JP2002249599A - Cellulose ester film and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cellulose ester film excellent in optical isotropy, particularly in optical isotropy in the direction of film thickness, a method of manufacturing the same, a polarizing plate for a display device, and a display device. SOLUTION: There is provided a cellulose ester film which has a plane orientation degree S, represented by the following formula (I) S=(Nx+Ny)/2-Nz, of 0.0004 or less wherein Nx is a refractive index in the lag phase axis direction in the film plane; Ny is a refractive index in the film plane in the direction perpendicular to the lag phase axis direction, and Nz is a refractive index in the thickness direction of the film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cellulose ester film (hereinafter simply referred to as a film), a method for producing the same, a polarizing plate for liquid crystal display, and a liquid crystal display device.

[0002]

2. Description of the Related Art A liquid crystal display device can be directly connected to an IC circuit with low voltage and low power consumption, and in particular, can be made thin, so that it can be used as a display device for a word processor or a personal computer. Widely adopted. This liquid crystal display device has a basic configuration in which, for example, polarizing plates are provided on both sides of a liquid crystal cell.

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 uses a super twisted nematic (STN) having a twist angle of 160 degrees or more. Liquid crystal display devices have been proposed.

In these liquid crystal display devices, it is important to increase the viewing angle, and a liquid crystal cell design, a driving method, a method using various optical compensation films, and the like have been proposed. The requirements for the optical films used are becoming increasingly stringent.

For example, a cellulose acetate film is widely used as a polarizing plate protective film because of its excellent optical isotropy. However, in designing a liquid crystal cell, an optical film having more excellent optical isotropy has been required. In particular, there is a demand for an optical film having more excellent optical isotropy not only in the in-plane direction but also in the film thickness direction.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a cellulose ester film having excellent optical isotropy, in particular, optical isotropy in a film thickness direction. A method, a polarizing plate for a display device, and a display device are provided.

[0007]

The above object of the present invention has been attained by the following constitutions.

[0008] 1. A cellulose ester film having a degree of plane orientation S represented by the following formula (I) of 0.0004 or less.

Formula (I) S = (Nx + Ny) / 2-Nz where Nx is the refractive index in the slow axis direction in the film plane, Ny
Represents a refractive index in a film plane in a direction perpendicular to the slow axis direction, and Nz represents a refractive index in a thickness direction of the film.

[0010] 2. S represented by the above formula (I) is 0.00
2. The cellulose ester film as described in 1 above, wherein R is ₀ to 0.0004, and R ₀ and θ satisfy the relationship of P of the following formula (II): 0.9999.

Formula (II) P ≦ 1−sin ² (2θ) sin ² (πR ₀ / λ) R ₀ = (Nx−Ny) × d where Nx is the refractive index in the slow axis direction in the film plane. , Ny
Is the in-plane refractive index in the direction perpendicular to the slow axis direction, and d is the film thickness (nm) of the film. θ is the angle (radian) between the slow axis direction in the film plane and the film forming direction (straight direction of the film), and λ is the above Nx, Ny,
The wavelength (nm) of light at the time of three-dimensional refractive index measurement for obtaining θ,
π is the pi.

3. 3. The cellulose ester film as described in 1 or 2, wherein a compound having a plurality of cyclic structures in a molecule is contained in an amount of 5 to 30% by mass based on the cellulose ester film.

4. Cellulose ester has a total degree of substitution of 2.8
The cellulose ester film according to any one of the above items 1 to 3, which is a cellulose ester of 5 to 3.00.

5. The cellulose ester film according to any one of the above items 1 to 4, wherein the film thickness is 10 to 60 µm.

6. In the method for producing a cellulose ester film, in which the cellulose ester solution is cast on a support and the film after peeling is further dried, the cellulose ester solution is cast on the support in a drying step. A cellulose ester, wherein when the amount of the residual solvent in the dope film on the support is in the range of 200% by mass to 120% by mass, the drying is performed such that the residual solvent amount decreasing rate is 4 to 15% by mass / second. Film production method.

[7] In the method for producing a cellulose ester film, in which the cellulose ester solution is cast on a support and the film after peeling is further dried, the cellulose ester solution is cast on the support in a drying step. The time during which the amount of the residual solvent in the dope film on the support is in the range of 200% by mass to 120% by mass for 10 seconds or more;
A method for producing a cellulose ester film, wherein drying is performed for less than 0 second.

8. In the method for producing a cellulose ester film, in which the cellulose ester solution is cast on a support and the film after peeling is further dried, the cellulose ester solution is cast on the support in a drying step. A drying step of drying the web in an atmosphere having an average temperature of 41 to 100 ° C., and separating the web in 25 to 90 seconds after casting.
A method for producing the cellulose ester film according to the above.

9. A method for producing a cellulose ester film, in which the cellulose ester solution is cast on a support and the film after peeling is dried, in a drying step on the support after the cellulose ester solution is cast on the support, After the low-temperature drying step of drying the web on the support in an atmosphere at an average temperature of 20 to 50 ° C., the substrate is further supported in an atmosphere set at +5 to 70 ° C. higher than the average temperature of the low-temperature drying step. 9. The method for producing a cellulose ester film as described in 6, 7, or 8, wherein drying is performed in a high-temperature drying step of drying on a body, and peeling is performed 25 to 90 seconds after casting.

10. The high-temperature drying step on the support is 4
The method for producing a cellulose ester film according to the item 9, wherein the method is performed in an atmosphere set at 1 ° C to 100 ° C.

11. 20-120 residual solvent amount at peeling
The method for producing a cellulose ester film according to any one of the above items 6 to 10, wherein the content is 0.1% by mass.

[12] 12. The method for producing a cellulose ester film according to any one of the above items 6 to 11, wherein the cellulose ester solution has a solid content concentration (concentration excluding a low boiling point solvent concentration) of 17 to 30% by mass.

13. Any of the above items 6 to 12, wherein the film separated from the support is dried until the residual solvent amount is 0 to 10% by mass, and the film is heated at 115 to 200 ° C for 5 to 60 minutes. The method for producing a cellulose ester film according to claim 1.

14. 14. The method for producing a cellulose ester film according to any one of the above items 6 to 13, wherein the support for solution casting is a metal belt.

[15] 15. A cellulose ester film, wherein the cellulose ester film according to any one of 1 to 5 is manufactured by the method according to any one of 6 to 14.

16. 16. A polarizing plate, wherein the cellulose ester film according to any one of 1 to 5 or 15 is used on at least one surface.

17. A display device using the cellulose ester film according to any one of the above items 1 to 5 or 15.

18. A display device using the polarizing plate according to 16 above. Hereinafter, the plane orientation degree S of the present invention is 0.0004 or less, particularly 0.00001 to 0.0004.
The cellulose ester film characterized by the following is described in detail.

In the present invention, as the cellulose ester, a lower fatty acid ester is preferable, and cellulose acetate, cellulose acetate propionate, cellulose acetate butyrate, or cellulose acetate propionate butyrate is preferably used. The cellulose ester used in the present invention has a degree of substitution of 2.8.
It is preferably from 5 to 3.00 because the degree of plane orientation can be kept lower, and particularly preferably from 2.92 to 3.00.

The method for measuring the degree of substitution of the acyl group is ASTM-
It can be measured according to the provisions of D817-96.

Cellulose esters having a degree of polymerization of from 250 to 400 are preferably used, and cellulose triacetate is particularly preferably used. The number average molecular weight Mn of the cellulose ester according to the present invention is 70,000 to 25.
0000 is preferable because it has excellent mechanical strength and has an appropriate dope viscosity, and more preferably 80,000 to 80,000.
150,000. Further, a cellulose ester having a ratio Mw / Mn to the weight average molecular weight Mw of 1.0 to 5.0 is preferably used.

As the cellulose ester, either a cellulose ester synthesized from cotton linter or a cellulose ester 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 having good releasability from a belt or a drum because productivity efficiency is high. The proportion of the cellulose ester synthesized from the cotton linter is preferably 60% by mass or more because the releasability effect becomes remarkable,
It is more preferably at least 85% by mass, and most preferably used alone.

As a solvent for dissolving the material of the film of the present invention to form a dope, it is preferable that a cellulose ester can be dissolved and the solvent has an appropriate boiling point. For example, methylene chloride, methyl acetate, ethyl acetate, amyl acetate , Acetone, tetrahydrofuran, 1,3-dioxolan, 1,4-dioxane, cyclohexanone, ethyl formate, 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, 1,3-dimethyl-2-imidazolidinone and the like Among them, organic halogen compounds such as methylene chloride, dioxolane derivatives, methyl acetate, ethyl acetate, acetone and the like are preferable organic solvents (that is, good solvents).

Further, as shown in the following film forming step, when the solvent is dried from the web (doped film) formed on the support in the solvent evaporation step, it is used from the viewpoint of preventing foaming in the web. The boiling point of the organic solvent
The boiling point of the good solvent described above is, for example, methylene chloride (boiling point 40.4 ° C), methyl acetate (boiling point 56.32 ° C), acetone (56.3).
° C) and ethyl acetate (76.82 ° C).

Among the above-mentioned good solvents, methylene chloride and methyl acetate which are excellent in solubility are preferably used.
In particular, it is preferable that methylene chloride is contained in an amount of 50% by mass or more based on the whole organic solvent.

In addition to the above organic solvent, 0.1 to 30% by mass
It is preferable to include an alcohol having 1 to 4 carbon atoms. Particularly preferably, the alcohol is contained at 5 to 30% by mass.

In these methods, after the dope described above is cast on a casting support, when the solvent starts to evaporate and the ratio of alcohol increases, the web (dope film) gels, and the web becomes durable. It is used as a gelling solvent for facilitating exfoliation, and when these are in a small proportion, it also has a role of promoting the dissolution of the cellulose ester of the non-chlorine organic solvent.

As the alcohol having 1 to 4 carbon atoms,
Methanol, ethanol, n-propanol, iso-
Propanol, n-butanol, sec-butanol,
Tert-butanol and the like can be mentioned.

Of these, ethanol is preferred because of its stability, the boiling point is relatively low, the drying property is good, and there is no toxicity. Further, preferably, 5 to 30% by mass of ethanol is added to 70 to 95% by mass of methylene chloride.
Is used. Methyl acetate can be used instead of methylene chloride.

The concentration of the cellulose ester in the dope is 1
It is preferably from 7 to 35% by mass, particularly preferably from 20 to 30% by mass. If the concentration is too high, the smoothness of the surface of the obtained film tends to deteriorate, and if the concentration is too low, the degree of plane orientation S tends to increase, and 0.00001 to 0.000.
It is difficult to obtain the film No. 4.

Using the above-mentioned cellulose ester and an organic solvent, a film is formed as follows. In the present invention, the cellulose ester solution is called a cellulose ester dope or simply a dope.

The film forming step used in the method for producing a cellulose ester film of the present invention comprises the following dissolving step:
It comprises a casting step, a solvent evaporation step, a peeling step, a drying step and a winding step. Hereinafter, each step will be described.

<< Dissolving Step >> This is a step of forming a dope by dissolving the flakes in a cellulose ester flake in a dissolving vessel in an organic solvent mainly composed of a good solvent as described above while stirring.

In the present invention, the solid content concentration in the dope is 17
It is preferably adjusted to at least 20% by mass, especially 20% by mass.
It is preferable if it is more than the above because the degree of plane orientation of the obtained film can be further reduced. Incidentally, the solid content in the dope referred to in the present invention, when producing the cellulose ester film of the present invention, refers to the components in the dope except for the low boiling point solvent component removed in the drying step, the solid content concentration in the dope The term "mass%" refers to the mass% of the components remaining in the film even after the drying step, based on the whole dope solution.

If the solid content concentration in the dope is too high, the viscosity of the dope becomes too high, and sharkskin or the like may be formed during casting to deteriorate the film flatness.
It is desirably less than mass%.

The viscosity of the dope is preferably in the range of 5 to 100 Pa · s, and more preferably in the range of 10 to 50 Pa · s.

The dissolution is carried out at normal pressure, at a temperature lower than the boiling point of the preferred organic solvent (ie, good solvent) as described above, at a pressure higher than the boiling point of the good solvent described above, and at cooling. There are various dissolving methods such as a dissolving method and a high-pressure method. As a method of dissolving at a temperature higher than the boiling point of a good solvent and applying a pressure that does not boil, 40.4 to
By applying a pressure of 0.11 to 1.50 MPa at 120 ° C., foaming can be suppressed and dissolution can be performed in a short time.

The solvent used in the dissolving step according to the present invention may be used alone or in combination. However, it is preferable to use a mixture of a good solvent and a poor solvent from the viewpoint of production efficiency, and more preferably to use a good solvent. The mixing ratio of the good solvent is 70 to 95% by mass, and the poor solvent is 30 to 5% by mass.
It is.

The good solvent and the poor solvent used in the present invention are:
Those that dissolve the cellulose ester used alone are defined as good solvents, and those that swell or do not dissolve alone are defined as poor solvents. Therefore, the good solvent and the poor solvent vary depending on the amount of bound acetic acid of the cellulose ester. For example, when acetone is used as a solvent, a good solvent is obtained when the amount of bound acetic acid of the cellulose ester is 55%, and the amount of bound acetic acid is 6%.
At 0%, it becomes a poor solvent.

When dissolving the cellulose ester, it is also possible to first dissolve the cellulose ester using a part of the good solvent and the poor solvent, and then add the remaining poor solvent. As the poor solvent used in the present invention,
For example, methanol, ethanol, n-butanol, cyclohexane and the like are preferably used.

As a cooling dissolution method, for example, Japanese Patent Application Laid-Open
No. 95538, No. 9-95544, No. 9-95557
The method described in the above item can be used. Further, the high-pressure melting method described in JP-A-11-21379 can also be preferably used.

After the dissolution, the dope is preferably filtered with a filter medium, defoamed, and sent to the next step by a pump. At that time, a plasticizer, an antioxidant, an ultraviolet absorber, a dye, a mat Agents, fine particles and the like may be added.

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

The plane orientation degree S of the present invention is 0.0004 or less,
In particular, in order to obtain a film having a thickness of 0.00001 to 0.0004, it is particularly preferable that a compound having a plurality of cyclic structures in the molecule is contained in an amount of 10% by mass or more based on the cellulose ester. Preferably, the content is 15% by mass or more. It is preferable that these compounds are contained alone in an amount of 10% by mass or more, but when a plurality of compounds are added, the total amount may be 10% by mass or more.

The compound to be added is preferably a compound having a molecular weight of 3000 or less, particularly preferably a compound having a molecular weight of 250 to 2000 or less. Regarding the ring structure,
The size of the ring is not particularly limited, but is preferably composed of 3 to 8 atoms, particularly a 6-membered ring and / or
Alternatively, it is preferably a 5-membered ring. These may contain carbon, oxygen, nitrogen, silicon or other atoms,
Some of the ring bonds may be unsaturated, for example, 6
The member ring may be a benzene ring or a cyclohexane ring. The compound of the present invention includes a plurality of such cyclic structures.For example, the compound has both a benzene ring and a cyclohexane ring in the molecule, or has two cyclohexane rings, A derivative of naphthalene or a derivative such as anthracene may be used. More preferably, it is a compound containing three or more such cyclic structures in the molecule. In addition, it is preferable that at least one bond of the cyclic structure does not include an unsaturated bond.

When these compounds are added in an amount of 10% by mass with respect to the cellulose ester, the compounds whose decrease in the glass transition point Tg is less than 25 ° C. with respect to the cellulose ester which has not been added are considered to have a low degree of plane orientation. It is preferable from the viewpoint of a reduction effect, and furthermore, the reduction of Tg is preferably less than 20 ° C, particularly preferably less than 15 ° C. If the decrease in Tg is less than 20 ° C. when 10% by mass is added, unnecessary stretching in the film forming step is suppressed, and even in the case of a thin film having a thickness of less than 60 μm, in-plane retardation can be reduced. It is particularly preferable for obtaining a film having excellent optical isotropy.

Even when these compounds are added, the haze of the film is less than 1.0% in terms of a film thickness of 60 μm, especially 0.1%.
Preferably it is less than 1%.

Specific examples of the compound for reducing the degree of plane orientation include abietic acid, dehydroabietic acid, parastric acid, KE-604 (Arakawa Chemical), and KE-85 (Arakawa Chemical). , Araldide EPN
1139 (manufactured by Asahi Chiba Co., Ltd.), Araldide GY260
(Made by Asahi Ciba Co., Ltd.). Also, a ketone resin, Hilac 1 shown in the following (Chemical Formula 3)
10H (manufactured by Hitachi Chemical Co., Ltd.), Hiluck 111 (manufactured by Hitachi Chemical Co., Ltd.) and the like can also be preferably used. The chemical formulas of these compounds are shown below, but they are not particularly limited as long as the degree of plane orientation is reduced by 0.0002 or more by addition.

[0058]

Embedded image

[0059]

Embedded image

[0060]

Embedded image

Incidentally, KE-85 is a mixture of abietic acid, dehydroabietic acid and parastolic acid.

Although it is not clear why the plane orientation degree S decreases, the addition of these compounds hinders the orientation of the cast cellulose ester. It is thought that we can do it.

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

For a liquid crystal display device, it is preferable to add a plasticizer for imparting heat and moisture resistance, or an antioxidant, an ultraviolet absorber, a matting agent, or the like.

As the above-mentioned antioxidant, hindered phenol compounds are preferably used.
-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], 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. Further, for example, a hydrazine-based metal deactivator such as N, N'-bis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionyl] hydrazine or tris (2,4
A phosphorus-based processing stabilizer such as (-di-t-butylphenyl) phosphite may be used in combination.

The addition amount of these compounds is preferably 1 ppm to 1.0% by mass relative to the cellulose ester, and more preferably 10 to 1000 ppm.

In addition, heat stabilizers such as inorganic fine particles such as kaolin, talc, diatomaceous earth, quartz, calcium carbonate, barium sulfate, titanium oxide and alumina, and salts of alkaline earth metals such as calcium and magnesium are added. You may.

Further, antistatic agents, flame retardants, lubricants, oils and the like can be added. << Casting Process >> A dope is fed to a pressurized die through a pressurized metering gear pump and, at a casting position, a casting support for an endless metal belt or a rotating metal drum that is transported infinitely (hereinafter simply referred to as a support). This is a step of casting a dope from a pressure die. The surface of the casting support is a mirror surface.

Other casting methods include a doctor blade method in which the thickness of the cast dope film is adjusted with a blade, and a reverse roll coater method in which the film is adjusted with a counter-rotating roll. A pressure die that can adjust the shape and easily make the film thickness uniform is preferable. Pressure dies include coat hanger dies and T dies.
Both are preferably used.

In order to increase the film forming speed, two or more pressure dies may be provided on the casting support, and the doping amount may be divided to form a plurality of layers.

As described above, the obtained dope is cast on a support such as a belt or a drum to form a film. The present invention is particularly effective in a solution casting method using a belt. This is because it is easy to finely adjust the drying conditions on the support as described later. Belt is 40-150 per lap
Those having a length of m are preferably used.

<< Solvent Evaporation Step >> A web (in the present invention, a dope is cast on a casting support and the formed dope film is called a web) is heated on the casting support to remove the solvent. This is the step of evaporating. In order to evaporate the solvent, there are a method of blowing air from the web side and / or a method of transferring heat with liquid from the back surface of the support and a method of transferring heat from the front and back by radiant heat. Drying efficiency is preferred. A method of combining them is also preferable.

In the present invention, a film having a low degree of plane orientation in which the residual solvent content of the web dried on the casting support is in the range of 200% by mass to 120% by mass is preferably less than 20 seconds. Is preferred to obtain Further, it is preferably 17 seconds or less, and more preferably 15 seconds or less. If the time is less than 10 seconds, there is a risk that bubbles may increase due to the boiling of the solvent, and careful attention is required. Therefore, it is particularly preferable to be 10 to 15 seconds. The shorter the time when the residual solvent content of the web dried on the casting support is in the range of 200% by mass to 120% by mass, the lower the degree of plane orientation can be obtained. The time referred to here is the time when the web is present on the casting support, and when the web is peeled from the support before reaching 120% by mass, it refers to the time from 200% by mass to the time when the web is separated.

In the method for producing a cellulose ester film of the present invention, the amount of the residual solvent in the web (dope membrane) dried on the support after casting is from 200% by mass to 120% by mass.
When the amount is within the range of 4% by mass, the decreasing rate of the residual solvent amount is 4 to 1%.
Drying at 5% by mass / second is preferable because the degree of plane orientation can be particularly reduced. Further, the rate of decrease in the amount of residual solvent is preferably 6% by mass / second or more, and particularly preferably 6 to 5% by mass.
It is preferably 8% by mass / second. This drying speed,
It is preferably maintained for at least 50% of the time required for the residual solvent amount to decrease from 200% by mass to 120% by mass, particularly preferably for 60% or more.

In order to obtain a predetermined drying rate, the web on the support has a drying step of drying the web in an atmosphere having an average temperature of 41 to 100 ° C.
It is particularly preferable that the film is peeled in 90 seconds. In particular, when the residual solvent amount of the web is 200% by mass or less, the average temperature is 41%.
It is desirable to dry the web in an atmosphere set at 100 ° C.

More preferably, it is peeled off within 75 seconds after casting, and particularly preferably, it is peeled off within 60 seconds. Thereby, the degree of plane orientation of the obtained film can be further reduced. In order to maintain the atmosphere at 41 to 100 ° C., it is preferable that hot air at this temperature be applied to the upper surface of the web or heated by means such as infrared rays.

During the drying process on the support, the support is preferably heated from the back side of the support by warm air, hot water, infrared rays, a heater or the like so that the temperature of the support becomes 30 ° C. or higher. However, the temperature of the web itself is desirably maintained at a temperature equal to or lower than the boiling point of the solvent due to the latent heat of evaporation of the contained solvent.

Immediately after casting, the web on the support is dried at a relatively low temperature (low-temperature drying step) and then dried under an atmosphere of 5 ° C. or higher (high-temperature drying step). It is particularly preferable to reduce the drying temperature,
1 to 100 ° C, more preferably 45 to 90 ° C, further 50
Drying at ~ 80 ° C is preferred.

The temperature distribution of the support is ± 3 ° C. in the width direction.
Is preferably within ± 1 ° C., more preferably within ± 0.5 ° C., and more preferably ± 0.1 ° C.
Most preferably, it is within ° C. In particular, it is desirable that the residual solvent amount is 200% by mass or less as a high-temperature drying step and a predetermined drying rate is set. In any case, it is desirable that bubbles and the like due to boiling of the solvent in the web are not generated.

<< Peeling Step >> In this step, the web from which the solvent has evaporated on the support is peeled from the support at the peeling position. The peeled web is sent to the next step.

If the residual solvent amount (the following formula) of the web at the time of peeling is too large, it is difficult to peel the web. Conversely, if the web is sufficiently dried on the support and then peeled, a part of the web peels in the middle. Or

The web on the support should be at least 41 to 10% until the amount of residual solvent contained in the web is less than 200% by mass.
It is more preferable that the film is dried on the support in an atmosphere of 0 ° C., and that the film is dried in the same atmosphere and then peeled off once in an atmosphere of less than 40 ° C. to keep the in-plane retardation of the film low. This is preferable because surface quality is also improved.

The temperature at the peeling position on the support is preferably 10 to 40 ° C., more preferably 11 to 30 ° C.
° C. In order to maintain the degree of plane orientation and / or the in-plane retardation R ₀ of the obtained film low, the amount of residual solvent in the web at the peeling position is preferably 20 to 120% by mass, more preferably 40 to 100% by mass. And particularly preferably 70 to 100 mass.

The residual solvent amount of the web according to the present invention is defined by the following equation. Residual solvent amount = (mass before heat treatment of web−mass after heat treatment of web) / (mass after heat treatment of web) × 100% The heat treatment when measuring the amount of residual solvent is 115
This means that heat treatment is performed at 1 ° C. for 1 hour.

As described above, in order to adjust the residual solvent amount at the time of peeling, the surface temperature of the casting support after casting is controlled so that the organic solvent can be efficiently evaporated from the web. It is preferable to set the temperature at the peeling position on the casting support within the above-mentioned temperature range. In order to control the temperature of the support, a heat transfer method having good heat transfer efficiency is preferably used. For example, a back surface heat transfer method using a liquid is preferable.

It is difficult to control the temperature of the support by the heat transfer method using radiant heat or hot air. However, in a belt (support) machine, the temperature of the belt where the belt to be transferred comes below is controlled by gentle wind. The temperature can be adjusted.

The temperature of the support can be partially changed by dividing the heating means, so that the temperature of the support is different at the casting position, drying section, peeling position, etc. of the casting support. Can be done.

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 the residual solvent is as large as possible), there is a gel casting method in which the film can be peeled even when the amount of the residual solvent is large. .

There are a method in which a poor solvent for the cellulose ester is added to the dope, gelling is performed after casting the dope, and a method in which gelling is performed by lowering the temperature of the support. There is also a method of adding a metal salt to the dope.

By gelling on the support to strengthen the film, peeling can be accelerated and the film forming speed can be increased.

In the case where the web is peeled off at a point where the residual solvent amount is larger, if the web is too soft, the flatness is impaired at the time of web peeling, and the web tends to be damaged due to peeling tension or vertical stripes. The amount of solvent can be determined.
The peeling tension when peeling the support and the film is usually 19
Peeling is performed at 6 to 245 N / m, but the content of the ultraviolet absorber per unit mass of the cellulose ester is large,
In addition, the cellulose ester film of the present invention, which is thinner than the conventional one, is likely to be wrinkled at the time of peeling. Therefore, it is preferable that the cellulose ester film be peeled at 190 N / m or less. / M, then
It is preferable to peel at a minimum tension of 137.2 N / m, but it is particularly preferable to peel at a minimum tension of 100 N / m. A lower peel tension is preferable not only because the in-plane retardation R ₀ can be kept low, but also preferable for obtaining a film with a low degree of plane orientation. The in-plane retardation R ₀ is preferably less than 20 nm, more preferably less than 10 nm and then preferably less than 5 nm, most preferably from ₀ to 1 nm. R ₀ can be kept low by adjusting the peeling tension and the transporting tension, and the contraction or stretching ratio in the width direction by a tenter described later.

In the present invention, the in-plane retardation R
₀ is measured at a wavelength of 590 nm using an automatic birefringence meter KOBRA-21ADH (manufactured by Oji Scientific Instruments).
The three-dimensional refractive index is measured, and the obtained refractive indices Nx, Ny,
It can be calculated from Nz. Further, a retardation value Rt in the film thickness direction of less than 30 nm is obtained, and a value of less than 20 nm and less than 10 nm is more preferably obtained,
Particularly, a cellulose ester of 0 to 8 nm is preferably obtained.

The cellulose ester film of the present invention comprises
The angle θ between the slow axis direction and the film forming direction and the in-plane retardation R ₀ have a relationship that P of the following formula (II) satisfies 0.9999, and particularly as an optical film such as a polarizing plate protective film. It is preferably used. In particular, P is 0.99
At 995, R ₀ and θ satisfy the following formula (II).

Formula (II) P ≦ 1−sin ² (2θ) sin ² (πR ₀ / λ) R ₀ = (Nx−Ny) × d where Nx is the refractive index in the slow axis direction in the film plane. , Ny
Is the in-plane refractive index in the direction perpendicular to the slow axis direction, and d is the film thickness (nm) of the film. θ is the angle (radian) between the slow axis direction in the film plane and the film forming direction (straight direction of the film), and λ is the above Nx, Ny,
Wavelength 590n of light at the time of three-dimensional refractive index measurement for obtaining θ
m and π are pi.

<< Drying Step >> While maintaining the width using a drying device that alternately transports the web through rolls arranged in a staggered manner and / or a tenter device that transports the web while holding both ends of the web with clips or pins, This is the step of drying the web. It is preferable to maintain the transport tension in the drying step as low as possible, because R ₀ can be kept low, and it is preferably 190 N / m or less. It is more preferably 170 N / m or less, more preferably 140 N / m or less, more preferably 100 N / m or less.
It is particularly preferred that the pressure is from 130 N / m to 130 N / m. In particular, it is effective to maintain the transport tension at or below the above-mentioned value until the amount of the residual solvent in the film becomes at least 5% by mass or less.

[0096] Drying is generally performed by blowing hot air on both sides of the web, but there is also a means of heating by applying microwaves instead of air. Too fast drying tends to impair the flatness of the finished film. Drying at a high temperature is preferably performed when the residual solvent is about 8% by mass or less. Throughout, the drying temperature is generally between 40 and 250 ° C.
In particular, in the present invention, it is preferable that the film dried with the residual solvent to 8% by mass or less is maintained at 115 to 200 ° C. for at least 5 to 60 minutes, whereby the degree of plane orientation is further reduced. More preferably 120 to 160 ° C
Is maintained in the range of 5 to 60 minutes, which may also serve as a part of the drying step. The heating temperature is T
g.

In the drying step after peeling off from the surface of the casting support, the web tends to shrink in the width direction due to evaporation of the solvent. In particular, shrinkage increases as the material dries rapidly at a high temperature. Drying while suppressing this shrinkage as much as possible is preferable for improving the flatness of the resulting film. On the other hand, when the film is contracted or stretched to some extent in the drying step after peeling, a low stretching ratio is preferable because the plane orientation can be kept low.

From this viewpoint, for example, Japanese Patent Application Laid-Open No. 62-46
No. 625, a method of drying the whole or a part of the web in the width direction while holding both ends of the web width with a clip or a pin (called a tenter method), in particular, a tenter using a clip A pin tenter method using a pin is preferably used.

Incidentally, the in-plane retardation of the obtained film can be reduced by drying while holding the film in such a manner. When the tenter is performed, the residual solvent amount of the web is preferably 100% by mass or less at the start of the tenter,
Further, it is preferable to perform drying while applying a tenter until the residual solvent amount of the web becomes 10% by mass or less, and more preferably 5% by mass or less.

In the drying step of the cellulose ester film, the film peeled from the support is further dried so that the residual solvent content is preferably 1% by mass or less, more preferably 0.5% by mass or less. is there.

In the film drying step, a method of drying the film while transporting the film by a roll hanging method or a pin tenter method as described above is generally employed. For liquid crystal display members, it is preferable to dry while maintaining the width by a pin tenter method in order to improve dimensional stability.
In particular, it is particularly preferable to maintain the width at a place where the amount of the residual solvent is large immediately after peeling off from the support, since the effect of improving the dimensional stability is further exhibited. The means for drying the film is not particularly limited, and is generally performed using hot air, infrared rays, a heating roll, a microwave, or the like. It is preferable to use hot air in terms of simplicity.

<< Winding Step >> This is a step of winding the cellulose ester film after the amount of the residual solvent in the web becomes 2% by mass or less.
A film having good dimensional stability can be obtained by the following.

As the winding method, a method generally used may be used, and there are a constant torque method, a constant tension method, a taper tension method, a program tension control method with constant internal stress, and the like. .

The thickness of the cellulose ester film varies depending on the purpose of use, but as a finished film, it is usually in the range of 5 to 500 μm, and more preferably 10 to 250 μm.
Is particularly preferable as a film for a liquid crystal image display device. In the present invention, a film having excellent optical isotropy and particularly having a low degree of plane orientation can be obtained even with a thin film having a thickness of 10 to 60 μm.

To adjust the film thickness, the dope concentration, the amount of liquid supplied by the pump, the slit gap of the die cap, the extrusion pressure of the die, the speed of the casting support, etc. are controlled so as to obtain the desired thickness. Good to do.

Further, as means for making the film thickness uniform, it is preferable that the programmed feedback information is fed back to each of the above-mentioned devices using a film thickness detecting means for adjustment. In the process from immediately after casting through the solution casting film forming method to drying, the atmosphere in the drying apparatus may be air, but may be performed in an inert gas atmosphere such as nitrogen gas or carbon dioxide gas.

However, it is a matter of course that the danger of the explosion limit of the evaporated solvent in the dry atmosphere must always be considered.

The cellulose ester film of the present invention can contain a plasticizer. The plasticizer according to the present invention is not particularly limited, but a plasticizer such as a phosphate plasticizer, a carboxylate plasticizer, a phthalate ester, a citrate ester, and a glycolate plasticizer is preferably used. However, the present invention is not particularly limited to these.

Examples of the phosphate ester plasticizer include triphenyl phosphate (TPP) and tricresyl phosphate (TCP), biphenyl-diphenyl phosphate, dimethylethyl phosphate, cresyl diphenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate, triphenyl phosphate and triphenyl phosphate. Octyl phosphate, tributyl phosphate and the like can be mentioned.

Representative examples of the carboxylic acid ester-based plasticizer include phthalic acid esters and citric acid esters. Examples of phthalates include dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), dioctyl phthalate (DOP) and diethylhexyl phthalate (DEH).
P), ethylphthalylethyl glycolate, methylphthalylethyl glycolate, butylphthalylbutyl glycolate and the like are used.

As the citrate-based plasticizer, acetyltriethyl citrate (OACTE) and acetyltributyl citrate (OACTB) are used.

Examples of other carboxylic esters include butyl oleate, methylacetyl ricinoleate, dibutyl sebacate, and various trimellitic esters. Triacetin, tributyrin and the like can also be used. These plasticizers may be used alone or in combination of two or more.

The amount of these plasticizers to be used is 1 to 1 with respect to cellulose ester in terms of film performance, processability and the like.
It is preferably 35% by mass, particularly preferably 5 to 30% by mass.

The workability refers to the process of slitting or punching a base film or a liquid crystal display member. If the workability is poor, the cut surface becomes saw-toothed and chips are generated. Is not preferred.

The ultraviolet absorbent according to the cellulose ester film of the present invention will be described. The cellulose ester film of the present invention is used for a polarizing plate or a liquid crystal display member or the like because of its high dimensional stability, and an ultraviolet absorber is preferably used from the viewpoint of preventing deterioration of the polarizing plate or the liquid crystal or the like.

As the ultraviolet absorber, those having excellent absorption of ultraviolet light having a wavelength of 370 nm or less and little absorption of visible light having a wavelength of 400 nm or more are preferably used from the viewpoint of good liquid crystal display properties. Specifically, the transmittance at 380 nm is preferably less than 10%, and more preferably less than 5%.

Specific examples of the ultraviolet absorber preferably used in the present invention include, for example, oxybenzophenone compounds, benzotriazole compounds, salicylate compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex salt compounds and the like. Can be
Further, a polymer ultraviolet absorber described in JP-A-6-148430 is also preferably used.

As the benzotriazole type ultraviolet absorber, a compound represented by the following general formula [1] is preferably used.

[0119]

Embedded image

In the formula, R ₁ , R ₂ , R ₃ , R ₄ and R ₅ may be the same or different and include a hydrogen atom, a halogen atom, a nitro group, a hydroxyl group, an alkyl group, an alkenyl group, an aryl group, alkoxy group, an acyloxy group, an aryloxy group, an alkylthio group, an arylthio group, a mono- or dialkylamino group, an acylamino group or a 5 to 6 membered heterocyclic group, R ₄ is a carbocyclic ring of 5-6 membered with R ₅ It may be formed.

Further, these groups described above may have an arbitrary substituent. Hereinafter, specific examples of the ultraviolet absorbent according to the present invention will be described, but the present invention is not limited thereto.

UV-1: 2- (2'-hydroxy-5 '
-Methylphenyl) benzotriazole UV-2: 2- (2'-hydroxy-3 ', 5'-di-
tert-butylphenyl) benzotriazole UV-3: 2- (2'-hydroxy-3'-tert-
Butyl-5'-methylphenyl) benzotriazole UV-4: 2- (2'-hydroxy-3 ', 5'-di-
tert-butylphenyl) -5-chlorobenzotriazole UV-5: 2- (2'-hydroxy-3 '-(3 ",
4 ", 5", 6 "-tetrahydrophthalimidomethyl)
-5'-methylphenyl) benzotriazole UV-6: 2,2-methylenebis (4- (1,1,3,
3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol) UV-7: 2- (2'-hydroxy-3'-tert-
Butyl-5'-methylphenyl) -5-chlorobenzotriazole UV-8: 2- (2H-benzotriazol-2-yl) -6- (linear and side chain dodecyl) -4-methylphenol (TINUVIN171, Ciba) UV-9: octyl-3- [3-tert-butyl-4
-Hydroxy-5- (chloro-2H-benzotriazol-2-yl) phenyl] propionate and 2-ethylhexyl-3- [3-tert-butyl-4-hydroxy-5- (5-chloro-2H-benzotriazole- 2
-Yl) phenyl] propionate mixture (TINU
(VIN109, manufactured by Ciba) Further, as the benzophenone-based ultraviolet absorber which is one of the ultraviolet absorbers according to the present invention, a compound represented by the following general formula [2] is preferably used.

[0123]

Embedded image

In the formula, Y represents a hydrogen atom, a halogen atom or an alkyl group, an alkenyl group, an alkoxyl group and a phenyl group, and these alkyl group, alkenyl group and phenyl group may have a substituent. A represents a hydrogen atom, an alkyl group, an alkenyl group, a phenyl group, a cycloalkyl group, an alkylcarbonyl group, an alkylsulfonyl group, or a -CO (NH) _n-1 -D group, and D represents an alkyl group, an alkenyl group, or a substituted group. Represents a phenyl group which may have a group. m and n represent 1 or 2.

In the above, the alkyl group represents, for example, a linear or branched aliphatic group having up to 24 carbon atoms, the alkoxyl group includes, for example, an alkoxyl group having up to 18 carbon atoms, and the alkenyl group includes, for example, An alkenyl group having up to 16 carbon atoms represents, for example, an allyl group or a 2-butenyl group. In addition, the alkyl group, the alkenyl group, as a substituent to the phenyl group, a halogen atom, for example, a chlorine atom, a bromine atom, a fluorine atom, a hydroxyl group,
And a phenyl group (this phenyl group may be substituted with an alkyl group or a halogen atom).

The specific examples of the benzophenone-based compound represented by the general formula [2] are shown below, but the present invention is not limited thereto.

UV-10: 2,4-dihydroxybenzophenone UV-11: 2,2'-dihydroxy-4-methoxybenzophenone UV-12: 2-hydroxy-4-methoxy-5-sulfobenzophenone UV-13: bis ( 2-methoxy-4-hydroxy-5
-Benzoylphenylmethane) The above-mentioned ultraviolet absorber preferably used in the present invention is a benzotriazole-based ultraviolet absorber or a benzophenone-based ultraviolet absorber having high transparency and an excellent effect of preventing deterioration of a polarizing plate or a liquid crystal element. Preferably, a benzotriazole-based ultraviolet absorber having less unnecessary coloring is particularly preferably used.

The method for adding the ultraviolet absorbent additive liquid according to the present invention includes the following methods.

<< Addition Method A >> As a method for preparing an ultraviolet absorber additive liquid, an ultraviolet absorber is dissolved in an organic solvent such as alcohol, methylene chloride, or dioxolane, and then added directly to the dope composition.

<< Addition Method B >> As a method for preparing an ultraviolet absorber additive liquid, an ultraviolet absorber and a small amount of a cellulose ester are dissolved in an organic solvent such as alcohol, methylene chloride or dioxolane, and then added to the dope with an in-line mixer. .

In the present invention, the addition method B is preferable because the addition amount of the ultraviolet absorber can be easily adjusted, so that the productivity is excellent.

The amount of the UV absorber used is not uniform depending on the kind of the compound and the conditions of use, but is usually preferably 0.2 to 2.0 g, and more preferably 0.4 to 1.5 g per 1 m ² of the cellulose ester film. Is more preferable, and 0.6-1.
0 g is particularly preferred.

Fine particles can be added to the cellulose ester film of the present invention in order to impart lubrication. Examples of the fine particles include fine particles of an inorganic compound and fine particles of an organic compound.

As the inorganic compound, a compound containing silicon,
Preferred are silicon dioxide, aluminum oxide, zirconium oxide, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate and calcium phosphate, more preferably containing silicon. Although inorganic compounds and zirconium oxide are used, silicon dioxide is particularly preferably used because turbidity of the cellulose ester laminated film can be reduced.

As fine particles of silicon dioxide, for example, Aerosil R972, R972V, R974, R812,
200, 200V, 300, R202, OX50, TT
Commercial products such as 600 (all manufactured by Nippon Aerosil Co., Ltd.) can be used.

As the fine particles of zirconium oxide, commercially available products such as Aerosil R976 and R811 (all manufactured by Nippon Aerosil Co., Ltd.) can be used.

As the organic compound, for example, polymers such as silicone resin, fluorine resin and acrylic resin are preferable, and among them, silicone resin is preferably used.

Among the silicone resins described above, those having a three-dimensional network structure are particularly preferable. For example, Tospearl 103, 105, 108, 120, and 1
Commercial products having trade names such as Nos. 45, 3120 and 240 (all manufactured by Toshiba Silicone Co., Ltd.) can be used.

The primary average particle diameter of the fine particles added to the cellulose ester film of the present invention is preferably 20 nm or less, more preferably 5 to 16 nm, particularly preferably 5 to 16 nm, from the viewpoint of suppressing haze.
5 to 12 nm. These fine particles are 0.1 to 5 μm
Is preferably included in the cellulose ester film by forming secondary particles having a particle diameter of 0.1, and a preferable average particle diameter is 0.1.
1-2 μm, more preferably 0.2-0.6 μm
It is. Thereby, the height of 0.1-1.
Irregularities of about 0 μm are formed, whereby an appropriate slip property can be given to the film surface.

The primary average particle size of the fine particles according to the present invention is measured by observing the particles with a transmission electron microscope (magnification: 500,000 to 2,000,000 times), observing 100 particles, and determining the average value. The primary average particle diameter was used.

The apparent specific gravity of the fine particles is preferably 70 g / liter or more, more preferably 90 to 200 g / liter.
g / liter, particularly preferably 100 to 200 g / l.
g / liter. As the apparent specific gravity is larger, it becomes possible to produce a high concentration dispersion, haze and aggregates are preferably improved, and when preparing a dope having a high solid content as in the present invention, Are particularly preferably used.

The fine particles of silicon dioxide having an average primary particle diameter of not more than 20 nm and an apparent specific gravity of not less than 70 g / liter are obtained, for example, by mixing a mixture of vaporized silicon tetrachloride and hydrogen.
It can be obtained by burning in air at 000 to 1200 ° C. Further, for example, they are commercially available under the trade names of Aerosil 200V and Aerosil R972V (all manufactured by Nippon Aerosil Co., Ltd.), and these can be used.

The apparent specific gravity described above was determined by taking a certain amount of silicon dioxide fine particles in a measuring cylinder and measuring the weight at this time.
It is calculated by the following equation.

Apparent specific gravity (g / liter) = mass of silicon dioxide (g) / volume of silicon dioxide (liter) The method for preparing the dispersion of fine particles according to the present invention is as follows.
For example, there are three types as shown below.

<< Preparation Method A >> After stirring and mixing a solvent and fine particles, dispersion is carried out with a disperser. This is used as a fine particle dispersion. The fine particle dispersion is added to the dope and stirred.

<< Preparation Method B >> After stirring and mixing the solvent and the fine particles, the mixture is dispersed with a disperser. This is used as a fine particle dispersion. Separately, a small amount of cellulose triacetate is added to a solvent and dissolved by stirring. The fine particle dispersion is added thereto and stirred. This is used as a fine particle addition liquid. The fine particle addition liquid is sufficiently mixed with the dope liquid using an in-line mixer.

<< Preparation Method C >> A small amount of cellulose triacetate is added to a solvent and dissolved by stirring. Fine particles are added thereto and dispersed by a disperser. This is used as a fine particle addition liquid.
The fine particle addition liquid is sufficiently mixed with the dope liquid using an in-line mixer.

The preparation method A is excellent in dispersibility of the silicon dioxide fine particles, and the preparation method C is excellent in that the silicon dioxide fine particles are hard to re-aggregate. Above all, the above-mentioned preparation method B is a preferable preparation method excellent in both the dispersibility of the silicon dioxide fine particles and the difficulty of re-aggregation of the silicon dioxide fine particles.

<< Dispersion Method >> When silicon dioxide fine particles are mixed with a solvent and dispersed, the concentration of silicon dioxide is 5 to 30.
% By mass, more preferably 10 to 25% by mass, and most preferably 15 to 20% by mass. The higher the dispersion concentration, the lower the liquid turbidity with respect to the amount added, which is preferable because haze and aggregates are improved.

The solvent used is preferably lower alcohols such as methyl alcohol, ethyl alcohol,
Examples thereof include propyl alcohol, isopropyl alcohol, and butyl alcohol. The solvent other than the lower alcohol is not particularly limited, but it is preferable to use a solvent used in forming a cellulose ester film.

The amount of the fine particles of silicon dioxide added to the cellulose ester is preferably 0.01 to 0.3 parts by mass, more preferably 0.05 to 0.2 parts by mass, based on 100 parts by mass of the cellulose ester. , 0.
08 to 0.12 parts by mass is most preferred. The larger the added amount, the better the dynamic friction coefficient, and the smaller the added amount, the lower the haze and the smaller the agglomerates.

As the disperser, an ordinary disperser can be used. Dispersers can be broadly divided into media dispersers and medialess dispersers. For dispersing the silicon dioxide fine particles, a medialess disperser is preferable because the haze is low.

Examples of the media dispersing machine include a ball mill, a sand mill, a dyno mill and the like.

As the medialess disperser, there are an ultrasonic type, a centrifugal type, a high-pressure type, and the like. In the present invention, a high-pressure disperser is preferable. The high-pressure dispersing device is a device that creates a special condition such as a high shear or a high pressure state by allowing a composition in which fine particles and a solvent are mixed to pass through a thin tube at a high speed. When processing with a high-pressure dispersion device, for example, a tube diameter of 1 to 2000 μm
The maximum pressure condition inside the device is 9.807MP
It is preferably at least a. More preferably, 19.6
13 MPa or more. At that time, the maximum arrival speed is 1
Over 100m / sec, heat transfer speed is 420kJ /
Those that reach more than an hour are preferred.

The high-pressure dispersion apparatus as described above includes Micro
There is an ultra-high pressure homogenizer (trade name: Microfluidizer) manufactured by Fluidics Corporation or a Nanomizer manufactured by Nanomizer, and a homogenizer of the Manton-Gaulin type such as a homogenizer manufactured by Izumi Food Machinery Co., Ltd .; 01 and the like.

It is preferable to cast the dope containing the fine particles so as to be in direct contact with the casting support because a film having high slip properties and low haze can be obtained.

In forming the film of the present invention, embossing can be performed on both sides of the film in addition to the addition of the matting agent in order to prevent blocking after winding and the like. Embossing can be performed to any height according to the purpose, but in the present invention, the height is preferably 5 μm or more, and more preferably, in order to volatilize unnecessary residual solvent after winding. Is 10 μm or more.

[0158] After being wound up in a roll form, it is usually packaged until it is shipped, in order to protect the product from dirt and adhesion of dust due to static electricity. The packaging material is not particularly limited as long as the above purpose can be achieved, but is preferably a material which does not prevent the evaporation of the residual solvent from the film. Specific examples include polyethylene, polyester, polypropylene, nylon, polystyrene, paper, various nonwoven fabrics, and the like. Fibers in the form of mesh cloth are more preferably used.

The cellulose ester film of the present invention may have a multilayer structure by a co-casting method using a plurality of dopes.

Co-casting is a sequential multi-layer casting method in which two or three layers are formed through different dies, and simultaneous multi-layering in a die having two or three slits to form two or three layers. Any of a casting method and a multilayer casting method combining sequential multilayer casting and simultaneous multilayer casting may be used.

The production of the cellulose ester film of the present invention will be described with reference to FIG. In FIG. 1, an endless stainless belt 1
Are circulating between the low-temperature drying zone 3 and the high-temperature drying zone 4. The dope composition is cast from the die 2 onto the endless stainless belt 1 at the casting section 5, is conveyed in the direction of the arrow, is dried in the low-temperature drying zone 3 and the high-temperature drying zone 4, and is released in the peeling section 6. 7 separates from the endless stainless belt to form a cellulose ester film. The cellulose ester film further passes through the first drying zone 8, is transported from the second drying zone 10 to the third drying zone 11, and is wound by the winding unit 12 as a product. The first drying zone 8 and the third drying zone 11
In order to lengthen the path, the sheet is transported by the transport roll 9.

The cellulose ester used in the present invention, which has little luminescent spot foreign matter when formed into a film, is particularly preferably used as a support for a polarizing plate protective film or an optical compensation film. In the present invention, the bright spot foreign matter refers to two polarizing plates arranged at right angles (crossed Nicols), a cellulose ester film is arranged therebetween, and light from a light source is applied from one surface to the other surface. When the cellulose ester film is observed from above, the light from the light source appears to leak.

At this time, the polarizing plate used in the evaluation is desirably formed of a protective film having no bright spot foreign matter, and a plate using a glass plate for protecting the polarizer is preferably used. It is thought that one of the causes of the generation of the bright spot foreign matter is unacetylated cellulose contained in the cellulose ester. As a countermeasure, it is possible to use a cellulose ester having a small amount of unacetylated cellulose or to use a cellulose ester. Removal and reduction can be achieved by filtering the dissolved dope solution or the like. Also, the smaller the film thickness, the smaller the number of bright spot foreign substances per unit area, and the smaller the content of cellulose ester contained in the film, the smaller the number of bright spot foreign substances.

It is preferable that the number of luminescent spot foreign matters having a luminescent spot diameter of 0.01 mm or more is 200 / cm ² or less.
More preferably, 100 / cm ² or less, 50 / cm ²
Hereinafter, 30 / cm ² or less, it is preferably 10 pieces / cm ² or less, and particularly preferably it is zero.

The number of luminescent spots of 0.005 to 0.01 mm or less is also preferably 200 / cm ² or less, more preferably 100 / cm ² or less, and 50 / cm ² or less.
cm ^2, 30 / cm ² or less, it is preferably 10 pieces / cm ² or less, particularly preferred is when the bright point is zero. It is preferable that the number of luminescent spots of 0.005 mm or less is small.

In the case of removing the bright spot foreign matter by filtration, it is preferable to filter the composition containing the added plasticizer and to remove the bright spot foreign matter, as compared with the case where the cellulose ester alone is dissolved. As the filter material, conventionally known materials such as glass fiber, cellulose fiber, filter paper, and fluororesin such as ethylene tetrafluoride resin are preferably used, but ceramics and metals are also preferably used. The absolute filtration accuracy is preferably 50 μm or less, more preferably 30 μm or less, and 10 μm or less.
Particularly preferably, it is 5 μm or less.

These can be used in appropriate combination. The filter medium may be either a surface type or a depth type, but the depth type is preferably used because it is relatively hard to clog.

The thickness of the optical film of the present invention is preferably 10 to 60 μm. Although the degree of plane orientation tends to increase as the film thickness decreases, the plane orientation degree can be kept low even though it is a thin film by the method for producing a cellulose ester film of the present invention. The retardation Rt in the film thickness direction is determined by the degree of plane orientation and the film thickness d as shown in the following equation.
According to the present invention, the cellulose ester film having an extremely low Rt can be obtained by not only maintaining the Rt low by simply reducing the film thickness but also reducing the degree of plane orientation according to the present invention. It could be provided.

Rt = ((Nx + Ny) / 2-Nz) × d In the present invention, the degree of plane orientation and the retardation value were measured by measuring a 35 mm square sample at 23 ° C. and 55% R
After leaving under the H condition for 8 hours, an automatic birefringence meter KOBRA-21ADH (manufactured by Oji Scientific Instruments) under the same condition.
Is used to measure the three-dimensional refractive index at a wavelength of 590 nm to obtain the refractive indices Nx, Ny, and Nz.

The polarizing plate according to the present invention will be described. The polarizing plate according to the present invention can be manufactured by a general method. For example, there is a method in which a cellulose ester film of the present invention is alkali-treated, and is immersed and stretched in an iodine solution, and bonded to both surfaces of a polarizing film using a completely saponified polyvinyl alcohol aqueous solution. The alkali saponification treatment described above refers to a treatment in which a cellulose ester film is immersed in a high-temperature strong alkaline solution in order to improve the wettability of the aqueous adhesive at this time and improve the adhesiveness.

The polarizing film, which is a main component of the polarizing plate, is an element that allows only light having a polarization plane in a certain direction. A typical polarizing film currently known is a polyvinyl alcohol-based polarizing film. Are dyed polyvinyl alcohol-based films with iodine and dyed with dichroic dyes. These are formed by forming a film of an aqueous polyvinyl alcohol solution and uniaxially stretching and dyeing the film, or dyeing the film and then uniaxially stretching the film, and then preferably performing a durability treatment with a boron compound. A transparent plastic film, which is a protective film for a polarizing plate made of the cellulose ester film of the present invention, is laminated on the surface of the polarizing film to form a polarizing plate.

The cellulose ester film obtained as described above is excellent in transparency, optically isotropic, and has sufficient mechanical strength represented by tear strength.
In addition, since the curl is small, it is useful as an optical film, particularly a protective film for a polarizing plate, and can be appropriately subjected to antireflection processing, antistatic processing, clear hard coat processing, and antiglare processing. Also, various functional layers including a metal oxide layer can be formed by plasma CVD or atmospheric pressure plasma treatment.

By using the cellulose ester film of the present invention having a degree of plane orientation of 0.00001 to 0.0004 or a polarizing plate using the same, an optical film more suited to the design of a liquid crystal display device can be provided. The display performance (contrast, tightness of black, etc.) of the liquid crystal display device can be further improved, and the liquid crystal display device can be freely combined with a retardation film or an optical compensation film as needed.

[0174]

EXAMPLES The present invention will now be described more specifically with reference to examples, but embodiments of the present invention are not limited thereto.

Example 1 <Preparation of Sample 1> (Dope Composition 1) Cellulose Triacetate Synthesized from Cotton Linter 2.92 70 kg Cellulose Triacetate Synthesized from Wood Pulp 2.92 30 kg Tinuvin 326 (Chiba) Specialty Chemicals UV absorber 1) 0.5 kg Tinuvin 328 (Ciba Specialty Chemicals UV absorber 2) 0.5 kg Triphenyl phosphate 8 kg Ethyl phthalyl ethyl glycolate 3 kg Aerosil R972V (Nippon Aerosil) 0. 2 kg Methylene chloride 391 kg Ethanol 34 kg The above composition was charged into a closed container, and completely dissolved under pressure while keeping the temperature at 80 ° C. and stirring. Aerosil R972
V (manufactured by Nippon Aerosil Co., Ltd.) was mixed and dispersed in advance with a part of ethanol to be added, and this was charged into a closed container. This was cooled to a temperature at which it was cast, and then allowed to stand to perform a defoaming operation. Then, the solution was subjected to Azumi Filter Paper No. Filtration using 244 gave Dope 1.

Solutions were prepared from the respective compositions in the same manner except that the dope compositions were changed to dope compositions 2 to 12, and dopes 2 to 12 were prepared.

(Dope Composition 2) Cellulose Triacetate Synthesized from Cotton Linter 2.96 85 kg Cellulose Triacetate Synthesized from Wood Pulp 2.96 15 kg Tinuvin 326 (UV absorber 1 manufactured by Ciba Specialty Chemicals) 0.5 kg Tinuvin 328 (UV absorber 2 manufactured by Ciba Specialty Chemicals) 0.5 kg KE-604 (Arakawa Chemical Co., Ltd.) 7.5 kg KE-85 (Arakawa Chemical Co., Ltd.) 7.5 kg Aerosil R972V ( 0.2 kg Methylene chloride 412 kg Ethanol 39.5 kg (Dope composition 3) Cellulose triacetate synthesized from cotton linter Substitution degree 2.88 80 kg Cellulose triacetate synthesized from wood pulp 2.88 20 kg Tinuvin 326 (UV absorber manufactured by Ciba Specialty Chemicals) 0.4 kg Tinuvin 109 (UV absorber manufactured by Ciba Specialty Chemicals) 0.3 kg Tinuvin 171 (UV absorber manufactured by Ciba Specialty Chemicals) 0.3 kg Araldide GY260 (manufactured by Asahi Chiba Co., Ltd.) 11 kg Aerosil R972V (manufactured by Nippon Aerosil Co., Ltd.) 0.2 kg methylene chloride 391 kg ethanol 34 kg (dope composition 4) Cellulose triacetate synthesized from cotton linters Substitution degree 2.92 90 kg Synthesized from wood pulp Cellulose triacetate Substitution degree 2.92 10 kg Tinuvin 326 (UV absorber 1 manufactured by Ciba Specialty Chemicals) 0.5 kg Tinuvin 328 (Ciba Specialty Ticket) UV-absorbent 2 manufactured by Calz Inc.) 0.5 kg KE-604 (manufactured by Arakawa Chemical Co., Ltd.) 10 kg KE-85 (manufactured by Arakawa Chemical Co., Ltd.) 10 kg Aerosil R972V (manufactured by Nippon Aerosil Co., Ltd.) 0.2 kg Methylene chloride 392 kg ethanol 26 kg (Dope composition 5) Cellulose triacetate synthesized from cotton linter 2.92 70 kg Cellulose triacetate synthesized from wood pulp 2.92 30 kg Tinuvin 326 (UV absorber 1 manufactured by Ciba Specialty Chemicals) 0. 5 kg Tinuvin 109 (UV absorber 2 manufactured by Ciba Specialty Chemicals) 1 kg Tinuvin 171 (UV absorber 2 manufactured by Ciba Specialty Chemicals) 1 kg Triphenyl phosphate 8 kg Ethyl phthalyl ethyl glycolate 3 kg Aerosil R972V (manufactured by Nippon Aerosil Co., Ltd.) 0.2 kg Methylene chloride 368 kg Ethanol 24.5 kg (Dope composition 6) Cellulose triacetate synthesized from cotton linter Substitution degree 2.94 81 kg Cellulose triacetate synthesized from wood pulp Degree 2.94 19 kg Tinuvin 326 (UV absorber made by Ciba Specialty Chemicals) 0.5 kg Tinuvin 109 (UV absorber made by Ciba Specialty Chemicals) 1.0 kg Tinuvin 171 (UV absorber made by Ciba Specialty Chemicals) 1.0 kg Araldide GY260 (manufactured by Asahi Ciba Co., Ltd.) 19 kg Aerosil R972V (manufactured by Nippon Aerosil Co., Ltd.) 0.2 kg Methylene chloride 387 kg Ethanol 25.5 kg (dope Product 7) Cellulose triacetate synthesized from cotton linter 2.92 85 kg Cellulose triacetate synthesized from wood pulp 2.92 15 kg Tinuvin 326 (UV absorber manufactured by Ciba Specialty Chemicals) 0.5 kg Tinuvin 109 ( 1.0kg Tinuvin 171 (UV absorber manufactured by Ciba Specialty Chemicals) 1.0kg KE-604 (Arakawa Chemical Co., Ltd.) 10kg KE-85 (Arakawa Chemical Co., Ltd.) 9 kg Aerosil R972V (manufactured by Nippon Aerosil Co., Ltd.) 0.2 kg Methylene chloride 419 kg Ethanol 36 kg (Dope composition 8) Cellulose acetate propionate synthesized from wood pulp Degree of acetyl group substitution 2.0 Propio Substitution degree 0.9 100 kg Tinuvin 326 (UV absorber 1 manufactured by Ciba Specialty Chemicals) 0.5 kg Tinuvin 328 (UV absorber 2 manufactured by Ciba Specialty Chemicals) 0.5 kg KE-604 (Arakawa Chemical Co., Ltd.) 10 kg KE-85 (Arakawa Chemical Co., Ltd.) 10 kg Aerosil R972V (Nippon Aerosil Co., Ltd.) 0.2 kg Methyl acetate 319 kg Ethanol 136 kg (Dope composition 9) Cellulose acetate propionate synthesized from wood pulp Acetyl group substitution Degree 2.0 Propionyl group substitution degree 0.9 100 kg Tinuvin 326 (UV absorber 1 manufactured by Ciba Specialty Chemicals) 0.5 kg Tinuvin 328 (UV absorber 2 manufactured by Ciba Specialty Chemicals) 0.5 kg Araldide GY26 20 kg Aerosil R972V (manufactured by Nippon Aerosil Co., Ltd.) 0.2 kg methylene chloride 419 kg ethanol 36 kg (dope composition 10) Cellulose triacetate synthesized from cotton linters Substitution degree 2.92 100 kg Tinuvin 326 (Chiba Specialty) Chemicals UV absorber 1) 0.5 kg Tinuvin 109 (UV absorber 1 from Ciba Specialty Chemicals) 1.0 kg Tinuvin 171 (UV absorber 1 from Ciba Specialty Chemicals) 1.0 kg Triphenyl phosphate 8 kg Ethyl phthalate Ruethyl glycolate 3 kg Aerosil R972V (Nippon Aerosil Co., Ltd.) 0.2 kg Methylene chloride 415 kg Ethanol 26.5 kg (Dope composition 11) Cotton linter Cellulose triacetate synthesized from pulp 2.88 60 kg Cellulose triacetate synthesized from wood pulp 2.88 40 kg Tinuvin 326 (UV absorber 1 manufactured by Ciba Specialty Chemicals) 0.5 kg Tinuvin 328 (manufactured by Ciba Specialty Chemicals) UV absorber 2) 0.5 kg Triphenyl phosphate 13 kg Aerosil R972V (manufactured by Nippon Aerosil Co., Ltd.) 0.2 kg Methylene chloride 460 kg Ethanol 40 kg (Dope composition 12) Cellulose triacetate synthesized from cotton linters Substitution degree 2.82 50 kg Wood Cellulose triacetate synthesized from pulp Degree of substitution 2.84 50 kg Tinuvin 326 (UV absorber 1 manufactured by Ciba Specialty Chemicals) 0.5 kg Chinu 328 (UV absorber 2 manufactured by Ciba Specialty Chemicals) 0.5 kg triphenyl phosphate 8 kg ethylphthalylethyl glycolate 3 kg Aerosil R972V (manufactured by Nippon Aerosil) 0.2 kg methylene chloride 437 kg ethanol 38 kg The production will be described. In each case, the apparatus shown in FIG. 1 was used.

Preparation of Cellulose Ester Film 1 of the Present Invention Using Dope 1 whose temperature was adjusted to 30 ° C., 3
It was uniformly cast on an endless stainless steel belt (support) heated with hot air at 0 ° C. (T2). Immediately after casting, hot air of 25 ° C. (T1) was applied to the doped film (web) on the belt to dry it. After 45 seconds from casting, the belt was heated with hot air of 55 ° C. (T4) from the back of the belt. At the same time, the web surface is dried by blowing hot air of 55 ° C. (T3) on the surface of the web, and after 90 seconds from the casting, the web is peeled at a peeling tension of 180 N / m and dried while being transported by a number of rolls at a transport tension of 150 N / m. I let it. The temperature of the endless stainless steel belt at the peeling part is 1
2 ° C. The residual solvent amount at the time of peeling was 26% by mass. Further, the time course after casting and the amount of residual solvent were determined by sampling the web being dried on the support, and it was found that 18 seconds after casting, the residual peeling amount was dried to 200 mass. The peeled film was transported through the first drying zone set at 50 ° C. for 1 minute, then transported through the second drying zone set at 90 ° C. for 30 seconds, and further dried at 115 ° C. It was conveyed in the zone for 10 minutes and dried. After drying, it is wound up in a roll form to give a roll length of 2000.
m, a cellulose ester film 1 of the present invention having a thickness of 47 μm was obtained. The residual solvent amount at the time of winding was 0.3%.

Preparation of Cellulose Ester Film 2 of the Present Invention Using Dope 1 whose temperature was adjusted to 30 ° C., 3
The mixture was uniformly cast on an endless stainless steel belt heated with hot air at 0 ° C. (T2). Immediately after the casting, the dope film (web) on the belt was dried by blowing warm air of 20 ° C. (T1), and then 45 seconds from the back of the belt 35 seconds after the casting.
(T4) hot air and 45
The film was dried by applying hot air at a temperature of (C3) (T3). After 75 seconds from the casting, the film was peeled at a peeling tension of 170 N / m and dried while being transported by a number of rolls at a transporting tension of 130 N / m. The temperature of the endless stainless belt at the peeling portion was 12 ° C. The residual solvent amount at the time of peeling was 40% by mass. Further, the web being dried on the support was dried to a residual peeling amount of 200 mass in 19 seconds after casting. The peeled film was transported through the first drying zone set at 50 ° C. for 1 minute, then transported through the second drying zone set at 90 ° C. for 30 seconds, and further dried at 115 ° C. It was conveyed in the zone for 10 minutes and dried. In the second drying zone, the film was stretched 1.05 times in the width direction by a tenter.
After drying, the cellulose ester film 2 of the present invention having a winding length of 2600 m and a film thickness of 40 μm was obtained by winding it into a roll. The residual solvent amount during winding was 0.2%.

Preparation of Cellulose Ester Film 3 of the Present Invention Using dope 2 whose temperature was adjusted to 30 ° C., 2
The mixture was uniformly cast on an endless stainless steel belt heated with hot air at 0 ° C. (T2). Immediately after the casting, the dope film (web) on the belt was dried by blowing warm air of 20 ° C. (T1), and then 45 seconds from the back of the belt 35 seconds after the casting.
(T4) hot air and 45
The film was dried by applying hot air at a temperature of (C3) (T3). After 75 seconds from the casting, the film was peeled at a peeling tension of 170 N / m and dried while being transported by a number of rolls at a transporting tension of 130 N / m. The temperature of the endless stainless belt at the peeling portion was 12 ° C. The residual solvent amount at the time of peeling was 28% by mass. In addition, the web being dried on the support had been dried to a residual peeling amount of 200 mass 10 seconds after casting. The peeled film is transported through the first drying zone set at 55 ° C. for 1 minute, then transported through the second drying zone set at 90 ° C. for 30 seconds, and further dried at 125 ° C. It was transported in the zone for 15 minutes and dried. In the second drying zone, the film was stretched 1.05 times in the width direction by a tenter.
After drying, the cellulose ester film 3 of the present invention having a winding length of 2600 m and a film thickness of 40 μm was obtained by winding it into a roll. The residual solvent amount during winding was less than 0.1%.

Production of Cellulose Ester Film 4 of the Present Invention Using dope 3 whose temperature was adjusted to 30 ° C., 2
The mixture was uniformly cast on an endless stainless steel belt heated with hot air at 0 ° C. (T2). Immediately after the casting, the dope film (web) on the belt was dried by blowing hot air at 20 ° C. (T1), and after 45 seconds from the back of the belt, 45 seconds from the casting.
(T4) hot air and 45
Drying was performed by applying hot air at a temperature of (C3) (T3), and after 40 seconds from the casting, the film was peeled at a peeling tension of 170 N / m and dried while being transported by a number of rolls at a transporting tension of 130 N / m. The temperature of the endless stainless belt at the peeling portion was 12 ° C. The residual solvent amount at the time of peeling was 80% by mass. Further, the web being dried on the support was dried to a residual peeling amount of 200 mass in 19 seconds after casting. The peeled film is transported through the first drying zone set at 55 ° C. for 1 minute, then transported through the second drying zone set at 90 ° C. for 30 seconds, and further dried at 125 ° C. It was transported in the zone for 15 minutes and dried. In the second drying zone, the film was stretched 1.05 times in the width direction by a tenter.
After drying, the cellulose ester film 4 of the present invention having a winding length of 2600 m and a film thickness of 40 μm was obtained by winding it into a roll. The residual solvent amount during winding was less than 0.1%.

Production of Cellulose Ester Film 5 of the Present Invention Using dope 4 whose temperature was adjusted to 30 ° C., 2
The mixture was uniformly cast on an endless stainless steel belt heated with hot air at 0 ° C. (T2). Immediately after the casting, the dope film (web) on the belt was dried by blowing warm air of 20 ° C. (T1), and after 20 seconds from the casting, the dope film was removed from the back surface of the belt.
C (T4) hot air and 41
Drying was performed by applying hot air at a temperature of (C3) (T3), and after 40 seconds from the casting, the film was peeled at a peeling tension of 170 N / m and dried while being transported by a number of rolls at a transporting tension of 130 N / m. The temperature of the endless stainless belt at the peeling portion was 11 ° C. The residual solvent amount at the time of peeling was 76% by mass. The web that was being dried on the support had been dried to a residual peeling amount of 200 mass 16 seconds after casting. The peeled film was transported through the first drying zone set at 55 ° C. for 1 minute, then transported through the second drying zone set at 90 ° C. for 30 seconds, and further dried at 127 ° C. It was transported in the zone for 15 minutes and dried. In the second drying zone, the film was stretched 1.07 times in the width direction by a tenter.
After drying, the cellulose ester film 5 of the present invention having a winding length of 2600 m and a film thickness of 40 μm was obtained by winding it into a roll. The residual solvent amount during winding was less than 0.1%.

Preparation of Cellulose Ester Film 6 of the Present Invention Using dope 5 whose temperature was adjusted to 30 ° C., 2
The mixture was uniformly cast on an endless stainless steel belt heated with hot air at 0 ° C. (T2). Immediately after the casting, the dope film (web) on the belt was dried by blowing warm air of 20 ° C. (T1), and after 20 seconds from the casting, the dope film was removed from the back surface of the belt.
C (T4) hot air and 41
Drying was performed by applying hot air at a temperature of (C3) (T3), and after 40 seconds from the casting, the film was peeled at a peeling tension of 170 N / m and dried while being transported by a number of rolls at a transporting tension of 130 N / m. The temperature of the endless stainless belt at the peeling portion was 11 ° C. The residual solvent amount at the time of peeling was 74% by mass. Further, the web being dried on the support had been dried to a residual peeling amount of 200 mass 15 seconds after casting. The peeled film was transported through the first drying zone set at 55 ° C. for 1 minute, then transported through the second drying zone set at 90 ° C. for 30 seconds, and further dried at 127 ° C. It was transported in the zone for 15 minutes and dried. In the second drying zone, the film was stretched 1.07 times in the width direction by a tenter.
After drying, the cellulose ester film 6 of the present invention having a winding length of 2600 m and a film thickness of 40 μm was obtained by winding it into a roll. The residual solvent amount during winding was less than 0.1%.

Preparation of Cellulose Ester Film 7 of the Present Invention Using dope 6 whose temperature was adjusted to 30 ° C., 2
The mixture was uniformly cast on an endless stainless steel belt heated with hot air at 0 ° C. (T2). Immediately after casting, the dope film (web) on the belt was dried by blowing hot air at 20 ° C. (T1), and then 22 seconds after casting, the film was removed from the back surface of the belt by 41 seconds.
C (T4) hot air and 41
The film was dried by applying hot air at a temperature of (C3) (T3). After 45 seconds from the casting, the film was peeled at a peeling tension of 170 N / m and dried while being transported by a number of rolls at a transporting tension of 130 N / m. The temperature of the endless stainless belt at the peeling portion was 11 ° C. The residual solvent amount at the time of peeling was 78% by mass. Further, the web being dried on the support had been dried to a residual peeling amount of 200 mass 15 seconds after casting. The peeled film was transported through the first drying zone set at 55 ° C. for 1 minute, then transported through the second drying zone set at 90 ° C. for 30 seconds, and further dried at 127 ° C. It was transported in the zone for 15 minutes and dried. In the second drying zone, the film was stretched 1.07 times in the width direction by a tenter.
After drying, the cellulose ester film 7 of the present invention having a winding length of 2600 m and a film thickness of 40 μm was obtained by winding the film into a roll. The residual solvent amount during winding was less than 0.1%.

Preparation of Cellulose Ester Film 8 of the Present Invention Using dope 7 whose temperature was adjusted to 35 ° C., 4
The mixture was uniformly cast on an endless stainless steel belt heated by warm air at 5 ° C. (T2). Immediately after the casting, the dope film (web) on the belt was dried by blowing hot air at 45 ° C. (T1).
(T4) hot air and 60
Drying was performed by applying hot air at a temperature of (C3) (T3), and after 50 seconds from the casting, the film was peeled at a peeling tension of 170 N / m and dried while being transported by a number of rolls at a transporting tension of 130 N / m. The temperature of the endless stainless belt at the peeling portion was 11 ° C. The residual solvent amount at the time of peeling was 40% by mass. Also, the web being dried on the support had been dried to a residual peeling amount of 200 mass 18 seconds after casting. The peeled film is transported through the first drying zone set at 55 ° C. for 1 minute, then transported through the second drying zone set at 90 ° C. for 30 seconds, and further dried at 125 ° C. It was transported in the zone for 15 minutes and dried. In the second drying zone, the film was stretched 1.07 times in the width direction by a tenter.
After drying, the cellulose ester film 8 of the present invention having a winding length of 2600 m and a film thickness of 40 μm was obtained by winding it into a roll. The residual solvent amount during winding was less than 0.1%.

Preparation of Cellulose Ester Film 9 of the Present Invention Using dope 8 temperature-controlled to 30 ° C., 3
The mixture was uniformly cast on an endless stainless steel belt heated by warm air at 5 ° C. (T2). Immediately after casting, the heated dope film (web) on the belt was dried by blowing warm air at 35 ° C. (T1).
C. (T4) with hot air and 57
Drying was performed by applying hot air at a temperature of (C3) (T3). After 60 seconds from the casting, the film was peeled at a peeling tension of 170 N / m and dried while being transported by a number of rolls at a transporting tension of 130 N / m. The temperature of the endless stainless belt at the peeling portion was 11 ° C. The residual solvent amount at the time of peeling was 70% by mass. Further, the web being dried on the support had been dried to a residual peeling amount of 200 mass 15 seconds after casting. The peeled film is transported through the first drying zone set at 55 ° C. for 1 minute, then transported through the second drying zone set at 90 ° C. for 30 seconds, and further dried at 125 ° C. It was transported in the zone for 15 minutes and dried. In the second drying zone, the film was stretched 1.07 times in the width direction by a tenter.
After drying, the cellulose ester film 9 of the present invention having a winding length of 2600 m and a film thickness of 40 μm was obtained by winding the film into a roll. The residual solvent amount during winding was less than 0.1%.

Production of Cellulose Ester Film 10 of the Present Invention Using dope 9 whose temperature was adjusted to 35 ° C., 4
The mixture was uniformly cast on an endless stainless steel belt heated with warm air at 5 ° C. (T2). Immediately after casting, the hot air of 45 ° C. (T1) was applied to the dope film (web) on the belt and dried, and then 60 seconds from the back of the belt 25 seconds after casting.
(T4) hot air and 60
Drying was performed by applying hot air at a temperature of (C3) (T3). After 50 seconds from the casting, the film was peeled at a peeling tension of 170 N / m and dried while being transported by a number of rolls at a transporting tension of 130 N / m. The temperature of the endless stainless belt at the peeling portion was 11 ° C. The residual solvent amount at the time of peeling was 40% by mass. Also, the web being dried on the support had been dried to a residual peeling amount of 200 mass in 15 seconds after casting. The peeled film was transported in the first drying zone set at 55 ° C. for 1 minute, then transported in the second drying zone set at 90 ° C. for 30 seconds, and further dried in the third drying zone set at 125 ° C. It was transported in the zone for 15 minutes and dried. In the second drying zone, the film was stretched 1.07 times in the width direction by a tenter.
After drying, the cellulose ester film 10 of the present invention having a winding length of 2600 m and a film thickness of 40 μm is taken up in a roll shape.
I got The residual solvent amount during winding was less than 0.1%.

Production of Cellulose Ester Film 11 of the Present Invention Using dope 10 whose temperature was adjusted to 35 ° C., it was uniformly cast from the back surface onto an endless stainless steel belt heated by warm air of 30 ° C. (T2). Immediately after the casting, the dope film (web) on the belt was dried by blowing hot air of 30 ° C. (T1).
While heating with warm air of 5 ° C (T4), 4
Drying was performed by applying hot air of 5 ° C. (T3), and after 36 seconds from the casting, the film was peeled at a peeling tension of 170 N / m and dried while being transported by a number of rolls at a transporting tension of 130 N / m. The temperature of the endless stainless belt at the peeling portion was 11 ° C. The residual solvent amount at the time of peeling was 63% by mass. Further, the web being dried on the support had been dried to a residual peeling amount of 200 mass in 9 seconds after casting. The peeled film is
After the first drying zone set at 55 ° C. is transported for 1 minute, the second drying zone set at 95 ° C. is transported for 30 seconds, and the first drying zone is further set at 125 ° C. for 1 second.
It was transported for 5 minutes and dried. In the second drying zone, the film was stretched 1.07 times in the width direction by a tenter. After drying, the film is wound into a roll to obtain a roll length of 2600 m and a film thickness of 4
A cellulose ester film 11 of the present invention having a thickness of 0 μm was obtained. The residual solvent amount during winding was less than 0.2%.

Production of Cellulose Ester Film 12 of the Present Invention Using dope 10 whose temperature was adjusted to 35 ° C., it was uniformly cast from the back surface onto an endless stainless steel belt heated by warm air at 35 ° C. (T2). Immediately after the casting, the dope film (web) on the belt was dried by blowing hot air at 35 ° C. (T1).
While heating with warm air of 5 ° C (T4), 4
Drying was performed by applying hot air at 5 ° C. (T3), and after 30 seconds from the casting, the film was peeled at a peeling tension of 170 N / m and dried while being transported by a number of rolls at a transporting tension of 130 N / m. The temperature of the endless stainless belt at the peeling portion was 11 ° C. The residual solvent amount at the time of peeling was 76% by mass. Further, the web being dried on the support had been dried to a residual peeling amount of 200 mass in 9 seconds after casting. The peeled film is
After the first drying zone set at 55 ° C. is transported for 1 minute, the second drying zone set at 95 ° C. is transported for 30 seconds, and the first drying zone is further set at 125 ° C. for 1 second.
It was transported for 5 minutes and dried. In the second drying zone, the film was stretched 1.07 times in the width direction by a tenter. After drying, the film is wound into a roll to obtain a roll length of 2600 m and a film thickness of 4
A cellulose ester film 12 of the present invention having a thickness of 0 μm was obtained. The residual solvent amount during winding was less than 0.2%.

Production of Comparative Cellulose Ester Film 1 Using the dope 11 whose temperature was adjusted to 30 ° C., it was uniformly cast from the back surface onto an endless stainless steel belt heated by warm air of 20 ° C. (T2). Immediately after casting, the dope film (web) on the belt was dried by blowing hot air at 20 ° C. (T1), and after 150 seconds from casting, the peeling tension was 180 °.
Peeling at N / m, transport tension 150 N / m with many rolls
And dried. The temperature of the endless stainless belt at the peeling portion was 11 ° C. The residual solvent amount at the time of peeling was 20% by mass, and the web being dried on the support was dried to a residual peeling amount of 200% by 32 seconds after casting. The peeled film was transported through the first drying zone set at 50 ° C. for 1 minute, and then transported through the second drying zone set at 90 ° C. for 30 seconds.
And dried in a third drying zone set for 15 minutes. In the second drying zone, the film was stretched 1.05 times in the width direction by a tenter. After drying, the film was wound into a roll to obtain a comparative cellulose ester film 1 having a winding length of 2600 m and a film thickness of 40 μm. The residual solvent amount during winding was less than 0.1%.

Preparation of Comparative Cellulose Ester Film 2 Using the dope 12 whose temperature was adjusted to 30 ° C., it was uniformly cast from the back surface onto an endless stainless steel belt heated with warm air of 20 ° C. (T2). Immediately after casting, the dope film (web) on the belt was dried by blowing hot air of 25 ° C. (T1), and after 120 seconds from casting, the peeling tension was 180 N /
m, and dried while being transported by a number of rolls at a transport tension of 150 N / m. The temperature of the endless stainless belt at the peeling portion was 11 ° C. The residual solvent amount at the time of peeling was 26% by mass. Further, the web being dried on the support had been dried to have a peeling residual dissolved amount of 200 mass in 30 seconds after casting. The peeled film was transported through the first drying zone set at 50 ° C. for 1 minute, and then transported through the second drying zone set at 90 ° C. for 30 seconds.
And dried in a third drying zone set for 15 minutes. In the second drying zone, the film was stretched 1.05 times in the width direction by a tenter. After drying, the film was wound into a roll to obtain a comparative cellulose ester film 2 having a winding length of 2600 m and a film thickness of 40 μm. The residual solvent amount during winding was less than 0.1%.

The obtained cellulose ester films 1 to 12 of the present invention and the comparative cellulose ester film 1
And 2, the degree of plane orientation S and the in-plane retardation R
₀ , the angle θ between the slow axis direction and the film forming direction
(゜) was requested. Table 1 shows the obtained results.

<Measurement of residual solvent amount of dope film on support>
Calculation of drying rate and time> The dope film on the support after casting was sampled at regular intervals, and the change in the amount of residual solvent from casting to peeling was plotted on a graph. From the graph, the time T until the residual solvent amount reaches 200% by mass after casting is T
₂₀₀ and time T ₁₂₀ to reach 120% by mass of residual solvent after casting.
And the difference was determined. The drying speed was determined from the time.

Drying speed S ₂₀₀ (mass% / sec) = (residual solvent amount 200 mass% −residual solvent amount 120 mass%) / (T ₂₀₀ −T ₁₂₀ ) S ₂₀₀ T ₂₀₀ −T ₁₂₀ (mass% / sec) (Second) Cellulose ester film 1 5.2 15.5 of the present invention Cellulose ester film 2 5.0 16 of the present invention Cellulose ester film 3 4.8 16.7 of the present invention Cellulose ester film 4 7.0 of the present invention 11.5 Cellulose ester film 5 6.7 12.0 Cellulose ester film 6 6.4 12.5 Cellulose ester film 7 6.4 12.5 Cellulose ester film 8 6 8.8 11.7 Cellulose ester film 9 of the present invention 9 5.0 16 Cellulose ester film 10 of the present invention 7.5 7.5 10.6 Inventive cellulose ester film 11 6.8 11.8 Inventive cellulose ester film 12 7.2 11.1 Comparative cellulose ester film 1 3.9 20.5 Comparative cellulose ester film 2 3.8 21 <plane orientation Measurement> Automatic birefringence meter KOBRA-21A
Using DH (manufactured by Oji Scientific Instruments), at 23 ° C. and 55 ° C.
Under an environment of% RH, a three-dimensional refractive index measurement was performed at a wavelength of 590 nm, and the refractive indexes Nx, Ny, and Nz were obtained.
According to the formula (I) of the first aspect, the plane orientation degree S and the second aspect
R ₀ was calculated according to the formula (II).

[0195]

[Table 1]

Thus, it can be seen that the cellulose ester film of the present invention has a low degree of plane orientation and is excellent in optical isotropy.

Example 2 The cellulose ester film 1 of the present invention was prepared at 40.degree.
Alkaline treatment was performed with a 5 mol / l aqueous solution of sodium hydroxide for 60 seconds, followed by washing with water for 3 minutes to form a saponified layer to obtain an alkali-treated film.

Next, a polyvinyl alcohol film having a thickness of 120 μm was immersed in 100 kg of an aqueous solution containing 1 kg of iodine and 4 kg of boric acid, and stretched 4 times at 50 ° C. to form a polarizing film. The polarizing plate 1 of the present invention was prepared by laminating the alkali-treated films on both sides of the polarizing film using a 5% aqueous solution of completely saponified polyvinyl alcohol as an adhesive.

Similarly, cellulose ester films 2 to
The polarizing plates 2 to 12 of the present invention and the polarizing plates 1 and 2 of the present invention were obtained using 12 or comparative cellulose ester films 1 and 2, respectively.

Evaluation of Polarizing Plate The degree of polarization of the obtained polarizing plate was determined in terms of the light transmittance between the case where two polarizing plates were arranged in parallel at every 50 nm and the case where two polarizing plates were arranged orthogonally in the light ray range of 400 to 700 nm. Was calculated from the average value according to the following equation.

The degree of polarization = ｛(H0−H90) / (H0 + H)
90)｝ 1/2 × 100 where H0 is the average parallel transmittance and H90 is the average orthogonal transmittance.

The change in the degree of polarization before and after the treatment at 80 ° C. and 90% RH for 500 hours was also examined. As a result, the polarizing plates 1 to 12 of the present invention all had an initial degree of polarization of 88 to 90, and the degree of polarization after treatment at 80 ° C. and 90% RH for 500 hours was 86 or more. The polarizing plates 1-2 have an initial degree of polarization of 88, and the degree of polarization after being treated at 80 ° C. and 90% RH for 500 hours is less than 85, confirming that the polarizing plate of the present invention is excellent. .

[0203]

According to the present invention, it is possible to provide a cellulose ester film having excellent optical isotropy, particularly excellent optical isotropy in a film thickness direction, a method for producing the same, a polarizing plate for a display device, and a display device. Was.

[Brief description of the drawings]

FIG. 1 is a schematic view of an apparatus for producing a cellulose ester film of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Endless stainless belt 2 Die 3 Low-temperature drying zone 4 High-temperature drying zone 5 Casting part 6 Peeling part 7 Peeling roll 8 First drying zone 9 Conveyance roll 10 Second drying zone 11 Third drying zone 12 Winding part

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08L 63/00 C08L 63/00 A G02B 5/30 G02B 5/30 G02F 1/1335 510 G02F 1/1335 510 // B29K 1:00 B29K 1:00 B29L 7:00 B29L 7:00 F term (reference) 2H049 BA02 BA27 BB18 BB33 BB43 BB51 BC22 2H091 FA08X FA08Z FB02 KA10 LA16 4F071 AA09 AE19 AF29 AF35 BA02 BB02 AC01 A05H73 AR08 AR11 GA07 GB02 GC07 GN22 GN24 GW06 4J002 AB021 CD022 EF086 GP00

Claims (18)

[Claims] 1. A cellulose ester film having a degree of plane orientation S represented by the following formula (I) of 0.0004 or less. Formula (I) S = (Nx + Ny) / 2−Nz In the formula, Nx is a refractive index in a slow axis direction in a film plane, Ny
Represents a refractive index in a film plane in a direction perpendicular to the slow axis direction, and Nz represents a refractive index in a thickness direction of the film. 2. S represented by the above formula (I) is 0.000
01 to 0.0004, and R ₀ and θ satisfy the following formula (I
2. The cellulose ester film according to claim 1, wherein P of I) satisfies the relationship of 0.9999. Formula (II) P ≦ 1−sin ² (2θ) sin ² (πR ₀ / λ) R ₀ = (Nx−Ny) × d where Nx is the refractive index in the slow axis direction in the film plane, Ny
Is the in-plane refractive index in the direction perpendicular to the slow axis direction, and d is the film thickness (nm) of the film. θ is the angle (radian) between the slow axis direction in the film plane and the film forming direction (straight direction of the film), and λ is the above Nx, Ny,
The wavelength (nm) of light at the time of three-dimensional refractive index measurement for obtaining θ,
π is the pi. 3. A compound having a plurality of cyclic structures in a molecule is 5 to 30% by mass based on the cellulose ester film.
The cellulose ester film according to claim 1, wherein the cellulose ester film is contained. 4. The cellulose ester has a total degree of substitution of 2.85.
The cellulose ester film according to any one of claims 1 to 3, wherein the cellulose ester film is a cellulose ester having a thickness of from 3.0 to 3.00. 5. The cellulose ester film according to claim 1, which has a thickness of 10 to 60 μm. 6. A method for producing a cellulose ester film, wherein the cellulose ester solution is cast on a support, and the film after peeling is further dried, wherein the cellulose ester solution is cast on the support. In the drying step, when the residual solvent amount of the dope film on the support is in the range of 200% by mass to 120% by mass, the drying is performed such that the residual solvent amount decreasing rate is 4 to 15% by mass / second. Characteristic method for producing a cellulose ester film. 7. A method for producing a cellulose ester film, in which a cellulose ester solution is cast on a support, and the film after peeling is further dried, wherein the cellulose ester solution is cast on the support. In the drying step, the amount of the residual solvent in the doped film on the support is in the range of 200% by mass to 120% by mass for 10 seconds or more and 20 minutes or more.
A method for producing a cellulose ester film, wherein the drying is performed for less than a second. 8. A method for producing a cellulose ester film, wherein the cellulose ester solution is cast on a support, and the film after peeling is further dried, wherein the cellulose ester solution is cast on the support. The drying step includes drying the web in an atmosphere having an average temperature of 41 to 100 ° C.
The peeling is performed in 5 to 90 seconds.
A method for producing the cellulose ester film according to the above. 9. A method for producing a cellulose ester film, comprising casting a cellulose ester solution on a support and drying the film after peeling, wherein the cellulose ester solution is cast on the support. At the time of the drying step, after the low temperature drying step of drying the web on the support in an atmosphere whose average temperature was set at 20 to 50 ° C., the temperature was set at +5 to 70 ° C. higher than the average temperature of the low temperature drying step. 9. The method for producing a cellulose ester film according to claim 6, wherein drying is performed in a high-temperature drying step of further drying on a support in an atmosphere, and peeling is performed 25 to 90 seconds after casting. 10. The high-temperature drying step on the support comprises:
The method for producing a cellulose ester film according to claim 9, wherein the method is performed in an atmosphere set at a temperature of from about 100 ° C. to about 100 ° C. 10. 11. The method for producing a cellulose ester film according to claim 6, wherein a residual solvent amount at the time of peeling is 20 to 120% by mass. 12. The cellulose ester solution has a solid content concentration (concentration excluding low-boiling-point solvent concentration) of 17 to 30% by mass.
The method for producing a cellulose ester film according to any one of claims 6 to 11, wherein 13. After the film removed from the support is dried to a residual solvent amount of 0 to 10% by mass, the film is heated at 115 to 200 ° C. for 5 to 60 minutes. 13. The method for producing a cellulose ester film according to any one of 6 to 12. 14. The method for producing a cellulose ester film according to claim 6, wherein the support for solution casting is a metal belt. 15. A cellulose ester film, wherein the cellulose ester film according to any one of claims 1 to 5 is produced by the method according to any one of claims 6 to 14. 16. A polarizing plate comprising the cellulose ester film according to claim 1 on at least one surface. 17. A display device using the cellulose ester film according to claim 1. Description: 18. A display device using the polarizing plate according to claim 16.