JP5292339B2 - Thermoplastic film stretching method and apparatus, and solution casting method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform a stretching process by suppressing deviation of a delayed phase axis in a carrying direction. <P>SOLUTION: A film travels in the Z1-direction within a clip tenter. A first preheating area 80ax, a second preheating area 80ay, a stretching area 80b and the like are provided from the upstream side in the Z1 direction within the clip tenter. In each area, an air blowing head for blowing temperature control air to the film is provided. A temperature control air controller controls the temperature of the temperature control air within a range determined with respect to each area. By blowing of the temperature control air, a difference &Delta;T (=Tf-Tg) between the film temperature Tf and a glass transition temperature (Tg) becomes within a predetermined range. The temperature control air controller controls the air speed of the temperature control air so that air pressure P in the first preheating area 80ax becomes larger than air pressure P in the second preheating area 80ay. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a thermoplastic film stretching method and apparatus, and a solution casting method.

  BACKGROUND ART A thermoplastic film having light permeability (hereinafter referred to as a film) is lightweight and easy to mold, and thus is widely used as an optical film. Among them, cellulose ester films using cellulose acylate and the like are used for retardation films which are constituent members of liquid crystal display devices whose market is expanding in recent years, including photographic photosensitive films.

  The main production methods of the film include a melt extrusion method and a solution casting method. The melt extrusion method is a method of producing a film by melting a polymer and then extruding it with an extruder, and has features such as high productivity and relatively low equipment cost. On the other hand, in the solution casting method, a polymer solution containing a polymer and a solvent (hereinafter referred to as a dope) is flowed to form a cast film on the support. Next, after the cast film becomes transportable, it is peeled from the support to form a wet film. Then, the solvent is evaporated from the wet film to form a film.

  In order to adjust the optical characteristics of the obtained film, a tenter device for stretching the film in a predetermined direction is known (for example, Patent Document 1). In this tenter apparatus, a stretching process is performed in which both edges in the width direction of the film (hereinafter referred to as ears) are gripped using gripping means such as clips, and the width of the film is expanded.

  In order to prevent film breakage and haze reduction due to the stretching process, the temperature of the film in the stretching process must be equal to or higher than the glass transition temperature of the substance constituting the film. However, due to heat radiation from the clip, the temperature of the ear portion of the film is easily cooled compared to the central portion. Therefore, in the stretching process, hot air is blown over the film in order to maintain the state where the entire temperature of the film is equal to or higher than the glass transition temperature. Furthermore, before the stretching process, a preheating process is performed in which hot air is blown onto the film to preheat the film.

JP 2009-178992 A

  In recent years, the demand for liquid crystal display devices has increased. For this reason, improvement of the production efficiency of a film is desired. Therefore, in order to realize improvement in film production efficiency, it is necessary to improve the film transport speed in the tenter apparatus. However, it is necessary to increase the length of the preheating zone for performing the preheating process in the tenter device as the film conveying speed in the tenter device increases. However, increasing the scale of the tenter device is not preferable in terms of installation space and energy cost.

  Therefore, in order to perform the preheating process on the film transported at a higher speed than before while maintaining the current scale of the tenter device, the temperature of the hot air blown on the film is made higher than before or the amount of this hot air It is conceivable to increase the value as compared with the conventional method. However, the former method is not preferable because the temperature distribution in the width direction becomes large. Therefore, the latter method had to be adopted. However, as in the latter method, a film that has undergone a preheating process in which hot air is applied to the film at a high wind speed has a variation in the slow axis in the longitudinal direction.

  The present invention solves such problems, and provides a method and apparatus for stretching a thermoplastic film and a solution casting method capable of efficiently producing a retardation film having a small variation in slow axis. With the goal.

  The present invention relates to a thermoplastic film stretching method for stretching a strip-shaped thermoplastic film whose temperature is controlled by blowing temperature-controlled air, and a pair of clips holding both edges in the width direction of the thermoplastic film. And a transporting process for transporting the thermoplastic film in the longitudinal direction is performed, and the transporting process widens the gap between the pair of clips in a state where both edges in the width direction are gripped, and the glass transition temperature or higher. A stretching step of stretching the thermoplastic film in the width direction, and a preheating step that is performed before the stretching step and preheats the thermoplastic film, and in the preheating step, the temperature of the thermoplastic film A first preheating step for preheating the thermoplastic film so as to approach the glass transition temperature, and the thermoplastic film so that the temperature of the thermoplastic film exceeds the glass transition temperature. A second preheating step for preheating the rum is sequentially performed, and the wind pressure of the temperature control air in the thermoplastic film is larger in the first preheating step than in the second preheating step and the stretching step. And

  In the transporting step, a cooling step of blowing the temperature adjusting air on the thermoplastic film is performed so that the temperature of the thermoplastic film is lower than a glass transition temperature, and the temperature adjusting air in the thermoplastic film The wind pressure is preferably greater in the cooling step than in the stretching step.

  The solution casting method of the present invention includes a step of forming a belt-like casting film made of a dope containing a polymer and a solvent on a support, and peeling the casting film from the support to form the wet film. And a step of evaporating the solvent from the wet film, and the thermoplastic film obtained by the drying step is subjected to the method for stretching a thermoplastic film according to claim 1 or 2. To do.

  The thermoplastic film stretching apparatus of the present invention is a conveyance path through which a strip-shaped thermoplastic film is conveyed in the longitudinal direction, and a pair of rails provided on both sides of the conveyance path, and is movable along the rails. A gripping means capable of gripping both edges in the width direction of the thermoplastic film, a transport means for transporting the thermoplastic film in a longitudinal direction, and a temperature-controlled wind on the transported thermoplastic film. And a temperature adjusting means for adjusting the temperature of the thermoplastic film, and a first preheating area and a second preheating area in which a distance between the pair of rails is constant in a conveyance path of the thermoplastic film And an extension area in which the distance between the rails of the pair increases from the upstream side in the transport direction toward the downstream side is sequentially provided from the upstream side in the transport direction, and the temperature adjusting means is the thermoplastic film. A temperature adjusting wind for controlling the temperature and wind speed of the blowing, and the adjusting unit is configured so that the temperature of the thermoplastic film in the first preheating area approaches the glass transition temperature and in the second preheating area. The temperature of the temperature adjusting air is adjusted so that the temperature of the thermoplastic film exceeds the glass transition temperature, and the adjusting unit is configured such that the wind pressure of the temperature adjusting air in the first preheating area is the second preheating area and the The air speed of the temperature control air blown to the thermoplastic film is adjusted so as to be larger than the wind pressure of the temperature control air in the stretching area.

  A cooling area in which the distance between the pair of rails is constant is provided in the conveyance direction downstream of the stretching area in the conveyance path of the thermoplastic film, and the adjustment unit is configured to adjust the wind pressure of the temperature adjustment air in the cooling area. It is preferable to adjust the wind speed of the temperature adjusting wind sprayed on the thermoplastic film so that the pressure is higher than the wind pressure of the temperature adjusting wind in the stretching area.

  According to the present invention, the preheating step performed prior to the stretching step includes the first preheating step of preheating the thermoplastic film so that the temperature of the thermoplastic film approaches the glass transition temperature, and the temperature of the thermoplastic film is the glass transition. This is divided into a second preheating step in which the thermoplastic film is preheated so as to exceed the temperature, and the temperature of the temperature-controlled air in the thermoplastic film is higher in the first preheating step than in the second preheating step and the stretching step. Variations in the slow axis due to an increase in the wind pressure of the adjusted wind can be suppressed.

It is explanatory drawing which shows the outline | summary of a 1st solution casting apparatus. It is a top view which shows the outline | summary of a clip tenter. It is a side view which shows the outline | summary of a clip tenter. It is a side view which shows the outline | summary of a 1st preheating area and a 2nd preheating area. It is a perspective view which shows the outline | summary of a ventilation head. It is a graph which shows the outline | summary of transition of the difference (DELTA) T (= Tf-Tg) of the temperature Tf of the wet film in each area of a clip tenter, and the glass transition temperature Tg, and the pressure P of the temperature control wind in a wet film. The vertical axis of (A) is the temperature difference ΔT, and the horizontal axis is the position of the clip tenter in the Z1 direction. The vertical axis | shaft of (B) is the pressure P of the temperature control wind in a wet film, and a horizontal axis is the position of the Z1 direction in a clip tenter. It is explanatory drawing which shows the outline | summary of the 2nd solution casting apparatus. It is sectional drawing which shows the outline | summary of a casting apparatus.

(Solution casting method)
As shown in FIG. 1, the solution casting apparatus 10 includes a casting chamber 12, a pin tenter 13, a clip tenter 14, a drying chamber 15, a cooling chamber 16, and a winding chamber 17. In the casting chamber 12, a casting die 21, a casting drum 22, a decompression chamber 23 and a peeling roller 24 are provided.

  The casting drum 22 is arranged so that the axial direction is horizontal, and is rotatable about the shaft. The casting drum 22 is rotated around a shaft by a driving device (not shown) under the control of the control unit. Due to the rotation of the casting drum 22, the peripheral surface of the casting drum 22 travels in the A direction at a predetermined speed.

  The casting drum 22 is preferably made of stainless steel, and more preferably made of SUS316 so as to have sufficient corrosion resistance and strength. The chrome plating treatment applied to the peripheral surface 30b of the casting drum 22 is preferably so-called hard chrome plating with a Vickers hardness of Hv 700 or more and a film thickness of 2 μm or more.

  A temperature control device 30 is connected to the casting drum 22. The temperature control device 30 includes a temperature adjustment unit that adjusts the temperature of the heat transfer medium. The temperature adjusting device 30 circulates a heat transfer medium adjusted to a desired temperature between the temperature adjusting unit and the flow path provided in the casting drum 22. By circulating the heat transfer medium, the temperature of the peripheral surface of the casting drum 22 can be maintained at a desired temperature.

(Casting die)
The casting die 21 is provided above the casting drum 22. The casting die 21 has a slit through which the dope 35 flows out at the tip. The casting die 21 is arranged so that the slit is close to the casting drum 22. The dope 35 that has flowed out of the casting die 21 flows on the peripheral surface of the moving casting drum 22, and as a result, forms a belt-like casting film 40.

  The stripping roller 24 is disposed downstream of the casting die 21 in the A direction. The stripping roller 24 strips the casting film 40 formed on the peripheral surface and guides it as a wet film 44 to the downstream side of the casting chamber 12.

  The decompression chamber 23 is provided upstream of the casting die 21 in the A direction and downstream of the peeling roller 24 in the A direction. Under the control of a control unit (not shown), the decompression chamber 23 can decompress the upstream side of the casting bead so that the upstream pressure of the casting bead is lower than the downstream side. Moreover, although illustration is abbreviate | omitted, it is gas in the casting chamber 12 by providing the condensing apparatus which condenses the solvent contained in the atmosphere in the casting chamber 12, and the collection | recovery apparatus which collect | recovers the condensed solvent. The temperature at which the solvent liquefies can be maintained within a predetermined range.

  A pin tenter 13, a clip tenter 14, a drying chamber 15, a cooling chamber 16, and a winding chamber 17 are sequentially installed downstream of the casting chamber 12. In the transfer part 45 between the casting chamber 12 and the pin tenter 13, the belt-shaped wet film 44 fed out from the casting chamber 12 is conveyed to the pin tenter 13 using a plurality of rollers 46. The pin tenter 13 has a large number of pin plates that pass through and hold both ends of the wet film 44 in the width direction, and the pin plates travel on a track. Dry air is sent to the wet film 44 that travels by holding the pin plate, and the wet film 44 is dried.

  As shown in FIGS. 1 and 2, the clip tenter 14 has a number of clips that grip both edges (ears) of the wet film 44 in the Z2 direction. This clip is movable along a rail described later. The wet film 44 is transported in the Z1 direction by the movement of the clip that grips the ear portion. Details of the clip tenter 14 will be described later. The film 50 is obtained from the wet film 44 by a predetermined process placed on the clip tenter 14.

  Returning to FIG. 1, ear clip devices 52 a and 52 b are provided downstream of the pin tenter 13 and the clip tenter 14, respectively. The ear clip devices 52a and 52b cut off the ears of the wet film 44 and the film 50. The separated ears are sent to a crusher (not shown) by air blowing, cut into small pieces, and reused as a raw material for dopes and the like.

  A large number of rollers 54 are provided in the drying chamber 15, and the film 50 is wound around and conveyed. The temperature and humidity of the atmosphere in the drying chamber 15 are adjusted by an air conditioner (not shown), and the film 50 is dried by passing through the drying chamber 15. An adsorption recovery device 55 is connected to the drying chamber 15. The adsorption recovery device 55 recovers the solvent evaporated from the film 50 by adsorption.

  In the cooling chamber 16, the film 50 is cooled until the temperature of the film 50 reaches approximately room temperature. In the winding chamber 17, a winding machine 58 having a press roller 56 and a winding core 57 is installed, and the film 50 is wound around the winding core 57 in a roll shape. Further, between the cooling chamber 16 and the winding chamber 17, a static elimination bar 61 that performs static elimination processing on the film 50 from the upstream side toward the downstream side in the Z1 direction, and a knurling for winding around the ear portion of the film 50. And a knurling roller 62 for sequentially providing the above.

(Clip tenter)
As shown in FIG. 2, the clip tenter 14 has a tenter body and a casing 80 in which the tenter body is built. The casing 80 is provided with an inlet 80i and an outlet 80o. In the casing 80, a conveyance path for conveying the wet film 44 in the Z1 direction is formed from the inlet 80i to the outlet 80o. Further, the inside of the casing 80 is partitioned into a preheating area 80a, a stretching area 80b, a relaxation area 80c, and a cooling area 80d in order from the upstream side in the Z1 direction. Furthermore, the preheating area 80a is partitioned into a first preheating area 80ax and a second preheating area 80ay in order from the upstream side in the Z1 direction. The relaxation area 80c and the cooling area 80d may be omitted.

  As shown in FIG. 2, the tenter body includes a clip 82 and a rail 83. The pair of rails 83 are installed on both sides of the transport path of the wet film 44 over the areas 80a to 80d, and the rails 83 are separated by a predetermined rail width.

  An annular chain (not shown) meshes with the sprockets 86 and 87 and is attached so as to be movable along the rail 83. A plurality of clips 82 are attached to the chain at predetermined intervals. In FIG. 2, only a part of the clip 82 is shown in order to avoid complication of the drawing. As the sprockets 86 and 87 rotate, the clip 82 moves along the rail 83. The position Pa on the rail 83 in the first preheating area 80ax is provided with a grip start means (not shown) for starting the gripping of the ear portion of the wet film 44 by the clip 82, and the position Pb on the rail 83 in the cooling area 80d. Is provided with a grip release means (not shown) for releasing the grip of the ear portion of the wet film 44 by the clip 82. When the clip 82 passes the position Pa on the rail 83, the clip 82 starts gripping the ear portion of the wet film 44. The clip 82 moves to the position Pb while holding the ear portion of the wet film 44. When the clip 82 passes the position Pb on the rail 83, the clip 82 releases the grip of the ear portion of the wet film 44.

  The rail width of the rail 83 in the extending area 80b becomes wider from the upstream side toward the downstream side in the Z1 direction. On the other hand, the rail width of the rail 83 in the relaxation area 80c becomes narrower from the upstream side toward the downstream side in the Z1 direction. Further, the rail width of the rail 83 in the preheating area 80a and the cooling area 80d is constant.

  Thus, when the clip 82 moves along the rail 83, the wet film 44 is conveyed in the Z1 direction, sequentially passes through the areas 80a to 80d, and a predetermined process is performed in each of the areas 80a to 80d.

  Furthermore, the tenter body has a blower 90 as shown in FIG. The blower 90 includes a large number of blower heads 92 and a temperature adjusting air controller 93. The blower heads 92 are respectively provided above the conveyance path of the wet film 44, and are arranged in the Z1 direction in each of the areas 80a to 80d. The blower head 92 may be provided below the conveyance path of the wet film 44 or may be provided both above and below the conveyance path of the wet film 44.

  As shown in FIGS. 4 and 5, the air blowing head 92 includes an internal duct 92 a provided inside the air blowing head 92 and a plurality of ejection nozzles 92 b. The ejection nozzles 92b are arranged so as to be arranged at a predetermined pitch in the Z1 direction. At the tip of the ejection nozzle 92b, a slit-shaped ejection port 92c communicating with the head internal duct is provided. The jet outlet 92c is formed to extend in the direction Z2. A feed duct 94 communicating with the head internal duct is provided on the side surface of each blower head 92.

  Each area 80ax, 80ay, 80b-80d is provided with a temperature sensor (not shown) and a pressure sensor (not shown). The temperature sensor measures the temperature of the wet film 44. The pressure sensor measures the pressure of the temperature adjustment air in the conveyance path of the film 50.

  The temperature control wind controller 93 creates a predetermined temperature control wind from the air supplied from an air supply unit (not shown). Furthermore, the temperature control wind controller 93 can individually adjust conditions such as the temperature and wind pressure of the temperature control wind for each of the air supply heads 92 to be supplied based on values read from the temperature sensor and the pressure sensor. Further, the temperature control air controller 93 supplies the temperature control air to each blow head 92 through the feed duct 94. In this way, the air blowing head 92 blows the temperature adjusting air on the wet film 44 conveyed in the casing 80.

  Next, the operation of the present invention will be described. As shown in FIG. 1, the dope 35 is sent to the casting die 21 by a pump (not shown). The temperature of the dope 35 is adjusted to be substantially constant in the range of 30 ° C. or more and 35 ° C. or less by the temperature controller provided in the casting die 21.

  The temperature control device 30 adjusts the temperature of the peripheral surface of the casting drum 22 to be substantially constant in a range of −20 ° C. or more and 20 ° C. or less. The casting drum 22 rotates about an axis. As a result, the peripheral surface travels in the A direction. The running speed of the peripheral surface is preferably 10 m / min or more and 200 m / min or less. The lower limit of the running speed on the circumferential surface is more preferably 20 m / min or more.

  The casting die 21 flows out of the dope 35 toward the peripheral surface of the casting drum 22 from the slit outlet. Due to the outflow of the dope 35, a belt-like casting film 40 is formed on the peripheral surface. The casting drum 22 cools the casting film 40 until the casting film 40 can be conveyed. As a result of the cooling by the casting drum 22, the dope 35 forming the casting film 40 becomes a gel, so that the casting film 40 can be conveyed. Thereafter, the stripping roller 24 strips the cast film 40 that can be transported from the casting drum 22 as a wet film 44 and guides it to the pin tenter 13 through the crossing portion 45.

  Here, the gelation includes a state in which the fluidity of the dope is lost in addition to a state in which the colloidal solution is solidified in a jelly shape. Note that “the fluidity of the dope is lost” means that when the solute is a polymer, the fluidity is lost while the solvent is retained in the molecular chain of the solute, and as a result, the fluidity of the solution is reduced. This includes a lost state and a state in which the fluidity of the solution is lost due to the interaction between the solvent molecules and the solute molecules when the solute is a low molecule.

  The amount of residual solvent in the cast film 40 at the time of peeling is preferably 200% by weight or more and 300% by weight or less. In the present invention, the amount of the solvent remaining in the casting film 40 and each film is shown on the basis of the dry amount as the residual solvent amount. Moreover, the measurement method takes a sample from the target film, and when the weight of this sample is x and the weight after drying the sample is y, it is calculated as {(xy) / y} × 100. .

  The pin tenter 13 conveys the wet film 44 by running pins that hold both ends of the wet film 44. Further, the pin tenter 13 applies dry air to the wet film 44 to evaporate the solvent from the wet film 44. The ear clip device 52a cuts both ends of the wet film 44 fed from the pin tenter 13. The wet film 44 whose both ends are cut is sent to the clip tenter 14a. The wet film 44 becomes the film 50 by the processing in the clip tenter 14a. The edge-cutting device 52b cuts both ends of the film 50 sent out from the clip tenter 14a.

  The film 50 from which both ends are separated passes through the drying chamber 15 and the cooling chamber 16 in sequence, and then is sent to the winding chamber 17. The film 50 sent to the winding chamber 17 is wound around the winding core 57 while being pressed by the press roller 56 and becomes a roll.

  In FIG. 2, in the clip tenter 14, the clip 82 moves along a rail 83 at a predetermined speed. The speed of the clip 82 is preferably 10 m / min or more and 200 m / min or less. Further, the lower limit of the speed of the clip 82 is more preferably 20 m / min or more.

  In the clip tenter 14, the wet film 44 fed into the casing 80 sequentially passes through the preheating area 80a, the stretching area 80b, the relaxation area 80c, and the cooling area 80d. The width of the wet film 44 in the preheating area 80a remains W1. The width of the wet film 44 in the stretching area 80b gradually increases from W1 to W2 toward the downstream side in the Z1 direction. The width of the wet film 44 in the relaxation area 80c gradually decreases from W2 to W3 as it goes downstream in the Z1 direction. The width of the wet film 44 in the cooling area 80d remains W3.

  As shown in FIG. 4, the temperature adjustment air controller 93 supplies the temperature adjustment air adjusted for each area to each blower head 92. The blower head 92 provided in each area blows individually adjusted temperature adjustment air onto the wet film 44. The temperature of the temperature adjusting air in the first preheating area 80ax is a range in which the temperature of the wet film 44 blown with the temperature adjusting air approaches the glass transition temperature. The temperature of the temperature adjusting air in the second preheating area 80ay is in a range in which the temperature of the wet film 44 blown with the temperature adjusting air exceeds the glass transition temperature. The temperature of the temperature control wind in the stretching area 80b and the relaxation area 80c is within a range in which the temperature of the wet film 44 blown with the temperature control wind can be maintained higher than the glass transition temperature. The temperature of the temperature adjusting air in the cooling area 80d is a range in which the temperature of the wet film 44 blown with the temperature adjusting air is lower than the glass transition temperature. Thereby, the temperature of the wet film 44 in each area changes as shown in FIG.

  Furthermore, the temperature control air controller 93 adjusts the speed of the temperature control air in the wet film 44 for each area. Thereby, the wind pressure sprayed on the wet film 44 can be adjusted for every area.

  In the present invention, as shown in FIG. 6B, the temperature adjusting wind controller 93 is set so that the wind pressure in the first preheating area 80ax is higher than the wind pressure in the second preheating area 80ay and the wind pressure in the extending area 80b. Adjust the wind speed of the control wind. For this reason, it is possible to suppress deformation of the wet film 44 due to an increase in the wind pressure of the temperature-controlled air. Such deformation of the wet film 44 induces variations in the slow axis of the wet film 44. Therefore, according to the present invention, variations in the slow axis of the film 50 can be suppressed.

(First preheating area)
The residual solvent amount of the wet film 44 introduced into the first preheating area 80ax is preferably 10% by weight or more and 80% by weight or less. In addition, ΔT 80ax in the first preheating area 80ax is _preferably − (Tg−60) ° C. or higher and −3 ° C. or lower. Then, it is preferable wind pressure _{P 80Ax} temperature control air in the first preheating area 80Ax is less 350Pa than 110 Pa.

(Second preheating area)
The residual solvent amount of the wet film 44 introduced into the second preheating area 80ay is preferably 5% by weight or more and 70% by weight or less. Further, it is preferable that [Delta] T _80Ay is 60 ° C. less than -10 ° C. in the second preheating area 80Ay. Then, it is preferable wind pressure _{P 80Ay} temperature control air in the second preheating area 80Ay is less than 10 Pa 110 Pa.

(Extension area)
The residual solvent amount of the wet film 44 introduced into the stretching area 80b is preferably 3% by weight or more and 50% by weight or less. Further, it is preferable that [Delta] T _80b is 80 ° C. or less 0 ℃ or higher in the stretching area 80b. Then, it is preferable wind pressure _{P 80b} of temperature control air in the stretching area 80b is less than or 10 Pa 110 Pa. The stretching ratio (= W2 / W1) is preferably greater than 100% and 200% or less, for example.

(Relaxation area)
The residual solvent amount of the wet film 44 introduced into the relaxation area 80c is preferably 0.1% by weight or more and 20% by weight or less. Further, [Delta] T _80c in the relaxation area 80c is preferably not less than 60 ° C. or higher -10 ° C.. The wind pressure _{P 80c} of temperature control air in the relaxation area 80c is preferably less than or 10 Pa 110 Pa. The relaxation rate (= W3 / W2) is preferably greater than 90% and less than 100%, for example.

(Cooling area)
The residual solvent amount of the wet film 44 introduced into the cooling area 80d is preferably 0.1% by weight or more and 20% by weight or less. Further, [Delta] T _80d in the cooling area 80d is - it is preferably (Tg-60) is ° C. or higher -3 ° C. or less. The wind pressure _{P 80d} the temperature adjustment air in the cooling area 80d is preferably larger than the temperature control air wind pressure _{P 80b} in the stretching area 80b. Wind pressure _{P 80d} the temperature adjustment air in the cooling area 80d is preferably less than 110 Pa 350 Pa.

In the above embodiment, air pressure _{P 80Ax} in the first preheating area 80Ax has been greater than the wind pressure _{P 80d} the temperature adjustment air in the cooling area 80d, the present invention is not limited thereto, and wind pressure _{P 80Ax} and wind pressure _{P 80d May} be equal, or the wind pressure P _80ax may be smaller than the wind pressure P _80d .

In the above embodiment, although the wind pressure _{P 80c} of temperature regulating air at a temperature regulating air wind pressure _{P 80b} and relaxation area 80c in the stretching area 80b is equal, the present invention is not limited thereto, wind pressure _{P 80b} are wind pressure _{P 80c} It may be larger or smaller. In addition, although the wind pressure _{P 80Ay} temperature control air in wind pressure _{P 80b} and the second preheating area 80Ay temperature control air in the stretching area 80b are equal, the present invention is not limited thereto, wind pressure _{P 80b} than wind pressure _{P 80Ay} May be small.

  Next, with reference to FIG. 7 and FIG. 8, the solution film-forming facility 110 having a casting band as a support will be described. In the description of the solution casting equipment 110, parts and members different from the solution casting equipment 10 will be described, and the same parts and members as those of the solution casting equipment 10 will be denoted by the same reference numerals, and description thereof will be omitted. .

  As shown in FIG. 7, the solution casting apparatus 110 includes a casting chamber 12, a first clip tenter 14 a, a second clip tenter 14 b, a drying chamber 15, a cooling chamber 16, and a winding chamber 17.

  A casting apparatus 111 is provided in the casting chamber 12. The casting apparatus 111 includes a feed block 112 and a casting die 113.

  As shown in FIG. 8, the feed block 112 joins the dopes 116 a to 116 c sent from the pipes 115 a to 115 c to form a laminated dope 117, and sends the laminated dope 117 having a predetermined flow rate to the casting die 113.

  In the feed block 112, a flow path 119 penetrating the block-shaped feed block main body is provided in the Z direction. An inflow port 119i is opened on the upper surface of the feed block body, and an outflow port 119o is opened on the lower surface. Two partition members 120 a and 120 b are arranged in the upstream portion of the flow path 119. The partition members 120a and 121b have a first flow path 121 communicating with the pipe 115a, a second flow path 122 communicating with the pipe 115b, and a third flow path 123 communicating with the pipe 115c in the upstream portion of the flow path 119. Partition. The first flow path 121 is provided between the second flow path 122 and the third flow path 123. In the flow path 119, a merging portion 125 is formed on the downstream side of the partition members 120a and 120b. In addition, a laminated dope flow path 126 through which the laminated dope 117 flows is formed in the flow path 119 on the downstream side of the merging portion 125.

  Distribution pins 131 a and 131 b are provided at the outlet of the second flow path 122 and the outlet of the third flow path 123 in the merging portion 125. The partition member 120a has a partition part 132a and a vane 133a, and the partition member 120b has a partition part 132b and a vane 133b.

  The casting die 113 includes lip plates 141 and 142 and side plates (not shown). The lip plates 141 and 142 provided in the width direction are arranged in the moving direction of the casting belt 154 so as to be separated from each other. The side plate is provided in the moving direction of the casting belt 154 so as to close the gap between the lip plates 141 and 142. A portion surrounded by the lip plates 141 and 142 and the side plate is a slot 143. The slot 143 communicates with an inlet 143 i that communicates with the outlet 119 o of the feed block 112 and an outlet 143 o that flows out of the laminated dope 117. The outflow port 143o is rectangular and is formed to extend long in the width direction.

  Returning to FIG. 7, rotating rollers 152 and 153 are provided below the casting die 113. A casting band 154 is stretched around the rotating rollers 152 and 153. One end and the other end of the casting band 154 are connected, and the casting band 154 has an annular shape. The rotating rollers 152 and 153 are rotated by a driving device (not shown), and the casting band 154 moves with the rotation. The laminated dope 117 that has flowed out of the casting die 113 forms a laminated casting film 155 on the moving casting band 154.

  It is preferable that the moving speed of the casting band 154, that is, the moving speed is 10 m / min or more and 200 m / min or less. The casting band 154 is preferably made of stainless steel, and more preferably made of SUS316 so as to have sufficient corrosion resistance and strength. Moreover, it is preferable to use the thickness unevenness of the entire casting band 154 of 0.5% or less.

  In order to set the surface temperature of the casting band 154 to a predetermined value, it is preferable that the temperature control device 30 is attached to the rotary rollers 152 and 153. The casting band 154 is preferably one whose surface temperature can be adjusted to -20 ° C to 40 ° C. The temperature adjusting device 30 circulates the heat transfer medium adjusted to a desired temperature under the control of the control unit in the flow path provided in the rotary rollers 152 and 153. Due to the circulation of the heat transfer medium, the temperature of the rotary rollers 152 and 153 can be maintained at a desired temperature.

  Further, the casting chamber 12 has blowers 157 to 159 that apply dry air to the laminated casting film 155. The blowers 157 to 159 are provided downstream of the casting die 113 in the traveling direction of the casting band 154. When dry air is applied to the laminated casting film 155, the solvent evaporates from the laminated casting film 155. A labyrinth seal that blocks dry air may be provided between the casting die 113 and the blower 157. By installing the labyrinth seal, it is possible to suppress the surface variation of the laminated cast film 155 caused by the contact between the laminated cast film 155 immediately after casting and the drying air. Further, a blower device (hereinafter referred to as a quick dry blower device) 161 that applies quick drying air to the laminated cast film 155 may be provided between the casting die 113 and the blower device 157. In the case where a labyrinth seal is provided between the casting die 113 and the blower 157, a quick drying blower 161 may be provided between the labyrinth seal and the blower 157. When the rapid drying wind is applied to the laminated cast film 155, the solvent contained in the laminated cast film 155 evaporates at a higher evaporation rate than when the dry cast air is applied. Thereby, a skin layer can be formed on the surface of the laminated casting film 155. In the initial stage of the process of evaporating the solvent from the laminated cast film 155, by providing a skin layer on the laminated cast film 155, a laminated film having an excellent surface shape can be produced.

  Thereafter, the peeling roller 24 peels the laminated cast film 155 that can be transported from the casting band 154 as a wet film 44 and guides it to the clip tenter 14 a via the crossing portion 45. The residual solvent amount of the laminated cast film 155 at the time of peeling is preferably 10% by weight or more and 80% by weight or less. The crossover 45 is provided with a blower 167. The blower 167 applies a predetermined wind to the wet film 44 conveyed by the roller 46.

  The clip tenter 14a has a number of clips that grip both side edges of the wet film 44 in the width direction, and these clips run on the stretching track. Dry air is sent to the wet film 44 that runs by the clip, and the wet film 44 is subjected to a drying process along with a stretching process in the width direction. As a result, the wet film 44 becomes a laminated film 168 and is sent to the drying chamber 15.

  The laminated film 168 delivered from the drying chamber 15 is introduced into the clip tenter 14b. Similarly to the clip tenter 14a, the clip tenter 14b performs a drying process along with a stretching process in the width direction on the laminated film 168.

  In the said embodiment, although this invention was used about the film manufactured with the solution casting apparatus, this invention can also be used about the film manufactured with the melt casting apparatus.

(Optical film)
The film 50 obtained by the present invention can be used particularly for a retardation film and a polarizing plate protective film.

  The width of the film 50 is preferably 600 mm or more, and more preferably 1400 mm or more and 2500 mm or less. The present invention is also effective when the width of the film 50 is larger than 2500 mm. Moreover, it is preferable that the film thickness of the film 50 is 30 micrometers or more and 120 micrometers or less.

  The in-plane retardation Re of the film 50 is preferably 5 nm to 300 nm, and preferably 20 nm to 300 nm. The thickness direction retardation Rth of the film 50 is preferably -100 nm or more and 300 nm or less.

The method for measuring the in-plane retardation Re is as follows. In-plane retardation Re is a letter obtained by conditioning a sample film at a temperature of 25 ° C. and a humidity of 60% RH for 2 hours, and measuring it from the vertical direction at 632.8 nm with an automatic birefringence meter (KOBRA21DH Oji Scientific Co., Ltd.). The foundation value was used. Re is expressed by the following equation.
Re = | n1-n2 | × d
n1 is the refractive index of the slow axis, n2 is the refractive index of the fast axis, and d is the film thickness (film thickness).

The measuring method of the thickness direction retardation Rth is as follows. The sample film was conditioned at a temperature of 25 ° C. and a humidity of 60% RH for 2 hours, and measured in the same manner while tilting the film surface with an ellipsometer (M150 manufactured by JASCO Corporation) measuring 632.8 nm from the vertical direction. It calculated according to the following formula from the extrapolated value of the retardation value.
Rth = {(n1 + n2) / 2−n3} × d
n3 represents the refractive index in the thickness direction.

  Further, the shift amount D of the slow axis of the film 50 in the Z1 direction is preferably 1.5 ° or less, more preferably 1.0 ° or less, and particularly preferably 0.6 ° or less. .

(Slow axis deviation D)
The amount of deviation D of the slow axis in the Z1 direction can be measured, for example, as follows. First, a measurement line in the Z1 direction is provided on the film. Ten measurement points are provided on this measurement line. The orientation angle θ at each measurement point is measured. In the obtained orientation angle θ, a value obtained by subtracting the minimum value from the maximum value can be used as the slow axis shift amount D.

(polymer)
The polymer that can be used in the present invention is not particularly limited as long as it is a thermoplastic resin, and examples thereof include cellulose acylate, a lactone ring-containing polymer, a 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.

(Cellulose acylate)
As the cellulose acylate, cellulose triacetate (TAC) is particularly preferable. Among the cellulose acylates, the substitution degree of the acyl group to the hydroxyl group of cellulose is represented by the following formulas (I) to (III), and 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 degree of substitution of the acetyl group, and B is the degree of substitution of the acyl group having 3 to 22 carbon atoms. 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) 2.0 ≦ 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 group of cellulose is 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, more preferably 0.30 or more, and particularly preferably 0.31 to 0.34. Here, DS2 is a ratio in which the hydrogen of the hydroxyl group at the 2-position in the glucose unit is substituted by an acyl group (hereinafter referred to as “acyl substitution degree at the 2-position”), and DS3 is the hydroxyl group at the 3-position in the glucose unit. The hydrogen is substituted with an acyl group (hereinafter referred to as “acyl substitution degree at the 3-position”), and DS6 is the ratio of the hydrogen at the 6-position hydroxyl group substituted with an acyl group (hereinafter referred to as “acyl substitution degree at the 3-position”). "The 6-position acyl substitution degree").

  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 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 of a hydroxyl group at the 6-position, more preferably 25% or more, further preferably 30% or more, and particularly preferably 33% or more. Further, the DSA + DSB value at the 6-position of the cellulose acylate is 0.75 or more, more preferably 0.80 or more, and particularly preferably cellulose acylate of 0.85 or more. By using it, a dope with better solubility can be produced. In particular, when a non-chlorine organic solvent is used, a dope having excellent solubility, low viscosity and excellent filterability can be produced.

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

  The acyl group having 2 or more carbon atoms of 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, olenoyl 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.

(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.).

  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. 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, and n-butanol, but methanol, ethanol, n-butanol, or a mixture thereof is preferably used.

  Recently, a solvent composition not using dichloromethane has been studied for the purpose of minimizing the influence 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 the solvent.

  Details of cellulose acylate are described in paragraphs [0140] to [0195] of JP-A-2005-104148, and these descriptions can also be applied to the present invention. The same applies to additives such as solvents and plasticizers, deterioration inhibitors, UV absorbers (UV agents), optical anisotropy control agents, retardation control agents, dyes, matting agents, release agents and release accelerators. JP-A-2005-104148 describes in detail in paragraphs [0196] to [0516], and these descriptions can also be applied to the present invention.

  Next, in order to confirm the presence or absence of the effects of the present invention, a laminated film 168 was manufactured using the solution casting apparatus 110 shown in FIG.

(Preparation of cellulose acylate)
Cellulose acylates having different types of acyl groups and different degrees of substitution described in Table 1 were prepared. This was carried out by adding sulfuric acid (7.8 parts by mass with respect to 100 parts by mass of cellulose) as a catalyst, adding carboxylic acid as a raw material for the acyl substituent, and carrying out an acylation reaction at 40 ° C. At this time, the kind and substitution degree of the acyl group were adjusted by adjusting the kind and amount of the carboxylic acid. The acylation reaction was followed by aging at 40 ° C. Furthermore, after this aging, it was washed with acetone to remove low molecular weight components from the cellulose acylate. In Table 1, the substitution degree A is the substitution degree of the acetyl group, and B is the substitution degree of the other substituent X.

  The components of the first to third dopes are shown below.

(First dope)
Cellulose acylate resin (C-2 described in Table 1) 100 parts by mass Additive A (A-3 described in Table 2) 19 parts by mass Compound D (Chemical Formula 1) 4 parts by mass Dichloromethane 428 parts by mass Methanol 64 parts by mass

(Second dope)
Cellulose acylate resin (C-1 described in Table 1) 100 parts by mass Additive A (A-3 described in Table 2) 11.3 parts by mass Compound D (Chemical Formula 1) 4 parts by mass Matting agent 0.13 parts by mass Parts dichloromethane 400 parts by mass methanol 60 parts by mass

(3rd dope)
Cellulose acylate resin (C-1 described in Table 1) 100 parts by mass Additive A (A-3 described in Table 2) 11.3 parts by mass Compound D (Chemical Formula 1) 4 parts by mass Matting agent (Nippon Aerosil ( AEROSIL R972, secondary average particle size 1.0 μm or less) 0.13 parts by mass Dichloromethane 400 parts by mass Methanol 60 parts by mass

  In Table 2, “PA” represents phthalic acid. Similarly, “TPA” represents terephthalic acid, “IPA” represents isophthalic acid, “AA” represents adipic acid, and “SA” represents succinic acid. “NPA” represents naphthalenedicarboxylic acid, and the number before “−” represents the substitution position of carboxylic acid. “PD” represents propanediol, “BD” represents butanediol, and “CH” represents cyclohexanedimethanol. “AE residue” represents an acetyl ester residue, and “PE residue” represents a propionyl ester residue.

  Each component of the first dope 116a was put into a mixing tank and stirred to dissolve the polymer in the solvent. Then, it filtered using the filter paper with an average hole diameter of 34 micrometers, and the sintered metal filter with an average hole diameter of 10 micrometers. Thereby, the first dope 116a was prepared. Similarly, the components of the second dope 116b were respectively added to the mixing tank to prepare the second dope 116b, and the components of the third dope 116c were respectively added to the mixing tank to prepare the third dope 116c.

(Experiment 1)
The moving speed V1 of the casting band 154 was 40 m / min. The temperature of the casting band 154 was adjusted to be substantially constant at 30 ° C. by the temperature control device 30. The feed block 112 made a laminated dope 117 from each dope 116 a to 116 c and sent the laminated dope 117 to the casting die 113. The casting die 113 flowed the laminated dope 117 onto the casting band 154 to form a laminated casting film 155. The laminated casting film 155 had a structure in which the second layer, the first layer, and the third layer overlapped in this order from the casting band 154 side. The thickness of the first layer made of the first dope 116a was 60 μm, and the thickness of the second layer made of the second dope 116b and the thickness of the third layer made of the third dope 116c were 3 μm, respectively. The quick drying blower 161 applied a quick drying air having a temperature of 50 ° C. to the laminated casting film 165 to form a skin layer on the surface of the laminated casting film 165. The blowers 157 to 159 applied dry air to the laminated casting film 165 to evaporate the solvent from the laminated casting film 165. Using the peeling roller 24, the laminated cast film 165 that can be conveyed was peeled from the casting band 154. The amount of residual solvent at the time of peeling off the laminated cast film 165 was 20% by mass or more and 50% by mass or less.

  The wet film 44 peeled off was sent to the clip tenter 14a. In the clip tenter 14a, the wet film 44 passed through the first preheating area 80ax, the second preheating area 80ay, the stretching area 80b, the relaxation area 80c, and the cooling area 80d in this order.

The residual solvent amount of the wet film 44 introduced into the first preheating area 80ax was 28% by weight. [Delta] T _80Ax in the first preheating area 80Ax was -10 ° C.. The wind pressure _{P 80Ax} temperature control air in the first preheating area 80Ax was P1 (see Table 3).

The residual solvent amount of the wet film 44 introduced into the second preheating area 80ay was 20% by weight. [Delta] T _80Ay in the second preheating area 80Ay was 15 ° C.. The wind pressure _{P 80Ay} temperature control air in the second preheating area 80Ay was P2 (see Table 3).

The residual solvent amount of the wet film 44 introduced into the stretching area 80b was 15% by weight. [Delta] T _80b in the stretching area 80b was 35 ° C.. The wind pressure _{P 80b} of temperature control air in the stretching area 80b was P2 (see Table 3). The draw ratio (= W2 / W1) was 125%.

The residual solvent amount of the wet film 44 introduced into the relaxation area 80c was 12% by weight. Moreover, ΔT 80c in the relaxation area 80 _c was 25 ° C. The wind pressure _{P 80c} of temperature control air in the relaxation area 80c was P2 (see Table 3). The relaxation rate (= W3 / W2) was 99%.

The residual solvent amount of the wet film 44 introduced into the cooling area 80d was 10% by weight. Further, [Delta] T _80d in the cooling area 80d was -30 ° C.. The wind pressure _{P 80d} the temperature adjustment air in the cooling area 80d was P3 (see Table 3).

The laminated film 168 delivered from the clip tenter 14a was sequentially sent to the drying chamber 15, the clip tenter 14b, the cooling chamber 16, and the winding chamber 17.

(Experiments 2-4)
A laminated film 168 was produced in the same manner as in Experiment 1 except that the moving speed V1 of the casting band 154 and the wind pressures P1 to P3 in each area were as shown in Table 3.

(Evaluation)
For the laminated film 168 obtained in Experiments 1 to 4, the amount of shift D of the slow axis in the Z1 direction was measured. The amount of shift D of the slow axis of each laminated film 168 is as shown in Table 3.

DESCRIPTION OF SYMBOLS 10 Solution casting apparatus 14 Clip tenter 50 Film 80a Preheating area 80ax 1st preheating area 80ay 2nd preheating area 80b Stretching area 90 Blower 92 Blower head 93 Temperature control wind controller

Claims (5)

In a method for stretching a thermoplastic film, the method of stretching a strip-shaped thermoplastic film whose temperature is controlled by blowing temperature-controlled air,
Using a pair of clips that grip both edges in the width direction of the thermoplastic film, a transporting step of transporting the thermoplastic film in the longitudinal direction is performed,
The transporting step extends the gap between the pair of clips in a state where the both edges in the width direction are gripped, and a stretching step of stretching the thermoplastic film that is equal to or higher than the glass transition temperature in the width direction, and the stretching step. And a preheating step for preheating the thermoplastic film,
In the preheating step, a first preheating step of preheating the thermoplastic film so that a temperature of the thermoplastic film approaches a glass transition temperature, and the thermoplastic film so that the temperature of the thermoplastic film exceeds the glass transition temperature. And a second preheating step for preheating the
The method for stretching a thermoplastic film, wherein the temperature of the temperature-controlled wind in the thermoplastic film is larger in the first preheating step than in the second preheating step and the stretching step. In the conveying step,
A cooling step of blowing the temperature control air on the thermoplastic film is performed so that the temperature of the thermoplastic film is lower than the glass transition temperature;
The method for stretching a thermoplastic film according to claim 1, wherein the temperature of the temperature-controlled wind in the thermoplastic film is larger in the cooling step than in the stretching step. Forming a belt-like cast film comprising a dope containing a polymer and a solvent on a support;
Peeling the cast film from the support to form the wet film;
A drying step of evaporating the solvent from the wet film,
3. A solution casting method comprising performing the method of stretching a thermoplastic film according to claim 1 or 2 on the thermoplastic film obtained by the drying step. A belt-shaped thermoplastic film is transported in the longitudinal direction, a pair of rails provided on both sides of the transport path, and movable along the rails. A gripping means capable of gripping the edge, a transport means for transporting the thermoplastic film in the longitudinal direction,
A temperature adjusting means for adjusting the temperature of the thermoplastic film by blowing a temperature adjusting air to the thermoplastic film being conveyed;
In the conveyance path of the thermoplastic film, a first preheating area and a second preheating area where the pair of rails are constant, and the pair of rails are stretched so that the distance between the pair of rails increases from the upstream side toward the downstream side in the conveyance direction. Area is provided sequentially from the upstream side in the transport direction,
The temperature adjusting means includes an adjusting unit that adjusts the temperature and wind speed of the temperature adjusting air blown to the thermoplastic film,
The adjusting unit is configured so that the temperature of the thermoplastic film in the first preheating area approaches the glass transition temperature, and the temperature of the thermoplastic film in the second preheating area exceeds the glass transition temperature. Adjust the temperature of the temperature control wind,
The temperature of the adjusting unit is sprayed onto the thermoplastic film so that the wind pressure of the temperature-controlled wind in the first preheating area is larger than the wind pressure of the temperature-controlled wind in the second preheating area and the stretching area. An apparatus for stretching a thermoplastic film, characterized by adjusting a wind speed of the control wind. In the conveyance path of the thermoplastic film, a cooling area in which the distance between the pair of rails is constant is provided downstream of the stretching area in the conveyance direction,
The adjusting unit adjusts a wind speed of the temperature adjusting wind blown to the thermoplastic film so that a wind pressure of the temperature adjusting wind in the cooling area is larger than a wind pressure of the temperature adjusting wind in the extending area. The thermoplastic film stretching apparatus according to claim 4.

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