JP2003165868A - Cellulose ester film, method for producing the same, polarizing plate and display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cellulose ester film having good moisture permeability and excellent dimensional stability, to provide a method for producing the film, a protective film for a polarizing plate having durability in high temperatures and high humilities and under ultraviolet rays, the polarizing plate and a display device using the protective film. <P>SOLUTION: This cellulose ester film contains 1-30 wt.% compound having a structure represented by general formula (1) (wherein, Y is a divalent organic group in which one of an aromatic ring and a cyclohexane ring may have a substituent). <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a cellulose ester film and a method for producing the same, and particularly to a cellulose ester film useful as a protective film for a polarizing plate,
The present invention relates to a polarizing plate using the same and a display device using the same.

[0002]

2. Description of the Related Art In recent years, the development of thin and lightweight notebook personal computers has advanced. Along with this, there is an increasing demand for thinning polarizing plates used in liquid crystal display devices, organic EL display devices and the like. In particular,
For the thinning of the polarizing plate, it is required to thin the protective film for the polarizing plate. However, it has been found that various problems can be caused by simply thinning the protective film for a polarizing plate. As one of them, the influence appears on the moisture permeability (moisture permeability). For example, as the protective film for a polarizing plate is made thinner, the water vapor transmission rate becomes higher, and as a result, the durability of the polarizing plate is lowered. Several means have been proposed for improving this moisture vapor transmission rate. Certainly, the lower the water vapor transmission rate, the higher the durability of the incorporated polarizing plate, but on the other hand, if the water vapor transmission rate is too low, it is difficult for the adhesive to dry when bonding the polarizing plate protective film and the polarizer. have.

Therefore, a protective film for a polarizing plate is required to have a moisture permeability characteristic that satisfies both of them. In particular,
In a protective film for a polarizing plate containing a cellulose ester, which is widely used, the moisture permeability is significantly deteriorated due to the thinning. On the other hand, it is known that when the content of the plasticizer etc. is increased, the moisture permeability is improved, but on the other hand, when the content of the plasticizer is excessively increased, there is a problem that the dimensional stability is deteriorated. The development of a protective film for a polarizing plate having good wettability and high film properties has been earnestly desired.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object thereof is to provide a cellulose ester film having good moisture permeability and excellent dimensional stability, and a method for producing the same. An object of the present invention is to provide a cellulose ester film which has excellent durability against high temperature and high humidity or ultraviolet rays and can be used as a protective film for a polarizing plate, and a polarizing plate and a display device using the same.

[0005]

The above object of the present invention has been achieved by the following constitution.

1. A cellulose ester film containing 1 to 30 mass% of the compound having the structure represented by the general formula (1).

2. 2. The cellulose ester film according to 1, wherein Y in the general formula (1) is a compound containing an ester bond.

3. 3. The cellulose ester film according to 1 or 2, which contains an ultraviolet absorber having a distribution coefficient of 8.5 or more.

4. 4. The cellulose ester film according to any one of 1 to 3, which contains fine particles of silicon oxide.

5. 5. The cellulose ester film according to any one of 1 to 4, which contains a cellulose ester having a total substitution degree of 2.55 to 2.85.

6. 6. The cellulose ester film according to any one of 1 to 5, which has a film thickness of 10 to 60 μm and a water vapor transmission rate of 20 to 220 g / m ² · 24 hr.

7. The film thickness is 10 to 60 μm, the water vapor transmission rate is ^{20 to} 220 g / m ² · 24 hr, and the temperature is 80 ° C.
Any one of 1 to 6 above, wherein the mass change rate before and after heat treatment at 90% RH for 48 hours is within ± 2%.
Item 7. A cellulose ester film.

8. In the method for producing a cellulose ester film by a solution casting film forming method, a cellulose ester solution containing a compound having a structure represented by the above general formula (1) is cast on a support, and the solution is cast on the support for 30 to 90 seconds. A method for producing a cellulose ester film, which comprises:

9. The content of the compound having the structure represented by the general formula (1) in the obtained cellulose ester film is 1 to 30% by mass.
A method for producing the described cellulose ester film.

10. 8 or 9 wherein Y in the general formula (1) is a compound containing an ester bond
A method for producing the described cellulose ester film.

11. The method for producing a cellulose ester film according to any one of 8 to 10, wherein the cellulose ester solution contains an ultraviolet absorber having a partition coefficient of 8.5 or more.

12. 12. The method for producing a cellulose ester film according to any one of 8 to 11, wherein the cellulose ester solution contains silicon oxide fine particles.

13. 13. The method for producing a cellulose ester film according to any one of 8 to 12, wherein the cellulose ester solution contains a cellulose ester having a total substitution degree of 2.55 to 2.85.

14. The obtained cellulose ester film has a film thickness of 10 to 60 μm and a water vapor transmission rate of 20 to 2
20g / m ² · 24hr, 80 ° C, 90% RH
14. The method for producing a cellulose ester film according to any one of 8 to 13, wherein the mass change rate before and after the heat treatment for 48 hours is within ± 2%.

15. Any one of 8 to 14, wherein the cellulose ester solution contains methyl acetate.
A method for producing a cellulose ester film according to item.

A polarizing plate comprising the cellulose ester film according to any one of 16.1 to 7.

A display device using the polarizing plate described in 17.16. The present inventors have conducted extensive studies to improve the above-mentioned problems, and as a result, even a thin cellulose ester film satisfies the water vapor transmission rate, and cellulose that can be used as a polarizing plate protective film having excellent dimensional stability. An ester film could be obtained.

That is, the present inventors have found that this can be achieved by containing the compound having the structure represented by the above-mentioned general formula (1) in an amount of 1 to 30% by mass of the cellulose ester film itself, leading to the present invention. It is a thing.

The amount of the compound having the structure represented by the general formula (1) is preferably 5 to 25% by mass, particularly preferably 10 to 20% by mass.

The compound having the structure represented by the general formula (1) will be described in more detail. It has a structure in which the cyclohexane ring and the aromatic ring are connected by a divalent organic group Y. The divalent organic group Y is not particularly limited, but preferably has an ester bond. The cyclohexane ring and the aromatic ring may have a substituent, and the kind of the substituent is not particularly limited, but an alkyl group is preferable. In the present invention, the cyclohexane ring preferably has a substituent.

In particular, it is preferable that the cyclohexane ring has at least one substituent other than hydrogen from the viewpoint of compatibility with cellulose ester, and the substituent is an alkyl group, an alkoxy group, an acyl group or an aryl group. , An acyloxy group and an aryloxy group are preferable.

The compound having the structure represented by the general formula (1) has at least one structure in which the cyclohexane ring and the aromatic ring are connected in the molecule, but it has two or more. Is particularly preferred. The structure is 2
Two or more for a common cyclohexane ring when having two or more
It is preferable to have a structure in which one or more aromatic rings are connected, or to have a structure in which two or more cyclohexane rings are connected to a common aromatic ring.

The following are specifically used, but the present invention is not limited to these. Two or more of these may be added at the same time.

[0029]

[Chemical 2]

[0030]

[Chemical 3]

[0031]

[Chemical 4]

[0032]

[Chemical 5]

[0033]

[Chemical 6]

[0034]

[Chemical 7]

The compound represented by the general formula (1) has a molecular weight of 2
It is preferably from 00 to 2000, and further from 300 to 1
It is preferably 500, and particularly preferably 350 to 1000. Most preferred is 350-500
Is.

1 to 30% by mass of the compound having the structure represented by the general formula (1) is added to the cellulose ester film.
By containing it, it is possible to obtain an effect that even a thin film has good moisture permeability and is excellent in dimensional stability. Further, it is particularly excellent in durability due to high temperature and high humidity or ultraviolet irradiation, and a remarkably excellent effect that it can be used as a protective film for a polarizing plate can be expected.

These may be commercially available products or can be synthesized by a known method such as an esterification reaction.

The preferred film forming process used in the method for producing a cellulose ester film of the present invention comprises the following dissolving process, casting process, solvent evaporation process, peeling process, drying process and winding process. Each step will be described below. << Dissolution Step >> In the present invention, the cellulose ester solution is referred to as a cellulose ester dope or simply dope. The dissolution step is a step of dissolving the flakes of the cellulose ester in an organic solvent mainly composed of a good solvent described later in a dissolution vessel while stirring the flakes to form a dope.

In the present invention, the solid content concentration in the dope is 15
It is preferable to adjust the content to be not less than mass%, particularly 18 to 35
Mass% is preferably used.

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 occur during casting, which may deteriorate the flatness of the film.
It is preferably 5% by mass or less.

The dope viscosity is preferably adjusted within the range of 10 to 50 Pa · s. For the dissolution, a method performed at normal pressure, a method performed at a boiling point of a preferred organic solvent (that is, a good solvent) or lower, a method performed by pressurizing at a boiling point of the good solvent or higher,
There are various dissolution methods such as a cooling dissolution method and a high pressure method. As a method of dissolving at a temperature not lower than the boiling point of a good solvent and applying a pressure that does not boil, 40.4 to 12
By pressurizing at 0.11 to 1.50 MPa at 0 ° C., foaming can be suppressed and dissolution can be performed in a short time.

As the cellulose ester used in the present invention, a lower fatty acid ester of cellulose is preferably used.

The lower fatty acid in the lower fatty acid ester of cellulose ester means a fatty acid having 6 or less carbon atoms, for example, cellulose acetate, cellulose propionate, cellulose butyrate, or the like.
Examples of lower fatty acid esters of cellulose include mixed fatty acid esters such as cellulose acetate propionate and cellulose acetate butyrate described in 0-45804, 8-231761, and US Pat. No. 2,319,052. As.

Particularly preferably, the total degree of substitution is 2.55-2.
A cellulose ester of 85 is preferably used.

A method for measuring the substitution degree of the acyl group of the cellulose ester can be carried out according to ASTM-D-817-96.

Among the above-mentioned fatty acids, cellulose acetate and cellulose acetate propionate are preferably used. In the case of the cellulose ester film of the present invention, the degree of polymerization is preferably 250 to 250 from the viewpoint of film strength.
Those of 400 are preferably used.

The cellulose ester film of the present invention is preferably a cellulose ester having a total degree of substitution of 2.5 to 3.0, and particularly preferably a cellulose ester having a total degree of substitution of 2.55 to 2.85. When the total substitution degree is 2.55 or more, the mechanical strength of the film containing the compound represented by the general formula (1) of the present invention increases, and when it is 2.85 or less, the solubility of cellulose ester is improved,
It is more preferable because the generation of foreign matter is reduced.

In the case of cellulose acetate propionate, the acetyl group substitution degree is X and the propionyl group substitution degree is Y.
Then, those in the range of 2.55 ≦ X + Y ≦ 2.85 1.5 ≦ X ≦ 2.4 are preferably used.

As the cellulose ester, a cellulose ester synthesized from cotton linter, a cellulose ester synthesized from wood pulp, and a cellulose ester synthesized from other raw materials can be used alone or in combination.

The solvent used for preparing the dope is not particularly limited as long as it is a solvent capable of dissolving the cellulose ester, and even a solvent which cannot be dissolved alone is mixed with another solvent, Any substance that can be dissolved can be used. Generally, a mixed solvent composed of a good solvent, methylene chloride, and a poor solvent of cellulose ester is used, and the poor solvent is 4 to 4 times in the mixed solvent.
Those containing 30% by mass are preferably used.

Other good solvents that can be used include methylene chloride, methyl acetate, ethyl acetate, amyl acetate, acetone, tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, cyclohexanone, ethyl formate, 2,2,2. 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 and the like can be mentioned, but organic halogen compounds such as methylene chloride, dioxolane derivatives, methyl acetate, ethyl acetate, acetone and the like can be mentioned as preferable organic solvents (that is, good solvents). The use of methyl acetate is particularly preferable because the resulting film has less curl.

Examples of the poor solvent for cellulose ester include methanol, ethanol, n-propanol and is
alcohols having 1 to 8 carbon atoms such as o-propanol, n-butanol, sec-butanol, tert-butanol, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, propyl acetate, monochlorobenzene,
Examples thereof include benzene, cyclohexane, tetrahydrofuran, methyl cellosolve, and ethylene glycol monomethyl ether. These poor solvents may be used alone or in combination of two or more kinds.

In the production of the cellulose ester film of the present invention, it is also preferable to use a cooling dissolution method when dissolving the cellulose ester. As a cooling dissolution method,
For example, JP-A-9-95538 and 9-95544,
The method described in No. 9-95557 can be used. Further, the high pressure dissolution method described in JP-A-11-21379 can also be preferably used.

Cellulose ester solution (dope) after dissolution
Is preferably filtered with a filter material, defoamed, and sent to the next step by a pump. At that time, a plasticizer, an antioxidant, an ultraviolet absorber, a dye, fine particles and the like are preferably added to the dope. .

These additives 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.

A plasticizer may be added to the cellulose ester film of the present invention. These are represented by the general formula (1)
It can be used in combination with a compound having a structure shown by.

Examples of the plasticizer that can be used include, but are not limited to, phosphoric acid ester plasticizers, phthalic acid ester plasticizers, and citric acid ester plasticizers. The phosphoric acid ester type includes triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate, tributyl phosphate, etc., and the phthalic acid ester type includes diethyl phthalate and dimethoxyethyl phthalate. , Dimethyl phthalate, dioctyl phthalate, dibutyl phthalate,
Di-2-ethylhexyl phthalate, butyl benzyl phthalate, dibenzyl phthalate, butyl phthalyl butyl glycolate, ethyl phthalyl ethyl glycolate,
There is methylphthalylethyl glycolate and the like, and as citric acid ester plasticizers, triethyl citrate, tri-n-butyl citrate, acetyl triethyl citrate, acetyl tri-n-butyl citrate, acetyl tri-n- ( 2-Ethylhexyl) citrate and the like can be preferably used.

These are preferably used alone or in combination, and two or more kinds of these plasticizers may be used in combination, if necessary. The amount of the plasticizer used is preferably 1 to 30% by mass, more preferably 2 to 25% by mass, further preferably 2 to 15% by mass, and particularly preferably 3 to 12% by mass relative to the cellulose ester. It is% by mass.

The cellulose ester film of the present invention may contain, in addition to the above-mentioned plasticizer, an additive having the same action as the plasticizer. If these additives are low-molecular weight organic compounds capable of plasticizing the cellulose ester film, the effects of the present invention can be obtained similarly to the plasticizer. These components are not added for the purpose of directly plasticizing the film as compared with the plasticizer, but show the same action as the plasticizer depending on the amount.

An ultraviolet absorber is preferably added to the cellulose ester film of the present invention. For example, from the viewpoint of preventing deterioration of the liquid crystal, those having excellent absorption of ultraviolet rays having a wavelength of 370 nm or less and having little absorption of visible light having a wavelength of 400 nm or more are preferably used from the viewpoint of good liquid crystal display property. In the present invention, the transmittance at a wavelength of 370 nm is preferably 10% or less, more preferably 5% or less, still more preferably 1% or less.

The ultraviolet absorber used in the present invention is not particularly limited, and examples thereof include oxybenzophenone compounds,
Examples thereof include benzotriazole compounds, salicylate compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex salt compounds, and inorganic powders.

The ultraviolet absorbers preferably used in the present invention are preferably benzotriazole type ultraviolet absorbers and benzophenone type ultraviolet absorbers, which have high transparency and are excellent in the effect of preventing deterioration of the polarizing plate and the liquid crystal element, and are unnecessary. Benzotriazole-based UV absorbers with less coloration are particularly preferred.

Particularly, the ultraviolet absorber added to the cellulose ester film of the present invention is preferably an ultraviolet absorber having a distribution coefficient of 8.5 or more. If the UV absorber is less than 8.5, foreign matter failure tends to increase, and it becomes remarkable especially when the below-mentioned fine particles are added. Partition coefficient is 8.5
The use of the above ultraviolet absorbers has the effect of reducing the moisture permeability. In the present invention, the distribution coefficient is more preferably 9.0 or more, and more preferably 10.0 or more. It is more preferable that the molecule does not contain halogen.

The following is an example of an ultraviolet absorber that can be used in the cellulose ester film of the present invention.
It is not limited to this.

[0065]

[Chemical 8]

The partition coefficient represents the partition ratio of octanol and water which can be defined by the following formula. log Po / w, Po / w = So / Sw So: Solubility of the organic compound in n-octanol at 25 ° C. Sw: Solubility of the organic compound in pure water at 25 ° C. These are thus n-octanol In the present invention, these partition coefficients were calculated by HPLC, although it can be measured using water and water. This is a method using high performance chromatography, which is described in OECD guideline 117 partition coefficient (n-octanol / water) high performance chromatography method (adopted March 30, 1989). Shown in.

Apparatus: LC module (manufactured by Waters) Column: Inertosil ODS-2 250 mm × 4.6
mm (manufactured by GL Sciences Inc.) Temperature: 40 ° C. Eluent: Methanol: 1% phosphoric acid aqueous solution = 90: 10 Flow rate: 1.0 ml / min Detection wavelength: 210 nm Injection sample: Methanol solution of about 50 ppm UV absorber alone It may be used, or may be a mixture of two or more kinds, and the use amount thereof is not uniform depending on the kind of compound, use conditions, etc., but is 0.2 to 5.0 g per 1 m ^{2 of} the cellulose ester film. Preferably 0.4
-2.0g is more preferable.

Further, in the present invention, for example, a blue dye or the like may be used as an additive in order to adjust the tint of the film. Anthraquinone dyes are preferred dyes. The anthraquinone dye can have an optional substituent at the 1st to 8th positions of the anthraquinone. Preferred substituents include an anilino group, a hydroxyl group, an amino group, a nitro group, or a hydrogen atom which may be substituted. The amount of these dyes added to the film is 0.1 to 100 to maintain the transparency of the film.
It is 0 μg / m ² , preferably 10 to 100 μg / m ² .

In addition, it is preferable to add fine particles as a matting agent to the cellulose ester film of the present invention in order to impart slipperiness to the film. It is preferable that these fine particles are surface-treated with an organic substance because the haze of the film can be reduced.

Preferred organic substances for the surface treatment include halosilanes, alkoxysilanes, silazanes, siloxanes and the like.

The larger the average diameter of the fine particles, the greater the matting effect, and the smaller the average diameter, the better the transparency. Therefore, in the present invention, the average diameter of the primary particles of the fine particles is preferably 5 to 50 nm, and more preferably. , 7 to 20 nm.

The fine particles are not particularly limited. For example, AEROSIL200 manufactured by Nippon Aerosil Co., Ltd.,
200V, 300, R972, R972V, R974,
R202, R812, OX50, TT600 and the like can be mentioned, preferably AEROSIL200V, R972V
And so on.

These fine particles usually have an average particle size of 0.01.
.About.1.0 .mu.m of secondary particles are formed, and these fine particles are present in the film as an agglomerate of primary particles to form irregularities of 0.01 to 1.0 .mu.m on the film surface. The content of these fine particles is preferably 0.005 to 0.3 mass% with respect to the cellulose ester.

In particular, the cellulose ester film of the present invention preferably contains fine particles of silicon dioxide, and a cellulose ester solution containing fine particles of silicon dioxide and a UV absorber having a partition coefficient of 8.5 or more is used. By casting the cellulose ester film using the method, foreign matter failure due to aggregation of fine particles in the cellulose ester solution is significantly reduced, which is particularly preferable.

As a method for preparing a dispersion liquid of fine particles in order to obtain the cellulose ester film of the present invention, there are, for example, the following three kinds. << Preparation Method A >> A solvent and fine particles are mixed by stirring, and then dispersed by a disperser. This is referred to as a fine particle dispersion liquid. The fine particle dispersion liquid is added to the dope liquid and stirred. << Preparation Method B >> The solvent and the fine particles are stirred and mixed, and then dispersed by a disperser. This is referred to as a fine particle dispersion liquid. Separately, a small amount of cellulose ester is added to the solvent and dissolved by stirring. The fine particle dispersion is added to this and stirred. This is used as a fine particle addition liquid. The fine particle added liquid is thoroughly mixed with the dope liquid by an in-line mixer. << Preparation Method C >> A small amount of cellulose ester is added to a solvent and dissolved by stirring. Fine particles are added to this and dispersed by a disperser. This is used as a fine particle addition liquid. The fine particle added liquid is thoroughly mixed with the dope liquid by an in-line mixer.

Preparation method A is excellent in dispersibility of fine particles of silicon dioxide, and preparation method C is excellent in that fine particles of silicon dioxide are unlikely to reaggregate. Above all, the above-mentioned preparation method B is a preferable preparation method which is 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 the silicon dioxide fine particles are mixed and dispersed with a solvent or the like, the concentration of silicon dioxide is preferably 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 more the liquid turbidity with respect to the added amount tends to be low, and the haze and the aggregates are improved, which is preferable.

The solvent used is a lower alcohol, preferably methyl alcohol, ethyl alcohol,
Propyl alcohol, isopropyl alcohol, butyl alcohol and the like can be mentioned. The solvent other than the lower alcohol is not particularly limited, but it is preferable to use the solvent used when forming the cellulose ester film.

Using the dope thus obtained, a cellulose ester film can be obtained through the casting process described below. <Casting step> A dope is sent to a pressurizing die through a pressurizing type quantitative gear pump and is transferred endlessly at a casting position. An endless metal belt or a rotating metal drum casting support (hereinafter, simply referred to as a support). In some cases), the step of casting the dope from the 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 method using a reverse roll coater in which the film is adjusted with a counter-rotating roll. A pressure die that can adjust the shape and facilitates uniform film thickness is preferable. The pressure die includes a coat hanger die and a T die, and any of them is preferably used.

In order to increase the film forming speed, two or more pressure dies may be provided on the casting support and the dope amount may be divided to form multiple layers. Alternatively, the inside of the die is divided by slits, and multiple dope solutions with different compositions are cast simultaneously (also called co-casting).
Then, a cellulose ester film having a laminated structure can be obtained.

Thus, the obtained dope is cast on a support such as a belt or a drum to form a film, and the present invention is particularly effective in a solution casting film forming method using a belt. This is because it is easy to finely adjust the drying conditions on the support as described later. << Solvent Evaporation Step >> A step of heating a web (in the present invention, a dope is cast on a casting support and the formed dope film is called a web) on the casting support to evaporate the solvent Is. In order to evaporate the solvent, there are a method of blowing air from the web side and / or a method of transferring heat from the back surface of the support by a liquid, a method of transferring heat from the front and back sides by radiant heat, and the like. Drying efficiency is preferred. A method of combining them is also preferable. The web on the support after casting is preferably dried on the support in an atmosphere of 40 to 100 ° C. In order to maintain the atmosphere at 40 to 100 ° C., it is preferable to apply hot air of this temperature to the upper surface of the web or heat it by means such as infrared rays.

In particular, the cellulose ester film of the present invention is desirably peeled from the support within 30 to 90 seconds after casting. If it is peeled off in less than 30 seconds, not only the surface quality of the film is deteriorated, but also the moisture permeability is not preferable. Drying for more than 90 seconds is not preferable because the surface quality is deteriorated due to deterioration of peelability and strong curling occurs in the film. << Peeling Step >> In this step, the web having the solvent evaporated on the support is peeled from the support at the peeling position. The peeled web is sent to the next step. If the amount of residual solvent of the web at the time of peeling (the following formula) is too large, it is difficult to peel, or conversely, if it is sufficiently dried on the support and then peeled,
A part of the web may come off on the way.

The temperature at the peeling position on the support is preferably 10 to 40 ° C., more preferably 11 to 30.
℃. The residual solvent amount of the web at the peeling position is 2
5 to 120 mass% is preferable, and 40 to 1 is more preferable.
It is 00 mass%.

The residual solvent amount of the web according to the present invention is defined by the following formula. 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 for measuring the amount of residual solvent is 115 ° C.
Represents that heat treatment is performed for 1 hour.

In order to adjust the amount of residual solvent at the time of peeling as described above, 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 in the above temperature range. To control the temperature of the support, it is preferable to use a heat transfer method having high heat transfer efficiency, and for example, a back surface heat transfer method using a liquid is preferable.

The heat transfer method using radiant heat or hot air is not a preferable method because it is difficult to control the temperature of the support, but in a belt (support) machine, it is possible to control the temperature at the place where the belt to be transferred comes to the lower side. The belt temperature can be adjusted by gentle wind.

The temperature of the support can be partially changed by dividing the heating means, and the temperature of the support for casting, the casting position of the casting support, the drying section, the peeling position, and the like are different. Can be done.

As a method of increasing the film-forming speed (the film-forming speed can be increased because the film is peeled off while the amount of residual solvent is as large as possible), there is a gel casting method (gel casting) in which the amount of residual solvent can be peeled off. .

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

It is possible to accelerate peeling and increase the film-forming speed by gelling on the support to strengthen the film.

In the case of peeling when the amount of residual solvent is larger, if the web is too soft, the flatness at the time of peeling may be impaired, and cracks and vertical lines due to peeling tension are likely to occur, and peeling remains due to a balance between economic speed and quality. The amount of solvent can be determined.
The peeling tension when peeling the support from the film is usually 19
Peeling is performed at 6 to 245 N / m, but if wrinkles are easily formed at the time of peeling, it is preferable to peel at 190 N / m or less, and further, the lowest tensile force at which peeling is possible to 166.6 N / m.
m, and then peeling at a minimum tension of -137.2 N / m is preferable, but a minimum tension of 100 N is particularly preferable.
/ M. The lower the peeling tension, the more preferable the in-plane retardation Ro can be kept low. The in-plane retardation Ro is preferably less than 20 nm, more preferably less than 10 nm and then less than 5 nm, but most preferably 0 to 1 nm.

In the present invention, the in-plane retardation R
o is an automatic birefringence meter KOBRA-21ADH (manufactured by Oji Scientific Instruments) at a wavelength of 590 nm,
Three-dimensional refractive index measurement is performed, and the obtained refractive indices nx, ny,
It can be calculated from nz. Further, a retardation value Rt in the film thickness direction of 0 to 300 nm is obtained, further preferably 0 to 150 nm, more preferably 0 to 70 nm.
Those of nm are preferably obtained depending on the application.

Ro = (nx−ny) × d Rt = ((nx + ny) / 2−nz) × d The cellulose ester film of the present invention has an angle θ (radian) between the slow axis direction and the film forming direction. The retardation Ro in the in-plane direction has the following relationship and is particularly preferably used as an optical film such as a protective film for a polarizing plate.

P ≦ 1-sin ² (2θ) sin ² (πRo / λ) P = 0.9999 Nx is the refractive index in the slow axis direction in the film plane, and Ny is the refractive index in the fast axis direction in the film plane. The index, Nz is the refractive index in the thickness direction of the film, and d is the film thickness (nm). θ is the angle (radian) between the slow axis direction in the plane of the film and the film forming direction (direct direction of the film), and λ is the above N
The wavelength of light at the time of three-dimensional refractive index measurement for determining x, Ny, Nz, and θ is 590 nm, and π is the circular constant. << Drying Step >> Drying the web while holding the width using a drying device that alternately conveys the web through staggered rolls and / or a tenter device that holds and holds both ends of the web with clips or pins. It is a process to do. It is preferable to keep the conveying tension in the drying step as low as possible so that Ro can be kept low, and it is preferably 190 N / m or less. More preferably 170 N / m
It is preferably below, and more preferably 140 N /
It is preferably m or less, and particularly preferably 100 to 130 N / m. In particular, it is effective to maintain the transport tension below the above value until the amount of residual solvent in the film becomes at least 5% by mass or less.

As a drying means, hot air is generally blown on both sides of the web, but a microwave may be applied instead of the air to heat the web. Drying too rapidly tends to impair the flatness of the finished film. Drying at a high temperature is preferably carried out when the residual solvent is about 8% by mass or less. Throughout the whole, the drying temperature is approximately 40 to 250 ° C.
It is particularly preferable to dry at 40 to 160 ° C.

In the drying step after peeling from the surface of the casting support, the web tends to shrink in the width direction due to the evaporation of the solvent. Shrinkage increases with rapid drying at high temperature.

Drying while suppressing this shrinkage as much as possible is preferable for improving the flatness of the finished film.

From this point of view, for example, JP-A-62-46.
No. 625, a method of drying all or a part of the drying step while holding the width ends of the web with clips or pins in the width direction (called a tenter method), among which a tenter using a clip The method and the pin tenter method using a pin are preferably used.

By drying while holding the width, the in-plane retardation of the obtained film can be reduced. At this time, the stretching ratio in the width direction is x1.00 to x
It is preferably 1.15, and x1.01 to x1.1
Is more preferable. When performing the tenter, the residual solvent amount of the web is 20 to 70% by mass at the start of the tenter.
And the amount of residual solvent in the web is 10
Drying is preferably performed while applying a tenter until the content becomes 5% by mass or less, and more preferably 5% by mass or less.

When the cellulose ester film of the present invention is used as a retardation film, x1.01 to x2.5 in the width direction and / or the film forming direction in the state of containing the residual solvent.
It can also be stretched. In this case, the more preferable draw ratio is x1.15 to x1.6, and Ro is 20 to 10
A 00 nm film can be obtained.

In the step of drying the cellulose ester film, it is preferable to further dry the film peeled from the support so that the residual solvent amount is 0.5% by mass or less, more preferably 0.1% by mass or less. And more preferably 0 to 0.01% by mass or less.

In the film drying step, generally, a roll suspension method or a method of drying while transporting the film by the pin tenter method as described above is adopted. For a liquid crystal display member, 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 hold the width at a place where the residual solvent amount is large immediately after peeling from the support, because the effect of improving the dimensional stability is further exhibited. The means for drying the film is not particularly limited, and generally, hot air, infrared rays, heating rolls, microwaves or the like is used. It is preferable to use hot air for the sake of simplicity. The drying temperature is preferably 40 to 150 ° C., divided into 3 to 5 stages, and gradually increased.
It is more preferable to carry out the treatment at a temperature in the range of ℃ because the dimensional stability is improved.

In the process from immediately after casting through the solution casting film forming method to drying, the atmosphere in the drying device may be air, but in an atmosphere of an inert gas such as nitrogen gas, carbon dioxide gas or argon. You can go.

However, it goes without saying that the danger of the explosion limit of the evaporating solvent in a dry atmosphere must always be taken into consideration. << Winding process >> This is a process of winding the cellulose ester film after the amount of residual solvent in the web is 2% by mass or less. By adjusting the amount of residual solvent to 0.4% by mass or less, good dimensional stability can be obtained. You can get a film.

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

In order to adjust the film thickness, the dope concentration, the amount of liquid to be pumped, the slit gap of the die die, the extrusion pressure of the die, the speed of the casting support, etc. are controlled so as to obtain a desired thickness. Good to do.

As means for making the film thickness uniform, it is preferable that the film thickness detecting means is used to feed back the programmed feedback information to each of the above-mentioned devices for adjustment.

Although the thickness of the cellulose ester film varies depending on the purpose of use, it is usually in the range of 5 to 500 μm as a finished film, and further 10 to 250 μm.
Is preferable, and a range of 10 to 120 μm is particularly used for a liquid crystal image display device film. The cellulose ester film of the present invention is a thin film having a thickness of 10 to 60 μm, but is excellent in moisture permeability and dimensional stability.

The water vapor transmission rate in the present invention means JIS Z
The value is measured at a temperature of 25 ± 0.5 ° C. and a relative humidity of 90 ± 2% under the condition A described in 0208. Moisture permeability is preferably 20~250g / m ² · 24 hours, but is preferably in particular 20~220g / m ² · 24 hours. When the moisture vapor permeability exceeds 250 g / m ² · 24 hours, the durability of the polarizing plate is remarkably reduced, and conversely 20 g.
If it is less than / m ² · 24 hours, it is difficult to dry the solvent such as water used for the adhesive during the production of the polarizing plate and the drying time becomes long, which is not preferable. More preferably 25 to 20
It is 0 g / m ² · 24 hours.

Further, in the cellulose ester film of the present invention, the dimensional stability can be further improved by reducing the mass change at 80 ° C. and 90% RH.

In the cellulose ester film of the present invention, it is more preferable that the mass change rate before and after the heat treatment at 80 ° C. and 90% RH for 48 hours is within ± 2%, whereby the thin film having improved moisture permeability. Although it is a film, a cellulose ester film having an excellent dimensional change rate can be obtained.

The cellulose ester film of the present invention comprises
The dimensional change rate when heat-treated for 48 hours at 80 ° C. and 90% RH was MD direction (film forming direction), TD
The direction (width direction of the film) is preferably within ± 0.5%, more preferably within ± 0.3%, further preferably within ± 0.1%, and further ± 0. It is preferably within 0.05%.

The dimensional change rate in the present invention is a characteristic value representing the dimensional change in the longitudinal and lateral directions of the film under severe conditions of temperature and humidity. Specifically, the film is placed under heating conditions, humidification conditions, and hot humidity conditions to force deterioration,
Measure vertical and horizontal dimensional changes. For example, a film sample to be measured is cut into a size of 150 mm in the width direction × 120 mm in the length direction, and the film surface is cut in two positions at 100 mm intervals in the width direction and the length direction, respectively.
Make a cross-shaped mark with a sharp blade such as a razor. The film is conditioned under an environment of 23 ° C. and 55% RH for 24 hours or more, and the distances L1 between the marks in the width direction and the longitudinal direction before processing are measured with a measuring microscope. Next, the sample was subjected to high temperature and high humidity treatment in an electric constant temperature bath (conditions: 80 ° C., 90% RH).
Left in the environment for 48 hours). Again, the sample is conditioned under the environment of 23 ° C. and 55% RH for 24 hours, and the distance L2 between the marks in the width direction and the length direction after the treatment is measured with a measuring microscope. The rate of change before and after this process is calculated by the following equation.

Dimensional change rate (%) = (L2−L1) / L1 × 100 In the formula, L1 represents the distance between marks before treatment, and L2 represents the distance between marks after treatment.

That is, a desired dimensional change rate can be measured by setting the positions of the marks to be applied in the longitudinal direction and the width direction of the film.

The dimensional change rate when treated at 105 ° C. for 5 hours is preferably within ± 0.5% in both MD and TD directions, more preferably within ± 0.3%, and further within ± 0.3%. It is preferably within 0.1%, and further ±
It is preferably within 0.05%.

The cellulose ester film of the present invention has a tensile strength of 90 to 170 N / mm ² in both MD and TD.
Is preferable, and particularly 120 to 160 N / mm ²
Is preferred.

The water content is preferably 0.1 to 5%,
0.3 to 4% is more preferable, and 0.5 to 2% is even more preferable.

The cellulose ester film of the present invention comprises
The transmittance is preferably 90% or more, more preferably 92% or more, further preferably 93% or more. Further, the haze is preferably 0.5% or less,
In particular, it is preferably 0.1% or less, more preferably 0%.

In the cellulose ester film of the present invention, the curl value preferably has a small absolute value, and the deformation direction may be the + direction or the-direction. The absolute curl value is preferably 30 or less, more preferably 2
It is 0 or less, and particularly preferably 10 or less.
The curl value is represented by the radius of curvature (1 / m).

The method for producing the cellulose ester film of the present invention by the solution casting film forming method will be described in more detail with reference to the drawings.

FIG. 1 is a schematic diagram showing a preferred example of a solution casting film forming method for a film. FIG. 1 (a) is a schematic diagram in the case of drying in a roll conveying / drying process after casting. Figure 1
(B) is a schematic diagram in the case where after casting, it is dried in a roll conveying / drying step and then dried in a tenter conveying / drying step. FIG. 1 (c) is a schematic diagram in the case where after casting, it is dried in a tenter conveying / drying step and then dried in a roll conveying / drying step. FIG. 1D is a schematic diagram in the case where after casting, it is dried in a roll carrying / drying process, then dried in a tenter carrying / drying process, and then dried in a roll carrying / drying process.

In the present invention, the step including the tenter transporting / drying step and the roll transporting / drying step means that the film peeled from the support is dried and wound at any point. A process having a tenter conveyance / drying step and a roll conveyance / drying step for adjusting the expansion / contraction rate. The tenter transport / drying process is a process of simultaneously drying while transporting with a tenter transport device and adjusting the drying expansion / contraction rate.The roll transport / drying process is simultaneous drying while transporting with a roll transport device, and drying expansion / contraction. The process of adjusting the rate.

In FIG. 1, reference numeral 1 denotes a support which runs endlessly. Mirror-like metal strips are used as the support. Reference numeral 2 denotes a die for casting a dope prepared by dissolving a cellulose ester resin in a solvent on the support 1. Reference numeral 3 denotes a peeling point for peeling the film on which the dope solidified on the support 1 is solidified, and 4 denotes the peeled film. 5 indicates a tenter conveying / drying process, 51 indicates an exhaust port, 5
2 shows a dry air intake. The exhaust port 51 and the dry air intake port 52 may be reversed. Reference numeral 6 indicates a tension cutting means. Examples of the tension cutting means include a nip roll and a suction roll. The tension cutting means may be provided between the steps.

Reference numeral 8 represents a roll conveying / drying process, 81 represents a drying box, 82 represents an exhaust port, and 83 represents a dry air intake port. The exhaust port 82 and the dry air intake port 83
May be reversed. 84 indicates an upper conveyance roll,
Reference numeral 85 denotes a lower conveyance roll. The transport roll 84,
The upper and lower parts 85 are one set, and are composed of a plurality of sets. Reference numeral 7 represents a rolled film.

In the step shown in FIG. 1D, the roll transfer / drying step before the tenter transfer / drying step 5 is referred to as a first roll transfer / drying step, and the roll transfer after the tenter transfer / drying step 5 is performed. -The drying process is called the second roll conveyance / drying process. It should be noted that a cooling step not shown in FIGS. 1A to 1D may be provided as necessary before winding.

In the present invention, the cellulose ester film may be produced by any of the above solution casting film forming methods.

The cellulose ester film of the present invention comprises
From the viewpoint of good moisture permeability, dimensional stability, etc., it is preferably used for a liquid crystal display member, specifically, a protective film for a polarizing plate.
In particular, the cellulose ester film of the present invention is preferably used in a protective film for a polarizing plate, which has severe requirements for both moisture permeability and dimensional stability.

The polarizing plate according to the present invention can be manufactured by a general method. For example, a method in which an optical film or a cellulose ester film is subjected to an alkali saponification treatment, a polyvinyl alcohol film is immersed in an iodine solution, and stretched on both surfaces of a polarizing film produced using a fully saponified polyvinyl alcohol aqueous solution is used. is there. The alkali saponification treatment refers to a treatment in which the cellulose ester film is immersed in a high temperature strong alkaline solution in order to improve the wettability of the water-based adhesive and improve the adhesiveness.

The cellulose ester film of the present invention comprises a hard coat layer, an antiglare layer, an antireflection layer, an antifouling layer, an antistatic layer, a conductive layer, an optically anisotropic layer, a liquid crystal layer, an alignment layer, an adhesive layer,
Various functional layers such as an adhesive layer and an undercoat layer can be provided. These functional layers can be provided by a method such as coating or vapor deposition, sputtering, plasma CVD, atmospheric pressure plasma treatment and the like.

The polarizing plate thus obtained is provided on one side or both sides of a liquid crystal cell, and by using this, a display device of the present invention, such as a liquid crystal display device or an organic EL display device, can be obtained.

By using the protective film for a polarizing plate comprising the cellulose ester film of the present invention, it is possible to provide a polarizing plate excellent in durability, dimensional stability and optical isotropy as well as thinning. Further, the display device using the polarizing plate or the retardation film of the present invention can maintain stable display performance for a long period of time.

The cellulose ester film of the present invention can be used as a base material for an antireflection film or an optical compensation film.

[0134]

EXAMPLES The present invention will now be described in detail with reference to examples, but the present invention is not limited thereto.

Example 1 1. Preparation of Dope The composition of dope A shown below was placed in a closed container and completely dissolved while maintaining the temperature and stirring at 80 ° C. under pressure.
Fine particles of AEROSIL 200V (manufactured by Nippon Aerosil Co., Ltd.) were mixed and dispersed with a part of ethanol to be added in advance, and this was put in a closed container. After cooling this to a casting temperature and allowing it to stand for defoaming operation, the solution was added to Azumi Filter Paper No. Azumi Filter Paper No. It filtered using 244 and the dope A was obtained. Dope B in the same way
~ G was prepared. (Measurement of degree of substitution of cellulose ester) ASTM-D8
17-96 according to the method specified. Dope A 1-14 (compound having a structure represented by the general formula (1)) 15 kg UV absorber UV-1 0.5 kg UV-2 0.5 kg UV-5 0.5 kg Fine particles AEROSIL 200V (Japan Aerosil Co., Ltd.) Made) 0.05 kg acetyl cellulose (substitution degree 2.7) 83.5 kg methylene chloride 290 L ethanol 25 L-dope B 1-30 (compound having a structure represented by the general formula (1)) 15 kg UV absorber UV-10 0.5 kg UV-2 0.5 kg UV-5 0.5 kg Fine particles AEROSIL200V (manufactured by Nippon Aerosil Co., Ltd.) 0.05 kg Cellulose acetate propionate (acetyl substitution degree 2.0 propionyl substitution degree 0.8) 83.5 kg Methylene Chloride 265 L Ethanol 50 L Dope C 1 12 (Compound having the structure represented by the general formula (1)) 15 kg Ultraviolet absorber UV-1 0.5 kg UV-2 0.5 kg UV-5 0.5 kg Fine particles AEROSIL 200V (manufactured by Nippon Aerosil Co., Ltd.) 0.05 kg Cellulose acetate propionate (acetyl substitution degree 2.0 propionyl substitution degree 0.8) 83.5 kg methyl acetate 210 L ethanol 90 L-dope D 1-16 (compound having the structure represented by the general formula (1)) 15 kg UV absorption Agent UV-1 0.5 kg UV-2 0.5 kg UV-5 0.5 kg Fine particles AEROSIL 200V (manufactured by Nippon Aerosil Co., Ltd.) 0.05 kg Triacetyl cellulose (substitution degree 2.88) 83.5 kg Methylene chloride 290 L Ethanol 25 L Dope E 1-16 (general formula ( Compound having structure represented by 1) 15 kg Ultraviolet absorber UV-6 1.5 kg Fine particles AEROSIL 200V (manufactured by Nippon Aerosil Co., Ltd.) 0.05 kg Triacetyl cellulose (substitution degree 2.88) 83.5 kg Methylene chloride 290L ethanol 25 L-Dope F Comparative compound 15 kg Ultraviolet absorber UV-1 0.5 kg UV-2 0.5 kg UV-5 0.5 kg Fine particles AEROSIL 200V (manufactured by Nippon Aerosil Co., Ltd.) 0.05 kg Triacetyl cellulose (substitution degree 2.88) ) 83.5 kg Methylene chloride 290 L Ethanol 25 L Dope G Triphenyl phosphate (TPP) 15 kg UV absorber UV-1 0.5 kg UV-2 0.5 kg UV-5 0.5 kg Fine particles AEROSIL 200V (day) Aerosil Co., Ltd.) 0.05 kg triacetyl cellulose (degree of substitution 2.88) 83.5Kg of methylene chloride 290L ethanol 25L

[0136]

[Chemical 9]

2. Production of Cellulose Ester Film Using the apparatus shown in FIG. 1D, a cellulose ester film was produced according to the following steps.

Using the dope A whose temperature was adjusted to 30 ° C., the dope A was uniformly cast on an endless stainless belt.
The casting part of the endless stainless belt is 35 ° C from the back
Heated with warm water. After casting, the dope film on the support is coated with 45
It was dried by applying warm air of ℃, peeled 60 seconds after casting, and dried while being conveyed by many rolls. The temperature of the endless stainless belt at the peeling portion was 10 ° C.
The peeled film was conveyed in the first drying zone set at 50 ° C. for 1 minute, then in the second drying zone set at 90 ° C. for 30 seconds, and then the third drying set at 115 ° C. It was transported in the zone for 10 minutes and dried. In the second drying zone, stretching was performed 1.05 times in the width direction using a tenter device. After drying, it was wound into a roll to obtain a cellulose ester film 1 having a winding length of 2500 m and a film thickness of 40 μm. The residual solvent amount at the time of winding was less than 0.01%.

Cellulose ester films 2 to 7 were produced in the same manner except that the dope was changed to B to G.
It was shown to.

The cellulose ester film obtained was evaluated as follows, and the results are also shown in Table 1. << Characteristic Evaluation of Cellulose Ester Film >> Measurement of Retardation Value Ro For each cellulose ester film, a three-dimensional refractive index was measured at a wavelength of 590 nm using an automatic birefringence meter KOBRA 21ADH (manufactured by Oji Scientific Instruments). And then
The refractive indexes Nx, Ny, and Nz were measured, and the retardation value Ro was calculated by the following formula.

Ro value = (Nx−Ny) × d Nx: Maximum refractive index Ny in the plane of the film Ny: Refractive index of the film in the in-plane direction perpendicular to Nx d: Film thickness (nm) Change rate measurement Each cellulose ester film, width direction 150mm
C. A size of 120 mm is cut in the longitudinal direction, and a cross-shaped mark is made on the film surface with a sharp blade such as a razor at two locations at 100 mm intervals in the width direction and the longitudinal direction. The film is conditioned under an environment of 23 ° C. and 55% RH for 24 hours or more, and the distances L1 between the marks in the width direction and the longitudinal direction before processing are measured with a measuring microscope. Next, the film was subjected to high temperature and high humidity treatment for 48 hours in an electric constant temperature bath under the environment of 80 ° C. and 90% RH. Next, the high-temperature and high-humidity treated sample was conditioned again under the environment of 23 ° C. and 55% RH for 24 hours, and the distance L2 between the marks in the width direction and the longitudinal direction after the treatment was measured with a measuring microscope. The rate of change before and after this treatment was determined by the following formula to calculate the rate of dimensional change.

Dimensional change rate (%) = (L2-L1) / L1 × 100 L1: Distance between marks before treatment L2: Distance between marks after treatment / water vapor permeability Temperature 25 ± according to condition A described in JIS Z 0208
The moisture permeability of each cellulose ester film was measured at 0.5 ° C. and a relative humidity of 90 ± 2%, and calculated as the amount of water (g) that evaporates in 24 hours per 1 m ^{2 of} area. -Retaining property Each cellulose ester film is cut into a size of 10 cm x 10 cm, and is cut under an atmosphere of 23 ° C and 55% RH for 24 hours.
The mass after standing for a time was measured, and the mixture was treated at 80 ° C. and 90% RH for 48 hours. The surface of the sample after the treatment was lightly wiped, the mass after standing for 1 day at 23 ° C. and 55% RH was measured, and the retention was calculated by the following method.

Retention property (mass%) = {(mass before treatment−mass after treatment) / mass before treatment} × 100. Each UV resistant cellulose ester film has an eye super UV tester (manufactured by Iwasaki Electric Co., Ltd.). ) Was irradiated with an ultraviolet ray of 1500 mW / cm ² for 96 hours using a metal halide lamp. The change in color of the film after irradiation was evaluated, and whether or not the film was broken when folded in two was evaluated.

∘: No change in tint was observed, it was not broken by bending ×: Coloring was observed, and it was broken by bending. Curl value measurement Each cellulose ester film was placed at 23 ° C. and 55% RH environment. After standing for 48 hours, the film is cut in a longitudinal direction (film forming direction) of 2 mm and a width direction of 50 mm. Furthermore, the film piece was conditioned at 23 ± 2 ° C. and 55% RH for 24 hours, and the curvature scale was used to confirm the radius of curvature having a curve that matches the film.
/ M) was defined as the curl value of the film. -Foreign matter failure It was determined by counting the number of agglomerates having a diameter of 30 µm or more present in 1 m ^{2 of} each cellulose ester film.

[0145]

[Table 1]

As is clear from Table 1, the cellulose ester film of the present invention was a thin film, but it was confirmed that it has a low moisture permeability, an excellent retaining property and an excellent dimensional stability. It was also confirmed that a film having a low in-plane retardation Ro was obtained. On the contrary,
It was confirmed that the cellulose ester film 6 of the comparative example had poor retention and dimensional stability. Also, it was confirmed that the ultraviolet resistance was extremely poor, that it was colored by ultraviolet irradiation and cracked by bending. It was confirmed that the cellulose ester film 7 of the comparative example was inferior in dimensional stability because not only the moisture permeability could not be made sufficiently low, but also the retention property was poor.

Cellulose Ester Film 1 of the Present Invention 1
No coloring was observed in any of No. 5 and no cracking was observed when bent, but the cellulose ester film 6 of the comparative example was observed to be colored as described above, and it was confirmed that the cellulose ester film 6 was cracked by bending, and was deteriorated by UV irradiation. It was confirmed that it was progressing.

Cellulose ester film 1 of the present invention to which the compound having the structure represented by the general formula (1) is added
A polarizing plate was prepared using No. 5, and the durability was evaluated. As a result, excellent durability was shown. On the other hand, it was confirmed that the polarizing plates using the cellulose ester films 6 and 7 of Comparative Examples were inferior in durability.

When the polarizing plate of the present invention was used for a display device, the obtained display device was able to maintain the initial contrast for a long period of time.

Example 2 Using the cellulose ester film produced in Example 1, a polarizing plate was produced and evaluated according to the method described below.

According to the following method, a polarizing plate 1 of the present invention using the cellulose ester film 1 as a protective film for polarizing plate was prepared. 1. Production of Polarizing Film A polyvinyl alcohol film having a thickness of 120 μm was uniaxially stretched (temperature: 110 ° C., stretch ratio: 5 times). This was immersed in an aqueous solution containing 0.075 g of iodine, 5 g of potassium iodide and 100 g of water for 60 seconds, and then immersed in an aqueous solution of 6 g of potassium iodide, 7.5 g of boric acid and 100 g of water at 68 ° C. This was washed with water and dried to obtain a polarizing film. 2. Production of Polarizing Plate Next, a polarizing film was produced by laminating a polarizing film and a protective film for polarizing plate according to the following steps 1 to 5. Step 1: The cellulose ester film 1 produced in Example 1 is cut into two pieces each having a size of 30 cm in the longitudinal direction and 18 cm in the width direction, immersed in a 2 mol / L sodium hydroxide solution at 60 ° C. for 90 seconds, and then washed with water, It was made to dry and the protective film sample 1 was produced. Step 2: The polarizing film cut into a size of 30 cm in the longitudinal direction and 18 cm in the width direction was immersed in a polyvinyl alcohol adhesive tank having a solid content of 2% by mass for 1 to 2 seconds. Step 3: Excessive adhesive attached to the polarizing film in Step 2 is lightly removed, and the protective film sample 1 prepared in Step 1 is removed.
And the same protective film sample 1 were further laminated and arranged so as to be in contact with the adhesive. Step 4: Excess adhesive and air bubbles were removed from the ends of the laminate of the polarizing film laminated in step 3 and the protective film sample 1 with a hand roller, and they were bonded together. The pressure of the hand roller is 20 to 30 N / cm ² , the roller speed is about 2 m / mi.
It was set to n. Step 5: The sample prepared in Step 4 was dried in an oven at 80 ° C. for 2 minutes to prepare a polarizing plate 1 of the invention.

Then, in the production of the polarizing plate 1, polarizing plates 2 to 7 were produced in the same manner except that the cellulose ester films 2 to 7 produced in Example 1 were used in place of the protective film sample 1. .

Each of the polarizing plates produced as described above was subjected to a high temperature humidification treatment in an atmosphere of 80 ° C. and 90% RH for 50 hours, and then the transmittance and the degree of polarization were measured according to the following methods. . -Measurement of Transmittance Transmittance T was calculated by the following mathematical formula 1 from the spectral transmittance τ (λ) of each polarizing plate obtained every 10 nm in the wavelength region of 400 to 700 nm. In the formula, P (λ) is the standard light (C
The spectral distribution of the light source), y (λ), is a color matching function based on the 2-degree visual field X, Y, Z system. Spectral transmittance τ (λ) is Shimadzu UV
It was measured using a 2200 spectrophotometer.

[0154]

[Equation 1]

Polarization Degree Measurement The transmittance when two polarizing plates, which are measurement samples, are stacked so that the orientation directions of the respective polarizers are the same, the parallel transmittance Tp and the two polarizing plates are The transmittance in the case where the respective polarizers were superposed so as to be orthogonal to each other was taken as the orthogonal transmittance Tc, and the polarization degree P was calculated by the following mathematical expression 2.

[0156]

[Equation 2]

Polarizing plate durability test: Two polarizing plates of 10 cm × 10 cm were subjected to high temperature and high humidity treatment (conditions: 80 ° C., 90% RH, 50 hours), and the vertical or horizontal center line portion when they were orthogonalized. The length of the white spot on the edge of the larger one was measured and judged to be the following level. The white spots on the edges can be visually determined because the edge portions of the polarizing plate, which are orthogonal to each other and do not pass light, are in a state of allowing light to pass.
In the state of the polarizing plate, the display of the edge portion becomes invisible, resulting in a failure. The evaluation was performed according to the following criteria.

If Δ or more, the level is practically no problem as a polarizing plate, x is problematic as a polarizing plate, and xx cannot be used as a polarizing plate.

∘: less than 5% of white spots on edges ○: 5% to less than 10% of white spots on edges Δ: 10% to less than 20% of white spots on edges × 20% or more and less than 50% XX ... Each of the polarizing plates 1 to 5 of the present invention has a transmittance of 45% as a result of measuring each of the polarizing plates with a green white defect of 50% or more. Below, polarization degree 9
It was 8% or more. On the other hand, a polarizing plate 6 as a comparative example
Had a transmittance of 52% and a polarization degree of 85%. Further, in the polarizing plate durability test, the polarizing plates 1 to 3 of the present invention were ⊚ and the polarizing plates 4 to 5 of the present invention were ∘.
And 7 were results of x. From the above, it was found that the polarizing plate of the present invention had apparently excellent durability as compared with the comparative example.

Example 3 Commercially available liquid crystal display panel (NEC color liquid crystal display MultiSync LCD1525J Model name
The polarizing plate on the outermost surface of (LA-1529HM) was carefully peeled off, and the polarizing plates 1 to 5 of the present invention and the polarizing plates 6 and 7 of Comparative Example produced in Example 2 in which the polarization directions were matched were attached to the polarizing plate. As a result of visually evaluating the contrast of each liquid crystal display panel, the liquid crystal display panel using the polarizing plate of the present invention has a high contrast over a long period of time with respect to the liquid crystal display panel using the polarizing plate of the comparative example. Was confirmed to be maintained.

Example 4 1. Preparation of Dope <Preparation of Silicon Oxide Dispersion Liquid> Aerosil R972V (manufactured by Nippon Aerosil Co., Ltd.) 2 kg Ethanol 18 kg After stirring and mixing the above with a dissolver for 30 minutes, dispersion was performed using a Manton-Gaulin type high-pressure dispersion device. <Preparation of Additive Liquid> Cellulose triacetate (acetyl substitution degree 2.88) 6 kg Methylene chloride 140 kg 5-chloro-2- (3,5-di-sec-butyl-2-hydroxyphenyl) -2H-benzotriazole 5 kg Tinuvin 171 (2- (2H-benzotriazol-2-yl) -6- (straight chain and side chain dodecyl) -4-methylphenol) Ciba Specialty Chemicals Co., Ltd. 1 kg or more is charged into a closed container and heated, It was completely dissolved and filtered with stirring. 13 kg of the above silicon oxide dispersion was added to this with stirring, and the mixture was further stirred for 30 minutes and then filtered to prepare an additive liquid. The silicon oxide fine particles had an average secondary particle diameter of 0.4 μm in the film. <Preparation of Dope Stock Solution> Methylene chloride 440 kg Ethanol 38 kg Cellulose triacetate (acetyl substitution degree 2.88) 100 kg 1-14 (compound having the structure represented by the general formula (1)) 16 kg The above solvent was charged into a closed container, The remaining ingredients were added while stirring, and the mixture was completely dissolved and mixed while heating and stirring. The dope was cooled to a casting temperature and left standing overnight, and after defoaming operation, the solution was made into Azumi filter paper N manufactured by Azumi filter paper N.
o. The solution was filtered twice using 244 to obtain a dope stock solution. Furthermore, the dope H was prepared by adding the additive solution at a rate of 3 kg per 100 kg of the above dope stock solution, thoroughly mixing with an in-line mixer (Toray static type in-tube mixer Hi-Mixer, SWJ), and filtering.

Using the apparatus shown in FIG. 1 (d), a cellulose ester film was prepared according to the following steps.

Using Dope H whose temperature was adjusted to 33 ° C., it was uniformly cast on an endless stainless belt.
The casting part of the endless stainless belt is 35 ° C from the back
Heated with warm water. After casting, the dope film on the support is coated with 45
It was dried by applying warm air of ℃, peeled 50 seconds after casting, and dried while being conveyed by a number of rolls. The temperature of the endless stainless belt at the peeling portion was 10 ° C.
The peeled film is conveyed in the first drying zone set at 60 ° C. for 1 minute, then in the second drying zone set at 80 ° C. for 30 seconds, and then the third drying set at 125 ° C. It was transported in the zone for 10 minutes and dried. In the second drying zone, when the residual solvent amount was 10% by mass, stretching was carried out 1.06 times in the width direction by a tenter device. After drying, roll length 250
A cellulose ester film having a thickness of 0 m and a thickness of 50 μm was obtained. The residual solvent amount at the time of winding was less than 0.01%.

When evaluated in the same manner as in Example 1, the moisture permeability was 178 g / m ² · 24 hr, and the dimensional change rate was −0.
It was 05% and the UV resistance was ⊚. Also, Ro is 0
nm film. A polarizing plate was prepared by using this film by the method described in Example 2. A durability test was conducted on the obtained polarizing plate in the same manner as in Example 2.
As a result, the level was ◎. As a result of visual evaluation using a liquid crystal display panel as in Example 3, it was confirmed that high contrast was maintained for a long period of time.

[0165]

EFFECTS OF THE INVENTION According to the present invention, it is possible to provide a cellulose ester film having good moisture permeability and excellent dimensional stability even though it is a thin film. Further, it was possible to provide a manufacturing method thereof, and a polarizing plate and a display device using the cellulose ester film of the present invention.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a solution casting film forming method of a film.

[Explanation of symbols]

1 Mirror-like strip metal casting support 2 dice 4 Cellulose ester film 5 Tenter transfer and drying process 6 Tension cutting means 8-roll transfer / drying process 84 Upper transport roll 85 Lower transport roll

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) // B29K 1:00 B29K 1:00 B29L 7:00 B29L 7:00 F term (reference) 2H049 BA02 BA06 BB13 BB33 BB49 BC09 BC10 BC22 4F071 AA09 AB26 AC10 AD02 AE05 AE17 AF08Y AF35 AH16 BA02 BC10 BC12 4F205 AA01J AB14 AB17 AH73 AR12 AR20 GA07 GB02 GC06 GE24 GF24 4J002 AB021 DJ018 EH116 EH126 EH136 EH146 FD

Claims (17)

[Claims] 1. A cellulose ester film comprising 1 to 30% by mass of a compound having a structure represented by the following general formula (1). [Chemical 1] Y is a divalent organic group, and at least one of the aromatic ring and the cyclohexane ring may have a substituent. 2. The cellulose ester film according to claim 1, wherein Y in the general formula (1) is a compound containing an ester bond. 3. The cellulose ester film according to claim 1, which contains an ultraviolet absorber having a distribution coefficient of 8.5 or more. 4. The cellulose ester film according to claim 1, which contains fine particles of silicon oxide. 5. The cellulose ester film according to claim 1, which contains a cellulose ester having a total substitution degree of 2.55 to 2.85. 6. A film having a thickness of 10 to 60 μm and a water vapor transmission rate.
20-220g / m ²・ Characterized by 24 hours
The cellulose ester according to any one of claims 1 to 5.
the film. 7. A film having a thickness of 10 to 60 μm and a water vapor transmission rate.
20-220g / m ²・ 24 hours, 80 ° C, 9
The mass change rate before and after heat treatment at 0% RH for 48 hours
It is within ± 2%, any of claims 1 to 6 characterized in that
The cellulose ester film according to item 1. 8. A method for producing a cellulose ester film by a solution casting film forming method, in which a cellulose ester solution containing a compound having a structure represented by the general formula (1) is cast on a support, A method for producing a cellulose ester film, which comprises drying for 90 seconds on a support, peeling, and further drying. 9. The cellulose ester film according to claim 8, wherein the content of the compound having the structure represented by the general formula (1) in the obtained cellulose ester film is 1 to 30% by mass. Production method. 10. The method for producing a cellulose ester film according to claim 8, wherein Y in the general formula (1) is a compound containing an ester bond. 11. The method for producing a cellulose ester film according to claim 8, wherein the cellulose ester solution contains an ultraviolet absorber having a partition coefficient of 8.5 or more. 12. The method for producing a cellulose ester film according to claim 8, wherein the cellulose ester solution contains silicon oxide fine particles. 13. The method for producing a cellulose ester film according to claim 8, wherein the cellulose ester solution contains a cellulose ester having a total substitution degree of 2.55 to 2.85. 14. The obtained cellulose ester film has a film thickness of 10 to 60 μm and a water vapor transmission rate of 20 to 22.
It is 0 g / m ² · 24 hr, and the mass change rate before and after the heat treatment at 80 ° C. and 90% RH for 48 hours is within ± 2%. 14. A method for producing the described cellulose ester film. 15. The method for producing a cellulose ester film according to any one of claims 8 to 14, wherein the cellulose ester solution contains methyl acetate. 16. A polarizing plate comprising the cellulose ester film according to any one of claims 1 to 7. 17. A display device using the polarizing plate according to claim 16.