JP2007261068A - Air blower for tenter and manufacturing process of polymer film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To inhibit the occurrence of uneven drying in stretching/drying a film while gripping it with a tenter. <P>SOLUTION: A tenter 47 is composed of a tenter body 100 and an air blower 101. The air blower 101 is composed of many air blow heads 110, air blow ducts 111, circulation ducts 112, an air blow fan 113 and a temperature adjusting apparatus 114. A plurality of nozzles 115 are provided on the air blow heads 110. Wind intercepting plates 117 are provided in a fixed pitch on the nozzles 115 in the film conveying direction. By the wind intercepting plates 117 the center parts of the nozzles 115 in the film width direction are blocked. The film surface temperature in the tenter 47 can be made almost constant, and a film 82 good in optical characteristics and having a uniform film thickness can be obtained. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a tenter blower and a method for producing a polymer film using the blower.

  Polymer films are widely used for optical applications, and in particular, cellulose acylate films have the advantage that they can be used as protective films for polarizing plates, so that it is possible to provide an inexpensive and thin liquid crystal display device. Widely used as an optical film.

  Such a polymer film is mainly produced by a solution casting method. This solution casting method is a method in which a cast film formed by casting a polymer solution (dope) containing a polymer such as cellulose acylate and a solvent on a traveling support is peeled off from the support and wetted. After forming a film, the wet film is dried to form a polymer film.

  When the wet film is dried, the wet film is dried while being transported while being supported by a plurality of rolls, or is dried by sending dry air to the wet film using a tenter dryer.

By the way, optical films are required to have far more uniform retardation values and width direction control of film thickness. Various conditions required at the time of drying the film are shown in, for example, Patent Document 1. According to this, the temperature of the film is controlled in the width direction when the film is dried, and specifically, it is shown as a condition that both end portions are set to a temperature higher by 1 ° C. or more and 30 ° C. or less than the central portion.
JP 2002-296422 A

  However, when a film is dried using a conventional air supply device, the purpose is to blow a uniform amount of air at a uniform temperature in the width direction of the film, and as a result, the vicinity of the center in the width direction is hotter than both ends. Due to the tendency to overdry, it was difficult to dry the film under various conditions as shown in Patent Document 1. Therefore, a drying method capable of obtaining a film having a uniform retardation value and film thickness under such conditions has been sought.

  The present invention is for solving the above-described problems, and an object thereof is to provide a tenter blower capable of obtaining a film having a uniform retardation value and film thickness, and a method for producing a polymer film using the blower. And

  In order to achieve the above-mentioned object, the tenter blower of the present invention blows dry air to the film gripped by the gripping means while the side edge of the film is gripped and transported by the gripping means to A tenter blower that dries while stretching in a direction, a blower head disposed parallel to the film surface held by the gripping means, and a plurality of fans disposed on a surface opposite to the film surface of the blower head It is characterized by having a blower nozzle and a windshield member that selectively winds dry air from a plurality of blower nozzles and makes the temperature distribution in the tenter of the film substantially uniform.

  The blowing nozzle is formed on the surface facing the film surface of the blowing head longer than the width of the film in the width direction of the film, and is arranged at a constant pitch in the film conveyance direction. It is preferable to block the central portion of the blower nozzle with respect to a part of the blower nozzles.

  Moreover, it is preferable that a wind-shielding member covers the range of 10 to 40% with respect to the film width direction length L1 of a ventilation nozzle.

  Furthermore, it is preferable that the wind shielding member is attached at a constant pitch with respect to the film conveyance direction.

  Furthermore, it is preferable that a plurality of blowing heads are provided in the film conveyance direction.

  In the method for producing a polymer film of the present invention, a dope containing a polymer and an organic solvent is cast on a traveling support to form a cast film, and the cast film is peeled off from the support to form a film. A method for producing a polymer film by gripping and transporting this film by a tenter gripping means and drying the film while stretching it in the width direction, wherein the film is gripped and transported by the tenter gripping means On the other hand, a drying air is sent to the film using a tenter blower to dry the film.

  The polymer is cellulose acylate, and it is preferable to keep the film surface temperature in the film width direction within a range of ± 2 ° C. in the section from the start of stretching by the tenter to the maximum stretching point.

  Further, the volatile content of the solvent in the film width direction in the section from the start of stretching by the tenter to the maximum stretching point is ± 0.4 wt% W.S. B. It is preferable to keep within the range.

  According to the present invention, the tenter blower device blows dry air on the film gripped by the gripping means while stretching the film in the width direction while the side edge of the film is gripped by the gripping means and conveyed. A blower for a tenter to be dried, a blower head arranged in parallel to the film surface held by the gripping means, a plurality of blower nozzles arranged on a surface facing the film surface of the blower head, and a plurality A film having a uniform retardation value and film thickness can be obtained by having a wind shielding member that selectively winds dry air from individual blow nozzles and makes the temperature distribution in the film tenter substantially uniform. .

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

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

  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 groups of cellulose are esterified at each of the 2-position, 3-position and 6-position (the substitution degree is 1 in the case of 100% esterification).

  The total degree of acylation substitution, that is, the value of DS2 + DS3 + DS6 is preferably 2.00 to 3.00, more preferably 2.22 to 2.90, and particularly preferably 2.40 to 2.88. Further, the value of DS6 / (DS2 + DS3 + DS6) is preferably 0.28 or more, more preferably 0.30 or more, and particularly preferably 0.31 to 0.34. Here, DS2 is the ratio of the hydrogen of the hydroxyl group at the 2-position in the glucose unit (hereinafter referred to as the acyl substitution degree at the 2-position), and DS3 is the hydroxyl group at the 3-position in the glucose unit. This is the rate at which hydrogen is substituted by an acyl group (hereinafter referred to as the 3-position acyl substitution degree), and DS6 is the rate at which the hydrogen at the 6-position hydroxyl group is substituted by an acyl group in a glucose unit (hereinafter, (Referred to as the degree of acyl substitution at the 6-position).

  Only one type of acyl group may be used in the cellulose acylate of the present invention, or two or more types of acyl groups may be used. When two or more kinds of acyl groups are used, it is preferable that one of them is an acetyl group. The sum of the degree of substitution of the hydroxyl groups at the 2nd, 3rd and 6th positions by acetyl groups is DSA, and the sum of the degree of substitution of the hydroxyl groups at the 2nd, 3rd and 6th positions by acyl groups other than acetyl groups When DSB is DSB, the value of DSA + DSB is preferably 2.22 to 2.90, and particularly preferably 2.40 to 2.88.

  The DSB is preferably 0.30 or more, particularly preferably 0.7 or more. Further, 20% or more of DSB is preferably a substituent at the 6-position hydroxyl group, more preferably 25% or more, further preferably 30% or more, and particularly preferably 33% or more. Further, the value of DSA + DSB at the 6-position of cellulose acylate is 0.75 or more, more preferably 0.80 or more, and particularly preferably cellulose acylate of 0.85 or more. These cellulose acylates By using, a solution (dope) having better solubility can be produced. In particular, a dope having excellent solubility and low viscosity and good filterability can be produced in a non-chlorine organic solvent.

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

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

  Among the above halogenated hydrocarbons, halogenated hydrocarbons having 1 to 7 carbon atoms are preferably used, and dichloromethane is most preferably used. From the viewpoint of physical properties such as solubility of TAC, peelability of cast film from the support, mechanical strength and optical properties of the film, one or several kinds of alcohols having 1 to 5 carbon atoms are mixed in addition to dichloromethane. It is preferable to do. As for content of alcohol, 2-25 mass% is preferable with respect to the whole solvent, More preferably, it is 5-20 mass%. Examples of the alcohol include methanol, ethanol, n-propanol, isopropanol, n-butanol, etc., but methanol, ethanol, n-butanol, or a mixture thereof is preferably used.

  Recently, a solvent composition that does not use dichloromethane has been studied for the purpose of minimizing the impact on the environment. In this case, an ether having 4 to 12 carbon atoms, a ketone having 3 to 12 carbon atoms, an ester having 3 to 12 carbon atoms, and an alcohol having 1 to 12 carbon atoms are preferable. Sometimes used. For example, a mixed solvent of methyl acetate, acetone, ethanol, and n-butanol can be mentioned. These ethers, ketones, esters and alcohols may have a cyclic structure. A compound having two or more functional groups of ether, ketone, ester and alcohol (that is, —O—, —CO—, —COO— and —OH) can also be used as a solvent.

  The details of cellulose acylate are described in paragraphs [0140] to [0195] of JP-A-2005-104148, and these descriptions can also be applied to the present invention. Also for 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, The details are described in paragraphs [0196] to [0516] of JP-A-2005-104148, and these descriptions can also be applied to the present invention.

[Dope production method]
First, a dope is manufactured using the above raw materials. FIG. 1 shows a dope production line 10. The dope production line 10 includes a solvent tank 11 for storing a solvent, a dissolution tank 12 for mixing the solvent and TAC, a hopper 13 for supplying TAC, and an additive for storing an additive. An agent tank 14 is provided. Furthermore, a heating device 15 for heating the swelling liquid 25 described later, a temperature controller 16 for adjusting the temperature of the prepared dope 27, and a first filtration device 17 for removing foreign matters in the dope were prepared. A flash device 30 for concentrating the dope 27, a second filtration device 31, and the like are also provided. A recovery device 32 for recovering the solvent and a regeneration device 33 for regenerating the recovered solvent are provided. The dope production line 10 is connected to the film production line 40 via a stock tank 41.

  The dope 27 is manufactured by the following procedure using the dope manufacturing line 10. First, the valve 18 is opened, and the solvent is sent from the solvent tank 11 to the dissolution tank 12. Next, an appropriate amount of TAC is sent from the hopper 13 to the dissolution tank 12. Further, a necessary amount of the additive solution is sent from the additive tank 14 to the dissolution tank 12 by opening and closing the valve 19.

  The method of feeding the additive is not limited to the method of feeding it as a solution as described above. For example, when the additive is liquid at normal temperature, it may be sent to the dissolution tank 12 in the liquid state, and when the additive is solid, it may be sent to the dissolution tank 12 using a hopper or the like. 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 14. Furthermore, a solution in which an additive is dissolved can be put into each additive tank using a large number of additive tanks, and can be sent to the dissolution tank 12 through independent pipes.

  In the above description, the order in which the material constituting the dope is placed in the dissolution tank 12 is the solvent (used in the meaning including the case of the mixed solvent), TAC, and additive. However, the order is not limited to this. Absent. For example, a preferred amount of solvent can be fed after the TAC is metered into the dissolution tank 12. Further, it is not always necessary to add the additive to the dissolution tank 12 in advance, and it can be mixed with a mixture of TAC and a solvent (hereinafter, these mixtures may also be referred to as dope) in a later step.

  As shown in FIG. 1, the dissolution tank 12 includes a jacket 20 that wraps the outer surface thereof, and a first stirrer 22 that is rotated by a motor 21. However, as shown in FIG. 1, it is preferable that a second agitator 24 rotated by a motor 23 is attached to the dissolution tank 12. The first stirrer 22 is preferably provided with an anchor blade, and the second stirrer 24 is preferably a dissolver type eccentric agitator. The temperature of the dissolution tank 12 is adjusted by flowing a heat transfer medium into the jacket 20. The temperature range is preferably −10 to 55 ° C. By appropriately selecting and using the first stirrer 22 and the second stirrer 24, a swelling liquid 25 in which TAC is swollen in a solvent is obtained.

  The swelling liquid 25 is sent to the heating device 15 by the pump 26. The heating device 15 is preferably a jacketed pipe, and further preferably has a configuration capable of pressurizing the swelling liquid 25. By using such a heating device 15, the dope 27 can be obtained by dissolving the solid content in the swelling liquid 25 under heating conditions or under pressure heating conditions. Hereinafter, this method is referred to as a heating dissolution method. The temperature of the swelling liquid 25 is preferably 50 to 120 ° C. A cooling dissolution method in which the swelling liquid 25 is cooled to a temperature of −100 to −30 ° C. can also be performed. By appropriately selecting such a heating dissolution method and a cooling dissolution method, TAC can be sufficiently dissolved in a solvent. After the dope 27 is brought to about room temperature by the temperature controller 16, the dope 27 is filtered by the first filtering device 17 to remove impurities contained in the dope 27. The filtration filter used in the first filtration device 17 preferably has an average pore diameter of 100 μm or less. The filtration flow rate is preferably 50 L / hour or more. The dope 27 after filtration is sent to the stock tank 41 via the valve 28 and stored therein.

  As described above, the method of preparing the dope 27 after preparing the swelling liquid 25 requires a longer time as the concentration of TAC is increased, which may cause a problem in terms of manufacturing cost. Therefore, when the dope 27 is manufactured by such a method, the dope 27 having a target concentration can be adjusted by preparing the dope 27 having a lower concentration than the target concentration and then performing the concentration step. preferable. In this case, the dope 27 filtered by the first filtration device 17 is sent to the flash device 30 via the valve 28, and a part of the solvent in the dope 27 is evaporated in the flash device 30. The solvent gas generated by the evaporation is condensed by a condenser (not shown) to become a liquid and is recovered by the recovery device 32. The recovered solvent is regenerated and reused as a solvent for dope preparation by the regenerator 33. This reuse is effective in terms of cost.

  Further, the concentrated dope 27 is extracted from the flash device 30 by the pump 34. At this time, in order to remove bubbles generated in the dope 27, it is preferable to perform a bubble removal process. Various known methods can be applied as a method for removing bubbles. For example, an ultrasonic irradiation method is mentioned. Subsequently, the dope 27 is sent to the second filtration device 31 and filtered to remove foreign substances. The temperature of the dope 27 during filtration is preferably 0 to 200 ° C. The filtered dope 27 is sent to the stock tank 41 and stored. A stirrer 61 that is rotated by a motor 60 is attached to the stock tank 41, and the dope 27 is constantly stirred by rotating the stirrer 61.

  The dope 27 can be manufactured by the above method. At this time, the TAC concentration in the dope 27 is preferably 5 to 40% by mass, more preferably 15 to 30% by mass, and particularly preferably 17 to 25% by mass. It is. Further, the concentration of the additive (mainly plasticizer) is preferably in the range of 1 to 20% by mass or less when the total solid content in the dope 27 is 100% by mass. In addition, about the manufacturing method of dope 27, such as the raw material in the solution casting method which obtains a TAC film, a raw material, the additive dissolution method and addition method, a filtration method, defoaming, [0517] of Unexamined-Japanese-Patent No. 2005-104148. Although described in detail from paragraph to [0616] paragraph, these descriptions are also applicable to the present invention.

[Solution casting method]
A method for producing a film using the dope 27 produced by the above-described method will be described. FIG. 2 is a schematic view showing a film production line 40. However, the present invention is not limited to the form shown in FIG.

  In the film production line 40, a stock tank 41, a third filtration device 42, a casting die 43, and a casting band 46 that is stretched around rotating rollers 44 and 45 are arranged. Further, on the downstream side, a tenter 47, an edge cutting device 50, a drying chamber 51, a cooling chamber 52, a winding chamber 53, and the like are arranged. Further, the stock tank 41 that connects the dope production line 10 and the film production line 40 is connected to the casting die 43 via the pump 62 and the third filtration device 42.

As a material of the casting die 43, precipitation hardening type stainless steel is preferable, and its thermal expansion coefficient is preferably 2 × 10 ⁻⁵ (° C. ⁻¹ ) or less. In a forced corrosion test with an electrolyte aqueous solution, it has a corrosion resistance substantially equivalent to that of SUS316, and even when immersed in a mixture of dichloromethane, methanol, and water for 3 months, it does not cause pitting (opening) at the gas-liquid interface. Those having corrosive properties can also be used as the material of the casting die 43. In addition, it is preferable that the casting die 43 is manufactured by grinding a material that has passed one month or more after casting. Thereby, it is possible to prevent the dope 27 from flowing uniformly in the casting die 43 and causing streaks or the like in the casting film 69 described later.

  The finishing accuracy of the wetted surface of the casting die 43 is preferably 1 μm or less in terms of surface roughness, and the straightness is preferably 1 μm / m or less in any direction. The slit clearance of the casting die 43 can be adjusted in the range of 0.5 to 3.5 mm by automatic adjustment. About the corner | angular part of the liquid-contacting part of the lip | tip end of the casting die 43, R is 50 micrometers or less over the whole width. Moreover, it is preferable that the shear rate inside the casting die 43 is adjusted to be 1 to 5000 (1 / second).

  The width of the casting die 43 is not particularly limited, but is preferably 1.1 to 2.0 times the width of the film to be the final product. Further, it is preferable to attach a temperature controller to the casting die 43 so that the temperature during film formation is maintained at a predetermined temperature, and the casting die 43 is preferably a coat hanger type. Furthermore, it is more preferable that a thickness adjusting bolt (heat bolt) is provided at a predetermined interval in the width direction of the casting die 43 and the casting die 43 is provided with an automatic thickness adjusting mechanism using a heat bolt. The heat bolt is preferably formed by setting a profile in accordance with a liquid feeding amount of the pump 62 by a preset program. The pump 62 is preferably a high precision gear pump.

  At this time, feedback control may be performed by an adjustment program based on a profile of a thickness gauge (not shown). Examples of the thickness gauge include an infrared thickness gauge, but are not particularly limited. The thickness difference between any two points in the width direction of the product film excluding the casting edge can be adjusted within 1 μm, and the difference between the minimum value and the maximum value in the width direction thickness can be adjusted to 3 μm or less. Preferably, adjusting to 2 μm or less is more preferable. In addition, it is preferable to use the one whose thickness accuracy is adjusted to ± 1.5 μm or less.

More preferably, a cured film is formed at the lip end of the casting die 43. A method for forming the cured film is not particularly limited, and examples thereof include ceramic coating, hard chrome plating, and a nitriding method. When using ceramics as the cured film, it can be ground, has low porosity, is not brittle and excellent in corrosion resistance, and has good adhesion to the casting die 43, while having good adhesion to the dope. Bad ones are preferred. Specific examples include tungsten carbide (WC), Al ₂ O ₃ , TiN, and Cr ₂ O ₃ , among which WC is preferable. This WC coating can be performed by a thermal spraying method.

  A solvent supply device (not shown) is preferably attached to the slit end of the casting die 43 in order to prevent the flowing out dope 27 from being locally dried and solidified. Further, a solvent for solubilizing the dope 27 (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) It is preferable to supply to the peripheral part of the three-phase contact line which external air forms. At this time, it is preferable to supply at 0.1 to 1.0 ml / min to one side of the end portion, because mixing of foreign matters into the cast film can be prevented. In addition, as a pump which supplies this liquid, it is preferable to use a pump with a pulsation rate of 5% or less.

  A casting band 46 is provided below the casting die 43 so as to span the rotating rollers 44 and 45. The rotating rollers 44 and 45 are rotated by a driving device (not shown), and the casting band 46 travels endlessly with the rotation. It is preferable that the casting band 46 can move at a moving speed, that is, a casting speed of 10 to 200 m / min. In order to set the surface temperature of the casting band 46 to a predetermined value, it is preferable that the heat transfer medium circulating device 63 is attached to the rotating rollers 44 and 45. The casting band 46 is preferably one whose surface temperature can be adjusted to -20 to 40 ° C. A heat transfer medium flow path (not shown) is formed in the rotating rollers 44 and 45 used in the present embodiment, and the heat transfer medium maintained at a predetermined temperature passes through the flow path. The temperatures of the rotating rollers 44 and 45 are maintained at a predetermined value.

  The width of the casting band 46 is not particularly limited, but it is preferable to use one having a casting width of 1.1 to 2.0 times the casting width of the dope 27, and its length is 20 to 200 m. The thickness is preferably 0.5 to 2.5 mm, and the surface is preferably polished so that the surface roughness is 0.05 μm or less. The casting band 46 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 that the thickness unevenness of the entire casting band 46 is 0.5% or less.

In addition, it can replace with the casting band 46 and can also use the rotating roller 45 as a support body directly. In this case, it is preferable that the rotation unevenness is 0.2 mm or less so that the rotation can be performed with high accuracy, and the average roughness of the surface of the rotating roller 45 is preferably 0.01 μm or less. . Therefore, the surface of the rotating roller is subjected to chrome plating so as to have sufficient hardness and durability. In addition, it is necessary to suppress the surface defects of the support (the casting band 46 and the rotating roller 45) to the minimum. Specifically, there are no pinholes of 30 μm or more as surface defects, and the number of pinholes of 10 μm or more and less than 30 μm is 1 / m ² or less, and the number of pinholes of less than 10 μm is 2 / m ² or less. .

  The casting die 43 and the casting band 46 are accommodated in the casting chamber 64. The casting chamber 64 is provided with a temperature control facility 65 for keeping the internal temperature at a predetermined value, and a condenser (condenser) 66 for condensing and recovering the volatile organic solvent. A recovery device 67 for recovering the condensed and liquefied organic solvent is provided outside the casting chamber 64. A decompression chamber 68 for controlling the pressure of the back surface of the casting bead formed from the casting die 43 to the casting band 46 is preferably disposed, and this is also used in this embodiment. An air duct 70 is provided near the peripheral surface of the casting band 46. Further, a roller 75 that supports the casting film 69 peeled off from the casting band 46, that is, the wet film 74 is provided.

  The crossover unit 80 includes a plurality of rollers 80 a and a blower 81. A tenter 47 and an ear clip device 50 are disposed downstream of the crossover unit 80. A crusher 90 for finely cutting the side end portion (ear) of the cut film 82 is connected to the ear clip device 50. The tenter 47 is a characteristic part of the present invention and will be described later in detail.

  The drying chamber 51 is provided with a number of rollers 91, and an adsorption / recovery device 92 for adsorbing / recovering the solvent gas generated by evaporation is attached. In FIG. 2, the cooling chamber 52 is provided downstream of the drying chamber 51, but a humidity control chamber (not shown) may be provided between the drying chamber 51 and the cooling chamber 52.

  A forced static elimination device (static elimination bar) 93 for adjusting the charged voltage of the film 82 to a predetermined range (for example, −3 to +3 kV) is provided downstream of the cooling chamber 52. In addition, in FIG. 2, although the form which makes the forced static elimination apparatus 93 the downstream of the cooling chamber 52 is shown, it is not limited to this form. Further, in this embodiment, a knurling application roller 94 for applying knurling to both edges of the film 82 by embossing is provided downstream of the forced static elimination device 93. In the winding chamber 53, a winding roller 95 for winding the film 82 and a press roller 96 for controlling the tension during winding are provided.

  Next, characteristic portions of the present invention will be described. As shown in FIG. 3, the tenter 47 is composed of a tenter body 100 and the blower 101 of the present invention. The tenter body 100 includes a tenter chain that runs on a pair of rails. A number of clips (gripping means) are attached to the tenter chain. The tenter chain circulates on the rail when the chain sprocket is rotated. The clip grips the side edge of the wet film 74 by being closed at the film gripping position. Moreover, the grip of the wet film 74 side edge part is opened by being opened at the film opening position. The tenter chain travels in a state where both side edges of the wet film 74 are gripped by this clip, whereby the film is stretched in the width direction at a distance between the pair of rails.

  The blower 101 is provided along the extending and conveying path of the wet film 74 by the tenter body 100. The blower 101 includes a large number of blower heads 110, a blower duct 111, a circulation duct 112, a blower fan 113, and a temperature controller 114. The blowing head 110 is provided so as to face the upper and lower surfaces of the wet film 74 conveyed by the clip, and is arranged side by side in the film conveying direction. The blower heads 110 provided on the upper and lower surfaces are the same. FIG. 3 shows the blower head 110 provided facing the upper surface of the wet film 74.

  The blower head 110 includes, for example, five nozzles 115. Each nozzle 115 is formed long in the film width direction, and a wind regulating plate 116 is disposed in the nozzle 115 for making the amount of blown dry air substantially constant. The film width direction length L1 of the nozzle 115 is, for example, 1.1 to 2.0 times longer than the film width. Further, the width W1 of the nozzle 115 is set to 1500 to 2500 mm. The air conditioning plate 116 is provided with round holes that are spaced apart in the film width direction. By changing the aperture ratio of the air conditioning plate 116, the amount of air blown out is adjusted, and a substantially uniform air blowout amount in the film width direction is obtained. In addition, the shape and quantity of the holes of the air conditioning plate 116 and the shape and quantity of the nozzles are not limited to those shown in the drawings, and may be changed as appropriate. Moreover, it is preferable that the pitch in the film conveyance direction of the nozzle 115 of each ventilation head 110 is made the same.

  For example, the windshield plate 117 is attached to the nozzle 115 at a rate of one in five. The wind shielding plate 117 is attached so as to cover the central portion of the nozzle 115, and its length L2 is formed to be 10 to 40% with respect to the nozzle length L1 in the film width direction. Preferably it is 15 to 30%. The mounting pitch P1 (= p1 × 5) and the mounting width L2 of the wind shielding plate 117 are appropriately changed according to the opening area and the opening ratio of the nozzle 115, and the film film surface temperature is ± 2 ° C., more preferably ± It is determined to be 0.5 ° C. Further, the mounting width L2 and the mounting pitch P1 do not need to be constant between the wind shielding plates 117, and may be changed as appropriate. For example, the mounting width L2 and the mounting pitch P1 are changed according to the film surface temperature distribution so that the film film surface temperature in the tenter 47 becomes more uniform.

  Instead of or in addition to the uniform film surface temperature, the solvent volatile content in the wet film 74 in the film width direction is ± 0.4 wt% W.S. B. More preferably, ± 0.1 wt% W.V. The opening area and the opening ratio of the nozzle 115 may be changed so as to be B.

  The structure of the wind shielding plate 117 in the present invention may be performed on the entire region in the tenter 47 or may be performed between the stretching start position of the tenter 47 and the maximum stretching point. It has been found that drying unevenness between the stretching start position of the tenter 47 and the maximum stretching point has a particularly adverse effect on the optical characteristics of the film 82, and drying between the stretching start position of the tenter 47 and the maximum stretching point is known. Even if unevenness is suppressed, the optical characteristics are improved.

  Further, the wind shield plate 117 may be a movable type instead of the fixed type in which the wind shield area is fixed. In this case, for example, a triangular or trapezoidal wind shield can be movably attached in the film transport direction, and the wind shield area can be changed by appropriately changing the position of the wind shield.

  The blower duct 111 is connected to a side surface of the blower head 110 and sends air to each blower head 110. The circulation duct 112 is connected to the other side surface of the blower head 110 facing the blower duct 111, and a part of the air sent from the blower duct 111 is directly discharged from the blower head 110 and returned to the blower duct 111.

  The blower head 110 and the blower duct 111 have double partition walls and are formed in a heat insulating structure using an air layer as a heat insulating material. The thickness of the air layer is preferably 5 mm or more. In addition, you may enclose heat insulating materials, such as rock wool and glass wool, in a partition as needed. Further, instead of the double heat insulating structure, if solvent resistance is not a problem, heat insulating properties may be imparted by attaching a heat insulating resin such as MC nylon or ceramics. Instead of separately encapsulating the heat insulating material, air may simply be used as the heat insulating material. The nozzle 115 may also have a double heat insulating structure, or a heat insulating material or the like may be disposed.

  The exhaust duct 118 is connected to the tenter chamber 119, discharges air accumulated in the tenter chamber 119, and returns the air to the blower duct 111. The dry air blowing unit 120 includes a blower fan 113 for circulating air and a temperature adjuster 114 that heats the air and adjusts the temperature. Then, the air in the tenter chamber 119 is sucked from the circulation duct 112 and the exhaust duct 118 and blown into the tenter chamber 119 through the blower duct 111. Although not shown, a solvent recovery facility for aggregating and recovering the solvent is provided in the tenter chamber 119 or the drying air circulation line including the ducts 111, 112, and 117. This solvent recovery equipment recovers the solvent volatilized from the wet film 74 and makes the solvent volatile content of the dry air blown out from the nozzle 115 substantially constant. In addition, an air intake is provided in the dry air circulation line, and fresh air is also introduced.

  In the present invention, the circulation duct 112 is connected to the blower head 110 so that the air circulates in the blower head 110, so that the drying air does not stay in the blower head 110 as in the prior art. The temperature distribution of the drying air blown out from 115 can be made more uniform. In addition, by forming the air duct 111 and the air head 110 in a heat insulating structure, the dry air that is blown onto the film surface of the wet film 74 and has a low temperature due to heat of vaporization touches the air head 110 and the air duct 111. Thus, the influence of the temperature drop due to the low temperature drying air is reduced, and the temperature unevenness of the drying air can be further eliminated. The circulation duct 112 and the heat insulating structure are provided as necessary, and may be omitted.

  In the above embodiment, the tenter 47 having a clip has been described. However, instead of the clip, a large number of pins are planted, and the present invention is used as a blower for a pin tenter of a type in which the pins are inserted into the side edge of the wet film 74 and held. The invention may be implemented.

  Next, an example of a method for producing the film 82 using the above-described film production line 40 will be described below. However, the present invention is not limited to the embodiment shown here.

The dope 27 is always made uniform by the rotation of the stirrer 61. The dope 27 can be mixed with additives such as a plasticizer and an ultraviolet absorber even during the stirring. After the dope 27 is sent to the third filtration device 42 by the pump 62 and filtered, the dope 27 is cast from the casting die 43 onto the casting band 46. The driving of the rotating rollers 44 and 45 is preferably adjusted so that the tension generated in the casting band 46 is 10 ⁴ to 10 ⁵ N / m. Further, the relative speed difference between the casting band 46 and the rotary rollers 44 and 45 is adjusted to be 0.01 m / min or less. The speed fluctuation of the casting band 46 is preferably 0.5% or less, and the meandering in the width direction when the casting band 46 rotates once is preferably 1.5 mm or less. In order to control the meandering, a detector (not shown) for detecting the positions of both ends of the casting band 46 is provided, and feedback control is performed by a position controller (not shown) of the casting band 46 based on the measured value. More preferably, the position of the casting band 46 is adjusted. The casting band 46 immediately below the casting die 43 is preferably adjusted so that the positional fluctuation in the vertical direction accompanying the rotation of the rotary roller 45 is 200 μm or less. Further, the temperature of the casting chamber 64 is preferably set to −10 to 57 ° C. by the temperature control equipment 65. The solvent evaporated inside the casting chamber 64 is recovered by the recovery device 67 and then regenerated and reused as a dope preparation solvent.

  A casting bead is formed from the casting die 43 to the casting band 46, and a casting film 69 is formed on the casting band 46. The temperature of the dope 27 at the time of casting is preferably −10 to 57 ° C. Further, in order to stabilize the casting bead, the back surface of the casting bead is preferably controlled to a desired pressure value by the decompression chamber 68. The back surface of the bead is preferably decompressed in the range of −2000 to −10 Pa than the front surface. Further, it is preferable that a jacket (not shown) is attached to the decompression chamber 68 and the temperature is controlled so that the internal temperature is kept at a predetermined temperature. The temperature of the decompression chamber 68 is not particularly limited, but is preferably set to be equal to or higher than the condensation point of the organic solvent used. In order to keep the shape of the casting bead as desired, it is preferable to attach a suction device (not shown) to the edge portion of the casting die 43. The edge suction air volume is preferably in the range of 1 to 100 L / min. Drying air is applied to the casting film 69 that moves along with the running of the casting band 46 by the air duct 70 to promote evaporation of the solvent.

  After the casting film 69 has a self-supporting property, it is peeled off from the casting band 46 as the wet film 74 and then supported by the roller 75. Next, the sheet is fed to the crossing section 80 provided with a large number of rollers, conveyed while being supported by the rollers, and then fed to the tenter 47. In the transfer part 80, the drying of the wet film 74 is advanced by sending the drying air of desired temperature from the air blower 81. FIG. At this time, the temperature of the drying air is preferably 20 to 250 ° C. In the transition section 80, tension can be applied to the wet film 74 by making the rotational speed of the downstream roller faster than the rotational speed of the upstream roller.

  In addition, the residual solvent amount at the time of peeling is set to 10 to 200% by mass based on the solid content. This residual solvent amount is based on the dry amount, and is calculated as {(xy) / y} × 100 where x is the film weight at the time of sampling and y is the weight after the sampling film is dried. Value. However, the dry weight standard is the content of the solvent when the weight when the dope 27 is completely dried and solidified is 100%.

  The wet film 74 is fed into the tenter 47. The side edge portion of the wet film 74 is gripped by the tenter clip, and is dried while the inside of the tenter 47 is conveyed. At this time, it is preferable that the inside of the tenter 47 is divided into temperature zones and the drying conditions are appropriately adjusted for each of the zones. In addition, the tenter 47 can be used to stretch the wet film 74 in the width direction. In addition, it is preferable that at the transition portion 80 and / or the tenter 47, at least one of the casting direction and the width direction of the wet film 74 is stretched by 0.5 to 300%.

  After the wet film 74 is dried by the tenter 47 to a predetermined residual solvent amount, it is sent to the downstream side as a film 82. At this time, both edges of the both ends of the film 82 are cut by the edge-cutting device 50. The cut side end portion is sent to a crusher 90 by a cutter blower (not shown) and crushed into chips. Since this chip can be reused for dope preparation, it is effective in terms of manufacturing cost. In addition, although it can also be skipped about the cutting process of the both-sides edge part of this film 82, it is preferable to carry out in any one from the said casting process to the process of winding up the film 82.

  The film 82 from which both end portions have been cut and removed is fed into the drying chamber 51 and further dried. Although the temperature in the drying chamber 51 is not specifically limited, It is preferable that it is the range of 50-160 degreeC. In the drying chamber 51, the film 82 is conveyed while being wound around the roller 91. The solvent gas generated by evaporation here is adsorbed and recovered by the adsorption recovery device 92. Thus, the air from which the solvent component has been removed is blown again as dry air inside the drying chamber 51. The drying chamber 51 is more preferably divided into a plurality of sections in order to change the drying temperature. In addition, if a preliminary drying chamber (not shown) is provided between the ear opener 50 and the drying chamber 51 and the film 82 is preliminarily dried, the temperature of the film 82 in the drying chamber 51 can be prevented from rapidly increasing. Therefore, generation | occurrence | production of the shape change of the film 82 can be suppressed more.

  The film 82 is cooled to approximately room temperature in the cooling chamber 52. A humidity control chamber (not shown) may be provided between the drying chamber 51 and the cooling chamber 52, and air adjusted to a desired humidity and temperature can be blown onto the film 82 in the humidity control chamber. Is preferred. Thereby, generation | occurrence | production of the curling of the film 82 and the winding defect at the time of winding can be suppressed.

  Further, the charged voltage while the film 82 is being conveyed is set to a predetermined range (for example, −3 to +3 kV) by the forced charge removal device (charge removal bar) 93. FIG. 2 illustrates an example provided on the downstream side of the cooling chamber 52, but the position is not limited thereto. Furthermore, it is preferable to provide a knurling roller 94 to give knurling to both edges of the film 82 by embossing. In addition, it is preferable that the unevenness | corrugation of the knurled location is 1-200 micrometers.

  Finally, the film 82 is taken up by the take-up roller 95 in the take-up chamber 53. At this time, it is preferable to wind up while applying a desired tension with the press roller 96. More preferably, the tension is gradually changed from the start to the end of winding. The film 82 to be wound is preferably at least 100 m in the longitudinal direction (casting direction). Moreover, it is preferable that the width | variety of the film 82 is 600 mm or more, and it is more preferable that it is 1400-1800 mm. The present invention is also effective when it is larger than 1800 mm. In addition, the thickness of the film 82 at the time of completion is adjusted so that it may become 30-300 micrometers.

  In the solution casting method of the present invention, when casting the dope 27, two or more kinds of dopes can be simultaneously co-casting or sequentially co-casting. Furthermore, you may combine both casting. When performing simultaneous lamination and co-casting, a casting die to which a feed block is attached may be used, or a multi-manifold casting die may be used. It is preferable that at least one of the thickness of the layer on the air surface side and the thickness of the layer on the support side is 0.5 to 30% of the thickness of the entire film of the film composed of multiple layers by co-casting. Furthermore, when performing simultaneous lamination co-casting, it is preferable that the high-viscosity dope is wrapped with the low-viscosity dope when the dope 27 is cast from the die slit to the support. Moreover, when performing simultaneous lamination co-casting, it is preferable that the dope 27 in contact with the outside of the casting bead formed from the die slit to the support has a higher alcohol composition ratio than the inner dope.

  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 Up to this point, the details are described in paragraphs [0617] to [0889] of JP-A-2005-104148, and these descriptions can also be applied to the present invention.

[Performance / Measurement method]
(Curl degree / thickness)
The performance of the wound cellulose acylate film and the measuring method thereof are described in paragraphs [1073] to [1087] of JP-A-2005-104148, and these descriptions are also applied to the present invention. Can do.

[surface treatment]
In the cellulose acylate film, at least one surface is preferably 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. As the functional layer, it is preferable to provide at least one of an antistatic layer, a cured resin layer, an antireflection layer, an easy adhesion layer, an antiglare layer, and an optical compensation layer.

The functional layer, at least it is preferable that a kind of surfactant 0.1 to 1000 mg / ^{m 2} containing, it is preferable that at least one of a slip agent 0.1 to 1000 mg / ^{m 2} containing. Further, the functional layers, at least it is preferable that a kind of matting agent 0.1 to 1000 mg / ^{m 2} containing preferably contain at least one 1 to 1000 mg / ^{m 2} containing an antistatic agent. In addition to the above, the method for applying a surface treatment functional layer for realizing various functions and properties on the cellulose acylate film is described in paragraphs [0890] to [1072] of JP-A-2005-104148. Detailed conditions and methods are also described, and these descriptions can also be applied to the present invention.

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

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

  Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to these examples. The manufacturing method and manufacturing conditions will be described in detail only in the first embodiment.

[Example]
Next, examples of the present invention will be described. The formulation for preparing the polymer solution (dope) used for film production is shown below.

[composition]
Cellulose triacetate (substitution degree 2.84, viscosity average polymerization degree 306, water content 0.2 mass%, viscosity 315 mPa · s 6 mass% in dichloromethane solution, average particle diameter 1.5 mm with standard deviation 0.5 mm Some powders) 100 parts by mass dichloromethane (first solvent) 320 parts by mass methanol (second solvent) 83 parts by mass 1-butanol (third solvent) 3 parts by mass plasticizer A (triphenyl phosphate) 7.6 parts by mass Plasticizer B (diphenyl phosphate) 3.8 parts by mass UV agent a: 2 (2′-hydroxy-3 ′, 5′-di-tert-butylphenyl) benzotriazole 0.7 part by mass UV agent b: 2 ( 2'-Hydroxy-3 ', 5'-di-tert-amylphenyl) -5-chlorobenzotriazole 0.3 parts by mass of citric acid ester mixture (citric acid, Ethyl ester, diethyl ester, triethyl ester mixture) 0.006 parts by weight fine particles (silicon dioxide (average particle size 15 nm), Mohs hardness: about 7)
0.05 parts by mass

[Cellulose triacetate]
The cellulose triacetate used here has a residual acetic acid content of 0.1% by mass or less, a Ca content of 58 ppm, a Mg content of 42 ppm, a Fe content of 0.5 ppm, free acetic acid 40 ppm, and sulfate ions. Was 15 ppm. The 6-position acyl substitution degree was 0.91, and 32.5% of all acetyl groups were acetyl groups substituted with the 6-position hydroxyl group. Moreover, the acetone extraction part which extracted this TAC with acetone was 8 mass%, and the weight average molecular weight / number average molecular weight ratio was 2.5. The obtained TAC had a yellow index of 1.7, a haze of 0.08, a transparency of 93.5%, a Tg (glass transition temperature) measured by DSC of 160 ° C., and a crystallization heating value of 6. It was 4 J / g. This TAC is synthesized using cellulose collected from cotton as a raw material. In the following description, this is called cotton raw material TAC.

  A dope 27 was prepared using the dope production line 10 shown in FIG. The plurality of solvents were mixed and stirred well in a 4000 L stainless steel dissolution tank 12 having a stirring blade to obtain a mixed solvent. In addition, as each raw material of a solvent, that whose water content is 0.5 mass% or less was used. Next, TAC flaky powder was gradually added from the hopper 13. The TAC powder is charged into a dissolution tank 12 and a dissolver type eccentric stirrer (second stirrer) 24 that stirs at a peripheral speed of 5 m / s at first and a stirrer (first stirrer) 22 having an anchor blade on the central shaft are provided. The dispersion was performed for 30 minutes under the condition of stirring at a peripheral speed of 1 m / s. The temperature at the start of dispersion was 25 ° C., and the final temperature reached 48 ° C.

  Further, the additive solution prepared in advance was fed from the additive tank 14 to the dissolution tank 12 so that the total amount would be 2000 kg while adjusting the liquid feed amount with the valve 19. After finishing the dispersion of the additive solution, the high speed stirring was stopped. And the peripheral speed of the anchor wing | blade of the stirrer 22 was made into 0.5 m / s, and also it stirred for 100 minutes, the TAC flakes were swollen and the swelling liquid 25 was obtained. Until the end of swelling, the inside of the dissolution tank 12 was pressurized to 0.12 MPa with nitrogen gas. At this time, the inside of the dissolution tank 12 had an oxygen concentration of less than 2 vol%, and maintained a state with no problem in terms of explosion prevention. Moreover, the water content in the swelling liquid 25 was 0.3 mass%.

  The swelling liquid 25 was sent from the dissolution tank 12 to the jacketed pipe 15 using the pump 26. Using a jacketed pipe as the heating device 15, the swelling liquid 25 was heated to 50 ° C., and further heated to 90 ° C. under a pressure of 2 MPa to be completely dissolved. At this time, the heating time was 15 minutes. Next, the temperature of the solution was lowered to 36 ° C. by the temperature controller 16 and then passed through a first filtration device 17 having a filter with a nominal pore diameter of 8 μm to obtain a dope (hereinafter referred to as a dope before concentration). . The primary pressure in the first filtration device 17 was 1.5 MPa, and the secondary pressure was 1.2 MPa. Filters and piping exposed to high temperatures were made of Hastelloy (trade name) alloy.

This pre-concentration dope was flash-evaporated in the flash device 30 at 80 ° C. and normal pressure to obtain a dope 27. The evaporated solvent was recovered with a condenser. The solid concentration of the dope 27 after the flash was 21.8% by mass. The condensed solvent was recovered by the recovery device 32, regenerated by the regenerator 33, then sent to the solvent tank 11 and reused as a dope preparation solvent. In the recovery device 32 and the regeneration device 33, distillation or dehydration was performed. The flash tank of the flash device 30 was provided with a stirrer (not shown) having an anchor blade on the stirring shaft, and the dope flashed at a peripheral speed of 0.5 m / s was stirred by the stirrer to perform defoaming. The temperature of the dope 27 in this flash tank was 25 ° C., and the average residence time of the dope 27 in the tank was 50 minutes. The shear viscosity of the dope 27 collected and measured at 25 ° C. was 450 Pa · s at a shear rate of 10 (seconds ⁻¹ ).

  Next, the weak ultrasonic wave was irradiated to the dope 27 to remove bubbles, and then passed through the second filtration device 31 while being pressurized to 1.5 MPa using the pump 34. In the 2nd filtration apparatus 31, after passing the sintered fiber metal filter with a nominal pore diameter of 10 micrometers first, it was allowed to pass through the sintered fiber filter with a nominal pore diameter of 10 micrometers. At this time, the primary side pressure was 1.5 MPa and 1.2 MPa, and the secondary side pressure was 1.0 MPa and 0.8 MPa. After filtration, the dope 27 whose temperature was adjusted to 36 ° C. was sent to and stored in a 2000 L stainless steel stock tank 41. Inside the stock tank 41, stirring was always performed at a peripheral speed of 0.3 m / s by a stirrer 61 having an anchor blade on the central axis.

  The film 82 was manufactured using the film manufacturing line 40 shown in FIG. The dope 27 was sent from the stock tank 41 to the third filtration device 42 using a high-precision gear pump (pump) 62 having a function of increasing the pressure on the primary side. At this time, feedback control for the upstream side of the gear pump 62 was performed by an inverter motor so that the primary pressure was 0.8 MPa. The gear pump 62 has a volumetric efficiency of 99.2% and a discharge rate variation rate of 0.5% or less. The discharge pressure was 1.5 MPa. After passing the dope 27 through the third filtration device 42, the dope 27 was fed to the casting die 43.

  The dope 27 is cast from the discharge port of the casting die 43 while adjusting the flow rate so that the width is 1.8 m and the film thickness of the dried film is 80 μm and the casting width of the dope 27 is 1700 mm. did. Further, a jacket (not shown) was attached to the casting die 43, and a heat transfer medium was supplied into the casting die 43 to adjust the temperature of the dope 27 to 36 ° C. During the film formation, the piping through which the casting die 43 and the dope 27 pass was all kept at 36 ° C. The casting die 43 is a coat hanger type die, and thickness adjusting bolts are provided at a pitch of 20 mm, and a die having an automatic thickness adjusting mechanism using a heat bolt is used. The heat bolt can set a profile according to the liquid feed amount of the gear pump 62 by a preset program, and is fed back by an adjustment program based on a profile of an infrared thickness meter (not shown) installed in the film production line 40. The thing which has the performance which can also be controlled was used. The film excluding the end 20 mm has a difference in thickness of any two points 50 mm apart within 1 μm, the thickness variation in the width direction is 3 μm / m or less, and the total thickness is ± 1.5% or less. Adjusted as follows.

  A decompression chamber 68 was installed on the primary side of the casting die 43. The decompression degree of the decompression chamber 68 was adjusted so as to produce a pressure difference of 1 to 5000 Pa before and after the casting bead according to the casting speed. Moreover, the pressure difference on both sides of the casting bead was set so that the length of the casting bead was 20 to 50 mm. The decompression chamber 68 was provided with a mechanism that can be set to a temperature higher than the condensation temperature of the gas around the casting portion. A labyrinth packing (not shown) was provided on the front and back surfaces of the bead at the discharge port of the casting die 43, and openings were provided at both ends of the discharge port. Further, an edge suction device (not shown) for adjusting the disturbance of both edges of the casting bead was attached to the casting die 43.

As the material of the casting die 43, precipitation hardening type stainless steel having a thermal expansion coefficient of 2 × 10 ⁻⁵ (° C. ⁻¹ ) or less was used. The finishing accuracy of the liquid contact surface of the casting die 43 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. A WC (tungsten carbide) coating was applied to the lip end of the casting die 43 by a thermal spraying method to provide a cured film. As for the corner portion of the wetted surface, R processed so as to be 50 μm or less over the entire width of the slit was used.

  In order to prevent the dope 27 to be cast from being locally dried and solidified at the discharge port of the casting die 43, 86.5 parts by mass of dichloromethane and 13 parts by mass of acetone are used as a solvent for solubilizing the dope 27. The mixed solvent A was prepared by mixing 0.5 parts by mass of 1-butanol and 0.5 ml / min was supplied to the interface between the both ends of the casting bead and the discharge port. At this time, the pulsation rate of the pump supplying the mixed solvent A was set to 5% or less. Further, the pressure on the back side of the casting bead was reduced by 150 Pa from the front side by the decompression chamber 68. The decompression chamber 68 was provided with a jacket (not shown), and the temperature was adjusted by supplying a heat transfer medium adjusted to 35 ° C. into the jacket. The edge suction device is capable of adjusting the edge suction air volume so as to be in the range of 1 to 100 L / min, and in the present embodiment, this is in the range of 30 to 40 L / min. It was adjusted.

The dope 27 was cast from the casting die 43 on the casting band 46 installed inside the casting chamber 64 having wind pressure fluctuation suppressing means (not shown). As the casting band 46, an endless band made of SUS316 was used which was polished to have a width of 2.1 m, a length of 70 m, a thickness of 1.5 mm, and a surface roughness of 0.05 μm or less. The thickness unevenness of the entire casting band 46 was 0.5% or less. The casting band 46 was driven by the two rotating rollers 44 and 45. At this time, the tension in the conveying direction of the casting band 46 is 1.5 × 10 ⁵ N / m ² , and the relative speed difference between the casting band 46 and the rotary rollers 44 and 45 is 0.01 m / min or less, The speed fluctuation of the casting band 46 was adjusted to 0.5% or less. Further, both end positions of the casting band 46 were detected, and the meandering in the width direction of one rotation was controlled to be 1.5 mm or less. The positional fluctuation in the vertical direction between the die lip tip and the casting band 46 immediately below the casting die 43 was set to 200 μm or less.

As the rotating rollers 44 and 45, those capable of feeding a heat transfer medium therein were used so that the temperature of the casting band 46 could be adjusted. A 40 ° C. heat transfer medium was passed through the rotating roller 44 for drying. On the other hand, a heat transfer medium at 5 ° C. was passed through the rotating roller 45. The surface temperature of the central part of the casting band 46 immediately before casting was 15 ° C., and the temperature difference between both side ends was 6 ° C. or less. The casting band 46 has no pinholes of 30 μm or more, the pinholes of 10 μm to 30 μm are 1 piece / m ² or less, and the pinholes of less than 10 μm are 2 pieces / m ² or less. No endless band used. The temperature of the casting chamber 64 was kept at 35 ° C. by the temperature control equipment 65. The casting film 69 on the casting band 46 was first dried by sending a drying air flowing parallel to the casting film 69. The overall heat transfer coefficient from the dry air to the cast film 69 was 24 kcal / (m ² · hour · ° C.).

  A blower duct 70 was disposed as an air blower on the upstream side of the upper part of the casting band 46, and 135 ° C. drying air was sent out to dry the casting film 69. Further, the oxygen concentration in the dry atmosphere on the casting band 43 was maintained at 5 vol% by replacing air with nitrogen gas. The solvent in the casting chamber 64 was condensed and recovered by setting the outlet temperature of the condenser (condenser) 66 to −10 ° C.

When the amount of residual solvent in the casting film 69 reached 50% by weight, the film was peeled off from the casting band 46 as a wet film 74 and supported by a roller 75. The stripping tension is 1 × 10 ² N / m ² and the stripping speed (stripping roller draw) is 100.1 to 110% with respect to the speed of the casting band 46 in order to suppress stripping failure. Adjusted within the range. The surface temperature of the peeled wet film 74 was 15 ° C. The solvent gas generated by drying was condensed and liquefied by a condenser 66 adjusted to −10 ° C. and then recovered by a recovery device 67, and the solvent was removed so that the water content was 0.5% or less. The drying air from which the solvent was removed was heated again and reused as drying air. The wet film 74 was conveyed through the roller of the crossing section 80 and sent to the tenter 47. In the transfer part 80, a drying air of 40 ° C. was blown from the blower 81 to the wet film 74 while being dried while applying a tension of about 30 N to the longitudinal direction of the wet film 74.

  In the tenter 47, dry air was blown from the nozzle 115 toward the wet film 74 using the blower head 110 shown in FIGS. 3 to 5. At this time, the wind shielding plate 117 was attached to the center portion at a ratio of one to five with respect to the nozzle 115 of the blower head 110. The wind shielding plate 117 is 30% of the length L1 of the nozzle 115 in the film width direction, and the nozzle 115 has a length L1 of 2000 mm and a width of 5 mm. The wind speed V of the drying air from the nozzle 115 at this time was 10 m / s. The wet film 74 was conveyed while being stretched in the width direction in a state where both side edges of the wet film 74 were gripped by a tenter clip. Further, the inside of the tenter 47 was partitioned into first to third three, and the drying air temperature in each section was made constant at 140 ° C. The first section is from the entrance to the stretching start position, the second section is from the stretching start position to the stretching end position, and the third section is from the end of stretching to the exit. At this time, the gas composition of the drying air was set to a saturated gas concentration at −10 ° C. And it dried so that the residual solvent amount of the film 82 might be 7 mass% at the exit of the tenter 47.

  The stretching ratio inside the tenter 47 is such that the difference between the substantial stretching ratios at any two points at a position 10 mm or more away from the biting start position by the clip is 10% or less, and the stretching at any two points separated by 20 mm. The difference in rate was 5% or less. Further, the ratio of the length from the clip clamping start position to the clamping release position with respect to the length from the inlet to the outlet of the tenter 47 was 90%. The solvent evaporated in the tenter 47 was condensed and recovered at a temperature of −10 ° C. by providing a condenser (condenser) and setting its outlet temperature to −8 ° C. This condensed solvent was reused after adjusting the water content to be 0.5% by mass or less. And it sent out from the tenter 47 as the film 82.

Within 30 seconds from the exit of the tenter 47, the ears 50 mm on both sides of the film 82 were cut using an NT-type cutter as the ear-cutting device 50. At this time, the separated ears were blown to a crusher 90 by a cutter blower (not shown) and crushed into chips of about 80 mm ² on average, and this chip was used again as a dope preparation raw material. The air in the tenter 47 was replaced with nitrogen gas, and the oxygen concentration in the dry atmosphere was maintained at 5 vol%. In addition, the film 82 was preheated in a predrying chamber (not shown) supplied with 100 ° C. drying air before being dried at a high temperature in the drying chamber 51 described later.

  The film 82 was dried at a high temperature in the drying chamber 51. The drying chamber 51 was divided into four sections, and drying air at 120 ° C., 130 ° C., 130 ° C., and 130 ° C. was sent from a blower (not shown) from the upstream side. The transport tension of the film 82 by the roller 91 was set to 100 N / m, and the film was dried for about 10 minutes until the residual solvent amount finally reached 0.3% by mass. At this time, the wrap angle (film winding center angle) of the roller 91 was 90 degrees and 180 degrees (shown exaggerated in FIG. 2). The material of the roller 91 was made of aluminum or carbon steel, and the surface was hard chrome plated. Moreover, the surface shape of the roller 91 used was a flat one or a mat formed by blasting. The film position fluctuations due to the rotation of the roller 91 were all 50 μm or less.

  The solvent gas contained in the drying air was adsorbed and recovered using an adsorption recovery device 92. The adsorbent used here was activated carbon, and desorption was performed using dry nitrogen. The collected solvent was reused as a dope preparation solvent after adjusting the water content to 0.3 mass% or less. The drying air contains plasticizers, UV absorbers and other high-boiling substances in addition to the solvent gas, so these were removed by a cooler and pre-adsorber to be removed by cooling and used for recycling. And adsorption / desorption conditions were set so that VOC (volatile organic compound) in the outdoor exhaust gas was finally 10 ppm or less. Moreover, the solvent amount collect | recovered by a condensation method among all the evaporation solvents was 90 mass%, and most of the remainder was collect | recovered by adsorption collection.

  The dried film 82 was conveyed to a first humidity control chamber (not shown). A drying air of 110 ° C. was sent out to the transition part between the drying chamber 51 and the first humidity control chamber. Air having a temperature of 50 ° C. and a dew point of 20 ° C. was sent to the first humidity control chamber. Further, the film 82 was conveyed to a second humidity control chamber (not shown) that suppresses the curling of the film 82. In the second humidity control chamber, air at 90 ° C. and humidity 70% was sent directly to the film 82.

  The film 82 after humidity control was cooled to 30 ° C. or lower in the cooling chamber 52, and then subjected to edge cutting at both ends again with an edge cutting device (not shown). Moreover, the forced static elimination apparatus (static elimination bar) 93 was installed, and the charged voltage of the film 82 in conveyance was always set to the range of -3 to +3 kV. Further, knurling was applied to both ends of the film 82 by a knurling roller 94. The knurling was imparted by embossing from one side of the film 82. At this time, the knurling width was 10 mm, and the pressing pressure by the knurling roller was set so that the height of the unevenness was 12 μm higher than the average thickness of the film 81.

  Finally, the film 82 was conveyed to the winding chamber 53. The winding chamber 53 was kept at a room temperature of 28 ° C. and a humidity of 70%. An ion wind neutralization device (not shown) was installed inside the winding chamber 53 so that the charged voltage of the film 82 was −1.5 to +1.5 kV. The film (thickness 80 μm) 82 thus obtained had a width of 1475 mm and a total winding length of 3940 m. The diameter of the winding roller 95 was 169 mm. The tension at the start of winding was 300 N / m, and the tension at the end of winding was 200 N / m. Further, the fluctuation width (sometimes referred to as an oscillating width) of the winding deviation at the time of winding was set to ± 5 mm, and the winding deviation period with respect to the winding roller 95 was set to 400 m. The pressing pressure of the press roller 96 against the winding roller 95 was set to 50 N / m. The temperature of the film 82 at the time of winding was 25 ° C., the water content was 1.4% by mass, and the residual solvent amount was 0.3% by mass.

[Comparative example]
A film 82 was manufactured using the same dope 27 and manufacturing method as in the example. Moreover, the film was manufactured on the same conditions as an Example except not having attached the windshield 117 of the air blower 101 of the tenter 47.

  In the example in which the wind shielding plate 117 is provided, the film surface temperature in the tenter 47 becomes substantially uniform, the error in the retardation distribution (Re distribution) of the obtained film is within 5%, and the evaluation is ◎. It was. The error in film thickness uniformity was within ± 1%, and the evaluation was ◎. On the other hand, in the comparative example, a portion where the film film surface temperature was high at the central portion was generated, and the error in the retardation distribution was within 10%, and the evaluation was Δ. In addition, the film thickness uniformity error is within ± 5%, and the evaluation is Δ.

  From the results of the above examples and comparative examples, the wind shielding plate 117 that closes 30% of the length L1 in the film width direction at the center of the nozzle 115 of the blower head 110 at a ratio of one to a plurality of nozzles 115 is obtained. It can be seen that the uneven drying of the film can be suppressed by attaching.

It is the schematic of the dope production line in this invention. It is the schematic of the film manufacturing line of this invention. It is a top view which shows the outline of a tenter shown with sectional drawing about a ventilation head. It is sectional drawing from the side which shows the outline of an air blower. It is an external appearance perspective view which shows the outline of a ventilation head.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Dope production line 27 Dope 40 Film production line 47 Tenta 74 Wet film 100 Tenta main body 101 Blower 110 Blower head 111 Blower duct 112 Circulation duct 113 Blower fan 114 Temperature controller 115 Nozzle 116 Air conditioning plate 117 Baffle plate 118 Exhaust duct 119 Tenter room 120 Drying air blower

Claims (8)

In a tenter blower that blows drying air on the film gripped by the gripping means while drying and stretching the film in the width direction while gripping and conveying the side edge of the film by the gripping means,
A blower head disposed parallel to the film surface gripped by the gripping means;
A plurality of blowing nozzles disposed on a surface facing the film surface of the blowing head;
A tenter blower comprising: a windshield member that selectively shields dry air from the plurality of blower nozzles to substantially uniform a temperature distribution in the tenter of the film. The blowing nozzle is formed on the surface facing the film surface of the blowing head longer than the width of the film in the width direction of the film, and is arranged at a constant pitch in the film conveyance direction,
The tenter blower according to claim 1, wherein the wind-shielding member closes a central portion of the blower nozzles with respect to some of the plurality of blower nozzles.   The tenter blower according to claim 2, wherein the wind shielding member covers a range of 10 to 40% with respect to a film width direction length L <b> 1 of the blower nozzle.   The tenter blower according to claim 3, wherein the wind-shielding member is attached at a constant pitch with respect to the transport direction of the film.   The tenter blower according to any one of claims 1 to 4, wherein a plurality of the blower heads are provided in a film conveyance direction. A dope containing a polymer and an organic solvent is cast on a traveling support to form a cast film, and the cast film is peeled off from the support to form a film. In the method for producing a polymer film, which is gripped and conveyed and dried while stretching the film in the width direction to produce a polymer film,
6. A polymer film characterized in that a drying air is sent to a film using the tenter blower according to any one of claims 1 to 5 and dried on the film held and conveyed by the tenter holding means. Manufacturing method.   The polymer according to claim 6, wherein the polymer is cellulose acylate, and the film film surface temperature in the film width direction is suppressed to a range of ± 2 ° C in a section from the start of stretching by the tenter to the maximum stretching point. A method for producing a film.   In the section from the start of stretching by the tenter to the maximum stretching point, the volatile content of the solvent in the film width direction is ± 0.4 wt% W.S. B. The method for producing a polymer film according to claim 7, wherein the polymer film is suppressed to a range of ≦ 2.

Images