JP2002210764A - Method for manufacturing cellulose acylate film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a cellulose acylate film excellent in surface properties by using a cellulose acylate solution excellent in stability with the elapse of time and low in viscosity in a practical dope concentration region. SOLUTION: The cellulose acylate film is manufactured by successively performing a process for dissolving cellulose acylate in a solvent to prepare the cellulose acylate solution, a process for casting the obtained solution on a smooth band or drum, a process for treating the undried film formed on the band or drum with a poor solvent of cellulose acylate, a process for peeling the undried film from the band or drum and a process for drying the undried film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a cellulose acylate film.

[0002]

2. Description of the Related Art Cellulose acylate films are used for various photographic materials and optical materials because of their toughness and flame retardancy. Cellulose acylate film is a typical support for photographic light-sensitive materials. Further, the cellulose acylate film has been used in a liquid crystal display device whose market has been expanding in recent years due to its optical isotropy. As a specific application in the liquid crystal display device, a protective film of a polarizing plate and a color filter are typical.

[0003] Cellulose acylate films are generally produced by a solvent casting method or a melt casting method. In the solvent casting method, a solution (dope) in which cellulose acylate is dissolved in a solvent is cast on a support, and the solvent is evaporated to form a film. In the melt casting method, a film obtained by melting cellulose acylate by heating is cast on a support and cooled to form a film. The solvent cast method can produce a good film having higher flatness than the melt cast method. For this reason, practically, the solvent cast method is generally employed. The solvent casting method is described in many documents. In the recent solvent casting method, it is an issue to improve the productivity of the film forming process by reducing the time required from casting the dope on the support to peeling off the formed film on the support. Has become. For example, Japanese Patent Publication No. 17844/1993 proposes to reduce the time from casting to stripping by casting a high concentration dope on a cooling drum.

[0004] The solvent used in the solvent casting method requires various conditions in addition to simply dissolving cellulose acylate. In order to economically and efficiently produce a film having excellent flatness and uniform thickness, it is necessary to prepare a solution (dope) having an appropriate viscosity and a polymer concentration and having excellent storage stability. About dope,
It is also required that gelation is easy and separation from the support is easy. To prepare such a dope, the choice of solvent type is very important. The solvent is required to be easily evaporated and to have a small residual amount in the film. Various organic solvents have been proposed as solvents for cellulose acylate. Practical organic solvents are practically limited to methylene chloride, but methylene chloride has problems such as its environmental suitability and boiling point, and a search for a substitute solvent has been conducted.

[0005] M. G. FIG. Cowie et al., Mak
romol, chem. 143, 105 (197
1 year) is obtained by converting cellulose acylate having a substitution degree of 2.80 to 2.90 into acetone from −80 ° C. to −70 ° C.
It was reported that a dilute solution in which cellulose acylate was dissolved in acetone at a concentration of 0.5 to 5% by mass was obtained by cooling and then heating (however, the acyl group here was used). Is limited to acetyl groups). Less than,
The method of cooling the mixture of the cellulose acylate and the organic solvent to obtain a solution is referred to as a “cooling dissolution method”. For dissolution of cellulose acylate in acetone, see Kenji Ude et al., "Dry spinning of cellulose triacetate from acetone solution", Journal of the Textile Machine Society, 34
Vol. 57, 1981. This paper, as its title, applied the cooling melting method to the technical field of spinning method. In the paper, the cooling dissolution method is studied while paying attention to the mechanical properties, dyeability and cross-sectional shape of the obtained fiber. In this paper, a solution of cellulose acetate having a concentration of 10 to 25% by weight is used for spinning the fibers. In addition to the above-mentioned cooling dissolution, a “high-temperature dissolution method” for dissolving a mixture under high-temperature and high-pressure conditions has been proposed.

[0006] In the casting method, a cellulose acylate solution (dope) dissolved in various solvents is cast on a support, the film is peeled off from the support and dried. In many cases, the surface state of the acylate film was not good. That is, since the viscosity of the dope is high, the streaks and the like at the time of casting remain without being smoothed, and the surface is not smooth or sometimes recognized as a streak failure. In order to obtain a good surface condition, the surface must be smoothed by diluting the dope or performing drying under mild conditions, and increasing the manufacturing cost and decreasing the manufacturing speed by taking measures against the surface condition Such problems occur, and countermeasures have been required.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to produce a cellulose acylate film having excellent planarity by using a cellulose acylate solution having excellent stability over time and having a low viscosity in a practical dope concentration region. It is also to do.

[0008]

The above objects of the present invention can be achieved by implementing the following methods (1) to (8). (1) a step of preparing a cellulose acylate solution by dissolving cellulose acylate in a solvent, a step of casting the obtained solution on a smooth band or drum, and a step of drying an undried film formed on the band or drum. A method for producing a cellulose acylate film, comprising: performing a step of treating with a poor solvent of cellulose acylate, a step of peeling the wet film from a band or a drum, and a step of drying the wet film in this order.

(2) The step of treating the undried film with a poor solvent is carried out by immersing the undried film in the poor solvent or spraying the undried film with the poor solvent. A method for producing a cellulose acylate film. (3) The method for producing a cellulose acylate film according to (1), wherein the poor solvent is water, alcohol or hydrocarbon. (4) The method for producing a cellulose acylate film according to (3), wherein the poor solvent is water, an alcohol having a boiling point of 120 ° C. or lower, or a hydrocarbon having 10 or less carbon atoms.

(5) The method for producing a cellulose acylate film according to (1), wherein the solvent for dissolving the cellulose acylate is a substantially non-chlorinated solvent. (6) The step of preparing a cellulose acylate solution comprises the step of preparing a mixture of cellulose acetate and a solvent from -80 to -1.
The method for producing a cellulose acylate film according to (1), comprising a treatment of cooling to 0 ° C. or a treatment of heating to 80 to 220 ° C. (7) The method for producing a cellulose acylate film according to (1), wherein the step of casting the solution is performed by a co-casting method of two or more layers. (8) The method for producing a cellulose acylate film according to (1), wherein silica particles having a mean particle diameter of 0.1 μm or less, a plasticizer or an ultraviolet absorber are added to the solution.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Cellulose Acylate Raw Material Cell
Loin includes cotton linters and wood pulp. two kinds
You may mix and use the above-mentioned raw material cellulose. cell
Loose acylate has an acetyl group or a carbon number of 3 to
It is a cellulose acylate having 22 acyl groups.
Examples of acyl groups having 3 to 22 carbon atoms include propanoyl
Group (C _TwoH_FiveCO-), butanoyl group (C_ThreeH₇CO
-) (N-, iso-), valeroyl group (C_FourH₉CO-)
(N-, iso-, sec-, tert-), octanoyl, dodeca
Contains noyl, octadecanoyl and oleoloyl
You. Propanoyl and butanoyl are preferred. Cellulo
Ostriacetate is the most preferred cellulose acylate
It is.

When the acylating agent for the acyl group is an acid anhydride or an acid chloride, an organic solvent is used as a reaction solvent. Examples of the organic solvent include an organic acid (eg, acetic acid) and methylene chloride. The degree of substitution of the hydroxyl group is 2.6
-3.0 is preferred. The polymerization degree (viscosity average) of the cellulose acylate is preferably from 200 to 700, and more preferably from 250 to
550 is more preferred. Cellulose acylate is commercially available from Daicel Chemical Industries, Ltd., Coatles, Hoechst and Eastman Kodak. Photographic grade cellulose acylate is preferred. The water content of the cellulose acylate is preferably 2% by mass or less.

A cellulose acylate film is produced by a solvent casting method. In the solvent casting method, a film is manufactured using a cellulose acylate dope. The organic solvent used for preparing the dope is preferably a substantially non-chlorine solvent. "Substantially non-chlorine" means that the content of a solvent containing one or more chlorine atoms in the structural formula (eg, dichloromethane, dichloroethane, chlorobenzene) is preferably 40 vol% or less,
It is more preferably 5 vol% or less, further preferably 5 vol% or less, still more preferably 1 vol% or less, and most preferably 0 vol%. The non-chlorinated solvent may be composed of a compound having 3 to 12 carbon atoms. The solvent is preferably selected from the group consisting of esters, ethers, ketones and alcohols. Esters, ethers, ketones and alcohols may have a linear, branched or cyclic structure. Functional groups of esters, ethers, ketones and alcohols (i.e., -COO-, -O-, -CO- and -O
Compounds having any two or more of H) can also be used as the solvent.

Examples of esters include methyl formate, ethyl formate, propyl formate, methyl acetate and ethyl acetate. Methyl formate, ethyl formate and methyl acetate are preferred, and methyl acetate is more preferred. Examples of ketones include:
Acetone, methyl ethyl ketone, diethyl ketone, methyl isobutyl ketone, cyclopentanone and cyclohexanone. Acetone, cyclopentanone and cyclohexanone are preferred, and acetone and cyclopentanone are more preferred. Examples of ethers include dibutyl ether, dimethoxymethane, dimethoxyethane, 1,4-dioxane, 1,3-dioxolan, tetrahydrofuran, anisole and phenetole. Examples of alcohol include methanol, ethanol,
1-propanol, 2-propanol, 1-butanol, 2-butanol, cyclohexanol, 2-fluoroethanol, 2,2,2-trifluoroethanol are included. Methanol, ethanol, 1-propanol, 2-propanol and 1-butanol are preferred, and methanol and ethanol are more preferred. Esters and ketones preferably have a solubility parameter of 19-21.

Two or more kinds of solvents may be mixed and used. It is preferable to use a mixture of an ester having a solubility parameter of 19 to 21 and a ketone having a solubility parameter of 19 to 21. It is preferable to mix an alcohol in addition to the ester and the ketone. As a combination of solvents, methyl acetate / cyclopentanone / acetone / methanol / ethanol (60/15/1
5/5/5, parts by mass), methyl acetate / acetone / methanol / ethanol (75/15/5/5, parts by mass), methyl acetate / cyclohexanone / methanol / 1-butanol (70/20/5/5, Parts by mass) and methyl formate / methyl ethyl ketone / acetone / methanol / ethanol (50/20/20/5/5, parts by mass), preferably methyl acetate / acetone / methanol / ethanol
(75/15/5/5, parts by mass), methyl acetate / cyclopentanone / methanol / ethanol (80/10/5
/ 5, parts by mass).

It is preferable that the polymer component of the cellulose acylate film is substantially composed of cellulose acetate having the above-mentioned definition. "Substantially" means at least 90% by weight of the polymer component (preferably at least 95% by weight, more preferably at least 98% by weight, most preferably at least 99% by weight). As a raw material for producing a film, it is preferable to use cellulose acetate particles. 90% by weight of the particles used
The above preferably has a particle diameter of 1 to 4 mm. Also, 50% by weight or more of the particles used is 2 to 3 m.
It preferably has a particle size of m. It is preferable that the cellulose acetate particles have a shape as close to spherical as possible.

In order to prepare a cellulose acylate solution, the above-mentioned cellulose acylate is added while stirring the solvent in the tank at room temperature to swell the solvent first. The swelling time must be at least 10 minutes or more, and if it is less than 10 minutes, insoluble matter remains. Further, in order to sufficiently swell the cellulose acylate, the temperature of the solvent is 0 to 40 ° C.
Is preferred. At 0 ° C. or lower, the swelling rate tends to decrease and insolubles tend to remain. At 40 ° C. or higher, the swelling occurs rapidly and the central portion does not swell sufficiently. In order to dissolve the cellulose acylate after the swelling step, it is preferable to use one or both of a cooling dissolution method and a high temperature dissolution method.

In the cooling dissolution method, first, a temperature around room temperature (-1)
(0 to 40 ° C.), the cellulose acylate is gradually added to the organic solvent with stirring. After adding the cellulose acylate to the main solvent (eg, ester, ketone), an auxiliary solvent (eg, alcohol) may be added. The main solvent may be added after moistening the cellulose acylate in advance with an auxiliary solvent (eg, alcohol). It is preferable to adjust the amount of cellulose acylate so that the amount is 10 to 40% by mass in the mixture. More preferably, the amount of cellulose acylate is 10 to 30% by mass. Further, an optional additive described below may be added to the mixture. Next, the mixture is -100 to -10
° C, more preferably -80 to -10 ° C, still more preferably -50 to -20 ° C, and most preferably -50 to-
Cool to 30 ° C. Cooling, for example, dry ice
It can be carried out in a methanol bath (−75 ° C.) or a cooled diethylene glycol solution (−30 to −20 ° C.). The faster the cooling rate, the better, and preferably 100 ° C./sec or more. In addition, it is desirable to use a closed container in order to avoid water contamination due to dew condensation during cooling. After cooling, 0-20
0 ° C. (preferably 0 to 150 ° C., more preferably 0 ° C.
To 120 ° C., most preferably 0 to 50 ° C.), a solution in which cellulose acylate is dissolved in an organic solvent is obtained. The heating may be simply left at room temperature. Also, the cooled mixture may be heated in a warm bath. When the pressure is increased during cooling and the pressure is decreased during heating, the dissolution time can be shortened. In order to perform pressurization and decompression, it is desirable to use a pressure-resistant container. The operation of cooling and heating may be repeated two or more times.

In the high-temperature melting method, the temperature around room temperature (-10
-40 ° C.), and slowly add the cellulose acylate to the organic solvent with stirring. After adding the cellulose acylate to the main solvent (eg, ester, ketone), an auxiliary solvent (eg, alcohol) may be added. The main solvent may be added after moistening the cellulose acylate in advance with an auxiliary solvent (eg, alcohol). Cellulose acylate can be added to a mixed organic solvent in advance to cause swelling. In any solvent at −10 to 40 ° C., cellulose acylate may be gradually added with stirring, or may be swelled in advance with a specific solvent in some cases, and then added with another combined solvent and mixed. And the remaining solvent may be added after swelling with two or more solvents. The dissolution concentration of cellulose acylate is 5% by mass or more.
30% by mass is preferable, and more preferably 15% by mass to 3% by mass.
0% by mass, more preferably 17% by mass to 25% by mass
It is. Next, the cellulose acylate and the solvent mixture are mixed in a pressure vessel at a pressure of 0.2 to 30 MPa under a pressure of 70 to 30 MPa.
240 ° C., more preferably 80-220 ° C., even more preferably 100-200 ° C., and most preferably 100-190 ° C.
Heat to ° C. Thereafter, the mixture is cooled to a temperature lower than the lowest boiling point of the solvent used. In that case, it is common to cool to −10 to 50 ° C. and return to normal pressure. The cooling may be performed only at room temperature, and more preferably a coolant such as cooling water may be used. The operation of heating and cooling may be repeated two or more times.

The cellulose acylate may be dissolved at a low concentration and then concentrated. When preparing the cellulose acylate solution, it is preferable to fill the inside of the container with an inert gas such as a nitrogen gas to cope with explosion-proof. The viscosity of the cellulose acylate solution immediately before film formation is adjusted within a range that can be cast during film formation. Viscosity is 10 Pa · s to 2000 Pa
· S, preferably 30 Pa · s to 40
More preferably, it is 0 Pa · s. The temperature during casting is preferably -5 to 70C, and -5 to 70C.
More preferably, it is 55 ° C. The concentration of the cellulose acylate solution is preferably 5 to 40% by mass,
30 mass% is more preferable.

Various additives can be added to the cellulose acylate solution in each preparation step according to the intended use. These additives are plasticizers, UV inhibitors and deterioration inhibitors (eg, antioxidants, peroxide decomposers, radical inhibitors, metal deactivators, acid scavengers, amines). Examples of plasticizers include triphenyl phosphate (TP
P), diphenylbiphenyl phosphate, tricresyl phosphate (TCP), dioctyl phthalate (D
OP), tributyl O-acetylcitrate (OACT
B) and acetyltriethyl citrate. As plasticizers for reducing optical anisotropy, (di) pentaerythritol esters (described in JP-A-11-124445) and glycerol esters (described in JP-A-11-2)
46704), diglycerol esters (described in JP-A-2000-63560), citrate esters (described in JP-A-11-92574), or substituted phenylphosphate esters (described in JP-A-11-909).
No. 46) may be used. Two or more plasticizers may be used in combination. The amount of the plasticizer is preferably 5 to 30% by mass based on the cellulose acylate,
-16 mass% is more preferable.

As for the deterioration inhibitor and the ultraviolet inhibitor, JP-A-60-235852 and JP-A-3-199201.
No., 5-1907073, 5-194789,
5-271471, 6-107854, 6-
Nos. 118233, 6-148430, 7-110
Nos. 56, 7-11055, 7-11056, 8-29619, 8-239509, JP-A-200
It is described in each publication of JP-A No. 0-204173. Examples of the deterioration inhibitor include butylated hydroxytoluene (BHT). The ultraviolet absorbent is preferably a compound having an ability to absorb ultraviolet light having a wavelength of 370 nm or less and having little absorption of visible light having a wavelength of 400 nm or more. Examples of UV absorbers include
Oxybenzophenone compounds, benzotriazole compounds, salicylate compounds, benzophenone compounds, cyanoacrylate compounds, and nickel complex compounds are included. Benzotriazole compounds and benzophenone compounds are preferred. The addition amount of the deterioration inhibitor and the ultraviolet inhibitor is preferably from 1 ppm to 10000 ppm, more preferably from 10 to 1000 ppm by mass ratio to the cellulose acylate.

The in-plane retardation (Re) of the cellulose acylate film is preferably in the range of 0 to 300 nm. Film thickness direction retardation (Rth)
Is preferably 0 nm to 600 nm, more preferably 0 nm to 400 nm, and most preferably 0 nm to 250 nm per 100 μm thickness.

Prior to casting the cellulose acylate solution, a release agent can be added. The release agent is preferably an acid having an acid dissociation index (pKa) of 1.93 to 4.50 in an aqueous solution, or an alkali metal salt or an alkaline earth metal salt thereof. The acid is preferably an organic acid. As the organic acid, an aliphatic monocarboxylic acid, an aliphatic polycarboxylic acid, an oxycarboxylic acid, an amino acid or a derivative thereof can be used. The number of carbon atoms of the aliphatic monocarboxylic acid is 1
It is preferably from 3 to 3. Examples of aliphatic monocarboxylic acids include formic acid, haloacetic acid (eg, chloroacetic acid), halopropionic acid, and acrylic acid. The aliphatic polycarboxylic acid preferably has 2 to 4 carbon atoms. Examples of the aliphatic polycarboxylic acid include malonic acid, succinic acid, glutaric acid and fumaric acid. The oxycarboxylic acid preferably has 1 to 6 carbon atoms. Examples of oxycarboxylic acids include glycolic acid, lactic acid,
Includes malic acid, tartaric acid and citric acid. Further, sulfonic acid or phosphoric acid can also be used as a release agent. A surfactant (described in JP-A-61-243837) can also be used as a release agent. Examples of the surfactant used as the release agent include C ₁₂ H ₂₅ O-P (=
_{O) - (OK) 2,} C 12 H 25 OCH 2 CH 2 O-P (=
O) - (OK) ₂ and _{(iso-C 9 H 19)} 2 -C 6 H 3
—O— (CH ₂ CH ₂ O) ₃ — (CH ₂ ) ₄ SO ₃ Na
Is included.

As the alkali metal forming a salt, lithium, potassium and sodium are preferred. Sodium is particularly preferred. As the alkaline earth metal forming the salt, calcium, magnesium, barium and strontium are preferred. Calcium and magnesium are particularly preferred. Alkali metals are preferred over alkaline earth metals. Two or more metals may be used in combination.

Addition of fine particles (matting agent)
It can also prevent creaking. Fine particles are made from inorganic substances
Preferably, Examples of inorganic substances include silica and chao.
Phosphorus, talc, diatomaceous earth, quartz, calcium carbonate, sulfur
Barium acid, titanium oxide, alumina, manganese colloid
, Titanium dioxide, strontium barium sulfate, diacid
Silicon oxide, alkaline earth metal (eg, calcium, magne
Salt). Film by adding fine particles
The average height of the surface projections is 0.005 to 10 μm.
Is preferably 0.01 to 5 μm.
Preferred. The shape of the particles is spherical or amorphous
Is preferred. The content of the fine particles in the film is 0.
5 to 600 mg / m^TwoAnd preferably 1 to 40
0mg / m ^TwoIs more preferable.

The solution before casting may be treated with a suitable filter medium (eg, wire mesh,
It is preferable to remove foreign matter (eg, undissolved matter, dust, impurities) using paper or flannel. The absolute filtration accuracy of the filter used for solution filtration is preferably 0.05 to 100 μm, and more preferably 0.5 to 10 μm. The filtration pressure is preferably at most 16 kg / cm ^2, more preferably at most 12 kg / cm ² , still more preferably at most 10 kg / cm ² , most preferably at most ² kg / cm ^2. .

As a method and equipment for producing a cellulose acylate film, a conventional solution casting film forming method and a conventional solution casting film forming apparatus used for producing a conventional cellulose triacetate film can be used. The dope (cellulose acylate solution) prepared from the dissolving tank (tank) is temporarily stored in a stock tank, and bubbles contained in the dope are defoamed or final prepared. The dope is fed from the dope discharge port to the pressurized die through a pressurized metering gear pump capable of, for example, high-precision quantitative liquid feeding according to the number of rotations, and the dope of the casting section running endlessly from the die (slit) of the pressurized die. At the peeling point where the support is evenly cast on the support and the support substantially makes a round, the freshly dried dope film (also referred to as a web) is peeled from the support. Clip the ends of the resulting web with clips,
While maintaining the width, the sheet is conveyed by a tenter and dried. Subsequently, the sheet is conveyed by a group of rolls of a drying device, dried, and wound up to a predetermined length by a winder. The combination of the tenter and the roll group drying device varies depending on the purpose. In a solution casting film forming method used for a silver halide photographic material or a functional protective film for an electronic display, in addition to a solution casting film forming apparatus, various layers (undercoat layer, antistatic layer, antihalation layer, etc.) , A protective layer) on the support is often provided with a coating device.

The obtained cellulose acylate solution is cast on a smooth band or a drum as a support. A plurality of cellulose acylate liquids may be successively cast or co-cast to produce two or more cellulose acylate films. For example, when casting a plurality of cellulose acylate solutions, a film containing cellulose acylate is cast from a plurality of casting ports provided at intervals in the traveling direction of the support, and a film is produced while being laminated. (Described in JP-A-11-198285). Also, a method of casting a cellulose acylate solution from two casting ports to form a film (described in JP-A-6-134933) can be performed. Also, a cellulose acylate film flow described in JP-A-56-162617, in which a flow of a high-viscosity cellulose acylate solution is wrapped with a low-viscosity cellulose acylate solution, and the high and low viscosity cellulose acylate solutions are simultaneously extruded. The spreading method may be used. By performing such co-casting,
As described above, since the smoothing in drying the surface proceeds, a great improvement in the surface state can be expected. The film thickness for co-casting is
The thickness of each layer is not particularly limited, but preferably the outer layer is preferably thinner than the inner layer. In this case, the thickness of the outer layer is preferably from 1 to 50 μm, particularly preferably from 1 to 30 μm. Here, the surface layer means a non-band surface (drum surface) in the case of two layers, and a layer on both surface sides of a completed film in the case of three or more layers. The inner layer is a band surface (drum surface) in the case of two layers. In the case of three or more layers, a layer inside the surface layer is shown. The cellulose acylate solution can be cast simultaneously with other functional layers (eg, an adhesive layer, a dye layer, an antistatic layer, an antihalation layer, a UV absorbing layer, and a polarizing layer).

In the step of peeling the freshly dried dope film from the support after casting, it has been reported that a peeling failure occurs and the peeled film is deformed by a tenter conveyance. As a result of the study of the present inventors, it has been found that if the solvent remaining in the freshly dried film is a poor solvent for cellulose acylate, peeling failure in the peeling step hardly occurs, and the film is hard and hardly deformed even in the tenter conveyance. did. However, if a poor solvent of cellulose acylate is added to the dope, the solubility of the dope is reduced, and the stability of the liquid is deteriorated. Therefore, in the present invention,
The above problem is solved by treating the cast film with a poor solvent before the peeling step. As a treatment for the poor solvent, a countermeasure can be taken by installing a bath composed of the poor solvent near the band or the drum before the peeling. A similar effect can be obtained by spraying a poor solvent on a freshly dried film before peeling.

As a specific poor solvent, water, alcohol or hydrocarbon is preferable. If the boiling point of the poor solvent is high, the drying load increases, and a problem occurs in productivity. Considering the boiling point, the poor solvent is preferably water, an alcohol having a boiling point of 120 ° C. or lower, or a hydrocarbon having 10 or less carbon atoms.
Examples of alcohol having a boiling point of 120 ° C. or lower include methanol,
Includes ethanol, propanol, isopropanol, butanol, isobutanol and tert-butanol. Examples of hydrocarbons having 10 or less carbon atoms include hexane, heptane and isoheptane.

The drying temperature in the drying step is 30-25.
0 ° C is preferable, and 40 to 180 ° C is more preferable. The drying step is described in JP-B-5-17844. A method of positively stretching the film in the width direction (Japanese Patent Application Laid-Open No. 62-115035, Japanese Patent Application Laid-Open No.
No. 5, 4-284221, 4-298310,
11-48271). Uniaxial stretching or biaxial stretching can be employed for stretching the film. The stretching ratio of the film (ratio of increase by stretching to the original length) is preferably 10 to 30%.

The thickness of the finished (after drying) cellulose acylate film varies depending on the purpose of use, but is usually in the range of 5 to 500 μm, and more preferably 20 to 250 μm.
Is particularly preferable, and the range of 30 to 180 μm is most preferable. In addition, the range of 30 to 110 μm is particularly preferable for optical use. The film thickness may be adjusted by adjusting the concentration of the solid content contained in the dope, the slit gap of the die, the extrusion pressure from the die, and the speed of the support so as to obtain the desired thickness.

The surface treatment of the cellulose acylate film may improve the adhesion between the cellulose acylate film and each functional layer (for example, an undercoat layer and a back layer). The surface treatment includes glow discharge treatment, ultraviolet irradiation treatment, corona treatment, flame treatment, acid or alkali treatment. Acid or alkali treatment is preferred, and alkali treatment is more preferred. The acid or alkali treatment functions as a saponification treatment for the cellulose acylate film. The alkali saponification treatment is preferably performed by immersing the film surface in an alkaline solution, neutralizing the film surface with an acidic solution, washing with water, and drying. Examples of the alkaline solution include a potassium hydroxide solution and a sodium hydroxide solution, and the specified concentration of the hydroxide ion is 0.1N to 3.0N.
Is preferable, and 0.5N to 2.0N is more preferable. The temperature of the alkali solution is preferably from room temperature to 90 ° C, more preferably from 30 ° C to 70 ° C. Next, the cellulose acylate film is generally washed with water and then passed through an acidic aqueous solution and then washed with water to obtain a surface-treated cellulose acylate film.
At this time, the acid includes hydrochloric acid, nitric acid, sulfuric acid, acetic acid, formic acid, chloroacetic acid, oxalic acid, etc., and the concentration thereof is 0.01N.
-3.0N is preferable and 0.05N-2.0N is more preferable. In order to achieve adhesion between the cellulose acylate film support and the functional layer, it is also preferable to provide an undercoat layer (adhesive layer) and apply the functional layer thereon.

In the constitution of the protective film for a polarizing plate, it is preferable that at least one layer of the cellulose acylate film is provided with an antistatic layer or a hydrophilic binder layer for bonding to a polarizer. As a conductive material,
Conductive metal oxides and conductive polymers are preferred. In addition,
A transparent conductive film formed by vapor deposition or sputtering may be used. The conductive layer may be the outermost layer or the inner layer without any problem.
Regarding the power transmission of the conductive layer, the resistance is preferably from 10 ⁰ to 10 ¹² Ω, and particularly preferably from 10 ⁰ to 10 ¹⁰ Ω. Metal oxides are preferred. Examples of metal oxides include Z
nO, TiO ₂ , SnO ₂ , Al ₂ O ₃ , In ₂ O ₃ ,
SiO ₂ , MgO, BaO, MoO ₂ , V ₂ O ₅ and composite oxides are included. ZnO, SnO ₂ and V ₂ O
₅₅ is preferred. Examples of the conductive ionic polymer compound include an ionene-type polymer having a dissociating group in the main chain and a cationic pendant polymer having a cationic dissociating group in a side chain. As the conductive material, an organic electron conductive material is preferable. Examples of the organic electron conductive material include a polyaniline derivative, a polythiophene derivative, a polypyrrole derivative, and a polyacetylene derivative.

A surfactant can be preferably added to any of the functional layers of the cellulose acylate film. Nonionic, cationic and betaine surfactants are preferred. Fluorinated surfactants can also be used. The surfactant can function as a coating agent or an antistatic agent in an organic solvent. It is preferable to include a slipping agent in any of the layers above the cellulose acylate film. Examples of the slipping agent include polyorganosiloxane (described in JP-B-53-292), higher fatty acid amide (described in U.S. Pat. No. 4,275,146), and higher fatty acid ester (British patent 927446, described in JP-B-58-33541). No., JP-A-55-126
238 and 58-90633). The higher fatty acid ester has 10 to 2 carbon atoms.
An ester of a fatty acid having 4 and an alcohol having 10 to 24 carbon atoms.

The cellulose acylate film formed from the cellulose acylate solution can be used for various purposes. The cellulose acylate film is particularly effective when used as an optical compensation sheet for a liquid crystal display. As the cellulose acylate film, the film itself can be used as an optical compensation sheet. When the film itself is used as the optical compensation sheet, the transmission axis of the polarizing element (described later) and the slow axis of the optical compensation sheet made of the cellulose acylate film are arranged so as to be substantially parallel or perpendicular. Is preferred. The arrangement of such a polarizing element and an optical compensation sheet is described in JP-A-10-48420.
The liquid crystal display device has a liquid crystal cell holding liquid crystal between two electrode substrates, two polarizing elements disposed on both sides thereof,
And at least one optical compensatory sheet is disposed between the liquid crystal cell and the polarizing element. The liquid crystal layer of a liquid crystal cell is usually formed by enclosing liquid crystal in a space formed by sandwiching a spacer between two substrates. The transparent electrode layer is formed on a substrate as a transparent film containing a conductive substance. The liquid crystal cell may further be provided with a gas barrier layer, a hard coat layer or an undercoat layer (used for bonding the transparent electrode layer). These layers are usually provided on a substrate. The substrate of the liquid crystal cell is generally 80 to 5
It has a thickness of 00 μm.

The optical compensation sheet is a birefringent film for removing coloring of the liquid crystal screen. The cellulose acylate film can be used as an optical compensation sheet. Further, a function may be provided as an antireflection layer, an antiglare layer, a λ / 4 layer, or a biaxially stretched cellulose acylate film. Also, to improve the viewing angle of the liquid crystal display device,
A cellulose acylate film and a film exhibiting the opposite birefringence (in a positive / negative relationship) may be overlapped and used as an optical compensation sheet. The range of the thickness of the optical compensation sheet is the same as the preferable thickness of the film described above. Examples of the polarizing film of the polarizing element include an iodine-based polarizing film, a dye-based polarizing film using a dichroic dye, and a polyene-based polarizing film. All polarizing films are generally manufactured using a polyvinyl alcohol-based film. The protective film of the polarizing plate preferably has a thickness of 25 to 350 μm, more preferably 30 to 200 μm. The liquid crystal display device may be provided with a surface treatment film. The functions of the surface treatment film include a hard coat, an anti-fog treatment, an anti-glare treatment and an anti-reflection treatment. As described above, an optical compensatory sheet in which an optically anisotropic layer containing a liquid crystal (particularly discotic liquid crystal molecules) is provided on a support has been proposed (JP-A-3-932).
Nos. 5, 6-148429, 8-50206, and 9-26572). A cellulose acylate film can also be used as a support for such an optical compensation sheet.

The cellulose acylate film is composed of a support of an optical compensation sheet of a VA-type liquid crystal display device having a VA mode liquid crystal cell, and an O having an OCB mode liquid crystal cell.
Support for optical compensation sheet of CB type liquid crystal display device or HAN type liquid crystal display device having HAN mode liquid crystal cell, ASM (Axially Symmetric Aligned Microcell)
It is preferably used as a support for an optical compensation sheet of an ASM type liquid crystal display device having a mode liquid crystal cell.

[0040]

EXAMPLES In each of the examples, cellulose acylate,
The chemical and physical properties of solutions and films are
It was measured and calculated as follows.

(1) Degree of substitution (%) of cellulose acylate The degree of acetylation was measured by a saponification method. The dried cellulose acylate is precisely weighed and dissolved in a mixed solvent of acetone and dimethylsulfoxide (volume ratio: 4: 1), and then a predetermined amount of a 1N aqueous solution of sodium hydroxide is added thereto, followed by saponification at 25 ° C for 2 hours. did. Phenolphthalein was added as an indicator, and excess sodium hydroxide was titrated with 1N-sulfuric acid (concentration factor: F). A blank test was performed in the same manner as described above. Then, the degree of acetylation (%) was calculated according to the following equation. Degree of acetylation (%) = (6.05 × (BA) × F) / W In the formula, A is the amount of 1N-sulfuric acid (ml) required for titration of the sample
B is the amount of 1N sulfuric acid (ml) required for the blank test, F
Represents a factor of 1N-sulfuric acid, and W represents a sample weight. In the case of a system containing a plurality of acyl groups, the amount of each acyl group was determined using the difference in pKa. In addition, literature (T.Se
i, K.Ishitani, R.Suzuki, K.Ikematsu PolymerJournal 17
1065, 1985). Further, the degree of substitution was converted into the degree of substitution from the determined degree of acetylation and the amount of other acyl groups in consideration of the molar molecular weight. Further, after the acyl substitution degree at the 2-, 3- and 6-positions of the cellulose acylate is acylated with an acyl group not used for the acylation of the cellulose acetate, Carbohydr.
es. 273 (1995) 83-91 (Tezuka et al.).
Determined by MR.

(2) Viscosity-average degree of polymerization (DP) of cellulose acylate Approximately 0.2 g of absolutely dried cellulose acylate is precisely weighed and dissolved in 100 ml of a mixed solvent of methylene chloride: ethanol = 9: 1 (weight ratio). did. This was measured for drop seconds at 25 ° C. using an Ostwald viscometer, and the degree of polymerization was determined by the following equation. ηrel = T / T0 T: Falling seconds of the measured sample [η] = (1nηrel) / C T0: Falling seconds of the solvent alone DP = [η] / Km C: Concentration (g / l) Km: 6 × 10 ^-Four

(3) Solution Stability The state of the obtained solution or slurry was observed while standing at room temperature (23 ° C.) for 20 days, and the following A, B, C,
D was evaluated in four stages. A: Shows transparency and liquid uniformity. B: There is some undissolved residue or slight cloudiness is observed. C: There is a clear undissolved residue or the solution is gelled. D: The liquid is opaque and non-uniform with no swelling / dissolution.

(4) Film Surface State The film was visually observed, and the surface state was evaluated as follows. A: The film surface is smooth and the surface state is very good. B: The film surface is smooth, but irregularities are rarely observed. C: The film surface is smooth, but relatively many weak irregularities are observed. D: Weak irregularities are observed on the entire surface of the film. E: Strong irregularities are seen on the film, and foreign matter is seen.

(6) Haze of film: Measured using a haze meter (Model 1001DP, manufactured by Nippon Denshoku Industries Co., Ltd.).

(1-1) Preparation of Cellulose Acylate Solution A cellulose acylate solution was prepared by the following two dissolution methods. Table 1 shows the detailed solvent composition.
In addition, silica particles (particle size: 20 nm), triphenyl phosphate / biphenyl diphenyl phosphate (1
/ 2), 2,4-bis- (n-octylthio) -6
(4-Hydroxy-3,5-di-tert-butylanilino) -1,3,5-triazine was added to each of 0.5% by mass, 10% by mass, and 1.0% by mass of cellulose acylate.
Was added. Further, 200 ppm of citric acid was added to cellulose acylate as a release agent. In addition, as the liquid for forming the inner layer and the outer layer of co-casting in the present invention, the above-mentioned cellulose acylate solution was used while changing its concentration.
Details are shown in Table 1.

(1-1a) Dissolution by cooling (described as "Cooling" in Table 1) Cellulose acylate shown in Table 1 was gradually added to a solvent with good stirring, and the mixture was stirred at room temperature (25 ° C.) for 3 hours. Leave to swell. The resulting swelled mixture was cooled to −30 ° C. at −8 ° C./min with slow stirring, then cooled to the temperature shown in Table 1, and after 6 hours, the temperature was raised at + 8 ° C./min to increase the sol content. At a stage where the conversion to a certain extent proceeded, stirring of the contents was started. The mixture was heated to 50 ° C. to obtain a dope.

(1-1b) High pressure and high temperature melting (Table 1 shows "high temperature")
The cellulose acylate shown in Table 1 was gradually added to the solvent with good stirring, and allowed to stand at room temperature (25 ° C.) for 3 hours to swell. The obtained swollen mixture was placed in a double-walled stainless steel closed container. The mixture was heated at + 8 ° C./min by passing high-pressure steam through the outer jacket of the vessel, and kept at 1 Mpa at the temperature shown in Table 1 for 5 minutes. Thereafter, water at 50 ° C is passed through the outer jacket and cooled to 50 ° C at -8 ° C / min.
A dope was obtained.

(1-2) Filtration of Cellulose Acylate Solution Next, the obtained dope was filtered at 50 ° C. at an absolute filtration accuracy of 0.0
Filter with 1 mm filter paper (Toyo Roshi Kaisha, Ltd., # 63),
Further, the solution was filtered through a filter paper (FH025, manufactured by Pall Corporation) having an absolute filtration accuracy of 0.0025 mm.

(1-3) Preparation of Cellulose Acylate Film The solution of (1-2) was cast using a casting machine described in JP-A-56-162617. After performing the poor solvent treatment shown below at some levels, after passing through the stripping process,
It was transported in a tenter and dried in an environment of 120 ° C. for 30 minutes, and the solvent was evaporated to obtain a cellulose acylate film. In the present invention, the layer structure is a two-layer or three-layer structure. The two layers have a structure of an inner layer / outer layer from the band surface, and the three layers have a sandwich-type structure of an outer layer / inner layer / outer layer. Details are shown in Table 1.

(1-3a) Poor solvent bath treatment (described as "solvent bath" in Table 1) A bath filled with a solvent is prepared before the stripping position, and the support before peeling is a bath with freshly dried film. It was immersed in the solvent for 2-3 seconds.

(1-1b) Poor solvent spray treatment (described as "spray" in Table 1) A step of spraying a solvent is provided before the stripping position, and the raw dry film adhered to the support before peeling is provided. A poor solvent was sprayed on the surface. Spray volume is about per film 1m ² 5g
Met.

[0053]

[Table 1]

(1-3) Result The obtained cellulose acylate solution and film were evaluated in accordance with the above-mentioned items. In the production method of the present invention,
No particular problems were found in the stability of the solution used, the mechanical and optical properties of the film. On the other hand, in the comparative example, a problem was recognized in the surface state of the obtained film.

Further, these films were stretched 10% to 30% MD and TD at 130 ° C. online or during the drying process during the film forming process. These are 40 nm to 160 nm in proportion to the draw ratio.
The retardation could be increased. The cellulose acylate film thus obtained contains the liquid crystal display device described in Example 1 of JP-A-10-48420 and the discotic liquid crystal molecules described in Example 1 of JP-A-9-26572. Optically anisotropic layer, alignment film coated with polyvinyl alcohol, JP-A-2000-15
VA type liquid crystal display device described in FIGS. 2 to 9 of JP-A-4261, and FIGS. 10 to 15 of JP-A-2000-154261.
When used in the OCB type liquid crystal display device described in (1), good performance was obtained. Further, when used as a polarizing plate described in JP-A-54-016575, good performance was obtained.

[0056]

[Table 2]

[0057]

After dissolving cellulose acylate in a solvent,
A method for producing a cellulose acylate film, characterized in that it is cast on a smooth band or a drum, then peeled off and dried to form a film, and is not dried before being peeled off from a band surface or a drum surface. By a method for producing a cellulose acylate film, which comprises treating the film with a poor solvent, a production method for improving the surface condition of the cellulose acylate film has been achieved.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme court ゛ (Reference) // B29K 1:00 B29K 1:00 B29L 7:00 B29L 7:00 9:00 9:00 C08L 1: 00 C08L 1:00 F term (reference) 4F071 AA09 AH19 BA02 BB02 BC01 4F205 AA01 AB07 AB11 AB14 AC05 AG01 AG03 AM26 AM27 GA07 GB02 GB26 GC02 GC07 GE22 GE24 GN22 GN29 GW06

Claims (8)

[Claims] 1. a step of preparing a cellulose acylate solution by dissolving cellulose acylate in a solvent; a step of casting the obtained solution on a smooth band or drum; A method for producing a cellulose acylate film, comprising: a step of treating the film with a poor solvent for cellulose acylate, a step of peeling off the wet film from a band or a drum, and a step of drying the wet film. 2. The cellulose according to claim 1, wherein the step of treating the wet film with a poor solvent is carried out by immersing the wet film in the poor solvent or spraying the poor film on the wet film. A method for producing an acylate film. 3. The method for producing a cellulose acylate film according to claim 1, wherein the poor solvent is water, alcohol or hydrocarbon. 4. The method for producing a cellulose acylate film according to claim 3, wherein the poor solvent is water, an alcohol having a boiling point of 120 ° C. or less, or a hydrocarbon having 10 or less carbon atoms. 5. The method for producing a cellulose acylate film according to claim 1, wherein the solvent for dissolving the cellulose acylate is a substantially non-chlorinated solvent. 6. The step of preparing a cellulose acylate solution comprises adding a mixture of cellulose acetate and a solvent to -80.
The method for producing a cellulose acylate film according to claim 1, further comprising a treatment of cooling to a temperature of from −10 ° C. to −10 ° C. or a treatment of heating to a temperature of 80 to 220 ° C. 7. The method for producing a cellulose acylate film according to claim 1, wherein the step of casting the solution is performed by a co-casting method of two or more layers. 8. The method for producing a cellulose acylate film according to claim 1, wherein silica particles having an average particle diameter of 0.1 μm or less, a plasticizer or an ultraviolet absorber are added to the solution.