JP2012007110A - Optical film and method for producing the same - Google Patents

Abstract

An optical film having good surface shape, high mechanical strength, excellent durability, and capable of exhibiting optical anisotropy suitable for an optical compensation film.
An optical film comprising a cellulose ester and an acrylic resin in a compatible state,
The weight average molecular weight of the cellulose ester is 75000 or more, the weight average molecular weight of the acrylic resin is 80000 or more, and the mass ratio of the cellulose ester to the acrylic resin is 70:30 to 5:95,
An optical film in which Re and Rth defined by the following formulas (I) and (II) satisfy the following formulas (III) and (IV) at a wavelength of 590 nm.
Formula (I) Re = (nx−ny) × d
Formula (II) Rth = {(nx + ny) / 2−nz} × d
Formula (III) −10 ≦ Re ≦ 10
Formula (IV) Rth ≧ 30
In the formula, nx is the refractive index in the slow axis direction in the film plane of the optical film, ny is the refractive index in the fast axis direction in the film plane, and nz is the refractive index in the thickness direction of the optical film. D is the thickness (nm) of the optical film.
[Selection figure] None

Description

  The present invention relates to an optical film and a method for producing the same.

In recent years, liquid crystal display devices have been widely used for liquid crystal panels such as liquid crystal televisions, personal computers, mobile phones, and digital cameras. Usually, a liquid crystal display device has a liquid crystal panel member provided with polarizing plates on both sides of a liquid crystal cell, and display is performed by controlling light from the backlight member with the liquid crystal panel member. Here, the polarizing plate is composed of a polarizer and protective films on both sides thereof, and a general polarizer is obtained by dyeing a stretched polyvinyl alcohol (PVA) film with iodine or a dichroic dye to protect it. A cellulose ester film or the like is used as the film.
In liquid crystal display devices, it is known to use a polymer film as an optical compensation film (retardation film) in order to increase the viewing angle, improve image coloring, and improve contrast. For a polymer film used as an optical compensation film, depending on the mode of the liquid crystal cell of the liquid crystal display device such as the VA mode, the optical properties of the film (for example, the retardation value Re in the film plane and the film thickness direction) It is required to provide desired optical anisotropy by controlling the birefringence such as the retardation value Rth.

  Recent liquid crystal display devices are becoming more and more demanding, and the demands for durability are becoming stricter as the quality of the liquid crystal display devices increases. For example, when used in outdoor applications, stability against environmental changes is required, and the optical film such as the protective film for polarizing plate and the optical compensation film used in the liquid crystal display device also has dimensions and optical characteristics against temperature and humidity changes. It is required to suppress changes in As a problem of liquid crystal display devices exposed to high temperature and high humidity, there is display unevenness, but this is due to changes in optical properties due to changes in the presence of polymers and additives in the film, and moisture penetrates into the polarizer. This is considered to be caused by the deterioration of the polarizer performance due to this, the change in optical characteristics caused by the stress caused by the dimensional change of the film and the polarizer, and the like. For this reason, improvement of humidity dependence and wet heat durability is calculated | required with respect to the protective film of a polarizing plate, the optical compensation film bonded with a polarizing plate, etc.

  Patent Documents 1 to 3 add a large amount of acrylic resin such as polymethyl methacrylate (PMMA) to cellulose ester for the purpose of providing an optical film with high transparency, low hygroscopicity, high heat resistance, and high mechanical strength. An optical film is disclosed. Furthermore, Patent Document 2 describes that a retardation developing agent (phase difference controlling agent) is added to provide optical anisotropy for optical compensation of a VA mode liquid crystal cell. On the other hand, Patent Document 3 describes an optically isotropic film with small Re and Rth.

International Publication No. 2009/047924 International Publication No. 2009/081607 International Publication No. 2009/096701

In order to optically compensate a liquid crystal cell having high optical anisotropy such as VA mode, TN mode, and OCB mode, in order to obtain a particularly wide viewing angle, high optical anisotropy with respect to the optical compensation film, in particular, Rth is required to be sufficiently large.
However, since the optical film described in Patent Document 1 has low birefringence in which the positive birefringence due to the cellulose ester and the negative birefringence due to the acrylic resin cancel each other and is expressed as a film, it is sufficiently required as an optical compensation film. Since optical anisotropy cannot be obtained, it is difficult to apply as an optical compensation film to a liquid crystal display device having high optical anisotropy such as VA mode.
In Patent Document 2, a retardation enhancer is added to develop optical anisotropy. However, Rth is not sufficiently developed with respect to Re, and further improvement is required. In addition, since the compatibility of the retardation developer with the cellulose ester and the acrylic resin is not good, variations in the orientation of the retardation developer in the film occur, and the Re and Rth values also vary. Also, the transparency of the film, particularly the transparency after aging in a high temperature environment or a high temperature and high humidity environment, tends to decrease. Therefore, it is required to use a retardation developer that has sufficient Rth expression and is highly compatible with cellulose ester and acrylic resin.
Furthermore, the optical film described in Patent Document 3 is an optically isotropic film and does not have Rth suitable for use as an optical compensation film or a support thereof.

In view of the situation as described above, the object of the present invention is to provide an optical film suitable for an optical compensation film, having excellent surface shape and transparency, high mechanical strength, excellent durability (heat resistance and low humidity dependency). An optical film capable of expressing anisotropy and a method for producing the same are provided.
Another object of the present invention is to provide a polarizing plate using the optical film. Still another object of the present invention is to provide a liquid crystal display device having high durability and improved display unevenness.

  The object of the present invention can be achieved by the following means.

[1]
An optical film containing a cellulose ester and an acrylic resin in a compatible state,
The weight average molecular weight of the cellulose ester is 75000 or more, the weight average molecular weight of the acrylic resin is 80000 or more, and the mass ratio of the cellulose ester to the acrylic resin is 70:30 to 5:95,
An optical film in which Re and Rth defined by the following formulas (I) and (II) satisfy the following formulas (III) and (IV) at a wavelength of 590 nm.
Formula (I) Re = (nx−ny) × d
Formula (II) Rth = {(nx + ny) / 2−nz} × d
Formula (III) −10 ≦ Re ≦ 10
Formula (IV) Rth ≧ 30
In the formula, nx is the refractive index in the slow axis direction in the film plane of the optical film, ny is the refractive index in the fast axis direction in the film plane, and nz is the refractive index in the thickness direction of the optical film. D is the thickness (nm) of the optical film.
[2]
The optical element according to the above [1], wherein the total substitution degree of the acyl group of the cellulose ester is 2.00 to 3.00, and the substitution degree of the acyl group having 3 to 7 carbon atoms is 1.20 to 3.00. the film.
[3]
The optical film as described in [1] or [2] above, wherein a difference in Rth at two points at 100 mm intervals is within 3.0 nm in the film plane of the optical film.
[4]
The optical film according to any one of [1] to [3], wherein the total haze value is 0.30 or less and the internal haze value is 0.10 or less.
[5]
The optical film according to any one of [1] to [4], wherein the optical film includes a retardation enhancer, and the retardation enhancer is a discotic compound.
[6]
A method for producing an optical film comprising a cellulose ester and an acrylic resin in a compatible state,
Forming a polymer film having a mass ratio of the cellulose ester and the acrylic resin of 70:30 to 5:95;
Stretching the polymer film in a width direction perpendicular to the transport direction of the polymer film,
The weight average molecular weight of the cellulose ester is 75000 or more, the weight average molecular weight of the acrylic resin is 80000 or more,
The method for producing an optical film, wherein Re and Rth defined by the following formulas (I) and (II) satisfy the following formulas (III) and (IV) at a wavelength of 590 nm.
Formula (I) Re = (nx−ny) × d
Formula (II) Rth = {(nx + ny) / 2−nz} × d
Formula (III) −10 ≦ Re ≦ 10
Formula (IV) Rth ≧ 30
In the formula, nx is the refractive index in the slow axis direction in the film plane of the optical film, ny is the refractive index in the fast axis direction in the film plane, and nz is the refractive index in the thickness direction of the optical film. D is the thickness (nm) of the optical film.
[7]
The method for producing an optical film according to [6], wherein the stretching of the polymer film is performed in a temperature range of Tg ± 30 ° C. with respect to Tg of the unstretched polymer film after drying.
[8]
The method for producing an optical film according to the above [6] or [7], wherein the acrylic resin contains 50% by mass or more of repeating units derived from methyl methacrylate and has a mass average molecular weight of 500,000 or less.
[9]
The cellulose ester comprises an acetyl group and a propionyl group;
The total substitution degree of the acyl group of the cellulose ester is 2.00 to 3.00, the substitution degree of the acyl group having 3 to 7 carbon atoms is 1.20 to 3.00,
The method for producing an optical film according to any one of [6] to [8], wherein the cellulose ester has a mass average molecular weight of 250,000 or less.
[10]
10. The method for producing an optical film according to any one of [6] to [9], wherein the optical film contains a retardation enhancer, and the retardation enhancer is a discotic compound.
[11]
A polarizing plate comprising at least one optical film according to any one of [1] to [5] above.
[12]
A liquid crystal display device comprising at least one of the optical film according to any one of [1] to [5] or the polarizing plate according to [11].

  According to the present invention, it is possible to provide an optical film that has good surface shape, high mechanical strength, excellent durability, and can exhibit optical anisotropy suitable for an optical compensation film. By using the optical film of the present invention, it is possible to provide a liquid crystal display device having high durability and suppressing occurrence of display unevenness.

It is the schematic of the film manufacturing line for enforcing the solution casting method.

Hereinafter, the present invention will be described in detail.
In the present specification, when numerical values represent physical property values, characteristic values, etc., the descriptions “(numerical value 1) to (numerical value 2)” and “(numerical value 1) to (numerical value 2)” are “(numerical value 1). ) ”(Numerical value 2) or less”.
“Acrylic resin” means a resin obtained by polymerizing methacrylic acid or a derivative of acrylic acid, and a resin containing the derivative. Further, when not particularly limited, “(meth) acrylate” represents acrylate and methacrylate, and “(meth) acryl” represents acryl and methacryl.
Further, the “slow axis direction” of the film is a direction in which the refractive index is maximum in the film plane, and the “true axis direction” means a direction orthogonal to the slow axis in the film plane.

[Optical film]
The optical film of the present invention is an optical film containing a cellulose ester and an acrylic resin in a compatible state, wherein the cellulose ester has a mass average molecular weight of 75,000 or more, and the acrylic resin has a mass average molecular weight of 80000 or more. The mass ratio of the cellulose ester and the acrylic resin is 70:30 to 5:95, and Re and Rth defined by the following formulas (I) and (II) are represented by the following formula (III) and Satisfies (IV).
Formula (I) Re = (nx−ny) × d
Formula (II) Rth = {(nx + ny) / 2−nz} × d
Formula (III) −10 ≦ Re ≦ 10
Formula (IV) Rth ≧ 30
(Where nx is the refractive index in the slow axis direction in the film plane of the optical film, ny is the refractive index in the fast axis direction in the film plane, and nz is the thickness direction of the optical film) (Refractive index, d is the thickness (nm) of the optical film.)
According to the above configuration, the mechanical strength is high, the durability is excellent, and the optical anisotropy suitable for the optical compensation film can be expressed.

(Cellulose acylate)
The cellulose used as a raw material for the cellulose ester used in the present invention includes cotton linter and wood pulp (hardwood pulp, softwood pulp), etc., and any cellulose ester obtained from any raw material cellulose can be used. May be. As for these raw material celluloses, for example, plastic material course (17) Fibrous resin (Maruzawa, Uda, Nikkan Kogyo Shimbun, published in 1970) and Invention Association Open Technical Report 2001-1745 (pages 7-8). However, the cellulose ester used in the present invention is not particularly limited to that described.

The cellulose ester used in the present invention is preferably an ester of cellulose and a fatty acid (including an aromatic fatty acid), and is in the 2nd, 3rd and 6th positions of β-1,4 bonded glucose units constituting the cellulose. A cellulose acylate acylated by substituting an acyl group of the fatty acid for a certain hydroxyl group is preferred.
For example, cellulose alkyl carbonyl ester, alkenyl carbonyl ester, aromatic carbonyl ester, aromatic alkyl carbonyl ester, etc., and cellulose ester in which acyl groups of two or more fatty acids are substituted are also preferable. These cellulose esters may further have a substituted group.
As the acyl group that substitutes for the hydroxyl group, an acetyl group having 2 carbon atoms and an acyl group having 3 to 22 carbon atoms can be preferably used. From the viewpoint of improving compatibility with the acrylic resin, an acetyl group having 2 carbon atoms and an acyl group having 3 to 7 carbon atoms are preferable.
The total substitution degree of acyl groups in the cellulose ester used in the present invention (the ratio of substitution of acyl groups with hydroxyl groups in the β-glucose unit of cellulose) The number of substituted groups is 3). However, it is preferable that the total substitution degree of the acyl group is higher because the compatibility with the acrylic resin is better and the humidity dependency is reduced. For this reason, the total substitution degree of the acyl group is preferably 2.00 to 3.00, more preferably 2.50 to 3.00, and still more preferably 2.50 to 2.90.
Furthermore, from the viewpoint of compatibility with the acrylic resin, the substitution degree of the acyl group having 3 to 7 carbon atoms is preferably 1.20 to 3.00, more preferably 1.50 to 3.00, and 2.00. -3.00 is more preferable, and 2.00-2.90 is particularly preferable.
In the cellulose ester of the present invention, examples of the method for measuring the degree of substitution of the acyl group substituted on the hydroxyl group of cellulose include a method according to ASTM D-817-91 and an NMR method.

The acyl group that substitutes for the hydroxyl group of the β-glucose unit of cellulose may be either an aliphatic group or an aromatic group, and is not particularly limited. Moreover, the acyl group substituted on the hydroxyl group may be a single acyl group or two or more kinds.
Examples of the acyl group include acetyl group, propionyl group, butanoyl group, heptanoyl group, hexanoyl group, octanoyl group, decanoyl group, dodecanoyl group, tridecanoyl group, tetradecanoyl group, hexadecanoyl group, octadecanoyl group, iso -Butanoyl group, t-butanoyl group, cyclohexanecarbonyl group, oleoyl group, benzoyl group, naphthylcarbonyl group, cinnamoyl group and the like can be mentioned. Among these, acetyl group, propionyl group, butanoyl group, dodecanoyl group, octadecanoyl group, t-butanoyl group, oleoyl group, benzoyl group, naphthylcarbonyl group, cinnamoyl group and the like are preferable, and acetyl group, propionyl group, butanoyl group are preferable. Group is more preferable, propionyl group or butanoyl group is still more preferable, and propionyl group is particularly preferable.
Acetyl and propionyl groups, acetyl and butanoyl groups, propionyl and butanoyl groups, acetyl, propionyl and butanoyl groups are used in combination for ease of synthesis, cost, and ease of control of substituent distribution. More preferably, acetyl group and propionyl group, acetyl group and butanoyl group, acetyl group, propionyl group and butanoyl group are used in combination, more preferably acetyl group and propionyl group, acetyl group and propionyl group. And a butanoyl group are used in combination, and an acetyl group and a propionyl group are particularly preferably used in combination.
Examples of the cellulose ester substituted with the acyl group include cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, cellulose acetate petitate, cellulose acetate propionate butyrate, and cellulose benzoate. Of these, cellulose propionate, cellulose butyrate, cellulose acetate propionate, cellulose acetate butyrate, and cellulose acetate propionate butyrate are preferable, and cellulose acetate propionate is more preferable.

  The degree of polymerization of the cellulose ester used in the present invention is 180 to 700 in terms of viscosity average polymerization degree. In particular, in cellulose acetate propionate substituted with an acetyl group and a propionyl group, 180 to 550 is more preferable, and 180 to 400 is more preferable, and 180 to 350 is particularly preferable. If the degree of polymerization is within this range, the viscosity of the dope solution containing the cellulose ester can be made suitable for film production by casting, and the compatibility with the acrylic resin is high, and the transparency and mechanical strength are high. It is preferable because a high film can be obtained. The viscosity average degree of polymerization can be measured by Uda et al.'S limiting viscosity method (Kazuo Uda, Hideo Saito, Journal of Textile Science, Vol. 18, No. 1, pages 105-120, 1962). This is described in detail in JP-A-9-95538.

The mass average molecular weight Mw of the cellulose ester used in the present invention is 75000 or more. If the mass average molecular weight Mw of a cellulose ester is 75000 or more, mechanical strength is high and it is excellent in the handling ability at the time of film manufacture. From this viewpoint, the mass average molecular weight Mw of the cellulose ester is preferably 100,000 or more, and more preferably 150,000 or more. Moreover, from a viewpoint of a compatibility improvement with an acrylic resin, it is preferable that the mass mean molecular weight Mw of a cellulose ester is 300000 or less, It is more preferable that it is 270000 or less, It is further more preferable that it is 250,000 or less.
From the viewpoint of achieving both the mechanical strength of the film, the handling suitability, and the compatibility improvement with the acrylic resin, the mass average molecular weight Mw of the cellulose ester is preferably 75,000 or more and 300,000 or less, and preferably 100,000 or more and 270000 or less. More preferably, it is 150,000 or more and 250,000 or less.
From the same viewpoint, the number average molecular weight Mn of the cellulose ester is preferably 18000 or more and 300000 or less, more preferably 25000 or more and 270000 or less, and further preferably 38000 or more and 250,000 or less.
The mass average molecular weight and number average molecular weight of the cellulose ester can be measured by gel permeation chromatography.
Further, regarding the molecular weight distribution of the cellulose ester, it is preferable that the polydispersity index Mw / Mn (Mw is a mass average molecular weight, Mn is a number average molecular weight) is small and the molecular weight distribution is narrow. The specific value of Mw / Mn is preferably 1.0 to 4.0, more preferably 2.0 to 3.5, and even more preferably 2.3 to 3.4. preferable.

When the low molecular weight component of the cellulose ester is removed, the average molecular weight (polymerization degree) is increased, but the viscosity is lower than that of a normal cellulose ester, which is useful. The removal of the low molecular component can be carried out by washing the cellulose ester synthesized by a usual method with an appropriate organic solvent. In addition, when manufacturing a cellulose acylate with few low molecular components, it is preferable to adjust the sulfuric acid catalyst amount in an acetylation reaction to 0.5-25 mass parts with respect to 100 mass parts of cellulose. When the amount of the sulfuric acid catalyst is within the above range, cellulose acylate having a narrow molecular weight distribution can be synthesized.
When used in the production of the optical film of the present invention, the moisture content of the cellulose ester is preferably 2% by mass or less, more preferably 1% by mass or less, and particularly preferably 0.7% by mass or less. It is. In general, the cellulose ester contains water. For example, the moisture content of cellulose acylate is known to be 2.5 to 5% by mass. In order to obtain the moisture content of the cellulose acylate as described above in the present invention, drying is preferable, and the method is not particularly limited as long as the desired moisture content is obtained.
Regarding the cellulose acylate that can be used in the present invention, the raw material cotton and the synthesis method thereof are disclosed in JIII Journal of Technical Disclosure (Publication No. 2001-1745, published on March 15, 2001, Invention Association), pages 7-12. It is described in detail on the page.

  In the present invention, from the viewpoint of the substituent, substitution degree, polymerization degree, molecular weight distribution, etc. of cellulose ester, a single or different two or more kinds of cellulose esters can be mixed and used.

  The content of the cellulose ester in the optical film of the present invention is preferably 69.9 to 3.3% by mass, more preferably 69.9 to 10.0% by mass in the optical film. It is more preferable that it is 9-20.0 mass%, and it is still more preferable that it is 49.9-20.0 mass%.

(acrylic resin)
The acrylic resin used in the present invention is a resin obtained by polymerizing a derivative of (meth) acrylic acid and a resin containing the derivative, and is not particularly limited as long as the effects of the present invention are not impaired.
Examples of the (meth) acrylic acid derivative include (meth) acrylate. For example, methyl acrylate, ethyl acrylate, N-propyl acrylate, N-butyl acrylate, tert-butyl acrylate, isopropyl acrylate, N-hexyl acrylate, cyclohexyl acrylate, t-butyl cyclohexyl acrylate, methyl methacrylate, ethyl methacrylate, N-propyl methacrylate, Homopolymers of alkyl (meth) acrylates such as N-butyl methacrylate, tert-butyl methacrylate, isopropyl methacrylate, N-hexyl methacrylate, cyclohexyl methacrylate, t-butylcyclohexyl methacrylate; 2-chloroethyl acrylate, 2-hydroxyethyl acrylate, 2,3,4,5-tetrahydroxypentyl acrylate, 2 Even in which any hydrogen atom of alkyl (meth) acrylate such as chloroethyl methacrylate, 2-hydroxyethyl methacrylate, 2,3,4,5-tetrahydroxypentyl methacrylate is substituted with a halogen group, a hydroxyl group and other organic residues Good. Here, the other organic residue is preferably a linear, branched, or cyclic alkyl group having 1 to 20 carbon atoms.

  As a main component of the acrylic resin used in the present invention, alkyl (meth) acrylate is preferable. The alkyl (meth) acrylate is preferably an alkyl (meth) acrylate composed of an alkyl group having 1 to 18 carbon atoms and (meth) acrylic acid, and an alkyl composed of an alkyl group having 1 to 12 carbon atoms and meth) acrylic acid. (Meth) acrylate is more preferred, methyl acrylate and methyl methacrylate are more preferred, and methyl methacrylate is particularly preferred.

The acrylic resin used in the present invention is a copolymer of one (meth) acrylic acid derivative or a copolymer of two or more (meth) acrylic acid derivatives. It may be a copolymer with other possible monomers.
Examples of copolymerizable components that can be copolymerized with (meth) acrylic acid derivatives include α, β-unsaturated acids such as acrylic acid and methacrylic acid, and unsaturated group-containing divalent carboxylic acids such as maleic acid, fumaric acid, and itaconic acid. Unsaturated acids such as acids, styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, 2,4-dimethylstyrene, p-ethylstyrene, p-tert-butylstyrene, α-methylstyrene, α- Aromatic vinyl compounds such as methyl-p-methylstyrene, α, β-unsaturated nitriles such as acrylonitrile and methacrylonitrile, lactone ring units, glutaric anhydride units, unsaturated carboxylic acid anhydrides such as maleic anhydride Examples include compounds, maleimides such as maleimide and N-substituted maleimide, and glutarimide units.
From the viewpoint of optical properties, an aromatic vinyl compound is preferable, and styrene is particularly preferable.

From the viewpoint of improving compatibility with cellulose ester, the acrylic resin is preferably a methyl methacrylate homopolymer or copolymer, more preferably containing 50% by mass or more of methyl methacrylate-derived repeating units, and 70% by mass or more. More preferably, it is more preferably 90% by mass or more. Furthermore, a copolymer of methyl methacrylate and another monomer is preferable, and the acrylic resin of the copolymer contains 1 to 50% by mass of a repeating unit derived from a monomer copolymerized with methyl methacrylate. Is preferable, it is more preferable that 1-30 mass% is contained, and it is still more preferable that 1-10 mass% is contained.
The monomer copolymerizable with methyl methacrylate comprises, in addition to those exemplified as the monomer copolymerizable with the alkyl (meth) acrylate, an alkyl group having 2 to 18 carbon atoms and methacrylic acid. Examples thereof include alkyl methacrylates and alkyl acrylates comprising an alkyl group having 1 to 18 carbon atoms and acrylic acid, and these can be used alone or in combination of two or more monomers. Of these, methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, s-butyl acrylate, 2-ethylhexyl acrylate, and the like are preferable from the viewpoint of thermal decomposition resistance and fluidity of the copolymer, and methyl acrylate and n- Butyl acrylate is particularly preferably used.
Examples of the acrylic resin and (meth) acrylic acid derivatives and other copolymerizable monomers of the present invention include JP2009-122664, JP2009-139661, JP2009-139754, and JP2009-. 294262, International Publication 2009/054376, and other publications can also be used. In addition, these do not limit this invention, These can be used individually or in combination of 2 or more types.
When two or more types of acrylic resins are used, it is preferable to use at least one type having the above structure.

The mass average molecular weight Mw of the acrylic resin used in the present invention is 80,000 or more. If the mass average molecular weight Mw of an acrylic resin is 80000 or more, mechanical strength is high and it is excellent in the handling ability at the time of film manufacture. In this respect, the acrylic resin preferably has a mass average molecular weight Mw of 100,000 or more. Moreover, from the viewpoint of improving compatibility with cellulose ester, the mass average molecular weight Mw of the acrylic resin is preferably 1100000 or less, and more preferably 500000 or less.
From the viewpoint of the compatibility of the mechanical strength of the film, the suitability for handling, and the compatibility with the cellulose ester, the mass average molecular weight Mw of the acrylic resin is preferably 80,000 to 11,000,000, more preferably 80,000 to 500,000. Preferably, it is 100,000 or more and 500,000 or less.
The mass average molecular weight of the acrylic resin can be measured by gel permeation chromatography.

  There is no restriction | limiting in particular as a manufacturing method of the acrylic resin in this invention, Any of well-known methods, such as suspension polymerization, emulsion polymerization, block polymerization, or solution polymerization, may be used. Here, as a polymerization initiator, a normal peroxide type and an azo type can be used, and a redox type can also be used. Regarding the polymerization temperature, it can be carried out at 30 to 100 ° C. for suspension or emulsion polymerization, and at 80 to 160 ° C. for bulk or solution polymerization. In order to control the reduced viscosity of the obtained copolymer, polymerization can be carried out using alkyl mercaptan or the like as a chain transfer agent.

A commercially available thing can also be used as an acrylic resin used for this invention. For example, Delpet 60N, 80N (Asahi Kasei Chemicals Co., Ltd.), Dianal BR80, BR85, BR88, BR102 (Mitsubishi Rayon Co., Ltd.), KT75 (Electrochemical Industry Co., Ltd.) and the like can be mentioned.
Two or more acrylic resins can be used in combination.

  The content of the acrylic resin in the optical film of the present invention is preferably 20.0 to 94.9% by mass, more preferably 20.0 to 84.9% by mass in the optical film, and 20. It is more preferable that it is 0-69.9%, and it is still more preferable that it is 34.0-69.9 mass%.

  In the optical film of the present invention, the ratio (mass ratio) between the cellulose ester and the acrylic resin is 70:30 to 5:95. By making the ratio of cellulose ester 70% by mass or less, humidity dependency is low, durability at high temperature and high humidity is improved, preferable optical characteristics can be obtained, and display unevenness of the liquid crystal display device can be prevented. . Moreover, heat resistance improves by making the ratio of an acrylic resin 95 mass% or less, and it is easy to express desired optical anisotropy. In addition, mechanical strength, mechanical strength, surface shape, hunting suitability, and film surface treatment suitability can be improved. The mass ratio of cellulose ester to acrylic resin is 70:30 to 5:95, preferably 70:30 to 15:85, more preferably 70:30 to 30:70, and even more preferably 49. : 51-30: 70.

In the optical film of the present invention, it is preferable that the cellulose ester and the acrylic resin are contained in a compatible state from the viewpoint of reducing the total haze and internal haze and increasing the transparency.
Whether the cellulose ester and the acrylic resin are in a compatible state can be determined by, for example, the glass transition temperature Tg. For example, when the glass transition temperatures of cellulose ester and acrylic resin are different, when both are mixed, there are two or more glass transition temperatures for each mixture, and the two are compatible. In some cases, the glass transition temperature inherent to each resin disappears and becomes one glass transition temperature, which is the glass transition temperature of the compatible resin.
The glass transition temperature is a temperature at which the baseline derived from the glass transition of the resin starts to change and a temperature at which the glass returns to the baseline again when measured at a heating rate of 10 ° C./min using a differential scanning calorimeter (DSC). It can be calculated as an average value.

  The cellulose ester and the acrylic resin are each preferably an amorphous resin, and either one may be a crystalline polymer or a partially crystalline polymer. It becomes preferable that it becomes a non-crystalline resin by being compatible.

The weight average molecular weight Mw and substitution degree of the cellulose ester in the optical film of the present invention, and the weight average molecular weight Mw of the acrylic resin can be obtained by measuring each after separation using the difference in solubility in both solvents. be able to. When fractionating the resin, it is possible to extract and separate the soluble resin by adding a compatible resin in a solvent that is soluble only in either one. At this time, heating operation or reflux is performed. May be. A combination of these solvents may be combined in two or more steps to separate the resin. The dissolved resin and the resin remaining as an insoluble matter are filtered off, and the solution containing the extract can be separated by an operation of evaporating the solvent and drying. These fractionated resins can be identified by general structural analysis of polymers. When the optical film of the present invention contains a resin other than cellulose ester or acrylic resin, it can be separated by the same method.
Further, when the mass average molecular weights Mw of the compatible resins are different from each other, the high molecular weight substances are eluted earlier by gel permeation chromatography, and the lower molecular weight substances are eluted after a longer time. It can be easily fractionated and the molecular weight can be measured.
In addition, the molecular weight of the compatible resin is measured by gel permeation chromatography. At the same time, the resin solution eluted every time is separated, the solvent is distilled off, and the structure of the dried resin is quantitatively analyzed. By detecting the resin composition for each fraction having a different molecular weight, the compatible resins can be respectively identified. The resins that have been separated in advance by the difference in solubility in a solvent can be detected by measuring the molecular weight distribution by gel permeation chromatography, respectively.
In addition, “containing cellulose ester and acrylic resin in a compatible state” means that each resin (polymer) is mixed to result in a compatible state. It is assumed that a mixed resin state by mixing a precursor of acrylic resin such as dimer or oligomer with cellulose ester and then polymerizing it is not included.

  Unless the function as an optical film is impaired, the optical film of this invention may contain resin and additives other than a cellulose ester and an acrylic resin, and may be comprised. When the resin other than the cellulose ester and the acrylic resin is contained, the added resin may be mixed without being dissolved even if the added resin is in a compatible state.

(Matting agent fine particles)
Fine particles can be added as a matting agent to the optical film of the present invention. Fine particles used as a matting agent include silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate and Mention may be made of calcium phosphate. Fine particles containing silicon are preferred in that the haze of the film is reduced, and silicon dioxide is particularly preferred. The silicon dioxide fine particles preferably have a primary average particle size of 20 nm or less and an apparent specific gravity of 70 g / liter or more. Those having an average primary particle size as small as 5 to 16 nm are more preferred because they can reduce the haze of the film. The apparent specific gravity is preferably 90 to 200 g / liter or more, and more preferably 100 to 200 g / liter or more. A larger apparent specific gravity is preferable because a high-concentration dispersion can be produced, and haze and aggregates are improved.

  These fine particles usually form secondary particles having an average particle diameter of 0.1 to 3.0 μm, and these fine particles are present as aggregates of primary particles in the film, and 0.1 to 0.1 μm on the film surface. An unevenness of 3.0 μm is formed. The average particle diameter of the secondary particles is preferably from 0.2 μm to 1.5 μm, more preferably from 0.4 μm to 1.2 μm, and most preferably from 0.6 μm to 1.1 μm. The particle diameter of the primary particles and the secondary particles was determined by observing the particles in the film with a scanning electron microscope and determining the diameter of a circle circumscribing the particles as the particle diameter. In addition, 200 particles were observed at different locations, and the average value was taken as the average particle size.

  As the fine particles of silicon dioxide, for example, commercially available products such as Aerosil R972, R972V, R974, R812, 200, 200V, 300, R202, OX50, TT600 (above Nippon Aerosil Co., Ltd.) can be used. Zirconium oxide fine particles are commercially available, for example, under the trade names Aerosil R976 and R811 (manufactured by Nippon Aerosil Co., Ltd.) and can be used.

  Among these, Aerosil 200V and Aerosil R972V are fine particles of silicon dioxide having an average primary particle diameter of 20 nm or less and an apparent specific gravity of 70 g / liter or more, while keeping the turbidity of the optical film low. This is particularly preferable because the effect of reducing the friction coefficient is great.

In order to obtain an optical film having particles having a small average particle size of secondary particles in the present invention, several methods are conceivable when preparing a dispersion of fine particles. For example, a fine particle dispersion prepared by stirring and mixing a solvent and fine particles is prepared in advance, and this fine particle dispersion is added to a small amount of a separately prepared cellulose ester or acrylic resin solution and dissolved by stirring. Further, a polymer solution for main film preparation There is a method of mixing with (dope solution). This method is a preferred preparation method in that the dispersibility of the silicon dioxide fine particles is good and the silicon dioxide fine particles are more difficult to reaggregate. In addition, after adding a small amount of cellulose ester or acrylic resin to the solvent and dissolving with stirring, add fine particles to this and disperse with a disperser. There is also a method of thoroughly mixing with the liquid. The present invention is not limited to these methods, but the concentration of silicon dioxide when the silicon dioxide fine particles are mixed and dispersed with a solvent or the like is preferably 5 to 30% by mass, more preferably 10 to 25% by mass, and 15 to 20%. Mass% is most preferred. A higher dispersion concentration is preferable because the liquid turbidity with respect to the added amount is lowered, and haze and aggregates are improved.
The addition amount of the matting agent in the final dope solution is preferably 0.01 to 1.0 g, more preferably 0.03 to 0.3 g, and most preferably 0.08 to 0.16 g per 1 m ² . The addition amount of the matting agent is preferably 0.001% by mass or more and 0.4% by mass or less, and preferably 0.001% by mass or more and 0% by mass with respect to the total amount of resin used in the dope solution such as cellulose ester resin and acrylic resin. .2% by mass or less is more preferable, and 0.01% by mass or more and 0.1% by mass or less is more preferable. In addition, when the optical film is formed from multiple layers, it is preferable to add only to the surface layer side without adding to the inner layer. In this case, the total amount of resin used for the dope solution such as cellulose ester resin and acrylic resin On the other hand, the addition amount of the matting agent in the surface layer is preferably 0.001% by mass or more and 0.4% by mass or less, more preferably 0.001% by mass or more and 0.2% by mass or less, and 0.01% by mass or more. 0.1 mass% or less is still more preferable.

  As the solvent used for dispersion, lower alcohols are preferable, and examples thereof include methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, and butyl alcohol. Although it does not specifically limit as solvents other than a lower alcohol, It is preferable to use the solvent used at the time of film forming of an optical film.

(Other additives)
In addition to the mat particles, a retardation enhancer described below can be added to the optical film of the present invention. Further, various other additives (for example, plasticizers, ultraviolet absorbers, deterioration inhibitors, release agents, infrared absorbers, wavelength dispersion adjusting agents, etc.) can be added, and these may be solid or oily. . That is, the melting point and boiling point are not particularly limited. For example, mixing of ultraviolet absorbing material 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. Furthermore, infrared absorbing dyes are described in, for example, JP-A No. 2001-194522. Moreover, the addition time may be added at any time in the dope preparation step, but may be added by adding an additive to the final preparation step of the dope preparation step. Furthermore, the amount of each material added is not particularly limited as long as the function is manifested. Moreover, when an optical film is formed from a multilayer, the kind and addition amount of the additive of each layer may differ. For example, it is described in Japanese Patent Application Laid-Open No. 2001-151902, and these are conventionally known techniques. For these details, materials described in detail on pages 16 to 22 in the Japan Institute of Invention Disclosure Technical Bulletin (Public Technical No. 2001-1745, published on March 15, 2001, Japan Institute of Invention) are preferably used.

A plasticizer having good compatibility with the cellulose ester and the acrylic resin is less likely to bleed out, has a low haze, and is effective for producing a film that realizes a liquid crystal display device excellent in light leakage, front contrast, and luminance.
You may use a plasticizer for the optical film of this invention. Although it does not specifically limit as a plasticizer, A phosphate ester plasticizer, a phthalate ester plasticizer, a polyhydric alcohol ester plasticizer, a polycarboxylic acid ester plasticizer, a glycolate plasticizer, a citrate ester Examples thereof include plasticizers, fatty acid ester plasticizers, carboxylic acid ester plasticizers, polyester oligomer plasticizers, sugar ester plasticizers, and ethylenically unsaturated monomer copolymer plasticizers.
Preferred are phosphate ester plasticizers, glycolate plasticizers, polyhydric alcohol ester plasticizers, polyester oligomer plasticizers, sugar ester plasticizers, ethylenically unsaturated monomer copolymer plasticizers, and more preferred. Is a polyester oligomer plasticizer, sugar ester plasticizer, ethylenically unsaturated monomer copolymer plasticizer, more preferably an ethylenically unsaturated monomer copolymer plasticizer, sugar ester plasticizer, particularly preferably Is an ethylenically unsaturated monomer copolymer plasticizer.
In particular, polyester oligomer plasticizers, ethylenically unsaturated monomer copolymer plasticizers, and sugar ester plasticizers are highly compatible with the optical film of the present invention, and are highly effective in reducing bleed out, low haze, and low moisture permeability. Further, since it is difficult for the plasticizer to be decomposed and the film to be altered or deformed due to changes in temperature and humidity, the film can be preferably used in the present invention.
In the present invention, the plasticizer may be used alone or in combination of two or more.

  The optical film of the present invention may contain acrylic particles. Japanese Patent Publication No. 60-17406, Japanese Patent Publication No. 3-39095 and the like describe that the addition of acrylic particles, particularly a multilayer structure acrylic granular composite, improves impact resistance and stress whitening resistance.

  In the optical film of the present invention, when these additives are added, the total amount of the additives is preferably 50% by mass or less, and preferably 30% by mass or less with respect to the optical film.

(Retardation)
In the optical film of the present invention, Re and Rth (defined by the following formulas (I) and (II)) measured at a wavelength of 590 nm satisfy the formulas (III) and (IV).
Formula (I) Re = (nx−ny) × d
Formula (II) Rth = {(nx + ny) / 2−nz} × d
Formula (III) −10 ≦ Re ≦ 10
Formula (IV) Rth ≧ 30
(Where nx is the refractive index in the slow axis direction in the film plane of the optical film, ny is the refractive index in the fast axis direction in the film plane, and nz is the thickness direction of the optical film) (Refractive index, d is the thickness (nm) of the optical film.)
Since the film satisfying the above formulas (III) and (IV) exhibits high optical anisotropy, it can be suitably used as an optical compensation film of a VA mode liquid crystal display device, and the contrast ratio of the display of the liquid crystal display device And the viewing angle and color can be improved.
In the optical film of the present invention, the above formulas (III) and (IV) may be satisfied at at least one point in the film plane, but the above formulas (III) and (IV) are arbitrary at any point in the film plane. ) Is preferably satisfied.

In the VA mode liquid crystal display device, the optical film of the present invention is used either between the upper polarizer and the liquid crystal cell or between the lower polarizer and the liquid crystal cell, and between the other polarizer and the liquid crystal cell. When optical compensation is performed using a film satisfying 30 ≦ Re ≦ 100, 70 ≦ Rth ≦ 300, and Nz ≧ 2.00, Re and Rth of the optical film of the present invention preferably have the following values.
As the value of Re, −7 ≦ Re ≦ 7 is preferable, and −5 ≦ Re ≦ 5 is more preferable.
The value of Rth is preferably 30 ≦ Rth ≦ 120, more preferably 40 ≦ Rth ≦ 100, and further preferably 45 ≦ Rth ≦ 85.

In the VA mode liquid crystal display device, the optical film of the present invention is used either between the upper polarizer and the liquid crystal cell or between the lower polarizer and the liquid crystal cell, and between the other polarizer and the liquid crystal cell. When optical compensation is performed using a film satisfying 90 ≦ Re ≦ 200, 45 ≦ Rth ≦ 100, and 0.73 ≦ Nz ≦ 1.11, Re and Rth of the optical film of the present invention preferably have the following values. As the value of Re, −7 ≦ Re ≦ 7 is preferable, and −5 ≦ Re ≦ 5 is more preferable.
The value of Rth is preferably 50 ≦ Rth ≦ 300, more preferably 80 ≦ Rth ≦ 250, and still more preferably 100 ≦ Rth ≦ 200.

Furthermore, in the optical film of the present invention, from the viewpoint of expressing optical anisotropy suitable as an optical compensation film for a VA mode liquid crystal display device, Nz defined by the following formula (V) is represented by the following formula ( It is preferable to satisfy VI).
Formula (V) Nz = (nx−nz) / (nx−ny) = Rth / Re + 1/2
Formula (VI) | Nz | ≧ 3.00
Further, the value of Nz is preferably | Nz | ≧ 3.00, more preferably | Nz | ≧ 4.00, further preferably | Nz | ≧ 6.00, and particularly preferably | Nz | ≧ 10.00. .

By limiting the value of Re to the above preferable range according to the mode of the liquid crystal display device to be applied, the front contrast can be further improved, and by limiting the values of Rth and Nz to the above preferable range, It becomes possible to further improve the viewing angle dependency of the oblique contrast and the color.
The optical film of the present invention is not limited to a VA mode liquid crystal display device, and can be used as an optical compensation film for various liquid crystal display devices including an IPS mode and a TN mode.

Re, Rth, and Nz at the wavelength λnm can be measured as follows.
Re is measured with KOBRA 21ADH (manufactured by Oji Scientific Instruments Co., Ltd.) by making light of wavelength λ nm incident in the normal direction of the film.
Rth was measured by making light having a wavelength λ nm incident from a direction inclined + 40 ° with respect to the normal direction of the film with the slow axis in the plane (determined by KOBRA 21ADH) as the tilt axis (rotation axis). A retardation value and a retardation value measured by making light of wavelength λ nm incident from a direction inclined by −40 ° with respect to the film normal direction with the in-plane slow axis as the tilt axis (rotation axis). Calculated by KOBRA 21ADH based on the retardation value measured in the direction. Here, as the assumed value of the average refractive index, values in the 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).
Nz is calculated by the formula (VI) based on Re and Rth. Note that nx, ny, and nz can be calculated by KOBRA 21ADH based on the assumed value of the average refractive index and the film thickness, and Nz can be calculated from the values of nx, ny, and nz by the formula (II).
In the measurement of the optical film of the present invention, the retardation is measured by setting the average refractive index of the optical film to 1.48.

  The above Re, Rth, and Nz can be adjusted by the substitution degree of cellulose ester, the ratio of cellulose ester and acrylic resin, the addition of a retardation developer, the film thickness, the stretching direction and stretching ratio of the film, and the like.

(Rth variation)
In the optical film of the present invention, a smaller variation in Rth in the film is preferable from the viewpoint of improving the contrast ratio, viewing angle, and color of the applied liquid crystal display device. Specifically, in the film plane, the difference in Rth at two points at 100 mm intervals is preferably within 3.0 nm, more preferably within 2.0 nm, and further within 1.5 nm. preferable.
The variation in Rth can be adjusted by stretching conditions, drying conditions, etc., but adjustment by stretching temperature is particularly preferable. The stretching temperature is preferably Tg ± 30 ° C., more preferably Tg ± 25 ° C., further preferably Tg ± 20 ° C., particularly preferably Tg ± 15 ° C., based on the Tg of the unstretched polymer film after film formation and drying. Tg ± 15 ° C. is most preferable.

<Retardation expression agent>
In the present invention, it is preferable to use a retardation enhancer in order to develop desired optical anisotropy.
As the retardation developer of the present invention, a compound having good compatibility with both cellulose ester and acrylic resin, and also having compatibility with a film containing cellulose ester and acrylic resin in a compatible state is used. It is preferable to do. Further, it is preferable to use a compound having a large intrinsic birefringence and molecular orientation along the stretching direction during stretching.
Examples of the retardation enhancer that can be used in the present invention include a discotic compound and a rod-shaped compound. In addition, a compound exhibiting liquid crystallinity can also be used as a retardation developer, and the discotic compound or rod-shaped compound may be a compound exhibiting liquid crystallinity.
Among these, from the viewpoint of optical compensation of a VA mode or TN mode liquid crystal display device, a retardation developer having good orientation in the film and large Rth expression is preferable. From this viewpoint, a discotic compound or a compound exhibiting liquid crystallinity is preferable, and a discotic compound is more preferable.

The retardation developer in the optical film is not particularly limited, but may be 0.1 to 50 parts by mass when the total amount of resins forming the film such as cellulose ester and acrylic resin is 100 parts by mass. It is preferably 0.1 to 30 parts by mass, more preferably 0.1 to 20 parts by mass, and particularly preferably 0.1 to 12 parts by mass.
Two or more types of retardation developing agents may be used. Combinations of discotic compounds, rod-shaped compounds, liquid crystalline compounds or different combinations may be used. Also good. When two or more types of retardation developing agents are used, the total amount is preferably in the above range.
The retardation developer preferably has a maximum absorption in the wavelength region of 250 to 400 nm, and preferably has substantially no absorption in the visible region.

The retardation developing agent for discotic compounds will be described.
As the discotic compound, it is preferable to use a compound having at least two aromatic rings.
Here, the “aromatic ring” includes an aromatic heterocycle in addition to an aromatic hydrocarbon ring.

The aromatic hydrocarbon ring in the discotic compound is particularly preferably a 6-membered ring (that is, a benzene ring).
The aromatic heterocycle is generally an unsaturated heterocycle. The aromatic heterocycle is preferably a 5-membered ring, 6-membered ring or 7-membered ring, more preferably a 5-membered ring or 6-membered ring. Aromatic heterocycles generally have the most double bonds. As the hetero atom, a nitrogen atom, an oxygen atom and a sulfur atom are preferable, and a nitrogen atom is particularly preferable. Examples of aromatic heterocycle include furan ring, thiophene ring, pyrrole ring, oxazole ring, isoxazole ring, thiazole ring, isothiazole ring, imidazole ring, pyrazole ring, furazane ring, triazole ring, pyran ring, pyridine ring, A pyridazine ring, a pyrimidine ring, a pyrazine ring and a 1,3,5-triazine ring are included.

  As the aromatic ring, benzene ring, furan ring, thiophene ring, pyrrole ring, oxazole ring, thiazole ring, imidazole ring, triazole ring, pyridine ring, pyrimidine ring, pyrazine ring and 1,3,5-triazine ring are preferable, In particular, a 1,3,5-triazine ring is preferably used.

The number of aromatic rings contained in the discotic compound is preferably 2 to 20, more preferably 2 to 12, still more preferably 2 to 8, and most preferably 2 to 6. preferable.
The bonding relationship between two aromatic rings can be classified into (a) when forming a condensed ring, (b) when directly connecting with a single bond, and (c) when connecting via a linking group (for aromatic rings). , Spiro bonds cannot be formed). The connection relationship may be any of (a) to (c).

Examples of the condensed ring (a condensed ring of two or more aromatic rings) include an indene ring, a naphthalene ring, an azulene ring, a fluorene ring, a phenanthrene ring, an anthracene ring, an acenaphthylene ring, a biphenylene ring, a naphthacene ring, Pyrene ring, indole ring, isoindole ring, benzofuran ring, benzothiophene ring, indolizine ring, benzoxazole ring, benzothiazole ring, benzimidazole ring, benzotriazole ring, purine ring, indazole ring, chromene ring, quinoline ring, isoquinoline Ring, quinolidine ring, quinazoline ring, cinnoline ring, quinoxaline ring, phthalazine ring, pteridine ring, carbazole ring, acridine ring, phenanthridine ring, xanthene ring, phenazine ring, phenothiazine ring, phenoxathiin ring, phenoxazine ring and thiantole Ring is included. Naphthalene ring, azulene ring, indole ring, benzoxazole ring, benzothiazole ring, benzimidazole ring, benzotriazole ring and quinoline ring are preferred.

The single bond (b) is preferably a bond between carbon atoms of two aromatic rings. Two aromatic rings may be bonded by two or more single bonds to form an aliphatic ring or a non-aromatic hetero ring between the two aromatic rings.

The linking group in (c) is also preferably bonded to carbon atoms of two aromatic rings. The linking group is preferably an alkylene group, an alkenylene group, an alkynylene group, —CO—, —O—, —NH—, —S—, or a combination thereof. Examples of linking groups consisting of combinations are shown below. In addition, the relationship between the left and right in the following examples of the linking group may be reversed.

c1: -CO-O-
c2: —CO—NH—
c3: -alkylene-O-
c4: —NH—CO—NH—
c5: —NH—CO—O—
c6: —O—CO—O—
c7: -O-alkylene-O-
c8: -CO-alkenylene-
c9: -CO-alkenylene-NH-
c10: -CO-alkenylene-O-
c11: -alkylene-CO-O-alkylene-O-CO-alkylene-
c12: -O-alkylene-CO-O-alkylene-O-CO-alkylene-O-
c13: -O-CO-alkylene-CO-O-
c14: -NH-CO-alkenylene-
c15: -O-CO-alkenylene-

The aromatic ring and the linking group may have a substituent of the following substituent group A.
(Substituent group A)
Examples of substituents include halogen atoms (F, Cl, Br, I), hydroxyl groups, carboxyl groups, cyano groups, amino groups, nitro groups, sulfo groups, carbamoyl groups, sulfamoyl groups, ureido groups, alkyl groups, alkenyls. Group, alkynyl group, aliphatic acyl group, aliphatic acyloxy group, alkoxy group, alkoxycarbonyl group, alkoxycarbonylamino group, alkylthio group, alkylsulfonyl group, aliphatic amide group, aliphatic sulfonamido group, aliphatic substituted amino group , An aliphatic substituted carbamoyl group, an aliphatic substituted sulfamoyl group, an aliphatic substituted ureido group and a non-aromatic heterocyclic group.

The substituents of the substituent group A will be described.
It is preferable that the alkyl group has 1 to 8 carbon atoms. A chain alkyl group is preferable to a cyclic alkyl group, and a linear alkyl group is particularly preferable. The alkyl group may further have a substituent (eg, hydroxy group, carboxy group, alkoxy group, alkyl-substituted amino group). Examples of alkyl groups (including substituted alkyl groups) include methyl, ethyl, n-butyl, n-hexyl, 2-hydroxyethyl, 4-carboxybutyl, 2-methoxyethyl and 2-methoxyethyl. A diethylaminoethyl group is included.
The alkenyl group preferably has 2 to 8 carbon atoms. A chain alkenyl group is preferable to a cyclic alkenyl group, and a linear alkenyl group is particularly preferable. The alkenyl group may further have a substituent. Examples of the alkenyl group include a vinyl group, an allyl group, and a 1-hexenyl group.
The alkynyl group preferably has 2 to 8 carbon atoms. A chain alkynyl group is preferable to a cyclic alkynyl group, and a linear alkynyl group is particularly preferable. The alkynyl group may further have a substituent. Examples of the alkynyl group include ethynyl group, 1-butynyl group and 1-hexynyl group.

The number of carbon atoms in the aliphatic acyl group is preferably 1-10. Examples of the aliphatic acyl group include an acetyl group, a propanoyl group, and a butanoyl group.
The number of carbon atoms in the aliphatic acyloxy group is preferably 1-10. Examples of the aliphatic acyloxy group include an acetoxy group.
The number of carbon atoms of the alkoxy group is preferably 1-8. The alkoxy group may further have a substituent (eg, an alkoxy group). Examples of the alkoxy group (including a substituted alkoxy group) include a methoxy group, an ethoxy group, a butoxy group, and a methoxyethoxy group.
The number of carbon atoms of the alkoxycarbonyl group is preferably 2-10. Examples of the alkoxycarbonyl group include a methoxycarbonyl group and an ethoxycarbonyl group.
The number of carbon atoms of the alkoxycarbonylamino group is preferably 2-10. Examples of the alkoxycarbonylamino group include a methoxycarbonylamino group and an ethoxycarbonylamino group.

The alkylthio group preferably has 1 to 12 carbon atoms. Examples of the alkylthio group include a methylthio group, an ethylthio group, and an octylthio group.
The alkylsulfonyl group preferably has 1 to 8 carbon atoms. Examples of the alkylsulfonyl group include a methanesulfonyl group and an ethanesulfonyl group.
The number of carbon atoms in the aliphatic amide group is preferably 1-10. Examples of the aliphatic amide group include an acetamide group.
The number of carbon atoms of the aliphatic sulfonamide group is preferably 1-8. Examples of the aliphatic sulfonamide group include a methane sulfonamide group, a butane sulfonamide group, and an n-octane sulfonamide group.
The number of carbon atoms of the aliphatic substituted amino group is preferably 1-10. Examples of the aliphatic substituted amino group include a dimethylamino group, a diethylamino group, and a 2-carboxyethylamino group.

The number of carbon atoms in the aliphatic substituted carbamoyl group is preferably 2-10. Examples of the aliphatic substituted carbamoyl group include a methylcarbamoyl group and a diethylcarbamoyl group.
The number of carbon atoms in the aliphatic substituted sulfamoyl group is preferably 1-8. Examples of the aliphatic substituted sulfamoyl group include a methylsulfamoyl group and a diethylsulfamoyl group.
The number of carbon atoms in the aliphatic substituted ureido group is preferably 2-10. Examples of the aliphatic substituted ureido group include a methylureido group.
Examples of the non-aromatic heterocyclic group include a piperidino group and a morpholino group.

  The molecular weight of the discotic compound retardation enhancer is preferably 300 to 800.

As the discotic compound, a compound represented by the following general formula (1) is preferable.
General formula (1):

In the general formula (1), each R ¹² independently represents an aromatic ring or a hetero ring having a substituent in at least one of the ortho, meta, and para positions. X ¹¹ each independently represents a single bond or —NR ¹³ —. Here, each R ¹³ independently represents a hydrogen atom, a substituted or unsubstituted alkyl group, alkenyl group, aryl group or heterocyclic group.
X ¹¹ is preferably —NR ¹³ —, and R ¹³ is preferably a hydrogen atom or an alkyl group, more preferably a hydrogen atom.

The aromatic ring represented by R ¹² is preferably phenyl or naphthyl, and particularly preferably phenyl. The aromatic ring represented by R ¹² has a substituent in at least one of the ortho, meta and para positions. Examples of the substituent include those of the substituent group A.
The substituent is preferably an alkyl group or an alkoxy group, the alkyl group is particularly preferably a methoxy group, and the alkoxy group is particularly preferably a methoxy group.
The position of the substituent is preferably the meta position or the para position, the alkyl group is particularly preferably the meta position, and the alkoxy group is particularly preferably the para position.

The heterocyclic group represented by R ¹² is preferably an aromatic heterocyclic group. The aromatic heterocycle is generally an unsaturated heterocycle, preferably a heterocycle having the largest number of double bonds. The hetero ring is preferably a 5-membered ring, 6-membered ring or 7-membered ring, more preferably a 5-membered ring or 6-membered ring, and most preferably a 6-membered ring. The hetero atom of the hetero ring is preferably a nitrogen atom, a sulfur atom or an oxygen atom, and particularly preferably a nitrogen atom. As the hetero ring, a pyridine ring (2-pyridyl or 4-pyridyl as a heterocyclic group) is particularly preferable. The aromatic hetero group may have a substituent. Examples of the substituent include those of the substituent group A.
When X ¹¹ is a single bond, the heterocyclic group is preferably a heterocyclic group having a free valence on the nitrogen atom. The heterocyclic group having a free valence on the nitrogen atom is preferably a 5-membered ring, 6-membered ring or 7-membered ring, more preferably a 5-membered ring or 6-membered ring, and a 5-membered ring. Is most preferred. The heterocyclic group may have a plurality of nitrogen atoms. Moreover, the heterocyclic group may have a hetero atom (eg, O, S) other than a nitrogen atom. Examples of the heterocyclic group having a free valence on the nitrogen atom are shown below.

In general formula (1), X ¹¹ represents a single bond or —NR ¹³ —. R ¹³ independently represents a hydrogen atom, a substituted or unsubstituted alkyl group, alkenyl group, aryl group or heterocyclic group.
The alkyl group represented by R ¹³ may be a cyclic alkyl group or a chain alkyl group, but a chain alkyl group is preferable, and a linear alkyl group is more preferable than a branched chain alkyl group. preferable. The number of carbon atoms in the alkyl group is preferably 1-30, more preferably 1-20, still more preferably 1-10, still more preferably 1-8, and 1-6. Most preferred. The alkyl group may have a substituent. Examples of the substituent include a halogen atom, an alkoxy group (for example, methoxy group, ethoxy group) and an acyloxy group (for example, acryloyloxy group, methacryloyloxy group).

The alkenyl group represented by R ¹³ may be a cyclic alkenyl group or a chain alkenyl group, but is preferably a chain alkenyl group and is more preferably a linear alkenyl group than a branched chain alkenyl group. More preferably it represents a group. The number of carbon atoms in the alkenyl group is preferably 2 to 30, more preferably 2 to 20, still more preferably 2 to 10, still more preferably 2 to 8, 6 is most preferred. The alkenyl group may have a substituent. Examples of the substituent include the same substituents as those of the alkyl group described above.
The aromatic ring group and heterocyclic group represented by R ¹³ are the same as the aromatic ring and heterocyclic ring represented by R ¹² , and the preferred range is also the same. The aromatic ring group and the heterocyclic group may further have a substituent, and examples of the substituent include the same substituents as those of the alkyl group described above.

  Specific examples of the discotic compound represented by the general formula (1) include compounds described in paragraphs [0087] to [0113] of JP-A-2007-249180.

Next, a rod-like compound retardation enhancer will be described.
The rod-shaped compound has a linear molecular structure. A linear molecular structure means that the molecular structure is linear in the most thermodynamically stable structure. The most thermodynamically stable structure can be obtained by crystal structure analysis or molecular orbital calculation. For example, molecular orbital calculation can be performed using molecular orbital calculation software (eg, WinMOPAC2000, manufactured by Fujitsu Limited) to obtain a molecular structure that minimizes the heat of formation of a compound. The molecular structure being linear means that in the thermodynamically most stable structure obtained by calculation as described above, the angle of the main chain in the molecular structure is 140 degrees or more and 180 degrees or less. To do.

  As the rod-shaped compound, those having at least two aromatic rings are preferable, and as the rod-shaped compound having at least two aromatic rings, a compound represented by the following general formula (2) is preferable.

Formula (2): Ar ¹ -L ¹ -Ar ²

In the general formula (2), Ar ¹ and Ar ² are each independently an aromatic group.
Here, the aromatic group includes an aryl group (aromatic hydrocarbon group), a substituted aryl group, an aromatic heterocyclic group, and a substituted aromatic heterocyclic group.

An aryl group and a substituted aryl group are more preferable than an aromatic heterocyclic group and a substituted aromatic heterocyclic group. The heterocycle of the aromatic heterocyclic group is generally unsaturated. The aromatic heterocycle is preferably a 5-membered ring, 6-membered ring or 7-membered ring, more preferably a 5-membered ring or 6-membered ring. Aromatic heterocycles generally have the most double bonds. As a hetero atom, a nitrogen atom, an oxygen atom or a sulfur atom is preferable, and a nitrogen atom or a sulfur atom is more preferable.
As the aromatic ring of the aromatic group, a benzene ring, a furan ring, a thiophene ring, a pyrrole ring, an oxazole ring, a thiazole ring, an imidazole ring, a triazole ring, a pyridine ring, a pyrimidine ring and a pyrazine ring are preferable, and a benzene ring is particularly preferable. .

  Examples of the substituent of the substituted aryl group and the substituted aromatic heterocyclic group include a halogen atom (F, Cl, Br, I), a hydroxyl group, a carboxyl group, a cyano group, an amino group, an alkylamino group (eg, methyl). Amino group, ethylamino group, butylamino group, dimethylamino group), nitro group, sulfo group, carbamoyl group, alkylcarbamoyl group (eg, N-methylcarbamoyl group, N-ethylcarbamoyl group, N, N-dimethylcarbamoyl group) ), Sulfamoyl group, alkylsulfamoyl group (eg, N-methylsulfamoyl group, N-ethylsulfamoyl group, N, N-dimethylsulfamoyl group), ureido group, alkylureido group (eg, N -Methylureido group, N, N-dimethylureido group, N, N, N'-trimethylureido group), alkyl group (eg, Til, ethyl, propyl, butyl, pentyl, heptyl, octyl, isopropyl, s-butyl, t-amyl, cyclohexyl, cyclopentyl), alkenyl (eg, vinyl, allyl) Group, hexenyl group), alkynyl group (eg, ethynyl group, butynyl group), acyl group (eg, formyl group, acetyl group, butyryl group, hexanoyl group, lauryl group), acyloxy group (eg, acetoxy group, butyryloxy group, Hexanoyloxy group, lauryloxy group), alkoxy group (eg, methoxy group, ethoxy group, propoxy group, butoxy group, pentyloxy group, heptyloxy group, octyloxy group), aryloxy group (eg, phenoxy group), Alkoxycarbonyl group (eg, methoxycarbonyl group, ethoxycarbonyl group, Ropoxycarbonyl group, butoxycarbonyl group, pentyloxycarbonyl group, heptyloxycarbonyl group), aryloxycarbonyl group (eg, phenoxycarbonyl group), alkoxycarbonylamino group (eg, butoxycarbonylamino group, hexyloxycarbonylamino group) , Alkylthio groups (eg, methylthio group, ethylthio group, propylthio group, butylthio group, pentylthio group, heptylthio group, octylthio group), arylthio groups (eg, phenylthio group), alkylsulfonyl groups (eg, methylsulfonyl group, ethylsulfonyl group) Propylsulfonyl group, butylsulfonyl group, pentylsulfonyl group, heptylsulfonyl group, octylsulfonyl group), amide group (eg, acetamido group, butylamide group, hexylamide group, Urilamide group) and non-aromatic heterocyclic groups (eg, morpholyl group, pyrazinyl group).

Examples of the substituent of the substituted aryl group and the substituted aromatic heterocyclic group include a halogen atom, a cyano group, a carboxyl group, a hydroxyl group, an amino group, an alkyl-substituted amino group, an acyl group, an acyloxy group, an amide group, an alkoxycarbonyl group, Alkoxy groups, alkylthio groups and alkyl groups are preferred.
The alkyl moiety of the alkylamino group, alkoxycarbonyl group, alkoxy group, and alkylthio group and the alkyl group may further have a substituent. Examples of alkyl moieties and substituents of alkyl groups include halogen atoms, hydroxyl, carboxyl, cyano, amino, alkylamino groups, nitro, sulfo, carbamoyl, alkylcarbamoyl groups, sulfamoyl, alkylsulfamoyl groups, ureido, alkylureido Group, alkenyl group, alkynyl group, acyl group, acyloxy group, acylamino group, alkoxy group, aryloxy group, alkoxycarbonyl group, aryloxycarbonyl group, alkoxycarbonylamino group, alkylthio group, arylthio group, alkylsulfonyl group, amide group And non-aromatic heterocyclic groups. As the substituent for the alkyl moiety and the alkyl group, a halogen atom, hydroxyl, amino, alkylamino group, acyl group, acyloxy group, acylamino group, alkoxycarbonyl group and alkoxy group are preferable.

In the general formula (2), L ¹ is a divalent linking group selected from an alkylene group, an alkenylene group, an alkynylene group, —O—, —CO—, and a combination thereof.
The alkylene group may have a cyclic structure. As the cyclic alkylene group, cyclohexylene is preferable, and 1,4-cyclohexylene is particularly preferable. As the chain alkylene group, a linear alkylene group is more preferable than a branched alkylene group.
The number of carbon atoms of the alkylene group is preferably 1-20, more preferably 1-15, still more preferably 1-10, still more preferably 1-8, and most preferably 1-6. It is.
The alkenylene group and the alkynylene group preferably have a chain structure rather than a cyclic structure, and more preferably have a linear structure rather than a branched chain structure.
The alkenylene group and the alkynylene group preferably have 2 to 10 carbon atoms, more preferably 2 to 8, more preferably 2 to 6, still more preferably 2 to 4, and most preferably 2. (Vinylene or ethynylene).
The arylene group preferably has 6 to 20 carbon atoms, more preferably 6 to 16, and still more preferably 6 to 12.

In the molecular structure of the general formula (3), the angle formed by Ar ¹ and Ar ² across L ¹ is preferably 140 degrees or more and 180 degrees or less.
As the rod-like compound, a compound represented by the following general formula (3) is more preferable.

Formula ^{(3): Ar 1 -L 2} -X-L 3 -Ar 2

In the general formula (3), Ar ¹ and Ar ² are each independently an aromatic group. The definition and examples of the aromatic group are the same as those of Ar ¹ and Ar ^{2 in} the general formula (1).

In the general formula (3), L ² and L ³ are each independently a divalent linking group selected from an alkylene group, —O—, —CO—, and a group consisting of a combination thereof.
The alkylene group preferably has a chain structure rather than a cyclic structure, and more preferably has a linear structure rather than a branched chain structure.
The number of carbon atoms of the alkylene group is preferably 1 to 10, more preferably 1 to 8, still more preferably 1 to 6, still more preferably 1 to 4, and 1 or 2 (methylene or Most preferred is ethylene).
L ² and L ³ are particularly preferably —O—CO— or —CO—O—.
In the general formula (2), X is 1,4-cyclohexylene, vinylene or ethynylene.

  Specific examples of the compound represented by the general formula (2) or (3) include compounds described in paragraphs [0089] to [0102] of JP-A-2007-254699.

Two or more rod-shaped compounds having a maximum absorption wavelength (λmax) shorter than 250 nm in the ultraviolet absorption spectrum of the solution may be used in combination.
The rod-like compound can be synthesized by a method described in the literature. As literature, Mol. Cryst. Liq. Cryst. 53, 229 pages (1979), 89, 93 pages (1982), 145, 111 pages (1987), 170 pages, 43 pages (1989), J. Am. Am. Chem. Soc. 113, p. 1349 (1991), p. 118, p. 5346 (1996), p. 92, p. 1582 (1970). Org. Chem. , 40, 420 (1975), Tetrahedron, 48, 16, 3437 (1992).

Next, a retardation developer for a compound exhibiting liquid crystallinity will be described.
The compound exhibiting liquid crystallinity 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 nematic phase or a smectic phase.

As the compound exhibiting liquid crystallinity, a compound represented by the following general formula (4) is preferable.
General formula (4):

In General Formula (4), L ₁ and L ₂ each represent a single bond or a divalent linking group. A ₁ and A ₂ are groups independently selected from —O—, —NR— (R is a hydrogen atom or a substituent), —S—, and —CO—. R ₁ , R ₂ , R ₃ , R ₄ and R ₅ represent substituents. n represents an integer of 0 to 2.

L ₁ and L ₂ are preferably the following examples.

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

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, bicyclo [2,2,2] octane-3-yl), alke 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. Bicyclo [2,2,1] hept-2-en-1-yl group, bicyclo [2,2,2] oct-2-en-4-yl group), alkynyl group ( It is preferred, and 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 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 group, ethoxy group, isopropoxy group, tert-butoxy group, n-octyloxy group, 2-methoxyethoxy group), aryloxy group (preferred) Is a substituted or unsubstituted aryloxy group having 6 to 30 carbon atoms, for example, phenoxy group, 2-methylphenoxy group, 4-tert-butylphenoxy group, 3-nitrophenoxy group, 2-tetradecanoylaminophenoxy group ), A silyloxy group (preferably a silyloxy group having 3 to 20 carbon atoms, such as trimethylsilyloxy group, tert-butyldimethylsilyloxy group), a heterocyclic oxy group (preferably substituted or unsubstituted having 2 to 30 carbon atoms) A heterocyclic oxy group, a 1-phenyltetrazole-5-oxy group, a 2-tetrahydropyranyloxy group), an acyloxy group (preferably a formyloxy group, a substituted or unsubstituted alkylcarbonyloxy group having 2 to 30 carbon atoms, A substituted or unsubstituted arylcarbonyloxy group having 6 to 30 carbon atoms, such as Rumyloxy group, acetyloxy group, pivaloyloxy group, stearoyloxy group, benzoyloxy group, p-methoxyphenylcarbonyloxy group), carbamoyloxy group (preferably a substituted or unsubstituted carbamoyloxy group having 1 to 30 carbon atoms, such as N, N-dimethylcarbamoyloxy group, N, N-diethylcarbamoyloxy group, morpholinocarbonyloxy group, N, N-di-n-octylaminocarbonyloxy group, Nn-octylcarbamoyloxy group), alkoxycarbonyl An oxy group (preferably a substituted or unsubstituted alkoxycarbonyloxy group having 2 to 30 carbon atoms, such as a methoxycarbonyloxy group, an ethoxycarbonyloxy group, a tert-butoxycarbonyloxy group, or an n-octylcarbonyloxy group), Aryloxycarbonyloxy group (preferably a substituted or unsubstituted aryloxycarbonyloxy group having 7 to 30 carbon atoms, such as phenoxycarbonyloxy group, p-methoxyphenoxycarbonyloxy group, pn-hexadecyloxyphenoxycarbonyl Oxy 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 2 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 having 1 to 30 carbon atoms) Carbonylamino group, for example, carbamoylamino group, N, N-dimethylaminocarbonyl Mino 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, ethoxycarbonylamino Group, tert-butoxycarbonylamino group, n-octadecyloxycarbonylamino group, N-methyl-methoxycarbonylamino group), aryloxycarbonylamino group (preferably substituted or unsubstituted aryloxycarbonyl having 7 to 30 carbon atoms) An amino group such as a phenoxycarbonylamino group, a p-chlorophenoxycarbonylamino group, an mn-octyloxyphenoxycarbonylamino group, a sulfamoylamino group (preferably a group having 0 to 30 carbon atoms). Or an unsubstituted sulfamoylamino group, such as a sulfamoylamino group, an N, N-dimethylaminosulfonylamino group, an Nn-octylaminosulfonylamino group, an alkyl and an arylsulfonylamino group (preferably having a carbon number) 1-30 substituted or unsubstituted alkylsulfonylamino, C6-C30 substituted or unsubstituted arylsulfonylamino group, for example, methylsulfonylamino group, butylsulfonylamino group, phenylsulfonylamino group, 2,3, 5-trichlorophenylsulfonylamino group, p-methylphenylsulfonylamino group),

A mercapto group, an alkylthio group (preferably a substituted or unsubstituted alkylthio group having 1 to 30 carbon atoms, such as a methylthio group, an ethylthio group or an n-hexadecylthio group), an arylthio group (preferably a substituted or unsubstituted group having 6 to 30 carbon atoms). A substituted arylthio group 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, such as 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-acetate Rusulfamoyl group, N-benzoylsulfamoyl group, N- (N′phenylcarbamoyl) sulfamoyl group), sulfo group, alkyl and arylsulfinyl group (preferably a substituted or unsubstituted alkylsulfinyl group having 1 to 30 carbon atoms, 6-30 substituted or unsubstituted arylsulfinyl groups such as methylsulfinyl group, ethylsulfinyl group, phenylsulfinyl group, p-methylphenylsulfinyl group), alkyl and arylsulfonyl groups (preferably having 1 to 30 carbon atoms) A substituted or unsubstituted alkylsulfonyl group, 6-30 substituted or unsubstituted arylsulfonyl groups such as methylsulfonyl group, ethylsulfonyl group, phenylsulfonyl group, p-methylphenylsulfonyl group), acyl group (preferably formyl) Base, charcoal 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 and a pivaloylbenzoyl group, and an aryloxycarbonyl group (preferably carbon A substituted or unsubstituted aryloxycarbonyl group of 7 to 30, for example, phenoxycarbonyl group, o-chlorophenoxycarbonyl group, m-nitrophenoxycarbonyl group, p-tert-butylphenoxycarbonyl group), alkoxycarbonyl group (preferably Is a substituted or unsubstituted alkoxycarbonyl group having 2 to 30 carbon atoms, such as a methoxycarbonyl group, an ethoxycarbonyl group, a tert-butoxycarbonyl group, or an n-octadecyloxycarbonyl group),

Carbamoyl group (preferably a substituted or unsubstituted carbamoyl group having 1 to 30 carbon atoms, such as carbamoyl group, N-methylcarbamoyl group, N, N-dimethylcarbamoyl group, N, N-di-n-octylcarbamoyl group N- (methylsulfonyl) carbamoyl group), aryl and heterocyclic azo group (preferably a substituted or unsubstituted arylazo group having 6 to 30 carbon atoms, substituted or unsubstituted heterocyclic azo group having 3 to 30 carbon atoms, For example, 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 Is a substituted or unsubstituted phosphino group having 2 to 30 carbon atoms, such as dimethylphosphino group, diphenylphospho A fino group, a methylphenoxyphosphino group), a phosphinyl group (preferably a substituted or unsubstituted phosphinyl group having 2 to 30 carbon atoms, such as a phosphinyl group, a dioctyloxyphosphinyl group, a diethoxyphosphinyl group), Phosphinyloxy group (preferably a substituted or unsubstituted phosphinyloxy group having 2 to 30 carbon atoms, such as diphenoxyphosphinyloxy group, dioctyloxyphosphinyloxy group), phosphinylamino group (Preferably a substituted or unsubstituted phosphinylamino group having 2 to 30 carbon atoms, such as a dimethoxyphosphinylamino group or a dimethylaminophosphinylamino group), a silyl group (preferably having 3 to 30 carbon atoms) Substituted or unsubstituted silyl groups such as trimethylsilyl group, tert-butyldimethylsilyl group, It represents the E sulfonyl dimethylsilyl 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. More preferred are a benzene ring having a substituent and a cyclohexane ring having a substituent, and further preferred are a benzene ring having a substituent at the 4-position and a cyclohexane ring having a substituent at the 4-position.

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 substituents, sigma _p value has an electron-withdrawing substituents from 0 to 1.5 More preferably. 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 be bonded to form a ring.
As for Hammett's substituent constants σ _p and σ _m , 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 Explanation" 217 (Tokyo Kagaku Doujin), Chemical Review, 91, 165-195 (1991) .

A ₁ and A ₂ are groups independently selected from —O—, —NR— (R is a hydrogen atom or a substituent), —S—, and —CO—. Preferably, it is a group independently selected from -O-, -NR- (R is a substituent), and -S-.

  n is preferably 0 or 1, and most preferably 0.

  Specific examples of the compound exhibiting liquid crystal properties represented by the general formula (4) include compounds described in paragraphs [0044] to [0051] of JP-A-2009-198822.

(Film thickness)
The thickness of the optical film of the present invention is preferably 10 to 120 μm, more preferably 25 to 90 μm, and particularly preferably 30 to 80 μm. If it is within this range, the warpage of the panel accompanying the change in temperature and humidity can be reduced.

(Haze of film)
The optical film of the present invention preferably has a total haze value of 2.00 or less. When the total haze value is 2.00 or less, the transparency of the film is high, and the contrast ratio and the luminance of the liquid crystal display device are improved. The total haze value is more preferably 1.00 or less, further preferably 0.50 or less, particularly preferably 0.30 or less, and most preferably 0.20 or less. The lower the total haze value, the better the optical performance, but it is preferably 0.01 or more in consideration of raw material selection, production control, and roll film handling.
The internal haze value of the optical film of the present invention is preferably 1.00 or less. By setting the internal haze value to 1.00 or less, the contrast ratio of the liquid crystal display device can be improved and excellent display characteristics can be realized. The internal haze value is more preferably 0.50 or less, further preferably 0.20 or less, particularly preferably 0.10 or less, and most preferably 0.05 or less. It is preferable that it is 0.01 or more from viewpoints, such as raw material selection and manufacture control.
In particular, the optical film of the present invention preferably has a total haze value of 0.30 or less and an internal haze value of 0.10 or less.
The total haze value and internal haze value are the types and addition amounts of cellulose ester and acrylic resin of the film material, selection of additives (particularly, the particle size, refractive index, addition amount of matting agent particles), and film production conditions. It can be adjusted by (temperature during stretching, stretching ratio, etc.).
In addition, the measurement of a haze can measure the film sample 40mm x 80mm of this invention by 25 degreeC and 60% RH with a haze meter (HGM-2DP, Suga test machine) according to JISK-6714.

(Elastic modulus of film)
The elastic modulus of the optical film of the present invention is preferably 1800 to 7000 MPa in the width direction (TD direction).
In the present invention, when the elastic modulus in the TD direction is within the above range, display unevenness at the time of black display after high humidity and high temperature and high humidity environment aging, transportability at the time of film production, end slit property and difficulty in breaking. It is preferable from the viewpoint of manufacturing suitability. If the TD elastic modulus is too small, display unevenness at the time of black display after high humidity and high temperature / humidity environment is apt to occur, and there is a problem in manufacturing suitability. If it is too large, the film processability is inferior. The elastic modulus is more preferably 1800 to 5000 MPa, and further preferably 1800 to 4000 MPa.
Moreover, 1800-4000 MPa is preferable and, as for the elasticity modulus of the conveyance direction (MD direction) of the optical film of this invention, it is more preferable that it is 1800-3000 MPa.
Here, the conveyance direction (longitudinal direction) of the film is the conveyance direction (MD direction) during film production, and the width direction is the direction (TD direction) perpendicular to the conveyance direction during film production.
The elastic modulus of the film depends on the type and amount of cellulose ester and acrylic resin used in the film material, selection of additives (particularly, the particle size, refractive index, and amount of addition of matting agent particles), and film production conditions (stretch ratio). Etc.).
The elastic modulus is obtained, for example, by measuring a stress at 0.5% elongation at a tensile rate of 10% / min in an atmosphere of 23 ° C. and 70 RH% using a universal tensile tester “STM T50BP” manufactured by Toyo Baldwin Co., Ltd. be able to.

(Glass transition temperature Tg)
The glass transition temperature Tg of the optical film of the present invention is preferably 100 ° C. or higher and 200 ° C. or lower, more preferably 100 ° C. or higher and 150 ° C. or lower, from the viewpoints of production suitability and heat resistance.
The glass transition temperature is a temperature at which the base line derived from the glass transition of the film starts to change and a temperature at which it returns to the base line again when measured at a heating rate of 10 ° C./min using a differential scanning calorimeter (DSC). It can be calculated as an average value.
Moreover, the measurement of a glass transition temperature can also be calculated | required using the following dynamic viscoelasticity measuring apparatuses. A dynamic viscoelasticity measuring apparatus (Vibron: DVA-225 (produced by IT Measurement Control Co., Ltd.)) after conditioning the film sample (unstretched) 5 mm × 30 mm of the present invention at 25 ° C. and 60% RH for 2 hours or more. The distance between the grips is 20 mm, the heating rate is 2 ° C./minute, the measurement temperature range is 30 ° C. to 250 ° C., the frequency is 1 Hz, the logarithmic axis is the storage elastic modulus, and the horizontal axis is the temperature (° C.). When the storage modulus is taken from the solid region to the glass transition region, the sharp decrease in the storage modulus is drawn in the solid region by straight line 1 and in the glass transition region by straight line 2 Since the storage elastic modulus suddenly decreases when the temperature rises, the temperature at which the film begins to soften and the temperature at which the film begins to transition to the glass transition region is obtained at the intersection of 1 and the straight line 2, so the glass transition temperature Tg (dynamic viscoelasticity) And

(Equilibrium moisture content of film)
The water content (equilibrium water content) of the optical film of the present invention is 25, regardless of the film thickness, so as not to impair the adhesion with a water-soluble polymer such as polyvinyl alcohol when used as a protective film for a polarizing plate. It is preferable that the moisture content in 80 degreeCRH is 0-4 mass%. More preferably, it is 0.1-2.5 mass%, and it is still more preferable that it is 0.5-1.5 mass%. If the equilibrium moisture content is 4% by mass or less, the dependence of retardation on humidity changes does not become too large, and the display unevenness of the liquid crystal display device during black display after normal temperature, high humidity, and high temperature and high humidity environments is suppressed. This is also preferable.
The moisture content was measured by measuring a film sample 7 mm × 35 mm by a Karl Fischer method using a moisture measuring device and sample drying apparatuses “CA-03” and “VA-05” (both manufactured by Mitsubishi Chemical Corporation). It can be calculated by dividing the amount of water (g) by the sample mass (g).

(Water permeability of film)
The moisture permeability of the film is measured under conditions of 60 ° C. and 95% RH based on JIS Z-0208.
The moisture permeability decreases as the film thickness increases, and increases as the film thickness decreases. Therefore, it is necessary to convert the samples having different film thicknesses by setting the reference to 80 μm. The film thickness can be converted according to the following mathematical formula.
Formula: Moisture permeability in terms of 80 μm = measured moisture permeability × measured film thickness (μm) / 80 (μm).
The measurement method of water vapor transmission rate is “Polymer Physical Properties II” (Polymer Experiment Course 4, Kyoritsu Shuppan), pages 285-294 “Measurement of vapor permeation amount (mass method, thermometer method, vapor pressure method, adsorption amount method) Can be applied.
The moisture permeability of the optical film of the present invention is preferably 100 to 2000 g / m ² · 24 h. It is more preferable that it is 150-1500 g / m < ² > * 24h, and it is still more preferable that it is 150-1200 g / m < ² > * 24h. If the water vapor transmission rate is 4000 g / m ² · 24 h or less, the humidity dependence of the Re value and Rth value of the film is small, and the display unevenness during black display after the normal temperature, high humidity and high temperature and high humidity environment of the liquid crystal display device Is also preferable from the standpoint of deterrence.

(Dimensional change of film)
The dimensional stability of the optical film of the present invention is the dimensional change rate when left standing for 24 hours under conditions of 60 ° C. and 90% RH (high humidity), and 80 ° C., DRY environment (5% RH or less). It is preferable that the dimensional change rate when standing for 24 hours under these conditions (high temperature) is 0.5% or less.
More preferably, it is 0.3% or less, More preferably, it is 0.15% or less.

(Photoelastic coefficient)
When the optical film of the present invention is used as a protective film for a polarizing plate, birefringence (Re, Rth) may change due to stress caused by the contraction of the polarizer. The change in birefringence due to such stress can be measured as a photoelastic coefficient, but the range is preferably 15 Br or less, more preferably −3 to 12 Br, and further preferably 0 to 11 Br. preferable.

[Method for producing optical film]
The method for producing an optical film of the present invention includes a step of forming a polymer film having a mass ratio of cellulose ester to acrylic resin of 70:30 to 5:95, and a width direction orthogonal to the transport direction of the polymer film. And a step of stretching the polymer film. Here, the mass average molecular weight of the cellulose ester is 75000 or more, the mass average molecular weight of the acrylic resin is 80000 or more, and the optical film to be produced is Re defined by the above formulas (I) and (II) Rth satisfies the above formulas (III) and (IV) at a wavelength of 590 nm.
In the polymer film, the mass ratio of cellulose ester to acrylic resin is 70:30 to 5:95, and the cellulose ester and acrylic resin are preferably in a compatible state. The polymer film used for stretching may be a dry film or a wet film, but is more preferably a wet film.
As the polymer film used for stretching, the glass transition temperature Tg of the unstretched polymer film after drying is preferably 100 to 200 ° C, more preferably 100 to 150 ° C.
Here, the polymer film after drying (dry film) means that the amount of residual solvent in the film is 3.0% by mass or less, preferably 1.0% by mass or less, more preferably 0.5% by mass or less, The polymer film is preferably 0.3% by mass or less, particularly preferably 0.2% by mass or less. The glass transition temperature can be adjusted by the kind and mass ratio of the cellulose ester and the acrylic resin.

  As a method for forming the polymer film, an inflation method, a T-die method, a calendar method, a cutting method, a casting method, an emulsion method, a hot press method, and the like can be used. From the viewpoints of suppression and suppression of optical defects such as die lines, solution casting by casting is preferred.

The method for producing the optical film of the present invention may use a solution casting method or a melt casting method.
In the case of the solution casting method, the polymer film is formed by casting a polymer solution (dope) containing a cellulose ester, an acrylic resin, and a solvent on a support.
In the dope, the mass ratio between the cellulose ester and the acrylic resin is 70:30 to 5:95, preferably 70:30 to 15:85, and more preferably 70:30 to 30:70. More preferably, it is 49:51 to 30:70.

(solvent)
A solvent useful for forming the dope can be used without limitation as long as it dissolves the cellulose ester, the acrylic resin, and other additives simultaneously.
In the present invention, any of a chlorinated solvent containing a chlorinated organic solvent as a main solvent and a non-chlorinated solvent not containing a chlorinated organic solvent can be used as the organic solvent. Two or more organic solvents may be mixed and used.

  In producing the dope, a chlorinated organic solvent is preferably used as the main solvent. In the present invention, the kind of the chlorinated organic solvent is not particularly limited as long as the object can be achieved within a range where the cellulose acylate can be dissolved, cast and formed. These chlorinated organic solvents are preferably dichloromethane and chloroform. Particularly preferred is dichloromethane. In addition, there is no particular problem in mixing an organic solvent other than the chlorinated organic solvent. In that case, it is necessary to use at least 50% by mass of dichloromethane in the total amount of the organic solvent. Other organic solvents used in combination with the chlorinated organic solvent in the present invention will be described below. That is, as another preferable organic solvent, a solvent selected from esters, ketones, ethers, alcohols, hydrocarbons and the like having 3 to 12 carbon atoms is preferable. The ester, ketone, ether and alcohol may have a cyclic structure. A compound having two or more functional groups of esters, ketones and ethers (that is, —O—, —CO— and —COO—) can also be used as a solvent. For example, other functional groups such as alcoholic hydroxyl groups can be used. You may have group simultaneously. In the case of a solvent having two or more types of functional groups, the number of carbon atoms may be within the specified range of the compound having any functional group.

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

The alcohol used in combination with the chlorinated organic solvent may be linear, branched or cyclic, and among them, saturated aliphatic hydrocarbon is preferable. The hydroxyl group of the alcohol may be any of primary to tertiary. Examples of the alcohol include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, t-butanol, 1-pentanol, 2-methyl-2-butanol and cyclohexanol. As the alcohol, fluorine-based alcohol is also used. Examples thereof include 2-fluoroethanol, 2,2,2-trifluoroethanol, 2,2,3,3-tetrafluoro-1-propanol and the like. Further, the hydrocarbon may be linear, branched or cyclic. Either aromatic hydrocarbons or aliphatic hydrocarbons can be used. The aliphatic hydrocarbon may be saturated or unsaturated. Examples of hydrocarbons include cyclohexane, hexane, benzene, toluene and xylene.
As other solvents, for example, the solvents described in JP-A-2007-140497 can be used.

(Preparation of dope)
The dope can be prepared by a general method including processing at a temperature of 0 ° C. or higher (ordinary temperature or high temperature). The dope of the present invention can be prepared by using a dope preparation method and apparatus in a normal solvent cast method. In the case of a general method, halogenated hydrocarbon (especially dichloromethane) and alcohol (especially methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, t-butanol, 1) -Pentanol, 2-methyl-2-butanol and cyclohexanol) are preferably used.
The total amount of cellulose ester and acrylic resin is adjusted so as to be contained in the obtained polymer solution in an amount of 10 to 40% by mass. The amount of cellulose acylate is more preferably 10 to 30% by mass. Arbitrary additives described later may be added to the organic solvent (main solvent).
The solution can be prepared by stirring the cellulose ester and the acrylic resin and the organic solvent at room temperature (0 to 40 ° C.). The high concentration solution may be stirred under pressure and heating conditions. Specifically, cellulose ester and acrylic resin and an organic solvent are placed in a pressure vessel and sealed, and stirred while being heated to a temperature equal to or higher than the boiling point of the solvent at room temperature and not boiling.
The heating temperature is usually 40 ° C or higher, preferably 60 to 200 ° C, more preferably 80 to 110 ° C.

Each component may be roughly mixed in advance and then placed in a container. Moreover, you may put into a container sequentially. The container needs to be configured so that it can be stirred. 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.
It is preferable to provide a stirring blade inside the container and stir using this. 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 the 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.

(Production of film-solution casting method)
Next, a method for producing the optical film of the present invention using the dope obtained above will be described.
FIG. 1 is a schematic view showing a film production line 20. However, the present invention is not limited to the film production line as shown in FIG. The film production line 20 includes a stock tank 21, a filtration device 30, a casting die 31, a casting band 34 stretched around rotating rollers 32 and 33, a tenter dryer 35, and the like. Further, an ear-cutting device 40, a drying chamber 41, a cooling chamber 42, a winding chamber 43, and the like are arranged.

  An agitator 61 that is rotated by a motor 60 is attached to the stock tank 21. The stock tank 21 is connected to the casting die 31 via the pump 62 and the filtration device 30.

  The width of the casting die 31 is not particularly limited, but is preferably 1.1 to 2.0 times the width of the film as the final product.

  A casting band 34 is provided below the casting die 31 so as to span the rotating rollers 32 and 33. The rotating rollers 32 and 33 are rotated by a driving device (not shown), and the casting band 34 travels endlessly with the rotation.

  In order to set the surface temperature of the casting band 34 to a predetermined value, it is preferable that a heat transfer medium circulation device 63 is attached to the rotary rollers 32 and 33. The casting band 34 is preferably one whose surface temperature can be adjusted to -20 ° C to 40 ° C.

The width of the casting band 34 is not particularly limited, but it is preferable to use a band having a range of 1.1 to 2.0 times the casting width of the dope 22. Further, it is preferable that the length is 20 m to 200 m, the thickness is 0.5 mm to 2.5 mm, and the surface roughness is polished to be 0.05 μm or less. The casting band 34 is preferably made of stainless steel, and more preferably made of SUS316 so as to have sufficient corrosion resistance and strength. Moreover, it is preferable to use the thickness unevenness of the entire casting band 34 of 0.5% or less.
It is also possible to use the rotating rollers 32 and 33 directly as a support.

  The casting die 31, the casting band 34 and the like are accommodated in the casting chamber 64. The casting chamber 64 is provided with a temperature control facility 65 for keeping the internal temperature at a predetermined value, and a condenser (condenser) 66 for condensing and recovering the volatile organic solvent. A recovery device 67 for recovering the condensed and liquefied organic solvent is provided outside the casting chamber 64. Further, it is preferable that a decompression chamber 68 for controlling the pressure of the back surface of the casting bead formed from the casting die 31 to the casting band 34 is disposed, and this is also used in this embodiment. .

  Air blowing ports 70, 71, 72 are provided near the peripheral surface of the casting band 34 in order to evaporate the solvent in the casting film 69.

  The crossover portion 80 is provided with a blower 81, and the ear-cutting device 40 downstream of the tenter dryer 35 is used for finely cutting the waste at the side end (referred to as an ear) of the cut film 82. Crusher 90 is connected.

  The drying chamber 41 is provided with a number of rollers 91, and an adsorption / recovery device 92 for adsorbing / recovering the solvent gas generated by evaporation is attached. A forced static elimination device (static elimination bar) 93 for adjusting the charged voltage of the film 82 to a predetermined range (for example, −3 kV to +3 kV) is provided downstream of the cooling chamber 42. Furthermore, in this embodiment, a knurling application roller 94 for applying knurling to both edges of the film 82 by embossing is appropriately provided downstream of the forced static elimination device 93. Further, a winding roller 95 for winding the film 82 and a press roller 96 for controlling the tension at the time of winding are provided in the winding chamber 43.

Next, an example of a method for producing the film 82 using the film production line 20 as described above will be described below.
The dope 22 is always made uniform by the rotation of the stirrer 61. The dope 22 may be mixed with additives such as a retardation developer, a plasticizer, and an ultraviolet absorber even during the stirring.

The dope 22 is sent to the filtration device 30 by the pump 62 and filtered there, and then is cast from the casting die 31 onto the casting band 34.
A casting bead is formed from the casting die 31 to the casting band 34, and a casting film 69 is formed on the casting band 34. The temperature of the dope 22 during casting is preferably −10 ° C. to 57 ° C.
The dope 22 from the casting die 31 forms a casting bead and is cast on the casting band 34.
The casting film 69 moves as the casting band 34 moves.

  Next, the casting film 69 is continuously transported to the place where the air blowing port 73 is disposed at the upper part. Dry air is blown toward the casting film 69 from the nozzle of the air blowing port 73.

The casting film 69 is self-supporting as a result of evaporation of the solvent by drying, and is then peeled off from the casting band 34 while being supported by the peeling roller 75 as a wet film 74. The amount of residual solvent at the time of stripping is preferably 20% by mass to 250% by mass based on the solid content.
Thereafter, the transfer section 80 provided with a large number of rollers is conveyed, and the wet film 74 is fed into the tenter dryer 35. In the transfer part 80, the drying of the wet film 74 is advanced by sending the drying air of desired temperature from the air blower 81. FIG. At this time, the temperature of the drying air is preferably 20 ° C to 250 ° C.

The wet film 74 is preferably stretched in the width direction (TD direction) orthogonal to the transport direction (MD direction). By stretching in the width direction, unevenness generated at the time of drying and stripping on the support can be reduced, and a good surface shape can be obtained in the film plane. The stretching ratio in the width direction is preferably 10% or more, more preferably 20% or more, and further preferably 30% or more.
The wet film 74 sent to the tenter dryer 35 is dried while being conveyed by being gripped by clips at both ends thereof. In this case, stretching in the width direction can be performed using a tenter dryer 35.
It is preferable to divide the inside of the tenter dryer 35 into temperature zones and adjust the drying conditions appropriately for each of the zones.
As described above, the wet film 74 can be stretched in the width direction by the crossover 80 and / or the tenter dryer 35.
The film may be stretched in the transport direction, and the wet film 74 is given a draw tension in the transport direction by making the rotational speed of the downstream roller faster than the upstream roller. Can do.
Here, in the transfer section 80 and / or the tenter dryer 35, the wet film 74 is dried without being stretched, and the residual solvent amount in the film is 3.0% by mass or less, preferably 1.0% by mass or less, More preferably, the stretched film may be stretched after a dry film of 0.5% by mass or less, more preferably 0.3% by mass or less, and particularly preferably 0.2% by mass or less.
In addition, when extending | stretching a dry film, after producing a dry film with unstretched and winding up once, you may extend | stretch further.
The polymer film used for stretching may be a dry film or a wet film, but is more preferably a wet film.

  The draw ratio in the width direction is preferably 1.15 to 2.0 times, more preferably 1.3 to 2.0 times, and particularly preferably 1.3 to 1.6 times. The draw ratio in the conveying direction is preferably 1.0 to 1.4. Note that even if the film is not stretched intentionally by applying draw tension in the transport direction, a tension is applied by the transport, and as a result, a film stretched at a magnification of about 1.01 to 1.1 times may be obtained. .

  The temperature during stretching is preferably in the temperature range of Tg ± 30 ° C. with respect to the glass transition temperature Tg of the unstretched polymer film after drying. Here, the glass transition temperature of the unstretched polymer film after drying is the glass transition temperature in a compatible state of the cellulose ester and the acrylic resin, and as described above, 100 to 200 ° C. is preferable, and 100 to 150 ° C. is more preferable. Stretching in this temperature range has good film handling suitability, and a desired optical film can be produced without breaking the polymer film. By stretching at (Tg−30 ° C.) or more, the film can be prevented from being broken, and variations in Rth within the film can be suppressed. Moreover, by extending | stretching below (Tg + 30 degreeC), extending | stretching can be prevented by the dead weight of a film, and the dispersion | variation in Rth within a film can be suppressed. Moreover, the increase in the total haze and internal haze due to phase separation in the film can be suppressed. The temperature during stretching is preferably a temperature range of Tg ± 25 ° C., and more preferably a temperature range of Tg ± 20 ° C.

As described above, the stretching treatment may be performed in a drying process after the wet film 74 is formed and then passed through the transfer section 80 and the tenter dryer 35, or may be performed after the wet film 74 is wound up after being dried.
The casting conditions of the present invention are preferably carried out under such a condition that when the film is unstretched, the thickness of the film is 10 to 200 μm, more preferably 20 to 150 μm, still more preferably 30 to 120 μm, Most preferably, the conditions are 40 to 100 μm.
If it is within this range, the film thickness after stretching can be reduced, the change in retardation at the time of humidity change, high temperature and high temperature and high humidity environment is reduced, and an inexpensive film with less resin to be used can be produced. Therefore, it is preferable.

  The wet film 74 is dried to a predetermined residual solvent amount by the tenter dryer 35 and then sent to the downstream side as a film 82. Both ends of the film 82 are cut at both edges by the edge-cutting device 40. The cut side end portion is sent to the crusher 90 by a cutter blower (not shown). The crusher 90 pulverizes the film side end portion into a chip. Since this chip is reused for dope preparation, this method is effective in terms of cost. In addition, although it can also abbreviate | omit about the cutting process of this film both ends, it is preferable to carry out in any one from the said casting process to the process of winding up the said film.

  The film 82 from which both side ends have been removed is sent to the drying chamber 41 and further dried. Although the temperature in the drying chamber 41 is not specifically limited, It is preferable that it is the range of 50 to 160 degreeC. In the drying chamber 41, the film 82 is conveyed while being wound around a roller 91, and the solvent gas generated by evaporation here is adsorbed and recovered by an adsorption recovery device 92. The air from which the solvent component has been removed is blown again as dry air inside the drying chamber 41. The drying chamber 41 is more preferably divided into a plurality of sections in order to change the drying temperature.

  The film 82 is cooled to approximately room temperature in the cooling chamber 42. A humidity control chamber (not shown) may be provided between the drying chamber 41 and the cooling chamber 42, and air adjusted to a desired humidity and temperature can be blown onto the film 82 in the humidity control chamber. It is preferable. Thereby, generation | occurrence | production of the curling of the film 82 and the winding defect at the time of winding can be suppressed.

  Further, the forcible charge removal device (charge removal bar) 93 sets the charged voltage while the film 82 is being conveyed to a predetermined range (for example, −3 kV to +3 kV). Furthermore, it is preferable to provide a knurling roller 94 and to impart knurling to both edges of the film 82 by embossing.

  Finally, the film 82 is taken up by the take-up roller 95 in the take-up chamber 43. At this time, it is preferable to wind the sheet while applying a desired tension with the press roller 96. More preferably, the tension is gradually changed from the start to the end of winding. The film 82 to be wound is preferably at least 100 m in the longitudinal direction (casting direction). The width of the film 82 is preferably 600 mm or more, more preferably 1100 mm or more and 2900 mm or less, and further preferably 1800 mm or more and 2500 mm or less.

  In the solution casting method of the present invention, when casting the dope, two or more kinds of dopes can be simultaneously laminated or sequentially laminated. Furthermore, you may combine both casting. When performing simultaneous lamination and co-casting, a casting die to which a feed block is attached may be used, or a multi-manifold casting die may be used. It is preferable that at least one of the thickness of the layer on the air surface side and the thickness of the layer on the support side is 0.5% to 30% of the thickness of the entire film of the film composed of multiple layers by co-casting. Furthermore, when performing simultaneous lamination co-casting, it is preferable that the high-viscosity dope is wrapped with the low-viscosity dope when the dope is cast from the die slit to the support. Moreover, when performing simultaneous lamination | stacking co-casting, it is preferable that the dope which contact | connects an external field has a larger alcohol composition ratio than an internal dope among the casting beads formed from a die slit to a support body.

From casting die, decompression chamber, support structure, co-casting, peeling method, stretching, drying conditions for each process, handling method, curl, winding method after flatness correction, solvent recovery method, film recovery method The details are described in paragraphs [0617] to [0889] of JP-A-2005-104148.
In the above description, an example of the method for producing an optical film of the present invention has been described with an example in which a dope is cast on a band. However, the dope may be cast on a drum.

(Contact angle of film surface by alkali saponification treatment)
One effective means of surface treatment when the optical film of the present invention is used as a protective film for a polarizing plate is alkali saponification treatment. In this case, the contact angle of the film surface after the alkali saponification treatment is preferably 55 ° or less. More preferably, it is 50 ° or less, and further preferably 45 ° or less.
As one example of the alkali saponification treatment, an optical film is immersed in an aqueous 1.5 N sodium hydroxide solution at 55 ° C. for 2 minutes, washed in a water bath at room temperature, and 0.05 N sulfuric acid at 30 ° C. Was neutralized. Although the method etc. which wash | clean again in the water-washing bath at room temperature and also dry with 100 degreeC warm air are mentioned, In this invention, it is not limited to this conditions and a method.
The alkali saponification solution is not particularly limited, but other than sodium hydroxide, for example, potassium hydroxide can also be used.
The concentration of the alkali saponification solution is not particularly limited, but from the viewpoint of the film surface and saponification performance, 0.1 to 10 rules are preferable, 1.0 to 8.0 rules are more preferable, and 1.0 to The 5.0 regulations are particularly preferred.

(surface treatment)
The optical film can achieve improved adhesion between the optical film and other layers (for example, a polarizer, an undercoat layer, and a back layer) by optionally performing a surface treatment. For example, glow discharge treatment, ultraviolet irradiation treatment, corona treatment, flame treatment, acid or alkali treatment can be used. The glow discharge treatment here may be low-temperature plasma that occurs under a low pressure gas of 10 ^{−3 to} 20 Torr, and plasma treatment under atmospheric pressure is also preferred. A plasma-excitable gas is a gas that is plasma-excited under the above conditions, and includes chlorofluorocarbons such as argon, helium, neon, krypton, xenon, nitrogen, carbon dioxide, tetrafluoromethane, and mixtures thereof. It is done. Details of these are described in detail on pages 30 to 32 in the Japan Institute of Invention Disclosure Technical Bulletin (Public Technical Number 2001-1745, published on March 15, 2001, Japan Institute of Invention), and are preferably used in the present invention. be able to.

(Functional layer)
The optical film of the present invention can be preferably used as an optical compensation film for a liquid crystal display device. A 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 is more preferable that the optical film of the present invention is arranged as an optical compensation film. These liquid crystal display devices are preferably TN, IPS, FLC, AFLC, OCB, STN, ECB, VA and HAN mode liquid crystal display devices, more preferably TN, OCB, IPS and VA mode liquid crystal display devices. A mode liquid crystal display device is more preferable.
In that case, you may provide various functional layers to the optical film of this invention. Examples of the functional layer include an antistatic layer, a cured resin layer (transparent hard coat layer), an antireflection layer, an easy adhesion layer, an antiglare layer, an optically anisotropic layer, an alignment layer, and a liquid crystal layer. Examples of these functional layers and materials thereof include surfactants, slip agents, matting agents, antistatic layers, hard coat layers, etc., and are disclosed by the Japan Institute of Technology (Technical Number 2001-1745, March 15, 2001). (Nippon Issuance, Invention Association), page 32 to page 45, and can be preferably used in the present invention.

[Polarizer]
The optical film of the present invention can also be used as a protective film for polarizing plates. In this case, the optical compensation film of the liquid crystal display device can also serve as a protective film for a polarizing plate. When using as a protective film for polarizing plates, the production method of a polarizing plate is not specifically limited, It can produce by a general method. There is a method in which the obtained optical 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. Further, the surface treatment as described above 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 further includes a protective film bonded to one surface of the polarizing plate and a separate film bonded to the other 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 adhesive layer bonded to a liquid crystal plate, and is used for the surface side which bonds a polarizing plate to a liquid crystal plate.
In a liquid crystal display device, a substrate including a liquid crystal cell is usually disposed between two polarizing plates. The protective film for polarizing plates to which the optical film of the present invention is applied is a protective film for any of the two polarizing plates. Although it can be used, it is preferable to use it as a protective film arrange | positioned at the liquid crystal cell side with respect to a polarizer among the two protective films of each polarizing plate.

(Optical compensation film)
The optical film of the present invention can be used in various applications, and is particularly effective when used as an optical compensation film for liquid crystal display devices. The optical compensation film is generally used for a liquid crystal display device and refers to an optical material that compensates for a retardation, and is synonymous with a retardation plate, an optical compensation sheet, and the like. The optical compensation film has birefringence and is used for the purpose of removing the color of the display screen of the liquid crystal display device or improving the viewing angle characteristics.

  The optical film of the present invention may itself be an optical compensation film, or may be used as a support for the optical compensation film, and an optically anisotropic layer may be provided thereon. When used in a VA mode liquid crystal display device, the optical film of the present invention is preferably used as an optical compensation film. The optically anisotropic layer is not limited to the optical performance or driving method of the liquid crystal cell of the liquid crystal display device in which the optical film of the present invention is used, and any optically anisotropic layer required as an optical compensation film Can be used together. The optically anisotropic layer used in combination may be formed from a composition containing a liquid crystalline compound or may be formed from a polymer film having birefringence. The liquid crystal compound is preferably a discotic liquid crystal compound or a rod-like liquid crystal compound.

(General liquid crystal display device configuration)
The liquid crystal display device includes a liquid crystal cell having a liquid crystal supported between two electrode substrates, two polarizing plates disposed on both sides thereof, and, if necessary, between the liquid crystal cell and the polarizing plate. At least one optical compensation film is arranged.
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 cellulose acylate 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 QuantNW). 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, reflective, and transflective liquid crystal display device.

(VA type liquid crystal display device)
The optical film of the present invention is particularly advantageously used as an optical compensation film for a VA liquid crystal display device having a VA mode liquid crystal cell or a support for the optical compensation film. The VA-type liquid crystal display device may be an alignment-divided system as described in, for example, JP-A-10-123576. In these embodiments, the polarizing plate using the optical film of the present invention contributes to widening the viewing angle and improving the contrast.

Hereinafter, the present invention will be specifically described based on examples. However, the present invention is not limited to the following examples.

  First, the cellulose ester, acrylic resin, and retardation developer used in the examples will be described.

(Cellulose ester)
The cellulose ester in which the kind of acyl group, substitution degree, and mass mean molecular weight Mw which are shown in following Table 1 differ was used.
These cellulose esters were synthesized as follows.
Sulfuric acid (7.8 parts by mass with respect to 100 parts by mass of cellulose) was added to cellulose as a catalyst, and carboxylic acid serving as a raw material for the acyl substituent was added to carry out an acylation reaction at 40 ° C. At this time, the substitution degree of the acetyl group and the propionyl group was adjusted by adjusting the amount of the carboxylic acid. In addition, aging was performed at 40 ° C. after acylation. Further, the low molecular weight component of this cellulose ester was removed by washing with acetone.

(acrylic resin)
The acrylic resin described below was used. These acrylic resins are commercially available or can be obtained by a known synthesis method.
AC-1 (copolymer of methyl methacrylate (MMA) and methacrylate (MA), MMA: MA = 97: 3 (mass%), mass average molecular weight 550000)
AC-2 (copolymer of methyl methacrylate (MMA) and methacrylate (MA), MMA: MA = 97: 3 (mass%), mass average molecular weight 1100000)
AC-3 (copolymer of methyl methacrylate (MMA) and methacrylate (MA), MMA: MA = 40: 60 (mass%), mass average molecular weight 100,000)
AC-4 (copolymer of methyl methacrylate (MMA) and methacrylate (MA), MMA: MA = 60: 40 (mass%), mass average molecular weight 100,000)
AC-5 (Delpet 80N (trade name), manufactured by Asahi Kasei Chemicals Corporation, mass average molecular weight 100,000)
AC-6 (Dianar BR83 (trade name), manufactured by Mitsubishi Rayon Co., Ltd., mass average molecular weight 40000)
AC-7 (Dynajar BR85 (trade name), manufactured by Mitsubishi Rayon Co., Ltd., mass average molecular weight 280000)
AC-8 (Dianar BR88 (trade name), manufactured by Mitsubishi Rayon Co., Ltd., mass average molecular weight 480000)
The ratio of the MMA unit in the molecule in the commercially available acrylic resins (AC-5 to AC-8) was 90% by mass or more and 99% by mass or less.

(Retardation expression agent)
The retardation developer described below was used. These retardation developing agents can be obtained by a known synthesis method.

(R-4: ester oligomer)
A polycondensate of terephthalic acid and 1,4-butanediol in which both ends of the polycondensate are sealed with benzoic acid. The weight average molecular weight is 800.

(Acrylic fine particles)
Three-layer structure acrylic fine particles were synthesized and used by the method described in [0292] to [0296] of WO2009 / 081607.

(UV absorber)
The ultraviolet absorber described below was used.
UV-1: Tinuvin 326 (Ciba Specialty Chemicals Co., Ltd.)
UV-2: Tinuvin 328 (Ciba Specialty Chemicals Co., Ltd.)

(Example 1)
[Production of Optical Film 101]
(Dope preparation)
The composition described below was put into a mixing tank and stirred while heating to dissolve each component to prepare a dope.
(Dope composition)
100 parts by mass of cellulose ester and acrylic resin (The ratio (mass ratio) of cellulose ester to acrylic resin is listed in Table 2)
Retardation developer R-1 4.3 parts by mass Dichloromethane 275.4 parts by mass Ethanol 37.5 parts by mass

  The solid content concentration of the dope (total concentration of cellulose ester, acrylic resin, and retardation developer) was 25.0% by mass.

The prepared dope was uniformly cast from a casting die onto a stainless steel endless band (casting support) having a width of 2000 mm using a band casting apparatus as shown in FIG. When the amount of residual solvent in the dope reaches 40% by mass, it is peeled off from the casting support as a polymer film, conveyed without being actively stretched by a tenter, and dried at 130 ° C. in a drying zone. Then, the film thickness and Tg of the obtained unstretched film were measured. This value is shown in Table 2.
Also, casting is performed in the same manner as described above, and both ends of the polymer film peeled off from the support are fixed with a tenter having a clip, and stretched in the width direction (TD direction) and the transport direction (MD direction). The film 101 was dried at 130 ° C. in the drying zone while being conveyed, and the ears were slit to obtain a film 101 having a width of 1500 mm and a film thickness of 49 μm. The amount of residual solvent in the polymer film when stretching with a tenter was 10% by mass. Various conditions such as the temperature during stretching and the stretching ratio are shown in Table 2 below.

[Production of Optical Films 102 to 163]
In the dope of the film 101, the dope of each film of the films 102 to 163 is changed to the type and ratio of cellulose ester and acrylic resin, the type and addition amount of the retardation developer, and the solid content concentration described in Table 2 below. did. Regarding the dope of the film 157, 5 parts by mass of acrylic fine particles were further added. In the dope of the film 158, 0.50 parts by mass of the UV absorber UV-1 and 1.00 parts by mass of UV-2 are added. In the dope of the film 159, 1.50 parts by mass of the UV absorber is UV-1. UV-2 was added in an amount of 3.00 parts by mass. In each dope, the amounts of dichloromethane and ethanol are adjusted so that the ratio of both is the same as the dope of the film 101 and the solid content concentration is as shown in Table 2, and the dope of the films 102 to 163 is adjusted. Produced.
Films 102 to 163 were produced using the produced dopes in the same manner as the film 101. Various conditions such as the temperature during stretching and the draw ratio are shown in Table 2 below.

[Preparation of optical films 164 and 165]
(Dope preparation)
The composition described below was put into a mixing tank and stirred while heating to dissolve each component to prepare a dope.

[Optical film 164]
(Dope composition)
100 parts by mass of cellulose ester and acrylic resin (The ratio (mass ratio) of cellulose ester to acrylic resin is listed in Table 2)
Dichloromethane 300 parts by mass Ethanol 40 parts by mass

[Optical film 165]
(Dope composition)
100 parts by mass of cellulose ester and acrylic resin (The ratio (mass ratio) of cellulose ester to acrylic resin is listed in Table 2)
Retardation developer R-4 10.0 parts by mass Acrylic fine particles 5 parts by mass Dichloromethane 300 parts by mass Ethanol 40 parts by mass

The prepared dope was uniformly cast from a casting die onto a stainless steel endless band (casting support) having a width of 2000 mm using a band casting apparatus as shown in FIG. When the amount of residual solvent in the dope reaches 40% by mass, it is peeled off from the casting support as a polymer film, conveyed without being actively stretched by a tenter, and dried at 130 ° C. in a drying zone. Then, the film thickness and Tg of the obtained unstretched film were measured. This value is shown in Table 2.
Further, casting is performed in the same manner as described above, both ends of the polymer film peeled off from the support are fixed with a tenter having a clip, stretched in the width direction (TD direction), and transported at 130 in the drying zone. The film was dried at 0 ° C., and the ears were slit to obtain films 164 and 165 having a width of 1500 mm. The residual solvent amount of the polymer film when starting stretching with a tenter was 10% by mass. Here, about the conveyance direction (MD direction), it extended | stretched actively by the difference of the rotational speed of a stainless steel band and a support body, and the movement speed of a tenter. Various conditions such as the temperature during stretching and the stretching ratio are shown in Table 2 below.

[Preparation of optical films 166 and 167]
(Dope preparation)
The composition described below was put into a mixing tank and stirred while heating to dissolve each component to prepare a dope.

[Optical film 166]
(Dope composition)
Cellulose ester CA-16 100 parts by weight Triphenyl phosphate 6.8 parts by weight Biphenyl diphenyl phosphate 4.9 parts by weight Silica particles having an average particle diameter of 16 nm (Aerosil R972 manufactured by Nippon Aerosil Co., Ltd.) 0.15 parts by weight Dichloromethane 414.8 Part by weight methanol 62.0 parts by weight

[Optical film 167]
(Dope composition)
Cellulose ester CA-16 100 parts by weight Triphenyl phosphate 6.8 parts by weight Biphenyldiphenyl phosphate 4.9 parts by weight Retardation agent R-1 1.0 part by weight Silica particles having an average particle diameter of 16 nm (Aerosil R972 Nippon Aerosil Co., Ltd.) 0.15 parts by mass Dichloromethane 418.6 parts by mass Methanol 62.5 parts by mass

  The prepared dope was uniformly cast from a casting die onto a stainless steel endless band (casting support) having a width of 2000 mm using a band casting apparatus as shown in FIG. When the amount of residual solvent in the dope reaches 40% by mass, it is peeled off as a polymer film from the casting support, and conveyed without being actively stretched by a tenter, and dried at 130 ° C. in a drying zone. The ears were slit to obtain films 166 and 167 having a width of 1500 mm.

(Tg of unstretched film)
An unstretched film is prepared with the same formulation as each optical film (but pre-stretching), and the glass transition temperature Tg of the unstretched film is measured by a viscoelasticity measuring device (Vibron: DVA-225 (IT measurement). Control Co., Ltd.)). The measured values are shown in Table 2 below. In the unstretched films of the films 101 to 165, the glass transition temperature to be measured was one, and it was confirmed that the cellulose ester and the acrylic resin were in a compatible state. Similarly, in the films 101 to 165 obtained by stretching the unstretched film, it was confirmed that the cellulose ester and the acrylic resin were in a compatible state.

  The produced films 101 to 167 were measured and evaluated for the following physical properties. Measurements and results are shown in Table 3 below.

(Break frequency)
As an index for film production suitability, the breaking frequency during film production (polymer film formation, stretching, and drying) was evaluated according to the following criteria.
○: Almost no breakage occurs during film production.
Δ: Rupture may occur rarely during film production.
X: Breaking frequently occurred during film production, and film production was difficult.

(Surface shape)
The produced film was arrange | positioned between the two polarizing plates of cross nicol arrangement | positioning, it observed visually through the polarizing plate, and the following references | standards evaluated.
○: Dan-like unevenness cannot be confirmed on the film surface.
(Triangle | delta): Dan-shaped unevenness was confirmed in the edge part of the film surface.
X: Dan-like unevenness was confirmed in the entire area of the film surface.

(Mechanical strength)
The produced film was cut out to 150 mm (MD direction) × 10 mm (TD direction), conditioned at 25 ° C. and 60% RH for 2 hours or more, and once for each of both sides of the film at the center. The breaking frequency when bent was evaluated as a standard of mechanical strength.
Here, the breakage means that the film is separated into two.
○: Fracture hardly occurs after film folding.
Δ: Rupture may occur rarely after film folding.
X: Breakage frequently occurs after film folding.

(Retardation value)
The produced film was conditioned at 25 ° C. and 60% RH for 2 hours or more, and using a birefringence measuring device (KOBRA 21ADH, manufactured by Oji Scientific Instruments), the Re value at a wavelength of 590 nm at 25 ° C. and 60% RH. And Rth value was measured and Nz was calculated | required based on the value further. Although the measurement was performed at one point in the center in the width direction of the obtained film, the measurement may be performed at an arbitrary point.

(Rth variation)
10 points at 100 mm intervals in the width direction of the film and 7 points at 100 mm intervals in the longitudinal direction (conveying direction), and Rth at each measurement point is measured with a birefringence measuring device (KOBRA 21ADH, manufactured by Oji Scientific Instruments). Measured. The difference in Rth between adjacent measurement points at intervals of 100 mm was determined, and the largest difference was evaluated according to the following criteria.
A: Difference is 1.5 nm or less B: Difference is greater than 1.5 nm and 2.0 nm or less C: Difference is greater than 2.0 nm and 3.0 nm or less D: Difference is greater than 3.0 nm

(Haze)
For the measurement of haze, a 40 mm × 80 mm sample was cut out from each film, and the total haze (H) and internal haze (Hi) were measured by the following measurements.
1) The total haze (H) of the film was measured using a haze meter NDH2000 (Nippon Denshoku Industries Co., Ltd.) according to JIS K-7136.
2) Add several drops of liquid paraffin to the front and back surfaces of the film, and use two glass plates (micro slide glass product number S9111, manufactured by MATAUNAMI) between the front and back surfaces of the two glass plates. The obtained film was optically adhered, the haze was measured in a state where the surface haze was removed, and the value obtained by subtracting the measured haze by sandwiching only liquid paraffin between two separately measured glass plates was used. Calculated as internal haze (Hi).

(Thermal deformation)
Dimensional change in width direction (TD direction) before and after aging for 24 hours in 80 ° C. DRY (5% RH or less) environment {(Dimension before aging) − (Dimension after aging) / (Dimension before aging) The absolute value of x100 (%)} was measured and evaluated according to the following criteria.
A: Dimensional change is 0.15% or less B: Dimensional change is greater than 0.15% and 0.30% or less C: Dimensional change is greater than 0.30% and 0.50% or less D: Dimensional change is 0 Greater than 50%

[Optical compensation film A]
[Preparation of optical film A]
(Dope preparation)
The composition described below was put into a mixing tank and stirred while heating to dissolve each component to prepare a dope.
(Dope composition)
Cellulose ester CA-15 100 parts by weight Triphenyl phosphate 6.8 parts by weight Biphenyl diphenyl phosphate 4.9 parts by weight Retardation agent R-1 7.0 parts by weight Silica particles having an average particle size of 16 nm (Aerosil R972 Nippon Aerosil Co., Ltd.) 0.15 parts by mass Dichloromethane 414.8 parts by mass Methanol 62.0 parts by mass

  The dope solution of the optical compensation film A was uniformly cast on a stainless steel band support with a width of 2000 mm using a band casting apparatus. With the stainless steel band support, the solvent was evaporated until the residual solvent amount was 40% by mass, and the stainless steel band support was peeled off. Next, both ends are held with a tenter, and stretched in the transverse direction (lateral stretching) so that the stretching ratio in the width (TD) direction is 1.22 times, and transported after stretching in a 115 ° C. drying zone. Dried. After drying, it was slit into a width of 1500 mm to obtain a cellulose acylate film (optical compensation film A) having a thickness of 82 μm. The longitudinal (MD) draw ratio due to the tension at the time of peeling was 1.02. When the optical properties of the film were measured, they were Re = 57 nm, Rth = 201 nm, and Nz = 4.03.

[Optical compensation film B]
A norbornene-based film (Zeonor, manufactured by Nippon Zeon Co., Ltd.) having a thickness of 100 μm was uniaxially stretched (temperature 180 ° C., continuous stretching). When the optical properties of the obtained norbornene-based film (optical compensation film B) were evaluated, Re was 140 nm, Rth was 70 nm, and Nz = 1.0.

[Preparation of polarizing plate]
(Optical films 101-167, polarizing plate using optical compensation film A)
1) Saponification of the film The prepared films 166 and 167, the optical compensation film A, and the commercially available cellulose triacetate film (Fujitac TD80UF, manufactured by Fuji Film Co., Ltd.) were maintained at 55 ° C. in a 1.5 mol / L NaOH aqueous solution (saponification). The film was washed with water for 2 minutes, then immersed in a 0.05 mol / L sulfuric acid aqueous solution at 25 ° C. for 30 seconds, and then passed through a washing bath for 30 seconds under running water to neutralize the film. It was in the state. Then, draining with an air knife was repeated three times, and after dropping the water, the film was retained in a drying zone at 70 ° C. for 15 seconds and dried to produce a saponified film.

2) Production of Polarizer According to Example 1 of Japanese Patent Application Laid-Open No. 2001-141926, iodine was adsorbed to a stretched polyvinyl alcohol film to produce a polarizer having a thickness of 20 μm.

3) Bonding After applying a corona treatment to the produced film 101 using an acrylic adhesive on one surface of this polarizer, bonding was performed. The saponified commercially available cellulose triacetate film was attached to the other side using a polyvinyl alcohol-based adhesive, and dried at 70 ° C. for 10 minutes or more to produce a polarizing plate using the film 101. Polarizing plates using the films 102 to 165 were similarly produced.
Further, using a polyvinyl alcohol-based adhesive, the saponified film 166 is attached to one side of the polarizer, and the saponified commercially available cellulose triacetate film is attached to the other side, and dried at 70 ° C. for 10 minutes or more. A polarizing plate using this was prepared. A polarizing plate using the film 167 and the optical compensation film A was produced in the same manner.
Here, it arrange | positioned so that the transmission axis of a polarizer and the conveyance direction of the films 101-167 may intersect orthogonally, ie, the transmission axis of a polarizer, and the slow axis of a film may become parallel or orthogonal. About the optical compensation film A, it arrange | positioned so that the transmission axis of a polarizer and the slow axis of the optical compensation film A may become parallel. The transmission axis of the polarizer and the slow axis of the commercially available cellulose triacetate film were arranged so as to be orthogonal.

(Polarizing plate using optical compensation film B)
An optical compensation film B was bonded to a polarizer having a commercially available cellulose acylate film (Fujitac TDY80UL (Fuji Film Co., Ltd.)) bonded to one surface with an adhesive. The transmission axis of the polarizer and the slow axis of the commercially available cellulose triacetate film are arranged so as to be orthogonal to each other, and the optical compensation film B is parallel to the transmission axis of the polarizer and the slow axis of the optical compensation film B. Were pasted together.

(Production of liquid crystal cell)
The liquid crystal cell has a cell gap between substrates of 3.6 μm, and a liquid crystal material having negative dielectric anisotropy (“MLC6608”, manufactured by Merck & Co., Inc.) is dropped and sealed between the substrates. A layer was formed to prepare a VA mode liquid crystal cell. The retardation of the liquid crystal layer (that is, the product Δn · d of the thickness d (μm) of the liquid crystal layer and the refractive index anisotropy Δn) was set to 300 nm. The liquid crystal material was aligned so as to be vertically aligned.

(Mounting on VA panel 1)
For the upper polarizing plate (viewing side) of the liquid crystal display device using the VA mode liquid crystal cell, the polarizing plate prepared above using the optical films 101 to 167 is used, and the optical films 101 to 167 are used with respect to the polarizer. It installed so that it might become the liquid crystal cell side. The polarizing plate prepared above using the optical compensation film A on the lower polarizing plate (backlight side) was placed so that the optical compensation film A was on the liquid crystal cell side. The upper polarizing plate and the lower polarizing plate were attached to the liquid crystal cell via an adhesive. The crossed nicols were arranged so that the transmission axis of the upper polarizing plate was in the vertical direction and the transmission axis of the lower polarizing plate was in the horizontal direction.

(Mounting on VA panel 2)
For the upper polarizing plate (viewing side) of the liquid crystal display device using the VA mode liquid crystal cell, the polarizing plate prepared above using the optical compensation film B is used so that the optical compensation film B is on the liquid crystal cell side. installed. The polarizing plate produced above using the optical films 101 to 167 on the lower polarizing plate (backlight side) was placed so that the optical films 101 to 167 were on the liquid crystal cell side with respect to the polarizer. The upper polarizing plate and the lower polarizing plate were attached to the liquid crystal cell via an adhesive. The crossed nicols were arranged so that the transmission axis of the upper polarizing plate was in the vertical direction and the transmission axis of the lower polarizing plate was in the horizontal direction.

The viewing angle characteristics of the liquid crystal display device produced as described above, black display unevenness when the humidity changed, and black display unevenness after aging in a high-temperature and high-humidity environment were evaluated. The results of mounting 1 are shown in Table 4, and the results of mounting 2 are shown in Table 5.
Each compensation method was evaluated by relative evaluation within the same method.

(Viewing angle characteristics)
The viewing angle characteristics of the liquid crystal display device produced above were evaluated as follows.
The produced liquid crystal display device displayed black, and was observed visually from an oblique direction, and the preference for color and brightness was evaluated in five stages according to the following criteria.
A: Color and brightness in an oblique direction are sufficiently small.
○: I don't care about the color and brightness in the diagonal direction.
○ △: The color in the diagonal direction is slightly worrisome, but the brightness is not worrisome.
Δ: Slightly concerned about color and brightness in an oblique direction.
X: The color and brightness in an oblique direction are conspicuous.

(Black display unevenness when humidity changes)
The liquid crystal display device was conditioned at 25 ° C. and 80% RH for 24 hours, then lit in an environment of 25 ° C. and 10% RH, and visually observed the degree of color unevenness when displaying black after 2 hours. Evaluation was made in four stages according to the standard.
A: Color unevenness was not observed.
○: Weak color unevenness was observed in an area less than half of the display surface.
Δ: Weak color unevenness was observed in an area of more than half of the display surface, or strong color unevenness was observed in an area of less than half.
X: Strong color unevenness was observed in an area of more than half of the display surface.

(Black display unevenness after high temperature and high humidity environment)
The liquid crystal display device was lit for 48 hours at 60 ° C. and 90% RH, then lit after being conditioned for 24 hours in an environment of 25 ° C. and 60% RH, and the degree of color unevenness during black display was visually observed. The evaluation was made in four stages according to the following criteria.
A: Color unevenness was not observed.
○: Weak color unevenness was observed in an area less than half of the display surface.
Δ: Weak color unevenness was observed in an area of more than half of the display surface, or strong color unevenness was observed in an area of less than half.
X: Strong color unevenness was observed in an area of more than half of the display surface.

When the films 119 to 127, 166, and 167 are compared, the films 120 to 126 in which the ratio of the cellulose ester and the acrylic resin is within the scope of the present invention are more than the liquid crystal display device using the films 119 and 127 that are outside the scope of the present invention. Also, the viewing angle characteristics are excellent, and the black display unevenness after aging in a high temperature and high humidity environment is superior to the liquid crystal display device using the films 119, 127, 166, and 167.
The film 127 having an acrylic resin ratio larger than the range of the present invention has problems such as insufficient optical development, further breakage during production, low mechanical strength, and easy thermal deformation. Not suitable for optical films. This is due to the strong appearance of the characteristics of the acrylic resin.
Films 119, 166, and 167 whose acrylic resin ratio is smaller than the range of the present invention are not suitable for an optical film because black display unevenness at the time of humidity change and black display unevenness after aging in a high-humidity and high-humidity environment are poor. This is because the cellulose ester ratio increases, the moisture content of the film increases, the effect of water birefringence during environmental changes increases, and the Tg decreases due to water, which tends to cause film deterioration during high temperature and high humidity durability. In addition, since the moisture permeability of the film increases and the amount of water that passes through the film increases, stress is generated between the polarizer and the film due to deterioration of the polarizer or deformation of the polarizer, resulting in a change in optical properties. Is presumed to be the cause.

  In the films 164 and 165, the ratio of the cellulose ester and the acrylic resin is within the range of the present invention, but the optical expression is insufficient, and the viewing angle characteristics of the films are inferior to the film of the present invention.

Films 138 to 151 with different cellulose ester substituents and different degrees of substitution are compared.
The film 140 using CA-9 having a low degree of propionyl substitution and the film 142 using CA-10 having a low degree of total substitution have a larger total haze and internal haze than other films. Regarding the total haze and internal haze, the cellulose ester resin having a high total substitution degree and a high substitution degree of the acyl group having 3 to 7 carbon atoms has higher compatibility with the acrylic resin, and is excellent in the scope of the present invention. It can be seen that it has characteristics.
Further, when the film 138 using CA-1 having a propionyl substitution degree of 2.56 and the film 139 using CA-8 having a propionyl substitution degree of 2.10, cellulose acetate propionate is compared. From the fact that the total haze and the internal haze are smaller, it is understood that a cellulose ester resin having a large propionyl substitution degree and a small acetyl substitution degree is more suitable for the optical film of the present invention.

When the films 138 and 143 to 148 having different molecular weights of cellulose ester are compared, only the film 148 using CA-2 whose molecular weight is outside the scope of the present invention has a high breaking frequency at the time of manufacture and lacks mechanical strength. I understand that.
The film 143 using CA-7 having a molecular weight of 320,000 has the largest haze, and then the film 144 using CA-6 having a molecular weight of 270000 is large. It can be seen that haze increases as the molecular weight increases in the region where the molecular weight is greater than 250,000.

  Comparing the films 138 and 152 to 158 with different acrylic resins, only the film 152 using AC-6 whose molecular weight is outside the scope of the present invention has a high breaking frequency at the time of manufacture, and the mechanical strength is insufficient. I understand.

In addition, when the films 138, 157 and 158 having different MMA ratios are compared, the film 138 using AC-5 having an MMA ratio of 90% or more and less than 99% has the smallest total haze and internal haze, and then the MMA ratio. The film 158 using AC-4 which is 60% is small, and the film 157 using AC-3 whose MMA ratio is 40% is the largest.
This is because the higher the MMA ratio, the higher the compatibility between the cellulose ester and the acrylic resin.

Comparing films 138 and 163 with different retardation developing agents,
The film 138 using a discotic compound and the film 163 using a liquid crystalline compound are superior to the film 138 using a discotic compound in terms of axial variation, Re, and Rth variation. Furthermore, the film 138 using a discotic compound is excellent in black display unevenness after aging in a high-temperature and high-humidity environment as compared with the film 163 using a liquid crystal compound.
It is presumed that the disk-like compound is less likely to be affected by orientation due to uneven temperature and stress during stretching and environmental changes at high temperature and high humidity and time, compared to liquid crystal compounds.

Comparing the films 138 and 159 having different stretching temperatures, the Re and Rth variations of the film 138 whose stretching temperature is within the range of Tg ± 30 ° C. of the unstretched film is smaller than that of the film 159 having Tg + 40 ° C.
When the stretching temperature is higher than Tg + 30 ° C., it is presumed that the film is softened and easily stretched, and the influence of the stress distribution in the film is increased. On the other hand, if it is lower than Tg-30 ° C., it will be stretched with low molecular mobility, and breakage will easily occur during stretching. A film with small variations in Re and Rth also has excellent viewing angle characteristics.

  It can be seen that the films 105, 128, 166, and 167 that are not actively subjected to TD and MD stretching are inferior in surface shape as compared with other films, and that it is preferable to actively stretch TD and MD. . This is presumed to be because the unevenness generated during drying and stripping on the support is stretched and becomes inconspicuous by stretching.

  In addition, Tables 4 to 5 show that preferable optical characteristics are different depending on the compensation method. As shown in the mounting 1, the film of the present invention is a liquid crystal that includes a polarizing plate having the film of the present invention. Polarized light having a film (optical compensation film A) that is used on the upper side or the lower side of the liquid crystal cell so that the cell side becomes the film of the present invention, and 30 ≦ Re ≦ 100, 70 ≦ Rth ≦ 300, and Nz ≧ 2.00 By adapting the plate to the VA mode liquid crystal cell used for the other so that the liquid crystal cell side is a film (optical compensation film A) with 30 ≦ Re ≦ 100, 70 ≦ Rth ≦ 300, and Nz ≧ 2.00. The most excellent effect is obtained.

[Polarizing film]
The optical film of this invention can be preferably used also as a protective film of the position far from a liquid crystal cell among the polarizing plate protective films located in both surfaces of a polarizer.

[Optical compensation film C]
[Preparation of optical film C]
(Dope preparation)
The composition described below was put into a mixing tank and stirred while heating to dissolve each component to prepare a dope.
(Dope composition)
Cellulose ester CA-15 100 parts by weight Triphenyl phosphate 6.8 parts by weight Biphenyl diphenyl phosphate 4.9 parts by weight Retardation agent R-1 4.5 parts by weight Silica particles having an average particle diameter of 16 nm (Aerosil R972 Nippon Aerosil Co., Ltd.) 0.15 parts by mass Dichloromethane 431.5 parts by mass Methanol 64.5 parts by mass

  The dope solution of the optical compensation film C was uniformly cast on a stainless steel band support with a width of 2000 mm using a band casting apparatus. With the stainless steel band support, the solvent was evaporated until the residual solvent amount was 40% by mass, and the stainless steel band support was peeled off. Next, both ends are held by a tenter, stretched in the transverse direction (lateral stretching) so that the stretching ratio in the width (TD) direction is 1.30 times, and transported after stretching in a 115 ° C. drying zone. Dried. After drying, it was slit to a width of 1500 mm to obtain a cellulose acylate film (optical compensation film C) having a film thickness of 54 μm. The longitudinal (MD) draw ratio due to the tension at the time of peeling was 1.02. When the optical properties of this film were measured, they were Re = 46 nm, Rth = 122 nm, and Nz = 3.15.

[Preparation of polarizing plate]
The prepared film 119 was subjected to corona treatment using an acrylic adhesive on one side of the polarizer and then bonded. On the other side, a saponified optical compensation film C was attached using a polyvinyl alcohol-based adhesive in the same manner as described above, and dried at 70 ° C. for 10 minutes or more to prepare a polarizing plate using the film 119.
Polarizers were similarly prepared for the films 120 to 127, 161, and 162.
Also, using a polyvinyl alcohol-based adhesive, the saponified film 166 is attached to one side of the polarizer, and the saponified optical compensation film C is attached to the other side, and dried at 70 ° C. for 10 minutes or more. The polarizing plate used was produced. A polarizing plate using the film 167 was produced in the same manner.
Here, the transmission axis of the polarizer and the transport direction of the films 119 to 127, 161, 162, 166, and 167 are orthogonal, that is, the transmission axis of the polarizer and the slow axis of the film are parallel or orthogonal. Arranged. About the optical compensation film C, it arrange | positioned so that the transmission axis of a polarizer and the slow axis of the optical compensation film C may become parallel.

The polarizing plate produced as described above is used for the upper polarizing plate (viewing side) and the lower polarizing plate (backlight side) of the VA mode liquid crystal cell, and the optical compensation film C is on the liquid crystal cell side with respect to the polarizer. It installed so that it might become. The upper polarizing plate and the lower polarizing plate were attached to the liquid crystal cell via an adhesive. The upper polarizing plate and the lower polarizing plate were arranged in a crossed Nicol arrangement so that the transmission axis of the upper polarizing plate and the transmission axis of the lower polarizing plate were orthogonal to each other.
About the liquid crystal display device produced as mentioned above, the black display nonuniformity at the time of humidity change and the periphery nonuniformity after high temperature high-humidity environment aging were evaluated. The results are shown in Table 6.

(Surrounding unevenness)
After the liquid crystal display device has been allowed to pass for 48 hours at 60 ° C. and 90% RH, it is lighted after being conditioned for 24 hours in an environment of 25 ° C. and 60% RH, and the color unevenness that occurs around the display surface during black display ( Peripheral unevenness) was visually observed and evaluated in four stages according to the following criteria.
A: No peripheral unevenness was observed.
○: Weak peripheral unevenness was observed.
Δ: Weak peripheral unevenness and some strong peripheral unevenness were observed.
X: Strong peripheral unevenness was observed as a whole.

  It was confirmed that the optical film of the present invention can be preferably used also as a protective film at a position farther from the liquid crystal cell among polarizing plate protective films located on both surfaces of the polarizer.

  As shown in Tables 3 to 6, the optical film of the present invention provides a liquid crystal display device having good surface shape, high durability, and improved display unevenness.

20 Film production line

Claims (12)

An optical film containing a cellulose ester and an acrylic resin in a compatible state,
The weight average molecular weight of the cellulose ester is 75000 or more, the weight average molecular weight of the acrylic resin is 80000 or more, and the mass ratio of the cellulose ester to the acrylic resin is 70:30 to 5:95,
An optical film in which Re and Rth defined by the following formulas (I) and (II) satisfy the following formulas (III) and (IV) at a wavelength of 590 nm.
Formula (I) Re = (nx−ny) × d
Formula (II) Rth = {(nx + ny) / 2−nz} × d
Formula (III) −10 ≦ Re ≦ 10
Formula (IV) Rth ≧ 30
In the formula, nx is the refractive index in the slow axis direction in the film plane of the optical film, ny is the refractive index in the fast axis direction in the film plane, and nz is the refractive index in the thickness direction of the optical film. D is the thickness (nm) of the optical film.   2. The optical film according to claim 1, wherein a total substitution degree of acyl groups of the cellulose ester is 2.00 to 3.00 and a substitution degree of acyl groups having 3 to 7 carbon atoms is 1.20 to 3.00. .   3. The optical film according to claim 1, wherein a difference in Rth at two points with an interval of 100 mm is within 3.0 nm in the film plane of the optical film.   4. The optical film according to claim 1, wherein the total haze value is 0.30 or less and the internal haze value is 0.10 or less.   The optical film according to claim 1, wherein the optical film contains a retardation enhancer, and the retardation enhancer is a discotic compound. A method for producing an optical film comprising a cellulose ester and an acrylic resin in a compatible state,
Forming a polymer film having a mass ratio of the cellulose ester and the acrylic resin of 70:30 to 5:95;
Stretching the polymer film in a width direction perpendicular to the transport direction of the polymer film,
The weight average molecular weight of the cellulose ester is 75000 or more, the weight average molecular weight of the acrylic resin is 80000 or more,
The method for producing an optical film, wherein Re and Rth defined by the following formulas (I) and (II) satisfy the following formulas (III) and (IV) at a wavelength of 590 nm.
Formula (I) Re = (nx−ny) × d
Formula (II) Rth = {(nx + ny) / 2−nz} × d
Formula (III) −10 ≦ Re ≦ 10
Formula (IV) Rth ≧ 30
In the formula, nx is the refractive index in the slow axis direction in the film plane of the optical film, ny is the refractive index in the fast axis direction in the film plane, and nz is the refractive index in the thickness direction of the optical film. D is the thickness (nm) of the optical film.   The method for producing an optical film according to claim 6, wherein the stretching of the polymer film is performed in a temperature range of Tg ± 30 ° C. with respect to Tg of the unstretched polymer film after drying.   The method for producing an optical film according to claim 6 or 7, wherein the acrylic resin contains 50% by mass or more of repeating units derived from methyl methacrylate and has a mass average molecular weight of 500,000 or less. The cellulose ester comprises an acetyl group and a propionyl group;
The total substitution degree of the acyl group of the cellulose ester is 2.00 to 3.00, the substitution degree of the acyl group having 3 to 7 carbon atoms is 1.20 to 3.00,
The method for producing an optical film according to claim 6, wherein the cellulose ester has a mass average molecular weight of 250,000 or less.   The method for producing an optical film according to claim 6, wherein the optical film contains a retardation enhancer, and the retardation enhancer is a discotic compound.   A polarizing plate comprising at least one optical film according to claim 1.   A liquid crystal display device comprising at least one optical film according to claim 1 or at least one polarizing plate according to claim 11.

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