KR102400213B1 - Polyvinyl alcohol polymer film and method for producing same - Google Patents

Abstract

The present invention is a PVA film having a thickness of 50 µm or less, and when a sample of the PVA film is immersed in water at 30°C for 30 seconds, the amount of elongation in the longitudinal direction in a portion of 250 mm in the longitudinal direction before immersion (W _MD30 ) is They are 35 mm or more and 60 mm or less, and the extension amount (W _TD300 ) of the width direction in the part of 250 mm of width directions before immersion when the sample of the said PVA film is immersed in 30 degreeC water for 300 second is 53 mm or more and 65 mm It is the following PVA film.

Description

Polyvinyl alcohol-type polymer film and its manufacturing method

The present invention relates to a polyvinyl alcohol-based polymer film having a thickness of 50 µm or less (hereinafter, “polyvinyl alcohol-based polymer” may be abbreviated as “PVA”), a manufacturing method thereof, and a polarizing film manufactured from the PVA film It relates to optical films, such as.

A polarizing plate having a light transmission and shielding function is an important component of a liquid crystal display device (LCD) together with a liquid crystal having a light switching function and the like. The fields of application of this LCD range from small devices such as electronic desk calculators and wrist watches in the early stages of development to notebook PCs, liquid crystal monitors, liquid crystal color projectors, liquid crystal televisions, in-vehicle navigation systems, mobile phones, and measuring instruments used indoors and outdoors. It is expanding into several fields. In particular, in uses, such as a wall-mounted television and a mobile phone, thickness reduction of LCD is strongly calculated|required from a viewpoint of weight reduction, cost reduction, etc., and thickness reduction of a polarizing plate is effective for this.

A polarizing plate generally unwinds a long PVA film wound in roll shape, uniaxially stretches it, then dyes it using iodine or a dichroic dye, dyes the unwound PVA film, and uniaxially stretches it A polarizing film is manufactured by the method of performing a fixation process with a boron compound, the method of performing a fixation process simultaneously with dyeing in any of the above methods, and a cellulose triacetate film or acetic acid butyric acid on one side or both surfaces of the polarizing film obtained thereby It is industrially manufactured by bonding protective films, such as a cellulose film.

For thinning the polarizing plate, thinning of the protective film, which accounts for a majority of the thickness of the polarizing plate, is effective. However, since the shrinkage stress is large in a polarizing film manufactured using a PVA film having a conventional thickness, if only the protective film is thinned, the entire polarizing plate is deformed. There is an easy problem. About this problem, using a thinner PVA film as a raw film, and thinning polarizing film itself is considered.

By the way, as a PVA film which is excellent in stretchability and can obtain a polarizing film with little dyeing nonuniformity (uniformity in the width direction of orthogonal transmittance), the width when the film is immersed in 30 degreeC water for 5 minutes and made to swell (TD) ) The PVA film in which the ratio (X _TD /X _MD ) of the swelling degree (X _TD ) in the direction and the swelling degree (X _MD ) in the machine (MD) direction is in the range of 1.000 to 1.020 is known (refer to Patent Document 1).

Japanese Patent Laid-Open No. 2012-32789

Usually, when a PVA film is immersed in water, it swells and stretches in the longitudinal and width directions, but in a thin PVA film, due to the fast drying rate in the film forming process, the width at the time of swelling is greater than that of a relatively thick PVA film The amount of extension in the longitudinal direction at the time of swelling with respect to the amount of extension in the direction tends to be relatively small. Here, by changing the crystallinity of the PVA film by changing the heat treatment conditions or the like, it is possible to increase or decrease the elongation amount in both the longitudinal direction and the width direction at the time of swelling. However, in a thin PVA film, if the amount of elongation in the longitudinal direction is set to be greater than or equal to a specific value in order to improve the stretchability, the elongation in the width direction becomes too large, for example, polarized light in the conventionally used polarizing film manufacturing apparatus. When manufacturing a film, the edge part of the swollen PVA film hits the wall of an apparatus, and an edge part abnormality becomes easy to generate|occur|produce. On the other hand, when the amount of elongation in the width direction is set to be less than or equal to a specific numerical value for the purpose of eliminating more than the edge portion, the amount of elongation in the longitudinal direction becomes too small, and stretchability decreases, and in some cases, non-uniformity of dyeing tends to occur in the polarizing film obtained. Therefore, the thin PVA film which can manufacture easily the thin PVA film which is excellent in stretchability and the edge part abnormality does not generate|occur|produce easily at the time of use, and also the thin polarizing film in which dyeing nonuniformity was reduced is the acquisition It is difficult, and this is not achieved even by the description of Patent Document 1 described above.

Therefore, the present invention provides a thin PVA film that is excellent in stretchability and less prone to end abnormalities during use, preferably a thin PVA film that can easily produce a thin polarizing film with reduced dyeing unevenness aim to do Moreover, this invention aims at providing optical films, such as a polarizing film manufactured from the said PVA film.

As a result of repeated intensive studies to achieve the above object, the present inventors have adjusted the amount of elongation in the longitudinal direction (MD) in a thin PVA film to a specific range when immersed in water at 30°C for 30 seconds to a specific range. , when the amount of elongation in the width direction (TD) when immersed in water at 30 ° C. for 300 seconds is adjusted to a specific range, despite the thin PVA film, the stretchability is excellent, and the end abnormality does not occur easily during use, Moreover, it discovered that it became the PVA film which can manufacture easily the thin polarizing film by which dyeing|dyeing nonuniformity was reduced. Further, the present inventors, in manufacturing a thin PVA film using a film forming apparatus having a plurality of drying rolls and a plurality of heat treatment rolls whose rotation shafts are parallel to each other, a heat treatment roll located on the upstream side and a heat treatment roll located on the most downstream side By making the ratio of the circumferential speed between the heat treatment rolls positioned on the side into a specific range, and making the surface temperature of the heat treatment roll into a specific range, it is found that the PVA film can be smoothly and continuously manufactured with good productivity. paid The inventors of the present invention completed further studies based on these findings and completed the present invention.

That is, the present invention is

[1] A PVA film having a thickness of 50 µm or less, when a sample of the PVA film is immersed in water at 30°C for 30 seconds, the amount of elongation in the longitudinal direction in a portion of 250 mm in the longitudinal direction before immersion (W _MD30 ) is 35 mm or more and 60 mm or less, and the amount of extension (W _TD300 ) in the width direction in the part of 250 mm in the width direction before immersion when the sample of the said PVA film is immersed in 30 degreeC water for 300 second is 53 mm or more and 65 mm or less , PVA film;

[2] The PVA film of the above [1], wherein the width is 2 m or more;

[3] The PVA film of the above [1] or [2], which is a raw film for optical film production;

[4] The PVA film of the above [3], wherein the optical film is a polarizing film;

[5] A method for producing a PVA film having a thickness of 50 µm or less, using a film forming apparatus having a drying roll and a heat treatment roll whose rotational axes are parallel to each other, and forming a film containing PVA on the first dry roll of the film forming apparatus The stock solution is discharged into a film and dried, and further dried with a drying roll following it, and then heat treated with a plurality of heat treatment rolls to prepare a PVA film, wherein the heat treatment roll located on the upstream side is heated with a heat treatment roll ( A) and when the heat treatment roll located on the most downstream side is the heat treatment roll (B), the volatile fraction of the PVA film immediately before contacting the heat treatment roll (A) is 3% by mass or more and 7% by mass or less , the ratio (SB /S _A ) of the circumferential speed S _B of the heat treatment roll B to the circumferential speed S _A of the heat treatment roll _A is 0.999 or less, and heat treatment from the heat treatment roll A The manufacturing method whose surface temperature of each heat treatment roll up to the roll (B) is all 87 degreeC or more and 121 degrees C or less;

[6] When the dry roll when the volatile matter ratio of the PVA film becomes 12 mass% is the dry roll (X), and the dry roll positioned immediately before the heat treatment roll (A) is the dry roll (Y), 1 The surface temperature of each drying roll from the drying roll to the drying roll (X) is 70 degreeC or more, and the surface temperature of each drying roll from the drying roll located immediately after the drying roll (X) to the drying roll (Y) is 70 degreeC or more The production method according to the above [5], wherein all are 40°C or more and less than 70°C;

[7] The above [5] or [6], wherein the ratio ( _SB /S ₁ ) of the peripheral speed (SB ) of the heat treatment roll ( _B ) to the peripheral speed (S ₁ ) of the first drying roll is 0.900 or more and 1.050 or less manufacturing method;

[8] When the dry roll positioned immediately before the heat treatment roll (A) is the dry roll (Y), between the first dry roll and the dry roll (Y), the front and back of the PVA film for each dry roll The manufacturing method in any one of said [5]-[7] which opposes both surfaces alternately;

[9] The manufacturing method in any one of said [5]-[8] which is a manufacturing method of the raw film for optical film manufacture;

[10] The manufacturing method of the above [9], wherein the optical film is a polarizing film;

[11] an optical film prepared from the PVA film of [3] above;

[12] A polarizing film produced from the PVA film of [4] above;

is about

According to the present invention, a thin PVA film capable of easily producing a thin polarizing film with excellent stretchability, less edge abnormality during use, and reduced dyeing unevenness, and a PVA film manufactured from the PVA film Optical films, such as a polarizing film, are provided. Moreover, according to this invention, the manufacturing method of the PVA film which can manufacture the said PVA film continuously with favorable productivity smoothly is provided.

Hereinafter, the present invention will be described in detail.

[PVA Film]

The PVA film of the present invention has a thickness of 50 µm or less. And as for the PVA film of this invention, when the sample is immersed in 30 degreeC water for 30 second, the extension amount (W _MD30 ) of the longitudinal direction in the part of 250 mm of longitudinal directions before immersion is 35 mm or more and 60 mm or less. Moreover, as for the PVA film of this invention, when the sample is immersed in 30 degreeC water for 300 second, the extension amount ( _WTD300 ) of the width direction in the part of 250 mm in the width direction before immersion exceeds 53 mm, and 65 mm or less am.

For the PVA film of the present invention, since a thin optical film can be obtained, etc., the thickness needs to be 50 µm or less, the thickness is preferably 45 µm or less, more preferably 40 µm or less, and 35 µm or less More preferably, it is especially preferable that it is 30 micrometers or less, and 20 micrometers or less may be sufficient. Thus, in a thinner PVA film, the effect of this invention becomes more remarkable. On the other hand, the lower limit of the thickness of the PVA film is not particularly limited, but considering the handleability of the PVA film, the process passability at the time of manufacturing the optical film, the optical performance of the obtained optical film (polarization performance of the polarizing film, etc.), the thickness It is preferable that it is 3 micrometers or more, It is more preferable that it is 5 micrometers or more, It is still more preferable that it is 7 micrometers or more, It is especially preferable that it is 10 micrometers or more. The thickness of a PVA film can measure the thickness of 5 arbitrary points, and can be calculated|required as the average value.

The amount of extension of the longitudinal direction (MD) when the PVA film of this invention is immersed in 30 degreeC water for 30 second exists in the specific range. When the sample cut out from the PVA film of this invention is specifically, immersed in 30 degreeC water for 30 second, the extension amount (W _MD30 ) of the longitudinal direction in the part of 250 mm of longitudinal directions before immersion is 35 mm or more and 60 mm or less is within the scope of When W _MD30 is less than 35 mm, plasticization of the film becomes insufficient due to insufficient swelling of the PVA film during use, and the stretchability is lowered. From this viewpoint, it is preferable that W _MD30 is 37 mm or more, It is more preferable that it is 39 mm or more, It is more preferable that it is 42 mm or more. In addition, when W _MD30 exceeds 60 mm, the swelling degree of the PVA film tends to be excessive, and wrinkles or folds occur in the PVA film due to the sagging of the PVA film generated thereby, and the possibility that the PVA film may break as it becomes the starting point. There is this. From this viewpoint, it is preferable that W _MD30 is 55 mm or less, It is more preferable that it is 50 mm or less, It is still more preferable that it is 47 mm or less, It is especially preferable that it is 46 mm or less. Moreover, although _WMD30 prescribes|regulates the amount of elongation when a sample is immersed in 30 degreeC water for 30 second, when this uses a thin PVA film to manufacture optical films, such as a polarizing film, a thin PVA film melt|dissolves A shorter time is often employed as the process time in the process performed before the stretching process, such as the swelling process, from the viewpoint of preventing am.

Moreover, the amount of extension of the width direction (TD) when the PVA film of this invention is immersed in 30 degreeC water for 300 second exists in the specific range. When the sample cut out from the PVA film of this invention is specifically, immersed in 30 degreeC water for 300 second, the extension amount (W _TD300 ) of the width direction in the part of 250 mm in the width direction before immersion is 53 mm or more and 65 mm or less is within the scope of If W _TD300 is less than 53 mm, it will be easy to generate|occur|produce dyeing nonuniformity in the polarizing film obtained. From this viewpoint, it is preferable that W _TD300 is 54 mm or more, It is more preferable that it is 55 mm or more, It is more preferable that it is 57 mm or more. Moreover, when _WTD300 exceeds 65 mm, a PVA film spreads too much in the width direction at the time of use, and edge part abnormality, such as a film|membrane fold, arises easily. From this viewpoint, it is preferable that W _TD300 is 62 mm or less, and it is more preferable that it is 60 mm or less. Moreover, although the amount of extension when a sample is immersed in 30 degreeC water for 300 second in _WTD300 is prescribed|regulated, this is because this _WMD300 and the edge part at the time of use are correlated with the dyeing|dyeing nonuniformity of the polarizing film obtained.

Said W _MD30 can be calculated|required with the following method. That is, first, the rectangular sample of 270 mm of width direction (TD) 40mm x length direction (MD) is cut out from the PVA film made into measurement object. What is necessary is just to cut out the said sample here from the width direction center part of the PVA film used as object, for example. Next, marks are placed on the inside by 10 mm from both ends of the sample having a length of 270 mm by using oily magic (thickness of the line is 0.3 mm). The outer part is sandwiched from the marked line at both ends with a commercially available clip (chuck width 40 mm, mass 7.8 g (weight 7.3 g in water)), and one clip is fixed with a rod-shaped jig such as a wire wire. After confirming that the distance between the marks is 250 mm, place the sample with a clip into pure water stored in a cylindrical transparent water tank (such as a scalpel cylinder) and temperature-controlled at 30 ° C. is immersed vertically (vertically). Immediately after immersion, a rod-shaped jig is hung on the upper part of the water tank to fix the long side of the sample so that it becomes vertical (vertical). Then, a metal ruler is immersed in water, and the distance between marks is measured 30 second after immersion of a sample. The amount of extension (W _MD30 ) (unit: mm) is calculated by subtracting the original distance between the marks (250 mm) from the measured value read at 0.5 mm intervals.

On the other hand, W _TD300 can be calculated|required by the following method. That is, first, a rectangular sample of 270 mm in the width direction (TD) × 40 mm in the longitudinal direction (MD) is cut out from the PVA film made into the measurement object. What is necessary is just to cut out the said sample here from the width direction center part of the PVA film used as object, for example. Next, marks are placed on the inside by 10 mm from both ends of the sample having a length of 270 mm by using oily magic (thickness of the line is 0.3 mm). The outer part is sandwiched from the marked line at both ends with a commercially available clip (chuck width 40 mm, mass 7.8 g (weight 7.3 g in water)), and one clip is fixed with a rod-shaped jig such as a wire wire. After confirming that the distance between the marks is 250 mm, place the sample with a clip into pure water stored in a cylindrical transparent water tank (such as a scalpel cylinder) and temperature-controlled at 30 ° C. is immersed vertically (vertically). Immediately after immersion, a rod-shaped jig is hung on the upper part of the water tank to fix the long side of the sample so that it becomes vertical (vertical). Then, a metal ruler is immersed in water, and the distance between marks is measured 300 second after immersion of a sample. An amount of extension (W _TD300 ) (unit: mm) is calculated by subtracting the original distance between marks (250 mm) from the measured value read at 0.5 mm intervals.

As PVA which comprises the PVA film of this invention, what is manufactured by saponifying the polyvinyl ester type polymer obtained by superposing|polymerizing a vinyl ester can be used. Examples of the vinyl ester include vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl pivalate, and vinyl versatate. Among the vinyl esters, vinyl acetate is preferred from the viewpoints of availability, cost, and ease of production of PVA.

The polyvinyl ester-based polymer is preferably obtained by using only one or two or more vinyl esters as a monomer, and more preferably obtained by using only one vinyl ester as a monomer, but one or two or more vinyl esters and a copolymer of another monomer copolymerizable therewith may be used.

As another monomer copolymerizable with such vinyl ester, For example, ethylene; C3-C30 olefins (alpha-olefin etc.), such as propylene, 1-butene, and isobutene; Acrylic acid or its salt; acrylic acid esters such as methyl acrylate, ethyl acrylate, n-propyl acrylate, i-propyl acrylate, n-butyl acrylate, i-butyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, and octadecyl acrylate; methacrylic acid or its salt; Methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, i-propyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, t-butyl methacrylate, 2- methacrylic acid methacrylic acid esters such as ethylhexyl, dodecyl methacrylate, and octadecyl methacrylate; acrylamide; N-methylacrylamide, N-ethylacrylamide, N,N-dimethylacrylamide, diacetoneacrylamide, acrylamidepropanesulfonic acid or a salt thereof, acrylamidepropyldimethylamine or a salt thereof, N-methylolacrylamide or its salt acrylamide derivatives such as derivatives; methacrylamide; methacrylamide derivatives such as N-methylmethacrylamide, N-ethylmethacrylamide, methacrylamidepropanesulfonic acid or a salt thereof, methacrylamidepropyldimethylamine or a salt thereof, N-methylolmethacrylamide or a derivative thereof; N-vinylamide, such as N-vinylformamide, N-vinylacetamide, and N-vinylpyrrolidone; Vinyls such as methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, n-butyl vinyl ether, i-butyl vinyl ether, t-butyl vinyl ether, dodecyl vinyl ether, and stearyl vinyl ether ether; vinyl cyanide, such as acrylonitrile and methacrylonitrile; vinyl halides such as vinyl chloride, vinylidene chloride, vinyl fluoride, and vinylidene fluoride; allyl compounds such as allyl acetate and allyl chloride; Maleic acid or its salt, ester, or acid anhydride; Itaconic acid or its salt, ester, or acid anhydride; vinylsilyl compounds such as vinyltrimethoxysilane; Isopropenyl acetate, etc. are mentioned. The polyvinyl ester-based polymer may have a structural unit derived from one or two or more of these other monomers.

The proportion of the structural units derived from the other monomers in the polyvinyl ester-based polymer is preferably 15 mol% or less, and 10 mol% or less, based on the number of moles of all the structural units constituting the polyvinyl ester-based polymer. It is more preferable, and it is still more preferable that it is 5 mol% or less.

The said PVA may be modified|denatured with 1 type, or 2 or more types of graft copolymerizable monomers. As the said graft copolymerizable monomer, For example, unsaturated carboxylic acid or its derivative(s); Unsaturated sulfonic acid or its derivative(s); C2-C30 (alpha)-olefin etc. are mentioned. It is preferable that the ratio of the structural unit derived from the monomer which can be graft copolymerized in PVA is 5 mol% or less based on the mole number of all the structural units which comprise PVA.

As for the said PVA, a part of the hydroxyl group may be bridge|crosslinked and it is not necessary to bridge|crosslink. Moreover, in said PVA, a part of the hydroxyl group may react with aldehyde compounds, such as acetaldehyde and butylaldehyde, etc. to form an acetal structure, and it does not need to form an acetal structure without reacting with these compounds.

The degree of polymerization of PVA is not particularly limited, but from the viewpoint of the strength of the PVA film or durability of an optical film produced from the PVA film, it is preferably 500 or more, more preferably 1,000 or more, still more preferably 1,500 or more, and 2,000 or more. It is particularly preferred. On the other hand, if the degree of polymerization is too high, it tends to lead to an increase in manufacturing cost and poor process passability at the time of film forming. Therefore, the degree of polymerization of PVA is preferably 10,000 or less, more preferably 9,000 or less, still more preferably 8,000 or less. , 7,000 or less are particularly preferred. In addition, the polymerization degree of PVA in this specification means the average degree of polymerization measured according to description of JISK6726-1994.

The degree of saponification of PVA is not particularly limited, but from the viewpoints of optical performance and durability of the optical film produced from the PVA film, it is preferably 90 mol% or more, more preferably 95 mol% or more, and furthermore, 98 mol% or more. It is preferable, and it is especially preferable that it is 99 mol% or more, and 99.2 mol% or more may be sufficient. On the other hand, when the dyeability with respect to a PVA film is considered, it is preferable that the saponification degree of PVA is 99.99 mol% or less. Incidentally, the degree of saponification of PVA in the present specification refers to the number of moles of the structural units (typically vinyl ester units) and vinyl alcohol units that PVA has that can be converted to vinyl alcohol units by saponification and the vinyl alcohol units. refers to the ratio (mol%) occupied by the number of moles of The saponification degree of PVA can be measured according to description of JISK6726-1994.

Said PVA may be used individually by 1 type of PVA, and may use together 2 or more types of PVA from which the kind of modification|denaturation, modification rate, polymerization degree, saponification degree, etc. mutually differ. However, in cases where excellent secondary workability is required for the PVA film of the present invention, such as when used as a raw film for manufacturing an optical film, the PVA film is PVA having an acidic functional group such as a carboxyl group or a sulfonic acid group; PVA having an acid anhydride group; PVA which has basic functional groups, such as an amino group; When PVA which has a functional group which accelerates|stimulates a crosslinking reaction, such as these neutralized products, is included, the secondary workability of a PVA film may fall by the crosslinking reaction between PVA molecules. Therefore, in the case as described above, the PVA film preferably does not contain all of PVA having an acidic functional group, PVA having an acid anhydride group, PVA having a basic functional group, and neutralized products thereof. As PVA, only vinyl ester is a monomer PVA prepared by saponifying the polyvinyl ester polymer obtained by using It is more preferable to include, as PVA, PVA prepared by saponifying a polyvinyl ester-based polymer obtained by using only vinyl ester as a monomer, and/or a polyvinyl ester-based polymer obtained by using only vinyl ester and ethylene as a monomer as a monomer. It is more preferable to include only the PVA produced by doing so.

It is preferable to exist in the range of 50-100 mass %, as for the content rate of PVA in a PVA film, it is more preferable to exist in the range of 80-100 mass %, It is more preferable to exist in the range which is 85-100 mass %.

It is preferable that the PVA film of this invention contains a plasticizer from the point which can improve mechanical properties, such as impact strength, process passability, etc. at the time of secondary processing. A polyhydric alcohol is preferably used as a plasticizer, For example, ethylene glycol, glycerol, diglycerol, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, trimethylol propane, etc. are mentioned. The PVA film of this invention can contain the 1 type(s) or 2 or more types of these plasticizers. Among these plasticizers, at the time of extending|stretching and using the PVA film of this invention, 1 type(s) or 2 or more types are preferable at the point excellent in the extending|stretching improvement effect of glycerol, diglycerol, and ethylene glycol.

It is preferable that content of the plasticizer in a PVA film is 1 mass part or more with respect to 100 mass parts of PVA contained in a PVA film, It is more preferable that it is 3 mass parts or more, It is still more preferable that it is 5 mass parts or more, 30 It is preferable that it is mass part or less, It is more preferable that it is 25 mass parts or less, It is more preferable that it is 20 mass parts or less. When the said content is 1 mass part or more, the ductility of a PVA film can be improved more. On the other hand, when the said content is 30 mass parts or less, the handleability of a PVA film improves.

It is preferable that the PVA film of this invention contains surfactant from viewpoints, such as the improvement of the handleability and the peelability from the film forming apparatus at the time of manufacturing a PVA film. There is no limitation in particular in the kind of surfactant, For example, anionic surfactant, nonionic surfactant, etc. are mentioned.

As anionic surfactant, For example, Carboxylic acid types, such as potassium laurate; Sulfuric acid ester types, such as octyl sulfate; Sulfonic acid types, such as dodecylbenzenesulfonate, etc. are mentioned.

As a nonionic surfactant, For example, alkyl ether types, such as polyoxyethylene oleyl ether; Alkylphenyl ether types, such as polyoxyethylene octylphenyl ether; Alkyl ester types, such as polyoxyethylene laurate; Alkylamine types, such as polyoxyethylene laurylamino ether; Alkylamide types, such as polyoxyethylene lauric acid amide; polypropylene glycol ether types such as polyoxyethylene polyoxypropylene ether; Alkanolamide types, such as lauric-acid diethanolamide and oleic-acid diethanolamide; Allylphenyl ether types, such as polyoxyalkylene allylphenyl ether, etc. are mentioned.

The PVA film of this invention can contain 1 type(s) or 2 or more types of these surfactant. Among these surfactants, nonionic surfactants are preferable, particularly alkanolamide surfactants are more preferable, and aliphatic carboxylic acids (for example, having 8 carbon atoms) Dialkanolamides (eg, diethanolamide, etc.) of -30 saturated or unsaturated aliphatic carboxylic acid etc.) are more preferable.

Since content of surfactant in a PVA film can reduce the handleability of a PVA film and the peelability from the film forming apparatus at the time of manufacturing a PVA film more, and can reduce generation|occurrence|production of a blocking, PVA It is preferable that it is 0.01 mass part or more with respect to 100 mass parts of PVA contained in a film, It is more preferable that it is 0.02 mass part or more, It is still more preferable that it is 0.05 mass part or more, It is also preferable that it is 1 mass part or less, 0.5 mass part It is more preferable that it is less than, and it is still more preferable that it is 0.3 mass part or less.

The PVA film of the present invention contains, if necessary, various additives such as stabilizers (antioxidants, ultraviolet absorbers, heat stabilizers, etc.), compatibilizers, antiblocking agents, flame retardants, antistatic agents, lubricants, dispersants, fluidizing agents, and antibacterial agents. may be doing The PVA film of the present invention may contain one or more of these additives.

It is preferable that the volatile fraction of a PVA film exists in the range of 1 mass % or more and 5 mass % or less from a viewpoint of the handleability etc., It is more preferable that the said volatile matter rate is 2 mass % or more, and it is 4 mass % or less more preferably. The volatile fraction of a PVA film can be calculated|required by carrying out similarly to the volatile fraction of a PVA film mentioned later.

The shape of the PVA film of the present invention is not particularly limited, but a more uniform PVA film can be continuously and smoothly produced, and can be used continuously even in the case of manufacturing an optical film such as a polarizing film using it. It is preferable that it is a long film from a point. It is preferable to make a long film into the form of a film roll, such as winding up on a cylindrical core. In the case of a long film, the length of the PVA film (length in the longitudinal direction (MD)) is not particularly limited, and can be appropriately set depending on the use, etc., but the length of the PVA film in the case of continuously unwinding it from a film roll and the like Since the loss when switching the film roll can be reduced as is longer, the length is preferably 5 m or more, more preferably 100 m or more, still more preferably 500 m or more, particularly preferably 1,000 m or more, 5,000 m or more, and further 8,000 m or more may be sufficient. Although there is no restriction|limiting in particular in the upper limit of the said length, The said length is 50,000 m or less, Furthermore, it can be made into 20,000 m or less, for example.

The width of the PVA film of the present invention is not particularly limited, and can be appropriately set depending on the use of the PVA film or an optical film such as a polarizing film produced therefrom. In this case, if the width of the PVA film is 2 m or more, more preferably 3 m or more, and still more preferably 4 m or more, it is preferable for these applications. On the other hand, when the width of the PVA film is too wide, it tends to be difficult to uniformly perform uniaxial stretching itself when manufacturing an optical film with an apparatus that is put into practical use, so the width of the PVA film is preferably 8 m or less, 7 m or less, and further 6 m or less may be sufficient.

[Method for producing PVA film]

Although the manufacturing method of the PVA film of this invention is not specifically limited, According to the manufacturing method of the following this invention, the PVA film of this invention can be manufactured continuously with favorable productivity smoothly.

That is, the manufacturing method of the present invention for producing a PVA film having a thickness of 50 µm or less uses a film forming apparatus having a drying roll and a heat treatment roll whose rotational axes are parallel to each other, and on the first dry roll of the film forming apparatus. The film forming undiluted solution containing PVA is discharged into a film, dried, and further dried with a drying roll following it, and then heat-treated with a plurality of heat treatment rolls to produce a PVA film, wherein a heat treatment roll located on the upstream side is the heat treatment roll (A), and when the heat treatment roll located on the most downstream side is the heat treatment roll (B), the volatile fraction of the PVA film immediately before contacting the heat treatment roll (A) is 3 mass% or more 7 mass% or less, the ratio ( _SB /SA) of the circumferential speed ( _SB ) of the heat treatment roll ( _B ) to the circumferential speed (SA) of the heat treatment roll ( _A ) is 0.999 or less, and the heat treatment roll ( All of the surface temperatures of the heat treatment rolls from A) to the heat treatment roll (B) are 87°C or more and 121°C or less.

In a film forming apparatus having a drying roll and a heat treatment roll whose rotational axes are parallel to each other, used for the production of the PVA film, from the viewpoint of obtaining a more uniform PVA film, the number of the drying rolls is preferably 4 or more, It is more preferable that it is 5 or more, It is still more preferable that it is 6 or more, It is especially preferable that it is 8 or more, It is preferable that it is 30 or less, It is more preferable that it is 20 or less. In addition, in the present specification, the drying roll (drying roll for discharging the film forming undiluted solution) located on the upstream side among the drying rolls is referred to as a first drying roll, and for the remaining drying rolls, the order is from the first drying roll to the downstream side. As is, the second dry roll, the third dry roll, the fourth dry roll, ... is called In addition, the dry roll when the volatile fraction of the PVA film|membrane during film forming became 12 mass % (when it became 12 mass % between two dry rolls, the dry roll on the downstream side of it) is called "dry roll (X)", , the dry roll positioned immediately before the heat treatment roll is called a “dry roll (Y)”.

In addition, in the film forming apparatus, the number of heat treatment rolls is not particularly limited as long as it is two or more, but from the viewpoint of uniformly heat-treating the front and back surfaces of the PVA film, the number of heat treatment rolls is preferably three or more, It is more preferable that it is 4 or more, Moreover, it is preferable that it is 10 or less, It is more preferable that it is 8 or less. In addition, as described above, in this specification, among the heat treatment rolls, the heat treatment roll located on the most upstream side is referred to as "heat treatment roll (A)", and the heat treatment roll located on the most downstream side is referred to as "heat treatment roll (B)" )” is called.

It is preferable that the drying roll and/or the heat treatment roll are formed from, for example, a metal such as nickel, chromium, copper, iron, or stainless steel, and in particular, the surface of the roll is not easily corroded and has a mirror gloss. It is more preferable that it is formed from the metal material which has. In addition, in order to increase the durability of the drying roll and/or heat treatment roll, a roll plated with a single layer or a combination of two or more layers of a nickel layer, a chromium layer, a nickel/chromium alloy layer, etc. is used as the drying roll and/or heat treatment roll It is preferable to do

In drying the PVA film using a plurality of drying rolls, the PVA film can be dried more uniformly, and in particular, the difference in physical properties between the front and back surfaces of the PVA film can be reduced. From being able to prevent curling, etc., between the 1st drying roll and the drying roll (Y) WHEREIN: It is preferable to make the front and back both surfaces of a PVA film|membrane oppose alternately with respect to each drying roll. That is, as the direction of the PVA film in the process from the first drying roll to the drying roll (Y), in any part of the PVA film, the film surface in contact with the first drying roll (the first drying roll contact surface), and the first It is preferable to dry so that the film surface (1st dry roll non-contact surface) which does not contact a drying roll may oppose each drying roll from a 1st drying roll to the drying roll (Y) alternately.

Moreover, even when heat-processing a PVA film|membrane using several heat treatment rolls, from the fact that heat treatment can be performed more uniformly, etc., between the heat treatment rolls (A) and the heat treatment rolls (B), each It is preferable to alternately oppose the front and back surfaces of the PVA film with respect to the heat treatment roll.

In the said manufacturing method, the film forming undiluted|stock solution containing PVA is discharged in the form of a film on the 1st drying roll of a film forming apparatus, and it is dried. In discharging the film forming undiluted solution, for example, using a known film discharging device (membrane casting device) such as a T-type slit die, a hopper plate, an I-die, and a lip coater die, the film forming undiluted solution is first What is necessary is just to discharge (cast) in a film|membrane form on a dry roll. At this time, the thickness of the PVA film obtained can be adjusted by adjusting the discharge amount by adjusting a film|membrane discharge apparatus etc.

The film forming undiluted solution containing PVA can be prepared by mixing PVA with a liquid medium to make a solution, or melting PVA chips containing a liquid medium etc. to make a molten solution. Preparation of the film forming undiluted|stock solution can be performed using a stirring type mixing apparatus, a melt extruder, etc. Examples of the liquid medium include water, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, ethylenediamine, and diethylenetriamine. Species may be used individually, or 2 or more types may be used together. Among these, water, dimethyl sulfoxide, or a mixture of both is preferably used, and especially water is used more preferably.

It is preferable to mix|blend 1 type, or 2 or more types of a plasticizer, surfactant, various additives, etc. which were mentioned above in description of a PVA film in an above-mentioned amount to a film forming undiluted|stock solution, if desired.

The volatile fraction of the film forming undiluted solution is preferably in the range of 50 mass% or more and 90 mass% or less, and the volatile fraction is more preferably 55 mass% or more, and more preferably 80 mass% or less. When the volatile fraction is too low, the viscosity of the film forming undiluted solution becomes too high, and film forming may become difficult. On the other hand, when the said volatile matter rate is too high, the uniformity of the thickness of the PVA film obtained may be impaired. In addition, the "volatile fraction of a film forming undiluted solution" as used in this specification means the volatile fraction calculated|required by following formula (1).

Volatile fraction (mass %) of the undiluted film forming solution = 100 × (W _a - W _b )/W _a (1)

(Here, W _a represents the mass (g) of the film forming undiluted solution, and W _b represents the mass (g) of the film forming undiluted solution of _Wa (g) dried in an electrothermal dryer at 105°C for 16 hours.)

The surface temperature of the first drying roll is preferably in the range of 80°C or more and 120°C or less from the viewpoint of uniformity of drying of the PVA film, productivity, etc., the surface temperature is more preferably 85°C or more, and 90°C It is still more preferable that it is more than, it is especially preferable that it is 93 degreeC or more, It is more preferable that it is 105 degrees C or less, It is more preferable that it is 99 degrees C or less. When the said surface temperature is 80 degreeC or more, the drying efficiency on a 1st drying roll improves. On the other hand, when the said surface temperature is 120 degrees C or less, foaming of a PVA film|membrane can be suppressed more effectively.

Drying on the first drying roll of the film forming undiluted solution discharged into the film may be performed only by heat from the first drying roll, and while heating with the first drying roll, hot air is sprayed on the non-contact surface of the first drying roll, or It is preferable from points, such as uniform drying property and drying speed, to apply heat from both surfaces of a PVA film|membrane and to dry by heating with an infrared heater from the non-contacting surface side of a drying roll, etc. Further, the PVA film may be heated by a dielectric heating device.

The circumferential speed (S ₁ ) of the first drying roll is preferably 8 m/min or more and 30 m/min or less, and 10 m/min or more from the viewpoints of the uniformity of drying of the PVA film, the drying rate, and the productivity of the PVA film. It is more preferable that they are 27 m/min or less, and it is still more preferable that they are 12 m/min or more and 25 m/min or less.

The film forming undiluted solution discharged in the form of a film on the first drying roll is dried on the first drying roll and peeled off from the first drying roll. If the volatile fraction of the PVA film at the time of peeling from the first dry roll is too low, the productivity of the PVA film tends to decrease easily. 1 Peeling from a dry roll becomes difficult easily, and it fractures|ruptures in some cases, or nonuniformity becomes easy to generate|occur|produce. From the above viewpoint, the volatile fraction of the PVA film at the time of peeling from the first dry roll is preferably 13 mass% or more, more preferably 14 mass% or more, still more preferably 15 mass% or more, and 30 It is preferable that it is mass % or less, It is more preferable that it is 27 mass % or less, It is still more preferable that it is 25 mass % or less.

Here, the "volatile fraction of a PVA film|membrane" in this specification means the volatile fraction calculated|required by following formula (2).

Volatile fraction of PVA film (mass %) = 100 × (W _c - W _d )/W _c ｝ (2)

(here, W _c represents the mass (g) of the sample taken from the PVA film, and W _d is the sample W _c (g) put in a vacuum dryer at a temperature of 50° C. and a pressure of 0.1 kPa or less and dried for 4 hours. Mass (g) is indicated.)

The PVA film dried on the first drying roll is peeled off from the first drying roll and further dried, this time with a drying roll following the second drying roll following the first drying roll. In drying with a 2nd drying roll, it is preferable to make a 1st dry roll non-contacting surface of a PVA film|membrane oppose a 2nd drying roll.

In drying the PVA film using a plurality of drying rolls, the surface temperature of each drying roll is not particularly limited, but the surface temperature of each drying roll from the first drying roll to the drying roll (X) is, In view of being able to more efficiently obtain the PVA film of the present invention, all are preferably 70°C or higher, more preferably 72°C or higher, still more preferably 73°C or higher, and more preferably 120°C or lower, and more preferably 105°C. It is more preferable that it is less than or equal to, and it is especially preferable that it is 99 degrees C or less. The surface temperature of each drying roll from the 2nd drying roll to the drying roll (X) is 90 degrees C or less, 85 degrees C or less, and also 80 degrees C or less, in that the PVA film of said this invention can be obtained more efficiently etc. may be

In addition, the surface temperature of each drying roll from the drying roll positioned immediately after the drying roll (X) to the drying roll (Y) can improve the uniformity of drying while maintaining an appropriate drying temperature, and the present invention described above In terms of being able to more efficiently obtain a PVA film of Moreover, it is more preferable that it is 65 degrees C or less, and it is still more preferable that it is 63 degrees C or less.

The PVA film dried with the drying roll is then heat-treated with a plurality of heat treatment rolls. By heat-treating with a plurality of heat treatment rolls, the difference in physical properties of the front and back surfaces of the PVA film can be reduced, and the secondary workability can be improved. The volatile fraction of the PVA film immediately before being subjected to the heat treatment, that is, the PVA film immediately before contacting the heat treatment roll (heat treatment roll (A)) located on the upstream side, is such that heat treatment can be effectively performed, etc. It is necessary that they are 3 mass % or more and 7 mass % or less, It is preferable that the said volatile matter rate is 4 mass % or more, and it is preferable that they are 6 mass % or less. Further, the volatile fraction of the PVA film may be changed during heat treatment.

In the heat treatment of the PVA film using a plurality of heat treatment rolls, the ratio ( _SB /S) of the circumferential speed (S _B ) of the heat treatment roll (B) to the circumferential speed (SA ) of the heat treatment roll ( _A ) _A ) needs to be 0.999 or less. When the said ratio ( _SB /SA) exceeds _{0.999, WMD30 of} the PVA film obtained will fall. It is preferable that it is 0.995 or less, and, as for the said ratio ( _{SB /S A )} , it is more preferable that it is 0.993 or less at the point which can obtain the PVA film of this invention more efficiently. Moreover, it is preferable that it is 0.985 or more, and, as for the said ratio (S _B /S _A ) from a viewpoint of preventing effectively that wrinkles generate|occur|produce in the PVA film obtained, it is more preferable that it is 0.988 or more.

Further, in heat-treating the PVA film using a plurality of heat treatment rolls, the surface temperature of each heat treatment roll from the heat treatment roll (A) to the heat treatment roll (B) is 87°C or more and 121°C or less. need. The value of W _TD300 of the PVA film obtained as the said surface temperature is less than 87 degreeC becomes high too much, and when the said surface temperature exceeds 121 degreeC, the value of W _TD300 of the PVA film obtained becomes low too much. In view of being able to obtain the PVA film of the present invention more efficiently, all of the surface temperatures are preferably 92°C or higher, more preferably 93°C or higher, further preferably 119°C or lower, and more preferably 117°C or lower. And, it is more preferable that it is 114 °C or less.

The surface temperatures of the heat treatment rolls from the heat treatment roll (A) to the heat treatment roll (B) may be the same as each other, or may differ in part or all of them. Similarly, the surface temperature of the heat treatment roll (A) and the heat treatment roll (B) may be the same as or different from each other, but the surface temperature of the heat treatment roll (B) is the surface temperature of the heat treatment roll (A) It is more preferably 5°C or higher, more preferably 10°C or higher, still more preferably 12°C or higher, particularly preferably 15°C or higher, further preferably 25°C or higher, and 20°C or higher high. It is more preferable, and it is still more preferable that it is 18 degrees C or less high.

The ratio ( _SB /S ₁ ) of the peripheral speed (SB) of the heat treatment roll ( _B ) to the peripheral speed (S ₁ ) of the first drying roll is that the above-described PVA film of the present invention can be obtained more efficiently etc., preferably in the range of 0.900 or more and 1.050 or less, the ratio (S _B /S ₁ ) is more preferably 0.920 or more, still more preferably 0.940 or more, particularly preferably 0.950 or more, and 1.020 or less It is more preferable, it is still more preferable that it is 1.010 or less, It is especially preferable that it is 1.000 or less.

The PVA film heat-processed as mentioned above can obtain the PVA film of this invention by performing a humidity control process etc. as needed, and winding up it in roll shape by predetermined length. Moreover, before winding up in roll shape, you may cut|disconnect and remove the width direction both ends (ear) of the said PVA film in any one or several steps after unwinding from the step in roll shape and the roll.

It is preferable to exist in the range of 1 mass % or more and 5 mass % or less, as for the volatile matter rate of the PVA film finally obtained by said series of processes, It is more preferable that the said volatile matter rate is 2 mass % or more, and 4 mass % % or less is more preferable.

[Use of PVA film]

Although there is no particular limitation on the use of the PVA film of the present invention, the PVA film of the present invention is used as a raw film for manufacturing an optical film in that it is excellent in stretchability and does not easily cause an edge abnormality during use. it is preferable As an optical film, a polarizing film, retardation film, etc. are mentioned. In particular, according to the PVA film of the present invention, since a thin polarizing film in which dyeing nonuniformity was reduced can be easily manufactured, it is more preferable to use the PVA film of the present invention as a raw film at the time of manufacturing a polarizing film.

The optical film can be manufactured by the manufacturing method which has the process of uniaxially stretching using the PVA film of this invention, Specifically, performing the PVA film itself of this invention, or the swelling process mentioned later etc. A PVA film derived from the PVA film of the present invention produced with in some cases) can be produced by a method having a step of uniaxially stretching.

The method in particular at the time of manufacturing a polarizing film using the PVA film of this invention as a raw film is not restrict|limited, Any method conventionally employ|adopted may be employ|adopted. In such a method, for example, dyeing and uniaxial stretching are performed on the PVA film based on the present invention, or uniaxial stretching is performed on the PVA film based on the present invention containing a dichroic dye. method can be found. As a more specific method for manufacturing a polarizing film, with respect to the PVA film based on this invention, swelling, dyeing, uniaxial stretching, and a method of further performing a fixing treatment, a drying treatment, a heat treatment, etc. as needed can be heard In this case, the order in particular of each process, such as swelling, dyeing|staining, uniaxial stretching, and a fixing process, is not restrict|limited, One or two or more processes may be implemented simultaneously. Moreover, one or two or more of each process can also be performed twice or more.

Swelling can be performed by immersing the PVA film based on this invention in water. The temperature of water when immersed in water is preferably within the range of 20°C or higher and 40°C or lower, the temperature is more preferably 22°C or higher, further preferably 25°C or higher, and 38°C or lower More preferably, it is still more preferable that it is 35 degrees C or less. Moreover, as time to be immersed in water, for example, it is preferable that it is 0.1 minute or more, It is more preferable that it is 0.3 minute or more, It is preferable that it is 5 minutes or less, It is more preferable that it is 3 minutes or less. In addition, the water at the time of immersion in water is not limited to pure water, The aqueous solution which various components melt|dissolved may be sufficient, and the mixture of water and an aqueous medium may be sufficient.

Dyeing can be performed by making a dichroic dye contact with respect to the PVA film based on this invention. As a dyeing|staining time, any step after uniaxial stretching may be sufficient as it before uniaxial stretching, at the time of uniaxial stretching. Dyeing is generally performed by immersing the PVA film in a solution (especially aqueous solution) containing iodine-potassium iodide as a dyeing bath, and also in the present invention, such a dyeing method is preferably employed. It is preferable that the density|concentration of the iodine in a dyeing bath exists in the range of 0.01 mass % or more and 0.5 mass % or less, and it is preferable that the density|concentration of potassium iodide exists in the range of 0.01 mass % or more and 10 mass % or less. Moreover, it is preferable that the temperature of a dyeing bath shall be 20 degreeC or more and 50 degrees C or less, especially 25 degreeC or more and 40 degrees C or less.

Examples of the dichroic dye include iodine-based dyes and dichroic organic dyes (eg, DirectBlack 17, 19, 154; DirectBrown 44, 106, 195, 210, 223; DirectRed 2, 23, 28, 31, 37, 39, 79, 81, 240, 242, 247 ; DirectBlue 1, 15, 22, 78, 90, 98, 151, 168, 202, 236, 249, 270 ; DirectViolet 9, 12, 51, 98 ; DirectGreen 1, 85 ; DirectYellow 8, 12, 44, 86, 87; DirectOrange 26, 39, 106, 107, etc.) etc. are mentioned, The iodine type pigment|dye is preferable. The iodine-based dye can be generated, for example, by bringing iodine (I ₂ ) into contact with potassium iodide (KI). These dichroic dyes may be used individually by 1 type, or may use 2 or more types together.

You may perform uniaxial stretching of the PVA film based on this invention by either the wet extending|stretching method or the dry-heat extending|stretching method. In the case of the wet stretching method, it may be carried out in an aqueous solution containing boric acid, or it may be carried out in the above-described dyeing bath or in a fixed treatment bath described later. Moreover, in the case of the dry heat extending|stretching method, it can carry out in air using the PVA film after water absorption. Among these, the wet stretching method is preferable, and it is more preferable to carry out uniaxial stretching in the aqueous solution containing boric acid. It is preferable that the density|concentration of the boric acid in boric-acid aqueous solution exists in the range of 0.5 mass % or more and 6.0 mass % or less, The said density|concentration is more preferable that it is 1.0 mass % or more, It is still more preferable that it is 1.5 mass % or more, and 5.0 mass % % or less is more preferable, and it is still more preferable that it is 4.0 mass % or less. The aqueous boric acid solution may contain potassium iodide, and it is preferable that the density|concentration of potassium iodide exists in the range of 0.01 mass % or more and 10 mass % or less.

Although the extending|stretching temperature in uniaxial stretching is not specifically limited, In the case of a wet stretching method, it is preferable to exist in the range of 30 degreeC or more and 90 degrees C or less, The said extending|stretching temperature is more preferably 40 degreeC or more, 45 degreeC or more It is still more preferable, and it is more preferable that it is 70 degrees C or less, and it is still more preferable that it is 65 degrees C or less. Moreover, in the case of a dry-heat extending|stretching method, it is preferable to exist in the range of 50 degreeC or more and 180 degrees C or less.

The draw ratio in uniaxial stretching (the overall draw ratio multiplied by each draw ratio when uniaxial stretching is performed in multiple stages) is preferably stretched as much as possible until just before the film is cut in terms of polarization performance, specifically It is preferable that it is 4 times or more, It is more preferable that it is 5 times or more, It is more preferable that it is 5.5 times or more. The upper limit of the draw ratio is not particularly limited as long as the film does not break, but it is preferably 8 times or less for uniform stretching. In addition, the draw ratio in this specification is based on the length of the film before extending|stretching, and the state which is not extending|stretching corresponds to draw ratio 1 time. The thickness of the film (polarizing film) after stretching is preferably 25 µm or less, more preferably 23 µm or less, still more preferably 20 µm or less, particularly preferably 18 µm or less, 15 µm or less, further 10 µm The following may be sufficient. The lower limit in particular of the thickness of the film (polarizing film) after the said extending|stretching is not restrict|limited, For example, 1 micrometer or more, 2 micrometers or more, 3 micrometers or more, Furthermore, 5 micrometers or more may be sufficient.

In the case of uniaxial stretching of a long PVA film, there is no particular limitation on the uniaxial stretching direction, and uniaxial stretching in the longitudinal direction or uniaxial stretching in the transverse direction can be adopted, but polarized light having better polarization performance From the viewpoint of obtaining a film, uniaxial stretching with respect to the longitudinal direction is preferable. Uniaxial stretching with respect to a longitudinal direction can be performed by changing the circumferential speed between each roll using the extending|stretching apparatus provided with the some roll mutually parallel. On the other hand, uniaxial stretching in the transverse direction may be performed using a tenter type stretching machine.

In manufacture of a polarizing film, in order to strengthen adsorption|suction of the dichroic dye with respect to a film, it is preferable to perform a fixation process. The fixing treatment can be performed by immersing the film in a fixing treatment bath. As a fixed treatment bath used for a fixed treatment, the aqueous solution containing 1 type, or 2 or more types of boron compounds, such as boric acid and borax, can be used. Moreover, you may add an iodine compound and a metal compound in a fixed process bath as needed. It is preferable that the density|concentration of the boron compound in a fixed treatment bath generally exists in the range of 2 mass % or more and 15 mass % or less, and especially exists in the range of 3 mass % or more and 10 mass % or less. It is preferable that the temperature of a fixed treatment bath exists in the range of 15 degreeC or more and 60 degrees C or less, especially in the range of 25 degreeC or more and 40 degrees C or less.

Drying treatment (heat treatment) is carried out within the range of 30°C or more and 150°C or less, particularly 50°C or more and 140°C or less, in order to improve the dimensional stability of the resulting polarizing film and suppress a decrease in polarization performance. It is preferable to do

The polarizing film obtained by making it above is normally used by bonding together the protective film which is optically transparent and has mechanical strength on the both surfaces or single side|surface, and is used as a polarizing plate. As the protective film, a cellulose triacetate (TAC) film, a cycloolefin polymer (COP) film, a cellulose acetate/butyrate (CAB) film, an acrylic film, a polyester film, or the like is used. Moreover, as an adhesive agent for bonding a protective film, a PVA type adhesive agent, a urethane type adhesive agent, an acrylate type adhesive agent, etc. are mentioned, Especially, a PVA type adhesive agent is preferable.

After coat|covering adhesives, such as an acrylic type, the polarizing plate obtained by making it above can be bonded together to a glass substrate, and can be used as a component of LCD. At this time, a retardation film, a viewing angle improvement film, a brightness improvement film, etc. may be further bonded together.

Example

Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited in any way by the Examples below. In addition, each measurement or evaluation method employ|adopted in the following Example, a comparative example, and a reference example is shown below.

[Measurement of W _MD30 ]

A rectangular sample of 40 mm in the width direction (TD) × 270 mm in the longitudinal direction (MD) was cut out from the central portion in the width direction of the PVA film. Next, marks were placed on the inside by 10 mm from both ends of the sample having a length of 270 mm by using oily magic (thickness of the line was 0.3 mm). The outer part was pinched|interposed from the mark on both ends with a commercially available clip (chuck width 40mm, mass 7.8g (weight 7.3g in water)), and one clip was fixed with a rod-shaped jig. After confirming that the distance between the marks is 250 mm, place the sample with a clip into the pure water stored at 30 ° C stored in a cylindrical, transparent water tank so that the entire sample enters the water, and quickly move the long side of the sample vertically (vertically) immersed in Immediately after immersion, a rod-shaped jig was hung on the upper part of the water tank and the long side of the sample was fixed so as to be vertical (vertical). Then, the metal ruler was immersed in water, and the distance between marked lines was measured 30 second after immersion of the sample. The amount of extension (W _MD30 ) (unit: mm) was calculated by subtracting the original distance between marks (250 mm) from the measured value read at 0.5 mm intervals.

[Measurement of W _TD300 ]

A rectangular sample of 270 mm in the width direction (TD) × 40 mm in the longitudinal direction (MD) was cut out from the central portion in the width direction of the PVA film. Next, marks were placed on the inside by 10 mm from both ends of the sample having a length of 270 mm by using oily magic (thickness of the line was 0.3 mm). The outer part was pinched|interposed from the mark on both ends with a commercially available clip (chuck width 40mm, mass 7.8g (weight 7.3g in water)), and one clip was fixed with a rod-shaped jig. After confirming that the distance between the marks is 250 mm, place the sample with a clip into the pure water stored at 30 ° C stored in a cylindrical, transparent water tank so that the entire sample enters the water, and quickly move the long side of the sample vertically (vertically) immersed in Immediately after immersion, a rod-shaped jig was hung on the upper part of the water tank and the long side of the sample was fixed so as to be vertical (vertical). Then, a metal ruler was immersed in water, and the distance between marked lines was measured 300 second after immersion of the sample. The amount of extension (W _TD300 ) (unit: mm) was calculated by subtracting the original distance between marks (250 mm) from the measured value read at 0.5 mm intervals.

[Evaluation of stretchability of PVA film]

As a parameter|index of the stretchability of a PVA film, the tension|tensile_strength at the time of extending|stretching in a extending|stretching bath was measured, and the following reference|standard evaluated stretchability.

◎: 10 MPa or more and 12 MPa or less

○ : Exceeds 12 MPa and less than 15 MPa

△: Exceeding 15 MPa and less than or equal to 18 MPa

x: Less than 10 MPa or more than 18 MPa.

[Evaluation beyond the end]

The following criteria evaluated the edge part or more of the film in the roll immediately after passing through a swelling bath.

(circle): An edge part abnormality cannot be confirmed at all.

(triangle|delta): An edge part abnormality can be confirmed slightly.

x: An edge part abnormality can be confirmed clearly.

[Evaluation of dyeing unevenness of polarizing film]

After sandwiching the produced polarizing film between two polarizing plates (single transmittance: 42.3%, polarization degree 99.99%) in a cross nicol state, in a dark room, using a light box with a luminance of 10,000 cd/m 2 was observed and evaluated according to the following criteria.

(double-circle): dyeing nonuniformity cannot be confirmed at all.

(circle): Slightly staining nonuniformity can be confirmed.

(triangle|delta): dyeing nonuniformity can be confirmed comparatively clearly.

x: Staining nonuniformity can be confirmed clearly.

[Example 1]

<<Preparation of PVA film>>

100 parts by mass of PVA (ethylene-modified PVA obtained by saponifying ethylene-modified polyvinyl acetate obtained by copolymerizing ethylene and vinyl acetate, 2.0 mol% of ethylene unit content, 2,400 degree of polymerization, 99.9 mol% of saponification), 10 parts by mass of glycerin, D A film forming undiluted solution having a volatile fraction of 66 mass% consisting of 0.1 parts by mass of diethanolamide uric acid and water is transferred from a T-slit die to a first dry roll in a film forming apparatus comprising a plurality of drying rolls whose rotational axes are parallel to each other and a plurality of heat treatment rolls. (Surface temperature 93.5° C., circumferential speed (S ₁ ) 14.5 m/min) is discharged as a film, and on the first drying roll, hot air of 90° C. is sprayed over the entire non-contact surface of the first drying roll at a wind speed of 5 m/sec. It dried until it became 15 mass % of volatile matter, and it peeled from the 1st drying roll.

Then, with the first drying roll non-contacting surface of the PVA film facing the second drying roll, while alternately opposing the front and back surfaces of the PVA film for each drying roll, the PVA film with a drying roll after the second drying roll has a volatile fraction of 5 mass % was further dried. In addition, the drying roll (drying roll (X)) when the volatile matter ratio of the PVA film|membrane became 12 mass % is a 5th drying roll, The surface temperature of each drying roll from a 2nd drying roll to a 5th drying roll is 75 degreeC and the surface temperature of each dry roll after the 6th dry roll was 60 degreeC.

Thereafter, the PVA film was heat-treated with a plurality of heat treatment rolls while alternately opposing the front and back surfaces of the PVA film with respect to each heat treatment roll. At this time, the circumferential speed S _B of the heat treatment roll (heat treatment roll B) located at the most downstream side with respect to the circumferential speed S _A of the heat treatment roll (heat treatment roll A) located at the most upstream side ratio ( _{SB /S A )} of 0.991 and the surface temperature of each heat treatment roll was set to 99 to 115°C (the surface temperature of the heat treatment roll (A) was 99°C, the surface temperature of the heat treatment roll (B)) 115 ° C). The ratio (SB /S ₁ ) of the circumferential speed S _B of the heat treatment roll _B to the circumferential speed S ₁ of the first drying roll was 0.965.

After heat-processing as mentioned above, it wound up and obtained the roll-shaped PVA film (45 micrometers in thickness, 3m in width, 5,000m in length, 3 mass % of volatile matter).

For the obtained PVA film, W _MD30 and W _TD300 were measured according to the method described above. The results are shown in Table 1.

<<Preparation of a polarizing film >>

The PVA film obtained above was unwound from the roll, it slitted, the part of width 650mm was cut out continuously from the width direction center part, Then, each process was performed and the polarizing film was manufactured continuously.

That is, the PVA film is immersed in a swelling bath (water temperature 30°C), followed by a dyeing bath (water temperature 32°C, an aqueous solution containing 0.07 mass% iodine and 1.6 mass% potassium iodide), a fixed treatment bath (water temperature 32°C) °C, aqueous solution containing 2.6 mass% of boric acid), stretching bath (water temperature 58 °C, aqueous solution containing 2.8 mass% boric acid and 5.0 mass% potassium iodide), washing bath (water temperature 22 °C, boric acid 1.5 mass% and iodide) It was sequentially immersed in the aqueous solution containing 5.0 mass % of potassium, and also it was made to dry by the drying furnace (temperature of 40 degreeC), and the polarizing film was manufactured. In addition, as time to be immersed in a swelling bath, in order to make it correspond to a thin PVA film, comparatively short 40 second was employ|adopted. Moreover, the total draw ratio was made into 6.3 times.

Manufacture of the said polarizing film WHEREIN: While evaluating the stretchability of the PVA film used according to the above-mentioned method, evaluation of the edge part or more was performed. Moreover, about the obtained polarizing film, the above-mentioned method evaluated dyeing nonuniformity. The results are shown in Table 1.

<Examples 2 and 3 and Comparative Examples 1 to 3>

A polarizing film was manufactured in the same manner as in Example 1 while producing a PVA film in the same manner as in Example 1 except that the manufacturing conditions of the PVA film were as in Table 1. And it carried out similarly to Example 1, and each evaluation was performed. The results are shown in Table 1.

Claims (12)

A polyvinyl alcohol-based polymer film having a thickness of 50 µm or less, wherein a sample of the polyvinyl alcohol-based polymer film is immersed in water at 30° C. for 30 seconds, the amount of elongation in the longitudinal direction in a portion of 250 mm in the longitudinal direction before immersion ( W _MD30 ) is 35 mm or more and 60 mm or less, and when the sample of the polyvinyl alcohol-based polymer film is immersed in water at 30° C. for 300 seconds, the amount of extension in the width direction in the portion of 250 mm in the width direction before immersion (W _TD300 ) is 53 mm or more and 65 mm or less, The polyvinyl alcohol-type polymer film. The method of claim 1,
A polyvinyl alcohol-based polymer film having a width of 2 m or more. 3. The method of claim 1 or 2,
A raw film for optical film production, a polyvinyl alcohol-based polymer film. 4. The method of claim 3,
The polyvinyl alcohol-type polymer film whose optical film is a polarizing film. A method for producing a polyvinyl alcohol-based polymer film having a thickness of 50 µm or less, using a film forming apparatus having a drying roll and a heat treatment roll whose rotational axes are parallel to each other, and placing the polyvinyl alcohol-based polymer film on a first drying roll of the film forming apparatus The film forming stock solution containing the polymer is discharged into a film, dried, and further dried with a drying roll following it, and then heat-treated with a plurality of heat treatment rolls to prepare a polyvinyl alcohol-based polymer film, where it is located on the upstream side When the heat treatment roll to be used is the heat treatment roll (A), and the heat treatment roll located on the most downstream side is the heat treatment roll (B), the polyvinyl alcohol polymer immediately before contacting the heat treatment roll (A) The film has a volatile fraction of 3 mass% or more and 7 mass% or less, and the ratio ( _SB /SA) of the circumferential speed ( _{SB) of the heat treatment roll (B) to the circumferential speed (SA) of the heat treatment roll (A ) is} It is 0.999 or less, and the surface temperature of each heat treatment roll from the heat treatment roll (A) to the heat treatment roll (B) is all 87 degreeC or more and 121 degreeC or less, The manufacturing method of the polyvinyl alcohol-type polymer film. 6. The method of claim 5,
When the drying roll when the volatile fraction of the polyvinyl alcohol-based polymer film becomes 12 mass % is used as the drying roll (X), and the drying roll positioned immediately before the heat treatment roll (A) is used as the drying roll (Y), The surface temperature of each of the drying rolls from the 1st drying roll to the drying roll (X) is all 70 degreeC or more, and the surface of each drying roll from the drying roll located immediately after the drying roll (X) to the drying roll (Y) A method for producing a polyvinyl alcohol-based polymer film, wherein the temperatures are all 40°C or higher and lower than 70°C. 7. The method according to claim 5 or 6,
The method for producing a polyvinyl alcohol-based polymer film, wherein the ratio ( _SB /S ₁ ) of the peripheral speed (SB) of the heat treatment roll ( _B ) to the peripheral speed (S ₁ ) of the first drying roll is 0.900 or more and 1.050 or less. 7. The method according to claim 5 or 6,
When the drying roll positioned immediately before the heat treatment roll (A) is used as the drying roll (Y), between the first drying roll and the drying roll (Y), the polyvinyl alcohol-based polymer film is formed with respect to each drying roll. A method for producing a polyvinyl alcohol-based polymer film in which front and back surfaces are alternately opposed. 7. The method according to claim 5 or 6,
A method for producing a raw film for optical film production, a method for producing a polyvinyl alcohol-based polymer film. 10. The method of claim 9,
The manufacturing method of the polyvinyl alcohol-type polymer film whose optical film is a polarizing film. An optical film produced from the polyvinyl alcohol-based polymer film according to claim 3 . A polarizing film produced from the polyvinyl alcohol-based polymer film according to claim 4.