TW201536509A - Solution casting method and apparatus - Google Patents

Abstract

There are provided a solution casting method and a solution casting apparatus capable of producing a film having no thickness unevenness and no stretching unevenness. A dope is discharged to a casting belt from a casting die such that a casting film is formed on the casting belt. Each side edge of the casting film is thicker than a central portion thereof. The side edges of the casting film are dried by infrared rays irradiated from side-edge infrared-ray irradiation devices. The casting film is peeled as a wet film by a peeling roller. In a clip tenter, the wet film is dried to be a film. A maximum thickness of each side edge of the film is set to 46.8 [mu]m, a maximum thickness of the central portion of the film is set to 40 [mu]m, a residual amount of solvent in each side edge of the casting film at the time of peeling the casting film is set to 100%DB, and a residual amount of solvent in the central portion of the casting film at the time of peeling the casting film is set to 110%DB.

Description

Solution film making method and equipment

The invention relates to a solution film forming method and device.

A translucent polymer film (hereinafter referred to as a film) is widely used as an optical film such as a protective film of a polarizing plate, a retardation film, an antireflection film, or a transparent conductive film. The uniformity and optical properties of the thickness are required for the film. In the past, a thick film having a thickness of 80 μm or more has been mainly used. However, in recent years, as the optical film is diversified, the film thickness of the film is increased, and a film having a thickness of about 15 μm or more and 40 μm or less is required.

As a method of producing a film, a solution film forming method is used. The solution film forming method is a method of obtaining a film by, for example, casting a solution in which a polymer is dissolved in a solvent (hereinafter referred to as a dope) by casting a casting die on a metal support to form a flow. The film is stretched, dried and stripped. As the support, there are a drum, a conveyor belt, and the like. The casting film drying process for evaporating the solvent from the casting film and drying the cast film to the extent that it can be peeled off is a process which takes a long time in the entire solution film forming method, and therefore it is desirable to shorten the casting film drying process.

In the solution film forming method described in Japanese Laid-Open Patent Publication No. 2012-066483, the infrared ray is irradiated during the period from the flow of the dope to the casting on the support, and the process is performed. The hot air around °C is brought into contact with the casting film formed on the support to heat and dry the cast film.

In order to obtain a film, a thin cast film (hereinafter referred to as a thin cast film) is formed. Therefore, in order to dry a thick cast film (hereinafter referred to as a thick cast film) for obtaining a conventional thick film and to dry the film by drying the wind, the dry wind is used. There is a problem that the thickness is uneven and the surface smoothness is impaired. Further, when the subsequent process is based on a drawing process such as a clip tenter described later, the thickness unevenness may also cause stretching unevenness. Therefore, in the solution film forming method described in Japanese Patent Laid-Open Publication No. 2012-066483, the liquid droplets composed of the concentrated liquid which flow out from the casting mold over the support are irradiated with infrared rays by the infrared heater to promote the liquid crystal. The evaporation of the solvent in the liquid bead is performed to efficiently dry the cast film.

At the stage where the drying is carried out to the extent that the cast film can be peeled off, the cast film is peeled off from the support to be sent as a wet film to the clip tenter, and the clip tenter is used to promote the drying of the wet film. In the clip tenter, both side edges of the wet film are held by the clips and conveyed, and drying is further promoted by the dry air during the conveyance. However, even if the evaporation of the solvent is promoted from the liquid bead stage only by the infrared heater, when it is a thin film, in the subsequent stretching process, the side edge portion of the film may be bitten by the clip, and it is desirable to Improvement.

Therefore, an object of the present invention is to provide a solution film forming method capable of producing a film having no thickness unevenness and uneven stretching without causing chipping of the side edge portion of the film during the stretching process. And equipment.

The solution film forming method of the present invention comprises a cast film forming step (A step), a cast film drying step (B step), a stripping step (C step), a film drying step (D step), and a side edge drying step ( Step E). In step A, the flow from the casting die to the moving support The dope is formed to form a cast film having a thicker side edge than the central portion on the support. The dope contains the polymer and solvent. In the step B, the solvent is evaporated from the cast film to be dried. In the step C, the cast film which passed through step B was peeled off from the support as a wet film. In the step D, the both side edges of the wet film are held by a clip, and the solvent is evaporated to form a film. In the step E, the both side edges of the casting film are heated by radiation in the step B, and the residual solvent amount on both side edges of the casting film when the casting film is peeled off is set to VS1, and the stripping is performed. When the amount of residual solvent in the center portion of the cast film at the time of casting a film is VC1, the following conditions are satisfied.

50%DB<VC1 When 100%DB, set to (VC1-15) VS1 Within the range of (0.96 × VC1 + 25).

20%DB<VC1 50% DB, set to (0.85 × VC1 - 7.86) VS1 Within the range of (1.28 × VC1 + 5.71).

VC1 20% DB, set to VS1 Within the range of (1.28 × VC1 + 5.71).

When the maximum thickness of the central portion of the film is TC and the maximum thickness of the side edge portion is TS, it is set to 1.1 × TC. TS is preferred.

In the step E, the amount of residual solvent in the center portion of the cast film before peeling and the amount of residual solvent in the side edge portion are detected, and it is preferable to control the amount of heating on both side edges depending on the amount of residual solvent detected.

In the E step, it is preferred to irradiate infrared rays to both side edges of the cast film.

Infrared infrared rays are preferred.

It is preferable that both side edges of the cast film include a range held by the clip.

The solution film forming apparatus of the present invention includes a cast film forming apparatus, a cast film drying section, a peeling roll, a film drying section, and a side edge drying section. Cast film forming device from casting die The moving support flows out of the dope to form a cast film having a thicker side edge than the central portion on the support. The dope contains the polymer and solvent. The cast film drying section evaporates the solvent from the casting film formed on the support, and dries it. The stripping roll strips the dried cast film as a wet film. The film drying section evaporates the solvent from the wet film as a film. The side edge portion drying portion is provided in the casting film drying portion, and both side edges of the casting film are heated by radiation, and the amount of residual solvent on both side edges of the casting film when the casting film is peeled off is set to VS1. When the amount of residual solvent in the center portion of the cast film when the cast film is peeled off is set to VC1, the following conditions are satisfied.

50%DB<VC1 When 100%DB, set to (VC1-15) VS1 Within the range of (0.96 × VC1 + 25).

20%DB<VC1 50% DB, set to (0.85 × VC1 - 7.86) VS1 Within the range of (1.28 × VC1 + 5.71).

VC1 20% DB, set to VS1 Within the range of (1.28 × VC1 + 5.71).

It is preferable that the side edge portion drying portion has an infrared heater that irradiates infrared rays to both side edges of the casting film.

According to the present invention, both side edges of the wet film after peeling are sufficiently dried, and it is possible to prevent the occurrence of chipping and biting defects in the side edge portion of the film in the stretching process, and it is possible to manufacture no thickness unevenness and stretching. Uneven film.

10‧‧‧solution film making equipment

12‧‧‧cast film forming device

13‧‧‧Clip tenter (film drying section)

18‧‧‧Liquor

19‧‧‧ Wet film

23‧‧‧ Film

41, 100‧‧‧ casting die

42‧‧‧casting belt (support)

44‧‧‧ Stripping roller

45‧‧‧cast film

45a‧‧‧lateral edge

45b‧‧‧Central Department

51, 52‧‧‧Infrared irradiation device (side edge drying part)

51a~54a‧‧‧Infrared heater

53, 54‧‧‧The central part uses infrared radiation

71‧‧‧cast film forming process

72‧‧‧ Side edge drying process

73‧‧‧cast film drying process

74‧‧‧Extraction process

75‧‧‧film drying process

Fig. 1 is a side view showing an outline of a solution film forming apparatus.

Fig. 2 is a side view showing a cast film forming apparatus.

Fig. 3 is a side view showing an example of a slit shape of a casting die.

Fig. 4 is a perspective view showing an example of a cast film having thicker side edges.

Fig. 5 is a cross-sectional view showing an example of a method of drying a cast film.

Figure 6 is a flow chart of a solution film forming method.

Fig. 7 is a perspective view showing an example of a cast film in which both side edges are thick by continuous casting.

Fig. 8 is a cross-sectional view showing an example of a cast film having thicker side edges formed by addition of a dope.

Fig. 9 is a side view showing another embodiment of a sensor provided with a thickness for measuring a cast film.

Fig. 10 is a graph showing the relationship between the residual solvent amount VC1 of the cast film and VS1.

As shown in Fig. 1, the solution film forming apparatus 10 according to the present invention has a cast film forming apparatus 12, a clip tenter (film drying section) 13, a drying chamber 15, and a cooling chamber 16 in this order from the upstream side of the manufacturing line. And the take-up chamber 17. The wet film 19 is formed in the cast film forming apparatus 12 from a dope 18 containing a polymer and a solvent.

The transition portion 21 between the cast film forming device 12 and the clip tenter 13 is provided with a blower 21a that sends dry air to the wet film 19, and a plurality of support rollers 21b that support the wet film 19. A plurality of support rollers 21b are arranged in the conveying direction of the wet film 19. The support roller 21b supports the wetting film 19 sent from the cast film forming device 12, and guides it to the clip tenter 13.

The clip tenter 13 conveys the both sides of the wet film 19 while holding them by a clip (not shown). The clip tenter 13 is formed into a film 23 by performing a predetermined process such as drying and stretching on the wet film 19. The film 23 is fed out from the clip tenter 13 to the drying chamber 15.

A plurality of rollers 27 are disposed in the drying chamber 15. The temperature, humidity, and the like of the atmosphere in the drying chamber 15 are adjusted by an air conditioner (not shown). The film 23 is wound around a plurality of rolls 27 and conveyed in the drying chamber 15, and is dried in the drying chamber 15. The drying chamber 15 is connected to the adsorption recovery device 28. The adsorption recovery device 28 recovers the solvent gas evaporated from the film 23 by adsorbing it to the adsorbent.

The cooling chamber 16 cools the film 23 until the temperature of the film 23 becomes substantially room temperature. A static eliminating rod 29 and a knurling applying roller 30 are provided between the cooling chamber 16 and the winding chamber 17 in this order from the upstream side. The static eliminating rod 29 discharges the charged film 23 which is sent out from the cooling chamber 16 and is charged. The knurling applying roller 30 applies a knurling for winding to both ends in the width direction of the film 23.

A coiler 36 having a pressure roller 34 and a winding core 35 is disposed in the winding chamber 17. The film 23 sent to the take-up chamber 17 is taken up by the pressure roller 34 while being wound around the winding core 35, and is wound.

(cast film forming device)

As shown in Fig. 2, in the casting film forming apparatus 12, a casting die 41, a casting tape 42, rollers 34a and 43b, and a peeling roller 44 are provided in the casting chamber 38. The casting chamber 38 is divided into a casting portion 38a, a drying portion 38b, and a stripping portion 38c by partition plates 39a to 39c. The partition plates 39a to 39c extend from the inner wall surface of the casting chamber 38 toward the casting belt 42, and a labyrinth seal 40 is formed at the front end. The labyrinth seal 40 is disposed close to the casting belt 42 and suppresses the entry and exit of the atmosphere gas between the casting portion 38a, the drying portion 38b, and the stripping portion 38c.

The casting tape 42 is formed by connecting one end and the other end in the longitudinal direction of the metal strip. The casting belt 42 is made of, for example, stainless steel (SUS316) having sufficient corrosion resistance and strength. The casting belt 42 is wound around the drums 43a and 43b. The rollers 43a, 43b are axially The way to be horizontal is arranged substantially parallel to each other at the same height. When one of the rollers 43a is rotated by driving of a motor (not shown), the casting tape 42 is circulated in the X direction. Thereby, on the upper side of the drums 43a and 43b, the casting belt 42 moves from the drum 43a toward the drum 43b, and when it contacts the drum 43b, the casting belt 42 moves from the upper side to the lower side along the drum 43b. Further, on the lower side of the drums 43a and 43b, the casting belt 42 moves from the drum 43b toward the drum 43a, and when it comes into contact with the drum 43a, the casting belt 42 moves from the lower side to the upper side along the drum 43a.

The casting die 41 is positioned above the drum 43a and disposed adjacent to the casting belt 42 as a support. As shown in Fig. 3, a slit outlet 41a is provided at the tip end of the casting die 41. The gap of the slit outlet 41a is adjusted by, for example, a slit gap adjusting bolt (not shown). Thereby, the both edge parts of the width direction (Y direction) of the slit exit hole 41a are the widths of the range of 25 mm from the end part, for example, and it is wider than the width center part. In addition, only the front end surface of the casting die 41 is shown in FIG.

As shown in Fig. 4, the cast dope 18 forms a strip-shaped cast film 45 extending in the X direction on the casting tape 42 which is circulated and moved. The casting film 45 is conveyed in the X direction by the movement of the casting tape 42. Further, the side edge portions 45a of the casting film 45 in the Y direction are thicker than the center portion 45b by the gap shape of the slit outlets 41a. In the present embodiment, the both side edge portions 45a are in the range of 25 mm from the end portion of the casting film 45, but the range is included in the range held by the clip of the clip tenter 13. For example, it is preferable that the end portion of the casting film 45 is in the range of 15 mm or more and 60 mm or less, and more preferably 15 mm or more and 40 mm or less. Further, since the thicknesses of the casting film 45 and the casting tape 42 are relatively small as compared with the widths of the casting film 45 and the casting tape 42, the thickness is exaggeratedly illustrated as compared with the width, and is simplified for the sake of easy understanding.

As shown in FIG. 2, a decompression chamber 47 is provided in contact with the casting die 41 on the upstream side in the X direction of the casting die 41. By the decompression chamber 47, from the casting die 41 to the casting tape 42 The concentrated liquid 18 and the upstream side region of the so-called cast liquid bead are decompressed. Thereby, the vibration of the casting bead caused by the wind-carrying due to the cyclic movement of the casting belt 42 is suppressed, and the thickness unevenness is suppressed.

The side of the casting belt 42 is provided with a side edge portion infrared ray irradiation device (side edge portion drying portion) 51 and 52 and a central portion infrared ray irradiation device 53 and 54 (see Fig. 5).

As shown in Fig. 4, the side edge portion infrared irradiation device 51 is disposed above the casting tape 42 on the downstream side in the X direction from the casting die 41 and from the drum 43a toward the drum 43b (see Fig. 2). It is opposed to both side edge portions 45a of the casting film 45. As shown in Fig. 5, the side edge portion infrared ray irradiation device 51 has an infrared heater 51a. Infrared heaters 51a are irradiated with infrared rays (wavelengths in a range of 0.7 μm or more and 1000 μm or less) from both side edges 45a of the casting film 45, and the solvents of the both side edge portions 45a are evaporated to dry the both side edge portions 45a.

The central portion is sandwiched by the infrared ray irradiation device 51 by the side edge portion of the infrared ray irradiation device 53, and is disposed to face the central portion 45b of the casting film 45. Similarly to the infrared ray irradiation device 51 for the side edge portion, the central portion of the infrared ray irradiation device 53 has an infrared ray heater 53a for drying the central portion 45b by irradiating infrared rays to the central portion 45b of the both side edge portions 45a of the casting film 45. In addition, in FIG. 4, the illustration of the infrared irradiation device 53 for center part is abbreviate|omitted.

The side edge portion infrared ray irradiation device 52 and the central portion infrared ray irradiation device 54 are disposed near the lower side of the casting belt 42 from the drum 43b toward the drum 43a. The side edge portion infrared ray irradiation device 52 and the central portion infrared ray irradiation device 54 are configured similarly to the side edge portion infrared ray irradiation device 51 and the central portion infrared ray irradiation device 53, and have infrared heaters 52a and 54a, and a pair of casting films 45. Dry. Casting by the infrared ray irradiation devices 51 to 54 The film drying section performs the casting film drying process 73 (see Fig. 6). Further, the infrared heaters 51a to 54a of the infrared irradiation devices 51 to 54 are composed of one or a plurality of them, and when a plurality of infrared heaters 51a to 54a are used, the temperature can be individually controlled. Further, as is well known, infrared rays are distinguished by a wavelength region, a wavelength region of 0.7 μm to 2.5 μm is referred to as near-infrared rays, and a wavelength region of 2.5 μm to 4 μm is referred to as mid-infrared rays, and a wavelength region of 4 μm to 1000 μm. It is called far infrared ray. Further, cellulose triacetate easily absorbs infrared rays having a wavelength of 4 μm or more and 20 μm or less, and methanol easily absorbs infrared rays having a wavelength of 2.5 μm or more and 4 μm or less. Further, when the concentrated liquid 18 contains cellulose triacetate and methanol, it is preferred that the infrared ray to be irradiated has a wavelength region of 2.5 μm or more and 20 μm or less. As a specific example, when cellulose triacetate is used as the polymer raw material of the dope 18, the infrared rays emitted from the infrared heaters 51a, 52a, 53a, and 54a are more preferably far infrared rays, whereby the casting film 45 is used. The drying is carried out more efficiently. When cellulose triacetate is used as the polymer raw material of the dope 18 and methanol is contained in the solvent of the dope 18, the infrared rays emitted from the infrared heaters 51a, 52a, 53a, 54a are preferably far infrared rays and medium infrared rays. . Thereby, the drying of the casting film 45 is further efficiently performed.

The side edge portion infrared irradiation devices 51 and 52 and the central portion infrared irradiation devices 53 and 54 are respectively connected to the controller 50 (see Fig. 2). The controller 50 controls the respective infrared irradiation devices 51 to 54 to dry the casting film 45 in accordance with the thickness variation in the Y direction of the casting film 45 so that the residual solvent amount of the casting film 45 at the time of peeling is within the following range. .

By the infrared irradiation of each of the infrared irradiation devices 51 to 54, the casting film 45 is dried until the amount of residual solvent in the central portion 45b becomes 100% DB (Dry Base). In the present embodiment, the amount of solvent remaining in the casting film 45 and each film is expressed as a residual solvent amount on a dry basis. Cast film 45 to be measured for the amount of residual solvent When the mass is x, and the mass after the casting film 45 is completely dried is y, the amount of residual solvent is determined by {(x - y) / y} × 100. Further, the so-called "completely dry", the amount of the solvent does not need to be strictly 0 (zero). For example, the mass after drying the film 23 to be measured at 110 ° C for 3 hours may be y.

The controller 50 controls the amount of residual solvent and the center of the both side edge portions 45a of the casting film 45 when the casting film 45 is peeled off by the infrared ray irradiation devices 51 and 52 and the central portion infrared ray irradiation devices 53 and 54. The amount of residual solvent in the portion 45b is set to a certain range. Specifically, the following conditions are met. Here, the residual solvent amount of both side edge portions 45a of the casting film 45 when the casting film 45 is peeled off is VS1, and the residual solvent of the center portion 45b of the casting film 45 when the casting film 45 is peeled off is removed. The amount is set to VC1.

50%DB<VC1 When 100%DB, set to (VC1-15) VS1 Within the range of (0.96 × VC1 + 25).

And, 20% DB<VC1 50% DB, set to (0.85 × VC1 - 7.86) VS1 Within the range of (1.28 × VC1 + 5.71).

Moreover, VC1 20% DB, set to VS1 Within the range of (1.28 × VC1 + 5.71).

That is, when VC1 is in a range of more than 50% DB and 100% DB or less, VS1 is set to be in a range of (VC1-15)%DB or more (0.96×VC1+25)%DB or less, when VC1 is larger than In the range of 20% DB and 50% DB or less, VS1 is set to a range of (0.85 × VC1 - 7.86)%DB or more (1.28 × VC1 + 5.71)% DB or less, and when VC1 is 20% DB or less, VS1 is set to (1.28 × VC1 + 5.71) %DB or less.

Temperature control of each of the infrared ray irradiation devices 51 to 54 in the controller 50 is performed as follows system. First, depending on the thickness of the film 23 to be the product, the thickness ratio of the side edge portions 45a of the casting film 45 to the center portion 45b, the concentration of the concentrated liquid which is delayed, the length of the casting tape 42, and the traveling speed, The amount of residual solvent of the both side edge portions 45a and the center portion 45b at the time of peeling and the temperature of each of the infrared ray irradiation devices 51 to 54 at this time (hereinafter referred to as control temperature) are obtained. For the calculation of the amount of the residual solvent, for example, the thickness of each portion of the casting film 45 at the time of peeling and the thickness of each portion of the film 23 are measured, and based on these measurement results, the residue of each portion of the casting film 45 at the time of peeling is calculated. The amount of solvent. For example, the thickness of each portion of the casting film 45 at the time of peeling can be measured using the spectral interference interferometer wafer thickness meter SI-F80R manufactured by KEYENCE Corporation. The thickness of each part of the film 23 can be measured by a digital linear gauge DG-525 of Ono Co., Ltd. The controller 50 controls each of the infrared irradiation devices 51 to 54 such that the temperature of each of the infrared irradiation devices 51 to 54 becomes a control temperature determined by various conditions.

As shown in Fig. 2, a peeling roller 44 is provided in the vicinity of the drum 43a on the upstream side in the X direction from the casting die 41. The stripping roller 44 peels the casting film 45 which is irradiated with infrared rays by the respective infrared irradiation devices 51 to 54 from the casting tape 42 to obtain self-supporting properties. The casting tape 42 from which the casting film 45 is peeled off moves to the lower side of the casting die 41, and the dope 18 is cast again to function as a support.

A temperature adjustment device 58 is connected to the drums 43a, 43b. A temperature adjustment unit that adjusts the temperature of the heat transfer medium is built in the temperature adjustment device 58. The temperature adjusting device 58 circulates the heat transfer medium adjusted to a desired temperature between the temperature adjusting portion and the flow path provided in the drums 43a, 43b. By the circulation of the heat transfer medium, the temperature of the casting belt 42 is maintained at a desired temperature.

Further, although not shown, a heater is provided inside the casting belt 42. The heater dries the casting film 45 by heating the casting tape 42 to evaporate the solvent from the casting film 45.

The casting film forming device 12 is provided with an exhausting device 59. The exhaust device 59 discharges the atmosphere of the cast film forming device 12. The condensing recovery device (not shown) provided outside the cast film forming apparatus 12 condenses the solvent gas contained in the discharged atmosphere, and recovers the condensed solvent gas. The condensate recovery device maintains the concentration of the container substrate contained in the atmosphere in the cast film forming device 12 within a certain range for the solvent gas contained in the atmosphere of the cast film forming apparatus 12. The exhaust device 59 controls the flow of the gas in the cast film forming device 12 by discharging the atmosphere.

(solution film forming method)

Next, a solution film forming method will be described. The solution film forming method shown in Fig. 6 is carried out by the solution film forming apparatus 10 shown in Fig. 1. In the solution film forming method, a cast film forming process 71, a cast film drying process 73 having a side edge drying process 72, a stripping process 74, and a film drying process 75 are sequentially performed.

(cast film forming process)

As shown in Fig. 2, the casting belt 42 is circulated in the X direction by the rotation of the rollers 43a and 43b. The moving speed of the casting belt 42 is, for example, in the range of 10 m/min or more and 150 m/min or less, and preferably 40 m/min or more and 120 m/min or less. When the dope 18 is cast on the casting tape 42 from the casting die 41, the tape-like casting film 45 which extends long in the X direction is formed. As shown in Fig. 3, the gap between the both side edges of the slit outlet 41a is wider than the central portion. Therefore, as shown in Fig. 4, the casting film 45 is on both sides of the range of 25 mm from the end portion in the width direction. The edge portion 45a becomes thicker than the central portion 45b.

(cast film drying process)

The casting film 45 is conveyed by the moving casting tape 42. As shown in Fig. 5, the side edge portion is directed toward the conveyed casting film 45 by the infrared heater 51a of the infrared ray irradiation device 51. The both side edges 45a are irradiated with infrared rays. The central portion is irradiated with infrared rays toward the central portion 45b of the casting film 45 by the infrared heater 53a of the infrared irradiation device 53.

The casting film 45 which is irradiated with infrared rays by the respective infrared irradiation devices 51 and 53 and dried is passed over the respective infrared irradiation devices 52 and 54 by the casting tape 42 which is moved. Each of the infrared irradiation devices 52 and 54 heats the casting film 45 in the same manner as each of the infrared irradiation devices 51 and 53.

The temperature of the infrared heaters 51a to 54a is preferably in the range of 100 ° C or more and 500 ° C or less, and more preferably in the range of 100 ° C or more and 350 ° C or less. The wavelength of the infrared ray is preferably in the range of 0.8 μm or more and 50 μm or less, and more preferably in the range of 2 μm or more and 30 μm or less. The temperature of the infrared heaters 51a and 52a of the side edge portion infrared irradiation devices 51 and 52 is, for example, 180° C., and the temperatures of the infrared heaters 53 a and 54 a of the central portion infrared irradiation devices 53 and 54 are combined with the infrared heaters 51 a and 52 a. The temperature is set appropriately. In the present embodiment, the infrared heaters 51a to 54a are irradiated with infrared rays having a wavelength in a range of 2 μm or more and 30 μm or less and a range of 4 μm or more and 20 μm or less more strongly than other ranges.

The stainless steel casting tape 42 reflects infrared rays, so heating of the casting tape 42 is suppressed. Further, the casting film 45 easily absorbs infrared rays. Therefore, the casting film 45 is heated in a state where the temperature rise of the casting tape 42 is suppressed, the solvent evaporates from the casting film 45, and the casting film 45 is dried. In the casting film 45, the both side edge portions 45a are thicker than the center portion 45b, but the infrared ray heaters 51a and 52a that irradiate the infrared ray infrared heaters 51a and 52a on the both side edge portions 45a are irradiated with the infrared ray infrared heaters 53a and 54a at the center portion 45b. high. Thereby, in the casting film 45, both side edge portions 45a are dried to be substantially the same as the center portion 45b. By this drying, the amount of residual solvent VC1 at the center portion at the time of peeling and the residual solvent amount VS1 at the side edge portion are within the following relationship.

50%DB<VC1 When 100% DB, become (VC1-15) VS1 Within the range of (0.96 × VC1 + 25), 20% DB < VC1 When 50%DB, it becomes (0.85×VC1-7.86) VS1 Within the range of (1.28 × VC1 + 5.71), VC1 20% DB, become VS1 Within the range of (1.28 × VC1 + 5.71).

That is, when VC1 is in the range of more than 50% DB and 100% DB or less, VS1 becomes in the range of (VC1-15)%DB or more (0.96×VC1+25)%DB or less, when VC1 is greater than 20%. In the range of DB and 50% DB or less, VS1 is in the range of (0.85 × VC1 - 7.86) % DB or more (1.28 × VC1 + 5.71) % DB or less, and when VC1 is 20% DB or less, VS1 becomes (1.28). ×VC1+5.71)%DB or less.

(stripping process)

The peeling roller 44 peels the self-supporting casting film 45 as the wet film 19 from the casting tape 42, and sends it to the clip tenter 13 via the transition portion 21.

(film drying process)

In the clip tenter 13, the both sides of the wet film 19 are gripped by the clips, and a predetermined dry air is sent to the wet film 19 to evaporate the solvent from the wet film 19. As a result, the film 23 is obtained from the wet film 19. When the casting film 45 is peeled off, the amount of residual solvent VC1 in the center portion and the residual solvent amount VS1 in the side edge portion are within the above-described predetermined ranges. Therefore, both side edges of the wet film 19 after peeling are sufficiently dried and do not occur. The grip of the clip causes the bite to break. Further, uneven thickness and uneven stretching of the film 23 can be prevented. In addition, the relationship between the maximum thickness TS of both side edges in the range of 25 mm from both ends in the width direction of the film 23 and the maximum thickness TC of the central portion in the width direction of the film 23 is 1.1 × TC. TS. As described above, the both side edges of the wet film 19 are formed thicker than the central portion, and therefore it is more effective in preventing the seizure caused by the gripping of the clip. Further, since the both side edges become thicker, the bite of the clip does not occur. Further, the TS is thicker than TC, and the more stable the grip is based on the grip, but considering the casting of the dope 18 based on the casting die 41 or the stabilization of the formation of the casting film 45 on the casting tape 42, TS 5 × TC is better, TS 2 × TC is better.

The film 23 fed from the clip tenter 13 passes through the drying chamber 15 and the cooling chamber 16 in order, and performs predetermined processing in each chamber. The discharge treatment from the cooling chamber 16 to the film 23 is sequentially performed by the static elimination treatment by the static elimination rod 29 and the knurling treatment by the knurling application roller 30, and is sent to the winding chamber 17. The film 23 that has been fed to the take-up chamber 17 is wound up by the pressure roller 34 and wound up in the winding core 35 to form a roll. In the above embodiment, the cast film 45 is formed by the infrared rays in the same manner as the both side edge portions 45a. The central portion 45b of the product is dried, but the drying method of the central portion 45b is not limited to the above method, and may be performed by hot air drying or by heating and drying by a casting belt 42 provided by a heater provided inside the casting belt 42. dry. When hot air drying is performed, the relative speed of the drying air with respect to the casting film 45 is reduced to avoid surface undulation of the casting film 45, thereby avoiding thickness unevenness.

In the above-described embodiment, the gap between the both side edges of the slit outlet 41a of the casting die 41 is formed to be wider than the central portion, so that both side edge portions 45a of the casting film 45 are thicker than the central portion 45b, but As shown in Fig. 7, the difference in thickness between the two can also be set by continuous casting. At this time, the casting die 100 in which the dope 18 is linearly formed from the slit outlet flows into the casting tape 42 to form the casting film 45, and the side edges of the casting film 45 are flowed from the side edge portion. The die 101 casts the dope 18 so that both side edge portions 45a of the casting film 45 are thicker than the center portion 45b.

As shown in Fig. 8, it can also be performed from the dope supply nozzle 111 to the slave casting die. The concentrated liquid 18 is supplied to both side edges of the concentrated liquid 18 flowing out of 100, and the both side edge portions 45a of the casting film 45 are made thicker than the central portion 45b instead of the above-described continuous casting. In addition, the confluence of the doped liquid (hereinafter referred to as additional dope) added may be carried out from the side of the casting bead, or from either of the front and rear directions of the casting bead or both. Direction. Further, it is possible to appropriately combine the thickening of the side edge portion based on the slit gap, the thickening of the side edge portion based on the continuous casting, and the thickening of the side edge portion based on the joining of the concentrated dope to the casting bead. Either the both side edge portions 45a of the casting film 45 are thicker than the center portion 45b.

In the above embodiment, the controller 50 sets the temperatures of the infrared heaters 51a to 54a of the respective infrared irradiation devices 51 to 54 to be constant at the control temperature. However, it is not limited to this method. For example, as shown in FIG. 9, in addition to controlling the temperature, the thickness is detected by the thickness of the first cast film thickness sensor 121 and the second cast film thickness sensor 122. Each of the infrared irradiation devices 51 to 54 dries the casting film 45 so that the amount of residual solvent of the casting film 45 at the time of peeling is within the above-described predetermined range. At this time, the first cast film thickness sensor 121 is disposed above the drum 43b, and the second cast film thickness sensor 122 is disposed below the drum 43a. The controller 50 calculates the amount of residual solvent in the central portion 45b of the cast film 45 before stripping and the cast film 45 before stripping, based on the thickness detection results of the cast film thickness sensors 121 and 122. The amount of residual solvent on both side edges 45a. In accordance with the calculation result, the controller 50 controls the infrared heaters 51a to 54a of the respective infrared irradiation devices 51 to 54 so that the center portion residual solvent amount VC1 and the side edge portion residual solvent amount VS1 at the time of stripping are within the predetermined range. For example, when the thickness of the casting film 45 is increased more than a predetermined value, the detection result by each of the casting film thickness sensors 121 and 122 also becomes a detection result of an increase in thickness. At this time, if the temperature of the infrared heaters 51a to 54a is still the control temperature, the residual solvent amount VC1 at the center portion and the residual solvent amount VS1 at the side edge portion are separated. The above specified range. In order to prevent this, the controller 50 increases the temperatures of the infrared heaters 51a to 54a in accordance with the detection results of the respective cast film thickness sensors 121 and 122. The number of cast film thickness sensors may be one or more, and the detection position of the cast film thickness sensor can be appropriately changed.

In the above embodiment, the casting tape 42 wound around the rolls 43a and 43b is used as the support of the casting film 45. However, the rotatable casting roll may be used as the support of the casting film instead of the flow. Extending band 42.

In the above-described embodiment, the both side edges 45a of the casting film 45 are heated by the infrared rays irradiated from the infrared heaters 51a and 52a of the infrared irradiation devices 51 and 52 at the respective side edges, but the near infrared rays may be convected. The both side edges 45a of the film 45 are heated. Further, if heating can be performed by radiation, other types of heaters can be used.

[Examples]

Hereinafter, an experimental example for confirming the effects of the present invention will be described, and the present invention will be specifically described. However, the examples shown herein are merely examples of the invention and are not intended to limit the invention.

As a raw material of the dope 18, the following polymer raw materials and solvent raw materials are used.

[polymer raw material]

Cellulose triacetate 100 parts by mass

Triphenyl phosphate 7 parts by mass

Biphenyl diphenyl phosphate 5.0 parts by mass

[solvent raw material]

Dichloromethane 92 parts by mass

Methanol 8 parts by mass

The polymer raw material was dissolved in a solvent raw material to prepare a dope 18 having a solid concentration of 19.0% by mass. Further, the cellulose triacetate has a degree of substitution of 2.84, a viscosity average degree of polymerization of 306, a water content of 0.2% by mass, and a viscosity of 6% by mass in a dichloromethane solution of 315 mPa. s, a powder having an average particle diameter of 1.5 mm and a standard deviation of 0.5 mm. Further, a triphenyl phosphate and a biphenyl diphenyl phosphate plasticizer. In the present embodiment, defoaming is carried out by standing for the prepared dope 18, and the film is passed through a liquid feeding pump.

Using the solution film forming apparatus 10 of Fig. 1, the cast film forming process 71 of Fig. 6, the casting film drying process 73 having the side edge drying process 72, the stripping process 74, and the film drying process 75 are sequentially performed. A film 23 having a maximum thickness of 40 μm at the center portion was produced. The width of the casting tape 42 was set to 2000 mm, and the width of the casting film 45 was set to 1500 mm. Further, the running speed of the casting belt 42 was set to 80 m/min.

In the first embodiment, the maximum thickness TS of both side edges in the range of 25 mm from both ends in the width direction of the film 23 is 46.8 μm, and the maximum thickness TC in the central portion in the width direction of the film 23 is 40 μm. The residual solvent amount VS1 of the both side edge portions 45a of the casting film 45 is set to 100% DB, and the residual solvent amount VC1 of the center portion 45b of the casting film 45 at the time of peeling is set to 110% DB. The temperatures of the infrared heaters 51a and 52a of the infrared irradiation devices 51 and 52 were set to 180 °C. The temperature of the infrared heaters 53a and 54a of the infrared irradiation devices 53 and 54 in the center portion was set to 250 °C.

In Examples 2 to 19 and Comparative Examples 1 to 17, experiments were carried out under the conditions shown in Table 1. Other conditions were set to be the same as in the first embodiment. The results of this experiment are shown in Table 1 and Figure 10. In the "crushing" of Table 1, when the both side edges of the wet film 19 were gripped by the clips of the clip tenter 13, whether or not the wetting of the wet film 19 was broken, and when it was not crushed, it was evaluated as A, and a bite was generated. Broken comment The price is B. This determination is made by visual inspection. In addition, the in-plane retardation Re was measured over the entire width of the film 23 in the Re width direction fluctuation amount, and was evaluated as A when the fluctuation amount was within a range of ±3 nm, and was evaluated as B when it exceeded a range of ±3 nm.

As a method of measuring the in-plane retardation Re, the sample film was conditioned for 2 hours at a temperature of 25 ° C and a humidity of 60% RH, and the vertical direction of 589.3 nm was obtained by an automatic birefringence meter (KOBRA 21ADH Prince Measurement Co., Ltd.). The extrapolated value of the measured retardation value was calculated according to the following formula.

Re=|nX-nY|×d

nX represents the refractive index in the X direction, nY represents the refractive index in the Y direction, and d represents the thickness (film thickness) of the film.

In Fig. 10, the horizontal axis represents the residual solvent amount VC1 at the center portion, and the vertical axis represents the residual solvent amount VS1 at the side edge portion. The experimental results of Examples 1 to 19 and Comparative Examples 1 to 17 are plotted as a two-dimensional graph. . In Fig. 10, the labels for Examples 1 to 19 were "○", and the labels for Comparative Examples 1 to 17 were "X". It is represented by the upper limit line L1 and the lower limit line L2 when 50<VC1 100 hours (VC1-15) VS1 (0.96×VC1+25), when 20<VC1 50 o'clock (0.85 × VC1 - 7.86) VS1 (1.28×VC1+5.71), when VC1 20 o'clock for VS1 The upper limit and lower limit of each conditional formula of (1.28 × VC1 + 5.71).

In Comparative Examples 1 to 4, when 50 < VC1 100 hours, not satisfied (VC1-15) VS1 (0.96 × VC1 + 25). In Comparative Example 1, VS1 is 125% DB, VC1 is 100% DB, and (0.96 × VC1+25) is 121% DB, which does not satisfy VS1. (0.96 × VC1 + 25). Similarly, in Comparative Example 3, VS1 was not satisfied. (0.96 × VC1 + 25). Therefore, in Comparative Examples 1 and 3, the side edge portion of the wet film 19 after peeling was not sufficiently dried, and seizure occurred.

In Comparative Example 2, VS1 is 80% DB, VC1 is 100% DB, and (VC1-15) is 85% DB, which is not satisfied (VC1-15) VS1. Similarly, in Comparative Example 4, it was not satisfied (VC1-15). VS1. Therefore, in Comparative Examples 2 and 4, the amount of variation in the Re width direction exceeded the range of ±3 nm.

In Comparative Examples 5 and 6, when 20 < VC1 At 50 o'clock, it is not satisfied (0.85×VC1-7.86) VS1 (1.28 × VC1 + 5.71). In Comparative Example 5, VS1 was 66% DB, and VC1 was 45% DB (1.28 × VC1 + 5.71) was 63.31% DB, which did not satisfy VS1. (1.28 × VC1 + 5.71). Therefore, bite was produced in Comparative Example 5. In Comparative Example 6, VS1 was 28% DB, VC1 was 45% DB, and (0.85×VC1-7.86) was 30.39% DB, which was not satisfied (0.85×VC1-7.86). VS1. Therefore, in Comparative Example 6, the amount of variation in the Re width direction exceeded the range of ±3 nm.

In Comparative Example 7, when 20 VC1 did not satisfy VS1 (1.28 × VC1 + 5.71), so there is a bite.

In Comparative Examples 8, 9, 14, and 15, when 50 < VC1 At 100 o'clock, it is not satisfied (VC1-15) VS1 (0.96 × VC1 + 25). Also, in Comparative Examples 10 to 13, 16, and 17, when 20 < VC1 At 50 o'clock, it was not satisfied (0.85×VC1-7.86) VS1 (1.28 × VC1 + 5.71). Therefore, in Comparative Examples 8 to 17, the chipping occurred or the range of variation in the Re width direction exceeded the range of ±3 nm.

In contrast, in Embodiment 1, when 50 < VC1 100 hours, satisfied (VC1-15) VS1 (0.96 × VC1 + 25). In the first embodiment, VS1 is 110% DB, VC1 is 100% DB, (VC1-15) is 85% DB, and (0.96×VC1+25) is 121% DB, which satisfies (VC1-15) VS1 (0.96 × VC1 + 25). Thereby, both edge portions of the wet film 19 after peeling were sufficiently dried, and no seizure occurred. Further, the amount of change in the Re width direction is within a range of ±3 nm.

In Examples 2 to 4, 9, 10, 15, and 16, when 50 < VC1 100 hours, satisfied (VC1-15) VS1 (0.96 × VC1 + 25), as in the case of Example 1, no seizure occurred, and the amount of change in the Re width direction was also within the range of ±3 nm.

In Examples 5, 6, 11~14, 17, and 18, when 20<VC1 50 o'clock, satisfied (0.85 × VC1 - 7.86) VS1 (1.28 × VC1 + 5.71). As a result, in Examples 5, 6, 11 to 14, 17, and 18, no chipping occurred, and the amount of change in the Re width direction was within a range of ±3 nm.

In Embodiments 7, 8, and 19, when VC1 20 o'clock, meet VS1 (1.28 × VC1 + 5.71). As a result, in Examples 7, 8, and 19, no chipping occurred, and the amount of change in the Re width direction was within a range of ±3 nm.

As described above, the residual solvent amount VS1 of both side edge portions 45a of the casting film 45 at the time of peeling and the residual solvent amount VC1 of the center portion 45b of the casting film 45 at the time of peeling satisfy the condition of 50 < VC1. 100 hours (VC1-15) VS1 (0.96×VC1+25), when 20<VC1 50 o'clock (0.85 × VC1 - 7.86) VS1 (1.28×VC1+5.71), when VC1 20 o'clock for VS1 (1.28 × VC1 + 5.71), the chipping is not caused, and the amount of change in the Re width direction is also within a range of ± 3 nm, and the film 23 having no thickness unevenness and uneven stretching can be produced.

As shown in Figure 10, the upper limit line L1 is at 50 < VC1 100 degrees inclination is less than 20<VC1 50 degrees of inclination. If 50<VC1 The inclination at 100 o'clock is equal to 20<VC1 When the amount of residual solvent VC1 in the center portion is 100% DB, the amount of residual solvent VS1 in the side edge portion exceeds 130% DB, and seizure occurs. In the present invention, by making 50<VC1 100 degrees inclination is less than 20<VC1 50 degrees of inclination to prevent chipping. And, the lower limit line L2 is at 50 < VC1 100 degrees inclination is greater than 20<VC1 50 degrees of inclination. If 50<VC1 The inclination at 100 o'clock is equal to 20<VC1 When the inclination is 50 degrees, the difference between the center portion residual solvent amount VC1 and the side edge portion residual solvent amount VS1 is larger than the lower limit line L2, and the amount of variation in the Rc width direction exceeds ±3 nm. In the present invention, by making 50<VC1 100 degrees inclination is greater than 20<VC1 The inclination at 50 o'clock was such that the amount of change in the Re width direction was within a range of ±3 nm.

51‧‧‧Infrared irradiation device for side edge (drying part at side edge)

51a‧‧‧Infrared heater

53‧‧‧The central part uses infrared radiation

53a‧‧‧Infrared heater

45‧‧‧cast film

45a‧‧‧ both sides

45b‧‧‧Central Department

42‧‧‧casting belt (support)

52‧‧‧Infrared irradiation device for side edge (drying part at side edge)

52a‧‧‧Infrared heater

54‧‧‧The central part uses infrared radiation

54a‧‧‧Infrared heater

Claims (10)

A solution film forming method comprising the steps of: (A), flowing a dope from a casting die toward a moving support, thereby forming a casting film having a side edge portion thicker than a central portion on the support body, The dope comprises a polymer and a solvent; (B) a step of evaporating the solvent from the casting film to perform drying; and (C), the stripping film is removed from the support by the step B as the wetting film (D), holding both sides of the wet film by a clip, and evaporating the solvent as a film; and (E), in the step B, heating the two of the cast film by radiation In the side edge portion, the residual solvent amount on both side edges of the cast film when the cast film is peeled off is VS1, and the residual solvent in the center portion of the cast film when the cast film is peeled off When the amount is set to VC1, the following conditions are met, 50% DB < VC1 When 100%DB, set to (VC1-15) VS1 Within the range of (0.96 × VC1 + 25), 20% DB < VC1 50% DB, set to (0.85 × VC1 - 7.86) VS1 Within the range of (1.28 × VC1 + 5.71), VC1 20% DB, set to VS1 Within the range of (1.28 × VC1 + 5.71). The solution film forming method according to claim 1, wherein the maximum thickness of the central portion of the film is TC, and when the maximum thickness of the side edge portion is TS, it is set to 1.1 × TC. TS. The solution film forming method according to claim 1 or 2, wherein In the above-described step E, the amount of residual solvent in the central portion of the cast film before peeling and the amount of residual solvent in the side edge portion are detected, and the amount of heating on the both side edges is controlled in accordance with the amount of residual solvent detected. The solution film forming method according to claim 1 or 2, wherein in the step E, infrared rays are irradiated to both side edges of the cast film. The solution film forming method according to claim 3, wherein in the step E, infrared rays are irradiated to both side edges of the cast film. The solution film forming method according to claim 4, wherein the infrared rays are far infrared rays. The solution film forming method according to the first or second aspect of the invention, wherein the both side edges of the cast film include a range held by the clip. The solution film forming method according to claim 3, wherein both side edges of the cast film include a range held by the clip. A solution film forming apparatus comprising: a cast film forming device that discharges a dope from a casting die toward a moving support, thereby forming a cast film having a side edge portion thicker than a central portion on the support body, the thick film The liquid contains a polymer and a solvent; the cast film drying section is configured to evaporate the solvent from the casting film formed on the support, and to remove the dried cast film as a wet film. a thin film drying unit that evaporates the solvent from the wet film as a film, and a side edge drying unit that is provided in the cast film drying unit and that radiates the both side edges of the casting film to be peeled off When the amount of the residual solvent in the center portion of the cast film when the cast film is peeled off is VS1, the amount of residual solvent in the center portion of the cast film when the cast film is peeled off is set to VC1. The following conditions are met, 50% DB<VC1 When 100%DB, set to (VC1-15) VS1 Within the range of (0.96 × VC1 + 25), 20% DB < VC1 50% DB, set to (0.85 × VC1 - 7.86) VS1 Within the range of (1.28 × VC1 + 5.71), VC1 20% DB, set to VS1 Within the range of (1.28 × VC1 + 5.71). The solution film forming apparatus according to claim 9, wherein the side edge portion drying portion has an infrared heater that irradiates infrared rays to both side edges of the casting film.