Casting device of polyvinyl alcohol optical film

Abstract

The invention relates to the technical field of polyvinyl alcohol optical film production equipment, and discloses a polyvinyl alcohol optical film casting device which comprises a casting roller and a die head, the side, to be coated, of the casting roller is provided with a first cover body close to the die head, and a first cavity with an opening facing the casting roller is formed in the first cover body; the first cover body is connected with a vacuumizing assembly for forming a negative pressure environment in the first cavity; in the direction away from the die head, the top of the inner side of the first cover body forms a first inclined plane which is inclined downwards, and a first liquid collecting groove is formed in the low-position end of the first inclined plane; the top of the inner side of the first cover body forms the first inclined plane which is inclined downwards, the first liquid collecting groove is formed in the low-position end of the first inclined plane, and the low-molecular material condensed into drops is collected through the first liquid collecting groove, so that the low-molecular material is effectively prevented from dropping to the casting roller to influence the quality of the polyvinyl alcohol optical film.

Description

Technical Field

[0001] The present invention relates to the technical field of polyvinyl alcohol optical film production equipment, and specifically relates to a casting device for polyvinyl alcohol optical films. Background Art

[0002] Polyvinyl alcohol optical film is a key material for manufacturing polarizers. To ensure that the polarizer has good light transmittance and polarization degree, it is required that the polyvinyl alcohol optical film has a uniform thickness, a flat film surface, and no defects such as bubbles and holes. The production process of polyvinyl alcohol optical film is generally: polyvinyl alcohol → homogenization → water washing → dissolution → extrusion → casting → drying and forming → polyvinyl alcohol optical film. In the extrusion and casting processes, the bubbles in the polyvinyl alcohol solution are removed by an extruder, and the polyvinyl alcohol solution is cast onto a casting roller through a die head. Hot water is passed through the casting roller to pre-dry the polyvinyl alcohol optical film.

[0003] In the existing casting process, due to a certain gap between the die head and the casting roller, the air at this gap easily enters the interior of the unformed film and forms bubbles, resulting in the quality of the film being affected. To solve this problem, the personnel in this field proposed a vacuum pumping scheme to reduce the amount of air at the aforementioned gap, reduce the probability of air entering the unformed film to reduce the formation of bubbles, and at the same time, this scheme is also beneficial to the adhesion between the unformed film and the casting roller, thereby facilitating the improvement of the flatness of the film.

[0004] The inventor of the present application found that the casting of polyvinyl alcohol solution is also suitable for arranging a cover body near the die head above the casting roller. The cover body has a cavity with an opening facing the casting roller, and the cavity is evacuated to prevent the air between the die head and the casting roller from entering the unformed polyvinyl alcohol optical film and forming bubbles. However, when the polyvinyl alcohol solution is pre-dried by the casting roller, the low molecular materials (such as glycerol) contained in the polyvinyl alcohol solution will form volatiles. Although the vacuum pumping device can evacuate part of the volatiles, some volatiles still condense at the top position of the cover body. When the volatiles condense into drops, they are likely to drip onto the casting roller, affecting the quality of the polyvinyl alcohol optical film. Summary of the Invention

[0005] The purpose of the present invention is to provide a casting device for polyvinyl alcohol optical films, which can solve the problem that the low molecular materials in the polyvinyl alcohol solution condense into drops and then drip onto the casting roller, thereby affecting the quality of the polyvinyl alcohol optical film.

[0006] To achieve the above object, the present invention provides a casting device for a polyvinyl alcohol optical film, which includes a casting roller and a die head for supplying a polyvinyl alcohol solution to the roller surface of the casting roller. A first cover body is arranged on the film coating side of the casting roller close to the die head. The first cover body forms a first cavity with an opening facing the casting roller, and a vacuum pumping assembly is connected to the first cover body to form a negative pressure environment in the first cavity;

[0007] In the direction away from the die head, the inner top of the first cover body is formed as a first inclined surface that slopes downward, and a first liquid collecting groove is arranged at the lower end of the first inclined surface.

[0008] Optionally, the inclination angle of the first inclined surface relative to the horizontal direction is 25 - 35°.

[0009] Optionally, the first cover body includes a top plate extending along the length direction of the casting roller. A first side plate is arranged on one side of the top plate close to the die head, and a second side plate is arranged on the other side of the top plate away from the die head. End plates are respectively arranged between the two ends of the first side plate and the second side plate; in the direction away from the die head, the top plate slopes downward to form the first inclined surface.

[0010] Optionally, a bottom plate is arranged on the upper side edge of the second side plate, and the bottom plate extends obliquely downward in the direction away from the second side plate. A baffle is arranged on the outer side of the bottom plate and extends upward. The upper end of the baffle is fixedly connected to the lower end of the top plate, and the bottom plate and the baffle enclose to form the first liquid collecting groove;

[0011] A liquid discharge port is arranged on the baffle, and a plug is detachably arranged at the liquid discharge port to open and close the liquid discharge port.

[0012] Optionally, a heating unit is arranged on the first cover body to heat the first inclined surface.

[0013] Optionally, the heating unit includes a heating cavity arranged on the inner top of the first cover body, and the first cover body has a water inlet and a water outlet communicating with the heating cavity;

[0014] Or, the heating unit includes an electric heating sheet arranged on the outer top of the first cover body.

[0015] Optionally, a second cover body is arranged on the film coating side of the casting roller close to the die head. The second cover body forms a second cavity with an opening facing the casting roller. The second cover body is connected to the vacuum pumping assembly to form a negative pressure environment in the second cavity, and the negative pressure in the second cavity is less than the negative pressure in the first cavity;

[0016] In the direction away from the die head, the inner top of the second cover body is formed as a second inclined surface that slopes downward, and a second liquid collecting groove is provided at the lower end of the second inclined surface.

[0017] Optionally, the vacuum pumping assembly includes an air extraction fan, a first air extraction pipe disposed between the air extraction fan and the first cover body, and a second air extraction pipe disposed between the air extraction fan and the second cover body;

[0018] The air extraction fan is configured to be able to form a first negative pressure environment in the first cavity of the first cover body through the first air extraction pipe, and form a second negative pressure environment in the second cavity of the second cover body through the second air extraction pipe.

[0019] Optionally, a plurality of the first air extraction pipes and the second air extraction pipes are respectively provided. The plurality of first air extraction pipes are spaced along the length direction of the first cover body, and the plurality of second air extraction pipes are spaced along the length direction of the second cover body;

[0020] A first air extraction current collecting assembly is disposed between the plurality of first air extraction pipes and the air extraction fan. The first air extraction current collecting assembly includes a first air collecting cover and a first air collecting pipe. The first air collecting cover is respectively connected to the plurality of first air extraction pipes, and the first air collecting pipe is used to connect the first air collecting cover and the air extraction opening of the air extraction fan;

[0021] A second air extraction current collecting assembly is disposed between the plurality of second air extraction pipes and the air extraction fan. The second air extraction current collecting assembly includes a second air collecting cover and a second air collecting pipe. The second air collecting cover is respectively connected to the plurality of second air extraction pipes, and the second air collecting pipe is used to connect the second air collecting cover and the air extraction opening of the air extraction fan.

[0022] Optionally, both sides of the upper surfaces of the first air collecting cover and the second air collecting cover are inclined upward toward their respective middle parts. The first air collecting pipe is connected to the middle part of the upper surface of the first air collecting cover, and the second air collecting pipe is connected to the middle part of the upper surface of the second air collecting cover.

[0023] In the technical solution provided by the present invention, by providing a first cover body close to the die head on the side of the casting roller to be coated with a film, the first cover body forms a first cavity with an opening facing the casting roller. When the vacuum pumping assembly forms a negative pressure environment in the first cavity, the first cover body can suck the gap between the casting roller and the die head, preventing the air at this gap from entering the interior of the unformed polyvinyl alcohol optical film and forming bubbles, and at the same time facilitating the adhesion of the polyvinyl alcohol optical film to the casting roller, effectively improving the flatness of the polyvinyl alcohol optical film.

[0024] The inventors of the present application found that after the low-molecular materials in the polyvinyl alcohol solution volatilize, they are likely to condense on the inner top of the first cover. According to the technical solution provided by the present invention, the inner top of the first cover is formed into a first inclined surface that slopes downward, and a first liquid collecting groove is provided at the lower end of the first inclined surface. The low-molecular materials that condense into drops are collected through the first liquid collecting groove, effectively preventing the low-molecular materials from dripping onto the casting roller and affecting the quality of the polyvinyl alcohol optical film. Description of the Drawings

[0025] Figure 1 is a schematic diagram of a casting device for a polyvinyl alcohol optical film provided by the present invention;

[0026] Figure 2 is Figure 1 an enlarged schematic diagram of the position of the die head and the casting roller in

[0027] Figure 3 is a front view of the first air extraction and liquid collection assembly in the present invention;

[0028] Figure 4 is a schematic diagram of another casting device for a polyvinyl alcohol optical film provided by the present invention;

[0029] Figure 5 is Figure 4 an enlarged schematic diagram of the position of the die head and the casting roller in.

[0030] Description of the Reference Numerals

[0031] 10. Casting roller; 10a. Side to be coated; 10b. Coated side; 20. Die head; 30. First cover; 301. First cavity; 302. First inclined surface; 303. First liquid collecting groove; 31. Top plate; 32. First side plate; 33. Second side plate; 331. Bottom plate; 332. Baffle; 333. Plug; 34. End plate; 40. Second cover; 401. Second cavity; 402. Second inclined surface; 403. Second liquid collecting groove; 50. Exhaust fan; 51. First exhaust pipe; 52. Second exhaust pipe; 53. First air extraction and liquid collection assembly; 531. First air collection cover; 532. First air collection pipe; 54. Second air extraction and liquid collection assembly; 541. Second air collection cover; 542. Second air collection pipe. Detailed Embodiments

[0032] The following detailed description of the specific embodiments of the present invention is provided in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are only for the purpose of illustrating and explaining the present invention, and are not intended to limit the present invention.

[0033] Please refer to Figure 1 and Figure 2, the present invention provides a casting device for a polyvinyl alcohol optical film, which includes a casting roller 10 and a die head 20 for supplying a polyvinyl alcohol solution to the roller surface of the casting roller 10. A first cover 30 is provided on the film-covering side 10a of the casting roller 10 close to the die head 20. The first cover 30 forms a first cavity 301 with an opening facing the casting roller 10. A vacuum pumping assembly is connected to the first cover 30 to form a negative pressure environment in the first cavity 301; in the direction away from the die head 20, the inner top of the first cover 30 is formed as a first inclined surface 302 that slopes downward, and a first liquid collecting groove 303 is provided at the lower end of the first inclined surface 302.

[0034] In the technical solution provided by the present invention, by providing the first cover 30 close to the die head 20 on the film-covering side 10a of the casting roller 10, and the first cover 30 forms a first cavity 301 with an opening facing the casting roller 10. When the vacuum pumping assembly forms a negative pressure environment in the first cavity 301, the first cover 30 can suck the gap between the casting roller 10 and the die head 20, preventing air at this gap from entering the interior of the unformed polyvinyl alcohol optical film and forming bubbles, and at the same time facilitating the adhesion of the polyvinyl alcohol optical film to the casting roller 10, effectively improving the flatness of the polyvinyl alcohol optical film.

[0035] The inventor of the present application found that the low-molecular materials in the polyvinyl alcohol solution are prone to condense on the inner top of the first cover 30 after volatilization. According to the technical solution provided by the present invention, by forming the inner top of the first cover 30 as a first inclined surface 302 that slopes downward, and providing a first liquid collecting groove 303 at the lower end of the first inclined surface 302, the low-molecular materials condensed into drops are collected by the first liquid collecting groove 303, effectively preventing the low-molecular materials from dripping onto the casting roller 10 and affecting the quality of the polyvinyl alcohol optical film.

[0036] In the present invention, by forming the inner top of the first cover 30 as a first inclined surface 302 that slopes downward, the low-molecular materials condensed into drops on the inner top can move along the first inclined surface 302 to the lower end under the action of their own weight, preventing them from dripping onto the casting roller 10 and affecting the quality of the polyvinyl alcohol optical film. In some embodiments, in order to ensure that the low-molecular materials condensed into drops can stably slide to the lower end of the first inclined surface 302, the inclination angle of the first inclined surface 302 with respect to the horizontal direction is 25-35°.

[0037] In the technical solution provided by the present invention, the first cover 30 is arranged close to the die head 20. When the vacuum pumping assembly forms a negative pressure environment in the first cavity 301 of the first cover 30, the first cover 30 forms a negative pressure environment at a position close to the die head 20 through its opening, thereby preventing air from entering the interior of the unfixed polyvinyl alcohol optical film through the gap between the die head 20 and the casting roller 10, and further avoiding the problem of air bubbles being generated in the polyvinyl alcohol optical film. In some embodiments, the first cover 30 includes a top plate 31 extending along the length direction of the casting roller 10. A first side plate 32 is arranged on one side of the top plate 31 close to the die head 20, and a second side plate 33 is arranged on the side of the top plate 31 away from the die head 20. End plates 34 are respectively arranged between the two ends of the first side plate 32 and the second side plate 33; in the direction away from the die head 20, the top plate 31 is inclined downward to form the first inclined surface 302. Further, the first side plate 32 is arranged in a bent shape and is arranged adjacent to the side part of the die head 20. In this way, the suction effect of the negative pressure environment in the first cavity 301 on the gap between the die head 20 and the casting roller 10 is improved, effectively avoiding the problem that air at this gap enters the interior of the unfixed film and causes air bubbles.

[0038] In the present invention, the first liquid collecting tank 303 is arranged at the low position end of the first inclined surface 302 for collecting low molecular materials, avoiding the problem that the quality of the polyvinyl alcohol optical film is affected due to the low molecular materials dripping onto the casting roller 10. In some embodiments, a bottom plate 331 is arranged on the upper side edge of the second side plate 33. The bottom plate 331 extends obliquely downward in a direction away from the second side plate 33. A baffle 332 extends upward on the outer side of the bottom plate 331. The upper end of the baffle 332 is fixedly connected to the low position end of the top plate 31. The bottom plate 331 and the baffle 332 enclose to form the first liquid collecting tank 303; a liquid discharge port is arranged on the baffle 332, and a plug 333 is detachably arranged at the liquid discharge port for opening and closing the liquid discharge port. After using for a period of time, pull out the plug 333 to discharge the low molecular materials accumulated in the first liquid collecting tank 303 through the liquid discharge port; after the low molecular materials are discharged, reinsert the plug 333 to resume use.

[0039] In some embodiments, a heating unit is arranged on the first cover 30 for heating the first inclined surface 302. The inventor of the present application also found that by heating the first inclined surface 302, it is also possible to effectively reduce the condensation of low molecular materials into drops at this position, and further enable more low molecular materials to be evacuated by the vacuum pumping assembly, avoiding the risk of affecting the quality of the polyvinyl alcohol optical film due to their staying in the first cavity 301 of the first cover 30.

[0040] It can be understood that the heating unit can adopt any suitable form as long as it can heat the first inclined surface 302. In some embodiments, the heating unit includes a heating chamber provided at the inner top of the first cover 30, and the first cover 30 has a water inlet and a water outlet communicating with the heating chamber; in specific use, by the water inlet and the water outlet, a flowing hot fluid is formed in the heating chamber of the first cover 30 to achieve heating of the first inclined surface 302. This solution has a lower cost and only requires leading a pipeline from the hot water pipeline of the casting roller 10.

[0041] In some embodiments, the heating unit includes an electric heating sheet provided at the outer top of the first cover 30, and the first inclined surface 302 can be heated by energizing the electric heating sheet. This solution can conveniently and quickly control the temperature of the first inclined surface 302.

[0042] In some embodiments, in combination Figure 4 and Figure 5 As shown, a second cover 40 is provided on the film coating side 10b of the casting roller 10 close to the die head 20. The second cover 40 forms a second cavity 401 with an opening facing the casting roller 10. The second cover 40 is connected to the vacuum pumping assembly to form a negative pressure environment in the second cavity 401, and the negative pressure in the second cavity 401 is less than the negative pressure in the first cavity 301; in the direction away from the die head 20, the inner top of the second cover 40 is formed as an inclined second inclined surface 402 that slopes downward, and a second liquid collecting groove 403 is provided at the low position end of the second inclined surface 402.

[0043] The inventors of the present application found that by providing a second cavity 401 with a negative pressure less than that of the first cavity 301 on the film coating side 10b of the casting roller 10, while not affecting the vacuum pumping to make the polyvinyl alcohol optical film better adhere to the casting roller 10, the volatiles in the polyvinyl alcohol solution are evacuated more quickly, thereby significantly improving the pre-drying efficiency of the polyvinyl alcohol solution. By providing an inclined second inclined surface 402 that slopes downward at the inner top of the second cover 40 and providing a second liquid collecting groove 403 at the low position end of the second inclined surface 402, the low molecular weight materials condensed into drops on the second inclined surface 402 are collected by the second liquid collecting groove 403, effectively preventing the low molecular weight materials from dripping onto the casting roller 10 and affecting the quality of the polyvinyl alcohol optical film.

[0044] It can be understood that the setting method of the second liquid collecting groove 403 can refer to the setting method of the first liquid collecting groove 303 on the first cover 30, and the present invention will not elaborate here.

[0045] In the present invention, the negative pressure in the second cavity 401 being less than the negative pressure in the first cavity 301 can be achieved by any suitable means. For example, the pipe connecting the second cover body 40 to the vacuum pumping device is set thinner than the pipe connecting the first cover body 30 to the vacuum pumping device, or valves are directly provided on the two groups of pipes respectively to control the negative pressures in the second cavity 401 and the first cavity 301.

[0046] In the present invention, the function of the vacuum pumping assembly is to create a negative pressure environment in the first cavity 301 of the first cover body 30 and the second cavity 401 of the second cover body 40. As a specific implementation manner of the vacuum pumping assembly, the vacuum pumping assembly includes an air extraction fan 50, a first air extraction pipe 51 disposed between the air extraction fan 50 and the first cover body 30, and a second air extraction pipe 52 disposed between the air extraction fan 50 and the second cover body 40; the air extraction fan 50 is configured to be able to create a first negative pressure environment in the first cavity 301 of the first cover body 30 through the first air extraction pipe 51, and create a second negative pressure environment in the second cavity 401 of the second cover body 40 through the second air extraction pipe 52. It can be understood that the negative pressure of the first negative pressure environment is greater than the negative pressure of the second negative pressure environment, ensuring the stable fitting of the unformed polyvinyl alcohol optical film to the casting roller 10.

[0047] In some embodiments, as shown in Figure 3 FIG. 8, a plurality of the first air extraction pipes 51 and the second air extraction pipes 52 are respectively provided. The plurality of first air extraction pipes 51 are spaced along the length direction of the first cover body 30, and the plurality of second air extraction pipes 52 are spaced along the length direction of the second cover body 40; a first air extraction flow collecting assembly 53 is disposed between the plurality of first air extraction pipes 51 and the air extraction fan 50. The first air extraction flow collecting assembly 53 includes a first air collecting cover 531 and a first air collecting pipe 532. The first air collecting cover 531 is respectively connected to the plurality of first air extraction pipes 51, and the first air collecting pipe 532 is used for connecting the first air collecting cover 531 and the air extraction port of the air extraction fan 50; a second air extraction flow collecting assembly 54 is disposed between the plurality of second air extraction pipes 52 and the air extraction fan 50. The second air extraction flow collecting assembly 54 includes a second air collecting cover 541 and a second air collecting pipe 542. The second air collecting cover 541 is respectively connected to the plurality of second air extraction pipes 52, and the second air collecting pipe 542 is used for connecting the second air collecting cover 541 and the air extraction port of the air extraction fan 50. Further, the first air collecting pipe 532 and the second air collecting pipe 542 can be connected to the air extraction port of the air extraction fan 50 through a main pipe.

[0048] In some embodiments, both sides of the upper surfaces of the first air collecting hood 531 and the second air collecting hood 541 are inclined upwardly towards their respective middles, the first air collecting pipe 532 is connected to the middle of the upper surface of the first air collecting hood 531, and the second air collecting pipe 542 is connected to the middle of the upper surface of the second air collecting hood 541. In this way, it can be ensured that the vacuum pumping assembly forms a stable suction in the first cavity 301 and the second cavity 401, and an uneven suction effect in the length direction of the first housing 30 or the second housing 40 is avoided.

[0049] The preferred embodiments of the present invention have been described in detail above in conjunction with the accompanying drawings. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention. To avoid unnecessary repetition, the present invention will not separately describe various possible combinations. But these simple modifications and combinations should also be regarded as the content disclosed by the present invention and all fall within the protection scope of the present invention.

Claims

1. A casting device for a polyvinyl alcohol optical film, characterized in that, it includes a casting roller (10) and a die head (20) for supplying a polyvinyl alcohol solution to the roller surface of the casting roller (10). A first cover body (30) is arranged on the film-covered side (10a) of the casting roller (10) close to the die head (20). The first cover body (30) forms a first cavity (301) with an opening facing the casting roller (10). A vacuum pumping assembly is connected to the first cover body (30) for forming a negative pressure environment in the first cavity (301); In the direction away from the die head (20), the inner top of the first cover body (30) is formed as a first inclined surface (302) that slopes downward. A first liquid collecting tank (303) is arranged at the lower end of the first inclined surface (302).

2. The casting device for a polyvinyl alcohol optical film according to claim 1, characterized in that, the inclination angle of the first inclined surface (302) relative to the horizontal direction is 25-35°.

3. The casting device for a polyvinyl alcohol optical film according to claim 1, characterized in that, the first cover body (30) includes a top plate (31) extending along the length direction of the casting roller (10). A first side plate (32) is arranged on one side of the top plate (31) close to the die head (20). A second side plate (33) is arranged on the side of the top plate (31) away from the die head (20). End plates (34) are respectively arranged between the two ends of the first side plate (32) and the second side plate (33); In the direction away from the die head (20), the top plate (31) slopes downward to form the first inclined surface (302).

4. The casting device for a polyvinyl alcohol optical film according to claim 3, characterized in that, a bottom plate (331) is arranged on the upper side edge of the second side plate (33). The bottom plate (331) extends obliquely downward in the direction away from the second side plate (33). A baffle (332) extends upward on the outside of the bottom plate (331). The upper end of the baffle (332) is fixedly connected to the lower end of the top plate (31). The bottom plate (331) and the baffle (332) enclose to form the first liquid collecting tank (303); a liquid discharge port is arranged on the baffle (332), and a plug (333) is detachably arranged at the liquid discharge port for opening and closing the liquid discharge port.

5. The casting device for a polyvinyl alcohol optical film according to claim 1, characterized in that, a heating unit is arranged on the first cover body (30) for heating the first inclined surface (302).

6. The casting device for a polyvinyl alcohol optical film according to claim 5, characterized in that, the heating unit includes a heating cavity arranged on the inner top of the first cover body (30). The first cover body (30) has a water inlet and a water outlet communicated with the heating cavity; Or, the heating unit includes an electric heating sheet arranged on the outer top of the first cover body (30).

7. The casting device for a polyvinyl alcohol optical film according to any one of claims 1-6, characterized in that, a second cover body (40) close to the die head (20) is arranged on the film covering side (10b) of the casting roller (10). A second cavity (401) with an opening facing the casting roller (10) is formed in the second cover body (40). The second cover body (40) is connected to the vacuum pumping assembly for forming a negative pressure environment in the second cavity (401), and the negative pressure in the second cavity (401) is less than the negative pressure in the first cavity (301); in the direction away from the die head (20), the inner top of the second cover body (40) is formed as a second inclined surface (402) that slopes downward. A second liquid collecting groove (403) is arranged at the lower end of the second inclined surface (402).

8. The casting device for a polyvinyl alcohol optical film according to claim 7, characterized in that, the vacuum pumping assembly includes an air extraction fan (50), a first air extraction pipe (51) arranged between the air extraction fan (50) and the first cover body (30), and a second air extraction pipe (52) arranged between the air extraction fan (50) and the second cover body (40); the air extraction fan (50) is arranged to be able to form a first negative pressure environment in the first cavity (301) of the first cover body (30) through the first air extraction pipe (51), and form a second negative pressure environment in the second cavity (401) of the second cover body (40) through the second air extraction pipe (52).

9. The casting device for a polyvinyl alcohol optical film according to claim 8, characterized in that, a plurality of the first air extraction pipes (51) and the second air extraction pipes (52) are respectively arranged. The plurality of first air extraction pipes (51) are arranged at intervals along the length direction of the first cover body (30), and the plurality of second air extraction pipes (52) are arranged at intervals along the length direction of the second cover body (40); a first air extraction flow collecting assembly (53) is arranged between the plurality of first air extraction pipes (51) and the air extraction fan (50). The first air extraction flow collecting assembly (53) includes a first air collecting cover (531) and a first air collecting pipe (532). The first air collecting cover (531) is respectively connected to the plurality of first air extraction pipes (51), and the first air collecting pipe (532) is used for connecting the first air collecting cover (531) and the air extraction port of the air extraction fan (50); a second air extraction flow collecting assembly (54) is arranged between the plurality of second air extraction pipes (52) and the air extraction fan (50). The second air extraction flow collecting assembly (54) includes a second air collecting cover (541) and a second air collecting pipe (542). The second air collecting cover (541) is respectively connected to the plurality of second air extraction pipes (52), and the second air collecting pipe (542) is used for connecting the second air collecting cover (541) and the air extraction port of the air extraction fan (50).

10. The casting device for a polyvinyl alcohol optical film according to claim 9, characterized in that, Both sides of the upper surfaces of the first air collecting hood (531) and the second air collecting hood (541) are inclined upward toward their respective middles. The first air collecting pipe (532) is connected to the middle of the upper surface of the first air collecting hood (531), and the second air collecting pipe (542) is connected to the middle of the upper surface of the second air collecting hood (541).

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