JP2008233814A - Optical film, polarizing plate using the same, and liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical film which realizes a high contrast, a polarizing plate using the optical film, and a liquid crystal display. <P>SOLUTION: The optical film contains a retardation developer (A) having liquid crystal properties and a retardation developer (B) different therefrom. Even when a mixture obtained by mixing the retardation developer (A) and the retardation developer (B) at a ratio of 1:1 is separately prepared, the same liquid crystal phase as the liquid crystal phase shown by the retardation developer (A) alone is formed in the mixture. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical film, a polarizing plate using the same, and a liquid crystal display device.

Liquid crystal display devices have been increasingly used year by year as space-saving image display devices with low power consumption. Conventionally, the large viewing angle dependence of images has been a major drawback of liquid crystal display devices, but in recent years, the high viewing angle liquid crystal mode of the VA mode has been put into practical use, which enables high-quality images such as televisions to be displayed. In demanded markets, the demand for liquid crystal display devices is expanding rapidly.
Accordingly, in the liquid crystal display device, further improvement in the optical compensation capability is required for the optical compensation member used for improving the color, contrast, and viewing angle dependency thereof.

  As an optical compensation film for a VA mode liquid crystal display device, Patent Document 1 discloses that a negative C plate and a positive A plate used for improving the viewing angle characteristics of a liquid crystal display device are combined with a specific wavelength dispersion characteristic. Thus, there is known a technology that enables a liquid crystal display device with high contrast and good color reproducibility without interference unevenness and color shift by using a laminated type. However, in this method, when the base films of the A plate and the C plate are used as the protective film for the polarizing plate, there is a problem that adhesion with the polarizing film is difficult and adhesive processing is required, which increases costs.

  Further, Patent Document 2 is a mixture of a resin having a positive refractive index anisotropy, a resin having a negative refractive index anisotropy, and a retardation adjusting agent exhibiting dichroism, or a positive refraction. 1 comprising: a repeating unit that forms a polymer having refractive index anisotropy; and a copolymer resin having the repeating unit that forms a polymer having negative refractive index anisotropy and the retardation adjusting agent. A phase difference film with excellent retardation characteristics in a wide band (short wavelength range to long wavelength range) due to a single retardation film, and a good anti-reflection effect even in the short wavelength range and long wavelength range when used in a reflective LCD. Techniques for providing films are disclosed. However, this method has a problem that the material for producing the film has to be expensive, and the production cost is high and the mass productivity is poor.

  Patent Document 3 has at least one first layer mainly composed of a material having a positive intrinsic birefringence value and at least one second layer mainly composed of a material having a negative intrinsic birefringence value. Disclosed is a technology that enables a liquid crystal display device that has high contrast, no interference unevenness, no color shift, and good color reproducibility by using a multilayered retardation plate formed by stretching a laminate. Yes. However, this method has a problem in that a laminate having a different softening temperature is stretched at a certain temperature, so that it deviates from the optimum stretching temperature of each layer and sufficient performance is not exhibited.

  As a means to solve these problems, an additive (hereinafter referred to as positive intrinsic birefringence) in which the angle between the direction in which the end-to-end distance of the molecule is maximum and the direction in which the polarizability anisotropy is maximum is substantially parallel is used. A technique has been already found in which in-plane retardation is arbitrarily developed by adding an additive) to an optical resin film and stretching the film. That is, when a positive intrinsic birefringent additive is added to the optical resin film, the additive has the major axis direction of the molecule substantially parallel to the direction in which the polarizability anisotropy is maximized. In-plane retardation of the resin film is easily developed. In particular, by using a positive intrinsic birefringent additive, it is possible to adjust the in-plane retardation over a wide range without excessively increasing the draw ratio, and it is possible to easily and stably produce a stretched resin film. It has become to.

  On the other hand, the demand for optical compensation capability has become increasingly severe. For example, Patent Document 4 shows so-called reverse wavelength dispersion in which the short wave side of retardation in the in-plane direction (hereinafter referred to as Re) is smaller than the long wave side as an ideal color shift improving means, and the film thickness direction. An optical compensation film exhibiting so-called forward wavelength dispersion in which the short wave side of the retardation (hereinafter referred to as Rth) is larger than the long wave side has been proposed.

  In general, Re and Rth exhibit the same wavelength dispersion. That is, Re reverse chromatic dispersion and Rth forward chromatic dispersion are in a trade-off relationship, and it is extremely difficult at this stage to realize Re reverse chromatic dispersion and Rth forward chromatic dispersion with a single material. Therefore, for example, a so-called asymmetric two-plate type in which a combination of an A plate with Re reverse chromatic dispersion and a C plate with Rth forward chromatic dispersion as described in Patent Document 1 is stacked. However, this method has a problem that the optical performance values required for the A plate and the C plate must be precisely matched. Furthermore, in order not to cause light leakage or the like as an optical compensation film, it must be bonded so that the optical axis of each film does not deviate, and there is a problem inferior in mass productivity.

  In order to avoid the trouble of matching the optical performance and matching the optical axes, a method of adding two types of retardation enhancers in one film has been proposed.

JP 2004-326089 A JP 2004-325523 A JP 2004-325971 A International Publication No. 2004/068226 Pamphlet

  An object of this invention is to provide the optical film which implement | achieves high contrast, the polarizing plate using this optical film, and a liquid crystal display device.

The inventor of the present invention has intensively studied by adding a plurality of retardation enhancers to solve the above problems.
However, when a plurality of retardation enhancers are added to one optical film, the retardation value of the obtained optical film is smaller than the sum of values when each retardation enhancer is added alone. Became clear. That is, it became clear that a plurality of retardation developing agents inhibit each other's retardation developing ability.
For this reason, the present inventors have further studied, and by making the combination of retardation enhancers specific, the expression of retardation of each of the enhancers is efficiently exhibited, and a material suitable as an optical compensation film I found out that

  The means for achieving the object of the present invention are specifically as follows.

[1]
An optical film containing a retardation developer (A) having liquid crystallinity and a retardation developer (B) different from the retardation developer, wherein the retardation developer (A) and the retardation developer (B) are separately added. Even when a mixture obtained by mixing at a ratio of 1: 1 is prepared, the liquid crystal phase identical to the liquid crystal phase which the retardation developing agent (A) shows alone is formed in the mixture. Optical film.
[2]
[1] The optical film according to [1], wherein the retardation developer (A) is a compound represented by the following general formula (1), and the retardation developer (B) is a compound represented by the general formula (2).
General formula (1):

(In General Formula (1), L ₁ and L ₂ each independently represent a single bond or a divalent linking group. A ₁ and A ₂ each independently represent —O—, —NR— (R represents a hydrogen atom) Or a linking group selected from the group consisting of —S— and —CO—, R ₁ , R ₂ , and R ₃ each independently represents a substituent, and X is the 14th to 16th. A hydrogen atom or a substituent may be bonded to X. n represents an integer of 0 to 2.
General formula (2):

(In general formula (2), R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁸ and R ⁹ each independently represents a hydrogen atom or a substituent.)
[3]
The optical film according to [1] or [2], wherein the optical film mainly contains cellulose ester, polycarbonate, cycloolefin polymer, cycloolefin copolymer, and polyimide.
[4]
The polarizing plate in which a protective film is bonded to both surfaces of a polarizer, wherein at least one of the protective films is the optical film according to any one of [1] to [3].
[5]
The polarizing plate according to [4], which has an optically anisotropic layer on at least one surface of the protective film.
[6]
A liquid crystal display device comprising a liquid crystal cell and two polarizing plates disposed on both sides thereof, wherein at least one polarizing plate is the polarizing plate according to [4] or [5].

  As described above, by using a plurality of specific combinations of retardation developing agents that do not inhibit the liquid crystallinity of the retardation developing agent, the expression of retardation values in the in-plane direction of each of the developing agents is efficiently exhibited. The present inventors have found that the material is suitable as an optical compensation film.

The present invention will be described in detail below.
An optical film containing a retardation developer (A) having liquid crystallinity and a retardation developer (B) different from the retardation developer, wherein the retardation developer (A) and the retardation developer (B) ) Are mixed at a ratio of 1: 1, the liquid crystal phase identical to the liquid crystal phase that the retardation developing agent (A) exhibits alone is formed in the mixture. To an optical film.

  That is, the present invention relates to an optical film containing a retardation developing agent (A) having an arbitrary liquid crystallinity and a retardation developing agent (B) different from this, but the retardation developing agent (A), (B ) Is selected depending on whether the liquid crystallinity of the mixture obtained by mixing the retardation enhancers (A) and (B) at a ratio of 1: 1 is impaired by the following evaluation method. It is what.

  The retardation enhancer (A) having liquid crystal properties used in the present invention preferably exhibits a liquid crystal phase in a temperature range of 100 ° C to 300 ° C. More preferably, it is 120 degreeC-200 degreeC. The liquid crystal phase is preferably a columnar phase, a nematic phase or a smectic phase, and more preferably a nematic phase or a smectic phase.

  The retardation enhancer (B) used in the present invention may be a liquid crystalline compound or a non-liquid crystalline compound. In the case of a liquid crystalline compound, the retardation developing agent (B) exhibits a liquid crystal phase in a temperature range of 100 ° C to 300 ° C. It is preferable to express. More preferably, it is 120 degreeC-200 degreeC. The liquid crystal phase is preferably a columnar phase, a nematic phase or a smectic phase, and more preferably a nematic phase or a smectic phase.

  The content of the retardation developer (A) in the film of the present invention is preferably 0.1 to 30 parts by mass, more preferably 0.5 to 20 parts by mass with respect to the polymer. It is more preferably 12 parts by mass, and most preferably 1 to 5 parts by mass.

  Further, the content of the retardation developing agent (B) in the film of the present invention is preferably 0.1 to 30 parts by mass, more preferably 0.5 to 20 parts by mass with respect to the polymer. It is more preferably 1 to 12 parts by mass, and most preferably 1 to 5 parts by mass.

  Furthermore, the use ratio of the retardation developer (A) and the retardation developer (B) may be any ratio that does not inhibit the liquid crystallinity of the retardation developer (A).

(Liquid crystallinity evaluation of the mixture)
In this specification, the liquid crystallinity evaluation of the retardation enhancer was measured by using an Eclipse E600POL polarizing microscope (manufactured by Nikon Co., Ltd.), and by using this, the presence or absence of a liquid crystal state and the phase transition temperature were measured. . Temperature control is controlled by using a hot stage FP82HT (Metler Toledo Co., Ltd.) connected to FP90 (Metler Toledo Co., Ltd.). Measuring.
Preparation of a mixture of compound (A) and compound (B) is carried out by weighing them at a mass ratio of 1: 1, separating them into sample bottles, and then forming a uniform solution system with an organic solvent (for example, methylene chloride) and then drying up the solvent. Do it.
The mixture prepared by the above method is sandwiched between a slide glass and a cover glass, and the change with time is observed with the polarizing microscope while being heated on the hot stage at a rate of 10 ° C./min.
As a result, when the above mixture forms a uniform liquid crystal phase, it is judged that there is no hindrance in liquid crystallinity, and the two do not mix uniformly and one phase is non-uniform, such as the liquid crystal phase and the other isotropic phase. If formed, it can be judged that there is an inhibition of liquid crystallinity.

In the present invention, the retardation developer (A) is preferably a compound represented by the following general formula (1), and the retardation developer (B) is a compound represented by the general formula (2).
Hereinafter, the compound represented by the general formula (1) will be described in detail.
General formula (1):

(In the formula, L ₁ and L ₂ each independently represents a single bond or a divalent linking group. A ₁ and A ₂ each independently represent —O—, —NR— (R represents a hydrogen atom or a substituent). Represents a linking group selected from the group consisting of —S— and —CO—, R ₁ , R ₂ , and R ₃ each independently represents a substituent, and X represents a nonmetal of Groups 14 to 16 Represents an atom (however, a hydrogen atom or a substituent may be bonded to X. n represents an integer of 0 to 2).

The compound represented by the general formula (1) used in the present invention is more preferably a compound represented by the general formula (1 ′).
General formula (1 ′):

(In General Formula (1 ′), L ₁ and L ₂ each independently represent a single bond or a divalent linking group. A ₁ and A ₂ each independently represent —O—, —NR— (R represents hydrogen And represents a group selected from the group consisting of —S— and —CO—, and R ₁ , R ₂ , R ₃ , R ₄ and R ₅ each independently represents a substituent. Represents an integer from 0 to 2.)

In the general formula (1) or (1 ′), the divalent linking group represented by L ₁ and L ₂ preferably includes the following examples.

  More preferred are -O-, -COO-, and -OCO-.

In general formula (1) or (1 ′), R ₁ is a substituent, and when a plurality of R ₁ are present, they may be the same or different and may form a ring. The following can be applied as examples of the substituent.

  A halogen atom (for example, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom), an alkyl group (preferably an alkyl group having 1 to 30 carbon atoms, for example, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, a tert- Butyl group, n-octyl group, 2-ethylhexyl group), cycloalkyl group (preferably a substituted or unsubstituted cycloalkyl group having 3 to 30 carbon atoms such as cyclohexyl group, cyclopentyl group, 4-n-dodecylcyclohexyl) Group), a bicycloalkyl group (preferably a substituted or unsubstituted bicycloalkyl group having 5 to 30 carbon atoms, that is, a monovalent group obtained by removing one hydrogen atom from a bicycloalkane having 5 to 30 carbon atoms. , Bicyclo [1,2,2] heptan-2-yl group, bicyclo [2,2,2] octane-3-yl group)

An alkenyl group (preferably a substituted or unsubstituted alkenyl group having 2 to 30 carbon atoms, such as a vinyl group or an allyl group), a cycloalkenyl group (preferably a substituted or unsubstituted cycloalkenyl group having 3 to 30 carbon atoms, That is, it is a monovalent group in which one hydrogen atom of a cycloalkene having 3 to 30 carbon atoms is removed, for example, a 2-cyclopenten-1-yl, 2-cyclohexen-1-yl group), a bicycloalkenyl group (substituted or substituted). An unsubstituted bicycloalkenyl group, preferably a substituted or unsubstituted bicycloalkenyl group having 5 to 30 carbon atoms, that is, a monovalent group in which one hydrogen atom of a bicycloalkene having one double bond is removed. A bicyclo [2,2,1] hept-2-en-1-yl group, a bicyclo [2,2,2] oct-2-en-4-yl group), Rukiniru group (preferably a substituted or unsubstituted alkynyl group having 2 to 30 carbon atoms, such as ethynyl group, propargyl group),

An aryl group (preferably a substituted or unsubstituted aryl group having 6 to 30 carbon atoms, such as a phenyl group, a p-tolyl group, a naphthyl group), a heterocyclic group (preferably a 5- or 6-membered substituted or unsubstituted aromatic group A monovalent group obtained by removing one hydrogen atom from an aromatic or non-aromatic heterocyclic compound, and more preferably a 5- or 6-membered aromatic heterocyclic group having 3 to 30 carbon atoms. 2-furyl group, 2-thienyl group, 2-pyrimidinyl group, 2-benzothiazolyl group), cyano group, hydroxyl group, nitro group, carboxyl group, alkoxy group (preferably substituted or unsubstituted having 1 to 30 carbon atoms) Alkoxy groups such as methoxy, ethoxy, isopropoxy, tert-butoxy, n-octyloxy, 2-methoxyethoxy), aryloxy Si group (preferably a substituted or unsubstituted aryloxy group having 6 to 30 carbon atoms such as phenoxy group, 2-methylphenoxy group, 4-tert-butylphenoxy group, 3-nitrophenoxy group, 2-tetradeca Noylaminophenoxy group),

A silyloxy group (preferably a silyloxy group having 3 to 20 carbon atoms, such as trimethylsilyloxy group or tert-butyldimethylsilyloxy group), a heterocyclic oxy group (preferably a substituted or unsubstituted heterocycle having 2 to 30 carbon atoms) Ring oxy group, 1-phenyltetrazole-5-oxy group, 2-tetrahydropyranyloxy group), acyloxy group (preferably formyloxy group, substituted or unsubstituted alkylcarbonyloxy group having 2 to 30 carbon atoms, carbon number 6-30 substituted or unsubstituted arylcarbonyloxy groups such as formyloxy group, acetyloxy group, pivaloyloxy group, stearoyloxy group, benzoyloxy group, p-methoxyphenylcarbonyloxy group), carbamoyloxy group (preferably Or substitution of 1 to 30 carbon atoms Is an unsubstituted carbamoyloxy group, for example, N, N-dimethylcarbamoyloxy group, N, N-diethylcarbamoyloxy group, morpholinocarbonyloxy group, N, N-di-n-octylaminocarbonyloxy group, Nn -Octylcarbamoyloxy group), alkoxycarbonyloxy group (preferably a substituted or unsubstituted alkoxycarbonyloxy group having 2 to 30 carbon atoms, for example, methoxycarbonyloxy group, ethoxycarbonyloxy group, tert-butoxycarbonyloxy group, n- Octylcarbonyloxy group), aryloxycarbonyloxy group (preferably substituted or unsubstituted aryloxycarbonyloxy group having 7 to 30 carbon atoms, such as phenoxycarbonyloxy group, p-methoxyphenoxycarbonyloxy group) , P-n-hexadecyloxycarbonyl phenoxycarbonyl group),

An amino group (preferably an amino group, a substituted or unsubstituted alkylamino group having 1 to 30 carbon atoms, a substituted or unsubstituted anilino group having 6 to 30 carbon atoms, such as an amino group, a methylamino group, a dimethylamino group; , Anilino group, N-methyl-anilino group, diphenylamino group), acylamino group (preferably formylamino group, substituted or unsubstituted alkylcarbonylamino group having 1 to 30 carbon atoms, substituted or unsubstituted 6 to 30 carbon atoms, or Unsubstituted arylcarbonylamino group, for example, formylamino group, acetylamino group, pivaloylamino group, lauroylamino group, benzoylamino group), aminocarbonylamino group (preferably substituted or unsubstituted amino acid having 1 to 30 carbon atoms) Carbonylamino group, for example, carbamoylamino group, N, N-dimethylamino Sulfonylamino group, N, N-diethylaminocarbonylamino group, morpholinocarbonylamino group), alkoxycarbonylamino group (preferably a substituted or unsubstituted alkoxycarbonylamino group having 2 to 30 carbon atoms, such as methoxycarbonylamino group, ethoxycarbonyl) Amino group, tert-butoxycarbonylamino group, n-octadecyloxycarbonylamino group, N-methyl-methoxycarbonylamino group), aryloxycarbonylamino group (preferably substituted or unsubstituted aryloxy having 7 to 30 carbon atoms) Carbonylamino group, for example, phenoxycarbonylamino group, p-chlorophenoxycarbonylamino group, mn-octyloxyphenoxycarbonylamino group),

Sulfamoylamino group (preferably a substituted or unsubstituted sulfamoylamino group having 0 to 30 carbon atoms such as sulfamoylamino group, N, N-dimethylaminosulfonylamino group, Nn-octylamino Sulfonylamino groups), alkyl and arylsulfonylamino groups (preferably substituted or unsubstituted alkylsulfonylamino groups having 1 to 30 carbon atoms, substituted or unsubstituted arylsulfonylamino groups having 6 to 30 carbon atoms, such as methylsulfonyl An amino group, a butylsulfonylamino group, a phenylsulfonylamino group, a 2,3,5-trichlorophenylsulfonylamino group, a p-methylphenylsulfonylamino group, a mercapto group, and an alkylthio group (preferably a substituent having 1 to 30 carbon atoms) Or an unsubstituted alkylthio group such as Luthio group, ethylthio group, n-hexadecylthio group), arylthio group (preferably a substituted or unsubstituted arylthio group having 6 to 30 carbon atoms, such as phenylthio group, p-chlorophenylthio group, m-methoxyphenylthio group), A heterocyclic thio group (preferably a substituted or unsubstituted heterocyclic thio group having 2 to 30 carbon atoms, for example, 2-benzothiazolylthio group, 1-phenyltetrazol-5-ylthio group),

Sulfamoyl group (preferably a substituted or unsubstituted sulfamoyl group having 0 to 30 carbon atoms such as N-ethylsulfamoyl group, N- (3-dodecyloxypropyl) sulfamoyl group, N, N-dimethylsulfamoyl group N-acetylsulfamoyl group, N-benzoylsulfamoyl group, N- (N′-phenylcarbamoyl) sulfamoyl group), sulfo group, alkyl and arylsulfinyl group (preferably having 1 to 30 carbon atoms substituted or Unsubstituted alkylsulfinyl group, substituted or unsubstituted arylsulfinyl group having 6 to 30 carbon atoms, such as methylsulfinyl group, ethylsulfinyl group, phenylsulfinyl group, p-methylphenylsulfinyl group), alkyl and arylsulfonyl groups ( Preferably, it has 1 to 3 carbon atoms A substituted or unsubstituted alkylsulfonyl group, a substituted or unsubstituted arylsulfonyl group having 6 to 30 carbon atoms, e.g., methylsulfonyl group, ethylsulfonyl group, phenylsulfonyl group, p- methylphenyl sulfonyl group),

An acyl group (preferably a formyl group, a substituted or unsubstituted alkylcarbonyl group having 2 to 30 carbon atoms, a substituted or unsubstituted arylcarbonyl group having 7 to 30 carbon atoms, such as an acetyl group or a pivaloylbenzoyl group), Aryloxycarbonyl group (preferably a substituted or unsubstituted aryloxycarbonyl group having 7 to 30 carbon atoms, such as phenoxycarbonyl group, o-chlorophenoxycarbonyl group, m-nitrophenoxycarbonyl group, p-tert-butylphenoxy Carbonyl group), alkoxycarbonyl group (preferably a substituted or unsubstituted alkoxycarbonyl group having 2 to 30 carbon atoms, such as methoxycarbonyl group, ethoxycarbonyl group, tert-butoxycarbonyl group, n-octadecyloxycarbonyl group), carbamoyl Base Preferably, the substituted or unsubstituted carbamoyl group having 1 to 30 carbon atoms, for example, carbamoyl group, N-methylcarbamoyl group, N, N-dimethylcarbamoyl group, N, N-di-n-octylcarbamoyl group, N- (Methylsulfonyl) carbamoyl group),

Aryl and heterocyclic azo groups (preferably substituted or unsubstituted arylazo groups having 6 to 30 carbon atoms, substituted or unsubstituted heterocyclic azo groups having 3 to 30 carbon atoms, such as phenylazo group, p-chlorophenylazo group, 5-ethylthio-1,3,4-thiadiazol-2-ylazo group), imide group (preferably N-succinimide group, N-phthalimide group), phosphino group (preferably substituted or non-substituted having 2 to 30 carbon atoms) Substituted phosphino groups such as dimethylphosphino group, diphenylphosphino group, methylphenoxyphosphino group), phosphinyl groups (preferably substituted or unsubstituted phosphinyl groups having 2 to 30 carbon atoms such as phosphinyl group, dioctyl Oxyphosphinyl group, diethoxyphosphinyl group), phosphinyloxy group (preferred Or a substituted or unsubstituted phosphinyloxy group having 2 to 30 carbon atoms, such as a diphenoxyphosphinyloxy group or a dioctyloxyphosphinyloxy group, or a phosphinylamino group (preferably having a carbon number) 2-30 substituted or unsubstituted phosphinylamino groups such as dimethoxyphosphinylamino group, dimethylaminophosphinylamino group, silyl groups (preferably substituted or unsubstituted groups having 3 to 30 carbon atoms) Silyl group, for example, trimethylsilyl group, tert-butyldimethylsilyl group, phenyldimethylsilyl group).

  Among the above substituents, those having a hydrogen atom may be substituted with the above groups after removing this. Examples of such functional groups include an alkylcarbonylaminosulfonyl group, an arylcarbonylaminosulfonyl group, an alkylsulfonylaminocarbonyl group, and an arylsulfonylaminocarbonyl group. Examples thereof include a methylsulfonylaminocarbonyl group, a p-methylphenylsulfonylaminocarbonyl group, an acetylaminosulfonyl group, and a benzoylaminosulfonyl group.

R ₁ is preferably a halogen atom, alkyl group, alkenyl group, aryl group, heterocyclic group, hydroxyl group, carboxyl group, alkoxy group, aryloxy group, acyloxy group, cyano group, amino group, more preferably A halogen atom, an alkyl group, a cyano group, and an alkoxy group.

R ₂ and R ₃ each independently represents a substituent. An example of R ₁ is given as an example. Preferred are a substituted or unsubstituted benzene ring and a substituted or unsubstituted cyclohexane ring. Preferred are a benzene ring having a substituent and a cyclohexane ring having a substituent, and more preferred are a benzene ring having a substituent at the 4-position and a cyclohexane ring having a substituent at the 4-position. More preferably, a benzene ring having a benzoyloxy group having a substituent at the 4-position at the 4-position, a benzene ring having a cyclohexyl group having a substituent at the 4-position at the 4-position, and a benzene ring having a substituent at the 4-position being at the 4-position And a cyclohexane ring having a cyclohexyl group having a substituent at the 4-position at the 4-position.

  In addition, the cyclohexane ring having a substituent at the 4-position includes cis- and trans-stereoisomers, but is not limited in the present invention, and a mixture of both may be used. A trans-cyclohexane ring is preferred.

R ₄ and R ₅ each independently represents a substituent. An example of R ₁ is given as an example. Preferably, it is preferred that substituent constant sigma _p value of Hammett is greater than zero electron withdrawing group, sigma _p value has an electron withdrawing substituent of 0 to 1.5 Further preferred. Examples of such a substituent include a trifluoromethyl group, a cyano group, a carbonyl group, and a nitro group. R ₄ and R ₅ may combine to form a ring.
Regarding σ _p and σ _m of Hammett's substituent constants, for example, Naoki Inamoto's “Hammett's rule-structure and reactivity-” (Maruzen), edited by the Chemical Society of Japan “New Experimental Chemistry Course 14 Synthesis of Organic Compounds” Reaction V "2605 (Maruzen), Tadao Nakatani" Theoretical Organic Chemistry "217 (Tokyo Kagaku Dojin), Chemical Review, 91, 165-195 (1991) .

A ₁ and A ₂ each independently represent a group selected from the group consisting of —O—, —NR— (wherein R is a hydrogen atom or a substituent), —S— and —CO—. Preferred is —O—, —NR— (R represents a substituent, and examples of R ₁ are given as examples) or —S—.

X represents a nonmetallic atom belonging to Groups 14-16. However, a hydrogen atom or a substituent may be bonded to X. X is preferably ═O, ═S, ═NR, ═C (R) R (wherein R represents a substituent, and examples thereof include the examples of R ₁ described above).
n represents an integer of 0 to 2, and is preferably 0 or 1.

  Specific examples of the compound represented by the general formula (1) or (1 ′) are shown below, but the present invention is not limited to the following specific examples. Regarding the following compounds, unless otherwise specified, the number in parentheses () indicates the exemplified compound (X).

  The synthesis of the compound represented by the general formula (1) or (1 ') can be performed with reference to a known method. For example, exemplary compound (1) can be synthesized according to the following scheme.

In the above scheme, the synthesis from the compound (1-A) to the compound (1-D) is described in “Journal of Chemical Crystallography” (1997); 27 (9); p.515-526. It can be performed with reference to the method described in 1.
Further, as shown in the above scheme, methanesulfonic acid chloride was added to a tetrahydrofuran solution of the compound (1-E), N, N-diisopropylethylamine was added dropwise and stirred, and then N, N-diisopropylethylamine was added. Exemplary solution (1) can be obtained by adding dropwise a tetrahydrofuran solution of compound (1-D) and then adding a tetrahydrofuran solution of N, N-dimethylaminopyridine (DMAP).

  By using the compound represented by the general formula (1) as the retardation developer (A), the in-plane retardation Re is brought close to a desired value, and the wavelength dispersion characteristics at each wavelength are improved. In particular, in the present invention, not only can the Re expression be facilitated by the above-described stretching operation of the optical film, but mainly the wavelength dispersion of Re can be brought close to a desired range. To bring the wavelength dispersion of Re close to the desired range, the compound represented by the general formula (1) is oriented in the stretching direction in the film, thereby making the transition dipole moment of absorption in the ultraviolet region in the stretching direction. It can be considered to be substantially orthogonal, and it can be considered that the wavelength dispersion of Re is relatively increased on the long wave side.

Next, the compound represented by formula (2) will be described in detail.
General formula (2)

In the formula, R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁸ and R ⁹ each independently represent a hydrogen atom or a substituent.
Examples of the substituent represented by each of R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁸ and R ⁹ include the same substituents as those exemplified as R 1 in the general formula (1).

The substituent represented by each of R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁸ and R ⁹ is preferably an alkyl group, an aryl group, a substituted or unsubstituted amino group, an alkoxy group, an alkylthio group or a halogen atom. It is. Although the specific example of a compound represented by General formula (2) below is given, it is not limited to this.

  The compound represented by the general formula (2) can be synthesized with reference to a known method. For example, it can be synthesized by introducing a substituent after condensing a benzene derivative.

  In the present invention, the content of the compound represented by the general formula (2) is preferably 0.1 to 20 parts by mass, more preferably 0.5 to 16 parts by mass with respect to the cellulose compound. 1 to 12 parts by mass is more preferable, and 1 to 9 parts by mass is most preferable.

The optical film of the present invention is preferably an optical film mainly containing cellulose acylate, polycarbonate, cycloolefin polymer, cycloolefin copolymer and polyimide, and particularly preferably an optical film mainly containing cellulose acylate.
Here, “mainly” is preferably 80 to 100% of the total mass of the optical film, more preferably 90 to 100%, and particularly preferably 95 to 100%.

  Cellulose acylate raw material cellulose used in the present invention includes cotton linter and wood pulp (hardwood pulp, softwood pulp) and the like, and any cellulose acylate obtained from any raw material cellulose can be used, optionally mixed. May be. Detailed descriptions of these raw material celluloses can be found in, for example, Marusawa and Uda, “Plastic Materials Course (17) Fibrous Resin”, published by Nikkan Kogyo Shimbun (published in 1970), and the Japan Institute of Invention and Technology Publication No. 2001. The cellulose described in No.-1745 (pages 7 to 8) can be used, and the optical film of the present invention is not particularly limited.

  The basic principle of the cellulose acylate synthesis method is described in Mita et al., “Wood Chemistry”, Kyoritsu Shuppan, 1968, pages 180-190. A typical synthesis method is a liquid phase acetylation method using a carboxylic acid anhydride-acetic acid-sulfuric acid catalyst. Specifically, cellulose raw materials such as cotton linter and wood pulp are pretreated with an appropriate amount of acetic acid, and then put into a pre-cooled carboxylic acid mixture to be esterified to complete cellulose acylate (2nd, 3rd and 6th). The total degree of acyl substitution at the position is approximately 3.00). The carboxylated mixed solution generally contains acetic acid as a solvent, carboxylic anhydride as an esterifying agent, and sulfuric acid as a catalyst. The carboxylic anhydride is usually used in a stoichiometric excess over the sum of the cellulose that reacts with it and the water present in the system. After completion of the acylation reaction, a neutralizing agent (for example, calcium, magnesium, iron, aluminum or zinc) is used for hydrolysis of excess carboxylic anhydride remaining in the system and neutralization of a part of the esterification catalyst. Of carbonate, acetate or oxide). Next, the obtained complete cellulose acylate is saponified and aged by maintaining it at 50 to 90 ° C. in the presence of a small amount of an acetylation reaction catalyst (generally, remaining sulfuric acid) to obtain the desired degree of acyl substitution and polymerization. The cellulose acylate having a degree is changed. When the desired cellulose acylate is obtained, the catalyst remaining in the system is completely neutralized with a neutralizing agent as described above, or in water or dilute sulfuric acid without neutralization. The cellulose acylate solution is added (or water or dilute sulfuric acid is added into the cellulose acylate solution) to coagulate and separate the cellulose acylate, and the cellulose acylate is obtained by washing and stabilizing treatment.

[Manufacture of optical films]
The optical film of the present invention can be produced by a solvent cast method. In the solvent cast method, a film is produced using a solution (dope) in which a polymer such as cellulose acylate is dissolved in an organic solvent.

The organic solvent is selected from ethers having 3 to 12 carbon atoms, ketones having 3 to 12 carbon atoms, esters having 3 to 12 carbon atoms, and halogenated hydrocarbons having 1 to 6 carbon atoms. It is preferable to include a solvent.
The ether, ketone and ester may have a cyclic structure. A compound having two or more functional groups of the ether, ketone and ester (that is, —O—, —CO— and COO—) can also be used as the organic solvent. The organic solvent may have another functional group such as an alcoholic hydroxyl group. In the case of an organic solvent having two or more types of functional groups, the number of carbon atoms is preferably within the above-described preferable range of carbon atoms of the solvent having any functional group.

Examples of the ether having 3 to 12 carbon atoms include diisopropyl ether, dimethoxymethane, dimethoxyethane, 1,4-dioxane, 1,3-dioxolane, tetrahydrofuran, anisole and phenetole.
Examples of the ketones having 3 to 12 carbon atoms include acetone, methyl ethyl ketone, diethyl ketone, diisobutyl ketone, cyclohexanone and methylcyclohexanone.
Examples of the esters having 3 to 12 carbon atoms include ethyl formate, propyl formate, pentyl formate, methyl acetate, ethyl acetate and pentyl acetate.
Examples of the organic solvent having two or more kinds of functional groups include 2-ethoxyethyl acetate, 2-methoxyethanol and 2-butoxyethanol.

The number of carbon atoms of the halogenated hydrocarbon having 1 to 6 carbon atoms is preferably 1 or 2, and most preferably 1. The halogen of the halogenated hydrocarbon is preferably chlorine. The proportion of halogenated hydrocarbon hydrogen atoms replaced with halogen is preferably 25 to 75 mol%, more preferably 30 to 70 mol%, and more preferably 35 to 65 mol%. More preferably, it is most preferable that it is 40-60 mol%. Methylene chloride is a representative halogenated hydrocarbon.
Two or more organic solvents may be mixed and used.

(Additive)
In the polymer solution such as cellulose acylate according to the present invention, various additives (for example, a plasticizer, an ultraviolet ray inhibitor, a deterioration inhibitor, a retardation (optical anisotropy) modifier, Fine particles, exfoliation accelerators, infrared absorbers, etc.) can be added and they can be solid or oily. That is, the melting point and boiling point are not particularly limited. For example, mixing of UV absorbing materials at 20 ° C. or lower and 20 ° C. or higher, and similarly mixing of a plasticizer is described in, for example, JP-A-2001-151901. Examples of the peeling accelerator include ethyl esters of citric acid. Furthermore, infrared absorbing dyes are described, for example, in JP-A No. 2001-194522. Moreover, the addition time may be added at any stage in the dope preparation process, but may be performed by adding an additive to the final preparation process of the dope preparation process. Furthermore, the amount of each material added is not particularly limited as long as the function is manifested. Moreover, when polymer films, such as a cellulose acylate, are formed in a multilayer, the kind and addition amount of the additive of each layer may differ. Examples thereof are described in Japanese Patent Application Laid-Open No. 2001-151902 and the like, but these are conventionally known techniques. It is preferable to adjust the glass transition temperature Tg of a polymer film such as cellulose acylate to 80 to 180 ° C. and the elastic modulus measured with a tensile tester to 1500 to 3000 MPa by selecting the type and amount of these additives.
Further, for these details, materials described in detail on page 16 and after in the Invention Association Public Technical Bulletin No. 2001-1745 (issued March 15, 2001, Invention Association) are preferably used.

  A polymer solution (dope) such as cellulose acylate can be prepared by a general method comprising processing at a temperature of 0 ° C. or higher (room temperature or high temperature). Preparation of a polymer solution such as cellulose acylate can be carried out using a dope preparation method and apparatus in a normal solvent cast method. In the case of a general method, it is preferable to use a halogenated hydrocarbon (particularly methylene chloride) as the organic solvent.

  The amount of the polymer such as cellulose acylate in the polymer solution such as cellulose acylate is adjusted so as to be contained by 10 to 40% by mass in the obtained solution. The amount of the polymer such as cellulose acylate is more preferably 10 to 30% by mass. Arbitrary additives described later may be added to the organic solvent (main solvent).

  A polymer solution such as cellulose acylate can be prepared by stirring a polymer such as cellulose acylate and an organic solvent at room temperature (0 to 40 ° C.). High concentration solutions may be stirred under pressure and heating conditions. Specifically, a polymer such as cellulose acylate and an organic solvent are placed in a pressure vessel and sealed, and stirred while being heated to a temperature not lower than the boiling point of the solvent at normal temperature and in a range where the solvent does not boil. The heating temperature is usually 40 ° C. or higher, preferably 60 to 200 ° C., and more preferably 80 to 110 ° C.

  Each component may be coarsely mixed in advance and then placed in a container. Moreover, you may put into a container sequentially. The container must be configured to allow stirring. The container can be pressurized by injecting an inert gas such as nitrogen gas. Moreover, you may utilize the raise of the vapor pressure of the solvent by heating. Or after sealing a container, you may add each component under pressure.

  When heating, it is preferable to heat from the outside of the container. For example, a jacket type heating device can be used. The entire container can also be heated by providing a plate heater outside the container and piping to circulate the liquid.

  Stirring is preferably performed using a stirring blade provided inside the container. The stirring blade preferably has a length that reaches the vicinity of the wall of the container. A scraping blade is preferably provided at the end of the stirring blade in order to renew the liquid film on the vessel wall.

  Instruments such as a pressure gauge and a thermometer may be installed in the container. Each component is dissolved in a solvent in a container. The prepared dope is taken out of the container after cooling, or taken out and then cooled using a heat exchanger or the like.

  A polymer solution such as cellulose acylate can also be prepared by a cooling dissolution method. In the cooling dissolution method, a polymer such as cellulose acylate can be dissolved in an organic solvent in which it is difficult to dissolve a polymer such as cellulose acylate by a normal dissolution method. In addition, even if it is a solvent which can melt | dissolve polymers, such as a cellulose acylate, by a normal melt | dissolution method, there exists an effect that a uniform solution can be obtained rapidly according to a cooling melt | dissolution method.

  In the cooling dissolution method, a polymer such as cellulose acylate is first gradually added to an organic solvent with stirring at room temperature. The amount of the polymer such as cellulose acylate is preferably adjusted so as to be contained in the mixture in an amount of 10 to 40% by mass. The amount of the polymer such as cellulose acylate is more preferably 10 to 30% by mass. Furthermore, you may add the arbitrary additive mentioned later in a mixture.

  The mixture is then cooled to -100 to -10 ° C (preferably -80 to -10 ° C, more preferably -50 to -20 ° C, most preferably -50 to -30 ° C). The cooling can be performed, for example, in a dry ice / methanol bath (−75 ° C.) or a cooled diethylene glycol solution (−30 to −20 ° C.). The mixture of the cellulose acylate and the organic solvent is solidified by cooling.

  The cooling rate is preferably 4 ° C./min or more, more preferably 8 ° C./min or more, and most preferably 12 ° C./min or more. The faster the cooling rate, the better. However, 10,000 ° C./second is the theoretical upper limit, 1000 ° C./second is the technical upper limit, and 100 ° C./second is the practical upper limit. The cooling rate is a value obtained by dividing the difference between the temperature at the start of cooling and the final cooling temperature by the time from the start of cooling to the final cooling temperature.

  Further, when the cooled mixture is heated to 0 to 200 ° C. (preferably 0 to 150 ° C., more preferably 0 to 120 ° C., most preferably 0 to 50 ° C.), a polymer such as cellulose acylate is formed in the organic solvent. Dissolve. The temperature may be increased by simply leaving it at room temperature or in a warm bath. The heating rate is preferably 4 ° C./min or more, more preferably 8 ° C./min or more, and most preferably 12 ° C./min or more. The higher the heating rate, the better. However, 10,000 ° C./second is the theoretical upper limit, 1000 ° C./second is the technical upper limit, and 100 ° C./second is the practical upper limit. The heating rate is a value obtained by dividing the difference between the temperature at the start of heating and the final heating temperature by the time from the start of heating until the final heating temperature is reached. .

  As described above, a uniform polymer solution such as cellulose acylate is obtained. If the dissolution is insufficient, the cooling and heating operations may be repeated. Whether or not the dissolution is sufficient can be determined by merely observing the appearance of the solution with the naked eye.

  In the cooling dissolution method, it is desirable to use a sealed container in order to avoid moisture mixing due to condensation during cooling. In the cooling and heating operation, when the pressure is applied during cooling and the pressure is reduced during heating, the dissolution time can be shortened. In order to perform pressurization and decompression, it is desirable to use a pressure-resistant container.

  In addition, according to the measurement by a differential scanning calorimeter (DSC), the 20 mass% solution which melt | dissolved cellulose acetate (acetylation degree: 60.9%, viscosity average polymerization degree: 299) in methyl acetate by the cooling dissolution method is. In the vicinity of 33 ° C., there exists a quasi-phase transition point between a sol state and a gel state, and a uniform gel state is obtained below this temperature. Accordingly, this solution is preferably kept at a temperature equal to or higher than the pseudo phase transition temperature, preferably about 10 ° C. plus the gel phase transition temperature. However, this pseudo phase transition temperature varies depending on the degree of acetylation of cellulose acetate, the degree of viscosity average polymerization, the concentration of the solution, and the organic solvent used.

  From the prepared polymer solution (dope) such as cellulose acylate, a polymer film such as cellulose acylate is produced by a solvent cast method. It is preferable to add a retardation developer to the dope. The dope is cast on a drum or band and the solvent is evaporated to form a film. The concentration of the dope before casting is preferably adjusted so that the solid content is 18 to 35%. The surface of the drum or band is preferably finished in a mirror state. The dope is preferably cast on a drum or band having a surface temperature of 10 ° C. or less.

  Regarding the drying method in the solvent cast method, US Pat. Nos. 2,336,310, 2,367,603, 2,492,078, 2,492,977, and 2,492,978 Nos. 2,607,704, 2,739,069 and 2,739,070, British Patent Nos. 640731 and 736892, and Japanese Patent Publication No. 45-4554 49-5614, JP-A-60-176834, JP-A-60-203430 and JP-A-62-115035. Drying on the band or drum can be performed by blowing an inert gas such as air or nitrogen.

  Further, the obtained film can be peeled off from the drum or band and further dried with high-temperature air whose temperature is successively changed from 100 ° C. to 160 ° C. to evaporate the residual solvent. The above method is described in Japanese Patent Publication No. 5-17844. According to this method, it is possible to shorten the time from casting to stripping. In order to carry out this method, it is necessary for the dope to gel at the surface temperature of the drum or band during casting.

  Using the prepared polymer solution (dope) such as cellulose acylate, two or more layers can be cast to form a film. In this case, it is preferable to produce a polymer film such as cellulose acylate by a solvent casting method. The dope is cast on a drum or band and the solvent is evaporated to form a film. It is preferable to adjust the concentration of the dope before casting so that the solid content is in the range of 10 to 40% by mass. The surface of the drum or band is preferably finished in a mirror state.

  When casting a polymer solution such as a plurality of cellulose acylates of two or more layers, a plurality of polymer solutions such as a cellulose acylate can be cast and provided at intervals in the traveling direction of the support. Alternatively, a film may be produced while casting and laminating a solution containing cellulose acylate from a plurality of casting ports. For example, the methods described in JP-A-61-158414, JP-A-1-122419, and JP-A-11-198285 can be used. Also, a film can be formed by casting a polymer solution such as cellulose acylate from two casting ports. For example, JP-B-60-27562, JP-A-61-94724, JP-A-61-947245, JP-A-61-104413, JP-A-61-158413, and JP-A-6-158413. The method described in each publication of No. 134933 can be used. Further, a polymer solution such as cellulose acylate having a high viscosity is wrapped in a polymer solution such as cellulose acylate having a low viscosity, and the flow of the polymer solution such as cellulose acylate having a high viscosity described in JP-A-56-162617. It is also possible to use a method of casting a polymer film such as cellulose acylate that simultaneously extrudes.

  Also, using two casting ports, the film formed on the support by the first casting port is peeled off, and the second casting is performed on the side in contact with the support surface to produce a film. You can also For example, the method described in Japanese Patent Publication No. 44-20235 can be mentioned.

  The same polymer solution such as cellulose acylate to be cast may be used, or two or more polymer solutions such as different cellulose acylates may be used. In order to give a function to a plurality of polymer layers such as cellulose acylate, a polymer solution such as cellulose acylate corresponding to the function may be extruded from each casting port. Furthermore, the polymer solution such as cellulose acylate in the present invention can be cast simultaneously with other functional layers (for example, an adhesive layer, a dye layer, an antistatic layer, an antihalation layer, an ultraviolet absorption layer, a polarizing layer, etc.). .

  In the conventional single-layer solution, it is necessary to extrude a cellulose acylate solution having a high concentration and a high viscosity in order to obtain a necessary film thickness. In such a case, the stability of the cellulose acylate solution is poor and solid matter is generated, which often causes problems due to defects or poor flatness. As a solution to this problem, by casting a plurality of cellulose acylate solutions from the casting port, it is possible to extrude a highly viscous solution onto the support at the same time, improving the flatness and improving the planar film. Not only can be produced, but also the use of a concentrated cellulose acylate solution can reduce the drying load and increase the production speed of the film.

  Degradation inhibitors (for example, antioxidants, peroxide decomposers, radical inhibitors, metal deactivators, acid scavengers, amines, etc.) may be added to polymer films such as cellulose acylate. The deterioration preventing agents are described in JP-A-3-199201, JP-A-51907073, JP-A-5-194789, JP-A-5-271471, and JP-A-6-107854. Moreover, it is preferable that the addition amount of the said deterioration inhibitor is 0.01-1 mass% of the solution (dope) to prepare, and it is further more preferable that it is 0.01-0.2 mass%. If the addition amount is 0.01% by mass or more, the effect of the deterioration inhibitor is sufficiently exhibited, and if the addition amount is 1% by mass or less, the deterioration inhibitor bleeds out to the film surface (bleeding). And the like are less likely to occur. Examples of particularly preferred deterioration inhibitors include butylated hydroxytoluene (BHT) and tribenzylamine (TBA).

  These steps from casting to post-drying may be performed in an air atmosphere or an inert gas atmosphere such as nitrogen gas. The winder used for the production of polymer films such as cellulose acylate in the present invention may be generally used, constant tension method, constant torque method, taper tension method, program tension control method with constant internal stress. It can be wound by a winding method such as

(Stretching)
The optical film in the present invention is preferably unstretched, but may be stretched. When extending | stretching, the biaxial stretching of the width direction and a conveyance direction is preferable.
Methods for stretching in the width direction are described in, for example, JP-A-62-115035, JP-A-4-152125, 4-284221, 4-298310, and 11-48271. Yes.

  The film is stretched at room temperature or under heating conditions. The heating temperature is preferably not higher than the glass transition temperature of the film. The film can be stretched by a treatment during drying, and is particularly effective when the solvent remains. In the case of stretching in the longitudinal direction, for example, the film is stretched by adjusting the speed of the film transport roller so that the film winding speed is higher than the film peeling speed. In the case of stretching in the width direction, the film can also be stretched by conveying while holding the width of the film with a tenter and gradually widening the width of the tenter.

  Biaxial stretching includes simultaneous biaxial stretching and sequential biaxial stretching, but sequential biaxial stretching is preferred from the viewpoint of continuous production, and after casting the dope, the film is peeled off from the band or drum, After stretching in the width direction (longitudinal method), the film is stretched in the longitudinal direction (width direction).

In the case of biaxial stretching, it is preferable that the stretching ratio in the transport direction and the width direction satisfy the relationship of the following formula (D).
Formula (D): 0.01 <(stretching ratio in the vertical direction) − (stretching ratio in the parallel direction) <0.1
More preferably in the formula (D), 0.02 <(stretch ratio in the vertical direction) − (stretch ratio in the parallel direction) <0.08.
By adjusting to these ranges, the orientation of the cellulose acylate molecular chain generated at the time of conveyance can be canceled, and the Re of the film can be adjusted to a preferable range, and the surface shape can be greatly improved.

[Thickness of optical film]
The thickness of the optical film after stretching in the present invention is preferably 10 μm to 200 μm, more preferably 20 μm to 150 μm, and most preferably 30 μm to 100 μm.

[Saponification]
The cellulose acylate film used in the optical film of the present invention can be used as a polarizing plate protective film by imparting adhesion to a polarizer material such as polyvinyl alcohol by alkali saponification treatment.

  The alkali saponification treatment of the cellulose acylate film used in the optical film of the present invention is preferably performed in a cycle in which the film surface is immersed in an alkali solution, neutralized with an acidic solution, washed with water and dried. Examples of the alkaline solution include a potassium hydroxide solution and a sodium hydroxide solution, and the concentration of hydroxide ions is preferably in the range of 0.1 to 5.0 mol / L, and 0.5 to 4.0 mol / L. More preferably, it is in the range of L. The alkaline solution temperature is preferably in the range of room temperature to 90 ° C, more preferably in the range of 40 to 70 ° C.

  The present invention further relates to a polarizing plate in which protective films are bonded to both sides of a polarizer, and at least one of the protective films is an optical film of the present invention.

  The polarizing plate is composed of a polarizer and two transparent protective films disposed on both sides thereof. The cellulose acylate film of the present invention can be used as at least one protective film. The other protective film may be a normal cellulose acetate film. Examples of the polarizer include an iodine polarizer, a dye polarizer using a dichroic dye, and a polyene polarizer. The iodine polarizer and the dye polarizer are generally produced using a polyvinyl alcohol film. When the cellulose acylate film of the present invention is used as a polarizing plate protective film, the method for producing the polarizing plate is not particularly limited, and can be produced by a general method. There is a method in which the obtained cellulose acylate film is treated with an alkali and bonded to both sides of a polarizer prepared by immersing and stretching a polyvinyl alcohol film in an iodine solution using a completely saponified polyvinyl alcohol aqueous solution. Instead of alkali treatment, easy adhesion processing as described in JP-A-6-94915 and JP-A-6-118232 may be performed. Examples of the adhesive used to bond the protective film-treated surface and the polarizer include polyvinyl alcohol adhesives such as polyvinyl alcohol and polyvinyl butyral, vinyl latexes such as butyl acrylate, and the like. The polarizing plate is composed of a polarizer and a protective film that protects both surfaces of the polarizer, and is further constructed by laminating a protective film on one surface of the polarizing plate and a separate film on the opposite surface. The protective film and the separate film are used for the purpose of protecting the polarizing plate at the time of shipping the polarizing plate and at the time of product inspection. In this case, the protect film is bonded for the purpose of protecting the surface of the polarizing plate, and is used on the side opposite to the surface where the polarizing plate is bonded to the liquid crystal plate. Moreover, a separate film is used in order to cover the contact bonding layer bonded to a liquid crystal plate, and is used for the surface side which bonds a polarizing plate to a liquid crystal plate.

  Furthermore, this invention relates to the polarizing plate which has an optically anisotropic layer on the at least one surface of the protective film of both surfaces of the said polarizing plate.

  The material of the optically anisotropic layer is not limited, such as a liquid crystal compound, a non-liquid crystal compound, an inorganic compound, and an organic / inorganic composite compound. As the liquid crystalline compound, a low molecular compound having a polymerizable group is aligned, and then the alignment is fixed by polymerization by light or heat, or the liquid crystalline polymer is heated and aligned and then cooled and aligned in a glassy state. You can use what you want to fix. As the liquid crystalline compound, those having a disk-like structure, those having a rod-like structure, and those having a structure showing optical biaxiality can be used. As the non-liquid crystalline compound, a polymer having an aromatic ring such as polyimide or polyester can be used.

  Various methods, such as application | coating, vapor deposition, sputtering, can be used for the formation method of an optically anisotropic layer.

  When an optically anisotropic layer is provided on the protective film of the polarizing plate, the adhesive layer is further provided outside the optically anisotropic layer from the polarizer side.

  The optically anisotropic layer preferably has an alignment layer and an optically anisotropic layer in this order on a transparent polymer film.

  The alignment layer can be provided by means such as a rubbing treatment of an organic compound (preferably a polymer), oblique deposition of an inorganic compound, or formation of a layer having a microgroup. Furthermore, an alignment layer in which an alignment function is generated by application of an electric field, application of a magnetic field or light irradiation is also known, but an alignment layer formed by a rubbing treatment of a polymer is particularly preferable. The rubbing treatment is preferably performed by rubbing the surface of the polymer layer several times in a certain direction with paper or cloth. As the polymer used for the alignment layer, polyimide, polyvinyl alcohol, a polymer having a polymerizable group described in JP-A-9-152509, and the like can be preferably used. The thickness of the alignment layer is preferably 0.01 to 5 μm, and more preferably 0.05 to 2 μm.

  The optically anisotropic layer preferably contains a liquid crystalline compound. The liquid crystal compound used in the present invention particularly preferably has a discotic compound (discotic liquid crystal). The discotic liquid crystal molecule has a disk-like core portion like the triphenylene derivative of D-1, and has a structure in which side chains extend radially therefrom. Further, in order to fix the once aligned state, it is also preferable to further introduce a group that reacts with heat, light or the like. Preferred examples of the discotic liquid crystal are described in JP-A-8-50206.

  The discotic liquid crystal molecules are aligned almost parallel to the film plane with a pretilt angle in the rubbing direction in the vicinity of the alignment layer, and the discotic liquid crystal molecules are oriented so that they are perpendicular to the plane on the opposite air side. is doing. The tilt angle of the discotic liquid crystal molecules near the alignment layer and near the air interface can be controlled by the type of the discotic liquid crystal material, the type of the alignment layer material, the rubbing conditions, and the use of additives. (Additional explanation in accordance with the actual situation) The entire discotic liquid crystal layer has a hybrid alignment, and this layer structure can realize an increase in the viewing angle of the liquid crystal display device using the protective film of the present invention.

  The optically anisotropic layer is generally formed by applying a solution obtained by dissolving a discotic compound and another compound (for example, a polymerizable monomer, a photopolymerization initiator) in a solvent onto the alignment layer, drying, and then discotic nematic. After heating to the phase formation temperature, it is obtained by polymerization by irradiation with UV light or the like and further cooling. The discotic nematic liquid crystal phase-solid phase transition temperature of the discotic liquid crystalline compound used in the present invention is preferably 70 to 300 ° C, particularly preferably 70 to 170 ° C.

In addition to the discotic compound added to the optically anisotropic layer, the compound has compatibility with the discotic compound and can give a preferable change in tilt angle to the liquid crystalline discotic compound or inhibit the alignment. Any compound can be used as long as it is not. Among these, additives for controlling the orientation on the air interface side such as polymerizable monomers (eg, compounds having vinyl group, vinyloxy group, acryloyl group and methacryloyl group), fluorine-containing triazine compounds, cellulose acetate, cellulose acetate Mention may be made of polymers such as pionate, hydroxypropylcellulose and cellulose acetate butyrate. These compounds are generally used in an amount of 0.1 to 50% by mass, preferably 0.1 to 30% by mass, based on the discotic compound.
The thickness of the optically anisotropic layer is preferably 0.1 to 10 μm, and more preferably 0.5 to 5 μm.

The optically anisotropic layer may be a non-liquid crystalline polymer layer prepared by dissolving a non-liquid crystalline compound in a solvent, applying the solution onto a support, and drying by heating. In this case, for example, the non-liquid crystalline compound is excellent in heat resistance, chemical resistance, transparency, and has high rigidity, so polyamide, polyimide, polyester, polyether ketone, polyaryl ether ketone, polyamide imide, polyester imide, etc. These polymers can be used. Any one of these polymers may be used alone, or a mixture of two or more having different functional groups such as a mixture of polyaryletherketone and polyamide may be used. . Among such polymers, polyimide is preferable because of its high transparency, high orientation, and high stretchability. Moreover, as a support body, a TAC film is preferable.
In addition, it is also preferable that the laminate of the non-liquid crystal layer and the support is stretched in the horizontal direction of the tenter from 1.05 times to 1.50 times and the support side is bonded to a polarizer.
Furthermore, the optically anisotropic layer may be an alignment solidified layer of cholesteric liquid crystal having a selective reflection wavelength region of 350 nm or less. Examples of the cholesteric liquid crystal are described in JP-A-3-67219, JP-A-3-140921, JP-A-5-61039, JP-A-6-186534, JP-A-9-133810, and the like. Any suitable material showing the selective reflection characteristics can be used. What can be preferably used from the viewpoint of stability of the alignment solidified layer is, for example, a cholesteric liquid crystal composed of a cholesteric liquid crystal polymer, a nematic liquid crystal polymer containing a chiral agent, a compound that forms such a liquid crystal polymer by polymerization treatment with light, heat, or the like. A layer can be formed.
In this case, the optically anisotropic layer can be formed by, for example, a method of coating a cholesteric liquid crystal on a support substrate. In that case, for the purpose of controlling the phase difference or the like, a method of overcoating the same type or different types of cholesteric liquid crystals may be employed as necessary. For the coating treatment, for example, an appropriate method such as a gravure method, a die method, or a dipping method can be adopted. An appropriate material such as a TAC film or other polymer film can be used as the support substrate.
In the above, when forming the optically anisotropic layer, a means for aligning the liquid crystal is employed. The alignment means is not particularly limited, and any appropriate means that can align the liquid crystal compound can be adopted. Incidentally, as an example, there is a method in which liquid crystal is coated on the alignment film and aligned. As the alignment film, a rubbing treatment film made of an organic compound such as a polymer, an oblique deposition film of an inorganic compound, a film having a microgroove, or an organic material such as ω-tricosanoic acid, dioctadecylmethylammonium chloride, or methyl stearylate. Examples thereof include a film obtained by accumulating LB films by the Langmuir-Blodgett method of compounds. Further examples include an alignment film that generates an alignment function by light irradiation. On the other hand, a method of aligning liquid crystal on a stretched film (Japanese Patent Application Laid-Open No. 3-9325), a method of aligning liquid crystal under application of an electric field or magnetic field, and the like are also included. The alignment state of the liquid crystal is preferably as uniform as possible, and is preferably a solidified layer fixed in the alignment state.

  The present invention also relates to a liquid crystal display device having a liquid crystal cell and two polarizing plates arranged on both sides thereof, at least one of which is the polarizing plate of the present invention.

The liquid crystal display device includes a liquid crystal cell having a liquid crystal supported between two electrode substrates, two polarizing elements disposed on both sides thereof, and at least one sheet between the liquid crystal cell and the polarizing element. It has the structure which has arrange | positioned the optical film.
The liquid crystal layer of the liquid crystal cell is usually formed by sealing liquid crystal in a space formed by sandwiching a spacer between two substrates. The transparent electrode layer is formed on the substrate as a transparent film containing a conductive substance. The liquid crystal cell may further be provided with a gas barrier layer, a hard coat layer, or an undercoat layer (undercoat layer) (used for adhesion of the transparent electrode layer). These layers are usually provided on the substrate. The substrate of the liquid crystal cell generally has a thickness of 50 μm to 2 mm.

(Types of liquid crystal display devices)
The optical film of the present invention can be used for liquid crystal cells in various display modes. TN (Twisted Nematic), IPS (In-Plane Switching), FLC (Ferroelectric Liquid Crystal), AFLC (Anti-Ferroly Liquid Liquid Crystal), OCB (Optically Charged STP). Various display modes such as ECB (Electrically Controlled Birefringence) and HAN (Hybrid Aligned Nematic) have been proposed. In addition, a display mode in which the above display mode is oriented and divided has been proposed. The optical film of the present invention is effective in any display mode liquid crystal display device. Further, it is effective in any of a transmissive type, a reflective type, and a transflective liquid crystal display device.

(TN type liquid crystal display device)
The optical film of the present invention may be used as a support for an optical compensation sheet of a TN type liquid crystal display device having a TN mode liquid crystal cell. TN mode liquid crystal cells and TN type liquid crystal display devices have been well known for a long time. The optical compensation sheet used in the TN type liquid crystal display device is described in JP-A-3-9325, JP-A-8-50206, and JP-A-9-26572. Moreover, it is described in Mori et al. (Jpn. J. Appl. Phys. Vol. 36 (1997) p. 143 and Jpn. J. Appl. Phys. Vol. 36 (1997) p. 1068). is there.

(STN type liquid crystal display device)
The optical film of the present invention may be used as a support for an optical compensation sheet of an STN type liquid crystal display device having an STN mode liquid crystal cell. In general, in a STN type liquid crystal display device, rod-like liquid crystalline molecules in a liquid crystal cell are twisted in the range of 90 to 360 degrees, and the refractive index anisotropy (Δn) and cell gap (d) of the rod-like liquid crystalline molecules. Product (Δnd) is in the range of 300 to 1500 nm. The optical compensation sheet used in the STN type liquid crystal display device is described in JP-A-2000-105316.

(VA type liquid crystal display device)
The optical film of the present invention is particularly advantageously used as a support for an optical compensation sheet of a VA liquid crystal display device having a VA mode liquid crystal cell. The VA-type liquid crystal display device may be an alignment-divided system as described in, for example, JP-A-10-123576.

(IPS liquid crystal display device and ECB liquid crystal display device)
The optical film of the present invention is also particularly advantageously used as a support for an optical compensation sheet of an IPS liquid crystal display device and an ECB liquid crystal display device having IPS mode and ECB mode liquid crystal cells, or as a protective film for a polarizing plate. In these modes, the liquid crystal material is aligned substantially in parallel during black display, and black is displayed by aligning liquid crystal molecules in parallel with the substrate surface in the absence of applied voltage. In these embodiments, the polarizing plate using the cellulose acylate film of the present invention contributes to widening the viewing angle and improving the contrast.

(OCB type liquid crystal display device and HAN type liquid crystal display device)
The optical film of the present invention is also advantageously used as a support for an optical compensation sheet of an OCB type liquid crystal display device having an OCB mode liquid crystal cell or a HAN type liquid crystal display device having a HAN mode liquid crystal cell. In the optical compensation sheet used for the OCB type liquid crystal display device or the HAN type liquid crystal display device, it is preferable that the direction in which the absolute value of retardation is minimum does not exist in the plane of the optical compensation sheet or in the normal direction. The optical properties of the optical compensation sheet used in the OCB type liquid crystal display device or the HAN type liquid crystal display device are also the optical properties of the optical anisotropic layer, the optical properties of the support, and the optical anisotropic layer and the support. Is determined by the arrangement of An optical compensation sheet used for an OCB type liquid crystal display device or a HAN type liquid crystal display device is described in JP-A-9-197397. Further, it is described in a paper by Mori et al. (Jpn. J. Appl. Phys. Vol. 38 (1999) p. 2837).

(Reflective liquid crystal display)
The optical film of the present invention is also advantageously used as an optical compensation sheet for TN-type, STN-type, HAN-type, and GH (Guest-Host) type reflective liquid crystal display devices. These display modes have been well known since ancient times. The TN-type reflective liquid crystal display device is described in International Publication No. 98/48320 pamphlet and Japanese Patent No. 3022477. The optical compensation sheet used in the reflective liquid crystal display device is described in International Publication No. 00/65384 pamphlet.

(Other liquid crystal display devices)
The optical film of the present invention is also advantageously used as a support for an optical compensation sheet of an ASM type liquid crystal display device having a liquid crystal cell in an ASM (Axial Symmetrical Microcell) mode. The ASM mode liquid crystal cell is characterized in that the thickness of the cell is maintained by a resin spacer whose position can be adjusted. Other properties are the same as those of the TN mode liquid crystal cell. The ASM mode liquid crystal cell and the ASM type liquid crystal display device are described in a paper by Kume et al. (Kume et al., SID 98 Digest 1089 (1998)).

[Example]
Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto.

(Evaluation method)
The material characteristic values and the like described in the present specification are obtained by the following evaluation methods.

(1) Retardation measurement method

  In this specification, Re (λ) and Rth (λ) represent in-plane retardation and retardation in the thickness direction at a wavelength λ, respectively. Re (λ) is measured by making light having a wavelength of λ nm incident in the normal direction of the film in KOBRA 21ADH or WR (manufactured by Oji Scientific Instruments).

When the film to be measured is represented by a uniaxial or biaxial refractive index ellipsoid, Rth (λ) is calculated by the following method.
Rth (λ) is Re (λ), with the in-plane slow axis (determined by KOBRA 21ADH or WR) as the tilt axis (rotation axis) (in the absence of the slow axis, any in-plane The light of wavelength λ nm is incident from each of the inclined directions in steps of 10 degrees from the normal direction to 50 degrees on one side with respect to the film normal direction (with the direction of the rotation axis as the rotation axis). KOBRA 21ADH or WR is calculated based on the measured retardation value, the assumed average refractive index, and the input film thickness value.

In the above case, in the case of a film having a direction in which the retardation value is zero at a certain tilt angle with the in-plane slow axis from the normal direction as the rotation axis, retardation at a tilt angle larger than the tilt angle. The value is calculated by KOBRA 21ADH or WR after changing its sign to negative.
In addition, the retardation value is measured from the two inclined directions, with the slow axis as the tilt axis (rotation axis) (in the absence of the slow axis, the arbitrary direction in the film plane is the rotation axis), Based on the value, the assumed value of the average refractive index, and the input film thickness value, Rth can also be calculated from the following formulas (1) and (2).

  Formula (1)

The above Re (θ) represents a retardation value in a direction inclined by an angle θ from the normal direction.
In formula (1), nx represents the refractive index in the slow axis direction in the plane, ny represents the refractive index in the direction perpendicular to nx in the plane, and nz represents the refractive index in the direction perpendicular to nx and ny. . d represents the film thickness of the film.

  Formula (2)

In the case where the film to be measured cannot be expressed by a uniaxial or biaxial refractive index ellipsoid, that is, a film having no so-called optical axis, Rth (λ) is calculated by the following method.
Rth (λ) is from −50 degrees to +50 degrees with respect to the normal direction of the film, with Re (λ) as the slow axis (indicated by KOBRA 21ADH or WR) as the tilt axis (rotation axis). The light of wavelength λ nm is incident from each inclined direction in 10 degree steps and measured at 11 points. Based on the measured retardation value, the assumed average refractive index, and the input film thickness value, KOBRA 21ADH or Calculated by WR.

  In the above measurement, as the assumed value of the average refractive index, the values of Polymer Handbook (John Wiley & Sons, Inc.) and catalogs of various optical films can be used. Those whose average refractive index is not known can be measured with an Abbe refractometer. The average refractive index values of main optical films are exemplified below: cellulose acylate (1.48), cycloolefin polymer (1.52), polycarbonate (1.59), polymethyl methacrylate (1.49), Polystyrene (1.59). The KOBRA 21ADH or WR calculates nx, ny, and nz by inputting the assumed value of the average refractive index and the film thickness. Nz = (nx−nz) / (nx−ny) is further calculated from the calculated nx, ny, and nz.

[Example]
The effects of the present invention were confirmed by the following examples.
In the following examples, the expression "retardation derived from the developing agent" is the one obtained by subtracting the retardation value due to the contribution of a compound other than the retardation developing agent, such as a polymer and a plasticizer, among the retardation of the optical film. That is, the retardation value derived only from the retardation developer.
That is, an optical film obtained by stretching a transparent film obtained by adding 11.3% and 3% of a plasticizer and a developing agent to the polymer mass in a uniaxial direction of 15% of the original length in an atmosphere of 160 ° C. The retardation of the produced film is measured, and this is defined as Re (A) or Rth (A).
Separately, an optical film obtained by stretching a transparent film obtained by adding only 11.3% of a plasticizer with respect to the mass of the polymer in a uniaxial direction of 15% of the original length in an atmosphere of 160 ° C. was obtained. The retardation of the obtained film is measured and set to Re (B) or Rth (B).
Re (A) -Re (B) or Rth (A) -Rth (B) is calculated from the respective retardation values obtained as a result of the above, and is used as “retardation of the expression agent alone”.
In this example, the wavelength for retardation value measurement is 550 nm unless otherwise specified.

  Table 1 shows the expression agents used in Examples and the retardation of each expression agent alone.

Expression agent (1)

Expression agent (2)

Expression agent (3)

Expression agent (4)

Expression agent (5)

Developing agent (6)

[Example 1]
When evaluated by the above-described (liquid crystallinity evaluation method of the mixture), a stable nematic phase was formed in the mixture of the retardation enhancers (1) and (3).
On the other hand, 3% of cellulose acetate (acetylation degree: 2.8 to 2.9) was added to each mass, and triphenyl phosphate / biphenyl diphenyl phosphate (mixing ratio 6: 5) was added as a plasticizer. By mixing the developing agents (1) and (3) calculated from an optical film obtained by stretching a transparent film obtained by adding 11.3% to the mass in a uniaxial direction by 15% of the original length in an atmosphere of 160 ° C. Retardation at 550 nm is Re (550) = 40.3, respectively.
Rth (550) = 52.4
The difference in Re between the retardation value by mixing and the theoretical value (the simple sum of the retardation values of the developing agents) is Re (550) = 0.5
Met.
That is, it can be seen that in the combination of the developing agents (1) and (3) that do not interfere with the liquid crystallinity, Re of each additive is efficiently expressed even when mixed.

[Example 2]
When the retardation developing agents (1) and (4) were mixed at a mass ratio of 1: 1, a stable nematic phase was observed. Retardation at 550 nm by mixing of the developing agents (1) and (4) calculated from the optical film prepared by the same method as in Example 1 is Re (550) = 23.9.
Rth (550) = 50.1
The difference between the retardation value by mixing and the theoretical value (simple sum of the retardation values of the developing agents) is Re (550) = 4.5
Met.
That is, it can be seen that when the developing agents (1) and (4) are mixed at a ratio that does not inhibit liquid crystal properties, Re of each additive is efficiently expressed.

[Example 3]
As a result of observing with a polarizing microscope a sample in which the retardation developing agents (1) and (5) were mixed at a mass ratio of 1: 1, it was found that the liquid crystallinity of the developing agent (1) alone was lost. The retardation at 550 nm by mixing of the developing agents (1) and (5) calculated from the optical film prepared in the same manner as in Example 1 is Re (550) = 21.9.
Rth (550) = 27.3
The difference between the retardation value by mixing and the theoretical value (simple sum of the retardation values of the developing agents) is Re (550) = − 2.4.
Met.
Table 2 summarizes the optical property evaluation results obtained by mixing the developing agents (1) and (5).

[Comparative Example 1]
As a result of observing with a polarizing microscope a sample in which the retardation enhancers (2) and (5) were mixed at a mass ratio of 1: 1, it was found that the liquid crystallinity disappeared. Retardation at 550 nm by mixing of the developing agents (2) and (5) calculated from the optical film prepared by the same method as in Example 1 is Re (550) = 32.9.
Rth (550) = 38.2
The difference between the retardation value by mixing and the theoretical value (the simple sum of the retardation values of the developing agents) is Re (550) = − 8
Met.
In other words, it was found that when the developing agents (2) and (5) that inhibit liquid crystallinity are mixed, the decrease in Re is larger than when the developing agents that are incompatible with each other are mixed.
Table 2 summarizes the optical property evaluation results obtained by mixing the developing agents (2) and (5).

[Comparative Example 2]
As a result of observing with a polarizing microscope a sample in which the retardation enhancers (1) and (6) were mixed at a mass ratio of 1: 1, it was found that the liquid crystallinity disappeared. Retardation at 550 nm by mixing of the developing agents (1) and (6) calculated from the optical film prepared by the same method as in Example 1 is Re (550) = 57, respectively.
Rth (550) = 66
The difference between the retardation value by mixing and the theoretical value (simple sum of the retardation values of the developing agents) is Re (550) = − 41
Met.
That is, it was found that when the developing agents (1) and (6) that lose their liquid crystallinity were mixed, Re was significantly reduced.
Table 2 summarizes the optical property evaluation results obtained by mixing the developing agents (1) and (6).

  From the above results, the liquid crystallinity of at least one retardation developing agent does not disappear in the mixture prepared by mixing two types of retardation developing agents 1: 1, and the liquid crystal phase before mixing the retardation developing agent In the case where the same liquid crystal phase is observed, even when an optical film containing both of these two types of retardation enhancers is produced, the respective retardation development properties are not hindered and high retardation is achieved. It was found that expression was exhibited.

Claims (6)

  An optical film containing a retardation developer (A) having liquid crystallinity and a retardation developer (B) different from the retardation developer, wherein the retardation developer (A) and the retardation developer (B) ) Are mixed at a ratio of 1: 1, the liquid crystal phase identical to the liquid crystal phase that the retardation developing agent (A) exhibits alone is formed in the mixture. An optical film. The optical film according to claim 1, wherein the retardation developer (A) is a compound represented by the following general formula (1), and the retardation developer (B) is a compound represented by the general formula (2).
General formula (1):

(In General Formula (1), L ₁ and L ₂ each independently represent a single bond or a divalent linking group. A ₁ and A ₂ each independently represent —O—, —NR— (R represents a hydrogen atom) Or a linking group selected from the group consisting of —S— and —CO—, R ₁ , R ₂ , and R ₃ each independently represents a substituent, and X is the 14th to 16th. A hydrogen atom or a substituent may be bonded to X. n represents an integer of 0 to 2.
General formula (2):

(In the general formula (2), R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁸ and R ⁹ each independently represents a hydrogen atom or a substituent.)   The optical film according to claim 1 or 2, wherein the optical film mainly contains cellulose ester, polycarbonate, cycloolefin polymer, cycloolefin copolymer, and polyimide.   The polarizing plate by which a protective film is bonded together on both surfaces of a polarizer, The polarizing plate whose at least 1 piece of this protective film is an optical film of any one of Claims 1-3.   The polarizing plate according to claim 4, further comprising an optically anisotropic layer on at least one surface of the protective film.   6. A liquid crystal display device comprising a liquid crystal cell and two polarizing plates disposed on both sides thereof, at least one of the polarizing plates being the polarizing plate according to claim 4 or 5.