TWI618621B - Method for manufacturing - Google Patents

Abstract

The present invention relates to a method for producing a polarizing film, comprising the steps of sequentially applying a swelling treatment, a dyeing treatment, a crosslinking treatment, and a washing treatment to a polyvinyl alcohol-based resin film, and using the steps before or in any of the foregoing steps. The two nip rolls extend the film toward one axis to produce a polarizing film, wherein when the film subjected to any of the above processes is taken out from the processing tank and transported to the next step, the film is guided through the state in which the liquid medicine is adhered to both sides of the film. The roller removes the chemical solution on the surface in contact with the guide roller; secondly, the both ends in the film width direction are subjected to a widening treatment. According to the above method, curling at both end portions in the film width direction can be prevented, and the film may be prevented from being pinched or broken.

Description

Method for manufacturing polarizing film

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

Conventionally, a polarizing film is used in a polyvinyl alcohol-based resin film to adsorb a dichroic dye. In other words, an iodine-based polarizing film containing iodine as a dichroic dye or a dye-based polarizing film containing a dichroic dye as a dichroic dye is known. The polarizing film is usually laminated on a single surface, preferably on both sides, with a protective film composed of a polyvinyl alcohol-based resin aqueous solution, and a protective film such as triacetyl cellulose is used as a polarizing plate. It is used in liquid crystal display devices such as LCD TVs, personal computer monitors, and mobile phones.

The polyvinyl alcohol-based resin film is subjected to a swelling treatment, a dyeing treatment, an elongation treatment, a crosslinking treatment (boric acid treatment), and a washing treatment, and is finally dried to produce a polarizing film. At this time, the nip roller disposed before and after the treatment tank is set to have a difference in rotation speed to perform film extension. Further, the film is introduced into the treatment bath or taken out from the treatment bath by changing the direction in which the film is conveyed through a guide roller disposed before or after the treatment bath or in the treatment bath.

In recent years, there has been a demand for a large-scale, thinner, lighter, and lower-cost raw material of a liquid crystal display device, and a manufacturing method capable of achieving a widening of a polarizing film and a thin film formation have been developed. In the case of producing a polarizing film of a thin polyvinyl alcohol-based resin film having a thickness of 10 to 50 μm, a film of 1000 N/m or less is applied to the film, as disclosed in Japanese Laid-Open Patent Publication No. 2004-20633 (Patent Document 1). The tension is extended and the method of manufacturing the polarizing film which is lightweight is achieved.

However, the polyvinyl alcohol-based resin film of the film is subjected to swelling treatment and dyeing treatment. In the case of the cross-linking treatment and the washing treatment, after the film is taken out from each of the treatment tanks, the surface tension of the chemical solution adhering to the surface is present at both ends in the film width direction before the water is removed from both surfaces of the film by the nip rolls. And the problem of curling. Therefore, when the moisture removal by the nip roller is continued, the curled portion may cause film sticking or cracking when the film is sandwiched.

Prior technical literature Patent literature

Patent Document 1: Japanese Patent Laid-Open No. 2004-20633.

When the thickness of the polyvinyl alcohol-based resin film is as small as 60 μm or less in order to meet the requirements of thin film formation and weight reduction of the polarizing film, the curling at both end portions in the film width direction described above is more frequently generated.

An object of the present invention is to provide a method for producing a polarizing film. In the method for producing a polarizing film of a thin polyvinyl alcohol-based resin film, it is possible to prevent the polyvinyl alcohol-based resin from being curled at both end portions in the film width direction. The resulting film is pinched or broken.

In the case of producing a polarizing film of a thin polyvinyl alcohol-based resin film, the present inventors can effectively widen the polyvinyl alcohol-based resin when the polyvinyl alcohol-based resin film is taken out from the treatment tank and transferred to the next step. The method of both end portions in the film width direction is the object, and the present invention has been completed.

In other words, the present invention provides a method for producing a polarizing film, which comprises the steps of sequentially applying a swelling treatment, a dyeing treatment, a crosslinking treatment, and a washing treatment to a polyvinyl alcohol-based resin film having a thickness of 60 μm or less. In the method of manufacturing a polarizing film in which a film is moved toward a shaft by a difference in rotational speed between two nip rolls, in which the film processed by any of the above processes is taken out from the processing tank and transferred to the next step. When the chemical solution is adhered to both sides of the film, the chemical solution is removed by the guide roller to remove the contact surface with the guide roller; secondly, both ends of the film width direction are subjected to the widening treatment.

As the guide roller used in the present invention, a roller having a function of widening the film to be conveyed can be used. Specifically, such a roll may be, for example, a widened roll, a curved roll, or the like.

The widening treatment at both end portions in the film width direction can be carried out using a cloth guide or a widening device such as a tube, an elbow, a widening roller, and a curved roller.

According to the method for producing a polarizing film of the present invention, it is possible to suppress the occurrence of curling of the polyvinyl alcohol-based resin at both end portions in the film width direction. Therefore, when the film is in contact with the nip rolls, it is possible to suppress pinching or cracking due to curling of the film.

10‧‧‧Material film

11‧‧‧feeding rolls

13‧‧‧Swelling trough

15‧‧‧Dyeing tank

17‧‧‧ Crosslinking slot

19‧‧‧cleaning trough

21‧‧‧ drying oven

23‧‧‧ polarizing film

30‧‧‧guide roller

35‧‧‧ nip rollers

L‧‧‧ area

Fig. 1 is a schematic cross-sectional view showing an arrangement example of a device for manufacturing a polarizing film.

Fig. 2 is an explanatory view showing a process of widening both ends of the film after the film is taken out from the treatment tank.

[Method of Manufacturing Polarizing Film]

Specifically, the polarizing film is used in a polyvinyl alcohol-based resin film to adsorb a dichroic dye. The polyvinyl alcohol-based resin as a raw material can be usually obtained by saponifying a polyvinyl acetate-based resin. The degree of saponification is usually about 85 mol% or more, preferably about 90 mol% or more, more preferably about 99 mol% or more. The polyvinyl acetate-based resin is, for example, a copolymer of vinyl acetate and another monomer copolymerizable therewith, in addition to polyvinyl acetate which is a copolymer of vinyl acetate. Other monomer copolymerizable may be, for example, an unsaturated carboxylic acid, an olefin, a vinyl ether, an unsaturated sulfonic acid or the like. The degree of polymerization of the polyvinyl alcohol-based resin is usually about 1,000 to 10,000, preferably about 1,500 to 5,000.

The polyvinyl alcohol-based resin may be modified, and for example, polyethylene formaldehyde, polyvinyl acetal, polyvinyl butyral or the like modified with an aldehyde may be used.

In the present invention, the starting material for producing a polarizing film is an unstretched polyvinyl alcohol-based resin film (raw material film) having a thickness of 60 μm or less, preferably about 10 to 50 μm. Industrially practical membranes have a width of about 1500 to 6000 mm.

The raw material film is sequentially subjected to a swelling treatment, a dyeing treatment, a crosslinking treatment, and a washing treatment, and before or during any of the treatment steps, wet or dry one-axis stretching is performed, and finally dried to produce a polarizing film. . Hereinafter, the manufacturing method of the present invention will be described in detail with reference to Fig. 1 .

Fig. 1 is a schematic cross-sectional view showing an appropriate arrangement example of a manufacturing apparatus used in the method for producing a polarizing film of the present invention. The manufacturing apparatus has a structure in which a raw material film 10 composed of a polyvinyl alcohol-based resin is taken up from a feeding roll 11, and sequentially passed through a swelling tank 13, a dyeing tank 15, a crosslinking tank 17, and a washing tank 19, and finally passed. Drying furnace 21.

Further, in the first drawing, the example in which the swelling tank 13, the dyeing tank 15, the crosslinking tank 17, and the washing tank 19 are each a single tank is shown, but a plurality of sheets may be provided for a single treatment as needed. Processing tank. The produced polarizing film 23 is directly transferred to the next protective film bonding step. Hereinafter, the processing carried out in the present invention will be described.

(swelling treatment)

The swelling treatment is performed for the purpose of removing foreign matter on the surface of the film, removing the plasticizer in the film, imparting dyeability, and plasticizing the film. The treatment conditions are within the range that can achieve the aforementioned purpose, and do not cause damage such as extreme dissolution and devitrification of the membrane.

In the case where the raw material film 10 is initially subjected to swelling treatment, the film is immersed in an aqueous solution of, for example, about 10 to 50 ° C, preferably about 20 to 40 ° C. The immersion time of the film is preferably about 30 to 300 seconds, more preferably about 60 to 240 seconds. Further, in the case where the film which has been previously extended in the gas is swollen, the film is immersed in an aqueous solution of, for example, about 20 to 70 ° C, preferably about 30 to 60 ° C. The immersion time of the film is preferably about 30 to 300 seconds, more preferably about 60 to 240 seconds.

In the swelling treatment, since the polyvinyl alcohol-based resin film is swollen in the width direction to cause wrinkles and the like, the widened roll, the spiral roll, the curved roll, the guide, the bent pipe, and the like are preferably used. Conventional widening devices such as tenter clips are used to treat the wrinkles of the film and transport the film. Further, in order to stabilize the film transport in the bath, the water flow in the swelling bath is controlled by a water shower, or an edge tracking device (EPC (Edge Position Control) device is used in combination to detect the end of the film. In order to prevent the device from being snaked, it has an effect.

In the swelling treatment, since the film is swollen in the direction of the film before the film is swollen, and the film is not actively stretched, in order to eliminate the problem of slack in the film in the transport direction, it is preferable to control, for example, before and after the treatment tank. The speed of the conveying roller, etc. Further, the raw material film 10 may be subjected to one-axis stretching in the swelling treatment, and in this case, the stretching ratio is usually 1.2 to 3 times, preferably 1.3 to 2.5 times.

For the treatment bath used in the swell treatment, in addition to pure water, boric acid in the range of about 0.01 to 10% by weight (Japanese Patent Laid-Open No. 10-153709) and chloride (Japanese Patent Laid-Open No. 06) can be used. -281816), an aqueous solution of an inorganic acid, an inorganic salt, a water-soluble organic solvent, or an alcohol.

The polyvinyl alcohol-based resin film taken out from the swelling tank 13 is continuously conveyed to the dyeing tank 15, and passes through the guide rolls 30 to remove the chemical liquid on the contact surface. Further, after passing through the guide roller 30, the medicinal solution on both sides of the film can be removed by passing the nip roller 35 provided between the swelling groove 13 and the dyeing tank 15. In general, after the film is taken out from the treatment tank, the film end portion is curled during the period leading to the nip roller 35, so that the widening treatment at both end portions in the film width direction described later can effectively prevent this problem. The removal of the chemical solution of the film and the widening of the both end portions in the film width direction can be suitably performed after the dyeing treatment, the crosslinking treatment, and the washing treatment which will be described later.

(dyeing treatment)

The dyeing treatment is carried out for the purpose of adsorbing and orienting a dichroic dye on a polyvinyl alcohol-based resin film. of. The treatment conditions are within the range that can achieve the aforementioned purpose, and do not cause damage such as extreme dissolution and devitrification of the membrane.

In the case where iodine is used as the dichroic dye, an aqueous solution having a concentration in a weight ratio [iodine/potassium iodide/water] = about 0.003 to 0.3 / about 0.1 to 10/100 in a treatment bath (dyeing bath) can be used. Other iodides such as zinc iodide may be used instead of potassium iodide, and potassium iodide and other iodides may also be used in combination. Further, a compound other than the iodide such as boric acid, zinc chloride, cobalt chloride or the like may be coexisted. In the case where boric acid is added, the portion containing iodine is different from the crosslinking treatment described later, and if the weight ratio of water to iodine in the aqueous solution is 100: about 0.003 or more, it can be regarded as a dyeing bath. The dye bath temperature when immersing the film is about 10 to 45 ° C, preferably 20 to 35 ° C, and the film soaking time is about 30 to 600 seconds, preferably 60 to 300 seconds.

In the case where a water-soluble dichroic dye is used as the dichroic dye, an aqueous solution having a concentration by weight (dichroic dye/water) = about 0.001 to 0.1/100 can be used in the treatment bath. In the treatment bath, a dye aid or the like may be coexisted, and for example, an inorganic salt such as sodium sulfate or a surfactant may be contained. The dichroic dye may be used singly or in combination of two or more dichroic dyes. The dye bath temperature at the time of immersing the film is, for example, about 20 to 80 ° C, preferably 30 to 70 ° C, and the film soaking time is about 30 to 600 seconds, preferably about 60 to 300 seconds.

When the polyvinyl alcohol-based resin film is sequentially subjected to a swelling treatment, a dyeing treatment, or a crosslinking treatment, the film is usually stretched in the dyeing tank 15 . The extension of the film is performed by a method in which the nip rollers 35 disposed before and after the dyeing tank 15 have a difference in rotation speed or the like. The cumulative stretching ratio until the dyeing treatment (the stretching ratio in the dyeing treatment in the case where there is no stretching step before the dyeing treatment) is usually 1.6 to 4.5 times, preferably 1.8 to 4 times. When the stretching ratio is less than 1.6 times, the frequency of film breakage increases, and the yield tends to deteriorate.

Further, in the dyeing treatment, in the same manner as the swelling treatment, the polyvinyl alcohol-based resin film is transported in order to remove the wrinkles of the film, and the widening roller, the spiral roller, the curved roller, the guide, the bend, and the like can be disposed. Inside the dyeing tank 15 and/or its inlet and outlet.

(cross-linking processing)

In the cross-linking treatment, the polyvinyl alcohol-based resin film dyed by the dichroic dye is immersed in a weight ratio of water and boric acid to 100 for the purpose of water-repellent and hue adjustment (preventing film bluing, etc.). : It is carried out in an aqueous solution of about 1 to 10. In the case where the dichroic dye used in the dyeing treatment is iodine, the treatment bath preferably contains an iodide to which boric acid is added, and the ratio of the weight of water to the weight of the iodide to which boric acid is added may be 100. : 1~30. The iodide may be, for example, potassium iodide, zinc iodide or the like. Further, a compound other than the iodide may be coexisted, such as zinc chloride, cobalt chloride, zirconium tetrachloride, sodium thiosulfate, potassium sulfite, sodium sulfate or the like.

The crosslinking treatment can appropriately change the concentrations of boric acid and iodide, and the temperature of the bath, depending on the purpose. The cross-linking treatment for the waterproofing use and the cross-linking treatment for the hue adjustment use need not be specifically distinguished, and are carried out under the following conditions. The purpose of the cross-linking treatment is to achieve water-repellent by cross-linking, and in the case where the raw material film composed of the polyvinyl alcohol-based resin is sequentially subjected to swelling treatment, dyeing treatment, and cross-linking treatment, the treatment bath can be used in a concentration ratio by weight [ Boric acid / iodide / water] = 3 ~ 10/1 ~ 20 / 100 aqueous solution. A crosslinking agent such as glyoxal or glutaraldehyde may be used instead of boric acid as needed, and boric acid and a crosslinking agent may also be used in combination. The treatment bath temperature is usually about 50 to 70 ° C, preferably 53 to 65 ° C, and the membrane soaking time is usually about 10 to 600 seconds, preferably 20 to 300 seconds, more preferably 20 to 200 seconds. Further, in the case where 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 aimed at water repellency, a crosslinking treatment aimed at hue adjustment can be performed. Regarding the crosslinking treatment conditions which are intended to adjust the hue, for example, in the case where iodine is used as the dichroic dye, a treatment in which the concentration is a weight ratio [boric acid/iodide/water] = 1 to 5/3 to 30/100 can be used. bath. The treatment bath temperature is usually about 10 to 45 ° C, and the membrane soaking time is usually about 1 to 300 seconds, preferably 2 to 100 seconds.

The above-described cross-linking treatment may be carried out in plural times, usually 2 to 5 times. In this case, the composition and temperature of each of the crosslinking treatment baths used may be the same as or different from the above range. Further, in each of the plurality of steps, cross-linking treatment for cross-linking to achieve water-repellent use and cross-linking for hue adjustment use may be carried out.

(washing treatment)

The washing treatment is performed to remove an additional agent such as boric acid or iodine adhering to the polyvinyl alcohol-based resin film after the crosslinking treatment. The rinsing treatment is performed by, for example, immersing the polyvinyl alcohol-based resin film which has been cross-linked to achieve water repellency and/or color tone adjustment in water, or spraying the water spray on the membrane, or using both of them in combination. .

In the first drawing, an example in which a polyvinyl alcohol-based resin film is immersed in water for washing treatment has been shown. The temperature of the water during the washing process is usually about 2 to 40 ° C, and the soaking time is about 2 to 120 seconds. Moreover, in the cross-linking treatment and the washing treatment, in order to remove wrinkles and convey the polyvinyl alcohol-based resin film, a widening roll can be used.

(Weightening treatment of both end portions in the film width direction of the polyvinyl alcohol resin)

The widening treatment of both end portions in the film width direction of the polyvinyl alcohol-based resin prevents the curling or pinching of the both ends in the width direction of the film. In the present invention, after at least one of the swelling treatment, the dyeing treatment, the crosslinking treatment, and the cleaning treatment, the film is taken out from the treatment tank and transferred to the next step, and the liquid medicine is adhered to both sides of the membrane. The chemical solution which is in contact with the guide roller is removed by the guide roller, and both ends of the polyvinyl alcohol-based resin in the film width direction are subjected to a widening treatment. In the present specification, the widening treatment of both end portions in the film width direction of the polyvinyl alcohol-based resin can be simply described as "widening treatment".

Here, first, the curl of the polyvinyl alcohol-based resin at both end portions in the film width direction will be described. The polyvinyl alcohol-based resin film is as described in Japanese Patent No. 3,429, 476 and Japanese Patent No. 3,478, 534, and the like, when the film is stretched, the water absorption rate of the film is high in a high humidity or underwater environment. Because of the curl at the ends, this is the cause of film jamming or snakes.

In addition to the case where the stretching is carried out under the aforementioned environment, the curl of the end portion of the film may be generated after the film is taken out from the treatment tank, which is caused by the amount of the chemical liquid attached to the surface of the film. For example, referring to Fig. 1, in the case where the film taken out from the treatment tank is passed through the guide rolls, one side of the film is removed by contact with the guide rolls. As a result, in the surface on which the amount of the chemical liquid adhering to the film is large (the surface not in contact with the guide roller), the surface tension of the chemical liquid acts larger than the other surface, so that the surface is wound into the inner side. curly.

Further, in the case where the film is not passed through the guide rolls, curling due to the amount of the chemical liquid adhering to the surface of the film may occur. In this case, for example, when the film is conveyed, the chemical solution adhering to the lower surface side of the film (the surface facing the indoor floor direction) naturally falls, and thus the amount of the chemical liquid attached to the upper surface side and the lower surface side of the film may be different. . In such an embodiment, for example, when the film is taken out from the processing tank and conveyed to the guide roller 30, the liquid level of the processing bath is conveyed at a non-perpendicular angle, and after being taken out from the previous processing tank and passed through the guide roller 30, The film is sprayed in the form of an aqueous solution used in the previous treatment or an aqueous solution used in the next treatment. In addition, the aqueous solution used in the previous treatment may be the same as the aqueous solution used in the previous treatment tank, or may be different.

In addition, the phenomenon in which the end portion of the film is curled after the polyvinyl alcohol-based resin film is taken out from each of the treatment tanks becomes more remarkable when the thickness of the polarizing film is thinner. When the raw material film is thicker than 60 μm, almost no curl occurs due to the mechanical strength of the film.

Next, the widening treatment of the both end portions in the width direction of the polyvinyl alcohol-based resin film defined in the present invention will be described. When the polyvinyl alcohol-based resin film is taken out from the treatment tank and transferred to the next step, the treatment is performed before coming into contact with the nip rolls 35 provided in front of the next step. In the first embodiment, an example in which the both ends in the film width direction are subjected to the widening treatment after the cross-linking treatment is exemplified, but the treatment may be performed in the swelling tank 13, the dyeing tank 15, the cross-linking tank 17, and the washing tank. Performed after any of the treatment tanks in 19. It can also be carried out after a plurality of processing tanks as required. As shown in Fig. 2, the widening treatment system is a polyvinyl alcohol tree. It is particularly effective that the lipid film is taken out from the treatment tank and passed through the guide rolls 30 to widen both end portions in the film width direction. Thereby, the curl generated at both end portions in the film width direction can be prevented, and the problem of film jamming or cracking due to curling of the portion in contact with the roller can be effectively prevented.

After the polyvinyl alcohol-based resin film is taken out from the treatment tank, the guide roller 30 provided to transport the film is subjected to a widening process in the region L, and then conveyed by the nip roller 35 to the next processing step (refer to the second Figure).

The widening process performed in the region L is not particularly limited, and can be performed, for example, by using a fabric guide to hold the film end. Further, in another embodiment, a widening device capable of correcting the curl of the end portion of the film by a shape such as a tube, an elbow, a widening roller or a curved roller can be used, and the widening treatment can be performed by correcting the curl of the end portion of the film. .

In the above-described widening device, in the case where a tube is used, one tube is disposed at an inclination of both ends of the film with respect to the film, and the film can be pressed to widen the film end portion. The tube may be configured to press down the film from the upper side of the film or may be configured to press the film upward from the underside (inner side) of the film. Preferably, the pipe system is configured to press the central portion of the film to be transported as a horizontal plane, press the film downward from the horizontal plane by 0 to 50 mm, or press upward, and more preferably, the end portion of the film is configured to be pressed downward from the horizontal plane. 5~50mm, or press up. Further, preferably, the tube system is disposed such that the direction of the film is 50° or less, preferably 5 to 30° from the end portion of the film toward the central portion of the film. The length of contact of the tube with the membrane (the length from the end of the membrane to the most distal end of the tube contacting the membrane) is preferably from 10 to 500 mm, more preferably from 20 to 300 mm. When the distance is too long, it is difficult to adjust the position of the end portion of the widened film, and it is considered that the tube is bent due to the weight, and when one of the sides is too short, a sufficient widening treatment effect cannot be obtained.

The tube may be arbitrarily selected from various materials such as stainless steel, rubber, and sponge, and may be of a non-rotating type or a rotary type like a roll. Further, the shape of the tube is preferably a cylindrical shape, and the surface of the contact film may be a curved surface. In the case of using a cylindrical tube, the diameter may be about 5 to 100 mm, preferably 10 to 50 mm. Smoothly carried out. Also, the front end of the tube may preferably be curved. The length of the tube may be about 50 to 1000 mm, preferably 100 to 500 mm, as long as it can be widened at the end of the film.

In the present invention, as the guide roller 30, an embodiment in which the widening roller is used may be suitably used. In this case, for example, it can be used to expand the combination of the roller and the guide, and the combination of the widening roller and the widening roller. Further, in the present invention, two or more widening processes may be used in combination. This example may be, for example, an embodiment in which the widening process is performed before the guide roller 30, and then the widening process is performed after the guide roller 30; and an embodiment in which two or more widening processes are performed after the guide roller 30.

(drying treatment)

After the washing treatment or the above-described widening treatment, the polarizing film can be produced by drying the polyvinyl alcohol resin film. The drying of the film can be carried out in the drying furnace 21, for example, at a temperature of about 30 to 100 ° C for about 30 to 600 seconds.

(extension step)

As described above, the axial extension of the film can be carried out in any of the steps or steps in the swelling treatment, the dyeing treatment, the crosslinking treatment, and the cleaning treatment, and can be carried out in only one extension step, or in two The above steps are carried out. In the case of two or more steps, in addition to at least one extension step, a conventional extension method can be employed. The conventional extension method is a heat roller extension, a tenter extension, and the like described in Japanese Patent No. 2731813, in which a difference in rotational speed is set between two nip rolls of a transfer film. Of course, a plurality of extension steps can also be performed. Further, the order of the steps is basically as described above, but the number of processing baths, processing conditions, and the like are not limited.

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

(other steps)

Further, processing other than the above processing may be added for other purposes. Examples of the additional treatment include, for example, a immersion treatment (complementing color treatment) of an aqueous solution of an iodide solution containing no boric acid, which is carried out after the crosslinking treatment. Or an immersion treatment (zinc treatment) of an aqueous solution containing zinc chloride or the like which does not contain boric acid.

The thickness of the polarizing film obtained in this manner is thinner than that of the raw material film, for example, about 5 to 30 μm.

[Polarizer]

The protective film is bonded to at least either side of the polarizing film manufactured in this manner with an adhesive to obtain a polarizing plate. The protective film is, for example, a film composed of a cellulose cefyl cellulose such as cellulose triacetate or Diacetyl Cellulose, or polyethylene terephthalate (Polyethylene). a film composed of a polyester resin such as terephthalate), a polyethylene naphthalate or a polybutylene terephthalate, or a film composed of a polycarbonate resin. A film composed of a cycloolefin resin, an acrylic resin film, or a polypropylene resin film.

In order to improve the adhesion between the adhesive and the polarizing film and/or the protective film, corona treatment, flame treatment, plasma treatment, ultraviolet irradiation, primer may be applied to the bonding surface of the polarizing film and/or the protective film. Surface treatment such as coating treatment or saponification treatment.

The adhesive for bonding the polarizing film and the protective film is not particularly limited as long as it can be mutually adhered to each other and has sufficient adhesion and transparency. From the above viewpoint, an ultraviolet curable adhesive or an aqueous adhesive can be used for bonding the polarizing film and the protective film. The aqueous adhesive is, for example, an aqueous solution of a polyvinyl alcohol-based resin, or an aqueous solution or a urethane-based latex adhesive which can be blended therewith.

The ultraviolet curable adhesive may be a mixture of an acrylic compound and a photoradical polymerization initiator, or a mixture of an epoxy compound and a photocationic polymerization initiator. Further, a cationically polymerizable epoxy compound and a radically polymerizable acrylic compound may be used in combination, and a photocationic polymerization initiator and a photoradical polymerization initiator may be used in combination as an initiator.

In the case of using an ultraviolet curable adhesive, the film is laminated with an adhesive interposed therebetween. Thereafter, the adhesive is cured by irradiation of ultraviolet rays. The light source of the ultraviolet light is not particularly limited, but preferably the light distribution wavelength is 400 nm or less. Specifically, a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultra high pressure mercury lamp, a chemical lamp, a black light lamp, and a microwave can be preferably used. Excited mercury lamps, metal halide lamps, etc.

The light irradiation intensity for curing the ultraviolet curable adhesive is appropriately determined by the composition of the adhesive, and is not particularly limited. However, it is preferable that the irradiation intensity in the effective wavelength range in which the polymerization initiator is activated is 0.1~. 6000mW/cm ² . When the irradiation intensity is appropriately selected between the ranges, the reaction time is not excessively long, and the yellowing of the adhesive or the deterioration of the polarizing film due to heat radiated from the light source and heat generation at the time of curing of the adhesive can be suppressed. The light irradiation time is also appropriately selected depending on the need for curing of the adhesive, and is not particularly limited. However, it is preferable that the cumulative light amount obtained by multiplying the irradiation intensity by the irradiation time is set to 10 to 10000 mJ/cm ² . By appropriately selecting the amount of accumulated light between the ranges, a sufficient amount of the original active species of the polymerization initiator can be generated and the hardening reaction can be surely performed, and the irradiation time can be prevented from being excessively long to maintain good productivity. The thickness of the adhesive layer after hardening is usually 0.1 to 10 μm, more preferably 0.2 to 4 μm.

In the case where the ultraviolet curable adhesive of the film containing the polarizing film or the protective film is cured by ultraviolet irradiation, it is preferable not to lower the polarization degree, the transmittance and the hue of the polarizing film, and the transparency of the protective film. The polarizing plate is hardened under the conditions of each function.

When an aqueous adhesive is used, for example, a method in which an adhesive is uniformly applied to the surface of the film or flows between the two films, and the two films are superposed on each other through the coating layer, and bonded to each other by a roll or the like. After drying, it may be further cured at room temperature or a slightly higher temperature, for example, at a temperature of about 20 to 45 °C. The thickness of the layer may be appropriately selected from the range of about 0.001 to 5 μm, in combination with the type of the adhesive or the combination of the two films. It is preferably 0.01 μm or more, and more preferably 2 μm or less.

[Examples]

Hereinafter, specific embodiments of the present invention will be described, but the present invention is not limited to these examples.

[Example 1]

For a polyvinyl alcohol film with a thickness of 60 μm [Kuraray Vinylon VF-PE # 6000 manufactured by Nissho Kuraray International Co., Ltd., a polymerization degree of 2400, a saponification degree of 99.9 mol% or more ], the film was kept in a state of no slack and immersed in a swelling tank to which pure water of 30 ° C was added for 100 seconds to allow the film to be sufficiently swollen. Next, it is immersed in an aqueous solution (dyeing tank) containing iodine and potassium iodide and subjected to one-axis extension to carry out cross-linking treatment for water repellent use, and immersed in a 55 ° C aqueous solution having a weight ratio [boric acid / potassium iodide / water] of 4.4/12/100. (First crosslinking tank); Next, while immersing in the same composition aqueous solution (second crosslinking tank) set to 59 ° C, one-axis stretching was performed until the cumulative stretching ratio (compared with the raw material state) was 5.5 times. Thereafter, the cross-linking treatment for the hue adjustment use was carried out, and the mixture was immersed in a 40° C aqueous solution (complementary color tank) having a weight ratio [boric acid/potassium iodide/water] of 2.9/9/100, and then immersed in a washing water having a pure water of 12° C. The clean tank was dried at 70 ° C for 3 minutes to prepare a polarizing film. At this time, the film transfer system on the exit side of the complementary color groove is performed as shown in Fig. 2, and the film taken out from the complementary color groove is widened at both ends in the film width direction by the guide after passing through the guide roller. deal with. The polarizing film produced by this method did not show that the film was sandwiched or the film was cut during the 24-hour operation period, and there was no film loss.

[Example 2]

A polyvinyl alcohol film having a thickness of 50 μm (trade name "Kura Reeve Nylon VF-PE #5000" manufactured by Nissho Kuraray International Co., Ltd., degree of polymerization 2400, saponification degree: 99.9 mol% or more) was used to carry out A polarizing film was produced in the same manner as in Example 1. The polarizing film produced by this method did not show that the film was sandwiched or the film was cut during the 24-hour operation period, and there was no film loss.

[Example 3]

The manufacturing apparatus was configured to use a polyvinyl alcohol film having a thickness of 30 μm (the product name "Kura Reeves VF-PE # 3000" manufactured by Nissho Kuraray International Co., Ltd., a polymerization degree of 2400, and a saponification degree of 99.9 mol. % or more], after performing the complementary color tank of the first embodiment, the widening treatment is added to the swelling tank and dyeing. On the side of the groove outlet, the film taken out from the swelling tank and the dyeing tank is passed through a widening roller (instead of the guide roller), and then the both ends in the film width direction are widened by the guide to remove the difference, A polarizing film was produced in the same manner as in Example 1. The polarizing film produced by this method did not show that the film was sandwiched or the film was cut during the 24-hour operation period, and there was no film loss.

[Example 4]

The manufacturing apparatus is configured such that the polyvinyl alcohol film taken out from the complementary color groove is subjected to a widening process by the guide to the both ends in the film width direction after passing through the widening roller, and in addition to the above difference, the first embodiment is used. A polarizing film was produced in the same manner. The polarizing film produced by this method did not show that the film was sandwiched or the film was cut during the 24-hour operation period, and there was no film loss.

[Example 5]

The manufacturing apparatus is configured such that the polyvinyl alcohol film taken out from the complementary color groove is subjected to a widening treatment at both end portions in the film width direction by the widening roller after passing through the guide roller, and the first embodiment is used in addition to the above difference. A polarizing film was produced in the same manner. The polarizing film produced by this method did not show that the film was sandwiched or the film was cut during the 24-hour operation period, and there was no film loss.

[Example 6]

The manufacturing apparatus is configured such that the polyvinyl alcohol film taken out from the swelling tank and the dyeing tank is subjected to a widening treatment at both ends in the film width direction by a stainless steel tube after passing through the widening roller, in addition to the above difference, A polarizing film was produced in the same manner as in Example 3. This stainless steel pipe was used in a length of 200 mm and a diameter of 25 mm, and was placed at an angle of 20 from the film end toward the center of the film in the film forming direction, and the film was pressed down by 20 mm. The polarizing film produced by this method did not show that the film was sandwiched or the film was cut during the 24-hour operation period, and there was no film loss.

[Comparative Example 1]

A polarizing film was produced in the same manner as in Example 1 except that the cloth guide was not provided. The end of the polyvinyl alcohol film was sandwiched by 7 mm on one side, and the sandwiched portion was broken when dried. In this way The polarizing film produced was cut three times during the 24-hour operation period, and although a polarizing film was produced, it was found that the film was sandwiched, and the productivity and efficiency were lowered.

[Comparative Example 2]

A polarizing film was produced in the same manner as in Example 3 except that the cloth guide was not provided. The polarizing film produced by the method has a single side 7 mm sandwiching at the end of the polyvinyl alcohol film at the swelling groove and the dyeing groove outlet where the film is extended, and the second crosslinking groove is extended. The film is often cut off, so that a polarizing film cannot be produced.

Table 1 summarizes the foregoing examples and comparative examples.

Comparing Example 1, Example 4, and Example 5 in which a polarizing film was produced according to the manufacturing method of the present invention, and using the same polyvinyl alcohol film (raw material film) as in Example 1 without using the manufacturing method of the present invention to produce a polarizing film In Comparative Example 1, it is known that after the film is taken out from the treatment tank, after the chemical solution is removed by using a guide roll or a widening roll, by widening the film width direction, it is possible to suppress the occurrence of the film at the end portion. embed. Moreover, from the results of Example 2, Example 3, and Example 6 in which the film thickness was thinner than that of Example 1, the results of the present invention were found to be in a manufacturing condition in which the film thickness was thin and the pinching was likely to occur. It is also possible to produce a polarizing film which is excellent in appearance and productivity.

According to the invention, it is possible to suppress the occurrence of curling of the polyvinyl alcohol-based resin at both end portions in the film width direction, so that when the film is brought into contact with the nip rolls, the pinching or cracking caused by the curling of the film can be suppressed. Since the polarizing film obtained by the manufacturing method of the present invention is suitable for use in a liquid crystal display device, the present invention is extremely useful industrially.

Claims (6)

A method for producing a polarizing film, comprising the steps of sequentially applying a swelling treatment, a dyeing treatment, a crosslinking treatment, and a washing treatment to a polyvinyl alcohol-based resin film having a thickness of 60 μm or less, before or in any of the foregoing steps. A method for manufacturing a polarizing film by stretching a film toward a shaft by using a difference in rotational speed between two nip rolls, wherein: when the film subjected to any of the foregoing processes is taken out from the processing tank and transported to the next step, when both sides of the film are attached In the state of the chemical liquid, the chemical solution which is in contact with the guide roller is removed by the guide roller; secondly, the both ends in the film width direction are subjected to the widening treatment. The method for producing a polarizing film according to the first aspect of the invention, wherein the widening of the both ends in the film width direction is performed by using a fabric guide. The method for producing a polarizing film according to claim 1, wherein the width direction selected by the group consisting of a tube, an elbow, a widening roller and a curved roller is used to perform two directions in the film width direction. Widening of the end. The method for producing a polarizing film according to any one of claims 1 to 3, wherein the method of selecting a group consisting of swelling treatment, dyeing treatment, crosslinking treatment, and washing treatment is selected. After at least one type of treatment, a process of widening both end portions in the film width direction is performed. The method for producing a polarizing film according to any one of claims 1 to 3, wherein a widening roller is used as the guide roller. The method for producing a polarizing film according to the fourth aspect of the invention, wherein a widening roller is used as the guide roller.