JP2011102867A - Optical compensation film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an in-plane retardation amount Re of 30 or more, an out-of-plane retardation amount Rth of 30 or more, no film warp (curl), a small wavelength dependency of the retardation amount, and excellent film smoothness. An optical compensation film is provided.
An optical film obtained by uniaxially stretching a film in which at least two maleimide-based resin layers are laminated on a transparent resin film substrate, wherein two arbitrary axes perpendicular to each other in the plane of the optical film are x-axis, When the y-axis, the 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, the refractive index in the z-axis direction is nz, and the stretching axis direction of the optical film is the x-axis, An optical compensation film, wherein the three-dimensional refractive index relationship is nx>ny> nz.
[Selection figure] None

Description

  The present invention is an optical film obtained by uniaxially stretching an optical compensation film, particularly a film in which two or more maleimide resin layers are laminated on a transparent resin film substrate, and is used for a liquid crystal display device having an optical compensation function and smoothness. The present invention relates to an optical compensation film.

  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. These films have problems such as the need for a biaxial stretching process and difficulty in obtaining uniformity of retardation in the stretching process. In particular, in a large-area film, it becomes even more difficult to control the retardation produced by biaxial stretching.

  As a method for solving the problem due to stretching, studies have been made on an optical compensation film that exhibits an uncompensated optical compensation function by coating.

  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 protective film of a polarizing plate is coated with a discotic liquid crystal compound (for example, Patent Document 4) and the like have been proposed.

  Moreover, the stretched film (for example, refer patent document 5) which consists of a phenylmaleimide-isobutene copolymer is proposed.

  Further, an optical compensation film formed by uniaxially stretching a coating film made of maleimide resin is disclosed (for example, see Patent Document 6).

US Pat. No. 5,344,916 Japanese National Patent Publication No. 10-508048 Japanese Patent Laid-Open No. 2005-070745 Japanese Patent No. 2565644 JP 2004-269842 A JP 2009-156908 A

  However, since the polymer used in the methods proposed in Patent Documents 1 to 3 is an aromatic polymer, the wavelength dependence of the retardation is large, and when used as an optical compensation film of a liquid crystal display element, image quality such as color shift is obtained. It had the subject of a fall.

  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 retardation is large.

  The stretched film obtained in Patent Document 5 does not develop a phase difference only by coating (nx = ny = nz).

  Patent Document 6 describes a coating film obtained by uniaxially stretching a coated film. Regarding the retardation property and the improvement effect of film smoothness when a film coated with two or more layers is uniaxially stretched. Not listed.

  Accordingly, the present invention aims to provide an optical compensation film having excellent optical properties, and more specifically, a specific maleimide type having excellent transparency of two or more layers on a transparent resin film substrate. An optical compensation film which is a film obtained by uniaxially stretching a film in which a resin layer is laminated, and has an improved in-plane retardation amount (hereinafter referred to as Re) and out-of-plane retardation amount (hereinafter referred to as Rth), which is superior in film smoothness. Is intended to provide.

  As a result of intensive studies in view of the above-mentioned problems, the present inventors have uniaxially stretched a film in which at least two maleimide-based resin layers are laminated on a transparent resin film substrate, particularly optical compensation for liquid crystal display elements. The present invention has been found to be a suitable optical compensation film.

  That is, the present invention is an optical film obtained by uniaxially stretching a film in which at least two maleimide resin layers are laminated on a transparent resin film substrate, and any two axes orthogonal in the plane of the optical film are x. When the axis, y-axis, out-of-plane direction is z-axis, x-axis direction refractive index is nx, y-axis direction refractive index is ny, z-axis direction refractive index is nz, and the stretching direction of the optical film is x-axis The present invention relates to an optical compensation film characterized in that the three-dimensional refractive index relationship is nx> ny> nz.

  Hereinafter, the present invention will be described in detail.

  Examples of the transparent resin film substrate used for the optical compensation film of the present invention include cellulose-based resins such as triacetyl cellulose, resin films such as cyclic polyolefin and polyethylene terephthalate (PET), and among them, transparency, strength, adhesion Cellulosic resin films are preferred, and triacetyl cellulose films are particularly preferred because they are optical compensation films with excellent properties. Here, the cellulose resin film may be a blend of a birefringence improver for controlling birefringence in addition to an additive such as a plasticizer and an ultraviolet stabilizer, and also a stretch-oriented cellulose. A resin film may be used. As the plasticizer, UV stabilizer and birefringence improver used here, known ones can be used. As a means for stretching a cellulose resin film, one stretched by a known method as a uniaxial or biaxial stretching method. It's okay.

  Examples of maleimide resins used in the maleimide resin layer in the optical compensation film of the present invention include N-substituted maleimide polymer resins and N-substituted maleimide-maleic anhydride copolymer resins. Examples of the constituting N-substituted maleimide residue unit include an N-substituted maleimide residue unit represented by the following general formula (1).

(Here, R ₁ is a linear alkyl group having 1 to 18 carbon atoms, a branched alkyl group having 1 to 18 carbon atoms, a cyclic alkyl group having 1 to 18 carbon atoms, a halogen group, an ether group, an ester group, Indicates 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 having 1 to 18 carbon atoms, or cyclic having 1 to 18 carbon atoms. An alkyl group, a halogen group, an ether group, an ester group, an amide group. Examples of the linear alkyl group having 1 to 18 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an n-butyl group, and an n- A hexyl group, an n-octyl group, an n-lauryl group and the like can be mentioned. Examples of the branched alkyl group having 1 to 18 carbon atoms include isopropyl group, isobutyl group, s-butyl group and t-butyl group. Examples of the cyclic alkyl group having 1 to 18 carbon atoms include a cyclohexyl group, and examples of the halogen group include chlorine, bromine, fluorine, iodine and the like, preferably an n-butyl group and an n-hexyl group. Group, n-octyl group, isobutyl group, s-butyl group and t-butyl group, particularly preferably n-butyl group, n-hexyl group and n-octyl group.

  Specific examples of the N-substituted maleimide residue unit represented by the general formula (1) include, for example, N-methylmaleimide residue unit, N-ethylmaleimide residue unit, Nn-propylmaleimide residue unit, N -N-butylmaleimide residue unit, N-hexylmaleimide residue unit, Nn-octylmaleimide residue unit, Nn-laurylmaleimide residue unit, N-isopropylmaleimide residue unit, N-isobutylmaleimide residue Group units, Ns-butylmaleimide residue units, Nt-butylmaleimide residue units, N-cyclohexylmaleimide residue units, N-chloroethylmaleimide residue units, N-methoxyethylmaleimide residue units, etc. An optical compensation film that includes one or two or more types, particularly that easily develops a phase difference, and is excellent in solubility in a solvent and mechanical strength. Therefore, Nn-butylmaleimide residue unit, Nn-hexylmaleimide residue unit, Nn-octylmaleimide residue unit, N-isobutylmaleimide residue unit, Ns-butylmaleimide residue unit Units and Nt-butylmaleimide residue units are preferable, and Nn-butylmaleimide residue units, Nn-hexylmaleimide residue units, and Nn-octylmaleimide residue units are particularly preferable.

  Specific N-substituted maleimide-maleic anhydride copolymer resins include, for example, N-methylmaleimide-maleic anhydride copolymer resin, N-ethylmaleimide-maleic anhydride copolymer resin, N-chloroethylmaleimide -Maleic anhydride copolymer resin, N-methoxyethylmaleimide-maleic anhydride copolymer resin, Nn-propylmaleimide-maleic anhydride copolymer resin, N-isopropylmaleimide-maleic anhydride copolymer resin Nn-butylmaleimide-maleic anhydride copolymer resin, N-isobutylmaleimide-maleic anhydride copolymer resin, Ns-butylmaleimide-maleic anhydride copolymer resin, Nt-butylmaleimide -Maleic anhydride copolymer resin, Nn-hexylmaleimide-maleic anhydride copolymer resin N- cyclohexyl maleimide - maleic anhydride copolymer resin, N-n-octyl maleimide - maleic anhydride copolymer resin, N-n-lauryl maleimide - can be mentioned maleic anhydride copolymer resin.

  Among them, the Nn-butylmaleimide polymer resin, the Nn-hexylmaleimide polymer resin, and the Nn-butylmaleimide polymer resin, which are particularly excellent in film forming properties during film formation, become an optical compensation film excellent in optical compensation function and heat resistance, Nn-octylmaleimide polymer resin and Nn-octylmaleimide-maleic anhydride copolymer resin are preferred.

  In addition, the maleimide resin constituting the maleimide resin layer in the optical compensation film of the present invention has a residue unit other than the N-substituted maleimide residue unit and the maleic anhydride residue unit as long as it does not depart from the purpose 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; Acrylic ester residue units such as ethyl acrylate residue units and butyl acrylate residue units; methacrylic acid residue units; methyl methacrylate residue units, ethyl methacrylate residue units, butyl methacrylate residue units, etc. Methacrylic acid ester residue units; vinyl acetate residue units such as vinyl acetate residue units and vinyl propionate residue units; acrylonitrile It can be exemplified one or two or more such methacrylonitrile residue unit; residue unit.

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 is an optical compensation film having excellent mechanical properties and excellent moldability during film formation.

  The maleimide resin constituting the maleimide resin layer in the optical compensation film of the present invention may be produced by any method as long as the maleimide resin can be obtained. For example, N-substituted maleimides and anhydrous maleic acid may be used. It can be produced by radical polymerization or radical copolymerization using an acid, and optionally a monomer copolymerizable with N-substituted maleimides. Examples of N-substituted maleimides include N-methylmaleimide, N-ethylmaleimide, N-chloroethylmaleimide, N-methoxyethylmaleimide, Nn-propylmaleimide, N-isopropylmaleimide, Nn- 1 such as butylmaleimide, N-isobutylmaleimide, Ns-butylmaleimide, Nt-butylmaleimide, Nn-hexylmaleimide, N-cyclohexylmaleimide, Nn-octylmaleimide, Nn-laurylmaleimide 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 Alcohol solvents such as cyclohexane, dioxane, tetrahydrofuran (THF), acetone, methyl ethyl ketone, dimethylformamide, isopropyl acetate, water, N-methylpyrrolidone, 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 an optical film obtained by uniaxially stretching a film containing at least two maleimide-based resin layers on a transparent resin film substrate. As a preferable production method, for example, a cellulose-based resin such as triacetyl cellulose is used. After coating a maleimide resin solution consisting of a maleimide resin and a solvent on a transparent resin film substrate such as cyclic polyolefin and PET, and drying to obtain a maleimide resin film on the transparent resin film substrate, the film is uniaxially stretched. The method of manufacturing by doing is mentioned.

  Here, the solvent to be used is not particularly limited as long as the maleimide resin can be dissolved. For example, aromatic solvents such as toluene, xylene, chlorobenzene and nitrobenzene; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone. Solvents; ether solvents such as dimethyl ether, diethyl ether, methyl-t-butyl ether, tetrahydrofuran, dioxane; acetate solvents such as methyl acetate, ethyl acetate, acetic acid-n-propyl, isopropyl acetate, butyl acetate; hexane, cyclohexane, Hydrocarbon solvents such as octane and decane; Alcohol solvents such as methanol, ethanol, propanol, and butanol; Chlorine solvents such as carbon tetrachloride, chloroform, methylene chloride, dichloroethane, and trichloroethane ; Dimethylformamide, amide solvents such as dimethylacetamide; N- methylpyrrolidone and the like, which may be used in combination of two or more.

  Moreover, as a method of removing a solvent, methods, such as natural drying and heat drying, can be used, for example.

  Examples of the method for coating the maleimide resin include a method in which a maleimide resin solution is coated on a transparent resin film substrate, and then the solvent is removed by heating or the like. As a coating method at that time, for example, a doctor blade method, a bar coater method, a gravure coater method, a slot die coater method, a lip coater method, a comma coater method or the like is used. 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. In order to apply at least two layers or more, a method of first coating the transparent resin film substrate using any one of the above-mentioned coating methods, repeating the coating after drying, or a transparent resin film substrate It is also possible to form two layers by simultaneously coating on both sides and drying. When two or more layers are repeatedly applied, it may be applied on both sides of the substrate, or may be applied on the already coated surface.

  The solvent used in the coating is not particularly limited as long as the maleimide resin can be dissolved. For example, aromatic solvents such as toluene, xylene, chlorobenzene, nitrobenzene; acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone. Ketone solvents such as dimethyl ether, diethyl ether, methyl-t-butyl ether, tetrahydrofuran and dioxane; ether solvents such as methyl acetate, ethyl acetate, acetic acid-n-propyl, isopropyl acetate and butyl acetate; Hydrocarbon solvents such as hexane, cyclohexane, octane, decane; alcohol solvents such as methanol, ethanol, propanol, butanol; carbon tetrachloride, chloroform, methylene chloride, dichloroethane, trichloroethane, etc. Motokei solvent; dimethylformamide, amide solvents such as dimethylacetamide; N- methylpyrrolidone and the like, which may be used in combination of two or more. In the coating of a solution comprising a maleimide resin and a solvent, an optical compensation film having higher transparency and excellent thickness accuracy and surface smoothness can be obtained more easily. It is preferable to set it as 2000 cps, and it is preferable to set it as 1-1000 cps especially.

  When coating this solution, an optical compensation film having excellent surface smoothness can be obtained. Therefore, the thickness of each layer of the coating film made of maleimide resin is the thickness after drying of each coating layer. It is preferable that it is 1-10 micrometers, Especially preferably, it is 2-10 micrometers.

  Examples of the method for drying the film coated with the maleimide resin solution include a batch oven, an explosion-proof air dryer, and a continuous drying furnace in continuous film formation.

  As a method for uniaxial stretching, a known stretching method can be used. As a known stretching method, for example, a continuous stretching apparatus such as a tenter stretching machine, a stretching machine for stretching a small sheet-like test piece, or the like can be used.

  The temperature in the uniaxial stretching process is preferably 100 ° C. or more and less than 200 ° C., and particularly preferably 145 ° C. or more and less than 190 ° C. The draw ratio is preferably 1.05 times or more and less than 3 times, and more preferably 1.05 times or more and less than 2 times.

  Examples of maleimide resins that can be used in the production method include N-substituted maleimide polymer resins, N-substituted maleimide-maleic anhydride copolymer resins, and the like, and N-substituted maleimides constituting the maleimide resins. Examples of the residue unit include an N-substituted maleimide residue unit represented by the general formula (1).

  The optical compensation film of the present invention is an optical film obtained by uniaxially stretching a film obtained by laminating at least two or more maleimide resin layers on a transparent resin film substrate, and is arbitrary biaxially orthogonal in the plane of the optical film. Are the x-axis and y-axis, the 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, the refractive index in the z-axis direction is nz, and the stretching axis direction of the optical film is The x-axis is an optical compensation film characterized in that the three-dimensional refractive index relationship is nx> ny> nz, and particularly has an excellent optical compensation function when used as an optical compensation film. The optical compensation film of the present invention inherently has a unique behavior in which the refractive index in the thickness direction of the film becomes small without being stretched, and further, the in-plane retardation can be manipulated by uniaxial stretching. I found out that I can do it. In addition, it was found that a smooth film with less film warpage can be obtained by uniaxially stretching a film in which at least two maleimide resin layers are laminated, as compared with a film in which a single layer of maleimide resin is laminated uniaxially. .

  The in-plane retardation amount (Re) of the optical compensation film of the present invention can be easily controlled by the film thickness and uniaxial stretching operation of the optical film in which the maleimide resin layer is laminated, and further, The amount of phase difference (Rth) can also be easily controlled by this thickness.

Since the optical compensation film of the present invention is an optical compensation film that can be expected to be applied as a retardation film, an in-plane retardation amount (Re) represented by the following formula (2) when measured with light having a measurement wavelength of 589 nm. Is preferably in the range of 10 to 150 nm, particularly preferably 35 to 150 nm.
Re = | (nx−ny) | × d (2)
(Where d represents the film thickness (nm) of the optical compensation film)
Further, the out-of-plane retardation (Rth) represented by the following formula (3) is preferably in the range of 30 to 2000 nm, more preferably 30 to 1000 nm, and particularly preferably 30 to 500 nm.
Rth = ((nx + ny) / 2−nz) × d (3)
(Here, d represents the film thickness (nm) of the optical compensation film.)
The thickness of each layer of the maleimide-based resin layer is preferably 10 μm or less, and particularly preferably 2 to 10 μm because it becomes an optical compensation film that can be expected to be adapted as a retardation 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 retardation amount is preferably small. The wavelength dependency (R450 / R589) of the phase difference amount indicated by the ratio of the phase difference amount (R450) measured with light having a measurement wavelength of 450 nm and the phase difference amount (R589) measured with light having a measurement wavelength of 589 nm is 1 .1 or less is preferable, and 1.08 or less is particularly preferable.

  Since the optical compensation film of the present invention has good image quality characteristics when used in a liquid crystal display element, the optical transmittance of the optical compensation film measured according to JIS K 7361-1 (1997 edition) is high. It is preferably 85% or more, and particularly preferably 90% or more. Further, the haze (haze) of the optical compensation film measured in accordance with JIS K 7136 (2000 version) is preferably 2% or less, and particularly preferably 1% or less.

  The optical compensation film of the present invention preferably has high heat resistance from the stability of quality when used in a liquid crystal display element, and the glass transition temperature of the maleimide resin constituting the maleimide resin layer is 100 ° C. or higher. Some are preferable, more preferably 120 ° C. or higher, and particularly preferably 135 ° C. or higher.

  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 0.5 to 1 with respect to 100 parts by weight of the maleimide resin constituting the maleimide resin layer in the optical compensation film of the present invention. A range of parts by weight is preferred.

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

  The optical compensation film of the present invention is blended with other polymers, polymer electrolytes, conductive complexes, inorganic fillers, pigments, dyes, antistatic agents, antiblocking agents, plasticizers, lubricants, etc. within the scope of the invention. It may be what was done.

  The optical compensation film of the present invention is an optical film obtained by uniaxially stretching a film in which at least two maleimide-based resin layers are laminated on a transparent resin film substrate, and particularly suitable for optical compensation for liquid crystal display elements. It becomes a film.

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

-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).

~ Measurement of refractive index ~
It measured using the Abbe refractometer (product made from Atago) based on JISK7142 (1981 edition).

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

Synthesis Example 1 (Example of production 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, washed sufficiently with methanol and dried at 80 ° C. to obtain 20 g of Nn-butylmaleimide polymer resin. The number average molecular weight of the obtained Nn-butylmaleimide polymer resin was 120,000. The glass transition temperature (hereinafter referred to as Tg) was 185 ° C.

Synthesis Example 2 (Production Example of Nn-Hexylmaleimide Polymer Resin)
In a glass sealed tube, 40 g of Nn-hexylmaleimide and 0.05 g of dimethyl-2,2′-azobisisobutyrate as a polymerization initiator are charged, and after nitrogen substitution, a polymerization temperature of 60 ° C. and a polymerization time of 5 hours. The radical polymerization reaction was performed under the following 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 32 g of Nn-hexylmaleimide polymer resin. The number average molecular weight of the obtained Nn-hexylmaleimide polymer resin was 160,000. Moreover, Tg was 148 degreeC.

Synthesis Example 3 (Production Example of Nn-Octylmaleimide Polymer Resin)
In a glass sealed tube, 28 g of Nn-octylmaleimide and 0.032 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 The radical polymerization reaction was performed under the following 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, washed sufficiently with methanol, and dried at 80 ° C. to obtain 15 g of Nn-octylmaleimide polymer resin. The number average molecular weight of the obtained Nn-octylmaleimide polymer resin was 270,000. Moreover, Tg was 138 degreeC.

Example 1
The Nn-butylmaleimide polymer resin obtained in Synthesis Example 1 was dissolved in a mixed solvent composed of 50% by weight of toluene and 50 parts by weight of methyl ethyl ketone to prepare a 13% by weight of resin solid content solution, and a film coater Is applied to both sides of a 60 μm thick triacetylcellulose resin film substrate (product of Fujifilm, product name Fujitac TD60UL, thickness 60 μm) and dried at room temperature for 24 hours, respectively 270 mm wide and 5 μm thick Two coating films (maleimide resin layer) were formed. Using a biaxial stretching apparatus manufactured by Imoto Seisakusho, the film on which this coating film was formed was temperature 145 ° C., stretching speed 10 mm / min. The film was stretched 1.2 times in the x-axis direction with a uniaxial free width. The physical properties of the obtained optical film are shown below.

  The obtained optical film has no film curl (warp), is smooth, has a thickness of 64 μm, a light transmittance of 91%, and a haze of 0.6%. The relationship of the three-dimensional refractive index of the film is nx> ny> nz. The refractive indexes are nx = 1.51531, ny = 1.51389, nz = 1.51251, the in-plane retardation amount Re = + 90 nm, the out-of-plane retardation amount Rth = + 135 nm, and the retardation amount The wavelength dependence (R450 / R589) is 1.05, and it has a function of optical compensation as a retardation film having both an in-plane retardation amount and an out-of-plane retardation amount.

Example 2
After forming the coating film in Example 1, a film was prepared in the same manner except that the film was stretched 1.05 times in the x-axis direction with a uniaxial free width.

  The obtained optical film is smooth without film curl (warp), has a light transmittance of 91%, and a haze of 0.4%. The relationship of the three-dimensional refractive index of the film is nx> ny> nz, The rates are nx = 1.51476, ny = 1.51433, nz = 1.51261, the in-plane retardation amount Re = + 30 nm, the out-of-plane retardation amount Rth = + 132 nm, and the wavelength dependence of the retardation amount ( R450 / R589) is 1.05 and has a function of optical compensation as a retardation film having both an in-plane retardation amount and an out-of-plane retardation amount.

Example 3
The same method as in Example 1 except that two coating films each having a width of 270 mm and a thickness of 7 μm were formed on both surfaces of a triacetyl cellulose resin film substrate (product of Fuji Film, product name Fujitac TD60UL, thickness 60 μm). After forming the coating film by using a biaxial stretching apparatus manufactured by Imoto Seisakusho, the film having the coating film formed thereon was heated at a temperature of 145 ° C. and a stretching speed of 10 mm / min. The film was stretched 1.2 times in the x-axis direction with a uniaxial free width. The physical properties of the obtained optical film are shown below.

  The obtained optical film is smooth without film curl (warp), has a light transmittance of 91%, and a haze of 0.4%. The relationship of the three-dimensional refractive index of the film is nx> ny> nz, The rates are nx = 1.51515, ny = 1.51404, nz = 1.51252, the in-plane retardation amount Re = + 75 nm, the out-of-plane retardation amount Rth = + 140 nm, and the wavelength dependence of the retardation amount ( R450 / R589) is 1.05 and has a function of optical compensation as a retardation film having both an in-plane retardation amount and an out-of-plane retardation amount.

Example 4
After forming the coating film in Example 1, the same method as in Example 1 except that the film on which the coating film was formed was set to 180 ° C. using a biaxial stretching apparatus manufactured by Imoto Seisakusho. Thus, the film was stretched 1.2 times in the x-axis direction with a uniaxial free width. The physical properties of the obtained optical film are shown below.

  The obtained optical film has no film curl (warp), is smooth, has a thickness of 83 μm, a light transmittance of 92.0%, and a haze of 0.3%. The relationship between the three-dimensional refractive indexes of the film is nx> ny. > Nz, the refractive indexes are nx = 1.51458, ny = 1.51395, nz = 1.51317, the in-plane retardation amount Re = + 40 nm, the out-of-plane retardation amount Rth = + 70 nm, and the retardation The wavelength dependency of the amount (R450 / R589) is 1.08, and it has an optical compensation function as a retardation film having both an in-plane retardation amount and an out-of-plane retardation amount.

Example 5
Example 1 except that two coating films each having a width of 270 mm and a thickness of 4 μm were formed on one side of a triacetyl cellulose resin film substrate (manufactured by Fuji Film, product name Fujitac TD60UL, thickness 60 μm) twice. After forming a coating film by the same method as that described above, the film on which this coating film was formed was 145 ° C. at a temperature of 145 ° C. and a stretching speed of 10 mm / min. Using a biaxial stretching apparatus manufactured by Imoto Seisakusho. The film was stretched 1.2 times in the x-axis direction with a uniaxial free width. The physical properties of the obtained optical film are shown below.

  The obtained optical film is smooth with no film curl (warp), has a light transmittance of 91% and a haze of 0.6%, and the relationship of the three-dimensional refractive index of the film is nx> ny> nz. The rates are nx = 1.51548, ny = 1.51403, nz = 1.51219, the in-plane retardation amount Re = + 90 nm, the out-of-plane retardation amount Rth = + 160 nm, and the wavelength dependence of the retardation amount ( R450 / R589) is 1.05 and has a function of optical compensation as a retardation film having both an in-plane retardation amount and an out-of-plane retardation amount.

Example 6
Using Nn-hexylmaleimide polymer resin obtained in Synthesis Example 2 and chloroform as a solvent, both sides of a triacetyl cellulose resin film substrate (product name: Fujitac TD60UL, thickness 60 μm, manufactured by Fuji Film) A biaxial stretching apparatus manufactured by Imoto Seisakusho was used to form a coating film by the same method as in Example 1 except that two coating films each having a width of 270 mm and a thickness of 3 μm were formed. Was used at a temperature of 145 ° C. and a stretching speed of 10 mm / min. The film was stretched 1.2 times in the x-axis direction with a uniaxial free width. The physical properties of the obtained optical film are shown below.

  The obtained optical film has no film curl (warp) and is smooth, has a light transmittance of 92% and a haze of 0.4%, and the relationship of the three-dimensional refractive index of the film is nx> ny> nz, and the refractive index. Nx = 1.52001, ny = 1.51932, nz = 1.51767, in-plane retardation amount Re = + 42 nm, out-of-plane retardation amount Rth = + 120 nm, and the wavelength dependence of the retardation amount (R450 / R589) is 1.05, and has a function of optical compensation as a retardation film having both an in-plane retardation amount and an out-of-plane retardation amount.

Example 7
Using Nn-octylmaleimide polymer resin obtained in Synthesis Example 3 as a solvent and chloroform, the width of each side of a triacetyl cellulose resin film substrate (product of Fuji Film, product name Fujitac TD60UL, thickness 60 μm) is provided. After forming a coating film by the same method as in Example 1 except that two coating films having a thickness of 270 mm and a thickness of 3 μm were formed, a biaxial stretching apparatus manufactured by Imoto Seisakusho was used to form the coating film. At a temperature of 145 ° C. and a stretching speed of 10 mm / min. The film was stretched 1.2 times in the x-axis direction with a uniaxial free width. The physical properties of the obtained optical film are shown below.

  The obtained optical film is smooth with no film curl (warp), has a light transmittance of 92% and a haze of 0.4%, and the relationship of the three-dimensional refractive index of the film is nx> ny> nz, The rates are nx = 1.51987, ny = 1.51929, nz = 1.51784, the in-plane retardation amount Re = + 35 nm, the out-of-plane retardation amount Rth = + 105 nm, and the wavelength dependence of the retardation amount ( R450 / R589) is 1.05 and has a function of optical compensation as a retardation film having both an in-plane retardation amount and an out-of-plane retardation amount.

Example 8
The film to be applied in Example 1 was a total of 3 layers of 2 layers on one side and 1 layer on the back side, and was coated and dried in the same manner except that each film thickness was 3 μm.

  The obtained optical film is smooth without any film curl (warp), has a light transmittance of 91% and a haze of 0.5%, and the relationship of the three-dimensional refractive index of the film is nx> ny> nz, The rates are nx = 1.51493, ny = 1.51422, nz = 1.51255, the in-plane retardation amount Re = + 45 nm, the out-of-plane retardation amount Rth = + 128 nm, and the wavelength dependence of the retardation amount ( R450 / R589) is 1.05 and has a function of optical compensation as a retardation film having both an in-plane retardation amount and an out-of-plane retardation amount.

Example 9
In Example 2, a coating film is formed in the same manner except that the thickness is 100 μm which is a cyclic polyolefin film (manufactured by ZEON, product name ZEONOR film ZF14, thickness 100 μm) as a film base material for coating. Then, the drawing process was carried out.

  The obtained optical film is smooth without any film curl (warp), has a light transmittance of 91% and a haze of 0.5%, and the relationship of the three-dimensional refractive index of the film is nx> ny> nz, The rates are nx = 1.51354, ny = 1.51389, nz = 1.51247, the in-plane retardation amount Re = + 35 nm, the out-of-plane retardation amount Rth = + 125 nm, and the wavelength dependence of the retardation amount ( R450 / R589) is 1.05 and has a function of optical compensation as a retardation film having both an in-plane retardation amount and an out-of-plane retardation amount.

Comparative Example 1
In Example 1, this film was manufactured by Imoto Seisakusho by the same method except that only a triacetyl cellulose resin film substrate was used without forming a coating film made of a solution of Nn-butylmaleimide polymer resin. Using a biaxial stretching apparatus, the temperature was 145 ° C. and the stretching speed was 10 mm / min. The film was stretched 1.2 times in the x-axis direction with a uniaxial free width. The physical properties of the obtained optical film are shown below.

  The obtained optical film is smooth with no film curl (warp), has a light transmittance of 92% and a haze of 0.4%, and the relationship of the three-dimensional refractive index of the film is nx> ny> nz, The rates are nx = 1.48008, ny = 1.48006, and nz = 1.47988, the in-plane retardation amount Re = 0 nm, and the out-of-plane retardation amount Rth = + 10 nm. The wavelength dependence of the retardation amount ( R450 / R589) is 1.02, but since the maleimide resin film was not used, the optical compensation function as a retardation film having both an in-plane retardation amount and an out-of-plane retardation amount was insufficient. is there.

Comparative Example 2
Stretching was carried out in the same manner as in Example 1 except that a coating film made of a solution of Nn-butylmaleimide polymer resin was formed with a single layer thickness of 12 μm on one side.

  The obtained optical film has a light transmittance of 91% and a haze of 0.6%, the relationship of the three-dimensional refractive index of the film is nx> ny> nz, and the refractive indices are nx = 1.51509, ny = 1.51372, nz = 1.51289, in-plane retardation amount Re = + 90 nm, out-of-plane retardation amount Rth = + 100 nm, and wavelength dependency (R450 / R589) of the retardation amount is 1.05. Since only one layer was formed on one side, the out-of-plane retardation amount was slightly lower than that in Example 1 in which one layer was applied on each side, and the film curl (warp) on the inner side of the coated surface. Was noticeable and did not become a smooth film.

Comparative Example 3
In Example 1, two coating films were formed, and then uniaxial stretching was not performed.

  The obtained optical film has a light transmittance of 91% and a haze of 0.6%, the relationship of the three-dimensional refractive index of the film is nx = ny> nz, and the refractive indexes are nx = 1.51442, ny = 1.51442, nz = 1.51285, and nx> ny> nz did not hold. Further, the in-plane retardation amount Re = 0 nm, the out-of-plane retardation amount Rth = + 110 nm, the wavelength dependency of the retardation amount (R450 / R589) is 1.05, and there is no film curl (warp) and it is smooth. Although it was a film, since it was not uniaxially stretched, an in-plane retardation could not be expressed.

  The above evaluation results are shown in Table 1.

Claims (6)

An optical film obtained by uniaxially stretching a film in which at least two maleimide-based resin layers are laminated on a transparent resin film substrate, and any two axes orthogonal to each other in the optical film plane are x-axis, y-axis, and out-of-plane Three-dimensional refractive index relationship when the direction is z-axis, the refractive index in the x-axis direction is nx, the refractive index in the y-axis direction is ny, the refractive index in the z-axis direction is nz, and the uniaxial stretching direction of the optical film is the x-axis Is an optical compensation film, wherein nx> ny> nz. 2. The optical compensation film according to claim 1, wherein the optical compensation film is a film in which two or more layers on one side of a transparent resin film base material or one or more maleimide resin layers are laminated on both sides. The optical compensation film according to claim 1 or 2, wherein the maleimide resin layer is made of a maleimide resin comprising an N-substituted maleimide residue unit represented by the following general formula (1).

(Here, R ₁ is a linear alkyl group having 1 to 18 carbon atoms, a branched alkyl group having 1 to 18 carbon atoms, a cyclic alkyl group having 1 to 18 carbon atoms, a halogen group, an ether group, an ester group, Indicates an amide group.) The in-plane retardation (Re) represented by the following formula (2) when measured with light having a measurement wavelength of 589 nm is in the range of 10 to 150 nm, and the out-of-plane retardation represented by the following formula (3). The optical compensation film according to claim 1, wherein the amount (Rth) is in the range of 30 to 2000 nm.
Re = | (nx−ny) | xd (2)
Rth = ((nx + ny) / 2−nz) × d (3)
(Here, d represents the film thickness (nm) of the optical compensation film.) The wavelength dependence of the phase difference (R450 / R589) indicated by the ratio of the phase difference (R450) measured with light having a measurement wavelength of 450 nm and the phase difference (R589) measured with light having a measurement wavelength of 589 nm. ) Is 1.1 or less, The optical compensation film according to claim 1. An optical compensation film for a liquid crystal display device, comprising the optical compensation film according to claim 1.