KR20150111946A - Process for manufacturing polarizing film - Google Patents

Abstract

The present invention relates to a method for producing a polyvinyl alcohol-based resin film, which comprises a step of subjecting a polyvinyl alcohol-based resin film to a swelling treatment, a dyeing treatment, a crosslinking treatment and a cleaning treatment in this order, A method for producing a polarizing film for performing uniaxial stretching of a film, comprising the steps of taking a film subjected to any one treatment from the treatment tank and transporting it to the next step, passing the guide roll Thereby removing the liquid on the side contacting the guide roll, and subsequently carrying out a process of widening both ends in the width direction of the film. According to this method, it is possible to prevent curling occurring at both end portions in the width direction of the film, and prevent the film from being folded or broken due to this.

Description

PROCESS FOR MANUFACTURING POLARIZING FILM [0002]

The present invention relates to a method for producing a polarizing film for use in a liquid crystal display device.

Conventionally, a polarizing film having a dichroic dye adsorbed on a polyvinyl alcohol resin film has been used. That is, an iodine-based polarizing film using iodine as a dichroic dye or a dye-based polarizing film using a dichroic dye as a dichroic dye are known. These polarizing films are usually polarized plates obtained by bonding a protective film such as triacetylcellulose through an adhesive composed of an aqueous solution of a polyvinyl alcohol resin to at least one side, preferably both sides, of a liquid crystal television, a personal computer monitor And is used in a liquid crystal display device such as a telephone.

The polarizing film is produced by subjecting the polyvinyl alcohol-based resin film to swelling treatment, dyeing treatment, stretching treatment, crosslinking treatment (boric acid treatment) and washing treatment, and finally drying. At this time, the film is stretched by placing a peripheral speed difference (peripheral speed difference) on the nip rolls arranged before and after the treatment tank. In addition, the direction of transporting the film is changed by a guide roll disposed before and after the treatment bath (treatment bath) or in the treatment bath to introduce and take out the film to the treatment bath.

In recent years, there has been a tendency to demand a larger, thinner, lighter, and lower cost raw material for a liquid crystal display in the market, and accordingly, a manufacturing method capable of achieving widening or thinning of a polarizing film has been developed. For example, Japanese Patent Application Laid-Open No. 2004-20633 (Patent Document 1) discloses that when a polarizing film is produced from a polyvinyl alcohol based resin film having a thickness of 10 to 50 占 퐉, And then stretching the film while stretching the film, thereby achieving thin film weight reduction.

However, in the case of performing the swelling treatment, the dyeing treatment, the cross-linking treatment and the cleaning treatment on the polyvinyl alcohol-based resin film of a thin film, the film is taken out from each treatment tank, and then, There is a problem in that curling is caused by the surface tension of the liquid adhering to the surface. Therefore, when water is removed by the subsequent nip roll, there is a case where the film is folded or broken at the curled portion when the film is sandwiched.

Japanese Patent Application Laid-Open No. 2004-20633

The curl at both ends in the width direction of the film frequently occurs due to the thickness of the polyvinyl alcohol based resin film being reduced to 60 占 퐉 or less in order to meet demands such as thinning of the polarizing film and lightening of the polarizing film .

It is an object of the present invention to provide a method for producing a polarizing film with a thin polyvinyl alcohol based resin film in which curling which occurs at both ends in the width direction of the polyvinyl alcohol based resin film is prevented, And a method of manufacturing a polarizing film capable of preventing entry and breakage of the polarizing film.

The present inventors have found that when a polarizing film is produced from a thin polyvinyl alcohol based resin film, when the polyvinyl alcohol based resin film is taken out from the treatment tank and carried to the next step, the widthwise ends of the polyvinyl alcohol- (Width) is effective. Thus, the present invention has been completed.

That is, the present invention has a step of performing a swelling treatment, a dyeing treatment, a crosslinking treatment and a cleaning treatment on a polyvinyl alcohol-based resin film having a thickness of 60 탆 or less in this order, A method for producing a polarizing film for performing uniaxial stretching of a film by using a main speed difference between two nip rolls is characterized in that, when the film subjected to any one of the above processes is taken out of the processing bath and is conveyed to the next step, And a process of removing the liquid on the side contacting the guide roll by passing the guide roll through the liquid on both sides and subsequently widening both end portions in the width direction of the film.

As the guide roll used in the present invention, a roll having a function of expanding the film to be transported may also be used. Specific examples of such rolls include expander rolls and crown rolls.

The processing for widening both ends in the width direction of the film can be carried out by a cloth guider or by a widening apparatus such as a bar, a bend bar, an expander roll and a crown roll.

According to the polarizing film producing method of the present invention, it is possible to suppress the generation of curling at both end portions in the width direction of the polyvinyl alcohol-based resin film. Therefore, when the film comes into contact with the nip roll, It is possible to suppress entry or breakage.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic cross-sectional view showing a suitable arrangement example of an apparatus in a polarizing film producing method. Fig.
Fig. 2 is an explanatory diagram showing wideness processing performed on both ends of the film after the film is taken out from the treatment tank.

[Production method of polarizing film]

Specifically, a polarizing film is adsorbed and oriented on a polyvinyl alcohol-based resin film. The polyvinyl alcohol-based resin to be a raw material is usually obtained by saponifying a polyvinyl acetate-based resin. This degree of saponification is usually at least about 85 mol%, preferably at least about 90 mol%, more preferably at least about 99 mol%. Examples of the polyvinyl acetate-based resin include polyvinyl acetate, which is a homopolymer of vinyl acetate, as well as copolymers of vinyl acetate and other monomers copolymerizable therewith. Examples of other copolymerizable monomers include unsaturated carboxylic acids, olefins, vinyl ethers, and unsaturated sulfonic acids. The degree of polymerization 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, an unoriented polyvinyl alcohol based resin film (original film) having a thickness of 60 占 퐉 or less, preferably about 10 to 50 占 퐉, is used as a starting material for polarizing film production. It is industrially practical that the width of the film is about 1500 to 6000 mm.

The polarizing film is obtained by subjecting the above original film to swelling, dyeing, crosslinking and washing in this order, and uniaxially stretching is carried out either wet or dry during one of the respective steps or during the respective steps, ≪ / RTI > Hereinafter, the manufacturing method of the present invention will be described in detail with reference to FIG.

Fig. 1 is a cross-sectional schematic view showing a suitable arrangement example of a production apparatus used in a method of manufacturing a polarizing film according to the present invention. In this manufacturing apparatus, an original film 10 made of a polyvinyl alcohol-based resin is unwound from a feeding roll 11 and is fed to a swelling tank 13, a staining tank 15, a crosslinking tank 17, (19), and finally passes through the drying furnace (21).

1 shows an example in which a swatch tank 13, a dyeing tank 15, a crosslinking tank 17 and a cleaning tank 19 are provided one by one, A plurality of treatment tanks may be provided. The produced polarizing film 23 is conveyed to a step of directly adhering the following protective film. Hereinafter, processing performed in the present invention will be described.

(Swelling treatment)

The swelling treatment is carried out for the purpose of removing foreign substances on the film surface, removing the plasticizer in the film, imparting easiness of dyeing, plasticizing the film, and the like. The treatment conditions are determined within a range in which these objects can be achieved and within a range in which problems such as extreme melting or devitrification of the film do not occur.

When the original film 10 is subjected to swelling treatment for the first time, the film is immersed in an aqueous solution of, for example, about 10 to 50 캜, preferably about 20 to 40 캜. The immersion time of the film is preferably about 30 to 300 seconds, more preferably about 60 to 240 seconds. When the film stretched in advance in the base body is swollen, the film is immersed in an aqueous solution of, for example, about 20 to 70 캜, preferably about 30 to 60 캜. The immersion time of the film is preferably about 30 to 300 seconds, more preferably about 60 to 240 seconds.

Since the polyvinyl alcohol-based resin film swells in the width direction and wrinkles are likely to occur in the film in the swelling treatment, it is necessary to use a known method such as an expander roll, a spiral roll, a crown roll, a closure guider, a bend bar, It is preferable to transport the film while removing the wrinkles of the film. For the purpose of stabilizing the film transportation in the bath, the water stream in the swelling bath is controlled by an underwater shower, or an EPC apparatus (Edge Position Control apparatus: detecting the end of the film, )) Or the like can be used in combination.

In the swelling treatment, since the film swells and expands even in the running direction of the film, when the film is not actively stretched, in order to eliminate the sagging of the film in the carrying direction, the speed of the transport roll disposed before and after the treatment tank is It is preferable to take measures such as control. On the other hand, the original film 10 may be subjected to uniaxial stretching in the swelling treatment. In this case, the stretching magnification is usually 1.2 to 3 times, preferably 1.3 to 2.5 times.

In addition to pure water, boric acid (Japanese Unexamined Patent Publication No. 10-153709), chloride (Japanese Unexamined Patent Publication No. 06-281816), inorganic acid, inorganic salt, water-soluble organic solvent, alcohol Or the like in an amount of about 0.01 to 10% by weight.

The polyvinyl alcohol-based resin film taken out from the swelling bath 13 is conveyed to the subsequent dyeing bath 15, and by passing the guide roll 30, the liquid on the side in contact therewith is removed. After passing through the guide roll 30, the nip roll 35 provided between the swelling tank 13 and the dyeing tank 15 is passed to remove the liquid on both sides of the film. Generally, since the film is curled at the end portion of the film before being passed through the nip roll 35 after being taken out from the treatment tank, the film is prevented from being processed by widening both end portions in the width direction of the film . The removal of the liquid of the film and the widening of both end portions in the width direction of the film can be suitably carried out after the dyeing treatment, the crosslinking treatment and the washing treatment to be described later.

(Dyeing treatment)

The dyeing treatment is carried out for the purpose of adsorbing and orienting a dichroic dye to a polyvinyl alcohol-based resin film. The processing conditions are determined within a range in which these objects can be achieved and within a range in which problems such as extreme melting or disintegration of the film do not occur.

When iodine is used as the dichroic dye, an aqueous solution having a concentration of iodine / potassium iodide / water of about 0.003 to 0.3 / about 0.1 to 10/100 at a concentration can be used for the treatment bath (dyeing bath). 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 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 with respect to 100 parts by weight of water, it can be regarded as a dyeing bath. The temperature of the dyeing bath when immersing the film is about 10 to 45 캜, preferably 20 to 35 캜, and the immersion time of the film is about 30 to 600 seconds, preferably 60 to 300 seconds.

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 can be used for the treatment bath. The treatment bath may be coexisted with a dyeing aid or the like, and may contain an inorganic salt such as sodium sulfate or a surfactant. The dichroic dye may be used singly or two or more kinds of dichroic dyes may be used in combination. The temperature of the dyeing bath when immersing the film is, for example, about 20 to 80 DEG C, preferably 30 to 70 DEG C, and the immersion time of the film is about 30 to 600 seconds, preferably about 60 to 300 seconds .

When the polyvinyl alcohol-based resin film is subjected to the swelling treatment, the dyeing treatment and the crosslinking treatment in this order, the film is usually stretched in the dyeing tank 15. The stretching of the film is performed by a method such that the nip roll 35 disposed before and after the dyeing bath 15 has a main speed difference. 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. If the stretch ratio is less than 1.6 times, the frequency of breakage of the film increases, and the yield tends to deteriorate.

Also in the dyeing treatment, an expander roll, a spiral roll, a crown roll, a cloth guider, a bent bar, and the like are placed in a dyeing tank 15 in order to transport the polyvinyl alcohol resin film while removing the wrinkles of the film, And / or at the entrance thereof.

(Crosslinking treatment)

The crosslinking treatment is preferably carried out in an aqueous solution containing about 1 to 10 parts by weight of boric acid per 100 parts by weight of water for the purpose of water resistance and color control (preventing the film from becoming blue) by crosslinking, Is performed by immersing a polyvinyl alcohol-based resin film dyed with a dye. When the dichroic dye used in the dyeing treatment is iodine, the treatment bath preferably contains iodide in addition to boric acid, and the amount thereof may be 1 to 30 parts by weight based on 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 be coexistent.

The crosslinking treatment can appropriately change the concentration of boric acid and iodide and the temperature of the treatment bath, depending on the purpose. The crosslinking treatment for water resistance and the crosslinking treatment for color adjustment are not particularly distinguished but are carried out under the following conditions. In the case where the purpose of the crosslinking treatment is water resistance by crosslinking, and swelling treatment, dyeing treatment and crosslinking treatment are carried out in this order on the original film made of a polyvinyl alcohol-based resin, the treatment bath has a boric acid / Iodide / water = 3 to 10/1 to 20/100. If necessary, a crosslinking agent such as glyoxal and glutaraldehyde may be used instead of boric acid, or boric acid and a crosslinking agent may be used in combination. The immersion time of the film is generally from about 10 to 600 seconds, preferably from 20 to 300 seconds, more preferably from 20 to 300 seconds, ~ 200 seconds. When the pre-stretched polyvinyl alcohol-based resin film is subjected to the dyeing treatment and the crosslinking treatment in this order, the temperature of the crosslinking treatment bath is usually about 50 to 85 ° C, preferably 55 to 80 ° C .

After the crosslinking treatment for the purpose of hydration, a crosslinking treatment for color adjustment may be carried out. As the conditions of the crosslinking treatment for the purpose of color adjustment, for example, when iodine is used as the dichroic dye, a treating bath having a concentration of boric acid / iodide / water = 1 to 5/3 to 30/100 in terms of the weight ratio can be used . The temperature of the treatment bath is usually about 10 to 45 占 폚, and the immersion time of the film is usually about 1 to 300 seconds, preferably 2 to 100 seconds.

These cross-linking treatments may be performed a plurality of times, usually two to five times. In this case, the composition and temperature of each crosslinking treatment bath to be used may be the same or different if they are within the above-mentioned range. The crosslinking treatment for water resistance by crosslinking and the crosslinking treatment for color adjustment may each be performed in a plurality of steps.

(Cleaning treatment)

The cleaning treatment is carried out after the crosslinking treatment for the purpose of removing excess boric acid or iodine adhered to the polyvinyl alcohol resin film. The cleaning treatment is carried out, for example, by immersing a polyvinyl alcohol-based resin film crosslinked for water resistance and / or color tone adjustment in water, spraying water to the film as a shower, or using them in combination.

Fig. 1 shows an example in which a polyvinyl alcohol-based resin film is immersed in water to perform a cleaning treatment. The temperature of the water in the cleaning process is usually about 2 to 40 캜, and the immersion time is about 2 to 120 seconds. On the other hand, also in the crosslinking treatment and the cleaning treatment, a wafers can be used for the purpose of conveying the polyvinyl alcohol resin film while removing wrinkles.

(Processing for widening both end portions in the width direction of the polyvinyl alcohol-based resin film)

The widening of both end portions in the width direction of the polyvinyl alcohol-based resin film is a treatment for preventing curling or folding at both ends in the width direction of the thin film. In the present invention, when at least one of the swelling treatment, the dyeing treatment, the crosslinking treatment and the cleaning treatment is carried out after the film is taken out from the treatment tank and conveyed to the next step, The liquid on the side contacting the guide roll is removed by passing through the guide roll and the widening of both ends in the width direction of the polyvinyl alcohol based resin film is performed. In the present specification, the process of widening both end portions in the width direction of the polyvinyl alcohol-based resin film may be simply referred to as " widening processing ".

Here, the curling that occurs at both ends in the width direction of the polyvinyl alcohol-based resin film will be described first. As described in Japanese Patent No. 3429476 and Japanese Patent No. 3478534, the polyvinyl alcohol based resin film is a film obtained by stretching a film due to the absorption rate of the film in an environment such as high humidity or underwater In some cases, curling is generated at the end portion thereof, which sometimes causes folding or skewing of the film.

The curling at the end portion of the film may occur not only in the case of drawing under the above-mentioned environment but also after the film is taken out from the treatment tank. This is thought to occur due to the amount of liquid adhering to the film surface. For example, referring to Fig. 1, when a film taken out of the treatment tank passes through a guide roll, liquid adhering to one side of the film is removed by contact with the guide roll. As a result, on the surface having a large amount of liquid adhered to the film (the surface not contacting the guide roll), the surface tension acting on the liquid becomes larger than the other side, so that the surface is curled inward to cause curling I think.

Further, the curl caused by the amount of liquid adhered to the surface of the film may also occur when the film does not pass through the guide roll. In this case, for example, when the film is transported, the liquid adhered to the lower surface side (the surface facing the bottom direction of the room) of the film falls on the upper surface side and the lower surface side of the film It is considered that the difference in liquid amount occurs. Such an embodiment is, for example, a mode in which the film is transported at an angle not perpendicular to the liquid surface of the treatment bath when it is taken out of the treatment tank and then transported to the guide roll 30, A mode in which the film is passed through the guide roll 30 and then the aqueous solution used in the immediately preceding process or the aqueous solution used in the next process is sprayed onto the film. On the other hand, the aqueous solution used in the immediately preceding treatment may be the same as or different from the aqueous solution used in the immediately preceding treatment tank.

On the other hand, the phenomenon called curl of the film edge portion generated after the polyvinyl alcohol-based resin film is taken out from each treatment tank becomes more remarkable when the thickness of the polarizing film is thinner. When the original film is thicker than 60 탆, curling hardly occurs due to the mechanical strength of the film.

Next, the process of widening both end portions in the width direction of the polyvinyl alcohol-based resin film specified in the present invention will be described. This process is carried out until the polyvinyl alcohol based resin film is taken out from the treatment tank and then conveyed to the next process until it comes into contact with the nip roll 35 provided immediately before the next process. 1 shows an example in which a process of widening both end portions in the width direction of the film is carried out after the crosslinking treatment. This treatment is carried out in such a manner that the swelling tank 13, the dyeing tank 15, the crosslinking tank 17, (19). If necessary, it may be performed after a plurality of treatment tanks. As shown in FIG. 2, it is effective to widen the width of the film after passing the guide roll 30 after the polyvinyl alcohol resin film is taken out from the treatment tank. As a result, it is possible to effectively prevent problems such as curling occurring at both end portions in the width direction of the film, and problems such as folding and breakage of the film caused by curling at a portion in contact with the roll afterward.

The polyvinyl alcohol based resin film is taken out of the treatment tank and then passes through a guide roll 30 provided for supporting the film and is subjected to a widening treatment in the region L. After passing through the nip roll 35 And returned to the next processing step (see Fig. 2).

The widening process carried out in the region L is not particularly limited, but is carried out, for example, by holding the end portion of the film with a cloth guider. As another mode, widening processing is performed by correcting the curl of the film end portion by using a widening device such as a bar, a bend bar, an expander roll, a crown roll, etc., in which the curl of the film end portion can be corrected .

In the case of using the bars in the above-mentioned widespread apparatus, one bar inclined with respect to the advancing direction of the film is disposed at both ends of the film, and the film is pushed against the film, thereby widening the film end. The bar may be arranged so as to push the film down from the upper surface of the film, or be arranged to push up the film from the lower surface (back surface) of the film. It is preferable that the bar is arranged such that the central portion of the film to be conveyed is a horizontal plane and the film is pushed down or pushed up by 0 to 50 mm from the horizontal plane and the end portion of the film is pushed 5 to 50 mm from the horizontal plane, Or to be pushed up. It is also preferable that the bar is disposed at an angle of 50 DEG or less, preferably 5 to 30 DEG from the film end toward the film center portion with respect to the film advancing direction. The length at which the bar and film are in contact (the length from the end of the film to the best end of the bar in contact with the film) is 10 to 500 mm, preferably 20 to 300 mm. If this distance is excessively long, it is difficult to adjust the position of the film end to a widened position, and the weight may cause the bar to be wobbled. On the other hand, if the distance is too short, the effect of widening processing can not be sufficiently obtained.

Any of the above materials may be selected from a variety of materials such as stainless steel, rubber, and sponge, and may be of a non-rotating type or a rotating type such as a roll. The shape of the bar is preferably a cylindrical shape, but the surface contacting the film may be curved. In the case of using a cylindrical bar, if the diameter is about 5 to 100 mm, preferably 10 to 50 mm, So that it is possible. It is also preferable that the tip of the bar is curved. The length of the bar may be as long as the width of the film can be widened, and may be about 50 to 1000 mm, preferably 100 to 500 mm.

In the present invention, as the guide roll 30, an embodiment using an expander roll is also suitable. In this case, for example, a combination of an expander roll and a cloth guide, and a combination of an expander roll and an expander roll are used. In the present invention, two or more widening processes may be used. As an example thereof, an embodiment in which the widening process is performed immediately before the guide roll 30, a widening process is performed after the guide roll 30, and an embodiment in which two or more widening processes are performed after the guide roll 30 can be exemplified.

(Dry treatment)

After the cleaning treatment or the widening treatment, the polarizing film can be produced by drying the polyvinyl alcohol-based resin film. The film may be dried in the drying furnace 21 at a temperature of about 30 to 100 DEG C for about 30 to 600 seconds, for example.

(Drawing step)

As described above, the uniaxial stretching of the film can be carried out before any one of the swelling treatment, the dyeing treatment, the crosslinking treatment and the washing treatment, or may be carried out by only one stretching step or by two or more steps It is also good. In the case of carrying out by two or more steps, a known stretching method can be adopted, except that at least one stretching step is employed. Examples of known stretching methods include inter-roll stretching in which stretching is carried out with a main speed difference between two nip rolls for transporting the film, thermal roll stretching as described in Japanese Patent No. 2731813, and tenter stretching. Of course, the stretching process may be performed a plurality of times. Basically, the order of the steps is as described above, but there is no limitation on the number of treatment baths or treatment conditions.

In the embodiment of the present invention, the final integral stretching magnification of the polarizing film is usually about 4.5 to 7 times, preferably about 5 to 6.5 times.

(Other processes)

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

The thickness of the polarizing film thus obtained is thinner than that of the original film, and is, for example, about 5 to 30 μm.

[Polarizer]

A polarizing plate can be obtained by bonding a protective film to at least one surface of the thus prepared polarizing film through an adhesive. As the protective film, for example, a film comprising an acetylcellulose resin such as triacetylcellulose or diacetylcellulose, a film comprising a polyester resin such as polyethylene terephthalate, polyethylene naphthalate and polybutylene terephthalate, a film made of a polycarbonate resin A film made of a cycloolefin resin, an acrylic resin film, and a polypropylene resin film.

In order to improve the adhesiveness between the adhesive and the polarizing film and / or the protective film, it is preferable that the bonding surface of the polarizing film and / or the protective film is subjected to a treatment such as corona treatment, flame treatment, plasma treatment, ultraviolet irradiation, primer coating, Surface treatment may be performed.

The adhesive for bonding the polarizing film and the protective film is not particularly limited as long as it can adhere the polarizing film and the protective film, but it is selected to satisfy the sufficient adhesive force and transparency. From these points, an ultraviolet curable adhesive or an aqueous adhesive is used for bonding the polarizing film and the protective film. Examples of the water-based adhesive include an aqueous solution of a polyvinyl alcohol-based resin, an aqueous solution containing a crosslinking agent, and 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.

When an ultraviolet curable adhesive is used, the film is laminated through an adhesive, and then the adhesive is cured by irradiating ultraviolet rays. The light source of ultraviolet rays is not particularly limited, but it is preferable that the light source has a light emission distribution at a wavelength of 400 nm or less. Specific examples thereof include low pressure mercury lamps, medium pressure mercury lamps, high pressure mercury lamps, ultra high pressure mercury lamps, chemical lamps, A metal halide lamp or the like is preferably used.

The light irradiation intensity for curing the ultraviolet curable adhesive is appropriately determined depending on the composition of the adhesive and is not particularly limited, but it is preferable that the irradiation intensity in the wavelength range effective for activating the polymerization initiator is 0.1 to 6000 mW / cm 2 . By appropriately selecting the irradiation intensity in this range, the reaction time does not become excessively long, and the yellowing of the adhesive due to the heat radiated from the light source and the heat generated at the time of curing of the adhesive and deterioration of the polarizing film can be suppressed. The light irradiation time is also selected according to the adhesive to be cured, and is not particularly limited, but it is preferable that the integrated light amount as a product of the irradiation intensity and the irradiation time is set to 10 to 10,000 mJ / cm 2. By appropriately selecting the accumulated light quantity in this range, a sufficient amount of active species originating from the polymerization initiator is sufficiently generated to surely advance the curing reaction, and the irradiation time is not excessively long, and good productivity can be maintained. The thickness of the adhesive layer after curing is usually 0.1 to 10 mu m, more preferably 0.2 to 4 mu m.

When the ultraviolet curable adhesive of a polarizing film or a film including a protective film is cured by irradiation of ultraviolet rays, the polarizing film is preferably cured under conditions that do not deteriorate various functions of the polarizing plate such as polarizing degree, transmittance and hue of the polarizing film, It is preferable to perform curing.

In the case of using an aqueous adhesive, for example, a method of uniformly applying an adhesive to the surface of a film or flowing between two films, superimposing two films through the coating layer, Can be adopted. After drying, it may be cured at a room temperature or a slightly higher temperature, for example, at a temperature of about 20 to 45 占 폚. The thickness of the adhesive layer is appropriately selected from the range of about 0.001 to 5 占 퐉 according to the kind of the adhesive and the combination of two films to be adhered. Preferably not less than 0.01 mu m, and more preferably not more than 2 mu m.

[Example]

Hereinafter, a more specific form of the present invention will be described below, but the present invention is not limited by these examples at all.

[Example 1]

(Trade name: " Kurarabinylon VF-PE # 6000 ", trade name, manufactured by Kuraray Co., Ltd., polymerization degree: 2400, degree of saponification: 99.9 mol% or more) having a thickness of 60 탆 was placed in a swelling tank containing pure water at 30 캜 The film was immersed in the film for 100 seconds while being kept in a stretched state so as not to be stretched. Next, in order to perform uniaxial stretching while immersing in an aqueous solution (dyeing bath) containing iodine and potassium iodide and carrying out a crosslinking treatment for the purpose of water resistance, potassium borate / potassium iodide / water was added in a ratio of 4.4 / 12/100 (Second crosslinking bath) of the same composition set at 59 占 폚, and then immersed in an aqueous solution (first crosslinking bath) at 55 占 폚 until the cumulative stretching magnification from the disc was 5.5 times And stretching was carried out. Thereafter, in order to carry out the crosslinking treatment for the purpose of color adjustment, it is immersed in an aqueous solution (a complementary color bath) at 40 캜 in which boric acid / potassium iodide / water is 2.9 / 9/100 by weight, Of pure water, and dried at 70 캜 for 3 minutes to prepare a polarizing film. At this time, the film is transported on the outlet side of the complementary color bath as shown in Fig. 2, and the film taken out from the auxiliary color trough is subjected to the widening treatment at both ends in the film width direction by the cloth guider after passing through the guide roll . As a result of the production of the polarizing film by this method, during the operation for 24 hours, the film was not folded or the film was cut due to this, and there was no loss of the film.

[Example 2]

Except that a polyvinyl alcohol film having a thickness of 50 占 퐉 (trade name "Kurarabinetron VF-PE # 5000" manufactured by Kuraray Co., Ltd., polymerization degree: 2400, degree of saponification: 99.9 mol% or more) To prepare a polarizing film. As a result of the production of the polarizing film by this method, during the operation for 24 hours, the film was not folded or the film was cut due to this, and there was no loss of the film.

[Example 3]

(Trade name: "Kurarabinylon VF-PE # 3000 ", trade name, manufactured by Kuraray Co., Ltd., polymerization degree: 2400, degree of saponification: 99.9 mol% or more) having a thickness of 30 탆 was used. The film taken out from the swelling bath and the dyeing bath on the outlet side of the swelling bath and the dyeing bath passes through the expander roll in place of the guide roll and is then fed to both ends of the film width direction by the cloth guider A polarizing film was produced in the same manner as in Example 1 except that the manufacturing apparatus was arranged so that widening processing was performed. As a result of the production of the polarizing film by this method, during the operation for 24 hours, the film was not folded or the film was cut due to this, and there was no loss of the film.

[Example 4]

A polarizing film was produced in the same manner as in Example 1 except that a polyvinyl alcohol film taken out from the sub-color trough was passed through an expander roll and then subjected to widening treatment at both ends in the film width direction by a cloth guider, Respectively. As a result of the production of the polarizing film by this method, during the operation for 24 hours, the film was not folded or the film was cut due to this, and there was no loss of the film.

[Example 5]

A polarizing film was produced in the same manner as in Example 1 except that the polyvinyl alcohol film taken out from the sub-color trough was arranged so that the widening treatment was performed on both end portions in the film width direction by the expander roll after passing through the guide rolls. Respectively. As a result of the production of the polarizing film by this method, during the operation for 24 hours, the film was not folded or the film was cut due to this, and there was no loss of the film.

[Example 6]

The same procedure as in Example 3 was carried out except that the polyvinyl alcohol film taken out from the swelling bath and the dyeing bath was arranged so that the widening treatment was performed on both end portions in the film width direction by a bar made of stainless steel after passing through the expander roll To prepare a polarizing film. The bar made of stainless steel was set to have a length of 200 mm and a diameter of 25 mm so that the angle of the film from the end of the film toward the center of the film was 20 ° and the film was pushed down by 20 mm Respectively. As a result of the production of the polarizing film by this method, during the operation for 24 hours, the film was not folded or the film was cut due to this, and there was no loss of the film.

[Comparative Example 1]

A polarizing film was produced in the same manner as in Example 1 except that no cloth guider was provided. At the end portion of the polyvinyl alcohol film, a folding-in of 7 mm on one side occurred, and a break occurred at the folded portion at the time of drying. As a result of producing the polarizing film by this method, the film was cut three times during the operation for 24 hours, and the polarizing film could be produced, but the film was shown to be folded in, and the productivity and efficiency were low.

[Comparative Example 2]

A polarizing film was produced in the same manner as in Example 3 except that no cloth guider was provided. As a result of the production of the polarizing film by this method, it was found that folding of one 7 mm was generated at the end of the swelling tank and the dyeing tank in which the film was stretched at the end portion of the polyvinyl alcohol film, and in the stretching in the second crosslinking tank, The polarizing film could not be produced.

Table 1 summarizes the above examples and comparative examples.

Examples 1, 4 and 5, in which a polarizing film was produced by the production method of the present invention, and the same polyvinyl alcohol film (original film) as in Example 1 were used to produce a polarizing film The film was taken out from the treatment tank and then subjected to wiping treatment in the film width direction after removing the liquid by using a guide roll or an expander roll so as to suppress the folding caused in the film end portion . Further, from the results of Examples 2, 3, and 6 using a disc film having a thinner film thickness than that of Example 1, the present invention can provide a polarizing film having excellent appearance and productivity, even in a manufacturing condition where a film thickness is thin, It can be seen that it is effective in that it can be manufactured.

According to the present invention, it is possible to suppress the generation of curl at both ends in the width direction of the polyvinyl alcohol-based resin film, and therefore, when the film comes into contact with the nip roll, the folding or breakage caused by curling of the film is suppressed Lt; / RTI > Since the polarizing film obtained by the production method of the present invention is suitably used for a liquid crystal display device, the present invention is industrially very useful.

10: original film of polyvinyl alcohol type resin
11: Feed roll
13: swelling tank
15: dyeing tank
17: Cross-linking tank
19: Washing machine
21: drying furnace
23: polarizing film
30: guide roll
35: Nip roll
L: area where processing is performed to widen both ends in the width direction of the film

Claims (5)

A step of performing a swelling treatment, a dyeing treatment, a crosslinking treatment and a cleaning treatment in this order on a polyvinyl alcohol-based resin film having a thickness of 60 탆 or less, and before or during any one of these steps, Of a polarizing film which is uniaxially stretched by using a difference in peripheral speed of the film (peripheral speed difference)
The liquid on the side contacting the guide roll is removed by passing the film through any one of the guide rolls in a state in which the liquid is adhered to both sides of the film,
Then, a process of widening both end portions in the width direction of the film is performed. The method of producing a polarizing film according to claim 1, wherein the process of widening both ends in the width direction of the film is carried out using a cloth guider. The method of manufacturing a polarizing film according to claim 1, wherein the processing of widening both ends in the width direction of the film is carried out using a widening apparatus selected from the group consisting of a bar, a bend bar, an expander roll and a crown roll. The method according to any one of claims 1 to 3, wherein the process of widening both ends in the width direction of the film is performed after at least one process selected from the group consisting of swelling treatment, dyeing treatment, ≪ / RTI > The method of manufacturing a polarizing film according to any one of claims 1 to 4, wherein an expander roll is used as a guide roll.

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