JP2011107281A - Optical-compensation film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical-compensation film which is formed from a fumarate-based copolymer resin, has a negative birefringence, and is excellent in optical properties such as retardation properties, retardation stability or wavelength dependency and mechanical properties. <P>SOLUTION: In the optical-compensation film formed from a fumarate-based copolymer resin, when the refractive index in the fast axis direction in the film plane is defined as nx, the refractive index in the direction orthogonal to the fast axis direction is defined as ny, and the refractive index in the film thickness direction is defined as nz, following relations: nx<ny≤nz are satisfied, and the ratio of a retardation measured with light having a wavelength of 450 nm to a retardation measured with light having a wavelength of 550 nm, (R450/R550), is ≤1.1. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an optical film having negative birefringence and excellent optical characteristics such as retardation characteristics, retardation stability and wavelength dependence, and more particularly to an optical compensation film for liquid crystal display elements.

  Liquid crystal displays are widely used as the most important display devices in the multimedia society, from mobile phones to computer monitors, notebook computers, and televisions. Many optical films are used in liquid crystal displays to improve display characteristics. In particular, the optical compensation film plays a major role in improving contrast and compensating for color tone when viewed from the front or obliquely. As conventional optical compensation films, polycarbonate and cyclic polyolefin are used, and these polymers are polymers having positive birefringence. Here, the sign of birefringence is defined as shown below.

  The optical anisotropy of the polymer film molecularly oriented by stretching or the like can be represented by a refractive index ellipsoid shown in FIG. Here, the refractive index in the fast axis direction in the film plane when the film is stretched is denoted by nx, the refractive index in the direction perpendicular thereto is denoted by ny, and the refractive index in the thickness direction of the film is denoted by nz. The fast axis is an axial direction having a low refractive index in the film plane.

  The negative birefringence means that the stretching direction is the fast axis direction, and the positive birefringence is that the direction perpendicular to the stretching direction is the fast axis direction.

  That is, the refractive index in the stretching axis direction is small in uniaxial stretching of a polymer having negative birefringence (fast axis: stretching direction), and the axis orthogonal to the stretching axis direction in uniaxial stretching of a polymer having positive birefringence. The refractive index in the direction is small (fast axis: direction perpendicular to the stretching direction).

  The in-plane retardation (Re) is expressed as a value obtained by multiplying the refractive index (ny) in the direction orthogonal to the fast axis direction minus the refractive index (nx) in the fast axis direction by the thickness of the film.

  Many polymers have positive birefringence. As a polymer having negative birefringence, there are acrylic resin and polystyrene. However, acrylic resin has low retardation and has insufficient characteristics as an optical compensation film. Polystyrene has a large photoelastic coefficient at room temperature and a phase difference that changes with a slight stress, such as a problem of stability of the phase difference, a problem of optical properties such as a large wavelength dependency of the phase difference, and low heat resistance. It is not used at present because of practical problems.

  Here, the wavelength dependence of the phase difference means that the phase difference changes depending on the measurement wavelength, and the ratio of the phase difference (R450) measured at a wavelength of 450 nm to the phase difference (R550) measured at a wavelength of 550 nm. It can be expressed as R450 / R550. In general, a polymer having an aromatic structure has a strong tendency to increase R450 / R550, and the contrast and viewing angle characteristics in a low wavelength region are deteriorated.

A stretched polymer film exhibiting negative birefringence has a high refractive index in the thickness direction of the film and becomes an unprecedented optical compensation film. For example, super twisted nematic liquid crystal (STN-LCD) and vertical alignment liquid crystal (VA) -LCD), in-plane oriented liquid crystal (IPS-LCD), reflective liquid crystal display, transflective liquid crystal display, and other optical compensation films for compensating the viewing angle characteristics and optical compensation for compensating the viewing angle of polarizing plates. There is a strong market demand for an optical compensation film that is useful as a film and has negative birefringence. A method for producing a film has been proposed in which a polymer having positive birefringence is used to increase the refractive index in the thickness direction of the film. One is a treatment method in which a heat-shrinkable film is bonded to one side or both sides of a polymer film, the laminate is subjected to a heat stretching treatment, and a shrinkage force is applied in the thickness direction of the polymer film (see, for example, Patent Documents 1 to 3). ). In addition, a method of uniaxially stretching in a plane while applying an electric field to a polymer film has been proposed (see, for example, Patent Document 4). Further, an optical compensation film composed of fine particles having negative optical anisotropy and a transparent polymer has been proposed (see, for example, Patent Document 5). In addition, an optical compensation film or an optical compensation layer in which a liquid crystalline polymer film is applied and homeotropically oriented has been proposed (see, for example, Patent Document 6). Furthermore, an optical compensation film coated with an aromatic polymer such as polyvinyl naphthalene or polyvinyl biphenyl has been proposed (see, for example, Patent Document 7 and Non-Patent Document 1). Further, an optical film using a polyvinyl carbazole polymer has been proposed (see, for example, Patent Document 8).

  A retardation film made of a fumarate ester resin has been proposed. (For example, see Patent Document 9)

Japanese Patent No. 2818983 JP 05-297223 A JP 05-323120 A Japanese Patent Laid-Open No. 06-088909 JP 2005-156862 A JP 2002-333524 A JP 2006-221116 A JP 2001-91746 A JP 2008-64817 A

Journal of the Japanese Society of Rheology Vol22, No. 2, 129-134 (1994)

  However, the methods proposed in Patent Documents 1 to 4 have a problem that the manufacturing process is very complicated and the productivity is inferior. In addition, the control of the uniformity of the phase difference and the like is significantly more difficult than the conventional control by stretching. When polycarbonate is used as the base film, the photoelastic constant at room temperature is large, and there is a problem in the stability of the phase difference, such as the phase difference being changed by a slight stress. Furthermore, there are problems such as the large wavelength dependence of the phase difference.

  In addition, the optical compensation film obtained in Patent Document 5 is an optical compensation film having negative birefringence by adding fine particles having negative optical anisotropy, and from the viewpoint of simplification of the manufacturing method and economy. There is a need for an optical compensation film that does not require the addition of fine particles. The method described in Patent Document 6 has a problem that it is difficult to uniformly homeotropically align the liquid crystalline polymer. In addition, the methods described in Patent Documents 7 and 8 have problems that the obtained film is easily broken and that the wavelength dependence of retardation is large. Further, as described in Non-Patent Document 1, there is a problem that the photoelastic coefficient of the glass region is high and the phase difference is not stable.

  Although the retardation film obtained in Patent Document 9 is excellent in optical characteristics such as retardation characteristics and wavelength dependency, there is a problem in retardation stability, and improvement in retardation stability is desired. It was.

  Therefore, the present invention provides an optical compensation film comprising a fumarate ester copolymer resin, having negative birefringence, and excellent optical characteristics such as retardation characteristics, retardation stability, wavelength dependence, and the like. It is intended to do.

  As a result of intensive studies in view of the above problems, the present inventors have found that an optical compensation film that is a film made of a specific resin and that satisfies the specific relationship in the three-dimensional refractive index of the film satisfies the above problems. The headline and the present invention were completed.

  That is, the present invention is a film made of a fumaric acid ester copolymer resin, in which the refractive index in the fast axis direction in the film plane is nx, the refractive index in the direction perpendicular thereto is ny, and the refractive index in the thickness direction of the film. Nx <ny ≦ nz, and the ratio of the phase difference measured with 450 nm light to the phase difference measured with 550 nm light (R450 / R550) is 1.1 or less. The present invention relates to a characteristic optical compensation film.

  Hereinafter, the optical compensation film of the present invention will be described in detail.

  Examples of the fumaric acid ester-based copolymer resin used in the present invention include fumaric acid ester copolymers, and among them, an optical compensation film having excellent retardation stability can be obtained. (A) is a copolymer represented by the following general formula (b) having a small steric hindrance, and a fumaric acid diester copolymer comprising 5 to 50 mol% of a fumaric acid diester residue unit represented by the general formula (b). Polymer resins are preferred.

（ここで、Ｒ_１、Ｒ_２はそれぞれ独立して炭素数３〜１２で、フマル酸骨格単位に結合する炭素が２級又は３級炭素である分岐状アルキル基又は環状アルキル基を示す。）

(Here, R ₁ and R ₂ each independently represent a branched alkyl group or a cyclic alkyl group having 3 to 12 carbon atoms, wherein the carbon bonded to the fumaric acid skeleton unit is a secondary or tertiary carbon.)

（ここで、Ｒ_３、Ｒ_４はそれぞれ独立して炭素数２〜１２の直鎖状アルキル基又は炭素数４〜１２で、フマル酸骨格単位に結合する炭素が１級炭素である分岐状アルキル基を示す。）
ここで、一般式（ａ）のフマル酸ジエステル残基単位のエステル置換基であるＲ_１、Ｒ_２は、それぞれ独立して、炭素数３〜１２で、フマル酸骨格単位に結合する炭素が２級又は３級炭素である分岐状アルキル基又は環状アルキル基であり、フッ素、塩素などのハロゲン基；エーテル基；エステル基若しくはアミノ基で置換されていても良く、例えばイソプロピル基、ｓ−ブチル基、ｔ−ブチル基、ｓ−ペンチル基、ｔ−ペンチル基、ｓ−ヘキシル基、ｔ−ヘキシル基、シクロプロピル基、シクロペンチル基、シクロヘキシル基等が挙げられ、特に耐熱性、機械特性に優れた光学補償フィルムとなることからイソプロピル基、ｓ−ブチル基、ｔ−ブチル基、シクロペンチル基、シクロヘキシル基等であることが好ましく、特に耐熱性、機械特性のバランスに優れた光学補償フィルムとなることからイソプロピル基が好ましい。

(Here, R ₃ and R ₄ are each independently a linear alkyl group having 2 to 12 carbon atoms or a branched alkyl having 4 to 12 carbon atoms, and the carbon bonded to the fumaric acid skeleton unit is a primary carbon. Group.)
Here, R ₁ and R ₂ which are ester substituents of the fumaric acid diester residue unit of the general formula (a) are each independently 3 to 12 carbon atoms and 2 carbon atoms bonded to the fumaric acid skeleton unit. A branched alkyl group or a cyclic alkyl group which is a tertiary or tertiary carbon, which may be substituted with a halogen group such as fluorine or chlorine; an ether group; an ester group or an amino group, such as an isopropyl group or an s-butyl group , T-butyl group, s-pentyl group, t-pentyl group, s-hexyl group, t-hexyl group, cyclopropyl group, cyclopentyl group, cyclohexyl group, etc., and particularly excellent in heat resistance and mechanical properties. It is preferably isopropyl group, s-butyl group, t-butyl group, cyclopentyl group, cyclohexyl group or the like because it becomes a compensation film. An isopropyl group is preferable because an excellent optical compensation film balance of sex.

  Specific examples of the fumaric acid diester residue unit represented by the general formula (a) include diisopropyl fumarate residue, di-s-butyl fumarate residue, di-t-butyl fumarate residue, dimer fumarate. -S-pentyl residue, di-t-pentyl fumarate residue, di-s-hexyl fumarate residue, di-t-hexyl fumarate residue, dicyclopropyl fumarate residue, dicyclopentyl fumarate residue Groups such as dicyclohexyl fumarate, diisopropyl fumarate, di-s-butyl fumarate, di-t-butyl fumarate, dicyclopentyl fumarate, dicyclohexyl fumarate. Residues and the like are preferable, and diisopropyl fumarate residue is particularly preferable.

R ₃ and R ₄ which are ester substituents of the fumaric acid diester residue unit of the general formula (b) are each independently a linear alkyl group having 2 to 12 carbon atoms or 4 to 12 carbon atoms. A branched alkyl group in which the carbon bonded to the fumaric acid skeleton unit is a primary carbon, which may be substituted with a halogen group such as fluorine or chlorine; an ether group; an ester group or an amino group, such as a methyl group, Examples include an ethyl group, an n-propyl group, an n-butyl group, an iso-butyl group, an n-hexyl group, an n-heptyl group, an n-octyl group, and a 2-ethylhexyl group. A methyl group, an ethyl group, an n-butyl group, an iso-butyl group, an n-octyl group, a 2-ethylhexyl group, and the like are preferable because it becomes a film, and particularly a balance between heat resistance and mechanical properties. Excellent n- butyl group from becoming an optical compensation film, n- octyl, 2-ethylhexyl group is preferred.

  Specific examples of the fumaric acid diester residue unit represented by the general formula (b) include dimethyl fumarate residue, diethyl fumarate residue, di-n-propyl fumarate residue, di-n-butyl fumarate. Residue, di-iso-butyl fumarate residue, di-n-hexyl fumarate residue, di-n-heptyl fumarate residue, di-n-octyl fumarate residue, bis (2-ethylhexyl fumarate) ) Residues, among which dimethyl fumarate residue, diethyl fumarate residue, di-n-butyl fumarate residue, di-iso-butyl fumarate residue, di-n-octyl fumarate residue Group, a bis (2-ethylhexyl) fumarate residue is preferable, and a di-n-butyl fumarate residue, a di-n-octyl fumarate residue, and a bis (2-ethylhexyl) fumarate residue are particularly preferable.

  Specific examples of the copolymer represented by the general formulas (a) and (b) include diisopropyl fumarate / dimethyl fumarate copolymer, diisopropyl fumarate / diethyl fumarate copolymer, diisopropyl fumarate / fumaric acid. Di-n-butyl copolymer, diisopropyl fumarate / di-iso-butyl fumarate copolymer, diisopropyl fumarate / di-n-octyl fumarate copolymer, diisopropyl fumarate / bis (2-ethylhexyl) fumarate ) Copolymer, Di-s-butyl fumarate / dimethyl fumarate copolymer, Di-s-butyl fumarate / diethyl fumarate copolymer, Di-s-butyl fumarate / Di-n-butyl fumarate Copolymer, di-s-butyl fumarate / di-iso-butyl fumarate copolymer, di-s-butyl fumarate / di-n-o fumarate Chill copolymer, di-s-butyl fumarate / bis (2-ethylhexyl) fumarate copolymer, di-t-butyl fumarate / dimethyl fumarate copolymer, di-t-butyl fumarate / fumaric acid Diethyl copolymer, di-t-butyl fumarate / di-n-butyl fumarate copolymer, di-t-butyl fumarate / di-iso-butyl fumarate copolymer, di-t-butyl fumarate · Di-n-octyl fumarate copolymer, di-t-butyl fumarate · bis (2-ethylhexyl) fumarate copolymer, dicyclopentyl fumarate · dimethyl fumarate copolymer, dicyclopentyl fumarate · fumarate Diethyl methacrylate copolymer, dicyclopentyl fumarate / di-n-butyl fumarate copolymer, dicyclopentyl fumarate / di-iso-butyl fumarate copolymer, dicyclo fumarate Di-n-octyl fumarate copolymer, dicyclopentyl fumarate / bis (2-ethylhexyl) fumarate copolymer, dicyclohexyl fumarate / dimethyl fumarate copolymer, dicyclohexyl fumarate / diethyl fumarate copolymer Copolymer, dicyclohexyl fumarate / di-n-butyl fumarate copolymer, dicyclohexyl fumarate / di-iso-butyl fumarate copolymer, dicyclohexyl fumarate / di-n-octyl fumarate copolymer, dicyclohexyl fumarate -Examples include bis (2-ethylhexyl) fumarate copolymer, among which diisopropyl fumarate / di-n-butyl fumarate copolymer, diisopropyl fumarate / bis (2-ethylhexyl) fumarate copolymer Is preferred.

  The ratio of the fumaric acid diester residue represented by the general formula (a) and the fumaric acid diester residue represented by the general formula (b) in the fumaric acid ester copolymer resin used in the present invention is determined by the optical compensation film obtained. A fumaric acid comprising 95 to 50 mol% of a fumaric acid diester residue represented by the general formula (a) and 5 to 50 mol% of a fumaric acid diester residue represented by the general formula (b) because of excellent heat resistance and mechanical properties. It is preferably an acid diester copolymer resin, particularly 90 to 60 mol% of a fumaric acid diester residue represented by the general formula (a) and 10 to 40 mol of a fumaric acid diester residue represented by the general formula (b). % Is preferred.

  Further, the fumaric acid ester copolymer resin constituting the optical compensation film of the present invention may contain other monomer residues as long as it does not depart from the object of the present invention. Examples of monomer residues include styrene residues such as styrene residues and α-methylstyrene residues; acrylic acid residues; methyl acrylate residues, ethyl acrylate residues, butyl acrylate residues, and acrylic residues. Acrylic acid ester residues such as acid 3-ethyl-3-oxetanylmethyl residue and tetrafuryl acrylate residue drofurfuryl residue; methacrylic acid residue; methyl methacrylate residue, ethyl methacrylate residue, butyl methacrylate residue Groups, methacrylic acid ester residues, such as 3-ethyl-3-oxetanylmethyl residue, tetrahydrofurfuryl methacrylate residue; 1 type or 2 types or more, such as vinyl ester residues, such as a vinyl residue, vinyl propionate residue; acrylonitrile residue; methacrylonitrile residue; olefin residue such as ethylene residue, propylene residue; Can be mentioned.

  The fumaric acid ester-based copolymer resin used in the present invention preferably has a glass transition temperature of 100 to 250 ° C., more preferably 120 to 200 ° C., particularly 140 because an optical compensation film having excellent heat resistance and processability is obtained. It is preferable that it is -200 degreeC.

The fumaric acid ester copolymer resin used in the present invention has a number average molecular weight (Mn) in terms of standard polystyrene obtained from an elution curve measured by gel permeation chromatography (hereinafter referred to as GPC). It is preferably 1 × 10 ³ or more, and is particularly preferably 2 × 10 ⁴ or more and 2 × 10 ⁵ or less because it becomes an optical compensation film having excellent mechanical properties and excellent moldability during film formation. preferable.

  The method for producing the fumarate ester copolymer resin constituting the optical compensation film of the present invention is not particularly limited as long as the fumarate ester copolymer resin can be obtained. For example, the following general formula ( The fumaric acid diesters represented by c) and the following general formula (d) having a small steric hindrance can be produced by radical copolymerization.

（ここで、Ｒ_５、Ｒ_６はそれぞれ独立して炭素数３〜１２で、フマル酸骨格単位に結合する炭素が２級又は３級炭素である分岐状アルキル基又は環状アルキル基を示す。）

(Here, R ₅ and R ₆ each independently represent a branched alkyl group or a cyclic alkyl group having 3 to 12 carbon atoms, wherein the carbon bonded to the fumaric acid skeleton unit is a secondary or tertiary carbon.)

（ここで、Ｒ_７、Ｒ_８はそれぞれ独立して炭素数２〜１２の直鎖状アルキル基又は炭素数４〜１２で、フマル酸骨格単位に結合する炭素が１級炭素である分岐状アルキル基を示す。）
ここで、一般式（ｃ）のフマル酸ジエステル類のエステル置換基であるＲ_５、Ｒ_６は、それぞれ独立して、炭素数３〜１２で、フマル酸骨格単位に結合する炭素が２級又は３級炭素である分岐状アルキル基又は環状アルキル基であり、フッ素、塩素などのハロゲン基；エーテル基；エステル基若しくはアミノ基で置換されていても良く、例えばイソプロピル基、ｓ−ブチル基、ｔ−ブチル基、ｓ−ペンチル基、ｔ−ペンチル基、ｓ−ヘキシル基、ｔ−ヘキシル基、シクロプロピル基、シクロペンチル基、シクロヘキシル基等が挙げられ、特に耐熱性、機械特性に優れた光学補償フィルムとなることからイソプロピル基、ｓ−ブチル基、ｔ−ブチル基、シクロペンチル基、シクロヘキシル基等であることが好ましく、特に耐熱性、機械特性のバランスに優れた光学補償フィルムとなることからイソプロピル基が好ましい。

(Here, R ₇ and R ₈ are each independently a linear alkyl group having 2 to 12 carbon atoms or a branched alkyl having 4 to 12 carbon atoms, and the carbon bonded to the fumaric acid skeleton unit is a primary carbon. Group.)
Here, R ₅ and R ₆ which are ester substituents of the fumaric acid diesters of the general formula (c) are each independently 3 to 12 carbon atoms, and the carbon bonded to the fumaric acid skeleton unit is secondary or A branched alkyl group or a cyclic alkyl group which is a tertiary carbon, which may be substituted with a halogen group such as fluorine or chlorine; an ether group; an ester group or an amino group, such as isopropyl group, s-butyl group, t -Butyl group, s-pentyl group, t-pentyl group, s-hexyl group, t-hexyl group, cyclopropyl group, cyclopentyl group, cyclohexyl group, etc., and optical compensation film having particularly excellent heat resistance and mechanical properties Therefore, an isopropyl group, a s-butyl group, a t-butyl group, a cyclopentyl group, a cyclohexyl group, and the like are preferable. An isopropyl group is preferable because an excellent optical compensation film lance.

  Specific examples of the fumaric acid diester represented by the general formula (c) include diisopropyl fumarate, di-s-butyl fumarate, di-t-butyl fumarate, di-s-pentyl fumarate, and di-fumarate. -T-pentyl, di-s-hexyl fumarate, di-t-hexyl fumarate, dicyclopropyl fumarate, dicyclopentyl fumarate, dicyclohexyl fumarate, etc. Among them, diisopropyl fumarate, di-fumarate Preferred are s-butyl, di-t-butyl fumarate, dicyclopentyl fumarate, dicyclohexyl fumarate and the like, and particularly preferred is diisopropyl fumarate.

R ₇ and R ₈ which are ester substituents of the fumaric acid diesters of the general formula (d) are each independently a linear alkyl group having 2 to 12 carbon atoms or 4 to 12 carbon atoms, A branched alkyl group in which the carbon bonded to the acid skeleton unit is a primary carbon, which may be substituted with a halogen group such as fluorine or chlorine; an ether group; an ester group or an amino group, such as a methyl group or an ethyl group , N-propyl group, n-butyl group, iso-butyl group, n-hexyl group, n-heptyl group, n-octyl group, 2-ethylhexyl group, and the like. Therefore, it is preferably a methyl group, an ethyl group, an n-butyl group, an iso-butyl group, an n-octyl group, a 2-ethylhexyl group, etc., and particularly excellent in balance between heat resistance and mechanical properties. n- butyl group from becoming an optical compensation film, n- octyl, 2-ethylhexyl group is preferred.

  Specific examples of the fumaric acid diester represented by the general formula (d) include dimethyl fumarate, diethyl fumarate, di-n-propyl fumarate, di-n-butyl fumarate, and di-iso-butyl fumarate. , Di-n-hexyl fumarate, di-n-heptyl fumarate, di-n-octyl fumarate, bis (2-ethylhexyl) fumarate, etc., among which dimethyl fumarate, diethyl fumarate, fumaric acid Di-n-butyl, di-iso-butyl fumarate, di-n-octyl fumarate and bis (2-ethylhexyl) fumarate are preferred, and di-n-butyl fumarate, di-n-octyl fumarate, Bis (2-ethylhexyl) fumarate is preferred.

  The ratio of the fumaric acid diester represented by the general formula (c) and the fumaric acid diester residue represented by the general formula (d) is such that the obtained optical compensation film is excellent in heat resistance and mechanical properties. The fumaric acid diester represented by the general formula (d) is preferably 95 to 50 mol% and the fumaric acid diester represented by the general formula (d) is preferably 5 to 50 mol%, and in particular, the fumaric acid diester represented by the general formula (c) 90 to 60 It is preferable that it is 10-40 mol% of fumaric acid diester shown by mol% and general formula (d).

  In addition, in the production of the fumaric acid ester copolymer resin constituting the optical compensation film of the present invention, other monomers copolymerizable with the fumaric acid diesters are used in combination without departing from the object of the present invention. can do. Examples of monomers copolymerizable with fumaric acid diesters include styrenes such as styrene and α-methylstyrene; acrylic acid; methyl acrylate, ethyl acrylate, butyl acrylate, 3-ethyl-3-acrylate Acrylic esters such as oxetanylmethyl and tetrahydrofurfuryl acrylate; methacrylic acid; methacrylic acid such as methyl methacrylate, ethyl methacrylate, butyl methacrylate, 3-ethyl-3-oxetanylmethyl methacrylate and tetrahydrofurfuryl methacrylate Examples thereof include one or more of esters; vinyl esters such as vinyl acetate and vinyl propionate; acrylonitrile; methacrylonitrile; olefins such as ethylene and propylene.

  Further, as the radical polymerization method to be used, it can be carried out by a known polymerization method, for example, any of a bulk polymerization method, a solution polymerization method, a suspension polymerization method, a precipitation polymerization method, an emulsion polymerization method and the like can be adopted. is there.

  Examples of the polymerization initiator used in the radical polymerization method include benzoyl peroxide, lauryl peroxide, octanoyl peroxide, acetyl peroxide, di-t-butyl peroxide, t-butyl cumyl peroxide, and dicumyl peroxide. , Organic peroxides such as t-butyl peroxyacetate, t-butyl peroxybenzoate, t-butyl peroxypivalate; 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2′- Azo series such as azobis (2-butyronitrile), 2,2′-azobisisobutyronitrile, dimethyl-2,2′-azobisisobutyrate, 1,1′-azobis (cyclohexane-1-carbonitrile) Initiators are mentioned.

  And there is no restriction | limiting in particular as a solvent which can be used in a solution polymerization method, a suspension polymerization method, a precipitation polymerization method, and an emulsion polymerization method, For example, aromatic solvents, such as benzene, toluene, xylene; Methanol, ethanol, propyl alcohol, butyl alcohol Examples include alcohol solvents such as cyclohexane, dioxane, tetrahydrofuran (THF), acetone, methyl ethyl ketone, dimethylformamide, isopropyl acetate, water, and the like, and mixed solvents thereof.

Moreover, the polymerization temperature at the time of performing radical polymerization can be suitably set according to the decomposition temperature of a polymerization initiator, and generally it is preferable to carry out in the range of 40-150 degreeC.
There is no restriction | limiting in particular as a manufacturing method of the optical compensation film of this invention, For example, it can manufacture by forming into a film by methods, such as a solution cast method and a melt-cast method, and extending | stretching this film uniaxially or biaxially. .

  The solution casting method is a method of obtaining a film by casting a solution (hereinafter referred to as a dope) in which a fumaric acid ester copolymer resin is dissolved in a solvent, and then removing the solvent by heating or the like. . In this case, as a method for casting the dope on the support substrate, for example, a T-die method, a doctor blade method, a bar coater method, a roll coater method, a lip coater method or the like is used. Particularly, industrially, a method of continuously extruding a dope from a die onto a belt-like or drum-like support substrate is most common. Examples of the support substrate used include a glass substrate; a metal substrate such as stainless steel or ferrotype; and a plastic substrate such as polyethylene terephthalate (PET) or triacetyl cellulose (TAC). In the solution casting method, when forming a film having high transparency and excellent thickness accuracy and surface smoothness, the solution viscosity of the dope is a very important factor, and preferably 700 to 30000 cps. It is preferable that it is 1000-10000 cps. The melt casting method is a molding method in which a fumaric acid ester copolymer resin is melted in an extruder, extruded into a film form from a slit of a T die, and then cooled and cooled with a roll or air.

  And the obtained film can be used as the optical compensation film of the present invention by controlling the phase difference by stretching uniaxially or biaxially. Examples of the uniaxial stretching method include a free-width uniaxial stretching method, a stretching method using a tenter, and a stretching method between rolls. The biaxial stretching method includes, for example, a stretching method using a tenter or a tube-like expansion. There are methods. As the stretching conditions, unevenness in thickness is unlikely to occur, and since the optical compensation film is excellent in mechanical properties and optical properties, the stretching temperature is preferably 80 to 270 ° C., particularly preferably 120 to 220 ° C., The draw ratio is preferably 1.01 to 5 times, particularly preferably 1.01 to 2 times.

  The optical compensation film of the present invention is a film made of a fumarate ester-based copolymer resin, and the refractive index in the fast axis direction in the film plane is nx, the refractive index in the direction perpendicular thereto is ny, and the thickness direction of the film Nx <ny ≦ nz, where the ratio of the phase difference measured with 450 nm light to the phase difference measured with 550 nm light (R450 / R550) is 1.1 or less. An optical compensation film characterized by having a STN-LCD, an IPS-LCD, a reflective LCD and a transflective type by using a fumarate copolymer resin and satisfying the relationship of nx <ny ≦ nz. It is an optical compensation film having negative birefringence with excellent viewing angle compensation performance, such as an LCD, and having optical characteristics such as phase difference characteristics, phase difference stability, and wavelength dependence.

In addition, since the optical compensation film of the present invention becomes an optical compensation film having more excellent optical characteristics, the in-plane retardation (Re) measured at a wavelength of 550 nm represented by the following formula (1) is 50 to 2000 nm. Is more preferable, and it is preferable that it is 50-1000 nm, and it is especially preferable that it is 100-500 nm.
Re = (ny−nx) × d (1)
(Here, d indicates the thickness of the film.)
In more detail regarding the in-plane retardation (Re) measured at a wavelength of 550 nm represented by the above formula (1), the optical compensation film of the present invention is used for viewing angle compensation of a liquid crystal display in TN, VA, IPS, or OCB mode. When used as an optical compensation film, the in-plane retardation (Re) is preferably 50 nm or more, more preferably 100 nm or more, and particularly preferably 135 nm or more.

  The in-plane retardation (Re) is preferably 100 to 200 nm when used as a circularly polarizing film formed by laminating and integrating an optical compensation film and a polarizing plate. The circularly polarizing film is useful for an antireflection film such as an organic EL display, a brightness enhancement film, and the like in addition to a compensation film for a reflective liquid crystal display.

  Further, the in-plane retardation (Re) when the optical compensation film of the present invention is used as a half-wave film is preferably 200 to 400 nm, and is used for STN mode liquid crystal displays and for viewing angle compensation of brightness enhancement films. The in-plane retardation (Re) at the time is preferably 50 to 1000 nm.

  In the optical compensation film of the present invention, the out-of-plane retardation (Rth) measured at a wavelength of 550 nm represented by the following formula (2) is preferably −30 to −2000 nm, more preferably −50 to −1000 nm. And particularly preferably from −100 to −500 nm.

Rth = [(nx + ny) / 2−nz] × d (2)
(Here, d indicates the thickness of the film.)
The wavelength dependence of the phase difference can be expressed as a ratio R450 / R550 of the phase difference (R450) measured at a wavelength of 450 nm and the phase difference (R550) measured at a wavelength of 550 nm. In the optical compensation film of the present invention, the R450 / R550 is 1.1 or less, more preferably 1.08 or less, and particularly preferably 1.05 or less.

  Moreover, it is preferable that the thickness of an optical compensation film is 10-400 micrometers, More preferably, it is 20-150 micrometers, Especially preferably, it is the range of 30-100 micrometers.

  The optical compensation film of the present invention preferably contains an antioxidant in order to increase the thermal stability of the film itself or in the film itself. Examples of the antioxidant include hindered phenol antioxidants, phosphorus antioxidants, and other antioxidants. These antioxidants may be used alone or in combination. And since an antioxidant effect | action improves synergistically, it is preferable to use together and use a hindered phenolic antioxidant and phosphorus antioxidant, for example, 100 weight part of hindered phenolic antioxidants in that case It is particularly preferable to use a phosphorous antioxidant mixed in an amount of 100 to 500 parts by weight. Further, the addition amount of the antioxidant is preferably 0.01 to 10 parts by weight, particularly 0.5 to 1 with respect to 100 parts by weight of the fumaric ester copolymer resin constituting the optical compensation film of the present invention. Part by weight is preferred.

  Furthermore, as an ultraviolet absorber, for example, an ultraviolet absorber such as benzotriazole, benzophenone, triazine, or benzoate may be blended as necessary.

  The optical compensation film of the present invention includes other polymers, surfactants, polymer electrolytes, conductive complexes, inorganic fillers, pigments, dyes, antistatic agents, antiblocking agents, lubricants, etc., as long as the gist of the invention is not exceeded. It may be blended.

  The optical compensation film of the present invention can be laminated with a polarizing plate to be used as a circular or elliptical polarizing plate, and further laminated with a polarizer made of polyvinyl alcohol / iodine or the like to form a polarizing plate. Moreover, it can also laminate | stack with the optical compensation films of this invention, or another optical compensation film.

  According to the present invention, useful as a compensation film or antireflection film for contrast and viewing angle characteristics of a liquid crystal display, the film has a large refractive index in the thickness direction, a large in-plane retardation, a small wavelength dependence, and a stable retardation. An optical compensation film having excellent optical properties such as excellent properties can be provided.

Change in refractive index ellipsoid by stretching

nx: Refractive index in the fast axis direction in the film plane.
ny: Refractive index in the direction perpendicular to nx.
nz: The refractive index in the thickness direction of the film.

  EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. Unless otherwise noted, commercially available reagents were used.

~ Composition of fumaric acid ester copolymer resin ~
It calculated | required from the proton nuclear magnetic resonance spectroscopy (1H-NMR) spectrum analysis using the nuclear magnetic resonance measuring apparatus (The JEOL make, brand name JNM-GX270).

~ Measurement of number average molecular weight ~
Using a gel permeation chromatography (GPC) (trade name HLC-8020, manufactured by Tosoh Corporation) equipped with a column (trade name TSK-GEL GMHHR-H, manufactured by Tosoh Corporation), a column temperature of 40 ° C. and a flow rate. Under a condition of 1.0 ml / min, THF was used as a solvent and a standard polystyrene conversion value was obtained.

~ Measurement of glass transition temperature (Tg) ~
A differential scanning calorimeter (manufactured by Seiko Denshi Kogyo Co., Ltd., trade name DSC2000) was used and the temperature was 10 ° C / min. It measured at the temperature increase rate of.

~ Measurement of light transmittance ~
The measurement was performed according to JIS K 7361-1 (1997 edition).

~ Measurement of haze ~
The measurement was performed according to JIS K 7136 (2000 edition).

~ Measurement of refractive index ~
Measurement was performed using an Abbe refractometer (manufactured by Atago) in accordance with JIS K 7142 (1981 edition).

-Positive / negative judgment of birefringence-
Birefringence by the additive color determination method with a λ / 4 plate using a polarizing microscope described in Introduction to Polarizing Microscope of Polymer Materials (Hiroshi Hiroya, Agne Technology Center Edition, Chapter 5, pp 78-82, (2001)) The positive / negative judgment was performed.

-Measurement of three-dimensional refractive index, calculation of out-of-plane retardation, in-plane retardation-
The three-dimensional refractive index was measured by changing the elevation angle using a sample tilt type automatic birefringence meter (trade name KOBRA-WR, manufactured by Oji Scientific Instruments). Further, an out-of-plane retardation (Rth) and an in-plane retardation (Re) were calculated from the three-dimensional refractive index.

~ Evaluation of stability of phase difference ~
After the heat treatment at 90 ° C. for 24 hours, the stability of the retardation was evaluated by the in-plane retardation ratio (retention ratio) before and after the heat treatment represented by the following formula (3).
Retention rate = Re2 / Re1 × 100 (3)
(Here, Re1 represents the in-plane retardation before heat treatment, and Re2 represents the in-plane retardation after heat treatment.)
Synthesis Example 1 (Production Example of Diisopropyl Fumarate / Bis (2-ethylhexyl) Fumarate Copolymer)
In a 30 L autoclave equipped with a stirrer, a condenser tube, a nitrogen inlet tube, and a thermometer, 48 g of hydroxypropyl methylcellulose (manufactured by Shin-Etsu Chemical Co., Ltd., trade name Metrose 60SH-50), 15601 g of distilled water, 4859 g of diisopropyl fumarate, bis fumarate ( 2-ethylhexyl) 3542 g and 45 g of polymerization initiator t-butyl peroxypivalate were added, nitrogen bubbling was performed for 1 hour, and then the suspension was held at 50 ° C. for 36 hours while stirring at 200 rpm to carry out radical suspension polymerization. went. After cooling to room temperature, the resulting suspension containing polymer particles was centrifuged. The obtained polymer particles were washed twice with distilled water and twice with methanol, and then dried under reduced pressure at 80 ° C. (yield: 83%).

  The number average molecular weight of the obtained polymer particles was 87,000, and the glass transition temperature was 161 ° C. By 1H-NMR measurement, the polymer particles were found to be diisopropyl fumarate residue unit / bis (2-ethylhexyl) fumarate residue unit = 74.3 / 25.7 (mol%) diisopropyl fumarate / bis fumarate (2 -Ethylhexyl) copolymer (fumaric acid ester copolymer resin) was confirmed.

Synthesis Example 2 (Production example of diisopropyl fumarate / di-n-butyl fumarate copolymer)
In a 30 L autoclave equipped with a stirrer, a condenser tube, a nitrogen inlet tube, and a thermometer, 48 g of hydroxypropyl methylcellulose (trade name Metroze 60SH-50, manufactured by Shin-Etsu Chemical Co., Ltd.), 15601 g of distilled water, 4774 g of diisopropyl fumarate, and di-n-fumarate are used. -Radical suspension polymerization was performed by adding 3627 g of butyl and 45 g of t-butyl peroxypivalate which is a polymerization initiator, carrying out nitrogen bubbling for 1 hour, and holding at 50 ° C for 36 hours while stirring at 200 rpm. . After cooling to room temperature, the resulting suspension containing polymer particles was centrifuged. The obtained polymer particles were washed twice with distilled water and twice with methanol, and then dried under reduced pressure at 80 ° C. (yield: 79%).

  The number average molecular weight of the obtained polymer particles was 122,000, and the glass transition temperature was 190 ° C. By 1H-NMR measurement, the polymer particles were diisopropyl fumarate residue units / di-n-butyl fumarate residue units = 69.9 / 30.1 (mol%) diisopropyl fumarate / di-n-butyl fumarate. It was confirmed that it was a copolymer (fumaric acid ester copolymer resin).

Synthesis Example 3 (Production Example of Diisopropyl Fumarate Homopolymer)
A 30 liter autoclave was charged with 18 kg of distilled water containing 0.2% by weight of partially saponified polyvinyl alcohol, 3 kg of diisopropyl fumarate, and 7 g of dimethyl-2,2′-azobisisobutyrate as a polymerization initiator. Radical suspension polymerization was performed under the conditions of 50 ° C. and a polymerization time of 24 hours. After cooling to room temperature, the resulting suspension containing polymer particles was centrifuged. The obtained polymer particles were washed twice with distilled water and twice with methanol, and then dried under reduced pressure at 80 ° C.

  The number average molecular weight of the obtained diisopropyl fumarate homopolymer was 160,000.

Film creation example 1
Dissolve the diisopropyl fumarate / bis (2-ethylhexyl) fumarate copolymer obtained in Synthesis Example 1 in a toluene / methyl ethyl ketone mixed solution (toluene / methyl ethyl ketone = 50 wt% / 50 wt%) to obtain a 20% solution, Furthermore, with respect to 100 parts by weight of diisopropyl fumarate / bis (2-ethylhexyl) fumarate copolymer, 0.35 parts by weight of tris (2,4-di-t-butylphenyl) phosphite as a hindered phenol-based antioxidant. And 0.15 parts by weight of pentaerythritol-tetrakis (3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate) as a phosphorus antioxidant and 2- (2H-benzotriazole- After adding 1 part by weight of 2-yl) -p-cresol, the solution is obtained by the T-die method. Cast the supporting substrate of the extending apparatus, and each 4 minutes drying at 80 ° C. and 130 ° C., then 6 hours drying under reduced pressure at 120 ° C., to obtain a width 250 mm, a film having a thickness of 70 [mu] m.

  The obtained film had a light transmittance of 93%, a haze of 0.4%, and a refractive index of 1.471.

Film creation example 2
The diisopropyl fumarate / di-n-butyl fumarate copolymer obtained in Synthesis Example 2 is dissolved in a toluene / methyl ethyl ketone mixed solution (toluene / methyl ethyl ketone = 50% by weight / 50% by weight) to form a 20% solution. Tris (2,4-di-t-butylphenyl) phosphite 0.35 parts by weight and phosphorus-based oxidation as a hindered phenolic antioxidant with respect to 100 parts by weight of diisopropyl fumarate di-n-butyl copolymer Pentaerythritol-tetrakis (3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate) 0.15 parts by weight as an inhibitor, 2- (2H-benzotriazol-2-yl) as an ultraviolet absorber -After adding 1 part by weight of p-cresol, it is cast on a support substrate of a solution casting apparatus by the T-die method, 0 ℃ and respectively 4 minutes drying at 130 ° C., then 6 hours drying under reduced pressure at 120 ° C., to obtain a width 250 mm, a film having a thickness of 105 .mu.m.

  The obtained film had a light transmittance of 93%, a haze of 0.4%, and a refractive index of 1.474.

Film production example 3
A polycarbonate resin (manufactured by Aldrich) is dissolved in a methylene chloride solution to make a 25% solution. Further, with respect to 100 parts by weight of the polycarbonate resin, 0.35 weight of tris (2,4-di-t-butylphenyl) phosphite as an antioxidant. Parts and pentaerythritol-tetrakis (3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate) 0.15 parts by weight, 2- (2H-benzotriazol-2-yl)-as UV absorber After adding 1 part by weight of p-cresol, it is cast on a support substrate of a solution casting apparatus by the T-die method, dried at 40 ° C., 80 ° C. and 120 ° C. for 15 minutes, respectively, and then a film having a width of 250 mm and a thickness of 100 μm Got.

  The obtained film had a light transmittance of 91%, a haze of 0.6%, and a refractive index of 1.583.

Film creation example 4
A cyclic polyolefin resin (polynorbornene having an ester group, manufactured by Aldrich) is dissolved in a methylene chloride solution to form a 25% solution. Further, tris (2,4-di-t-) is used as an antioxidant for 100 parts by weight of the cyclic polyolefin resin. Butylphenyl) phosphite 0.35 parts by weight and pentaerythritol-tetrakis (3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate) 0.15 parts by weight, 2- (2H as UV absorber) After adding 1 part by weight of -benzotriazol-2-yl) -p-cresol, it was cast on a support substrate of a solution casting apparatus by the T-die method and dried at 40 ° C, 80 ° C and 120 ° C for 15 minutes each. Thereafter, a film having a width of 250 mm and a thickness of 100 μm was obtained.

  The obtained film had a light transmittance of 92%, a haze of 0.4%, and a refractive index of 1.510.

Film creation example 5
The diisopropyl fumarate homopolymer obtained in Synthesis Example 3 was dissolved in a toluene / methyl ethyl ketone mixed solution (toluene / methyl ethyl ketone = 50% by weight / 50% by weight) to give a 20% solution, and further 100% by weight of the diisopropyl fumarate homopolymer. Parts, 0.35 parts by weight of tris (2,4-di-t-butylphenyl) phosphite as a hindered phenol-based antioxidant and pentaerythritol-tetrakis (3- (3,5) as a phosphorus-based antioxidant -Di-t-butyl-4-hydroxyphenyl) propionate) 0.15 parts by weight, 2- (2H-benzotriazol-2-yl) -p-cresol 1 part by weight as UV absorber, Cast on a support substrate of a solution casting apparatus by the method, and dry at 80 ° C. and 130 ° C. for 4 minutes, respectively. After 6 hours drying under reduced pressure at 120 ° C., to obtain a width 250 mm, a film having a thickness of 120 [mu] m.

  The obtained film had a light transmittance of 93%, a haze of 0.4%, and a refractive index of 1.470.

Example 1
The film obtained in Film Production Example 1 was cut into a 50 mm square, and the temperature was 160 ° C. and the stretching speed was 10 mm / min. With a biaxial stretching apparatus (manufactured by Imoto Seisakusho). The film was subjected to uniaxial stretching with a free width under the conditions of 1.25 times. As a result of measuring the three-dimensional refractive index of the stretched film, the refractive index in the stretching axis direction was small, and thus the obtained film had negative birefringence.

  From the results of the three-dimensional refractive index measurement (nx = 1.4692, ny = 1.4715, nz = 1.4723), the obtained film had a large refractive index in the thickness direction of nx <ny <nz. The in-plane retardation Re = (ny−nx) × d was as large as 171 nm. Further, the out-of-plane retardation Rth = [(nx + ny) / 2−nz] × d was as negative as −148 nm. Furthermore, the phase difference ratio (R450 / R550) (wavelength dependence) was as low as 1.02. The retention ratio of the phase difference was 95%, and the stability of the phase difference was excellent.

  From these results, the obtained film has a negative birefringence, a large refractive index in the thickness direction, a large in-plane retardation, a large out-of-plane retardation, a small wavelength dependence, Since it was excellent in retardation stability, it was suitable for an optical compensation film.

Example 2
The film obtained in Film Production Example 1 was cut into a 50 mm square, and the temperature was 170 ° C. and the stretching speed was 10 mm / min. With a biaxial stretching apparatus (manufactured by Imoto Seisakusho). The film was subjected to uniaxial stretching with a free width under the conditions of 1.25 times. As a result of measuring the three-dimensional refractive index of the stretched film, the refractive index in the stretching axis direction was small, and thus the obtained film had negative birefringence.

  From the results of the three-dimensional refractive index measurement (nx = 1.4691, ny = 1.4715, nz = 1.4724), the obtained film had a large refractive index in the thickness direction of nx <ny <nz. The in-plane retardation Re = (ny−nx) × d was as large as 150 nm. Further, the out-of-plane phase difference Rth = [(nx + ny) / 2−nz] × d was as negative as −136 nm. Furthermore, the phase difference ratio (R450 / R550) (wavelength dependence) was as low as 1.02. The retention ratio of the phase difference was 95%, and the stability of the phase difference was excellent.

  From these results, the obtained film has a negative birefringence, a large refractive index in the thickness direction, a large in-plane retardation, a large out-of-plane retardation, a small wavelength dependence, Since it was excellent in retardation stability, it was suitable for an optical compensation film.

Example 3
The film obtained in Film Production Example 2 was cut into a 50 mm square, and the temperature was 190 ° C. and the stretching speed was 10 mm / min. With a biaxial stretching apparatus (manufactured by Imoto Seisakusho). The film was subjected to uniaxial stretching with a free width under the conditions of 1.25 times. As a result of measuring the three-dimensional refractive index of the stretched film, the refractive index in the stretching axis direction was small, and thus the obtained film had negative birefringence.

  From the results of the three-dimensional refractive index measurement (nx = 1.4710, ny = 1.4728, nz = 1.4755), the obtained film had a large refractive index in the thickness direction of nx <ny <nz. The in-plane retardation Re = (ny−nx) × d was as large as 182 nm. Further, the out-of-plane phase difference Rth = [(nx + ny) / 2−nz] × d was as negative as −364 nm. Furthermore, the phase difference ratio (R450 / R550) (wavelength dependence) was as low as 1.02. The retention ratio of the phase difference was 95%, and the stability of the phase difference was excellent.

  From these results, the obtained film has a negative birefringence, a large refractive index in the thickness direction, a large in-plane retardation, a large out-of-plane retardation, a small wavelength dependence, Since it was excellent in retardation stability, it was suitable for an optical compensation film.

Comparative Example 1
The film obtained in Film Preparation Example 3 was cut into a square of 50 mm, and the temperature was 170 ° C. and the stretching speed was 10 mm / min. The film was subjected to uniaxial stretching with a free width under the conditions of 1.10 times. As a result of measuring the three-dimensional refractive index of the stretched film, the obtained film had positive birefringence because the refractive index in the axial direction perpendicular to the stretching axis direction was small.

  From the results of three-dimensional refractive index measurement (nx = 1.5844, ny = 1.5823, nz = 1.5823), the obtained film had a refractive index of nx> ny = nz and the thickness direction of the film was not large. .

  From these results, since the fumaric acid ester copolymer resin was not used, the obtained film was not suitable for the optical compensation film of the viewing angle compensation performance of STN-LCD and IPS-LCD.

Comparative Example 2
The film obtained in Film Production Example 4 was cut into a square of 50 mm each, and using a biaxial stretching apparatus (manufactured by Imoto Seisakusho), the temperature was 180 ° C. and the stretching speed was 15 mm / min. The film was stretched 2.0 times by free-width uniaxial stretching under the following conditions. As a result of measuring the three-dimensional refractive index of the stretched film, the obtained film had positive birefringence because the refractive index in the axial direction perpendicular to the stretching axis direction was small.

  From the results of the three-dimensional refractive index measurement (1.5124, ny = 1.590, nz = 1.090), the obtained film had a refractive index in the thickness direction of nx> ny = nz and was not large.

  From these results, since the fumaric acid ester copolymer resin was not used, the obtained film was not suitable for the retardation film of the viewing angle compensation performance of STN-LCD and IPS-LCD.

Comparative Example 3
The film obtained in Film Preparation Example 5 was cut into a 50 mm square, and the temperature was 140 ° C. and the stretching speed was 10 mm / min. With a biaxial stretching apparatus (manufactured by Imoto Seisakusho). The film was subjected to uniaxial stretching with a free width under the conditions of 1.25 times. As a result of measuring the three-dimensional refractive index of the stretched film, the refractive index in the stretching axis direction was small, and thus the obtained film had negative birefringence.

  From the results of the three-dimensional refractive index measurement (nx = 1.4667, ny = 1.4705, nz = 1.4728), the obtained film had a large refractive index in the thickness direction of nx <ny <nz. The in-plane retardation Re = (ny−nx) × d was as large as 414 nm. Further, the out-of-plane retardation Rth = [(nx + ny) / 2−nz] × d was as negative as −458 nm. The retention of the phase difference was 85%.

  From these results, since the fumaric acid ester copolymer resin was not used, the obtained film had a problem in stability of retardation.

Comparative Example 4
The film obtained in Film Preparation Example 5 was cut into a 50 mm square, and the temperature was 100 ° C. and the stretching speed was 10 mm / min. With a biaxial stretching apparatus (manufactured by Imoto Seisakusho). The film was subjected to uniaxial stretching with a free width under the conditions of 1.25 times. As a result of measuring the three-dimensional refractive index of the stretched film, the refractive index in the stretching axis direction was small, and thus the obtained film had negative birefringence.

  From the results of the three-dimensional refractive index measurement (nx = 1.4666, ny = 1.4705, nz = 1.4726), the obtained film had a large refractive index in the thickness direction of nx <ny <nz. The in-plane retardation Re = (ny−nx) × d was as large as 425 nm. Further, the out-of-plane phase difference Rth = [(nx + ny) / 2−nz] × d was as negative as −441 nm. The retention of the phase difference was 30%.

  From these results, since the fumaric acid ester copolymer resin was not used, the obtained film had a problem in stability of retardation.

Claims (5)

A film made of a fumarate-based copolymer resin, where the refractive index in the fast axis direction in the film plane is nx, the refractive index in the direction perpendicular to it is ny, and the refractive index in the thickness direction of the film is nz And the ratio of the phase difference measured with 450 nm light and the phase difference measured with 550 nm light (R450 / R550) is 1.1 or less, wherein nx <ny ≦ nz. the film. The in-plane retardation (Re) measured at a wavelength of 550 nm represented by the following formula (1) is 50 to 2000 nm, and the out-of-plane retardation (Rth) measured at a wavelength of 550 nm represented by the following formula (2) is The optical compensation film according to claim 1, which has a wavelength of −30 to −2000 nm.
Re = (ny−nx) × d (1)
Rth = [(nx + ny) / 2−nz] × d (2)
(Where d is the thickness of the film) The fumaric acid ester copolymer resin is a copolymer represented by the following formulas (a) and (b), and the fumaric acid diester residue unit represented by the following formula (b) is 5 to 50 mol%. The optical compensation film according to claim 1 or 2.

(Here, R ₁ and R ₂ each independently represent a branched alkyl group or a cyclic alkyl group having 3 to 12 carbon atoms, wherein the carbon bonded to the fumaric acid skeleton unit is a secondary or tertiary carbon.)

(Here, R ₃ and R ₄ are each independently a linear alkyl group having 2 to 12 carbon atoms or a branched alkyl having 4 to 12 carbon atoms, and the carbon bonded to the fumaric acid skeleton unit is a primary carbon. Group.) The optical compensation film according to any one of claims 1 to 3, wherein the glass transition temperature of the fumarate ester copolymer resin is 100 to 250 ° C. The optical compensation film according to claim 1, wherein the optical compensation film is produced by stretching at least uniaxially.

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