Polarizing film manufacturing method and manufacturing device

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

[Technical field]

[0001] The present invention relates to a method and an apparatus for producing a polarizing film from a polyvinyl alcohol-based resin film. [Background technology]

[0002] Polarizing plates are widely used as polarizing elements in image display devices such as liquid crystal display devices. A polarizing plate generally has a structure in which a transparent resin film (such as a protective film) is bonded to one or both sides of a polarizing film using an adhesive or the like.

[0003] Polarizing films are mainly produced by subjecting a raw film made of a polyvinyl alcohol resin to a process of immersing the film in a dye bath containing a dichroic dye such as iodine, followed by a process of immersing the film in a crosslinking bath containing a crosslinking agent such as boric acid, and uniaxially stretching the film at any stage. The uniaxial stretching includes dry stretching in which stretching is performed in air, and wet stretching in which stretching is performed in a liquid such as the dye bath or crosslinking bath.

[0004] Conventionally, in the manufacturing method of polarizing film, there have been efforts to suppress the variation in optical properties in the width direction. JP 2018-32026 A (Patent Document 1) describes a method of suppressing the variation in optical properties in the width direction by irradiating a polyvinyl alcohol-based resin film with electromagnetic waves including infrared rays with an irradiation heat amount having a distribution in the width direction. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2018-32026 A Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a novel method and apparatus for producing a polarizing film that can reduce variation in optical properties in the width direction. [Means for solving the problem]

[0007] The present invention provides a method and an apparatus for producing a polarizing film as described below. [1] A method for producing a polarizing film from a polyvinyl alcohol-based resin film, comprising the steps of: The polyvinyl alcohol-based resin film is subjected to a treatment in a treatment liquid. At least one of the plurality of treatment steps is a multi-stage treatment step including a uniform contact step of contacting the polyvinyl alcohol-based resin film with a uniform amount of treatment liquid over the entire width, and a controlled contact step of contacting the polyvinyl alcohol-based resin film with an amount of the treatment liquid controlled according to a position in the width direction of the entire width, The method for producing a polarizing film, wherein the treatment liquid used in the multi-stage treatment process 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 process, the treatment liquid is a dye liquid, a crosslinking liquid, or a complementary liquid. [3] The method for producing a polarized film according to [1] or [2], wherein in the adjusting contacting step, the polyvinyl alcohol-based resin film is divided into a center portion and both end portions across its entire width, and the amount of the treatment liquid brought into contact with the center portion is adjusted to be greater than the amount of the treatment liquid brought into contact with the both end portions. [4] The method for producing a polarized film according to [3], wherein in the adjusting and contacting step, the central portion of the polyvinyl alcohol-based resin film occupies 5 to 80% of the entire width. [5] The method for producing a polarized film according to [3] or [4], wherein in the adjusting 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 not brought into contact with both end portions of the polyvinyl alcohol-based resin film. [6] The method for producing a polarized 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 a treatment tank. [7] The method for producing a polarized film according to any one of [1] to [6], wherein the conditioning contact step is a step of showering the treatment liquid onto the polyvinyl alcohol-based resin film. [8] The method for producing a polarized film according to any one of [1] to [9], wherein the polyvinyl alcohol-based resin film has a total width of 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, comprising: a plurality of processing sections for contacting the polyvinyl alcohol-based resin film with a processing solution; At least one of the plurality of treatment sections is a multi-stage treatment section having a uniform contact section for contacting the polyvinyl alcohol-based resin film with a uniform amount of treatment liquid over the entire width, and an adjusted contact section for contacting the polyvinyl alcohol-based resin film with an amount of the treatment liquid adjusted depending on a position in the width direction of the entire width, The apparatus for producing a polarizing film, wherein the processing liquid used in the multi-stage processing section contains at least one of a dichroic dye and a boron compound. Effect of the Invention

[0008] According to the present invention, it is possible to provide a method and an apparatus for producing a polarizing film that reduces the variation in optical properties of the polarizing film in the width direction. [Brief description of the drawings]

[0009] [Figure 1] 1 is a cross-sectional view that illustrates an example of a polarizing film manufacturing method and a polarizing film manufacturing apparatus used in the method according to the present invention. [Diagram 2] FIG. 2 is a top view of the dyeing section of the production apparatus shown in FIG. [Diagram 3]11 is a cross-sectional view for explaining a method for adjusting the amount of dye liquid sprayed from the shower device. FIG. [Figure 4] 1 is a graph plotting the luminosity-corrected polarization degree Py of Examples 1 and 2 and Comparative Example 1. [Diagram 5] 1 is a graph plotting the luminosity-corrected polarization degree Py of Examples 3 and 4 and Comparative Example 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] <Method of manufacturing polarizing film> The present invention relates to a method for producing a polarizing film from a polyvinyl alcohol-based resin film, the method comprising a plurality of treatment steps of contacting the polyvinyl alcohol-based resin film with a treatment liquid, at least one of which is a multi-stage treatment step having a uniform contact step of contacting the polyvinyl alcohol-based resin film with a uniform amount of the treatment liquid over the entire width and an adjusted contact step of contacting the polyvinyl alcohol-based resin film with an amount of the treatment liquid adjusted according to the position in the width direction of the entire width. The treatment liquid used in the multi-stage treatment step contains at least one of a dichroic dye and a boron compound, and is, for example, a dyeing liquid, a crosslinking liquid, a complementary color liquid, or the like.

[0011] In the present invention, the polarizing film is a uniaxially stretched polyvinyl alcohol resin film in which a dichroic pigment (iodine, dichroic dye, etc.) is adsorbed and aligned. The polyvinyl alcohol resin constituting the polyvinyl alcohol resin film is usually obtained by saponifying a polyvinyl acetate resin. The degree of saponification is usually about 85 mol% or more, preferably about 90 mol% or more, more preferably about 99 mol% or more. The polyvinyl acetate resin may be, for example, polyvinyl acetate, which is a homopolymer of vinyl acetate, or a copolymer of vinyl acetate and other monomers copolymerizable therewith. Examples of the other copolymerizable monomers include unsaturated carboxylic acids, olefins, vinyl ethers, and unsaturated sulfonic acids. The degree of polymerization of the polyvinyl alcohol resin is usually about 1000 to 10000, preferably about 1500 to 5000.

[0012] These polyvinyl alcohol resins may be modified, and for example, polyvinyl formal, polyvinyl acetal, polyvinyl butyral, etc., which are modified with aldehydes may also be used.

[0013] In the present invention, an unstretched polyvinyl alcohol-based resin film (raw 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, and even more preferably 30 μm or less, is used as a starting material for the production of a polarizing film. This makes it possible to obtain a thin polarizing film, which is increasingly in demand in the market. 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 properties of the polarizing film in the width direction tend to vary, but the manufacturing method of the present invention can reduce the variation. The raw film is prepared, for example, as a roll (raw roll) of a long unstretched polyvinyl alcohol-based resin film.

[0014] The polyvinyl alcohol-based resin film used in the present invention may be laminated on a substrate film that supports it, i.e., the polyvinyl alcohol-based resin film may be prepared as a laminate film of a substrate film and a polyvinyl alcohol-based resin film laminated thereon. 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 substrate film and then drying the coating liquid.

[0015] The substrate film may be, for example, a film made of a thermoplastic resin. Specific examples include a film made of a thermoplastic resin having light transmission, preferably an optically transparent thermoplastic resin, such as a polyolefin resin such as a chain polyolefin resin (polypropylene resin, etc.) or a cyclic polyolefin resin (norbornene resin, etc.); a cellulose resin such as triacetyl cellulose or diacetyl cellulose; a polyester resin such as polyethylene terephthalate or polybutylene terephthalate; a polycarbonate resin; a (meth)acrylic resin such as a methyl methacrylate resin; a polystyrene resin; a polyvinyl chloride resin; an acrylonitrile-butadiene-styrene resin; an acrylonitrile-styrene resin; a polyvinyl acetate resin; a polyvinylidene chloride resin; a polyamide resin; a polyacetal resin; a modified polyphenylene ether resin; a polysulfone resin; a polyethersulfone resin; a polyarylate resin; a polyamideimide resin; a polyimide resin, etc.

[0016] The polarizing film can be continuously manufactured as a long polarizing film by continuously conveying the long raw film from the raw roll along the film conveying path of the polarizing film manufacturing apparatus, immersing the film in a treatment liquid (hereinafter also referred to as a "treatment bath") contained in a treatment tank, withdrawing the film, and then drying the film. 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 may be a method of showering the film surface with the treatment liquid. As a method of showering the film surface with the treatment liquid, a method of showering the film surface with a shower of the treatment liquid is suitable. Here, the shower of the treatment liquid means a flow of the treatment liquid sprayed from a plurality of spray ports, and the treatment liquid may be included intermittently in the flow (for example, in the form of particles or mist) or may be included continuously. The shower device is a device that has a plurality of spray ports and sprays the liquid from them to create a flow of the liquid. A shower device is usually used to shower the film surface with the treatment liquid. When the processing step is carried out by immersing the film in a processing bath, the number of processing baths for one processing step is not limited to one, and one processing step may be completed by sequentially immersing the film in two or more processing baths.

[0017] Examples of the treatment liquid include a swelling liquid, a dyeing liquid, a crosslinking liquid, a color-complementing liquid, and a cleaning liquid. Examples of the treatment process include a swelling process in which a swelling liquid is brought into contact with the raw film to perform a swelling process, a dyeing process in which a dyeing liquid is brought into contact with the film after the swelling process to perform a dyeing process, a crosslinking process in which a crosslinking liquid is brought into contact with the film after the dyeing process to perform a crosslinking process, a color-complementing liquid is brought into contact with the film after the crosslinking process to perform a color adjustment process, and a cleaning process in which a cleaning liquid is brought into contact with the film after the color-complementing process to perform a cleaning process. In addition, between these series of treatment processes (i.e., before and after any one or more treatment processes and / or during any one or more treatment processes), a uniaxial stretching process is performed in a wet or dry manner. Other treatment processes may be added as necessary.

[0018] The present inventors have found that, from the viewpoint of suppressing the variation in optical properties in the width direction in a treatment process using a treatment liquid containing at least one of a dichroic dye and a boron compound, a multi-stage treatment process having a uniform contact step in which the film is contacted with a uniform treatment liquid over the entire width, and a controlled contact step in which the film is contacted with an amount of treatment liquid controlled according to the position in the width direction of the entire width is preferable, and have arrived at the present invention. Examples of treatment processes using a treatment liquid containing at least one of a dichroic dye and a boron compound include a dyeing step, a crosslinking step, a complementary color step, etc.

[0019] Hereinafter, an example of a method for producing a polarizing film according to the present invention will be described with reference to FIG. 1. FIG. 1 is a cross-sectional view that shows a schematic example of a method for producing a polarizing film according to the present invention and a polarizing film production apparatus used therein. The polarizing film production apparatus shown in FIG. 1 is configured such that an original (unstretched) film 10 made of a polyvinyl alcohol resin is transported along a film transport path while being continuously unwound from an original roll 11, so that the film passes through a swelling bath (swelling liquid contained in a swelling tank) 13, a dyeing bath (dyeing liquid contained in a dyeing tank) 15, a crosslinking bath (crosslinking liquid contained in a crosslinking tank) 17a, a complementary color bath (complementary color liquid contained in a crosslinking tank) 17b, and a cleaning bath (cleaning liquid contained in a cleaning tank) 19 provided on the film transport path in sequence, and finally passes through a drying oven 21. The obtained polarizing film 23 can be transported directly to the next polarizing plate production process (a process of laminating a protective film on one or both sides of the polarizing film 23), for example. The arrow in FIG. 1 indicates the film transport direction. A shower device 16 is provided in the dye bath 15, and the film 10 that has passed through the dye bath 15 is then configured to pass through the shower device 16.

[0020] In the explanation of Fig. 1, "treatment tank" is a general term including a swelling tank, a dyeing tank, a crosslinking tank, a complementary color tank, and a washing tank, "treatment liquid" is a general term including a swelling liquid, a dyeing liquid, a crosslinking liquid, a complementary color tank liquid, and a washing liquid, and "treatment bath" is a general term including a swelling bath, a dyeing bath, a crosslinking bath, a complementary color bath, and a washing bath. The swelling bath, the dyeing bath and the shower device, the crosslinking bath, the complementary color bath, and the washing bath respectively constitute the swelling section, the dyeing section, the crosslinking section, the complementary color section, and the washing section in the production apparatus of the present invention.

[0021] In the manufacturing apparatus shown in Fig. 1, the dyeing section is configured to carry out a multi-stage treatment process, in which a uniform contact step is carried out in a dyebath 15, and then a conditioning contact step is carried out by passing through a shower device 16. That is, the dyeing section is configured as a multi-stage treatment section including the dyebath 15 which is a uniform contact section, and the shower device 16 which is a conditioning contact section.

[0022] The film transport path of the polarizing film manufacturing apparatus can be constructed by arranging guide rolls 30-35, 37-48, 60, 61 that support the transported film or can further change the film transport direction, and nip rolls 50-56 that press and pinch the transported film and can apply a driving force to the film by rotating it or can further change the film transport direction at appropriate positions, in addition to the above-mentioned treatment baths and shower devices. The guide rolls and nip rolls can be arranged before and after each treatment bath or in the treatment bath, and this allows the film to be introduced into, immersed in, and withdrawn from the treatment bath (see FIG. 1). For example, one or more guide rolls can be provided in each treatment bath, and the film can be immersed in each treatment bath by transporting the film along these guide rolls.

[0023] 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), and this makes it possible to perform inter-roll stretching in which longitudinal uniaxial stretching is performed by applying a peripheral speed difference between the nip rolls arranged before and after the treatment bath in one or more of the treatment baths. Each step will be described below.

[0024] (Swelling process) The swelling process is carried out for the purposes of removing foreign matter on the surface of the raw film 10, removing plasticizers in the raw film 10, imparting ease of dyeing, plasticizing the raw film 10, etc. The treatment conditions are determined within a range in which the purposes can be achieved and in which defects such as extreme dissolution or devitrification of the raw film 10 do not occur.

[0025] 1, the swelling step can be performed by continuously unwinding raw film 10 from raw film roll 11, transporting raw film 10 along a film transport path, immersing raw film 10 in swelling bath 13 for a predetermined time, and then pulling it out. In the example of FIG. 1, from when raw film 10 is unwound until when it is immersed in swelling bath 13, raw film 10 is transported along a film transport path formed by guide rolls 60, 61 and nip roll 50. In the swelling treatment, raw film 10 is transported along a film transport path formed by guide rolls 30 to 32 and nip roll 51.

[0026] As the swelling liquid for the swelling bath 13, in addition to pure water, it is also possible to use an aqueous solution containing boric acid (JP Patent Publication No. 10-153709), chlorides (JP Patent Publication No. 06-281816), inorganic acids, inorganic salts, water-soluble organic solvents, alcohols, etc., in an amount of about 0.01 to 10 mass %.

[0027] 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, and more preferably about 20 to 200 seconds. When the raw film 10 is a polyvinyl alcohol resin film that has been stretched in advance 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 film 10 is preferably about 30 to 300 seconds, and more preferably about 60 to 240 seconds.

[0028] In the swelling process, the original film 10 is likely to swell in the width direction, causing wrinkles in the film. One method for conveying the film while removing the wrinkles is to use a roll having a width-expanding function such as an expander roll, a spiral roll, or a crown roll as the guide rolls 30, 31, and / or 32, or to use other width-expanding devices such as a cross guider, a bend bar, or a tenter clip. Another method for suppressing the occurrence of wrinkles is to perform a stretching process. For example, a uniaxial stretching process can be performed in the swelling bath 13 by utilizing the difference in peripheral speed between the nip rolls 50 and 51.

[0029] In the swelling treatment, the film also swells and expands in the film transport direction, so when the film is not actively stretched, it is preferable to take measures such as controlling the speed of nip rolls 50, 51 disposed before and after the swelling bath 13 in order to eliminate slack in the film in the transport direction. In addition, for the purpose of stabilizing the film transport in the swelling bath 13, it is also useful to control the water flow in the swelling bath 13 with a submerged shower device or to use an EPC device (Edge Position Control device: a device that detects the edge of the film and prevents the film from meandering) in combination.

[0030] In the example shown in FIG. 1, the film pulled out from the swelling bath 13 passes through a guide roll 32, a nip roll 51 and a guide roll 33 in this order, and is introduced into the dyeing bath 15.

[0031] (dying process) The dyeing process is carried out for the purpose of adsorbing and orienting a dichroic dye such as iodine on the polyvinyl alcohol resin film after the swelling process. The treatment conditions are determined within a range in which the purpose can be achieved and in which defects such as extreme dissolution or devitrification of the film do not occur. With reference to FIG. 1, the dyeing process can be carried out by conveying the film along a film conveying path constructed by a nip roll 51, guide rolls 33 to 35, and nip rolls 56 and 52, immersing the film after the swelling process in a dye bath 15 (a treatment liquid contained in a dyeing tank) for a predetermined time, and then passing through a shower device 16 after being pulled out. In order to enhance the dyeability of the dichroic dye, it is preferable that the film to be subjected to the dyeing process is a film that has been subjected to at least some degree of uniaxial stretching, or it is preferable to perform a uniaxial stretching process during the dyeing process instead of or in addition to the uniaxial stretching process before the dyeing process.

[0032] It is preferable to use iodine as the dichroic dye, and the dyeing solution of the dye bath 15 may be, for example, an aqueous solution having a mass ratio of iodine / potassium iodide / water=0.003-0.3 / 0.1-10 / 100. Instead of potassium iodide, other iodides such as zinc iodide may be used, or potassium iodide may be used in combination with other iodides. In addition, compounds other than iodides, such as boric acid, zinc chloride, cobalt chloride, etc., may be allowed to coexist. When boric acid is added, it is distinguished from the crosslinking solution described later in that it contains a dichroic dye, and if the aqueous solution contains 0.003 parts by mass or more of a dichroic dye per 100 parts by mass of water, it can be considered as a dyeing solution. The temperature of the dye bath 15 when the film is immersed is usually about 10 to 45°C, preferably 10 to 40°C, and more preferably 20 to 35°C, and the immersion time of the film is usually about 30 to 600 seconds, and preferably 60 to 300 seconds.

[0033] A water-soluble dichroic dye may be used together with iodine as the dichroic pigment, and the dyeing solution of the dye bath 15 may be, for example, an aqueous solution having a mass ratio of dichroic dye / water of about 0.001 to 0.1 / 100. This dyeing solution may contain dyeing auxiliaries, for example, inorganic salts such as sodium sulfate, surfactants, etc. One type of dichroic dye may be used alone, or two or more types of dichroic dyes may be used in combination.

[0034] As described above, in the dyeing step, the film can be uniaxially stretched in the dye bath 15. The film can be uniaxially stretched by, for example, providing a difference in peripheral speed between the nip rolls 51 and 56 disposed before and after the dye bath 15.

[0035] In the dyeing process, in order to transport the polyvinyl alcohol-based resin film while removing wrinkles from the film, similarly to the swelling process, rolls having a width-expanding function such as expander rolls, spiral rolls, and crown rolls may be used as the guide rolls 33, 34, and / or 35, or other width-expanding devices such as cross guiders, bend bars, and tenter clips may be used. Another means for suppressing the occurrence of wrinkles is to perform a stretching process, similarly to the swelling process.

[0036] In the example shown in Fig. 1, the film pulled out from the dye bath 15 passes through the shower device 16, and then passes through the nip roll 56, the nip roll 52, and the guide roll 37 in this order, before being introduced into the crosslinking bath 17a. Thus, in the example shown in Fig. 1, the dyeing process is a multi-stage process. The details of the multi-stage process will be described later.

[0037] (Crosslinking process) The crosslinking process is a treatment carried out for the purpose of making the film water-resistant by crosslinking. The crosslinking process may be carried out multiple times. With reference to Fig. 1, the crosslinking process can be carried out by conveying the film after the dyeing process along a film conveying path formed by nip rolls 52, guide rolls 37 to 40, and nip rolls 53a, immersing the film in a crosslinking bath 17a (a crosslinking liquid contained in a crosslinking tank) for a predetermined time, and then pulling out the film.

[0038] The crosslinking liquid may be a solution in which a crosslinking agent is dissolved in a solvent. Examples of the crosslinking agent include boron compounds such as boric acid and borax, glyoxal, and glutaraldehyde. These may be used alone or in combination of two or more. The solvent may be, for example, water, and may further contain an organic solvent compatible with water. The concentration of the crosslinking agent in the crosslinking solution is not limited thereto, but is preferably in the range of 1 to 20% by mass, and more preferably 4 to 15% by mass.

[0039] The crosslinking liquid may be an aqueous solution containing, for example, about 1 to 10 parts by mass of boric acid per 100 parts by mass of water. When the dichroic dye used in the dyeing process is iodine, the crosslinking liquid preferably contains an iodide in addition to boric acid, and the amount of the iodide may be, for example, 1 to 30 parts by mass per 100 parts by mass of water. Examples of the iodide include potassium iodide and zinc iodide. In addition, compounds other than iodide, such as zinc chloride, cobalt chloride, zirconium chloride, sodium thiosulfate, potassium sulfite, and sodium sulfate, may be allowed to coexist.

[0040] In the crosslinking treatment, the concentrations of boric acid and iodide, and the temperature of the crosslinking bath 17 can be appropriately changed depending on the purpose. For example, the solution may have a concentration of boric acid / iodide / water=3-10 / 1-20 / 100 by mass ratio. If necessary, another crosslinking agent may be used instead of boric acid, or boric acid may be used in combination with another crosslinking agent. The temperature of the crosslinking bath 17a when the film is immersed is usually about 50-70°C, preferably 53-65°C, and the immersion time of the film is usually about 10-600 seconds, preferably 20-300 seconds, more preferably 20-200 seconds.

[0041] The crosslinking treatment may be performed multiple times, usually 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. In addition, uniaxial stretching treatment can be performed in the crosslinking bath 17a by utilizing the difference in peripheral speed between the nip roll 52 and the nip roll 53a.

[0042] In the crosslinking treatment, in order to transport the polyvinyl alcohol-based resin film while removing wrinkles from the film, similarly to the swelling treatment, rolls having a width-expanding function such as expander rolls, spiral rolls, and crown rolls may be used as the guide rolls 38, 39, 40, 41, 42, 43, and / or 44, or other width-expanding devices such as cross guiders, bend bars, and tenter clips may be used. Another means for suppressing the occurrence of wrinkles is to perform a stretching treatment, similarly to the swelling treatment.

[0043] (complementary color process) As a complementary color liquid for adjusting the hue, for example, when iodine is used as a dichroic dye in a dyeing solution, a concentration of boric acid / iodide / water=1-5 / 3-30 / 100 in mass ratio can be used. The temperature of the complementary color bath 17b when the film is immersed is usually about 20-65° C., and the immersion time of the film is usually about 1-300 seconds, preferably 2-100 seconds.

[0044] The uniaxial stretching treatment can be performed in the crosslinking bath 17a by utilizing the difference in peripheral speed between the nip roll 52 and the nip roll 53a. Also, 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.

[0045] In the example shown in FIG. 1, the film withdrawn from the complementary color bath 17b passes through a guide roll 44 and a nip roll 53b in this order before being introduced into the washing bath 19.

[0046] (Cleaning process) In the example shown in Fig. 1, 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 step is performed, for example, by immersing the crosslinked polyvinyl alcohol-based resin film in a cleaning bath 19. Note that the cleaning step can also be performed by showering the film with a cleaning liquid instead of immersing the film in the cleaning bath 19, or by combining immersion in the cleaning bath 19 and showering the film with a cleaning liquid.

[0047] 1 shows an example of a case where a cleaning treatment is performed by immersing a polyvinyl alcohol-based resin film in a cleaning bath 19. The temperature of the cleaning bath 19 in the cleaning treatment is usually about 2 to 50° C., and the immersion time of the film is usually about 2 to 120 seconds.

[0048] In addition, in the cleaning treatment, for the purpose of transporting the polyvinyl alcohol-based resin film while removing wrinkles, a roll having a width expanding function such as an expander roll, a spiral roll, or a crown roll, or other width expanding devices such as a cross guider, a bend bar, or a tenter clip, may be used as the guide rolls 45, 46, 47, and / or 48. In addition, in the film cleaning treatment, a stretching treatment may be performed to suppress the occurrence of wrinkles.

[0049] (Stretching process) As described above, the raw film 10 is uniaxially stretched in a wet or dry manner during the series of processing steps (i.e., before and after any one or more processing steps and / or during any one or more processing steps). Specific methods of uniaxial stretching include, for example, inter-roll stretching in which longitudinal uniaxial stretching is performed by applying a peripheral speed difference between two nip rolls (e.g., two nip rolls arranged before and after a processing bath) constituting a film transport path, hot roll stretching as described in Japanese Patent No. 2731813, tenter stretching, etc., and preferably inter-roll stretching. The uniaxial stretching step can be performed multiple times from the raw film 10 until the polarizing film 23 is obtained. As described above, the stretching process is also advantageous in suppressing the occurrence of wrinkles in the film.

[0050] The final cumulative stretch ratio of the polarizing film 23 based on the original film 10 is usually about 4.5 to 7 times, and preferably 5 to 6.5 times. The stretching step may be performed in any processing step, and even when the stretching treatment is performed in two or more processing steps, the stretching treatment may be performed in any processing step.

[0051] (drying process) After the washing step, it is preferable to carry out a process of drying the polyvinyl alcohol-based resin film. The drying of the film is not particularly limited, but can be carried out using a drying oven 21 as in the example shown in FIG. 1. The drying oven 21 can be equipped 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 carried out using a far-infrared heater. The polarizing film 23 obtained in the above manner has a thickness of, for example, about 5 to 30 μm.

[0052] (Multi-stage processing) In the polarizing film production apparatus shown in Fig. 1, the dyeing process is a multi-stage process, and includes a uniform contact process using a dye bath 15 and a controlled contact process using a shower device 16. The dyeing liquid in the dye bath 15 and the dyeing liquid sprayed from the shower device 16 preferably have the same or similar composition. The temperature of the dyeing liquid sprayed from the shower device 16 is preferably adjusted within the temperature range of the dye bath described above. The dyeing liquid sprayed from the shower device 16 is preferably a dyeing liquid derived from within the dye bath 15, and is preferably collected in the dye bath 15 after being sprayed onto the film.

[0053] The shower device 16 is configured to be able to shower the film to be treated with an amount of dye solution adjusted according to the position in the width direction of the entire width. In this way, by making the dyeing process a multi-stage processing process having a uniform contacting process and an adjusted contacting process, it is possible to suppress uneven dyeing in the width direction of the film and reduce variation in the optical properties of the obtained polarizing film.

[0054] FIG. 2 is a top view of the dyeing section in the polarizing film manufacturing apparatus shown in FIG. 1, where the dyeing step is performed. As shown in FIG. 2, the film 10 is transported in the direction of the arrow in the figure by the transport guide roll 33. As a result, the film 10 is immersed in the dye bath 15 and then passes through the shower device 16. The shower device 16 is composed of two shower bars 16a and 16b arranged to face each other on both sides of the film 10, and each shower bar 16a and 16b has a plurality of shower nozzles 161 arranged in the width direction of the film, and the dyeing liquid is sprayed from each shower nozzle 161. By adjusting the amount of the dyeing liquid sprayed from each shower nozzle 161, it is possible to contact the film 10 with an amount of dyeing liquid adjusted according to the position in the width direction of the entire width of the film 10. After passing through the shower device 16, the film 10 is sent to the nip roll 56. The nip roll 56 also functions as a liquid removing means for removing the dyeing liquid attached to the surface of the film 10.

[0055] 3 is a cross-sectional view illustrating a method for adjusting the amount of dyeing liquid sprayed from shower device 16. One method for adjusting the amount of dyeing liquid sprayed from shower device 16 is to divide shower nozzles 161 arranged in the width direction of film 10 into shower nozzles 161a in a portion corresponding to the center of film 10 and shower nozzles 161b in portions corresponding to both ends of film 10, and to adjust the spray amount from shower nozzle 161a in the portion corresponding to the center of film 10 and the spray amount from shower nozzle 161b in the portions corresponding to both ends of film 10.

[0056] For example, as shown in FIG. 3, a specific embodiment of the shower device 16 is such that dyeing liquid is sprayed only from shower nozzle 161a in a portion of the shower nozzle 161 that corresponds to the center of the film 10, and dyeing liquid is not sprayed from shower nozzle 161b in portions that correspond to both ends of the film 10.

[0057] The central portion of the film is preferably 5 to 80% of 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 depending on the degree of variation in the optical properties to be improved. The 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 is the same as the width of the other end.

[0058] It is presumed that one of the reasons for the variation in optical properties of the polarizing film is that the treatment liquid penetrates more easily from the edge of the polyvinyl alcohol-based resin film than from the surface, resulting in a difference in the amount of the treatment liquid penetrating between the edge and the center in each of the above-mentioned treatment steps, and thus the degree of treatment differs. It is also presumed that one of the reasons is that the thickness varies in the width direction due to stretching, resulting in a difference in the degree of treatment in each treatment step depending on the thickness. Based on such factors, the polyvinyl alcohol-based resin film is not limited to the method of dividing the film into "edge / center / edge" in the width direction as described above, but may be divided so that there is one or more regions between the edge and center, and an adjustment contact step may be performed in which the amount of dyeing liquid contacted in each region is adjusted.

[0059] The order of the uniform contact step and the conditioning contact step in the multi-stage treatment step is not limited. Therefore, the position of the shower device is not limited to the outlet side of the dye bath 15 as shown in FIG. 1, and may be the inlet side, or may be configured to be provided on both the inlet side and the outlet side. Furthermore, in a configuration in which the shower device is provided on the outlet side, the shower device may be located upstream or downstream of the nip roll 56, which is also a liquid removing means. From the viewpoint of showering a specific area, it may be located downstream of the nip roll 56, which is a liquid removing means. Also, from the viewpoint of suppressing the formation of a clear boundary in the optical properties between two areas with different contact amounts of the dyeing liquid, it may be located upstream of the nip roll 56, which is a liquid removing means, and the conditioning contact step may be performed in a state in which the dyeing liquid remains on the film surface immediately after immersion.

[0060] The shower may be applied to both surfaces of the film, or only one surface. When showering a film transported in a direction having a predetermined angle with respect to the vertical direction, that is, when showering a film transported in a state in which both sides of the film can be distinguished into an upper side and a lower side with respect to the vertical direction, it is preferable to shower at least the upper side of the film from the viewpoint of liquid cutting and uniformity. In the area to be showered, the total amount of the shower applied per unit area of ​​the film is, for example, 0.05 to 20 L / m 2 and 0.1 to 10 L / m 2 The total amount of the shower applied to the film can be adjusted by adjusting the amount of the treatment liquid ejected from the shower device, adjusting the film transport speed, etc.

[0061] As a liquid removing means for removing the dye liquid from the surface of the film, in addition to the nip roll 56 shown in FIG. 1, a means for removing liquid by blowing air onto the film, a scraper for removing liquid by contacting the film, etc. may be used.

[0062] At least one of the dyeing step, crosslinking step and color-complementing step is preferably a multi-stage processing step, and all of the dyeing step, crosslinking step and color-complementing step may be multi-stage processing steps. When the crosslinking step and / or color-complementing step are multi-stage processing steps, the crosslinking section and color-complementing section may have the same configuration as the dyeing section. When the processing step to which the multi-stage processing step is applied is configured to sequentially immerse the film in two or more processing baths, it is sufficient that a shower device is installed in any of the processing baths.

[0063] In addition, the multi-stage treatment step is not limited to the dyeing step, the crosslinking step, and the color complementing step, and the washing step may be a multi-stage treatment step. When the washing step is a multi-stage treatment step, it is preferable that the adjusted contact step is adjusted so that the amount of the washing liquid brought into contact with both ends of the film is greater than the amount of the washing liquid brought into contact with the center of the film.

[0064] When the plurality of treatment steps are multi-stage treatment steps, a different conditioning method may be adopted for each conditioning contact step of each multi-stage treatment step, and for example, the width of the central portion may be different for each conditioning contact step.

[0065] (Other processing steps for polyvinyl alcohol-based resin film) Treatments other than those described above may also be added. Examples of treatments that can be added include immersion treatment in an aqueous solution containing zinc chloride or the like but not a boron compound (zinc treatment) performed after the crosslinking step.

[0066] <Polarizing film> The above-mentioned method can provide a polarizing film with reduced variation in optical properties in the width direction. The luminosity-corrected single transmittance Ty of the obtained polarizing film is preferably 40 to 47%, more preferably 41 to 45%, in consideration of the balance with the luminosity-corrected polarization degree Py. The luminosity-corrected polarization degree Py is preferably 99.9% or more, more preferably 99.95% or more at any position in the width direction. The difference between the maximum and minimum values ​​of the luminosity-corrected polarization degree Py in the width direction is preferably 0.0015% or less, and the smaller the difference, the better.

[0067] The MD transmittance and TD transmittance of the polarizing film were measured in the wavelength range of 380 to 780 nm using a spectrophotometer equipped with an integrating sphere ("V7100" manufactured by JASCO Corporation), and the following formula was calculated: Single layer transmittance (%) = (MD + TD) / 2 Degree of polarization (%)={(MD-TD) / (MD+TD)}×100 The single transmittance and the degree of polarization at each wavelength are calculated based on the above.

[0068] "MD transmittance" is the transmittance when the direction of polarized light exiting the Glan-Thompson prism is parallel to the transmission axis of the polarizing film sample, and is represented as "MD" in the above formula. "TD transmittance" is the transmittance when the direction of polarized light exiting the Glan-Thompson prism is perpendicular to the transmission axis of the polarizing film sample, and is represented as "TD" in the above formula. The obtained single transmittance and polarization degree were measured in accordance with JIS Z 8701:1999 "Method of displaying color - XYZ color system and XYZ color system". 10 Y 10 Z 10 Luminosity correction is performed using the 2-degree visual field (C light source) of the "Color Space Specification System," and the luminosity-corrected single transmittance (Ty) and luminosity-corrected degree of polarization (Py) are calculated.

[0069] The width of the polarizing film of the present invention is, for example, 50 mm to 5000 mm, preferably 500 mm to 4000 mm. The obtained polarizing film may be wound up on a winding roll to form a roll, or may be directly subjected to a polarizing plate production step (a step of laminating a protective film or the like on one or both sides of the polarizing film) without being wound up.

[0070] <Polarizing plate> A polarizing plate can be obtained by bonding a protective film to at least one side of the polarizing film produced as described above via an adhesive. Examples of the protective film include films made of acetylcellulose-based resins such as triacetylcellulose and diacetylcellulose; films made of polyester-based resins such as polyethylene terephthalate, polyethylene naphthalate, and polybutylene terephthalate; polycarbonate-based resin films, cycloolefin-based resin films; acrylic-based resin films; and films made of linear olefin-based resins such as polypropylene-based resins.

[0071] In order to improve the adhesion between the polarizing film and the protective film, the bonding surface of the polarizing film and / or the protective film may be subjected to a surface treatment such as a corona treatment, a flame treatment, a plasma treatment, ultraviolet irradiation, a primer coating treatment, or a saponification treatment. Examples of adhesives used for bonding the polarizing film and the protective film include active energy ray curable adhesives such as ultraviolet curable adhesives, aqueous solutions of polyvinyl alcohol resins or aqueous solutions containing crosslinking agents, and water-based adhesives such as urethane emulsion adhesives. The ultraviolet curable adhesive may be a mixture of an acrylic compound and a photoradical polymerization initiator, or a mixture of an epoxy compound and a photocationic polymerization initiator. It is also possible to use a cationic polymerizable epoxy compound and a radical polymerizable acrylic compound in combination, and to use a photocationic polymerization initiator and a photoradical polymerization initiator in combination as initiators. EXAMPLES

[0072] The present invention will be described in more detail below by way of examples, but the present invention is not limited to these examples.

[0073] [Production of polarizing film] <Example 1> The polarized film of Example 1 was produced using a production apparatus having, in order from the upstream side, a swelling bath, two dyeing baths (a first dyeing bath and a second dyeing bath), two crosslinking baths (a first crosslinking bath and a second crosslinking bath), a complementary color bath, and a washing bath, with shower devices disposed at the inlet and outlet sides of the first dyeing bath, the inlet side of the second dyeing bath, and the inlet and outlet sides of the complementary color bath, the other configuration of which is the same as that of the production apparatus shown in FIG. 1.

[0074] Specifically, a long polyvinyl alcohol (PVA) raw film having a width of 4260 mm and a thickness of 60 μm [trade name "M6000" manufactured by Mitsubishi Chemical, saponification degree 99.9 mol% or more] was continuously transported while being unwound from a roll, and was immersed in a swelling bath (26 ° C) consisting of pure water for a residence time of 15 seconds (swelling step). After that, the film pulled out from the swelling bath was continuously immersed in a first dyeing bath (100 parts by mass of water, 0.028 parts by mass of iodine, 1.3 parts by mass of potassium iodide) at 30 ° C containing iodine and a second dyeing bath (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) at 30 ° C for a total residence time of 58 seconds in the first dyeing bath and the second dyeing bath (dyeing step). Next, the film pulled out from the second dyeing bath was immersed in a first crosslinking bath at 56°C with a potassium iodide / boric acid / water ratio of 12 / 5 / 100 (mass ratio) for 20 seconds, and in a second crosslinking bath at 58°C with the same liquid composition for 38 seconds. It was further immersed in a complementary color bath at 40°C with a potassium iodide / boric acid / water ratio of 13 / 5 / 100 (mass ratio) for 17 seconds (complementary color step). Thereafter, the film was immersed in a washing bath consisting of pure water at 5°C (washing step).

[0075] In the first dyeing bath, the shower device installed on the inlet side and the outlet side of the first dyeing bath showered only the central 2420 mm (50% of the central part to the total width) of the film width 4803 mm with the dyeing solution of the same composition as the first dyeing bath. In the second dyeing bath, the shower device installed on the inlet side showered only the central 2310 mm (50% of the central part to the total width) of the film width 4646 mm with the dyeing solution of the same composition as the second dyeing bath. In the complementary color bath, the shower device installed on the inlet side and the outlet side showered only the central 1210 mm (50% of the central part to the total width) of the film width 2406 mm with the complementary color solution of the same composition as the complementary color bath. In the dyeing process, crosslinking process, and complementary color process, longitudinal uniaxial stretching was performed by inter-roll stretching in the bath, and the total stretching ratio based on the original film was 6 times. After the washing step, the film was first dried at a temperature of 48° C., and then dried at a temperature of 91° C. to obtain a polarizing film having a thickness of 24 μm and a width of 1920 mm.

[0076] <Example 2> In Example 1, the process of spraying the treatment liquid using a shower device was performed by showering only the central 2,420 mm of the film width of 4,803 mm (the central portion accounts for 50% of the total width) with dyeing liquid having the same composition as that of the first dyeing bath using only the shower devices installed on the inlet and outlet sides of the first dyeing bath, and the shower devices installed in the second dyeing bath and complementary color bath were not operated, except that the polarized film was produced in the same manner as in Example 1.

[0077] <Comparative Example 1> Polarizing films were produced in the same manner as in Example 1, except that in Example 1, 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.

[0078] <Measurement of the degree of polarization> In the obtained polarizing films of Examples 1 and 2 and Comparative Example 1 having a width of 1920 mm, the luminosity-corrected polarization degree (Py) was measured based on the above-mentioned method at seven positions, 20 mm (position 1), 100 mm (position 2), 500 mm (position 3), 960 mm (position 4), 1420 mm (position 5), 1820 mm (position 6), and 1900 mm (position 7) from the left end, for three straight lines extending in the width direction. Table 1 shows the average luminosity-corrected polarization degree (Py) of the three straight lines at the seven positions (the average value is taken as the luminosity-corrected polarization degree (Py) at each position). Table 1 also shows the calculated values ​​of the difference between the maximum and minimum luminosity-corrected polarization degrees at the seven positions. FIG. 4 is a graph plotting the polarization degrees shown in Table 1.

[0079] [Table 1]

[0080] The results shown in Table 1 and FIG. 4 show that the polarizing films of Examples 1 and 2 have a smaller difference between the maximum and minimum values ​​of the visibility-corrected polarization degree in the width direction than that of Comparative Example 1, and thus the variation in the visibility-corrected polarization degree in the width direction is suppressed.

[0081] <Example 3> In Example 1, a polyvinyl alcohol raw film having a width of 3390 mm was used as the polarizing film.

[0082] In the first dye bath, shower devices installed on the inlet and outlet sides of the first dye bath showered dyeing solution with the same composition as the first dye bath only on the central 1925 mm of the 3859 mm film width (50% of the central portion of the total width). In the second dye bath, shower devices installed on the inlet side showered dyeing solution with the same composition as the second dye bath only on the central 1760 mm of the 3751 mm film width (47% of the central portion of the total width). In the complementary color bath, shower devices installed on the inlet and outlet sides showered complementary color solution with the same composition as the complementary color bath only on the central 990 mm of the 1962 mm film width (50% of the central portion of the total width).

[0083] In the dyeing process, crosslinking process, and color-complementing process, the film was uniaxially stretched longitudinally by roll-to-roll stretching in a bath, and the total stretch ratio based on the original film was 6 times. After the washing process, the film was first dried at a temperature of 46°C, and then dried at a temperature of 92°C to obtain a polarizing film having a thickness of 24 μm and a width of 1460 mm. A polarizing film was produced by the same manufacturing method as in Example 1 except for the above.

[0084] <Example 4> In Example 3, the process of showering the treatment liquid using a shower device was performed by showering only the central 1925 mm of the film width of 3859 mm (the central portion accounts for 50% of the total width) with dyeing liquid having the same composition as that of the first dyeing bath using only the shower devices installed on the inlet and outlet sides of the first dyeing bath, and the shower devices installed in the second dyeing bath and complementary color bath were not operated, except that the polarized film was produced in the same manner as in Example 3.

[0085] <Comparative Example 2> In Example 3, a polarizing film was produced in the same manner as in Example 1, except that the step of showering the treatment solution using a shower device was not carried out for any of the treatment baths.

[0086] <Measurement of the degree of polarization> For the obtained polarizing films of Examples 3 and 4 and Comparative Example 2 with a width of 1460 mm, the luminosity-corrected polarization degree (Py) was calculated according to the above-mentioned method at five positions, 20 mm (position 1), 100 mm (position 2), 730 mm (position 3), 1360 mm (position 4), and 1440 mm (position 5) from the left end of the four straight lines extending in the width direction. Table 2 shows the average luminosity-corrected polarization degree (Py) of the four straight lines at the five positions (the average value is taken as the luminosity-corrected polarization degree (Py) at each position). Table 2 also shows the calculated difference between the maximum and minimum luminosity-corrected polarization degree (Py) at the five positions. FIG. 5 is a graph plotting the luminosity-corrected polarization degree (Py) shown in Table 2.

[0087] [Table 2]

[0088] The results shown in Table 2 and FIG. 5 show that the polarizing films of Examples 3 and 4 have a smaller difference between the maximum and minimum values ​​of the visibility-corrected polarization degree in the width direction than that of Comparative Example 2, and thus the variation in the visibility-corrected polarization degree in the width direction is suppressed. [Explanation of symbols]

[0089] 10 raw film made of polyvinyl alcohol resin, 11 raw film roll, 13 swelling bath, 15 dyeing bath, 16 shower device, 17a crosslinking bath, 17b complementary color bath, 19 cleaning bath, 21 drying furnace, 23 polarizing film, 30 to 35, 37 to 48, 60, 61 guide rolls, 50 to 52, 53a, 53b, 54, 55, 56 nip rolls.

Claims

1. A method for producing a polarizing film from a polyvinyl alcohol-based resin film, comprising the steps of: The method includes a plurality of treatment steps of contacting the polyvinyl alcohol-based resin film with a treatment liquid, At least one of the plurality of treatment steps is a multi-stage treatment step including a uniform contact step of contacting the polyvinyl alcohol-based resin film with a uniform amount of treatment liquid over the entire width, and a controlled contact step of contacting the polyvinyl alcohol-based resin film with an amount of treatment liquid controlled according to a position in the width direction of the entire width, In the adjusted contact step, the polyvinyl alcohol-based resin film is divided into a central portion and both end portions across the entire width, and the amount of the treatment liquid brought into contact with the central portion is adjusted to be greater than the amount of the treatment liquid brought into contact with the both end portions, and the treatment liquid is brought into contact with the central portion and not brought into contact with the both end portions, In the multi-stage treatment process, the treatment liquid used in the uniform contact step and the treatment liquid used in the conditioning contact step are both a dyeing liquid, a crosslinking liquid, or a complementary liquid, and further, both have the same composition; The composition includes at least one of a dichroic dye and a boron compound. A method for producing a polarizing film.

2. The method for producing a polarizing film according to claim 1 , wherein in the adjusting and contacting step, the central portion of the polyvinyl alcohol-based resin film occupies 5 to 80% of the entire width.

3. 3 . The method for producing a polarizing film according to claim 1 , wherein the uniform contact step is a step of immersing the polyvinyl alcohol-based resin film in the treatment liquid contained in a treatment tank.

4. The method for producing a polarizing film according to any one of claims 1 to 3, wherein the conditioning contact step is a step of showering the treatment liquid onto the polyvinyl alcohol-based resin film.

5. The method for producing a polarizing film according to any one of claims 1 to 4, wherein the polyvinyl alcohol-based resin film has a total width of 400 mm or more and 8000 mm or less.

6. A polarizing film manufacturing apparatus for producing a polarizing film from a polyvinyl alcohol-based resin film, comprising: a plurality of processing sections for contacting the polyvinyl alcohol-based resin film with a processing solution; At least one of the plurality of treatment sections is a multi-stage treatment section having a uniform contact section for contacting the polyvinyl alcohol-based resin film with a uniform amount of treatment liquid over the entire width, and an adjusted contact section for contacting the polyvinyl alcohol-based resin film with an amount of treatment liquid adjusted depending on a position in the width direction of the entire width, In the adjusted contact portion, the polyvinyl alcohol-based resin film is divided into a central portion and both end portions across the entire width, and the amount of the treatment liquid brought into contact with the central portion is adjusted to be greater than the amount of the treatment liquid brought into contact with the both end portions, and the treatment liquid is brought into contact with the central portion and not brought into contact with the both end portions; In the multi-stage treatment section, the treatment liquid used in the uniform contact section and the treatment liquid used in the adjusted contact section are both a dyeing liquid, a crosslinking liquid, or a complementary liquid, and further, both have the same composition; The composition includes at least one of a dichroic dye and a boron compound.

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