WO2009087905A1

WO2009087905A1 - Laminated retardation film, polarizing plate and liquid crystal display device

Info

Publication number: WO2009087905A1
Application number: PCT/JP2008/073540
Authority: WO
Inventors: Ayako Ouchi; Shigeki Oka
Original assignee: Konica Minolta Opto, Inc.
Priority date: 2008-01-10
Filing date: 2008-12-25
Publication date: 2009-07-16
Also published as: JPWO2009087905A1

Abstract

Disclosed is a laminated retardation film suitable for continuous production, which is free from problems such as cracks and fractures and does not cause display unevenness when used in a liquid crystal display device. Specifically disclosed is a laminated retardation film which is a laminate of a positively birefringent resin layer and a negatively birefringent resin layer. The laminated retardation film is characterized in that the negatively birefringent resin layer contains a copolymer having a monomer unit L represented by general formula (1) and an ethylenically unsaturated monomer unit M. general formula (1)

Description

Laminated retardation film, polarizing plate and liquid crystal display device

The present invention relates to a laminated retardation film, a polarizing plate, and a liquid crystal display device, and more specifically, a laminated retardation film suitable for continuous production with no unevenness in the screen and failure such as cracks or cracks when used in a liquid crystal display device. Related to film.

Conventionally, retardation films for optical compensation have been used in liquid crystal display devices. As a general method for producing the retardation film, there is a method in which a polymer film is uniaxially or biaxially stretched by various stretching techniques. Can be mentioned. However, since the retardation produced by stretching depends on the optical properties of the polymer, the retardation control range is limited, and a sufficient viewing angle expansion effect cannot be obtained.

Therefore, in order to obtain a further viewing angle widening effect, optical compensation using a plurality of polymer films having birefringence different from positive and negative has been proposed as a viewing angle compensation method for liquid crystal display devices. (For example, refer patent document 1.) As this realization method, although the method of laminating | stacking and laminating | stacking and laminating | stacking several retardation films produced separately is mentioned, in order to bond, an adhesive layer is interposed. Therefore, the thickness of the entire retardation film is increased accordingly, which is unsuitable as a member for use in a liquid crystal display device that is required to be thin. Moreover, there also existed problems, such as a shaft gap occurring between films at the time of bonding. Therefore, as a method for producing a laminate having birefringence different from positive and negative, a method of co-casting and stretching a positive birefringent resin and a negative birefringent resin is disclosed (for example, Patent Documents). 2).

Therefore, the inventors have found that there is a problem that unevenness occurs on the entire screen when a laminated retardation film is produced based on this method and used in a liquid crystal display device. Further, when continuous production of the retardation film was attempted, defects such as cracks and cracks occurred in the negative birefringent resin layer during roll conveyance, and it was difficult to produce a long film.
JP 2006-235576 A US Pat. No. 7,211,304

Therefore, an object of the present invention is to provide a laminated phase difference film suitable for continuous production with no unevenness in the screen and no failure such as cracks when used in a liquid crystal display device.

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

1. A laminate of a positive birefringent resin layer and a negative birefringent resin layer, wherein the negative birefringent resin layer is a monomer unit L represented by the following general formula (1) and an ethylenically unsaturated monomer A laminated retardation film comprising a copolymer having units M.

(Only one of R ₁ to R ₆ is a substituent represented by the general formula (2), and other than that, halogen such as hydrogen, F, Cl, Br, hydroxyl group, carboxyl group, amino Group, cyano group, nitro group, nitroso group, thiol group, saturated hydrocarbon group having 1 to 12 carbon atoms, alkoxyl group having 1 to 12 carbon atoms, acyl group having 1 to 12 carbon atoms, acyloxy having 1 to 12 carbon atoms Groups, alkyloxycarbonyl groups having 1 to 12 carbon atoms, hydrocarbon groups having 1 to 4 carbon atoms having a hydroxyl group, hydrocarbon groups having 1 to 4 carbon atoms having an amino group, and hydrocarbon groups having 1 to 4 carbon atoms. Represents a secondary or tertiary amino group.

R in the general formula (2) is hydrogen, hydroxyl group, carboxyl group, amino group, saturated hydrocarbon group having 1 to 12 carbon atoms, alkoxyl group having 1 to 12 carbon atoms, acyl group having 1 to 12 carbon atoms, It represents an acyloxy group having 1 to 12 carbon atoms, an alkyloxycarbonyl group having 1 to 12 carbon atoms, or a hydrocarbon group having 1 to 4 carbon atoms having a hydroxyl group. )
2. 2. The laminated retardation film as described in 1 above, wherein the copolymer contains 20 to 70% by mass of monomer units L.

3. 3. The laminated retardation film as described in 1 or 2 above, wherein the positive birefringent resin layer is made of cellulose ester.

4. An esterified compound obtained by esterifying all or part of the OH group in the compound (A) having a (meth) acrylic polymer and one furanose structure or one pyranose structure on the positive birefringent resin layer, or And 1) an esterified compound obtained by esterifying all or part of the OH groups in the compound (B) in which 2 or more and 12 or less furanose structures or pyranose structures are bonded. 4. The laminated retardation film according to any one of items 1 to 3.

5). The phase difference of the positive birefringent resin layer is Ro = 0 to 50 nm, Rt = 80 to 150 nm, and the phase difference of the negative birefringent resin layer is Ro = 80 to 200 nm, Rt = −70 to −150 nm. 5. The laminated retardation film as described in any one of 1 to 4 above, wherein when each has an in-plane slow axis, the in-plane slow axes are orthogonal to each other.
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 resin layer, 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 resin) (Represents the thickness (nm) of each layer. The measurement wavelength of the refractive index is 590 nm.)
6). 6. A polarizing plate comprising the laminated retardation film according to any one of 1 to 5 on at least one surface.

7. 7. A liquid crystal display device comprising the polarizing plate according to 6 on at least one surface of a liquid crystal cell.

According to the present invention, it is possible to provide a laminated phase difference film suitable for continuous production with no unevenness in the screen when used in a liquid crystal display device and without failure such as cracks or cracks.

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

The laminated retardation film of the present invention is a laminate of a positive birefringent resin layer and a negative birefringent resin layer, and the negative birefringent resin layer is represented by the general formula (1). It includes a copolymer having a monomer unit L and an ethylenically unsaturated monomer unit M, and is used for a liquid crystal display device, so that there is no unevenness in the screen, and there is no failure such as cracks or cracks. It is a suitable laminated retardation film.

Furthermore, it is preferable that the copolymer contains 20 to 70% by mass of the monomer unit L, and that the positive birefringent resin layer is made of a cellulose ester in order to achieve the effects of the present invention.

Hereinafter, the present invention will be described in detail.

The positive birefringent resin and negative birefringent resin of the present invention are determined by the following method as to whether the resin exhibits positive birefringence or negative birefringence in the stretching direction. Is.

<Resin birefringence test method>
The resin is dissolved in a solvent alone and cast to form a film, followed by drying by heating, and birefringence is evaluated for a film having a transmittance of 80% or more.

The Abbe refractometer-4T (manufactured by Atago Co., Ltd.) uses a multi-wavelength light source to measure the refractive index, and when the film is stretched in the width direction, the refractive index in the stretching direction is Nx, or in an orthogonal plane The refractive index in the direction is Ny. For each refractive index at 590 nm, for a film where (Nx−Ny)> 0, the resin is judged to have positive birefringence in the stretching direction. Similarly, when (Nx−Ny) <0, it is determined to have negative birefringence.

(Negative birefringent resin)
The negative birefringent resin layer includes a copolymer having a monomer unit L and an ethylenically unsaturated monomer unit M represented by the following general formula (1).

R in the general formula (2) is hydrogen, hydroxyl group, carboxyl group, amino group, saturated hydrocarbon group having 1 to 12 carbon atoms, alkoxyl group having 1 to 12 carbon atoms, acyl group having 1 to 12 carbon atoms, It represents an acyloxy group having 1 to 12 carbon atoms, an alkyloxycarbonyl group having 1 to 12 carbon atoms, or a hydrocarbon group having 1 to 4 carbon atoms having a hydroxyl group. )
The monomer unit L is not particularly limited as long as it is a structure represented by the general formula (1). Specific examples include compounds represented by the following formula.

Preferred are L-1 to L-18 which are vinylcarbazole derivatives, more preferred are N-vinylcarbazole and 2-vinylcarbazole, and particularly preferred is N-vinylcarbazole.

Next, as the ethylenically unsaturated monomer unit M, for example, methacrylic acid and ester derivatives thereof (methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, i-butyl methacrylate, t-butyl methacrylate, methacrylic acid) Octyl, cyclohexyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, tetrahydrofurfuryl methacrylate, benzyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, etc.), acrylic acid and its ester derivatives ( Methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, i-butyl acrylate, t-butyl acrylate, octyl acrylate, cyclohexyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, tetrahydrofurfuryl acrylate, 2-ethoxyethyl acrylate, diethylene glycol ethoxylate acrylate, 3-methoxybutyl acrylate, benzyl acrylate, dimethylaminoethyl acrylate, Diethylaminoethyl acrylate, etc.), alkyl vinyl ethers (methyl vinyl ether, ethyl vinyl ether, butyl vinyl ether, etc.), alkyl vinyl esters (vinyl formate, vinyl acetate, vinyl butyrate, vinyl caproate, vinyl stearate, etc.), styrene derivatives (eg, styrene) , Α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, vinylnaphthalene, etc.), crotonic acid, maleic acid, fumaric acid, itako Examples thereof include unsaturated compounds such as acid, acrylonitrile, methacrylonitrile, vinyl chloride, vinylidene chloride, acrylamide, N, N-dimethylacrylamide, and methacrylamide. These can be copolymerized with the monomer unit L represented by the general formula (1) alone or in combination of two or more.

In addition, ethylenically unsaturated monomer units as shown below can also be used.

Among these ethylenically unsaturated monomer units M, acrylic acid ester or methacrylic acid ester (for example, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, methyl acrylate, ethyl acrylate, propyl acrylate, Butyl acrylate) and alkyl vinyl esters (vinyl formate, vinyl acetate, vinyl butyrate, vinyl caproate, vinyl stearate, etc.), preferably methyl methacrylate, methyl acrylate, butyl methacrylate, butyl acrylate, In particular, methyl methacrylate, methyl acrylate, butyl methacrylate, butyl acrylate, and N-acryloylmorpholine are preferable.

These ethylenically unsaturated monomers can be used alone or in combination.

The method for polymerizing the copolymer in the present invention is not particularly limited, but conventionally known methods can be widely employed, and examples thereof include radical polymerization, anionic polymerization, and cationic polymerization. Examples of the initiator for the radical polymerization method include azo compounds and peroxides, and examples thereof include azobisisobutyronitrile (AIBN), azobisisobutyric acid diester derivatives, benzoyl peroxide, and lauroyl peroxide. . The polymerization solvent is not particularly limited. For example, aromatic hydrocarbon solvents such as toluene and chlorobenzene, halogenated hydrocarbon solvents such as dichloroethane and chloroform, ether solvents such as tetrahydrofuran and dioxane, and amide solvents such as dimethylformamide. And alcohol solvents such as methanol, ester solvents such as methyl acetate and ethyl acetate, ketone solvents such as acetone, cyclohexanone and methyl ethyl ketone, and water solvents. Depending on the choice of solvent, solution polymerization that polymerizes in a homogeneous system, precipitation polymerization in which the produced polymer precipitates, emulsion polymerization that polymerizes in a micelle state, suspension polymerization that polymerizes in a suspension state, or in some cases bulk polymerization may be performed. it can.

The copolymer preferably contains 20 to 70% by mass of monomer units L. Moreover, if it is in the said range, it is also possible to copolymerize monomers other than the monomer units L and M in the range which does not lose negative birefringence. When the monomer unit L is less than 20% by mass, the retardation development property is lowered and it is difficult to form a retardation layer. When the monomer unit L is more than 70% by mass, the resin layer becomes too hard to be stretched.

The weight average molecular weight (Mw) of the copolymer is preferably in the range of 10,000 to 2,000,000. More preferably, it is in the range of 100,000 to 1,000,000. The copolymer preferably has a weight average molecular weight Mw / number average molecular weight Mn ratio of 1.5 to 10.0.

Mw and Mw / Mn were calculated by gel permeation chromatography in the following manner.

The measurement conditions are as follows.
Solvent: Tetohydrofuran Equipment: HLC-8220 (manufactured by Tosoh Corporation)
Column: TSKgel SuperHM-M (manufactured by Tosoh Corporation)
Column temperature: 40 ° C
Sample concentration: 0.1% by mass
Injection volume: 10 μl
Flow rate: 0.6ml / min
Calibration curve: Standard polystyrene: PS-1 (manufactured by Polymer Laboratories) Mw = 2, 560,000 to 580 A calibration curve with 9 samples was used.

The negative birefringent resin in the present invention is only required to develop a negative phase difference as a mixture containing a plurality of materials, and the component having the largest mass fraction and volume fraction has negative birefringence. You don't have to. For example, the UV curable monomer and the polymerization initiator are dissolved in a solvent together with the negative birefringent resin in advance as long as the negative birefringence is not impaired, and UV curing is performed after coating and drying. It is also possible to form a coating film. By UV curing, the adhesion of the coating film and the enhancement of the film strength can be obtained. Examples of the UV curable monomer include methyl methacrylate, butyl methacrylate, acrylamide, N, N-dimethylacrylamide, methacrylamide, N-acryloylmorpholine, ethylene glycol diacrylate, diethylene glycol diacrylate, and 1,6-hexanediol diester. Acrylate, neopentyl glycol diacrylate, trimethylol propane triacrylate, trimethylol ethane triacrylate, tetramethylol methane triacrylate, tetramethylol methane tetraacrylate, pentaglycerol triacrylate, pentaerythritol diacrylate, pentaerythritol triacrylate, pentaerythritol tetra Acrylate, glycerin triacrylate, dipentae Thritol triacrylate, dipentaerythritol tetraacrylate, dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate, tris (acryloyloxyethyl) isocyanurate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, 1,6-hexanediol dimethacrylate, Neopentyl glycol dimethacrylate, trimethylolpropane trimethacrylate, trimethylolethane trimethacrylate, tetramethylolmethane trimethacrylate, tetramethylolmethane tetramethacrylate, pentaglycerol trimethacrylate, pentaerythritol dimethacrylate, pentaerythritol trimethacrylate, pentaerythritol Tetramethacrylate, glycerol trimethacrylate, dipentaerythritol trimethacrylate, dipentaerythritol tetramethacrylate, dipentaerythritol penta methacrylate, dipentaerythritol hexa methacrylate. Moreover, you may mix cellulose ester resin etc. previously.

The structure of the monomer unit L has a form in which a polymerizable site and a wide aromatic ring site are bonded. In the case of a polymer containing this monomer as a copolymerization component, the aromatic ring site is oriented in a direction perpendicular to the stretching direction. Thus, a negative birefringent layer can be obtained. However, when polymerization is carried out using only this monomer unit L, the distance between adjacent aromatic rings becomes very close and a strong π-π interaction is exhibited. Due to this interaction, the resulting polymer is hard and inflexible, and exhibits a characteristic that it is weak against bending and stretching and readily cracks. On the other hand, in the polymer obtained by copolymerizing the monomer unit L and the ethylenically unsaturated monomer unit M, a space is forcibly formed between the aromatic rings, so that the π-π interaction is weakened, and the resulting polymer has flexibility. It is estimated that cracks and cracks do not occur when used as a retardation layer.

(Positive birefringent resin layer)
The laminate of the present invention is not particularly limited as long as it has a structure in which at least the positive birefringent resin layer and the negative birefringent resin layer are laminated. Therefore, each resin layer may have a plurality of layers, and a plurality of positive birefringent resin layers and a plurality of negative birefringent resin layers are laminated in this order or alternately, or A structure in which layers are randomly stacked may be used.

In the present invention, from the viewpoint of thinning, it is preferable to use a positive birefringent resin layer as a substrate and provide a negative birefringent resin layer on the substrate to form a laminate. The positive birefringent resin layer is manufactured by a solution casting method or a melt casting method, and is manufactured as a film having an appropriate birefringence in consideration of subsequent installation of a negative birefringent layer. Is preferred.

As a means for adjusting the birefringence, a known means is used. For example, in addition to film thickness, stretching temperature, stretching ratio, etc., in the solution casting method, solution composition, solution temperature, time, peeling temperature from the casting belt / drum, subsequent drying temperature, amount of solvent remaining at stretching The subsequent drying temperature, transport tension, and the like. It is the same in the melt casting method that changes depending on these factors.

The positive birefringent resin in the present invention is preferably a polymer having a slow axis in the direction parallel to the stretching direction at the time of stretching, and is preferably highly transparent and thermoplastic. However, a positive phase difference may be expressed as a mixture including a plurality of materials, and the component having the largest mass fraction and volume fraction need not have positive birefringence. Specifically, for example, cellulose resins such as triacetyl cellulose (TAC) and cellulose acetate propionate (CAP), polynorbornene resin, polycarbonate resin, polyester resin, polyether sulfone resin, polysulfone resin, polyamide resin, polyimide resin , Polyolefin resins, polyarylate resins, polyvinyl alcohol resins, polyvinyl chloride resins, polyvinylidene chloride resins, and mixtures thereof. In particular, a cellulose resin is preferable, and a cellulose ester is preferable.

<Cellulose ester>
The cellulose ester is not particularly limited, and for example, an aromatic carboxylic acid ester or the like is also used. However, in view of characteristics of the obtained film such as optical characteristics, it is preferable to use a lower fatty acid ester of cellulose.

In the present invention, the lower fatty acid in the lower fatty acid ester of cellulose means a fatty acid having 5 or less carbon atoms. For example, cellulose acetate, cellulose propionate, cellulose butyrate, cellulose pivalate and the like are preferable lower cellulose esters of cellulose. It is mentioned as a thing.

This is because the cellulose ester substituted with a fatty acid having 6 or more carbon atoms has good film forming properties, but the resulting optical film has low mechanical properties and is substantially difficult to use as an optical film.

In order to achieve both the mechanical properties and the melt film-forming property, for example, cellulose acetate pro described in JP-A Nos. 10-45804, 8-231761, U.S. Pat. No. 2,319,052, etc. Mixed fatty acid esters such as pionate and cellulose acetate butyrate may be used.

Among the above cellulose esters, cellulose acetate propionate and cellulose acetate butyrate are preferably used.

Next, the substitution degree of the acyl group of the cellulose ester preferably used in the present invention will be described.

Cellulose has a total of three hydroxyl groups, one at each of the 2nd, 3rd and 6th positions of 1 glucose unit. The total degree of substitution is the average number of acyl groups bonded to 1 glucose unit. It is a numerical value indicating whether or not

Therefore, the maximum degree of substitution is 3.0. These acyl groups may be substituted on the 2nd, 3rd and 6th positions of the glucose unit on average, or may be substituted with a distribution.

As the substitution degree of the mixed fatty acid ester, more preferable cellulose acetate propionate and lower fatty acid ester of cellulose acetate butyrate have an acyl group having 2 to 4 carbon atoms as a substituent, and the substitution degree of the acetyl group is X, When the substitution degree of the propionyl group or butyryl group is Y, it is preferably a cellulose ester satisfying the following formulas (i) and (ii).

Formula (i) 2.3 ≦ X + Y ≦ 3.0
Formula (ii) 0 ≦ X ≦ 2.5
Of these, cellulose acetate propionate is preferably used, and it is particularly preferable that 1.9 ≦ X ≦ 2.5 and 0.1 ≦ Y ≦ 0.9. The portion that is not substituted with an acyl group is usually present as a hydroxyl group. These can be synthesized by known methods. The method for measuring the substitution degree of the acyl group can be measured according to ASTM-D817-96.

Further, the cellulose ester used in the present invention preferably has a weight average molecular weight Mw / number average molecular weight Mn ratio of 1.5 to 5.5, particularly preferably 2.0 to 4.0.

The cellulose ester used in the present invention preferably has a number average molecular weight (Mn) of 50,000 to 150,000, more preferably a number average molecular weight of 55,000 to 120,000, and a number average molecular weight of 60000 to 100,000. Most preferred.

Mn and Mw / Mn were calculated by gel permeation chromatography in the following manner.

The raw material cellulose of the cellulose ester used in the present invention may be wood pulp or cotton linter, and the wood pulp may be softwood or hardwood, but softwood is more preferable. A cotton linter is preferably used from the viewpoint of peelability during film formation. The cellulose ester made from these can be mixed suitably or can be used independently.

For example, the ratio of cellulose ester derived from cellulose linter: cellulose ester derived from wood pulp (coniferous): cellulose ester derived from wood pulp (hardwood) is 100: 0: 0, 90: 10: 0, 85: 15: 0, 50:50: 0, 20: 80: 0, 10: 90: 0, 0: 100: 0, 0: 0: 100, 80:10:10, 85: 0: 15, 40:30:30.

The cellulose ester can be obtained, for example, by substituting the hydroxyl group of the raw material cellulose with acetic anhydride, propionic anhydride and / or butyric anhydride in the usual manner using an acetyl group, propionyl group and / or butyl group within the above range. . The method for synthesizing such a cellulose ester is not particularly limited, and for example, it can be synthesized with reference to the method described in JP-A-10-45804 or JP-A-6-501040.

The alkaline earth metal content of the cellulose ester used in the present invention is preferably in the range of 1 to 50 ppm. If it exceeds 50 ppm, lip adhesion stains increase or breakage tends to occur at the slitting part during or after hot stretching. Even if it is less than 1 ppm, it tends to break, but the reason is not well understood. In order to make it less than 1 ppm, since the burden of a washing | cleaning process will become large too much, it is unpreferable also in that point. Further, the range of 1 to 30 ppm is preferable. The alkaline earth metal as used herein refers to the total content of Ca and Mg, and can be measured using an X-ray photoelectron spectrometer (XPS).

The residual sulfuric acid content in the cellulose ester used in the present invention is preferably in the range of 0.1 to 45 ppm in terms of elemental sulfur. These are considered to be contained in the form of salts. In order to make it less than 0.1 ppm, since the burden of the cellulose ester washing process becomes too large, the range of 1 to 30 ppm is preferable. The residual sulfuric acid content can be measured according to the method prescribed in ASTM-D817-96.

The free acid content in the cellulose ester used in the present invention is preferably 1 to 500 ppm. Since it is difficult to make it less than 1 ppm by washing, it is preferably in the range of 1 to 100 ppm. The free acid content can be measured according to the method prescribed in ASTM-D817-96.

The thickness of the positive birefringent resin layer is not particularly limited, but 10 to 200 μm is used. In particular, the film thickness is particularly preferably 10 to 100 μm. More preferably, it is 20 to 60 μm.

In the positive birefringent resin layer, a plasticizer can be contained as necessary.

The plasticizer may have a function of appropriately adjusting not only the plasticizing effect but also the birefringence expression (phase difference after stretching) and wavelength dispersion of the positive birefringent resin layer. A material that reduces the absolute value of the photoelastic coefficient is also preferable. The plasticizer is not particularly limited, but is preferably a polycarboxylic acid ester plasticizer, a glycolate plasticizer, a phthalate ester plasticizer, a fatty acid ester plasticizer, a polyhydric alcohol ester plasticizer, or a polyester plasticizer. Agent, acrylic plasticizer and the like. In addition, in order to control the phase difference of the positive birefringent resin layer, the phase difference includes a material that exhibits positive birefringence, a material that adjusts wavelength dispersion, a material that makes the photoelastic coefficient close to zero, and the like. Also good.

The present invention provides an esterified compound obtained by esterifying all or part of the OH group in the compound (A) having a (meth) acrylic polymer and one furanose structure or one pyranose structure on a positive birefringent resin layer, Or it is preferable to contain the esterified compound which esterified all or one part of OH group in the compound (B) which couple | bonded 2 or more and 12 or less of furanose structure or the pyranose structure.

<(Meth) acrylic polymer>
The (meth) acrylic polymer used in the present invention preferably exhibits negative birefringence as a function in the stretching direction when incorporated in a laminated retardation film, and the structure is particularly limited. However, a polymer having a weight average molecular weight of 500 to 30,000 obtained by polymerizing an ethylenically unsaturated monomer is preferred.

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.

By controlling the composition of the polymer with a weight average molecular weight of 500 or more and 30000 or less, for example, when a cellulose ester is contained in the positive birefringent resin layer, the cellulose ester and the polymer The compatibility of 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 positive birefringent resin layer after film formation has excellent transparency and extremely low moisture permeability, and exhibits excellent performance even when applied to, for example, 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 positive birefringent resin layer of the present invention has an ethylenically unsaturated monomer Xa having no aromatic ring and no hydroxyl group in the molecule, and no aromatic ring in the molecule. A polymer X having a weight average molecular weight of 2,000 to 30,000 obtained by copolymerizing an ethylenically unsaturated monomer Xb having a hydroxyl group 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 obtained by polymerizing an ethylenically unsaturated monomer Ya that does not contain bismuth and an ethylenically unsaturated monomer copolymerizable with Ya.

[Polymer X, Polymer Y]
As a method for adjusting Ro and Rt of the positive birefringent resin layer according to the present invention, an ethylenically unsaturated monomer Xa having no aromatic ring and a hydroxyl group in the molecule, an hydroxyl group having no aromatic ring in the molecule, A high molecular weight polymer X having a weight average molecular weight of 2,000 to 30,000 obtained by copolymerization of an ethylenically unsaturated monomer Xb having Xa and a copolymerizable ethylenically unsaturated monomer excluding Xa and Xb, and Preferably, a low molecular weight polymer Y 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 and an ethylenically unsaturated monomer copolymerizable with Ya. It is preferable to contain.

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 that does not have an aromatic ring and a hydroxyl group in the molecule, and Xb is an acrylic or methacrylic monomer that does not have an aromatic ring in the molecule and has a hydroxyl group.

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 represents —CH ₂ —, —C ₂ H ₄ — or —C ₃ H ₆ —. 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.

The monomers as monomer units constituting the polymer X used in the present invention are listed below, but are not limited thereto.

In X, a 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. Of 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 an acrylic acid or a methacrylic acid ester as a monomer unit having a hydroxyl group. For example, 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, 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 5000 or more and 30000 or less, and still more preferably 8000 or more and 25000 or less.

It is preferable that the weight average molecular weight be 5000 or more because advantages such as little dimensional change of the positive birefringent resin layer 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, the 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 used in 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., but this temperature or the polymerization reaction time can be adjusted.

The measuring method of the weight average molecular weight can be obtained 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 Corp.) Mw = 1000,000 to 500 13 calibration curves 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 to 3000 or less in order to maintain the retardation value Rt lowering 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. 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 (—R5) (— CO ₂ R6)]. k and q each represent a molar composition ratio. However, k ≠ 0 and k + q = 100.

Yb is not particularly limited as long as it is an ethylenically unsaturated monomer copolymerizable with [CH ₂ —C (—R 5) (— CO ₂ R 6)] which is Ya. 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 Heptyl acid (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-hydroxypro) ), Acrylic acid (4-hydroxybutyl), acrylic acid (2-hydroxybutyl), methacrylic acid ester, the above acrylic acid ester replaced by methacrylic acid ester; unsaturated acid such as acrylic acid, methacrylic acid Examples thereof include acid, 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 does not increase the molecular weight and that can make the molecular weight as uniform as possible.

Examples of such a polymerization method 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 usual polymerization, and a mercapto compound in addition to the polymerization initiator. And a method using a chain transfer agent such as carbon tetrachloride, a method using a polymerization terminator such as benzoquinone and dinitrobenzene in addition to the polymerization initiator, and further disclosed in JP-A Nos. 2000-128911 and 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 value of the polymers X and Y is 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. Attach an air cooling tube to the mouth of the flask and heat in a glycerol bath at 95-100 ° C. After 1 hour and 30 minutes, the mixture is cooled and 1 ml of purified water is added from an air cooling tube to decompose acetic anhydride 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, titrate without putting a sample, and obtain the inflection point of the titration curve. 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 positive birefringent resin layer 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 preferred 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.

Polymer X and 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.

<Compound with furanose structure or pyranose structure>
The positive birefringent resin layer of the present invention is esterified by esterifying all or part of the OH group in the compound (A) having one furanose structure or pyranose structure together with a (meth) acrylic polymer. It is preferable to include a compound or an esterified compound obtained by esterifying all or part of the OH group in the compound (B) in which 2 or more and 12 or less of at least one of a furanose structure or a pyranose structure are bonded.

In the present invention, the esterified compound of the compound (A) and the esterified compound of the compound (B) are collectively referred to as a sugar ester compound.

In addition, the esterified compound is a monosaccharide (α-glucose, β-fructose) benzoate, or a monosaccharide —OR ₁₂ , —OR ₁₅ , —OR ₂₂ , — It is preferable that any two or more positions of OR ₂₅ are benzoic acid esters of polysaccharides of m + n = 2 to 12 produced by dehydration condensation.

The benzoic acid in the above general formula may further have a substituent, for example, an alkyl group, an alkenyl group, an alkoxyl group, and a phenyl group, and these alkyl group, alkenyl group, and phenyl group have a substituent. You may have.

Examples of the preferred compound (A) and compound (B) include the following, but the present invention is not limited to these.

Examples of the compound (A) include glucose, galactose, mannose, fructose, xylose, or arabinose.

Examples of the compound (B) include lactose, sucrose, nystose, 1F-fructosyl nystose, stachyose, maltitol, lactitol, lactulose, cellobiose, maltose, cellotriose, maltotriose, raffinose or kestose.

Other examples include gentiobiose, gentiotriose, gentiotetraose, xylotriose, and galactosyl sucrose.

Among these compounds (A) and (B), compounds having both a furanose structure and a pyranose structure are particularly preferable. As examples, sucrose, kestose, nystose, 1F-fructosyl nystose, stachyose and the like are preferable, and sucrose is more preferable.

In addition, in the compound (B), it is also a preferred embodiment that the compound is a compound in which at least one furanose structure or pyranose structure is bonded in an amount of 2 or more and 3 or less.

The monocarboxylic acid used for esterifying all or part of the OH groups in the compound (A) and the compound (B) according to the present invention is not particularly limited, and known aliphatic monocarboxylic acids and fats A cyclic monocarboxylic acid, 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 cyclopentane carboxylic acid, cyclohexane carboxylic acid, cyclooctane carboxylic 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-pyro Technic 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.

Among the esterified compounds obtained by esterifying the compound (A) and the compound (B), an acetylated compound having an acetyl group introduced by esterification is preferable.

A method for producing these acetylated compounds is described, for example, in JP-A-8-245678.

In addition to the esterified compounds of the above compounds (A) and (B), the oligosaccharide esterified compound can be applied as a compound in which 3 to 12 of the furanose structure or the pyranose structure according to the present invention are bonded. .

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, and xylooligos. Sugar.

Oligosaccharide can also be acetylated in the same manner as the above compound (A) and compound (B).

Next, an example of production of an esterified compound will be described.

Acetic anhydride (200 ml) was added dropwise to a solution obtained by adding pyridine (100 ml) to glucose (29.8 g, 166 mmol) and allowed to react for 24 hours. Thereafter, the solution was concentrated by evaporation and poured into ice water.

After standing for 1 hour, the mixture was filtered through a glass filter to separate the solid and water. The solid on the glass filter was dissolved in chloroform and separated with cold water until it became neutral.

The organic layer was separated and dried over anhydrous sodium sulfate. After removing anhydrous sodium sulfate by filtration, chloroform was removed by evaporation and further dried under reduced pressure to obtain glycolose pentaacetate (58.8 g, 150 mmol, 90.9%). In addition, the above-mentioned monocarboxylic acid can be used instead of the acetic anhydride.

Specific examples of the esterified compound used in the present invention are listed below, but the present invention is not limited thereto.

The positive birefringent resin layer of the present invention can be used in the compound (A) having one furanose structure or one pyranose structure in order to suppress the fluctuation of the retardation value and stabilize the display quality. It is preferable to contain 1 to 30% by mass of an esterified compound obtained by esterifying all or part of the OH group in the compound (B) in which 2 to 12 of at least one of the structure or the pyranose structure are bonded. It is preferable to contain ~ 30% by mass. Within this range, it is preferable that the excellent effects of the present invention are exhibited and there is no bleeding out.

Further, in a compound (A) having one (meth) acrylic polymer and one furanose structure or pyranose structure, or in a compound (B) in which 2 to 12 at least one furanose structure or pyranose structure is bonded. An esterified compound obtained by esterifying all or a part of the OH group may be used in combination with another plasticizer.

Further, fine particles can be added to these positive birefringent resin layers as necessary. As fine particles, examples of inorganic compounds include silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, Mention may be made of magnesium silicate and calcium phosphate.

The average primary particle size 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.

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

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

Further, polymer type fine particles may be added. 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.

In both inorganic and organic fine particles, the fine particles in the present invention are preferably close to the average refractive index of the positive birefringent resin layer.

Furthermore, an ultraviolet absorber may be included. As the ultraviolet absorber, a material suitable for an optical film, such as no coloring and excellent transparency, is preferable. Examples thereof include oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex compounds, and the like. Further, polymer ultraviolet absorbers described in JP-A Nos. 2002-169020 and 2006-113175 are also preferably used.

Other components may include an antioxidant, an antistatic agent, a lubricant, a release material, a colorant, a colorant, a flame retardant, and the like. In particular, when producing by melt casting film formation, it is preferable to introduce an antioxidant, and in particular, as a method for maximizing the transparency of the film, instead of the fine particles, a lubricant and a release material are also preferable. Used.

Further, an antistatic layer, a slipping layer, and an easy adhesion layer may be provided on any surface of the positive birefringent resin layer.

(Method for producing positive birefringent resin layer)
Next, the manufacturing method of the cellulose-ester film which is preferable one Embodiment of the positive birefringent resin layer 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 produced by dissolving the cellulose ester and the additive in a solvent to prepare a dope, casting the dope on an endless metal support that moves infinitely, and casting the dope. Is performed 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 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. The concentration that achieves both of these is preferably 10 to 35% by mass, and more preferably 15 to 25% by 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.

A 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.

The good solvent used in the present invention is not particularly limited, and examples thereof include organic halogen compounds such as methylene chloride, dioxolanes, acetone, methyl acetate, and methyl acetoacetate. Particularly preferred is methylene chloride or methyl acetate.

The poor solvent used in the present invention is not particularly limited, but for example, methanol, ethanol, n-butanol, cyclohexane, cyclohexanone and the like are preferably used. The dope preferably contains 0.01 to 2% by mass of water.

Also, the solvent used for dissolving the cellulose ester is used by collecting the solvent removed from the film by drying in the film-forming process and reusing it. 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.

As a method for dissolving the cellulose ester when preparing the dope described above, a general method can be used. 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 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 formation of massive undissolved material called gel or mamako. Moreover, after mixing a cellulose ester with a poor solvent and making it wet or swell, the method of adding a good solvent and melt | dissolving is also used preferably.

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 the 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 preferred 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, the cellulose ester solution is filtered using an appropriate 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 likely to be 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, still more preferably 50 pieces / m ² or less, still more preferably 0 to 10 pieces / cm ² . 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 preferable. 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 process is preferably a mirror-finished surface, and a stainless steel belt or a drum whose surface is plated with a casting is preferably used as the metal support. The cast width can be 1 to 4 m.

The surface temperature of the metal support in the casting step is −50 ° C. to less than the boiling point of the solvent, and a higher temperature is preferable because the web drying speed can be increased. May deteriorate.

A preferable support temperature is 0 to 40 ° C., more preferably 5 to 30 ° 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, but 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 optical compensation film to exhibit good flatness, the amount of residual solvent 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. Particularly preferred is 20 to 30% by mass or 70 to 120% by mass.

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

Residual solvent amount (% by mass) = {(MN) / N} × 100
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 115 ° C. for 1 hour.

In the step of drying the optical compensation 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, Particularly preferred is 0 to 0.01% by mass or less.

In the film drying process, 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 according to 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 is preferably performed with hot air in terms of simplicity.

It is preferable that the drying temperature in the web drying process is increased stepwise from 40 to 200 ° C.

The film thickness of the cellulose ester film is not particularly limited, but 10 to 200 μm is used. In particular, the film thickness is particularly preferably 10 to 100 μm. More preferably, it is 20 to 60 μm.

A cellulose ester film having a width of 1 to 4 m is used. Particularly, those having a width of 1.4 to 4 m are preferably used, and particularly preferably 1.6 to 3 m. If it exceeds 4 m, conveyance becomes difficult.

(Stretching operation, refractive index control)
The positive birefringent resin layer of the present invention preferably has retardation values Ro and Rt of Ro = 0 to 50 nm and Rt = 80 to 150 nm.

Note that 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 resin layer, 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 resin) Represents the thickness (nm) of each layer.)
The refractive index can be obtained at a wavelength of 590 nm in an environment of 23 ° C. and 55% RH using, for example, KOBRA-21ADH (Oji Scientific Instruments).

By combining the (meth) acrylic polymer and a compound having a furanose structure or a pyranose structure and appropriately containing them, not only the desired retardation but also wavelength dispersion can be adjusted.

The stretching operation can be performed at once after laminating the negative birefringent layer on the unstretched positive birefringent resin layer, but only the positive birefringent resin layer is stretched in advance. Furthermore, a desired retardation can be adjusted by stretching again after laminating a negative birefringent layer.

In order to obtain the retardation values Ro and Rt, it is preferable that the cellulose ester film, which is a positive birefringent resin layer, has the configuration of the present invention, and further the refractive index is controlled by a stretching operation.

For example, biaxial stretching or uniaxial stretching can be performed sequentially or simultaneously with respect to the longitudinal direction (film forming direction) of the film and the direction orthogonal to the longitudinal direction of the film, that is, the width direction.

The draw ratios in the biaxial directions perpendicular to each other are preferably in the range of 0.8 to 2.0 times in the casting direction and 1.1 to 2.5 times in the width direction, respectively. It is preferable to carry out in the range of 0.8 to 1.5 times in the direction and 1.2 to 2.0 times in the width direction.

The stretching temperature is preferably 120 ° C. to 200 ° C., more preferably 160 ° C. to 200 ° C. or less.

The residual solvent in the film is preferably 20 to 0%, more preferably 15 to 0%. Specifically, the residual solvent is preferably stretched at 11% at 175 ° C., or the residual solvent is stretched at 2% at 175 ° C. Alternatively, it is preferred that the residual solvent is stretched at 11% at 185 ° C., or it is preferred that the residual solvent is stretched at less than 1% at 185 ° C.

There is no particular limitation on the method of stretching the web. For example, a method in which a circumferential speed difference is applied to a plurality of rolls, and the roll circumferential speed difference is used to stretch the rolls in the longitudinal direction. And a method of stretching in the vertical direction, a method of stretching in the horizontal direction and stretching in the horizontal direction, or a method of stretching in the vertical and horizontal directions and stretching in both the vertical and horizontal directions.

Of course, these methods may be used in combination. In the case of the so-called tenter method, driving the clip portion by the linear drive method is preferable because smooth stretching can be performed and the risk of breakage and the like can be reduced.

It is preferable to carry out the width maintenance or lateral stretching in the film forming step by a tenter, and it may be a pin tenter or a clip tenter.

(Negative birefringent resin layer)
The thickness of the negative birefringent resin layer containing the copolymer having the monomer unit L and the ethylenically unsaturated monomer unit M represented by the general formula (1) is not particularly limited, but 2 to 50 μm is used. In particular, the film thickness is particularly preferably 3 to 40 μm. More preferably, it is 5 to 30 μm.

When it is desired to further improve the adhesion between the positive birefringent resin layer and the negative birefringent resin layer, the positive birefringent layer may be surface-treated, or an easy-adhesion layer may be provided between the two layers. There is no limitation in particular as a material of an easily bonding layer, A well-known material can be used suitably. The film thickness of the easy adhesion layer is preferably 1 μm or less, and more preferably 0.5 μm or less.

(Coating of negative birefringent resin layer)
There are no particular restrictions on the coating method, but specific examples include gravure coating, comma coating, bar coating, die coating, lip coating, roll coating, flow coating, print coating, dip coating, casting film formation, and spin coating. Can be mentioned. These methods are appropriately selected from the solution viscosity and the film thickness.

Commonly known organic solvents are used as the solvent, for example, alcohols such as methanol, ethanol, propanol and butanol, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone, and aromatic carbonization such as benzene, toluene and xylene. Hydrogens, glycols such as ethylene glycol, propylene glycol, hexylene glycol, etc., glycol ethers such as ethyl cellosolve, butyl cellosolve, ethyl carbitol, butyl carbitol, diethyl cellosolve, diethyl carbitol, esters such as methyl acetate and ethyl acetate , Organic solvents such as N-methylpyrrolidone, dimethylformamide, dichloromethane, chloroform and tetrahydrofuran, or water. These can be used alone or in admixture of two or more. Further, when the UV curable monomer and the negative birefringent resin are mixed in advance, the UV curable monomer can be used as a solvent.

After coating, in order to ensure the physical properties of the coating film, for example, heat treatment or active energy ray irradiation treatment such as ultraviolet light is preferably performed. It is also effective to previously contain a crosslinkable material in the coating solution, and the Tg of the film can be controlled.

The phase difference of the negative birefringent resin layer is preferably Ro = 80 to 200 nm, Rt = −70 to −150 nm, and when the positive and negative birefringent layers have in-plane slow axes, the mutual planes It is preferable that the inner slow axes are orthogonal in terms of improving the viewing angle expansion effect.

The retardation values Ro and Rt are obtained by performing a stretching operation after laminating a negative birefringent layer on a positive birefringent resin layer. For example, biaxial stretching or uniaxial stretching can be performed sequentially or simultaneously with respect to the longitudinal direction (coating direction) of the film and the direction orthogonal to the longitudinal direction of the film, that is, the width direction. The draw ratios in the biaxial directions perpendicular to each other are preferably in the range of 1.01 to 2.5 times in the coating direction and 0.5 to 1.5 times in the width direction, respectively. It is preferable to carry out in the range of 1.05 to 1.5 times in the direction and 0.5 to 1.0 times in the width direction.

The haze of the laminated retardation film of the present invention is preferably less than 1%, particularly preferably 0 to 0.5%.

The visible light transmittance of the laminated retardation film of the present invention is preferably 90% or more, and more preferably 93% or more.

The laminated retardation film of the present invention can be suitably used for a polarizing plate as a viewing angle widening film of a liquid crystal display device. In that case, it can bond directly to at least one surface of a polarizer, and can also serve as a polarizing plate protective film. In this case, it is preferable to bond the positive birefringent resin layer side to the polarizer.

The polarizing plate can be produced by a general method. The positive birefringent resin layer side of the laminated retardation film of the present invention is subjected to alkali saponification treatment. The saponified retardation film is preferably bonded to at least one surface of a polarizer produced by immersing and stretching a polyvinyl alcohol film in an iodine solution using a completely saponified aqueous polyvinyl alcohol solution. A laminated retardation film may be used on the other surface, or another polarizing plate protective film may be used. When the negative birefringent resin layer side is bonded to the polarizer, a known adhesive can be used, but an aqueous adhesive is preferable.

Any appropriate material can be adopted as the polarizing plate protective film used on the back side. As such a material, for example, a plastic film excellent in transparency, mechanical strength, thermal stability, moisture barrier property, isotropy and the like can be mentioned. Specific examples of resins constituting the plastic film include acylate resins such as triacetyl cellulose (TAC), polyester resins, polyethersulfone resins, polysulfone resins, polycarbonate resins, polyamide resins, polyimide resins, polyolefin resins, acrylic resins, poly Examples include norbornene resin, cellulose resin, polyarylate resin, polystyrene resin, polyvinyl alcohol resin, polyacrylic resin, and mixtures thereof. Also, thermosetting resins such as acrylic, urethane, acrylic urethane, epoxy, and silicone, or ultraviolet curable resins may be used. From the viewpoint of polarization characteristics and durability, a TAC film whose surface is saponified with alkali or the like is preferable. In addition, as commercially available cellulose acylate films, KC8UX, KC4UX, KC5UX, KC8UCR3, KC8UCR4, KC8UCR5, KC8UY, KC4UY, KC12UR, KC4UE, KC8UE, KC8UY-HA, KC8UX-RHU, KC8UX-RUX NC, KC4UXW-RHA-NC (manufactured by Konica Minolta Opto Co., Ltd.) and the like are preferably used.

The laminated retardation film of the present invention is industrially produced as a long film, and an aspect in which a polarizing plate is constituted by laminating with a polarizer produced as a long film is most useful. Moreover, it can also be used as a mere retardation film that does not have a function as a polarizing plate protective film, such as further bonding to a polarizing plate.

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 ones in which iodine is dyed on a system film and ones in which a dichroic dye is dyed, but it is not limited to this. 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. A polarizer having a thickness of 5 to 30 μm is preferably used.

The laminated retardation film of the present invention can be used for liquid crystal display devices of various drive systems such as STN, TN, OCB, HAN, VA (MVA, PVA), IPS, FFS, OCB. An IPS, FFS, and VA (MVA, PVA) type liquid crystal display device is preferable. When used in an STN, OCB, or TN type liquid crystal display device, the absorption axis direction of the polarizer and the respective stretching axes do not necessarily have to be parallel or orthogonal, and an offset form is also preferably used. By using these liquid crystal display devices, a liquid crystal display device having a wide viewing angle and high front contrast and excellent visibility can be obtained.

An example of the configuration when the laminated retardation film of the present invention is used in an IPS or FFS type liquid crystal display device will be described. The laminated retardation film of the present invention is disposed between a polarizer disposed so as to have an absorption axis in a direction orthogonal to the slow axis direction of the liquid crystal during black display and the glass substrate. When the negative birefringent resin layer is arranged on the polarizer side, the negative birefringent layer is arranged on the glass substrate side so that the slow axis of the negative birefringent resin layer and the absorption axis of the polarizer are parallel to each other. In that case, an excellent viewing angle can be obtained by arranging the slow axis of the negative birefringent layer and the absorption axis of the polarizer to be orthogonal to each other.

In this case, if the retardation Ro of the positive birefringent resin layer is 0 nm or the retardation of the positive birefringent resin layer is Ro> 0 nm, the slow axis of the positive birefringent resin layer and the negative birefringent layer The laminated retardation film of the present invention in which the slow axis is orthogonal is preferably used. At this time, a polarizer disposed so as to have an absorption axis parallel to the slow axis direction of the liquid crystal during black display, that is, a polarizer located on the opposite side across the liquid crystal cell, and the glass substrate It is preferable that the in-plane retardation Ro of the retardation film disposed therebetween is substantially zero. More preferably, the retardation Rt in the thickness direction is | Rt | ≦ 45 nm, more preferably | Rt | ≦ 5 nm. Such a retardation film can also serve as a polarizing plate protective film.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

Example 1
<< Production of Laminated Retardation Film >>
<Preparation and Stretching of Positive Birefringent Resin Layer P1>
Fine particles (Aerosil R972V 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.

<In-line additive solution>
Cellulose ester A was added to a dissolution tank containing methylene chloride and heated to completely dissolve, and this was then added to Azumi filter paper No. 3 manufactured by Azumi Filter Paper Co., Ltd. Filtered using 244.

While finely stirring the filtered cellulose ester solution, the fine particle dispersion was slowly added thereto. Further, the particles were dispersed by an attritor so that the secondary particles had a predetermined particle size. This was filtered with Finemet NF manufactured by Nippon Seisen Co., Ltd. to prepare an in-line additive solution.

Methylene chloride 99 parts by weight Cellulose ester A 4 parts by weight Fine particle dispersion 11 parts by weight A main dope solution having the following composition was prepared. First, methylene chloride and ethanol were added to the pressure dissolution tank. Cellulose ester A was added to a pressurized 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 380 parts by weight Ethanol 70 parts by weight Cellulose ester A 100 parts by weight (Meth) acrylic polymer A 5.5 parts by weight Sugar ester compound A 5.5 parts by weight The above is put into a sealed container, heated and stirred. However, Azumi Filter Paper No. manufactured by Azumi Filter Paper Co., Ltd. 24, and the dope liquid A was prepared.

The dope solution was filtered with Finemet NF manufactured by Nippon Seisen Co., Ltd. in the film production line. In the inline additive solution line, the inline additive solution was filtered with Finemet NF manufactured by Nippon Seisen Co., Ltd. Add 2 parts by weight of the filtered in-line additive to 100 parts by weight of the filtered dope solution, mix thoroughly with an in-line mixer (Toray static type in-pipe mixer Hi-Mixer, SWJ), and then use a belt casting apparatus. It was cast at a temperature of 35 ° C. and a width of 2 m uniformly on a stainless steel band support. With the stainless steel band support, the solvent was evaporated until the residual solvent amount became 120%, and then peeled off from the stainless steel band support. The peeled cellulose ester web was evaporated at 50 ° C. and the solvent was slit to a width of 1.65 m, and then 1.2 times at 160 ° C. in the TD direction (direction perpendicular to the film transport direction) (20 %), And further applied with a transport tension to stretch 1.1 times (10%) in the MD direction (film transport direction). Drying is completed while transporting through a 120 ° C drying zone with many rolls, slitting to a width of 1500mm, knurling with a width of 15mm and an average height of 10μm at both ends of the film, and positive birefringence with an average film thickness of 52μm Resin layer P1 was produced. The film width was 1.5 m and the winding length was 5000 m.

The following are the materials used in the examples.

Cellulose ester A: acetyl group substitution degree 1.8, propionyl group substitution degree 0.9, total acyl group substitution degree 2.7
(Meth) acrylic polymer A: Bulk polymerization was performed by the polymerization method described in JP-A No. 2000-128911. That is, methyl acrylate was introduced as a monomer into a flask equipped with a stirrer, a nitrogen gas inlet tube, a thermometer, an inlet, and a reflux condenser, and nitrogen gas was introduced and the inside of the flask was replaced with nitrogen gas while stirring. Added.

After the addition of thioglycerol, polymerization was carried out for 4 hours, the contents were returned to room temperature, and 20 parts by mass of a 5% by mass benzoquinone tetrahydrofuran solution was added thereto to terminate the polymerization. The contents were transferred to an evaporator, and tetrahydrofuran, residual monomer and residual thioglycerol were removed under reduced pressure at 80 ° C. to obtain a (meth) acrylic polymer A having a molecular weight of 1000.

Sugar ester compound A: Sugar ester compound exemplified compound 3
<Preparation and Stretching of Positive Birefringent Resin Layer P2>
After the dope fluency and peeling, the same procedure as in P1 was performed, and then the peeled cellulose ester film web was evaporated at 55 ° C., then clipped with a tenter and 1.3 times (160 times in the TD direction at 160 ° C.) %). Thereafter, drying is completed while being conveyed at 120 ° C., slitting to 1500 mm width, a knurling process of 15 mm width and average height of 12 μm is applied to both ends of the film, and a positive birefringent resin layer P2 having an average film thickness of 38 μm. Got. The film thickness variation was within ± 1 μm in both the width direction and the longitudinal direction, and the winding length was 5000 m.

<Preparation and Stretching of Positive Birefringent Resin Layer P3>
After the dope fluency and peeling, the same procedure as in P1 was performed, and then the peeled cellulose ester film web was evaporated at 55 ° C., then clipped with a tenter and 1.1 times (160 times in the TD direction at 160 ° C.) %), And further by applying a transport tension, the film was stretched 1.25 times (25%) in the MD direction. Thereafter, drying is completed while being conveyed at 120 ° C., slitting is performed to a width of 1500 mm, and both ends of the film are subjected to a knurling process having a width of 15 mm and an average height of 12 μm. Got. The film thickness variation was within ± 1 μm in both the width direction and the longitudinal direction, and the winding length was 5000 m.

<Preparation and Stretching of Positive Birefringent Resin Layer P4>
Cellulose acetate propionate (acetyl group substitution degree 1.9, propionyl group substitution degree 0.7, total acyl group substitution degree 2.6, number average molecular weight 80000, weight average molecular weight 220,000) 100 parts by mass Triphenyl phosphate 8 parts by mass Ethylphthalyl ethyl glycolate 4 parts by mass Silicon dioxide fine particles (Aerosil R972V manufactured by Nippon Aerosil Co., Ltd.)
0.2 parts by mass Methylene chloride 330 parts by mass Ethanol 60 parts by mass The above was put into a sealed container, heated, dissolved completely with stirring, and manufactured by Azumi Filter Paper No. No. 24 was used for filtration to prepare a dope solution. Further, the dope solution was filtered with Finemet NF manufactured by Nippon Seisen Co., Ltd. The silicon dioxide fine particles were dispersed and added using a part of ethanol added in advance.

Next, using a belt casting apparatus, the belt was uniformly cast on a stainless band support (surface temperature 25 ° C.) with a width of 2 m. The solvent was evaporated until the residual solvent amount reached 100%, and then peeled off from the stainless steel band support. The web of the peeled cellulose ester film was evaporated at 55 ° C, then clipped with a tenter and stretched 1.01 times (1%) at 125 ° C in the TD direction, and further conveyed tension was applied in the MD direction. The film was stretched 1.2 times (20%). Then, drying was completed while being rolled at 120 ° C., slitting to a width of 1500 mm, and knurling with a width of 15 mm and an average height of 12 μm were applied to both ends of the film to obtain a positive birefringent resin layer P4. The film average film thickness was 80 μm, the film thickness variation was within ± 1 μm in both the width direction and the longitudinal direction, and the winding length was 5000 m.

<Preparation and Stretching of Positive Birefringent Resin Layer P5>
(Silicon dioxide dispersion)
Aerosil 972V (manufactured by Nippon Aerosil Co., Ltd.) 12 parts by mass (average primary particle diameter 16 nm, apparent specific gravity 90 g / liter)
88 parts by mass of ethanol or more was stirred and mixed with a dissolver for 30 minutes, and then dispersed with Manton Gorin. The liquid turbidity after dispersion was 200 ppm. 88 parts by mass of methylene chloride was added to the silicon dioxide dispersion while stirring, and the mixture was stirred and mixed for 30 minutes with a dissolver to prepare a silicon dioxide dispersion dilution.

(Production of in-line additive solution)
Tinuvin 109 (manufactured by Ciba Specialty Chemicals) 11 parts by weight Tinuvin 171 (manufactured by Ciba Specialty Chemicals) 5 parts by weight 100 parts by weight of methylene chloride Dissolved and filtered.

To this was added 36 parts by mass of silicon dioxide dispersion diluted solution while stirring, and further stirred for 30 minutes, and then cellulose acetate propionate (acetyl group substitution degree 1.9, propionyl group substitution degree 0.8, total acyl group). The degree of substitution was 2.7) 6 parts by mass was added with stirring, and the mixture was further stirred for 60 minutes, and then filtered through a polypropylene wind cartridge filter TCW-PPS-1N manufactured by Advantech Toyo Co., Ltd. to prepare an in-line additive solution.

(Preparation of dope solution)
Cellulose ester (cellulose triacetate synthesized from linter cotton)
100 parts by mass (Mn = 148000, Mw = 310000, Mw / Mn = 2.1, acetyl group substitution degree 2.92)
Trimethylolpropane tribenzoate 5.0 parts by weight Ethylphthalylethyl glycolate 5.5 parts by weight Methylene chloride 440 parts by weight Ethanol 40 parts by weight The above is put into a closed container, heated and stirred, and completely dissolved. Azumi Filter Paper No. manufactured by Azumi Filter Paper Co., Ltd. No. 24 was used for filtration to prepare a dope solution.

The dope solution was filtered with Finemet NF manufactured by Nippon Seisen Co., Ltd. in the film production line. In the inline additive solution line, the inline additive solution was filtered with Finemet NF manufactured by Nippon Seisen Co., Ltd. Add 2 parts by weight of the filtered in-line additive to 100 parts by weight of the filtered dope solution, mix thoroughly with an in-line mixer (Toray static type in-pipe mixer Hi-Mixer, SWJ), and then use a belt casting apparatus. Used at a temperature of 35 ° C. and a width of 1800 mm and uniformly cast on a stainless steel band support. With the stainless steel band support, the solvent was evaporated until the residual solvent amount became 120%, and then peeled off from the stainless steel band support. The peeled cellulose ester web was evaporated at 35 ° C., slit to 1650 mm width, and then dried at a drying temperature of 135 ° C. while stretching 1.1 times in the TD direction with a tenter. At this time, the residual solvent amount when starting stretching with a tenter was 30%.

Thereafter, drying is completed while transporting the drying zone of 110 ° C. and 120 ° C. with a number of rolls, slitting to a width of 1400 mm, a knurling process having a width of 15 mm and an average height of 10 μm is applied to both ends of the film, and an initial winding tension of 220 N / M and a final tension of 110 N / m were wound around a 6-inch inner diameter core to obtain a positive birefringent resin layer P5. The draw ratio in the MD direction immediately after peeling calculated from the rotational speed of the stainless steel band support and the operating speed of the tenter was 1.07. The positive birefringent resin layer P5 had an average film thickness of 84 μm and a winding length of 5000 m.

<Preparation and Stretching of Positive Birefringent Resin Layer P6>
Norbornene resin (Arton G JSR) 80 parts by mass AEROSIL 200V (Nippon Aerosil Co., Ltd.) 0.1 parts by mass Methylene chloride 250 parts by mass Ethanol 10 parts by mass While heating the temperature to 70 ° C. and stirring, the norbornene resin was completely dissolved to obtain a norbornene resin solution (dope). Then, stirring was stopped and the liquid temperature was lowered to 43 ° C. The dope was filtered using a filter paper (Azumi filter paper No. 244, manufactured by Azumi Filter Paper Co., Ltd.) to obtain a dope. Subsequently, using a belt casting apparatus, it was uniformly cast on a stainless steel band support (surface temperature 35 ° C.) with a width of 2 m. The solvent was evaporated until the residual solvent amount reached 100%, and then peeled off from the stainless steel band support. The peeled web was evaporated at 55 ° C., then clipped with a tenter and stretched 1.2 times (20%) at 125 ° C. in the TD direction. Thereafter, drying was completed while being conveyed by a roll at 120 ° C., slitting to a width of 1500 mm, and knurling with a width of 15 mm and an average height of 12 μm were applied to both ends of the film to obtain a positive birefringent resin layer P6. The film average film thickness was 45 μm, the film thickness variation was within ± 1 μm in both the width direction and the longitudinal direction, and the winding length was 5000 m.

The obtained positive birefringent resin layers P1 to P6 were subjected to refractive index measurement using a multi-wavelength light source for Abbe refractometer-4T (manufactured by Atago Co., Ltd.), and the refractive index in the stretching direction was set to Nx Further, when the refractive index in the orthogonal in-plane direction is Ny, (Nx−Ny)> 0 and positive birefringence was exhibited.

<Negative birefringent resin>
Production Example 1
In an autoclave, 50 parts by mass of a monomer mixture of 20% by mass of N-vinylcarbazole and 80% by mass of methyl methacrylate and 2 parts by mass of azobisisobutyronitrile were added and dissolved by adding 800 parts by mass of toluene. After sealing, the mixture was allowed to stand for 48 hours in an atmosphere of 60 ° C. for copolymerization. After completion of the polymerization, methanol was added to precipitate the polymer. A negative birefringent resin N1 was obtained as a white powder through cooling, filtration, washing, and drying steps. This copolymer had a weight average molecular weight of 520000 by GPC analysis based on standard polystyrene. From the NMR spectrum, it was confirmed that the copolymer was a copolymer of N-vinylcarbazole and methyl methacrylate. The composition of the polymer was approximately N-vinylcarbazole: methyl methacrylate = 20: 80.

Similarly, negative birefringent resins N2 to N7 were synthesized. The copolymer contained N-vinylcarbazole monomer units and methyl methacrylate monomer units in the proportions shown in Table 1, respectively.

The film obtained by film formation and stretching alone was subjected to refractive index measurement using Abbe refractometer-4T (manufactured by Atago Co., Ltd.) using a multi-wavelength light source to determine the refractive index in the stretching direction. When the refractive index in the in-plane direction perpendicular to Nx is Ny, (Nx−Ny) <0 and negative birefringence was exhibited.

<Preparation of Laminated Retardation Films 1-12>
<Formation and stretching of laminate>
Negative birefringent resin N1 30 mass parts Methyl ethyl ketone 70 mass parts The above was put into an airtight container and completely dissolved with heating and stirring to prepare a coating solution. It coated on the positive birefringent resin layer P1 using the comma coater, and dried at 80 degreeC, and the laminated body was formed. While the obtained laminate was heated to 130 ° C., the laminate retardation film 1 was obtained by stretching 10% in the transport direction using a longitudinal stretching machine. The film thickness of the negative birefringent resin layer was 19 μm, and the film thickness of the positive birefringent resin layer was 50 μm.

Further, when the phase difference of the laminate was measured by AxoScan ^™ , the phase difference of the negative birefringent resin layer was Ro = 150 nm, Rt = −90 nm, the phase difference of the positive birefringent resin layer was Ro = 0 nm, Rt = 100 nm.

In the same manner as in the laminated retardation film 1, a laminate was formed according to the combinations in Table 2, and stretched in the transport direction under the conditions in Table 2 to produce laminated retardation films 2 to 5 and 8 to 12. Tables 2 and 3 show the film thickness and retardation of the obtained film.

When an attempt was made to stretch the laminated retardation film 7, the coating film was broken at a stretching ratio of less than 1% and did not form a retardation film. In addition, regarding the laminated retardation film 6 that was stretched at 250 ° C. where the coating film can be stretched, the retardation of the base material layer was relaxed by heat and a sufficient retardation was not exhibited.

<< Evaluation of Laminated Retardation Film >>
(Measurement of retardation Ro and Rt)
Using AxoScan ^™ manufactured by AXOMETRICS, the Mueller matrix of the laminate at a wavelength of 590 nm was measured at 23 ° C. and 55% relative humidity.

Using the value and the thickness of each layer measured in advance, Ro and Rt of the positive birefringent resin layer and the negative birefringent resin layer were calculated by the analysis software Multi-Layer Software.

Ro and Rt here are
Ro = (nx + ny) × d
Rt = ((nx + ny) / 2−nz) × d
Nx is the refractive index in the slow axis direction in each layer surface, ny is the refractive index in the direction perpendicular to the slow axis in each layer surface, and d is the thickness (nm) of each layer. .

(Measurement of film thickness)
After embedding the film in an epoxy resin, it was sliced using a microtome (RUB-2100, manufactured by Daiwa Kogyo Co., Ltd.), and the cross section was observed and measured using a scanning electron microscope.

(Roll transportability)
The produced laminated phase difference film was conveyed by rolls, the state after completion of conveyance was observed, and roll conveyance suitability was evaluated according to the following criteria.

○ There are no cracks in the coating layer. △ Some cracking occurs at the end of the coating layer. × Cracks occur in the entire coating layer. << Application to polarizing plates and liquid crystal display devices >>
<Preparation of polarizing plate>
The cellulose ester side (positive birefringent resin layer side) of the laminated retardation films 1 to 6 and 8 to 11 was subjected to alkali saponification treatment to obtain the following polarizing plate protective film. Next, a 120 μm-thick polyvinyl alcohol film was immersed in 100 kg of an aqueous solution containing 1 kg of iodine and 4 kg of boric acid, and stretched 6 times at 50 ° C. to produce a polarizer, and the laminated retardation film was formed on one side of the polarizer. Using a fully saponified polyvinyl alcohol 5% aqueous solution as an adhesive, the laminate was aligned with the stretching direction of the polarizer and the stretching direction of the polarizer, and the positive birefringent resin layer side was bonded to the polarizer side. On the other side, Konica Minolta-tack film KC8UX (manufactured by Konica Minolta Opto Co., Ltd.) was similarly subjected to alkali saponification treatment and bonded to produce polarizing plates 1 to 6 and 8 to 11.

Similarly, a polarizer was prepared, and an aqueous emulsion of a polyester-based ionomer type urethane resin (trade name “Hydran AP-20” manufactured by Dainippon Ink & Chemicals, Inc., solid content concentration 30%, viscosity 30 mPa · sec) Stretching direction and polarization of laminate of laminated retardation film 12 with 100 parts added with 3 parts of polyisocyanate compound (trade name “Hydran Assister C1” manufactured by Dainippon Ink & Chemicals, Inc.) The stretching directions of the polarizers were matched, and each was bonded so that the positive birefringent resin layer surface side was the polarizer side. The other side of the polarizer was subjected to alkali saponification treatment with Konica Minolta Tack Film KC8UX (manufactured by Konica Minolta Opto Co., Ltd.) to produce a polarizing plate 12.

<Production and evaluation of liquid crystal display devices>
Remove the polarizing plate on the viewing side of the LCD TV VIERALX60 (26 inches) manufactured by Matsushita Electric Industrial Co., Ltd., and replace the polarizing plates 1 to 6 and 8 to 12 that were produced in the same manner as the axis of the original polarizer. A polarizing plate using a Konica Minolta-tack film KC4UE (manufactured by Konica Minolta Opto Co., Ltd.) as a polarizing plate protective film is pasted together through an adhesive CS9621 manufactured by Nitto Denko Corporation. Liquid crystal display devices 1 to 6 and 8 to 12 were used.

(Screen unevenness evaluation)
The black display screens of the produced liquid crystal display devices 1 to 6 and 8 to 12 were visually observed in a dark place (10 persons), and unevenness was evaluated according to the following criteria.

◎ Number of people who observed unevenness 0 Number of people who observed unevenness 1-3 people △ Number of people who observed unevenness 4-9 people × Number of people who observed unevenness 10 people (Evaluation of viewing angle)
The viewing angles of the liquid crystal display devices 1 to 6 and 8 to 12 manufactured using EZcontrast 160D manufactured by ELDIM were measured, and the tilt angle from the normal direction showing a contrast ratio of 10 or more in the azimuth angle 45 ° direction was evaluated according to the following criteria. The sample of the present invention had extremely high viewing angle improvement characteristics.

○ 50 degrees or more △ 30 degrees or more and less than 50 degrees × less than 30 degrees

Example 2
(Preparation of laminated retardation film 13)
In the same manner as in Production Example 1, except that 80% by mass of methyl methacrylate and 70% by mass of acryloylmorpholine and 30% by mass of N-vinylcarbazole were used instead of 20% by mass of N-vinylcarbazole. N8 was synthesized. This resin had negative birefringence. A laminated retardation film 13 was produced in the same manner as the laminated retardation film 1 except that this negative birefringent resin N8 was used. The phase difference of the negative birefringent resin layer is Ro = 160 nm, Rt = −100 nm, and the phase difference of the positive birefringent resin layer is Ro = 0 nm, Rt = 100 nm. When used in a display device, no unevenness was observed and a wide viewing angle was shown.

(Preparation of laminated retardation film 14)
In the same manner as in Production Example 1, except that 80% by mass of methyl methacrylate and 20% by mass of N-vinylcarbazole were replaced by 60% by mass of methyl methacrylate, 10% by mass of butyl methacrylate, and 30% by mass of N-vinylcarbazole. A negative birefringent resin N9 was synthesized. This resin had negative birefringence. A laminated retardation film 14 was produced in the same manner as the laminated retardation film 1 except that this negative birefringent resin N9 was used. The phase difference of the negative birefringent resin layer is Ro = 150 nm, Rt-90 nm, the phase difference of the base material layer is Ro = 0 nm, Rt = 100 nm, there is no crack at the time of roll conveyance, and the liquid crystal display device is used. In this case, no unevenness was observed and a wide viewing angle was shown.

(Preparation of laminated retardation film 15)
Negative birefringent resin N1 27 parts by mass Cellulose acetate butyrate (acetyl group substitution degree 1.1, butyryl group substitution degree 1.8, weight average molecular weight 24) 3 parts by mass Methyl ethyl ketone 70 parts by mass The solution was completely dissolved with heating and stirring to prepare a coating solution. This resin mixture had negative birefringence. A laminated retardation film 15 was produced in the same manner as in the laminated retardation film 1 except that this coating solution was used. The phase difference of the negative birefringent resin layer is Ro = 135 nm, Rt = -80 nm, the phase difference of the positive birefringent resin layer is Ro = 0 nm, Rt = 100 nm, there is no crack at the time of roll conveyance, and the liquid crystal When used in a display device, no unevenness was observed and a wide viewing angle was shown.

(Preparation of laminated retardation film 16)
In the same manner as in Production Example 1, except that 80% by mass of methyl methacrylate and 20% by mass of N-vinylcarbazole were replaced by 70% by mass of methyl methacrylate and 30% by mass of 2-vinylcarbazole. N10 was synthesized. This resin had negative birefringence. A laminated retardation film 16 was produced in the same manner as the laminated retardation film 1 except that this negative birefringent resin N10 was used. The phase difference of the negative birefringent resin layer is Ro = 160 nm, Rt−100 nm, the phase difference of the base material layer is Ro = 0 nm, Rt = 100 nm, there is no crack at the time of roll conveyance, and the liquid crystal display device is used. In this case, no unevenness was observed and a wide viewing angle was shown.

Claims

A laminate of a positive birefringent resin layer and a negative birefringent resin layer, wherein the negative birefringent resin layer is a monomer unit L represented by the following general formula (1) and an ethylenically unsaturated monomer A laminated retardation film comprising a copolymer having units M.

(Only one of R 1 to R 6 is a substituent represented by the general formula (2), and other than that, halogen such as hydrogen, F, Cl, Br, hydroxyl group, carboxyl group, amino Group, cyano group, nitro group, nitroso group, thiol group, saturated hydrocarbon group having 1 to 12 carbon atoms, alkoxyl group having 1 to 12 carbon atoms, acyl group having 1 to 12 carbon atoms, acyloxy having 1 to 12 carbon atoms Groups, alkyloxycarbonyl groups having 1 to 12 carbon atoms, hydrocarbon groups having 1 to 4 carbon atoms having a hydroxyl group, hydrocarbon groups having 1 to 4 carbon atoms having an amino group, and hydrocarbon groups having 1 to 4 carbon atoms. Represents a secondary or tertiary amino group.
R in the general formula (2) is hydrogen, hydroxyl group, carboxyl group, amino group, saturated hydrocarbon group having 1 to 12 carbon atoms, alkoxyl group having 1 to 12 carbon atoms, acyl group having 1 to 12 carbon atoms, It represents an acyloxy group having 1 to 12 carbon atoms, an alkyloxycarbonyl group having 1 to 12 carbon atoms, or a hydrocarbon group having 1 to 4 carbon atoms having a hydroxyl group. )
The laminated retardation film according to claim 1, wherein the copolymer contains 20 to 70% by mass of monomer units L.
The laminated retardation film according to claim 1 or 2, wherein the positive birefringent resin layer is made of cellulose ester.
An esterified compound obtained by esterifying all or part of the OH group in the compound (A) having a (meth) acrylic polymer and one furanose structure or one pyranose structure on the positive birefringent resin layer, or And an esterified compound obtained by esterifying all or part of the OH groups in the compound (B) in which 2 or more and 12 or less of at least one of a furanose structure or a pyranose structure are bonded. 4. The laminated retardation film according to any one of items 1 to 3 in the range.
The phase difference of the positive birefringent resin layer is Ro = 0 to 50 nm, Rt = 80 to 150 nm, and the phase difference of the negative birefringent resin layer is Ro = 80 to 200 nm, Rt = −70 to −150 nm. 5. The laminate according to any one of claims 1 to 4, wherein when each has an in-plane slow axis, the in-plane slow axes are orthogonal to each other. Retardation film.
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 resin layer, 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 resin) (Represents the thickness (nm) of each layer. The measurement wavelength of the refractive index is 590 nm.)
A polarizing plate comprising the laminated retardation film according to any one of claims 1 to 5 on at least one surface.
A liquid crystal display device comprising the polarizing plate according to claim 6 on at least one surface of a liquid crystal cell.