JP2019086542A - Apparatus for manufacturing polarization film and method for manufacturing polarization film - Google Patents

Abstract

To provide an apparatus which can continuously manufacture a polarization film with stable optical characteristics.SOLUTION: A manufacturing apparatus for manufacturing a polarization film from a polyvinyl alcohol resin film includes a conveyance path of a polyvinyl alcohol resin film formed of a plurality of rolls, and two or more treatment tanks that are arranged on the conveyance path and store treatment liquid in which the polyvinyl alcohol resin film is immersed, in which the two or more treatment tanks include a dyeing treatment tank for storing dyeing treatment liquid and a first crosslinking treatment tank that stores first crosslinking treatment liquid in this order from an upstream side of the conveyance path, and in which the polyvinyl alcohol resin film in the first crosslinking treatment liquid is subjected to drawing treatment, the dyeing treatment tank and the first crosslinking treatment tank are arranged so as to be adjacent to each other, and a depth of the first crosslinking treatment tank is smaller than a depth of the dyeing treatment tank.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an apparatus and a method for producing a polarizing film that can be used, for example, as a component of a polarizing plate.

  As a polarizing film, a uniaxially stretched polyvinyl alcohol-based resin film in which a dichroic dye such as iodine is adsorbed and oriented is conventionally used. In general, a polarizing film is sequentially subjected to a dyeing process of dyeing a polyvinyl alcohol-based resin film with a dichroic dye, a crosslinking process of treating with a crosslinking agent, and a film drying process, and to the polyvinyl alcohol-based film during the manufacturing process. Manufactured by subjecting to a stretching treatment [e.g., JP-A-2001-141926 (Patent Document 1)].

JP 2001-141926 A

  In general, the polarizing film industrially transports a long polyvinyl alcohol-based resin film continuously along the transport path of the film possessed by the apparatus for producing a polarizing film while the above-mentioned polarizing membrane is on the transport path. It is manufactured including a wet treatment process of sequentially immersing in a dyeing treatment tank for performing a dyeing treatment and a crosslinking treatment tank for performing a crosslinking treatment.

  An object of the present invention is to provide an apparatus and method capable of continuously producing a polarizing film having stable optical properties.

The present invention provides an apparatus for producing a polarizing film described below and a method for producing a polarizing film.
[1] An apparatus for producing a polarizing film from a polyvinyl alcohol resin film,
A conveying path of a polyvinyl alcohol-based resin film constituted by a plurality of rolls;
Two or more processing baths disposed on the transport path and for containing a processing liquid in which the polyvinyl alcohol resin film is immersed;
Including
The two or more treatment vessels are, in order from the upstream side of the transport path, a staining treatment vessel for accommodating the staining treatment solution, and a treatment vessel for accommodating the first crosslinking treatment solution, and the first crosslinking treatment solution And a first crosslinking treatment tank in which the polyvinyl alcohol resin film is subjected to a stretching treatment,
The staining treatment tank and the first crosslinking treatment tank are disposed adjacent to each other,
An apparatus for producing a polarizing film, wherein the depth of the first crosslinking treatment tank is smaller than the depth of the staining treatment tank.
[2] The plurality of rolls include one or more guide rolls disposed in a first crosslinking treatment tank,
The manufacturing apparatus according to [1], wherein the one or more guide rolls are arranged such that the difference between the highest position and the lowest position of the transport path in the first crosslinking treatment tank is 500 mm or less.
[3] The plurality of rolls include two or more guide rolls disposed in a first crosslinking treatment tank,
The two or more guide rolls are two guide rolls adjacent to each other, and include two guide rolls arranged so that the holding angle of the polyvinyl alcohol resin film is 30 degrees or less in any of the guide rolls. The manufacturing apparatus as described in [1] or [2].
[4] The plurality of rolls further include a first nip roll and a second nip roll as stretching means for performing the stretching process,
The first nip roll is disposed upstream of the transport path with respect to the two adjacent guide rolls.
The second nip roll is disposed downstream of the transport path with respect to the two adjacent guide rolls.
The first nip roll and the second nip roll each include two rolls disposed one above the other, and the upper ends of the lower rolls thereof are positioned lower than the upper end of the first crosslinking treatment tank, and the lower side The manufacturing apparatus according to [3], wherein the lower end of the roll is positioned higher than the lower end of the first crosslinking treatment tank.
[5] The treatment tank disposed downstream of the first crosslinking treatment tank on the downstream side of the transport path, further including a second crosslinking treatment tank for containing a second crosslinking treatment liquid,
The manufacturing apparatus according to any one of [1] to [4], wherein the depth of the second crosslinking treatment tank is smaller than the depth of the staining treatment tank.
[6] The manufacturing apparatus according to any one of [1] to [5], wherein the length in the transport path direction of the first crosslinking treatment tank is longer than the length in the transport path direction of the staining treatment tank.
[7] A method for producing a polarizing film from a polyvinyl alcohol resin film,
Immersing the polyvinyl alcohol-based resin film in a dyeing treatment tank containing a dyeing treatment solution;
A step of subjecting the polyvinyl alcohol-based resin film after the step of immersing in a dyeing treatment tank to a stretching treatment while immersing in a first crosslinking treatment tank containing the first crosslinking treatment liquid;
Including
The staining treatment tank and the first crosslinking treatment tank are disposed adjacent to each other,
The manufacturing method of a polarizing film whose depth of a 1st crosslinking treatment tank is smaller than the depth of a dyeing processing tank.

  An apparatus and method capable of continuously producing a polarizing film having stable optical properties can be provided.

It is a schematic diagram which shows an example of a polarizing film manufacturing apparatus. It is a schematic diagram explaining the holding angle to the roll of a film.

  Hereinafter, the manufacturing apparatus and manufacturing method of a polarizing film are demonstrated, showing embodiment.

The present invention relates to a production apparatus and a production method for producing a polarizing film from a polyvinyl alcohol-based resin film (hereinafter also referred to as "PVA-based resin film"). The polarizing film can be manufactured by subjecting a PVA-based resin film to immersion treatment (wet treatment) in a treatment tank.
The polarizing film is one in which a dichroic dye is adsorbed and oriented on a stretched PVA-based resin film.

An example of a polarizing film manufacturing apparatus is shown in FIG. The polarizing film manufacturing apparatus shown by FIG. 1 is an apparatus for manufacturing the elongate polarizing film 25 continuously from the elongate PVA-type resin film 10 which is a raw material film. Arrows in FIG. 1 indicate the transport direction of the film.
In FIG. 1, reference numeral 30 denotes the position of the work floor surface, and an example of the liquid level of the treatment liquid stored in each treatment tank is indicated by a dotted line.
In the production of the polarizing film 25 using the production apparatus shown in FIG. 1, the swelling treatment tank 13, the dyeing treatment tank 15, the first crosslinking treatment, while continuously unwinding the PVA-based resin film 10 from the unwinding roll 11 The film is dipped in the tank 17, the second crosslinking tank 18 and the cleaning tank 19 in order, and finally passed through the drying furnace 21 to perform the drying process to obtain the polarizing film 25. The polarizing film 25 manufactured as a long product may be wound up sequentially on the winding roll 27, or a thermoplastic resin film such as a protective film is adhered to one side or both sides of the polarizing film 25 without being wound up. It may be provided to a polarizing plate manufacturing process.

The polarizing film manufacturing apparatus includes a wet processing unit (a zone where wet processing is performed using a processing tank containing a processing solution in which the film is immersed), preferably, a drying processing unit such as a drying furnace 21 (after wet processing) Further includes a zone for performing a drying process on the film of
The wet processing unit includes at least a dyeing treatment tank and a crosslinking treatment tank, and preferably includes a swelling treatment tank, a dyeing treatment tank, a crosslinking treatment tank, and a washing treatment tank.
The polarizing film manufacturing apparatus has a conveyance path for conveying the PVA-based resin film 10, and a wet processing unit and a drying processing unit are disposed on the conveyance path.
In the example shown by FIG. 1, the polarizing film manufacturing apparatus has a conveyance path | route of the PVA-type resin film 10 containing a wet process part and a drying process part. By conveying the PVA-based resin film 10 along this conveyance path, a series of treatments including wet treatment and drying treatment are performed to obtain the polarizing film 25.
The conveyance speed of the PVA-based resin film 10 conveyed along the conveyance path is usually 1 to 50 m / min, and preferably 5 m / min or more from the viewpoint of production efficiency.

As shown in FIG. 1, the transport path supports and guides the traveling film (PVA-based resin film 10 and polarizing film 25) so as to pass through the wet processing unit, and preferably the drying processing unit. It can be built by roles.
The plurality of rolls consists of a guide roll, which is a free roll supporting one side of the film, and / or a pair of rolls (usually including a drive roll), which, for example, have two sides of the film. It is a nip roll which sandwiches or presses from there.
In the example shown in FIG. 1, the polarizing film manufacturing apparatus includes guide rolls 1a to 1bb and nip rolls 2a to 2i. The plurality of rolls defining the transport path may include a suction roll (a suction roll) which is one of drive rolls. Usually, these rolls support the film in contact with one or both surfaces (main surfaces) of the film in the transport path. These rolls can be disposed at appropriate positions, such as before and after each treatment tank and drying means (drying oven), or in the treatment tank and drying means (drying oven).

  The drive roll refers to a roll that can provide a driving force for film transport to the film in contact therewith, and can be a roll or the like to which a roll drive source such as a motor is directly or indirectly connected. . The free roll plays a role of supporting a traveling film and refers to a roll that can freely rotate in accordance with the transport of the film.

  The polarizing film 25 obtained is one that has been subjected to a stretching process (usually a uniaxial stretching process). For this reason, the manufacturing apparatus of a polarizing film can include a stretching means (wet stretching means) of the PVA-based resin film 10, and a method of producing a polarizing film comprises a stretching process step (wet stretching process) of the PVA-based resin film 10. Process) can be included.

(1) PVA-Based Resin Film The PVA-based resin film 10 to be subjected to wet treatment (introduced to the wet treatment section) is a film composed of a polyvinyl alcohol-based resin (hereinafter also referred to as "PVA-based resin"). It is. The PVA-based resin refers to a resin containing 50% by weight or more of a structural unit derived from vinyl alcohol. As PVA system resin, what saponified polyvinyl acetate system resin can be used. Examples of polyvinyl acetate 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, (meth) acrylamides having an ammonium group, and the like.
In addition, "(meth) acryl" represents at least 1 sort (s) chosen from the group which consists of an acryl and methacryl. The same applies to other terms with "(meth)".

  The saponification degree of the PVA-based 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 94.0 to 0. It is in the range of 100.0 mol%, more preferably in the range of 98.0 to 100.0 mol%. If the degree of saponification is less than 80.0 mol%, the water resistance and moist heat resistance of the resulting polarizing film 25 and the polarizing plate including the same may be reduced.

Saponification degree is the ratio of acetic acid group (acetoxy group: -OCOCH ₃ ) contained in polyvinyl acetate resin, which is a raw material of polyvinyl alcohol resin, changed to hydroxyl group in the saponification process in unit ratio (mol%) It is represented and the following formula:
Degree of saponification (mol%) = 100 × (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-based 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 polyvinyl alcohol 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 the polarizing film 25 having preferable polarization performance, and when it exceeds 10000, the solubility in a solvent is deteriorated and the formation (film formation) of the PVA resin film 10 is difficult. It can be

An example of the PVA-based resin film 10 is an unstretched film formed by forming the PVA-based resin. The film forming method is not particularly limited, and a known method such as a melt extrusion method or a solvent casting method can be adopted.
Another example of the PVA-based resin film 10 is a stretched film obtained by stretching the unstretched film. This stretching is usually uniaxial stretching, preferably longitudinal uniaxial stretching. Longitudinal stretching refers to stretching in the machine flow direction (MD) of a film, that is, in the longitudinal direction of the film.
In the case where the PVA-based resin film 10 to be subjected to wet treatment (introduced to the wet treatment section) is a stretched film, this stretching is preferably dry stretching. Dry stretching refers to stretching performed in the air, and usually is longitudinal uniaxial stretching.

In dry stretching, a film is passed between a heat roll whose surface is heated and a guide roll (or a heat roll) having a circumferential speed different from that of the heat roll, and heating is performed using the heat roll. Hot roll drawing which performs longitudinal drawing under; between rolls performing longitudinal drawing by the circumferential speed difference between these two nip rolls while passing a heating means (such as an oven) between two nip rolls placed at a distance. Stretching; tenter stretching; compression stretching etc. can be mentioned.
The stretching temperature (the surface temperature of the heat roll, the temperature in the oven, etc.) is, for example, 80 to 150 ° C., preferably 100 to 135 ° C.

  The stretching ratio of the above stretching is usually 1.1 to 8 times, preferably 2.5 to 5, although it depends on whether or not wet stretching is performed during wet processing, and the stretching ratio in the wet stretching. It is five times.

The PVA-based resin film 10 can contain an additive such as a plasticizer. Preferred examples of the plasticizer are polyhydric alcohols, and specific examples thereof include ethylene glycol, glycerin, propylene glycol, diethylene glycol, diglycerin, triethylene glycol, triglycerin, tetraethylene glycol, trimethylolpropane, polyethylene glycol etc. It can be mentioned. The PVA-based resin film 10 can contain one or more plasticizers.
The content of the plasticizer is usually 5 to 20 parts by weight, preferably 7 to 15 parts by weight with respect to 100 parts by weight of the PVA-based resin constituting the PVA-based resin film 10.

  The thickness of the PVA-based resin film 10 to be subjected to wet treatment (introduced to the wet-treated part) is usually 10 to 150 μm, although it depends on whether the PVA-based resin film 10 is a stretched film or not. Preferably, the thickness is 100 μm or less, more preferably 65 μm or less, still more preferably 50 μm or less, and particularly preferably 35 μm or less (for example, 30 μm or less, further 20 μm or less).

(2) Wet treatment unit and wet treatment The wet treatment unit in which the wet treatment is performed is a zone disposed on the conveyance path of the PVA-based resin film 10, and contains the treatment liquid in which the PVA-based resin film 10 is immersed. Containing two or more treatment vessels. In the wet processing unit, the wet processing is performed in which the PVA-based resin film 10 is immersed in the processing liquid while transporting the PVA-based resin film 10.

In the wet processing unit, the two or more processing tanks include the dyeing processing tank 15 and the first crosslinking processing tank 17, and preferably further include the swelling processing tank 13 and the cleaning processing tank 19. These treatment tanks are usually arranged in the order of the swelling tank 13, the dyeing tank 15, the crosslinking tank 17, and the cleaning tank 19 in this order from the upstream side of the transport path (see FIG. 1).
The first crosslinking treatment tank 17 is a tank disposed adjacent to the staining treatment tank 15. That is, when the wet processing unit includes two or more crosslinking treatment vessels, the first crosslinking treatment vessel 17 is a vessel disposed on the most upstream side (most dyeing process vessel side) of the transport path.
In FIG. 1, one swelling processing tank 13, one staining processing tank 15, and one washing processing tank 19 are provided, and two crosslinking processing tanks are provided (first crosslinking processing tank 17 and second crosslinking processing tank 18). Although an example is shown, if necessary, two or more staining treatment tanks 15 may be provided, and three or more crosslinking treatment tanks may be provided. The crosslinking treatment tank may be only one tank of the first crosslinking treatment tank 17.
The same applies to the swelling treatment tank 13 and the washing treatment tank 19, and two or more tanks may be provided.
When the wet processing unit includes two or more dyeing treatment vessels, the first crosslinking treatment vessel 17 is disposed adjacent to the dyeing treatment vessel disposed on the most downstream side of the transport path.

(2-1) Swelling treatment tank and swelling treatment step Swelling treatment is carried out as necessary for the purpose of removing foreign matter, removing plasticizer, imparting easy dyeability, plasticizing film, etc. of the PVA-based resin film 10 It is a process.
Referring to FIG. 1, in the swelling treatment step, the PVA-based resin film 10 is conveyed along the film conveyance path while being unwound continuously from the unwinding roll 11, and the PVA-based resin film 10 is subjected to the swelling treatment solution. It can be implemented by immersing in the swelling treatment tank 13 to be stored for a predetermined time and then withdrawing.

The treatment liquid (swelling treatment liquid) contained in the swelling treatment tank 13 may be, for example, water (pure water or the like), or may be water containing an organic solvent such as alcohol. The swelling treatment solution can also contain boric acid, chlorides, inorganic acids, inorganic salts and the like.
The temperature of the swelling treatment solution is usually 10 to 70 ° C, preferably 15 to 50 ° C, and more preferably 15 to 35 ° C. The immersion time (retention time in the swelling treatment liquid) of the PVA-based resin film 10 is usually 10 to 600 seconds, preferably 15 to 300 seconds.

During the swelling process, the PVA-based 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. Referring to FIG. 1, uniaxial stretching can be performed in swelling treatment tank 13 using, for example, the difference in peripheral speed between nip roll 2a and nip roll 2b.
In the example shown in FIG. 1, the film drawn from the swelling treatment tank 13 is introduced into the dyeing treatment tank 15 sequentially through the guide roll 1 c and the nip roll 2 b.

(2-2) Dyeing Treatment Tank and Dyeing Treatment Step Dyeing treatment is a treatment carried out for the purpose of adsorbing and orienting a dichroic dye on the PVA-based resin film 10.
Referring to FIG. 1, the dyeing process can be carried out by conveying along the film conveying path, immersing the PVA-based resin film 10 in the dyeing tank 15 for a predetermined time, and then pulling it out. The dyeing processing tank 15 is a tank for immersing the PVA-based resin film 10 in the dyeing processing solution contained therein. The PVA-based resin film 10 to be immersed in the dyeing treatment solution is preferably a film after the swelling treatment step (immersed in the swelling treatment tank 13).
The staining solution contained in the staining tank 15 is a solution (usually an aqueous solution) containing a dichroic dye. The dichroic dye can be iodine or a dichroic organic dye, preferably iodine. The dichroic dyes may be used alone or in combination of two or more.

  When iodine is used as the dichroic dye, an aqueous solution containing iodine and potassium iodide can be used as the staining solution. Instead of potassium iodide, other iodides such as zinc iodide may be used, and potassium iodide and other iodides may be used in combination. In addition, compounds other than iodide, for example, boric acid, zinc chloride, cobalt chloride and the like may coexist. When boric acid is added, it is distinguished from the crosslinking treatment solution described later in that it contains iodine. For example, if the aqueous solution contains about 0.003 parts by weight or more of iodine with respect to 100 parts by weight of water, it can be regarded as a staining solution. The content of iodine in the dyeing solution is usually 0.003 to 1 part by weight per 100 parts by weight of water. The content of iodide such as potassium iodide in the dyeing solution is usually 0.1 to 20 parts by weight per 100 parts by weight of water.

  The temperature of the staining solution is usually 10 to 45 ° C, preferably 10 to 40 ° C, and more preferably 20 to 35 ° C. The immersion time (residence time in the staining solution) of the PVA-based resin film 10 is usually 20 to 600 seconds, preferably 30 to 300 seconds.

  As described above, the polarizing film manufacturing apparatus can include two or more dyeing treatment vessels 15. In this case, the composition and temperature of each staining solution may be the same or different.

In order to enhance the dyeability of the dichroic dye, the PVA-based resin film 10 to be subjected to the dyeing process is preferably at least partially subjected to a stretching process (usually a uniaxial stretching process). Instead of the stretching process before the dyeing process, or in addition to the stretching process before the dyeing process, the stretching process may be performed while performing the dyeing process. The stretching ratio of integration up to the dyeing process (the stretching ratio in the dyeing process when there is no drawing process up to the dyeing process) is usually 1.6 to 4.5 times, preferably 1.8 to 4 times . Referring to FIG. 1, for example, uniaxial stretching can be performed in the dyeing processing tank 15 by utilizing the peripheral speed difference between the nip roll 2b and the nip roll 2c.
In the example shown in FIG. 1, the film drawn from the dyeing treatment tank 15 is introduced into the first crosslinking treatment tank 17 by sequentially passing through the guide roll 1 g, the nip roll 2 c, and the guide roll 1 h.

(2-3) Crosslinking Treatment Tank and Crosslinking Treatment Step Crosslinking treatment is treatment to be carried out for the purpose of water resistance by crosslinking, hue adjustment (complementary color) and the like.
Referring to FIG. 1, the crosslinking treatment is carried along the film conveyance path, and the PVA-based resin film 10 after the dyeing treatment step (immersed in the dyeing treatment tank 15) is transferred to the first crosslinking treatment tank 17 for a predetermined time It can be carried out by immersion and then withdrawal. The same applies to the case where two or more crosslinking treatment tanks are provided as in the second crosslinking treatment tank 18.
The crosslinking treatment tank is a tank for immersing the PVA-based resin film 10 in the crosslinking treatment liquid contained therein. Hereinafter, the crosslinking treatment liquid contained in the first crosslinking treatment tank 17 is also referred to as “first crosslinking treatment liquid”, and the crosslinking treatment liquid contained in the second crosslinking treatment tank 18 is also referred to as “second crosslinking treatment liquid”.
The crosslinking treatment liquid accommodated in the crosslinking treatment tank is a liquid (usually, an aqueous solution) containing a crosslinking agent. The crosslinking treatment is performed by immersing the PVA-based resin film 10 after the dyeing treatment step in the crosslinking treatment solution.

Examples of the crosslinking agent contained in the crosslinking solution include boric acid, glyoxal, glutaraldehyde and the like, with preference given to boric acid. Two or more crosslinkers can also be used in combination.
The content of the crosslinking agent in the crosslinking treatment solution is generally 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 solution preferably contains an iodide in addition to the crosslinking agent.
Examples of the iodide include potassium iodide and zinc iodide.
The content of iodide in the crosslinking solution is generally 0.1 to 20 parts by weight, preferably 5 to 15 parts by weight, per 100 parts by weight of water.

  The crosslinking treatment solution may contain compounds other than iodide. Examples of the compound include zinc chloride, cobalt chloride, zirconium chloride, sodium thiosulfate, potassium sulfite, sodium sulfate and the like.

  The temperature of the crosslinking solution is generally in the range of usually 20 to 85 ° C, preferably 30 to 70 ° C. The immersion time (residence time in the crosslinking treatment solution) of the PVA-based resin film 10 is generally 10 to 600 seconds, preferably 20 to 300 seconds.

As described above, the polarizing film production apparatus can include two or more crosslinking treatment vessels. In this case, the composition and temperature of each crosslinking treatment solution may be the same or different. The crosslinking treatment liquid may have a concentration of a crosslinking agent, an iodide, or the like according to the purpose of immersing the PVA-based resin film 10, or a temperature. The crosslinking treatment for waterproofing by crosslinking and the crosslinking treatment for hue adjustment (complementary color) may be performed in a plurality of steps.
Generally, when carrying out both the crosslinking treatment for water resistance-ization by crosslinking and the crosslinking treatment for hue adjustment (complementary color), the tank (complementary vessel) for carrying out the crosslinking treatment for hue adjustment (complementary color) is Be placed. The temperature of the processing solution stored in the complementary color tank is, for example, 10 to 55 ° C., preferably 20 to 50 ° C. The content of the crosslinking agent in the treatment liquid contained in the complementary color tank is, for example, 1 to 5 parts by weight per 100 parts by weight of water. The content of iodide in the processing solution contained in the complementary color tank is, for example, 3 to 30 parts by weight per 100 parts by weight of water.

In the first crosslinking treatment tank 17, the stretching treatment (usually, uniaxial stretching treatment) is performed together with the crosslinking treatment. With reference to FIG. 1, uniaxial stretching can be performed in the first crosslinking treatment tank 17 using, for example, the peripheral speed difference between the nip roll 2d and the nip roll 2e.
The draw ratio of the drawing performed in the first crosslinking treatment tank 17 is usually 1.05 to 2.5 times, preferably 1.1 to 2.2 times.
When the wet treatment part includes two or more cross-linking treatment tanks, the cross-linking treatment tank other than the first cross-linking treatment tank 17 may perform the stretching treatment.
In the example shown in FIG. 1, the film drawn from the second crosslinking treatment tank 18 is introduced into the cleaning treatment tank 19 by sequentially passing through the guide roll 1 s and the nip roll 2 g.

(2-4) Washing treatment tank and washing treatment process The manufacturing method of a polarizing film can further include the washing treatment process after a crosslinking treatment process, for this reason, a polarizing film manufacturing device is downstream of a crosslinking treatment tank. It may further include a cleaning tank 19 disposed. The washing treatment is a treatment to be carried out for the purpose of removing an excess drug attached to the PVA-based resin film 10 after the crosslinking treatment step.
With reference to FIG. 1, the cleaning process is carried along the film conveyance path, and the PVA-based resin film 10 after the crosslinking process (immersed in the crosslinking process tank) is immersed in the cleaning process tank 19 for a predetermined time. It can then be carried out by withdrawal. Alternatively, the cleaning process may be a process of spraying the cleaning solution as a shower, for example, on the PVA-based resin film 10 after the crosslinking process step, or the immersion in the cleaning processing tank 19 and the spraying of the cleaning solution may be combined. . In FIG. 1, the example in the case of immersing the PVA-type resin film 10 in the washing process tank 19 and performing a washing process is shown.

  The cleaning treatment liquid contained in the cleaning treatment tank 19 and the cleaning liquid to be sprayed may be, for example, water (such as pure water), or may be an aqueous solution to which a water-soluble organic solvent such as alcohol is added. The temperature of the washing bath is, for example, 2 to 40 ° C.

  Stretching (usually uniaxial stretching) may be performed while washing. Referring to FIG. 1, uniaxial stretching can be performed in cleaning treatment tank 19 using, for example, the circumferential speed difference between nip roll 2g and nip roll 2h.

(2-5) Stretching Means and Stretching Treatment Process In the first crosslinking treatment tank 17, a wet treatment is applied together with the crosslinking treatment. Wet stretching may be further performed in one or more other processing tanks as described above. Wet stretching is usually uniaxial stretching.
The stretching magnification of the wet stretching is preferably the final cumulative stretching magnification of the polarizing film 25 (in the case where the PVA-based resin film 10 to be subjected to the wet processing is a stretched film), from the viewpoint of the polarization properties of the polarizing film 25 obtained. In this case, the cumulative stretching ratio (including this stretching) is adjusted to be 3 to 8 times.

  The polarizing film manufacturing apparatus includes a wet stretching means of the PVA-based resin film 10. The wet stretching means is preferably a stretching means that performs inter-roll stretching. This stretching means has at least a stretching means for performing wet stretching in the first crosslinking treatment tank 17. If the manufacturing apparatus shown by FIG. 1 is mentioned as an example, the extending | stretching means for performing wet extending | stretching in the 1st crosslinking treatment tank 17 will be two arrange | positioned respectively upstream and downstream of the 1st crosslinking treatment tank 17. The nip rolls 2d and 2e. Similarly, in the case of performing stretching during other wet processing, two nip rolls arranged at a distance can be used as a wet stretching means.

(3) Drying Processing Unit and Drying Processing Step The drying processing unit in which the drying processing step is performed is disposed on the conveyance path of the PVA-based resin film 10 and downstream of the wet processing unit, after the wet processing step. This is a zone for drying the PVA-based resin film 10. A drying process can be performed by introducing the said film into a drying process part, conveying continuously the PVA-type resin film 10 after a wet processing process, and, thereby, the polarizing film 25 is obtained (refer FIG. 1).

  The drying processing unit includes a drying unit (heating unit) of the film. A preferred example of the drying means is a drying oven such as the drying oven 21 shown in FIG. The drying furnace is preferably capable of controlling the temperature in the furnace. The drying furnace is, for example, a hot air oven capable of increasing the temperature in the furnace by supply of hot air or the like. Further, the drying process by the drying means is a process of bringing the PVA-based resin film 10 after the wet treatment process into close contact with one or more heating members having a convex curved surface, or a process of heating the film using a heater. Good.

  As said heating body, a heat source (for example, heat mediums, such as warm water, infrared heater) can be included inside, and the roll (for example, guide roll which served as the heat roll) which can raise surface temperature can be mentioned. As said heater, an infrared heater, a halogen heater, a panel heater etc. can be mentioned. FIG. 1 shows an example in which the PVA-based resin film 10 after the wet treatment process is introduced into the drying furnace 21 and dried.

  The temperature of the drying treatment (for example, the temperature in the furnace of the drying furnace 21, the surface temperature of the heat roll, etc.) is usually 30 to 100 ° C, preferably 50 to 90 ° C.

  The polarizing film 25 is one in which a dichroic dye is adsorbed and oriented on a stretched (usually uniaxially stretched) PVA-based resin film. The thickness of the polarizing film 25 is usually 2 to 40 μm. From the viewpoint of thinning 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, and still more preferably 10 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%, in consideration of the balance with the visibility correction polarization degree Py. The visibility correction polarization degree Py is preferably 99.9% or more, and more preferably 99.95% or more.
Ty and Py can be measured by using an absorptiometer equipped with an integrating sphere and performing visibility correction on the obtained transmittance and polarization degree with a two-degree field of view (C light source) of JIS Z 8701.

  The obtained polarizing film 25 may be sequentially wound on a winding roll 27 to form a roll form, or a polarizing plate production process (a thermoplastic resin film (protective film etc. on one side or both sides of the polarizing film 25 as it is) without being wound. ) Can also be used in the step of laminating).

(4) Configuration of polarizing film manufacturing apparatus (4-1) Depth of crosslinking treatment tank The depth of the first crosslinking treatment tank 17 provided in the polarizing film manufacturing apparatus is adjacent to the transport path of the dyeing process The depth of the processing tank 15 (as described above, when the wet processing unit includes two or more staining processing tanks, the staining processing tank disposed on the most downstream side of the transport path) is smaller (see FIG. 1).
In the first crosslinking treatment tank 17 in which the stretching treatment is performed together with the crosslinking treatment, it is required that the crosslinking treatment on the PVA-based resin film 10 continuously immersed in the crosslinking treatment solution be uniformly performed in the film longitudinal direction, It is required that the stretching process be performed uniformly over the longitudinal direction of the film. If the uniformity of the crosslinking treatment is not high, the uniformity of the optical properties (degree of polarization, transmittance, etc.) of the obtained polarizing film 25 may be reduced. If the uniformity of the stretching process is not high, the film may be broken during the stretching process, and the uniformity of the optical properties of the obtained polarizing film 25 may be reduced.
According to the first crosslinking treatment tank 17 satisfying the above depth relationship, the amount of the first crosslinking treatment liquid contained in the first crosslinking treatment tank 17 can be reduced, and the liquid of the first crosslinking treatment liquid can be reduced. As a result of reducing the height (depth), it is possible to reduce fluctuations in the liquid temperature and the concentration of the first crosslinking solution during the crosslinking treatment and the stretching treatment in the first crosslinking treatment tank 17. Thereby, the uniformity over the film longitudinal direction of the crosslinking process and the extending | stretching process in the 1st crosslinking treatment tank 17 can be improved.

The reduction of the liquid volume of the first crosslinking treatment liquid also contributes to the reduction of the amount of the reagent (crosslinking agent, iodide etc.) used. Being able to reduce the height (depth) of the first crosslinking treatment solution also contributes to the improvement of the workability, and for example, it becomes easy to pass a sheet (the work of setting the film on the conveyance path), or The recovery operation of foreign substances (film fragments and the like when the film is broken) mixed in the crosslinking treatment solution may be facilitated. Using the first crosslinking treatment tank 17 which satisfies the above depth relationship is also advantageous in terms of the compactness of the polarizing film manufacturing apparatus.
If the bottom surface of the first crosslinking treatment tank 17 is at a position higher than the bottom surface of the staining treatment tank 15, it is advantageous for improving the workability.

Assuming that the depth of the first crosslinking treatment tank 17 is D17 and the depth of the staining treatment tank 15 is D15, the ratio of D17 to D15 (D17 / D15) is, for example, 0.9 or less, from the viewpoint of the above effect Preferably, it is 0.8 or less, More preferably, it is 0.7 or less. D17 / D15 is, for example, 0.2 or more, and in view of more easily accommodating a guide roll for conveyance and a nip roll for stretching treatment in the first crosslinking treatment liquid of the first crosslinking treatment tank 17, it is preferably 0 .3 or more, more preferably 0.35 or more. When stretching is performed in the first crosslinking treatment tank 17, it is necessary to apply a large tension to the film, so a large diameter nip roll having a diameter of 300 to 500 mm is usually used as the first crosslinking treatment liquid of the first crosslinking treatment tank 17. Place in, stretch and transport the film.
D17 may be, for example, 300-1500 mm, and D15 may be, for example, 400-2000 mm.

  In the case where the wet processing unit includes another crosslinking treatment tank other than the first crosslinking treatment tank 17 on the downstream side of the first crosslinking treatment tank 17 (for example, the second crosslinking treatment tank 18 shown in FIG. 1), the other crosslinking treatment The depth of the bath is not particularly limited. However, the amount of the second crosslinking treatment liquid contained in the second crosslinking treatment tank 18 can be reduced, and the liquid height (depth) of the second crosslinking treatment liquid can be reduced. Since the same effect as in the first embodiment can be obtained, the depth of the second crosslinking treatment tank 18 is determined as follows: if the wet treatment section includes two or more staining treatment tanks as described above, It is preferable that the depth is smaller than the depth of the staining treatment tank) disposed downstream. The same applies to the third and subsequent crosslinking treatment tanks installed as necessary.

The polarizing film manufacturing apparatus can include a floor surface adjacent to the first crosslinking treatment tank 17. This floor is typically a work floor on which a worker works. The work floor is generally adjacent not only to the first crosslinking treatment tank 17 but also to other treatment tanks and the like.
Referring to FIG. 1, it is preferable that the position 30 of the work floor be disposed at substantially the same height as the bottom surface of the first crosslinking treatment tank 17. The substantially the same height means that the absolute value of the difference in height is about 0 to 300 mm. The absolute value of the height difference is preferably 0 to 200 mm, more preferably 0 to 100 mm.
When the position 30 of the work floor surface is disposed at substantially the same height as the bottom surface of the first crosslinking treatment tank 17, the above-described workability can be further enhanced.
It is preferable that the position 30 of the work floor be approximately the same height throughout the polarizing film manufacturing apparatus.

(4-2) Film transport path in the crosslinking treatment tank From the viewpoint of continuously producing the polarizing film 25 having stable optical characteristics, the film transport path in the first crosslinking treatment tank 17 is the following [a] and [b] It is preferable to satisfy at least one of them.
[A] One or more guide rolls are disposed in the first crosslinking treatment tank 17, and the difference between the highest position and the lowest position of the conveyance path in the first crosslinking treatment tank 17 is one or more guide rolls. It is arranged to be 500 mm or less.
[B] Two or more guide rolls disposed in the first crosslinking treatment tank 17. The two or more guide rolls are two guide rolls adjacent to each other, and any of the guide rolls is a PVA resin It includes two guide rolls arranged so that the holding angle of the film 10 is 30 degrees or less.

  By arranging a guide roll in the first crosslinking treatment tank 17 so as to satisfy the above [a], positional fluctuation in the depth direction of the PVA-based resin film 10 traveling in the first crosslinking treatment tank 17 is reduced. be able to. Thereby, even when the first crosslinking solution has a temperature distribution or a concentration distribution in the depth direction, it is possible to suppress an adverse effect of the distribution on the optical properties of the polarizing film 25.

The difference between the highest position and the lowest position is preferably 400 mm or less, more preferably 350 mm or less. The difference may be 0 mm.
In addition, 2 or more, 3 or more can be arrange | positioned in a 1st bridge | crosslinking process tank 17 (refer FIG. 1).
It is preferable that the bridge | crosslinking treatment tank of the 2nd tank or subsequent one arrange | positioned as needed also satisfy | fills said [a].

  Also by disposing a guide roll in the first crosslinking treatment tank 17 so as to satisfy the above [b], the positional variation in the depth direction of the PVA-based resin film 10 traveling in the first crosslinking treatment tank 17 is reduced. can do. Thereby, even when the first crosslinking solution has a temperature distribution or a concentration distribution in the depth direction, it is possible to suppress an adverse effect of the distribution on the optical properties of the polarizing film 25.

The holding angle may be 20 degrees or less, and further 10 degrees or less. The hugging angle may be 0 degrees.
Referring to FIG. 2, the holding angle of film A to roll B is a straight line connecting the center of roll B and the contact point between film A and roll B at the moment film A contacts roll B for the first time. When a straight line connecting the contact point between the film A and the roll B at the moment when the film A leaves the roll B and the center of the roll B is Y, the angle α between the straight line X and the straight line Y is said.
When three or more guide rolls are disposed in the first crosslinking treatment tank 17, the guide angle of the PVA-based resin film 10 is 30 degrees or less in as many guide rolls as possible among the three or more guide rolls. It is preferred to place the roll. In addition, it is preferable to continuously arrange as many guide rolls as possible in which the holding angle is 30 degrees or less.
It is preferable that the bridge | crosslinking treatment tank of the 2nd tank or subsequent one arrange | positioned as needed also satisfy | fills said [b].

The wet processing unit has a stretching means for stretching the PVA-based resin film 10 in the first crosslinking treatment tank 17. As an example of this stretching means, referring to the example shown in FIG. 1, a nip roll 2d (first nip roll) disposed on the upstream side of the transport path and a nip roll 2e (second nip roll) disposed on the downstream side It is a combination.
In the case where the above [b] is satisfied, the polarizing film production apparatus preferably further satisfies the following [c-1] and [c-2].
[C-1] The first nip roll is disposed upstream of the two adjacent guide rolls described in [b] above in the conveyance path, and the second nip roll is the two adjacent nip rolls described in [b] above It is disposed downstream of the transport path from the guide roll.
[C-2] The first nip roll and the second nip roll each include two rolls disposed one above the other, and the upper ends of the lower rolls thereof are lower than the upper end of the first crosslinking treatment tank 17 And the lower end of the lower roll is positioned higher than the lower end of the first crosslinking treatment tank 17.

  The above [c-2] means that the entire lower rolls of the first and second nip rolls are disposed at such a height position that they can be immersed in the first crosslinking treatment liquid. In addition to satisfying the above [b], by satisfying the above [c-1] and [c-2], the first crosslinking treatment tank 17 occupies the entire transport route in the first crosslinking treatment tank 17 It is possible to further increase the ratio of the transport path portion that can reduce the positional variation in the depth direction of the PVA-based resin film 10 traveling inside. This is advantageous for continuously producing the polarizing film 25 having stable optical properties. In addition to satisfying the above [b], satisfying the above [c-1] and [c-2] is also advantageous in enhancing the uniformity of stretching in the first crosslinking treatment solution.

  The number of guide rolls disposed between the first nip roll and the second nip roll may be three or more. Of the three or more guide rolls, it is preferable to arrange the guide rolls so that the holding angle of the PVA-based resin film 10 is 30 degrees or less in as many guide rolls as possible. In addition, it is preferable to continuously arrange as many guide rolls with a holding angle of at most 30 degrees as possible between the first nip roll and the second nip roll.

  As described above, when the polarizing film manufacturing apparatus satisfies the above [a], [b], [c-1] and [c-2], the PVA-based resin film 10 traveling in the first crosslinking treatment tank 17 In the depth direction of the first crosslinking treatment tank 17, the positional variation in the depth direction of the first crosslinking treatment tank 17 can be reduced, or the depth direction of the PVA resin film 10 traveling in the first crosslinking treatment tank 17 can be reduced. The ratio of the transport path portion that can reduce the positional fluctuation with respect to The position with respect to the depth direction of the PVA-based resin film 10 in which the polarizing film manufacturing apparatus satisfies the above [a], [b], [c-1] and [c-2] and travels in the first crosslinking treatment tank 17 The smaller variation means that the guide roll and the nip roll of the first crosslinking treatment tank 71 are disposed in a more specific area of specific depth. In this case, the first crosslinking treatment liquid in the first crosslinking treatment tank 17 is agitated by the rotation of each roll at the time of film conveyance or film conveyance, and the temperature of the first crosslinking treatment liquid in the film conveyance path portion by convection. It can be expected that the concentration leveling is promoted.

(4-3) Length of Crosslinking Treatment Tank The length of the first crosslinking treatment tank 17 in the transport direction is preferably longer than the length of the staining processing tank 15 in the transport path direction. This length relationship is preferably satisfied particularly when the above [a] or [b] is satisfied.
When the above [a] or [b] is satisfied, the residence time (the length of the transport path) of the PVA-based resin film 10 in the first crosslinking treatment tank 17 is rather than the depth direction of the tank. It is secured by the transport route in the transport direction.
By making the length in the transport direction of the first crosslinking treatment tank 17 longer than the length in the transport route direction of the dyeing processing tank 15, the polarizing film 25 with stable optical characteristics is secured while securing the necessary crosslinking processing time. It can be manufactured.

When the length of the first crosslinking treatment tank 17 in the conveyance direction is L17 and the length of the staining treatment tank 15 in the conveyance direction is L15, the ratio of L17 to L15 (L17 / L15) is, for example, 1.1 or more. From the viewpoint of the above effects, it is preferably 1.2 or more, more preferably 1.3 or more. L17 / L15 is, for example, 2.5 or less, preferably 2 or less, and 1.8 or less from the viewpoint of the occupied area of the polarizing film manufacturing apparatus.
L17 may be, for example, 3 to 10 m, and L15 may be, for example, 1 to 8 m.

  In the case where the wet processing unit includes another crosslinking treatment tank other than the first crosslinking treatment tank 17 on the downstream side of the first crosslinking treatment tank 17, the length in the transport direction of the other crosslinking treatment tank is not particularly limited. However, from the same viewpoint as described above, it is preferable to satisfy the same length relationship as the first crosslinking treatment tank 17 for the second and subsequent crosslinking treatment tanks installed as necessary.

  1a, 1b, 1c, 1e, 1f, 1g, 1i, 1j, 1k, 1l, 1m, 1n, 1o, 1p, 1q, 1r, 1s, 1t, 1u, 1v, 1w, 1x, 1y, 1y 1z, 1aa, 1bb guide roll, 2a, 2b, 2c, 2d, 2e, 2f, 2g, 2h, 2i nip roll, 10 polyvinyl alcohol resin film (PVA resin film), 11 unwind roll, 13 swelling treatment tank, 15 dyeing treatment tank, 17 first crosslinking treatment tank, 18 second crosslinking treatment tank, 19 washing treatment tank, 21 drying furnace, 25 polarizing film, 27 winding roll, 30 working floor position.

Claims (7)

An apparatus for producing a polarizing film from a polyvinyl alcohol resin film,
A conveying path of a polyvinyl alcohol-based resin film constituted by a plurality of rolls;
Two or more processing baths disposed on the transport path and for containing a processing liquid in which the polyvinyl alcohol resin film is immersed;
Including
The two or more treatment vessels are, in order from the upstream side of the transport path, a staining treatment vessel for accommodating the staining treatment solution, and a treatment vessel for accommodating the first crosslinking treatment solution, and the first crosslinking treatment solution And a first crosslinking treatment tank in which the polyvinyl alcohol resin film is subjected to a stretching treatment,
The staining treatment tank and the first crosslinking treatment tank are disposed adjacent to each other,
An apparatus for producing a polarizing film, wherein the depth of the first crosslinking treatment tank is smaller than the depth of the staining treatment tank. The plurality of rolls include one or more guide rolls disposed in a first crosslinking treatment tank,
The manufacturing apparatus according to claim 1, wherein the one or more guide rolls are arranged such that the difference between the highest position and the lowest position of the transport path in the first crosslinking treatment tank is 500 mm or less. The plurality of rolls include two or more guide rolls disposed in a first crosslinking treatment tank,
The two or more guide rolls are two guide rolls adjacent to each other, and include two guide rolls arranged so that the holding angle of the polyvinyl alcohol resin film is 30 degrees or less in any of the guide rolls. The manufacturing apparatus according to claim 1. The plurality of rolls further include a first nip roll and a second nip roll as stretching means for performing the stretching process,
The first nip roll is disposed upstream of the transport path with respect to the two adjacent guide rolls.
The second nip roll is disposed downstream of the transport path with respect to the two adjacent guide rolls.
The first nip roll and the second nip roll each include two rolls disposed one above the other, and the upper ends of the lower rolls thereof are positioned lower than the upper end of the first crosslinking treatment tank, and the lower side The manufacturing apparatus according to claim 3, wherein the lower end of the roll is positioned higher than the lower end of the first crosslinking treatment tank. The processing tank further disposed on the downstream side of the transport path with respect to the first crosslinking treatment tank, further including a second crosslinking treatment tank for containing a second crosslinking treatment liquid,
The manufacturing apparatus according to any one of claims 1 to 4, wherein the depth of the second crosslinking treatment tank is smaller than the depth of the staining treatment tank.   The manufacturing apparatus according to any one of claims 1 to 5, wherein a length of the first crosslinking treatment tank in the transport route direction is longer than a length of the dyeing processing tank in the transport route direction. A method for producing a polarizing film from a polyvinyl alcohol resin film,
Immersing the polyvinyl alcohol-based resin film in a dyeing treatment tank containing a dyeing treatment solution;
A step of subjecting the polyvinyl alcohol-based resin film after the step of immersing in a dyeing treatment tank to a stretching treatment while immersing in a first crosslinking treatment tank containing the first crosslinking treatment liquid;
Including
The staining treatment tank and the first crosslinking treatment tank are disposed adjacent to each other,
The manufacturing method of a polarizing film whose depth of a 1st crosslinking treatment tank is smaller than the depth of a dyeing processing tank.

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