JP2023175387A - Manufacturing device and manufacturing method for polarization film - Google Patents

Abstract

To provide a manufacturing device for a polarization film capable of recycling a volatilized dichroic dye.SOLUTION: Provided is a manufacturing device for manufacturing a polarization film from a polyvinyl alcohol resin film. The manufacturing device comprises one or more processing tanks that store processing liquid in which the polyvinyl alcohol resin film is immersed. The one or more processing tanks comprise a dyeing processing tank that stores dyeing processing liquid containing a dichroic dye. The manufacturing device further comprises a collection unit that collects a dichroic dye floating in the air.SELECTED DRAWING: Figure 1

Description

The present invention relates to a polarizing film manufacturing apparatus and manufacturing method.

As a polarizing film, one in which a dichroic dye such as iodine or a dichroic dye is adsorbed and oriented on a uniaxially stretched polyvinyl alcohol resin film is conventionally known. The polarizing film is produced by sequentially subjecting a polyvinyl alcohol resin film to a dyeing process in which it is dyed with a dichroic dye, a crosslinking process in which it is treated with a crosslinking agent, and a film drying process, as well as a uniaxial stretching process during the manufacturing process. [For example, Japanese Patent Laid-Open No. 2001-141926 (Patent Document 1)].

Dichroic dyes, such as iodine, sublimate and float in the air in the _I2 state. JP 2018-021983 A (Patent Document 2) describes that iodine contained in a solution (for example, a staining solution) is recovered and reused, but iodine floating in the air is There was no disclosure or suggestion of a recall.

Japanese Patent Application Publication No. 2001-141926 Japanese Patent Application Publication No. 2018-021983

An object of the present invention is to provide a polarizing film manufacturing apparatus and a polarizing film manufacturing method that can reuse the volatilized dichroic dye.

The present invention provides the following polarizing film manufacturing apparatus and manufacturing method.

[1] A manufacturing device for manufacturing a polarizing film from a polyvinyl alcohol resin film, comprising:
The manufacturing apparatus includes one or more processing tanks containing a processing liquid in which the polyvinyl alcohol resin film is immersed,
The one or more processing tanks include a dyeing processing tank containing a dyeing processing solution containing a dichroic dye,
The manufacturing apparatus further includes a collection unit for collecting dichroic dye floating in the air.

[2] The collection section includes an adsorption/absorption section that adsorbs or absorbs the dichroic dye floating in the air, and an airflow generation section that generates an airflow toward the adsorption/absorption section. [1] The manufacturing equipment described in .

[3] The manufacturing apparatus according to [1] or [2], wherein the adsorption/absorption section is an adsorption sheet containing activated carbon.

[4] The production device according to any one of [1] to [3], wherein the dichroic dye is iodine.

[5] A method for producing a polarizing film from a polyvinyl alcohol resin film, comprising:
The method includes the step of immersing the polyvinyl alcohol resin film in one or more treatment tanks containing a treatment liquid,
The one or more processing tanks include a dyeing processing tank containing a dyeing processing solution containing a dichroic dye,
The method further includes the step of collecting dichroic dye floating in the air.

[6] Dichroic dyes floating in the air are captured using a collection unit that includes an adsorption/absorption unit that adsorbs or absorbs the dye, and an airflow generation unit that generates an airflow toward the adsorption/absorption unit. The method according to [5], wherein the information is collected.

[7] The method according to [5] or [6], wherein the adsorption/absorption section is an adsorption sheet containing activated carbon.

[8] The method according to any one of [5] to [7], wherein the dichroic dye is iodine.

It is possible to provide a polarizing film manufacturing apparatus and a polarizing film manufacturing method that can reuse the volatilized dichroic dye.

BRIEF DESCRIPTION OF THE DRAWINGS It is a cross-sectional schematic diagram which shows an example of the polarizing film manufacturing apparatus based on this invention.

The present invention relates to a manufacturing apparatus and a manufacturing method (hereinafter simply referred to as "manufacturing apparatus" and "manufacturing method", respectively) for manufacturing a polarizing film from a polyvinyl alcohol resin film (hereinafter also referred to as "PVA resin film"). (also referred to as ). A polarizing film is manufactured by subjecting a PVA-based resin film to a series of treatments including immersion treatment (wet treatment) in a treatment tank containing a predetermined treatment liquid, drying treatment, and the like. A polarizing film is a stretched PVA resin film in which a dichroic dye is adsorbed and oriented.

The manufacturing device includes a collection section for collecting dichroic dye floating in the air. The manufacturing method includes a step of collecting dichroic dye floating in the air. By providing the collecting section and the collecting step, the dichroic dye floating in the air can be collected, so that the dichroic dye can be reused.

The manufacturing device includes one or more processing tanks containing a processing solution in which the PVA resin film is immersed, and the one or more processing tanks include a dyeing processing tank containing a dyeing processing solution containing a dichroic dye. At least including. An example of the manufacturing equipment is shown in FIG. 1. The manufacturing apparatus shown in FIG. 1 is an apparatus for continuously manufacturing a long polarizing film 25 from a long PVA resin film 10 that is a raw material film. In FIG. 1, the arrow attached to the film indicates the direction in which the film is transported. In manufacturing the polarizing film 25 using the manufacturing apparatus shown in FIG. and a cleaning treatment tank 19, and finally passed through a drying oven 20 for drying treatment to obtain a polarizing film 25. The polarizing film 25 manufactured as a long product may be sequentially wound onto a winding roll 27.

The manufacturing apparatus has a transport path for the PVA resin film that is constructed to pass through a processing tank in which the PVA resin film is immersed and a drying oven. By conveying the PVA-based resin film along this conveyance path, a series of treatments are performed to obtain a polarizing film.

As shown in FIG. 1, the conveyance path is constructed by a plurality of rolls that support and guide the running films (PVA resin film 10 and polarizing film 25). The plurality of rolls consists of a guide roll, which is a free roll that supports one side of the film, and/or a pair of rolls (usually a drive roll), and may include a nip roll that sandwiches or presses the film from both sides. can. In the example shown in FIG. 1, the polarizing film manufacturing apparatus includes guide rolls 1a to 1l and nip rolls 2a to 2f. The plurality of rolls that define the conveyance path can also include a suction roll (suction roll), which is one type of drive roll. Normally, each of these rolls supports the film in contact with one or both surfaces (principal surfaces) of the film within the transport path. These rolls can be placed at appropriate positions, such as before and after each processing tank and drying oven, or inside the processing tank and drying oven.

Note that the drive roll refers to a roll that can provide driving force for transporting the film to the film that comes into contact with it, and is a roll that is directly or indirectly connected to a roll drive source such as a motor. I can do it. A free roll is a roll that simply supports a running film and cannot provide a driving force for transporting the film.

A polarizing film can be manufactured by a manufacturing method including the following steps.

A wet treatment step S101 in which the PVA resin film is transported along a transport path of the PVA resin film and immersed in one or more processing tanks containing a processing liquid, and the PVA resin film is transported along the transport route. A drying treatment step S102 in which the PVA-based resin film after the wet treatment is dried while the wet treatment is performed.

In the manufacturing method according to the present invention, the one or more processing tanks include a dyeing processing tank containing a dyeing solution containing a dichroic dye.

The polarizing film 25 obtained has been subjected to a stretching process (usually a uniaxial stretching process). For this purpose, the manufacturing apparatus may include a stretching means (wet stretching means) for the PVA resin film 10, and the manufacturing method may include a stretching process (wet stretching process) for the PVA resin film 10. I can do it.

(1) PVA-based resin film The PVA-based resin film 10, which is a raw material film, is a film made of polyvinyl alcohol-based resin (PVA-based resin). As the PVA resin, a saponified polyvinyl acetate resin can be used. Examples of polyvinyl acetate-based resins include polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers of vinyl acetate and other monomers copolymerizable therewith. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and (meth)acrylamides having an ammonium group. In addition, "(meth)acrylic" represents at least one type selected from the group consisting of acrylic and methacryl.

The degree of saponification of the PVA resin can be in the range of 80.0 to 100.0 mol%, preferably in the range of 90.0 to 100.0 mol%, and more preferably in the range of 94.0 to 100.0 mol%. The range is 100.0 mol%, more preferably 98.0 to 100.0 mol%. If the saponification degree is less than 80.0 mol%, the water resistance and moist heat resistance of the polarizing film 25 obtained may decrease.

Saponification degree is the rate at which acetic acid groups (acetoxy groups: -OCOCH ₃ ) contained in polyvinyl acetate resin, which is the raw material for PVA resin, is converted into hydroxyl groups during the saponification process, expressed as a unit ratio (mol%). The following formula:
Degree of saponification (mol%) = 100 x (number of hydroxyl groups) / (number of hydroxyl groups + number of acetic acid groups)
Defined by The degree of saponification can be determined in accordance with JIS K 6726 (1994).

The average degree of polymerization of the PVA resin is preferably 100 to 10,000, more preferably 1,500 to 8,000, and still more preferably 2,000 to 5,000. The average degree of polymerization of the PVA resin can also be determined in accordance with JIS K 6726 (1994). When the average degree of polymerization is less than 100, it is difficult to obtain a polarizing film 25 with preferable polarizing performance, and when it exceeds 10,000, solubility in a solvent deteriorates, making it difficult to form (film forming) the PVA-based resin film 10. It can be.

An example of the PVA resin film 10 is an unstretched film made of the above polyvinyl alcohol resin. The film forming method is not particularly limited, and known methods such as melt extrusion and solvent casting can be employed. Another example of the PVA-based resin film 10 is a stretched film obtained by stretching the above-mentioned unstretched film. This stretching is usually uniaxial stretching, preferably longitudinal uniaxial stretching. Longitudinal stretching refers to stretching in the machine direction (MD) of the film, that is, in the longitudinal direction of the film. This stretching is preferably dry stretching. Dry stretching refers to stretching performed in the air, and is usually longitudinal uniaxial stretching. For dry stretching, a film is passed between a heated roll whose surface is heated and a guide roll (or a heated roll may be used) that has a different circumferential speed from the heated roll, and the film is heated using the heated roll. Hot roll stretching that performs vertical stretching at the bottom; A process between two nip rolls installed at a distance that performs longitudinal stretching by the difference in circumferential speed between the two nip rolls while passing through a heating means (such as an oven) between the rolls. Stretching; tenter stretching; compression stretching, etc. can be mentioned. The stretching temperature (surface temperature of a hot roll, oven temperature, etc.) is, for example, 80 to 150°C, preferably 100 to 135°C.

The stretching ratio of the above-mentioned stretching depends on whether or not wet stretching is performed in the wet processing step S101 described later and the stretching ratio in the wet stretching, but is usually 1.1 to 8 times, preferably 2. .5 to 5 times.

The PVA resin film 10 can contain additives such as plasticizers. Preferred examples of plasticizers are polyhydric alcohols, specific examples of which include ethylene glycol, glycerin, propylene glycol, diethylene glycol, diglycerin, triethylene glycol, triglycerin, tetraethylene glycol, trimethylolpropane, polyethylene glycol, etc. . The PVA-based resin film 10 can contain one or more types of plasticizer. The content of the plasticizer is usually 5 to 20 parts by weight, preferably 7 to 15 parts by weight, based on 100 parts by weight of the PVA resin constituting the PVA resin film 10.

The thickness of the PVA resin film 10, which is the raw material film, is usually 10 to 150 μm, depending on whether the PVA resin film 10 has been stretched or not. From this point of view, the thickness is preferably 100 μm or less, more preferably 65 μm or less, even more preferably 50 μm or less, particularly preferably 35 μm or less.

(2) Wet Processing The manufacturing apparatus includes one or more processing tanks that contain a processing liquid in which the PVA-based resin film 10 is immersed. In this zone, the above-mentioned wet processing step S101 is performed. The one or more treatment tanks include a dyeing tank 15 containing a dyeing solution containing a dichroic dye, and usually further include a swelling tank 13, a crosslinking tank 17, and a washing tank 19. These processing tanks are normally arranged in the order of swelling processing tank 13, dyeing processing tank 15, crosslinking processing tank 17, and cleaning processing tank 19 from the upstream side of the transport route (see FIG. 1). Although FIG. 1 shows an example in which one swelling treatment tank 13, one dyeing treatment tank 15, one crosslinking treatment tank 17, and one cleaning treatment tank 19 are provided, two or more tanks may be provided in each if necessary. good.

The treatment liquid contained in the swelling treatment tank 13 may be, for example, water (pure water, etc.), or may be an aqueous solution containing a water-soluble organic solvent such as alcohol. Further, this treatment liquid (swelling bath) can also contain boric acid, chloride, inorganic acid, inorganic salt, etc. Swelling treatment is performed by immersing the PVA-based resin film 10 in a swelling bath. The swelling treatment is a treatment carried out as necessary for the purpose of removing foreign matter from the PVA-based resin film 10, removing a plasticizer, imparting dyeability, plasticizing the film, and the like. During the swelling process, the PVA resin film 10 may be subjected to a wet stretching process (usually a uniaxial stretching process). In that case, the stretching ratio is usually 1.2 to 3 times, preferably 1.3 to 2.5 times. The temperature of the swelling bath is usually 10 to 70°C, preferably 15 to 50°C. The immersion time (residence time in the swelling bath) of the PVA resin film 10 is usually 10 to 600 seconds, preferably 20 to 300 seconds.

The processing solution stored in the dyeing treatment tank 15 is a dyeing solution containing a dichroic dye. Dyeing treatment is performed by immersing the PVA-based resin film 10 in this dyeing treatment liquid. As a result, the dichroic dye is adsorbed onto the PVA-based resin film 10. The dichroic dye can be iodine or a dichroic organic dye, preferably iodine. One type of dichroic dye may be used alone or two or more types may be used in combination.

When using iodine as the dichroic dye, an aqueous solution containing iodine and potassium iodide can be used as the dyeing solution. Instead of potassium iodide, other iodides such as zinc iodide may be used, or potassium iodide and other iodides may be used together. Further, compounds other than iodide, such as boric acid, zinc chloride, cobalt chloride, etc., may be coexisting. The content of iodine in the dyeing solution is usually 0.003 to 1 part by mass per 100 parts by mass of water. The content of iodide such as potassium iodide in the dyeing solution is usually 0.1 to 20 parts by mass per 100 parts by mass of water. The temperature of the dyeing solution is usually 10 to 45°C, preferably 10 to 40°C, more preferably 20 to 35°C. The immersion time (residence time in the dyeing solution) of the PVA resin film 10 is usually 20 to 600 seconds, preferably 30 to 300 seconds.

In order to improve the dyeability of the dichroic dye, the PVA resin film 10 to be subjected to the dyeing process is preferably subjected to at least some stretching treatment (usually uniaxial stretching treatment). Instead of the stretching treatment before the dyeing treatment, or in addition to the stretching treatment before the dyeing treatment, the stretching treatment may be performed while the dyeing treatment is being performed. The cumulative stretching ratio up to the dyeing process (or the stretching ratio in the dyeing process if there is no stretching process before the dyeing process) is usually 1.6 to 4.5 times, preferably 1.8 to 4 times. .

The treatment liquid contained in the crosslinking treatment tank 17 is a crosslinking treatment liquid containing a crosslinking agent. The crosslinking treatment is performed by immersing the dyed PVA resin film 10 in this crosslinking treatment liquid. As a result, the PVA resin film 10 is made water resistant by crosslinking, hue is adjusted (complementary color processing), and the like. Stretching treatment (usually uniaxial stretching treatment) may be performed while performing crosslinking treatment.

Examples of the crosslinking agent include boric acid, glyoxal, glutaraldehyde, etc., and boric acid is preferably used. Two or more types of crosslinking agents can also be used in combination. The content of the crosslinking agent in the crosslinking treatment liquid is usually 0.1 to 15 parts by weight, preferably 1 to 12 parts by weight per 100 parts by weight of water. When the dichroic dye is iodine, the crosslinking treatment liquid preferably contains iodide in addition to the crosslinking agent. The iodide content in the crosslinking solution is usually 0.1 to 20 parts by weight, preferably 5 to 15 parts by weight, per 100 parts by weight of water. Examples of iodides include potassium iodide and zinc iodide. Further, the crosslinking treatment liquid may contain compounds other than iodide, such as zinc chloride, cobalt chloride, zirconium chloride, sodium thiosulfate, potassium sulfite, and sodium sulfate. The temperature of the crosslinking solution is usually 50 to 85°C, preferably 50 to 70°C. The immersion time (residence time in the crosslinking treatment liquid) of the PVA resin film 10 is usually 10 to 600 seconds, preferably 20 to 300 seconds.

The processing liquid stored in the cleaning processing tank 19 may be water (pure water, etc.), for example, or may be an aqueous solution containing a water-soluble organic solvent such as alcohol. A cleaning treatment is performed by immersing the crosslinked PVA resin film 10 in this treatment liquid (cleaning bath). The cleaning process is a process that is performed as necessary for the purpose of removing chemicals such as excess crosslinking agent and dichroic dye attached to the PVA-based resin film 10. The temperature of the cleaning bath is, for example, 2 to 40°C. Stretching treatment (usually uniaxial stretching treatment) may be performed while performing washing treatment.

The cleaning treatment may be a treatment in which the PVA resin film 10 after the crosslinking treatment is sprayed with a cleaning liquid as a shower, or immersion in the above-mentioned cleaning bath and spraying of the cleaning liquid may be combined. FIG. 1 shows an example in which a PVA-based resin film 10 is immersed in water in a cleaning tank 19 for cleaning treatment.

As described above, wet stretching may be performed on the PVA resin film 10 in the wet processing step S101. Wet stretching is usually uniaxial stretching, and can be performed while performing any one of swelling treatment, dyeing treatment, crosslinking treatment, and washing treatment, or during two or more treatments selected from these. Wet stretching is preferably carried out in the crosslinking process or at one or more stages prior to the crosslinking process. From the viewpoint of the polarizing properties of the resulting polarizing film 25, the stretching ratio of the wet stretching is preferably the final cumulative stretching ratio of the polarizing film 25 (the PVA resin film 10 subjected to the wet processing is stretched). In this case, the cumulative stretching ratio (including this stretching) is adjusted to be 3 to 8 times.

When carrying out the wet stretching process, the manufacturing apparatus includes wet stretching means for the PVA resin film 10. The wet stretching means is preferably a stretching means that performs stretching between rolls. Taking as an example the case where wet inter-roll stretching is performed during crosslinking treatment, the stretching means for performing inter-roll stretching are two nip rolls 2c and 2d arranged before and after the crosslinking treatment tank 17. Similarly, when stretching is performed during other wet treatments, two nip rolls placed apart from each other can be used as the wet stretching means.

(3) Drying Process The PVA resin film 10 after the wet processing step S101 can be subjected to a drying process by introducing the film into the drying oven 20 while continuing to be transported, thereby obtaining the polarizing film 25. The drying oven is preferably one in which the temperature inside the oven can be controlled. The drying oven is, for example, a hot air oven that can increase the temperature inside the oven by supplying hot air or the like.

The drying process may be performed by means other than a drying oven. Examples of the drying process using means other than a drying oven include a process in which the PVA resin film 10 is brought into close contact with one or more heating bodies having a convex curved surface, and a process in which the film is heated using a heater. Examples of the heating body include a roll (for example, a guide roll that also serves as a heat roll) that is equipped with a heat source (for example, a heat medium such as hot water or an infrared heater) inside and can increase the surface temperature. Examples of the heater include infrared heaters, halogen heaters, panel heaters, and the like.

The temperature of the drying process (for example, the temperature inside the drying oven 20, the surface temperature of the heat roll, etc.) is usually 30 to 100°C, preferably 50 to 90°C. The drying time is not particularly limited, but is, for example, 30 to 600 seconds.

The polarizing film 25 is a stretched (usually uniaxially stretched) PVA resin film on which a dichroic dye is adsorbed and oriented. The thickness of the polarizing film 25 is usually 2 to 40 μm. From the viewpoint of reducing the thickness of the polarizing plate including the polarizing film 25, the thickness of the polarizing film 25 is preferably 20 μm or less, more preferably 15 μm or less.

The visibility correction single transmittance Ty of the obtained polarizing film 25 is preferably 40 to 47%, more preferably 41 to 45%, taking into consideration the balance with the visibility correction polarization degree Py. The visibility correction polarization degree Py is preferably 99.9% or more, more preferably 99.95% or more. Ty and Py can be obtained by using an absorbance photometer with an integrating sphere and performing visibility correction on the obtained transmittance and degree of polarization using a 2-degree field of view (C light source) according to JIS Z 8701.

The obtained polarizing film 25 may be sequentially wound onto a take-up roll 27 to form a roll, or it may be used in a polarizing plate manufacturing process (a process of laminating a protective film or the like on one or both sides of the polarizing film 25) without being wound up. You can also serve it.

(4) Collection of dichroic dye The manufacturing apparatus includes a collection section for collecting dichroic dye floating in the air. The manufacturing method includes a step of collecting dichroic dye floating in the air. By providing the collecting section and the collecting step, the dichroic dye floating in the air can be collected, so that the dichroic dye can be reused. The production apparatus including a collection unit and the production method including a collection step are particularly advantageous when the dichroic dye contained in the dyeing solution is volatile, and such dichroic dyes include iodine. can be mentioned.

From the perspective of increasing the collection efficiency of dichroic dyes, the collection section includes an adsorption/absorption section that adsorbs or absorbs dichroic dyes floating in the air, and an airflow that generates an airflow toward the adsorption/absorption section. It is preferable to include a generating part.

An example of the collection section is shown in FIG. The collection section 50 shown in FIG. 1 includes an adsorption sheet (adsorption filter) 51 as an adsorption/absorption section and a blower 52 as an airflow generation section. The dichroic dye in the air can be adsorbed onto the adsorption sheet 51 by drawing in air containing the dichroic dye using the blower 52 and creating an airflow toward the adsorption sheet 51 . The adsorption sheet 51 may be placed downstream of the blower 52. The outlet 54 for air from which the dichroic dye has been removed, which is provided downstream of the adsorption sheet 51 and the blower 52, is not particularly limited, but may be arranged outside the room or building housing the manufacturing equipment.

The adsorption sheet 51 is not particularly limited as long as it has adsorption ability for dichroic dyes such as iodine, but is preferably an adsorption sheet containing activated carbon because of its high adsorption ability. Examples of the adsorption sheet containing activated carbon include woven fabrics of activated carbon fibers, nonwoven fabrics of activated carbon fibers, and sheets in which granular activated carbon is supported on a base material. From the viewpoint of increasing adsorption efficiency, the mesh size of the adsorption sheet containing activated carbon is preferably 2 to 10 mesh, more preferably 4 to 10 mesh, and even more preferably 6 to 10 mesh.

The thickness of the adsorption sheet (adsorption filter) 51 is preferably 1 inch (2.54 cm) or more, more preferably 2 inches (5.08 cm) or more, and even more preferably 3 inches (7.62 cm) from the viewpoint of increasing the adsorption efficiency. ) That's it. When the thickness is within the above range and the opening is within the above range, it is possible to obtain a high adsorption effect. The thickness of the suction sheet 51 is preferably 10 inches (25.4 cm) or less so that the pressure of the air required to pass through the suction sheet 51 does not become excessively high.

The collection unit 50 may constitute a draft chamber (local exhaust device). In the example shown in FIG. 1, the collection unit 50 further includes a receiver-type (canopy-type) hood 53, and sucks air containing the dichroic dye from the opening (suction port) of the hood 53, and The air from which the color pigment has been removed is discharged from the discharge port 54.

The main source of volatilization of the dichroic dye is the dyeing tank 15 containing a dyeing solution containing the dichroic dye. Therefore, it is preferable that the hood 53 be provided directly above the dyeing treatment tank 15. When the manufacturing apparatus is viewed from above, the size of the opening (suction port) of the hood 53 and the size of the dyeing treatment tank 15 (substantially the area of the surface of the dyeing treatment liquid) are the same or approximately the same. It is preferable that there be. If the size of the opening of the hood 53 is excessively large relative to the size of the dyeing treatment tank 15, pressure loss will become excessively large. Furthermore, if the size of the opening of the hood 53 is too small relative to the size of the dyeing treatment tank 15, there is a risk that sufficient collection efficiency of the dichroic dye may not be obtained. When the manufacturing apparatus includes two or more dyeing tanks, it is preferable to provide a hood 53 directly above each dyeing tank.

Although the crosslinking treatment liquid stored in the crosslinking treatment tank 17 is not prepared by actively adding dichroic dye, since the film immersed in the dyeing treatment tank 15 is immersed, the crosslinking treatment liquid contained in the crosslinking treatment tank 17 is With continuous production, it gradually comes to contain dichroic dyes. As described above, since the crosslinking treatment tank 17 can become a source of volatilization of the dichroic dye, it is preferable to provide a hood 53 also directly above the dyeing treatment tank 15 (see FIG. 1). The preferable relationship between the size of the opening of the hood 53 and the size of the crosslinking treatment tank 17 is the same as the preferable relationship between the size of the opening of the hood 53 and the size of the dyeing treatment tank 15 described above. When the manufacturing apparatus includes two or more crosslinking treatment tanks, it is preferable to provide a hood 53 directly above each crosslinking treatment tank.

The dichroic dye adsorbed on the adsorption sheet 51 can be isolated and recovered by a method such as immersing the adsorption sheet 51 in water. The recovered dichroic dye can be reused as a raw material for a dyeing solution.

Another example of the collection section 50 is a collection section that uses a bubble column instead of the adsorption sheet 51 as the adsorption/absorption section of the collection section 50 shown in FIG. For example, the dichroic dye can be absorbed into the liquid by a bubbling process in which air containing the dichroic dye is introduced from the bottom of a bubble column containing the liquid using the blower 52. The air from which the dichroic dye has been removed is led out from the top of the bubble column. Air discharged from the top of the bubble column may be guided to the outlet 54 via piping or the like.

The longer the contact time between the liquid and air in the bubble column, the higher the dichroic dye collection efficiency. Considering this point, it is preferable to use a sufficiently high bubble column.

The air containing the dichroic dye is preferably introduced into the bottom of the bubble column using a gas disperser. Thereby, the contact area between the air and the liquid in the bubble column can be increased, so that the collection efficiency (absorption efficiency) of the dichroic dye can be increased. Examples of the gas disperser include a perforated plate, a nozzle, a sparger, and the like. The collection efficiency (absorption efficiency) can be increased by introducing air from a large number of small-diameter discharge ports using these gas dispersers.

In bubbling treatment using a bubble column, mist may be generated on the surface of the liquid in the bubble column. When a mist is generated, the dichroic dye can be discharged along with it. To prevent this, a mist separator (demister) may be installed at the top of the bubble column. Thereby, it is possible to suppress a decrease in the collection efficiency of the dichroic dye.

The liquid filled in the bubble column is, for example, water or an aqueous solution. When the dichroic dye is iodine, the aqueous solution is preferably an aqueous potassium iodide solution. By using a potassium iodide aqueous solution, the potassium iodide aqueous solution that has absorbed iodine after bubbling treatment can be reused as a dyeing treatment solution after adjusting the concentration of iodine and potassium iodide as necessary. I can do it. The concentration of potassium iodide in the potassium iodide aqueous solution filled in the bubble column may be adjusted to be the same as the concentration of potassium iodide in the dyeing solution, it may be higher than this, or it may be lower than this. It may also be a concentration.

According to the present invention, dichroic dyes that were conventionally left to volatilize can be recovered and reused, making it possible to improve production efficiency and reduce production costs for polarizing films. At the same time, since dichroic pigments floating in the air can be recovered, deterioration in air cleanliness can be suppressed.

1a, 1b, 1c, 1d, 1e, 1f, 1g, 1h, 1i, 1j, 1k, 1l Guide roll, 2a, 2b, 2c, 2d, 2e, 2f Nip roll, 10 Polyvinyl alcohol resin film (PVA resin film ), 11 unwinding roll, 13 swelling treatment tank, 15 dyeing treatment tank, 17 crosslinking treatment tank, 19 cleaning treatment tank, 20 drying oven, 25 polarizing film, 27 winding roll, 50 collection unit, 51 adsorption sheet, 52 Blower, 53 hood, 54 outlet.

Claims (8)

A manufacturing device for manufacturing a polarizing film from a polyvinyl alcohol resin film,
The manufacturing apparatus includes one or more processing tanks containing a processing liquid in which the polyvinyl alcohol resin film is immersed,
The one or more processing tanks include a dyeing processing tank containing a dyeing processing solution containing a dichroic dye,
The manufacturing apparatus further includes a collection unit for collecting dichroic dye floating in the air. The collection unit includes an adsorption/absorption unit that adsorbs or absorbs the dichroic dye floating in the air, and an airflow generation unit that generates an airflow toward the adsorption/absorption unit. Manufacturing equipment. The manufacturing apparatus according to claim 1 or 2, wherein the adsorption/absorption section is an adsorption sheet containing activated carbon. The manufacturing apparatus according to claim 1 or 2, wherein the dichroic dye is iodine. A method for producing a polarizing film from a polyvinyl alcohol resin film, the method comprising:
The method includes the step of immersing the polyvinyl alcohol resin film in one or more treatment tanks containing a treatment liquid,
The one or more processing tanks include a dyeing processing tank containing a dyeing processing solution containing a dichroic dye,
The method further includes the step of collecting dichroic dye floating in the air. Dichroic dyes floating in the air are collected using a collection unit that includes an adsorption/absorption unit that adsorbs or absorbs the dye, and an airflow generation unit that generates an airflow toward the adsorption/absorption unit. , the method according to claim 5. The method according to claim 5 or 6, wherein the adsorption/absorption section is an adsorption sheet containing activated carbon. The method according to claim 5 or 6, wherein the dichroic dye is iodine.

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