JP2000176950A - Method for producing cellulose triacetate film and method for handling the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cellulose triacetate film generating no longitudinal and lateral wrinkles and excellent in surface quality. SOLUTION: In a method for producing a cellulose triacetate film by a soln. casting film forming method, in a drying process having at least two drive rolls and a large number of free rolls between a start point and a terminal point, the draw ratio of a cellulose triacetate film (web) between the drive rolls is set to 1.00-1.05 in such a state that the residual solvent of the web is 20 wt.% or less and the surface temp. of the web becomes 80 deg.C or higher and the feed tension of the web in the drive roll at the start point of the drying process is set to 10 kgf/m or more and the total contact time of the fed web and the free rolls in the drying process is set to 10 sec or more to feed the web.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a cellulose triacetate film used for a silver halide photographic material, a liquid crystal image display device, and the like, and a method for handling the same.

[0002]

2. Description of the Related Art Cellulose triacetate film is a useful industrial material as described above, but its demand is steadily increasing, and it is required to improve quality and reduce price year by year. For this reason, it has been responded by manufacturing at a high speed, but it becomes more difficult to improve the quality as the speed increases. This is because high-speed production requires a higher drying temperature in order to increase the drying speed, and the temperature is applied in places where the residual solvent is high. The elastic modulus of the web is reduced, and as a result, the web is easily deformed, vertical wrinkles due to transport tension become easier, and slight horizontal fluctuations occur due to slight fluctuations in tension. And the flatness has deteriorated. Such a defect as a film causes fine coating unevenness when a silver halide emulsion layer is coated in the case of a silver halide photographic light-sensitive material, and transmission of light in a protective film of a liquid crystal image display device. However, there is a possibility that slight uneven unevenness may occur.

In order to solve such a problem, Japanese Patent Laid-Open Publication No.
Nos. 814, 4-286611, 4-152125
In Japanese Patent Application Laid-Open Publication No. H11-264, there is proposed a method of forcing a continuous wrinkle generated by setting a flatness forcing step.

[0004]

However, when a silver halide emulsion layer is coated at a higher speed by using the cellulose triacetate film obtained by these methods, unevenness still occurs. The task has not been overcome.

An object of the present invention is to provide a cellulose triacetate film excellent in surface quality which does not cause vertical wrinkles or horizontal wrinkles even when transported at an elevated drying temperature by high-temperature drying.

[0006]

The present invention comprises the following constitutions.

(1) In a method for producing a cellulose triacetate film by a solution casting method, a web (cellulose triacetate film) is formed in a drying step having at least two drive rolls and a large number of free rolls between a starting point and an end point. A) the residual solvent is 20% by weight or less and the web has a surface temperature of 80 ° C. or more,
The draw ratio of the web between the drive rolls is 1.00 to
1.05, the web transport tension in the drive roll at the starting point of the drying step is 10 kgf / m or more, and the total contact time between the transport web and the free roll in the drying step is 10 seconds or more. A method for producing a cellulose triacetate film.

(2) The method for producing a cellulose triacetate film according to (1), wherein the free roll has a mechanism for applying tension to the web in a widthwise outward direction from the center of the roll.

(3) The method for producing a cellulose triacetate film according to (1) or (2), wherein the free roll has a surface roughness of less than 3.0 μm.

(4) A coating solution containing a solvent which does not normally dissolve in cellulose triacetate and is capable of swelling before being transported in the drying step according to any one of (1) to (3). A method for producing a cellulose triacetate film, characterized in that the method is applied by:

(5) After the cellulose triacetate film formed and wound by the solution casting method is wound up, the drying step described in any one of (1) to (3) is carried. Characteristic handling method of cellulose triacetate film.

The present invention will be described in detail.

[0013] The solution casting film forming method and apparatus referred to in the present invention are: a polymer dope having a high viscosity is cast from a die onto a stainless steel mirror belt (casting support) for endlessly transferring the polymer dope; When the solvent evaporates and dried on the support and the belt makes one round, the dope film is peeled from the belt,
This is a method and apparatus for producing a dried polymer film through a drying step.

First, configurations (1) to (3) of the present invention will be described.

According to a solution casting method, a cellulose triacetate dope is cast on a casting support, dried on the support, and the peeled dope film is peeled off. In the step of drying by applying heat using air such as air as a heat medium from both sides of the web in the process, the solvent ratio remaining in the web (residual solvent ratio) is 20% by weight.
Two drive rolls (hereinafter abbreviated as DR) serving as power for transporting the web at the starting point and the ending point of the drying process after the surface temperature of the web during drying becomes 80 ° C. or higher. The web is transported with the draw ratio of pulling the web between 1.00 and 1.05, and the transport tension of the web at the DR at the start point of the drying process at that time is 10 kg.
The web is conveyed and dried at f / m (width) or more.

At this time, for the DRs other than the DR, the draw ratio between the DR at the starting point and the ending point of the drying step and another DR adjacent to the inside or outside of the drying step is fixed or gradually increased. Preferably, the web transport tension between the DRs at the start and end points of the drying step and another DR adjacent to the inside or outside of the drying step is constant or gradually increased.

Here, the residual solvent ratio is defined as the weight A of the web sample at the time of collection and the weight B of the same sample dried at 115 ° C. for 3 hours. Residual solvent ratio = ｛(AB) / B It is represented by｝ × 100.

In the drying step in which the web is dried while being conveyed by a free roll, tension is applied to the web in the conveying direction, and the web is brought into close contact with a plurality of rolls and conveyed. However, when the roll is conveyed with the residual solvent ratio of 20% or more, the drying becomes insufficient, so that wrinkles may be generated again in the subsequent drying step, and the effect is reduced. Even when the temperature of the web during drying is 80 ° C. or less, wrinkles are likely to occur.

Regarding the draw ratio of DR in the drying step,
If it is less than 1.00, the web tends to shrink, which makes transporting difficult. If it is 1.05 or more, the thickness distribution of the web becomes non-uniform, and the web may be broken in some cases. Therefore, the range of 1.00 to 1.05 is desirable.

Regarding the transport tension, 10 kg / m (width)
If it is below, the adhesion between the web and the free roll is weakened, and the flatness is deteriorated. The contact time between the web being conveyed and the surface of all rotating free rolls in the drying step is preferably 10 seconds or more, and below this time, the surface properties may be reduced. By changing the web transport speed, roll diameter, number of rolls, roll arrangement style, wrap angle, span interval between rolls, etc.,
The contact time can be adjusted. In order to make the drying process compact from the viewpoint of cost, it is desirable that the roll diameter and the wrap angle are as large as possible and the free span is small.

The place where the wrinkle of the web is apt to be apt tends to be biased toward the central portion in the web width direction. Therefore, in the present invention, under the above-described conditions, the so-called drum-shaped roll or a roll that is thickened toward the end in the vicinity of the center in the width direction of the free roll, and grooves are cut outward on both ends of the roll. Even if the roll is used, it has the effect of extending the web in the width direction, and can easily produce the effect of increasing the adhesion of the web.

Under the above-mentioned conditions, it is preferable that the surface of the free roll has a certain roughness rather than a mirror surface.
It is better to make the roughness as fine as possible. In the present invention, it is 3.0 μm or less, preferably 1.0 to 2.5 μm.
μm is preferred.

In the constitution (4) of the present invention, after a cellulose triacetate is coated with a coating solution containing a solvent having a swelling property, treatment is performed in accordance with the conditions of the constitutions (1) to (3). Thereby, a cellulose triacetate film having excellent flatness can be obtained. Swellable solvents include ethyl acetate, propyl acetate, acetone,
Examples thereof include methyl ethyl ketone, methyl isobutyl ketone, dioxane, formamide, acetamide, dimethylformamide, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol dimethyl ether, and ethylene glycol methyl acetate.

In the constitution (5) of the present invention, a film formed by a solution casting method, dried by any process and wound up once is dried under the conditions of the constitutions (1) to (4). A cellulose triacetate film having excellent flatness can also be obtained through the steps.

[0025]

EXAMPLES [Evaluation Method] (Flatness) After winding, a cellulose triacetate film was cut out in a length direction of 1 m and a width direction as a width itself, and placed on a flat surface in parallel from 2 m above the fluorescent lamp 3. The book was illuminated and the reflection and distortion and wrinkles were observed and evaluated at the following levels.

A: The fluorescent lamp was seen straight, and fine wrinkles were hardly seen. B: The fluorescent lamp was seen almost straight, and fine wrinkles were hardly seen. Wrinkles were visible. D: Fluorescent lamps were seen in several bends and wrinkles were seen. E: Fluorescent lamps were uneven and many wrinkles were visible.

(Uneven coating) A coating solution of the undercoat layer described below was coated on a dried cellulose triacetate film and dried, and then a coating solution of the following dye gelatin was uniformly coated, set at a low temperature, and dried. The web was cut out, and the unevenness of the web was observed through light on a shakasten.

A: There was no density of the dye corresponding to wrinkles and unevenness, and the entire surface of the sample was uniform. B: It seemed that there was slight unevenness in the density of the dye, like a little large unevenness. C: Slow. D: The density of the pigment corresponding to fine wrinkles is visible in the unevenness. D: The density of the pigment corresponding to vertical unevenness, vertical and horizontal wrinkles is seen. E: The density of the pigment corresponding to unevenness and wrinkles is clearly visible. .

<Coating solution for undercoat layer> Vinyl acetate / maleic anhydride (1: 1) copolymer 0.5 part by weight Acetone 79.5 parts by weight Ethyl acetate 15 parts by weight Isopropanol 5 parts by weight <Dye gelatin coating solution> Gelatin 3 parts by weight Methyl violet 1 part by weight Methanol 10 parts by weight Water 86 parts by weight Example 1 A dope having the following formulation was prepared and formed into a film having a dry film thickness of 120 μm by a solution casting film forming apparatus. Is 100
%, And the end point of drying was set to a residual solvent ratio of 2%.

The cellulose triacetate film dried under the processing conditions in the drying step shown in Table 1 below and the sample coated with the dye gelatin layer were evaluated.

[0031]

[Table 1]

Symbols a, b, and c in Table 1 are as follows: a: A film was formed, and then a drying process was performed. B: A film was formed, dried, wound up, and then dried according to the present invention. C: formed into a film, dried to some extent, and applied with a swelling solvent, and then subjected to the drying treatment of the present invention. Those with a groove on the outside.

Comparative Example 1 A sample was prepared and evaluated in the same manner as in Example 1 under the conditions shown in Table 1.

The results are shown in Table 2.

[0035]

[Table 2]

(Results) It was found that those which passed the drying step of the present invention and the conditions of the present invention also had excellent flatness and coatability.

[0037]

According to the present invention, a cellulose triacetate film having excellent flatness can be provided.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B29L 7:00 (72) Inventor Toshiyuki Hagiwara 1 Konica Corporation, Sakuracho, Hino-shi, Tokyo Internal F-term (reference) 2H023 FA01 FA13 4F071 AA09 AF06Y AH19 BA02 BC01 4F205 AA01 AC05 AG01 AK07 AM32 AR11 AR13 GA07 GB02 GC06 GF01 GF24 GF36 GN22 GN24 GW06 4J002 AB021 FD206 GP03

Claims (5)

[Claims] 1. A method for producing a cellulose triacetate film by a solution casting method, wherein a cellulose triacetate film (web) is formed in a drying step having at least two drive rolls and a large number of free rolls between a starting point and an end point. When the residual solvent is 20% by weight or less and the surface temperature of the web is 80 ° C. or more, the draw ratio of the web between the drive rolls is adjusted to 1.00 to 1.0.
5, the transporting tension of the web on the drive roll at the start of the drying step is 10 kgf / m or more, and the total contact time between the transporting web and the free roll in the drying step is 10
A method for producing a cellulose triacetate film, wherein the film is transported for at least seconds. 2. The method for producing a cellulose triacetate film according to claim 1, wherein the free roll has a mechanism for applying tension to the web in a widthwise outward direction from the center of the roll. 3. The free roll having a surface roughness of less than 3.0 μm.
3. The method for producing a cellulose triacetate film according to 1.). 4. A coating solution containing a solvent that does not normally dissolve in cellulose triacetate but can swell without being dissolved in cellulose triacetate before being transported in the drying step according to claim 1. A method for producing a cellulose triacetate film, comprising: 5. The drying step according to claim 1, wherein the film is formed by a solution casting method and the finished cellulose triacetate film is wound up, and then the drying step according to claim 1 is conveyed. How to handle cellulose triacetate film.