JP5192569B2 - Method for producing polymer film - Google Patents

Description

  The present invention relates to a method for producing a polymer film.

  Cellulose acylate film, which is a typical example of polymer film, has advantages such as being able to be a protective film for polarizing plates, so it is widely used as an optical film that can provide inexpensive and thin liquid crystal display devices. Has been.

  The cellulose acylate film is mainly produced by a solution casting method. The solution casting method is a method of preparing a dope by filtering a polymer solution containing a polymer such as cellulose acylate and a solvent with a filtration device, and casting the dope on a traveling support. In this method, the film is peeled off from the support as a film containing a solvent after being formed, and then dried.

  In this solution casting method, the amount of the solvent, which is a volatile component, in the film peeled off from the support is reduced by the drying equipment, and is finally made as close to zero as possible. The film shrinks as the volatile components evaporate, which may cause deformation such as wrinkles and wrinkles. By using multiple drying equipment, the film is dried in stages to suppress wrinkles and wrinkles. be able to. Examples of drying equipment include a blower that blows dry air on the film, a tenter dryer that dries the film while gripping both ends of the wet film with gripping means, and a plurality of support rollers and temperatures that support the film. For example, a drying chamber having a control device. Usually, while transporting the film while being supported by a plurality of support rollers, it is dried by blowing dry air with the blower, and then the film is fed into the tenter dryer to be dried to a predetermined solvent amount. Finally, it is dried in the drying chamber.

  Most of the large amount of solvent in the film evaporates to the outlet of the tenter dryer, but still contains about 5 to 30% of the solvent on a dry basis. If the solvent remains in the film, the film shrinks during drying in the drying chamber. However, in the drying chamber, tension is applied and restrained in the film transport direction, that is, the longitudinal direction of the film, so that the film contracts only in the width direction without contracting in the longitudinal direction. Note that the shrinkage in the width direction is proportional to the magnitude of the applied tension.

  Thus, when the film shrinks in the width direction after the tenter dryer exit, wrinkles and wrinkles occur on the surface. Therefore, there arises a problem that the optical characteristics of the film are deteriorated. In order to suppress shrinkage in the width direction of the film, for example, a method of drying by specifying the amount of residual solvent in the film (see, for example, Patent Document 1) has been proposed.

JP 2003-033931 A

  In the method described in Patent Document 1, the amount of volatile solvent (component) is reduced by defining the amount of solvent in the film when drying, thereby reducing the shrinkage rate in the width direction during drying. However, the optical properties required for cellulose acylate films, which are optical films, are becoming stricter year by year, and it is desired to provide a method that can produce films having more excellent optical properties.

  The present invention provides a polymer capable of obtaining a film having excellent optical characteristics by reducing the amount of volatile components as much as possible while suppressing shrinkage in the width direction, that is, dimensional change in the width direction, when drying a wet film. A method for producing a film is provided.

  A polymer solution containing a polymer and a solvent is cast on a support to form a cast film, and the cast film is continuously peeled off from the support to form a solvent-containing film. In the method for producing a polymer film to be dried, a first drying step in which both side ends of the polymer film containing the solvent are gripped by gripping means and dried while being conveyed while being stretched in the width direction, After the first drying step, a tension of 2 × 9.8 (N / m) or more and 8 × 9.8 (N / m) or less is applied in the longitudinal direction of the polymer film, and the polymer film is formed by a plurality of rollers. A second drying step of drying while supporting and conveying, wherein at least one of the plurality of rollers is longer than the width of the polymer film and symmetrical with respect to the longitudinal center. A drum-shaped roller having a shape and an outer diameter that increases from the center in the longitudinal direction toward both ends. The maximum outer diameter D1 (mm) and the minimum outer diameter d1 of the drum-shaped roller in the range of supporting the polymer. (Mm) satisfies the condition of 0.9 <d1 / D1 <0.99.

  The polymer is preferably cellulose acylate. A winding step of winding the polymer film having undergone the second drying step, wherein the width of the polymer film immediately after being gripped by the gripping means is L1 (mm), and after the end of the second drying step When the width of the polymer film immediately before being wound is L2 (mm), it is preferable that L2 / L1 satisfies the condition of 1.1 ≦ L2 / L1 ≦ 1.5. The polymer film at the start of the second drying step preferably contains 5% by weight or more and 20% by weight or less of the solvent on a dry basis. Note that one of the most upstream of the plurality of rollers is preferably the drum roller.

  According to the present invention, drying can be performed while suppressing shrinkage in the width direction and gradually reducing the amount of volatile components. Therefore, since the film surface can be dried without causing wrinkles or wrinkles, a film having excellent flatness can be obtained.

  Further, the film can be dried while suppressing the expansion / contraction width of the film as much as possible.

  In addition, stress can be applied toward the outside in the width direction of the film. Therefore, it can dry, suppressing shrinkage | contraction in the width direction, As a result, the film excellent in planarity can be obtained, without using special drying equipment.

The flow of the manufacturing process of the cellulose acylate film in this invention is shown. The schematic of the dope production line in this invention is shown. The schematic of the film production line in this invention is shown. It is a front view of an example of the support roller in the drying chamber in the present invention. It is a front view of an example of a step type support roller.

The polymer for producing the dope is not particularly limited, but cellulose acylate is preferable, and the cellulose acylate in which the substitution degree of acyl group to hydrogen of hydroxyl group of cellulose satisfies all of the following formulas (I) to (III) More preferred.
(I): 2.5 ≦ A + B ≦ 3.0
(II): 0 ≦ A ≦ 3.0
(III): 0 ≦ B ≦ 2.9
However, A and B in a formula represent the ratio by which the hydrogen in the hydroxyl group of a cellulose is substituted by the acyl group, A is a substitution degree of an acetyl group, B is an acyl having 3 to 22 carbon atoms. The degree of substitution of the group. In addition, it is preferable to use a cellulose acylate in which the ratio of particles of 0.1 mm or more and 4 mm or less is 90% by weight or more based on the total weight.

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

  The total acyl substitution degree, that is, the value of 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. Moreover, the value of D6S / (DS2 + DS3 + DS6) is preferably 0.28 or more, more preferably 0.30 or more, and particularly preferably 0.31 to 0.34. DS2 is the ratio of the hydrogen of the hydroxyl group at the 2-position in the glucose unit (hereinafter referred to as the degree of acyl substitution at the 2-position), and DS3 is the hydrogen of the hydroxyl group at the 3-position in the glucose unit. Is the rate of substitution with an acyl group (hereinafter referred to as the degree of acyl substitution at the 3-position), and DS6 is the rate at which the hydrogen of the hydroxyl group at the 6-position in the glucose unit is substituted with an acyl group (hereinafter, Referred to as the degree of acyl substitution at the 6-position).

  The cellulose acylate may have only one type of acyl group, or may contain two or more types of acyl groups. When there are two or more types of acyl groups, one of them is preferably an acetyl group. The total number of substitutions of hydroxyl groups at the 2nd, 3rd and 6th positions by acetyl groups is DSA, and the total number of substitutions of the 2nd, 3rd and 6th hydroxyl groups by acyl groups other than acetyl groups When DSB is DSB, the value of DSA + DSB is preferably 2.22 to 2.90, and more preferably 2.40 to 2.88. The DSB is preferably 0.30 or more, particularly preferably 0.7 or more. Further, 20% or more of DSB is preferably a substituent at the 6-position hydroxyl group, more preferably 25% or more, further preferably 30% or more, and particularly preferably 33% or more. Further, the DSA + DSB value at the 6-position of the cellulose acylate is preferably 0.75 or more, more preferably 0.80 or more, and particularly preferably 0.85 or more. By using these cellulose acylates, an excellent soluble cellulose acylate solution can be prepared. The cellulose acylate may be obtained from either one of linter cotton or pulp cotton, or may be a mixture of both, but is preferably obtained from linter cotton.

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

  Solvents for dissolving cellulose acylate include aromatic hydrocarbons (eg benzene, toluene, etc.), halogenated hydrocarbons (eg dichloromethane, chloroform, 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 above halogenated hydrocarbons, halogenated hydrocarbons having 1 to 7 carbon atoms and dichloromethane are preferably used. From the viewpoints of physical properties such as solubility of cellulose acylate, peelability from cast film support, mechanical strength of the film, and optical properties, one or more alcohols having 1 to 5 carbon atoms in addition to dichloromethane It is preferable to mix several types. The content of the alcohol is preferably 2% by mass or more and 25% by mass or less, and more preferably 5% by mass or more and 20% by mass or less with respect to the entire solvent. Examples of the alcohol include methanol, ethanol, n-propanol, isopropanol, and n-butanol, but methanol, ethanol, n-butanol, or a mixture thereof is preferably used.

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

  The details of cellulose acylate are described in paragraphs [0140] to [0195] of JP-A-2005-104148. These descriptions can be applied 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]. These descriptions can be applied to the present invention.

The optical properties of the cellulose acylate film of the present invention are as follows. Re retardation values and Rth retardation values represented by the following formulas (IV) and (V) are the following formulas (VI) and (VII), respectively. It is preferable to satisfy.
(IV): Re (λ) = (nx−ny) × d
(V): Rth (λ) = {(nx + ny) / 2−nz} × d
(VI): 46 nm ≦ Re (630) ≦ 200 nm
(VII): 70 nm ≦ Rth (630) ≦ 350 nm
Re (λ) in the formula (IV) is the front retardation value (unit: nm) at the wavelength λnm, and Rth (λ) in the formula (V) is the retardation value in the film thickness direction at the wavelength λnm ( Unit; nm). Also, nx is the refractive index in the slow axis direction in the film plane, ny is the refractive index in the fast axis direction in the film plane, nz is the refractive index in the film thickness direction, and d is the film refractive index. Is the thickness. More preferably, the following formulas (VIII) and (IX) are satisfied.
(VIII): 46 nm ≦ Re (630) ≦ 100 nm
(IX): 180 nm ≦ Rth (630) ≦ 350 nm

The optical property values of Re and Rth change with changes in humidity and mass over time at high temperatures, but the smaller the changes in the values of Re and Rth, the better. In order to reduce the change of the optical property value due to humidity, the film is made with cellulose acylate having a high degree of substitution at the 6-position acyl and various hydrophobic additives (plasticizer, retardation control agent, ultraviolet absorber, etc.). Reduce moisture permeability and equilibrium moisture content. The moisture permeability is preferably 400 g or more and 2300 g or less per square meter at 60 ° C. and 95% RH for 24 hours, and the equilibrium moisture content is preferably 3.4% or less at 25 ° C. and 80% RH. . In addition, when the humidity at 25 ° C. is changed from 10% RH to 80% RH, the amount of change in optical characteristics is preferably 12 nm or less in Re value and 32 nm or less in Rth value. The amount of the hydrophobic additive is preferably from 10% to 30%, more preferably from 12% to 25%, particularly preferably from 14.5% to 20. 0% or less. Further, when the additive has volatility or decomposability, a change in the mass or dimensional change of the film occurs, resulting in a change in optical characteristics. Therefore, the mass change amount is preferably 5% or less after 48 hours at 80 ° C. and 90% RH, and the dimensional change amount is 5% or less after 24 hours at 60 ° C. and 95% RH. It is preferable that Even if there is a small dimensional change or mass change, if the photoelastic coefficient of the film is small, the amount of change in optical characteristics is small. Therefore, the photoelastic coefficient of the film is preferably 50 × 10 ⁻¹³ cm ² / dyne or less.

  In FIG. 1, the flow of the manufacturing process of the cellulose acylate film in this invention is shown. The film production process of the present invention includes a dope production process 12, a casting process 14, a peeling process 16, and a drying process 18.

  In the dope manufacturing step 12, a dope 13 that is a raw material for the cellulose acylate film is manufactured. A cellulose acylate solution prepared by sequentially mixing a solvent, cellulose acylate, which is the main component of the film, and an additive is filtered through a filtration device having a metal filter to obtain a dope 13.

  In the casting step 14, the casting film 15 is formed by casting the dope 13 on a support. After the cast film 15 has self-supporting properties, it is continuously peeled off from the support to form a wet film 17 containing a solvent. Subsequently, in the drying step 18, the solvent is evaporated from the wet film 17 to obtain a cellulose acylate film (hereinafter referred to as a film) 19. The drying step 18 includes first and second drying steps 18a and 18b for drying the wet film under different conditions. The drying conditions in the first and second drying steps include temperature, humidity, presence / absence of blowing, blowing conditions, etc. for each area.

  FIG. 2 shows a dope production line 20 for performing the dope production process 12. However, the manufacturing method of the dope 13 that can be used in the present invention is not limited to the form shown in FIG. The dope production line 20 includes a solvent tank 21, an additive tank 22, a hopper 23, a dissolution tank 24, a filtration device 25, and a stock tank 26. These various members constituting the dope production line 20 are connected to each other by a plurality of pipes.

  Various materials constituting the dope 13 are supplied to the solvent tank 21, the additive tank 22, and the hopper 23, respectively. The solvent stored in the solvent tank 21 dissolves cellulose acylate. As this solvent, for example, a mixed solvent in which dichloromethane is used as a main solvent and alcohols are mixed therewith is used. The additive tank 22 stores additives for imparting various functions to the film. Examples of such additives include plasticizers, retardation control agents, ultraviolet absorbers (for example, benzotriazole compounds), matting agents (for example, silica particles), deterioration inhibitors, optical anisotropy control agents, and dyes. And a release agent, which are appropriately selected according to the purpose. The hopper 23 is supplied with cellulose acylate which is the main raw material of the film.

  When the additive is liquid at room temperature, it can be fed into the dissolution tank 24 in a liquid state. Moreover, when the said additive is solid, it can also send in to the dissolution tank 24 using a hopper. In addition, when using a plurality of types of additives, a solution in which a plurality of types of additives are dissolved may be placed in the additive tank 22, and the valve 31 may be appropriately adjusted and sent out. Depending on the type, a plurality of additive tanks containing a solution in which these additives are dissolved are prepared, and the various additive tanks and the dissolution tank 24 are connected by a pipe provided with a valve. It can also be fed by adjusting the valve.

  The order in which the solvent, additive and cellulose acylate are mixed is not particularly limited. In the present embodiment, the solvent, the additive, and the cellulose acylate are fed into the dissolution tank 24 in this order and mixed. However, as other methods, for example, a predetermined amount of cellulose acylate is dissolved. After feeding into the tank 24, a predetermined amount of solvent and additive can be sent in to produce a cellulose acylate solution, or a mixed solution in which a solvent and an additive are mixed in advance is prepared. The rate may be mixed. Moreover, you may add a solvent to what mixed the additive in the cellulose acylate.

  The dissolution tank 24 is provided with a jacket 32 disposed on the outer periphery of the dissolution tank 24, a first stirring blade 34 rotated by a motor 33, and a second stirring blade 36 rotated by a motor 35. The first stirring blade 34 is preferably an anchor blade, and the second stirring blade 36 is preferably a dissolver type eccentric stirring machine. By attaching the jacket 32, a flow path through which the heat transfer medium flows is formed. The internal temperature of the dissolution tank 13 is adjusted by flowing a heat transfer medium whose temperature is adjusted in this flow path. At this time, it is preferable to adjust the temperature in the dissolution tank 13 in the range of −10 ° C. to 55 ° C.

  The heating device 41 preferably uses a jacketed pipe and has a function of pressurizing the swelling liquid 37. The heating device 41 is not particularly limited as long as it can maintain the swelling liquid 37 at a predetermined temperature. Thus, the cellulose acylate solution in which the cellulose acylate is sufficiently dissolved in the solvent can be produced by holding the swelling liquid 37 under heating or pressure heating conditions. At this time, the temperature of the swelling liquid 37 is preferably 0 ° C. or higher and 97 ° C. or lower. In addition, the cooling solution method which melt | dissolves a cellulose acylate in a solvent can also be implemented by cooling the swelling liquid 37 to the temperature of -150 degreeC or more and -10 degrees C or less. When such a heating dissolution method or a cooling dissolution method is appropriately selected and performed, the cellulose acylate can be sufficiently dissolved in the solvent. Further, a temperature controller 43 for bringing the cellulose acylate solution to substantially room temperature is provided downstream of the heating device 41.

  The filtration device 25 has a metal filter, and by passing the cellulose acylate solution therethrough, foreign substances such as additives having a large particle diameter, cellulose acylate, or impurities can be removed. Regarding the metal filter, the material and the hole diameter thereof are not particularly limited, but the average hole diameter is preferably 100 μm or less.

  The stock tank 26 has a stirring blade 47 interlocked with a motor 46, and the stirring blade 47 is rotated to stir the dope 13 to maintain a state where various materials are uniformly mixed. In addition, it is preferable that the dope 13 performs a bubble removal operation. In this defoaming method, any known method can be applied, and the place of implementation is not particularly limited.

  A method for manufacturing the dope 13 by the dope manufacturing line 20 will be described. First, the solvent is sent from the solvent tank 21 to the dissolution tank 24. At this time, the amount of the solvent is adjusted by the valve 30. Similarly, the valve 31 is adjusted to feed the additive from the additive tank 22 and the cellulose acylate from the hopper 23 to the dissolution tank 24. In the dissolution tank 24, the motor 33 or the motor 35 is selected as appropriate, and the first stirring blade 34 and the second stirring blade 36 are rotated to produce the swelling liquid 37 in which cellulose acylate is swollen in the solvent. Next, the swelling liquid 37 is sent to the heating device 41 using the pump 40. The dope 13 is manufactured by opening the valve 44 and sending the cellulose acylate solution, which has been brought to substantially room temperature by the temperature controller 43, to the filtration device 25 and filtering. The dope 13 obtained in this way is sent to the stock tank 26 by the valve 45 and stored therein.

  In addition, about the raw material in the solution film forming method which obtains a cellulose acylate film, the raw material, the dissolution method and addition method of an additive, the filtration method, and the manufacturing methods of dopes, such as defoaming, [0517] of Unexamined-Japanese-Patent No. 2005-104148 It is described in detail from paragraph to [0616] paragraph. These descriptions can be applied to the present invention.

  FIG. 3 shows a film production line 50. The film production line 50 includes a casting chamber 51, a peeling roller 52, a crossing portion 53, a tenter dryer 54, a drying chamber 55, and a winding chamber 56. However, the present invention is not limited to the form shown in FIG.

The casting chamber 51 includes a casting die 60, a pair of rotating rollers 61 and 62, a casting band 63, a heat transfer medium circulation device 64, a temperature control facility 65, a recovery device 66, and a decompression chamber 67. The air supply ducts 68 to 70 are provided. The material of the casting die 60 is preferably a duplex stainless steel, and its thermal expansion coefficient is preferably 2 × 10 ⁻⁵ (° C. ⁻¹ ) or less. Further, the finishing accuracy of the liquid contact surface, that is, the surface in contact with the dope is 1 μm or less in terms of surface roughness, the straightness is 1 μm / m or less in any direction, and the slit clearance is 0. A casting die that can be in the range of 5 mm to 3.5 mm is preferred. When such a casting die 60 is used, a film having more excellent flatness can be obtained. R (chamfer radius) at the corner of the liquid contact part at the lip end of the casting die 60 is 50 μm or less over the entire width of the slit. The shear rate in the casting die 60 is preferably adjusted to be 1 (1 / second) or more and 5000 (1 / second) or less.

  The width of the casting die 60 is not particularly limited, but is preferably about 1.0 to 2.0 times the width of the film as the final product. Further, the casting die 60 is preferably a coat hanger type casting die, and thickness adjusting bolts (heat bolts) are provided at predetermined intervals, and an automatic thickness adjusting mechanism using heat bolts is attached. preferable. The heat bolt sets a profile according to the amount of liquid delivered by a pump (for example, a high-precision gear pump) 48 according to a preset program, but a thickness gauge (for example, an infrared thickness gauge) is provided in the film production line 50. The feedback control may be performed by an adjustment program based on the profile. The thickness difference between any two points excluding the casting edge is preferably adjusted to within 1 μm, the largest difference in the minimum thickness in the width direction is adjusted to 3 μm or less, and the thickness accuracy is preferably adjusted to ± 1.5 μm or less. .

It is more preferable that a cured film is formed at the lip end of the casting die 60. The method for forming the cured film is not particularly limited, and methods such as ceramic coating, hard chrome plating, and nitriding treatment may be used. However, when ceramic is used as the cured film, it is excellent in machinability and corrosion resistance, has a low porosity, is not brittle, has good adhesion with the casting die 71, and has poor adhesion with the dope 13. Is preferred. Specific examples include tungsten carbide (WC), Al ₂ O ₃ , TiN, Cr ₂ O _{3 and the} like, but it is particularly preferable to use WC. The WC coating can be performed by a thermal spraying method.

  A solvent supply device (not shown) is preferably attached to the slit end of the casting die 60 in order to prevent the cast dope 13 from locally drying and solidifying. More preferably, a solvent that solubilizes the dope 13 (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 a gas-liquid solution at the end of the casting bead and the slit. To supply the interface. At this time, it is preferable to use a pump having a pulsation rate of 5% or less.

  The casting band 63 is stretched over rotating rollers 61 and 62 provided downstream of the casting die 60, and travels endlessly when the rotating rollers 61 and 62 are rotated by a driving device (not shown). . The moving speed of the casting band 63, that is, the casting speed is preferably 10 m / min or more and 200 m / min or less. A heat transfer medium circulation device 64 is attached to the rotating rollers 61 and 62. In addition, a heat transfer medium flow path (not shown) is formed inside the rotation rollers 61 and 62, and the heat transfer medium maintained at a predetermined temperature by the heat transfer medium circulation device 64 is circulated to rotate. By maintaining the rollers 61 and 62 at a predetermined temperature, the surface temperature of the casting band 63 is adjusted to a predetermined value. At this time, the surface temperature of the casting band 63 is preferably −20 ° C. or higher and 40 ° C. or lower.

  The shape and material of the casting band 63 are not particularly limited, but the width of the casting band 63 should be 1.1 to 3.0 times the casting width of the dope 13. Preferably, the length is 10 m or more and 200 m or less, the thickness is 0.3 mm or more and 10 mm or less, and the surface is polished so that the surface roughness is 0.05 μm or less. More preferably, the material is stainless steel and is made of SUS316 so as to have sufficient corrosion resistance and strength. Further, it is preferable to use a non-uniform thickness of the entire casting band 63 of 0.5% or less.

The tension generated in the casting band 63 when the rotating rollers 61 and 62 are driven is preferably adjusted to be 1.5 × 10 ⁴ kg / m. Further, the relative speed difference between the rotary rollers 61 and 62 and the casting band 63 is adjusted to be 0.01 m / min or less. The speed variation of the casting band 63 is preferably 0.5% or less, and the meandering in the width direction when the casting band 63 rotates once is preferably 1.5 mm or less. In order to control this meandering, it is more preferable to provide a detector (not shown) for detecting both ends of the casting band 63 and perform feedback control based on the measured value. Furthermore, it is preferable to adjust the vertical position fluctuation accompanying the rotation of the rotary roller 61 directly below the casting die 60 to 200 μm or less.

The rotating rollers 61 and 62 can also be used directly as a support. At this time, it is preferable to rotate with high accuracy so that the rotation unevenness is 0.2% or less, and the average roughness of the surfaces of the rotary rollers 61 and 62 to be used is 0.01 μm or less. Therefore, chrome plating is performed to provide sufficient hardness and durability. It should be noted that surface defects of the support (rotating rollers 61 and 62 and casting band 63) must be minimized. Specifically, it is preferable that there are no pinholes of 30 μm or more, pinholes of 10 μm or more and less than 30 μm are 1 / m ² or less, and pinholes of less than 10 μm are 2 / m ² or less.

  The casting chamber 51 is provided with a temperature control facility 65, thereby maintaining the internal temperature at a predetermined value. The internal temperature of the casting chamber 51 is preferably -10 ° C or higher and 57 ° C or lower. Further, a condenser (condenser) 71 is provided in order to condense and recover the organic solvent that volatilizes from the casting film 15 and floats inside the casting chamber 51. The condensed and liquefied organic solvent is condensed by the condenser 71, recovered by the recovery device 66, regenerated as a dope preparation solvent, and reused. In this way, when the recovered solvent is used as the dope adjusting solvent, the raw material cost can be reduced, and as a result, the production cost can be reduced.

  The temperature of the dope 13 at the time of casting is preferably −10 ° C. or more and 57 ° C. or less. Further, it is preferable that the decompression chamber 67 is provided in the vicinity of the back surface of the dope 13 to be cast and cast while adjusting to a desired pressure. The decompression chamber 67 is not particularly limited, but preferably includes a jacket (not shown) for maintaining a predetermined temperature, and the temperature is maintained in a range of 10 ° C. or more and 50 ° C. or less. It is preferable.

  The casting film 15 moves as the casting band 63 travels. At this time, dry air is blown from the air supply ducts 68 to 70 to evaporate the solvent in the casting film 15. The mounting positions of the air supply ducts 68 to 70 are not particularly limited. For example, as in the present embodiment, the air supply duct 68 is disposed on the upper upstream side of the casting band 63 and the air supply duct 69 is disposed on the downstream side. Then, an air supply duct 70 may be provided below the casting band 63 to blow dry air. In this way, when the drying air is blown from the lower part in addition to the upper part of the casting band 63, the casting film 15 can be dried more effectively. In addition, in order to suppress the surface shape fluctuation | variation of the film surface by a dry wind being sprayed on the cast film 15 immediately after formation, it is preferable that the wind shield device (not shown) is provided. In FIG. 3, the casting band 63 is used as a support for the casting film 15, but the present invention is not limited to this form, and for example, a casting drum can be used. At this time, the surface temperature of the casting drum is preferably -20 ° C or higher and 40 ° C or lower.

  The crossing part 53 includes a plurality of pass rollers 90 and a blower (not shown). The wet film 17 is dried by blowing dry air from a blower. At this time, the temperature of the drying air is preferably 20 ° C. or higher and 250 ° C. or lower. In the crossing portion 53, it is also possible to give the wet film 17 a draw by making the rotational speed of the downstream pass roller faster than the rotational speed of the upstream pass roller.

  The tenter dryer 54 has a gripping member (for example, a clip) that grips both end portions of the wet film 17 and a compartment having different temperatures. In the tenter dryer 54, a first drying process is performed in which the solvent is evaporated and dried while the both end portions of the wet film 17 are gripped and transported by the gripping member. The tenter dryer 54 is preferably provided with compartments having different temperatures and dried while adjusting the drying conditions. In at least one of the transfer section 53 and the tenter dryer 54, it is preferable to stretch the wet film 17 in a range of 0.5% to 300% in at least one of the casting direction and the width direction. As described above, when the wet film 17 is stretched in the width direction, it is preferably relaxed thereafter.

  The drying chamber 55 for performing the second drying step is provided with a plurality of support rollers 82 for supporting the wet film 17. The support roller 82 is rotatably provided in the conveyance path. Some of the plurality of support rollers 82 are provided with a drive controller for rotationally driving the wet film 17. The means for transporting the wet film 17 in the drying chamber 55 is not limited to the support roller 82 provided with a drive controller, and may be other than that or in addition. The wet film 17 is dried by the evaporation of the solvent while being conveyed in the drying chamber 55. Although the internal temperature of the drying chamber 55 is not specifically limited, It is preferable that it is the range of 50 to 180 degreeC. In addition, an adsorption recovery device 83 is attached to the drying chamber 55, and thereby volatile components are adsorbed and recovered. The air from which the volatile component solvent and the like have been removed is blown again into the drying chamber 55 as drying air. The drying chamber 55 is more preferably divided into a plurality of compartments in order to change the drying temperature. It is preferable that a preliminary drying chamber (not shown) is provided between the ear opener 80 and the drying chamber 55 to perform preliminary drying of the wet film 17. When the wet film 17 is fed into the pre-drying chamber in this way, the rapid temperature rise of the wet film 17 can be suppressed, and the accompanying change in the shape of the film can be prevented.

  When the wet film 17 is dried in the drying chamber 55, the tension in the longitudinal direction (hereinafter referred to as the conveying length) is 0.5 × 9.8 N / m or more and 10 × 9.8 N / m or less. In this way, the film 19 is conveyed. The unit of tension “N / m” here means a force (unit N) applied per 1 m width of the wet film 17. Therefore, for example, in order to apply a tension of 0.5 × 9.8 N / m in the longitudinal direction when the width of the wet film 17 is 1.5 m, the wet film 17 is 1.5 × 0.5 × 9.8. The tensile force (N) is applied. The tension in the longitudinal direction is more preferably 1 × 9.8 Nm to 9 × 0.8 N / m, and particularly preferably 2 × 9.8 N / m to 8 × 9.8 N / m. When the tension in the longitudinal direction is larger than 10 × 9.8 N / m, the transporting force is too strong, so that the wet film 17 is easily deformed in the longitudinal direction or the width direction. On the other hand, when the tension in the longitudinal direction is smaller than 0.5 × 9.8 N / m, the conveying force is too weak and wrinkles and wrinkles occur, so that the optical characteristics of the wet film 17 are deteriorated. End up. The tension (tension) as described above is measured by installing a tension pickup device (not shown) using a strain gauge method between the support rollers 82. In addition, tension | tensile_strength can be adjusted with the dancer (not shown) which can carry out load control with an air cylinder. However, the installation location of the tension pickup device is not particularly limited.

  The support roller 82 inside the drying chamber 55 has a length in the longitudinal direction larger than the width of the wet film 17 and has a symmetrical shape with respect to the central portion in the longitudinal direction. The material and form are not particularly limited.

  FIG. 4 shows a schematic diagram of an example of the support roller 82. At least one of the plurality of support rollers 82 preferably has a cylindrical structure or a columnar structure having different diameters in the longitudinal direction. When the maximum outer diameter in the range of supporting the wet film 17 is D1 and the minimum outer diameter is d1, d1 / D1 satisfies the condition of 0.9 <d1 / D1 <0.99, and the width of the wet film 17 It is preferably a drum-shaped roller whose outer diameter increases in the direction, that is, the center in the longitudinal direction of the support roller 82, and more preferably a cone-cave roller. d1 / D1 is more preferably 0.91 <d1 / D1 <0.98. However, when the value of d1 / D1 is larger than 0.99, the wet film 17 cannot be effectively wound, so that a shear occurs between the wet film 17 and the roller. The shape of the wet film 17 is deformed. On the other hand, when the value of d1 / D1 is less than 0.9, since the peripheral speed when rotating is greatly different between the central portion and both end portions having a larger diameter than the central portion, the central portion of the wet film 17 In some cases, wrinkles that are kinked from both ends to the opposite ends, and the conveyance is not performed properly (conveyance failure) may occur. Further, in the drying chamber 55, since the amount of solvent in the film is larger as it is upstream, the upstream side of the plurality of support rollers 82 is more effectively a cone cave roller in the width direction. It can be dried while suppressing the shrinkage. Therefore, it is preferable that at least one of the plurality of support rollers 82 is a cone cave roller.

The solvent content of the wet film 17 at the entrance of the drying chamber 55, that is, at the start of the second drying process, is preferably 5% by weight or more and 20% by weight or less based on the dry weight. More preferably, it is 6 to 18% by weight, and particularly preferably 7 to 15% by weight. When the solvent content of the wet film 17 is more than 20% by weight, the amount of solvent volatilized in the drying chamber 55 becomes large, so that the wet film 17 is easily contracted and deformed. On the other hand, when the solvent content of the wet film 17 is less than 5% by weight, the wet film 17 may be deteriorated in the drying chamber 55. The solvent content of the wet film 17 is a value represented by the following formula (X).
(X) Solvent content (% by weight) = (A−B) × 100 / A
In the formula (X), A is the weight of the wet film 17 at the time of sampling, and B is the weight (g) after the sampled wet film 17 is dried with hot air at 110 ° C. for 1 hour.

  The film 19 exiting the drying chamber is conveyed to the cooling chamber 84, and then the charged voltage is within a predetermined range (for example, -3 kV or more and +3 kV or less by a forced neutralization device (static elimination bar) 85 provided downstream of the cooling chamber 84. ). However, the installation location of this forced static elimination apparatus 85 is not limited to this embodiment. Further, it is preferable to provide a knurling roller 86 and emboss the both edges of the film 19 to give the knurling. In addition, it is preferable that the unevenness | corrugation of the knurled location is 1 micrometer or more and 200 micrometers or less.

  A method for producing the cellulose acylate film 19 using the film production line 50 will be described. First, the dope 13 is cast from a casting die 60 onto a casting band 63 that is continuously supported by rotating rollers 61 and 62 and travels endlessly, thereby forming a casting film 15. After the casting film 15 has self-supporting properties, the casting film 15 is continuously peeled off from the casting band 63 while being supported by the peeling roller 52, thereby forming the wet film 17. Thereafter, the wet film 17 is sent to the crossover portion 53 and is dried until it reaches a predetermined solvent amount while being transported while being supported by a plurality of rollers, and then sent into the tenter dryer 54.

  The film 19 is sent to the drying chamber 55 which is the second drying step and sufficiently dried. In addition, an edge cutting device 80 is provided between the tenter dryer 54 and the drying chamber 55 to cut both ends of the film 19. Both ends of the cut film 19 are sent to a crusher 81 by a cutter blower (not shown) and crushed there to become chips. This chip can be reused for dope preparation, and the production cost can be reduced. Although the process of cutting both edges of the film 19 can be omitted, it is preferable to carry out any of the processes from the casting process 14 to the winding process.

  The dried film 19 is conveyed to the cooling chamber 84 and cooled to approximately room temperature. A humidity control chamber (not shown) may be provided between the drying chamber 55 and the cooling chamber 84. By blowing air adjusted to a desired humidity and temperature to the film 19 in the humidity control chamber, curling on the film 19 and occurrence of winding failure during winding can be suppressed. it can.

  The film 19 is fed into the take-up chamber 56 and continuously taken up by a take-up roller 87 provided therein. At this time, it is preferable to wind with the press roller 88 while applying a desired tension. More preferably, the tension is gradually changed from the start to the end of winding. The film 19 to be wound is at least 100 m in the longitudinal direction (casting direction) and the width direction is preferably 600 mm or more, more preferably 1400 mm or more and 1800 mm or less. However, it is also effective when it is larger than 1800 mm.

  However, in the present invention, it is preferable that the ratio between the width of the wet film 17 immediately before the first drying step and the width of the film 19 immediately before being wound is a predetermined value. That is, in the first drying step, the width of the wet film 17 immediately after gripping both end portions is set to L1 (mm), and after the second drying step, the width of the film 19 immediately before being wound is set to L2. (Mm), L2 / L1 is preferably set to satisfy 1.1 ≦ L2 / L1 ≦ 1.5. More preferably, 1.1 ≦ L2 / L1 ≦ 1.4, and particularly preferably 1.1 ≦ L2 / L1 ≦ 1.3. Thus, the shrinkage | contraction at the time of winding can be prevented by suppressing the shrinkage | contraction rate of the film before and after the 1st and 2nd drying as much as possible. When L2 / L1 is less than 1.1, a sufficient retardation value may not be expressed. Moreover, when L2 / L1 is larger than 1.5, since extending | stretching to the width direction will be too strong, there exists a possibility that a wrinkle, a twist, etc. may arise. During the stretching or relaxation, the film drying temperature is preferably maintained substantially constant in the range of 50 ° C. to 180 ° C.

  In this embodiment, an example in which a corn cave roller is used as the support roller 82 in the drying chamber 55 has been described. However, the length of the support roller 82 in the longitudinal direction is larger than the width of the film 19 and the width direction It has different diameters and is not particularly limited as long as it has a symmetrical shape with respect to the center in the longitudinal direction. For example, a support roller 100 having a step as shown in FIG. 5 may be used. The maximum outer diameter and the minimum outer diameter of the support roller 100 are denoted by the same reference numerals as those in FIG. The support roller 100 has support portions 100a that support side edges of the film 19 formed on both edges, and a recess 100b that does not contact the film is formed between the support portions 100a. The outer diameter of the support portion 100 a and the outer diameter of the recess portion 100 b are constant in the longitudinal direction of the support roller 100. The length L4 of the concave portion 100b in the longitudinal direction of the support roller 100, that is, the length between both the support portions 100a is 10 mm or more and 100 mm or less, and the step L5 between the both support portions 100a and the recess 100b is 0.1 mm or more and 20 mm or less. It is preferable that When such a support roller 100 is used, tension acts in the width direction of the film 19, so that the film 19 can be conveyed while suppressing the occurrence of contraction in the width direction, and the contact area between the film 19 and the support roller 100 is also increased. Since it is small, generation | occurrence | production of the planar defect by friction can be suppressed.

  From casting die, 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, etc. This is described in detail in paragraphs [0617] to [0889] of Kai 2005-104148. These descriptions can be applied 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 descriptions can be applied 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 this cellulose acylate film as a base film as a functional material provided with other functional layers. 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 layer preferably contains 0.1 mg / m ² or more and 1000 mg / m ² or less of at least one surfactant. Further, the functional layers preferably contain at least one sort of plasticizers in the 0.1 mg / ^{m 2} or more 1000 mg / ^{m 2} or less. Furthermore, it is preferable that the functional layer contains at least one kind of matting agent in a range of 0.1 mg / m ^{2 to} 1000 mg / m ² . Furthermore, it is preferable that the functional layer contains 1 mg / m ² or more and 1000 mg / m ² or less of at least one antistatic agent.

  A method for imparting a surface-treated functional layer to a cellulose acylate film in order to realize various functions and properties is described in detail in paragraphs [0890] to [1087] of JP-A-2005-104148. It is included. These descriptions can be applied 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 may be used. 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 description can be applied to the present invention. The application also describes an optically anisotropic layer and a cellulose acylate film provided with antireflection and antiglare functions. Furthermore, a use as an optical compensation film having a biaxial cellulose acylate film imparted with appropriate optical performance is also described. This can also be used as a polarizing plate protective film. Details are described in paragraphs [1088] to [1265] of JP-A-2005-104148. These descriptions can be applied to the present invention.

  Next, examples of the present invention will be described. The formulation for preparing the dope 13 used for film production is shown below.

[composition]
Cellulose triacetate (substitution degree 2.84, viscosity average polymerization degree 306, water content 0.2 mass%, viscosity 6 mass% 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 parts 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 mass 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 mass%, 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.

  A dope 13 was prepared using a dope production line 20 shown in FIG. The plurality of solvents were mixed and stirred well in a 4000 L stainless steel dissolution tank 24 having stirring blades to obtain a mixed solvent. In addition, as each raw material of a solvent, that whose water content is 0.5 mass% or less was used. Next, TAC flaky powder was gradually added from the hopper 23. The TAC powder is put into the dissolution tank 24 and is initially stirred at a peripheral speed of 5 m / second using a dissolver type second stirring blade 36 and an anchor blade as the first stirring blade 34 on the central axis. The dispersion was performed for 30 minutes under the condition of stirring at 1 m / second. The temperature at the start of dispersion was 25 ° C., and the final temperature reached 48 ° C. Furthermore, the amount of the additive solution prepared in advance was adjusted from the additive tank 22 by the valve 31 so that the total amount became 2000 kg. After finishing the dispersion of the additive solution, the high speed stirring was stopped. And the peripheral speed of the 1st stirring blade 34 was made into 0.5 m / sec, and also it stirred for 100 minutes, the TAC flakes were swollen and the swelling liquid 37 was obtained. Until the end of the swelling, the inside of the dissolution tank 24 was pressurized to 0.12 MPa with nitrogen gas. At this time, the inside of the dissolution tank 24 was kept in a state of no problem in terms of explosion prevention because the oxygen concentration was less than 2 vol%. The water content in the swelling liquid 37 was 0.3% by mass.

  The swelling liquid 37 is sent from the dissolution tank 24 to the heating device 41 by the pump 40, and the swelling liquid 37 is heated to 50 ° C. and then heated to 90 ° C. under a pressure of 2 MPa to completely dissolve the cellulose acylate solution. Got. The heating time at this time was 15 minutes. Next, after the temperature of the cellulose acylate solution was lowered to 36 ° C. by the temperature controller 43, the cellulose acylate solution was passed through a filtration device 25 having a filter medium having a nominal pore diameter of 8 μm to obtain a dope (hereinafter referred to as “pre-concentration dope”). At this time, the primary pressure in the filtration device 25 was 1.5 MPa, and the secondary pressure was 1.2 MPa. Since the filter provided in the filtration device 25 is exposed to high temperatures, use a product made of Hastelloy (trade name) alloy having excellent corrosion resistance and a jacket for circulating a heat transfer medium for heat insulation and heating. did.

The pre-concentration dope thus obtained was flash-evaporated in a flash device (not shown) at 80 ° C. and normal pressure. At this time, the evaporated solvent was recovered by a condenser. The solid content concentration of the dope 13 after the flash was 21.8% by mass. The condensed solvent was recovered by a recovery device (not shown) to be reused as a dope preparation solvent, regenerated by a regeneration device (not shown), and then sent to the solvent tank 21. Further, 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 flashed at a peripheral speed of 0.5 m / sec was stirred and defoamed. The temperature of the dope in this flash tank was 25 ° C., and the average residence time of the dope in the tank was 50 minutes. The dope 13 was sampled and the shear viscosity measured at 25 ° C. was 450 Pa · s at a shear rate of 10 (second ⁻¹ ).

  Next, foam was removed by irradiating the dope 13 with weak ultrasonic waves, and then the temperature of the dope 13 was adjusted to 36 ° C., and the solution was fed into a 2000 L stainless steel stock tank 26 and stored. In the stock tank 26, the agitation blade 47 was used, and an anchor blade provided on the central shaft was used, and the agitation was always performed at a peripheral speed of 0.3 m / sec. In addition, when preparing the dope 13 from the dope before concentration, no problem such as corrosion occurred at all in the wetted part of the dope.

  The film 19 was manufactured using the film manufacturing line 50 shown in FIG. The dope 13 in the stock tank 26 was sent to the casting die 60. The casting die 60 was cast by adjusting the flow rate of the dope 13 at the discharge port of the casting die 60 so that the width of the casting die 60 was 1.8 m and the film thickness of the dried film was 80 μm. The casting width of the dope 13 from the discharge port of the casting die 60 was 1700 mm. Further, when supplying the dope 13 from the casting die 60, the temperature of the dope 13 was adjusted to 36 ° C.

  The casting die 60 and the piping were all kept at 36 ° C. during film formation. As the casting die 60, a coat hanger type die was used. The casting die 60 was provided with thickness adjusting bolts at a pitch of 20 mm and equipped with an automatic thickness adjusting mechanism using a heat bolt. In the film excluding the end portion of 20 mm, the thickness difference between two arbitrary points separated by 50 mm 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.

  Further, a decompression chamber 67 for decompressing this portion was installed on the primary side of the casting die 60. The degree of decompression of the decompression chamber 67 is adjusted so that a pressure difference of 1 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 to 50 mm. The decompression chamber 67 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. Openings were provided at both ends of the die discharge port of the casting die 60, and edge suction devices (not shown) for adjusting the disturbance of both edges of the casting bead were attached. The edge suction device can adjust the edge suction air volume so as to be in the range of 1 to 100 L / min.

The material of the casting die 60 was a precipitation hardening type stainless steel having a thermal expansion coefficient of 2 × 10 ⁻⁵ (° C. ⁻¹ ) or less. The finishing accuracy of the liquid contact surface of the casting die 60 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. In addition, a WC (tungsten carbide) coating is applied to the lip tip of the casting die 60 by a thermal spraying method to provide a cured film, and the corner R of the wetted part at the lip tip extends over the entire width of the slit. What was processed so that it might become 50 micrometers or less was used. The shear rate of the dope 13 in the casting die 60 was in the range of 1 to 5000 (1 / second).

  In order to prevent the outflowing dope 13 from being locally dried and solidified, the mixed solvent A for dissolving the dope 13 (86.5 parts by mass of dichloromethane, acetone 13 parts by mass and 0.5 parts by mass of 1-butanol) were respectively supplied to the interface between the both ends of the casting bead and the discharge port at 0.5 ml / min. At this time, the pulsation rate of the pump supplying the mixed solvent A was 5% or less. Further, the pressure on the back side of the casting bead was reduced by 150 Pa from the front side by the decompression chamber 67. In this example, the edge suction air volume of the edge suction device was appropriately adjusted to be in the range of 30 to 40 L / min.

The dope 13 was cast from the casting die 60 on a support provided in the casting chamber 51 having wind pressure fluctuation suppressing means (not shown). As the 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 63. The material of the casting band 63 is made of SUS316, and a material that is polished so that the thickness is 1.5 mm, the surface roughness is 0.05 μm or less, and the overall thickness unevenness is 0.5% or less is used. The casting band 60 was driven by two rotating rollers 61 and 62. At this time, the tension in the conveyance direction of the casting band 60 is 1.5 × 10 ⁵ N / m ² , and the relative speed difference between the casting band 63 and the rotary rollers 61 and 62 is 0.01 m / min or less. Each was adjusted as follows. The speed fluctuation of the casting band 63 was set to 0.5% or less. Further, both end positions of the casting band 63 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 63 immediately below the casting die 60 was set to 200 μm or less.

As the rotating rollers 61 and 62, those capable of feeding a heat transfer medium therein were used so that the temperature of the casting band 63 could be adjusted. A 5 ° C. heat transfer medium was passed through the rotating roller 61 on the casting die 60 side, and a 40 ° C. heat transfer medium was passed through the other rotating roller 62 for drying. The surface temperature of the center part of the casting band 63 immediately before casting was 15 ° C., and the temperature difference between both side ends was 6 ° C. or less. The casting band 63 preferably has no surface defects, has no pinholes of 30 μm or more, has no pinholes of 10 to 30 μm, 1 pin / m ² or less, and ² pinholes of less than 10 μm / It was used at m ² or less.

  The temperature of the casting chamber 51 was kept at 35 ° C. using the temperature control equipment 65. The casting film 15 formed from the dope 13 cast on the casting band 63 was dried by blowing 135 ° C. drying air in parallel to the casting film 15 from the air supply duct 68. Further, dry air of 140 ° C. and 65 ° C. was blown in order from the air supply duct 69 on the downstream side and the air supply duct 70 below the casting band 63. The saturation temperature of each drying wind was around -8 ° C. Note that the air was replaced with nitrogen gas, and the oxygen concentration in the dry atmosphere on the casting band 63 was maintained at 5 vol%. A condenser (condenser) 71 was provided in the casting chamber 51, the outlet temperature was set to −10 ° C., the solvent was condensed and recovered, and then recovered by the 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.

For 5 seconds from the start of casting, a wind shielding plate (not shown) is installed so that the dry air does not directly hit the casting bead and the casting film 15, and the static pressure fluctuation in the vicinity of the casting die 60 is ± 1 Pa. The following were suppressed. When the solvent ratio in the casting film 15 reached 50% by mass on the dry basis, the film was peeled off as the wet film 17 while being supported by the peeling roller 52 from the casting band 63. 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 63 in order to suppress stripping failure. It adjusted suitably so that it might become the range of. The surface temperature of the peeled wet film 17 was 15 ° C. At this time, the average drying rate on the casting band 63 was 60% by mass (dry weight reference solvent) / min. The wet film 17 was sent to the tenter dryer 54 through the roller of the crossing part 53. In the transfer part 53, a dry air of 40 ° C. was blown from the blower (not shown) to the wet film 17, and a tension of about 30 N was applied in the transport direction of the wet film 17.

  In the tenter dryer 54, the film 19 was dried by blowing dry air while being transported while fixing both side ends of the wet film 17 with clips. The clip was cooled by supplying a heat transfer medium at 20 ° C. The clip was conveyed by a chain. At this time, the speed fluctuation of the clip sprocket was 0.5% or less.

  The tenter dryer 54 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 conditions of the drying zone are adjusted so that the residual solvent amount in the film 19 is 7% by mass at the outlet of the tenter dryer 54, and the average drying speed is 120% by mass (dry weight reference solvent) / min. And dried. In the tenter dryer 54, when the width of the wet film 17 before stretching was 100%, the film was transported while stretching in the width direction so that the width after stretching was 103%. The stretch ratio (tenter-driven draw) from the peeling roller 52 to the entrance of the tenter dryer 54 was 102%. In the tenter dryer 54, the wet film 17 was dried until the volatile component amount was 12% by weight while holding both ends of the wet film 17 with the clip.

  The ratio of the length from the clip grip start position to the grip release position with respect to the length from the inlet to the outlet of the tenter dryer 54 was 90%. In the tenter dryer 54, a condenser (condenser) is provided for condensation recovery, the outlet temperature thereof is set to -8 ° C, and the evaporated solvent is condensed at a temperature of -10 ° C (liquefaction) and recovered. did. The condensed solvent was reused after adjusting the water content to 0.5% by mass or less. Note that the air in the tenter dryer 54 was replaced with nitrogen gas, and the oxygen concentration in the dry atmosphere was maintained at 5 vol%. Further, the film 19 was preheated in a predrying chamber (not shown) supplied with 100 ° C. drying air before being dried at a high temperature in the drying chamber 55.

Within 30 seconds from the outlet of the tenter dryer 54, both ends of the wet film 17 were cut by an NT-type cutter as an edge cutting device 50 by 50 mm width. The cut ends were sent to a crusher 81 by a cutter blower (not shown) and crushed into chips of about 80 mm ^{2 on} average. This chip was used again as a dope 13 raw material together with TAC flakes as a dope preparation raw material.

  The wet film 17 was dried at a high temperature in the drying chamber 55. The drying chamber 55 is divided into four sections, a plurality of support rollers 82 are arranged in the section, and drying air of 120 ° C., 130 ° C., 130 ° C., and 130 ° C. is blown into the compartment from the upstream side. (Not shown). In the drying chamber 55, a tension of 8 kg / m was applied in the conveying direction of the wet film 17, and the film was dried for about 10 minutes until the volatile content finally became 0.3% by mass. The plurality of support rollers 82 were arranged on the conveyance path so that the wrap angle (film wrapping central angle) was in the range of 90 to 180 degrees. The uppermost support roller 82 is a cone cave roller shown in FIG. This cone cave roller has a D1 of 100 mm, a d1 of 98 mm, a longitudinal length W of 1800 mm, and is made of aluminum and has a hard chrome plated surface. Film position fluctuations due to the rotation of the support roller 82 were all 50 μm or less. The roller deflection when the tension was 8 kg / m was selected to be 0.5 mm or less.

  The solvent gas contained in the drying air was adsorbed and recovered by the adsorption recovery device 82. At this time, activated carbon was used as the adsorbent, 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 mass% or less. The dry air contains plasticizers, UV absorbers, and other high-boiling substances in addition to the solvent gas, and these were removed by a cooler and a pre-adsorber that were cooled and removed, and were recycled and used. In addition, 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 mass%, and most of the remainder was collect | recovered by adsorption collection.

  The dried film 19 was conveyed to a first humidity control chamber (not shown). A drying air of 110 ° C. was supplied between the drying chamber 55 and the first humidity control chamber. The first humidity control chamber was supplied with air having a temperature of 50 ° C. and a dew point of 20 ° C. Then, the film 19 was conveyed to the 2nd humidity control chamber (not shown) which suppresses generation | occurrence | production of curl. In the second humidity control chamber, the film 19 was directly supplied with dry air of 90 ° C. and humidity of 70%.

  After the humidity-controlled film 19 was cooled to 30 ° C. or less in the cooling chamber 84, the charged voltage of the film 19 being conveyed was adjusted to be always in the range of −3 to +3 kV by the forced static eliminating device 85. Further, knurling was applied to both ends of the film 19 by a knurling roller 85. The knurling was embossed from one side of the film 19. At this time, the pressure applied by the knurling roller was set so that the width for knurling was 10 mm, and the height of the unevenness was 12 μm higher than the average thickness of the film 19 on average.

  Finally, the film 19 was conveyed to the take-up chamber 56 and taken up by a take-up roller 87 having a diameter of 169 mm. An ion wind neutralization device (not shown) is provided inside the winding chamber 56 to adjust the charged voltage of the film 19 to −1.5 to +1.5 kV, and the room temperature is 28 ° C. and the humidity is 70%. Held on. The temperature of the film 19 at the time of winding was 25 ° C., the water content was 1.4% by mass, and the residual solvent amount was 0.3% by mass. The product width of the film (thickness 80 μm) 19 thus obtained was 1475 mm, and the total winding length was 3940 m. At this time, the tension at the start and end of winding is adjusted to be 300 N / m and 200 N / m, respectively, and the variation width of winding deviation at the time of winding (sometimes referred to as oscillating width). Was set to ± 5 mm, and the winding shift period with respect to the winding roller 87 was set to 400 m. The pressing pressure of the press roller 88 against the winding roller 87 was set to 50 N / m. Moreover, the average drying rate was 20 mass% (dry weight reference solvent) / min throughout the whole process. L2 / L1 was set to 1.3.

[Evaluation of flatness]
The surface of the film 19 produced in this example was visually observed to observe the presence or absence of wrinkles and wrinkles.

The composition of the dope 13 of Example 1 was changed to the following.
[composition]
Cellulose triacetate (TAC) 100 parts by mass (acetyl group substitution degree 2.81 (acetylation degree 60.2%), Mw / Mn = 2.7, viscosity average polymerization degree 305, viscosity of 6% by mass in dichloromethane solution 350 mPa · s)
-Dichloromethane (first solvent) 430 parts by mass-Methanol (second solvent) 48 parts by mass-Plasticizer A 7.6 parts by mass-Plasticizer B 3.8 parts by mass The above-mentioned plasticizer A is triphenyl phosphate ( TPP), plasticizer B is biphenyl diphenyl phosphate (BDP).

  The additive liquid A was prepared with the retardation control agent shown in Chemical Formula 1, a part of the dope 13 and a solvent of dichloromethane: methanol = 9: 1 (mass ratio), and filtered.

  Furthermore, fine particles (trade name; Aerosil R972, Nippon Aerosil Co., Ltd.), a part of the dope 13 and a solvent of dichloromethane: methanol = 9: 1 (mass ratio) were mixed to make an additive liquid B. . In the additive liquid B, the following fine particles were dispersed by an attritor so that the volume average particle diameter was 0.7 μm. The additive liquid B after dispersion was filtered.

  The additive liquid B was mixed with the additive liquid A using an in-line mixer, and this mixed liquid was mixed with the dope 13 using an in-line mixer. In this way, a liquid having a matting agent content of 1% by mass and a retardation control agent of 6% by mass was obtained for casting when the film 19 was prepared. Other conditions are the same as those in the first embodiment.

  As a result of evaluating the flatness of the produced film 19 in both Examples 1 and 2, almost no wrinkles or wrinkles due to shrinkage could be confirmed. In Examples 1 and 2, the tenter dryer 54 was dried with the volatile component amount on a dry basis as a predetermined value. Then, the width of the wet film 17 immediately after gripping both end portions by the tenter dryer 54 is set to L1 (mm), the drying in the drying chamber 55 is finished, and the width of the film immediately before being wound is set to L2 ( mm), the value of L2 / L1 was set within a predetermined range. As a result, it is considered that the film 19 could be dried while suppressing shrinkage in the width direction.

  In addition, the most upstream support roller 82 in the drying chamber 55 was a cone-cave roller, and the wet film 17 was dried by adjusting the tension in the transport direction. Therefore, even if the wet film 17 is displaced in the width direction, the wet film 17 does not slide down due to its shape, and the contact area between the wet film 17 and the support roller 82 can be reduced, thereby suppressing the occurrence of wrinkles and wrinkles due to friction. I was able to. In addition, it has been found that when a corn cave roller is used, the stability (hereinafter referred to as conveyance stability) when the wet film 17 is conveyed can be improved as described above. From the above, it was confirmed that the film 19 can be produced by using the present invention while having excellent flatness with almost no wrinkles and wrinkles due to shrinkage and improved conveyance stability.

17 Wet film 19 Film 50 Film production line 54 Tenta dryer 55 Drying chamber 82 Support roller

Claims (5)

A polymer solution containing a polymer and a solvent is cast on a support to form a cast film, and the cast film is continuously peeled from the support to obtain a polymer film containing the solvent. In the method for producing a polymer film for drying a film,
A first drying step in which both sides of the polymer film containing the solvent are gripped by gripping means and dried while being transported while stretching the polymer film in the width direction;
After the first drying step, a tension of 2 × 9.8 (N / m) or more and 8 × 9.8 (N / m) or less is applied in the longitudinal direction of the polymer film, and the polymer is applied by a plurality of rollers. A second drying step for drying while supporting and transporting the film,
At least one of the plurality of rollers is a drum-shaped roller that is longer than the width of the polymer film, has a symmetrical shape with respect to the center in the longitudinal direction, and has an outer diameter that increases from the center in the longitudinal direction toward both ends. And the maximum outer diameter D1 (mm) and the minimum outer diameter d1 (mm) in the range of supporting the polymer of the drum roller satisfy the condition of 0.9 <d1 / D1 <0.99. A method for producing a polymer film.   2. The method for producing a polymer film according to claim 1, wherein the polymer is cellulose acylate. A winding step of winding the polymer film that has undergone the second drying step;
When the width of the polymer film immediately after being gripped by the gripping means is L1 (mm), and the width of the polymer film just after being wound up after the end of the second drying step is L2 (mm),
3. The method for producing a polymer film according to claim 1, wherein L2 / L1 satisfies a condition of 1.1 ≦ L2 / L1 ≦ 1.5.   The polymer film according to any one of claims 1 to 3, wherein the polymer film at the start of the second drying step contains the solvent in an amount of 5 wt% to 20 wt% on a dry basis. Method.   The method for producing a polymer film according to any one of claims 1 to 4, wherein one of the most upstream of the plurality of rollers is the drum-type roller.

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