JP2003041015A - Method of production for cellulose acrylate film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cellulose acylate solution excellent in stability with time and productivity, and to provide a cellulose acylate film excellent in productivity and surface condition. SOLUTION: This method for manufacturing the cellulose acylate film consists of dissolving the cellulose acylate I a mixed solvent comprising a non-chlorine type solvent and an alcohol and casting to forms the film, by adding the alcoholic solvent to the cellulose acylate solution just before casting.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a cellulose acylate film and a method for producing the same.

[0002]

2. Description of the Related Art Cellulose acylate film is used in various photographic materials and optical materials because of its toughness and flame retardancy. Cellulose acylate film is a typical photographic light-sensitive material support. The cellulose acylate film is also used in liquid crystal display devices whose market is expanding recently due to its optical isotropy. Typical applications for liquid crystal display devices are protective films for polarizing plates and color filters.

The cellulose acylate film is generally produced by a solvent casting method or a melt casting method. In the solvent cast method, a solution (dope) in which cellulose acylate is dissolved in a solvent is cast on a metal support and the solvent is evaporated to form a film. In the melt cast method, a film obtained by melting cellulose acylate by heating is cast on a metal support and cooled to form a film. The solvent cast method can produce a good film having higher flatness than the melt cast method. Therefore, practically, the solvent casting method is usually adopted. The solvent cast method is described in many documents. In the recent solvent cast method, it is possible to improve the productivity of the film-forming process by shortening the time required from casting the dope onto the metal support to peeling off the molding film on the metal support. It is an issue. For example, Japanese Examined Patent Publication 5-1784
Japanese Patent Publication No. 4 proposes that a high-concentration dope is cast on a cooling drum to reduce the time required for stripping after casting.

The solvent used in the solvent casting method is required not only to dissolve the cellulose acylate but also to various conditions. In order to economically and efficiently produce a film having excellent flatness and a uniform thickness, it is necessary to prepare a solution (dope) having an appropriate viscosity and polymer concentration and excellent storage stability. For dope,
It is also required to be easy to gel and to be easily peeled from the metal support. In order to prepare such a dope, the selection of solvent type is extremely important. The solvent is also required to be easily evaporated and to have a small residual amount in the film. Various organic solvents have been proposed as a solvent for cellulose acylate, but the practically practical organic solvents have been practically limited to methylene chloride.

However, the use of chlorine-based solvents such as methylene chloride has been significantly restricted in recent years from the viewpoint of global environment protection. Further, since methylene chloride has a low boiling point (41 ° C.), it easily volatilizes in the manufacturing process. Therefore, it is also a problem in the work environment. In order to prevent these problems, the manufacturing process is closed, but there is a technical limit even if it is sealed. Therefore, there is an urgent need to find a solvent for cellulose acylate that can substitute for methylene chloride.

By the way, acetone (boiling point: 56 ° C.), which is a general-purpose organic solvent, has a relatively low boiling point, and its drying load is not so large. In addition, it has less problems with the human body and the global environment than chlorine-based organic solvents. However, acetone has a low solubility in cellulose acylate. Acetone shows some solubility in cellulose acetate having a substitution degree of 2.70 (acetylation degree of 58.8%) or less. If the degree of substitution of cellulose acylate exceeds 2.70, the solubility of acetone will further decrease. Substitution degree 2.
When the cellulose acylate has a degree of acetylation of 80 (degree of acetylation 60.1%) or more, acetone only exhibits a swelling action and does not exhibit solubility.

J. M. G. Papers by Cowie et al., Mak
romol, chem. , 143, 105 (197
1 year) is a cellulose acylate having a degree of substitution of 2.80 to 2.90 in acetone at −80 ° C. to −70 ° C.
It was reported that a dilute solution in which the cellulose acylate was dissolved in acetone in an amount of 0.5 to 5% by mass was obtained by cooling after cooling to 0. Is limited to acetyl groups). Less than,
A method of cooling a mixture of cellulose acylate and an organic solvent to obtain a solution in this manner is called a "cooling dissolution method". Regarding dissolution of cellulose acylate in acetone, Kenji Uede et al., "Dry-spinning of cellulose triacetate from acetone solution", Journal of the Textile Machinery Society, 34
Volume, page 57 (1981). As its title suggests, this paper applies the cooling dissolution method to the technical field of spinning method. In this paper, the cooling dissolution method is examined, paying attention to the mechanical properties, dyeability and cross-sectional shape of the fiber obtained. In this paper, a solution of cellulose acetate having a concentration of 10 to 25% by weight is used for fiber spinning.

The inventors of the present invention investigated the type of cellulose acylate solvent and the film forming method, and peeled the film from the metal support after casting by adding alcohol to the dope, and the transportability during drying. I found that it greatly improved. However, on the other hand, it was also confirmed that the addition of alcohol deteriorates the stability of the dope. That is, it is feasible that the film can be easily peeled off, and that the peeled film in the undried state has a strength that does not deform in the transporting process, but it is difficult to achieve compatibility with the stability of the dope.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to provide a cellulose acylate solution which is excellent in dope stability over time and is excellent in productivity. Another object of the present invention is to produce a cellulose acylate film having excellent dope stability over time and excellent surface condition.
Still another object of the present invention is to provide a polarizing plate protective film made of a cellulose acylate film having an excellent surface condition.

[0010]

The object of the present invention is to provide a method for producing a cellulose acylate film of the following (1) to (13), a cellulose acylate film of the following (14) and (15), and the following ( This was achieved by the polarizing plate protective film described in 16). (1) A method for producing a cellulose acylate film, which comprises dissolving a cellulose acylate in a single solvent or a plurality of main solvents substantially composed of a chlorine-free solvent, and casting the film. A method for producing a cellulose acylate film, which comprises adding alcohol to the cellulose acylate solution immediately before casting. (2) The method for producing a cellulose acylate film according to (1), wherein the alcohol is an aliphatic alcohol having 6 or less carbon atoms. (3) The method for producing a cellulose acylate film according to (1) or (2), characterized in that the alcohol is added in-line.

(4) A method for producing a cellulose acylate film, which comprises casting two or more layers by a co-casting method, wherein both the solution in the inner layer and the solution in the outer layer are used. The method for producing a cellulose acylate film according to any one of (1) to (3), characterized in that alcohol is added. (5) Alcohol is immediately added to only the inner layer, or the amount of alcohol added to the inner layer is 1.0 relative to the outer layer.
The method for producing a cellulose acylate film according to any one of (1) to (4), which is 5 times to 6.0 times. (6) The main solvent of the cellulose acylate solution is a mixed solvent of at least a ketone having a solubility parameter of 19 to 21 and an ester having a solubility parameter of 19 to 21. (1) to (5) The method for producing a cellulose acylate film according to any one of the above.

(7) The cellulose acylate film according to any one of (1) to (6), wherein the amount of alcohol added is in the range of 2 to 30% by mass based on the total amount of the solvent. Manufacturing method. (8) The mixture of the solvent and the cellulose acylate is -80
The method for producing a cellulose acylate film according to any one of (1) to (7), characterized in that it is exposed to a temperature of -10 ° C or 80 to 220 ° C to be dissolved. (9) The cellulose acylate film has a multilayer structure of two or more layers, and the thickness of the outer layer on at least one side of the cellulose acylate film is in the range of 1 to 50 μm (4) A method for producing a cellulose acylate film according to any one of (8) to (8).

(10) The cellulose acylate film has a multilayer structure of three or more layers, and the thickness of the outer layer on at least one side of the cellulose acylate film is 1 to 50.
The method for producing a cellulose acylate film according to any one of (4) to (8), wherein the method is in the range of μm. (11) The method for producing a cellulose acylate film according to (9) or (10), wherein the outer layer has a thickness in the range of 1 to 20 μm. (12) The method for producing a cellulose acylate film according to any one of (4) to (11), wherein the respective layers are cast at the same time. (13) The method for producing a cellulose acylate film according to any one of (4) to (12), characterized in that at least one of the outer layers contains a release agent.

(14) A cellulose acylate film formed by the method described in any one of (1) to (13). (15) The cellulose acylate film described in (14), to which silica particles, a plasticizer and an ultraviolet absorber are added. (16) A polarizing plate protective film formed from the cellulose acylate film according to (14) or (15).

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Regarding the cellulose acylate raw material cotton preferably used in the present invention, the Institute of Invention and Innovation Technical Report 2
001-1745, the description regarding "4. Cellulose acylate raw material cotton" described in the 26th line after the right side of page 7 can be used.

In the present invention, the cellulose acylate film is preferably produced by the solvent casting method, and the film is produced by using the cellulose acylate dope. The organic solvent used is not particularly limited,
It is a mixture of ketones and esters, and a solvent having a solubility parameter of 19 to 21 is preferably used. These esters and ketones may have a cyclic structure or may have two or more kinds of functional groups.

Examples of esters include methyl formate, ethyl formate, propyl formate, methyl acetate, ethyl acetate and the like. Of these, methyl acetate is particularly preferable. Examples of ketones include acetone, methyl ethyl ketone, diethyl ketone, methyl isobutyl ketone, cyclopentanone, cyclohexanone and the like. Of these, acetone, cyclopentanone, and cyclohexanone are particularly preferable.

Next, the solubility parameter of the solvent will be described. Solubility parameter is calculated by
H is a quantity defined by (ΔH / V) ^1/2 where V is the molar volume, and the solubility increases as the difference between the solubility parameters of the two becomes smaller. There are many books that describe solubility parameters, but for example, J. Brandru
p, E. H et al. (Polymer Handbook (fourth edit
ion), VII / 671 to VII / 714). The solubility parameters of the main ketones are shown below. Acetone (20.3), methyl ethyl ketone (19.0), diethyl ketone (18.2), diisobutyl ketone (18.
0), cyclopentanone (20.9), cyclohexanone (20.3) and methylcyclohexanone (20.
1). The solubility parameters of the esters are shown below. Ethyl formate (19.2), propyl formate (18.
4), n-pentyl formate (18.1), methyl acetate (1
9.6), ethyl acetate (18.2) and n-pentyl acetate (17.6).

By the way, from the viewpoint of the global environment and the working environment,
The organic solvent preferably contains substantially no chlorine-based solvent. "Substantially free" means that the proportion of chlorine-based solvent in the organic solvent is less than 10% by mass, preferably 5% by mass.
It means less than 3% by mass, more preferably less than 3% by mass. Further, it is preferable that no chlorine-based solvent such as methylene chloride is detected in the produced cellulose acylate film.

Further, examples of alcohol include methanol,
Ethanol, 1-propanol, 2-propanol, 1
-Butanol, 2-butanol and cyclohexanol, 2-fluoroethanol, 2,2,2-trifluoroethanol and the like. Of these, alcohols having 6 or less carbon atoms are preferably used, and particularly preferred are methanol, ethanol, 1-propanol, 2-propanol and 1-butanol.

In an actual solvent system, the ester is a total solvent of 4
0 to 95% by mass, preferably 50 to 80% by mass,
The ketones are 5 to 50% by mass of the total solvent, preferably 10 to
It is preferably 40% by mass. Further, the amount of ketones and esters is preferably 70% by mass or more of the total solvent. Moreover, it is preferable that the alcohols are contained in an amount of 2 to 30% by mass of all the solvents.

Specific examples of preferable combinations of these solvents in the present invention are disclosed in JIII Journal of Technical Disclosure No. 2001-1745,1.
The first line on the right side of page 5 to the eighth line on the left side of page 16 can be mentioned. Also, the use of chlorine-based solvent is not particularly limited.

In order to prepare a cellulose acylate solution, the above-mentioned cellulose acylate is added to the solvent in a tank at room temperature with stirring to swell the solvent. The swelling time must be at least 10 minutes or longer, and if it is 10 minutes or less, insoluble matter remains. In order to swell the cellulose acylate sufficiently, the temperature of the solvent is 0 to 40 ° C.
Is preferred. When the temperature is 0 ° C. or lower, the swelling rate decreases and insoluble matter tends to remain, and when the temperature is 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 either the cooling dissolution method or the high temperature dissolution method, or both.

Specific examples of the cooling and melting methods and the high temperature melting method are disclosed in JIII Journal of Technical Disclosure 2001-1745,
Examples thereof include those described in (Cooling melting method) and (High temperature melting method) on page 15, left column, line 15 to page 25, left column, line 9.

In some cases, the dope cellulose acylate obtained above may be dissolved at a low concentration in order to make it more soluble, and then concentrated by using a concentration means. As a concrete method, the Institute of Invention and Innovation Public Technical Report 20
01-1745, page 25, left column, line 10 to line 28 (solution concentration).

Prior to casting, it is preferable to remove foreign matters such as undissolved substances, dust and impurities by filtration using a suitable filter material such as wire mesh, paper and flannel. For example, those described in the association publication technical report 2001-1745, page 25, from the 29th line on the left side to the 33rd line on the right side (filtration).

The cellulose acylate solution of the present invention contains
Various additives can be added in each preparation step depending on the application. Examples of additives include plasticizers, ultraviolet ray inhibitors and deterioration inhibitors (eg, antioxidants, peroxide decomposers,
Examples thereof include radical inhibitors, metal deactivators, acid scavengers, amines), strippers, and fine particles. Specific examples include those described in JIII Journal of Technical Disclosure 2001-1745, page 16, left column, line 28 to page 22, right column, bottom line, 5th line.

A method for producing a film using the cellulose acylate solution of the present invention will be described. As the method and equipment for producing the cellulose acylate film of the present invention, the solution casting film forming method and the solution casting film forming apparatus conventionally used for the production of cellulose triacetate film are used. The dope (cellulose acylate solution) prepared from the dissolution tank (pot) is once stored in a stock tank, and the bubbles contained in the dope are removed or final preparation is performed. The dope is sent from the dope outlet to the pressurizing die through a pressurizing constant quantity gear pump that can deliver the dope with high accuracy by the number of rotations, and the dope of the casting part running endlessly from the die (slit) of the pressurizing die. The dope film (also referred to as a web), which is dry and dried, is peeled from the metal support at a peeling point which is evenly cast on the metal support and the metal support makes one round. Both ends of the obtained web are sandwiched by clips and conveyed by a tenter while keeping the width and dried, and then conveyed by rolls of a drying device to complete the drying and wound by a winder to a predetermined length. The combination of the tenter and the roll group drying device varies depending on the purpose. In the solution casting film forming method used for the silver halide photographic light-sensitive material and the functional protective film for electronic displays, in addition to the solution casting film forming device, an undercoat layer, an antistatic layer, an antihalation layer, a protective layer, etc. A coating device is often added for the surface treatment of the film.

In the present invention, the obtained cellulose acylate solution is cast as a single layer on a smooth band or a drum as a metal support, or as a co-cast with two or more layers of cellulose acylate solution. To do. In co-casting, for example, when casting a plurality of cellulose acylate solutions, a solution containing cellulose acylate is cast from a plurality of casting ports arranged at intervals in the traveling direction of the metal support. The film can be manufactured while being laminated. Such a casting method is described in, for example, Japanese Patent Laid-Open No. 11-198285. The film can also be produced by casting a cellulose acylate solution from two casting ports. For such a casting method, see Japanese Patent Laid-Open No. 6-134933.
It is described in Japanese Patent Publication No. Also, JP-A-56-1626
Alternatively, a film may be produced by a casting method in which the 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 as described in JP-A No. it can. By carrying out such co-casting, smoothing during drying of the surface progresses as described above, and thus a great improvement in surface condition can be expected.

In the case of co-casting, the thickness of each layer is not particularly limited, but the outer layer is preferably thinner than the inner layer. At that time, the thickness of the outer layer is preferably 1 to 50 μm, particularly preferably 1 to 30 μm. Here, the outer layer is the band surface (drum surface) in the case of two layers
However, in the case of three or more layers, the layers on both surface sides of the completed film are shown. The inner layer is the band surface (drum surface) in the case of two layers. When there are three or more layers, the layers are inside the outer layer. Further, 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, an ultraviolet absorbing layer, a polarizing layer).

The solution constituting the outer layer and the inner layer in the present invention will be described. In the case of single layer casting, the outer layer,
Although there is no distinction between the inner layers, in the case of co-casting, the layers are considered separately as described above. The undried film obtained by casting needs to be peeled from the metal support, and in practice, the undried film is cooled to gel and peeled.
As a result of earnest studies by the present inventors, it has been clarified that the addition of a large amount of alcohols to the inner layer facilitates the progress of gelation of the whole and improves the transportability in an undried state. However, since the stability of the liquid is lowered by adding alcohol, the film can be formed before the liquid becomes cloudy or precipitated by adding alcohol immediately before casting. Adding just before casting means mixing the alcohol within 1 hour of casting, more preferably within 10 minutes, and further preferably within 3 minutes. In addition, in-line addition is most preferable because the addition can be performed within 1 minute by adding in-line during casting.

In the case of co-casting, there is no problem even if the amount of alcohol added is the same in the inner and outer layers, but it is appropriate to add alcohol only to the inner layer or to the inner layer in a large amount to suit the gelation suitability of the entire film. It is preferable from the viewpoint of surface condition.

The drying temperature of the dope on the metal support is preferably 30 to 250 ° C., and 40 to 18
Even more preferably 0 ° C. The drying temperature of the dope is described in JP-B-5-17844. Further, there is also a method of positively stretching in the width direction, and in the present invention, for example, JP-A-62-115035, JP-A-4-152125, JP-A-4-284221, and JP-A-4-284111.
The stretching methods described in JP-A No. 298310 and JP-A No. 11-48271 can be used. The film may be stretched uniaxially or biaxially. The stretch ratio of the film (the ratio of the increase due to stretching to the original length) is
It is preferably 10 to 30%.

The thickness of the cellulose acylate film after drying varies depending on the purpose of use, but is usually 5 to 500 μm.
m, preferably 20 to 250 μm, and most preferably 30 to 180 μm. The thickness of the film is
It is particularly preferable that it is in the range of 30 to 110 μm. The film thickness is adjusted so that the solid content concentration in the dope, the slit gap of the die die,
The extrusion pressure from the die, the speed of the metal support, etc. may be adjusted.

Here, in some cases, by performing the surface treatment of the cellulose acylate film, the adhesion between the cellulose acylate film and each functional layer (for example, the undercoat layer and the back layer) can be improved. Specific examples thereof include those described in JIII Journal of Technical Disclosure 2001-1745, page 32, left column, line 16 to page 32, right column, line 42.

Depending on the application, 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 adhering to the polarizer. Specifically, the Invention Association Open Technical Report 2001-
1745, the layer from the bottom row of page 32 right to the third row from the bottom row of page 45 left can be provided.

The cellulose acylate film composed of the cellulose acylate solution can be used for various purposes. Specifically, the Institute of Invention and Innovation Technical Report 2001-17
An example of the item “14. Use” described in the fifth and subsequent lines from the bottom on the right side of pages 45 and 45 can be mentioned.

[0038]

Examples In each example, cellulose acylate,
The chemical and physical properties of solutions and films are:
It was measured and calculated as follows.

(0) Substitution degree (%) of cellulose acylate The acetylation degree was measured by a saponification method. The dried cellulose acylate was precisely weighed, dissolved in a mixed solvent of acetone and dimethylsulfoxide (volume ratio 4: 1), added with a predetermined amount of 1N-sodium hydroxide aqueous solution, and saponified 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 conducted by the same method as above. Then, the acetylation degree (%) was calculated according to the following formula. Acetylation degree (%) = (6.005 × (B−A) × F) / W In the formula, A is the amount of 1N-sulfuric acid (ml) required for titration of the sample,
B: 1N-sulfuric acid amount (ml) required for the blank test, F
Indicates a factor of 1N-sulfuric acid, and W indicates a sample mass. still,
For systems containing multiple acyl groups, the difference in pKa was used to determine the amount of each acyl group. In addition, publicly known literature (T. Sei,
K.Ishitani, R.Suzuki, K.Ikematsu PolymerJournal 17 1
065 (1985)) and the value was confirmed separately. Further, the degree of acetylation and the amount of other acyl groups obtained from these were converted into the degree of substitution in consideration of the molar molecular weight.

(1) Viscosity average degree of polymerization (DP) of cellulose acylate About 0.2 g of absolutely dried cellulose acylate was precisely weighed and dissolved in 100 ml of a mixed solvent of methylene chloride: ethanol = 9: 1 (mass ratio). did. The number of seconds of dropping of this was measured with an Ostwald viscometer at 25 ° C., and the degree of polymerization was determined by the following formula. ηrel = T / T0 T: Falling seconds of measurement sample [η] = (1nηrel) / C T0: Falling seconds of solvent alone DP = [η] / Km C: Concentration (g / l) Km: 6 × 10 ^-Four

(2) Stability of Solution The state of the obtained solution or slurry was observed by leaving it at room temperature (23 ° C.) for 20 days while keeping it still.
It was evaluated in four grades of D. A: Shows transparency and liquid uniformity. B: Some undissolved residue or a little 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 or dissolution observed.

(3) Viscosity of Solution Cellulose Acylate Solution Prepared at 0 ° C. and 50 ° C.
The apparent viscosity in Rh was measured using a Cone-plate type sensor.
It was measured with an eometer (TA Instruments).

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

(5) Haze of film The haze was measured using a 1001DP type (manufactured by Nippon Denshoku Industries Co., Ltd.).

Examples will be given below, but the present invention is not limited thereto. (1-1) Preparation of Cellulose Acylate Solution A cellulose acylate solution was prepared by the following two dissolution methods. The detailed solvent compositions of the present invention and comparative examples are shown in Table 1. Silica particles (particle size 20n
m), 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 the cellulose acylate at 0.5% by mass, 10% by mass and 1.0% by mass, respectively. Further, 200 ppm of citric acid as a release agent was added to the cellulose acylate. As a liquid for forming the inner layer and the outer layer of the co-casting in the present invention, a cellulose acylate solution was prepared without containing alcohol, and alcohol was added immediately before. Details are also shown in Table 1.

(1-1a) Dissolution by cooling (described as "cooling" in Table 1) The cellulose acylate described 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. It was left to swell. The resulting swollen mixture was slowly stirred and cooled at −8 ° C./min to −30 ° C., then cooled to the temperature shown in Table 1 for 6 hours, and then heated at + 8 ° C./min to raise the sol content. The stirring of the contents was started at a stage where the reaction had progressed to some extent. The dope was obtained by heating to 50 ° C. (1-1b) High-pressure high-temperature dissolution (described as “high temperature” in Table 1) The cellulose acylate described in Table 1 was gradually added to a solvent while stirring well, and left at room temperature (25 ° C.) for 3 hours. Allowed to swell. The obtained swelling mixture was placed in a stainless steel closed container having a double structure. By passing high-pressure steam through the outer jacket of the container, it is heated at + 8 ° C / min and under 1 MPa.
The temperature shown in Table 1 was maintained for 5 minutes. After that, water at 50 ° C. was passed through the outer jacket and cooled to 50 ° C. at −8 ° C./min to obtain a dope.

(1-2) Filtration of Cellulose Acylate Solution The dope thus obtained was subjected to absolute filtration accuracy of 0.0 at 50 ° C.
Filter with 1 mm filter paper (# 63 manufactured by Toyo Roshi Kaisha, Ltd.),
Further, filtration was performed with a filter paper (FH025, manufactured by Pall Ltd.) having an absolute filtration accuracy of 0.0025 mm.

The solutions of (1-3) and (1-2) were prepared according to the method described in Japanese Patent Application Laid-Open No.
The cellulose acylate film was cast by using a casting machine described in JP-A No. 6-162617, dried in an environment of 120 ° C. for 30 minutes, and the solvent was evaporated. In the present invention, the layer structure is two layers or three layers. The two layers have a sandwich type structure of an inner layer / outer layer from the band surface, and the three layers have an outer layer / inner layer / outer layer sandwich structure. Details are shown in Table 1. Further, for some of the examples, alcohol was added in-line to prepare a solution just before casting. In this system, casting is performed within 1 minute from the addition of alcohol (in the table, it is described as "in-line addition").

[0049]

[Table 1]

(1-3) The resulting cellulose acylate solution and film were evaluated according to the above items. With the cellulose acylate solution and film of the present invention, no particular problems were observed in the mechanical properties and optical properties of the film. On the other hand, in Comparative Example, a problem was recognized in the surface condition of the obtained film.

These films were stretched 10% to 30% MD and TD at 130 ° C. online during the drying step in the film forming step or thereafter offline. These are 40 nm to 160 nm in proportion to the draw ratio.
It was possible to increase the retardation. 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 shown in FIGS. 2 to 9 of Japanese Patent No. 4261, and FIGS. 10 to 15 of Japanese Patent Laid-Open No. 2000-154261.
When used in the OCB type liquid crystal display device described in 1., good performance was obtained. Further, when it was used as a polarizing plate described in JP-A No. 54-016575, good performance was obtained.

[0052]

[Table 2]

[0053]

EFFECT OF THE INVENTION A method for producing a cellulose acylate film, which comprises dissolving a cellulose acylate in a mixed solvent of a main solvent substantially composed of a chlorine-free solvent and an alcohol, and then forming a film by casting. There is a method for producing a cellulose acylate film, characterized in that alcohol is added to the cellulose acylate solution immediately before casting, thereby improving the surface condition of the film and causing no problem in mechanical properties and the like. A film manufacturing method was achieved.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C08K 3/36 C08K 3/36 C08L 1/10 C08L 1/10 G02B 5/30 G02B 5/30 // B29K 1:00 B29K 1:00 B29L 7:00 B29L 7:00 9:00 9:00 9:00 F term (reference) 2H049 BA02 BB13 BB33 BB63 BC09 4F071 AA09 AB26 AC05 AC07 AC10 AE04 AE05 AE19 AF29 AF35 AH16 BA02 BB02 BC01 BC02 4F100 AA20A AA20B AA20C AJ06A AJ06B AJ06C AL05A AL05B AL05C BA02 BA03 BA10A BA10C BA15 CA04A CA04B CA04C CA07A CA07B CA07C CA30A CA30B CA30C DE01A DE01B DE01C EA061 EG002 EH312 GB41 JA20A JA20B JA20C JL00 JL02 4F205 AA01J AB01 AB06 AB07 AB17 AC05A AG01 AG03 AH73 4J002 AB01 AB02 DJ01 EC01 EE02 EH02 FD02 FD05 GP00

Claims (13)

[Claims] 1. A method for producing a cellulose acylate film, which comprises dissolving a cellulose acylate in a single solvent or a plurality of main solvents substantially composed of a non-chlorine solvent, and casting the film. And a method for producing a cellulose acylate film, which comprises adding alcohol to the cellulose acylate solution immediately before casting. 2. The method for producing a cellulose acylate film according to claim 1, wherein the alcohol is an aliphatic alcohol having 6 or less carbon atoms. 3. The method for producing a cellulose acylate film according to claim 1, wherein the alcohol is added by in-line addition. 4. A method for producing a cellulose acylate film, which comprises casting two or more layers by a co-casting method, wherein both the solution in the inner layer and the solution in the outer layer are alcohol. The method for producing a cellulose acylate film according to any one of claims 1 to 3, further comprising: 5. The method according to claim 1, wherein alcohol is immediately added to only the inner layer, or the amount of alcohol added to the inner layer is 1.05 to 6.0 times that of the outer layer. 4. The method for producing a cellulose acylate film according to any one of 4 above. 6. The main solvent of the cellulose acylate solution is composed of a mixed solvent of at least a ketone having a solubility parameter of 19 to 21 and an ester having a solubility parameter of 19 to 21. The method for producing a cellulose acylate film according to any one of items. 7. A mixture of a solvent and cellulose acylate is exposed to a temperature of −80 to −10 ° C. or 80 to 220 ° C. to dissolve the mixture, and the mixture is dissolved. The method for producing a cellulose acylate film according to item 1. 8. The cellulose acylate film has a multilayer structure of two or more layers, and the thickness of the outer layer on at least one side of the cellulose acylate film is in the range of 1 to 50 μm. Item 8. A method for producing a cellulose acylate film according to any one of Items 4 to 7. 9. The cellulose acylate film has a multilayer structure of three or more layers, and the thickness of the outer layer on at least one side of the cellulose acylate film is in the range of 1 to 50 μm. Item 8. A method for producing a cellulose acylate film according to any one of Items 4 to 7. 10. The method for producing a cellulose acylate film according to claim 4, wherein the respective layers are cast simultaneously. 11. The method for producing a cellulose acylate film according to claim 4, wherein at least one of the outer layers contains a release agent. 12. A cellulose acylate film formed by the method according to claim 1. 13. The cellulose acylate film according to claim 12, further comprising silica particles, a plasticizer and an ultraviolet absorber.