JP2008248030A - Cellulosic composition, cellulosic film, retardation film, optical compensation sheet, polarizing plate and image display apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a cellulosic composition, a cellulosic film, an optical compensation sheet, a polarizing plate and a liquid crystal display device, in more detail, a cellulosic film having slight humidity dependence of inplane retardation (Re) and retardation (Rth) in the thickness direction, and a retardation film, an optical compensation sheet, a polarizing plate and a liquid crystal display device using the same. <P>SOLUTION: The cellulosic composition comprises a cellulosic containing a 5-30C aliphatic acyl group (A) and a 2-4C aliphatic acyl group (B) in which the substitution degree of the acyl group (A) satisfies a specific range. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a cellulose composition, a cellulose film, a retardation film, an optical compensation sheet, a polarizing plate and an image display device, and more specifically, in-plane retardation (Re) and thickness direction retardation (Rth). The present invention relates to a cellulosic film that has low humidity dependency and a wide range of solvent composition choices and is less likely to become cloudy, an optical compensation sheet using the same, a polarizing plate, and an image display device.

In recent years, with the widespread use of liquid crystal display devices, demands for display performance and durability have increased, and response speeds have been improved, and a wider viewing angle such as contrast and color balance when viewed from an oblique direction with respect to the display image. It has become a problem to compensate with. In order to solve these problems, VA (Vertical Alignment), OCB (Optical Compensated Bend), or IPS (In-Plane Switching) display devices have been developed. There is a demand for an optical film material having a foundation development property. In particular, the retardation film is required to control the in-plane retardation (Re) and the thickness direction retardation (Rth) according to each of various liquid crystal systems.
Conventionally, cellulose acylate films have been widely used as polarizing plate protective films for liquid crystal display devices because of their moderate hydrophilicity, transparency, toughness, and optical isotropy. For example, an optical film that uses a mixed acylate cellulose ester of cellulose ester such as cellulose acetate propionate or cellulose acetate butyrate has been proposed (Patent Document 1). It has also been proposed to use a cellulose acylate film as an optical compensation film (Patent Document 2).
On the other hand, a film has been proposed in which a change in retardation due to humidity fluctuation is suppressed by introducing a hydrophobic non-acyl substituent into cellulose acylate (Patent Document 3).
A film using cellulose acylate substituted with a long-chain acyl group having a large carbon number has been proposed (Patent Document 4).
However, further improvement in display quality is demanded in liquid crystal display devices, and for this reason, further improvement in performance is demanded from the above viewpoint for the cellulose acylate film used for this purpose.

JP 2005-352620 A European Patent Application No. 91656 JP 2006-335842 A JP 2006-249221 A

  In view of the above problems, the object of the present invention is that there are few changes in in-plane retardation (Re) and thickness direction retardation (Rth) due to humidity fluctuations, it is difficult to cause white turbidity with respect to changes in solvent composition, and Re , Rth and wavelength dispersion can be freely controlled in a wide range, a cellulose film, a cellulose composition forming the film, a retardation film using the cellulose film, an optical compensation film, a polarizing plate, and an image display device are provided. Objective.

  As a result of intensive studies to solve the above problems, the present inventors have used a cellulose body having an aliphatic acyl group having 5 to 30 carbon atoms and an aliphatic acyl group having 2 to 4 carbon atoms, It has been found that a cellulosic film can be obtained with little change in in-plane retardation (Re) and thickness direction retardation (Rth) due to humidity fluctuations.

  As a result of further diligent investigations by the present inventors, the solvent composition at the time of film formation is changed by replacing more of the aliphatic acyl group having 5 to 30 carbon atoms with respect to the hydroxyl groups at the 2- and 3-positions of the glucose unit. However, it has been found that no cloudiness is produced, and the present invention has been completed.

That is, the present invention has the following configuration.
[1]
It has an aliphatic acyl group (A) having 5 to 30 carbon atoms and an aliphatic acyl group (B) having 2 to 4 carbon atoms, and the degree of substitution of the aliphatic acyl group (A) is represented by the following formula ( Cellulose body composition containing a cellulose body that satisfies I).
Formula (I) DSA6 / DSA2 + DSA3 + DSA6 <0.5
(Wherein DSA2 is the degree of substitution of the hydroxyl group at the 2-position of the glucose unit with the acyl group (A), DSA3 is the degree of substitution of the hydroxyl group at the 3-position of the glucose unit with the acyl group (A), and DSA6 is (This is the degree of substitution of the hydroxyl group at the 6-position of the glucose unit with the acyl group (A).)
[2]
The cellulose composition according to [1], wherein the acyl group (B) is an acetyl group.
[3]
The cellulose body film formed with the cellulose body composition as described in [1] or [2].
[4]
The retardation film which consists of a cellulose body film as described in [3].
[5]
An optical compensation film comprising an optically anisotropic layer formed by aligning a liquid crystalline compound on the cellulose body film according to [3] or the retardation film according to [4].
[6]
A polarizing plate comprising a polarizing film and two protective films sandwiching the polarizing film, wherein at least one of the two protective films is a cellulose body film according to [3], and a position according to [4] A polarizing plate comprising at least one of a phase difference film or the optical compensation film according to [5].
[7]
An image display device comprising at least one of the cellulose-based film according to [3], the retardation film according to [4], the optical compensation film according to [5], and the polarizing plate according to [6].

  With the cellulose composition of the present invention, it is possible to obtain a cellulose film that hardly causes white turbidity at the time of film formation and has little change in in-plane retardation (Re) and thickness direction retardation (Rth) due to humidity fluctuations. In addition, there is an excellent effect that Re, Rth and chromatic dispersion can be freely controlled in a wide range. The cellulose film of the present invention can be suitably used for a retardation film, an optical compensation sheet, a polarizing plate, an image display device and the like, and can exhibit excellent display performance.

  The contents of the present invention will be described in detail below.

[Cellulose composition]
The cellulose composition of the present invention has an aliphatic acyl group (A) having 5 to 30 carbon atoms and an aliphatic acyl group (B) having 2 to 4 carbon atoms, and the aliphatic acyl group ( The cellulose body which the substitution degree of A) satisfy | fills following formula (I) is contained.
Formula (I) DSA6 / DSA2 + DSA3 + DSA6 <0.5
(In the formula, DSA2 is the degree of substitution of the hydroxyl group at the 2-position of the glucose unit with the acyl group (A) (hereinafter also referred to as “(A) substitution degree at the 2-position”), and DSA3 is the 3-position of the glucose unit. The degree of substitution of the hydroxyl group with the acyl group (A) (hereinafter also referred to as “the degree of substitution (A) at the 3-position”). DSA6 is the degree of substitution of the hydroxyl group at the 6-position of the glucose unit with the acyl group (A). Yes (hereinafter also referred to as “(A) degree of substitution at the 6-position”)

  The aliphatic acyl group (A) in the present invention is an acyl group having 5 to 30 carbon atoms, and may contain a linear, branched or cyclic structure or an unsaturated bond, and is not particularly limited. An acyl group having 5 to 20 carbon atoms, more preferably 6 to 18 carbon atoms, and most preferably 8 to 18 carbon atoms is preferable. Specific examples include pentanoyl group, hexanoyl group, heptanoyl group, octanoyl group, nonanoyl group, decanoyl group, undecanoyl group, dodecanoyl group, tridecanoyl group, tetradecanoyl group, pentatetradecanoyl group, hexadecanoyl group, heptadecanoyl. Group, octadecanoyl group, nonadecanoyl group, eicosanoyl group, heneicosanoyl group, docosanoyl group, tricosanoyl group, tetracosanoyl group, hexacosanoyl group, heptacosanoyl group, octacosanoyl group, triacosanoyl group, 2-ethylbutyryl group, 2,2-dimethyl Butyryl, t-butylacetyl, 2-methylvaleryl, 3-methylvaleryl, 4-methylvaleryl, 2-propylpentanoyl, 2-methylhexanoyl, 2-ethylhexa Noyl group, 2-methyl-2-pentenoyl group, 2,2-dimethylpentenoyl group, 2-octenoyl group, citronellyl group, undecylenoyl group, myristolyl group, palmitoleyl group, oleyl group, elaidyl group, eicosenoyl group, erucyl group , Nerbonyl group, 2,4-pentadienoyl group, 2,4-hexadienoyl group, 2,6-pentadienoyl group, geranyl group, linoleyl group, 11,14-eicosadienoyl group, linolenyl group, 8,11,14- Eicosatrienoyl group, aratidonyl group, 5,8,11,14,17-eicosapentaenoyl group, 4,7,10,13,16,19-docosahexanoyl group, cyclobutylacetyl group, cyclopentanoyl Group, cyclopentylacetyl group, cyclopentylpropionyl group, cyclohexane Sanoyl group, cyclohexylacetyl group, cyclohexylpropionyl group, cyclohexylbutyryl group, cyclohexylpentanoyl group, dicyclohexylacetyl group, 1-methyl-1-cyclohexanecarbonyl group, 2-methyl-1-cyclohexanecarbonyl group, 3-methyl-1-cyclohexanecarbonyl Group, 4-methyl-1-cyclohexanecarbonyl group, 4-t-butyl-1-cyclohexanecarbonyl group, 4-pentyl-1-cyclohexanecarbonyl group, 4-methyl-cyclohexaneacetyl group, cycloheptyl group, 2-norborneneacetyl group 4-pentylbicyclo [2,2,2] octane-1-carbonyl group, 3-oxotricyclo [2,2,1,0 (2,6)]-heptane-7-carbonyl group, 3-noradamantanca Boni group, 1-adamantanecarbonyl group, 1-adamantaneacetyl group, 1-cyclopentene-1-carbonyl group, 1-cyclopentene-1-acetyl group, 1-cyclohexene-1-carbonyl group, 1-methyl-2-cyclohexene Examples thereof include 1-carbonyl group.

  Among these, a pentanoyl group, hexanoyl group, heptanoyl group, octanoyl group, nonanoyl group, decanoyl group, undecanoyl group, dodecanoyl group, tridecanoyl group, tetradecanoyl group, pentatetradecanoyl group, hexadecanoyl group, heptadecanoyl group , Octadecanoyl group, nonadecanoyl group, 2-ethylbutyryl group, 2,2-dimethylbutyryl group, t-butylacetyl group, 2-methylvaleryl group, 3-methylvaleryl group, 4-methylvaleryl group, 2-propylpentanoyl group 2-methylhexanoyl group, 2-ethylhexanoyl group, 2-methyl-2-pentenoyl group, 2,2-dimethylpentenoyl group, 2-octenoyl group, citronellyl group, undecylenoyl group, myristolyl group, palmitoleyl group , Rail group, cyclobutylacetyl group, cyclopentanoyl group, cyclopentylacetyl group, cyclopentylpropionyl group, cyclohexanoyl group, cyclohexylacetyl group, cyclohexylpropionyl group, cyclohexylbutyryl group, cyclohexylpentanoyl group, dicyclohexylacetyl group, 1- Methyl-1-cyclohexanecarbonyl group, 2-methyl-1-cyclohexanecarbonyl group, 3-methyl-1-cyclohexanecarbonyl group, 4-methyl-1-cyclohexanecarbonyl group, 4-t-butyl-1-cyclohexanecarbonyl group, 4-pentyl-1 -Cyclohexanecarbonyl group and 4-methyl-cyclohexaneacetyl group can be mentioned.

  More preferably, pentanoyl group, hexanoyl group, heptanoyl group, octanoyl group, nonanoyl group, decanoyl group, undecanoyl group, dodecanoyl group, hexadecanoyl group, heptadecanoyl group, octadecanoyl group, nonadecanoyl group, 2-ethylbutyryl group, 2 , 2-dimethylbutyryl group, t-butylacetyl group, 2-methylvaleryl group, 3-methylvaleryl group, 4-methylvaleryl group, 2-propylpentanoyl group, 2-methylhexanoyl group, 2-ethylhexanoyl group, Undecylenoyl group, myristolyl group, palmitoleyl group, oleyl group, cyclopentanoyl group, cyclopentylacetyl group, cyclopentylpropionyl group, cyclohexanoyl group, cyclohexylacetyl group, cyclohexylpropionyl group, cyclyl Examples thereof include a cyclohexylbutyryl group, a cyclohexylpentanoyl group, a dicyclohexylacetyl group, a 4-t-butyl-1-cyclohexanecarbonyl group, a 4-pentyl-1-cyclohexanecarbonyl group, and a 4-methyl-cyclohexaneacetyl group.

  More preferably, a hexanoyl group, octanoyl group, nonanoyl group, decanoyl group, dodecanoyl group, hexadecanoyl group, octadecanoyl group, 2-ethylbutyryl group, 2,2-dimethylbutyryl group, t-butylacetyl group, 2 -Methylvaleryl group, 3-methylvaleryl group, 4-methylvaleryl group, 2-ethylhexanoyl group, palmitoleyl group, oleyl group, cyclohexanoyl group, cyclohexylacetyl group, cyclohexylpropionyl group, cyclohexylbutyryl group, 4-t- A butyl-1-cyclohexanecarbonyl group and a 4-pentyl-1-cyclohexanecarbonyl group.

  Most preferred are an octanoyl group, a hexanoyl group, and a dodecanoyl group.

  Examples of the aliphatic acyl group (B) having 2 to 4 carbon atoms in the present invention include an acetyl group, a propionyl group, and a butyryl group, and is preferably an acetyl group.

Furthermore, the cellulose body used in the present invention satisfies the following formula (I).
Formula (I): DSA6 / DSA2 + DSA3 + DSA6 <0.5
(In the formula, DSA2 is the degree of substitution of the hydroxyl group at the 2-position of the glucose unit with the acyl group (A) (hereinafter also referred to as “the degree of substitution (A) at the 2-position”), and DSA3 is the hydroxyl group at the 3-position. The degree of substitution with the acyl group (A) (hereinafter also referred to as “the degree of substitution (A) at the 3-position”), and DSA6 is the degree of substitution of the hydroxyl group at the 6-position with the acyl group (A) (hereinafter referred to as “6”). (Also referred to as (A) degree of substitution ”))

  The β-1,4-bonded glucose unit constituting cellulose has free hydroxyl groups at the 2nd, 3rd and 6th positions. In the present invention, the degree of substitution indicates a ratio in which any one of hydroxyl groups at the 2-position, 3-position and 6-position is substituted with a specific substituent. When the hydroxyl groups at the 2nd, 3rd and 6th positions are all substituted with substituents, the degree of substitution is 3.0.

In the present invention, the degree of substitution of substituents is determined by ¹ H-NMR or ¹³ C-NMR using the method described in Cellulose Communication 6, 73-79 (1999) and Chrality 12 (9), 670-674. Can be determined.

The cellulose body used in the present invention preferably satisfies the following formula (Ia), more preferably the following formula (Ib), and most preferably the following formula (Ic).
Formula (Ia): DSA6 / DSA2 + DSA3 + DSA6 <0.6
Formula (Ib): DSA6 / DSA2 + DSA3 + DSA6 ≦ 0.75
Formula (Ic): DSA6 / DSA2 + DSA3 + DSA6 = 1
It is preferable to set DSA6 / DSA2 + DSA3 + DSA6 within the above range because white turbidity is less likely to occur with respect to changes in the solvent composition during film formation.

Moreover, it is preferable that the cellulose body used for this invention satisfy | fills following formula (II). More preferably, the following formula (IIa) is satisfied, and most preferably, the following formula (IIb) is satisfied.
Formula (II): 2.2 <DSA + DSB ≦ 3.0
Formula (IIa): 2.5 ≦ DSA + DSB ≦ 3.0
Formula (IIb): 2.7 ≦ DSA + DSB ≦ 3.0
(In the formula, DSA is the substitution degree of the aliphatic acyl group (A) having 5 to 30 carbon atoms replacing the hydrogen atom of the hydroxyl group of cellulose, and DSA is the sum of DSA2, DSA3, and DSA6. DSB is the degree of substitution of the aliphatic acyl group (B) having 2 to 4 carbon atoms that replaces the hydrogen atom of the hydroxyl group of cellulose.)

  It is preferable to set DSA + DSB to 2.7 or more because the moisture content of the cellulosic film is lowered and the change in optical properties due to humidity fluctuations can be sufficiently reduced.

  In the present invention, the cellulose body refers to a compound having a cellulose skeleton obtained by introducing a functional group biologically or chemically using cellulose as a raw material, and cellulose acylate is preferred. . The cellulose used as a raw material for the cellulose body used in the present invention is a polymerization degree obtained by acid hydrolysis of wood pulp such as microcrystalline cellulose as well as natural cellulose such as cotton linter and wood pulp (hardwood pulp, conifer pulp). Cellulose having a low degree of polymerization (degree of polymerization of 100 to 300) may be used, and in some cases, it may be used in combination. Detailed descriptions of these raw material celluloses can be found in, for example, “Plastic Materials Course (17) Fibrous Resin” (Marusawa, Uda, Nikkan Kogyo Shimbun, published in 1970) and Invention Association Publication Technical Report 2001-1745 ( 7 to 8) and “Encyclopedia of Cellulose (page 523)” (edited by Cellulose Society, Asakura Shoten, published in 2000) can be used, and is not particularly limited.

  The average degree of polymerization of the cellulose used in the present invention is 10 to 1500, preferably 50 to 1000, and most preferably 100 to 500. By setting the average degree of polymerization to 500 or less, the viscosity of the dope solution of the cellulose body does not become too high, and the film production by casting tends to be easy. Moreover, it is preferable for the degree of polymerization to be 140 or more because the strength of the produced film tends to be further improved. The average degree of polymerization can be measured by the intrinsic viscosity method of Uda et al. (Kazuo Uda, Hideo Saito, “Journal of the Textile Society”, Vol. 18, No. 1, pages 105-120, 1962). Specifically, it can be measured according to the method described in JP-A-9-95538.

  Cellulose bodies used in the present invention include, for example, cellulose acetate manufactured by Aldrich (acetyl substitution degree 2.45), or cellulose acetate manufactured by Daicel Corporation (acetyl substitution degree 2.41 (trade name: L-70), 2.15 ( The product name: FL-70)) can be used as a starting material and can be obtained by reaction with the corresponding acid chloride.

  The cellulose body composition of the present invention preferably contains 70% by weight or more of the whole cellulose composition, more preferably 80% by weight or more, and most preferably 90% by weight or more.

The cellulose composition of the present invention can take various shapes such as particles, powders, fibers, lumps, solutions, melts, and films.
Since the raw material for film production is preferably in the form of particles or powder, the cellulose acylate composition after drying is crushed and sieved in order to make the particle size uniform and improve handling. Also good. When the cellulose acylate composition is in the form of particles, 90% by mass or more of the particles used preferably have a particle size of 0.5 to 5 mm. Moreover, it is preferable that 50 mass% or more of the particle | grains to be used have a particle size of 1-4 mm. The cellulose acylate composition particles preferably have a shape as close to a sphere as possible. The cellulose acylate composition of the present invention preferably has an apparent density of 0.5 to 1.3 g / cm ³ , more preferably 0.7 to 1.2 g / cm ³ , and particularly preferably 0.8 to 1. .15 g / cm ³ . The method for measuring the apparent density is defined in JIS K-7365.

  In the present invention, only one type of cellulose body may be used, or two or more types may be mixed and used. Moreover, polymer components other than the cellulose body and various additives can be appropriately mixed. The component to be mixed is preferably one having excellent compatibility with the cellulose body, and the transmittance when formed into a film is preferably 80% or more, more preferably 90% or more, and particularly preferably 92% or more. Is preferred.

<Additives>
In the cellulose body composition according to the present invention, various additives (for example, plasticizers, ultraviolet inhibitors, deterioration inhibitors, retardation (optical anisotropy) modifiers, fine particles, Peeling accelerators, infrared absorbers, etc.) can be added and they can be solid or oily. That is, the melting point and boiling point are not particularly limited. For example, mixing of UV absorbing materials at 20 ° C. or lower and 20 ° C. or higher, and similarly mixing of a plasticizer is described in, for example, JP-A-2001-151901. Examples of the peeling accelerator include ethyl esters of citric acid. Furthermore, infrared absorbing dyes are described, for example, in JP-A No. 2001-194522. Moreover, the addition time may be added at any stage in the dope preparation process, but may be performed by adding an additive to the final preparation process of the dope preparation process. Furthermore, the amount of each material added is not particularly limited as long as the function is manifested. Moreover, when a cellulose acylate film is formed in a multilayer, the kind and addition amount of the additive of each layer may differ. Examples thereof are described in Japanese Patent Application Laid-Open No. 2001-151902 and the like, but these are conventionally known techniques. It is preferable to adjust the glass transition temperature Tg of the cellulose acylate film to 80 to 180 ° C. and the elastic modulus measured with a tensile tester to 900 to 4000 MPa, depending on the selection of the kind and the amount of these additives, and 1200 to 3000 MPa. More preferably, it is prepared.
Further, for these details, materials described in detail on page 16 and after in the Invention Association Public Technical Bulletin No. 2001-1745 (issued March 15, 2001, Invention Association) are preferably used.

  The cellulose body film of the present invention can be obtained by forming a film using a solution (cellulose body composition) in which the aforementioned cellulose body and, if necessary, an additive are dissolved in an organic solvent.

(Organic solvent for cellulose acylate solution)
In the present invention, it is preferable to produce a cellulose acylate film by a solvent cast method, and the film is produced using a solution (dope) in which cellulose acylate is dissolved in an organic solvent. The organic solvent preferably used as the main solvent of the present invention is preferably a solvent selected from esters, ketones, ethers having 3 to 12 carbon atoms, and halogenated hydrocarbons having 1 to 7 carbon atoms. The ester, ketone and ether 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 main solvent, such as an alcoholic hydroxyl group. It may have a functional group of In the case of the main solvent having two or more kinds of functional groups, the number of carbon atoms may be within the specified range of the compound having any functional group.

  As described above, chlorine-based halogenated hydrocarbons may be used as the main solvent for the cellulose acylate film of the present invention, and as described in JIII Journal of Technical Disclosure 2001-1745 (pages 12-16), A non-chlorinated solvent may be used as the main solvent, and is not particularly limited to the cellulose acylate film of the present invention.

  When dissolving a cellulose acylate having an aliphatic acyl group having 5 to 30 carbon atoms, the optimum solvent usually varies depending on the type and degree of substitution, and the range of the optimum solvent composition is narrow. For example, when dissolving a cellulose acylate having an aliphatic acyl group having 18 or more carbon atoms, only a halogenated hydrocarbon must be used as a solvent. When an alcoholic solvent such as cellulose triacetate is added, the film becomes cloudy, and an optical film Cannot be used as Moreover, when dissolving the cellulose acylate having an aliphatic acyl group having about 5 to 12 carbon atoms, in addition to the halogen-based solvent, an alcohol solvent having 1 to 3 carbon atoms and an alcohol solvent having 4 to 6 carbon atoms are used. It must be mixed and used, and white turbidity occurs only when the mixing ratio differs by several percent. The cellulose acylate of the present invention solves this problem and can be dissolved using various solvents as described above.

  In addition, the solvent for the cellulose acylate solution and the film of the present invention is disclosed in the following patents, including its dissolution method, and is a preferred embodiment. They are, for example, JP 2000-95876 A, JP 12-95877 A, JP 10-324774 A, JP 8-152514 A, JP 10-330538 A, JP 9-95538 A. JP, 9-95557, JP 10-235664, JP 12-63534, JP 11-21379, JP 10-182853, JP 10-278056. JP-A-10-279702, JP-A-10-323853, JP-A-10-237186, JP-A-11-60807, JP-A-11-152342, JP-A-11-292988, This is described in, for example, Kaihei 11-60752 and JP-A-11-60752. According to these patents, not only the preferred solvent for the cellulose acylate of the present invention but also the physical properties of the solution and the coexisting substances to be coexisted are described, which is a preferred embodiment in the present invention.

[Dissolution process]
The method for dissolving the cellulose acylate solution (dope) of the present invention is not particularly limited, and may be performed at room temperature, further by a cooling dissolution method or a high temperature dissolution method, or a combination thereof. Regarding the preparation of the cellulose acylate solution in the present invention, and further the steps of solution concentration and filtration accompanying the dissolution step, the technical report of the Japan Society of Invention (Publication number 2001-1745, published on March 15, 2001, Japan Society of Invention) The manufacturing process described in detail on pages 22 to 25 is used.

  An example of a preferred dissolution method in the present invention is pressurized high temperature dissolution. As described in JP-A-5-163301, cellulose acylate is put into a solvent and stirred at normal pressure of 10 to 35 ° C. for 20 to 180 minutes, and then this solution is sent to a heat exchanger by a gear pump to 60 ° C. This is a method of heating and pressurizing to form a complete solution, and further cooling to room temperature with a cooling heat exchanger. The heating temperature is preferably 60 to 120 ° C, more preferably 70 to 100 ° C. At that time, a pressure corresponding to the vapor pressure of the solvent at the melting temperature is applied. The heating time needs 1 minute or more, and it is preferable to heat for 10 minutes to 6 hours. More preferably, heating is performed for 30 minutes to 3 hours. The concentration of cellulose acylate in the solution is preferably 12 to 30% by mass, more preferably 14 to 25% by mass. When the concentration is high, dissolution becomes difficult, and when the concentration is low, the viscosity is low and casting becomes difficult, and the concentration is burdened, which is not preferable. Therefore, 15 to 20% by mass is particularly preferable.

Each component may be coarsely mixed in advance and then placed in a container. Moreover, you may put into a container sequentially. The container must be configured to allow stirring. The container can be pressurized by injecting an inert gas such as nitrogen gas. Moreover, you may utilize the raise of the vapor pressure of the solvent by heating. Or after sealing a container, you may add each component under pressure.
When heating, it is preferable to heat from the outside of the container. For example, a jacket type heating device can be used. The entire container can also be heated by providing a plate heater outside the container and piping to circulate the liquid.

It is preferable to provide a stirring blade inside the container and use this to stir. The stirring blade preferably has a length that reaches the vicinity of the wall of the container. A scraping blade is preferably provided at the end of the stirring blade in order to renew the liquid film on the vessel wall.
Instruments such as a pressure gauge and a thermometer may be installed in the container. Each component is dissolved in a solvent in a container. The prepared dope is taken out of the container after cooling, or taken out and then cooled using a heat exchanger or the like.

[Cooling process]
Performing a cooling step of cooling the dope to −100 to −10 ° C. before the heating step is also effective for obtaining a film having good optical properties. In a system that cannot be easily dissolved at room temperature and a system that has a large amount of insoluble matter, a good dope can be prepared by using cooling, heating, or a combination of both. By cooling, the solvent can be rapidly and effectively infiltrated into the cellulose acylate, and dissolution is promoted. An effective temperature condition is −100 to −10 ° C. In the cooling process, it is desirable to use an airtight container in order to avoid moisture mixing due to condensation during cooling. Further, if the pressure is reduced during cooling, the cooling time can be shortened. In order to perform decompression, it is desirable to use a pressure-resistant container. It is also effective in the present invention that this cooling step is performed after the heating step. When the dissolution is insufficient, the cooling process to the heating process may be repeated.

  Prior to casting, undissolved matter, dust, impurities, etc. are removed using a filter medium made of wire mesh laminate, sintered metal, woven fabric, nonwoven fabric or paper. For the filtration of the cellulose acylate solution, it is preferable to use a filter having an absolute filtration accuracy of 1 to 100 μm. Filtration may be performed with a fine filter sequentially from a filter having a high filtration accuracy over a plurality of stages. The filtration accuracy of the preferred final stage filter medium is 1 to 50 μm. A filter medium of 3 to 20 μm is more preferable. The filtration pressure is preferably 1.6 MPa or less, more preferably 1.2 MPa or less, and particularly preferably 1 MPa or less. Although the filtration pressure is low, there is no problem. However, if the filtration pressure is too high, there is a high possibility that the filter medium will be damaged, and there is a high possibility that impurities and insoluble matters will leak, which is not preferable. When the dope is concentrated before casting, it is desirable to filter once before concentration.

(Casting)
As a solution casting method, a method in which the prepared dope is uniformly extruded from a pressure die onto a metal support, and a method using a doctor blade in which the film thickness of the dope once cast on the metal support is adjusted with a blade. Alternatively, there is a method using a reverse roll coater that adjusts with a reverse rotating roll, and a method using a pressure die is preferable. The pressure die includes a coat hanger type and a T die type, and any of them can be preferably used. In addition to the methods listed here, it can be carried out by various methods of casting a cellulose triacetate solution known in the art, and by setting each condition in consideration of differences in the boiling point of the solvent used, etc. The same effects as described in the above publication can be obtained. The endlessly running metal support used for producing the cellulose acylate film of the present invention includes a drum whose surface is mirror-finished by chrome plating and a stainless steel belt whose surface is mirror-finished by surface polishing (referred to as a band). May be used). One or two or more pressure dies used for producing the cellulose acylate film of the present invention may be installed above the metal support. Preferably 1 or 2 groups. When two or more units are installed, the amount of dope to be cast may be divided into various ratios for each die, or the dope may be fed to the dies from each of a plurality of precision quantitative gear pumps. The temperature of the cellulose acylate solution used for casting is preferably −10 to 55 ° C., more preferably 25 to 50 ° C. In that case, all of the steps may be at the same temperature or may be different at different points in the step. If they are different, the temperature may be a desired temperature just before casting.

(Dry)
The drying of the dope on the metal support involved in the production of the cellulose acylate film is generally performed by applying hot air from the surface side of the metal support (drum or belt), that is, the surface of the web on the metal support, A method of applying hot air from the back of the drum or belt, contacting the temperature-controlled liquid from the back of the belt or drum opposite the dope casting surface, and heating the drum or belt by heat transfer to control the surface temperature Although there is a heat transfer method, the back surface liquid heat transfer method is preferable. The surface temperature of the metal support before casting may be any number as long as it is not higher than the boiling point of the solvent used for the dope. However, in order to promote drying and to lose fluidity on the metal support, the temperature should be set to 1 to 10 degrees lower than the boiling point of the lowest boiling solvent used. Is preferred. This is not the case when the casting dope is cooled and peeled off without drying.

  Regarding the drying method in the solvent cast method, U.S. Pat. Nos. 45-4554, 49-5614, JP-A-60-176834, JP-A-60-203430, and JP-A-62-115035. Drying on the band or drum can be performed by blowing an inert gas such as air or nitrogen.

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

  The winder used for the production of the cellulose acylate film used in the present invention may be a commonly used winder such as a constant tension method, a constant torque method, a taper tension method, or a program tension control method with a constant internal stress. It can be wound up by a take-up method.

[Glass transition temperature of cellulose acylate film]
The glass transition temperature of the cellulose acylate film can be measured by the method described in JIS standard K7121.
The glass transition temperature of the cellulose acylate film of the present invention is preferably from 80 ° C. to 200 ° C., more preferably from 100 ° C. to 170 ° C. The glass transition temperature can be lowered by including a low molecular compound such as a plasticizer or a solvent.

[Film thickness]
The thickness (dry film thickness) of the cellulose acylate film of the present invention is preferably 20 μm or more and 180 μm or less, and more preferably 25 μm or more and 140 μm or less. Most preferably, it is 35 μm or more and 110 μm or less.

[Equilibrium moisture content]
The moisture content is measured by the Karl Fischer method using a cellulose acylate film sample of 7 mm × 35 mm of the present invention with a moisture meter and a sample drying apparatus (Aqua Counter AQ-200, LE-20S, both Hiranuma Sangyo Co., Ltd.). taking measurement. It is calculated by dividing the amount of water (g) by the sample mass (g).

  The equilibrium moisture content of the cellulose acylate film of the present invention is preferably 0 to 3% at 25 ° C. and 80% RH. It is more preferably 0.1 to 2%, and particularly preferably 0.3 to 1.5%. An equilibrium water content of 3% or more is not preferable because the dependency of retardation on humidity change is large when used as a support for an optical compensation film, and the optical compensation performance is lowered.

[Elastic modulus of cellulose acylate film]
The elastic modulus of the cellulose acylate film can be determined by a tensile test. The cellulose acylate film of the present invention is preferably 0.9 GPa or more and 6.0 GPa or less, more preferably 1.2 GPa or more and 5.0 GPa or less in at least one direction of the width direction or the casting direction, more preferably 2.0 GPa or more and 4.5 GPa or less. Is most preferred.

(Extension process)
In the cellulose acetate film of the present invention, the retardation can be adjusted by a stretching treatment. Furthermore, there is also a method of positively stretching in the width direction. For example, JP-A-62-115035, JP-A-4-152125, JP-A-4-284111, JP-A-4-298310, and JP-A-11 -48271, and the like. In order to increase the in-plane retardation value of the cellulose acylate film, the produced film is stretched.
The film is stretched at room temperature or under heating conditions. The heating temperature is preferably not higher than the glass transition temperature of the film. The stretching of the film may be uniaxial stretching only in the longitudinal or lateral direction, or may be simultaneous or sequential biaxial stretching. Stretching is performed at 1 to 300%. The stretching is preferably 1 to 200%, particularly preferably 1 to 100%. The birefringence of the optical film is preferably such that the refractive index in the width direction is larger than the refractive index in the length direction. Therefore, it is preferable to stretch more in the width direction. The stretching process may be performed in the middle of the film forming process, or the raw material wound by BR> A film forming may be stretched. In the former case, the stretching may be performed in a state including the residual solvent amount, and the stretching can be preferably performed at a residual solvent amount of 2 to 30%.

[Optical properties of cellulose film]

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

When the film to be measured is represented by a uniaxial or biaxial refractive index ellipsoid, Rth (λ) is calculated by the following method.
Rth (λ) is the above-mentioned Re (λ), with the in-plane slow axis (determined by KOBRA 21ADH or WR) as the tilt axis (rotary axis) (if there is no slow axis, any in-plane The light of wavelength λ nm is incident from each of the inclined directions in steps of 10 degrees from the normal direction to 50 degrees on one side with respect to the film normal direction (with the direction of the rotation axis as the rotation axis). KOBRA 21ADH or WR is calculated based on the measured retardation value, the assumed average refractive index, and the input film thickness value.

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

  Formula (1)

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

  Formula (2)

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

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

(surface treatment)
The cellulose acylate film of the present invention can achieve improved adhesion between the cellulose acylate film and each functional layer (for example, the undercoat layer and the 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 JIII Journal of Technical Disclosure No. 2001-1745 (issued on March 15, 2001, Invention Association). Note that, in the plasma treatment at atmospheric pressure which has been attracting attention in recent years, for example, irradiation energy of 20 to 500 Kgy is used under 10 to 1000 Kev, and more preferably irradiation energy of 20 to 300 Kgy is used under 30 to 500 Kev. Among these, an alkali saponification treatment is particularly preferable, and it is extremely effective as a surface treatment of a cellulose acylate film.

The alkali saponification treatment is preferably carried out by a method of directly immersing the cellulose acylate film in a saponification solution tank or a method of applying a saponification solution to the cellulose acylate film.
Examples of the coating method include a dip coating method, a curtain coating method, an extrusion coating method, a bar coating method, and an E-type coating method. The solvent of the alkali saponification coating solution has good wettability because it is applied to the transparent support of the saponification solution, and the surface state remains good without forming irregularities on the surface of the transparent support by the saponification solution solvent. It is preferred to select a solvent to keep. Specifically, an alcohol solvent is preferable, and isopropyl alcohol is particularly preferable. An aqueous solution of a surfactant can also be used as a solvent. The alkali of the alkali saponification coating solution is preferably an alkali that dissolves in the above solvent, and more preferably KOH or NaOH. The pH of the saponification coating solution is preferably 10 or more, more preferably 12 or more. The reaction conditions during the alkali saponification are preferably 1 second to 10 minutes at room temperature, more preferably 5 seconds to 7 minutes, and particularly preferably 20 seconds to 5 minutes. After the alkali saponification reaction, it is preferable to wash the surface on which the saponification solution is applied with water or with an acid and then with water.

[Phase difference film]
The cellulose body film of the present invention can be used as a retardation film.
In addition, the functional layer described in detail on pages 32 to 45 of the Invention Association public technical bulletin (public technical number 2001-1745, issued March 15, 2001, Invention Association) on the cellulose body film of the present invention. It is preferable to combine them. Among these, application of a polarizing film (formation of a polarizing plate), application of an optical compensation layer (optical compensation film), and application of an antireflection layer (antireflection film) are preferable.

[Optical compensation film]
The optical compensation film of the present invention has an optically anisotropic layer formed by orienting a liquid crystalline compound on the cellulose film or retardation film of the present invention.
The optically anisotropic layer is for compensating the liquid crystal compound in the liquid crystal cell in the black display of the liquid crystal display device, and forms an alignment film on the cellulose body film and further imparts optical anisotropy. Formed with.

(Functionalization of polarizing plate)
The polarizing plate of the present invention includes an optical compensation film for LCD, a retardation film such as a λ / 4 plate for application to a reflective LCD, an antireflection film for improving display visibility, a brightness enhancement film, and a hard coat. It is preferably used as a functionalized polarizing plate combined with an optical film having functional layers such as a layer, a forward scattering layer, and an antiglare (antiglare) layer.

The functional optical film used in combination with the polarizing plate of the present invention will be described below.
(1) Optical Compensation Film The polarizing plate of the present invention includes TN (Twisted Nematic), IPS (In-Plane Switching), OCB (Optically Compensated Bend), VA (Vertically Aligned), ECB (Electrically Bold). It can be used in combination with the optical compensation film proposed for the mode.

As an optical compensation film for TN mode, Journal of the Japan Printing Society, Vol. 36, No. 3 (1999) p. 40-44, monthly display August issue (2002) p. No. 20-24, JP-A-4-229828, JP-A-6-75115, JP-A-6-214116, JP-A-8-50206, etc. are preferably used in combination with WV film (manufactured by Fuji Photo Film Co., Ltd.). The
A preferable configuration of the optical compensation film for the TN mode has an alignment layer and an optically anisotropic layer in this order on a transparent polymer film. The optical compensation film may be used by being bonded to a polarizing plate via an adhesive, but SID'00 Dig. , P. As described in 551 (2000), it is particularly preferable from the viewpoint of thinning that one of the protective films of the polarizer is also used.

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

The optically anisotropic layer preferably contains a liquid crystalline compound. The liquid crystal compound used in the present invention particularly preferably has a discotic compound (discotic liquid crystal). The discotic liquid crystal molecule has a disk-like core portion like the triphenylene derivative represented by the general formula B, and has a structure in which side chains extend radially therefrom. In order to impart stability over time, it is also preferable to further introduce a group that reacts with heat, light or the like. Preferred examples of the discotic liquid crystal are described in JP-A-8-50206.
The discotic liquid crystal molecules are aligned almost parallel to the film plane with a pretilt angle in the rubbing direction in the vicinity of the alignment layer, and the discotic liquid crystal molecules are oriented so that they are perpendicular to the plane on the opposite air side. is doing. The discotic liquid crystal layer as a whole has a hybrid alignment, and this layer structure can realize a wide viewing angle of a TN mode TFT-LCD.

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

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

  A preferred embodiment of the optical compensation film of the present invention is a cellulose acylate film as a transparent substrate film, an alignment layer provided thereon, and an optically anisotropic layer comprising a discotic liquid crystal formed on the alignment layer And the optically anisotropic layer is crosslinked by UV light irradiation.

  In addition to the above, when the optical compensation film and the polarizing plate of the present invention are combined, for example, as described in JP-A-07-198942, the birefringence has an optical axis in the direction intersecting the plate surface. It is also preferable to laminate with a retardation plate exhibiting anisotropy, or to make the dimensional change rate of the protective film and the optically anisotropic layer substantially the same as described in JP-A No. 2002-258052. be able to. Further, as described in JP-A-12-258632, the moisture content of the polarizing plate bonded to the optical compensation film is set to 2.4% or less, or as described in JP-A-2002-267839. It is also preferable to make the contact angle of the optical compensation film surface with water 70 ° or less.

  The IPS mode liquid crystal cell optical compensation film is used for optical compensation of liquid crystal molecules aligned in parallel to the substrate surface and improvement of viewing angle characteristics of the orthogonal transmittance of the polarizing plate during black display without an electric field. In the IPS mode, black is displayed when no electric field is applied, and the transmission axes of the pair of upper and lower polarizing plates are orthogonal. However, when observed from an oblique direction, the crossing angle of the transmission axes is not 90 °, and leakage light is generated, resulting in a decrease in contrast. When the polarizing plate of the present invention is used in an IPS mode liquid crystal cell, the in-plane retardation as described in JP-A-10-54982 is close to 0 and the thickness direction is reduced in order to reduce leakage light. It is preferably used in combination with an optical compensation film having a retardation.

  An optical compensation film for OCB mode liquid crystal cells is used to improve the viewing angle characteristics of black display by optically compensating the liquid crystal layer that is vertically aligned at the center of the liquid crystal layer by applying an electric field and tilted in the vicinity of the substrate interface. Is done. When the polarizing plate of the present invention is used in an OCB mode liquid crystal cell, it is preferably used in combination with an optical compensation film in which a discotic liquid crystalline compound as described in US Pat. No. 5,805,253 is hybrid-aligned.

  The VA mode liquid crystal cell optical compensation film improves the viewing angle characteristics of black display in a state in which liquid crystal molecules are vertically aligned with respect to the substrate surface when no electric field is applied. As such an optical compensation film, a film having an in-plane retardation close to 0 and having a retardation in the thickness direction as described in Japanese Patent No. 2866372, or a discotic compound is applied to the substrate. In order to prevent the deterioration of the orthogonal transmittance in the oblique direction of the polarizing plate, the film in which the parallel film, the stretched film having the same in-plane retardation value are laminated so that the slow axes are orthogonal, It is preferably used in combination with a laminate of films made of such rod-like compounds.

(Hard coat film, antiglare film, antireflection film)
The cellulose-based film of the present invention can be preferably applied to a hard coat film, an antiglare film and an antireflection film. For the purpose of improving the visibility of flat panel displays such as LCD, PDP, CRT, EL, etc., any or all of a hard coat layer, an antiglare layer and an antireflection layer are provided on one or both sides of the cellulose acylate film of the present invention. Can be granted. Preferred embodiments of such an antiglare film and antireflection film are described in detail in pages 54 to 57 of the Japan Society of Invention and Innovation Technical Bulletin No. 2001-1745 (issued on March 15, 2001, Japan Society of Invention). The cellulose acylate film of the present invention can be preferably used.

〔Polarizer〕
The polarizing plate of the present invention is a polarizing plate comprising a polarizing film and two protective films sandwiching the polarizing film, and at least one of the two protective films is a cellulose body film or a retardation film of the present invention. Alternatively, at least one optical compensation film is included.

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

  The cellulose acylate film of the present invention is preferably bonded to the polarizer so that the transmission axis of the polarizer matches the slow axis of the cellulose acylate film of the present invention. In addition, when the polarizing plate produced under polarizing plate crossed Nicols was evaluated, the orthogonality accuracy between the slow axis of the cellulose acylate film of the present invention and the absorption axis of the polarizer (axis orthogonal to the transmission axis) was 1. It was found that when it was larger than 0 °, the polarization degree performance under the polarizing plate crossed Nicols was lowered and light leakage occurred. In this case, when combined with a liquid crystal cell, sufficient black level and contrast cannot be obtained. Therefore, the deviation between the direction of the main refractive index nx of the cellulose acylate film of the present invention and the direction of the transmission axis of the polarizing plate is preferably within 1 °, and preferably within 0.5 °.

  UV3100PC (made by Shimadzu Corp.) was used for the single plate transmittance TT, the parallel transmittance PT, and the orthogonal transmittance CT of the polarizing plate. In the measurement, measurement was performed in the range of 380 nm to 780 nm, and the average value of 10 measurements was used for each of the single plate, parallel, and orthogonal transmittance. The polarizing plate durability test was performed as follows in two types of forms in which (1) only the polarizing plate and (2) the polarizing plate were bonded to glass via an adhesive. For the measurement of only the polarizing plate, two orthogonal and identical ones were prepared and measured so that the optical compensation film was sandwiched between the two polarizers. Two samples (approx. 5 cm × 5 cm) are prepared by attaching a polarizing plate on glass so that the optical compensation film is on the glass side. In single-plate transmittance measurement, the sample is set with the film side facing the light source. Each of the two samples is measured, and the average value is taken as the transmittance of the single plate. The preferable range of polarization performance is 40.0 ≦ TT ≦ 45, 0, 30.0 ≦ PT ≦ 40.0, CT ≦ 2 in the order of single plate transmittance TT, parallel transmittance PT, and orthogonal transmittance CT, respectively. 0.0, and more preferable ranges are 41.0 ≦ TT ≦ 44.5, 34 ≦ PT ≦ 39.0, and CT ≦ 1.3 (the unit is%). In the polarizing plate durability test, the amount of change is preferably smaller.

  In addition, the polarizing plate of the present invention has an orthogonal single plate transmittance change ΔCT (%) and a polarization degree change ΔP when left at 60 ° C. and 95% RH for 500 hours, with the following formulas (j) and (k It is preferable that at least one of the above is satisfied.

(J) −6.0 ≦ ΔCT ≦ 6.0
(K) -10.0 ≦ ΔP ≦ 0.0

Here, the amount of change is a value obtained by subtracting the measured value before the test from the measured value after the test.
Satisfying this requirement is preferable because stability during use or storage of the polarizing plate can be ensured.

(Image display device)
The image display device of the present invention includes at least one of the cellulose body film, retardation film, optical compensation film, and polarizing plate of the present invention.

(Image display device using polarizing plate)
Next, a liquid crystal display device will be described as an example of an image display device in which the polarizing plate of the present invention is used. In the present invention, the liquid crystal display device has two polarizing plates arranged on both sides of the liquid crystal cell, and at least one of the polarizing plates is the polarizing plate of the present invention.

The liquid crystal display device includes a liquid crystal cell having a liquid crystal supported between two electrode substrates, two polarizing elements disposed on both sides thereof, and at least one sheet between the liquid crystal cell and the polarizing element. The 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 film of the present invention can be used for liquid crystal cells in various display modes. TN (Twisted Nematic), IPS (In-Plane Switching), FLC (Ferroelectric Liquid Crystal), AFLC (Anti-Ferroly Liquid Liquid Crystal), OCB (Optically Charged STP). Various display modes such as ECB (Electrically Controlled Birefringence) and HAN (Hybrid Aligned Nematic) have been proposed. In addition, a display mode in which the above display mode is oriented and divided has been proposed. The cellulose film of the present invention is effective in any display mode liquid crystal display device. Further, it is effective in any of a transmissive type, a reflective type, and a transflective liquid crystal display device.

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

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

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

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

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

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

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

Example 1
Cellulose acetate was used as a starting material and reacted with acid chloride to obtain cellulose bodies shown in Table 1, respectively. Hereinafter, the production of each cellulose body will be described in detail.

[Synthesis Example 1: Synthesis of Intermediate Compound T-1]
200 g of cellulose acetate having a substitution degree of 2.95, 4000 mL of dimethyl sulfoxide, and 90 mL of water were weighed in a 5 L three-necked flask equipped with a mechanical stirrer, thermometer, condenser, and dropping funnel, and stirred at room temperature. 380 mL of 50% dimethylamine aqueous solution (Wako Pure Chemical Industries, Ltd.) was slowly added dropwise thereto, followed by stirring at 60 ° C. for 10 hours. After the reaction, the mixture was allowed to cool to room temperature, and the reaction solution was poured into 20 L of methanol with vigorous stirring, whereby a white solid was precipitated. The white solid was filtered off by suction filtration and washed with a large amount of methanol three times. The obtained white solid was dried at 60 ° C. overnight and then vacuum-dried at 90 ° C. for 6 hours to obtain 170 g of the intended comparative compound intermediate compound T-1 as a white powder.

[Synthesis Example 2: Synthesis of Exemplary Compound A-1]
To a 2 L three-necked flask equipped with a mechanical stirrer, thermometer, condenser, and dropping funnel, 40 g of cellulose acetate of intermediate compound T-1 and 400 mL of pyridine (manufactured by Aldrich) were weighed and stirred at room temperature. Here, 16 mL of octanoyl chloride (manufactured by Aldrich) was slowly added dropwise and stirred at 50 ° C. for 5 hours. After the reaction, the mixture was allowed to cool to room temperature, and the reaction solution was poured into 20 L of methanol with vigorous stirring, whereby a white solid was precipitated. The white solid was filtered off by suction filtration and washed with a large amount of methanol three times. The obtained white solid was dried at 60 ° C. overnight and then vacuum-dried at 90 ° C. for 6 hours to obtain 42 g of the objective exemplified compound A-1 as a white powder.

[Synthesis Example 3: Synthesis of Intermediate Compound T-2]
200 g of diacetylcellulose (acetyl substitution degree 2.15) was dissolved in 1500 mL of tetrahydrofuran. To this, 215 mL of pyridine and 633 g of triphenylmethyl chloride were added and stirred at 70 ° C. for 11 hours. After adding 300 mL of methanol and confirming that the exotherm had subsided, the polymer was precipitated by mixing with 7000 mL of methanol and purified by continuous washing with methanol at 40-50 ° C. to obtain 216 g of intermediate compound T-2. .

[Synthesis Example 4: Synthesis of Intermediate Compound T-3]
In the production of the exemplified compound A-1, 40 g of the intermediate compound T-1 is changed to 80 g of T-2, and 36 mL of octanoyl chloride (manufactured by Aldrich) is changed to 96 mL of hexanoyl chloride (manufactured by Aldrich). 82 g of the intermediate compound T-3 was obtained as a white powder in the same manner.

[Synthesis Example 5: Synthesis of Exemplary Compound A-2]
82 g of intermediate compound T-3 was dissolved in 500 mL of dichloromethane, and 31 parts by mass of a 25% hydrobromic acid / acetic acid solution was added. After stirring at room temperature for 5 minutes, 10 parts by mass of triethylamine dissolved in 70 parts by mass of methanol was added and further stirred for 20 minutes. The polymer was precipitated by mixing with methanol, continuously washed with methanol at 40 to 50 ° C., filtered, and dried under vacuum to obtain 40 g of Exemplified Compound A-2.

[Synthesis Example 6: Synthesis of Intermediate Compound T-4]
In the production of the exemplified compound A-1, 40 g of the intermediate compound T-1 is changed to 80 g of T-2, and 36 mL of octanoyl chloride (Aldrich) is 192 mL of lauroyl chloride (Dodecanoyl chloride) (Aldrich). 82 g of intermediate compound T-4 was obtained as a white powder in the same manner except for changing to

[Synthesis Example 7: Synthesis of Exemplary Compound A-3]
82 g of intermediate compound T-4 was dissolved in 500 mL of dichloromethane, and 31 parts by mass of a 25% hydrobromic acid / acetic acid solution was added. After stirring at room temperature for 5 minutes, 10 parts by mass of triethylamine dissolved in 70 parts by mass of methanol was added and further stirred for 20 minutes. The polymer was precipitated by mixing with methanol, continuously washed with methanol at 40 to 50 ° C., filtered, and dried under vacuum to obtain 45 g of exemplary compound A-3.

[Synthesis Example 8: Synthesis of Exemplary Compound A-4]
Into a 3 L three-necked flask equipped with a mechanical stirrer, thermometer, condenser, and dropping funnel, 40 g of cellulose acetate having a substitution degree of 2.15 and 400 ml of pyridine were weighed and stirred at room temperature. To this, 69 mL of n-octanoyl chloride obtained in the previous reaction was slowly added dropwise, and after addition, the mixture was further stirred at 60 ° C. for 6 hours. After the reaction, the mixture was allowed to cool to room temperature, and the reaction solution was poured into 10 L of methanol with vigorous stirring, whereby a white solid was precipitated. The white solid was filtered off by suction filtration and washed with a large amount of methanol three times. The obtained white solid was dried at 60 ° C. overnight and then vacuum dried at 90 ° C. for 6 hours to obtain 40 g of the intended exemplified compound A-4 as a white powder. The average degree of polymerization was 256.

[Synthesis Example 9: Synthesis of Intermediate Compound T-5]
To a 2 L three-necked flask equipped with a mechanical stirrer, thermometer, condenser, and dropping funnel, 40 g of cellulose acetate having a substitution degree of 2.15, 18 mL of pyridine (manufactured by Aldrich), and 400 mL of acetone were weighed and stirred at room temperature. Here, 36 mL of octanoyl chloride (manufactured by Aldrich) was slowly added dropwise and stirred at 50 ° C. for 5 hours. After the reaction, the mixture was allowed to cool to room temperature, and the reaction solution was poured into 20 L of methanol with vigorous stirring, whereby a white solid was precipitated. The white solid was filtered off by suction filtration and washed with a large amount of methanol three times. The obtained white solid was dried at 60 ° C. overnight and then vacuum dried at 90 ° C. for 6 hours to obtain 41 g of the intended intermediate compound T-5 as a white powder.

[Synthesis Example 10: Synthesis of Comparative Compound B-1]
40 g of intermediate compound T-5 obtained in the previous reaction, 400 mL of pyridine (manufactured by Aldrich), and 400 mL of dichloromethane were weighed into a 3 L three-necked flask equipped with a mechanical stirrer, thermometer, condenser, and dropping funnel, and room temperature. And stirred. To this, 400 mL of acetic anhydride was slowly added dropwise, 0.05 g of dimethylaminopyridine was added, and the mixture was stirred at 50 ° C. for 5 hours. After the reaction, the mixture was allowed to cool to room temperature, and the reaction solution was poured into 20 L of methanol with vigorous stirring, whereby a white solid was precipitated. The white solid was filtered off by suction filtration and washed with a large amount of methanol three times. The obtained white solid was dried at 60 ° C. overnight and then vacuum dried at 90 ° C. for 6 hours to obtain 40 g of the intended comparative compound B-1 as a white powder.

[Synthesis Example 11: Synthesis of Comparative Compound B-2]
In the production of the intermediate compound T-5, cellulose acetate having a substitution degree of 2.15 is changed to cellulose acetate having a substitution degree of 2.42, 36 mL of octanoyl chloride (manufactured by Aldrich) is added to 24 mL of hexanoyl chloride (manufactured by Aldrich). 40 g of the target comparative compound B-2 was obtained as a white powder in the same manner except that 18 mL of pyridine was changed to 14 mL.

[Synthesis Example 12: Synthesis of Comparative Compound B-3]
In the production of the intermediate compound T-5, cellulose acetate having a substitution degree of 2.15 is changed to cellulose acetate having a substitution degree of 2.42, and 36 mL of octanoyl chloride (manufactured by Aldrich) is added to lauroyl chloride (dodecanoyl chloride) (Aldrich). 40 g and pyridine 18 mL were changed to 14 mL in the same manner to obtain 40 g of the target comparative compound B-3 as a white powder.

[Synthesis Example 13: Synthesis of Comparative Compound B-4]
A 3 L three-necked flask equipped with a mechanical stirrer, thermometer, condenser, and dropping funnel was weighed with 40 g of cellulose acetate having a substitution degree of 2.15, 36 ml of pyridine, and 400 ml of acetone and stirred at room temperature. To this, 60 mL of n-hexanoyl chloride (manufactured by Aldrich) obtained in the previous reaction was slowly added dropwise, followed by further stirring at 50 ° C. for 2 hours. After the reaction, the mixture was allowed to cool to room temperature, and the reaction solution was poured into 10 L of methanol with vigorous stirring, whereby a white solid was precipitated. The white solid was filtered off by suction filtration and washed with a large amount of methanol three times. The obtained white solid was dried at 60 ° C. overnight and then vacuum-dried at 90 ° C. for 6 hours to obtain 39 g of the objective exemplified compound B-4 as a white powder. The average degree of polymerization was 255.

[Synthesis Example 14: Synthesis of triacetylcellulose (intermediate compound T-6)]
In a 5 L three-necked flask equipped with a mechanical stirrer, thermometer, condenser, and dropping funnel, 200 g of cellulose acetate having a substitution degree of 2.93 and 2000 mL of pyridine were weighed and stirred at room temperature. To this, 2000 mL of anhydrous benzoyl chloride (manufactured by Aldrich) was slowly added dropwise, 0.5 g of dimethylaminopyridine was added, and the mixture was stirred at 40 ° C. for 2 hours. After the reaction, the mixture was allowed to cool to room temperature, and the reaction solution was poured into 20 L of methanol with vigorous stirring, whereby a white solid was precipitated. The white solid was filtered off by suction filtration and washed with a large amount of methanol three times. The obtained white solid was dried at 60 ° C. overnight and then vacuum-dried at 90 ° C. for 6 hours to obtain 201 g of an intermediate compound T-6 with eyes / BR> I as a white powder.

[Synthesis Example 15: Synthesis of Comparative Compound B-5]
200 g of intermediate compound T-6 obtained in the previous reaction, 4000 mL of dimethyl sulfoxide, and 90 mL of water were weighed into a 5 L three-necked flask equipped with a mechanical stirrer, thermometer, condenser, and dropping funnel, and stirred at room temperature. 380 mL of 50% dimethylamine aqueous solution (Wako Pure Chemical Industries, Ltd.) was slowly added dropwise thereto, followed by stirring at 60 ° C. for 3 hours. After the reaction, the mixture was allowed to cool to room temperature, and the reaction solution was poured into 20 L of methanol with vigorous stirring, whereby a white solid was precipitated. The white solid was filtered off by suction filtration and washed with a large amount of methanol three times. The obtained white solid was dried at 60 ° C. overnight, and then vacuum-dried at 90 ° C. for 6 hours to obtain 180 g of the intended comparative compound B-5 as a white powder.

[Synthesis Example 16: Synthesis of Intermediate Compound T-7]
In the production of the exemplified compound A-1, except that 40 g of the intermediate compound T-1 is changed to 80 g of T-2, and octanoyl chloride (manufactured by Aldrich) 36 mL is changed to acetyl chloride (manufactured by Aldrich) 36 mL. Similarly, 80 g of intermediate compound T-7 was obtained as a white powder in the same manner except that.

[Synthesis Example 17: Synthesis of Comparative Compound B-6]
80 g of the intermediate compound T-7 was dissolved in 500 mL of dichloromethane, and 31 parts by mass of a 25% hydrobromic acid / acetic acid solution was added. After stirring at room temperature for 5 minutes, 10 parts by mass of triethylamine dissolved in 70 parts by mass of methanol was added and further stirred for 20 minutes. The polymer was precipitated by mixing with methanol, continuously washed with methanol at 40 to 50 ° C., filtered and dried under vacuum to obtain 39 g of Comparative Compound B-6.

(Example 2)
<Preparation of cellulose body dope>
The following raw materials were put into a mixing tank, stirred while heating, dissolved, and a dope having a cellulose body was prepared. At this time, instead of A-1, cellulose bodies A-2 to 4 and B-1 to 7 were used to prepare cellulose body dopes D1 to 11 of the formulation A in the same manner as described above.

<Cellulose body dope (formulation A)>
Cellulose body A-1 100 parts by mass Methylene chloride (first solvent) 614 parts by mass

  Furthermore, the following raw materials were put into a mixing tank, stirred while heating, dissolved, and a dope having a cellulose body was prepared. At this time, in place of A-1, cellulose bodies A-2 to 4 and B-1 to 7 were used, and cellulose body dopes D12 to 22 of Formulation B were prepared in the same manner as described above.

<Cellulose body dope (prescription B)>
Cellulose body A-1 100 parts by mass Methylene chloride (first solvent) 534 parts by mass Methanol (second solvent) 80 parts by mass

  Furthermore, the following raw materials were put into a mixing tank, stirred while heating, dissolved, and a dope having a cellulose body was prepared. At this time, instead of A-1, cellulose bodies A-2 to 4 and B-1 to 7 were used to prepare cellulose body dopes D23 to 33 of the formulation C in the same manner as described above.

<Cellulose body dope (prescription C)>
Cellulose body A-1 100 parts by mass Methylene chloride (first solvent) 510 parts by mass Methanol (second solvent) 80 parts by mass 1-butanol (third solvent) 25 parts by mass

<Preparation of Cellulose Film Samples F1 to 33>
A solution having a cellulose body solution composition was cast using a band casting machine. In the tenter, it was stretched by about 20% in the width direction while drying with hot air, and then contracted by about 5%, then transferred from the tenter conveyance to the roll conveyance, further dried, knurled and wound up at a width of 1500 mm. . A film sample F1 (thickness: 80 μm) was produced. Hereinafter, all the thicknesses of the produced films are 80 μm unless otherwise specified. Next, film samples F2 to 33 of the present invention were prepared in the same manner.

For evaluation of the film sample, a part (120 mm × 120 mm) of each film sample obtained above was taken out, and the retardation value was 10% at 25 ° C. by “KOBRA 21ADH” (manufactured by Oji Scientific Instruments). ΔRe and ΔRth, which are differences between Re and Rth for light with a wavelength of 590 nm in RH and Re and Rth for light with a wavelength of 590 nm at 25 ° C. and 80% RH, were measured and shown in Table 2. As for the surface shape, a case where no white turbidity was seen was indicated by ◯, a case where some white turbidity was observed was indicated by Δ, and a case where the entire surface was white turbid was indicated by ×. The results are shown in Table 2.
From the results in Table 2, it can be seen that the cellulose acylate film of the present invention has a small fluctuation range due to the humidity of the retardation, and even when the solvent composition is changed, white turbidity hardly occurs.

(Example 3)
<Drying speed of cellulose body dope>
Cellulose body dope D12-14 and cellulose body dope D27-29 were cast using a band casting machine under exactly the same conditions as in Example 2. It dried on the completely same conditions and obtained the cellulose body film F34-39. This cellulose body film was dried at 120 ° C. for 2 hours, and the amount of residual solvent in the film was measured from the change in weight before and after drying. The results are shown in Table 3.

  As shown in Table 3, it can be seen that the film of the present invention using the solvent of the formulation B is quickly dried, has a small drying load, and is excellent in productivity. On the other hand, since the compound of the comparative example cannot use the solvent of the prescription | regulation B so that Table 2 may show, it turns out that drying load is large and it is inferior to productivity.

Example 4
[Alkaline saponification treatment of cellulose film]
10 cc of a 1.0 N potassium hydroxide solution (solvent: water / isopropyl alcohol / propylene glycol = 69.2 parts by mass / 15 parts by mass / 15.8 parts by mass) is formed on one side of the produced cellulose body films F1 and F11. / M ^{2 was} applied and held at about 40 ° C. for 30 seconds, and then the alkaline solution was scraped off, washed with pure water, and water droplets were removed with an air knife. Then, it dried at 100 degreeC for 15 second, and obtained film K1, K9. The contact angle of the films K1 and K11 with respect to pure water was determined to be 42 °.

(Preparation of alignment film)
On the films K1 and K11, an alignment film coating solution having the following composition was coated at 28 ml / m ² with a # 16 wire bar coater. The film was dried with warm air of 60 ° C. for 60 seconds and further with warm air of 90 ° C. for 150 seconds to produce an alignment film.

────────────────────────────────────────
Alignment film coating solution composition ────────────────────────────────────────
Denatured polyvinyl alcohol 10 parts by weight Water 371 parts by weight Methanol 119 parts by weight Glutaraldehyde (crosslinking agent) 0.5 parts by weight Citrate ester (AS3 manufactured by Sankyo Chemical) 0.35 parts by weight ──────── ────────────────────────────────

  Drying was performed at 25 ° C. for 60 seconds, 60 ° C. warm air for 60 seconds, and 90 ° C. warm air for 150 seconds. The alignment film thickness after drying was 1.1 μm. Further, the surface roughness of the alignment film was measured with an atomic force microscope (AFM: Atomic Force Microscope, SPI3800N, manufactured by Seiko Instruments Inc.), and found to be 1.147 nm.

(Formation of optically anisotropic layer)
On the alignment film, an alignment film coating solution having the following composition was applied at 24 ml / m ² with a # 14 wire bar coater. Drying was performed with warm air of 60 ° C. for 60 seconds, and further with warm air of 90 ° C. for 150 seconds.
Next, the formed film was rubbed in a direction of 45 ° with the direction of stretching of the alignment film (substantially perpendicular to the slow axis).

────────────────────────────────────────
Coating liquid composition of discotic liquid crystal layer ─────────────────────────────────────────
The following discotic liquid crystalline compound 32.6% by mass
The following compound A 0.1 mass%
Ethylene oxide modified trimethylolpropane triacrylate (V # 360, manufactured by Osaka Organic Chemical Co., Ltd.) 3.2% by mass
Sensitizer (Kayacure DETX, manufactured by Nippon Kayaku Co., Ltd.) 0.4% by mass
Photopolymerization initiator (Irgacure 907, manufactured by Ciba Geigy) 1.1% by mass
Methyl ethyl ketone 62.0% by mass
────────────────────────────────────────

  Compound A:

  In the step of continuously heating from room temperature to 100 ° C., the solvent is dried, and thereafter, the film surface wind speed of the discotic liquid crystal compound layer is about 90 m so as to be 2.5 m / sec in the 130 ° C. drying zone. The discotic liquid crystal compound was aligned by heating for 2 seconds. Next, with the surface temperature of the film being about 130 ° C., an ultraviolet irradiation device (ultraviolet lamp: output 120 W / cm) is irradiated with ultraviolet rays for 4 seconds to advance the crosslinking reaction, and the discotic liquid crystal compound is aligned. Fixed to. Then, it was allowed to cool to room temperature and wound into a cylindrical shape to form a roll. Thus, roll-shaped optical compensation films KH1 and KH11 were produced.

(Example 5)
[Preparation of polarizing plate]
A polyvinyl alcohol (PVA) film having a thickness of 80 μm is dyed by immersing it in an aqueous iodine solution having an iodine concentration of 0.05% by mass at 30 ° C. for 60 seconds, and then in an aqueous boric acid solution having a boric acid concentration of 4% by mass. The film was vertically stretched to 5 times the original length while being immersed for 2 seconds, and then dried at 50 ° C. for 4 minutes to obtain a polarizing film having a thickness of 20 μm.
The optical compensation films KH1 and KH11 produced in Example 3 were attached to one side of the polarizer using a polyvinyl alcohol-based adhesive. The saponification treatment was performed under the following conditions.
A 1.5N aqueous sodium hydroxide solution was prepared and kept at 55 ° C. A 0.01 N dilute sulfuric acid aqueous solution was prepared and kept at 35 ° C. The produced polymer film was immersed in the aqueous sodium hydroxide solution for 3 minutes, and then immersed in water to sufficiently wash away the aqueous sodium hydroxide solution. Subsequently, after being immersed in the above-mentioned dilute sulfuric acid aqueous solution for 1 minute, it was immersed in water to sufficiently wash away the dilute sulfuric acid aqueous solution. Finally, the sample was thoroughly dried at 120 ° C.
A commercially available cellulose triester film (Fujitac TD80UF, manufactured by Fuji Photo Film Co., Ltd.) is saponified, attached to the opposite side of the polarizer using a polyvinyl alcohol adhesive, and dried at 70 ° C. for 10 minutes or more. Polarizing plates P1 and P9 were produced.
An acrylic adhesive was applied to the cell side surface of the polarizing plate prepared above, and a separate film was attached on the adhesive. A protective film was attached to the surface opposite to the cell.

Example 6
[Evaluation with TN liquid crystal cell]
A pair of polarizing plates provided in a liquid crystal display device (AQUAS LC20C1S, manufactured by Sharp Corporation) using a TN type liquid crystal cell is peeled off, and polarizing plates P1 and P11 prepared in Example 5 are used as optical compensation films instead. One sheet was attached to the observer side and the backlight side through an adhesive so that KH1 and KH11 were on the liquid crystal cell side. The transmission axis of the polarizing plate on the viewer side and the transmission axis of the polarizing plate on the backlight side were arranged to be in the O mode.
About the produced liquid crystal display device, using a measuring machine (EZ-Contrast160D, made by ELDIM), a viewing angle is set in 8 steps from black display (L1) to white display (L8), humidity 10% RH, 60% RH. , And 80% RH. Table 4 shows the measurement results.

  As can be seen from Table 4, the viewing angle of the liquid crystal display device mounted with P1 does not change even when the environmental humidity varies.

Claims (7)

It has an aliphatic acyl group (A) having 5 to 30 carbon atoms and an aliphatic acyl group (B) having 2 to 4 carbon atoms, and the degree of substitution of the aliphatic acyl group (A) is represented by the following formula ( Cellulose body composition containing a cellulose body that satisfies I).
Formula (I) DSA6 / DSA2 + DSA3 + DSA6 <0.5
(Wherein DSA2 is the degree of substitution of the hydroxyl group at the 2-position of the glucose unit with the acyl group (A), DSA3 is the degree of substitution of the hydroxyl group at the 3-position of the glucose unit with the acyl group (A), and DSA6 is (This is the degree of substitution of the hydroxyl group at the 6-position of the glucose unit with the acyl group (A).)   The cellulose composition according to claim 1, wherein the acyl group (B) is an acetyl group.   The cellulose body film formed with the cellulose body composition of Claim 1 or 2.   The retardation film which consists of a cellulose body film of Claim 3.   An optical compensation film comprising an optically anisotropic layer formed by aligning a liquid crystalline compound on the cellulose body film according to claim 3 or the retardation film according to claim 4.   A polarizing plate comprising a polarizing film and two protective films sandwiching the polarizing film, wherein at least one of the two protective films is the cellulosic film according to claim 3, and the rank according to claim 4. A polarizing plate comprising at least one of a phase difference film or an optical compensation film according to claim 5.   An image display device comprising at least one of the cellulose body film according to claim 3, the retardation film according to claim 4, the optical compensation film according to claim 5, and the polarizing plate according to claim 6.