Optical film feeding method

Abstract

To provide a feeding method of an optical film hardly causing a poor appearance in an optical film.SOLUTION: A method is for feeding an optical film F0 in a path line of a conveyance facility, in a manufacturing facility of the optical film F0 having the conveyance facility equipped with a plurality of conveyance rollers R11a-R15 and a plurality of processing tanks 2. In the method, after immersing the optical film F0 in a processing bath L inside a processing tank 2 (for instance, a swelling processing tank 21) located in an upstream side in a conveyance direction of the optical film F0, the optical film F0 is fed to the conveyance rollers R2 and R12 arranged at a processing tank 2 (for instance, a dyeing processing tank 22) located at a downstream side in the conveyance direction of the optical film F0.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a method for passing an optical film such as a raw film of a polarizing film, and in particular to a method for passing an optical film that is less likely to cause defects in the appearance of the optical film. [Background technology]

[0002] Conventionally, optical films have been used in image display devices such as liquid crystal display devices and organic EL display devices. Examples of optical films include polarizing films (polarizers), polarizing plates including polarizing films, retardation films, and anti-glare films. Optical films are usually manufactured using long strip-shaped raw film. Usually, the raw film is conveyed in the longitudinal direction by a conveying device having conveying rollers, and various processes are sequentially performed to produce a long strip-shaped optical film as a product (see, for example, Patent Documents 1 and 2). The long strip-shaped optical film is cut to a size according to the application, and used in an image display device or the like. Hereinafter, in this specification, the term "optical film" refers not only to optical films as products, but also to raw films and films in intermediate products.

[0003] For example, when the optical film is a raw film of a polarizing film, the raw film is transported by a transport facility and sequentially immersed in treatment baths in a plurality of treatment tanks, whereby the raw film is dyed with a dichroic substance such as iodine or a dichroic dye and uniaxially stretched (see, for example, Patent Document 2).

[0004] When starting the production of optical film products, it is necessary to perform the task of passing the optical film along a pass line (the transport path of the optical film determined by the position of the transport rollers) of the transport equipment having the above-mentioned transport rollers. The paper passing is a task in which a person manually pulls the leading end of the optical film, hangs the optical film on the transport rollers, and aligns the optical film with the pass line.

[0005] For example, when the optical film is a raw film of a polarizing film, it is not possible to splice one raw film and the next raw film (connecting the rear end of the first raw film and the leading end of the next raw film) and transport them. Because the raw film of the polarizing film is stretched in the treatment bath, the spliced ​​part will come off even if it is spliced ​​with a general tape or laser welding. Therefore, every time the raw film wound around the pay-out roller runs out, the raw film wound around the next pay-out roller is manually fed.

[0006] Conventionally, when passing an optical film through the above-mentioned processing tank, it has been common to pass the optical film through a conveying roller provided in the processing tank without immersing it in the processing bath in the processing tank, and to immerse the optical film in the processing bath after the paper passing operation is completed. Specifically, it has been common to pass the optical film through the processing tank without immersing it in the processing bath in a state where a lifting roller, which is a conveying roller that can be raised and lowered in the processing tank, is raised above the liquid level of the processing bath in the processing tank, and to lower the lifting roller to immerse the optical film in the processing bath after the paper passing operation is completed. In the above-mentioned conventional paper-passing method, the optical film may be rubbed or cut. In particular, the thinner the optical film, such as the original film of the polarizing film, the more likely it is that the optical film will be rubbed or cut during the paper-passing operation. Even if the leading edge of the optical film is rubbed or cut and damaged, no particular problem will occur as long as the leading edge that has been subjected to the paper-passing operation is not used as a product. However, problems may occur due to the wear and tear of the optical film, such as the generation of unevenness on the surface of the conveying roller (usually made of rubber material) and the generation of foreign matter made of the material forming the optical film or the rubber material on the surface of the conveying roller. Specifically, once unevenness occurs on the surface of the conveying roller, it cannot be fixed until it is replaced, so the unevenness on the surface of the conveying roller may be transferred to the optical film during normal conveyance after the paper feed operation is completed, resulting in a defective appearance of the optical film. In addition, the foreign matter generated floats for a long time in the atmosphere or treatment tank in which the optical film conveying equipment is installed, and the foreign matter may adhere to the optical film, resulting in a defective appearance of the optical film. For example, even if the unevenness or foreign matter is only a few tens of μm in size, if it is visible, the optical film will have a defective appearance and may lead to a decrease in the product yield. For this reason, it is desired to prevent the occurrence of defective appearance of the optical film caused by wear and tear of the optical film during the paper feed operation as much as possible. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2013-248590 A [Patent Document 2] JP 2004-341515 A Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention has been made to solve the problems of the conventional techniques as described above, and an object of the present invention is to provide a method for passing an optical film which is less likely to cause defects in the appearance of the optical film. [Means for solving the problem]

[0009] In order to solve the above problems, the present inventors conducted extensive research and found that one of the causes of the abrasion and tearing during paper-passing operation is the hardness of the optical film. Specifically, it was found that the optical film was hard because it was not immersed in the treatment bath of the treatment tank during paper-passing operation, and the optical film was easily abraded or cut due to friction with the conveying roller during paper-passing operation.

[0010] The present invention has been completed based on the above-mentioned findings of the present inventors. That is, in order to solve the above-mentioned problems, the present invention provides a method for passing an optical film through a pass line of a conveying facility having a plurality of conveying rollers in an optical film manufacturing facility including a plurality of treatment tanks, the method comprising: immersing the optical film in a treatment bath in a treatment tank located on the upstream side of a conveying direction of the optical film, and then passing the optical film through conveying rollers provided in the treatment tank located on the downstream side of the conveying direction of the optical film; the manufacturing facility includes, as the plurality of treatment tanks, a cleaning treatment tank that performs a cleaning treatment on the optical film, a stretching treatment tank that performs a stretching treatment on the optical film, and an upstream treatment tank that performs a predetermined treatment on the optical film, in that order from the downstream side of the conveying direction of the optical film, and among the conveying rollers provided in the stretching treatment tank, a lifting roller that is a conveying roller that can be raised and lowered within the stretching treatment tank is provided as a lifting roller. the optical film is passed through the conveying rollers provided in the stretching treatment tank and the cleaning treatment tank without being immersed in the treatment bath in the stretching treatment tank and the treatment bath in the cleaning treatment tank in a state in which a lowering roller is raised above the liquid level of the treatment bath in the stretching treatment tank, and a lifting roller, which is a conveying roller that can be raised and lowered in the cleaning treatment tank, among the conveying rollers provided in the cleaning treatment tank, is raised above the liquid level of the treatment bath in the cleaning treatment tank, and then the lifting roller provided in the cleaning treatment tank is lowered below the liquid level of the treatment bath in the cleaning treatment tank to immerse the optical film in the treatment bath in the cleaning treatment tank, and then the lifting roller provided in the stretching treatment tank is lowered below the liquid level of the treatment bath in the stretching treatment tank to immerse the optical film in the treatment bath in the stretching treatment tank. The pass line refers to the transport path of the optical film that is determined by the position of the transport rollers, and the paper passing refers to the task of a person manually pulling the leading end of the optical film, wrapping the optical film around the transport rollers, and aligning the optical film along the pass line.

[0011] According to the present invention, the optical film is immersed in a treatment bath in a treatment tank located upstream in the transport direction of the optical film, and then the optical film is passed through a transport roller provided in the treatment tank located downstream in the transport direction of the optical film. That is, when the optical film is passed through the transport roller provided in the treatment tank located downstream in the transport direction, the optical film is softened after being immersed in the treatment bath in the treatment tank located upstream in the transport direction, and the optical film is less likely to be rubbed or cut when passed through the transport roller provided in the treatment tank located downstream in the transport direction. As a result, the optical film is less likely to have poor appearance. In the present invention, the optical film may be immersed in the treatment bath in a treatment tank located upstream in the transport direction after the optical film is passed through transport rollers provided in the treatment tank located upstream in the transport direction, or the optical film may be immersed while being passed through the transport rollers.

[0012] According to the present invention, the manufacturing equipment includes, as the multiple treatment tanks, a cleaning treatment tank that performs a cleaning treatment on the optical film, a stretching treatment tank that performs a stretching treatment on the optical film, and an upstream treatment tank that performs a predetermined treatment on the optical film, in that order from the downstream side in the transport direction of the optical film.

[0013] For example, when the upstream treatment tank is composed of a plurality of treatment tanks, the optical film immersed in the treatment bath in the upstream treatment tank may be oversoftened by repeating the paper passing and immersion (or repeating the immersion while paper passing). On the other hand, the treatment bath in the stretching treatment tank is generally at a high temperature. Therefore, when an oversoftened optical film is immersed in the treatment bath in the stretching treatment tank, the optical film may be cut or melted. According to the present invention, for example, after cutting off the leading end of the optical film that has been immersed in the treatment bath in the upstream treatment tank, the optical film following the cut leading end can be passed through the conveying rollers provided in the stretching treatment tank and the cleaning treatment tank. Specifically, it is possible to take up the leading end of the optical film that has been immersed in the treatment bath in the upstream treatment tank with a portable winding roller, cut off the rear end of the leading end, and recover the leading end. Since the paper passing operation on the conveying rollers provided in the upstream treatment tank is completed, the leading end of the optical film is taken up by the portable winding roller, so that the optical film following the leading end is immersed in the treatment bath in the upstream treatment tank. Therefore, the optical film following the leading end is softened, and the optical film is less likely to be rubbed or cut when passing through the conveying rollers provided in the stretching treatment tank and the cleaning treatment tank. Furthermore, the time that the optical film following the leading edge is immersed in the processing bath in the upstream processing tank is shorter than the time that the leading edge of the cut optical film is immersed in the processing bath in the upstream processing tank (the immersion time of the leading edge is longer by the time required to pass the leading edge through the conveying rollers provided in the upstream processing tank), so that the optical film following the leading edge does not soften excessively, and the risk of it breaking or dissolving in the processing bath in the stretching processing tank can be reduced.

[0014] According to the present invention, among the transport rollers provided in the stretching treatment tank, the lift rollers which are transport rollers that can be raised and lowered in the stretching treatment tank are raised above the liquid level of the treatment bath in the stretching treatment tank, and among the transport rollers provided in the cleaning treatment tank, the lift rollers which are transport rollers that can be raised and lowered in the cleaning treatment tank are raised above the liquid level of the treatment bath in the cleaning treatment tank. In this state, the optical film is passed through the transport rollers provided in the stretching treatment tank and the cleaning treatment tank without being immersed in the treatment bath in the stretching treatment tank and the treatment bath in the cleaning treatment tank, and then the lift rollers provided in the cleaning treatment tank are lowered below the liquid level of the treatment bath in the cleaning treatment tank to immerse the optical film in the treatment bath in the cleaning treatment tank, and then the lift rollers provided in the stretching treatment tank are lowered below the liquid level of the treatment bath in the stretching treatment tank to immerse the optical film in the treatment bath in the stretching treatment tank.

[0015] According to the present invention, the optical film is first immersed in the treatment bath in the cleaning tank and then in the treatment bath in the stretching tank. By immersing the optical film in the treatment bath in the cleaning tank before the treatment bath in the stretching tank in this way, the time for immersion in the high-temperature treatment bath in the stretching tank is shorter than in the case where the order is reversed, and the risk of the optical film being cut or melted can be further suppressed.

[0016] In the present invention, it is preferable that, among the transport rollers provided in a treatment tank located upstream in the transport direction of the optical film, a lift roller which is a transport roller that can be raised and lowered within the treatment tank is raised above the liquid level of the treatment bath in the treatment tank, and then the optical film is passed through the transport roller, and the lift roller is lowered below the liquid level of the treatment bath to immerse the optical film in the treatment bath.

[0017] According to the above-mentioned preferred method, it is possible to reliably immerse the optical film in the treatment bath. However, the present invention is not limited to this, and it is also possible to employ a method in which, for example, the optical film is passed through a lifting roller in a state in which the lifting rollers are raised above the liquid level of the treatment bath, thereby slackening the optical film between the lifting rollers and immersing it in the treatment bath.

[0018] In the present invention, the upstream treatment tank may be, for example, a swelling treatment tank that applies a swelling treatment to the optical film, a dyeing treatment tank that applies a dyeing treatment to the optical film, and a crosslinking treatment tank that applies a crosslinking treatment to the optical film, in that order from the upstream side in the transport direction of the optical film.

[0019] In the above-mentioned preferred method, when the lifting rollers are provided as multiple lifting rollers in the transport direction of the optical film in a treatment tank located upstream of the transport direction of the optical film, it is preferable that the multiple lifting rollers are lowered in sequence when being lowered below the liquid level of the treatment bath.

[0020] According to the above-mentioned preferred method, the inclination angle (angle with respect to the horizontal plane) of the optical film pressed by the first lifting roller to descend becomes larger than when all the lifting rollers are lowered at the same time, which makes it easier for air bubbles accumulated on the lower surface of the optical film to escape along the optical film, and reduces the occurrence of problems caused by air bubbles during the treatment of the optical film in the treatment bath.

[0021] In addition, when there are lifting / lowering rollers among the plurality of lifting / lowering rollers that are located at different vertical positions after being lowered, it is preferable to lower the lifting / lowering roller that will be located at the lowest position after being lowered first, because lowering the lifting / lowering roller that will be located at the lowest position after being lowered first increases the inclination angle of the optical film and makes it easier for air bubbles to escape than lowering the lifting / lowering roller that will be located at a higher position after being lowered first.

[0022] The present invention is suitably used when the optical film is a raw film (including an intermediate product film) of a polarizing film. Effect of the Invention

[0023] According to the present invention, the optical film is less likely to be rubbed or cut when the optical film is passed through, and the optical film is less likely to have poor appearance. [Brief description of the drawings]

[0024] [Figure 1] 1 is a schematic diagram showing an example of the schematic configuration of a manufacturing facility for a polarizing plate manufactured from a raw film to which a paper-passing method according to an embodiment of the present invention is applied. [Diagram 2] 2 is a schematic diagram showing an example of a schematic configuration of the treatment tank shown in FIG. 1 and a transfer facility provided in the treatment tank. [Diagram 3] FIG. 3 is an explanatory diagram showing the steps of passing a raw film through a pass line determined by a conveying roller provided in the swelling treatment tank shown in FIG. 2 and the steps of immersing the raw film in a treatment bath using a paper passing method according to one embodiment of the present invention. [Figure 4] 3 is a diagram showing another example of a lifting roller provided in the swelling treatment tank shown in FIG. 2. FIG. [Diagram 5] 1 is an explanatory diagram showing the procedure of passing and immersing a paper in a stretching treatment tank and a cleaning treatment tank using a paper passing method according to an embodiment of the present invention. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] Hereinafter, with reference to the accompanying drawings as appropriate, a method for passing an optical film according to one embodiment of the present invention will be described, taking as an example a case in which the optical film is a raw film of a polarizing film.

[0026] 1 is a schematic diagram showing an example of the schematic configuration of a manufacturing facility for a polarizing plate manufactured from a raw film to which the paper-passing method according to the present embodiment is applied. The arrows shown in FIG. 1 indicate the transport direction of each film. In manufacturing a polarizing plate F using the manufacturing equipment shown in Fig. 1, first, a raw film F0 such as a polyvinyl alcohol-based film wound around a pay-out roller 1 is paid out and immersed in a treatment bath in a treatment tank 2, where it is dyed with a dichroic substance such as iodine or a dichroic dye and uniaxially stretched. Then, it is dried in an oven 3 to obtain a polarizing film F1. The thickness of the polarizing film F1 (thickness of the polarizer) is not particularly limited, but is generally about 1 to 80 µm, and preferably 1 to 20 µm.

[0027] Next, a gravure coater 6 applies an ultraviolet-curing adhesive (hereinafter referred to as a UV adhesive) to one side of the protective film F2 paid out from the pay-out roller 5. Then, a lamination roller 7 laminates the protective film F2 coated with the UV adhesive to both sides of the polarizing film F1. Next, the UV adhesive is cured by an ultraviolet irradiator 8, and then dried in an oven 9. Finally, a surface protective film F3 paid out from a pay-out roller 10 is laminated by a lamination roller 11 to one side of the polarizing film F1 with the protective film F2 laminated to both sides, thereby obtaining a polarizing plate F. The obtained polarizing plate F is taken up by a take-up roller 12.

[0028] Fig. 2 is a schematic diagram showing an example of the schematic configuration of the treatment tank 2 and the conveying equipment provided in the treatment tank 2 shown in Fig. 1. Fig. 2 shows a state in which the raw film F0 (including the film of the intermediate product) after passing through is normally conveyed. As shown in Fig. 2, in this embodiment, a plurality of treatment tanks are provided as the treatment tank 2. The treatment tanks shown in Fig. 2 are, in order from the upstream side (left side in Fig. 2) in the transport direction (rightward in Fig. 2) of the raw film F0, an upstream treatment tank, a stretching treatment tank 24, and a cleaning treatment tank 25. The upstream treatment tanks are, in order from the upstream side in the transport direction of the raw film F0, a swelling treatment tank 21, a dyeing treatment tank 22, and a crosslinking treatment tank 23.

[0029] The swelling treatment tank 21 is a treatment tank in which the raw film F0 is subjected to a swelling treatment. For example, water is used as the treatment bath L in the swelling treatment tank 21. By immersing the raw film F0 in the treatment bath L in the swelling treatment tank 21, the raw film F0 can be washed, and the raw film F0 can be swelled to prevent unevenness such as uneven dyeing. Glycerin, potassium iodide, etc. may be added appropriately to the treatment bath L. The temperature of the treatment bath L is preferably 20 to 45°C, and more preferably 25 to 40°C. The immersion time of the raw film F0 in the treatment bath L during the production of the polarizing plate F is preferably 2 to 180 seconds, more preferably 10 to 150 seconds, and particularly preferably 60 to 120 seconds. The raw film F0 may be stretched in the treatment bath L in the swelling treatment tank 21, and the stretching ratio at this time is about 1.1 to 3.5 times, including the extension due to swelling.

[0030] The dyeing treatment tank 22 is a treatment tank for performing a dyeing treatment on the raw film F0 that has been subjected to the swelling treatment. As the treatment bath L in the dyeing treatment tank 22, a solution in which a dichroic substance such as iodine is dissolved in a solvent is used. Water is generally used as the solvent, but an organic solvent compatible with water may be further added. When the raw film F0 is immersed in the treatment bath L in the dyeing treatment tank 22, the dichroic substance is adsorbed on the raw film F0. The temperature of the treatment bath L is preferably 5 to 42°C, more preferably 10 to 35°C. The immersion time of the raw film F0 in the treatment bath L during the production of the polarizing plate F is preferably 1 to 20 minutes, more preferably 2 to 10 minutes. The raw film F0 may be stretched in the treatment bath L in the dyeing treatment tank 22, and the accumulated total stretching ratio at this time is about 1.1 to 4.0 times.

[0031] The crosslinking treatment tank 23 is a treatment tank for performing a crosslinking treatment on the original film F0 that has been subjected to a dyeing treatment. For the treatment bath L in the crosslinking treatment tank 23, a solution in which a crosslinking agent such as boric acid is dissolved in a solvent is used. Water is generally used as the solvent, but an organic solvent compatible with water may be further added. The original film F0 is immersed in the treatment bath L in the crosslinking treatment tank 23, whereby the original film F0 is crosslinked. The temperature of the treatment bath L is usually 20 to 70°C. The immersion time of the original film F0 in the treatment bath L during the production of the polarizing plate F is usually 1 second to 15 minutes, and preferably 5 seconds to 10 minutes. The original film F0 may be stretched in the treatment bath L in the crosslinking treatment tank 23, and the accumulated total stretching ratio at this time is about 1.1 to 4.0 times.

[0032] The stretching tank 24 is a treatment tank in which the raw film F0 that has been subjected to the crosslinking treatment is stretched. As the treatment bath L in the stretching tank 24, for example, a solution containing various metal salts or compounds of iodine, boron, or zinc is used. As the solvent, water, ethanol, or various organic solvents are appropriately used. With the raw film F0 immersed in the treatment bath L in the stretching tank 24, the raw film F0 is stretched so that the accumulated total stretch ratio is about 2 to 7 times. The temperature of the treatment bath L is preferably 40 to 67°C, more preferably 50 to 62°C.

[0033] The cleaning treatment tank 25 is a treatment tank that performs a cleaning treatment on the raw film F0 that has been subjected to a stretching treatment. For example, an aqueous solution containing an iodide such as sodium iodide or potassium iodide is used as the treatment bath L in the cleaning treatment tank 25. The raw film F0 is immersed in the treatment bath L in the cleaning treatment tank 25, whereby the raw film F0 is cleaned (washed with water). The temperature of the treatment bath L is preferably 10 to 60°C, and more preferably 15 to 40°C.

[0034] The paper passing method according to this embodiment is used in the transport equipment provided in the treatment tank 2 described above. As shown in FIG. 2, the transport facility provided in the treatment tank 2 includes a plurality of transport rollers R11a to R15. The conveying roller R11a is a nip roller provided at the entrance of the swelling treatment tank 21, and is composed of a pair of rollers arranged opposite to each other in the vertical direction. The conveying roller R11b is a nip roller provided at the exit of the swelling treatment tank 21 (entrance of the dyeing treatment tank 22), and is composed of a pair of rollers arranged opposite to each other in the horizontal direction (left and right direction in FIG. 2). The conveying roller R12 is a nip roller provided at the exit of the dyeing treatment tank 22 (entrance of the crosslinking treatment tank 23), and is composed of a pair of rollers arranged opposite to each other in the horizontal direction. The conveying roller R13 is a nip roller provided at the exit of the crosslinking treatment tank 23 (entrance of the stretching treatment tank 24), and is composed of a pair of rollers arranged opposite to each other in the horizontal direction. The conveying roller R14 is a nip roller provided at the exit of the stretching treatment tank 24 (entrance of the washing treatment tank 25), and is composed of a pair of rollers arranged opposite to each other in the horizontal direction. The transport roller R15 is a nip roller provided at the outlet of the cleaning treatment tank 25, and is composed of a pair of rollers arranged opposite each other in the horizontal direction. Hereinafter, the transport rollers R11a to R15 will be referred to as nip rollers R11a to R15 as appropriate. In this embodiment, one of the pair of rollers constituting the nip rollers R11a to R15 is a drive roller (a roller that is driven to rotate by a motor and transports the original film F0 in the longitudinal direction by frictional force), and the other roller is a driven roller (a roller that rotates freely and guides the original film F0 transported in the longitudinal direction).

[0035] The transport rollers R2 are lift rollers that can rise and fall (can move up and down in FIG. 2) in each of the treatment tanks 2 (swelling treatment tank 21 to cleaning treatment tank 25). Hereinafter, the transport rollers R2 will be referred to as lift rollers R2 as appropriate. The lift rollers R2 are configured to be able to rise and fall by lifting means (not shown) such as a jack. In this embodiment, a pair of lift rollers R2 are provided at positions upstream and downstream of each treatment tank 2 in the transport direction of the raw film F0.

[0036] Fig. 3 is an explanatory diagram showing the procedure for passing the original film F0 along a pass line determined by the transport rollers R11a and R11b provided in the swelling treatment tank 21 shown in Fig. 2 using the paper passing method according to this embodiment, and the procedure for immersing the original film F0 in the treatment bath L. Note that the pass line is an imaginary line determined by the positions of the transport rollers (transport rollers R11a and R11b) when the paper passing operation is performed, and includes a common tangent to two adjacent transport rollers used in the paper passing operation. First, as shown in Fig. 3(a), the nip rollers R11a and R11b are opened. Specifically, one of the rollers constituting the nip roller R11a (e.g., a driven roller) is moved in the direction of the arrow A. Similarly, one of the rollers constituting the nip roller R11b (e.g., a driven roller) is moved in the direction of the arrow B. Also, the lift roller R2 provided in the swelling treatment tank 21 is raised above the liquid level of the treatment bath L in the swelling treatment tank 21. In this embodiment, the lift roller R2 is raised above the nip rollers R11a and R11b, but the present invention is not limited to this, and the lift roller R2 may be raised to any position above the liquid level of the treatment bath L. When the lift roller R2 is raised below the nip rollers R11a and R11b, the raw film F0 is passed through a pass line determined by the conveying rollers R11a, R2, and R11b in the procedure described below.

[0037] Next, as shown in FIG. 3(a), a person manually pulls the leading end of the original film F0 (the end on the right side in FIG. 3(a)) and wraps the original film F0 around the lower roller constituting the nip roller R11a, the left roller constituting the nip roller R11b, and the right roller constituting the nip roller R11b, in that order, and aligns the original film F0 along the path line determined by the positions of these three rollers. This completes the paper passing operation up to the nip roller R11b. At this time, it is preferable to pass the paper while driving and rotating the drive roller constituting the nip roller R11a (the lower roller in this embodiment) and the drive roller constituting the nip roller R11b (the right roller in this embodiment).

[0038] When the paper passing operation is completed as described above, the nip roller R11a is closed. Specifically, one of the rollers constituting the nip roller R11a is moved in the direction of the arrow C shown in FIG. 3(b) to contact the original film F0.

[0039] Next, the lifting roller R2 is lowered below the liquid level of the treatment bath L in the swelling treatment tank 21 to immerse the raw film F0 in the treatment bath L. In this embodiment, when the pair of lifting rollers R2 are lowered below the liquid level of the treatment bath L, one of the pair of lifting rollers R2 is first lowered in the direction of arrow D as shown in Fig. 3(b), and then the other lifting roller R2 is lowered in the direction of arrow E as shown in Fig. 3(c).

[0040] Finally, the nip roller R11b is closed. Specifically, one of the rollers constituting the nip roller R11b is moved in the direction of the arrow F shown in FIG.

[0041] After the raw film F0 is immersed in the treatment bath L in the swelling treatment tank 21 as described above, the leading end of the raw film F0 is passed through a path determined by the conveying roller R11b and the conveying roller R12 provided in the dyeing treatment tank 22, and after passing through, the raw film F0 is immersed in the treatment bath L in the dyeing treatment tank 22. The procedure for passing and immersing the raw film F0 in the dyeing treatment tank 22 is the same as that of the swelling treatment tank 21 described above. That is, the lifting roller R2 is first lowered to immerse the raw film F0 in the treatment bath L, and then the conveying roller R12 is closed. In this embodiment, the same procedure for passing and immersing as in the swelling treatment tank 21 is performed up to the crosslinking treatment tank 23.

[0042] According to the above-described paper-passing method of the present embodiment, the raw film F0 is immersed in the treatment bath L in the treatment tank 2 located upstream in the conveying direction of the raw film F0, and then the raw film F0 is passed through the conveying rollers provided in the treatment tank 2 located downstream in the conveying direction of the raw film F0. That is, when the raw film F0 is passed through the conveying rollers provided in the treatment tank 2 (e.g., the dyeing treatment tank 22) located downstream in the conveying direction, the raw film F0 has been softened since it has been immersed in the treatment bath L in the treatment tank 2 (e.g., the swelling treatment tank 21) located upstream in the conveying direction, and the raw film F0 is less likely to be rubbed or cut when it is passed through the conveying rollers provided in the treatment tank 2 located downstream in the conveying direction. As a result, the raw film F0 is less likely to have poor appearance.

[0043] In addition, according to the paper passing method of the present embodiment, one of the pair of lift rollers R2 is lowered first. Therefore, in a state where only one of the lift rollers R2 is lowered (see FIG. 3(b)), the inclination angle (angle with respect to the horizontal plane) of the original film F0 pressed by the pair of lift rollers R2 becomes larger than when the pair of lift rollers R2 are lowered simultaneously. As a result, air bubbles B accumulated on the lower surface of the original film F0 can easily escape along the original film F0 to the other lift roller R2 (the lift roller R2 on the left side in the example shown in FIG. 3(b)), and defects caused by air bubbles B during the treatment of the original film F0 in the treatment tank 2 are less likely to occur.

[0044] FIG. 4 is a diagram showing another example of the lift roller R2 provided in the swelling treatment tank 21. The pair of lift rollers R2 shown in FIG. 3 have the same vertical position after lowering (see FIG. 3(c)). In contrast, the pair of lift rollers R2 shown in FIG. 4 have different vertical positions after lowering. In the example shown in FIG. 4(a), the position of the lift roller R2 on the downstream side in the transport direction of the original film F0 (right side in FIG. 4(a)) after lowering is lower than the position of the lift roller R2 on the upstream side in the transport direction of the original film F0 (left side in FIG. 4(a)) after lowering. In the example shown in FIG. 4(b), the position of the lift roller R2 on the upstream side in the transport direction after lowering is lower than the position of the lift roller R2 on the downstream side in the transport direction after lowering. As shown in Fig. 4, when the vertical positions of a pair of lift rollers R2 after lowering are different from each other, it is preferable to lower one of the lift rollers R2, which will be lower than the other lift roller R2 after lowering, first. In the example shown in Fig. 4(a), it is preferable to lower the lift roller R2 on the downstream side in the conveying direction first, and in the example shown in Fig. 4(b), it is preferable to lower the lift roller R2 on the upstream side in the conveying direction first. This is because the inclination angle of the original film F0 becomes larger and the air bubbles B become easier to escape when the lift roller R2, which will be lower after lowering, is lowered first than when the other lift roller R2, which will be higher after lowering, is lowered first.

[0045] In this embodiment, an example has been described in which a pair of lifting rollers R2 are provided upstream and downstream in the transport direction of the raw film F0 in each processing tank 2. However, the present invention is not limited to this, and can also be applied to a case in which each processing tank 2 is provided with three or more lifting rollers R2 in the transport direction of the raw film F0. When three or more lift rollers R2 are provided, it is preferable to lower them in order rather than lowering all of them at the same time. Also, when three or more lift rollers R2 are provided and there are lift rollers R2 that are lowered to different vertical positions, it is preferable to lower the lift roller R2 that is lowered to the lowest position first. The number of lifting rollers R2 provided in each of the above-mentioned treatment tanks 2 may be three or more, and the preferred order in which the lifting rollers R2 are lowered is not limited to the upstream treatment tanks (swelling treatment tank 21, dyeing treatment tank 22, and crosslinking treatment tank 23), but is also the same for the stretching treatment tank 24 and the washing treatment tank 25.

[0046] The paper passing and immersion procedures in the stretching treatment tank 24 and the cleaning treatment tank 25 using the paper passing method according to this embodiment will be described below.

[0047] FIG. 5 is an explanatory diagram showing the procedure of passing and immersing paper in the stretching treatment tank 24 and the cleaning treatment tank 25 using the paper passing method according to this embodiment. 5(a) shows a state where the paper feed and immersion in the upstream treatment tanks (swelling treatment tank 21, dyeing treatment tank 22, and crosslinking treatment tank 23) have been completed according to the above-mentioned procedure. Specifically, the figure shows a state where the paper feed of the original film F0 from the conveying rollers R11a to R13 provided in the swelling treatment tank 21, dyeing treatment tank 22, and crosslinking treatment tank 23 has been completed, and the original film F0 has been immersed in the treatment bath L in the swelling treatment tank 21, dyeing treatment tank 22, and crosslinking treatment tank 23. In this embodiment, the leading end of the original film F0 that has finished immersing in the treatment bath L in the upstream treatment tank shown in Fig. 5(a) (the entirety or a part of the original film F0 from the transport roller R11a provided in the swelling treatment tank 21 to the transport roller R13 provided in the crosslinking treatment tank 23) is cut off. Specifically, the leading end of the original film F0 that has finished immersing in the treatment bath L in the upstream treatment tank is wound up by hand or with a portable winding roller (not shown), and the rear end of this leading end is cut off to recover the leading end.

[0048] 5(b), the raw film F0 following the cut-off leading end is passed through the conveying rollers R14, R15 provided in the stretching tank 24 and the cleaning tank 25. Specifically, the lifting roller R2 provided in the stretching tank 24 is raised above the liquid level of the treatment bath L in the stretching tank 24, and the lifting roller R2 provided in the cleaning tank 25 is raised above the liquid level of the treatment bath L in the cleaning tank 25. In this state, the raw film F0 is passed through the conveying rollers R14, R15 provided in the stretching tank 24 and the cleaning tank 25 without being immersed in the treatment bath L in the stretching tank 24 and the treatment bath L in the cleaning tank 25.

[0049] Next, as shown in Fig. 5(c), the lifting roller R2 provided in the cleaning tank 25 is lowered below the liquid level of the treatment bath L in the cleaning tank 25 to immerse the original film F0 in the treatment bath L in the cleaning tank 25. Thereafter, as shown in Fig. 5(d), the nip roller R15 is closed.

[0050] Finally, as shown in Fig. 5(d), the lift roller R2 provided in the stretching tank 24 is lowered below the liquid level of the treatment bath L in the stretching tank 24 to immerse the original film F0 in the treatment bath L in the stretching tank 24. Thereafter, the nip roller R14 is closed. Since the treatment bath L in the stretching tank 24 is generally hotter than the other treatment tanks 2, there is a risk that the original film F0 may break or melt if it is immersed in the treatment bath L. For this reason, it is preferable to immerse the original film F0 with the nip rollers R13 and R15 closed (with the original film F0 stretched). After the above procedure is performed, the sheet is passed through a conveying roller (not shown) located downstream in the conveying direction.

[0051] The raw film F0 immersed in the treatment bath L in the upstream treatment tanks (swelling treatment tank 21, dyeing treatment tank 22, and crosslinking treatment tank 23) may become oversoftened by repeated passing and immersion. Meanwhile, as described above, the treatment bath L in the stretching treatment tank 24 is generally hotter than the other treatment tanks 2. For this reason, when an oversoftened optical film is immersed in the treatment bath L of the stretching treatment tank 24, the raw film F0 may break or melt. According to the paper passing method of this embodiment, after cutting off the leading end of the original film F0 that has finished immersing in the treatment bath L in the upstream treatment tank, the original film F0 following the cut leading end is passed through the conveying rollers R14 and R15 provided in the stretching treatment tank 24 and the cleaning treatment tank 25. Since the paper passing operation to the conveying rollers provided in the upstream treatment tank (paper passing operation up to the conveying roller R13) is completed, the leading end of the original film F0 is taken up by hand or with a portable take-up roller, so that the original film F0 following the leading end is immersed in the treatment bath L in the upstream treatment tank. Therefore, the original film F0 following the leading end is softened, and when passing through the conveying rollers R14 and R15 provided in the stretching treatment tank 24 and the cleaning treatment tank 25, the original film F0 is less likely to be rubbed or cut. Furthermore, the time that the leading end of the cut original film F0 is immersed in the processing bath L in the upstream processing tank is shorter than the time that the leading end of the original film F0 is immersed in the processing bath L in the upstream processing tank (the immersion time of the leading end is longer by the time required to pass through the conveying rollers provided in the upstream processing tank), so that the original film F0 following the leading end does not soften excessively, and the risk of it breaking or dissolving in the processing bath L of the stretching processing tank 24 can be reduced.

[0052] Furthermore, according to the paper passing method of this embodiment, the raw web film F0 is first immersed in the treatment bath L in the cleaning treatment tank 25, and then immersed in the treatment bath L in the stretching treatment tank 24. By immersing the raw web film F0 in the treatment bath L in the cleaning treatment tank 25 before the treatment bath L in the stretching treatment tank 24 in this way, the time spent immersed in the high-temperature treatment bath L in the stretching treatment tank 24 is shorter than when the order is reversed, and the risk of the raw web film F0 being cut or melted can be further reduced.

[0053] In the embodiment described above, the optical film is an original film F0 of a polarizing film F1, but the present invention is not limited to this and can be applied to various other optical films. [Explanation of symbols]

[0054] 2. Treatment tank 21....Swelling treatment tank 22 Dyeing tank 23... Cross-linking treatment tank 24... Stretching tank 25 Cleaning treatment tank F0···Optical film (raw film) F1...Polarizing Film L Treatment bath R11a, R11b, R12, R13, R14, R15...Transport rollers (nip rollers) R2: Transport roller (lifting roller)

Claims

1. A method for manufacturing an optical film, comprising: a conveying facility having a plurality of conveying rollers; and a plurality of treatment tanks; and comprising the steps of: After the optical film is immersed in a treatment bath in a treatment tank located on the upstream side of a transport direction of the optical film, the optical film is passed through a transport roller provided in the treatment tank located on the downstream side of the transport direction of the optical film; the manufacturing facility includes, as the plurality of treatment tanks, a cleaning treatment tank for cleaning the optical film, a stretching treatment tank for stretching the optical film, and an upstream treatment tank for performing a predetermined treatment on the optical film, in this order from a downstream side in a transport direction of the optical film; a lift roller that is a transport roller capable of rising and falling within the stretching treatment tank among the transport rollers provided in the stretching treatment tank, raised above a liquid level of the treatment bath in the stretching treatment tank, and a lift roller that is a transport roller capable of rising and falling within the cleaning treatment tank among the transport rollers provided in the cleaning treatment tank, raised above the liquid level of the treatment bath in the cleaning treatment tank, while the optical film is passed through the transport rollers provided in the stretching treatment tank and the cleaning treatment tank without being immersed in the treatment bath in the stretching treatment tank and the treatment bath in the cleaning treatment tank, and then the lift roller provided in the cleaning treatment tank is lowered below the liquid level of the treatment bath in the cleaning treatment tank to immerse the optical film in the treatment bath in the cleaning treatment tank, and then the lift roller provided in the stretching treatment tank is lowered below the liquid level of the treatment bath in the stretching treatment tank to immerse the optical film in the treatment bath in the stretching treatment tank. The pass line refers to the transport path of the optical film that is determined by the position of the transport rollers, and the paper passing refers to the task of a person manually pulling the leading end of the optical film, wrapping the optical film around the transport rollers, and aligning the optical film along the pass line.

2. 2. The method for passing an optical film according to claim 1, further comprising: raising a lift roller, which is a transport roller that can be raised and lowered within the treatment tank, among transport rollers provided in a treatment tank located upstream in the transport direction of the optical film, above the liquid level of the treatment bath in the treatment tank; passing the optical film through the transport roller; and then lowering the lift roller below the liquid level of the treatment bath to immerse the optical film in the treatment bath.

3. 3. The method for passing an optical film according to claim 1 or 2, wherein the upstream treatment tanks are, in order from the upstream side in the transport direction of the optical film, a swelling treatment tank that applies a swelling treatment to the optical film, a dyeing treatment tank that applies a dyeing treatment to the optical film, and a crosslinking treatment tank that applies a crosslinking treatment to the optical film.

4. The optical film passing method according to claim 2 or 3, wherein the lifting rollers are a plurality of lifting rollers provided in a transport direction of the optical film in a treatment tank located upstream of the transport direction of the optical film, and when the plurality of lifting rollers are lowered below the liquid level of the treatment bath, they are lowered in sequence.

5. 5. The method for passing an optical film according to claim 4, wherein among the plurality of lifting rollers, there are lifting rollers which have different vertical positions after being lowered, and the lifting roller which has the lowest position after being lowered is lowered first.

6. The method for passing an optical film according to claim 1 , wherein the optical film is a raw film of a polarizing film.

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