KR20190139852A - Polyvinyl alcohol-based film, polarizing film and polarizing plate, and polyvinyl alcohol-based film production method - Google Patents

Abstract

Polyvinyl alcohol-based film, polyvinyl alcohol thereof, which has a very good balance between swelling and stretchability in the production of a polarizing film, does not cause breakage during the production of the polarizing film, exhibits high polarization performance, and obtains a polarizing film with less color unevenness. Provided are a polarizing film and a polarizing plate using a system film, and a method for producing the polyvinyl alcohol film. The polyvinyl alcohol-based film of the present invention has a length before immersion when a first rectangular sample having a width direction (TD) of 40 mm x a length direction (MD) of 270 mm cut out from the width direction center part is immersed in water at 30 ° C. for 30 seconds. 30 _degreeC is taken for the rectangular 2nd sample of the width direction (TD) 270 mm x length direction (MD) 40 mm which are _{extended |} stretched 30 mm or more and 50 mm or less in the longitudinal direction in the part of 250 mm of directions, and cut out from the width direction center part. The amount of elongation W _TD300 in the width direction in the portion in the width direction of 250 mm before immersion for 300 seconds is 15 mm or more and 60 mm or less.

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 is a material for forming a polarizing film with high polarization and little color unevenness, a polarizing film and a polarizing plate using a polyvinyl alcohol-based film thereof, and a method for producing the polyvinyl alcohol-based film. It is about.

Conventionally, a polyvinyl alcohol 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 off 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 conveyance step, the film formed is attracted in the flow direction (MD), so that the polyvinyl alcohol polymer is easily oriented in the flow direction (MD).

On the other hand, generally, a polarizing film is manufactured by first swelling the polyvinyl alcohol-type film which is a disk, 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 the dye can easily penetrate the inside of the film in 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 opposite to the above is also performed. That is, it is a case where the polyvinyl alcohol-type film which is a disk is first swelled with water (including warm water), and 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 the favorable stretchability 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. By the way, a thin film has a problem of productivity, such as breaking by extending | 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), while adjusting the amount of elongation in the longitudinal direction (MD) when immersed in water at 30 ° C. for 30 seconds to a specific range, and in the width direction (TD) when immersed in water at 30 ° C. for 300 seconds. A method of adjusting the amount of elongation to a specific range (see Patent Document 5, for example) has 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 WO2016 / 093259A

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

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 taken into consideration, and in the flow direction (MD) at the time of manufacturing the polarizing film 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.

The technique described in Patent Document 2 specifies the degree of stretching (tension state) in the flow direction (MD) at the time of manufacturing the polyvinyl alcohol-based film, but without considering the stretching in the width direction (TD), the polarizing film It is insufficient to improve the stretchability at the time of manufacture.

In the technique described in Patent Document 3, the film formed can be dried uniformly, but the orientation of the polymer can not be controlled, and it is insufficient to improve the swelling property and the 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, although the polyvinyl alcohol-based film having a thickness of about 45 µm used in the Examples has a certain improvement effect on the swelling property in manufacturing the polarizing film, it is difficult to cope with new thinning of the polarizing film, In the polyvinyl alcohol film of the thin film whose film thickness is 40 micrometers or less, it is insufficient in order to improve the swelling property and stretchability at the time of polarizing film manufacture.

Accordingly, the present invention has a very good balance between swelling and stretchability in the production of a polarizing film under such a background, does not cause breakage even in the production of a thin polarizing film, exhibits high polarization performance, and obtains a polarizing film with less color unevenness. It provides a polyvinyl alcohol-based film, a polarizing film and a polarizing plate using a polyvinyl alcohol-based film thereof, and a method for producing the polyvinyl alcohol-based film.

The present inventors have made intensive studies in view of such circumstances, and as a result, the amount of elongation (MD) in the longitudinal direction (MD) and the length of the long polyvinyl alcohol-based film having a thickness of 40 μm or less when immersed in 30 ° C. for 30 seconds for 30 seconds. In relation to the amount of elongation in the width direction (TD) when immersed in water at 300 ° C for 300 seconds, the amount of elongation in the width direction (TD) when immersed in water at 30 ° C for 300 seconds is more than that of conventional polyvinyl alcohol films. When it made small, it was discovered that the balance of swelling property and stretchability at the time of manufacturing a polarizing film is very excellent, a fracture does not arise at the time of manufacture of a thin polarizing film, showing a high polarization performance, and obtaining a polarizing film with few color unevenness.

That is, the present invention is a rectangular polyvinyl alcohol-based film having a thickness of 40 μm or less, the rectangular shape having a width direction (TD) of 40 mm x a length direction (MD) of 270 mm cut out from the widthwise center portion of the polyvinyl alcohol-based film. For the first sample, when the first sample was immersed in water at 30 ° C. for 30 seconds, the amount of elongation W _MD30 in the longitudinal direction MD in the 250 mm portion excluding both ends of the longitudinal direction MD before immersion was 30 degreeC or more and 50 mm or less, On the other hand, about a 2nd rectangular sample of the width direction (TD) 270mm x length direction (MD) which cut out from the width direction center part of the said polyvinyl alcohol-type film, 30 degreeC of this 2nd sample is carried out. The first key point is a polyvinyl alcohol-based film having an elongation amount W _TD300 in the width direction (TD) in a portion of 250 mm excluding the width direction (TD) both ends before immersion for 300 seconds in water of 15 mm or more and 60 mm or less. do.

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 the at least single side | surface of this polarizing film is set as the 3rd summary.

And the film forming process of forming the aqueous solution of polyvinyl alcohol-type resin by the continuous casting method, and the drying and extending | stretching which carry out 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 process, about a rectangular 1st sample of the width direction 40mm x flow direction 270mm cut out from the width direction center part of the polyvinyl alcohol-type film manufactured, this 1st sample is Of the polyvinyl alcohol-based film produced so that the amount of elongation W _MD30 in the longitudinal direction in the portion of 250 mm except for both ends in the longitudinal direction before being immersed in water at 30 ° C. for 30 seconds was 30 mm or more and 50 mm or less. When the second sample was immersed in water at 30 ° C. for 300 seconds for a rectangular second sample having a width of 270 mm × a flow direction of 40 mm to be cut out from the width direction center part, The method of producing a poly vinyl alcohol-based film, characterized in that the kinds of the previous width W _TD300 expansion amount in the width direction of a portion of 250mm, except for opposite ends so that a range from 15mm to 60mm the fourth aspect.

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 the elongation amount W _MD30 in the longitudinal direction (MD) and the width direction when immersed in water at 30 ° C. for a specific time. Since the said amount of elongation W _TD300 of (TD) is in a specific range, it is excellent in swelling _property and _{stretchability} at the time of manufacturing a polarizing film, and even if it uses itself for manufacture of a thin polarizing film by making it thin (40 micrometers or less in thickness), You can prevent this from happening. Moreover, when this polyvinyl alcohol-type film is used, the polarizing film which shows high polarization performance and little color unevenness can be obtained.

In particular, when the width of the polyvinyl alcohol-based film is 2 m or more, the productivity of the polarizing film using the polyvinyl alcohol-based film is improved.

Moreover, since the said polyvinyl alcohol-type film is used for the polarizing film of this invention, it shows high polarization performance and there are few color unevenness.

Moreover, since the said polarizing film is used for the polarizing plate of this invention, it shows high polarization performance and there are 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 cast 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 elongation amount W _MD30 in the longitudinal direction MD and the elongation in the width direction TD when the manufacturing conditions in each of these steps are engaged and immersed in water at 30 ° C. for a specific time. The said polyvinyl alcohol-type film of this invention which _WTD300 becomes a specific range can be obtained.

In particular, in the drying and stretching step, in the case where the film-formed film is stretched by 1.05 to 1.3 times in the width direction (TD), the elongation amount W _MD30 and the elongation amount W _TD300 are suitable, and the swelling _property and the elongation at the time of polarizing film production The polyvinyl alcohol-type film more excellent in ductility can be obtained.

Moreover, in the said drying and extending process, after extending | stretching the said film-forming film in the width direction (TD) temporarily beyond 1.3 times, dimensionally shrinking so that the draw ratio of the final width direction (TD) may be 1.3 times or less. In this case, the stress applied to the film thus formed can be alleviated. 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-based film of the present invention, in a long polyvinyl alcohol-based film having a thickness of 40 μm or less, when immersed in water at 30 ° C., exhibits a specific amount of elongation in the longitudinal direction (MD) and in the width direction (TD). Indicates. That is, in the rectangular 1st sample of the width direction (TD) 40mm x length direction (MD) 270mm cut out from the width direction center part of the said polyvinyl alcohol-type film, this 1st sample was immersed in 30 degreeC water for 30 second. The amount of elongation W _MD30 in the longitudinal direction in the portion of 250 mm except for both ends in the longitudinal direction before immersion is 30 mm or more and 50 mm or less. Moreover, with respect to the rectangular 2nd sample of the width direction (TD) 270mm x length direction (MD) 40mm cut out from the width direction center part of the said polyvinyl alcohol-type film, this second sample is immersed in 30 degreeC water for 300 second. The amount of elongation W _TD300 in the width direction in the 250 mm portion excluding the width direction both ends before immersion is 15 mm or more and 60 mm or less.

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 10 from the viewpoint of avoiding breakage. 40 micrometers, More preferably, it is 10-38 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 elongation amount of the longitudinal direction (MD) and the width direction (TD) at the time of being immersed in 30 degreeC water may become a specific range. By this controlled amount of elongation, the polyvinyl alcohol-based film is made extremely thin with a thickness of 40 µm or less, and has excellent performance.

As described above, the elongation amount in the longitudinal direction MD is equal to the longitudinal direction MD in the portion of 250 mm except for both ends in the longitudinal direction before immersion when the first sample is immersed in water at 30 ° C. for 30 seconds. The amount of stretch W _MD30 is controlled to be 30 mm or more and 50 mm or less. Expansion amount in a longitudinal direction (MD) W _MD30 is preferably 31mm≤W ≤48mm _{MD30, MD30} and particularly preferably 32mm≤W ≤45mm, more preferably 33mm≤W _MD30 ≤43mm.

If the value of W _MD30 is too small, the _elongation at the time of manufacturing the polarizing film described later deteriorates, and thus, the object of the present invention is not achieved, and if the value of W _MD30 is too large, it is loose at the time of polarizing film production. Generation | occurrence | production, wrinkles and a fold generate | occur | produce, and the objective of this invention cannot be achieved.

As described above, the amount of elongation in the width direction TD is the amount of elongation in the width direction TD in the portion of 250 mm excluding the both ends of the width direction before immersion when the second sample is immersed in water at 30 ° C. for 300 seconds. W _TD300 is controlled to be 15 mm or more and 60 mm or less. The amount of stretching W _TD300 in the width direction TD is preferably 16 _mm ≦ W _TD300 ≦ ₅₅ mm, particularly preferably 17 _mm ≦ W _TD300 ≦ ₅₀ mm, more preferably ₁₈ mm ≦ _W TD300 ≦ ₄₅ mm.

If the value of the W _TD300 is too small, color unevenness occurs during the manufacture of the polarizing film, and thus, the object of the present invention is not achieved, and _if the value of the W _TD300 is too large, the film is too spread in the width direction during the manufacturing of the polarizing film and is wrinkled. Since folding occurs, the object of the present invention cannot be achieved.

As a method of controlling the said W _MD30 and W _TD300 in this invention, in the manufacturing method of the said polyvinyl alcohol-type film by the continuous casting method mentioned later, after peeling the film formed into the cast form from the cast form, width The method of extending | stretching in the direction TD is preferable. In this case, conditions to another process are appropriately 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 cast type temperature), and the film formed above Drying conditions (temperature, time) which dries it, the conveyance speed in the flow direction (MD) of the said film forming, etc. are mentioned. The W _MD30 and the W _TD300 are controlled by matching at least one of these conditions with the stretching condition in the width direction TD.

The value of said W _MD30 and W _TD300 in this invention is measured by the following method, for example. In addition, the measurement positions of these W _MD30 and W _TD300 are in the area of 500 mm x 500 mm of the polyvinyl alcohol-based film.

[Measurement Method of W _MD30 ]

The rectangular first sample of the width direction (TD) 40 mm x the length direction (MD) 270 mm is cut out from the width direction center part of a polyvinyl alcohol-type film. Subsequently, a mark line is put in oily ink (thickness of a line 0.3 mm) inside by 10 mm from both edges of the longitudinal direction MD of this 1st sample. A commercially available clip (zipper width 40 mm, mass 7.3 g) is fitted to the outside portion from the marks on both ends, and one of the clips is fixed with a rod-shaped jig. After confirming that the distance between the marks was 250 mm, the long side of the first sample was promptly placed so that the entirety of the first sample with the clip could be submerged in pure water heated to 30 ° C accumulated in a cylindrical transparent water bath. Is immersed vertically (vertical). Immediately after the immersion, the rod-shaped jig is applied to the upper portion of the water tank to fix the long side of the first sample vertically (vertical). Thereafter, the metal reference is immersed in water to measure the distance between marks after 30 seconds from the immersion of the first sample. The distance between the original marks (250 mm) is drawn from the measured value read in 0.5 mm pieces, and the amount of elongation W _MD30 (unit is mm) is calculated.

[Measurement method of W _TD300 ]

The rectangular 2nd sample of width direction (TD) 270 mm x length direction (MD) 40 mm is cut out from the width direction center part of a polyvinyl alcohol-type film. Subsequently, a mark line is put in oily ink (thickness of a line 0.3 mm) inside by 10 mm from both edges of the width direction TD of this 2nd sample. The outer part is inserted with a commercially available clip (zip width 40mm, mass 7.3g) from the mark of both ends, and the said one clip is fixed with a rod-shaped jig. After confirming that the distance between the marks was 250 mm, the long side of the second sample was promptly placed in pure water heated at 30 ° C accumulated in a cylindrical transparent water bath so that the whole of the second sample with the clip entered the water. Is immersed vertically (vertical). Immediately after immersion, the rod-shaped jig is applied to the upper part of the water tank to fix the long side of the second sample vertically (vertical). Thereafter, the metallic reference is immersed in water, and the distance between marks is measured 300 seconds after the immersion of the second sample. The distance between the original marks (250 mm) is drawn from the measured value read in 0.5 mm pieces, and the amount of elongation (WTD300) (unit is mm) is calculated.

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

[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 with 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 sulfonates, 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 decarboxylation of a copolymer of vinyl acetate and vinyl ethylene carbonate, (iii) saponification and dequenching of a copolymer of vinyl acetate and 2,2-dialkyl-4-vinyl-1,3-dioxolane It is obtained by the method of deoxidation, (i) 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. When 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. When the weight average molecular weight is too large, the stretching of the polyvinyl alcohol-based film when the polarizing film is produced tends to be 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 the polyvinyl alcohol-based resin aqueous solution, in addition to polyvinyl alcohol-based resins, plasticizers generally used, such as glycerin, diglycerin, triglycerine, ethylene glycol, triethylene glycol, polyethylene glycol, and trimetholpropane, if necessary, It is preferable to contain a nonionic, anionic, and cationic at least 1 surfactant from a film forming viewpoint. 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%. If the resin concentration of the aqueous solution is too low, the drying load increases, and thus the production capacity tends to be lowered. If the resin concentration of the aqueous solution is 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 process in the case where the cast mold 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 the said especially preferable temperature of 85-98 degreeC ) 70 to 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 to the width direction TD, and, on the contrary, before the adjustment of the said moisture content, and before extending | stretching of the width direction TD When the moisture content of a film is too low, it is preferable to humidify before extending | stretching to the width direction (TD). Especially 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 stretch especially the film formed into a film in this invention in the flow direction (MD), and it is sufficient if it conveys by the tensile tension of the film not to 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, before and after extending | stretching of the width direction TD, the rate of change of the dimension of the flow direction MD is 0.8-1.2, It is especially preferable. Preferably 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 drying to become inadequate.

Although the method of carrying out the conveyance to the flow direction MD of the film formed into a film, and the 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 perform conveyance and extending | stretching simultaneously. In this case, it is preferable that arrangement | positioning of the clip to each end is 200 mm or less in pitch, Especially preferably, it is 100 mm or less in pitch, More preferably, it is 50 mm or less in pitch.

If the pitch of the clip is too wide, there is a tendency for the in-plane uniformity of the polyvinyl alcohol-based film to bend or be obtained in the film after stretching. Moreover, as for the clamping position (tip 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 too 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 plural steps (several times) such that the total draw ratio is in the range of the draw 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 can be performed, and continuous extending | stretching after a 2nd stage can also be performed after that. In particular, in the case of a thin film, after the continuous stretching of the first step is performed, by inserting a simple width-fixed conveying step, stress relaxation of the film can be achieved and breakage can be avoided.

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 these shrinkage widths. 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, a film can be simply conveyed by the fixed width of draw ratio 1.05-1.3. This method relaxes the film and makes it possible to avoid fracture, especially in the case of thin films.

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 in order, 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 extending | stretching time can also be changed in each extending | stretching step.

In this invention, after extending | stretching the film formed into a width direction (TD), you may heat-process both surfaces of the said film with a floating dryer etc. as needed. 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 processing by the said floating dryer is a process which blows hot air, The heat processing temperature means the temperature of the said 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 in a core in a roll form in the flow direction (MD) for a long time and is produced in a film winding body.

As mentioned above, the thickness of the polyvinyl alcohol-based film of the present invention needs to be very thin, 40 µm or less, and preferably 5 to 40 µm from the viewpoint of thinning of the polarizing film, and particularly preferably It is 10-40 micrometers from a viewpoint of break 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 2-7 m, More preferably, it is 3-6 m from a viewpoint of fracture 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 removes the said polyvinyl alcohol-type film from the said film winding body, 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 a 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 at a concentration of about 10 to 100 g / L in the form of an aqueous solution or a water-organic solvent mixture solution, 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 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 in multiple times in a polarizing film manufacturing process as well as 1 step (once).

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 is generally a direction in which the light transmittance (H ₁₁ ) and the two polarizing films measured at the wavelength? Are perpendicular to each other in a state where the two polarizing films are superimposed so that their alignment directions are in the same direction. In the state superimposed so that it may be calculated from the light transmittance H ₁ measured at wavelength lambda according to the following formula.

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 this single transmittance is too low, it will tend to be impossible to achieve high luminance of the liquid crystal display.

A single transmittance is a value obtained by measuring the light transmittance of the polarizing film single body 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 on 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 are carried out, for example. It is carried out by investigation.

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, antiglare 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.

And the measurement and evaluation of the characteristic (W _MD30 , W _TD300 ) of the polyvinyl alcohol-type film in a later Example and a comparative example and the characteristic (polarization degree, single transmittance, color unevenness) of a polarizing film were performed as follows. .

[Measurement Method of W _MD30 ]

The rectangular 1st sample of width direction (TD) 40mm x length direction (MD) 270mm was cut out from the width direction center part of the polyvinyl alcohol-type film. Subsequently, a marking line was put in oil-based ink (thickness of line 0.3mm) in 10 mm from both ends of the 270 mm length of this 1st sample. The outer part was inserted into a commercial clip (zip width 40mm, mass 7.3g) from the mark of both ends, and one clip was fixed with the rod-shaped jig. After confirming that the distance between the marks was 250 mm, the first sample long side was quickly vertically placed in pure water heated at 30 ° C. accumulated in a cylindrical transparent water bath so that the entirety of the first sample with the clip could enter the water. It was immersed in (vertical). Immediately after immersion, a rod-shaped jig was applied to the top of the water tank to fix the first sample long side to be vertical (vertical). Thereafter, the metallic reference was immersed in water, and the distance between marks was measured 30 seconds after the immersion of the first sample. The distance between the original marks (250 mm) was drawn from the measured value read in 0.5 mm pieces, and the amount of elongation W _MD30 (unit is mm) was calculated.

(Measurement method of W _TD300 )

The rectangular 2nd sample of width direction (TD) 270 mm x length direction (MD) 40 mm was cut out from the width direction center part of the polyvinyl alcohol-type film. Subsequently, a mark line was put in oil-based ink (thickness of a line 0.3 mm) in 10 mm inside from the both ends of 270 mm length of this 2nd sample. The outer part is inserted with a commercially available clip (zip width 40mm, mass 7.3 g) from the mark of both ends, and one clip is fixed with a rod-shaped jig. After confirming that the distance between the marks was 250 mm, the second sample long side was quickly vertically placed in pure water heated at 30 ° C. accumulated in a cylindrical transparent water bath so that the entire second sample with the clip could enter the water. Vertical). Immediately after immersion, a rod-shaped jig was applied to the top of the water tank to fix the second sample long side to be vertical (vertical). Thereafter, the metal reference was immersed in water, and the distance between marks was measured 300 seconds after the immersion of the second sample. The distance between the original marks (250 mm) was drawn from the said measured value read in 0.5 mm piece, and the _{amount of} elongation W _TD300 (unit is mm) was computed.

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

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

(Color unevenness)

The test piece of length 30cm X width 30cm is cut out from the center part of the width direction of the obtained polarizing film, and it sandwiched between two polarizing plates (43.5% of single transmittance, 99.9% of polarization degree) in the cross nicol state at an angle of 45 degrees. Thereafter, optical color unevenness was observed in the transmission mode using a light box having a surface roughness of 14,000 lx, and the following criteria were 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-L melt 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 is set to 95 degreeC, and it discharges to the cast drum of surface temperature of 80 degreeC from a T-type slit discharge opening (discharge rate 1.3m / Min) and flexible 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). After that, the film was conveyed into a dryer at 130 ° C. at a fixed width of 2.4 m to obtain a polyvinyl alcohol-based film (2.4 m in width, 25 μm in thickness, and 2 km in length). 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 tube in roll shape, and the film winding body was obtained.

(Production of Polarizing Film and Polarizing Plate)

The polyvinyl alcohol-based film thus obtained was stretched 1.7 times in the flow direction (MD) while being swelled by immersion in a water bath at a water temperature of 30 ° C. while being removed from the film recommended body and conveyed in the horizontal direction. In the swelling step, no folds or wrinkles occurred in the film. Then, the film was drawn 1.6 times in the flow direction (MD) while immersed and dyed in an aqueous solution at 30 ° C. composed of 0.5 g / L iodine and 30 g / L potassium iodide. Uniaxially stretched 2.1 times in the flow direction (MD) while immersing in an aqueous solution (50 ° C) having a composition of 40 g / L boric acid and 30 g / L potassium iodide. Finally, it wash | cleaned with the potassium iodide aqueous solution, it dried for 2 minutes at 50 degreeC, and obtained the polarizing film of 5.8 times of total draw ratio. No breakage occurred during the production of this polarizing film. In addition, the characteristic of the obtained polarizing film is as showing in Table 1 of late.

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>

After extending | stretching 1.4 times in the width direction (TD) at 80 degreeC using a drawing machine in Example 1, it carries out except shrinking | contraction and conveyance by stress relaxation to a fixed width of 2.4 m (equivalent to 1.2 times extending | stretching) at 130 degreeC. In the same manner as in Example 1, a polyvinyl alcohol 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>

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, using a drawing machine and stretching 1.1 times in the width direction (TD) at 80 ° C., the film formed above was conveyed into a dryer at 135 ° C. at a fixed width of 2.2 m, and then polyvinyl alcohol-based. A film (2.2 m wide, 38 μm thick, 2 km long) was obtained. The characteristic of the obtained polyvinyl alcohol-type film is as showing in Table 1.

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 a later stage.

<Comparative Example 1>

A polyvinyl alcohol film (2 m in width, 30 µm in thickness, 2 km in length) in the same manner as in Example 1 except that the film formed in Example 1 was not stretched in the width direction (TD) using a stretching machine. Got. The characteristic of the obtained polyvinyl alcohol-type film is as showing in Table 1 as follows.

In addition, similarly to Example 1 using the said polyvinyl alcohol-type film, the polarizing film and the polarizing plate were manufactured, and the fold and wrinkles generate | occur | produced in the film in the swelling process. The characteristic of the obtained polarizing film is as showing in following Table 1.

From the result of the said Example and a comparative example, the elongation amount of the longitudinal direction (MD) when the polyvinyl alcohol-type film was immersed in 30 degreeC water for 30 second, and the width direction (TD) when immersed in 30 degreeC water for 300 second It can be seen that the polarizing films obtained from the polyvinyl alcohol-based films of Examples 1 to 3 in which all of the amount of elongation satisfy the above specific range have high polarization characteristics and are uniform without color unevenness.

On the other hand, it turns out that the polarizing film obtained with the polyvinyl alcohol-type film of the comparative example 1 in which the extension amount of the width direction TD is larger than the said specifying range is inferior, and color unevenness is also observed.

In the said Example, although shown 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 be 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, photo Liquid crystal display devices such as albums, thermometers, audio, instruments for automobiles and machinery, sunglasses, anti-glare glasses, stereoscopic glasses, wearable displays, reflection reduction layers for display elements (CRT, LCD, organic EL, electronic paper, etc.), optical communication devices, It is preferably used for medical devices, building materials, toys and the like.

Claims (7)

In the long polyvinyl alcohol-type film whose thickness is 40 micrometers or less,
About the rectangular 1st sample of the width direction 40mm x length direction 270mm cut out from the width direction center part of this polyvinyl alcohol-type film,
The amount of elongation W _MD30 of the said longitudinal direction in the part of 250 mm except the longitudinal direction both ends before immersion when this 1st sample was immersed in 30 degreeC water for 30 second is 30 mm or more and 50 mm or less,
On the other hand, about the rectangular 2nd sample of the width direction 270mm x length direction 40mm cut out from the width direction center part of the said polyvinyl alcohol-type film,
When the second sample was immersed in water at 30 ° C. for 300 seconds, the amount of elongation W _TD300 in the width direction in the 250 mm portion except the width direction both ends before immersion was 15 mm or more and 60 mm or less. . The method according to claim 1,
The polyvinyl alcohol-based film, characterized in that the width of the polyvinyl alcohol-based film is 2m or more. The polyvinyl alcohol-type film of Claim 1 or 2 is used, The polarizing film characterized by the above-mentioned. The polarizing film of Claim 3 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,
The length before immersion when the first sample was immersed in water at 30 ° C. for 30 seconds for a rectangular first sample having a width direction of 40 mm × a flow direction of 270 mm to be cut out from the width direction center part of the polyvinyl alcohol-based film to be produced. The amount of elongation W _MD30 in the longitudinal direction in the 250 mm portion excluding the both ends in the direction should be 30 mm or more and 50 mm or less,
On the other hand, with respect to the rectangular 2nd sample of the width direction 270mm x flow direction 40mm cut out from the width direction center part of the polyvinyl alcohol-type film manufactured, the immersion when this second sample was immersed in 30 degreeC water for 300 second. A method for producing a polyvinyl alcohol-based film, characterized in that the _amount of elongation W _TD300 in the width direction in a portion of 250 mm except for the full width direction both ends is 15 mm or more and 60 mm or less. The method according to claim 5,
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 5 or 6,
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.