JP2011209753A - Polarizing plate and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cellulose ester film that easily improves viewing angle characteristic, a polarizing plate using the same, and a liquid crystal display device in which a viewing angle is improved with a simple configuration.SOLUTION: A long roll polarizing plate has a long roll cellulose ester film and a long roll triacetyl cellulose film on both sides of a polarizer containing dichroic substance as protective films, the long roll cellulose ester film being optically biaxial, having the maximum axis with which refractive index becomes maximum in its widthwise direction, having a 30-300 nm in-plane retardation value Rand a 30-300 nm retardation value Rin its thickness direction.

Description

  The present invention relates to a polarizing plate and a method for producing a polarizing plate.

  Conventionally, as an optical compensation film used for widening the viewing angle of a liquid crystal display device, the following three types of configurations have been tried, and each has been proposed as an effective method.

(1) A method of supporting a discotic liquid crystalline compound, which is a compound having negative uniaxiality, on a support. (2) A nematic polymer liquid crystalline compound having positive optical anisotropy is liquid crystal in the depth direction. Method of supporting on substrate a substrate having a hybrid orientation in which the pretilt angle of the molecule changes (3) Each layer having a nematic liquid crystal compound having positive optical anisotropy in a two-layer structure on the substrate However, each of the above-described configurations has the following problems.

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

  In the method described in (2) above, the liquid crystal expression 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, it needs to be transferred to a support such as TAC, which complicates the process and extremely reduces the productivity.

  As an example of the method described in the above (3), for example, JP-A-8-15681 discloses a polarizer having alignment ability as an optically anisotropic layer using a rod-like positive uniaxial low-molecular liquid crystalline compound. A rod-shaped layer composed of a positive uniaxial low-molecular liquid crystalline compound oriented through a rod is formed, fixed, and further oriented again through a polarizer having orientation ability on this layer. An optically anisotropic layer having a four-layer structure is disclosed in which a layer composed of a positive uniaxial low-molecular liquid crystalline compound is formed and immobilized. In this case, it is possible to provide a pseudo disk-like characteristic by shifting the alignment directions projected in the plane of the two liquid crystal layers by 90 degrees, for example.

  Therefore, unlike the case of the discotic liquid crystalline compound, the method described in the above (3) has no problem of coloring, and thus has a very advantageous characteristic in applications such as a liquid crystal TV (TV) where color reproducibility is important. Have.

  However, this method dares to achieve what is achieved in one layer in the discotic liquid crystalline compound with two liquid crystal layers, and has a problem that the efficiency is very low.

  Furthermore, both of these methods have more fundamental and common problems. That is, according to these methods, it is necessary to precisely apply a thin film of a liquid crystalline compound in order to obtain an optical compensation capability. In order to apply the liquid crystal compound by aligning it, an alignment layer is applied in advance and a treatment for imparting an alignment regulating force (rubbing treatment, polarization exposure treatment, etc.) is performed. This is a simple optical compensation film. This also means that the cost of viewing angle improvement is very high. In addition, as a method not using a liquid crystalline compound, a resin usually used as a retardation plate such as polycarbonate is stretched to produce a biaxially oriented retardation plate, and this is post-bonded to a polarizing plate so-called elliptical. There is a method of expanding a viewing angle by forming a polarizing plate, and for example, it is commercially available as a VAC film or a New VAC film from Sumitomo Chemical Co., Ltd. However, such a biaxially oriented retardation plate is very difficult to stretch uniformly in terms of material, and requires advanced stretching techniques. There was also a problem that the yield was low. Furthermore, since this retardation plate is used by being bonded and bonded to a polarizing plate, the number of manufacturing steps increases, and an increase in cost cannot be avoided. Thus, there has been no polarizing plate having a viewing angle widening effect at low cost by the same manufacturing method as that of the conventional polarizing plate.

  Therefore, there has been a demand for a solution to the above problems.

JP 2000-154261 A JP 2000-053784 A

  An object of the present invention is a viewing angle widening polarizing plate that can easily improve the viewing angle characteristics of a TN type LCD such as a TN-TFT, that is, the contrast, coloring, and contrast inversion when viewed from an oblique direction. Another object of the present invention is to provide a cellulose ester film used for a polarizing plate, and further to provide a liquid crystal display device having a simple structure and remarkably improved viewing angle using the viewing angle widening polarizing plate.

The above object of the present invention has been achieved by the following configurations 1 to 4.
1. In-plane retardation value R ₀ having an axis that is optically biaxial and has a maximum refractive index in the width direction is 30 to 300 nm, and the retardation value R _{t in the} thickness direction is 30 to 300 nm. A long roll polarizing plate comprising a long roll cellulose ester film and a long roll triacetyl cellulose film as protective films on both surfaces of a polarizer containing a dichroic substance.
2. 2. The polarizing plate according to 1 above, wherein the cellulose ester film satisfies the following formulas (1) and (2) simultaneously.

Formula (1) 2.4 <= A + B <= 2.8
Formula (2) 1.4 ≦ A ≦ 2.0
[Wherein, A represents the degree of substitution of the acetyl group, and B represents the degree of substitution of the acyl group having 3 or 4 carbon atoms. ]
3. In optically has a biaxial, stretching 1.0 to 3.5 times the least width direction during casting film, in-plane retardation value R _0, which is produced as a long roll 30~300nm There, a feature that the thickness direction retardation value R _t is a cellulose ester film is 30 to 300 nm, and a long roll triacetyl cellulose film, be bonded in a long roll polarizer containing a dichroic substance A method for producing a long roll polarizing plate.
4). 4. The method for producing a long roll polarizing plate according to 3, wherein the film is stretched by 0.4 to 1.2 times in a direction orthogonal to the width direction.

  Hereinafter, the present invention will be described in detail.

  According to the present invention, a viewing angle widening polarizing plate that can easily improve the viewing angle characteristics of a TN type LCD such as a TN-TFT, that is, the contrast, coloring, and contrast inversion when viewed from an oblique direction, and the polarizing plate By using the cellulose ester film used in the present invention and the polarizing plate for expanding the viewing angle, it was possible to provide a liquid crystal display device in which the viewing angle was remarkably improved with a simple configuration.

It is a schematic diagram which shows the structure of the liquid crystal display device of this invention. It is a schematic diagram of the elongate cellulose ester film of this invention produced by casting film forming. It is a schematic diagram which shows the structure of the polarizing plate of this invention.

  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 oriented on a transparent support, or a biaxially stretched phase difference using a resin such as polycarbonate and a complicated stretching technique. In practice, a method using a plate, that is, an optical film having such complicated optical anisotropy is bonded to a polarizing plate for use. The present inventors have now shown that the optically biaxial cellulose ester film of the present invention has sufficient optical compensation ability and can maintain stable optical compensation ability even under high temperature and high humidity conditions. As a result, the inventors have found an elliptical polarizing plate that uses 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, and also has a wide viewing angle, and there is no coloring of the screen when viewed from an oblique direction, and an inversion region is also present. It was found that the optical compensation ability was excellent such as narrowing.

  Furthermore, although the cellulose ester film used for the polarizing plate having the viewing angle widening effect of the present invention has a characteristic of being optically biaxial, in order to obtain such optical characteristics when the cellulose ester film is used. It is not necessary to perform biaxial stretching, and optically biaxiality can be obtained simply by performing uniaxial stretching. This is because the cast cellulose ester film itself was originally negative uniaxial (nX = nY> nZ; nX, nY are the in-plane X and Y direction refractive indices, and nZ is the film thickness direction refraction. It is thought that this is because of

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

  In addition, by preparing a polarizing plate using the cellulose ester film of the present invention, it is possible to replace the type of cellulose ester film used for the support by simply using the conventional polarizing plate preparation process as it is. It becomes possible to produce a viewing angle widening polarizing plate by the same method as that for the plate, and there is a great practical advantage. That is, the cellulose ester film is a very suitable support because it can be bonded by performing an alkali saponification treatment with a polarizer in the polarizing plate production process and has excellent water removability after bonding. As the polarizer, usually, a stretched polyvinyl alcohol film doped with a dichroic substance is preferably used.

  The present invention provides a viewing angle widening polarizing plate having a viewing angle widening function only by a polarizing plate, a long optically biaxial cellulose ester film used therefor, a method for producing the viewing angle widening polarizing plate, and the viewing angle widening It is possible to provide a liquid crystal display device using a polarizing plate. More specifically, the contrast change due to the viewing angle peculiar to twisted nematic (TN) type liquid crystal, in particular, the viewing angle dependency of the display of an active matrix type TN type liquid crystal display device used as a full color display is improved.

  The optical characteristics of the cellulose ester film of the present invention will be described.

  In the present invention, an optically biaxial cellulose ester film is used, but the above optical characteristics are usually obtained by applying tension in a certain direction in the process of producing cellulose ester by casting. be able to. For example, it is particularly effective to perform an operation such as stretching under conditions where a residual solvent exists after casting the cellulose ester film. 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 substitution degree only needs to exceed 2.0, and in particular, a cellulose ester having a total substitution degree of all acyl groups of 2.8 or more is preferably used. It is done. Furthermore, in order to obtain a certain level or more 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 preferably has an acyl group having 2 to 4 carbon atoms as a substituent and satisfies the above formulas (1) and (2) at the same time.

  Furthermore, in this invention, the cellulose-ester film which satisfy | fills following formula (3) and (4) simultaneously is used preferably.

Formula (3) 2.5 <= A + B <= 2.75
Formula (4) 1.7 ≦ A ≦ 1.95
These acyl groups may be substituted on the 2nd, 3rd and 6th positions of the glucose unit on average, and may be substituted with a distribution such as substitution at a high ratio at the 6th position, for example. good.

  Here, the degree of substitution refers to a 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 in ASTM-D817-91 (test method for cellulose acetate and the like). The measuring method of the substitution degree of an acyl group can be measured according to ASTM-D817-96.

  The total substitution degree of the acetyl group and the acyl group having 3 to 4 carbon atoms is in the above range, so that the longer wavelength has the property of increasing the phase difference, and has a good moisture content and water barrier property. A cellulose ester film can be obtained.

  In particular, it is preferable that the average degree of substitution of the acetyl group is less than 2.0 because there is little variation in retardation during stretching.

  In addition, from the viewpoint of obtaining an optical compensation film having excellent mechanical strength, the viscosity average polymerization degree (polymerization degree) of the cellulose ester used in the present invention is preferably 200 or more and 700 or less, and particularly preferably 250 or more and 500 or less. preferable.

  The viscosity average degree of polymerization (DP) described above is determined by the following method.

<< Measurement of viscosity average degree of polymerization (DP) >>
0.2 g of completely 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 by an Ostwald viscometer at 25 ° C., and the number of seconds of fall is measured, and the degree of polymerization is determined by the following equation.

(A) ηrel = T / Ts
(B) [η] = (lnηrel) / C
(C) DP = [η] / Km
Here, T is the falling seconds of the measurement sample, Ts is the falling seconds of the solvent, C is the cellulose ester concentration (g / l), and Km = 6 × 10 ⁻⁴ .

"Retardation value _R t, measurement of _{R 0"}
From the viewpoint of obtaining a viewing angle expansion effect more preferably, the cellulose ester film according to the present invention preferably has a relationship defined by the formula (I).

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

In addition, the optically biaxial cellulose ester support of the present invention is optically biaxial, and an effect of improving the viewing angle is recognized, but the preferred condition is that the retardation value R _{t in the} thickness direction. Value and the in-plane retardation value R ₀ , and the viewing angle expansion effect can be remarkably improved by appropriately controlling these values. As a specific control method, a stretching method described later can be used.

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, and more preferably from 60～250Nm.

Formula (II) ((nx + ny) / 2-nz) × d
Further, the retardation value R ₀ in the in-plane direction is represented by the following formula.

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

In the present invention, R ₀ is preferably in the range of 30 to 300 nm, more preferably 40 to 150 nm.

The retardation value, R _t , and R ₀ described above were measured using an automatic birefringence meter KOBRA-21ADH (manufactured by Oji Scientific Instruments) under the environment of 23 ° C. and 55% RH. It is obtained by measuring a three-dimensional refractive index at 590 nm and obtaining refractive indexes nx, ny, and 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. 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 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 industrially most common synthesis method, cellulose is mixed with an organic acid component containing an organic acid (acetic acid, propionic acid) corresponding to acetyl group and propionyl group or an acid anhydride thereof (acetic anhydride, propionic anhydride). The cellulose ester is synthesized by esterification. The amount of the acetylating agent and propionylating agent used is adjusted so that the ester to be synthesized falls within the range of the substitution degree described above. The amount of the reaction solvent used is preferably 100 to 1000 parts by mass, and more preferably 200 to 600 parts by mass with respect to 100 parts by mass of cellulose. It is preferable that the sample amount of an acidic catalyst is 0.1-20 mass parts with respect to 100 mass parts of cellulose, More preferably, it is 0.4-10 mass parts.

  The reaction temperature is preferably 10 to 120 ° C, more preferably 20 to 80 ° C. Other acylating agents (eg, butyrating agents) and esterifying agents (eg, sulfuric acid esterifying agents) may be used in combination. Further, after 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 using 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 a cotton linter that has good releasability from a belt or drum because of high production efficiency. When the ratio of cellulose ester synthesized from cotton linter is 60% by mass or more and the effect of peelability becomes remarkable, 60% by mass or more is preferable, more preferably 85% by mass or more, and most 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.

  Examples of the acyl group having 3 or 4 carbon atoms include a propionyl group and a butyryl group. A propionyl group or an n-butyryl group is preferred, and a propionyl group is particularly preferred from the viewpoint of mechanical strength when formed into a film, ease of dissolution, and the like.

  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-dioxolane, cyclohexanone, 2,2,2-trifluoroethanol, 2, Examples include 2,3,3-hexafluoro-1-propanol and 1,3-difluoro-2-propanol.

  Among them, a chlorinated solvent such as methylene chloride can be preferably 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 together with methyl acetate with respect to the total organic solvent because the viscosity of the dope solution can be reduced.

  In the present invention, the phrase “substantially free of chlorinated solvent” means that the chlorinated solvent is 10% or less by mass, preferably 5% or less, and most preferably not contained at all, with respect to the total amount of organic solvent.

  In addition to the organic solvent, the fatty acid cellulose ester dope used in the present invention preferably contains 1 to 30% by mass of an alcohol having 1 to 4 carbon atoms. After casting the dope onto the casting support, the solvent begins to evaporate, and when the alcohol ratio increases, the web (dope film) gels, making the web strong and peeling from the casting support. And the effect of promoting 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, iso-propanol, n-butanol, sec-butanol, and tert-butanol. Of these, ethanol is preferred because it has good dope stability, a relatively low boiling point, good drying properties, and no toxicity.

  The solid concentration of the dope is usually preferably 10 to 40% by mass, and the dope viscosity is preferably adjusted to a range of (10 to 50 Pa · sec) from the viewpoint of obtaining good film flatness.

  The dope prepared as described above is filtered with a filter medium, defoamed, and sent to the next process with 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 itself exhibits an effect as a plasticizer, sufficient film properties can be obtained without adding a plasticizer or with a small addition amount. However, 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, carboxylic acid esters and the like can be mentioned.

  Examples of alkyl phthalyl alkyl glycolates include methyl phthalyl methyl glycolate, ethyl phthalyl ethyl glycolate, propyl phthalyl propyl glycolate, butyl phthalyl butyl glycolate, octyl phthalyl octyl 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, octyl phthalate Ethyl glycolate, and the like.

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

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

  Examples of citrate esters include acetyl triethyl citrate, acetyl triethyl citrate, and acetyl tributyl citrate.

  In addition, butyl oleate, methylacetyl ricinoleate, dibutyl sebacate, triacetin and the like are preferably used alone or in combination. Two or more plasticizers may be used in combination as required. When used for cellulose esters, the use ratio of the phosphate ester type plasticizer is preferably 50% or less because it hardly causes hydrolysis of the cellulose ester film and is excellent in durability. It is more preferable that the ratio of the phosphate ester plasticizer is small, and it is particularly preferable to use only the phthalate ester or glycolate ester 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 preferable, and ethyl phthalyl ethyl glycolate is particularly preferable. . Moreover, you may use these alkylphthalyl alkyl glycolates in mixture of 2 or more types.

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

  These compounds may be added together with the cellulose ester and the solvent during the preparation of the cellulose ester solution, or may be added during or after the solution preparation.

  A dye may be added for the purpose of improving the yellowness of the film. The tint is preferably one that can be colored in gray as found in ordinary photographic supports. However, unlike the photographic support, there is no need to prevent light piping, so the content may be small, and the mass ratio to the cellulose ester is preferably 1 to 100 ppm, more preferably 2 to 50 ppm.

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

  If the film is difficult to slip, the films may block each other, resulting in poor handling. In that case, the film according to the present invention is provided with a matting agent such as inorganic fine particles such as silicon dioxide, titanium dioxide, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate, and calcium phosphate, and a crosslinked polymer. It is preferable to contain.

  Further, it is preferable that fine particles such as silicon dioxide are surface-treated with an organic substance because the haze of the film can be reduced. Preferred organic materials for the surface treatment include halosilanes, alkoxysilanes, silazanes, siloxanes, and the like. The larger the average diameter of the fine particles, the greater the mat effect, and the smaller the average diameter, the better the transparency. Therefore, the preferable average primary particle diameter of the fine particles is 5 to 50 nm, more preferably 7 to 14 nm. These fine particles are usually present as aggregates in the film, and it is preferable to generate irregularities of 0.01 to 1.0 μm on the film surface. Examples of the silicon dioxide fine particles include Aerosil 200, 300, R972, R974, R202, R812, OX50, and TT600 manufactured by Aerosil Co., Ltd., and preferably AEROSIL R972V, 200V, R972, R974, R202, and R812. .

  The matting agent is preferably blended 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 preferably 0.005 to 0.3% by mass with respect to the fatty acid cellulose ester.

  In addition, since the cellulose ester film of the present invention is incorporated in a liquid crystal display device and often used outdoors, it preferably 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 which are excellent in the ability to absorb ultraviolet rays having a wavelength of 370 nm or less from the viewpoint of deterioration of the liquid crystal and have the least possible absorption of visible light having a wavelength of 400 nm or more from the viewpoint of good liquid crystal display properties are preferably used. It is done. 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 salicylic acid ester compounds.

  Examples of these include 2- (2'-hydroxy-5'-methylphenyl) benzotriazole, 2- (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, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, phenyl salicylate, methyl salicylate and the like.

  In this invention, it is preferable to use 1 or more types of these ultraviolet absorbers, and you may contain 2 or more types of different ultraviolet absorbers.

  The ultraviolet absorber may be added to the dope after dissolving the ultraviolet absorber in an organic solvent such as alcohol, methylene chloride, dioxolane, or directly into the dope composition. For an inorganic powder that does not dissolve in an organic solvent, a dissolver or a sand mill is used in the organic solvent and cellulose ester to disperse and then added to the dope.

  The usage-amount of a ultraviolet absorber is 0.1-5% by the mass with respect to a cellulose ester, Preferably, it is 0.5-2.5%, More preferably, it is 0.8-2.0%. When the amount of the ultraviolet 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-based compounds are preferably used, and the amount of these compounds added is preferably 1 ppm to 1.0% by mass with respect to the cellulose ester, and 10 to 1000 ppm. Further preferred. In addition, a heat stabilizer such as a salt of an alkaline earth metal such as calcium or magnesium may be added.

  In addition to the above, an antistatic agent, a flame retardant, a slip agent, and the like may be added as appropriate.

  Moreover, since the cellulose-ester film support based on this invention is arrange | positioned between polarizing plates, the foreign material which generate | occur | produces abnormal refractive light will cause a performance degradation. In that respect, a so-called bright spot-like abnormality becomes a problem.

  In the present invention, the bright spot recognized in the polarization crossed Nicol state is observed when two polarizing plates are placed in an orthogonal (crossed Nicol) state, a cellulose ester film is placed between them, and light from the light source is applied from the opposite side. Means something. In the polarization crossed Nicol state, such luminescent spots are observed by shining only in the bright field in the dark field, so that the size and number can be easily identified.

The number of bright spots is preferably 200 or less bright spots having a size of 5 to 50 μm and 0 bright spots having a diameter of 50 μm or more, which are recognized in a polarized crossed Nicol state per 250 mm ² area. More preferably, the number of bright spots of 5 to 50 μm is 100 or less, particularly preferably 0 to 10. If there are many such bright spots, the image on the liquid crystal display is seriously adversely affected.

  The manufacturing method of the cellulose-ester film of this invention is demonstrated.

  As a method for producing a cellulose ester film, a dope solution is cast on a support for casting, a film is formed, the resulting film is peeled off from the support, and then the tension is applied while transporting through the drying zone. A solution casting film forming method is preferred. The solution casting film forming method will be described below.

  (1) Dissolution step: In this step, the flakes are dissolved in an organic solvent mainly composed of a good solvent for cellulose ester flakes in a dissolution vessel while stirring to form a cellulose ester solution (dope). For dissolution, a method carried out at normal pressure, a method carried out below the boiling point of the main solvent, a method carried out under pressure above the boiling point of the main solvent, M.M. G. Makromol. chem. 143, page 105 (1971), as described in JP-A-9-95544 and JP-A-9-95557, a cooling dissolution method that dissolves at a low temperature, a method performed at a high pressure, etc. There is a dissolution method. After dissolution, the dope is filtered with a filter medium, defoamed, and sent to the next process with a pump.

  (2) Casting step: The dope is fed to a pressure die through a pressurized metering gear pump, and an endless metal belt for infinite transfer or a support for casting a rotating metal drum at the casting position (hereinafter simply referred to as “casting”). This is a step of casting a dope from a pressure die onto a support. The surface of the casting support is a mirror surface. Other casting methods include a doctor blade method in which the film thickness of the cast dope film is adjusted with a blade, or a reverse roll coater method in which the film is adjusted with a reverse-rotating roll, but the slit shape of the die part is adjusted. A pressure die that is easy to make uniform in film thickness 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 dope amount may be divided and stacked. Or it can also be set as the cellulose-ester film of a laminated structure using a co-casting method.

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

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

  As a method for increasing the film forming speed (the film forming speed can be increased because the film is peeled off while the amount of residual solvent is as large as possible), there is a gel casting method (gel casting) that can peel even if there is a large amount of residual solvent (residual solvent amount). However, it can be peeled off as much as possible to increase the film-forming speed). For example, a poor solvent for the cellulose ester is added to the dope, and after the dope is cast, the gel is formed, and the temperature of the support is lowered to form a gel. There is also a method of adding a metal salt in the dope. By gelling on the support and strengthening the film, it is possible to speed up the peeling and increase the film forming speed. When peeling at a time when the amount of residual solvent is larger, if the web is too soft, the flatness at the time of peeling will be damaged, or slippage and vertical stripes due to peeling tension will tend to occur, and the amount of residual solvent will be reduced in consideration of economic speed and quality. It is decided.

  (5) Drying step: a step of drying the web using a drying device that alternately conveys the web through rolls arranged in a staggered manner and / or a tenter device that clips and conveys both ends of the web with a clip. As a drying means, hot air is generally blown on both sides of the web, but there is also a means for heating by applying a microwave instead of the wind. Too much drying tends to impair the flatness of the finished film. Drying at a high temperature is preferably performed from about 8% by mass or less of the residual solvent. 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 differ 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 from the casting support surface, the web tends to shrink in the width direction due to evaporation of the solvent. Shrinkage increases as the temperature rapidly dries. Drying while suppressing this shrinkage as much as possible is preferable for improving the flatness of the finished film. From this point of view, for example, a method of drying the entire drying process or a part of the process as shown in Japanese Patent Application Laid-Open No. 62-46625 while holding the width at both ends of the web with a clip in the width direction (tenter method ) Is preferred.

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

  To adjust the film thickness of the fatty acid cellulose ester film, control the dope concentration, pump feed volume, slit gap in the die cap, die extrusion pressure, and casting support speed. It is good to do. Further, it is preferable that the film thickness detecting means is used as a means for making the film thickness uniform, and the programmed feedback information is fed back to each of the above devices 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, or may be performed in an inert gas atmosphere such as nitrogen gas or carbon dioxide gas. . Of course, the danger of the explosion limit of the evaporating solvent in the dry atmosphere must always be taken into account.

  The cellulose ester support having optically biaxial properties according to the present invention can take any method for obtaining an orientation that is optically biaxial (shows the relationship of nx> ny> nz). However, a stretching method can be adopted as one of the most effective methods.

  The cellulose ester film of the present invention can be stretched at a high temperature by controlling the residual solvent in the film as will be described later in the production thereof. It is also possible to stretch. When stretching at a high temperature, the stretching temperature is stretched at a temperature equal to or higher than the glass transition temperature of the cellulose ester. However, with the plasticizer as described above, the effect is diminished and sufficient stretchability may not be obtained. is there. A plasticizer capable of imparting sufficient stretchability even at high temperatures is required. However, as such a plasticizer, it has been found that a non-volatile plasticizer can be preferably used. The non-volatile plasticizer is a compound having a vapor pressure at 200 ° C. of 1330 Pa or less, having a very low vapor pressure and low volatility. More preferably, the vapor pressure is 665 Pa or less, and still more preferably 133 Pa or less. For example, arylene bis (diaryl phosphate) esters are preferred. In addition, tricresyl phosphate (38.6 Pa, 200 ° C.), trimellitic acid tris (2-ethylhexyl) (66.5 Pa, 200 ° C.) and the like are also preferably used. Alternatively, a non-volatile phosphate ester described in JP-T-6-501040 is also preferably used. In addition, a high molecular weight plasticizer such as a polymer or an oligomer such as a copolymer containing polyester, acrylic resin, or polyvinyl acetate can also be preferably used. In this case, the content of the plasticizer is preferably 0.1 to 30% by mass, and particularly preferably 0.5 to 15% by mass with respect to the cellulose ester. Thus, by using a plasticizer, the stretchability of the cellulose ester at a high temperature can be improved, and in particular, a cellulose ester film excellent in surface quality and flatness of the film can be produced with high productivity.

  As a method for imparting optical biaxiality to the cellulose ester film of the present invention, 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, after casting the cellulose ester-dissolved dope solution onto the casting support, the web (film) peeled from the casting support is then subjected to a residual solvent amount of 100 in the web. While being in the range of 10% by mass or less, particularly 10 to 100% by mass, it is preferable to stretch 1.0 to 4.0 times in at least one direction.

  The residual solvent amount can be expressed by the following formula.

Residual solvent amount (% by mass) = {(MN) / N} × 100
Here, M is the mass of the web at any point, and N is the mass when M is dried at 110 ° C. for 3 hours.

  If the amount of residual solvent in the web is too large, the effect of stretching cannot be obtained, and if it is too small, stretching becomes extremely difficult and the web may break. The more preferable range of the residual solvent amount in the web is 10% by mass to 50% by mass, and most preferably 12% by mass to 40% by mass. Further, if the stretching ratio is too small, a sufficient phase difference cannot be obtained, and if it is too large, stretching may become difficult and breakage may occur. A more preferable range of the draw ratio is 1.0 to 3.5 times.

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

  Further, stretching in the biaxial directions perpendicular to each other is an effective method for bringing the refractive indexes nx, ny, and nz of the film within the scope of the present invention.

  Furthermore, the film thickness fluctuation | variation of the film obtained by extending | stretching in the biaxial direction orthogonal to each other can be reduced. When the film thickness variation of the cellulose ester film support is too large, the retardation becomes uneven, and problems such as coloring occur when used as an optical compensation film. The film thickness variation of the cellulose ester film support is preferably in the range of ± 3%, more preferably ± 1%. For the purposes as described above, a method of stretching in the biaxial directions perpendicular to each other is effective, and the stretching ratios in the biaxial directions perpendicular to each other are 0.8 to 4.0 times and 0.4 to 1.2, respectively. It is preferable that the range be doubled.

  There is no particular limitation on the method of stretching the web. For example, a method in which a difference in peripheral speed is applied to a plurality of rolls, and the roll peripheral speed difference is used to stretch in the longitudinal direction between the rolls. And a method of stretching in the vertical direction, a method of stretching in the horizontal direction and stretching in the horizontal direction, a method of stretching in the vertical and horizontal directions and stretching in both the vertical and horizontal directions, and the like. Of course, these methods may be used in combination. In the case of the so-called tenter method, driving the clip portion by a linear drive method is preferable because smooth stretching can be performed and the risk of breakage and the like can be reduced.

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

  In the present invention, it is preferable to adjust the various conditions described above so that the refractive index in the width direction of the cellulose ester film formed on the casting support is maximized during casting film formation.

  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 phrase “the refractive index in the width direction is maximized” means that the nx direction 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 formed by the respective axes is within ± 10 °, preferably within ± 3 °, and more preferably within ± 1 °.

  In the polarizing plate of the present invention, the light transmission axis of a polarizer containing a dichroic substance and the width at the time of casting film formation of an optically biaxial cellulose ester film to be bonded to the polarizer Bonding is preferably performed so that the stretching direction in the hand direction is substantially parallel. In the present invention, orthogonal means that the axes are substantially orthogonal as described above, and that the directions are the same means that the directions of the axes are substantially parallel. Indicates. Here, “substantially parallel” represents a case where the angle formed by each axis is within ± 10 °, preferably within ± 3 °, and more preferably within ± 1 °.

  Furthermore, at the time of producing the polarizing plate, a polarizer containing a dichroic substance and an optically biaxial cellulose ester film are bonded together, but from the viewpoint of improving production efficiency, it was produced as a long roll. A cellulose ester film is preferably used. In the present invention, the long length indicates 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 device of the present invention will be described.

A conventionally well-known thing can be used as a polarizer used for the polarizing plate of this invention. For example, a film made of a hydrophilic polymer such as polyvinyl alcohol is treated with a dichroic dye such as iodine and stretched, or a plastic film such as vinyl chloride is treated and oriented. The polarizer thus obtained is bonded with a cellulose ester film.
At this time, at least one of the cellulose ester films needs to use the cellulose ester film of the present invention, but the cellulose triacetate (TAC) film that has been used as a conventionally known polarizing plate support is used. Although it may be used for bonding of other polarizer surfaces, in order to obtain the effect described in the present invention to the maximum, all constituting the polarizing plate in terms of the same physical properties of both surfaces of the polarizing plate protective film The cellulose ester film of the present invention is preferably used as the cellulose ester film.

  When the polarizing plate is formed by laminating the cellulose ester film of the present invention, the polarizer, and the cellulose triacetate (TAC) film in this order, the temperature / humidity is obtained by using the cellulose triacetate film that has been stretched in the width direction. It is possible to obtain a polarizing plate with a retardation function that maintains excellent optical characteristics and has low resistance to dimensional changes (shape changes) against environmental changes. The stretching operation may be performed at the time of casting film formation or may be performed off-line after film forming, but may be performed continuously at the time of casting film formation from the viewpoint of uniformity of stretching, productivity, and the like. preferable. The draw ratio is preferably in the range of 1.01 times to 1.2 times, particularly preferably 1.03 times to 1.15 times, and most preferably 1.05 times to 1.10 times.

  Further, during the production of the polarizing plate, the cellulose ester film is applied to the other surface on the opposite side across the polarizer with the draw ratio A of the cellulose ester film of the present invention applied to one surface of the polarizer. As a relation with the draw ratio B, A / B is preferably in the range of 1000 to 0.001, more preferably 200 to 0.005, and particularly preferably in the range of 100 to 0.01. is there.

  Moreover, when producing a 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 be substantially parallel. The polarizing plate thus obtained is bonded to both surfaces of the liquid crystal cell, preferably arranged as follows.

  The polarizing plate of the present invention is bonded so that the rubbing axis direction of the substrate surface adjacent to the liquid crystal cell and the polarizing plate transmission axis (here, the extending direction of the polarizer and the light transmission axis are orthogonal) are orthogonal to each other. Thus, a liquid crystal display device can be obtained. Here, FIG. 1 shows a schematic diagram of a liquid crystal display device which is the best mode of the present invention. A liquid crystal display device 9 shown in FIG. 1 includes a single 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, and the polarizing plate 6b is composed of two cellulose ester films 1b and one polarizer 2b.

  In the polarizing plates 6a and 6b, the casting directions 3a and 3b represent the casting directions when the cellulose ester films 1a and 1b are cast. The stretching directions 4a and 4b represent the stretching directions 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. A liquid crystal display device with a remarkably improved viewing angle can be obtained with such a simple configuration.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to these.

Example 1
<< Production of cellulose ester film >>
(Preparation of cellulose ester film 1)
100 parts by mass of 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, 5 parts by mass of ethylphthalylethyl glycolate, 3 parts by mass of triphenyl phosphate Then, 290 parts by mass of methylene chloride and 60 parts by mass of ethanol were placed in a sealed container, and the mixture was gradually heated while being slowly stirred, and was heated up to 45 ° C. and dissolved over 60 minutes. The inside of the container was 1.2 atm. This dope was added to Azumi Filter Paper No. After filtering using 244, it left still for 24 hours and the bubble in dope was removed.

  Separately from this, 5 parts by mass of the above cellulose acetate propionate, 6 parts by mass of TINUVIN 326 (manufactured by BASF Japan), 4 parts by mass of TINUVIN 109 (manufactured by BASF Japan), TINUVIN 171 (BASF Japan) 4 parts by mass of methylene chloride and 8 parts by mass of ethanol were mixed and dissolved by stirring to prepare an ultraviolet absorber 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 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 stainless steel belt whose temperature is controlled by contacting hot water at a temperature of 25 ° C. from the back surface of the stainless steel belt, and further holding 15 ° C. cold water on the back surface of the stainless steel belt for 15 seconds, Peeled from the stainless steel belt. The amount of residual solvent in the web at the time of peeling was 100% by mass. Subsequently, the both ends of the web which peeled using the extending | stretching tenter were grasped with the clip, and it extended | stretched 1.65 times only in the width direction at 120 degreeC by changing the width direction of a clip space | interval. Furthermore, it was made to dry at 130 degreeC for 10 minute (s) by roller conveyance, and the cellulose-ester film 1 with a film thickness of 100 micrometers 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, an embossing ring having a temperature of 250 ° C. was pressed against the end of the film, and the thickness was processed to prevent adhesion between the films.

The film roll was sampled from the center in the width direction of the film, and the refractive index nx in the slow axis direction, the refractive index ny in the fast axis direction, and the refractive index nz in the thickness direction were measured as follows, and in-plane retarder was measured. When the retardation value R ₀ and the retardation value R _t in the thickness direction were calculated, they were R ₀ 78 nm and R _t 175 nm at the center. R ₀ and R _t are defined by the following formula.

R ₀ = (nx−ny) × d, R _t = ((nx + ny) / 2−nz) × d
Where d is the thickness (nm) of the film. The direction of the slow axis was within a range of ± 0.8 degrees with respect to the width direction of the film for each sample.

  Using an automatic birefringence meter KOBRA-21ADH (manufactured by Oji Scientific Instruments), a three-dimensional refractive index measurement is performed at a wavelength of 590 nm in an environment of 23 ° C. and 55% RH, and refractive indexes nx, ny, nz was determined. Moreover, it was 1.8% as a result of measuring using the moisture content measuring method mentioned later.

<< Production of Cellulose Ester Film 2 >>
100 parts by mass of cellulose acetate propionate having a degree of substitution of acetyl group of 1.60, a degree of substitution of propionyl group of 1.20 and a viscosity average polymerization degree of 400, 5 parts by mass of ethylphthalyl ethyl glycolate, 3 parts by mass of triphenyl phosphate Then, 290 parts by mass of methylene chloride and 60 parts by mass of ethanol were placed in a sealed container, and the mixture was gradually heated while being slowly stirred, and was heated up to 45 ° C. and dissolved over 60 minutes. The inside of the container was 1.2 atm. This dope was added to Azumi Filter Paper No. After filtering using 244, it left still for 24 hours and the bubble in dope was removed. Separately from this, 5 parts by mass of the above cellulose acetate propionate, 6 parts by mass of TINUVIN 326 (manufactured by BASF Japan), 4 parts by mass of TINUVIN 109 (manufactured by BASF Japan), TINUVIN 171 (BASF Japan) 1 part by mass) and AEROSIL R972V (manufactured by Nippon Aerosil 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 absorber solution. R972V was previously dispersed in ethanol and added.

  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 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 stainless steel belt whose temperature is controlled by contacting hot water at a temperature of 25 ° C. from the back surface of the stainless steel belt, and further holding 15 ° C. cold water on the back surface of the stainless steel belt for 15 seconds, Peeled from the stainless steel belt. The amount of residual solvent in the web at the time of peeling was 80% by mass. Subsequently, the both ends of the web which peeled using the extending | stretching tenter were grasped with the clip, and it extended | stretched 1.5 times in the width direction at 120 degreeC by changing the width direction of a clip space | interval. Furthermore, it was made to dry at 130 degreeC for 10 minutes, carrying a roller, and the 50-micrometer-thick cellulose ester film 2 was obtained.

  The cellulose ester film 2 was wound up by a taper tension method in a film roll shape having a width of 1 m and a length of 1000 m on a glass fiber reinforced resin core having a core diameter of 200 mm. At this time, an embossing ring having a temperature of 250 ° C. was pressed against the end of the film, and the thickness was processed to prevent adhesion between the films.

Sampling from the obtained film roll from the center in the width direction of the film, the refractive index nx in the slow axis direction, the refractive index ny in the fast axis direction, and the refractive index nz in the thickness direction are produced and evaluated for the cellulose ester film 1 In the same manner as above, R ₀ and R _t were calculated, and both were 85 nm and 93 nm at the center.
In addition, the direction of the slow axis was within a range of ± 0.4 degrees with respect to the width direction of the film for each sample. The moisture content was measured and found to be 2.1%.

<< Production of Cellulose Ester Film 3 >>
100 parts by mass of 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, 5 parts by mass of ethylphthalylethyl glycolate, 3 parts by mass of triphenyl phosphate Then, 175 parts by mass of methyl acetate and 75 parts by mass of ethanol were placed in a sealed container, and the mixture was gradually heated while being slowly stirred, and was heated up to 65 ° C. and dissolved over 60 minutes. The inside of the container was 1.2 atm. This dope was added to Azumi Filter Paper No. After filtering using 244, it left still for 24 hours and the bubble in dope was removed. Separately from this, 5 parts by mass of the above cellulose acetate propionate, 6 parts by mass of TINUVIN 326 (manufactured by BASF Japan), 4 parts by mass of TINUVIN 109 (manufactured by BASF Japan), TINUVIN 171 (BASF Japan) 94 parts by mass of methyl acetate and 8 parts by mass of ethanol were mixed and dissolved with stirring by mixing 5 parts by mass to prepare an ultraviolet absorber 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 after sufficiently mixing with a static mixer, the solution was cast from a die onto a stainless steel belt at a dope temperature of 50 ° C. After drying for 1 minute on a stainless steel belt whose temperature is controlled by contacting hot water at a temperature of 55 ° C. from the back surface of the stainless steel belt, and further holding cold water at 15 ° C. on the back surface of the stainless steel belt for 15 seconds, Peeled from the stainless steel belt. The amount of residual solvent in the web at the time of peeling was 70% by mass. Next, grasp both ends of the peeled web using a simultaneous biaxial stretching tenter with a clip, and simultaneously change the clip interval in the width direction and casting direction (length direction) at 150 ° C in the width direction 1.8 times. The film was stretched 1.05 times in the casting direction (length direction). Furthermore, it was made to dry at 130 degreeC for 10 minutes, conveying with a roller, and the cellulose-ester film 3 with a film thickness of 120 micrometers was obtained.

  The cellulose ester film 3 was wound up by a taper tension method in a film roll shape having a width of 1 m and a length of 1000 m on a glass fiber reinforced resin core having a core diameter of 200 mm. At this time, an embossing ring having a temperature of 250 ° C. was pressed against the end of the film, and the thickness was processed to prevent adhesion between the films.

Sampling from the center of the film width direction from the obtained film roll, measuring the refractive index nx in the slow axis direction, the refractive index ny in the fast axis direction, the refractive index nz in the thickness direction in the same manner as described above, R ₀ and R _t were calculated to be 165 nm and 184 nm, respectively. The direction of the slow axis was within a range of ± 1.2 degrees with respect to the width direction of the film for each sample. The moisture content was measured and found to be 1.6%.

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

  This dope was added to Azumi Filter Paper No. After filtering using 244, it left still for 24 hours and the bubble in dope was removed. Separately, 3 parts by mass of the above cellulose acetate propionate, 3 parts by mass of TINUVIN 326 (manufactured by BASF Japan), 4 parts by mass of TINUVIN 109 (manufactured by BASF Japan), TINUBIN 171 (BASF Japan) 5 parts by mass were mixed with 90 parts by mass of methylene chloride and 10 parts by mass of ethanol and dissolved by stirring to prepare an ultraviolet absorber 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. After sufficiently mixing with a static mixer, the solution was cast from a die onto a stainless steel belt at a dope temperature of 35 ° C. After drying for 1 minute on a stainless steel belt whose temperature is controlled by contacting hot water at a temperature of 35 ° C. from the back surface of the stainless steel belt, 15 ° C. cold water is brought into contact with the back surface of the stainless steel belt and held for 15 seconds. Peeled from the stainless steel belt. The amount of residual solvent in the web at the time of peeling was 70% by mass.

  Next, while roll-feeding in an oven at 120 ° C., the roll peripheral speed immediately before the oven outlet is 2.1 times the roll peripheral speed immediately after the oven inlet, and the casting direction (long film direction) ) Was stretched 2.1 times. Immediately after stretching, it was cooled to 60 ° C. Furthermore, both ends of the web were gripped with clips using a tenter, and dried at 140 ° C. for 5 minutes with the clip interval fixed, to obtain a cellulose ester film 4 having a film thickness of 160 μm.

  The cellulose ester film 4 was wound around a glass fiber reinforced resin core having a core diameter of 200 mm in a film roll shape having a width of 1 m and a length of 1000 m by a taper tension method. At this time, an embossing ring having a temperature of 270 ° C. was pressed against the end of the film, and a 10 μm thickening process was performed to prevent adhesion between the films.

Sampling from the center of the film width direction from the obtained film roll, measuring the refractive index nx in the slow axis direction, the refractive index ny in the fast axis direction, the refractive index nz in the thickness direction in the same manner as described above, When R ₀ and R _t were calculated, they were 147 nm and 142 nm at the center. The direction of the slow axis was within a range of ± 0.5 degrees with respect to the width direction of the film for each sample. The moisture content was measured and found to be 2.0%.

<< Production of Cellulose Ester Film 5 >>
The cellulose ester used in 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 polymerization degree of 300. Thus, a cellulose ester film 5 having a thickness of 100 μm and a film roll thereof were produced.

Sampling from the center of the film width direction from the obtained film roll, measuring the refractive index nx in the slow axis direction, the refractive index ny in the fast axis direction, the refractive index nz in the thickness direction in the same manner as described above, When R ₀ and R _t were respectively calculated, they were 111 nm and 139 nm at the center.

  The direction of the slow axis was within a range of ± 1.2 degrees with respect to the width direction of the film for each sample. The moisture content was measured and found to be 1.3%.

<< Production of Cellulose Ester Film 6 >>
100 parts by mass of cellulose acetate propionate having a substitution degree of acetyl group of 1.90, a substitution degree of propionyl group of 0.75, and a viscosity average polymerization degree of 350, 2 parts by mass of ethylphthalylethyl glycolate, 8.5 of triphenyl phosphate Part by mass, 290 parts by mass of methylene chloride, and 60 parts by mass of ethanol were placed in a sealed container, and the temperature of the mixture was gradually increased while slowly stirring, and the temperature was raised to 45 ° C. over 60 minutes and dissolved. The inside of the container was 1.2 atm. This dope was added to Azumi Filter Paper No. After filtering using 244, it left still for 24 hours and the bubble in dope was removed.

  Separately from this, 5 parts by mass of the above cellulose acetate propionate, 6 parts by mass of TINUVIN 326 (manufactured by BASF Japan), 4 parts by mass of TINUVIN 109 (manufactured by BASF Japan), TINUVIN 171 (BASF Japan) 4 parts by mass of methylene chloride and 8 parts by mass of ethanol were mixed and dissolved by stirring to prepare an ultraviolet absorber 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 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 stainless steel belt whose temperature is controlled by contacting hot water at a temperature of 25 ° C. from the back surface of the stainless steel belt, and further holding 15 ° C. cold water on the back surface of the stainless steel belt for 15 seconds, Peeled from the stainless steel belt. The amount of residual solvent in the web at the time of peeling was 70%. Next, both ends of the peeled web were gripped with a clip using a stretching tenter, and the width direction of the clip interval was changed, and the web was stretched 1.40 times at 115 ° C. only in the width direction. Furthermore, it was made to dry at 130 degreeC for 10 minute (s) by roller conveyance, and the cellulose-ester film 6 with a film thickness of 80 micrometers was obtained.

  The cellulose ester film 6 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, an embossing ring having a temperature of 250 ° C. was pressed against the end of the film, and the thickness was processed to prevent adhesion between the films.

The film roll was sampled from the center in the width direction of the film, and the refractive index nx in the slow axis direction, the refractive index ny in the fast axis direction, and the refractive index nz in the thickness direction were measured as follows, and in-plane retarder was measured. When the retardation value R ₀ and the retardation value R _t in the thickness direction were calculated, they were R ₀ 50 nm and R _t 122 nm at the center. R ₀ and R _t are defined by the following formula.

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 within a range of ± 0.7 degrees with respect to the width direction of the film for each sample.

  Using an automatic birefringence meter KOBRA-21ADH (manufactured by Oji Scientific Instruments), a three-dimensional refractive index measurement is performed at a wavelength of 590 nm in an environment of 23 ° C. and 55% RH, and refractive indexes nx, ny, nz was determined. Moreover, it was 1.8% as a result of measuring using the moisture content measuring method mentioned later.

<< Production 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.

The film roll was sampled from the center in the width direction of the film, and the refractive index nx in the slow axis direction, the refractive index ny in the fast axis direction, and the refractive index nz in the thickness direction were measured as follows, and in-plane retarder was measured. When the retardation value R ₀ and the retardation value R _t in the thickness direction were calculated, they were R ₀ 32 nm and R _t 105 nm at the center. R ₀ and R _t are defined by the following formula.

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 within a range of ± 0.7 degrees with respect to the width direction of the film for each sample.

  Using an automatic birefringence meter KOBRA-21ADH (manufactured by Oji Scientific Instruments), a three-dimensional refractive index measurement is performed at a wavelength of 590 nm in an environment of 23 ° C. and 55% RH, and refractive indexes nx, ny, nz was determined. Moreover, it was 1.8% as a result of measuring using the moisture content measuring method mentioned later.

<< Production 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 film roll was sampled from the center in the width direction of the film, and the refractive index nx in the slow axis direction, the refractive index ny in the fast axis direction, and the refractive index nz in the thickness direction were measured as follows, and in-plane retarder was measured. When the retardation value R ₀ and the retardation value R _t in the thickness direction were calculated, R _{0 was} 28 nm and R _t was 91 nm at the center. R ₀ and R _t are defined by the following formula.

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 within a range of ± 0.7 degrees with respect to the width direction of the film for each sample.

  Using an automatic birefringence meter KOBRA-21ADH (manufactured by Oji Scientific Instruments), a three-dimensional refractive index measurement is performed at a wavelength of 590 nm in an environment of 23 ° C. and 55% RH, and refractive indexes nx, ny, nz was determined. Moreover, it was 1.1% as a result of measuring using the moisture content measuring method mentioned later.

<Production of comparative control film>
The cellulose triacetate film (comparative film) conventionally used as a support body for polarizing plates was produced by the following procedures.

  100 parts by mass of cellulose triacetate having an acetyl group substitution degree of 2.92 and a viscosity average polymerization degree of 300, ethyl phthalyl ethyl glycolate 2 parts by mass, triphenyl phosphate 10 parts by mass, methylene chloride 350 parts by mass, ethanol 50 parts by mass The mixture was put in an airtight container and the temperature of the mixture was gradually raised while stirring slowly, and the temperature was raised to 45 ° C. over 60 minutes for dissolution. The inside of the container was 1.2 atm.

  This dope was added to Azumi Filter Paper No. After filtering using 244, it left still for 24 hours and the bubble in dope was removed.

  Separately, 5 parts by mass of the above cellulose triacetate, 3 parts by mass of Tinuvin 326 (manufactured by BASF Japan), 7 parts by mass of Tinuvin 109 (manufactured by BASF Japan), and TINUVIN 171 (BASF Japan) 5 parts by mass) and 1 part by mass of AEROSIL 200V (manufactured by Nippon Aerosil Co., Ltd.) were mixed with 90 parts by mass of methylene chloride and 10 parts by mass of ethanol and dissolved by stirring to prepare an ultraviolet absorber 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. After sufficiently mixing with a static mixer, the solution was cast from a die onto a stainless steel belt at a dope temperature of 35 ° C. After drying for 1 minute on a stainless steel belt whose temperature is controlled by contacting hot water at a temperature of 35 ° C. from the back surface of the stainless steel belt, 15 ° C. cold water is brought into contact with the back surface of the stainless steel belt and held for 15 seconds. Peeled from the stainless steel belt.

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

Sampling from the center of the film width direction from the obtained film roll, measuring the refractive index nx in the slow axis direction, the refractive index ny in the fast axis direction, the refractive index nz in the thickness direction in the same manner as described above, When R ₀ and R _t were respectively calculated, they were 2 nm and 42 nm at the center. Also, the direction of the slow axis was below the measurement limit because the _R0 value was small. The moisture content was measured and found to be 1.3%.

<Method of measuring moisture content>
Each cellulose ester film sample obtained in the above description was cut to a size of 10 cm ² and left for 48 hours under conditions of 23 ° C. and 80% RH, and then its mass was measured to be W1. Next, the film was subjected to a heat drying treatment at 120 ° C. for 45 minutes, and the mass was measured to obtain W2. From each measured value, the moisture content at 23 ° C. and 80% RH is measured by the following formula. The results are shown below.

Moisture content (%) = ((W1-W2) / W2) × 100
<Production of polarizing plate>
(Preparation of polarizing plate 1)
A 120 μm thick polyvinyl alcohol film 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, 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, as shown in FIG. 2, two cellulose ester film supports cut out in the shape of a 30 cm × 18 cm rectangular ABCD were immersed in a 2 mol / liter sodium hydroxide solution at 60 ° C. for 1 minute. Further, it was washed with water and dried.

  FIG. 2 is a schematic view of a long cellulose ester film of the present invention produced by casting film formation. In the long cellulose ester film 10 of the present invention that has been cast and formed, the casting direction 11 is the casting direction during casting film formation, and the width direction 12 is the width direction during casting film formation. Represents. The cellulose ester film used for producing the polarizing plate is cut and used, for example, like a rectangular ABCD, but the angle formed by one side AB of the rectangular ABCD and the casting direction 12 of the cellulose ester film 10 is 45 degrees. Cut out as follows.

  (2) The polarizing film (polarizer) described above adjusted to the same size as 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) Gently remove excess adhesive adhered to the polarizing film (polarizer), place it on the surface of the cellulose ester film sample in the arrangement as shown in FIG. 3, and another cellulose ester film sample Laminate and arrange so that the surface of the adhesive and the adhesive are in contact.

  FIG. 3 is a schematic diagram 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) Excess adhesive and bubbles are removed and bonded from the end of the laminate of the polarizing film and the cellulose ester film laminated by the hand roller. The hand roller was subjected to a pressure of 20 to 30 N / cm ² and the roller speed was about 2 m / min.

  (5) The sample obtained in an oven at 80 ° C. was left for 2 minutes to produce a polarizing plate.

  Subsequently, the obtained polarizing plate (viewing angle widening polarizing plate 1) was incorporated into a liquid crystal cell as shown below, and the characteristics as a display device were evaluated.

<< Production of Polarizing Plate 2 >>
Using the cellulose ester film 2, a polarizing plate was produced 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.

<< Production of Polarizing Plate 3 >>
A polarizing plate was produced 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.

<< Production of Polarizing Plate 4 >>
Using the cellulose ester film 4, a polarizing plate was produced 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.

<< Production of Polarizing Plate 5 >>
Using the cellulose ester film 5, a polarizing plate was produced 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.

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

First, a 120 μm-thick polyvinyl alcohol film 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. 2, each of the 30 cm × 18 cm rectangular ABCD, the cut cellulose ester film 1 and the same comparative control film were respectively added to a 2 mol / liter sodium hydroxide solution at 60 ° C. It was immersed for a minute, further washed with water and dried.

  (2) The polarizing film described above adjusted to the same size as these 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) Excess adhesive adhered to the polarizing film is lightly removed, and the same arrangement as in FIG. 3 is used except that one of the two cellulose ester films of the present invention is replaced with the above-described comparative control film. A cellulose ester film was laminated on the polarizer.

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

  (5) The sample obtained in an oven at 80 ° C. was left for 2 minutes to produce a polarizing plate.

  Next, the viewing angle measurement was performed on the viewing angle widening polarizing plate 1 by the following method.

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

<< Production of Polarizing Plate 7 >>
100 parts of polyvinyl alcohol having an average polymerization degree of 3800 and a saponification degree of 99.5 mol% was dissolved in water to obtain a 5.0% by mass solution. The liquid was cast on polyethylene terephthalate and then dried to obtain a raw film. This film is immersed in an aqueous solution of 0.2 g / l iodine and 60 g / l potassium iodide at 30 ° C. for 240 seconds, and then immersed in an aqueous solution having a composition of boric acid 70 g / l and potassium iodide 30 g / l. At the same time, it was treated with boric acid for 5 minutes and dried while being transported while being uniaxially stretched 6.0 times in the transport direction. On the other hand, a cellulose ester raw film obtained by winding the cellulose ester film 1 on a glass fiber reinforced resin core having a core diameter of 200 mm in a film roll shape having a width of 1 m and a length of 1000 m into a 2 mol / liter sodium hydroxide solution. It was immersed for 1 minute at 60 ° C., further washed with water and dried. This saponification-treated cellulose ester raw film was continuously bonded roll-to-roll by using a polyvinyl alcohol-based adhesive as a protective film on both surfaces of the stretched and wound polyvinyl alcohol film. As shown in FIG. 2, a rectangular ABCD of 30 cm × 18 cm was cut out.

  Next, viewing angle measurement was performed on the viewing angle widening polarizing plate 11 by the following method.

  The viewing angle widening polarizing plate 11 was bonded to both surfaces of the liquid crystal cell so that the rubbing axis direction of the substrate surface adjacent to the liquid crystal cell and the polarizing plate transmission axis were orthogonal to each other. The viewing angle was measured by the same method as described above.

<< Preparation of polarizing plate 8 for comparison >>
A polarizing plate was prepared using two comparative cellulose ester films in the same manner as when the cellulose ester film 1 was used, and the viewing angle was measured by the same method as described above.

<Viewing angle measurement>
Next, the viewing angle measurement was performed on the viewing angle widening polarizing plate 1 by the following method.

  The viewing angle widening polarizing plate 1 was placed on both surfaces of the liquid crystal cell and bonded as follows, and evaluated with 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 and the polarizing plate transmission axis were orthogonal. The liquid crystal cell used was a 15-inch display Multi Sync LCD 1525J manufactured by NEC, from which the optical compensation film and polarizing plate previously bonded were peeled off. The viewing angle of the liquid crystal display device thus obtained was measured by EZ-contrast manufactured by ELDIM. The viewing angle was expressed in the range of the tilt angle from the normal direction with respect to the panel surface where the contrast ratio at the time of white display and black display of the liquid crystal cell is 10 or more. As a result, the viewing angle values obtained using the viewing angle widening polarizing plate 1 of the present invention are shown below.

Viewing angle Sample Left Right Upper Lower Remark Polarizing plate 1 65 ° 65 ° 28 ° 29 ° Present polarizing plate 2 57 ° 57 ° 27 ° 23 ° Present polarizing plate 3 60 ° 60 ° 27 ° 27 ° Present polarizing plate 4 55 ° 55 ° 25 ° 25 ° The present polarizing plate 5 62 ° 62 ° 27 ° 25 ° The present polarizing plate 6 65 ° 65 ° 28 ° 28 ° The present polarizing plate 7 64 ° 64 ° 27 ° 26 ° The present polarizing plate Plate 8 35 ° 35 ° 25 ° 20 ° Comparative Example From the above evaluation results, it is clear that the viewing angle of the sample of the present invention is remarkably improved as compared with the comparative example.

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

<< Production 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 produced by the following procedure.

  100 parts by mass of cellulose triacetate having an acetyl group substitution degree of 2.92 and a viscosity average polymerization degree of 300, ethylphthalylethyl glycolate 2 parts by mass, triphenyl phosphate 8.5 parts by mass, methylene chloride 350 parts by mass, ethanol 50 parts by mass The mixture was placed in a sealed container, the temperature of the mixture was gradually increased while stirring slowly, and the temperature was raised to 45 ° C. over 60 minutes for dissolution. The inside of the container was 1.2 atm.

  This dope was added to Azumi Filter Paper No. After filtering using 244, it left still for 24 hours and the bubble in dope was removed.

  Separately, 5 parts by mass of the above cellulose triacetate, 3 parts by mass of Tinuvin 326 (manufactured by BASF Japan), 7 parts by mass of Tinuvin 109 (manufactured by BASF Japan), and TINUVIN 171 (BASF Japan) 5 parts by mass) and 1 part by mass of AEROSIL 200V (manufactured by Nippon Aerosil Co., Ltd.) were mixed with 90 parts by mass of methylene chloride and 10 parts by mass of ethanol and dissolved by stirring to prepare an ultraviolet absorber 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. After sufficiently mixing with a static mixer, the solution was cast from a die onto a stainless steel belt at a dope temperature of 35 ° C. After drying for 1 minute on a stainless steel belt whose temperature is controlled by contacting hot water at a temperature of 35 ° C. from the back surface of the stainless steel belt, 15 ° C. cold water is brought into contact with the back surface of the stainless steel belt and held for 15 seconds. Peeled from the stainless steel belt.

  The amount of residual solvent in the web at the time of peeling was 80% by mass. Subsequently, the both ends of the web which peeled using the extending | stretching tenter were grasped with the clip, and it extended | stretched 1.07 times only to the width direction at 105 degreeC by changing the width direction of a clip space | interval. Furthermore, it was made to dry at 130 degreeC for 10 minutes, carrying a roller, and the cellulose-ester film A with a film thickness of 80 micrometers was obtained.

  Using the obtained cellulose ester film A and the cellulose ester 6 described in Example 1, a polarizing plate 9 was prepared in the same manner as the polarizing plate 1 of Example 1.

  After measuring the viewing angle of the polarizing plate 9 in the same manner as described in Example 1 (before storage), and after allowing the polarizing plate 9 after preparation to stand at 80 ° C. and 90% humidity for 500 hours (after storage) The viewing angle was measured by the same method as described above.

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

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

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

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

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

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

<< Production of Polarizing Plate 13 >>
A cellulose triacetate film (cellulose ester film E) for a polarizing plate protective film was prepared in the same procedure as the cellulose ester film A except that stretching in the width direction after peeling was not performed.

  Using this cellulose ester film E, a polarizing plate 13 was produced in the same manner as 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 Upper Lower polarizing plate 9 (before storage) 64 ° 64 ° 28 ° 27 °
Polarizing plate 9 (after storage) 64 ° 64 ° 27 ° 28 ° (no deterioration)
Polarizing plate 10 (before storage) 65 ° 65 ° 27 ° 27 °
Polarizing plate 10 (after storage) 65 ° 65 ° 28 ° 26 ° (no deterioration)
Polarizing plate 11 (before storage) 65 ° 65 ° 27 ° 27 °
Polarizing plate 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 deteriorated)
Polarizing plate 13 (before storage) 65 ° 65 ° 27 ° 27 °
Polarizing plate 13 (after storage) 55 ° 57 ° 23 ° 23 ° (slightly deteriorated)
From said evaluation result, it is clear that the polarizing plate 9-13 which has a cellulose-ester film of this invention has a favorable viewing angle improvement effect. In addition, when the treatment after storage over time is performed, for the polarizing plate 13 using only one of the two cellulose ester films constituting the polarizing plate, the viewing angle after storage is slightly deteriorated, In addition, light leakage and the like were observed during black display, but both of the polarizing plates 9 to 12 using the cellulose ester film of the present invention showed excellent viewing angle improvement effects after storage over time as well as before storage. I understand that.

  In addition, the polarizing plates 9 to 13 each use the cellulose ester film 6 having a draw ratio of 1.40 on one surface, but the curling of the polarizing plate after the temporal storage treatment (60 ° C., 90%, 500 hours treatment). As a result of visually observing the characteristics, the polarizing plate 13 using the cellulose ester film E which was not subjected to the stretching operation as a protective film on one side was observed to curl due to the dimensional change of the polarizing plate itself, whereas the stretching ratio was 2%. When each of the cellulose ester films (cellulose ester film D), 20% (cellulose ester film C), 15% (cellulose ester film B), and 7% (cellulose ester film A) is a protective film on one side, stretched Improvements were observed at magnifications of 2% and 20%, and curl was hardly generated at 15% and 7%.

1a, 1b Cellulose ester film 2a, 2b Polarizer 3a, 3b Casting direction during casting of cellulose ester film 4a, 4b Polarizer stretching direction 5a, 5b Liquid crystal cell rubbing direction 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 during casting film formation 12 Width direction during casting film formation ABCD Cut out rectangle

Claims (4)

In-plane retardation value R ₀ having an axis that is optically biaxial and has a maximum refractive index in the width direction is 30 to 300 nm, and the retardation value R _{t in the} thickness direction is 30 to 300 nm. A long roll polarizing plate comprising a long roll cellulose ester film and a long roll triacetyl cellulose film as protective films on both surfaces of a polarizer containing a dichroic substance. The polarizing plate according to claim 1, wherein the cellulose ester film satisfies the following formulas (1) and (2) simultaneously.
Formula (1) 2.4 <= A + B <= 2.8
Formula (2) 1.4 ≦ A ≦ 2.0
[Wherein, A represents the degree of substitution of the acetyl group, and B represents the degree of substitution of the acyl group having 3 or 4 carbon atoms. ] In optically has a biaxial, stretching 1.0 to 3.5 times the least width direction during casting film, in-plane retardation value R _0, which is produced as a long roll 30~300nm There, a feature that the thickness direction retardation value R _t is a cellulose ester film is 30 to 300 nm, and a long roll triacetyl cellulose film, be bonded in a long roll polarizer containing a dichroic substance A method for producing a long roll polarizing plate.   The method for producing a long roll polarizing plate according to claim 3, wherein the film is stretched 0.4 to 1.2 times in a direction orthogonal to the width direction.

Images