KR20190039001A - Method for manufacturing polarizing film and appartus for manufacturing polarizing film - Google Patents

Abstract

The present invention provides a method for stably and continuously manufacturing a polarizing film while suppressing adhesion, to the film, of a precipitate from a treatment liquid used for the wet treatment of a polyvinyl alcohol-based resin film. The present invention provides a method for manufacturing a polarizing film, which comprises the steps of immersing a polyvinyl alcohol-based resin film in a dyeing treatment tank containing a dyeing treatment liquid; immersing the polyvinyl alcohol-based resin film after the step of immersing in the dyeing treatment tank, in a cross-linking treatment tank containing a cross-linking treatment liquid; obtaining a liquid containing particles including the polyvinyl alcohol-based resin by imparting shear force to at least a part of the cross-linking treatment liquid withdrawn from the cross-linking treatment liquid in the cross-linking treatment tank; and removing the particles from the particle-containing liquid.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polarizing film,

The present invention relates to a polarizing film production method usable, for example, as a constituent member of a polarizing plate and an apparatus for producing a polarizing film.

As a polarizing film, a monoaxially stretched polyvinyl alcohol-based resin film is conventionally used in which a dichroic dye such as iodine is adsorbed and oriented. In general, a polarizing film is formed by sequentially performing a dyeing treatment for dyeing a polyvinyl alcohol-based resin film with a dichroic dye, a crosslinking treatment for treating with a crosslinking agent, and a film drying treatment, (For example, Japanese Patent Application Laid-Open No. 2001-141926 (Patent Document 1)).

Patent Document 1: Japanese Patent Application Laid-Open No. 2001-141926

Normally, the polarizing film is industrially made to carry out the above-described dyeing treatment on the conveying path while continuously conveying the elongated polyvinyl alcohol resin film along the conveying path of the film possessed by the apparatus for producing a polarizing film A dyeing treatment tank for carrying out a crosslinking treatment and a wet treatment treatment for sequentially immersing in a crosslinking treatment tank for carrying out a crosslinking treatment.

When the polarizing film is continuously produced according to the above method, the polyvinyl alcohol-based resin is gradually eluted into the treatment liquid for immersing the polyvinyl alcohol-based resin film. The eluted polyvinyl alcohol-based resin may be precipitated from the treatment liquid for some reason. When precipitation occurs, the precipitate is adhered to the surface of the polyvinyl alcohol-based resin film under wet processing, that is, the polarizing film, It can adversely affect the appearance and quality of the printed circuit board.

When the concentration of the polyvinyl alcohol-based resin eluted into the treatment liquid gradually increases, the surface of the polyvinyl alcohol-based resin film drawn out from the treatment liquid after immersed in the treatment liquid becomes solid May be precipitated. Such a precipitate may also adversely affect the appearance and quality of the polarizing film.

An object of the present invention is to provide a method and an apparatus capable of stably and continuously producing a polarizing film while suppressing the deposition of the precipitate on the film.

The present invention provides a method and an apparatus for producing a polarizing film described below.

[1] a step of immersing a polyvinyl alcohol-based resin film in a dyeing treatment tank containing a dyeing treatment liquid;

A step of immersing the polyvinyl alcohol-based resin film after the step of immersing in a dyeing treatment tank in a crosslinking treatment tank containing a crosslinking treatment liquid,

A step of applying a shearing force to at least a part of the crosslinking treatment liquid ejected from the crosslinking treatment liquid in the crosslinking treatment tank to obtain a particle containing liquid containing particles comprising a polyvinyl alcohol based resin,

A step of removing the particles from the particle-containing liquid

≪ / RTI >

[2] The production method according to [1], wherein the step of obtaining the particle-containing liquid includes a step of controlling the content of the particles or the particle diameter distribution of the particles in the particle-containing liquid.

[3] The manufacturing method according to [2], wherein the controlling step includes a step of cooling at least a part of the crosslinking treatment liquid.

[4] The production method according to [3], wherein a shearing force is applied to the at least part of the crosslinking treatment liquid after cooling or while cooling.

[5] The production method according to any one of [1] to [4], further comprising a step of returning at least a part of the liquid from which the particles have been removed to the crosslinking treatment tank.

[6] A dye for immersing a polyvinyl alcohol-based resin film, comprising a dyeing treatment tank for containing a dyeing treatment liquid,

As a tank for immersing a polyvinyl alcohol-based resin film immersed in a dyeing treatment tank, a crosslinking treatment tank for containing a crosslinking treatment liquid,

Shearing force imparting means for applying a shearing force to at least a part of the crosslinking treatment liquid withdrawn from the crosslinking treatment liquid in the crosslinking treatment tank to apply a shearing force to obtain a particle containing liquid containing particles comprising a polyvinyl alcohol based resin,

A particle removal apparatus for removing particles from a particle-

Polarizing film.

[7] The production apparatus according to [6], further comprising a cooling section for cooling at least a part of the crosslinking treatment liquid.

[8] The production apparatus according to [6] or [7], further comprising a circulation path for returning at least a part of the liquid from which the particles have been removed to the crosslinking treatment tank.

It is possible to provide a method and an apparatus capable of stably and continuously producing a polarizing film while suppressing adhesion of a precipitate containing a polyvinyl alcohol-based resin to a film.

1 is a schematic view showing an example of a polarizing film producing apparatus and a polarizing film producing method using the same.
Fig. 2 is a diagram showing the results of Experimental Example 1. Fig.
3 is a diagram showing the results of Experimental Example 2;

Hereinafter, the polarizing film producing method and the polarizing film producing apparatus will be described while showing the embodiments.

The present invention relates to a production method and apparatus for producing a polarizing film from a polyvinyl alcohol-based resin film (hereinafter also referred to as " PVA-based resin film "). The polarizing film is produced by subjecting a PVA resin film to a series of treatments including an immersion treatment (wet treatment) with a treatment tank, a drying treatment and the like.

In the polarizing film according to the present invention, the dichroic dye is adsorbed and oriented on the stretched PVA-based resin film.

Fig. 1 shows an example of a polarizing film producing apparatus according to the present invention. The polarizing film producing apparatus shown in FIG. 1 is an apparatus for continuously producing a long polarizing film 25 from a long PVA-based resin film 10 which is a raw film. Arrows in Fig. 1 indicate the transport direction of the film or the flow direction of the liquid.

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 and the dyeing treatment tank 15 are continuously fed while the PVA- , The crosslinking treatment tank 17 and the washing treatment tank 19 and finally passed through the drying furnace 21 to obtain a polarizing film 25 by drying treatment. The polarizing film 25 produced as the elongated product may be sequentially wound on the take-up roll 27 or may be formed by winding a thermoplastic resin film such as a protective film on one or both sides of the polarizing film 25 Or may be provided in a polarizing plate producing step for bonding.

The polarizing film producing apparatus includes a wet processing section including a swelling treatment tank 13, a dyeing treatment tank 15, a crosslinking treatment tank 17, and a cleaning treatment tank 19 And a drying treatment section such as a drying furnace 21 (zone for performing a drying treatment on the film after wet treatment).

The polarizing film producing apparatus shown in Fig. 1 has a conveying path of a PVA resin film 10 including a wet processing section and a drying processing section. By carrying the PVA resin film 10 along this conveyance path, a series of treatments including a wet treatment and a drying treatment are carried out to obtain the polarizing film 25.

The conveying speed of the PVA-based resin film 10 conveyed along the conveying 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 conveying path is constituted by a plurality of rolls for supporting and guiding the running film (the PVA resin film 10 and the polarizing film 25) so as to pass through the wet processing section and the drying processing section . The plurality of rolls may comprise a guide roll and / or a pair of rolls (usually including a drive roll) which is a pre-roll for supporting one side of the film, and the pair of rolls may be, for example, Lt; / RTI > In the example shown in Fig. 1, the polarizing film producing apparatus includes guide rolls 1a to 1l and nip rolls 2a to 2f. The plurality of rolls defining the transport path may include a suction roll (suction roll) which is one type of drive roll. Normally, all of these rolls contact the surface (main surface) of one or both sides of the film in the transport path to support the film. These rolls can be disposed at appropriate positions such as before and after each treatment tank and drying means (drying furnace), in the treatment bath, and in the drying means (drying furnace).

The drive roll is a roll capable of imparting a driving force for film transportation to a film contacting the film, and may be a roll directly or indirectly connected to a roll driving source such as a motor. The pre-roll refers to a roll capable of supporting a running film and being freely rotatable in accordance with the conveyance of the film.

A method for producing a polarizing film according to the present invention comprises the steps of:

(Step S101) of immersing the PVA resin film in a dyeing treatment tank containing a dyeing treatment liquid containing a dichroic dye,

(Step S102) of immersing the PVA resin film after the dyeing treatment step (S101) in a crosslinking treatment tank containing a crosslinking treatment liquid containing a crosslinking agent,

(Step S201) of obtaining a particle-containing liquid containing particles containing a polyvinyl alcohol-based resin by imparting a shearing force to at least a part of the crosslinking treatment liquid ejected from the crosslinking treatment liquid in the crosslinking treatment tank, And

A step of removing the particles from the particle-containing liquid (particle removing step (S202))

.

The obtained polarizing film 25 is a stretching treatment (usually uniaxially stretching treatment). For this reason, the apparatus for producing a polarizing film may include a stretching means (wet stretching means) of the PVA-based resin film 10, and a method for producing the polarizing film may be a stretching treatment step of the PVA- Treatment process).

(1) PVA-based resin film

The PVA resin film 10 (provided in the wet processing step) introduced into the wet processing section is a film composed of a polyvinyl alcohol-based resin (hereinafter also referred to as " PVA-based resin "). The PVA-based resin means a resin containing at least 50% by weight of constituent units derived from vinyl alcohol. As the PVA-based resin, a saponified polyvinyl acetate-based resin can be used. Examples of the polyvinyl acetate resin 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.

The term " (meth) acrylic " refers to at least one member selected from the group consisting of acrylic and methacrylic. The same applies to the term to which the other "(meta)" is added.

The degree of saponification of the PVA resin may be in the range of 80.0 to 100.0 mol%, preferably 90.0 to 100.0 mol%, more preferably 94.0 to 100.0 mol%, and still more preferably 98.0 to 100.0 mol% 100.0 mol%. When the degree of saponification is less than 80.0 mol%, the water resistance and the moisture resistance of the resultant polarizing film 25 and the polarizing plate including the polarizing film 25 may deteriorate.

Saponification degree, and the unit ratio (mol%) of the acetic acid group (acetoxy group: -OCOCH ₃ ) contained in the polyvinyl acetate resin as the raw material of the PVA resin to the hydroxyl group by the saponification process, :

Saponification degree (mol%) = 100 占 (number of hydroxyl groups) / (number of hydroxyl groups + number of acetic acid groups)

. The saponification degree can be obtained according to 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 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 a desired polarizing performance. When the average degree of polymerization is more than 10,000, the solubility in a solvent deteriorates and it is difficult to form the PVA resin film 10 .

An example of the PVA-based resin film 10 is an unstretched film obtained by film-forming the PVA-based resin. The membrane production 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 vertical uniaxial stretching. The longitudinal stretching means stretching in the machine direction (MD) of the film, that is, in the longitudinal direction of the film.

When the PVA-based resin film 10 (provided in the wet processing step) introduced into the wet processing section is a stretched film, this stretching is preferably dry stretching. Dry stretching refers to stretching performed in the air, and usually longitudinal uniaxial stretching.

As the dry stretching, thermal roll stretching in which a film is passed between a heat roll whose surface is heated and a guide roll (or a heat roll) whose main speed is different from that of the heat roll is subjected to longitudinal stretching under heating using a heat roll; Inter-roll stretching in which longitudinal stretching is performed by a main speed difference between these two nip rolls while passing heating means (oven or the like) between two nip rolls installed at a distance; Tenter stretching; Compression stretching, and the like.

The stretching temperature (surface temperature of the heat roll, temperature in the oven, etc.) is, for example, 80 to 150 占 폚, preferably 100 to 135 占 폚.

The drawing magnification of the drawing is usually from 1.1 to 8 times, preferably from 2.5 to 5 times, depending on whether wet drawing is to be carried out in the wet processing step described later and the drawing magnification in the wet drawing.

The PVA resin film 10 may contain an additive such as a plasticizer. Preferable examples of the plasticizer are polyhydric alcohols. Specific examples thereof include ethylene glycol, glycerin, propylene glycol, diethylene glycol, diglycerin, triethylene glycol, triglycerin, tetraethylene glycol, trimethylol propane and polyethylene glycol. The PVA resin film (10) may contain one or two or more plasticizers.

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-based resin film 10 introduced into the wet processing section (provided in the wet processing step) depends on whether the PVA-based resin film 10 is a drawn film, but is usually 10 to 150 탆, More preferably not more than 50 mu m, particularly preferably not more than 35 mu m (for example, not more than 30 mu m, further not more than 20 mu m )to be.

(2) Wet processing section and wet processing section

The wet treatment section is a zone disposed on the conveyance path of the PVA based resin film 10 and includes a treatment tank for containing the treatment liquid in which the PVA based resin film 10 is immersed. In this wet processing section, a wet processing step of immersing the PVA based resin film 10 in the treatment liquid while conveying the PVA based resin film 10 is carried out.

The wet processing section includes a dyeing treatment tank 15 and a crosslinking treatment tank 17 as the treatment tank and preferably further includes a swelling treatment tank 13 and a cleaning treatment tank 19 . These treatment vessels are usually arranged in the order of the swelling treatment tank 13, the dyeing treatment tank 15, the crosslinking treatment tank 17, and the cleaning treatment tank 19 in this order from the upstream side of the conveyance path ).

1 shows only one set of the swelling treatment tank 13, the dyeing treatment tank 15, the crosslinking treatment tank 17 and the cleaning treatment tank 19, Two or more sets of the crosslinking treatment tank 17 may be provided, or two or more sets of the crosslinking treatment tank 17 may be provided. The swelling treatment tank 13 and the cleaning treatment tank 19 are also the same, and two or more pairs may be provided.

(2-1) swelling treatment tank and swelling treatment process

The swelling treatment is carried out as necessary for the purpose of removing the PVA resin film 10, removing the plasticizer, imparting the dyeability, and plasticizing the film.

1, in the swelling treatment step, the PVA-based resin film 10 is continuously fed from the unwinding roll 11 while being conveyed along the film conveying path, and the PVA-based resin film 10 is fed to the swelling treatment liquid In a swelling treatment tank 13 for holding the slurry for a predetermined time, and then withdrawing it.

The treatment liquid (swelling treatment liquid) contained in the swelling treatment tank 13 may be, for example, water (pure water) or an aqueous solution to which a water-soluble organic solvent such as an alcohol is added. The swelling treatment liquid may contain boric acid, a chloride, an inorganic acid, an inorganic salt and the like.

The temperature of the swelling treatment liquid is usually 10 to 70 占 폚, preferably 15 to 50 占 폚, and more preferably 15 to 35 占 폚. The immersion time (residence time in the swelling treatment liquid) of the PVA resin film 10 is generally 10 to 600 seconds, preferably 15 to 300 seconds.

During the swelling treatment, the PVA resin film 10 may be subjected to a wet stretching treatment (usually uniaxial stretching treatment). In this case, the draw ratio is usually 1.2 to 3 times, preferably 1.3 to 2.5 times. Referring to Fig. 1, uniaxial stretching processing can be performed in the swelling treatment tank 13 by using, for example, the main speed difference between the nip roll 2a and the nip roll 2b.

In the example shown in Fig. 1, the film drawn out from the swelling treatment tank 13 is introduced into the dyeing treatment tank 15 through the guide roll 1c and the nip roll 2b in order.

(2-2) Dyeing treatment tank and dyeing treatment process (S101)

The dyeing treatment is carried out for the purpose of adsorbing and orienting the dichroic dye to the PVA resin film 10.

Referring to Fig. 1, the dyeing step (S101) can be carried out by conveying along the film conveying path, immersing the PVA resin film 10 in the dyeing treatment tank 15 for a predetermined time, and then withdrawing it. The dyeing treatment tank 15 is a tank for immersing the PVA-based resin film 10 in the dyeing solution contained therein. The PVA resin film 10 to be immersed in the dyeing treatment liquid is preferably a film after the swelling treatment step (immersed in the swelling treatment tank 13).

The dyeing solution contained in the dyeing treatment tank 15 is a solution (usually an aqueous solution) containing a dichroic dye. The dichroic dye may be iodine or a dichroic organic dye, preferably iodine. The dichroic dye may be used alone, or two or more dichroic dyes may be used in combination.

When iodine is used 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 in combination. Further, compounds other than iodide such as boric acid, zinc chloride, cobalt chloride, etc. may be coexistent. When boric acid is added, it is distinguished from the later-described crosslinking treatment solution in that it contains iodine. For example, if the aqueous solution contains about 0.003 part by weight or more of iodine per 100 parts by weight of water, it can be regarded as a dyeing treatment liquid. The content of iodine in the dyeing treatment 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 dyeing treatment liquid is usually 10 to 45 占 폚, preferably 10 to 40 占 폚, and more preferably 20 to 35 占 폚. 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.

As described above, the polarizing film producing apparatus can include two or more dye-treating baths 15. In this case, the composition and temperature of each dyeing treatment liquid may be the same or different.

In order to increase the dyeability of the dichroic dye, it is preferable that the PVA resin film 10 provided in the dyeing treatment is subjected to at least some degree of drawing 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 carried out while performing the dyeing treatment. The stretching magnification of the totalization up to the dyeing treatment (the stretching magnification in the dyeing treatment in the absence of a stretching step until dyeing treatment) is usually 1.6 to 4.5 times, preferably 1.8 to 4 times. Referring to Fig. 1, uniaxial stretching processing can be performed in the dyeing treatment tank 15 using, for example, the main speed difference between the nip roll 2b and the nip roll 2c.

In the example shown in Fig. 1, the film drawn out from the dyeing treatment tank 15 is introduced into the crosslinking treatment tank 17 through the guide roll 1f and the nip roll 2c in order.

(2-3) Cross-linking treatment tank and cross-linking treatment step (S102)

The crosslinking treatment is a treatment carried out for the purpose of water resistance and color adjustment by crosslinking.

1, the crosslinking treatment is carried out along the film conveying path, and the PVA resin film 10 after the dyeing treatment step (S101) (immersed in the dyeing treatment tank 15) is transferred to the crosslinking treatment tank 17, For a predetermined time, and then withdrawing it. The crosslinking treatment tank 17 is a tank for immersing the PVA-based resin film 10 in the crosslinking treatment liquid accommodated therein.

The crosslinking treatment liquid contained in the crosslinking treatment tank 17 is a liquid (usually an aqueous solution) containing a crosslinking agent. A crosslinking treatment is carried out by immersing the PVA resin film 10 after the dyeing treatment step (S101) in the crosslinking treatment liquid.

Examples of the crosslinking agent contained in the crosslinking treatment liquid include boric acid, glyoxal, glutaraldehyde and the like, preferably boric acid. Two or more crosslinking agents may be used in combination.

The content of the crosslinking agent in the crosslinking treatment liquid 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, it is preferable that the crosslinking treatment liquid contains iodide in addition to the crosslinking agent.

Examples of the iodide include potassium iodide and zinc iodide.

The content of iodide in the crosslinking treatment liquid is generally from 0.1 to 20 parts by weight, preferably from 5 to 15 parts by weight, per 100 parts by weight of water.

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

The temperature of the crosslinking treatment liquid is generally from 20 to 85 캜, preferably from 30 to 70 캜. The immersion time (residence time in the crosslinking solution) of the PVA resin film 10 is generally 10 to 600 seconds, preferably 20 to 300 seconds.

As described above, the polarizing film producing apparatus may include two or more crosslinking treatment tanks 17. In this case, the composition and temperature of each crosslinking treatment liquid may be the same or different. The crosslinking treatment liquid may have a concentration or temperature of a crosslinking agent and iodide depending on the purpose of immersing the PVA resin film 10. The crosslinking treatment for water resistance by crosslinking and the crosslinking treatment for color adjustment may be carried out by a plurality of steps, respectively.

(Usually, uniaxial stretching treatment) may be carried out while performing the crosslinking treatment. With reference to Fig. 1, uniaxial stretching treatment can be performed in the crosslinking treatment tank 17 by using, for example, the main speed difference between the nip roll 2c and the nip roll 2d.

In the example shown in Fig. 1, the film drawn out of the crosslinking treatment tank 17 is introduced into the washing treatment tank 19 through the guide roll 1i and the nip roll 2d in order.

(2-4) Cleaning treatment tank and cleaning treatment process

The polarizing film producing apparatus may further include a washing treatment step after the crosslinking treatment step (S102). Therefore, the polarizing film producing apparatus includes the cleaning treatment tank 19 disposed on the downstream side of the crosslinking treatment tank 17, As shown in FIG. The cleaning treatment is carried out for the purpose of removing an extra medicine attached to the PVA resin film 10 after the crosslinking treatment step (S102).

1, the cleaning process is carried out along the film transport path, and the PVA resin film 10 after the cross-linking process (S102) (immersed in the cross-linking treatment tank 17) For a predetermined time, and then withdrawing it. The cleaning treatment may be performed by spraying the cleaning liquid onto the PVA resin film 10 after the crosslinking treatment step (S102), for example, as a shower, or by combining the immersion into the cleaning treatment tank 19 and the spraying of the cleaning liquid good. Fig. 1 shows an example in which the PVA resin film 10 is immersed in a cleaning treatment tank 19 to perform a cleaning treatment.

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

A stretching treatment (usually, uniaxial stretching treatment) may be carried out while performing a washing treatment. With reference to Fig. 1, uniaxial stretching treatment can be performed in the cleaning treatment tank 19 using, for example, the main speed difference between the nip roll 2d and the nip roll 2e.

(2-5) Stretching Means and Stretching Process

The PVA resin film 10 may be subjected to wet drawing in the wet treatment process. The wet stretching is usually a uniaxial stretching and can be carried out while performing any one of the swelling treatment, the dyeing treatment, the crosslinking treatment and the cleaning treatment, or during two or more treatments selected therefrom.

The wet stretching may preferably be performed in one or two or more steps before or during the cross-linking treatment step (S102). As described above, in order to obtain the polarizing film 25 having a good polarizing property by increasing the dyeability of the dichroic dye, the PVA resin film 10 provided in the dyeing process S101 is subjected to a stretching process at least to some extent Is more preferable.

The stretching magnification of the wet stretching is preferably such that the polarizing film 25 has a final cumulative stretching magnification (the PVA-based resin film 10 provided for the wet treatment is stretched In the case of a film, the cumulative stretching magnification including this stretching] is adjusted to be 3 to 8 times.

In the case of carrying out the wet stretching treatment step, the polarizing film producing apparatus includes the wet stretching means of the PVA based resin film 10. The wet stretching means is preferably stretching means for performing inter-roll stretching. As an example of the case where the roll-to-roll stretching is performed in the crosslinking treatment step (S102) as an example, the stretching means for performing inter-roll stretching is two nip rolls 2c and 2d disposed before and after the crosslinking treatment tank 17. Likewise, two nip rolls spaced apart can be used as the wet stretching means in the case of stretching in another wet process.

(3) Drying process and drying process

The drying processing section is a zone for drying the PVA based resin film 10 after the wet processing step, which is disposed on the downstream side of the wet processing section on the conveyance path of the PVA based resin film 10. The PVA resin film 10 after the wet treatment process is continuously conveyed, and the film is introduced into the drying treatment section, whereby the drying treatment can be carried out, whereby the polarizing film 25 can be obtained (see Fig. 1).

The drying treatment section includes drying means (heating means) of the film. A suitable example of drying means is a drying oven. The drying furnace is preferably capable of controlling the temperature in the furnace. The drying furnace is a hot air oven capable of raising the temperature in the furnace by supplying hot air or the like. The drying treatment by the drying means may be a treatment of bringing the PVA resin film 10 after the wet treatment process into contact with one or more heating bodies having convex curved surfaces, or a process of heating the film by using a heater.

As the heating body, there can be mentioned a roll (for example, a guide roll which also serves as a heat roll) capable of raising the surface temperature by providing a heat source (for example, a heating medium such as hot water or an infrared heater) inside. Examples of the heater include an infrared heater, a halogen heater, and a panel heater. Fig. 1 shows an example in which the PVA resin film 10 after the wet treatment process is introduced into the drying furnace 21 and subjected to a drying treatment.

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 占 폚, preferably 50 to 90 占 폚.

The polarizing film 25 is such that a dichroic dye is adsorbed and oriented on a stretched (usually uniaxially stretched) PVA resin film. The thickness of the polarizing film 25 is usually 2 to 40 占 퐉. From the viewpoint of thinning of the polarizing plate including the polarizing film 25, the thickness of the polarizing film 25 is preferably 20 占 퐉 or less, more preferably 15 占 퐉 or less, and further preferably 10 占 퐉 or less.

The visible light transmittance corrected by the visible light transmittance Ty of the obtained polarizing film 25 is preferably 40 to 47% and more preferably 41 to 45% in consideration of the balance with the visual sensitivity correction polarization degree Py. The visual sensitivity correction degree of polarization Py is preferably 99.9% or more, and more preferably 99.95% or more.

Ty and Py can be measured by using a spectrophotometer having an integrating sphere and by performing visibility correction using the two-view field (C light source) of JIS Z 8701 for the obtained transmittance and polarization degree.

The obtained polarizing film 25 may be wound in turn on the take-up roll 27 to form a roll, and the polarizing film 25 may be directly wound on one side or both sides of the polarizing film 25 And the like) can be provided.

(4) Production and removal of particles containing a polyvinyl alcohol-based resin

A method of producing a polarizing film according to the present invention comprises:

A step of obtaining a particle-containing liquid containing particles containing a polyvinyl alcohol-based resin by applying a shearing force to at least a part of the crosslinking treatment liquid ejected from the crosslinking treatment liquid in the crosslinking treatment tank 17 )], And

A step of removing the particles from the particle-containing liquid (particle removing step (S202))

.

Therefore, in the polarizing film producing apparatus according to the present invention,

A shearing force imparting portion for imparting a shearing force to at least a part of the crosslinking treatment liquid ejected from the crosslinking treatment liquid in the crosslinking treatment tank 17 to give a shearing force for obtaining a particle containing liquid containing particles comprising a polyvinyl alcohol resin,

A particle removal apparatus for removing particles from a particle-

.

Fig. 1 is a schematic diagram showing an example of a polarizing film producing apparatus in which a shearing force applying section and a particle removing section are provided in a crosslinking treatment tank 17 and a polarizing film producing method using the same.

The polarizing film producing apparatus shown in Fig. 1 comprises a cooling section 30 connected to the crosslinking treatment tank 17 for cooling at least a part of the crosslinking treatment liquid withdrawn from the crosslinking treatment liquid in the crosslinking treatment tank 17; A shearing force imparting unit (40) connected to the cooling unit (30) for applying a shearing force to at least a part of the crosslinking treatment liquid after cooling to obtain the particle containing liquid; And a particle removing unit (50) connected to the shearing force imparting unit (40) for removing the particles from the particle containing liquid.

The cross-linking treatment tank 17 and the cooling section 30 are connected by a connection line (connection line) 28. The cooling section 30 and the shear force imparting section 40 are connected to each other via a connection line 29, and the shearing force imparting unit 40 and the particle removing unit 50 are connected to each other by a connection path (connection line) 41.

The concentration of the polyvinyl alcohol resin in the crosslinking solution discharged from the crosslinking treatment tank 17 may be, for example, about 5 ppm to 5000 ppm on the basis of weight.

In the method for producing a polarizing film using the polarizing film producing apparatus shown in Fig. 1, at first, at least a part of the crosslinking treatment liquid is taken out from the crosslinking treatment tank 17 through the connecting path (connecting line) 28, The crosslinking treatment liquid is cooled in the cooling section 30 (cooling step). A part of the particles may be precipitated from the crosslinking treatment liquid by cooling. The temperature of the crosslinking treatment liquid after cooling is, for example, 0 to 60 캜, preferably 10 to 40 캜.

The cooling unit 30 may be a known means, for example, a chamber (or a tank) having a cooling means such as a jacket capable of introducing a coolant, a heat exchanger, a connection line (cooling line, cooling piping) or the like. The cooling unit 30 preferably has a connection line (a cooling line, a cooling line, and a cooling line) having cooling means in that the crosslinking treatment liquid after cooling can be derived continuously while cooling the introduced crosslinking treatment liquid continuously. )to be.

The cooling section 30 is an arbitrary part, and there is no need to provide the cooling section 30 depending on the temperature of the crosslinking treatment liquid in the crosslinking treatment tank 17. [

In the method for producing a polarizing film using the polarizing film producing apparatus shown in Fig. 1, the crosslinking treatment liquid after cooling is introduced into the shearing force imparting unit 40 to impart a shearing force, Thereby generating particles (particle production step (S201)). The particles to be precipitated may further contain, in addition to the polyvinyl alcohol-based resin, a crosslinking agent or iodide contained in the crosslinking treatment liquid.

The shearing force imparting unit 40 may be, for example, a chamber (or a set) having a shear force applying means or a connecting path (line, piping) or the like. The shearing force imparting unit 40 preferably has a shear force applying unit 40 in that the shearing force is continuously applied to the crosslinking treatment liquid introduced into the shearing force imparting unit 40 while continuously applying the shearing force, (Line, piping) having the providing means.

As the shearing force applying means, for example, a stirring blade; A convection generating means for generating convection in the liquid according to a method such as a method of drawing a liquid by rotation or the like of a member such as a general homomixer; An impact applying means such as a protruding portion and a baffle protruding into the space through which the liquid passes; A high frequency generating means; Ultrasonic wave generating means; And combinations of two or more of them.

The shearing force applied to the crosslinking treatment liquid is preferably 40 to 350 Pa, more preferably 50 to 260 Pa. By setting the shearing force applied to the crosslinking treatment liquid within this range, it is possible to effectively deposit particles (particles containing a polyvinyl alcohol resin), and further to perform separation and separation at the time of solid-liquid separation in the particle removing step (S202) It is easy to control with easy particle diameter. When a shearing force is applied to the liquid by rotation of a member such as a stirring blade, the shearing force applied to the crosslinking treatment liquid can be calculated according to the following formula.

Shear force [Pa] = Cross-linking solution viscosity [mPa · s] × Number of stirrer revolutions [rpm] × 0.001 × 60

In the above formula, the viscosity of the crosslinking treatment liquid is usually from 0.65 to 1.20 mPa s at a liquid temperature of 10 to 40 캜.

In the polarizing film producing apparatus shown in Fig. 1, the shearing force imparting unit 40 is disposed behind the cooling unit 30, but the shearing force imparting unit 40 may include the cooling unit 30. Fig. Thereby, in the particle producing step (S201), the crosslinking treatment liquid can be given a shearing force while being cooled.

The particle generation step (S201) preferably includes a step of controlling the content of the particles in the resulting particle-containing liquid or the particle diameter distribution of the particles (control step). By controlling the content of the particles or the particle size distribution of the particles, it is possible to improve the removal efficiency of the particles and the operability of the particle removing step (S202) described later.

An example of the control process is the above-described cooling process (process of controlling the temperature of the crosslinking solution). By applying a shearing force to the crosslinking treatment liquid after cooling or while cooling, the precipitation amount of the particles can be increased.

Other examples of the control process include a process of controlling the application time of the shearing force, a process of controlling the size of the shearing force, and a flow rate of the crosslinking solution passing through the shearing force imparting device 40. [ The temperature of the crosslinking treatment liquid to which the shearing force is applied, the application time of the shearing force, the magnitude of the shearing force, the flow rate of the crosslinking treatment liquid passing through the shearing force imparting unit 40, The precipitation amount of the particles) and the particle diameter distribution (particle diameter of the particles) of the particles can be adjusted.

After the particle containing liquid is obtained in the particle generating step (S201), the particles precipitated from the particle containing liquid are removed (particle removing step (S202)). By this step, a liquid from which the precipitated particles have been removed (a crosslinked treatment liquid from which particles have been removed) is obtained.

The polarizing film producing apparatus includes a particle removing unit 50 for removing the particles from the particle containing liquid.

A step of cooling the particle containing liquid may be provided after the particle producing step (S201) before the particle removing step (S202). In this case, the polarizing film producing apparatus may be provided with a shearing force applying part (40) (50), a cooling section for cooling the particle-containing liquid is further provided.

As the particle removing unit 50, a known solid-liquid separating unit such as a filter may be used.

The polarizing film manufacturing method further includes a step of returning at least a part of the crosslinking treatment liquid from which the particles have been removed to the crosslinking treatment tank 17, so that the amount of the polyvinyl alcohol based crosslinking treatment solution in the crosslinking treatment tank 17 The concentration of the resin can be reduced or maintained to such a low concentration as not to precipitate in the crosslinking treatment tank 17 that the precipitate precipitated in the crosslinking treatment tank 17 is a PVA based resin film during the wet treatment, The problem of sticking to the surface of the polarizing film can be suppressed.

When the polarizing film manufacturing method further includes a step of returning at least a part of the crosslinking treatment liquid from which the particles have been removed to the crosslinking treatment tank 17, the polarizing film producing apparatus includes at least a part To return to the cross-linking treatment tank (17). The circulation path 51 is a connection path for connecting the particle removing unit 50 and the crosslinking treatment tank 17.

An operation of extracting at least a portion of the crosslinking treatment liquid from the crosslinking treatment tank 17 and performing treatment on the resulting crosslinking treatment liquid and returning at least a part of the liquid obtained by the treatment to the crosslinking treatment tank 17 , A pump, or the like.

At least a part of the crosslinking treatment liquid from which the particles are removed is returned to the crosslinking treatment tank 17 or at least a part of the crosslinking treatment liquid from which the particles have been removed The crosslinking treatment liquid may be added to the crosslinking treatment tank 17 at a timing different from the timing of returning the crosslinking treatment tank 17 to the crosslinking treatment tank 17.

When the polarizing film producing apparatus includes two or more crosslinking treatment tanks 17, the shearing force imparting unit 40 and the particle removing unit 50 (and the cooling unit if necessary) 17, or may be provided in two or more or all the crosslinking treatment tanks 17. Preferably, the shearing force imparting unit 40 and the particle removing unit 50 (and the cooling unit provided as needed) are provided at least in a cross-linking treatment tank in which precipitation of the polyvinyl alcohol-based resin in the cross- 17. As the crosslinking treatment tank 17, for example, there can be mentioned a crosslinking treatment tank in which the temperature of the crosslinking treatment liquid is relatively higher than that of the other crosslinking treatment tank.

(5) Experimental Example 1: Production of particles using homodisperse

Using the polarizing film producing apparatus shown in Fig. 1, a polarizing film 25 was continuously produced from a long polyvinyl alcohol film. The polyvinyl alcohol film used was a polyvinyl alcohol film having a thickness of 30 탆 which was uniaxially stretched 4.1 times in a dry state. The polyvinyl alcohol constituting the film had a saponification degree of 99.9 mol% or more and an average degree of polymerization of 2,400.

While the polyvinyl alcohol film 10 was unwound from the unwinding roll 11, the film was continuously conveyed while being stretched under tension, and immersed in a swelling treatment tank 13 containing pure water at 40 DEG C for a retention time of 60 seconds To swell the polyvinyl alcohol film 10 (swelling processing step). The film drawn out from the swelling treatment tank 13 was immersed in a dyeing treatment tank 15 containing a dyeing treatment liquid of 30 DEG C having a weight ratio of iodine / potassium iodide / water of 0.1 / 6/100 for a retention time of 60 seconds, In the meantime, uniaxial stretching (roll-to-roll stretching in a bath) was performed (dyeing step). The film drawn out from the dyeing treatment tank 15 was immersed in a crosslinking treatment tank 17 containing a crosslinking treatment liquid of 68 ° C having a weight ratio of 15 / 5.5 / 100 of potassium iodide / boric acid / water at a retention time of 130 seconds, In the meantime, uniaxial stretching (roll-to-roll stretching in a bath) was carried out (crosslinking step). The film drawn out from the crosslinking treatment tank 17 was immersed in a cleaning treatment tank 19 containing pure water at 20 캜 for a retention time of 3 seconds to perform cleaning (cleaning treatment step). The cumulative stretching ratio based on the polyvinyl alcohol film before dry uniaxial stretching was 4.5 times.

The crosslinking treatment liquid was sampled from the crosslinking treatment tank 17 after continuous production of the polarizing film, and the following particle precipitation experiment was carried out. The polyvinyl alcohol concentration in the cross-linking treatment liquid sampled was measured by GPC (gel permeation chromatography) and found to be about 1500 ppm by weight.

The sampled crosslinking treatment liquid was placed in a homodisper (homodisperter 2.5 type (blade type), capacity 800 mL) manufactured by Primix Co., and a shearing force was applied to the crosslinking treatment liquid under the following conditions to give polyvinyl alcohol To obtain a particle-containing liquid containing solid particles.

Temperature: 14 ° C, 29 ° C, 39 ° C 3 conditions

The number of revolutions of the stirring wing: 1000 rpm, 2 conditions of 5000 rpm

Treatment time by homo dispenser: 10 minutes

The measurement results of the particle diameter distribution of the obtained solid particles are shown in Fig. The abscissa represents the particle diameter of the solid particles produced, and the ordinate axis (the number of the detected particles) corresponds to the number of solid particles. The particle diameter distribution of the solid particles shown in Fig. 2 is the result of measurement using a liquid particle counter ("light-shielding particle detector (KS-42D)" manufactured by RION Co., Ltd.) for the obtained particle containing liquid The same applies to the particle diameter distribution of the solid particles shown in Fig.

(6) Experimental Example 2: Production of particles using a homomixer

To give a shearing force to the cross-linking treatment liquid, a homomixer (homomixer 2.5 type (cylindrical type), capacity 800 mL) manufactured by FRIMICS Co., Ltd. was used in place of the homodisperser, A particle-containing liquid containing solid particles containing polyvinyl alcohol was obtained in the same manner as in Experimental Example 1 except that a shear force was applied.

The measurement results of the particle diameter distribution of the obtained solid particles are shown in Fig.

Temperature: 14 ° C, 29 ° C, 39 ° C 3 conditions

The number of revolutions of the inner blade of the homomixer: 1000 rpm, 2 conditions of 5000 rpm

Treatment time by homodisperse: 10 seconds, 1 minute, 3/10 condition

1b, 1c, 1d, 1e, 1f, 1g, 1h, 1i, 1j, 1k,
2a, 2b, 2c, 2d, 2e, 2f:
10: Polyvinyl alcohol based resin film (PVA based resin film)
11: unwinding roll
13: swelling treatment tank
15: Dyeing treatment tank
17: Cross-linking treatment tank
19: Cleaning treatment tank
21: drying furnace
25: polarizing film
27: Winding roll
28, 29: Connection path
30: cooling section
40: Shearing force
41:
50: Particle removal
51: circulation path

Claims (8)

A step of immersing a polyvinyl alcohol based resin film in a dyeing treatment tank containing a dyeing treatment liquid,
A step of immersing the polyvinyl alcohol-based resin film after the step of immersing in a dyeing treatment tank in a crosslinking treatment tank containing a crosslinking treatment liquid,
A step of applying a shearing force to at least a part of the crosslinking treatment liquid ejected from the crosslinking treatment liquid in the crosslinking treatment tank to obtain a particle containing liquid containing particles comprising a polyvinyl alcohol based resin,
A step of removing the particles from the particle-containing liquid
≪ / RTI > The production method according to claim 1, wherein the step of obtaining the particle-containing liquid includes a step of controlling the content of the particles in the particle-containing liquid or the particle size distribution of the particles. The manufacturing method according to claim 2, wherein the controlling step includes a step of cooling at least a part of the crosslinking treatment liquid. The production method according to claim 3, wherein a shearing force is applied to the at least a part of the crosslinking treatment liquid after cooling or while cooling. The production method according to any one of claims 1 to 4, further comprising the step of returning at least a part of the liquid from which the particles have been removed to the crosslinking treatment tank. A dyeing bath for immersing a polyvinyl alcohol-based resin film, comprising: a dyeing tank for containing a dyeing solution;
As a tank for immersing a polyvinyl alcohol-based resin film immersed in a dyeing treatment tank, a crosslinking treatment tank for containing a crosslinking treatment liquid,
Shearing force imparting means for applying a shearing force to at least a part of the crosslinking treatment liquid withdrawn from the crosslinking treatment liquid in the crosslinking treatment tank to apply a shearing force to obtain a particle containing liquid containing particles comprising a polyvinyl alcohol based resin,
A particle removal apparatus for removing particles from a particle-
Polarizing film. The manufacturing apparatus according to claim 6, further comprising a cooling section for cooling at least a part of the crosslinking treatment liquid. The manufacturing apparatus according to claim 6 or 7, further comprising a circulation path for returning at least a part of the liquid from which the particles have been removed to the crosslinking treatment tank.

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