that is equal to or higher than the boiling point of the solvent at normal pressure and that the solvent does not boil under pressure, in order to prevent the generation of massive undissolved materials called gels and mamaco.

  A method in which a cellulose ester is mixed with a poor solvent and wetted or swollen, and then a good solvent is added and dissolved is also preferably used.

  The pressurization may be performed by a method of injecting an inert gas such as nitrogen gas or a method of increasing the vapor pressure of the solvent by heating. Heating is preferably performed from the outside. For example, a jacket type is preferable because temperature control is easy.

  The heating temperature with the addition of a solvent is preferably higher from the viewpoint of the solubility of the cellulose ester, but if the heating temperature is too high, the required pressure increases and the productivity deteriorates.

  A preferable heating temperature is 45 to 120 ° C, more preferably 60 to 110 ° C, and still more preferably 70 ° C to 105 ° C. The pressure is adjusted so that the solvent does not boil at the set temperature.

  Alternatively, a cooling dissolution method is also preferably used, whereby the cellulose ester can be dissolved in a solvent such as methyl acetate.

  Next, this cellulose ester solution is filtered using a suitable filter medium such as filter paper. As the filter medium, it is preferable that the absolute filtration accuracy is small in order to remove insoluble matters and the like, but there is a problem that the filter medium is easily clogged if the absolute filtration accuracy is too small.

  For this reason, a filter medium with an absolute filtration accuracy of 0.008 mm or less is preferable, a filter medium with 0.001 to 0.008 mm is more preferable, and a filter medium with 0.003 to 0.006 mm is still more preferable.

  There are no particular restrictions on the material of the filter medium, and ordinary filter media can be used. However, plastic filter media such as polypropylene and Teflon (registered trademark), and metal filter media such as stainless steel do not drop off fibers. preferable.

  It is preferable to remove and reduce impurities, particularly bright spot foreign matter, contained in the raw material cellulose ester by filtration.

Bright spot foreign matter means that when two polarizing plates are placed in a crossed Nicol state, an optical film or the like is placed between them, light is applied from one polarizing plate side, and observation is performed from the other polarizing plate side. It is a point (foreign matter) where light from the opposite side appears to leak, and the number of bright spots having a diameter of 0.01 mm or more is preferably 200 / cm ² or less.

More preferably, it is 100 pieces / cm < ² > or less, More preferably, it is 50 pieces / m < ² > or less, More preferably, it is 0-10 pieces / cm < ² > or less. Further, it is preferable that the number of bright spots of 0.01 mm or less is small.

  The dope can be filtered by a normal method, but the method of filtering while heating at a temperature not lower than the boiling point of the solvent at normal pressure and in a range where the solvent does not boil under pressure is the filtration pressure before and after filtration. The increase in the difference (referred to as differential pressure) is small and preferable.

  A preferred temperature is 45 to 120 ° C, more preferably 45 to 70 ° C, and still more preferably 45 to 55 ° C.

  A smaller filtration pressure is preferred. The filtration pressure is preferably 1.6 MPa or less, more preferably 1.2 MPa or less, and further preferably 1.0 MPa or less.

  Here, the dope casting will be described.

  The metal support in the casting (casting) step preferably has a mirror-finished surface. As the metal support, a stainless steel belt or a drum whose surface is plated with a casting is preferably used.

  The cast width can be 1 to 4 m. The surface temperature of the metal support in the casting step is −50 ° C. to a temperature lower than the boiling point of the solvent, and a higher temperature is preferable because the web can be dried faster. May deteriorate.

  A preferable support temperature is 0 to 55 ° C, and more preferably 25 to 50 ° C. Alternatively, it is also a preferable method that the web is gelled by cooling and peeled from the drum in a state containing a large amount of residual solvent.

  The method for controlling the temperature of the metal support is not particularly limited, and there are a method of blowing hot air or cold air, and a method of contacting hot water with the back side of the metal support. It is preferable to use warm water because heat transfer is performed efficiently, so that the time until the temperature of the metal support becomes constant is short. When warm air is used, wind at a temperature higher than the target temperature may be used.

  In order for the cellulose ester film to exhibit good flatness, the residual solvent amount when peeling the web from the metal support is preferably 10 to 150% by mass, more preferably 20 to 40% by mass or 60 to 130% by mass. Especially preferably, it is 20-30 mass% or 70-120 mass%.

  In the present invention, the amount of residual solvent is defined by the following formula.

Residual solvent amount (% by mass) = {(MN) / N} × 100
Note that M is the mass of a sample collected during or after the production of the web or film, and N is the mass after heating M at 114 ° C. for 1 hour.

  Further, in the drying step of the cellulose ester film, the web is peeled off from the metal support, and further dried, and the residual solvent amount is preferably 1% by mass or less, more preferably 0.1% by mass or less, Especially preferably, it is 0-0.01 mass% or less.

  In the film drying step, generally, a roll drying method (a method in which webs are alternately passed through a plurality of rolls arranged above and below) and a method in which the web is dried while being conveyed by a tenter method are employed.

  In order to produce the cellulose ester film of the present invention, it is particularly preferable to perform stretching in the width direction (lateral direction) by a tenter method in which both ends of the web are held with clips or the like. Peeling is preferably performed at a peeling tension of 300 N / m or less.

  The means for drying the web is not particularly limited, and can be generally performed with hot air, infrared rays, a heating roll, microwave, or the like, but it is preferably performed with hot air in terms of simplicity.

  The drying temperature in the web drying step is preferably increased stepwise from 40 to 200 ° C.

  Although the film thickness of a cellulose-ester film is not specifically limited, 10-200 micrometers is used. In particular, the film thickness is particularly preferably 10 to 100 μm. More preferably, it is 20-60 micrometers.

  The cellulose ester film of the present invention has a width of 1 to 4 m. In particular, those having a width of 1.4 to 4 m are preferably used. If it exceeds 4 m, conveyance becomes difficult.

(Tilt treatment step of cellulose ester film of the present invention)
The retardation film of the present invention is a biaxial retardation film having an optically distorted axis, and has a refractive index inclined to the minimum or maximum direction, and generates shear stress on the film surface. It can also be produced by performing a rolling process (also called a shear rolling process or a shearing process).

  More specifically, a method of sandwiching between two or more rollers whose loads are changed at a constant speed, a process of sandwiching between rollers (drive roller and follower roller shown in FIG. 1) or a belt having different peripheral speeds. The method, the method of controlling the peeling angle and peeling tension when peeling the film from the substrate (drum, belt, etc.) at the time of film formation, or the axis tilting treatment by wind described in Reference 4 and the film transporting by roller It is also possible to produce by shear rolling using a roller that does not rotate / drive the opposite side of the roller.

  Here, as shown in FIG. 1, the following roller is a rotating roller that freely rotates or forcibly rotates according to the contact pressure with the film to be conveyed, and is opposite to the film surface on which a force for conveying the film by the driving roller is applied. A rotating roller used to apply a force in the opposite direction so that a brake is applied on the film surface. Various brakes can be used for the load required for rotation. As a point, it is important to have a structure in which the load torque does not fluctuate, and it is necessary to perform control so that the torque including the driving roller is constant.

  These treatments are generally preferably carried out at a film treatment temperature in the range of Tg (glass transition temperature of the film) -50 ° C. to Tg + 40 ° C. However, in order to produce the retardation film of the present invention by these methods, variations occur, and it is necessary to further devise the process in order to produce it stably.

  In order to more stably produce the retardation film of the present invention, for example, after the rolling process for generating a shearing stress in the conveying direction, a process for generating a shearing stress in an oblique direction is performed with another side of the width. One side of the film is subjected to the rolling process with a roller that generates shear stress in the opposite direction and a roller that rotates in the conveying direction after the processing between the rollers of different peripheral speeds is performed once. And the other surface can be produced by a method such as shearing in an oblique direction with a residual solvent difference.

  In order to obtain the retardation film described in the present invention, it seems that it is necessary to make a difference between one side of the film and the other side during the shearing process, but physical properties that are directly effective are seen. Is not fully understood, temperature difference between one side of the film and the other side, residual melting difference, surface roughness difference, glass transition point difference, if the same glass transition point, such as hardness difference at that time The effect comes out. It is also effective to have a concentration gradient of additives such as a plasticizer and a phase difference developing agent in the film thickness direction.

  The retardation film of the present invention expresses a necessary function by generating a shear stress and deforming it by giving a difference in speed or path length between one side of the film and the other side. When this process is performed with a roller, drum, or belt sandwiched, if the film edge is subjected to a knurling process such as embossing in advance, the processing width should be carried out only inside the knurling part. Can do. You may slit an edge part after processing and knurling again.

  The retardation film of the present invention can be processed by a plurality of rollers or drums, but these must be different in surface hardness or elastic modulus, such as resin, elastic metal, rubber-coated metal, or metal-coated rubber. Are preferably combined.

  In that case, the surface material of the hard roller (or drum) is hard chrome plated, nickel plated, or a ceramic super hard material tungsten-carbide. For example, it is preferable that the material has good releasability and can be polished to a mirror surface. The surface roughness is 0.2 s or less, particularly preferably 0.1 s or less.

  The retardation film of the present invention may be processed by changing the temperature of the upper and lower rollers (or drums) to be processed at different temperatures, and may have a difference of about 150 ° C., for example. When rollers (or drums) having different surface hardness are used and a temperature difference is given to the rollers, it is preferable to increase the high hardness side at a high temperature because it is easy to stabilize from the viewpoint of control.

  Further, when the elasticity of the rollers is different and the peripheral speed difference is set, it is preferable that the roller on the lower elastic side is driven at a low speed or accompanied.

  Moreover, when performing these processes, you may carry out in the state in which the solvent remained in the web.

  For the roller peripheral speed, the peripheral speed ratio of the two rollers is important. In this case, when the contact distance is night and the drive is performed independently, the value of (high speed side speed / low speed side speed) is preferably 1.05 to 1.80, and 1.60 or less. More preferred.

  These are considered to be processes necessary for inclining the direction of the refractive index minimum of the refractive index ellipsoid, but other processes may be added to further flatten the axis.

  The pressure-bonding force of the two rollers is preferably 0.01 to 10 MPa, and more preferably 0.03 to 5 MPa. If the crimping force is too great, it is difficult to generate an inclination, which is not preferable, and it is important to carry out with a crimping force as low as possible. The crimping force at this time is the minimum force that prevents the roller and the web from slipping, and it is necessary to suppress deformation in the crushing direction as much as possible.

  The temperature at which the treatment of the present invention is carried out is preferably carried out at or above the glass transition point of the material used. If the temperature is at or below the glass transition point, variations are likely to occur during processing, making it difficult to ensure stability.

  In particular, it is preferable to treat at a high temperature as much as possible in a state in which a necessary amount of birefringence can be ensured because suppressing the pressure-bonding force during the treatment has an effect on stability.

  The practice of the present invention may be processed using a metal belt.

  The thickness of the metal belt to be used is preferably 0.2 mm or more in order to ensure a necessary crimping force so as not to slip.

  The film thickness of the film is preferably 150 μm or less before the process when the process of making a speed difference between the one side and the other side of the film is performed, but it is not limited to this when the birefringence is small. If it exceeds 150 μm, curling is likely to occur, and phase stability and unevenness of the optical axis are likely to occur, and stability may not be ensured.

  Although the detailed cause of the occurrence of unevenness is unknown, it is presumed that when force is transmitted in the thickness direction, the difference due to the distribution of the material in the thickness direction and the like is more noticeable.

  From this point of view, it is necessary to keep the thickness distribution as small as possible. The average value is usually within ± 10%, preferably within ± 5%, more preferably within ± 1%, and particularly preferably within ± 0.5%.

  The thickness variation per 1 cm is usually 1% or less, preferably 0.1% or less, more preferably 0.01% or less, and particularly preferably 0.005% or less. By controlling the thickness distribution of the optical film within the above range, it is possible to prevent the occurrence of uneven retardation and uneven alignment of the optical axis when the stretching process is performed in some cases.

(Stretching process)
In order to produce the retardation film of the present invention, stretching may optionally be performed. Specific examples include a known uniaxial stretching method or biaxial stretching method.

  That is, a horizontal uniaxial stretching method using a tenter method, a compression stretching method between rollers, a longitudinal uniaxial stretching method using two sets of rollers having different circumferences, or a stretching method using a biaxial stretching method combining a horizontal uniaxial and a longitudinal uniaxial. Etc. can be used.

  In the case of the uniaxial stretching method, the stretching speed is usually 0.1 to 200% / second, preferably 0.1 to 100% / second.

  In the case of the biaxial stretching method, stretching may be performed in two directions at the same time, or the stretching may be performed in a direction different from the first stretching direction after uniaxial stretching.

  At this time, the intersecting angle of the two stretching axes for controlling the shape of the refractive index ellipsoid of the film after stretching is not particularly limited because it is determined by desired characteristics, but is usually in the range of 45 to 120 degrees. It is.

  The stretching speed may be the same in each stretching direction or may be different, and is preferably 0.1 to 200% / second. The draw ratio is not particularly limited because it is determined by desired properties, but is usually 1.01 to 10 times, preferably 1.03 to 5 times, and more preferably 1.03 to 3 times. When the draw ratio exceeds 10 times, it may be difficult to control the phase difference.

  The stretched film may be cooled as it is, but it is preferably 1 second or longer in a temperature atmosphere of Tg-20 ° C to Tg.

  These stretching treatments may be carried out at any stage, but from the viewpoint of finishing the final product, it is preferable to carry out after the treatment with a roller or the like. In particular, in order to make the flatness, the film thickness distribution and the like more uniform, it is preferable to carry out after the treatment with a roller.

(Final process)
As the final step of film formation, after slitting the edge of the film to the product width with a slitter, the film is subjected to knurling (embossing) on both ends of the film with a knurling device consisting of an embossing ring and a back roll. By winding with a winder, the cellulose ester film (original winding) is prevented from sticking and scratches are prevented.

  The knurling method can process a metal ring having an uneven pattern on its side surface by heating or pressing. In addition, since the grip part of the clip of the both ends of a film is deform | transforming normally and cannot be used as a film product, it is cut out and reused as a raw material.

  In general, it is known that the melt-extrusion tends to increase the residence time on the end side due to the shape of the casting die, and this is thought to promote the coloring of the film end.

  In the present invention, the yellow index Ye at the end in the width direction of the film immediately after melt extrusion and the yellow index Yc at the center of the film preferably satisfy the following formula, more preferably Ye / Yc is 3.0 or less. If Ye / Yc is greater than 5.0, the color of the produced film increases when the film edge is cut off and reused as a raw material.

  In the present invention, the yellow index at the end is defined as the maximum value within 30 mm from both ends in the width direction of the film.

Formula 1.0 ≦ Ye / Yc ≦ 5.0
In the case of an optical film application, the thickness of the film is preferably 10 to 500 μm. In particular, the lower limit is 20 μm or more, preferably 30 μm or more. The upper limit is 150 μm or less, preferably 120 μm or less. A particularly preferable range is 25 to 90 μm.

  The film thickness variation of the cellulose ester film of the present invention is preferably in the range of ± 3%, and more preferably ± 1%.

  The glass transition temperature Tg mentioned here is a temperature increase / decrease process after performing temperature increase / decrease at 10 ° C./min using a differential scanning calorimeter (DSC-7 type manufactured by Perkin Elmer). Then, the Tg at that time was measured, and the intermediate glass transition temperature (Tmg) determined according to JIS K7121 (1987) was used.

(Formation of functional layer)
In producing the cellulose ester film of the present invention, before and / or after stretching, a transparent conductive layer, a hard coat layer, an antireflection layer, a slippery layer, an easy adhesion layer, an antiglare layer, a barrier layer, an optical compensation layer, etc. A functional layer may be applied.

In particular, it is preferable to provide at least one layer selected from a transparent conductive layer, a hard coat layer, an antireflection layer, an easy adhesion layer, an antiglare layer, and an optical compensation layer. At this time, various surface treatments such as corona discharge treatment, plasma treatment, and chemical treatment can be performed as necessary.
<Polarizing plate>
The polarizing plate can be produced by a general method. The cellulose ester film of the present invention is preferably subjected to alkali saponification treatment, and the treated film is bonded to at least one surface of a polarizer prepared by immersing and stretching in an iodine solution using a completely saponified polyvinyl alcohol aqueous solution. . The cellulose ester film of the present invention may be used on the other surface, or another optical film or a polarizing plate protective film may be used.

  With respect to the cellulose ester film of the present invention, a commercially available cellulose ester film can be used as the optical film and the polarizing plate protective film used on the other surface. For example, as a commercially available cellulose ester film, KC8UX, KC4UX, KC5UX, KC8UCR3, KC8UCR4, KC8UCR5, KC8UY, KC4UY, KC10UDR, KC4FR, KC4UE, KC8UE, KC8UY-HA, HC8UY-HA, KC8UX -NC, KC4UXW-RHA-NC (manufactured by Konica Minolta Opto Co., Ltd.) and the like are preferably used.

  Alternatively, it is also preferable to use an optical film that also serves as an optical compensation film having an optical anisotropic layer formed by aligning liquid crystal compounds such as discotic liquid crystal, rod-shaped liquid crystal, and cholesteric liquid crystal.

  For example, the optically anisotropic layer can be formed by the method described in JP-A-2003-98348. By using it in combination with the cellulose ester film of the present invention, a polarizing plate having excellent flatness and a stable viewing angle expansion effect can be obtained.

  A polarizer, which is a main component of a polarizing plate, is an element that allows only light of a plane of polarization in a certain direction to pass. A typical polarizer currently known is a polyvinyl alcohol-based polarizing film, which is polyvinyl alcohol. There are one in which iodine is dyed on a system film and one in which dichroic dye is dyed.

  For the polarizer, a polyvinyl alcohol aqueous solution is formed into a film and dyed by uniaxial stretching or dyed or uniaxially stretched and then preferably subjected to a durability treatment with a boron compound. On the surface of the polarizer, one side of the cellulose ester film of the present invention is bonded to form a polarizing plate. It is preferably bonded with an aqueous adhesive mainly composed of completely saponified polyvinyl alcohol or the like.

  The long cellulose ester film produced by the melt casting film-forming method according to the present invention can be bonded with a long polarizer (polarizing film) by subjecting it to alkali saponification treatment. The productive effect is obtained with a long length of 1, and the longer the length is 1500 m, 2500 m, and 5000 m, the higher the productive effect of manufacturing the polarizing plate.

Moreover, since the polarizing plate using the cellulose ester film of this invention is excellent in rework property, the effect that a polarizing plate yield improves can also be acquired.
<Liquid crystal display device>
The polarizing plate containing the cellulose ester film of the present invention can exhibit high display quality as compared with a normal polarizing plate.

  The polarizing plate of the present invention can be used in a TN mode, an OCB (Optical Compensated Bend) mode, an IPS (In-Plane Switching) mode, and the like.

  The liquid crystal display device is applied as a device for colorization and moving image display, and the display quality is improved by the present invention, and the contrast is improved and the resistance of the polarizing plate is improved. .

The present invention will be specifically described below with reference to examples.
Example 1
<Production of retardation film>
Hereinafter, although an example is given and the present invention is explained, the present invention is not limited to these. In addition, the conditions which perform a shearing process were made into the range of Tg-30 degreeC-Tg + 100 degreeC in preparation of all the retardation films. The cellulose esters used are listed in Table 1.
<Production of Cellulose Ester Film 101>
<Fine particle dispersion 1>
Fine particles (Aerosil R812 manufactured by Nippon Aerosil Co., Ltd.) 11 parts by weight Ethanol 89 parts by weight The above was stirred and mixed with a dissolver for 50 minutes, and then dispersed with Manton Gorin.

<Fine particle addition liquid 1>
The fine particle dispersion 1 was slowly added to the dissolution tank containing methylene chloride with sufficient stirring. Further, the particles were dispersed by an attritor so that the secondary particles had a predetermined particle size. This was filtered through Finemet NF manufactured by Nippon Seisen Co., Ltd. to prepare a fine particle additive solution 1.

Methylene chloride 99 parts by mass Fine particle dispersion 1 5 parts by mass A main dope solution having the following composition was prepared. First, methylene chloride and ethanol were added to the pressure dissolution tank. Cellulose esters A and B were added to a pressure dissolution tank containing a solvent while stirring. This is completely dissolved with heating and stirring. This was designated as Azumi Filter Paper No. The main dope solution was prepared by filtration using 244.

<Composition of main dope solution>
Methylene chloride 340 parts by mass Ethanol 64 parts by mass Cellulose ester CE1 of the present invention 100 parts by mass Polyester compound 14 of the present invention 6.5 parts by mass Sugar ester compound 3 of the present invention 6.0 parts by mass Fine particle additive solution 1 1 part by mass or more Was put into a sealed container and dissolved while stirring to prepare a dope solution. Next, using an endless belt casting apparatus, the dope solution was uniformly cast on a stainless steel belt support at a temperature of 33 ° C. and a width of 1500 mm. The temperature of the stainless steel belt was controlled at 30 ° C.

  With the stainless steel band support, the solvent was evaporated until the residual solvent amount became 105%, and the film was peeled from the stainless steel band support with a peeling tension of 162 N / m.

  Then, after drying at 120 ° C., the web is conveyed at a speed of 85 m / min, and the web is set to a pressure of 2.1 MPa (contact width is 6 mm) with a metal roller having a diameter of 35 cm and an elastic metal roller. The speed of the elastic metal roller was made the same as the conveying speed, the speed of the metal roller was set to 98 m / min, and the first shearing process was performed. The residual solvent when passing through this roller was 1.2% by mass.

  Subsequently, with the same setting, the second shearing process by the metal roller (driving roller) / elastic metal roller (following roller) whose rotation direction is 50 degrees and the conveyance direction, and further, the conveyance direction and the −50 degrees direction. A third shearing treatment was performed with a metal roller / elastic metal roller. During the second shearing process, the speed of the metal roller was set to 99 m / min, and during the third shearing process, the rotation speed of the metal roller was set to 98.5 m / min. The set temperatures of the metal rollers were all 185 ° C.

  Then, the extending | stretching process was performed in the direction orthogonal to a conveyance direction with the tenter. The stretching temperature was set at 155 ° C., the stretching ratio was 1.08 times, and the stretching speed was 15% / second.

  After stretching with a tenter and releasing the width holding by releasing the width tension at 130 ° C., drying is terminated while conveying the drying zone at 120 ° C. and 130 ° C. with a number of rolls, and slitting to a width of 1.75 m, A knurling process with a width of 10 mm and a height of 7 μm was applied to both ends of the film, and the film was wound around a core having an inner diameter of 6 inches with an initial tension of 220 N / m and a final tension of 110 N / m to obtain a retardation film 101 with a film thickness of 42 μm.

<Phase difference film 102>
In the production of the phase difference film 101, the speed of the metal roller in the second and third shearing treatments was 104 m / min, and the stretching by the tenter was 1.2 times (stretching speed was 40% / second). A retardation film 102 having a thickness of 34 μm was produced in the same manner as the retardation film 101.
<Phase difference films 103, 104, 105, 106>
In the production of the retardation film 101, a dope was produced and formed in the same manner except that the composition of the main dope solution was changed to the following.

<Composition of main dope solution>
Methylene chloride 340 parts by mass Ethanol 64 parts by mass Cellulose ester CE2 of the present invention 100 parts by mass Polyester compound 14 of the present invention 8.0 parts by mass Sugar ester compound 3 of the present invention 5.0 parts by mass Fine particle additive solution 1 1 part by mass The phase difference film 103 having a film thickness of 50 μm at a shearing process of 1st, 2nd and 3rd times, a metal roller speed of 85.6 m / min, a stretching ratio of 1.20 times with a tenter, a stretching temperature of 165 ° C., A retardation film 104 having a film thickness of 60 μm was prepared by setting the temperature of the metal roller to 195 ° C., the stretching ratio of the tenter to 1.15 times, and the stretching temperature to 145 ° C. Both residual solvents during the metal roller treatment were 2.2% by mass.

The stretching condition of the retardation film 103 in the tenter is 1.55 times at 175 ° C., the retardation film 105 having a film thickness of 25 μm, the second metal roller temperature of the retardation film 103 is 195 ° C., and the third temperature is 175 A retardation film 106 having a thickness of 70 μm was produced at a temperature of 0 ° C.
<Preparation of retardation film 107>
In the production of the retardation film 101, a dope was produced and formed in the same manner except that the composition of the main dope solution was changed to the following.

<Composition of main dope solution>
Methylene chloride 340 parts by mass Ethanol 64 parts by mass Cellulose ester CE2 of the present invention 100 parts by mass Polyester compound 14 of the present invention 8.0 parts by mass Sugar ester compound 3 of the present invention 5.0 parts by mass Fine particle additive 1 1 part by mass In the production of the phase difference film 101, the film thickness is the same as that of the phase difference film 102 except that the second treatment angle of the metal roller is 5 degrees with respect to the conveying direction and the speed of the metal roller is 121 m / min. A 45 μ retardation film 107 was produced.
<Preparation of retardation films 108 and 109>
In the production of the retardation film 101, a dope was produced and formed in the same manner except that the composition of the main dope solution was changed to the following.

<Composition of main dope solution>
Methylene chloride 340 parts by mass Ethanol 64 parts by mass Cellulose ester CE2 of the present invention 100 parts by mass Polyester compound 14 of the present invention 9.0 parts by mass Sugar ester compound 3 of the present invention 5.0 parts by mass Fine particle additive solution 1 1 part by mass In the preparation of the phase difference film 101, the first treatment of the shearing process was performed using a 2.8 mm metal belt made of SUS instead of the metal roller, the pressure was set to 2.8 MPa, and the contact width was set to 15 cm. The processing was performed at a speed of 88 m / min, an atmospheric temperature of 200 ° C., a tenter stretching temperature of 176 ° C., and a stretching ratio of 1.68 times. The phase difference of the retardation film 108 was changed except that the speed of the metal belt was 86.5 m / min and the stretch ratio of the tenter was 1.9 times. A retardation film was prepared 109 having a thickness of 34μm in the same way as Irumu 101.
<Preparation of retardation film 110>
In the production of the retardation film 101, a dope was produced and formed in the same manner except that the composition of the main dope solution was changed to the following.

<Composition of main dope solution>
Methylene chloride 340 parts by mass Ethanol 64 parts by mass Cellulose ester CE2 of the present invention 100 parts by mass Polyester compound 14 of the present invention 9.0 parts by mass Sugar ester compound 3 of the present invention 5.0 parts by mass Fine particle additive solution 1 1 part by mass In the preparation of the phase difference film 101, the first treatment of the shearing process was performed using a 2.8 mm metal belt made of SUS instead of the metal roller, the pressure was set to 2.8 MPa, and the contact width was set to 15 cm. The process was performed at a speed of 88 m / min, an atmospheric temperature of 200 ° C., a tenter stretching temperature of 175 ° C., and a stretching ratio of 1.70 times. A retardation film 110 was produced.
<Preparation of retardation film 111>
In the production of the retardation film 101, a dope was produced and formed in the same manner except that the composition of the main dope solution was changed to the following.

<Composition of main dope solution>
Methylene chloride 340 parts by mass Ethanol 64 parts by mass Cellulose ester CE2 of the present invention 100 parts by mass Polyester compound 14 of the present invention 9.0 parts by mass Sugar ester compound 3 of the present invention 5.0 parts by mass Fine particle additive solution 1 1 part by mass In the production of the phase difference film 101, the first treatment of the shearing process was performed using a 2.8 mm metal belt made of SUS instead of the metal roller, the pressure was set to 2.6 MPa, and the contact width was set to 15 cm. The film was processed at a speed of 88 m / min, an atmospheric temperature of 186 ° C., a tenter stretching temperature of 158 ° C., and a stretching ratio of 1.50 times. A retardation film 111 was produced.

(Preparation of polarizing plates 101-111)
Using the produced cellulose ester films 101 to 111, a polarizing plate was produced after the alkali saponification treatment described below.

<Alkali saponification treatment>
Saponification step 2M-NaOH 50 ° C. 90 seconds Water washing step Water 30 ° C. 45 seconds Neutralization step 10% HCl 30 ° C. 45 seconds Water washing step Water 30 ° C. 45 seconds After saponification treatment, water washing, neutralization, water washing are performed in this order. Subsequently, it dried at 80 degreeC.

<Production of polarizer>
A 120 μm-thick long roll polyvinyl alcohol film was immersed in 100 parts by mass of an aqueous solution containing 1 part by mass of iodine and 4 parts by mass of boric acid, and stretched 6 times at 50 ° C. in the transport direction to produce a polarizer.

  The KC8UX manufactured by Konica Minolta Opto Co., Ltd. was similarly saponified on one side of the polarizer, and the cellulose ester film of the present invention that had been subjected to the alkali saponification treatment was bonded to the opposite side with a completely saponified polyvinyl alcohol 5% aqueous solution. As an agent, each was bonded and dried so that the transmission axis of the polarizer and the in-plane slow axis of the film were parallel to each other.

The polarizing plate 107 was produced by rotating the retardation film 107 by 90 degrees so that the in-plane slow axis of the retardation film and the transmission axis of the polarizer were orthogonal to each other.
<Preparation of retardation film 112>
ZEONOR film ZF-14 (manufactured by Optes Co., Ltd.) is transported at a speed of 2.2 m / min with a metal roller having a diameter of 35 cm and an elastic metal roller, resulting in a pressing force of 8.8 MPa (contact width is 6 mm). The elastic metal roller was set at the same speed as the conveying speed, and the metal roller was sheared so that the speed of the metal roller was 2.5 m / min.

  Subsequently, with the same setting, the second treatment by the metal roller / elastic metal roller whose rotation direction is the conveyance direction and the 50 degree direction, and the third treatment by the metal roller / elastic metal roller whose rotation direction is the -50 degree direction. Was processed. During the second treatment, the speed of the metal roller was set to 2.7 m / min, and during the third treatment, the rotation speed of the metal roller was set to 2.75 m / min. The set temperatures of the metal rollers were all 165 ° C.

Then, the extending | stretching process was performed in the direction orthogonal to a conveyance direction with the tenter. The retardation film 112 was produced by setting the stretching temperature to 148 ° C., the stretching ratio to 1.15 times, and the stretching speed to 15% / second.
<Preparation of retardation film 113>
Film formation is performed in the same manner as the phase difference film 112, and the web is conveyed at 2.2 m / min with a metal roller having a diameter of 35 cm and an elastic metal roller so that the pressure is 8.8 MPa (contact width is 6 mm). The speed of the elastic metal roller was set to be the same as the conveying speed, and the speed of the metal roller was set to 3.2 m / min.

  Subsequently, with the same setting, the second treatment by the metal roller / elastic metal roller whose rotation direction is the conveyance direction and the 50 degree direction, and the third treatment by the metal roller / elastic metal roller whose rotation direction is the -50 degree direction. Was processed. During the second treatment, the speed of the metal roller was set to 2.9 m / min, and during the third treatment, the rotation speed of the metal roller was set to 2.85 m / min. The set temperatures of the metal rollers were all 155 ° C.

Then, the extending | stretching process was performed in the direction orthogonal to a conveyance direction with the tenter. The retardation temperature was set to 148 ° C., the stretching ratio was 1.3 times, and the stretching speed was 20% / second to prepare the retardation film 113.
<Preparation of retardation films 201 and 202>
A retardation film 201 was produced in the same manner as the retardation film 112 except that film formation was performed in the same manner as the retardation film 112 and the second and third roller treatments were not performed.

  Film formation was performed in the same manner as the phase difference film 113, and the phase difference film 202 was produced at 148 ° C. without performing the second and third roller treatments, with a draw ratio of 1.28 times and a draw rate of 19% / second. did.

(Preparation of polarizing plates 112, 113, 201, 202)
Using the produced retardation film, it was bonded to a polarizer produced as follows through an acrylic adhesive (manufactured by Sumitomo 3M, product name “DP-8005 clear”).

<Production of polarizer>
A 120 μm-thick long roll polyvinyl alcohol film was immersed in 100 parts by mass of an aqueous solution containing 1 part by mass of iodine and 4 parts by mass of boric acid, and stretched 6 times at 50 ° C. in the transport direction to produce a polarizer.

On the opposite side of the polarizer to which the retardation film is bonded, the saponified KC8UX manufactured by Konica Minolta Opto Co., Ltd. is used as a fully saponified polyvinyl alcohol 5% aqueous solution as an adhesive, and the transmission axis of the polarizer and the film Each of them was bonded and dried so that the in-plane slow axes were parallel to each other.
<Preparation of retardation film 203>
In the production of the retardation film 101, a dope was produced and formed in the same manner except that the composition of the main dope solution was changed to the following.

<Composition of main dope solution>
Methylene chloride 340 parts by mass Ethanol 64 parts by mass Cellulose ester CE2 of the present invention 100 parts by mass Polyester compound 14 of the present invention 8.0 parts by mass Sugar ester compound 3 of the present invention 5.0 parts by mass Fine particle additive 1 1 part by mass In the production of the phase difference film 101, a shearing 2.8 mm metal belt was used instead of the metal roller for the first treatment, the pressure was 2.2 MPa, the conveyance speed was 14 m / min, and the contact width was 15 cm. The retardation film 203 is manufactured by setting the speed of the metal roller to 15 m / min, setting the atmosphere temperature to 210 ° C., setting the stretching temperature in the tenter to 178 ° C., and the stretching ratio to 2.1 times. did.
<Preparation of retardation films 204 and 205>
The film was formed in the same manner as the phase difference film 101, and the second roller treatment and the third roller treatment were not performed, and the stretching conditions in the tenter were the stretching temperature of 130 ° C., the stretching ratio of 1.21 times, and 114 ° C. Retardation films 204 and 205 were produced at a double magnification.
<Preparation of retardation film 206>
It produced according to the optical compensation film of Unexamined-Japanese-Patent No. 2000-155216 Example 1.
<Preparation of retardation film 207>
It was produced according to the optical compensation film described in Example 1 of JP-A-7-98412.

(Preparation of polarizing plates 203 to 207)
The retardation films 203 to 207 were saponified under the above conditions and adhered to a polarizer to produce polarizing plates 203 to 207.

  For the polarizing plate 207, a polarizing plate was prepared such that the slow axis and the transmission axis of the polarizer were parallel to each other through an adhesive layer on a polarizing plate using Konica Minolta Op KC8UX.

<Production of liquid crystal display device>
(Production of liquid crystal display device)
The obtained polarizing plate was carefully peeled off from the polarizing plate previously bonded to the NEC 17-type liquid crystal display LCD72V, which is a TN type liquid crystal display device, and adjusted in accordance with the transmission axis of the polarizing plate originally applied. A liquid crystal display device was produced by attaching a polarizing plate produced through the film.

(Evaluation)
<Measurement of phase difference (Ro, Nz) and tilt angle β>
The measurement was performed at a wavelength of 590 nm in an atmosphere of 23 ° C. and 55% RH using KOBRA-31WR manufactured by Oji Scientific Instruments and DVA36VW manufactured by Mizoji Engineering.

<Viewing angle evaluation>
Using EZ-Contrast 160D manufactured by ELDIM, the angle at which contrast 10 was obtained from the brightness measurement of white and black was taken as the viewing angle. Grain reversal and color shift were visually evaluated by 20 people.

<Gradation inversion>
Using a wedge that displays white to black in 8 steps, observe the angle at which the brightness begins to change up, down, sideways, and diagonally down, ◯ over 30 degrees in all directions, and down over 30 degrees in all other directions The direction is 20 to 30 degrees, and Δ is 20 degrees in any one direction.

<Color shift>
Observe the four colors red, blue, green, and white in the top, bottom, diagonally down, and horizontal directions. If the color change is not more than 30 degrees, the color change in one direction is between 20 and 30 degrees. Those that can be clearly recognized are Δ, and those that can be clearly recognized within 20 degrees in two directions or within 10 degrees in one direction are marked with ×. Furthermore, the color at a tilt angle of 60 degrees was confirmed in the horizontal direction during white display.

<Frame unevenness>
The display device was treated at 50 ° C. and 90% RH for 200 hours. Immediately after the display device was taken out, it was displayed in black and allowed to stand at room temperature for 2 hours, and was judged by the magnitude and strength of unevenness generated on the entire surface and the frame shape. ○ If there is no noticeable unevenness or a non-problematic non-uniformity occurs in one place, ○ If there is a non-practical unevenness in two places △ If there is a noticeable unevenness in one place What was there was marked with x.

  The results are shown in Table 2.

  From Table 2, it is clear that the present invention has a wide contrast viewing angle and small phase difference unevenness.

1R Driving roller 2R Following roller MD Film transport direction F Film X Direction of maximum in-plane refractive index of refractive index ellipsoid Y In-plane direction of refractive index ellipsoid of refractive index ellipsoid and orthogonal to in-plane maximum refractive index Direction Z Refractive index minimum direction of refractive index ellipsoid A Angle formed by X axis and Z axis B Angle formed by X axis and Y axis C Angle formed by Y axis and Z axis β Angle formed by normal direction of film and Z axis

Claims (2)

When optically a biaxial retardation film and the X-axis, Y-axis, Z-axis, A, B, C, and β are defined as follows, all the following relationships (1) to (6) are satisfied. A retardation film comprising:
(1) 0 ≦ β ≦ 50 degrees (2) B = 90 degrees (3) A ≠ 90 degrees (4) C ≠ 90 degrees (5) 80 degrees <A <90 degrees (6) 80 degrees <C <90 degrees X axis: direction of the in-plane maximum refractive index of the refractive index ellipsoid Y axis: direction in the plane of the refractive index ellipsoid of the refractive index ellipsoid and perpendicular to the in-plane maximum refractive index Z axis: refractive index ellipsoid A: X-axis and Z-axis angle B: X-axis and Y-axis angle C: Y-axis and Z-axis angle β: Film normal direction and Z-axis angle   The retardation film according to claim 1, wherein the retardation film is a cellulose ester film.