JP4496115B2 - Solution casting method - Google Patents

Description

  The present invention relates to a solution casting method for producing an optical film, and particularly to a solution casting method for producing an optical film suitable for coating by secondary processing.

  Various polymer films used for optical applications are generally produced by casting a dope onto a support using a casting die, peeling it off from the support, and then drying in a drying step. The And it rolls up and preserve | saves in roll form for secondary processes, such as the following saponification process and an application | coating process.

Among the polymer film rolls wound in the form of rolls in this way, especially in the case of plastic film rolls, the film charging potential and the film charging potential at the time of winding do not affect the flatness and secondary processability of the film. Conventionally known and various improvement methods have been proposed. For example, as described in Patent Document 1 or 2, the static eliminator is installed immediately before or immediately after the winding part to neutralize the film, or fine uneven knurling is imparted to both side edges of the film, There is a method such as winding a film on a film roll using a pressing roller that contacts only the knurling.
JP 2002-283370 A JP 2002-255409 A

  By the way, with the recent high performance and thinning of liquid crystal display devices, there is an increasing demand for high quality plastic films as various functional films. It has become difficult to provide high quality plastic films. For example, when a plastic film roll formed into a roll and wound in the form of a roll is subjected to saponification treatment or coating treatment as secondary processing, uneven coating may occur, and improvement has been desired.

  Therefore, as a result of earnestly examining the cause of the above-described coating unevenness, the present inventor found that the conventional static elimination method did not sufficiently eliminate static electricity and found that uneven coating occurred due to this. It came to complete. That is, when the film formed and wound up in the form of a roll was sent out, the charged potential of the film 130a was measured on the pass roller 132 using the surface potential meter 131 as shown in FIG. The film charging potential was measured. In this surface potential meter 131, a surface potential meter (manufactured by Trek Japan, model 344) 131 which is a non-contact type potential meter is used in a state where the pass roller 132 supporting the film 130 a is grounded. The measurement was performed in a measurement range of 2000 V, and the charging potential of the film 130a could be measured with high accuracy of ± 0.05%. According to this measurement method, it was found that when the film was wound by a method of performing charge removal immediately before and after the conventional winding, complete charge removal was not performed and the charge was charged to about −50V to + 50V. . Then, it was found that uneven coating occurred in the saponification treatment or coating treatment in the next process due to the incomplete charge removal of the film.

  Various experiments were conducted in order to reduce the charged potential, and it was found that it is necessary not only to remove static electricity immediately before and immediately after winding but also to remove static electricity further upstream of the winding process in the film manufacturing process. That is, even if the charge is removed immediately before or after winding of the film, the charge cannot be completely removed.For example, the outlet portion of the drying step on the upstream side, for example, the drying chamber and the cooling chamber following the drying step are provided. When equipped, a static elimination device is provided in the cooling chamber or the like to neutralize the charge, thereby controlling the charging history over a certain section including the winder of the production line and the drying process, thereby reducing the charging potential of the film from 0 to It was found that the charge can be removed to about ± 10 V, and in such a charge removal state, there is no occurrence of coating unevenness in the subsequent saponification treatment or coating treatment step.

Based on the above findings, the present invention has been made. In the present invention, the polymer solution is cast on an endless support, and then peeled off as a polymer film. After the polymer film is dried in a drying chamber, In the solution casting method in which cooling is performed in a downstream cooling chamber, and a knurling made of unevenness is imparted to both side edges of the polymer film, and then wound around a winding core, cooling is performed by the first static elimination device disposed in the cooling chamber. The first static elimination step of neutralizing the polymer film that has been discharged and the second static elimination device that neutralizes the polymer film exiting the cooling chamber before the knurling is applied by the second static elimination device disposed downstream of the cooling chamber. It has a step, and a third neutralization step of neutralizing the third static eliminator polymer films knurling is applied, disposed upstream of the winding core, the polymer Fi When winding the arm is configured as characterized in that the range charge potential below -5V or + 5V of the polymer film. It is preferable that the polymer film is wound around the winding core while performing static elimination by the third static elimination device. The first static eliminator is a blow-type static eliminator that emits ionic wind. The first static eliminator is provided inside the cooling chamber, and the surface potential of the polymer film is measured with a surface potential meter on a grounded path roller downstream of the first static eliminator. It is preferable to measure and control the amount of ion wind in the first static elimination device based on the measured surface potential. The third static eliminator is a blow-type static eliminator that discharges ionic wind. The third static eliminator is provided inside a winding chamber that houses the winding core, and on the grounded path roller upstream of the third static eliminator, the polymer film It is preferable to measure the surface potential with a surface potential meter and to control the amount of ion wind in the third static elimination device based on the measured surface potential. Measure the charged potential of the polymer film with high accuracy by grounding the pass roller supported by the polymer film and measuring the charged potential using a surface potentiometer on the polymer film on the grounded pass roller. can do.

In the solution casting method, in the cooling chamber, when the polymer film exiting the drying chamber having an internal temperature of 100 to 150 ° C. is cooled to 30 ° C. or less, the winding tension is 300 N or more and 410 N or less. When the polymer film is wound around a winding core, the effect is more effective when the knurling is imparted by embossing with a knurling roller.

  In the solution film-forming method of the present invention, since the static elimination is performed in the drying process upstream of the winding process, the surface potential value and unevenness on the coated surface side when the wound roll is sent out are reduced, and the secondary It is possible to reduce coating unevenness during processing. Further, by measuring the charging potential of the film on a grounded pass roller, the charging potential can be measured with higher accuracy than in the case of measuring at a place not grounded. Furthermore, by optimizing the tension at the time of winding the film, it is possible to improve coating unevenness and roll misalignment failure in the next step.

[material]
As the cellulose acylate, it is preferable to use a cellulose acylate in which the substitution degree of the hydroxyl group of cellulose satisfies all of the following formulas (I) to (III). In the formula, A and B represent the substitution degree of the acyl group substituted with the hydroxyl group of cellulose, A is the substitution degree of the acetyl group, and B is the substitution degree of the acyl group having 3 to 22 carbon atoms. . In this embodiment, cellulose triacetate (TAC) was used as the cellulose acylate. In addition, it is preferable that 90 mass% 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

  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.).

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

  Recently, a solvent composition not using dichloromethane has been proposed in order to minimize the influence on the environment. For this purpose, ethers having 4 to 12 carbon atoms, ketones having 3 to 12 carbon atoms, and esters having 3 to 12 carbon atoms are preferable, and these are used by being appropriately mixed. These ethers, ketones and esters may have a cyclic structure. A compound having two or more functional groups of ether, ketone and ester (that is, —O—, —CO— and —COO—) can also be used as a solvent. The solvent may have another functional group such as an alcoholic hydroxyl group. In the case of a solvent having two or more kinds of functional groups, 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 Japanese Patent Application No. 2004-264464. 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. The details are described in paragraphs [0196] to [0516] of Japanese Patent Application No. 2004-264464.

[Manufacture of dope]
FIG. 1 shows a dope production line 10. In the production of a dope as a film raw material, first, the valve 12 is opened from the solvent tank 11, and the solvent is sent to the dissolution tank 13. Next, the TAC contained in the hopper 14 is fed into the dissolution tank 13 while being measured. The additive solution is sent from the additive tank 15 to the dissolution tank 13 by opening and closing the valve 16. In addition to the method of sending the additive as a solution, for example, when the additive is liquid at room temperature, it is also possible to send the additive into the dissolution tank 13 in the liquid state. In addition, when the additive is solid, it can be fed into the dissolution tank 13 using a hopper. When a plurality of types of additives are added, a solution in which a plurality of types of additives are dissolved can be placed in the additive tank 15. Alternatively, a solution in which an additive is dissolved can be put in each of a plurality of additive tanks and sent to the dissolution tank 13 through independent pipes.

  In the above description, the order of putting into the dissolution tank 13 is the solvent (used in the meaning including the case of the mixed solvent), TAC, and additive, but it is not limited to this order. It is also possible to send a preferable amount of the solvent after sending the TAC to the dissolution tank 13 while measuring it. Further, the additive does not necessarily need to be put in the dissolution tank 13 in advance, and can be mixed in a mixture of TAC and a solvent in a later step.

  A jacket 17 is provided so as to enclose the dissolution tank 13. Moreover, it is preferable that the 1st stirring blade 19 rotated by the motor 18 is attached to the dissolution tank 13, and the 2nd stirring blade rotated by the motor 20 is further attached. The first stirring blade is preferably an anchor blade, and the second stirring blade 21 is preferably a dissolver type eccentric stirring machine. It is preferable to adjust the temperature in the melting tank 13 to a range of −10 ° C. to 55 ° C. by flowing a heat transfer medium through the jacket 17. By appropriately selecting and rotating the first stirring blade 19 and the second stirring blade 21, the swelling liquid 22 in which the TAC is swollen in the solvent can be obtained.

  The swelling liquid 22 is sent to the heating device 26 by the pump 25. The heating device 26 preferably uses a jacketed pipe, and preferably has a configuration capable of pressurizing the swelling liquid 22. A raw material dope is obtained by dissolving TAC or the like in a solvent under heating or pressure heating conditions of the swelling liquid 22. In this case, the temperature of the swelling liquid 22 is preferably 0 ° C to 97 ° C. Moreover, it replaces with the heating melt | dissolution by the heating apparatus 26, and the cooling melt | dissolution method which further cools the swelling liquid 22 to -100 degreeC--10 degreeC can also be applied. TAC can be sufficiently dissolved in a solvent by appropriately selecting the heating dissolution method and the cooling dissolution method. After the temperature of the dope is set to about room temperature by the temperature controller 27, the dope is filtered by the filtering device 28 to remove impurities in the dope. The average pore diameter of the filtration filter of the filtration device 28 is preferably 100 μm or less. The filtration flow rate is preferably 50 L / hr or more. The dope after filtration is put into the stock tank 30 through the valve 29.

  The dope can be used as it is for solution film formation as described later. However, the method of dissolving TAC after preparing the swelling liquid 22 takes time as the concentration of TAC is increased, and may cause a problem in terms of cost. In that case, it is preferable to carry out a concentration step in which a dope having a concentration lower than the target TAC concentration is once prepared and then adjusted to the target concentration. The dope filtered by the filtering device 28 is sent to the flash device 31 through the valve 29. A part of the solvent in the dope is evaporated in the flash device 31. The evaporated solvent is made liquid by a condenser (not shown), and then recovered by the recovery device 32. It is advantageous from the viewpoint of cost that the solvent is regenerated and reused as a solvent for dope preparation by the regenerator 33.

  The concentrated dope is extracted from the flash unit 31 using the pump 34. Furthermore, it is preferable to remove bubbles in the dope. Defoaming may be performed by any known method, for example, an ultrasonic irradiation method. Thereafter, the liquid is fed to the filtration device 35 to remove foreign matters. In addition, it is preferable that the temperature of dope is 0 degreeC-200 degreeC in this case. In this way, the dope 36 having a TAC concentration of 5% by mass to 40% by mass can be manufactured. The manufactured dope 36 is stored in the stock tank 30.

  In addition, from the [0517] paragraph of Japanese Patent Application No. 2004-264464 about the raw material in the solution casting method which obtains a TAC film, the raw material, the additive dissolution method and addition method, the filtration method, and the dope production methods such as defoaming [0616] The paragraph is detailed. These descriptions are also applicable to the present invention.

[Solution casting method]
FIG. 2 shows a film production line 40. A stirring blade 42 that is rotated by a motor 41 is attached to the stock tank 30. The dope 36 is always made uniform by rotating the stirring blade 42. Connected to the stock tank 30 are an intermediate layer dope channel 43, a support surface dope channel 44, and an air surface dope channel 45. The dope 36 is fed by pumps 46, 47, 48 provided in the respective flow paths 43, 44, 45, fed to the feed block 70, and then merged from the casting die 71 onto the casting band 72. To be cast.

[Dope manufacturing process]
The intermediate layer additive 51 contained in the stack tank 50 is fed to the dope in the intermediate layer dope channel 43 (hereinafter referred to as the intermediate layer dope) by the pump 52 and mixed therewith. Thereafter, the mixture is stirred and mixed by the in-line mixer 53 to be uniform. Thereby, the dope for the intermediate layer is generated. In the intermediate layer additive 51, for example, a solution (or dispersion) containing additives such as an ultraviolet absorber and a retardation control agent in advance is placed.

  The support surface additive 56 contained in the stock tank 55 is fed to the dope in the support surface dope channel 44 (hereinafter referred to as support surface dope) by the pump 57 and mixed. Thereafter, the mixture is stirred and mixed by the in-line mixer 58 to be uniform. Thereby, the dope for the support surface is generated. The support surface additive 56 includes a peeling accelerator (e.g., citrate ester) that facilitates peeling from the casting band as the support, and the film surface between the film surfaces when the film is wound into a roll. Additives such as a matting agent (for example, silicon dioxide) for suppressing adhesion are contained in advance. The support surface additive 56 may contain additives such as a plasticizer and an ultraviolet absorber.

  The air surface additive 61 contained in the stock tank 60 is fed to the dope in the air surface dope channel 45 (hereinafter referred to as air surface dope) by the pump 62 and mixed. Thereafter, the mixture is stirred and mixed by the in-line mixer 63 to be uniform. Thereby, the dope for air surfaces is produced | generated. The air surface additive 61 contains in advance an additive such as a matting agent (for example, silicon dioxide) that suppresses adhesion between the film surfaces when the film is wound into a roll. The air surface additive 61 may contain additives such as a peeling accelerator, a plasticizer, and an ultraviolet absorber.

  Each dope to which various additives are added is fed to the feed block 70 at a desired flow rate, and after the dopes merge in the feed block 70, the dope is cast from the casting die 71 onto the casting band 72. .

[Casting process]
It is preferable to use precipitation hardening type stainless steel as the material of the casting die 71. It is preferable to use a material having a thermal expansion coefficient of 2 × 10 ⁻⁵ (° C. ⁻¹ ) or less. Moreover, what has corrosion resistance substantially equivalent to SUS316 in the forced corrosion test in electrolyte aqueous solution can also be used. Further, a material having corrosion resistance that does not cause pitting (opening) at the gas-liquid interface even when immersed in a mixed solution of dichloromethane, methanol, and water for 3 months is used. Further, it is preferable that the casting die 71 is manufactured by grinding a material that has passed one month or more after casting. Thereby, the surface shape of the dope flowing in the casting die 71 is kept constant. It is preferable to use a finishing accuracy of the wetted surfaces of the casting die 71 and the feed block 70 in terms of surface roughness of 1 μm or less and straightness of 1 μm / m or less in any direction. The slit clearance that can be adjusted in the range of 0.5 mm to 3.5 mm by automatic adjustment is used. About the corner | angular part of the liquid-contacting part of the lip | tip end of the casting die 71, R uses 50 micrometers or less over the full width of a slit. Moreover, it is preferable to use what was adjusted so that the shear rate in the casting die 71 might be set to 1 (1 / sec)-5000 (1 / sec).

  The width of the casting die 71 is not particularly limited. Further, during film formation, it is preferable to attach a temperature controller so as to be maintained at a predetermined temperature. The casting die 71 is preferably a coat hanger type. Furthermore, it is more preferable to provide a thickness adjusting bolt (heat bolt) at a predetermined interval and attach an automatic thickness adjusting mechanism using a heat bolt. It is preferable that the heat bolt is subjected to film formation by setting a profile according to the amount of pump 46 (preferably high precision gear pump) 46 to 48 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 40. It is preferable that the thickness difference between any two points except the casting edge is adjusted within 1 μm, and the maximum difference in the width direction thickness is adjusted to 3 μm or less. Moreover, it is preferable to use the one whose thickness accuracy is adjusted to ± 1.5 μm or less.

More preferably, a cured film is formed at the tip of the lip. A method for forming the cured film is not particularly limited, and examples thereof include ceramic coating, hard chrome plating, and a nitriding method. In the case of using ceramics as the cured film, it is preferable to use ceramics that can be ground, have a low porosity, are not brittle, have good corrosion resistance, and have no adhesion to the casting die 71. Specific examples include tungsten carbide (WC), Al ₂ O ₃ , TiN, Cr ₂ O _{3 and the} like, but it is particularly preferable to use WC. The WC coating can be performed by a thermal spraying method.

  In order to prevent the dope flowing out to the slit end of the casting die 71 from locally drying and solidifying, it is preferable to attach a solvent supply device (not shown) to the slit end. 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 supplied to the gas-liquid interface between the end of the casting bead and the slit. preferable. 3 mL / min. On each side of the end. To 10 mL / min. It is preferable to supply within the range because foreign matter can be prevented from mixing in the cast film. In addition, it is preferable to use a pump having a pulsation rate of 5% or less for supplying the liquid.

  A casting band 72 is provided below the casting die 71 so as to span the rotating rollers 73 and 74. The casting band 72 travels endlessly as the rotating rollers 73 and 74 are rotated by a driving device (not shown). The moving speed of the casting band 72, that is, the casting speed is preferably 10 m / min to 200 m / min. In order to make the surface temperature of the casting band 72 a predetermined value, it is preferable that a heat transfer medium circulation device 75 is attached to the rotary rollers 73 and 74. The surface temperature of the casting band 72 is preferably −20 ° C. to 40 ° C. A heat transfer medium flow path is formed in the rotation rollers 73 and 74, and the temperature of the rotation rollers 73 and 74 is set to a predetermined value by passing through the heat transfer medium maintained at a predetermined temperature. Can hold.

  The width of the casting band 72 is not particularly limited, but it is preferable to use one having a range of 1.1 to 1.3 times the casting width of the dope. Moreover, it is preferable to use what was grind | polished so that surface roughness might be 0.05 micrometer or less. The material 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 a thickness unevenness of the entire casting band 72 of 0.5% or less.

It is preferable to adjust the tension generated in the casting band 72 when the rotary rollers 73 and 74 are driven to be 1.5 × 10 ⁴ kg / m. The relative speed difference between the casting band 72 and the rotating rollers 73 and 74 is 0.01 m / min. Adjust so that: The speed fluctuation of the casting band 72 is preferably 0.5% or less, and the meandering in the width direction that occurs when the casting band 72 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 72 and perform feedback control based on the measured value. Furthermore, it is preferable to adjust so that the vertical position fluctuation accompanying the rotation of the rotary roller 73 on the surface of the casting band 72 immediately below the casting die 71 is 200 μm or less.

It is also possible to use the rotating rollers 73 and 74 directly as a support. In this case, it is preferable to rotate 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 73 and 74 is 0.01 μm or less. Therefore, chrome plating is performed to provide sufficient hardness and durability. In addition, it is necessary to suppress the surface defects of the support (the casting band 72 and the rotating rollers 73 and 74) to the minimum. Specifically, there are no pinholes of 30 μm or more, pinholes of 10 μm or more and less than 30 μm are 1 / m ² or less, and pinholes of less than 10 μm are preferably ² / m ² or less.

  The casting die 71, the casting band 72, etc. are accommodated in the casting chamber 76. A temperature control facility 77 is attached to keep the temperature in the casting chamber 76 at a predetermined value. It is preferable that the temperature of the casting chamber 76 is −10 ° C. to 57 ° C. Further, a condenser (condenser) 78 for condensing and recovering the volatile organic solvent is provided. The condensed and liquefied organic solvent is recovered and regenerated by the recovery device 79 and then reused as a dope preparation solvent.

  A casting film 80 is formed by co-casting a dope (air surface dope, intermediate layer dope, support surface dope) from the casting die 71 on the casting band 72 while forming a casting bead. In addition, it is preferable that the temperature of each dope at this time is -10 degreeC-57 degreeC. In order to stabilize the formation of the casting bead, the decompression chamber 81 is preferably attached to the rear surface of the casting bead and adjusted to a desired pressure. Furthermore, in order to keep the temperature of the decompression chamber 81 at a predetermined temperature, it is preferable to attach a jacket (not shown). The temperature of the decompression chamber 81 is not particularly limited. Further, it is preferable to attach a suction device (not shown) to the edge portion of the casting die 71 in order to have the desired shape of the casting bead. The edge suction air volume is preferably in the range of 1 L / min to 100 L / min.

  The casting film 80 moves as the casting band 72 travels. At this time, air outlets 82, 83, 84 are provided near the peripheral surface of the casting band 72 in order to evaporate the solvent in the casting film 80. Further, in order to suppress the surface variation of the film surface due to the drying air being blown onto the casting film 80 immediately after casting, a wind shielding device 85 is provided at the air blowing port 82 in the vicinity of the casting die 71. It is preferable. Although the figure shows an example in which a casting band is used as a support, a casting drum can also be used. The surface temperature of the casting drum is preferably -20 ° C to 40 ° C.

[Peeling and drying process]
After the casting film 80 has self-supporting properties, the casting film 80 is peeled off from the casting band 72 as a wet film 87 while being supported by the peeling roller 86. Thereafter, the transfer section 90 provided with a large number of rollers is conveyed and then fed into the tenter 100. In the transfer part 90, the drying of the wet film 87 is advanced by sending the drying air of desired temperature from the air blower 91. FIG. At this time, the temperature of the drying air is preferably 20 ° C to 250 ° C. In the crossing section 90, it is possible to make the wet film 87 draw by making the rotation speed of the downstream roller faster than the rotation speed of the upstream roller.

  The wet film 87 sent to the tenter 100 is dried while its both edges are gripped by a clip and conveyed. Moreover, it is preferable to divide the inside of the tenter 100 into different temperature zones to adjust the drying conditions. It is also possible to stretch the wet film 87 in the width direction using the tenter 100. Thus, it is preferable to stretch at least one direction between the casting direction and the width direction of the wet film 87 by 0.5% to 300% by the crossing portion 90 and / or the tenter 100.

  The wet film 87 dried to a predetermined residual solvent amount by the tenter 100 is sent out as a film 101. Both end portions of the film 101 are cut by the ear clip device 102. The cut film is sent to the crusher 103 by a cutter blower (not shown). The edge of the film is crushed by the crusher 103 into chips. It is advantageous in terms of cost to reuse this chip for dope preparation. In addition, although the process of cut | disconnecting the both edges of this film can also be abbreviate | omitted, it is preferable to carry out in either from the said casting process to the process of winding up the said film.

  Next, the film 101 is sent to a drying chamber 105 provided with a number of rollers 104. Although the temperature in the drying chamber 105 is not specifically limited, It is preferable that it is the range of 100 to 150 degreeC. In the drying chamber 105, the film 101 is conveyed while being wound around the roller 104, and the solvent is volatilized and dried. Further, an adsorption recovery device 106 is attached to the drying chamber 105. The volatile solvent is adsorbed and recovered by the adsorption recovery device 106. The air from which the solvent component has been removed by the adsorption / recovery device 106 is blown again as dry air into the drying chamber 105. The drying chamber 105 is more preferably divided into a plurality of sections in order to change the drying temperature. In addition, a preliminary drying chamber (not shown) is provided between the ear opener 102 and the drying chamber 105, and the preliminary drying of the film 101 can suppress the change in the shape of the film due to the rapid increase in the film temperature. preferable.

  The film 101 is conveyed to the cooling chamber 107 and cooled to approximately room temperature. Note that a humidity control chamber (not shown) may be provided between the drying chamber 105 and the cooling chamber 107. Air adjusted to the desired humidity and temperature of the film 101 is blown in the humidity control chamber. Thereby, generation | occurrence | production of the curling of the film 101 and the winding defect at the time of winding can be suppressed. Furthermore, it is preferable that a knurling roller 109 is provided to give knurling to both edges of the film 101 by embossing. In addition, it is preferable that the unevenness | corrugation of the knurled location is 1 micrometer-200 micrometers.

[Winding process]
Finally, the film 101 is taken up by the take-up roller 111 in the take-up chamber 110. At this time, it is preferable to wind the sheet while applying a desired tension with the press roller 112. More preferably, the tension is gradually changed from the start to the end of winding. The film 101 to be wound is preferably at least 100 m in the longitudinal direction (casting direction). Further, the width direction is preferably 600 mm or more, and more preferably 1400 mm or more and 1800 mm or less. Also, it is effective when it is larger than 1800 mm. The thickness of the film can also be applied when producing a thin film having a thickness of 15 μm to 100 μm.

  In the solution casting method of the present invention, when casting dopes, two or more kinds of dopes are simultaneously laminated or sequentially laminated. Furthermore, you may combine both casting. When performing simultaneous lamination and co-casting, a casting die 71 to which a feed block 70 is attached may be used as shown in FIG. 2, or a multi-manifold casting die may be used. The film composed of multiple layers by co-casting preferably has a layer thickness on the air side and / or a layer on the support side of 0.5% to 30% of the total film thickness. Furthermore, when performing simultaneous lamination co-casting, it is preferable that the high-viscosity dope is wrapped with the low-viscosity dope when casting the dope from the die slit to the support. Moreover, when performing simultaneous lamination co-casting, it is preferable that the dope inside is encapsulated with a dope having a higher alcohol composition ratio than the dope when the dope is cast from the die slit to the support.

  As shown in FIG. 2, the desired characteristics of the film 101 can be easily obtained by co-casting three types of dopes. That is, when winding the film 101 as a roll, it is necessary to prevent adhesion between the film surfaces. Therefore, it is preferable to add a matting agent in the dope, but the matting agent usually causes deterioration of optical properties (for example, deterioration of transparency). Therefore, as in the present embodiment, the matting agent is included in the support surface dope and the air surface dope which are the front and back surfaces of the film, and the dope for the intermediate layer is not included, thereby reducing surface adhesion and desired. It is possible to obtain the optical characteristics.

  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 The details are described in paragraphs [0617] to [0889] of Japanese Patent Application No. 2004-264464. 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 Japanese Patent Application No. 2004-264464. 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 000mg / 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. A method for applying a surface-treated functional layer for realizing various functions and properties on a cellulose acylate film is described in Japanese Patent Application No. 2004-264464, from [0890] paragraph to [1087] paragraph. It is included. 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 No. 2004-264464 describes in detail TN type, STN type, VA type, OCB type, reflection 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 Japanese Patent Application No. 2004-264464.

  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 charge removal process will be described in detail. However, the present invention is not limited to the following embodiments. FIG. 3 is a schematic view of the present invention from the drying process to the winding process, and the static eliminators 120, 121, and 122 are provided between the cooling chamber 107 and the winding chamber 110. Further, the pass rollers 123 and 124 are grounded, and surface potential meters 125 and 126 are provided close to the pass rollers 123 and 124, respectively.

  The film 101 exiting the drying chamber 105 is discharged while being cooled to room temperature by the discharging device 120 in the cooling chamber 107. The static eliminator 120 neutralizes the generated ions by directly applying the generated ions to the film 101 with a blower. By installing the static eliminator 120 in the drying chamber 105, the charging potential of the film can be lowered. FIG. 4 is an outline of the static elimination process of the film 101 performed in the cooling chamber 107 by the blower type static elimination device 120. As shown in FIG. 4, the blower type static eliminator 120 generates ions by the ion generator 120b housed in the blower head 120a, sends wind from the blower 120c through the ventilation duct 120e, and sends ion wind from the slit 120d. Release toward the film 101. In order to measure the charging voltage of the film at the time of leaving the drying chamber 105, the pass roller 123 is grounded, and the surface potential is measured with respect to the film 101 in contact with the pass roller 123 using a surface potential meter 125. It is preferable to perform the measurement. In this case, when the charge is not neutralized to a predetermined charging potential based on the measured surface potential, the amount of ion wind generated is controlled so as to be an appropriate surface potential, for example, −10V to + 10V.

  Further, the film 101 that has exited the cooling chamber 107 is neutralized by using the neutralization device 121. Further, knurling is imparted to both ends of the film 101 by embossing using a knurling roller 109. FIG. 3 shows an example in which the static eliminator 121 is provided on the upstream side of the knurling roller, but it is not limited to that position.

  Next, in the winding chamber 110, the pass roller 124 is grounded, a surface potential meter is installed on the film 101 in contact with the pass roller 124, and the surface potential of the film 101 is measured. Then, based on the measured surface potential, the amount of ion wind generated is controlled so as to be an appropriate surface potential, for example, −5 V or more and +5 V or less. The take-up roller 111 is wound up.

  In addition, although the static elimination apparatus 121-123 is performing static elimination by blowing ion wind, you may neutralize with various known static elimination apparatuses. Further, each surface neutralization device is controlled from the value of the surface potential measured by the surface potential meters 122 and 124 by using a controller (not shown) to perform more uniform static elimination. May be omitted, and neutralization may be simply performed by various neutralization devices.

  Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited thereto.

[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 100 parts by weight dichloromethane (first solvent) 320 parts by weight methanol (second solvent) 83 parts by weight 1-butanol (third solvent) 3 parts by weight plasticizer A (triphenyl phosphate) 7.6 parts by weight plastic Agent B (diphenyl phosphate) 3.8 parts by mass

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

(1) Dope preparation The raw material dope production line 10 shown in FIG. 1 was used. The cellulose triacetate powder (flakes) is gradually added from the hopper 14 to the 4000 L stainless steel dissolution tank 13 having the stirring blades 19 and 21 while mixing and dispersing the plurality of solvents as a mixed solvent. Was adjusted to 2000 kg. In addition, all the solvents used that the water content is 0.5 mass% or less. A dissolver-type eccentric stirring shaft 21 that stirs in the dissolution tank 13 at a peripheral speed of 5 m / sec (shear stress 5 × 10 ⁴ / m / sec ² ) at first, and an anchor blade 19 on the central axis. And dispersed for 30 minutes under the condition of stirring at a peripheral speed of 1 m / sec (shear stress 1 × 10 ⁴ kgf / m / sec ² ). The starting temperature of dispersion was 25 ° C., and the final temperature reached 48 ° C. After completion of the dispersion, the high-speed stirring was stopped, the peripheral speed of the anchor blade 19 was set to 0.5 m / sec, and the mixture was further stirred for 100 minutes to swell the cellulose triacetate flakes to obtain a swelling liquid 22. Until the end of swelling, the inside of the tank was pressurized to 0.12 MPa with nitrogen gas. At this time, the oxygen concentration in the tank was less than 2 vol%, and the state of no problem was maintained in terms of explosion protection. The water content in the dope was 0.3% by mass.

(2) Dissolution / filtration The swelling liquid 22 was fed from the dissolution tank 13 to the jacketed pipe 26 by the pump 25. It heated to 50 degreeC with the piping 26 with a jacket, and also heated to 90 degreeC under the pressurization of 2 MPa, and was dissolved completely. The heating time was 15 minutes. The temperature was lowered to 36 ° C. with a temperature controller 27 and passed through a filtering device 28 having a filter medium having a nominal pore diameter of 8 μm, to obtain a dope having a solid content concentration of 18% by mass (hereinafter referred to as a dope before concentration). At this time, the primary pressure of filtration was 1.5 MPa, and the secondary pressure was 1.2 MPa. In addition, the filter, housing, and piping exposed to high temperature used the thing which has a jacket which distribute | circulates the heat medium for heat insulation heating using the thing made from Hastelloy alloy and excellent in corrosion resistance.

(3) Concentration, filtration and defoaming The dope before concentration was flushed in the flash device 31 adjusted to 80 ° C. and normal pressure, and the evaporated solvent was liquefied with a condenser and recovered and separated by the recovery device 32. The solid concentration of the dope after flashing was 21.8% by mass. The recovered solvent was adjusted for reuse by the regenerator 33. The flash tank of the flash device 31 has an anchor blade on the center axis, and deaeration was performed by stirring at a peripheral speed of 0.5 m / sec. The temperature of the raw material dope in the flash tank was 25 ° C., and the average residence time in the tank was 50 minutes. The shear viscosity measured at 25 ° C. after collecting this dope was 450 Pa · s at a shear rate of 10 (1 / s).

  Next, bubbles were removed by irradiating the dope with weak ultrasonic waves. Thereafter, the liquid was fed to the filtration device 35 while being pressurized to 1.5 MPa using the pump 34. In the filter device 35, first, the sintered fiber metal filter having a nominal pore diameter of 10 μm was passed, and then, the sintered fiber filter having the same pore diameter of 10 μm was passed. Respective primary pressures were 1.5 MPa and 1.2 MPa, and secondary pressures were 1.0 MPa and 0.8 MPa. The temperature of the dope after filtration was adjusted to 36 ° C. and stored in a 2000 L stainless steel stock tank 30. The stock tank 30 had an anchor blade 42 on the central axis and was constantly stirred at a peripheral speed of 0.3 m / sec. It should be noted that no problem such as corrosion occurred at all in the wetted part of the dope in each apparatus between before concentration and immediately after concentration. Moreover, the mixed solvent 37 of 86.5 mass parts of dichloromethane, 13 mass parts of acetone, and 0.5 mass part of n-butanol was produced.

(4) Discharge Film was formed using the fail film-forming line 40 shown in FIG. Subsequently, the dope 36 in the stock tank 30 was fed by the feedback control by the inverter motor so that the primary pressure of the high precision gear pump became 0.8 MPa with the gear pumps 46, 47, 48 for primary pressure increase. The high-precision gear pumps 46 to 48 had a volume efficiency of 99.2% and a discharge rate variation rate of 0.5% or less. The discharge pressure was 1.5 MPa.

  The casting die 71 is equipped with a feed block 70 having a width of 1.8 m and adjusted for co-casting, and is capable of forming a three-layer film by laminating on both sides in addition to the mainstream. Was used. In the following description, a layer formed from the mainstream is referred to as an intermediate layer, a support surface side layer is referred to as a support surface, and an opposite surface is referred to as an air surface. In addition, the dope liquid supply flow path used three flow paths: an intermediate layer dope flow path 43, a support surface dope flow path 44, and an air surface dope flow path 45.

(5) Production of dope 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-chlorobenzotriazole: 0.3 part by mass) and a retardation control agent (N, N-di-m-toluyl-Nm-methoxyphenyl-1) , 3,5 triazine-2,4,6-triamine), the mixed solvent 37 and the dope 36 were mixed, and the intermediate layer additive solution 51 was put into the stock tank 50. The intermediate layer additive solution 51 was fed to the dope 36 in the intermediate layer dope channel 43 by the pump 52. And it mixed through the in-line mixer 53, and the dope for intermediate | middle layers was produced | generated. The mixing amount is adjusted so that the total solid content is 21.8% by mass, the ultraviolet absorbers a and b are 4.6% by mass in the film form, and the retardation control agent is 1.0% by mass in the film form. It was.

  0.05 parts by mass of silicon dioxide (particle size: 15 nm, Mohs hardness: about 7) as a matting agent and citric acid ester mixture (citric acid, citric acid monoethyl ester, citric acid diethyl ester, citric acid triethyl ester) as a peeling accelerator ) Was dissolved or dispersed in 0.006 part by mass, the raw material dope 36 and the mixed solvent 37 to obtain a support surface addition liquid 56. The support surface additive liquid 56 was placed in the stock tank 55 and fed to the raw material dope 36 flowing in the support surface dope channel 44 at a desired flow rate using a pump 57. And it mixed with the in-line mixer 58, and the dope for support surfaces was produced | generated. The addition amount was such that the total solid concentration was 20.5% by mass, the matting agent concentration was 0.05% by mass in the film form, and the peeling accelerator concentration was 0.03% by mass in the film form.

  An air surface additive solution 61 was prepared by dispersing 0.1 part by mass of silicon dioxide in the mixed solvent 37 and placed in the stock tank 60. The air surface additive solution 61 was fed to the dope 36 in the air surface dope channel 45 by the pump 62. And it mixed through the in-line mixer 63, and the dope for air surfaces was produced | generated. The amount added was such that the total solid concentration was 20.5% by mass, and the matting agent concentration was 0.1% by mass in the form of a film.

(6) Casting Each dope has a casting width of 1700 mm so that the target TAC film thickness (air surface, intermediate layer, support surface) is 4 μm, 73 μm, and 3 μm, respectively, and the product thickness is 80 μm. The casting was performed by adjusting the flow rate of the dope for the intermediate layer, the dope for the support surface, and the dope for the air surface. In order to adjust the temperature of each dope to 36 ° C, a jacket (not shown) was provided on the casting die 71, and the inlet temperature of the heat transfer medium supplied into the jacket was set to 36 ° C.

  The casting die 71, the feed block 70, and the piping were all kept at 36 ° C. during film formation. The casting die 71 was a coat hanger type, and thickness adjusting bolts (heat bolts) were provided at a pitch of 20 mm, and those equipped with an automatic thickness adjusting mechanism using heat bolts were used. The heat bolt can also set a profile according to the liquid feed amount of the high precision gear pump by a preset program, and feedback by an adjustment program based on the profile of an infrared thickness meter (not shown) installed in the film production line 40 It has performance that can be controlled. The thickness difference between two arbitrary points 50 mm apart in the film excluding the casting edge portion 20 mm was within 1 μm, and the largest difference in the width direction thickness was adjusted to 3 μm / m or less. The average thickness accuracy of each layer was controlled so that both outer layers were controlled to ± 2% or less, the mainstream was controlled to ± 1% or less, and the total thickness was adjusted to ± 1.5% or less.

  A decompression chamber 81 for decompressing was installed on the primary side of the casting die 71. The degree of decompression of the decompression chamber 81 is such that a pressure difference of 1 Pa to 5000 Pa occurs before and after the casting bead and can be adjusted according to the casting speed. At that time, the pressure difference was set so that the length of the bead was 4 mm ± 2 mm. Moreover, the temperature of the decompression chamber 81 was equipped with the mechanism which can be set higher than the condensation temperature of the gas around a casting part. Labyrinth packings (not shown) were provided at the front and rear of the bead. Moreover, the opening part was provided in both ends. Furthermore, in order to adjust the disturbance of both edges of the casting bead, the one to which an edge suction device (not shown) is attached was used.

The material of the casting die 71 is a precipitation hardening type stainless steel, and the material has a thermal expansion coefficient of 2 × 10 ⁻⁵ (° C. ⁻¹ ) or less, which is almost the same as that made of SUS316 in a forced corrosion test with an aqueous electrolyte solution. A material having corrosion resistance was used. Further, a corrosion-resistant material that does not cause pitting (opening) at the gas-liquid interface even when immersed in a mixed solution of dichloromethane, methanol, and water for 3 months was used. The finishing accuracy of the wetted surfaces of the casting die 71 and the feed block 70 was 1 μm or less in terms of surface roughness, the straightness was 1 μm / m or less in any direction, and the slit clearance was adjusted to 1.5 mm. About the corner | angular part of the liquid-contact part of die-tip tip, it processed so that R might be 50 micrometers or less over the slit full width. The shear rate inside the die was in the range of 1 (1 / sec) to 5000 (1 / sec). Further, a WC coating was applied to the lip end of the casting die 71 by a thermal spraying method to provide a cured film.

  Furthermore, in order to prevent the dope flowing out from the slit end of the casting die 71 from locally drying and solidifying, the mixed solvent solubilizing the dope is placed on one side of the casting bead end and the slit gas-liquid interface. It was supplied at 0.5 ml / min. The pulsation rate of the pump supplying this liquid was 5% or less. Further, the pressure on the back surface of the bead was reduced by 150 Pa by the decompression chamber 81. In order to keep the temperature of the decompression chamber 81 constant, a jacket (not shown) was attached. A heat transfer medium adjusted to 35 ° C. was supplied into the jacket. The edge suction air volume that can be adjusted in the range of 1 L / min to 100 L / min was used, and in this example, it was appropriately adjusted in the range of 30 L / min to 40 L / min.

A stainless steel endless band having a width of 2.1 m and a length of 70 m was used as the casting band 72 as a support. The casting band 72 was 1.5 mm in thickness and polished so that the surface roughness was 0.05 μm or less. The material was made of SUS316 and had sufficient corrosion resistance and strength. The thickness unevenness of the entire casting band 72 was 0.5% or less. The casting band 72 was driven by two rotating rollers 73 and 74. At this time, the tension of the casting band 72 is adjusted to 1.5 × 10 ⁴ kg / m so that the relative speed difference between the casting band 72 and the rotating rollers 73 and 74 is 0.01 m / min or less. did. The speed fluctuation of the casting band 72 was 0.5% or less. Further, both ends of the casting band 72 were detected and controlled so that the meandering in the width direction of one rotation was limited to 1.5 mm or less. Further, the positional fluctuation in the vertical direction between the die lip tip and the casting band 72 immediately below the casting die 71 was set to 200 μm or less. The casting band 72 is installed in a casting chamber 76 having wind pressure fluctuation suppressing means (not shown). Three layers of dope (air surface, intermediate layer, support surface) were co-cast on the casting band 72 from the casting die 71.

As the rotating rollers 73 and 74, those capable of feeding a heat transfer medium therein were used so that the temperature of the casting band 72 could be adjusted. A heat transfer medium at 5 ° C. was passed through the rotary roller 73 on the casting die 71 side, and a heat transfer medium at 40 ° C. was passed through the other rotary roller 74. The surface temperature of the center part of the casting band 72 immediately before casting was 15 ° C., and the temperature difference between both ends was 6 ° C. or less. The casting band 72 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 has 2 pinholes of less than 10 μm / m2. What was ² or less was used.

The temperature of the casting chamber 76 was kept at 35 ° C. using the temperature control equipment 77. The casting film 80 formed from the dope cast on the casting band 72 was first dried by parallel-flow drying air. The overall heat transfer coefficient from the drying air to the cast film 80 during drying was 24 kcal / m ² · hr · ° C. The temperature of the drying air was 135 ° C. on the upstream side of the upper part of the casting band 72 and 140 ° C. on the downstream side. Further, the lower part of the casting band 72 was blown from the blowers 82, 83, and 84 so that the temperature was 65 ° C. The saturation temperature of each drying wind was around -8 ° C. The oxygen concentration in the dry atmosphere on the casting band 72 was kept at 5 vol%. Note that the air was replaced with nitrogen gas in order to maintain the oxygen concentration at 5 vol%. Further, in order to condense and recover the solvent in the casting chamber 76, a condenser (condenser) 78 was provided, and the outlet temperature thereof was set to -10 ° C.

(7) Stripping / Drying For 5 seconds after casting, the wind-shielding device 85 prevents the drying air from directly hitting the dope and casting film 80, and the static pressure fluctuation in the immediate vicinity of the casting die 71 is suppressed to ± 1 Pa or less. did. When the ratio of the solvent in the casting film 80 reached 150% by mass on the dry basis, the film was peeled off from the casting band 72 as a film (hereinafter referred to as a wet film) 87 while being supported by a peeling roller. The peeling tension at this time is 10 kgf / m, and the peeling speed (peeling roller draw) is in the range of 100.1% to 110% with respect to the speed of the casting band 72 in order to suppress the peeling failure. Adjusted appropriately. The surface temperature of the wet film 87 was 15 ° C. The drying speed on the casting band 72 was an average of 60% by mass dry weight reference solvent / min. The solvent gas generated by drying was condensed and liquefied by a condenser 78 at −10 ° C. and recovered by a recovery device 79. The recovered solvent was adjusted and then reused as a dope preparation solvent. At that time, the amount of water contained in the solvent was adjusted to 0.5% or less. The drying air from which the solvent was removed was heated again and reused as drying air. The wet film 87 was conveyed through the roller of the crossing section 90 and sent to the tenter 100. At this time, 40 ° C. dry air was blown from the blower 91 to the wet film 87.

  The wet film 87 sent to the tenter 100 was conveyed through the drying zone of the tenter 100 while being fixed at both ends with clips, and was dried with drying air. The clip was cooled by supplying a heat transfer medium at 20 ° C. The tenter was driven by a chain, and the speed fluctuation of the sprocket was 0.5% or less. Further, the tenter 100 was divided into three zones, and the drying air temperature of each zone was set to 90 ° C., 100 ° C., and 110 ° C. from the upstream side. The gas composition of the drying air was set to a saturated gas concentration of −10 ° C. The average drying speed in the tenter 100 was 120% by mass (dry weight reference solvent) / min. At the outlet of the tenter 100, the conditions of the drying zone were adjusted so that the amount of residual solvent in the film was 7% by mass. In the tenter 100, stretching in the width direction was also performed while transporting. When the width of the wet film 87 when transported to the tenter 100 is 100%, the widening amount is 103%. The stretching ratio (tenter driven draw) from the peeling roller 86 to the tenter 100 inlet was 102%. As for the stretching ratio in the tenter 100, the difference in the actual stretching ratio in the portion separated by 10 mm or more from the tenter biting portion was 10% or less, and the difference in the stretching ratio at any two points 20 mm apart was 5% or less. . The ratio of the length of the base end fixed with a tenter was 90%. The solvent evaporated in the tenter 100 was condensed and liquefied at a temperature of −10 ° C. and recovered. A condenser (not shown) was provided for condensation recovery, and the outlet temperature was set to -8 ° C. The water content contained in the solvent was adjusted to 0.5% by mass or less and reused. And it sent out from the tenter 100 as the film 101.

Then, the ear-cleaving device 102 cuts the ears at both ends within 30 seconds from the exit of the tenter 100. Ears 50 mm on both sides were cut with an NT-type cutter, and the cut ears were blown to a crusher 103 with a cutter blower (not shown) and crushed into chips of about 80 mm ² on average. This chip was used again as a raw material for dope preparation together with TAC flakes as a dope preparation raw material. The oxygen concentration in the dry atmosphere of the tenter 100 was kept at 5 vol%. Note that the air was replaced with nitrogen gas in order to maintain the oxygen concentration at 5 vol%. Prior to drying at a high temperature in a drying chamber 105 described later, the film 101 was preheated in a predrying chamber (not shown) to which 100 ° C. drying air was supplied.

  The film 101 was dried at a high temperature in the drying chamber 105. The drying chamber 105 was divided into four sections, and drying air at 120 ° C., 130 ° C., 130 ° C., and 130 ° C. was supplied from the blower (not shown) from the upstream side. The conveyance tension of the film 101 by the roller 104 was 100 N / width, and the film was dried for about 10 minutes until the residual solvent amount finally reached 0.3% by mass. The wrap angle of the roller 104 was 90 degrees and 180 degrees (exaggerated in FIG. 2). The roller 104 was made of aluminum or carbon steel, and a hard chrome plating was applied to the surface. The roller 104 has a flat surface shape and a matt-processed surface by blasting. The shake due to the rotation of the roller 104 was all 50 μm or less. The roller deflection at a tension of 100 N / width was selected to be 0.5 mm or less.

  The solvent gas contained in the drying air was adsorbed and recovered using the adsorption recovery device 106. The adsorbent 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% by mass or less. In addition to solvent gas, the drying air contains plasticizers, UV absorbers, and other high-boiling substances, so these were removed by a cooler and a pre-adsorber that were cooled and removed, and were recycled and used. And adsorption / desorption conditions were set so that VOC (volatile organic compound) in the outdoor exhaust gas was finally 10 ppm or less. Moreover, the solvent amount collect | recovered by the condensation method among all the evaporation solvents was 90 mass%, and most of the remainder was collect | recovered by adsorption collection.

  The dried film 101 was conveyed to a first humidity control chamber (not shown). A drying air of 110 ° C. was supplied to the transition portion between the drying chamber 105 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 101 was conveyed to a second humidity control chamber (not shown) that suppresses the curling of the film 101. In the second humidity control chamber, air of 90 ° C. and humidity 70% was directly applied to the film 101.

  The film 101 after humidity control was cooled to 30 ° C. or lower in the cooling chamber 107, and both ends were cut off. Further, knurling was performed on both ends of the film 101 by a knurling roller 109. Knurling was applied by embossing from one side.

(8) Winding Then, the film 101 was conveyed to the winding chamber 110. The winding chamber 110 was kept at a room temperature of 28 ° C. and a humidity of 70%. The period during winding was 400 m, and the oscillating width was ± 5 mm. Further, the pressing roller 112 was pressed against the winding roller 111 and the pressure was set to 50 N / width. The winding tension was set to 300 to 350N. The temperature of the film during winding was 25 ° C., the water content was 1.4% by mass, and the residual solvent amount was 0.3% by mass. The average drying rate was 20% by mass (dry weight reference solvent) / min throughout the entire process. Moreover, there was no winding looseness and wrinkles, and no winding slip occurred in the impact test at 10G. The roll appearance was also good.

(9) Static elimination This embodiment is described in detail below. First, a surface potentiometer (not shown) was installed near the film outlet in the drying chamber 105 to measure the charging potential of the film 101. The measured value at this time is defined as a charging potential A (unit: V). Then, the charge was removed using the charge removing device 120 in the cooling chamber 107, and the charged potential of the film 101 was measured using the surface potential meter 125 on the grounded pass roller 123. This measured value is defined as a charging potential B (unit: V). Next, the film width is obtained by oscillating by performing oscillating while performing the neutralization of 12 μm using the knurling roller 109 while controlling the edge position of the film with an edge position controller (not shown) while performing the neutralization using the static eliminator 121. Was cut to 1340 mm. Next, a surface potential meter 126 was installed on the grounded pass roller 124, and the charging potential of the film 101 was measured. The measured value at this time is defined as a charging potential C (unit: V).

  Furthermore, while performing static elimination using the static elimination apparatus 122, the film was wound up on the winding apparatus 110 whose outer periphery diameter is 168 mm, and the film roll of 3900 m winding length was created. Here, the thickness of the film was 80 μm, and the winding tension was 300 N or more and 350 N or less. Finally, as shown in FIG. 5, the film 101 was pulled out from the wound film roll 130, and the charged potential was measured using the surface potentiometer 131 on the grounded pass roller 132. The measured value at this time is defined as a charging potential D (unit: V). And the coating liquid for hard-coat layers was apply | coated with respect to the obtained film 101, and the generation | occurrence | production state of the coating nonuniformity was confirmed visually. These results are shown in Table 1 as Example 1-1. In Table 1, a case where no coating unevenness was confirmed was marked with ◯, a coating unevenness was found, but a case where there was no problem as a product was marked with △, and a case where coating unevenness was present and it was not desirable as a product was marked with x. . The hard coat layer coating solution will be described later. The surface electrometers used are all Model 344 manufactured by Trek Japan. The winding tension is shown in the tension column in Table 1.

(Coating liquid for hard coat layer and coating method on film)
250 g of a mixture of dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate (DPHA, manufactured by Nippon Kayaku Co., Ltd.) was dissolved in 439 g of a mixed solvent of methyl ethyl ketone / cyclohexanone = 50/50 mass%. A solution obtained by dissolving 7.5 g of a photopolymerization initiator (Irgacure 907, manufactured by Ciba Geigy) and 5.0 g of a photosensitizer (Kayacure DETX, manufactured by Nippon Kayaku Co., Ltd.) in 49 g of methyl ethyl ketone was added to the obtained solution. added. The refractive index of the coating film obtained by applying this solution and curing with ultraviolet rays was 1.51. Further, this solution was filtered through a polypropylene filter having a pore diameter of 30 μm to prepare a coating solution for a hard coat layer.

The above hard coat layer coating solution was applied using a bar coater, dried at 120 ° C., and then 160 W / cm air-cooled metal halide lamp (manufactured by Eye Graphics Co., Ltd.), with an illuminance of 400 mW / cm ² , The coating layer was cured by irradiating with an irradiation amount of 300 mJ / cm ² to form a 4 μm thick hard coat layer.

  Next, the surface potential meter 126 of Example 1-1 was replaced with a statillon (model: STA TIRON-DZ3, manufactured by Shishido electrostatic Co., Ltd.), and the charged potential C was measured. The results are shown in Table 1 as Example 1-2.

  The same procedure as in Example 1-1 and Example 1-2 was performed except that the tension in winding was adjusted to 360 N or more and 410 N or less. The results of Example 1-1 and Example 1-2 are also shown in Table 1.

  Ear cutting was performed so that the film width was 1475 mm, and the same procedure as in Example 1-1 and Example 1-2 was performed except that the tension in winding was set to 320N or more and 390N or less. The results of Example 3-1 and Example 3-2 are also shown in Table 1.

  In the cooling chamber 107, the film 101 was not neutralized by the static eliminator 120. The neutralization by the neutralization devices 121 and 122 was performed, and the winding tension was adjusted to 310N or more and 350N or less. About other conditions, it carried out similarly to Example 1-1 and Example 1-2. The results of Examples 4-1 and 4-2 are also shown in Table 1.

  The film 101 was not neutralized by the neutralization devices 120, 121, and 122. The winding tension was 310N or more and 350N or less. About other conditions, it implemented similarly to Example 1-1 and Example 1-2. The results of Examples 5-1 and 5-2 are also shown in Table 1.

  The film 101 was neutralized by the neutralization devices 120 and 122, but the neutralization by the neutralization device 121 was not performed. Further, the winding tension was adjusted to 310N or more and 350N or less. About other conditions, it implemented similarly to Example 1-1 and Example 1-2. Table 1 also shows the results of Examples 6-1 and 6-2.

  From the above results, in the method of measuring only the charging potential only at the time of winding with the conventional surface potentiometer, the correlation between the coating unevenness and the charging potential was not clear, but according to the present invention, both The correlation can be clarified. Furthermore, according to the present invention, the static elimination is performed not only in the winding process but also in the soft drying process on the upstream side of the winding process, so that the charging history of the film is improved and a slight charging potential of −5V to + 5V is obtained. It was possible to suppress the occurrence of coating unevenness in the secondary processing.

It is explanatory drawing showing the production line of dope. It is explanatory drawing showing a film manufacturing line. It is explanatory drawing from the drying process which implemented this invention to the winding-up process. It is explanatory drawing showing the static elimination method using a ventilation type static elimination apparatus. It is explanatory drawing of the surface potential measurement method of the film roll after winding.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Dope production line 40 Film production line 105 Drying room 107 Cooling room 110 Winding room 120 Blow-type static elimination apparatus 121,122 Static elimination apparatus 123,124 Pass roller 125,126 Surface potential meter

Claims (7)

After casting the polymer solution on an endless support, the polymer film is peeled off as a polymer film, and the polymer film is dried in a drying chamber and then cooled in a cooling chamber downstream of the drying chamber. In the solution casting method in which the knurling is applied and then wound around the core,
A first static elimination step of neutralizing the polymer film being cooled by a first static elimination device disposed in the cooling chamber;
A second charge eliminating step for removing the polymer film exiting the cooling chamber before the knurling is applied by a second charge eliminating device disposed downstream of the cooling chamber;
A third static elimination step of neutralizing the polymer film provided with the knurling by a third static elimination device disposed upstream of the core;
A solution casting method, wherein a charging potential of the polymer film at the time of winding the polymer film is in a range of −5 V or more and +5 V or less. 2. The solution casting method according to claim 1, wherein the polymer film is wound around the winding core while performing static elimination by the third static elimination device. The first static eliminator is a blower type static eliminator that emits ionic wind,
A surface potential of the polymer film is measured with a surface potential meter on a grounded pass roller provided in the cooling chamber and downstream of the first static elimination device, and the first static elimination device is based on the measured surface potential. 3. The solution casting method according to claim 1, wherein the amount of ion wind is controlled. The third static eliminator is a blower type static eliminator that emits ionic wind,
  The surface potential of the polymer film is measured with a surface potential meter on a grounded pass roller provided upstream of the third static eliminator provided inside the winding chamber that houses the winding core, and the surface potential is measured based on the measured surface potential. 4. The solution casting method according to claim 1, wherein the amount of ion wind in the third static elimination device is controlled. 5. The solution casting method according to claim 1, wherein in the cooling chamber, the polymer film exiting the drying chamber having an internal temperature of 100 to 150 ° C. is cooled to 30 ° C. or less. . 6. The solution casting method according to claim 1, wherein the polymer film is wound around the core with a winding tension of 300 N or more and 410 N or less. 7. The solution casting method according to claim 1, wherein the knurling is applied by embossing with a knurling roller.

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