TW201819490A - Film processing method and polarizing film production method - Google Patents

Abstract

This film processing comprises a staining step of immersing a film B into a staining bath, a cross-linking step of immersing the stained film B into a cross-linking bath, and an adjustment step of immersing the cross-linked film B into an adjustment bath. The adjustment bath has a solution containing a boron compound and an iodine compound. A portion of the solution is taken from the adjustment bath, and this solution is separated, using a reverse osmosis membrane, into a solution containing the boron compound and a solution containing the iodine compound. The solution containing the iodine compound is refilled into the adjustment bath. The present invention allows an effective component to be separated from a surplus solution and re-used in series with the film processing.

Description

Processing method of film and manufacturing method of polarizing film

FIELD OF THE INVENTION The present invention relates to a method for processing a thin film when a polarizing film or the like is produced.

BACKGROUND ART Conventionally, a polarizing film is used as a constituent material of a liquid crystal display device, polarized sunglasses, and the like. As the polarizing film, for example, an iodine-based polarizing film is known. An iodine-based polarizing film can be prepared by performing the following film treatment: the film is adsorbed with iodine, and crosslinked by a boron compound. Specifically, an iodine-based polarizing film can be prepared by performing a series of film treatments: immersing the film in a dyeing bath having an iodine-containing solution for dyeing, and immersing the dyed film in a compound containing a boron compound. Crosslinking is performed in a combined bath, and the crosslinked film is immersed in an extension bath for stretching, and the stretched film is immersed in an adjustment bath containing an iodine compound such as potassium iodide for hue adjustment.

If such thin film processing is performed in series, as the film moves, the solution in the front processing bath will be mixed with the solution in the rear processing bath, and the concentration of the solution in the rear processing bath will change. For example, a film immersed in a dyeing bath is introduced into a crosslinking bath with an iodine-containing solution (solution in the dyeing bath) attached, and a film immersed in a crosslinking bath is attached with a solution containing a boron compound (Solution in the crosslinking bath) was introduced into the adjustment bath. Therefore, if the thin film treatment is actually performed, for example, the solution of the cross-linking bath will constitute a solution containing boron compounds and iodine and the concentration of the boron compounds will be relatively reduced. Relatively reduced solution. Accordingly, since the solution of the front-side processing bath is mixed into the back-side processing bath, the solution concentration of the back-side processing bath will be changed from the original setting value. Therefore, for example, in the cross-linking bath, the concentration of the active ingredient in the solution in the cross-linking bath is maintained within the allowable range by supplementing the boron compound. The concentration of the active ingredient is maintained within the allowable range.

The aforementioned supplementary iodine compounds and the like are generally made of raw materials. In this regard, by extracting active ingredients from the residual liquid (including residual liquid such as overflow liquid) of each processing bath and supplementing it, the waste liquid can be discarded and the material cost can be reduced. In particular, potassium iodide is more expensive than boron compounds and the like, and therefore its reuse can greatly contribute to reduction in material cost.

Patent Document 1 discloses that each residual liquid from a dyeing bath, a cross-linking bath, and a cleaning bath is collected and stored in a storage tank, and the residual liquid in the storage tank is transferred to an electrodialysis device, and the electrodialysis device is used. , Separated into concentrated potassium iodide, and reused potassium iodide.

Prior technical documents Patent documents Patent document 1: Japanese Patent Application Laid-Open No. 2009-22921

SUMMARY OF THE INVENTION However, with respect to the thin film processing such as dyeing, cross-linking, and stretching, a series of film processing is performed, and the separation using the aforementioned electrodialysis apparatus cannot be performed in conjunction with such a series of thin film processing. Specifically, in the separation using the aforementioned electrodialysis device, the residual liquid is collected from each bath and stored in a storage tank, and the residual liquid is transferred to the electrodialysis to which a DC current has been applied at a stage where a predetermined amount of residual liquid is stored. The device, after performing the dialysis for a predetermined time, removes the potassium iodide concentrate. The concentration of the prepared potassium iodide concentrate was adjusted, and then it was added to a dyeing bath or the like. In this way, the electrodialysis device cannot sequentially separate the residual liquid generated in association with the thin film processing, but is performed separately and independently from the thin film processing (so-called batch processing method). Therefore, it is impossible to perform separation and reuse of the residual liquid in series with the treatment of the thin film. In addition, when an electrodialysis device is used, a large installation space is required, and maintenance and management of the electrodialysis membrane are complicated, and often the cost of electricity and the like increases.

Problems to be Solved by the Invention The object of the present invention is to provide a method for processing a series of films capable of separating an active ingredient from a residual liquid in combination with a film, and a method for manufacturing a polarizing film.

Means for Solving the Problem The first film processing method of the present invention includes a step (X) of immersing a film in a bath, the bath having a solution containing a boron compound and an iodine compound, and the aforementioned processing method is obtained from the bath A part of the aforementioned solution was taken out, and the solution was separated into a solution containing a boron compound and a solution containing an iodine compound using a reverse osmosis membrane. The aforementioned step (X) of the ideal first thin film processing method of the present invention is a step of immersing a thin film taken out in a bath having a solution containing a boron compound as an active ingredient, and immersing the thin film having an iodine compound as an active ingredient In solution in the bath. The processing of the film of the ideal first processing method of the present invention has the following steps: a dyeing step, immersing the film in a dyeing bath; a crosslinking step, immersing the dyed film in a crosslinking bath; and an adjusting step, The crosslinked film is immersed in an adjustment bath; the aforementioned adjustment step is the aforementioned step (X), and a solution containing an iodine compound separated by the aforementioned reverse osmosis membrane is added to the aforementioned adjustment bath. In the preferred first film processing method of the present invention, the film includes a polyvinyl alcohol-based film, the boron compound includes boric acid, and the iodine compound includes potassium iodide.

The second film processing method of the present invention includes a step (Y) of immersing the film in a bath, the bath having a solution containing a boron compound and iodine, and the processing method taking a part of the solution from the bath and using The reverse osmosis membrane separated the solution into a solution containing a boron compound and a solution containing iodine. The aforementioned step (Y) of the ideal second thin film processing method of the present invention is a step of immersing the thin film taken out in a bath having a solution containing iodine as an active ingredient, and immersing the thin film in a bath having a boron compound as an active ingredient. Solution in the bath. The processing of the film of the ideal second film processing method of the present invention has the following steps: a dyeing step, immersing the film in a dyeing bath; a crosslinking step, immersing the dyed film in a crosslinking bath; The crosslinked film is immersed in a conditioning bath; the aforementioned crosslinking step is the aforementioned step (Y), and a solution containing a boron compound separated by using the aforementioned reverse osmosis membrane is added to the aforementioned crosslinking bath.

According to other aspects of the present invention, a method for manufacturing a polarizing film can be provided. The manufacturing method of the polarizing film of the present invention includes any one of the aforementioned processing methods of the film.

Effects of the Invention The method for processing a thin film and the method for manufacturing a polarizing film of the present invention use a reverse osmosis membrane to separate into a solution containing a boron compound and a solution containing an iodine compound, or a solution containing a boron compound and a solution containing iodine. By using a reverse osmosis membrane, the active ingredient can be separated from the residual liquid in series with the membrane treatment and supplemented to the optional bath in conjunction with the membrane treatment.

Form for Carrying Out the Invention The method for processing a film of the present invention includes a step of impregnating a optional film with a solution containing an active ingredient. This step includes causing the optional film to adsorb, adhere, contain, or bind the active ingredients in the solution. As used herein, the term "active ingredient" means an ingredient necessary for the purpose of using the solution. In addition, the film processing method of the present invention can be used for optional film modification treatment, surface treatment, and the like. For example, the processing method of the film of the present invention can be used to manufacture a polarizing film. Hereinafter, the present invention will be specifically described with a focus on the film processing used in the production of a polarizing film.

[First Embodiment] The film treatment of the first embodiment includes a step (X) of immersing the film in a bath, the bath having a solution containing a boron compound and an iodine compound, and the film treatment is taken out of the bath As part of the aforementioned solution, the solution was separated into a solution containing a boron compound and a solution containing an iodine compound using a reverse osmosis membrane. This step (X) is, for example, a step of immersing a film taken out in a bath having a solution containing a boron compound as an active ingredient, and immersing it in a bath having a solution containing an iodine compound as an active ingredient.

(Thin Film Processing Device) FIG. 1 is a reference view showing a thin film processing device according to a first embodiment, and FIG. 2 is a reference view showing a separation device including a reverse osmosis membrane provided in the processing device. The inverted white arrows in the figure indicate the travel direction (conveying direction) of the film, and the arrow marks indicate the flow direction of each liquid. In addition, in the embodiment described focusing on the film processing used in the production of the polarizing film, the aforementioned film processing device is also a device for manufacturing a polarizing film. The film processing apparatus A includes a transporting unit 9 which transports a long strip-shaped film B in a longitudinal direction, a plurality of baths, which have a solution, and a separation device 6, which separates an active ingredient from the solution. The plurality of baths have a swelling bath 1, a dyeing bath 2, a crosslinking bath 3, an extension bath 4, and an adjustment bath 5 in this order from the front side (the upstream side in the traveling direction of the film B). The separation device 6 is configured to take out a solution from at least one of the plurality of baths, and has a reverse osmosis membrane for separating an active ingredient from the solution.

<Long strip-shaped film> The film B which comprises a process target is a long strip. The long strip shape is a rectangular shape whose length in the long direction is sufficiently larger than the length in the short direction (the short direction is a direction orthogonal to the long direction). The length of the long strip-shaped film B is, for example, 10 m or more, and preferably 50 m or more. The film B is not particularly limited, and it is preferably a hydrophilic polymer film from the viewpoint of excellent dyeability with iodine (easy to stain with iodine). The hydrophilic polymer film is not particularly limited, and a conventionally known film can be used. Specific examples of the hydrophilic polymer film include a polyvinyl alcohol (PVA) film, a partially formalized PVA film, a polyethylene terephthalate (PET) film, and ethylene. Vinyl acetate copolymer-based films, such partially saponified films, and the like. In addition to these, a polyolefin oriented film such as a dehydrated processed product of PVA or a dehydrochlorinated processed product of polyvinyl chloride, a polyvinyl chloride-based film stretched and oriented, and the like may be used. Among these, a PVA-based polymer film is particularly preferred from the viewpoint of excellent dyeability using iodine. Examples of the raw material polymer of the PVA-based polymer film include a polymer obtained by polymerizing vinyl acetate and saponifying, and copolymerizing a small amount of copolymerizable monomers such as unsaturated carboxylic acid or unsaturated sulfonic acid with vinyl acetate. Of polymers, etc. The polymerization degree of the aforementioned PVA-based polymer is not particularly limited. From the viewpoint of solubility in water, etc., it is preferably 500 to 10,000, and more preferably 1,000 to 6000. The saponification degree of the PVA polymer is preferably 75 mol% or more, and more preferably 98 mol% to 100 mol%. The thickness of the aforementioned film B is not particularly limited, and is, for example, 15 μm to 110 μm, more preferably 38 μm to 110 μm, and even more preferably 50 μm to 100 μm.

<Swelling bath> The swelling bath 1 is provided in order to swell the said film B. The swelling bath 1 includes a tank 11 and a solution 12 placed in the tank 11. Hereinafter, the solution of the swelling bath 1 is called "swelling solution". When a sufficiently swollen film B is used in the dyeing bath 2 described later, the swelling bath may be omitted. In the example shown in the figure, only one swelling bath 1 is provided. However, two or more swelling baths 1 (not shown) may be provided at the same time in the traveling direction of the film B. As the swelling liquid, for example, water can be used. Furthermore, water having been added with an appropriate amount of glycerin and / or potassium iodide to the water may be used as a swelling liquid. When glycerin is added, its concentration is preferably 5 wt% or less, and when potassium iodide is added, its concentration is preferably 10 wt% or less.

<Dyeing Bath> The dyeing bath 2 is provided for dyeing the aforementioned film B. The dyeing bath 2 includes a tank 21 and a solution 22 placed in the tank. Hereinafter, the solution of the dyeing bath 2 is called "staining solution." In the example shown in the figure, only one dyeing bath 2 is provided. However, two or more dyeing baths 2 (not shown) may be provided at the same time in the traveling direction of the film B. The aforementioned dyeing solution is a solution for dyeing the film B, and a solution containing iodine as an active ingredient can be used. For example, a solution in which iodine has been dissolved in a solvent may be used as the dyeing solution. The solvent is generally water, but an organic solvent compatible with water may be further added. There is no particular limitation on the concentration of iodine in the dyeing solution, but it is preferably 0.01% to 10% by weight, more preferably 0.02% to 7% by weight, and most preferably 0.025% to 5% by weight. . Furthermore, in order to further improve the dyeing efficiency, it is suitable to add an iodine compound to the dyeing solution. Iodine compounds are compounds containing iodine and elements other than iodine in the molecule. Examples of the iodine compound include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and titanium iodide. When the iodine compound is added, its concentration is preferably 0.01% to 10% by weight, and more preferably 0.1% to 5% by weight. Among iodine compounds, it is desirable to add potassium iodide. When the dyeing solution contains iodine and an iodine compound, iodine may be a main component of the solution, or iodine compound may be a main component of the solution. Generally, a solution containing more iodine compounds than iodine is used as the dyeing solution. That is, although iodine is an effective component in this dyeing liquid, an iodine compound is a main component. Herein, in the present specification, the term “main component” means a component (excluding a solvent) that is contained most in a solution on a weight basis.

<Crosslinking Bath> The crosslinking bath 3 is provided to crosslink the iodine-adsorbed film B. The crosslinking bath 3 includes a tank 31 and a solution 32 placed in the tank 31. Hereinafter, the solution of the crosslinking bath 3 is referred to as a "crosslinking solution". In the example shown in the figure, only one cross-linking bath 3 is provided. However, two or more cross-linking baths 3 (not shown) may be provided at the same time in the traveling direction of the film B. The aforementioned crosslinking solution is a solution for crosslinking the film B, and a solution containing a boron compound as an active ingredient can be used. For example, a solution in which a boron compound has been dissolved in a solvent can be used as the crosslinking solution. The solvent is generally water, but an organic solvent compatible with water may be further added. Examples of the boron compound include boric acid and borax. Among these, boric acid is preferably used. The concentration of the boron compound in the crosslinking solution is not particularly limited, but it is preferably 1% to 10% by weight, more preferably 2% to 7% by weight, and most preferably 2% to 6% by weight. %. Moreover, glyoxal, glutaraldehyde, etc. may be added to the said crosslinking liquid as needed. Furthermore, from the viewpoint that a polarizing film having uniform optical properties can be obtained, it is preferable to add an iodine compound to the aforementioned crosslinking solution. The iodine compound is not particularly limited, and examples thereof include those exemplified in the above-mentioned dyeing solution. Among them, potassium iodide is preferable. The concentration of the iodine compound is not particularly limited, but it is preferably 0.05% to 15% by weight, and more preferably 0.5% to 8% by weight. When an iodine compound is added, the ratio of the boron compound (preferably boric acid) to the iodine compound (preferably potassium iodide) is preferably in a range of 1: 0.1 to 1: 6 by weight ratio, and more preferably 1 : 0.5 ~ 1: 3.5, the most ideal is 1: 1 ~ 1: 2.5. When the crosslinking solution contains a boron compound and an iodine compound, the boron compound may be a main component of the solution, or the iodine compound may be a main component of the solution.

<Extension Bath> The extension bath 4 is provided to orient the aforementioned film B which has adsorbed iodine and is crosslinked. The extension bath 4 includes a tank 41 and a solution 42 placed in the tank 41. Hereinafter, the solution of the extension bath 4 is called "extension liquid". In the example shown in the figure, only one extension bath 4 is provided. However, two or more extension baths 4 (not shown) may be provided at the same time in the traveling direction of the film B. Since the film B can be stretched in the dyeing bath 2 or the crosslinking bath 3, etc., the stretching bath 4 can be omitted. The extension liquid is not particularly limited. For example, a solution containing a boron compound as an active ingredient may be used. The extension liquid may be, for example, a solution in which a boron compound has been dissolved in a solvent, or a solution in which a boron compound and optionally an iodine compound, various metal salts, zinc compounds, etc. have been dissolved in a solvent. The solvent is generally water, but an organic solvent compatible with water may be further added. Examples of the boron compound include boric acid and borax. Among them, boric acid is preferably used. The concentration of the boron compound in the extension liquid is not particularly limited, but it is preferably 1% to 10% by weight, and more preferably 2% to 7% by weight. In addition, from the viewpoint of suppressing the elution of iodine that has been adsorbed on the film B, it is preferable that the extension liquid contains an iodine compound. The iodine compound is not particularly limited, and examples thereof include those exemplified in the above-mentioned dyeing solution. Among them, potassium iodide is preferable. The concentration of the iodine compound in the extension liquid is not particularly limited, but it is preferably 0.05% to 15% by weight, and more preferably 0.5% to 8% by weight. When the extension liquid contains a boron compound and an iodine compound, the boron compound may be the main component of the solution, or the iodine compound may be the main component of the solution. Generally, a solution containing more iodine compounds than boron compounds is used as the extension liquid.

<Adjustment Bath> The adjustment bath 5 is provided for adjusting the hue of the film B, removing boron compounds, and the like. This adjustment bath 5 is a bath arranged behind the cross-linking bath having the cross-linking liquid (the cross-linking liquid is a solution containing a boron compound as an active ingredient). The adjustment bath 5 is a bath arranged on the rear side of the extension bath having the aforementioned extension solution (the extension solution is a solution containing a boron compound as an active ingredient). The film B taken out of the crosslinking bath and / or the extension bath after being immersed in the aforementioned bath is immersed in the adjustment bath 5. The adjustment bath 5 includes a tank 51 and a solution 52 placed in the tank 51. Hereinafter, the solution of the adjustment bath 5 is referred to as "adjustment solution". In the example shown in the figure, only one adjustment bath 5 is provided. However, two or more adjustment baths 5 (not shown) may be provided at the same time in the traveling direction of the film B. The adjusting solution is a solution for adjusting the hue of the thin film B, and a solution containing an iodine compound as an active ingredient can be used. For example, a solution in which an iodine compound has been dissolved in a solvent may be used as the adjustment liquid. The solvent is generally water, but an organic solvent compatible with water may be further added. The iodine compound is not particularly limited, and examples thereof include those exemplified in the above-mentioned dyeing solution. Among them, potassium iodide is preferable. The concentration of the iodine compound in the adjustment liquid is not particularly limited, but it is preferably 0.5% to 20% by weight, and more preferably 1% to 15% by weight.

In addition, after adjusting the bath 5, a washing unit (not shown) such as a washing bath may be disposed as necessary. The cleaning section is provided to remove the residual components such as iodine compounds and boron compounds remaining on the surface of the film B after adjusting the bath 5 by adjusting the bath 5. Water can be used as a cleaning solution. If necessary, a drying section (not shown) may be arranged after adjusting the bath 5. The drying section is provided to remove moisture and the like remaining on the surface of the film B.

Effective ingredient concentration of the swelling liquid, dyeing liquid, cross-linking liquid, elongating liquid, and adjusting liquid described in the <Swelling bath>, <Dyeing bath>, <Crosslinking bath>, <Extending bath>, and <Adjusting bath> column Wait for the original set value. As described later, if the processing device is actually operated, the solution of the front side bath will be mixed into the solution of the back side bath, and the active ingredients will infiltrate into the film B. Therefore, pay attention to the concentration of each bath at any time from the original setting The value changes.

<Separation device> The separation device 6 is provided for separating and recovering an active ingredient from a solution selected from at least one of the aforementioned baths. The separation device 6 is arranged in at least one of the foregoing baths. In this embodiment, the separation device 6 is disposed in the adjustment bath 5. In FIG. 2, the separation device 6 includes, for example, a transfer pump 612, a safety filter 632, a pressure feed pump 613, a reverse osmosis membrane 71, a mixer 671, a conductivity meter 652, and a return pipe 691 in this order. The separation device 6 may include components other than these.

Specifically, a water intake pump 611 is disposed in the adjustment bath 5. A part of the adjusting liquid 52 is taken out from the adjusting bath 5 by the water taking pump 611. Hereinafter, a part of the solution taken out from the bath is called "residual liquid", and a part of the adjustment liquid 52 taken out from the adjustment bath 5 is called "residual adjustment liquid". An auxiliary tank 621 is provided behind the water intake pump 611. The auxiliary tank 621 is a tank for temporarily storing the residual adjustment liquid. A transfer pump 612 is provided behind the auxiliary tank 621. The auxiliary groove 621 is provided as necessary. When the auxiliary tank 621 is not provided, the transfer pump 612 takes out the residual adjustment liquid and sends it to the pressure feed pump 613. Between the transfer pump 612 and the pressure feed pump 613, a universal filter 631, a safety filter 632, and an adsorption filter 633 containing activated carbon are sequentially arranged. The universal filter 631 is provided to remove large foreign matter that may be mixed into the residual conditioning solution. The safety filter 632 is provided to remove small foreign matters to prevent the reverse osmosis membrane 71 from being blocked or broken. For example, the safety filter 632 includes a filter element having an opening of 1 μm. The activated carbon-containing adsorption filter 633 is provided for the purpose of removing organic matter and the like. The pressure feed pump 613 pressurizes the residual adjustment liquid and transports it to the reverse osmosis membrane 71. There are no special restrictions on the pressure feed pump 613. Examples include scroll pumps, diffusion pumps, scroll diagonal flow pumps, piston pumps, plunger pumps, diaphragm pumps, gear pumps, screw pumps, vane pumps, and cascade pumps. , Jet pump, etc.

A reverse osmosis membrane 71 is provided after the pressure feed pump 613. A flow meter 641 is provided between the pressure feed pump 613 and the reverse osmosis membrane 71. In this embodiment, a reverse osmosis membrane 71 capable of separating an iodine compound and a boron compound contained in the residual adjustment liquid is used. The reverse osmosis membrane 71 is not particularly limited as long as it can be separated as described above, and a conventionally known one can be used. For example, the reverse osmosis membrane 71 may include a spiral membrane element, a hollow fiber membrane element, a tubular membrane element, a frame plate membrane element, and the like. The reverse osmosis membrane 71 may be a singular or plural membrane element. A plurality of membrane elements are usually connected in series. The reverse osmosis membrane 71 may be singular, or a plurality of reverse osmosis membranes 71 may be connected in parallel or in parallel. The material constituting the membrane element is not particularly limited, and various polymer materials such as cellulose acetate, polyvinyl alcohol, polyamide, and polyester can be used. As the reverse osmosis membrane 71, a commercially available product may be used. Examples of commercially available products that can be used in the present invention include the product name "LFC3LD" made by Nitto Denko Corporation, and the product name "ESPA4-7" made by Nitto Denko Corporation.

Through the reverse osmosis membrane 71, the residual conditioning solution is separated into a permeate containing a boron compound and a concentrated solution containing an iodine compound. On the permeate side of the reverse osmosis membrane 71, a flow meter 642 and a conductivity meter 651 are provided as necessary, and a storage tank 622 capable of containing the permeate is provided later as necessary. The conductivity meter 651 measures the conductivity of the permeate. On the concentrated liquid side of the reverse osmosis membrane 71, a flow rate adjustment unit 661 (for example, a valve) and a flow meter 643 are provided as necessary. Furthermore, a mixer 671 and a conductivity meter 652 are provided afterward, and a storage tank 623 is provided afterward if necessary. In addition, before the mixer 671, a diluting section 662 for introducing a diluting liquid into the concentrated liquid is provided. A return pipe 691 provided with a transfer pump 614 is connected to the aforementioned storage tank 623, and the front end of the return pipe 691 is opened to the adjustment bath 5.

(Processing method of film and manufacturing method of polarizing film) In this embodiment, the film processing has the following steps: a step of transporting the film in the longitudinal direction; a swelling step of swelling the film; a dyeing step of dyeing the film; A step of crosslinking, a step of extending the film, and a step of adjusting the hue of the film. If necessary, there may be other steps. In at least one step selected from the steps, the active ingredient is separated from the solution and recovered, and returned for use again. That is, the active ingredients in the solution are recycled. These steps can be performed using the thin-film processing apparatus A described above.

<Swelling step, dyeing step, cross-linking step, extending step, adjusting step, and other steps> These steps can be carried out in the same manner as the manufacturing steps of a conventional iodine-based polarizing film. Referring to FIG. 1, a brief description is given. The long strip-shaped film B is guided to the swelling bath 1 by the conveying unit 9 and is immersed in the swelling liquid 12. The temperature of the swelling liquid is, for example, 20 ° C to 45 ° C, and the immersion time in the swelling liquid is, for example, 20 seconds to 300 seconds. The film B drawn from the swelling bath 1 is introduced into a dyeing bath 2 and immersed in a dyeing solution 22. The temperature of the dyeing liquid is, for example, 10 ° C to 35 ° C, and the immersion time in the dyeing liquid is, for example, 10 seconds to 200 seconds. The film B drawn from the dyeing bath 2 is introduced into the crosslinking bath 3 and immersed in the crosslinking solution 32. The temperature of the crosslinking solution is, for example, 20 ° C to 70 ° C, and the immersion time in the crosslinking solution is, for example, 5 seconds to 400 seconds. The film B drawn from the cross-linking bath 3 is introduced into the stretching bath 4 and subjected to a stretching treatment. The stretching ratio is, for example, 2 to 6.5 times the total stretching ratio with respect to the original length of the film B. The stretching treatment can also be performed in the aforementioned dyeing step and cross-linking step. When stretching is performed in these steps, the stretching magnification in the stretching step is set to a total stretching magnification of 2 to 6.5 in consideration of the stretching magnification in these steps. Times. In addition, when extending to the total extension ratio in the dyeing step and the cross-linking step, it is also possible to omit a separate and independent extension step. The stretched film B is introduced into the adjustment bath 5 and immersed in the adjustment liquid 52. The temperature of the adjustment liquid is, for example, 15 ° C to 40 ° C, and the immersion time in the adjustment liquid is, for example, 2 seconds to 20 seconds. The film B drawn from the adjustment bath 5 is washed as necessary, and is wound into a roll shape after drying. Through this treatment, a polarizing film can be obtained. For example, a polarizing plate can be produced by laminating a protective film on at least one side of the polarizing film produced.

The film processing in each of the steps described above is performed in series on the long strip-shaped film B to be transported. Therefore, the solution of the front-side bath (front-side processing bath) is mixed into the back-side bath (back-side processing bath). Therefore, the concentration of the solution in the back-side treatment bath will be changed from the original setting value. For example, in the cross-linking bath 3, the dye solution containing iodine in the dyeing bath 2 is mixed into the cross-linking solution. Therefore, the cross-linking solution has a relatively lower concentration since the original boron compound was set. Furthermore, in the crosslinking bath 3, since the boron compound is impregnated into the thin film B, the cross-linking solution will also have a relatively reduced concentration from the original boron compound. Similarly, in the adjustment bath 5, the cross-linking bath 3 and / or the extension bath 4 containing the boron compound-containing cross-linking solution and / or the extension solution will be mixed into the adjustment solution. Therefore, the adjustment solution will be set from the original iodine compound The concentration is relatively reduced. Moreover, in the adjustment bath 5, since the iodine compound is impregnated into the film B, the adjustment solution will also relatively decrease from the original set concentration of the iodine compound. In order to correct the concentration change of the solution in each bath, the solution in each bath is taken out as a residual liquid, and a new solution containing an active ingredient is supplemented at the same time. For example, in the adjustment bath 5, a part of the adjustment solution (residual adjustment solution) is taken out, and on the other hand, a solution containing an iodine compound (preferably, potassium iodide) is added to the adjustment bath 5. The present invention is characterized in that the effective component is separated from the residual liquid by the separation device 6 using a reverse osmosis membrane 71 and recovered and reused.

In this embodiment, in the step (X), the film is immersed in a bath having a solution containing a boron compound and an iodine compound, a part of the solution is taken out from the bath, and the solution is separated into a boron compound containing solution using a reverse osmosis membrane. Solutions and solutions containing iodine compounds. Among the above swelling step, dyeing step, crosslinking step, extension step, and adjustment step, for example, the adjustment step is performed continuously after the crosslinking step or extension step. That is, the adjustment step is a step of taking out a thin film taken out by immersion in a crosslinking solution containing a boron compound as an active ingredient, or taking out a thin film taken out by sequentially immersing in the aforementioned crosslinking bath and extension bath, It is immersed in the adjustment bath which has the adjustment liquid containing an iodine compound as an active ingredient. This adjustment step corresponds to step (X) of the present specification.

<Separation Step> As shown in FIG. 2, in the separation device 6 of the film processing device A, a part of the adjustment liquid is taken out as a residual liquid (residual adjustment liquid) through a water pump 611. In addition, the residual liquid (residual adjustment liquid) does not mean excess liquid, but means a solution partially taken out of the bath for separation processing. In addition, the residual adjustment liquid is not limited to those directly extracted from the adjustment bath 5, but may include liquid overflowing from the adjustment bath 5. In addition, the residual adjustment liquid is taken out from the adjustment bath 5 at a flow rate that does not hinder the film processing in the adjustment bath 5. The residual adjustment solution is a solution mainly containing a boron compound (preferably boric acid) and an iodine compound (preferably potassium iodide) contained in a crosslinking solution and / or an extension solution. The residual adjustment liquid usually contains an iodine compound as a main component. The removed residual adjustment liquid is temporarily stored in the auxiliary tank 621 as necessary. In the adjustment liquid mainly using water as a solvent, the residual adjustment liquid is generally approximately neutral (around pH 7). If the residual adjustment solution is alkaline, it is advisable to mix it with a neutralizing agent to make the residual adjustment solution neutral or acidic. If the residual adjusting solution is alkaline, a boron compound such as boric acid may be ionized, and there is a possibility that the boron compound and the iodine compound cannot be separated well by the reverse osmosis membrane 71 described later.

The residual adjustment liquid is conveyed by the transfer pump 612, and the residual adjustment liquid is passed through the universal filter 631, the safety filter 632, and the adsorption filter 633. The residual adjustment liquid that has passed through each of the filters is pressed into the reverse osmosis membrane 71 through the pressure feed pump 613. The discharge pressure of the pressure feed pump 613 is appropriately set according to the performance of the reverse osmosis membrane 71 and the like, and is, for example, 1 MPa to 10 MPa. The amount of the residual adjustment liquid that enters the reverse osmosis membrane 71 from the pressure feed pump 613 can be measured by the flow meter 641. In the reverse osmosis membrane 71, the residual conditioning liquid is separated into a concentrated liquid and a permeated liquid. The concentrated liquid contains a reduced concentration of a boron compound and contains an iodine compound as an active ingredient at a high concentration. The permeate contains substantially no iodine compound and contains a boron compound at a high concentration as an active ingredient. For example, when the weight of the boron compound contained in the residual adjustment solution before entering the reverse osmosis membrane 71 is 100%, the aforementioned permeation solution contains 60% to 90% of the boron compound, and ideally contains 70% to 90%. .

The permeate that has penetrated the reverse osmosis membrane 71 passes through the flow meter 642 and the conductivity meter 651 and is temporarily placed in the storage tank 622 and discarded. It is also possible to discard the permeate without putting it into the storage tank 622. The conductivity meter 651 arranged on the permeate side shows a substantially constant value during implementation. When the value of the conductivity meter is increased, it is generally considered that the membrane element of the reverse osmosis membrane 71 is broken or its performance is deteriorated. If the reverse osmosis membrane 71 is damaged or the like, an iodine compound such as potassium iodide that has been ionized may be excessively mixed into the permeate. As a result, the value of the conductivity meter 651 of the permeate will increase. Accordingly, the conductivity meter 651 disposed on the permeate side has a function of indicating the maintenance time of the reverse osmosis membrane 71. The flow meter 642 measures the flow rate of the permeate. In order to maintain the value of the flow meter 642 at a set value, the opening degree of the flow rate adjustment unit 661 is controlled by a control device (not shown). The flow rate of the concentrated liquid that has been separated by the reverse osmosis membrane 71 is measured by a flow meter 643 disposed behind the flow rate adjustment unit 661. In order to maintain the set value of the flow meter, the discharge amount of the pressure feed pump 613 is controlled by a control device (not shown).

The concentrated liquid obtained from the reverse osmosis membrane 71 may also be directly added to the adjustment bath 5; however, it is generally preferable to perform concentration adjustment before replenishing it. In the example shown in the figure, the diluent is introduced during the return of the concentrated solution from the reverse osmosis membrane 71 to the adjustment bath 5, and the concentration of the iodine compound constituting the effective component of the concentrated solution is adjusted. The concentration of the iodine compound in the concentrated liquid obtained from the reverse osmosis membrane 71 is usually greater than the concentration of the iodine compound in the residual adjustment liquid. Therefore, by diluting with a diluent, the concentration of the concentrated liquid is adjusted to the same concentration as the adjustment liquid in the adjustment bath, or the reference concentration for replenishment. As the diluent, it is preferable to use the same solvent as the adjusting solution, and examples thereof include water or water to which an organic solvent compatible with water has been added.

The mixer 671 is used to mix the concentrated solution that has been diluted with the aforementioned diluted solution (hereinafter, the concentrated solution that has been diluted to adjust the concentration is referred to as a first supplementary solution), and the concentration is uniformized. The conductivity of the first replenishing liquid that has been mixed by the mixer 671 can be measured by the conductivity meter 652. The conductivity meter 652 is used to monitor whether the concentration of the iodine compound constituting the effective component of the first supplementary liquid is as set, and according to the change of the value of the conductivity meter 652, the introduction amount of the diluent is controlled by the control device. For example, the following control is performed: when the value 652 of the conductivity meter is greater than the set value, the introduction amount of the diluent is increased, and when it is lower than the set value, the introduction amount of the diluent is decreased. The first replenishment liquid adjusted to a set concentration is put into the storage tank 623 as required, and then is drawn out by the transfer pump 614 and replenished to the adjustment bath 5 through the return pipe 691. By temporarily putting the first replenishing liquid in the storage tank 623, a replenishing liquid having no uneven concentration can be obtained. Of course, the first supplement liquid that has been adjusted to the set concentration may be directly replenished to the adjustment bath 5.

The present invention relates to a thin film process, and uses a reverse osmosis membrane to separate an effective component from a residual liquid and reuse it. By using a reverse osmosis membrane, a series of membranes can be used to separate and reuse the residual liquid. That is, in the present invention, during the thin film treatment in each bath, the residual liquid can be taken out from the bath, and the active ingredient can be separated. The first supplement liquid having the active ingredient adjusted to a concentration suitable for each bath can be prepared, and It was replenished into the bath. In addition, according to the present invention, by using a reverse osmosis membrane, a small installation place can be constituted, and further, regular costs such as power costs can be reduced and suppressed. In particular, although potassium iodide is relatively expensive, as in this embodiment, by recycling iodine compounds such as potassium iodide and recycling them, it is possible to further reduce the regular cost.

In addition, in this embodiment, the solution containing the boron compound and the iodine compound is used to take out the residual liquid from the adjustment solution, but it is not limited to this. For example, when the extension solution and the like contain the boron compound and the iodine compound, In the reverse osmosis membrane, the residual liquid is similarly separated into a permeate liquid and a concentrated liquid and reused.

In this embodiment, the first supplementary liquid prepared by the separation device (separation step) is replenished to the adjustment bath. However, it may be replaced or used in combination and used in other baths (not shown).示). For example, as described above, when a solution containing an iodine compound is used in a dyeing bath or a cross-linking bath, etc., the first supplementary solution containing the iodine compound that has been separated from the residual conditioning solution can also be used in these baths. in.

Furthermore, in this embodiment, the permeate containing substantially a boron compound is discarded, however, it may be used in another bath. For example, as described above, a solution containing a boron compound is used in a cross-linking bath or an extension bath, etc. However, a permeate containing a boron compound that has been separated from a residual conditioning liquid may be used in these baths. At this time, the permeate obtained from the reverse osmosis membrane can also be used directly in the bath. However, since the concentration of the boron compound as the effective component of the permeate is usually high, it is suitable to use it after adjusting the concentration. In addition, as the method for adjusting the density, the following second embodiment can be appropriately used.

[Second Embodiment] The thin film treatment according to the second embodiment includes a step (Y) of immersing the thin film in a bath, the bath having a solution containing a boron compound and iodine, and the thin film treatment taking out the aforementioned from the bath As part of the solution, the solution was separated into a solution containing a boron compound and a solution containing iodine using a reverse osmosis membrane. This step (Y) is, for example, a step of immersing a film taken out in a bath having a solution containing iodine as an active ingredient, and immersing the film in a bath having a solution containing a boron compound as an active ingredient. The second embodiment will be described below, but in this description, the structure and the like that are different from the first embodiment are mainly described. As for the same structure and the like, the description thereof may be omitted.

(Thin Film Processing Device) FIG. 3 is a reference view showing a thin film processing device according to a second embodiment, and FIG. 4 is a reference view showing a separation device including a reverse osmosis membrane provided in the processing device. Similar to the first embodiment, the thin film processing device A of the second embodiment also includes a transporting unit 9 that transports a long strip-shaped film B in a longitudinal direction, a plurality of baths, which have a solution, and a separation device 6, It separates the active ingredients from the solution. Since the film B, the transfer unit 9, and the plurality of baths 1, 2, 3, 4, and 5 are the same as those in the first embodiment, descriptions are omitted and terms and symbols are directly used.

<Separation device> The separation device 6 is provided for separating and recovering an active ingredient from a solution selected from at least one of the aforementioned baths. In this embodiment, the separation device 6 is arranged in the crosslinking bath 3. In this embodiment, the structure of the separation device 6 up to the reverse osmosis membrane 71 is substantially the same as that of the first embodiment. That is, a water intake pump 611, a storage tank 621, a transfer pump 612, filters 631, 632, 633, a pressure feed pump 613, and a flow meter 641 are provided between the cross-linking bath 3 and the reverse osmosis membrane 71. The functions of these components are as described in the first embodiment, and a part of these components may be omitted if necessary.

The reverse osmosis membrane 71 can be the same as that of the first embodiment. On the permeate side of the reverse osmosis membrane 71, as in the first embodiment, a flow meter 642, a conductivity meter 651, and a storage tank 622 are provided. In the present embodiment, a return path is provided to return the permeate to the cross-linking bath 3 and the like. Specifically, the storage tank 622 storing the permeate is provided with a concentration meter 681 for measuring the concentration of the boron compound. The concentration meter 681 may be, for example, a concentration meter for measuring the concentration of boric acid. As such a boric acid concentration meter, for example, a boric acid concentration constant-time monitor (a model "SRM-1DB" manufactured by CERES) can be used. Further, a transfer pump 615 is provided in the storage tank 622, and a concentration adjustment unit 663 and a mixer 672 capable of adjusting the concentration of the boron compound are provided thereafter. After the mixer 672, a storage tank 624 is provided as necessary. The return pipe 692 provided with the transfer pump 616 is connected to the aforementioned storage tank 624, and the front end of the return pipe 692 is opened to the crosslinking bath 3.

On the concentrated liquid side of the reverse osmosis membrane 71, as in the first embodiment, a flow rate adjustment unit 661 and a flow meter 643 are provided as necessary. Furthermore, if necessary, a storage tank 625 is provided thereafter. A return pipe 693 provided with a transfer pump 617 is connected to the aforementioned storage tank 625, and the front end of the return pipe 693 is opened to the dyeing bath 2.

(Processing method of film and manufacturing method of polarizing film) In this embodiment, the same as the first embodiment, the film processing has the following steps: a step of transporting the film in a long direction; a swelling step of swelling the film; and dyeing the film A dyeing step; a crosslinking step for crosslinking the film; an extending step for extending the film; and an adjusting step for adjusting the hue of the film. If necessary, there may be other steps. In at least one step selected from the steps, the active ingredient is separated from the solution and recovered, and returned for use again. That is, the active ingredients in the solution are recycled. These steps can be performed using the thin film processing apparatus A shown in FIGS. 3 and 4.

<Swelling step, dyeing step, crosslinking step, stretching step, adjustment step, and other steps> Each step such as the swelling step is the same as the first embodiment described above. This embodiment is a step (Y) of dipping a thin film in a bath having a solution containing a boron compound and iodine, and using a reverse osmosis membrane to separate the solution into a solution containing a boron compound and a solution containing iodine. Among the above swelling step, dyeing step, cross-linking step, extension step, and adjusting step, for example, the cross-linking step is continuously performed after the dyeing step. That is, the crosslinking step is a step of immersing the thin film taken out by immersing in a dyeing solution containing iodine as an active ingredient, and immersing the film in a crosslinking bath having a crosslinking solution containing a boron compound as an active ingredient. This crosslinking step corresponds to step (Y) of the present specification.

<Separation Step> As shown in FIG. 4, in the separation device 6 of the film processing device A, a part of the cross-linked liquid is taken out as a residual liquid (residual cross-linked liquid) through a water pump 611. In addition, the residual cross-linking liquid is not limited to those directly extracted from the cross-linking bath 3, and may include liquid overflowing from the self-cross-linking bath 3. In addition, the residual cross-linking liquid was taken out from the cross-linking bath 3 at a flow rate that did not hinder the film processing in the cross-linking bath 3. The residual crosslinking solution mainly contains iodine and iodine compounds (preferably potassium iodide) contained in the dyeing solution, and boron compounds (preferably boric acid) and iodine compounds (preferably potassium iodide) contained in the crosslinking solution. The solution. That is, the residual crosslinking solution is a solution containing iodine, a boron compound, and an iodine compound. The residual crosslinking solution usually contains a boron compound as a main component. Of course, depending on the composition of the cross-linking liquid, the residual cross-linking liquid may sometimes contain an iodine compound as a main component. The removed residual crosslinking solution is temporarily stored in the auxiliary tank 621 as necessary. In a cross-linking solution mainly using water as a solvent, the residual cross-linking solution is generally approximately neutral (around pH 7). If the residual crosslinking solution is alkaline, it is advisable to mix it with a neutralizing agent to make the residual crosslinking solution neutral or acidic.

The residual cross-linked liquid is transported through the transfer pump 612, and the residual cross-linked liquid is passed through the universal filter 631, the safety filter 632, and the adsorption filter 633, and is pressed into the reverse osmosis membrane 71 through the pressure feed pump 613. The amount of residual cross-linked liquid that enters the reverse osmosis membrane 71 from the pressure feed pump 613 can be measured by the flow meter 641. In the reverse osmosis membrane 71, the residual crosslinking solution is separated into a concentrated solution and a permeate. The concentration of the boron compound in the concentrated solution is reduced, and iodine and the iodine compound are contained in high concentrations as an active ingredient. The permeate contains substantially no iodine and an iodine compound and contains a boron compound at a high concentration as an active ingredient. For example, when the weight of the boron compound contained in the residual cross-linking solution before entering the reverse osmosis membrane 71 is 100%, the aforementioned permeate contains 60% to 90% of the boron compound, and more preferably 70% to 90%. %.

The aforementioned permeate may also be directly added to the crosslinking bath 3, however, it is usually appropriate to adjust the concentration before replenishing it. For example, the concentration of the boron compound constituting the effective component of the permeate is adjusted while the permeate is returned from the reverse osmosis membrane 71 to the crosslinking bath 3. Specifically, the permeate that has penetrated the reverse osmosis membrane 71 is temporarily placed in the storage tank 622 through the flow meter 642 and the conductivity meter 651. With the concentration meter 681, the boron compound concentration of the permeate which has been placed in the storage tank 622 is constantly measured. Based on the measurement results, the concentration of the boron compound in the permeate is adjusted by the concentration adjustment unit 663 while the permeate is being transported from the tank 622 through the transfer pump 615. For example, when the concentration of the boron compound measured by the above-mentioned concentration meter 681 is less than a set concentration (the concentration of the boron compound of the crosslinking solution in the crosslinking bath 3), the boron compound is introduced into the permeate through the concentration adjustment section 663 To increase its concentration. When the concentration of the boron compound measured by the aforementioned concentration meter 681 is greater than the set concentration, a diluent such as water is introduced into the permeate through the concentration adjustment section 663 to reduce its concentration. The mixer 672 mixes the permeate after the concentration adjustment (hereinafter, the permeate after the concentration adjustment is referred to as the second supplementary liquid), and stores the permeate in the storage tank 624 as necessary. Then, the second replenishment liquid is drawn out by the transfer pump 616 and is replenished to the crosslinking bath 3 through the return pipe 692.

On the other hand, the concentrated liquid obtained from the reverse osmosis membrane 71 mainly contains iodine and an iodine compound. After the iodine concentration of the concentrated solution is adjusted, it can be added to the dyeing bath 2. However, in the example shown in the figure, the concentrated solution is directly added to the dyeing bath 2. Specifically, as in the first embodiment, the flow rate of the concentrated liquid separated by the reverse osmosis membrane 71 is measured by a flow meter 643, and the opening degree or pressure feed of the flow rate adjustment unit 661 is controlled by a control device. The output of the pump 613. After the concentrated liquid is put into the storage tank 625 as needed, it is pumped out by the transfer pump 617 and replenished to the dyeing bath 2 through the return pipe 693. If the concentrated solution that has not been adjusted for concentration is added to the dyeing bath 2, the iodine concentration of the dyeing solution may be changed from the set concentration. Therefore, it is suitable to perform the concentration adjustment in the dyeing bath 2. For example, the iodine concentration of the dyeing liquid in the dyeing bath 2 is constantly measured by a method such as titration. When the measured iodine concentration of the dyeing liquid is greater than a set concentration, a dilution solution such as water is introduced into the dyeing bath 2 to reduce the concentration. When the measured iodine concentration of the dyeing solution is less than the set concentration, iodine (containing potassium iodide for dissolving iodine as necessary) is introduced into the dyeing bath 2 to increase its concentration.

According to this embodiment, it is possible to separate a solution containing iodine and a boron compound into a solution containing iodine and a solution containing a boron compound and reuse them.

In addition, in this embodiment, the solution containing iodine and boron compound is used to take out the residual liquid from the cross-linking solution, but it is not limited to this. For example, when the extension solution and the like contain iodine and boron compound, The osmotic membrane is similarly separated and reused as a permeate and a concentrated solution.

In this embodiment, the second supplementary liquid (permeation liquid containing boron compound after concentration adjustment) prepared by the separation device (separation step) is replenished to the crosslinking bath. However, it can be replaced or used in combination. , Use it in other baths (not shown). For example, as described above, when a solution containing a boron compound is used in an extension bath or the like, the second replenishing solution may be replenished into the bath.

Furthermore, in this embodiment, the permeate containing the boron compound is adjusted to the cross-linking bath 3 and the like after concentration adjustment, however, the permeate may be replenished to the cross-linking bath 3 and the like without performing the concentration adjustment in advance. In addition, if the permeate without concentration adjustment is supplemented to the crosslinking bath 3 or the like, the concentration of the boron compound in the crosslinking solution or the like may change from the set concentration. Therefore, it is desirable to perform the concentration adjustment in the crosslinking bath 3 or the like. For example, the concentration of the boron compound in the crosslinking solution 3 in the crosslinking bath 3 is constantly measured by a method such as titration. When the concentration of the boron compound in the measured crosslinking solution is greater than the set concentration, a diluent such as water is introduced into the crosslinking bath. 3. When the boron concentration of the above-mentioned measured dyeing solution is less than a set concentration, a boron compound is introduced into the crosslinking bath 3.

A‧‧‧ film processing equipment

B‧‧‧ film

1‧‧‧ Swelling bath

2‧‧‧ dyeing bath

3‧‧‧ Cross-linking bath

4‧‧‧ extension bath

5‧‧‧Adjust bath

6‧‧‧ separation device

9‧‧‧ Transport Department

11, 21, 31, 41, 51‧‧‧ slots

12‧‧‧ solution (swelling solution)

22‧‧‧ solution (staining solution)

32‧‧‧ solution (crosslinking solution)

42‧‧‧ solution (extension liquid)

52‧‧‧ solution (adjusting solution)

71‧‧‧ reverse osmosis membrane

611‧‧‧ water pump

612, 614, 615, 616, 617‧‧‧ transfer pump

613‧‧‧pressure feed pump

621‧‧‧ auxiliary tank

622, 623, 624, 625‧‧‧ storage tanks

631‧‧‧General Filter

632‧‧‧security filter

633‧‧‧adsorption filter

641, 642, 643‧‧‧‧flow meter

651, 652‧‧‧ Conductivity Meter

661‧‧‧Flow adjustment department

662‧‧‧Dilution Department

663‧‧‧ Density Adjustment Department

671, 672‧‧‧ mixer

681‧‧‧Concentration meter

691, 692, 693‧‧‧

FIG. 1 is a schematic reference view showing a thin film processing apparatus according to a first embodiment. FIG. 2 is a schematic reference view showing a separation device of the same thin film processing device. Fig. 3 is a schematic reference view showing a thin film processing apparatus according to a second embodiment. FIG. 4 is a schematic reference view showing a separation apparatus of the same thin film processing apparatus.

Claims (8)

A method for processing a thin film, comprising a step (X) of immersing the thin film in a bath, the bath having a solution containing a boron compound and an iodine compound, and the aforementioned processing method taking a part of the aforementioned solution from the aforementioned bath and using a reverse The permeable membrane separates this solution into a solution containing a boron compound and a solution containing an iodine compound. The method for processing a thin film as claimed in claim 1, wherein the aforementioned step (X) is a step of immersing the thin film taken out in a bath having a solution containing a boron compound as an active ingredient, and immersing the thin film The solution of ingredients in a bath. The processing method of the film according to claim 1 or 2, wherein the processing of the film has the following steps: a dyeing step, immersing the film in a dyeing bath; a cross-linking step, immersing the dyed film in a crosslinking bath; and adjusting In the step, the crosslinked film is immersed in the adjustment bath; the adjustment step is the step (X), and a solution containing an iodine compound separated by the reverse osmosis membrane is added to the adjustment bath. The method for processing a film according to claim 1 or 2, wherein the film includes a polyvinyl alcohol film, the boron compound includes boric acid, and the iodine compound includes potassium iodide. A method for processing a thin film, which comprises a step (Y) of immersing the thin film in a bath, the bath having a solution containing a boron compound and iodine, and the aforementioned processing method takes a part of the solution from the bath and uses reverse osmosis The membrane separates this solution into a solution containing a boron compound and a solution containing iodine. The method for processing a thin film according to claim 5, wherein the aforementioned step (Y) is a step of immersing the thin film taken out in a bath having a solution containing iodine as an active ingredient, and dipping the thin film having a boron compound as an active ingredient. In solution in the bath. The processing method of the film according to claim 5 or 6, wherein the processing of the film has the following steps: a dyeing step, immersing the film in the dyeing bath; a crosslinking step, immersing the dyed film in the crosslinking bath; and adjusting In the step, the crosslinked film is immersed in a conditioning bath; the aforementioned crosslinking step is the aforementioned step (Y), and a solution containing a boron compound separated by using the aforementioned reverse osmosis membrane is added to the aforementioned crosslinking bath. A method for manufacturing a polarizing film, including the method for processing a film according to claim 1 or 5.