JP2024059875A - Feeding method of optical film - Google Patents

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

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

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.
An optical film is usually manufactured using a long strip of raw film. Usually, the raw film is conveyed in the longitudinal direction by a conveying device having a conveying roller, and various processes are sequentially performed on the raw film to produce a long strip of optical film as a product (see, for example, Patent Documents 1 and 2). The long strip of 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 finished products, but also to raw films and films in intermediate products.

For example, if the optical film is a raw film of a polarizing film, the raw film is transported by a transport device and immersed in the treatment baths in multiple treatment tanks in sequence, 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).

When starting the production of optical film products, it is necessary to pass the optical film through the 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. Passing the optical film 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.

For example, if the optical film is a raw film of polarizing film, it is not possible to transport one raw film and the next raw film by splicing them together (connecting the rear end of the first raw film to the leading end of the next raw film). This is because the raw film of polarizing film is stretched in the treatment bath, so even if it is spliced with ordinary tape or laser welding, the spliced part will come off. Therefore, every time the raw film wound on the pay-out roller runs out, the raw film wound on the next pay-out roller must be passed by hand.

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 worn 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 worn or cut during the paper-passing operation. Even if the leading edge of the optical film is worn 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 about several tens of μm in size, if it is visible, the optical film will have a defective appearance, which 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 the wear and tear of the optical film during the paper feed operation as much as possible.

JP 2013-248590 A JP 2004-341515 A

The present invention has been made to solve the problems of the conventional technology as described above, and aims to provide a method for passing an optical film through which the appearance of the optical film is less likely to be impaired.

In order to solve the above problem, the inventors conducted extensive research and discovered that one of the causes of abrasion and tearing during paper feed operations is the hardness of the optical film. Specifically, it was found that, conventionally, the optical film is hard because it is not immersed in the treatment bath of the treatment tank during paper feed operations, and that the optical film is prone to abrasion and tearing due to friction with the transport rollers during paper feed operations.

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, a lifting treatment tank that is a conveying roller that can be raised and lowered within the stretching treatment tank, among the conveying rollers provided in the stretching treatment tank. 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.

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.

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.

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 paper passing and immersion). On the other hand, the treatment bath in the stretching treatment tank is generally at a high temperature. Therefore, when the 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 treatment bath in the upstream treatment tank is shorter than the time that the leading edge of the cut optical film is immersed in the treatment bath in the upstream treatment tank (the immersion time of the leading edge is longer by the time required for the leading edge to pass through the conveying rollers provided in the upstream treatment tank), so that excessive softening of the optical film following the leading edge does not progress, and the risk of it being cut or dissolved in the treatment bath of the stretching treatment tank can be reduced.

According to the present invention, among the transport rollers provided in the stretching treatment tank, the lift rollers that 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 that 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.

According to the present invention, the optical film is first immersed in the treatment bath in the cleaning tank, and then immersed 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 spent immersed in the high-temperature treatment bath in the stretching tank is shorter than when the order is reversed, and the risk of the optical film being cut or melted can be further reduced.

In the present invention, it is preferable that, among the transport rollers provided in the 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.

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.

In the present invention, the upstream treatment tank may be, in order from the upstream side in the transport direction of the optical film, a swelling treatment tank that performs a swelling treatment on the optical film, a dyeing treatment tank that performs a dyeing treatment on the optical film, and a crosslinking treatment tank that performs a crosslinking treatment on the optical film.

In the above preferred method, when the lift rollers are multiple lift rollers provided in the transport direction of the optical film in a processing tank located upstream in the transport direction of the optical film, it is preferable that the multiple lift rollers are lowered in sequence when being lowered below the liquid level of the processing bath.

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 lifting rollers are lowered simultaneously. This makes it easier for air bubbles that have accumulated on the underside of the optical film to escape along the optical film, making it less likely that problems caused by air bubbles will occur during the treatment of the optical film in the treatment bath.

When some of the multiple lift rollers have different vertical positions after lowering, it is preferable to lower the lift roller that will be at the lowest position after lowering first. Lowering the lift roller that will be at the lowest position after lowering first makes the inclination angle of the optical film larger, making it easier for air bubbles to escape, compared to lowering the lift roller that will be at a higher position after lowering first.

The present invention is preferably used when the optical film is a raw film of a polarizing film (including an intermediate product film).

According to the present invention, the optical film is less likely to be scratched or cut when passing through a paper, and the optical film is less likely to have poor appearance.

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. 2 is a schematic diagram showing an example of a schematic configuration of the treatment tank shown in FIG. 1 and a transport facility provided in the treatment tank; FIG. 3 is an explanatory diagram showing the procedure for 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 procedure for immersing the raw film in a treatment bath, using a paper passing method according to one embodiment of the present invention. 3 is a diagram showing another example of a lifting roller provided in the swelling treatment tank shown in FIG. 2. FIG. 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.

The following describes a method for passing an optical film according to one embodiment of the present invention, taking as an example a case in which the optical film is a raw film of a polarizing film, with appropriate reference to the attached drawings.

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 the present embodiment is applied. The arrows shown in FIG. 1 indicate the conveyance direction of each film.
1, a raw film F0 such as a polyvinyl alcohol-based film wound around a feed roller 1 is first fed 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.

Next, a gravure coater 6 applies an ultraviolet-curing adhesive (hereinafter referred to as UV adhesive) to one side of the protective film F2 that has been unwound from the unwinding roller 5. Then, the protective film F2 coated with the UV adhesive is laminated to both sides of the polarizing film F1 by the lamination roller 7. Next, the UV adhesive is cured by the ultraviolet irradiation device 8, and then dried in an oven 9. Finally, a surface protective film F3 that has been unwound from the unwinding roller 10 is laminated to one side of the polarizing film F1, both sides of which have been laminated with the protective film F2, by the lamination roller 11, to obtain a polarizing plate F. The obtained polarizing plate F is taken up by the winding roller 12.

Fig. 2 is a schematic diagram showing an example of the schematic configuration of the treatment tank 2 shown in Fig. 1 and the conveying equipment provided in the treatment tank 2. 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 of the raw film F0 (rightward in Fig. 2), 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.

The swelling treatment tank 21 is a treatment tank in which the original 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 original film F0 in the treatment bath L in the swelling treatment tank 21, the original film F0 can be washed, and the original film F0 can be swelled to prevent unevenness such as uneven dyeing. Glycerin, potassium iodide, etc. may be added to the treatment bath L as appropriate. The temperature of the treatment bath L is preferably 20 to 45°C, more preferably 25 to 40°C. The immersion time of the original film F0 in the treatment bath L during the manufacture 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 original 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.

The dyeing treatment tank 22 is a treatment tank in which the original film F0 that has been subjected to the swelling treatment is dyed. The treatment bath L in the dyeing treatment tank 22 is a solution in which a dichroic substance such as iodine is dissolved in a solvent. 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 dyeing treatment tank 22, so that the dichroic substance is adsorbed to the original film F0. The temperature of the treatment bath L is preferably 5 to 42°C, and more preferably 10 to 35°C. The immersion time of the original film F0 in the treatment bath L during the manufacture of the polarizing plate F is preferably 1 to 20 minutes, and more preferably 2 to 10 minutes. The original 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.

The crosslinking tank 23 is a tank for crosslinking the dyed raw film F0. The treatment bath L in the crosslinking tank 23 is a solution in which a crosslinking agent such as boric acid is dissolved in a solvent. Water is generally used as the solvent, but an organic solvent compatible with water may be further added. The raw film F0 is crosslinked by immersing it in the treatment bath L in the crosslinking tank 23. The temperature of the treatment bath L is usually 20 to 70°C. The immersion time of the raw film F0 in the treatment bath L during the manufacture of the polarizing plate F is usually 1 second to 15 minutes, and preferably 5 seconds to 10 minutes. The raw film F0 may be stretched in the treatment bath L in the crosslinking tank 23, and the accumulated total stretching ratio at this time is about 1.1 to 4.0 times.

The stretching tank 24 is a treatment tank in which the raw film F0 that has been subjected to the crosslinking treatment is stretched. The treatment bath L in the stretching tank 24 is, for example, a solution containing various metal salts or compounds of iodine, boron or zinc. 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.

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.

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 has 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 conveying roller R15 is a nip roller provided at the exit of the washing treatment tank 25, and is composed of a pair of rollers arranged opposite to each other in the horizontal direction. Hereinafter, the above-mentioned conveying rollers R11a to R15 will be referred to as nip rollers R11a to R15 as appropriate. In this embodiment, of the pairs of rollers constituting the nip rollers R11a to R15, one roller is a drive roller (a roller that is driven to rotate by a motor and conveys 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 conveyed in the longitudinal direction).

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

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. 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. 3A, the nip rollers R11a and R11b are opened. Specifically, one roller (e.g., a driven roller) constituting the nip roller R11a is moved in the direction of the arrow A. Similarly, one roller (e.g., a driven roller) constituting the nip roller R11b 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.

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 of FIG. 3(a)) and wraps the original film F0 around the lower roller that constitutes the nip roller R11a, the left roller that constitutes the nip roller R11b, and the right roller that constitutes the nip roller R11b, in that order, and aligns the original film F0 with 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 that constitutes the nip roller R11a (the lower roller in this embodiment) and the drive roller that constitutes the nip roller R11b (the right roller in this embodiment).

Once the paper feed operation is completed as described above, the nip roller R11a is closed. Specifically, one of the rollers that make up the nip roller R11a is moved in the direction of the arrow C shown in Figure 3(b) to contact the original film F0.

Next, the lift 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 lift rollers R2 are lowered below the liquid level of the treatment bath L, one of the pair of lift rollers R2 is first lowered in the direction of arrow D as shown in FIG. 3(b), and then the other lift roller R2 is lowered in the direction of arrow E as shown in FIG. 3(c).

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. 3(c) to contact the original film F0.

After the raw film F0 is immersed in the treatment bath L in the swelling treatment tank 21 in the above manner, 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 leading end 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 in the swelling treatment tank 21 described above. In other words, 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.

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 of the raw film F0 in the conveying direction, and then the raw film F0 is passed through the conveying rollers provided in the treatment tank 2 located downstream of the raw film F0 in the conveying direction. That is, when the raw film F0 is passed through the conveying rollers provided in the treatment tank 2 located downstream in the conveying direction (e.g., the dyeing treatment tank 22), the raw film F0 has been softened after being immersed in the treatment bath L in the treatment tank 2 located upstream in the conveying direction (e.g., the swelling treatment tank 21), and when the raw film F0 is passed through the conveying rollers provided in the treatment tank 2 located downstream in the conveying direction, it is less likely to be rubbed or cut. As a result, the raw film F0 is less likely to have poor appearance.

In addition, according to the paper passing method of this embodiment, one of the pair of lift rollers R2 is lowered first. Therefore, when only one of the lift rollers R2 is lowered (see FIG. 3B), 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. This makes it easier for air bubbles B that have accumulated on the underside of the original film F0 to escape along the original film F0 to the other lift roller R2 (the lift roller R2 on the left in the example shown in FIG. 3B), making it less likely that problems caused by air bubbles B will occur during the treatment of the original film F0 in the treatment tank 2.

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 of the transport direction of the raw film F0 (right side of FIG. 4(a)) after lowering is lower than the position of the lift roller R2 on the upstream side of the transport direction of the raw film F0 (left side of FIG. 4(a)) after lowering. In the example shown in FIG. 4(b), the position of the lift roller R2 on the upstream side of the transport direction after lowering is lower than the position of the lift roller R2 on the downstream side of 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. 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 is larger 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, and the air bubbles B are more easily removed.

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 cleaning treatment tank 25.

The following describes the paper passing and immersion procedures in the stretching tank 24 and cleaning tank 25 using the paper passing method according to this embodiment.

FIG. 5 is an explanatory diagram showing the procedure of passing and immersing a sheet in the stretching treatment tank 24 and the cleaning treatment tank 25 using the sheet passing method according to this embodiment.
5A 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 by the above-mentioned procedure. Specifically, the figure shows a state where the paper feed operation 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 has been completed.
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 entire 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.

Next, as shown in FIG. 5(b), the raw film F0 following the cut-off tip 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.

Next, as shown in FIG. 5(c), the lift 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. After that, the nip roller R15 is closed as shown in FIG. 5(d).

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. After this, 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 transport roller (not shown) located downstream in the transport direction.

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 be oversoftened by repeated paper 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 be cut or melted.
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 winding 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 original film F0 following the leading edge is immersed in the processing bath L in the upstream processing tank is shorter than the time that the leading edge of the cut original film F0 is immersed in the processing bath L in the upstream processing tank (the immersion time of the leading edge 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 edge 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.

In addition, according to the paper passing method of this embodiment, the raw 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 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 film F0 being torn or melted can be further reduced.

In the above embodiment, the optical film is the original film F0 of the polarizing film F1, but the present invention is not limited to this and can be applied to various other optical films.

2: Treatment tank 21: Swelling tank 22: Dyeing tank 23: Crosslinking tank 24: Stretching tank 25: Cleaning 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 (lift roller)

Claims (6)

A method for manufacturing an optical film, the method comprising: passing an optical film through a pass line of a conveying facility having a plurality of conveying rollers and a plurality of treatment tanks;
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 provided in the stretching treatment tank that is a transport roller capable of rising and falling within the stretching treatment tank, being raised above a liquid level of a treatment bath in the stretching treatment tank, and a lift roller provided in the cleaning treatment tank that is a transport roller capable of rising and falling within the cleaning treatment tank, being 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. The method for passing an optical film according to claim 1, in which, among the transport rollers provided in a treatment tank located upstream in the transport direction of the optical film, a lift roller that 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, the optical film is passed through the transport roller, and then the lift roller is lowered below the liquid level of the treatment bath to immerse the optical film in the treatment bath. 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 performs a swelling treatment on the optical film, a dyeing treatment tank that performs a dyeing treatment on the optical film, and a crosslinking treatment tank that performs a crosslinking treatment on the optical film. The optical film passing method according to claim 2 or 3, wherein a plurality of lifting rollers are provided in the transport direction of the optical film in a processing tank located upstream in the transport direction of the optical film as the lifting rollers, and the plurality of lifting rollers are lowered in sequence when lowering below the liquid surface of the processing bath. The optical film passing method according to claim 4, wherein among the plurality of lift rollers, there are lift rollers that are in different vertical positions after lowering, and the lift roller that is in the lowest position after lowering is lowered first. The method for passing an optical film according to any one of claims 1 to 5, wherein the optical film is a raw film of a polarizing film.

Images