JP2002187960A - Cellulose ester film, process for manufacturing the same polarizing plate and liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prepare a cellulose ester film wherein the angle of visibility may be easily improved, to provide a polarizing plate using this film and a liquid crystal display device wherein the angle of visibility may be improved with a simple structure. SOLUTION: An optically biaxial cellulose ester film is obtained by casting a cellulose ester dope liquid in a casting support, releasing a web (film) from the casting support and at least monoaxially stretching the web by a factor of from 1.0 to 4.0 while the amount of a residual solvent within the web is <=100 mass%, specifically from 10 to 100 mass%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a cellulose ester film, a method for producing the film, a polarizing plate, and a liquid crystal display.

[0002]

2. Description of the Related Art Conventionally, the following three types of optical compensation films have been used for expanding the viewing angle of liquid crystal display devices.
Various configurations have been attempted, each proposed as an effective method.

(1) A method of supporting a discotic liquid crystal compound, which is a compound having negative uniaxiality, on a support (2) Depth of a nematic polymer liquid crystal compound having positive optical anisotropy (3) Nematic liquid crystal compound having positive optical anisotropy in a two-layer configuration on a support, in which a hybrid orientation in which the pretilt angle of the liquid crystal molecules changes in the direction is supported. A method of giving pseudo-negative uniaxial similar optical characteristics by setting the orientation direction of each layer to approximately 90 ° However, each of the above-described configurations has the following problems. I have.

In the method described in the above (1), when applied to a TN mode liquid crystal cell, a disadvantage peculiar to a discotic liquid crystal compound that a screen is colored yellow when viewed from an oblique direction appears.

In the method described in (2), the liquid crystal development temperature is high, and the orientation of the liquid crystal cannot be fixed on an isotropic transparent support such as TAC (cellulose triacetate). After the orientation is fixed on the body, it is necessary to transfer to a support such as TAC, which complicates the process and extremely lowers the productivity.

As an example of the method described in the above (3), for example, Japanese Patent Application Laid-Open No. Hei 8-15681 discloses that a rod-shaped optically anisotropic layer using a positive uniaxial low-molecular liquid crystal compound has an alignment ability. A layer composed of a rod-like positive uniaxial low-molecular liquid crystal compound oriented via a polarizer having a polarizer is formed, fixed, and further re-aligned on this layer via a polarizer having an alignment ability. There is disclosed a four-layer optically anisotropic layer in which a layer formed of a rod-shaped positive uniaxial low-molecular liquid crystal compound is formed and fixed. In this case, by giving the orientation directions projected in the plane of the two liquid crystal layers shifted by, for example, 90 degrees, it becomes possible to give a pseudo disk-like characteristic.

Therefore, the method described in the above (3) has no coloring problem unlike the case of a discotic liquid crystalline compound, and therefore, a liquid crystal TV (television) in which color reproduction is important.
It has a very advantageous feature in such uses.

However, this method is intended to be achieved with two liquid crystal layers, which is achieved with a discotic liquid crystal compound with one layer, and has a problem that the efficiency is extremely low.

Furthermore, each of these methods has a more fundamental and common problem. That is, according to these methods, it is necessary to precisely apply a liquid crystal compound in a thin film in order to obtain optical compensation ability. In order to orient and apply the liquid crystal compound, a process of applying an orientation layer in advance and applying an alignment regulating force (rubbing process, polarization exposure process, etc.) is performed, and this is a simple optical compensation film. Means that the cost is very high even in the method of improving the viewing angle. In addition, as a method not using a liquid crystal compound, a resin such as polycarbonate which is usually used as a retardation plate is stretched to produce a biaxially oriented retardation plate, which is subsequently bonded to a polarizing plate, and a so-called elliptic plate is formed. There is a method of expanding the viewing angle by forming a polarizing plate, and for example, it is commercially available as VAC film or New VAC film from Sumitomo Chemical Co., Ltd. However, it is very difficult for such a biaxially oriented retardation plate to be uniformly stretched in terms of material, and requires an advanced stretching technique. In addition, there was a problem that the yield was low. Furthermore, since this retardation plate is used after being bonded and bonded to a polarizing plate, the number of manufacturing steps is increased, and the increase in cost cannot be avoided. As described above, there has been no polarizing plate having a viewing angle expanding effect at low cost by the same manufacturing method as that of the conventional polarizing plate.

Therefore, there has been a demand for solving the above-mentioned problems.

[0011]

SUMMARY OF THE INVENTION An object of the present invention is to provide a TN
-Viewing angle characteristics of a TN type LCD such as a TFT,
Contrast of the screen when viewed from an oblique direction, coloring, providing a viewing angle expansion polarizing plate and a cellulose ester film used for the polarizing plate that can easily improve the reversal phenomenon of light and dark, furthermore, the viewing angle expansion polarizing plate The object of the present invention is to provide a liquid crystal display device in which the viewing angle is remarkably improved by using a simple structure.

[0012]

The above objects of the present invention have been attained by the following constitutions 1 to 19.

1. A cellulose ester film having optically biaxial properties. 2. 2. The cellulose ester film as described in 1 above, wherein the cellulose ester film is prepared and prepared so as to have a maximum refractive index in the width direction during casting.

3. 3. The cellulose ester film according to the above item 2, which is produced as a long roll.

4. In-plane retardation value R ₀ is 30 or more
4. The cellulose ester film according to the above item 2 or 3, wherein the thickness is 300 nm.

5. The cellulose ester film as claimed in any one of 2-4 thickness direction retardation value R _t is characterized in that it is a 30 to 300 nm.

6. The cellulose ester film according to any one of the above items 2 to 5, which satisfies the formulas (1) and (2) simultaneously.

[7] A polarizing plate, comprising the cellulose ester film according to any one of the above items 1 to 6.

8. 7. In a polarizing plate having a cellulose ester film according to any one of 1 to 6 and a polarizer containing a dichroic substance, the direction of orientation of the dichroic substance and the maximum refraction in the plane of the cellulose ester film. A polarizing plate, wherein an angle between the polarizing plate and a direction for giving a ratio is 80 ° to 100 °.

9. 7. In a polarizing plate having a cellulose ester film according to any one of 1 to 6 and a polarizer containing a dichroic substance, the light transmission axis of the polarizer and the maximum refractive index in the plane of the cellulose ester film. Wherein the angle between the polarizing plate and the direction in which is given is −10 ° to 10 °.

10. The cellulose ester film according to any one of the above 1 to 6, a cellulose ester film B different from or the same as the cellulose ester film, and a polarizing plate having a polarizer containing a dichroic substance, wherein the cellulose ester A polarizing plate, wherein the film B is stretched in the same direction as the cellulose ester film.

11. Cellulose ester film B is
The polarizing plate according to the item 10, wherein the polarizing plate is stretched in the width direction at the time of film formation or after the film formation.

12. The stretch ratio of the cellulose ester film or cellulose ester film B is 1.02 to
12. The polarizing plate as described in 10 or 11, wherein the polarizing plate is stretched so as to be 1.2 times.

13. The stretch ratio of the cellulose ester film or cellulose ester film B is 1.05 to
13. The polarizing plate as described in any one of 10 to 12, wherein the polarizing plate is stretched so as to be 1.15 times.

14. (10) The cellulose ester film (B) comprising triacetyl cellulose.
14. The polarizing plate according to any one of items 13 to 13.

15. 15. A liquid crystal display device comprising the polarizing plate and the liquid crystal cell according to any one of the items 7-14, wherein the cellulose ester film of the polarizing plate comprises a polarizer containing the dichroic substance of the polarizing plate, the liquid crystal cell, A liquid crystal display device, which is disposed between the liquid crystal display devices.

16. 16. The liquid crystal display device as described in 15 above, wherein a light transmission axis of the polarizing plate is orthogonal to a rubbing axis or a liquid crystal alignment axis of a liquid crystal cell on which the polarizing plate is disposed.

17. The angle between the direction in which the refractive index of the cellulose ester film of the polarizing plate disposed on the bonding surface side of the polarizing plate and the liquid crystal cell and the light transmission axis of the polarizing plate is −10 ° to 10 °. 17. The liquid crystal display device according to the item 16, wherein the liquid crystal display device is adjusted to:

18. In producing the cellulose ester film according to any one of the above items 1 to 6, an operation of optically imparting biaxiality to the cellulose ester film is performed, and the cellulose ester film is produced as a long roll. A method for producing a cellulose ester film.

19. 15. A method for producing a polarizing plate, comprising: producing the polarizing plate according to any one of the above items 7-14 through the following steps (1) to (3).

(1) Producing a long roll of a cellulose ester film which has been subjected to an operation of optically imparting biaxiality and which has been adjusted so that the refractive index in the width direction at the time of casting is maximum. (2) Forming a polarizer containing a dichroic substance (3) Laminating the polarizer on the long roll Hereinafter, the present invention will be described in detail.

The cellulose ester film of the present invention will be described. Conventionally used optical compensation film is a method using a liquid crystal compound uniformly coated and aligned on a transparent support, or a biaxial stretching retardation using a complicated stretching technique of a resin such as polycarbonate. In practice, a method using a plate, that is, an optical film having such a complicated optical anisotropy, is bonded to a polarizing plate and used. The present inventors have found that the optically biaxial cellulose ester film of the present invention has a sufficient optical compensation ability and can maintain a stable optical compensation ability even under high temperature and high humidity conditions. To find an elliptically polarizing plate using as a protective film. Here, the polarizing plate of the present invention can include a so-called elliptically polarizing plate having a phase difference function.

The polarizing plate using the cellulose film of the present invention has a high contrast when viewed from an oblique direction, not only has a wide viewing angle, but also has no coloring on the screen when viewed from an oblique direction. It was found that excellent optical compensation ability was exhibited, such as a narrow inversion region.

Further, the cellulose ester film used in the polarizing plate having a viewing angle widening effect of the present invention has a feature of being optically biaxial. It is not necessary to perform biaxial stretching in order to obtain, and optical biaxiality can be obtained only by performing uniaxial stretching. This means that the cast cellulose ester film itself has a negative uniaxiality (nX = nY>nZ; nX and nY are the in-plane X and Y directions of refractive index, and nZ is the refraction in the thickness direction of the film). Rate).

An optically biaxial cellulose ester film is used as a protective film on the liquid crystal cell side (between the dichroic substance constituting the polarizing plate and the liquid crystal cell) when producing a polarizing plate. Since the optical properties of the support on the opposite side (outermost surface side) are not particularly limited, a commonly used cellulose triacetate film (TAC film) may be used as the type of the protective film. In this case, for example, by stretching this TAC film at least in the width direction at a constant magnification,
An elliptically polarizing plate that can maintain very stable optical characteristics even under high temperature and high humidity conditions can be obtained.

Further, by manufacturing a polarizing plate using the cellulose ester film of the present invention, the conventional polarizing plate manufacturing process can be used as it is by merely replacing the type of the cellulose ester film used for the support. It becomes possible to produce a viewing angle widening polarizing plate by the same method as a normal polarizing plate, and there is a great merit in practical use.
That is, the cellulose ester film is an extremely suitable support because it can be adhered to the polarizer by performing an alkali saponification treatment in the polarizing plate production step, and has excellent water removal properties after bonding. As the polarizer, generally, a stretched polyvinyl alcohol film doped with a dichroic substance is preferably used.

The present invention provides a viewing angle expanding polarizing plate having a viewing angle expanding function using only a polarizing plate, a long optically biaxial cellulose ester film used for the polarizing plate, a method for producing the viewing angle expanding polarizing plate, and a method for manufacturing the same. An object of the present invention is to provide a liquid crystal display device using a viewing angle widening polarizing plate. More specifically, a change in contrast due to a viewing angle specific to a twisted nematic (TN) type liquid crystal, particularly an active matrix type TN used as a full color display
In this case, the viewing angle dependence of the display of the liquid crystal display device is improved.

The optical properties of the cellulose ester film of the present invention will be described. In the present invention, a cellulose ester film having optically biaxial properties is used, but the above-described optical properties are usually obtained by applying tension in a certain direction in the process of producing a cellulose ester by casting. be able to. For example, it is particularly effective to perform an operation such as stretching after casting the cellulose ester film under the condition where the residual solvent is present. Also,
It can also be produced by stretching a heated cellulose ester film.

As the cellulose ester, for example, cellulose triacetate can be used, but the total degree of substitution may be more than 2.0, and especially, the total of the degree of substitution of all acyl groups is 2.8 or more. Is preferably used. Further, in order to obtain a certain level of optical compensation performance, it is extremely effective to use a lower fatty acid cellulose ester having a specific substituent, that is, an acetyl group and a propionyl group.

The cellulose ester used for producing the cellulose ester film of the present invention has an acyl group having 2 to 4 carbon atoms as a substituent, and a cellulose ester which satisfies the above formulas (1) and (2) simultaneously. preferable.

Further, in the present invention, a cellulose ester film satisfying the following formulas (3) and (4) at the same time is preferably used.

Formula (3) 2.5 ≦ A + B ≦ 2.75 Formula (4) 1.7 ≦ A ≦ 1.95 These acyl groups are the 2-position, 3-position and 6-position of the glucose unit.
The substitution may be carried out on the average, or may be carried out with a distribution such as substitution at a high ratio at the 6th position.

Here, the degree of substitution refers to the so-called percentage of the amount of bound fatty acid, and is a numerical value calculated according to the measurement and calculation of the degree of acetylation according to ASTM-D817-91 (test method for cellulose acetate and the like). The substitution degree of the acyl group can be measured according to ASTM-D817-96.

When the total substitution degree of the acetyl group and the acyl group having 3 to 4 carbon atoms is within the above range, the retardation becomes larger as the wavelength becomes longer, and the water content and the water barrier property are improved. Thus, a cellulose ester film having properties can be obtained.

In particular, it is preferable that the average degree of substitution of the acetyl group is less than 2.0 because the dispersion of the retardation during stretching is small.

From the viewpoint of obtaining an optical compensation film having excellent mechanical strength, the viscosity average degree of polymerization (degree of polymerization) of the cellulose ester used in the present invention is 200 to 700.
The following is preferable, and those having 250 or more and 500 or less are particularly preferable.

The viscosity average degree of polymerization (DP) described above is determined by the following method. << Measurement of Viscosity Average Polymerization Degree (DP) >> 0.2 g of absolutely dried cellulose ester is precisely weighed and dissolved in 100 ml of a mixed solvent of methylene chloride and ethanol (mass ratio 9: 1). This is measured for drop seconds at 25 ° C. using an Ostwald viscometer, and the degree of polymerization is determined by the following equation.

(A) ηrel = T / Ts (b) [η] = (lnηrel) / C (c) DP = [η] / Km, where T is the number of seconds during which the sample falls, and Ts is the number of drops of the solvent. Seconds, C is the concentration of cellulose ester (g / l), Km =
It is 6 × 10 ^-4 .

The "retardation value R _t, the measurement of R _0" from the viewpoint of obtaining more preferable viewing angle expansion effect, in the cellulose ester film according to the present invention preferably have a relationship defined by formula (I) .

Formula (I) (nx + ny) / 2−nz> 0 where nx is the refractive index in the direction in which the refractive index is maximized in the plane of the cellulose ester film, and ny is in-plane and perpendicular to nx. And nz is the refractive index of the film in the thickness direction.

The optically biaxial cellulose ester support of the present invention can improve the viewing angle if it is optically biaxial, but the preferred condition is that the retardation in the thickness direction is good. value R _t value, the in-plane retardation value R ₀
The values can be specified by values, and by appropriately controlling these values, the viewing angle expanding effect can be significantly improved. As a specific control method, a stretching method described later or the like can be used.

[0052] The thickness direction retardation value R _t is preferably retardation value defined by the following formula (II) (R _t value) is 30 to 300 nm,
More preferably, it is 60 to 250 nm.

Equation (II) ((nx + ny) / 2−nz) × d Further, regarding the retardation value R ₀ in the in-plane direction,
It is represented by the following equation.

R ₀ = (nx−ny) × d where d is the thickness (nm) of the film.

In the present invention, R ₀ is 30 to 300
nm, more preferably 40 nm.
１５０150 nm.

The above described retardation values, R _t and R ₀
Is measured using an automatic birefringence meter KOBRA-21ADH (manufactured by Oji Scientific Instruments) at a temperature of 23 ° C. and 55% RH at a wavelength of 590 nm and a three-dimensional refractive index. It is obtained by calculating the ratios nx, ny, nz.

The optically biaxial cellulose ester film of the present invention is preferably a transparent support having a light transmittance of 80% or more, more preferably 92% or more. Further, the cellulose ester film of the present invention preferably has a thickness of 30 to 150 μm.

The mixed fatty acid ester of cellulose used in the present invention can be synthesized using an acid anhydride or an acid chloride as an acylating agent. When the acylating agent is an acid anhydride, an organic acid (eg, acetic acid) or methylene chloride is used as a reaction solvent. As the catalyst, an acidic catalyst such as sulfuric acid is used. When the acylating agent is an acid chloride, a basic compound is used as a catalyst. In the synthesis method most commonly used industrially, cellulose is mixed with an organic acid (acetic acid, propionic acid) corresponding to an acetyl group and a propionyl group or a mixed organic acid component containing an anhydride thereof (acetic anhydride, propionic anhydride). Esterification synthesizes a cellulose ester. The amounts of the acetylating agent and the propionylating agent are adjusted so that the ester to be synthesized falls within the above-mentioned substitution degree. The amount of the reaction solvent used is cellulose 10
The amount is preferably from 100 to 1,000 parts by mass, more preferably from 200 to 600 parts by mass, based on 0 parts by mass. The amount of the acidic catalyst sample is preferably from 0.1 to 20 parts by mass, more preferably from 0.4 to 10 parts by mass, based on 100 parts by mass of the cellulose.

The reaction temperature is preferably from 10 to 120 ° C., more preferably from 20 to 80 ° C.
Note that another acylating agent (eg, a butylating agent) or an esterifying agent (eg, a sulfuric esterifying agent) may be used in combination. Also,
After the completion of the acylation reaction, the degree of substitution may be adjusted by hydrolysis (saponification) as necessary. After completion of the reaction, the reaction mixture is separated by a conventional means such as precipitation, washed and dried to obtain a mixed fatty acid ester of cellulose (cellulose acetate propionate).

As the cellulose ester used in the present invention, either cellulose triacetate synthesized from cotton linter or cellulose triacetate synthesized from wood pulp can be used alone or in combination. It is preferable to use a large amount of cellulose ester synthesized from cotton linter which has good releasability from a belt or a drum because the production efficiency is high. When the proportion of the cellulose ester synthesized from the cotton linter is 60% by mass or more, the effect of the releasability becomes remarkable, the amount is preferably 60% by mass or more, more preferably 85% by mass or more, and even more preferably used alone. preferable.

The cellulose ester acylated with an acetyl group and an acyl group having 3 or 4 carbon atoms used in the present invention is also called a mixed fatty acid ester of cellulose.

The acyl group having 3 or 4 carbon atoms includes, for example, a propionyl group and a butyryl group. Propionyl group or n-butyryl group is preferable from the viewpoint of mechanical strength and ease of dissolution when formed into a film,
Particularly, a propionyl group is preferable.

Solvents for dissolving the fatty acid cellulose ester to form a dope include methylene chloride, methyl acetate, ethyl acetate, amyl acetate, acetone, tetrahydrofuran, 1,3-dioxolan, cyclohexanone,
2,2,2-trifluoroethanol, 2,2,3,3
-Hexafluoro-1-propanol, 1,3-difluoro-2-propanol and the like.

Among them, chlorinated solvents such as methylene chloride can be suitably used, but methyl acetate, ethyl acetate, acetone and the like are also preferably used. In particular, it is preferable that methyl acetate is contained in an amount of 50% or more based on the total organic solvent, and it is preferable to use 5 to 30% by mass of acetone based on the total organic solvent in combination with methyl acetate because the viscosity of the dope solution can be reduced.

In the present invention, the phrase "contains substantially no chlorine-based solvent" means that the chlorine-based solvent is not more than 10%, preferably not more than 5%, and most preferably not contained at all, in terms of the mass of the total organic solvent.

The fatty acid cellulose ester dope used in the present invention contains, in addition to the above organic solvent, 1 to 30% by mass.
It is preferable to include an alcohol having 1 to 4 carbon atoms. As a result, after casting the dope on the casting support, the solvent starts to evaporate, and when the ratio of alcohol increases, the web (dope film) gels, and the web becomes strong and peels off from the casting support. And the effect of accelerating the dissolution of the fatty acid cellulose ester in the organic solvent can be obtained. Examples of the alcohol having 1 to 4 carbon atoms include methanol, ethanol, n-propanol, and is
Examples thereof include o-propanol, n-butanol, sec-butanol and tert-butanol. Among these, the stability of the dope is good, the boiling point is relatively low,
Ethanol is preferred because it has good drying properties and has no toxicity.

The solid content concentration of the dope is usually 10 to 10% by mass.
The dope viscosity is preferably (10 to 50 Pa · s).
It is preferable to adjust to the range of ec) from the viewpoint of obtaining good film flatness.

The dope prepared as described above is filtered by a filter medium, defoamed, and sent to the next step by a pump. In the dope, a plasticizer, a matting agent, an ultraviolet absorber, an antioxidant, a dye, a moisture permeability improving agent, and the like may be added.

Since the fatty acid cellulose ester having an acetyl group and a propionyl substituent used in the present invention manifests its effect as a plasticizer itself, a sufficient film can be obtained without adding a plasticizer or with a small amount. Although characteristics can be obtained, a plasticizer may be added for other purposes. For example, for the purpose of improving the moisture resistance of the film, alkylphthalylalkyl glycolates, phosphate esters, carboxylate esters, and the like can be mentioned.

Examples of the alkylphthalylalkyl glycolates include methylphthalylmethyl glycolate, ethylphthalylethyl glycolate, propylphthalylpropyl glycolate, butylphthalylbutyl glycolate, octylphthalyloctyl glycolate, Methyl phthalyl ethyl glycolate, ethyl phthalyl methyl glycolate, ethyl phthalyl propyl glycolate, methyl phthalyl butyl glycolate, ethyl phthalyl butyl glycolate, butyl phthalyl methyl glycolate, butyl phthalyl ethyl glycolate, propyl Phthalyl butyl glycolate, butyl phthalyl propyl glycolate, methyl phthalyl octyl glycolate, ethyl phthalyl octyl glycolate, octyl phthalyl methyl glycolate, Chi Le phthalyl ethyl glycolate, and the like.

Examples of the phosphates include triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, phenyl diphenyl phosphate, octyl diphenyl phosphate, trioctyl phosphate, tributyl phosphate and the like.

Examples of the carboxylic acid esters include phthalic acid esters and citric acid esters. Examples of the phthalic acid esters include dimethyl phthalate, diethyl phthalate, dimethoxyethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, and the like. And di-2-ethylhexyl phthalate.

Examples of the citrate esters include acetyltriethyl citrate, acetyltriethyl citrate and acetyltributyl citrate.

In addition, butyl oleate, methylacetyl ricinoleate, dibutyl sebacate, triacetin and the like are preferably used alone or in combination. If necessary, two or more plasticizers may be used in combination. When used for a cellulose ester, the use ratio of a phosphate ester-based plasticizer is preferably 50% or less because hydrolysis of the cellulose ester film hardly occurs and durability is excellent. It is more preferable that the ratio of the phosphate plasticizer is smaller, and it is particularly preferable to use only the phthalate or glycolate plasticizer.

Among them, methyl phthalyl methyl glycolate, ethyl phthalyl ethyl glycolate, propyl phthalyl propyl glycolate, butyl phthalyl butyl glycolate and octyl phthalyl octyl glycolate are preferred, and ethyl phthalyl ethyl glycolate is particularly preferred. It is preferably used. Further, two or more of these alkylphthalylalkyl glycolates may be used as a mixture.

The amount of the plasticizer used for this purpose is preferably from 1 to 30% by mass relative to the cellulose ester, particularly preferably 4 to 30%.
~ 13% is preferred.

These compounds may be added together with the cellulose ester and the solvent when preparing the cellulose ester solution, or may be added during or after the solution is prepared.

A dye may be added for the purpose of improving the yellowness of the film. It is preferable that the color can be colored gray as seen in a usual photographic support. However, unlike a photographic support, there is no need to prevent light piping, so the content may be small, and the content is preferably 1 to 100 ppm by mass relative to the cellulose ester, and 2 to 50 ppm.
ppm is more preferred.

Since the cellulose ester has a slightly yellow tint, a blue or purple dye is preferably used. A plurality of dyes may be appropriately combined so as to be gray.

If the films are not slippery, the films may be blocked with each other, resulting in poor handling. In that case, the film according to the present invention, silicon dioxide,
It is preferable to include a matting agent such as inorganic fine particles such as titanium dioxide, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate, and calcium phosphate, and a crosslinked polymer.

Fine particles such as silicon dioxide are preferably surface-treated with an organic substance, because the haze of the film can be reduced. Preferred organic substances for the surface treatment include halosilanes, alkoxysilanes, silazanes, siloxanes and the like. The larger the average diameter of the fine particles, the greater the matting effect, and the smaller the average diameter, the better the transparency. Therefore, the average diameter of the primary particles of the fine particles is preferably 5 to 50 nm, more preferably 7 to 14 nm. These fine particles are usually present in the film as aggregates, and it is preferable to form irregularities of 0.01 to 1.0 μm on the film surface. AEROSIL 200, 3 manufactured by Aerosil Co., Ltd.
00, R972, R974, R202, R812, OX
50, TT600, etc., preferably AERO
SIL R972V, 200V, R972, R974,
R202, R812 and the like.

The matting agent is preferably compounded so that the haze of the film is 0.6% or less and the dynamic friction coefficient is 0.5 or less.

The content of the matting agent used for this purpose is 0.000 by mass with respect to the fatty acid cellulose ester.
5% to 0.3% is preferred.

Since the cellulose ester film of the present invention is incorporated in a liquid crystal display and is often used outdoors, it is preferable that the cellulose ester film has a function of cutting off ultraviolet rays. From such a viewpoint, the cellulose ester film support according to the present invention preferably contains an ultraviolet absorber.

As the ultraviolet absorber, those having an excellent ability to absorb ultraviolet light having a wavelength of 370 nm or less from the viewpoint of deterioration of the liquid crystal, and having a minimum absorption of visible light having a wavelength of 400 nm or more from the viewpoint of good liquid crystal display properties. Is preferably used. In particular, the transmittance at a wavelength of 370 nm needs to be 10% or less, and more preferably 5% or less.

The ultraviolet absorber used for this purpose preferably has no absorption in the visible light region, and examples thereof include benzotriazole compounds, benzophenone compounds, and salicylate compounds.

Examples of these are 2- (2'-hydroxy-5'-methylphenyl) benzotriazole,
-(2'-hydroxy-3 ', 5'-di-tert-butylphenyl) benzotriazole, 2- (2'-hydroxy-3'-tert-butyl-5'-methylphenyl) benzotriazole, 2,4 -Dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-n-octoxybenzophenone, 4-dodecyloxy-2-hydroxybenzophenone, 2,2 ', 4,4'-tetrahydroxybenzophenone, , 2'-dihydroxy-4,4'-dimethoxybenzophenone, phenyl salicylate, methyl salicylate and the like.

In the present invention, one of these ultraviolet absorbers
It is preferable to use at least two kinds of UV absorbers, and two or more different UV absorbers may be contained.

The method of adding the ultraviolet absorber may be such that the ultraviolet absorber is dissolved in an organic solvent such as alcohol, methylene chloride or dioxolane and then added to the dope, or may be added directly to the dope composition. Those that do not dissolve in an organic solvent, such as inorganic powders, are dispersed in an organic solvent and a cellulose ester using a dissolver or a sand mill, and then added to the dope.

The UV absorber is used in an amount of 0.1 to 5%, preferably 0.5 to 5% by mass based on the cellulose ester.
-2.5%, more preferably 0.8-2.0%.
If the amount of the UV absorber used is more than 2.5%, the transparency tends to deteriorate, which is not preferable.

For the purpose of improving the heat resistance of the film,
Hindered phenol compounds are preferably used,
The addition amount of these compounds is preferably 1 ppm to 1.0% by mass relative to the cellulose ester, and 10 to 1%.
000 ppm is more preferred. In addition, a heat stabilizer such as a salt of an alkaline earth metal such as calcium and magnesium may be added.

In addition to the above, antistatic agents, flame retardants,
A slipping agent and the like may be appropriately added. In addition, since the cellulose ester film support according to the present invention is disposed between the polarizing plates, a foreign substance that generates abnormally refracted light causes performance degradation. At that point, a so-called bright spot abnormality becomes a problem.

In the present invention, the luminescent spot recognized in the polarization crossed Nicols state means that two polarizing plates are in a crossed (crossed Nicols) state, a cellulose ester film is interposed therebetween, and light from a light source is applied from the opposite side. What is observed. In the crossed Nicols state, such bright spots are observed in the dark field with only the bright spots shining, so that their size and number can be easily identified.

The number of the bright spots is 5 per area of 250 mm ² , which is recognized in the polarization crossed Nicols state.
It is preferable that the number of luminescent spots of 50 μm to 200 μm is 200 or less and the number of luminescent spots of 50 μm or more is 0. More preferably, 5 to 5
The number of luminescent spots of 0 μm is 100 or less, particularly preferably 0
10 to 10. If there are many such bright spots, it will have a serious adverse effect on the image on the liquid crystal display.

The method for producing the cellulose ester film of the present invention will be described. As a method for producing a cellulose ester film, a dope solution was cast on a casting support, a film was formed, and the obtained film was peeled off from the support.
Thereafter, a solution casting film forming method in which the film is dried while being transported through a drying zone under tension is preferable. The solution casting method is described below.

(1) Dissolution step: This step is a step of dissolving the flakes in an organic solvent mainly containing a good solvent for the cellulose ester flakes in a dissolving vessel with stirring to form a cellulose ester solution (dope). The dissolution is carried out at normal pressure, at a temperature below the boiling point of the main solvent, at a pressure above the boiling point of the main solvent, and J. M. G. FIG. Makromol. chem. 143, 105
Page (1971), and JP-A-9-9
There are various dissolving methods such as a cooling dissolving method dissolving at a low temperature as described in JP-A Nos. 5544 and 9-95557 and a method dissolving at a high pressure. After dissolution, the dope is filtered with a filter medium, defoamed and sent to the next step by a pump.

(2) Casting step: The dope is fed to a pressurizing die through a pressurized metering gear pump.
This is a step of casting a dope from a pressure die onto a casting support of an endless metal belt or a rotating metal drum that is transported infinitely.
The surface of the casting support is a mirror surface. As other casting methods, there are a doctor blade method of adjusting the film thickness of the cast dope film with a blade, and a reverse roll coater method of adjusting the film with a counter-rotating roll. A pressure die that can be formed and is easy to make the film thickness uniform is preferable. Examples of the pressure die include a coat hanger die and a T die, and any of them is preferably used. In order to increase the film forming speed, two or more pressure dies may be provided on the casting support, and the doping amount may be divided to form an overlap.
Alternatively, a cellulose ester film having a laminated structure can be formed by using a co-casting method.

(3) Solvent evaporation step: The web (the web is referred to as a dope film after dope is cast on the casting support) is heated on the casting support to evaporate the solvent. It is a process. In order to evaporate the solvent, there are a method of blowing air from the web side and / or a method of transferring heat with liquid from the back surface of the support and a method of transferring heat from the front and back by radiant heat. Good drying efficiency is preferable. A method of combining them is also preferable.

(4) Peeling step: This is a step of peeling the web from which the solvent has evaporated on the support at the peeling position. The peeled web is sent to the next step. If the residual solvent amount (the following formula) of the web at the time of peeling is too large, the web is difficult to peel, or conversely, if the web is sufficiently dried on the support and then peeled, a part of the web is peeled off in the middle.

As a method for increasing the film forming speed (the film forming speed can be increased because the film is peeled off while the residual solvent amount is as large as possible), there is a gel casting method in which the film can be peeled even when the residual solvent is large ( The film forming speed can be increased because the film is removed while the amount of the residual solvent is as large as possible). It is a method of adding a poor solvent for the cellulose ester in the dope, casting the dope, and then gelling.
There is a method of gelling by lowering the temperature of the support. Also,
There is also a method of adding a metal salt to the dope. By gelling on the support and strengthening the film, peeling can be accelerated and the film forming speed can be increased. If the residual solvent amount is greater at the time of peeling, if the web is too soft, the flatness at the time of peeling will be impaired, or shear and vertical streaks will easily occur due to peel tension, and the amount of the residual solvent peeled will be reduced in consideration of economic speed and quality. I can decide.

(5) Drying step: a step of drying the web using a drying device that alternately transports the web through rolls arranged in a staggered manner and / or a tenter device that transports the web by clipping both ends of the web with clips. It is. In general, hot air is blown to both sides of the web as a drying means, but there is also a method of heating by applying a microwave instead of the wind. Too fast drying tends to impair the flatness of the finished film. Drying at a high temperature is preferably performed when the residual solvent is about 8% by mass or less. Throughout, the drying temperature is usually 40 to 250 ° C, preferably 70 to 180 ° C. The drying temperature, the amount of drying air, and the drying time vary depending on the solvent used, and the drying conditions may be appropriately selected according to the type and combination of the solvents used.

In the drying step after peeling off from the surface of the casting support, the web tends to shrink in the width direction due to evaporation of the solvent. The quicker it dries at higher temperatures, the greater the shrinkage. Drying while suppressing this shrinkage as much as possible is preferable for improving the flatness of the resulting film. From this viewpoint, for example, Japanese Patent Application Laid-Open No. 62-4662.
The method of drying all the steps or a part of the steps as described in Japanese Patent Publication No. 5 (tenter method) while holding both ends of the width of the web with a clip in the width direction is preferable.

(6) Winding step: This is a step of winding the web as a film after the residual solvent amount becomes 2% or less by mass. By setting the amount of the residual solvent to 0.4% or less, a film having good dimensional stability can be obtained. As the winding method, a generally used method may be used, and there are a constant torque method, a constant tension method, a taper tension method, a program tension control method with constant internal stress, and the like.

To adjust the film thickness of the fatty acid cellulose ester film, the dope concentration, the amount of liquid sent from the pump, the slit gap of the die cap, the extrusion pressure of the die, and the thickness of the casting support are adjusted so as to obtain the desired thickness. It is good to control the speed. In addition, as means for making the film thickness uniform, it is preferable that the programmed feedback information is fed back to each of the above-described devices using a film thickness detecting means for adjustment.

In the process from immediately after casting through the solution casting film forming method to drying, the atmosphere in the drying apparatus may be air, but the drying is performed in an inert gas atmosphere such as nitrogen gas or carbon dioxide gas. You may. However, it is a matter of course that the danger of the explosion limit of the evaporated solvent in the dry atmosphere must always be considered.

The cellulose ester support having optically biaxial properties according to the present invention can be obtained by any method for obtaining an optically biaxial orientation (representing the relationship of nx>ny> nz). Although the stretching method can be used, a stretching method can be adopted as one of the most effective methods.

The cellulose ester film of the present invention can be stretched even at a high temperature by controlling the residual solvent in the film as described later in the production thereof, but when this method is not used, It is also possible to stretch at a high temperature. In the case of stretching at a high temperature, the stretching is performed at a temperature equal to or higher than the glass transition temperature of the cellulose ester.However, in the case of the plasticizer as described above, the effect may be weakened and the stretchability may not be sufficiently obtained. is there. It is necessary to use a plasticizer capable of imparting sufficient stretchability even at a high temperature, and it has been found that a non-volatile plasticizer can be preferably used as such a plasticizer. The non-volatile plasticizer is a compound having a vapor pressure at 200 ° C. of 1,330 Pa or less, has a very low vapor pressure, and has a low volatility. The vapor pressure is more preferably 665 Pa or less, and even more preferably 133 Pa or less. For example, an arylene bis (diaryl phosphate) ester is preferred. In addition, tricresyl phosphate (38.6 Pa, 200 ° C.),
Tris (2-ethylhexyl) trimellitate (66.
5 Pa, 200 ° C.) and the like are also preferably used. Alternatively, a nonvolatile phosphate ester described in JP-A-6-501040 is also preferably used. In addition, high-molecular-weight plasticizers such as polymers or oligomers such as copolymers containing polyester, acrylic resin, and polyvinyl acetate can also be preferably used. In this case, the content of the plasticizer is 0.1 to 3 with respect to the cellulose ester.
0 mass% is preferable, and especially 0.5 to 15 mass% is preferable. By using a plasticizer in this manner, the stretchability of the cellulose ester at a high temperature can be improved, and in particular, a cellulose ester film having excellent surface quality and flatness can be produced with high productivity.

In the cellulose ester film of the present invention,
As a method for imparting optical biaxiality, a method of performing a stretching operation in a state containing a solvent as described above is used as an example of a preferable method. Hereinafter, the stretching method will be described.

In the production of the cellulose ester film of the present invention, the dope solution for dissolving cellulose ester is cast on a casting support, and then the web (film) peeled off from the casting support is removed from the residual solvent in the web. While the amount is below 100% by weight, in particular between 10 and 100% by weight,
It is preferable that the film is stretched 1.0 to 4.0 times in at least one direction.

The residual solvent amount can be represented by the following equation. Residual solvent amount (% by mass) = {(M−N) / N} × 100 where M is the mass of the web at any time, and N is M
The mass when dried at 0 ° C. for 3 hours.

If the amount of the residual solvent in the web is too large, the effect of stretching cannot be obtained, and if the amount is too small, the stretching becomes extremely difficult and the web may be broken. A more preferable range of the residual solvent amount in the web is from 10% by mass to
Most preferred is 50% by weight, especially 12% to 40% by weight. On the other hand, if the stretching ratio is too small, a sufficient phase difference cannot be obtained, and if it is too large, stretching becomes difficult and breakage may occur. A more preferable range of the stretching ratio is 1.0.
It is in the range of times to 3.5 times.

The solution cast film formed by using the cellulose ester according to the present invention can be stretched without heating to a high temperature if the residual solvent amount is within a specific range. This is preferable because the process can be shortened. However, if the temperature of the web is too high, the plasticizer volatilizes, so the temperature is preferably in the range of room temperature (15 ° C) to 180 ° C or less.

Stretching in biaxial directions orthogonal to each other is an effective method for keeping the refractive indexes nx, ny, and nz of the film within the scope of the present invention.

Further, the film thickness fluctuation of the film obtained by stretching in the biaxial directions perpendicular to each other can be reduced.
If the film thickness fluctuation of the cellulose ester film support is too large, the phase difference becomes uneven, which causes problems such as coloring when used as an optical compensation film. The thickness variation of the cellulose ester film support is preferably in the range of ± 3%, more preferably ± 1%. For the above purpose, a method of stretching in biaxial directions orthogonal to each other is effective, and the stretching ratio in the biaxial directions orthogonal to each other is 0.8 to 0.8.
It is preferable to set the range to 4.0 times, 0.4 to 1.2 times.

There is no particular limitation on the method of stretching the web. For example, a method in which a circumferential speed difference is applied to a plurality of rolls, and a longitudinal stretching is performed using the circumferential speed difference between the rolls, and both ends of the web are fixed with clips or pins, and the intervals between the clips and pins are widened in the traveling direction. And a method in which the film is spread in the horizontal direction and stretched in the horizontal direction, or a method in which the film is spread vertically and horizontally at the same time and stretched in both the vertical and horizontal directions. Of course, these methods may be used in combination. Further, in the case of the so-called tenter method, it is preferable to drive the clip portion by the linear drive method since smooth stretching can be performed and the risk of breakage can be reduced.

In the film obtained as described above, the amount of the residual solvent in the final finished film is preferably 2% by mass or less, more preferably 0.4% by mass or less, in order to obtain a film having good dimensional stability. Is preferred.

In the present invention, at the time of casting, various conditions described above may be adjusted so that the refractive index in the width direction of the cellulose ester film formed on the casting support is maximized. preferable.

As described above, in the optically biaxial cellulose ester support according to the present invention, the refractive indexes nx, ny, and nz of the film satisfy the relationship of nx>ny> nz. In the present invention, "the refractive index in the width direction is maximized" means that the direction of nx is substantially equal to the width direction.

Here, that the directions are substantially equal indicates that the directions of the axes are substantially parallel. Here, “substantially parallel” means that the angle between the axes is within ± 10 °, preferably within ± 3 °, and more preferably within ± 1 °.

Further, in the polarizing plate of the present invention, the light transmission axis of a polarizer containing a dichroic substance and the casting of an optically biaxial cellulose ester film bonded to the polarizer. It is preferable that the lamination is performed so that the stretching direction in the width direction at the time becomes substantially parallel. In the present invention,
The term “perpendicular” indicates that the axes are substantially perpendicular to each other as described above, and the term “matching in direction” indicates that the directions of the axes are substantially parallel. Here, “substantially parallel” means that the angle between the axes is within ± 10 °, preferably within ± 3 °, and more preferably within ± 1 °.

Further, at the time of producing a polarizing plate, a polarizer containing a dichroic substance and an optically biaxial cellulose ester film are bonded together.
A cellulose ester film produced as a long roll is preferably used. In the present invention, the long is
The length is 500 m or more, preferably 1000 m or more, and particularly preferably 1000 m to 4000 m.

The polarizing plate and the liquid crystal display of the present invention will be described. As the polarizer used for the polarizing plate of the present invention, a conventionally known polarizer can be used. For example, a film made of a hydrophilic polymer such as polyvinyl alcohol and stretched by treating with a dichroic dye such as iodine, or a film obtained by treating and orienting a plastic film such as vinyl chloride is used. The polarizer thus obtained is
Laminate with cellulose ester film. At this time, it is necessary that at least one of the cellulose ester films uses the cellulose ester film of the present invention, but a cellulose triacetate (TAC) film conventionally used as a support for a polarizing plate is used. Although it may be used for laminating the surfaces of other polarizers, in order to maximize the effect described in the present invention, all of the components constituting the polarizing plate in terms of the same physical properties of both surfaces of the polarizing plate protective film It is preferable to use the cellulose ester film of the present invention as the cellulose ester film.

When the polarizing plate is formed by laminating the cellulose ester film, the polarizer, and the cellulose triacetate (TAC) film in this order, a cellulose triacetate film obtained by stretching in the width direction is used. Accordingly, it is possible to obtain a polarizing plate with a phase difference function that maintains excellent optical characteristics and has little resistance to dimensional change (shape change) against changes in temperature and humidity environment. The stretching operation may be performed at the time of casting film formation, or may be performed offline after film formation, but may be continuously performed during casting film formation from the viewpoint of uniformity of stretching, productivity, and the like. preferable. The stretching ratio is preferably in the range of 1.01 to 1.2 times, particularly preferably 1.03 to 1.15 times, and most preferably 1.05 to 1.10 times.

Further, when producing a polarizing plate, the stretching ratio A of the cellulose ester film of the present invention to be stuck on one surface of the polarizer and the cellulose to be stuck to the other surface opposite to the polarizer. As for the relationship with the draw ratio B of the ester film, A / B is preferably in the range of 1000 to 0.001, more preferably 200 to 0.001.
5, particularly preferably in the range of 100 to 0.01.

In the production of the polarizing plate, it is preferable that the casting direction of the cellulose ester film of the present invention during casting and the stretching direction of the polarizer are substantially parallel. The polarizing plate thus obtained is bonded to both sides of a liquid crystal cell, preferably arranged as follows.

The polarizing plate of the present invention is arranged such that the rubbing axis direction of the substrate surface adjacent to the liquid crystal cell and the polarizing plate transmission axis (here, the stretching direction of the polarizer and the light transmission axis are orthogonal). By bonding, a liquid crystal display device can be obtained. Here, FIG. 1 shows a schematic diagram of a liquid crystal display device in the best mode of the present invention. The liquid crystal display device 9 shown in FIG.
Is composed of one liquid crystal cell 7 and two polarizing plates 6a and 6b.

The polarizing plate 6a is composed of two cellulose ester films 1a and one polarizer 2a.
Sheet of cellulose ester film 1b and one sheet of polarizer 2
b.

In the polarizing plates 6a and 6b, the casting direction 3
a, 3b are cellulose ester films 1a, 1
b represents the casting direction during casting. Stretching direction 4a, 4b
Represents the stretching direction of the polarizers 2a and 2b, respectively. The light transmission axes 8a and 8b represent the light transmission axes of the polarizing plates 6a and 6b, respectively, and are orthogonal to the rubbing axes 5a and 5b of the liquid crystal cell 7, respectively. With the simple structure as described above, it is possible to obtain a liquid crystal display device with a remarkably improved viewing angle.

[0129]

EXAMPLES Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to these examples.

Example 1 << Preparation of Cellulose Ester Film >> (Preparation of Cellulose Ester Film 1) Cellulose acetate propionate having a substitution degree of acetyl group of 2.00, a substitution degree of propionyl group of 0.80 and a viscosity average polymerization degree of 350. 100 parts by mass, 5 parts by mass of ethylphthalylethyl glycolate, 3 parts by mass of triphenyl phosphate, 290 parts by mass of methylene chloride, and 60 parts by mass of ethanol are placed in a closed container, and the mixture is gradually heated while slowly stirring. The temperature was raised to 45 ° C. over 60 minutes to dissolve. The pressure in the container was 1.2 atm. Azumi Filter Paper No. No. manufactured by Azumi Filter Paper Co., Ltd. After filtration using 244, the mixture was allowed to stand for 24 hours to remove bubbles in the dope.

Separately, 5 parts by mass of the above-mentioned cellulose acetate propionate, 6 parts by mass of Tinuvin 326 (manufactured by Ciba Specialty Chemicals), and Tinuvin 109 (manufactured by Ciba Specialty Chemicals) 4 parts by mass and 5 parts by mass of Tinuvin 171 (manufactured by Ciba Specialty Chemicals Co., Ltd.) were mixed with 94 parts by mass of methylene chloride and 8 parts by mass of ethanol and dissolved by stirring to prepare an ultraviolet absorbent solution.

The above-mentioned ultraviolet absorbent solution was added at a ratio of 2 parts by mass to 100 parts by mass of the above-mentioned dope, and the mixture was sufficiently mixed by a static mixer, and then cast from a die onto a stainless steel belt at a dope temperature of 30 ° C. After drying for 1 minute on a temperature-controlled stainless steel belt by contacting warm water at a temperature of 25 ° C. from the back surface of the stainless steel belt, further contacting 15 ° C. cold water on the back surface of the stainless steel belt and holding for 15 seconds, Peeled from stainless steel belt. The residual solvent amount in the web at the time of peeling was 100% by mass. Next, by grasping both ends of the peeled web with a clip using a stretching tenter and changing the width direction of the clip interval,
The film was stretched 1.65 times only in the width direction at 120 ° C. Further, the film was dried at 130 ° C. for 10 minutes while being transported by a roller.
A 00 μm cellulose ester film 1 was obtained.

The cellulose ester film 1 was wound around a glass fiber reinforced resin core having a core diameter of 200 mm into a film roll having a width of 1 m and a length of 1000 m by a taper tension method. At this time, a temperature of 250 ° C.
Press the emboss ring of
The adhesion between films was prevented.

From the obtained film roll, a sample was taken from the center in the width direction of the film to obtain a refractive index n in the slow axis direction.
x, the refractive index of the fast axis direction ny, and the refractive index nz in the thickness direction was measured by the following in-plane retardation value R _0, a thickness direction retardation value R _t were calculated, respectively, at the central portion , R _{0 of} 78 nm, and R _{t of} 175 nm.
R ₀ and R _t are defined by the following equations.

R ₀ = (nx−ny) × d, R _t = ((nx
+ Ny) / 2-nz) × d where d is the thickness (nm) of the film. In addition, the direction of the slow axis was ±
It was in the range of 0.8 degrees.

Using an automatic birefringence meter KOBRA-21ADH (manufactured by Oji Scientific Instruments), a three-dimensional refractive index was measured at 23 ° C. and 55% RH at a wavelength of 590 nm to obtain a refractive index nx. , Ny and nz were determined. In addition, as a result of measurement using a moisture content measurement method described later, 1.8%
Met.

<< Preparation of Cellulose Ester Film 2 >>
100 parts by mass of cellulose acetate propionate having a degree of substitution of an acetyl group of 1.60, a degree of substitution of a propionyl group of 1.20, and a viscosity average polymerization degree of 400, 5 parts by mass of ethyl phthalyl ethyl glycolate, and triphenyl phosphate 3
Parts by mass, 290 parts by mass of methylene chloride, and 60 parts by mass of ethanol were placed in a closed vessel, and the mixture was gradually heated while slowly stirring, and then heated to 45 ° C. over 60 minutes to dissolve.
The pressure in the container was 1.2 atm. Azumi Filter Paper No. No. manufactured by Azumi Filter Paper Co., Ltd. After filtration using 244, the mixture was allowed to stand for 24 hours to remove bubbles in the dope. Separately, the above cellulose acetate propionate 5
Parts by mass, 6 parts by mass of Tinuvin 326 (manufactured by Ciba Specialty Chemicals), 4 parts by mass of Tinuvin 109 (manufactured by Ciba Specialty Chemicals), and 171 (Ciba Specialty Chemicals, Inc.)
1 part by mass of AEROSIL R972V (manufactured by Nippon Aerosil Co., Ltd.) and 94 parts by mass of methylene chloride and 8 parts by mass of ethanol were stirred and dissolved to prepare an ultraviolet absorbent solution. R972V was previously dispersed and added to the ethanol.

The above ultraviolet absorbent solution was added at a ratio of 2 parts by mass to 100 parts by mass of the above dope, and the mixture was sufficiently mixed by a static mixer, and then cast from a die onto a stainless steel belt at a dope temperature of 30 ° C. After drying for 1 minute on a temperature-controlled stainless steel belt by contacting warm water at a temperature of 25 ° C. from the back surface of the stainless steel belt, further contacting 15 ° C. cold water on the back surface of the stainless steel belt and holding for 15 seconds, Peeled from stainless steel belt. The residual solvent amount in the web at the time of peeling was 80% by mass. Then, both ends of the peeled web are gripped with clips using a stretching tenter, and the width direction of the clip interval is changed to
The film was stretched 1.5 times in the width direction at 20 ° C. Further, the film was dried at 130 ° C. for 10 minutes while being transported by a roller to obtain a cellulose ester film 2 having a thickness of 50 μm.

The cellulose ester film 2 was wound on a glass fiber reinforced resin core having a core diameter of 200 mm into a film roll having a width of 1 m and a length of 1000 m by a taper tension method. At this time, a temperature of 250 ° C.
Press the emboss ring of
The adhesion between films was prevented.

From the obtained film roll, a sample was taken from the center in the width direction of the film to obtain a refractive index n in the slow axis direction.
x, the refractive index ny in the fast axis direction, and the refractive index nz in the thickness direction were calculated for R ₀ and R _t in the same manner as in the production and evaluation of the cellulose ester film 1, respectively. , 93 nm. The direction of the slow axis was ± 0.4 with respect to the width direction of the film for each sample.
It was in the range of degrees. As a result of measuring the moisture regain, 2.1
%Met.

<< Preparation of Cellulose Ester Film 3 >>
100 parts by mass of cellulose acetate propionate having a degree of substitution of acetyl group of 2.00, a degree of substitution of propionyl group of 0.80, and a viscosity average polymerization degree of 350, 5 parts by mass of ethylphthalylethyl glycolate, and triphenyl phosphate 3
Parts by mass, 175 parts by mass of methyl acetate, and 75 parts by mass of ethanol were put in a closed container, and the mixture was gradually heated while slowly stirring, and was heated to 65 ° C. over 60 minutes to dissolve. The pressure in the container was 1.2 atm. Azumi Filter Paper No. No. manufactured by Azumi Filter Paper Co., Ltd. After filtration using 244, the mixture was allowed to stand for 24 hours to remove bubbles in the dope. Separately, the above cellulose acetate propionate 5
Parts by mass, 6 parts by mass of Tinuvin 326 (manufactured by Ciba Specialty Chemicals), 4 parts by mass of Tinuvin 109 (manufactured by Ciba Specialty Chemicals), and 171 (Ciba Specialty Chemicals, Inc.)
5 parts by mass) were mixed with 94 parts by mass of methyl acetate and 8 parts by mass of ethanol and dissolved by stirring to prepare an ultraviolet absorbent solution. The ultraviolet absorbent solution was added at a ratio of 2 parts by mass with respect to 100 parts by mass of the dope, and the mixture was sufficiently mixed by a static mixer, and then cast from a die onto a stainless steel belt at a dope temperature of 50 ° C. 55 from the back of the stainless steel belt
After drying for 1 minute on a stainless steel belt whose temperature was controlled by contacting with hot water at a temperature of 150 ° C., the back surface of the stainless steel belt was contacted with cold water of 15 ° C. and held for 15 seconds, and then separated from the stainless steel belt. The residual solvent amount in the web at the time of peeling was 70% by mass. Then, both ends of the peeled web are gripped with clips using a simultaneous biaxial stretching tenter, and the intervals between the clips are simultaneously changed in the width direction and the casting direction (length direction), so that the width is 1.8 at 150 ° C. in the width direction.
The film was stretched 1.05 times in the casting direction (length direction). Further, the film was dried at 130 ° C. for 10 minutes while being transported by a roller to obtain a cellulose ester film 3 having a thickness of 120 μm.

The cellulose ester film 3 was wound around a glass fiber reinforced resin core having a core diameter of 200 mm into a film roll having a width of 1 m and a length of 1000 m by a taper tension method. At this time, a temperature of 250 ° C.
Press the emboss ring of
The adhesion between films was prevented.

From the obtained film roll, a sample was taken from the center in the width direction of the film to obtain a refractive index n in the slow axis direction.
x, the refractive index ny in the fast axis direction, and the refractive index nz in the thickness direction were measured in the same manner as above, and R ₀ and R _t were calculated to be 165 nm and 184 nm, respectively. In addition, the direction of the slow axis was ±
It was in the range of 1.2 degrees. As a result of moisture content measurement,
1.6%.

<< Preparation of Cellulose Ester Film 4 >>
100 parts by mass of cellulose acetate propionate having a degree of substitution of acetyl groups of 2.30, a degree of substitution of propionyl groups of 0.5, and a viscosity average degree of polymerization of 300, 5 parts by mass of ethylphthalylethyl glycolate, 3 parts by mass of triphenyl phosphate , 290 parts by mass of methylene chloride and 60 parts by mass of ethanol were placed in a closed container, and the mixture was gradually heated while slowly stirring to 45 ° C. over 60 minutes to dissolve. The pressure in the container was 1.2 atm.

The dope was prepared using Azumi Filter Paper No. After filtration using 244, the mixture was allowed to stand for 24 hours to remove bubbles in the dope. Separately, 3 parts by mass of the above-mentioned cellulose acetate propionate and Tinuvin 32
6 (manufactured by Ciba Specialty Chemicals), 4 parts by mass of Tinuvin 109 (manufactured by Ciba Specialty Chemicals), and 5 parts by mass of Tinuvin 171 (manufactured by Ciba Specialty Chemicals). 90 parts by mass of methylene chloride and 10 parts by mass of ethanol were mixed and dissolved by stirring to prepare an ultraviolet absorbent solution.

The ultraviolet absorbent solution was added at a ratio of 2 parts by mass with respect to 100 parts by mass of the above-mentioned dope, and the mixture was sufficiently mixed by a static mixer, and then cast from a die onto a stainless steel belt at a dope temperature of 35 ° C. After drying for 1 minute on a temperature-controlled stainless steel belt by contacting warm water at a temperature of 35 ° C. from the back surface of the stainless steel belt, further contacting cold water of 15 ° C. with the back surface of the stainless steel belt and holding for 15 seconds, Peeled from stainless steel belt. The residual solvent amount in the web at the time of peeling was 70% by mass.

Next, while the roll is conveyed in an oven at 120 ° C., the peripheral speed of the roll immediately before the exit of the oven is 2.1 times the peripheral speed of the roll immediately after the entrance of the oven. It was stretched 2.1 times in the longitudinal direction). Immediately after stretching, it was cooled to 60 ° C. Further, the both ends of the web were gripped with clips using a tenter, and the web was dried at 140 ° C. for 5 minutes while keeping the clip interval.
A μm cellulose ester film 4 was obtained.

The cellulose ester film 4 was wound on a glass fiber reinforced resin core having a core diameter of 200 mm into a film roll having a width of 1 m and a length of 1000 m by a taper tension method. At this time, a temperature of 270 ° C.
Was pressed to apply a 10 μm-thick processing to prevent adhesion between the films.

From the obtained film roll, a sample was taken from the center in the width direction of the film, and the refractive index n in the slow axis direction was obtained.
x, the refractive index ny in the fast axis direction, and the refractive index nz in the thickness direction were measured in the same manner as described above, and R ₀ and R _t were calculated. The values were 147 nm and 142 nm at the center.
In addition, the direction of the slow axis was within ± 0.5 degrees with respect to the width direction of the film for each sample. As a result of a measurement of the moisture regain, it was 2.0%.

<< Preparation of Cellulose Ester Film 5 >>
Except that the cellulose ester used for the cellulose ester film was changed to cellulose acetate butyrate having a substitution degree of acetyl group of 1.90, a substitution degree of butyryl group of 0.75, and a viscosity average degree of polymerization of 300, the same as in the production of cellulose ester film 1, Thus, a cellulose ester film 5 having a thickness of 100 μm and a film roll thereof were produced.

From the obtained film roll, a sample was taken from the center in the width direction of the film to obtain a refractive index n in the slow axis direction.
x, the refractive index ny in the fast axis direction, and the refractive index nz in the thickness direction were measured in the same manner as described above, and R ₀ and R _t were calculated. The results were 111 nm and 139 nm at the center.

The direction of the slow axis was within ± 1.2 degrees with respect to the width direction of the film for each sample. As a result of a measurement of the moisture content, it was 1.3%.

<< Preparation of Cellulose Ester Film 6 >>
100 parts by mass of cellulose acetate propionate having a degree of substitution of an acetyl group of 1.90, a degree of substitution of a propionyl group of 0.75, and a viscosity average polymerization degree of 350, 2 parts by mass of ethylphthalylethyl glycolate, and 8.5 parts of triphenyl phosphate Parts by mass, 290 parts by mass of methylene chloride, and 60 parts by mass of ethanol were placed in a closed vessel, and the mixture was gradually heated while slowly stirring, and then heated to 45 ° C. over 60 minutes to dissolve. The pressure in the container was 1.2 atm. Azumi Filter Paper No. No. manufactured by Azumi Filter Paper Co., Ltd. After filtration using 244, the mixture was allowed to stand for 24 hours to remove bubbles in the dope.

Separately, 5 parts by mass of the above-mentioned cellulose acetate propionate, 6 parts by mass of Tinuvin 326 (manufactured by Ciba Specialty Chemicals), and Tinuvin 109 (manufactured by Ciba Specialty Chemicals) 4 parts by mass and 5 parts by mass of Tinuvin 171 (manufactured by Ciba Specialty Chemicals Co., Ltd.) were mixed with 94 parts by mass of methylene chloride and 8 parts by mass of ethanol and dissolved by stirring to prepare an ultraviolet absorbent solution.

The ultraviolet absorbent solution was added at a ratio of 2 parts by mass with respect to 100 parts by mass of the above dope, and the mixture was sufficiently mixed by a static mixer, and then cast from a die onto a stainless steel belt at a dope temperature of 30 ° C. After drying for 1 minute on a temperature-controlled stainless steel belt by contacting warm water at a temperature of 25 ° C. from the back surface of the stainless steel belt, further contacting 15 ° C. cold water on the back surface of the stainless steel belt and holding for 15 seconds, Peeled from stainless steel belt. The residual solvent amount in the web at the time of peeling was 70%. Next, both ends of the peeled web were gripped with clips using a stretching tenter, and the width direction of the clip interval was changed to 115.
The film was stretched 1.40 times only in the width direction at ℃. Further dried at 130 ° C. for 10 minutes while transporting with a roller.
Of cellulose ester film 6 was obtained.

Cellulose ester film 6, core diameter 2
The film was wound around a 00 mm glass fiber reinforced resin core into a film roll having a width of 1 m and a length of 1000 m by a taper tension method. At this time, an embossing ring at a temperature of 250 ° C. was pressed against the end of the film, and the film was subjected to thickness processing to prevent adhesion between the films.

From the obtained film roll, a sample was taken from the center in the width direction of the film to obtain a refractive index n in the slow axis direction.
x, the refractive index of the fast axis direction ny, and the refractive index nz in the thickness direction was measured by the following in-plane retardation value R _0, a thickness direction retardation value R _t were calculated, respectively, at the central portion , R _{0 of} 50 nm, and R _{t of} 122 nm.
R ₀ and R _t are defined by the following equations.

R ₀ = (nx−ny) × d, R _t = ((nx
+ Ny) / 2-nz) × d where d is the thickness (nm) of the film. In addition, the direction of the slow axis was ±
It was within the range of 0.7 degrees.

Using an automatic birefringence meter KOBRA-21ADH (manufactured by Oji Scientific Instruments), the three-dimensional refractive index was measured at 23 ° C. and 55% RH at a wavelength of 590 nm to obtain a refractive index nx. , Ny and nz were determined. In addition, as a result of measurement using a moisture content measurement method described later, 1.8%
Met.

<< Preparation of Cellulose Ester Film 7 >>
A cellulose ester film 7 having a thickness of 80 μm was produced in the same manner as the cellulose ester film 6, except that the stretching ratio was 1.30 times in the width direction.

From the obtained film roll, a sample was taken from the center in the width direction of the film to obtain a refractive index n in the slow axis direction.
x, the refractive index of the fast axis direction ny, and the refractive index nz in the thickness direction was measured by the following in-plane retardation value R _0, a thickness direction retardation value R _t were calculated, respectively, at the central portion , R _{0 of} 32 nm and R _{t of} 105 nm.
R ₀ and R _t are defined by the following equations.

R ₀ = (nx−ny) × d, R _t = ((nx
+ Ny) / 2-nz) × d where d is the thickness (nm) of the film. In addition, the direction of the slow axis was ±
It was within the range of 0.7 degrees.

Using an automatic birefringence meter KOBRA-21ADH (manufactured by Oji Scientific Instruments), a three-dimensional refractive index measurement was performed at 23 ° C. and 55% RH at a wavelength of 590 nm to obtain a refractive index nx. , Ny and nz were determined. In addition, as a result of measurement using a moisture content measurement method described later, 1.8%
Met.

<< Preparation of Cellulose Ester Film 8 >>
A cellulose ester film 8 was produced in the same manner as the cellulose ester film 6, except that the final film thickness after stretching was 40 μm.

The width of the film from the obtained film roll
Sampled from the center in the direction, and the refractive index n in the slow axis direction
x, the refractive index ny in the fast axis direction, and the refractive index nz in the thickness direction
Measured according to the following, and the in-plane retardation value R₀,thickness
Direction retardation value R_tWhere each was calculated
R, in the center, R₀28 nm, R_tIt was 91 nm. R
₀, R_tIs defined by the following equation.

R ₀ = (nx−ny) × d, R _t = ((nx
+ Ny) / 2-nz) × d where d is the thickness (nm) of the film. In addition, the direction of the slow axis was ±
It was within the range of 0.7 degrees.

Using an automatic birefringence meter KOBRA-21ADH (manufactured by Oji Scientific Instruments), the three-dimensional refractive index was measured at a wavelength of 590 nm in an environment of 23 ° C. and 55% RH to obtain a refractive index nx. , Ny and nz were determined. Further, as a result of measurement using a moisture content measurement method described later, 1.1%
Met.

<< Preparation of Comparative Control Film >> A cellulose triacetate film (comparative film) conventionally used as a support for a polarizing plate was prepared by the following procedure.

100 parts by mass of cellulose triacetate having a degree of substitution of acetyl group of 2.92 and a viscosity average degree of polymerization of 300,
2 parts by mass of ethyl phthalylethyl glycolate, 10 parts by mass of triphenyl phosphate, 350 parts by mass of methylene chloride, and 50 parts by mass of ethanol are put in a closed container, and the mixture is gradually heated while slowly stirring, and takes 60 minutes. 4
The temperature was raised to 5 ° C. and dissolved. The pressure in the container was 1.2 atm.

This dope was prepared using Azumi Filter Paper No. manufactured by Azumi Filter Paper Co., Ltd. After filtration using 244, the mixture was allowed to stand for 24 hours to remove bubbles in the dope.

Separately, 5 parts by mass of the above-mentioned cellulose triacetate, 3 parts by mass of Tinuvin 326 (manufactured by Ciba Specialty Chemicals Co., Ltd.), 10 parts by mass of Tinuvin 10
9 (manufactured by Ciba Specialty Chemicals), 5 parts by mass of Tinuvin 171 (manufactured by Ciba Specialty Chemicals), and AEROSIL 200
V (manufactured by Nippon Aerosil Co., Ltd.) (1 part by mass) was mixed with 90 parts by mass of methylene chloride and 10 parts by mass of ethanol and dissolved by stirring to prepare an ultraviolet absorbent solution. The ultraviolet absorbent solution was added at a ratio of 2 parts by mass with respect to 100 parts by mass of the dope, and the mixture was sufficiently mixed by a static mixer, and then cast from a die onto a stainless steel belt at a dope temperature of 35 ° C.
After drying for 1 minute on a temperature-controlled stainless steel belt by contacting warm water at a temperature of 35 ° C. from the back surface of the stainless steel belt, further contacting cold water of 15 ° C. with the back surface of the stainless steel belt and holding for 15 seconds, Peeled from stainless steel belt.

The amount of residual solvent in the web at the time of peeling was 70% by mass. Next, the peeled web was dried at 120 ° C. for 10 minutes while fixing both ends of the peeled web to obtain a cellulose triacetate film (comparative film) having a thickness of 80 μm.

From the obtained film roll, a sample was taken from the center in the width direction of the film to obtain a refractive index n in the slow axis direction.
x, the refractive index ny in the fast axis direction, and the refractive index nz in the thickness direction were measured in the same manner as described above, and R ₀ and R _t were calculated to be 2 nm and 42 nm at the center. Also,
The direction of the slow axis was below the measurement limit due to the small _R0 value. As a result of a measurement of the moisture content, it was 1.3%.

<< Moisture Retention Method >> Each cellulose ester film sample obtained above was cut into a size of 10 cm 2, left at 23 ° C. and 80% RH for 48 hours, and the mass was measured. W1. Next, the film was subjected to a heat-drying treatment at 120 ° C. for 45 minutes, and the mass was measured to be W2. The moisture content at 23 ° C. and 80% RH is measured from the obtained measured values by the following formula. The results are shown below.

Water content (%) = ((W1-W2) / W2)
× 100 << Preparation of Polarizing Plate >> (Preparation of Polarizing Plate 1) A polyvinyl alcohol film having a thickness of 120 μm was immersed in an aqueous solution containing 1 part of iodine, 2 parts of potassium iodide and 4 parts of boric acid, and was quadrupled at 50 ° C. The film was stretched to obtain a polarizing film. Next, the above-mentioned cellulose ester film 1 was laminated on this polarizing film by the following procedure to obtain the polarizing plate 1 of the present invention.

(1) As a protective film, the above-mentioned two cellulose ester film supports cut into a rectangular ABCD of 30 cm × 18 cm as shown in FIG. 2 were placed in a 2 mol / l sodium hydroxide solution at 60 ° C. for 1 hour. The sample was immersed for another minute, washed with water and dried.

FIG. 2 is a schematic view of a long cellulose ester film of the present invention produced by casting.
In the long cellulose ester film 10 of the present invention, which is cast and formed, the casting direction 11 is the casting direction at the time of casting, and the width direction 12 is the width direction at the time of casting. Represents The cellulose ester film used for producing the polarizing plate is cut and used, for example, as a rectangular ABCD. The angle between one side AB of the rectangular ABCD and the casting direction 12 of the cellulose ester film 10 is 4 °.
Cut off to be 5 degrees.

(2) The above-mentioned polarizing film (polarizer) adjusted to the same size as the two cellulose ester film samples
Is immersed in a polyvinyl alcohol adhesive tank having a solid content of 2% by mass for 1 to 2 seconds.

(3) The excess adhesive adhering to the polarizing film (polarizer) was gently removed, and placed on the surface of the cellulose ester film sample in an arrangement as shown in FIG. Laminate and arrange so that the surface of the ester film sample is in contact with the adhesive.

FIG. 3 is a schematic view of the polarizing plate of the present invention.
The polarizing plate 6a is arranged and configured so that the polarizer 2a is sandwiched between two cellulose ester films 1a of the present invention. The casting direction during casting of the cellulose ester film 1a and the stretching direction of the polarizer 2a are parallel.

(4) Excessive adhesive and air bubbles are removed from the end of the laminate of the polarizing film and the cellulose ester film laminated by a hand roller, and the laminate is laminated. The hand roller applied a pressure of 20 to 30 N / cm ² and the roller speed was about 2 m / min.

(5) The obtained sample was left in a dryer at 80 ° C. for 2 minutes to prepare a polarizing plate. Next, the obtained polarizing plate (viewing angle expanding polarizing plate 1) was incorporated in a liquid crystal cell as described below, and the characteristics as a display device were evaluated.

<< Preparation of Polarizing Plate 2 >> Using the above-mentioned cellulose ester film 2, a polarizing plate was prepared in the same manner as in the case of the cellulose ester film 1, and the viewing angle was measured by the same method as described above. .

<< Preparation of Polarizing Plate 3 >> A polarizing plate was prepared using the cellulose ester film 3 in the same manner as in the case of the cellulose ester film 1, and the viewing angle was measured by the same method as described above.

<< Preparation of Polarizing Plate 4 >> A polarizing plate was prepared using the cellulose ester film 4 in the same manner as in the case of the cellulose ester film 1, and the viewing angle was measured by the same method as described above.

<< Preparation of Polarizing Plate 5 >> Using the cellulose ester film 5, a polarizing plate was prepared in the same manner as in the case of the cellulose ester film 1, and the viewing angle was measured by the same method as described above.

<< Preparation of Polarizing Plate 6 >> A polarizing plate was prepared by the following procedure using a combination of the above-mentioned comparative control film (cellulose triacetate film) and cellulose ester film 1 as a support for lamination.

First, a polyvinyl alcohol film having a thickness of 120 μm was immersed in an aqueous solution containing 1 part of iodine, 2 parts of potassium iodide and 4 parts of boric acid, and stretched 4 times at 50 ° C. to obtain a polarizing film. Next, (1) as a protective film, as shown in FIG.
Each of the cut cellulose ester film 1 and the same comparative control film was cut into a 2 mol / liter sodium hydroxide solution on a rectangular ABCD of cm × 18 cm.
It was immersed at 0 ° C. for 1 minute, further washed with water and dried.

(2) The above-mentioned polarizing film adjusted to the same size as the two cellulose ester film samples was placed in a polyvinyl alcohol adhesive tank having a solid content of 2% by mass.
Soak for ~ 2 seconds.

(3) As in FIG. 3, except that the excess adhesive adhering to the polarizing film was lightly removed and one of the two cellulose ester films of the present invention was replaced with the comparative film described above. The cellulose ester film was laminated on the polarizer in an appropriate arrangement.

(4) Excessive adhesive and air bubbles are removed from the end of the laminate of the polarizing film and the cellulose ester film laminated by a hand roller, and the laminate is bonded. The hand roller applied a pressure of 20 to 30 N / cm ² and the roller speed was about 2 m / min.

(5) The obtained sample was left in a dryer at 80 ° C. for 2 minutes to produce a polarizing plate. Next, the viewing angle of the polarizing plate 1 with a wide viewing angle was measured by the following method.

The viewing angle widening polarizing plate 1 is provided on both sides of the liquid crystal cell.
The rubbing axis direction of the substrate surface adjacent to the liquid crystal cell was orthogonal to the polarizing plate transmission axis, and the cellulose ester film 1 as a support was bonded to the liquid crystal cell side (inside). The viewing angle was measured by the same method as described above.

<< Preparation of Polarizing Plate 7 >>
Polyvinyl alcohol 100 having a saponification degree of 99.5 mol%
Was dissolved in water to obtain a solution having a concentration of 5.0% by mass. The liquid was cast on polyethylene terephthalate and dried to obtain a raw film. 0.2 g / l of iodine,
It is immersed in an aqueous solution of potassium iodide 60 g / l at 30 ° C. for 240 seconds, and then immersed in an aqueous solution of boric acid 70 g / l and potassium iodide 30 g / l, and at the same time, 6.0 times in the transport direction. The resultant was subjected to a boric acid treatment for 5 minutes while being transported while being uniaxially stretched, and dried. On the other hand, the above-mentioned cellulose ester film 1 was wound around a glass fiber reinforced resin core having a core diameter of 200 mm into a film roll having a width of 1 m and a length of 1000 m to obtain a 2 mol / l sodium hydroxide solution. It was immersed at 60 ° C. for 1 minute, further washed with water and dried. This saponified cellulose ester film was continuously bonded on both sides of the above-mentioned stretched and wound-up polyvinyl alcohol film by roll-to-roll using a polyvinyl alcohol-based adhesive as a protective film. As shown in FIG. 2, a rectangular ABCD of 30 cm × 18 cm
Was cut out.

Next, the viewing angle of the polarizing plate 11 with a wide viewing angle was measured by the following method.

The viewing angle widening polarizing plate 11 was bonded to both surfaces of the liquid crystal cell such that the rubbing axis direction of the substrate surface close to the liquid crystal cell was perpendicular to the polarizing plate transmission axis. The viewing angle was measured by the same method as described above.

<< Preparation of Comparative Polarizing Plate 8 >> Using two comparative cellulose ester films, a polarizing plate was prepared in the same manner as in the case of using the cellulose ester film 1, and this was subjected to the same method as described above. Was used to measure the viewing angle.

<< Measurement of Viewing Angle >> Next, by the following method,
The viewing angle of the viewing angle-enlarging polarizing plate 1 was measured.

The viewing angle widening polarizing plate 1 is provided on both sides of the liquid crystal cell.
They were arranged and bonded as follows, and evaluated by a panel. That is, the polarizing plate of the present invention was bonded so that the rubbing axis direction of the substrate surface adjacent to the liquid crystal cell was perpendicular to the polarizing plate transmission axis. The liquid crystal cell is NEC's 15-inch display Mu
The lti Sync LCD1525J was obtained by peeling off the optical compensation film and the polarizing plate that had been bonded in advance. The liquid crystal display device obtained in this manner was
The viewing angle was measured by EZ-contrast manufactured by DIM. The viewing angle was expressed as a range of the inclination angle from the normal direction to the panel surface where the contrast ratio between white display and black display of the liquid crystal cell was 10 or more. As a result, the values of the viewing angles obtained using the viewing angle widening polarizing plate 1 of the present invention are shown below.

Viewing angle Sample Left Right Top Bottom Remarks Polarizer 1 65 ° 65 ° 28 ° 29 ° Present invention Polarizer 2 57 ° 57 ° 27 ° 23 ° Present invention Polarizer 3 60 ° 60 ° 27 ° 27 ° Present invention Polarizing Plate 4 55 ° 55 ° 25 ° 25 ° Present Invention Polarizing Plate 5 62 ° 62 ° 27 ° 25 ° Present Invention Polarizing Plate 6 65 ° 65 ° 28 ° 28 ° Present Invention Polarizing Plate 7 64 ° 64 ° 27 ° 26 ° The present invention polarizing plate 8 35 ° 35 ° 25 ° 20 ° Comparative Example From the above evaluation results, the sample of the present invention was
It is clear that the viewing angle has been significantly improved.

Example 2 Polarizing plates 9 to 13 were produced as follows.

<< Preparation of Polarizing Plate 9 >> (Preparation of Cellulose Ester Film A) A cellulose triacetate film (cellulose ester film A) for a polarizing plate protective film was prepared by the following procedure.

100 parts by mass of cellulose triacetate having a degree of substitution of acetyl group of 2.92 and a viscosity average degree of polymerization of 300,
2 parts by mass of ethylphthalylethyl glycolate, 8.5 parts by mass of triphenyl phosphate, 350 parts of methylene chloride
Parts by mass and 50 parts by mass of ethanol were placed in a closed container, and the mixture was gradually heated while slowly stirring, and then heated to 45 ° C. over 60 minutes to dissolve. The pressure in the container was 1.2 atm.

This dope was prepared using Azumi Filter Paper No. manufactured by Azumi Filter Paper Co., Ltd. After filtration using 244, the mixture was allowed to stand for 24 hours to remove bubbles in the dope.

Separately, 5 parts by mass of the above-mentioned cellulose triacetate, 3 parts by mass of Tinuvin 326 (manufactured by Ciba Specialty Chemicals Co., Ltd.), 10 parts of Tinuvin 10
9 (manufactured by Ciba Specialty Chemicals), 5 parts by mass of Tinuvin 171 (manufactured by Ciba Specialty Chemicals), and AEROSIL 200
V (manufactured by Nippon Aerosil Co., Ltd.) (1 part by mass) was mixed with 90 parts by mass of methylene chloride and 10 parts by mass of ethanol and dissolved by stirring to prepare an ultraviolet absorbent solution. The ultraviolet absorbent solution was added at a ratio of 2 parts by mass with respect to 100 parts by mass of the dope, and the mixture was sufficiently mixed by a static mixer, and then cast from a die onto a stainless steel belt at a dope temperature of 35 ° C.
After drying for 1 minute on a temperature-controlled stainless steel belt by contacting warm water at a temperature of 35 ° C. from the back surface of the stainless steel belt, further contacting cold water of 15 ° C. with the back surface of the stainless steel belt and holding for 15 seconds, Peeled from stainless steel belt.

The amount of residual solvent in the web at the time of peeling was 80% by mass. Next, both ends of the peeled web were gripped with clips using a stretching tenter, and the web was stretched 1.07 times only in the width direction at 105 ° C. by changing the width direction of the clip interval. Further, the film was dried at 130 ° C. for 10 minutes while being transported by a roller to obtain a cellulose ester film A having a thickness of 80 μm.

Obtained cellulose ester film A
And using the cellulose ester 6 described in Example 1,
A polarizing plate 9 was manufactured in the same manner as the manufacturing of the polarizing plate 1 of Example 1.

The viewing angle of the polarizing plate 9 was measured in the same manner as described in Example 1 (before storage).
After standing (after storage) under a condition of 90 ° C. and 90% humidity for 500 hours, the viewing angle was measured by the same method as described above.

<< Preparation of Polarizing Plate 10 >> A cellulose triacetate film for a polarizing plate protective film (cellulose ester film) was prepared in the same procedure as for the cellulose ester film A, except that the stretching ratio in the width direction after peeling was 1.15. B) was prepared.

Using this cellulose ester film B, a polarizing plate 10 was produced in the same manner as in the case of the polarizing plate 9. The obtained polarizing plate 10 was evaluated in the same manner as the polarizing plate 9.

<< Preparation of Polarizing Plate 11 >> A cellulose triacetate film for a polarizing plate protective film (a cellulose ester film) was prepared in the same procedure as for the cellulose ester film A except that the stretching ratio in the width direction after peeling was 1.20. C) was prepared.

Using this cellulose ester film C, a polarizing plate 11 was produced in the same manner as in the case of the polarizing plate 9. The obtained polarizing plate 11 was evaluated in the same manner as the polarizing plate 9.

<< Preparation of Polarizing Plate 12 >> A cellulose triacetate film for a polarizing plate protective film (cellulose ester film) was prepared in the same procedure as for the cellulose ester film A, except that the stretching ratio in the width direction after peeling was changed to 1.02. D) was prepared.

Using this cellulose ester film D, a polarizing plate 12 was produced in the same manner as in the case of the polarizing plate 9. The obtained polarizing plate 12 was evaluated in the same manner as the polarizing plate 9.

<< Preparation of Polarizing Plate 13 >> Cellulose ester film A except that stretching in the width direction after peeling was not performed.
According to the same procedure as described above, a cellulose triacetate film (cellulose ester film E) for a polarizing plate protective film was produced.

Using this cellulose ester film E, a polarizing plate 13 was produced in the same manner as in the case of the polarizing plate 9. The obtained polarizing plate 13 was evaluated in the same manner as the polarizing plate 9.

Viewing angle Sample Left Right Top Bottom Polarizer 9 (before storage) 64 ° 64 ° 28 ° 27 ° Polarizer 9 (after storage) 64 ° 64 ° 27 ° 28 ° (no deterioration) Polarizer 10 (before storage) 65 ° 65 ° 27 ° 27 ° Polarizer 10 (after storage) 65 ° 65 ° 28 ° 26 ° (no deterioration) Polarizer 11 (before storage) 65 ° 65 ° 27 ° 27 ° Polarizer 11 (after storage) 61 ° 60 ° 28 ° 25 ° (slightly degraded) Polarizing plate 12 (before storage) 65 ° 65 ° 27 ° 27 ° Polarizing plate 12 (after storage) 62 ° 62 ° 25 ° 27 ° (slightly degraded) Polarizing plate 13 (before storage) 65 ° 65 ° 27 ° 27 ° Polarizing plate 13 (after storage) 55 ° 57 ° 23 ° 23 ° (Slightly degraded) From the above evaluation results, polarizing plates 9 to having the cellulose ester film of the present invention can be obtained. 13 clearly shows that a good viewing angle improving effect is seen. That. Further, when the treatment after storage over time, the polarizing plate 13 using only one of the two cellulose ester films constituting the polarizing plate, deterioration of the viewing angle after storage is slightly observed, Although light leakage was observed during black display, both of the polarizing plates 9-1 using the cellulose ester film of the present invention were used.
It can be seen that Sample No. 2 shows an excellent viewing angle improving effect after storage over time as well as before storage.

Further, the polarizing plates 9 to 13 each use a cellulose ester film 6 having a draw ratio of 1.40 on one surface, and the polarizing plate after storage treatment with time (60 ° C., 90%, 500 hours). As a result of visually observing the curl characteristics of the plate, the polarizing plate 13 using the cellulose ester film E, which had not been subjected to the stretching operation, as a protective film on one side, while the curl due to the dimensional change of the polarizing plate itself was observed,
Stretch ratio 2% (cellulose ester film D), 20
% (Cellulose ester film C), 15% (cellulose ester film B), and 7% (cellulose ester film A) when each of the cellulose ester films was used as a single-sided protective film, the stretching ratio was 2%, 20%
The improvement was observed in the case of No. 1 and 15% and 7%, and almost no curling occurred.

[0219]

According to the present invention, a TN-TFT
Viewing angle characteristics of the LCD, that is, the viewing angle expansion polarizing plate and the cellulose ester film used for the polarizing plate, which can easily improve the contrast of the screen when viewed from an oblique direction, coloring, and the reversal phenomenon of light and dark. A liquid crystal display device with a remarkably improved viewing angle can be provided with a simple configuration using a viewing angle widening polarizing plate.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a configuration of a liquid crystal display device of the present invention.

FIG. 2 is a schematic view of a long cellulose ester film of the present invention produced by casting.

FIG. 3 is a schematic diagram illustrating a configuration of a polarizing plate of the present invention.

[Explanation of symbols]

1a, 1b Cellulose ester film 2a, 2b Polarizer 3a, 3b Casting direction during casting of cellulose ester film 4a, 4b Stretching direction of polarizer 5a, 5b Rubbing direction of liquid crystal cell 6a, 6b Polarizing plate 7 Liquid crystal cell 8a, 8b Light transmission axis of polarizing plate 9 Liquid crystal display device 10 Long cellulose ester film 11 Casting direction in casting film 12 Width direction in casting film ABCD Rectangle to be cut

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) G02B 5/30 G02B 5/30 G02F 1/1335 510 G02F 1/1335 510 // B29K 1:00 B29K 1: 00 B29L 7:00 B29L 7:00 C08L 1:10 C08L 1:10 (72) Inventor Nobuyuki Takiyama No. 1 Sakura-cho, Hino-shi, Tokyo In-house (72) Inventor Takatoshi Yajima 1 Sakura-cho, Hino-shi, Tokyo Address Konica Stock Company In-house (72) Koji Tasaka Inventor Koshi Co., Ltd. 1 Sakuracho, Hino-shi, Tokyo F-term (reference) 2H049 BA02 BA06 BA25 BA27 BB03 BB20 BB33 BB43 BB51 BB62 BC03 BC09 BC14 BC22 2H091 FA08X FA08Z FB02 HA07 KA01 KA02 LA17 LA19 4F071 AA09 AH19 BA02 BB02 BB07 BC01 4F100 AJ06A AJ06C AK21B AS00B BA03 BA06 BA10A BA10C CB00 EH312 EJ182 E J373 EJ943 GB41 JA20A JA20C JM02B JN18A JN18C 4F205 AA01 AG01 AH81 AP20 AR20 GA07 GB02 GE21 GF24 GN30 GW26

Claims (19)

[Claims] 1. A cellulose ester film having optically biaxial properties. 2. The cellulose ester film according to claim 1, wherein the cellulose ester film is prepared so as to have a maximum refractive index in the width direction during casting. 3. The cellulose ester film according to claim 2, produced as a long roll. 4. An in-plane retardation value R ₀ of 30 to 3.
The cellulose ester film according to claim 2, wherein the thickness is 00 nm. 5. The thickness direction retardation value R _t is 3
The cellulose ester film according to any one of claims 2 to 4, wherein the thickness is from 0 to 300 nm. 6. The cellulose ester film according to claim 2, wherein the following formulas (1) and (2) are simultaneously satisfied. Formula (1) 2.4 ≦ A + B ≦ 2.8 Formula (2) 1.4 ≦ A ≦ 2.0 [wherein A represents the degree of substitution of an acetyl group, and B represents the acyl group having 3 or 4 carbon atoms. Indicates the degree of substitution. ] 7. A polarizing plate comprising the cellulose ester film according to any one of claims 1 to 6. 8. A polarizing plate comprising a cellulose ester film according to claim 1 and a polarizer containing a dichroic substance, wherein the orientation direction of the dichroic substance and the cellulose ester film A polarizing plate, wherein an angle between the polarizing plate and a direction giving the maximum refractive index in the plane of the above is 80 ° to 100 °. 9. A polarizing plate having a cellulose ester film according to claim 1 and a polarizer containing a dichroic substance, wherein the light transmission axis of the polarizer and the cellulose ester film are different from each other. A polarizing plate, wherein the angle between the in-plane direction and the direction giving the maximum refractive index is -10 ° to 10 °. 10. Polarized light having the cellulose ester film according to any one of claims 1 to 6, a cellulose ester film B different from or the same as the cellulose ester film, and a polarizer containing a dichroic substance. A polarizing plate, wherein the cellulose ester film B is stretched in the same direction as the cellulose ester film. 11. The polarizing plate according to claim 10, wherein the cellulose ester film B is stretched in the width direction during or after film formation. 12. The stretch ratio of the cellulose ester film or cellulose ester film B is 1.02 to 1.02.
The polarizing plate according to claim 10, wherein the polarizing plate is stretched so as to be 1.2 times. 13. The stretch ratio of the cellulose ester film or cellulose ester film B is 1.05 to 1.05.
The polarizing plate according to any one of claims 10 to 12, wherein the polarizing plate is stretched so as to be 1.15 times. 14. The cellulose ester film B is triacetyl cellulose.
14. The polarizing plate according to any one of items 13 to 13. 15. A liquid crystal display device comprising the polarizing plate and the liquid crystal cell according to claim 7, wherein the cellulose ester film of the polarizing plate contains the dichroic substance of the polarizing plate. A liquid crystal display device, which is disposed between a cell and the liquid crystal cell. 16. The liquid crystal display device according to claim 15, wherein a light transmission axis of the polarizing plate is orthogonal to a rubbing axis or a liquid crystal alignment axis of a liquid crystal cell on which the polarizing plate is disposed. 17. An angle between a direction in which the refractive index of the cellulose ester film of the polarizing plate disposed on the side of the surface where the polarizing plate and the liquid crystal cell are bonded to each other and a light transmission axis of the polarizing plate is − The liquid crystal display device according to claim 16, wherein the angle is adjusted to 10 to 10 degrees. 18. In producing the cellulose ester film according to any one of claims 1 to 6, an operation of imparting optically biaxiality to the cellulose ester film is performed, and a long roll is provided. A method for producing a cellulose ester film, which is produced. 19. A method for manufacturing a polarizing plate, wherein the polarizing plate according to claim 7 is manufactured through the following steps (1) to (3). (1) Produce a long roll of a cellulose ester film that has been subjected to an operation of optically imparting biaxiality and has been adjusted so that the refractive index in the width direction during casting film formation is maximized. ) Forming a polarizer containing a dichroic substance (3) Laminating the polarizer on the long roll