JP4925856B2 - Casting apparatus, solution casting equipment, and solution casting method - Google Patents

Description

The present invention relates to a casting apparatus, a solution casting apparatus, and a solution casting method .

  Polymer films (hereinafter referred to as films) are widely used as optical functional films because of their features such as excellent light transmittance, flexibility, and reduction in weight of thin films. Among them, cellulose ester film using cellulose acylate has high toughness, low optical anisotropy, low retardation, and is inexpensive, so that it is a liquid crystal display (LCD). It is widely used as a protective film for a polarizing plate as a member, an optical compensation film, an antireflection film, a viewing angle widening film, and the like.

  As a method for producing these optical functional films, a solution casting method is used. The solution casting method can produce a film having excellent physical properties such as optical properties as compared with other production methods such as a melt casting method. In the solution casting method, a dope is prepared by dissolving a polymer in a solvent (mainly an organic solvent), and then the dope is cast on a support that is continuously run over a plurality of rotating drums. A film is produced by peeling off and drying. In the solution casting method, stainless steel is used as the support forming material that comes into contact with the dope and is rubbed against the rotating drum during traveling. Among them, austenitic materials with excellent workability and excellent corrosion resistance and wear resistance are used. Stainless steel is generally used.

  However, when solution casting is performed for a long time, the dope stays at the discharge port (lip) of the casting die, or the dope wets and spreads from the discharge port to the periphery thereof. When these dopes are dried as they are, they become burrs and adhere to the vicinity of the discharge port of the casting die. This river burr causes streaks to the casting bead formed from the discharge port of the casting die to the support, and streaks also remain on the casting film. If the film production is continued in this state, streaky defects extending in the longitudinal direction are confirmed in the film, which causes a problem as uneven thickness of the film in the width direction.

In order to eliminate streak-like thickness unevenness, in addition to eliminating scratches on the casting die itself, a method for suppressing stagnation of the dope at the lip of the casting die, and a method for suppressing the occurrence of burrs at the tip of the casting die. Various methods have been proposed. For example, Patent Document 1 defines the dope viscosity, the temperature of hot air sent immediately after casting, the moving speed of the support, and the shape of the lip tip of the casting die so that the dope stays on the lip of the casting die. We propose a method to prevent this. Patent Document 2 proposes a method for suppressing the occurrence of burrs at the tip of the casting die by setting the tensile stress of the casting bead within a predetermined range. Patent Document 3 discloses a solution casting method in which the hardness Hv at the tip of the casting die is set to 400 or more, so that the tip of the casting die is prevented from being damaged at the time of maintenance work or the like, and streaks are eliminated. Patent Document 4 discloses a solution casting method that suppresses the occurrence of burrs at the lip tip of the casting die by reducing the force required for peeling between the dope and the lip tip of the casting die to 40 g / cm or less. Has been proposed.
Japanese Patent Laid-Open No. 8-25381 JP 2001-71338 A JP 2002-254453 A JP 2004-66613 A

  However, even when the above measures are taken, if the solution casting method is performed for about 2000 hours, for example, streak-like deformation occurs on the support surface of the support that supports the casting membrane. Thickness irregularities frequently occurred. Film thickness unevenness failure causes variations in optical characteristics and decreases the product value as an optical functional film, and therefore, the suppression of the occurrence of streak-like deformation on the support surface in the solution casting method is a major issue. It was one.

In view of the above problems, an object of the present invention is to provide a casting apparatus, a solution casting apparatus, and a solution casting method that suppress the occurrence of a film thickness unevenness failure.

The casting apparatus of the present invention supports a dope containing a polymer as a raw material and a solvent, an annular casting band made of austenitic stainless steel, and the traveling means has an inner circumferential surface of the casting band on the circumferential surface. A rotating drum that supports and rotates the casting band by rotation; and a casting die that flows the dope into the casting band. The austenitic stainless steel has a Mn content of 1.35% by weight or more. 2% by weight or less, Ni content is 11% by weight or more and 14% by weight or less, or Cr content is 16% by weight or more and 17% by weight or less, and Mo content is 2% by weight or more. It consists of SUS316 or SUS316L which is 2.07 weight% or less.

A control unit that adjusts the distance between the plurality of rotating drums is provided, and the tension applied to the casting band by the adjustment is 30 N / mm. ² 100 N / mm or more ² The following is preferable. Rotating drum temperature adjusting means for adjusting the temperature of the plurality of rotating drums is provided, and the plurality of rotating drums are a first rotating drum and a second rotating drum disposed below the casting die. Preferably, the rotating drum temperature adjusting means adjusts the temperature of the first and second rotating drums so that the first rotating drum has a lower temperature than the second rotating drum. The speed fluctuation of the casting band is preferably 5% or less. The rotating drum is preferably made of stainless steel. It is preferable that the width of the casting band is 1500 mm or more and 3000 mm or less.

The solution casting apparatus of the present invention includes the above casting apparatus, stripping means formed on the casting band, for stripping the casting film made of the dope to form a wet film, and drying the wet film. And a drying means.

The solution casting method of the present invention is a plurality of rotating drums that support an austenitic stainless steel casting band formed in an annular shape, and the casting band is caused to travel by rotation of the rotating drum to be a raw material. A dope containing a polymer and a solvent is flowed out to the casting band, a casting film is formed on the casting band, the casting film is peeled off to form a wet film, the wet film is dried, In the austenitic stainless steel, the Mn content is 1.35 wt% or more and 2 wt% or less, the Ni content is 11 wt% or more and 14 wt% or less, or the Cr content is 16 wt% or more. It is characterized by comprising SUS316 or SUS316L having a Mo content of 17 wt% or less and a Mo content of 2 wt% or more and 2.07 wt% or less. The tension applied to the casting band is 30 N / mm by adjusting the distance between the plurality of rotating drums. ² 100 N / mm or more ² The following is preferable. The plurality of rotating drums are preferably a first rotating drum disposed below the casting die and a second rotating drum having a higher temperature than the first rotating drum. The speed fluctuation of the casting band is preferably 5% or less. The rotating drum is preferably made of stainless steel. It is preferable to use the casting band having a width of 1500 mm or more and 3000 mm or less.

  According to the present invention, even when the solution casting method is performed for a long time, it is possible to suppress the occurrence of streak-like deformation on the support surface. A film having a uniform thickness and no unevenness can be produced with high production efficiency.

  Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the embodiments given here.

[material]
As the cellulose acylate, it is preferable to use a cellulose acylate in which the degree of substitution of the hydroxyl group of cellulose satisfies all of the following formulas (I) to (III). Hereinafter, cellulose acylate satisfying the following formula is referred to as TAC.
(I) 2.5 ≦ A + B ≦ 3.0
(II) 0 ≦ A ≦ 3.0
(III) 0 ≦ B ≦ 2.9
In the formula, A and B represent the substitution degree of the acyl group to the hydrogen atom of the hydroxyl group of cellulose, A is the substitution degree of the acetyl group to the hydrogen atom of the hydroxyl group of cellulose, and B is the carbon to the hydrogen atom of the hydroxyl group of cellulose. It is a substitution degree of an acyl group having 3 to 22 atoms. In addition, it is preferable to use particles having 90% by weight or more of TAC of 0.1 mm to 4 mm. The polymer used in the present invention is not limited to TAC.

  Glucose units having β-1,4 bonds constituting cellulose have free hydroxyl groups at the 2nd, 3rd and 6th positions. Cellulose acylate is a polymer obtained by esterifying some or all of these hydroxyl groups with an acyl group having 2 or more carbon atoms. The degree of acyl substitution means the ratio in which the hydroxyl group of cellulose is esterified at each of the 2-position, 3-position and 6-position (100% esterification has a substitution degree of 1).

  The total acyl substitution degree, that is, DS2 + DS3 + DS6 is preferably 2.00 to 3.00, more preferably 2.22 to 2.90, and particularly preferably 2.40 to 2.88. Further, DS6 / (DS2 + DS3 + DS6) is preferably 0.28 or more, more preferably 0.30 or more, and particularly preferably 0.31 to 0.34. Here, DS2 is the degree of substitution of the hydroxyl group at the 2-position of the glucose unit with an acyl group (hereinafter also referred to as “degree of acyl substitution at the 2-position”), and DS3 is the degree of substitution of the hydroxyl group at the 3-position with an acyl group (hereinafter, referred to as “acyl group”). DS6 is the substitution degree of the hydroxyl group at the 6-position with an acyl group (hereinafter also referred to as “acyl substitution degree at the 6-position”).

  Only one type of acyl group may be used in the cellulose acylate of the present invention, or two or more types of acyl groups may be used. When two or more kinds of acyl groups are used, it is preferable that one of them is an acetyl group. DSA + DSB, where DSA is the sum of the substitution degrees of the hydroxyl groups at the 2nd, 3rd and 6th positions with an acetyl group, and DSB is the sum of the substitution degrees of the 2nd, 3rd and 6th hydroxyl groups with an acyl group other than the acetyl group The value of is more preferably 2.2 to 2.90, and particularly preferably 2.40 to 2.88. The DSB is preferably 0.30 or more, particularly preferably 0.7 or more. Further, 20% or more of DSB is a 6-position hydroxyl group substituent, more preferably 25% or more is a 6-position hydroxyl group substituent, and particularly 33% or more is a 6-position hydroxyl group substituent. preferable. Furthermore, it is preferable to use cellulose acylate having a substitution degree of 6-position of cellulose acylate of 0.75 or more, more preferably 0.80 or more, and particularly preferably 0.85 or more. With these cellulose acylates, a solution having a preferable solubility (dope) can be produced. In particular, in a non-chlorine organic solvent, a good solution can be produced. Furthermore, a solution having a low viscosity and good filterability can be produced.

  Cellulose acylate may be obtained from either linter or pulp, but is preferably obtained from linter.

  The acyl group having 2 or more carbon atoms of the cellulose acylate of the present invention may be an aliphatic group or an aryl group and is not particularly limited. These are, for example, cellulose alkylcarbonyl esters, alkenylcarbonyl esters, aromatic carbonyl esters, aromatic alkylcarbonyl esters, and the like, each of which may further have a substituted group. Preferred examples of these include propionyl group, butanoyl group, keptanoyl group, hexanoyl group, octanoyl group, decanoyl group, dodecanoyl group, tridecanoyl group, tetradecanoyl group, hexadecanoyl group, octadecanoyl group, iso-butanoyl group , T-butanoyl group, cyclohexanecarbonyl group, oleoyl group, benzoyl group, naphthylcarbonyl group, cinnamoyl group and the like. Among these, a propionyl group, a butanoyl group, a dodecanoyl group, an octadecanoyl group, a t-butanoyl group, an oleoyl group, a benzoyl group, a naphthylcarbonyl group, a cinnamoyl group, and the like are more preferable, and a propionyl group and a butanoyl group are particularly preferable. is there.

  Solvents for preparing the dope include aromatic hydrocarbons (eg, benzene, toluene, etc.), halogenated hydrocarbons (eg, dichloromethane, chlorobenzene, etc.), alcohols (eg, methanol, ethanol, n-propanol, n-butanol, Diethylene glycol, etc.), ketones (eg, acetone, methyl ethyl ketone, etc.), esters (eg, methyl acetate, ethyl acetate, propyl acetate, etc.) and ethers (eg, tetrahydrofuran, methyl cellosolve, etc.). In the present invention, the dope means a polymer solution or dispersion obtained by dissolving or dispersing a polymer in a solvent.

  A halogenated hydrocarbon having 1 to 7 carbon atoms is preferably used, and dichloromethane is most preferably used. From the viewpoint of physical properties such as solubility of TAC, peelability of cast film from the support, mechanical strength of the film, and optical properties of the film, in addition to dichloromethane, one or more alcohols having 1 to 5 carbon atoms are used. It is preferable to mix several types. The content of the alcohol is preferably 2% by weight to 25% by weight and more preferably 5% by weight to 20% by weight with respect to the whole solvent. Specific examples of the alcohol include methanol, ethanol, n-propanol, isopropanol, n-butanol and the like, but methanol, ethanol, n-butanol or a mixture thereof is preferably used.

  Recently, a solvent composition not using dichloromethane has been proposed in order to minimize the influence on the environment. For this purpose, ethers having 4 to 12 carbon atoms, ketones having 3 to 12 carbon atoms, and esters having 3 to 12 carbon atoms are preferable, and methyl acetate is particularly preferably used. Moreover, these are used in mixture as appropriate. These ethers, ketones and esters may have a cyclic structure. A compound having two or more functional groups of ether, ketone and ester (that is, —O—, —CO— and —COO—) can also be used as a solvent. The solvent may have another functional group such as an alcoholic hydroxyl group. In the case of a solvent having two or more types of functional groups, the number of carbon atoms may be within the specified range of the compound having any functional group.

(Additive)
Various additives (for example, peeling accelerators, plasticizers, UV inhibitors, deterioration inhibitors, fine particles, optical property modifiers, etc.) according to applications are added to the cellulose acylate solution of the present invention in each preparation step. be able to. Further, the addition may be performed at any time in the dope preparation process, but may be performed by adding an additive to the final preparation process of the dope preparation process.

(Plasticizer)
The plasticizer is preferably a solid having a boiling point of 200 ° C. or higher and a liquid at 25 ° C. or a melting point of 25 to 250 ° C., a boiling point of 250 ° C. or higher, and a liquid at 25 ° C. More preferably, it is a solid having a melting point of 25 to 200 ° C. When the plasticizer is a liquid, the purification is usually carried out by distillation under reduced pressure, but higher vacuum is preferred, and the degree of vacuum is preferably 100 Pa or less, for example. It is also particularly preferable to purify using a molecular distillation apparatus or the like. When the plasticizer is a solid, it is generally carried out by recrystallization using a solvent, filtering, washing and drying.

  As the plasticizer used in the present invention, a phosphate ester or a carboxylic acid ester is preferably used. Phosphate esters include triphenyl phosphate (TPP) and tricresyl phosphate (TCP), cresyl diphenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate, tributyl phosphate. Representative examples of the carboxylic acid ester include phthalic acid esters and citric acid esters. Examples of the phthalic acid ester include dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), dioctyl phthalate (DOP), diphenyl phthalate (DPP), and diethylhexyl phthalate (DEHP). Citrate esters include O-acetyl triethyl citrate (OACTE) and O-acetyl tributyl citrate (OACTB), acetyl triethyl citrate, and acetyl tributyl citrate. Among these, a particularly preferable plasticizer is TPP (melting point: about 50 ° C.) or a liquid at 25 ° C., and a boiling point is 250 ° C. or more.

  Examples of other carboxylic acid esters include butyl oleate, methylacetyl ricinoleate, dibutyl sebacate, and various trimellitic acid esters. Examples of glycolic acid esters include triacetin, tributyrin, butyl phthalyl butyl glycolate, ethyl phthalyl ethyl glycolate, methyl phthalyl ethyl glycolate, butyl phthalyl butyl glycolate, methyl phthalyl methyl glycolate, propyl phthalyl Examples include propyl glycolate, butyl phthalyl butyl glycolate, and octyl phthalyl octyl glycolate. Of these, triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, tributyl phosphate, dimethyl phthalate, diethyl phthalate, dibutyl phthalate, dioctyl phthalate, diethyl hexyl phthalate, triacetin, and ethyl phthalyl ethyl glycolate are preferable. Triphenyl phosphate, diethyl phthalate, and ethyl phthalyl ethyl glycolate are particularly preferable. These plasticizers may be used alone or in combination of two or more. The addition amount of the plasticizer is preferably 2 to 30% by mass, particularly 5 to 20% by mass with respect to the cellulose acylate.

  The ultraviolet absorber preferably used for the cellulose acylate film of the present invention will be described. The cellulose acylate film of the present invention is used for a polarizing plate or a liquid crystal display member because of its high dimensional stability, but an ultraviolet absorber is preferably used from the viewpoint of preventing deterioration of the polarizing plate or the liquid crystal. As the ultraviolet absorber, those excellent in the ability to absorb ultraviolet rays having a wavelength of 370 nm or less and having little absorption of visible light having a wavelength of 400 nm or more are preferably used from the viewpoint of good liquid crystal display properties. Specific examples of the ultraviolet absorber preferably used in the present invention include oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex compounds, and the like.

  Although the specific example as a benzotriazole type ultraviolet absorber is listed below, this invention is not limited to these. 2- (2'-hydroxy-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-3 ', 5'-di-tert-butylphenyl) benzotriazole, 2- (2'-hydroxy-3) '-Tert-butyl-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-3', 5'-di-tert-butylphenyl) -5-chlorobenzotriazole, 2- (2'-hydroxy -3 '-(3 ", 4", 5 ", 6" -tetrahydrophthalimidomethyl) -5'-methylphenyl) benzotriazole, 2,2-methylenebis (4- (1,1,3,3-tetramethyl) Butyl) -6- (2H-benzotriazol-2-yl) phenol), 2- (2'-hydroxy-3'-tert-butyl-5'-methylphenyl)- -Chlorobenzotriazole, 2,4-dihydroxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxy-5-sulfobenzophenone, bis (2-methoxy-4-hydroxy-5-benzoyl) Phenylmethane), (2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-tert-butylanilino) -1,3,5-triazine, 2 (2'-hydroxy- 3 ′, 5′-di-tert-butylphenyl) -5-chlorobenzotriazole, (2 (2′-hydroxy-3 ′, 5′-di-tert-amylphenyl) -5-chlorobenzotriazole, 2, 6-di-tert-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di-tert- Til-4-hydroxyphenyl) propionate], triethylene glycol-bis [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) propionate], 1,6-hexanediol-bis [3- (3 , 5-di-tert-butyl-4-hydroxyphenyl) propionate], 2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-tert-butylanilino) -1,3 , 5-triazine, 2,2-thio-diethylenebis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], octadecyl-3- (3,5-di-tert-butyl- 4-hydroxyphenyl) propionate, N, N′-hexamethylenebis (3,5-di-tert-butyl-4-hydroxy-) Hydrocinnamide), 1,3,5-trimethyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl) benzene, tris- (3,5-di-tert-butyl-4) -Hydroxybenzyl) -isocyanurate and the like. In particular, (2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-tert-butylanilino) -1,3,5-triazine, 2 (2′-hydroxy-3 ′, 5'-di-tert-butylphenyl) -5-chlorobenzotriazole, (2 (2'-hydroxy-3 ', 5'-di-tert-amylphenyl) -5-chlorobenzotriazole, 2,6-di -Tert-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis [3- (3-tert-butyl -5-methyl-4-hydroxyphenyl) propionate], for example, N, N'-bis [3- (3,5-di-tert-butyl-4 Hydrazine-based metal deactivators such as (hydroxyphenyl) propionyl] hydrazine and phosphorus-based processing stabilizers such as tris (2,4-di-tert-butylphenyl) phosphite may be used in combination. The amount is preferably 1 ppm to 1.0%, more preferably 10 to 1000 ppm in terms of mass ratio with respect to cellulose acylate.

  In addition, other light stabilizers listed in the catalog of “Adeka Stub”, an outline of additives for Asahi Denka Plastics, can be used. Light stabilizers and UV absorbers from Ciba Special Chemicals' Tinuvin Product Guide can also be used. SESORB (registered trademark), SEENOX (registered trademark), SEETEC (registered trademark), etc. can also be used in the catalog of SHIPROKASEI KAISYA. Jouhoku Chemical's UV absorbers and antioxidants can also be used. Kyosho's VIOSORB (registered trademark) and Yoshitomi Pharmaceutical's UV absorbers can also be used.

(Fine particles)
By adding fine particles to the dope, when the produced cellulose acylate film is handled, it is possible to prevent damage and deterioration of transportability. They are called matting agents, anti-blocking agents or anti-scratching agents and have been used conventionally. They are not particularly limited as long as they are materials exhibiting the above-mentioned functions, but preferred specific examples of these matting agents include inorganic compounds such as compounds containing silicon, silicon dioxide, titanium oxide, zinc oxide, aluminum oxide, and oxidation. Barium, zirconium oxide, strongtium oxide, antimony oxide, tin oxide, tin / antimony oxide, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate and calcium phosphate More preferred are inorganic compounds containing silicon and zirconium oxide, but since the turbidity of the cellulose acylate film can be reduced, silicon dioxide is particularly preferably used. As the silicon dioxide fine particles, for example, commercially available products having a trade name such as Aerosil R972, R974, R812, 200, 300, R202, OX50, TT600 (manufactured by Nippon Aerosil Co., Ltd.) can be used. As the fine particles of zirconium oxide, for example, those commercially available under trade names such as Aerosil R976 and R811 (manufactured by Nippon Aerosil Co., Ltd.) can be used.

  As the organic compound, for example, polymers such as silicone resin, fluorine resin and acrylic resin are preferable, and among them, silicone resin is preferably used. Among the silicone resins, those having a three-dimensional network structure are particularly preferable. For example, Tospearl 103, Tospearl 105, Tospearl 108, Tospearl 120, Tospearl 145, Tospearl 3120 and Tospearl 240 (manufactured by Toshiba Silicone Co., Ltd.) A commercial product having a trade name can be used.

  The details of cellulose acylate are described in paragraphs [0141] to [0195] of JP-A-2005-104148. These descriptions are also applicable to the present invention. Also, additives such as solvents and plasticizers, deterioration inhibitors, ultraviolet absorbers, optical anisotropy control agents, retardation control agents, dyes, matting agents, release agents, and the like, [0196] of JP-A-2005-104148 It is described in detail from paragraph to [0516] paragraph.

(Dope manufacturing method)
FIG. 1 shows a dope production line 10. In the dope production line 10, a solvent tank 11 for storing a solvent, a dissolution tank 13 for mixing the solvent and TAC, a hopper 14 for supplying TAC, and an additive liquid are stored. Additive tank 15, heating device 18 for heating the swelling liquid described later, temperature controller 19 for adjusting the temperature of the prepared dope, filtration device 20 for filtering the dope, and flash device for concentrating the dope 21 is provided with a filtration device 22 for filtering the concentrated dope. In addition, a recovery device 23 for recovering the solvent and a regeneration device 24 for regenerating the recovered solvent are provided. A pump 25 is provided downstream of the dissolution tank 13, and a pump 26 is provided downstream of the flash device 21. The pump 25 sends the swelling liquid 44 in the dissolution tank 13 to the heating device 18, and the pump 26 sends it to the filtration device 22 after concentration in the flash device 21. A stock tank 30 is connected to the downstream side of the filtration devices 20 and 22. The dope production line 10 is connected to a film film production line 32 through a stock tank 30.

  First, a valve 35 provided in a pipe connecting the solvent tank 11 and the dissolution tank 13 is opened, and the solvent is sent from the solvent tank 11 to the dissolution tank 13. Next, the TAC contained in the hopper 14 is fed into the dissolution tank 13 while being measured. A valve 36 provided in a pipe connecting the additive tank 15 and the dissolution tank 13 is opened / closed to feed a necessary amount of the additive solution from the additive tank 15 to the dissolution tank 13. In addition to the method of sending the additive as a solution, for example, when the additive is liquid at room temperature, it is also possible to send the additive into the dissolution tank 13 in the liquid state. In addition, when the additive is solid, it can be fed into the dissolution tank 13 using a hopper. When a plurality of types of additives are added, a solution in which a plurality of types of additives are dissolved can be placed in the additive tank 15. Alternatively, a solution in which an additive is dissolved can be put in each of a plurality of additive tanks and sent to the dissolution tank 13 through independent pipes.

  In the above description, the order of putting into the dissolution tank 13 is the solvent (used in the meaning including the case of the mixed solvent), TAC, and additive, but it is not limited to this order. It is also possible to send a preferable amount of the solvent after sending the TAC to the dissolution tank 13 while measuring it. Further, it is not always necessary to add the additive to the dissolution tank 13 in advance, and it can be mixed with a mixture of TAC and a solvent (hereinafter, these mixtures may also be referred to as a dope) in a later step.

  The dissolution tank 13 is provided with a jacket 37 that wraps the outer surface thereof, and a first stirring blade 39 that is rotated by a motor 38. Furthermore, it is preferable that a second stirring blade 41 that is rotated by a motor 40 is attached to the dissolution tank 13. The first stirring blade 39 is preferably an anchor blade, and the second stirring blade 41 is preferably a dissolver type. It is preferable to flow the heat transfer medium through the jacket 37 and adjust the temperature in the dissolution tank 13 in the range of −10 ° C. to 55 ° C. By appropriately selecting and rotating the first stirring blade 39 and the second stirring blade 41, the swelling liquid 44 in which the TAC is swollen in the solvent can be obtained.

  The swelling liquid 44 is sent to the heating device 18 by the pump 25. The heating device 18 preferably uses a jacketed pipe, and preferably has a configuration capable of pressurizing the swelling liquid 44. The dope is obtained by dissolving TAC or the like in a solvent under a condition where the swelling liquid 44 is heated or heated under pressure. In this case, the temperature of the swelling liquid 44 is preferably 0 ° C. or higher and 97 ° C. or lower. TAC can be sufficiently dissolved in a solvent by appropriately selecting the heating dissolution method and the cooling dissolution method. After the temperature of the dope is set to about room temperature by the temperature controller 19, the dope is filtered by the filtering device 20 to remove impurities in the dope. The average pore diameter of the filtration filter of the filtration device 20 is preferably 100 μm or less. The filtration flow rate is preferably 50 L / hour or more. The dope after filtration is put into the stock tank 30 through the valve 46.

  The dope can be used as a raw material dope described later. However, the method of dissolving TAC after preparing the swelling liquid 44 takes time as the concentration of TAC is increased, and may cause a problem in terms of cost. In that case, it is preferable to perform a concentration step of preparing a dope having a target concentration after preparing a dope having a concentration lower than the target TAC concentration. The dope filtered by the filtering device 20 is sent to the flash device 21 through the valve 46. A part of the solvent in the dope is evaporated in the flash device 21. The evaporated solvent is made liquid by a condenser (not shown), and then recovered by the recovery device 23. It is advantageous from the viewpoint of cost that the solvent is regenerated and reused as a solvent for dope preparation by the regenerator 24.

  The concentrated dope is extracted from the flash device 21 using the pump 26. Furthermore, it is preferable to remove bubbles in the dope. Defoaming may be performed by any known method, for example, an ultrasonic irradiation method. Thereafter, the liquid is sent to the filtration device 22 to remove foreign matters. At this time, the temperature of the dope is preferably 0 ° C. or higher and 200 ° C. or lower. Then, the dope is put into the stock tank 30.

  By these methods, a dope having a TAC concentration of 10 wt% or more and 30 wt% or less can be manufactured. The produced dope (hereinafter referred to as a raw material dope) 48 is stored in the stock tank 30.

Regarding the material, raw material, additive dissolution method, filtration method, defoaming, and addition method in the dope production line 10 described above, paragraphs [0517] to [0616] of JP-A-2005-104148 are detailed. These descriptions are also applicable to the present invention.

(Film manufacturing process) Next, the film manufacturing process 50 of this invention is demonstrated. As shown in FIG. 2, the film production process 50 includes a casting dope preparation process 52 for preparing a casting dope 51 from the raw material dope 48 obtained above, and a casting dope 51 that is cast on a support. A casting process 54 for forming the casting film 53, a peeling process 56 for peeling the casting film 53 having a self-supporting property from the support to form a wet film 55, and drying the wet film 55 to form a film 57. And obtaining a drying step 58. In addition, you may perform the winding process which winds up this film 57 and uses it as a film roll.

(Solution casting equipment)
FIG. 3 shows a film production line 32. A stirring blade 62 that is rotated by a motor 61 is attached to the stock tank 30. The raw material dope 48 is agitated by rotating the agitating blade 62 so that the concentration and the like are always uniform. An intermediate layer dope channel 63, a back layer dope channel 64, and a surface layer dope channel 65 are connected between the stock tank 30 and a feed block described later. Gear pumps 66 to 68 are provided in the respective flow paths 63 to 65.

  In the present embodiment, the intermediate layer dope 71 is used as the dope for forming the base layer (hereinafter referred to as base layer forming dope), and the back layer dope is used as the dope for forming the surface layer (hereinafter referred to as surface layer forming dope). 72, a surface layer dope 73 is used. As the dope for forming the base layer, a dope suitable for the strength and optical function of the optical functional film to be produced is used, and as the dope for forming the surface layer, a dope for improving the planarity and slipperiness of the optical functional film is used. . In addition to the above, it is preferable to use a surface layer forming dope having a lower viscosity than the base layer forming dope. Thereby, it is possible to prevent the generation of streaks or unevenness on the surface of a cast film or wet film described later, thickness unevenness, or the like in the drying step described later.

  The gear pumps 66 to 68 are connected to a control unit (not shown). By this control unit, the gear pumps 66 to 68 feed the raw material dope 48 from the stock tank 30 and also feed the intermediate layer dope 71, the back surface layer dope 72, and the surface layer dope 73 made from the raw material dope 48. Liquid is sent to block 74.

  A stock tank 75 is connected to the intermediate layer dope channel 63 via a pipe. The stock tank 75 stores an intermediate layer additive solution 76. A pump 77 is provided in the pipe connecting the flow path 63 and the stock tank 75. The intermediate layer additive solution 76 in the stock tank 75 is fed to the intermediate layer dope channel 63 by the pump 77 and added to the raw material dope 48 in the intermediate layer dope channel 63. Thereafter, the raw material dope 48 and the intermediate layer additive solution 76 are stirred and mixed by a static mixer (static mixer) 78 provided in the intermediate layer dope flow path 63 to be uniform. Hereinafter, this dope is referred to as an intermediate layer dope 71. In the intermediate layer additive liquid 76, for example, a solution (or dispersion liquid) containing additives such as an ultraviolet absorber, a retardation control agent, and a plasticizer in advance is placed.

  A stock tank 80 is connected to the back surface layer dope channel 64 via a pipe. The stock tank 80 stores a back layer additive solution 81. A pump 82 is provided in a pipe connecting the flow path 64 and the stock tank 80. The back layer additive liquid 81 in the stock tank 80 is fed to the back layer dope channel 64 by the pump 82 and added to the raw material dope 48 in the back layer dope channel 64. Thereafter, the raw material dope 48 and the back surface layer additive solution 81 are agitated and mixed by a static mixer 83 provided in the back surface layer dope channel 64 to be uniform. Hereinafter, this dope is referred to as a back surface layer dope 72. The back surface layer additive solution 81 includes a peeling accelerator (e.g., citrate ester) that facilitates peeling from the casting band as a support, and between the film surfaces when the film is wound into a roll. Additives such as a matting agent (for example, silicon dioxide) and an anti-deterioration agent for suppressing adhesion are contained in advance. In addition, the additive solution 81 for the back layer may contain additives such as an optical property control agent such as a plasticizer, an ultraviolet absorber, and a retardation control agent.

  A stock tank 85 is connected to the surface layer dope channel 65 through a pipe. The stock tank 85 stores the surface layer additive solution 86. A pump 87 is provided in the pipe connecting the flow path 65 and the stock tank 85. The surface layer additive solution 86 in the stock tank 85 is sent to the surface layer dope channel 65 by the pump 87 and added to the raw material dope 48 in the surface layer dope channel 65. Thereafter, the raw material dope 48 and the surface layer additive solution 86 are agitated and mixed by the static mixer 88 provided in the surface layer dope flow path 65 to be uniform. Hereinafter, this dope is referred to as a surface layer dope 73. In the surface layer additive solution 86, additives such as a matting agent (for example, silicon dioxide) and a deterioration preventing agent that suppress adhesion between the film surfaces when the film is wound into a roll shape are contained in advance. Yes. The surface layer additive solution 86 may contain additives such as a peeling accelerator, a plasticizer, an optical property control agent such as an ultraviolet absorber and a retardation control agent.

  Three internal flow paths are provided inside the feed block 74. These internal flow paths are connected to flow paths 63 to 65, respectively. The first internal channel passes through the feed block 74 from the channel 63 and extends to the casting die 91 so as to extend vertically downward. A junction is provided in the middle of the first internal flow path. The second internal flow path and the third internal flow path are formed to extend from the flow paths 64 and 65 to the junction. The casting dope 51 in which the dopes 71 to 73 form a layer is formed at this junction. It is preferable that the feed block 74 includes a temperature controller (for example, a heater, a jacket, or the like) that holds the dopes 71 to 73 at a predetermined temperature.

(Casting room)
The casting die 91 is arranged so as to be connected to the downstream side of the feed block 74. Rotating drums 93 and 94 and a casting band 95 are provided downstream of the casting die 91. Details of the casting band 95 and the rotating drums 93 and 94 will be described later. In addition to the casting die 91, the rotating drums 93 and 94, and the casting band 95, the casting chamber 96 is provided with a temperature control equipment 97 that keeps the temperature in the casting chamber 96 at a predetermined value. It is preferable that the temperature of the casting chamber 96 is maintained at −10 ° C. or more and 57 ° C. or less by the temperature control equipment 97. Further, a condenser (condenser) 98 for condensing and recovering the solvent evaporated in the casting chamber 96 is provided. The condensed organic solvent is recovered and regenerated by the recovery device 99 and then reused as a dope preparation solvent.

The material of the feed block 74 and the casting die 91 is preferably a precipitation hardening type stainless steel. It is preferable to use a material having a thermal expansion coefficient of 2 × 10 ⁻⁵ (° C. ⁻¹ ) or less. Moreover, what has corrosion resistance substantially equivalent to SUS316 in the forced corrosion test in electrolyte aqueous solution can also be used. Further, a material having corrosion resistance that does not cause pitting (opening) at the gas-liquid interface even when immersed in a mixed solution of dichloromethane, methanol, and water for 3 months is used. Furthermore, it is preferable that the casting die 91 is manufactured by grinding a material that has passed one month or more after casting. Thereby, the surface shape of the dope flowing in the casting die 91 is kept constant. It is preferable to use the finishing accuracy of the wetted surfaces of the casting die 91 and the feed block 74 in terms of surface roughness of 1 μm or less and straightness of 1 μm / m or less in any direction. A slit whose average value is adjustable within a range of 0.5 mm to 3.5 mm by automatic adjustment is used. About the corner | angular part of the liquid-contact part of the lip | tip end of the casting die 91, R uses 50 micrometers or less over the full width of a slit. Moreover, it is preferable to use what is adjusted so that the shear rate of the dopes 71 to 73 in the casting die 91 may be 1 (1 / second) to 5000 (1 / second).

(Casting die)
The casting die 91 preferably includes a temperature controller (for example, a heater, a jacket, etc.) that keeps the casting dope 51 at a predetermined temperature. The casting die 91 is preferably a coat hanger type. Furthermore, it is more preferable to provide a thickness adjusting bolt (heat bolt) at a predetermined interval and attach an automatic thickness adjusting mechanism using a heat bolt. The heat bolt is preferably formed by setting a profile in accordance with the amount of liquid fed from the gear pumps 66 to 68 by a preset program. Further, feedback control may be performed by an adjustment program based on a profile of a thickness meter (for example, an infrared thickness meter) (not shown) in the film forming line 32. It is preferable that the thickness difference between any two points except the casting edge is adjusted within 1 μm, and the maximum difference in the width direction thickness is adjusted to 3 μm or less. Moreover, it is preferable to use the one whose thickness accuracy is adjusted to ± 1.5 μm or less.

More preferably, a cured film is formed at the lip end of the casting die 91. A method for forming the cured film is not particularly limited, and examples thereof include ceramic coating, hard chrome plating, and a nitriding method. When ceramics are used as the cured film, those that can be ground, have low porosity, are not brittle, have good corrosion resistance, have good adhesion to the casting die 91, and have no adhesion to the dope are preferable. Specific examples include tungsten carbide (WC), Al ₂ O ₃ , TiN, Cr ₂ O _{3 and the} like, but it is particularly preferable to use WC. The WC coating can be performed by a thermal spraying method.

  In order to prevent the dope flowing out to the slit end of the casting die 91 from locally drying and solidifying, it is preferable to attach a solvent supply device (not shown) to the slit end. Supplying a dope solubilizing solvent (for example, a mixed solvent of 86.5 parts by weight of dichloromethane, 13 parts by weight of methanol, and 0.5 parts by weight of 1-butanol) to the gas-liquid interface between the end of the casting bead and the slit. Is preferred. In addition, it is preferable to use a pump having a pulsation rate of 5% or less for supplying the liquid.

(Decompression chamber)
In order to stabilize the formation of the casting bead, the decompression chamber 100 is preferably attached to the rear surface of the casting bead and adjusted to a desired pressure. The back surface of the casting bead (the upstream side in the running direction of the casting band 95) is preferably decompressed in the range of 10 Pa or more and 2000 Pa or less than the pressure on the front surface (the downstream side in the running direction of the casting band 95). Furthermore, in order to keep the temperature of the decompression chamber 100 at a predetermined temperature, it is preferable to attach a jacket (not shown). The temperature of the decompression chamber 100 is not particularly limited, but is preferably in the range of 10 ° C. or more and 50 ° C. or less. Further, it is preferable to attach a suction device (not shown) to the edge portion of the casting die 91 in order to have the desired shape of the casting bead. The edge suction air volume is preferably in the range of 1 L / min to 100 L / min.

(Transition part)
A crossing portion 105 is provided on the downstream side of the casting chamber 96. A roller 106 and a blower 107 are arranged in the crossing part 105. The roller 106 forms a transport path for transporting the wet film 55 fed from the casting chamber 96 in a predetermined direction. In the crossover part 105, the drying of the wet film 55 is advanced by sending the drying air of desired temperature from the air blower 107. FIG. At this time, the temperature of the drying air is preferably 20 ° C. or higher and 250 ° C. or lower. In the crossing section 105, the wet film 55 can be stretched in the casting direction by making the rotation speed of the downstream roller faster than the rotation speed of the upstream roller.

(Tenta)
A tenter 110 is provided on the downstream side of the transition part 105. The tenter 110 is provided with a clip that supports both end portions of the wet film 55 and a blower that applies dry air to the wet film 55 supported by the clip. It is preferable to divide the tenter 110 into different temperature zones to adjust the drying conditions. It is also possible to stretch and relax the wet film 55 in the width direction using the tenter 110. As described above, it is preferable that at least one of the casting direction and the width direction of the wet film 55 is stretched by 0.5% to 300% by the crossing part 105 or the tenter 110.

(Ear opener)
An ear clip device 112 is provided on the downstream side of the tenter 110. The ear clip device 112 cuts both ends of the film 57. The cut film is sent to the crusher 113 by a cutter blower (not shown). The edge of the film 57 is crushed by the crusher 113 to form a chip. It is advantageous in terms of cost to reuse this chip for dope preparation. In addition, although the process of cutting both edges of the film 57 can be omitted, it is preferable to carry out any of the processes from the casting to the winding of the film 57.

(Drying room)
A drying chamber 115 is provided on the downstream side of the ear clip device 112. The drying chamber 115 includes a number of rollers 116 and a temperature controller (not shown). The roller 116 conveys the film 57 sent from the ear clip device 112 in a predetermined direction. The temperature controller maintains the temperature and humidity of the drying chamber 115 under predetermined conditions. Although the temperature of the drying chamber 115 is not specifically limited, It is preferable that it is the range of 60 to 145 degreeC. In the drying chamber 115, the film 57 is conveyed while being wound around the roller 116, and the solvent in the film 57 evaporates. Thereby, the film 57 is dried. Further, an adsorption recovery device 117 is attached to the drying chamber 115. The adsorption / recovery device 117 adsorbs and recovers the solvent vaporized in the drying chamber 115. The adsorption recovery device 117 blows the gas from which the solvent component has been removed into the drying chamber 115 again as dry air. The drying chamber 115 is more preferably divided into a plurality of sections in order to change the drying temperature. In addition, a preliminary drying chamber (not shown) is provided between the ear opener 112 and the drying chamber 115, and the preliminary drying of the film 57 is preferable because the shape change of the film 57 due to a rapid rise in temperature can be suppressed. .

  A cooling chamber 118 is provided on the downstream side of the drying chamber 115. In the cooling chamber 118, the film 57 sent out from the drying chamber 115 is cooled to approximately room temperature. Note that a humidity control chamber (not shown) may be provided between the drying chamber 115 and the cooling chamber 118. A wind adjusted to the desired humidity and temperature of the film 57 is blown in the humidity control chamber. Thereby, generation | occurrence | production of the curling of the film 57 and the winding-up defect at the time of winding up the film 57 can be suppressed.

  A winding chamber 120 is provided on the downstream side of the cooling chamber 118. A winding roller 121 is provided in the winding chamber 120. The take-up roller 121 is rotated by a control unit (not shown) and takes up the film 57 placed from the cooling chamber 118. When winding the film 57, it is preferable to wind the film 57 using a press roller 122 while applying a desired tension. More preferably, the tension is gradually changed from the start to the end of winding. The film 57 to be wound is preferably at least 100 m in the longitudinal direction (casting direction). Moreover, it is preferable that the width | variety of the film 57 is 500 mm or more, and it is more preferable that it is 500 mm or more and 2800 mm or less. The film forming line 32 has a thickness of 15 μm or more and 100 μm or less, and can produce a film 57 having a thickness variation of 5% or less and a thickness variation of 2% or less in the width direction.

  A forced static elimination device (static elimination bar) 125 or a knurling roller pair 126 may be provided between the cooling chamber 118 and the winding chamber 120. The forced charge removal device (charge removal bar) 125 is provided with a forced charge removal device (charge removal bar) 125 so that the charged voltage while the film 57 is conveyed is within a predetermined range (for example, −3 kV to +3 kV). In FIG. 3, an example provided on the downstream side of the cooling chamber 118 is illustrated, but the position is not limited thereto. Furthermore, it is preferable to provide a knurling roller pair 126 and to apply knurling to both edges of the film 57 by embossing. In addition, it is preferable that the deformation | transformation of the knurled location is 1 micrometer-200 micrometers.

  Next, details of the inside of the casting chamber 96 will be described. As shown in FIGS. 3 and 4, a stripping roller 140 is provided in the vicinity of the casting band 95. The casting dope 51 flowing out from the casting die 91 forms a casting film 53 on the casting band 95 and is conveyed in a predetermined direction. The casting film 53 on the casting band 95 is peeled off by the peeling roller 140 and is sent to the transfer section 105 as a wet film 55.

  Further, blowers 141 to 143 are provided in the vicinity of the casting band 95. The blowers 141 to 143 have an air outlet that sends out dry air for evaporating the solvent in the casting film 53. Although the upper and lower upstream sides of the casting band 95 and the lower part of the casting band 95 are illustrated as the attachment positions of the fans 141 to 143, the present invention is not limited to this. Further, it is preferable that a wind shield device 145 is provided between the casting die 91 and the blower 141. The wind shield device 145 can suppress the surface variation of the film surface due to the dry air being blown onto the casting film 53.

(Rotating drum)
In order to set the temperature of the membrane support surface 95a of the casting band 95 to a predetermined value, it is preferable that a heat transfer medium circulation device 146 is attached to the rotary drums 93 and 94. A heat transfer medium flow path is formed in the rotary drums 93 and 94, and the temperature of the rotary drums 93 and 94 is set to a predetermined range by passing through the heat transfer medium maintained at a predetermined temperature. Can hold. Thereby, the temperature of the film | membrane support surface 95a of the casting band 95 can be hold | maintained in a desired range.

  The rotating drum 94 has a rotating shaft 94b. The rotating shaft 94b is connected to a load cell 94c and a driving unit (not shown). By this drive unit, the rotating shaft 94b rotates the rotating drum 94. The load cell 94c detects an external force received by the rotating shaft 94b as a distortion amount.

  The rotary drums 93 and 94 are formed in a substantially cylindrical shape. The outer diameter is not particularly limited. When the casting band 95 travels along the peripheral surfaces of the rotating drums 93 and 94, it is preferable that the stress generated in the rotating drums 93 and 94 and the casting band 95 is small. The average roughness of the peripheral surfaces 93a and 94a of the rotating drums 93 and 94 is preferably set to 0.01 μm or less. The rotating drums 93 and 94 are not limited to a columnar shape but may be a cylindrical shape.

  The material for forming the rotary drums 93 and 94 is preferably stainless steel having high wear resistance. It is preferable to use a material equivalent to a material for forming the casting band 95 described later. It is preferable that the peripheral surfaces 93a and 94a be subjected to chrome plating or the like to have sufficient hardness and durability.

(Casting band)
The casting band 95 is formed in an annular shape, and has a membrane support surface 95a on its outer peripheral surface and a contact surface 95b on its inner peripheral surface. The film support surface 95 a supports the casting dope 51, forms a casting film 53, and supports the casting film 53. The contact surface 95b is supported by the peripheral surfaces 93a and 94a of the rotary drums 93 and 94.

  The temperature of the membrane support surface 95a of the casting band 95 is preferably maintained at 0 ° C. or higher and 40 ° C. or lower.

The width of the casting band 95 is not particularly limited, but it is preferable to use one having a range of 1.1 to 3.0 times the casting width of the dope. The width W1 of the casting band 95 is preferably 1500 mm or more and 3000 mm or less. Moreover, the length of the casting band 95 is 10 m or more and 200 m or less, and the thickness is 0.3 mm or more and 10 mm or less. In order to suppress the thickness unevenness failure of the casting film 53, it is preferable to use a thickness unevenness of the casting band 95 of 0.5% or less, and the thickness unevenness in the width direction is 0.1% or less. Preferably there is. The roughness of the membrane support surface 95a is preferably 0.05 μm or less. It is necessary to minimize the surface defects of the casting band 95. Specifically, there are no pinholes of 30 μm or more, pinholes of 10 μm or more and less than 30 μm are 1 / m ² or less, and pinholes of less than 10 μm are preferably ² / m ² or less.

  The material for forming the casting band 95 is preferably made of stainless steel, and austenitic stainless steel is preferably used because it has sufficient corrosion resistance, wear resistance, and strength. Among austenitic stainless steels, SUS316, SUS316L, SUS316LN, SUS316N, or the like is preferably used, and SUS316 is more preferably used. Moreover, in SUS316, it is preferable that there are many austenite production | generation elements and there are few ferrite production | generation elements, or what satisfy | fills any one. Examples of the austenite generating element include C, N, Ni, Mn, and Cu, and examples of the ferrite generating element include Cr, Si, Mo, Ti, and Al. Among these, 1.35 wt% to 2 wt% Mn, 11 wt% to 14 wt% Ni, 16 wt% to 17 wt% Cr, 2 wt% to 2.07 wt% It is preferable that it is stainless steel satisfying at least one of Mo and less than%. In addition to the above, P (phosphorus) or S (sulfur) that suppresses work hardening may be added.

  Further, it is preferable that the residual stress in the casting band 95 is small. This is because the residual stress in the casting band 95 induces streak-like deformation in the film support surface 95a. Therefore, it is preferable that the cast band 95 is produced by grinding a material that has passed for one month or more after casting. Furthermore, it is preferable to use a casting band 95 in which the residual stress generated during processing is relaxed after the production.

(Control part)
The control unit 147 is connected to the rotation shaft 94b and the load cell 94c. The control unit 147 moves the rotating drum 94 closer to or away from the rotating drum 93. Further, the control unit 147 reads the strain amount detected by the load cell 94c. And the control part 147 obtains the external force F1 based on this distortion amount, the cross-sectional area of the casting band 95, and the elasticity modulus of the load cell 94c. Further, the control unit 147 calculates the tension T1 applied to the casting band 95. Here, the tension T1 is expressed by the following equation.
T1 = F1 / (2 · S1)
F1 is an external force applied to the casting band 95 by the position of the rotary drum 93.94, and S1 is a cross-sectional area of the casting band 95. Therefore, the control unit 147 can apply a desired value of tension T1 to the casting band 95.

  The running speed of the casting band 95 is preferably 45 m / min or more and 200 m / min or less. If it is less than 45 m / min, the thickness unevenness of the film due to the stripe-like deformation of the film supporting surface 95a is small, so that the thickness unevenness does not cause a problem and does not cause a problem. The relative speed difference between the casting band 95 and the rotating drums 93 and 94 is preferably 0.01 m / min or less. The speed fluctuation of the casting band 95 is preferably 0.5% or less. If the speed fluctuation exceeds 0.5%, the stress generated on the contact surface 95b increases, and this tends to cause martensitic transformation on the peripheral surface 94a and the contact surface 95b. It is preferable that the meandering in the width direction generated when the casting band 95 rotates once is 1.5 mm or less. In order to control this meandering, it is more preferable to provide a detector (not shown) for detecting both ends of the casting band 95 and perform feedback control based on the measured value. Furthermore, it is preferable to adjust so that the vertical position fluctuation accompanying the rotation of the rotary drum 93 on the surface of the casting band 95 immediately below the casting die 91 is 200 μm or less.

  Next, the operation of the present invention will be described.

  In the dope production line 10 (FIG. 1), the raw material dope 48 is adjusted from the solvent, TAC, additive liquid, etc., and stored in the stock tank 30.

  As shown in FIG. 3, the raw material dope 48 stored in the stock tank 30 is sent to the intermediate layer dope channel 63, the back layer dope channel 64, and the surface layer dope channel 65 by the gear pumps 66 to 68. The In the flow paths 63 to 65, a predetermined additive or the like is added to the raw material dope 48, and the intermediate layer dope 71, the back layer dope 72, and the surface layer dope by static mixers (static mixers) 78, 83, 88. A dope 73 is created. In this way, the intermediate layer dope 71, the back surface layer dope 72, and the front surface layer dope 73 are respectively fed to the feed block 74 at a desired flow rate. The respective dopes 71 to 73 are merged in the feed block 74 to become the casting dope 51 and sent to the casting die 91 (FIG. 4).

  The casting die 91 causes the casting dope 51 to flow out to the casting band 95. From the casting die 91 to the casting band 95, the casting dope 51 forms a casting bead. The casting dope 51 that has flowed out onto the casting band 95 forms a casting film 53. In the casting film 53, the dopes 71 to 73 are layered similarly to the casting dope 51. In addition, it is preferable that the temperature of dope 71-73 at this time is hold | maintained substantially constant in the range of -10 degreeC or more and 57 degrees C or less.

  The rotary drums 93 and 94 are maintained at a predetermined temperature by the heat transfer medium circulation device 146. Further, the rotating drum 93 is rotated at a predetermined speed by a driving unit (not shown). Following the rotation of the rotating drum 93, the casting band 95 travels at a predetermined speed, and the rotating drum 94 rotates according to the traveling of the casting band 95. The casting film 53 is guided in the casting chamber 96 by the casting band 95 until it is peeled off by the peeling roller 140. While being guided in the casting chamber 96, the blowers 141 to 143 apply dry air to the casting film 53 to evaporate the solvent in the casting film 53. Thus, the cast film 53 dried to a desired degree is peeled off by the peeling roller 140 to become a wet film 55.

  After the casting film 53 becomes self-supporting, it is peeled off from the casting band 95 as a wet film 55 while being supported by the peeling roller 140. Thereafter, the transfer unit 105 provided with a large number of rollers is conveyed and then fed into the tenter 110. In the crossover part 105, the drying of the wet film 55 is advanced by sending the drying air of desired temperature from the air blower 107. FIG.

  The tenter 110 is provided with a temperature zone maintained at a predetermined drying condition. The wet film 55 sent to the tenter 110 is conveyed to the temperature zone while its both edges are gripped by clips or the like. In conveyance or passage to this temperature zone, the solvent contained in the wet film 55 evaporates and the wet film 55 is dried. The tenter 110 preferably dries the wet film 55 until the residual solvent amount on a dry basis is 250 wt% or more and 10 wt% or less. The amount of residual solvent based on this dry amount is a value calculated by {(xy) / y} × 100, where x is the film weight at the time of sampling and y is the weight after drying the sampling film. It is.

  The wet film 55 dried to a predetermined residual solvent amount by the tenter 110 is fed out as a film 57, and both edges thereof are cut by the edge cutting device 102. Next, the film 57 is sent to the drying chamber 115. In the drying chamber 115, the residual solvent amount of the wet film 55 is preferably 5% by weight or less based on the dry amount. Thereafter, the film 57 is conveyed to the cooling chamber 118 and cooled to approximately room temperature. Finally, the film 57 is taken up by the take-up roller 121 in the take-up chamber 120.

  Next, the details in the casting step 54 will be described. In the casting process 54, the rotating drums 93 and 94 rotate, and the peripheral surfaces 93a and 94a travel in a predetermined direction at a predetermined speed according to the rotation. Since the contact surface 95b of the casting band 95 is in contact with the peripheral surfaces 93a and 94a of the rotating drums 93 and 94, the casting band 95 follows the traveling of the peripheral surfaces 93a and 94a in the casting chamber 96 in the traveling direction Z1. At a predetermined speed.

The controller 147 adjusts the position of the rotating shaft 94b while reading the amount of strain from the load cell 94c so that the tension T1 falls within a predetermined range. Control unit 147, it is preferable to retain the tension T1 to 30 N / m ² or more 100 N / m ² or less in the range, it is more preferable to keep the range of 35N / m ² or more 90 N / m ² or less, 40N / it is most preferable to hold the m ² or more 80 N / m ² or less. In particular, when the tension T1 is less than 30 N / m ² , the contact force between the casting band 95 and the rotary drums 93 and 94 becomes small, and the casting band 95 meanders. On the other hand, when the tension T1 exceeds 100 N / m ² , the stress generated on the contact surface 95b due to rubbing with the peripheral surfaces 93a and 94a increases, which is not preferable.

  When the casting band 95 travels, the casting band 95 hung on the rotary drums 93 and 94 is curved in a shape along the peripheral surfaces 93a and 94a, and the contact surface 95b rubs against the peripheral surfaces 93a and 94a. . Stress is generated in the casting band 95 by these rubbing and bending. Due to this stress, the austenitic stainless steel phase P1 (FIG. 5A) in the vicinity of the film support surface 95a of the casting band 95 tends to become a martensitic stainless steel phase Q1 (FIG. 5B) due to this stress. The change from an austenitic stainless steel phase to a martensitic stainless steel phase is called martensitic transformation. This martensitic transformation is known to involve a volume increase of about 4%. Further, since a greater stress is generated as the contact surface 95b is approached, martensitic transformation is more likely to occur and the volume increase is greater as the contact surface 95b is approached. Accordingly, streak-like deformation occurs on the membrane support surface 95a side due to martensitic transformation in the vicinity of the contact surface 95b.

  In addition, martensitic stainless steel has lower wear resistance and corrosion resistance than austenitic stainless steel. Therefore, if the solution casting method is continuously performed using the casting band 95 having the martensitic stainless phase Q1, the passive film near the martensitic stainless phase Q1 is peeled off due to rubbing with the rotating drums 93 and 94. Cheap. Corrosion tends to proceed at the portion where the passive film is peeled off. The casting chamber 96 in which a casting band and a rotating drum are provided has a substantially sealed structure. Therefore, since the atmosphere in the vicinity of the casting band 95 is high temperature and contains a high concentration solvent, the corrosion further easily proceeds in the portion where the passive film is peeled off. Further, since the corroded portion is raised, stress due to friction and compression between the casting band 95 and the rotary drums 93 and 94 tends to concentrate, and the martensitic transformation is further promoted.

  In the present invention, the martensitic transformation is unlikely to occur because the casting band 95 formed of austenitic stainless steel having a small amount of ferrite forming elements and a large amount of austenite generating elements is used. Therefore, streak-like deformation on the membrane support surface 95a side can be suppressed. Furthermore, in the present invention, since the control unit 147 controls the value of the tension T1 to be within a predetermined range, martensitic transformation of the austenitic stainless steel that forms the casting band 95 can be prevented. Therefore, according to the present invention, the martensite transformation that induces the streak-like deformation on the membrane support surface 95a is suppressed, and the film 57 having no thickness unevenness can be manufactured.

  When this streak-like deformation occurs, the traveling speed of the casting band 95 is reduced to about 45 m / min in order to avoid a thickness unevenness failure caused by this deformation, or a new casting band is used. Although the entire solution film forming facility needs to be decelerated or stopped for replacement, the present invention eliminates the need for decelerating the casting band 95, decelerating the entire solution film forming facility, and stopping it. Therefore, this invention can manufacture the film without thickness unevenness with high production efficiency.

  In the above embodiment, the casting method and the outflow film forming apparatus, the film manufacturing method, and the manufacturing apparatus for forming a casting film having a plurality of layers using a casting dope in which a plurality of dopes form a layer are described. The present invention is not limited to this, and can also be applied to a casting method, an outflow film forming apparatus, a film manufacturing method, and a manufacturing apparatus for producing a casting film using a casting dope composed of a single layer dope.

  In the above embodiment, it has been described that the rotary drum 94 is rotated by the drive unit, but instead, the rotary drum 93 or the rotary drums 93 and 94 may be rotated by the drive unit. Further, the load cell may be connected to any shaft of the rotary drums 93 and 94.

  From casting die, decompression chamber, support structure, co-casting, peeling method, stretching, drying conditions of each process, handling method, curl, winding method after flatness correction, solvent recovery method, film recovery method Until now, it is described in detail in paragraphs [0617] to [0889] of JP-A-2005-104148. These descriptions are also applicable to the present invention.

[Performance / Measurement method]
(Curl degree / thickness)
The performance of the wound cellulose acylate film and the measuring method thereof are described in paragraphs [0112] to [0139] of JP-A-2005-104148. These are also applicable to the present invention.

[surface treatment]
It is preferable that at least one surface of the cellulose acylate film is surface-treated. The surface treatment is preferably at least one of vacuum glow discharge treatment, atmospheric pressure plasma discharge treatment, ultraviolet irradiation treatment, corona discharge treatment, flame treatment, acid treatment or alkali treatment.

[Functional layer]
(Antistatic, hardened layer, antireflection, easy adhesion, antiglare)
At least one surface of the cellulose acylate film may be undercoated.

  Further, it is preferable to use the cellulose acylate film as a base film as a functional material provided with another functional layer. The functional layer is preferably provided with at least one layer selected from an antistatic layer, a cured resin layer, an antireflection layer, an easy adhesion layer, an antiglare layer and an optical compensation layer.

The functional layers preferably contain at least one surfactant 0.1mg ^{/ m 2} ~1000mg ^/ m 2 containing. Further, the functional layers preferably contain at least one sort of plasticizers in the 0.1mg ^{/ m 2} ~1000mg ^/ m 2 containing. Further, the functional layers preferably contain at least one sort of matting agents in the 0.1mg ^{/ m 2} ~1000mg ^/ m 2 containing. Further, the functional layers preferably contain at least one sort of antistatic agents ^1mg / ^{m 2 ~1000mg} / m 2 containing. In addition to the above, the method for applying a surface-treated functional layer to cellulose acylate film to realize various functions and characteristics is described in detail in paragraphs [0890] to [1087] of JP-A-2005-104148. It also includes the conditions and methods. These are also applicable to the present invention.

(Use)
The cellulose acylate film is particularly useful as a polarizing plate protective film. Usually, two polarizing plates each having a cellulose acylate film bonded to a polarizer are bonded to a liquid crystal layer to produce a liquid crystal display device. However, the arrangement of the liquid crystal layer and the polarizing plate is not limited, and various known arrangements can be employed. Japanese Patent Application Laid-Open No. 2005-104148 describes in detail TN type, STN type, VA type, OCB type, reflective type, and other examples of liquid crystal display devices. This method can also be applied to the present invention. The application also describes a cellulose acylate film provided with an optically anisotropic layer and a cellulose acylate film provided with antireflection and antiglare functions. Furthermore, the use as an optical compensation film is also described as a biaxial cellulose acylate film imparting appropriate optical performance. This can also be used as a polarizing plate protective film. These descriptions are also applicable to the present invention. Details are described in paragraphs [1088] to [1265] of JP-A-2005-104148.

  Moreover, the cellulose triacetate film (TAC film) which is excellent in an optical characteristic by the manufacturing method of this invention can be obtained. The TAC film can be used as a polarizing plate protective film or a base film of a photographic photosensitive material. Further, it can be used as an optical compensation film for improving the viewing angle dependency of a liquid crystal display device such as a television. In particular, it is effective for applications that also serve as a protective film for a polarizing plate. Therefore, it is used not only for the conventional TN mode but also for the IPS mode, OCB mode, VA mode, and the like. Moreover, you may comprise a polarizing plate using the said film for polarizing plate protective films.

  Next, examples of the present invention will be described. In each of the following examples, details will be described in Example 1, and only the conditions different from Example 1 will be described in Examples 2 to 5. Examples 1 to 3 are examples of the embodiment of the present invention, and Examples 4 and 5 are comparative experiments with respect to Examples 1 to 3.

Example 1 will be given below, but the present invention is not limited thereto. The parts by weight used are shown below.
[composition]
Cellulose triacetate (substitution degree 2.84, viscosity average polymerization degree 306, water content 0.2% by weight, viscosity 6% by weight in dichloromethane solution 315 mPa · s, average particle diameter 1.5 mm with standard deviation 0.5 mm) Some powders) 100 parts by weight dichloromethane (first solvent) 320 parts by weight methanol (second solvent) 83 parts by weight 1-butanol (third solvent) 3 parts by weight plasticizer A (triphenyl phosphate) 7.6 parts by weight Plasticizer B (diphenyl phosphate) 3.8 parts by weight Dye (Dye Example: 115 (I-4)) 0.0005 parts by weight

[Cotton compound]
The cellulose triacetate used here has a residual acetic acid content of 0.1% by weight or less, a Ca content of 58 ppm, a Mg content of 42 ppm, a Fe content of 0.5 ppm, a free acetic acid of 40 ppm, It contained 15 ppm of sulfate ions. The degree of substitution of the 6-position acetyl group was 0.91, 32.5% of the total acetyl. The acetone extract was 8% by weight, and the weight average molecular weight / number average molecular weight ratio was 2.5. The yellow index is 1.7, the haze is 0.08, the transparency is 93.5%, the Tg (glass transition temperature; measured by DSC) is 160 ° C., and the crystallization heat generation is 6.4 J / g. Met. This cellulose triacetate was synthesized from cellulose collected from cotton as a raw material.

(1-1) Dope preparation The dope production line 10 shown in FIG. 1 was used. The cellulose triacetate powder (flakes) is gradually added from the hopper 14 to the 4000 L stainless steel dissolution tank 13 having a stirring blade root while the plurality of solvents are mixed and stirred and dispersed as a mixed solvent. It prepared so that it might become 2000 kg. All solvents used had a water content of 0.5% by weight or less. First, a dissolver type second stirring blade 41 that stirs at a peripheral speed of 5 m / sec (shear stress 5 × 10 ⁴ kgf / m / sec ² ) in the dissolution tank 13 and an anchor type anchor shaft on the central axis. The dispersion was carried out for 30 minutes under the condition of having a first stirring blade 39 and stirring at a peripheral speed of 1 m / sec (shear stress 1 × 10 ⁴ kgf / m / sec ² ). The starting temperature of dispersion was 25 ° C., and the final temperature reached 48 ° C. After completion of the dispersion, the high-speed stirring was stopped, the peripheral speed of the first stirring blade 39 was set to 0.5 m / second, and the mixture was further stirred for 100 minutes to swell the cellulose triacetate flakes to obtain a swelling liquid 44. Until the end of swelling, the inside of the tank was pressurized to 0.12 MPa with nitrogen gas. At this time, the oxygen concentration in the tank was less than 2 vol%, and the state of no problem was maintained in terms of explosion protection. The water content in the dope was 0.3% by weight.

(1-2) Dissolution / Filtration The swelling liquid 44 was fed from the dissolution tank 13 to the jacketed pipe as the heating device 18 by the pump 25. It heated to 50 degreeC with piping with a jacket, and also heated to 90 degreeC under the pressurization of 2 MPa, and was dissolved completely. The heating time was 15 minutes. The temperature was lowered to 36 ° C. with a temperature controller 19 and passed through a filtration device 20 having a filter medium having a nominal pore diameter of 8 μm, to obtain a dope having a solid content concentration of 19% by weight (hereinafter referred to as a dope before concentration). At this time, the primary pressure of filtration was 1.5 MPa, and the secondary pressure was 1.2 MPa. In addition, the filter, housing, and piping exposed to high temperature used the thing made from Hastelloy (trademark) alloy and having the jacket which distribute | circulated the heat medium for heat insulation heating using the thing excellent in corrosion resistance.

(1-3) Concentration / Filtration / Defoaming / Additive The dope before concentration is flushed in a flash device 21 adjusted to normal pressure at 80 ° C., and the evaporated solvent is liquefied by a condenser, and the recovery device 23 And separated. The solid concentration of the dope after flashing was 21.8% by weight. The recovered solvent was adjusted for reuse by the regenerator 24. The flash tank of the flash device 21 has an anchor blade on the center axis, and deaerated by stirring at a peripheral speed of 0.5 m / sec. The temperature of the dope in the flash tank was 25 ° C., and the average residence time in the tank was 50 minutes. The shear viscosity measured at 25 ° C. after collecting this dope was 450 Pa · s at a shear rate of 10 (seconds ⁻¹ ).

  Next, bubbles were removed by irradiating the dope with weak ultrasonic waves. Thereafter, the liquid was fed to the filtration device 22 while being pressurized to 1.5 MPa using the pump 26. In the filtration apparatus 22, first, the sintered fiber metal filter having a nominal pore diameter of 10 μm was passed, and then the sintered fiber filter having the same pore diameter of 10 μm was passed. Respective primary pressures were 1.5 MPa and 1.2 MPa, and secondary pressures were 1.0 MPa and 0.8 MPa. The temperature of the dope after filtration was adjusted to 36 ° C. and stored in a 2000 L stainless steel stock tank 30. Hereinafter, this dope is referred to as a raw material dope 48. The stock tank 30 had a stirring blade 62 as an anchor blade on the central axis and was constantly stirred at a peripheral speed of 0.3 m / sec. When the raw material dope 48 was prepared from the pre-concentration dope, no problems such as corrosion occurred in the dope wetted part of each device. Moreover, the mixed solvent A of 86.5 parts by weight of dichloromethane, 13 parts by weight of methanol, and 0.5 parts by weight of 1-butanol was prepared.

(1-4) Discharge / Previous Addition / Casting / Bead Depressurization Using the film forming line 32 shown in FIG. 3, the film manufacturing process 50 shown in FIG. 2 was performed. The raw material dope 48 in the stock tank 30 was fed using a primary pressure-increasing gear pumps 66 to 68 under feedback control by an inverter motor so that the primary side pressure became 0.8 MPa. The gear pumps 66 to 68 had a volume efficiency of 99.2% and a discharge rate variation rate of 0.5% or less. The discharge pressure was 1.5 MPa.

  The casting die 91 is equipped with a feed block 74 which is 1.8 m in width and adjusted for co-casting, and is capable of forming a three-layer film by laminating on both sides in addition to the mainstream. Using. In addition, the dope liquid supply flow path uses three flow paths: an intermediate layer dope flow path 63, a back surface layer dope flow path 64, and a surface layer dope flow path 65.

UV agent a (2 (2′-hydroxy-3 ′, 5′-di-tert-butylphenyl) benzotriazole), UV agent b (2 (2′-hydroxy-3 ′, 5′-di-tert-amyl) Phenyl) 5-chlorobenzotriazole) and retardation control agent (N, N'-di-
M-tolyl-N ″ -p-methoxyphenyl-1,3,5-triazine-2,4,6-triamine), mixed solvent A and raw material dope 48 are mixed, and stock solution 76 for intermediate layer Placed in tank 75. The intermediate layer additive solution 76 was sent to the raw material dope 48 in the intermediate layer dope channel 63 by the pump 77. And it was made to mix through the static mixer 78, and it was set as the dope 71 for intermediate | middle layers.

  0.05 parts by weight of silicon dioxide (particle size: 15 nm, Mohs hardness: about 7) as a matting agent and citric acid ester mixture (citric acid, citric acid monoethyl ester, citric acid diethyl ester, citric acid triethyl ester) as a peeling accelerator ) Was dissolved or dispersed in 0.006 part by weight, the raw material dope 48 and the mixed solvent A to obtain a back layer additive solution 81. The back surface layer additive solution 81 was placed in the stock tank 80 and fed to the raw material dope 48 flowing in the back layer dope channel 67 at a desired flow rate using the pump 82. And it mixed with the static mixer 83, and dope 72 for back surface layers was produced. The addition amount was such that the total solid content concentration was 20.5% by weight, the matting agent concentration was 0.05% by weight in the film form, and the release accelerator concentration was 0.03% by weight in the film form.

  The surface layer additive solution 86 was prepared by dispersing 0.05 part by weight of silicon dioxide in the mixed solvent A and put into the stock tank 85. The surface layer additive solution 86 was fed to the raw material dope 48 in the surface layer dope channel 65 by the pump 87. Then, the dope 73 for the surface layer was produced by mixing through the static mixer 88. The amount added was such that the total solid concentration was 20.5% by weight, and the matting agent concentration was 0.1% by weight in the film form.

  The film thicknesses (surface layer, intermediate layer, and back layer) of the target TAC film are 4 μm, 73 μm, and 3 μm, respectively, and the casting width is 1700 mm so that the product thickness is 80 μm. The dope for dope, the dope for the back surface layer, and the dope for the surface layer were adjusted to adjust the flow rate. In order to adjust the temperature of each dope to 36 ° C, a jacket (not shown) was provided on the casting die 91, and the inlet temperature of the heat transfer medium supplied into the jacket was set to 36 ° C.

  The casting die 91, the feed block 74, and the piping were all kept at 36 ° C. during film formation. The casting die 91 was of a coat hanger type, and thickness adjusting bolts (heat bolts) were provided at a pitch of 20 mm, and those equipped with an automatic thickness adjusting mechanism using heat bolts were used. The heat bolt can also set a profile according to the liquid feed amount of the high-precision gear pump by a preset program, and can be set by an adjustment program based on the profile of an infrared thickness meter (not shown) installed in the film forming line 32. The feedback control also has a possible performance. The thickness difference between two arbitrary points separated by 50 mm in the film excluding the casting edge portion of 20 mm was within 1 μm, and the maximum difference in the width direction thickness was adjusted to be 3 μm / m or less. The average thickness accuracy of each layer was controlled so that both outer layers were controlled to ± 2% or less, the mainstream was controlled to ± 1% or less, and the total thickness was adjusted to ± 1.5% or less.

  Each dope 71 to 73 became a casting dope 51 in which each dope 71 to 73 formed a layer through the feed block 74. The casting dope 51 was sent to the casting die 91.

  A decompression chamber 100 for decompressing was installed on the primary side of the casting die 91. The degree of decompression of the decompression chamber 100 is such that a pressure difference of 1 Pa to 5000 Pa occurs before and after the casting bead, and can be adjusted according to the casting speed. At that time, the pressure difference was set so that the length of the bead was 4 mm ± 20 mm. Moreover, the temperature of the decompression chamber 100 was equipped with the mechanism which can be set higher than the condensation temperature of the gas around a casting part. Labyrinth packings (not shown) were provided at the front and rear of the bead. Moreover, the opening part was provided in both ends. Furthermore, in order to adjust the disturbance of both edges of the casting bead, the one to which an edge suction device (not shown) is attached was used.

The material of the casting die 91 is a precipitation hardening type stainless steel, and the material has a thermal expansion coefficient of 2 × 10 ⁻⁵ (° C. ⁻¹ ) or less, which is substantially the same as that made of SUS316 in a forced corrosion test with an aqueous electrolyte solution. A material having corrosion resistance was used. Further, a corrosion-resistant material that does not cause pitting (opening) at the gas-liquid interface even when immersed in a mixed solution of dichloromethane, methanol, and water for 3 months was used. The finishing accuracy of the wetted surfaces of the casting die 91 and the feed block 74 was 1 μm or less in terms of surface roughness, the straightness was 1 μm / m or less in any direction, and the slit clearance was adjusted to 1.5 mm. About the corner | angular part of the liquid-contact part of die-tip tip, it processed so that R might be 50 micrometers or less over the slit full width. The shear rate inside the die ranged from 1 (1 / second) to 5000 (1 / second). Further, a WC coating was applied to the lip end of the casting die 91 by a thermal spraying method to provide a cured film.

  Furthermore, in order to prevent the dope flowing out from the slit end of the casting die 91 from locally drying and solidifying, the mixed solvent solubilizing the dope is placed on one side of the casting bead end and the slit gas-liquid interface. It was supplied at 0.5 ml / min. The pulsation rate of the pump supplying this liquid was 5% or less. Further, the pressure on the back side of the casting bead (upstream in the running direction of the casting band) was reduced by 150 Pa by the decompression chamber 100. In order to keep the temperature of the decompression chamber 100 constant, a jacket (not shown) was attached. A heat transfer medium adjusted to 35 ° C. was supplied into the jacket. The edge suction air volume that can be adjusted in the range of 1 L / min to 100 L / min was used, and in this example, it was appropriately adjusted in the range of 30 L / min to 40 L / min.

  A stainless steel endless band having a width of 2.1 m and a length of 70 m was used as the casting band 95 as a support. The casting band 95 was polished to have a thickness of 1.5 mm and a surface roughness of 0.05 μm or less. The material of the casting band 95 was austenitic SUS316 (1) shown in Table 1. The thickness unevenness of the entire casting band 95 was 0.5% or less, and the thickness unevenness in the width direction was 0.1% or less. The casting band 95 was stretched over the two rotating drums 93 and 94 so that the contact surface 95b and the peripheral surfaces 93a and 94a were in contact with each other. And the rotating shaft 94b was rotated by the drive part. The casting band 95 traveled endlessly by the rotation of the rotating shaft 94b.

The control unit 147 adjusts the position of the rotating shaft 94b, reads the strain amount from the load cell 94c, and obtains an external force F1 based on the strain amount. Further, the control unit 147 calculates the tension T1 applied to the casting band 95 using the above-described equation. Thus, the control unit 147 adjusts the tension T1 applied to the casting band 95 to 70 N / m ² , and the relative speed difference between the casting band 95 and the rotary drums 93 and 94 becomes 0.01 m / min or less. Adjusted as follows. The speed fluctuation of the casting band 95 was 0.5% or less. Further, both ends of the casting band 95 were detected and controlled so that the meandering in the width direction of one rotation was limited to 1.5 mm or less. Further, the positional fluctuation in the vertical direction between the die lip tip and the casting band 95 immediately below the casting die 91 was set to 200 μm or less. The casting band 95 is installed in a casting chamber 96 having wind pressure fluctuation suppressing means (not shown). On the casting band 95, a casting dope 51 composed of three layers of dope (a surface layer, an intermediate layer, and a back layer) was flowed out from the casting die 91.

As the rotating drums 93 and 94, those capable of feeding a heat transfer medium therein were used so that the temperature of the casting band 95 could be adjusted. A heat transfer medium of approximately 5 ° C. was passed through the rotary drum 93 on the casting die 91 side, and a heat transfer medium of approximately 40 ° C. was passed through the other rotary drum 94. The surface temperature of the central part of the casting band 95 immediately before casting was approximately 15 ° C., and the temperature difference between both ends was 6 ° C. or less. The casting band 95 preferably has no surface defects, has no pinholes of 30 μm or more, has 1 to 30 μm pinholes / m ² or less, and has 2 pinholes of less than 10 μm / m2. What was ² or less was used. The moving speed of the casting band 95 was adjusted to a range of 10 m / min to 200 m / min.

The temperature of the casting chamber 96 was kept at 35 ° C. using the temperature control equipment 97. The casting film 53 formed from the dope cast on the casting band 95 was first dried with parallel-flow drying air. The overall heat transfer coefficient from the drying air to the casting film 53 during drying was 24 kcal / m ² · hour · ° C. The temperature of the drying air was 135 ° C. on the upstream side of the upper part of the casting band 95 and 140 ° C. on the downstream side. Further, the lower part of the casting band 95 was blown from the fans 141 to 143 so that the temperature was 65 ° C. The saturation temperature of the solvent contained in each drying wind was around -8 ° C. The oxygen concentration in the dry atmosphere on the casting band 95 was kept at 5 vol%. Note that the air was replaced with nitrogen gas in order to maintain the oxygen concentration at 5 vol%. Further, in order to condense and recover the solvent in the casting chamber 96, a condenser (condenser) 98 was provided, and its outlet temperature was set to -10 ° C.

  For 5 seconds after casting, the static air pressure fluctuation in the immediate vicinity of the casting die 91 was suppressed to ± 1 Pa or less so that the dry wind did not directly hit the casting dope 51 and the casting film 53 by the wind shield 145. When the solvent ratio in the casting film 53 reached 150% by weight on the dry basis, the film was peeled off as a wet film 55 while being supported by the peeling roller 140 from the casting band 95. The stripping tension at this time is 10 kgf / m, and the stripping speed (stripping roller draw) is in the range of 100.1% to 110% with respect to the speed of the casting band 95 in order to suppress stripping failure. Adjusted appropriately. The surface temperature of the wet film 55 was 15 ° C. The drying speed on the casting band 95, that is, the amount of decrease in the residual solvent amount on the basis of the dry amount was an average of 60% by weight / min. The solvent gas generated by drying was condensed and liquefied by a condenser 98 at −10 ° C. and recovered by a recovery device 99. The recovered solvent was adjusted and then reused as a dope preparation solvent. At that time, the amount of water contained in the solvent was adjusted to 0.5% or less. The drying air from which the solvent was removed was heated again and reused as drying air.

  The wet film 55 peeled off by the peeling roller 140 was conveyed through the roller 106 of the crossing section 105 and sent to the tenter 110. At this time, 40 ° C. dry air was blown from the blower 107 to the wet film 55. In addition, a tension of about 100 N was applied to the wet film 55 in the casting direction while being transported by the roller 106 of the transfer section 105.

  The wet film 55 sent to the tenter 110 was transported in the drying zone of the tenter 110 while being fixed at both ends with clips, and was dried by the drying air. The clip was cooled by supplying a heat transfer medium at 20 ° C. The clip was driven by a chain, and the speed fluctuation of the sprocket was 0.5% or less. Further, the tenter 110 was divided into three zones, and the drying air temperature in each zone was set to 90 ° C., 100 ° C., and 110 ° C. from the upstream side. The saturation temperature of the solvent contained in the drying air was -10 ° C. The average drying rate in the tenter 110 was 120% by weight / min. The conditions of the drying zone were adjusted so that the amount of residual solvent in the film was 7% by weight at the exit of the tenter 110. Further, in the tenter 110, it was stretched in the width direction while being conveyed. The amount of widening when the width of the wet film 55 when transported to the tenter 110 was 100% was 103%. The stretch rate (tenter drive draw) from the peeling roller 140 to the tenter 110 inlet was set to 102%. The stretch ratio in the tenter 110 was 10% or less of the difference in the substantial stretch ratio in the portion separated from the tenter biting portion by 10 mm or more, and the difference in stretch ratio at any two points 20 mm apart was 5% or less. . The ratio of the length of the base end fixed by the tenter 110 was 90%. The solvent evaporated in the tenter 110 was condensed and liquefied at a temperature of −10 ° C. and recovered. A condenser (not shown) was provided for condensation recovery, and the outlet temperature was set to -8 ° C. The water content in the solvent was adjusted to 0.5% by weight or less and reused. And it sent out from the tenter 110 as the film 57.

Then, both ends of the film 57 were cut by the ear clip device 112 within 30 seconds after being sent out from the exit of the tenter 110. Ears 50 mm on both sides were cut with an NT-type cutter, and the cut ears were blown to a crusher 113 with a cutter blower (not shown) and crushed into chips of about 80 mm ² on average. This chip was used again as a raw material for dope preparation together with TAC flakes as a dope preparation raw material. The oxygen concentration in the dry atmosphere of the tenter 110 was kept at 5 vol%. Note that the air was replaced with nitrogen gas in order to maintain the oxygen concentration at 5 vol%. Before drying at a high temperature in a drying chamber 115 described later, the film 57 was preheated in a preliminary drying chamber (not shown) to which 100 ° C. drying air was supplied.

  The film 57 was dried at a high temperature in the drying chamber 115. The drying chamber 115 was divided into four sections, and drying air at 120 ° C., 130 ° C., 130 ° C., and 130 ° C. was supplied from a blower (not shown) from the upstream side. The conveyance tension of the film 57 by the roller 116 was 100 N / width, and the film was dried for about 10 minutes until the residual solvent amount finally reached 0.3% by weight. The wrap angle of the roller 116 was 90 degrees and 180 degrees. The roller 116 is made of aluminum or carbon steel, and hard chrome plating is applied to the surface. As the surface shape of the roller 116, a flat one and a matt-finished one by blasting were used. All the vibrations caused by the rotation of the roller 116 were 50 μm or less. The roller deflection at a tension of 100 N / width was selected to be 0.5 mm or less.

  The solvent gas contained in the drying wind was removed by adsorption using the adsorption / recovery device 117. The adsorbent was activated carbon, and desorption was performed using dry nitrogen. The recovered solvent was adjusted to a water content of 0.3% by weight or less and reused as a dope preparation solvent. In addition to solvent gas, the drying air contains plasticizers, UV absorbers, and other high-boiling substances, so these were removed by a cooler and a pre-adsorber that were cooled and removed, and were recycled and used. And adsorption / desorption conditions were set so that VOC (volatile organic compound) in the outdoor exhaust gas was finally 10 ppm or less. Moreover, the solvent amount collect | recovered by a condensation method among all the evaporation solvents was 90 weight%, and most of the remainder was collect | recovered by adsorption collection.

  The dried film 57 was conveyed to a first humidity control chamber (not shown). A drying air of 110 ° C. was supplied to the transition portion between the drying chamber 115 and the first humidity control chamber. Air having a temperature of 50 ° C. and a dew point of 20 ° C. was supplied to the first humidity control chamber. Further, the film 57 was conveyed to a second humidity control chamber (not shown) that suppresses the curling of the film 57. In the second humidity control chamber, air of 90 ° C. and humidity of 70% was directly applied to the film 57.

  The film 57 after humidity control was cooled to 30 ° C. or lower in the cooling chamber 118 and both ends were cut off. The forced charge removal device (charge removal bar) 125 was installed so that the film voltage during conveyance was always in the range of -3 kV to +3 kV. Further, knurling was performed on both ends of the film 57 by a knurling roller 126. The knurling was applied by embossing from one side, the knurling width was 10 mm, and the pressing pressure was set so that the maximum height was 12 μm higher than the average thickness on average.

  Then, the film 57 was conveyed to the winding chamber 120. The winding chamber 120 was kept at a room temperature of 28 ° C. and a humidity of 70%. Furthermore, an ion wind static elimination device (not shown) was also installed so that the film voltage would be -1.5 kV to +1.5 kV. The product width of the film 57 (thickness 60 μm) obtained in this way was 1500 mm. The diameter of the winding roller 121 was 169 mm. The tension pattern was such that the winding start tension was 360 N / width and the winding end was 250 N / width. The total winding length was 3940 m. The period during winding was 400 m, and the oscillating width was ± 5 mm. Further, the pressing roller 122 was pressed against the winding roller 121 and the pressure was set to 50 N / width. The temperature of the film at the time of winding was 25 ° C., the water content was 1.4% by weight, and the residual solvent amount was 0.3% by weight. The average drying rate was 20% by weight (dry weight reference solvent) / min throughout the entire process. Moreover, there was no winding looseness and wrinkles, and no winding slip occurred in the impact test at 10G. The roll appearance was also good.

  The film roll of film 57 was stored in a storage rack at 25 ° C. and 55% RH for 1 month and further examined in the same manner as described above. As a result, no significant change was observed. Further, no adhesion was observed in the roll. Further, after the film 57 was formed, no peeling residue of the casting film 53 formed from the dope was observed on the casting band 95.

  In the present embodiment, instead of the casting band 95, a casting band formed from SUS316 (2) shown in Table 1 was used. A solution casting method was performed in the same manner as in Example 1 except that the material for forming the casting band was changed.

  In this embodiment, instead of the casting band 95, a casting band formed from SUS316 (3) shown in Table 1 was used. A solution casting method was performed in the same manner as in Example 1 except that the material for forming the casting band was changed.

  In this embodiment, instead of the casting band 95, a casting band formed from SUS316 (4) shown in Table 1 was used. A solution casting method was performed in the same manner as in Example 1 except that the material for forming the casting band was changed.

  In this embodiment, instead of the casting band 95, a casting band formed from SUS316 (5) shown in Table 1 was used. A solution casting method was performed in the same manner as in Example 1 except that the material for forming the casting band was changed.

  The solution casting method of Examples 1 to 5 was continuously performed for 2000 hours, and the following evaluation was performed on the state of the membrane support surface of the casting band and the obtained film. The evaluation results are shown below.

1. Evaluation of Membrane Support Surface The membrane support surface of the casting band was visually observed and the surface condition was evaluated as follows.
A: The membrane support surface of the casting band is smooth.
○: Weak deformation is observed on the membrane support surface of the casting band.
X: Deformation is clearly seen on the membrane support surface of the casting band.

2. Evaluation of film surface state The film was visually observed and the surface state was evaluated as follows.
A: The film surface is smooth.
○: Weak deformation is observed on the film surface.
X: Deformation is clearly seen on the film surface.

  The evaluation results in each example are shown in Table 2. In addition, the numbers 1-4 attached | subjected in Table 2 are the evaluation results about the used casting band forming material, tension T1, and the film | membrane support surface and film surface state of a casting band, respectively.

  In Example 2, since there are many austenite generation elements contained in the material for forming the casting band, and in Example 3, since there are few ferrite forming elements in the material for forming the casting band, it depends on the stress generated during traveling. It is considered that martensitic transformation was suppressed and streak-like deformation on the membrane support surface was suppressed. In Example 1, since the austenite-forming elements contained in the material for forming the casting band are large and the ferrite-forming elements are few, the martensitic transformation of the casting band is suppressed more than in Examples 2 and 3, and the film It is thought that streak-like deformation was further suppressed on the support surface. On the other hand, in Examples 4 and 5, since the austenite forming elements contained in the casting band forming material are small and the ferrite forming elements are large, martensitic transformation occurs near the contact surface side of the casting band due to stress generated during traveling. This is considered to be caused by the suppression of streak-like deformation on the membrane support surface.

It is the schematic which shows the outline of a dope manufacturing line. It is the schematic which shows the outline of a solution casting method. It is the schematic which shows the outline of solution casting apparatus. It is the perspective view which expanded the casting band periphery. (A) is a sectional view of a casting band before martensitic transformation occurs, and (B) is a sectional view of the casting band after martensitic transformation occurs.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Dope production line 32 Film production line 48 Raw material dope 50 Film production process 53 Casting film 54 Casting process 55 Wet film 56 Stripping process 57 Film 58 Drying process 93, 94 Rotating drum
93a, 94a Circumferential surface 94b Rotating shaft 94c Load cell 95 Casting band 95a Membrane support surface 95b Contact surface 140 Stripping roller 147 Controller 190 Guide roll

Claims (13)

Supporting a dope containing a raw material polymer and a solvent, an annular casting band made of austenitic stainless steel ,
The traveling means supports an inner peripheral surface of the casting band with a peripheral surface, and rotates the rotating drum to travel the casting band by rotation.
A casting die for flowing the dope into the casting band ;
With
The austenitic stainless steel is
The Mn content is 1.35 wt% or more and 2 wt% or less, and the Ni content is 11 wt% or more and 14 wt% or less, or the Cr content is 16 wt% or more and 17 wt% or less, And the Mo content is 2 wt% or more and 2.07 wt% or less.
A casting apparatus comprising SUS316 or SUS316L . A controller for adjusting the distance between the plurality of rotating drums;
The adjustment by the casting apparatus according to claim 1, wherein the tension applied to the casting band is 30 N / mm ² or more 100 N / mm ² or less. A rotating drum temperature adjusting means for adjusting the temperature of the plurality of rotating drums;
The plurality of rotating drums are a first rotating drum and a second rotating drum disposed below the casting die,
3. The rotary drum temperature adjusting means adjusts the temperature of the first and second rotary drums so that the first rotary drum is cooler than the second rotary drum. The casting apparatus as described. The casting apparatus according to any one of claims 1 to 3, wherein a speed fluctuation of the casting band is 5% or less. The casting apparatus according to any one of claims 1 to 4, wherein the rotating drum is made of stainless steel. The casting apparatus according to any one of claims 1 to 5, wherein a width of the casting band is 1500 mm or more and 3000 mm or less. A casting apparatus according to any one of claims 1 to 6;
Stripping means formed on the casting band and stripping the casting film made of the dope to form a wet film;
Drying means for drying the wet film;
A solution casting apparatus characterized by comprising: A plurality of rotating drums supporting austenitic stainless steel casting band formed in an annular shape, and running the casting band by rotation of the rotating drum,
A dope containing a raw material polymer and a solvent is flowed out to the casting band, and a casting film is formed on the casting band,
Peel off the casting film to make a wet film,
Drying the wet film ;
The austenitic stainless steel is
The Mn content is 1.35 wt% or more and 2 wt% or less, and the Ni content is 11 wt% or more and 14 wt% or less, or the Cr content is 16 wt% or more and 17 wt% or less, And the Mo content is 2 wt% or more and 2.07 wt% or less.
A solution casting method comprising SUS316 or SUS316L . Wherein by adjusting the distance between the plurality of rotating drums, solution casting method according to claim 8, wherein the tension is 100 N / mm ² or less 30 N / mm ² or more applied to the casting band. 9. The plurality of rotating drums are a first rotating drum disposed below the casting die and a second rotating drum having a higher temperature than the first rotating drum. 9. The solution casting method according to 9. The solution casting method according to any one of claims 8 to 10, wherein a speed fluctuation of the casting band is 5% or less. 12. The solution casting method according to claim 8, wherein the rotating drum is made of stainless steel.
The solution casting method according to any one of claims 8 to 12 , wherein the casting band having a width of 1500 mm or more and 3000 mm or less is used.

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