JP2001055402A - Cellulose ester and film for protecting polarizing plate by using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject film excellent in adhesion to a polarizer and useful for protecting a polarizing plate by specifying the tensile modulus and the content of a plasticizer. SOLUTION: This film has >=340 kgf/mm2 tensile modulus and 1-20 wt.% plasticizer content. Preferably, the film has <=1% haze, <=8% water content and 20-120 &mu;m thickness, and contains polysaccharides (especially chitin or chitosan) except the cellulose, a cross-linking agent having a vinylsulfone group or the like, especially a metallic compound and an ultraviolet absorber. The objective film can preferably be obtained through a step for dissolving a cellulose ester, especially a cellulose ester of a lower fatty acid in a step for raising the temperature after cooling an organic solvent to (-100)-(-10) deg.C, to 0-120 deg.C, and coating the obtained solution of the cellulose ester dissolved in the organic solvent on an endless belt or on a drum.

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, and more particularly, to a cellulose ester film for protecting a polarizing plate having excellent adhesion to a polarizer.

[0002]

2. Description of the Related Art In general, a polarizing plate used for forming a liquid crystal image display device usually comprises a polarizer made of uniaxially stretched polyvinyl alcohol colored with a dichroic dye having a polarizing function and a polarizing plate made of triacetyl cellulose. It is manufactured by laminating two plate protective films from both sides. In this case, in order to enhance the adhesion between the triacetyl cellulose film and the polarizing film, immersion and saponification in an alkaline aqueous solution such as caustic soda are performed before the triacetyl cellulose film is bonded.

In recent years, liquid crystal image display devices are frequently used externally as represented by car navigation systems and mobile phone display devices, and high durability under various environments is strongly demanded. However, the conventional polarizing plate has a drawback that the polarizing plate is torn in a part of the process of attaching the polarizing plate to the glass substrate.

The present inventors have conducted intensive studies and found that the cause was insufficient adhesion between the polarizer and the protective film for a polarizing plate.

[0005]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a cellulose ester film for protecting a polarizing plate having excellent adhesion to a polarizer.

[0006]

SUMMARY OF THE INVENTION The above objects of the present invention are as follows.
This has been achieved by the following configuration.

[0007] 1. Tensile elastic modulus is 340kgf / m
cellulose ester film, characterized in that in m ² or more and a plasticizer content of from 1 to 20 wt%.

[0008] 2. A cellulose ester film comprising a polysaccharide other than cellulose.

3. A cellulose ester film crosslinked by a crosslinking agent.

[0010] 4. 4. The cellulose ester film according to the above item 3, wherein the crosslinking agent is a metal compound.

5. The cross-linking agent has at least one group selected from a vinyl sulfone group, an epoxy group, an isocyanate group, a blocked isocyanate group, an active halogen group, an aldehyde group, an ethyleneimine group, and an active ester-forming group. 4. The cellulose ester film according to claim 3.

6. A cellulose ester film containing a polysaccharide other than cellulose and being crosslinked with a crosslinking agent.

7. 7. The cellulose ester film according to the above item 2 or 6, wherein the polysaccharide is chitin or chitosan.

8. The cellulose ester film according to any one of Items 1 to 7, wherein the haze is 1% or less.

9. Item 9. The cellulose ester film according to any one of Items 1 to 8, wherein the moisture content is 8% or less.

10. 10. The cellulose ester film according to any one of the items 1 to 9, further comprising an ultraviolet absorber.

11. The cellulose ester is dissolved in the process of cooling the organic solvent to −100 to −10 ° C. and then heating to 0 to 120 ° C., and applying the obtained cellulose ester organic solvent solution on an endless belt or a drum. Characterized in that it is manufactured through a process of
11. The cellulose ester film according to any one of items 10 to 10.

[12] Wherein the cellulose ester is a cellulose lower fatty acid ester;
Item 2. The cellulose ester film according to any one of items 1.

13. The cellulose ester film according to any one of Items 1 to 12, wherein the film thickness is 20 to 120 μm.

[14] 14. The cellulose ester film according to any one of the above items 1 to 13, which is a protective film for a polarizing plate.

Hereinafter, the present invention will be described in detail.

The cellulose ester film according to the present invention will be described.

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

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 and the like are preferred examples of the lower fatty acid ester of cellulose. No.

Further, in addition to the above, JP-A-10-458
04, 08-231761, U.S. Pat. No. 2,31
Mixed fatty acid esters such as cellulose acetate propionate and cellulose acetate butyrate described in JP-A-9,052 and the like can be used.

In the above description, a particularly preferred lower fatty acid ester of cellulose is cellulose triacetate.

Further, from the viewpoint of the base strength, a polymerization degree of 250 to 400 and an amount of bound acetic acid of from 54 to 62.5% are particularly preferably used.
62.5% cellulose triacetate.

As the cellulose triacetate, either cellulose triacetate synthesized from cotton linter or cellulose triacetate synthesized from wood pulp can be used alone or in combination. If the releasability from the belt or drum becomes a problem, it is preferable to use a large amount of cellulose triacetate synthesized from cotton linter having good releasability from the belt or drum because the productivity is high. When a mixture of cellulose triacetate synthesized from wood pulp is used, the ratio of cellulose triacetate synthesized from cotton linter is 40% by weight or more,
It is preferable because the effect of the releasability becomes remarkable, more preferably 60% by weight or more, and it is most preferable to use it alone.

The polarizing plate used in the present invention can be manufactured by a general method. For example, there is a method in which a cellulose ester film is subjected to alkali treatment, and immersed and drawn in an iodine solution, and bonded to both surfaces of the polarizing film using a completely saponified polyvinyl alcohol aqueous solution. 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 aqueous adhesive at this time and improve the adhesiveness.

The polarizing film, which is a main component of the polarizing plate used in the present invention, is an element that allows only light having a polarization plane in a certain direction to pass therethrough. A currently known representative polarizing film is a polyvinyl alcohol-based polarizing film. Polarizing films include polyvinyl alcohol-based films dyed with iodine and 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, is laminated on the surface of the polarizing film to form a polarizing plate.

However, it has been found that the conventional polarizing plate has a serious disadvantage that the polarizing plate is torn in a part of the step of attaching the polarizing plate to the substrate. The present inventors have found that the cause is insufficient adhesion between the polarizer and the protective film for a polarizing plate. As a result of intensive studies, the present inventors have found that the drawback of tearing between the polarizer and the polarizing plate is improved by making the tensile elastic modulus of the polarizer and the protective film for the polarizing plate close to each other.

As a method of adjusting the tensile elastic modulus,
A method of performing a strong heat treatment at the final stage of the production process, mixing a polymer having a large tensile elasticity, and a method of crosslinking are exemplified.

The tensile modulus is 23 ° C. and relative humidity 55%.
Was measured with a tensile tester and determined from the SS curve. The tensile modulus is 340 to 400 Kgf / mm ²
And more preferably 345-395 Kgf / m.
m ² , particularly preferably 350 to 390 Kgf / mm ² .

The polymer in the present invention includes polysaccharides from the viewpoint of compatibility with the cellulose ester film, and chitin and chitosan are particularly preferable.

The chitin of the present invention is produced mainly from crab shells. In general, the crab shells that have been pulverized and washed are treated with dilute hydrochloric acid to remove inorganic substances, then treated with dilute caustic soda to remove organic substances, and chitin is obtained as an insoluble residue. The chitosan in the present invention is obtained by deacetylation of chitin. Deacetylation of chitin is performed by treating chitin with about 50% hot caustic soda solution. Usually, the degree of deacetylation of chitosan is from 0 to 100%, preferably from 50 to 9%.
0%. What has become soluble in dilute acetic acid (1%) even if it is not 100% deacetylated is generally called chitosan and can be used in the present invention.

In the present invention, film strength and solubility can be controlled by using chitosan as a chitosan derivative. Derivatives include acetylated, alkylated, carboxyalkylated, sulfonated, alkylsulfonated and the like.

In the present invention, the preferred molecular weight Mw of the chitosan or chitosan derivative is from 10,000 to 5
00,000.

The addition amount of chitin and chitosan can be arbitrarily selected, but is preferably 0.5 to 50% by weight, more preferably 1 to 50% by weight, based on the cellulose ester film.
-20% by weight.

The cellulose ester film according to the present invention contains a plasticizer. There is no particular limitation on the plasticizer that can be used, but in the case of phosphate esters, triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate, tributyl phosphate, etc. Phthalates are diethyl phthalate, dimethoxyethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate, etc. It is preferable to use ethyl glycolate, methylphthalylethyl glycolate, butylphthalylbutyl glycolate or the like alone or in combination. There.

The amount of these plasticizers to be used is 1 to 1 with respect to the cellulose ester in terms of film performance, processability and the like.
20% by weight is preferred. For a liquid crystal display member, from the viewpoint of dimensional stability, 2 to 10% by weight is preferable, and particularly preferably 3 to 7% by weight.

The term "workability" as used herein refers to slitting or punching of a base film or a liquid crystal display member. If the workability is poor, the cut surface becomes saw-toothed and chips are generated, and the chips adhere to the product. It is not preferable because it becomes a defect.

If necessary, fine particles such as silicon oxide may be added to the cellulose ester film used in the present invention as a matting agent. It is preferable that the fine particles are surface-treated with an organic substance because the haze of the film can be reduced.

The haze of the film is at most 1%, preferably at most 0.8%.

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.
To 50 nm, more preferably 7 to 14 nm.
It is.

As fine particles of silicon oxide, AEROSIL 200, 300, R972, manufactured by Aerosil Co., Ltd .;
R974, R202, R812, OX50, TT600
And preferably AEROSIL R97.
2, R974, R202, R812 and the like.

The cellulose ester film of the invention according to claim 3 contains a crosslinking agent.

As the crosslinking agent, metal oxides such as aluminum oxide, boric acid and cobalt oxide are preferred. A compound having a vinyl sulfone group such as meta-xylene vinyl sulfonic acid; a compound having an epoxy group such as bisphenol glycidyl ether; a compound having an isocyanate group; a compound having a blocked isocyanate group; Chlortriazine, 2-
Compounds having an active halogen group such as sodium oxy-4,6-dichlorotriazine, compounds having an aldehyde group such as formaldehyde and glyoxal, mucochloric acid, tetramethylene-1,4-bis (ethyleneurea), hexamethylene-1 And compounds having at least one group selected from compounds having an ethyleneimine group and compounds having an active ester-forming group, such as 2,6-bis (ethyleneurea). You may use together.

Of these, a metal oxide, a compound having a vinyl sulfone group, a compound having an ethyleneimine group, and a compound having an epoxy group are particularly preferable.

In the present invention, the compound having a vinylsulfone group is a compound having a vinyl group bonded to a sulfonyl group or a group having a group capable of forming a vinyl group, preferably a vinyl group or a vinyl group bonded to a sulfonyl group. A compound having at least two groups that can be formed and represented by the following general formula (1) is preferable.

Formula (1) (CH ₂ ＣＨCHSO ₂ ) _n A In the formula, A is an n-valent linking group, for example, an alkylene group,
It is a substituted alkylene group, a phenylene group, or a substituted phenylene group, and may have an amide linkage, an amino linkage, an ether linkage, or a thioether linkage in between. As the substituent, a halogen atom, a hydroxy group,
Examples include a hydroxyalkyl group, an amino group, a sulfonic group, and a sulfate group. n is 1, 2, 3 or 4.

The following are typical specific examples of the vinyl sulfone crosslinking agent.

[0052]

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[0053]

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As the compound having an ethyleneimine group, a compound having a bifunctional or trifunctional structure and a molecular weight of 700 or less is preferably used. Specific examples of the crosslinking agent having an ethyleneimine group are described below.

[0055]

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[0056]

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The compound having an epoxy group is particularly preferably a compound having two or more epoxy groups and having a molecular weight of 300 or less per functional group. Specific examples of the crosslinking agent having an epoxy group are described below.

[0058]

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[0059]

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The amount of the crosslinking agent used in the present invention varies depending on the cellulose ester film to be applied, but is preferably 0.1 to 10% by weight of the added polysaccharide, preferably 1 to 8%.

Next, the ultraviolet absorbent contained in the cellulose ester film of the tenth aspect will be described.

The ultraviolet absorbent used in the present invention has a melting point of 100 ° C. or higher, preferably 135 ° C. or higher, more preferably 140 ° C. or higher.

Further, from the viewpoint of preventing the deterioration of the liquid crystal, the wavelength 3
From the viewpoint of excellent absorbability of ultraviolet light of 70 nm or less and good liquid crystal display properties, those having little absorption of visible light having a wavelength of 400 nm or more are preferably used.

Specific examples of the ultraviolet absorbent used in the present invention include oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex salt compounds, and inorganic powders. And the like, and a benzotriazole-based ultraviolet absorber is preferably used. Specific examples are shown below, but the present invention is not limited to these.

UV-1: 2- (2'-hydroxy-5 '
-Methylphenyl) benzotriazole UV-2: 2- (2'-hydroxy-3 ', 5'-di-
ter-butylphenyl) benzotriazole UV-3: 2- (2'-hydroxy-3'-ter-butyl-5'-methylphenyl) benzotriazole UV-4: 2- (2'-hydroxy-3 ', 5 '-Di-
ter-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) Specific examples of a benzophenone-based ultraviolet absorber, which is one of the ultraviolet absorbers used in the present invention, are shown below. It is not limited to.

UV-7: 2,4-dihydroxybenzophenone UV-8: 2,2'-dihydroxy-4-methoxybenzophenone UV-9: 2-hydroxy-4-methoxy-5-sulfobenzophenone UV-10: 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. A benzotriazole-based ultraviolet absorber which causes less unnecessary coloring is particularly preferable.

As a method of adding the ultraviolet absorber, the ultraviolet absorber is dissolved in an organic solvent such as alcohol, methylene chloride, or dioxolane and then added to the dope.
Alternatively, it may be added directly into the dope composition. For those that do not dissolve in organic solvents such as inorganic powders, use a dissolver or sand mill in the organic solvent and cellulose ester,
Disperse and add to dope.

The amount of the ultraviolet absorber used is not uniform depending on the kind of the compound and the conditions of use, but it is usually preferably 0.2 g to 2.0 g, more preferably 0.4 g to 1.5 g per 1 m ² of the cellulose ester film. Is more preferred, and 0.6 g
~ 1.0 g is particularly preferred.

In the invention according to claim 10, at least one ultraviolet absorber having a melting point of 100 ° C. or higher is contained in the cellulose ester film.
You may use together less than less ultraviolet absorbers. The effect of the amount of the ultraviolet absorber having a melting point of 100 ° C. or higher is greater as the ratio to the total ultraviolet absorber contained in the cellulose ester film is larger. It is preferably 30% by weight or more, more preferably 50% by weight, and most preferably the total amount of the ultraviolet absorber having a melting point of 100 ° C. or more.

The cellulose ester film of the present invention comprises
It is preferably used for a liquid crystal display member because of its high dimensional stability and good ultraviolet ray cutting performance. The liquid crystal display member is a member used for a liquid crystal display device, and includes, for example, a polarizing plate, a protective film for a polarizing plate, a retardation plate, a reflector, a viewing angle improving film, an antiglare film, a non-reflective film, and charging. Prevention films and the like. Among the above descriptions, the cellulose ester film of the present invention is particularly preferably used in a polarizing plate and a protective film for a polarizing plate, which have strict requirements for dimensional stability.

Next, a method for producing the cellulose ester film of the present invention will be described.

In the present invention, the dope solution in which the cellulose ester is dissolved is a state in which the cellulose ester is dissolved in a solvent (solvent). The dope solution is prepared by adding an additive such as a plasticizer. Of course, other additives can be added as needed. The concentration of the cellulose ester in the dope solution is 10 to 30% by weight.
And more preferably 18 to 20% by weight.

The solvents used in 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. More preferably, a mixture of a good solvent and a poor solvent is used. The ratio is 70 to 95% by weight for the good solvent and 30 to 5% by weight for the poor solvent.

The good solvent and the poor solvent used in the present invention include:
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 cellulose ester is 55%, and the amount of bound acetic acid is 6%.
At 0%, it becomes a poor solvent.

Examples of good solvents used in the present invention include organic halogen compounds such as methylene chloride and dioxolanes. Further, as the poor solvent used in the present invention, for example, methanol, ethanol, n-butanol, cyclohexane and the like are preferably used.

As a method for dissolving the cellulose ester at the time of preparing the dope solution, a general method can be used. A preferred method is to mix the cellulose ester with a poor solvent, wet or swell, A method of mixing with a good solvent is preferably used. At this time, under pressure, the method of heating at a temperature not lower than the boiling point of the solvent at room temperature and the solvent does not boil and dissolving while stirring, in order to prevent the generation of a mass undissolved substance called gel or mamako, More preferred.

In the present invention, the type of the pressure vessel used for dissolving the cellulose ester is not particularly limited, as long as it can withstand a predetermined pressure and can be heated and stirred under pressure. For the pressurized container, other instruments such as a pressure gauge and a thermometer are appropriately arranged. Pressurization may be performed by a method of injecting an inert gas such as nitrogen gas or by increasing the vapor pressure of the solvent by heating. Heating is preferably performed from the outside. For example, a jacket type is preferable because temperature control is easy.

The heating temperature after the addition of the solvent is preferably in the range of not less than the boiling point of the solvent used and not boiling the solvent, and is preferably set in the range of, for example, 40 ° C. or more and 50 to 110 ° C. . The pressure is adjusted at the set temperature so that the solvent does not boil.

After dissolution, it is taken out of the container while cooling, or is taken out of the container by a pump or the like, cooled with a heat exchanger or the like, and supplied to a film formation. The cooling temperature at this time may be cooled to room temperature, but it is more preferable to cool to a temperature 5 to 10 ° C. lower than the boiling point and perform casting at that temperature because the dope viscosity can be reduced.

In the present invention, a dope solution in which a cellulose ester is dissolved in a solvent and a solution in which a small amount of a cellulose ester is dissolved in fine particles, an ultraviolet absorber and the like are added and mixed in-line. (Casting step), heating to remove a part of the solvent (drying step on the support), then peeling off the support, drying the peeled film (film drying step), and producing the cellulose of the present invention. An ester film is obtained.

As the support in the casting step, a support in which a belt-shaped or drum-shaped stainless steel is mirror-finished is preferably used. The temperature of the support in the casting step can be cast in a general temperature range of 0 ° C. to a temperature lower than the boiling point of the solvent, but casting on the support at 0 to 30 ° C. causes gelation of the dope. It is preferable because the separation time can be increased, and it is more preferable to cast on a support at 5 to 15 ° C. The peeling limit time is the limit of the casting speed at which a transparent and flat good film can be continuously obtained.
The time during which the cast dope remains on the support. It is preferable that the peeling limit time is short because the productivity is excellent.

The surface temperature of the support on the side to be cast (cast) is 10 to 55 ° C., the temperature of the solution is 25 to 60 ° C.
Further, the temperature of the solution is preferably higher than the temperature of the support by 0 ° C. or more, and more preferably 5 ° C. or more. The solution temperature and the support temperature are preferably higher as the drying speed of the solvent can be increased, but if the temperature is too high, foaming or
Flatness may be deteriorated.

A more preferred range of the temperature of the support is 20
~ 40 ° C, a more preferred range of solution temperature is 35-45.
° C.

Further, the temperature of the support at the time of peeling is set to 10 to 4
The temperature is preferably set to 0 ° C, more preferably 15 to 30 ° C, because the adhesion between the film and the support can be reduced.

In order for the cellulose ester film at the time of production to exhibit good flatness, the amount of residual solvent when peeled from the support is preferably from 10 to 80%, more preferably from 20 to 40%, or from 60 to 40%. 80%, particularly preferably 20 to 30%.

In the present invention, the amount of the residual solvent is defined by the following equation.

Residual solvent amount = (weight before heat treatment−weight after heat treatment) × 100 / (weight after heat treatment)% The heat treatment when measuring the amount of residual solvent means that the film is heated at 115 ° C. This indicates that heat treatment is performed for one hour.

The peeling force at the time of peeling the film from the support is usually 20 to 25 kg / m. However, when the cellulose ester film is thinned, wrinkles are likely to be formed at the time of peeling. , Minimum tension that can be peeled ~
Peeling is preferably performed at 17 kg / m, more preferably at a minimum tension of 14 kg / m.

In the drying step of the cellulose ester film, the film separated from the support is preferably further dried to reduce the residual solvent amount to 3% by weight or less, more preferably 0.5% by weight or less. is there.

In the film drying step, generally, a method of drying while transporting the film by a roll hanging method or a pin tenter method is 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 in a place where the amount of the residual solvent is large immediately after being peeled 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. Drying temperature is 40
It is preferable that the temperature is gradually increased in three to five steps in the range of 150 to 150 ° C., and it is more preferable to perform in the range of 80 to 140 ° C. in order to improve dimensional stability.

If the thickness of the cellulose ester film is too small, the strength of the polarizing plate as a protective film is insufficient.
The dimensional stability of the polarizing plate and the storage stability under wet heat deteriorate.
When the film thickness is large, the thickness of the polarizing plate becomes large, and it is difficult to reduce the thickness of the liquid crystal display. The film thickness of the cellulose ester film satisfying both requirements is 20 to 120 μm, preferably 3 to
0 to 60 μm, more preferably 35 to 45 μm,
Most preferred is 40 μm.

The water content of the cellulose ester film in the case of thinning is preferably 0.5 to 4.0%, more preferably 1.5 to 3.5%, and still more preferably 1.5 to 3. 0%.

The water content of the cellulose ester film was
It can be measured by the following method.

[0094] The cellulose ester film sample was
After being cut to a size of m ² and left for 48 hours at 23 ° C. and a relative humidity of 80%, the weight was measured and designated as W1.
Then, after subjecting the film to a heat drying treatment at 120 ° C. for 45 minutes, its weight was measured and defined as W2. 23 ° C. and relative humidity of 80 were obtained from the measured values obtained by the following formula.
The moisture percentage in% is measured.

Water content (%) = ((W1−W2) / W2) × 100

[0096]

The embodiments of the present invention will be specifically described below with reference to examples, but the present invention is not limited thereto.

A cellulose ester film sample was prepared according to the following method.

<< Preparation of Sample 1 >> (Preparation of dope solution) Cellulose triacetate synthesized from cotton linter 85 parts by weight (degree of acetylation: 61.0%) Cellulose triacetate synthesized from wood pulp 15 parts by weight (degree of acetylation) 61.0%) UV-2 (ultraviolet ray absorber) 1 part by weight Ethylphthalylethyl glycolate (plasticizer) 4 parts by weight Methylene chloride 475 parts by weight Ethanol 50 parts by weight Aerosil L200 dispersed to an average particle diameter of 0.3 μm 2 parts by weight The above components were placed in a sealed container, and cellulose triacetate (TAC) was completely dissolved with heating and stirring to 70 ° C. to prepare a dope solution. The time required for dissolution was 4 hours.

After the dope solution prepared above was filtered, it was uniformly cast on a stainless steel band support at a dope solution temperature of 35 ° C. and 30 ° C. using a belt casting device, and the film was blown with dry air of 110 ° C. or less. The solvent was evaporated until the residual solvent amount in the inside became 25%, and then the film was peeled from the stainless steel band support. The time required from the casting of the dope solution to the peeling was 3 minutes. After peeling from the stainless steel band support, 50
℃, 90 ℃, end the drying in the drying zone of 120 ℃,
Sample 1 of a cellulose triacetate film having a thickness of 40 μm was obtained.

<< Preparation of Sample 2 >>
Sample 2 was prepared in the same manner as Sample 1, except that the sample passed through a drying zone at 5 ° C. for 5 minutes.

<< Preparation of Samples 3 and 4 >> Instead of cellulose triacetate (TAC), acetylpropylcellulose (CAP482-0. Manufactured by Eastman Chemical Company) was used.
Samples 3 and 4 were prepared in the same manner as Samples 1 and 2, except that the sample was changed to 5).

<< Preparation of Samples 5 and 6 >> Samples 5 and 6 were prepared in the same manner as Samples 1 and 2 except that the following cooling method was used for dissolving and preparing the dope solution. did.

The following composition was prepared by changing the solvent of the dope composition of Example 1 from methylene chloride to methyl acetate.

Ethylphthalylethyl glycolate (plasticizer) 4 parts by weight Methyl acetate 475 parts by weight Ethanol 50 parts by weight After cooling the obtained composition to −100 ° C., the remaining triacetylcellulose, UV-2, Aerosil A sample was prepared in the same manner as in Example 1, except that L200 was added and the organic solvent was completely dissolved in the process of heating from 0 ° C to 120 ° C.

<< Preparation of Samples 7 to 14 >> As shown in Table 1, Samples 7 to 14 were prepared in the same manner as in Sample 1 except that a polymer and a crosslinking agent were added during the preparation of the dope solution.

Samples 1 to 14 obtained as described above
, The elastic modulus, the water content and the haze were measured, and the obtained results are shown in Table 1. In addition, haze is ASTM-D1
003-52.

Next, a polarizing plate was prepared by the following method using each of the obtained cellulose ester films.

Samples 1 to 14 were immersed in a 2.5N sodium hydroxide solution at 40 ° C. for 60 seconds and alkali-treated.
After washing with water for 3 minutes, a saponified layer was formed to obtain an alkali-treated film.

Next, a polyvinyl alcohol film having a thickness of 120 μm was immersed in 100 parts by weight of an aqueous solution containing 1 part by weight of iodine and 4 parts by weight of boric acid, and stretched 4 times at 50 ° C. to produce respective polarizing films. . The alkali-treated sample films were bonded to both sides of the obtained polarizing film using a 5% aqueous solution of completely saponified polyvinyl alcohol as an adhesive to prepare a polarizing plate sample. For each of the obtained polarizing plate samples, the brittleness was measured by a brittleness tester. Table 1 shows the obtained results. The brittleness was measured using a wedge brittleness apparel under the conditions of 23 ° C. and a relative humidity of 55% after preparing a 35 mm × 1 m sample. The lower the numerical value, the higher the breaking strength.

[0110]

[Table 1]

(Results) As is clear from Table 1, the sample according to the present invention has a higher elastic modulus than the comparative sample.
It can be seen that the brittleness is improved and the breaking strength is improved. In particular, those subjected to a cooling treatment during the production of the dope according to the present invention, an additive polymer, and a sample using a cross-linking agent,
It is clear that it has a very high breaking strength.

[0112]

According to the present invention, a cellulose ester film for protecting a polarizing plate having excellent adhesion to a polarizer can be provided.

Continued on the front page F term (reference) 4C090 AA07 BA25 BA26 BA46 BA47 BD01 BD05 BD10 BD19 BD24 CA04 CA06 CA25 CA35 DA21 4F070 AA01 AA02 AC13 AC15 AC35 AC38 AC39 AC43 AC45 AC50 AC55 AC66 AE02 AE08 AE23 CA11 CB04 GC09 4F071 AA08 AAC08 AC12 AC14 AE02 AF15 AF20 AF27 AG05 AH19 BA02 BB02 BC01 BC02 BC08 BC16 4J002 AB00X AB02W AB05X DE096 DE146 DK006 ED026 EE016 EE037 EH038 EH106 EH148 EL026 EP026 ER006 EU016 EU136 EU177 EU186 EV207 EV216 EW048 EW048 156

Claims (14)

[Claims] 1. A tensile modulus of elasticity of 340 kgf / mm
A cellulose ester film having a plasticizer content of ² or more and a plasticizer content of 1 to 20% by weight. 2. A cellulose ester film comprising a polysaccharide other than cellulose. 3. A cellulose ester film crosslinked by a crosslinking agent. 4. The cellulose ester film according to claim 3, wherein said crosslinking agent is a metal compound. 5. The crosslinking agent has at least one group selected from a vinyl sulfone group, an epoxy group, an isocyanate group, a blocked isocyanate group, an active halogen group, an aldehyde group, an ethyleneimine group, and an active ester-forming group. The cellulose ester film according to claim 3, characterized in that: 6. A cellulose ester film containing a polysaccharide other than cellulose and being crosslinked with a crosslinking agent. 7. The cellulose ester film according to claim 2, wherein the polysaccharide is chitin or chitosan. 8. The cellulose ester film according to claim 1, wherein the haze is 1% or less. 9. The cellulose ester film according to claim 1, wherein the moisture content is 8% or less. 10. The cellulose ester film according to claim 1, further comprising an ultraviolet absorber. 11. An organic solvent is cooled to −100 to −10 ° C. and then heated to 0 to 120 ° C. to dissolve the cellulose ester, and the obtained cellulose ester organic solvent solution is placed on an endless belt. 2. The method according to claim 1, wherein the substrate is manufactured through a step of coating on a drum.
The cellulose ester film according to any one of claims 10 to 10. 12. The cellulose ester according to claim 1, wherein said cellulose ester is a cellulose lower fatty acid ester.
The cellulose ester film according to any one of claims 1 to 7. 13. The cellulose ester film according to claim 1, wherein the film thickness is 20 to 120 μm. 14. The cellulose ester film according to claim 1, which is a protective film for a polarizing plate.