CN101669049A - Optical compensation films, optically compensating film, and processes for producing these - Google Patents

Abstract

Optical compensation films which have an optically compensating function imparted thereto by uniaxial stretching conducted during or after application and which are reduced in the wavelength dependence of retardation. One of the optical compensation films comprises a coating film made of a maleimide resin, and is characterized in that when any two axes perpendicularly crossing within the plane ofthe coating film are taken as x-axis and y-axis, respectively, an out-of-plane direction perpendicularly crossing that direction is taken as z-axis, and the refractive indices in the x-axis direction,y-axis direction, and z-axis direction are expressed by nx, ny, and nz, respectively, then the three-dimensional refractive indices satisfy the relationship nx'ny>nz. Also provided is an optically compensating film characterized by comprising a coating film layer (A) made of a maleimide resin and a stretched film layer (B). Another optical compensation film is one obtained by uniaxially stretching a coating film made of a maleimide resin, characterized in that when an axis in the stretch direction for the coating film is taken as x-axis, an in-plane direction and an out-of-plane direction which perpendicularly cross that direction are taken as y-axis and z-axis, respectively, and the refractive indices in the x-axis direction, y-axis direction, and z-axis direction are expressed by nx4, ny4, and nz4, respectively, then the three-dimensional refractive indices satisfy the relationship nx4>ny4>nz4. [Chemical formula 1] (1) (In the formula, R1 represents C1-18 linear alkyl, branched alkyl, cycloalkyl, a halogen-containing group, or an ether, ester, or amide group).

Description

Optical compensation layer, optical compensation film and their manufacturing method

technical field

The present invention relates to an optical compensation layer and an optical compensation film. More specifically, the present invention relates to an optical compensation layer and an optical compensation film which are used in a liquid crystal display element and have an optical compensation function even when the coated fluid-coated film is in an unstretched state or a uniaxially stretched state, and their method of manufacture.

Background technique

Liquid crystal displays are the most important displays in the multimedia society, and are widely used in applications ranging from portable phones to computer monitors, notebook personal computers, and TVs. Many optical films are used in liquid crystal displays to improve display characteristics.

In particular, the optical compensation film plays an important role in contrast improvement, color tone compensation, and the like in the case of viewing the display from the front or oblique directions. Optical compensation films that have been used so far are stretched films of polycarbonate, cyclic polyolefin, or cellulose resin. However, these films have problems such as that a biaxial stretching step is necessary and it is difficult to perform the biaxial stretching step to obtain uniformity of retardation. Also, especially in a film having a large area, it is more difficult to adjust the retardation imparted by biaxial stretching.

As a technique for eliminating those problems associated with biaxial stretching, an optical compensation layer formed by application (coating) of a coating fluid and exhibiting an optical compensation function in an unstretched state is being studied.

Harris and Cheng at the University Of Akron proposed optical compensation layers consisting of rigid rods of polyimide, polyester, polyamide, poly(amide-imide) or poly(ester-imide) (see e.g. patent Literature 1 and 2). These materials have the property of undergoing molecular orientation spontaneously, and are therefore characterized by the application by the coating fluid without going through a stretching step showing a delay.

Also, an optical compensation layer formed of polyimide having improved coating fluid applicability (solubility in solvent) has been proposed (see, for example, Patent Document 3), a layer having a discotic liquid crystal compound coated with A polarizer of a protective film (see, for example, Patent Document 4) and the like.

Stretched films made of phenylmaleimide/isobutylene copolymers have also been proposed (see e.g. Patent Document 5).

Patent Document 1: US Patent No. 5,344,916

Patent Document 2: JP-T-10-508048

Patent Document 3: JP-A-2005-070745

Patent Document 4: Japanese Patent No. 2565644

Patent Document 5: JP-A-2004-269842

Contents of the invention

Problem to be solved by the present invention

However, the retardation of the polymers obtained by the methods proposed in Patent Documents 1 to 3 has strong wavelength dependence because they are aromatic polymers. When used as an optical compensation layer of a liquid crystal display element, these polymers cause problems regarding image quality degradation, such as color shift.

The technique proposed in Patent Document 4 in which a discotic liquid crystalline compound is used has problems such as that the liquid crystalline compound must be uniformly aligned and this complicates the coating process, and that orientation nonuniformity is enhanced. In addition, since the liquid crystal compound is also mainly an aromatic compound, this technique also has a quality problem of strong wavelength dependence of retardation.

The stretched film obtained according to Patent Document 5 shows no retardation (nx=ny=nz) when it is in a state formed only by coating of the coating fluid. For its three-dimensional refractive index after stretching, nz4 is the highest.

Accordingly, an object of the present invention is to provide an optical compensation layer and an optical compensation film having excellent optical properties. More specifically, the object is to provide an optical fiber having an optical compensating function imparted at the time of coating of a coating fluid or at the time of coating of a coating fluid and subsequent uniaxial stretching and whose retardation has a weak wavelength dependence. Compensation layer and optical compensation film.

means of solving problems

Due to these problems, the inventors have diligently conducted research. As a result, they found that: a coating layer formed of a maleimide resin, a coating layer obtained by uniaxially stretching the coating layer, or an optical compensation film including a maleimide resin may have optical compensation Functional films, especially coating-type optical compensation layers or optical compensation films suitable for optical compensation in liquid crystal display elements. The present invention has thus been accomplished.

That is, the present invention provides: an optical compensation layer, wherein the compensation layer is a coating layer comprising a maleimide resin, and wherein when two arbitrary axes perpendicular to each other in the plane of the coating layer are referred to as x-axis and y-axis, and the out-of-plane direction is called the z-axis, then the coating layer satisfies the three-dimensional refractive index relationship nx≈ny>nz, where nx is the refractive index in the x-axis direction, ny is the refractive index in the y-axis direction, and nz is the refractive index on the z-axis direction; Optical compensation film, it comprises coating layer (A) and stretched film layer (B) that comprise maleimide resin; And optical compensation layer, it is stretched by uniaxial An optical compensation layer obtained by stretching a coating layer comprising a maleimide resin, wherein the direction of the stretching axis in the coating layer is called the x4 axis, the direction perpendicular to the stretching direction is called the y4 axis, and the plane When the outer direction is called the z4 axis, then the optical compensation layer satisfies the three-dimensional refractive index relationship nx4>ny4>nz4, where nx4 is the refractive index in the direction of the x4 axis, ny4 is the refractive index in the direction of the y4 axis, and nz4 is the direction of the z4 axis on the refractive index.

Effect of the present invention

The optical compensation layer and the optical compensation film of the present invention can be manufactured while easily adjusting their optical compensation functions. They are therefore useful as optical compensation layers and optical compensation films effective in improving the contrast and viewing angle characteristics of liquid crystal display elements (especially liquid crystal TVs operating in VA mode).

Detailed ways

The present invention will be described in detail below.

A description is given to the optical compensation layer, characterized in that it is a coating layer comprising a maleimide resin, and when two arbitrary axes perpendicular to each other in the plane of the coating layer are called x-axis and y-axis respectively , and the out-of-plane direction is called the z-axis, then the coating layer satisfies the three-dimensional refractive index relationship nx≈ny>nz, where nx is the refractive index in the x-axis direction, ny is the refractive index in the y-axis direction, and nz is The index of refraction in the z-axis direction.

Examples of maleimide resins include N-substituted maleimide polymer resins and N-substituted maleimide-maleic anhydride copolymer resins. Examples of the N-substituted maleimide residue unit constituting the maleimide resin include N-substituted maleimide residue units represented by the following general formula (1).

[chemical 1]

(wherein R ₁ represents a straight-chain alkyl group, branched-chain alkyl group or cycloalkyl group, a halogen group, an ether group, an ester group or an amide group) having 1-18 carbon atoms.

Specific examples of N-substituted maleimide residue units include one or more selected from the group consisting of: N-methylmaleimide residue units, N-ethylmaleimide residues unit, N-chloroethylmaleimide residue unit, N-methoxyethylmaleimide residue unit, N-n-propylmaleimide residue unit, N-isopropyl Maleimide residue unit, N-n-butylmaleimide residue unit, N-isobutylmaleimide residue unit, N-sec-butylmaleimide residue unit , N-tert-butylmaleimide residue unit, N-hexylmaleimide residue unit, N-cyclohexylmaleimide residue unit, N-octylmaleimide residue unit base unit, N-laurylmaleimide residue unit, etc. Particularly preferred are N-n-butylmaleimide residue units, N-isobutylmaleimide residue units, N-sec-butylmaleimide residue units, N-tert-butyl An ylmaleimide residue unit, an N-hexylmaleimide residue unit, and an N-octylmaleimide residue unit. These units therefore give a maleimide resin which tends to show retardation and is excellent in solubility in solvents and mechanical strength.

Examples of N-substituted maleimide polymer resins include N-methylmaleimide polymer resins, N-ethylmaleimide polymer resins, N-chloroethylmaleimide polymer resins, Amine polymer resin, N-methoxyethylmaleimide polymer resin, N-n-propylmaleimide polymer resin, N-isopropylmaleimide polymer resin, N- N-butylmaleimide polymer resin, N-isobutylmaleimide polymer resin, N-sec-butylmaleimide polymer resin, N-tert-butylmaleimide Polymer resin, N-hexylmaleimide polymer resin, N-cyclohexylmaleimide polymer resin, N-octylmaleimide polymer resin and N-laurylmaleimide Amine polymer resin.

Examples of N-substituted maleimide-maleic anhydride copolymer resins include N-methylmaleimide-maleic anhydride copolymer resin, N-ethylmaleimide-maleic anhydride copolymer resin, Resin, N-chloroethylmaleimide-maleic anhydride copolymer resin, N-methoxyethylmaleimide-maleic anhydride copolymer resin, N-n-propylmaleimide -Maleic anhydride copolymer resin, N-isopropylmaleimide-maleic anhydride copolymer resin, N-n-butylmaleimide-maleic anhydride copolymer resin, N-isobutylmaleimide Laimide-maleic anhydride copolymer resin, N-sec-butylmaleimide-maleic anhydride copolymer resin, N-tert-butylmaleimide-maleic anhydride copolymer resin, N- Hexylmaleimide-maleic anhydride copolymer resin, N-cyclohexylmaleimide-maleic anhydride copolymer resin, N-octylmaleimide-maleic anhydride copolymer resin and N- Laurylmaleimide-maleic anhydride copolymer resin.

Particularly preferred among these are N-n-butylmaleimide polymer resin, N-hexylmaleimide polymer resin, N-octylmaleimide polymer resin and N-octylmaleimide polymer resin. Laimide-maleic anhydride copolymer resin. These resins therefore have excellent film-forming properties in layer formation and give an optical compensation layer excellent in optical compensation function and heat resistance.

The maleimide resin constituting the optical compensation layer of the present invention may include residue units other than N-substituted maleimide residue units and maleic anhydride residue units, as long as this does not depart from the scope of the present invention. Purpose. Examples of such optional residue units include one or more of the following: styrene compound residue units such as styrene residue units and α-methylstyrene residue units; acrylic acid residue units; acrylate residues Base units such as methyl acrylate residue units, ethyl acrylate residue units and butyl acrylate residue units; methacrylate residue units; methacrylate residue units such as methyl methacrylate residue units, methyl Ethyl acrylate residue units and butyl methacrylate residue units; vinyl ester residues such as vinyl acetate residues, vinyl propionate residues, vinyl pivalate residues, vinyl laurate residues and Vinyl stearate residues; acrylonitrile residues; methacrylonitrile residues, etc.

Preferably, the maleimide resin should have a number-average molecular weight (Mn) of 1 x ¹⁰³ or higher in terms of standard polystyrene based on the elution profile obtained from gel permeation chromatography (hereinafter referred to as GPC). resin. The number average molecular weight thereof is particularly preferably 2×10 ⁴ to 2×10 ⁵ , since such a maleimide resin gives an optical compensation layer having excellent mechanical properties and excellent formability in layer formation.

In order to manufacture the maleimide resin constituting the optical compensation layer of the present invention, any method may be used as long as the maleimide resin is obtained. For example, the resin can be produced by combining at least one N-substituted maleimide and maleic anhydride, optionally with one or more monomers copolymerizable with the N-substituted maleimide Carry out free radical polymerization or free radical copolymerization together. Examples of N-substituted maleimides include one or more of the following: N-methylmaleimide, N-ethylmaleimide, N-chloroethylmaleimide , N-methoxyethylmaleimide, N-n-propylmaleimide, N-isopropylmaleimide, N-n-butylmaleimide, N-isobutyl Basemaleimide, N-sec-butylmaleimide, N-tert-butylmaleimide, N-hexylmaleimide, N-cyclohexylmaleimide, N- Octylmaleimide, etc. Examples of the copolymerizable monomer include one or more of the following: styrene compounds such as styrene and α-methylstyrene; acrylic acid; acrylates such as methyl acrylate, ethyl acrylate, and butyl acrylate; Acrylic acid; methacrylates such as methyl methacrylate, ethyl methacrylate, and butyl methacrylate; vinyl esters such as vinyl acetate, vinyl propionate, vinyl pivalate, vinyl laurate, and hard Vinyl fatty acid; Acrylonitrile; Methacrylonitrile, etc.

Free radical polymerization can be carried out using known polymerization techniques. For example, all polymerization techniques such as bulk polymerization, solution polymerization, suspension polymerization, precipitation polymerization and emulsion polymerization can be used.

Examples of usable polymerization initiators in the case of performing radical polymerization include organic peroxides such as benzoyl peroxide, lauryl peroxide, octanoyl peroxide, acetyl peroxide, di-tert-butyl peroxide, tert-butylcumyl peroxide, dicumyl peroxide, tert-butyl peroxyacetate and tert-butyl peroxybenzoate; and azo initiators such as 2,2'-azobis(2,4- Dimethylvaleronitrile), 2,2'-azobis(2-butyronitrile), 2,2'-azobisisobutyronitrile, 2,2'-azobisisobutyrate and 1 , 1'-Azobis(cyclohexane-1-carbonitrile).

Solvents usable in solution polymerization, suspension polymerization, precipitation polymerization and emulsion polymerization are not particularly limited. Examples thereof include aromatic solvents such as benzene, toluene, and xylene; alcohol solvents such as methanol, ethanol, propanol, and butanol; cyclohexane; dioxane; tetrahydrofuran (THF); acetone; methyl ethyl ketone; dimethylformamide; acetic acid isopropyl ester; water; and N-methylpyrrolidone. Examples thereof also include mixed solvents composed of two or more of these.

The polymerization temperature in the case of performing radical polymerization can be appropriately set according to the decomposition temperature of the polymerization initiator. Generally, it is preferred to carry out the polymerization at a temperature of 40-150°C.

The optical compensation layer of the present invention is a coating layer including a maleimide resin, and is excellent in an optical compensation function particularly when used as an optical compensation layer. In the case where a film made of a polymer is used as an optical compensation film, the three-dimensional refractive index of the film is usually adjusted by, for example, biaxial stretching of the film. However, the step of biaxial stretching has problems such as manufacturing steps and quality control becoming complicated. On the contrary, the optical compensation layer of the present invention is a coating layer comprising maleimide, and is an optical compensation layer characterized in that when two arbitrary axes perpendicular to each other in the plane of the coating layer are respectively referred to as the x-axis and the y-axis, and the out-of-plane direction is called the z-axis, then the coating layer satisfies the three-dimensional refractive index relationship nx≈ny>nz, where nx is the refractive index in the x-axis direction, and ny is the refractive index in the y-axis direction ( When nx is not equal to ny, the lowest refractive index is taken as nx), and nz is the refractive index in the z-axis direction. The layer has been found to exhibit the unique behavior of the layer in the unstretched state having a lower refractive index in the thickness direction of the layer.

The thickness direction retardation (Rth) of the optical compensation layer of the present invention can be easily adjusted by changing the thickness of the coating layer including maleimide. Its out-of-plane retardation (Rth) measured with light having a measurement wavelength of 589 nm and represented by the following expression (2) is preferably in the range of 30 to 2000 nm, since this optical compensation layer is expected to be suitable as a retardation film. In particular, its retardation (Rth) is preferably in the range of 50-1000 nm, more preferably 80-500 nm, because such an optical compensation layer has an excellent effect of improving viewing angle characteristics of a liquid crystal display element.

Rth＝((nx+ny)/2-nz)×d (2)

(In Expression (2), d represents the thickness (nm) of the optical compensation layer).

Preferably, the optical compensation layer of the present invention should be a layer with weak wavelength dependence of retardation, because the use of such an optical compensation layer in a liquid crystal display element enables the liquid crystal display element to be reduced in color shift. In particular, the wavelength dependence (R450/R589) of its retardation is preferably 1.1 or less, particularly 1.08 or less. The ratio of the retardation (R450) of the optically detected coating layer to the retardation (R589) of the optically detected coating layer inclined at 40 degrees and having a measurement wavelength of 589 nm is expressed.

Preferably, the light transmittance measured according to JIS K 7361-1 (1997 edition) of the optical compensation layer of the present invention is 85% or higher, especially 90% or higher, because this optical compensation layer is used for liquid crystal Imparts satisfactory image quality when displaying components. Also preferably, the haze of the optical compensation layer measured according to JIS K 7136 (2000 edition) is 2% or less, especially 1% or less.

From the viewpoint of quality stability in a liquid crystal display element, the optical compensation layer of the present invention preferably has high heat resistance. Its glass transition temperature is preferably 100°C or higher, particularly preferably 120°C or higher, even more preferably 135°C or higher.

The optical compensation layer of the present invention is characterized by being a coating layer comprising a maleimide resin. Examples of preferred methods for making this layer include where a maleimide resin in solution state is coated on a glass substrate or made of triacetyl cellulose, poly(ethylene terephthalate) (PET), etc. into a film-on-substrate method. For coating, a method in which a solution prepared by dissolving a maleimide resin in a solvent is applied on a glass substrate or a film and then the solvent is removed by heating or the like can be used. As a technique for coating, for example, a doctor blade method, a bar coating method, a gravure coating method, a slot die coating method, a lip coater method, a comma coater method (comma coater method) are used )wait. Industrially, the gravure coating method and the batch coating method are generally used for thin coating and thick coating, respectively. The solvent used is not particularly limited. Examples include aromatic solvents such as toluene, xylene, chlorobenzene, and nitrobenzene; ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; ether solvents such as dimethyl ether, diethyl ether, methyl tertiary Butyl ether, tetrahydrofuran and dioxane; acetate solvents such as methyl acetate, ethyl acetate, n-propyl acetate, isopropyl acetate and butyl acetate; hydrocarbon solvents such as hexane, cyclohexane, octane and decane; alcohol solvents such as methanol, ethanol, propanol, and butanol; chlorinated compound solvents such as carbon tetrachloride, chloroform, methylene chloride, dichloroethane, and trichloroethane; amide solvents such as dimethylformamide and methylacetamide; and N-methylpyrrolidone. A combination of two or more of these solvents may be used. In solution coating, it is preferable to adjust the viscosity of the solution to 10-10000 cp, especially 10-5000 cp, because an optical compensation layer with high transparency, thickness accuracy and excellent surface smoothness is more easily obtained from this solution.

The thickness of the maleimide resin to be coated in this operation is determined by the retardation in the thickness direction of the coating layer. In particular, its thickness after drying is in the range of preferably 1-100 μm, more preferably 3-50 μm, particularly preferably 5-30 μm, from the viewpoint of obtaining excellent surface smoothness and excellent effects of improving viewing angle characteristics.

The optical compensation layer of the present invention may be used after being peeled off from a base, ie, a glass substrate, or another optical film, or may be used in the form of a layered product including the base, ie, a glass substrate, or another optical film. In particular, in the case where the optical compensation layer is formed on another optical film and the layered product is used as the optical compensation film, the other optical film is preferably a film made of cellulose resin, and particularly preferably A film made of triacetyl cellulose because this optical film is excellent in transparency, strength and adhesion.

The optical compensation layer of the present invention can also be used as a layered product including a polarizer. Antioxidants can be introduced into the optical compensation layer of the present invention to enhance thermal stability. Examples of antioxidants include hindered phenol antioxidants, phosphorus compound antioxidants, and other antioxidants. These antioxidants can be used alone or in combination. It is preferable to use hindered phenolic antioxidants in combination with phosphorus compound antioxidants because these antioxidants synergistically achieve an improved function of preventing oxidation. In this case, it is particularly preferable to mix 100-500 parts by weight of the phosphorus compound antioxidant with 100 parts by weight of the hindered phenol antioxidant. As for the amount of the antioxidant to be added, the amount is preferably in the range of 0.01-10 parts by weight, particularly preferably 0.5-1 part by weight, per 100 parts by weight of the maleimide resin constituting the optical compensation layer of the present invention.

Furthermore, ultraviolet absorbents such as benzotriazoles, benzophenones, triazines or benzoates may be introduced as required.

The optical compensation layer of the present invention can introduce additional polymers and other components such as surfactants, polymer electrolytes, conductive complexes, inorganic fillers, pigments, dyes, antistatic agents without departing from the spirit of the present invention , anti-blocking agent and lubricant layer.

Next, an optical compensation film including a coating layer (A) containing a maleimide resin and a stretched film layer (B) is explained.

The coating layer (A) as a composition of the optical compensation film is a coating layer including a maleimide resin. Examples of maleimide resins include N-substituted maleimide polymer resins and N-substituted maleimide-maleic anhydride copolymer resins. Examples of the N-substituted maleimide residue unit constituting the maleimide resin include residue units of N-substituted maleimide represented by the general formula (1) given above.

Specific examples of N-substituted maleimide residue units include one or more selected from the group consisting of: N-methylmaleimide residue units, N-ethylmaleimide residues unit, N-chloroethylmaleimide residue unit, N-methoxyethylmaleimide residue unit, N-n-propylmaleimide residue unit, N-isopropyl Maleimide residue unit, N-n-butylmaleimide residue unit, N-isobutylmaleimide residue unit, N-sec-butylmaleimide residue unit , N-tert-butylmaleimide residue unit, N-hexylmaleimide residue unit, N-cyclohexylmaleimide residue unit, N-octylmaleimide residue unit base unit, N-laurylmaleimide residue unit, etc. Particularly preferred are N-n-butylmaleimide residue units, N-isobutylmaleimide residue units, N-sec-butylmaleimide residue units, N-tert-butyl An ylmaleimide residue unit, an N-hexylmaleimide residue unit, and an N-octylmaleimide residue unit. These units therefore give a maleimide resin which tends to show retardation and is excellent in solubility in solvents and mechanical strength.

Examples of N-substituted maleimide polymer resins include N-methylmaleimide polymer resins, N-ethylmaleimide polymer resins, N-chloroethylmaleimide polymer resins, Amine polymer resin, N-methoxyethylmaleimide polymer resin, N-n-propylmaleimide polymer resin, N-isopropylmaleimide polymer resin, N- N-butylmaleimide polymer resin, N-isobutylmaleimide polymer resin, N-sec-butylmaleimide polymer resin, N-tert-butylmaleimide Polymer resin, N-hexylmaleimide polymer resin, N-cyclohexylmaleimide polymer resin, N-octylmaleimide polymer resin and N-laurylmaleimide Amine polymer resin.

Examples of N-substituted maleimide-maleic anhydride copolymer resins include N-methylmaleimide-maleic anhydride copolymer resin, N-ethylmaleimide-maleic anhydride copolymer resin, Resin, N-chloroethylmaleimide-maleic anhydride copolymer resin, N-methoxyethylmaleimide-maleic anhydride copolymer resin, N-n-propylmaleimide -Maleic anhydride copolymer resin, N-isopropylmaleimide-maleic anhydride copolymer resin, N-n-butylmaleimide-maleic anhydride copolymer resin, N-isobutylmaleimide Laimide-maleic anhydride copolymer resin, N-sec-butylmaleimide-maleic anhydride copolymer resin, N-tert-butylmaleimide-maleic anhydride copolymer resin, N- Hexylmaleimide-maleic anhydride copolymer resin, N-cyclohexylmaleimide-maleic anhydride copolymer resin, N-octylmaleimide-maleic anhydride copolymer resin and N- Laurylmaleimide-maleic anhydride copolymer resin.

Particularly preferred among these are N-n-butylmaleimide polymer resin, N-hexylmaleimide polymer resin, N-octylmaleimide polymer resin and N-octylmaleimide polymer resin. Laimide-maleic anhydride copolymer resin. These resins therefore have excellent layering properties in layer formation and give an optical compensation film excellent in optical compensation function and heat resistance.

The maleimide resin constituting the coating layer (A) may include residue units other than N-substituted maleimide residue units and maleic anhydride residue units as long as this does not deviate from the object of the present invention . Examples of such optional residue units include one or more of the following: styrene compound residue units such as styrene residue units and α-methylstyrene residue units; acrylic acid residue units; acrylate residues Base units such as methyl acrylate residue units, ethyl acrylate residue units and butyl acrylate residue units; methacrylate residue units; methacrylate residue units such as methyl methacrylate residue units, methyl Ethyl acrylate residue units and butyl methacrylate residue units; vinyl ester residues such as vinyl acetate residues, vinyl propionate residues, vinyl pivalate residues, vinyl laurate residues and Vinyl stearate residues; acrylonitrile residues; methacrylonitrile residues, etc.

Preferably, the maleimide resin is one having a number-average molecular weight (Mn) of 1×10 ³ or higher in terms of standard polystyrene from an elution curve obtained in gel permeation chromatography (hereinafter referred to as GPC). resin. The number average molecular weight thereof is particularly preferably 2×10 ⁴ to 2×10 ⁵ , because such a maleimide resin gives a coating layer having excellent mechanical properties and excellent formability in layer formation (A ).

For producing the maleimide resin constituting the coating layer (A), any method may be used as long as the maleimide resin is obtained. For example, the resin can be produced by combining at least one N-substituted maleimide and maleic anhydride, optionally with one or more monomers copolymerizable with the N-substituted maleimide Carry out free radical polymerization or free radical copolymerization together. Examples of N-substituted maleimides include one or more of the following: N-methylmaleimide, N-ethylmaleimide, N-chloroethylmaleimide , N-methoxyethylmaleimide, N-n-propylmaleimide, N-isopropylmaleimide, N-n-butylmaleimide, N-isobutyl Basemaleimide, N-sec-butylmaleimide, N-tert-butylmaleimide, N-hexylmaleimide, N-cyclohexylmaleimide, N- Octylmaleimide, N-laurylmaleimide, etc. Examples of the copolymerizable monomer include one or more of the following: styrene compounds such as styrene and α-methylstyrene; acrylic acid; acrylates such as methyl acrylate, ethyl acrylate, and butyl acrylate; Acrylic acid; methacrylates such as methyl methacrylate, ethyl methacrylate, and butyl methacrylate; vinyl esters such as vinyl acetate, vinyl propionate, vinyl pivalate, vinyl laurate, and hard Vinyl fatty acid; Acrylonitrile; Methacrylonitrile, etc.

Free radical polymerization can be carried out using known polymerization techniques. For example, all polymerization techniques such as bulk polymerization, solution polymerization, suspension polymerization, precipitation polymerization and emulsion polymerization can be used.

Examples of usable polymerization initiators in the case of performing radical polymerization include organic peroxides such as benzoyl peroxide, lauryl peroxide, octanoyl peroxide, acetyl peroxide, di-tert-butyl peroxide, tert-butylcumyl peroxide, dicumyl peroxide, tert-butyl peroxyacetate and tert-butyl peroxybenzoate; and azo initiators such as 2,2'-azobis(2,4- Dimethylvaleronitrile), 2,2'-azobis(2-butyronitrile), 2,2'-azobisisobutyronitrile, 2,2'-azobisisobutyrate and 1 , 1'-Azobis(cyclohexane-1-carbonitrile).

Solvents usable in solution polymerization, suspension polymerization, precipitation polymerization and emulsion polymerization are not particularly limited. Examples thereof include aromatic solvents such as benzene, toluene, and xylene; alcohol solvents such as methanol, ethanol, propanol, and butanol; cyclohexane; dioxane; tetrahydrofuran (THF); acetone; methyl ethyl ketone; dimethylformamide; acetic acid isopropyl ester; water; and N-methylpyrrolidone. Examples thereof also include mixed solvents composed of two or more of these.

The polymerization temperature in the case of performing radical polymerization can be appropriately set according to the decomposition temperature of the polymerization initiator. Generally, it is preferred to carry out the polymerization at a temperature of 40-150°C.

The coating layer (A) constituting the optical compensation film of the present invention is a coating layer including a maleimide resin, and is particularly excellent in optical compensation function. In the case where a film made of a polymer is used as an optical compensation film, the three-dimensional refractive index of the film is usually adjusted by, for example, biaxial stretching of the film. However, the step of biaxial stretching has problems such as manufacturing steps and quality control becoming complicated. The inventors have found that, contrary to the above, a coating layer including a maleimide resin exhibits a unique behavior that the coating layer in an unstretched state has a lower refractive index in the thickness direction of the film.

Preferably, the optical compensation film of the present invention is a film in which the coating layer (A) is a coating layer in which two arbitrary axes perpendicular to each other in the plane of the coating layer are called x1 axis and y1 axis, respectively, And when the out-of-plane direction (thickness direction) is called the z1 axis, then the coating layer satisfies the three-dimensional refractive index relationship nx1≈ny1>nz1, where nx1 is the refractive index in the direction of the x1 axis, and ny1 is the refractive index in the direction of the y1 axis ( When nx1 is not equal to ny1, the lowest refractive index is taken as nx1), and nz1 is the refractive index in the direction of the z1 axis. Therefore, the optical compensation film is particularly excellent in optical compensation function.

The thickness-direction retardation (Rth1) of the coating layer (A) can be easily adjusted by changing the thickness of the coating layer comprising maleimide. Its out-of-plane retardation (Rth1) measured with light having a measurement wavelength of 589 nm and expressed by the following expression (3) is preferably in the range of 30 to 2000 nm because this coating layer (A) enables the optical compensation film to predict Suitable for use as a retardation film. In particular, its retardation (Rth1) is preferably in the range of 50-1000 nm, more preferably 80-500 nm, because such a coating layer (A) has an excellent effect of improving the viewing angle characteristics of a liquid crystal display element.

Rth1＝((nx1+ny1)/2-nz1)×d1 (3)

(In Expression (3), d1 represents the thickness (nm) of the coating layer (A)).

Preferably, the coating layer (A) is a layer having a small wavelength dependence of retardation, because the use of an optical compensation film including such a coating layer in a liquid crystal display element enables the liquid crystal display element to be reduced in color shift. In particular, the wavelength dependence of its retardation (R450/R589) obtained from a coating inclined at 40 degrees and detected with light having a measurement wavelength of 450 nm is preferably 1.1 or less, particularly 1.08 or less. The retardation (R450) of the cloth layer is represented by the ratio of the retardation (R589) of the coating layer inclined at 40 degrees and detected with light having a measurement wavelength of 589 nm.

Preferably, the light transmittance of the coating layer (A) measured according to JIS K 7361-1 (1997 edition) is 85% or higher, especially 90% or higher, because the obtained optical compensation film is used for liquid crystal display imparts satisfactory image quality when using components. Also preferably, the haze of the coating layer (A) measured according to JIS K 7136 (2000 edition) is 2% or less, especially 1% or less.

From the viewpoint of quality stability required when the obtained optical wavelength film is used for a liquid crystal display element, the coating layer (A) preferably has high heat resistance. Its glass transition temperature is preferably 100°C or higher, particularly preferably 120°C or higher, even more preferably 135°C or higher.

The stretched film layer (B) as a composition of the optical compensation film of the present invention includes a stretched transparent film. Examples thereof include films made of polycarbonate resins, polyethersulfone resins, cyclic polyolefin resins, and cellulose resins. Preferred among these are a uniaxially stretched film made of polycarbonate, a uniaxially stretched film made of polyethersulfone, a uniaxially stretched film made of cyclic polyolefin, and a uniaxially stretched film made of cellulose resin. into uniaxially stretched films, each of which has positive birefringence. Particularly preferably, the layer (B) is a stretched film layer made of a cyclic polyolefin resin, since such a layer makes the wavelength dependence of the retardation of the optical compensation film small. The term positive birefringence here refers to the property that when the stretching direction in the plane of the stretched film is called the x2 axis, the in-plane direction perpendicular to the stretching direction is called the y2 axis, and the out-of-plane (thickness) of the film ) direction is called the z2 axis, then the film satisfies the three-dimensional refractive index relationship nx2>ny2≥nz2, where nx2 is the refractive index in the direction of the x2 axis, ny2 is the refractive index in the direction of the y2 axis, and nz2 is the refractive index in the direction of the z2 axis of the refractive index.

The stretched film layer (B) is preferably a layer in which the in-plane retardation (Re) expressed by the following expression (4) measured with light having a measurement wavelength of 589 nm is in the range of 20 to 1000 nm because the resulting optical compensation The film is expected to be suitable for use as a retardation film. In particular, its retardation (Re) is in the range of preferably 50-500 nm, more preferably 80-300 nm, because an optical compensation film using such a layer (B) has an excellent effect of improving viewing angle characteristics of a liquid crystal display element. In this regard, the stretched film layer (B) may consist of two or more stretched films. For example, in the case where two films are used on each side of the liquid crystal cell, the in-plane retardation (Re) of each film may be half of the retardation shown above.

Re＝(nx2-ny2)×d2 (4)

(In expression (4), d2 represents the thickness (nm) of the stretched film layer (B)).

The stretched film constituting the stretched film layer (B) can be produced by stretching a film produced by a solution casting method or a melt extrusion method with a known stretcher. Commercially available stretch films are also available.

The optical compensation film of the present invention includes a coating layer (A) and a stretched film layer (B), and is suitable for use as an optical compensation film for a liquid crystal display element. In particular, it is preferable that the light transmittance of the optical compensation film measured according to JIS K 7361-1 (1997 edition) is 85% or higher, especially 90% or higher, because this optical compensation film is used for liquid crystal display elements. while giving satisfactory image quality. It is also preferable that the haze of the optical compensation film measured according to JIS K7136 (2000 edition) is 2% or less, especially 1% or less.

Also, the optical compensation film of the present invention is preferably one in which when the direction of the in-plane slow axis of the optical compensation film is referred to as the x3 axis, the in-plane direction perpendicular to the x3 axis is referred to as the y3 axis, and the out-of-plane (thickness) direction of the film When the film is referred to as the z3 axis and is detected with light having a measurement wavelength of 589 nm, then the film has an orientation parameter (Nz) of preferably 1.1 or greater, particularly preferably 1.3 or greater, more preferably 2.0 or greater, wherein the The orientation parameter is represented by the following expression (5), where nx3 is the average refractive index in the direction of the x3 axis, ny3 is the average refractive index in the direction of the y3 axis, and nz3 is the average refractive index in the direction of the z3 axis. The term slow axis refers to the direction of the axis in which the refractive index is highest.

Nz＝(nx3-nz3)/(nx3-ny3) (5)

Its in-plane retardation (Re2) represented by the following expression (8) is preferably 20-1000 nm, particularly preferably 50-500 nm.

Re2＝(nx3-ny3)×d5 (8)

(In Expression (8), d5 represents the thickness (nm) of the film).

Examples of preferred methods for producing the optical compensation film comprising the coating layer (A) comprising a maleimide resin and the stretched film layer (B) of the present invention include: 1) wherein the A method of laminating a coating layer produced by coating a glass substrate or a film base with an amine resin solution to a stretched film; 2) arranging a coating layer including a maleimide resin on one side of a liquid crystal cell and placing A method in which a stretched film is arranged on the other side; and 3) a method in which a maleimide resin solution is coated on a stretched film and dried to produce a coating layer. Preferred among these is a method in which a maleimide resin solution is coated on a stretched film and dried to produce a coating layer and thereby obtain an optical compensation film. Therefore, the optical compensation film of the present invention can be produced more easily by this method.

Examples of the method for producing the coating layer (A) include one in which a solution prepared by dissolving a maleimide resin in a solvent is applied on a glass substrate, a film base, or a stretched film and thereafter heated or the like Method for removing solvent. As a technique for coating, for example, a doctor blade method, a bar coating method, a gravure coating method, a slot die coating method, a lip die coating method, a batch coating method, and the like are used. Industrially, the gravure coating method and the batch coating method are generally used for thin coating and thick coating, respectively. The solvent used is not particularly limited. Examples include aromatic solvents such as toluene, xylene, chlorobenzene, and nitrobenzene; ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; ether solvents such as dimethyl ether, diethyl ether, methyl tertiary Butyl ether, tetrahydrofuran and dioxane; acetate solvents such as methyl acetate, ethyl acetate, n-propyl acetate, isopropyl acetate and butyl acetate; hydrocarbon solvents such as hexane, cyclohexane, octane and decane; alcohol solvents such as methanol, ethanol, propanol, and butanol; chlorinated compound solvents such as carbon tetrachloride, chloroform, methylene chloride, dichloroethane, and trichloroethane; amide solvents such as dimethylformamide and methylacetamide; and N-methylpyrrolidone. A combination of two or more of these solvents may be used. In solution coating, it is preferable to adjust the solution viscosity of the maleimide resin solution to 10-10000cp, especially 10-5000cp, because the coating of this solution can achieve high transparency, excellent thickness accuracy and excellent surface finish and enables the manufacture of optical compensation films of excellent quality.

The thickness of the maleimide resin to be coated is determined by the retardation in the thickness direction of the coating layer (A). In particular, the thickness after drying is in the range of preferably 1-100 μm, more preferably 3-50 μm, particularly preferably 5-30 μm, from the viewpoint of obtaining excellent effects of having excellent surface smoothness and having improved viewing angle characteristics.

The optical compensation film of the present invention can also be used as a layered product including a polarizer.

Antioxidants can be introduced into the optical compensation film of the present invention to enhance thermal stability. Examples of antioxidants include hindered phenol antioxidants, phosphorus compound antioxidants, and other antioxidants. These antioxidants can be used alone or in combination. It is preferable to use hindered phenolic antioxidants in combination with phosphorus compound antioxidants because these antioxidants synergistically achieve an improved function of preventing oxidation. In this case, it is particularly preferable to mix 100-500 parts by weight of the phosphorus compound antioxidant with 100 parts by weight of the hindered phenol antioxidant. As for the amount of the antioxidant to be added, the amount is preferably in the range of 0.01-10 parts by weight, particularly preferably 0.5-1 part by weight, per 100 parts by weight of the maleimide resin constituting the optical compensation film of the present invention.

Furthermore, ultraviolet absorbents such as benzotriazoles, benzophenones, triazines or benzoates may be introduced as required.

The optical compensation film of the present invention can introduce additional polymers and other components such as surfactants, polymer electrolytes, conductive complexes, inorganic fillers, pigments, dyes, antioxidants, Anti-blocking agent and lubricant film.

An explanation is given below for an optical compensation layer characterized in that it is an optical compensation layer obtained by uniaxially stretching a coating layer comprising a maleimide resin, and when the stretching direction of the coating layer is referred to as x4 axis, the direction perpendicular to the stretching direction is called the y4 axis, and the out-of-plane direction is called the z4 axis, then the optical compensation layer satisfies the three-dimensional refractive index relationship nx4>ny4>nz4, where nx4 is the refraction in the direction of the x4 axis , ny4 is the refractive index in the direction of the y4 axis, and nz4 is the refractive index in the direction of the z4 axis.

The optical compensation film of the present invention is characterized in that it is obtained by uniaxially stretching a coating layer including a maleimide resin. Examples of maleimide resins include N-substituted maleimide polymer resins and N-substituted maleimide-maleic anhydride copolymer resins.

The N-substituted maleimide residue units constituting the N-substituted maleimide polymer resin include residues of N-substituted maleimides represented by the formula (1) given above unit.

_R in the residue unit of the N-substituted maleimide represented by formula (1) is a straight chain alkyl, branched chain alkyl or cycloalkyl having 1-18 carbon atoms, a halogen group group, ether group, ester group or amide group. Examples of straight-chain alkyl groups having 1 to 18 carbon atoms include methyl, ethyl, n-propyl, n-butyl, n-hexyl, n-octyl and n-lauryl. Examples of the branched alkyl group having 1 to 18 carbon atoms include isopropyl, isobutyl, sec-butyl and tert-butyl. Examples of the cycloalkyl group having 1 to 18 carbon atoms include cyclohexyl group. Examples of halo groups include chlorine, bromine and iodine.

Specific examples of the N-substituted maleimide residue unit represented by formula (1) include one or more selected from the following: N-methylmaleimide residue unit, N-ethyl Maleimide residue unit, N-chloroethylmaleimide residue unit, N-methoxyethylmaleimide residue unit, N-n-propylmaleimide residue Unit, N-n-butylmaleimide residue unit, N-n-hexylmaleimide residue unit, N-n-octylmaleimide residue unit, N-n-laurylmaleimide Imide residue unit, N-isopropylmaleimide residue unit, N-isobutylmaleimide residue unit, N-sec-butylmaleimide residue unit, N - tert-butylmaleimide residue units and N-cyclohexylmaleimide residue units. Particularly preferred are N-ethylmaleimide residue units, N-n-butylmaleimide residue units, N-isobutylmaleimide residue units, N-sec-butyl Maleimide residue units, N-tert-butylmaleimide residue units, N-n-hexylmaleimide residue units, and N-n-octylmaleimide residue units. These units therefore give an optical compensation layer that readily exhibits retardation and is excellent in solubility in solvents and mechanical strength.

Specific examples of N-substituted maleimide polymer resins include one or more of the following: N-methylmaleimide polymer resins, N-ethylmaleimide polymer resins, N-chloroethylmaleimide polymer resin, N-methoxyethylmaleimide polymer resin, N-n-propylmaleimide polymer resin, N-n-butylmaleimide Imide polymer resin, N-n-hexyl maleimide polymer resin, N-n-octyl maleimide polymer resin, N-n-lauryl maleimide polymer resin, N- Isopropylmaleimide polymer resin, N-isobutylmaleimide polymer resin, N-sec-butylmaleimide polymer resin, N-tert-butylmaleimide Polymer resins and N-cyclohexylmaleimide polymer resins. Particularly preferred are N-ethylmaleimide polymer resins, N-n-butylmaleimide polymer resins, N-isobutylmaleimide polymer resins, N-sec-butyl Maleimide polymer resin, N-tert-butylmaleimide polymer resin, N-n-hexylmaleimide polymer resin, N-n-octylmaleimide polymer resin, etc. . These resins thus give an optical compensation layer that readily exhibits retardation and is excellent in solubility in solvents and mechanical strength.

Also, examples of N-substituted maleimide-maleic anhydride copolymer resins include N-methylmaleimide-maleic anhydride copolymer resin, N-ethylmaleimide-maleic anhydride copolymer resin, Anhydride copolymer resin, N-chloroethylmaleimide-maleic anhydride copolymer resin, N-methoxyethylmaleimide-maleic anhydride copolymer resin, N-n-propylmaleic acid Imine-maleic anhydride copolymer resin, N-n-butylmaleimide-maleic anhydride copolymer resin, N-n-hexylmaleimide-maleic anhydride copolymer resin, N-octyl Maleimide-maleic anhydride copolymer resin, N-lauryl maleimide-maleic anhydride copolymer resin, N-isopropylmaleimide-maleic anhydride copolymer resin, N -Isobutylmaleimide-maleic anhydride copolymer resin, N-sec-butylmaleimide-maleic anhydride copolymer resin, N-tert-butylmaleimide-maleic anhydride copolymer material resin and N-cyclohexylmaleimide-maleic anhydride copolymer resin.

Particularly preferably, the maleimide resin is N-n-ethylmaleimide polymer resin, N-n-butylmaleimide polymer resin, N-n-hexylmaleimide polymer resin among these resins. Imine polymer resin, N-n-octylmaleimide polymer resin, or N-n-octylmaleimide-maleic anhydride copolymer resin. These resins therefore have excellent layering properties in layer formation and give an optical compensation film excellent in optical compensation function and heat resistance.

The maleimide resin constituting the optical compensation layer of the present invention may include residue units other than N-substituted maleimide residue units and maleic anhydride residue units, as long as this does not depart from the scope of the present invention. Purpose. Examples of such optional residue units include one or more of the following: styrene compound residue units such as styrene residue units and α-methylstyrene residue units; acrylic acid residue units; acrylate residues Base units such as methyl acrylate residue units, ethyl acrylate residue units and butyl acrylate residue units; methacrylate residue units; methacrylate residue units such as methyl methacrylate residue units, methyl Ethyl acrylate residue units and butyl methacrylate residue units; vinyl ester residues such as vinyl acetate residues, vinyl propionate residues, vinyl pivalate residues, vinyl laurate residues and Vinyl stearate residues; acrylonitrile residues; methacrylonitrile residues, etc.

Preferably, the maleimide resin is one having a number-average molecular weight (Mn) of 1×10 ³ or higher in terms of standard polystyrene from an elution curve obtained in gel permeation chromatography (hereinafter referred to as GPC). resin. The number average molecular weight thereof is particularly preferably 2×10 ⁴ to 2×10 ⁵ , since such a maleimide resin gives an optical compensation layer having excellent mechanical properties and excellent formability in layer formation.

In order to manufacture the maleimide resin constituting the optical compensation layer of the present invention, any method may be used as long as the maleimide resin is obtained. For example, the resin can be produced by combining at least one N-substituted maleimide and maleic anhydride, optionally with one or more monomers copolymerizable with the N-substituted maleimide Carry out free radical polymerization or free radical copolymerization together. Examples of N-substituted maleimides include one or more of the following: N-methylmaleimide, N-ethylmaleimide, N-chloroethylmaleimide , N-methoxyethylmaleimide, N-n-propylmaleimide, N-n-butylmaleimide, N-n-hexylmaleimide, N-n-octyl Maleimide, N-Lauryl Maleimide, N-Isopropyl Maleimide, N-Isobutyl Maleimide, N-Second Butyl Maleimide, N-tert-butylmaleimide, N-cyclohexylmaleimide, etc. Examples of the copolymerizable monomer include one or more of the following: styrene compounds such as styrene and α-methylstyrene; acrylic acid; acrylates such as methyl acrylate, ethyl acrylate, and butyl acrylate; Acrylic acid; methacrylates such as methyl methacrylate, ethyl methacrylate, and butyl methacrylate; vinyl esters such as vinyl acetate, vinyl propionate, vinyl pivalate, vinyl laurate, and hard Vinyl fatty acid; Acrylonitrile; Methacrylonitrile, etc.

Free radical polymerization can be carried out using known polymerization techniques. For example, all polymerization techniques such as bulk polymerization, solution polymerization, suspension polymerization, precipitation polymerization and emulsion polymerization can be used.

Examples of usable polymerization initiators in the case of performing radical polymerization include organic peroxides such as benzoyl peroxide, lauryl peroxide, octanoyl peroxide, acetyl peroxide, di-tert-butyl peroxide, tert-butylcumyl peroxide, dicumyl peroxide, tert-butyl peroxyacetate and tert-butyl peroxybenzoate; and azo initiators such as 2,2'-azobis(2,4- Dimethylvaleronitrile), 2,2'-azobis(2-butyronitrile), 2,2'-azobisisobutyronitrile, 2,2'-azobisisobutyrate and 1 , 1'-Azobis(cyclohexane-1-carbonitrile).

Solvents usable in solution polymerization, suspension polymerization, precipitation polymerization and emulsion polymerization are not particularly limited. Examples thereof include aromatic solvents such as benzene, toluene, and xylene; alcohol solvents such as methanol, ethanol, propanol, and butanol; cyclohexane; dioxane; tetrahydrofuran (THF); acetone; methyl ethyl ketone; dimethylformamide; acetic acid isopropyl ester; water; N-methylpyrrolidone; and dimethylformamide. Examples thereof also include mixed solvents composed of two or more of these.

The polymerization temperature in the case of performing radical polymerization can be appropriately set according to the decomposition temperature of the polymerization initiator. Generally, it is preferred to carry out the polymerization at a temperature of 40-150°C.

The optical compensation layer of the present invention is a film obtained by uniaxially stretching a coating layer including a maleimide resin. This optical compensation layer is excellent in optical compensation function especially when used as an optical compensation layer. Generally, it is very difficult to biaxially stretch to adjust the three-dimensional refractive index. As the screen area of the display increases and thus the area of the optical compensation layer increases, it becomes difficult to uniformly adjust the entire area, resulting in decreased yield and the like. In the present invention, an optical compensation layer having an excellent optical compensation function can be obtained by uniaxially stretching a specific coating layer. The optical compensation layer of the present invention is characterized in that it is an optical compensation layer obtained by uniaxially stretching a coating layer comprising a maleimide resin, when the direction of the stretching axis of the coating layer is called the x4 axis, and The direction perpendicular to the stretching direction is called the y4 axis, and the out-of-plane direction is called the z4 axis, then the optical compensation layer satisfies the three-dimensional refractive index relationship nx4>ny4>nz4, where nx4 is the refractive index in the direction of the x4 axis, and ny4 is the refractive index in the y4-axis direction, and nz4 is the refractive index in the z4-axis direction.

The in-plane retardation (Re1) of the optical compensation layer of the present invention can be easily adjusted by changing the thickness of the coating layer made of maleimide resin and changing the conditions of uniaxial stretching. Its in-plane retardation (Re1) measured with light having a measurement wavelength of 589 nm and represented by the following expression (6) is preferably 20 nm or more, particularly 30 nm to 200 nm, more preferably 40 nm to 150 nm, because this optical The compensation layer is expected to be suitable for use as a retardation film.

Re1＝(nx4-ny4)×d3 (6)

(In Expression (6), d3 represents the thickness (nm) of the optical compensation layer).

Also, the out-of-plane retardation (Rth2) of the optical compensation layer of the present invention can be easily adjusted by changing the thickness of the coating layer made of maleimide resin and changing the conditions of uniaxial stretching. Its out-of-plane retardation (Rth2) measured with light having a measurement wavelength of 589 nm and represented by the following expression (7) is preferably in the range of 30 to 2000 nm, since this optical compensation layer is expected to be suitable as a retardation film. In particular, its retardation (Rth2) is preferably in the range of 50-1000 nm, more preferably 80-400 nm, because such an optical compensation layer has an excellent effect of improving the viewing angle characteristics of a liquid crystal display element.

Rth2＝((nx4+ny4)/2-nz4)×d4 (7)

(In Expression (7), d4 represents the thickness (nm) of the optical compensation layer).

Preferably, the optical compensation layer of the present invention is a layer having a small wavelength dependence of retardation, because the use of such an optical compensation layer in a liquid crystal display element enables the liquid crystal display element to be reduced in color shift. The wavelength dependence (R450/R589) of its retardation is preferably 1.1 or less, particularly 1.08 or less, and the wavelength dependence (R450/R589) of this retardation is determined by the retardation (R450) with the measuring wavelength of 450nm and the The ratio of retardation (R589) measured at a measurement wavelength of 589 nm is expressed.

The thickness of the optical compensation layer of the present invention is preferably 1-100 μm, more preferably 3-50 μm, particularly preferably 5-30 μm, because an optical compensation layer having such a thickness has excellent surface smoothness and excellent effects of improving viewing angle characteristics.

Preferably, the light transmittance of the optical compensation layer of the present invention is 85% or higher, particularly 90% or higher, because such an optical compensation layer imparts satisfactory image quality when used in a liquid crystal display element. Also preferably, the optical compensation layer has a haze of 2% or less, especially 1% or less.

From the viewpoint of quality stability in a liquid crystal display element, the optical compensation layer of the present invention preferably has high heat resistance. Its glass transition temperature is preferably 100°C or higher, particularly preferably 120°C or higher, even more preferably 135°C or higher.

The optical compensation layer of the present invention is characterized in that it is obtained by uniaxially stretching a coating layer including a maleimide resin. Examples of preferred methods for making this layer include where a maleimide resin in solution is coated on a film made of, for example, cellulose resin or poly(ethylene terephthalate) resin (PET). A method of drying and uniaxially stretching the resulting coated substrate onto the substrate. For coating, a method in which a solution prepared by dissolving a maleimide resin in a solvent is coated on a film and then the solvent is removed by heating or the like and then the resulting coating layer is uniaxially stretched can be used. As a technique for coating, for example, a doctor blade method, a bar coating method, a gravure coating method, a slot die coating method, a lip die coating method, a batch coating method, and the like are used. Industrially, the gravure coating method and the batch coating method are generally used for thin coating and thick coating, respectively.

The solvent used is not particularly limited. Examples include aromatic solvents such as toluene, xylene, chlorobenzene, and nitrobenzene; ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; ether solvents such as dimethyl ether, diethyl ether, methyl tertiary Butyl ether, tetrahydrofuran and dioxane; acetate solvents such as methyl acetate, ethyl acetate, n-propyl acetate, isopropyl acetate and butyl acetate; hydrocarbon solvents such as hexane, cyclohexane, octane and decane; alcohol solvents such as methanol, ethanol, propanol, and butanol; chlorinated compound solvents such as carbon tetrachloride, chloroform, methylene chloride, dichloroethane, and trichloroethane; amide solvents such as dimethylformamide and methylacetamide; and N-methylpyrrolidone. A combination of two or more of these solvents may be used. In solution coating, the viscosity of a coating solution is a very important factor for forming a coating layer having high transparency and excellent in thickness accuracy and surface smoothness. The viscosity of the coating solution is preferably 10-10000 cp, particularly preferably 10-5000 cp.

The thickness of the maleimide resin to be coated in this operation is determined by the retardation in the thickness direction of the coating layer. In particular, from the viewpoint of obtaining an optical compensation layer having an excellent surface smoothness and an excellent effect of improving viewing angle characteristics, its thickness after drying is preferably in the range of 1-100 μm, more preferably 3-50 μm, particularly preferably 5-30 μm Inside.

The uniaxial stretching for obtaining the optical compensation film of the present invention is not particularly limited. Generally, the coating layer may be stretched at a stretching ratio of 1.1 to 5 under the condition of a stretching temperature of -30 to 50° C. higher than the glass transition temperature of the coating layer measured with a differential scanning calorimeter. Minimization of thickness non-uniformity is preferred since optical properties such as inter alia retardation, light transmission and haze are considerably affected by thickness. In the stretching of the coating layer of the present invention, the stretching temperature can be lowered by adjusting the drying conditions in the production of the coating layer to allow a part of the solvent to remain. The coating layer may be stretched after peeling from the base film, or may be stretched together with the base film.

Examples of the method of uniaxial stretching usable in the present invention include, for example, methods in which the coating layer is stretched with a tenter, methods in which the coating layer is stretched by rolling with a calender, and methods in which A method of stretching a coated layer between rolls.

The optical compensation layer of the present invention may be used after being peeled from the base film, or may be used in the form of a layered product including the base film or another optical film. In particular, in the case where the optical compensation layer is used as a layered product including an additional optical film, the additional optical film is preferably a cellulose film or a cyclic polyolefin film from the viewpoint of transparency and strength.

The optical compensation layer of the present invention can also be used as a layered product including a polarizer.

Antioxidants may have been introduced into the optical compensation layer of the present invention to enhance thermal stability. Examples of antioxidants include hindered phenol antioxidants, phosphorus compound antioxidants, and other antioxidants. These antioxidants can be used alone or in combination. It is preferable to use hindered phenolic antioxidants in combination with phosphorus compound antioxidants because these antioxidants synergistically achieve an improved function of preventing oxidation. In this case, it is particularly preferable to mix 100-500 parts by weight of the phosphorus compound antioxidant with 100 parts by weight of the hindered phenol antioxidant. As for the amount of the antioxidant to be added, the amount is preferably in the range of 0.01-10 parts by weight, particularly preferably 0.5-1 part by weight, per 100 parts by weight of the maleimide resin constituting the optical compensation layer of the present invention.

Furthermore, ultraviolet absorbents such as benzotriazoles, benzophenones, triazines or benzoates may be introduced as required.

The optical compensation layer of the present invention can introduce additional polymers and other components such as surfactants, polymer electrolytes, conductive complexes, inorganic fillers, pigments, dyes, antistatic agents without departing from the spirit of the present invention , anti-blocking agent and lubricant layer.

Example

Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention should not be construed as being limited by the following examples in any way.

Determination of number average molecular weight:

Gel permeation chromatography (GPC) (trade name, HLC-802A; manufactured by Tosoh Corp.) was used, and dimethylformamide was used as a solvent. The number average molecular weight is determined as a value calculated for standard polystyrene.

Measurement of glass transition temperature:

A differential scanning calorimeter (trade name, DSC2000; manufactured by Seiko Instruments & Electronics Ltd.) was used for measurement at a heating rate of 10°C/min.

Measurement of light transmittance:

The light transmittance is measured according to JIS K 7361-1 (1997 edition) as a measure of transparency.

Determination of haze:

Haze is measured according to JIS K 7136 (2000 edition) as a measure of transparency.

Calculation of three-dimensional refractive index:

A sample tilting type automatic birefringencer (trade name, KOBRA-WR; manufactured by Oji Scientific Instruments) was used to measure a three-dimensional refractive index with light having a measurement wavelength of 589 nm while changing the elevation angle. Also, the out-of-plane retardation (Rth, Rth1 or Rth2) is calculated from the three-dimensional refractive index.

The wavelength dependence (R450/R589) of the retardation is shown as the ratio of the retardation (R450) measured at a measurement wavelength of 450 nm to the retardation (R589) measured at a measurement wavelength of 589 nm.

Synthesis example 1 (production example of N-n-butylmaleimide polymer resin)

Into the sealed glass tube were introduced 32.4 g of N-n-butylmaleimide and 0.054 g of dimethyl 2,2'-azobisisobutyrate as a polymerization initiator. After nitrogen substitution, radical polymerization was performed under conditions of a polymerization temperature of 60° C. and a polymerization time of 5 hours. Chloroform was added after the reaction to obtain a polymer solution. After that, the solution was mixed with excess methanol to thereby precipitate a polymer. The resulting polymer was taken out by filtration, then washed well with methanol, and dried at 80°C. Thus, an N-n-butylmaleimide polymer resin was obtained in an amount of 20 g. The obtained N-n-butylmaleimide polymer resin had a number average molecular weight of 120,000.

Synthesis example 2 (production example of N-n-hexylmaleimide polymer resin)

Into the sealed glass tube were introduced 40 g of N-n-hexylmaleimide and 0.05 g of dimethyl 2,2'-azobisisobutyrate as a polymerization initiator. After nitrogen substitution, radical polymerization was performed under conditions of a polymerization temperature of 60° C. and a polymerization time of 5 hours. Chloroform was added after the reaction to obtain a polymer solution. After that, the solution was mixed with excess methanol to thereby precipitate a polymer. The resulting polymer was taken out by filtration, then washed well with methanol, and dried at 80°C. Thus, N-n-hexylmaleimide polymer resin was obtained in an amount of 32 g. The obtained N-n-hexylmaleimide polymer resin had a number average molecular weight of 160,000.

Synthesis example 3 (production example of N-n-octylmaleimide polymer resin)

Into the sealed glass tube were introduced 28 g of N-n-octylmaleimide and 0.032 g of dimethyl 2,2'-azobisisobutyrate as a polymerization initiator. After nitrogen substitution, radical polymerization was performed under conditions of a polymerization temperature of 60° C. and a polymerization time of 5 hours. Chloroform was added after the reaction to obtain a polymer solution. After that, the solution was mixed with excess methanol to thereby precipitate a polymer. The resulting polymer was taken out by filtration, then washed well with methanol, and dried at 80°C. Thus, an N-n-octylmaleimide polymer resin was obtained in an amount of 15 g. The obtained N-n-octylmaleimide polymer resin had a number average molecular weight of 270,000.

Synthesis Example 4 (Production Example 1 of N-n-octylmaleimide-maleic anhydride copolymer resin)

Into the sealed glass tube were introduced 26 g of N-n-octylmaleimide, 2.4 g of maleic anhydride, and 0.036 g of dimethyl 2,2'-azobisisobutyrate as a polymerization initiator. After nitrogen substitution, radical polymerization was performed under conditions of a polymerization temperature of 60° C. and a polymerization time of 5 hours. Chloroform was added after the reaction to obtain a polymer solution. After that, the solution was mixed with excess methanol to thereby precipitate a polymer. The resulting polymer was taken out by filtration, then washed well with methanol, and dried at 80°C. Thus, an N-n-octylmaleimide-maleic anhydride copolymer resin was obtained in an amount of 19 g. The obtained N-n-octylmaleimide-maleic anhydride copolymer resin contained maleic anhydride residues in an amount of 20% by weight and had a number average molecular weight of 120,000.

Synthesis Example 5 (Production Example 2 of N-n-octylmaleimide-maleic anhydride copolymer resin)

Into the sealed glass tube were introduced 26 g of N-n-octylmaleimide, 4.8 g of maleic anhydride, and 0.04 g of dimethyl 2,2'-azobisisobutyrate as a polymerization initiator. After nitrogen substitution, radical polymerization was performed under conditions of a polymerization temperature of 60° C. and a polymerization time of 5 hours. Chloroform was added after the reaction to obtain a polymer solution. After that, the solution was mixed with excess methanol to thereby precipitate a polymer. The resulting polymer was taken out by filtration, then washed well with methanol, and dried at 80°C. Thus, an N-n-octylmaleimide-maleic anhydride copolymer resin was obtained in an amount of 18 g. The obtained N-n-octylmaleimide-maleic anhydride copolymer resin contained maleic anhydride residue units in an amount of 40% by weight and had a number average molecular weight of 140,000.

Synthesis Example 6 (Production Example 3 of N-n-octylmaleimide-maleic anhydride copolymer resin)

Into the sealed glass tube were introduced 26 g of N-n-octylmaleimide, 4.8 g of maleic anhydride, and 0.04 g of dimethyl 2,2'-azobisisobutyrate as a polymerization initiator. After nitrogen substitution, radical polymerization was performed under conditions of a polymerization temperature of 60° C. and a polymerization time of 5 hours. Chloroform was added after the reaction to obtain a polymer solution. After that, the solution was mixed with excess methanol to thereby precipitate a polymer. The resulting polymer was taken out by filtration, then washed well with methanol, and dried at 80°C. Thus, an N-n-octylmaleimide-maleic anhydride copolymer resin was obtained in an amount of 18 g. The obtained N-n-octylmaleimide-maleic anhydride copolymer resin contained maleic anhydride residue units in an amount of 20% by weight and had a number average molecular weight of 140,000.

Synthesis example 7 (production example of N-n-ethylmaleimide polymer resin)

Into the sealed glass tube were introduced 45 g of N-n-ethylmaleimide and 0.05 g of dimethyl 2,2'-azobisisobutyrate as a polymerization initiator. After nitrogen substitution, radical polymerization was performed under conditions of a polymerization temperature of 60° C. and a polymerization time of 5 hours. Chloroform was added after the reaction to obtain a polymer solution. After that, the solution was mixed with excess methanol to thereby precipitate a polymer. The resulting polymer was taken out by filtration, then washed well with methanol, and dried at 80°C. Thus, N-n-ethylmaleimide polymer resin was obtained in an amount of 20 g. The obtained N-n-ethylmaleimide polymer resin had a number average molecular weight of 80,000.

Synthesis Example 8 (Production Example 4 of N-n-octylmaleimide-maleic anhydride copolymer resin)

Into the sealed glass tube were introduced 26 g of N-n-octylmaleimide, 2.4 g of maleic anhydride, and 0.036 g of dimethyl 2,2'-azobisisobutyrate as a polymerization initiator. After nitrogen substitution, radical polymerization was performed under conditions of a polymerization temperature of 60° C. and a polymerization time of 5 hours. Chloroform was added after the reaction to obtain a polymer solution. After that, the solution was mixed with excess methanol to thereby precipitate a polymer. The resulting polymer was taken out by filtration, then washed well with methanol, and dried at 80°C. Thus, an N-n-octylmaleimide-maleic anhydride copolymer resin was obtained in an amount of 19 g. The obtained N-n-octylmaleimide-maleic anhydride copolymer resin contained maleic anhydride residues in an amount of 20% by weight and had a number average molecular weight of 140,000.

Manufacturing Example 1 (Manufacturing Example of Uniaxially Stretched Film of Cyclic Polyolefin Resin)

A cyclic polyolefin resin (hydrogenated polynorbornene having an ester group; manufactured by Aldrich Co.) was dissolved in a methylene chloride solution to obtain a 25% solution. Added thereto 0.35 parts by weight of tris(2,4-di-tert-butylphenyl) phosphite and 0.15 parts by weight of pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl) ) propionate) and 1 part by weight of 2-(2H-benzotriazol-2-yl)-p-cresol as an ultraviolet absorber per 100 parts by weight of the cyclic polyolefin resin. After that, the resulting mixture was cast on a support of a solution casting apparatus by a T-die method and dried at 40° C., 80° C. and 120° C. to obtain a film having a width of 250 mm and a thickness of 100 μm. The resulting film was cut into a square with a side length of 50 mm. The cut film was subjected to free-width uniaxial stretching with a biaxial stretching device (manufactured by Imoto Machinery Co. Ltd.) under conditions of a temperature of 180° C. and a stretching speed of 15 mm/min. The film is thus stretched +100%.

The resulting stretched film exhibited positive birefringence, and its three-dimensional refractive indices were nx2 = 1.5124, ny2 = 1.5090 and nz2 = 1.5090. That is, nx2>ny2=nz2. The stretched film had an in-plane retardation (Re) of 121 nm. The wavelength dependence (R450/R550) of its in-plane retardation was 1.01.

Example 1

The N-n-butylmaleimide polymer resin obtained in Synthesis Example 1 was dissolved in chloroform to prepare a 12% solution. The solution was cast on a glass substrate by a coater and dried at room temperature for 24 hours to obtain a coating layer on the glass substrate. Thus, a coating layer film having a width of 50 mm and a thickness of 20 μm was produced. The glass transition temperature (Tg) of this coating layer film was measured and found to be 179°C.

The obtained coating layer had a light transmittance of 91.6% and a haze of 0.6%, and its three-dimensional refractive index was nx=1.51607, ny=1.51607 and nz=1.50954. This layer has an in-plane retardation of 0 nm and an Rth of 130.6 nm. Its value of R450/R589 indicating the wavelength dependence of the retardation was 1.06, showing that the coating layer had the function of an optical compensation layer.

Example 2

The N-n-hexylmaleimide polymer resin obtained in Synthesis Example 2 was dissolved in chloroform to prepare a 15% solution. The solution was cast on a glass substrate by a coater and dried at room temperature for 24 hours to obtain a coating layer on the glass substrate. Thus, a coating layer film having a width of 50 mm and a thickness of 30 μm was produced. The Tg of this coating layer film was measured and found to be 149°C.

The obtained coating layer had a light transmittance of 91.8% and a haze of 0.7%, and its three-dimensional refractive index was nx=1.52000, ny=1.52002 and nz=1.51638. This layer has an in-plane retardation of 0.6 nm and an Rth of 108.9 nm. The value of R450/R589 thereof, which indicates the wavelength dependence of the retardation, was 1.05, showing that the coating layer functions as an optical compensation layer.

Example 3

The N-n-octylmaleimide polymer resin obtained in Synthesis Example 3 was dissolved in chloroform to prepare a 16% solution. The solution was cast on a glass substrate by a coater and dried at room temperature for 24 hours to obtain a coating layer on the glass substrate. Thus, a coating layer film having a width of 50 mm and a thickness of 50 μm was produced. The Tg of this coating layer film was measured and found to be 145°C.

The obtained coating layer had a light transmittance of 92.78% and a haze of 0.9%, and its three-dimensional refractive index was nx=1.51049, ny=1.51049 and nz=1.50833. This layer has an in-plane retardation of 0 nm and an Rth of 108 nm. The value of R450/R589 thereof, which indicates the wavelength dependence of the retardation, was 1.05, showing that the coating layer functions as an optical compensation layer.

Example 4

The N-n-octylmaleimide-maleic anhydride copolymer resin obtained in Synthesis Example 4 was dissolved in chloroform to prepare a 16% solution. The solution was cast on a glass substrate by a coater and dried at room temperature for 24 hours to obtain a coating layer on the glass substrate. Thus, a coating layer film having a width of 50 mm and a thickness of 50 μm was produced. The Tg of this coating layer film was measured and found to be 150°C.

The obtained coating layer had a light transmittance of 92.2% and a haze of 0.8%, and its three-dimensional refractive index was nx=1.50680, ny=1.50680 and nz=1.50422. This layer has an in-plane retardation of 0 nm and an Rth of 129 nm. The value of R450/R589 thereof, which indicates the wavelength dependence of the retardation, was 1.05, showing that the coating layer functions as an optical compensation layer.

Example 5

The N-n-octylmaleimide-maleic anhydride copolymer resin obtained in Synthesis Example 5 was dissolved in chloroform to prepare a 16% solution. The solution was cast on a glass substrate by a coater and dried at room temperature for 24 hours to obtain a coating layer on the glass substrate. Thus, a coating layer film having a width of 50 mm and a thickness of 50 μm was produced. The Tg of this coating layer film was measured and found to be 156°C.

The obtained coating layer had a light transmittance of 92.0% and a haze of 0.9%, and its three-dimensional refractive index was nx=1.51593, ny=1.51594 and nz=1.51193. This layer has an in-plane retardation of 0.3 nm and an Rth of 200 nm. The value of R450/R589 thereof, which indicates the wavelength dependence of the retardation, was 1.05, showing that the coating layer functions as an optical compensation layer.

Example 6

The N-n-butylmaleimide polymer resin obtained in Synthesis Example 1 was dissolved in chloroform to prepare a 12% solution. This solution was cast on a film made of triacetyl cellulose (hereinafter referred to as TAC film) by a coater and dried at room temperature for 24 hours to obtain a coating layer on the TAC film. This coating layer was peeled off from the TAC film. Thus, a coating layer film having a width of 50 mm and a thickness of 20 μm was produced. The glass transition temperature (Tg) of this coating layer was measured and found to be 179°C.

The obtained coating layer had a light transmittance of 91.5% and a haze of 0.6%, and its three-dimensional refractive index was nx=1.51606, ny=1.51606 and nz=1.50954. This layer has an in-plane retardation of 0 nm and an Rth of 130.4 nm. Its value of R450/R589 indicating the wavelength dependence of the retardation was 1.06, showing that the coating layer had the function of an optical compensation layer. These properties are almost equal to those obtained in Example 1. The optical properties of the layered product were evaluated without peeling off the coating layer from the TAC film. As a result, the layered product was found to have a light transmittance of 90.2%, a haze of 0.8%, an in-plane retardation of 0 nm, and an Rth of 156.8 nm. Its value of R450/R589 indicating the wavelength dependence of the retardation was 1.05, showing that the layered product had the function of an optical compensation film.

Example 7

The N-n-butylmaleimide polymer resin obtained in Synthesis Example 1 was dissolved in chloroform to prepare a 12% solution. The solution was cast on a glass substrate by a coater and dried at room temperature for 24 hours to obtain a coating layer on the glass substrate. Thus, a coating layer film having a width of 50 mm and a thickness of 20 μm was produced. The glass transition temperature (Tg) of this coating layer film was measured and found to be 179°C.

The obtained coating layer had a light transmittance of 91.6% and a haze of 0.6%, and its three-dimensional refractive index was nx1=1.51607, ny1=1.51607 and nz1=1.50954. This layer has an in-plane retardation of 0 nm and an Rth1 of 130.6 nm. Its value of R450/R589 indicating the wavelength dependence of the retardation was 1.06, showing that the coating layer had the function of an optical compensation layer.

The obtained coating layer was laminated on the stretched film obtained in Production Example 1 to produce a laminated film.

The obtained laminated film had a light transmittance of 90.2%, a haze of 0.8%, an in-plane retardation (Re2) of 121 nm, and an orientation parameter (Nz) of 2.14, showing that the laminated film functions as an optical compensation film.

Example 8

The N-n-octylmaleimide polymer resin obtained in Synthesis Example 3 was dissolved in chloroform to prepare a 16% solution. The solution was cast on a glass substrate by a coater and dried at room temperature for 24 hours to obtain a coating layer on the glass substrate. Thus, a coating layer film having a width of 50 mm and a thickness of 50 μm was produced. The Tg of this coating layer film was measured and found to be 145°C.

The obtained coating layer had a light transmittance of 92.78% and a haze of 0.9%, and its three-dimensional refractive index was nx1=1.51049, ny1=1.51049 and nz1=1.50833. This layer has an in-plane retardation of 0 nm and an Rth1 of 108 nm. The value of R450/R589 thereof, which indicates the wavelength dependence of the retardation, was 1.05, showing that the coating layer functions as an optical compensation layer.

The obtained coating layer was laminated on the stretched film obtained in Production Example 1 to produce a laminated film.

The obtained laminated film had a light transmittance of 90.2%, a haze of 0.8%, an in-plane retardation (Re2) of 121 nm, and an orientation parameter (Nz) of 1.36, showing that the laminated film functions as an optical compensation film.

Example 9

The N-n-octylmaleimide-maleic anhydride copolymer resin obtained in Synthesis Example 6 was dissolved in chloroform to prepare a 16% solution. The solution was cast on a glass substrate by a coater and dried at room temperature for 24 hours to obtain a coating layer on the glass substrate. Thus, a coating layer film having a width of 50 mm and a thickness of 50 μm was produced. The Tg of this coating layer film was measured and found to be 156°C.

The obtained coating layer had a light transmittance of 92.0% and a haze of 0.7%, and its three-dimensional refractive index was nx1=1.51593, ny1=1.51593 and nz1=1.51193. This layer has an in-plane retardation of 0.3 nm and an Rth1 of 200 nm. The value of R450/R589 thereof, which indicates the wavelength dependence of the retardation, was 1.05, showing that the coating layer functions as an optical compensation layer.

The obtained coating layer was laminated on the stretched film obtained in Production Example 1 to produce a laminated film.

The obtained laminated film had a light transmittance of 90.4%, a haze of 0.9%, an in-plane retardation (Re2) of 121 nm, and an orientation parameter (Nz) of 2.53, showing that the laminated film functions as an optical compensation film.

Example 10

The N-n-butylmaleimide polymer resin obtained in Synthesis Example 1 was dissolved in chloroform to prepare a 12% solution. This solution was cast on the stretched film obtained in Production Example 1 and dried at room temperature for 24 hours to obtain a laminated film including a stretched film of a cyclic polyolefin resin and a coating layer. This coating layer was peeled off from the part of the laminated film. Thus, a coating layer having a width of 50 mm and a thickness of 20 μm was produced. The glass transition temperature (Tg) of this coating layer was measured and found to be 179°C.

The obtained coating layer had a light transmittance of 91.5% and a haze of 0.6%, and its three-dimensional refractive index was nx1=1.51606, ny1=1.51606 and nz1=1.50954. This layer has an in-plane retardation of 0 nm and an Rth1 of 130.4 nm. Its value of R450/R589 indicating the wavelength dependence of the retardation was 1.06, showing that the coating layer had the function of an optical compensation layer. These properties are almost equal to those obtained in Example 1. Also, the optical properties of the obtained laminated film were evaluated as they were. As a result, the laminated film was found to have a light transmittance of 91.5%, a haze of 0.6%, an in-plane retardation (Re2) of 121 nm, and an orientation parameter (Nz) of 2.14, showing that the laminated film functions as an optical compensation film.

Example 11

The N-n-ethylmaleimide polymer resin obtained in Synthesis Example 7 was dissolved in chloroform to prepare a 12% solution. The solution was cast on a silicone-treated PET film by a coater and dried at 90° C. for 15 minutes to obtain a coating layer. Thus, a coating layer having a width of 100 mm and a thickness of 30 μm was produced. The glass transition temperature (Tg) of this coating layer was measured and found to be 255°C.

The obtained coating layer was peeled off and uniaxially stretched at 270° C. at a draw ratio of 1.5. The resulting layer had a thickness of 30 μm, a light transmittance of 92%, and a haze of 0.6%, and its three-dimensional refractive indices were nx4=1.5252, ny4=1.5232 and nz4=1.5168. This layer has an in-plane retardation (Re1) of 60 nm and an out-of-plane retardation (Rth2) of 222 nm. Its value of R450/R589 showing the wavelength dependence of the retardation was 1.07, showing that this layer functions as an optical compensation layer.

Example 12

The N-n-butylmaleimide polymer resin obtained in Synthesis Example 1 was dissolved in chloroform to prepare a 12% solution. The solution was cast on a silicone-treated PET film by a coater and dried at 90° C. for 15 minutes to obtain a coating layer. Thus, a coating layer having a width of 50 mm and a thickness of 25 μm was produced. The glass transition temperature (Tg) of this coating layer was measured and found to be 179°C.

The obtained coating layer was peeled off and uniaxially stretched at 190° C. at a draw ratio of 1.5. The resulting layer had a thickness of 20 μm, a light transmittance of 91.6%, and a haze of 0.5%, and its three-dimensional refractive indices were nx4=1.5182, ny4=1.5145 and nz4=1.5078. This layer has an in-plane retardation (Re1) of 74 nm and an out-of-plane retardation (Rth2) of 171 nm. Its value of R450/R589 showing wavelength dependence of retardation was 1.06, showing that this layer functions as an optical compensation layer.

Example 13

The N-n-octylmaleimide-maleic anhydride copolymer resin obtained in Synthesis Example 8 was dissolved in tetrahydrofuran to prepare a 15% solution. This solution was cast on a circular polyolefin film by a coater and dried at 90° C. for 10 minutes to obtain a coating layer having a thickness of 75 μm. The coating layer has a Tg of 150°C. The obtained coating layer was uniaxially stretched at 160° C. at a stretch ratio of 1.5 together with the cyclic polyolefin substrate. After stretching, the coating layer was peeled off from the base film and optical properties were evaluated.

The resulting layer had a thickness of 20 μm, a light transmittance of 92.2%, and a haze of 0.5%, and its three-dimensional refractive indices were nx4=1.5079, ny4=1.5056 and nz4=1.5033. This layer has an in-plane retardation (Re1) of 115 nm and an Rth2 of 172.5 nm. Its value of R450/R589 showing the wavelength dependence of retardation was +1.04, showing that this layer functions as an optical compensation layer.

Comparative example 1

Into a 1-liter autoclave were introduced 400 mL of toluene as a polymerization solvent, 0.001 mol of tert-butyl neodecanoate as a polymerization initiator, 0.42 mol of N-(2,6-diethylphenyl)maleyl imine and 4.05 moles of isobutene. Polymerization was performed at a polymerization temperature of 60°C with a polymerization time of 5 hours to obtain an N-(2,6-diethylphenyl)maleimide-isobutylene alternating copolymer. The obtained N-(2,6-diethylphenyl)maleimide-isobutylene alternating copolymer had a number average molecular weight of 65,000.

A solution consisting of 20% by weight of the obtained N-(2,6-diethylphenyl)maleimide-isobutylene alternating copolymer and 80% by weight of dichloromethane was prepared. The solution was cast on a PET film, and dichloromethane was evaporated from the solution. The obtained cured film of N-(2,6-diethylphenyl)maleimide-isobutylene alternating copolymer was peeled off. The peeled film was dried at 100°C for 4 hours and then at 10°C intervals at a temperature of 120°C-160°C, 1 hour for each temperature, followed by 4 hours at 180°C in a vacuum desiccator to obtain a film with a thickness of about 100 μm. (The three-dimensional refractive indices of the obtained film were nx=1.5400, ny=1.5400 and nz=1.5400).

A small piece of 5 cm x 5 cm was cut out from the film, and subjected to stretching with a biaxial stretching device (manufactured by Shibayama Scientific Co. Ltd.) at a temperature of 220° C. and a stretching speed of 15 mm/min. Free width uniaxial stretching. The film was thus stretched by +50% to obtain a stretched film. The three-dimensional refractive indices of the obtained stretched film were nx4 = 1.53913, ny4 = 1.54042 and nz4 = 1.54045.

Although the invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention.

The present invention is based on Japanese Patent Application (Application No. 2007-109052) filed on April 18, 2007, Japanese Patent Application (Application No. 2007-109053) filed on April 18, 2007, and Japanese Patent Application (Application No. 2007-109053) filed on December 25, 2007. Patent Application (Application No. 2007-331825), the contents of which are incorporated herein by reference.

Industrial applicability

According to the present invention, an optical compensation layer and an optical compensation film having excellent optical properties can be provided. More specifically, it is possible to provide an optical compensation layer having an optical compensation function imparted upon application of a coating fluid or upon application of a coating fluid and subsequent uniaxial stretching and having a small wavelength dependence of retardation and Optical compensation film.

Claims (27)

1. Optical compensation layer, wherein the compensation layer is a coating layer comprising a maleimide resin, and wherein two arbitrary axes perpendicular to each other in the plane of the coating layer are called x-axis and y-axis respectively, And when the out-of-plane direction is called the z-axis, the coating layer satisfies the three-dimensional refractive index relationship nx≈ny>nz, where nx is the refractive index in the direction of the x-axis, ny is the refractive index in the direction of the y-axis, and nz is the refractive index in the direction of the z-axis. 2. The optical compensation layer of claim 1, comprising a maleimide resin comprising N-substituted maleimide residue units represented by the following formula (1): [chemical 1] Wherein R ₁ represents a straight-chain alkyl group, branched-chain alkyl group or cycloalkyl group with 1-18 carbon atoms, a halogen group, an ether group, an ester group or an amide group. 3. The optical compensation layer of claim 1 or 2, wherein the layer has an out-of-plane retardation Rth of 30-2000 nm, wherein the out-of-plane retardation is represented by the following expression (2) when detected with light having a measurement wavelength of 589 nm: Rth＝((nx+ny)/2-nz)×d (2) Wherein, d represents the thickness of the optical compensation layer, and the unit is nm. 4. The optical compensation layer of claim 1 or 2, which has a wavelength dependence of 1.1 or lower retardation, i.e. R450/R589, wherein the wavelength dependence of this retardation is detected by tilting 40 degrees and with a measurement wavelength of 450nm The ratio of the retardation R450 of the coating layer to the retardation R589 of the coating layer inclined at 40 degrees and detected with light having a measurement wavelength of 589 nm is expressed. 5. The optical compensation layer of claim 1 or 2, wherein the coating layer is an unstretched film. 6. The optical compensation layer according to claim 1 or 2, which is an optical compensation layer for a liquid crystal display element. 7. An optical compensation film which is a layered product comprising the optical compensation layer according to claim 1 or 2 and a film made of cellulose resin. 8. The optical compensation film according to claim 7, which is an optical compensation film for a liquid crystal display element. 9. A method of manufacturing an optical compensation layer, comprising coating a maleimide resin solution on a substrate and drying the coated solution. 10. The method for manufacturing an optical compensation layer according to claim 9, wherein the maleimide resin solution is a maleimide resin comprising a maleimide residue unit represented by the following general formula (1) The solution: [Chem 2]

Wherein R ₁ represents a straight-chain alkyl group, branched-chain alkyl group or cycloalkyl group with 1-18 carbon atoms, a halogen group, an ether group, an ester group or an amide group. 11. An optical compensation film comprising a coating layer (A) comprising a maleimide resin and a stretched film layer (B). 12. The optical compensation film according to claim 11, wherein the coating layer (A) contains the following maleimide resin, and the maleimide resin comprises N-substitution represented by the following general formula (1) The maleimide residue unit: [Chem 3]

Wherein R ₁ represents a straight-chain alkyl group, branched-chain alkyl group or cycloalkyl group with 1-18 carbon atoms, a halogen group, an ether group, an ester group or an amide group. 13. The optical compensation film of claim 11 or 12, wherein said layer (A) comprises a coating layer, wherein when two arbitrary axes perpendicular to each other in the plane of the coating layer are called x1 axis and y1 axis respectively, And when the out-of-plane direction is called the z1 axis, then the coating layer satisfies the three-dimensional refractive index relationship nx1≈ny1>nz1, where nx1 is the refractive index in the direction of the x1 axis, ny1 is the refractive index in the direction of the y1 axis, and nz1 is the refractive index in the direction of the z1 axis. 14. The optical compensation film of claim 11 or 12, wherein said layer (A) comprises a coating layer having an out-of-plane retardation Rth1 of 30-2000 nm, wherein the out-of-plane retardation Rth1 is when detected with light having a measurement wavelength of 589 nm. The delay is represented by the following expression (3): Rth1＝((nx1+ny1)/2-nz1)×d1 (3) Wherein d1 represents the thickness of the coating layer (A), and the unit is nm. 15. The optical compensation film of claim 11 or 12, wherein said layer (A) comprises a coating layer having a wavelength dependence of retardation of 1.1 or lower, i.e. R450/R589, wherein the wavelength dependence of the retardation is determined by the slope The ratio of the retardation R450 of the coating layer at 40 degrees and detected with light having a measurement wavelength of 450 nm to the retardation R589 of the coating layer inclined at 40 degrees and detected with light having a measurement wavelength of 589 nm is represented. 16. The optical compensation film of claim 11 or 12, wherein said layer (B) comprises a stretched film layer, wherein when the in-plane stretching direction of the stretched film is referred to as the x2 axis, the plane perpendicular to the stretching direction When the inner direction is called the y2 axis, and the out-of-plane direction of the film, that is, the thickness direction is called the z2 axis, then the film satisfies the three-dimensional refractive index relationship nx2>ny2≥nz2, where nx2 is the refractive index in the direction of the x2 axis, ny2 is the refractive index in the direction of the y2 axis, and nz2 is the refractive index in the direction of the z2 axis, wherein the stretched film layer (B) has an in-plane retardation Re of 20 nm or more, wherein the in-plane retardation is represented by the following expression (4) when detected with light having a measurement wavelength of 589 nm: Re＝(nx2-ny2)×d2 (4) Wherein d2 represents the thickness of the stretched film layer (B), and its unit is nm. 17. The optical compensation film of claim 11 or 12, wherein the layer (B) comprises a stretched film layer (B) comprising at least one resin selected from the group consisting of polycarbonate resins, polyethersulfone resins, cyclic Polyolefin resins and cellulose resins. 18. The optical compensation film of claim 11 or 12, wherein the in-plane slow axis direction in the optical compensation film is referred to as the x3 axis, the in-plane direction perpendicular to the x3 axis is referred to as the y3 axis, and the out-of-plane direction of the film That is, when the thickness direction is referred to as the z3 axis, the film has an orientation parameter Nz of 1.1 or more when detected with light having a measurement wavelength of 589 nm, wherein the orientation parameter is represented by the following expression (5), where nx3 is the x3 axis The average refractive index in the direction, ny3 is the average refractive index in the direction of the y3 axis, and nz3 is the average refractive index in the direction of the z3 axis, Nz＝(nx3-nz3)/(nx3-ny3) (5). 19. The optical compensation film according to claim 11 or 12, which is an optical compensation film for a liquid crystal display element. 20. A method of manufacturing an optical compensation film, comprising coating a maleimide resin solution on a stretched film (B) and drying the coated solution to become a coating layer (A). 21. The method for manufacturing an optical compensation film according to claim 20, wherein the maleimide resin solution is a solution of a maleimide resin comprising a maleimide residue unit represented by the following formula (1) : [chemical 4] Wherein R ₁ represents a straight-chain alkyl group, branched-chain alkyl group or cycloalkyl group with 1-18 carbon atoms, a halogen group, an ether group, an ester group or an amide group. 22. An optical compensation layer, which is an optical compensation layer obtained by uniaxially stretching a coating layer comprising a maleimide resin, wherein when the direction of the stretching axis in the coating layer is referred to as the x4 axis, the same as the stretching axis When the direction perpendicular to the stretching direction is called the y4 axis, and the out-of-plane direction is called the z4 axis, then the optical compensation layer satisfies the three-dimensional refractive index relationship nx4>ny4>nz4, where nx4 is the refractive index in the direction of the x4 axis, ny4 is the refractive index in the direction of the y4 axis, and nz4 is the refractive index in the direction of the z4 axis. 23. The optical compensation layer according to claim 22, characterized in comprising a maleimide resin comprising N-substituted maleimide residue units represented by the following general formula (1) : [chemical 5]

Wherein R ₁ represents a straight-chain alkyl group, branched-chain alkyl group or cycloalkyl group with 1-18 carbon atoms, a halogen group, an ether group, an ester group or an amide group. 24. The optical compensation layer according to claim 22 or 23, characterized in that the optical compensation layer has an in-plane retardation Re1 of 20 nm or more, wherein the in-plane retardation is given by the following expression ( 6) means: Re1＝(nx4-ny4)×d3 (4) Wherein d3 represents the thickness of the optical compensation layer, and its unit is nm. . 25. The optical compensation layer of claim 22 or 23, wherein the optical compensation layer has an out-of-plane retardation Rth2 of 30-2000 nm, wherein the out-of-plane retardation is given by the following expression (7) when using light detection with a measurement wavelength of 589 nm express: Rth2＝((nx4+ny4)/2-nz4)×d4 (2) Wherein d4 represents the thickness of the optical compensation layer, and its unit is nm. . 26. The optical compensation layer of claim 22 or 23, which has a wavelength dependence of 1.1 or lower i.e. R450/R589, wherein the wavelength dependence of the retardation is determined by the retardation R450 and the retardation at 589nm at a measurement wavelength of 450nm Retardation R589 ratio expressed at the measured wavelength. 27. An optical compensation layer for a liquid crystal display element, comprising the optical compensation layer according to claim 22 or 23.