JP2006272954A - Process and equipment for solvent casting of film, and polymer film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and equipment for solvent casting a film, which can reduce fluctuation of a slow axis, and a polymer film with a reduced fluctuation of the slow axis. <P>SOLUTION: A tenter device 100 is equipped with clips 150 and 152, which travel along respective rails 120 and 122 on either side, and conveys a wet film 87 gripping at both side parts by the clips 150 and 152. Width between a left rail 120 and a right rail 122 is expanded along the way from a tenter inlet port 134 to a tenter outlet port 136 and stretching of the wet film 87 is carried out during the conveyance. Respective rails 120 and 122 are arranged to meet -0.03<(A-B)/(A+B)<0.03; where A stands for the distance from a central axis 155 of the tenter device 100 to the clip 150, and B stands for the distance from the central axis 155 to the clip 152. The wet film 87 can thereby be uniformly stretched to both sides of the width direction, and a fluctuation of the slow axis is controlled. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention comprises first and second gripping means facing each other in the width direction of the film, and transports the film while gripping the film by the gripping means, and the width of the first and second gripping means during the transport. And a solution film forming method and equipment for stretching the film in the width direction, and a polymer film formed by such a method and equipment.

  A solution film forming method is known as a method for forming a polymer film. In this method, a polymer is dissolved in a solvent to form a dope, and then the dope is cast from a die on a rotating support such as a band or a drum to form a cast film, and the cast film is supported. It is peeled off from the body and dried to obtain a polymer film.

  The cast film (wet film) peeled off from the support is conveyed by a tenter device and dried during this conveyance. The tenter device conveys the wet film while holding both sides of the wet film with clips. In the tenter device, the wet film may be stretched by expanding the width of the clip during conveyance. By this stretching, refractive index anisotropy can be expressed. For this reason, stretching is frequently used when a polymer film used in a liquid crystal display device or the like is formed.

However, although the refractive index anisotropy can be expressed by performing stretching, if the proper stretching is not performed, the angle of the slow axis varies. When such a film having a slow axis variation is used in a liquid crystal display device or the like, it becomes a factor that deteriorates the contrast or changes in color. For this reason, the present applicant has proposed a method in Patent Document 1 that defines conditions for stretching and suppresses variations in the slow axis.
JP-A-2005-316614

  However, as the brightness of liquid crystal display devices increases and the screen size increases, it is required to further reduce the variation in the slow axis.

  The present invention has been made in view of the above background, and an object of the present invention is to provide a solution casting method and equipment capable of reducing the variation of the slow axis, and a polymer film having a small variation of the slow axis. It is said.

  In order to achieve the above object, the solution casting method and apparatus according to the present invention provides a distance from the central axis of the tenter device parallel to the longitudinal direction of the film to the first gripping means A, and from the central axis to the first axis. (2) When the distance to each gripping means is B, −0.03 <(A−B) / (A + B) <0.03 is satisfied.

  It is preferable to dry the film by blowing dry air during the conveyance and to keep the temperature of the dry air constant while the width of the film is changing.

  Further, the polymer film may be formed by such a solution casting method and equipment.

  According to the present invention, since the film can be stretched and relaxed in a balanced manner in both directions by making the distances from the central axis of the tenter device to the first and second gripping means substantially equal, the slow axis Can suppress the variation of

  Furthermore, by using such a solution casting method and equipment, it is possible to form a high-quality polymer film with little variation in the slow axis.

  Hereinafter, the case where a cellulose acylate film is formed as a polymer film will be described.

[material]
As the cellulose acylate, it is preferable to use cellulose acylate (hereinafter referred to as TAC) in which the substitution degree of the hydroxyl group of cellulose satisfies all of the following formulas (1) to (3).
(1) 2.5 ≦ A + B ≦ 3.0
(2) 0 ≦ A ≦ 3.0
(3) 0 ≦ B ≦ 2.9
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 addition, it is preferable to use particles having 90% by mass or more of TAC of 0.1 mm to 4 mm.

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

  The total acyl substitution degree, that is, DS2 + DS3 + DS6 is preferably 2.00 to 3.00, more preferably 2.22 to 2.90, and particularly preferably 2.40 to 2.88. Further, D6S / (DS2 + DS3 + DS6) is preferably 0.28 or more, more preferably 0.30 or more, and particularly preferably 0.31 to 0.34. Here, DS2 is the degree of substitution of the hydroxyl group at the 2-position of the glucose unit with an acyl group (hereinafter also referred to as “degree of acyl substitution at the 2-position”), and DS3 is the degree of substitution of the hydroxyl group at the 3-position with an acyl group (hereinafter, referred to as “acyl group”). DS6 is the substitution degree of the hydroxyl group at the 6-position with an acyl group (hereinafter also referred to as “acyl substitution degree at the 6-position”).

  Only one type of acyl group may be used in the cellulose acylate of the present invention, or two or more types of acyl groups may be used. When two or more types of acyl groups are used, one of them is preferably an acetyl group. DSA + DSB, where DSA is the total substitution degree of hydroxyl groups at the 2nd, 3rd and 6th positions with acetyl groups, and DSB is the total substitution degree with hydroxyl groups other than the acetyl groups at the 2nd, 3rd and 6th hydroxyl groups The value of is preferably 2.22 to 2.90, 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 is a substituent at the 6-position hydroxyl group, more preferably 30% or more, and particularly 33% or more is 6%. A substituent of a hydroxyl group is preferred. The cellulose acylate preferably has a substitution degree value at the 6-position of 0.75 or more, more preferably 0.80 or more, and particularly preferably 0.85 or more. . With these cellulose acylates, a solution having a preferable solubility (dope) can be produced. In particular, in a non-chlorine organic solvent, a good solution can be produced. Further, a solution having a low viscosity and good filterability can be produced.

  The cellulose acylate may be obtained from either linter cotton or pulp cotton, but is preferably obtained from linter cotton.

  The acyl group having 2 or more carbon atoms of the cellulose acylate of the present invention may be an aliphatic group or an aryl group and is not particularly limited. These are, for example, cellulose alkylcarbonyl esters, alkenylcarbonyl esters, aromatic carbonyl esters, aromatic alkylcarbonyl esters, and the like, each of which may further have a substituted group. Preferred examples of these include propionyl 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. is there.

  Solvents for preparing the dope include aromatic hydrocarbons (eg, benzene, toluene, etc.), halogenated hydrocarbons (eg, dichloromethane, chlorobenzene, etc.), alcohols (eg, methanol, ethanol, n-propanol, n-butanol, Diethylene glycol, etc.), ketones (eg, acetone, methyl ethyl ketone, etc.), esters (eg, methyl acetate, ethyl acetate, propyl acetate, etc.) and ethers (eg, tetrahydrofuran, methyl cellosolve, etc.).

  A halogenated hydrocarbon having 1 to 7 carbon atoms and dichloromethane are preferably used. From the viewpoint of physical properties such as solubility of TAC, peelability of cast film from the support, mechanical strength of the film, and optical properties of the film, in addition to dichloromethane, one or more alcohols having 1 to 5 carbon atoms are used. It is preferable to mix several types. 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. Examples of the alcohol include methanol, ethanol, n-propanol, isopropanol, n-butanol, and a mixture thereof is also 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 JP-A-2005-104148, [0140] to [0195], and can be applied to the present invention. Similarly, additives such as solvents and plasticizers, deterioration inhibitors, ultraviolet absorbers, optical anisotropy control agents, dyes, matting agents, release agents and the like are also described in JP-A-2005-104148, from [0196] to [0516]. ] And is applicable to the present invention.

[Production of raw material dope]
FIG. 1 shows a raw material dope production line 10. In manufacturing the raw material dope, 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 to 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. A first stirring blade 19 that is rotated by a motor 18 is attached. Furthermore, it is preferable that the 2nd stirring blade rotated by the motor 20 is 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 flow the heat transfer medium through the jacket 17 and adjust the temperature in the dissolution tank 13 in the range of −10 ° C. to 55 ° C. By appropriately selecting and rotating the first stirring blade 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, the cooling dissolution method which cools the swelling liquid 22 to the temperature of -150 degreeC--10 degreeC can also be performed. TAC can be sufficiently dissolved in a solvent by appropriately selecting the heating dissolution method and the cooling dissolution method. After the temperature of the raw material dope is set to about room temperature by the temperature controller 27, filtration by the filtering device 28 is performed to remove impurities in the raw material 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 raw material dope after filtration is put into the stock tank 30 through the valve 29.

  The raw material dope can be used as a solution film-forming dope 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 of preparing a raw material dope having a target concentration after preparing a raw material dope having a concentration lower than the target TAC concentration. The raw material 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 raw material 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 preparing the raw material dope by the regenerator 33.

  The concentrated raw material dope is extracted from the flash unit 31 using the pump 34. Furthermore, it is preferable to remove bubbles in the raw material 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. At this time, the temperature of the raw material dope is preferably 0 ° C. to 200 ° C. Thus, the raw material dope 36 having a TAC concentration of 5% by mass to 40% by mass can be manufactured. The produced raw material dope 36 is stored in the stock tank 30.

  The materials, raw materials, additives dissolution method, filtration method, defoaming, and addition method in the solution casting method for obtaining the TAC film are described in detail in [0517] to [0616] of JP-A-2005-104148. And is 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 material 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 raw material dope 36 is fed by pumps 46, 47, 48 provided in the respective flow paths 43, 44, 45. After being fed to the feed block 70 and merged, it is cast from the casting die 71 onto the casting band 72.

"Dope manufacturing process"
The intermediate layer additive 51 contained in the stack tank 50 is fed by the pump 52 and mixed with the raw material dope in the intermediate layer dope flow path 43 (hereinafter referred to as the intermediate layer raw material dope). . Thereafter, the mixture is stirred and mixed by a static mixer (static 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 raw material dope (hereinafter referred to as support surface raw material dope) in the support surface dope channel 44 by a pump 57 and mixed. . Thereafter, the mixture is stirred and mixed by the static 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, fine particle powder such as 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 raw material dope in the air surface dope channel 45 (hereinafter referred to as air surface raw material dope) by the pump 62 and mixed. . Thereafter, the mixture is stirred and mixed by the static mixer 63 to be uniform. Thereby, the dope for air surfaces is produced | generated. The air surface additive 61 contains an additive such as a matting agent (for example, fine particle powder such as silicon dioxide) that suppresses adhesion between the film surfaces when the film is wound into a roll. Yes. The air surface additive 61 may contain additives such as a peeling accelerator, a plasticizer, and an ultraviolet absorber.

  Each dope generated by adding various additives to each raw material dope is fed to the feed block 70 at a desired flow rate. After the dopes merge in the feed block 70, they are cast from the casting die 71 onto the casting band 72.

"Casting process"
The material of the casting die 71 is preferably a double layer stainless steel. It is preferable to use a material having a thermal expansion coefficient of 2 × 10 ⁻⁵ (° C. ⁻¹ ) or less. Moreover, what has corrosion resistance substantially equivalent to SUS316 in the forced corrosion test in electrolyte aqueous solution can also be used. Further, a material having corrosion resistance that does not cause pitting (opening) at the gas-liquid interface even when immersed in a mixed solution of dichloromethane, methanol, and water for 3 months is used. 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, but it is preferable to use a casting die having a width of about 1.0 to 2.0 times the width of the final film. 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 forming 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 a ceramic that can be ground, has a low porosity, is not brittle, has good corrosion resistance, has good adhesion to the casting die 71, and does not have adhesion to the dope. 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. Supplying 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) to the gas-liquid interface between the end of the casting bead and the slit. Is preferred. In addition, it is preferable to use a pump having a pulsation rate of 5% or less for supplying the liquid.

  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 3.0 times the casting width of the dope. Moreover, it is preferable to use what was polished so that length may be 10 m-200 m, thickness may be 0.3 mm-10 mm, and surface roughness may 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. Further, the relative speed difference between the casting band 72 and the rotating rollers 73 and 74 is adjusted to be 0.01 m / min or less. 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% 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. The back surface of the bead is preferably decompressed in the range of −10 Pa to −2000 Pa rather than the pressure with the front surface. 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, but is preferably in the range of 10 ° C to 50 ° C. 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, it is preferable to provide the blowers 82, 83, and 84 in order to evaporate the solvent in the casting film 80. Although the attachment position of the blower is illustrated as being provided on the upper upstream side 82, the downstream side 83, and the lower part 84 of the casting band 72, the present invention is not limited to this. Further, it is preferable that a wind shield device 85 is provided in order to suppress the surface variation of the film surface due to the drying air being blown onto the cast film 80 immediately after the formation. 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 a self-supporting property, it is peeled off from the casting band 72 as a wet film 87 while being supported by a peeling roller 86. After that, it is sent to the crossing section 90 where many rollers are provided. In the transfer part 90, the drying of the wet film 87 is advanced by sending the drying air of predetermined 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 crossover section 90, it is also possible to give the wet film 87 a draw by making the rotation speed of the downstream roller faster than the rotation speed of the upstream roller.

  A tenter device 100 is provided on the downstream side of the crossover unit 90. The tenter device 100 conveys the wet film 87 by holding both sides of the wet film 87 with clips 150 and 152 (see FIG. 3). The wet film 87 is transported into a dry casing 99 in which a dry air blower 98 is installed. While being transported in the dry casing 99, a dry air of a predetermined temperature is blown from the dry air blower 98 and further dried. Is done. In addition, the tenter device 100 performs stretching for stretching the wet film 87 in the width direction during the conveyance. The wet film 87 dried and stretched by the tenter device 100 is sent out as a film 101. As will be described later in detail, the present invention suppresses variations in the slow axis that occur in the film 101 by devising the tenter device 100.

  The side edges of the film 101 sent from the tenter device 100 are cut by the ear clip device 102. The cut edge portions are 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 cutting of both side edge parts can be omitted, it is preferably performed at any time from a casting process to a film winding process described later.

  Next, the film 101 is sent to a drying chamber 105 provided with a large 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 50 to 180 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 is blown into the drying chamber 105 as dry air. The drying chamber 105 is more preferably divided into a plurality of sections in order to change the drying temperature. In addition, it is preferable to provide a preliminary drying chamber (not shown) between the ear clip device 102 and the drying chamber 105 to perform preliminary drying of the film 101 to suppress a rapid increase in the film temperature. By performing preliminary drying in this way, it is possible to prevent a change in the shape of the film accompanying a rapid increase in the film temperature.

  The film 101 is conveyed to the cooling chamber 107 and cooled to approximately room temperature. 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, it is possible to suppress the occurrence of curling of the film 101 and the occurrence of winding failure during winding.

  A forced charge removal device (charge removal bar) 108 is provided so that the charged voltage during the conveyance of the film 101 falls within a predetermined range (for example, −3 kV to +3 kV). In the figure, an example provided on the downstream side of the cooling chamber 107 is illustrated, but the position is not limited thereto. Further, 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.

  As described above, since the three types of dopes are co-cast in the present embodiment, the intended characteristics of the film 101 can be easily obtained. 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 this embodiment, the matting agent is contained in the dope for the support surface and the dope for the air surface, which are the front and back surfaces of the film, and is not included in the dope for the intermediate layer. It is possible to obtain the optical characteristics.

  For co-casting, as in the above-described embodiment, simultaneous lamination co-casting in which two or more types of dopes are cast at the same time, and sequential lamination co-casting in which two or more types of dopes are cast in order from the lower layer side. The present invention can be applied to any of these. Moreover, you may combine these both casting. Moreover, when performing casting, the casting die 71 which attached the feed block 70 as shown in FIG. 2 may be used, and a multi-manifold type casting die may be used. It is preferable that the thickness of the layer on the air surface side and / or the thickness of the layer on the support side is 0.5% to 30% in the total film thickness of the film composed of multiple layers by co-casting. Furthermore, when performing simultaneous lamination co-casting, it is preferable to enclose the high-viscosity dope 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.

  From casting die, decompression chamber, support structure, co-casting, peeling method, stretching, drying conditions of each process, handling method, curl, winding method after flatness correction, solvent recovery method, film recovery method JP-A 2005-104148 describes in detail in [0617] to [0889]. 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 JP-A-2005-104148, [0112] to [0139]. These are also applicable to the present invention.

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

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

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

The functional layers preferably contain at least one surfactant 0.1mg ^{/ m 2} ~1000mg ^/ m 2 containing. Moreover, it is preferable that the said functional layer contains 0.1 mg / m2-1000 mg / m < ² > of at least 1 type of slip agent. Further, the functional layers preferably contain at least one sort of matting agents in the 0.1mg ^{/ m 2} ~1000mg ^/ m 2 containing. Further, the functional layers preferably contain at least one sort of antistatic agents ^1mg / ^{m 2 ~1000mg} / m 2 containing. In addition to the above, the method for imparting a surface-treated functional layer to the cellulose acylate film to achieve various functions and properties is described in detail in [0890] to [1087] of JP-A-2005-104148. , Including methods. These are also applicable to the present invention.

(Use)
The cellulose acylate film thus formed is particularly useful as a polarizing plate protective film used in a liquid crystal display device. Japanese Patent Application Laid-Open No. 2005-104148 describes in detail examples of using a cellulose acylate film in a TN type, STN type, VA type, OCB type, reflective type, and other liquid crystal display devices. 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 same application also describes an example in which a biaxial cellulose acylate film imparted with appropriate optical performance is used as an optical compensation film, and the formed cellulose acylate film can be used for various applications. it can.

  Although the cellulose acylate film has been described as an example, the present invention can also be applied to a polymer film using a polymer other than cellulose acylate as a dope raw material. The polymer film is preferably an optical film. The polymer film is preferably a cellulose ester film. The cellulose ester film is preferably a cellulose acylate film, more preferably a cellulose acetate film, and most preferably a cellulose triacetate film. Moreover, what uses the said cellulose-ester film for various optical functional films is also contained in this invention. For example, a photographic material base film, a polarizing plate protective film, an optical compensation film base film, and the like. Furthermore, the present invention includes a liquid crystal display device configured using the optical functional film. The present invention can also be applied to the production of a thin film having a film thickness of 15 μm or more and 100 μm or less.

  Hereinafter, the tenter device 100 according to the present invention will be described in detail. As shown in FIG. 3, the tenter device 100 is provided with a left rail 120, a right rail 122, and endless chains 130 and 132 guided by the rails 120 and 122 in the dry casing 99 described above. ing. The endless chains 130 and 132 are stretched between driving sprockets 140 and 142 provided on the tenter inlet 134 side and driven sprockets 141 and 143 provided on the tenter outlet 136 side. The driving sprockets 140 and 142 are rotationally driven by a driving mechanism (not shown) to move the endless chains 130 and 132.

  A plurality of clips 150 and 152 are attached to the endless chains 130 and 132, respectively, and the clips 150 and 152 move as the endless chains 130 and 132 move. Each of the clips 150 and 152 grips the side portion of the wet film 87 at the tenter inlet 134, transports it to the tenter outlet 136 as it is, and then releases the grip at the tenter outlet 136. The tenter device 100 blows dry air during the conveyance to dry the wet film 87.

  Further, in the tenter device 100, the width between the left rail 120 and the right rail 122 is expanded from the tenter inlet 134 to the tenter outlet 136, and the width between the clips 150 and 152 is widened during conveyance. Thus, the wet film 87 is stretched. The degree of stretching is appropriately set. For example, the wet film 87 is stretched in the range of 0.5% to 300%. And by performing this extending | stretching, the refractive index anisotropy expresses in the film 101 sent from the tenter apparatus 100. FIG.

However, if the wet film 87 is not uniformly stretched to both sides in the width direction, the wet film 87 will be twisted, resulting in large variations in the slow axis. For this reason, in the tenter apparatus 100 of the present invention, when the distance from the central axis 155 to the clip 150 of the tenter apparatus 100 is A and the distance from the central axis 155 to the clip 152 is B at an arbitrary position in the transport direction. ,
−0.03 <(A−B) / (A + B) <0.03
The left and right rails 120 and 122 are formed so as to satisfy the above. In this way, by uniformly stretching the wet film 87 to both sides in the width direction, the wetting of the wet film 87 can be eliminated and the variation in the slow axis can be reduced.

  In the above-described embodiment, an example has been described in which the film is conveyed to the tenter outlet without changing the width of the wet film after stretching. However, the present invention is not limited to this. For example, like the tenter device 200 shown in FIG. 4, the width between the left rail 220 and the right rail 222 may be relaxed after the wet film 87 is stretched by being slightly narrowed and then slightly narrowed. Also in this case, when the distance from the central axis 155 of the tenter device 200 to the clip 220 is A and the distance from the central axis 155 to the clip 222 is B at an arbitrary position in the transport direction, −0.03 <(A The left and right rails 220 and 222 are formed so as to satisfy −B) / (A + B) <0.03. By doing so, the twist of the wet film 87 can be eliminated and the variation of the slow axis can be reduced. In FIG. 4, members similar to those in the above-described embodiment are denoted by the same reference numerals and description thereof is omitted.

  Further, when relaxation is performed after stretching in this way, the width between the clips of the left and right rails when gripping the wet film is set to L1 (mm), and the wet film is stretched to the maximum in the width direction. When the width between the clips is L2 (mm) and the width between the clips when the wet film is released and the wet film is released is L3 (mm), 1 <(L2−L3) / L1 × 100 <15 It is preferable that

  Furthermore, in the said embodiment, although the example which blows the dry wind of predetermined temperature from one dry wind blower was demonstrated with respect to the wet film conveyed by a tenter apparatus, this invention is not limited to this. Absent. A plurality of dry air blowers that blow dry air at different temperatures may be provided. In this case, the drying casing may be divided into a plurality of drying zones by providing a partition plate or the like in the drying casing, and the temperature of the drying air may be set for each drying zone. In addition, it is preferable that the temperature of dry wind is the substantially same temperature for every dry wind blower in the range of 50 to 180 degreeC. In addition, while the width of the wet film is changed by stretching or relaxation, it is preferable that the temperature of the drying air to be blown is made equal.

Hereinafter, specific examples of the present invention will be described in comparison with comparative examples. The composition of the raw material dope is shown below.
(1) Composition: 100 parts by mass of cellulose triacetate (TAC) (Degree of substitution with acetyl group 2.81 (acetylation degree 60.2%), Mw / Mn = 2.7, viscosity average degree of polymerization 305, in dichloromethane solution 6 (Mass% viscosity 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 cellulose triacetate 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. Contained 15 ppm. 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.

(2) 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 kgf / m / sec ² ) at the beginning and an anchor blade 19 on the central shaft. And dispersed at a peripheral speed of 1 m / sec (shear stress of 1 × 10 ⁴ kgf / m / sec ² ) for 30 minutes. 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 raw material dope was 0.3% by mass.

(3) Dissolution / filtration The swelling liquid 22 was sent 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 filtration device 28 having a filter medium having a nominal pore diameter of 8 μm to obtain a raw material dope having a solid content concentration of 19% by mass (hereinafter referred to as a raw material 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.

(4) Concentration, filtration, and defoaming The raw material 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 content concentration of the raw material dope after the flash 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 of this raw material dope collected and measured at 25 ° C. was 450 Pa · s at a shear rate of 10 (1 / s).

  Next, bubbles were removed by irradiating the raw material 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 raw material 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. When preparing the raw material dope from the pre-concentration dope, no problems such as corrosion occurred at all in the wetted parts of the dope of each apparatus.

(5) Discharge Film deposition was performed using the film deposition line 40 shown in FIG. Subsequently, the raw material 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 primary pressure increasing gear pumps 46, 47, 48. 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. As the dope liquid supply channel, three channels of an intermediate layer dope channel 43, a support surface dope channel 44, and an air surface dope channel 45 were used. The casting die 71 was equipped with a feed block 70 having a width of 1.8 m and adjusted for co-casting to form a three-layer film.

(6) Dope production Retardation control agent (N, N′-di-m-tolyl-N ″ -p-methoxyphenyl-1,3,5-triazine-2,4,6-triamine) and dichloromethane An intermediate layer additive solution 51 in which a mixed solvent of 86.5 parts by mass, methanol 13 parts by mass, and n-butanol 0.5 part by mass and the raw material dope 36 was mixed was placed in the stock tank 50. The intermediate layer additive solution 51 was fed to the raw material dope 36 in the intermediate layer dope channel 43 by the pump 52. And it mixed through the static mixer 53, and the dope for intermediate | middle layers was produced | generated.

  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 to obtain a support surface addition liquid 56. This mixed solvent is a mixture of 86.5 parts by mass of dichloromethane, 13 parts by mass of methanol, and 0.5 parts by mass of n-butanol. 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 was made to mix with the static mixer 58, and the dope for support body surfaces was produced | generated.

  Silicon dioxide was dispersed in a mixed solvent to prepare an air surface additive solution 61 and put into the stock tank 60. This mixed solvent is a mixture of 86.5 parts by mass of dichloromethane, 13 parts by mass of methanol, and 0.5 parts by mass of n-butanol. The air surface additive solution 61 was fed to the raw material dope 36 in the air surface dope channel 45 by the pump 62. And it was made to mix through the static mixer 63 and the dope for air surfaces was produced | generated.

(7) Casting Each of the dopes so that the film thickness (exposed surface side layer, intermediate layer, support surface side layer) of the target TAC film 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. The casting was performed such that the width W2 of the casting film 80 was 1570 mm. 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 can be set by an adjustment program based on the profile of an infrared thickness meter (not shown) installed in the film deposition line 40 The feedback control also has a possible performance. The thickness difference between two arbitrary points separated by 50 mm in the film excluding the casting edge portion of 20 mm was within 1 μm, and the maximum difference in the width direction thickness was adjusted to be 3 μm / m or less. The average thickness accuracy of each layer was controlled so that both outer layers were controlled to ± 2% or less, the mainstream was controlled to ± 1% or less, and the total thickness was adjusted to ± 1.5% or less.

  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. 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 two-layer stainless steel, and has a thermal expansion coefficient of 2 × 10 ⁻⁵ (° C. ⁻¹ ) or less, and is approximately the same corrosion resistance as that of SUS316 in a forced corrosion test with an aqueous electrolyte solution. The material which has the property 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, and the relative speed difference between the casting band 72 and the rotating rollers 73 and 74 is adjusted to 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. 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 (water) at 5 ° C. was passed through the rotary roller 73 on the casting die 71 side, and a heat transfer medium (water) 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 10 μm or less. 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 casting 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.

(8) Stripping / Drying By the wind shield device 85, the static pressure fluctuation in the immediate vicinity of the casting die 71 is suppressed to ± 1 Pa or less so that the drying wind does not directly hit the casting film 80 for 5 seconds after casting. . When the solvent ratio in the casting film 80 reached 150% by mass on a dry basis, the casting film 80 was peeled off 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 device. At this time, 40 ° C. dry air was blown from the blower 91 to the wet film 87. In addition, a tension of about 20 N was applied to the wet film 87 during the conveyance with the roller of the crossing section 90.

  In this example, a tenter device 200 of a type that performs relaxation after stretching, as shown in FIG. 4, was used instead of the tenter device 100 shown in FIG. In the tenter device 200, a width range corresponding to 5% of the width of the wet film 87 is conveyed in the drying casing 99 while holding the clips 150 and 152 of the left and right rails 220 and 222, and dried by blowing dry air. I let you. The clips 150 and 152 were cooled by supplying a heat transfer medium at 20 ° C. The speed fluctuation of the driving sprockets 140 and 142 was set to 0.5% or less. Further, the inside of the dry casing 99 was divided into three zones, and the drying air temperature in each zone was set to 90 ° C., 100 ° C., and 110 ° C. from the upstream side. The gas composition of the drying air was set to a saturated gas concentration of −10 ° C. The average drying speed in the tenter apparatus 200 was 120% by mass (dry weight reference solvent) / min. At the tenter outlet 136, the tenter apparatus 200 conditions were adjusted so that the amount of residual solvent in the wet film 87 was 7% by mass. The solvent evaporated in the tenter device 200 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. The wet film 87 dried and stretched while being conveyed by the tenter apparatus 200 was sent out as a film 101.

Then, the ear-cleaving device 102 cuts the ears at both ends within 30 seconds from the exit of the tenter device 200. 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 apparatus 200 was kept at 5 vol%. Note that the air was replaced with nitrogen gas in order to maintain the oxygen concentration at 5 vol%. Before drying at a high temperature in a drying chamber 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 a 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 conveying 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. All the vibrations due to the rotation of the roller 104 were 50 μm or less. The roller deflection at a tension of 100 N / width was selected to be 0.5 mm or less.

  The solvent gas contained in the drying 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. The forced charge removal device (charge removal bar) 108 was installed so that the film voltage during conveyance was always in the range of -3 kV to +3 kV. Further, knurling was performed on both ends of the film 101 by a knurling roller 109. The knurling was applied by embossing from one side, the knurling width was 10 mm, and the pressing pressure was set so that the maximum height was 12 μm higher than the average thickness on average.

(9) 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%. Furthermore, an ion wind static elimination device (not shown) was also installed so that the film voltage would be -1.5 kV to +1.5 kV. The product width of the film (thickness 80 μm) 101 thus obtained was 1475 mm. The diameter of the winding roller 111 was 169 mm. The tension pattern was such that the winding start tension was 360 N / width and the winding end was 250 N / width. The total winding length was 3940 m. The period during winding was 400 m, and the oscillating width was ± 5 mm. Further, the pressing roller 112 was pressed against the winding roller 111 and the pressure was set to 50 N / width. The temperature of the film at the time of winding was 25 ° C., the water content was 1.4% by mass, and the residual solvent amount was 0.3% by mass.

(10) Comparative Evaluation Among the processes for manufacturing the film 101 as described above, in the tenter device 200 described in (8), the film 101 is manufactured while changing the specifications of the left and right rails 220 and 222. The film 101 was examined for variations in the slow axis and evaluated. Table 1 shows the relationship between the specifications of the left and right rails and the variation of the slow axis of the film. As shown in Table 1, in the specification change, the width L1 (mm), L2 (mm), L3 (mm) between the clips 150 and 152 at the tenter inlet 134, at the time of maximum expansion, and the tenter outlet 136, respectively, The distance A from the central axis 155 of the tenter device 200 to the clip 150 and the distance B from the central axis 155 to the clip 152 were changed. The example in which the ratio (| A−B | / (A + B) × 100) of the difference between the distance A and the distance B with respect to the width between the clips 150 and 152 is less than 3% was taken as an example. On the other hand, a comparative example in which the ratio (| A−B | / (A + B) × 100) of the difference between the distance A and the distance B with respect to the width between the clips 150 and 152 is 3% or more was used.

[Comparative Example 1]
In Comparative Example 1, L1 is 1478 mm, L2 is 1918 mm, L3 is 1780 mm, and the ratio of the difference between the distance A and the distance B with respect to the width between the clips 150 and 152 (hereinafter simply referred to as the left-right difference) is 3.2%. did. In Comparative Example 1, the minimum axis angle of the slow axis was 89.7 degrees, and the maximum axis angle of the slow axis was 91.8. In Comparative Example 1, the difference between the minimum axis angle and the maximum axis angle (variation of the slow axis) was 2.1 degrees over a wide range, and the evaluation was x.

[Comparative Example 2]
In Comparative Example 2, L1 is 1475 mm, L2 is 1918 mm, L3 is 1826 mm, and the ratio of the difference between the distance A and the distance B with respect to the width between the clips 150 and 152 (hereinafter simply referred to as the left-right difference) is 4.0%. did. In Comparative Example 2, the minimum axis angle of the slow axis was 88.4 degrees, and the maximum axis angle of the slow axis was 91.6. In Comparative Example 2, the difference between the minimum axis angle and the maximum axis angle (variation of the slow axis) was 3.2 degrees over a wide range, and the evaluation was x.

[Comparative Example 3]
In Comparative Example 3, L1 is 1478 mm, L2 is 1888 mm, L3 is 1765 mm, and the ratio of the difference between the distance A and the distance B with respect to the width between the clips 150 and 152 (hereinafter simply referred to as the left-right difference) is 3.5%. did. In Comparative Example 3, the minimum axis angle of the slow axis was 89.0 degrees, and the maximum axis angle of the slow axis was 91.6. In Comparative Example 3, the difference between the minimum axis angle and the maximum axis angle (variation of the slow axis) was 2.6 degrees over a wide range, and the evaluation was x.

[Example 1]
In Example 1, L1 is 1478 mm, L2 is 1803 mm, L3 is 1765 mm, and the ratio of the distance A and the distance B with respect to the width between the clips 150 and 152 (hereinafter simply referred to as the left-right difference) is 0.8%. did. In Example 1, the minimum axis angle of the slow axis was 89.5 degrees, and the maximum axis angle of the slow axis was 90.5. In Example 1, since the difference between the minimum axis angle and the maximum axis angle (variation of the slow axis) was within a narrow range of 1.0 degree, the evaluation was “good”.

[Example 2]
In Example 2, L1 is 1478 mm, L2 is 1841 mm, L3 is 1765 mm, and the ratio of the difference between the distance A and the distance B with respect to the width between the clips 150 and 152 (hereinafter simply referred to as the left-right difference) is 0.3%. did. In Example 2, the minimum axis angle of the slow axis was 90.3 degrees, and the maximum axis angle of the slow axis was 90.9. In Example 2, since the difference between the minimum axis angle and the maximum axis angle (variation of the slow axis) was within a narrow range of 0.6 degrees, the evaluation was “good”.

[Example 3]
In Example 3, L1 is 1478 mm, L2 is 1871 mm, L3 is 1765 mm, and the ratio of the difference between the distance A and the distance B with respect to the width between the clips 150 and 152 (hereinafter simply referred to as the left-right difference) is 0.5%. did. In Example 3, the minimum axis angle of the slow axis was 90.0 degrees, and the maximum axis angle of the slow axis was 90.7. In Example 3, the difference between the minimum axis angle and the maximum axis angle (variation of the slow axis) was within a narrow range of 0.7 degrees.

[Example 4]
In Example 4, L1 is 1478 mm, L2 is 1888 mm, L3 is 1765 mm, and the ratio of the difference between the distance A and the distance B with respect to the width between the clips 150 and 152 (hereinafter simply referred to as the left-right difference) is 1.0%. did. In Example 4, the minimum axis angle of the slow axis was 89.3 degrees, and the maximum axis angle of the slow axis was 90.2. In Example 4, since the difference between the minimum axis angle and the maximum axis angle (variation of the slow axis) was within a narrow range of 0.9 degrees, the evaluation was good.

[Example 5]
In Example 5, L1 is 1478 mm, L2 is 1903 mm, L3 is 1765 mm, and the ratio of the difference between the distance A and the distance B with respect to the width between the clips 150 and 152 (hereinafter simply referred to as the left-right difference) is 1.2%. did. In Example 5, the minimum axis angle of the slow axis was 89.4 degrees, and the maximum axis angle of the slow axis was 90.7. In Example 5, since the difference between the minimum axis angle and the maximum axis angle (variation of the slow axis) was within a narrow range of 1.3 degrees, the evaluation was “good”.

[Example 6]
In Example 6, L1 is 1478 mm, L2 is 1918 mm, L3 is 1765 mm, and the ratio of the difference between the distance A and the distance B with respect to the width between the clips 150 and 152 (hereinafter simply referred to as the left-right difference) is 0.2%. did. In Example 6, the minimum axis angle of the slow axis was 89.8 degrees, and the maximum axis angle of the slow axis was 90.2. In Example 6, since the difference between the minimum axis angle and the maximum axis angle (variation of the slow axis) was within a narrow range of 0.4 degrees, the evaluation was “good”.

[Example 7]
In Example 7, L1 is 1478 mm, L2 is 1918 mm, L3 is 1780 mm, and the ratio of the difference between the distance A and the distance B to the width between the clips 150 and 152 (hereinafter simply referred to as the left-right difference) is 0.3%. did. In Example 7, the minimum axis angle of the slow axis was 89.6 degrees, and the maximum axis angle of the slow axis was 90.3. In Example 7, since the difference between the minimum axis angle and the maximum axis angle (variation of the slow axis) was within a narrow range of 0.7 degrees, the evaluation was good.

[Example 8]
In Example 8, L1 is 1475 mm, L2 is 1918 mm, L3 is 1826 mm, and the ratio of the difference between the distance A and the distance B with respect to the width between the clips 150 and 152 (hereinafter simply referred to as the left-right difference) is 0.1%. did. In Example 8, the minimum axis angle of the slow axis was 89.8 degrees, and the maximum axis angle of the slow axis was 90.2. In Example 8, since the difference between the minimum axis angle and the maximum axis angle (variation of the slow axis) was within a narrow range of 0.4 degrees, the evaluation was “good”.

[Example 9]
In Example 9, L1 is 1475 mm, L2 is 1932 mm, L3 is 1838 mm, and the ratio of the difference between the distance A and the distance B with respect to the width between the clips 150 and 152 (hereinafter simply referred to as the left-right difference) is 1.1%. did. In Example 9, the minimum axis angle of the slow axis was 89.4 degrees, and the maximum axis angle of the slow axis was 90.6. In Example 9, since the difference between the minimum axis angle and the maximum axis angle (variation of the slow axis) was within a narrow range of 1.2 degrees, the evaluation was “good”.

[Example 10]
In Example 10, L1 is 1475 mm, L2 is 1947 mm, L3 is 1849 mm, and the ratio of the difference between the distance A and the distance B with respect to the width between the clips 150 and 152 (hereinafter simply referred to as the left-right difference) is 0.5%. did. In Example 10, the minimum axis angle of the slow axis was 89.9 degrees, and the maximum axis angle of the slow axis was 90.7. In Example 10, the difference between the minimum axis angle and the maximum axis angle (variation of the slow axis) was within a narrow range of 0.8 degrees.

[Example 11]
In Example 11, L1 is 1465 mm, L2 is 1841 mm, and L3 is 1765 mm, and the ratio of the difference between the distance A and the distance B to the width between the clips 150 and 152 (hereinafter simply referred to as the left-right difference) is 0.8%. did. In Example 11, the minimum axis angle of the slow axis was 89.5 degrees, and the maximum axis angle of the slow axis was 90.4. In Example 11, since the difference between the minimum axis angle and the maximum axis angle (variation of the slow axis) was within a narrow range of 0.9 degrees, the evaluation was “good”.

[Example 12]
In Example 12, L1 is 1478 mm, L2 is 1803 mm, L3 is 1765 mm, and the ratio of the difference between the distance A and the distance B with respect to the width between the clips 150 and 152 (hereinafter simply referred to as the left-right difference) is 0.7%. did. In Example 12, the minimum axis angle of the slow axis was 89.4 degrees, and the maximum axis angle of the slow axis was 90.2. In Example 12, the difference between the minimum axis angle and the maximum axis angle (variation of the slow axis) was within a narrow range of 0.8 degrees.

[Example 13]
In Example 13, L1 is 1478 mm, L2 is 1841 mm, L3 is 1765 mm, and the ratio of the difference between the distance A and the distance B with respect to the width between the clips 150 and 152 (hereinafter simply referred to as the left-right difference) is 0.4%. did. In Example 13, the minimum axis angle of the slow axis was 89.9 degrees, and the maximum axis angle of the slow axis was 90.5. In Example 13, since the difference between the minimum axis angle and the maximum axis angle (variation of the slow axis) was within a narrow range of 0.6 degrees, the evaluation was “good”.

[Example 14]
In Example 14, L1 is 1478 mm, L2 is 1871 mm, L3 is 1765 mm, and the ratio of the difference between the distance A and the distance B with respect to the width between the clips 150 and 152 (hereinafter simply referred to as the left-right difference) is 0.6%. did. In Example 14, the minimum axis angle of the slow axis was 89.8 degrees, and the maximum axis angle of the slow axis was 90.5. In Example 14, the difference between the minimum axis angle and the maximum axis angle (variation of the slow axis) was within a narrow range of 0.7 degrees.

(11) Overall Review As described above, it was confirmed that the smaller the ratio of the difference between the distance A and the distance B (the difference between the left and right) with respect to the width between the clips 150 and 152, the smaller the variation in the slow axis. Further, it was confirmed that a film having good optical characteristics in which the variation in the slow axis was suppressed to a small range could be produced by setting the difference between left and right to be less than 3%.

It is explanatory drawing showing the production line of dope. It is explanatory drawing showing a film forming line. It is a top view of a tenter device. It is a top view of the tenter apparatus which performs relaxation after extending | stretching.

Explanation of symbols

10 Dope Production Line 40 Film Filming Line 87 Wet Film 100, 200 Tenter Device 101 Film 120, 220 Left Rail 122, 222 Right Rail 130, 132 Endless Chain 134 Tenter Inlet 136 Tenter Outlet 150, 152 Clip 155 Central Axis

Claims (4)

A tenter device having first and second gripping means facing each other in the width direction of the film. The tenter device transports the film while gripping both sides in the width direction of the film. In the solution casting method of expanding the width of the gripping means 2 and stretching the film in the width direction,
When the distance from the central axis of the tenter device parallel to the longitudinal direction of the film to the first holding means is A, and the distance from the central axis to the second holding means is B,
−0.03 <(A−B) / (A + B) <0.03
The solution casting method characterized by satisfy | filling.   2. The solution casting according to claim 1, wherein the film is dried by blowing dry air during the conveyance, and the temperature of the dry air is kept constant while the width of the film is changing. Method.   A polymer film formed by the solution casting method according to claim 1 or 2. A tenter device having first and second gripping means facing each other in the width direction of the film is transported while gripping both sides in the width direction of the film by the tenter device, and the first and second during the transport. In the solution film-forming equipment for extending the width of the gripping means and extending the film in the width direction,
When the distance from the central axis of the tenter device parallel to the longitudinal direction of the film to the first holding means is A, and the distance from the central axis to the second holding means is B,
−0.03 <(A−B) / (A + B) <0.03
A solution casting apparatus characterized by satisfying

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