TW201522027A - Method for making a polarizing film - Google Patents

Abstract

This invention provides a method for making a polarizing film, the method including a swelling conditioning of an elongate polyvinyl alcohol type resin film having a thickness of 65 [mu]m or less by pulling the film out of a wetting bath after the film is dipped in the wetting bath while the film is being continuously moved, a dying treatment of the film by pulling the film out of a dying bath after the film is dipped in the dying bath, and a cross-linking treatment of the film by pulling the film out from a cross-linking bath after the film is dipped in the cross-linking bath, the method further including a process for reducing the amount of liquid adhered to the two widthwise side portions of two surfaces of the film when the film is pulled out of at least one treating bath selected from the group consisting of the swelling bath, the dying bath, and the cross-linking bath.

Description

Method for manufacturing polarizing film

The present invention relates to a method of producing a polarizing film which can be used as a constituent member of a polarizing plate.

The polarizing film has been conventionally used to adsorb a dichroic dye such as iodine or a dichroic dye using a polyvinyl alcohol-based resin film which is stretched by one axis. In general, a polarizing film is used as a polarizing plate by laminating a protective film on one surface or both sides, and is used for a liquid crystal display device such as a liquid crystal television, a screen for a personal computer, and a mobile phone.

In general, the polarizing film is produced by subjecting a long-length polyvinyl alcohol-based resin film continuously conveyed to a treatment bath such as a swelling bath, a dye bath, or a crosslinking bath. At the same time, a one-axis extension process is performed between the series of processes.

In recent years, there has been a tendency to increase the size, thickness, weight, and cost of a liquid crystal display device in the market, and accordingly, a production method capable of achieving a widening or thinning of a polarizing film has been developed. For example, Japanese Laid-Open Patent Publication No. 2004-20633 (Patent Document 1) discloses a method for producing a polarizing film which is a thin polyvinyl alcohol-based resin film having a thickness of 65 μm or less, specifically, 10 to 50 μm. system When the polarizing film is formed, the film is stretched while applying a tension of 1000 N/m or less to achieve weight reduction of the film.

[Previous Technical Literature]

[Patent Document] Japanese Patent Laid-Open Publication No. 2004-20633

As described above, although a thinner polarizing film is required, in order to satisfy this requirement, when a polyvinyl alcohol-based resin film having a thin thickness as a raw material film is used, when the film is pulled out from the processing bath, it is adhered to The surface tension of the liquid at both ends in the width direction of the film causes the both end portions to be warped in a circular shape toward the inner side, or the portion which is warped strongly and which is curled toward the inner side is folded in a state of being adhered to the inner side portion of the film. problem. Further, when the film which is warped or folded is passed through the nip roll or when the stretching treatment is applied, creases may occur, or the crease may be cracked to cause cracking.

Therefore, an object of the present invention is to provide a method for producing a polarizing film from a thin polyvinyl alcohol-based resin film, which can be prevented from occurring at both end portions in the width direction of the polyvinyl alcohol-based resin film. Warping and folding.

The present invention provides a method of producing a polarizing film shown below.

[1] A method for producing a polarizing film by applying a long-length polyvinyl alcohol-based resin film having a thickness of 65 μm or less while applying a dip a method of producing a long strip-shaped polarizing film by swelling treatment after being swelled by a swelling bath, immersing in a dyeing bath, dyeing treatment, immersing in a crosslinking bath, and pulling out the cross-linking treatment, wherein the method is as follows: The film drawn by at least one of the dye bath and the cross-linking bath is subjected to a treatment for reducing the amount of liquid adhering to both end portions in the width direction of both sides.

[2] The method for producing a polarizing film according to [1], wherein the treatment for reducing the amount of liquid adhesion comprises a treatment of a film blowing gas drawn from the at least one processing bath.

[3] The method for producing a polarizing film according to [1], wherein the treatment for reducing the amount of adhesion of the liquid comprises a treatment for a film contact roll or a rod pulled out from the at least one processing bath.

[4] The method for producing a polarizing film according to [2], wherein the treatment for reducing the amount of liquid adhering is performed only on both end portions in the width direction.

[5] The method for producing a polarizing film according to [1], wherein the treatment for reducing the amount of adhesion of the liquid comprises the treatment that the film drawn from the at least one treatment bath is directly introduced to a level relative to the ground. Set the nip rolls.

[6] The method for producing a polarizing film according to [4], wherein the film to which the treatment for reducing the amount of liquid adhesion has been applied is transported using a flat roll.

[7] The method for producing a polarizing film according to [6], wherein the film width after being pulled out from the at least one processing bath is immersed The stretching treatment is applied to the treatment bath in such a manner that the film width is less than the width of the film before the treatment bath.

[8] The method for producing a polarizing film according to [7], wherein the cumulative stretching ratio of the stretching treatment is 2.0 to 4.5 times.

[9] The method for producing a polarizing film according to [7], wherein the temperature of the treatment bath to which the stretching treatment is applied is 15 to 40 °C.

[10] The method for producing a polarizing film according to any one of [1] to [9] wherein the at least one treatment bath is a swelling bath and/or a dye bath.

[11] The method for producing a polarizing film according to [10], wherein the at least one treatment bath is a swelling bath.

According to the method of the present invention, it is possible to effectively suppress warpage and folding of both end portions in the width direction of the film which are conventionally produced in the method of producing a polarizing film from a thin polyvinyl alcohol-based resin film.

10‧‧‧The membrane of polyvinyl alcohol resin

11‧‧‧Send rolls

13‧‧‧Swelling bath

15‧‧‧dye bath

17‧‧‧Cross-link bath

19‧‧‧ Washing bath

21‧‧‧ drying oven

23‧‧‧ polarizing film

30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41‧‧‧ guide rollers

50, 51, 52, 53, 54, 55‧‧‧ nip rolls

60, 61‧‧‧ gas blowing device

Fig. 1 is a cross-sectional view schematically showing an example of a method for producing a polarizing film of the present invention and an apparatus for producing a polarizing film used therefor.

Fig. 2 (a) and (b) are schematic views showing an example of a process for reducing the amount of liquid adhering to the nip roll.

<Method of Manufacturing Polarized Film>

In the present invention, the polarizing film is a method in which a polyvinyl alcohol-based resin film is adsorbed and oriented to a dichroic dye (iodine or a dichroic dye). Composition of polyvinyl alcohol resin film The polyvinyl alcohol-based resin is 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 may be, for example, a polyvinyl acetate of a single polymer of vinyl acetate, or a copolymer of vinyl acetate and another monomer copolymerizable therewith. The other monomer which can be copolymerized may, for example, be an unsaturated carboxylic acid, an olefin, a vinyl ether or an unsaturated sulfonic acid. The degree of polymerization of the polyvinyl alcohol-based resin is usually from about 1,000 to 10,000, preferably from about 1,500 to 5,000.

These polyvinyl alcohol-based resins may be modified, and for example, polyvinyl formal, polyvinyl acetal, or polyvinyl butyral modified with an aldehyde may be used. Wait.

In the present invention, as the starting material for producing a polarizing film, an unstretched polyvinyl alcohol-based resin film (sheath film) having a thickness of 65 μm or less is used, preferably about 10 to 50 μm, more preferably about 10 to 35 μm. When the thickness of the embryonic membrane is thicker than 65 μm, since the mechanical strength of the film is sufficiently high, curling or folding of the end portion in the film width direction which occurs after the film is taken out from the treatment bath is hardly generated.

The width of the germ film is not particularly limited, and may be, for example, about 400 to 6000 mm, but the larger the film width, the more likely the warpage and folding are caused. Therefore, when the manufacturing method of the present invention is such that the width of the germ film is large, specifically, when the film width is 1000 mm or more, it is particularly effective.

The embryonic membrane system is prepared as a roll (rewinding product) of a long strip-shaped unstretched polyvinyl alcohol-based resin film.

The polarizing film can be continuously manufactured into a long polarizing film by performing a predetermined processing step by continuously transporting the above-mentioned germ film along the film transport path of the polarizing film manufacturing apparatus. The predetermined processing steps include: a swelling treatment step of immersing in the swelling bath, a dyeing treatment step of immersing the film after the swelling treatment in the dyeing bath, and immersing the dyed film in the crosslinking bath. Cross-linking processing steps. Further, a one-axis stretching process is applied wet or dry between the series of processing steps (i.e., before or during one or more of the processing steps). Additional processing steps can be added as needed.

Hereinafter, the method for producing a polarizing film of the present invention will be described in further detail with reference to Fig. 1 . Fig. 1 is a cross-sectional view schematically showing an example of a method for producing a polarizing film of the present invention and an apparatus for producing a polarizing film used therefor. The polarizing film manufacturing apparatus shown in Fig. 1 is conveyed along the film transport path while continuously ejecting the embryonic film 10 made of a polyvinyl alcohol-based resin from the delivery roller 11 to sequentially swell. The bath 13, the dye bath 15, the cross-linking bath 17, and the washing bath 19 are finally formed by the drying oven 21. The obtained polarizing film 23 can be directly conveyed to the next polarizing plate manufacturing step (step of bonding the protective film on one side or both sides of the polarizing film 23).

In addition, the first figure shows an example in which the swelling bath 13, the dye bath 15, the crosslinking bath 17, and the washing bath 19 are provided in a single groove and a groove, and a treatment bath of two or more tanks may be provided as needed. (for example, the swelling bath 13, the dyeing bath 15, the crosslinking bath 17, and the washing bath 19, and also the place where the polyvinyl alcohol-based resin film provided on the film transport path is accommodated and treated. The bath of the chemistry is collectively referred to as the "treatment bath." ).

The film transport path of the polarizing film manufacturing apparatus can support the transported film in addition to the above-mentioned processing bath, or further press and hold the guide rolls 30 to 41 or the transported film which can change the film transport direction, and can provide The driving force generated by the rotation is applied to the film, or further configured by arranging the nip rolls 50 to 55 which can change the film conveying direction at appropriate positions. For example, the guide roller system can be disposed before or after the treatment bath, whereby the film of the treatment bath can be introduced, immersed, and pulled out from the treatment bath (see Fig. 1).

Further, the polarizing film manufacturing apparatus shown in Fig. 1 is disposed before and after each processing bath, and the nip rolls (nip rolls 50 to 54) are disposed, whereby the processing rolls can be disposed before and after the processing rolls in any one or more of the processing baths. The circumferential speed difference is imparted between the nip rolls to extend between the rolls extending in the longitudinal direction.

The polyvinyl alcohol-based resin film is pulled out from the treatment bath in a state in which the treatment liquid is adhered to both sides. In the present invention, in order to suppress the above-mentioned warpage and folding, a polyvinyl alcohol-based resin film which is pulled out from at least one treatment bath selected from the group consisting of the swelling bath 13, the dye bath 15, and the crosslinking bath 17 is used. The treatment for reducing the amount of liquid adhering to both end portions in the width direction of both sides is performed. Hereinafter, each processing procedure will be described.

(swelling treatment)

The swelling treatment is carried out for the purpose of removing foreign matter on the surface of the embryonic membrane 10, removing the plasticizer in the embryonic membrane 10, imparting dyeability, plasticizing the embryonic membrane 10, and the like. The treatment conditions are within the range in which the object can be achieved without causing problems such as excessive dissolution or devitrification of the membrane 10 set.

Referring to Fig. 1, the swelling treatment can be carried out by the film transport path constructed by the guide rolls 30 to 32 and the nip roll 50, and the blast film 10 is immersed in the swelling bath 13 (the treatment liquid accommodated by the swell tank). The predetermined time is then pulled out and implemented. It is also possible to apply a shaft extension treatment in the swelling bath 13 by using the circumferential speed difference between the nip roll 50 and the nip roll 51.

When the germplasm 10 is initially subjected to swelling treatment, the temperature of the swelling bath 13 is, for example, about 10 to 50 ° C, preferably about 10 to 40 ° C, more preferably about 15 to 30 ° C. The immersion time of the membrane 10 is preferably from about 10 to 300 seconds, more preferably from about 20 to 200 seconds. Further, when the film which has been extended in advance in the gas is swollen, the temperature of the swelling bath 13 is preferably, for example, about 20 to 70 ° C, preferably about 30 to 60 ° C. The immersion time of the film is preferably from about 30 to 300 seconds, more preferably from about 60 to 240 seconds.

In addition to the pure water, boric acid (Japanese Patent Laid-Open No. Hei 10-153709), chloride (Japanese Patent Laid-Open No. Hei 06-281816), and inorganics may be added to the swell bath 13 in addition to the pure water. An aqueous solution of an acid, an inorganic salt, a water-soluble organic solvent, an alcohol or the like.

In the swelling treatment, there is a problem in that the germ film 10 is swollen in the width direction to cause wrinkles in the film. As a means for eliminating the wrinkles while conveying the film, it is possible to use, for example, an expander roll, a spiral roll, or a crown roll for the guide rolls 30, 31 and/or 32. Rollers having an expanded width function, or other widened width devices such as a cross guide, a bend rod, and a tenter crip. Another means of inhibiting the occurrence of wrinkles is to apply the extension For this, it is described in the project of extension processing.

In the swelling treatment, since the film is swollen and enlarged in the direction in which the film is conveyed, it is preferable to control the pressure before and after the swelling bath 13 in order to eliminate the relaxation of the film in the conveying direction when the film is not stretched. The speed of the rolls 50, 51 and the like.

Further, in order to stabilize the film transport in the swell bath 13, the water flow in the swell bath 13 is controlled by a shower in the water, or an EPC device (Edge Position Control device: the end portion of the film is detected to prevent the film from being snaking) is also used. it works.

The film drawn from the swelling bath 13 is sequentially introduced into the dyeing bath 15 by the guide rolls 32 and the nip rolls 51.

(dyeing treatment)

The dyeing treatment is carried out for the purpose of adsorbing the dichroic dye, orienting it to the polyvinyl alcohol-based resin film after the swelling treatment. The treatment conditions are determined in such a range that the object can be achieved without causing problems such as excessive dissolution or devitrification of the film. Referring to Fig. 1, the dyeing process can be carried along the film transport path constructed by the guide rolls 33 to 35 and the nip roll 51, and the swollen film is immersed in the dye bath 15 (contained by the dyeing tank). The predetermined time in the treatment liquid is then carried out by pulling out.

When iodine is used as the dichroic dye, the dyeing bath 15 can use, for example, an aqueous solution having a concentration by weight of iodine/potassium iodide/water = about 0.003 to 0.3/about 0.1 to 10/100. Other iodides such as zinc iodide may be used instead of potassium iodide, and 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 used. coexist. When boric acid is added, the point containing iodine is different from the crosslinking treatment described later, and if the aqueous solution contains about 0.003 part by weight or more of iodine per 100 parts by weight of water, it can be regarded as the dyeing bath 15. The temperature of the dyeing bath 15 when the film is impregnated is usually about 10 to 45 ° C, preferably 10 to 40 ° C, preferably 20 to 35 ° C, and the immersion time of the film is usually about 30 to 600 seconds, and 60 to 300. Seconds is better.

When a water-soluble dichroic dye is used as the dichroic dye, an aqueous solution having a concentration of dichroic dye/water = about 0.001 to 0.1/100 by weight may be used in the dyeing bath 15. In the dyeing bath 15, a dyeing aid or the like may be allowed to coexist, and an inorganic salt such as sodium sulfate or a surfactant may be contained. The dichroic dye may be used alone or in combination of two or more kinds of dichroic dyes. The temperature of the dyeing bath 15 when the film is impregnated is, for example, about 20 to 80 ° C, preferably 30 to 70 ° C, and the immersion time of the film is usually about 30 to 600 seconds, preferably about 60 to 300 seconds.

In the dyeing treatment step, it is preferred to carry out one of the stretching of the film by the dyeing bath 15. One of the axial extension of the film can be carried out by a method such as a circumferential speed difference between the nip roll 51 and the nip roll 52 disposed before and after the dyeing bath 15.

Even in the dyeing process, as in the case of the swelling treatment, in order to remove the wrinkles of the film while conveying the polyvinyl alcohol-based resin film, for example, a spreader roll, a spiral roll, or a crown roll can be used for the guide rolls 33, 34 and/or 35. Rollers with expanded width function, using other width-enhancing devices such as transverse guides, curved rods, and tenter clamps. Another means for suppressing the occurrence of wrinkles is the same as the swelling treatment, and the stretching treatment is applied.

The film drawn from the dyeing bath 15 is introduced into the crosslinking bath 17 through the guide rolls 35 and the nip rolls 52 in this order.

(cross-linking processing)

The crosslinking treatment is carried out by the purpose of crosslinking resistance to water hydration or hue adjustment (preventing film bluing, etc.). Referring to Fig. 1, the cross-linking treatment can be carried out by the film transport path constructed by the guide rolls 36 to 38 and the nip roll 52, and the dyed film is immersed in the cross-linking bath 17 (by the cross-linking tank) The predetermined time in the contained treatment liquid is carried out by pulling out.

The crosslinking bath 17 may contain an aqueous solution of about 1 to 10 parts by weight of boric acid with respect to 100 parts by weight of water. When the dichroic dye used in the dyeing treatment is iodine, the cross-linking bath 17 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. The iodide may, for example, be potassium iodide or zinc iodide. Further, a compound other than the iodide such as zinc chloride, cobalt chloride, zirconium chloride, sodium thiosulfate, potassium sulfite, sodium sulfate or the like may be allowed to 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. The cross-linking treatment for the hydration resistance and the cross-linking treatment for the hue adjustment were not particularly distinguished, and were carried out under the following conditions. The purpose of the cross-linking treatment is to achieve water resistance by cross-linking. When the polyvinyl alcohol-based resin film is applied in the order of swelling treatment, dyeing treatment, and cross-linking treatment, the cross-linking bath 17 can be in a concentration ratio by weight. It is an aqueous solution of boric acid/iodide/water = 3 to 10/1 to 20/100. If necessary, a boronic acid such as glyoxal or glutaraldehyde may be used instead of boric acid, and boric acid and a crosslinking agent may be used in combination. The temperature of the crosslinking bath 17 when the film is impregnated is usually 50 to Preferably, the immersion time of the film is about 10 to 600 seconds, preferably 20 to 300 seconds, preferably 20 to 200 seconds, at about 70 ° C. Further, when the polyvinyl alcohol-based resin film which is stretched in advance is applied in the order of dyeing treatment and crosslinking treatment, the temperature of the crosslinking bath 17 is usually about 50 to 85 ° C, preferably 55 to 80 ° C.

After the crosslinking treatment for the purpose of water resistance, a crosslinking treatment for the purpose of color adjustment can also be performed. In the cross-linking treatment for the purpose of hue adjustment, for example, when iodine is used as the dichroic dye, a cross-linking bath having a concentration of boric acid/iodide/water = 1 to 5/3 to 30/100 by weight may be used. . The temperature of the crosslinking bath 17 when the film is impregnated is usually about 10 to 45 ° C, and the immersion time of the film is usually about 1 to 300 seconds, preferably 2 to 100 seconds.

The cross-linking treatment can also be carried out plural times, usually 2 to 5 times. In this case, the composition and temperature of each of the crosslinking baths to be used may be within the above range, and may be the same or different. The cross-linking treatment for the hydration resistance and the cross-linking treatment for the hue adjustment by cross-linking can be carried out in a plurality of steps, respectively.

It is also possible to apply a shaft extension treatment in the crosslinking bath 17 by using the difference in circumferential speed between the nip roll 52 and the nip roll 53.

Even in the cross-linking treatment, in the same manner as the swelling treatment, in order to remove the wrinkles of the film and simultaneously transport the polyvinyl alcohol-based resin film, it is also possible to use the guide rolls 36, 37 and/or 38 such as a spreader roll or a spiral roll. Rolls with crown-expanding width function, or other wide-width devices such as cross-guides, curved rods, and tenter clamps. In order to suppress the occurrence of wrinkles One means is applied to the extension treatment as in the swelling treatment.

The film drawn from the crosslinking bath 17 is introduced into the washing bath 19 through the guide rolls 38 and the nip rolls 53 in this order.

(washing treatment)

The production method of the present invention may include a washing treatment after the crosslinking treatment. The cleaning treatment is carried out for the purpose of removing excess boric acid or iodine adhering to the polyvinyl alcohol-based resin film. In the washing treatment, for example, the crosslinked polyvinyl alcohol resin film may be immersed in the washing bath 19 (water), or the film may be sprayed with water as a shower, or may be used in combination therewith.

In the first embodiment, the polyvinyl alcohol-based resin film is immersed in the washing bath 19 to carry out a washing treatment. The temperature of the washing bath 19 (water) in the washing treatment is usually about 2 to 40 ° C, and the immersion time of the film is usually about 2 to 120 seconds.

Further, even in the cleaning process, the purpose of removing the wrinkles while transporting the polyvinyl alcohol-based resin film can be expanded in the guide rolls 39, 40, and/or 41 using, for example, a spreader roll, a spiral roll, or a crown roll. Width-function rolls, or other wide-width devices such as cross-guides, curved rods, and tenter clamps. Further, in the washing treatment, in order to suppress the occurrence of wrinkles, an extension treatment may be applied.

(Process for lowering the amount of liquid adhesion at both end portions in the width direction of the polyvinyl alcohol-based resin film)

In the present invention, in order to suppress the above-mentioned warpage or folding, the polyvinyl alcohol-based resin film drawn from at least one of the treatment baths selected from the group consisting of the swelling bath 13, the dye bath 15, and the crosslinking bath 17 is Make it double sided The treatment of reducing the amount of liquid adhesion at both ends in the width direction. The both end portions in the width direction of the film are preferably about 2 to 20% of the entire film width as a total of both end portions. The treatment for reducing the amount of liquid adhering at both end portions in the width direction can be carried out by, for example, the following methods 1) to 3).

1) a double-side blowing gas for a polyvinyl alcohol-based resin film drawn from at least one processing bath, thereby removing a liquid adhering to a surface of at least both end portions in the film width direction, thereby reducing the amount of liquid adhesion The method. Fig. 1 is a view showing an example of a treatment for reducing the amount of liquid adhering by using this method, and using gas blowing devices 60 and 61, the gas is ejected to both ends in the width direction of both sides of the film drawn from the swelling bath 13, and The liquid adhering to the surfaces of the both end portions is removed.

As shown in Fig. 1, when the film drawn from the processing bath passes through the nip roll (the nip roll 51 in Fig. 1), the gas blowing treatment is performed before passing through the nip roll. Further, as in the example shown in Fig. 1, the film drawn from the processing bath is first passed through a guide roll (guide roll 32 in Fig. 1), and thereafter passed through a nip roll (the nip roll in Fig. 1). 51), the gas blowing treatment may be performed before the guiding roller and between the guiding roller and the nip roller (as shown in FIG. 1), or only Implemented in either. Preferably, the gas blowing treatment is carried out on a film which is drawn at least from the liquid level of the treatment bath.

The type of the gas used for the gas blowing treatment is not particularly limited, but is usually a gas inert to the film such as air, nitrogen, or argon, and air is preferred. The injection pressure of the gas is not particularly limited as long as it is a level at which the adhered liquid can be blown off.

In order to suppress warpage or folding of the film pulled out from the processing bath, it is sufficient to perform gas blowing treatment on both ends of the film in the width direction, except for the both ends in the width direction. Gas blowing treatment is also performed on the surface areas of other films. For example, the entire surface of the film may be subjected to a gas blowing treatment.

The gas blowing devices 60 and 61 may be, for example, a pipe (pipe) having one or a plurality of injection holes for injecting gas, a hose or an air knife, or the like.

2) a double-sided contact roller or a rod (pressure-bonding) of a polyvinyl alcohol-based resin film drawn from at least one treatment bath, whereby at least two of the film width directions are adhered by the roller or the rod A method in which the liquid on the surface of the end falls and the amount of liquid adhered is lowered.

When the film drawn from the processing bath passes through a nip roll (for example, the nip roll 51 in Fig. 1), the contact treatment with the roll or the rod is performed before passing through the nip roll. Further, the film drawn from the processing bath first passes through a guide roll (for example, the guide roll 32 in Fig. 1), and then passes through a nip roll (for example, the nip roll 51 in Fig. 1), The contact treatment of the roller or the bar may be performed before passing the guide roller and between the guide roller and the nip roller, or may be performed only by any of the above. Preferably, it is carried out at least before passing through the above-mentioned guide rolls. More preferably, the contact treatment with the roll or rod is carried out at least for the film drawn from the liquid level of the treatment bath.

The roller which is in contact with the surface of both end portions in the width direction of the film may be, for example, a transverse guide from which a pair of rolls of a polyvinyl alcohol-based resin film drawn from the treatment bath is sandwiched. The film after passing between the pair of rolls is attached to the surface area in contact with the roll to peel off the adhered liquid. The other side The rod that is in contact with the surface at both end portions in the width direction of the film is not clamped by the self-rotating roller, but is a polyvinyl alcohol-based resin film that is pulled out from the processing bath from both sides thereof, or One side is in contact with the film in one pair of rods. Even when such a rod is used, the adhered liquid peels off by the film between the rods being tied to the surface area in contact with the rod.

The surface of the roller and the rod that is in contact with the film may be made of a metal such as stainless steel, or may be made of rubber, sponge or the like. The shape of the roller and the rod is preferably a cylindrical shape as long as the surface in contact with the film is curved. When a cylindrical roller or a rod is used, the diameter is about 5 to 100 mm, preferably 10 to 50 mm. As long as the diameter is within this range, the film can be smoothly conveyed.

In order to suppress the warpage or folding of the film pulled out from the processing bath, it is sufficient to perform only the treatment in which both ends in the width direction of the film are in contact with the roller or the bar, except for the both ends in the width direction. In addition, the contact treatment can be carried out together with other film surface regions. This contact treatment can also be carried out, for example, on the entire sides of the film. The angle at which the roller and the rod are disposed is not particularly limited, and the longitudinal direction of the roller and the rod may be parallel to the width direction of the film or may be inclined in the width direction of the film.

3) A method in which a polyvinyl alcohol-based resin film drawn from at least one processing bath is introduced into a nip roll, and the nip is used to drop a liquid adhering to the surface of the film to reduce the amount of liquid adhesion. In this method, usually, the liquid adhering to the entire both sides of the film is peeled off. An example based on this method is shown in Fig. 2.

In Fig. 2, it is shown that it will be pulled out from the swelling bath 13. The film is introduced into a nip roll. In the example of Fig. 2(a), first, the conveying direction of the film pulled out from the swelling bath 13 is changed by the guide roller, and then introduced into a nip roll which is horizontally disposed with respect to the floor. In the example of Fig. 2(b), the film pulled out from the swelling bath 13 is directly introduced into a nip roll which is horizontally disposed with respect to the ground. In any of the examples, the nip which is disposed horizontally with respect to the ground prevents the liquid adhering to the film from flowing into the both end portions in the film width direction, so that the warpage and the folding of the both ends of the film can be effectively suppressed. .

When the treatment for reducing the amount of liquid adhesion is applied to both end portions in the width direction of the film by the method of the above 1) or 2), the film which is pulled out from the treatment bath and which reduces the amount of liquid adhesion is usually used. A flat roller of a cylindrical guide roller having a full width and a constant diameter is conveyed. That is, the film which is applied to be pulled out from the treatment bath to reduce the amount of liquid adhesion first passes through the guide roller, and when it passes through the nip roll, it is preferred that the one or more guide rolls are flat rolls. . By using a flat roll disposed horizontally with respect to the ground, the film subjected to the treatment for lowering the amount of adhesion of the liquid is transported, and the liquid in the central portion in the width direction of the film can be prevented from flowing into the both end portions during the film transport, so that it can be further Effectively prevents warping and folding of the both ends of the film.

Fig. 1 is a view showing an example of a treatment for lowering the amount of liquid adhering to the film drawn from the swelling bath 13, but the treatment may be selected from the group consisting of a swelling bath 13, a dyeing bath 15, and a crosslinking bath 17. The film drawn from at least one of the treatment baths in the group is carried out. In these treatment baths, since the swelling amount of the film is large, warping and folding are also likely to occur, so Preferably, the film which is drawn from at least the swelling bath 13 is subjected to a treatment for reducing the amount of liquid adhering. A preferred embodiment of the present invention is a form in which the film which is pulled out from the swelling bath 13 is subjected to a treatment for lowering the amount of liquid adhesion, and the film which is pulled out from the swelling bath 13 and pulled out from the dyeing bath 15 The film is subjected to a treatment for reducing the amount of liquid adhering.

In general, the higher the temperature of the treatment bath, the more likely to cause warpage and folding, but according to the present invention, even if the temperature of the treatment bath is relatively high, the warpage or folding of the both ends of the film can be effectively suppressed. . As described above, when the germicidal membrane 10 is initially subjected to the swelling treatment, the temperature of the swelling bath 13 can be set to about 10 to 50 ° C. However, even if the temperature is 30 ° C or higher, the temperature can be 35 ° C or more, and the temperature can be effectively suppressed. Warping and folding of the ends of the film. Further, as described above, when iodine is used as the dichroic dye, the temperature of the dyeing bath 15 can be set to about 10 to 45 ° C. However, even if the temperature is 30 ° C or higher and further 35 ° C or higher, the film can be effectively suppressed. Warping or folding at both ends. When a dichroic dye is used as the dichroic dye, even if the temperature of the dye bath 15 is high, warpage or folding in can be effectively suppressed similarly.

(extension step)

As described above, the embryonic film 10 is subjected to a one-axis stretching treatment in a wet or dry manner between the above-described series of processing steps (i.e., before or during any one or more of the processing steps). The specific method of the one-axis stretching process may be, for example, a roll-to-roll extension in which a longitudinal one-axis extension is imparted between two nip rolls (for example, two nip rolls disposed before and after the processing bath) constituting the film transport path, For example, the heat roller extension, the tenter extension, and the like described in Japanese Patent No. 2731813 are preferably extended between rolls. One-axis extension processing step The plurality of polarizing films 23 can be obtained from the embryonic film 10 several times.

The final cumulative stretching ratio of the polarizing film 23 based on the germ film 10 is usually about 4.5 to 7 times, preferably 5 to 6.5 times.

The stretching step can be carried out in any of the processing steps. When the stretching treatment is performed in more than two processing steps, the stretching treatment can be performed in any of the processing steps, but in the swelling treatment step and/or the dyeing treatment step. It is better to carry out the extension process.

As described above, when transporting a film which is pulled out from the processing bath and which reduces the amount of liquid adhesion, in order to prevent the liquid in the center portion in the width direction of the film from flowing into the both end portions during film transport, only flat is used. The roller is effective as a guide roller until it passes through the nip roll. On the other hand, when the film is immersed in the treatment bath, particularly the swelling bath 13 or the dyeing bath 15, the film is easily creped by wrinkles. When only a flat roll is used as the guide roll until passing through the nip roll, in order to suppress such wrinkles, it is preferred to apply an extension treatment in the treatment bath so that the film width after the treatment bath is pulled out is immersed in the It is preferable to apply such an extension treatment to the swelling bath 13 and/or the dyeing bath 15 (especially the swelling bath 13) below the width of the film before the treatment of the bath. This extension treatment is usually an inter-roll extension (longitudinal-axis extension) using the circumferential speed difference between the nip rolls.

The stretching ratio (the cumulative stretching ratio based on the embryonic film 10) accumulated in the swelling treatment and the dyeing treatment is preferably 2.0 to 4.5 times, preferably 2.3 to 4.0 times. As long as it is within this range, it is easy to realize that the film width after being pulled out from the processing bath becomes an extension process of immersing the film width before the processing bath.

The higher the temperature of the wrinkle treatment bath caused by the swelling, the more likely it is to occur, but by applying the stretching treatment as described above, even if, for example, the temperature of the treatment bath is 15° C. or higher, and further 20° C. or higher, Effectively suppress wrinkles. Further, in order not to cause excessive swelling, the temperature of the treatment bath is preferably 40 ° C or lower.

(drying treatment)

After the washing treatment, the polyvinyl alcohol-based resin film is dried. The drying of the film is not particularly limited, but it can be carried out using a drying oven 21. The drying temperature is, for example, about 30 to 100 ° C, and the drying time is, for example, about 30 to 600 seconds.

(other steps)

Processing other than the above processing may be added. Examples of the treatment which can be added include immersion treatment (complementing treatment) in an aqueous solution of iodide containing no boric acid after the crosslinking treatment, or immersion treatment in an aqueous solution containing zinc chloride or the like without boric acid ( Zinc treatment).

The thickness of the polarizing film 23 obtained as described above is thinner than the germ film 10, for example, about 5 to 30 μm.

<Polarizing plate>

The polarizing plate can be obtained by bonding a protective film to at least one surface of the polarizing film manufactured as described above via an adhesive. The protective film may, for example, be a film made of a cellulose acetate resin of cellulose triacetate or cellulose diacetate; for example, polyethylene terephthalate, polyethylene naphthalate, and polyparaic acid. a film made of a polyester resin of butylene ester; a film made of a polycarbonate resin; a film made of a cycloolefin resin; an acrylic resin film; 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, and primer may be applied to the bonding surface of the polarizing film and/or the protective film. Primer) 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 adhere to both, but it is selected to satisfy sufficient adhesion or transparency. From this point of view, an ultraviolet curable adhesive or an aqueous adhesive can be used for bonding the polarizing film and the protective film. Examples of the aqueous adhesive include an aqueous solution of a polyvinyl alcohol-based resin, or an aqueous solution in which a crosslinking agent is added, and a urethane-based emulsion adhesive.

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 a starting agent.

When an ultraviolet curable adhesive is used, the polarizing film and the protective film are laminated via an adhesive, and then the ultraviolet rays are irradiated, whereby the adhesive is cured. The light source of the ultraviolet light is not particularly limited, but it is preferably a light-emitting distribution having a wavelength of 400 nm or less. Specifically, a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, an ultrahigh pressure mercury lamp, a chemical lamp, a black light lamp are suitably used. (black light lamp), microwave excited mercury lamp, metal halide lamp, and the like.

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, and the irradiation intensity in the wavelength region effective for activation of the polymerization initiator is 0.1 to 6000 mW/cm. ^{2 is} better. By appropriately selecting the irradiation intensity from this range, the reaction time does not become too long, and the yellowing of the adhesive or the deterioration of the polarizing film caused by the heat radiated from the light source and the heat generation at the time of curing of the adhesive can be suppressed. The light irradiation time is not particularly limited as long as it is selected according to the adhesive to be hardened, but it is preferably set such that the integrated light amount expressed by the product of the irradiation intensity and the irradiation time is 10 to 10000 mJ/cm ² . . By appropriately selecting the cumulative amount of light from this range, a sufficient amount of the active species derived from the polymerization initiator can be generated to carry out the curing reaction reliably, and the irradiation time does not become too long, and good productivity can be maintained. The thickness of the adhesive layer after hardening is usually from 0.1 to 10 μm, preferably from 0.2 to 4 μm.

When an aqueous adhesive is used, for example, an adhesive may be uniformly applied to the surface of the film or may flow between two films, and two films may be laminated via the adhesive layer, and adhered and dried by a roller or the like. The method. After drying, it may be further cooked at room temperature or a slightly higher temperature, for example, at a temperature of about 20 to 45 °C. The thickness of the adhesive layer can be appropriately selected in the range of about 0.001 to 5 μm depending on the kind of the adhesive or the combination of the two films to be adhered. It is preferably 0.01 μm or more, and more preferably 2 μm or less.

[Examples]

Hereinafter, the present invention will be specifically described by way of examples, but the invention is not limited thereto.

<Example 1>

In addition to using three cross-linking baths 17 (hereinafter, the first cross-linking bath is referred to as 17a, the second cross-linking bath is referred to as 17b, and the third cross-linking bath is referred to as 17c.), and the first graph is used. A polarizing film is produced in the same manner as the polarizing film manufacturing apparatus shown. Each of the guide rollers 30 to 41 uses a flat roller.

First, a polyvinyl alcohol film having a thickness of 30 μm [trade name "KURARAY POVAL FILM VF-PE #3000" manufactured by KURARAY, a polymerization degree of 2400, a saponification degree of 99.9 mol% or more] was continuously conveyed and immersed in a package. There is a swelling bath 13 of pure water at 20 ° C for 30 seconds. In the swelling treatment, the width of the film drawn from the swelling bath 13 is equal to or less than the width of the film immersed in the swell bath 13, and a circumferential speed difference is applied between the nip rolls 50 and 51. Extension (longitudinal extension). The stretching ratio based on the embryo film 10 was set to 2.5 times.

For the film pulled out from the swelling bath 13, a gas blowing device 60 (air jet nozzle) provided in front of the guide roller 32 and a gas blowing device 61 provided between the guide roller 32 and the nip roller 51 are used ( The air jet nozzle sprays air to both ends in the width direction of both sides of the film to remove the liquid adhering thereto.

Next, the film which passed through the nip roll 51 was immersed in the iodine/potassium iodide/water in a dyeing bath 15 of 30° C. at a weight ratio of 0.05/2/100 for 120 seconds. Even in this dyeing process, the film width after being pulled out from the dyeing bath 15 is equal to or less than the width of the film before the dyeing bath 15, and the difference between the nip rolls 51 and 52 is applied to the roll. Extension (longitudinal extension). The cumulative stretching ratio in the swelling treatment and the dyeing treatment based on the embryo film 10 was 2.7 times.

Next, in order to apply the first crosslinking treatment for the purpose of hydration resistance, the film which passed through the nip roll 52 was immersed in the potassium iodide/boric acid/water at a weight ratio of 15/4.4/100 at 55 ° C in the crosslinking bath 17a. second. In the first crosslinking treatment, the film width after being pulled out from the crosslinking bath 17a is equal to or less than the film width before the crosslinking bath 17a, and is applied to the nip roll 52 and the crosslinking bath 17a. Between the nip rolls provided between the joint baths 17b, a circumferential speed difference is imparted to extend between the rolls (longitudinal one-axis extension). The cumulative stretching ratio in the swelling treatment, the dyeing treatment, and the first crosslinking treatment with the embryo film 10 as a reference was 5.5 times.

Next, the film after the first crosslinking treatment was immersed in the 59° C. crosslinking bath 17b having the same composition as that of the crosslinking bath 17a for 30 seconds (second crosslinking treatment), and the coloration was adjusted for the purpose of crosslinking. After the treatment, the potassium iodide/boric acid/water was immersed in a 40° C cross-linking bath 17c at a weight ratio of 9/2.9/100 for 15 seconds (third crosslinking treatment).

Thereafter, the film after the third crosslinking treatment was immersed in a washing bath 19 containing pure water at 5 ° C, and then passed through a drying oven 21 to dry at 70 ° C for 3 minutes to prepare a polarized light. Membrane 23.

After the continuous production of the above-mentioned polarizing film for 24 hours, in the dyeing bath 15, the both ends of the film were folded, and the nip roll 52 was passed in this state, so that creases were formed at the end portions of the film, and cracking of the film occurred. However, the rupture of this film was only one time in a 24 hour run.

<Example 2>

Even for the film pulled out from the dyeing bath 15, the gas blowing device 60 (air jet nozzle) and the guide provided before the guide roller 35 are used. The gas blowing device 61 (air jet nozzle) provided between the take-up roll 35 and the nip roll 52 sprays air on both ends in the width direction of both sides of the film to remove the liquid adhering thereto, and the first embodiment In the same manner, the production of the polarizing film was continuously performed for 24 hours. During the 24 hours of operation, warpage and folding of both end portions in the width direction of the film, and creases or cracks of the film which may accompany it were not observed in any of the processing steps.

<Example 3>

The same procedure as in the second embodiment was carried out except that a rod was placed in front of the guide roller 32 instead of the gas blowing device, and the film after the swelling treatment was subjected to a process of bringing the rod into contact with both end portions in the width direction of both sides of the film. The production of the polarizing film was continuously performed for 24 hours. During the 24 hours of operation, warpage and folding of both end portions in the width direction of the film, and creases or cracks of the film which may accompany it were not observed in any of the processing steps.

<Example 4>

The production of the polarizing film was continuously carried out for 24 hours in the same manner as in Example 3 except that the rod was brought into contact with the entire width of both sides of the film. During the 24 hours of operation, warping and folding of both end portions in the width direction of the film, and creases or cracks of the film which may accompany it were not observed in any of the processing steps.

<Example 5>

The production of the polarizing film was continuously carried out for 24 hours in the same manner as in Example 2 except that the temperature of the swelling bath 13 was changed to 30 ° C and the stretching ratio of the germ film 10 in the swelling bath 13 was 3.0 times. In the 24 hours of operation, no film width direction ends were observed in any of the processing steps. The warpage and folding of the part, as well as the crease or rupture of the film that may accompany it.

<Comparative Example 1>

The production of the polarizing film was continuously carried out for 24 hours in the same manner as in Example 1 except that the film after the swelling treatment was not subjected to the treatment of jetting air to both end portions in the width direction of both sides of the film. In the 24 hours of operation, the following problems occurred 10 times: folding occurred at both ends of the film, and the nip roll 51 was passed in this state, so that the film was creased or the crease was cracked.

10‧‧‧The membrane of polyvinyl alcohol resin

11‧‧‧Send rolls

13‧‧‧Swelling bath

15‧‧‧dye bath

17‧‧‧Cross-link bath

19‧‧‧ Washing bath

21‧‧‧ drying oven

23‧‧‧ polarizing film

30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41‧‧‧ guide rollers

50, 51, 52, 53, 54, 55‧‧‧ nip rolls

60, 61‧‧‧ gas blowing device

Claims (11)

A method for producing a polarizing film, which is obtained by applying a long-length polyvinyl alcohol-based resin film having a thickness of 65 μm or less, applying a swell treatment after being immersed in a swelling bath, immersing in a dye bath, and then immersing it in a dyeing treatment. a method of producing a long strip-shaped polarizing film by cross-linking after cross-linking bath, wherein the film is pulled out from at least one processing bath selected from the group consisting of a swelling bath, a dye bath, and a crosslinking bath The film is treated by reducing the amount of liquid adhering to both end portions in the width direction of both sides. The method for producing a polarizing film according to claim 1, wherein the treatment for reducing a liquid adhesion amount includes a treatment of a film blowing gas drawn from the at least one processing bath. The method for producing a polarizing film according to claim 1, wherein the treatment for reducing the amount of liquid adhering includes a treatment for a film contact roller or a rod pulled from the at least one processing bath. The method for producing a polarizing film according to claim 2, wherein the treatment for reducing the amount of the liquid to adhere is performed only at both end portions in the width direction. The method for producing a polarizing film according to claim 1, wherein the treatment for reducing the amount of the liquid adhering includes a process of directly introducing the film drawn from the at least one processing bath to the ground. A nip roll that is horizontally placed. The method for producing a polarizing film according to claim 4, wherein the treatment for reducing the amount of the liquid adhered by the flat roller is used. Film. The method for producing a polarizing film according to claim 6, wherein the film width after being pulled out from the at least one processing bath is smaller than the width of the film immersed in the processing bath, The extension treatment is applied in the bath. The method for producing a polarizing film according to claim 7, wherein the extension stretching ratio of the stretching treatment is 2.0 to 4.5 times. The method for producing a polarizing film according to claim 7 or 8, wherein the temperature of the treatment bath to which the elongation treatment is applied is 15 to 40 °C. The method for producing a polarizing film according to any one of claims 1 to 9, wherein the at least one treatment bath is a swelling bath and/or a dye bath. The method for producing a polarizing film according to claim 10, wherein the at least one treatment bath is a swelling bath.