JP2009234075A - Method and apparatus for drawing polymer film and solution film formation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To control occurrence of recessed defects with a simple configuration of the apparatus by energizing the grasper in the closing direction by the shrinking force of the drawn polymer film so as to stabilize the grasping. <P>SOLUTION: A clip tenter 2 is divided into a preheating zone 2a, a grasp stabilization zone 2b, a width retention zone 2c, a main drawing zone 2d and a drawing relaxing zone 2e in the film-carrying direction A. In the grasp stabilization zone 2b, with the width of a polymer film 3 before drawing taken as 100%, the polymer film 3 is drawn so as to give a width after drawing of 104%. In the width retention zone 2c, the polymer film 3 is carried while keeping the state drawn to 104%. In the main drawing zone 2d, with the width of the polymer film 3 before drawing in the grasp stabilization zone 2b taken as 100%, the polymer film 3 is drawn so as to give a width after drawing of 140%. In the grasp stabilization zone 2b, the clip 5 is energized in the closing direction by the shrinking force of the polymer film 3 so as to stabilize the grasp of the film with the clip 5, and the polymer film 3 is drawn stably without recessed defects in the main drawing zone 2d. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method and apparatus for stretching a polymer film and a solution casting method.

  Among various polymer films used for optical applications, in particular, a cellulose acylate film is produced by a solution casting method. In this solution casting method, a dope is cast on a support using a casting die, the film is peeled off from the support, and then wound through a drying process to produce a film.

  The cellulose acylate film produced by the solution casting equipment is stretched in the film width direction in order to improve the flatness, mechanical strength, optical properties and the like. This stretching is carried out by pulling in the film width direction while conveying the film by gripping both side edges of the film with clips.

During film stretching, since the film around the portion bitten by the clip becomes thin by stretching, the film gripping force of the clip is reduced, and the film may come off from the clip during or after stretching. For this reason, Patent Document 1 proposes a tenter device provided with a clip closer that applies a force in the direction of closing the clip in the range from the grip start position to the grip release position.
JP 2004-106422 A

  However, as in Patent Document 1, in order to urge the clip in the closing direction in order to eliminate gripping looseness, it is necessary to provide gripping force urging means, and there is a problem that the device configuration becomes complicated. Further, in Patent Document 1 in which a gripping force is applied to eliminate gripping slack, a film deformation margin is small when a thin film having a thickness of 110 μm or less or a film in a low volatile content region having a low solvent content is used. Therefore, there is a problem that a sufficient effect cannot be obtained.

  Further, when the film is gripped by the clip, the film gripping portion of the clip needs to bite into the film without a gap. If there is a gap unevenness in the film gripping portion, the film cannot be gripped in the gap unevenness portion. FIGS. 5A and 5B are enlarged views of the film 100 in which gripping unevenness has occurred. FIG. 5A shows a single biting state and FIG. 5B shows a hollow state. A portion indicated by hatching indicates a gripping area 101 by a clip. In (A), it can be seen that the left and right gripping areas 101a and 101b grip the film 100 without any gap, but in the central gripping area 101c, there is a gap on the right side in FIG. Can no longer be gripped, and the film 100 is gripped only in the left area of the clip. Thus, if there is a gap on one side of the middle clip, the film 100 cannot be gripped at this gap generation part, so the film side edge 100a corresponding to this part is in a state of being depressed toward the center side, Ear twist 102 is made.

  Similarly, as shown in (B), even when a gap is generated in the center portion of the clip gripping area 101d in the middle clip, the film side edge 100a corresponding to this center portion is recessed toward the center side. Similarly, the ear twist 104 occurs. For example, in the case of (A), such ear twists 102 and 104 are concentrated in the gripping portion of the clip in which a gap is generated on one side in the case of (A). A bite-up occurs starting from. In the case of (B), the biting occurs in the same manner.

  If the bite is broken, the portion is not sufficiently stretched, and thus the optical characteristics may be uneven at the insufficiently stretched portion, which is not preferable. In addition, the film 100 may be broken from the bitten portion, and in this case, the stretching is stopped, which is a problem.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a polymer film stretching method and apparatus, and a solution casting method, which are capable of suppressing the occurrence of twisting with a simple configuration. .

  In order to achieve the above-mentioned object, the polymer film stretching method of the present invention is configured such that the polymer film is held in the width direction by holding both side edges of the polymer film with an openable / closable holding tool that moves in the running direction of the polymer film. In the method for stretching a polymer film that is stretched at a predetermined magnification, after the polymer film is gripped by the gripping tool, the grip width of the polymer film is gradually increased to be stretched below the predetermined ratio, and the stretched polymer Provided after the gripping stabilization step of stabilizing the gripping by urging the gripping tool in the closing direction by the shrinking force of the film, and after the gripping stabilization step, gradually increasing the gripping width of the polymer film and stretching it to the predetermined magnification And a main stretching step.

  Moreover, it is preferable that the said holding | grip stabilization process starts extending | stretching within 10 second after holding the said polymer film with the said holding tool.

  Furthermore, it is preferable to have the conveyance process which hold | maintains the holding | grip width of the said polymer film substantially constant between the said holding | grip stabilization process and the said main extending process.

  Further, the polymer film is a cellulose acylate film in which a solvent remains, and in the grasping stabilization step and the main stretching step, the residual solvent amount of the cellulose acylate film is 5% or more and 12.5% or less. It is preferable to do.

  Further, the cellulose acylate film has a film thickness before stretching of 70 μm or more and 110 μm or less, the predetermined magnification is 130% or more and 140% or less, and the stretching ratio of the grip stabilization step is 101.5% or more and 125% or less. It is preferable that In addition, the draw ratio of the grip stabilization step is more preferably 101.5% to 110%, and most preferably 101.5% to 105%.

  Further, the solution casting method of the present invention comprises casting a dope containing a polymer and a solvent on a support that runs endlessly, forming a cast film from the dope on the support, and cooling to form a gel. The cast film is peeled off from the support, and the stretching method of the polymer film is performed using the cast film peeled off from the support as a polymer film.

  In addition, the polymer film stretching apparatus of the present invention is capable of stretching the polymer film at a predetermined magnification in the width direction by gripping both side edges of the polymer film with an openable / closable gripper that moves in the running direction of the polymer film. In the polymer film stretching apparatus, after gripping the polymer film by the gripping tool, the gripping width of the polymer film is gradually increased to be stretched below the predetermined magnification, and the stretched polymer film is contracted by the contraction force. A gripping stabilizing means that urges the gripping tool in the closing direction to stabilize gripping, and a main stretching means that is provided after the gripping stabilizing means and that gradually increases the gripping width of the polymer film and stretches to the predetermined magnification; It is provided with.

  According to the present invention, since the gripping tool is urged in the closing direction by the contracting force of the stretched polymer film to stabilize the gripping, it is possible to prevent the polymer film from being bitten by the gripping tool. Thereby, generation | occurrence | production of the ear | edge twist of a polymer film can be suppressed, and a polymer film can be extended | stretched uniformly without unevenness.

  As shown in FIG. 1, the clip tenter 2 is stretched in the film width direction B while gripping both side edges of the polymer film 3 with a clip (gripping tool) 5 and transporting the film in the film transporting direction A. Dry.

  The clip tenter 2 includes a first rail 11, a second rail 12, and first and second chains (endless chains) 13 and 14 guided by the rails 11 and 12.

  The clip tenter 2 is disposed in a drying chamber (not shown). The drying chamber is partitioned in the film transport direction A into a preheating zone 2a, a gripping stabilization zone 2b, a width holding zone 2c, a main stretching zone 2d, and a stretching relaxation zone 2e. In the preheating zone 2a, the polymer film 3 is preheated at a predetermined temperature of, for example, 80 ° C. or higher and 145 ° C. or lower. In the preheating zone 2a and the width holding zone 2c, the distance between the pair of clips is not changed, and the stretching in the film width direction B by the clip 5 is not performed.

  In the holding stability zone 2b, the width holding zone 2c, and the main stretching zone 2d, the polymer film 3 is heated at, for example, 80 ° C. or higher and 145 ° C. or lower. In the holding stability zone 2b and the main stretching zone 2d, the distance between the pair of clips gradually increases, and the polymer film 3 is stretched in the film width direction B by the clip 5. In the stretching relaxation zone 2e, the polymer film 3 is heated at, for example, 80 ° C. or more and 145 ° C. or less, and the distance between the pair of clips does not change or gradually decreases, and stretching relaxation is performed.

  In the holding stability zone 2b, the polymer film 3 is stretched with a residual solvent amount of 12%, and in the main stretching zone 2d, the polymer film 3 is stretched with a residual solvent amount of 10%. In addition, it is possible to change within the range of the residual solvent amount of 5 to 12.5% in the holding stability zone 2b and the main stretching zone 2d without being limited to the above-described residual solvent amount. In this embodiment, the amount of residual solvent in the polymer film 3 indicates the amount of solvent remaining in the film on a dry basis. The measurement method is calculated by {(xy) / y} × 100, where a sample is taken from the target film, x is the weight of the sample, and y is the weight after drying the sample.

  A number of clips 5 are attached to the first and second chains 13 and 14 at regular intervals. The clip 5 stretches the polymer film 3 in the film width direction B by moving along the rails 11 and 12 while gripping the side edge of the polymer film 3. In the present embodiment, when the thickness of the polymer film 3 before stretching is 70 μm and the width is 100%, the polymer film 3 is stretched so that the width after stretching is 140%. The magnification is appropriately changed according to desired optical characteristics and the like, and is preferably 130% or more and 140% or less.

  The first and second chains 13 and 14 are spanned between the driving sprockets 21 and 22 and the driven sprockets 23 and 24, and the first chain 13 is connected by the first rail 11 between these sprockets 21 to 24. The second chain 14 is guided by the second rail 12. The driving sprockets 21 and 22 are provided on the tenter outlet 27 side, these are rotationally driven by a driving mechanism (not shown), and the driven sprockets 23 and 24 are provided on the tenter inlet 26 side.

  As shown in FIG. 2, the clip 5 includes a clip main body 31 and a rail attachment portion 32. The clip main body 31 includes a substantially U-shaped frame 33 and a flapper 34, and the flapper 34 is rotatably attached to the frame 33 by an attachment shaft 33a. The flapper 34 rotates between a film gripping position (see FIG. 3) in a substantially vertical state and an open position (see FIG. 2) in which the engaging head 34a contacts the clip opener 40 and rotates obliquely. In general, the film is biased to the film gripping position by its own weight. At the film grip start position PA, the polymer film 3 is gripped by the film gripping surface 33b and the flapper lower surface 34b.

  The rail attachment portion 32 includes an attachment frame 35 and guide rollers 36, 37, and 38. The first chain 13 or the second chain 14 is attached to the attachment frame 35. The guide rollers 36 to 38 rotate in contact with the support surfaces of the driving sprockets 21 and 22 or in contact with the support surfaces of the first rail 11 or the second rail 12. Thus, the clip body 31 is guided along the rails 11 and 12 without dropping from the sprockets 21 and 22 and the rails 11 and 12.

  As shown in FIG. 1, a clip opener 40 for opening the clip 5 is disposed in the vicinity of the sprockets 21 to 24. As shown in FIG. 2, in the driven sprockets 23 and 24 of the tenter inlet 26, the clip opener 40 is brought into contact with the engaging head 34a of the clip 5 before the film grip start position PA, thereby opening it. Allows reception of the side edges of the polymer film 3. Then, when passing the film grip start position PA, the clip opener 40 is separated from the engaging head 34a, the clip 5 is set to the grip position from the open position by its own weight, and the side edge of the polymer film 3 is gripped. . Similarly, in the driving sprockets 21 and 22 at the tenter outlet 27, the clip 5 is opened by the clip opener 40 at the grip open position PB of the polymer film 3, and the grip of the side edge of the polymer film 3 is released. .

  In the clip tenter 2, stretching of the polymer film 3 is started at the stretching start position PC (see FIG. 1), and stretching of the polymer film 3 is finished at the stretching end position PD. In the preheating zone 2a from the film grip start position PA to the stretching start position PC, the polymer film 3 is conveyed without being stretched. Furthermore, in the stretching relaxation zone 2e from the stretching end position PD to the grip opening position PB, the polymer film 3 is conveyed without being stretched.

  As shown in FIG. 1, the range from the stretching start position PC to the stretching pause position PE is the gripping stability zone 2b, and the section from the stretching pause position PE to the stretching restart position PF is the width holding zone 2c, and the stretching restart position. The area from PF to the stretching end position PD is the main stretching zone 2d. The stretching start position PC is provided at a position where the clip 5 that grips the polymer film 3 at the film gripping start position PA reaches after 4 seconds. The number of seconds is not limited to 4 seconds, and can be changed as appropriate within 10 seconds.

  In the holding stability zone 2b, when the width of the polymer film 3 before stretching is 100%, stretching is performed such that the width after stretching is 104%. As shown in FIG. 3, the polymer film 3 stretched in the width direction generates a force that shrinks to the original shape in the shrinkage direction C. The polymer film 3 is sandwiched between the film gripping surface 33b and the flapper lower surface 34b, and is a clip that moves along the rail 11 by a force that the polymer film 3 contracts in the contraction direction C (hereinafter referred to as contraction force). In the case of 5, the flapper 34 is rotated in the clockwise direction, and in the case of the clip 5 moving along the rail 12, the flapper 34 is rotated in the counterclockwise direction, and the clips 5 are each urged in the closing direction. The Thereby, the gripping force by the clip 5 increases, and the film gripping by the clip 5 is stabilized. In the present embodiment, the first and second rails 11 and 12 in the grip stabilization zone 2 b function as grip stabilization means for stabilizing grip by the clip 5. In addition, the draw ratio in the holding | maintenance stable zone 2b is changed suitably, and it is preferable that they are 101.5% or more and 125% or less.

  In the width holding zone 2c, the polymer film 3 is conveyed while maintaining a state stretched to 104%. For this reason, in the width holding zone 2c, the force for rotating the clip 5 in the closing direction due to the contraction force of the polymer film 3 is larger than that in the holding stability zone 2b, and the film holding by the clip 5 is further stabilized.

  In the main stretching zone 2d, when the width of the polymer film 3 before being stretched in the holding stability zone 2b is 100%, the stretched width is stretched to be 140% (predetermined magnification). When the width of the polymer film 3 before being stretched in the holding stability zone 2b is 100%, the polymer film 3 stretched to 104% is conveyed to the main stretching zone 2d. That is, in the main stretching zone 2d, when the width of the polymer film 3 before being stretched in the holding stability zone 2b is 100%, the width of the polymer film 3 is stretched from 104% to 140%. In the present embodiment, the first and second rails 11 and 12 in the main stretching zone 2d function as main stretching means for stretching the polymer film 3 to 140% as a predetermined magnification.

  Next, a method for producing the polymer film 3 will be described. However, the manufacturing method and manufacturing apparatus described below are examples of the present invention, and the present invention is not limited thereto.

[Solution casting method]
FIG. 4 shows a schematic diagram of the solution casting apparatus 50 used in this embodiment. The solution casting apparatus 50 includes a stock tank 51, a casting chamber 52, a pin tenter 53, a clip tenter 2, a drying chamber 54, a cooling chamber 55, and a winding chamber 56.

  The stock tank 51 includes a stirring blade 51b and a jacket 51c that are rotated by a motor 51a, and a dope 61 that is a raw material for the polymer film 3 is stored therein. The dope 61 in the stock tank 51 is adjusted by the jacket 51c so that the temperature becomes substantially constant. Further, the rotation of the stirring blade 51b keeps the dope 61 in a uniform quality while suppressing the aggregation of polymers and the like. A gear pump 65 and a filtering device 66 are installed downstream of the stock tank 51, and the dope 61 is sent to the casting die 70 through these gear pumps 65 and a filtering device 66.

  In the casting chamber 52, a casting die 70, a casting drum 72, a peeling roller 74, temperature control devices 75 and 76, and a decompression chamber 77 are installed. The casting drum 72 is rotated by a drive device (not shown), and the dope 61 is discharged from the casting die 70 toward the peripheral surface 72b of the rotating casting drum 72 during rotation. A casting film 73 is formed on the surface 72b.

  The temperature in the casting chamber 52 and the casting drum 72 is set to a temperature at which the casting film 73 is easily cooled and gelled by the temperature control devices 75 and 76. While the casting drum 72 rotates about 3/4, the casting film 73 reaches a gel strength having self-supporting properties, and is peeled off from the casting drum 72 by the peeling roller 74.

  The decompression chamber 77 is disposed upstream of the casting die 70 in the drum traveling direction, and maintains a negative pressure in the chamber 77. As a result, the back side of the casting bead (the surface that comes into contact with the peripheral surface 72b of the casting drum 72 later) is reduced to a desired pressure, and the influence of the accompanying wind generated by the casting drum 72 rotating at high speed is affected. A stable casting bead is formed between the casting die and the casting drum, and the casting film 73 with little film thickness unevenness is formed. Then, after the casting film 73 has self-supporting properties, the peeling roller 74 peels off the casting film 73 on the casting drum 72 as a wet film 78.

  The material of the casting die 70 is formed of a material having high corrosion resistance against an electrolyte aqueous solution, a mixed liquid such as dichloromethane or methanol, and a low coefficient of thermal expansion. It is preferable to use a finishing accuracy of the wetted surface of the casting die 70 with a surface roughness of 1 μm or less and a straightness of 1 μm / m or less in any direction.

  The peripheral surface 72b of the casting drum 72 is subjected to chrome plating, and has sufficient corrosion resistance and strength. The temperature control device 76 circulates the heat transfer medium through the casting drum 72 in order to keep the temperature of the peripheral surface 72b of the casting drum 72 at a desired temperature. The heat transfer medium is maintained at a desired temperature. By passing through the heat transfer medium flow path in the casting drum 72, the temperature of the peripheral surface 72b of the casting drum 72 is maintained at the desired temperature.

  The width of the casting drum 72 is not particularly limited, but it is preferable to use a casting drum having a width in the range of 1.1 to 2.0 times the casting width of the dope. The material of the casting drum 72 is preferably made of stainless steel, and more preferably made of SUS316 so as to have sufficient corrosion resistance and strength. The chromium plating treatment applied to the peripheral surface 72b of the casting drum 72 is preferably so-called hard chromium plating with a Vickers hardness of Hv 700 or more and a film thickness of 2 μm or more.

  In the casting chamber 52, a condenser (condenser) 79 for condensing and recovering the evaporated organic solvent and a recovery device 80 for recovering the condensed and liquefied solvent are provided. The organic solvent condensed and liquefied by the condenser 79 is recovered by the recovery device 80. The solvent is regenerated as a solvent for preparing a dope after being regenerated by a regenerator.

  On the downstream side of the casting chamber 52, a crossing portion 81, a pin tenter 53, and a clip tenter 2 are installed in this order. The crossing part 81 introduces the wet film 78 peeled off by the conveying roller 82 into the pin tenter 53. The pin tenter 53 has a large number of pin plates that pass through and hold both ends of the wet film 78, and the pin plates travel on the track. During this traveling, dry air is sent to the wet film 78, and the wet film 78 is dried while traveling to become the polymer film 3.

  Desired optical properties are imparted to the polymer film 3 exiting the clip tenter 2 by the stretching process under the predetermined conditions in the clip tenter 2. In addition, you may perform the optical characteristic provision to the polymer film 3 offline after winding of the polymer film 3, and in this case, you may abbreviate | omit the clip tenter 2 from the solution casting apparatus 50.

  At the downstream of the pin tenter 53 and the clip tenter 2, an ear clip device 83 is provided. The ear-cutting device 83 cuts the ears that are both ends of the film. The cut ears are sent to the crusher 84 by air sending, and are crushed and reused as a raw material such as a dope.

  The drying chamber 54 is provided with a plurality of rollers 87, and drying is performed by winding the polymer film 3 around these rollers and transporting them. An adsorption recovery device 88 is connected to the drying chamber 54, and the solvent evaporated from the polymer film 3 is absorbed and recovered.

  A cooling chamber 55 is provided on the outlet side of the drying chamber 54, and the polymer film 3 is cooled to room temperature in the cooling chamber 55. A forced static eliminating device (static neutralization bar) 89 is provided downstream of the cooling chamber 55 to neutralize the polymer film 3. Further, a knurling application roller 90 is provided on the downstream side of the forced static elimination device 89, and knurling is applied to both side edges of the polymer film 3. In the winding chamber 56, a winding machine 91 having a press roller 92 is installed, and the polymer film 3 is wound around the winding core in a roll shape.

  Next, an example of a method for producing the polymer film 3 by the solution casting apparatus 50 will be described. In the stock tank 51, the temperature of the dope 61 is adjusted to 25 to 35 ° C. by flowing a heat transfer medium inside the jacket 51c, and is always made uniform by the rotation of the stirring blade 51b. An appropriate amount of the dope 61 is sent from the stock tank 51 to the filtration device 66 by the gear pump 65 and filtered to remove impurities in the dope 61. The dope 61 is cast from the casting die 70 onto the peripheral surface 72b of the casting drum 72 cooled to a predetermined surface temperature while forming a casting bead. It is preferable that the temperature of the dope 61 at the time of casting is kept substantially constant within a range of 30 to 35 ° C.

  The casting drum (support) 72 is rotated about a shaft 72a by a driving device. By this rotation, the peripheral surface 72b travels in the direction Z1 at a constant speed (from 30 m / min to 200 m / min). The temperature of the peripheral surface 72b of the casting drum 72 is adjusted to be substantially constant within a range of -10 to 10 ° C. When the casting drum 72 cooled in this way is used, the casting film 73 can be gelled to have a self-supporting property. The temperature of the peripheral surface 72b is managed by the temperature control device 76, and the temperature of the peripheral surface 72b of the casting drum 72 is maintained at a predetermined value. When the casting film 73 is cooled, a cross-linking point serving as a crystal base is formed, and gelation of the casting film 73 is promoted.

  After the gelation progresses, the casting film 73 becomes self-supporting, and is peeled off from the casting drum 72 by the peeling roller 74 to form a wet film 78. The wet film 78 is pinned by the transport roller 82. 53.

  The internal temperature of the casting chamber 52 is adjusted by the temperature controller 75 so as to be substantially constant within a range of 10 to 57 ° C. In the casting chamber 52, the dope 61 to be cast and the solvent in the casting film 73 are volatilized and floated. Therefore, in the present embodiment, the floating solvent is condensed and liquefied by the condenser 79, and then recovered by the recovery device 80, further regenerated by the regenerator, and reused as the dope preparation solvent.

  In the pin tenter 53, a large number of pins are inserted and fixed to both end portions of the wet film 78, and then drying is promoted while the wet film 78 is conveyed to form the polymer film 3. Then, the polymer film 3 still containing the solvent is fed into the clip tenter 2. At this time, the residual solvent amount of the polymer film 3 immediately before being sent to the clip tenter 2 is preferably 50 to 150% by weight.

  In the clip tenter 2, the polymer film 3 is stretched in the width direction. Thus, by the stretching process in the width direction of the polymer film 3, the molecules in the polymer film 3 are oriented, and a desired retardation value can be imparted to the polymer film 3.

  The polymer film 3 that has exited the pin tenter 53 and the clip tenter 2 is cut at both end portions by the edge-cutting device 83. The polymer film 3 whose both end portions are cut is wound up by the winder 91 in the winding chamber 56 via the drying chamber 54 and the cooling chamber 55. Further, both end portions cut by the ear-cutting device 83 are crushed by the crusher 84 to be reused as a dope preparation chip.

  The polymer film 3 wound by the winder 91 is preferably at least 100 m in the longitudinal direction (casting direction). In addition, the width of the polymer film 3 is 600 mm or more, further preferably 1400 mm or more and 3000 mm or less, and more preferably 1700 mm or more and 2100 mm or less. The present invention is also effective when the width is greater than 3000 mm. Furthermore, the present invention is effective when a thin film having a film thickness of 110 μm or less is produced.

  The present invention can also be applied to a solution casting method using a casting band that moves around a rotating drum instead of the casting drum 72. Also in this case, as a method for giving the casting film self-supporting property, it may be dried by blowing dry air or the like in addition to cooling gelation. When the film on the support is given self-supporting property by drying, the pin tenter 53 is omitted and the clip tenter 2 is used for drying.

  Hereinafter, the raw material used when preparing dope 61 in this invention is demonstrated.

In the present embodiment, cellulose acylate is used as the polymer, and cellulose triacetate (TAC) is particularly preferable as the cellulose acylate. Of the 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 is the substitution degree of the acetyl group, and B is 3 carbon atoms. The substitution degree of the acyl group of ˜22. In addition, it is preferable that 90 weight% 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 dope with better solubility can be produced. In particular, when a non-chlorine organic solvent is used, a dope having excellent solubility, low viscosity and excellent filterability can be produced.

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

  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.).

  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. The content of alcohol is preferably 2 to 25% by weight, more preferably 5 to 20% by weight, based on the entire solvent. 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.

  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. The same applies to additives such as solvents and plasticizers, deterioration inhibitors, UV absorbers (UV agents), optical anisotropy control agents, retardation control agents, dyes, matting agents, release agents, release accelerators, etc. JP-A-2005-104148 describes in detail in paragraphs [0196] to [0516], and these descriptions can also be applied to the present invention.

  In the solution casting method of the present invention, when casting a dope, two or more types of dopes are simultaneously co-cast and laminated, or a plurality of dopes are sequentially co-cast. Sequential lamination co-casting can be performed. In addition, 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. However, 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. . In addition, when performing simultaneous lamination and co-casting, it is preferable that the high-viscosity dope is enveloped by the low-viscosity dope when the dope is cast from the die slit to the support, and is formed from the die slit to the support. Of the casting beads, the dope in contact with the outside world preferably 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 step, handling method, curling, winding method after flatness correction, solvent recovery method, film recovery method Until now, 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.

[Film production]
In the solution casting apparatus 50 shown in FIG. 4, the surface is subjected to chrome plating and mirror finishing, and the dope 61 is cast on the surface of a cylindrical casting drum 72 having a diameter of 1000 mm to a thickness of 70 μm before stretching. A cast film 73 was formed. The casting film 73 having the self-supporting property was peeled off while being supported by the peeling roller 74 to obtain a wet film 78.

  In the pin tenter 53, pins were inserted and held at both end portions of the wet film 78 in the vicinity of the entrance, and then the wet film 78 was dried to obtain a polymer film (TAC film) 3. Subsequently, while feeding both ends of the polymer film 3 to the clip tenter 2 with the clips 5, the preheating zone 2a, the holding stability zone 2b, the width holding zone 2c, the main stretching zone 2d, and the stretching relaxation are performed at a drying temperature of 120 ° C. It sent to the zone 2e and preheating, extending | stretching, and extending | stretching relaxation were performed.

  When the width of the polymer film 3 before stretching was 100%, the stretching ratio in the holding stability zone 2b was 104.7%, and the stretching ratio in the main stretching zone 2d was 140%. In the holding stability zone 2b, the polymer film 3 was stretched with a residual solvent amount of 12%, and in the main stretching zone 2d, it was stretched with a residual solvent amount of 10%.

  After cutting both side ends of the polymer film 3 with the edge-cutting device 83 installed downstream of the clip tenter 2, the polymer film 3 is sufficiently promoted to be dried while being wound around a plurality of rollers 87 in the drying chamber 54. I let you. After the polymer film 3 was cooled to approximately room temperature in the cooling chamber 55, the polymer film 3 was sent to the winding chamber 56 and wound around a winding core while being pressed by a press roller 92, thereby obtaining a roll-shaped polymer film 3. In addition, before winding, the charged voltage was adjusted by the forced static eliminating device 89, and knurling was imparted by the knurling imparting roller 90.

[Dope]
The dope raw materials used in Example 1 are as follows.
Cellulose triacetate 100 parts by weight Dichloromethane 320 parts by weight Methanol 83 parts by weight 1-butanol 3 parts by weight Plasticizer A 7.6 parts by weight Plasticizer B 3.8 parts by weight UV agent a 0.7 part by weight UV agent b 0.3 part by weight Part fine particles 0.05 parts by weight

  The cellulose triacetate has a substitution degree of 2.84, a viscosity average polymerization degree of 306, a water content of 0.2% by weight, a viscosity of 6% by weight in a dichloromethane solution of 315 mPa · s, an average particle diameter of 1.5 mm, and a standard deviation of 0.8. 5 mm powder, plasticizer A is triphenyl phosphate, plasticizer B is diphenyl phosphate, and UV agent a is 2 (2′-hydroxy-3 ′, 5′-di- tert-butylphenyl) benzotriazole, UV agent b is 2 (2′-hydroxy-3 ′, 5′-di-tert-amylphenyl) -5-chlorobenzotriazole, and the citrate ester compound is It is a mixture of acid, monoethyl ester, diethyl ester and triethyl ester, and the fine particles have a mean particle size of 15 nm and a Mohs hardness of about 7 It is silicon.

  In Example 1, when the film thickness before stretching of the polymer film 3 which is a TAC film is 70 μm and the width of the polymer film 3 before stretching is 100%, the stretching ratio in the gripping stability zone 2b is 104.7%. The draw ratio in the main draw zone 2d was 140%. The film gripping stability of the clip 5 in the main stretching zone 2d at that time was observed with a television camera, and by visual observation, x was indicated when the film was broken, x was indicated when the film was dropped, and ◯ was indicated otherwise. Hereinafter, Examples 2 to 5 and Comparative Examples 1 and 2 were obtained by changing the film thickness before stretching and the stretching ratio in the holding stability zone 2b with respect to Example 1. Other film production conditions were the same as those in Example 1. The results of this experiment are shown in Table 1.

  As a result of this experiment, in Examples 1 to 5, the film holding stability was good. In Comparative Examples 1 and 2, film biting or film falling off occurred, and film gripping stability was poor. Similar results were obtained when the holding stability zone 2b and the main stretching zone 2d were directly connected without providing the width holding zone 2c.

  In this way, the contraction force of the polymer film 3 in the gripping stabilization zone 2b urges the clip 5 in the closing direction to stabilize the gripping by the clip 5, so that the film does not tear and fall off, and the main stretching zone 2d Can stably hold the film. Thereby, even if the film thickness before extending | stretching is thin (for example, 70 micrometers) and the high stretch ratio (for example, 130-140%), the polymer film 3 can be extended | stretched reliably, and an ear | edge twist and extending | stretching nonuniformity are possible. It is possible to produce a polymer film 3 having no surface.

  Further, since the width holding zone 2c is provided between the holding stability zone 2b and the main drawing zone 2d, the film can be held more stably in the main drawing zone 2d more reliably.

It is a top view which shows a clip tenter. It is a side view which shows a clip. It is a perspective view which shows a clip, a clip opener, and a clip closer. It is the schematic of solution casting apparatus. An example of a biting failure is shown. (A) shows an example of a single bite and (B) shows an example of a hollow.

Explanation of symbols

2 Clip tenter 2a Preheating zone 2b Grasping stability zone 2c Width holding zone 2d Full stretching zone 2e Stretching relaxation zone 3 Polymer film 5 Clip (gripping tool)
11 First rail 12 Second rail 72 Casting drum (support)

Claims (7)

In the stretching method of the polymer film, by gripping both side edges of the polymer film and stretching the polymer film at a predetermined magnification in the width direction by an openable / closable gripper that moves in the running direction of the polymer film,
After gripping the polymer film by the gripping tool, the gripping width of the polymer film is gradually increased to be stretched below the predetermined magnification, and the gripping tool is biased in the closing direction by the contraction force of the stretched polymer film. A gripping stabilization process that stabilizes gripping, and
A main stretching step that is provided after the gripping stabilization step, and that gradually increases the grip width of the polymer film and stretches the polymer film at the predetermined magnification.   The method for stretching a polymer film according to claim 1, wherein the gripping stabilization step starts stretching within 10 seconds after gripping the polymer film by the gripping tool.   The method for stretching a polymer film according to claim 1 or 2, further comprising a transporting step for transporting the polymer film while maintaining a grip width substantially constant between the gripping stabilization step and the main stretching step. . The polymer film is a cellulose acylate film in which a solvent remains,
The polymer film according to any one of claims 1 to 3, wherein, in the grasping stabilization step and the main stretching step, a residual solvent amount of the cellulose acylate film is 5% or more and 12.5% or less. Stretching method.   The cellulose acylate film has a film thickness before stretching of 70 μm or more and 110 μm or less, the predetermined magnification is 130% or more and 140% or less, and the stretching ratio of the grip stabilization step is 101.5% or more and 125% or less. The method for stretching a polymer film according to claim 4. Casting a dope containing a polymer and a solvent onto a support that runs endlessly,
Forming a cast film from the dope on the support;
The cast film gelled by cooling is peeled off from the support,
The cast film peeled off from the support as a polymer film,
6. A solution casting method, wherein the polymer film stretching method according to claim 1 is performed. In a polymer film stretching apparatus that grips both side edges of the polymer film and stretches the polymer film at a predetermined magnification in the width direction by an openable / closable gripper that moves in the running direction of the polymer film.
After gripping the polymer film by the gripping tool, the gripping width of the polymer film is gradually increased to be stretched below the predetermined magnification, and the gripping tool is biased in the closing direction by the contraction force of the stretched polymer film. Grip stabilization means for stabilizing the grip, and
A stretching apparatus for a polymer film, comprising: a main stretching means that is provided after the gripping stabilizing means and gradually stretches the grip width of the polymer film and stretches the polymer film at the predetermined magnification.

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