JP2003103544A - Method for manufacturing cellulose ester film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a cellulose ester film of high quality with enhanced productivity even if a condition such as feed tension, a temperature or the like after a web peeling process is set to a slightly high level by enhancing the flatness (fluctuation) of the surface of a web by the drying on an endless belt, in manufacturing the cellulose ester film suitable as the protective film of a polarizing plate, for example, in a liquid crystal image display device by a solution casting film-forming method. SOLUTION: In the method for manufacturing the cellulose ester film with a thickness of 20-200 μm by the solution casting film-forming method, the blowing of drying air against the surface of the film (web), which is obtained by casting a cellulose ester solution on the casting surface of the upper transfer part 1a of the rotary endless belt 1 made of a metal, is started from such a state that the amount of the residual solvent on the surface of the web W is set to 300% or less in the drying zone 11 provided to the upper transfer part 1a of the endless belt 1 to dry the web W.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a cellulose ester film suitable as a protective film for a polarizing plate in a liquid crystal image display device, for example.

[0002]

2. Description of the Related Art A liquid crystal image display device (LCD) is widely used as a display device for a word processor, a personal computer or the like because it can be directly connected to an IC circuit with low voltage and low power consumption and can be thinned. It is used. By the way, the basic configuration of this LCD is one in which polarizing plates are provided on both sides of a liquid crystal cell. Since the polarizing plate allows only the light of the polarization plane in a certain direction to pass, in the LCD,
It plays an important role in visualizing the change in the alignment of liquid crystal due to the electric field, and the performance of the LCD largely depends on the performance of the polarizing plate. The polarizing plate comprises a polarizer and protective films laminated on both sides of the polarizer. A cellulose ester film having a film thickness of 20 to 200 μm is widely used as a protective film for such a polarizing plate.

An important characteristic of the cellulose ester film used as a protective film for such a polarizing plate is the flatness of the film surface (so-called uragi),
For example, when the flatness of the film surface is viewed in terms of the degree of reflection of a fluorescent lamp, a film in which the light of the fluorescent lamp is reflected straight and little fine irregularities are seen on the surface can be said to be a film suitable as a protective film for a polarizing plate.

[0004]

[Problems to be Solved by the Invention] However, in the past,
In the method for producing a cellulose ester film by the solution casting method, it was recognized that the flatness of the film surface depends on the manufacturing conditions on the endless belt, but the search for that condition was determined by trial and error. It was
Therefore, when changing the conditions such as the film thickness of the cellulose ester film, the film forming speed, and the amount of the residual solvent for peeling, it is necessary to search the conditions from 1, which is very troublesome and troublesome. There was a problem.

The inventors of the present invention have conducted extensive studies in view of the above points, and as a result, in a method for producing a cellulose ester film by a solution casting film forming method, the amount of residual solvent on the surface of the web on the endless belt is within the appropriate range. It has been found that the flatness (flatness) of the film surface can be improved by blowing dry air, and the present invention has been completed.

An object of the present invention is to solve the above-mentioned problems of the prior art and to produce a cellulose ester film by a solution casting film forming method. In the method, drying on an endless belt causes the flatness (uragity) of the web surface. Therefore, it is possible to produce a good quality cellulose ester film suitable as a protective film for a polarizing plate even if the conditions such as the transport tension and the temperature after the web peeling step are slightly higher. The object of the present invention is to provide a method capable of significantly improving the productivity of cellulose ester film.

[0007]

The method for producing a cellulose ester film according to the invention of claim 1 is a method for producing a cellulose ester film having a thickness of 20 to 200 μm by a solution casting film forming method, in which the cellulose ester solution is rotated. Film obtained by casting on the cast surface of the upper transition part of the metal endless belt (hereinafter referred to as "web")
On the other hand, in the drying zone provided in the upper transition part of the endless belt, the drying air is blown onto the web surface from the state where the residual solvent amount on the web is 300% or less to dry the web. It is characterized by that.

According to a second aspect of the present invention, in the first aspect, the drying zone provided in the upper transition portion of the endless belt is provided with a header for blowing dry air, and the temperature of the web surface is 20 to 60 ° C. And static pressure in header 500 to 1
It is characterized by blowing a dry air of 500 Pa.

According to a third aspect of the present invention, in the second aspect, two drying zones are provided on the endless belt, the temperature is 20 to 60 ° C., and the static pressure in the header is 500 to 15
After passing through the first drying zone in which a drying air of 00 Pa is blown, the web surface in a state where the amount of residual solvent on the surface is less than 100% is further used, and the temperature is 40 to 8 in the second drying zone.
It is characterized by blowing dry air of 0 ° C. and static pressure of 100 to 1200 Pa in the header.

According to a fourth aspect of the present invention, in the second or third aspect, a nozzle having a slit-shaped opening is attached to the dry air blowing header of the drying zone provided on the endless belt, and the slit-shaped opening is provided. Dry air is blown onto the surface of the web from a nozzle having a portion.

[0011] The invention of claim 5, in claim 4, the pitch of the drying air blowing nozzles in the first drying zone is less than and 100% or more 300% surface residual solvent amount of the web, made with 50 to 3 300 mm, pitch of the dry air blowing nozzles in the second drying zone is a surface residual solvent content less than 100% of the web is characterized by being made with 150 mm to 6 300 mm.

According to a sixth aspect of the present invention, in the fourth or fifth aspect, the arrangement gap of the nozzle having the slit-shaped opening is
It is characterized in that it is 2 to 10 mm.

According to a seventh aspect of the present invention, in any one of the fourth to sixth aspects, a gap between the tip of the nozzle having the slit-shaped opening and the upper surface of the endless belt is set to 5 mm.
It is characterized in that it is set to 100 mm.

According to an eighth aspect of the present invention, in any one of the fourth to seventh aspects, a blowing angle of dry air from a nozzle having a slit-shaped opening is 90 to 90 on the web on the endless belt. The feature is that the angle is 45 degrees.

According to a ninth aspect of the present invention, in any one of the first to eighth aspects, a zone for drying the web on the endless belt from the surface side of the belt is at least three drying zones having different drying conditions. It is characterized by being divided into.

According to a tenth aspect of the present invention, in any one of the first to ninth aspects, a zone for drying the web on the endless belt from the back side of the belt is at least two drying zones having different drying conditions. It is characterized by being divided into.

According to an eleventh aspect of the present invention, in any one of the first to tenth aspects, 10 to 200 are provided upstream from the first drying zone in which the blowing of the drying air onto the web is started.
A feature is that an exhaust means is provided at a position separated by mm.

According to a twelfth aspect of the present invention, in any one of the first to eleventh aspects, the web is dried in a drying zone on the endless belt, then peeled from the endless belt by a peeling roll, and further the peeled web. Is provided with a means for pulling the web in the width direction.

According to a thirteenth aspect of the present invention, in the twelfth aspect, the means for pulling the web in the width direction is at least one means selected from the group consisting of an expander roll, a tenter, and a heat straightening roll. Is characterized by.

The invention of claim 14 is characterized in that, in claim 13, the tenter is one biaxial tenter and / or a plurality of monoaxial or biaxial tenters.

According to a fifteenth aspect of the present invention, in any one of the first to fourteenth aspects, after drying the web in a drying zone on the endless belt, the web is peeled from the endless belt by a peeling roll, When the average residual solvent amount of the film that has passed through the steps becomes 10% or less, the film is passed through a zone having a temperature of 20 to 140 ° C., and the average speed of temperature increase or temperature decrease of the film in the zone. Is set to 15 ° C./second or less.

According to a sixteenth aspect of the present invention, in any one of the first to fifteenth aspects, when the average residual solvent amount of the film after peeling is 10% or less, the film is fed with a tension of 62 to 135N. It is characterized by passing through a zone with / m.

In the above, in the method for producing a cellulose ester film according to the present invention, the film thickness in a product state is 20.
A film having a thickness of ˜200 μm, preferably 20 to 85 μm, and more preferably 20 to 60 μm is targeted for production. The cellulose ester film targeted by the present invention comprises a lower fatty acid ester of cellulose. Here, the lower fatty acid in the lower fatty acid ester of cellulose means a fatty acid having 6 or less carbon atoms, for example, cellulose acetate such as cellulose diacetate or cellulose triacetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate. And mixed fatty acid esters such as cellulose acetate butyrate. The most preferred lower fatty acid ester of cellulose is cellulose triacetate.

Improving the performance of a liquid crystal image display device due to the cellulose ester film by incorporating a plasticizer, an ultraviolet absorber, an antioxidant, a processing stabilizer, a matting agent and the like into the cellulose ester film. You can

In the invention of the above-mentioned claim 1, the film (web) obtained by casting on the cast surface of the upper transition portion of the endless belt, the web in the drying zone provided in the upper transition portion of the endless belt. It is limited to start the blowing of the dry air onto the web surface from the state where the amount of the residual solvent on the surface is 300% or less to dry the web.

The amount of residual solvent used in the present invention can be represented by the following formula.

Residual solvent amount (mass%) = {(M−N) /
N} × 100 Here, M is the mass of the web at an arbitrary time point, and N is the mass of the mass M when dried at 110 ° C. for 3 hours.

In the drying zone provided at the upper transition part of the endless belt, the amount of residual solvent on the surface of the web is 300.
%, The drying of the web is started by starting to blow the drying air onto the web surface. The reason is that the amount of residual solvent on the surface of the web exceeds 300%. This is because a rough surface is formed on the dried cellulose ester film when the blowing of dry air onto the film is started.

According to the second aspect of the present invention, the header for drying air blowing in the drying zone provided at the upper transition portion of the endless belt has a temperature of 20 to 60 ° C. and a static pressure in the header of 500 to 1500 Pa with respect to the web surface. Spraying dry air is limited. The reason is that if the temperature of the dry air is lower than 20 ° C., the required spraying zone of the dry air becomes too long, which is not preferable, and if it exceeds 60 ° C., the film formation on the upper surface proceeds and the spraying effect is increased. This is because it is not preferable since If the static pressure of the dry air in the header is less than 500 Pa, the spraying force is weak,
When the cellulose ester film after drying has a rough surface and the static pressure in the header of the dry air exceeds 1500 Pa,
It is not preferable because the trace of the blowing wind remains.

According to the invention of claim 3, two drying zones are provided on the endless belt, and the temperature is 20 to 60.
C., and after passing through the first drying zone in which a dry air having a static pressure of 500 to 1500 Pa in the header is blown, the web surface in a state where the amount of residual solvent on the surface is less than 100%, and a temperature of 40 to 80 in the second drying zone. It is limited to spray dry air of 100 ° C and static pressure of 100 to 1200 Pa in the header. The reason is that, after passing through the first drying zone, the solidification of the web surface has progressed, so the temperature of the drying air and the static pressure in the header in the second drying zone are higher and lower than those in the first drying zone. It is good with pressure. If the temperature of the drying air in the second drying zone is lower than 40 ° C., the drying capacity is too low, the peeling residual solution rises, and peeling failure occurs, which is not preferable. This is because it is not preferable. Further, if the static pressure in the header of the dry air in the second drying zone is less than 100 Pa, the drying capacity is too low, the peeling residual solution increases, and peeling failure occurs. 120
If it exceeds 0 Pa, the drying capacity is sufficient, and making it higher will waste the energy used.
Not preferable.

According to the invention of claim 4, a nozzle having a slit-shaped opening is attached to the header for blowing dry air in the drying zone provided on the endless belt, and the slit-shaped opening of the nozzle is used to feed the surface of the web. A dry wind is sprayed on.

In the invention of claim 5, the pitch of the dry air blowing nozzles in the first drying zone is 50 to 300 m.
m, and the pitch of the dry air blowing nozzles in the second drying zone is limited to 150 to 600 mm. The reason is that if the pitch of the dry air blowing nozzles in the first drying zone is less than 50 mm, the number of nozzles is too large and the required wind speed cannot be obtained, which is not preferable. If the nozzle pitch exceeds 300 mm, uneven drying occurs in the longitudinal direction of the web.
Not preferable. In the second drying zone after passing through the first drying zone, solidification of the web surface is progressing, so the pitch of the drying air blowing nozzles in the second drying zone is 150 m.
There is no need to make it smaller than m. If the pitch of the dry air blowing nozzles in the second drying zone exceeds 600 mm, the drying does not proceed and the residual peeling solution increases,
Not preferable.

In the invention of claim 6 , the gap between the slit-shaped openings of the nozzle is limited to 2 to 10 mm. The reason is that if the gap between the slit-shaped openings of the nozzle is less than 2 mm, accuracy is not obtained and wind velocity unevenness occurs in the web width direction, which is not preferable. If the gap between the slit-shaped openings exceeds 10 mm, the desired wind speed cannot be obtained, which is not preferable.

In the invention of claim 7, the gap between the tip of the nozzle having the slit-shaped opening and the upper surface of the endless belt is limited to 5 to 100 mm. The reason is that if the gap between the tip of the nozzle having the slit-shaped opening and the upper surface of the endless belt is less than 5 mm, when the thick film base passes through due to troubles during casting of the dope, this will hit the nozzle. However, in some cases, the belt may be scratched, which is not preferable, and if the gap exceeds 100 mm, the wind velocity impinging on the web on the belt is too low, and the effect of the present invention cannot be obtained.

In the invention of claim 8, the blowing angle of the dry air from the nozzle having the slit-shaped opening to the web on the endless belt is limited to 90 to 45 degrees. The reason is that if the angle of spray of dry air from the nozzle exceeds 90 degrees, the spray of dry air will be against the belt conveyance and uneven drying will occur. Spray angle is 45
If it is less than 100 degrees, the distance between the slit-shaped opening and the belt becomes too wide, and the collision wind speed becomes too low, which is not preferable.

In the invention of claim 9, the zone for drying the web on the endless belt from the surface side of the belt is divided into at least three drying zones under different drying conditions, and the solvent remaining on the surface of the web is as described above. Quantity is 30
A first drying zone in which the drying of the web is started by starting the blowing of drying air onto the surface of the web from a state of 0% or less;
And in a state where the amount of residual solvent on the surface of the web is less than 100%, the amount of residual solvent on the surface of the web is further 5 after the second drying zone in which drying air is blown to the surface of the web to dry.
In the state of less than 0%, by providing the third drying zone in which the drying air is blown onto the web surface to perform drying, efficient drying can be performed.

In the tenth aspect of the invention, the zone on the endless belt for drying the web from the back side of the belt is divided into at least two drying zones under different drying conditions. This is because by providing a drying zone also on the back surface side of the endless belt, the temperature of the drying air blown onto the web is stabilized as constant as possible from both front and back surfaces of the belt to realize efficient drying. In addition, the reason why the drying zone from the back side of the belt is divided into at least two drying zones under different drying conditions is that the temperature zones are set in the first half and the latter half of the endless belt as in the case of drying from the front side of the belt. This is because the efficient drying can be achieved by dividing.

According to the eleventh aspect of the present invention, 10 webs are provided on the upstream side from the first drying zone where the blowing of the drying air onto the web is started.
Exhaust means is provided at a position 200 mm apart. The reason is that when the first drying zone is close to the casting part of the dope and the static pressure in the header is high, the casting film cast from the die is blown with air and causes a failure. This is to prevent this, in some cases.

According to the twelfth aspect of the invention, the web is dried in a drying zone on the endless belt, and then peeled from the endless belt by a peeling roll. Further, a drying step or a cooling step of the peeled web is provided. Is equipped with a means for pulling in the width direction.
In the invention of claim 13, as means for pulling the web in the width direction, at least one means selected from the group consisting of an expander roll, a tenter, and a heat straightening roll is used.

In the fourteenth aspect of the invention, as the tenter,
One 2-axis tenter and / or multiple 1-axis or 2
It is preferable to use an axial tenter, and it is preferable to use such a tenter because the tension in the width direction of the web is further emphasized and the flatness of the cellulose ester film is improved.

In the invention of claim 15, after drying the web in the drying zone on the endless belt, the web is peeled from the endless belt by a peeling roll, and the average residual solvent amount of the film after several steps is 10% or less. At this stage, the film is passed through a zone having a temperature of 20 to 140 ° C. The reason is that when the temperature of the drying zone is less than 20 ° C., the drying length of the film (the length required for drying) becomes remarkably long, and the temperature of the drying zone is 140 ° C.
This is because if the temperature exceeds ℃, the flatness of the film is significantly deteriorated. Further, if the average rate of temperature increase or temperature decrease of the film in the zone exceeds 15 ° C./sec, the flatness of the film is significantly deteriorated, which is not preferable.

In the sixteenth aspect of the present invention, the film is limited to pass through the zone having the transport tension of 62 to 135 N / m when the average residual solvent amount of the film after peeling is 10% or less. . The reason is that if the transport tension of the film in the zone is less than 62 N / m, roll slip occurs, and this causes scratches on the film, which is not preferable. Also, the transport tension of the film is 1
When it exceeds 35 N / m, the flatness of the film is significantly deteriorated, which is not preferable.

[0043]

BEST MODE FOR CARRYING OUT THE INVENTION Next, an embodiment of the present invention will be described.
A description will be given with reference to the drawings.

Referring to FIG. 1, an apparatus used in a method for producing a cellulose ester film having a film thickness of 20 to 200 μm by a solution casting method is a rotating metal wound around a pair of front and rear drums (2) and (3). Made endless belt (1), a die (4) that casts the dope that is the raw material solution of the cellulose ester film on the cast surface of the upper transition part (1a) of the endless belt (1), and the endless belt by the die (4)
(1) A film (web) (W) formed above, a peeling roll (5) for peeling from the endless belt (1), and a winding means (not shown) for winding the peeled web (W) or film It is equipped with.

According to the method for producing a cellulose ester film of the present invention, the upper transition portion (1) of the endless belt (1) is
For the web (W) obtained by casting on the cast surface of a), the drying zone (1) provided on the endless belt (1)
In 1), the web (W) is dried by starting to blow dry air onto the surface of the web (W) from a state where the amount of residual solvent on the surface of the web (W) is 300% or less.

The upper transition part of the endless belt (1)
The total length of (1a) and the lower transition part (1b) is, for example, usually 20 to 20.
The width of the upper transition part (1a) and the lower transition part (1b) depends on the width of the cellulose ester film to be produced, but is usually 1.5 to 3.0 m.

In this embodiment, the drying zone from the surface side of the endless belt (1) is divided into three, and the drying zone is located on the belt surface side facing the upper transition part (1a) of the endless belt (1). First and second drying zones (11) and (12) are provided, and a belt surface side third drying zone (13) is provided facing the lower transition portion (1b) of the endless belt (1).

First, in the first drying zone (11) on the belt surface side, the blowing of dry air onto the surface of the web (W) is started from the state where the amount of residual solvent on the web (W) is 300% or less. In this case, the web (W) is dried. In this case, the drying air blowing header (14) causes the temperature of the surface of the web (W) to be 20 to 60 ° C. and the static pressure in the header to be 500 to 1500 Pa. Blow dry air. In addition,
As shown in FIG. 2, the header (14) is forced to send drying air from a fan (17).

Next, after passing through the first drying zone (11) on the front side, in the second drying zone (12) on the front side of the belt,
On the surface of the web (W) in which the amount of residual solvent on the surface is less than 100%, the temperature (40 to 80 ° C.) and the static pressure in the header (100 to 1200 Pa) are applied by the dry air blowing header (14).
Blow dry air. Furthermore, this second drying zone (1
After passing 2), the lower transition (1b) of the endless belt (1)
A web (W) in which the amount of residual solvent on the surface is less than 50% in the third drying zone (13) provided opposite to
On the surface, the temperature of 50 ~ by the dry air blowing header (14)
A dry air of 85 ° C. and a static pressure of 70 to 1100 Pa in the header is blown.

As shown in detail in FIG. 2 and FIG. 3, each of the surface side first to third drying zones (11), (12) and (13) is provided with the dry air blown so as to face the surface of the endless belt (1). The header (14) for a nozzle (1) has a slit-shaped opening (16).
5) is installed, and the slit-shaped opening of the nozzle (15)
Dry wind is blown onto the surface of the web (W) from (16).

Here, the pitch (P) of the dry air blowing nozzles in the front side first drying zone (11) is 50 to 300 m.
m, and the pitch (P) of the dry air blowing nozzles (15) in the front side second drying zone (12) is 150 to 600 mm.
Furthermore, the pitch (P) of the drying air blowing nozzles (15) in the third drying zone (13) is 150 to 600 mm.
Has been made.

Further, the slit-shaped opening (1
The gap (S) in 6) is 2 to 10 mm. The distance (T) between the tip of the nozzle (15) having the slit-shaped opening (16) and the upper surface of the endless belt (1) is 5 to 100 m.
m.

With respect to the web (W) on the endless belt (1), slit-shaped openings of the headers (14) for spraying dry air
The spray angle (α) of the dry air from the nozzle (15) having (16) is preferably 90 to 45 degrees.

When the surface-side first drying zone (11) is close to the dope casting die (4) and the static pressure in the header is high, the web cast from the die (4) is used. The wind may hit the (W) and cause a failure. Therefore, the web (W) was separated from the first drying zone (11) on the front surface side where the blowing of the dry air was started by 10 to 200 mm upstream. Exhaust means (6) is provided at the location (see FIG. 1).

Further, in this embodiment, the zone for drying the web (W) on the endless belt (1) from the back surface side of the belt (1) is divided into three drying zones under different drying conditions. ing.

In the method of the present invention, the web (W) is
After drying in the drying zone provided on the endless belt (1), it is peeled from the endless belt (1) by the peeling roll (5), and a drying or cooling step of the peeling web (W) is further provided. Is equipped with a means for pulling the web (W) in the width direction. As a means for pulling the web (W) in the width direction, at least one means selected from the group consisting of an expander roll, a tenter, and a heat straightening roll is used.

In FIG. 4, the peeling web (W) peeled from the endless belt (1) by the peeling roll (5).
Is stretched in the width direction by an expander roll (31) arranged in the middle of the pair of transfer rolls (32) and (33) and having an arc shape when viewed from the plane. In this case, the web (W) is pulled by the expander roll (31) in the width direction at a ratio of, for example, 1.02 to 1.2 times,
It can be enlarged.

In FIG. 5, the peeling web (W) peeled from the endless belt (1) by the peeling roll (5).
Is pulled in the width direction by a uniaxial tenter (34) having clips (35) (35) arranged in the middle of the pair of transfer rolls (36) (37) and arranged at predetermined intervals on both left and right sides. Has been. In this case, the web (W) is stretched by the tenter (34) in the width direction at a ratio of, for example, 1.02 to 1.2 times and is expanded. Such tenter (3
As 4), one biaxial tenter and / or a plurality of monoaxial or biaxial tenters are used. Thus, the tenter (3
By using 4), the tension in the width direction of the web (W) is further emphasized, and the flatness of the cellulose ester film becomes good.

The illustration of the heat straightening roll as a means for pulling the peeling web (W) in the width direction is omitted.

[0060]

EXAMPLES Next, examples of the present invention will be described, but the present invention is not limited to these examples.

Examples 1 to 3 and Comparative Example Film forming conditions Transport tension 100 to 120 N / m Dry film thickness 40 μm Dope formulation Cellulose triacetate 100 parts by weight Methylene chloride 350 parts by weight Ethanol 12 parts by weight Triphenyl phosphate 12 parts by weight Tinuvin 3260 0.5 parts by weight (manufactured by Ciba Specialty Chemicals) Aerosil 200V 0.1 parts by weight (manufactured by Nippon Aerosil Co., Ltd.) First, a dope of the above-mentioned cellulose triacetate composition was prepared, and the manufacturing apparatus shown in FIGS. 1 to 3 was used. A cellulose triacetate film was prepared from this dope by a solution casting film forming method. The film forming conditions are shown in Table 1.

In Examples 1 to 3, as with the endless belt (1), on the belt surface side, three drying zones (11), (12) and (13) are provided, and
On the back side of the belt, the first and third parts are divided into two.
A drying zone (21) (23) was provided. Also, endless belt
Front drum around which the front turn part (1c) of (1) is wound
The backside second drying zone (22) in (2) was omitted. On the other hand, in the comparative example, as with the endless belt (1), the drying zone divided into two was provided on the front surface side of the belt, and the drying zone divided into two was also provided on the back surface side of the belt.

Next, the flatness of the formed film surface (unevenness) was evaluated by the degree of reflection of the fluorescent lamp.

Evaluation Criteria for Flatness of Film Surface (Erularity) ◎ A fluorescent lamp appears straight and almost no fine irregularities are observed.

○ The fluorescent lamp appears straight, with very slight irregularities.

△ The fluorescent lamp is slightly distorted and appears.

× The fluorescent lamp is distorted and appears in the image.

[0068]

[Table 1]

As is clear from the results of Table 1 above, in Examples 1 to 3 according to the method of the present invention, the flatness (flatness) of the web surface can be improved by drying on the endless belt, and thus, Even if the conditions such as the transport tension and the temperature after the web peeling step were set to be slightly higher, a good quality cellulose ester film suitable for a protective film of a polarizing plate could be produced. On the other hand, in the method of Comparative Example, the obtained cellulose ester film had a fluorescent lamp considerably distorted in the image and did not have a quality suitable for the protective film of the polarizing plate.

[0070]

INDUSTRIAL APPLICABILITY As described above, the present invention is a method for producing a cellulose ester film having a film thickness of 20 to 200 μm by the solution casting film forming method, in which the cellulose ester solution is added to the upper transition portion of the rotating metal endless belt. With respect to the web obtained by casting on the cast surface, in the drying zone provided in the upper transition part of the endless belt, the amount of the residual solvent on the surface of the web is 300% or less Since the spraying is started to dry the web, the flatness (unevenness) of the web surface can be improved, and the conditions such as the conveyance tension and the temperature after the web peeling process are somewhat high. Even with eyes, it is possible to produce a good quality cellulose ester film suitable as a protective film for a polarizing plate. An effect that can greatly improve the beam of productivity.

[Brief description of drawings]

FIG. 1 is a schematic side view of an apparatus used in a method for producing a cellulose ester film of the present invention.

FIG. 2 is an enlarged side view of a main part of FIG.

FIG. 3 is an enlarged side view of an essential part of FIG.

FIG. 4 is a schematic plan view of an expander roll portion after web peeling.

FIG. 5 is a schematic plan view of a tenter portion after peeling the web.

[Explanation of symbols]

1 Rotating metal endless belt 2 front drum 3 rear drum 4 casting die 5 peeling roll 6 exhaust means 11 Belt surface side first drying zone 12 Belt surface side second drying zone 13 Belt surface side third drying zone 14 Dry air blowing header 15 nozzles 16 slit-shaped opening 21 Belt 1st drying zone on the back side 22 Second drying zone on back side of belt 23 Belt 3rd drying zone on the back side 24 Dry air blowing header

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Claims (16)

[Claims] 1. A film thickness of 20 to 200 by a solution casting film forming method.
In the method for producing a cellulose ester film having a thickness of μm, a film (hereinafter, referred to as “web”) obtained by casting a cellulose ester solution on a cast surface of an upper transition portion of a rotating metal endless belt is used as an endless belt. In the drying zone provided in the upper transition part, the amount of residual solvent on the surface of the web is set to 300% or less, and the blowing of dry air onto the web surface is started to dry the web. A method for producing a cellulose ester film. 2. A drying zone provided at the upper transition part of the endless belt is provided with a drying air blowing header, and the web surface is dried at a temperature of 20 to 60 ° C. and a static pressure in the header of 500 to 1500 Pa. The method for producing a cellulose ester film according to claim 1, which comprises blowing air. 3. Two drying zones are provided on the endless belt, and a temperature of 20 to 60 is applied to the web surface.
C., and after passing through the first drying zone in which a dry air having a static pressure of 500 to 1500 Pa in the header is blown, the web surface in a state where the amount of residual solvent on the surface is less than 100%, and a temperature of 40 to 80 in the second drying zone. The method for producing a cellulose ester film according to claim 2, wherein a dry air having a static pressure of 100 to 1200 Pa in the header and 100 ° C is blown. 4. A nozzle having a slit-shaped opening is attached to a header for blowing dry air in a drying zone provided on the endless belt, and the drying air is blown from the nozzle having the slit-shaped opening onto the surface of the web. Spraying is carried out, The manufacturing method of the cellulose-ester film of Claim 2 or 3 characterized by the above-mentioned. 5. The pitch of the dry air blowing nozzles in the first drying zone where the amount of residual solvent on the surface of the web is 300% or less and 100% or more is 50 to 300 mm, and the amount of residual solvent on the surface of the web is less than 100%. The pitch of the dry air blowing nozzles in the second drying zone is 150 to 6
The method for producing a cellulose ester film according to claim 4, wherein the cellulose ester film has a thickness of 00 mm. 6. The method for producing a cellulose ester film according to claim 4, wherein the gap between the nozzles having the slit-shaped openings is set to 2 to 10 mm. 7. A gap between the tip of the nozzle having a slit-shaped opening and the upper surface of the endless belt is 5 to 100.
mm, The manufacturing method of the cellulose-ester film of any one of Claims 4-6 characterized by the above-mentioned. 8. The spray angle of dry air from a nozzle having a slit-shaped opening with respect to the web on the endless belt is set to 90 to 45 degrees.
7. The method for producing a cellulose ester film according to any one of 7. 9. A web on an endless belt,
The method for producing a cellulose ester film according to any one of claims 1 to 8, wherein the zone for drying from the surface side of the belt is divided into at least three drying zones under different drying conditions. 10. The endless belt according to claim 1, wherein a zone for drying the web from the back side of the belt is divided into at least two drying zones under different drying conditions. The method for producing a cellulose ester film according to the item 1. 11. The exhaust means is provided at a position 10 to 200 mm upstream from the first drying zone where the blowing of the dry air onto the web is started.
10. The method for producing a cellulose ester film according to any one of 10. 12. The web is dried in a drying zone on an endless belt, and then peeled from the endless belt by a peeling roll, and a peeling web drying step or cooling step is provided, in which the web is stretched in the width direction. The method for producing a cellulose ester film according to any one of claims 1 to 11, which is equipped with a pulling means. 13. The means for pulling the web in the width direction comprises:
The method for producing a cellulose ester film according to claim 12, which is at least one means selected from the group consisting of an expander roll, a tenter, and a heat straightening roll. 14. The method for producing a cellulose ester film according to claim 13, wherein the tenter is one biaxial tenter and / or a plurality of uniaxial or biaxial tenters. 15. The web is dried in a drying zone on an endless belt, and then peeled from the endless belt by a peeling roll. After several steps, the average residual solvent amount of the film becomes 10% or less. The film is passed through a zone having a temperature of 20 to 140 ° C., and the average rate of temperature increase or temperature decrease of the film in the zone is set to 15 ° C./second or less. The method for producing a cellulose ester film according to any one of the above. 16. When the average residual solvent amount of the film after peeling is 10% or less, the film is fed at a tension of 62 to 60.
The method for producing a cellulose ester film according to claim 1, wherein the cellulose ester film is passed through a zone having 135 N / m.