JP2000319412A - Preparation of cellulose ester film, apparatus for preparing the same and cellulose ester film for liquid crystal image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an apparatus and method for preparing a cellulose ester film having a thickness of less than 85 μm excellent in flatness and to provide a cellulose ester film for a liquid crystal image display device having a thickness of less than 85 μm excellent in flatness. SOLUTION: There is provided a method for preparing a cellulose ester film having a thickness of less than 85 μm by a solution-casting film-forming method, wherein cellulose ester dope is cast from a casting die 2 on a traveling support 3 for casting thereby to form a web 1, which is dried to form a film by exposure of the surface thereof to drying air 7 having an absolute value of a static pressure of 20-100 mmAq and a deviation of the static pressure between that in a width direction and that in a longer direction at an outlet of the drying air, of not more than ±20%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method and an apparatus for producing a thin cellulose ester film having a thickness of less than 85 μm, and also relates to a thin cellulose ester film for a liquid crystal display.

[0002]

2. Description of the Related Art A cellulose ester film, particularly a cellulose triacetate film, used as a support for a silver halide photographic light-sensitive material is usually from 120 to 12%.
It has a thickness of 5 μm, especially 90 μm, which is particularly thin. This is due to the mechanical strength and stiffness of the cellulose triacetate film, and a thinner support for a silver halide photographic light-sensitive material is made of another material such as a polyethylene terephthalate film or polyethylene-2,6. -Has been replaced by a naphthalate film.

In recent years, a cellulose triacetate film has been used as a film for a liquid crystal image display device, for example, as a protective film, and the quality requirements have been strict. Further, there is a demand for a thinner film having better flatness.

[0004]

It is very difficult to produce a thin cellulose triacetate film, and various defects tend to occur immediately after casting until drying is completed. For example, casting unevenness during casting, blown unevenness after casting,
Streaks and frays at the time of peeling and streaks and frays during transport and drying are likely to occur. If the film for liquid crystal image display device has any of the above-mentioned defects, the image distortion and the reflection of light may be different, so that any defect is not allowed. From a film manufacturer's point of view, there is a large loss due to the occurrence of defects, and there is a lot of time and material loss before the occurrence of the defects disappears. Therefore, improvement of productivity is an important issue.

[0005] It is an object of the present invention to provide an excellent flatness.
An object of the present invention is to provide a film manufacturing method and a manufacturing apparatus for manufacturing a cellulose ester film having a thickness of less than 5 μm. A second object of the present invention is to provide a cellulose ester film for a liquid crystal image display device having excellent flatness and a thickness of less than 85 μm.

[0006]

The present invention comprises the following constitutions.

(1) A film thickness of 8 is obtained by a solution casting method.
A method for producing a cellulose ester film having a thickness of less than 5 μm, comprising: casting a cellulose ester dope from a casting die onto a casting support being transferred to form a web; A method for producing a cellulose ester film, wherein the absolute value of the static pressure of the wind is 20 to 100 mmAq, and the static pressure deviation in the width and longitudinal direction of the outlet of the dry wind is ± 20% or less.

(2) The method for producing a cellulose ester film according to (1), wherein the static pressure is 25 to 90 mmAq.

(3) The temperature of the casting support is set at 10
The method for producing a cellulose ester film according to (1) or (2), wherein the film is formed in a range of a boiling point of a main solvent among the solvents used for the dope.

(4) The film is formed by reducing the pressure from 1 to 100 mmAq from the back side (upstream in the transfer direction) of the dope ribbon cast from the die onto the casting support. The method for producing a cellulose ester film according to any one of (1) to (3).

(5) A film thickness of 8 is obtained by a solution casting method.
An apparatus for producing a cellulose ester film having a size of less than 5 μm, wherein a dope is cast from a casting position to a take-up position.
An apparatus for producing a cellulose ester film, comprising at least one flatness detecting means, flatness information feedback means, and flatness condition setting fine adjustment means.

(6) The flatness condition setting fine adjustment means is at least one selected from a temperature adjustment means for the casting support, a static air pressure adjustment means for drying, a conveyance tension adjustment means after peeling, and a drying temperature adjustment means. (5) The apparatus for producing a cellulose ester film according to (5).

(7) A method for producing a cellulose ester film, comprising forming a film using the production apparatus according to (5) or (6).

(8) A film thickness of 8 is obtained by a solution casting method.
An apparatus for producing a cellulose ester film having a thickness of less than 5 μm, comprising a humidifying unit and a flatness correcting unit between the peeling position and the winding.

(9) The apparatus for producing a cellulose ester film according to (8), wherein the humidifying means is at least one selected from a dipping means, a coating means and an air conditioning means.

(10) The apparatus for producing a cellulose ester film according to (8), wherein the flatness correcting means has one or more heating rolls, and then one or more cooling rolls.

(11) Any one of (8) to (10)
A method for producing a cellulose ester film, which comprises forming a film using the apparatus described in the above section.

(12) The temperature of the heating roll is 90 to
The method for producing a cellulose ester film according to (11), wherein the web is heated so that the temperature is set to 180 ° C. and the total contact time between the web and the heating roll is 2 seconds or more.

(13) After the heating roll treatment, the temperature of the cooling roll is set to 20 to 80 ° C., and the web is cooled so that the total contact time between the web and the cooling roll is 2 seconds or more. (11) or (1)
The method for producing a cellulose ester film according to 2).

(14) During or after humidification by the humidification means, when the water content of the web becomes 1.5 to 7% by weight, the web is treated with the heating roll and the cooling roll,
The method for producing a cellulose ester film according to any one of (11) to (13), wherein the film is formed.

(15) (1), (2), (3),
(4), (7), (11), (12), (13) and a cellulose ester film for a liquid crystal image display device, characterized by being formed by a method according to at least one selected from (14). .

The present invention will be described in detail.

The cellulose ester used in the present invention is
A cellulose ester having an acyl group having 2 to 4 carbon atoms as a substituent, wherein the degree of substitution of the acetyl group is A, and the degree of substitution of at least one acyl group selected from 3 and 4 carbon atoms is B, It satisfies the following formulas (I) and (II) simultaneously.

(I) 2.6 ≦ A + B ≦ 3.0 (II) 0 ≦ A ≦ 3.0 Specifically, cellulose triacetate, cellulose acetate propionate, cellulose acetate butyrate, cellulose propionate, etc. is there.

The cellulose as a raw material is preferably a material having cellulose fibers such as cotton linter, wood pulp, and kenaf.

In the cellulose ester, these acyl groups react with the hydroxyl group of the cellulose molecule. The cellulose molecule is composed of a glucose unit, and the glucose unit has three hydroxyl groups. The number of acyl groups derived from these three hydroxyl groups is called the degree of substitution. For example, cellulose triacetate has all three hydroxyl groups bound to an acetyl group (actually, 2.6 to 3.0). The cellulose ester of the present invention is a cellulose ester in which a propionate group or a butyrate group is bonded to an acetyl group such as cellulose acetate propionate or cellulose acetate butyrate in addition to cellulose triacetate.

The method for measuring the degree of substitution of the acyl group is ASTM-
It can be measured according to D817-96.

The cellulose ester used in the present invention preferably has a number average degree of polymerization in the range of 70,000 to 300,000 because of its high mechanical strength when molded. 8000 more
0 to 200,000 is preferred.

The solution casting method for forming the cellulose ester film of the present invention will be described.

The solution casting film forming method of the present invention is the same as that usually used for film formation of a cellulose triacetate film of a silver halide photographic light-sensitive material.

That is, the above-mentioned cellulose ester is dissolved in an organic solvent to form a dope, and the film is formed through the following steps. This will be described below with reference to FIG.

FIG. 1 is a schematic view showing an example of an apparatus for a solution casting film forming method.

Casting: A dope is fed through a pressurized metering gear pump (not shown), and an endless casting support 3 (metal belt or rotating metal) that transfers the dope from the press die 2 infinitely. On the drum). The surface of the metal belt (or metal drum) is a mirror surface.
As the pressure die 2, a die which can be prepared so as to make the dope film (hereinafter referred to as the web 1) uniform by the slit shape of the die portion is preferably used. The pressure die 2 includes a coat hanger die and a T die, and any of them is preferably used. Two or more pressure dies 2 may be provided on the casting support 3 and may be overlaid. The method of heating the web 1 on the casting support 3 to evaporate the solvent is a method of blowing air from the web side (the surface drying means 10 after casting, the lower surface drying means 1).
2) and / or a method of transferring heat from the back surface of the support by liquid or wind (back surface heat transfer means 11, lower back surface heat transfer means 1)
There is 3). Reference numeral 9 denotes a support drum that supports an endless belt.

Peeling: The web 1 from which the solvent has been evaporated on the support 3 is peeled at a peeling position 4 immediately before the support makes one round from the casting position. When the amount of the residual solvent (the following formula) is too large at the time of peeling, the film cannot be peeled off. However, when the film is sufficiently dried on the support 3, it takes a long time to dry the film, and the film forming speed becomes slow. As a result, a part of the web 1 is peeled off. Conversely, the film formation speed can be increased by gelling the web so that the web 1 can be peeled off quickly. However, the web 1 is too soft, so that the web 1 is liable to generate shear and vertical stripes due to the peeling tension. Therefore, the balance between economic speed and quality can be determined by the amount of solvent remaining after stripping. The residual solvent amount is measured as follows, and the residual solvent amount (% by weight) = {(M−N) / N} × 100. M is the weight of the web (or the doped film) at an arbitrary point, and N is the weight of M when dried at 110 ° C. for 1 hour.

Drying: The web 1 is preferably dried by a drying device 5 for transporting the rolls 6 arranged in a staggered manner alternately and / or a tenter device 8 for transporting the web by clipping both ends of the web with clips. In general, hot air is blown on both sides of the web as a drying means, but there is also a method of heating using a microwave instead of the wind.
Usually, the drying temperature is from 15 to 250C, preferably from 70 to 180C.

In the drying step through the solution casting film forming method, the drying air 7 in the drying device may be air, or may be an inert gas atmosphere such as nitrogen gas or carbon dioxide gas. However,
Of course, the danger of explosive limits of the evaporated solvent in a dry atmosphere must always be considered.

Winding up 14: The web 1 is wound up as a film when the amount of the residual solvent becomes 2% by weight or less, but from the viewpoint of dimensional stability, the amount of the residual solvent at the time of winding up is 0.4% by weight or less. preferable. The method of winding can be used without limitation as long as it is generally used, for example, a method such as a constant torque method, a constant tension method, a taper tension method, a program tension control method with a constant internal stress may be used. .

Examples of the organic solvent (good solvent) for dissolving the cellulose ester of the present invention include methylene chloride, methylene chloride / methanol, methylene chloride / ethanol, trichloroethane, chloroform, methyl acetate, ethyl acetate, amyl acetate, acetone, tetrahydrofuran. 1,3-dioxolan, 1,4-dioxane,
Cyclohexanone, ethyl formate, 2,2,2-trifluoroethanol, 2,2,3,3-hexafluoro-1
-Propanol, 1,3-difluoro-2-propanol, 1,1,1,3,3,3-hex-2-methyl-2
-Propanol, 1,1,1,3,3,3-hexafluoro-2-propanol, 2,2,3,3,3-pentafluoro-1-propanol, nitroethane and the like. Among them, methylene chloride or methyl acetate has excellent solubility and is preferably used in the present invention.

As a method for forming the dope of the cellulose ester of the present invention, a method such as a stirring and dissolving method in a dissolving vessel, a heating dissolving method, an ultrasonic dissolving method and the like are usually used. Cooling dissolution method described,
Further, a method of dissolving under high pressure described in JP-A-11-21379 may be used.

In the dope, in addition to the above-mentioned good solvent for dissolving the cellulose ester, a poor solvent having 1 to 1 carbon atoms is used.
Alcohol 4, cyclohexane, etc. of No. 4 may be used as a mixture, and by adding them, gelation occurs after casting, peeling can be accelerated, and the film forming speed as a whole can be increased. .

The solid content of the dope is usually about 10 to 40% by weight, and the viscosity of the dope is adjusted to the range of 100 to 500 poise.

The dope usually contains a plasticizer, an antioxidant, a dye, an ultraviolet absorber and the like. In many cases, a plasticizer, an antioxidant for imparting heat resistance and moisture resistance, an ultraviolet ray inhibitor, and the like are added to the dope of the film for a liquid crystal display device.

Examples of the plasticizer include phosphate esters and carboxylate esters such as triphenyl phosphate, tricresyl phosphate and phenyldiphenyl phosphate; carboxylate esters such as phthalate ester and citrate ester; phthalate esters such as Dimethyl phthalate, diethyl phosphate, dioctyl phthalate, diethylhexyl phthalate, etc .; citrates such as acetyl triethyl citrate, acetyl tributyl citrate; and others, butyl oleate, methyl acetyl ricinoleate, ethyl phthalyl ethyl glycolate, dibutyl sebacate And triacetin. The amount of the plasticizer added is 1 to 30% by weight, preferably 3 to 16% by weight, based on the cellulose ester.
These compounds may be added together with the cellulose ester and the solvent when preparing the cellulose ester solution, or may be added during or after the solution preparation.

The thickness of the cellulose ester film in the present invention is less than 85 μm, preferably 20 to 80 μm.
It is. To adjust the film thickness, the dope concentration, the flow rate of the liquid feed pump, the slit gap of the die of the pressure die, the extrusion pressure of the pressure die, the speed of the casting support, etc. are adjusted so as to obtain the desired thickness. This is done by adjusting In order to obtain a web having a more uniform film thickness over the entire length, it is preferable to measure the total film thickness by a film thickness detector or the like installed after casting, and feed back to the above-mentioned adjusting means to adjust the film thickness. .

The constitution (1) of the present invention is a method for producing a cellulose ester film having a film thickness of less than 85 μm by a solution casting method. A web cast from a die on a casting support being transported. A method for producing a cellulose ester film in which the absolute value of the static pressure of the dry air applied to the surface of the dry air is set to 20 to 100 mmAq, and the static pressure deviation in the width and the longitudinal direction of the outlet of the dry air is ± 20% or less. .

In the present invention, Japanese Patent Application Laid-Open No. 62-55214
An apparatus and a method for applying a drying air described in Japanese Patent Application Laid-Open No. H10-260, can be preferably used. In the publication, after casting, within 15 seconds, the direction of the drying air is obliquely directed forward in the traveling direction of the support, and the angle formed with the support surface is 45 to 80 °,
It is described that the static pressure of the drying air is 5 mmAq or more, the gap between the outlet of the drying air and the surface of the support is 5 to 50 mm, and the static pressure is preferably 10 to 20 mmAq. Poor properties, if it exceeds 20 mmAq,
It is described that since the drying wind hits the film surface too strongly, the smoothness of the film surface is easily hindered.

The inventor of the present invention has found that a thin film can be used to obtain a film having excellent flatness at 20 mmAq or more, particularly 25 to 90 mmAq. And importantly, even if the static pressure of such a dry wind is in the above range,
Although the appearance of streak-like flatness is slightly likely to occur, the occurrence of streaks can be suppressed by keeping the width and longitudinal deviation of the static pressure at the outlet of the drying air within ± 20%. More preferable static pressure deviation is ± 10%, and further ± 5%.
% Is preferred.

In the present invention, the angle at which the drying air is applied to the web surface is 30 to 90 °, preferably 45 to 90 °.
°.

FIG. 2 is a diagram schematically showing the state of dope casting. After the dope ribbon 15 is cast from the pressure die 2 onto the support 3, the dope film 16 becomes a dope film 16 (drying proceeds to form the web 1) for a while.

FIG. 3 is an example of a schematic diagram showing a side cross section of the surface drying means after casting. Drying air 20 blows out from the slit 17 to the dope film 16 cast on the casting support 3 to remove a vapor film on the surface of the dope film 16 and promote drying.
The drying air is supplied from the blowing header 21. Dry wind 20
Is preferably 25 to 90 mmAq, more preferably 30 to 90 mmAq.
80 mmAq is preferable (configuration (2)). Slit 17
And the gap 19 between the tip of the slit and the doped film (web) is 3 to 1 mm.
By blowing it out as 00 mm, the slit gap 18 is preferably 2 to 10 mm, and the gap 19 between the tip of the slit and the dope film is 5 to 50 mm, so that a thinner film having a flatter surface can be formed. .

In the constitution (3) of the present invention, the temperature of the casting support is further reduced to 10 ° C. or less under the conditions of the constitution (1) or (2).
By setting the range of the boiling point of the main solvent among the solvents used for the dope, it is possible to provide a temperature at which heat transfer from under the web does not activate the fluidity of the film and at the same time to speed up the drying. is there. The main solvent in the solvent used for doping is 55% by weight or more, preferably 6% by weight of the solvent composition.
0% by weight or more of a solvent. For example, methylene chloride corresponds to the usual cellulose triacetate dope formulation. If the temperature is lower than 10 ° C., dew condensation may occur, or leveling may become difficult after the dope ribbon is grounded on the casting support, and fine irregularities may remain.

FIG. 4 is a diagram schematically showing a state in which the pressure of the dope ribbon during casting is reduced from the upstream side in the transport direction.

The structure (4) of the present invention comprises the structures (1) to (3)
In addition to the conditions described above, the upstream side (the opposite side to the transfer direction) between the back side of the dope ribbon 15 cast from the pressing die 2 and the casting support is further subjected to a pressure of 1 to 100 mmAq ( -ΔP) to form a film under reduced pressure. When a thin film is formed, the dope ribbon 15 is thin, and is stretched in the transport direction during the time when the ribbon 15 is thin from the die slit 23 to contact with the surface of the support 3, so that it is difficult to contact the ground. The quality of the film is liable to be degraded due to entrainment of air, expansion of the dope film, and folds. This tendency is stronger as the doped film 16 is thinner. Therefore, it is necessary to reduce the grounding distance of the dope ribbon 15 to the casting support 3. By reducing the pressure (−ΔP) from behind the dope ribbon 15, the dope ribbon 15 is pulled back toward the casting support 3. 3 can be quickly grounded. 22 is a decompression chamber. Although not shown, the method of depressurizing the decompression chamber can be used without limitation as long as it can suck the inside of the chamber (such as a blower). In addition, a buffer tank may be provided in the middle of the path in order to eliminate the uneven pressure reduction (irregular pressure reduction state).

In the present invention, if the web is conveyed with a large tension after the web is peeled off, the web which has not dried much and has a large amount of the residual solvent is liable to be frayed. Therefore, it is preferable to set the transport tension to 4 to 35 kgf / m. The residual solvent amount of the web at the peeling position is peeled in the range of 20 to 150% by weight. When the residual solvent amount is lower than 20% by weight, the film forming speed is slow, and when the residual solvent amount is higher than 150% by weight. However, in spite of the fact that the production speed can be increased, there is a concern that the flatness after peeling, for example, rubbing, is concerned, and this is even more so for a thin web. Even when peeling with the highest possible residual solvent amount, it is necessary to lower the web tension after peeling in order not to deteriorate the flatness. With a weak tension of about 4 kgf / m and a relatively low residual solvent amount of 35 kF / m
Strong tension of about gf / m or less can be applied, and a film can be formed without deteriorating flatness.

In the present invention, the web after peeling is
Drying at a drying temperature of 160 ° C. is preferred. What is necessary is just to adjust the temperature in a drying process according to the residual solvent amount of the web on the casting support, but is generally low immediately after peeling,
160 for webs with 50% or less residual solvent
It is preferable to apply a temperature of not more than about ° C. for drying.

According to the constitutions (5) and (6) of the present invention, at least one means for detecting the flatness of the web, means for feeding back the flatness information of the web, and each device are provided between the casting position and the winding. This is an apparatus for producing a cellulose ester film having means for finely adjusting the condition setting.

The flatness detecting means is preferably applied to a portion where the flatness is easily disturbed. In particular, in the case of a thin film having a thickness of 85 μm or less, it is preferable that the film is provided in a place where streaks, frays, unevenness, and the like are easily generated and easily detected. For example, it is preferable to apply the composition immediately after casting, immediately after peeling, inside a drying device, or before winding, on the upper side of the casting support after casting.

The detection results are fed back through feedback means, for example, the shape of the die slit, the static pressure of the drying air immediately after casting, the shape of the blowing slit, the slit gap or the distance between the support and the slit, and the degree of pressure reduction behind the dope ribbon. Alternatively, it is preferable to feed back and control the uniformity, the temperature of the casting support, the peeling tension or the transporting tension, the temperature of the drying device, etc., and to control the location. Good.

FIG. 5 is an example of a schematic view showing a solution casting film forming apparatus having flatness detecting means, flatness information feedback means and flatness condition setting means. In this example, flatness detecting means 2 for detecting flatness after the peeling position
4. Flatness information feedback means 25 for feeding back the information, flatness condition (static pressure) setting fine adjustment means 26 for adjusting and controlling the drying air static pressure, and flatness condition (tension) setting fine adjustment for adjusting and controlling the tension The means for improving the flatness by means 27 is shown. 28 is a drive roll.

As the flatness detecting means, a generally used flatness detector, a flatness inspection machine, a defect detector and the like can be used. For example, Japanese Patent Publication No. 6-4396
The sheet-like defect detection means described in Japanese Patent Application Laid-Open No. 9-1997 can be preferably used.

The constitution (7) of the present invention is a method for producing a cellulose ester film formed by using the means of the constitution (5) or (6). Can be done.

The constitutions (8) to (10) of the present invention are an apparatus for producing a cellulose ester film having a humidifying means and a flatness correcting means for a web being conveyed after peeling a dope film.

Structures (11) to (14) are methods for producing a cellulose ester film formed by using these humidifying means and flatness correcting means.

The humidifying means of the present invention is at least one selected from dipping means, coating means and air humidity controlling means.

The immersion means can be used without limitation as long as the web can be continuously immersed in water. For example, several guide rolls are arranged in a water tank, and water can be passed through the guide roll. When it comes out, the water is cut off by a squeeze roll.

Examples of the coating means include a general coating machine, for example, a dip coating method, a roll coating method, a wire bar coating method, a spray coating method, a curtain coating method, and an ejector coating method.

As the air humidity control means, the web is roll-transported in the transport chamber to be in a humidified state, and the relative humidity is preferably 70 to 100% RH. The humidification temperature is not limited, but is preferably in the range of 20 to 100C.

In any humidifying means, the moisture content of the humidified web (% by weight of moisture in the dry web) is 1.5 to 7% by weight.
In this range, not only the flatness can be corrected by the flatness correcting means but also the water content of the final finished film can be reduced to 0.1% by weight or less.

The means for humidifying the web of the present invention and the means for correcting the flatness of the humidified web include one or more heating rolls and one or more cooling rolls. It was found that thin webs were easier to correct by humidification than thicker webs, and that the straightening finish was excellent.

As a means having one or more heating rolls of the flatness correcting means, a calender roll capable of heating and pressurizing, or a close roll having a small interval between the rolls is preferable. In particular, a tight roll is preferred from the viewpoint of good heat transfer. The heating temperature is preferably in the range of 100 to 180 ° C.

Subsequent to the heating roll of the flatness correcting means, a means having one or more cooling rolls of the flatness correcting means is provided. What is necessary is just to have the structure similar to the said heating roll. The cooling temperature is preferably in the range of 20 to 80C.

As the close roll of the flatness correcting means, there are JP-A-6-278149, JP-A-4-286611 and JP-A-4-152125, and Japanese Patent Application No. 9-31341.
No. 7 flatness correction step. In particular, for a thin cellulose ester film, a cooling system closely-spaced roll described in Japanese Patent Application No. 9-313417 can be preferably used.

FIG. 6 is an example of a schematic view showing a solution casting film forming apparatus having humidifying means and flatness correcting means. 29 is a humidifying means, 30 is a close roll type flatness correcting means, and 31 is a close roll. Closely rolled flatness correcting means 30
There are a heated dense roll and a cooled dense roll, but these are collectively represented as 30 here.

In the constitution (12), the heating roll is set at 90 to 1
It is characterized in that the web is heated so that the temperature is 80 ° C. and the total contact time between the web and the roll is 2 seconds or more, whereby the flatness can be corrected and the cellulose having excellent flatness can be obtained. An ester film can be obtained. The heating roll in this case is preferably a dense roll.

In the constitution (13), after the heating roll treatment (the constitution (12)), the cooling roll is set at a temperature of 20 to 80 ° C., and the total contact time between the web and the roll is 2 seconds or more. In this manner, the web is cooled. This is a method in which the web which has been heated and corrected by the heating roll treatment is subsequently cooled. Also in this case, the cooling roll is preferably a close roll. By performing the cooling roll treatment after the heat treatment, a more excellent flatness cellulose ester film can be obtained.

The constitution (14) is that when the moisture content of the web is 1.5 to 7% by weight during or after humidification by the humidification means, the web is treated with the heating roll and the cooling roll. Features. If the moisture content of the web to be straightened is too low or too high, an excellent flatness film cannot be obtained, and this range is appropriate.

The configuration (15) of the present invention is the same as the configuration (1),
(2), (3), (4), (7), (11), (1
2) A cellulose ester film for a liquid crystal image display device formed using at least one method selected from (13) and (14). The greater the number of combinations of the above configurations, the more excellent a flatness film can be obtained.

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited thereto.

[0079]

[Example] <Evaluation method><Evaluation of streaks> An undercoat layer and a back layer of the following formulation were applied to a cellulose ester film after film formation and dried, and a gelatin solution containing methyl violet dye was applied to the undercoat layer surface side. A sample was formed by coating and drying, and placed on a shark caster, and coating unevenness caused by streaks was evaluated as follows.

A: There is no unevenness and it is very smooth. B: Fine unevenness and streaks are slightly scattered, but the whole is smooth. C: Fine unevenness and streaks are slightly visible, but not so noticeable. D: Unevenness and streaks are visible E: Unevenness and streaks are noticeable F: Unevenness and streaks are very large.

(Coating solution for undercoat layer) Vinyl acetate / maleic anhydride, alternating copolymer 3 g Acetone 810 g Isopropanol 150 g (Coating solution for back layer) Tin oxide / antimony oxide composite fine particles (average particle diameter 0.05 μm) 14 g Cellulose di Acetate 6 g Acetone 800 g Cyclohexanone 200 g (Coating solution for gelatin layer) Gelatin 4 g Water 100 g Methyl violet 0.2 g Saponin 0.1 g Example 1 (dope formulation) Cellulose triacetate (degree of substitution A = 2.80) 100 parts by weight Methylene chloride 350 parts by weight Part ethanol 12 parts by weight triphenyl phosphate 12 parts by weight A dope having the above formulation was cast to a dry film thickness of 80 μm, and a film was formed at a tension of 20 kgf / m and a drying temperature of 160 ° C., and cellulose triacetate (abbreviated). TAC) film was obtained. The amount of residual solvent in the finished film was 0.2% by weight.

The above-mentioned dopes were formed under the conditions shown in Table 1 below to obtain Samples 1 to 11. The sample No. 3, 9 and 10 were comparative examples. To these samples, the undercoat layer,
The back layer and the gelatin layer were applied, and the streaks were evaluated. The results are shown in Table 2 below.

(Results) Each of the cellulose triacetate films formed by the production method of the present invention was excellent in flatness.

Example 2 (Dope formulation) Cellulose acetate propionate (degree of substitution A = 2.40, degree of substitution B = 0.40) 100 parts by weight Methyl acetate 140 parts by weight Methylene chloride 210 parts by weight Triphenyl phosphate 5 parts by weight Part ethylphthalylethyl glycolate 7 parts by weight The above dope was formed under the same conditions as in Example 1 (Table 1).
Cellulose acetate propionate (CAP for short)
Film samples 12 to 22 were obtained. The sample No. 1
4, 20, and 21 were comparative examples. The undercoat layer, the back layer, and the gelatin layer were coated in the same manner as in Example 1, and the streaks were evaluated. The results are shown in Table 3.

[0085]

[Table 1]

[0086]

[Table 2]

[0087]

[Table 3]

(Results) The sample using cellulose acetate propionate (CAP) gave exactly the same results as those of cellulose triacetate.

[0089]

As described above, it is possible to obtain a thin film for a liquid crystal image display device having excellent flatness, which can contribute to the liquid crystal image display device industry.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an example of an apparatus for a solution casting film forming method.

FIG. 2 is a diagram schematically showing a state of dope casting.

FIG. 3 is a schematic diagram 1 showing a side cross section of the surface drying means after casting.
It is an example.

FIG. 4 is a diagram schematically illustrating a state in which the pressure of the dope ribbon during casting is reduced from the upstream side in the transport direction.

FIG. 5 is an example of a schematic view showing a solution casting film forming apparatus having a flatness detecting means, flatness information feedback means and flatness condition setting means.

FIG. 6 is an example of a schematic view showing a solution casting film forming apparatus having humidifying means and flatness correcting means.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Web 2 Pressure die 3 Casting support 4 Peeling position 5 Drying device 6 Roll 7 Drying air 8 Tenter device 9 Support drum 10 After casting surface drying means 11 Backside heat transfer means 12 Lower surface drying means 13 Lower side Back surface heat transfer means 14 Winding 15 Dope ribbon 16 Dope film 17 Slit 18 Slit gap 19 Gap between slit tip and dope film (web) 20 Dry air 21 Blow header 22 Decompression chamber 23 Die slit 24 Flatness detection means 25 Flatness Information feedback means 26 Flatness condition (static pressure) setting fine adjustment means 27 Flatness condition (tension) setting fine adjustment means 28 Drive roll 29 Humidification means 30 Close roll type flatness correction means 31 Close roll

Claims (15)

[Claims] 1. A film thickness of 85 μm by a solution casting film forming method.
A method for producing a cellulose ester film of less than, comprising: casting a cellulose ester dope from a casting die onto a casting support being transported to form a web; and applying a dry air to the surface of the web. The absolute value of the static pressure of
A method for producing a cellulose ester film, characterized in that the film is formed with a static pressure deviation of ± 20% or less in the width direction and the longitudinal direction of the outlet of the drying air at 00 mmAq. 2. The method for producing a cellulose ester film according to claim 1, wherein the static pressure is 25 to 90 mmAq. 3. The cellulose according to claim 1, wherein a temperature of the casting support is in a range of from 10 ° C. to a boiling point of a main solvent among the solvents used for the dope. A method for producing an ester film. 4. A method of forming a film under reduced pressure of 1 to 100 mmAq from the back side (upstream side in the transfer direction) of the dope ribbon cast from the die on the casting support. The method for producing a cellulose ester film according to claim 1. 5. A film thickness of 85 μm by a solution casting film forming method.
An apparatus for producing a cellulose ester film of less than, having at least one of flatness detecting means, flatness information feedback means and flatness condition setting fine adjustment means between the dope casting position and the winding. An apparatus for producing a cellulose ester film. 6. The flatness condition setting fine adjustment means is at least one selected from the group consisting of a temperature adjustment means for a casting support, a static pressure adjustment means for drying air, a conveyance tension adjustment means after peeling, and a drying temperature adjustment means. 6. The method according to claim 5, wherein
3. The apparatus for producing a cellulose ester film according to item 1. 7. A method for producing a cellulose ester film, comprising forming a film using the production apparatus according to claim 5 or 6. 8. A film thickness of 85 μm by a solution casting film forming method.
What is claimed is: 1. An apparatus for producing a cellulose ester film having a humidifying means and a flatness correcting means between a peeling position and a winding step. 9. The apparatus according to claim 8, wherein the humidifying unit is at least one selected from a dipping unit, a coating unit, and an air conditioning unit. 10. The apparatus for producing a cellulose ester film according to claim 8, wherein said flatness correcting means has one or more heating rolls and thereafter one or more cooling rolls. 11. A method for producing a cellulose ester film, comprising forming a film using the apparatus according to claim 8. Description: 12. The temperature of the heating roll is 90 to 180.
The method for producing a cellulose ester film according to claim 11, wherein the web is heat-treated so that the total temperature of the web is 2 seconds or more. 13. After the heating roll treatment, the temperature of the cooling roll is set to 20 to 80 ° C., and the web is cooled so that the total contact time between the web and the cooling roll is 2 seconds or more. The method for producing a cellulose ester film according to claim 11 or 12, wherein 14. During or after humidification by humidification means,
14. When the water content of the web reaches 1.5 to 7% by weight, the web is treated with the heating roll and the cooling roll to form a film. A method for producing a cellulose ester film. 15. The method of claim 1, 2, 3, 4, 7, 11, 1.
A cellulose ester film for a liquid crystal image display device, which is formed by a method according to at least one selected from 2, 13, and 14.