KR101990222B1 - Production method for polarizing film - Google Patents

Abstract

A swelling treatment step in which a polyvinyl alcohol based resin film having a thickness of 65 m or less is transported while being withdrawn from a disk roll so that the polyvinyl alcohol based resin film is dipped in a swelling bath and then drawn out; And a dyeing treatment step in which the polarizing film is drawn out after immersing in a bath, and a dyeing treatment step in which the polarizing film having a curling angle at at least one of both end portions in the film width direction at the time of immersing the polyvinyl alcohol- A manufacturing method is provided.

Description

[0001] PRODUCTION METHOD FOR POLARIZING FILM [0002]

The present invention relates to a method for producing a polarizing film usable as a constituent member of a polarizing plate.

In the polarizing film, a uniaxially stretched polyvinyl alcohol-based resin film is conventionally used in which a dichromatic dye such as iodine or a dichromatic dye is adsorbed and oriented. The polarizing film is usually used as a polarizing plate by bonding a protective film to one side or both sides thereof with an adhesive and is used in an image display apparatus represented by a liquid crystal display device such as a liquid crystal television, a personal computer monitor, and a cellular phone.

In general, a polarizing film is formed by successively immersing a continuous long-length polyvinyl alcohol-based resin film in a treating bath such as a swelling bath, a dyeing bath or a crosslinking bath, and conducting a stretching treatment between these series of treatments (For example, Japanese Patent Application Laid-Open No. 2001-315140 (Patent Document 1)). Patent Literature 1 discloses a polyvinyl alcohol-based resin film in which the polyvinyl alcohol-based resin film is immersed in water at 30 ° C for 5 minutes in order to suppress curling of the end portion of the film during stretching of the polyvinyl alcohol- The curl angle is set to be 180 DEG or less.

Patent Document 1: JP-A-2001-315140

The polarizing film is produced by continuously feeding a film from a roll (wound product) of a polyvinyl alcohol-based resin film along a film transport path passing through various treatment baths as described above, immersing the film in a swelling bath, It can be continuously produced by performing the stretching treatment at any one or more of the stages from the time of drawing from the bath. However, there is a case where the film is broken during continuous production, particularly during stretching treatment, and improvement has been demanded from the viewpoints of productivity and yield of the polarizing film. The problem of film breakage in the stretching process is particularly remarkable when the thickness of the polyvinyl alcohol-based resin film is small.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a polarizing film production method capable of effectively suppressing film breakage during stretching treatment even when a thin polyvinyl alcohol based resin film is used.

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

[1] a swelling treatment step of immersing the polyvinyl alcohol-based resin film in a swelling bath and withdrawing by transporting a long polyvinyl alcohol-based resin film having a thickness of not more than 65 탆,

A dyeing treatment step of immersing the film drawn from the swelling bath in a dyeing bath and drawing the film,

Wherein the angle of curl in at least one of both end portions in the film width direction when the polyvinyl alcohol based resin film is immersed in the swelling bath is less than 90 °.

[2] The production method according to [1], wherein the time taken for the polyvinyl alcohol-based resin film to be immersed in a swelling bath after being unwound from a roll is 750 seconds or less.

[3] The polyvinyl alcohol-based resin film as described in [1] or [2] above, wherein the polyvinyl alcohol-based resin film is subjected to a drying treatment before the polyvinyl alcohol-based resin film is unwound from the master roll and then immersed in a swelling bath. Gt;

[4] The production method according to [3], wherein the drying treatment is carried out so that the dryness of the curled surface in the polyvinyl alcohol-based resin film becomes smaller than that on the opposite side.

[5] The method for producing a polyvinyl alcohol-based resin film according to any one of [1] to [4], wherein the polyvinyl alcohol-based resin film is subjected to a widening treatment before being dipped in a swelling bath after being unwound from a roll of a disc. Lt; / RTI >

[6] In the swelling treatment step, the polyvinyl alcohol-based resin film wound from a master roll is conveyed along two or more rolls selected from a guide roll and a nip roll to immerse the film in a swelling bath,

When L is 2 m or less, or T is 30 seconds or less when the maximum value of the distance between adjacent rolls is L and the maximum value of the time required for conveying between adjacent rolls is T, Or less, based on the total weight of the composition.

According to the method of the present invention, it is possible to effectively suppress the film breakage in the stretching process which has been conventionally occurred in the method of producing a polarizing film from a thin polyvinyl alcohol-based resin film.

1 is a cross-sectional view schematically showing an example of a polarizing film producing method and a polarizing film producing apparatus used therefor according to the present invention.
2 is a cross-sectional view schematically showing a curling state of a polyvinyl alcohol-based resin film and a curling angle thereof.

≪ Polarizing Film Production Method >

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

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

In the present invention, as a starting material for producing a polarizing film, an unstretched poly (meth) acrylate having a thickness of 65 占 퐉 or less (for example, 60 占 퐉 or less), preferably 50 占 퐉 or less, more preferably 35 占 퐉 or less, Vinyl alcohol resin film (original film) is used. As a result, a polarizing film of a thin film which is increasingly in demand in the market can be obtained. Thinning of the original film tends to cause film breakage in the stretching treatment. However, according to the present invention, even when the original film is thin, breakage of the film can be effectively suppressed. When the thickness of the original film is thicker than 65 占 퐉, breaking of the film during stretching treatment due to bending (curling) is not a problem in many cases. The original film may be a polyvinyl alcohol-based resin film subjected to stretching treatment in advance in the gas phase.

The width of the original film is not particularly limited and may be, for example, about 400 to 6000 mm. However, as the film width is larger, the film tends to be broken at the time of the stretching treatment.

In the present invention, the original film is prepared as a roll (disk roll) of a long unoriented polyvinyl alcohol based resin film.

The polarizing film can be continuously produced as a long polarizing film by continuously carrying the long original film along the film conveying path of the polarizing film producing apparatus while drawing the long original film from the disk roll and performing a predetermined treatment process. The predetermined process includes a swelling process in which the original film is dipped in a swelling bath and then drawn out, a dyeing process in which the film after the swelling process is dipped in a dyeing bath and then drawn out, and the film after dyeing is dipped in a crosslinking bath And a crosslinking treatment step of withdrawing the crosslinking agent. In addition, uniaxial stretching treatment is carried out either wet or dry between the series of treatment steps (that is, before and / or after at least one treatment step and / or during any one or more treatment steps). If necessary, other treatment steps may be added. Each treatment step may be a treatment for immersing the film in one bath or a treatment for sequentially immersing the film in two or more baths.

Hereinafter, a method for producing a polarizing film according to the present invention will be described in more detail with reference to FIG. 1 is a cross-sectional view schematically showing an example of a polarizing film producing method and a polarizing film producing apparatus used therefor according to the present invention. The polarizing film producing apparatus shown in Fig. 1 is configured such that an original (non-stretchable) film 10 made of a polyvinyl alcohol-based resin is conveyed along a film conveying path while being continuously unwound from the original roll 11, A dyeing bath 15, a crosslinking bath 17 and a cleansing bath 19 provided in the drying bath 21 and finally passing through the drying furnace 21. [ The obtained polarizing film 23 can be conveyed to the next polarizing plate producing step (the step of bonding the protective film to one surface or both surfaces of the polarizing film 23). The arrows in Fig. 1 indicate the transport direction of the film.

1 shows an example in which a swirl bath 13, a staining bath 15, a crosslinking bath 17 and a cleansing bath 19 are provided one by one for each bath, [Process liquid for treating the polyvinyl alcohol based resin film provided on the film transport path, such as swelling bath 13, dye bath 15, crosslinking bath 17 and cleansing bath 19) Two or more baths "may be collectively referred to as a" treatment bath ").

The film transport path of the polarizing film producing apparatus includes, in addition to the above treatment bath, guide rolls 30 to 41, 60 and 61 capable of supporting the transported film or changing the film transport direction, And the nip rolls 50 to 55 capable of changing the film transport direction can be disposed at appropriate positions. The guide rolls and nip rolls can be disposed in front of and behind the respective treatment baths and in the treatment bath, whereby the introduction and immersion of the film in the treatment bath and the withdrawal from the treatment bath can be performed (see Fig. 1). For example, one or more guide rolls may be provided in each treatment bath, and the film may be transported along these guide rolls to immerse the film in each treatment bath.

In the polarizing film producing apparatus shown in Fig. 1, nip rolls are arranged before and after each treatment bath (nip rolls 50 to 54), whereby in any one or more treatment baths, It is possible to carry out roll-to-roll stretching in which longitudinal uniaxial stretching is carried out with a main speed difference between the rolls. Hereinafter, each processing step will be described.

(Swelling treatment)

The swelling process is performed for the purpose of removing foreign substances on the surface of the original film 10, removing the plasticizer in the original film 10, imparting the back dyeing property, plasticizing the original film 10, and the like. The processing conditions are determined within a range in which the object can be achieved and within a range in which extreme melting of the original film 10 and loss of transparency do not occur.

1, the swelling process is carried out in such a manner that the original film 10 is conveyed along the film conveying path while continuously withdrawing the original film 10 from the original roll 11 to transfer the original film 10 to the swelling bath 13 Processing solution) for a predetermined period of time, and then withdrawing it. 1, the original film 10 is held by the guide rolls 60 and 61 and the nip roll 50 while the original film 10 is unwound and then immersed in the swelling bath 13 And is transported along the constructed film transport path. In the swelling process, the film is transported along the film transport path established by the guide rolls 30 to 32.

In addition to pure water, boric acid (JP 10-153709 A), chloride (JP 06-281816 A), inorganic acid, inorganic salt, water-soluble organic solvent, alcohols and the like are added to the swelling bath 13 It is also possible to use an aqueous solution added in the range of 0.01 to 10% by weight.

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

In the present invention, the curl angle of at least one of both end portions in the film width direction when the original film 10 is dipped in the swelling bath 13 is made less than 90 degrees. At least one (more typically, both ends in the width direction) of the both end portions in the width direction of the original film 10 wound from the original roll 11 becomes warped (floated) Curling occurs in which both ends of the original film are turned upside down toward the center in the width direction and curling when the original film 10 is immersed in the swelling bath 13 is less than 90 DEG, It is possible to suppress breakage. In order to more effectively suppress the breakage of the film, it is preferable that both curl angles at both ends in the film width direction are less than 90 degrees. Also, for the same reason, the curling angle at at least one of both end portions in the film width direction is preferably 80 DEG or less, and more preferably less than 75 DEG. It is more preferable that the curl angle of both ends of the both end portions in the film width direction is made less than 90 deg. Until the film is immersed in the swelling bath 13 immediately after being wound from the disk roll 11. [

2 is a cross-sectional view schematically showing a state in which a polyvinyl alcohol-based resin film is curled and a curl angle thereof. 2 (a) and 2 (b) show examples in which both ends in the film width direction are curled. FIG. 2 (a) c) shows a case where the curl angle is 150 °. As shown in Fig. 2, the curl angle is? Degrees, which means that the end of the curled film portion is oriented in the direction of? ° with respect to the extrude surface of the film surface that does not curl. The curling angle at both end portions in the width direction of the original film 10 continuously immersed in the swelling bath 13 can be measured according to the method described in the embodiment.

In order to make the curl angle of at least one (preferably both) of both end portions in the film width direction when the original film 10 is dipped in the swelling bath 13 to be less than 90 degrees, for example, the following measures are taken . The following means may be adopted alone, or two or more may be combined.

[A] The atmosphere in the winding step from the original roll 10 to the original roll 11 is immersed in the swelling bath 13 is adjusted to an appropriate condition. The preferable atmosphere conditions are a temperature of 23 占 占 폚 and a relative humidity of 20 to 70% RH. A more preferable relative humidity is 20 to 65% RH, and a more preferable relative humidity is 25 to 60% RH. By performing the winding process under such an atmosphere, moisture absorption of the original film 10, and further, growth of curl can be suppressed.

[B] The time required for the above-described unwinding process (the time from when the original film 10 is unwound from the original roll 11 to when it is immersed in the swelling bath 13) is suppressed to a short time. Shortening the time is advantageous in suppressing the growth of curl during the winding process, and is also advantageous from the viewpoint of production efficiency. Generally, the thinner the original film, the more likely curl grows during the winding process. In the case of using the original film 10 of 35 to 65 占 퐉, the time is preferably 750 seconds or less, more preferably 600 seconds or less, still more preferably 300 seconds or less. In the case of using the original film 10 of less than 35 탆, it is preferably 650 seconds or less, more preferably 300 seconds or less, further preferably 150 seconds or less. On the other hand, if the required time is extremely excessively short, it becomes difficult to control the tension of the film in the unwinding step and the film transportation becomes unstable, so that the required time is usually 10 seconds or more, preferably 20 seconds or more.

[C] In the winding process, the original film 10 to be conveyed is subjected to a drying treatment. The term " drying treatment " as used herein refers to a treatment in which water content in the original film 10 is volatilized to lower the moisture content of the original film 10. The drying treatment is advantageous in reducing or eliminating curl. In order to reduce or eliminate the curl, it is particularly preferable to carry out the drying treatment so that the dryness of the curled surface of the original film 10 (that is, the degree of decrease in moisture content by drying) becomes smaller than the surface on the opposite side. The curled face is the original film face including the inner face of the curl, and referring to Fig. 2, it is the upper main face in the figure.

As a method for reducing the drying degree of the curled surface to be smaller than the surface on the opposite side, there is a method in which hot air, dry air, infrared heaters are hit from the opposite side, or the original film 10 is sandwiched between a pair of rolls having different temperatures Method.

[D] In the unwinding process, widening processing is performed on the original film 10 to be transported. The widening treatment for widening the film width is advantageous in reducing or eliminating curl when the original film 10 is immersed in the swelling bath 13. As the widening processing, a roll having a widening function such as an expander roll, a spiral roll, and a crown roll may be used for the guide roll, or another widening apparatus such as a cross guider, a bend bar, and a tenter clip may be used. Among them, the process using the roll having the widening function is preferable because it is simple. For example, as the guide rolls 60 and / or 61 shown in Fig. 1, a roll having a widening function can be used.

[E] In the winding process, the curl portion is forcibly pressed against the original film 10 to be transported. This process is also advantageous in reducing or eliminating curl when the original film 10 is immersed in the swelling bath 13, as in the wider process. Specific examples of the method include a method in which a film is transported by a device such as a conveyor, a method in which a roll or a bar (a rod that is not rotated by itself such as a roll) is pressed against a curled portion, 10) is sprayed onto the curled portion, and the like.

(F) In the case where the original film 10 is transported along a film transport path constituted by two or more rolls selected from a guide roll and a nip roll in the winding process, as in the example shown in Fig. 1, The maximum value L of the distance between the adjacent rolls is shortened and / or the maximum value T of the time required for transportation between adjacent rolls is shortened. Shortening of L and / or T is advantageous in suppressing the growth of curl during the winding process.

The maximum value L of the distance between adjacent rolls is the largest value among the distances between adjacent rolls. The distance between adjacent rolls is determined as the distance between adjacent roll centers. In the case of a nip roll, instead of the roll center, the center of the line connecting the centers of the pair of rolls constituting the nip roll is employed. L is usually 0.01 m or more, preferably 2 m or less, and more preferably 0.05 to 1.5 m.

Likewise, the maximum value (T) of time required for conveying between adjacent rolls means the time required for conveyance between adjacent rolls (in the example shown in FIG. 1) to the conveyance from the guide roll 60 to the guide roll 61 is the greater of the time required (T ₁₎ and the guide time (T ₂₎ required for the transfer to the nip roll 50 from the roll (61) to. The time required for conveyance between adjacent rolls is obtained as the time from when the roll is separated from one of the adjacent rolls to when it comes into contact with the other roll. T is generally 0.5 seconds or more, preferably 30 seconds or less, and more preferably 0.1 to 20 seconds.

[G] In the winding step, the transfer is usually carried out while keeping the tensile force of the original film 10 constant by one or more nip rolls arranged before being immersed in the swelling bath. In this case, The tension applied to the original film 10 between the nip rolls disposed just before immersing in the swelling bath is made higher than the tension applied after the nip roll. As a result, the curl growth during the winding process can be suppressed. The tension applied to the original film 10 between the original roll 11 and the nip roll disposed just before immersion in the swelling bath is, for example, 5 to 300 N / mm, preferably 10 to 200 N / mm . The difference between the tensile force applied to the original film 10 between the original roll 11 and the nip roll disposed immediately before being immersed in the swelling bath and the tensile force applied after the nip roll is preferably 10 N / It is more than 50 N / m. The tension of the original film 10 between the original roll 11 and the nip roll disposed immediately before being dipped in the swelling bath or the difference in the tension difference is within the above range is an effect of suppressing the curling of the edge of the original film 10 But also from the point of suppressing the generation of wrinkles of the original film 10.

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

In the swelling treatment, since the film swells and expands even in the transport direction of the film, when the film is not positively stretched, for example, it is disposed in front of and behind the swelling bath 13 in order to eliminate the looseness of the film in the transport direction It is preferable to take measures such as controlling the speed of the nip rolls 50 and 51 or the like. In order to stabilize film transportation in the swelling bath 13, the water stream in the swirl bath 13 is controlled by an underwater shower, or an EPC apparatus (Edge Position Control apparatus: detecting the end of the film, Or the like) may be used in combination.

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

(Dyeing treatment)

The dyeing treatment is carried out for the purpose of adsorbing and orienting the dichroic dye to the polyvinyl alcohol-based resin film after the swelling treatment. The treatment conditions are determined within a range in which the object can be achieved and within a range in which extreme melting of the film or loss of transparency does not occur. 1, the dyeing process is carried out along the film transport path established by the guide rolls 33 to 35 and the nip roll 51, and the film after the swelling process is transferred to the dyeing bath 15 Solution) for a predetermined time, and subsequently withdrawing the solution. In order to enhance the dyeability of the dichroic dye, the film provided in the dyeing treatment step is preferably a film subjected to uniaxial stretching treatment at least to some degree, or may be a film obtained by the uniaxial stretching treatment before the dyeing treatment, , It is preferable to perform uniaxial stretching treatment at the time of dyeing treatment.

When iodine is used as the dichroic dye, an aqueous solution having an iodine / potassium iodide / water concentration of about 0.003 to 0.3 / about 0.1 to 10/100 in terms of the concentration by weight can be used for the dyeing bath 15. Instead of potassium iodide, other iodides such as zinc iodide may be used, or potassium iodide and other iodides may be used in combination. Further, compounds other than iodide such as boric acid, zinc chloride, cobalt chloride, etc. may be coexistent. When boric acid is added, it is distinguished from a crosslinking treatment to be described later in that it contains iodine. If the aqueous solution contains about 0.003 part by weight or more of iodine with respect to 100 parts by weight of water, it is regarded as a dyeing bath 15 . The temperature of the dyeing bath 15 at the time of immersing the film is usually about 10 to 45 占 폚, preferably 10 to 40 占 폚, more preferably 20 to 35 占 폚, 600 seconds, preferably 60 to 300 seconds.

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

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

As in the case of the swelling treatment, in the dyeing treatment, the guide rolls 33, 34 and / or 35 are provided with widening functions such as an expander roll, a spiral roll, and a crown roll in order to transport the polyvinyl alcohol- Or other widening devices such as cross guiders, bend bars, tenter clips or the like. Another means for suppressing the occurrence of wrinkles is to perform a stretching treatment in the same manner as in the swelling treatment.

In the example shown in Fig. 1, the film drawn out from the dyeing bath 15 passes through the guide roll 35 and the nip roll 52 in order, and is introduced into the crosslinking bath 17.

(Crosslinking treatment)

The crosslinking treatment is a treatment for the purpose of, for example, water resistance by cross-linking and color adjustment (preventing the film from becoming bluish). 1, the cross-linking treatment is carried out along the film conveyance path constructed by the guide rolls 36 to 38 and the nip roll 52, and the cross-linking treatment is performed on the cross-linking bath 17 By immersing the film for a predetermined period of time, and subsequently withdrawing the film.

The crosslinking bath 17 may be an aqueous solution containing, for example, about 1 to 10 parts by weight of boric acid per 100 parts by weight of water. The crosslinking bath 17 preferably contains iodide in addition to boric acid when the dichroic dye used in the dyeing treatment is iodine, and the amount thereof may be, for example, 1 to 30 parts by weight relative to 100 parts by weight of water . Examples of the iodide include potassium iodide and zinc iodide. Further, compounds other than iodide such as zinc chloride, cobalt chloride, zirconium chloride, sodium thiosulfate, potassium sulfite, sodium sulfate and the like may be coexistent.

In the crosslinking treatment, the concentration of boric acid and iodide and the temperature of the crosslinking bath 17 can be appropriately changed depending on the purpose. For example, when the purpose of the crosslinking treatment is water resistance by crosslinking, and the swelling treatment, the dyeing treatment and the crosslinking treatment are carried out in this order on the polyvinyl alcohol resin film, the crosslinking agent- And an aqueous solution of boric acid / iodide / water = 3 to 10/1 to 20/100. If necessary, other crosslinking agents such as glyoxal or glutaraldehyde may be used instead of boric acid, or boric acid and another crosslinking agent may be used in combination. The temperature of the crosslinking bath at the time of immersing the film is usually about 50 to 70 DEG C, preferably 53 to 65 DEG C, and the immersion time of the film is usually about 10 to 600 seconds, preferably 20 to 300 seconds, Preferably 20 to 200 seconds. When the dyeing treatment and the crosslinking treatment are performed in this order on the polyvinyl alcohol-based resin film previously drawn before the swelling treatment, the temperature of the crosslinking bath 17 is usually about 50 to 85 캜, preferably about 55 to 85 캜, 80 ° C.

In the crosslinking treatment for color adjustment, for example, when iodine is used as the dichroic dye, a solution containing a crosslinking agent having a concentration of boric acid / iodide / water = 1 to 5/3 to 30/100 can be used . The temperature of the crosslinking bath at the time of immersing the film is usually about 10 to 45 DEG C, and the immersing time of the film is usually about 1 to 300 seconds, preferably 2 to 100 seconds.

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

It is also possible to perform uniaxial stretching treatment in the crosslinking bath 17 by using the peripheral speed difference between the nip roll 52 and the nip roll 53. [

In the crosslinking treatment, as in the case of the swelling treatment, a widening function such as an expander roll, a spiral roll, and a crown roll is applied to the guide rolls 36, 37 and / or 38 in order to transport the polyvinyl alcohol- Or other widening devices such as cross guiders, bend bars, tenter clips or the like. Another means for suppressing the occurrence of wrinkles is to perform a stretching treatment in the same manner as in the swelling treatment.

In the example shown in Fig. 1, the film drawn out from the crosslinking bath 17 passes through the guide roll 38 and the nip roll 53 in order, and is introduced into the cleansing bath 19.

(Cleaning treatment)

The production method of the present invention may include a washing treatment step after the crosslinking treatment step. The cleaning treatment is carried out for the purpose of removing excess boric acid or iodine adhered to the polyvinyl alcohol-based resin film. The cleaning treatment can be carried out, for example, by immersing a crosslinked polyvinyl alcohol-based resin film in a cleansing bath 19 (water), spraying water on the film as a shower, or using them in combination.

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

Also in the cleaning process, the rolls having the widening function such as the expander roll, the spiral roll, and the crown roll may be provided on the guide rolls 39, 40 and / or 41 for the purpose of transporting the polyvinyl alcohol- Or using other widening devices such as cross guiders, bend bars, tenter clips or the like. Further, in the cleaning treatment, a stretching treatment may be performed to suppress the occurrence of wrinkles.

(Drawing process)

As described above, the original film 10 is uniaxially stretched in a wet or dry manner during the series of processing steps (that is, before and / or after any one or more processing steps) and / or during any one or more processing steps. Specific methods of the uniaxial stretching process include, for example, interlabial stretching in which longitudinal uniaxial stretching is performed with a main speed difference between two nip rolls (for example, two nip rolls disposed on the front and back sides of the treatment bath) A hot roll stretching as described in Japanese Patent No. 2731813, a tenter stretching, and the like, and preferably a roll-to-roll stretching. The uniaxial stretching process can be performed a plurality of times until the polarizing film 23 is obtained from the original film 10. As described above, the stretching treatment is also advantageous in suppressing the occurrence of wrinkles of the film.

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

The stretching treatment step may be carried out in any treatment step, and in the case of performing the stretching treatment in two or more treatment steps, the stretching treatment may be performed in any treatment step. According to the present invention, even when the uniaxial stretching treatment is performed at any stage after the swelling treatment step (including the swelling treatment step), the film breakage during the stretching treatment can be effectively suppressed.

(Dry treatment)

After the cleaning treatment, it is preferable to perform the treatment of drying the polyvinyl alcohol-based resin film. The drying of the film is not particularly limited, but can be carried out using the drying furnace 21 as in the example shown in Fig. The drying temperature is, for example, about 30 to 100 DEG C, and the drying time is about 30 to 600 seconds. The thickness of the polarizing film 23 obtained as described above is, for example, about 5 to 30 占 퐉.

(Other processing steps)

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

<Polarizer>

A polarizing plate can be obtained by bonding a protective film to at least one side of a polarizing film produced as described above through an adhesive. As the protective film, for example, a film comprising an acetylcellulose-based resin such as triacetylcellulose or diacetylcellulose; A film made of a polyester resin such as polyethylene terephthalate, polyethylene naphthalate and polybutylene terephthalate; A polycarbonate-based resin film; Cycloolefin-based resin films; (Meth) acrylic resin film; And a film made of a polyolefin-based resin of a polypropylene-based resin.

In the present specification, the term &quot; (meth) acrylic &quot; means at least one selected from acrylic and methacrylic.

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

Example

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. In the following examples, curling angles at both end portions in the width direction of the original film 10 continuously immersed in the swelling bath 13 were measured according to the following method.

[Measurement of curl angle]

The film is visually observed along the direction of the first guide roll in the swelling bath 13 from the roll passed immediately before immersing in the swelling bath 13 and the film (For example, when the angular range is from 0 to less than 15, the measurement angle is 0, and when the angular range is from 15 to less than 30, the measurement angle is 15 The measurement angle becomes the minimum value of the angular region, the same is applied hereinafter). In addition, an angle mark was provided immediately before the roll that passed through the roll before it was immersed in the swelling bath 13 immediately after the winding, and the curl angle was measured in the same manner.

&Lt; Example 1 >

A polarizing film was produced by using the same apparatus as the polarizing film producing apparatus shown in Fig. 1 except that two crosslinking baths 17 (hereinafter, the first crosslinking bath was referred to as 17a and a second crosslinking bath was referred to as 17b) were used . All flat rolls were used for the guide rolls 30 to 41.

(1) swelling treatment process

A polyvinyl alcohol film having a thickness of 60 占 퐉 (trade name "Kurarupoval film VF-PE # 6000" manufactured by Kuraray Co., Ltd., polymerization degree of 2400, degree of saponification of 99.9 mol% or more) And the film was immersed in a swelling bath 13 having pure water at 30 DEG C for 100 seconds while keeping the film in a relaxed state so as not to loosen the film. The time for the polyvinyl alcohol film to be immersed in the swelling bath 13 after the polyvinyl alcohol film was unwound from the roll 11 was 60 seconds and the atmosphere in the unwinding step was 23 DEG C and 60% RH. The curl angle at both end portions in the film width direction through the polyvinyl alcohol film from the original roll 11 to the immersion in the swelling bath 13 was 30 DEG or less.

(2) Dyeing process

Next, the film having passed through the nip roll 51 was dipped in a dyeing bath 15 at 30 DEG C for 120 seconds, in which iodine / potassium iodide / water (weight ratio) was 0.05 / 2/100. In this dyeing treatment, roll-to-roll stretching (longitudinal uniaxial stretching) was performed with a major difference in speed between the nip rolls 51 and 52.

(3) Crosslinking treatment process

Next, in order to carry out the first crosslinking treatment for the purpose of water resistance, the film passed through the nip roll 52 was coated with a first crosslinking agent of 56 占 폚 at a weight ratio of 12 / 4.4 / 100 of potassium iodide / boric acid / water And immersed in the crosslinking bath 17a for 30 seconds. In this first cross-linking treatment, inter-roll stretching (longitudinal uniaxial stretching) was performed until the cumulative stretching ratio based on the original film 10 was 5.5 times, with a difference in speed between the nip rolls. Subsequently, the film after the first crosslinking treatment was immersed in a second crosslinking bath 17b at 40 占 폚 for 15 seconds (second crosslinking treatment) in which potassium iodide / boric acid / water (weight ratio) was 9 / 2.9 / 100.

Thereafter, the film after the second cross-linking treatment was immersed in a cleansing bath 19 having pure water at 6 DEG C and then dried at 70 DEG C for 3 minutes by passing through a drying furnace 21 to produce a polarizing film 23 Respectively.

The polarizing film was continuously produced for 24 hours. During the operation for 24 hours, no film breakage occurred in any of the processing steps. Further, neither bending of both ends in the film width direction was recognized.

&Lt; Example 2 >

The polarizing film was continuously produced for 24 hours in the same manner as in Example 1 except that the atmosphere in the winding step was a temperature of 23 캜 and a relative humidity of 40% RH. The curl angle at both ends in the film width direction through the polyvinyl alcohol film from the original roll 11 to the immersion in the swelling bath 13 was 15 DEG or less. During 24 hours of operation, no film breakage occurred in any of the processing steps, and no bending of both ends in the film width direction was recognized.

&Lt; Example 3 >

Except that a polyvinyl alcohol film having a thickness of 30 占 퐉 (trade name: KurarupoPhaval Film VF-PE # 3000, manufactured by Kuraray Co., Ltd., degree of polymerization: 2400, degree of saponification: 99.9 mol% or more) In the same manner, the polarizing film was continuously produced for 24 hours. The curl angle at both ends in the film width direction was 60 DEG or less through the time from the polyvinyl alcohol film being unwound from the rolls 11 to immersing in the swelling bath 13. [ During the operation for 24 hours, no film breakage occurred in any of the processing steps, and no bending of both ends in the film width direction was recognized.

<Example 4>

The polarizing film was continuously produced for 24 hours in the same manner as in Example 3 except that the time of the unwinding process was changed to 480 seconds. The curling angle at both ends in the film width direction through the polyvinyl alcohol film from the original roll 11 to the immersion in the swelling bath 13 was 75 DEG or less. During the operation for 24 hours, no film breakage occurred in any of the processing steps, and no bending of both ends in the film width direction was recognized.

&Lt; Example 5 >

The polarizing film was continuously produced for 24 hours in the same manner as in Example 1 except that the time of the unwinding process was changed to 600 seconds. The curl angle at both ends in the film width direction was 60 DEG or less through the time from the polyvinyl alcohol film being unwound from the rolls 11 to immersing in the swelling bath 13. [ During the operation for 24 hours, no film breakage occurred in any of the processing steps, and no bending of both ends in the film width direction was recognized.

&Lt; Example 6 >

The polarizing film was continuously produced for 24 hours in the same manner as in Example 1 except that the time of the unwinding process was changed to 720 seconds. The curling angle at both ends in the film width direction through the polyvinyl alcohol film from the original roll 11 to the immersion in the swelling bath 13 was 75 DEG or less. During the operation for 24 hours, no film breakage occurred in any of the processing steps, and no bending of both ends in the film width direction was recognized.

&Lt; Example 7 >

The polarizing film was continuously produced for 24 hours in the same manner as in Example 3 except that the time of the unwinding process was changed to 600 seconds. The curling angle at both ends in the film width direction through the polyvinyl alcohol film from the original roll 11 to the immersion in the swelling bath 13 was 75 DEG or less. During the operation for 24 hours, no film breakage occurred in any of the processing steps, and no bending of both ends in the film width direction was recognized.

&Lt; Comparative Example 1 &

A polarizing film was produced in the same manner as in Example 3 except that the time of the unwinding step was changed to 720 seconds. When the polyvinyl alcohol film was immersed in the swelling bath 13, the curling angle at both ends in the film width direction was 105 °. The film was broken during the stretching treatment in the crosslinking treatment, and thus a polarizing film could not be obtained.

&Lt; Example 8 >

Except that the hot air of 30 DEG C was sprayed for 30 seconds from the surface side opposite to the curled surface of the polyvinyl alcohol film while the polyvinyl alcohol film was unwound from the rolls 11 and then immersed in the swelling bath 13 In the same manner as in Comparative Example 1, the polarizing film was continuously produced for 24 hours. The curling angle at both ends in the film width direction through the polyvinyl alcohol film from the original roll 11 to the immersion in the swelling bath 13 was 75 DEG or less. During the operation for 24 hours, no film breakage occurred in any of the processing steps, and no bending of both ends in the film width direction was recognized.

&Lt; Example 9 >

Just as in the case of Comparative Example 1, except that a metal bar for firmly pressing both end portions in the film width direction was provided immediately before the nip roll 50 of the unwinding process and widening processing was performed on both end portions in the width direction of the polyvinyl alcohol film, The film was continuously produced for 24 hours. The curl angle at both ends in the film width direction was 60 DEG or less through the time from the polyvinyl alcohol film being unwound from the rolls 11 to immersing in the swelling bath 13. [ During the operation for 24 hours, no film breakage occurred in any of the processing steps, and no bending of both ends in the film width direction was recognized.

&Lt; Example 10 >

The polarizing film was continuously produced for 24 hours in the same manner as in Example 3 except that the time of the unwinding step was changed to 300 seconds. The curling angle at both ends in the film width direction was 45 DEG or less through the time from the polyvinyl alcohol film being unwound from the rolls 11 to the immersion in the swelling bath 13. During the operation for 24 hours, no film breakage occurred in any of the processing steps, and no bending of both ends in the film width direction was recognized.

&Lt; Example 11 >

The polarizing film was continuously produced for 24 hours in the same manner as in Example 3 except that the time of the unwinding step was changed to 150 seconds. The curling angle at both ends in the film width direction was 45 DEG or less through the time from the polyvinyl alcohol film being unwound from the rolls 11 to the immersion in the swelling bath 13. During the operation for 24 hours, no film breakage occurred in any of the processing steps, and no bending of both ends in the film width direction was recognized.

10 original film made of polyvinyl alcohol resin, 11 disks, 13 swelling bath, 15 dyeing bath, 17 crosslinking bath, 19 year old liquor, 21 drying furnace, 23 polarizing film, 30, 31, 32, 33, 34, 35 , 36, 37, 38, 39, 40, 41, 60, 61 guide rolls, 50, 51, 52, 53, 54, 55 nip rolls.

Claims (9)

A swelling treatment step of immersing the polyvinyl alcohol-based resin film in a swelling bath and drawing the polyvinyl alcohol-based resin film by transporting a long polyvinyl alcohol-based resin film having a thickness of less than 35 m from the disk roll,
A dyeing treatment step of immersing the film drawn from the swelling bath in a dyeing bath and drawing the film,
The temperature of the atmosphere in the step of unwinding the polyvinyl alcohol based resin film from the original roll to the step of immersing in the swelling bath is 23 占 폚 and the relative humidity of the atmosphere is 20 to 70%
The time required for the winding step is 650 seconds or less,
Wherein a curl angle of at least one of both end portions in the film width direction when the polyvinyl alcohol based resin film is immersed in a swelling bath is less than 90 DEG,
Wherein the polyvinyl alcohol-based resin film is subjected to a drying treatment until the polyvinyl alcohol-based resin film is unwound from a master roll and then immersed in a swelling bath. A swelling treatment step of immersing the polyvinyl alcohol-based resin film in a swelling bath and drawing the polyvinyl alcohol-based resin film by transporting a long polyvinyl alcohol-based resin film having a thickness of less than 35 m from the disk roll,
A dyeing treatment step of immersing the film drawn from the swelling bath in a dyeing bath and drawing the film,
The temperature of the atmosphere in the step of unwinding the polyvinyl alcohol based resin film from the original roll to the step of immersing in the swelling bath is 23 占 폚 and the relative humidity of the atmosphere is 20 to 70%
The time required for the winding step is 650 seconds or less,
Wherein a curl angle of at least one of both end portions in the film width direction when the polyvinyl alcohol based resin film is immersed in a swelling bath is less than 90 DEG,
Wherein the polyvinyl alcohol-based resin film is subjected to a widening treatment before the polyvinyl alcohol-based resin film is unwound from a roll and then immersed in a swelling bath. The production method according to claim 1, wherein the drying treatment is carried out so that the dryness of the curled surface in the polyvinyl alcohol-based resin film becomes smaller than that on the opposite side. A swelling treatment step of immersing the polyvinyl alcohol-based resin film in a swelling bath and withdrawing the swollen polyvinyl alcohol-based resin film while withdrawing a long polyvinyl alcohol-based resin film having a thickness of 65 占 퐉 or less from the disk roll;
A dyeing treatment step of immersing the film drawn from the swelling bath in a dyeing bath and drawing the film,
The temperature of the atmosphere in the step of unwinding the polyvinyl alcohol based resin film from the original roll to the step of immersing in the swelling bath is 23 占 폚 and the relative humidity of the atmosphere is 20 to 70%
The time required for the winding step is 750 seconds or less,
The polyvinyl alcohol based resin film is subjected to a drying treatment until the polyvinyl alcohol based resin film is unwound from the original roll and then immersed in a swelling bath,
Wherein the curl angle of at least one of both end portions in the film width direction when the polyvinyl alcohol based resin film is immersed in a swelling bath is less than 90 deg. The production method according to claim 4, wherein the drying treatment is carried out so that the dryness of the curled surface in the polyvinyl alcohol-based resin film becomes smaller than that on the opposite side. A swelling treatment step of immersing the polyvinyl alcohol-based resin film in a swelling bath and withdrawing the swollen polyvinyl alcohol-based resin film while withdrawing a long polyvinyl alcohol-based resin film having a thickness of 65 占 퐉 or less from the disk roll;
A dyeing treatment step of immersing the film drawn from the swelling bath in a dyeing bath and drawing the film,
The temperature of the atmosphere in the step of unwinding the polyvinyl alcohol based resin film from the original roll to the step of immersing in the swelling bath is 23 占 폚 and the relative humidity of the atmosphere is 20 to 70%
The time required for the winding step is 750 seconds or less,
The polyvinyl alcohol based resin film is subjected to a widening treatment before being dipped in a swelling bath after being unwound from the roll of the original,
Wherein the curl angle of at least one of both end portions in the film width direction when the polyvinyl alcohol based resin film is immersed in a swelling bath is less than 90 deg. The method according to any one of claims 1 to 6, wherein in the swelling treatment step, the polyvinyl alcohol-based resin film wound from a master roll is conveyed along two or more rolls selected from a guide roll and a nip roll Immersed in a swelling bath,
When L is 2 m or less, or T is 30 seconds or less when the maximum value of the distance between adjacent rolls is L and the maximum value of the time required for conveying between adjacent rolls is T, Or less. delete delete

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