JP2009156908A - Optical compensation film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical compensation film in which the relationship of three-dimensional refractive index becomes nx>ny> nz by uniaxial stretching of a coating film, and the wavelength dependence of the retardation amount is small.
An optical compensation film obtained by uniaxially stretching a coating film made of a maleimide resin, in which the stretching axis direction of the coating film is an x axis, a direction perpendicular to the y axis is a y axis, and an out-of-plane direction is z. The three-dimensional refractive index relationship when the refractive index in the x-axis direction is nx, the refractive index in the y-axis direction is ny, and the refractive index in the z-axis direction is nz is nx>ny> nz. Optical compensation film.
[Selection figure] None

Description

  The present invention relates to an optical compensation film, and more particularly to an optical compensation film for a liquid crystal display element.

  Liquid crystal displays are widely used as the most important display devices in the multimedia society, from mobile phones to computer monitors, notebook computers, and televisions. Many optical films are used in liquid crystal displays to improve display characteristics.

  In particular, the optical compensation film plays a major role in improving the contrast when viewed from the front or obliquely, compensating for the color tone, and the like. As a conventional optical compensation film, a biaxially stretched film of polycarbonate, cyclic polyolefin, or cellulose resin is used. However, these films have problems such as the need for a biaxial stretching process and difficulty in obtaining uniformity of retardation in the biaxial stretching process. In addition, it becomes even more difficult to control the retardation, particularly in a large-area film.

  As a method for solving the problem due to biaxial stretching, an optical compensation film by coating (coating) has been studied.

  Harris and Chen of Akron University have proposed an optical compensation film made of rigid rod-like polyimide, polyester, polyamide, poly (amide-imide), and poly (ester-imide) (see, for example, Patent Documents 1 and 2). Since these materials have spontaneous molecular orientation, they are characterized by developing a phase difference without undergoing a stretching process by coating.

  Furthermore, an optical compensation film made of polyimide with improved polyimide coating properties (solubility in a solvent) (see, for example, Patent Document 3), and a polarizing plate in which a discotic liquid crystal compound is coated on a protective film of a polarizing plate ( For example, refer to Patent Document 4).

US Pat. No. 5,344,916 Japanese National Patent Publication No. 10-508048 Japanese Patent Laid-Open No. 2005-070745 Japanese Patent No. 2565644

  However, since the polymer used in the methods proposed in Patent Documents 1 to 3 is an aromatic polymer, the wavelength dependency of the phase difference amount is large, and when used as an optical compensation film of a liquid crystal display element, color misregistration, etc. It has a problem of image quality degradation.

  In addition, the method using the discotic liquid crystal compound proposed in Patent Document 4 not only has problems such as requiring uniform alignment of the liquid crystal compound, complicating the coating process, and large alignment unevenness. Since the liquid crystal compound is mainly composed of an aromatic compound, it also has a quality problem that the wavelength dependency of the retardation amount is large.

  Therefore, the present invention is intended to provide an optical compensation film having excellent optical characteristics, and more specifically, the optical compensation function is expressed by uniaxially stretching after coating, and its An object of the present invention is to provide an optical compensation film having a small wavelength dependency of the phase difference amount.

  As a result of intensive studies on the above problems, the inventors of the present invention are coating films obtained by uniaxially stretching a coating film made of a maleimide resin, and an optical compensation film having a specific relationship in three-dimensional refractive index is optical compensation. It has been found that an optical compensation film having a function, particularly an optical compensation film suitable for optical compensation for a liquid crystal display device, has been completed.

  That is, the present invention is an optical compensation film obtained by uniaxially stretching a coating film made of a maleimide resin, wherein the stretching axis direction of the coating film is an x-axis, the direction orthogonal to the y-axis is an out-of-plane direction Is the z-axis, the refractive index in the x-axis direction is nx, the refractive index in the y-axis direction is ny, and the refractive index in the z-axis direction is nz, the three-dimensional refractive index relationship is nx> ny> nz. The present invention relates to a characteristic optical compensation film.

  The present invention is described in detail below.

  The optical compensation film of the present invention is an optical compensation film obtained by uniaxially stretching a coating film made of a maleimide resin. Examples of the maleimide resin include an N-substituted maleimide polymer resin and an N-substituted maleimide. -Maleic anhydride copolymer resin and the like.

  Examples of the N-substituted maleimide residue unit constituting the N-substituted maleimide polymer resin include an N-substituted maleimide residue unit represented by the following general formula (1).

（ここで、Ｒ_１は、炭素数１〜１８の直鎖状アルキル基，分岐状アルキル基，環状アルキル基、ハロゲン基、エーテル基、エステル基、アミド基を示す。）
一般式（１）で示されるＮ−置換マレイミド残基単位におけるＲ_１は、炭素数１〜１８の直鎖状アルキル基，分岐状アルキル基，環状アルキル基、ハロゲン基、エーテル基、エステル基、アミド基であり、炭素数１〜１８の直鎖状アルキル基としては、例えばメチル基、エチル基、ｎ−プロピル基、ｎ−ブチル基、ｎ−ヘキシル基、ｎ−オクチル基、ｎ−ラウリル基等が挙げられ、炭素数１〜１８の分岐状アルキル基としては、例えばイソプロピル基、イソブチル基、ｓ−ブチル基、ｔ−ブチル基等が挙げられ、炭素数１〜１８の環状アルキル基としては、例えばシクロヘキシル基が挙げられ、ハロゲン基としては、例えば塩素、臭素、フッ素、ヨウ素等があげられる。

(Here, R ₁ represents a linear alkyl group having 1 to 18 carbon atoms, a branched alkyl group, a cyclic alkyl group, a halogen group, an ether group, an ester group, or an amide group.)
R ₁ in the N-substituted maleimide residue unit represented by the general formula (1) is a linear alkyl group having 1 to 18 carbon atoms, a branched alkyl group, a cyclic alkyl group, a halogen group, an ether group, an ester group, Examples of the linear alkyl group having 1 to 18 carbon atoms that is an amide group include a methyl group, an ethyl group, an n-propyl group, an n-butyl group, an n-hexyl group, an n-octyl group, and an n-lauryl group. Examples of the branched alkyl group having 1 to 18 carbon atoms include isopropyl group, isobutyl group, s-butyl group, t-butyl group and the like, and examples of the cyclic alkyl group having 1 to 18 carbon atoms include Examples include a cyclohexyl group, and examples of the halogen group include chlorine, bromine, fluorine, iodine and the like.

  Specific examples of the N-substituted maleimide residue unit represented by the general formula (1) include an N-methylmaleimide residue unit, an N-ethylmaleimide residue unit, an N-chloroethylmaleimide residue unit, and N-methoxy. Ethylmaleimide residue unit, Nn-propylmaleimide residue unit, Nn-butylmaleimide residue unit, Nn-hexylmaleimide residue unit, Nn-octylmaleimide residue unit, Nn- Laurylmaleimide residue unit, N-isopropylmaleimide residue unit, N-isobutylmaleimide residue unit, Ns-butylmaleimide residue unit, Nt-butylmaleimide residue unit, N-cyclohexylmaleimide residue unit, etc. 1 type or 2 types or more are mentioned, and it is easy to express a phase difference, and it becomes an optical compensation film excellent in solubility in a solvent and mechanical strength. N-ethylmaleimide residue unit, Nn-butylmaleimide residue unit, N-isobutylmaleimide residue unit, Ns-butylmaleimide residue unit, Nt-butylmaleimide residue unit, N -N-Hexylmaleimide residue units and Nn-octylmaleimide residue units are preferred.

  Specific N-substituted maleimide polymer resins include, for example, N-methylmaleimide polymer resin, N-ethylmaleimide polymer resin, N-chloroethylmaleimide polymer resin, N-methoxyethylmaleimide polymer resin, N- n-propylmaleimide polymer resin, Nn-butylmaleimide polymer resin, Nn-hexylmaleimide polymer resin, Nn-octylmaleimide polymer resin, Nn-laurylmaleimide polymer resin, N- One or more of isopropylmaleimide polymer resin, N-isobutylmaleimide polymer resin, Ns-butylmaleimide polymer resin, Nt-butylmaleimide polymer resin, N-cyclohexylmaleimide polymer resin, etc. Optical compensation that is particularly easy to express phase difference, has excellent solubility in solvents, and mechanical strength N-ethylmaleimide polymer resin, Nn-butylmaleimide polymer resin, N-isobutylmaleimide polymer resin, Ns-butylmaleimide polymer resin, Nt-butylmaleimide polymer resin Nn-hexylmaleimide polymer resin, Nn-octylmaleimide polymer resin, and the like are preferable.

  Examples of N-substituted maleimide-maleic anhydride copolymer resins include N-methylmaleimide-maleic anhydride copolymer resins, N-ethylmaleimide-maleic anhydride copolymer resins, and N-chloroethylmaleimide- Maleic anhydride copolymer resin, N-methoxyethylmaleimide-maleic anhydride copolymer resin, Nn-propylmaleimide-maleic anhydride copolymer resin, Nn-butylmaleimide-maleic anhydride copolymer Resin, Nn-hexylmaleimide-maleic anhydride copolymer resin, Nn-octylmaleimide-maleic anhydride copolymer resin, Nn-laurylmaleimide-maleic anhydride copolymer resin, N-isopropyl Maleimide-maleic anhydride copolymer resin, N-isobutylmaleimide-maleic anhydride copolymer tree , N-s-butyl maleimide - can be exemplified maleic anhydride copolymer resin and the like - maleic anhydride copolymer resin, N-t-butyl maleimide - maleic anhydride copolymer resin, N- cyclohexyl maleimide.

  Among them, as the maleimide resin, the Nn-ethylmaleimide polymer resin, Nn-, and the like can be obtained as an optical compensation film having excellent film-forming properties during film formation, optical compensation function, and heat resistance. A butylmaleimide polymer resin, an Nn-hexylmaleimide polymer resin, an Nn-octylmaleimide polymer resin, and an Nn-octylmaleimide-maleic anhydride copolymer resin are preferable.

  Further, the maleimide resin constituting the optical compensation film of the present invention contains a residue unit other than the N-substituted maleimide residue unit and the maleic anhydride residue unit without departing from the object of the present invention. The residue unit may be, for example, a styrene residue unit such as a styrene residue unit or an α-methylstyrene residue unit; an acrylic acid residue unit; a methyl acrylate residue unit, or an ethyl acrylate residue. Units, acrylate residue units such as butyl acrylate residue units; methacrylic acid residue units; methacrylic acid ester residues such as methyl methacrylate residue units, ethyl methacrylate residue units, butyl methacrylate residue units Unit: vinyl ester residue such as vinyl acetate residue and vinyl propionate residue; acrylonitrile residue; one or two of methacrylonitrile residue It can be mentioned more.

Moreover, as this maleimide-type resin, the number average molecular weight (Mn) of standard polystyrene conversion obtained from the elution curve measured by gel permeation chromatography (henceforth GPC) is 1 * 10 < ³ > or more. In particular, it is preferably 2 × 10 ⁴ or more and 2 × 10 ⁵ or less because it becomes an optical compensation film having excellent mechanical properties and excellent moldability during film formation.

  The maleimide resin constituting the optical compensation film of the present invention may be produced by any method as long as the maleimide resin is obtained. For example, N-substituted maleimides, maleic anhydride, and in some cases It can be produced by performing radical polymerization or radical copolymerization using a monomer copolymerizable with N-substituted maleimides. Examples of N-substituted maleimides include N-methylmaleimide, N-ethylmaleimide, N-chloroethylmaleimide, N-methoxyethylmaleimide, Nn-propylmaleimide, Nn-butylmaleimide, N- 1 such as n-hexylmaleimide, Nn-octylmaleimide, Nn-laurylmaleimide, N-isopropylmaleimide, N-isobutylmaleimide, Ns-butylmaleimide, Nt-butylmaleimide, N-cyclohexylmaleimide Examples of the copolymerizable monomer include styrenes such as styrene and α-methylstyrene; acrylic acid; acrylic esters such as methyl acrylate, ethyl acrylate, and butyl acrylate. Methacrylic acid; methyl methacrylate, methacrylate Methacrylic acid esters such as butyl methacrylate, vinyl acetate, vinyl propionate, vinyl pivalate, vinyl laurate, vinyl stearate, etc .; acrylonitrile; one or more of methacrylonitrile, etc. Can be mentioned.

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

  Examples of the polymerization initiator used in the radical polymerization method include benzoyl peroxide, lauryl peroxide, octanoyl peroxide, acetyl peroxide, di-t-butyl peroxide, t-butylcumyl peroxide, and dicumyl peroxide. , Organic peroxides such as t-butylperoxyacetate and t-butylperoxybenzoate; 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2′-azobis (2-butyronitrile), 2 , 2′-azobisisobutyronitrile, dimethyl-2,2′-azobisisobutyrate, 1,1′-azobis (cyclohexane-1-carbonitrile) and the like.

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

  Moreover, the polymerization temperature at the time of performing radical polymerization can be suitably set according to the decomposition temperature of a polymerization initiator, and generally it is preferable to carry out in the range of 40-150 degreeC.

  The optical compensation film of the present invention is a film characterized by uniaxially stretching a coating film made of the maleimide resin, and particularly has an excellent optical compensation function when used as an optical compensation film. In general, biaxial stretching makes it very difficult to control the three-dimensional refractive index. If the display area of the display is increased and the area of the optical compensation film is increased accordingly, it is difficult to uniformly control all areas, resulting in deterioration of yield and the like. In this invention, it can be set as the optical compensation film excellent in the optical compensation function by uniaxially stretching a specific coating film. The optical compensation film of the present invention is an optical compensation film obtained by uniaxially stretching a coating film made of a maleimide resin, wherein the stretching axis direction of the coating film is an x-axis, and a direction orthogonal to that is a y-axis, a surface The three-dimensional refractive index relationship is nx> ny> nz when the outer direction is the z-axis, the refractive index in the x-axis direction is nx, the refractive index in the y-axis direction is ny, and the refractive index in the z-axis direction is nz. This is an optical compensation film characterized by the above.

Further, the retardation amount (Re) in the in-plane direction of the optical compensation film of the present invention can be easily controlled by the thickness of the coating film made of the maleimide resin and the uniaxial stretching conditions, and the retardation film Therefore, the in-plane retardation amount (Re) measured with light having a measurement wavelength of 589 nm represented by the following formula (2) is preferably 20 nm or more, particularly 30 nm or more. It is preferably 200 nm or less, more preferably 40 nm or more and 150 nm or less.
Re = (nx−ny) × d (2)
(Here, d represents the film thickness (nm) of the optical compensation film.)
Further, the out-of-plane retardation amount (Rth) of the optical compensation film of the present invention can be easily controlled by the thickness of the coating film made of the maleimide resin and the uniaxial stretching conditions. Therefore, the out-of-plane retardation (Rth) measured with light having a measurement wavelength of 589 nm represented by the following formula (3) is preferably in the range of 30 to 2000 nm. It is preferably in the range of 50 to 1000 nm, and more preferably in the range of 80 to 400 nm because the viewing angle improvement effect of the liquid crystal display element is excellent.
Rth = ((nx + ny) / 2−nz) × d (3)
(Here, d represents the film thickness (nm) of the optical compensation film.)
The optical compensation film of the present invention is preferably a liquid crystal display element having a small color shift when used in a liquid crystal display element, so that the wavelength dependency of the phase difference amount is preferably small. The wavelength dependency (R450 / R589) of the phase difference amount indicated by the ratio of the phase difference amount (R450) and the phase difference amount (R589) measured at a measurement wavelength of 589 nm is 1.1 or less, particularly 1.08 or less. preferable.

  The film thickness of the optical compensation film of the present invention is preferably from 1 to 200 μm, particularly preferably from 5 to 100 μm, more preferably from 10 to 10 μm because an optical compensation film having excellent surface smoothness and viewing angle improvement effects can be obtained. 30 μm.

  Since the optical compensation film of the present invention has good image quality characteristics when used in a liquid crystal display element, the light transmittance of the optical compensation film is preferably 85% or more, particularly preferably 90% or more. is there. Further, the haze (cloudiness) of the optical compensation film is preferably 2 or less, particularly preferably 1 or less.

  The optical compensation film of the present invention is preferably one having high heat resistance from the stability of quality when used in a liquid crystal display device, and preferably has a glass transition temperature of 100 ° C. or higher, particularly preferably 120 ° C. or higher, and further preferably. Is 135 ° C. or higher.

  The optical compensation film of the present invention is characterized in that a coating film made of a maleimide resin is uniaxially stretched, and as a preferred production method, a solution of a maleimide resin on a film substrate such as cellulose resin or polyethylene terephthalate resin (PET) is used. A method of uniaxial stretching after coating, drying, and the like. The coating method is a method in which a solution obtained by dissolving a maleimide resin in a solvent is applied on a film, and then the solvent is removed by heating or the like, followed by uniaxial stretching. As a coating method at that time, for example, a doctor blade method, a bar coater method, a gravure coater method, a slot die coater method, a lip coater method, a comma coater method or the like is used. In industry, the gravure coater method is generally used for thin film coating, and the comma coater method is generally used for thick film coating.

  There are no particular restrictions on the solvent used, for example, aromatic solvents such as toluene, xylene, chlorobenzene, nitrobenzene; ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone; dimethyl ether, diethyl ether, methyl-t-butyl ether Ether solvents such as tetrahydrofuran, dioxane, etc .; acetate solvents such as methyl acetate, ethyl acetate, acetic acid-n-propyl, isopropyl acetate, butyl acetate; hydrocarbon solvents such as hexane, cyclohexane, octane, decane; methanol, Alcohol solvents such as ethanol, propanol and butanol; Chlorine solvents such as carbon tetrachloride, chloroform, methylene chloride, dichloroethane and trichloroethane; dimethylformamide and dimethylacetate Amide solvents amide; N- methylpyrrolidone and the like, which may be used in combination of two or more. In solution coating, the coating solution viscosity is an extremely important factor for coating with high transparency and excellent thickness accuracy and surface smoothness. The coating solution viscosity is 10 to 10,000 cps. Is preferable, and in particular, 10 to 5000 cps is preferable.

  The coating thickness of the maleimide resin at this time is determined by the amount of retardation in the thickness direction of the coating film, and among them, an optical compensation film having excellent surface smoothness and viewing angle improvement effect can be obtained. It is preferably 1 to 200 μm, more preferably 5 to 100 μm, and still more preferably 10 to 30 μm.

  The uniaxial stretching of the optical compensation film of the present invention is not particularly limited, and is generally stretched under a stretching temperature condition that is −30 to 50 ° C. higher than the glass transition temperature of the coating film measured using a differential scanning calorimeter. The film can be stretched at a magnification of 1.1 to 5 times. In particular, since the optical characteristics such as phase difference, light transmittance, and haze are greatly affected by thickness, it is preferable to reduce the thickness unevenness as much as possible. In stretching the coating film of the present invention, it is possible to lower the stretching temperature by controlling the drying conditions during the production of the coating film and leaving the solvent. Moreover, it can also peel from a base film and can be extended | stretched, and it can also be extended with a base film.

  Examples of the uniaxial stretching method that can be employed in the present invention include a method of stretching with a tenter, a method of rolling and stretching with a calendar, and a method of stretching between rolls.

  The optical compensation film of the present invention can be peeled off from the base film and used as a laminate with the base film or another optical film. In particular, as another optical film when used as a laminate with another optical film, a cellulose-based film and a cyclic polyolefin film are preferable in terms of transparency and strength.

  The optical compensation film of the present invention can be used by being laminated with a polarizing plate.

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

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

  The optical compensation film of the present invention includes other polymers, surfactants, polymer electrolytes, conductive complexes, inorganic fillers, pigments, dyes, antistatic agents, antiblocking agents, lubricants and the like within the scope of the invention. It may be blended.

  The optical compensation film of the present invention is a liquid crystal display element, particularly a VA-mode because the coating film made of maleimide resin is uniaxially stretched to express the optical compensation function and the control of the optical compensation function is easy. It is useful as an optical compensation film effective for improving the contrast and viewing angle characteristics of a liquid crystal television in the OCB mode.

  EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

-Measurement of number average molecular weight of maleimide resin-
Using gel permeation chromatography (GPC) (manufactured by Tosoh Corporation, trade name HLC-802A), dimethylformamide was used as a solvent to obtain a standard polystyrene equivalent value.

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

~ Measurement of light transmittance ~
As an evaluation of transparency, light transmittance was measured in accordance with JIS K 7361-1 (1997 edition).

~ Measurement of haze ~
As an evaluation of transparency, haze was measured according to JIS K 7136 (2000 version).

~ Calculation of 3D refractive index ~
Using a sample tilt type automatic birefringence meter (trade name KOBRA-WR, manufactured by Oji Scientific Instruments Co., Ltd.), the elevation angle was changed and the three-dimensional refractive index was measured with light having a measurement wavelength of 589 nm. Further, the in-plane retardation amount (Re) and the out-of-plane retardation amount (Rth) were calculated from the three-dimensional refractive index.

  The wavelength dependence (R450 / R589) of the phase difference amount is indicated by the ratio of the phase difference amount measured with light having a measurement wavelength of 450 nm and the phase difference amount measured with light having a measurement wavelength of 589 nm.

Synthesis Example 1 (Production Example of Nn-Ethylmaleimide Polymer Resin)
In a glass sealed tube, 45 g of Nn-ethylmaleimide and 0.05 g of dimethyl-2,2′-azobisisobutyrate as a polymerization initiator were charged, and after nitrogen substitution, a polymerization temperature of 60 ° C. and a polymerization time of 5 hours were obtained. A radical polymerization reaction was performed under the conditions. After the reaction, chloroform was added to form a polymer solution, and the polymer was precipitated by mixing with excess methanol. The obtained polymer was filtered, sufficiently washed with methanol, and dried at 80 ° C. to obtain 20 g of Nn-ethylmaleimide polymer. The number average molecular weight of the obtained Nn-ethylmaleimide polymer resin was 80,000. Synthesis example 2 (Production example of Nn-butylmaleimide polymer resin)
A glass sealed tube was charged with 32.4 g of Nn-butylmaleimide and 0.054 g of dimethyl-2,2′-azobisisobutyrate as a polymerization initiator, and after substitution with nitrogen, a polymerization temperature of 60 ° C. and a polymerization time of 5 The radical polymerization reaction was performed under time conditions. After the reaction, chloroform was added to form a polymer solution, and the polymer was precipitated by mixing with excess methanol. The obtained polymer was filtered, sufficiently washed with methanol, and dried at 80 ° C. to obtain 20 g of Nn-butylmaleimide polymer. The number average molecular weight of the obtained Nn-butylmaleimide polymer resin was 120,000.

Synthesis Example 3 (Production Example of Nn-Octylmaleimide-Maleic Anhydride Copolymer Resin)
In a glass sealed tube, 26 g of Nn-octylmaleimide, 2.4 g of maleic anhydride, 0.036 g of dimethyl-2,2′-azobisisobutyrate as a polymerization initiator were charged, and after substitution with nitrogen, the polymerization temperature A radical polymerization reaction was carried out under conditions of 60 ° C. and a polymerization time of 5 hours. After the reaction, chloroform was added to form a polymer solution, and the polymer was precipitated by mixing with excess methanol. The obtained polymer was filtered, sufficiently washed with methanol, and dried at 80 ° C. to obtain 19 g of Nn-octylmaleimide-maleic anhydride copolymer resin. The obtained Nn-octylmaleimide-maleic anhydride copolymer resin contained 20% by weight of maleic anhydride residue, and the number average molecular weight was 140000.

Example 1
The Nn-ethylmaleimide polymer resin obtained in Synthesis Example 1 is dissolved in chloroform to form a 12% solution, cast onto a siliconized PET film by a coater, and dried at 90 ° C. for 15 minutes to form a coating film. Obtained. And it was 255 degreeC when it was set as the coating film of width 100mm and thickness 30 micrometers, and the glass transition temperature (Tg) of the coating film was measured.

  The obtained coating film was peeled and uniaxially stretched 1.5 times at 270 ° C. The obtained film had a thickness of 30 μm, a light transmittance of 92%, a haze of 0.6, and a three-dimensional refractive index of nx = 1.5252, ny = 1.5232, and nz = 1.5168. . The in-plane retardation amount (Re) of the film was 60 nm, and the out-of-plane retardation amount (Rth) was 222 nm. Further, R450 / R589 showing the wavelength dependence of the retardation amount was 1.07, and it had a function as an optical compensation film.

Example 2
The Nn-butylmaleimide polymer resin obtained in Synthesis Example 2 is dissolved in chloroform to form a 12% solution, cast onto a siliconized PET film by a coater, and dried at 90 ° C. for 15 minutes to form a coating film. Obtained. And when it was set as the coating film of width 50mm and thickness 25 micrometers, and the glass transition temperature (Tg) of the coating film was measured, it was 179 degreeC.

  The obtained coating film was peeled and uniaxially stretched 1.5 times at 190 ° C. The obtained film has a thickness of 20 μm, a light transmittance of 91.6%, a haze of 0.5, and a three-dimensional refractive index of nx = 1.5182, ny = 1.5145, nz = 1.5078. there were. The in-plane retardation amount (Re) of the film was 74 nm, and the out-of-plane retardation amount (Rth) was 171 nm. Further, R450 / R589 showing the wavelength dependence of the retardation amount was 1.06, and it had a function as an optical compensation film.

Example 3
The Nn-octylmaleimide-maleic anhydride copolymer resin obtained in Synthesis Example 3 is dissolved in tetrahydrofuran to give a 15% solution, cast onto a cyclic polyolefin film substrate with a coater, and dried at 90 ° C. for 10 minutes. A coating film having a thickness of 75 μm was obtained. The Tg of the coating film was 150 ° C. The obtained coated film was uniaxially stretched 1.5 times at 160 ° C. together with the cyclic polyolefin substrate. After stretching, the film was peeled off from the substrate film and evaluated for optical properties.

  The obtained film has a thickness of 20 μm, a light transmittance of 92.2%, a haze of 0.5, and a three-dimensional refractive index of nx = 1.5079, ny = 1.05056, nz = 1.5033. there were. The in-plane retardation amount of the film was 115 nm, and Rth = 172.5 nm. Further, R450 / R589 showing the wavelength dependence of the retardation amount was 1.04, and it had a function as an optical compensation film.

Claims (7)

An optical compensation film obtained by uniaxially stretching a coating film made of a maleimide resin, wherein the stretching axis direction of the coating film is an x axis, a direction perpendicular to the x axis is a y axis, an out-of-plane direction is a z axis, and x An optical compensation film characterized in that the three-dimensional refractive index relationship is nx> ny> nz when the refractive index in the axial direction is nx, the refractive index in the y-axis direction is ny, and the refractive index in the z-axis direction is nz. . 2. The optical compensation film according to claim 1, comprising a maleimide resin composed of an N-substituted maleimide residue unit represented by the following general formula (1).

(Here, R ₁ represents a linear alkyl group having 1 to 18 carbon atoms, a branched alkyl group, a cyclic alkyl group, a halogen group, an ether group, an ester group, or an amide group.) 3. The optical compensation film according to claim 1, comprising a maleimide-maleic anhydride copolymer resin comprising a maleimide residue unit and a maleic anhydride residue unit represented by the general formula (1). The optical compensation film according to any one of claims 1 to 3, wherein an in-plane retardation (Re) measured with light having a measurement wavelength of 589 nm represented by the following formula (2) is 20 nm or more.
Re = (nx−ny) × d (2)
(Here, d represents the film thickness (nm) of the optical compensation film.) 5. The optical according to claim 1, wherein an out-of-plane retardation amount (Rth) measured with light having a measurement wavelength of 589 nm represented by the following formula (3) is in a range of 30 to 2000 nm. Compensation film.
Rth = ((nx + ny) / 2−nz) × d (3)
(Here, d represents the film thickness (nm) of the optical compensation film.) The wavelength dependence (R450 / R589) of the phase difference indicated by the ratio of the phase difference (R450) measured at a measurement wavelength of 450 nm and the phase difference (R589) measured at a measurement wavelength of 589 nm is 1.1 or less. The optical compensation film according to any one of claims 1 to 5. An optical compensation film for a liquid crystal display device, comprising the optical compensation film according to claim 1.