JP2003279729A - Retardation film and method for manufacturing the same, polarization plate, liquid crystal display and optical compensation film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a retardation film with less change of a retardation characteristic and a polarization plate and an optical compensation film using the retardation film, and also to provide a liquid crystal display using the polarization plate and maintaining a wide and excellent viewing angle although used for a long time. <P>SOLUTION: The retardation film has a retardation Ro of 30-200 nm in a plane, a retardation Rt of 70-400 nm in the direction of a thickness and cellulose ester with a degree of total substitution of an acyl group of 2.55-2.85, a content of an alkali earth metal of 1-50 ppm, a quantity of residual sulfuric acid as a content of sulfur elements of 1-50 ppm, and a quantity of free acid of 1-100 ppm. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a retardation film, a method for producing the same, a polarizing plate using the retardation film, a liquid crystal display device and an optical compensation film.

[0002]

2. Description of the Related Art Liquid crystal display devices are widely used as display devices for word processors, personal computers, etc. because they can be directly connected to IC circuits with low voltage and low power consumption and can be made particularly thin. Has been done. This liquid crystal display device has a basic configuration in which polarizing plates are provided on both sides of a liquid crystal cell, for example.

In such a liquid crystal display device, from the viewpoint of contrast and the like, a liquid crystal display device using a twisted nematic (TN) having a twist angle of 90 degrees is replaced with a super twisted nematic (STN) having a twist angle of 160 degrees or more. The liquid crystal display device used has been shifting.

However, the liquid crystal display device using the STN is
Since it uses the birefringence of liquid crystal, there is a problem that the background that was white in normally white in a liquid crystal display device using TN is colored blue or yellow. Therefore, in black and white display, contrast and viewing angle are increased. Is narrow and it is difficult to colorize.

In order to solve this problem, that is, in order to compensate for the birefringence, a technique of using a retardation plate under the polarizing plate has been proposed. According to this technique, the coloring problem is solved, but the viewing angle is hardly improved.

In order to solve this problem, a technique has been proposed in which a birefringent film having a refractive index in the thickness direction larger than that in the direction perpendicular to the optical axis of the birefringence is produced and used as a retardation plate. It was Furthermore, a technique has been proposed in which one film each having positive and negative intrinsic birefringence values or a laminated film is used as a retardation plate.

Further, as disclosed in JP-A-7-218724, the retardation value of the protective film for a polarizing plate on at least one surface of the polarizer is 30 to 30 as an in-plane retardation value measured with light having a wavelength of 590 nm. 70n
A polarizing plate using m triacetyl cellulose was proposed.

By these proposed techniques, the change in contrast depending on the viewing angle is reduced, and the viewing angle characteristics are improved. However, the problem of a narrow viewing angle, which is the biggest problem in a liquid crystal display device that has low voltage, low power consumption, and great features that other display devices do not have in thinning, cannot be improved. The demand for wider corners is increasing, and further development is underway.

As one of such developments, TN and ST
A liquid crystal of a type different from the N type has been proposed. That is, in the TN or STN type liquid crystal cell, when the voltage is off, the liquid crystal molecules are parallel to the alignment plate, and when the voltage is on, the liquid crystal molecules are aligned vertically to the alignment plate. A type in which liquid crystal molecules are perpendicular to the alignment plate and parallel to the alignment plate when the voltage is turned on, for example, a so-called vertical alignment type using negative liquid crystal with negative dielectric anisotropy has been developed. . Such a vertical alignment type liquid crystal display device is disclosed in, for example, Japanese Patent Laid-Open No. 2-176625. This Vertical Alignment (Vertical Alignment)
nt, abbreviated as VA and hereinafter VA) type liquid crystal display device is a so-called vertical alignment mode liquid crystal in which liquid crystal molecules are aligned perpendicularly to the alignment plate when the voltage is off and parallel to the alignment plate when the voltage is on. Since it is a cell, black is displayed as solid black, and the contrast is high.
Compared with the N type, it has a characteristic that the viewing angle is relatively wide.

However, as the liquid crystal screen becomes larger, there is an increasing demand for further widening the viewing angle.

By the way, for the purpose of protecting the polarizer, a protective film is attached to at least one surface of the polarizer to form a polarizing plate. This protective film is called a protective film for a polarizing plate, and a cellulose triacetate film has been conventionally used for this protective film for a polarizing plate because of its excellent optical isotropy and transparency. However, with the cellulose triacetate film,
There is an upper limit for increasing the retardation value in the thickness direction, and it is difficult to increase the viewing angle. To obtain a larger retardation value in the thickness direction, it is necessary to increase the thickness of the film.

Further, stretching was carried out to obtain a desired retardation value in the in-plane direction. It is proposed that the retardation film thus formed can be used as a protective film for a polarizing plate. However, when a cellulose ester having a lower total degree of substitution of acyl groups than a normal cellulose triacetate film is used, the phase difference may largely change due to long-term use or the influence of environmental changes, and its improvement is required. Has been.

In recent years, liquid crystal display devices are also required to be portable, and there is a demand for downsizing, especially thinning, and it is possible to further improve the viewing angle of vertical alignment type liquid crystal display devices. There is a demand for a protective film for a polarizing plate, which has a large retardation value in the thickness direction even though the protective film has a small thickness.

[0014]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object thereof is a retardation film with little change in retardation characteristics, a polarizing plate using the same, and an optical compensation film. And to provide a liquid crystal display device having a wide viewing angle using this polarizing plate and capable of maintaining an excellent viewing angle even when used for a long period of time.

[0015]

The above objects of the present invention can be achieved by the following constitutions.

1. In-plane retardation Ro is 30 to 2
00 nm, retardation Rt in the thickness direction is 70 to 4
In the retardation film having a thickness of 00 nm, the total degree of substitution of acyl groups is 2.55 to 2.85, the content of alkaline earth metal is 1 to 50 ppm, and the amount of residual sulfuric acid (as the content of elemental sulfur) is 1 to 50 ppm. , The amount of free acid is 1-100ppm
A retardation film having a cellulose ester of

2. The acyl group is an acetyl group and a propionyl group or a butyryl group, and the substitution degree of the acetyl group is X,
1. When the total substitution degree of propionyl groups or butyryl groups is Y, 1.75 ≦ X ≦ 2.15 0.60 ≦ Y ≦ 0.80, wherein the retardation film described in 1 above.

3. 3. The retardation film according to 1 or 2 above, which contains 0.5 to 30 mass% of an additive having 3 or more aromatic rings in the molecule.

4. The above-mentioned 1 characterized in that the film is formed by a solution casting method using substantially only a non-chlorine organic solvent.
The retardation film according to any one of 1 to 3.

5. A solution prepared by dissolving a cellulose ester in an organic solvent is cast on a support, the solvent is evaporated to peel off the film, and the in-plane retardation Ro obtained by stretching the film is 30 to 200 nm, in the thickness direction. In the method for producing a retardation film having a retardation of 70 to 400 nm, the total degree of substitution of acyl groups in the cellulose ester is 2.55 to 2.85, the content of alkaline earth metal is 1 to 50 ppm, and residual sulfuric acid is used. Amount (as content of elemental sulfur) 1 to 50 ppm, free acid amount 1 to 1
It is 00 ppm, The manufacturing method of the retardation film characterized by the above-mentioned.

6. At least one of the organic solvents that dissolves the cellulose ester is methyl acetate, and when the residual amount of methyl acetate after peeling is 2 to 20% by mass, 1.01 to
Stretching to 2.0 times, The manufacturing method of the retardation film of said 5 characterized by the above-mentioned.

7. A polarizing plate comprising the retardation film according to any one of the above 1 to 4 bonded to at least one surface of a polarizing film.

8. A liquid crystal display device comprising the polarizing plate described in 7 above attached to a liquid crystal cell of TN type, VA type, or OCB type so that the retardation film is on the liquid crystal cell side.

9. An optical compensatory film having an optically anisotropic layer formed by aligning a liquid crystal compound on the retardation film according to any one of the above 1 to 4.

The present invention will be described in detail below. An object of the present invention is to provide a retardation film having stable retardation, a method for producing the retardation film, a polarizing plate using the retardation film, a liquid crystal display device, and an optical compensation film. With the increase in definition and function of display devices, improvement in display quality is required. For example, Japanese Patent Laid-Open No. 2002-14
In 230, it is shown that a viewing angle is improved by applying a retardation film to various display devices. However, it has been found that it is difficult for a retardation film using a cellulose ester film to maintain stable retardation characteristics for a long period of time.

The present inventor has conducted extensive studies to improve this point, and as a result, the content of alkaline earth metal contained in cellulose ester, the amount of residual sulfuric acid (as the content of elemental sulfur), and the amount of free acid are determined. It has been found that this problem can be solved by setting a predetermined range. The reason is not clear, but it is presumed that the chains of the cellulose ester oriented by stretching are more stably retained. In order to impart a stable retardation by such stretching, the acyl group substitution degree of the cellulose ester film needs to be 2.55 to 2.85. 2.55
When it is less than the above, the phase difference is likely to change due to the passage of time and environmental conditions. It is considered that this is due to the interaction between the unsubstituted hydroxyl group of the cellulose ester, the alkaline earth metal, the amount of residual sulfuric acid, the amount of free acid and the like. Further, the acyl group substitution degree needs to be 2.85 or less, and if it exceeds this, it becomes difficult to obtain a desired retardation by stretching.

Further, in the present invention, when the acyl group is an acetyl group and a propionyl group and / or butyryl group, the substitution degree of the acetyl group is X, and the total substitution degree of the propionyl group and / or butyryl group is Y, It is preferable that 1.75 ≦ X ≦ 2.15 0.60 ≦ Y ≦ 0.80, and a retardation film having a more stable retardation can be obtained.

More preferably, by containing 0.5 to 30% by mass of an additive having 3 or more aromatic rings in the molecule, a retardation film that is even less susceptible to temperature and humidity fluctuations can be obtained. it can. In the present invention, the additive means a plasticizer, an ultraviolet absorber, an antioxidant, a matting agent and the like.

Further, the retardation film of the present invention is produced by stretching a cellulose ester film formed by a solution casting method, but the solvent for dissolving the cellulose ester is substantially only a non-chlorine organic solvent. The one showed a more stable phase difference. Substantially only non-chlorine organic solvent means that the chlorine-based organic solvent is 10% by mass with respect to the total amount of the organic solvent.
It means the following, preferably not more than 5% by mass, and most preferably not contained at all. Methyl acetate is preferably used as the non-chlorine organic solvent. In particular, when the residual solvent amount of methyl acetate is 2 to 15% by mass, it is preferable to stretch the film in at least one direction by 1.01 to 2.0 times from the viewpoint of obtaining a stable retardation.

By laminating the retardation film of the present invention with a polarizer, a polarizing plate having stable retardation properties can be obtained, and a display device using the same exhibits excellent viewing angle properties for a long period of time. be able to.

Generally, a polarizing plate used in a liquid crystal display device comprises a polarizing film and two transparent protective films arranged on both sides of the polarizing film. The polarizing film includes an iodine-based polarizing film, a dye-based polarizing film using a dichroic dye, and a polyene-based polarizing film. The iodine type polarizing film and the dye type polarizing film are generally manufactured by using a polyvinyl alcohol type film. Then, one of the protective films of the polarizing plate is an optical compensation sheet made of the above polymer film, or an optical compensation sheet made by laminating a polymer film and an optically anisotropic layer containing a liquid crystalline compound, The polarizing plate of the present invention can be manufactured.
Adhesion between the polarizing film and the optical compensation sheet is preferably produced by using an adhesive whose solvent is water as a main component. Further, a normal cellulose acetate film may be laminated as the other protective film of the polarizing film. In the polarizing plate of the present invention, the relationship between the slow axis of the polymer film and the transmission axis of the polarizing film is preferably arranged as follows depending on the type of liquid crystal display device applied. When the polarizing plate of the present invention is used in a liquid crystal display device of TN, MVA, and OCB modes, the slow axis of the polymer film and the transmission axis of the polarizing film are arranged so as to be substantially parallel to each other, and the reflective liquid crystal is used. When used in a display device, it is preferable that the slow axis of the polymer film and the transmission axis of the polarizing film are arranged at substantially 45 °.

The optical compensation sheet of the present invention or the polarizing plate using the same is advantageously used in a transmission type liquid crystal display device or a reflection type liquid crystal display device. Examples of transmissive liquid crystal display devices include TN, MVA, and OCB mode liquid crystal display liquid crystals. These liquid crystal display devices include a cell and two polarizing plates arranged on both sides of the cell. The liquid crystal cell carries liquid crystal between two electrode substrates. OC
In the case of a B-mode liquid crystal display device, the optical compensation sheet of the present invention preferably has an optically anisotropic layer containing a discotic compound or a rod-shaped liquid crystal compound on a polymer film. Further, the reflective liquid crystal display device has a liquid crystal cell sandwiched between a polarizing plate and a reflective plate.

When the optical compensation sheet of the present invention is used in a liquid crystal display device, one optical compensation sheet is arranged between the liquid crystal cell and one of the polarizing plates, or the liquid crystal cell and both polarizing plates are arranged. Place two pieces between. In this way, the optical compensation sheet of the present invention can be inserted between the ordinary polarizing plate and the liquid crystal cell to optically compensate the liquid crystal cell as in the conventional case. When the polarizing plate of the present invention is used in a liquid crystal display device, at least one of the two polarizing plates of the liquid crystal display device may be the polarizing plate of the present invention. By using the polarizing plate of the present invention, it is possible to prevent moisture present in the polarizing film in the usage environment of the liquid crystal display device from penetrating into the polarizing film, and it is possible to maintain display performance excellent in viewing angle characteristics for a long period of time. .

In the VA mode liquid crystal cell, rod-like liquid crystal molecules are aligned substantially vertically when no voltage is applied. VA
The mode liquid crystal cell includes (1) a VA mode liquid crystal cell in a narrow sense in which rod-like liquid crystal molecules are aligned substantially vertically when no voltage is applied and are aligned substantially horizontally when voltage is applied (Japanese Patent Application Laid-Open No. 2-176625). (2) In order to widen the viewing angle, the VA mode is multi-domain (M
VA mode liquid crystal cell (SID97, Digest
of tech. Papers 28 (19)
97) 845), (3) Liquid crystal cell in a mode (n-ASM mode) in which rod-like liquid crystal molecules are substantially vertically aligned when no voltage is applied and twisted in multi-domain alignment when a voltage is applied (preliminary report of the Japan Liquid Crystal Conference). Vol 58-59 (199
8) description) and (4) SURVAIVAL mode liquid crystal cell (announced at LCD International 98).

The OCB mode liquid crystal cell is a liquid crystal display device using a bend alignment mode liquid crystal cell in which rod-shaped liquid crystal molecules are aligned in a substantially opposite direction (symmetrically) in the upper part and the lower part of the liquid crystal cell. No. 4,583,825 and U.S. Pat. No. 5,410,422. Since the rod-shaped liquid crystalline molecules are symmetrically aligned in the upper part and the lower part of the liquid crystal cell, the bend alignment mode liquid crystal cell has a self-optical compensation function. Therefore, this liquid crystal mode is
(Optically Compensation B
end) Also called liquid crystal mode. The bend alignment mode liquid crystal display device has an advantage of high response speed. TN
In the liquid crystal cell of the mode, rod-like liquid crystal molecules are substantially horizontally aligned when no voltage is applied, and further twisted and aligned at 60 to 120 °. The TN mode liquid crystal cell is a color TFT.
It is most widely used as a liquid crystal display device and is described in many documents.

The inventors of the present invention have focused on not only the in-plane retardation value Ro that has been conventionally investigated but also the retardation value Rt in the thickness direction, and examined a method for increasing the retardation value in the thickness direction. As a result,
The present invention has been reached. Here, the in-plane retardation value Ro (nm) is Ro = (nx−ny) × d, and the thickness direction retardation value Rt (nm) is Rt = [(nx
+ Ny) / 2−nz] × d, where nx is the refractive index in the slow axis direction in the film plane, ny is the refractive index in the fast axis direction in the film plane, and nz is the thickness direction of the film. , And d is the film thickness (nm).

The cellulose ester used in the retardation film of the present invention has a degree of acetyl group substitution of 1.75 to.
The cellulose ester having a total degree of substitution of propionyl groups and / or butyryl groups of 2.15 is preferably 0.60 to 0.80, and the degree of substitution of acetyl groups is 1.75 to 1.95. , The total degree of substitution of propionyl groups and / or butyryl groups is preferably 0.61 to 0.76.

Such a cellulose ester is obtained by substituting the acetyl group, propionyl group and / or butyl group in the above range for the hydroxyl group of cellulose with acetic anhydride, propionic anhydride and / or butyric anhydride by a conventional method. can get. The method for synthesizing such a cellulose ester is not particularly limited, but for example, JP-A-10-4580.
It can be synthesized by the method described in No. 4.

The substitution degree of the acetyl group, the propionyl group and / or the butyl group can be measured according to ASTM-D817-96.

The amount of alkaline earth metal in the cellulose ester of the present invention is in the range of 1 to 50 ppm. 1 more
The range of ˜30 ppm is preferred. The alkaline earth metal referred to here is the total content of Ca and Mg, and the content of the alkaline earth metal atom here can be measured using an X-ray photoelectron spectroscopy analyzer (XPS). .

The amount of residual sulfuric acid in the cellulose ester of the present invention is in the range of 1 to 50 ppm. 1 to 30p
A range of pm is preferred. The amount of residual sulfuric acid is ASTM-D8.
17-96.

The amount of free acid in the cellulose ester of the present invention is in the range of 1 to 100 ppm. 1-70p
A range of pm is preferred. Free acid amount is ASTM-D817
It can be measured by -96.

By sufficiently washing the synthesized cellulose ester so that the amount of alkaline earth metal, the amount of residual sulfuric acid and the amount of free acid in the cellulose ester fall within the above ranges, dimensional change, mechanical strength, transparency, Moisture resistance, Rt
A film having a good value and a good Ro value can be obtained.

The intrinsic viscosity of the cellulose ester is preferably 1.50 to 1.75 g / cm ³ , and more preferably 1.53 to 1.63, in order to obtain the desired mechanical strength as a protective film for a polarizing plate. preferable.

The water content of the cellulose ester is preferably 0.01 to 2.0% by mass, and more preferably 0.01 to 1.5% by mass, from the viewpoint of obtaining high transparency of the obtained film. preferable. These characteristic values are ASTM
-D817-96.

Next, a method for producing a cellulose ester film by the solution casting film forming method will be described.

The cellulose used as the raw material of the cellulose ester used in the cellulose ester film of the present invention is not particularly limited, and cotton linter, wood pulp, kenaf and the like can be used. You may mix and use these.
It is preferable to use a large amount of a cellulose ester synthesized from cotton linter, which has good peelability from a belt or a drum, because the productivity efficiency is high. When the ratio of the cellulose ester synthesized from cotton linter is 60% by mass or more, the effect of releasability becomes remarkable, so 60% by mass or more is preferable, 85% by mass or more is more preferable, and further, it may be used alone. Most preferred. Regarding the cellulose ester used in the present invention, the substitution degree of the acetyl group, the propionyl group and / or the butyl group is as described above.

It is also possible to use a mixture of two or more cellulose esters having different substitution degrees. First, the dope is formed by dissolving the cellulose ester in an organic solvent capable of dissolving it. The cellulose ester flakes and the organic solvent are mixed and dissolved with stirring to form a dope. The dissolution is carried out under normal pressure, below the boiling point of the main solvent, under pressure above the boiling point of the main solvent, and disclosed in JP-A-9-955.
No. 44, No. 9-95557 or No. 9-95538, the method of cooling dissolution method, JP-A-11-2.
As described in 1379, there are various dissolution methods such as a method of performing at high pressure. After dissolution, the dope is filtered with a filter material, defoamed, and sent to the next step with a pump. The concentration of cellulose ester in the dope is preferably about 10 to 35% by mass.

As the organic solvent for dissolving the cellulose ester, methyl acetate, ethyl acetate, amyl acetate, ethyl formate, acetone, cyclohexanone, methyl acetoacetate, tetrahydrofuran, 1,3-dioxolane, 1,
4-dioxane, 2,2,2-trifluoroethanol, 2,2,3,3-hexafluoro-1-propanol, 1,3-difluoro-2-propanol, 1,1,
1,3,3,3-hexafluoro-2-methyl-2-propanol, 1,1,1,3,3,3-hexafluoro-2-propanol, 2,2,3,3,3-pentafluoro -1-Propanol, nitroethane, methylene chloride and the like can be mentioned. Chlorine-based organic solvents such as methylene chloride may not be used in some cases due to recent severe environmental problems, and non-chlorine-based organic solvents are preferable. Of these, methyl acetate and acetone can be preferably used. Further, it is preferable to use a lower alcohol such as methanol, ethanol or butanol in combination with these organic solvents because the solubility of the cellulose ester in the organic solvent can be improved and the dope viscosity can be reduced. Particularly, ethanol having a low boiling point and low toxicity is preferable.

Additives such as plasticizers such as phthalates and phosphates, ultraviolet absorbers, antioxidants and matting agents may be added to the dope. It is preferable that these additives have three or more aromatic rings in the molecule, and the addition amount is preferably 0.5 to 30 mass%.

In the present invention, it is preferable to add a plasticizer to the cellulose ester film. The plasticizer that can be used is not particularly limited, but in the phosphoric acid ester system, triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate, tributyl phosphate, etc., phthalate. For acid ester type, diethyl phthalate, dimethoxyethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate,
Di-2-ethylhexyl phthalate, dicyclohexyl phthalate, dibenzyl phthalate, and the like, in glycolate ester systems, triacetin, tributyrin, butylphthalylbutyl glycolate, ethylphthalylethyl glycolate, methylphthalylethyl glycolate, butylphthalylbutyl. It is preferred to use glycolate alone or in combination. If desired, two or more plasticizers may be used in combination. When used in cellulose ester, the use ratio of the phosphoric acid ester-based plasticizer is preferably 50% by mass or less based on the total amount of the plasticizer because hydrolysis of the cellulose ester film is unlikely to occur and durability is excellent. It is more preferable that the phosphoric acid ester-based plasticizer ratio is small, and it is particularly preferable to use a phosphoric acid ester-based plasticizer, a phthalic acid ester-based or glycolic acid ester-based plasticizer, a citric acid ester, or a polyhydric alcohol ester. preferable.

Further, in the present invention, it is preferable that the cellulose ester film contains an ultraviolet absorber, and the ultraviolet absorber has an excellent ability to absorb ultraviolet rays having a wavelength of 370 nm or less from the viewpoint of preventing deterioration of liquid crystal and is good. From the viewpoint of liquid crystal display property, a material that absorbs visible light having a wavelength of 400 nm or more as little as possible is preferably used. In particular, the transmittance at a wavelength of 370 nm needs to be 10% or less, preferably 5% or less, and more preferably 2% or less. Examples of the ultraviolet absorber used include oxybenzophenone compounds, benzotriazole compounds, salicylate compounds, benzophenone compounds, triazine compounds, cyanoacrylate compounds, nickel complex salt compounds, and the like. Not limited. The benzotriazole compound described in Registration No. 3265393 can also be preferably used. You may use 2 or more types of ultraviolet absorbers. The method of adding the ultraviolet absorber to the dope is alcohol, methylene chloride,
Add it after dissolving it in an organic solvent such as dioxolane,
Alternatively, it may be added directly in the dope composition. For inorganic powders that are not soluble in an organic solvent, a dissolver or a sand mill is used in an organic solvent and a cellulose ester to disperse them and then added to the dope. In the present invention, the amount of the ultraviolet absorber used is 0.1 to 0.1% with respect to the cellulose ester.
The content is 5.0% by mass, preferably 0.5 to 2.0% by mass, more preferably 0.8 to 2.0% by mass.

Further, the cellulose ester film of the present invention preferably contains an antioxidant,
As the antioxidant, hindered phenol compounds are preferably used, and 2,6-di-t-butyl-p-cresol and pentaerythrityl-tetrakis [3-
(3,5-di-t-butyl-4-hydroxyphenyl)
Propionate], triethylene glycol-bis [3
-(3-t-butyl-5-methyl-4-hydroxyphenyl) propionate], 1,6-hexanediol-
Bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], 2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-t
-Butylanilino) -1,3,5-triazine, 2,2
-Thio-diethylenebis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, N , N'-hexamethylenebis (3,5-di-t-butyl-4-hydroxy-
Hydrocinnamamide), 1,3,5-trimethyl-2,
4,6-Tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene, Tris- (3,5-di-t-)
Butyl-4-hydroxybenzyl) -isocyanurate and the like. Especially 2,6-di-t-butyl-p-cresol, pentaerythrityl-tetrakis [3-
(3,5-di-t-butyl-4-hydroxyphenyl)
Propionate], triethylene glycol-bis [3
-(3-t-butyl-5-methyl-4-hydroxyphenyl) propionate] is preferred. Also, for example, N,
Hydrazine-based metal deactivators such as N'-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyl] hydrazine and tris (2,4-di-t-butylphenyl) phosphine. You may use together phosphorus processing stabilizers, such as a fight. The addition amount of these compounds is preferably 1 ppm to 1.0% by mass ratio with respect to the cellulose ester, and more preferably 10 to 1000 ppm.

In the present invention, in order to improve the handling property in the cellulose ester film, for example, silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, kaolin, talc, calcined calcium silicate, hydrated silicic acid. It is preferable to include inorganic fine particles such as calcium, aluminum silicate, magnesium silicate, and calcium phosphate, and a matting agent such as a crosslinked polymer. Of these, silicon dioxide is preferable because it can reduce the haze of the film. The average particle diameter of the secondary particles of the fine particles is in the range of 0.01 to 1.0 μm, and the content thereof is preferably 0.005 to 0.3 mass% with respect to the cellulose ester. Particles such as silicon dioxide are often surface-treated with an organic substance, but such particles are preferable because they can reduce the haze of the film. Preferred organic substances for the surface treatment include halosilanes, alkoxysilanes, silazanes, siloxanes, and the like, and a treatment in which a methyl group is present on the surface is preferable. The larger the average particle size of the fine particles, the greater the matte effect, and the smaller the average particle size, the more excellent the transparency is. Therefore, the average primary particle size of the fine particles is preferably 5 to 50 nm, more preferably 7 to 16 nm.
Is. It is preferable that these fine particles usually exist as an aggregate in the film and generate irregularities of 0.01 to 1.0 μm on the film surface. As fine particles of silicon dioxide, Aerosil 200 manufactured by Aerosil Co.,
200V, 300, R972, R972V, R974,
R202, R812, OX50, TT600 and the like can be mentioned, preferably AEROSIL R972, R
972V, R974, R202, and R812. Two or more kinds of these matting agents may be used in combination. When two or more kinds are used in combination, they can be mixed and used at an arbitrary ratio. In this case, a matting agent having different average particle diameters and materials, for example, AEROSIL 200V and R972V can be used in a mass ratio of 0.1: 99.9 to 99.9: 0.1.

In the solution casting film forming method, the above dope is filtered and sent to a die by a metering pump, and the dope is cast from a die onto a stainless belt or a metal drum whose surface is polished, and the metal support In the above, the organic solvent is evaporated or cooled to be solidified, the web is peeled off before the metal support makes one round, and dried in the drying step to form a film.

In the process of peeling the web from the metal support, as a means for increasing Rt, it is preferable to reduce the residual solvent amount at the time of peeling, and the residual solvent amount is 5 to 100% by mass relative to the web. The content is preferably 5 to 80% by mass, more preferably 10 to 45% by mass.

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

When peeling, the peeling tension is 50 to 390 N /
m is preferably about 100, more preferably 100
~ 300 N / m, more preferably 100-250 N
/ M.

In the drying step, the peeled web is dried by passing it through a roll-conveying dryer and / or a tenter dryer, and finally the residual solvent amount of the film is adjusted to 0.5% by mass or less, preferably 0.01% by mass. It is not more than mass%. When drying with a tenter, it is sufficient to apply tension between the clips so that the web shrinks due to drying so that the width is held by the clips, but if the stretching ratio is increased, Rt and Ro can be increased, When the residual solvent amount is 2 to 20% by mass, it is preferable to stretch to a stretching ratio of 1.01 to 2.0. In the present invention, it is preferable to control the stretching conditions so that Ro is 30 to 200 nm. Also, R
70 to 400 nm is preferable as t.

Also, in the drying process by roll conveyance, Ro, Rt can be controlled by controlling the conveyance tension.
Can be increased. Conveyance tension is 50-2
The range is preferably 00 N / m, more preferably 75 to 150 N / m, further preferably 75 to 1
20 N / m.

The retardation film of the present invention preferably has a thickness of 20 to 200 μm, and further 4
0 to 160 μm is preferable, and more preferably 60 to 14
It is 0 μm.

The retardation film having the cellulose ester of the present invention produced as described above is preferably used for a polarizing plate as a protective film for a polarizing plate. As described above, the polarizing plate is formed by bonding and laminating a protective film for polarizing plate on at least one surface of a polarizer (polarizing film). A conventionally known polarizer can be used as the polarizer. For example, a hydrophilic polymer film such as a polyvinyl alcohol film is treated with a dichroic dye such as iodine and stretched. The bonding of the cellulose ester film and the polarizer is not particularly limited, but can be performed with an adhesive composed of an aqueous solution of a water-soluble polymer. In the present invention, as the water-soluble polymer adhesive, a completely saponified polyvinyl alcohol aqueous solution is preferably used.

The polarizing plate thus obtained can be used in various liquid crystal display devices. However, the retardation film used as the protective film for polarizing plate of the present invention has a high retardation value, and therefore has a VA type. It is particularly useful for liquid crystal display devices.

A polarizing plate using the cellulose ester film of the present invention is provided on one side or both sides of a TN type, VA type, OCB type liquid crystal cell to obtain a liquid crystal display device having a stable wide viewing angle. be able to. It is preferable to attach the retardation film of the polarizing plate so that the retardation film is on the liquid crystal cell side.

By setting Ro and Rt of the cellulose ester film of the protective film for polarizing plate within the above range, the liquid crystal display device of the present invention can have a wide viewing angle.

The retardation film of the present invention can be used as an optical compensation film by providing an optically anisotropic layer. The optically anisotropic layer is formed by directly forming a subbing layer on the retardation film or further forming an alignment layer on the retardation film, coating a liquid crystal compound on it, aligning it, and fixing the alignment state. can do.

The alignment layer according to the present invention is arranged on the transparent support and is used for aligning the liquid crystal compound in the optical anisotropic layer adjacent to the optical anisotropic layer described later.

Here, the materials constituting the alignment layer will be described. Specific materials for forming the alignment layer include, but are not limited to, the following resins and substrates. For example, polyimide, polyamide imide, polyamide, polyether imide, polyether ether ketone, polyether ketone, polyketone sulfide, polyether sulfone, polysulfone, polyphenylene sulfide, polyphenylene oxide, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyacetal. , Polycarbonate,
Examples thereof include polyarylate, acrylic resin, polyvinyl alcohol, polypropylene, polyvinylpyrrolidone, cellulosic plastics, epoxy resin and phenol resin.

A well-known method can be used for the alignment treatment, but a treatment method widely adopted as a liquid crystal alignment treatment step for LCD such as a rubbing treatment can be used, and a well-known photo-alignment layer is used. It can also be used.

Next, the optically anisotropic layer according to the present invention will be described. The optical anisotropic layer according to the optical compensation film of the present invention is for improving the viewing angle characteristics of a liquid crystal display. Therefore, the thickness of the optical anisotropic layer is determined by the birefringence of the liquid crystal compound constituting it and the alignment of the liquid crystal compound. Although depending on the condition, the film thickness is generally 0.2 to 5 μm, preferably 0.4 to 3
μm.

The optical anisotropic layer according to the present invention can be provided in at least one layer for the retardation film, but a plurality of optical anisotropic layers can be provided for one retardation film. When the liquid crystal compound contained in the anisotropic layer is arranged in an oriented state or in a state in which the orientation of the liquid crystal compound is fixed, the orientation can be designed to have an optical characteristic suitable for the display.

In the present invention, since the retardation film has predetermined optical characteristics, it is preferable that the liquid crystal layer coated on the retardation film is a single layer from the viewpoints of cost reduction and productivity.

When the optical compensation film of the present invention is installed, the upper polarizer and the lower polarizer are usually arranged above and below a pair of substrates located on both sides of the driving liquid crystal cell. It is preferable to install at least one optical compensation film of the present invention between at least one of the upper and lower polarizers, in particular, in order to achieve the desired effects of the present invention regardless of the viewpoint of cost reduction. It is preferable to install one optical compensation film of the present invention between the substrate and each of the upper polarizer and the lower polarizer.

When the liquid crystal display device is a twisted nematic type (TN type) liquid crystal display device, the retardation film surface side of the optical compensation film of the present invention is placed so that the substrate side is closest to the TN type liquid crystal cell. Excellent by bonding a compensating film and bonding in a direction in which the maximum refractive index direction in the retardation film plane of the optical compensation film is substantially orthogonal to the alignment direction of the nematic liquid crystal of the substrate closest to the liquid crystal cell. It is possible to exhibit the effect. Substantially orthogonal is 90 ± 5 °, but 90 ° is particularly preferable.

In the optically anisotropic layer formed by orienting and fixing the liquid crystal molecules according to the present invention, the average tilt angle of the liquid crystal molecules is preferably oblique when observed from the cross sectional direction of the optically anisotropic layer. The orientation angle may change with respect to the thickness direction. Further, the inclination angle is high on the retardation film side and decreases as it approaches the polarizer, and this change is preferably continuous. The average tilt angle is in the range of 10 to 70 °, preferably 25 to 5 although it depends on the design of the display in order to compensate the viewing angle of the display.
0 ° is particularly preferable in the TN type liquid crystal display device.

In the present invention, the direction in which the maximum refractive index direction of the optically anisotropic layer is projected on the retardation film surface (direction A) is substantially equal to the Ny direction (direction B) of the retardation film. Is preferred. Here, being substantially equal to the Ny direction means that the angle formed by the direction A and the direction B is within ± 2 °, preferably within ± 1 °.

Next, the liquid crystal compound according to the present invention will be described. The liquid crystal compound according to the present invention is not particularly limited as long as the liquid crystal compound can be aligned, and as a result, the orientation imparts optical anisotropy without light scattering in the visible light region.

Examples of the liquid crystal compound according to the present invention other than the polymer liquid crystal include liquid crystal compounds such as discotic compounds and generally rod-shaped liquid crystal compounds, and liquid crystal compounds exhibiting optically positive birefringence are preferred, and more preferred. Is preferably a positive birefringent liquid crystal compound having an unsaturated ethylenic group, from the viewpoint of fixing the alignment, for example, JP-A-9-28.
Examples thereof include compounds having a structure described in Nos. 1480 and 9-281481, but are not particularly limited thereto.

The structure of the liquid crystal compound according to the present invention is not particularly limited, but the optical anisotropic layer according to the present invention exhibits a desired optical anisotropy, so that the liquid crystal molecules are aligned in a chemical reaction or The orientation of the liquid crystal compound can be fixed by the treatment utilizing the temperature difference. In addition, when a solution containing a liquid crystal compound and an organic solvent is prepared, and the solution is applied and dried to form an optically anisotropic layer, alignment treatment of the liquid crystal compound is performed at a temperature not higher than the liquid crystal transition temperature without heating the liquid crystal transition temperature or higher. It is also possible to

When a solution containing a liquid crystal compound is applied, the solvent is dried and removed after application to obtain a liquid crystal layer having a uniform film thickness. The liquid crystal layer can fix the alignment of the liquid crystal by the action of heat or light energy or a chemical reaction by the combined use of heat and light energy.

Examples of the radical polymerization initiator for the above-mentioned unsaturated ethylenic group polymerization reaction include, for example, azobis compounds, peroxides, hydroperoxides, redox catalysts, etc., such as potassium persulfate, ammonium persulfate, and tert-butyl. Peroctoate, benzoyl peroxide, isopropyl percarbonate, 2,
4-dichlorobenzoyl peroxide, methyl ethyl ketone peroxide, cumene hydroperoxide,
Examples thereof include dicumyl peroxide, azobisisobutyronitrile, 2,2'-azobis (2-amidinopropane) hydrochloride, benzophenones, acetophenones, benzoins, thioxanthones and the like. Details of these are described in "Ultraviolet Curing System", Comprehensive Technical Center, pp. 63-147, 1989.

Further, when the curing reaction is carried out by using the radical reaction, it is possible to shorten the reaction time by irradiating the active ray under a nitrogen atmosphere in order to avoid the delay of the polymerization reaction due to the presence of oxygen in the air. It is preferable in that it can be cured with a small amount of light.

On the other hand, when the liquid crystal compound is a polymer liquid crystal, it is not necessary to fix the orientation of the liquid crystal by carrying out the curing reaction by the above chemical reaction. For example, the alignment can be fixed by heat-treating the polymer liquid crystal at a glass transition temperature or higher and allowing it to cool to the glass transition temperature or lower.

When the glass transition temperature of the polymer liquid crystal is higher than the heat resistance temperature of the support, the alignment film is placed on the heat resistant support, the polymer liquid crystal is applied, and then the glass of the polymer liquid crystal is applied. It can be oriented by heating above the transition temperature. It is also possible to cool this to room temperature, fix the orientation of the polymer liquid crystal, and then transfer it to a support using an adhesive to prepare an optically anisotropic body.

In the present invention, an optically anisotropic layer may be formed on the retardation film to obtain the optical compensation film of the present invention.

[0086]

The present invention will be described below with reference to examples, but the embodiments of the present invention are not limited to these.

Example 1 [Preparation of Retardation Film] (Retardation Film 1) The substitution degree of acetyl group is 1.75,
The degree of substitution of propionyl group is 0.80, the content of alkaline earth metal is 6 ppm, the amount of residual sulfuric acid (as sulfur element) is 16 ppm, the amount of free acid is 20 ppm, and the intrinsic viscosity is 1.5.
4, 100 kg of cellulose acetate propionate (average particle size 1500 μm) having a water content of 0.1% by mass,
2 kg of ethylphthalylethyl glycolate, 10 kg of triphenyl phosphate, 300 kg of methylene chloride,
60 kg of ethanol was placed in a closed container, and the mixture was gradually stirred and slowly heated to 45 ° C. over 60 minutes to be dissolved. The inside of the container became 120 kPa. This dope was manufactured by Azumi Filter Paper Co., Ltd. After filtering 3 times using 244, it was left still and the foam in the dope was removed. Also,
Separately, 5 kg of the above cellulose acetate propionate, 3 kg of TINUVIN 326 (manufactured by Ciba Specialty Chemicals), TINUVIN 171 (manufactured by Ciba Specialty Chemicals), 5 kg of TINUVIN 109 (manufactured by Ciba Specialty Chemicals), and AEROSI.
1 kg of LR972V (manufactured by Nippon Aerosil Co., Ltd.) was mixed with 94 kg of methylene chloride and 8 kg of ethanol and dissolved by stirring to prepare an ultraviolet absorbent solution. 100k above dope
The ultraviolet absorber solution was added at a ratio of 2 kg to g and thoroughly mixed by a static mixer, and then cast from a die onto a stainless belt at a dope temperature of 35 ° C. After the hot water of 35 ° C. is brought into contact with the back surface of the stainless belt to dry it on the temperature-controlled stainless belt, the back surface of the stainless belt is further brought into contact with cold water of 12 ° C.
After holding for a second, it was peeled from the stainless belt. The amount of residual solvent in the web at the time of peeling was 90% by mass. Next, hold both ends of the peeled web with a tenter, and 115 ° C
The film was stretched 1.3 times in the width direction with a residual solvent amount of 15% by mass and then dried at 120 ° C. to obtain a retardation film 1 having a film thickness of 80 μm. The residual solvent amount was 0.01% by mass.

The degree of substitution of fatty acid cellulose ester and the amount of residual solvent were measured as follows.

(Substitution degree of fatty acid cellulose ester) The substitution degree is measured by a saponification method. The dried cellulose ester was precisely weighed, dissolved in a mixed solvent of acetone and dimethyl sulfoxide (volume ratio 4: 1), and then dried at a predetermined 1mo.
Add 1 / L aqueous sodium hydroxide solution and saponify at 25 ° C. for 2 hours. Excess sodium hydroxide is titrated with 0.5 mol / L sulfuric acid using phenolphthalein as an indicator. A blank test is conducted by the same method as above. Furthermore, dilute the supernatant of the solution after titration,
The composition of the organic acid is measured by an ordinary method using an ion chromatograph. Then, the substitution degree (%) is calculated according to the following.

TA = (Q−P) × F / (1000 × W) DSac = (162.14 × TA) / (1−42.14)
× TA + (1-56.06 × TA) × (AL / AC)) DSpr = DSsc × (AL / AC) where P is 0.5 mol / L sulfuric acid amount (ml) required for titration of the sample, and Q is 0.5 mol / required for blank test
L sulfuric acid amount (ml), F is the titer of 0.5 mol / L sulfuric acid,
W is the sample mass (g), TA is the total organic acid amount (mol /
g), AL / AC is the molar ratio of acetic acid (AC) and other organic acid (AL) measured by ion chromatography, DSsc
Indicates the substitution degree of the acetyl group, and DSpr indicates the substitution degree of the propionyl group.

(Amount of Residual Solvent) Amount of Residual Solvent (%) = (M−N) / N × 100 M is the mass of the film (web) before heating, N is M
It is the mass after drying at 0 ° C. for 3 hours.

(Retardation film 2) The substitution degree of the acetyl group is 1.92, the substitution degree of the propionyl group is 0.76, the content of the alkaline earth metal is 15 ppm, the residual sulfuric acid amount (as a sulfur element) is 20 ppm, Cellulose acetate propionate (average particle size 350 μm) having a free acid amount of 8 ppm, an intrinsic viscosity of 1.61, and a water content of 0.2% by mass.
00 kg, ethylphthalylethyl glycolate 2 kg,
Triphenyl phosphate 10kg, methyl acetate 30
0 kg and 60 kg of ethanol were placed in a closed container, the temperature of the mixture was gradually raised while slowly stirring, and the mixture was stirred for 5 minutes over 5 minutes.
It was raised to 0 ° C. and dissolved. This dope was manufactured by Azumi Filter Paper Co., Ltd. After filtering 3 times using 244, it was left still and the foam in the dope was removed. Separately from this, 5 kg of the above cellulose acetate propionate and 32 tinubin
6 (manufactured by Ciba Specialty Chemicals) 3 kg, Tinuvin 171 (manufactured by Ciba Specialty Chemicals) 5k
g, 5 kg of TINUVIN 109 (manufactured by Ciba Specialty Chemicals), and 1 kg of AEROSIL R972V (manufactured by Nippon Aerosil Co., Ltd.) were mixed with 75 kg of methyl acetate and 25 kg of ethanol and dissolved by stirring to prepare an ultraviolet absorber solution. The ultraviolet absorber solution was added at a ratio of 2 kg with respect to 100 kg of the dope, thoroughly mixed by a static mixer, and then cast from a die onto a stainless belt at a dope temperature of 50 ° C. 50 from the back of the stainless belt
After drying on a temperature-controlled stainless steel belt by contacting hot water at ℃, 1 on the back surface of the stainless steel belt.
After contacting cold water at 2 ° C. for 15 seconds and then peeling from the stainless belt. The amount of residual solvent in the web at the time of peeling was 85% by mass. Then, both ends of the peeled web are held by tenter, and the residual solvent amount is 10% by mass at 115 ° C.
At that time, the film is stretched 1.3 times in the width direction and then 120
It was dried at 0 ° C. to obtain a retardation film 2 having a film thickness of 80 μm. The residual solvent amount was 0.01% by mass.

(Retardation film 3) Cellulose acetate propionate used in the preparation of retardation film 2 was
Degree of substitution of acetyl group is 1.94, degree of substitution of propionyl group is 0.63, content of alkaline earth metal is 8 ppm,
Amount of residual sulfuric acid (as elemental sulfur) is 25 ppm, amount of free acid is 70 ppm, intrinsic viscosity is 1.54, moisture content is 0.9 mass% except that cellulose acetate propionate (average particle size 150 μm) is used. A retardation film 3 having a thickness of 80 μm was obtained in the same manner as the retardation film 2.

(Retardation film 4) The cellulose acetate propionate used in the preparation of the retardation film 2 was
Degree of substitution of acetyl group is 2.11, degree of substitution of propionyl group is 0.70, content of alkaline earth metal is 30 pp
m, the amount of residual sulfuric acid (as elemental sulfur) is 50 ppm, the amount of free acid is 50 ppm, the intrinsic viscosity is 1.73, and the water content is 0.
A retardation film 4 having a film thickness of 80 μm was obtained in the same manner as the retardation film 2, except that the content was changed to 5% by mass of cellulose acetate propionate (average particle diameter 1000 μm).

(Retardation film 5) Cellulose acetate propionate used in the preparation of retardation film 2 was
The substitution degree of acetyl group is 1.92, the substitution degree of propionyl group is 0.70, the content of alkaline earth metal is 6 ppm,
Amount of residual sulfuric acid (as elemental sulfur) is 12 ppm, amount of free acid is 20 ppm, intrinsic viscosity is 1.59, and moisture content is 0.1% by mass. Cellulose acetate propionate (average particle size 500 μm) A retardation film 5 having a thickness of 80 μm was obtained in the same manner as the retardation film 2.

(Retardation film 6) Ethylphthalylethyl glycolate 2k used in the preparation of retardation film 2
A retardation film 6 was obtained in the same manner as the retardation film 2, except that g and triphenyl phosphate 10 kg were changed to ethyl phthalyl ethyl glycolate 4 kg and dibenzyl phthalate 8 kg.

(Retardation film 7) Ethylphthalylethyl glycolate 2k used in the production of retardation film 3
Retardation film 7 was obtained in the same manner as in retardation film 3 except that g and triphenyl phosphate 10 kg were changed to ethyl phthalyl ethyl glycolate 4 kg and dibenzyl phthalate 8 kg.

(Retardation film 8) Ethylphthalylethyl glycolate 2k used in the production of retardation film 4
A retardation film 8 was obtained in the same manner as the retardation film 4, except that g and triphenyl phosphate 10 kg were changed to ethyl phthalyl ethyl glycolate 4 kg and dibenzyl phthalate 8 kg.

(Phase retardation film 9) 3 kg of tinuvin 326 (manufactured by Ciba Specialty Chemicals) used in the preparation of retardation film 2, 5 kg of tinuvin 171 (manufactured by Ciba Specialty Chemicals), 5 kg of tinuvin 109 (manufactured by Ciba Specialty Chemicals) A retardation film 9 was obtained in the same manner as the retardation film 2, except that the amount of 2-hydroxy-4-benzyloxybenzophenone was changed to 8 kg.

(Retardation Film 10) Retardation Film 9
Ethylphthalylethyl glycolate 2 used in the preparation of
A retardation film 10 was obtained in the same manner as the retardation film 9 except that 4 kg of ethyl phthalyl ethyl glycolate and 8 kg of dibenzyl phthalate were used instead of 10 kg of triphenyl phosphate and 8 kg of triphenyl phosphate.

(Retardation Film 11) Retardation Film 1
Retardation film 11 was obtained in the same manner as retardation film 10 except that 8 kg of 2-hydroxy-4-benzyloxybenzophenone used in the production of 0 was changed to compound T-18 8 kg.

[0102]

[Chemical 1]

(Retardation Film 12) Retardation Film 1
The same as the retardation film 10 except that the cellulose acetate propionate used in the preparation of No. 0 was swollen with methyl acetate, then cooled to -20 ° C and the temperature was raised to 50 ° C to dissolve the cellulose ester. Then, a retardation film 12 was obtained.

(Retardation film 13) Retardation film 1
The cellulose acetate propionate used in the preparation of No. 2 had an acetyl substitution degree of 2.75, an alkaline earth metal content of 25 ppm, a residual sulfuric acid amount (as a sulfur element) of 25 ppm, and a free acid amount of 10 ppm. A retardation film 13 was obtained in the same manner as the retardation film 12 except that it was changed to.

(Preparation of Retardation Film 14) 8 kg of 2-hydroxy-4-benzyloxybenzophenone used in the preparation of retardation film 13 was replaced with 8 kg of compound T-1.
A retardation film 14 was obtained in the same manner as the retardation film 13 except that the above was changed to.

(Retardation Film 15) Retardation Film 1
Cellulose acetate propionate used in the preparation of 2. had an acetyl group substitution degree of 2.75, an alkaline earth metal content of 50 ppm, and a residual sulfuric acid amount (as elemental sulfur).
Of retardation film 15 was obtained in the same manner as in retardation film 1 except that the cellulose acetate was changed to 45 ppm and the free acid amount was 110 ppm.

(Retardation Film 16) Retardation Film 1
Cellulose acetate propionate used in the preparation of 1. had an acetyl group substitution degree of 2.10, a propionyl group substitution degree of 0.82, and an alkaline earth metal content of 105.
ppm, residual sulfuric acid amount (as elemental sulfur) 80 ppm,
Retardation film similar to retardation film 1 except that the amount of free acid was changed to 110 ppm, intrinsic viscosity was 1.61, and water content was 0.5% by mass, cellulose acetate propionate (average particle size 350 μm). I got 16.

(Retardation film 17) Retardation film 1
The cellulose acetate propionate used in the preparation of 1. had an acetyl group substitution degree of 1.60, a propionyl group substitution degree of 0.82, and an alkaline earth metal content of 100.
ppm, residual sulfuric acid amount (as elemental sulfur) 70 ppm,
Retardation in the same manner as in the retardation film 1 except that the amount of free acid is 100 ppm, the intrinsic viscosity is 1.5, and the water content is 0.7% by mass containing cellulose acetate propionate (average particle size 350 μm). A film 17 was obtained.

(Retardation Film 18) Retardation Film 1
The cellulose acetate propionate used in the preparation of 1. had an acetyl group substitution degree of 1.75, a propionyl group substitution degree of 0.80, and an alkaline earth metal content of 55 pp.
m, the amount of residual sulfuric acid (as elemental sulfur) was 60 ppm, the amount of free acid was 110 ppm, the intrinsic viscosity was 1.57, and the moisture content was changed to cellulose acetate propionate (average particle size 1000 μm) of 0.1% by mass. A retardation film 18 was obtained in the same manner as the retardation film 1 except for the above.

[Evaluation of Retardation Fluctuation] The produced retardation film was stored at 60 ° C. and 80% RH for 2 weeks and 1 month to be forcibly deteriorated, and the automatic birefringence meter KOBRA-2 was used.
1 ADH (manufactured by Oji Scientific Instruments), 23 ° C, 55
In an environment of% RH, a three-dimensional refractive index was measured at a wavelength of 590 nm, refractive indices nx, ny, and nz were obtained, and Ro and Rt were calculated according to the above formula. Table 1 shows changes due to forced deterioration together with Ro and Rt of the sample before forced deterioration.

[0111]

[Table 1]

It has been confirmed that the retardation film of the present invention has little variation in retardation during storage and has stable characteristics.

[Production of Polarizing Plate] (Polarizing Plate 1) The retardation film 1 of the present invention and a commercially available cellulose triacetate film (Konicatac KC8UX)
2 MW, manufactured by Konica Corporation) was used as a protective film for a polarizing plate, and the polarizing plate 1 was produced by laminating the both sides of a polarizer according to the following procedure.

(Production of Polarizing Plate) (a) Production of Polarizer A polyvinyl alcohol film having a thickness of 120 μm is uniaxially stretched (110 ° C., stretching ratio 5 times).
did. 0.075 g of iodine and 5 parts of potassium iodide
g, 100 g of water for 60 seconds, and then 6 g of potassium iodide, 7.5 g of boric acid, and 1 part of water.
It was immersed in an aqueous solution of 68 g at a ratio of 00 g. This was washed with water and dried to obtain a long polarizer.

(B) Preparation of Polarizing Plate Then, according to the following steps 1 to 5, a polarizer and a protective film for each polarizing plate were attached to each other to prepare a polarizing plate.

Step 1: The retardation film 1 and the cellulose triacetate film were each immersed in a 2 mol / L sodium hydroxide solution at 55 ° C. for 90 seconds, then washed with water and dried.

Step 2: The above-mentioned polarizer was immersed in a polyvinyl alcohol adhesive tank having a solid content of 2% by mass for 1 to 2 seconds.

Step 3: Excessive adhesive attached to the polarizer in Step 2 was lightly removed, and it was sandwiched between the cellulose triacetate film alkali-treated in Step 1 and the retardation film 1 and laminated. The retardation film 1 was arranged so that the slow axis direction and the absorption axis of the polarizer were orthogonal to each other.

Step 4: 20 to 20 with two rotating rollers
Bonding was performed at a pressure of 30 N / cm ² and a speed of about 2 m / min. At this time, care was taken to prevent bubbles from entering.

Step 5: The sample prepared in Step 4 was dried in an oven at 80 ° C. for 3 minutes to prepare a polarizing plate 1.

(Polarizing Plates 2 to 19) Polarizing plates 2 to 18 were prepared in the same manner except that the retardation film 1 was changed to the retardation films 2 to 18. Further, a polarizing plate 1 produced by using a cellulose triacetate film on both sides
Got 9.

[Production of Liquid Crystal Display Device] Commercial liquid crystal display device (manufactured by NEC, color liquid crystal display Multi
Sync LCD1525J: Model name LA-1529H
The polarizing plates on both surfaces of the M and TN type liquid crystals) are carefully peeled off, the polarization direction of the original polarizing plate is aligned with that of the above polarizing plate, and the surface on which the retardation film is bonded is on the liquid crystal cell side. To 19 are attached to each other, and liquid crystal display panel 1-
1 to 1-19 were produced.

Further, a commercially available liquid crystal display device (manufactured by Fujitsu Limited,
(15-inch display VL-1530S, VA type liquid crystal) The polarizing plates on both surfaces are carefully peeled off, the polarization direction is aligned with the original polarizing plate, and the surface on which the retardation film is bonded becomes the liquid crystal cell side. The above-mentioned polarizing plates 1 to 19 were attached to each other in this manner to prepare liquid crystal display devices 2-1 to 2-19.

[Evaluation of Viewing Angle Characteristic] The manufactured liquid crystal display device was subjected to white display, black display and gray 8 gradation display by a VG365N video pattern generator manufactured by AMT Co., and a contrast ratio at the time of white / black display. Was measured with LCD-7000 manufactured by Otsuka Electronics. The angle at which the contrast ratio ≧ 10 was defined as the viewing angle.

As a result of the measurement, as compared with the comparative polarizing plate 19 (horizontal viewing angle 125 °), the polarizing plates 1 to 14 of the invention were compared.
The viewing angle was widened. Especially for the TN type liquid crystal cell, the viewing angles of the polarizing plates 5 and 7 in the left-right direction were remarkably improved and were 160 °. Regarding the VA type liquid crystal cell, when the polarizing plate 6 and the polarizing plates 9 to 14 were used, the viewing angle was remarkably improved, and the vertical and horizontal directions were 160 °, and no long-term fluctuation in the viewing angle was observed. On the other hand, the polarizing plates 15 to 18 for comparison are poor in the effect of improving the viewing angle and 130 to 130
It was about 145 °, and it was confirmed that the viewing angle fluctuated over time, which was not preferable.

Example 2 Degree of substitution of acetyl group was 1.94, degree of substitution of propionyl group was 0.76, content of alkaline earth metal was 5 ppm,
100 kg of residual sulfuric acid amount (as elemental sulfur), 7 ppm of free acid amount, 1.62 of intrinsic viscosity, 0.1 mass% of water content, 100 kg of cellulose acetate propionate (average particle diameter 1000 μm), ethylphthalyl Ethyl glycolate 3kg, Triphenyl phosphate 8k
g, 300 kg of methyl acetate and 100 kg of ethanol were placed in a closed container, and the mixture was gradually stirred and gradually heated up to 55 ° C. over 60 minutes to be dissolved. This dope was manufactured by Azumi Filter Paper Co., Ltd. Using 244,
After filtering 3 times, it was left still and the bubbles in the dope were removed. Also,
Separately, 5 kg of the above cellulose acetate propionate, 5 kg of TINUVIN 171 (manufactured by Ciba Specialty Chemicals), 5 kg of TINUVIN 109 (manufactured by Ciba Specialty Chemicals), and AEROSIL R9.
72V (manufactured by Nippon Aerosil Co., Ltd.) 1 kg is methyl acetate 75
kg and 25 kg of ethanol were mixed and dissolved by stirring to prepare an ultraviolet absorbent solution. The ultraviolet absorber solution was added at a ratio of 2 kg to 100 kg of the above dope, thoroughly mixed by a static mixer, and then cast from a die onto a stainless belt at a dope temperature of 45 ° C. On the stainless belt whose temperature was controlled by contacting hot water of 45 ° C from the back surface of the stainless belt, apply hot air of 65 ° C from the top to dry it, and after half the time of the belt, set hot air to 45 ° C. After drying, on the back of the stainless belt, 11 ℃
After contacting with cold water of 10 minutes and holding for 10 seconds, it was peeled from the stainless belt. The amount of residual solvent in the web during peeling is 9
It was 0 mass%. Next, after slitting both ends of the peeled web to cut it to a predetermined width,
Grasping with a biaxial stretching tenter, the residual solvent amount is 1 at 120 ° C.
At 2% by mass, the film was stretched 1.4 times in the width direction and relaxed 0.97 times in the longitudinal direction. Then, the width retention is released, and the part gripped by the tenter clip is cut off to a predetermined width, followed by drying at 120 ° C., and knurling having a height of 10 μm and a width of 1 cm is provided at both ends of the width, Film thickness 8
A retardation film 20 having a thickness of 0 μm, a width of 1.3 m and a length of 2500 m was obtained. The residual solvent amount was less than 0.01% by mass. The film scraps cut off before and after the tenter were reused as a part of the cellulose ester raw material.

Using the obtained retardation film 20 as a polarizing plate protective film, a polarizing plate 20 was prepared in the same manner as in Example 1.

[Evaluation] The obtained retardation film 20 was evaluated as follows.

(Film Elastic Modulus, Elongation at Break, Stress at Break) A film was cut into a sample having a width of 10 mm and a length of 200 mm, and the chuck distance was 100 m at 23 ° C. and 55% RH.
m, and a tensile test was conducted at a tensile speed of 100 mm / min.

(Measurement of refractive index in slow axis direction (width direction), fast axis direction (longitudinal direction), thickness direction (thickness direction) and slow axis direction) Refractometer KOBR
Using A-21ADH (manufactured by Oji Scientific Instruments), 2
Three-dimensional refractive index measurement was performed at a wavelength of 590 nm in an environment of 3 ° C. and 55% RH, and the refractive indices Nx, Ny, and Nz were measured.
I asked.

(Retardation (Ro, Rt) Values and Distributions of Each) Automatic Birefringence Meter KOBURA.21ADH
(Oji Keisoku Co., Ltd.), 23 ℃, 55% RH
Under the environment, the three-dimensional birefringence was measured at 1 cm intervals in the width direction of the sample at a wavelength of 590 nm. The standard deviations of the obtained retardations in the plane and in the thickness direction were obtained. For the retardation distribution, the coefficient of variation (CV%) shown below was obtained and used as an index. In the actual measurement, n was set to 130 to 140.

Coefficient of variation (CV%) = (standard deviation / retardation average value) × 100 (wavelength dispersion characteristic) automatic birefringence meter KOBURA-21AD
Using H (manufactured by Oji Scientific Instruments), 23 ° C, 55% R
Under the H environment, the three-dimensional birefringence was measured at wavelengths of 450, 590 and 650 nm. The values respectively obtained were designated as R ₄₅₀ , R ₅₉₀ and R ₆₅₀ .

The wavelength dispersion characteristics are R ₄₅₀ / R ₅₉₀ and R _650.
/ R ₅₉₀ was evaluated. (Dry film tear strength)
After conditioned for 4 hours in a room conditioned at 55 ° C and relative humidity of 55%, cut into sample size sample width 50 mm x 64 mm, and
It was determined by measurement according to SO 6383 / 2-1983.

(Dimensional change rate) The film was placed at a temperature of 23 ° C.
After conditioned for 4 hours in a room conditioned at a relative humidity of 55%,
The width (L1) was measured by making marks on the width and the length at intervals of about 10 cm with a cutter. Next, 60 ℃ 9
The film was stored for 24 hours in a thermostat whose humidity was adjusted to 0%. After the film was conditioned again in a room conditioned at a temperature of 23 ° C and a relative humidity of 55% for 4 hours, the mark distance (L2)
Was measured. The dimensional change rate was evaluated by the following formula.

Dimensional change (%) = (L2-L1) / L1 × 100 (Hygroscopic expansion coefficient) The film was measured at a temperature of 23 ° C. and a relative humidity of 55.
After conditioning the humidity for 4 hours in a room where the humidity is controlled to%, mark the width and the length with a cutter at intervals of about 20 cm,
The distance (L3) was measured. Next, the film is stored for 24 hours in a thermostatic chamber whose humidity is controlled at 60 ° C and 90%. After the film was taken out from the constant temperature bath, the distance (L4) of the mark was measured within 2 minutes. The hygroscopic expansion coefficient was evaluated by the following formula.

Hygroscopic expansion rate (%) = (L4−L3) / L3 × 100 (film thickness distribution) The sample film was heated at a temperature of 23 ° C. and a relative humidity of 55.
% In the room after humidity control for 4 hours in the room
The film thickness was measured at 0 mm intervals. From the obtained film thickness distribution data, R (max): maximum film thickness, R (min):
Minimum film thickness, R (ave): The average film thickness was determined.

(Haze value) According to JIS K-6714, a haze meter (1001DP type, manufactured by Nippon Denshoku Industries Co., Ltd.) was used as an index of transparency.

(Measurement of Transmittance) Transmittance T was measured with a spectrophotometer U-3400 (Hitachi Ltd.) using 3
The transmittances of 380, 400 and 500 nm were calculated from the spectral transmittance τ (λ) obtained every 10 nm in the wavelength range of 50 to 700 nm.

(Curl) The film sample was heated at 25 ° C. for 5
After standing in a 5% RH environment for 3 days, the film was cut into a width direction of 50 mm and a longitudinal direction of 2 mm. Further, the film pieces are conditioned under an environment of 23 ° C. ± 2 ° C. and 55% RH for 24 hours, and the curl value of the film is measured using a curvature scale. The curl degree is measured according to JIS-K7619-19.
88 A method was followed.

The curl value is represented by 1 / R, where R is the radius of curvature and the unit is m. (Bright spot foreign material) Two polarizers are sandwiched between two polarizers in an orthogonal state (crossed Nicols state), and light is applied from the outside of one polarizing plate.
From the outside of the other polarizing plate, use a microscope (30
The number of foreign matters that appear to be white and shiny per 25 mm ² was measured. Measurements were a bright spot foreign matter from the number of total 250 mm ² per C over 10 locations to evaluate seek pieces / cm ^2. In the present invention, the size of the bright spot foreign matter is 5 to 5
It was 0 μm ² and nothing more than that was observed.

(Contact angle after saponification treatment) Sample was 2.5 mo
1 / L NaOH was treated at 50 ° C. for 2.5 minutes, and then washed with pure water for 2.5 minutes. The sample after treatment is treated at a temperature of 23
The humidity was adjusted to 24 H under the conditions of ° C and 55% relative humidity and measured using a contact angle meter CA-D type manufactured by Kyowa Interface Science Co., Ltd.

(Center Line Average Roughness Ra) The center line average roughness (Ra) was measured using a non-contact surface fine shape measuring device WYKO NT-2000.

(Orientation Angle) The orientation angle means the direction of the slow axis in the plane of the cellulose ester film (the angle formed by the width direction during casting). The orientation angle was measured using an automatic birefringence meter KOBURA-21ADH.

(Plasticizer content ratio) A part of the cellulose ester film was cut out, the mass was measured, this was dissolved in acetone, and the amount of the plasticizer contained was quantitatively analyzed by GC. The plasticizer content after the completion of the drying step was G2. The plasticizer content G1 at the time of casting is a theoretical value obtained from the formulation.

Regarding the physical properties of the obtained retardation film,
It is summarized below. Nx 1.4800 Ny 1.4792 Nz 1.4779 Ro 60nm Rt 140nm Rt / Ro 2.3 R ₄₅₀ / R ₅₉₀ 0.9 R ₆₅₀ / R ₅₉₀ 1.1 Orientation angle distribution ± 0.1 ° Retardation distribution ( Ro) 1% Retardation distribution (Rt) 1% Film thickness R (ave) 80.0 μm Maximum film thickness R (max) 80.2 μm Minimum film thickness R (min) 79.8 μm Transmittance (500 nm) 93% Transmittance (400 nm) 60% Transmittance (380 nm) 5% Haze 0.3% Center line average roughness (Ra) 5 nm Dimensional change rate (Smd) -0.03% Dimensional change rate (Std) -0.06% Hygroscopic expansion Rate (MD) 0.1% hygroscopic expansion rate (TD) 0.07% tear strength (MD) 2.6 N / μm tear strength (TD) 2.3 N / μm stress at break (MD) 95 MPa fracture Point stress (TD) 90 MPa elongation at break (MD) 43% elongation at break (TD) 48% modulus (MD) 3.6 GPa elastic modulus (TD) 4.0 GPa curl (23 ℃ 55% RH) 1m - ¹ bright spot foreign matter 1 / cm ² plasticizer content ratio (G2 / G1) 0.99 contact angle after saponification treatment 17 ° Further, as a result of measuring retardation in the same manner as in Example 1, Ro was 60 nm and Rt was Rt. Is 140 nm and 6
The retardations after storage at 0 ° C. and 80% RH for 1000 hours were Ro of 58 nm and Rt of 138 nm,
It was confirmed to be stable.

As a result of being attached to a liquid crystal display device and evaluated in the same manner as in Example 1, it was confirmed that the viewing angle was similarly expanded before and after storage. (1 up and down with VA type liquid crystal
Example 3 (Preparation of Solution 1) Compound 1 was dissolved in a solvent of water: methanol = 3: 2 to prepare solution 1.

(Preparation of Solution 2) Compound 2 was dissolved in a solvent of water: methanol = 3: 1 to prepare solution 2.

(Preparation of Solution LC-1) Solution L having the following composition
C-1 was prepared.

Compound 3 3 parts by mass Compound 4 5 parts by mass Compound 5 4 parts by mass Compound 6 8 parts by mass Irgacure 369 (manufactured by Ciba Specialty Chemicals) 1 part by mass 2-butanone 80 parts by mass Cyclohexanone 5 parts by mass (solution LC- Preparation of 2) A solution LC-2 having the following composition was prepared.

[0150]   Compound 3 4 parts by mass   Compound 4 3 parts by mass   Compound 5 6 parts by mass   Compound 6 8 parts by mass   Irgacure 369 (manufactured by Ciba Specialty Chemicals) 1 part by mass   2-butanone 84 parts by mass

[0151]

[Chemical 2]

[0152]

[Chemical 3]

(Preparation of Optical Compensation Films 1 and 2) On the retardation film 20 prepared in Example 2, gelatin was subbed to a thickness of 0.1 μm and dried, and then the solutions 1 and 2 were added. Dry film thickness 0.2μ using wire bar # 3
m and then dried with hot air at 70 ° C,
A rubbing process was performed. The rubbing treatment was performed so as to be orthogonal to the slow axis direction of the retardation film 20. After applying the above-mentioned solution LC-1 on this using a wire bar # 5, it is dried at 90 ° C. for 1 minute in a windless state while being conveyed, and 500 m under a nitrogen atmosphere (oxygen concentration is less than 0.1%).
An optical compensation film 1 was prepared by irradiating an ultraviolet ray of J / cm ² to fix the orientation of the liquid crystalline compound. Ro of the obtained optically anisotropic layer was 80 nm.

Next, 0.1 μm is formed on the retardation film 20.
Subsequent to gelatin thickness and dried, Solution 1 and Solution 2 are dried with wire bar # 3 to a dry thickness of 0.2μ.
m and then dried with hot air at 70 ° C,
A rubbing process was performed. The rubbing treatment was performed so as to be orthogonal to the slow axis direction of the retardation film 20. After applying the above-mentioned solution LC-2 on this using a wire bar # 5, it is dried for 1 minute at 90 ° C. in a windless state while being conveyed, and 500 m under a nitrogen atmosphere (oxygen concentration is less than 0.1%).
An optical compensation film 2 was prepared by irradiating UV of J / cm ² to fix the orientation of the liquid crystalline compound. The obtained optical anisotropic layer had a Ro of 100 nm.

Next, the tilt angle of the alignment film interface and the tilt angle of the air interface and the average tilt angle of the combination of the alignment film material and the liquid crystal material were measured, and the obtained results are shown in Table 2.

(Measurement of Tilt Angle) The tilt angle was measured by applying the solutions LC-1 and LC-2 on the alignment layer and then drying the solvent so that the alignment layers were antiparallel.
Furthermore, an orthoscopic image and a conoscopic image were observed in a liquid crystal temperature range using a hot stage, and an average tilt angle was measured when antiparallel processing was performed using the above automatic birefringence meter. Further, solutions LC-1 and LC-2 were applied to each alignment layer, dried and heat-treated to prepare a sample in which the alignment layer was arranged only on one side of the liquid crystal compound and the other side was an air interface. The tilt angles of the alignment film and the air interface were measured by the crystal rotation method.

Although each solution was shown as the material for the alignment film, this solution was applied, dried and rubbed, and then evaluated using the solution of each liquid crystalline compound.

[0158]

[Table 2]

Next, in the production of the polarizing plate 1 of Example 1, the retardation film 1 was changed to the optical compensation film 1, and the surface having no optically anisotropic layer was laminated on the side of the polarizer, which was polarized in the same manner. A plate 21 was produced. Similarly, except that the retardation film 1 was changed to an optical compensation film 2, a polarizing plate 2 was obtained in the same manner.
2 was produced.

In the same manner as in Example 1, the polarizing plates 21 and 22 of the present invention were arranged on both surfaces of a commercially available TN type liquid crystal cell so that the surface having the optically anisotropic layer was on the liquid crystal cell side, and a liquid crystal display device was prepared. It was made. As a result, it was confirmed that a wide viewing angle of 150 ° or more in the vertical direction and 150 ° or more in the horizontal direction was obtained in each case. In addition, it was confirmed that there was no significant change in the viewing angle even after being used for several months, and it was stable.

[0161]

EFFECTS OF THE INVENTION To provide a retardation film having a small change in retardation characteristics, a polarizing plate using the same, and an optical compensation film, and a wide viewing angle using the polarizing plate and an excellent visual field even for long-term use. A liquid crystal display device that can maintain a corner can be provided.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C08L 1/10 C08L 1/10 4J002 G02F 1/1335 G02F 1/1335 510 510 // B29K 1:00 B29K 1 : 00 B29L 7:00 B29L 7:00 11:00 11:00 F term (reference) 2H049 BA02 BA06 BA42 BB03 BB49 BC03 BC09 BC22 2H091 FA08X FA08Z FA11X FA11Z FB02 FB12 LA16 LA19 LA20 4F071 AA09 AB18 AB21 AB25 AB26 AB11 AC07 AC10 AC10 AC10 AC10 AC10 AC10 AC12 AC15 AC19 AE04 AE05 AE12 AF31 AF35 AH19 BA02 BB02 BB07 BC01 BC02 4F205 AA01 AC05 AG01 AH73 GA07 GB02 GC07 GE21 GW21 4F210 AA01 AG01 AH73 QC03 Q37 QD E0E DJE0H DJO0E0H0 DJ0H0 DJ0H0E0H0E0D099D0H0D099DE139H0D099DE139H0 EJ038 EJ048 EJ068 EP028 ET007 EU177 EU187 EU198 EV078 EV348 EW046 FD026 FD057 FD078 FD209 GP00

Claims (9)

[Claims] 1. An in-plane retardation Ro is 30 to 20.
0 nm, retardation Rt in the thickness direction is 70 to 40
In the retardation film of 0 nm, the total degree of substitution of acyl groups is 2.55 to 2.85, the content of alkaline earth metal is 1 to 50 ppm, and the amount of residual sulfuric acid (as the content of elemental sulfur) is 1 to 50 ppm. And a cellulose ester having a free acid amount of 1 to 100 ppm. 2. When the acyl group is an acetyl group and a propionyl group or a butyryl group and the substitution degree of the acetyl group is X and the total substitution degree of the propionyl group or butyryl group is Y, 1.75 ≦ X ≦ 2 0.15 0.60 ≦ Y ≦ 0.80 The retardation film according to claim 1, wherein 3. The retardation film according to claim 1, which contains 0.5 to 30% by mass of an additive having 3 or more aromatic rings in the molecule. 4. The film is formed by a solution casting method using substantially only a non-chlorine organic solvent.
The retardation film according to any one of 1 to 3. 5. An in-plane retardation Ro obtained by casting a solution prepared by dissolving a cellulose ester in an organic solvent on a support, evaporating the solvent to peel off the film, and stretching the film is 30. In the method for producing a retardation film having a thickness retardation of 70 to 400 nm and a retardation in the thickness direction of 70 to 400 nm, the cellulose ester has a total degree of substitution of acyl groups of 2.55 to 2.85 and an alkaline earth metal content of 1 -50 ppm, residual sulfuric acid content (as content of elemental sulfur) 1-50 ppm, free acid content 1-10
It is 0 ppm, The manufacturing method of the retardation film characterized by the above-mentioned. 6. At least one of the organic solvents that dissolves the cellulose ester is methyl acetate, and when the residual amount of methyl acetate after peeling is 2 to 20 mass%, 1.01 to 2.
Stretching to 0 times, The manufacturing method of the retardation film of Claim 5 characterized by the above-mentioned. 7. A polarizing plate comprising the retardation film according to claim 1 attached to at least one surface of a polarizing film. 8. The polarizing plate according to claim 7 is attached to a liquid crystal cell of TN type, VA type, or OCB type so that the retardation film is on the liquid crystal cell side. Liquid crystal display device. 9. An optical compensation film, comprising an optical anisotropic layer formed by aligning a liquid crystalline compound on the retardation film according to claim 1. Description: