JP4849927B2 - Solution casting method - Google Patents

Description

  The present invention relates to a solution casting method, and more particularly to a solution casting method of a cellulose acylate film suitably used for a functional membrane for electronic materials.

  A TAC film formed from a cellulose ester film, particularly a cellulose triacetate (hereinafter referred to as TAC) having an average degree of acetylation of 58.0% to 62.5% is a photographic photosensitive material because of its toughness and flame retardancy. It is used as a film support. In addition, since TAC films are excellent in optical isotropy, they are used in optical films such as protective films for liquid crystal display devices and optical compensation films (for example, viewing angle widening films, etc.), which are expanding in the market in recent years. Yes.

  The TAC film is usually produced by a solution casting method. 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 polymer solution (hereinafter referred to as a dope) in which a polymer or the like is dissolved in a solvent is prepared, and the dope is cast on a support by forming a casting bead from a casting die. Form a film. As the solvent, a mixture containing dichloromethane or methyl acetate as a main component is used. Note that a casting band wound around a rotating roller is used as the support. After the casting membrane has become self-supporting on the support, it is peeled off from the support as a solvent-containing film, that is, a wet film, and the wet film is dried to form a polymer film (hereinafter simply referred to as a film). And take up (see, for example, Non-Patent Document 1).

In the solution casting method, the planar properties of the film vary greatly depending on the conditions when the casting film is peeled off as a wet film from the casting band. Therefore, conventionally, the surface temperature of the rotating roller is set to 6 ° C. or more and 15 ° C. or less, and the time for which the casting film is wound around the rotating roller is set to 0.5 seconds or more and 20 seconds or less, thereby peeling off the casting film. A film which is easy to remove and does not fog on the surface of the film is obtained. Moreover, it is suppressed further that cloudiness arises on a film surface by making the dew point of a peeling part 7 degrees C or less (for example, refer patent document 1).
Japan Society for Invention and Innovation Public Technical Bulletin No. 2001-1745 JP 2003-071863 A

  However, in recent years, the film forming speed has been increased in order to improve productivity. For this reason, there is a problem in that so-called step unevenness undulating in the film conveyance direction occurs. In addition, there is a strong demand for an increase in the size of a liquid crystal display device and an increase in the accuracy of the screen, and accordingly, the optical characteristics of optical films are also required to be extremely high. Therefore, the peeling condition described in Patent Document 1 has a problem that a film having the required optical characteristics cannot be obtained in recent years.

  An object of the present invention is to provide a solution casting method in which a film having no optical unevenness, in particular, unevenness on the film surface, is produced with high productivity.

  As a result of intensive studies by the present inventor, it was found that under the experimental conditions described in Patent Document 1, the surface temperature of the rotating roller is high, so that the effect of promoting gelation of the cast film cannot be obtained sufficiently. Cooling the rotating roller arranged in the stripping section and cooling the casting film via the casting band improves the gelling strength of the casting film, improves the stripping stability, It has been found that the occurrence of is suppressed. Moreover, since the dew point in a peeling part was high, it discovered that a dew condensation produced on the casting film (wet film) surface in a peeling part. It has also been found that even if the condensed moisture is dried and volatilized in a later step, the film surface is clouded.

The solution casting method of the present invention includes a polymer and a solvent on the band wound around the first rotating roller by causing the band to run endlessly around the two rotating rollers. dope by casting die or al-casting to form a casting film on said band, said casting membrane drying air dried addressed to the first of the rotating roller to the take-over its dependent the band In the solution casting method in which the casting film is peeled off as a film at the upper peeling position to form a polymer film, the casting bead formed by the dope from the casting die to the band is upstream in the traveling direction of the band. A pressure reducing means that depressurizes the side of the casting film from the first rotating roller toward the second rotating roller with a drying air; and a step of drying from the second rotating roller to the second rotating roller. A first cooling step of cooling the casting film directed to one rotating roller to 5 ° C. or less by a cooling means disposed upstream of the first rotating roller in the traveling direction of the band; and the first rotating roller of the contact start position where the band starts to contact with the bottom, and said peeling position is an angle theta (°) range from 85 ° to 175 ° or less to form around the rotation axis of the rotating roller, the surface And a second cooling step of cooling the cast film through the band by the first rotating roller having a temperature of 6 ° C. or less.

The first cooling step is preferably performed in a cooling section that is 25% or less of the length of the casting band from the stripping position to the upstream side in the traveling direction of the band. It is preferable that the casting film is cooled by the cooling means for sending cooling air to the casting film. When the cooling roller as the cooling means is brought into contact with the band surface opposite to the band surface on which the casting film is formed, the flow on the band from the second rotating roller to the first rotating roller is set. It is preferable to cool the cast film. By adjusting the temperature inside the casting chamber for accommodating the first rotating roller and a second rotating roller, to Rukoto preferably a dew point of stripping position under 0 ℃ or less. It is preferable that the solvent content on the basis of the dry weight at the stripping position of the cast film is 20 wt% or more and 200 wt% or less.

The polymer film has a multilayer structure of two or more layers, and it is preferable to include a peeling accelerator in at least the dope cast directly on the band. When the polymer in the polymer film is 100% by weight, the dope directly cast on the belt preferably contains 1 × 10 ⁻⁴ wt% or more and 1.0 wt% or less of the peeling accelerator. When the polymer in the polymer film is 100% by weight , the polymer film contains 3 to 20% by weight of a plasticizer, 0.001 to 5% by weight of an ultraviolet absorber, and fine particles It is preferable to contain 0.001 wt% or more and 5 wt% or less of the powder. The polymer is preferably cellulose acylate.

According to the solution casting method of the present invention, the mechanical strength is improved gelation of the casting film peeling technique up immediately before proceeding. Thereby, peelability is stabilized and film surface defects such as step unevenness can be suppressed. In this case, the effect is more manifested by setting the surface temperature of the rotating roller below the casting die to less than 6 ° C.

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

[material]
In the present embodiment, cellulose acylate is used as the polymer, and triacetyl cellulose (TAC) is particularly preferable as the cellulose acylate. Of the cellulose acylates, those in which the substitution degree of the acyl group with respect to the hydrogen atom of the hydroxyl group of cellulose satisfies all of the following formulas (I) to (III) are more preferable. In the following formulas (I) to (III), A and B represent the substitution degree of the acyl group with respect to the hydrogen atom of the hydroxyl group of cellulose, A represents the substitution degree of the acetyl group, and B represents 3 to 3 carbon atoms. 22 is the substitution degree of the acyl group. In addition, it is preferable that 90 weight% or more of TAC is a particle | grain of 0.1 mm-4 mm.
(I) 2.5 ≦ A + B ≦ 3.0
(II) 0 ≦ A ≦ 3.0
(III) 0 ≦ B ≦ 2.9
The polymer used in the present invention is not limited to cellulose acylate.

  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 of the hydroxyl group of cellulose esterified at each of the 2-position, 3-position and 6-position (100% esterification has a substitution degree of 1).

The total acylation 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. When the sum of the substitution degrees by the hydroxyl groups at the 2nd, 3rd and 6th positions is DSA, and the sum of the substitution degree by an acyl group other than the acetyl group at the 2nd, 3rd and 6th hydroxyl groups is DSB, the value of DSA + DSB is More preferably, it is 2.22 to 2.90, and particularly preferably 2.40 to 2.88. The DSB is 0.30 or more, particularly preferably 0.7 or more. Further, 20% or more of DSB is a substituent at the 6-position hydroxyl group, more preferably 25% or more is a substituent at the 6-position hydroxyl group, more preferably 30% or more, and particularly 33% or more is a 6-position hydroxyl group. It is preferable that it is a substituent. Furthermore, the cellulose acylate having a substitution degree of 6-position of cellulose acylate of 0.75 or more, further 0.80 or more, and particularly 0.85 or more can be mentioned. These cellulose acylates can produce a preferable dope having solubility. In particular, in a non-chlorine organic solvent, a good solution can be produced. Furthermore, a dope having a low viscosity and good filterability can be produced.

  Cellulose, which is a raw material for cellulose acylate, may be obtained from either linter cotton or pulp cotton, but is preferably obtained from linter cotton.

  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, butanoyl, pentanoyl, hexanoyl, octanoyl, decanoyl, dodecanoyl, tridecanoyl, tetradecanoyl, hexadecanoyl, octadecanoyl, iso-butanoyl, t-butanoyl, cyclohexanecarbonyl, oleoyl, benzoyl , Naphthylcarbonyl, cinnamoyl group and the like. Among these, propionyl, butanoyl, dodecanoyl, octadecanoyl, t-butanoyl, oleoyl, benzoyl, naphthylcarbonyl, cinnamoyl and the like are more preferable, and propionyl and butanoyl are particularly preferable.

  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.

  Among these, halogenated hydrocarbons having 1 to 7 carbon atoms are preferably used, and dichloromethane is most preferably used. One kind of alcohol having 1 to 5 carbon atoms in addition to dichloromethane 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 It is preferable to mix several kinds. 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.

  By the way, recently, for the purpose of minimizing the influence on the environment, studies have been conducted on the solvent composition when dichloromethane is not used. For this purpose, ethers having 4 to 12 carbon atoms, carbon atoms A ketone having 3 to 12 carbon atoms, an ester having 3 to 12 carbon atoms, and an alcohol having 1 to 12 carbon atoms are preferably used. These may be used in combination as appropriate. For example, a mixed solvent of methyl acetate, acetone, ethanol, and n-butanol can be mentioned. These ethers, ketones, esters and alcohols may have a cyclic structure. A compound having two or more functional groups of ether, ketone, ester, and alcohol (that is, —O—, —CO—, —COO—, and —OH) can also be used as the solvent.

(Peeling accelerator)
Furthermore, in the present invention, it is preferable to add a release agent in order to reduce the load at the time of peeling. Of these, surfactants are effective, and phosphoric acid type, sulfonic acid type, carboxylic acid type, nonionic type, cationic type and the like are not particularly limited. These are described in, for example, JP-A-61-243837 and JP-A-2000-99847.

  As for the release agent, Japanese Patent Application Laid-Open No. 2003-055501 discloses a cellulose acylate solution dissolved in a non-chlorine solvent in order to prevent white turbidity of the cellulose acylate solution and improve film production peelability and film surface shape. In addition, there is a description of a cellulose acylate solution containing an additive selected from a polybasic acid partial ester having an acid dissociation index pKa of 1.93 to 4.5, an alkali metal salt, and an alkaline earth metal salt.

  Further, JP-A-2003-103545 discloses a two-layer or more cellulose casting method for improving the peelability during production, improving the film surface shape, and providing a film having no problem in durability. In the rate film production method, a non-chlorinated solvent is dissolved, and a partial ester of a polybasic acid having an acid dissociation index pKa of 1.93 to 4.50, an alkali metal salt or an alkaline earth metal salt thereof is selected in any solution. Per group of an amine compound having an acid dissociation index pKa of 4.50 or more in a solution of at least one layer not containing additive A and not containing additive A, or having substantially no volatility. There is a description of a method for producing a cellulose acylate film containing additive B which is an amine compound having a molecular weight of 200 or less. Examples of the peeling accelerator preferably used in the present invention include citric acid and citric acid ester. Also, as will be described later, when co-casting. When the peeling accelerator is contained only in the dope cast directly on the support, the cast film is peeled off (hereinafter also referred to as peelability) without deteriorating the optical properties. Can do.

The release accelerator is preferably 1 × 10 ⁻⁴ wt% or more and 1.0 wt% or less, more preferably 5 × 10 ⁻⁴ wt% when the polymer in the produced film is 100 wt%. The content is 0.5% by weight or less and most preferably 1 × 10 ⁻³ % by weight or more and 0.1% by weight or less. If it is less than 1 × 10 ⁻⁴ wt%, the effect of improving the peelability of the cast film may not be exhibited. On the other hand, if it exceeds 1.0% by weight, the optical properties of the film may be adversely affected.

[Plasticizer]
The plasticizer is preferably a phosphoric acid ester or a carboxylic acid ester. The plasticizer may be triphenyl phosphate (TPP), tricresyl phosphate (TCP), cresyl diphenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate, tributyl phosphate, dimethyl phthalate (DMP), diethyl Phthalate (DEP), dibutyl phthalate (DBP), dioctyl phthalate (DOP), diphenyl phthalate (DPP), diethyl hexyl phthalate (DEHP), triethyl O-acetylcitrate (OACTE), tributyl O-acetylcitrate (OACTB), Acetyl triethyl citrate, acetyl tributyl citrate, butyl oleate, methyl acetyl ricinoleate, dibutyl sebacate, triacetin, Buchirin, butyl phthalyl butyl glycolate, ethyl phthalyl ethyl glycolate, methyl phthalyl ethyl glycolate, and more preferably one selected from butyl phthalyl butyl glycolate. Furthermore, the plasticizer is preferably (di) pentaerythritol esters, glycerol esters, diglycerol esters.

  In the present invention, triphenyl phosphate is preferably used as the plasticizer. Further, when the polymer in the film is 100% by weight, it is preferably contained in an amount of 3% by weight to 20% by weight, more preferably 5% by weight to 18% by weight, most preferably 8% by weight to 15%. % By weight or less. There exists a possibility that the effect which improves the flexibility of a film may not fully express that a plasticizer content is less than 3 weight%. On the other hand, when the content exceeds 20% by weight, the optical properties of the film may be deteriorated or may be deposited from the film (so-called crying) to cause deterioration of the surface condition of the film.

[Ultraviolet absorber]
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 -Tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol), 2- (2'-hydroxy-3'-tert-butyl-5'-methylphenyl) -5-chloro Nzotriazole, 2,4-dihydroxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxy-5-sulfobenzophenone, bis (2-methoxy-4-hydroxy-5-benzoylphenyl) Methane), (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-hydride Xylphenyl) 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-hydroxy) Rokishifeniru) may be used in combination with phosphorus-based processing stabilizer such as metal hydrazine systems such as propionyl] hydrazine deactivator and tris (2,4-di -tert- butylphenyl) phosphite.

  In addition, light stabilizers 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, SEENOX, SEETEC, etc. in the catalog of SHIPROKASEI KAISYA can also be used. Jouhoku Chemical's UV absorbers and antioxidants can also be used. UV absorbers from Kyosho's VIOSORB and Yoshitomi Pharmaceutical can also be used.

  Moreover, the ultraviolet absorber described in JP-A-6-148430 can also be preferably used. The ultraviolet absorber described above preferably used in the present invention has high transparency, is excellent in the effect of preventing the deterioration of the polarizing plate and the liquid crystal element, and is particularly preferably a benzotriazole-based ultraviolet absorber with less unnecessary coloring.

  Regarding the spectral transmittance in the ultraviolet region, Japanese Patent Application Laid-Open No. 2003-043259 discloses a 390 nm necessary for obtaining an optical film, a polarizing plate and a display device excellent in color reproducibility and durability in ultraviolet irradiation. An optical film having a spectral transmittance of 50% to 95% at 350 nm and a spectral transmittance of 350% at 350 nm is described.

  Examples of the ultraviolet absorber preferably used in the present invention include benzotriazole compounds, benzophenones, triazine compounds, and the like, and particularly preferably, benzotriazole compounds. Further, when the polymer in the film is 100% by weight, it is preferably contained in an amount of 0.001% to 5% by weight, more preferably 0.01% to 3% by weight, and most preferably 0%. .1 wt% or more and 2 wt% or less. When the ultraviolet absorber content is less than 0.001% by weight, deterioration of the film due to ultraviolet irradiation may not be sufficiently prevented. Moreover, when it exceeds 5 weight%, there exists a possibility of deteriorating the optical characteristic of a film.

(Fine particle powder)
In particular, in the present invention, when the produced cellulose acylate film is handled, it is generally performed to add fine particles in order to prevent scratching or 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 Etc., more preferably an inorganic compound containing silicon or 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.

  Examples of the fine particle powder preferably used in the present invention include silicon dioxide and titanium oxide, and particularly preferably silicon dioxide. Further, when the polymer in the film is 100% by weight, the content is preferably 0.001% by weight to 5% by weight, more preferably 0.1% by weight to 3% by weight, and most preferably 0%. .5 wt% or more and 2 wt% or less. If the content of the fine particle powder is less than 0.001% by weight, there is a possibility that adhesion between the films when the film is wound cannot be sufficiently prevented. Moreover, when it exceeds 5 weight%, there exists a possibility that the planar smoothness of a film may deteriorate.

  The details of cellulose acylate are described in paragraphs [0140] to [0195] of JP-A-2005-104148. These descriptions are also applicable to the present invention. The same applies to additives such as solvents and plasticizers, deterioration inhibitors, UV absorbers (UV agents), optical anisotropy control agents, retardation control agents, dyes, matting agents, release agents, release accelerators, etc. JP-A-2005-104148 describes in detail in paragraphs [0196] to [0516].

[Dope production method]
First, a dope is manufactured using the above raw materials. First, the solvent is sent from the solvent tank to the mixing tank. Next, the TAC contained in the hopper is fed into the mixing tank while being measured. The required amount of additive solution is fed from the additive tank to the mixing tank. In addition to the method of sending the additive as a solution, for example, when the additive is liquid at normal temperature, it can be sent to the mixing tank in the liquid state. Further, when the additive is solid, a method of feeding into the mixing tank using a hopper or the like is also possible. 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. Alternatively, a solution in which an additive is dissolved can be put in each of a plurality of additive tanks and sent to the mixing tank through independent pipes.

  In the above description, the order of putting into the mixing tank is the solvent (used in the meaning including the case of the mixed solvent), TAC, and additive, but is not limited to this order. For example, a preferred amount of solvent can be fed after the TAC is metered into the mixing tank. In addition, the additive does not necessarily need to be put in the mixing tank in advance, and can be mixed in a mixture of TAC and a solvent (hereinafter, these mixtures may also be referred to as dope) in a later step.

  The mixing tank is provided with a jacket that wraps the outer surface thereof and a first stirrer that is rotated by a motor. Furthermore, it is preferable that the 2nd stirrer rotated by a motor is attached to the mixing tank. The first stirrer is preferably provided with anchor blades, and the second stirrer is preferably a dissolver type eccentric stirrer. The temperature of the mixing tank is adjusted by flowing a heat transfer medium between the mixing tank and the jacket, and a preferable temperature range is -10 ° C to 55 ° C. By appropriately selecting and using the types of the first stirrer and the second stirrer, a swelling liquid in which TAC is swollen in a solvent is obtained.

  The swelling liquid is sent to the heating device by a pump. The heating device is preferably a jacketed pipe, and further preferably has a configuration capable of pressurizing the swelling liquid. By using such a heating apparatus, the dope is obtained by dissolving the solid content in the swelling liquid under heating conditions or under pressure heating conditions. Hereinafter, this method is referred to as a heating dissolution method. In this case, the temperature of the swelling liquid is preferably 50 ° C to 120 ° C. Moreover, the cooling dissolution method which cools a swelling liquid to the temperature of -100 degreeC--30 degreeC can also be performed. TAC can be sufficiently dissolved in a solvent by appropriately selecting the heating dissolution method and the cooling dissolution method. After the dope is brought to about room temperature with a temperature controller, the impurities contained in the dope are removed by filtration with a filtration device. The filtration filter used in the filtration device preferably has an average pore diameter of 100 μm or less. The filtration flow rate is preferably 50 L / hr or more. The dope 22 after filtration is sent to the stock tank 21 in the film production line 20 of FIG. 1 and stored therein.

  By the way, as described above, the method of once preparing the swelling liquid and then using the swelling liquid as a dope increases the time required as the concentration of TAC is increased, which may be problematic in terms of manufacturing cost. . In that case, it is preferable to prepare a dope having a concentration lower than the target concentration and then perform a concentration step for obtaining the target concentration. When using such a method, the dope filtered by the filtration device is sent to the flash device, and a part of the solvent in the dope is evaporated in the flash device. The solvent gas generated by the evaporation is condensed by a condenser (not shown) to become a liquid and recovered by a recovery device. The recovered solvent is regenerated and reused as a solvent for preparing a dope by a regenerator. This reuse is effective in terms of cost.

  Further, the concentrated dope is extracted from the flash device by a pump. Furthermore, it is preferable that a bubble removal process is performed to remove bubbles generated in the dope. As this defoaming method, various known methods are applied, for example, an ultrasonic irradiation method. The dope is then sent to a filtration device to remove foreign matter. In addition, it is preferable that the temperature of dope at the time of filtration is 0 degreeC-200 degreeC. The dope 22 is sent to the stock tank 21 and stored.

  By the above method, a dope having a TAC concentration of 5 wt% to 40 wt% can be manufactured. More preferably, the TAC concentration is in the range of 15% by weight to 30% by weight, and most preferably in the range of 17% by weight to 25% by weight. The concentration of the additive (mainly a plasticizer) is preferably in the range of 1% by weight to 20% by weight when the total solid content in the dope is 100% by weight. In addition, from the [0517] paragraph of Unexamined-Japanese-Patent No. 2005-104148 about the manufacturing methods of dope, such as the raw material in the solution casting method which obtains a TAC film, a raw material, the additive dissolution method and addition method, a filtration method, and defoaming. [0616] The paragraph is detailed. These descriptions are also applicable to the present invention.

[Solution casting method]
Next, a method for producing a film using the dope 22 obtained above will be described. FIG. 1 is a schematic view showing a film production line 20. However, the present invention is not limited to the film production line as shown in FIG. The film production line 20 includes a stock tank 21, a filtration device 30, a casting die 31, a casting band 34 stretched around rotating rollers 32 and 33, a tenter dryer 35, and the like. In addition, an ear clip device 40, a drying chamber 41, a cooling chamber 42, a winding chamber 43, and the like are arranged.

  An agitator 61 that is rotated by a motor 60 is attached to the stock tank 21. The stock tank 41 is connected to the casting die 31 via the pump 62 and the filtration device 30.

As a material of the casting die 31, precipitation hardening type stainless steel is preferable, and its thermal expansion coefficient is preferably 2 × 10 ⁻⁵ (° C. ⁻¹ ) or less. And what has corrosion resistance substantially equivalent to SUS316 in the forced corrosion test with the electrolyte aqueous solution can be used as the material of the casting die 31 and further immersed in a mixed solution of dichloromethane, methanol and water for 3 months. Even if it has corrosion resistance that does not cause pitting (perforation) at the gas-liquid interface, it is used. Furthermore, it is preferable to manufacture the casting die 31 by grinding a material that has passed one month or more after casting. This prevents the dope 22 from flowing uniformly in the casting die 31 and prevents streaks or the like from occurring in the casting film described later. The finishing accuracy of the liquid contact surface of the casting die 31 is preferably 1 μm or less in terms of surface roughness, and the straightness is preferably 1 μm / m or less in any direction. The slit clearance of the casting die 31 can be adjusted in the range of 0.5 mm to 3.5 mm by automatic adjustment. About the corner | angular part of the liquid-contacting part of the lip | tip end of the casting die 31, the R shall be 50 micrometers or less over the whole width. Moreover, it is preferable that the shear rate in the casting die 31 is adjusted to be 1 (1 / sec) to 5000 (1 / sec).

  The width of the casting die 31 is not particularly limited, but is preferably 1.1 to 2.0 times the width of the film as the final product. Further, it is preferable to attach a temperature controller (not shown) to the casting die 31 so that the temperature during film formation is maintained at a predetermined temperature. The casting die 31 is preferably a coat hanger type. Further, it is more preferable that thickness adjusting bolts (heat bolts) are provided at predetermined intervals in the width direction of the casting die 31 and the casting die 31 is provided with an automatic thickness adjusting mechanism using a heat bolt. The heat bolt is preferably formed into a film by setting a profile according to the amount of pump 62 (preferably a high precision gear pump) according to 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 production line 20. The thickness difference between any two points in the width direction of the product film, excluding the casting edge portion, is adjusted within 1 μm, and the difference between the minimum value and the maximum value in the width direction thickness is adjusted to 3 μm or less. Preferably, adjusting to 2 μm or less is more preferable. 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 31. 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, it is preferable to use a ceramic that can be ground, has a low porosity, is not brittle, has good corrosion resistance, has good adhesion to the casting die 31, and does not have adhesion to the dope 22. Specific examples include tungsten carbide (WC), Al ₂ O ₃ , TiN, Cr ₂ O _{3 and the} like, and WC is particularly preferable. 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 31 from locally drying and solidifying, it is preferable to attach a solvent supply device (not shown) to the slit end. In this case, a solvent for solubilizing the dope (for example, a mixed solvent of 86.5 parts by mass of dichloromethane, 13 parts by mass of acetone, and 0.5 parts by mass of n-butanol) is used at both ends of the casting bead and at the end of the die slit. And it is preferable to supply to the periphery vicinity of the three-phase contact line which external air forms. Supplying at 0.1 mL / min to 1.0 mL / min to each one side of the end is preferable in order to prevent mixing of foreign matters into the cast film. In addition, as a pump which supplies this liquid, it is preferable to use a pump with a pulsation rate of 5% or less.

  A casting band 34 is provided below the casting die 31 so as to span the rotating rollers 32 and 33. The rotating rollers 32 and 33 are rotated by a driving device (not shown), and the casting band 34 travels endlessly with the rotation. The casting band 34 is preferably one that can move at a moving speed of 10 m / min to 200 m / min. Further, in order to set the surface temperature of the casting band 46 to a predetermined value, it is preferable that the heat transfer medium circulation device 63 is attached to the rotary rollers 32 and 33. The casting band 34 is preferably one whose surface temperature can be adjusted to -20 ° C to 40 ° C. A heat transfer medium flow path (not shown) is formed in the rotating rollers 32 and 33 used in the present embodiment, and the heat transfer medium maintained at a predetermined temperature passes through the flow path. The temperatures of the rotary rollers 32 and 33 are maintained at a predetermined value.

  The width of the casting band 34 is not particularly limited, but it is preferable to use a band having a range of 1.1 to 2.0 times the casting width of the dope 22. Further, it is preferable that the length is 20 m to 200 m, the thickness is 0.5 mm to 2.5 mm, and the surface roughness is polished to be 0.05 μm or less. The casting band 34 is preferably made of stainless steel, and more preferably made of SUS316 so as to have sufficient corrosion resistance and strength. Moreover, it is preferable to use the thickness unevenness of the entire casting band 34 of 0.5% or less.

It is also possible to use the rotating rollers 32 and 33 directly as a support. In this case, it is preferable that the rotation can be performed with high accuracy so that the rotation unevenness is 0.2 mm or less. In this case, it is preferable that the average roughness of the surfaces of the rotary rollers 32 and 33 is 0.01 μm or less. Therefore, the surface of the rotating roller is subjected to chrome plating or the like so as to have sufficient hardness and durability. In addition, it is necessary to suppress the surface defects of the support (the casting band 34 and the rotating rollers 32 and 33) to the minimum. Specifically, there is no pinhole of 30 μm or more, and the number of pinholes of 10 μm or more and less than 30 μm is 1 / m ² or less, and the number of pinholes of less than 10 μm is preferably ² / m ² or less.

  The casting die 31, the casting band 34 and the like are accommodated in the casting chamber 64. The casting chamber 64 is provided with a temperature control facility 65 for keeping the internal temperature at a predetermined value, and a condenser (condenser) 66 for condensing and recovering the volatile organic solvent. A recovery device 67 for recovering the condensed and liquefied organic solvent is provided outside the casting chamber 64. Further, it is preferable that a decompression chamber 68 for controlling the pressure of the back surface of the casting bead formed from the casting die 31 to the casting band 34 is disposed, and this is also used in this embodiment. .

  Air blowing ports 70, 71, 72 are provided near the peripheral surface of the casting band 34 in order to evaporate the solvent in the casting film 69. Further, a cooler 73 for cooling the casting film 69 is disposed in the vicinity of the stripped portion of the casting film 69. A thermometer 74 for measuring the surface temperature of the rotating roller 33 is attached to the rotating roller 33. Further, a wind shielding plate 75 is provided at the air blowing port 70 in the vicinity of the casting die 31 in order to suppress variation in the surface state of the casting film 69 caused by blowing dry air to the casting film 69 immediately after casting. It is preferable.

  The crossover portion 80 is provided with a blower 81, and the ear-cutting device 40 downstream of the tenter dryer 35 is used for finely cutting the waste at the side end (referred to as an ear) of the cut film 82. Crusher 90 is connected.

  The drying chamber 41 is provided with a number of rollers 91, and an adsorption / recovery device 92 for adsorbing / recovering the solvent gas generated by evaporation is attached. In FIG. 1, the cooling chamber 42 is provided downstream of the drying chamber 41, but a humidity control chamber (not shown) may be provided between the drying chamber 41 and the cooling chamber 42. A forced static elimination device (static elimination bar) 93 for adjusting the charged voltage of the film 82 to a predetermined range (for example, −3 kV to +3 kV) is provided downstream of the cooling chamber 42. In FIG. 1, the forced static eliminating device 93 is illustrated on the downstream side of the cooling chamber 42, but is not limited to this installation position. Furthermore, in this embodiment, a knurling roller 94 for applying knurling to both edges of the film 82 by embossing is appropriately provided downstream of the forced static elimination device 93. Further, a winding roller 95 for winding the film 82 and a press roller 96 for controlling the tension at the time of winding are provided in the winding chamber 43.

  Next, an example of a method for producing the film 82 using the film production line 20 as described above will be described below. The dope 22 is always made uniform by the rotation of the stirrer 61. The dope 22 can also be mixed with additives such as a peeling accelerator, a plasticizer, an ultraviolet absorber, and a fine particle powder during the stirring.

The dope 22 is sent to the filtration device 30 by the pump 62 and filtered there, and then is cast from the casting die 31 onto the casting band 34. The driving of the rotary rollers 32 and 33 is preferably adjusted so that the tension generated in the casting band 34 is 10 ⁴ N / m to 10 ⁵ N / m. Further, the relative speed difference between the casting band 34 and the rotating rollers 32 and 33 is adjusted to be 0.01 m / min or less. The speed fluctuation of the casting band 34 is preferably 0.5% or less, and the meandering in the width direction that occurs when the casting band 34 makes one rotation is preferably 1.5 mm or less. In order to control this meandering, a detector (not shown) for detecting the positions of both ends of the casting band 34 is provided, and based on the measured value, feedback control is performed on a position controller (not shown) of the casting band 34, More preferably, the position of the casting band 34 is adjusted. Further, it is preferable to adjust the casting band 34 immediately below the casting die 31 so that the vertical position fluctuation accompanying the rotation of the rotary roller 33 is 200 μm or less. Moreover, it is preferable that the atmosphere of the casting chamber 64 is adjusted by the temperature control equipment 65 so that the dew point in the vicinity of the peeling portion of the casting film is 0 ° C. or less. Thereby, dew condensation in the stripped portion is suppressed, and deterioration of the surface state of the film 82 can be prevented. In addition, it is more preferable that a dew point is -3 degrees C or less. Moreover, it is preferable that the temperature in the casting chamber 64 shall be -10 degreeC-57 degreeC.

  The solvent evaporated in the casting chamber 64 is recovered by the recovery device 67 and then regenerated and reused as a dope preparation solvent.

  A casting bead is formed from the casting die 31 to the casting band 34, and a casting film 69 is formed on the casting band 34. The temperature of the dope 22 during casting is preferably −10 ° C. to 57 ° C. Further, in order to stabilize the casting bead, the back surface of the casting bead is preferably controlled to a desired pressure value by the decompression chamber 68. The back surface of the bead is preferably decompressed in the range of −2000 Pa to −10 Pa than the front surface. Further, it is preferable that a jacket (not shown) is attached to the decompression chamber 68 and the temperature is controlled so that the internal temperature is kept at a predetermined temperature. The temperature of the decompression chamber 68 is not particularly limited, but is preferably set to be equal to or higher than the condensation point of the organic solvent used. In order to keep the shape of the casting bead desired, it is preferable to attach a suction device (not shown) to the edge portion of the casting die 31. The edge suction air volume is preferably in the range of 1 L / min to 100 L / min.

  The casting film 69 moves as the casting band 34 travels. At this time, drying air is applied to the casting film 69 through the air blowing ports 70, 71, 72 to promote evaporation of the solvent. The surface of the casting film 69 may fluctuate due to the blowing of the dry air, but the wind shielding plate 73 suppresses the fluctuation. The surface temperature of the casting band 34 is preferably −20 ° C. to 40 ° C.

  Further, when the casting film 69 travels and moves, it is cooled by the cooling air from the cooler 73. When the casting film 69 is cooled, gelation proceeds, the mechanical strength of the casting film 69 is improved, and peeling failure is suppressed. The cooling temperature of the cast film 69 is preferably less than 6 ° C., more preferably 5 ° C. or less. Although the lower limit of the cooling temperature is not particularly limited, it is preferably practically −20 ° C. or higher in consideration of the cooling capacity of the cooler.

  The cooling by the cooler 73 may be 25% or less of the length of the casting band from the stripping position of the casting film 69 to the upstream side of the casting film 69 (hereinafter referred to as a cooling section). More preferably, it is 20% or less, and most preferably 15% or less. If the cooling section is longer than 25%, the solvent in the cast film 69 may not sufficiently evaporate. Further, the lower limit value of the cooling section is not particularly limited. However, it is preferably 2% or more, more preferably 5% or more, and most preferably 8% in order to cool the casting film 69 in order to gel the casting film 69 and improve the mechanical strength. % Or more. In addition, although what has arrange | positioned the arrangement position of the cooler 73 in the position facing the casting film 69 is shown in figure, the position of the cooler 73 is not limited to it. A cooler may be provided on the side of the casting band 34 where the casting film 69 is not formed. In this case, the cold air cools the casting film 69 via the casting band 34.

  The surface temperature of the rotating roller 33 is measured by a thermometer 74. The surface temperature of the rotating roller 33 is preferably −20 ° C. or higher and 6 ° C. or lower, more preferably −15 ° C. or higher and 5 ° C. or lower, and most preferably −10 ° C. or higher and 5 ° C. or lower. If the surface temperature is lower than −20 ° C., dew condensation or the like may occur, which may cause deterioration of the surface condition of the cast film 69. Moreover, when it exceeds 6 degreeC, there exists a possibility that the temperature of the casting film 69 may rise and mechanical strength may become weak.

As shown in FIG. 2, the casting band 34 that has traveled from the rotating roller 32 is wound around the rotating roller 33 at the contact start position A. Then, after the casting film 69 on the casting band 34 on the rotating roller 33 becomes self-supporting, the casting film 69 is supported by the peeling roller 77 as the wet film 76 at the peeling position B. It is peeled off from the extension band 34. Casting film 69 is preferably more cooled rotating low La 33 through the belt 34. Thereby, the gelation of the cast film 69 is promoted, and the stripping stability is improved. In FIG. 2, a straight line connecting the contact start position A and the rotating shaft of the rotating roller 33 is denoted by a symbol (a), and a straight line connecting the stripping position B and the rotating shaft of the rotating roller 33 is denoted by a symbol (b). In the present invention, the angle (hereinafter referred to as the peeling position angle) θ (°) formed by the straight line (a) and the straight line (b) is preferably in the range of 85 ° to 175 °, more preferably 90 °. It is not less than 170 ° and not more than 170 °, most preferably not less than 95 ° and not more than 165 °. If the stripping position angle θ is less than 85 °, the cooling time on the rotating roller 33 may be short and the gelation may not proceed sufficiently. If the stripping position angle exceeds 175 °, it may be difficult to dispose the casting die 31 and the decompression chamber 68 provided as desired.

  By setting the stripping position angle θ (°) within the above range, gelation of the cast film 69 immediately before stripping proceeds and mechanical strength is improved. As a result, the peelability of the casting film 69 from the casting band 34 is stabilized and surface defects such as step unevenness can be prevented.

The residual solvent amount at the time of stripping is preferably 20% by weight or more and 200% by weight or less, more preferably 30% by weight or more and 200% by weight or less, and most preferably 50% by weight or more and 150% by weight or less on a dry basis. % Or less. When the solvent content is less than 20% by weight, the flexibility of the film is reduced, and there is a possibility that defects such as tearing may occur during transportation. On the other hand, if the solvent content exceeds 200% by weight, the mechanical strength of the wet film 76 is weak, and there is a risk that a dripping or the like will occur, resulting in poor conveyance. In addition, it takes time for the subsequent drying step, and there is a possibility that productivity is deteriorated.

  Thereafter, the transfer section 80 provided with a large number of rollers is conveyed, and the wet film 76 is fed into the tenter dryer 35. In the transfer part 80, the drying of the wet film 76 is advanced by sending the drying air of desired temperature from the air blower 81. FIG. At this time, the temperature of the drying air is preferably 20 ° C to 250 ° C. In the transition section 80, it is also possible to apply a draw tension to the wet film 76 by making the rotational speed of the downstream roller faster than the rotational speed of the upstream roller.

  The wet film 76 fed to the tenter dryer 35 is dried while being conveyed while being gripped by clips at both ends thereof. Moreover, it is preferable to divide the inside of the tenter dryer 35 into temperature zones and adjust the drying conditions appropriately for each of the zones. It is also possible to stretch the wet film 76 in the width direction using the tenter dryer 35. Thus, it is preferable to stretch at least one direction between the casting direction and the width direction of the wet film 76 by 0.5% to 300% with the crossover 80 and / or the tenter dryer 35.

  The wet film 76 is dried to a predetermined solvent content by the tenter dryer 35 and then sent to the downstream side as a film 82. Both ends of the film 82 are cut at both edges by the edge-cutting device 40. The cut side end portion is sent to the crusher 90 by a cutter blower (not shown). The crusher 90 pulverizes the film side end portion into a chip. Since this chip is reused for dope preparation, this method is effective in terms of cost. In addition, although it can also abbreviate | omit about the cutting process of this film both ends, it is preferable to carry out in any one from the said casting process to the process of winding up the said film.

  The film 82 from which both side ends have been removed is sent to the drying chamber 41 and further dried. Although the temperature in the drying chamber 41 is not specifically limited, It is preferable that it is the range of 50 to 160 degreeC. In the drying chamber 41, the film 82 is conveyed while being wound around a roller 91, and the solvent gas generated by evaporation here is adsorbed and recovered by an adsorption recovery device 92. The air from which the solvent component has been removed is blown again as dry air inside the drying chamber 41. The drying chamber 41 is more preferably divided into a plurality of sections in order to change the drying temperature. In addition, if a preliminary drying chamber (not shown) is provided between the ear opener 40 and the drying chamber 41 and the film 82 is preliminarily dried, the film temperature is prevented from rising rapidly in the drying chamber 41. The shape change of the film 82 can be further suppressed.

  The film 82 is cooled to approximately room temperature in the cooling chamber 42. A humidity control chamber (not shown) may be provided between the drying chamber 41 and the cooling chamber 42, and air adjusted to a desired humidity and temperature can be blown onto the film 82 in the humidity control chamber. It is preferable. Thereby, generation | occurrence | production of the curling of the film 82 and the winding defect at the time of winding can be suppressed.

  Further, the forcible charge removal device (charge removal bar) 93 sets the charged voltage while the film 82 is being conveyed to a predetermined range (for example, −3 kV to +3 kV). Although FIG. 1 illustrates an example provided on the downstream side of the cooling chamber 42, the position is not limited thereto. Furthermore, it is preferable to provide a knurling roller 94 to give knurling to both edges of the film 82 by embossing. In addition, it is preferable that the unevenness | corrugation of the knurled location is 1 micrometer-200 micrometers.

  Finally, the film 82 is taken up by the take-up roller 95 in the take-up chamber 43. At this time, it is preferable to wind the sheet while applying a desired tension with the press roller 96. More preferably, the tension is gradually changed from the start to the end of winding. The film 82 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 82 is 600 mm or more, and it is more preferable that they are 1400 mm or more and 1800 mm or less. The present invention is also effective when it is larger than 1800 mm. The present invention is also applied when a thin film having a thickness of 15 μm or more and 100 μm or less is manufactured.

  The principal part schematic of the film manufacturing line of other embodiment used for the solution casting method of this invention in FIG. 3 is shown. In addition, the same code | symbol is attached | subjected to the location of the same structure as FIG. 1, and description is abbreviate | omitted. A casting band 34 is provided in the casting chamber 100. A cooling roller 101 is provided from the stripping position A of the casting film 69 toward the upstream side. Further, the cooling roller 101 suppresses deterioration of the surface of the casting film 69 by providing the casting film 69 on the surface opposite to the surface on which the casting band 34 is formed. The number of cooling rollers 101, the cooling mechanism, etc. are not particularly limited. However, the number of cooling rollers is preferably 3 or more and 30 or less, more preferably 5 or more and 25 or less, and most preferably 8 or more and 20 or less.

  Although the cooling mechanism is not particularly limited, a method of supplying a heat transfer medium by forming a liquid flow path in the cooling roller 101 can be mentioned. Alternatively, a method in which a Peltier element is attached to the cooling roller 101 for cooling is also included. Other cooling conditions are the same as those described in FIG. The cast film 69 is cooled to a desired temperature by the cooling roller 101 and then peeled off as the wet film 102 while being supported by the peeling roller 77, and then a drying process or the like is performed.

  In the solution casting method of the present invention, when casting the dope, two or more kinds of dopes can be simultaneously laminated or sequentially laminated. Furthermore, you may combine both casting. When performing simultaneous lamination and co-casting, a casting die to which a feed block is attached may be used, or a multi-manifold casting die may be used. It is preferable that at least one of the thickness of the layer on the air surface side and the thickness of the layer on the support side is 0.5% to 30% of the thickness of the entire film of the film composed of multiple layers by co-casting. Furthermore, when performing simultaneous lamination co-casting, it is preferable that the high-viscosity dope is wrapped with the low-viscosity dope when the dope is cast from the die slit to the support. Moreover, when performing simultaneous lamination | stacking co-casting, it is preferable that the dope which contact | connects an external field has a larger alcohol composition ratio than an internal dope among the casting beads formed from a die slit to a support body.

  FIG. 4 shows a schematic view of an embodiment in which co-casting is performed using a multi-manifold co-casting die 110. In the multi-manifold co-casting die 110, three manifolds 111, 112, and 113 are formed. The manifolds 111 to 113 are respectively supplied with an intermediate layer dope 115, an air surface layer dope 116, and a support surface layer dope 117. In this case, when the support surface layer dope 117 contains a release accelerator, the peelability of the cast film is improved. The respective dopes 115 to 117 are joined at the joining portion 120 of the multi-manifold co-casting die 110 and then cast onto the casting band 121 as a support to form a casting film 122. In this case, at least the support surface layer 122a contains a peeling accelerator, so that peeling from the casting band 121 becomes easy. Thereafter, the film is produced under the same conditions as in the above method.

  From casting die, decompression chamber, support structure, co-casting, peeling method, stretching, drying conditions for 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.

  Furthermore, 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 treatment functional layer for realizing various functions and properties on the cellulose acylate film 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 moderate 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) excellent in an optical characteristic can be obtained with the manufacturing method of this invention. The TAC film can be used as a polarizing plate protective film or a base film for a photographic photosensitive material. Furthermore, it can also be used as an optical compensation film for improving the viewing angle dependency of a liquid crystal display device for television applications. 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.

  Hereinafter, the present invention will be described with reference to Example 1, but the present invention is not limited thereto. The description will be made in detail in Experiment 1 according to the present invention. Experiments 2 to 5 according to the present invention and Experiments 6 to 8 which are comparative examples are shown in Table 1 together with experimental conditions and results.

[Experiment 1]
Next, examples of the present invention will be described. The composition of the dope used for film production is as shown below, and the dope obtained in this experiment 1 is designated as dope A.

[composition]
Cellulose triacetate (substitution degree 2.84, viscosity average degree of polymerization 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 mass dichloromethane (first solvent) 320 parts by mass methanol (second solvent) 83 parts by mass 1-butanol (third solvent) 3 parts by mass plasticizer A (triphenyl phosphate) 7.6 parts by mass Plasticizer B (diphenyl phosphate) 3.8 parts by mass UV agent a: 2 (2′-hydroxy-3 ′, 5′-di-tert-butylphenyl) benzotriazole 0.7 part by mass UV agent b: 2 ( 2'-hydroxy-3 ', 5'-di-tert-amylphenyl) -5
Chlorbenzotriazole 0.3 parts by mass Citric acid ester mixture (citric acid, monoethyl ester, diethyl ester, triethyl ester mixture) 0.006 parts by mass fine particles (silicon dioxide (average particle size 15 nm), Mohs hardness about 7) 0. 05 parts by mass

[Cellulose triacetate]
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, free acetic acid of 40 ppm, It contained 15 ppm of sulfate ion. The degree of substitution of the acetyl group with respect to the hydrogen at the 6-position hydroxyl group was 0.91. Further, 32.5% of all acetyl groups were acetyl groups in which the hydrogen of the hydroxyl group at the 6-position was substituted. Moreover, the acetone extraction part which extracted this TAC with acetone was 8 weight%, and the weight average molecular weight / number average molecular weight ratio was 2.5. The obtained TAC has a yellow index of 1.7, a haze of 0.08, a transparency of 93.5%, a Tg (glass transition temperature; measured by DSC) of 160 ° C., and a crystallization calorific value of It was 6.4 J / g. This TAC is synthesized using cellulose collected from cotton as a raw material. In the following description, this is called cotton raw material TAC.

(1-1) Preparation The above-mentioned plurality of solvents were mixed and stirred well in a 4000 L stainless steel mixing tank having stirring blades to obtain a mixed solvent. In addition, as each raw material of a solvent, the thing whose water content is 0.5 weight% or less was used. Next, TAC flaky powder was gradually added from the hopper. The TAC powder is placed in a mixing tank and is initially stirred under a condition in which a dissolver type eccentric agitator that stirs at a peripheral speed of 5 m / sec and a stirrer having an anchor blade on the central shaft are agitated at a peripheral speed of 1 m / sec. Dispersed for minutes. The temperature at the start of dispersion was 25 ° C., and the final temperature reached 48 ° C. Further, the additive solution prepared in advance was adjusted so that the amount of the additive tank was fed, and the whole was sent to 2000 kg. After finishing the dispersion of the additive solution, the high speed stirring was stopped. Then, the peripheral speed of the anchor blade was set at 0.5 m / sec, and the mixture was further stirred for 100 minutes to swell the TAC flakes to obtain a swelling liquid. Until the end of swelling, the inside of the mixing tank was pressurized to 0.12 MPa with nitrogen gas. At this time, the oxygen concentration in the mixing tank was less than 2 vol%, and the state of no problem in explosion prevention was maintained. The amount of water in the swelling liquid was 0.3% by weight.

(1-2) Dissolution / filtration The swelling liquid was sent to a pipe with a mixing tank jacket. The swelling liquid was heated to 50 ° C. with a jacketed pipe, and further heated to 90 ° C. under a pressure of 2 MPa to completely dissolve. The heating time at this time was 15 minutes. Next, the temperature of the dissolved liquid was lowered to 36 ° C. with a temperature controller, and the dope A (hereinafter referred to as dope A before concentration) was obtained by passing through a filtration device having a filter medium having a nominal pore diameter of 8 μm. At this time, the primary pressure in the filtration device was 1.5 MPa, and the secondary pressure was 1.2 MPa. The filters, housings and pipes exposed to high temperatures were made of Hastelloy (trade name) alloy and had excellent corrosion resistance, and were equipped with a jacket for circulating a heat transfer medium for heat insulation and heating.

(1-3) Concentration / Filtration / Defoaming / Additive The dope A before concentration thus obtained is flash-evaporated in a flash apparatus at 80 ° C. and normal pressure, and the evaporated solvent is removed by a condenser. It was collected. The solid concentration of the dope A22 after flashing was 21.8% by weight. The condensed solvent was recovered by a recovery device to be reused as a solvent for preparing the dope A. After regenerating with a regenerator, the solution was sent to a solvent tank. Distillation and dehydration were performed in the recovery device and the regeneration device. The flash tank of the flash device was provided with a stirrer (not shown) having an anchor blade on the stirring shaft, and the dope A22 flashed at a peripheral speed of 0.5 m / sec was stirred and defoamed by the stirrer. The temperature of the dope A22 in the flash tank was 25 ° C., and the average residence time of the dope A22 in the tank was 50 minutes. The dope A22 was sampled and the shear viscosity measured at 25 ° C. was 450 Pa · s at a shear rate of 10 (sec ⁻¹ ).

  Next, bubbles were removed by irradiating the dope A22 with weak ultrasonic waves. After that, it was passed through a filtration device while being pressurized to 1.5 MPa using a pump. In the filtration apparatus, first, a sintered fiber metal filter having a nominal pore diameter of 10 μm was passed, and then a sintered fiber filter having a 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 A after filtration was adjusted to 36 ° C., and the dope A22 was fed into a 2000 L stainless steel stock tank 21 and stored. The stock tank 21 has a stirrer 61 having an anchor blade on the central axis, and was constantly stirred at a peripheral speed of 0.3 m / sec. In addition, when preparing the dope A from the dope A before concentration, no problem such as corrosion occurred at all in the liquid contact portion in contact with the dope A.

  Moreover, the mixed solvent B with 86.5 parts by mass of dichloromethane, 13 parts by mass of acetone, and 0.5 parts by mass of 1-butanol was prepared.

(1-4) Discharge / Previous Addition / Casting / Bead Depressurization Using the film production line 20 shown in FIG. The dope A22 in the stock tank 21 was sent to the filtration device 30 by a high-precision gear pump 62. The gear pump 62 has a function of increasing the pressure on the primary side of the pump 62. The inverter pump performs feedback control on the upstream side of the gear pump 62 so that the pressure on the primary side becomes 0.8 MPa, and the liquid is sent. . A gear pump 62 having a volume efficiency of 99.2% and a discharge rate variation rate of 0.5% or less was used. The discharge pressure was 1.5 MPa. Then, the dope A22 that passed through the filtration device 30 was fed to the casting die 31.

  The casting die 31 was cast by adjusting the flow rate of the dope 22 at the outlet of the casting die 31 so that the width of the casting die 31 was 1.8 m and the thickness of the dried film 82 was 80 μm. The casting width of the dope A22 from the discharge port of the casting die 31 was 1700 mm. The casting speed was 30 m / min. In order to adjust the temperature of the dope A22 to 36 ° C., a jacket (not shown) is provided on the casting die 31 and the inlet temperature of the heat transfer medium supplied into the jacket is set to 36 ° C.

  The casting die 31 and the piping were all kept at 36 ° C. during film formation. The casting die 31 was a coat hanger type die. The casting die 31 was provided with thickness adjusting bolts at a pitch of 20 mm and equipped with an automatic thickness adjusting mechanism using a heat bolt. The heat bolt can set a profile corresponding to the liquid feed amount of the gear pump 62 by a preset program, and is fed back by an adjustment program based on a profile of an infrared thickness meter (not shown) installed in the film production line 20. The thing which has the performance which can also be controlled was used. In the film excluding the edge 20 mm, the thickness difference between two arbitrary points 50 mm apart was within 1 μm, and the thickness variation in the width direction was adjusted to 3 μm / m or less. The overall thickness was adjusted to ± 1.5% or less.

  In addition, a decompression chamber 68 for decompressing this portion was installed on the primary side of the casting die 31. The degree of decompression of the decompression chamber 68 is adjusted so that a pressure difference of 1 Pa to 5000 Pa is generated before and after the casting bead, and this adjustment is made according to the casting speed. At that time, the pressure difference on both sides of the casting bead was set so that the length of the casting bead was 20 mm to 50 mm. The decompression chamber 68 was provided with a mechanism that can be set to a temperature higher than the condensation temperature of the gas around the casting portion. Labyrinth packings (not shown) were provided on the front and back surfaces of the beads at the die discharge port. Also, openings were provided at both ends of the die discharge port of the casting die. Further, an edge suction device (not shown) for adjusting the disturbance of both edges of the casting bead was attached to the casting die 31.

(1-5) Casting Die As a material of the casting die 31, precipitation hardening type stainless steel having a thermal expansion coefficient of 2 × 10 ⁻⁵ (° C. ⁻¹ ) or less was used. This had a corrosion resistance substantially equal to that of SUS316 in a forced corrosion test with an aqueous electrolyte solution. Further, even when immersed in a mixed solution of dichloromethane, methanol and water for 3 months, it had corrosion resistance that did not cause pitting (opening) at the gas-liquid interface. The finishing accuracy of the wetted surface of the casting die 31 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-contacting part of the lip | tip end of the casting die 31, what was processed so that R might be set to 50 micrometers or less over the full width of a slit was used. The shear rate of the dope 22 inside the casting die 31 was in the range of 1 (1 / sec) to 5000 (1 / sec). Further, a WC (tungsten carbide) coating was performed on the lip end of the casting die 31 by a thermal spraying method to provide a cured film.

  Further, in order to prevent the dope 22 flowing out from being locally dried and solidified, a mixed solvent B for solubilizing the dope A22 is discharged from both sides of the casting bead to the discharge port of the casting die 31. Each 0.5 ml / min was supplied to the interface with the outlet. The pulsation rate of the pump supplying the mixed solvent was 5% or less. Further, the pressure on the back side of the casting bead was lowered by 150 Pa from the front side by the decompression chamber 68. A jacket (not shown) was attached to make the internal temperature of the decompression chamber 68 constant at a predetermined temperature. A heat transfer medium adjusted to 35 ° C. was supplied into the jacket. The edge suction device can adjust the edge suction air volume so as to be in the range of 1 L / min to 100 L / min, and in the present embodiment, this is in the range of 30 L / min to 40 L / min. Adjusted appropriately.

(1-6) Metal Support A stainless steel endless band having a width of 2.1 m and a length of 70 m was used as the casting band 34 as a support. The casting band 34 was polished so that the thickness was 1.5 mm and the surface roughness was 0.05 μm or less. The material is made of SUS316 and has sufficient corrosion resistance and strength. The thickness unevenness of the entire casting band 34 was 0.5% or less. The casting band 34 was driven by two rotating rollers 32 and 33. At that time, the tension in the transport direction of the casting band 34 was adjusted to 1.5 × 10 ⁵ N / m ² . The relative speed difference between the casting band 34 and the rotating rollers 32 and 33 was adjusted to be 0.01 m / min or less. At this time, the speed fluctuation of the casting band 34 was set to 0.5% or less. Further, both end positions of the casting band 34 were detected and controlled so that the meandering in the width direction of one rotation was limited to 1.5 mm or less. The positional fluctuation in the vertical direction between the die lip tip and the casting band 34 immediately below the casting die 31 was set to 200 μm or less. The casting band 34 was installed in a casting chamber 64 having wind pressure fluctuation suppressing means (not shown). On the casting band 34, the dope A22 was cast from the casting die 31.

As the rotating rollers 32 and 33, those capable of feeding a heat transfer medium therein were used so that the temperature of the casting band 34 could be adjusted. A heat transfer medium at 32 ° C. was passed through the rotary roller 33 on the casting die 34 side, and a heat transfer medium at 40 ° C. was passed through the other rotary roller 32 for drying. The surface temperature of the rotating roller 33 was measured with a thermometer 74 and adjusted so that the surface temperature was 3 ° C. The surface temperature of the central part of the casting band 34 immediately before casting was 3 ° C., and the temperature difference between both side ends was 1 ° C. or less. The dew point in the vicinity of the stripping position A was adjusted with the temperature control equipment 65 so that it would be -5 ° C. The casting band 34 preferably has no surface defects, has no pinholes of 30 μm or more, has no pinholes of 10 μm to 30 μm, 1 pin / m ² or less, and ² pinholes of less than 10 μm / Those with m ² or less were used.

(1-7) Casting drying The casting film 69 formed from the dope A22 cast on the casting band 34 is first fed with drying air flowing parallel to the casting film 69, and cast. Membrane 69 was dried. The overall heat transfer coefficient from the dry air to the cast film 69 was 24 kcal / (m ² · hr · ° C.). As for the temperature of the drying air, 135 ° C. drying air was blown from the upstream air blowing port 70 above the casting band 34. Further, 140 ° C. dry air was blown from the air blowing port 71 on the downstream side, and 65 ° C. dry air was blown from the air blowing port 72 below the casting band 34. The saturation temperature of each drying wind was around -8 ° C. The cooler 73 was not used. The oxygen concentration in the dry atmosphere on the casting band 34 was kept at 5 vol%. In order to maintain this oxygen concentration at 5 vol%, the air was replaced with nitrogen gas. Further, in order to condense and recover the solvent in the casting chamber 64, a condenser (condenser) 66 was provided, and the outlet temperature thereof was set to -10 ° C.

For 5 seconds after casting, a wind shielding plate 75 is installed so that the dry wind does not directly hit the casting bead and the casting film 69, and the static pressure fluctuation in the vicinity of the casting die 31 is suppressed to ± 1 Pa or less. . When the solvent ratio in the casting film 69 reached 50% by weight on the dry basis, the film was peeled off from the casting band 34 as a wet film 76 while being supported by the peeling roller 77. The solvent content on the basis of the dry weight 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 stripping tension is 1 × 10 ² N / m ^2, and the stripping speed (stripping roller draw) is 100.1% to 110% with respect to the speed of the casting band 34 in order to suppress stripping failure. Adjusted appropriately in range. The surface temperature of the wet film 76 peeled off was 10 ° C. The average drying speed on the casting band 34 was 60% by weight / min on a dry basis. The solvent gas generated by the drying was condensed and liquefied by a condenser 66 at −10 ° C. and recovered by a recovery device 67. The recovered solvent was adjusted so that the water content was 0.5% or less. The drying air from which the solvent was removed was heated again and reused as drying air. The wet film 76 was conveyed through the roller of the crossing section 80 and sent to the tenter dryer 35. In the crossover 80, 40 ° C. dry air was blown from the blower 81 to the wet film 76. Note that a tension of about 30 N was applied to the wet film 76 during the conveyance by the roller of the crossover 80.

(1-8) Tenter Transport / Drying / Ear Cutting The wet film 76 sent to the tenter dryer 35 is transported in the drying zone of the tenter dryer 35 while being fixed at both ends with clips. Dried. The clip was cooled by supplying a heat transfer medium at 20 ° C. The clip was conveyed by a chain, and the speed fluctuation of the sprocket was 0.5% or less. Further, the interior of the tenter dryer 35 was divided into three zones, and the drying air temperature in each zone was set to 90 ° C., 110 ° C., and 120 ° C. from the upstream side. The gas composition of the drying air was set to a saturated gas concentration at −10 ° C. The average drying speed in the tenter dryer 35 was 120% by weight / min on a dry basis. The conditions of the drying zone were adjusted so that the residual solvent amount in the film 82 was 7% by weight at the outlet of the tenter dryer 35. In the tenter dryer 35, the film was stretched in the width direction while being conveyed. When the width of the wet film 76 before stretching was 100%, the film was stretched so that the width after stretching was 103%. The stretch ratio (tenter driven draw) from the peeling roller 77 to the entrance of the tenter dryer 35 was 102%.

  The stretching ratio in the tenter dryer 35 is 10% or less in the difference between the actual stretching ratios at any two points at a position 10 mm or more away from the biting start position by the clip, and any two at 20 mm. The difference in the stretching ratio of points was 5% or less. Further, the ratio of the length from the clip clamping start position to the clamping release position with respect to the length from the inlet to the outlet of the tenter dryer 35 was 90%. The solvent evaporated in the tenter dryer 35 was condensed and liquefied at a temperature of −10 ° C. and recovered. A condenser (condenser) was provided for condensation recovery, and the outlet temperature was set to -8 ° C. The condensed solvent was reused after adjusting the water content to 0.5 wt% or less. Then, the film was sent out from the tenter dryer 35 as a film 82.

The ear-cutting device 40 cuts off both ends of the film 82 within 30 seconds from the exit of the tenter dryer 35. Ears 50 mm on both sides were cut with an NT-type cutter, and the cut ears were blown to a crusher 90 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 production together with TAC flakes as a raw material for preparing Dope A. The oxygen concentration in the drying atmosphere of the tenter dryer 35 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 the drying chamber 41 described later, the film 82 was preheated in a predrying chamber (not shown) to which 100 ° C. drying air was supplied.

(1-9) Post-drying / static elimination The film 82 was dried at high temperature in the drying chamber 41. The drying chamber 41 was divided into four sections, and drying air of 120 ° C., 130 ° C., 130 ° C., and 130 ° C. was supplied from a blower (not shown) from the upstream side. The conveying tension of the film 82 by the roller 91 was set to 100 N / m, 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 91 (film winding center angle) was 90 degrees and 180 degrees. The material of the roller 91 was made of aluminum or carbon steel, and hard chrome plating was applied to the surface. The roller 91 has a flat surface shape and a blasted matte surface. The film position fluctuations due to the rotation of the roller 91 were all 50 μm or less. The roller deflection at a tension of 100 N / m was selected to be 0.5 mm or less.

  The solvent gas contained in the drying air was adsorbed and recovered using an adsorption recovery device 92. The adsorbent used here was activated carbon, and desorption was performed using dry nitrogen. The recovered solvent was reused as a dope preparation solvent after adjusting the water content to 0.3 wt% or less. The drying air contains plasticizers, UV absorbers and other high-boiling substances in addition to the solvent gas, so these were removed by a cooler and pre-adsorber to be removed by cooling and used for recycling. 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 82 was conveyed to a first humidity control chamber (not shown). A drying air of 110 ° C. was supplied to the transition part between the drying chamber 41 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 82 was conveyed to a second humidity control chamber (not shown) that suppresses the curling of the film 82. In the second humidity control chamber, air of 90 ° C. and humidity of 70% was directly applied to the film 82.

(1-10) Knurling and Winding Conditions The film 82 after humidity control was cooled to 30 ° C. or lower in the cooling chamber 42 and then subjected to ear cutting at both ends again with an ear cutting device (not shown). A forced charge removal device (charge removal bar) 93 was installed so that the charged voltage of the film 82 during conveyance was always in the range of −3 kV to +3 kV. Further, knurling was applied to both ends of the film 82 by a knurling roller 94. The knurling is applied by embossing from one side of the film 82, the width for applying the knurling is 10 mm, and the knurling is pressed by the knurling roller 94 so that the height of the irregularities is 12 μm higher than the average thickness of the film 82. The pressure was set.

  Then, the film 82 was conveyed to the winding chamber 43. The winding chamber 43 was kept at a room temperature of 28 ° C. and a humidity of 70%. Inside the winding chamber 43, an ion wind static elimination device (not shown) was also installed so that the charged voltage of the film 82 was −1.5 kV to +1.5 kV. The product width of the film (thickness 80 μm) 82 thus obtained was 1475 mm. The diameter of the winding roller 95 was 169 mm. The tension pattern was such that the winding start tension was 300 N / m and the winding end was 200 N / m. The total winding length was 3940 m. The fluctuation range of winding deviation at the time of winding (sometimes referred to as oscillating width) was ± 5 mm, and the winding deviation period with respect to the winding roller 95 was 400 m. The pressing pressure of the press roller 96 against the winding roller 95 was set to 50 N / m. The temperature of the film 82 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 / min on the basis of the dry weight 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 the film 82 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 82 was formed, no peeling residue of the cast film 69 formed from the dope was observed on the cast band 34.

The peelability of the cast film 69 at the stripping position B was visually confirmed and evaluated by the following three-level evaluation, which was good (◯).
There was no change in the stripping position, and the cast film was stripped uniformly.
There was some variation in the peeling position, and the cast film was peeled off with some fluctuations, but it was at a level where there was no problem in film production.
The variation of the stripping position was clearly seen ...

Moreover, when the unevenness of the obtained film 82 was observed with reflected light and evaluated by the following three-stage evaluation, it was good (◯).
No unevenness occurs.
Step unevenness was weak, but it was at a level where there was no problem as a product.
Step unevenness occurred strongly and could not be used as a product.

  In Experiment 4, a cooler 73 was used. Cold air at 20 ° C. was sent from the cooler 73 to the casting film 69 at a wind speed of 15 m / s. In addition, the cooler 73 used what can send cold air to substantially half of the casting band 34 lower part.

A film having a thickness of 80 μm was produced by replacing the dope A of Example 1 with the dope B having the following composition. Since other conditions are the same as those in the first embodiment, description thereof is omitted. Table 2 shows experimental conditions and evaluation results for Experiments 1 to 8 of Example 2.
Cellulose triacetate (substitution degree 2.94, viscosity average polymerization degree 305.6%, viscosity of dichloromethane solution 6% by mass 350 mPa · s) 100 parts by weight dichloromethane (first solvent) 390 parts by weight methanol (second solvent) 60 parts by weight Retardation reducing agent shown in Chemical formula 12 parts by weight Wavelength dispersion adjusting agent shown in Chemical formula 1.8 parts by weight Citric acid ester mixture (citric acid, monoethyl ester, diethyl ester, triethyl ester mixture) 0.006 part by weight Fine particles ( Silicon dioxide (average particle size 15 nm), Mohs hardness about 7) 0.05 parts by weight

  According to Experiments 1 to 5 in Tables 1 and 2, the peeling position angle θ is 85 ° or more and 175 ° or less, and the temperature of the rotating roller 33 is 6 ° C. or less. I understand that. Further, it can be seen that by providing the cooler 73 and cooling the casting film 69 with cold air, the peelability is further improved and step unevenness does not occur.

It is the schematic of the film manufacturing line for enforcing the solution casting method concerning this invention. It is a principal part enlarged view of FIG. It is a principal part schematic of the film manufacturing line of other embodiment for enforcing the solution casting method which concerns on this invention. It is the schematic of a casting die.

Explanation of symbols

20 Film production line 33 Rotating roller 34 Casting band 69 Casting film 76 Wet film 82 Film A Contact start position B Stripping position θ Stripping position angle

Claims (10)

And the band is run by wound in endless in at least two rotating rollers, the first of said rollers onto wound around it and the band, dope casting die or al casting comprising a polymer and a solvent to form a casting film on the band, the casting membrane drying air dried addressed to, the first at the peeling position on wound around it and the band to the rotating roller prior Kiryunobe In the solution casting method for stripping the membrane as a film and making it a polymer film,
With respect to the casting bead formed by the dope from the casting die to the band, the upstream side in the traveling direction of the band is decompressed by the decompression means,
A drying step of drying the cast film from the first rotating roller toward the second rotating roller with a drying air;
1st cooling which cools the said casting film which goes to the said 1st rotation roller from a said 2nd rotation roller to 5 degrees C or less with the cooling means distribute | arranged to the upstream of the said 1st rotation roller in the running direction of the said band. Process,
A contact start position of the band at the bottom of the first rotation roller starts to contact the peeling angle position and forms centered on the rotation axis of the front Symbol rollers theta (°) of 85 ° or more 175 And a second cooling step in which the casting film is cooled through the band by the first rotating roller having a surface temperature of 6 ° C. or less within a range of 0 ° C. or less. Method. The said 1st cooling process is performed in the cooling area made into 25% or less of the length of the said casting band with respect to the upstream in the running direction of the said band from the said stripping position. Solution casting method. The solution casting method according to claim 1 or 2 , wherein the casting film is cooled by the cooling means for sending cooling air to the casting film. The cooling roller as the cooling means, the Rukoto into contact with the band surface opposite to the band plane casting film is formed, the on band from the second rotating roller toward the first rotating roller 3. The solution casting method according to claim 1, wherein the cast film is cooled. By adjusting the temperature inside the casting chamber for accommodating the first rotating roller and a second rotating roller, we claim 1, characterized in to Rukoto under 0 ℃ than the dew point of the stripping position 4 The solution casting method according to any one of the above.   The solution casting method according to any one of claims 1 to 5, wherein the solvent content on a dry weight basis at the stripping position of the cast film is 20 wt% or more and 200 wt% or less. The polymer film has a multilayer structure of two or more layers,
The solution casting method according to any one of claims 1 to 6, wherein a stripping accelerator is contained in at least the dope cast directly on the band. When the polymer in the polymer film is 100% by weight,
The solution casting method according to claim 7, wherein the dope directly cast on the belt contains 1 × 10 ⁻⁴ wt% to 1.0 wt% of the peeling accelerator. When the polymer in the polymer film is 100% by weight
The polymer film contains 3 wt% or more and 20 wt% or less of a plasticizer,
Containing 0.001 wt% or more and 5 wt% or less of an ultraviolet absorber;
The solution casting method according to any one of claims 1 to 8, wherein the fine particle powder is contained in an amount of 0.001 wt% to 5 wt%.   The solution casting method according to claim 1, wherein the polymer is cellulose acylate.

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