JP2003291160A - Solution film making method, cellulose ester film, protective film, and polarizing plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To define optimal conditions for manufacturing a film free from peeling when the film produced by the solution film making method is processed into a polarizing plate, etc. <P>SOLUTION: In the method, a polymer solution pressurized at a given temperature is discharged from a flow casting die to be flowed into a base. The polymer solution on the base is coagulate to the extent that its mass is less than 320% of its dry mass and exceeds 200% to form a film, and then the film is removed and dried by applying a tensile force of over 0.049 Newton and below 14.7 Newton per 1 m of the film width to the film. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a solution film-forming method used for producing a photographic light-sensitive material or a film for optical use, a cellulose ester film formed by the film-forming method, and a polarizing plate comprising the cellulose ester film. The present invention relates to a protective film for use, and a polarizing plate using the protective film.

[0002]

2. Description of the Related Art In recent years, transparent plastic films have been
In addition to conventional demand for photographic supports and OHP films, demand for optical materials such as protective films for polarizing plates for liquid crystal display devices, optical compensation films such as retardation films, transparent substrates, optical filters, etc. is increasing. However, as a result, quality requirements are becoming stricter.

Particularly, a plastic film as an optical material such as a protective film for a polarizing plate is required to have high transparency, low optical anisotropy, flatness, easy surface treatment, high durability and scratch resistance. .

As the plastic film having these characteristics, there are cellulose ester, nobornene resin, acrylic resin, polyacetate resin, polycarbonate resin and the like, but from the viewpoint of productivity and material cost, cellulose ester is mainly used. Especially, cellulose triacetate (TAC) is advantageously used because of its high transparency, low optical anisotropy, and low retardation.

In the cellulose ester film, a polymer liquid (dope) obtained by dissolving a polymer in an organic solvent is cast from a casting die onto a drum whose surface is cooled, or a support composed of an endless band, and the cast on the support. It is generally manufactured by a solution film-forming method in which the solidified film is cooled and dried, separated from the support, and dried while being conveyed by a roll or a tenter.

In order to increase the production rate of the film by this solution film-forming method and to improve the production efficiency, a poor solvent is added to the main solvent to promote gelation of the dope and shorten the peeling time from the support. A method has been proposed (US Pat. No. 2)
No. 607704).

However, since the boiling point of the poor solvent to be used is generally high, it takes a long time to dry the film after peeling, and the overall film manufacturing time does not change so much. Therefore, in order to reduce this drying load, it is possible to cast a dope with a higher concentration on the support, but if the concentration of the dope is high, melt fracture will occur and the surface quality of the film will be extremely reduced. There is a problem of doing.

Melt fracture is a phenomenon in which irregular asperity is generated on the film surface or the gloss of the surface is lost. The shear stress of the dope flow increases, and the flow state of the dope is disturbed at the inlet of the die and the flow is parallel. It is considered that the cause is that a blind spot is generated in the dope flow channel in the die when a large flow is not formed, or when the dope viscosity is too large and it takes time to relax the internal stress.

In Japanese Patent Publication No. 62-43846, a flow of a high-viscosity polymer solution is wrapped with a low-viscosity solution.
A method for preventing the occurrence of melt fracture is disclosed by simultaneously extruding a solution having both high and low viscosities from a die slit to reduce the shear stress in the die slit to a limit value or less.

On the other hand, when the content ratio of the organic solvent at the time of peeling the film from the support exceeds a predetermined value, the film peeled from the support is slackened by the conveying means, and the film is a soft film because the film is a soft film. There is a problem that instability of conveyance occurs such as rattling, and surface defects such as scratches, knicks, and wrinkles occur.

In order to solve this problem, it is necessary to apply an appropriate tension to the film for transportation, but if the content ratio of the organic solvent exceeds a predetermined value, the tension causes the film to expand or contract. Therefore, Japanese Patent Laid-Open No. 5-1
Japanese Patent No. 85445 discloses a method of applying tension while applying dry air in a constant temperature range for a predetermined time after separating from a support.

On the other hand, in order to peel the film from the support, it is necessary to set the peripheral speed of the peeling roll close to the support to be higher than the peripheral speed of the support, and the peeling is further performed. Hold the film with a tenter,
When carrying and drying while winding around the carrying roll,
Unless the conveying speed is set higher than the peripheral speed of the stripping roll, the film will sag.

However, if the peripheral speed of the peeling roll or the transfer speed of the tenter or the transfer roll is too fast as compared with the peripheral speed of the support, a large tension is applied in the process direction of the film, and the film is processed as a protective film for a polarizing plate. In addition, there is a problem that the bonded surface in the direction intersecting with the process direction is peeled off.

[0014]

In view of the above circumstances, the present invention forms a polymer film which does not peel off when the polymer film produced by the solution film forming method is processed into a polarizing plate or the like. The purpose is to set the optimum conditions. Further, another object of the present invention also includes a cellulose ester film having good processability formed by the solution film forming method, a protective film made of the cellulose ester film, and a polarizing plate constituted by using the protective film.

[0015]

According to the present invention, a pressurized polymer liquid is discharged from a casting die to be cast on a support, and a film solidified on the support is peeled off from the support. In the solution film-forming method, in which the polymer film is dried and dried to obtain a polymer film,
A film is formed by coagulation until it is less than 20% and exceeds 200% of the dry mass, and the film has a width of 1
Over 0.049 Newton per meter and 1
It is characterized in that the film is peeled off by applying a tension of less than 4.7 Newton.

In the present invention, when the tension applied when peeling off the solidified film is large, the molecules are oriented and hardened in the direction in which the tension is applied, and the polymer film is unbalanced in elasticity in the longitudinal direction and the width direction. Occurs, and it is made based on the finding that it causes the peeling of the polymer film and the polarizer when the polymer film and the polarizer represented by polyvinyl alcohol are laminated and processed into a polarizing plate. This makes it possible to suppress the molecules from being oriented in the direction in which tension is applied. The present invention also includes a production step of co-casting two or more kinds of polymer liquids in the casting step in the above solution casting method.

Further, a cellulose ester film formed by the solution film forming method of the present invention, a protective film made of a cellulose ester film, and a polarizing plate constituted by using the protective film are also included.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the solution film forming method of the present invention will be described below.

In the solution casting method of the present embodiment, a polymer film production apparatus in which the support for casting the polymer solution is a casting band or a polymer film production apparatus in which the support is a casting drum is used. Therefore, the polymer manufacturing apparatus will be described first.

FIG. 1 is a view showing a manufacturing apparatus using a casting band as a support in the manufacturing apparatus of the polymer film used in this embodiment.

The manufacturing apparatus of the present embodiment shown in FIG. 1 has three dope supplying devices for supplying a dope composed of cellulose ester solutions having different concentrations, and the first dope supplying device 11 is internally heated and melted. A storage tank 1 having a stirring blade 2 for stirring the prepared dope 3, and a liquid delivery pump 4 for delivering the dope 3 stirred in the storage tank 1 at a predetermined pressure.
And a static mixer 5 for mixing a poor solvent supplied from a poor solvent supply device 14 via a liquid feed pump 4 with the fed dope to obtain a polymer liquid having a predetermined formulation, and removing impurities. And a filter 6.

Here, the poor solvent such as butanol is mixed with the dope 3 by casting the polymer solution on the casting belt 17 to solidify it to form a film, and peeling the film from the casting belt 17. This is to obtain the required gel strength. When a poor solvent such as butanol is mixed with the dope, it is more effective to continuously mix a fixed amount in order to reduce the viscoelasticity, and the static mixer 5 is used.

Second and third dope supply devices 12, 13
Is composed of a storage tank 1 having a stirring blade 2 for stirring the heated and melted dope, and a liquid feed pump 4 for feeding the dope stirred in the storage tank 1 at a predetermined pressure. The poor solvent supply device 14 is not connected to the liquid supply pipe.

Here, the storage tank 1 is provided in each of the first to third dope supply devices 11, 12, and 13, but the storage tank 1 does not necessarily have to be provided in all the dope supply devices and is common. One storage tank 1 may be provided, and the liquid supply pipe for supplying the dope from the common storage tank 1 to the next step may be branched midway to supply the dope to another dope supply device. A diluted solvent supply device may be joined to the branched liquid supply pipe to supply the diluted polymer solution. Further, the dope supply device does not necessarily have to be provided in three, and may be one or two.

The dope supplied from each dope supply device 11, 12, 13 is pressurized by the liquid feed pump 4 and sent to the casting die 15. From the first dope supply device 11, the surface layer of the film is obtained. The surface layer dope constituting the film is fed, the base layer dope constituting the central portion of the film is fed from the second dope feeding device 12, and the third dope feeding device 13 is fed.
The backside layer dope forming the backside layer of the film is fed from the solution, and they are merged by the casting die 15 and then discharged to be cast on the casting band 17.

Here, each dope fed to the casting die 15 is configured to be pressurized by the liquid feeding pump 4 and discharged, but the present invention is not limited to this, and the casting die 1 is not limited thereto.
A decompression chamber may be provided at the rear of 5, and the dope may be sucked toward the casting band by depressurizing the casting portion by the decompression chamber. Further, here, a multi-manifold type co-casting die is used as the casting die 15 to form a film having a three-layer structure. However, a plurality of T dies are sequentially cast to form a film having a plurality of structures. Alternatively, a film having a plurality of structures may be formed by using a feed block type co-casting die that is a combination of a feed block and a T die for combining a plurality of layers of dope. Furthermore, a T-die may be used to form a film having a single layer structure.

The casting band 17 comprises a pair of rotating drums 16.
An endless belt having a mirror-finished surface is wrapped around the belt and moves circularly in the direction of arrow A. Rotating drum 1
A casting die 15 is arranged above one of the peripheral surfaces of 6 and at a position slightly away from the surface, and the polymer liquid pressurized by the liquid feed pump 4 is discharged from the casting die 15 and indicated by an arrow. The film is cast and stretched on the casting band 17 moving in the direction A, and is cooled and solidified by warm air or cooling air sent toward the belt surface during traveling to form a film. Then, after the casting band 17 circulates approximately once, the film is peeled off by the peeling roll 20,
The peeled film is sent in the roll carrying zone 21 in the direction of arrow B.

Here, in the casting band 17, the mass of the cast polymer solution at the peeling point is less than 320% of the mass of the polymer film when dried, and 200 of the mass when dried.
It is cooled until it exceeds%. If it is 320% or more, peeling is difficult, and if it is 200% or less, the orientation of the molecules constituting the film is not affected regardless of the tension.

The film solidified until the mass falls within the above-mentioned range is peeled off from the casting band 17 so that the film has a width of 1 meter or more than 0.049 Newton and less than 14.7 Newton. Relative speed with the take-off roll 20, the stripping roll 20 and the roll transport zone 21
The relative speed with is adjusted.

The film separated from the casting band 17 and conveyed in the roll conveying zone 21 is dried in the drying zone 22.
After being sent to a roll 23 and wound around a plurality of rolls 23 to be dried, it is cooled to room temperature via a cooling zone 24 and wound by a winder 25.

In the film thus peeled and conveyed, the tension applied is within a suitable range, and the orientation of molecules constituting the film is hardly biased in one direction (for example, the longitudinal direction of the film). . Therefore, since the hardness of the film is hardly unbalanced in the longitudinal direction and the width direction, even if the film is cut into a predetermined size and attached to the polarizing element, the film does not peel off. .

FIG. 2 is a view showing a part of a manufacturing apparatus using a drum as a support in the manufacturing apparatus of the polymer film of this embodiment.

The polymer film manufacturing apparatus shown in FIG.
A casting drum 18 instead of the casting band 17 shown in FIG.
Is used. Since the casting band 17 has a longer cooling time than the casting drum 18, it is possible to accelerate gelation by using a poor solvent having a high boiling point, but there is a limit to increase the production rate. On the other hand, since the casting drum 18 can be positively cooled, there is a difference in that it can accelerate gelation and cooling, thereby increasing the production speed. However, the casting drum 18 is cooled until the volume of the cast polymer solution at the separation point is less than 320% and more than 200% of the polymer film when dried, and the cooled and solidified film is Width of the membrane 1
Over 0.049 Newton per meter, and 14.
Casting band 1 so that tension of 7 Newton or less is applied
The relative speed between 7 and the stripping roll 20, the relative speed between the stripping roll 20 and the roll transport zone 21, and the relative speed between the roll transport zone 21 and the tenter transport zone 26 are adjusted as described with reference to FIG. This is the same as the case of the manufacturing apparatus using the casting band 17.

Further, in the manufacturing apparatus using a drum as a support shown here, the film peeled by the peeling roll 20 is conveyed while being dried in a predetermined roll conveying zone 21 with dry air, and then the film is removed. A tenter transfer zone 26 in which both ends are held by the tenter 26a and dried while being drawn and transferred.
Sent to.

Next, the dope used in this embodiment will be described.

The dope includes cellulose ester, polycarbonate and the like. As the cellulose ester, a lower fatty acid ester of cellulose (eg, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, etc.) is representative. The lower fatty acid means a fatty acid having 6 or less carbon atoms. Cellulose acetate includes cellulose triacetate (TAC) and cellulose diacetate (DA).
C) is included. In the present invention, it is particularly preferable to prepare the dope from the cellulose acylate solution, and the cellulose acylate is more preferably cellulose triacetate.

As a solvent for the dope, a lower aliphatic hydrocarbon chloride or a lower aliphatic alcohol is generally used. Examples of chlorides of lower aliphatic hydrocarbons include methylene chlorite, chloroform and the like. Examples of lower aliphatic alcohols include methanol, ethanol, n-propanol, iso-propanol, 1
-Butanol, t-butanol, 2-methyl-2-butanol, 2-methoxyethanol and 2-butoxyethanol, and the like, but not limited to, alcohols having 1 to 6 carbon atoms. Examples of the other solvent include ketones having substantially no halogenated hydrocarbon such as acetone, for example, ketones having 4 to 12 carbon atoms such as methyl ethyl ketone, diethyl ketone, diisobutyl ketone, cyclohexanone and methylcyclohexanone. However, it is not limited to these. Also,
Esters having 3 to 12 carbon atoms can also be used. Examples include, but are not limited to, ethyl formate, propyl formate, pentyl formate, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, pentyl acetate and 2-ethoxy-ethyl acetate. Furthermore, ethers having 3 to 12 carbon atoms can also be used. For example, diisopropyl ether, dimethoxymethane, dimethoxyethane, 1,4-dioxane, 1,3-
Examples include, but are not limited to, dioxolane, tetrahydrofuran, anisole and phenetole.
Furthermore, cyclic hydrocarbons having 5 to 8 carbon atoms can also be used. Examples include, but are not limited to, cyclopentane, cyclohexane, cycloheptane, cyclooctane, and the like.

Of these, methylene chlorite is particularly preferable as the solvent. Further, other solvent may be mixed with methylene chlorite. However, the mixing ratio of methylene chlorite is preferably 70% by mass or more.
A particularly preferable mixing ratio is 75 to 93% by mass of methylene chlorite and 7 to 25% by mass of the other solvent. The solvent is removed in the film forming process of the cellulose ester film, and the residual amount of the solvent is generally less than 5% by mass. However, the residual amount is preferably less than 1% by mass, more preferably less than 0.5% by mass.

In consideration of the effects on the human body and environment, it is preferable to use a solvent that does not use methylene chlorite. In this case, it is preferable to use a mixed solvent of methyl acetate, the above-mentioned ketones and alcohols. In particular, when cellulose acylate is selected as the polymer for preparing the dope, it is preferable to use methyl acetate as the main solvent in terms of solubility. Also,
Methyl acetate may be mixed with a solvent such as a ketone or an alcohol for the purpose of improving the solubility of the polymer. In this case, the component ratio of each solvent is 20% for methyl acetate.
˜90% by mass, ketones 0 to 60% by mass, and alcohols 5 to 30% by mass.

As additives, plasticizers, ultraviolet absorbers, deterioration inhibitors, etc. may be added to the dope.

Next, the preparation of a polymer solution using cellulose triacetate which is the main raw material of the polymer film of this embodiment will be described.

First, a swelling step of mixing the cellulose triacetate particles with a solvent and swelling the cellulose triacetate particles with the solvent is performed. The temperature of the swelling step is preferably −10 ° C. to 55 ° C., and usually performed at room temperature. The ratio of cellulose triacetate and solvent is determined according to the concentration of the finally obtained solution.
Generally, the amount of cellulose triacetate in the mixture is
It is preferably 5 to 30% by mass, and 8 to 20% by mass.
Is more preferable, and 10 to 15 mass% is the most preferable. The mixture of the solvent and cellulose triacetate is preferably stirred until the cellulose triacetate is sufficiently swollen. Usually, the mixing and stirring time is 1 to 180 minutes. In some cases, swelling to dissolution may proceed only by mixing and stirring, and in this case, the step of dissolving cellulose triacetate in a solvent, such as the heating step described later, does not necessarily have to be performed. Further, in the swelling step, a component other than the solvent and cellulose triacetate, for example, a plasticizer, a deterioration inhibitor, a dye or an ultraviolet absorber may be added.

Next, a heating step of heating the dope to 130 ° C. or higher is performed. The heating temperature is 130 ° C or higher, preferably 160 ° C or higher, and most preferably 180 ° C or higher. However, when the temperature exceeds 250 ° C., the cellulose triacetate in the dope is decomposed, which deteriorates the quality of the film, which is not preferable. In this case, the heating rate is preferably 1 ° C./min or more, more preferably 2 ° C./min or more, further preferably 4 ° C./min or more, and 8 ° C./min or more. Is most preferred. The higher the heating rate, the more preferable, but 10,000
° C / sec is the theoretical upper limit, 1000 ° C / sec is the technical upper limit, and 100 ° C / sec is the practical upper limit. The heating rate is a value obtained by dividing the difference between the temperature at the start of heating and the final heating temperature by the time from the start of heating until the final heating temperature is reached. The heating method may be any method such as an autoclave system, a shell-and-tube heat exchanger, a screw extruder, a static mixer and the like.

The heating time is preferably 20 seconds or more and 4 hours or less. If the heating time is less than 20 seconds, the insoluble matter remains in the dope that is heated and melted, and a high quality film cannot be manufactured. Further, even when the insoluble matter is removed by the filter, the life of the filter is extremely shortened. The beginning of the heating time shall be measured when the target temperature is reached, and the ending is when the cooling is started from the target temperature. The cooling of the device may be natural cooling or forced cooling.

Here, in the heating step, it is preferable to heat the dope to a temperature equal to or higher than the boiling point of the solvent at atmospheric pressure under a pressure adjusted so that the solution does not boil. Pressurization prevents foaming of the dope,
A uniform dope can be obtained. At this time, the pressure to be applied is determined by the relationship between the heating temperature and the boiling point of the solvent.

Further, when the dope is cooled before the heating step, the solvent is quickly and effectively permeated into the cellulose triacetate and the dissolution is promoted, whereby a film having good optical properties can be obtained. For a system that cannot be easily dissolved at room temperature and a system in which the amount of insoluble matter is large, a good dope can be prepared by using cooling or heating or a combination of both. Effective temperature condition is -100 ℃
It is 10 ° C. In the cooling process, it is desirable to use a closed container in order to avoid mixing of water due to dew condensation during cooling. Further, if the pressure is reduced during cooling, the cooling time can be shortened. In order to carry out depressurization, it is desirable to use a pressure resistant container. It is also effective to carry out this cooling step after the heating step. When the dissolution is insufficient, the cooling step to the heating step may be repeated, and whether the dissolution is sufficient can be judged by visually observing the appearance of the solution.

When two or more kinds of dopes are prepared and co-cast in the solution abdominal method of the present embodiment, for example, when a film having a three-layer structure is simultaneously formed, cellulose triacetate is used as the inner layer dope. In the dope for the outer layer formed on the front surface and the back surface of the inner layer, by containing a relatively small amount of cellulose triacetate, a cellulose triacetate polymer excellent in flatness, transparency or molding processability is contained. The film can be formed, but the adjustment of the dope is not limited to this.

Next, the use of the obtained cellulose ester film will be described.

The obtained cellulose ester film is
It can be used as a polarizing plate protective film. A polarizing plate can be formed by sticking this polarizing plate protective film on both sides of a polarizing element formed of polyvinyl alcohol or the like.

[0050]

EXAMPLES Next, examples of the solution casting method of the present embodiment will be described.

First, a polymer solution cast from a casting die was mixed into the following two types of formulations.

First polymer liquid Second polymer liquid TAC 200 parts by mass 200 parts by mass Plasticizer 24 parts by mass 24 parts by mass Methylene chloride 620 parts by mass 650 parts by mass Methanol 154 parts by mass 112 parts by mass Butanol 0 12 parts by mass UV agent 2 parts by mass 2 parts by mass Here, the plasticizer includes triphenyl phosphate (T
PP) + biphenyl diphenyl phosphate (BD
P) and UV agents include 2 (2'-hydroxy-3 ', 5'
-Di-t-amylphenyl) -5-benzotriazole, 2 (2'-hydroxy-3 ', 5'-t-butylphenyl) -5-chlorobenzotriazole was used. A casting drum was used as the support, and the temperature of the support was set to -5 ° C.

Next, a polymer film was manufactured using the above-described polymer film manufacturing apparatus using the first polymer liquid, and the processing suitability of the polarizing plate was evaluated. The results are shown in the following Examples and Comparative Examples. Is the street. Regarding the workability of the polarizing plate, the polarizing plate was formed by sticking the protective film on both sides of the polarizer, and the polarizing plate was punched out with a circular blade of φ60 mm, resulting in peeling of 2 mm or more from the cut end. The samples were judged to be defective, and the number of defects in 15 samples was evaluated in each Example.

[Example 1] Residual volatile content (%) at the time of peeling on the basis of drying 320 Tension applied to the film (N / film width 1 m) 14.7 Peeling stability Peeling was possible, but peeling at the edges There is remaining stability of conveyance until reaching the tenter after peeling Stable suitability for processing to a polarizing plate 0/15 [Example 2] Residual volatile content (%) at the time of peeling based on dry time Tension applied to 260 film (N / Film width 1 m) 14.7 Peeling stability Stable conveying stability after peeling until reaching the tenter Stable suitability for polarizing plate 2/15 [Example 3] Residual volatilization during peeling based on dry time Min (%) 200 Tension applied to film (N / film width 1 m) 14.7 Peeling stability Stable conveyance stability until peeling to the tenter Stable suitability for polarizing plate 5/15 [Example 4] ] Residual volatiles during peeling (%) based on dry time 260 Tension applied to film (N / film width 1 m) 0.98 Peeling stability Stable transport stability until peeling tenter Stable Polarizing plate Suitability for processing 0/15 [Example 5] Residual volatile content (%) during peeling based on dry time 320 Tension applied to film (N / film width 1 m) 0.049 Peeling stability Peeling is possible, Unpeeled residue on the edge, just before floating from the peeling roll. Stable transport from peeling to the tenter. Film slackness Flapping at the edge Applicability to polarizing plate 0/15 [Implementation] Example 6] Residual volatile content (%) at the time of peeling based on dry time Tension applied to 260 film (N / film width 1 m) 0.049 Peeling stability Peelable, until tenter after peeling Stability of transport in the film Flapping of the film is observed at the edge. Applicability to polarizing plate 0/15 [Comparative example 1] Residual volatiles (%) during peeling based on dry time 330 film Tension applied (N / film width 1 m) -Peeling stability Difficulty peeling Stability of conveyance until peeling to tenter-Applicability to polarizing plate- [Comparative example 2] Residue at peeling based on dry time Volatile content (%) 180 Tension applied to the film (N / film width 1 m) 14.7 Peeling stability Stable conveyance stability until reaching the tenter after peeling Stable processability to polarizing plate 9/15 or more The result of producing the polymer film using the polymer film producing apparatus described above using the polymer solution of No. 2 is also the same as the above-mentioned Example and Comparative Example of the polymer film produced using the first polymer solution. The conclusion It was obtained.

Based on the results of the above Examples and Comparative Examples, the residual volatile content (%) when peeling the film from the support should be less than 320, and the tension (N It has been found that a film whose film width is 1 m) exceeds 0.049 and is less than 14.7 can be produced without peeling when processed into a polarizing plate. Further, a polarizing plate using this film as a protective film also had good optical characteristics.

[0056]

As described above, according to the polymer film peeled and conveyed by the solution film-forming method of the present invention, the applied tension is suitable, and the longitudinal direction and width of the polymer film are suitable. Since there is no imbalance in elasticity with respect to the direction, peeling of the film hardly occurs when the film is attached to a polarizer, and a polarizing plate having good optical characteristics can be obtained.

[Brief description of drawings]

FIG. 1 is a view showing a manufacturing apparatus using a casting band as a support in a manufacturing apparatus of a polymer film used in the present embodiment.

FIG. 2 is a diagram showing a part of a manufacturing apparatus using a drum as a support in the manufacturing apparatus for a polymer film of the present embodiment.

[Explanation of symbols]

1 storage tank 2 stirring blades 4 Liquid feed pump 5 static mixer 6 filters 11 First Dope Supply Device 12 Second dope supply device 13 Third Dope Supply Device 14 Poor solvent supply device 15 Casting die 16 rotating drum 17 casting band 17a Casting point 17b Stripping point 18 Casting drum 20 stripping drum 21 roll transport zone 22 Drying zone 23 rolls 24 cooling zones 25 winder 26 Tenter Transport Zone 26a tenter

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C08L 1:10 C08L 1:10 F term (reference) 2H049 BA02 BB33 BC09 BC22 4F071 AA09 AF58 AG34 AH19 BA02 BB02 BC01 4F205 AA01 AC05 AG01 AH73 AR04 GA07 GC06 GE30 GF03 GF24 GN30

Claims (5)

[Claims] 1. A pressurized polymer solution is discharged from a casting die to be cast on a support, and the polymer solution on the support is less than 320% of the mass when dried and dried. To solidify until it exceeds 200% of its mass
A polymer film, characterized in that a polymer film is obtained by applying a tension of more than 0.049 newtons per meter width of the film and less than 14.7 newtons to the film to separate and dry the film. Membrane method. 2. The solution film-forming method according to claim 1, wherein the polymer solution is a cellulose ester solution. 3. A cellulose ester film produced by using the solution film-forming method according to claim 2. 4. A protective film for polarizing plate, comprising the cellulose ester film according to claim 3. 5. A polarizing plate comprising the protective film according to claim 4.