KR101810523B1 - Drying apparatus and solution film-forming method - Google Patents

Abstract

The second drying unit for drying the flexible film 30 has a box-shaped supply duct, a vertical nozzle 32b for delivering the dry air 402 and a suction duct 32c for sucking the dry air 402. The supply duct is provided above the flexible film 30. The vertical nozzle 32b protrudes from the supply duct to the flexible membrane 30 at the lower surface of the supply duct. The suction ducts 32c are installed on both sides of the vertical nozzles 32b arranged in the A direction. A suction port 32cx for sucking the drying air 402 is installed in the suction duct 32c. The suction port 32cx is provided at a position away from the flexible film 30 than the blowing slit 32bx provided in the vertical nozzle 32b. A dry air suction route is formed between the plurality of vertical nozzles 32b.

Description

[0001] DRYING APPARATUS AND SOLUTION FILM-FORMING METHOD [0002]

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

A light-transmitting polymer film (hereinafter referred to as a film) is lightweight and easy to mold, and thus is used as an optical film in various fields. Among them, a cellulose ester film using cellulose acylate or the like is used for an optical film (for example, a retardation film or a polarizing plate protective film), which is a constituent member of a liquid crystal display device, have.

Such a film is produced by a solution casting method. The outline of the solution film-forming method is as follows. First, a polymer solution containing a polymer and a solvent (hereinafter referred to as a " dope ") is flowed to form a flexible film on a support. Secondly, the solvent is evaporated from the flexible film until the flexible film is self-supporting and can be transported. Third, the flexible film is peeled from the support to form a wet film. The film can then be obtained from the wet film by evaporating the solvent from the wet film.

As a method for drying the flexible film, for example, a method of spraying dry air from above the flexible film is known as disclosed in Japanese Patent Application Laid-Open No. 2007-290375. In the drying method described in Japanese Patent Laid-Open No. 2007-290375, as shown in Fig. 15, the drying device 202 is provided above the flexible film 201 conveyed by the flexible band 200 as a support. The drying apparatus 202 is provided with an air blowing slit 202a and a suction port 202b alternately in the conveying direction of the flexible film 201. [ The blowing slit 202a sends the drying wind 203 toward the flexible film 201. [ The suction port 202b sucks the drying wind 203. The drying air 203 is applied to the flexible film 201 by using the drying device 202 to evaporate the solvent contained in the flexible film 201.

2. Description of the Related Art In recent years, with the increase in demand for liquid crystal display devices and the enlargement of display panels for LCDs and the like, manufacturing of wide optical films has become a new challenge for providers of optical films.

In the case of using the method described in Japanese Patent Application Laid-Open No. 2007-290375, it is necessary to make the blowing slit 202a and the suction port 202b longer in the width direction of the flexible film in accordance with the widening of the flexible film. However, by making the suction port 202b longer, it becomes difficult to make the suction amount of the drying wind uniform in the width direction. For this reason, the drying condition becomes irregular in the width direction of the flexible film. Optical properties (for example, Re and Rth) of the optical film subjected to the drying process under such conditions become irregular in the width direction.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a drying apparatus that performs a drying process under uniform conditions in a width direction of a flexible film, and a solution film formation method having the drying step.

Means for Solving the Problems In order to solve the above problems, a drying apparatus of the present invention comprises a duct, a plurality of nozzles, a blowing slit, and a suction port. The duct is disposed so as to face a band-shaped flexible film conveyed in the longitudinal direction. The flexible film includes a polymer and a solvent. The plurality of nozzles are arranged in the transport direction of the flexible film. The nozzle is installed to protrude from the duct toward the flexible film. The blowing slit feeds the dry gas from the duct to the coarse membrane as dry wind. The blowing slit is formed at the tip of the nozzle so as to extend in the width direction of the flexible film. The suction port sucks the drying air sent out from the air blowing slit. The suction port is located between the nozzle and the nozzle in the transport direction. The suction port is located on both sides of the flexible film in the width direction. The distance between the suction port and the flexible film is larger than the distance between the air blowing slit and the flexible film.

In this drying apparatus, it is preferable that the air blowing slit and the suction port are alternately arranged from the upstream side to the downstream side in the carrying direction.

It is preferable that the suction port is formed from the upstream side of the at least one nozzle selected from the plurality of nozzles in the conveying direction to the downstream side of the at least one nozzle in the conveying direction.

It is preferable that the suction port faces the flexible band.

The suction port is preferably directed toward the widthwise center side.

The amount of the residual solvent in the flexible film to which the drying wind is applied is preferably 150 mass% or more and 350 mass% or less.

The duct is preferably disposed above the flexible film.

The width of the flexible film is preferably 1500 mm or more and 2400 mm or less.

The solution casting method of the present invention is a solution casting method for obtaining a film by evaporating the solvent from a flexible film containing a polymer and a solvent. The solution film-forming method of the present invention includes a step (feeding step) for sending dry wind and a step (suction step) for sucking the dry wind. The supplying step sends dry wind to the strip-shaped flexible film conveyed in the longitudinal direction. The drying air is blown out by using an air blowing slit arranged in the conveying direction of the flexible film. The blowing slit faces the flexible film. The blowing slit extends in the width direction of the flexible film. In the suction step, the drying air sucks from a position spaced apart from the flexible film by a distance from the air blowing slit. In the suction step, the drying air sucks from the positions on both sides in the width direction of the flexible film.

In the solution film-forming method, it is preferable that the amount of the residual solvent in the flexible film to which the drying wind touches is 150% by mass or more and 350% by mass or less.

The width of the flexible film is preferably 1500 mm or more and 2400 mm or less.

According to the present invention, since the suction port for sucking the drying air is provided at both ends in the width direction of the flexible membrane, even when the width of the flexible membrane is increased, the drying air can be uniformly suctioned. In addition, since the distance between the suction port and the flexible film is larger than the distance between the air blowing slit and the flexible film, it is possible to suppress the adverse effect caused by the suction of the dry air. Therefore, according to the present invention, it is possible to produce an optical film in which unevenness in optical characteristics is suppressed.

The above objects and advantages will be readily apparent to those skilled in the art from a reading of the detailed description of the preferred embodiments with reference to the accompanying drawings.

1 is an explanatory diagram showing an outline of a solution film-forming apparatus.
2 is a side view showing an outline of the first drying unit and the second drying unit.
3 is a perspective view showing the outline of the second drying unit.
4 is a perspective view showing an outline of a second blowing duct and a vertical nozzle.
5 is a sectional view taken along the line VV in Fig. 1 showing the outline of the second drying unit.
6 is a cross-sectional view schematically showing the tip of the vertical nozzle.
7 is a cross-sectional view showing the outline of the tip of the vertical nozzle.
8 is a perspective view showing an outline in which the vertical nozzle feeds out the second drying wind and the suction duct sucks the second drying wind.
9 is a cross-sectional view schematically showing the suction cross-sectional area formed between the vertical nozzles.
10 is a sectional view schematically showing a second drying unit having a first wind blocking plate.
11 is a sectional view schematically showing a second drying unit having a second wind blocking plate.
12 is a cross-sectional view schematically showing the second suction duct.
13 is a cross-sectional view showing the outline of the third suction duct.
Fig. 14 is a sectional view schematically showing the fourth suction duct. Fig.
15 is a perspective view showing an outline of a conventional drying apparatus.

(Solution film-forming method)

1, the solution film-forming equipment 10 has a flexible chamber 12, a clip tenter 13, a drying chamber 15, a cooling chamber 16, and a winding chamber 17. The flexible chamber 12 is provided with a flexible die 21, a flexible band 22, rotating rollers 23a and 23b, and a peeling roller 24.

The flexible band 22 is formed by connecting both ends in the longitudinal direction of a band-shaped band member, and is formed in an annular shape. The rotary rollers 23a and 23b, which are rotatable about the axis, are arranged so that their axial directions are horizontal. An annular flexible band 22 is wound around the rotary rollers 23a and 23b. When at least one of the rotary rollers 23a and 23b is rotated by the driving of a motor (not shown), the flexible band 22 wound around the rotary rollers 23a and 23b is circularly moved in a predetermined direction do.

The flexible die 21 is for continuously discharging the dope 28 containing the polymer and the solvent and has a slit outlet at the tip for discharging the dope 28. The flexible die 21 is positioned above the rotary roller 23a and the slit outlet is arranged so as to face the flexible band 22. [

The flexible die 21, the flexible band 22 and the rotating rollers 23a and 23b are preferably made of stainless steel and more preferably made of SUS316 because they have sufficient corrosion resistance and strength.

The dope 28 continuously flowing out from the slit outlet of the flexible die 21 forms a band-like flexible film 30 extending in the direction A as a result of extending on the flexible band 22. [ The flexible film 30 is transported in the A direction by the cyclic flexible band 22.

The first drying unit 31 to the third drying unit 33 are disposed in order in the vicinity of the flexible band 22 on the downstream side of the flexible die 21 in the A direction. The first drying unit 31 to the second drying unit 32 are provided above the rotary rollers 23a and 23b and the third drying unit 33 is provided below the rotary rollers 23a and 23b.

The first drying unit (31) to the third drying unit (33) send a predetermined drying air toward the flexible film (30). The solvent is evaporated from the flexible film 30 by the drying air from the first drying unit 31 to the third drying unit 33,

The peeling roller 24 is disposed in the vicinity of the flexible band 22 and between the third drying unit 33 and the flexible die 21. The flexible film 30 that has become self-supporting and ready to be conveyed is peeled off by the peeling roller 24 and guided to the downstream side of the flexible chamber 12 as the wet film 37.

A temperature controller 39 is connected to the rotating rollers 23a and 23b. The temperature control unit 39 incorporates a temperature control unit for controlling the temperature of the heat transfer medium. The temperature control unit 39 circulates the heat transfer medium adjusted to a desired temperature between the temperature regulating unit and the flow path formed in the rotating rollers 23a and 23b. By circulating the heat transfer medium, the temperature of the flexible band 22 can be maintained at a desired temperature.

The temperature of the rotating roller 23a is preferably lower than the temperature of the rotating roller 23b. The temperature of the rotating roller 23a is preferably 3 deg. C or more and 30 deg. C or less, for example. The temperature of the rotating roller 23b is preferably 20 deg. C or more and 50 deg. C or less, for example.

Although not shown, a condensing device for condensing the solvent contained in the atmosphere in the flexible chamber 12 and a recovery device for recovering the condensed solvent are provided to maintain the concentration of the solvent contained in the atmosphere in the flexible chamber 12 within a predetermined range .

It is also possible to provide a decompression chamber for sucking the gas on the upstream side in the moving direction of the flexible bead formed from the flexible die 21 to the flexible band 22 by the dope 28. [ It is preferable that the pressure reducing chamber is arranged so as to be adjacent to the flexible die 21 on the upstream side in the A direction than the flexible die 21. [ The pressure on the upstream side of the flexible bead can be made lower than the pressure on the downstream side of the flexible bead by suction of the gas by the decompression chamber. It is preferable that the pressure difference between the upstream side and the downstream side of the flexible bead is 10 Pa or more and 2000 Pa or less.

A clip tenter 13, a drying chamber 15, a cooling chamber 16, and a winding chamber 17 are provided in this order in the downstream of the flexible chamber 12. The moving part 51 between the flexible chamber 12 and the clip tenter 13 is provided with the blower 51a for applying the drying wind to the wet film 37 and the supporting roller 51b for supporting the wet film 37 do. The plurality of support rollers 51b are arranged in the conveying direction of the wet film 37. [ The support roller 51b is rotated about an axis by a motor (not shown). The support roller 51b supports the wet film 37 delivered from the flexible chamber 12 and guides the wet film 37 to the clip tenter 13. Although two support rollers 51b are arranged on the moving portion 51 in the drawing, the present invention is not limited to this, and three or more support rollers 51b may be arranged on the moving portion 51 .

The clip tenter 13 obtains the film 55 from the wet film 37 by subjecting the wet film 37 to a predetermined treatment. The film 55 delivered from the clip tenter 13 is delivered to the drying chamber 15.

The drying chamber 15 is provided with a plurality of rollers 57 on which a film 55 is wound and transported. The temperature and humidity of the atmosphere in the drying chamber 15 are controlled by an air conditioner (not shown). In the drying chamber 15, drying of the film 55 is performed. The adsorption / recovery device 58 is connected to the drying chamber 15. The adsorption recovery device 58 recovers the solvent evaporated from the film 55 by adsorption.

The cooling chamber 16 cools the film 55 until the temperature of the film 55 is approximately room temperature. The nulling bar 59, the nulling roller 60 and the edge cutting device 61 are provided in this order from the upstream side between the cooling chamber 16 and the winding chamber 17. The static electricity removing bar 59 performs a static eliminating process for removing electricity from the charged film 55 discharged from the cooling chamber 16. The knurling imparting roller 60 imparts a winding knurling to both ends of the film 55 in the width direction. The edge cutting device 61 cuts both ends in the width direction of the film 55 so that the knurling remains at both ends in the width direction of the film 55 after cutting.

The winding chamber 17 is provided with a winder 66 having a press roller 64 and a winding core 65. The film 55 sent to the winding chamber 17 is pressed by the press roller 64 And wound on the winding core 65 to be rolled.

As shown in Fig. 2, the first drying unit 31 has a first supply duct 31a and an inclined nozzle 31b. The first supply duct 31a is supplied with dry gas by a supply unit (not shown). The inclined nozzle 31b feeds the dry gas supplied to the first supply duct 31a as the first drying wind 401. The inclined nozzles 31b are provided on the lower surface of the first supply duct 31a and the plurality of inclined nozzles 31b are arranged in the A direction. The first drying air 401 having a predetermined temperature and a predetermined air velocity is delivered from the inclined nozzle 31b toward the flexible film 30 by the controller not shown and the solvent is evaporated from the flexible film 30.

It is preferable that the inclined nozzle 31b is arranged such that the direction of spraying of the drying wind 401 is an acute angle with the direction A. [ This makes it possible to prevent the drying air 401 discharged from the inclined nozzle 31b from flowing to the flexible die 21 side and causing the flexible beads formed between the flexible die 21 and the flexible band 22 to vibrate .

2 and 3, the second drying unit 32 includes a second supply duct 32a, a vertical nozzle 32b, and a suction duct 32c. The second supply duct 32a is supplied with the dry gas by the supply unit 32p. The vertical nozzle 32b sends the dry gas supplied to the second supply duct 32a as the second drying air 402. [ The suction duct 32c sucks the second drying wind 402.

As shown in Figs. 4 and 5, the second supply duct 32a is formed in a box shape and is installed so as to cover the flexible band 22. The vertical nozzles 32b are provided on the lower surface 32au of the second supply duct 32a and are arranged in the direction A on the lower surface 32au and protrude from the lower surface 32au toward the flexible film 30. [

A blowing slit 32bx through which the second drying air 402 is fed is formed at the tip of the vertical nozzle 32b. The blowing slit 32bx is elongated in the width direction of the flexible film 30 (hereinafter referred to as the B direction). The vertical nozzles 32b are installed such that the spraying direction of the drying wind 402 is substantially perpendicular to the direction A. [ As a result, the heat transfer coefficient and the mass transfer coefficient can be increased as compared with the case of inclining, and as a result, the drying efficiency can be increased.

The length L1 of the blowing slit 32bx in the direction B may be such that the drying wind 402 can be transmitted to the entire area of the flexible film 30 in the direction B. [ It is preferable that the length L1 of the blowing slit 32bx in the direction B is equal to or greater than the width of the flexible film 30, for example. It is also preferable that the length of the second supply duct 32a in the B direction is equal to or greater than the width of the flexible film 30.

As shown in Figs. 6 and 7, when the second drying air 402 is blown from the air blowing slit 32bx, the air in the vicinity of the air blowing slit 32bx is swept in. As a result, the air comes into contact with the flexible film 30 together with the second drying air 402 (see Fig. 6). As a result, it is difficult to adjust the drying conditions of the flexible film 30 by adjusting the conditions of the second drying air 402. Therefore, it is preferable to provide the folded back portion 32by at the periphery of the blowing slit 32bx in the vertical nozzle 32b (see FIG. 7). It is possible to prevent the air in the vicinity of the air blowing slit 32bx from coming into contact with the flexible film 30 together with the second drying air 402 due to the folded back portion 32by.

As shown in Figs. 5 and 8, it is preferable that the suction duct 32c is provided between the vertical nozzles 32b in the direction A and on both sides in the direction B than the vertical nozzles 32b. A second suction port 32cx for sucking the second drying air 402 is installed in the suction duct 32c. The second suction port 32cx is located above the blowing slit 32bx. It is preferable that the opening direction of the second suction port 32cx is the center side in the B direction.

Returning to Fig. 1, the third drying unit 33 uses the dry air supplied from the unillustrated supply unit as the third drying air 403. The third drying unit 33 is provided with a parallel nozzle 33a for sending out toward the flexible film 30 and a suction nozzle 33b for sucking the third drying wind 403. The parallel nozzle 33a and the suction nozzle 33b are disposed in order from the upstream side in the direction A to the downstream side. The parallel nozzle (33a) has a third supply port (33ax) for discharging the third drying air (403). The third supply port 33ax is opened toward the downstream side in the direction A. The suction nozzle 33b has a third suction port 33bx for suctioning the third drying air 403. The third suction port 33bx is opened toward the upstream side in the direction A. The third drying wind 403 can be made to flow substantially parallel to the flexible film 30 by the parallel nozzle 33a and the suction nozzle 33b.

Next, the operation of the present invention will be described. In the solution deposition apparatus 10, in the flexible chamber 12, a film forming step, a film drying step, and a peeling step are performed in sequence. In the clip tenter 13 and the drying chamber 15, a film drying process is performed, and in the winding chamber 17, a winding process is performed. Hereinafter, the details of each step will be described.

(Film forming step)

In the flexible chamber 12, the flexible die 21 continuously drains the dope 28 toward the flexible band 22 which circulates in the A direction. A flexible film (30) composed of a dope (28) is formed on the flexible band (22).

(Film drying process)

The flexible film 30 is transported in the direction A by the flexible band 22. The conveying speed is, for example, 10 m / min or more and 60 m / min or less. The first to third drying units 31 to 33 send predetermined drying winds 401 to 403 toward the flexible film 30 conveyed by the flexible band 22. The solvent is evaporated from the flexible film 30 by contact with the drying winds 401 to 403. The details of the film drying process will be described later.

(Peeling process)

The peeling roller 24 is peeled off as a wet film 37 and guided to the clip tenter 13 through the moving part 51. The peeling roller 24 peels off the flexible film 30 in a self-

The amount of the residual solvent in the flexible film 30 at the time of peeling is preferably 25 wt% or more and 50 wt% or less. In the present invention, the amount of solvent remaining in the flexible film (30) or each film is expressed as a residual solvent amount. In addition, the measurement method is calculated as {(x-y) / y} x 100 when a sample is taken from a target film and the weight of the sample is x and the weight after drying the sample is y.

(Film drying process and winding process)

The clip tenter 13 supports the both ends of the wet film 37 to transport the wet film 37. [ Further, the clip tenter 13 makes the wet film 37 come into contact with the drying air to evaporate the solvent from the wet film 37. [ As a result, the film 55 can be obtained from the wet film 37. The edge cutting device 47 cuts both ends of the film 55 delivered from the clip tenter 13. The film 55 cut at both ends passes through the drying chamber 15 and the cooling chamber 16 in order, and predetermined processing is performed in each chamber. The film 55 delivered from the cooling chamber 16 is subjected to a discharge treatment by the discharge bar 59, a knurling treatment by the knurling roller 60 and an edge cutting treatment by the edge cutting device 61 . The film 55 sent to the winding chamber 17 is wound on the winding core 65 while being pressed by the press roller 64 to form a roll.

Next, the details of the film drying process will be described. In the film drying step, the first film drying step by the first drying wind 401, the second film drying step by the second drying wind 402, the third film drying step by the third drying wind 403 In this order.

(First film drying step)

As shown in Figs. 1 and 2, the first drying unit 31 sends the first drying wind 401 to the flexible film 30. The solvent is evaporated from the flexible film 30 by contact with the first drying air 401. The first film drying step is preferably performed on the flexible film 30 in which the residual solvent amount is not less than 250 mass% and not more than 400 mass%, and more preferably, on the flexible film 30 in which the residual solvent amount is not less than 300 mass% and not more than 350 mass% . It is preferable that the temperature of the first drying wind 401 is 30 ° C or more and 80 ° C or less. In addition, the wind speed of the first drying wind 401 is preferably 5 m / sec to 25 m / sec.

(Second film drying step)

The vertical nozzle 32b feeds the second drying wind 402 toward the flexible film 30. The solvent is evaporated from the flexible film 30 by contact with the second drying air 402. It is preferable that the second film drying process is performed on the flexible film 30 in which the residual solvent amount is not less than 150 mass% and not more than 300 mass%. The temperature of the second drying wind 402 is preferably 30 ° C or more and 80 ° C or less. Also, the wind velocity of the second drying wind 402 is preferably 5 m / sec to 25 m / sec.

(Third film drying step)

The third drying unit 33 sends the third drying wind 403 to the flexible film 30. The solvent is evaporated from the flexible film 30 by contact with the third drying air 403. It is preferable that the third film drying process is performed on the flexible film 30 in which the residual solvent amount is 20 mass% or more and 150 mass% or less. The temperature of the third drying air 403 is preferably 40 ° C or more and 80 ° C or less. It is preferable that the wind speed of the third drying wind 403 is 5 m / sec to 20 m / sec.

8, the second suction port 32cx for sucking the second drying air 402 is provided between the vertical nozzles 32b in the A direction and on both sides in the B direction from the flexible film 30 The space located between the flexible film 30 and the vertical nozzles 32b arranged in the A direction between the second drying unit 32 and the second drying air 402 is located above the blowing slit 32bx, (Refer to Fig. 9).

As described above, since the second suction port 32cx is provided between the vertical nozzles 32b in the direction A and on both sides in the B direction with respect to the flexible film 30, the second suction The population (32 cx) does not need to be long-lasting. Therefore, according to the present invention, it is possible to uniformly suck the second drying wind 402 in the B direction.

It is also necessary to increase the suction amount in the second suction port 32cx in accordance with the elongation of the blowing slit 32bx. However, when the second suction port 32cx is close to the flexible film 30, Streaks or the like are formed in the direction in which the drying wind 402 flows, and the surface of the finally obtained film 55 is deteriorated. According to the present invention, since the second suction port 32cx is farther away from the flexible film 30 than the blowing slit 32bx, even if the suction amount is increased, the surface of the film 55 due to the suction of the drying air 402 Deterioration can be avoided.

Sectional area (hereinafter referred to as the exhaust cross sectional area) of the suction route 70 located between the adjacent vertical nozzles 23b between the second supply duct 32a and the flexible band 22 (= S1 / S2) of the opening area S2 of the blowing slit 32bx and the opening area S2 of the blowing slit 32bx is preferably 15 or more, and more preferably 25 or more.

The ratio CL1 / CL2 of the distance CL1 between the suction port 32cx and the flexible membrane 30 to the distance CL2 between the air blowing slit 32bx and the flexible membrane 30 is preferably 2 or more, Is more preferable.

10 and 11, the wind blocking plate 80 may be provided on both sides of the vertical nozzle 32b in the B direction. The wind blocking plate 80 may be provided so as to cover the entire portion exposed from both sides of the suction route in the direction B (see Fig. 10), or to cover a part of the portion exposed from both sides in the direction B (see Fig. 11) . By installing the wind blocking plate 80 in this way, it becomes difficult for the drying wind to flow out to the outside. Therefore, the pressure of the suction route can be kept higher than the pressure outside the second drying unit. By keeping the pressure of the suction route high, it is possible to prevent the air outside the second drying unit from flowing into the suction route. As a result, it becomes easy to maintain the drying conditions uniformly. Further, instead of the wind blocking plate 80, a wind blocking member such as a block shape may be used.

In this embodiment, the suction port 32cx is provided inside the direction B, but the present invention is not limited to this, and the suction port 32cx may be provided so as to face downward, that is, opposite to the flexible band 22 ).

In the above embodiment, a plurality of suction ducts 32c are provided between the vertical nozzles 32b, but the present invention is not limited to this. A plurality of suction ducts 32c may be provided integrally (see Figs. 13 and 14). In order to stabilize the flow of the second drying air 402, the supply of the second drying air 402 in the vertical nozzle 32b and the supply of the second drying air 402 in the suction duct 32c It is necessary to adjust the balance of suction. It is preferable that the suction duct 32c is provided for each of the vertical nozzles 32b from the viewpoint of ease of adjustment of the balance of supply and suction of the second drying air 402. [

Although the suction duct 32c is provided on both sides of the vertical nozzle 32b in the B direction in the above embodiment, the present invention is not limited to this and the suction duct 32c may be provided on both sides of the flexible film 30 in the B direction.

The flexible film 30 on the upper surface of the flexible band 22 is dried using the second drying unit 32. The present invention is not limited to this and the flexible film 22 on the lower surface of the flexible band 22 30) may be dried. In the case of the solution film-forming apparatus 10 shown in Fig. 1, the third drying unit 33 may be replaced by a structure having the same structure as that of the second drying unit 32. That is, the suction port 32cx may be located between the vertical nozzles 32b.

The film (55) obtained by the present invention can be used particularly for a retardation film or a polarizing plate protective film.

The width of the film 55 is preferably 600 mm or more, more preferably 1400 mm or more and 2500 mm or less. Further, the present invention is effective even when the width of the film 55 is larger than 2500 mm. The film thickness of the film 55 is preferably 30 占 퐉 or more and 120 占 퐉 or less.

The in-plane retardation (Re) of the film 55 is preferably 20 nm or more and 300 nm or less, and the retardation (Rth) in the thickness direction of the film 55 is preferably -100 nm or more and 300 nm or less.

The measurement method of in-plane retardation (Re) is as follows. The in-plane retardation (Re) was measured by measuring the retardation value measured from the vertical direction at 632.8 nm by an automatic birefringence meter (KOBRA21DH Oji Scientific Instruments.) At a temperature of 25 DEG C and a humidity of 60% RH for 2 hours . Re is expressed by the following equation.

 Re = | n1-n2 | xd

n1 represents the refractive index of the slow axis, n2 represents the refractive index of the fast axis 2, and d represents the thickness (film thickness) of the film.

A method of measuring the retardation in the thickness direction (Rth) is as follows. The sample film was conditioned at 25 ° C and 60% RH for 2 hours, measured with an ellipsometer (M150 manufactured by JASCO Corporation) at 632.8 nm from the vertical direction, and the retardation value Value was calculated from the extrapolated value by the following equation.

 Rth = {(n1 + n2) / 2-n3} xd

and n3 represents the refractive index in the thickness direction.

(Polymer)

In the above embodiment, the polymer to be a raw material of the polymer film is not particularly limited, and examples thereof include cellulose acylate and cyclic polyolefin.

(Cellulose acylate)

The acyl group used in the cellulose acylate of the present invention may be only one kind, or two or more kinds of acyl groups may be used. When two or more kinds of acyl groups are used, one of them is preferably an acetyl group. It is preferable that the ratio of the esterification of the hydroxyl group of the cellulose with the carboxylic acid, that is, the degree of substitution of the acyl group satisfies all of the following formulas (I) to (III). In the following formulas (I) to (III), A and B represent the degree of substitution of the acyl group, A represents the substitution degree of the acetyl group, and B represents the substitution degree of the acyl group of 3 to 22 carbon atoms . It is also preferable that at least 90% by weight of triacetyl cellulose (TAC) be particles of 0.1 mm to 4 mm.

(I) 2.0? A + B? 3.0

(II) 1.0? A? 3.0

(III) 0? B? 2.0

The total degree of substitution (A + B) of the acyl group is more preferably 2.20 or more and 2.90 or less, and particularly preferably 2.40 or more and 2.88 or less. The substitution degree B of the acyl group having 3 to 22 carbon atoms is more preferably 0.30 or more, and particularly preferably 0.5 or more.

Cellulose as a raw material of cellulose acylate may be obtained from any of linter and pulp.

The acyl group having 2 or more carbon atoms in the cellulose acylate of the present invention may be an aliphatic group or an aryl group and is not particularly limited. They may be, for example, an alkylcarbonyl ester, an alkenylcarbonyl ester or an aromatic carbonyl ester, an aromatic alkylcarbonyl ester, etc. of cellulose, and each may have a further substituted group. Preferable examples thereof include propionyl, butanoyl, pentanoyl, hexanoyl, octanoyl, decanoyl, dodecanoyl, tridecanoyl, tetradecanoyl, hexadecanoyl, octadecanoyl, iso-butanoyl, Nonyl, cyclohexanecarbonyl, oleoyl, benzoyl, naphthylcarbonyl, cinnamoyl and the like. Among them, propionyl, butanoyl, dodecanoyl, octadecanoyl, t-butanoyl, oleoyl, benzoyl, naphthylcarbonyl and cinnamoyl are more preferable, and propionyl and butanoyl are particularly preferable .

(solvent)

Examples of the solvent for preparing the dope include aromatic hydrocarbons such as benzene and toluene, halogenated hydrocarbons such as dichloromethane and chlorobenzene, alcohols such as methanol, ethanol, n-propanol, n- Diethyleneglycol, etc.), ketones (e.g., acetone, methyl ethyl ketone, etc.), esters (such as methyl acetate, ethyl acetate and acetic acid), and ethers (e.g., tetrahydrofuran, methyl Cellosolve, etc.) and the like. In the present invention, it means a polymer solution or dispersion obtained by dissolving or dispersing a dross polymer in a solvent.

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

However, in recent years, studies have also been made on the solvent composition when dichloromethane is not used for the purpose of minimizing the influence on the environment. For this purpose, an ether having 4 to 12 carbon atoms, an ether having 3 to 3 carbon atoms Ketones having 1 to 12 carbon atoms, esters having 3 to 12 carbon atoms, and alcohols having 1 to 12 carbon atoms are preferably used. They may be suitably mixed and used. Examples thereof include mixed solvents of methyl acetate, acetone, ethanol and n-butanol. These ethers, ketones, esters and alcohols may have a cyclic structure. Further, a compound having two or more functional groups of ether, ketone, ester and alcohol (i.e., -O-, -CO-, -COO- and -OH) can also be used as a solvent.

Further, details of the cellulose acylate are described in paragraphs [0140] to [0195] of Japanese Patent Application Laid-Open No. 2005-104148. Such a description is also applicable to the present invention. The additives such as a solvent and a plasticizer, a deterioration inhibitor, an ultraviolet absorber (UV), an optically anisotropic control agent, a retardation control agent, a dye, a matting agent, a stripping agent and a peeling accelerator are likewise described in Japanese Patent Application Publication No. 2005-104148 0196] to [0516].

[Example]

(Experiment 1)

A film 55 was formed in the solution film-forming equipment 10 shown in Fig. In the flexible chamber 12, the dope is softened on the flexible band 22 by using the flexible die 21, and the flexible film 30 is formed on the flexible band 22. [ The flexible width at this time was 1800 mm. Thereafter, the flexible film 30 was dried using the first to third drying units 31 to 33. 5) of the blowing slit 32bx in the B direction is 1800 mm, CL1 (see Fig. 9) is 150 mm, CL2 (see Fig. 9) See Fig. 9) was 150 mm. Then, the second drying wind 402 having a temperature of 50 占 폚 was ejected from the nozzle 32b at an air velocity of 20 m / sec.

(Experiment 2)

A film 55 was prepared in the same manner as in Experiment 1 except that CL1 was changed to 250 mm.

(Experiment 3)

A film 55 was prepared in the same manner as in Experiment 1 except that CL1 was changed to 350 mm.

(Experiment 4)

A film 55 was made in the same manner as in Experiment 1 except that the suction duct 32c shown in Fig. 14 was used and the CL1 was set to 250 mm.

(Experiment 5)

A film 55 was formed in the same manner as in Experiment 1 except that the drying unit 202 shown in Fig. 15 was used as the second drying unit 32.

(Experiment 6)

A film 55 was prepared in the same manner as in Experiment 5 except that the time required for the second film drying step was increased by 40 seconds.

(evaluation)

The film (55) obtained in Experiments 1 to 6 was evaluated for the following items.

1. Surface evaluation

It was examined whether or not the stripes could be observed in the film obtained by using the Schlieren method. Evaluation was based on the following criteria.

A: I could not observe the stripes.

B: Streaks were observed.

2. Drying efficiency

The amount of residual solvent (ZY1) in the flexible film at the time of peeling was measured.

3. Rth measurement

The retardation (Rth) in the thickness direction of the film was measured in the width direction, and the value of the unevenness (Rth) of the retardation (Rth) was calculated. ? Rth is the average of the measured values of the retardation (Rth) is Xav, the maximum value of the retardation (Rth) is Xmax, and the minimum value of the retardation (Rth) ) / Xav} x100.

The time required for the film drying process in Experiments 1 to 6 and the evaluation results are shown in Table 1.

Drying time
(second) Surface evaluation ZY1
(mass%) ΔRth Experiment 1 150 B 34 ± 7% Experiment 2 150 B 32 ± 5% Experiment 3 150 A 32 ± 2% Experiment 4 150 A 33 ± 2% Experiment 5 150 A 41 ± 2% Experiment 6 190 A 32 ± 2%

In Experiment 5, the amount of the residual solvent (ZY1) of the flexible film at the time of peeling was 41% by mass, and thus the obtained film showed nonuniformity of the ground axis due to the peeling tension. On the other hand, in Experiments 1 to 4, since the flexible film at the time of peeling was undergoing drying, there was no irregularity of the ground axis due to the peeling tension in the finally obtained film. It is necessary to increase the time required for the second film drying step in order that the amount ZY1 of the residual solvent of the flexible film at the time of peeling under the condition of Experiment 5 becomes as same as Experiments 1 to 4. From the results of Experiments 5 and 6, it can be said that according to the present invention, the second film drying process can be shortened by 40 seconds as compared with the conventional drying method. Therefore, according to the present invention, it is possible to dry the flexible film more efficiently than in the prior art.

Claims (11)

A duct disposed so as to face a band-shaped flexible membrane conveyed in the longitudinal direction,
A plurality of nozzles arranged in the transport direction of the flexible film,
An air blowing slit for sending the dry gas from the duct to the coarse membrane as dry air,
And a suction port for sucking the drying air blown out from the air blowing slit,
The flexible film comprising a polymer and a solvent;
The nozzle being installed to protrude from the duct toward the flexible film;
The blowing slit is formed at the tip of the nozzle so as to extend in the width direction of the flexible film;
Wherein the suction port is located between the nozzle and the nozzle in the carrying direction and the suction slit and the suction port are alternately arranged from the upstream side to the downstream side in the carrying direction and the suction port is arranged on both sides in the width direction of the flexible film And the distance between the suction port and the flexible film is larger than the distance between the air blowing slit and the flexible film. delete The method according to claim 1,
Wherein the suction port is formed from an upstream side of the at least one nozzle selected from the plurality of nozzles in the conveying direction to a downstream side of the at least one nozzle in the conveying direction. The method according to claim 1,
Wherein the flexible film is conveyed by a flexible band as a support, and the suction port faces the flexible band. The method according to claim 1,
And the suction port faces the center side in the width direction. The method according to claim 1,
Wherein the amount of the residual solvent in the flexible film to which the drying air is applied is 150 mass% or more and 350 mass% or less. The method according to claim 1,
Wherein the duct is installed above the flexible film. The method according to claim 1,
Wherein the width of the flexible film is 1500 mm or more and 2400 mm or less. A solution casting method for obtaining a film by evaporating the solvent from a flexible film containing a polymer and a solvent,
A step of delivering the drying air to the strip-shaped flexible film conveyed in the longitudinal direction; and a step of sucking the drying air through a suction port located on both sides in the width direction of the flexible film;
Wherein said blowing slit faces said flexible film, said blowing slit extends in a width direction of said flexible film;
The blowing slit and the suction port are alternately arranged from the upstream side to the downstream side in the carrying direction;
Wherein the drying air is sucked from a position distant from the flexible film and away from the blowing slit. 10. The method of claim 9,
Wherein the amount of the residual solvent in the flexible film that comes in contact with the drying air is 150 mass% or more and 350 mass% or less. 10. The method of claim 9,
Wherein the width of the flexible film is 1500 mm or more and 2400 mm or less.

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