JP5664736B2 - Optical compensation film - Google Patents

Description

  The present invention is an optical compensation film, particularly a N-substituted maleimide polymer resin or an N-substituted maleimide-maleic anhydride copolymer resin having at least two layers on a transparent resin film substrate which is a cellulose resin film. An optical compensation film containing a maleimide resin film, for liquid crystal display elements that have an in-plane retardation and an out-of-plane retardation and exhibit an optical compensation function without being curled by biaxial stretching under specific conditions. 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.

  Examples of optical compensation films that exhibit an optical compensation function by coating (coating) include, for example, Harris and Chen of Akron University, rigid rod-shaped polyimide, polyester, polyamide, poly (amide-imide) Have proposed an optical compensation film made of poly (ester-imide) (see, for example, Patent Documents 1 and 2), and these materials have spontaneous molecular orientation and are stretched by coating. There is a feature that a phase difference is expressed without going through a process.

  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 coated film obtained by uniaxially stretching a coated film, but retardation characteristics, wavelength dependency, film smoothness, etc. when a film coated with two or more layers is biaxially stretched. There is no mention of the improvement effect.

  Then, this invention aims at providing the optical compensation film excellent in the optical characteristic, and more specifically, the transparency of two or more layers on the transparent resin film substrate which is a cellulose resin film. Is an optical compensation film including a specific maleimide resin film excellent in, having an in-plane retardation amount (hereinafter referred to as Re) and an out-of-plane retardation amount (hereinafter referred to as Rth), and wavelength dispersion of the retardation amount. An object of the present invention is to provide an optical compensation film that has no film curl (warping) with excellent control and has excellent film smoothness.

  As a result of intensive studies in view of the above problems, the present inventors have found that a biaxially stretched optical compensation film comprising at least two or more maleimide-based resin films on a transparent resin film substrate is suitable for optical compensation for liquid crystal display elements. The inventors have found that the film is an optical compensation film and have completed the present invention.

  That is, the present invention relates to a maleimide resin which is an N-substituted maleimide polymer resin or an N-substituted maleimide-maleic anhydride copolymer resin having at least two layers on a transparent resin film substrate which is a cellulose resin film. A biaxially stretched optical compensation film including a film, wherein the maleimide resin film is a coated film obtained by coating a maleimide resin solution having a solution viscosity of 1 to 1000 cps, and the thickness of each layer after drying is 1 to 10 μm The biaxial stretching process temperature of the biaxial stretching is from 130 ° C. to 200 ° C., the stretching axis direction is the x axis and y axis in the film plane, and the out-of-plane direction perpendicular to this is the z axis, 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, nx = ny> nz or ny> n > Relates an optical compensation film characterized in that nz a is film warping (curling) is smooth film without.

  Hereinafter, the present invention will be described in detail.

  Examples of the transparent resin film substrate used in the optical compensation film of the present invention include cellulose resins such as triacetyl cellulose resin, cellulose acetate butyrate resin, and cellulose acetate acetate propionate resin; cyclic olefin resin; polyethylene terephthalate (PET) ) And the like. Among them, a cellulose resin film is preferable because it is an optical compensation film excellent in transparency, strength, and adhesiveness.

  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 further a stretched and oriented transparent resin. It may be a film. As the plasticizer, ultraviolet stabilizer and birefringence improver used here, known ones can be used, and they may be stretched by a known method as a uniaxial or biaxial stretching method.

  Examples of the maleimide resin used for the maleimide resin film in the optical compensation film of the present invention include N-substituted maleimide polymer resin, N-substituted maleimide-maleic anhydride copolymer resin, and the like. Examples of the constituting N-substituted maleimide residue unit 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，炭素数１〜１８の分岐状アルキル基，炭素数１〜１８の環状アルキル基、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Ｒ１は、炭素数１〜１８の直鎖状アルキル基，炭素数１〜１８の分岐状アルキル基，炭素数１〜１８の環状アルキル基、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、好ましくはｎ−ブチル基、ｎ−ヘキシル基、ｎ−オクチル基、イソブチル基、ｓ−ブチル基、ｔ−ブチル基であり、特に好ましくはｎ−ブチル基、ｎ−ヘキシル基、ｎ−オクチル基である。

(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.)
R1 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 a cyclic alkyl group having 1 to 18 carbon atoms. Group, halogen group, ether group, ester group, amide group, and examples of the linear alkyl group having 1 to 18 carbon atoms include methyl group, ethyl group, n-propyl group, n-butyl group, and n-hexyl. Group, n-octyl group, n-lauryl group and the like. 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, an isobutyl group, s- butyl group, a t- butyl group, particularly preferably n- butyl, n- hexyl, 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 film 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 unless 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; 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 ester residue units such as vinyl acetate residue units and vinyl propionate residue units; acrylo It can be exemplified one or two or more such methacrylonitrile residue unit; tolyl 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 film 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-butyl cumyl 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 a biaxially stretched optical compensation film comprising at least two layers of a maleimide resin film on a transparent resin film substrate. As a preferred production method, for example, a maleimide resin film on a transparent resin film substrate is used. Examples thereof include a method in which a maleimide resin solution composed of a resin and a solvent is applied and dried to obtain a maleimide resin film on a transparent resin film substrate and then biaxially stretched.

  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 applying the maleimide resin include a method in which a solution in which a maleimide resin is previously dissolved in a solvent is applied 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 maleimide resin solution, an optical compensation film having excellent surface smoothness can be obtained, so the thickness of each layer of the coating film made of maleimide resin is the film after drying each coating layer. The thickness is preferably 1 to 10 μm, particularly preferably 2 to 10 μm.

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

  As a biaxial stretching method, 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.

  In the biaxial stretching process, the biaxial stretching process temperature is the glass transition temperature range of the transparent resin film substrate determined by dynamic viscoelasticity measurement or differential scanning calorimeter, that is, when the transparent resin film is in the glass state. The glass transition temperature range in which the material state transitions from the material elastic modulus to the rubber-like elastic modulus on the high temperature side is preferably stretched, and the glass transition temperature of the transparent resin film is 130 ° C. or more and less than 200 ° C. Particularly, it is preferably 130 ° C. or higher and lower than 180 ° C. The draw ratio is preferably 1.05 times or more and less than 3 times, and particularly 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 a biaxially stretched optical film comprising at least two or more maleimide-based resin films on a transparent resin film substrate, wherein the stretching axis directions are the x axis and the y axis in the film plane, The three-dimensional refractive index relationship is nx> where the out-of-plane direction perpendicular to this 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. ny> nz, ny> nx> nz or nx = ny> nz, preferably nx> ny> nz, ny> nx> nz, particularly when used as an optical compensation film Excellent optical compensation function.

  The coating film used for the optical compensation film of the present invention has a unique behavior that the refractive index in the thickness direction of the film becomes small even when unstretched. In addition, it has been found that the in-plane retardation can be manipulated. Further, nx> ny> nz, nx = ny> nz or ny> nx> nz is shown as in-plane birefringence for controlling the in-plane retardation amount while expressing the out-of-plane retardation amount, and the film warpage It has been found that it can be obtained in a state of a few smooth films.

  The in-plane retardation amount (Re) and the out-of-plane retardation amount (Rth) of the optical compensation film of the present invention can be easily controlled by a biaxial stretching operation. It is possible to manipulate the three-dimensional refractive index of the optical film obtained by a method in which stretching in the y-axis direction, a speed, and a stretching mode are performed simultaneously or sequentially by stretching the x-axis and the y-axis. For example, the refractive index nx in the x-axis direction can be made larger than the refractive index ny in the y-axis by making the x-axis stretch ratio larger than the y-axis stretch ratio as the stretch direction, and the y-axis stretch ratio Ny can be made larger than nx by making x larger than the draw ratio of the x axis.

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 550 nm. Is preferably in the range of 10 to 150 nm, particularly preferably 30 to 150 nm.
Re = | (nx−ny) | × d (2)
(Here, 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 film is preferably 10 μm or less, particularly preferably 2 to 10 μm, since 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 effective in improving color misregistration when used in a liquid crystal display element. Therefore, when an optical compensation film having a small wavelength dependence of retardation is produced, particularly an optical film is used. Wavelength dependence of the phase difference amount (R450 / R550) indicated by the ratio of the phase difference amount (R450) measured with light having a measurement wavelength of 450 nm and tilted by 40 degrees and the phase difference amount (R550) measured with light having a measurement wavelength of 550 nm. (R630 / R550) expressed by the ratio of the phase difference amount (R630) measured with light having a measurement wavelength of 630 nm and the phase difference amount (R550) measured with light having a measurement wavelength of 550 nm. An optical compensation film showing less than 1.0 or an optical film tilted by 40 degrees and measured with light having a measurement wavelength of 450 nm and light having a measurement wavelength of 550 nm The phase difference amount (R630) measured with light having a measurement wavelength of 630 nm and the phase difference amount measured with light having a measurement wavelength of 550 nm (R450 / R550) indicated by the ratio of the determined phase difference amount (R550) is less than 1.0. It is preferable that the optical compensation film has a reverse wavelength dispersion in which (R630 / R550) represented by a ratio of (R550) exceeds 1.0.

  The optical film is tilted by 40 degrees, and the wavelength dependence of the retardation amount (R450) indicated by the ratio of the retardation amount (R450) measured with light having a measurement wavelength of 450 nm and the retardation amount measured with light having a measurement wavelength of 550 nm (R550). / R550) is 1.0 or more and 1.1 or less, and is represented by the ratio of the phase difference amount (R630) measured with light having a measurement wavelength of 630 nm and the phase difference amount (R550) measured with light having a measurement wavelength of 550 nm (R630 / R550) is less than 1.0, and the optical compensation film or optical film is tilted by 40 degrees, and the phase difference amount (R450) measured with light having a measurement wavelength of 450 nm and the phase difference amount measured with light having a measurement wavelength of 550 nm (R550) The wavelength dependence (R450 / R550) of the phase difference amount indicated by the ratio of the phase difference is less than 1.0 and the phase difference amount (R630) measured with light having a measurement wavelength of 630 nm is measured. In order to obtain an optical compensation film having a reverse wavelength dispersion in which (R630 / R550) represented by a ratio of retardation (R550) measured with light having a wavelength of 550 nm exceeds 1.0, the temperature is from 130 ° C. to 200 ° C. It is necessary to perform biaxial stretching. In particular, using a cellulose-based film as a transparent film substrate, selectively biaxially stretching in the glass transition temperature range of the cellulose-based film within the range of 130 ° C to 200 ° C. Of the retardation amount (R450 / R550) of less than 1.0 and the retardation amount (R630) measured with light having a measurement wavelength of 630 nm and the retardation amount (R550) measured with light having a measurement wavelength of 550 nm. (R630 / R550) indicated by the ratio can exhibit reverse wavelength dispersion exceeding 1.0, and the glass transition temperature range of the cellulosic material When the cyclic polyolefin or PET film is used as the other resin film, the optical film is tilted by 40 degrees by biaxial stretching at an arbitrary temperature, and the measurement wavelength is 450 nm. The wavelength dependency (R450 / R550) of the phase difference indicated by the ratio of the phase difference (R450) measured with the light of R and the phase difference (R550) measured with the light having the measurement wavelength of 550 nm is 1.0 or more. 1 or less and an optical ratio (R630 / R550) indicated by a ratio of a phase difference amount (R630) measured with light having a measurement wavelength of 630 nm and a phase difference amount (R550) measured with light having a measurement wavelength of 550 nm being less than 1.0 A compensation film can be obtained.

  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 of the maleimide resin used for the maleimide resin film constituting the optical compensation film. The temperature is preferably 100 ° C. or higher, 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. Moreover, as an addition amount of antioxidant, 0.01-10 weight part is preferable with respect to 100 weight part of maleimide-type resin which comprises the optical compensation film of this invention, Especially in the range of 0.5-1 weight part. 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 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 a maleimide which is an N-substituted maleimide polymer resin or an N-substituted maleimide-maleic anhydride copolymer resin having at least two layers on a transparent resin film substrate which is a cellulose resin film. Is a biaxially stretched optical compensation film including a resin film, and its optical compensation function is easy to control. Therefore, the optical compensation film is effective for improving the contrast and viewing angle characteristics of liquid crystal display elements, particularly VA-mode liquid crystal televisions. As useful as.

  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 550 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.

Synthesis Example 4 (Production Example 1 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 120,000. Moreover, Tg was 150 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 Coating film (maleimide type) with a width of 270 mm and a thickness of 7 μm on one side of a triacetyl cellulose resin film substrate (product of Fujifilm, product name Fujitac TD60UL, thickness 60 μm, glass transition temperature range 150 to 180 ° C.) Two layers of resin film) were applied and dried at room temperature for 24 hours to form a film. Using the biaxial stretching apparatus manufactured by Imoto Seisakusho, the film on which this coating film was formed was heated at a temperature of 150 ° C. and a stretching speed of 10 mm / min. In the simultaneous biaxial stretching, the film was stretched 1.2 times in the x-axis direction and 1.05 times in the y-axis direction. The physical properties of the obtained film are shown below.

  The obtained film is smooth without any film curl (warp), has a light transmittance of 91%, and a haze of 0.7%. The relationship of the three-dimensional refractive index of the film is nx> ny> nz, and the refractive index. Nx = 1.51497, ny = 1.51413, nz = 1.51260, in-plane retardation amount Re = + 60 nm, out-of-plane retardation amount Rth = + 138 nm, in-plane retardation amount and out-of-plane amount As a retardation film having both retardation amounts, it appears with the wavelength, and the wavelength dependency of the retardation amount is R450 / R550 = 0.82 and R630 / R550 = 1.09, and the retardation amount increases with the wavelength. It has a function of optical compensation.

Example 2
After forming the coating film in Example 1, the film on which the coating film was formed was heated at a temperature of 150 ° C. and a stretching speed of 10 mm / min. Using a biaxial stretching apparatus manufactured by Imoto Seisakusho. In the simultaneous biaxial stretching, the film was stretched 1.1 times in the x-axis direction and 1.05 times in the y-axis direction. The physical properties of the obtained film are shown below.

  The obtained 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, and the refractive index. Nx = 1.51466, ny = 1.51426, nz = 1.51278, in-plane retardation amount Re = + 30 nm, out-of-plane retardation amount Rth = + 125 nm, in-plane retardation amount and out-of-plane position An optical film that develops with a wavelength as a retardation film having both retardation amounts, and that the wavelength dependency of the retardation amount is R450 / R550 = 0.87 and R630 / R550 = 1.05, and the retardation amount increases with wavelength. It has a compensation function.

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 one side of a triacetyl cellulose resin film substrate (product of Fuji Film, product name Fujitac TD80UL, thickness 80 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 155 ° C. and a stretching speed of 10 mm / min. In the simultaneous biaxial stretching, the film was stretched 1.2 times in the x-axis direction and 1.05 times in the y-axis direction. The physical properties of the obtained film are shown below.

  The obtained 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, and the refractive index is Nx = 1.51453, ny = 1.51417, nz = 1.51301, in-plane retardation amount Re = + 33 nm, out-of-plane retardation amount Rth = + 122 nm, in-plane retardation amount and out-of-plane position An optical film that develops with retardation as a retardation film having both retardation amounts, and the wavelength dependence of retardation amounts is R450 / R550 = 0.86 and R630 / R550 = 1.06, and the retardation amount increases with wavelength. It has a compensation function.

Example 4
After forming the coating film in Example 1, simultaneous biaxial stretching was performed in the same manner as in Example 1 except that the stretching temperature was 160 ° C. The physical properties of the obtained film are shown below.

  The obtained film was smooth without any film curl (warp), had a thickness of 83 μm, a light transmittance of 92.0%, and a haze of 0.4%. The relationship of the three-dimensional refractive index of the film was nx> ny>. nz, and the refractive indexes are nx = 1.51481, ny = 1.51420, and nz = 1.51269, the in-plane retardation amount Re = + 40 nm, the out-of-plane retardation amount Rth = + 120 nm, and the in-plane level. The retardation film having both the retardation amount and the out-of-plane retardation amount is expressed with the wavelength, and the wavelength dependency of the retardation amount is R450 / R550 = 0.88 and R630 / R550 = 1.05, and the retardation amount is the wavelength. It has a function of optical compensation which increases with the increase in the number.

Example 5
In Example 1, when the simultaneous biaxial stretching is performed, the stretching ratio in the x-axis direction is 1.05 times and the stretching ratio in the y-axis direction is 1.20 times. Axial stretched. The physical properties of the obtained film are shown below.

  The obtained film was smooth without any film curl (warp), had a thickness of 83 μm, a light transmittance of 91.0%, and a haze of 0.7%. The relationship of the three-dimensional refractive index of the film was ny> nx>. nz, the refractive indices are nx = 1.51412, ny = 1.51506, nz = 1.51252, the in-plane retardation amount Re = + 62 nm, the out-of-plane retardation amount Rth = + 136 nm, and the in-plane retardation value. As a retardation film having both an amount and an out-of-plane retardation amount, it is expressed with a wavelength, and the wavelength dependency of the retardation amount is R450 / R550 = 0.82 and R630 / R550 = 1.09, and the retardation amount is with wavelength. It has a function of increasing optical compensation.

Example 6
Using Nn-hexylmaleimide polymer resin obtained in Synthesis Example 2 and chloroform as a solvent, a triacetyl cellulose resin film substrate (product name: Fujitac TD60UL, thickness 60 μm, manufactured by Fuji Film) on one side. Except that two coating films (maleimide resin films) each having a width of 270 mm and a thickness of 4 μm were formed, a coating film was formed by the same method as in Example 1, and then the film on which this coating film was formed was manufactured by Imoto Seisakusho. Using a biaxial stretching apparatus manufactured by the company, a temperature of 150 ° C. and a stretching speed of 10 mm / min. The film was stretched 1.2 times in the x-axis direction and 1.05 times in the y-axis direction by simultaneous biaxial stretching. The physical properties of the obtained film are shown below.

  The obtained film is smooth without any film curl (warp), has a light transmittance of 91%, and a haze of 0.5%. The relationship of the three-dimensional refractive index of the film is nx> ny> nz, and the refractive index is Nx = 1.51263, ny = 1.51214, nz = 1.510106, in-plane retardation amount Re = + 30 nm, out-of-plane retardation amount Rth = + 106 nm, in-plane retardation amount and out-of-plane retardation value Optical compensation that is manifested with a wavelength as a retardation film having both quantities, and that the wavelength dependence of the retardation quantity is R450 / R550 = 0.85 and R630 / R550 = 1.05, and the retardation quantity increases with wavelength It has the function of.

Example 7
Using the Nn-octylmaleimide polymer resin obtained in Synthesis Example 3 as a solvent and chloroform, a width of each side of a triacetyl cellulose resin film substrate (manufactured by Fuji Film, product name Fujitac TD60UL, thickness 60 μm). A coating film was formed by the same method as in Example 1 except that two layers of a coating film (maleimide-based resin film) having a thickness of 270 mm and a thickness of 6.5 μm were formed. Using a biaxial stretching apparatus manufactured by the company, the temperature was 155 ° C. and the stretching speed was 10 mm / min. The film was stretched 1.2 times in the x-axis direction and 1.05 times in the y-axis direction by simultaneous biaxial stretching. The physical properties of the obtained film are shown below.

  The obtained film is smooth without any film curl (warp), has a light transmittance of 90%, and a haze of 0.5%. The relationship of the three-dimensional refractive index of the film is nx> ny> nz, and the refractive index. Nx = 1.51440, ny = 1.50991, nz = 1.50849, in-plane retardation amount Re = + 32 nm, out-of-plane retardation amount Rth = + 108 nm, in-plane retardation amount and out-of-plane position An optical film that develops with retardation as a retardation film having both retardation amounts, and that the wavelength dependence of retardation amounts is R450 / R550 = 0.86 and R630 / R550 = 1.08, and the retardation amount increases with wavelength. It has a compensation function.

Example 8
In Example 1, a coating film was formed in the same manner except that a cyclic polyolefin film (manufactured by ZEON Corporation, product name ZEONOR film ZF14, thickness 100 μm) was used as a film base material for coating. Stretching was performed.

  The obtained 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, and the refractive index. Nx = 1.51443, ny = 1.51406, nz = 1.51320, the in-plane retardation amount Re = + 38 nm, the out-of-plane retardation amount Rth = + 106 nm, and R450 as the wavelength dependence of the retardation amount. /R550=1.03 and R630 / R550 = 0.95, and the phase difference gradually decreased with increasing wavelength.

Example 9
A film was obtained in the same manner as in Example 1 except that biaxial stretching was performed at 140 ° C.

  The obtained film is smooth without any film curl (warp), has a light transmittance of 91%, and a haze of 0.7%. The relationship of the three-dimensional refractive index of the film is nx> ny> nz, and the refractive index. Nx = 1.51475, ny = 1.51440, nz = 1.51254, the in-plane retardation amount Re = + 23 nm, the out-of-plane retardation amount Rth = + 134 nm, and the wavelength dependence of the retardation amount is R450. /R550=1.02 and R630 / R550 = 0.98, and the phase difference gradually decreased with increasing wavelength.

Example 10
A film was obtained in the same manner as in Example 1 except that biaxial stretching was performed at 145 ° C.

  The obtained film is smooth without any film curl (warp), has a light transmittance of 91%, and a haze of 0.7%. The relationship of the three-dimensional refractive index of the film is nx> ny> nz, and the refractive index. Nx = 1.51474, ny = 1.51439, nz = 1.51257, the in-plane retardation amount Re = + 26 nm, the out-of-plane retardation amount Rth = + 132 nm, and R450 as the wavelength dependence of the retardation amount. /R550=0.98 and R630 / R550 = 1.02, and the phase difference gradually decreased with increasing wavelength.

Example 11
A film was obtained in the same manner as in Example 1 except that biaxial stretching was performed at 185 ° C.

  The obtained film is smooth without any 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, and the refractive index. Are nx = 1.51481, ny = 1.51402, nz = 1.51288, the in-plane retardation amount Re = + 52 nm, the out-of-plane retardation amount Rth = + 101 nm, and R450 as the wavelength dependence of the retardation amount. /R550=1.08 and R630 / R550 = 0.92, and the phase difference gradually decreased with increasing wavelength.

Example 12
In Example 1, two coating films were formed and stretched 1.12 times in both the x-axis direction and the y-axis direction as biaxial stretching.

  The obtained film has a light transmittance of 91% and a haze of 0.7%. The relationship of the three-dimensional refractive index of the film is nx = ny> nz, and the refractive indexes are nx = 1.51457, ny = 1, respectively. 51457 and nz = 1.51257. The in-plane retardation amount is Re = 0 nm, the out-of-plane retardation amount Rth = + 132 nm, and the wavelength dependency of the retardation amount is R450 / R550 = 0.95 and R630 / R550 = 1.04. It has a function of optical compensation such that the amount of phase difference increases with wavelength.

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 150 ° C. and the stretching speed was 10 mm / min. At the same time biaxial stretching. The physical properties of the obtained film are shown below.

  The obtained film has a light transmittance of 92% and a haze of 0.4%, and the three-dimensional refractive index relationship of the film is nx> ny> nz, and the refractive indexes are nx = 1.49033 and ny = 1, respectively. .49023, nz = 1.894944, in-plane retardation amount Re = + 5 nm, out-of-plane retardation amount Rth = + 45 nm, and wavelength dependency of the retardation amount is R450 / R550 = 1.02 and R630 / R550 = It was 1.02 and was a smooth film with no film curl (warp), but since the maleimide resin film was not used, the in-plane retardation was very small, and the retardation amount was almost constant regardless of the wavelength. showed that.

Comparative Example 2
In Example 1, two coating films were formed, but were not stretched thereafter.

  The obtained 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 = 1.51440 and ny = 1, respectively. 51440 and nz = 1.52991. Further, the in-plane retardation amount is Re = 0 nm, the out-of-plane retardation amount Rth = + 110 nm, and the wavelength dependency of the retardation amount is R450 / R550 = 1.03 and R630 / R550 = 1.05. In-plane retardation could not be expressed because the film was not biaxially stretched, and the amount of retardation showed a substantially constant value regardless of the wavelength.

Comparative Example 3
Stretching was carried out in the same manner as in Example 1 except that the coating film was formed in a single layer of 7 μm on one side. The obtained film has a light transmittance of 91% and a haze of 0.5%, the relationship of the three-dimensional refractive index of the film is nx>ny> nz, and the refractive indexes are nx = 1.51446 and ny = 1, respectively. .51432, nz = 1.51292. Further, the in-plane retardation amount Re = 10 nm, the out-of-plane retardation amount Rth = + 101 nm, and the wavelength dependency of the retardation amount is R450 / R550 = 1.05 and R630 / R550 = 0.98. Since only the maleimide resin film was formed, an inward film curl was generated, and the retardation amount gradually decreased with increasing wavelength.

  The above evaluation results are shown in Table 1.

Claims (4)

Biaxially stretched containing a maleimide resin film that is a Nn -butylmaleimide polymer resin having at least two layers on one side or at least one layer on both sides on a transparent resin film substrate that is a cellulose resin film An optical compensation film, wherein the maleimide resin film is a coating film obtained by coating a maleimide resin solution having a solution viscosity of 1 to 1000 cps, and the thickness of each layer after drying is 1 to 10 μm. The biaxial stretching temperature is 130 ° C. to 200 ° C., the stretching axis direction is the x-axis and y-axis in the film plane, the out-of-plane direction perpendicular thereto is the z-axis, and the refractive index in the x-axis direction is nx, y-axis direction of the refractive index ny, 3-dimensional refractive index relationship of nx when the refractive index of the z-axis direction is nz>ny> nz, nx = ny> nz or ny>nx> nz der is, And As the wavelength dependence of the phase difference amount, the optical compensation film is tilted by 40 degrees, and the ratio of the phase difference amount (R450) measured with light having a measurement wavelength of 450 nm and the phase difference amount (R550) measured with light having a measurement wavelength of 550 nm. (R450 / R550) shown is a ratio of a phase difference amount (R630) measured with light having a measurement wavelength of 630 nm and a phase difference amount (R550) measured with light having a measurement wavelength of 550 nm. (R630 / R550) is less than 1.0 . 2. The optical compensation film according to claim 1, wherein the optical compensation film is biaxially stretched in a range of a stretching ratio of 1.05 times or more and less than 3 times. An optical film that has been coated on a transparent resin film substrate so as to be 10 μm or less as a coating film composed of at least two layers of maleimide resin, further dried, and biaxially stretched. The in-plane retardation amount (Re) represented by the following formula (2) when the phase difference amount Re and the out-of-plane retardation amount Rth are each measured with light having a measurement wavelength of 550 nm is in the range of 10 to 150 nm, and The optical compensation film according to claim 1 or 2 , wherein an out-of-plane retardation (Rth) represented by the formula (3) is in a 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.) LCD optical compensation film for element characterized by consisting of an optical compensation film according to any one of claims 1-3.