JP2009037110A - Optical compensation film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical compensation film excellent in optical characteristics such as: large refractive index in a thickness direction of a film; large in-plane retardation; and small wavelength dependency, and also excellent in mechanical characteristics such as ductility. <P>SOLUTION: The optical compensation film consists of a fumarate ester-based resin and a plasticizer. Assuming that the refractive index within a film plane in a fast axis direction is nx; the refractive index within the film plane perpendicular to the fast axis direction is ny; and the refractive index outside the film plane in a perpendicular direction is nz, the relation nx≤ny<nz is satisfied. Furthermore, the ratio (R450/R550) in the retardation measured by the wavelength of 450 nm and the retardation measured by the wavelength of 550 nm is ≤1.1. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical compensation film having excellent optical properties such as a large refractive index in the thickness direction of the film and low wavelength dependence, and excellent mechanical properties such as elongation.

  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 retardation film plays a large role in improving contrast and compensating for color tone when viewed from the front or obliquely. As a conventional retardation film, polycarbonate or cyclic polyolefin is 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 represented by nx, the refractive index in the film in-plane direction orthogonal thereto is represented by ny, and the refractive index in the vertical direction outside the film plane is represented by nz. The fast axis is an axial direction having a low refractive index in the film plane.

  Negative birefringence means that the stretching direction is the fast axis direction, and positive birefringence means 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).

  In addition, the in-plane retardation (Re) is obtained by multiplying the film thickness by the refractive index (ny) in the fast axis direction in the film plane and the refractive index (nx) in the fast axis direction in the film plane. Expressed as a value.

  Many polymers have positive birefringence. As a polymer having negative birefringence, there are acrylic resin and polystyrene, but acrylic resin has a small phase difference, and its characteristics as an optical compensation film are not sufficient. 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.

  Since 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, a super twist nematic liquid crystal display (STN-LCD) or a vertical alignment liquid crystal display (VA-LCD), in-plane alignment type liquid crystal display (IPS-LCD), reflection type liquid crystal display (reflection type LCD), etc. There is a strong market demand for an optical compensation film that is useful as an optical compensation 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 or both sides of a polymer film, the laminate is heated and stretched, and a shrinkage force is applied in the film 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). In addition, a retardation film composed of fine particles having negative optical anisotropy and a transparent polymer has been proposed (see, for example, Patent Document 5). 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).

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

  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 control by the conventional 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.

  Further, the retardation film obtained in Patent Document 5 is a retardation film having negative birefringence by adding fine particles having negative optical anisotropy, and from the viewpoint of simplification of the production method and economical efficiency. There is a need for a retardation 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. Further, the methods described in Patent Documents 7 and 8 have problems that the obtained film is easily broken and that the wavelength dispersion of retardation is large.

  Therefore, an object of the present invention is to provide an optical compensation film excellent in optical characteristics such as small wavelength dependency and mechanical characteristics such as elongation.

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

  That is, the present invention is a film comprising a fumarate ester resin and a plasticizer, and the three-dimensional refractive index of the film is nx in the fast axis direction in the film plane, and in the in-plane direction perpendicular to the film. When the refractive index is ny and the refractive index in the vertical direction outside the film surface is nz, the relationship is nx ≦ ny <nz, and the ratio of the phase difference measured at a wavelength of 450 nm to the phase difference measured at a wavelength of 550 nm (R450 / R550) relates to an optical compensation film having a value of 1.1 or less.

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

  The optical compensation film of the present invention is a film comprising a fumaric acid ester resin and a plasticizer, wherein the refractive index in the fast axis direction in the film plane is nx, the refractive index in the film in-plane direction orthogonal to it is ny, Each relationship when the refractive index in the vertical direction outside the film surface is nz is a relationship of nx ≦ ny <nz, particularly preferably a relationship of nz> ny≈nx, and the phase difference measured at a wavelength of 450 nm and the wavelength An optical compensation film having a phase difference ratio (R450 / R550) measured at 550 nm of 1.1 or less. Here, the refractive index nx in the fast axis direction in the film plane is the refractive index in the axial direction having the lowest refractive index in the film plane. And these nx, ny, and nz can be calculated | required by using a sample inclination type | mold automatic birefringence meter, for example.

  In general, the control of the three-dimensional refractive index of the film is performed by stretching the film, which makes the manufacturing process and quality control complicated. However, the film made of a fumarate ester resin and a plasticizer is not stretched. It has been found that it exhibits a unique behavior that the refractive index in the film thickness direction increases.

  In the optical compensation film of the present invention, when the film thickness is d, the out-of-plane retardation (Rth) represented by the following formula (1) is preferably −30 to −2000 nm, particularly preferably. It is −50 to −1000 nm, more preferably −100 to −500 nm.

Rth = [(nx + ny) / 2−nz] × d (1)
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, preferably 1.08 or less, particularly preferably 1.05 or less.

  Moreover, it is preferable that the thickness of an optical compensation film is 5-400 micrometers, Most preferably, it is 10-150 micrometers, More preferably, it is the range of 20-100 micrometers.

  Examples of the fumaric acid ester resin used in the present invention include fumaric acid ester polymers. Among them, fumaric acid diester resin comprising 50 mol% or more of fumaric acid diester residue units represented by the general formula (a) is used. preferable.

（ここで、Ｒ_１、Ｒ_２はそれぞれ独立して炭素数３〜１２の分岐状アルキル基又は環状アルキル基を示す。）
ここで、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の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、さらに耐熱性、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 ₁ and R ₂ each independently represents a branched or cyclic alkyl group having 3 to 12 carbon atoms.)
Here, R ₁ and R ₂ which are ester substituents of the fumaric acid diester residue unit are each independently a branched alkyl group having 3 to 12 carbon atoms or a cyclic alkyl group, and halogen such as fluorine and chlorine. Group; ether group; may be substituted with ester group or amino group, for example, isopropyl group, s-butyl group, t-butyl group, s-pentyl group, t-pentyl group, s-hexyl group, t-hexyl group Group, cyclopropyl group, cyclopentyl group, cyclohexyl group and the like, and since it is an optical compensation film having particularly excellent heat resistance and mechanical properties, isopropyl group, s-butyl group, t-butyl group, cyclopentyl group, cyclohexyl group It is preferable that the isopropyl group has an excellent balance between heat resistance and mechanical properties. Masui.

  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 Etc., and particularly preferred is a diisopropyl fumarate residue.

  The fumaric acid ester resin comprising 50 mol% or more of the fumaric acid diester residue unit represented by the general formula (a), preferably used as the fumaric acid ester resin used in the present invention, is represented by the general formula (a). Monomer capable of copolymerization with fumaric acid diesters, a resin comprising 50 mol% or more of fumaric acid diester residue units and 50 mol% or less of residue units composed of monomers copolymerizable with fumaric acid diesters Residue units comprising, for example, styrene residues such as styrene residues and α-methylstyrene residues; acrylic acid residues; methyl acrylate residues, ethyl acrylate residues, butyl acrylate residues, acrylics Acrylic acid ester residues such as acid 3-ethyl-3-oxetanylmethyl residue and tetrahydrofurfuryl acrylate residue; methacrylic acid residue Methacrylic acid ester residues such as methyl methacrylate residue, ethyl methacrylate residue, butyl methacrylate residue, 3-ethyl-3-oxetanylmethyl methacrylate residue, tetrahydrofurfuryl methacrylate methacrylate; vinyl acetate Residues, vinyl ester residues such as vinyl propionate residues; acrylonitrile residues; methacrylonitrile residues; olefin residues such as ethylene residues and propylene residues; Among them, 3-ethyl-3-oxetanylmethyl acrylate and 3-ethyl-3-oxetanylmethyl methacrylate are preferable, and 3-ethyl-3-oxetanylmethyl acrylate is particularly preferable. Among these, the fumaric acid diester residue unit represented by the general formula (a) is preferably 70 mol% or more, and the fumaric acid diester residue is particularly excellent in heat resistance and mechanical properties. The unit is preferably 80 mol% or more, and more preferably 90 mol% or more.

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

  As a method for producing the fumaric acid ester resin constituting the optical compensation film of the present invention, any method may be used as long as the fumaric acid ester resin is obtained. For example, fumaric acid diesters, and in some cases fumaric acid ester It can be produced by performing radical polymerization or radical copolymerization using a monomer copolymerizable with acid diesters. Examples of the fumaric acid diesters include diisopropyl fumarate, di-s-butyl fumarate, di-t-butyl fumarate, di-s-pentyl fumarate, di-t-pentyl fumarate, and di-fumarate. -S-hexyl, di-t-hexyl fumarate, dicyclopropyl fumarate, dicyclopentyl fumarate, dicyclohexyl fumarate and the like. Examples of monomers copolymerizable with fumarate diester include styrene, α -Styrenes such as methylstyrene; Acrylic acid; Acrylic acid esters such as methyl acrylate, ethyl acrylate, butyl acrylate, 3-ethyl-3-oxetanylmethyl acrylate, tetrahydrofurfuryl acrylate; methacrylic acid; methacrylic acid Methyl acid, ethyl methacrylate, butyl methacrylate, methacrylic acid 3 Methacrylic acid esters such as ethyl-3-oxetanylmethyl and tetrahydrofurfuryl methacrylate; Vinyl esters such as vinyl acetate and vinyl propionate; Acrylonitrile; Methacrylonitrile; Olefins such as ethylene and propylene; Two or more types can be mentioned. Among them, 3-ethyl-3-oxetanylmethyl acrylate and 3-ethyl-3-oxetanylmethyl methacrylate are preferable, and 3-ethyl-3-oxetanylmethyl acrylate is particularly preferable.

  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.

  The plasticizer used in the optical compensation film of the present invention is not particularly limited, and for example, dimethyl phthalate, diethyl phthalate, dibutyl phthalate, dihexyl phthalate, dinormal octyl phthalate, 2-ethylhexyl phthalate, diisooctyl phthalate, dicapryl phthalate, dicap Nonyl phthalate, diisononyl phthalate, didecyl phthalate, diisodecyl phthalate, diundecyl phthalate, dilauryl phthalate, ditridecyl phthalate, dibenzyl phthalate, dicyclohexyl phthalate, butyl benzyl phthalate, octyl decyl phthalate, butyl octyl phthalate, octyl benzyl phthalate, normal hexyl Normal decyl phthalate, normal octyl normal decyl phthalate, di-2- Phthalate ester plasticizers such as tilhexyl isophthalate and di-2-ethylhexyl terephthalate; tricresyl phosphate, tri (2-ethylhexyl phosphate), trixylenyl phosphate, bisphenol A bis (diphenyl phosphate), triphenyl phosphate, 2 -Phosphate plasticizers such as ethylhexyl diphenyl phosphate, cresyl diphenyl phosphate, trimethyl phosphate, triethyl phosphate, tris (butoxyethyl) phosphate; di-2-ethylhexyl adipate, diisodecyl adipate, normal octyl-normal decyl adipate Normal heptyl-normal nonyl adipate, diisooctyl adipate, diisonormal octyl Adipate plasticizers such as adipate, di-normal octyl adipate, didecyl adipate; sebacate plasticizers such as dibutyl sebacate, di-2-ethylhexyl sebacate, diisooctyl sebacate, butylbenzyl sebacate; Azelaic acid ester plasticizers such as di-2-ethylhexyl azelate, dihexyl azelate, diisooctyl azelate; triethyl citrate, acetyl triethyl citrate, tributyl citrate, acetyl tributyl citrate, triacetyl citrate (2 Citric acid ester plasticizers such as ethyl hexyl); Glycolic acid ester plasticizers such as methyl phthalyl ethyl glycolate, ethyl phthalyl ethyl glycolate and butyl phthalyl butyl glycolate; Tributyl trimellitate Trimellitic acid ester plasticizers such as tri-normal hexyl trimellitate, tri (2-ethylhexyl) trimellitate, tri-normal octyl trimellitate, tri-isoctyl trimellitate, tri-isodecyl trimellitate Tri (2-ethylhexyl) pyromellitate, tetrabutylpyromellitate, tetra-normal hexyl pyromellitate, tetra (2-ethylhexyl) pyromellitate, tetra-normal octyl pyromellitate, tetra-isooctyl pyromellitate, tetra-iso Pyromellitic acid ester plasticizers such as decyl pyromellitate; Ricillinoleic acid ester plasticizers such as methyl acetyl ricinolate and butyl acetyl ricinolate; Polypropylene adipate, Polypropylene sebacate and the like Polyester plasticizers such as modified polyesters of epoxy; Epoxy plasticizers such as epoxidized soybean oil, epoxybutyl stearate, epoxy (2-ethylhexyl) stearate, epoxidized linseed oil, 2-ethylhexyl epoxy torate; glyceryl triacetate And acetate ester plasticizers such as 2-ethylhexyl acetate. Among these, phosphate ester plasticizers, trimellitic acid, etc. from the viewpoint of compatibility with fumarate ester resins, heat resistance and film surface properties. It is preferable to use an ester plasticizer and a pyromellitic acid ester plasticizer. From the viewpoint of compatibility, a phosphate ester plasticizer is particularly preferable, and tricresyl phosphate, tri (2-ethylhexyl) phosphate, and trixylenyl. Phosphate, bisphenol A bis (diphenyl phosphate) are preferable. These may be used alone or in combination of two or more as required.

  Since the blending ratio of the fumaric acid ester resin and the plasticizer in the optical compensation film of the present invention can improve mechanical properties such as film elongation, the plasticizer is 0.1 to 40 parts per 100 parts by weight of the fumaric acid ester resin. Part by weight is preferred, 1 to 20 parts by weight is particularly preferred, and 3 to 10 parts by weight is more preferred.

  Moreover, there is no restriction | limiting in particular as a blending method of a fumarate ester-type resin and a plasticizer, For example, it can carry out by adding a plasticizer to the solution which melt | dissolved the fumarate ester-type resin in the soluble solvent. There are no particular limitations on the soluble solvent of the fumaric acid ester resin at that time, for example, benzene, toluene, xylene, ethylbenzene, cumene, chlorobenzene, etc. as aromatic solvents, acetone, methyl ethyl ketone, methyl isobutyl as non-aromatic solvents. Ketone solvents such as ketone, diisopropyl ketone and diisobutyl ketone; ester solvents such as methyl acetate, ethyl acetate, isopropyl acetate, butyl acetate and isobutyl acetate; ether solvents such as tetrahydrofuran, dioxane and 1,3-dioxolane It is done. Among these solvents, a mixture of an aromatic solvent and a non-aromatic solvent is preferable, and a mixture of toluene and methyl ethyl ketone is particularly preferable.

  In the film (film (A)) comprising the fumarate ester resin of the present invention and a plasticizer, the three-dimensional refractive index of the film is nx the refractive index in the fast axis direction in the film plane, and in the film plane orthogonal thereto When the refractive index in the direction is ny and the refractive index in the vertical direction out of the film plane is nz, the relationship is ny> nx ≧ nz, and when the film thickness is d, the following formula (2) is satisfied. An optical compensation film (film (C)) composed of a film (B) having a film in-plane retardation (Re) of 50 nm or more measured at a wavelength of 550 nm may be used.

Re = (ny−nx) × d (2)
As the film (B), for example, a film having a three-dimensional refractive index of ny> nx ≧ nz can be obtained by uniaxially stretching a polymer having positive birefringence.

  Further, the polymer of the film (B) is not particularly limited as long as it is a polymer having positive birefringence. Among them, preferred examples from the viewpoint of heat resistance and transparency include polycarbonate resin and polyether sulfone. Examples thereof include resins, cyclic olefin resins, and N-substituted maleimide resins. The film in-plane retardation (Re) of the film (B) is preferably 50 nm or more, particularly preferably 100 nm or more, and further preferably 120 nm or more.

  In the film (C), the three-dimensional refractive index of the film is nx as the refractive index in the fast axis direction in the film plane, ny as the refractive index in the film in-plane direction perpendicular thereto, and in the vertical direction outside the film plane. When the refractive index is nz and the thickness of the film is d, the orientation parameter (Nz) represented by the following formula (3) is preferably −0.1 to 0.95, particularly STN-LCD, IPS-LCD, reflection type. For viewing angle compensation of LCDs and transflective LCDs, Nz is preferably 0.40 to 0.60, more preferably 0.45 to 0.55, and for viewing angle compensation of polarizing plates, Nz is −0.10. -0.10 is preferable, -0.05-0.05 is especially preferable, and 0-0.05 is more preferable.

Nz = (ny−nz) / (ny−nx) (3)
Further, in the film (C), the film in-plane retardation (Re) represented by the formula (2) is preferably 50 to 1000 nm, particularly preferably 100 to 500 nm, and 130 for a quarter wavelength plate. ˜140 nm is preferable, and for a half-wave plate, 270 to 280 nm is preferable.

  There is no restriction | limiting in particular as a manufacturing method of the optical compensation film which consists of a fumaric-ester resin of this invention, and a plasticizer, For example, it can manufacture by methods, such as a solution cast method and a melt cast method.

  The solution casting method is a method in which a solution obtained by dissolving a fumaric acid ester resin and a plasticizer in a solvent (hereinafter referred to as a dope) is cast on a support substrate, and then the solvent is removed by heating or the like to obtain a film. . 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 supporting substrate used include a glass substrate; a metal substrate such as stainless steel or ferrotype; a plastic substrate such as a cellulose resin such as polyethylene terephthalate (PET) or triacetyl cellulose (TAC). The film made of the fumarate ester resin and the plasticizer thus obtained can be used after being peeled off from the support substrate, and when a glass substrate or a plastic substrate is used as the support substrate, the film is peeled off. It can also be used as it is as a laminate. 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 fumarate ester resin and a plasticizer are melted in an extruder and extruded from a slit of a T die into a film shape, and then cooled and cooled with a roll or air.

  The method for producing an optical compensation film comprising the optical compensation film (film (A)) and the film (B) preferably used for the optical compensation film of the present invention is not particularly limited. For example, from a fumaric ester resin and a plasticizer. A method of laminating an unstretched film and a uniaxially stretched film having positive birefringence (hereinafter referred to as production method 1), a solution comprising a fumaric acid ester resin and a plasticizer having positive birefringence It can manufacture by the method (henceforth manufacturing method 2) etc. which apply | coat to the uniaxially stretched film which has.

  Examples of the film having positive birefringence in Production Methods 1 and 2 include films made of polycarbonate resin, polyether sulfone resin, cyclic olefin resin, N-substituted maleimide resin, and the like. The film having positive birefringence is uniaxially stretched, for example, at a temperature of 150 to 200 ° C. and a stretching speed of 10 to 30 mm / min. A uniaxially stretched film that is stretched under conditions of a stretching ratio of 30 to 70% and has positive birefringence can be produced.

  In production method 1, an optical compensation film can be produced by laminating a uniaxially stretched film having positive birefringence to an unstretched film made of a fumarate ester resin and a plasticizer. As a bonding method in this case, it can be manufactured, for example, by a continuous roll-to-roll process, and can be bonded using a known adhesive.

  In Production Method 2, an optical compensation film can be produced by applying a solution comprising a fumarate resin and a plasticizer to a uniaxially stretched film having positive birefringence. In this case, the coating method is a method in which a solution (coating solution) in which a fumaric ester resin and a plasticizer are dissolved in a solvent is coated on the film, and then the solvent is removed by heating or the like. As a coating method at that time, for example, a doctor blade method, a bar coater method, a gravure coater method, a slot die coater method, a lip coater method, a comma coater method or the like is used. Industrially, the gravure coater method is generally used for thin film coating, and the comma coater method is generally used for thick film coating. In solution coating, in order to perform coating with high transparency and excellent thickness accuracy and surface smoothness, the coating solution viscosity is a very important factor, preferably 10 to 10000 cps, particularly 10 to 5000 cps. It is preferable. Further, the surface of the film (B) can be subjected to an easy adhesion treatment in advance.

  The coating solution is a solution in which a fumarate ester resin and a plasticizer are dissolved in a solvent, and the solvent to be used is not particularly limited. For example, aromatic solvents such as benzene, toluene, xylene, ethylbenzene, cumene, Non-aromatic solvents such as chlorobenzene, acetone solvents such as methyl ethyl ketone, methyl isobutyl ketone, diisopropyl ketone, diisobutyl ketone; ester solvents such as methyl acetate, ethyl acetate, isopropyl acetate, butyl acetate, isobutyl acetate; tetrahydrofuran, dioxane And ether solvents such as 1,3-dioxolane. Among these solvents, a mixture of an aromatic solvent and a non-aromatic solvent is preferable, and a mixture of toluene and methyl ethyl ketone is particularly preferable.

  Moreover, it can also laminate | stack with the optical compensation films of this invention, or another optical compensation film.

  In order to improve the thermal stability of the optical compensation film of the present invention, an antioxidant is preferably blended. 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. Moreover, as an addition amount of antioxidant, 0.01-10 weight part is preferable with respect to 100 weight part of fumaric acid ester-type resin which comprises the optical compensation film of this invention, and 0.5-1 weight part is especially preferable. preferable.

  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 and used as a circular or elliptical polarizing plate. Moreover, it is useful as an optical compensation film such as a viewing angle improving film or a color compensation film of a liquid crystal display element, and a circularly polarizing plate can also be used as an antireflection film. Furthermore, it can also be used as an optical compensation film that improves the viewing angle characteristics of a brightness enhancement film used in a liquid crystal display.

  According to the present invention, the machine has excellent optical properties such as a large refractive index in the thickness direction of the film, which is useful for improving the contrast and viewing angle characteristics of a liquid crystal display, and has a small wavelength dependency, and also has a degree of elongation that can withstand various processing steps. An optical compensation film having characteristics can be provided.

  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.

~ Fumarate ester resin composition ~
Using a nuclear magnetic resonance measuring apparatus (manufactured by JEOL, trade name JNM-GX270), it was determined by proton nuclear magnetic resonance spectroscopy ( ¹ H-NMR) spectrum analysis.

~ 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 GMH _HR- H, manufactured by Tosoh Corporation), a column temperature of 40 ° C., The standard polystyrene conversion value was determined using THF as a solvent under a flow rate of 1.0 ml / min.
-Measurement of light transmittance and haze of film-
The light transmittance and haze of the produced film were measured using a haze meter (trade name NDH2000, manufactured by Nippon Denshoku Industries Co., Ltd.). The light transmittance was measured according to JIS K 7361-1 (1997 edition), and the haze was measured according to JIS. K 7136 (2000 version) was measured in accordance with each.

~ Measurement of film strength ~
A test piece punched out to 10 mm × 100 mm (SSK 1874-1) was pulled at a speed of 5 mm / min with a Tensilon type tensile tester (manufactured by Orientec Co., Ltd., trade name UTM-2.5T). The maximum point stress was determined.

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

~ Measurement of three-dimensional refractive index, out-of-plane retardation of film, in-plane retardation of film and orientation parameter ~
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). Furthermore, the out-of-plane retardation (Rth), in-plane retardation (Re), and orientation parameter (Nz) were calculated from the three-dimensional refractive index.

~ Positive birefringence ~
Positive and negative birefringence was determined from the three-dimensional refractive index of the film.

Synthesis Example 1 (Synthesis of fumaric acid ester resin)
In a 30 L autoclave equipped with a stirrer, a condenser tube, a nitrogen inlet tube and a thermometer, 48 g of hydroxypropylmethylcellulose (manufactured by Shin-Etsu Chemical Co., Ltd., trade name Metrose 60SH-50), 15601 g of distilled water, 8161 g of diisopropyl fumarate, 3-ethyl acrylate Radical suspension polymerization by adding 240 g of oxetanylmethyl and 45 g of t-butyl peroxypivalate as a polymerization initiator, carrying out nitrogen bubbling for 1 hour, and holding at 49 ° C. for 24 hours while stirring at 200 rpm. Was done. 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: 80%).

The number average molecular weight of the obtained polymer particles was 142,000. ^{According to 1} H-NMR measurement, the polymer particles are diisopropyl fumarate copolymer in which diisopropyl fumarate residue unit / 3-ethyl-3-oxetanylmethyl acrylate residue unit = 96/4 (mol%). confirmed.

Synthesis Example 2 (Synthesis of a film having positive birefringence)
A methylene chloride solution containing 25% by weight of polycarbonate (trade name Panlite L1225, manufactured by Teijin Ltd.) and 75% by weight of methylene chloride was prepared, the methylene chloride solution was cast on a polyethylene terephthalate film, and the solvent was volatilized. The film was obtained by solidifying and peeling. The peeled film thus obtained was further dried at 100 ° C. for 4 hours, from 110 ° C. to 130 ° C. at 10 ° C. intervals for 1 hour, respectively, and then dried at 120 ° C. for 4 hours in a vacuum drier for about 90 μm The film (henceforth a film (1)) which has thickness of this was obtained.

  The obtained film (1) had a light transmittance of 90.0%, a haze of 0.6%, and the three-dimensional refractive index of the film was nx = 1.5830, ny = 1.5830, and nz = 1.5830. . The obtained film in-plane retardation (Re) and out-of-plane retardation (Rth) were 0 nm.

  Further, the obtained film (1) was cut into a 50 mm square, and the temperature was 170 ° C. and the stretching speed was 10 mm / min. By a biaxial stretching apparatus (manufactured by Imoto Seisakusho). The film was subjected to free width uniaxial stretching under the conditions of + 33% stretching. The stretched film (referred to as film 1 (a)) exhibited positive birefringence. The three-dimensional refractive index of the obtained film 1 (a) is nx = 1.5826, ny = 1.5839, nz = 1.5825 (ny> nx> nz), and the in-plane retardation (Re) is It was 113 nm.

Example 1
The fumarate ester resin obtained in Synthesis Example 1 is dissolved in a toluene / methyl ethyl ketone mixed solution (toluene / methyl ethyl ketone = 50 wt% / 50 wt%) to form a 20% solution, and further to 100 parts by weight of the fumarate ester resin. On the other hand, after adding 5 parts by weight of tricresyl phosphate as a plasticizer, it was cast on a support substrate of a solution casting apparatus by the T-die method, dried at 80 ° C. and 130 ° C. for 4 minutes, respectively, width 250 mm, thickness A 30 μm film was obtained. Table 1 shows the physical properties of the obtained film.

  Further, from the results of the three-dimensional refractive index (nx = 1.4729, ny = 1.4730, nz = 1.4767), the obtained film has a large refractive index in the thickness direction of nx≈ny <nz, and the thickness A large negative phase difference was developed in the direction. Furthermore, the phase difference ratio (R450 / R550) (wavelength dependence) was as low as 1.01.

  From these results, the obtained film has negative birefringence, has a large refractive index in the thickness direction, and is small in wavelength dependence, so it is suitable for an optical compensation film, and has excellent elongation. Met.

Example 2
A film having a width of 250 nm and a thickness of 30 nm was obtained in the same manner as in Example 1 except that the amount of tricresyl phosphate added was 10 parts by weight, and the physical properties were evaluated. The results are shown in Table 1.

  Further, from the results of the three-dimensional refractive index (nx = 1.4766, ny = 1.4766, nz = 1.4802), the obtained film has a large refractive index in the thickness direction of nx = ny <nz, A large negative phase difference was developed in the thickness direction. Furthermore, the phase difference ratio (R450 / R550) (wavelength dependence) was as low as 1.01.

  From these results, the obtained film has negative birefringence, has a large refractive index in the thickness direction, and is small in wavelength dependence, so it is suitable for an optical compensation film, and has excellent elongation. Met.

Example 3
A film having a width of 250 mm and a thickness of 30 μm was obtained in the same manner as in Example 1 except that the plasticizer was changed to tri (2-ethylhexyl) phosphate, and physical properties were evaluated. The results are shown in Table 1.

  Further, from the results of the three-dimensional refractive index (nx = 1.4673, ny = 1.4673, nz = 1.4712), the obtained film has a large refractive index in the thickness direction of nx = ny <nz, and the thickness A large negative phase difference was developed in the direction. Furthermore, the phase difference ratio (R450 / R550) (wavelength dependence) was as low as 1.01.

  From these results, the obtained film has negative birefringence, has a large refractive index in the thickness direction, and is small in wavelength dependence, so it is suitable for an optical compensation film, and has excellent elongation. Met.

Example 4
A film having a width of 250 nm and a thickness of 30 nm was obtained in the same manner as in Example 3 except that the amount of tri (2-ethylhexyl) phosphate added was 10 parts by weight, and physical properties were evaluated. The results are shown in Table 1.

  From the results of the three-dimensional refractive index (nx = 1.661, ny = 1.4661, nz = 1.4697), the obtained film has a large refractive index in the thickness direction of nx = ny <nz, A large negative phase difference was developed in the thickness direction. Furthermore, the phase difference ratio (R450 / R550) (wavelength dependence) was as low as 1.01.

  From these results, the obtained film has negative birefringence, has a large refractive index in the thickness direction, and is small in wavelength dependence, so it is suitable for an optical compensation film, and has excellent elongation. Met.

Example 5
A film having a width of 250 mm and a thickness of 30 μm was obtained in the same manner as in Example 1 except that the plasticizer was changed to trixylenyl phosphate, and the physical properties were evaluated. The results are shown in Table 1.

  Moreover, from the results of the three-dimensional refractive index (nx = 1.4726, ny = 1.4727, nz =, 1.4764), the obtained film has a large refractive index in the thickness direction of nx≈ny <nz, A large negative phase difference was developed in the thickness direction. Furthermore, the phase difference ratio (R450 / R550) (wavelength dependence) was as low as 1.01.

  From these results, the obtained film has negative birefringence, has a large refractive index in the thickness direction, and is small in wavelength dependence, so it is suitable for an optical compensation film, and has excellent elongation. Met.

Example 6
A film having a width of 250 nm and a thickness of 30 nm was obtained in the same manner as in Example 5 except that the amount of trixylenyl phosphate added was 10 parts by weight, and physical properties were evaluated. The results are shown in Table 1.

  Moreover, from the results of the three-dimensional refractive index (nx = 1.4767, ny = 1.4767, nz = 1.4803), the obtained film has a large refractive index in the thickness direction of the film, nx = ny <nz, A large negative phase difference was developed in the thickness direction. Furthermore, the phase difference ratio (R450 / R550) (wavelength dependence) was as low as 1.01.

  From these results, the obtained film has negative birefringence, has a large refractive index in the thickness direction, and is small in wavelength dependence, so it is suitable for an optical compensation film, and has excellent elongation. Met.

Example 7
A film having a width of 250 mm and a thickness of 30 μm was obtained by the same method as in Example 1 except that the plasticizer was changed to bisphenol A bis (diphenyl phosphate), and physical properties were evaluated. The results are shown in Table 1.

  Further, from the results of the three-dimensional refractive index (nx = 1.4742, ny = 1.4743, nz =, 1.4780), the obtained film has a large refractive index in the thickness direction of nx≈ny <nz, A large negative phase difference was developed in the thickness direction. Furthermore, the phase difference ratio (R450 / R550) (wavelength dependence) was as low as 1.01.

  From these results, the obtained film has negative birefringence, has a large refractive index in the thickness direction, and is small in wavelength dependence, so it is suitable for an optical compensation film, and has excellent elongation. Met.

Example 8
A film having a width of 250 mm and a thickness of 30 μm was obtained by the same method as in Example 1 except that the plasticizer was changed to tributyl trimellitate, and the physical properties were evaluated. The results are shown in Table 1.

  Further, from the results of the three-dimensional refractive index (nx = 1.4711, ny = 1.4711, nz =, 1.4751), the obtained film has a large refractive index in the thickness direction of nx = ny <nz, A large negative phase difference was developed in the thickness direction. Furthermore, the phase difference ratio (R450 / R550) (wavelength dependence) was as low as 1.01.

  From these results, the obtained film has negative birefringence, has a large refractive index in the thickness direction, and is small in wavelength dependence, so it is suitable for an optical compensation film, and has excellent elongation. Met.

Example 9
A film having a width of 250 nm and a thickness of 30 nm was obtained in the same manner as in Example 8 except that the amount of tributyl trimellitate added was 10 parts by weight, and the physical properties were evaluated. The results are shown in Table 1.

  Further, from the results of the three-dimensional refractive index (nx = 1.4737, ny = 1.4737, nz =, 1.4770), the obtained film has a large refractive index in the thickness direction of the film, nx = ny <nz, A large negative phase difference was developed in the thickness direction. Furthermore, the phase difference ratio (R450 / R550) (wavelength dependence) was as low as 1.01.

  From these results, the obtained film has negative birefringence, has a large refractive index in the thickness direction, and is small in wavelength dependence, so it is suitable for an optical compensation film, and has excellent elongation. Met.

Example 10
A film having a width of 250 mm and a thickness of 30 μm was obtained in the same manner as in Example 1 except that the plasticizer was changed to tri (2-ethylhexyl) trimellitate, and physical properties were evaluated. The results are shown in Table 1.

  Further, from the results of the three-dimensional refractive index (nx = 1.4694, ny = 1.4695, nz =, 1.4733), the obtained film has a large refractive index in the thickness direction of nx≈ny <nz, A large negative phase difference was developed in the thickness direction. Furthermore, the phase difference ratio (R450 / R550) (wavelength dependence) was as low as 1.01.

  From these results, the obtained film has negative birefringence, has a large refractive index in the thickness direction, and is small in wavelength dependence, so it is suitable for an optical compensation film, and has excellent elongation. Met.

Example 11
A film having a width of 250 nm and a thickness of 30 nm was obtained in the same manner as in Example 10 except that the amount of tri (2-ethylhexyl) trimellitate added was 10 parts by weight, and physical properties were evaluated. The results are shown in Table 1.

  Moreover, from the results of the three-dimensional refractive index (nx = 1.4701, ny = 1.4702, nz =, 1.43736), the obtained film has a large refractive index in the thickness direction of nx≈ny <nz, A large negative phase difference was developed in the thickness direction. Furthermore, the phase difference ratio (R450 / R550) (wavelength dependence) was as low as 1.01.

  From these results, the obtained film has negative birefringence, has a large refractive index in the thickness direction, and is small in wavelength dependence, so it is suitable for an optical compensation film, and has excellent elongation. Met.

Example 12
A film having a width of 250 mm and a thickness of 30 μm was obtained by the same method as in Example 1 except that the plasticizer was changed to tri (2-ethylhexyl) pyromellitate, and physical properties were evaluated. The results are shown in Table 1.

  Further, from the results of the three-dimensional refractive index (nx = 1.4693, ny = 1.4693, nz = 1.4730), the obtained film has a large refractive index in the thickness direction of nx = ny <nz, and the thickness A large negative phase difference was developed in the direction. Furthermore, the phase difference ratio (R450 / R550) (wavelength dependence) was as low as 1.01.

  From these results, the obtained film has negative birefringence, has a large refractive index in the thickness direction, and is small in wavelength dependence, so it is suitable for an optical compensation film, and has excellent elongation. Met.

Example 13
The film created in Example 1 was bonded onto the film 1 (a) obtained in Synthesis Example 2 to obtain a film having a thickness of 113 μm. The three-dimensional refractive index of the film was nx = 1.5494, ny = 1.5504, nz = 1.5502, the in-plane retardation (Re) was 113 nm, and the orientation parameter (Nz) was 0.20. It was.

  From these results, the obtained film was suitable for an optical compensation film.

Example 14
The film created in Example 4 was bonded onto the film 1 (a) obtained in Synthesis Example 2 to obtain a film having a thickness of 113 μm. The three-dimensional refractive index of the film was nx = 1.5494, ny = 1.5504, nz = 1.5502, the in-plane retardation (Re) was 113 nm, and the orientation parameter (Nz) was 0.20. It was.

  From these results, the obtained film was suitable for an optical compensation film.

Comparative Example 1
Under a nitrogen atmosphere, 9.0 g of poly (2-vinylnaphthalene) (Aldrich, weight average molecular weight: 175,000) was added to 49.6 g of methylene chloride using a small disper and dissolved at 2500 rpm for 1 hour at room temperature. did. The resulting polymer solution was filtered using a 25 μm filter. Next, this polymer solution was applied onto a 188 μm-thick PET film by a bar coater method, and then air-dried overnight under a nitrogen stream to produce a poly (2-vinylnaphthalene) film on the PET substrate. .

  A part of this poly (2-vinylnaphthalene) film was peeled off from the PET substrate, and the film thickness and optical properties were measured. The film thickness after drying was 58 μm. During peeling, the film was brittle and partially damaged.

  The three-dimensional refractive index of the obtained film was nx = 1.6557, ny = 1.6558, nz = 1.6578. The out-of-plane retardation (Rth) of the film was −120.2 nm, and the retardation ratio (R450 / R550) (wavelength dependence) was 1.12.

  From these results, although the obtained film had a relationship of nz> ny ≧ nx, it was not suitable for an optical compensation film because of its large wavelength dependence.

Comparative Example 2
Using a small disper, add 13.2 g of poly (9-vinylcarbazole) (Aldrich, weight average molecular weight: about 1.1 million) to N-methyl-2-pyrrolidone (NMP) and dissolve at 6000 rpm for 1 hour at room temperature did. The resulting polymer solution was filtered using a 25 μm filter. Next, this polymer solution was applied onto a PET film having a thickness of 188 μm by the bar coater method, and then dried with hot air at 60 ° C. for 1 hour and at 100 ° C. for 15 minutes, so that the poly (9- Vinylcarbazole) film was prepared.

  A part of this poly (9-vinylcarbazole) film was peeled off from the PET substrate, and the film thickness and optical characteristics were measured. The film thickness after drying was 33 μm. During peeling, the film was brittle and partially damaged.

  The three-dimensional refractive index of the obtained film was nx = 1.68819, ny = 1.6820, and nz = 1.6926. The out-of-plane retardation (Rth) of the film was −350.0 nm, and the retardation ratio (R450 / R550) (wavelength dependence) was 1.14.

  From these results, although the obtained film had a relationship of nz> ny ≧ nx, it was not suitable for an optical compensation film because of its large wavelength dependence.

Change in refractive index ellipsoid by stretching nx; Refractive index in the fast axis direction in the film plane. ny: Refractive index in the film in-plane direction orthogonal to nx. nz: The refractive index in the vertical direction outside the film surface.

Claims (14)

A film composed of a fumarate ester resin and a plasticizer, wherein the refractive index in the fast axis direction in the film plane is nx, the refractive index in the film plane direction orthogonal to it is ny, and the refractive index in the vertical direction outside the film plane When the rate is nz, the relationship is nx ≦ ny <nz, and the ratio of the phase difference measured at a wavelength of 450 nm to the phase difference measured at a wavelength of 550 nm (R450 / R550) is 1.1 or less. An optical compensation film characterized by the above. 2. The optical compensation film according to claim 1, wherein when the thickness of the film is d, an out-of-plane retardation (Rth) represented by the following formula (1) is −30 to −2000 nm.
Rth = [(nx + ny) / 2−nz] × d (1) The optical compensation film according to claim 1 or 2, wherein the fumaric acid ester resin comprises 50 mol% or more of a fumaric acid diester residue unit represented by the following formula (a).

(Here, R ₁ and R ₂ each independently represents a branched or cyclic alkyl group having 3 to 12 carbon atoms.) The optical compensation film (film (A)) according to any one of claims 1 to 3, and the three-dimensional refractive index of the film is nx the refractive index in the fast axis direction in the film plane, and the film in-plane direction perpendicular thereto Where ny is the refractive index of the film, and nz is the refractive index in the vertical direction outside the film surface, the relationship is ny> nx ≧ nz, and when the thickness of the film is d, the wavelength represented by the following formula (2) An optical compensation film comprising a film (B) having a film in-plane retardation (Re) measured at 550 nm of 50 nm or more.
Re = (ny−nx) × d (2) 5. The optical compensation film according to claim 4, wherein the three-dimensional refractive index of the film is nx as the refractive index in the fast axis direction in the film plane, ny as the refractive index in the film in-plane direction perpendicular thereto, and out of the film plane. When the refractive index in the vertical direction is nz and the thickness of the film is d, the orientation parameter (Nz) represented by the following formula (3) is in the range of −0.1 to 0.95. Optical compensation film.
Nz = (ny−nz) / (ny−nx) (3) 6. The optical compensation film according to claim 4, wherein the orientation parameter (Nz) is 0.40 to 0.60. The optical compensation film according to any one of claims 4 to 6, wherein an orientation parameter (Nz) is -0.05 to 0.05. The optical compensation film according to any one of claims 4 to 7, wherein a film in-plane retardation (Re) represented by the formula (2) is 50 to 1000 nm. 9. The optical compensation film according to claim 4, wherein the film (B) is a uniaxially stretched film having a positive birefringence. The optical compensation film according to any one of claims 4 to 9, wherein the film (B) is a polycarbonate resin, a polyether sulfone resin, a cyclic polyolefin resin, or an N-substituted maleimide resin. The film in-plane retardation (Re) of the film (A) measured at a wavelength of 550 nm represented by the above formula (2) when the thickness of the film (A) is d is less than 50 nm. The optical compensation film according to any one of 4 to 10. The optical compensation film according to any one of claims 4 to 11, wherein an unstretched film composed of a fumarate-based resin and a plasticizer is bonded to a uniaxially stretched film having positive birefringence. Production method. The method for producing an optical compensation film according to any one of claims 4 to 11, wherein a solution comprising a fumaric acid ester resin and a plasticizer is applied to a uniaxially stretched film having positive birefringence. It uses for a liquid crystal display element, The optical compensation film in any one of Claims 1-11 characterized by the above-mentioned.

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