KR20180072677A - Polyvinyl alcohol film for polarizing film production and production of polarizing film, polarizing plate and polyvinyl alcohol film for polarizing film using the same - Google Patents

Abstract

(%) In the width direction (TD direction) when the polyvinyl alcohol film is immersed in water at 30 占 폚 for 15 minutes, the polyvinyl alcohol film having a thickness of 5 to 60 占 퐉, a width of 2 m or more, And the swelling degree Y (%) in the longitudinal direction (MD direction) satisfy the following conditions (1) and (2).
(1) 110? Y? 140
(2) 1.01? Y / X? 1.2

Description

Polyvinyl alcohol film for polarizing film production and production of polarizing film, polarizing plate and polyvinyl alcohol film for polarizing film using the same

The present invention relates to a polyvinyl alcohol-based film for producing a polarizing film (hereinafter, simply referred to as a " polyvinyl alcohol-based film "), and more particularly to a polyvinyl alcohol film having excellent dyeability and high polarizability, A polarizing film using the polyvinyl alcohol film, a polarizing plate, and a method for producing a polyvinyl alcohol film for producing a polarizing film.

Background Art [0002] Conventionally, a polyvinyl alcohol-based film is used for many applications as a film having excellent transparency, and polarizing films are one of useful applications. Such a polarizing film is used as a basic constituent element of a liquid crystal display, and in recent years, its use as a high-quality and highly reliable apparatus has been expanding.

Of these, a polarizing film excellent in polarization performance is required in accordance with a high luminance, a high definition, a large screen, and a thinness of a screen of a liquid crystal TV or a multifunctional portable terminal. Concretely, it is a further improvement of the polarization degree and resolution of unevenness.

In general, a polyvinyl alcohol film for producing a polarizing film is produced from an aqueous solution of a polyvinyl alcohol resin by a continuous casting method. Specifically, the film is cast by casting an aqueous solution of a polyvinyl alcohol-based resin into a casting mold such as a cast drum or an endless belt, and the film thus formed is peeled off from the casting mold. Thereafter, ), And drying using a heat roll or a floating dryer. In such a conveying step, the film formed is pulled in the flow direction (MD direction), so that the polyvinyl alcohol-based polymer is liable to be oriented in the MD direction.

On the other hand, in general, a polarizing film is produced by swelling a polyvinyl alcohol film as a raw material thereof with water (including hot water), then dying and stretching the film with a dichroic dye such as iodine. In such a swelling step, it is necessary to rapidly swell the polyvinyl alcohol-based film in the thickness direction. In addition, it is necessary to uniformly swell the dye so that the dye penetrates into the film smoothly in the dyeing step.

In the stretching process, the film after the dyeing is stretched in the flow direction (MD direction) to highly orient the dichroic dye in the film. In order to improve the polarizing performance of the polarizing film, the polyvinyl alcohol- It is necessary to have a good stretchability in the direction

In addition, a case where the order of the stretching process and the dyeing process in the polarizing film production are opposite to those described above is also carried out. That is, in the case of swelling a polyvinyl alcohol film as a disc with water (including hot water), stretching and dying with a dichroic dye such as iodine, in order to improve the polarizing performance of the polarizing film even in such a case, It is necessary for the alcoholic film to have good swelling properties in the thickness direction and also to have good stretchability in the MD direction.

In addition, in recent years, in order to make the polarizing film thinner, the polyvinyl alcohol film is also thinned. Such a thin film has problems of productivity such as breakage by stretching when the polarizing film is produced.

As a method for improving the swelling property, there has been proposed, for example, a method of adding a polyhydric alcohol to a polyvinyl alcohol-based resin as a water swelling auxiliary (for example, see Patent Document 1). As a method for improving the stretchability, for example, there is a method of specifying the ratio between the speed of the cast drum at the time of film formation and the final film winding speed (see, for example, Patent Document 2) There has been proposed a method of suspending a film (for example, refer to Patent Document 3), and a method of controlling a tensile state in a drying process of a film formed (see, for example, Patent Document 4).

Patent Document 1 JP 2001-302867A Patent Document 2 JP 2001-315141A Patent Document 3 JP 2001-315142A Patent Document 4 JP 2002-79531 A

However, even with the method of the patent document, it is insufficient to improve the swelling property and the stretchability at the time of producing the polarizing film.

Although the swelling property of the entire polyvinyl alcohol-based film can be improved, the orientation state of the polyvinyl alcohol-based polymer is not taken into consideration, and the stretching property in the flow direction (MD direction) It is difficult to improve the efficiency. On the contrary, by the addition of the water swelling agent, the orientation of the polymer is disturbed and uniform drawing in the flow direction (MD direction) tends to become difficult.

Patent Document 2 specifies the degree of stretching (pulled state) in the MD direction when producing a polyvinyl alcohol-based film. However, if stretching in the TD direction is not taken into account, It is insufficient. In general, it is difficult to stretch a polyvinyl alcohol-based film oriented in the MD direction in the MD direction at the time of producing the polarizing film. That is, pulling the polyvinyl alcohol-based polymer oriented in the MD direction again in the MD direction makes it difficult to stretch the molecular chains forcibly. On the contrary, it is relatively easy to pull the polyvinyl alcohol-based polymer oriented in the TD direction in the MD direction. However, if the orientation of the polymer in the TD direction is not uniform, the film can not be stretched uniformly in the MD direction during the production of the polarizing film. Patent Document 2 discloses an example in which the polyvinyl alcohol film is not stretched as much in the MD direction as in the case of producing a polyvinyl alcohol film. However, the shrinkage stress due to the Poisson's ratio and the shrinkage stress due to dehydration are not sufficient There is a problem that the polymer orientation can not be sufficiently made uniform. That is, unless the film is elongated to some extent in the TD direction or at least fixed in the width direction, a uniform orientation state of the polymer in the TD direction is not obtained, which is insufficient for improving the stretchability in the MD direction at the time of producing the polarizing film. Further, there is no description about the orientation in the thickness direction, and the swelling property at the time of producing the polarizing film is not controlled.

In the technique disclosed in Patent Document 3, the film after film formation can be uniformly dried, but the orientation of the polymer can not be controlled and is insufficient for improving the swelling property and the stretchability at the time of producing the polarizing film.

In the technique disclosed in Patent Document 4, although the film thickness of the polyvinyl alcohol-based film can be made uniform, it can not control the orientation of the polymer, and is insufficient for improving the swelling property and the stretchability at the time of producing the polarizing film.

Therefore, in the present invention, a polyvinyl alcohol-based film for producing a polarizing film capable of obtaining a polarizing film having a high polarizing performance and excellent in polarizing performance and excellent in swelling property and stretching property at the time of producing a polarizing film under such a background, The present invention also provides a polarizing film and a polarizing plate including the polarizing film-forming polyvinyl alcohol film, and a process for producing a polarizing film-producing polyvinyl alcohol film, .

Accordingly, the present inventors have conducted intensive studies in view of such circumstances, and as a result, have found that the ratio of the swelling degree X (%) in the width direction (TD direction) to the swelling degree Y (% It has been found that a polyvinyl alcohol film is excellent in swelling property and stretchability in producing a polarizing film and that a polarizing film obtained by using such a polyvinyl alcohol film has a high polarization performance and also a small polarizing film.

That is, the first aspect of the present invention is a polyvinyl alcohol-based film having a thickness of 5 to 60 μm, a width of 2 m or more, and a length of 2 km or more. When the polyvinyl alcohol film is immersed in water at 30 ° C. for 15 minutes, And the swelling degree Y (%) in the longitudinal direction (MD direction) satisfies the following conditions (1) and (2).

(1) 110? Y? 140

(2) 1.01? Y / X? 1.2

Particularly, the polyvinyl alcohol film for producing a polarizing film is characterized in that when the polyvinyl alcohol film is immersed in water at 30 占 폚 for 15 minutes, the swelling degree Z (%) in the thickness direction satisfies the following condition (3) The second point of the present invention is as follows.

(3) 140? Z? 170

The deviation ΔY (%) of the swelling degree Y (%) in the longitudinal direction (MD direction) and the swelling degree Z (%) of the swelling degree X (%) in the width direction The polyvinyl alcohol film for polarizing film production according to the third aspect of the present invention is characterized in that the deviation? Z (%) is all within 5%.

A fourth aspect of the present invention is a polyvinyl alcohol-based film for polarizing film production, which satisfies the following conditions (4) and (5).

(4) In-plane retardation Rxy (nm): 100 to 200 nm

(5) When the angle of intersection &thetas; (DEG) in the width direction, that is, the TD direction, with respect to the orientation axis, that is,

When the refractive index in the width direction (TD direction) is nx, the refractive index in the longitudinal direction (MD direction) is ny, and the thickness is d (nm) in the polyvinyl alcohol film, Is a value calculated by equation (A).

(A) Rxy (nm) = | nx-ny | xd (nm)

Particularly, the fifth aspect of the present invention is a polarizing film-forming polyvinyl alcohol-based film characterized in that the deviation? Rxy (nm) of the in-plane retardation Rxy (nm) in the transverse direction (TD direction) is 10 nm or less.

Among them, the polyvinyl alcohol-based film for polarizing film production is characterized in that a deviation ?? (°) of the crossing angle? (°) is 10 ° or less.

The seventh object of the present invention is a polyvinyl alcohol-based film for producing a polarizing film, wherein the thickness of the polyvinyl alcohol-based film is 5 to 30 占 퐉.

Further, the present invention is a polarizing film characterized in that a polyvinyl alcohol film for producing a polarizing film is used.

The present invention also provides a polarizing plate characterized by comprising a polarizing film and a protective film provided on at least one surface of the polarizing film.

The present invention also relates to a process for continuously drying a polyvinyl alcohol resin aqueous solution by a continuous casting method, a step of peeling off from a cast mold while being conveyed in a flow direction (MD direction) ), Wherein when the polyvinyl alcohol film to be produced is immersed in water at 30 占 폚 for 15 minutes, the degree of swelling X (%) in the width direction (TD direction) and the degree of swelling Wherein the swelling degree Y (%) in the flow direction (MD direction) satisfies the following conditions (1) and (2).

(1) 110? Y? 140

(2) 1.01? Y / X? 1.2

In particular, a method for producing a polyvinyl alcohol film for polarizing film production is characterized in that the film is stretched at a draw ratio of 1.05 to 1.5 times in the transverse direction (TD direction).

Further, a twelfth aspect of the present invention is a method for producing a polyvinyl alcohol-based film for polarizing film production, wherein stretching in the transverse direction (TD direction) is performed at 50 to 150 캜.

And the moisture content of the film before stretching in the transverse direction (TD direction) is 0.5 to 15% by weight. The method for producing a polyvinyl alcohol film for polarizing film production according to the thirteenth aspect of the present invention.

Among them, polyvinyl alcohol for producing a polarizing film (hereinafter referred to as " polyvinyl alcohol ") for producing a polarizing film, which is stretched beyond 1.3 times in the width direction (TD direction) temporarily and then shrunk to 1.05 to 1.5 times in the final width direction Based film according to the present invention.

The method for producing a polarizing film-producing polyvinyl alcohol film is characterized in that the dimensional change ratio in the film flow direction (MD direction) before and after stretching in the width direction (TD direction) is 0.8 to 1.0. 15 to the point.

The polyvinyl alcohol film for producing a polarizing film of the present invention is excellent in swelling property and stretching property at the time of production of a polarizing film, so that even when a thin polarizing film is produced, a polarizing film exhibiting a high polarization performance without occurrence of breakage, can do.

Further, the present invention is based on the technical idea of improving the swelling property and the stretching property in the polarizing film production by improving the swelling property in the flow direction (MD direction) of the polyvinyl alcohol film.

Hereinafter, the present invention will be described in detail.

The polyvinyl alcohol film for producing a polarizing film of the present invention is a polyvinyl alcohol film having a thickness of 5 to 60 탆, a width of 2 m or more, a length of 2 km or more and having the following characteristics. Specifically, an aqueous solution of a polyvinyl alcohol-based resin is formed by a continuous casting method, and after the film is peeled from the cast mold, the film is continuously dried and transported in the transverse direction (TD direction ). ≪ / RTI >

The polyvinyl alcohol film of the present invention has a swelling degree X (%) in the width direction (TD direction) and a swelling degree X (%) in the direction of flow (MD) when the polyvinyl alcohol film produced by the above method is immersed in water at 30 ° C for 15 minutes. Direction) Y (%) satisfies both of the following conditions (1) and (2). This is a feature of the present invention. Even if only one property value is satisfied, the object of the present invention is not achieved.

(1) 110? Y? 140

(2) 1.01? Y / X? 1.2

The above conditions (1) and (2) can be achieved, for example, by a stretching process in the transverse direction (TD direction) with respect to the film formed. In this case, the stretching magnification is preferably 1.05 to 1.5, Preferably 1.1 to 1.45 times, and more preferably 1.2 to 1.4 times. It is difficult to control the swelling degree X (%) in the width direction (TD direction) and the swelling degree Y (%) in the flow direction (MD direction) and to control the phase difference even if the draw ratio in the width direction And the swelling property and the stretching property at the time of producing the polarizing film tend to be lowered.

Condition (1) specifies swelling degree Y (%) in the flow direction (MD direction), but is within the range of the known art. Such swelling degree Y (%) is required to be 110% or more and 140% or less, preferably 115% or more and 135% or less, and particularly preferably 120% or more and 130% or less. When the degree of swelling Y (%) is less than the lower limit value, the stretchability at the time of producing the polarizing film is lowered, which is undesirable. Conversely, if the degree of swelling exceeds the upper limit, the degree of polarization of the polarizing film is undesirably low.

Condition (2) specifies the ratio (Y / X) of the swelling degree Y (%) in the flow direction (MD direction) to the swelling degree X (%) in the width direction (TD direction). The greatest feature of the present invention resides in that the swelling degree Y (%) in the flow direction (MD direction) is larger than the swelling degree X (%) in the width direction (TD direction) in a specific range.

Conventional polyvinyl alcohol films have such a ratio of 1 or less. This is because the molecular chain of the polyvinyl alcohol-based polymer is usually oriented in the flow direction (MD direction), and it is hard to swell in this direction.

The ratio (Y / X) of the swelling degree Y (%) in the flow direction (MD direction) to the swelling degree X (%) in the width direction (TD direction) satisfies the condition (2) 1.01? Y / , And it is particularly desirable to satisfy the following condition (2 ') and satisfy the following condition (2' ').

(2 ') 1.03? Y / X? 1.15

(2 ") 1.05? Y / X? 1.1

If Y / X is less than the lower limit value, the stretchability at the time of production of the polarizing film is not sufficient, and if it exceeds the upper limit, the degree of polarization of the polarizing film is undesirably low.

In the polyvinyl alcohol film of the present invention, when the polyvinyl alcohol film is immersed in water at 30 占 폚 for 15 minutes, the swelling degree Z (%) in the thickness direction preferably satisfies the following condition (3) Preferably, it satisfies the following condition (3 '), more preferably the following condition (3' ').

(3) 140? Z? 170

(3 ') 143? Z? 169

(3 ") 145? Z? 168

The degree of swelling Z (%) in the present invention is a value obtained by measuring the degree of swelling X (%) in the width direction (TD direction), the degree Y of swelling in the flow direction (MD direction) and the weight after immersing the film, Is a value calculated from the weight according to the following formula.

Swelling degree Z (%) = 1000000 Weight after immersion (g) / Weight after drying (g) / X / Y

When the degree of swelling Z (%) is too low, the swelling property at the time of production of the polarizing film tends to decrease. On the contrary, when the swelling degree Z (%) is too high, the degree of polarization of the polarizing film tends to decrease. The swelling degree Z (%) is larger than the degree of swelling in the width direction (TD direction) or swelling degree in the flow direction (MD direction), as evident from the conditions (1), (2) and (3). This is because the molecular chain of the polyvinyl alcohol-based polymer is oriented mainly in the plane direction and has a chemical structure which tends to swell in the thickness direction. With such a chemical structure, the polyvinyl alcohol-based film can be rapidly and uniformly swollen in the swelling process at the time of producing the polarizing film.

The polyvinyl alcohol film of the present invention has a deviation ΔX (%) of the swelling degree X (%) in the width direction (TD direction), a deviation ΔY (%) of the swelling degree Y The deviation? Z (%) of the swelling degree Z (%) in the direction is preferably 5% or less, particularly preferably 4% or less, more preferably 3% or less. If such a deviation is too large, color irregularity tends to occur in the polarizing film.

As a method for satisfying the conditions (1), (2), and (3) in the present invention, in addition to the method of stretching the film peeled from the cast mold like the present invention in the width direction (TD direction) A method of controlling the drying condition of the aqueous alcoholic resin solution, a method of controlling the chemical structure of the polyvinyl alcohol resin, and the like.

It is also preferable that the polyvinyl alcohol film produced by the above method satisfies both of the following properties (4) and (5).

(4) In-plane retardation Rxy (nm): 100 to 200 nm

(5) Cross angle θ (°) between the orientation axis (slow axis) and the width direction (TD direction) is 20 ° or less

Herein, the in-plane retardation Rxy (nm) satisfies the following formula (1) when the refractive index in the width direction (TD direction) is nx, the refractive index in the flow direction (MD direction) is ny and the thickness is d A).

(A) Rxy (nm) = | nx-ny | xd (nm)

The in-plane retardation Rxy (nm) is particularly preferably 110 to 180 nm, and more preferably 130 to 170 nm. When the in-plane retardation Rxy (nm) is too small, the elongation in the MD direction during the production of the polarizing film tends to decrease. When the in-plane retardation Rxy (nm) is too large, color unevenness tends to occur in the polarizing film.

The deviation? Rxy (nm) of the in-plane retardation Rxy (nm) in the width direction (TD direction) is preferably 10 nm or less, particularly preferably 5 nm or less, more preferably 3 nm or less. If the deviation DELTA Rxy is too large, color irregularity tends to occur in the polarizing film.

The angle of intersection? (°) between the orientation axis (slow axis) and the width direction (TD direction) is preferably 20 ° or less, particularly preferably 10 ° or less, more preferably 5 ° or less. If the crossing angle? (°) is too large, the elongation in the MD direction during the production of the polarizing film tends to be lowered.

(占) of the crossing angle? (占 in the width direction (TD direction) is preferably 10 占 or less, particularly preferably 5 占 or less, more preferably 3 占 or less. If such deviation ?? (?) Is too large, color unevenness tends to occur in the polarizing film.

In addition to the method of controlling the in-plane retardation Rxy (nm) and the crossing angle? (°), in addition to the method of stretching the film peeled off from the cast mold in the present invention in the width direction (TD direction) A method of controlling the chemical structure of the polyvinyl alcohol-based resin, and the like.

Hereinafter, the method of producing the polyvinyl alcohol film for polarizing film production of the present invention will be described in more detail in the order of steps.

[Film material]

First, the polyvinyl alcohol resin and its aqueous solution used in the present invention will be described.

As the polyvinyl alcohol-based resin constituting the polyvinyl alcohol-based film in the present invention, a resin produced by saponification of an unmodified polyvinyl alcohol-based resin, that is, polyvinyl acetate obtained by polymerizing vinyl acetate, is used. If necessary, a resin obtained by saponifying a copolymer of vinyl acetate and a small amount (usually 10 mol% or less, preferably 5 mol% or less) of a copolymerizable component of vinyl acetate can be used. Examples of the component copolymerizable with vinyl acetate include unsaturated carboxylic acids (including salts, esters, amides, nitriles, etc.), olefins having 2 to 30 carbon atoms (e.g., Butene, isobutene, etc.), vinyl ethers, and unsaturated sulfonate salts. It is also possible to use a modified polyvinyl alcohol-based resin obtained by chemically modifying a hydroxyl group after saponification. These may be used alone or in combination of two or more.

As the polyvinyl alcohol-based resin, a polyvinyl alcohol-based resin having a 1,2-diol structure in the side chain may also be used. Such a polyvinyl alcohol-based resin having a 1,2-diol structure in the side chain can be obtained by, for example, (i) saponifying a copolymer of vinyl acetate and 3,4-diacetoxy-1-butene, (Ii) a method of saponifying and decarboxylating a copolymer of vinyl acetate and vinylethylene carbonate, (iii) saponifying and copolymerizing a copolymer of vinyl acetate and 2,2-dialkyl-4-vinyl-1,3-dioxolane, (Iv) a method of saponifying a copolymer of vinyl acetate and glycerin monoallyl ether, and the like.

The weight average molecular weight of the polyvinyl alcohol-based resin is preferably 100,000 to 300,000, particularly preferably 110,000 to 280,000, and more preferably 120,000 to 260,000. If the weight average molecular weight is too small, it tends to be difficult to obtain sufficient optical performance when the polyvinyl alcohol resin is used as an optical film. If it is too large, stretching becomes difficult when a polarizing film is produced using a polyvinyl alcohol film There is a tendency. The weight average molecular weight of the polyvinyl alcohol resin is a weight average molecular weight measured by the GPC-MALS method.

The average saponification degree of the polyvinyl alcohol-based resin used in the present invention is preferably 98 mol% or more, particularly preferably 99 mol% or more, more preferably 99.5 mol% or more, particularly preferably 99.8 mol% or more to be. When the average degree of saponification is too small, sufficient optical performance tends not to be obtained when a polarizing film is used as the polyvinyl alcohol-based film.

Here, the average degree of saponification in the present invention is measured in accordance with JIS K 6726.

As the polyvinyl alcohol-based resin to be used in the present invention, two or more kinds of modified species, modified amount, weight average molecular weight, average saponification degree and the like may be used in combination.

The polyvinyl alcohol resin aqueous solution may contain, in addition to the polyvinyl alcohol-based resin, a commonly used plasticizer such as glycerin, diglycerin, triglycerin, ethylene glycol, triethylene glycol, polyethylene glycol, trimethylolpropane, , It is preferable to include at least one surfactant of anionic and cationic in view of film formability. These may be used alone or in combination of two or more.

The resin concentration of the polyvinyl alcohol-based resin solution thus obtained is preferably 15 to 60% by weight, particularly preferably 17 to 55% by weight, and more preferably 20 to 50% by weight. If the concentration of the resin in such an aqueous solution is too low, the production load tends to decrease because the drying load becomes large. If the resin concentration is too high, the viscosity tends to become too high and uniform dissolution becomes impossible.

Then, the resulting polyvinyl alcohol-based resin aqueous solution is defoamed. Examples of the defoaming method include a defoaming method using a static deformation or a multi-screw extruder. The multi-screw extruder may be a multi-screw extruder having a vent, and a twin-screw extruder usually having a vent is used.

[Film forming process]

After the defoaming treatment, the polyvinyl alcohol-based resin solution is introduced into the T-shaped slit die by a predetermined amount, and is discharged and cast on the rotating casting drum, and is formed by the continuous casting method.

The continuous casting method in the present invention is a method of forming a film by discharging and casting an aqueous solution of a polyvinyl alcohol-based resin into a casting mold such as a cast drum, endless belt, resin film or the like rotating in a T-shaped slit die to be. The film thus formed is peeled off from the cast mold and then continuously dried with a heat roll while being conveyed in the flow direction (MD direction), for example, may be heat-treated with a floating dryer.

The resin temperature of the polyvinyl alcohol-based resin solution at the outlet of the T-shaped slit die is preferably 80 to 100 占 폚, particularly preferably 85 to 98 占 폚.

When the resin temperature of such a polyvinyl alcohol-based resin aqueous solution is too low, flow defects tend to occur. When the resin temperature is too high, foaming tends to occur.

The viscosity of such a polyvinyl alcohol-based resin aqueous solution is preferably 50 to 200 Pa · s, more preferably 70 to 150 Pa · s at the time of discharging.

If the viscosity of such an aqueous solution is too low, the flow tends to become defective. If the viscosity is too high, casting tends to be difficult.

The discharge speed of the polyvinyl alcohol-based resin solution discharged from the T-shaped slit die to the cast drum is preferably 0.2 to 5 m / min, particularly preferably 0.4 to 4 m / min, and more preferably 0.6 to 3 m / min.

If the discharge speed is too low, productivity tends to decrease, and if it is too fast, casting becomes difficult.

The diameter of such a cast drum is preferably 2 to 5 m, particularly preferably 2.4 to 4.5 m, and more preferably 2.8 to 4 m.

If the diameter is too small, the drying section on the casting drum is shortened, and the speed tends to increase. When the diameter is too large, the transportability tends to decrease.

The width of such a cast drum is preferably 4 m or more, particularly preferably 4.5 m or more, more preferably 5 m or more, particularly preferably 5 to 6 m.

If the width of the cast drum is too small, productivity tends to decrease.

The rotation speed of the casting drum is preferably 3 to 50 m / min, particularly preferably 4 to 40 m / min, and more preferably 5 to 35 m / min.

If the rotation speed is too low, the productivity tends to decrease. If the rotation speed is too fast, the drying tends to be insufficient.

The surface temperature of such a cast drum is preferably 40 to 99 占 폚, particularly preferably 60 to 95 占 폚.

If the surface temperature is too low, drying tends to be poor, and if it is too high, it tends to foam.

[Coated film]

The water content of the film thus formed (film before stretching in the width direction (TD direction)] is preferably 0.5 to 15% by weight, particularly preferably 1 to 13% by weight, more preferably 2 to 12% %to be. Even if the water content is too low or too high, the orientation of the desired polymer, that is, the intended degree of swelling and elongation, tends to become difficult.

When the water content of the film before stretching in the width direction (TD direction) is too high, it is preferable to dry the film before stretching in the width direction (TD direction), and conversely, Direction) is too low, it is preferable that the moisture is adjusted before stretching in the width direction (TD direction). More preferably, the conditions of the drying process are adjusted so that the water content falls within the above range.

Such drying can be carried out by a known method using a heating roll or an infrared heater, but in the present invention, it is preferable to carry out drying with a plurality of heating rolls, and particularly preferably, the temperature of the heating roll is 40 to 150 DEG C And preferably 50 to 120 캜. Further, because of the adjustment of the water content, a humidity control area may be provided before stretching in the width direction (TD direction).

[Carrying / Stretching Process]

Then, the film formed as described above and stretched in the transverse direction (TD direction) is continuously or intermittently stretched while conveying the film having the moisture content adjusted in the flow direction (MD direction).

It is not necessary to stretch the film formed in the present invention particularly in the flow direction (MD direction), and it is sufficient to carry the film with a pulling tension sufficient for not bending the film. As a matter of course, the stretching in the width direction (TD direction) results in necking depending on the Poisson's ratio in the flow direction (MD direction) and dehydration shrinkage occurs in the flow direction (MD direction) Direction (MD direction).

Rather, as the dimension in the flow direction (MD direction) grows, stretching in the flow direction (MD direction) is not preferable. The dimensional change ratio in the flow direction (MD direction) before and after the stretching in the width direction (TD direction) is preferably 0.8 to 1.0, particularly preferably 0.9 to 1.0, more preferably 0.95 to 1.0. If the rate of dimensional change is too small or too large, the degree of swelling tends to increase, and the orientation of the desired polymer, that is, the degree of swelling desired, tends to become difficult.

The preferred range of the conveying speed in the flow direction (MD direction) of the film-formed film is 5 to 30 m / min, particularly preferably 7 to 25 m / min, and more preferably 8 to 20 m / min. If the conveying speed is too low, the productivity tends to decrease. If the conveying speed is too high, the color unevenness of the polarizing film tends to increase.

There is no particular limitation on the method of carrying the formed film in the flow direction (MD direction) and the stretching in the width direction (TD direction) at the same time. For example, both ends of the film in the width direction are sandwiched by a plurality of clips, It is preferable to perform carrying and stretching at the same time. In such a case, the arrangement of the clips at each end is preferably 200 mm or less in pitch, particularly preferably 100 mm or less in pitch, and more preferably 50 mm or less in pitch.

If the pitch of the clips is too wide, there is a tendency that the film after stretching is bent or the thickness of both ends in the width direction of the obtained polyvinyl alcohol film becomes uneven and the phase difference unevenness increases. It is preferable that the clip holding position (distal end portion of the clip) is 100 mm or less from both ends in the width direction of the film formed. If the gripping position (distal end) of the clip is located too far in the center of the width direction of the film, the end of the film to be discarded increases and the product width tends to become narrow.

As described above, the polyvinyl alcohol-based film specified in the present invention can be achieved by stretching treatment in the transverse direction (TD direction) to the film formed, but in this case, the stretching magnification is preferably 1.05 to 1.5 times , Particularly preferably 1.1 to 1.45 times, more preferably 1.15 to 1.4 times, and particularly preferably 1.2 to 1.3 times. If the stretching magnification in the width direction (TD direction) is too low or too high, the swelling property and elongation tendency at the time of production of the polarizing film tend to decrease.

The continuous stretching process in the width direction (TD direction) may be one step (one time), and may be a plurality of steps (multiple times) (also called continuous stretching) so that the total stretching magnification falls within the range of the stretching magnification. For example, it is also possible to carry out a simple conveyance in which the width direction (TD direction) is fixed after the stretching in one step, and then the stretching in the second step and the subsequent steps can be carried out.

Particularly, in the case of a thin film, by inserting such a simple carrying step, stress relaxation of the film can be carried out, and breakage can be avoided.

In the case of inserting a conveying step of fixed width, the fixing width may be narrower than the width after the one-step stretching. The film immediately after stretching is liable to shrink in order to relax the stress and the fixing width can be narrowed to such a contraction width in order to cause shrinkage accompanying dehydration. However, if the film is narrowed beyond the shrinkage width, the film may be bent, which is not preferable.

Such a stretching step is preferably carried out after the drying step of the film, but may be carried out independently of at least one of before and after the drying step of the film, or may be carried out during the drying step.

As a preferred form of the present invention, a method of temporarily shrinking the film in the transverse direction (TD direction) beyond 1.3 times and then shrinking the film so that the final stretching magnification in the transverse direction (TD direction) is 1.05 to 1.5 times It is possible. In such a case, the film may be simply transported with a fixed width of 1.05 to 1.5 times the drawing magnification after the film is temporarily stretched beyond 1.3 times. By such a method, stress relaxation of the film is achieved, and in particular, in the case of a thin film, breakage can be avoided.

The stretching in the transverse direction (TD direction) of the film formed in the present invention is preferably performed at 50 to 150 占 폚, particularly preferably 60 to 140 占 폚, and more preferably 70 to 130 占 폚. If the stretching temperature is too low or too high, the stretching property at the time of producing the polarizing film tends to be lowered. In the case of continuous or intermittent stretching, such a stretching temperature may be changed in each stretching step, or a temperature gradient may be set during stretching.

The stretching time in the transverse direction (TD direction) of the film formed in the present invention is preferably 2 to 60 seconds, particularly preferably 5 to 45 seconds, and more preferably 10 to 30 seconds. If the stretching time is too short, the film tends to be broken. On the other hand, if the stretching time is too long, the equipment load tends to increase. In the case of the sequential stretching, such stretching time may be changed in each stretching step.

In the present invention, after the film is stretched in the transverse direction (TD direction), it may be subjected to heat treatment with a floating dryer or the like. The temperature for the heat treatment is preferably 60 to 200 占 폚, particularly preferably 70 to 150 占 폚, and more preferably 100 to 140 占 폚.

When the heat treatment temperature is too low, the dimensional stability tends to deteriorate. On the other hand, if the heat treatment temperature is too high, the elongation at the time of producing the polarizing film tends to decrease.

The heat treatment time is preferably 1 to 60 seconds, particularly preferably 5 to 30 seconds. If the heat treatment time is too short, the dimensional stability tends to decrease. On the other hand, if the heat treatment time is too long, the swelling property and the stretchability of the polarizing film tend to be lowered.

[Polyvinyl alcohol film for polarizing film production]

Thus, a polyvinyl alcohol-based film for producing a polarizing film of the present invention can be obtained, and finally wound on a roll to be a product. The thickness of such a polyvinyl alcohol film is preferably 5 to 60 占 퐉 in view of the in-plane retardation, particularly preferably 5 to 45 占 퐉, more preferably 5 to 30 占 퐉, Is 10 to 20 占 퐉 from the viewpoint of avoiding breakage. The thickness of such a polyvinyl alcohol-based film is adjusted by the resin concentration in the polyvinyl alcohol-based resin aqueous solution, the discharge amount (discharge speed) into the cast mold, the draw ratio, and the like.

The width of such a polyvinyl alcohol-based film is 2 m or more, particularly preferably 3 m or more from the standpoint of large-area enlargement, and more preferably 4 to 6 m from the viewpoint of avoiding breakage.

The length of such a polyvinyl alcohol-based film is 2 km or more, particularly preferably 3 km or more from the standpoint of large-scale surface area, and more preferably 3 to 50 km from the viewpoint of transportation weight.

The polyvinyl alcohol film for producing a polarizing film of the present invention is very useful as a original film of a polarizing film. Hereinafter, a polarizing film made of the above polyvinyl alcohol film and a producing method of the polarizing plate will be described.

[Polarizing film production method]

The polarizing film of the present invention is produced by loosening the polyvinyl alcohol-based film from a roll, transferring it in a horizontal direction, and swelling, dyeing, boric acid crosslinking, stretching, washing, drying and the like.

The swelling process is carried out before the dyeing process. In addition to being able to clean the surface of the polyvinyl alcohol film by the swelling process, the polyvinyl alcohol film is also swollen to prevent uneven dyeing. As the treatment liquid in the swelling process, water is usually used. If the main component is water, the treatment liquid may contain a small amount of an additive such as a iodinated compound, a surfactant, or an alcohol. The temperature of the swelling bath is usually about 10 to 45 DEG C, and the immersion time in the swelling bath is usually about 0.1 to 10 minutes.

The degree of swelling of the polyvinyl alcohol-based film of the present invention in the swelling step, as described above, was measured by measuring the swelling degree X (%) in the width direction (TD direction) , And the degree of swelling Y (%) in the flow direction (MD direction) satisfies both of the following conditions (1) and (2).

(1) 110? Y? 140

(2) 1.01? Y / X? 1.2

Further, as described above, it is preferable that the swelling degree Z (%) in the thickness direction satisfies the following condition (3).

(3) 140? Z? 170

The dyeing process is carried out by bringing the film into contact with a liquid containing iodine or a dichroic dye. Normally, an aqueous solution of iodine-potassium iodide is used, the concentration of iodine is 0.1 to 2 g / L, and the concentration of potassium iodide is preferably 1 to 100 g / L. Dyeing time is practically about 30 to 500 seconds. The temperature of the treatment bath is preferably 5 to 50 占 폚. The aqueous solution may contain a small amount of an organic solvent compatible with water in addition to the water solvent.

The boric acid crosslinking process is carried out using a boron compound such as boric acid or borax. The boron compound is used at a concentration of about 10 to 100 g / L in the form of an aqueous solution or a water-organic solvent mixture, and it is preferable that potassium iodide coexists in the liquid from the viewpoint of stabilization of the polarization performance. The temperature for the treatment is preferably about 30 to 70 占 폚, and the treatment time is preferably about 0.1 to 20 minutes, and if necessary, the stretching operation may be carried out during the treatment.

In the stretching step, the film is preferably stretched in the uniaxial direction by 3 to 10 times, preferably by 3.5 to 6 times. At this time, a slight stretching (a degree of preventing the stretching in the width direction or further stretching) may also be performed in the direction perpendicular to the stretching direction. The temperature at the time of stretching is preferably from 40 to 170 캜. The stretching magnification may be finally set within the above range, and the stretching operation may be performed not only once but also several times in the manufacturing process.

The cleaning process is carried out, for example, by immersing the polyvinyl alcohol film in an aqueous iodide solution such as water or potassium iodide, and the precipitates generated on the surface of the film can be removed. When potassium iodide aqueous solution is used, the concentration of potassium iodide may be about 1 to 80 g / L. The temperature at the time of the washing treatment is usually 5 to 50 占 폚, preferably 10 to 45 占 폚. The treatment time is usually from 1 to 300 seconds, preferably from 10 to 240 seconds. The washing with water and the washing with aqueous potassium iodide solution may be carried out in appropriate combination.

The drying process is carried out, for example, by drying the film at 40 to 80 DEG C for 1 to 10 minutes in the atmosphere.

Although a polarizing film can be obtained in this way, the degree of polarization of such a polarizing film is preferably 99.5% or more, particularly preferably 99.8% or more. When the degree of polarization is too low, the contrast in the liquid crystal display tends to decrease. Generally, the degree of polarization is determined by the relationship between the light transmittance (H ₁₁ ) measured for the wavelength? And the transmittance (H ₁₁ ) of the two polarizing films measured in the direction of the alignment direction of the two polarizing films And the light transmittance (H ₁ ) measured with respect to the wavelength? In a superimposed state so as to satisfy the following formula.

Degree of polarization = _{[(H 11 -H 1) / (} H 11 + H 1) ] ^{/ 2}

The single transmittance of the polarizing film of the present invention is preferably 44% or more. If such a simple mass transmittance is too low, the brightness of the liquid crystal display tends to be unable to be achieved.

The mass transmittance is a value obtained by measuring the light transmittance of the single polarizing film by using a spectrophotometer.

Next, a method for producing a polarizing plate of the present invention using the polarizing film of the present invention will be described.

The polarizing film of the present invention is very suitable for producing a polarizing plate having less unevenness and excellent polarization performance.

[Polarizing plate production method]

The polarizing plate of the present invention is produced by bonding an optically isotropic resin film as a protective film to one or both surfaces of the polarizing film of the present invention through an adhesive. Examples of the protective film include cellulose triacetate, cellulose diacetate, polycarbonate, polymethyl methacrylate, cycloolefin polymer, cycloolefin copolymer, polystyrene, polyether sulfone, polyarylene ester, And films or sheets such as polyethylene, polypropylene, polyethylene, polypropylene, polyethylene, polypropylene, polyethylene, polypropylene,

For example, a liquid adhesive composition is uniformly applied to a polarizing film, a protective film, or both, and then the two are adhered to each other, pressed, heated and irradiated with active energy rays .

It is also possible to apply a curable resin such as a urethane resin, an acrylic resin, or a urea resin to one surface or both surfaces of the polarizing film and cure the same to form a cured layer to form a polarizing plate. In this case, the cured layer becomes a substitute for the protective film, and the thin film can be formed.

The polarizing film and the polarizing plate using the polyvinyl alcohol film of the present invention are excellent in the polarizing performance and can be used in portable information terminals, PCs, televisions, projectors, signage, electronic tabletop calculators, electronic clocks, word processors, An antireflection layer for a display device (CRT, LCD, organic EL, electronic paper, etc.), a liquid crystal display device such as a camera, a photo album, a thermometer, Optical communication equipment, medical equipment, building materials, toys, and the like.

(Example)

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples unless the gist thereof is exceeded.

In the examples, " part " means weight basis.

(Swelling degree, swelling degree deviation, in-plane retardation, deviation of in-plane retardation, intersection angle between orientation axis and width direction, and dimensional change ratio) of the polyvinyl alcohol-based film in the following Examples and Comparative Examples and the characteristics Polarization transmittance, color unevenness) were measured and evaluated as follows.

<Measurement Conditions>

[Swelling degree (%) of polyvinyl alcohol-based film]

One piece of a film having a width of 100 mm and a length of 100 mm was cut out from the central portion in the width direction of the obtained polyvinyl alcohol film and both the left and right ends thereof and was swollen by immersion in water at 30 DEG C for 15 minutes. The swelling degree X (%) in the width direction (TD direction) and the swelling degree Y (%) in the flow direction (MD direction) were calculated from the dimensions before and after immersion according to the following formula. The swelling degree Z (%) in the thickness direction is obtained by cutting one film having a width of 100 mm and a length of 100 mm from the center portion and both the left and right ends of the polyvinyl alcohol film in the width direction and immersing the film in water at 30 캜 for 15 minutes, The filter paper 5A was placed on the film and the SUS plate of 150 mm x 150 mm x 4 mm (4.4 x 10 ^-2 g / mm &lt; ² &gt;) was placed thereon for 5 seconds, And the number of adhered surfaces was removed. This film was quickly weighed into a weighing bottle and its weight was determined as &quot; weight after immersion &quot;. The above operation was performed in an environment of 23 ° C and 50% RH.

Subsequently, the film was allowed to stand in a dryer at 105 ° C for 16 hours to remove water from the film, and then the film was taken out and quickly put into a weighing bottle to measure the weight, which was used as "weight after drying". Then, the swelling degree Z (%) in the thickness direction was calculated according to the following formula.

Width of swelling X (%) = 100 占 Width in TD direction after immersion (mm) / Width in mm in TD before immersion (mm)

Width of swelling Y (%) = 100 占 Width in MD direction after immersion (mm) / Width in MD direction before immersion (mm)

Swelling degree Z (%) = 1000000 Weight after immersion (g) / Weight after drying (g) / X / Y

[Variation (%) of swelling degree]

The difference between the maximum value and the minimum value is taken from the value of the degree of swelling X (%) in the width direction (TD direction) obtained in the above measurement (three points of the center portion and both the left and right ends) %). In the same manner, the deviation ΔY (%) of the swelling degree in the flow direction (MD direction) and the deviation ΔZ (%) of the swelling degree in the thickness direction were obtained.

The in-plane retardation Rxy (nm), the in-plane retardation deviation? Rxy (nm), the intersection angle? (Degrees) between the alignment axis (slow axis) and the width direction (TD direction) and the deviation?

A test piece having a length of 4 cm and a width of 4 cm was cut from the center portion in the width direction of the obtained polyvinyl alcohol film and the left and right end portions (10 cm inward from the film edge), and the film was measured with a retardation measuring apparatus (&quot; KOBRA- ) Was used to measure the in-plane retardation Rxy (nm) and the crossing angle? (°) between the orientation axis (slow axis) and the width direction (TD direction). Further, the in-plane retardation Rxy (nm) was obtained by taking the difference between the maximum value and the minimum value among the in-plane retardation Rxy (nm) of the center portion and both left and right ends in the width direction obtained in the measurement. Further, the difference between the maximum value and the minimum value was taken out of the crossing angle? (°) between the center portion and the left and right ends in the width direction obtained in the above measurement, and the deviation?

[Dimensional change rate]

Prior to stretching in the width direction (TD direction), a distance of 1 m was displayed (two points) in the flow direction (MD direction) with the magic ink. After stretching in the width direction (TD direction), the distance L (m) between such two points was measured with calipers, and the dimensional change ratio was calculated according to the following formula.

Dimensional change ratio = L (m) / 1 (m)

[Polarization degree (%), unit transmittance (%)]

A test piece having a length of 4 cm and a width of 4 cm was cut from the central portion in the width direction of the obtained polarizing film and the degree of polarization (%) and the unit transmissivity (%) were measured using an automatic polarizing film measuring device (VAP7070, manufactured by JASCO Corporation).

[Uneven color]

A test piece having a length of 30 cm and a width of 30 cm was cut from the central portion in the width direction of the obtained polarizing film and sandwiched between two polarizing plates (single light transmittance: 43.5%, polarization degree: 99.9% Optical color unevenness was observed in a transmission mode using a light box with a surface illuminance of 14,000 lx and evaluated according to the following criteria.

(Evaluation standard)

○ · · · No staining

△ · · · There is faint smudge

× · · With dirt

&Lt; Example 1 &gt;

(Production of polyvinyl alcohol film)

1,000 kg of a polyvinyl alcohol resin having a weight average molecular weight of 142,000, a saponification degree of 99.8 mol%, 2,500 kg of water, 105 kg of glycerin as a plasticizer and 0.25 kg of polyoxyethylene laurylamine as a surfactant were placed in a 5,000 L dissolution can, , The solution was heated up to 150 DEG C and subjected to pressure melting, and an aqueous solution of a polyvinyl alcohol-based resin having a resin concentration of 25 wt% was obtained by adjusting the concentration. Subsequently, the polyvinyl alcohol resin aqueous solution was fed to a twin-screw extruder and defoamed. Thereafter, the temperature of the aqueous solution was set to 95 占 폚, and the sheet was discharged from the T-shaped slit die discharge port into a rotating casting drum at a discharge speed of 2.5 m / Casting and casting. The formed film was peeled off from the cast drum and dried while being conveyed in the flow direction (MD direction) while alternately contacting the surface and the back of the film with a total of ten heat rolls. Thus, a film having a moisture content of 10% by weight (2 m wide and 60 m thick) was obtained. Then, both right and left ends of the film were held at a clip pitch of 45 mm, and stretched 1.2 times in the transverse direction (TD direction) at 120 캜 using a stretching machine while the film was transported at a speed of 8 m / min in the flow direction (MD direction). The dimensional change ratio in the flow direction (MD direction) before and after the stretching in the width direction (TD direction) was 0.96. Finally, the film was heat-treated at 120 DEG C for 10 seconds to obtain a polyvinyl alcohol film (width 2.4 m, thickness 50 m, length 2 km). The characteristics of the obtained polyvinyl alcohol-based film are shown in Tables 1 and 2.

(Preparation of Polarizing Film and Polarizing Plate)

The resulting polyvinyl alcohol film was unwound from the roll and stretched 1.7 times in the flow direction (MD direction) while being swollen by immersing in a water bath at a temperature of 30 DEG C while being transported in the horizontal direction. Subsequently, the resultant was immersed in an aqueous solution of 30 g / l of iodine and 0.5 g / l of potassium iodide and stretched 1.6 times in the flow direction (MD direction) while dyeing. Subsequently, 40 g / L of boric acid and 30 g / L of potassium iodide (50 占 폚), and uniaxially stretched 2.1 times in the flow direction (MD direction) while crosslinking the boric acid. Finally, the film was washed with an aqueous solution of potassium iodide and dried at 50 DEG C for 2 minutes to obtain a polarizing film having a total draw ratio of 5.8 times. No breakage occurred during such manufacturing. The properties of the obtained polarizing film are shown in Table 2. Using a polyvinyl alcohol aqueous solution as an adhesive on both surfaces of the polarizing film obtained above, a triacetylcellulose film having a thickness of 40 탆 was laminated and dried at 70 캜 to obtain a polarizing plate.

&Lt; Example 2 &gt;

The same procedure as in Example 1 was carried out except that the film formed in Example 1 was stretched 1.4 times in the transverse direction (TD direction) at 120 占 폚 using a stretching machine, and then conveyed at a fixing width of 2.4 m (1.2 times stretching equivalent) To obtain a polyvinyl alcohol film (width 2.4 m, thickness 50 m, length 2 km). The dimensional change ratio in the flow direction (MD direction) before and after the stretching in the width direction (TD direction) was 0.96. The characteristics of the obtained polyvinyl alcohol-based film are shown in Tables 1 and 2. Using the polyvinyl alcohol film, a polarizing film and a polarizing plate were obtained in the same manner as in Example 1. No breakage occurred during such manufacturing. The properties of the obtained polarizing film are shown in Table 2.

&Lt; Example 3 &gt;

(2 m in width and 20 m in thickness) having a moisture content of 5% by weight was stretched 1.4 times in the width direction (TD direction) at a discharge speed of 0.8 m / min at the time of film formation in Example 1, Polyvinyl alcohol film (width 2.6 m, thickness 15 m, length 2 km) was obtained in the same manner as in Example 1, The dimensional change ratio in the flow direction (MD direction) before and after the stretching in the width direction (TD direction) was 0.98. The characteristics of the obtained polyvinyl alcohol-based film are shown in Tables 1 and 2.

Using the polyvinyl alcohol film, a polarizing film and a polarizing plate were obtained in the same manner as in Example 1. Although the original polyvinyl alcohol film was thin, no breakage occurred in the drawing process during the production of the polarizing film. Properties of the obtained polarizing film are as shown in Table 3. &lt; tb &gt; &lt; TABLE &gt;

&Lt; Comparative Example 1 &

A polyvinyl alcohol film (width 2 m, thickness 60 m, length 2 km) was produced in the same manner as in Example 1 except that the film formed in Example 1 was not stretched in the width direction (TD direction) . The characteristics of the obtained polyvinyl alcohol-based film are shown in Tables 1 and 2.

Using the polyvinyl alcohol film, a polarizing film and a polarizing plate were obtained in the same manner as in Example 1. Properties of the obtained polarizing film are as shown in Table 3. &lt; tb &gt; &lt; TABLE &gt;

&Lt; Comparative Example 2 &

A polyvinyl alcohol film (width 2 m, thickness 20 탆, length 2 km) was prepared in the same manner as in Example 3 except that the film formed in Example 3 was not stretched in the width direction (TD direction) &Lt; / RTI &gt; The characteristics of the obtained polyvinyl alcohol-based film are shown in Tables 1 and 2.

The polarizing film and the polarizing plate were obtained in the same manner as in Example 1 except that the polyvinyl alcohol film was used. Properties of the obtained polarizing film are as shown in Table 3. &lt; tb &gt; &lt; TABLE &gt;

The results of the above Examples and Comparative Examples show that the ratio of the swelling degree X (%) in the width direction (TD direction) to the swelling degree Y (%) in the flow direction (MD direction) Of the polarizing films of Examples 1 to 3 obtained with a polyvinyl alcohol-based film satisfying the above conditions had a high degree of polarization and had no color unevenness. On the other hand, when the ratio of the swelling degree X (%) in the width direction (TD direction) to the swelling degree Y (%) in the flow direction (MD direction) exceeds the range specified in the above conditions (1) It can be seen that the polarization degree of the polarizing films of Comparative Examples 1 and 2 obtained as a film is lowered and color irregularities are also observed.

It is also preferable that the in-plane retardation Rxy and the cross-sectional angle? (°) between the orientation axis (slow axis) and the width direction (TD direction) satisfy a range specified by the above- The polarizing films of Examples 1 to 3 obtained as a film had a high degree of polarization and no color unevenness. On the other hand, when the in-plane retardation Rxy and the cross angle θ (°) between the orientation axis (slow axis) and the width direction (TD direction) are outside the range specified by the above conditions (4) It can be seen that the polarization degree of the polarizing films of Comparative Examples 1 and 2 obtained by the film is lowered and the stain is also observed.

Although the embodiment has been described in the concrete form of the present invention, the embodiment is merely an example and is not to be construed as limiting. Various modifications that are obvious to those skilled in the art are expected to be within the scope of the present invention.

The polarizing film and the polarizing plate using the polyvinyl alcohol film of the present invention are excellent in the polarizing performance and can be used in portable information terminals, PCs, televisions, projectors, signage, electronic tabletop calculators, electronic clocks, word processors, An antireflection layer for a display device (CRT, LCD, organic EL, electronic paper, etc.), a liquid crystal display device such as a camera, a photo album, a thermometer, Optical communication equipment, medical equipment, building materials, toys, and the like.

Claims (15)

A polyvinyl alcohol film having a thickness of 5 to 60 탆, a width of 2 m or more, and a length of 2 km or more is used. When the polyvinyl alcohol film is immersed in water at 30 캜 for 15 minutes, the degree of swelling X ( And the swelling degree Y (%) in the longitudinal direction (i.e., the MD direction) satisfy the following conditions (1) and (2).
(1) 110? Y? 140
(2) 1.01? Y / X? 1.2 The method according to claim 1,
Characterized in that when the polyvinyl alcohol film is immersed in water at 30 캜 for 15 minutes, the swelling degree Z (%) in the thickness direction satisfies the following condition (3).
(3) 140? Z? 170 The method according to claim 1 or 2,
The deviation ΔY (%) of the swelling degree Y (%) in the longitudinal direction (ie, the MD direction) and the swelling degree Z (%) of the swelling degree X (%) in the width direction ) Is within 5% of the total film thickness of the polyvinyl alcohol film. 4. The method according to any one of claims 1 to 3,
A polyvinyl alcohol film for polarizing film production, characterized by satisfying the following conditions (4) and (5).
(4) In-plane retardation Rxy (nm): 100 to 200 nm
(5) When the angle of intersection &amp;thetas; (DEG) in the width direction, that is, the TD direction, with respect to the orientation axis, that is,
Herein, the in-plane retardation Rxy (nm) is represented by nx, the refractive index in the longitudinal direction (i.e., the MD direction) is ny, the thickness is d (nm), the refractive index in the transverse direction In one case, it is a value calculated by the following formula (A).
(A) Rxy (nm) = | nx-ny | xd (nm) The method of claim 4,
Wherein the deviation? Rxy (nm) of the in-plane retardation Rxy (nm) in the width direction (i.e., the TD direction) is 10 nm or less. The method according to claim 4 or 5,
And the deviation ?? (?) Of the crossing angle? (°) is 10 ° or less. 7. The method according to any one of claims 1 to 6,
Wherein the polyvinyl alcohol film has a thickness of 5 to 30 占 퐉. A polarizing film characterized in that the polyvinyl alcohol film for producing a polarizing film according to any one of claims 1 to 7 is used. The method of claim 8,
And a protective film provided on at least one surface of the polarizing film and the polarizing film. A step of continuously drying an aqueous solution of a polyvinyl alcohol-based resin by continuous casting, a step of carrying out the film-forming method in the flow direction (that is, in the MD direction) ), And when the polyvinyl alcohol film to be produced is immersed in water at 30 占 폚 for 15 minutes, the swelling degree X (%) in the width direction (i.e., the TD direction) And the swelling degree Y (%) in the flow direction (i.e., the MD direction) satisfy the following conditions (1) and (2).
(1) 110? Y? 140
(2) 1.01? Y / X? 1.2 The method of claim 10,
And stretching the film at a draw ratio of 1.05 to 1.5 in the transverse direction (i.e., the TD direction). 12. The method according to claim 10 or 11,
And the stretching in the transverse direction (i.e., the TD direction) is performed at 50 to 150 占 폚. The method according to any one of claims 10 to 12,
And the water content of the film before stretching in the transverse direction (i.e., the TD direction) is 0.5 to 15% by weight. The method according to any one of claims 10 to 13,
Is stretched beyond 1.3 times in the transverse direction (i.e., the TD direction), and then shrinkage is performed so that the stretching magnification in the final width direction (i.e., TD direction) is 1.05 to 1.5 times. A method for producing an alcoholic film. The method according to any one of claims 10 to 14,
Wherein the dimensional change ratio of the film in the flow direction (i.e., the MD direction) before and after stretching in the width direction (i.e., the TD direction) is 0.8 to 1.0.