KR20190139854A - Polyvinyl alcohol-based film, polarizing film and polarizing plate, and polyvinyl alcohol-based film production method - Google Patents

Abstract

Polyvinyl alcohol-based film, poly of which is excellent in the balance between swelling and stretchability in the production of polarizing film, does not cause breakage in the production of thin polarizing film, exhibits high polarization performance, and can obtain a polarizing film with less color unevenness. Provided are a polarizing film and a polarizing plate using a vinyl alcohol film, and the polyvinyl alcohol film. The polyvinyl alcohol-based film of the present invention has a swelling degree (S _A ) and a swelling degree (S _X ) in a long polyvinyl alcohol-based film having a thickness of 40 μm or less when immersed in water at 30 ° C. for 5 minutes. , degree of swelling in the longitudinal direction _(Y S), the following equation (1) to (3 degree of swelling (S _B) when the uniaxial stretching the draw ratio in the water of 30 ℃ to 0.12m / min stretching speed of three times that It is characterized by satisfying).
190% ≤S _A ≤230% ... (1)
220% ≤S _B ≤310% ... (2)
1.01≤S _Y / S _X ≤1.20 (3)

Description

Polyvinyl alcohol-based film, polarizing film and polarizing plate, and polyvinyl alcohol-based film production method

 The present invention provides a polyvinyl alcohol-based film which has excellent dyeability and can be a material for forming a polarizing film having high polarization and low color unevenness, a polarizing film and a polarizing plate using the polyvinyl alcohol-based film, and a polyvinyl alcohol-based film. It relates to a manufacturing method.

Conventionally, a polyvinyl alcohol-type film is used for many uses as a film excellent in transparency, and a polarizing film is mentioned as one of the useful uses. The polarizing film is used as a basic component of a liquid crystal display, and in recent years, its use has been expanded to devices requiring high quality and high reliability.

Among these, polarizing films excellent in optical characteristics are demanded as high brightness, high definition, large area, and thinning of screens such as liquid crystal TVs and multifunctional portable terminals are required. The specific requirements are the improvement of the new degree of polarization and the elimination of color unevenness.

Generally, a polyvinyl alcohol-type film is manufactured by the continuous casting method using the aqueous solution of polyvinyl alcohol-type resin as a material. Specifically, first, an aqueous solution of polyvinyl alcohol-based resin is cast into a cast mold such as a cast drum or an endless belt to form a film, and then the film is peeled from the cast mold, and then flows using a nip roll or the like. It is manufactured by drying using a hot roll, a floating dryer, etc., conveying in the direction MD. In the said conveyance process, since the film formed into a film is pulled in the flow direction MD, a polyvinyl alcohol-type polymer is easy to orientate in a flow direction MD.

On the other hand, generally, a polarizing film is manufactured by first swelling the polyvinyl alcohol-type film which is the raw material with water (including warm water), then dyeing with dichroic dyes, such as iodine, and extending | stretching after that.

In the swelling process, it is important to rapidly swell the polyvinyl alcohol-based film in the thickness direction, and to uniformly swell the polyvinyl alcohol-based film so that dye can easily penetrate into the film during the dyeing process. .

Moreover, the said extending process is a process of extending | stretching the film after dyeing in the flow direction (MD), and orienting the dichroic dye in a polyvinyl alcohol-type film highly, and in order to improve the polarization performance of a polarizing film, a disk is produced in this extending process. It is important that the polyvinyl alcohol-based film to be exhibiting good stretchability in the flow direction (MD).

Moreover, the case where the order of an extending process and a dyeing process in the polarizing film manufacture is reverse to the above is also implemented. That is, it is a case where the original polyvinyl alcohol-type film is first swollen with water (including warm water), then stretched, and then dyed with dichroic dyes such as iodine. Also in this case, in order to improve the polarization performance of a polarizing film, what is important is that the polyvinyl alcohol-type film of a disk shows favorable swelling property in the thickness direction, and shows favorable elongation property in a flow direction (MD).

In addition, recently, in order to reduce the thickness of the polarizing film, a polyvinyl alcohol-based film that is a disc has also been reduced in thickness. By the way, the thin film has a problem of productivity, such as breaking by stretching at the time of manufacturing a polarizing film.

As a method of improving the swelling property of a polyvinyl alcohol-type film, the method (for example, refer patent document 1) of adding polyhydric alcohol as a water swelling adjuvant to polyvinyl alcohol-type resin is proposed, for example.

Moreover, as a method of improving the stretchability of a polyvinyl alcohol-type film, for example, the method of specifying the ratio of the speed of the cast drum at the time of film forming and the final polyvinyl alcohol-type film winding speed (for example, (See Patent Document 2), a method of floating a film after film formation with a cast drum (see Patent Document 3, for example), and a method of controlling the tensile state in the drying step of the film formed (for example, Patent Document 4) and a film having a swelling degree before and after stretching in water at 30 ° C. at a thickness of 40 μm or less (for example, see Patent Document 5) have been proposed.

Patent document 1 JP 2001-302867A Patent document 2 JP 2001-315141A Patent document 3 JP 2001-315142A Patent document 4 JP 2002-79531A Patent Document 5 WO 2014 / 050697A

However, with respect to the thin polyvinyl alcohol-based film, in the method of Patent Document 1, the improvement of the swelling property is insufficient, and in the methods of Patent Documents 2 to 5, in order to improve the stretchability at the time of polarizing film production Insufficient

That is, in the technique described in Patent Document 1, even though the swelling property of the entire polyvinyl alcohol-based film can be improved, the alignment state of the polyvinyl alcohol-based polymer is not considered, and the polarization film production time in the flow direction (MD) is not considered. It is difficult to efficiently improve the stretchability. On the contrary, by the addition of the water swelling aid, the orientation state of the polymer is disturbed, so that uniform stretching in the flow direction MD tends to be difficult.

Although the technique specified in the said patent document 2 specifies the degree of extension (tensile state) in the flow direction (MD) at the time of manufacturing a polyvinyl alcohol-type film, when extending | stretching also in the width direction (TD) is not considered, It is insufficient to improve the stretchability in the film production.

In the technique described in Patent Document 3, the film formed can be dried uniformly, but the orientation of the polymer is not controlled, and it is insufficient to improve the swelling property and stretchability at the time of manufacturing the polarizing film.

Moreover, although the film thickness of the polyvinyl alcohol-type film can be made uniform in the technique of the said patent document 4, it cannot control even the orientation of a polymer, and it is inadequate to improve swelling property and stretchability at the time of polarizing film manufacture.

In the technique described in Patent Document 5, the degree of swelling before and after stretching in water at 30 ° C. is a specific polyvinyl alcohol-based film, and the polyvinyl alcohol-based film having high stretchability is prevented from being wrinkled at the time of stretching. Although it can obtain, it cannot control even the wrinkle at the time of swelling, and it is insufficient to manufacture the polarizing film which is excellent in uniformity. Moreover, since a relatively long wet heat treatment is required, it is insufficient in terms of productivity of the polyvinyl alcohol-based film.

Therefore, the present invention is very excellent in the balance of swelling property and stretchability at the time of manufacturing a polarizing film under such a background, and it does not generate | occur | produce a break even at the time of manufacturing a thin polarizing film, shows the high polarization performance, and the polyvinyl alcohol from which a polarizing film with little color unevenness is obtained is obtained. It provides a polarizing film and a polarizing plate using a system film, a polyvinyl alcohol-based film thereof, and a method for producing the polyvinyl alcohol-based film.

The present inventors made extensive research in view of such a situation, and as a result, in the elongate polyvinyl alcohol-type film whose swelling degree of mass is 190-230% at 40 micrometers or less in thickness, the dimension-based swelling degree of the longitudinal direction (MD) If the range of ratio with respect to the swelling degree of the dimensional reference of the width direction (TD) is adjusted to a specific range, and the swelling degree of the mass reference after extending | stretching in water is adjusted to a specific range, the swelling property and extending | stretching at the time of polarizing film manufacture It was found that the polarizing film was very excellent in the balance of the performances, the fracture did not occur during the production of the thin polarizing film, exhibited a high polarization performance, and had little color unevenness.

That is, this invention makes the polyvinyl alcohol-type film which satisfy | fills following formula (1)-(3) in the elongate polyvinyl alcohol-type film whose thickness is 40 micrometers or less makes it the 1st summary.

190% ≤S _A ≤230% ... (1)

220% ≤S _B ≤310% ... (2)

1.01≤S _Y / S _X ≤1.20 (3)

[In Formula (1), S _A represents a swelling degree based on mass when the polyvinyl alcohol-based film is immersed in water at 30 ° C. for 5 minutes,

The formula (2):, S _B represents the degree of swelling of the mass basis when the uniaxial stretching the draw ratio at a draw speed of 0.12m / min for the polyvinyl alcohol film in water of 30 ℃ to three times,

The formula (3) of the, S _X represents the degree of swelling of the dimension criteria in the transverse direction (TD) when immersed for 5 minutes of the polyvinyl alcohol film in a 30 ℃ water, S _Y is the polyvinyl alcohol-based film The swelling degree of the dimension reference | standard of the longitudinal direction (MD) at the time of being immersed in 30 degreeC water for 5 minutes is shown.]

Moreover, this invention makes a polarizing film characterized by the above-mentioned polyvinyl alcohol-type film used a 2nd summary. Moreover, the polarizing plate provided with the polarizing film and the protective film provided in at least one surface of this polarizing film is set as the 3rd summary.

And the film forming process which forms the aqueous solution of polyvinyl alcohol-type resin by a continuous cast method, and the drying and extending process which carries out continuous drying and continuous drawing with respect to the film, conveying the film formed into a flow direction. In the manufacturing method of the polyvinyl alcohol-type film provided, the polyvinyl alcohol-type film manufactured makes it satisfy the following formula (1)-(3), The manufacturing method of the polyvinyl alcohol-type film characterized by the above-mentioned. We assume 4 points.

190% ≤S _A ≤230% ... (1)

220% ≤S _B ≤310% ... (2)

1.01≤S _Y / S _X ≤1.20 (3)

[In Formula (1), S _A represents the swelling degree on a mass basis when the polyvinyl alcohol-based film is immersed in water at 30 ° C. for 5 minutes,

The formula (2):, S _B represents the degree of swelling of the mass basis when the uniaxial stretching the draw ratio at a draw speed of 0.12m / min for the polyvinyl alcohol film in water of 30 ℃ to three times,

The formula (3) of the, S _X represents the degree of swelling of the dimension criteria in the transverse direction (TD) when immersed for 5 minutes of the polyvinyl alcohol film in a 30 ℃ water, S _Y is the polyvinyl alcohol-based film The swelling degree of the dimension reference | standard of the longitudinal direction (MD) at the time of being immersed in 30 degreeC water for 5 minutes is shown.]

The polyvinyl alcohol-based film of the present invention is a long polyvinyl alcohol-based film having a thickness of 40 μm or less and a swelling degree (S _A ) based on mass of 190 to 230%, and a swelling degree (S) based on the dimension in the longitudinal direction (MD). _The ratio (S _Y / S _X ) to the swelling degree (SX) of the dimensional reference in the width direction (TD) of _Y ) is within a specific range, and the swelling degree (S _B ) based on the mass after stretching in water Since it is in a specific range, it is excellent in swelling property and stretchability at the time of manufacturing a polarizing film, and can make it itself thin (40 micrometers or less in thickness), and it can prevent a breakage even if it uses for manufacture of a thin polarizing film. Moreover, when this polyvinyl alcohol-type film is used, the polarizing film which shows high polarization performance and little color unevenness can be obtained.

Moreover, since the said polyvinyl alcohol-type film is used for the polarizing film of this invention, it exhibits high polarization performance and becomes a thing with few color unevenness.

Moreover, since the said polarizing film is used for the polarizing plate of this invention, it shows the high polarization performance and becomes a thing with few color unevenness.

And the manufacturing method of the polyvinyl alcohol-type film of this invention carries out the film forming process by a continuous casting method, and drying which carries out continuous drying and continuous drawing with respect to the film, conveying the film formed into a flow direction. Since the stretching step is provided, the polyvinyl alcohol-based film of the present invention satisfying the above formulas (1) to (3) can be obtained by incorporating the manufacturing conditions in each of these steps.

In particular, when in the dry-stretching process for stretching the film-forming from 1.05 to 1.3 times the film in the transverse direction (TD), S _A, S _B, S _Y / S in the above formulas (1) - (3) Each value of _X becomes suitable, and the polyvinyl alcohol-type film excellent in swelling property and stretchability at the time of polarizing film manufacture can be obtained.

Moreover, when extending | stretching the said film forming in the said drying and extending process temporarily 1.3 times or more in width direction (TD), and then dimensionally shrinking so that the draw ratio of final width direction (TD) may be 1.3 times or less. The stress applied to the film thus formed can be relaxed. For this reason, even if the film formed into a film is thin, breakage of the film can be avoided.

Next, the present invention will be described in detail.

The polyvinyl alcohol-type film of this invention is a polyvinyl alcohol-type film characterized by satisfy | filling following formula (1)-(3) in the elongate polyvinyl alcohol-type film of 40 micrometers or less.

190% ≤S _A ≤230% ... (1)

220% ≤S _B ≤310% ... (2)

1.01≤S _Y / S _X ≤1.20 (3)

[In Formula (1), S _A represents a swelling degree based on mass when the polyvinyl alcohol-based film is immersed in water at 30 ° C. for 5 minutes,

The formula (2):, S _B is the mass when the uniaxial stretching the draw ratio at a draw rate of the polyvinyl alcohol film in water of 30 ℃ 0.12m / min (240% / min.) So that the three times The degree of swelling of the reference,

The formula (3) of the, S _X represents the degree of swelling of the dimension criteria in the transverse direction (TD) when immersed for 5 minutes of the polyvinyl alcohol film in a 30 ℃ water, S _Y is the polyvinyl alcohol-based film The swelling degree of the dimension reference | standard of the longitudinal direction (MD) at the time of being immersed in 30 degreeC water for 5 minutes is shown.]

The thickness of the polyvinyl alcohol-based film of the present invention needs to be very thin (40 µm or less), preferably 5 to 40 µm from the viewpoint of thinning of the polarizing film, and particularly preferably from the viewpoint of avoiding breakage. 10-40 micrometers, More preferably, it is 10-30 micrometers.

If the thickness of the polyvinyl alcohol-based film is too thick, the tension is high at the time of stretching in the polarizing film production process described later, which is not preferable. Moreover, even if it is too thin, there exists a tendency which becomes easy to fracture at the time of polarizing film manufacture.

That is, the polyvinyl alcohol-type film of this invention is controlled so that the said specific swelling degree at the time of being immersed in 30 degreeC water as mentioned above may become a specific range. By this controlled degree of swelling, the polyvinyl alcohol-based film is made extremely thin with a thickness of 40 µm or less, and has excellent performance.

And, based polyvinyl alcohol film of the present invention is controlled such that the degree of swelling (S _A) of a mass basis when immersed for 5 minutes in a 30 ℃ water, 190% ≤S _A ≤230% as described above. Degree of swelling (S _A) of a mass basis is preferably a 195% ≤S _A ≤225%, particularly preferably 195% ≤S _A ≤220%.

If the value of the swelling degree (S _A ) is too small, the stretchability at the time of manufacturing the polarizing film described later is lowered. Therefore, if the object of the present invention is not achieved and the value of the swelling degree (S _A ) is too large, the polarizing film Since wrinkles generate | occur | produce in the swelling process at the time of manufacture, and a color unevenness tends to arise in a polarizing film, the objective of this invention cannot be achieved.

The swelling degree (S _A ) is an index indicating the water-retaining ability when the polyvinyl alcohol-based film is immersed in water, and after immersing the polyvinyl alcohol-based film in water at 30 ° C. for 5 minutes without stretching. A mass can be calculated | required as a percentage by dividing by the mass after drying at 105 degreeC for 16 hours after immersion, and can be measured by the method of mentioning about an Example later.

As described above, the polyvinyl alcohol-based film of the present invention is based on mass when uniaxially stretched so that the draw ratio is tripled at a stretching speed of 0.12 m / min (240% / min) in water at 30 ° C. it is the degree of swelling (S _B) being controlled to be 220% ≤S _B ≤310%. The swelling degree SB based on this mass is preferably 225% ≦ S _B ≦ 300%, particularly preferably 230% ≦ S _B ≦ 280%, particularly preferably 230% ≦ S _B ≦ 260%.

If the value of the swelling degree (S _B ) is too small, the elongation at the time of manufacturing the polarizing film described later deteriorates, and thus the object of the present invention cannot be achieved, and if the value of the swelling degree (S _B ) is too large, the polarizing film Since wrinkles generate | occur | produce in the swelling and dyeing process at the time of manufacture, and a color unevenness tends to arise in a polarizing film, the objective of this invention cannot be achieved.

The swelling degree (S _B ) is an index showing the water-retaining ability of the polyvinyl alcohol-based film after stretching the polyvinyl alcohol-based film at a draw ratio 3 times in water at 30 ° C., and the polyvinyl alcohol-based film is 30 ° C. It can be calculated as a percentage by dividing the mass after stretching at a draw ratio 3 times at a stretching speed of 0.12 m / min (240% / min) by the mass after stretching at 105 ° C. for 16 hours after stretching. For example, it can measure by the method mentioned later in an Example. Generally, when manufacturing a polarizing film from a polyvinyl alcohol-type film, a film is introduce | transduced into a high temperature drawing tank after swelling and dyeing at 30 degreeC.

In the swelling and dyeing process, the polyvinyl alcohol-based film is stretched to less than three times, and the swelling degree (S _B ) when stretched to three times the draw ratio in water is an index of the stretchability of the film in the high temperature drawing bath. To be.

In addition, the polyvinyl alcohol-based film of the present invention, as described above, immersion for 5 minutes in water at 30 ℃ and swelling degree (S _X ) of the dimension reference in the width direction (TD) when immersed in water at 30 ℃ for 5 minutes. the degree of swelling (S _Y) of standard dimensions in the longitudinal direction (MD) at the time sikyeoteul, is controlled so as to satisfy the relationship 1.01≤S _Y / S _X ≤1.20. This is the ratio _(Y S / _X S) is preferably 1.03≤S _Y / S _X ≤1.18, more preferably 1.05≤S _Y / S _X≤ 1.15. If the value of the ratio (S _Y / S _X ) is too small, the stretchability at the time of manufacturing the polarizing film described later deteriorates, and thus the object of the present invention cannot be achieved, and the value of the ratio (S _Y / S _X ) If too large, wrinkles may occur in the swelling step in manufacturing the polarizing film, and color unevenness is likely to occur in the polarizing film, and thus the object of the present invention cannot be achieved.

The swelling degree (S _X and S _Y ) is an indicator of the expansion when the polyvinyl alcohol-based film is immersed in water, and the polyvinyl alcohol-based film is immersed in water at 30 ° C. for 5 minutes as it is (without stretching). After that, it can obtain | require as a percentage by dividing the dimension of the longitudinal direction (MD) and the width direction (TD) by the dimension before immersion in water, respectively, For example, it measures by the method mentioned later about an Example Can be.

As a method of controlling said Formula (1)-(3) in this invention, in the manufacturing method of the said polyvinyl alcohol-type film by the continuous casting method mentioned later, the film formed into the cast form peeled from the cast form. Then, the method of extending | stretching in the width direction TD is preferable. In this case, conditions to another process are suitably adjusted according to the extending | stretching conditions (stretching ratio, the atmospheric temperature at the time of extending | stretching, extending | stretching time, etc.) of the width direction TD. As the conditions, for example, the chemical structure of the polyvinyl alcohol-based resin which is a forming material of the polyvinyl alcohol-based film, the kind and amount of the plasticizer, the film forming conditions (such as the temperature of the cast type) of the film, the film formed into the film Drying conditions (temperature, time) which dries it, the conveyance speed in the flow direction (MD) of the said film forming, etc. are mentioned. The above formulas (1) to (3) are controlled by matching at least one of these conditions with the stretching conditions in the width direction TD.

Further, the formulas (1) to measure the position of the degree of swelling (S _A, S _B, S _X, S _Y) in (3) is in the region of 500mm × 500mm of the polyvinyl alcohol-based film.

Here, the manufacturing method of the polyvinyl alcohol-type film of this invention is demonstrated in process order.

[Film material]

First, the polyvinyl alcohol-type resin used by this invention and its polyvinyl alcohol-type resin aqueous solution are demonstrated.

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

Moreover, polyvinyl alcohol-type resin which has a 1,2-diol structure in a side chain can also be used as polyvinyl alcohol-type resin. The polyvinyl alcohol-based resin having a 1,2-diol structure in the side chain is, for example, (i) a method of saponifying a copolymer of vinyl acetate and 3,4-diacetoxy-1-butene, (ii ) Saponification and decarbonization of a copolymer of vinyl acetate and vinyl ethylene carbonate, (iii) saponification and decarburization of a copolymer of vinyl acetate and 2,2-dialkyl-4-vinyl-1,3-dioxolane It can obtain by the method of deoxidation, the method of saponifying a copolymer of vinyl acetate and glycerol monoallyl ether, etc.

It is preferable that the weight average molecular weights of polyvinyl alcohol-type resin are 100,000-300,000, Especially preferably, it is 110,000-280,000, More preferably, it is 120,000-260,000. If the weight average molecular weight is too small, when the polyvinyl alcohol-based resin is used as an optical film, it tends to be difficult to obtain sufficient optical performance, and if too large, the stretching of the polyvinyl alcohol-based film at the time of polarizing film production becomes difficult. have. In addition, the weight average molecular weight of the said polyvinyl alcohol-type resin is a weight average molecular weight measured by GPC-MALS method.

The average saponification degree of the polyvinyl alcohol-based resin used in the present invention is preferably at least 98 mol%, particularly preferably at least 99 mol%, more preferably at least 99.5 mol%, particularly preferably at least 99.8 mol%. to be. If the average saponification degree is too small, when the polyvinyl alcohol-based film is used as a polarizing film, there is a tendency that sufficient optical performance cannot be obtained.

Here, the average saponification degree in this invention is measured according to JISK6726.

As polyvinyl alcohol-type resin used by this invention, you may use together 2 or more types from which a modified species, a modification amount, a weight average molecular weight, average saponification degree, etc. differ.

In addition to polyvinyl alcohol-based resins, polyvinyl alcohol-based resin aqueous solutions are generally used plasticizers such as glycerin, diglycerin, triglycerine, ethylene glycol, triethylene glycol, polyethylene glycol, trimetholpropane, and BBs as necessary. It is preferable from a viewpoint of film forming property to contain at least 1 type of surfactant which is warm, anionic, and cationic. These may be used alone or in combination of two or more.

It is preferable that the resin concentration of the polyvinyl alcohol-type resin aqueous solution obtained in this way is 15 to 60 weight%, Especially preferably, it is 17 to 55 weight%, More preferably, it is 20 to 50 weight%. When the resin concentration of the aqueous solution is too low, the production load tends to decrease because the drying load increases, and when too high, the viscosity tends to be too high and uniform dissolution becomes impossible.

Next, the obtained polyvinyl alcohol-type resin aqueous solution is degassed | defoamed. As a defoaming method, methods, such as stationary defoaming and the degassing by a multiaxial extruder, are mentioned. The multiaxial extruder may be a multiaxial extruder having a vent, and a twin screw extruder having a vent is usually used.

[Film forming process]

Although the polyvinyl alcohol-based film of the present invention is produced by the casting method or the melt extrusion method, in the present invention, the casting method is preferable from the viewpoints of transparency, thickness degree, surface smoothness and the like, and particularly preferably from the viewpoint of productivity, continuous casting It is a law.

The continuous casting method is, for example, a method in which an aqueous solution of the polyvinyl alcohol-based resin is continuously discharged from the T-type slit die to a cast type such as a rotating cast drum, an endless belt, a resin film, and cast to form a film. .

Here, the film forming method in the case where the cast type is a cast drum will be described.

It is preferable that the temperature of the polyvinyl alcohol-type resin aqueous solution of a T-type slit die exit is 80-100 degreeC, Especially preferably, it is 85-98 degreeC. If the temperature of the aqueous polyvinyl alcohol-based resin solution is too low, there is a tendency to become poor in flow, and if too high, there is a tendency to foam.

It is preferable that the viscosity of the said polyvinyl alcohol-type resin aqueous solution is 50-200 Pa.s at the time of discharge (with respect to the said preferable temperature of 80-100 degreeC), Especially preferably (with respect to said especially preferable temperature of 85-98 degreeC) 70-150 Pa.s.

If the viscosity of the aqueous polyvinyl alcohol-based resin solution is too low, there is a tendency to become poor in flow, and if too high, softness tends to be difficult.

It is preferable that the discharge speed of the polyvinyl alcohol-type resin aqueous solution discharged from a T-type slit die to a cast drum is 0.2-5 m / min, Especially preferably, it is 0.4-4 m / min, More preferably, it is 0.6-3 m / min. If the discharge speed is too low, the productivity tends to be lowered, and if it is too fast, the softness tends to be difficult.

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

If the diameter is too small, there is a tendency that the drying length is insufficient and the speed is less likely to occur, and if too large, the transportability tends to be lowered.

The width of the 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 7 m.

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

It is preferable that the rotational speed of the said cast drum is 5-50 m / min, Especially preferably, it is 6-40 m / min, More preferably, it is 7-35 m / min.

If the rotational speed is too slow, productivity tends to decrease, and if too fast, drying tends to be insufficient.

It is preferable that the surface temperature of the said cast drum is 40-99 degreeC, Especially preferably, it is 60-95 degreeC.

If the surface temperature is too low, there is a tendency to become poor in drying, and if it is too high, there is a tendency to foam.

In this way, a film forming process is performed. And the film formed into a film is peeled from the said cast drum, and it is conveyed in the flow direction MD. It is preferable that the moisture content of the film formed into a film is 0.5-15 weight%, Especially preferably, it is 1-13 weight%, More preferably, it is 2-12 weight%. Even if the said moisture content is too low or too high, it exists in the tendency for expression of the swelling property and stretchability made into the objective become difficult.

[Drying, stretching process]

When the moisture content of the film before extending | stretching in the width direction TD is too high, it is preferable to dry the film before extending | stretching in the width direction TD, and, on the contrary, the adjustment of the said water content is a film before extending | stretching in the width direction TD. When the moisture content of is too low, it is preferable to humidify before extending | stretching to the width direction TD. More preferably, the conditions of a drying process are adjusted so that a moisture content may become the said range.

The drying takes place continuously. Although this continuous drying can be performed by a well-known method using a heating roll, an infrared heater, etc., in this invention, it is preferable to carry out by several heating rolls, Especially preferably, the temperature of a heating roll is 40-150 degreeC. More preferably, it is 50-140 degreeC. Moreover, a humidity control area can also be provided before extending | stretching to the width direction TD for adjustment of a moisture content.

It is not necessary to extend | stretch the film formed into a film in this invention in the flow direction MD in particular, and it is sufficient if it conveys by the tension force to the extent that a film does not bend. Naturally, stretching in the width direction TD causes neck-in depending on the Poisson's ratio in the flow direction MD, and dehydration shrinkage occurs in the flow direction MD during drying. Because of this shrinkage, even if the rotational speed of the conveying roll or the heating roll is constant, an appropriate tension is obtained in the flow direction MD, and control of complicated rotational speed as in Patent Document 2 is unnecessary. It is preferable that the dimension of the flow direction MD of a film is constant from a manufacturing viewpoint, Especially preferably, the rate of change of the dimension of the flow direction MD before and after extending | stretching of the width direction TD is 0.8-1.2, Especially preferably, Is 0.9 to 1.1.

It is preferable that the conveyance speed in the flow direction MD of the film formed into a film is 5-30 m / min, Especially preferably, it is 7-25 m / min, More preferably, it is 8-20 m / min. When this conveyance speed is too slow, there exists a tendency for productivity to fall, and when too fast, there exists a tendency for in-plane uniformity to fall.

Although the method of carrying out conveyance to the flow direction MD of the film-formed film, and extending | stretching to the width direction TD simultaneously is not specifically limited, For example, the width direction both ends of a film are clamped with a some clip, It is preferable to carry out conveyance and extending | stretching simultaneously. In this case, the arrangement of the clips to 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 clip is too wide, bending occurs in the film after stretching or the in-plane uniformity of the obtained polyvinyl alcohol-based film tends to be lowered. Moreover, as for the clamping position (tip end part of a clip) of a clip, 100 mm or less is preferable from the width direction both edges of the film formed into a film. When the clamping position (tip part) of a clip is located too much in the film width direction center part, the film edge part to destroy will increase and the product width | variety tends to become narrow.

It is preferable that the draw ratio of the width direction TD in this invention is 1.05 to 1.3 times, Especially preferably, it is 1.05 to 1.25 times, More preferably, it is 1.1 to 1.2 times. Even if the draw ratio of the width direction TD is too high or low, there exists a tendency for in-plane uniformity to fall.

Stretching of the said width direction TD is performed continuously. This continuous stretching may be one step (once), or may be a plurality of stages (several times) such that the total stretching ratio is in the range of the stretching ratio (also called sequential stretching). For example, after performing continuous extending | stretching of a 1st stage, the simple conveyance which fixed the width direction TD is implemented, and continuous extending | stretching after a 2nd stage may also be performed after that. In particular, in the case of a thin film, by performing the continuous stretching of the first stage, by inserting a simple width fixing conveying step, it becomes possible to relax the stress of the film and avoid breakage.

When inserting the conveyance process of width fixation, it is also possible to narrow a fixed width rather than the width | variety after the continuous extending | stretching of the 1st step. Since the film immediately after stretching tends to shrink for stress relaxation, and shrinkage accompanying dehydration also occurs, it is possible to narrow the fixed width to this shrinkage width. However, narrowing down more than the shrinkage width is not preferable because curvature occurs in the film.

As described above, the continuous stretching is preferably performed after the drying step of the film, but is performed at least one of the drying step, the drying step, and the drying step before the film.

In one preferred embodiment of the present invention, a film is stretched beyond 1.3 times in the width direction (TD) of a film formed into a film, and thereafter, a method of dimensional shrinkage is used so that the stretching ratio in the final width direction (TD) becomes 1.05 to 1.3 times. Can be.

In this case, after extending | stretching beyond 1.3 times temporarily, what is necessary is just to convey a film simply by the fixed width of draw ratio 1.05-1.3. By this method, the stress of the film is relieved, and in particular, in the case of a thin film, it becomes possible to avoid fracture.

It is preferable to perform extending | stretching of the width direction (TD) with respect to the film formed into a film in this invention at 50-150 degreeC atmospheric temperature. Atmosphere temperature at the time of this extending | stretching becomes like this. Especially preferably, it is 60-140 degreeC, More preferably, it is 70-130 degreeC. Even if the atmospheric temperature at the time of extending | stretching is too low or too high, there exists a tendency for in-plane uniformity to fall. When extending | stretching sequentially, the atmospheric temperature at the said extending | stretching can be changed in each extending | stretching step.

As for extending | stretching time at the time of extending | stretching in the width direction (TD) with respect to the film formed into a film in this invention, 2 to 60 second is preferable, Especially preferably, it is 5 to 45 second, More preferably, it is 10 to 30 second. If this stretching time is too short, breakage tends to occur in the film. On the contrary, if it is too long, the equipment load tends to increase. When extending | stretching sequentially, the said extending time can be changed in each extending | stretching step.

After extending | stretching the film formed into a film in this invention in the width direction (TD), as needed, heat processing may be performed with respect to both surfaces of the said film by a floating dryer etc. It is preferable that the temperature of this heat processing is 60-200 degreeC, Especially preferably, it is 70-150 degreeC. In addition, the heat treatment by the floating dryer is a process of blowing hot air, the heat treatment temperature means the temperature of the blowing hot air.

If the heat treatment temperature is too low, the dimensional stability tends to be lowered. On the contrary, if the heat treatment temperature is too high, the stretchability at the time of manufacturing the polarizing film tends to be lowered.

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 be lowered. On the contrary, if it is too long, the stretchability at the time of polarizing film production tends to be lowered.

[Polyvinyl alcohol film]

In this way, the polyvinyl alcohol-based film of the present invention is obtained. The polyvinyl alcohol-based film is wound on a core pipe in a rolled state in the flow direction (MD) for a long time and is produced in a film winding body.

As described above, the thickness of the polyvinyl alcohol-based film of the present invention needs to be extremely thin, preferably 40 µm or less, and preferably 5 to 40 µm from the viewpoint of thinning of the polarizing film, particularly preferably fracture. It is 10-40 micrometers from a viewpoint of avoidance, More preferably, it is 10-38 micrometers.

It is preferable that the width | variety of the polyvinyl alcohol-type film of this invention is 2 m or more, Especially preferably, it is 2-6 m from a viewpoint of break avoidance.

It is preferable that the length of the polyvinyl alcohol-type film of this invention is 2 km or more, Especially preferably, it is 3 km or more from a viewpoint of large area, More preferably, it is 3-50 km from a transportation weight point.

Since the polyvinyl alcohol-type film of this invention is excellent in stretchability, it is used especially suitably as a raw material for polarizing films.

Next, the manufacturing method of the polarizing film obtained using the polyvinyl alcohol-type film of this invention is demonstrated.

[Production Method of Polarizing Film]

The polarizing film of this invention is continuously manufactured by carrying out the said polyvinyl alcohol-type film from the said film winding body, and conveys it to a horizontal direction, and is manufactured through processes, such as swelling, dyeing, boric acid bridge | crosslinking, extending | stretching, washing | cleaning, and drying.

The swelling process is carried out before the dyeing process. By the swelling step, the contamination of the surface of the polyvinyl alcohol-based film can be washed, and the polyvinyl alcohol-based film is swelled to prevent staining and the like. As the treatment liquid in the swelling step, water is usually used. The treatment liquid may contain a small amount of an additive such as an iodide compound, a surfactant, alcohol, etc., if the main component is water. The temperature of the swelling bath is usually about 10 to 45 ° C, and the immersion time in the swelling bath is usually about 0.1 to 10 minutes.

The dyeing step is carried out by bringing a polyvinyl alcohol-based film into contact with a liquid containing iodine or dichroic dye. Usually, the aqueous solution of iodide-potassium iodide is used, the concentration of iodine is 0.1-2 g / L, and the concentration of potassium iodide is 1-100 g / L. The dyeing time is practically about 30 to 500 seconds. As for the temperature of a process bath, 5-50 degreeC is preferable. In addition to the aqueous solvent, the aqueous solution may contain a small amount of an organic solvent compatible with water.

A boric acid crosslinking process is performed using boron compounds, such as boric acid and borax. The boron compound is used in the form of an aqueous solution or a water-organic solvent mixture at a concentration of about 10 to 100 g / L, and it is preferable to coexist potassium iodide in the liquid from the viewpoint of stabilization of polarization performance. As for the temperature at the time of a process, about 30-70 degreeC and a processing time, about 0.1 to 20 minutes are preferable, and you may perform an extending | stretching operation during a process as needed.

In the stretching step, the polyvinyl alcohol-based film is preferably stretched 3 to 10 times, preferably 3.5 to 6 times, in the uniaxial direction (flow direction (MD)). At this time, some extending | stretching (stretching degree which prevents shrinkage of the width direction TD, or more) can also be performed also to the perpendicular direction of a extending | stretching direction. As for the temperature at the time of extending | stretching, 40-70 degreeC is preferable. In addition, a draw ratio may be finally set to the said range, and extending | stretching operation can also be performed not only 1 step (once) but also several times in a polarizing film manufacturing process.

A washing process is performed by immersing a polyvinyl alcohol-type film in the iodide aqueous solution, such as water and potassium iodide, for example, and can remove the precipitate which arises on the surface of this polyvinyl alcohol-type film. The potassium iodide concentration in the case of using an aqueous potassium iodide solution is about 1 to 80 g / L. The temperature at the time of washing | cleaning process is 5-50 degreeC normally, Preferably it is 10-45 degreeC. The treatment time is usually 1 to 300 seconds, preferably 10 to 240 seconds. In addition, water washing | cleaning and washing | cleaning by aqueous potassium iodide solution can also be performed combining suitably.

As for a drying process, drying a polyvinyl alcohol-type film for 1 to 10 minutes at 40-80 degreeC in air | atmosphere is performed, for example.

Moreover, the polarization degree of a polarizing film becomes like this. Preferably it is 99.5% or more, More preferably, it is 99.8% or more. If the degree of polarization is too low, there is a tendency that the contrast in the liquid crystal display cannot be secured.

In addition, the polarization degree generally aligns two light polarizing films in a state in which the alignment directions thereof are in the same direction, and the light transmittances (H ₁₁ ) and two polarizing films measured for wavelength lambda are perpendicular to each other. in the superimposed state so that the direction, from a light transmittance (H ₁₎ measured for the wavelength λ, is calculated according to the formula shown below.

Polarization degree (%) = [(H ₁₁ -H ₁ ) / (H ₁₁ + H ₁ )] ^1/2

In addition, the single transmittance of the polarizing film of the present invention is preferably 42% or more. If the single transmittance is too low, there is a tendency that high luminance of the liquid crystal display cannot be achieved.

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

Hereinafter, the manufacturing method of the polarizing plate of this invention using the polarizing film of this invention is demonstrated.

The polarizing film of this invention has little color unevenness, and is suitable for manufacturing the polarizing plate excellent in polarization performance.

[Method of Manufacturing Polarizing Plate]

The polarizing plate of this invention is produced by bonding the optically isotropic resin film as a protective film to one or both surfaces of the polarizing film of this invention through an adhesive agent. As a protective film, for example, cellulose triacetate, cellulose diacetate, polycarbonate, polymethyl methacrylate, cycloolefin polymer, cycloolefin copolymer, polystyrene, polyethersulfone, polyallylene ester, poly-4-methyl Films or sheets, such as a pentene and polyphenylene oxide, are mentioned.

Although the bonding method is performed by a well-known method, for example, after apply | coating a liquid adhesive composition uniformly to a polarizing film, a protective film, or both, they are bonded together and crimped | bonded, and heating and an active energy ray It is carried out by examining.

Moreover, curable resin, such as a urethane resin, an acrylic resin, and a urea resin, is apply | coated and hardened | cured to one side or both surfaces of a polarizing film, and a hardened layer can also be formed and it can also be set as a polarizing plate. By doing in this way, the said hardened layer becomes a substitute for the said protective film, and it can aim at thin film.

The polarizing film and the polarizing plate using the polyvinyl alcohol-based film of the present invention are excellent in polarizing performance, portable information terminal, PC, television, projector, signage, electronic desk calculator, electronic clock, word processor, electronic paper, game machine, video, LCDs, photo albums, thermometers, audio, liquid crystal displays such as automobiles and machinery, sunglasses, anti-glare glasses, stereoscopic glasses, wearable displays, reflection reduction layers for display elements (CRT, LCD, organic EL, electronic paper, etc.), It is preferably used for optical communication devices, medical devices, building materials, toys and the like.

(Example)

Hereinafter, although an Example is given and this invention is demonstrated further more concretely, this invention is not limited to a later Example unless the summary is exceeded.

Then, the examples and the comparative polyvinyl alcohol-based properties of the film [degree of swelling (S _A, S _B, S _X, S _Y) and the polarization film characteristics of the examples of the latter (the degree of polarization, simple substance transmittance, color non-uniformity) analysis of And evaluation was performed as follows.

[Measurement Method for Swelling Degree (S _A ) of Polyvinyl Alcohol-Based Film]

A rectangular film-like sample of 10 cm in the width direction (TD) and 20 cm in the flow direction (MD) is cut out from the center of the width direction of the polyvinyl alcohol-based film, and the film-like sample is again 3 mm in width and 20 cm in length. Cut into rectangles. Then, all of these rectangular 1st samples were immersed as it is in 1,000g of water of 30 degreeC. After immersion for 30 minutes, the rectangular first sample was taken out, centrifuged for 5 minutes at 3,000 rpm using a centrifugal separator, and the mass "N" (the total sum of all rectangular first samples) after dehydration was measured. Subsequently, the calculated the degree of swelling (S _A) by the first sample of the rectangle and dried 16 hours drier at 105 ℃, mass to measure the (first sample all the sum of the rectangle) "M", and expression. In addition, the same measurement was performed 3 times and the average value was employ | adopted.

Swelling degree (S _A ) (%) = 100 × N / M

[Measurement Method for Swelling Degree (S _B ) of Polyvinyl Alcohol-Based Film]

A rectangular sample of 5 cm in the width direction (TD) and 15 cm in the flow direction (MD) is cut out from the center of the width direction of the polyvinyl alcohol-based film, and the flow direction of the second sample is such that the distance between the zippers is 5 cm. After fastening both ends of (MD) with a zipper, it was immersed in water of 30 degreeC, and the draw ratio tripled in the water at the drawing speed of 0.12 m / min (240% / min) immediately (of the 2nd sample after extending | stretching). It uniaxially stretched so that the distance between the said zippers might be 15 cm). After stretching, the second sample was taken out of water, and within 1 minute in an environment having a temperature of 20 ° C. and a relative humidity of 65% RH, the filter paper was used to wipe off moisture on the surface of the second sample after stretching, and the mass of the second sample L ”was measured. Subsequently, after drying the 2nd sample for 16 hours with a 105 degreeC dryer, the mass "K" is measured and the swelling degree (S _B ) after extending | stretching to draw ratio 3times in 30 degreeC water by the following formula is measured. Calculated. In addition, the same measurement was performed 5 times and the average value was employ | adopted.

Swelling degree (S _B ) (%) = 100 × L / K

[Measurement method of the swelling degree (S _X and S _Y ) of the polyvinyl alcohol-based film]

The square third sample of the width direction (TD) 10 cm and the flow direction (MD) 10 cm is cut out from the center part of the width direction of a polyvinyl alcohol-type film, and this 3rd sample is put on the flat glass plate, and the width direction of the 3rd sample ( TD) and the dimension of the flow direction (MD) were measured by the caliper, respectively. Subsequently, the third sample was immersed in an ion exchange bath adjusted to 30 ° C. for 5 minutes, then taken out, immediately placed on a flat glass plate, and the dimensions of the third sample in the width direction (TD) and the flow direction (MD), respectively. The swelling degree (S _X and S _Y ) was computed by the following formula and calculated by the following formula. Moreover, the said operation was performed in the environment of 23 degreeC and 50% RH.

Swelling degree (S _X ) (%) = (Dimension of TD after dipping / Dimension of TD before dipping) × 100

Swelling degree (S _Y ) (%) = (dimension of MD after immersion / dimension of MD before immersion) * 100

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

The test piece of length 4cm x width 4m is cut out from the center part of the width direction of the obtained polarizing film, and the polarization degree (%) and a single transmittance (%) are measured using the automatic polarizing film measuring apparatus (made by Nippon Bunko Corp .: VAP7070). did.

(Color unevenness)

After cutting the test piece of length 30cm x width 30cm from the center part of the width direction of the obtained polarizing film, and inserting it at the angle of 45 degrees between two polarizing plates (43.5% of single transmittance, 99.9% of polarization degree) of cross nicol state, Optical color unevenness was observed in transmission mode using the light box of surface roughness 14,000lx, and the following references | standards evaluated.

(Evaluation standard)

○ ··· There was no stain.

△ ··· There was a faint stain.

× ... There was a clear stain.

<Example 1>

(Production of Polyvinyl Alcohol Film)

Into a 5,000-liter can, 1,000 kg of polyvinyl alcohol-based resin having a weight average molecular weight of 142,000 and 99.8 mol% of saponification, 2,500 kg of water, 105 kg of glycerin as a plasticizer, and 0.25 kg of polyoxyethylene laurylamine as a surfactant were added and stirred. It heated up to 150 degreeC, carrying out pressure melt | dissolution, and obtained the aqueous solution of polyvinyl alcohol-type resin of 25 weight% of resin concentration by density | concentration adjustment. Subsequently, after supplying this polyvinyl alcohol-type resin aqueous solution to a twin-screw extruder and defoaming, the aqueous solution temperature was set to 95 degreeC, and it discharges to the cast drum of surface temperature of 80 degreeC from a T-type slit die injection opening (discharge rate 1.3). m / min) and casting to form a film. The film formed into a film was peeled from the cast drum, and it dried while conveying the surface and back surface of the film in contact with ten heat rolls in total, while conveying in a flow direction (MD). This obtained the film (width 2m, thickness 30micrometer) of 7weight% of moisture content. Then, the left and right both ends of the film were sandwiched with a clip having a clip pitch of 45 mm, and the film was stretched 1.2 times in the width direction (TD) at 80 ° C. using a drawing machine while conveying the film at a speed of 8 m / min in the flow direction (MD). Then, the film was conveyed in a 130 degreeC drier at 2.4 m of fixed width, and the polyvinyl alcohol-type film (2.4 m in width, 25 micrometers in thickness, length 2km) was obtained. The characteristic of the obtained polyvinyl alcohol-type film is as showing in Table 1 of late. Finally, this polyvinyl alcohol-type film was wound up to the core pipe in roll state, and the film winding body was obtained.

(Production of Polarizing Film and Polarizing Plate)

The obtained polyvinyl alcohol-based film was stretched 1.7 times in the flow direction (MD) while immersing and swelling in a water bath at a water temperature of 30 ° C. while continuously being released from the film recommended body and conveyed in the horizontal direction. In the swelling step, no folding or wrinkles occurred in the film. Subsequently, it was drawn 1.6 times in the flow direction (MD) while immersing and dyeing in an aqueous solution at 30 ° C. composed of 0.5 g / L of iodine and 30 g / L of potassium iodide, followed by 40 g / L of boric acid and 30 g / L of potassium iodide. It was uniaxially stretched 2.1 times in the flow direction (MD) while immersing in aqueous solution (50 degreeC) and bridge | crosslinking boric acid. Finally, it wash | cleaned with the potassium iodide aqueous solution, it dried at 50 degreeC for 2 minutes, and obtained the polarizing film of 5.8 times of total draw ratio. No breakage occurred during the production of this polarizing film, and the properties of the obtained polarizing film are as shown in Table 1 below.

Using a polyvinyl alcohol aqueous solution as an adhesive agent on both surfaces of the polarizing film obtained above, the triacetyl cellulose film of 40 micrometers in thickness was bonded together, and it dried at 70 degreeC, and obtained the polarizing plate.

<Example 2>

In Example 1, after extending | stretching 1.4 time in the width direction (TD) at 80 degreeC using a drawing machine, except shrinking and conveying by stress relaxation to a fixed width of 2.4 m (1.2 times extending | stretching equivalent) at 130 degreeC, In the same manner as in Example 1, a polyvinyl alcohol-based film (width 2.4 m, thickness 25 µm, length 2 km) was obtained. The characteristic of the obtained polyvinyl alcohol-type film is as showing in Table 1 of late.

In addition, the polarizing film and the polarizing plate were obtained like Example 1 using the said polyvinyl alcohol-type film. In the swelling step at the time of manufacturing a polarizing film, the said polyvinyl alcohol-type film did not generate | occur | produce fold and wrinkles, and neither fracture | rupture occurred. The characteristic of the obtained polarizing film is as showing in Table 1 of late.

<Example 3>

In Example 1, the polyvinyl alcohol-based aqueous resin solution was discharged to a cast drum having a surface temperature of 88 ° C. (discharge rate of 1.9 m / min) and flexibly formed to form a film, the film having a water content of 10% by weight ( 2m in width and 45 micrometers in thickness) were formed into a film. Subsequently, in the same manner as in Example 1, the film was stretched 1.2 times in the width direction (TD) at 80 ° C. using a drawing machine, and then the film formed above was conveyed into a dryer at 135 ° C. at a fixed width of 2.4 m, and a polyvinyl alcohol system was used. The film (2.4m in width, 35 micrometers in thickness, length 2km) was obtained. The characteristic of the obtained polyvinyl alcohol-type film is as showing in Table 1 of a later stage

Moreover, using the said polyvinyl alcohol-type film, it carried out similarly to Example 1, and obtained the polarizing film and the polarizing plate. In the swelling step at the time of manufacturing a polarizing film, the said polyvinyl alcohol-type film did not generate | occur | produce fold and wrinkles, and neither fracture | rupture occurred. The characteristic of the obtained polarizing film is as showing in Table 1 of late.

<Example 4>

A film having a water content of 10% by weight (2 m in width) was carried out in the same manner as in Example 1 except that the aqueous polyvinyl alcohol-based resin solution was discharged to a cast drum having a surface temperature of 88 ° C. (discharge rate of 1.9 m / min) and flexibly formed into a film. And 45 µm in thickness) were formed into a film. Subsequently, in the same manner as in Example 1, the film was drawn 1.4 times in the width direction (TD) at 80 ° C. using a drawing machine, and then contracted by stress relaxation to a fixed width of 2.4 m (equivalent to 1.2 times stretching) at 135 ° C. A vinyl alcohol film (2.4 m in width, 34 mu m in thickness, 2 km in length) was obtained. The characteristic of the obtained polyvinyl alcohol-type film is as showing in Table 1 of late. In addition, the polarizing film and the polarizing plate were obtained like Example 1 using the said polyvinyl alcohol-type film. In the swelling step at the time of manufacturing a polarizing film, the said polyvinyl alcohol-type film did not generate | occur | produce fold and wrinkles, and neither fracture | rupture occurred. The characteristic of the obtained polarizing film is as showing in Table 1 of late.

<Comparative Example 1>

In Example 1, the polyvinyl alcohol-type resin aqueous solution was discharged (ejection rate 1.3 m / min) and cast into a film to the cast drum of surface temperature of 80 degreeC. About the film formed into a film, it carried out similarly to Example 1 except having performed heat processing at 130 degreeC using the floating dryer, without extending | stretching to the width direction (TD) using a drawing machine, and the polyvinyl alcohol-type film (Width 2m, thickness 30 micrometers, length 2km) was obtained. The characteristic of the obtained polyvinyl alcohol-type film is as showing in Table 1 of late. In addition, a polarizing film and a polarizing plate were produced in the same manner as in Example 1 using the polyvinyl alcohol-based film, whereby folds and wrinkles occurred in the polyvinyl alcohol-based film in the swelling step. The characteristic of the obtained polarizing film is as showing in Table 1 of late.

<Comparative Example 2>

In Example 1, the polyvinyl alcohol-type resin aqueous solution was discharged (ejection rate 1.3 m / min) and cast into a film to the cast drum of surface temperature of 80 degreeC. About the film formed into a film, it carried out similarly to Example 1 except having performed heat processing at 120 degreeC using the floating dryer, without extending | stretching to the width direction (TD) using a drawing machine, and the polyvinyl alcohol-type film (2 m in width, 30 mu m in thickness, and 2 km in length) was obtained. The characteristic of the obtained polyvinyl alcohol-type film is as showing in following Table 1.

In addition, the polarizing film and the polarizing plate were produced like Example 1 using the said polyvinyl alcohol-type film, When the swelling process, the polyvinyl alcohol-type film folded and wrinkled. The characteristic of the obtained polarizing film is as showing in following Table 1.

The embodiment and the comparative example results from the polyvinyl alcohol the degree of swelling (S _B) when the film have in the degree of swelling (S _A), 30 ℃ when immersed in a 30 ℃ water 3-fold uniaxial stretching, of 30 ℃ represents the expansion of the film after immersion in water the degree of swelling (S _X and S _Y) has the formula (1) to (3) are all satisfied in example polarization is obtained from a polyvinyl alcohol film of the film 1-4, a high polarization It can be seen that it has a characteristic and is uniform without color unevenness. On the other hand, it turns out that the polyvinyl alcohol-type films of the comparative example 1 and the comparative example 2 which do not satisfy Formula (3) are inferior to polarization characteristic and color unevenness is also observed.

Although the said Example showed about the specific form in this invention, the said Example is only a mere illustration and is not interpreted limitedly. Various modifications apparent to those skilled in the art are expected to fall within the scope of the present invention.

The polarizing film made of the polyvinyl alcohol-based film of the present invention is excellent in polarization performance, portable information terminal, PC, television, projector, signage, electronic desk calculator, electronic clock, word processor, electronic paper, game machine, video, camera, Liquid crystal display devices such as photo albums, thermometers, audio, instruments for automobiles and machinery, sunglasses, anti-glare glasses, stereoscopic glasses, wearable displays, antireflection layers for display elements (CRT, LCD, organic EL, electronic paper, etc.), optical communication devices It is preferably used for medical equipment, building materials, toys and the like.

Claims (6)

The long polyvinyl alcohol-type film whose thickness is 40 micrometers or less WHEREIN: The polyvinyl alcohol-type film characterized by satisfy | filling following formula (1)-(3).
190% ≤S _A ≤230% ... (1)
220% ≤S _B ≤310% ... (2)
1.01≤S _Y / S _X ≤1.20 (3)
The formula (1) of, S _A represents the degree of swelling of the mass basis when immersed for 5 minutes of the polyvinyl alcohol film in a 30 ℃ water,
The formula (2):, S _B represents the degree of swelling of the mass basis when the uniaxial stretching the draw ratio at a draw speed of 0.12m / min for the polyvinyl alcohol film in water of 30 ℃ to three times,
The above formula (3) of the, S _X is the polyvinyl alcohol-based film shows a wide degree of swelling of the dimension of the direction when immersed 5 minutes in a 30 ℃ water, S _Y is the polyvinyl alcohol-based film 30 ℃ The swelling degree of the dimension reference in the longitudinal direction when immersed in water for 5 minutes is shown. The polyvinyl alcohol-type film of Claim 1 is used, The polarizing film characterized by the above-mentioned. The polarizing film of Claim 2 and the protective film provided in at least one surface of this polarizing film are provided, The polarizing plate characterized by the above-mentioned. The film forming process of forming the aqueous solution of polyvinyl alcohol-type resin by the continuous casting method, and the drying which performs continuous drying and continuous extending | stretching to the film, conveying the film formed into the flow direction. In the manufacturing method of the polyvinyl alcohol-type film provided with the extending process WHEREIN: The manufacturing method of the polyvinyl alcohol-type film characterized by that the polyvinyl alcohol-type film manufactured satisfies following formula (1)-(3). .
190% ≤S _A ≤230% ... (1)
220% ≤S _B ≤310% ... (2)
1.01≤S _Y / S _X ≤1.20 (3)
The formula (1) of, S _A represents the degree of swelling of the mass basis when immersed for 5 minutes of the polyvinyl alcohol film in a 30 ℃ water,
The formula (2):, S _B represents the degree of swelling of the mass basis when the uniaxial stretching the draw ratio at a draw speed of 0.12m / min for the polyvinyl alcohol film in water of 30 ℃ to three times,
The above formula (3) of the, S _X is the polyvinyl alcohol-based film shows a wide degree of swelling of the dimension of the direction when immersed 5 minutes in a 30 ℃ water, S _Y is the polyvinyl alcohol-based film 30 ℃ The swelling degree of the dimension reference in the longitudinal direction when immersed in water for 5 minutes is shown. The method according to claim 4,
A method for producing a polyvinyl alcohol-based film, wherein the film formed in the drying and stretching step is stretched from 1.05 to 1.3 times in the width direction. The method according to claim 4 or 5,
Polyvinyl alcohol-based film, characterized in that the film formed in the drying and stretching step in the width direction temporarily stretched more than 1.3 times, and then dimensional shrinkage so that the draw ratio in the final width direction is 1.3 times or less. Method of preparation.