JP2009233889A - Solution film-forming facility and solution film-forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently produce a film with excellent optical characteristics. <P>SOLUTION: A dope 12 flows out of a casting die 25 and forms a cast film 14 on a casting drum 13. The cast film 14 is gelled by cooling to have self-supporting property. A release roller 29 peels the cast film 14 as a moist film 38. A transfer part 17 includes a carrying roller group 39. Each carrying roller 39a-39z constituting the carrying roller group 39 support and carry the moist film 38 containing a large quantity of solvent. The drive rollers 39a and 39b are provided as the uppermost stream side and lowermost stream side carrying rollers of the carrying roller group 39. The downstream drive roller 39b is rotated under the control of a drive control part 56 so as to be larger in circumferential speed than the drive roller 39a. Free rollers 39x-39z are closely disposed between the pair of drive rollers 39a and 39b. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a solution casting apparatus and a solution casting method.

  Polymer films (hereinafter referred to as “films”) are widely used as optical functional films because of their features such as excellent light transmittance, flexibility, and light weight thinning. Among them, cellulose ester films using cellulose acylate have toughness and excellent isotropy of optical properties such as birefringence, and the market has recently expanded, including photographic photosensitive films. It is used as an optical functional film such as a protective film for a polarizing plate, an optical compensation film, and a viewing angle widening film, which are constituent members of a display device such as a liquid crystal display device (hereinafter referred to as LCD).

  Main film production methods include a melt extrusion method and a solution casting method. The melt extrusion method is a method in which a polymer is heated and dissolved as it is, and then extruded with an extruder to produce a film, which has features such as high productivity and relatively low equipment cost. However, it is difficult to adjust the film thickness accuracy, and because fine lines (die lines) can be formed on the film, it is difficult to produce a high-quality film that can be used for optical functional films. is there. On the other hand, since the solution casting method is excellent in optical isotropy and thickness uniformity as compared with the melt extrusion method, and can obtain a film with few contained foreign substances, the optical functional film used for a display device or the like is It is mainly manufactured by a solution casting method.

  An outline of this solution casting method will be described. First, a polymer such as cellulose triacetate is dissolved in a mixed solvent containing methylene chloride or methyl acetate as a main solvent to prepare a dope. Next, a predetermined additive is mixed with this dope to prepare a casting dope. Third, the casting dope is cast on a support (such as a casting drum or an endless band) that travels from the outlet of the casting die (hereinafter referred to as a casting step). At this time, the casting dope between the outlet of the casting die and the support forms a casting bead. Thus, a casting film is formed on the support in the casting step. Fourth, the support conveys the casting membrane at a predetermined traveling speed. Fifth, after making the cast film exhibit self-supporting properties, the cast film is peeled off from the support as a wet film. Sixth, the wet film is transported from the support to the drying means, and a drying process is performed in the drying means to evaporate the solvent remaining on the wet film. Finally, the wet film that has undergone the drying step is wound up as a film.

In the above solution casting method, when a wet film is transported using a plurality of transport rollers, a wet film is used by using a pair of drive rollers in order to prevent the wet film from being damaged during transport. There is known a method of conveying while applying tension in the conveying direction to a wet film (for example, Patent Document 1).
JP 2000-176950 A

  However, when a wet film with a high residual solvent amount is transported by a plurality of rollers, the portions that are not supported by the rollers are loosened. As a result, the polymer molecules in the wet film are oriented in the direction of tension, and eventually the optical film Anisotropy occurs in the characteristics. Further, even when a tension for preventing this slack is applied to a wet film having a high residual solvent amount using a pair of drive rollers, the polymer molecules in the wet film are oriented in the direction of the tension due to this tension. .

  This invention solves the said subject, and it aims at providing the solution casting apparatus and solution casting method which manufacture efficiently the film excellent in optical isotropy.

  The present invention flows out to a support running on a dope containing a polymer and a solvent, forms a cast film on the support, and uses the peeling roller to provide the self-supporting flow. The cast film is peeled off as a wet film from the support, and transported to a drying device while supporting the wet film using a plurality of transport rollers, and the solvent remaining in the wet film is removed by the drying device. In the solution casting method for producing a film, a path length of the wet film from the peeling roller to the drying device is 0.5 m or more and 3.0 m or less, and a pitch of 30 cm or less in the conveyance direction of the wet film. The plurality of transport rollers is arranged, and at least one of the plurality of transport rollers is rotationally driven using a flat roller as the transport roller. Characterized by the symptoms.

  It is preferable that a gap between the peripheral surfaces of the respective transport rollers is 1 cm or more. In addition, it is preferable that the plurality of transport rollers include a concave roller having a diameter that increases from the central portion in the width direction toward both end portions and transports the wet film while supporting the wet film. Furthermore, it is preferable that the residual solvent amount of the wet film conveyed by the plurality of conveying rollers is 100 wt% or more and 250 wt% or less.

  Further, the present invention flows out to a support that runs a dope containing a polymer and a solvent, forms a cast film on the support, and has a self-supporting property using a peeling roller. The casting film is peeled off as a wet film from the support, and transported to a drying device while supporting the wet film using a plurality of transport rollers, and the solvent remaining in the wet film is removed by the drying device. In a solution casting apparatus for removing and manufacturing a film, a path length of the wet film from the peeling roller to the drying device is 0.5 m or more and 3.0 m or less, and the transport roller is the wet film The flat rollers are arranged at a pitch of 30 cm or less in the transport direction, and at least one of the plurality of transport rollers is a drive roller.

  It is preferable that a gap between the peripheral surfaces of the flat rollers is 1 cm or more. In addition, it is preferable that the plurality of transport rollers include a concave roller having a diameter that increases from the central portion in the width direction toward both end portions and transports the wet film while supporting the wet film. Furthermore, it is preferable that the support is a casting drum that cools the casting film and exhibits self-supporting property by gelation.

  The present invention uses a plurality of transport rollers that are densely arranged in the transport direction of the wet film to transport the wet film while supporting the wet film, so that the wet film is transported upstream and downstream by two drive rollers. Compared with this type, the tension applied to the wet film during conveyance can be dispersed. The dispersion of the tension suppresses the elongation of the wet film, and as a result, the orientation of the polymer molecules can be reduced. Therefore, according to this invention, the film excellent in optical isotropy can be manufactured efficiently.

  Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the embodiments given here.

  As shown in FIG. 1, a film production facility 10 is cast on a casting drum (casting drum) 13 that travels (rotates) a dope 12 supplied from a dope production facility 11 connected via a pipe. A casting film 14 is formed, and the casting film 14 is peeled off from the casting drum 13 and dried to form a film 15. The film manufacturing facility 10 is roughly composed of a casting device 16, a crossover 17, a tenter device 18, a drying chamber 21, a cooling chamber 22, and a winding chamber 23.

  The casting apparatus 16 includes a casing 24, a casting die (exclusion die) 25 that discharges the dope 12 supplied from the dope production facility 11, a casting drum 13, and a casting film 14 from the casting drum 13. A peeling roller 29 for stripping off, a temperature adjusting device 30 for adjusting the temperature, humidity, and condensation temperature of the solvent in the casing 24, and a pressure reduction disposed on the upstream side of the casting die 25 in the rotating direction of the casting drum. And a chamber 33.

  A slit-like discharge port for discharging the dope 12 is provided at the tip of the casting die 25, and a casting drum 13 is disposed below the discharge port. The dope 12 discharged from the casting die 25 is cast on the drum peripheral surface 13 a of the casting drum 13. The material of the casting die 25 is formed of a material (for example, a steel material such as SUS316) having a high corrosion resistance with respect to a mixed solution of an electrolyte aqueous solution, methylene chloride, methanol, or the like and a low coefficient of thermal expansion.

  The casting drum 13 formed in a cylindrical shape is rotated around the rotation shaft 13b by the driving device 35. Thereby, the drum peripheral surface 13a of the casting drum 13 rotates at a predetermined speed (10 to 300 m / min) in a predetermined traveling direction. The drum peripheral surface 13a is chrome-plated and has sufficient corrosion resistance and strength. The dimensions and material of the casting drum 13 are not particularly limited, but those having a width of about 1.1 to 2.0 times the casting width of the dope 12 are preferable. A material having corrosiveness or high strength is preferred.

  A flow path through which the heat transfer medium passes is formed in the casting drum 13 and its rotating shaft 13b. The temperature controller 36 circulates a heat transfer medium maintained at a desired temperature through these flow paths. Thereby, the temperature of the drum peripheral surface 13a is maintained in a desired range, for example, −10 ° C. or more and 10 ° C. or less. Further, in order to form the casting film 14 having excellent flatness, the drum peripheral surface 13a is preferably subjected to polishing treatment.

  When the dope 12 is discharged from the casting die 25 as a casting bead, a casting film 14 is formed on the drum peripheral surface 13a. The casting film 14 is conveyed at a predetermined traveling speed by the rotation of the casting drum 13. At this time, the temperature adjustment device 30 adjusts so that the internal temperature of the casting device 16 becomes substantially constant.

  The suction device 37 sucks air on the back side of the casting bead through the decompression chamber 33. Thus, the decompression chamber 33 makes the back side of the casting bead a negative pressure. Thereby, the landing position of the casting bead on the casting drum 13 is fixed without wobbling. The decompression chamber 33 decompresses in the range of −2000 Pa to −50 Pa in the present embodiment. The casting film 14 having self-supporting property by drying and cooling on the casting drum 13 is peeled off from the casting drum 13 by the peeling roller 29 to become a wet film 38. The wet film 38 is conveyed to the crossover unit 17.

  A plurality of transport roller groups 39 that support and transport the wet film 38 and a blower 40 that blows dry air on the wet film 38 that is being transported are disposed in the crossover portion 17. The tenter device 18 dries both sides of the wet film 38 while holding it with tenter clips (not shown). Further, the tenter device 18 is stretched at a predetermined stretch ratio in the width direction TD or the like while drying the wet film 38 by applying a drying air inside. Thereby, the wet film 38 is sent to the ear clip device 41 as the film 15 in a state where the drying has progressed.

  The ear clip device 41 cuts out a side end portion (ear portion) of the film 15. The film 15 with the ears cut off is sent to the drying chamber 21. Further, the cut ear scraps (ear scrap film) are finely cut by the crusher 42 to become a recycled chip. This recycled chip is reused as a raw material for the dope 12.

  The drying chamber 21 is provided with a number of pass rollers 44. These pass rollers 44 cover the film 15 and dry both surfaces of the film 15 evenly. Note that solvent gas is generated from the film 15 during drying. This solvent gas is adsorbed and recovered by an adsorption recovery device 45 provided outside the drying chamber 21. The dried film 15 is guided to the cooling chamber 22 and cooled to approximately room temperature.

  On the downstream side of the cooling chamber 22, a forced static elimination device 47 (static elimination bar) that neutralizes static electricity charged on the film 15 is provided. Further, on the downstream side of the forced static elimination device 47, a knurling application roller 48 for applying embossing knurling to both edges of the film 15 is provided.

  The film 15 that has been subjected to the static neutralization process and the knurling application process is taken up by the take-up roller 50 in the take-up chamber 23. In the winding chamber 23, a press roller 51 that presses the film 15 during film winding is provided on the outer periphery of the winding roller 50.

(Peeling roller)
As shown in FIG. 2, the driving device (not shown) rotates around the axis of the peeling roller 29. And it becomes possible to give moderate tension to the wet film 38 by making the peripheral speed of the peeling roller 29 larger than the peripheral speed of the drum peripheral surface 13a. In this way, the peeling roller 29 can peel off the casting film 14 on the drum peripheral surface 13 a as the wet film 38.

(Conveying roller group)
As shown in FIGS. 2 and 3, the transport roller group 39 transports the wet film 38 from the upstream side to the downstream side in the direction MD while supporting the wet film 38. The transport roller group 39 includes a plurality of transport rollers, that is, drive rollers 39a and 39b and free rollers 39x to 39z. The drive rollers 39a and 39b and the free rollers 39x to 39z extend in a direction substantially perpendicular to the direction MD, that is, in the width direction TD of the wet film 38, and between the peeling roller 29 and the tenter device 18, Closely lined up. The distance LF between the rollers 39a to 39z is preferably 1 cm or more and 30 cm or less. Moreover, each roller 39a-39z is a flat roller which has a substantially the same diameter from the center part of the width direction TD to a both-ends part, and it is preferable that the diameter D1 (refer FIG. 3) is 5 cm or more and 20 cm or less.

(Distance LF)
The distance LF is a distance between the rollers 39a to 39z in the transport direction MD. The transport roller 39m and the transport roller 39n may be any of the drive rollers 39a and 39b and the free rollers 39x to 39z.

(Drive roller)
As shown in FIG. 2, the drive roller 39b is provided on the downstream side of the drive roller 39a in the direction MD. The distance LA between the drive rollers 39a and 39b is preferably 0.5 m or more and 3.0 m or less. The distance LA is preferably 10% or more of the width W and 500% or less of the width W, where W is the width of the wet film 38. The drive rollers 39a and 39b are connected to the drive units 55a and 55b, respectively. The drive units 55a and 55b rotate and drive the drive rollers 39a and 39b around the shafts under the control of the drive control unit 56, respectively. Thus, the tension | tensile_strength of direction MD can be given to the wet film 38 by adjusting the peripheral speed of drive roller 39a, 39b independently. The wet film 38 sent to the transfer section 17 by the peeling roller 29 is sent to the tenter device 18 by the rotation of the drive rollers 39a and 39b.

(Free roller)
Free rollers 39x to 39z are sequentially provided from the upstream side between the drive roller 39a and the drive roller 39b. The free rollers 39x to 39z come into contact with the wet film 38 conveyed by the drive rollers 39a and 39b, and rotate around the axis according to the conveyance of the wet film 38.

(Tenter device)
The tenter device 18 includes a carrying start portion 18a, a carrying release portion, and a chain 18b. The chain 18b provided with innumerable pins is stretched around a pulley 18c provided at the carrying start portion 18a and the carrying release portion. Under the control of a control unit (not shown), the pulley 18c rotates about the axis. Due to the rotation of the pulley 18c, the chain 18b sequentially circulates the carrying start portion 18a and the carrying release portion in an endless manner. Then, the carrying start portion 18a starts carrying the both end portions of the wet film 38 by the pins provided on the chain 18b, and the carrying releasing portion releases carrying the both end portions of the wet film 38 by the pins. In this way, the wet film 38 sent from the casting device 16 sequentially passes through the carrying start portion 18a and the carrying release portion, and then becomes the film 20 and is sent to the ear clip device 43.

  The tenter device 18 is provided with a duct (not shown). The dry air adjusted to a predetermined condition is sent out from the duct toward the wet film 38. When the drying air hits the wet film 38, the solvent contained in the wet film 38 evaporates and the wet film 38 is dried.

  Further, the distance LZ from the peeling position P on the drum peripheral surface 13a of the casting drum 13 (see FIG. 1, hereinafter referred to as the peeling point P) to the carrying start portion 18a of the tenter device 18 is 0.5 m. It is preferable that it is 3 m or less. If the path LZ is less than 0.5 m, it is difficult to prevent the tar film of the wet film 38, and if the path LZ is greater than 3 m, it is difficult to adjust the stretch ratio in the direction MD to a desired range. Because.

  Next, an example of a method for manufacturing the film 15 by the film manufacturing facility 10 (see FIG. 1) will be described. When the operation of the film production facility 10 is started, the casting drum 13 rotates a predetermined amount, and the drum peripheral surface 13a travels at a predetermined speed, for example, 30 m / min or more. At this time, the temperature of the drum peripheral surface 13 a is maintained at −10 ° C. or more and 0 ° C. or less by the temperature controller 36. The temperature control device 30 adjusts the atmosphere inside the casting device 16 to a predetermined condition. Thereby, since the condensation point of the solvent in the atmosphere inside the casting apparatus 16 is kept low, the casting film 14 can be dried while the casting film 14 is cooled.

  Next, when the dope 12 is supplied from the dope supply facility 11 toward the casting die 25, the dope 12 is discharged from the casting die 25 as a casting bead, and a casting film 14 is formed on the drum peripheral surface 13a. Is done. At this time, the suction device 37 is activated and the pressure reducing chamber 33 reduces the pressure on the back side of the casting bead in the range of −2000 Pa to −50 Pa. This decompression can suppress a certain amount of the vibration of the casting bead 41.

  The cast film 14 on the drum peripheral surface 13a held at a predetermined temperature is gelled by cooling and drying. When gelation proceeds more than a certain level, the casting film 14 exhibits self-supporting properties. The casting film 14 having self-supporting property is peeled off from the casting drum 13 by the peeling roller 29 to become a wet film 38. The residual solvent amount of the wet film 38 peeled off from the casting drum 13 is preferably 100% by weight or more and 250% by weight or less on the dry basis. The residual solvent amount based on the dry amount is a value calculated by {(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. . In addition, the gelation may be promoted by evaporating the solvent contained in the casting film 14 together with the cooling of the casting film 14.

  The wet film 38 peeled off from the casting drum 13 is conveyed to the transfer section 17 at a speed of 1.03 to 1.20 times that at the time of conveyance by the casting drum 13. The wet film 38 is dried at the transfer section 17 and then sent to the tenter device 18. The residual solvent amount of the wet film 38 when it is sent to the tenter device 18 is preferably 100% by weight or more and 250% by weight or less on a dry basis. The wet film 38 is subjected to a stretching process as well as a drying process in the tenter device 18, and is then transported to the ear clip device 41 as a film 15. The film 15 is conveyed to the drying chamber 21 after the ear portion is cut by the ear clip device 41.

  After the film 15 is dried in the drying chamber 21, it is guided to the cooling chamber 22 and cooled to approximately room temperature. Next, the film 15 is subjected to a static elimination process and a knurling imparting process by the forced static elimination device 47 and the knurling imparting roller 48, and then taken up by the take-up roller 50 in the take-up chamber 23.

  The length of the film 15 wound around the winding roller 50 is preferably at least 100 m in the direction MD. Moreover, it is preferable that the width | variety of the film 15 is 600 mm or more, it is more preferable that it is 1400 mm or more and 2500 mm or less, and the effect of this invention is expressed also when larger than 2500 mm. Moreover, it is preferable that the thickness of the film 15 is 20 micrometers or more and 200 micrometers or less, and it is more preferable that they are 40 micrometers or more and 100 micrometers or less.

  Next, details of the crossover unit 17 will be described. As shown in FIG. 2, under the control of the drive control unit 56, the drive rollers 39a and 39b rotate around a shaft at a predetermined peripheral speed. When the peripheral speed Va of the drive roller 39a and the peripheral speed Vb of the drive roller 39b are set, the peripheral speed ratio VR of each drive roller 39a, 39b given by Vb / Va is 1.00 or more and 1.50 or less. Is preferred. The peeling roller 29 sends the wet film 38 to the upstream drive roller 39a. The upstream drive roller 39a conveys the wet film 38 sent by the peeling roller 29 to the downstream free rollers 39x to 39z and the downstream drive roller 39b. The downstream drive roller 39b conveys the wet film 38 to the tenter device 18 while supporting the wet film 38 sent by the upstream drive roller 39a.

  At this time, since the peripheral speed of the downstream drive roller 39b is larger than the peripheral speed of the upstream drive roller 39a, the wet film 38 between the upstream drive roller 39a and the downstream drive roller 39b has a direction MD. Tension is applied. By applying this tension, it is possible to prevent the wet film 38 from being damaged or distorted during conveyance. The stretch ratio of the wet film 38 by this tension is preferably 1.0 or more and 1.5 or less. The stretching ratio is obtained by dividing the length of the wet film 38 in the direction MD after stretching by the length of the wet film 38 in the direction MD before stretching.

  Further, since the free rollers 39x to 39z contacting the wet film 38 are closely arranged along the transport direction MD of the wet film 38 between the upstream drive roller 39a and the downstream drive roller 39b, As a result of the dispersion of the tension in the direction MD applied to the wet film 38, the orientation of the polymer molecules due to the tension along the direction MD can be suppressed.

  Therefore, according to the present invention, by applying tension in the direction MD to the wet film 38 by the pair of drive rollers, the pair of drive rollers can be prevented while preventing the occurrence of stagnation or slippage of the wet film 38 during conveyance. By contacting the free rollers 39x to 39z that are closely arranged between the two, the orientation of polymer molecules in the wet film 38 due to the tension can be suppressed.

  In the above embodiment, the three transport rollers, that is, the free rollers 39x to 39z are provided between the two transport rollers, that is, the drive rollers 39a and 39b. However, the present invention is not limited thereto, and the drive roller 39a, One, two, or four or more transport rollers may be provided between 39b. Further, these transport rollers may be drive rollers or free rollers. In addition, it is good also as a conveyance roller group which does not provide a conveyance roller between drive roller 39a, 39b, and consists only of drive roller 39a, 39b. In place of the drive rollers 39a and 39b, free rollers may be used.

  In the above embodiment, the dry air is applied to the wet film 38 that passes through the crossing part 17 using the blower 40. However, the present invention is not limited to this, and any method for maintaining the gelation of the wet film 38 may be used. For example, the wet film 38 may be cooled, dried, or a combination thereof. For example, as a method of cooling the wet film 38, dry air adjusted to a predetermined temperature may be applied to the wet film 38, or a temperature control device is provided for each of the rollers 39a to 39z, and the temperature control device is controlled. The temperature of the peripheral surface of each of the rollers 39a to 39z may be maintained in a desired range.

  In the above embodiment, the free rollers 39x to 39z are provided between the drive rollers 39a and 39b. However, the present invention is not limited to this, and the drive rollers 39a and 39b are similar to the drive rollers 39a and 39b. One or a plurality of intermediate drive rollers may be provided. Further, the intermediate drive rollers may be arranged alternately with other free rollers, or may be arranged continuously with other drive rollers.

  In the above embodiment, a flat roller is provided as the transport roller. However, the present invention is not limited to this, and the diameter gradually increases from the center portion in the width direction TD to both end portions in the width direction TD as shown in FIG. The concave concave roller 60 may be used as a conveying roller. By using the concave roller 60, the outward force from the central portion in the width direction TD is applied to the wet film 38, so that the wrinkle and curl of the wet film 38 are prevented, and it is caused by the tension along the direction MD. It is possible to cancel the fluctuation of the birefringence.

  When the diameter of the central portion of the concave roller 60 in the width direction TD is E2, the diameter of both end portions in the width direction TD is D2, and the length in the width direction is W2, D2− (W2 × 0.005) ≦ E2 ≦ D2− (W2 × 0.0001) is preferably satisfied. When the diameter E2 of the central portion in the width direction TD is less than D2- (W2 × 0.005), the force toward the outside from the central portion in the width direction TD becomes too strong, and the transport position of the wet film 38 is in the width direction. It becomes easy to shift from the center of TD. When the diameter E2 of the central portion is larger than D2- (W2 × 0.0001), the force from the central portion in the width direction TD toward the outside is weakened, so the effect of suppressing the fluctuation of the birefringence of the wet film 38 is reduced. End up.

  Further, instead of the concave roller 60 as described above, as shown in FIG. 5, a stepped roller formed so that the diameter E3 of the width direction both side portions 65e is larger than the diameter E3 of the width direction center portion 65c. 65 can also be used. Even when such a stepped roller 65 is used, as in the case where the concave roller 60 is used, the outward force from the center in the width direction TD is applied to the wet film 38, so that the wrinkle of the wet film 38 is reduced. It is possible to suppress the variation in the birefringence of the wet film 38 due to the tension along the direction MD while preventing the occurrence of curling and curling.

  At this time, the diameter D3 of the widthwise both side portions 65e of the stepped roller 65 is preferably larger than the diameter E3 of the widthwise central portion 65c in the range of 0.4 mm to 3 mm. When the diameter D3 is less than 0.4 mm, the effect of preventing wrinkles and curling and the effect of suppressing the fluctuation of the birefringence are weakened. On the other hand, when the diameter D3 exceeds 3 mm, the effect of preventing wrinkles and curling and the effect of suppressing the fluctuation of the birefringence increase, but the slanted wrinkle on the wet film 38 is generated and the conveyance becomes unstable. turn into. Furthermore, it is preferable that the width W3 of the central portion 65c in the width direction is shorter than the width W of the wet film 38 in a range of 20 mm to 100 mm. Note that the concave roller 60 and the stepped roller 65 may be arranged alternately with the flat roller, or may be arranged continuously.

  It is not restricted to the said embodiment, You may arrange | position the free rollers 39x-39z in zigzag between drive rollers 39a and 39b. The upstream side conveyance roller 39s shown in FIG. 6 supports the first support 71 on the air surface 38a of the wet film 38, and the downstream side conveyance roller 39t is disposed on the downstream side of the upstream side conveyance roller 39s and is wet. The second support portion 72 on the support surface 38b of the film 38 is supported. Here, the support surface 38b refers to the surface of the surface of the wet film 38 that has been in contact with the drum peripheral surface 13a of the casting drum 13, and the air surface 38a refers to the surface of the wet film 38 that is supported. The surface opposite to the surface 38b is indicated. At this time, the distance LA between the downstream end portion 71a of the first support portion 71 and the upstream end portion 72a of the second support portion 72 is 10% or more of the width W of the wet film 38 and 500% or less of the width W. It is preferable that

  The transport rollers 39s and 39t arranged in a staggered pattern supported the support surface 38b and the air surface 38a of the wet film 38, respectively. However, the present invention is not limited to this, and the support surface 38b and the air surface are supported. Only one of the surfaces with 38a may be supported. Further, a pair of nip rollers that respectively support the support surface 38b of the wet film 38 and the air surface 38a may be used as the transport roller.

  In the above embodiment, the free rollers 39x to 39z are provided between the drive rollers 39a and 39b. However, the present invention is not limited thereto, and an endless band that is wound around a pair of drive rollers and travels endlessly, The wet film 38 may be supported and conveyed between the drive rollers 39a and 39b.

  In the above embodiment, the free rollers 39x to 39z are provided between the pair of drive rollers 39a and 39b, but the present invention is not limited to this, and (1) between the casting drum 13 and the crossover portion 17, (2) The conveying rollers may be arranged closely between the transfer unit 17 and the tenter device 18 and (3) between the casting drum 13 and the tenter device 18. In the form (1), the casting drum 13 and the peeling roller 29 are a pair of drive rollers, the peeling roller 29 and the upstream drive roller 39a are a pair of drive rollers, The extending drum 13 and the upstream drive roller 39a may be a pair of drive rollers. On the other hand, in the form (2), the downstream drive roller 39b and the pulley 18c provided in the tenter carrying start portion 18a may be a pair of drive rollers. In the form (3), the casting drum 13 and the pulley 18c may be a pair of drive rollers.

  When the circumferential speed Vf of the casting drum 13 is set, the circumferential speed of the peeling roller 29 from the casting drum 13 is preferably 101% or more of Vf and 110% or less of Vf. The stretch ratio of the wet film 38 between the casting drum 13 and the peeling roller 29 is preferably 1.0 or more and 1.5 or less. The draw ratio is obtained by dividing the length in the direction MD of the wet film 38 after peeling by the length in the direction MD of the cast film before peeling.

(Dope raw material)
Hereinafter, the raw material used when preparing dope 12 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. Furthermore, 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, 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.

  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.

  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. 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.

  In the said embodiment, although demonstrated using a cellulose acylate and TAC as a polymer, it is not restricted to these.

  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.

  The present invention can also be applied to a solution casting method using a casting band that moves over a rotating roller instead of the casting drum 32. Also, from the structure of casting die, decompression chamber, support, etc., co-casting, peeling method, stretching, drying conditions of each step, handling method, curling, winding method after flatness correction, solvent recovery method, film The recovery method is described in detail in paragraphs [0617] to [0889] of JP-A-2005-104148, and these descriptions can also be applied to the present invention.

  Examples 1 to 3 and Comparative Examples 1 and 2 performed for the present invention are shown below to specifically describe the present invention. However, the present invention is not limited to Examples 1 to 3 and Comparative Examples 1 and 2.

  The dope 12 used for film production was prepared by dissolving a solute composed of cellulose acylate and a small amount of plasticizer in a solvent composed of a mixed solution of methylene claloid, methanol, and butanol. The solute ratio in the dope 12 was adjusted to 20 to 25 wt%. The composition of the solvent (methylene claroid: methanol: butanol) was adjusted to 80 to 95 Wt%: 7 to 20 Wt%: 0 to 3 Wt%.

  Subsequently, the film 15 was manufactured using the dope manufacturing equipment 10 shown in FIG. An appropriate amount of the dope 12 is sent from the dope production facility 11 to the casting die 25 and discharged from the discharge port of the casting die 25 onto the rotating drum 13 that rotates as the casting bead, and onto the drum peripheral surface 13a. A cast film 14 was formed. The discharge amount of the dope 12 was adjusted so that the film thickness of the film 15 after drying was 80 μm. The decompression chamber 33 decompressed the back side of the casting bead at −100 Pa.

  After the casting film 14 became self-supporting, it was peeled off from the casting drum 13 by the peeling roller 29 to form a wet film 38, and the wet film 38 was conveyed toward the crossing part 17. The film conveyance speed after the peeling point P was set to 1.10 to 1.20 times the traveling speed of the casting drum 13. The distance LZ from the peeling point P to the carrying start portion 18a of the tenter device 18 was 2.5 m.

  The wet film 38 peeled off from the casting drum 13 was conveyed to the transfer section 17. The crossing portion 17 is provided with a pair of drive rollers 39a and 39b, and 16 free rollers 39z are provided therebetween. As each of the rollers 39a to 39z, a flat roller having a diameter D1 of 10 cm was used. The rollers 39a to 39z are arranged so that the distance LA between the drive rollers 39a and 39b is 2 m and the distance LF between the rollers 39a to 39z is 2.67 cm. The surface temperature of each of the rollers 39a to 39z was kept at 20 ° C. or lower.

  The drive control unit 56 adjusted the peripheral speed ratio VR of the drive rollers 39a and 39b to be in a desired range. In the transfer part 17, the wet film 38 was conveyed by the rollers 39 a to 39 z while applying dry air to the wet film 38 by the blower 40.

  The wet film 38 that passed through the crossing part 17 was sent to the carrying start part 18 a of the tenter device 18. The wet film 38 was dried by the tenter device 18, and the film 15 obtained by this drying was cut by the ear cutting device 41. Next, the film 15 is dried in the drying chamber 21, cooled to approximately room temperature in the cooling chamber 22, and further subjected to static elimination processing and knurling imparting processing by the forced static elimination device 47 and the knurling imparting roller 48, and then in the winding chamber 23. The take-up roller 50 was wound up.

  A film was produced in the same manner as in Example 1 except that the number of free rollers 39z was 12 and the interval LF was 7.27 cm.

  A film was produced in the same manner as in Example 1 except that the number of free rollers 39z was set to 8 and the interval LF was set to 17.1 cm.

(Comparative Example 1)
A film was produced in the same manner as in Example 1 except that the number of free rollers 39z was set to 5 and the interval LF was set to 37.5 cm.

(Comparative Example 2)
A film was produced in the same manner as in Example 1 except that the number of free rollers 39z was 19 and the interval LF was 0.56 cm.

[Evaluation of film]
The films obtained in the above Examples and Comparative Examples were measured for sound speed and evaluated based on the measurement results. Table 1 shows the diameter D1 of each of the rollers 39a to 39z, the distance LF between the rollers 39a to 39z, the number n of the rollers 39a to 39z installed in the transition portion 17, and the distance between the rollers 39a to 39b. LA, the circumferential speed ratio VR of the drive rollers 39a and 39b, the direction TD, the sound speeds Vtd and Vmd in the direction MD, and the evaluation results are collectively shown. The numbers of the evaluation results in Table 1 correspond to the numbers given to the following evaluation items.

(Measurement and evaluation of sound velocity ratio)
The sound speeds Vtd and Vmd in the direction TD and direction MD in the films obtained in the above examples and comparative examples were measured using an SST-2500 type manufactured by Nomura Corporation. And the value of Vmd / Vtd was evaluated according to the following criteria.
A: Vmd / Vtd is 1.0 or more and 1.2 or less.
X: Vmd / Vtd is larger than 1.2.

  In Examples 1 to 3, films having excellent optical isotropy could be obtained. In Comparative Example 2, although a film excellent in optical isotropy could be obtained, it was difficult to clean each of the transport rollers 39a to 39z. There was a roller contamination failure that adhered to the surface. In Comparative Example 1, no roller smear failure occurred, but the optical isotropy of the obtained film was low.

It is the schematic of a film manufacturing equipment. It is the schematic of a transition part. It is an enlarged view about a pair of conveyance roller which is supported and conveyed with a wet film. It is a front view which shows the outline | summary of a concave roller. It is a front view which shows the outline | summary of a stepped roller. It is explanatory drawing which shows the outline | summary of the conveyance roller arrange | positioned in zigzag form.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Film manufacturing equipment 12 Dope 13 Casting drum 14 Casting film 15 Film 16 Casting device 17 Transition part 25 Casting die 29 Peeling roller 39 Conveying roller group 39a, 39b Drive roller 39x-39z Free roller 55a, 55b Drive part 56 Drive controller

Claims (8)

The dope containing a polymer and a solvent flows out to a support that runs, forms a cast film on the support, and uses the peeling roller to form the cast film that has self-supporting property. The wet film is peeled off from the support, and transported to the drying device while supporting the wet film using a plurality of transport rollers. The solvent remaining in the wet film is removed by the drying device, and the film is removed. In the solution casting method to be manufactured,
The path length of the wet film from the peeling roller to the drying device is 0.5 m to 3.0 m, and the plurality of transport rollers are arranged at a pitch of 30 cm or less in the transport direction of the wet film,
Using a flat roller as the transport roller,
A solution casting method, wherein at least one of the plurality of transport rollers is rotationally driven.   The solution casting method according to claim 1, wherein a gap between the peripheral surfaces of each of the conveying rollers is 1 cm or more.   The convex roller which has a diameter which becomes large as it goes to a both-sides edge part from the width direction center part in the said some conveyance roller, and conveys it while supporting the said wet film is included. Solution casting method.   4. The solution casting method according to claim 1, wherein a residual solvent amount of the wet film conveyed by the plurality of conveying rollers is 100 wt% or more and 250 wt% or less. 5. . The dope containing a polymer and a solvent flows out to a support that runs, forms a cast film on the support, and uses the peeling roller to form the cast film that has self-supporting property. The wet film is peeled off from the support, and transported to the drying device while supporting the wet film using a plurality of transport rollers. The solvent remaining in the wet film is removed by the drying device, and the film is removed. In the solution casting equipment to be manufactured,
A path length of the wet film from the peeling roller to the drying device is 0.5 m or more and 3.0 m or less,
The transport roller is a flat roller disposed at a pitch of 30 cm or less in the transport direction of the wet film;
A solution casting apparatus, wherein at least one of the plurality of transport rollers is a drive roller.   6. The solution casting apparatus according to claim 5, wherein a gap between the peripheral surfaces of each of the conveying rollers is 1 cm or more.   7. The concave roller having a diameter that increases from the central portion in the width direction toward both side end portions and conveying the wet film while supporting the wet film. Solution casting equipment.   The solution casting apparatus according to any one of claims 5 to 7, wherein the support is a casting drum that cools the casting film and exhibits self-supporting property by gelation. .

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