JP2003041053A - Cellulose acylate solution and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the surface state of film by lowering the viscosity of a cellulose acylate solution. SOLUTION: This cellulose acylate solution is composed of a blend of a cellulose acylate having the total of whole acyl substitution degree of >=2.75 and <=2.90 and the substitution degree of the 6-position of >=0.90 and a cellulose acylate having the total of whole acyl substitution degree of >=2.70 and <=2.75 and the acyl substitution degree of the 6-position of <0.90.

Description

Detailed Description of the Invention

[0001]

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

[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 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. Therefore, practically, the solvent casting method is usually adopted. The solvent cast method is described in many documents. In the recent solvent cast method, the problem is to improve the productivity of the film-forming process by shortening the time required from casting the dope onto the support to peeling the molding film on the support. Has become. For example, Japanese Examined Patent Publication No. 5-17844 proposes casting a high-concentration dope 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 that gelation is easy and peeling from the support is easy. 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 solvents for cellulose acylate. Practically limited organic solvents are practically limited to methylene chloride, but methylene chloride has problems such as environmental suitability and boiling point, and a solvent that can substitute for it has been searched. There is.

J. M. G. Papers by Cowie et al., Mak
romol, chem. , 143, p. 105 (197
1 year), a cellulose acylate having a degree of substitution of 2.80 to 2.90 is added in acetone at −80 ° C. to −70.
It was reported that a dilute solution in which 0.5 to 5% by mass of cellulose acylate was dissolved in acetone was obtained by heating after cooling to ℃ (however,
Acyl groups here are limited to acetyl groups). Hereinafter, a method of cooling a mixture of cellulose acylate and an organic solvent in this manner to obtain a solution is referred to as a "cooling dissolution method". Regarding the dissolution of cellulose acylate in acetone, Kenji Uede et al., “Dry-spinning of cellulose triacetate from acetone solution”, Journal of the Textile Machinery Society, 3
4, 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. In addition to the above-mentioned cooling dissolution, a "high temperature melting method" has been proposed in which the mixture is melted under high temperature and high pressure conditions.

In this way, in the casting method in which the cellulose acylate solution (dope) dissolved in various solvents is cast on the support, the film is peeled from the support and dried, the obtained cellulose is obtained. In many cases, the surface state of the acylate film was not good, and the optical properties such as transparency were not good. On the other hand, if the degree of acyl substitution of cellulose acylate is lowered for the purpose of improving the surface state and optical properties, the strength of the film is lowered, and it is difficult to satisfy both requirements.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a cellulose acylate solution which has excellent stability over time and has a low viscosity in a practical dope concentration range. Still another object of the present invention is to provide a method for producing a cellulose acylate film having excellent surface properties, optical characteristics and film strength. Still another object of the present invention is to provide a polarizing plate protective film made of a cellulose acylate film having excellent surface properties, optical characteristics and film strength.

[0008]

An object of the present invention is to provide a cellulose acylate solution described in (1) to (7) below, a method for producing a cellulose acylate solution described in (8) below, and (9) below. To (13), and the polarizing plate protective film described in (14) below. (1) A cellulose acylate having a total acyl substitution degree of 2.75 or more and 2.90 or less and an acyl substitution degree of 6-position of 0.90 or more, and a total acyl substitution degree of 2.70. A cellulose acylate solution substantially composed of a blend with a cellulose acylate having a degree of acyl substitution at the 6-position of less than 2.75 and not more than 2.75. (2) Cellulose acylate having a total acyl substitution degree of 2.75 or more and 2.90 or less and an acyl substitution degree of 6-position of 0.90 or more, and a total acyl substitution degree of 2.70. The blend ratio with the cellulose acylate having a degree of acyl substitution at the 6-position of less than 2.75 and not more than 2.75 and less than 0.90 is in the range of 98: 2 to 2:98 (1). The described cellulose acylate solution.

(3) The sum of all acyl substitution degrees is 2.75 or more and 2.90 or less, and the 6-position acyl substitution degree is 0.
The cellulose acylate solution according to (1) or (2), wherein the acyl group of the cellulose acylate having 90 or more is an acetyl group. (4) In the cellulose acylate having a total acyl substitution degree of 2.70 or more and 2.75 or less and an acyl substitution degree of 6-position of less than 0.90, the substitution degree of 0.02 to 0.4 is equivalent. Is an acyl group having 3 to 8 carbon atoms, and the rest is an acetyl group, wherein the cellulose acylate solution according to any one of (1) to (3).

(5) All the acyl groups are essentially composed of acetyl groups (1) to (3)
The cellulose acylate solution according to any one of 1. (6) The cellulose acylate solution according to any one of (1) to (5), wherein the solvent is formed substantially from a chlorine-free solvent. (7) The cellulose acylate solution according to any one of (1) to (6), wherein silica particles having an average particle diameter of 0.1 μm or less, a plasticizer, and an ultraviolet absorber are added. (8) The mixture of the solvent and the cellulose acylate is -80
The method for producing a cellulose acylate solution according to any one of (1) to (7), characterized in that the cellulose acylate solution is exposed to a temperature of -10 ° C or 80 to 220 ° C to be dissolved.

(9) A cellulose acylate film, characterized in that the cellulose acylate film is formed by applying the cellulose acylate solution described in any one of (1) to (8) onto a support. Manufacturing method. (10) The method for producing a cellulose acylate film according to (9), wherein two or more layers are cast by a co-casting method. (11) 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 (10). The method for producing a cellulose acylate film according to item 1.

(12) 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 5
The method for producing a cellulose acylate film as described in (10) or (11), which is in the range of 0 μm. (13) The method for producing a cellulose acylate film according to any one of (10) to (12), wherein the outer layer has a thickness of 1 to 20 μm. (14) A polarizing plate protective film comprising a cellulose acylate film produced by the method according to any one of (10) to (13).

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The cellulose acylate raw material cotton preferably used in the present invention is described in "4. Cellulose acylate raw material cotton" described in the Technical Bulletin of the Invention, Technical Disclosure No. 2001-1745, p. Can be used.

The basic principle of the method for synthesizing cellulose acylate is described in Ueda et al., Wood Chemistry, pages 180-190 (Kyoritsu Shuppan, 1968). A typical synthesis method is a liquid phase acetylation method using an acetic anhydride-acetic acid-sulfuric acid catalyst. Specifically, after pre-treating a cellulose raw material such as wood pulp with an appropriate amount of an organic acid, it is put into a pre-cooled acylation mixture to be esterified to obtain a complete cellulose acylate (2nd, 3rd and 6th positions). The total degree of acyl substitution is about 3.00). The above acylation mixture is generally
It contains an organic acid as a solvent, an anhydrous organic acid as an esterifying agent and sulfuric acid as a catalyst. The organic acid anhydride is usually used in a stoichiometric excess amount over the total amount of the cellulose which reacts with the water and the water present in the system. After the completion of the acylation reaction, a neutralizing agent (for example, calcium, magnesium, iron, aluminum or zinc) is used for hydrolysis of excess organic acid anhydride remaining in the system and neutralization of a part of the esterification catalyst. Aqueous solution of carbonate, acetate or oxide). Next, a small amount of the acetylation reaction catalyst (generally,
In the presence of residual sulfuric acid), the temperature is maintained at 50 to 90 ° C. to effect saponification and ripening, and change to cellulose acylate having a desired degree of acyl substitution and degree of polymerization. When the desired cellulose acylate is obtained, the catalyst remaining in the system is completely neutralized with the above-mentioned neutralizing agent, or without neutralization, water or diluted sulfuric acid is used. A cellulose acylate solution is charged therein (or water or diluted sulfuric acid is charged into the cellulose acylate solution) to separate the cellulose acylate, and the cellulose acylate is obtained by washing and stabilizing treatment.

Next, the cellulose acylate described in the open technical report in which the 6-position acetylation degree is specifically increased will be described. In the usual method for synthesizing cellulose acylate, 2
The degree of acyl substitution at the 3-position or the 3-position is higher than that at the 6-position. Cellulose acylate having a specifically increased acetylation degree at the 6-position means one having a high degree of acyl substitution at the 6-position with respect to the 2-position and 3-position. As specific conditions for synthesizing the cellulose acylate, it is preferable to reduce the amount of an acid catalyst such as sulfuric acid in the usual cellulose acylate acylation step and lengthen the acylation time. When the amount of the sulfuric acid catalyst is large, the acylation reaction proceeds quickly, but a sulfuric acid ester is formed between the cellulose and the cellulose depending on the amount of the catalyst, and liberated at the end of the reaction to form a residual hydroxyl group. Sulfate is produced more in the 6-position, which is highly reactive.
Therefore, when the amount of the sulfuric acid catalyst is large, the acyl substitution degree at the 6-position becomes small. Therefore, in order to reduce the amount of sulfuric acid catalyst in the synthesis as much as possible, thereby compensating for the lowered reaction rate,
The reaction time needs to be extended.

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 types 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.

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.

Examples of alcohols include methanol,
Ethanol, 1-propanol, 2-propanol, 1
-Butanol, 2-butanol and cyclohexanol, 2-fluoroethanol, 2,2,2-trifluoroethanol and the like. Of these, particularly preferred are methanol, ethanol, 1-propanol, 2-propanol and 1-butanol.

The actual solvent system may be chlorine-based or non-chlorine-based, without any particular limitation. Among them, the esters are 40 to 95% by mass of the total solvent, preferably 50 to 8%.
0 mass%, ketones 5 to 50 mass% of the total solvent,
It is preferably 10 to 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 2001-17.
45, page 15 right column, 1st line to page 16 left column, 8th line. Also, the use of chlorine-based solvent is not particularly limited.

Next, the substitution degree of cellulose acylate will be described. The β-1,4-bonded glucose unit that constitutes cellulose has free hydroxyl groups at the 2-position, 3-position and 6-position, and cellulose acylate has a structure in which some or all of these hydroxyl groups are converted to acetic acid. It is an esterified polymer. The degree of acyl substitution means the ratio of esterification of cellulose at each of the 2-position, 3-position and 6-position (1.00 is 100% esterification). The cellulose acylate used in the present invention has a total degree of acyl substitution of 2.75 or more and 2.90 or less, and an acyl substitution degree of 6-position of 0.90 or more, and a cellulose acylate having a total degree of acyl substitution. Total 2.70 or more 2.7
It is obtained by blending with a cellulose acylate having an acyl substitution degree at the 6-position of 5 or less and less than 0.90. When the total degree of all acyl substitution is 2.75 or less, the film is apt to absorb moisture and is easily hydrolyzed, so that the durability of the film is deteriorated. In addition, dimensional changes due to humidity and the like also increase. On the other hand, when it is 2.90 or more, the organic property of the cellulose acylate increases, the affinity with the solvent increases, and the viscosity of the dope increases. Therefore, the total sum of all acyl substitution degrees is preferably 2.75 or more and 2.90.

By the way, it has been found that the 6-position hydroxyl group is a primary hydroxyl group, unlike the 2- and 3-position hydroxyl groups, and therefore hydrogen bonds of the hydroxyl groups are extremely likely to occur. Therefore, by setting the degree of acyl substitution at the 6-position to 090 or more, the solubility in a solvent is remarkably improved and the viscosity is lowered, so that it becomes possible to obtain a dope suitable for casting suitability. The range of the degree of acyl substitution at the 6-position is preferably 0.92 or more and 0.99 or less, more preferably 0.92 or more and 0.98 or less in consideration of synthesis suitability and the like.

However, if the degree of acyl substitution at the 6-position is improved, there is a problem that the stability of the dope with time deteriorates, and it is difficult to satisfy both of them. As a result of intensive studies by the present inventors, it was found that these problems can be solved by blending cellulose acylate. Specifically, when the cellulose acylate and the total degree of acyl substitution are 2.70 or more and 2.75 or less and the degree of acyl substitution at the 6-position is less than 0.90, the dope is stable over time. It has been found that the best thing is obtained from the viewpoint of the property and the viscosity, and the present invention has been completed. Since the problem of stability over time can be solved by blending as described above, the total substitution degree is 2.75 to 2.9.
It is preferable to use a cotton having a substitution degree of 6-position of 0, which is 0.92 or more. Further, the degree of acyl substitution at the 6-position is 0.9
From the viewpoint of film strength, it is preferable that the number of carbon atoms of the acyl substituent in the cellulose acylate of 0 or more is smaller, and it is preferable that all of them are acetyl groups.

It should be noted that in JP-A No. 11-5851, the total of all acetyl substituents is 2.67 or more, and the 2-position, 3-position
Cellulose acetate having a total of acetyl substituents at positions of 1.97 or less is described, but this is a preferable range from the optical suitability of the film, such as casting suitability, surface condition, and film strength. From the viewpoint, the range described in this patent is more preferable.

In order to prepare the cellulose acylate solution, the above-mentioned cellulose acylate is added to the solvent in the 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 melting method 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 may be dissolved at a low concentration in order to make it more soluble, and then concentrated by using a concentration means. As a specific method, the Institute of Invention and Innovation Public Technical Report 2001-174
Examples thereof include those described in the 10th to 28th lines (solution concentration) on the left side of pages 5, 25.

Prior to casting, it is preferable to filter and remove foreign matters such as undissolved substances, dust and impurities using a suitable filter material such as wire mesh, paper or flannel before casting. 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, UV inhibitors and deterioration inhibitors (eg, antioxidants, peroxide decomposers, radical inhibitors, metal deactivators, acid scavengers, amines), strippers. , Fine particles, and the like. Specifically, 28 of the left side of page 16 of the Technical Bulletin of the Institute of Invention and Innovation, 2001-1745.
From the second line to the fifth line from the bottom on the right side of page 22 can be mentioned.

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 used to co-cast two or more layers on a smooth band or a drum as a metal support. For example, when casting a plurality of cellulose acylate solutions,
The film can be manufactured by casting a solution containing cellulose acylate from a plurality of casting holes arranged at intervals in the traveling direction of the metal support and laminating the solutions. Such a casting method is described, for example, in JP-A No. 11-198285. The film can also be produced by casting a cellulose acylate solution from two casting ports. Such a casting method is described in JP-A-6-134933. Further, as described in JP-A-56-162617, the flow of a high-viscosity cellulose acylate solution is wrapped with a low-viscosity cellulose acylate solution,
The film can also be produced by a casting method in which a low-viscosity cellulose acylate solution is simultaneously extruded. By performing such co-casting, smoothing of the surface during drying progresses as described above, and thus a large 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 means a surface which is not a band surface (drum surface) in the case of two layers and a layer on both surface sides of the completed film in the case of three or more layers. 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 of the present invention can be simultaneously cast with other functional layers (for example, an adhesive layer, a dye layer, an antistatic layer, an antihalation layer, an ultraviolet absorbing layer, a polarizing layer, etc.).

The drying temperature of the dope on the metal support is preferably from 30 to 250 ° C, and particularly from 40 to 40 ° C.
It is preferably 180 ° C. For the drying temperature,
It is described in JP-B-5-17844. Further, there is a method of positively stretching in the width direction, and in the present invention, for example, JP-A-62-115035 and JP-A-4-1521 are used.
No. 25, No. 4-284111, No. 4-298310
No. 11-48271, etc. can be used. The film may be stretched uniaxially or biaxially. The draw ratio of the film (the ratio of the increase due to the drawing to the original length) is 10 to 30%.
Is preferred.

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
The layers described on page 12, right column, bottom row 12 to page 45, left column, third row from bottom 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.

(1) 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 their pKa was used to determine the amount of each acyl group. In addition, publicly known documents (T.Se
i, K.Ishitani, R.Suzuki, K.Ikematsu Polymer Journal 1
7 1065 (1985)).
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.
Further, the degree of acyl substitution at the 2-position, 3-position and 6-position of cellulose acylate can be determined by acylating cellulose acetate with an acyl group which is not used for acylation, followed by Tezuka et al. (Carbohydr. Res. 273 (1995)). ) 83-91).

(2) 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

(3) Viscosity of Solution The obtained cellulose acylate solution was measured with a measuring instrument (TA Ins
The viscosity at 40 ° C. was measured by a truments company (Rheometer).

(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 This was measured using a haze meter (1001DP type, manufactured by Nippon Denshoku Industries Co., Ltd.).

(6) Tear test of film ISO 638 is a sample cut into 50 mn × 64 mm.
The tear load required for tearing was determined according to the standard of 3 / 2-1983.

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. The above-mentioned cellulose acylate solution was used as the liquid for forming the inner and outer layers of the co-casting in the present invention by changing the concentration and the solvent. 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) Gradually add the cellulose acylate described in Table 1 to a solvent while stirring well, and leave 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) are described in JP-A-56.
Casting using the casting machine described in Japanese Patent Publication No. 162617.
It was 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 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.

[0049]

[Table 1]

[0050]

[Table 2]

(1-3) The resulting cellulose acylate solution and film were evaluated according to the above items. The cellulose acylate solution and film of the present invention showed no particular problems with respect to solution stability, film mechanical properties and optical properties. On the other hand, in Comparative Examples, there was a problem in the surface condition of the obtained film or the film strength tended to be low.

Further, these films were TD stretched and stretched 10% to 30% MD 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.

[0053]

[Table 3]

[0054]

The total degree of acyl substitution is 2.75 or more and 2.90 or less, and the degree of acyl substitution at the 6-position is 0.9.
Substantially from a blend of a cellulose acylate having 0 or more and a total acyl substitution degree of 2.70 or more and 2.75 or less and an acyl substitution degree of 6-position of less than 0.90. With the cellulose acylate solution constituted, the production method of reducing the viscosity of the cellulose acylate solution and improving the surface condition of the film was achieved.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C08J 5/18 C08J 5/18 4J002 G02B 5/30 G02B 5/30 // B29K 1:00 B29K 1:00 B29L 7:00 BB29L 7:00 9:00 9:00 9:00 F term (reference) 2H049 BA02 BB13 BB33 BC09 BC22 4F070 AA02 AC23 BA02 BA03 CB04 CB11 4F071 AA09 AB26 AC05 AC07 AC10 AE19 AF29 AF35 AF47 AH16 BA02 BB02 BC01 BC02 4F100 A02 AA20C AJ06A AJ06B AJ06C AL05A AL05B AL05C BA02 BA03 BA10A BA10C BA15 CA04A CA04B CA04C CA07A CA07B CA07C DE01A DE01B DE01C EG002 EH312 JA20A JA20B JA20C 4F205 AA01J AB06 AB07 AB17 AC05A AG01 AG03 AH73 AR06 GA07 GB01 GB26 GC06 GE24 GF03 GF24 GN19 4J002 AB01W AB01X AB02W AB02X DJ016 EC01 EE02 EH02 FD02 FD05 GP00

Claims (11)

[Claims] 1. The sum of all acyl substitution degrees is 2.75 or more and 2.90 or less, and the 6-position acyl substitution degree is 0.9.
Substantially a blend of a cellulose acylate having 0 or more and a cellulose acylate having a total degree of acyl substitution of 2.70 or more and 2.75 or less and an acyl substitution degree of 6-position of less than 0.90. A cellulose acylate solution composed of. 2. The total acyl substitution degree is 2.75 or more and 2.90 or less, and the 6-position acyl substitution degree is 0.9.
The cellulose acylate solution according to claim 1 or 2, wherein the acyl group of the cellulose acylate having 0 or more is an acetyl group. 3. The total acyl substitution degree is 2.70 or more and 2.75 or less, and the 6-position acyl substitution degree is 0.9.
In a cellulose acylate having a degree of substitution of less than 0, the degree of substitution is 0.
The cellulose acylate solution according to claim 1 or 2, wherein the equivalent of 02 to 0.4 is an acyl group having 3 to 8 carbon atoms and the rest is an acetyl group. 4. The cellulose acylate solution according to claim 1, wherein all the acyl groups are substantially composed of acetyl groups. 5. The cellulose acylate solution according to claim 1, wherein the solvent is formed substantially from a chlorine-free solvent. 6. The cellulose acylate solution according to claim 1, wherein silica particles having an average particle diameter of 0.1 μm or less, a plasticizer and an ultraviolet absorber are added. 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 solution according to item 1. 8. A method for producing a cellulose acylate film, which comprises applying the cellulose acylate solution according to claim 1 on a support to form a cellulose acylate film. . 9. The method for producing a cellulose acylate film according to claim 8, wherein two or more layers are cast by a co-casting method. 10. The cellulose acylate film has a multi-layer structure of two or more layers, and the outer layer on at least one side of the cellulose acylate film has a thickness of 1 to 50 μm.
10. The method for producing a cellulose acylate film according to claim 9, characterized in that 11. 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 μm.
The method for producing a cellulose acylate film according to claim 8 or 9, characterized in that it is in the range of m.