JP2006350371A - Retardation film and method of producing same, and optical film, liquid crystal panel and liquid crystal display apparatus using the retardation film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a retardation film which hardly causes shift or unevenness in retardation values due to stress even when used in a liquid crystal display apparatus and which has a relationship of nx>nz>ny and also has wide ranges of retardation values. <P>SOLUTION: The retardation film comprises a stretched polymer film containing a styrene-based resin and a polycarbonate-based resin, which satisfies the expression (1): 100 nm≤Re[590]≤350 nm and the expression (2): 0.2≤Rth[590]/Re[590]≤0.8, wherein Re[590] and Rth[590] are an in-plane retardation value and a through-thickness retardation value of the film, respectively, measured with light having a wavelength of 590 nm at 23°C. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a retardation film and a method for producing the same. More specifically, the present invention relates to a retardation film that is unlikely to cause a shift or unevenness of a retardation value, has excellent mechanical strength, and can be applied to a large liquid crystal display device, and a method for manufacturing the retardation film. The present invention also relates to an optical film, a liquid crystal panel, and a liquid crystal display device using the retardation film.

  A liquid crystal display device is generally provided with polarizers on both sides of a liquid crystal cell. Conventionally, in order to optically compensate for a phase difference due to birefringence of the liquid crystal cell in a front direction and a perspective direction, the liquid crystal cell and the polarizer A retardation film is disposed between them. In order to improve the display characteristics of the liquid crystal display device in the perspective direction, it is very important how the retardation value of the retardation film varies with the angle in the perspective direction.

  Thus, a retardation film is disclosed in which the retardation value is substantially constant regardless of the angle (Patent Document 1). Said retardation film shows the relationship of nx> nz> ny, when the refractive index of the slow axis direction of a film, a fast axis direction, and the thickness direction is set to nx, ny, nz, respectively. A polarizing plate using such a retardation film, and an IPS mode or VA mode liquid crystal display device with improved viewing angle characteristics in a perspective direction using the above retardation film are also disclosed (Patent Document 2,). Patent Document 3 and Patent Document 4).

As a method for producing a retardation film showing a relationship of nx>nz> ny, a shrinkable film is bonded to one or both sides of a polymer film to form a laminate, and the laminate is produced by heating and stretching. A method is disclosed (Patent Document 5). In this production method, it is necessary to change the refractive index distribution of the polymer film largely before and after stretching. For this reason, as the polymer film to be used, those that are likely to cause a phase difference at a low stretch ratio are preferable. Usually, an aromatic polymer film such as a polycarbonate resin, a polyarylate resin, or a polysulfone resin is used. ing. However, since the aromatic polymer film as described above has a large photoelastic coefficient, the phase difference is likely to change with respect to stress. Therefore, the phase difference value may deviate from the design value due to the contraction stress of the polarizer when used in a liquid crystal display device when exposed to high temperatures in a state of being bonded between the liquid crystal cell and the polarizer. In addition, there is a problem that display characteristics are deteriorated due to unevenness of a retardation value due to unevenness of stress generated by heat of a backlight. On the other hand, an aliphatic resin film such as a norbornene resin film has a small photoelastic coefficient. However, since an aliphatic resin film hardly causes retardation, it can obtain a desired retardation value even when stretched at a high stretch ratio as well as at a low stretch ratio like an aromatic polymer film. Can not. Moreover, when extending | stretching by a high draw ratio, it has become a problem that a film will fracture | rupture.
JP-A-2-160204 JP-A-11-305217 JP 2000-39610 A JP-A-4-305602 JP-A-5-157911

  The present invention has been made to solve such a problem. The object of the present invention is to make it difficult for phase difference values to be shifted or uneven due to stress, and to have a relationship of nx> nz> ny (that is, 0 < Rth [590] / Re [590] <1) and a manufacturing method thereof. Another object of the present invention is to provide an optical film, a liquid crystal panel, and a liquid crystal display device using such a retardation film.

  As a result of intensive studies, the present inventors have found that the above object can be achieved by the retardation film and the method for producing a retardation film described below, and have completed the present invention.

The retardation film of the present invention is a stretched film of a polymer film containing a styrene resin and a polycarbonate resin, and satisfies the following formulas (1) and (2):
100 nm ≦ Re [590] ≦ 350 nm (1)
0.2 ≦ Rth [590] / Re [590] ≦ 0.8 (2)
In the formulas (1) and (2), Re [590] and Rth [590] are a retardation value in the film plane and a retardation value in the thickness direction measured with light having a wavelength of 590 nm at 23 ° C., respectively.

  In preferable embodiment, content of the said styrenic resin is 10-40 weight part with respect to 100 weight part of total solid.

In preferable embodiment, the said polycarbonate-type resin contains the repeating unit represented by following formula (3) and (4):
In formulas (3) and (4), n is an integer of 2 or more.

In a preferred embodiment, the absolute value of photoelastic coefficient was measured with light having a wavelength of 590nm at 23 ° C. of the phase difference film is a ^{2.0 × 10 -11 ~8.0 × 10 -11} m 2 / N .

  According to another aspect of the present invention, an optical film is provided. The optical film includes a polarizer and the retardation film laminated on at least one side of the polarizer, and a slow axis of the retardation film is parallel or orthogonal to an absorption axis of the polarizer. is there.

In a preferred embodiment, the optical film further has a transparent protective film on at least one side of the polarizer. In a more preferred embodiment, the optical film has a transparent protective film on both sides of the polarizer, the retardation film is laminated on at least one of the transparent protective films, and the retardation film is laminated. The protective film satisfies the following formulas (5) and (6):
0 nm <Re [590] ≦ 5 nm (5)
0 nm <Rth [590] ≦ 10 nm (6).

  According to still another aspect of the present invention, a liquid crystal panel is provided. The liquid crystal panel includes the retardation film or the optical film and a liquid crystal cell.

  In a preferred embodiment, the liquid crystal cell is in a TN mode, a VA mode, an IPS mode, an FFS mode, or an OCB mode.

  According to still another aspect of the present invention, a liquid crystal display device is provided. The liquid crystal display device includes the liquid crystal panel.

  According to still another aspect of the present invention, a liquid crystal television is provided. The liquid crystal television includes the liquid crystal panel.

  According to still another aspect of the present invention, a method for producing a retardation film is provided. This manufacturing method includes pasting a shrinkable film on one side or both sides of a polymer film containing a styrene-based resin and a polycarbonate-based resin, followed by heating and stretching.

  In a preferred embodiment, the shrinkable film is a biaxially stretched polypropylene film.

In a preferred embodiment, the shrinkable film in the longitudinal direction at 140 ° C .: S ¹⁴⁰ (MD) of the shrinkable film is 2.7 to 9.4%, and the shrinkage in the width direction is S ¹⁴⁰ (TD ) Is 4.6 to 15.8%.

In a preferred embodiment, the shrinkage ratio of the shrinkable film at 160 ° C. in the film longitudinal direction: S ¹⁶⁰ (MD) is 13 to 23%, and the shrinkage ratio in the width direction: S ¹⁶⁰ (TD) is 30 to 30%. 48%.

In a preferred embodiment, the difference between the shrinkage ratio in the width direction and the shrinkage ratio in the longitudinal direction at 140 ° C. of the shrinkable film: ΔS ¹⁴⁰ = S ¹⁴⁰ (TD) −S ¹⁴⁰ (MD) is 0.1% ≦ ΔS ¹⁴⁰ ≦ 3.9% of range.

In a preferred embodiment, the difference between the shrinkage ratio in the width direction and the shrinkage ratio in the longitudinal direction at 160 ° C. of the shrinkable film: ΔS ¹⁶⁰ = S ¹⁶⁰ (TD) −S ¹⁶⁰ (MD) is 8% ≦ ΔS ¹⁶⁰ ≦ 30% of range.

  In preferable embodiment, the shrinkage stress of the said shrinkable film in the width direction in 140 degreeC is 0.15-0.75N / 2mm.

  In a preferred embodiment, the shrinkage stress in the width direction at 150 ° C. of the shrinkable film is 0.20 to 0.85 N / 2 mm.

  In a preferred embodiment, the stretching temperature of the polymer film is Tg + 1 ° C. to Tg + 30 ° C. of the polymer film.

  In preferable embodiment, the draw ratio of the said polymer film is 1.05-2.00 times.

The retardation film of the present invention is a stretched film of a polymer film containing a polycarbonate resin and a styrene resin. Since such a retardation film contains a polycarbonate-based resin and a styrene-based resin, the photoelastic coefficient is reduced. Therefore, when used in a liquid crystal display device, the retardation value is less likely to be shifted or uneven. Conventionally, a retardation film having a relationship of nx>nz> ny (that is, 0 <Rth [590] / Re [590] <1) is obtained by stretching a polymer film having a small photoelastic coefficient. However, in the present invention, a shrinkable film having a predetermined shrinkage rate is bonded to one side or both sides of the polymer film, and heated and stretched to have a relationship of nx>nz> ny, and A retardation film satisfying the following formulas (1) and (2) can be obtained:
100 nm ≦ Re [590] ≦ 350 nm (1)
0.2 ≦ Rth [590] / Re [590] ≦ 0.8 (2)
In addition, according to the production method of the present invention, when a polymer film containing a polycarbonate-based resin and a styrene-based resin is stretched, a wide range of retardation values can be controlled at a low stretch ratio. An excellent retardation film can be obtained. Therefore, a retardation film for a large liquid crystal display device can be provided.

A. Retardation Film The retardation film of the present invention is a stretched film of a polymer film containing a styrene resin and a polycarbonate resin, and satisfies the following formulas (1) and (2):
100 nm ≦ Re [590] ≦ 350 nm (1)
0.2 ≦ Rth [590] / Re [590] ≦ 0.8 (2)
In the formulas (1) and (2), Re [590] and Rth [590] are a retardation value in the film plane and a retardation value in the thickness direction measured with light having a wavelength of 590 nm at 23 ° C., respectively.

  The styrene resin used in the present invention is a styrene polymer obtained by polymerizing a styrene monomer. Specific examples of the styrene monomer include styrene, α-methylstyrene, 2,4-dimethylstyrene and the like. Commercially available styrene resins can also be used. Examples include styrene resins, acrylonitrile / styrene resins, acrylonitrile / butadiene / styrene resins, acrylonitrile / ethylene / styrene resins, styrene / maleimide copolymers, styrene / maleic anhydride copolymers, and the like. These may be used alone or in combination of two or more. Moreover, you may use together the said styrene-type resin and a styrene-type monomer.

  The weight average molecular weight (Mw) of the styrenic resin is preferably less than 20,000, more preferably less than 20,000 in terms of polystyrene measured by gel permeation chromatography (GPC) method using tetrahydrofuran as a developing solvent. 1,000 to 10,000, particularly preferably 1,000 to 6,000, and most preferably 1,000 to 3,000. If it is said range, a styrene-type resin and a polycarbonate-type resin will be mixed homogeneously, and a highly transparent film can be obtained.

  The content of the styrenic resin contained in the retardation film of the present invention is preferably 10 to 40 parts by weight, more preferably 20 to 40 parts by weight, particularly preferably 100 parts by weight of the total solid content. Is 22 to 38 parts by weight, most preferably 25 to 35 parts by weight. Styrenic resin is used to reduce the absolute value of the photoelastic coefficient of the retardation film of the present invention. Within the above range, the absolute value of the photoelastic coefficient of the retardation film is made sufficiently small, and a glass transition temperature (also referred to as Tg) and rigidity suitable for durability, self-supporting property, stretchability, etc. are secured. can do. As a result, a retardation film having a relationship of nx> nz> ny can be obtained which is less likely to cause a shift or unevenness in the retardation value due to stress.

  The content of the styrene resin can be determined by GPC measurement of the retardation film. Specifically, the above retardation film is dissolved in tetrahydrofuran to give a 0.1 wt% solution, allowed to stand for 8 hours, and then filtrated through a 0.45 μm membrane filter is subjected to GPC measurement. The obtained differential molecular weight distribution curve can be divided into a low molecular weight component and a high molecular weight component in two at the peak valley. The content of the styrenic resin can be determined from the formula: [total area of low molecular weight component peak / (total area of low molecular weight component peak + total area of high molecular weight component peak)] × 100.

  As the polycarbonate resin used in the present invention, an aromatic polycarbonate composed of an aromatic dihydric phenol component and a carbonate component is preferably used. The aromatic polycarbonate can be usually obtained by a reaction between an aromatic dihydric phenol compound and a carbonate precursor. That is, an aromatic dihydric phenol compound is obtained by a phosgene method in which phosgene is blown in the presence of caustic alkali and a solvent, or a transesterification method in which an aromatic dihydric phenol compound and bisaryl carbonate are transesterified in the presence of a catalyst. Can do. Here, specific examples of the carbonate precursor include phosgene, bischloroformate of the above dihydric phenols, diphenyl carbonate, di-p-tolyl carbonate, phenyl-p-tolyl carbonate, di-p-chlorophenyl carbonate, di- Examples thereof include naphthyl carbonate, and phosgene and diphenyl carbonate are particularly preferable.

  Specific examples of the aromatic dihydric phenol compound to be reacted with the carbonate precursor include 2,2-bis (4-hydroxyphenyl) propane and 2,2-bis (4-hydroxy-3,5-dimethylphenyl) propane. Bis (4-hydroxyphenyl) methane, 1,1-bis (4-hydroxyphenyl) ethane, 2,2-bis (4-hydroxyphenyl) butane, 2,2-bis (4-hydroxy-3,5- Dimethylphenyl) butane, 2,2-bis (4-hydroxy-3,5-dipropylphenyl) propane, 1,1-bis (4-hydroxyphenyl) cyclohexane, 1,1-bis (4-hydroxyphenyl)- 3,3,5-trimethylcyclohexane and the like. These may be used alone or in combination of two or more. Preferably, 2,2-bis (4-hydroxyphenyl) propane, 1,1-bis (4-hydroxyphenyl) cyclohexane, 1,1-bis (4-hydroxyphenyl) -3,3,5-trimethylcyclohexane are Used. In particular, it is preferable to use both 2,2-bis (4-hydroxyphenyl) propane and 1,1-bis (4-hydroxyphenyl) -3,3,5-trimethylcyclohexane.

  As an aromatic dihydric phenol compound, when 2,2-bis (4-hydroxyphenyl) propane and 1,1-bis (4-hydroxyphenyl) -3,3,5-trimethylcyclohexane are used in combination, By changing the use ratio, the Tg and photoelastic coefficient of the retardation film can be adjusted. If the content of 1,1-bis (4-hydroxyphenyl) -3,3,5-trimethylcyclohexane in the polycarbonate-based resin is increased, Tg can be increased and the photoelastic coefficient can be decreased. The weight ratio of 2,2-bis (4-hydroxyphenyl) propane to 1,1-bis (4-hydroxyphenyl) -3,3,5-trimethylcyclohexane in the polycarbonate resin is preferably 2: 8. -8: 2, more preferably 3: 7-6: 4, particularly preferably 3: 7-5: 5, and most preferably 4: 6. With such a weight ratio, the photoelastic coefficient of the obtained retardation film can be made sufficiently small, and Tg and rigidity suitable for durability, self-supporting property, stretchability and the like can be realized.

In the present invention, 2,2-bis (4-hydroxyphenyl) propane and 1,1-bis (4-hydroxyphenyl) -3,3,5-trimethylcyclohexane are used in combination as the aromatic dihydric phenol compound. A polycarbonate-based resin containing a repeating unit represented by the following formulas (3) and (4) is preferably used (where n is an integer of 2 or more).

  The weight average molecular weight (Mw) of the polycarbonate resin used in the present invention is preferably 25,000 to 200,000, more preferably 30, in terms of polystyrene measured by the GPC method using tetrahydrofuran as a developing solvent. 000 to 150,000, particularly preferably 40,000 to 100,000, and most preferably 50,000 to 80,000. By setting the weight average molecular weight of the polycarbonate resin in the above range, a retardation film having excellent mechanical strength can be obtained.

  The difference in weight average molecular weight (Mw) between the polycarbonate resin and the styrene resin (Mw of the polycarbonate resin-Mw of the styrene resin) is preferably 24,000 to 92,000, more preferably 29, 000 to 87,000, particularly preferably 39,000 to 77,000, and most preferably 49,000 to 67,000. If it is said range, a highly transparent polymer film can be obtained.

  As described above, the retardation film of the present invention can be obtained by stretching (preferably, heating stretching) a polymer film containing the polycarbonate resin and the styrene resin. The thickness of the polymer film before stretching can be appropriately set according to the designed retardation value, stretchability, ease of occurrence of retardation value, and the like. More specifically, the thickness of the polymer film before stretching is preferably 20 to 500 μm, more preferably 30 to 300 μm, particularly preferably 40 to 100 μm, and most preferably 50 to 80 μm. . If it is said range, sufficient self-supporting property of a film will be obtained and a wide range retardation value can be obtained according to the objective.

  Both the polymer film before stretching and the light transmittance of the retardation film (stretched film) of the present invention are preferably as large as possible. Specifically, the light transmittance is preferably 80% or more, more preferably 85% or more, and particularly preferably 90% or more at a wavelength of 590 nm. The theoretical upper limit of light transmittance is 100% and the realizable upper limit is 94%.

  The glass transition temperature (Tg) of the polymer film is not particularly limited. The glass transition temperature (Tg) is preferably 110 to 185 ° C, more preferably 120 to 170 ° C, and particularly preferably 125 to 150 ° C. If Tg is 110 ° C. or higher, a film having good thermal stability can be easily obtained. If the temperature is 185 ° C. or lower, the in-plane and thickness direction retardation values can be easily controlled by stretching. The glass transition temperature (Tg) can be determined by a DSC method according to JIS K7121.

  The polymer film can be obtained by mixing a styrene resin and a polycarbonate resin and molding the mixture. Any suitable mixing and molding method can be employed. Specific examples of the molding method include a casting method from a solution and a melt extrusion method. More specifically, it is as follows. For example, when a film is produced using a casting method, a styrene resin and a polycarbonate resin can be stirred and mixed together with a solvent at a predetermined ratio to prepare a uniform solution, which can be formed from the solution. On the other hand, when a film is produced using a melt extrusion method, a styrene resin and a polycarbonate resin can be melted and mixed at a predetermined ratio. The polymer film is preferably obtained using a casting method. The polymer film obtained by the casting method has high smoothness and good optical uniformity.

  Examples of the solvent used in the casting method include aromatic hydrocarbons such as benzene, toluene, xylene, methoxybenzene, and 1,2-dimethoxybenzene, chloroform, dichloromethane, carbon tetrachloride, dichloroethane, tetrachloroethane, trichloroethylene, Halogenated hydrocarbons such as tetrachloroethylene, chlorobenzene and orthodichlorobenzene, phenols such as phenol and parachlorophenol, ethers such as diethyl ether, dibutyl ether, tetrahydrofuran, anisole, dioxane and tetrahydrofuran, acetone, methyl isobutyl ketone, methyl ethyl ketone, Cyclohexanone, cyclopentanone, 2-pentanone, 3-pentanone, 2-hexanone, 3-hexanone, 2-heptanone Ketones such as 3-heptanone, 4-heptanone, 2,6-dimethyl-4-heptanone, 2-pyrrolidone, N-methyl-2-pyrrolidone, n-butanol, 2-butanol, cyclohexanol, isopropyl alcohol, t- Alcohols such as butyl alcohol, glycerin, ethylene glycol, triethylene glycol, ethylene glycol monomethyl ether, diethylene glycol dimethyl ether, propylene glycol, dipropylene glycol, 2-methyl-2,4-pentanediol, amides such as dimethylformamide and dimethylacetamide , Nitriles such as acetonitrile and butyronitrile, cellosolves such as methyl cellosolve and methyl cellosolve, esters such as ethyl acetate, butyl acetate and methyl lactate, chloride Styrene, carbon disulfide, ethyl cellosolve, butyl cellosolve, and the like. These can be used alone or in admixture of two or more.

  Preferred solvents are dichloromethane, chloroform, 1,2-dichloroethane, cyclopentanone, cyclohexanone, methyl isobutyl ketone, methyl ethyl ketone, diglyme, toluene, ethyl acetate, tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, chlorobenzene. . Particularly preferred solvents are tetrahydrofuran or dichloromethane. These have particularly good solubility and dope stability.

  The total solid concentration of the solution used in the casting method can be appropriately set according to the solubility of the resin, the coating viscosity, the wettability on the substrate, the thickness after coating, and the like. More specifically, the total solid content concentration is preferably 2 to 100 parts by weight, more preferably 4 to 50 parts by weight, and particularly preferably 5 to 40 parts by weight with respect to 100 parts by weight of the solvent. By adopting the total solid content concentration in such a range, a polymer film having high smoothness can be obtained.

  The said polymer film can contain arbitrary appropriate additives as needed in the range which does not impair the objective of this invention. Specific examples of the additive include a stabilizer, a plasticizer, an ultraviolet absorber, and an antistatic agent.

  As described above, the retardation film of the present invention is a stretched film of the polymer film. In the present specification, the “stretched film” refers to a film in which a tension is applied to an unstretched film at an appropriate temperature and the molecular orientation is increased along the tensile direction. The “stretched film” in the present specification includes a film obtained by further applying tension to a previously stretched film to increase molecular orientation along the tensile direction.

  The thickness of the retardation film (stretched film) is preferably 22 to 550 μm, more preferably 33 to 330 μm, particularly preferably 44 to 110 μm, and most preferably 55 to 88 μm. If it is said range, sufficient self-supporting property of a film will be acquired and the wide range retardation value according to the objective can be obtained.

  In this specification, Re [590] refers to a retardation value in the film plane measured with light having a wavelength of 590 nm at 23 ° C. Re [590] is expressed by the formula: Re [590] = (respectively, assuming that the refractive index in the slow axis direction and the fast axis direction of the film at a wavelength of 590 nm is nx and ny, and d (nm) is the thickness of the film. nx−ny) × d. The slow axis refers to the direction in which the refractive index in the film plane becomes maximum.

  Re [590] of the retardation film of the present invention is 100 to 350 nm, preferably 200 to 350 nm, more preferably 240 to 300 nm, and particularly preferably 260, as described in the above formula (1). It is -280nm, Most preferably, it is 265-275nm. By setting the value of Re [590] to about ½ of the measurement wavelength, the display characteristics of the liquid crystal display device can be further improved.

  In this specification, Rth [590] refers to a retardation value in the film thickness direction measured with light having a wavelength of 590 nm at 23 ° C. Rth [590] is expressed by the formula: Rth [590] = (nx−) where the refractive index in the slow axis direction and the thickness direction of the film at a wavelength of 590 nm is nx and nz, and d (nm) is the thickness of the film. nz) × d.

  Rth [590] of the retardation film of the present invention is preferably 35 to 190 nm, more preferably 90 to 190 nm, particularly preferably 100 to 165 nm, and most preferably 120 to 155 nm.

Re [590] and Rth [590] can be measured using a trade name “KOBRA21-ADH” manufactured by Oji Scientific Instruments. In-plane retardation value (Re) at a wavelength of 590 nm at 23 ° C., retardation value measured by tilting 40 ° with the slow axis as the tilt axis (R40), retardation film thickness (d), and retardation film Nx, ny, and nz can be obtained by computer numerical calculation from the following formulas (i) to (iii), and then Rth can be calculated by formula (iv). Here, φ and ny ′ are represented by the following equations (v) and (vi), respectively.
Re = (nx−ny) × d (i)
R40 = (nx−ny ′) × d / cos (φ) (ii)
(Nx + ny + nz) / 3 = n0 (iii)
Rth = (nx−nz) × d
… (Iv)
φ = sin ⁻¹ [sin (40 °) / n0] (v)
ny ′ = ny × nz [ny ² × sin ² (φ) + nz ² × cos ² (φ)] ^1/2 (vi)

  In this specification, Rth [590] / Re [590] refers to the ratio between the retardation value in the thickness direction measured with light having a wavelength of 590 nm at 23 ° C. and the retardation value in the film plane (this ratio is the Nz coefficient). Also called).

  Rth [590] / Re [590] of the retardation film of the present invention is 0.2 to 0.8 as described in the above formula (2), preferably 0.2 to 0.7, More preferably, it is 0.2-0.6, Most preferably, it is 0.4-0.6, Most preferably, it is 0.45-0.55. By bringing the Rth [590] / Re [590] value of the retardation film close to 0.5, it is possible to achieve a characteristic in which the retardation value is substantially constant regardless of the angle, and the display characteristics of the liquid crystal display device are improved. It can be further improved. Furthermore, by making Rth [590] / Re [590] more than 0 and less than 1, a retardation film having a refractive index distribution of nx> nz> ny can be obtained.

  The photoelastic coefficient of the retardation film refers to the ease with which birefringence occurs when an external force is applied to the optical film to cause stress therein. Generally, it is preferable that the photoelastic coefficient of the retardation film has a smaller absolute value. This is because the optical uniformity is excellent and phase difference unevenness due to distortion hardly occurs. The photoelastic coefficient is measured by applying light at a wavelength of 590 nm while applying a stress to a 2 cm × 10 cm test piece at 23 ° C. using a spectroscopic ellipsometer product name “M-220” manufactured by JASCO Corporation. The phase difference value can be measured and calculated from the slope of the function of the phase difference value and stress.

As for the photoelastic coefficient of the retardation film of the present invention, the absolute value of the value measured with light having a wavelength of 590 nm at 23 ° C .: C [590] (m ² / N) is preferably 2.0 × 10 ⁻¹¹ to 8. a .0 × ^{10 -11,} still more preferably ^{2.0 × 10 -11 ~6.0 × 10 -11} , and particularly preferably be 3.0 × ^{10 -11} ~6.0 × ¹⁰ -11 The most preferred range is 4.0 × 10 ^{−11 to} 6.0 × 10 ⁻¹¹ . By setting it as the above range, a retardation film having a refractive index distribution of nx>nz> ny can be obtained without causing a shift or unevenness of the retardation value due to the contraction stress of the polarizer or the heat of the backlight.

  The wavelength dispersion characteristic of the retardation film generally refers to the wavelength dependence of the retardation value. The wavelength dispersion characteristic can be represented by a ratio of retardation values in a film plane measured with light having a wavelength of 480 nm and 590 nm at 23 ° C .: Re [480] / Re [590].

  The wavelength dispersion characteristic (Re [480] / Re [590] value) of the retardation film of the present invention is preferably 1.02 to 1.30, more preferably 1.02 to 1.20. Most preferably, it is 1.02-1.10. The smaller the Re [480] / Re [590] value is in the above range, the more constant the phase difference value in a wide visible light region, so that the contrast ratio and color shift of the liquid crystal panel can be improved. Re [480] and Re [590] are in-plane retardation values measured with light of wavelengths 480 nm and 590 nm at 23 ° C., respectively.

  The variation in the direction of the slow axis of the retardation film (also referred to as the orientation angle) is preferably as small as possible. If the variation is large, the degree of polarization may be lowered when the film is laminated on a polarizer or a polarizing plate. The range of variation in the orientation angle at five measurement points provided at equal intervals in the film width direction is preferably ± 2.0 ° to ± 1.0 °, more preferably ± 1.0 ° to ± 0. 0.5 °, particularly preferably ± 0.5 ° to ± 0.1 °. In addition, the said orientation angle can be calculated | required, for example using the product name "KOBRA21-ADH" by Oji Scientific Instruments.

B. Method for Producing Retardation Film The method for producing a phase difference film of the present invention includes bonding a shrinkable film on one or both sides of a polymer film containing a styrene resin and a polycarbonate resin, followed by heating and stretching.

  The shrinkable film used in the present invention is used for imparting a shrinkage force in a direction orthogonal to the stretching direction during heat stretching. Examples of the material used for the shrinkable film include polyester, polystyrene, polyethylene, polypropylene, polyvinyl chloride, and polyvinylidene chloride. From the viewpoint of excellent shrinkage uniformity and heat resistance, a polypropylene film is preferably used.

  The shrinkable film is preferably a stretched film such as a biaxially stretched film or a uniaxially stretched film. The shrinkable film can be obtained, for example, by stretching an unstretched film formed into a sheet by an extrusion method in the longitudinal and / or transverse direction at a predetermined magnification with a simultaneous biaxial stretching machine or the like. The molding and stretching conditions can be appropriately selected depending on the composition, type and purpose of the resin used. In view of excellent shrinkage uniformity and heat resistance, a biaxially stretched polypropylene film is particularly preferably used.

Preferably, the shrinkage ratio of the shrinkable film in the film longitudinal direction at 140 ° C .: S ¹⁴⁰ (MD) is 2.7 to 9.4%, and the shrinkage ratio in the width direction: S ¹⁴⁰ (TD) is 4. .6 to 15.8%. S ¹⁴⁰ (MD) is more preferably 2.7 to 8.7%, particularly preferably 3.7 to 7.7%, and most preferably 4.7 to 6.7%. S ¹⁴⁰ (TD) is more preferably 4.6 to 10.6%, particularly preferably 5.6 to 9.6%, and most preferably 6.6 to 8.6%. If it is said range, the target phase difference value will be obtained and the phase difference film excellent in uniformity can be obtained.

Preferably, the shrinkage ratio of the shrinkable film at 160 ° C. in the longitudinal direction of the film: S ¹⁶⁰ (MD) is 13 to 23%, and the shrinkage ratio in the width direction: S ¹⁶⁰ (TD) is 30 to 48%. is there. S ¹⁶⁰ (MD) is more preferably 15 to 21%, particularly preferably 16 to 20%, and most preferably 17 to 19%. S ¹⁶⁰ (TD) is more preferably 31 to 44%, particularly preferably 32 to 40%, and most preferably 33 to 38%. If it is said range, the target phase difference value will be obtained and the phase difference film excellent in uniformity can be obtained.

The difference between the shrinkage in the width direction and the shrinkage in the longitudinal direction at 140 ° C. of the shrinkable film: ΔS ¹⁴⁰ = S ¹⁴⁰ (TD) −S ¹⁴⁰ (MD) is preferably 0.1% ≦ ΔS ¹⁴⁰ ≦ 3. 9%, more preferably 0.9% ≦ ΔS ¹⁴⁰ ≦ 2.9%, particularly preferably 1.4% ≦ ΔS ¹⁴⁰ ≦ 2.4%, and most preferably 1.8% ≦ ΔS. ¹⁴⁰ ≦ 2.1%. If the shrinkage rate in the MD direction is large, in addition to stretching tension, the shrinking force of the shrinkable film may be applied to a stretching machine, and uniform stretching may be difficult. On the other hand, if it is said range, uniform extending | stretching can be performed, without applying excessive load to facilities, such as a drawing machine.

The difference between the shrinkage in the width direction and the shrinkage in the longitudinal direction at 160 ° C. of the shrinkable film: ΔS ¹⁶⁰ = S ¹⁶⁰ (TD) −S ¹⁶⁰ (MD) is preferably 8% ≦ ΔS ¹⁶⁰ ≦ 30%. More preferably, 10% ≦ ΔS ¹⁶⁰ ≦ 28%, particularly preferably 12% ≦ ΔS ¹⁶⁰ ≦ 26%, and most preferably 14% ≦ ΔS ¹⁶⁰ ≦ 22%. If the shrinkage rate in the MD direction is large, in addition to stretching tension, the shrinking force of the shrinkable film may be applied to a stretching machine, and uniform stretching may be difficult. If it is said range, uniform extending | stretching can be performed, without applying excessive load to facilities, such as a drawing machine.

The shrinkage stress per 2 mm width in the width direction at 140 ° C. of the shrinkable film: T _A ¹⁴⁰ (TD) is preferably 0.15 to 0.75 N / 2 mm, more preferably 0.15 to 0.70 N. / 2 mm, particularly preferably 0.25 to 0.65 N / 2 mm, and most preferably 0.35 to 0.55 N / 2 mm. Also, the shrinkage stress per unit area at 140 ° C. of shrinkable _film: ^{T B} 140 (TD) is preferably 2.5~12.5N / mm ^2. If it is said range, the target phase difference value will be obtained and uniform extending | stretching can be performed.

The shrinkage stress per 2 mm width in the width direction at 150 ° C. of the shrinkable film: T _A ¹⁵⁰ (TD) is preferably 0.20 to 0.85 N / 2 mm, more preferably 0.25 to 0.80 N. / 2 mm, particularly preferably 0.35 to 0.75 N / 2 mm, and most preferably 0.45 to 0.65 N / 2 mm. Also, the shrinkage stress per unit area at 0.99 ° C. of shrinkable _film: ^{T B} 150 (TD) is preferably 3.3~14.2N / mm ^2. If it is said range, the target phase difference value will be obtained and uniform extending | stretching can be performed.

  The shrinkage rates S (MD) and S (TD) can be determined according to the heating shrinkage rate A method of JIS Z 1712 (however, the heating temperature is 140 ° C or 160 ° C instead of 120 ° C as described above). The difference is that a weight of 3 g was added to the test piece). Specifically, five test pieces each having a width of 20 mm and a length of 150 mm were taken from the vertical (MD) and horizontal (TD) directions, and a test piece with a mark at a distance of about 100 mm at the center was prepared. To do. The test piece is suspended vertically in an air circulation type thermostatic bath maintained at a temperature of 140 ° C. ± 3 ° C. or 160 ° C. ± 3 ° C. with a weight of 3 g, heated for 15 minutes, taken out, and in a standard state ( Room temperature) for 30 minutes, and then using a caliper specified in JIS B 7507, the distance between the standards was measured to obtain an average value of the five measured values, and S (%) = [(before heating Distance between standards (mm) −Distance between standards after heating (mm)) / Distance between standards before heating (mm)] × 100.

  As the shrinkable film, if it satisfies the object of the present invention, it is used for general packaging, food packaging, pallet packaging, shrinkage label, cap seal, and electrical insulation. A commercially available shrinkable film can also be appropriately selected and used. These commercially available shrinkable films may be used as they are, or after being subjected to secondary processing such as stretching treatment or shrinkage treatment. Specific examples of commercially available shrinkable films include Oji Paper Co., Ltd. product name “Alphan Series”, Gunze Co., Ltd. product name “Fancy Top Series”, and Toray Industries, Inc. product name “Trephan Series”. , Santox Co., Ltd., trade name “Santox-OP Series”, Tosero Co., Ltd., trade name “Tosero OP Series”, and the like.

  As the thickness of the shrinkable film before heating and stretching, any appropriate thickness can be adopted depending on the shrinkage ratio, the retardation value, and the like. Specifically, the thickness is preferably 10 to 500 μm, more preferably 20 to 300 μm, particularly preferably 30 to 100 μm, and most preferably 40 to 80 μm. A sufficient shrinkage ratio can be obtained within the above range, so that a retardation film having good optical uniformity can be produced.

  The shrinkable film is bonded to the polymer film so that the shrinkable direction of the shrinkable film includes at least a component in a direction orthogonal to the stretching direction. That is, all or part of the shrinkage force of the shrinkable film acts in a direction perpendicular to the stretching direction of the polymer film. Therefore, the shrinking direction of the shrinkable film may be oblique to the stretching direction of the polymer film, and does not have to be completely orthogonal.

  Arbitrary appropriate methods may be employ | adopted as a bonding method of the said shrinkable film. For example, a method in which a pressure-sensitive adhesive layer is provided between the polymer film and the shrinkable film and bonded is preferable. Such a method is excellent in workability and productivity. The pressure-sensitive adhesive layer can be formed on one or both of the polymer film and the shrinkable film. Usually, since the shrinkable film is peeled after producing the retardation film, the pressure-sensitive adhesive is excellent in adhesiveness and heat resistance in the heat stretching process, and can be easily peeled off in the subsequent peeling process. It is preferable that the pressure-sensitive adhesive does not remain on the surface of the retardation film. The pressure-sensitive adhesive layer is preferably provided on the shrinkable film. In such a case, the peelability is excellent.

  Examples of the pressure-sensitive adhesive that forms the pressure-sensitive adhesive layer include acrylics, synthetic rubbers, rubbers, and silicones. An acrylic pressure-sensitive adhesive having an acrylic polymer as a base polymer is preferable. It is because it is excellent in adhesiveness, heat resistance, and peelability. The weight average molecular weight (Mw) of the acrylic polymer is preferably 30,000 to 2,500,000 in terms of polystyrene. The weight average molecular weight (Mw) is calculated by the GPC method using tetrahydrofuran as a developing solvent.

  Examples of the monomer used in the acrylic polymer include various alkyl (meth) acrylates. Specific examples include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, ( Isononyl (meth) acrylate, isodecyl (meth) acrylate, dodecyl (meth) acrylate, lauryl (meth) acrylate, tridecyl (meth) acrylate, pentadecyl (meth) acrylate, hexadecyl (meth) acrylate, (meta And C1-C20 alkyl esters of (meth) acrylic acid such as heptadecyl acrylate, octadecyl (meth) acrylate, nonadecyl (meth) acrylate, and eicosyl (meth) acrylate. These can be used alone or in combination.

  In one embodiment, polarity is imparted to the resulting acrylic polymer. Examples of the method for imparting polarity include a method of copolymerizing the above (meth) acrylic acid alkyl ester and a predetermined monomer. Monomers used for copolymerization include carboxyl group-containing monomers such as (meth) acrylic acid and itaconic acid, and hydroxyl group-containing monomers such as hydroxyethyl (meth) acrylate and hydroxypropyl (meth) acrylate , Amide group-containing monomers such as N-methylolacrylamide, cyano group-containing monomers such as (meth) acrylonitrile, epoxy group-containing monomers such as glycidyl (meth) acrylate, vinyl esters such as vinyl acetate And styrene monomers such as styrene and α-methylstyrene.

  Any appropriate method can be adopted as a method for polymerizing the acrylic polymer. Specific examples include solution polymerization, emulsion polymerization, suspension polymerization, and UV polymerization.

  In one embodiment, the pressure-sensitive adhesive (composition) may further contain a crosslinking agent. Examples of the crosslinking agent include polyisocyanate compounds, polyamine compounds, melamine resins, urea resins, and epoxy resins. Furthermore, the said adhesive can contain arbitrary appropriate additives as needed. By selecting the kind of additive, the amount added, and the like, a pressure-sensitive adhesive layer having an appropriate adhesive force and / or other characteristics can be formed according to the purpose. Specific examples of the additive include catalysts, tackifiers (for example, natural resins and synthetic resins), plasticizers, fillers, antioxidants, ultraviolet absorbers, silane coupling agents, and the like.

  Arbitrary appropriate methods may be employ | adopted as a formation method of an adhesive layer. Specific examples include a direct copy method and a transfer method. The direct copy method is a method in which an adhesive is directly applied to the shrinkable film and dried. The transfer method is a method in which a pressure-sensitive adhesive is applied to a release film, dried, and transferred to the shrinkable film.

  As the thickness of the pressure-sensitive adhesive layer, any appropriate thickness can be adopted depending on the adhesive strength, the surface state of the retardation film, and the like. Specifically, the thickness is preferably 1 to 100 μm, more preferably 5 to 50 μm, and particularly preferably 10 to 30 μm. If it exists in said range, sufficient shrinkage will be obtained and the retardation film which has favorable optical uniformity can be produced. The pressure-sensitive adhesive layer may be formed by laminating a plurality of pressure-sensitive adhesives having different types and / or compositions.

  A separator is temporarily attached to the exposed surface of the pressure-sensitive adhesive layer until it is practically used to cover the surface. Thereby, an operator etc. contact with an adhesive layer at the time of handling, and the said adhesive layer is prevented from being contaminated. Any appropriate release paper or release film can be adopted as the separator. More specifically, a release paper or release film obtained by coating a thin substrate with a release agent can be used. Examples of the substrate include plastic film, rubber sheet, paper, cloth, nonwoven fabric, net, foamed sheet, metal foil, and laminates thereof. Examples of the release agent include silicone release agents, long-chain alkyl release agents, fluorine release agents, molybdenum sulfide, and the like.

The adhesive strength at 23 ° C. at the interface between the polymer film and the pressure-sensitive adhesive layer is not particularly limited as long as the effects of the present invention are not impaired. Specifically, the adhesive force is preferably 0.1 to 10.0 N / 50 mm, more preferably 0.1 to 5.0 N / 50 mm, and particularly preferably 0.2 to 3.0 N / 50 mm. It is. The adhesive force was obtained by subjecting the shrinkable film to the polymer film by three reciprocations with a manual roller in accordance with JIS Z 0237, and using it as an adhesive force measurement sample, and subjecting the sample to autoclaving (50 ° C., 15 Min., 5 kg / cm ² ), and 90 degree pulling according to JIS Z 0237 (pickup speed: 300 mm / min) can be measured with an apparatus according to JIS B 7721. The adhesive force can be controlled in any suitable manner. For example, a method in which an appropriate surface treatment such as corona treatment or plasma treatment is performed on the surface of the polymer film on which the pressure-sensitive adhesive layer is provided, heat treatment or autoclave with the polymer film and the shrinkable film adhered. A method of performing an appropriate process such as a process and a combination thereof can be mentioned.

  One or two or more appropriate numbers of the shrinkable films can be bonded to one side or both sides of the polymer film according to the shrinkage force to be designed, desired optical characteristics, and the like. When a plurality of shrinkable films are used (for example, when pasted on both sides, when two or more are pasted on one side), the shrinkage rate of the plurality of shrinkable films can be appropriately set according to the purpose. Accordingly, the shrinkage rates of the plurality of shrinkable films may be the same or different from each other.

  Next, the polymer film (hereinafter referred to as a laminate) on which the shrinkable film is bonded is stretched (typically, heat-stretched). As a stretching method, any appropriate stretching method can be used as long as it can provide tension in the stretching direction of the polymer film and shrinkage force in the direction orthogonal to the stretching direction in the film plane. Can be used. Specific examples include a longitudinal uniaxial stretching method, a transverse uniaxial stretching method, a longitudinal and transverse simultaneous biaxial stretching method, and a longitudinal and transverse sequential biaxial stretching method. The stretching process is performed using any appropriate stretching machine. Specific examples of the stretching machine include a roll stretching machine, a tenter, and a biaxial stretching machine. Stretching may be performed in one stage or in two or more stages. The stretching direction may be the film longitudinal direction (MD direction) or the width direction (TD direction). Or it can also be set as the diagonal direction using the extending | stretching method of FIG. 1 of Unexamined-Japanese-Patent No. 2003-262721.

  The temperature at which the laminate is stretched (stretching temperature) is preferably equal to or higher than the glass transition temperature (Tg) of the polymer film. This is because the retardation value of the obtained retardation film tends to be uniform, and the film is difficult to crystallize (white turbidity). The stretching temperature is more preferably Tg + 1 ° C. to Tg + 30 ° C. of the polymer film, more preferably Tg + 2 ° C. to Tg + 20 ° C., particularly preferably Tg + 3 ° C. to Tg + 15 ° C., and most preferably Tg + 5 ° C. to Tg + 10 ° C. It is. When the stretching temperature is in the above range, uniform heating and stretching can be performed. Furthermore, the stretching temperature is preferably constant in the film width direction. This is because a retardation film having good optical uniformity with small variation in retardation value can be produced.

  Any appropriate temperature control means can be adopted as means for keeping the stretching temperature constant. As specific examples, an air circulation type constant temperature oven in which hot air or cold air circulates, a heater using microwaves or far infrared rays, a roll heated or cooled for temperature control, a heat pipe roll, a metal belt, or the like was used. Heating or cooling means may be mentioned.

  The stretching temperature is preferably as small as possible (typically, variation in the film width direction). If the variation is large, stretching unevenness increases, and the retardation value of the finally obtained retardation film may vary. The variation of the stretching temperature in the film width direction is preferably ± 3.0 ° C. or less, particularly preferably ± 1.0 ° C. or less.

  The draw ratio at the time of stretching can be appropriately set according to the content of the styrenic resin in the polymer film to be used, the type of volatile component, the residual amount of volatile component, the designed retardation value, and the like. Specifically, the draw ratio is preferably 1.05 to 2.00 times, more preferably 1.10 to 1.50 times, and particularly preferably 1.20 to 1.40 times. Most preferably, it is 1.25 to 1.30 times. If it is said range, there will be little shrinkage | contraction of a film width | variety and the retardation film excellent in mechanical strength can be provided.

  There is no restriction | limiting in particular in the feeding speed at the time of the said extending | stretching. For example, considering the mechanical accuracy and stability of the stretching apparatus, the feed rate is preferably 0.5 m / min or more, more preferably 1 m / min or more.

  An example of the method for producing the retardation film of the present invention will be described with reference to FIG. FIG. 1 is a schematic view showing the concept of a typical production process of the retardation film of the present invention. For example, a polymer film 402 containing a styrene-based resin and a polycarbonate-based resin is unwound from the first unwinding portion 401, and the second unwinding portion 403 is formed on both surfaces of the high-molecular film 402 by the laminate rolls 407 and 408. The shrinkable film 404 provided with the pressure-sensitive adhesive layer drawn out from the film and the shrinkable film 406 provided with the pressure-sensitive adhesive layer drawn out from the third feed-out portion 405 are attached. A laminate in which a shrinkable film is adhered to both sides of a polymer film is applied with tension in the longitudinal direction of the film by rolls 410, 411, 412 and 413 having different speed ratios while being held at a constant temperature by a drying means 409. The film is subjected to a stretching treatment while being simultaneously given a tension in the thickness direction by the shrinkable film. In the first winding part 414 and the second winding part 416, the shrinkable films 404 and 406 are peeled off from the stretched laminate together with the pressure-sensitive adhesive layer, and a retardation film (stretched film) 418 is obtained. . The obtained retardation film 418 is wound up by the third winding portion 419.

C. Combination Use of Retardation Film of the Present Invention and Other Retardation Film The retardation film of the present invention can be used by being laminated on another retardation film via an adhesive, an adhesive or the like. As another retardation film used in combination with the retardation film of the present invention, a retardation film having any appropriate optical property, chemical property, and mechanical property may be selected according to the purpose. Specific examples of the other retardation film include polyester resins such as polyethylene terephthalate and polyethylene naphthalate, cellulose resins such as diacetyl cellulose and triacetyl cellulose, acrylic resins such as polymethyl methacrylate, polystyrene, acrylonitrile and styrene. Copolymers, styrene resins, acrylonitrile / styrene resins, acrylonitrile / butadiene / styrene resins, acrylonitrile / ethylene / styrene resins, styrene / maleimide copolymers, styrene / maleic anhydride copolymers and other styrene resins, polycarbonate resins Etc. In addition, cycloolefin resin, norbornene resin, polyolefin resin such as polyethylene, polypropylene, ethylene / propylene copolymer, vinyl chloride resin, amide resin such as nylon and aromatic polyamide, aromatic polyimide, polyimide amide, etc. Imide resins, sulfone resins, polyether sulfone resins, polyether ether ketone resins, polyphenylene sulfide resins, vinyl alcohol resins, vinylidene chloride resins, vinyl butyral resins, arylate resins, polyoxymethylene resins Examples include a film obtained by imparting birefringence characteristics to a polymer film made of a resin, an epoxy resin, or a blend of the above resins, or a film obtained by applying a mixed solution containing a liquid crystalline compound on a substrate and curing the film. . The birefringence characteristic may occur spontaneously when the polymer film is formed, or may be imparted by stretching the polymer film uniaxially or biaxially.

  As the birefringence characteristics of the other retardation film, any appropriate birefringence characteristics can be adopted depending on the birefringence characteristics of the retardation film of the present invention, the display mode of the liquid crystal display device used, and the like. For example, when used in a TN mode, IPS mode, FFS mode, VA mode, and OCB mode liquid crystal display device, Re [590] = 80 to 140 nm (Rth [590] / Re [590] = 0.9 to 1). .3) Uniaxial retardation film, negative uniaxial retardation film in which Re [590] = 0 to 5 nm and Rth [590] = 90 to 400 nm, optical axis from the substrate normal to 10 to 80 ° Uniaxially tilted phase difference film tilted in a biaxial direction, Re [590] = 30-60 nm (Rth [590] / Re [590] = 2.0-6.0), Re [590] = 100 to 300 nm (Rth [590] / Re [590] = 0.2 to 0.8) Biaxial retardation film, discotic liquid crystal molecules or rod-like liquid crystal molecules gradually with respect to the substrate normal Hybrid orientation phase difference film or the like obliquely are preferably used. By using such a retardation film in combination with the retardation film of the present invention, the viewing angle characteristics of the liquid crystal display device can be further improved.

D. Optical film The optical film of the present invention has a polarizer and the retardation film of the present invention laminated on at least one side of the polarizer. The polarizer and the retardation film are laminated by any appropriate means (for example, via an adhesive layer or an adhesive layer). In the optical film of the present invention, the retardation film of the present invention may be used alone, or two or more may be laminated and used. When two or more sheets are laminated and used, the respective retardation films may be the same or different. When different retardation films are laminated and used, the optical characteristics of the respective retardation films can be appropriately set according to the purpose. For example, in one embodiment of the optical film of the present invention, the retardation film is a λ / 2 plate. In this case, a single-layer λ / 2 plate may be used as a retardation film, or two λ / 4 plates may be used with their slow axes being substantially parallel. The optical film of the present invention may further include any appropriate other retardation film (for example, other retardation film described in the above section C) as necessary.

  In one embodiment, the optical film of the present invention further has a transparent protective film on at least one side of the polarizer. In this case, the retardation film of the present invention is typically laminated on the opposite side of the polarizer from the transparent protective film. In another embodiment, the optical film of the present invention has a transparent protective film on both sides of the polarizer, and the retardation film of the present invention is laminated on at least one of the transparent protective film. In other words, in the optical film of the present invention, the retardation film of the present invention is laminated on at least one of polarizing plates (usually having a polarizer and a transparent protective film laminated on at least one of the polarizers). ing. When the said transparent protective film is provided in the both sides of the polarizer, each transparent protective film may be formed from the same material and may be formed from a different material.

  In the optical film of the present invention, preferably, the retardation axis of the retardation film is substantially parallel or orthogonal to the absorption axis of the polarizer. In this specification, “substantially parallel” includes the case where the angle formed by the slow axis of the retardation film and the absorption axis of the polarizer is 0 ° ± 2.0 °, preferably 0 °. It is ± 1.0 °, and more preferably 0 ° ± 0.5 °. In the present specification, “substantially orthogonal” includes a case where the angle formed by the slow axis of the retardation film and the absorption axis of the polarizer is 90 ° ± 2.0 °, preferably 90 °. It is ± 1.0 °, and more preferably 90 ° ± 0.5 °. As the degree of deviation from these angular ranges increases, the degree of polarization of the polarizing plate decreases, and the contrast decreases when used in a liquid crystal display device.

  Hereinafter, the specific configuration of the optical film of the present invention will be exemplified with reference to the drawings. FIG. 2 is a schematic perspective view illustrating an optical film according to a preferred embodiment of the present invention. In the optical film 3A of FIG. 2, the transparent protective film 1c is disposed on one surface of the polarizer 1a, and the retardation film 2 of the present invention is disposed on the other surface. In other words, in the optical film 3A of FIG. 2, the retardation film 2 is laminated on the polarizing plate 1A (having the polarizer 1a and the transparent protective film 1c). Although FIG. 2 shows the case where the slow axis of the retardation film 2 is parallel to the absorption axis of the polarizer 1a, it may be orthogonal.

  FIG. 3 is a schematic perspective view illustrating an optical film according to another embodiment of the present invention. In the optical film 3B of FIG. 3, the transparent protective film 1b and the transparent protective film 1c are disposed on both sides of the polarizer 1a, and the retardation film 2 is disposed on the surface of the transparent protective film 1b opposite to the polarizer 1a. . In other words, in the optical film 3B of FIG. 3, the retardation film 2 is laminated on the polarizing plate 1B (having the polarizer 1a, the transparent protective film 1b, and the transparent protective film 1c). Although FIG. 3 shows a case where the slow axis of the retardation film 2 is parallel to the absorption axis of the polarizer 1a, this may be orthogonal.

  FIG. 4 is a schematic perspective view illustrating an optical film according to still another embodiment of the present invention. In the optical film 3C of FIG. 4, the transparent protective film 1c is disposed on one surface of the polarizer 1a, and the two retardation films 2a and 2b of the present invention are disposed on the other surface. In other words, in the optical film 3C of FIG. 4, two retardation films 2a and 2b are laminated on a polarizing plate 1C (having a polarizer 1a and a transparent protective film 1c). Although FIG. 4 shows a case where the slow axes of the retardation films 2a and 2b are parallel to the absorption axis of the polarizer 1a, this may be orthogonal. Furthermore, in FIG. 4, although the slow axes of the retardation films 2a and 2b are parallel to each other, they may be orthogonal depending on the purpose.

  FIG. 5 is a schematic perspective view illustrating an optical film according to still another embodiment of the present invention. In the optical film 3D of FIG. 5, a transparent protective film 1b and a transparent protective film 1c are arranged on both sides of a polarizer 1a, and two retardation films of the present invention are provided on the surface of the transparent protective film 1b opposite to the polarizer 1a. 2a and 2b are arranged. In other words, in the optical film 3D of FIG. 5, two retardation films 2a and 2b are laminated on a polarizing plate 1D (having a polarizer 1a, a transparent protective film 1b, and a transparent protective film 1c). Although FIG. 5 shows the case where the slow axes of the retardation films 2a and 2b are parallel to the absorption axis of the polarizer 1a, this may be orthogonal. Furthermore, in FIG. 5, although the slow axes of the retardation films 2a and 2b are parallel to each other, they may be orthogonal depending on the purpose.

  Any appropriate polarizer can be adopted as the polarizer used in the optical film of the present invention depending on the purpose. For example, dichroic substances such as iodine and dichroic dyes are adsorbed on hydrophilic polymer films such as polyvinyl alcohol films, partially formalized polyvinyl alcohol films, and ethylene / vinyl acetate copolymer partially saponified films. And polyene-based oriented films such as a uniaxially stretched product, a polyvinyl alcohol dehydrated product and a polyvinyl chloride dehydrochlorinated product. Among these, a polarizer obtained by adsorbing a dichroic substance such as iodine on a polyvinyl alcohol film and uniaxially stretching is particularly preferable because of its high polarization dichroic ratio. The thickness of these polarizers is not particularly limited, but is generally about 5 to 80 μm. The polarizers disposed on both sides of the liquid crystal cell may be the same or different.

  A polarizer uniaxially stretched by adsorbing iodine to a polyvinyl alcohol film can be produced by, for example, dyeing polyvinyl alcohol in an aqueous solution of iodine and stretching it 3 to 7 times the original length. . If necessary, it may contain boric acid, zinc sulfate, zinc chloride, or the like, or may be immersed in an aqueous solution such as potassium iodide. Further, if necessary, the polyvinyl alcohol film may be immersed in water and washed before dyeing.

  By washing the polyvinyl alcohol film with water, not only can the surface of the polyvinyl alcohol film be cleaned and the anti-blocking agent can be washed, but also the effect of preventing unevenness such as uneven dyeing can be obtained by swelling the polyvinyl alcohol film. is there. Stretching may be performed after dyeing with iodine, may be performed while dyeing, or may be dyed with iodine after stretching. The film can be stretched in an aqueous solution of boric acid or potassium iodide or in a water bath.

  As the transparent protective film, those having excellent transparency, mechanical strength, thermal stability, moisture shielding property, retardation value stability and the like are preferable. Examples of the material for forming the transparent protective film include polyester resins such as polyethylene terephthalate and polyethylene naphthalate, cellulose resins such as diacetyl cellulose and triacetyl cellulose, acrylic resins such as polymethyl methacrylate, polystyrene, acrylonitrile, Styrene copolymers, styrene resins, acrylonitrile / styrene resins, acrylonitrile / butadiene / styrene resins, acrylonitrile / ethylene / styrene resins, styrene / maleimide copolymers, styrene resins such as styrene / maleic anhydride copolymers, polycarbonate Examples thereof include resins. In addition, cycloolefin resin, norbornene resin, polyolefin resin such as polyethylene, polypropylene, ethylene / propylene copolymer, vinyl chloride resin, amide resin such as nylon and aromatic polyamide, aromatic polyimide, polyimide amide, etc. Imide resins, sulfone resins, polyether sulfone resins, polyether ether ketone resins, polyphenylene sulfide resins, vinyl alcohol resins, vinylidene chloride resins, vinyl butyral resins, arylate resins, polyoxymethylene resins Examples of the resin that forms the transparent protective film include a polymer film made of a resin, an epoxy resin, or a blend of the above resins. The transparent protective film can also be formed as a cured layer of a thermosetting or ultraviolet curable resin such as acrylic, urethane, acrylic urethane, epoxy, or silicone.

  As the transparent protective film, cellulose resins such as triacetyl cellulose and norbornene resins are preferably used. These are excellent in polarization characteristics and durability. Specific examples of the cellulose resin include “Fujitac” manufactured by Fuji Photo Film Co., Ltd. Specific examples of the norbornene-based resin include a product name “ZEONOR” manufactured by Nippon Zeon Co., Ltd. and a product name “ARTON” manufactured by JSR Corporation.

  The thickness of the transparent protective film can be appropriately set according to the purpose. Typically, the thickness of the transparent protective film is about 1 to 500 μm. If it is such thickness, it is excellent in workability | operativity, such as handleability, and intensity | strength, and can also contribute to thickness reduction of a liquid crystal display device. The thickness of the transparent protective film is more preferably 5 to 200 μm, and particularly preferably 10 to 150 μm. Within such a range, the polarizer is mechanically protected, and even when exposed to high temperature and high humidity, the polarizer does not shrink and stable optical characteristics can be maintained.

  As the transparent protective film, it is preferable to use a film with optimized optical characteristics. By doing so, the influence which the said film has on the viewing angle characteristic of a liquid crystal display device can be eliminated substantially. More specifically, the smaller the birefringence and the photoelastic coefficient of the transparent protective film, the better. In addition, the transparent protective film in which optimization of a retardation value is desired is a transparent protective film arrange | positioned between a polarizer and a liquid crystal cell. Since the transparent protective film disposed outside the polarizer (the side far from the liquid crystal cell) does not affect the optical characteristics of the liquid crystal display device, it is not necessary to optimize the retardation value.

  In the optical film of the present invention, the retardation film is usually disposed on the liquid crystal cell side. Therefore, in the optical film of the present invention, it is preferable that the transparent protective film on the side where the retardation film is laminated (for example, the transparent protective film 1b in FIGS. 3 and 5) optimizes the optical characteristics.

The transparent protective film (particularly the transparent protective film on which the retardation film of the present invention is laminated) preferably satisfies the following formulas (5) and (6):
0 nm <Re [590] ≦ 5 nm (5)
0 nm <Rth [590] ≦ 10 nm (6).

  Re [590] of the transparent protective film is preferably more than 0 and 5 nm or less, more preferably more than 0 and 3 nm or less, and particularly preferably more than 0 and 2 nm or less as described in the above formula (5). And most preferably more than 0 and 1 nm or less. Rth [590] of the transparent protective film is preferably more than 0 and 10 nm or less, more preferably more than 0 and 6 nm or less, and particularly preferably more than 0 and 4 nm or less as described in the above formula (6). And most preferably more than 0 and 3 nm or less. When the in-plane retardation and the thickness direction retardation are in the above ranges, good display characteristics can be obtained without adversely affecting display characteristics such as contrast ratio and color shift when used in a liquid crystal display device. .

The photoelastic coefficient of the transparent protective film is preferably an absolute value of a value measured with light having a wavelength of 590 nm at 23 ° C .: C [590] (m ² / N), preferably 2.0 × 10 ^{−13 to} 2.0. × 10 ⁻¹¹ , more preferably 5.0 × 10 ^{−13 to} 8.0 × 10 ⁻¹² , particularly preferably 2.0 × 10 ^{−12 to} 6.0 × 10 ⁻¹² , preferably ^{2.0 × 10 -12 ~5.0 × 10 -12} .

  Since the retardation film of the present invention has a photoelastic coefficient smaller than that of a conventional aromatic polymer film, even if it is laminated directly on a polarizer (substantially via an adhesive or a pressure-sensitive adhesive), liquid crystal When used in a display device, it is difficult to cause a shift or unevenness in the retardation value due to the contraction stress of the polarizer or the heat of the backlight, and good display characteristics can be obtained. However, the retardation film of the present invention having such a very small photoelastic coefficient is applied to the transparent protective film having optical properties optimized as described above (more specifically, the birefringence and the photoelastic coefficient are small). By laminating on the surface of the transparent protective film), the shrinkage stress of the polarizer propagating to the retardation film and the heat of the backlight can be reduced, so that the shift and unevenness of the retardation value can be further reduced. .

  Examples of the material for forming the transparent protective film having a small birefringence and a small photoelastic coefficient include, for example, a ring-opening (co) polymer of a norbornene-based monomer described in JP-A-6-511117. Norbornene resin hydrogenated after polymer modification such as addition or cyclopentadiene addition; norbornene resin obtained by addition polymerization of norbornene monomer; addition of norbornene monomer and olefin monomer such as ethylene or α-olefin A norbornene-based resin that has been copolymerized with a mold is used. Further, at least one kind of a polycyclic cycloolefin monomer such as norbornene described in JP-A No. 2002-348324, a monocyclic cycloolefin monomer, or an acyclic 1-olefin monomer is in a solution state, a suspension state, a monomer melt state, or A cycloolefin resin polymerized in the gas phase under a metallocene catalyst may also be used.

  Further, polycarbonate resins having 9,9-bis (4-hydroxyphenyl) fluorene in the side chain described in JP-A No. 2001-253960 and cellulose resins described in JP-A No. 7-112446 are used. It is done. Furthermore, the polymer film described in JP-A-2001-343529, for example, (A) a thermoplastic resin having a substituted and / or unsubstituted imide group in the side chain, and (B) a substituted and / or unsubstituted side chain. Resin compositions containing a thermoplastic resin having phenyl and nitrile groups are also used. As a specific example, a polymer film of a resin composition containing an alternating copolymer composed of isobutylene and N-methylmaleimide and an acrylonitrile / styrene copolymer is used.

  In addition, NTS Publishing Co., Ltd. “Development and application technology of optical polymer materials” 2003 edition p. 194-p. A random copolymer of a monomer constituting a polymer exhibiting positive orientation birefringence and a monomer constituting a polymer exhibiting negative orientation birefringence as described in 207, an anisotropic small molecule and / or a birefringent crystal. Also used are polymers.

  The method for laminating the transparent protective film and the polarizer is not particularly limited. For example, an adhesive containing an acrylic polymer or a vinyl alcohol polymer, or a vinyl alcohol polymer and boric acid or borax, or glutaraldehyde or melamine. Or it can carry out through the adhesive agent etc. which contain the water-soluble crosslinking agent with respect to vinyl alcohol-type polymers, such as oxalic acid. By using such an adhesive, the polarizer and the transparent protective film are hardly peeled off even by humidity or heat, and an optical film excellent in light transmittance and degree of polarization can be obtained. As said adhesive agent, it is preferable to use a polyvinyl alcohol-type adhesive agent from the point which is excellent in adhesiveness with the polyvir alcohol which is a raw material of a polarizer.

  When a polymer film containing a norbornene-based resin is used as the transparent protective film, the pressure-sensitive adhesive for laminating the film and the polarizer is excellent in transparency, has a small birefringence, and is used as a thin layer. However, a pressure-sensitive adhesive capable of exhibiting sufficient adhesive strength is preferable. As such an adhesive, for example, an adhesive for dry lamination, a styrene butadiene rubber adhesive, an epoxy two-component curable adhesive (for example, an epoxy resin) used by mixing a polyurethane resin solution and a polyisocyanate resin solution And a polythiol two-component, an epoxy resin and a polyamide two-component, etc., particularly a solvent-type adhesive and an epoxy two-component curable adhesive are preferable, and a transparent one is more preferable. . Some adhesives can improve the adhesive force by using an appropriate adhesive primer, and when such an adhesive is used, it is preferable to use an adhesive primer.

  As the adhesive primer, any appropriate primer that can form a layer capable of improving adhesiveness may be employed. Specific examples of the primer include silane coupling agents having a reactive functional group such as amino group, vinyl group, epoxy group, mercapto group, chloro group and hydrolyzable alkoxysilyl group in the same molecule. Titanate coupling agent having hydrolyzable hydrophilic group and organic functional group containing titanium in the molecule, and hydrolyzable hydrophilic group and organic functional group containing aluminum in the same molecule Examples include so-called coupling agents such as aluminate coupling agents; and resins having an organic reactive group such as epoxy resins, isocyanate resins, urethane resins, and ester urethane resins. Of these, a silane coupling agent is preferred from the viewpoint of easy handling industrially.

  The optical film is preferably provided with an adhesive layer or a pressure-sensitive adhesive layer on both sides or one side in order to facilitate lamination to the liquid crystal cell.

  The adhesive layer or the pressure-sensitive adhesive layer is not particularly limited. Examples of the adhesive for forming the adhesive layer and / or the pressure-sensitive adhesive for forming the pressure-sensitive adhesive layer include acrylic polymers, silicone-based polymers, polyesters, polyurethanes, polyamides, polyvinyl ethers, vinyl acetate / vinyl chloride copolymers, and modified polyolefins. A polymer having a base polymer such as an epoxy-based polymer, a fluorine-based polymer, a natural rubber, a synthetic rubber, or the like can be appropriately selected and used. In particular, an acrylic pressure-sensitive adhesive is preferably used because it is excellent in optical transparency, exhibits adhesive properties such as appropriate wettability, cohesiveness, and adhesiveness, and is excellent in weather resistance and heat resistance.

  The adhesive or pressure-sensitive adhesive can contain a crosslinking agent corresponding to the base polymer. Furthermore, the adhesive or pressure-sensitive adhesive can contain any appropriate additive depending on the purpose. Specific examples of the additive include a filler such as a resin such as a natural resin or a synthetic resin, glass fiber or glass bead, metal powder or other inorganic powder, a pigment, a colorant, and an antioxidant. In one embodiment, an adhesive layer showing light diffusibility can be formed by containing transparent fine particles.

  Examples of the transparent fine particles include inorganic fine particles that can be conductive, such as silica or calcium oxide having an average particle size of 0.5 to 20 μm, alumina, titania, zirconia, tin oxide, indium oxide, cadmium oxide, or antimony oxide; Alternatively, crosslinked or uncrosslinked organic fine particles made of an appropriate polymer such as polymethyl methacrylate or polyureta can be used. These can be used alone or in combination of two or more.

  The adhesive or pressure-sensitive adhesive is usually used in the form of an adhesive solution or dispersion having a solid content concentration of about 10 to 50% by weight in which a base polymer or a composition thereof is dissolved or dispersed in a solvent. As said solvent, arbitrary appropriate solvents (For example, organic solvents, such as toluene and ethyl acetate; water) can be used according to the kind of adhesive agent.

  The adhesive or pressure-sensitive adhesive may be used by forming a laminate of adhesive layers and / or pressure-sensitive adhesive layers having different compositions or types. The thickness of the adhesive (layer) or the pressure-sensitive adhesive (layer) can be appropriately determined according to the purpose of use and adhesive force, and is preferably 1 to 500 μm, more preferably 5 to 200 μm, and particularly preferably. 10-100 μm.

  On the exposed surface such as the adhesive layer or the pressure-sensitive adhesive layer, a separator is temporarily attached to cover the surface until it is put to practical use. Thereby, an operator etc. contact with an adhesive layer at the time of handling, and the said adhesive layer is prevented from being contaminated. Specific examples of the separator are as described above in connection with the bonding of the shrinkable film.

  The surface of the transparent protective film to which the polarizer is not adhered can be subjected to a hard coat treatment, an antireflection treatment, an antisticking treatment, or a diffusion treatment (also referred to as an antiglare treatment).

  The hard coat treatment is performed for the purpose of preventing scratches on the surface of the polarizing plate. For example, a cured film excellent in hardness, slipping property, etc. by an appropriate ultraviolet curable resin such as acrylic or silicone is used for the transparent coating. It can be formed on the surface of the protective film. The antireflection treatment is performed for the purpose of preventing reflection of external light on the surface of the polarizing plate. The anti-sticking treatment is performed for the purpose of preventing adhesion with an adjacent layer. The anti-glare treatment is performed for the purpose of preventing the outside light from being reflected on the surface of the polarizing plate and obstructing the viewing of the light transmitted through the polarizing plate. For example, the surface is roughened by a sandblasting method or an embossing method. It can be formed by imparting a fine concavo-convex structure to the surface of the transparent protective film by an appropriate method such as a blending method of transparent fine particles. The antiglare layer formed by the antiglare treatment may also serve as a diffusion layer (viewing angle expanding function or the like) for diffusing the light transmitted through the polarizing plate and expanding the viewing angle.

  Next, another optical member used in combination with the retardation film or the optical film of the present invention will be described. The other optical member is not particularly limited, and examples thereof include an optical film subjected to the hard coat treatment, antireflection treatment, sticking prevention treatment, and diffusion treatment (also referred to as antiglare treatment). Further, a reflective polarizing plate or a semi-transmissive polarizing plate in which a reflecting plate or a semi-transmissive reflecting plate is further laminated on an elliptical polarizing plate or a circular polarizing plate can be used. In addition, a reflective elliptical polarizing plate, a semi-transmissive elliptical polarizing plate, or the like, which is a combination of the above-described reflective polarizing plate or transflective polarizing plate and a retardation plate, may be used. Further, when the retardation film or optical film of the present invention is used for a transmissive or transflective liquid crystal display device, a commercially available brightness enhancement film (a polarized light separation film having a polarization selective layer, for example, manufactured by Sumitomo 3M Co., Ltd.). In combination with D-BEF, etc., a display device with higher display characteristics can be obtained.

  The optical film of the present invention may be formed by sequentially laminating each layer separately in the manufacturing process of the liquid crystal display device, or may be put to practical use in the form of a laminated film in which the respective layers are laminated in advance. It is preferable to use it as a laminated film. This is because the production efficiency of the liquid crystal display device and the like can be improved because the quality stability and workability are excellent.

E. Liquid Crystal Panel The liquid crystal panel of the present invention includes the retardation film of the present invention or the optical film of the present invention and a liquid crystal cell. Specific examples will be described below.

  The liquid crystal panel 6A of FIG. 6 has the optical film 3A of the present invention (having the transparent protective film 1c, the polarizer 1a, and the retardation film 2 of the present invention) on one surface of the liquid crystal cell 5, and the retardation film 2 is It arrange | positions so that it may become the side close | similar to a liquid crystal cell. A polarizing plate 4 (having transparent protective films 4b and 4c on both sides of the polarizer 4a) is disposed on the other surface of the liquid crystal cell 5 so that the transparent protective film 4b is closer to the liquid crystal cell 5. . Although the slow axis of the retardation film 2 is parallel to the absorption axis of the polarizer 1a, it may be orthogonal.

  In the liquid crystal panel 6B of FIG. 7, the optical film 3B (having the transparent protective film 1c, the polarizer 1a, the transparent protective film 1b, and the retardation film 2 of the present invention) is provided on one surface of the liquid crystal cell 5. 2 is arranged on the side close to the liquid crystal cell 5. A polarizing plate 4 (having transparent protective films 4b and 4c on both sides of the polarizer 4a) is disposed on the other surface of the liquid crystal cell 5 so that the transparent protective film 4b is closer to the liquid crystal cell 5. ing. Although the slow axis of the retardation film 2 is parallel to the absorption axis of the polarizer 1a, it may be orthogonal.

  The liquid crystal panel 6C of FIG. 8 has an optical film 3A (having the transparent protective film 1c, the polarizer 1a, and the retardation film 2 of the present invention) on both surfaces of the liquid crystal cell 5, and each retardation film 2 is the liquid crystal cell 5. It is arranged to be on the side closer to The slow axes of the respective retardation films 2 are arranged so as to be orthogonal to each other. Although the slow axis of the retardation film 2 in each optical film shows a case where it is parallel to the absorption axis of the polarizer 1a, it may be orthogonal.

  The liquid crystal panel 6D of FIG. 9 has an optical film 3B (having the transparent protective film 1c, the polarizer 1a, the transparent protective film 1b, and the retardation film 2 of the present invention) on both surfaces of the liquid crystal cell 5, respectively. 2 is arranged on the side close to the liquid crystal cell 5. The slow axes of the respective retardation films 2 are arranged so as to be orthogonal to each other. Although the slow axis of the retardation film 2 in each optical film shows a case where it is parallel to the absorption axis of the polarizer 1a, it may be orthogonal.

  The liquid crystal panel 6E of FIG. 10 is a case where the retardation film of the present invention is a laminate. In the liquid crystal panel 6E of FIG. 10, an optical film 3C (having a transparent protective film 1c, a polarizer 1a, and two retardation films 2a and 2b of the present invention) is provided on one surface of the liquid crystal cell 5. 2 is arranged on the side close to the liquid crystal cell 5. A polarizing plate 4 (having transparent protective films 4b and 4c on both sides of the polarizer 4a) is disposed on the other surface of the liquid crystal cell 5 so that the transparent protective film 4b is closer to the liquid crystal cell. Although the slow axes of the retardation films 2a and 2b in the laminate are parallel to each other, they may be orthogonal. Although the slow axis of the said retardation film 2 (2a and 2b) has shown the case where it is parallel to the absorption axis of the said polarizer 1a, this may be orthogonal.

  The liquid crystal panel 6F of FIG. 11 is also a case where the retardation film of the present invention is a laminate. The liquid crystal panel 6F in FIG. 11 has an optical film 3D (transparent protective film 1c, polarizer 1a, transparent protective film 1b, and two retardation films 2a and 2b of the present invention) on one surface of the liquid crystal cell 5. However, the retardation film 2 is arranged so as to be closer to the liquid crystal cell 5. A polarizing plate 4 (having transparent protective films 4b and 4c on both sides of the polarizer 4a) is disposed on the other surface of the liquid crystal cell 5 so that the transparent protective film 4b is closer to the liquid crystal cell. Although the slow axes of the retardation films 2a and 2b in the laminate are parallel to each other, they may be orthogonal. Although the slow axis of the said retardation film 2 (2a and 2b) has shown the case where it is parallel to the absorption axis of the said polarizer 1a, this may be orthogonal.

F. Applications of Retardation Film and Optical Film The retardation film and optical film of the present invention are used for liquid crystal display devices such as personal computers, liquid crystal televisions, mobile phones, and personal digital assistants (PDAs), organic electroluminescence displays (organic EL), and projectors. It can be used for image display devices such as projection televisions and plasma televisions.

  The type of the liquid crystal display device is not particularly limited, and any of a transmissive type, a reflective type, and a reflective transflective type can be used. Examples of liquid crystal cells used in the liquid crystal display device include twisted nematic (TN) mode, super twisted nematic (STN) mode, horizontal alignment (ECB) mode, vertical alignment (VA) mode, and in-plane switching (IPS) mode. And various liquid crystal cells such as fringe field switching (FFS) mode, hybrid alignment (HAN) mode, bend nematic (OCB) mode, ferroelectric liquid crystal (SSFLC) mode, and antiferroelectric liquid crystal (AFLC) mode. It is done. Among these, the retardation film and optical film of the present invention are particularly preferably used in combination with TN mode, VA mode, IPS mode, FFS mode, and OCB mode liquid crystal cells. Most preferably, the retardation film and optical film of the present invention are used in combination with an IPS mode or FFS mode liquid crystal cell.

  The twisted nematic (TN) mode liquid crystal cell is a liquid crystal cell in which a nematic liquid crystal having positive dielectric anisotropy is sandwiched between two base materials. The one that is twisted. Specifically, Baifukan “Liquid Crystal Dictionary” p. 158 (1989 version) and the liquid crystal cell described in JP-A-63-279229.

  The vertical alignment (VA) mode liquid crystal cell uses a voltage-controlled birefringence (ECB) effect, and nematic liquid crystal having a negative dielectric anisotropy between transparent electrodes when no voltage is applied. Means a vertically aligned liquid crystal cell. Specific examples include liquid crystal cells described in JP-A-62-210423 and JP-A-4-153621. Further, as described in JP-A No. 11-258605, the VA mode liquid crystal cell includes a substrate provided with a slit in a pixel or a projection formed on the surface in order to enlarge a viewing angle. May be used to provide a multi-domain MVA mode liquid crystal cell. Further, as described in Japanese Patent Application Laid-Open No. 10-123576, a VATN mode in which a chiral agent is added to a liquid crystal, the liquid crystal is substantially vertically aligned when no nematic liquid crystal voltage is applied, and twisted multi-domain alignment is applied when a voltage is applied. A liquid crystal cell may be used.

  The in-plane switching (IPS) mode liquid crystal cell is formed of, for example, a metal that is a nematic liquid crystal that uses a voltage controlled birefringence (ECB) effect and is oriented homogeneously in the absence of an electric field. It is a device that responds with an electric field (also called a transverse electric field) parallel to the substrate generated by the counter electrode and the pixel electrode. More specifically, for example, Techno Times publication “Monthly Display July” p. 83-p. 88 (1997 edition) and “Liquid Crystal vol. 2 No. 4” published by the Japanese Liquid Crystal Society. 303-p. 316 (1998 edition), in the normally black system, the alignment direction when no voltage is applied to the liquid crystal cell and the absorption axis of the polarizer on one side are made to coincide with each other so that the upper and lower polarizing plates are If they are arranged orthogonally, the display is completely black without an electric field. When there is an electric field, the transmittance according to the rotation angle can be obtained by rotating the liquid crystal molecules while keeping them parallel to the substrate. The IPS mode includes a super-in-plane switching (S-IPS) mode and an advanced super-in-plane switching (AS-IPS) mode using a V-shaped electrode or a zigzag electrode. Commercially available liquid crystal display devices adopting the IPS mode as described above include, for example, Hitachi, Ltd. 20V type wide liquid crystal television product name “Wooo”, Eyama Co., Ltd. 19 type liquid crystal display product name “ProLite E481S-1”. ", 17 type TFT liquid crystal display made by Nanao Co., Ltd., trade name" FlexScan L565 "and the like.

  The FFS mode liquid crystal cell uses a voltage-controlled birefringence effect, nematic liquid crystal aligned in a homogeneous molecular arrangement in the absence of an electric field, for example, a counter electrode and a pixel electrode formed of a transparent conductor It responds with an electric field (also referred to as a transverse electric field) parallel to the substrate generated in step 1. Note that the lateral electric field in the FFS mode is also referred to as a fringe electric field. This fringe electric field can be generated by setting the distance between the counter electrode made of a transparent conductor and the pixel electrode to be narrower than the distance between the upper and lower substrates. More specifically, SID (Society for Information Display) 2001 Digest, p. 484-p. As described in 487 and JP 2002-031812 A, in the normally black method, the alignment direction when no voltage is applied to the liquid crystal cell is matched with the absorption axis of the polarizer on one side, When the upper and lower polarizing plates are arranged orthogonally, the display is completely black in the absence of an electric field, and when there is an electric field, the liquid crystal molecules rotate while maintaining parallel to the substrate, so that the transmittance according to the rotation angle is obtained. Can be obtained. The FFS mode includes an advanced fringe field switching (A-FFS) mode and an ultra fringe field switching (U-FFS) mode using a zigzag electrode. As a commercially available liquid crystal display device that employs the FFS mode as described above, for example, “M1400”, a product name of Tablet PC manufactured by Motion Computing, Inc., may be mentioned.

  The above-mentioned bend nematic (OCB: Optically Compensated Bend or Optically Compensated Birefringence) mode liquid crystal cell uses a voltage-controlled birefringence effect, and a nematic liquid crystal having a positive dielectric anisotropy between transparent electrodes when no voltage is applied. The liquid crystal cell is a bend-aligned liquid crystal cell having a twisted alignment in the center. The OCB mode liquid crystal cell is also referred to as a “π cell”. Specifically, Kyoritsu Publishing Co., Ltd. “Next Generation Liquid Crystal Display” (2000) p. 11-p. 27 and those described in JP-A-7-084254.

  By using the retardation film and / or optical film of the present invention for such various liquid crystal cells, the contrast ratio and color shift in the oblique direction can be improved, and the function can be maintained for a long time. Can do.

G. Applications of the liquid crystal panel and the liquid crystal display device The application of the liquid crystal panel and the liquid crystal display device of the present invention is not particularly limited, but OA equipment such as a personal computer monitor, a notebook personal computer, a copy machine, a mobile phone, a clock, a digital camera, Personal digital assistants (PDAs), portable devices such as portable game consoles, household electrical devices such as video cameras, liquid crystal televisions, and microwave ovens, back monitors, monitors for car navigation systems, in-vehicle devices such as car audio, and commercial stores It can be used for various applications such as exhibition equipment such as information monitors, security equipment such as monitoring monitors, nursing care and medical equipment such as nursing monitors and medical monitors.

  Particularly preferably, the liquid crystal panel and the liquid crystal display device of the present invention are used for a large-sized liquid crystal television. The screen size of the liquid crystal television in which the liquid crystal panel and the liquid crystal display device of the present invention are used is preferably a wide 17 type (373 mm × 224 mm) or more, more preferably a wide 23 type (499 mm × 300 mm) or more, particularly Preferably, it is wide 26 type (566 mm × 339 mm) or more, and most preferably wide 32 type (687 mm × 412 mm) or more.

The present invention will be further described using the following examples and comparative examples. In addition, this invention is not limited only to these Examples. In addition, each analysis method used in the Example is as follows.
(1) Identification of polycarbonate-based resin: ¹ H-NMR measurement was performed with the following apparatus and conditions, and was determined from the peak integration ratio of the obtained spectrum.
・ Analyzer: JEOL “JNM-EX400”
・ Observation nucleus: 1H
・ Frequency: 400 MHz
・ Pulse width: 45 degrees ・ Pulse repetition time: 10 seconds ・ Measurement temperature: Room temperature (2) Method of measuring molecular weight and styrene resin content: Polystyrene as a standard sample by gel permeation chromatography (GPC) method Calculated as Specifically, it measured with the following apparatuses, instruments, and measurement conditions.
Measurement sample: The sample was dissolved in tetrahydrofuran to give a 0.1% by weight solution, allowed to stand overnight, and then filtered through a 0.45 μm membrane filter.
・ Analyzer: “HLC-8120GPC” manufactured by TOSOH
Column: TSKgel Super HM-H / H4000 / H3000 / H2000
Column size: 6.0 mmI. D. × 150mm
-Eluent: Tetrahydrofuran-Flow rate: 0.6 ml / min.
・ Detector: RI
-Column temperature: 40 ° C
・ Injection volume: 20 μl
(3) Measuring method of glass transition temperature (Tg): It was determined according to JISK7121 using the following apparatus and measuring conditions.
・ Analyzer: Differential scanning calorimeter “DSC5500” manufactured by Seiko Electronics Corporation
・ Measurement atmosphere: under nitrogen of 20 ml / min ・ Raising rate: 10 ° C./min (4) Measuring method of retardation value, wavelength dispersion characteristic, slow axis angle, light transmittance: Based on parallel Nicol rotation method Using a phase difference meter [product name “KOBRA21-ADH” manufactured by Oji Scientific Instruments Co., Ltd.], a value at a wavelength of 590 nm at 23 ° C. was measured.
(5) Photoelastic coefficient measurement method: Using a spectroscopic ellipsometer [manufactured by JASCO Corporation, product name “M-220”], the retardation value of a sample is measured under stress, and the function of the stress and the retardation value It was calculated from the slope of. Specifically, the retardation value in the film plane at a wavelength of 590 nm when a stress of 5N to 15N was applied to a 2 cm × 10 cm test piece at 23 ° C. was measured.
(6) Thickness measurement method: Measured using an Anritsu digital micrometer “K-351C type”.
(7) Measuring method of shrinkage rate of shrinkable film: It was determined according to the heating shrinkage rate A method of JIS Z 1712 (however, the heating temperature was set to 140 ° C. or 160 ° C. instead of 120 ° C., and the weight of the test piece was 3 g. Is different). Specifically, five test pieces each having a width of 20 mm and a length of 150 mm were taken from the vertical (MD) and horizontal (TD) directions, and a test piece with a mark at a distance of about 100 mm at the center was prepared. To do. The test piece is suspended vertically in an air circulation type thermostatic bath maintained at a temperature of 140 ° C. ± 3 ° C. or 160 ° C. ± 3 ° C. with a weight of 3 g, heated for 15 minutes, taken out, and in a standard state ( After standing at room temperature for 30 minutes, the distance between the standards was measured using a caliper specified in JIS B7507, and the average value of the five measured values was obtained. S (%) = [(between the standards before heating S (MD) and S (TD) were calculated from distance (mm) −distance between standards after heating (mm)) / distance between standards before heating (mm)] × 100.
(8) Measuring method of shrinkage stress in width (TD) direction of shrink film: Using the following apparatus, the shrinkage stress in the width (TD) direction at 140 ° C. and 150 ° C. was measured by the TMA method.
・ Device: “TMA / SS 6100” manufactured by Seiko Instruments Inc.
Data processing: “EXSTAR6000” manufactured by Seiko Instruments Inc.
・ Measurement mode: Constant temperature rise measurement (10 ℃ / min)
・ Measurement atmosphere: In air (room temperature)
・ Load: 20mN
Sample size: 15mm x 2mm (long side is width (TD) direction)
-Film thickness: 60 μm
(9) Evaluation method of display unevenness of liquid crystal panel: A display screen was photographed using the following liquid crystal cell and measuring apparatus. In Table 2, “◯” indicates that the difference in luminance is 1.5680 or less over the entire panel surface. “X” indicates that the difference in luminance is 1.77920 or more on the entire panel surface.
・ Liquid crystal cell: mounted on Sony KLV-17HR2
・ Panel size: 375mm x 230mm
・ Measuring device: Minolta 2-dimensional color distribution measuring device “CA-1500”
・ Measurement environment: Dark room (23 ℃)

[Example 1]
Phosgene as the carbonate precursor, (A) 2,2-bis (4-hydroxyphenyl) propane and (B) 1,1-bis (4-hydroxyphenyl) -3,3,5- as the aromatic dihydric phenol component Using trimethylcyclohexane, a repeating unit of the following formulas (3) and (4) having a weight ratio of (A) :( B) of 4: 6 and a weight average molecular weight (Mw) of 60,000 according to a conventional method A polycarbonate-based resin [number average molecular weight (Mn) = 33,000, Mw / Mn = 1.78] was obtained. 70 parts by weight of the above polycarbonate resin and 30 parts by weight of a styrene resin having a weight average molecular weight (Mw) of 1,300 [number average molecular weight (Mn) = 716, Mw / Mn = 1.78] (Sanyo Kasei Heimer SB75) Was added to 300 parts by weight of dichloromethane and stirred and mixed at room temperature for 4 hours to obtain a transparent solution. This solution was cast on a glass plate, allowed to stand at room temperature for 15 minutes, then peeled off from the glass plate, dried in an oven at 80 ° C. for 10 minutes, and then at 120 ° C. for 20 minutes, and had a thickness of 55 μm and a glass transition temperature (Tg ) Obtained a polymer film of 140 ° C. The polymer film obtained had a light transmittance of 93% at a wavelength of 590 nm. The in-plane retardation value of the polymer film: Re [590] was 5.0 nm, and the retardation value in the thickness direction: Rth [590] was 12.0 nm. The average refractive index was 1.576.

  The polymer film obtained in Example 1 was dissolved in tetrahydrofuran to give a 0.1% by weight solution, allowed to stand for 8 hours, and then filtrated through a 0.45 μm membrane filter to obtain the filtrate by GPC measurement. The content of the styrenic resin was 27 parts by weight with respect to 100 parts by weight of the total solid content.

The weight ratio of the aromatic divalent phenol compound component was determined by measuring the polymer film obtained in Example 1 by ¹ H-NMR. Specifically, the polymer film is dissolved in chloroform, the chloroform solution is dropped into 100 times by weight of methanol to precipitate a white solid at 23 ° C. (reprecipitation), and the solution is filtered to give methanol. Separated into soluble and methanol insoluble. The methanol-insoluble matter was dissolved in deuterated chloroform, and ¹ H-NMR measurement was performed. As a result, 1.68 ppm (6H) derived from the methyl group of 2,2-bis (4-hydroxyphenyl) propane and 1,1-bis (4-hydroxyphenyl) in the spectrum obtained by ¹ H-NMR measurement. ) The weight ratio of each component calculated from the peak integration ratio of 2.69 ppm (6H) methyl group substituted at the 3-position of the cyclohexyl ring of -3,3,5-trimethylcyclohexane was 4: 6.

  On both sides of the polymer film (thickness: 55 μm), a biaxially stretched polypropylene film having the characteristics shown in Table 1 below (trade name “Trephan” (thickness: 60 μm) manufactured by Toray) was applied to an acrylic pressure-sensitive adhesive layer (thickness: 15 μm). Pasted through. Thereafter, the film was held in the longitudinal direction with a roll stretching machine and stretched 1.29 times in a 147 ° C. air circulation type thermostatic oven (measured at a distance of 3 cm from the film back surface / temperature variation ± 1 ° C.). (Feeding speed 1m / min). The properties of the obtained retardation film are as shown in Table 2.

  As the acrylic pressure-sensitive adhesive in this example, isononyl acrylate (weight average molecular weight = 550,000) synthesized by solution polymerization was used as a base polymer, and the polyisocyanate compound was used with respect to 100 parts by weight of the polymer. A mixture of 3 parts by weight of a crosslinking agent [trade name “Coronate L” manufactured by Nippon Polyurethane Co., Ltd.] and 10 parts by weight of a catalyst [trade name “OL-1” manufactured by Tokyo Fine Chemicals Co., Ltd.] was used.

[Example 2]
A retardation film was produced in the same manner as in Example 1 except that the stretching temperature was changed from 147 ° C. to 146 ° C. and the draw ratio was changed from 1.29 times to 1.09 times. The properties of the obtained retardation film are as shown in Table 2.

[Example 3]
A retardation film was produced in the same manner as in Example 1 except that the stretching temperature was changed from 147 ° C. to 141 ° C. and the draw ratio was changed from 1.29 times to 1.10 times. The properties of the obtained retardation film are as shown in Table 2.

[Example 4]
A retardation film was produced in the same manner as in Example 1 except that the stretching temperature was changed from 147 ° C. to 145 ° C. and the draw ratio was changed from 1.29 times to 1.14 times. The properties of the obtained retardation film are as shown in Table 2.

[Example 5]
A retardation film was produced in the same manner as in Example 1 except that the stretching temperature was changed from 147 ° C. to 153 ° C. and the stretching ratio was changed from 1.29 times to 1.18 times. The properties of the obtained retardation film are as shown in Table 2.

[Example 6]
A retardation film was produced in the same manner as in Example 1 except that the stretching temperature was changed from 147 ° C. to 154.5 ° C. and the stretching ratio was changed from 1.29 times to 1.22 times. The properties of the obtained retardation film are as shown in Table 2.

[Example 7]
A retardation film was produced in the same manner as in Example 1 except that the stretching temperature was changed from 147 ° C. to 146 ° C. and the draw ratio was changed from 1.29 times to 1.25 times. The properties of the obtained retardation film are as shown in Table 2.

[Example 8]
A retardation film was produced in the same manner as in Example 1 except that the draw ratio was changed from 1.29 times to 1.27 times. The properties of the obtained retardation film are as shown in Table 2.

[Example 9]
Using a polymer film containing a styrene-based resin and a polycarbonate-based resin [trade name “Elmec PF” (thickness: 55 μm) manufactured by Kaneka Chemical Co., Ltd.], a retardation film was formed by the same heating and stretching method as in Example 1. Produced. The properties of the obtained retardation film are as shown in Table 2.

[Comparative Example 1]
A biaxially oriented polypropylene film is acrylic on both sides of a polymer film (thickness 60 μm) made of a polycarbonate resin obtained by a conventional method using phosgene as a carbonate precursor and bisphenol A as an aromatic dihydric phenol component. It bonded together through the adhesive layer. Then, the longitudinal direction of the film was held with a roll stretching machine and stretched 1.10 times at 160 ° C. (feed speed 1 m / min). The properties of the obtained retardation film are as shown in Table 2. The biaxially stretched polypropylene film and acrylic pressure-sensitive adhesive used in this comparative example were the same as those in Example 1. The polymer film made of the polycarbonate resin had a glass transition temperature (Tg) of 150 ° C., Re [590] before stretching was 7.0 nm, and Rth [590] was 15.0 nm.

[Comparative Example 2]
A retardation film was produced in the same manner as in Comparative Example 1 except that the thickness of the polymer film of Comparative Example 1 was changed from 60 μm to 40 μm and the draw ratio was changed from 1.10 times to 1.05 times. The properties of the obtained retardation film are as shown in Table 2.

[Comparative Example 3]
A biaxially stretched polypropylene film was bonded to both sides of a norbornene-based resin film [trade name “Arton F” manufactured by JSR Corporation] via an acrylic pressure-sensitive adhesive layer. Thereafter, the film was stretched 1.75 times at 175 ° C. while maintaining the longitudinal direction of the film with a roll stretching machine. The properties of the obtained retardation film are as shown in Table 2. The biaxially stretched polypropylene film and acrylic pressure-sensitive adhesive used in this comparative example were the same as those in Example 1. The polymer film made of the norbornene-based resin had a glass transition temperature (Tg) of 171 ° C., Re [590] before stretching was 2.0 nm, and Rth [590] was 10.0 nm.

[Example 10]
(Preparation of polarizing plate)
The polyvinyl alcohol film was dyed in an aqueous solution containing iodine, and then uniaxially stretched between rolls having different speed ratios in an aqueous solution containing boric acid to obtain a polarizer. On one surface of the polarizer, a 40 μm-thick norbornene-based resin film (trade name “ZEONOR ZF14-040” manufactured by Nippon Zeon Co., Ltd.) and an adhesive primer (manufactured by Nippon Unicar Co., Ltd.) are used. Name “A-1110”) with a thickness of 0.1 μm, and then bonded via a polyvinyl alcohol adhesive (trade name “Goseifamer Z” manufactured by Nippon Synthetic Chemical Co., Ltd.) A polarizing plate P was obtained by adhering a 40 μm-thick triacetylcellulose film (trade name “Fujitac” manufactured by Fuji Photo Film Co., Ltd.) via the polyvinyl alcohol-based adhesive. The norbornene-based resin film has Re [590] of 1.0 nm and Rth [590] of 3.0 nm, and the absolute value of the photoelastic coefficient: C [590] is 3.10 × 10 ⁻¹² (m ² / N )Met.

(Production of optical film)
The retardation film obtained in Example 1 is placed on the surface of the norbornene resin film of the polarizing plate P, and the slow axis of the retardation film is parallel to the absorption axis of the polarizer (0 ° ± 1.0 °). The optical film Q was obtained by bonding through an acrylic pressure-sensitive adhesive.

(Production of liquid crystal display device)
The liquid crystal panel was taken out from the liquid crystal display device [SONY KLV-17HR2] including an IPS mode liquid crystal cell, the polarizing plates arranged above and below the liquid crystal cell were removed, and the glass surfaces (front and back) were washed. Subsequently, the optical film Q is bonded to the viewing side of the liquid crystal cell via an acrylic pressure-sensitive adhesive, and the polarizing plate P is bonded to the backlight side of the liquid crystal cell via an acrylic pressure-sensitive adhesive. A liquid crystal panel I was produced. The optical film Q was arranged so that the retardation film was closer to the liquid crystal cell. The polarizing plate P was disposed so that the norbornene-based resin film was closer to the liquid crystal cell.

  After the liquid crystal panel I is incorporated in the original liquid crystal display device and the backlight is lit for 8 hours, the liquid crystal display is performed in a dark room using a two-dimensional color distribution measuring device “CA-1500” manufactured by Minolta Co., Ltd. The display screen of the device was taken. As a result, as shown in FIG. 12, display unevenness due to the heat of the backlight was small.

[Comparative Example 4]
A liquid crystal panel II was produced using the retardation film obtained in Comparative Example 1 instead of the retardation film obtained in Example 1 (preparation of optical film) described in Example 10. This was incorporated into a liquid crystal display device [KLV-17HR2 manufactured by SONY], the backlight of the liquid crystal display device was turned on for 8 hours, and then the display screen was photographed in the same manner as in Example 10. As a result, as shown in FIG. 13, the display unevenness due to the heat of the backlight was very large.

[Evaluation]
FIG. 14 shows the relationship between in-plane retardation values: Re [590] and Rth [590] / Re [590] of the retardation films described in Examples 1 to 9 and the retardation films of Comparative Examples 1 to 3. It is a graph to show. As shown in FIG. 14, in Examples 1 to 9, 0 <Rth [590] / Re [590] <1 (that is, a relationship of nx>nz> ny), and a wide range of phase difference values. The retardation film which has was obtained. In addition, the retardation films obtained in Examples 1 to 9 were difficult to tear in the direction parallel to the stretching direction and had practically sufficient mechanical strength. Further, in the liquid crystal display device described in Example 10 in which the liquid crystal panel using the retardation film described in Example 1 was incorporated, display unevenness due to the heat of the backlight was small as shown in FIG. When Examples 2 to 9 were also evaluated in the same manner as Example 1, the display unevenness was small. In Examples 2 to 5, two retardation films were used so that the slow axes were parallel. On the other hand, as shown in Comparative Example 3, an aliphatic resin film having an Rth [590] / Re [590] value smaller than 0.90 could not be obtained. Moreover, the retardation film obtained in Comparative Example 3 was easily torn in the direction parallel to the stretching direction, and the mechanical strength was not practically sufficient. On the other hand, in Comparative Example 1 and Comparative Example 2, retardation films showing Rth [590] / Re [590] values similar to those in Example 1 and Example 3 could be produced. However, a liquid crystal display device incorporating a liquid crystal panel in which the retardation film according to the prior art shown in Comparative Example 1 is used instead of the retardation film in Example 10 is shown in FIG. The unevenness was very large. When Comparative Example 2 was evaluated in the same manner as Comparative Example 1, the display unevenness was very large. From this, display unevenness due to the heat of the backlight is remarkably improved by stretching a polymer film formed from a blend of a predetermined amount of styrene resin and polycarbonate resin to produce a retardation film. You can see that In Comparative Example 2, two retardation films were used so that the slow axes were parallel.

  As described above, according to the retardation film of the present invention, even if it is used in a liquid crystal display device, a shift or unevenness in retardation value hardly occurs due to stress, and has a relationship of nx> nz> ny and has a wide range of positions. Since a retardation film having a retardation value can be provided, it can be said that it is extremely useful for improving display characteristics of a liquid crystal display device.

It is the schematic explaining an example of the manufacturing method of the retardation film of this invention. It is the schematic which shows an example of the optical film of this invention. It is the schematic which shows an example of the optical film of this invention. It is the schematic which shows an example of the optical film of this invention. It is the schematic which shows an example of the optical film of this invention. It is the schematic which shows an example of the liquid crystal panel of this invention. It is the schematic which shows an example of the liquid crystal panel of this invention. It is the schematic which shows an example of the liquid crystal panel of this invention. It is the schematic which shows an example of the liquid crystal panel of this invention. It is the schematic which shows an example of the liquid crystal panel of this invention. It is the schematic which shows an example of the liquid crystal panel of this invention. It is a photograph which shows the display nonuniformity of the liquid crystal display device of this invention. It is a photograph which shows the display nonuniformity of the liquid crystal display device in a prior art. It is a graph which shows the relationship between Re [590] and Rth [590] / Re [590] of the retardation film of this invention.

Explanation of symbols

1: Polarizing plate 1a: Polarizer 1b, 1c: Transparent protective film 2: Retardation film 3: Optical film 4: Polarizing plate 4a: Polarizer 4b, 4c: Transparent protective film 5: Liquid crystal cell 6: Liquid crystal panel

Claims (13)

A stretched polymer film containing a styrene-based resin and a polycarbonate-based resin, satisfying the following formulas (1) and (2), and having an absolute photoelastic coefficient measured at 23 ° C. with light having a wavelength of 590 nm value is ^{2.0 × 10 -11 ~8.0 × 10 -11} m 2 / N, the phase difference film:
100 nm ≦ Re [590] ≦ 350 nm (1)
0.2 ≦ Rth [590] / Re [590] ≦ 0.8 (2)
In the formulas (1) and (2), Re [590] and Rth [590] are a retardation value in the film plane and a retardation value in the thickness direction measured with light having a wavelength of 590 nm at 23 ° C., respectively.   The retardation film according to claim 1, wherein the content of the styrenic resin is 10 to 40 parts by weight with respect to 100 parts by weight of the total solid content. The retardation film according to claim 1 or 2, wherein the polycarbonate-based resin includes repeating units represented by the following formulas (3) and (4):
In formulas (3) and (4), n is an integer of 2 or more. Retardation film in any one of Claim 1 to 3 whose Re [480] / Re [590] is 1.02-1.30:
Here, Re [480] is an in-plane retardation value measured with light having a wavelength of 480 nm at 23 ° C.   The retardation film according to any one of claims 1 to 4, wherein the variation in orientation angle is in the range of ± 2.0 ° to ± 1.0 °.   The retardation film according to claim 1, which is used for an IPS mode or FFS mode liquid crystal display device. A polarizer and a retardation film according to any one of claims 1 to 6 laminated on at least one side of the polarizer,
An optical film in which a slow axis of the retardation film is parallel or orthogonal to an absorption axis of the polarizer.   The optical film according to claim 7, further comprising a transparent protective film on at least one side of the polarizer. Having a transparent protective film on both sides of the polarizer, the retardation film is laminated on at least one of the transparent protective film,
The optical film according to claim 8, wherein the transparent protective film on which the retardation film is laminated satisfies the following formulas (5) and (6):
0 nm <Re [590] ≦ 5 nm (5)
0 nm <Rth [590] ≦ 10 nm (6).   A liquid crystal panel comprising the retardation film according to any one of claims 1 to 6 or the optical film according to any one of claims 7 to 9 and a liquid crystal cell.   The liquid crystal panel according to claim 10, wherein the liquid crystal cell is in an IPS mode or an FFS mode.   A liquid crystal display device comprising the liquid crystal panel according to claim 10. A liquid crystal television comprising the liquid crystal panel according to claim 10.