JP5438581B2 - Manufacturing method of polarizing film - Google Patents

Description

  The present invention relates to a method for producing a polarizing film used for producing a polarizing plate used in a liquid crystal display device, and a method for producing a polarizing plate using a polarizing film obtained by this production method.

  Conventionally, a polarizing film in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol film has been used. That is, an iodine polarizing film using iodine as a dichroic dye, a dye polarizing film using a dichroic dye as a dichroic dye, and the like are known. These polarizing films are usually used as polarizing plates by laminating a protective film such as triacetyl cellulose via an adhesive made of an aqueous solution of a polyvinyl alcohol resin on at least one surface, preferably both surfaces of the polarizing film. (LCD), for example, used for liquid crystal televisions, personal computer monitors, mobile phone display screens, etc.

As a method for producing a polarizing film, a nip roll and a guide roll are used, and after the polyvinyl alcohol film is immersed in water and swollen, it is dyed with the dichroic dye, stretched, and then iodine is formed into the film. In order to fix it, a method is known in which a polyvinyl alcohol film is treated with boric acid (crosslinking treatment), washed with water and then dried.
Further, in recent years, along with the increase in size, function and brightness of liquid crystal display devices, the polarizing film used for the liquid crystal display device is also required to increase in optical properties and in-plane uniformity at the same time. However, in order to obtain a large polarizing film, it is necessary to uniaxially stretch a wide original film, but the light absorption axis (hereinafter sometimes referred to as absorption axis) of the obtained polarizing film varies. The optical characteristics (contrast, etc.) tend to deteriorate.

  On the other hand, in Patent Document 1, when the film is immersed in the boric acid solution in the boric acid treatment step, the film is immersed in a non-contact state, and after the film is immersed, the film is first contacted with the boric acid solution. 0 to 0. It is described that a polarizing film with little color unevenness and a uniform film thickness can be obtained by adjusting to 4 to 5 seconds.

  However, even with such a method, the deterioration of the optical characteristics due to the variation of the absorption axis cannot be sufficiently suppressed. Here, the absorption axis (°) of the polarizing film indicates the direction in which the polarization component is absorbed, and the smaller the variation (absorption between the maximum and minimum) of the absorption axis, the better the optical characteristics. . That is, the polarizing film allows only one of the orthogonally polarized components of incident light to pass and absorbs (or reflects or scatters) the other so as to shield it. If the absorption axis varies greatly, the contrast of the image Deteriorates, and good optical characteristics cannot be obtained.

JP 2006-189559 A

  The subject of this invention is providing the manufacturing method of the polarizing film which has a favorable optical characteristic, and the manufacturing method of a polarizing plate using the polarizing film obtained by this manufacturing method.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors are arranged in the order of the atmosphere and the liquid immediately before the boric acid treatment step while being immersed in the same treatment liquid as the boric acid treatment step. In addition, a stretching process for uniaxial stretching with two nip rolls is provided, and in performing the uniaxial stretching in this process, the reduction rate of the film width is reduced by shortening the dipping time, etc. The present inventors have completed the present invention by discovering a new fact that a polarizing film having improved optical characteristics can be obtained while suppressing homogenization and the optical axis variation is improved.

That is, the manufacturing method of the polarizing film of this invention has the following structures.
(1) A polarizing film that is uniaxially stretched using a difference in peripheral speed between two nip rolls before or during a process of treating a polyvinyl alcohol film in the order of swelling treatment, dyeing treatment, boric acid treatment, and washing treatment. In the production method, immediately before the boric acid treatment step, while being immersed in the same treatment liquid as the boric acid treatment step, a stretching step is performed in which uniaxial stretching is performed by two nip rolls arranged in order in the air and in the liquid, A method for producing a polarizing film, wherein a reduction rate of the film width after immersion with respect to the film width immediately before immersion in the step is 6% or less.
(2) The method for producing a polarizing film according to (1), wherein the immersion time in the treatment liquid in the stretching step is 0.5 to 3 seconds and the stretching ratio is 1.01 to 1.3 times.
(3) In the boric acid treatment step, the polarizing film according to (1) or (2), wherein one or more guide rolls are disposed between the time the film is immersed and the time when the film is conveyed to the submerged nip roll. Method.
(4) The guide roll in the boric acid treatment step is a sponge rubber roll, the hardness of the sponge is 20 to 60 degrees on a JIS Shore C scale, the density is 0.4 to 0.6 g / cm ^3, and the surface roughness is 10 The manufacturing method of the polarizing film in any one of (1)-(3) which is -30S.
(5) A method for producing a polarizing plate, wherein a protective film is bonded to at least one surface of the polarizing film according to any one of (1) to (4).

  The method for producing a polarizing film of the present invention can suppress variations in the absorption axis of the polarizing film, and can produce a polarizing film and a polarizing plate excellent in optical properties.

It is explanatory drawing which shows one Embodiment of the extending process before the boric-acid process in this invention.

(Production method of polarizing film)
Examples of the polyvinyl alcohol-based resin that forms the polyvinyl alcohol-based film in the present invention include those obtained by saponifying a polyvinyl acetate-based resin. The degree of saponification is about 85 mol% or more, preferably about 90 mol% or more, more preferably about 99 mol% to 100 mol%. Polyvinyl acetate resins include polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers of vinyl acetate and other monomers copolymerizable therewith, such as ethylene-vinyl acetate copolymer. Examples include coalescence. Examples of other copolymerizable monomers include unsaturated carboxylic acids, olefins, vinyl ethers, and unsaturated sulfonic acids. The degree of polymerization of the polyvinyl alcohol resin is about 1000 to 10000, preferably about 1500 to 5000.

These polyvinyl alcohol resins may be modified. For example, polyvinyl formal modified with aldehydes, polyvinyl acetal, polyvinyl butyral, and the like may be used. Usually, an unstretched film of a polyvinyl alcohol-based resin film having a thickness of about 20 μm to 100 μm, preferably about 30 μm to 80 μm is used as a starting material for manufacturing a polarizing film. Industrially, the width of the film is practically about 1500 mm to 6000 mm.
The unstretched film is processed in the order of swelling treatment, dyeing treatment, boric acid treatment (crosslinking treatment), water washing treatment, and finally dried to obtain a polyvinyl alcohol polarizing film having a thickness of, for example, about 5 to 50 μm. is there.

  The polarizing film of the present invention is a polyvinyl alcohol uniaxially stretched film in which a dichroic dye is adsorbed and oriented. As a method for producing the same, an unstretched polyvinyl alcohol film is swollen with an aqueous solution, dyeing treatment, boric acid. This is a method in which solution treatment is performed in the order of treatment and water washing treatment, borax treatment step and, if necessary, uniaxial stretching is performed in a wet or dry manner in the previous step, and finally drying is performed.

Uniaxially stretching in the present invention may be carried out in one step containing boric acid treatment step, but it may also be carried out in two or more steps. As the stretching method, a known method can be adopted except for uniaxial stretching in the boric acid treatment process described later, and stretching between rolls in which stretching is performed with a peripheral speed difference between two nip rolls for transporting the film. There are a hot roll stretching method and a tenter stretching method as described in Japanese Patent No. 2731813. The order essentially process is as described above, the number of the treatment bath or, like the processing conditions constraints have greens.
Further, it is needless to say it is free to insert a name process according to the process for another purpose. As an example of this process, after boric acid treatment, immersion treatment (iodide treatment) with an aqueous iodide solution not containing boric acid or immersion treatment (zinc treatment) step with an aqueous solution containing zinc chloride not containing boric acid, etc. Can be mentioned.

  The swelling step is performed for the purpose of removing foreign matter from the film surface, removing the plasticizer in the film, imparting easy dyeability in the next step, and plasticizing the film. The treatment conditions are determined within a range in which these objects can be achieved and within a range in which problems such as extreme dissolution and devitrification of the base film do not occur. When the film previously stretched in gas is swollen, for example, the film is immersed in an aqueous solution of about 20 ° C. to 70 ° C., preferably about 30 ° C. to 60 ° C. The immersion time of the film is about 30 seconds to 300 seconds, more preferably about 60 seconds to 240 seconds. When the unstretched raw film is swollen from the beginning, the film is immersed in an aqueous solution of, for example, about 10 ° C to 50 ° C, preferably about 20 ° C to 40 ° C. The immersion time of the film is about 30 seconds to 300 seconds, more preferably about 60 seconds to 240 seconds.

In the swelling process, problems such as the film swelling in the width direction and wrinkling into the film are likely to occur, so known widening rolls such as widening rolls (expander rolls), spiral rolls, crown rolls, cross guiders, bend bars, tenter clips, etc. It is preferable to transport the film while removing wrinkles of the film with an apparatus. In order to stabilize the film transport in the bath, the water flow in the swelling bath is controlled with an underwater shower, or an EPC device (Edge Position Control device: a device that detects the edge of the film and prevents meandering of the film) It is also useful to use these together. In this step, since the film in the running direction of the film to swell expanding, sagging such a Kusutame the transport direction of the film, preferably to take means such as controlling the speed of the transport rolls before and after the example processing tank. In addition to pure water, the swelling treatment bath used is boric acid (described in JP-A-10-153709), chloride (described in JP-A-06-281816), inorganic acid, inorganic salt, water-soluble An aqueous solution to which an organic solvent, alcohol or the like is added in an amount of about 0.01 to 10% by weight can also be used.

The dyeing step with the dichroic dye is performed for the purpose of adsorbing and orienting the dichroic dye on the film. The treatment conditions are determined within a range in which these objects can be achieved and within a range in which problems such as extreme dissolution and devitrification of the base film do not occur. When iodine is used as the dichroic dye, for example, at a temperature of about 10 ° C. to 45 ° C., preferably about 20 ° C. to 35 ° C., and in a weight ratio, iodine / KI / water = about 0.003 to 0.2 / The immersion treatment is performed at a concentration of about 0.1 to 10/100 for about 30 seconds to 600 seconds, preferably about 60 seconds to 300 seconds. Instead of potassium iodide, other iodides such as zinc iodide may be used. In addition, the other iodide but it may also be used in combination with potassium iodide. Further, compounds other than iodide, such as boric acid, zinc chloride, cobalt chloride, etc. may coexist. When boric acid is added, it is distinguished from the following boric acid treatment in that it contains iodine. Any dye containing about 0.003 parts by weight or more of iodine with respect to 100 parts by weight of water can be regarded as a dyeing tank.

  When a water-soluble dichroic dye is used as the dichroic dye, for example, at a temperature of about 20 ° C. to 80 ° C., preferably about 30 ° C. to 70 ° C., and a weight ratio of dichroic dye / water = about 0.001. The immersion treatment is performed at a concentration of about 0.1 / 100 for about 30 seconds to 600 seconds, preferably about 60 seconds to 300 seconds. The aqueous solution of the dichroic dye to be used may have a dyeing assistant or the like, and may contain, for example, an inorganic salt such as sodium sulfate, a surfactant or the like. The dichroic dye may be used alone, or two or more dichroic dyes may be used at the same time.

  As described above, the film may be stretched in a dyeing tank. Stretching is performed by a method of giving a peripheral speed difference between the nip rolls before and after the dyeing tank. Similarly to the swelling step, a widening roll (expander roll), a spiral roll, a crown roll, a cross guider, a bend bar, and the like can be installed in the dyeing bath and / or at the bath entrance / exit.

The boric acid treatment is performed by immersing a polyvinyl alcohol film dyed with a dichroic dye in an aqueous solution containing about 1 to 10 parts by weight of boric acid with respect to 100 parts by weight of water. When the dichroic dye is iodine, it is preferable to contain about 1 to 30 parts by weight of iodide.
Examples of iodide include potassium iodide and zinc iodide. Further, compounds other than iodide, for example, zinc chloride, cobalt chloride, zirconium chloride, sodium thiosulfate, potassium sulfite, but it may also be allowed to coexist, such as sodium sulfate.
This boric acid treatment is carried out for water resistance, hue adjustment (preventing bluishness, etc.) by crosslinking, and the like. In the case of water resistance by cross-linking, a cross-linking agent such as glyoxal or glutaraldehyde can be used in addition to or together with boric acid, if necessary.
In addition, the boric acid treatment for water resistance may be referred to by names such as water resistance treatment, crosslinking treatment, and immobilization treatment. In addition, boric acid treatment for hue adjustment may be referred to by a name such as complementary color treatment or re-dyeing treatment.

This boric acid treatment is performed by appropriately changing the concentrations of boric acid and iodide and the temperature of the treatment bath according to the purpose.
The boric acid treatment for water resistance and the boric acid treatment for hue adjustment are not particularly distinguished, but are carried out under the following conditions.
When the raw film is swollen, dyed or treated with boric acid, and the boric acid treatment is aimed at water resistance by crosslinking, about 3 to 10 parts by weight of boric acid and 100% by weight of iodide, iodide Is carried out at a temperature of about 50 ° C. to 70 ° C., preferably 53 ° C. to 65 ° C. The immersion time is usually about 10 to 600 seconds, preferably 20 to 300 seconds, and more preferably 20 to 200 seconds.
In addition, when dye | staining and boric-acid treatment the film extended | stretched previously, the temperature of a boric-acid treatment bath is about 50 to 85 degreeC normally, Preferably it is about 55 to 80 degreeC.

After the boric acid treatment for water-resistant, but it may also be made of boric acid treatment for the hue adjustment. For example, when the dichroic dye is iodine, a boric acid treatment bath containing about 1 to 5 parts by weight of boric acid and about 3 to 30 parts by weight of iodide for 100 parts by weight of water is used for this purpose. And is usually performed at a temperature of about 10 ° C to 45 ° C. The immersion time is usually about 1 to 300 seconds, preferably 10 to 240 seconds.

These boric acid treatment rather it may also be carried out in multiple steps, usually performed are often in 2-5 steps. In this case, the aqueous solution composition and temperature of the boric acid treatment tank used in each step may be the same or different within the above range. The water boration for reduction, the boric acid treatment for hue adjustment but it may also be carried out in a plurality of steps.

  After boric acid treatment, it is washed with water. The water washing treatment is performed, for example, by immersing a polyvinyl alcohol film treated with boric acid for water resistance and / or color tone adjustment in water, spraying water as a shower, or combining immersion and spraying. The water temperature in the water washing treatment is usually about 2 to 40 ° C., and the immersion time is preferably about 2 to 120 seconds.

  Thereafter, the polyvinyl alcohol film is washed with water and dried in a drying furnace at a temperature of about 40 to 100 ° C. for about 60 to 600 seconds, whereby a polarizing film can be obtained.

(Uniaxial stretching in the stretching process before boric acid treatment)
FIG. 1 is an explanatory view showing an embodiment of uniaxial stretching in the stretching step before boric acid treatment in the present invention.
In the stretching treatment tank 1 shown in FIG. 1, the same treatment liquid 4 as that in the boric acid treatment step is put, and a nip roll 3 on the upstream side in the transport direction of the polyvinyl alcohol film 10 immersed in the treatment liquid 4 is provided. In the air, downstream nip rolls 3 ′ are respectively installed in the liquid.

In this way, the two nip rolls 3 and 3 ′ are installed in order in the air and in the liquid in order to perform uniaxial stretching by performing boric acid treatment uniformly in the surface of the film 10 in the next boric acid treatment step. This is because the stretching is preferably performed in a liquid.
In the stretching step, one or a plurality of guide rolls 2 can be arranged between the two nip rolls 3 and 3 ′ arranged on the upstream side and the downstream side as necessary. The guide roll 2 may be either air or liquid.

  As described above, the uniaxial stretching in the stretching step before the boric acid treatment is performed in a state where the upstream nip roll 3 is placed in the air and the downstream nip roll 3 ′ is placed in the liquid. The immersion time is 0.5 to 3 seconds, the draw ratio is 1.01 to 1.3 times, and the film width reduction rate after immersion with respect to the film width immediately before immersion (hereinafter simply referred to as “film width reduction rate”) To 6% or less.

  When the immersion time is shorter than 0.5 seconds, uneven color is likely to occur, and the film thickness in the film width direction becomes nonuniform. On the other hand, if it is longer than 3 seconds, the reduction rate of the film width exceeds 6%, and therefore it is difficult to reduce the variation of the absorption axis.

Moreover, if the draw ratio in the drawing step before the boric acid treatment is less than 1.01, the film is easily wrinkled or the film is easily cut, and conversely if the draw ratio is greater than 1.3 times, the film width The rate of decrease in the amount tends to exceed 6%, which makes it difficult to reduce the variation of the absorption axis.
The final integrated draw ratio in all steps is about 4.5 to 7.0 times, preferably about 5.0 to 6.5 times.

  In the present invention, the reduction rate (%) of the film width due to immersion is 6% or less, more preferably 5% or less. If the reduction rate of the film width due to immersion is larger than 6%, the variation of the absorption axis becomes large, and the optical properties of the obtained polarizing film are deteriorated.

The guide roll 2 may be any of a rubber roll, a stainless steel polishing roll, and a sponge rubber roll, but is preferably a sponge rubber roll.
The rubber roll is made of NBR or the like, and has a hardness of about 60 to 90 degrees, preferably about 70 to 8 degrees on the JIS Shore C scale measured by the test method of JISK6300. The average interval S between the local peaks of the roughness curve having a surface roughness of JI S B 0 6 0 1 (surface roughness) of about 0. 1 to 5 S, preferably about 0. It is preferable that it is 5-1.
The stainless steel polishing roll is composed of SUS3 04, SUS3 1 6 and the like, and in order to make the film thickness uniform, the surface roughness is JIS B 0 6 0 1 ( Expressed by the average interval S 1 between the local peaks of the roughness curve of the surface roughness) 2-1. 0 S is preferable, and the coefficient of dynamic friction is about 0. 1-0. 4, preferably about 0. 1 5-0. Those that are 3 5 are preferred. The dynamic friction coefficient in this invention is represented by the value measured in the polyvinyl alcohol-type film and water based on the test method of JISK7 1 2 5.
The sponge rubber guide roll used in the present invention has a sponge hardness of 20 to 60 degrees, preferably 25 to 50 degrees, and a density of 0.4 on the JIS Shore C scale measured by the test method of JIS K 6301. ˜0.6 g / cm ³ , preferably 0.42 to 0.57 g / cm ^3, and the surface roughness is 10-30S expressed by the average interval S of the local peaks of the roughness curve of JIS B 0601 (surface roughness). , Preferably 15 to 25S.

In each step after the stretching treatment, tension control may be performed so that the tension of the film becomes substantially constant.
When the above-described iodide treatment or zinc treatment is performed after the boric acid treatment, tension control is also performed for these steps.

Tension in each of the process rather than good may be the same, but it may also be different. The tension to the film in the tension control is not particularly limited, and is appropriately set within a range of about 150 N / m to 2000 N / m, preferably about 600 N / m to 1500 N / m per unit width. When the tension is less than about 150 N / m, the film is likely to be wrinkled. On the other hand, if the tension exceeds about 2000 N / m, problems such as film breakage and shortened life due to bearing wear occur. The tension per unit width is calculated from the film width near the entrance of the process and the tension value of the tension detector.
In addition, when tension control is performed, there are cases where the film is inevitably slightly stretched or shrunk, but in the present invention, this is not included in the stretching process.

(Manufacture of polarizing plates)
A polarizing plate is obtained by bonding a protective film with an adhesive on at least one side of the polarizing film produced as described above.
As the protective film, for example, a film made of an acetyl cellulose resin such as triacetyl cellulose or diacetyl cellulose, a film made of a polyester resin such as polyethylene terephthalate, polyethylene naphthalate or polybutylene terephthalate, or a film made of a polycarbonate resin And a film made of cycloolefin resin, a film made of acrylic resin, and a film made of polypropylene resin.

  In order to improve the adhesiveness between the adhesive and the polarizing film and / or protective film, the polarizing film and / or protective film may be subjected to corona treatment, flame treatment, plasma treatment, ultraviolet irradiation, primer coating treatment, saponification treatment, etc. A surface treatment may be applied.

EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples. The reduction rate of film width and the absorption axis in each example were measured by the following methods.
(Reduction rate of film width)
The film width immediately after passing through the submerged nip roll is subtracted from the film width immediately before immersion, and this is divided by the film width immediately before immersion.
(Measurement method of absorption axis)
Using the width direction of the film as a reference, the longitudinal direction is 50 mm with respect to the reference axis, and the width direction is the full width of the strip-shaped film piece. The absorption axis angle was measured for each portion obtained by dividing the film piece into 9 parts in the width direction, and the value obtained by subtracting the maximum value and the minimum value among the obtained axis angles was adopted as the variation of the absorption axis.

[Example 1]
A 75 μm thick, 450 mm wide polyvinyl alcohol film (Kuraray Vinylon VF-PS # 7500, polymerization degree 2,400, saponification degree 99.9 mol% or more) is tensioned to 30 ° C. pure water so that the film does not loosen. The film was immersed while maintaining the state to sufficiently swell the film.
Next, uniaxial stretching was performed so that the integration ratio was 2.4 times while being immersed in a dyeing tank of 0.02 / 2.0 / 100 in weight ratio of iodine / potassium iodide / water.
Next, using a nip roll in the air and in the liquid, the film was stretched 1.1 times while immersed in a 55 ° C. aqueous solution of potassium iodide / boric acid / water in a weight ratio of 12 / 4.4 / 100 for 2 seconds. (Drawing process before boric acid treatment). Further, after being uniaxially stretched until the cumulative draw ratio from the raw material becomes 5.5 times while being immersed in the same solution (first boric acid treatment step), the weight ratio of potassium iodide / boric acid / water is Was immersed in an aqueous solution of 9 / 2.9 / 100 of 40 ° C. (second boric acid treatment step).
Subsequently, the film was washed with pure water at 5 ° C. for 8 seconds and dried at 70 ° C. for 3 minutes to obtain a polarizing film. At this time, the reduction rate of the film width in the stretching step was 2.5%, and the dispersion (absorption between the maximum and minimum) of the absorption axis of the obtained polarizing film was 0.08 °.

[Example 2]
A polarizing film was obtained in the same manner as in Example 1 except that the stretching ratio in the stretching step before the boric acid treatment was 1.3. At this time, the reduction rate of the film width in the stretching step was 5.0%, and the variation (absorption between the maximum and minimum) of the absorption axis of the obtained polarizing film was 0.12 °.

Example 3
In the stretching step before the boric acid treatment, a sponge rubber guide roll (sponge hardness is 25 degrees on JIS Shore C scale, density is 0.42 g / cm ³ , and surface roughness is 20S immediately before the nip roll in the liquid. ) And a polarizing film was obtained in the same manner as in Example 1 except that the immersion time was 2.5 seconds. At this time, the reduction rate of the film width in the stretching step was 4.0%, and the variation (absorption between the maximum and minimum) of the absorption axis of the obtained polarizing film was 0.11 °.

[Comparative Example 1]
A polarizing film was obtained in the same manner as in Example 1 except that the immersion time in the stretching step before boric acid treatment was 5 seconds. At this time, the reduction rate of the film width in the stretching step was 6.7%, and the variation (absorption between the maximum and minimum) of the absorption axis of the obtained polarizing film was 0.21 °.

[Comparative Example 2]
A polarizing film was obtained in the same manner as in Example 1 except that the stretching ratio in the stretching step before the boric acid treatment was 1.4. At this time, the reduction rate of the film width in the stretching step was 7.5%, and the variation (absorption between the maximum and minimum) of the absorption axis of the obtained polarizing film was 0.22 °.

[Comparative Example 3]
A polarizing film was obtained in the same manner as in Example 1 except that the stretching ratio in the stretching step before the boric acid treatment was set to 1.0. Could not get.

上記した表１より、実施例１〜３は、フィルム幅の減少率が６％以下であると、吸収軸のバラツキが少なくなることがわかる。また、比較例１、２は、いずれもフィルム幅の減少率が６％を超えているため、吸収軸のバラツキが大きくなっていることがわかる。 The results of Examples 1 to 3 and Comparative Examples 1 to 3 are shown below.

From Table 1 described above, it can be seen that in Examples 1 to 3, the variation in the absorption axis is reduced when the reduction rate of the film width is 6% or less. Further, in Comparative Examples 1 and 2, since the reduction rate of the film width exceeds 6%, it can be seen that the variation of the absorption axis is large.

1: stretching tank, 2: guide roll, 3, 3 ′: nip roll, 4: treatment liquid, 10: polyvinyl alcohol film,

Claims (4)

Swelling the polyvinyl alcohol-based film treatment, dyeing treatment, boric acid treatment, and processed in the order of the cleaning, of which at least during the dyeing process and each step of the boric acid treatment, uniaxial and utilizing the peripheral speed difference between the two nip rolls respectively In the method for producing a polarizing film for stretching,
Immediately before the boric acid treatment, while immersed in the boric acid treatment same treatment liquid and, provided the stretching step of performing uniaxial stretching by two nip rolls which are arranged in this order and during the liquid air, in the stretching step The immersion time is 0.5 to 3 seconds, the draw ratio is 1.01 to 1.3 times, the reduction rate of the film width after immersion to the film width immediately before immersion is 6% or less , and
The manufacturing method of the polarizing film characterized by making the integral draw ratio of the polarizing film obtained through the said washing process 5.0 to 6.5 times . 2. The method for producing a polarizing film according to claim 1 , wherein in the stretching step, one or more guide rolls are disposed between the time when the film is immersed and the time when the film is conveyed to a submerged nip roll. The guide roll in the stretching step is a sponge rubber roll, the hardness of the sponge is 20 to 60 degrees on a JIS Shore C scale, the density is 0.4 to 0.6 g / cm ^3, and the surface roughness is 10 to 30 S. Item 3. A method for producing a polarizing film according to Item 1 or 2 . The manufacturing method of the polarizing plate characterized by bonding a protective film to the at least single side | surface of the polarizing film manufactured by the manufacturing method in any one of Claims 1-3 .

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