JP2021047398A - Method and apparatus for manufacturing polarization film - Google Patents

Abstract

To provide a method for manufacturing a new polarization film, capable of reducing a variation in optical properties in the width direction.SOLUTION: The method for manufacturing a polarization film, capable of manufacturing the polarization film from a polyvinyl alcohol resin film comprises a plurality of processing steps of contacting the polyvinyl alcohol resin film to a treatment solution. At least one of the plurality of processing steps is a multi stage processing step comprising the uniform contact step of contacting the polyvinyl alcohol resin film to a uniform amount of the treatment solution over a full width and the control contact step of contacting the polyvinyl alcohol resin film to the treatment solution having an amount controlled corresponding to a position in the width direction of the full width, and the treatment solution used in the multi stage processing step includes at least one of dichroic dye and a boron compound.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for producing a polarizing film from a polyvinyl alcohol-based resin film, and a production apparatus.

The polarizing plate is widely used as a polarizing element or the like in an image display device such as a liquid crystal display device. As the polarizing plate, a transparent resin film (protective film or the like) is generally attached to one or both sides of the polarizing film using an adhesive or the like.

The polarizing film is mainly a process of immersing a raw film made of a polyvinyl alcohol-based resin in a dyeing bath containing a dichroic dye such as iodine, and then immersing it in a cross-linking bath containing a cross-linking agent such as boric acid. It is manufactured by uniaxially stretching the film at any stage while subjecting it to a process of allowing the film to grow. The uniaxial stretching includes a dry stretching performed in the air and a wet stretching performed in a liquid such as the dyeing bath and the cross-linking bath.

Conventionally, in the method for manufacturing a polarizing film, a device has been devised to suppress variations in optical characteristics in the width direction. Japanese Patent Application Laid-Open No. 2018-32026 (Patent Document 1) irradiates a polyvinyl alcohol-based resin film with an electromagnetic wave containing infrared rays with an irradiation heat amount having a distribution in the width direction to suppress variations in optical characteristics in the width direction. The method is described.

JP-A-2018-32026

An object of the present invention is to provide a novel method and apparatus for manufacturing a polarizing film capable of reducing variations in optical characteristics in the width direction.

The present invention provides the following method and apparatus for manufacturing a polarizing film.
[1] A method for producing a polarizing film for producing a polarizing film from a polyvinyl alcohol-based resin film.
A plurality of treatment steps for bringing the polyvinyl alcohol-based resin film into contact with the treatment liquid are provided.
At least one of the plurality of treatment steps includes a uniform contact step of bringing the polyvinyl alcohol-based resin film into contact with a uniform amount of the treatment liquid over the entire width, and the polyvinyl alcohol-based resin film at a position in the width direction of the entire width. It is a multi-stage treatment step including an adjustment contact step of contacting the treatment liquid in an amount adjusted accordingly.
A method for producing a polarizing film, wherein the treatment liquid used in the multi-step treatment step contains at least one of a dichroic dye and a boron compound.
[2] The method for producing a polarizing film according to [1], wherein in the multi-stage treatment step, the treatment liquid is a dyeing liquid, a cross-linking liquid, or a complementary color liquid.
[3] In the adjustment contact step, the polyvinyl alcohol-based resin film is divided into a central portion and both end portions with respect to the entire width, and the amount of the treatment liquid to be brought into contact with the central portion is the treatment liquid to be brought into contact with the both end portions. The method for producing a polarizing film according to [1] or [2], which is adjusted so as to be larger than the amount of.
[4] The method for producing a polarizing film according to [3], wherein in the adjustment contact step, the central portion of the polyvinyl alcohol-based resin film is 5 to 80% based on the total width.
[5] In the adjustment contact step, the treatment liquid is brought into contact with the central portion of the polyvinyl alcohol-based resin film, and the treatment liquid is adjusted so as not to come into contact with both ends of the polyvinyl alcohol-based resin film [3] or [4]. ]. The method for producing a polarizing film.
[6] The polarizing film according to any one of [1] to [5], wherein the uniform contact step is a step of immersing the polyvinyl alcohol-based resin film in the treatment liquid contained in the treatment tank. Production method.
[7] The method for producing a polarizing film according to any one of [1] to [6], wherein the adjusting contact step is a step of showering the polyvinyl alcohol-based resin film with a shower of the treatment liquid.
[8] The method for producing a polarizing film according to any one of [1] to [9], wherein the overall width of the polyvinyl alcohol-based resin film is 400 mm or more and 8000 mm or less.
[9] A polarizing film manufacturing apparatus for producing a polarizing film from a polyvinyl alcohol-based resin film.
A plurality of processing units for bringing the polyvinyl alcohol-based resin film into contact with the processing liquid are provided.
At least one of the plurality of processing portions is a uniform contact portion for contacting the polyvinyl alcohol-based resin film with a uniform amount of the treatment liquid over the entire width, and the polyvinyl alcohol-based resin film at positions in the width direction of the entire width. It is a multi-stage processing unit having an adjusting contact portion for contacting the treatment liquid in an amount adjusted accordingly.
The treatment liquid used in the multi-stage treatment unit is a polarizing film manufacturing apparatus containing at least one of a dichroic dye and a boron compound.

According to the present invention, it is possible to provide a method and an apparatus for manufacturing a polarizing film that reduces variations in optical characteristics in the width direction of the polarizing film.

It is sectional drawing which shows typically an example of the polarizing film manufacturing method which concerns on this invention, and the polarizing film manufacturing apparatus used for it. It is a figure which looked at the dyeing part of the manufacturing apparatus shown in FIG. 1 from the upper surface side. It is sectional drawing for demonstrating the method of adjusting the amount of the dyeing liquid ejected from a shower apparatus. It is a graph which plotted the luminosity factor correction polarization degree Py of Examples 1 and 2 and Comparative Example 1. It is a graph which plotted the luminosity factor correction polarization degree Py of Examples 3 and 4 and Comparative Example 2.

<Manufacturing method of polarizing film>
The present invention is a method for producing a polarizing film from a polyvinyl alcohol-based resin film, which comprises a plurality of treatment steps for bringing the polyvinyl alcohol-based resin film into contact with a treatment liquid, and at least one of the treatment steps. Is a uniform contact step in which the polyvinyl alcohol-based resin film is brought into contact with a uniform amount of the treatment liquid over the entire width, and an amount of the treatment liquid adjusted according to the position of the polyvinyl alcohol-based resin film in the width direction of the entire width. It is a multi-stage processing step having an adjustment contact step of contacting with. The treatment liquid used in the multi-step treatment step contains at least one of a dichroic dye and a boron compound, and is, for example, a dyeing liquid, a cross-linking liquid, a complementary color liquid, or the like.

In the present invention, the polarizing film is a uniaxially stretched polyvinyl alcohol-based resin film in which a dichroic dye (iodine, dichroic dye, etc.) is adsorbed and oriented. The polyvinyl alcohol-based resin constituting the polyvinyl alcohol-based resin film is usually obtained by saponifying the polyvinyl acetate-based resin. The degree of saponification 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 can be, for example, a polyvinyl acetate which is a homopolymer of vinyl acetate, a copolymer of vinyl acetate and another monomer copolymerizable therewith, or the like. Examples of other copolymerizable monomers include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids and the like. The degree of polymerization of the polyvinyl alcohol-based resin is usually about 1000 to 10000, preferably about 1500 to 5000.

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 for producing a polarizing film, an unstretched polyvinyl alcohol-based resin film having a thickness of 65 μm or less (for example, 60 μm or less), preferably 50 μm or less, more preferably 35 μm or less, still more preferably 30 μm or less (raw fabric). Film) is used. As a result, it is possible to obtain a thin-film polarizing film whose market demand is increasing more and more. The width of the raw film is not particularly limited, and is, for example, 400 mm or more and 8000 mm or less, preferably 2000 mm or more and 5500 mm or less. In particular, when the width of the raw film is 2000 mm or more, the characteristics in the width direction of the polarizing film are likely to vary, but the variation can be reduced according to the production method of the present invention. The raw fabric film is prepared, for example, as a roll of a long unstretched polyvinyl alcohol-based resin film (raw fabric roll).

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

As the base film, for example, a film made of a thermoplastic resin can be used. As a specific example, a film composed of a translucent thermoplastic resin, preferably an optically transparent thermoplastic resin, for example, a chain polyolefin resin (polypropylene resin or the like), a cyclic polyolefin resin, etc. Polyolefin resins such as (norbornen resins, etc.); Cellulosic resins such as triacetyl cellulose, diacetyl cellulose; polyester resins such as polyethylene terephthalate and polybutylene terephthalate; polycarbonate resins; methyl methacrylate resins (Meta) acrylic resin; polystyrene resin; polyvinyl chloride resin; acrylonitrile / butadiene / styrene resin; acrylonitrile / styrene resin; polyvinyl acetate resin; polyvinylidene chloride resin; polyamide resin; polyacetal type Resins; modified polyphenylene ether-based resins; polysulfone-based resins; polyether sulfone-based resins; polyarylate-based resins; polyamideimide-based resins; polyimide-based resins and the like can be used.

The polarizing film is a treatment liquid contained in a treatment tank by unwinding the above-mentioned long raw fabric film from the raw fabric roll and continuously transporting the polarizing film along the film transport path of the polarizing film manufacturing apparatus (hereinafter, It can be continuously produced as a long polarizing film by carrying out a predetermined treatment step of immersing the film in a "treatment bath" and then drawing it out, and then carrying out a drying step. The treatment step is not limited to the method of immersing the film in the treatment bath as long as the treatment liquid is brought into contact with the film, and the treatment liquid may be exposed to the surface of the film. As a method of spraying the treatment liquid on the film surface, a method of showering the treatment liquid on the film surface is preferable. Here, the shower of the treatment liquid means a flow of the treatment liquid ejected from a plurality of spouts, and even if the treatment liquid is intermittently contained in the flow (for example, it is contained in a granular or mist form). , May be included continuously. A shower device is a device that has a plurality of spouts and ejects liquid from the spouts to create a flow of liquid. A shower device is usually used to shower the surface of the film with a shower of treatment liquid. When the treatment step is performed by a method of immersing the film in a treatment bath, the treatment bath for performing one treatment step is not limited to one, and the film is sequentially immersed in two or more treatment baths. One processing step may be completed.

Examples of the treatment liquid include a swelling liquid, a dyeing liquid, a cross-linking liquid, a complementary color liquid, and a cleaning liquid. The treatment steps include a swelling step in which the swelling liquid is brought into contact with the raw fabric film to perform the swelling treatment, a dyeing step in which the dyeing liquid is brought into contact with the film after the swelling treatment to perform the dyeing treatment, and a dyeing step after the dyeing treatment. A cross-linking step in which a cross-linking liquid is brought into contact with a film to perform a cross-linking treatment, a complementary color step in which a complementary color liquid is brought into contact with the cross-linked film to perform a color adjustment treatment, and a cleaning treatment in which the cleaning liquid is brought into contact with the film after the cross-linking treatment An example is a cleaning process in which the above is performed. In addition, uniaxial stretching treatment is performed wet or dry between these series of treatment steps (that is, before and after any one or more treatment steps and / or during any one or more treatment steps). Other processing steps may be added if necessary.

The present inventors have made the film uniform over the entire width from the viewpoint of suppressing variations in optical characteristics in the width direction in a treatment step using a treatment liquid containing at least one of a dichroic dye and a boron compound. Based on the finding that it is preferable to have a multi-stage treatment step including a uniform contact step of contacting with the treatment liquid and an adjustment contact step of contacting the film with the treatment liquid in an amount adjusted according to the position in the width direction of the entire width. It led to the invention. Examples of the treatment step using the treatment liquid containing at least one of the dichroic dye and the boron compound include a dyeing step, a cross-linking step, a complementary color step and the like.

Hereinafter, an example of a method for producing a polarizing film according to the present invention will be described with reference to FIG. FIG. 1 is a cross-sectional view schematically showing an example of a polarizing film manufacturing method according to the present invention and a polarizing film manufacturing apparatus used therefor. The polarizing film manufacturing apparatus shown in FIG. 1 transports a raw fabric (unstretched) film 10 made of a polyvinyl alcohol-based resin along a film transport path while continuously unwinding the raw fabric (unstretched) film 10 from the raw fabric roll 11. A swelling bath (swelling liquid housed in the swelling tank) 13, a dyeing bath (staining liquid housed in the dyeing tank) 15, and a cross-linking bath (cross-linking liquid housed in the cross-linking tank) 17a provided on the transport path. , The complementary color bath (complementary color liquid housed in the cross-linking tank) 17b, and the washing bath (cleaning liquid housed in the washing tank) 19 are sequentially passed, and finally passed through the drying furnace 21. The obtained polarizing film 23 can be conveyed as it is to, for example, the next polarizing plate manufacturing step (step of laminating a protective film on one side or both sides of the polarizing film 23). The arrows in FIG. 1 indicate the film transport direction. A shower device 16 is installed in the dyeing bath 15, and the film 10 that has passed through the dyeing bath 15 is configured to pass through the shower device 16 after that.

In the description of FIG. 1, "treatment tank" is a general term including a swelling tank, a dyeing tank, a cross-linking tank, a complementary color tank, and a cleaning tank, and "treatment liquid" is a swelling liquid, a dyeing liquid, a cross-linking liquid, and a complementary color tank. It is a general term including a liquid and a washing liquid, and the "treatment bath" is a general term including a swelling bath, a dyeing bath, a cross-linking bath, a complementary color bath, and a washing bath. The swelling bath, the dyeing bath and the shower device, the cross-linking bath, the complementary color bath, and the washing bath each constitute a swelling part, a dyeing part, a cross-linking part, a complementary color part, and a washing part in the manufacturing apparatus of the present invention.

In the manufacturing apparatus shown in FIG. 1, the dyeing unit is configured such that after the uniform contact step is performed in the dyeing bath 15, the adjustment contact step is performed by passing through the shower device 16 and the multi-stage processing step is performed. ing. That is, the dyeing section is configured as a multi-stage processing section including a dyeing bath 15 which is a uniform contact section and a shower device 16 which is an adjustment contact section.

In addition to the above-mentioned treatment bath and shower device, the film transport path of the polarizing film manufacturing apparatus includes guide rolls 30 to 35, 37 to 48, 60, which can support the film to be transported or further change the film transport direction. By arranging 61, or nip rolls 50 to 56 capable of pressing and holding the film to be transported and applying a driving force due to the rotation to the film, or further changing the film transport direction, at appropriate positions. Can be built. The guide roll and the nip roll can be arranged before and after each treatment bath or in the treatment bath, whereby the film can be introduced and immersed in the treatment bath and pulled out from the treatment bath [see FIG. 1]. For example, by providing one or more guide rolls in each treatment bath and transporting the film along these guide rolls, the film can be immersed in each treatment bath.

In the polarizing film manufacturing apparatus shown in FIG. 1, nip rolls are arranged before and after each treatment bath (nip rolls 50 to 54, 56), whereby the nip rolls are arranged before and after in any one or more of the treatment baths. It is possible to carry out inter-roll stretching in which longitudinal uniaxial stretching is performed with a difference in peripheral speed between the nip rolls. Hereinafter, each step will be described.

(Swelling process)
The swelling step is performed for the purpose of removing foreign matter on the surface of the raw film 10, removing the plasticizer in the raw film 10, imparting easy dyeability, and plasticizing the raw film 10. The treatment conditions are determined within a range in which the object can be achieved and within a range in which problems such as extreme dissolution and devitrification of the raw film 10 do not occur.

In the swelling step, referring to FIG. 1, the raw film 10 is continuously unwound from the raw film roll 11 and conveyed along the film transport path, and the raw film 10 is immersed in the swelling bath 13 for a predetermined time. , Then can be carried out by pulling out. In the example of FIG. 1, from unwinding the raw film 10 to immersing it in the swelling bath 13, the raw film 10 is conveyed along the film conveying path constructed by the guide rolls 60 and 61 and the nip roll 50. Will be done. In the swelling treatment, the film is conveyed along the film transfer path constructed by the guide rolls 30 to 32 and the nip roll 51.

The swelling liquid of the swelling bath 13 includes pure water, boric acid (Japanese Patent Laid-Open No. 10-153709), chloride (Japanese Patent Laid-Open No. 06-281816), inorganic acids, inorganic salts, water-soluble organic solvents, and alcohols. It is also possible to use an aqueous solution to which the like and the like are added in the range of about 0.01 to 10% by mass.

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 film 10 is preferably about 10 to 300 seconds, more preferably about 20 to 200 seconds. When the raw 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, preferably about 30 to 60 ° C. The immersion time of the raw film 10 is preferably about 30 to 300 seconds, more preferably about 60 to 240 seconds.

In the swelling treatment, a problem that the raw film 10 swells in the width direction and the film is wrinkled tends to occur. As one means for transporting the film while removing the wrinkles, a roll having a widening function such as an expander roll, a spiral roll, or a crown roll is used for the guide rolls 30, 31 and / or 32, or a cross guider or a bend bar is used. , Other widening devices such as tenter clips may be used. Another means for suppressing the occurrence of wrinkles is to apply a stretching treatment. For example, the uniaxial stretching treatment can be performed in the swelling bath 13 by utilizing the difference in peripheral speed between the nip roll 50 and the nip roll 51.

In the swelling treatment, the film swells and expands in the transport direction of the film. Therefore, when the film is not actively stretched, it is arranged before and after the swelling bath 13, for example, in order to eliminate the slack of the film in the transport direction. It is preferable to take measures such as controlling the speeds of the nip rolls 50 and 51. Further, for the purpose of stabilizing the film transfer in the swelling bath 13, the water flow in the swelling bath 13 is controlled by an underwater shower device, or an EPC device (Edge Position Control device: the edge of the film is detected to detect the edge of the film. It is also useful to use a device to prevent meandering) in combination.

In the example shown in FIG. 1, the film drawn from the swelling bath 13 passes through the guide roll 32, the nip roll 51, and the guide roll 33 in this order and is introduced into the dyeing bath 15.

(Dyeing process)
The dyeing step is performed for the purpose of adsorbing and orienting a dichroic dye such as iodine on the polyvinyl alcohol-based resin film after the swelling treatment. The treatment conditions are determined within a range in which the object can be achieved and within a range in which problems such as extreme melting and devitrification of the film do not occur. With reference to FIG. 1, in the dyeing step, the film is conveyed along the film transfer path constructed by the nip rolls 51, guide rolls 33 to 35, and nip rolls 56 and 52, and the film after the swelling treatment is transferred to the dyeing bath 15 (in the dyeing tank). It can be carried out by immersing it in the contained treatment liquid) for a predetermined time, then pulling it out, and then passing it through the shower device 16. In order to improve the dyeability of the bicolor dye, the film subjected to the dyeing step is preferably a film that has undergone at least some uniaxial stretching treatment, or instead of the uniaxial stretching treatment before the dyeing treatment, or. In addition to the uniaxial stretching treatment before the dyeing treatment, it is preferable to perform the uniaxial stretching treatment during the dyeing treatment.

It is preferable to use iodine as the bicolor dye, and in the dyeing solution of the dyeing bath 15, for example, the concentration is iodine / potassium iodide / water = 0.003 to 0.3 / 0.1 / 10 / in terms of mass ratio. An aqueous solution of 100 can be used. Instead of potassium iodide, other iodides such as zinc iodide may be used, or potassium iodide and other iodides may be used in combination. Further, compounds other than iodide, for example, boric acid, zinc chloride, cobalt chloride and the like may coexist. When boric acid is added, it is distinguished from the cross-linking solution described later in that it contains a dichroic dye, and the aqueous solution contains 0.003 parts by mass or more of the dichroic dye with respect to 100 parts by mass of water. For example, it can be regarded as a dyeing solution. 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 immersing time of the film is usually 30 to 600 seconds. The degree, preferably 60 to 300 seconds.

A water-soluble dichroic dye may be used together with iodine as the dichroic dye, and the dyeing solution of the dyeing bath 15 has, for example, a dichroic dye / water in terms of mass ratio of about 0.001 to 0.1. An aqueous solution of / 100 can be used. The dyeing solution may contain a dyeing aid or the like, and may contain, for example, an inorganic salt such as sodium sulfate or a surfactant. Only one kind of dichroic dye may be used alone, or two or more kinds of dichroic dyes may be used in combination.

As described above, in the dyeing step, the film can be uniaxially stretched in the dyeing bath 15. The uniaxial stretching of the film can be performed by a method of providing a peripheral speed difference between the nip rolls 51 and the nip rolls 56 arranged before and after the dyeing bath 15.

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

In the example shown in FIG. 1, the film drawn from the dyeing bath 15 passes through the shower device 16 and sequentially passes through the nip roll 56, the nip roll 52, and the guide roll 37 and is introduced into the crosslinked bath 17a. As described above, in the example shown in FIG. 1, the dyeing step is a multi-step treatment step. Details of the multi-stage processing process will be described later.

(Crosslinking process)
The cross-linking step is a process performed for the purpose of making water resistant by cross-linking. The cross-linking step may be performed a plurality of times. With reference to FIG. 1, the cross-linking step is carried out along a film transport path constructed by the nip roll 52, the guide rolls 37 to 40 and the nip roll 53a, and dyed in the cross-linking bath 17a (cross-linking liquid contained in the cross-linking tank). It can be carried out by immersing the treated film for a predetermined time and then pulling it out.

As the cross-linking solution, a solution in which a cross-linking agent is dissolved in a solvent can be used. Examples of the cross-linking agent include boron compounds such as boric acid and borax, glyoxal, and glutaraldehyde. These may be one kind, or two or more kinds may be used in combination. As the solvent, for example, water can be used, but an organic solvent compatible with water may be further contained. The concentration of the cross-linking agent in the cross-linking solution is not limited to this, but is preferably in the range of 1 to 20% by mass, and more preferably 4 to 15% by mass.

The cross-linking solution can be an aqueous solution containing, for example, about 1 to 10 parts by mass of boric acid with respect to 100 parts by mass of water. When the dichroic pigment used in the dyeing treatment is iodine, the cross-linking solution preferably contains iodide in addition to boric acid, and the amount thereof is, for example, 1 to 30 parts by mass with respect to 100 parts by mass of water. Can be. Examples of the iodide include potassium iodide and zinc iodide. Further, compounds other than iodide, for example, zinc chloride, cobalt chloride, zirconium chloride, sodium thiosulfate, potassium sulfite, sodium sulfate and the like may coexist.

In the cross-linking treatment, the concentrations of boric acid and iodide and the temperature of the cross-linking bath 17 can be appropriately changed depending on the purpose. For example, it can be an aqueous solution having a concentration of boric acid / iodide / water = 3 to 10/1 to 20/100 in terms of mass ratio. If necessary, another cross-linking agent may be used instead of boric acid, or boric acid and another cross-linking agent may be used in combination. The temperature of the cross-linked bath 17a when immersing the film is usually about 50 to 70 ° C., preferably 53 to 65 ° C., and the immersing time of the film is usually about 10 to 600 seconds, preferably 20 to 300 seconds. It is preferably 20 to 200 seconds.

The cross-linking treatment may be performed a plurality of times, and is usually performed 2 to 5 times. In this case, the composition and temperature of each crosslinked bath used may be the same or different as long as it is within the above range. Further, the uniaxial stretching treatment can be performed in the cross-linked bath 17a by utilizing the difference in peripheral speed between the nip roll 52 and the nip roll 53a.

In the cross-linking treatment as well, in order to convey the polyvinyl alcohol-based resin film while removing the wrinkles of the film as in the swelling treatment, the expander roll and the spiral roll are placed on the guide rolls 38, 39, 40, 41, 42, 43 and / or 44. , A roll having a widening function such as a crown roll can be used, or another widening device such as a cross guider, a bend bar, or a tenter clip can be used. Another means for suppressing the occurrence of wrinkles is to perform a stretching treatment as in the swelling treatment.

(Complementary color process)
As the complementary color solution for the purpose of adjusting the hue, for example, when iodine is used as the dichroic dye in the dyeing solution, the concentration is boric acid / iodide / water = 1 to 5/3 to 30/100 in terms of mass ratio. Can be used. The temperature of the complementary color bath 17b when immersing the film is usually about 20 to 65 ° C., and the immersing time of the film is usually about 1 to 300 seconds, preferably 2 to 100 seconds.

Uniaxial stretching treatment can also be performed in the cross-linked bath 17a by utilizing the difference in peripheral speed between the nip roll 52 and the nip roll 53a. Further, the uniaxial stretching treatment can be performed in the complementary color bath 17b by utilizing the difference in peripheral speed between the nip roll 53a and the nip roll 53b.

In the example shown in FIG. 1, the film drawn from the complementary color bath 17b passes through the guide roll 44 and the nip roll 53b in this order and is introduced into the washing bath 19.

(Washing process)
The example shown in FIG. 1 includes a cleaning step after the cross-linking step. The cleaning treatment is performed for the purpose of removing excess chemicals such as boric acid and iodine adhering to the polyvinyl alcohol-based resin film. The cleaning step is performed, for example, by immersing the crosslinked polyvinyl alcohol-based resin film in the cleaning bath 19. In the cleaning step, instead of the step of immersing the film in the cleaning bath 19, the film is showered with the cleaning liquid, or the film is immersed in the cleaning bath 19 and showered with the cleaning liquid in combination. You can also do it.

FIG. 1 shows an example in which a polyvinyl alcohol-based resin film is immersed in a cleaning bath 19 to perform a cleaning treatment. The temperature of the washing bath 19 in the washing treatment is usually about 2 to 50 ° C., and the immersion time of the film is usually about 2 to 120 seconds.

In the cleaning treatment, the guide rolls 45, 46, 47 and / or 48 have widening functions such as an expander roll, a spiral roll, and a crown roll for the purpose of transporting the polyvinyl alcohol-based resin film while removing wrinkles. Or other widening devices such as cross guiders, bend bars and tenter clips can be used. Further, in the film cleaning treatment, a stretching treatment may be performed in order to suppress the occurrence of wrinkles.

(Stretching process)
As described above, the raw film 10 is uniaxially stretched wet or dry during the series of treatment steps (that is, before and after any one or more treatment steps and / or during any one or more treatment steps). It is processed. A specific method of uniaxial stretching treatment is, for example, between rolls for longitudinal uniaxial stretching with a difference in peripheral speed between two nip rolls constituting a film transport path (for example, two nip rolls arranged before and after the treatment bath). Stretching, thermal roll stretching, tenter stretching, etc. as described in Japanese Patent No. 2731813 can be performed, and inter-roll stretching is preferable. The uniaxial stretching step can be performed a plurality of times until the polarizing film 23 is obtained from the raw film 10. As described above, the stretching treatment is also advantageous in suppressing the occurrence of wrinkles in the film.

The final cumulative draw ratio of the polarizing film 23 based on the raw film 10 is usually about 4.5 to 7 times, preferably 5 to 6.5 times. The stretching step may be performed in any of the treatment steps, and even when the stretching treatment is performed in two or more treatment steps, the stretching treatment may be performed in any of the treatment steps.

(Drying process)
After the washing step, it is preferable to carry out a treatment for drying the polyvinyl alcohol-based resin film. The drying of the film is not particularly limited, but it can be carried out using the drying oven 21 as in the example shown in FIG. The drying oven 21 may be provided with, for example, a hot air dryer. The drying temperature is, for example, about 30 to 100 ° C., and the drying time is, for example, about 30 to 600 seconds. The process of drying the polyvinyl alcohol-based resin film can also be performed using a far-infrared heater. The thickness of the polarizing film 23 obtained as described above is, for example, about 5 to 30 μm.

(Multi-stage processing process)
In the polarizing film manufacturing apparatus shown in FIG. 1, the dyeing step is a multi-stage treatment step, and a uniform contact treatment step by the dyeing bath 15 and an adjustment contact step by the shower device 16 are performed. It is preferable that the dyeing solution in the dyeing bath 15 and the dyeing solution ejected from the shower device 16 have the same or similar composition. Further, it is preferable that the temperature of the dyeing liquid ejected from the shower device 16 is adjusted within the temperature range of the dyeing bath described above. The dyeing solution ejected from the shower device 16 is preferably a dyeing solution derived from the dyeing bath 15, and is preferably collected in the dyeing bath 15 after being exposed to the film.

The shower device 16 is configured so that the film to be treated can be exposed to an amount of the dyeing solution adjusted according to the position in the width direction of the entire width. As described above, since the dyeing step is a multi-step treatment step having an adjustment contact step as well as a uniform contact step, it is possible to suppress dyeing unevenness in the width direction of the film and reduce variations in the optical characteristics of the obtained polarizing film. Can be made to.

FIG. 2 is a view of a dyed portion for performing a dyeing step in the polarizing film manufacturing apparatus shown in FIG. 1 as viewed from the upper surface side. As shown in FIG. 2, the film 10 is conveyed by the conveying guide roll 33 in the direction of the arrow in the drawing. As a result, the film 10 passes through the shower device 16 after being immersed in the dyeing bath 15. The shower device 16 includes two shower bars 16a and 16b arranged so as to face both sides of the film 10, and a plurality of shower nozzles 161 are arranged in each of the shower bars 16a and 16b in the width direction of the film. , The dyeing liquid is ejected from each shower nozzle 161. By adjusting the amount of dyeing liquid ejected from each shower nozzle 161, the amount of dyeing liquid adjusted according to the position of the entire width of the film 10 in the width direction can be brought into contact with the film 10. The film 10 is sent to the nip roll 56 after passing through the shower device 16. The nip roll 56 also functions as a liquid removing means for removing the dyeing liquid adhering to the surface of the film 10.

FIG. 3 is a cross-sectional view for explaining a method of adjusting the amount of the dyeing liquid ejected from the shower device 16. The method of adjusting the amount of the dyeing liquid ejected from the shower device 16 is as follows: for the shower nozzles 161 arranged in the width direction of the film 10, the shower nozzles 161a of the portion corresponding to the central portion of the film 10 and both ends of the film. The amount of the shower nozzle 161a corresponding to the central portion of the film 10 and the amount of the shower nozzle 161b corresponding to both ends of the film 10 are adjusted separately from the shower nozzle 161b of the portion corresponding to the above. A mode of showering can be mentioned.

For example, as shown in FIG. 3, in the shower device 16, in the shower nozzle 161, the dyeing liquid is ejected only from the shower nozzle 161a of the portion corresponding to the central portion of the film 10, and the portion corresponding to both ends of the film 10. A specific embodiment for preventing the dyeing liquid from being ejected from the shower nozzle 161b of the above can be mentioned.

The central portion of the film is preferably 5 to 80% based on the total width of the film, more preferably 20 to 70%, and even more preferably 40 to 60%. The ratio of the central portion to the total width of the film can be selected according to the situation of variation in optical characteristics to be improved. Both ends of the film are located at both ends of the central portion of the film, and it is preferable that the width of one end and the width of the other end are the same.

The variation in the optical characteristics of the polarizing film is such that in each of the above-mentioned treatment steps, the treatment liquid easily penetrates from the end face rather than the surface of the polyvinyl alcohol-based resin film, and the amount of the treatment liquid penetrated differs between the vicinity of the end portion and the vicinity of the center portion. It is presumed that one factor is that there is a difference in the degree of generation processing. Further, it is presumed that one factor is that the thickness varies in the width direction due to stretching, and the degree of treatment in each treatment step differs depending on the thickness. Based on such factors, the polyvinyl alcohol-based resin film is not limited to the method of classifying the polyvinyl alcohol-based resin film into "edge / center / edge" in the width direction as described above, and is not limited to the end and center. The adjustment contact step may be performed by dividing the portions so that one or more regions are further present and adjusting the amount of the dyeing liquid to be contacted for each region.

The order of the uniform contact step and the adjustment contact step in the multi-step processing step is not limited. Therefore, the arrangement position of the shower device is not limited to the outlet side of the dyeing bath 15 as shown in FIG. 1, and may be the inlet side, and is provided on both the inlet side and the outlet side. There may be. Further, in the configuration in which the shower device is provided on the outlet side, the position of the shower device may be the upstream side or the downstream side of the nip roll 56 which is also a liquid removing means. From the viewpoint of showering a specific area, it may be arranged on the downstream side of the nip roll 56 which is a liquid removing means. Further, from the viewpoint of suppressing the formation of a clear boundary of optical characteristics between two regions having different contact amounts of the dyeing liquid, it is arranged on the upstream side of the nip roll 56, which is a liquid removing means, and is placed on the film surface immediately after immersion. The adjustment contact step may be performed with the dyeing solution remaining.

The shower may be showered on both surfaces of the film, or only on one surface. When showering a film transported in a direction having a predetermined angle with respect to the vertical direction, that is, the film is transported in a state where both sides of the film can be distinguished from the upper side and the lower side with respect to the vertical direction. When showering the film, it is preferable to shower at least the upper surface of the film from the viewpoint of liquid drainage and uniformity. In the shower area, the total amount of shower per unit area of the film is, for example, 0.05 to 20 L / m ² , preferably 0.1 to 10 L / m ^2. The total amount of showers showered on the film can be adjusted by adjusting the amount of the treatment liquid ejected from the shower device, adjusting the transport speed of the film, and the like.

As the liquid removing means for removing the dyeing liquid from the surface of the film, in addition to the nip roll 56 shown in FIG. 1, a means for blowing air on the film to remove the liquid, a scraper for removing the liquid in contact with the film, or the like is used. You may.

It is preferable that at least one of the dyeing step, the cross-linking step and the complementary color step is a multi-step treatment step, and all of the dyeing step, the cross-linking step and the complementary color step may be a multi-step treatment step. When the cross-linking step and / or the complementary color step is a multi-step treatment step, the above-mentioned structure of the dyed section can be applied to the structure of the cross-linked portion and the complementary color section. When the treatment step to which the multi-stage treatment step is applied is a configuration in which the film is sequentially immersed in two or more treatment baths, a shower device may be installed in any of the treatment baths.

Further, the multi-step treatment step is not limited to the dyeing step, the cross-linking step and the complementary color step, and the cleaning step may be a multi-step treatment step. When the cleaning step is a multi-step treatment step, the adjustment contact step is preferably adjusted so that the amount of the cleaning liquid in contact with both ends of the film is larger than the amount of the cleaning liquid in contact with the central portion of the film.

When a plurality of processing steps are multi-step processing steps, a different adjustment method can be adopted for each adjustment contact step of each multi-step treatment step. For example, the width of the central portion is different for each adjustment contact step. Good.

(Other processing steps for polyvinyl alcohol-based resin film)
It is also possible to add a process other than the above process. Examples of the treatment that can be added include a dipping treatment (zinc treatment) in an aqueous solution containing zinc chloride or the like that does not contain a boron compound, which is performed after the crosslinking step.

<Polarizing film>
By the above-mentioned method, it is possible to obtain a polarizing film in which variations in optical characteristics in the width direction are suppressed. The visible sensitivity-corrected simple substance transmittance Ty of the obtained polarizing film is preferably 40 to 47%, more preferably 41 to 45%, in consideration of the balance with the visual sensitivity-corrected polarization degree Py. The luminous efficiency correction degree of polarization Py is preferably 99.9% or more, and more preferably 99.95% or more at any position in the width direction. The difference between the maximum value and the minimum value in the width direction of the luminous efficiency correction polarization degree Py is preferably 0.0015% or less, and the smaller the difference, the more preferable.

For the polarizing film, the MD transmittance and TD transmittance in the wavelength range of 380 to 780 nm were measured using a spectrophotometer with an integrating sphere [“V7100” manufactured by JASCO Corporation], and the following formula:
Elemental transmittance (%) = (MD + TD) / 2
Polarization degree (%) = {(MD-TD) / (MD + TD)} × 100
The simple substance transmittance and the degree of polarization at each wavelength are calculated based on.

The "MD transmittance" is the transmittance when the direction of polarized light emitted from the Gran Thomson prism and the transmission axis of the polarizing film sample are parallel to each other, and is expressed as "MD" in the above formula. The "TD transmittance" is the transmittance when the direction of polarized light emitted from the Gran Thomson prism and the transmission axis of the polarizing film sample are orthogonal to each other, and is expressed as "TD" in the above equation. Luminosity factor is corrected for the obtained single transmittance and polarization degree by the two-degree field (C light source) of JIS Z 8701: 1999 "Color display method-XYZ color system and X ₁₀ Y ₁₀ Z _{10 color system".} This is performed to obtain the luminosity factor correction single transmittance (Ty) and the luminosity factor correction polarization degree (Py).

The width of the polarizing film of the present invention is, for example, 50 mm or more and 5000 mm or less, preferably 500 mm or more and 4000 mm or less. The obtained polarizing film may be sequentially wound on a winding roll to form a roll, or the obtained polarizing film may be directly subjected to a polarizing plate manufacturing step (a step of laminating a protective film or the like on one or both sides of the polarizing film) without winding. You can also.

<Polarizer>
A polarizing plate can be obtained by laminating a protective film on at least one surface of the polarizing film produced as described above via an adhesive. Examples of the protective film include a film made of an acetyl cellulose resin such as triacetyl cellulose and diacetyl cellulose; a film made of a polyester resin such as polyethylene terephthalate, polyethylene naphthalate and polybutylene terephthalate; a polycarbonate resin film and cyclo. Examples thereof include an olefin resin film; an acrylic resin film; and a film made of a chain olefin resin of a polypropylene resin.

In order to improve the adhesiveness between the polarizing film and the protective film, the surface to which the polarizing film and / or the protective film is bonded is subjected to corona treatment, flame treatment, plasma treatment, ultraviolet irradiation, primer coating treatment, saponification treatment, etc. Treatment may be applied. The adhesive used for bonding the polarizing film and the protective film is an active energy ray-curable adhesive such as an ultraviolet curable adhesive, an aqueous solution of a polyvinyl alcohol-based resin, or an aqueous solution containing a cross-linking agent. , Water-based adhesives such as urethane-based emulsion adhesives can be mentioned. The ultraviolet curable adhesive may be a mixture of an acrylic compound and a photoradical polymerization initiator, a mixture of an epoxy compound and a photocationic polymerization initiator, or the like. Further, a cationically polymerizable epoxy compound and a radically polymerizable acrylic compound may be used in combination, and a photocationic polymerization initiator and a photoradical polymerization initiator may be used in combination as an initiator.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these examples.

[Manufacturing of polarizing film]
<Example 1>
From the upstream side, it has a swelling bath, two dyeing baths (first dyeing bath and second dyeing bath), two cross-linking baths (first cross-linking bath, second cross-linking bath), complementary color bath, and washing bath. 1 is a manufacturing device in which shower devices are arranged on the inlet side and the outlet side of the dyeing bath, the inlet side of the second dyeing bath, and the inlet side and the outlet side of the complementary color bath, and the other configurations are the manufacturing devices shown in FIG. The polarizing film of Example 1 was manufactured using a manufacturing apparatus having the same configuration.

Specifically, a long polyvinyl alcohol (PVA) raw film [trade name "M6000" manufactured by Mitsubishi Chemical Co., Ltd., saponification degree 99.9 mol% or more) having a width of 4260 mm and a thickness of 60 μm is continuously unwound from the roll. The film was immersed in a swelling bath (26 ° C.) made of pure water so that the residence time was 15 seconds (swelling step). Then, the film pulled out from the swelling bath was subjected to a first dyeing bath containing iodine (100 parts by mass of water, 0.028 parts by mass of iodine, 1.3 parts by mass of potassium iodide) and a second dyeing bath at 30 ° C. (100 parts by mass of water, 0.023 parts by mass of iodine, 1.7 parts by mass of potassium iodide, 0.4 parts by mass of boric acid), the total residence time of the first dyeing bath and the second dyeing bath was 58 seconds. It was continuously immersed so as to be (dyeing step). Next, the film drawn from the second dyeing bath was placed in a first crosslinked bath at 56 ° C. having potassium iodide / boric acid / water of 12/5/100 (mass ratio) for a residence time of 20 seconds and the same liquid composition. It was immersed in a second crosslinked bath at 58 ° C. with a residence time of 38 seconds. Further, potassium iodide / boric acid / water was immersed in a complementary color bath at 40 ° C., which is 13/5/100 (mass ratio), with a residence time of 17 seconds (complementary color step). Then, the film was immersed in a washing bath made of pure water at 5 ° C. (cleaning step).

In the first dyeing bath, the shower devices installed on the inlet side and the outlet side of the first dyeing bath respectively allow the first dyeing bath to cover only the central portion of 2420 mm (50% of the total width of the central portion) with respect to the film width of 4803 mm. I took a shower of the dyeing solution with the same composition as. In the second dyeing bath, a shower device installed on the inlet side showers the dyeing solution having the same composition as the second dyeing bath only in the central portion 2310 mm (50% of the total width of the central portion) with respect to the film width of 4646 mm. I showered it. In the complementary color bath, shower devices installed on the inlet side and the outlet side shower the complementary color solution having the same composition as the complementary color bath only on the central portion 1210 mm (50% of the total width of the central portion) with respect to the film width of 2406 mm. It was. Further, in the dyeing step, the cross-linking step, and the complementary color step, longitudinal uniaxial stretching was performed by stretching between rolls in a bath, and the total stretching ratio based on the raw film was set to 6 times. After the washing step, first drying was performed at a temperature of 48 ° C., and then drying was performed at a temperature of 91 ° C. to obtain a polarizing film having a thickness of 24 μm and a width of 1920 mm.

<Example 2>
In the first embodiment, in the step of showering the treatment liquid with the shower device, only the shower devices installed on the inlet side and the outlet side of the first dyeing bath have a film width of 4803 mm and a central portion of 2420 mm (50% of the total width of the central portion). ) Only showered with a dyeing solution having the same composition as that of the first dyeing bath, and the shower devices installed in the second dyeing bath and the complementary color bath were not operated. The film was manufactured.

<Comparative example 1>
In Example 1, a polarizing film was produced by the same method as in Example 1 except that the shower device was not operated in any of the treatment baths and the step of showering the film with the treatment liquid was not performed.

<Measurement of degree of polarization>
Of the obtained polarizing films of Examples 1 and 2 and Comparative Example 1 having a width of 1920 mm, in three straight lines extending in the width direction, 20 mm (position 1), 100 mm (position 2), and 500 mm (position) from the left end. Luminosity factor correction polarization (Py) was measured at seven positions of 3), 960 mm (position 4), 1420 mm (position 5), 1820 mm (position 6), and 1900 mm (position 7) based on the above method. Table 1 shows the average value of the luminosity factor correction polarization (Py) of the three straight lines at the seven positions (the average value is defined as the luminosity factor correction polarization (Py) at each position). Table 1 shows the calculated values of the difference between the maximum value and the minimum value of the luminous efficiency correction polarization degree at the seven positions. FIG. 4 is a graph plotting the degree of polarization shown in Table 1.

From the results shown in Table 1 and FIG. 4, the polarizing films of Examples 1 and 2 have a smaller difference between the maximum value and the minimum value of the luminosity factor correction polarization degree in the width direction than those of Comparative Example 1, and are in the width direction. It can be seen that the variation in the luminosity factor correction polarization degree is suppressed.

<Example 3>
In Example 1, a polyvinyl alcohol raw film having a width of 3390 mm was used as the polarizing film.

In the first dyeing bath, shower devices installed on the inlet side and the outlet side of the first dyeing bath are used to perform the first dyeing only on the central portion 1925 mm (the ratio of the central portion to the total width is 50%) with respect to the film width of 3859 mm. I took a shower of dyeing solution with the same composition as the bath. In the second dyeing bath, a shower device installed on the inlet side showers the dyeing solution having the same composition as the second dyeing bath only in the central portion 1760 mm (ratio of the central portion to the total width 47%) with respect to the film width of 3751 mm. I showered it. In the complementary color bath, shower devices installed on the inlet side and the outlet side shower the complementary color solution having the same composition as the complementary color bath only on the central portion 990 mm (50% of the total width of the central portion) with respect to the film width of 1962 mm. It was.

Further, in the dyeing step, the cross-linking step, and the complementary color step, longitudinal uniaxial stretching was performed by stretching between rolls in a bath, and the total stretching ratio based on the raw film was set to 6 times. After the washing step, first drying was performed at a temperature of 46 ° C., and then drying was performed at a temperature of 92 ° C. to obtain a polarizing film having a thickness of 24 μm and a width of 1460 mm. Except for the above, a polarizing film was produced by the same production method as in Example 1.

<Example 4>
In Example 3, in the step of showering the treatment liquid with the shower device, the central portion is 1925 mm (ratio of the central portion to the total width) with respect to the film width of 3859 mm only by the shower devices installed on the inlet side and the outlet side of the first dyeing bath. The same method as in Example 3 except that only 50%) was showered with a dyeing solution having the same composition as that of the first dyeing bath, and the shower devices installed in the second dyeing bath and the complementary color bath were not operated. Produced a polarizing film.

<Comparative example 2>
In Example 3, the polarizing film was produced by the same method as in Example 1 except that the step of showering the treatment liquid with the shower device was not performed in any of the treatment baths.

<Measurement of degree of polarization>
Of the obtained polarizing films of Examples 3, 4 and Comparative Example 2 having a width of 1460 mm, in four straight lines extending in the width direction, 20 mm (position 1), 100 mm (position 2), and 730 mm (position 2) from the left end. Luminosity factor correction polarization (Py) was calculated according to the above method at five positions of position 3), 1360 mm (position 4), and 1440 mm (position 5). Table 2 shows the average value of the luminosity factor correction polarization (Py) of the four straight lines at the five positions (the average value is defined as the luminosity factor correction polarization (Py) at each position). Table 2 shows the calculated values of the difference between the maximum value and the minimum value of the luminous efficiency correction polarization degree (Py) at the five positions. FIG. 5 is a graph in which the luminous efficiency correction polarization degree (Py) shown in Table 2 is plotted.

From the results shown in Tables 2 and 5, the difference between the maximum value and the minimum value of the luminous efficiency correction polarization degree in the width direction of the polarizing films of Examples 3 and 4 is smaller than that of Comparative Example 2, and the difference in the width direction is small. It can be seen that the variation in the luminosity factor correction polarization degree is suppressed.

10 Raw fabric film made of polyvinyl alcohol resin, 11 Raw fabric roll, 13 Swelling bath, 15 Dyeing bath, 16 Shower device, 17a Cross-linked bath, 17b Complementary color bath, 19 Washing bath, 21 Drying furnace, 23 Polarizing film, 30 ~ 35,37-48,60,61 guide rolls, 50-52,53a, 53b, 54,55,56 nip rolls.

Claims (9)

A method for producing a polarizing film from a polyvinyl alcohol-based resin film.
A plurality of treatment steps for bringing the polyvinyl alcohol-based resin film into contact with the treatment liquid are provided.
At least one of the plurality of treatment steps includes a uniform contact step of bringing the polyvinyl alcohol-based resin film into contact with a uniform amount of the treatment liquid over the entire width, and the polyvinyl alcohol-based resin film at a position in the width direction of the entire width. It is a multi-stage treatment step including an adjustment contact step of contacting the treatment liquid in an amount adjusted accordingly.
A method for producing a polarizing film, wherein the treatment liquid used in the multi-step treatment step contains at least one of a dichroic dye and a boron compound. The method for producing a polarizing film according to claim 1, wherein in the multi-stage treatment step, the treatment liquid is a dyeing liquid, a cross-linking liquid, or a complementary color liquid. In the adjustment contact step, the polyvinyl alcohol-based resin film is divided into a central portion and both ends with respect to the entire width, and the amount of the treatment liquid to be brought into contact with the central portion is larger than the amount of the treatment liquid to be brought into contact with the both ends. The method for producing a polarizing film according to claim 1 or 2, which is adjusted so as to increase the number. The method for producing a polarizing film according to claim 3, wherein in the adjustment contact step, the central portion of the polyvinyl alcohol-based resin film is 5 to 80% based on the total width. The polarized light according to claim 3 or 4, wherein in the adjustment contact step, the treatment liquid is brought into contact with the central portion of the polyvinyl alcohol-based resin film, and the treatment liquid is adjusted so as not to come into contact with both ends thereof. Film manufacturing method. The method for producing a polarizing film according to any one of claims 1 to 5, wherein the uniform contact step is a step of immersing the polyvinyl alcohol-based resin film in the treatment liquid contained in the treatment tank. The method for producing a polarizing film according to any one of claims 1 to 6, wherein the adjusting contact step is a step of showering the polyvinyl alcohol-based resin film with a shower of the treatment liquid. The method for producing a polarizing film according to any one of claims 1 to 7, wherein the total width of the polyvinyl alcohol-based resin film is 400 mm or more and 8000 mm or less. A polarizing film manufacturing device that manufactures a polarizing film from a polyvinyl alcohol-based resin film.
A plurality of processing units for bringing the polyvinyl alcohol-based resin film into contact with the processing liquid are provided.
At least one of the plurality of processing portions is a uniform contact portion for contacting the polyvinyl alcohol-based resin film with a uniform amount of the treatment liquid over the entire width, and the polyvinyl alcohol-based resin film at positions in the width direction of the entire width. It is a multi-stage processing unit having an adjusting contact portion for contacting the treatment liquid in an amount adjusted accordingly.
The treatment liquid used in the multi-stage treatment unit is a polarizing film manufacturing apparatus containing at least one of a dichroic dye and a boron compound.

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