TWI675735B - Solution film forming method - Google Patents

Abstract

Provided are a solution film-forming method and equipment for manufacturing a thin film having a thickness of 40 μm or less which suppresses non-directional thickness unevenness.

The casting device 11 of the solution film forming apparatus 10 includes an air-drying element 41 and an air-supplying element 42. The air-extraction drying element 41 includes an infrared heater 50 and first to third extraction units 51 to 53. The infrared heater 50 is dried by heating the casting film 29 until the solvent content reaches 300% after formation. The first to third extraction sections 51 to 53 extract the gas from the outer side of the side 23e of the conveyor belt 23, thereby suppressing the solvent in the gaseous environment where the wind speed on the casting film 29 is 0.5 m / sec or less and the casting film 29 The concentration of gas is suppressed to 10% or less. The air-supply drying element 42 promotes the drying of the casting film 29 after the air-extraction drying process through the air-extraction drying element 41.

Description

Solution film forming method

The present invention relates to a solution film forming method and equipment.

In the small and medium-sized display market equipped with smart phones and tablets, further refinement is sought. Therefore, for the films used in these displays, a higher surface smoothness of the film is required than in the past. In addition, thinner films are required for these displays, and specifically, the thickness is 40 μm or less.

Films are usually made industrially long and cut to the required size for use. The manufacturing method of the elongated film is roughly classified into a solution film forming method and a melt film forming method. Among them, the solution film forming method is better than the melt film forming method from the viewpoint of making a film with a smoother film surface. The solution film-forming method is to discharge a dope in which a polymer is dissolved in a solvent from a casting die onto a moving casting support to form a casting film, and peel the casting film from the casting support to form a film. A method of drying the formed film. The casting film is cured on the casting support so that the film formed by peeling can be transported. The method for curing the casting film on the casting support includes a method of drying the casting film, and a method of drying includes heating and / or supplying a drying gas. The method of supplying gas to the casting film and drying it may cause unevenness on the film surface of the casting film due to the flow of the supply gas. Therefore, the smoothness of the film surface of the obtained film is impaired, and the unevenness extending in the length direction of the film can be identified.

The following methods are known to improve the smoothness of the film. For example, Japanese Patent Application Laid-Open No. 2012-066483 describes a method of irradiating far-infrared rays of liquid beads of a coating material flowing out of a casting die to dry it, improving the smoothness of the casting film, and smoothing the obtained film. Also, Japanese Patent Application Laid-Open No. 2004-322535 describes a method in which a conveyor is used as a casting support, a heating device is provided on the reverse casting surface on the back side of the casting surface on which the casting film is formed on the conveyor, and the heating is performed through the conveyor A method of casting a film and recovering a vaporized solvent by a coagulation device. As described in Japanese Patent Application Laid-Open No. 2006-306055, there is a method of forming a film on the film surface by supplying a dry gas to the casting film after casting, and the method is intended to smooth the film surface by the film.

However, when manufacturing a film having a thickness of 40 μm or less, in the method described in Japanese Patent Application Laid-Open No. 2006-306055, the supplied gas causes unevenness on the surface of the cast film, and it is dried soon after the film is smoothened. Therefore, the method described in Japanese Patent Application Laid-Open No. 2006-306055 cannot be applied to a film having a thickness of 40 μm or less.

Further, in the methods described in Japanese Patent Application Laid-Open No. 2012-066483 and Japanese Patent Application Laid-Open No. 2004-322535, the casting film is dried by not supplying gas to the casting film, from the viewpoint of preventing unevenness extending in the longitudinal direction due to gas flow. See has a certain effect. However, even if the methods described in Japanese Patent Application Laid-Open No. 2012-066483 and Japanese Patent Application Laid-Open No. 2004-322535 are used, when a film having a thickness of 40 μm or less is produced, no unevenness extending in the longitudinal direction is generated on the film surface, but instead Subtle unevenness in the direction dispersion occurs. The difference in height of the unevenness on the film surface corresponds to the difference in thickness of the film, and even if it is small, it means that there is a difference in thickness in the film. The uneven thickness dispersion in this direction, that is, non-directional thickness unevenness, was only discovered when the film was less than 40 μm in thickness, which could not meet the level of smoothness required for high definition of small and medium-sized displays.

The purpose of the present invention is to provide a solution film forming method and a solution film forming apparatus for manufacturing a thin film having a thickness of 40 μm or less which suppresses non-directional thickness unevenness.

The solution film-forming method of the present invention includes a casting film forming step, an air-drying step, an air-supplying drying step, a peeling step, and a film drying step to produce a film having a thickness in a range of 10 μm to 40 μm. The casting film forming step is to form a casting film by continuously casting a coating in which a polymer is dissolved in a solvent due to a moving casting support. The air-drying step is to dry the casting film by heating. While the solvent content in the casting film is 300%, the wind speed on the casting film is suppressed to 0.5 m / sec or less, and it is on the casting support side. The gas is extracted by the gas extraction part on the outer side of the side, and the concentration of the solvent vaporized in the gas environment on the casting film is suppressed to 10% or less. The air-supply drying step is to supply a drying gas to the casting film after the first casting film drying step to promote drying of the casting film. The peeling step is to peel the casting film in a state containing a solvent from the casting support to form a film. The film drying step is to dry the film.

The pumping and drying step is preferably to adjust the concentration of the gasification solvent by adjusting the amount of gas to be extracted.

The gas extraction part preferably includes an extraction port disposed outside the casting support, and an opening adjustment member which is located at the extraction port and can freely move the opening of the extraction port, and is adjusted by adjusting the opening of the extraction port. Gas extraction volume. The opening adjustment member is preferably attached in the up-down direction. Freely move and move between the open position and the closed position. The open position is to make the extraction port open by displacement upward, and the closed position is to make the extraction port closed by displacement downward.

The air-extraction drying step includes a first air-extraction step for extracting gas at the first position and a second air-extraction step for extracting gas at a second position that is closer to the downstream of the casting support than the first position. Preferably, the gas extraction volume is less than the first gas extraction step.

The cast film is preferably heated by irradiating the cast film with infrared rays.

It is also possible to heat the casting film through the casting support by irradiating infrared rays onto the reverse casting surface on the back side of the casting surface of the casting support casting film.

The solution film forming equipment of the present invention includes a moving casting support, a casting die, a heating section, a gas extraction section, a gas supply drying section, a peeling section, and a film drying device, and the thickness ranges from 10 μm to 40 μm. film. The casting die is a continuous flow of paint that dissolves the polymer in the solvent. The heating section dries the casting film formed by coating on the casting support. The gas extraction portion is disposed outside the side of the casting support formed by the casting film being heated by the heating portion, and suppresses the concentration of the solvent vaporized in the gas environment on the casting film by extracting the gas. The air-supply drying section is disposed downstream of the heating section closer to the heating section in the moving direction of the casting support, and supplies the casting film with drying gas to promote the drying of the casting film. The peeling part peels a casting film in the state containing a solvent from a casting support body, and forms a film. The film drying device dries the film.

The gas extraction unit preferably includes an extraction port disposed outside the side of the casting support, and an opening adjustment member located at the aforementioned extraction port and capable of freely moving to adjust the opening of the extraction port.

It is preferable that two gas extraction sections are provided along the moving direction of the casting support, and the openings of the gas extraction sections on the upstream side and the openings of the gas extraction sections on the downstream side are larger than the openings of the gas extraction sections on the upstream side and Smaller.

The heating part is preferably provided facing the casting surface of the casting coating material in the casting support, and emits infrared rays toward the casting film.

The heating part is preferably provided on a reverse casting surface facing the back side of the casting surface of the casting coating material in the casting support, and irradiates the reverse casting surface with infrared rays.

According to the present invention, a film having a thickness of 40 μm or less which suppresses non-directional thickness unevenness can be manufactured.

10‧‧‧Solution film forming equipment

11‧‧‧casting device

12‧‧‧Stenter

12a‧‧‧Clamp

12b‧‧‧Ventilation pipe

15‧‧‧ drum drying device

15a‧‧‧ roller

16‧‧‧Cutting Machine

17‧‧‧ Winding device

21‧‧‧ Coating

22‧‧‧ Film

23‧‧‧ conveyor belt

23a‧‧‧cast surface

23b‧‧‧Anti-casting surface

23e‧‧‧side

23s‧‧‧Side

26‧‧‧The first roller

27‧‧‧ 2nd roller

28‧‧‧die

28a‧‧‧ Outlet

29‧‧‧cast film

29e‧‧‧side

31‧‧‧ roller

32‧‧‧ stripping roller

41‧‧‧Exhaust air drying element

42‧‧‧Air supply drying element

45‧‧‧The first gas supply department

45a‧‧‧ Outlet

46‧‧‧Exhaust

46a‧‧‧extraction mouth

47‧‧‧ 2nd gas supply department

47a‧‧‧ Outlet

48‧‧‧controller

50‧‧‧ Infrared heater

50a‧‧‧ Injection Department

50b‧‧‧ substrate

51‧‧‧The first extraction department

52‧‧‧The second extraction section

53‧‧‧The third extraction department

51a ~ 53a‧‧‧Drawing mouth

56‧‧‧ chamber

61, 62‧‧‧ labyrinth seal

63‧‧‧Sensor

68‧‧‧ Extraction Agency

70‧‧‧ multi-well plate

70a‧‧‧hole

71‧‧‧ opening adjustment plate

72‧‧‧ Displacement mechanism

73‧‧‧controller

D1‧‧‧First distance

D2‧‧‧ 2nd distance

PC‧‧‧casting position

PP‧‧‧ stripping position

RH‧‧‧Heating area

X‧‧‧ direction of movement

Y‧‧‧Width direction

The foregoing objects and advantages should be easily understood by those with ordinary knowledge in the technical field by reading the detailed description of the preferred embodiments with reference to the accompanying drawings.

Fig. 1 is a schematic diagram of a solution film forming equipment.

Fig. 2 is a schematic plan view of an air-extracting drying element.

Fig. 3 is a sectional view taken along line III-III of Fig. 2.

Fig. 4 is a schematic diagram of the air supply unit.

Figure 5 is a photomicrograph of transmitted light of the films obtained in Examples 1-3.

Fig. 6 is a photomicrograph of transmitted light of the films obtained in Comparative Examples 1-4.

The solution film forming equipment 10 shown in the first figure for carrying out the present invention is used to manufacture a thin film 22 having a thickness of 10 μm to 40 μm. From the upstream side, a casting device 11, a tenter 12, a drum drying device 15, a cutter 16 and a winding device 17 are provided in this order. In addition, in this specification, the solvent content rate (unit:%) is a value on a dry basis. Specifically, when the mass of the solvent is MS and the mass of the film 22 is MF, {MS / (MF-MS)} is used. × 100 The percentage obtained.

The casting device 11 is a coating material 21 for dissolving a polymer from a solvent to form a polymer film (hereinafter simply referred to as a "film") 22. The coating material 21 is a polymer solution in which a polymer is dissolved in a solvent, and a solid component forming the thin film 22 may contain a substance other than the polymer. Examples of solid components other than the polymer include a plasticizer, an ultraviolet absorber, a retardation inhibitor, and fine particles. The plasticizer is contained in the present embodiment. The fine particles are so-called matting agents used for the purpose of imparting lubricity and / or scratch resistance to the film 22 and / or suppressing sticking when the films 22 overlap. The solid content in coating 21 is when the solid content is MP and the solvent mass is MS as described above, the percentage obtained from MP / (MP + MS) × 100 is within the range of 10% to 23%. The implementation form was 19%.

The solvent used in this embodiment is a mixture of dichloromethane and methanol. The solvent used in the solution film formation is generally heavier than air in a gas state, and the solvent in this embodiment is also heavier than air in a gas state. The solvent is not limited to the examples of this embodiment, and for example, butanol, ethanol, and propanol may be used, and these may be used in combination of two or more kinds.

The casting device 11 includes a conveyor belt 23 forming an endless casting support in a ring shape, and a first roller 26 and a second roller 27 that rotate in the circumferential direction. The conveyor belt 23 is wound and covered on the first roller 26 and the second roller The circumference of 27. At least one of the first roller 26 and the second roller 27 may be a driving roller having a driving device. In this embodiment, both the first roller 26 and the second roller 27 are driving rollers. By rotating the driving roller in the circumferential direction, the conveyor belt 23 contacting the circumferential surface is cyclically moved in the longitudinal direction. In addition, an arrow with a symbol X in FIG. 1 indicates the moving direction of the conveyor belt 23 and the conveying direction of the film 22.

A casting die (hereinafter referred to as a die) 28 for discharging the coating material 21 is provided above the conveyor belt 23. The coating material 21 is continuously flowed out on the moving conveyor belt 23 from the outflow port 28a (see FIG. 2) of the die head 28, so that the coating material 21 is cast on the conveyor belt 23 to form a casting film 29. The position at which the coating material 21 starts to contact the conveyor belt 23 is hereinafter referred to as the casting position PC.

In this embodiment, the die head 28 is provided above the conveyor belt 23 on the first drum 26, and the casting position PC is on the first drum 26. However, the position of the die head 28 is not limited to this. For example, it may be provided above the conveyor belt 23 from the first roller 26 to the second roller 27. At this time, it is preferable to arrange the roller 31 below the conveyor belt 23 from the first roller 26 to the second roller 27, and to arrange the die head 28 above the conveyor belt 23 supported by the roller 31.

The first roller 26 and the second roller 27 are each provided with a temperature controller (not shown) that controls the temperature of the peripheral surface. For example, the first drum 26 cools the temperature of the peripheral surface to a predetermined range. By cooling the first roller 26, the conveyor belt 23 is cooled every time it runs for one week. This makes it possible to suppress the temperature rise of the conveyor belt 23, particularly the two side portions 23s (see FIG. 2), even if the continuous operation is continuously heated by the exhaust drying element 41 and the air supply drying element 42 described later. The second roller 27 is a peripheral surface The temperature is heated to a predetermined range. By heating the first drum 27, the casting film 29 can be dried more efficiently.

The temperature of the circumferential surface of the first roller 26 is preferably in a range of 3 ° C to 30 ° C, more preferably in a range of 5 ° C to 25 ° C, and still more preferably in a range of 8 ° C to 20 ° C. The temperature of the circumferential surface of the second roller 27 is preferably in the range of 20 ° C to 50 ° C, more preferably 25 ° C to 45 ° C, and even more preferably 30 ° C to 40 ° C.

The so-called liquid beads of the coating material 21 reaching the conveyor belt 23 from the die head 28 are provided with a decompression chamber upstream of the moving direction of the conveyor belt 23, and the illustration is omitted. This decompression chamber extracts the gas in the region upstream of the dope 21 flowing out to decompress the aforementioned region.

After the casting film 29 is cured (gelled) to such an extent that it can be transported to the tenter 12, it is peeled from the conveyor belt 23 in a state containing a solvent to form a film 22. The peeling is preferably performed after the solvent content reaches 70% or less, more preferably within a range of 10% to 70%, and still more preferably within a range of 20% to 50%.

During peeling, the film 22 is supported by a roller (hereinafter referred to as a peeling roller) 32 of the peeling section, and the peeling position PP at which the cast film 29 is peeled from the conveyor belt 23 is kept constant. The peeling roller 32 may be a driving roller provided with a driving device and rotating in the circumferential direction. The stripping of the conveyor belt 23 attached to the first roller 26 is performed. When the conveyor belt 23 circulates and returns from the stripping position PP to the casting position PC, a new coating material 21 is cast again.

The casting device 11 includes a suction drying element 41 and an air supply drying element 42. The air-extracting drying element 41 includes an infrared heater 50, a first extraction unit 51, a second extraction unit 52, and a third extraction unit 53. The exhaust drying element 41 is disposed beside the moving path of the conveyor 23 from the first roller 26 to the second roller 27. The cast film 29 was dried after the formation until the solvent content reached 300%. The details of the suction drying element 41 will be described later using other drawings.

The air-supply-drying element 42 is an air-supply-drying unit that further dries the casting film 29 that has been dried by the air-extracting drying element 41 to the extent that it can be transported after being stripped from the conveyor belt 23. The air supply drying element 42 is disposed at a position closer to the downstream than the air extraction drying element 41 in the moving direction of the conveyor belt 23, and the first air supply unit 45, the exhaust unit 46, and the second air supply unit 47 are sequentially arranged from the upstream side. The moving directions of the conveyor belts 23 are aligned. The first air supply unit 45 is arranged beside the moving path of the conveyor belt 23 from the first drum 26 to the second drum 27, and the exhaust unit 46 and the second air supply unit 47 are arranged from the second drum 27 to the first drum 26 Next to the moving path of the conveyor belt 23.

The first gas supply unit 45 and the second gas supply unit 47 flow out dry gas, and the exhaust unit 46 extracts gas and exhausts the gas. Here, the conveyor belt 23, the die 28, the infrared heater 50, the first extraction portion 51, the second extraction portion 52, the third extraction portion 53, the first air supply portion 45, the exhaust portion 46, and the second air supply The portion 47 and the like are housed inside the chamber 56 isolated from the external space, and the exhaust portion 46 discharges the extracted gas to the outside of the chamber 56. The air supply drying element 42 is provided with a controller 48 outside the chamber 56. The controller 48 sends dry gas (hereinafter referred to as dry gas), such as air, to the first air supply unit 45 and the second air supply unit 47, and independently adjusts the temperature, humidity, and temperature of the gas from the first air supply unit. The flow rate of 45 and the second air supply part 47 and the gas suction force in the exhaust part 46. In this embodiment, the dry gas sent from the first air supply unit 45 and the second air supply unit 47 is It is heated to about 100 ° C by the controller 48. The warm air of the gas heated in this manner is circulated on the casting film 29, thereby heating the casting film 29 to promote drying. The temperature of the drying gas is preferably within a range of 50 ° C to 140 ° C.

In the first air supply unit 45, an outflow port 45a flowing out of the dry gas is arranged toward the moving direction X of the conveyor belt 23, so that the dry gas is supplied to the cast film 29 conveyed by the wind. This dry gas system has a parallel air flow with respect to the film surface of the casting film 29. In the second air supply unit 47, the outflow port 47a flowing out of the drying gas is arranged in a direction opposite to the moving direction X of the conveyor belt 23, whereby the drying gas is supplied to the transported casting film 29 against the wind. This dry gas also becomes a parallel air flow with respect to the film surface of the casting film 29. In the exhaust section 46, an extraction port 46a for extracting the gas is arranged to face the casting film 29 passing therethrough, and extracts gas between the first air supply section 45 and the second air supply section 47. In addition, the outflow port 45a, the outflow port 47a, and the extraction port 46a are slit-like openings extending in the width direction of the conveyor belt 23 (the depth direction on the paper surface of the first figure).

In this embodiment, the first air supply unit 45, the exhaust unit 46, and the second air supply unit 47 are independently controlled by the controller 48, but are not limited to this aspect. For example, a controller (not shown) may be provided in each of the first air supply unit 45, the exhaust unit 46, and the second air supply unit 47, and the first air supply unit 45 and the exhaust unit 46 may be controlled by each controller. And the second air supply unit 47.

The film 22 formed by stripping from the conveyor belt 23 is introduced into the tenter 12. An air blowing device (not shown) may be disposed on a conveying path between the casting device 11 and the tenter 12. Drying of the film 22 is promoted by the air supply from the air supply device.

The tenter 12 is a first film drying device that conveys and dries the film 22 at the same time. The tenter 12 of this embodiment is configured to transport each side portion of the film 22 in the longitudinal direction by holding it with the clamp 12a of the holding member, and at the same time, perform tension in the width direction to apply the film 22 in the width direction. Extended processing. In the tenter 12, a preheating zone, an extension zone, and a relaxation zone are sequentially formed from the upstream side. It is not necessary to have a relaxation zone.

The tenter 12 includes a pair of rails (not shown) and a chain (not shown). The rails are arranged on both sides of the transport path of the film 22, and a pair of rails are separated and arranged at predetermined intervals. The track interval remains constant in the preheating zone, gradually widens as it moves downstream, and remains constant in the relaxation zone. In addition, the track interval in the relaxation zone can be gradually narrowed as it moves downstream.

The chain is erected on the original sprocket and driven sprocket (not shown) and can move freely along the track. The plurality of clamps 12a are attached to the chain at predetermined intervals. With the rotation of the motive sprocket, the clamp 12a moves cyclically along the track. The clamp 12 a starts to clamp the introduced film 22 near the entrance of the tenter 12 and moves toward the exit, and the clamp is released near the exit. The clamp 12 a which has been released from gripping moves again to the vicinity of the entrance, and clamps the newly introduced film 22.

The preheating zone, the extension zone, and the relaxation zone are spaces formed by sending dry air from the ventilation pipe 12b, and have no clear boundaries. The ventilation pipe 12b is provided above the transport path of the film 22. The ventilation duct 12b has a slit through which a dry gas (for example, dry air) is sent, and the dry gas is supplied by a blower (not shown). The blower will be adjusted to a predetermined temperature and / or humidity The dry wind is sent to the ventilation pipe 12b. The ventilation duct 12 b is arranged as a conveyance path in which the slit faces the film 22. Each slit is formed in a shape elongated in the width direction of the film 22, and is maintained at a predetermined interval from each other in the conveying direction. In addition, a ventilation pipe having the same structure may be provided below the film 22 conveying path, or may be provided on both sides of the film 22 conveying path.

The drum drying device 15 is a second drying device for further drying the film 22. The gas environment inside the drum drying device 15 is controlled by an air conditioner (not shown) such as temperature and / or humidity. In the drum drying device 15, the film 22 is wound around a plurality of drums 15 a and conveyed.

The cutter 16 is used to cut both sides of the film 22 to obtain a desired width. This cutting is performed by cutting both sides of the film 22 in such a manner as to include clamping marks caused by the clamp 12a. The winding device 17 winds the film 22 around a winding core to form a roll.

The suction drying element 41 will be described with reference to FIG. 2. As mentioned above, the air-drying element 41 is used to dry the casting film to an air-drying portion having a solvent content of 300% after being formed, and is disposed downstream of the casting position PC. In this embodiment, a labyrinth seal 61 is provided near the downstream side of the casting position PC, and the air-drying element 41 is arranged as close to the labyrinth seal 61 as possible. The labyrinth seal 61 has its front end facing the conveyor belt 23 from the inner wall of the chamber 56 and is set in a standing posture relative to the conveyor belt 23. In addition to the labyrinth seal 61, a labyrinth seal 62 (see FIG. 1) is also provided upstream of the die head 28. These labyrinth seals 61 and 62 are used to form a space surrounding the die head 28. Thereby, the shape of the liquid beads can be stabilized, and the unevenness of the air pressure and / or the change of the air pressure around the die head 28 can be suppressed.

The infrared heater 50 in the heating section is used to heat and dry the casting film 29. The infrared heater 50 includes a plurality of injection portions 50 a arranged facing the conveyor belt, and a substrate 50 b that supports the emission portions 50 a. The emitting portion 50a emits infrared rays to irradiate the casting film 29. In the second figure, the drawing of each emitting portion 50a is greatly exaggerated. Therefore, the number of the injection portions 50a in the second figure is 9 in the width direction Y of the conveyor belt 23 and 20 in the conveyor belt moving direction X, but the actual number is larger. In the present embodiment, the plurality of emitting portions 50a are arranged in a matrix. However, other arrangements may be adopted or they may be arranged irregularly. The width direction Y of the conveyor belt 23 and the width directions of the casting film 29 and the film 22 coincide with each other. In the following description, the width direction Y is abbreviated to the width direction and the symbol Y is attached.

The cast film 29 is heated and heated to promote drying by infrared irradiation from the emitting portion 50a. Here, the infrared heater 50 is formed so that the length in the width direction Y is smaller than the width of the casting film 29, and the emission portion 50a is positioned more inward than the side 29e of the casting film 29 in the width direction Y. Since the casting film 29 is not formed on both sides 23s of the casting surface 23a on which the coating material 21 of the conveyor belt 23 is cast, the both sides 23s pass through in an exposed state, and the infrared heater 50 is set to the aforementioned size. And the arrangement can suppress the heating of both sides 23s. By suppressing the heating of both side portions 23s, excessive heating of the side portions of the casting film 29 is also suppressed, and no blistering occurs on the side portions of the casting film 29.

In the moving direction X of the conveyor belt 23, a first extraction section 51, a second extraction section 52, and a third extraction section 53 are provided in a heating region RH of the infrared heater 50. In the moving direction X of the conveyor belt 23, the second extraction section 52 is provided downstream of the first extraction section 51, and the third extraction section 53 is provided downstream of the second extraction portion 52. In this way, the first extraction unit 51, the second extraction unit 52, and the third extraction unit 53 are provided along the moving direction X of the conveyor belt 23.

The first extraction section 51, the second extraction section 52, and the third extraction section 53 are designed to suppress the solvent gas in the gas environment on the casting film 29 in a state that the wind speed on the casting film 29 is 0.5 m / sec or less. Suppressed to a low concentration. In addition, the wind speed of 0.5 m / sec is a relative speed with respect to the moving speed of the conveyor belt 23, and a negative (-) value is not considered. The smaller the wind speed, the better. Specifically, it is more preferably 0.5 m / sec or less, and still more preferably 0.3 m / sec or less. The lower the solvent gas concentration, the better. If it is 10% or less, it has a certain effect. The concentration of the solvent gas is more preferably 5% or less, and still more preferably 2% or less. Since the second extraction unit 52 and the third extraction unit 53 have the same configuration as the first extraction unit 51, the first extraction unit 51 will be described in the following description, and the description of the second extraction unit 52 and the third extraction unit 53 will be omitted. In addition, a coagulation device that cools and condenses the solvent gas may be used instead of the first extraction unit 51, the second extraction unit 52, and the third extraction unit 53.

The first extraction section 51 is formed with an extraction port 51a (refer to FIG. 3) extending along the moving direction X of the conveyor belt 23, and the gas velocity is extracted from the extraction port 51a to maintain the aforementioned state of suppressing the wind speed while suppressing the solvent gas to be low concentration. The first extraction portion 51 is disposed outside in the width direction Y from the side edge 23 e of the conveyor belt 23. In this embodiment, the width of the conveyor belt 23 is relatively large, approximately 2 m. In order to more reliably extract gas, a pair is provided on the outside of the two sides 23e. Similarly, a pair of the second extraction portion 52 and the third extraction portion 53 are provided on the outside of both side edges 23e.

In FIG. 3, the first extraction unit 51 is connected to the extraction mechanism 68, and the extraction quantity of the gas (hereinafter referred to as the extraction quantity) is adjusted by the extraction mechanism 68. Further, the extraction mechanism 68 includes a gas cleaning device (not shown), and removes the solvent gas from the gas introduced from the first air supply unit, and becomes a gas having a very low concentration of the solvent gas. The extraction port 51 a of the first extraction unit 51 is provided so as to face the side 23 e of the conveyor belt 23. The lower end position of the extraction port 51a is preferably lower than the counter-cast surface 23b on the back side of the casting surface 23a of the conveyor belt 23, and the same is true in this embodiment. The position of the upper end of the extraction port 51a is higher than the casting surface 23a of the conveyor belt 23, but the position may be lower than the reverse casting surface 23b.

When the distance between the extraction port 51a of the first extraction unit 51 and the side 23e of the conveyor belt 23 is referred to as a first distance D1, the first extraction port 51 is arranged so that the first distance D1 is 100 mm. However, the first distance D1 is not limited to this, but is preferably within a range of 50 mm to 500 mm, and more preferably within a range of 50 mm to 200 mm.

The extraction port 51a is provided with a perforated plate 70 and an opening degree adjusting plate 71 as an opening degree adjusting member. The perforated plate 70 is used to average the gas extraction amount of the first extraction portion 51 at the extraction port 51a to be constant. The perforated plate 70 is provided with a plurality of holes 70a, and gas is sucked into the first extraction portion 51 from the holes 70a. In the present embodiment, the shape of the hole 70a is circular (perfect circle), but may be oval or polygon, and the shape is not particularly limited. The pore diameter of the hole 70a is approximately 20 mm in this embodiment, but it is not limited thereto, and is preferably within a range of 10 mm to 100 mm. In addition, in FIG. 3, the drawing of the holes 70a is greatly exaggerated relative to the perforated plate 70. The opening adjustment plate 71 is used to adjust the extraction amount. In this embodiment, the adjustment of the extraction amount The festival is performed by both the extraction mechanism 68 and the opening degree adjustment plate 71. Specifically, after the adjustment by the extraction mechanism 68, the so-called fine adjustment is performed by the opening degree adjustment plate 71. The opening degree adjustment plate 71 is provided on the side of the perforated plate 70 facing the conveyor belt 23. The opening adjustment plate 71 is provided with a displacement mechanism 72. With the displacement mechanism 72, it is possible to freely move between the open position where all the holes 70a are open and the closed position where all the holes 70a are closed, and set in the open position and the closed position Anywhere. Since the opening degree adjustment plate 71 of this embodiment can move freely in the vertical direction, the extraction opening 51 a can be set to a certain opening degree in the moving direction X of the conveyor belt 23.

An inductor 63 is provided between the conveyor belt 23 and the infrared heater 50 and approximately at the center in the width direction Y. In this example, the sensor 63 is provided on the lower surface of the infrared heater 50. The sensor 63 includes a first detection unit (not shown) that detects the wind speed on the casting film 29, and a second detection unit (not shown) that detects the solvent vaporized from the casting film 29, that is, the concentration of the solvent gas.示).

The extraction amount is preferably adjusted according to the wind speed and the concentration of the solvent gas detected by the sensor 63. In the present embodiment, the extraction amount is adjusted by the controller 73 controlling the displacement mechanism 72 and the extraction mechanism 68 based on the wind speed and the concentration of the solvent gas detected by the sensor 63.

In this example, the infrared heater 50 is provided facing the casting surface 23 a of the conveyor belt 23, and the casting film 29 emits infrared rays. However, the infrared heater 50 may be provided at a position facing the casting surface 23a and / or a position facing the reverse casting surface 23b. When it is set to face the counter-cast surface 23b, the infrared heater 50 emits infrared rays toward the counter-cast surface 23b. In addition, When the distance between the casting surface 23a and the infrared heater 50 is referred to as the second distance D2, the second distance D2 in this embodiment is 50 mm, but it is not limited to this, as long as it is within a range of 10 mm to 200 mm.

In FIG. 4, the second extraction unit 52 and the third extraction unit 53 are provided with a perforated plate 70, an opening degree adjustment plate 71, and an extraction mechanism 68 like the first extraction unit 51. The drawing of the extraction mechanism 68 is omitted in FIG. 4. Here, the amount of the solvent gas generated from the casting film 29 is the largest after formation, and decreases as it goes downstream. Therefore, in this embodiment, in the moving direction X of the conveyor belt 23, the opening degree of the extraction section decreases as it goes downstream. In other words, in the order of the first extraction unit 51, the second extraction unit 52, and the third extraction unit 53, the openings of the extraction ports 51a, 52a, and 53a decrease. The suction force set by the extraction mechanism is also reduced in the order of the first extraction unit 51, the second extraction unit 52, and the third extraction unit 53. Thereby, the first extraction unit 51 in the first position at the most upstream position extracts the gas at the maximum extraction amount (the first extraction step), and the second extraction unit 52 located in the second position downstream of the first position takes the first extraction part. The gas is extracted with a smaller amount of 51 (second extraction step), and the third extraction section 53 located at a third position downstream of the second position extracts gas with a smaller extraction amount than the second extraction section 52 (third extraction step).

The effect of the foregoing configuration will be described. The paint 21 is continuously discharged from the moving conveyor belt 23 through the die head 28 to form a casting film 29 on the conveyor belt 23. The casting film 29 is guided by the moving conveyor belt 23 to the air-drying element 41. The casting film 29 is directly irradiated with infrared rays by passing under the infrared heater 50. Drying is promoted by this heating. When the infrared heater 50 is disposed below the conveyor belt 23, the casting film 29 is heated through the conveyor belt 23. Since the infrared heater 50 The solvent content of the casting film 29 after heating and passing through the infrared heater 50 is 300% or less.

In the heating region RH, the first extraction unit 51, the second extraction unit 52, and the third extraction unit 53 perform gas extraction. This extraction is performed at a very small extraction amount (for example, within a range of 0.1 m ³ / sec to 0.7 m ³ / sec), and the cast film 29 is cast until the solvent content of the cast film 29 reaches 300% or less. The upper wind speed is suppressed to 0.5 m / sec or less (exhaust drying step). By reducing the wind speed in this way, even if the casting film 29 has a high solvent content, the smoothness of the film surface is not impaired, and the obtained film 22 does not have non-directional thickness unevenness. In the method of drying the film by supplying air at a strong wind speed, the film surface of the casting film 29 is dried in a state of unevenness caused by the supply of air, and it is not possible to obtain a film by forming a film that is effective for a thick film having a thickness of 80 μm or more Smooth the film surface. On the other hand, as described above, the casting film 29 is heated by the infrared heater 50 under the so-called no-air supply state, and the wind speed on the casting film 29 is suppressed to a small method. 29 will keep the film surface smooth and dry uniformly in the thickness direction.

Even if the wind speed on the casting film 29 is 0, if the concentration of the solvent gas is high, convection of the solvent gas will occur, and non-uniform thickness unevenness will occur in the film 22. However, the gas is extracted by the first extraction unit 51, the second extraction unit 52, and the third extraction unit 53, and the concentration of the solvent gas in the environment on the casting film 29 is suppressed to be low. For example, it can be suppressed to 10%. The following low concentrations. By suppressing the concentration of the solvent gas to 10% or less, the convection of the solvent gas on the casting film 29 is suppressed, and the occurrence of non-directional thickness unevenness can be reliably suppressed.

Since the first extraction unit 51, the second extraction unit 52, and the third extraction unit 53 are disposed outside the side 23e of the conveyor belt 23, even if the extraction amount is increased, the wind speed on the casting film 29 can be suppressed from rising sharply. Further, since the wind speed on the casting film 29 is controlled to a stable state, the wind speed does not change sharply. In addition, the extraction ports 51a, 52a, and 53a are respectively formed to extend along the moving direction X of the conveyor belt 23, so the wind speed on the casting film 29 can be controlled within a wide range of the moving direction X of the conveyor belt 23, and the solvent gas can be suppressed to a low concentration .

The solvent of the coating material 21 is usually heavier than air in a gas state, and the dichloromethane in this embodiment is also heavier than air in a gas state. Here, as in the present embodiment, the lower end of the extraction port 51a is positioned lower than the counter-cast surface of the conveyor belt 23, so that the solvent gas can be extracted more reliably.

Since the first distance D1 is within a range of 50 mm to 500 mm, the wind speed on the casting film 29 can be more reliably suppressed to 0.5 m / sec or less, and the concentration of the solvent gas can be reduced to, for example, 10% or less. When the first distance D1 is 50 mm or more and the phase is smaller than 50 mm, the wind speed on the casting film 29 can be controlled more stably and the rapid change in the wind speed can be suppressed. When the first distance D1 is 500 mm or less and the phase is larger than 500 mm, the wind speed on the casting film 29 can be more reliably suppressed to 0.5 m / sec or less, and the solvent gas concentration can be surely reduced to 10% or less.

Since the extraction amount is adjusted by the extraction mechanism 68 and the opening degree adjustment plate 71, the concentration of the solvent gas can be adjusted more surely. In addition, the first extraction unit 51, the second extraction unit 52, and the third extraction unit 53 sequentially reduce the extraction amount, so that the concentration of the solvent gas can be reduced, and the wind speed can be suppressed to 0.5 m / sec or less under a stable change. .

The casting film 29 passed through the suction drying element 41 is introduced into the air supply drying element 42. The cast film 29 is dried by the air supplied from the first air supply unit 45 and the second air supply unit 47 (with a wind speed of approximately 3 m / sec or more and 20 m / sec or less). In the exhaust portion 46, the extraction port 46a for extracting the gas is disposed to face the casting film 29 passing therethrough, and extracts gas between the first air supply portion 45 and the second air supply portion 47. Therefore, the first air supply portion 45 and The dry gas flowing out of the second air supply unit 47 can more surely flow through the casting film 29. Therefore, the drying of the casting film 29 can be effectively promoted. In addition, the casting film 29 reduces the solvent content rate to 300% or less by the suction drying element 41. Therefore, even if the dry gas flow rates of the first and second air supply units 47 are set to be large, it can be maintained. The smoothness of the surface of the casting film 29 exposed.

The film 22 formed by peeling the casting film 29 from the conveyor belt 23 is carried by the tenter 12, and is dried by the drying wind from the ventilation pipe 12b. The clamp 12a is extended in the width direction to exert the required functions. Optical characteristics. The film 22 is further dried by the drum drying device 15, the side is removed by the cutter 16, and then the film 22 is wound into a roll shape by the winding device 17.

In the present invention, the greater the moving speed of the conveyor belt 23, the wider the width of the conveyor belt 23, and the wider the width of the manufactured film 22, the more effective it is. The present invention is particularly advantageous when producing a film for use as a retardation film such as a liquid crystal display.

In this embodiment, cellulose triacetate (hereinafter referred to as TAC) is used as the polymer of the coating material 21, but other halogenated celluloses other than TAC may be used. The fluorene group of the tritiated cellulose may be only one type, or may have two or more types of fluorene groups. When there are two or more fluorene groups, one of them is Preferred is ethenyl. The ratio of the hydroxyl group of cellulose to carboxylic acid esterification, that is, the degree of substitution of the fluorenyl group, preferably satisfies all of the following formulae (I) to (III). In the following formulae (I) to (III), A and B represent the degree of substitution of the fluorenyl group, A is the degree of substitution of the ethenyl group, and B is the degree of substitution of the fluorenyl group having 3 to 22 carbon atoms.

(I) 2.0 ≦ A + B ≦ 3.0

(II) 1.0 ≦ A ≦ 3.0

(III) 0 ≦ B ≦ 2.0

The total substitution degree of the fluorenyl group is more preferably 2.20 to 2.90, and particularly preferably 2.40 to 2.88. The degree of substitution B of a fluorenyl group having 3 to 22 carbon atoms is more preferably 0.30 or more, particularly preferably 0.5 or more.

The polymer of the coating material 21 is not limited to tritiated cellulose. For example, acrylic resins and cyclic olefin resins (for example, ARTON (registered trademark) manufactured by JSR Corporation) may be used.

Examples

Hereinafter, examples of the present invention and comparative examples comparing the present invention will be listed. Details are described in Example 1. In other examples and comparative examples, only conditions different from those in Example 1 are described.

[Example 1]

The solid content of the film 22 was dissolved in a mixture of 92 parts by mass of dichloromethane as the first component of the solvent and 8 parts by mass of methanol as the second component of the solvent to prepare a paint 21 having a solid content of 19.0% by mass. The solid content is the following TAC and the first plasticizer and the second plasticizer. The first plasticizer is triphenyl phosphate, and the second plasticizer is diphenyl diphenyl phosphate. After the prepared coating material 21 is left standing to defoam, the foreign material is removed through a filter by a liquid-feeding pump, and the coating material 21 after removing the foreign material is provided to the casting.

A thin film 22 having a thickness of 40 μm was produced from the coating material 21 by the solution film forming apparatus 10 shown in FIG. 1. The moving speed of the conveyor belt 23 is 50 m / min. Examples 1-1 to 1-15 were performed by extracting the drying element 41 so that the concentration of the solvent gas in the gas environment on the casting film 29 and the wind speed on the casting film 29 were the conditions shown in Table 1. The thickness of the obtained film 22 was measured with a thickness measuring machine DG125 manufactured by Ono Measurement Co., Ltd. and confirmed to be 40 μm.

Each of the obtained films 22 was evaluated for non-uniform thickness unevenness. The evaluation is based on the observation of transmitted light, and the evaluation is performed with the difference in shades. In addition, if the difference in shade is confirmed to be small, if it is not visually identifiable, it is regarded as passing without non-uniform thickness unevenness, and those who can be visually confirmed are regarded as having non-directional thickness unevenness and evaluated as unqualified. As an example of a qualified case, the photograph of Example 1-3 is shown in FIG. In addition, as an example of a failure, a photograph of Comparative Example 1-4 described later is shown in FIG. 6. In FIGS. 5 and 6, the upper direction corresponds to the moving direction X of the conveyor belt 23. The results are shown in the "Evaluation Results" column in Table 1.

[Comparative Example 1]

Comparative Examples 1-1 to 1-20 were performed by using the air-drying element 41 so that the concentration of the solvent gas in the gas environment on the casting film 29 and the wind speed on the casting film 29 were the conditions shown in Table 1. The other conditions are the same as in Example 1.

For each of the obtained films, the presence or absence of non-directional thickness unevenness was evaluated by the same method and evaluation criteria as in Example 1. The evaluation results are shown in Table 1.

[Example 2]

Examples 2-1 to 2-15 in which a coating film 21 was used to produce a 25 μm thin film 22 were implemented. The other conditions are the same as in Example 1.

For each of the obtained films 22, the same method as in Example 1 and the evaluation criteria were used to evaluate the presence or absence of non-uniform thickness unevenness. The evaluation results are shown in Table 2.

[Comparative Example 2]

Comparative Examples 2-1 to 2-20 were performed by using the air-drying element 41 so that the concentration of the solvent gas in the gas environment on the casting film 29 and the wind speed on the casting film 29 were the conditions shown in Table 1. The other conditions are the same as in Example 1.

For each of the obtained films, the presence or absence of non-directional thickness unevenness was evaluated by the same method and evaluation criteria as in Example 1. The evaluation results are shown in Table 2.

Claims (9)

A solution film-forming method is a solution film-forming method for manufacturing a thin film having a thickness in the range of 10 μm to 40 μm. The method includes the following steps, a casting film forming step, which is a continuous flow of a coating by dissolving a polymer in a solvent. The casting film is formed by extending on the moving conveyor belt; the air-drying step is performed by an infrared heater that faces the casting surface of the conveyor belt and casts the coating material and emits infrared rays to the casting film. The cast film was irradiated with infrared rays, and the cast film was dried by heating under no air supply so that the solvent content of the cast film reached 300%, and the wind speed on the cast film was suppressed to 0.5 m / sec. In the following state, the solvent is vaporized in the gaseous environment on the casting film by a gas extraction part having an extraction port facing the side of the conveyor belt, and the gas is extracted outside the side of the conveyor belt. The concentration is suppressed to 10% or less; the air supply drying step is to promote the drying of the casting film by supplying a drying gas to the casting film after the pumping drying step; the stripping step is to include the solvent The cast film in the state Peeling from the conveyor belt to form a film; and a film drying step, which is to dry the film. The solution film-forming method according to claim 1, wherein the extraction port is provided in a heating area configured by the infrared heater in a moving direction of the conveyor belt. The solution film forming method according to claim 1 or 2, wherein the extraction port extends along the moving direction of the conveyor belt. For example, the solution film forming method of claim 1 or 2, wherein the casting film forming step flows out of the coating material from a casting die set above the conveyor belt, and the lower end of the extraction port is lower than the reflux of the conveyor belt. Yannian. For example, the solution film forming method of claim 1 or 2, wherein the evacuation and drying step is to adjust the concentration of the gasification solvent by adjusting the amount of the gas to be extracted. For example, the solution film-forming method of claim 5, wherein the gas extraction unit is provided with an opening adjustment member for adjusting the opening degree of the extraction port, which is located at the extraction port and is movably arranged, and adjusts the opening degree by adjusting the opening degree of the extraction port. Gas extraction volume. For example, the solution film-making method of claim 6, wherein the opening degree adjusting member is freely movable in the up-down direction and moves between the open position and the closed position, and the open position is caused by the upward movement of the extraction port. In the open state, the closed position causes the extraction port to be closed by a downward displacement. The solution film-forming method according to claim 6, wherein the air-extraction drying step includes a first air-extraction step for extracting the gas at the first position and a gas-extraction step for extracting the gas at a second position that is closer to the first position than to the downstream of the conveyor belt The second pumping step. The second pumping step is smaller than the first pumping step. The solution film forming method according to claim 1 or 2, wherein the cast film is heated through the conveyor belt by irradiating the counter-cast surface on the back side of the casting surface on which the coating material is cast with the conveyor belt.