KR20180020894A - Process for producing polarizing film and apparatus for producing polarizing film - Google Patents

Abstract

The present invention provides a process for producing a polarizing film to obtain a polarizing film with excellent optical characteristics and durability and an apparatus for producing a polarizing film. According to the present invention, the process for producing a polarizing film produces a polarizing film from a polyvinyl alcohol resin film, and comprises: a dyeing process of dyeing and treating the polyvinyl alcohol resin film with a dichromatic pigment; a cross-linking process of cross-linking and treating the polyvinyl alcohol resin film with a cross-linking agent after the dyeing process; an electromagnetic wave irradiation process of irradiating an electromagnetic wave containing infrared light to the polyvinyl alcohol resin film after the cross-linking process; and a high humidity treatment process of exposing the polyvinyl alcohol resin film to an environment more than 80 g/m^3 of absolute humidity after irradiating the electromagnetic wave.

Description

TECHNICAL FIELD [0001] The present invention relates to a polarizing film,

The present invention relates to a method and an apparatus for producing a polarizing film from a polyvinyl alcohol-based resin film.

The polarizing plate is widely used as a polarizing element or the like in an image display apparatus such as a liquid crystal display apparatus. As the polarizing plate, a polarizing film is generally formed by bonding a transparent resin film (protective film or the like) to one or both sides of a polarizing film by using an adhesive or the like.

The polarizing film is mainly made by immersing the original film made of a polyvinyl alcohol resin in a dyeing bath containing a dichroic dye such as iodine or the like and subsequently immersing the film in a crosslinking bath containing a crosslinking agent such as boric acid And uniaxially stretching the film at a certain stage. Uniaxial stretching includes wet stretching in which stretching is performed in air, and stretching in a liquid such as a dyeing bath and a crosslinking bath.

Since the polarizing film is crosslinked, it tends to shrink when it is heated, resulting in insufficient durability. In addition, if the stretching magnification is increased to improve the optical characteristics, the film tends to shrink and the durability may not be sufficient. Japanese Patent Application Laid-Open No. 2013-148806 (Patent Document 1) discloses that a boron content is as low as 1 to 3.5 wt%, and a polarizing film having excellent durability is provided.

Patent Document 1: JP-A-2013-148806

However, in the polarizing film, if the boron content is reduced, a sufficient degree of crosslinking can not be obtained, and the optical characteristics may be lowered. An object of the present invention is to provide a method for producing a polarizing film and a method for producing the same that can obtain a polarizing film excellent in both optical characteristics and durability in a polarizing film producing method.

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

[1] A method for producing a polarizing film from a polyvinyl alcohol-based resin film,

A dyeing step of dyeing the polyvinyl alcohol-based resin film with a dichroic dye,

A cross-linking step of cross-linking the polyvinyl alcohol-based resin film after the dyeing step with a cross-

An electromagnetic wave irradiation step of irradiating the polyvinyl alcohol based resin film after the crosslinking step with an electromagnetic wave including infrared rays;

And a high-humidity treatment step of exposing the polyvinyl alcohol-based resin film after irradiating the electromagnetic wave to an atmosphere having an absolute humidity of 80 g / m 3 or more.

[2] The method for producing a polarizing film according to [1], further comprising a cleaning step of cleaning the polyvinyl alcohol based resin film between the electromagnetic wave irradiation step and the high moisture treatment step.

[3] In the electromagnetic wave irradiating step, the electromagnetic wave is a polarizing film according to [1] or [2], wherein the ratio of the radiant energy of infrared rays having a wavelength of more than 2 탆 and not more than 4 탆 is not less than 25% Gt;

[4] The method according to any one of [1] to [3], wherein the irradiation energy of the electromagnetic wave in the electromagnetic wave irradiation step is 100 J / cm3 or more and 50 kJ / cm3 or less per unit volume of the polyvinyl alcohol- ≪ / RTI >

[5] The method for producing a polarizing film according to any one of [1] to [4], wherein the polyvinyl alcohol-based resin film is uniaxially stretched at 1.04 to 1.2 times in the high-humidity treatment step.

[6] A production apparatus for producing a polarizing film from a polyvinyl alcohol-based resin film,

A dyeing section for dyeing the polyvinyl alcohol-based resin film with a dichroic dye,

A cross-linking portion for cross-linking the polyvinyl alcohol-based resin film after the dyeing treatment with a cross-linking agent,

An electromagnetic wave irradiating section for irradiating the crosslinked polyvinyl alcohol resin film with an electromagnetic wave including infrared rays;

And a high-humidity treatment section for exposing the polyvinyl alcohol-based resin film after irradiating the electromagnetic wave to an atmosphere having an absolute humidity of 80 g / m 3 or more.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a polarizing film producing method and apparatus capable of obtaining a polarizing film excellent in optical characteristics and durability.

1 is a cross-sectional view schematically showing an example of a polarizing film producing method and a polarizing film producing apparatus used therefor according to the present invention.
Fig. 2 is a view showing a radiant energy spectrum for each type of electromagnetic wave irradiator.

≪ Polarizing Film Production Method >

In the polarizing film of the present invention, a dichroic dye (iodine or a dichroic dye) is adsorbed and oriented on a uniaxially stretched polyvinyl alcohol resin film. The polyvinyl alcohol-based resin constituting the polyvinyl alcohol-based resin film is usually obtained by saponifying a polyvinyl acetate-based resin. The saponification degree is usually at least about 85 mol%, preferably at least about 90 mol%, more preferably at least about 99 mol%. The polyvinyl acetate resin may be, for example, a polyvinyl acetate which is a homopolymer of vinyl acetate, a copolymer of vinyl acetate and other monomers copolymerizable therewith, and the like. Examples of other copolymerizable monomers include unsaturated carboxylic acids, olefins, vinyl ethers, and unsaturated sulfonic acids. The polymerization degree of the polyvinyl alcohol-based resin is usually about 1000 to 10000, and preferably about 1500 to 5000.

These polyvinyl alcohol resins may be modified, and examples thereof include polyvinyl formal modified with aldehydes, polyvinyl acetal, polyvinyl butyral, and the like.

In the present invention, as a starting material for polarizing film production, an unoriented polyvinyl (meth) acrylate having a thickness of 65 占 퐉 or less (for example, 60 占 퐉 or less), preferably 50 占 퐉 or less, more preferably 35 占 퐉 or less, Alcohol-based resin film (original film) is used.

As a result, a polarizing film of a thin film, which is increasingly in demand in the market, can be obtained. The width of the original film is not particularly limited, and may be, for example, about 400 to 6000 mm. The original film is prepared, for example, as a roll (disk roll) of a long unoriented polyvinyl alcohol based resin film.

The polyvinyl alcohol-based resin film used in the present invention may be laminated on a base film supporting the polyvinyl alcohol-based resin film. That is, the polyvinyl alcohol-based resin film may include a base film and a polyvinyl alcohol-based resin film May be prepared as a laminated film. In this case, the polyvinyl alcohol-based resin film can be produced, for example, by coating a coating solution containing a polyvinyl alcohol-based resin on at least one surface of a base film and then drying it.

As the base film, for example, a film made of a thermoplastic resin can be used. Specific examples thereof include a film made of a light-transmitting thermoplastic resin, preferably an optically transparent thermoplastic resin, such as a film-like polyolefin resin (polypropylene resin), a cyclic polyolefin resin (norbornene resin, etc.) Polyolefin resin; Cellulose-based resins such as triacetylcellulose and diacetylcellulose; Polyester-based resins such as polyethylene terephthalate and polybutylene terephthalate; Polycarbonate resin; (Meth) acrylic resins such as methyl methacrylate resins; Polystyrene type resin; Polyvinyl chloride resins; Acrylonitrile-butadiene-styrene-based resin; Acrylonitrile-styrene series resin; Polyvinyl acetate resin; Polyvinylidene chloride resins; Polyamide based resin; A polyacetal-based resin; Modified polyphenylene ether-based resin; Polysulfone resins; Polyether sulfone type resin; Polyarylate resins; Polyamideimide series resin; A polyimide-based resin, or the like.

The polarizing film is continuously transported along the film transport path of the polarizing film producing apparatus while being unwound from the master roll, and is immersed in the processing liquid (hereinafter also referred to as " processing bath " The film can be continuously produced as a long polarizing film by carrying out a drying process after carrying out a predetermined process for drawing out. Here, the treatment step is not limited to the method in which the film is immersed in the treatment bath if the treatment is conducted by bringing the treatment solution into contact with the film, and a method of treating the film by adhering the treatment solution to the film surface by spraying, . In the case where the treatment process is performed by a method in which the film is immersed in a treatment bath, the treatment bath for performing one treatment process is not limited to one, and one process may be completed by sequentially immersing the film in two or more treatment baths .

Examples of the treatment liquid include a swelling liquid, a staining liquid, a crosslinking liquid, a cleaning liquid and the like. Examples of the processing steps include a swelling step of swelling the original film by bringing the swelled liquid into contact with the original film, a dyeing step of performing a dyeing treatment by bringing the dye after contact with the swelled film into contact with the film, A cross-linking step of carrying out a cross-linking treatment, and a cleaning step of carrying out a cleaning treatment by bringing a cleaning liquid into contact with the film after the cross-linking treatment. In addition, uniaxial stretching treatment is carried out either wet or dry during these series of treatment steps (that is, before and / or after any one or more treatment steps). Other treatment steps may be added as necessary.

In the present invention, after the crosslinking treatment, an electromagnetic wave irradiation step of irradiating the film with an electromagnetic wave including infrared rays is performed. After the electromagnetic wave irradiation step, the film is subjected to a high-humidity treatment step in which the film is exposed to an atmosphere having an absolute humidity of 80 g / m < 3 > By having these two processes, the optical characteristics of the resulting polarizing film can be further improved and the shrinking force can be further suppressed. The shrinkage force can be suppressed, and a polarizing film having excellent durability can be obtained.

Hereinafter, an example of a method for producing a polarizing film according to the present invention will be described in detail with reference to FIG. 1 is a cross-sectional view schematically showing an example of a polarizing film producing method and a polarizing film producing apparatus used therefor according to the present invention. The polarizing film producing apparatus shown in Fig. 1 is configured such that an original (non-stretchable) film 10 made of a polyvinyl alcohol-based resin is conveyed along a film conveying path while being continuously unwound from the original roll 11, (Swelling liquid contained in the swelling bath) 13, a dyeing bath (dyeing solution contained in the dyeing bath) 15, a first crosslinking bath (the first crosslinking liquid contained in the crosslinking bath) 17a, (Second bridging solution) 17b contained in a crosslinking bath (a second crosslinking solution contained in the crosslinking bath) and a cleansing bath (a cleansing solution contained in the cleansing bath) 19 to pass through the high-humidity treatment section 21 for performing the high-humidity treatment . Further, in order to further adjust the moisture percentage of the film that has passed through the high-humidity treatment section 21, it may be passed through a drying furnace (not shown). The obtained polarizing film 23 can be conveyed as it is, for example, in the next polarizing plate producing step (a step of bonding a protective film to one side or both sides of the polarizing film 23). The arrows in Fig. 1 indicate the transport direction of the film.

In the description of Fig. 1, the term " treatment tank " is a general term including a swelling bath, a dye bath, a crosslinking tank and a washing tank, and the term " treatment liquid " is a generic term including a swollen liquid, Treatment bath " is a generic term including a swelling bath, a dyeing bath, a crosslinking bath, and a cleansing bath. The swelling bath, the dyeing bath, the crosslinking bath and the cleansing bath constitute a swelling portion, a dyeing portion, a crosslinking portion and a cleansing portion in the production apparatus of the present invention.

The film transport path of the polarizing film producing apparatus includes, in addition to the above treatment bath, guide rolls 30 to 48, 60 and 61 which support the film to be transported or which can further change the film transport direction, And the nip rolls 50 to 55 capable of changing the film transport direction can be disposed at appropriate positions. The guide rolls and nip rolls can be disposed before or after each treatment bath and the treatment bath, whereby the introduction and immersion of the film in the treatment bath and the withdrawal from the treatment bath can be performed (see Fig. 1). For example, one or more guide rolls may be provided in each treatment bath, and the film may be transported along these guide rolls to immerse the film in each treatment bath.

1, nip rolls (nip rolls 50 to 54) are arranged before and after each treatment bath, and thus, in any one or more treatment baths, a nip roll It is possible to carry out roll-to-roll stretching in which longitudinally uniaxial stretching is carried out by attaching a main speed difference (circumferential speed difference) therebetween.

In the polarizing film producing apparatus shown in Fig. 1, an electromagnetic wave irradiating section 71 is disposed downstream of the second crosslinking bath 17b and on the conveying path upstream of the cleansing bath 19, and an electromagnetic wave irradiating step is performed. Further, the high-humidity treatment section 21 is disposed on the conveyance path downstream of the cleansing bath 19, and the high-humidity treatment process is performed. Each step will be described below.

(Swelling process)

The swelling process is performed for the purpose of removing foreign substances on the surface of the original film 10, removing the plasticizer in the original film 10, imparting this coloring property, plasticizing the original film 10, and the like. The processing conditions are determined within a range that can achieve the object and within a range that does not cause problems such as extreme dissolution of the original film 10 and loss of transparency.

1, in the swelling step, the original film 10 is conveyed along the film conveying path while continuously winding the original film 10 from the original roll 11, and the original film 10 is immersed in the swelling bath 13 for a predetermined time And then withdrawing it. 1, the original film 10 is held by the guide rolls 60, 61 and the nip roll 50 until the original film 10 is unwound and then immersed in the swelling bath 13 And is transported along the constructed film transport path. In the swelling process, the film is conveyed along the film conveyance path established by the guide rolls 30 to 32 and the nip rolls 51.

As the swelling liquid of the swelling bath 13, boric acid (Japanese Unexamined Patent Application Publication No. 10-153709), chloride (Japanese Unexamined Patent Application Publication No. 06-281816), inorganic acid, inorganic salt, water-soluble organic solvent, alcohol Or the like may be added in an amount of about 0.01 to 10% by weight.

The temperature of the swelling bath 13 is, for example, about 10 to 50 占 폚, preferably about 10 to 40 占 폚, and more preferably about 15 to 30 占 폚. The immersion time of the original film 10 is preferably about 10 to 300 seconds, more preferably about 20 to 200 seconds. Further, when the original film 10 is a polyvinyl alcohol-based resin film stretched in advance in a gas, the temperature of the swelling bath 13 is, for example, about 20 to 70 캜, preferably about 30 to 60 캜. The immersion time of the original film 10 is preferably about 30 to 300 seconds, more preferably about 60 to 240 seconds.

In the swelling process, there is a problem that the original film 10 is swollen in the width direction and the film is wrinkled. As a means for transporting the film while removing the wrinkles, a roll having a wider width function such as an expander roll, a spiral roll, and a crown roll may be used for the guide rolls 30, 31 and / or 32, Or other widening devices such as cross gauders, bend bars, tenter clips or the like. Another means for suppressing the occurrence of wrinkles is to perform stretching treatment. For example, the uniaxial stretching process can be performed in the swelling bath 13 using the difference in speed between the nip roll 50 and the nip roll 51.

In the swelling treatment, since the film swells and expands even in the transport direction of the film, when the film is not actively stretched, in order to eliminate sagging of the film in the transport direction, for example, It is preferable to take measures such as controlling the speed of the rolls 50 and 51 or the like. Further, for the purpose of stabilizing film transportation in the swelling bath 13, the water flow in the swelling bath 13 may be controlled by an underwater shower, or an EPC apparatus (Edge Position Control apparatus: Or the like) may be used in combination.

1, the film drawn out from the swelling bath 13 is introduced into the dyeing bath 15 through the guide roll 32, the nip roll 51 and the guide roll 33 in order.

(Dyeing process)

The dyeing step is carried out for the purpose of adsorbing and orienting the dichroic dye to the polyvinyl alcohol-based resin film after the swelling treatment. The treatment conditions are determined within a range in which the object can be achieved and within a range in which problems such as extreme melting of the film and loss of transparency do not occur. 1, the dyeing process is carried out along a film transport path established by the nip roll 51, the guide rolls 33 to 36 and the nip roll 52, and the film after the swelling process is transferred to the dyeing bath 15 ) (A treatment solution contained in a dyeing bath) for a predetermined time, and then withdrawing it. In order to enhance the dyability of the dichroic dye, the film provided in the dyeing step is preferably a film subjected to at least some uniaxial stretching treatment, or in place of the uniaxial stretching treatment before the dyeing treatment or in addition to the uniaxial stretching treatment before the dyeing treatment , It is preferable to carry out the uniaxial stretching treatment at the time of the dyeing treatment.

When iodine is used as the dichroic dye, an aqueous solution having an iodine / potassium iodide / water concentration of about 0.003 to 0.3 / about 0.1 to 10/100 in terms of the concentration by weight can be used for the dyeing solution of the dyeing bath 15. 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, and the like may coexist. When boric acid is added, it is distinguished from a crosslinking treatment to be described later in that it contains iodine. If the aqueous solution contains about 0.003 part by weight or more of iodine per 100 parts by weight of water, it is regarded as a dyeing bath 15 . The temperature of the dyeing bath 15 at the time of immersing the film is usually about 10 to 45 캜, preferably 10 to 40 캜, more preferably 20 to 35 캜, and the immersion time of the film is usually 30 to 600 Sec, preferably 60 to 300 sec.

When a water-soluble dichroic dye is used as the dichroic dye, an aqueous solution having a dichroic dye / water concentration of about 0.001 to 0.1 / 100 in terms of the concentration by weight, for example, may be used for the dyeing bath of the dyeing bath 15. The dyeing bath 15 may be provided with a dyeing assistant or the like, and may contain an inorganic salt such as sodium sulfate or a surfactant. The dichroic dye may be used alone, or two or more dichroic dyes may be used in combination. The temperature of the dyeing bath 15 at the time of immersing the film is, for example, about 20 to 80 캜, preferably 30 to 70 캜, and the immersion time of the film is usually about 30 to 600 seconds, preferably about 60 to 300 seconds to be.

In the dyeing step as described above, uniaxial stretching of the film can be performed in the dyeing bath 15. The uniaxial stretching of the film can be performed by a method of attaching a speed difference between the nip roll 51 and the nip roll 52 disposed before and after the dyeing bath 15.

In the dyeing treatment, as in the case of the swelling treatment, the guide rolls 33, 34, 35, and / or 36 are provided with the same rolls as the expander rolls, spiral rolls, crown rolls A roll having a widening function, or another widening device such as a cloth guider, a bent bar, and a tenter clip. Another means for suppressing the occurrence of wrinkles is to perform the stretching treatment in the same manner as the swelling treatment.

1, the film drawn out from the dyeing bath 15 is introduced into the crosslinking bath 17 through the guide roll 36, the nip roll 52 and the guide roll 37 in order.

(Crosslinking step)

The crosslinking process is a process performed for the purpose of, for example, water resistance by crosslinking and color adjustment (preventing the film from becoming blue). In the example shown in Fig. 1, two crosslinking baths are arranged as a crosslinking bath for carrying out a crosslinking process, and a first crosslinking process for the purpose of water resistance is performed in the first crosslinking bath 17a, Is carried out in the second crosslinking bath 17b. 1, the first crosslinking process is carried out along the film conveyance path constructed by the nip roll 52, the guide rolls 37 to 40 and the nip roll 53a, and the first crosslinking bath 17a, (The first crosslinking solution contained in the crosslinking tank) for a predetermined time, and then withdrawing the film. The second crosslinking process is carried out along the film conveyance path constructed by the nip roll 53a, the guide rolls 41 to 44 and the nip roll 53b, and the second crosslinking bath 17b Crosslinking solution) by immersing the film after the first crosslinking step for a predetermined time, and then withdrawing the film. Hereinafter, in the case of a crosslinking bath, it includes both the first crosslinking bath 17a and the second crosslinking bath 17b, and in the case of a crosslinking bath, it includes both the first crosslinking bath and the second crosslinking bath.

As the crosslinking solution, a solution prepared by dissolving a crosslinking agent in a solvent can be used. Examples of the crosslinking agent include boron compounds such as boric acid and borax, and glyoxal and glutaraldehyde. These may be used alone or in combination of two or more. As the solvent, for example, water may be used, and further, an organic solvent compatible with water may be contained. The concentration of the cross-linking agent in the cross-linking solution is not limited to this, but is preferably in the range of 1 to 20 wt%, and more preferably in the range of 6 to 15 wt%.

The crosslinking solution may be an aqueous solution containing, for example, about 1 to 10 parts by weight of boric acid per 100 parts by weight of water. When the dichroic dye used in the dyeing treatment is iodine, the crosslinking solution preferably contains iodide in addition to boric acid, and the amount thereof may be, for example, 1 to 30 parts by weight relative to 100 parts by weight of water. Examples of the iodide include potassium iodide and zinc iodide. Further, compounds other than iodide such as zinc chloride, cobalt chloride, zirconium chloride, sodium thiosulfate, potassium sulfite, sodium sulfate and the like may coexist.

In the crosslinking treatment, the concentration of boric acid and iodide and the temperature of the crosslinking bath 17 can be appropriately changed depending on the purpose. For example, in the case of the first crosslinking solution in which the purpose of the crosslinking treatment is water-resisting by crosslinking, it may be an aqueous solution having a concentration of boric acid / iodide / water = 3 to 10/1 to 20/100 in terms of weight ratio. If necessary, other crosslinking agents may be used instead of boric acid, or boric acid and other crosslinking agents may be used in combination. The temperature of the first crosslinking bath 17a when immersing the film is usually about 50 to 70 占 폚, preferably 53 to 65 占 폚, and the immersion time of the film is usually about 10 to 600 seconds, preferably 20 to 300 Sec, and more preferably 20 to 200 seconds. When the dyeing treatment and the first cross-linking treatment are performed in this order on the polyvinyl alcohol-based resin film previously drawn before the swelling treatment, the temperature of the first cross-linking bath 17a is usually about 50 to 85 캜, Lt; / RTI >

When iodine is used as the dichroic dye, for example, boric acid / iodide / water = 1/5/3 to 30/100 can be used in a concentration by weight ratio in the second crosslinking liquid for color adjustment purpose. The temperature of the second crosslinking bath 17b at the time of immersing the film is usually about 10 to 45 DEG C, and the immersion time of the film is usually about 1 to 300 seconds, preferably 2 to 100 seconds.

The crosslinking treatment may be carried out several times, usually 2 to 5 times. In this case, the composition and temperature of each crosslinking bath to be used may be the same or different if they are within the above-mentioned range. The cross-linking treatment for water resistance by cross-linking and the cross-linking treatment for color adjustment may be carried out by a plurality of steps, respectively.

It is also possible to perform the uniaxial stretching process in the first crosslinking bath 17a using the peripheral speed difference between the nip roll 52 and the nip roll 53a. In addition, the uniaxial stretching process may be performed in the second crosslinking bath 17b using the difference in speed between the nip roll 53a and the nip roll 53b.

39, 40, 41, 42, 43 and / or 44) is fed to the guide rolls 38, 39, 40, 41, 42, 43 and / or 44 in order to transport the polyvinyl alcohol resin film while removing the wrinkles of the film, A roll having a widening function such as a roll, a crown roll, or another widening device such as a cloth guider, a bent bar, and a tenter clip. Another means for suppressing the occurrence of wrinkles is to perform the stretching treatment in the same manner as the swelling treatment.

In the example shown in Fig. 1, the film drawn out from the second crosslinking bath 17b passes through the guide roll 44 and the nip roll 53b, and is introduced into the cleansing bath 19 sequentially.

(Cleaning process)

In the example shown in Fig. 1, a cleaning step after the crosslinking step is included. The cleaning treatment is carried out for the purpose of removing excess boric acid or iodine adhered to the polyvinyl alcohol-based resin film. The cleaning step is carried out, for example, by immersing the crosslinked polyvinyl alcohol-based resin film in the cleansing bath 19. The cleaning step may be performed by spraying the cleaning liquid on the film as a shower or by using both the immersion in the cleansing bath 19 and the spraying of the cleaning liquid in place of the step of immersing the film in the cleansing bath 19.

Fig. 1 shows an example in which a polyvinyl alcohol based resin film is immersed in a cleansing bath 19 to perform a cleaning treatment. The temperature of the cleansing bath 19 in the cleansing treatment is usually about 2 to 40 DEG C, and the immersion time of the film is usually about 2 to 120 seconds.

Also, in the cleaning process, a widening function such as an expander roll, a spiral roll, and a crown roll is applied to the guide rolls 45, 46, 47 and / or 48 for the purpose of transporting the polyvinyl alcohol- , Or by using other widening devices such as cloth guiders, bend bars, tenter clips, or the like. Further, in the film washing treatment, a stretching treatment may be performed to suppress the occurrence of wrinkles.

(High-humidity treatment process)

In the example shown in Fig. 1, after a cleansing bath 19, a high-humidity treatment unit 21 is provided, and a film is passed through the high-humidity treatment unit 21 to perform a high-humidity treatment for exposing the film to a high humidity atmosphere.

The shrinking force of the film can be suppressed by performing the high humidity treatment in which the film is exposed to a high humidity atmosphere. The absolute humidity in the high humidity treatment section 21 is 80 g / cm 3 or higher, preferably 100 g / cm 3 or higher, and more preferably 120 g / cm 3 or higher, from the viewpoint of suppressing the shrinking force of the film. If the absolute humidity is excessively high, there is a risk of dew condensation or contamination of the film due to dew condensation in the high humidity treatment section. Therefore, the absolute humidity is preferably 550 g / m 3 or less, more preferably 400 g / m 3 or less , More preferably not more than 300 g / m 3, particularly preferably not more than 180 g / m 3. By suppressing the shrinkage force, a polarizing film having excellent durability can be obtained.

The atmosphere temperature in the high-humidity treatment section 21 is preferably 40 ° C or higher, more preferably 55 ° C or higher, from the viewpoint of easy adjustment of the absolute humidity to the preferable numerical value range described above, Or more, more preferably 60 ° C or more. The temperature of the atmosphere is preferably 100 占 폚 or lower, and preferably 90 占 폚 or lower from the viewpoint of obtaining excellent optical characteristics.

The high-humidity treatment for exposing the film to an atmosphere having a high humidity of at least 80 g / cm 3 is preferably 5 seconds or more, and more preferably 10 seconds or more. The time may vary depending on the temperature, but is preferably 60 minutes or shorter, more preferably 30 minutes or shorter, still more preferably 10 minutes or shorter, 5 minutes or less.

The high-humidity treatment process is preferably performed after the cleaning process. However, the high-humidity treatment and the cleaning treatment may be performed at the same time by spraying the cleaning liquid during the high-humidity treatment process, or the film may be substantially cleaned Or the like may be combined with the cleaning treatment.

The high-humidity treatment step may also be a treatment for drying the polyvinyl alcohol-based resin film, that is, a treatment for lowering the moisture content. Accordingly, when the moisture content can be appropriately adjusted, there is no need to separately perform the drying treatment before or after the high-humidity treatment step.

The moisture content of the film provided in the high-moisture treatment process depends on the thickness of the film, but is generally about 13 to 50% by weight, preferably 30 to 50% by weight. The difference in moisture percentage due to the high moisture treatment process, that is, the difference between the moisture percentage before the high humidity treatment and the moisture percentage after the high humidity treatment (moisture content difference? S) also depends on the thickness of the film, but is in the range of 5 to 45 wt% Weight%. For example, when the thickness of the original film is about 40 占 퐉 or less, the moisture content difference? S can be less than 15% by weight.

The moisture content of the film after the high-humidity treatment process (the polarizing film when the high-humidity treatment process is the final process) also depends on the thickness of the film, but is preferably 5 to 30% by weight, More preferably 15% by weight. If the moisture content is too low, the film tends to be torn during transportation, and if the moisture content is too high, curling of the film ends is liable to occur due to moisture release.

In general, the thinner the film, the more easily the moisture is scattered. Therefore, the thinner the original film, the lower the moisture content after the high-humidity treatment process. If the moisture content is too low, the transportability of the film tends to deteriorate.

The high-humidity treatment step may be performed immediately after the crosslinking step or the cleaning step, or may be carried out after the crosslinking step or the cleaning step, followed by another step. Examples of other processes include a drying process. However, from the viewpoint of more effectively suppressing the rise of the shrinkage force, it is preferable to provide the film of the crosslinking step or the washing step to the high-moisture treatment step as it is.

(Drawing step)

As described above, the original film 10 is uniaxially stretched in a wet or dry manner during the series of processing steps (that is, before and / or after any one or more processing steps). A specific method of the uniaxial stretching treatment is, for example, a roll-to-roll stretching in which longitudinal uniaxial stretching is performed by attaching a main speed difference between two nip rolls constituting a film transport path (for example, two nip rolls disposed before and after the treatment bath) A hot roll stretching method, a tenter stretching method, and the like as described in Japanese Patent No. 2731813, and is preferably a roll-to-roll stretching method. The uniaxial stretching process can be performed several times between the original film 10 and the polarizing film 23. As described above, the stretching treatment is also advantageous in suppressing the occurrence of wrinkles in the film.

The final cumulative stretch magnification of the polarizing film 23 based on the original film 10 is usually about 4.5 to 7 times, preferably 5 to 6.5 times. The stretching process may be performed in any process step, and in the case of performing the stretching process in two or more process steps, the stretching process may be performed in any process step.

From the viewpoint of suppressing the shrinking force of the film, it is preferable that the stretching step includes a first stretching step for performing uniaxial stretching treatment until completion of the cleaning step and a second stretching step for performing uniaxial stretching treatment in the high humidity treatment step. By having the first stretching step and the second stretching step, contraction force can be suppressed as compared with the case where the same stretching ratio is achieved only in the first stretching step.

The uniaxial stretching treatment in the second stretching step may be either dry stretching or wet stretching, but in the case of stretching under a high humidity atmosphere, it is usually dry stretching. The uniaxial stretching treatment by dry stretching may be roll stretching, thermal roll stretching, tenter stretching, or the like, in which longitudinal uniaxial stretching is performed by attaching a main speed difference between two nip rolls. The drawing magnification of the second drawing step is preferably 1.01 to 1.4 times, more preferably 1.04 to 1.2 times.

The tension applied to the film in the second stretching step is preferably 50 to 5000 N / m from the viewpoint of more effectively suppressing the increase of the contracting force. From the viewpoint of suppressing the generation of wrinkles of the film, the film tension is more preferably 300 to 1500 N / m.

(Electromagnetic wave irradiation process)

In the apparatus shown in Fig. 1, after the film is drawn out from the second crosslinking step 17b, passed through the nip roll 53b, and then immersed in the cleansing bath 19, the film is irradiated with electromagnetic waves Irradiation step) is performed. In the apparatus shown in Fig. 1, electromagnetic waves are irradiated from the electromagnetic wave irradiating unit 71. Fig. The electromagnetic wave used in the electromagnetic wave irradiation process of the present invention includes infrared rays, and it is preferable that the ratio of the radiant energy of infrared rays having a wavelength of more than 2 탆 to 4 탆 or less is preferably 25% or more of the total radiant energy of electromagnetic waves, 28% or more, and more preferably 35% or more. By irradiating such an electromagnetic wave to the film, the optical characteristics of the resulting polarizing film can be improved. With respect to the electromagnetic wave used in the present invention, the upper limit value of the ratio of the radiant energy of infrared rays having a wavelength of 2 탆 or more and 4 탆 or less is not particularly limited, but is 80% or less, for example. An electromagnetic wave having a wavelength of 0.75 mu m to 1000 mu m is called an infrared ray.

The present invention is a method for carrying out a high-humidity treatment step and for carrying out an electromagnetic wave irradiation step before that, thereby further suppressing the shrinking force of the polarizing film and further improving the optical characteristics. Although the mechanism capable of restraining the shrinking force of the polarizing film and improving the optical characteristics is not clear, the molecular motion in the film is excited by the electromagnetic wave irradiation process, and thereby the dichroic dye such as iodine Immobilization is promoted and high-humidity treatment is performed in this state, which is presumed to contribute to suppression of contraction force and improvement of optical characteristics.

Fig. 2 shows a radiant energy spectrum for each type of electromagnetic wave irradiator. Table 1 shows the ratio of the radiant energy of the electromagnetic waves in each wavelength range (expressed in the range of wavelength x 占 퐉) to the total radiant energy for each type of electromagnetic wave irradiator. The electromagnetic wave irradiator shown in Fig. 2 and Table 1 is a halogen heater (heat source temperature 2600 캜), a short wavelength infrared heater (heat source temperature 2200 캜), a fast response medium wave infrared heater (heat source temperature 1600 캜), a carbon heater ), A carbon heater (heat source temperature 950 캜), and a medium-frequency infrared heater (heat source temperature 900 캜).

In the electromagnetic-wave irradiator 71 of the present invention, the ratio of the radiant energy of infrared rays having a wavelength of more than 2 탆 and not more than 4 탆 is not less than 25% of the total radiant energy from the viewpoint of further suppressing the contractive force and further improving the optical characteristics . As shown in Table 1, it is possible to use a short wavelength infrared heater (heat source temperature 2200 ° C), a high-speed response medium-wave infrared heater (heat source temperature 1600 ° C), a carbon heater (heat source temperature 1200 ° C), a carbon heater The infrared heater (heat source temperature 900 캜) has a ratio of radiant energy of infrared rays having a wavelength of more than 2 탆 and 4 탆 or less of 25% or more of the total radiant energy.

The electromagnetic wave irradiating unit 71 may be constituted by one electromagnetic wave irradiator or may be constituted by a plurality of electromagnetic wave irradiators. In the case where it is constituted by several electromagnetic wave irradiators, the radiation energy of infrared rays having a wavelength of more than 2 탆 and not more than 4 탆 radiated from the plurality of electromagnetic wave irradiators is not less than 25% of the total radiation energy of electromagnetic waves emitted from the plurality of electromagnetic wave irradiators It is preferable to select several electromagnetic wave irradiators as much as possible. 1, the electromagnetic wave irradiating unit 71 is configured to irradiate electromagnetic waves only on one side of the film, but a plurality of electromagnetic wave irradiators may be disposed so that electromagnetic waves are irradiated on both sides of the film. It is preferable that the electromagnetic wave irradiator 71 is configured so that electromagnetic waves are irradiated to the entire width direction of the polyvinyl alcohol resin film to be irradiated.

In the electromagnetic wave irradiation process, it is preferable that the electromagnetic wave is irradiated from the upper side in the vertical direction with respect to the film surface. The distance between the electromagnetic wave radiator of the electromagnetic wave irradiator and the film in the electromagnetic wave irradiator 71 is preferably 2 to 40 cm, more preferably 5 to 20 cm. However, it is preferable that the distance is appropriately selected in consideration of the amount of radiant energy of the electromagnetic wave radiated from the electromagnetic wave irradiator, the temperature of the film surface, and the like. The temperature of the film surface at the time of electromagnetic wave irradiation is preferably maintained at 30 to 90 캜, and more preferably at 40 to 80 캜.

In the electromagnetic wave irradiation process, the irradiation calorific value of the electromagnetic wave per unit volume of the film may be generally 100 J / cm3 or more and 50 kJ / cm3 or less. From the viewpoint of improving the optical characteristics of the polarizing film, it is preferably 100 J / cm3 or more, more preferably 500 J / cm3 or more, and still more preferably 1000 J / cm3 or more. The irradiation heat amount of the electromagnetic wave per unit volume of the film is preferably 10 kJ / cm3 or less, more preferably 5,000 J / cm3 or less, and more preferably 3,000 J / cm3 or less from the viewpoint of suppressing film deterioration due to temperature rise More preferable. Usually, the water content of the film is decreased in proportion to the irradiation heat amount of the electromagnetic wave. However, the electromagnetic wave irradiation step of the present invention is not intended to reduce the moisture content of the film, and the irradiation heat amount can be appropriately selected, Select appropriately within the range.

The electromagnetic wave irradiation step only needs to be performed on a film immersed in at least one crosslinking bath, and is not limited to the case where the film is immersed in all the crosslinking baths as shown in Fig. That is, in the example shown in Fig. 1, the electromagnetic wave irradiation process may be performed on the film before being immersed in the first crosslinking bath and before being immersed in the second crosslinking bath, or the electromagnetic wave irradiation process may be performed on the film immersed in the second crosslinking bath An irradiation step may be performed. However, since the crosslinking of the boric acid introduced into the film can be advanced by immersing in the crosslinking bath by the electromagnetic wave irradiation step, it is more preferable to carry out the electromagnetic wave irradiation process on the film having been immersed in all the crosslinking baths So that it can be effectively advanced. The electromagnetic wave irradiation step may be performed before or after the cleaning step, as long as it is after the crosslinking step and before the high-humidity treatment step.

The irradiation of the electromagnetic wave is preferably performed within 10 seconds after the film is drawn out from the crosslinking bath, more preferably within 5 seconds. The shorter the time from the drawing of the crosslinking bath to the irradiation of the electromagnetic wave, the more the optical characteristics of the polarizing film by the electromagnetic wave irradiation can be improved. Further, in the electromagnetic wave irradiation step, it is preferable that the number of water molecules attached to the surface of the film is small. If water molecules are present on the surface of the film, water molecules on the surface of the film absorb infrared rays, and the excitation effect of molecular motion in the film due to electromagnetic wave irradiation is lowered. Immediately after being drawn out from the crosslinking bath, since the crosslinking liquid adheres to the surface of the film, it is preferable to provide a liquid removing means for removing the crosslinking liquid before the electromagnetic wave irradiation step. In Fig. 1, the nip roll 53b also functions as a liquid remover for removing the cross-linking liquid attached to the surface of the film. In addition to the nip roll, a means for blowing air to the film to perform the solution, a scraper for contacting the film and performing the solution may be used as the solution remover.

From the viewpoint of economical efficiency, when the film processing speed is set to a high speed, specifically, when the processing speed is set at a high processing speed of 10 to 100 m / min, the electromagnetic wave irradiation time is shortened and the irradiation heat amount may be insufficient. As a countermeasure, a sufficient amount of irradiation heat can be obtained by providing several electromagnetic wave irradiators in parallel.

(Drying step)

The polyvinyl alcohol based resin film can be dried after the cleaning step or before or after the high moisture treatment step. The drying method of the film is not particularly limited.

For example, a drying furnace equipped with a hot air dryer can be used. The drying temperature is, for example, about 30 to 100 DEG C, for example, about 30 to 600 seconds. The treatment of drying the polyvinyl alcohol-based resin film can be performed using a far-infrared heater. The thickness of the polarizing film 23 obtained as described above is, for example, about 5 to 30 占 퐉.

The visual sensitivity correction Ty of the obtained polarizing film 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 polarization degree Py is preferably 99.9% or more, more preferably 99.95% or more, and the larger the value, the more preferable. Visual Sensitivity Correction of Polarizing Film The larger the single transmittance Ty is, the greater the effect of improving the optical characteristics obtained by the present invention. Therefore, the present invention is particularly advantageous in the case of producing a polarizing film having a visual sensitivity-corrected amature transmittance Ty of 41% or more, more preferably 42% or more, and furthermore 43.5% or more. According to the present invention, for example, a polarizing film having a Ty of 43.5% or more and a Py of 99.994% or more can be obtained. Ty and Py are measured according to the description of the embodiment to be described later.

The obtained polarizing film may be rolled into a roll by sequentially winding on a winding roll, or may be provided to a polarizing plate production step (a step of laminating a protective film or the like on one side or both sides of a polarizing film) as it is without winding.

(Other Treatment Processes for Polyvinyl Alcohol-based Resin Film)

Processing other than the above-described processing may be added. Examples of the treatment that can be added include an immersion treatment (complementary treatment) in an iodide aqueous solution containing no boric acid, which is carried out after the crosslinking step, an immersion treatment in an aqueous solution containing zinc chloride or the like without containing boric acid Processing).

<Polarizer>

A polarizing plate can be obtained by bonding a protective film to at least one surface of a polarizing film produced as described above through an adhesive. As the protective film, for example, a film comprising an acetylcellulose-based resin such as triacetylcellulose or diacetylcellulose; A film made of a polyester resin such as polyethylene terephthalate, polyethylene naphthalate and polybutylene terephthalate; Polycarbonate resin film, cycloolefin resin film; Acrylic resin film; And a film made of a chain olefin resin of a polypropylene type resin.

A surface treatment such as a corona treatment, a flame treatment, a plasma treatment, an ultraviolet irradiation, a primer coating treatment, or a saponification treatment is performed on the bonding surfaces of the polarizing film and / or the protective film to improve the adhesion between the polarizing film and the protective film It is also good. Examples of the adhesive used for bonding the polarizing film and the protective film include an active energy ray curable adhesive such as an ultraviolet ray curable adhesive or an aqueous solution of a polyvinyl alcohol resin or an aqueous solution containing a crosslinking agent and an aqueous adhesive such as a urethane emulsion adhesive . The ultraviolet curable adhesive may be a mixture of an acrylic compound and a photo radical polymerization initiator, a mixture of an epoxy compound and a cationic photopolymerization initiator, and the like. In addition, a cationic polymerizable epoxy compound and a radical polymerizable acrylic compound may be used in combination, and a photocationic polymerization initiator and a photo radical polymerization initiator may be used together as an initiator.

[Example]

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

&Lt; Example 1 >

Using the production apparatus shown in Fig. 1, a polarizing film of Example 1 was produced with a polyvinyl alcohol-based resin film. Specifically, a long original polyvinyl alcohol (PVA) film having a thickness of 60 占 퐉 (trade name "Kurarabinetron VF-PE # 6000" manufactured by Kuraray Co., Ltd., average degree of polymerization: 2400, degree of saponification: 99.9 mol% , And immersed in a swelling bath made of pure water at 30 캜 for a residence time of 89 seconds (swelling step). Thereafter, the film drawn out from the swelling bath was immersed in a dyeing bath at 30 DEG C containing iodine with potassium iodide / boric acid / water of 2 / 0.3 / 100 (weight ratio) at a residence time of 156 seconds (dyeing step). Subsequently, the film drawn out from the dyeing bath was immersed in a first crosslinking bath at 56 ° C of 12/4/100 (weight ratio) of potassium iodide / boric acid / water at a residence time of 67 seconds, and then potassium iodide / boric acid / Was immersed in a second crosslinking bath at 40 캜, which was 9/3/100 (weight ratio), at a residence time of 11 seconds (crosslinking step). In the dyeing step and the crosslinking step, longitudinal uniaxial stretching was performed by roll-to-roll stretching in a bath. The total draw ratio based on the original film was 5.69 times.

Subsequently, the film was taken out from the second crosslinking bath 17b and passed through the nip roll 53b. The film was irradiated with an electromagnetic wave irradiator (medium wave infrared heater (MW heater), product name: Golden 8 Medium-wave twin tube emitter, And a maximum energy density of 60 kW / m 2 at a heat source temperature of 900 ° C.), an electromagnetic wave radiation hole was disposed at a position 5 cm away from the surface of the film, and an electromagnetic wave was irradiated with an output power of 30% did. The irradiation calorific value of the electromagnetic wave per film unit was 560 J / cm 3. The calorific value of the irradiation of the electromagnetic wave per film unit volume was calculated by the following formula.

(Irradiation amount of electromagnetic wave per film unit) = {(maximum energy density) x (heater heating surface area) x output (%) / (electromagnetic wave irradiation area)

The output (%) indicates the ratio (%) of the actually irradiated output to the maximum irradiation output of the electromagnetic wave irradiator.

After the film was taken out from the second crosslinking bath 17b, the film was transported, and the time taken until reaching the irradiating position of the electromagnetic wave irradiator and irradiating the electromagnetic wave was 5 seconds.

The film irradiated with the electromagnetic wave was immersed in a cleansing bath 19 made of pure water at 5 캜 for a retention time of 3 seconds (cleaning step). Thereafter, the film was exposed in a high humidity environment at a temperature of 75 deg. C, an absolute humidity of 147 g / cm3, and a relative humidity of 61% in a high humidity treatment section 21 at a residence time of 60 seconds. At this time, uniaxial stretching treatment of 1.14 times was also performed. Finally, the film was dried in a drying furnace at a temperature of 30 DEG C, an absolute humidity of 10 g / cm &lt; 3 &gt; and a residence time of 120 seconds to obtain a polarizing film. The thickness of the obtained polarizing film was 23 m.

&Lt; Examples 2 to 3 &

A polarizing film was obtained in the same manner as in Example 1, except that the output (%) of the electromagnetic wave irradiator and the irradiation calorific value of the electromagnetic wave per film unit volume in the electromagnetic wave irradiation process were as shown in Table 2. The thickness of the obtained polarizing film was all 23 占 퐉.

&Lt; Comparative Example 1 &

A polarizing film was obtained in the same manner as in Example 1 except that the electromagnetic wave irradiation step was not performed. The thickness of the obtained polarizing film was 23 占 퐉.

&Lt; Comparative Example 2 &

The output (%) of the electromagnetic wave irradiator in the electromagnetic wave irradiation process and the irradiation calorific value of the electromagnetic wave per film unit volume are shown in Table 2, the high humidity treatment step was not performed, A polarizing film was obtained in the same manner as in Example 1 except for one point. The thickness of the obtained polarizing film was 23 m.

&Lt; Comparative Example 3 &

A polarizing film was obtained in the same manner as in Example 1, except that the electromagnetic wave irradiation process and the high humidity treatment process were not performed, the high humidity treatment process was not performed, and the temperature in the drying process was changed as shown in Table 2. The thickness of the obtained polarizing film was 23 m.

[Evaluation of polarizing film]

(a) Measurement of b-value of the unit transmittance, polarization degree and orthogonal color

With respect to the polarizing films obtained in the respective Examples and Comparative Examples, the MD transmittance and the TD transmittance in a wavelength range of 380 to 780 nm were measured using a spectrophotometer ("V7100", manufactured by Nippon Bunko Co., Ltd.) , The following formula:

Bulk transmittance (%) = (MD + TD) / 2

Polarization degree (%) = {(MD-TD) / (MD + TD)} 100

, The single light transmittance and the polarization degree at each wavelength were calculated.

The "MD transmittance" is the transmittance when the direction of the polarized light emerging from the Glan Thompson prism is parallel to the transmittance axis of the sample of the polarizing film, and is expressed by "MD" in the above expression. The term &quot; TD transmittance &quot; means the transmittance when the direction of the polarization of light emerging from the Glan Thompson prism is orthogonal to the transmittance axis of the sample of the polarizing film, and is represented by &quot; TD &quot; The obtained transmittance and polarization degree were subjected to visual sensitivity correction by a 2-degree visual field (C light source) of JIS Z 8701: 1999 "Color display method-XYZ color system and X ₁₀ Y ₁₀ Z ₁₀ color system" Ty, the visual sensitivity correction polarization degree Py, and the b value of the orthogonal color. Table 2 shows the calculation results.

(b) Measurement of contraction force

Measurement samples having a width of 2 mm and a length of 10 mm were cut out from the polarizing films obtained in the respective Examples and Comparative Examples, each having a long side in the absorption axis direction (MD, stretching direction). This sample was set on a thermomechanical analyzer (TMA) &quot; EXSTAR-6000 &quot;, manufactured by Esa Eye Nanotechnology Co., Ltd., and maintained at 80 DEG C for 4 hours while keeping the dimensions constant. (MD shrinkage force) of the absorbent core (absorption axis direction, MD) was measured. The smaller the shrinkage force to be measured, the better the durability is, and for example, 4 N / 2 mm or less is preferable.

As shown in Table 2, the polarizing films of Examples 1 to 3 had better optical characteristics than the polarizing films of Comparative Examples 1 to 3. In addition, as shown in Table 2, the polarizing films of Examples 1 to 3 had a higher total draw ratio as compared with the polarizing films of Comparative Examples 2 and 3, but the shrinking force was further suppressed.

A first crosslinking bath; 17b: a second crosslinking bath; 19: a wash liner; and 21: a high-humidity processing unit. , 23: polarizing film, 30-48, 60, 61: guide roll, 50-52, 53a, 53b, 54, 55: nip roll, 71: electromagnetic wave irradiation part.

Claims (6)

A method for producing a polarizing film from a polyvinyl alcohol-based resin film,
A dyeing step of dyeing the polyvinyl alcohol-based resin film with a dichroic dye,
A cross-linking step of cross-linking the polyvinyl alcohol-based resin film after the dyeing step with a cross-
An electromagnetic wave irradiation step of irradiating the polyvinyl alcohol based resin film after the crosslinking step with an electromagnetic wave including infrared rays;
And a high-humidity treatment step of exposing the polyvinyl alcohol-based resin film after irradiating the electromagnetic wave to an atmosphere having an absolute humidity of 80 g / m 3 or more. The polarizing film manufacturing method according to claim 1, further comprising a cleaning step of cleaning the polyvinyl alcohol based resin film between the electromagnetic wave irradiation step and the high moisture treatment step. The method of manufacturing a polarizing film according to claim 1 or 2, wherein in the electromagnetic wave irradiation step, the electromagnetic wave has a ratio of radiant energy of infrared rays having a wavelength of more than 2 탆 and not more than 4 탆 to not less than 25% of total radiant energy. The polarizing film according to any one of claims 1 to 3, wherein in the electromagnetic wave irradiation step, the irradiation heat amount of the electromagnetic wave is not less than 100 J / cm 3 and not more than 50 kJ / cm 3 per unit volume of the polyvinyl alcohol- &Lt; / RTI &gt; The method of producing a polarizing film according to any one of claims 1 to 4, wherein the polyvinyl alcohol-based resin film is uniaxially stretched at 1.04 to 1.2 times in the high-humidity treatment step. A production apparatus for producing a polarizing film from a polyvinyl alcohol-based resin film,
A dyeing section for dyeing the polyvinyl alcohol-based resin film with a dichroic dye,
A cross-linking portion for cross-linking the polyvinyl alcohol-based resin film after the dyeing treatment with a cross-linking agent,
An electromagnetic wave irradiating section for irradiating the crosslinked polyvinyl alcohol resin film with an electromagnetic wave including infrared rays;
And a high-humidity treatment section for exposing the polyvinyl alcohol-based resin film after irradiating the electromagnetic wave to an atmosphere having an absolute humidity of 80 g / m 3 or more.

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