KR102646511B1 - Method and apparatus for conveying film, amd method and apparatus for manufacturing treated film - Google Patents

Abstract

The object of the present invention is to provide a film transport method that can reduce the difference in rotation speed between a pair of rolls.
This has a nip roll conveyance process in which the film is conveyed by rotation of a nip roll having a first roll and a second roll opposing each other, and in the nip roll conveyance process, a rotational force is applied to the first roll from a first drive source, A film comprising a first roll rotation process in which the first roll rotates and a second roll rotation process in which the second roll rotates, wherein a rotational force is applied to the second roll from a second drive source in the second roll rotation process. This is achieved by the return method.

Description

Film transport method and transport device, and manufacturing method and manufacturing apparatus for treated film {METHOD AND APPARATUS FOR CONVEYING FILM, AMD METHOD AND APPARATUS FOR MANUFACTURING TREATED FILM}

The present invention relates to a method and device for transporting a film, and a method and device for producing a treated film.

A conveyance device that continuously feeds the film while passing it through a predetermined conveyance path and contacting a plurality of rolls while continuously supplying the film is common as a film conveyance device. The various rolls used in the above-mentioned conveyance device include guide rolls that support only one side of the film, nip rolls that are disposed on both sides of the film and support the film from both sides, and the like. Among them, the nip roll is used for purposes such as adjusting the tension of the film, transporting the film, and adding a pressing force to the film.

For example, Japanese Patent Application Laid-Open No. 2017-76107 (Patent Document 1) discloses a conveyance device for an optical film including a nip roll.

Patent Document 1: Japanese Patent Publication No. 2017-76107

Conventionally, in a film transport device, when a film is passed between a pair of rolls, a problem occurs in which the surface of the film is scratched. The degree to which the surface of the film is chipped varies depending on the type, thickness, moisture content, transport speed, etc. of the film being transported. This problem not only reduces the yield of the product but also causes contamination within the equipment. In particular, when the film is an optical film used for optical purposes, a high quality film is required, so coping with this problem has been a challenge.

The present inventors have found that one of the causes of the problem of the surface of the film being chipped when the film is passed between a pair of rolls is that the rotation speed between the pair of rolls may be different. The purpose of the present invention is to provide a film transport method and transport apparatus that can reduce the difference in rotation speed between a pair of rolls, and a manufacturing method and manufacturing apparatus for a treated film.

The present invention provides a film transport method and transport apparatus shown below, and a manufacturing method and manufacturing apparatus for a treated film.

[1] It has a nip roll conveyance process in which the film is conveyed by rotation of a nip roll provided with a first roll and a second roll facing each other,

The nip roll conveyance process includes a first roll rotation process in which a rotational force is applied to the first roll from a first drive source to rotate the first roll, and a second roll rotation process in which the second roll rotates,

A film transport method in which a rotational force is applied to the second roll from a second drive source in the second roll rotation process.

[2] In the second roll rotation process, the second roll rotates in response to the rotation of the first roll, and at the same time, further rotational force is applied from the second drive source. Conveyance of the film described in [1] method.

[3] The rotational force applied to the second roll from the second drive source in the second roll rotation step is smaller than the rotational force applied to the first roll from the first drive source in the first roll rotation step, [1] or [2 〕The film transport method described in.

[4] The film transport method according to any one of [1] to [3], wherein the film is an optical film or a raw material film thereof.

[5] A nip roll having a first roll and a second roll facing each other and conveying the film by rotation,

A first drive source that provides rotational force to the first roll,

A second driving source that provides rotational force to the second roll

A film transport device having a film transport device.

[6] The film transport device according to [5], wherein the film is an optical film or a raw material film thereof.

[7] A treatment step of treating the raw film to obtain a treated film;

[1] A method for producing a treated film, comprising a transport step of transporting the raw material film or the treated film by the film transport method according to any one of [1] to [3].

[8] The method for producing a treated film according to [7], wherein the treated film is an optical film.

[9] An apparatus for producing a treated film, comprising a processing unit that processes a raw material film to obtain a treated film, and a transport unit that transports the raw material film or the treated film by the film transport apparatus described in [5].

[10] The apparatus for producing a treated film according to [9], wherein the treated film is an optical film.

According to the film transport method of the present invention, the difference in rotation speed between a pair of rolls can be reduced.

1 is a schematic cross-sectional view showing an example of an optical film transport device according to the present invention.
FIG. 2 is a perspective view of a nip roll portion in the conveyance device shown in FIG. 1.
Figure 3 is a cross-sectional view taken along line XX of Figure 2.
4 is a cross-sectional view schematically showing an example of a polarizing film manufacturing apparatus according to the present invention.
Figure 5 is a diagram plotting the measurement results of the rotational speeds of the first roll and the second roll in Example 1.
Figure 6 is a diagram plotting the measurement results of the rotational speeds of the first roll and the second roll in Example 2.

[Film transport method]

The film conveyance method of this invention has a nip roll conveyance process of conveying a film by rotation of a nip roll provided with the 1st roll and 2nd roll which oppose each other. The nip roll consists of a first roll and a second roll disposed on both sides of the film to be conveyed. The nip roll plays the role of transporting the film by rotation, and in addition to this role, it also plays the role of adjusting the tension of the film, adding a pressing force to the film, controlling the transport speed of the film, and controlling the transport direction of the film. You can.

The nip roll conveyance process includes a first roll rotation process in which a rotational force is applied to the first roll from a first drive source and the first roll rotates, and a second roll rotation process in which the second roll rotates. In the second roll rotation process, rotational force is applied to the second roll from the second drive source.

In this specification, the first drive source and the second drive source mean a power drive source such as a motor, and a drive source that generates rotational force from electric energy. The film transport method of the present invention transports the film using a film transport device that is individually provided with a first drive source for applying rotational force to the first roll and a second drive source for providing rotational force to the second roll.

In the film transport method of the present invention, a rotational force is applied to the first roll from a first drive source. And, separately from this, rotational force is applied to the second roll from the second drive source. In this way, by applying rotational force to the first roll and the second roll from separate drive sources, the rotation speed of the first roll and the second roll can be individually controlled, and the rotation that occurs between the first roll and the second roll The speed difference can be reduced. And, when the film is conveyed by sandwiching it between the first roll and the second roll, the occurrence of the problem of the surface of the film being chipped can be reduced.

In the second roll rotation process, the second roll is preferably controlled to rotate in accordance with the rotation of the first roll. That is, the second roll is preferably controlled so that rotational force is applied not only from the second drive source but also from the rotation of the first roll. In the second roll, it is preferable that the rotational force applied from the second drive source is controlled so that the difference with the rotational speed of the first roll is adjusted. In this way, by using the rotation of the first roll in the rotation of the second roll, the rotational force applied to the second roll from the second drive source in the second roll rotation process is transferred from the first drive source to the first roll in the first roll rotation process. It can be made smaller than the rotational force given to , and the efficiency of energy use can be improved.

In the nip roll, if the rotational speed of the first roll is V1 and the rotational speed of the second roll is V2, the following equation:

R(%)=[(V1-V2)/V1]×100

The smaller the value of the rotational speed difference ratio R calculated from , the smaller the difference in rotational speed between the first roll and the second roll is preferable. The value of R is preferably 0.2% or less, more preferably 0.1% or less, and even more preferably 0.05% or less.

In the second roll rotation process, the second roll is controlled to rotate in accordance with the rotation of the first roll, and a rotational force is applied to the second roll from the second drive source to change the rotation speed of the second roll to the rotation speed of the first roll. It is desirable to control it so that it is close to . In the first roll rotation process, the rotational force applied to the first roll from the first drive source is T1, and in the second roll rotation process, the rotational force applied to the second roll from the second drive source is T2, for example, 0.01 T1 to 0.6 T1. By providing T2 within the range to the second roll from the second drive source in the second roll rotation process, the rotation speed of the second roll can be brought close to the rotation speed of the first roll.

The rotational speed of the first roll and the second roll can be measured by a measuring device. As a measuring device, for example, a rotary encoder that detects the amount of rotational displacement of the rotation axis of the roll in a contact or non-contact manner and outputs a pulse train according to the amount of rotational displacement can be used.

The rotational force resulting from rotation of the first roll can be applied to the second roll through the conveyed film. From the viewpoint of being able to more effectively apply the rotational force generated by the rotation of the first roll to the second roll, the first roll and the second roll are in direct contact with the outer peripheral surfaces of the first roll and the second roll without intervening a film. It is desirable to have a contact area.

In the nip roll, the positional relationship between the first roll and the second roll is not limited, but the two rolls are disposed at different positions in the vertical direction, and the rotational force applied to the first roll from the first drive source is the second drive source. When the rotational force applied to the second roll is greater than the first roll, it may be desirable to use the roll located vertically downward as the first roll. For example, in a nip roll, when the roll located vertically above is pressed against the roll located vertically below using an air cylinder, since the air cylinder is installed in the roll located vertically above, It is easily affected by disturbances such as fluctuations in syringe pressure or changes in set pressure. If a servomotor, etc., which is susceptible to such disturbances, is used as a drive source for a roll located vertically upward, it becomes difficult to accurately control the rotation speed of the roll, and the rotational force generated by the rotation of the roll is transferred to the other roll. When given to , accurate control of the rotation speed of the other roll also tends to become difficult. Therefore, it becomes easy to accurately control the rotational speed of the nip roll by making the first roll, to which a relatively large rotational force is applied, a roll located below the vertical direction. In addition, when a relatively large rotational force is applied to the first roll, the first drive source for applying the rotational force to the first roll tends to be larger than the second drive source for applying the rotational force to the second roll, so the nip Also in terms of roll maintenance and layout, it is preferable to use the roll whose drive source is located vertically below as the first roll. In addition, the first drive source and the second drive source may be installed within the roll, respectively, or may be installed outside the roll in contact with the roll.

Hereinafter, with reference to FIGS. 1 to 3, an example of a film transport method according to the present invention and a transport device used in the transport method will be described in detail. 1 is a cross-sectional view schematically showing an example of a film transport device according to the present invention. FIG. 2 is a perspective view of the nip roll 7 portion in the conveying device A shown in FIG. 1, and FIG. 3 is a cross-sectional view taken along line X-X of FIG. 2.

FIG. 1 shows a state in which the long film 1 is continuously conveyed along the conveyance path of the conveyance device A. The conveying device A shown in FIG. 1 includes a feeding device 5 that continuously unwinds the film by its rotation; A guide roll (6) supporting the running film; It has a nip roll 7 having a first roll 71 and a second roll 72 facing each other. Although not shown, a winding device for winding the film is usually provided at the downstream end of the conveyance path, and the films that have passed the conveyance path are sequentially wound to form a film roll. In FIG. 1, the solid arrow indicates the transport direction of the film or the rotation direction of the feeding device.

Transport of the film in the transport device A can be performed, for example, as follows. First, the long film 1 is passed through the conveyance path to begin continuous conveyance. The long film 1 is usually prepared as a film roll wound into a roll shape. This film roll is set in a feeding device (feeding device 5 or a separate feeding device), and the film 1 is continuously unwound from the feeding device while continuously conveyed in the direction of the solid arrow in FIG. 1. .

The first roll 71 constituting the nip roll 7 is configured to be given a rotational force by a first drive source not shown, and the second roll 72 is configured to be given a rotational force by a second drive source not shown. Consists of. The first drive source and the second drive source are electrically connected to the control device 8, and are configured to control the rotational force applied to the first roll 71 and the second roll 72 by the control device 8. there is.

As shown in FIG. 3, the first roll 71 and the second roll 72 constituting the nip roll 7 have conveyance areas 71b and 72b in contact with the film to be conveyed, and the outer peripheral surface of the roll. At both ends in the width direction, there are contact areas 71a and 72a where the respective outer peripheral surfaces are in direct contact without contacting the film to be conveyed. By having the contact areas 71a and 72a, the rotational force resulting from rotation of the first roll 71 can be efficiently transmitted to the second roll 72.

The surface material of the first roll 71 and the second roll 72 is not limited, and examples include metal, rubber, etc. The surface materials of the first roll 71 and the second roll 72 may be the same material or different materials.

When the surface material of the first roll 71 or the second roll 72 is rubber, the rubber includes chloroprene rubber (CR), silicone rubber (Si), natural rubber (NR), styrene butadiene rubber (SBR), Examples include nitrile rubber (NBR), ethylene propylene rubber (EPDM), fluorine rubber (FPM), butyl rubber (IIR), urethane rubber (U), and chlorosulfonated polyethylene (CSM). The surface hardness of the rubber roll is preferably 20 to 95 degrees, and more preferably 7 to 90 degrees.

When the first roll 71 or the second roll 72 is a metal roll, various known materials can be used as the base material of the metal roll, but it is preferably SUS304, and the surface is chrome plated. It is more desirable.

The diameters of the first roll 71 and the second roll 72 may be the same or different from each other, and are, for example, 10 mm to 800 mm, and are preferably 30 mm to 500 mm. In addition, the widths of the first roll 71 and the second roll 72 are not limited, but the center of the width direction of the conveyed film is the center of the width direction of the first roll 71 and the second roll 72. In the case of matching, the length from the end of the film to the ends of the first roll 71 and the second roll 72 is preferably 50 mm to 800 mm, and more preferably 100 mm to 600 mm. . The width of the first roll 71 and the second roll 72 is, for example, 400 mm to 2500 mm, and is preferably 600 mm to 2000 mm.

In a film transport device, the film transport speed when continuously transporting a film is, for example, in the range of 2 to 120 m/min, and preferably in the range of 10 to 50 m/min.

The film transport device may include two or more nip rolls for transport. When it includes two or more nip rolls for conveyance, at least one nip roll for conveyance is a nip in which a rotational force is applied to the first roll from a first drive source and a rotational force is applied to the second roll from a second drive source. Any roll will do. The remainder can be, for example, a nip roll composed of a drive roll that rotates by applying a rotational force from a drive source, and a driven roll that follows the rotation of the drive roll. In addition, all of the nip rolls for conveyance may be nip rolls in which a rotational force is provided to the first roll from the first drive source as described above, and a rotational force is provided to the second roll from the second drive source.

<Film subject to return>

The film transport device of the present invention is suitably used as a transport device for optical films requiring high quality films or their raw material films. The raw film referred to herein includes the raw film used to manufacture the optical film and all intermediate films obtained by processing the raw film used to manufacture the optical film.

Optical films include polarizing films; protective film; retardation film; An optical compensation film in which a liquid crystalline compound is applied and oriented on the surface of a substrate; A reflective polarizing film that transmits certain types of polarized light and reflects polarized light showing opposite properties; An anti-glare function imparting film having a concavo-convex shape on the surface; Film imparting surface anti-reflection function; A reflective film having a reflective function on its surface; A semi-transmissive reflective film that has both reflective and transmissive functions; A viewing angle compensation film, etc. may be mentioned.

Examples of the polarizing film include those in which iodine is adsorbed and oriented in a polyvinyl alcohol-based resin film. The raw material film of this polarizing film is a polyvinyl alcohol-based resin film. When a polyvinyl alcohol-based resin film with a high moisture content conveyed in the polarizing film manufacturing process is passed between a pair of rolls, if there is a difference in rotation speed between the pair of rolls, one roll is likely to slip. , it is easy to cause problems with the surface of the film being chipped. The occurrence of such problems can be suppressed by transporting the polyvinyl alcohol-based resin film using the film transport method of the present invention.

The protective film may be a thermoplastic resin having light transparency (preferably optically transparent), such as polyolefin resins such as chain polyolefin resins (polypropylene resins, etc.), cyclic polyolefin resins (norbornene resins, etc.); Cellulose ester-based resins such as triacetylcellulose and diacetylcellulose; polyester resin; polycarbonate-based resin; (meth)acrylic resin; polystyrene-based resin; Alternatively, films made of mixtures, copolymers, etc. thereof may be mentioned.

Commercially available products corresponding to retardation films made of cyclic polyolefin-based resin include “Aton Film” (manufactured by JSR Co., Ltd.), “Scina” (manufactured by Sekisui Chemicals Co., Ltd.), and “Zeonoa Film” (manufactured by Nippon Zeon) Manufacturing Co., Ltd.) and the like can be mentioned.

Commercial products corresponding to optical compensation films include “WV film” (manufactured by Fujifilm Co., Ltd.), “NH film” (manufactured by Nippon Petrochemical Co., Ltd.), and “NR film” (manufactured by Nippon Petrochemical Co., Ltd.). etc. can be mentioned.

Commercially available products corresponding to reflective polarizing films include, for example, “DBEF” (manufactured by 3M, available from Sumitomo 3M Co., Ltd.), “APF” (manufactured by 3M, available from Sumitomo 3M Co., Ltd.) possible).

Examples of the viewing angle compensation film include an optical compensation film in which a liquid crystal compound is applied and oriented on the surface of a substrate, a retardation film made of polycarbonate-based resin, and a retardation film made of cyclic polyolefin-based resin.

The optical film may be a single-layer optical film composed only of any of the above optical films, or may be a laminated optical film composed of a multilayer structure of two, three, or more layers. When the laminated optical film is passed between a pair of rolls, if there is a difference in the rotation speed between the pair of rolls, deviation is likely to occur between the laminated films. When the transport device of the present invention is used, the occurrence of misalignment between laminated films can also be suppressed.

Examples of the laminated optical film include those in which a protective film is bonded to a polarizing film through a water-based adhesive. Misalignment between the laminated films occurs especially when different protective films (e.g., triacetylcellulose (TAC) film and cyclic polyolefin resin (COP) film) are bonded to both sides of the polarizing film using a water-based adhesive. It's easy to happen. The present invention is suitably applied to optical films prone to such problems.

Furthermore, even when using a laminated optical film in which a plurality of films are bonded together through an adhesive or pressure-sensitive adhesive, the optical film transport method of the present invention can be suitably used.

[Method for manufacturing treated film]

The method for producing a treated film of the present invention includes a treatment step of treating a raw material film to obtain a treated film, and a conveyance step of continuously conveying the raw material film or the treated film using the film conveyance method. The raw film referred to here includes all films before completion of processing performed in the processing step, and the treated film refers to the film after processing in the processing step.

In the processing step of the manufacturing method of the present invention, when processing to obtain an optical film is performed, the processed film is an optical film. In the processing step of the manufacturing method of the present invention, when processing to obtain an intermediate film of an optical film is performed, the treated film is an intermediate film. The optical film is as described above.

The manufacturing method of the treated film of this invention has a nip roll conveyance process using the nip roll to which a rotational force is given to a 1st roll from a 1st drive source as mentioned above, and a rotational force is given to a 2nd roll from a 2nd drive source. As a result, the difference in rotational speed between a pair of nip rolls can be reduced. In addition, the occurrence of problems such as chipping of the film surface caused by differences in rotational speed in the nip roll can be reduced.

The apparatus for manufacturing a treated film of the present invention includes a processing unit that processes a raw film to obtain a treated film, and a transport unit that continuously transports the raw film or the treated film by the film transport device. Hereinafter, with reference to FIG. 4, an example of the apparatus for manufacturing a treated film according to the present invention and a method for manufacturing a treated film using the same will be described in detail.

<Polarizing film manufacturing device>

Fig. 4 is a cross-sectional view schematically showing an example of a processing film manufacturing apparatus according to the present invention. The manufacturing apparatus of the processed film shown in FIG. 4 is specifically, a manufacturing apparatus of a polarizing film. That is, in the manufacturing device of the treated film shown in FIG. 4, the treated film is a polarizing film, and processing for obtaining a polarizing film from a polyvinyl alcohol-based resin film is performed in the processing unit.

The polarizing film manufacturing apparatus shown in FIG. 4 transports the raw material film 10 (unstretched) made of polyvinyl alcohol-based resin along the film transport path while continuously unwinding from the raw roll 11, thereby transporting the film. A swelling bath (swelling liquid contained in the swelling tank) (13), a dyeing bath (dying liquid contained in the dyeing tank) (15), and a first cross-linking bath (first cross-linking liquid contained in the cross-linking tank) (17a) installed on the path. , sequentially passing through the second cross-linking bath (second cross-linking liquid contained in the cross-linking tank) 17b and the washing bath (cleaning liquid contained in the washing tank) 19, and finally passing through the drying furnace 21. there is. The obtained polarizing film 23 can, for example, be conveyed as is to the next polarizing plate manufacturing process (a process of bonding a protective film to one or both sides of the polarizing film 23).

In the following description, the “treatment tank” is a general term including a swelling tank, a dyeing tank, a cross-linking tank, and a washing tank, and the “treatment liquid” is a general term including a swelling liquid, a dyeing liquid, a cross-linking liquid, and a washing liquid, “Treatment bath” is a general term that includes a swelling bath, a dyeing bath, a cross-linking bath, and a washing bath. When applied to the manufacturing apparatus of the treated film according to the present invention, the processing section is comprised of a swelling bath, a dyeing bath, a crosslinking bath, a washing bath, and a drying furnace. In addition, the polarizing film 23, which is a film after passing through the drying furnace and completing processing in the processing section of the polarizing film manufacturing apparatus, corresponds to the processed film, and all other films in the process of processing correspond to raw materials films.

The polarizing film is processed by continuously conveying the long raw material film along the film conveyance path of the polarizing film manufacturing apparatus while unwinding the long raw material film from the raw roll, immersing it in the processing liquid contained in the processing tank, and then contacting it with a predetermined processing liquid withdrawn. By performing a drying process after performing a liquid contact process, it can be continuously manufactured as a long polarizing film. In addition, in the treatment liquid contact process, if treatment can be carried out by contacting the film with the treatment liquid, it is not limited to the method of immersing the film in a treatment bath, and the treatment liquid is attached to the film surface by spraying, dripping, dripping, etc. It may be a way to handle . When the treatment liquid contact process is performed by immersing the film in a treatment bath, the treatment bath for performing one treatment liquid contact process is not limited to one, and the film is sequentially immersed in two or more treatment baths to form one treatment bath. A treatment liquid contact process may be performed.

The film transport path of the polarizing film manufacturing apparatus includes, in addition to the above-described treatment bath, guide rolls 30 to 48, 60, 61 that support the transport film or change the film transport direction, and press and hold the transport film. It can be constructed by applying a conveyance force to the film by its rotation, or by arranging nip rolls 50 to 55, which can additionally change the direction of film conveyance, at appropriate positions.

The guide roll or nip roll can be disposed before or after each treatment bath or within the treatment bath, thereby allowing the film to be introduced into, immersed in, and extracted from the treatment bath (see Fig. 4). For example, the film can be immersed in each treatment bath by installing one or more guide rolls in each treatment bath and transporting the film along these guide rolls.

At least one of the nip rolls 50, 51, 52, 53a, 53b, 54, and 55 is provided with a rotational force applied to the first roll from a first drive source, as described in the film transport device, and further from a second drive source. It is a nip roll in which rotational force is given to the second roll. The higher the moisture content of the film, the more likely it is that the surface of the film will be chipped due to the difference in rotation speed between a pair of rolls. Therefore, the nip rolls 51, 52, 53a, 53b, and 54 through which the film passes until it is immersed in the swelling tank 13 and introduced into the drying device 21 are as described in the film transport device, A nip roll in which a rotational force is applied to the first roll from a first drive source and a rotational force to the second roll from a second drive source is preferable from the viewpoint of reducing the occurrence of problems with the surface of the film being chipped. Additionally, since the surface of the film after the crosslinking treatment has been performed becomes brittle, the problem of the surface of the film being chipped tends to occur. Accordingly, the nip rolls 53a, 53b, and 54 are nips in which a rotational force is applied to the first roll from a first drive source and a rotational force is applied to the second roll from a second drive source, as described in the film transport device. A roll is preferable from the viewpoint of reducing the occurrence of problems with the surface of the film being chipped.

In the polarizing film manufacturing apparatus shown in FIG. 4, nip rolls are arranged before and after each treatment bath (nip rolls 50 to 54), and accordingly, within one or more treatment baths, between nip rolls arranged before and after them. It is possible to perform inter-roll stretching, which is longitudinal uniaxial stretching, by providing a peripheral speed difference. Hereinafter, each process will be described.

(swelling process)

The swelling process is performed for the purposes of removing foreign matter from the surface of the raw film 10, removing the plasticizer in the raw film 10, imparting discoloration, and plasticizing the raw film 10. Processing conditions are determined within a range that can achieve the above-mentioned purpose and in a range that does not cause problems such as extreme dissolution or devitrification of the raw material film 10.

Referring to FIG. 4, the swelling process involves conveying the raw material film 10 along a film conveyance path while continuously unwinding it from the raw roll 11, and immersing the raw material film 10 in the swelling bath 13 for a predetermined period of time. , which can then be carried out by withdrawing. In the example of FIG. 4, while the raw material film 10 is unwound and immersed in the swelling bath 13, the raw material film 10 is constructed by the guide rolls 60, 61 and the nip roll 50. is transported along the film transport path. In the swelling process, the film is conveyed along a film conveyance path constructed by the guide rolls 30 to 32 and the nip roll 51.

The swelling liquid of the swelling bath 13 includes, in addition to pure water, boric acid (Japanese Patent Application Laid-open No. 10-153709), chloride (Japanese Patent Application Laid-Open No. 06-281816), inorganic acid, inorganic salt, water-soluble organic solvent, and alcohol. It is also possible to use an aqueous solution added in an amount of about 0.01 to 10% by weight.

The temperature of the swelling bath 13 is, for example, about 10 to 50°C, preferably about 10 to 40°C, and more preferably about 15 to 30°C. The immersion time of the raw material film 10 is preferably about 10 to 300 seconds, more preferably about 20 to 200 seconds. In addition, when the raw material film 10 is a polyvinyl alcohol-based resin film previously stretched in a gas, the temperature of the swelling bath 13 is, for example, about 20 to 70°C, and preferably about 30 to 60°C. The immersion time of the raw material film 10 is preferably about 30 to 300 seconds, more preferably about 60 to 250 seconds.

In the swelling treatment, a problem such as swelling of the raw material film 10 in the width direction and wrinkles forming in the film is likely to occur. As a means to convey the film while removing this wrinkle, a roll having a widening function such as an expander roll, spiral roll, or crown roll is used on the guide rolls 30, 31, and/or 32, or a cloth guider or bend roll is used. Other widening devices such as bars and tenter clips may be used. Another means to suppress the occurrence of wrinkles is to perform stretching treatment. For example, uniaxial stretching treatment can be performed in the swelling bath 13 using the difference in peripheral speed between the nip roll 50 and the nip roll 51.

In the swelling treatment, the film swells and expands also in the transport direction of the film, so when the film is not actively stretched, for example, nip rolls are placed before and after the swelling bath 13 to eliminate slackening of the film in the transport direction. It is desirable to devise means such as controlling the speed of (50, 51). In addition, for the purpose of stabilizing the transport of the film in the swelling bath 13, the water flow in the swelling bath 13 is controlled by an underwater shower, or an EPC device (Edge Position Control device: detects the edge of the film and controls the meandering of the film). It is also useful to use a device to prevent it.

In the example shown in FIG. 4, the film taken out from the swelling bath 13 passes through the guide roll 32, the nip roll 51, and the guide roll 33 in that order and is introduced into the dyeing bath 15.

(Dyeing process)

The dyeing process is performed for the purpose of adsorbing and orienting the dichroic dye to the polyvinyl alcohol-based resin film after the swelling treatment. Processing conditions are determined within a range that can achieve the above-mentioned purpose and in a range that does not cause problems such as extreme dissolution or devitrification of the film. Referring to FIG. 4, the dyeing process is carried out along a film transport path constructed by the nip roll 51, guide rolls 33 to 36, and nip roll 52, and the film after the swelling treatment is placed in the dyeing bath 15. ) (treatment solution contained in a dye bath) for a predetermined period of time, and then withdrawn. In order to increase the dyeability of the dichroic dye, it is preferable that the film used in the dyeing process is a film that has undergone at least a certain degree of uniaxial stretching treatment, or instead of the uniaxial stretching treatment before the dyeing treatment, or in the uniaxial stretching treatment before the dyeing treatment. In addition, it is preferable to perform uniaxial stretching treatment during dyeing treatment.

When using iodine as a dichroic dye, for example, an aqueous solution having a concentration of iodine/potassium iodide/water = about 0.003 to 0.3/about 0.1 to 10/100 in weight ratio can be used as the dyeing solution of the dyeing bath 15. Instead of potassium iodide, other iodides such as zinc iodide may be used, or potassium iodide and other iodides may be used together. Additionally, compounds other than iodide, such as boric acid, zinc chloride, cobalt chloride, etc., may coexist. The case of adding boric acid is different from the crosslinking treatment described later in that it contains iodine, and if the aqueous solution contains about 0.003 parts by weight or more of iodine based on 100 parts by weight of water, it can be regarded as the dyeing bath 15. You can. The temperature of the dyeing bath 15 when immersing the film is usually about 10 to 45°C, preferably 10 to 40°C, more preferably 20 to 35°C, and the immersion time of the film is usually 30 to 35°C. About 600 seconds, preferably 60 to 300 seconds.

When using a water-soluble dichroic dye as a dichroic dye, for example, an aqueous solution having a concentration of dichroic dye/water = about 0.001 to 0.1/100 in weight ratio can be used as the dyeing solution of the dyeing bath 15. This dyeing bath 15 may contain a dyeing aid or the like, and may contain, for example, an inorganic salt such as sodium sulfate or a surfactant. One type of dichroic dye may be used individually, and two or more types of dichroic dyes may be used together. The temperature of the dyeing bath 15 when immersing the film is, for example, about 20 to 80°C, preferably 30 to 70°C, and the immersion time of the film is usually about 30 to 600 seconds, preferably 60 to 300 seconds. It's about a second.

As described above, in the dyeing process, the film can be uniaxially stretched in the dyeing bath 15. Uniaxial stretching of the film can be performed by a method such as providing a peripheral speed difference between the nip rolls 51 and nip rolls 52 arranged before and after the dye bath 15.

In the dyeing treatment, as in the swelling treatment, in order to convey the polyvinyl alcohol-based resin film while removing wrinkles in the film, the guide rolls 33, 34, 35 and/or 36 are provided with expansion rolls such as expander rolls, spiral rolls, and crown rolls. Functional rolls can be used, or other widening devices such as cloth guiders, bend bars, and tenter clips can be used. Another means to suppress the occurrence of wrinkles is to perform stretching treatment similar to the swelling treatment.

In the example shown in FIG. 4, the film drawn out from the dyeing bath 15 passes through the guide roll 36, the nip roll 52, and the guide roll 37 in that order and is introduced into the first crosslinking bath 17a. do.

(Cross-linking process)

The crosslinking process is a treatment performed for purposes such as water resistance and color adjustment (preventing the film from turning bluish, etc.) by crosslinking. In the example shown in Fig. 4, two cross-linking baths are arranged as cross-linking baths for the cross-linking process, the first cross-linking process for the purpose of water resistance is performed in the first cross-linking bath 17a, and the second cross-linking bath for the purpose of color adjustment is performed in the first cross-linking bath 17a. 2 The cross-linking process is performed in the second cross-linking bath 17b. Referring to FIG. 4, the first crosslinking process involves conveying the film along a film conveyance path constructed by the nip roll 52, guide rolls 37 to 40, and nip roll 53a, and forming the first crosslinking bath 17a. This can be carried out by immersing the film after dyeing treatment in (the first crosslinking liquid contained in the crosslinking tank) for a predetermined period of time and then taking it out. In the second cross-linking process, the film is conveyed along the film conveyance path constructed by the nip roll 53a, guide rolls 41 to 44, and nip roll 53b, and the film is transferred to the second cross-linking bath 17b (the second cross-linking bath 17b contained in the cross-linking bath). This can be carried out by immersing the film after the first crosslinking process in a crosslinking solution for a predetermined period of time and then taking it out. Hereinafter, in the case of a cross-linking bath, both the first cross-linking bath (17a) and the second cross-linking bath (17b) are included, and in the case of a cross-linking solution, both the first and second cross-linking solutions are included.

As the crosslinking solution, a solution in which a crosslinking agent is dissolved in a solvent can be used. Examples of the crosslinking agent include boron compounds such as boric acid and borax, glyoxal, and glutaraldehyde. These may be one type or two or more types may be used together. As a solvent, for example, water can be used, but an organic solvent compatible with water may also be included. The concentration of the crosslinking agent in the crosslinking solution is not limited to this, but is preferably in the range of 1 to 20% by weight, and more preferably 6 to 15% by weight.

The crosslinking solution may be an aqueous solution containing, for example, about 1 to 10 parts by weight of boric acid per 100 parts by weight of water. When the dichroic dye used in the dyeing treatment is iodine, the crosslinking liquid preferably contains iodide in addition to boric acid, and the amount can be, for example, 1 to 30 parts by weight based on 100 parts by weight of water. Examples of iodide include potassium iodide and zinc iodide. Additionally, compounds other than iodide, such as zinc chloride, cobalt chloride, zirconium chloride, sodium thiosulfate, potassium sulfite, sodium sulfate, etc., may coexist.

In the crosslinking treatment, the concentrations of boric acid and iodide and the temperature of the crosslinking bath can be appropriately changed depending on the purpose. For example, in the case of the first crosslinking solution where the purpose of the crosslinking treatment is water resistance by crosslinking, it may be an aqueous solution with a concentration of boric acid/iodide/water = 3 to 10/1 to 20/100 by weight ratio. If necessary, other cross-linking agents may be used instead of boric acid, or boric acid and other cross-linking agents may be used together. The temperature of the first crosslinking bath 17a when immersing the film is usually about 50 to 70°C, preferably 53 to 65°C, and the immersion time of the film is usually about 10 to 600 seconds, preferably 20°C. ~300 seconds, more preferably 20~200 seconds. In addition, when dyeing treatment and first cross-linking treatment are performed in this order on a polyvinyl alcohol-based resin film stretched in advance before swelling treatment, the temperature of the first cross-linking bath 17a is usually about 50 to 85 ° C., preferably is 55∼80℃.

In the second crosslinking solution for the purpose of color adjustment, for example, when iodine is used as a dichroic dye, the concentration can be used in a weight ratio of boric acid/iodide/water = 1 to 5/3 to 30/100. The temperature of the second crosslinking bath 17b when immersing the film is usually about 10 to 45°C, and the immersion time of the film is usually about 1 to 300 seconds, preferably 2 to 100 seconds.

The crosslinking treatment may be performed multiple times, and is usually performed 2 to 5 times. In this case, the composition and temperature of each crosslinking bath used may be the same or different as long as they are within the above range. The crosslinking treatment for water resistance by crosslinking and the crosslinking treatment for color adjustment may each be performed in a plurality of processes.

Uniaxial stretching treatment can also be performed in the first crosslinking bath 17a by using the difference in peripheral speed between the nip roll 52 and the nip roll 53a. In addition, uniaxial stretching treatment can also be performed in the second crosslinking bath 17b using the difference in peripheral speed between the nip roll 53a and the nip roll 53b.

In the crosslinking treatment, as in the swelling treatment, in order to convey the polyvinyl alcohol-based resin film while removing wrinkles in the film, rolls with a widening function such as expander rolls, spiral rolls, and crown rolls are used as the guide rolls 38 to 44. Alternatively, you can use other widening devices such as cloth guiders, bend bars, or tenter clips. Another means to suppress the occurrence of wrinkles is to perform stretching treatment similar to the swelling treatment.

In the example shown in Fig. 4, the film taken out from the second crosslinking bath 17b passes through the guide roll 44 and the nip roll 53b in that order and is introduced into the washing bath 19.

(Cleaning process)

In the example shown in FIG. 4, a cleaning step is included after the crosslinking step. The cleaning treatment is performed for the purpose of removing excess chemicals such as boric acid and iodine attached to the polyvinyl alcohol-based resin film. The cleaning process is performed, for example, by immersing the crosslinked polyvinyl alcohol-based resin film in the cleaning bath 19. In addition, instead of the step of immersing the film in the cleaning bath 19, the cleaning process can also be performed by spraying the cleaning liquid on the film as a shower, or by using a combination of immersion in the cleaning bath 19 and spraying the cleaning liquid.

Figure 4 shows an example in which a polyvinyl alcohol-based resin film is immersed in a cleaning bath 19 and subjected to cleaning treatment. The temperature of the washing bath 19 in the washing process is usually about 2 to 7°C, and the immersion time of the film is usually about 2 to 120 seconds.

In addition, in the cleaning treatment, for the purpose of conveying the polyvinyl alcohol-based resin film while removing wrinkles, the guide rolls 45, 46, 47 and/or 48 have a widening function such as an expander roll, a spiral roll, or a crown roll. This can be done using rolls or other widening devices such as cloth guiders, bend bars, or tenter clips. Additionally, in the film cleaning treatment, stretching treatment may be performed to suppress the occurrence of wrinkles.

(Stretching process)

As described above, the raw material film 10 is wet or dry between the series of treatment liquid contact processes (i.e., before and/or during any one or more treatment liquid contact processes). It is uniaxially stretched. A specific method of uniaxial stretching treatment is, for example, inter-roll stretching in which longitudinal uniaxial stretching is performed by providing a peripheral speed difference between two nip rolls (e.g., two nip rolls disposed before and after the treatment bath) constituting the film transport path, Japanese patent. This may be heat roll stretching, tenter stretching, etc. as described in Publication No. 2731813, and is preferably inter-roll stretching. The uniaxial stretching process can be performed multiple times from unwinding the raw material film 10 from the raw roll 11 to obtaining the polarizing film 23. As described above, stretching treatment is also advantageous for suppressing wrinkles in the film.

The final cumulative stretch ratio of the polarizing film 23 based on the raw material film 10 immediately after unwinding from the raw roll 11 is usually about 4.5 to 7 times, and preferably 5 to 6.5 times. The stretching process may be performed in any treatment liquid contact process, and even when the stretching process is performed in two or more treatment liquid contact processes, the stretching process may be performed in any treatment liquid contact process.

(Polarizing film)

In the present invention, the polarizing film is a uniaxially stretched polyvinyl alcohol-based resin film in which a dichroic dye (iodine or dichroic dye) is adsorbed and oriented. The polyvinyl alcohol-based resin constituting the polyvinyl alcohol-based resin film is usually obtained by saponifying polyvinyl acetate-based resin. The saponification degree is usually about 85 mol% or more, preferably about 90 mol% or more, and more preferably about 99 mol% or more. The polyvinyl acetate-based resin may be, for example, polyvinyl acetate, which is a homopolymer of vinyl acetate, as well as a copolymer of vinyl acetate and other monomers copolymerizable therewith. Other monomers that can be copolymerized include, for example, unsaturated carboxylic acids, olefins, vinyl ethers, and unsaturated sulfonic acids. The degree of polymerization of the polyvinyl alcohol-based resin is usually about 1,000 to 10,000, preferably about 1,500 to 5,000.

These polyvinyl alcohol-based resins may be modified, and for example, polyvinyl formal, polyvinyl acetal, polyvinyl butyral, etc. modified with aldehydes can also be used.

In the present invention, as a starting material (raw film 10) for producing a polarizing film, a thickness of 65 ㎛ or less (for example, 60 ㎛ or less), preferably 50 ㎛ or less, more preferably 35 ㎛ or less, even more preferably An unstretched polyvinyl alcohol-based resin film (raw film 10) of 30 μm or less can be used. Accordingly, it is possible to obtain a thin polarizing film for which market demand is increasing. The width of the starting material (raw film 10) is not particularly limited and may be, for example, about 70 to 6000 mm. The starting material (raw film 10) is prepared, for example, as a roll (raw roll) of a long unstretched polyvinyl alcohol-based resin film, as described above.

In addition, the polyvinyl alcohol-based resin film used in the present invention may be laminated on a base film supporting it, that is, the polyvinyl alcohol-based resin film is a base film and a polyvinyl alcohol-based resin film laminated thereon. It may be prepared as a laminated film. In this case, the polyvinyl alcohol-based resin film can be produced, for example, by applying a coating solution containing a polyvinyl alcohol-based resin to at least one side of the base film and then drying it.

As the base film, for example, a film made of a thermoplastic resin can be used. A specific example is a film composed of a light-transmitting thermoplastic resin, preferably an optically transparent thermoplastic resin, such as chain polyolefin resin (polypropylene resin, etc.), cyclic polyolefin resin (norbornene resin, etc.) Polyolefin-based resins such as; Cellulose-based resins such as triacetylcellulose and diacetylcellulose; Polyester resins such as polyethylene terephthalate and polybutylene terephthalate; polycarbonate-based resin; (meth)acrylic resins such as methyl methacrylate resins; polystyrene-based resin; polyvinyl chloride-based resin; Acrylonitrile, butadiene, and styrene-based resin; Acrylonitrile/styrene resin; polyvinyl acetate-based resin; polyvinylidene chloride-based resin; polyamide-based resin; polyacetal resin; Modified polyphenylene ether-based resin; polysulfone-based resin; polyethersulfone-based resin; polyarylate-based resin; polyamideimide-based resin; It may be a polyimide-based resin, etc.

Example

Hereinafter, the present invention will be described in more detail by giving examples, but the present invention is not limited to these examples.

<Example 1>

The film was transported using the film transport device shown in FIG. 1. As the film to be conveyed, a polyvinyl alcohol-based resin film was used. As the first roll 71 and the second roll 72, rolls with a diameter of 300 mm, a width of 2000 mm, and a surface material of NBR were used, respectively. The rotational force T1 applied to the first roll 71 from the first drive source is set to a constant 51.5 N·m, and the ratio P of the rotational force T2 applied to the second roll 72 from the second drive source to T1 is P. (=(T2/T1)×100) is varied within the range of 0 to 4.5%, and the rotational speed of the first roll 71 and the second roll 72 is measured using a measuring device (contact type digital handy tachometer manufactured by Ono Keiki Co., Ltd.) ) was measured. Additionally, the film tension was adjusted so that the film tension was 570 N on the downstream side of the nip roll 7.

FIG. 5 is a diagram plotting the measurement results of the rotational speed V1 of the first roll 71 and the measurement results of the rotational speed V2 of the second roll 72 in Example 1. In Figure 5, the value of the rotational force T1 applied to the first roll 71 is also shown. When P was 0%, the rotation speed V1 of the first roll 71 was 30.074 m/min, and the rotation speed V2 of the second roll 72 was 29.974 m/min. In addition, when P is 4.5% (when T2 is 2.32 N·m), the rotational speed (V1) of the first roll 71 is 30.052 m/min, and the rotational speed (V2) of the second roll 72 is 30.052 m/min. It was 30.046 m/min, and the rotational speed difference ratio R ([(V1-V2)/V1] × 100) was 0.02%.

From FIG. 5, it can be seen that in Example 1, the rotational speed ratio R can be controlled to be 0.2% or less by applying a rotational force of 4.5% of T1 from the second drive source to the second roll 72.

<Example 2>

The film was transported using the film transport device shown in FIG. 1. A polyvinyl alcohol-based resin film was used as the film to be conveyed. As the first roll 71 and the second roll 72, rolls with a diameter of 420 mm, a width of 2100 mm, and a surface material of NBR were used, respectively. While measuring the rotational speed (V1) of the first roll with a measuring device (rotary encoder), a rotational force is applied to the first roll (71) from the first drive source so that the rotational speed (V1) of the first roll (71) is 22.928 m/min. At the same time as applying (T1), the ratio P (=(T2/T1) × 100) of the rotational force (T2) applied to the second roll 72 from the second drive source with respect to T1 is in the range of 0 to 60%. The rotational speed of the second roll 72 was measured with the measuring device. Additionally, the film tension was adjusted so that the film tension was 1000 N on the downstream side of the nip roll 7.

FIG. 6 is a diagram plotting the measurement results of the rotational speed V1 of the first roll 71 and the measurement results of the rotational speed V2 of the second roll 72 in Example 2. In Figure 6, the rotational force T1 of the first roll 71 and the rotational force T2 of the second roll 72 are shown together. Additionally, Table 1 shows the values of V1, V2, T1, and T2 in Example 2. From these results, it can be seen that when P is 60% (when T2 is 144 N·m), the rotational speed difference ratio R ([(V1-V2)/V1] × 100) is 0.19%.

From Figure 6 and Table 1, it can be seen that in Example 2, by applying a rotational force of 60% of T1 from the second drive source to the second roll 72, the rotation speed ratio R can be controlled to be 0.2% or less. there is.

P[%] 30 40 50 60 1st roll T1[N·m] 260 260 260 240 V1[m/min] 22.928 22.928 22.928 22.928 2nd roll T2[N·m] 78 103 130 144 V2[m/min] 6.522 13.044 22.175 22.885

A: Conveying device
1: film
5: Feeding device
6: Guide roll
7: Nip roll
10: Raw film
11: disc roll
13: Swelling bath
15: Dye bath
17a: First cross-linking bath
17b: Second cross-linking bath
30∼48, 60, 61: Guide roll
50∼55: Nip roll
71: 1st roll
72: 2nd roll
71a, 72a: contact area
71b, 72b: Conveyance area

Claims (10)

It has a nip roll conveyance process in which the film is conveyed by rotation of a nip roll having a first roll and a second roll opposing each other,
The nip roll conveyance process includes a first roll rotation process in which a rotational force is applied to the first roll from a first drive source to rotate the first roll, and a second roll rotation process in which the second roll rotates,
The first roll and the second roll have a conveyance area in contact with the film, and a contact area at both ends in the width direction of the outer peripheral surface of the roll, where the respective outer peripheral surfaces are in direct contact without contacting the film,
In the second roll rotation step, the second roll rotates in accordance with the rotation of the first roll, and further rotational force is applied from the second drive source,
In the first roll rotation step, when the rotational force applied to the first roll from the first drive source is T1 and the rotational force applied to the second roll from the second drive source in the second roll rotation step is T2, T2 is 0.5 A film transport method within the range of T1 to 0.6T1. delete delete The film transport method according to claim 1, wherein the film is an optical film or a raw material film thereof. A nip roll having a first roll and a second roll facing each other and conveying the film by rotation,
A first drive source that provides rotational force to the first roll,
A second driving source that provides rotational force to the second roll
With
The first roll and the second roll have a conveyance area in contact with the film, and a contact area at both ends in the width direction of the outer peripheral surface of the roll, where the respective outer peripheral surfaces are in direct contact without contacting the film,
The second roll rotates in response to the rotation of the first roll, and further rotational force is applied from the second drive source,
When the rotational force applied to the first roll from the first drive source is T1 and the rotational force applied to the second roll from the second drive source is T2, T2 operates within the range of 0.5T1 to 0.6T1. The film transport device according to claim 5, wherein the film is an optical film or a raw material film thereof. A processing step of treating a raw material film to obtain a treated film,
A method for producing a treated film, comprising a conveyance step of conveying the raw material film or the treated film by the film conveyance method according to claim 1. 8. The method of claim 7, wherein the treated film is an optical film. a processing unit that processes the raw film to obtain a treated film;
An apparatus for producing a treated film, comprising a conveyance unit that conveys the raw material film or the treated film by the film conveyance apparatus according to claim 5. 10. The apparatus of claim 9, wherein the treated film is an optical film.