JP6713372B2 - Film processing method and polarizing film manufacturing method - Google Patents

Description

The present invention relates to a film processing method and the like when producing a polarizing film and the like.

Conventionally, polarizing films have been used as constituent materials for liquid crystal display devices, polarized sunglasses, and the like. As the polarizing film, for example, an iodine-based polarizing film is known.
The iodine-based polarizing film is obtained by performing a film treatment of adsorbing iodine on the film and crosslinking with a boron compound.
Specifically, the iodine-based polarizing film is dyed by immersing the film in a dyeing bath having a solution containing iodine, dipping the dyed film in a crosslinking bath containing a boron compound to crosslink, and stretching the crosslinked film. It is obtained by performing a series of film treatments of dipping in a bath and stretching, and dipping the stretched film in a conditioning bath containing an iodine compound such as potassium iodide to adjust the hue.

When such film processing is performed in series, the solution in the front processing bath mixes with the solution in the rear processing bath as the film moves, and the concentration of the solution in the rear processing bath changes. ..
For example, the film after being immersed in the dyeing bath is introduced into the crosslinking bath with a solution containing iodine (solution of the dyeing bath) attached, and the film after being immersed in the crosslinking bath is a solution containing a boron compound. It is introduced into the conditioning bath with the (solution of the crosslinking bath) attached.
Therefore, when the film treatment is actually performed, for example, the solution of the crosslinking bath is a solution containing a boron compound and iodine, and the concentration of the boron compound is relatively low, and the adjustment bath is an iodine compound and a boron compound. And a solution having a relatively low iodine compound concentration. By thus mixing the solution of the front side treatment bath with the rear side treatment bath, the concentration of the solution of the rear side treatment bath changes from the initially set value. Therefore, for example, in the crosslinking bath, the concentration of the active ingredient of the solution in the crosslinking bath is maintained within an allowable range by supplementing the boron compound, and in the adjusting bath, the iodine compound is supplemented to adjust the concentration. The concentration of the active ingredient in the solution in the bath is kept within an acceptable range.

A virgin material is generally used as the iodine compound to be supplemented. In this respect, by extracting the effective component from the excess liquid (excess liquid containing overflow liquid etc.) of each treatment bath and replenishing it, the waste of the excess liquid can be reduced and the material cost can be reduced. In particular, since potassium iodide is more expensive than a boron compound or the like, its reuse can greatly contribute to the reduction of material cost.

In Patent Document 1, excess liquids from the dyeing bath, the crosslinking bath and the washing bath are collectively stored in a storage tank, and the excess liquids in the storage tank are transferred to an electrodialysis device, and potassium iodide is electrodialysed. It is disclosed that potassium iodide is reused by separating it as a concentrated liquid.
However, while film treatments such as dyeing, crosslinking, and stretching are performed in series, separation using the electrodialysis device cannot be performed in conjunction with these series of film treatments.
Specifically, in the separation using the electrodialysis device, excess liquid is collected from each bath and stored in a storage tank, and when a predetermined amount of excess liquid is stored, electrodialysis in which a direct current is applied The excess liquid is transferred to the apparatus, dialyzed for a predetermined time, and then the potassium iodide concentrated liquid is taken out. Then, after adjusting the concentration of the obtained potassium iodide concentrated solution, it is replenished in a dyeing bath or the like. As described above, the electrodialysis device cannot sequentially separate the excess liquid generated in a chain accompanying the film processing, and performs it independently of the film processing (so-called batch processing method). For this reason, the separation and reuse of the excess liquid cannot be performed in series according to the film processing.
In addition, the use of the electrodialysis device requires a relatively large installation site, the maintenance of the electrodialysis membrane is complicated, and the running cost such as electric power cost becomes high.

JP, 2009-22921, A

An object of the present invention is to provide a method for treating a film and a method for producing a polarizing film, which are capable of separating the active ingredient from the excess liquid in series in accordance with the treatment of the film.

The first film treatment method of the present invention has a step (X) of immersing the film in a bath having a solution containing a boron compound and an iodine compound, and after removing a part of the solution from the bath, The solution is separated into a solution containing a boron compound and a solution containing an iodine compound by using a reverse osmosis membrane without cooling the solution to precipitate the boron compound.
In a preferred first film treatment method of the present invention, the step (X) comprises a solution containing an iodine compound as an active ingredient, the film taken out by immersing the film in a bath having a solution containing a boron compound as an active ingredient. It is a step of immersing in a bath.
A preferred first treatment method of the present invention is that the treatment of the film includes a dyeing step of immersing the film in a dyeing bath, a crosslinking step of immersing the dyed film in a crosslinking bath, an adjusting step of immersing the crosslinked film in an adjusting bath, And the adjusting step is the step (X), and the solution containing the iodine compound separated through the reverse osmosis membrane is replenished in the adjusting bath.
In a preferred first method for treating a film of the present invention, the film comprises a polyvinyl alcohol film, the boron compound comprises boric acid, and the iodine compound comprises potassium iodide.

The second film treatment method of the present invention includes a step (Y) of immersing the film in a bath having a solution containing a boron compound and iodine, and removing a part of the solution from the bath, The solution is separated into a solution containing a boron compound and a solution containing iodine by using a reverse osmosis membrane without cooling to precipitate the boron compound.
In a preferred second method for treating a film according to the present invention, in the step (Y), a film having a solution containing a boron compound as an active ingredient is taken out by immersing the film taken out in a bath having a solution containing iodine as an active ingredient. It is a step of immersing in.
In a preferred second method for treating a film of the present invention, the treatment of the film comprises a dyeing step of immersing the film in a dyeing bath, a crosslinking step of immersing the dyed film in a crosslinking bath, and an adjustment of immersing the crosslinked film in an adjusting bath. And the cross-linking step is the step (Y), and the cross-linking bath is replenished with a solution containing the boron compound separated using the reverse osmosis membrane.

According to another aspect of the present invention, a method for manufacturing a polarizing film is provided.
The method for producing a polarizing film of the present invention includes any one of the methods for treating a film described above.

In the film processing method and the polarizing film manufacturing method of the present invention, a reverse osmosis membrane is used 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 the reverse osmosis membrane, the active ingredient can be separated from the excess liquid in series with the film treatment, and this can be replenished in any bath in conjunction with the film treatment.

FIG. 3 is a schematic reference diagram showing the film processing apparatus of the first embodiment. FIG. 3 is a schematic reference diagram showing a separation device of the film processing apparatus. The schematic reference drawing which shows the film processing apparatus of 2nd Embodiment. FIG. 3 is a schematic reference diagram showing a separation device of the film processing apparatus.

The method for treating a film of the present invention has a step of immersing a solution containing an active ingredient in an arbitrary film. The process involves adsorbing, adhering, containing or binding the active ingredient in solution to any film. In the present specification, the 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 modifying and surface-treating any film.
For example, a polarizing film can be manufactured using the film processing method of the present invention.
Hereinafter, the present invention will be specifically described by focusing on the film treatment used in the production of the polarizing film.

[First Embodiment]
The film treatment of the first embodiment includes a step (X) of immersing the film in a bath having a solution containing a boron compound and an iodine compound, removing a part of the solution from the bath, and removing the solution from the reverse osmosis membrane. Is used to separate a solution containing a boron compound and a solution containing an iodine compound.
This step (X) is, for example, a step of immersing the film taken out by immersing it in a bath having a solution containing a boron compound as an active ingredient, and immersing the film in a bath having a solution containing an iodine compound as an active ingredient.

(Film processing equipment)
FIG. 1 is a reference view showing a film processing apparatus of the first embodiment, and FIG. 2 is a reference view showing a separation apparatus including a reverse osmosis membrane, which the processing apparatus has. The white arrows in the figure indicate the film advancing direction (conveying direction), and the arrows indicate the flow direction of each liquid.
In addition, in the embodiment described centering on the film processing used in the production of the polarizing film, the film processing apparatus is also an apparatus for manufacturing the polarizing film.
The film processing apparatus A includes a transport unit 9 that transports a long strip-shaped film B in the longitudinal direction, a plurality of baths containing a solution, and a separation device 6 that separates an active ingredient from the solution.
The plurality of baths have, for example, a swelling bath 1, a dyeing bath 2, a crosslinking bath 3, a stretching bath 4, and a conditioning bath 5 in this order from the front side (the upstream side in the traveling direction of the film B).
The separation device 6 has a reverse osmosis membrane that removes a solution from at least one of the plurality of baths and separates the active ingredient from the solution.

<Long strip film>
The film B to be processed has a long strip shape. The long strip shape means a rectangular shape whose length in the longitudinal direction is sufficiently larger than the length in the lateral direction (direction orthogonal to the longitudinal direction). The length of the long strip film B in the longitudinal direction is, for example, 10 m or more, and preferably 50 m or more.
The film B is not particularly limited, but a hydrophilic polymer film is preferable because it has excellent dyeability with iodine. The hydrophilic polymer film is not particularly limited, and a conventionally known film can be used. Specifically, as the hydrophilic polymer film, for example, polyvinyl alcohol (PVA)-based film, partially formalized PVA-based film, polyethylene terephthalate (PET) film, ethylene/vinyl acetate copolymer-based film, and partial saponification thereof Examples include films. In addition to these, polyene oriented films such as PVA dehydrated products and polyvinyl chloride dehydrochlorinated products, stretch-oriented polyvinylene films, and the like can also be used. Among these, the PVA-based polymer film is preferable because it is particularly excellent in dyeability with iodine.
Examples of the raw material polymer of the PVA-based polymer film include a polymer obtained by saponifying vinyl acetate after polymerization, and a small amount of a copolymerizable monomer such as unsaturated carboxylic acid or unsaturated sulfonic acid with vinyl acetate. And the like. The degree of polymerization of the PVA-based polymer is not particularly limited, but is preferably 500 to 10000, more preferably 1000 to 6000 in view of solubility in water. The saponification degree of the PVA-based polymer is preferably 75 mol% or more, more preferably 98 mol% to 100 mol %. The thickness of the film B is not particularly limited, but is, for example, 15 μm to 110 μm, preferably 38 μm to 110 μm, and more preferably 50 μm to 100 μm.

<Swelling bath>
The swelling bath 1 is provided to swell the film B.
The swelling bath 1 has a tank 11 and a solution 12 contained in the tank 11. Hereinafter, the solution in the swelling bath 1 is referred to as "swelling liquid". The swelling bath may be omitted when the film B that swells sufficiently in the dyeing bath 2 described later is used.
Although only one swelling bath 1 is provided in the illustrated example, two or more swelling baths 1 may be provided in parallel in the traveling direction of the film B (not shown).
As the swelling liquid, for example, water can be used. Further, water obtained by adding an appropriate amount of glycerin or potassium iodide to water may be used as the swelling liquid. When glycerin is added, its concentration is preferably 5% by weight or less, and when potassium iodide is added, its concentration is preferably 10% by weight or less.

<Dyeing bath>
The dyeing bath 2 is provided to dye the film B.
The dyeing bath 2 has a bath 21 and a solution 22 contained in the bath. Hereinafter, the solution in the dyeing bath 2 is referred to as a "dyeing solution".
Although only one dyeing bath 2 is provided in the illustrated example, two or more dyeing baths 2 may be provided in parallel in the traveling direction of the film B (not shown).
The 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 is dissolved in a solvent can be used as the dyeing solution. Water is generally used as the solvent, but an organic solvent compatible with water may be further added. The concentration of iodine in the dyeing solution is not particularly limited, but is preferably 0.01% by weight to 10% by weight, more preferably 0.02% by weight to 7% by weight, and 0.025% by weight. It is more preferable that the content is ˜5 wt %.
Furthermore, in order to further improve the dyeing efficiency, it is preferable to add an iodine compound to the dyeing solution. The iodine compound is a compound containing iodine and an element 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 iodide. Examples include titanium. When the iodine compound is added, its concentration is preferably 0.01% by weight to 10% by weight, more preferably 0.1% by weight to 5% by weight. Among the iodine compounds, it is preferable to add potassium iodide.
When the dyeing solution contains iodine and an iodine compound, iodine may be the main component of the solution or the iodine compound may be the main component of the solution. Usually, a solution containing an iodine compound in a larger amount than iodine is used as the dyeing solution. That is, this dyeing solution has iodine as an active ingredient, but an iodine compound as a main ingredient. Here, in the present specification, the main component refers to a component that is most contained in the solution on a weight basis.

<Cross-link bath>
The cross-linking bath 3 is provided to cross-link the film B having adsorbed the iodine.
The crosslinking bath 3 has a tank 31 and a solution 32 contained in the tank 31. Hereinafter, the solution of the crosslinking bath 3 is referred to as "crosslinking liquid".
In the illustrated example, only one cross-linking bath 3 is installed, but two or more cross-linking baths 3 may be arranged in parallel in the traveling direction of the film B (not shown).
The 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 obtained by dissolving a boron compound in a solvent can be used as the crosslinking liquid. Water is generally used as the solvent, but an organic solvent compatible with water may be further added. Examples of the boron compound include boric acid and borax. Of these, boric acid is preferably used. The concentration of the boron compound in the crosslinking solution is not particularly limited, but is preferably 1% by weight to 10% by weight, more preferably 2% by weight to 7% by weight, and 2% by weight to 6% by weight. Is more preferable. If necessary, glyoxal, glutaraldehyde, or the like may be added to the cross-linking liquid.
Furthermore, it is preferable to add an iodine compound to the cross-linking solution, since a polarizing film having uniform optical properties can be obtained. The iodine compound is not particularly limited, and examples thereof include those exemplified for the above dyeing solution. Of these, potassium iodide is preferable. The concentration of the iodine compound is not particularly limited, but is preferably 0.05% by weight to 15% by weight, more preferably 0.5% by weight to 8% by weight. When an iodine compound is added, the weight ratio of the boron compound (preferably boric acid) to the iodine compound (preferably potassium iodide) is preferably in the range of 1:0.1 to 1:6. , 1:0.5 to 1:3.5, more preferably 1:1 to 1:2.5.
When the cross-linking 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.

<Drawing bath>
The stretching bath 4 is provided for orienting the film B in which iodine is adsorbed and crosslinked.
The stretching bath 4 has a tank 41 and a solution 42 contained in the tank 41. Hereinafter, the solution in the stretching bath 4 will be referred to as "stretching liquid".
In the illustrated example, only one drawing bath 4 is provided, but two or more drawing baths 4 may be provided in parallel in the traveling direction of the film B (not shown).
Since the film B can be stretched with the dyeing bath 2 or the crosslinking bath 3, the stretching bath 4 can be omitted.
The stretching solution is not particularly limited, but for example, a solution containing a boron compound as an active ingredient can be used. The stretching liquid, for example, boron compounds, and optionally, an iodine compound, various metal salts, solutions of zinc compounds and the like dissolved in solvent can be used. Water is generally used as the solvent, but an organic solvent compatible with water may be further added. Examples of the boron compound include boric acid and borax, and among them, boric acid is preferably used. The concentration of the boron compound in the stretching liquid is not particularly limited, but is preferably 1% by weight to 10% by weight, more preferably 2% by weight to 7% by weight.
Further, from the viewpoint of suppressing the elution of iodine adsorbed on the film B, it is preferable to add an iodine compound to the stretching liquid. The iodine compound is not particularly limited, and examples thereof include those exemplified for the above dyeing solution. Of these, potassium iodide is preferable. The concentration of the iodine compound in the stretching liquid is not particularly limited, but is preferably 0.05% by weight to 15% by weight, more preferably 0.5% by weight to 8% by weight.
When the stretching 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. Usually, a solution containing more iodine compounds than boron compounds is used as the stretching liquid.

<Adjusting bath>
The adjusting bath 5 is provided for adjusting the hue of the film B and for removing the boron compound and the like. The adjusting bath 5 is a bath arranged on the rear side of the crosslinking bath containing the crosslinking liquid (the crosslinking liquid is a solution containing a boron compound as an active ingredient). The adjusting bath 5 is a bath arranged on the rear side of the stretching bath containing the stretching liquid (the stretching liquid is a solution containing a boron compound as an active ingredient). In the adjusting bath 5, the film B taken out from the bath after being immersed in the crosslinking bath and/or the drawing bath is immersed.
The conditioning bath 5 has a tank 51 and a solution 52 contained in the tank 51. Hereinafter, the solution of the adjusting bath 5 is referred to as "adjusting solution".
Although only one adjusting bath 5 is installed in the illustrated example, two or more adjusting baths 5 may be installed in parallel in the traveling direction of the film B (not shown).
The adjusting solution is a solution for adjusting the hue of the film B, and a solution containing an iodine compound as an active ingredient can be used. For example, a solution prepared by dissolving an iodine compound in a solvent can be used as the adjustment liquid. Water is generally used as the solvent, but an organic solvent compatible with water may be further added. The iodine compound is not particularly limited, and examples thereof include those exemplified for the above dyeing solution, and among them, potassium iodide is preferable. The concentration of the iodine compound in the adjustment liquid is not particularly limited, but is preferably 0.5% by weight to 20% by weight, more preferably 1% by weight to 15% by weight.

A cleaning unit (not shown) such as a cleaning bath may be arranged after the adjusting bath 5 as necessary. The cleaning unit is provided to remove residual components such as iodine compounds and boron compounds remaining on the surface of the film B after passing through the conditioning bath 5. Water can be used as the cleaning liquid.
Moreover, you may arrange|position a drying part (not shown) after the adjustment bath 5 as needed. The drying unit is provided to remove moisture and the like remaining on the surface of the film B.

Concentrations of the active ingredients of the swelling solution, the dyeing solution, the crosslinking solution, the drawing solution and the adjusting solution described in the above sections of <swelling bath>, <dyeing bath>, <crosslinking bath>, <stretching bath> and <adjusting bath> Etc. are initial setting values. As will be described later, when the processing device is actually operated, the solution of the front bath mixes with the solution of the rear bath and the film B is impregnated with the active ingredient. Please note that from time to time.

<Separator>
The separation device 6 is provided to separate and recover the active ingredient from at least one solution selected from each of the baths.
The separation device 6 is provided in at least one of the baths. In the present embodiment, the separation device 6 is provided in the conditioning bath 5.
The separation device 6 has, 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 that order. The separation device 6 may have members other than these.

Specifically, the adjustment bath 5 is provided with a water intake pump 611. A part of the adjustment liquid 52 is taken out from the adjustment bath 5 by the water intake pump 611. Hereinafter, a part of the solution taken out from the bath is referred to as "excess liquid", and particularly, a part of the adjustment liquid 52 taken out from the adjustment bath 5 is called "excess adjustment liquid". An auxiliary tank 621 is provided after the water intake pump 611. The auxiliary tank 621 is a tank that temporarily stores the excess adjustment liquid. A transfer pump 612 is provided after the auxiliary tank 621. The auxiliary tank 621 is provided as needed. When the auxiliary tank 621 is not provided, the transfer pump 612 takes out the excess adjustment liquid and sends it out to the pressure feed pump 613. A general-purpose filter 631, a safety filter 632, and an adsorption filter 633 containing activated carbon are arranged in this order between the transfer pump 612 and the pressure feed pump 613. The general-purpose filter 631 is provided to remove relatively large foreign matter that may be mixed in the excess adjustment liquid. The safety filter 632 is provided to remove relatively small foreign matter in order to prevent the reverse osmosis membrane 71 from being clogged or damaged. For example, the safety filter 632 includes a filter element having an opening of about 1 μm. The adsorption filter 633 containing activated carbon is provided for the purpose of removing organic substances.
The pressure pump 613 pressurizes the excess adjustment liquid and sends it to the reverse osmosis membrane 71. The pressure pump 613 is not particularly limited, and examples thereof include a spiral pump, a diffuser pump, a spiral mixed flow pump, a piston pump, a plunger pump, a diaphragm pump, a gear pump, a screw pump, a vane pump, a cascade pump, and a jet pump.

A reverse osmosis membrane 71 is provided after the pressure pump 613. Further, a flow meter 641 is provided between the pressure pump 613 and the reverse osmosis membrane 71.
In this embodiment, the reverse osmosis membrane 71 that can separate the iodine compound and the boron compound contained in the excess adjustment liquid is used.
The reverse osmosis membrane 71 is not particularly limited as long as it can separate as described above, and a conventionally known one can be used. For example, as the reverse osmosis membrane 71, a spiral wound type membrane element, a hollow fiber type membrane element, a tubular type membrane element, a frame and plate type membrane element and the like can be mentioned. As the reverse osmosis membrane 71, one having a single or a plurality of membrane elements can be used. The plurality of membrane elements are usually connected in series.
The reverse osmosis membrane 71 may be a single piece, or a plurality of reverse osmosis membranes 71 may be connected in series or in parallel.
The material forming the membrane element is not particularly limited, and various polymer materials such as cellulose acetate, polyvinyl alcohol, polyamide, polyester can be used.
A commercial item may be used as the reverse osmosis membrane 71. Examples of commercially available products that can be used in the present invention include a product name “LFC3LD” manufactured by Nitto Denko Corporation and a product name “ESPA4-7” manufactured by Nitto Denko Corporation.

Through the reverse osmosis membrane 71, the excess adjusting liquid is separated into a permeating liquid containing a boron compound and a concentrated liquid containing an iodine compound. A flow meter 642 and a conductivity meter 651 are provided, if necessary, on the permeate side of the reverse osmosis membrane 71, and further a storage tank 622 for containing the permeate is subsequently provided as necessary. The conductivity meter 651 measures the conductivity of the permeated liquid.
On the concentrated liquid side of the reverse osmosis membrane 71, a flow rate adjusting unit 661 (for example, a valve) and a flow meter 643 are provided as needed. Further, a mixer 671 and a conductivity meter 652 are provided after that, and a storage tank 623 is provided after that, if necessary. Further, in front of the mixer 671, there is provided a diluting unit 662 for introducing a diluting liquid into the concentrated liquid. A return pipe 691 equipped with a transfer pump 614 is connected to the storage tank 623, and the tip of the return pipe 691 is open to the adjustment bath 5.

(Film processing method and polarizing film manufacturing method)
In the present embodiment, the film treatment includes a step of conveying the film in the longitudinal direction, a swelling step of swelling the film, a dyeing step of dyeing the film, a crosslinking step of crosslinking the film, a stretching step of stretching the film, and a hue of the film. It has an adjusting step of adjusting. You may have another process as needed. In at least one step selected from these steps, the active ingredient is separated from the solution, recovered, and returned and used again. That is, the active ingredient in the solution is circulated and used.
These steps are performed using the film processing apparatus A.

<Swelling process, dyeing process, crosslinking process, stretching process, adjusting process, other process>
Each of these steps can be carried out in the same manner as the conventional steps for producing an iodine-based polarizing film.
Briefly described with reference to FIG. 1, the long strip-shaped film B is guided to the swelling bath 1 by the transport unit 9 and 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 the dyeing bath 2 and immersed in the dyeing solution 22. The temperature of the dyeing solution is, for example, 10° C. to 35° C., and the immersion time in the dyeing solution 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 liquid 32. The temperature of the crosslinking liquid is, for example, 20° C. to 70° C., and the immersion time in the crosslinking liquid is, for example, 5 seconds to 400 seconds.
The film B drawn from the crosslinking bath 3 is introduced into the stretching bath 4 and subjected to a stretching treatment. The draw ratio is, for example, 2 to 6.5 times the total draw ratio with respect to the original length of the film B. The stretching treatment can also be carried out in the dyeing step and the crosslinking step, and when the stretching is performed in these steps, the stretching ratio in the stretching step is the total stretching in consideration of the stretching ratio in these steps. The magnification is set to be 2 to 6.5 times. When the dyeing step and the crosslinking step are performed up to the total draw ratio, a separate and independent stretching step may be omitted.
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 2 seconds to 20 seconds.
The film B drawn from the conditioning bath 5 is washed as needed, dried, and then wound into a roll.
A polarizing film is obtained through such a treatment. For example, a polarizing plate is obtained by laminating a protective film on at least one surface of the obtained polarizing film.

Since the film treatment in each of the above steps is carried out in series on the conveyed long strip-shaped film B, the solution in the treatment bath on the front side is mixed in the treatment bath on the rear side. Therefore, the concentration of the solution in the treatment bath on the rear side changes from the initially set value. For example, in the cross-linking bath 3, the dyeing solution containing iodine in the dyeing bath 2 is mixed into the cross-linking solution, so that the cross-linking solution is relatively lowered from the initial set concentration of the boron compound. Further, since the film B is impregnated with the boron compound in the crosslinking bath 3, the crosslinking liquid is relatively lowered from the initial set concentration of the boron compound.
Similarly, in the adjusting bath 5, since the crosslinking liquid and/or the drawing liquid containing the boron compound in the crosslinking bath 3 and/or the drawing bath 4 is mixed in the adjusting liquid, the adjusting liquid is adjusted from the initial set concentration of the iodine compound. It decreases relatively. Furthermore, since the film B is impregnated with the iodine compound in the adjustment bath 5, the adjustment liquid is relatively lowered from the initial set concentration of the iodine compound.
In order to correct such a change in the concentration of the solution in each bath, conventionally, the solution in each bath is taken out as an excess liquid and a new solution containing an active ingredient is replenished. For example, in the adjustment bath 5, a part of the adjustment liquid (excess adjustment liquid) is taken out, while the solution containing an iodine compound (preferably potassium iodide) is replenished to the adjustment bath 5.
The present invention is characterized in that the separating device 6 separates the active ingredient from the excess liquid by the reverse osmosis membrane 71, recovers it, and reuses it.

In the present embodiment, in the step (X) of immersing the film in a bath having a solution containing a boron compound and an iodine compound, a part of the solution is taken out of the bath and the solution contains the boron compound using a reverse osmosis membrane. Separate into a solution and a solution containing an iodine compound.
Among the swelling step, dyeing step, crosslinking step, stretching step and adjusting step, for example, the adjusting step is continuously performed after the crosslinking step or the stretching step. That is, in the adjusting step, the film taken out by immersing in a crosslinking bath or a drawing bath having a crosslinking liquid or a drawing liquid containing a boron compound as an active ingredient is immersed in an adjusting bath having an adjusting liquid containing an iodine compound as an active ingredient. It is a process. This adjusting step corresponds to step (X) in the present specification.

<Separation process>
As shown in FIG. 2, in the separator 6 of the film processing apparatus A, a part of the adjustment liquid is taken out as excess liquid (excess adjustment liquid) through the water intake pump 611. The excess liquid (excess adjustment liquid) does not mean an excess liquid, but a solution that is partially taken out of the bath for separation treatment. The excess adjustment liquid is not limited to the one directly extracted from the adjustment bath 5, and may include a liquid overflowing from the adjustment bath 5. The excess adjusting liquid is taken out from the adjusting bath 5 at a flow rate that does not hinder the film processing in the adjusting bath 5. The surplus adjustment liquid is a solution mainly containing a boron compound (preferably boric acid) and an iodine compound (preferably potassium iodide) contained in the crosslinking liquid and/or the drawing liquid. Usually, the excess adjustment liquid contains an iodine compound as a main component.
The extracted excess adjustment liquid is temporarily stored in the auxiliary tank 621 as needed.
In the adjustment liquid which mainly uses water as a solvent, the excess adjustment liquid is usually almost neutral (around pH 7). If the excess adjustment liquid is alkaline, it is preferable to mix a neutralizing agent or the like to change the excess adjustment liquid to neutral or acidic. If the excess adjustment liquid is alkaline, the boron compound such as boric acid may be ionized, and the boron compound and the iodine compound may not be well separated by the reverse osmosis membrane 71 described later.

The excess adjustment liquid is sent through the transfer pump 612, and the excess adjustment liquid is passed through the general-purpose filter 631, the safety filter 632, and the adsorption filter 633. The excess adjustment liquid that has passed through each filter is pressed into the reverse osmosis membrane 71 through the pressure pump 613. The discharge pressure of the pressure pump 613 is appropriately set according to the performance of the reverse osmosis membrane 71 and the like, and is, for example, about 1 MPa to 10 MPa. The amount of the excess adjustment liquid that enters the reverse osmosis membrane 71 from the pressure pump 613 is measured by the flow meter 641.
In the reverse osmosis membrane 71, the excess adjustment liquid is separated into a concentrated liquid and a permeated liquid. The concentrated liquid has a reduced concentration of the boron compound and contains a high concentration of the iodine compound as an active ingredient. Further, the permeated liquid contains substantially no iodine compound and contains a high concentration of a boron compound as an active ingredient. For example, the permeate contains 60% to 90% of the boron compound, preferably 70% to 90%, when the weight of the boron compound contained in the excess adjustment liquid before entering the reverse osmosis membrane 71 is 100%. Including.

The permeated liquid that has permeated the reverse osmosis membrane 71 passes through the flow meter 642 and the conductivity meter 651, is once stored in the storage tank 622, and is then discarded. Further, the permeated liquid may be directly discarded without being put in the storage tank 622.
The conductivity meter 651 arranged on the permeate side shows a substantially constant value during the implementation. When the value of the conductivity meter rises, the membrane element of the reverse osmosis membrane 71 may be damaged or its performance may be deteriorated. When the reverse osmosis membrane 71 is damaged, ionized iodine compounds such as potassium iodide are excessively mixed in the permeate. Then, the value of the conductivity meter 651 of the permeated liquid increases. Thus, the conductivity meter 651 arranged on the permeated liquid side has a function of indicating the maintenance time of the reverse osmosis membrane 71.
Further, the flow meter 642 measures the flow rate of the permeated liquid. The opening of the flow rate adjusting unit 661 is controlled by a control device (not shown) so that the value of the flow meter 642 maintains the set value.
A flow meter 643 disposed after the flow rate adjusting unit 661 measures the flow rate of the concentrated liquid separated by the reverse osmosis membrane 71. The discharge amount of the pressure feed pump 613 is controlled by a control device (not shown) so that the value of the flow meter maintains the set value.

The concentrated solution obtained from the reverse osmosis membrane 71 may be directly replenished in the adjusting bath 5, but it is usually preferable to adjust the concentration before replenishing it.
In the illustrated example, while the concentrated solution is being returned from the reverse osmosis membrane 71 to the adjustment bath 5, the diluted solution is introduced to adjust the concentration of the iodine compound that is the active ingredient of the concentrated solution. The concentration of the iodine compound in the concentrated liquid obtained from the reverse osmosis membrane 71 is higher than the concentration of the iodine compound in the excess adjustment liquid. Therefore, 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 by diluting with the dilution liquid. As the diluting liquid, it is preferable to use the same solvent as the preparation liquid, and examples thereof include water or water to which an organic solvent compatible with water is added.

The concentrated solution diluted with the diluent (hereinafter, the concentrated concentrated solution whose concentration has been adjusted is referred to as a first replenisher) is mixed by a mixer 671 to make the concentration uniform. The conductivity of the first replenisher mixed in the mixer 671 is measured by the conductivity meter 652. The conductivity meter 652 is for monitoring whether or not the concentration of the iodine compound, which is the active ingredient of the first replenisher, is as set, and the conductivity of the diluent meter changes according to the value of the conductivity meter 652. The introduction amount of is controlled by the control device. For example, when the value 652 of the conductivity meter is larger than the set value, the introduction amount of the diluting liquid is increased, and when it is lower than the set value, the introduction amount of the diluting liquid is decreased.
The first replenisher solution adjusted to the set concentration is put into the storage tank 623 as needed, then drawn out by the transfer pump 614 and replenished to the adjusting bath 5 through the return pipe 691. Once the first replenisher solution is put into the storage tank 623, a replenisher solution without unevenness in concentration can be obtained. However, the adjusting bath 5 may be directly replenished with the first replenisher solution adjusted to the set concentration.

The present invention uses a reverse osmosis membrane to separate active ingredients from excess liquid and reuse them in film processing. By using a reverse osmosis membrane, separation and reuse of excess liquid can be performed in series according to film processing. That is, according to the present invention, while the film is being processed in each bath, the excess liquid is taken out from the bath, the active ingredient is separated, and the active ingredient is adjusted to a concentration suitable for each bath. And refill it in the bath.
Further, as in the present invention, by using the reverse osmosis membrane, the installation place can be made relatively small, and running costs such as electric power costs can also be kept low.
In particular, where potassium iodide is relatively expensive, it is possible to further reduce the running cost by reusing and circulating an iodine compound such as potassium iodide as in the present embodiment.

In the present embodiment, the surplus liquid is taken out from the adjustment liquid as the solution containing the boron compound and the iodine compound, but the present invention is not limited to this. For example, when the stretching liquid contains the boron compound and the iodine compound, the surplus liquid is extracted. Similarly, the liquid may be separated into a permeated liquid and a concentrated liquid by a reverse osmosis membrane and reused.

Further, in the present embodiment, the first replenisher obtained in the separation device (separation step) is replenished in the adjusting bath, but instead of or in combination therewith, this may be used in another bath. (Not shown). For example, as described above, when a solution containing an iodine compound is used in a dyeing bath or a crosslinking bath, the first replenisher containing the iodine compound separated from the excess preparation liquid is used in these baths. Good.

Furthermore, although the permeate containing substantially the boron compound is discarded in the present embodiment, it may be used in other baths. For example, as described above, a solution containing a boron compound is used in a crosslinking bath, a drawing bath, etc., but a permeate containing a boron compound separated from an excess adjusting solution may be used in these baths. In this case, the permeate obtained from the reverse osmosis membrane may be directly used in the bath, but since the concentration of the boron compound, which is the active ingredient of the permeate, is usually high, use it after adjusting the concentration. Is preferred. As the method of adjusting the density, the following second embodiment can be used as appropriate.

[Second Embodiment]
The film treatment of the second embodiment includes a step (Y) of immersing the film in a bath having a solution containing a boron compound and iodine, removing a part of the solution from the bath, and applying the solution to a reverse osmosis membrane. And separating it into a solution containing a boron compound and a solution containing iodine.
This step (Y) is, for example, a step of immersing the film taken out by immersing it in a bath having a solution containing iodine as an active ingredient, and immersing it in a bath having a solution containing a boron compound as an active ingredient.
Hereinafter, the second embodiment will be described. In the description, the configuration different from the first embodiment will be mainly described, and the description of the same configuration may be omitted.

(Film processing equipment)
FIG. 3 is a reference diagram showing the film processing apparatus of the second embodiment, and FIG. 4 is a reference diagram showing a separation apparatus including a reverse osmosis membrane, which the processing apparatus has.
Similarly to the first embodiment, the film processing apparatus A of the second embodiment also conveys the long strip-shaped film B in the longitudinal direction, a conveying unit 9, a plurality of baths containing a solution, and separates the active ingredient from the solution. And a separating device 6 for
The film B, the transport unit 9, and the plurality of baths 1, 2, 3, 4, and 5 are the same as those in the first embodiment, and thus the description thereof will be omitted and the terms and reference numerals will be used as they are.

<Separator>
The separation device 6 is provided to separate and recover the active ingredient from at least one solution selected from each of the baths. In this embodiment, the separation device 6 is provided in the crosslinking bath 3.
In this embodiment, the configuration of the separation device 6 up to the reverse osmosis membrane 71 is almost 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 pump 613, and a flowmeter 641 are provided between the crosslinking bath 3 and the reverse osmosis membrane 71. The functions of these members are as described in the first embodiment, and if necessary, some of these members may be omitted.

As the reverse osmosis membrane 71, the same one as in the first embodiment can be used.
A flow meter 642, a conductivity meter 651, and a storage tank 622 are provided on the permeate side of the reverse osmosis membrane 71 as in the first embodiment. A return route is provided for returning to 3 or the like.
Specifically, the storage tank 622 that stores the permeated liquid is provided with a densitometer 681 that measures the concentration of the boron compound. As the densitometer 681, for example, a densitometer for measuring the boric acid concentration can be used. As such a boric acid concentration meter, for example, a boric acid concentration constant monitor (model “SRM-1DB” manufactured by Ceres Co., Ltd.) or the like can be used. Further, the storage tank 622 is provided with a transfer pump 615, and after that, a concentration adjusting unit 663 for adjusting the concentration of the boron compound and a mixer 672 are provided. Further, after the mixer 672, a storage tank 624 is provided as needed. A return pipe 692 equipped with a transfer pump 616 is connected to the storage tank 624, and the tip of the return pipe 692 is open to the crosslinking bath 3.

A flow rate adjusting unit 661 and a flow meter 643 are provided on the concentrated liquid side of the reverse osmosis membrane 71 as needed, as in the first embodiment. Further, after that, a storage tank 625 is provided as needed. A return pipe 693 equipped with a transfer pump 617 is connected to the storage tank 625, and the tip of the return pipe 693 is opened to the dyeing bath 2.

(Film processing method and polarizing film manufacturing method)
In the present embodiment, as in the first embodiment, the film treatment includes 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 crosslinking step of crosslinking the film, and a stretching of the film. The stretching step and the adjusting step of adjusting the hue of the film. You may have another process as needed. In at least one step selected from these steps, the active ingredient is separated from the solution, recovered, and returned and used again. That is, the active ingredient in the solution is circulated and used.
These steps are carried out using a film processing apparatus A as shown in FIGS.

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

<Separation process>
As shown in FIG. 4, in the separation device 6 of the film processing apparatus A, a part of the crosslinking liquid is taken out as an excess liquid (excess crosslinking liquid) through the water intake pump 611. The surplus cross-linking liquid is not limited to the one that is directly withdrawn from the cross-linking bath 3, and may include a liquid that overflows from the cross-linking bath 3. The excess cross-linking liquid is taken out of the cross-linking bath 3 at a flow rate that does not hinder the film treatment in the cross-linking bath 3. The excess crosslinking liquid is mainly iodine and iodine compounds (preferably potassium iodide) contained in the dyeing liquid, and boron compounds (preferably boric acid) and iodine compounds (preferably potassium iodide) contained in the crosslinking liquid. ), and a solution containing. That is, the surplus crosslinking solution is a solution containing iodine, a boron compound, and an iodine compound. Usually, the excess crosslinking liquid contains a boron compound as a main component. However, depending on the composition of the crosslinking solution, the excess crosslinking solution may contain an iodine compound as a main component.
The extracted excess crosslinking liquid is temporarily stored in the auxiliary tank 621 as needed. In a cross-linking liquid that mainly uses water as a solvent, the surplus cross-linking liquid is usually almost neutral (pH around 7). If the excess crosslinking liquid is alkaline, it is preferable to mix a neutralizing agent or the like to change the excess crosslinking liquid into neutral or acidic.

The surplus cross-linking liquid is sent through the transfer pump 612, the surplus cross-linking liquid is passed through the general-purpose filter 631, the safety filter 632, and the adsorption filter 633, and is press-fitted into the reverse osmosis membrane 71 through the pressure-feeding pump 613. The flowmeter 641 measures the amount of the surplus crosslinking liquid that enters the reverse osmosis membrane 71 from the pressure pump 613.
In the reverse osmosis membrane 71, the excess crosslinking liquid is separated into a concentrated liquid and a permeated liquid. The concentrated liquid has a reduced concentration of boron compounds and contains iodine and iodine compounds at high concentrations as active ingredients. In addition, the permeated liquid contains substantially no iodine and iodine compounds and contains a boron compound as an active ingredient in a high concentration. For example, the permeate contains 60% to 90% of the boron compound, preferably 70% to 90%, when the weight of the boron compound contained in the excess crosslinking liquid before entering the reverse osmosis membrane 71 is 100%. Including.

The permeate may be directly replenished in the crosslinking bath 3, but it is usually preferable to adjust the concentration before replenishing it. For example, while returning the permeated liquid from the reverse osmosis membrane 71 to the crosslinking bath 3, the concentration of the boron compound, which is an effective component of the permeated liquid, is adjusted. Specifically, the permeated liquid that has permeated the reverse osmosis membrane 71 passes through the flow meter 642 and the conductivity meter 651, and is once stored in the storage tank 622. The concentration of the boron compound in the permeated liquid stored in the storage tank 622 is constantly measured by the densitometer 681. Based on the measurement result, while the permeate is being sent from the tank 622 through the transfer pump 615, the concentration adjusting unit 663 adjusts the concentration of the boron compound in the permeate. For example, when the concentration of the boron compound measured by the densitometer 681 is lower than the set concentration (the concentration of the boron compound in the crosslinking liquid in the crosslinking bath 3), the concentration adjusting unit 663 introduces the boron compound into the permeate. And increase its concentration. When the concentration of the boron compound measured by the densitometer 681 is higher than the set concentration, the concentration adjusting unit 663 introduces a diluent such as water into the permeate to reduce the concentration. The concentration-adjusted permeate (hereinafter, the concentration-adjusted permeate is referred to as the second replenisher) is mixed by the mixer 672 and stored in the storage tank 624 as necessary. After that, the second replenisher is drawn out by the transfer pump 616 and replenished in 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 iodine compounds. Although the iodine concentration of this concentrated solution may be adjusted and then replenished to the dyeing bath 2, the concentrated solution is directly replenished to the dyeing bath 2 in the illustrated example.
Specifically, the flow rate of the concentrated liquid separated by the reverse osmosis membrane 71 is measured by the flow meter 643 as in the first embodiment, and the control device controls the opening degree of the flow rate adjusting unit 661 and the pressure pump. The discharge amount of 613 is controlled.
The concentrated liquid is put into a storage tank 625 as needed, then drawn out by a transfer pump 617, and replenished in the dyeing bath 2 through a return pipe 693. When the concentrated solution whose concentration has not been adjusted is replenished in the dyeing bath 2, the iodine concentration of the dyeing solution may change from the set concentration, so it is preferable to adjust the concentration in the dyeing bath 2. For example, the iodine concentration of the dyeing solution in the dyeing bath 2 is constantly measured by a method such as titration, and when the measured iodine concentration of the dyeing solution is higher than the set concentration, a diluting solution such as water is added to the dyeing bath 2. Introduce and reduce its concentration. When the measured iodine concentration of the dyeing solution is lower than the set concentration, iodine (if necessary, including potassium iodide for dissolving iodine) is introduced into the dyeing bath 2, and the concentration is changed. Increase.

According to this embodiment, a solution containing iodine and a boron compound can be separated into a solution containing iodine and a solution containing a boron compound, which can be reused.

In the present embodiment, the surplus liquid is taken out from the cross-linking liquid as a solution containing iodine and boron compounds, but the present invention is not limited to this. For example, when the stretching liquid contains iodine and boron compounds, the surplus liquid is Similarly, a reverse osmosis membrane may be separated into a permeated liquid and a concentrated liquid for reuse.

Further, in the present embodiment, the second replenisher (permeate containing boron compound after concentration adjustment) obtained in the separator (separation step) is replenished in the crosslinking bath, but instead of this, It may be used in combination with other baths (not shown). For example, as described above, when a solution containing a boron compound is used in the drawing bath or the like, the bath may be supplemented with the second replenisher.

Further, in the present embodiment, the concentration of the permeated liquid containing the boron compound is adjusted and then replenished to the crosslinking bath 3 or the like. However, even if the concentration is not adjusted in advance, the permeated liquid may be replenished to the crosslinking bath 3 or the like. Good. When the permeated liquid whose concentration is not adjusted is replenished in the crosslinking bath 3 or the like, the concentration of the boron compound in the crosslinking liquid may change from the set concentration, so it is preferable to adjust the concentration in the crosslinking bath 3 or the like. For example, the boron compound concentration of the cross-linking solution in the cross-linking bath 3 is constantly measured by a method such as titration, and when the measured boron compound concentration of the cross-linking solution is higher than the set concentration, a diluting solution such as water is added to the cross-linking bath. Introduced into No. 3, when the measured boron concentration of the dyeing solution is lower than the set concentration, the boron compound is introduced into the crosslinking bath 3.

A film processing device B film 1 swelling bath 2 dyeing bath 3 crosslinking bath 4 stretching bath 5 adjusting bath 6 separation device 71 reverse osmosis membrane

Claims (8)

A step (X) of immersing the film in a bath having a solution containing a boron compound and an iodine compound,
After taking out a part of the solution from the bath, the solution is separated into a solution containing a boron compound and a solution containing an iodine compound by using a reverse osmosis membrane without cooling the solution to precipitate the boron compound. , Film processing method. The step (X) is a step of immersing the film taken out by immersing in a bath having a solution containing a boron compound as an active ingredient, and immersing the film in a bath having a solution containing an iodine compound as an active ingredient. Film processing method. The film treatment includes a dyeing step of immersing the film in a dyeing bath, a crosslinking step of immersing the dyed film in a crosslinking bath, and an adjusting step of immersing the crosslinked film in an adjusting bath,
The method for treating a film according to claim 1 or 2, wherein the adjusting step is the step (X), and a solution containing an iodine compound separated through the reverse osmosis membrane is replenished in the adjusting bath. The film processing method according to claim 1, wherein the film includes a polyvinyl alcohol-based film, the boron compound includes boric acid, and the iodine compound includes potassium iodide. A step (Y) of immersing the film in a bath having a solution containing a boron compound and iodine,
After removing a portion of the solution from the bath, without cooling the solution to precipitate the boron compound, the solution is separated into a solution containing a boron compound and a solution containing iodine using a reverse osmosis membrane, Film processing method. The step (Y) is a step of immersing a film taken out by immersing 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. Film processing method. The film treatment includes a dyeing step of immersing the film in a dyeing bath, a crosslinking step of immersing the dyed film in a crosslinking bath, and an adjusting step of immersing the crosslinked film in an adjusting bath,
7. The method for treating a film according to claim 5, wherein the crosslinking step is the step (Y), and the solution containing the boron compound separated by using the reverse osmosis membrane is replenished in the crosslinking bath. A method for producing a polarizing film, comprising the method for treating the film according to claim 1.

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