JP5235792B2 - Method for stretching polymer film and method for producing optical film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stretch a polymer film while suppressing breaking of the film. <P>SOLUTION: An off-line stretching apparatus includes a housing chamber and a tenter. The housing chamber houses a preceding film roll and a succeeding film roll. The tenter holds a preceding film sent out of the preceding film roll and widens the preceding film. After all preceding films are sent out, a succeeding film is sent out of the succeeding film roll to the tenter. At a joint provided before the tenter, a rear end 3ax of the preceding film 3a and a top end 3bx of the succeeding film 3b are superposed to provide an overlapping 60. The overlapping 60 is held by a horn 66 vibrating in a C direction and a receiving surface 55 and welding processing is performed. The tenter widens the film which is subjected to the welding processing. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a method for stretching a polymer film and a method for producing an optical film.

  Polymer films (hereinafter referred to as “films”) are widely used as optical films because of their features such as excellent light transmission, flexibility, and reduction in weight. Among them, a TAC film formed from cellulose acylate, particularly cellulose triacetate (hereinafter referred to as TAC) having an average degree of acetylation of 57.5% to 62.5% is a protective film for a polarizing plate of a liquid crystal display device, It is used as an optical film such as an optical compensation film (for example, a viewing angle widening film).

  A solution casting method is known as a main method for producing a film. The solution casting method is a method in which a polymer solution containing a polymer and a solvent (hereinafter referred to as a dope) is cast on a traveling support (hereinafter referred to as a casting step) and has a self-supporting property. The cast film thus formed is peeled off from the support to form a film (hereinafter referred to as a peeling step), and the film is dried (hereinafter referred to as a drying step). And when removing wrinkles, tarmi, etc. generated in the film, or when giving desired optical properties to the film, the film is transported at a predetermined transport speed using a stretching device such as a clip tenter. A process of stretching in the width direction (hereinafter referred to as a stretching process) is performed in a drying process. Finally, using a winder or the like, the film is wound around a winding core to form a film roll. And a film can be manufactured continuously and efficiently by performing a casting process, a peeling process, and a drying process continuously.

  In recent years, the demand for optical films has increased due to the rapid development and spread of liquid crystal display devices and the like. With this increase in demand, it is desired to improve the productivity of optical films. From such a background, a cooling gelling solution film forming method that can develop self-supporting property in a cast film by cooling in a short time while improving the running speed of the support is adopted as a method for manufacturing an optical film. There are many cases.

  However, the optimum speed is different between the traveling speed of the support and the transport speed of the film in the stretching apparatus. In particular, when the cooling gelation method is adopted, the film forming speed of the solution film forming method is determined by the conveying speed by the stretching apparatus, and the substantial production efficiency cannot be improved. Therefore, a solution film-forming facility for producing a film without performing a stretching treatment and a separate stretching facility for performing a stretching treatment on the produced film (hereinafter referred to as off-line stretching facility) are separately provided, and these facilities are used in combination. A method has been proposed (see, for example, Patent Document 1).

  Moreover, as described in Patent Document 1, in an off-line stretching facility, it is preferable to perform a stretching process continuously on the film fed from the winding core. Therefore, when the film roll is switched, the rear end portion and the front end portion are welded at the overlapping portion where the rear end portion of the film fed from the core and the front end portion of the new film overlap (hereinafter referred to as a welding process). Is performed uniformly. By performing such a welding process in an off-line stretching facility, it is possible to continuously perform a film stretching process while switching the film roll.

JP 2008-238682 A

  As a welding apparatus used for this welding process, an ultrasonic welding apparatus as described in Patent Document 1 can be cited. The ultrasonic welding apparatus has a vibrating horn and a pedestal. When performing the welding process, the vibrating horn is traversed in the width direction of the film using the vibrating horn and the pedestal while sandwiching the overlapping portion. By the ultrasonic welding apparatus, a welding line is formed in the overlapping portion so as to extend in the width direction of the film.

  When the horn in a vibrating state is traversed in the width direction, the occurrence of misalignment and wrinkles at the front end and the rear end forming an overlapping portion becomes a problem. In order to suppress the occurrence of such shifts and wrinkles, a columnar horn whose peripheral surface is in contact with the film is rolled in the width direction of the film while being vibrated in the cutting direction of the film surface, thereby performing a welding process.

  However, when the film that has undergone the above-described welding process is subjected to a stretching process, many failures occur in which the film breaks at the overlapping portion. As a result of the inventor's earnest study, it was found that the breakage of the film is caused by a decrease in the thickness of the front end and rear end in the welding process.

  This invention solves the said subject, and it aims at providing the extending | stretching method of a polymer film and the manufacturing method of an optical film which can perform an extending | stretching process efficiently, preventing the fracture | rupture of a film.

In the method for stretching a polymer film of the present invention, the rear end of the polymer film transported in advance and the front end of the subsequent polymer film overlap with the overlapping portion , and the shape of the tip is an arc shape in a cross section perpendicular to the transport direction of the polymer film. In a state where the welding head that vibrates in the thickness direction of the polymer film is in contact, the welding head is moved in the width direction of the polymer film, so that the overlapping portion is welded, and a series of bonding films are formed, characterized by chromatic and stretching step of stretching the junction film in the width direction.

Upon contacting the dissolved adhesion head onto an overlapping portion in soluble Chakukotei, it is preferable to urge pressing the soluble adhesive head relative weight becomes part is less than 20 N / mm. Further, it is preferable that the thickness of the port Rimmer film before the solvent Chakukotei is 40μm or more 150μm or less. Further, it is preferable that the arc radius of curvature of the circular arc shape is 1mm or 10mm or less. Moreover, positive Rimmer film preferably comprises a cellulose acylate. Further, when the width of the bonding film before the stretching step is W1 and the width of the bonding film after the stretching step is W2, the temperature of the bonding film in the stretching step is 100 ° C. or more and 250 ° C. or less, and W2 / W1. Is preferably 1.1 or more and 1.7 or less.

  Moreover, the method for producing an optical film of the present invention is characterized by using the above-described method for stretching a polymer film.

According to the present invention, in the welding process, the tip shape is an arc shape in a cross section orthogonal to the transport direction of the polymer film, and the overlapping portion is sandwiched by using the welding head and the base that vibrate in the thickness direction of the polymer film. Therefore, the pressing force required for welding is reduced, and as a result, a reduction in film thickness after the welding process can be prevented. Therefore, according to this invention, since it becomes possible to perform an extending | stretching process efficiently in an off-line extending | stretching installation, a polymer film can be manufactured efficiently.

It is a side view which shows the outline | summary of an offline extending | stretching installation. It is a top view which shows the outline | summary of a tenter part. It is sectional drawing of a tenter part when a flapper exists in a grip open position. It is sectional drawing of a tenter part when a flapper exists in a holding position. It is a perspective view which shows the outline | summary of a junction part. It is the elements on larger scale of the receiving surface of a base. It is sectional drawing which shows the outline | summary of the front-end | tip of a welding head. It is a perspective view which shows the outline | summary of a welding process. It is explanatory drawing which shows the outline | summary of solution casting apparatus. It is explanatory drawing which shows the outline | summary of a fusion | melting film forming facility. It is a perspective view which shows the arrangement | positioning state of the some roll in a heat processing zone. It is explanatory drawing which shows the roll wrap length (D) of a some roll in a heat processing zone, and the length (G) between rolls.

  As shown in FIG. 1, the off-line stretching equipment 2 includes a film storage chamber 4 that stores a belt-shaped film 3, a reservoir 5, a tenter unit 6, a thermal relaxation chamber 7, a cooling chamber 8, and a film winding chamber. 9 in order.

  The film storage chamber 4 includes a turret type film delivery section 10 and a joining section 11. The film delivery unit 10 has a turret arm 13. A pair of mounting shafts 12 a are provided at both ends of the turret arm 13. The turret arm 13 rotates intermittently by 180 degrees, thereby setting one attachment shaft 12 a at the film delivery position 16 and setting the other attachment shaft 12 a at the core replacement position 17. The film roll 14 is attached to the attachment shaft 12 a at the winding core replacement position 17, and the film roll 14 attached to the attachment shaft 12 a is set to the film delivery position 16 by the rotation of the turret arm 13. An empty core is taken out from the mounting shaft 12a at the core replacement position 17, and a new film roll 15 is set.

  The film sending unit 10 sends a film (hereinafter referred to as a preceding film) from the film roll 14 at the film sending position 16 to the joining unit 11. When the film delivery unit 10 detects that the film roll 14 set at the film delivery position 16 has run out, the turret arm 13 is rotated 180 degrees to deliver a new film roll 15 at the core replacement position 17 to the film delivery. Set to position 16. Then, a film (hereinafter referred to as a subsequent film) is sent out from the new film roll 15 to the joint portion 11.

  In the joining part 11, the rear end part of the preceding film and the front end part of the subsequent film are joined by a welding process, and a welding process is performed to form a series of films 3. The details of the joint 11 and the welding process will be described later.

  The film 3 sent out from the joint portion 11 is sent out to the reservoir 5. In the reservoir 5, a part of the preceding film is retained. The length of the preceding film retained in the reservoir 5 is set to be equal to or more than the product of the time required for the welding process and the transport speed of the preceding film in the tenter unit 6.

  The film 3 having passed through the reservoir 5 is sent to the tenter unit 6 where the stretching process is performed. The tenter unit 6 grips both side edges of the film 3, stretches the film 3 in the width direction, and then sends the film 3 to the edge-cutting device 21. The edge-cutting device 21 cuts off both side edges of the film 3. The film 3 from which both side edges are cut off by the edge-cutting device 21 is sent to the thermal relaxation chamber 7. On the other hand, both side edges separated from the film 3 are sent to the cut blower 22 and finely cut into small pieces. The cut ear dust pieces are sent to the crusher 23 by an air feeding device (not shown), and crushed into chips. This chip is reused for dope preparation.

  The heat relaxation chamber 7 is provided with a large number of rollers 25 and a drying duct (not shown). The film 3 is conveyed through the heat relaxation chamber 7 by the rollers 25 and is heat relaxed by heating, and then is transferred to the cooling chamber 8. Sent. In addition, it is preferable that the temperature of the wind from a dry wind duct is 20 degreeC or more and 250 degrees C or less.

  The film 3 after heat relaxation is cooled to 30 ° C. or less in the cooling chamber 8 and then sent to the film winding chamber 9. In the film winding chamber 9, a winder 28 having a press roller 26 and a winding core 27 is provided. The winder 28 winds the film 3 around the winding core 27 while pressing using the press roller 26.

(Tenter part)
As shown in FIG. 2, the tenter unit 6 applies a tension in the width direction (hereinafter referred to as direction B) to the film 3 while transporting the film 3 in the longitudinal direction, so that the width 3 of the film 3 changes from W1 to W2. It is something to expand. The tenter unit 6 is provided with a preheating area 6a, a stretching area 6b, and a relaxation area 6c in order from the upstream side in the transport direction of the film 3 (hereinafter referred to as direction A). A duct (not shown) is provided in each of the areas 6a to 6c. Each duct sends a predetermined drying air to the film 3 in each area 6a-6c. Thereby, it adjusts so that the temperature of the film 3 in each area 6a-6c may become the optimal range.

  The tenter unit 6 includes a clip 31, rails 32 and 33, and chains 34 and 35. The rails 32 and 33 are installed on both sides of the conveyance path of the film 3, and the rails 32 and 33 are arranged so as to be separated at a predetermined rail interval. This rail interval is constant in the preheating area 6a, gradually increases in the extending area 6b in the direction A, and is constant in the relaxation area 6c. A driving sprocket 38 is provided in the vicinity of the downstream ends of the rails 32 and 33 in the direction A, and a driven sprocket 39 is provided in the vicinity of the upstream ends of the rails 32 and 33 in the direction A.

  As shown in FIG. 2, the chains 34 and 35 are spanned between the driving sprocket 38 and the driven sprocket 39 and are movably attached along the rails 32 and 33. A plurality of clips 31 are attached to the chains 34 and 35 at a predetermined interval. In order to avoid complication of the figure, only a part of the clip 31 is shown in FIG.

  As shown in FIGS. 3 and 4, the clip 31 includes a clip body 40 and a rail attachment portion 41. The clip main body 40 includes a substantially U-shaped frame 42 and a flapper 43 rotatably attached to the frame 42 by an attachment shaft 42a. The flapper 43 is provided so as to be freely displaceable between a grip open position (see FIG. 3) that stands obliquely (see FIG. 3) and a grip position (see FIG. 4) that stands up substantially vertically, and is not self-weighted or illustrated. The spring is biased to the gripping position.

  The rail attachment portion 41 includes an attachment frame 44 and a guide roller 45. The chain 34 or the chain 35 is attached to the attachment frame 44. The guide roller 45 rotates while contacting each support surface of each sprocket 38 to 39 (see FIG. 2) or the support surface of the rail 32 or the rail 33. Thus, the clip body 40 is guided along the rails 32 and 33 without dropping from the sprockets 38 to 39 and the rails 32 and 33.

  As shown in FIGS. 2 to 4, a grip start position Pi is provided in the vicinity of the upstream end in the direction A of the rails 32 and 33. Further, a grip release position Po is provided in the vicinity of the downstream end in the direction A of the rails 32 and 33. An opening member 48 of the clip 31 is provided on the upstream side in the direction A of the grip start position Pi, and an opening member 49 of the clip 31 is provided on the downstream side in the direction A of the grip release position Po. The release members 48 and 49 are in contact with the engaging head 43a of the flapper 43 of the clip 31 passing through the vicinity of the upstream side in the direction A of the grip start position Pi and the vicinity of the downstream side of the direction A of the grip release position Po. Arranged.

  When the engagement head 43a comes into contact with the release member 48 by the travel of the clip 31 along the rails 32 and 33, the flapper 43 is displaced to the grip release position (see FIG. 3). Thereby, the clip 31 is in a state in which the side edge portion of the film 3 can be received. Subsequently, when the traveling clip 31 passes the grip start position Pi, the contact between the release member 48 and the engagement head 43a is released, and the flapper 43 is displaced to the grip position (see FIG. 4). Thus, at the grip start position Pi, the clip 31 grips both side edges (hereinafter referred to as gripping area) 3w of the film 3 by the film gripping surface 42b and the flapper lower surface 43b. Thereafter, the film 3 is sequentially conveyed to each of the areas 6a to 6c in a state where the grip area 3w is gripped by the clip 31. In the stretching area 6b, a stretching process is performed in which the film 3 is stretched in the direction B and the width of the film 3 is expanded from W1 to W2. The stretching ratio ER (= W2 / W1) is preferably 1.1 or more and 1.7 or less. Moreover, it is preferable that the temperature of the film 3 in the extending | stretching area 6b is 100 degreeC or more and 250 degrees C or less. Thereafter, when the clip 31 passes the grip release position Po, the engaging head 43 a comes into contact with the release member 49. The flapper 43 is displaced to the grip opening position by the contact between the opening member 49 and the engaging head 43a. Thereby, the clip 31 releases the grip of the grip area 3w.

(Joint part)
As shown in FIG. 1, a nip roller 51 and a nip roller 52 are disposed in the joining portion 11 from the upstream side in the direction A, and an ultrasonic joining device 53 and a base 54 are disposed between the nip roller 51 and the nip roller 52. The

(pedestal)
As shown in FIG. 5, the pedestal 54 has a receiving surface 55. As shown in FIG. 6, the receiving surface 55 is subjected to knurling, and numerous projections 56 are formed. The protrusion 56 is formed in a truncated pyramid shape. The shape of the protrusion 56 is not limited to a truncated pyramid, and may be a truncated cone, a cone, a pyramid, a cone, or other shapes. The pedestal 54 is provided so as to be movable in the direction C under the control of a control unit (not shown).

  The flatness of the receiving surface 55 is preferably 0.1 mm or less. Moreover, it is preferable that the thickness of the base 54 is 20 mm or more. Furthermore, a jack bolt may be provided on the base 54, and the height of the receiving surface 55 may be adjusted by rotating the jack bolt. The flatness of the receiving surface 55 represents the flatness of the surface including the top of the protrusion 56.

(Nip roller)
Returning to FIG. 1 and FIG. 5, the nip rollers 51 and 52 perform superposition processing under the control of a control unit (not shown). In the superimposing process, the nip rollers 51 and 52 sandwich the preceding film 3a and the succeeding film 3b, feed the films 3a and 3b in the direction A or the direction opposite to the direction A, and the position of the rear end 3ax of the preceding film 3a. And the position of the front-end | tip part 3bx of the subsequent film 3b is adjusted so that it may become on the receiving surface 55. FIG. Thus, an overlapping portion 60 where the rear end portion 3ax of the preceding film 3a and the front end portion 3bx of the subsequent film 3b overlap is formed on the receiving surface 55.

(Ultrasonic bonding equipment)
As shown in FIG. 5, the ultrasonic bonding apparatus 53 includes a welding head 61, a slide mechanism 62, and a bellowram cylinder 63 that attaches the welding head 61 to the slide mechanism 62.

(Ultrasonic bonding body)
The welding head 61 welds the target using frictional heat caused by mechanical vibration, and includes a vibrator 65, a horn 66, and an oscillator (not shown). Under the control of a control unit (not shown), the oscillator mechanically vibrates the vibrator 65 at a predetermined frequency (10 kHz to 50 kHz). The horn 66 vibrates in the thickness direction of the film 3 (hereinafter referred to as direction C) as a result of resonating with the vibration of the vibrator 65.

  As shown in FIG. 7, the tip 66a of the horn 66 in contact with the target is formed in an arc shape in a cross section orthogonal to the direction A. The radius R of the cross section is preferably 1 mm or more and 10 mm or less. Thereby, the pressing force P required for the welding process can be reduced as compared with the conventional case. The tip 66a may be a spherical surface.

(Slide mechanism)
The slide mechanism 62 makes the welding head 61 movable in at least one of the directions A, B, and C. The first slide mechanism 62a, the second slide mechanism 62b, and the third slide mechanism 62c. Consists of. The third slide mechanism 62 c has an attachment member 70 that holds the bellofram cylinder 63. The attachment member 70 is provided so as to be movable in the direction C. The third slide mechanism 62c is attached to the first slide mechanism 62a so as to be movable in the direction A. The first slide mechanism 62a is attached to the second slide mechanism 62b so as to be movable in the direction B.

  The second slide mechanism 62b includes a pair of pulleys 76 that are rotatably provided, a belt 77 that is stretched over the pair of pulleys 76, an LM guide 78 that is attached to the belt 77, and the pulley 76. And a control unit (not shown) that rotates by a predetermined amount in the direction. A first slide mechanism 62 a is attached to the LM guide 78. Since the belt 77 travels in the B direction by the rotation of the pulley 76, the first slide mechanism 62a attached to the LM guide 78 is movable in the B direction.

  Under the control of the control unit, the welding head 61 and the pedestal 54 are movable between a sandwiching position for sandwiching the overlapping portion 60 and a retracting position for retracting from the sandwiching position. When the joining process is not performed, the welding head 61 and the pedestal 54 are in the retracted position, and move to the clamping position only when the joining process is performed.

  Next, the welding process performed in the junction part 11 is demonstrated. As shown in FIGS. 1 and 5, the film delivery unit 10 sends the preceding film 3 a from the film roll 14 to the joining unit 11, and the nip rollers 51 and 52 send the preceding film 3 a to the reservoir 5. Thereafter, when the control unit detects that the film roll set at the film delivery position 16 has run out, the film delivery unit 10 rotates the turret arm 13 by 180 degrees to create a new film at the core replacement position 17. The roll 15 is set at the film delivery position 16. Then, the subsequent film 3b is sent out from the new film roll 15.

  The nip rollers 51 and 52 align the rear end portion 3ax and the front end portion 3bx by conveying the preceding film 3a and the subsequent film 3b. Thus, an overlapping portion 60 where the rear end 3ax of the preceding film 3a and the front end 3bx of the subsequent film 3b overlap is formed on the receiving surface 55.

  The welding head 61 and the base 54 are set in the retracted position in advance. The first slide mechanism 62 a and the second slide mechanism 62 b set the welding head 61 at a predetermined position on the receiving surface 55 based on a welding area set in advance in the overlapping portion 60.

  As shown in FIG. 8, since the welding head 61 is attached to the bellowram cylinder 63, when the welding head 61 and the base 54 in the retracted position are positioned in the clamping position, the horn 66 and the receiving surface 55 are overlapped with each other. Can be held with a predetermined pressing force. By sandwiching the vibrating horn 66 and the receiving surface 55, frictional heat is generated between the rear end 3ax of the preceding film 3a and the leading end 3bx of the subsequent film 3b. The portion and the rear end portion 3ax and the front end portion 3bx in the vicinity thereof are welded. Further, as a result of the slidable movement of the horn 66 in contact with the overlapping portion 60 in the B direction by the second slide mechanism 62b, a welding line 80 extending in the B direction is formed in the overlapping portion 60.

  In the present invention, since the vibration direction of the horn 66 is set to the thickness direction of the film in the welding process of sandwiching the overlapping portion 60 serving as a welding target using the pedestal 54 and the vibrating horn 66, the pressing force required for welding is reduced. As a result of being reduced, it is possible to prevent a decrease in the thickness of the front end and the rear end while welding the front end and the rear end. Therefore, according to the present invention, the stretching process can be efficiently performed while preventing the film from being broken.

In the welding process, the bonding work W _TH per unit thickness is preferably 0.4 W / μm or more and 1.1 W / μm or less, and more preferably 0.6 W / μm or more and 0.9 W / μm or less. When the joining work W _TH is less than 0.4 W / μm, vibrations sufficient for welding are not transmitted to the overlapping portion 60, so that the rear end portion 3ax and the front end portion 3bx cannot be welded. If the joining work W _TH is larger than 1.1 W / μm, the vibration of the overlapping portion 60 becomes excessively large and is therefore not preferable. The joining work W _TH per unit thickness is obtained by dividing the work amount W given to the overlapping portion 60 by the horn 66 by the thickness of one film 3.

  In the welding process, it is preferable that the pressing force P of the overlapping portion 60 by holding the pedestal 54 and the vibrating horn 66 is 20 N / mm or less. The pressing force P can be measured using a push-pull gauge. As a method for measuring the pressing force P, first, a push-pull gauge is provided instead of the base 54. Next, the push-pull gauge and the welding head 61 are moved to the clamping position, and the welding head 61 is brought into contact with the push-pull gauge. Thus, the pressing force P can be measured.

  The amplitude of the tip 66a of the horn 66 is preferably 10 μm or more and 60 μm or less. The lower limit of the traverse speed V of the horn 66 is preferably 40 mm / second or more. The upper limit of the traverse speed V is not particularly limited, but is preferably 200 mm / second or less.

  The width W1 of the preceding film or the succeeding film is preferably 600 mm or more, more preferably 1300 mm or more and 2500 mm or less, and the effect of the present invention is also exhibited when the width is greater than 2500 mm. Further, as shown in FIG. 5, the upper limit of the thickness TH1 of the preceding film or the succeeding film is preferably 80 μm or less, and more preferably 60 μm or less. The lower limit of the thickness TH1 of the preceding film or the subsequent film is preferably 20 μm or less.

(Solution casting method)
The film in the above embodiment can be obtained by a solution casting method. As shown in FIG. 9, the solution casting apparatus 210 that performs the solution casting method includes a stock tank 211, a casting chamber 212, a pin tenter 213, a drying chamber 215, a cooling chamber 216, and a winding chamber 217.

  The stock tank 211 includes a stirring blade 211b and a jacket 211c that are rotated by a motor 211a. The stock tank 211 stores a dope 221 in which a polymer that is a raw material of the film 3 is dissolved in a solvent. The dope 221 in the stock tank 211 is adjusted by the jacket 211c so that the temperature becomes substantially constant. Further, the rotation of the stirring blade 211b keeps the dope 221 in a uniform quality while suppressing agglomeration of a polymer or the like. The pipe 222 connects the stock tank 211 and the casting die 230.

  In the casting chamber 212, a casting die 230, a casting drum 232 as a support, a peeling roller 234, temperature control devices 235 and 236, and a decompression chamber 237 are installed. The casting drum 232 is rotated in the direction Z1 about the shaft 232a by a driving device (not shown). The temperature in the casting chamber 212 and the casting drum 232 are set to temperatures at which the casting film 233 is easily cooled and solidified (gelled) by the temperature control devices 235 and 236.

  The casting die 230 has a slit formed so as to extend in the width direction. The casting die 230 discharges the dope 221 toward the peripheral surface 232b of the casting drum 232 rotating from the slit. Thereafter, a casting film 233 is formed from the dope 221 on the peripheral surface 232 b of the casting drum 232. Then, the casting film 233 is cooled while the casting drum 232 rotates about 3/4, and the gelation of the solution occurs in the casting film 233 by this cooling. By this gelation, self-supporting property is expressed in the casting film 233, and the casting film 233 is peeled off from the casting drum 232 by the peeling roller 234 to become a wet film 238. The residual solvent amount of the cast film 233 at the time of peeling is preferably 150% by weight or more and 320% by weight or less. Here, the residual solvent amount indicates the amount of solvent remaining in the casting film 233 or the like on a dry basis, and the measurement method is to take a sample from the target film or the like and calculate the weight of the sample. x, where y is the weight after drying the sample, it is calculated as {(xy) / y} × 100.

  The decompression chamber 237 is disposed upstream of the casting die 230 in the direction Z1, and maintains the inside of the decompression chamber 237 at a negative pressure, and the rear surface of the casting bead (later on the peripheral surface 232b of the casting drum 232). The surface to be contacted) is reduced to a desired pressure. By reducing the pressure on the back side of the casting bead, the influence of the accompanying air generated by the rotation of the casting drum 232 is reduced, and a stable casting bead is formed between the casting die 230 and the casting drum 232, and the membrane A cast film 233 with little thickness unevenness can be formed.

  The material of the casting die 230 is formed of a material having a 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 230 with a surface roughness of 1 μm or less and a straightness of 1 μm / m or less in any direction.

  The peripheral surface 232b of the casting drum 232 is subjected to a chrome plating process and has sufficient corrosion resistance and strength. The temperature control device 236 circulates the heat transfer medium through the casting drum 232 in order to keep the temperature of the peripheral surface 232b of the casting drum 232 at a desired temperature. The heat transfer medium is maintained at a desired temperature, and the temperature of the peripheral surface 232b of the casting drum 232 is maintained at a desired temperature by passing through the heat transfer medium flow path in the casting drum 232.

  The width of the casting drum 232 is not particularly limited, but it is preferable to use a casting drum in the range of 1.1 to 2.0 times the casting width of the dope. The material of the casting drum 232 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 232b of the casting drum 232 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.

  The casting chamber 212 includes a condenser (condenser) 239 for condensing the evaporated solvent and a recovery device 240 for recovering the condensed liquid. The solvent condensed and liquefied by the condenser 239 is recovered by the recovery device 240. The solvent is regenerated as a solvent for preparing a dope after being regenerated by a regenerator.

  A crossover 241 and a pin tenter 213 are sequentially installed downstream of the casting chamber 212. In the transfer section 241, the transport roller 242 introduces the wet film 238 into the pin tenter 213. The pin tenter 213 has a large number of pin plates that pass through and hold both side edges of the wet film 238, and the pin plates travel on a track. Dry air is sent to the wet film 238 traveling by the pin plate, and the wet film 238 is dried to be a film 220.

  An ear clip device 243 is provided downstream of the pin tenter 213. The edge-cutting device 243 cuts both side edges of the film 220. The cut side edges are sent to the crusher 244 by air blowing, pulverized, and reused as a raw material such as a dope.

  A large number of rollers 247 are provided in the drying chamber 215, and the film 220 is wound around and conveyed. A cooling chamber 216 is provided on the outlet side of the drying chamber 215, and the film 220 is cooled in this cooling chamber 216 until it reaches room temperature. A forced static elimination device (static elimination bar) 249 is provided downstream of the cooling chamber 216, and the film 220 is neutralized. Further, a knurling application roller 250 is provided on the downstream side of the forced static elimination device 249, and knurling is applied to both side edges of the film 220. In the winding chamber 217, a winding machine 251 having a press roller 252 is installed, and the film 220 is wound around the winding core in a roll shape, and a film roll 255 is obtained by the winding machine 251. The film roll 255 is stored in the film storage chamber 4 (see FIG. 1) of the off-line stretching equipment 2 from the winding chamber 217. The amount of residual solvent in the film 220 delivered from the drying chamber 215 is preferably 5% by weight or less, and more preferably 3% by weight or less.

(polymer)
Hereinafter, the polymer used as the raw material of the film will be described. In the present embodiment, cellulose acylate is used as the polymer, and cellulose triacetate (TAC) is particularly preferable as the cellulose acylate. Among cellulose acylates, those in which the substitution degree of the acyl group to the hydroxyl group of cellulose satisfies all of the following formulas (I) to (III) are more preferable. In the following formulas (I) to (III), A and B represent the substitution degree of the acyl group with respect to the hydrogen atom in the hydroxyl group of cellulose, A 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 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.

(solvent)
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 these, halogenated hydrocarbons having 1 to 7 carbon atoms are preferably used, and dichloromethane is most preferably used. One kind of alcohol having 1 to 5 carbon atoms in addition to dichloromethane from the viewpoint of physical properties such as solubility of TAC, peelability of cast film from the support, mechanical strength of the film, and optical properties of the film It is preferable to mix several kinds. The content of the alcohol is preferably 2% by weight to 25% by weight and more preferably 5% by weight to 20% by weight with respect to the whole solvent. Specific examples of the alcohol include methanol, ethanol, n-propanol, isopropanol, n-butanol and the like, but methanol, ethanol, n-butanol or a mixture thereof is preferably used.

  By the way, recently, for the purpose of minimizing the influence on the environment, studies have been conducted on the solvent composition when dichloromethane is not used. For this purpose, ethers having 4 to 12 carbon atoms, 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 preferably used. These may be used in combination as appropriate. 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 the solvent.

  In the above-described embodiment, it has been described that cellulose acylate is used as a polymer as a raw material of the film. However, the present invention is not limited thereto, and is applicable to cyclic olefins and other cellulose esters such as cellulose acetate propionate. . Moreover, it can also apply to the polymer film manufactured by the melt film-forming method.

(Melting film forming equipment)
Next, a manufacturing facility for manufacturing a polymer film by a melt film forming method (hereinafter referred to as a melt film forming facility) will be described. As shown in FIG. 10, the melt film-forming facility 410 is an apparatus that manufactures a thermoplastic film F that can be used for a liquid crystal display device or the like. A pellet-shaped thermoplastic resin, which is a raw material of the thermoplastic film F, is introduced into a dryer 412 and dried, and then the pellet is extruded by an extruder 414 and supplied to a filter 418 by a gear pump 416. Next, foreign matters are filtered by the filter 418, and molten resin (molten thermoplastic resin) is extruded from the die 420. The molten resin is sandwiched between the first casting roll 428 and the touch roll 424 and press-molded, and then cooled and solidified by the first casting roll 428 to form a film having a predetermined surface roughness. Further, the second casting is performed. The unstretched film Fa is obtained by being conveyed by the roll 426 and the third casting roll 427. This unstretched film Fa may be wound up at this stage, or may be supplied to a lateral stretching section 442 that continuously performs long-span stretching. Further, even if the unstretched film Fa once wound up is supplied again to the transverse stretching section 442, the same effect as that obtained when the unstretched film Fa is supplied to the transverse stretching section 442 that performs continuous long span stretching can be obtained.

  In the laterally stretched portion 442, the unstretched film Fa is stretched in the width direction (hereinafter referred to as the direction Y) orthogonal to the transport direction (hereinafter referred to as the direction X) to obtain a laterally stretched film Fb. The preheating unit 436 may be provided on the upstream side of the lateral stretching unit 442, or the heat fixing unit 444 may be provided on the downstream side of the lateral stretching unit 442. Thereby, the bowing (shift of the optical axis) during stretching can be reduced. The preheating temperature is preferably higher than the transverse stretching temperature, and the heat setting temperature is preferably lower than the transverse stretching temperature. That is, normally, the center part in the width direction becomes concave toward the traveling direction, but bowing can be reduced by setting preheating temperature> lateral stretching temperature and transverse stretching temperature> heat setting temperature. Either pre-heat treatment or heat setting treatment may be performed, or both may be performed.

  After the transverse stretching, post-heat treatment is performed, and then the transversely stretched film Fb is contracted in the direction X in the heat treatment zone 446. In the heat treatment zone 446, as shown in FIG. 11, a plurality of rolls 448a are used so that only the contraction in the direction X occurs without contracting in the direction Y without holding the side end portion of the laterally stretched film Fb with the chuck. The horizontally stretched film Fb is conveyed at ˜448d. At this time, as shown in FIG. 12, the plurality of rolls 448a to 448d are arranged so that the ratio (G / D) of the roll wrap length (D) to the inter-roll length (G) is 0.01 or more and 3 or less. Is done. Thereby, the shrinkage | contraction of the direction Y is suppressed by the friction with the transversely stretched film Fb and each roll 448-448d. The laterally stretched film Fb is conveyed at a ratio (V2 / V1) of the peripheral speed (V1) by the upstream roll 448a and the peripheral speed (V2) by the downstream roll 448d at 0.6 or more and 0.999 or less. While being heat treated. That is, the laterally stretched film Fb shrinks in the direction X in the heat treatment zone.

  The transversely stretched film Fb is heat-treated in the heat treatment zone, whereby the thermoplastic film F, which is the final product with the adjusted orientation angle and retardation, is produced. The film F is taken up by a take-up unit 449.

  Stretching in the direction X may be performed before or after stretching in the direction Y. Stretching in the direction X can be achieved by transporting the film using a plurality of nip roll pairs aligned in the direction X and increasing the peripheral speed of the downstream nip roll pair from the peripheral speed of the upstream nip roll pair. The stretching method differs depending on the distance (L) between the nip rolls in the direction X and the ratio (L / W) of the film width W between the pair of nip rolls on the upstream side. A stretching method in the direction X as described in JP-A-2006-348114 can be employed. This method tends to increase Rth, but can make the apparatus compact. On the other hand, when L / W is large, a stretching method in the direction X as described in JP-A-2005-301225 can be used. Although this method can reduce Rth, the apparatus tends to be long.

  The polymer that can be used in the melt film-forming method is not particularly limited as long as it is a thermoplastic resin, and examples thereof include cellulose acylate, lactone ring-containing polymer, cyclic olefin, and polycarbonate. Of these, cellulose acylate and cyclic olefin are preferred, cellulose acylate containing an acetate group and propionate group, and cyclic olefin obtained by addition polymerization, more preferably cyclic olefin obtained by addition polymerization. It is.

(Cyclic olefin)
The cyclic olefin is preferably polymerized from a norbornene compound. This polymerization can be carried out by either ring-opening polymerization or addition polymerization. Examples of the addition polymerization include those described in Japanese Patent No. 3517471, Japanese Patent No. 3559360, Japanese Patent No. 3867178, Japanese Patent No. 3817721, Japanese Patent No. 3907908, Japanese Patent No. 3945598, Japanese Patent Publication No. 2005-527696, Japanese Patent Laid-Open No. 2006-2006. No. 28993 and International Publication No. 2006/004376 pamphlet. Particularly preferred is the one described in Japanese Patent No. 3517471.

  Examples of the ring-opening polymerization include WO 98/14499 pamphlet, Japanese Patent No. 30605532, Japanese Patent No. 3320478, Japanese Patent No. 3273046, Japanese Patent No. 3404027, Japanese Patent No. 3428176, Japanese Patent No. 3687231, Japanese Patent No. 3873934, Patent No. 3912159 is mentioned. Among them, those described in WO98 / 14499 pamphlet and Japanese Patent No. 30605532 are preferable.

  Of these cyclic olefins, those of addition polymerization are more preferred.

(Lactone ring-containing polymer)
The thing which has the lactone ring structure represented by the following (general formula 1) is pointed out.

In (General Formula 1), R ¹ , R ² , and R ³ each independently represent a hydrogen atom or an organic residue having 1 to 20 carbon atoms. The organic residue may contain an oxygen atom.

  The content ratio of the lactone ring structure of (General Formula 1) is preferably 5 to 90% by weight, more preferably 10 to 70% by weight, and still more preferably 10 to 50% by weight.

  In addition to the lactone ring structure represented by (General Formula 1), at least selected from (meth) acrylic acid esters, hydroxyl group-containing monomers, unsaturated carboxylic acids, and monomers represented by the following (General Formula 2). A polymer structural unit (repeating structural unit) constructed by polymerizing one kind is preferred.

In (General Formula 2), R ⁴ represents a hydrogen atom or a methyl group, X is a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an aryl group, an —OAc group, a —CN group, a —CO—R ⁵ group, or an ^{-C-O-R 6} group, Ac group represents an acetyl group, ^{R 5} and ^{R 6} represents a hydrogen atom or an organic residue having 1 to 20 carbon atoms.

  For example, those described in International Publication No. 2006/025445, JP 2007-70607 A, JP 2007-63541 A, JP 2006-171464 A, and JP 2005-162835 A can be used. .

(Experiments 1-9)
Using the ultrasonic bonding apparatus 53 and the pedestal 54, the overlapping portion 60 was welded. Each condition in the welding process is as shown in Table 1. In Table 1, “vibration direction” is the vibration direction of the horn 66 and indicates either direction B or direction C. “Amplitude” is the amplitude of vibration of the horn 66. “P” is a pressing force when the overlapping portion 60 is clamped by the ultrasonic bonding device 53 and the pedestal 54. “V” is a traverse speed in the direction B of the welding head 61.

  The bonding film that had undergone the above-described welding process was stretched. In the stretching treatment, the bonding film whose temperature was adjusted within the range of 150 ° C. to 230 ° C. was stretched in the direction B. The draw ratio ER (= W2 / W1) was 1.6.

(Evaluation)
The following evaluation was performed about the film which passed through the welding process and the extending | stretching process of Experiment 1-9.

1. Evaluation of Bonding Strength One bonding film subjected to welding treatment was stretched in the width direction, and the tensile stress when the bonded portion was broken was measured using a tensile tester (Tensilon tester). And the measured tensile stress was evaluated based on the following criteria.
(Circle): The measured tensile stress was more than the tensile stress (5N / mm < ² >) of the film provided at the time of conveyance.
X: The measured tensile force was less than the tensile stress (5 N / mm < ² >) of the film provided at the time of conveyance.

2. Evaluation of Breaking Failure Whether or not the film was broken by the stretching process was evaluated based on the following criteria.
○: The bonding film was not broken at the overlapping portion.
X: The bonding film was broken at the overlapping portion.

  Table 1 shows the evaluation results. In addition, the number attached | subjected to the evaluation result of Table 1 represents the number attached | subjected to said evaluation item.

2 offline stretching equipment 3 film 3a preceding film 3b succeeding film 3w gripping area 4 film storage chamber 6 tenter part 11 joining part 53 ultrasonic joining device 54 pedestal 60 overlapping part 66 horn

Claims (7)

With respect to the overlapping portion of the rear end of the polymer film transported in advance and the front end of the succeeding polymer film , the shape of the front end is an arc shape in a cross section perpendicular to the transport direction of the polymer film, and in the thickness direction of the polymer film In a state where the vibrating welding head is in contact, the welding head is moved in the width direction of the polymer film, thereby welding the overlapping portion to form a series of bonding films; and
The method of stretching a polymer film, which comprises organic and stretching step of stretching the bonding film in the width direction. The stretching of the polymer film according to claim 1, wherein when the welding head is brought into contact with the overlapping portion in the welding step, a pressing force for pressing the welding head against the overlapping portion is 20 N / mm or less. Method. The method for stretching a polymer film according to claim 1 or 2, wherein the thickness of the polymer film before the welding step is 40 µm or more and 150 µm or less. Stretching method of a polymer film of any one of claims 1 to 3, wherein the arc of curvature radius of the arc shape is 1mm or 10mm or less. The method for stretching a polymer film according to any one of claims 1 to 4 , wherein the polymer film contains cellulose acylate. When the width of the bonding film before the stretching step is W1, and the width of the bonding film after the stretching step is W2, the temperature of the bonding film in the stretching step is 100 ° C. or more and 250 ° C. or less. The method of stretching a polymer film according to any one of claims 1 to 5 , wherein a value of W2 / W1 is 1.1 or more and 1.7 or less. A method for producing an optical film, wherein the method for stretching a polymer film according to any one of claims 1 to 6 is used.

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