KR20200090959A - Polyvinyl alcohol film - Google Patents

Abstract

The present invention is a long polyvinyl alcohol film (1) having a thickness of 55 µm or less and a length of 500 m or more, wherein at least one of the two ends along the longitudinal direction of the film is formed by a cutting edge (A, A '), and the maximum height roughness (Rz) of the cut sections (B, B') of the cut ends is 2.5 µm or less over a section of 500 m or more in length of the film, and the polyvinyl alcohol film (1). It relates to a roll formed by winding an alcohol film in a roll shape.

Description

Polyvinyl alcohol film {POLYVINYL ALCOHOL FILM}

The present invention provides a thin polyvinyl alcohol film having a specific cutting cross-section (hereinafter, "polyvinyl alcohol" may be abbreviated as "PVA"), a roll in which it is wound in a roll, and such a PVA film is obtained. It relates to a method of manufacturing a PVA film.

A polarizing plate having a function of transmitting and shielding light is a basic component of a liquid crystal display (LCD) together with a liquid crystal having a function of switching light. The field of application of this LCD is also from small devices such as electronic desk calculators and wrist watches in the early stages of development. Recently, laptop PCs, word processors, liquid crystal color projectors, in-vehicle navigation systems, liquid crystal televisions, personal phones and indoor and outdoor measurement devices It has been expanded to a wide range of fields such as, and in this regard, a higher quality and low cost polarizing plate is required.

In general, a polarizing plate is uniaxially stretched after dyeing a PVA film, or uniaxially stretched or dyed after dyeing to produce a dyed uniaxially stretched film, and fixing it with a boron compound, After producing a polarizing film by a method such as dyeing and fixing treatment with a boron compound at the same time as the above uniaxial stretching and dyeing treatment, a cellulose acetate (TAC) film, acetic acid and butyrate cellulose on the surface of the polarizing film ( CAB) It is manufactured by bonding a protective film such as a film.

In the manufacture of a polarizing plate, a method of continuously performing processes such as uniaxial stretching, dyeing, fixing, bonding of a protective film, and the like is continuously performed using a raw film film in which a long PVA film is wound in a roll to reduce production cost and the like. Is being adopted.

In the PVA film, since both ends in the width direction of the film are easily different from each other in the width direction after film formation, it is difficult to achieve stable stretching by uniaxial stretching while leaving both ends in the width direction difficult. It has been generally practiced that after cutting and removing both ends in the direction, it is wound up in a roll shape and supplied to a customer such as a polarizer manufacturer.

Moreover, in order to provide the thing of the film width which conforms to the request of a customer, such as a polarizing plate manufacturer, the film-formed PVA film is cut off at the same time with or without removal of the ear, and the central portion in the width direction of the film or the like. It is also practiced as necessary to cut the film in a lengthwise direction from the outside position, make the film a desired predetermined width, wind it up in a roll shape and deliver it to the customer.

In producing a polarizing film from a PVA film, in order to obtain high polarization performance, it is generally practiced that the PVA film is uniaxially stretched in the longitudinal direction at a high draw ratio, but the cut section of the film is roughened. If it is, the rough surface portion at the time of uniaxial stretching becomes the starting point of cracking, cracks are generated at the ends, and in severe cases, the film may break from the cracked portion. When the film breaks, it is necessary to temporarily stop the uniaxial stretching treatment, remove the fracture portion, and then perform the stretching treatment again, resulting in a significant decrease in productivity and a decrease in the yield of the polarizing film. In view of this, there is a demand for a PVA film having a smooth cut cross-section along the longitudinal direction of the film, which does not generate cracks or breaks during stretching.

So far, several methods of cutting PVA films have been known (see Patent Documents 1 to 3, etc.). Patent Document 1 describes a method in which the temperature and volatile content of the PVA film provided for cutting are respectively within a specific range, and as a cutting method, a method of cutting a film between two rolls or a method of cutting on a grooved roll This is described. Patent document 2 describes a PVA film for optics having a specific surface average roughness (Ra), and as a cutting method, a method using a share blade composed of an upper blade and a lower blade or a method using a laser blade is described. have. Patent Document 3 describes a long PVA film in which the maximum height (Ry) of the cut section is in a specific range over the entire length of the film, and as a cutting method, one rotating round blade each for the formation of one cut end The method of using is described, it is described that a groove forming roll is used, and that the blade end angle of the round blade is preferably 3 to 20°.

Japanese Patent Application Publication No. 2002-144418 Japanese Patent Publication No. 2003-12827 Japanese Patent Application Publication No. 2005-306981

Recently, a thinner polarizing film is required, and in this regard, as a raw film for manufacturing a polarizing film, a PVA film having a thickness of about 75 μm has been generally used, but recently, a PVA film having a thickness smaller than 70 μm Is required. However, there is a problem that a thin PVA film is more likely to break than those of a conventional thickness during processing such as uniaxial stretching.

An object of the present invention is to provide a thin PVA film that is difficult to break during processing such as uniaxial stretching, and a roll formed by winding it into a roll. Another object of the present invention is to provide a method for producing a PVA film for smoothly producing such a PVA film.

The present inventors have repeatedly studied in order to achieve the above object, and as a result, in a long PVA film having a thickness of 55 µm or less, the maximum height in the cut section of the cut end over a specific section in the longitudinal direction of the film. By setting the roughness (Rz) to a specific range, it has been found that despite being a thin PVA film, it is difficult to break during processing such as uniaxial stretching. In addition, the present inventors, when cutting the PVA film along the longitudinal direction by a round blade that rotates while transferring the PVA film before cutting into contact with the groove forming roll, the round blade has a specific blade end angle and a blade end portion It has been found that the use of those having a hardness in a specific range can smoothly produce the thin PVA film that is difficult to break. The present inventors have further studied based on their knowledge to complete the present invention.

That is, the present invention,

[1] A long PVA film having a thickness of 55 µm or less and a length of 500 m or more, wherein at least one of the two ends along the length direction of the film is a cutting end formed by a cutting blade, and the maximum cutting end of the cutting end A PVA film whose height roughness (Rz) is 2.5 µm or less over a section of 500 m or more in length of the film;

[2] The PVA film of [1] above, wherein the arithmetic mean roughness (Ra) of the cut section is 0.4 µm or less over the section;

[3] The PVA film of [1] or [2] above, wherein the length of the film is 1,000 m or more;

[4] PVA film according to any one of the above [1] to [3], which is a raw film for optical film production;

[5] The PVA film according to any one of [1] to [4], wherein the optical film is a polarizing film;

[6] A roll in which the PVA film of any one of [1] to [5] above is wound in a roll shape;

[7] A method for producing a long PVA film having a thickness of 55 µm or less and a length of 500 m or more, wherein at least one of the two ends along the length direction of the film is a cutting end formed by a cutting blade, and the film contacts The position of the small-diameter portion of the groove-forming roll while using a groove-forming roll having a small-diameter portion in which the neck portion does not contact the film in the roll axis direction is contacted with a long PVA film on the surface of the large-diameter portion of the groove-forming roll. The manufacturing method, which has the process of cutting a PVA film along a longitudinal direction by a round blade which rotates in the said blade, has a blade tip angle of 25-50 °, and a Vickers hardness of a blade tip portion of 1,500 HV or more;

[8] The production method of the above [7], in which the PVA film is brought into contact at an angle of 10 to 100° along the circumference of the groove forming roll;

[9] The production method for the above [7] or [8], which is a production method for producing the PVA film according to any one of the above [1] to [5];

It is about.

ADVANTAGE OF THE INVENTION According to this invention, the thin PVA film which is hard to break|rupture at the time of processing, such as uniaxial stretching, and the roll which it winds up in roll shape are provided. In addition, according to the present invention, a method for manufacturing a PVA film capable of smoothly producing such a PVA film is provided.

1 is a diagram schematically showing a part of the PVA film of the present invention.
2 is a diagram schematically showing an example of a cross section in the thickness direction of a round blade.
3 is a view schematically showing an example of a groove forming roll and an example of a method of cutting a PVA film using the groove forming roll.

The present invention will be described in detail below.

The PVA film of the present invention is a long film, and at least one of the two ends along the longitudinal direction of the film is a cut end formed by a cutting blade. The PVA film may be either an end portion along the longitudinal direction of the film, or an end portion of both sides along the longitudinal direction of the film, or an end portion of both sides along the longitudinal direction of the film. It is preferably a cut end. The cutting edge forming the cutting end is not particularly limited, and examples include a shear blade, a laser blade, a round blade, and the like, and a round blade described later is preferred.

In the PVA film of the present invention, the maximum height roughness (Rz) of the cut section of the cut end is 2.5 μm or less over a section of 500 m or more in length of the film. That is, for example, when the length of the PVA film of the present invention is 3,000 m, the maximum height roughness (Rz) is in the above range at least in a continuous section of 500 m of any of the lengths of the cut section.

Here, as shown in FIG. 1, the cutting section is cut end portions A and A'along the longitudinal direction of the PVA film 1 (FIG. 1 shows both ends cut along the longitudinal direction of the PVA film 1). It means the surface (cut surface) (B, B') which corresponds to the thickness part of the PVA film 1 in the case of an end part).

The maximum height roughness (Rz) is, for example, using a super-depth shape measuring microscope or the like to measure the surface roughness of the cut section in a range of a predetermined length (L) along the longitudinal direction of the cut section to obtain an illuminance curve, It is a value obtained as the sum (Rz = Rp + Rv) of the sum of the maximum mountain height (Rp) of the upper portion and the maximum bone depth (Rv) of the lower portion of the average line (average line in the longitudinal direction of the film) of the roughness curve. This is described in JIS B 0601: 2001. The said roughness curve can be calculated|required from the surface state on the line in the longitudinal direction of the film in the thickness direction center part on the cutting cross section to be measured. Usually, when cutting a PVA film, since the cut surface gradually becomes rough as time elapses from the start of cutting, the values of the maximum height roughness (Rz) and the arithmetic mean roughness (Ra) described later in the cut section Silver grows over time from the start of cutting. Therefore, the maximum height roughness (Rz) to the arithmetic mean roughness (Ra) in the cut section of the section (measurement point) after cutting a specific length (for example 500 m) in the longitudinal direction of the film from the starting point of cutting is determined. When measured, and their measurements are below a certain value, the maximum height roughness (Rz) to the arithmetic mean roughness (Ra) in the cut cross-section can be said to be less than or equal to their measurements, at least across the entire area from the start of cutting to the measurement point. have.

In the PVA film of the present invention, from the viewpoint of preventing breakage during processing such as uniaxial stretching, it is necessary that the maximum height roughness (Rz) of the cut section is 2.5 μm or less over a section of 500 m or more in length of the film, and 2 It is preferably less than or equal to µm, more preferably less than or equal to 1.5 µm, even more preferably less than or equal to 1 µm, and particularly preferably less than or equal to 0.9 µm. Although there is no restriction|limiting in particular as the lower limit of the said maximum height roughness (Rz), From the viewpoint of the ease of manufacture of the PVA film of this invention, etc., the maximum height roughness (Rz) of a cut section is 0.01 micrometers over the section of 500 m in length of a film. A PVA film without the corresponding section below is preferable, and a PVA film without the section having a maximum height roughness (Rz) of the cut section of 0.1 μm or less over a section of 500 m in length of the film is more preferable, and a cut section It is more preferred that the PVA film without the section has a maximum height roughness (Rz) of 0.3 m or less over a section of 500 m in length.

In the PVA film of the present invention, if the arithmetic mean roughness (Ra) of the cut section is 0.4 µm or less over the above section regarding the maximum height roughness (Rz), breakage during processing such as uniaxial stretching can be more effectively prevented. It is desirable. From such a viewpoint, the PVA film of the present invention is more preferably 0.3 µm or less, more preferably 0.2 µm or less, and particularly preferably 0.14 µm or less, in the arithmetic mean roughness (Ra) of the cut section over the section. . Although there is no restriction|limiting in particular as the lower limit of the said arithmetic mean roughness (Ra), From the viewpoint of the ease of manufacture of the PVA film of this invention, etc., the section in which the arithmetic mean roughness (Ra) of a cut section becomes 0.001 micrometer or less over the said section A PVA film without this is preferred, and a PVA film without a section in which the arithmetic mean roughness (Ra) of the cut section is 0.01 µm or less over the section is more preferred, and the arithmetic mean roughness (Ra) of the cut section is in the section More preferably, the PVA film without the section having a thickness of 0.03 µm or less over.

Here, the arithmetic mean roughness (Ra) can be obtained according to the description of JIS B 0601: 2001 with respect to the roughness curve (reference length: L) obtained in the measurement of the maximum height roughness (Rz).

The PVA film of the present invention has a maximum height roughness (Rz) and an arithmetic mean roughness (A) over the above-mentioned section regarding the maximum height roughness (Rz), from the viewpoint of further effectively preventing breakage during processing such as uniaxial stretching. The ratio (Rz/Ra) of Ra) is preferably 5 or more, more preferably 6 or more, further preferably 25 or less, and more preferably 11 or less. The ratio (Rz/Ra) can be used as an index of the degree of wear of the blade used to cut the PVA film, and when the wear of the blade is severe, the ratio (Rz/Ra) often decreases, and accordingly the cut section The degree of roughening is easy to increase.

The thickness of the PVA film of the present invention is 55 µm or less, preferably 50 µm or less, more preferably 45 µm or less, and even more preferably 40 µm or less for reasons such as meeting the need for a thinner PVA film. And particularly preferably 30 µm or less. The lower limit of the thickness of the PVA film is not particularly limited, but from the viewpoints of practicality, ease of production of the film, and ease of stretching treatment, the thickness is preferably 3 μm or more, more preferably 5 μm or more, and more preferably 15 μm. It is more preferable that the above.

The width of the PVA film of the present invention can be selected according to the use of the PVA film, the demand of the PVA film, and the like, but in general, it is preferably 2 m or more, more preferably 2.5 m or more, and more preferably 3 m or more It is preferable, and it is preferable that it is 8 m or less.

The PVA film of the present invention has a length of 500 m or more. The length of the PVA film is preferably 1,000 m or more, more preferably 5,000 m or more, and even more preferably 8,000 m or more from the viewpoint of being able to be used continuously for a long time during use. The upper limit of the length is not particularly limited, and the length can be, for example, 30,000 m or less. From the viewpoint of ease of transportation, storage and use, the PVA film of the present invention is preferably in the form of a roll wound in a roll form.

As the PVA constituting the PVA film of the present invention, for example, unmodified PVA obtained by saponifying a polyvinyl ester obtained by polymerizing a vinyl ester, modified PVA obtained by graft copolymerization of a comonomer on the main chain of PVA, vinyl ester and nose And so-called polyvinyl acetal resins in which a part of hydroxyl groups of modified PVA, unmodified PVA or modified PVA prepared by saponifying a modified polyvinyl ester copolymerized with monomers is crosslinked with aldehydes such as formalin, butylaldehyde, and benzaldehyde. .

When the PVA forming the PVA film of the present invention is a modified PVA, the amount of modification in the PVA is preferably 15 mol% or less, more preferably 5 mol% or less.

Examples of the vinyl esters used in the production of PVA include, for example, vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl valerate, vinyl pivalate, vinyl laurate, vinyl stearate, vinyl benzoate, and vinyl basatate. And the like. These vinyl esters can be used alone or in combination. Of these vinyl esters, vinyl acetate is preferred from the viewpoint of productivity.

Moreover, as said comonomer, C2-C30 olefins, such as ethylene, propylene, 1-butene, and isobutene (alpha-olefin, etc.); acrylic acid or its salt; methyl acrylate, ethyl acrylate, acrylic acid n -Acrylic acid esters such as propyl, i-propyl acrylate, n-butyl acrylate, i-butyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, and octadecyl acrylate (for example, carbon number of acrylic acid 1 ~18 alkyl esters); methacrylic acid or a salt thereof; methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, i-propyl methacrylate, n-butyl methacrylate, i-butyl methacrylate , Methacrylic acid esters such as t-butyl methacrylate, 2-ethylhexyl methacrylate, dodecyl methacrylate, and octadecyl methacrylate (for example, methacrylic acid 1 to 18 alkyl esters); Acrylamide; N-methylacrylamide, N-ethylacrylamide, N,N-dimethylacrylamide, diacetoneacrylamide, acrylamidepropanesulfonic acid or salts thereof, acrylamidepropyldimethylamine or salts thereof, N-methylolacryl Acrylamide derivatives such as amides or derivatives thereof; methacrylamides; N-methylmethacrylamide, N-ethylmethacrylamide, methacrylamidepropanesulfonic acid or salts thereof, methacrylamidepropyldimethylamine or salts thereof, N-methyl Methacrylamide derivatives such as all methacrylamide or derivatives thereof; N-vinylamides such as N-vinyl formamide, N-vinyl acetamide, and N-vinyl pyrrolidone; methyl vinyl ether, ethyl vinyl ether, and n- Vinyl ethers such as 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; acrylonitrile and methacryl Nitriles such as nitriles; vinyl halides such as vinyl chloride, vinylidene chloride, vinyl fluoride, and vinylidene fluoride; allyl compounds such as allyl acetate and allyl chloride; unsaturated dicarboxylic acids such as maleic acid and itaconic acid; Derivatives such as esters thereof; vinylsilyl compounds such as vinyl trimethoxysilane; isopropenyl acetate ; Unsaturated sulfonic acid or derivatives thereof. These comonomers may be used alone or in combination of two or more. Among these comonomers, α-olefins are preferred, and ethylene is particularly preferred.

The degree of polymerization of PVA is preferably 1,000 or more, more preferably 2,000 or more, and more preferably 2,500 or more, in that a polarizing film excellent in polarization performance and durability is obtained when the PVA film of the present invention is uniaxially stretched to produce a polarizing film. May be In addition, from the viewpoint of ease of production, elongation, and the like for obtaining a homogeneous PVA film, the polymerization degree of PVA is preferably 8,000 or less, more preferably 6,000 or less. The polymerization degree of PVA in this specification means the average polymerization degree measured according to the description of JIS K6726-1994, and is obtained from the intrinsic viscosity measured in water at 30° C. after resaponification and purification of PVA.

The saponification degree of PVA is preferably 95 mol% or more, and more preferably 98 mol% or more, in that a polarizing film excellent in polarization performance and durability is obtained when the PVA film of the present invention is uniaxially stretched to produce a polarizing film. It is preferable, more preferably 99 mol% or more, and particularly preferably 99.3 mol% or more. The saponification degree of PVA in the present specification is the ratio of the number of moles of the vinyl alcohol unit to the total number of moles of the structural unit (typically a vinyl ester unit) and the vinyl alcohol unit that can be converted into a vinyl alcohol unit by saponification ( Mol%). The saponification degree of PVA can be measured according to JIS K6726-1994.

It is preferable that the PVA film of this invention contains a plasticizer from the point which can improve handling property, dyeability, stretchability, etc. As the plasticizer, a polyhydric alcohol-based plasticizer is preferred from the viewpoint of affinity with PVA. Examples of the polyhydric alcohol-based plasticizer include, for example, ethylene glycol, glycerin, propylene glycol, diethylene glycol, diglycerin, triethylene glycol, tetraethylene glycol, trimethylolpropane, and the like, or one or more of these. Can be used. Among these, one or two or more of glycerin, diglycerin and ethylene glycol are preferably used from the viewpoint of improving the stretchability, handling properties, and the like.

The content of the plasticizer is preferably 1 part by mass or more, more preferably 5 parts by mass or more, more preferably 30 parts by mass or less, and even more preferably 20 parts by mass or less with respect to 100 parts by mass of PVA. When the content of the plasticizer is more than the above lower limit, dyeability and stretchability are improved. On the other hand, when the content of the plasticizer is equal to or less than the above upper limit, it is possible to prevent the PVA film from becoming too flexible, and handling properties, cutting uniformity, and the like are improved.

It is preferable that the PVA film of this invention contains surfactant from a viewpoint of the handling property, and also the peelability improvement from the film forming apparatus at the time of manufacturing a PVA film. The type of surfactant is not particularly limited, and examples thereof include anionic surfactants and nonionic surfactants. Examples of the anionic surfactant include carboxylic acid type, sulfuric acid ester type, and sulfonic acid type. Examples of the nonionic surfactant include alkyl ether type, alkylphenyl ether type, alkyl ester type, alkylamide type, polypropylene glycol ether type, alkanolamide type, and allylphenyl ether type. The PVA film of this invention can contain 1 type(s) or 2 or more types of these surfactants.

It is preferable that content of surfactant is 0.01 mass part or more with respect to 100 mass parts of PVA, it is more preferable that it is 0.05 mass parts or more, and it is preferable that it is 1 mass part or less, and it is more preferable that it is 0.3 mass parts or less. When the content of the surfactant is less than or equal to the above upper limit, it is possible to prevent the surfactant from eluting on the surface of the PVA film, causing blocking, and deteriorating handling.

The PVA film of the present invention may further contain other components such as dichroic dyes, antioxidants, ultraviolet absorbers, lubricants, colorants, preservatives, antiseptics, polymer compounds other than the above components, and moisture, if necessary. do. The PVA film of the present invention may contain one or two or more of these other components. The content ratio of PVA in the PVA film of the present invention is preferably 70 mass% or more, more preferably 80 mass% or more, and even more preferably 90 mass% or more.

Although there is no restriction|limiting in particular as a manufacturing method of the PVA film of this invention, According to the manufacturing method of this invention below, since the PVA film of this invention can be manufactured smoothly, it is preferable. That is, the manufacturing method of the present invention is a method for producing a long PVA film having a thickness of 55 µm or less and a length of 500 m or more, wherein at least one of the two ends along the longitudinal direction of the film is a cutting end formed by a cutting blade. , Using a groove forming roll having a large diameter portion in contact with the film and a small diameter portion in which the film does not contact in the roll axis direction, the groove is formed while conveying a long PVA film to the surface of the large diameter portion of the groove forming roll It has a process of cutting the PVA film along the longitudinal direction by a round blade that rotates at the position of the small-diameter portion of the roll, wherein the round blade has an edge angle of 25 to 50° and a Vickers hardness at the edge of the blade is 1,500 HV or more, It is a manufacturing method. In general, a thin PVA film tends to have a roughened cross-section when cutting, compared to a thick PVA film, but according to the production method of the present invention, despite being a thin PVA film, the present invention A PVA film that satisfies the regulations can be manufactured smoothly.

The groove forming roll used in the production method of the present invention has a large diameter portion to which the film contacts and a small diameter portion to which the film does not contact in the roll axis direction. As the groove forming roll, for example, a metal one can be preferably used. In particular, when a chrome plated material is used, the surface hardness of the groove forming roll is high, and it is preferable from the viewpoint of preventing the occurrence of a wound. . As the groove forming roll, having at least three large diameter portions (convex portions) in the roll axis direction, and having a small diameter portion (groove, concave portion) between the large diameter portion and the large diameter portion (that is, having at least two small diameter portions) Thing) can be used.

The diameter of the large-diameter portion of the groove forming roll is 5 cm in terms of good transfer of the PVA film, good cutting of the PVA film in the groove forming roll, and manufacturing cost of the groove forming roll. More preferably, it is more than 7.5 cm, more preferably, more preferably 10 cm or more, still more preferably 30 cm or less, still more preferably 25 cm or less, still more preferably 20 cm or less. The PVA film can be cut more uniformly because the diameter of the large-diameter portion of the groove-forming roll is greater than or equal to the above lower limit. On the other hand, when the diameter of the large diameter portion of the groove forming roll is equal to or less than the above upper limit, the manufacturing cost of the groove forming roll can be reduced. When a plurality of large-diameter portions are present in the groove forming roll, it is preferable that all of these large-diameter portions have the same diameter, because the PVA film is held in a flat state and is brought into contact with and transferred to the surfaces of the plurality of large-diameter portions.

The width of the large-diameter portion of the groove-forming roll (the length in the roll axis direction; when a plurality of large-diameter portions are present) is 1 mm or more, particularly 3 to 10 mm, and the conveyance of the PVA film, It is preferable in that the size of the slit width (width after cutting) of the film can be changed freely. When a plurality of large diameter portions are present in the groove forming roll, the widths of these large diameter portions may be the same in all large diameter portions, or some or all of them may be different from each other.

The diameter of the small-diameter portion of the grooved roll is such that the neighboring large-diameter portion is prevented from breakage of the round blade, smooth cutting of the PVA film at the position of the small-diameter portion, and ease of processing of the groove in the grooved roll. With respect to the diameter of, it is preferably 0.5 cm or more, more preferably 1 cm or less, more preferably 2 cm or less, and more preferably 1.5 cm or less.

It is preferable that the width of the small-diameter portion of the groove-forming roll (length in the roll axis direction; when a plurality of small-diameter portions are present) is equal to or less than the width of the adjacent large-diameter portion. Moreover, the width of the small-diameter portion is such that the cutting edge of the PVA film can be satisfactorily performed in a stable state without the blade tip of the round blade contacting the groove forming roll, the point of suppressing the film from being displaced, and the like. It is preferable that it is 2 times or more, more preferably 5 times or more, and even more preferably 50 times or less for the thick portion of the non-tapered base in the portion of the blade (dimension of d in FIG. 2 ). And more preferably 30 times or less.

The round blade used in the manufacturing method of the present invention is a blade having a blade for cutting a film around the entire circumference of the disk-shaped body rotating around the shaft. The round blade is preferably made of metal or ceramic, and specifically, iron, iron alloy, high-speed tool steel, alloy tool steel, stainless steel, martensitic stainless steel, tungsten steel and the like can be mentioned. Further, the portion of the blade of the round blade may be made of the above-mentioned material, and the surface thereof may be treated with titanium nitride, titanium carbide, tungsten carbide, or the like. Particularly, a round blade made of tungsten steel is preferable because it is hard to wear and has excellent durability, and also has good smoothness in a cut section.

The Vickers hardness of at least the edge portion of the round blade is preferably 1,500 HV or more, and preferably 1,800 HV or more, from the viewpoint of smoothly producing the PVA film of the present invention. The upper limit of the Vickers hardness is not particularly limited, and for example, the Vickers hardness can be 2,400 HV or less. In addition, in this specification, the unit of Vickers hardness is kgf/mm 2.

The diameter of the round blade (the length of Ea in the cross-sectional view in the thickness direction of the round blade 2 illustrated in (a) and (b) in FIG. 2) is preferably 15 mm or more, and more preferably 20 mm or more. It is preferable, and it is more preferable that it is 40 mm or more. When the diameter of the round blade is in the above range, the progress of wear is suppressed, and it becomes easy to form a smooth cut section over the entire length of the long PVA film. The upper limit of the diameter of the round blade is not particularly limited, but if the diameter of the round blade is too large, the mass of the round blade itself becomes large, making it difficult to freely rotate when cutting the PVA film, and furthermore, to prevent damage, the base of the blade base is thick. From the point where it is necessary to enlarge the portion, the diameter of the round blade is preferably 200 mm or less, and more preferably 120 mm or less.

As shown in Fig. 2(a), the shape of the blade tip of the round blade is a mountain shape (amount where the polished surfaces 4, 4'on both sides converge in a tapered shape at the center blade tip 3). Blade), or as illustrated in Fig. 2(b), the other polished tapered surface 6 converges toward the blade tip 3 at the tip of one perpendicular surface 5 It may be a single blade shape. Among them, the blade end of the round blade is preferably an acid-like shape as shown in Fig. 2(a), because it is preferable that the PVA film is stably cut and a smooth cut section is formed by smoothness.

In the manufacturing method of the present invention, it is necessary that the blade end angle [angle α shown in (a) and (b) of FIG. 2) is within a range of 25 to 50°. If the angle of the blade tip of the round blade is less than 25°, the reason is not necessarily clear, but when cutting a thin PVA film having a thickness of 55 µm or less, the blade tip becomes easily abrasive and is required when manufacturing a long PVA film roll. It becomes difficult to continuously obtain the cut section to be made. Good sharpness can be maintained over a long period of time while suppressing wear of the blade tip, and accordingly, even if the length of the PVA film is long, the degree of roughening is small over the entire length of the film, and in order to form a smooth cut section, the blade edge angle of the round blade It is preferable that it is 30 degrees or more, and it is more preferable that it is 35 degrees or more. On the other hand, when the blade end angle of the round blade exceeds 50°, the sharpness becomes dull, and the degree of roughening is low, making it difficult to form a smooth cut section. From this point of view, the blade end angle of the round blade is preferably 45° or less, and more preferably 43° or less.

It is preferable that the thick portion of the base of the blade in the round blade (thick portion immediately before the thickness gradually decreases toward the tip of the blade; the dimension of d shown in Figs. 2A and 2B) is 0.05 mm or more, It is more preferable that it is 0.1 mm or more, and it is preferable that it is 1 mm or less, and it is more preferable that it is 0.5 mm or less. When the thick portion of the base of the blade tip is more than the lower limit, damage to the round blade itself can be suppressed. On the other hand, since the thick portion of the base of the blade tip is less than or equal to the above upper limit, it is possible to form a smooth cut section with a small degree of roughening over the entire length of the film.

It is preferable that the length of the blade (the distance from the base of the blade to the tip of the blade: the dimensions of e shown in Figs. 2(a) and 2(b)) in a round blade is one or more times the thickness of the PVA film to be cut. And more preferably 5 times or more, more preferably 50 times or less, and more preferably 45 times or less. When the length of the blade is equal to or greater than the above lower limit, it is possible to suppress that the cut section of the PVA film is damaged at the base of the blade. On the other hand, when the length of the blade is less than or equal to the above upper limit, wear or breakage of the blade portion can be suppressed.

In cutting the PVA film along the longitudinal direction by a round blade that rotates at the position of the small diameter portion of the groove forming roll while contacting and conveying a long PVA film to the surface of the large diameter portion of the groove forming roll, the groove It is the same as the circumferential speed of the large diameter portion of the forming roll and the feed rate of the PVA film, and that the PVA film is being transported in a tense state without being loosened on the groove forming roll. It is important. In this regard, in cutting the PVA film along the lengthwise direction, the PVA film is brought into contact with an angle (shell angle) of 10 to 100 degrees (contact angle β shown in Fig. 3(b)) along the circumference of the groove forming roll. , It is preferable to cut the PVA film by a rotating round blade arranged at the position of the small diameter portion of the groove forming roll in a state where the PVA film is made to pour along the groove forming roll. At that time, it is preferable to arrange the round blade at the center or almost the center of the shell. By doing so, at the time of cutting, the circumferential speed of the large-diameter portion of the groove-forming roll and the feed rate of the PVA film become substantially the same, and in addition, the small-diameter portion of the groove-forming roll is conveyed by the groove-forming roll while the PVA film is in tension. Since it is cut by a rotating round blade arranged at the position, it is possible to form a smooth cut section with a low degree of roughening. From the above viewpoint, the shell angle is more preferably 30° or more, more preferably 45° or more, further preferably 98° or less, and even more preferably 95° or less.

In cutting the PVA film along the lengthwise direction by a rotating round blade, the PVA film may be cut while actively driving and rotating the round blade, but the cut section is made by reducing the difference between the rotational speed of the round blade and the feed rate of the PVA film. From the standpoint of being able to make the degree of roughening smaller, etc., rather than actively driving and rotating the round blade, it is preferable to cut while rotating the round blade freely with the conveyance of the PVA film. If the cutting is performed while freely rotating the round blade, a large difference between the rotational speed of the round blade and the feed rate of the PVA film can be prevented, and accordingly, the PVA film is smoothly cut smoothly, and the degree of roughening is achieved. Can form a smaller smooth cut cross-section. The method for freely rotating the round blade is not particularly limited, and, for example, as illustrated in the schematic view of Fig. 2 (cross-sectional view in the thickness direction of the round blade 2), the round blade 2 is rounded on a disc. It is fixedly mounted on the blade mounting member 7 and formed by extending or rotating the rotating shaft 8 integrally or fixedly at the center (center position) of the circular blade-shaped mounting member 7, and around the rotating shaft 8. A method in which a bearing 9 such as a ball bearing is disposed, and the rotating shaft 8, the round blade mounting member 7 and the round blade 2 are integrally freely rotated can be adopted.

In cutting the PVA film along the lengthwise direction by a rotating round blade, the feed rate of the PVA film is preferably 40 m/min or less, more preferably 30 m/min or less, and further preferably 25 m/min or less desirable. When the said conveyance speed is below the said upper limit, the degree of roughening of a cut section can be made smaller. On the other hand, if the feed speed is too slow, it is preferable that the feed speed is 5 m/min or more from the viewpoint that cutting may take too long and productivity may decrease.

When the PVA film is cut along the longitudinal direction by a rotating round blade, the volatilization fraction of the PVA film is preferably 0.1 mass% or more, more preferably 2 mass% or more, and further preferably 10 mass% or less. And more preferably 6% by mass or less. When the said volatile fraction is more than the said lower limit, a PVA film will not become too hard, and it will be easy to cut|disconnect. On the other hand, when the said volatile fraction is below the said upper limit, it can suppress that a PVA film becomes too soft, and the degree of roughening of a cut section can be made smaller. In addition, the "volatilization fraction of a PVA film" in this specification means the content rate of volatile components contained in a PVA film. As such a volatile component, the organic solvent used when manufacturing a PVA film, a solvent, such as water, and the moisture etc. which were taken into the film by moisture absorption after manufacture of a PVA film are mentioned, for example. The volatilization fraction of the PVA film is dried by using a heated metal roll, a floating dryer, or a combination of two or more to a desired value; a PVA film having a volatilization fraction lower than the above range is treated with a humidifier or the like. It can be adjusted by a method such as; The volatilization fraction of the PVA film can be determined from the mass reduction rate when the PVA film is placed in a vacuum dryer at a temperature of 50° C. and a pressure of 0.1 kPa or less and dried until there is no loss of mass.

Moreover, the film temperature at the time of cutting a PVA film along a longitudinal direction with a rotating round blade is preferably 10°C or higher, more preferably 20°C or higher, further preferably 70°C or lower, and 60°C or lower It is more preferable. When the film temperature is more than the above lower limit, the PVA film does not become too hard, and cutting is facilitated. Furthermore, water droplets based on condensation adhere to the PVA film, and it is possible to suppress the occurrence of blocking when the PVA film after the cutting treatment is rolled up and stored, or breakage from the part where the water droplets adhere when the PVA film is stretched. have. On the other hand, when the said film temperature is below the said upper limit, it can suppress that a PVA film becomes too flexible, and can make the degree of roughening of a cut cross section smaller. In addition, the film temperature of a PVA film can be measured using a spot type digital radiation thermometer (for example, "Therometer 505A" manufactured by Minolta Co., Ltd.).

Cutting along the longitudinal direction of the PVA film by a rotating round blade may be performed continuously in the manufacturing process of the PVA film, or after the PVA film is manufactured and wound up in a roll shape, the PVA film is rewound from the roll. May be

The method for producing the PVA film provided for cutting is not particularly limited, and can be prepared by a method known in the art, for example, the above-described PVA constituting the PVA film, and the above-described plasticizer and surfactant, if necessary. And one or two or more of the other components, etc., a film-forming stock solution dissolved in a liquid medium, PVA, and, if necessary, one or two or more of plasticizers, surfactants, and other components. It can be produced using a molten film forming stock solution. When the said film forming undiluted|stock solution contains at least 1 sort(s) of a plasticizer, surfactant, and other components, it is preferable that these components are mixed uniformly.

Examples of the liquid medium used in the preparation of the membrane-forming stock solution include water, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, ethylene glycol, glycerin, propylene glycol, diethylene glycol, and tri And ethylene glycol, tetraethylene glycol, trimethylolpropane, ethylenediamine, diethylenetriamine, and the like, and one or two or more of them can be used. Among them, water is preferred from the viewpoint of environmental load and recoverability.

Examples of the film forming method for forming a PVA film using the above-mentioned film forming undiluted solution include a cast film forming method, an extrusion film forming method, a wet film forming method, and a gel film forming method. These film-forming methods may be employed alone or in combination of two or more. Among these film forming methods, the cast film forming method and the extrusion film forming method are preferable from the viewpoint of smoothly producing a PVA film that provides a good polarizing film. Drying or heat treatment may be performed on the formed film as necessary.

As an example of a specific manufacturing method of the PVA film provided for cutting, for example, by using a T-shaped slit die, a hopper plate, an I-die, a lip coater die, etc., the above-mentioned film forming stock solution is rotated and heated to the uppermost side Uniformly discharged or pliable on the circumferential surface of one first roll (or belt), evaporated and dried by volatile components from one side of the film ejected or plied on the circumferential surface of the first roll (or belt), The method of re-driing on the circumferential surface of one or a plurality of rotating heated rolls arranged on the downstream side thereof again, or drying again by passing through a hot-air drying apparatus, and then winding up by a winding apparatus It can be preferably employed. Drying with a heated roll and drying with a hot air drying device may be performed in appropriate combination.

There are no particular limitations on the use of the PVA film of the present invention, for example, a film for pharmaceutical packaging, a base film for liquid pressure transfer, a base film for embroidery, a release film for artificial marble molding, a film for seed packaging, a film for dirt storage bag, etc. Although it can be used for various water-soluble films, the PVA film of the present invention in which at least one of the two ends along the longitudinal direction of the film, preferably both of them forms a cutting end, has a "maximum height roughness of the cut end of the cutting end." (Rz)” is below a certain value, and the cut section has a very low degree of roughening and excellent smoothness, so that cracks are generated at the cut end (end in the width direction of the film) when stretched in the longitudinal direction. It is difficult, and as a result, it is difficult to break the film. From this point of view, it is preferable to use the PVA film of the present invention as a raw film for manufacturing an optical film (a raw film for optical film production). As such an optical film, a polarizing film, a retardation film, etc. are mentioned, for example, A polarizing film is preferable. Such an optical film can be produced, for example, by performing treatment such as uniaxial stretching using the film of the present invention.

The method at the time of manufacturing a polarizing film using the PVA film of this invention is not specifically limited, You may employ|adopt any method known conventionally. As such a method, the method of dyeing and uniaxial stretching is performed using the PVA film of this invention, for example, or the method of uniaxial stretching is performed for the PVA film of this invention containing a dye. . As a more specific method for producing a polarizing film, a method of subjecting the PVA film of the present invention to swelling, dyeing, uniaxial stretching, and further crosslinking treatment, fixing treatment, drying, heat treatment, and the like as necessary. have. In this case, the order of each treatment such as swelling, dyeing, crosslinking treatment, uniaxial stretching, fixing treatment, etc. is not particularly limited, and one or two or more treatments may be simultaneously performed. Moreover, 1 or 2 or more of each process can also be performed twice or more.

Swelling can be performed by immersing a PVA film in water. The temperature of the water when immersed in water is preferably in the range of 20 to 40°C, more preferably in the range of 22 to 38°C, and more preferably in the range of 25 to 35°C. Moreover, as time to immerse in water, it is preferable to exist in the range of 0.1-5 minutes, for example, and it is more preferable to exist in the range of 0.5-3 minutes. In addition, water when immersed in water is not limited to pure water, and may be an aqueous solution in which various components are dissolved, or a mixture of water and an aqueous medium.

Dyeing can be performed by bringing the dichroic dye into contact with the PVA film. It is common to use an iodine dye as a dichroic dye. As a period of dyeing, any stage before uniaxial stretching, upon uniaxial stretching, or after uniaxial stretching may be used. Dyeing is generally performed by immersing the PVA film in a solution (especially an aqueous solution) containing iodine-potassium iodide as a dyeing bath, and in the present invention, such a dyeing method is preferably employed. The concentration of iodine in the dyeing bath is preferably in the range of 0.01 to 0.5% by mass, and the concentration of potassium iodide is preferably in the range of 0.01 to 10% by mass. Moreover, it is preferable to set the temperature of a dyeing bath to 20-50 degreeC, especially 25-40 degreeC.

By subjecting the PVA film to a crosslinking treatment, it is possible to more effectively prevent elution of PVA in water when wet stretching at a high temperature. From this viewpoint, the crosslinking treatment is preferably performed after uniaxial stretching as a treatment after contacting the dichroic dye. The crosslinking treatment can be performed by immersing the PVA film in an aqueous solution containing a crosslinking agent. As said crosslinking agent, 1 type(s) or 2 or more types of boron compounds, such as borates, such as boric acid and borax, can be used. The concentration of the crosslinking agent in the aqueous solution containing the crosslinking agent is preferably in the range of 1 to 15% by mass, more preferably in the range of 2 to 7% by mass, and more preferably in the range of 3 to 6% by mass. When the concentration of the crosslinking agent is in the range of 1 to 15% by mass, sufficient stretchability can be maintained. The aqueous solution containing a crosslinking agent may contain an auxiliary agent such as potassium iodide. The temperature of the aqueous solution containing the crosslinking agent is preferably in the range of 20 to 50°C, particularly in the range of 25 to 40°C. Crosslinking can be performed efficiently by setting the temperature within the range of 20 to 50°C.

The uniaxial stretching may be performed by either a wet stretching method or a dry heat stretching method. In the case of the wet stretching method, it may be carried out in an aqueous solution containing boric acid, or in the above-described dyeing bath or in a fixed treatment bath described later. Further, in the case of the dry stretching method, stretching may be performed at room temperature, stretching may be performed while heating, or may be carried out in air using a PVA film after absorption. Among these, a wet stretching method is preferred, and more preferably uniaxial stretching in an aqueous solution containing boric acid. The concentration of boric acid in the boric acid aqueous solution is preferably in the range of 0.5 to 6.0 mass%, more preferably in the range of 1.0 to 5.0 mass%, and particularly preferably in the range of 1.5 to 4.0 mass%. Moreover, the aqueous solution of boric acid may contain potassium iodide, and the concentration is preferably within the range of 0.01 to 10% by mass.

The stretching temperature in uniaxial stretching is not particularly limited, but in the case of the wet stretching method, it is preferably in the range of 30 to 90°C, more preferably in the range of 40 to 80°C, and more preferably in the range of 50 to 70°C It is particularly preferable that it is inner. Moreover, in the case of a dry heat drawing method, it is preferable to exist in the range of 50-180 degreeC.

Moreover, it is preferable that the draw ratio in uniaxial stretching (stretching ratio of the total multiplied by each draw ratio in the case of performing uniaxial stretching in multiple stages) is 4 times or more from the point of polarization performance of the obtained polarizing film, 5 More preferably, it is twice or more. The upper limit of the stretching ratio is not particularly limited, but is preferably 8 times or less in order to perform uniform stretching.

Although there is no particular limitation in the direction of uniaxial stretching, uniaxial stretching or transverse uniaxial stretching of a long PVA film can be employed, but a uniaxial direction in a long direction from the viewpoint of obtaining a polarizing film having excellent polarization performance. Stretching is preferred. The uniaxial stretching in the long direction can be carried out by changing the peripheral speed between the rolls by using a stretching device having a plurality of rolls parallel to each other. On the other hand, transverse uniaxial stretching can be performed using a tenter-type stretching machine.

In the manufacture of a polarizing film, it is preferable to perform a fixing treatment in order to strengthen the adsorption of a dichroic dye (iodine dye, etc.) to a PVA film. The fixing treatment can be carried out by immersing the PVA film in the fixing treatment bath. As the fixed treatment bath, an aqueous solution containing one or two or more types of boron compounds such as boric acid and borax can be used. Moreover, you may add an iodine compound or a metal compound in a fixed treatment bath as needed. The concentration of the boron compound in the fixed treatment bath is generally about 2 to 15 mass%, particularly preferably about 3 to 10 mass%. Adsorption of the dichroic dye can be made stronger by setting the concentration within the range of 2 to 15 mass%. The temperature of the fixed treatment bath is preferably 15 to 60°C, particularly 25 to 40°C.

Although conditions for drying are not particularly limited, drying is preferably performed at a temperature in the range of 30 to 150°C, particularly in the range of 50 to 140°C. It is easy to obtain a polarizing film excellent in dimensional stability by drying at a temperature within the range of 30 to 150°C, and suppressing a decrease in polarization performance based on decomposition of the dichroic dye.

Although the thickness of the polarizing film obtained as mentioned above differs depending on the thickness of the PVA film to be used, etc., from the viewpoints of polarization performance, handleability, durability, etc., it is preferably 30 µm or less, more preferably 25 µm or less, and more preferably 20 µm. It is more preferable that it is the following, particularly preferably 15 µm or less, further preferably 1 µm or more, more preferably 2 µm or more, further preferably 4 µm or more, and particularly preferably 6 µm or more.

The polarizing film obtained as described above is usually used in the form of a polarizing plate by bonding a protective film having optically transparent and mechanical strength to both sides or one side thereof. As the protective film, a cellulose acetate (TAC) film, a cycloolefin polymer (COP) film, an acetic acid-butyrate cellulose (CAB) film, an acrylic film, or a polyester film is used. Moreover, although a PVA system adhesive, a urethane system adhesive, etc. are mentioned as an adhesive for bonding, a PVA system adhesive is especially preferable.

The polarizing plate obtained as mentioned above can be used as a component of an LCD by coating an adhesive such as an acrylic system and then bonding it to a glass substrate. At the same time, a retardation film, a viewing angle improvement film, and a brightness enhancement film may be combined.

Example

Hereinafter, the present invention will be specifically described by examples and the like, but the present invention is not limited at all by the following examples.

In the following examples, evaluation of each physical property was performed by the following method.

(1) Measurement of "maximum height roughness (Rz)" and "arithmetic mean roughness (Ra)" of the cut section of the PVA film:

The film portion of the outermost layer of the roll of the PVA film (PVA film having a cutting end along the longitudinal direction) wound in a roll shape after cutting along the longitudinal direction of the film (especially 500 m in the longitudinal direction of the film from the starting point of cutting) From the portion immediately after), a sample containing a cut end of 30 mm in length is taken along the length direction of the film (sample sampling score 3), and along the length direction of the film at any position of the cut section of the sample taken. The cut section was measured using a super depth shape measuring microscope "VK-8500" manufactured by Keyence Corporation over a length of 100 µm, and the surface state on the line in the longitudinal direction of the film in the center of the thickness direction on the cut section Based on the calculation of the "maximum height roughness (Rz)" and "arithmetic mean roughness (Ra)" specified in JIS B 0601: 2001, the "maximum height roughness (Rz)" of the cut section and "Arithmetic mean roughness (Ra)" was calculated respectively, and the average value of three points was calculated.

In addition, at the start and intermediate stages of cutting, since the cutting edge has no or little wear, and a smooth cutting section with a low degree of roughening is formed, the cutting section at the start of winding into the roll and at the intermediate point of winding. The measurement of the degree of roughening is omitted, and the maximum height of the cut section is shown at the point immediately before the end of the cut (the film portion of the outermost layer of the roll of the PVA film rolled after cutting) where the wear of the cutting blade is greatest. Roughness (Rz)” and arithmetic mean roughness (Ra) were determined, and the degree of roughening of the cut section was evaluated.

(2) Confirmation of the presence or absence of breakage at the time of stretching of the PVA film (stretch magnification at the time of film breakage):

(i) Confirmation of whether or not the PVA film having a cut end along the longitudinal direction breaks during stretching is originally required to be performed in a continuous stretching operation when producing a polarizing film, but the PVA film during stretching The rupture of is usually a frequency of whether it occurs once every several hours, and since it is difficult to conduct a test based on practical use, evaluation was conducted by the model test of (ii) below.

(ii) the film portion of the outermost layer of the roll of the PVA film (PVA film having a cutting end along the longitudinal direction) wound in a roll shape after cutting along the longitudinal direction of the film (especially 500 in the longitudinal direction of the film from the starting point of cutting) 1) As shown in Fig. 1, as shown in Fig. 1, parallel to the longitudinal direction of the film, one side (long side) in the longitudinal direction of the sample was the cutting end, and the length x width = 15 cm x 10 cm. A rectangular sample of size (sample S shown in Fig. 1) was collected (sample sampling score 3). In addition, at that time, the cutter blades whose cutting edges were renewed so that the cuts of the three sides other than the side corresponding to the cut end were cut off with every cut of one side so as to form a smooth cut surface that was not roughened (made by Enuti Co., Ltd. Blade”).

(iii) Samples from both ends (two transverse sides) in the longitudinal direction of the sample taken in (ii) were gripped with a pair of chucks at a distance of 4 cm between the chucks, mounted on a batch stretching machine, and the entire sample was 30°C. After immersing in water for 1 minute and swelling with water, the whole sample is immediately immersed in a 4% aqueous solution of boric acid at 50° C., and immersed in water for 1 minute, and then stretched in a boric acid aqueous solution under conditions of a stretching rate of 0.15 m/min. Then, the distance between the chucks at the time of breakage of the sample was measured, the stretching ratio at breakage was obtained from the following equation, and the average value of the three samples was adopted.

Elongation at break (times) = distance between chucks at sample break (cm)/4 (cm)

(iv) As a control, the film portion of the outermost layer of the roll of the PVA film (PVA film having a cut end along the lengthwise direction) wound on the same roll as the sample taken in (ii) above (especially the film from the point of cut start) A rectangular sample of length × width = 15 cm × 10 cm was taken parallel to the lengthwise direction of the film from the almost central portion in the width direction (the portion immediately after cutting 500 m in the longitudinal direction of ). (A sample having no cutting cross-section) (Sampling score 3). In addition, in the sampling of this sample (iv), the cutter blade was renewed so that the four sides (four cut cross-sections) of the sample were cut smoothly for each cut of one side so as not to be roughened and finished smoothly. The cut operation was performed using ("A blade" manufactured by Enuti Co., Ltd.).

(v) Using the control sample obtained in (iv) above, the draw ratio at break was determined in the same manner as in (iii) above, and the average value of the three samples was adopted.

[Example 1]

(1) PVA chip (polymerization degree of PVA 2,400, saponification degree 99.9 mol%) After impregnating 12 parts by mass of glycerin and 220 parts by mass of water, PVA chips after impregnation are fed to an extruder and melted under heat and pressure to form PVA. Prepare a molten film forming stock solution, extrude the film forming stock solution on a first metal roll (surface temperature of the metal roll of 95° C. and a diameter of 3.8 m of the metal roll), and alternately change the front and back surfaces on 10 metal rolls. By drying with, a long PVA film was continuously produced (film width 3 m, thickness 20 µm).

(2) As a cutting device for cutting a PVA film, a groove forming roll 10 as illustrated in Fig. 3(a) on the upstream side of a winder for winding the formed PVA film into a roll shape (metal; The diameter Eb 20 cm of the large diameter portion, the width Wa 8 mm of the large diameter portion Eb; the diameter Ec 19 cm of the small diameter portion, the width Wb 2 mm of the small diameter portion), and the amount in the width direction of the groove forming roll 10 However, the new two-blade round blade (2) illustrated in Fig. 3(a) freely rotated by a ball bearing at the position of the small-diameter portion in the vicinity (Vickers hardness 1,850 HV at the tip of the blade; diameter Ea 45 mm of the round blade; Blade tip angle α 40 ˚ ； Thick portion of the blade base (thick portion just before the thickness gradually decreases toward the blade tip) d 0.3 mm ； Length of the blade (distance from the blade base to the tip of the blade) e 0.85 mm) each 1 Dogs were placed.

(3) The PVA film (3% by mass of volatile content in the film) prepared in (1) was supplied to the cutting device prepared in (2) above, and at that time, the PVA of the PVA to the circumferential surface of the groove forming roll (10). The PVA film was brought into contact with the surface of the large-diameter portion of the groove forming roll 10 in a state where the PVA film was poured along a part of the circumference of the groove forming roll 10 with a contact angle β (shell angle) of 90 degrees. The both ends of the PVA film are cut along the longitudinal direction with a new rounded blade (2) of a new product which is fed at a speed of 17 m/min and freely rotates by a ball bearing to form a film with a width of 2.6 m. , Winding continuously in a roll shape on an aluminum tube (about 15.2 cm in diameter) with a winder, to obtain a PVA film having a total length of 500 m or more (winding length of 500 m or more) having a cut section at both ends along the longitudinal direction. The temperature of the PVA film at the time of cutting by a rotating round blade was 30 degreeC.

(4) Using the PVA film wound in a roll shape with a length of 500 m or more obtained in (3) above, the above-described method of "maximum height roughness (Rz)" and "arithmetic mean roughness (Ra)" of the cut section As a result, the maximum height roughness (Rz) was 0.85 µm, the arithmetic mean roughness (Ra) was 0.13 µm, and Rz/Ra was 6.8, and the cut section along the longitudinal direction (overall length) was adjusted over a section of 500 m or more. The degree of cotton was very low, and the smoothness was excellent.

(5) Moreover, it was 6.1 times as a result of measuring the draw ratio at the time of film breaking using the above-mentioned method using the PVA film wound up in roll shape with the length of 500 m or more obtained in said (3). On the other hand, the draw ratio at the time of film breakage in the control sample (the sample taken from the almost central portion in the width direction of the PVA film) was also 6.1 times.

[Example 2]

(1) In (2) of Example 1, both ends along the longitudinal direction in the same manner as in (1) to (3) of Example 1, except that a new round blade having a blade tip angle α of 45° was used. To obtain a PVA film with a total length of 500 m or more (winding length of 500 m or more) having a cut section.

(2) Using the PVA film wound in a roll shape with a length of 500 m or more obtained in (1) above, the above-described method of "maximum height roughness (Rz)" and "arithmetic mean roughness (Ra)" of the cut section As a result of measurement, the maximum height roughness (Rz) was 0.98 µm, the arithmetic mean roughness (Ra) was 0.15 µm, and Rz/Ra was 6.7, and the cut section along the longitudinal direction (overall length) was roughly over 500 m. The degree of cotton was very low, and the smoothness was excellent.

(3) Moreover, it was 6.0 times as a result of measuring the draw ratio at the time of film breaking using the above-mentioned method using the PVA film wound up in roll shape with the length of 500 m or more obtained in said (1).

[Example 3]

(1) In (2) of Example 1, both ends along the longitudinal direction in the same manner as in (1) to (3) of Example 1, except that a new round blade having a blade tip angle α of 30° was used. To obtain a PVA film with a total length of 500 m or more (winding length of 500 m or more) having a cut section.

(2) Using the PVA film wound in a roll shape with a length of 500 m or more obtained in (1) above, the above-described method of "maximum height roughness (Rz)" and "arithmetic mean roughness (Ra)" of the cut section As a result of measurement, the maximum height roughness (Rz) was 1.19 μm, the arithmetic mean roughness (Ra) was 0.15 μm, and Rz/Ra was 7.8, and the cut section along the longitudinal direction (total length) was roughly over 500 m. The degree of cotton was very low, and the smoothness was excellent.

(3) Moreover, it was 5.9 times as a result of measuring the draw ratio at the time of film breaking using the above-mentioned method using the PVA film wound up in roll shape with the length of about 500 m obtained in said (1).

[Comparative Example 1]

(1) In (3) of Example 1, the Vickers hardness of the blade end part is the same as (1) to (3) of Example 1, except that a new round blade of (SKS-7) having a HV of 300 HV or less is used. Thus, a PVA film having a total length of 500 m or more (winding length of 500 m or more) having a cut section at both ends along the length direction was obtained.

(2) Using the PVA film wound in a roll shape with a length of 500 m or more obtained in (1) above, the above-described method of "maximum height roughness (Rz)" and "arithmetic mean roughness (Ra)" of the cut section As a result, the maximum height roughness (Rz) was 2.68 µm, the arithmetic mean roughness (Ra) was 0.50 µm, and Rz/Ra was 5.4, and the degree of roughening of the cut section was higher than those in Examples 1 to 3.

(3) In addition, using the PVA film wound in a roll shape with a length of 500 m or more obtained in the above (1), the stretching magnification at the time of film breakage was measured by the method described above, which was 5.6 times, Examples 1 to It was easy to break when stretched compared to 3.

[Comparative Example 2]

(1) In (3) of Example 1, both ends along the longitudinal direction in the same manner as in (1) to (3) of Example 1, except that a new round blade having a blade end angle α of 23° was used. To obtain a PVA film with a total length of 500 m or more (winding length of 500 m or more) having a cut section.

(2) Using the PVA film wound in a roll shape with a length of 500 m or more obtained in (1) above, the above-described method of "maximum height roughness (Rz)" and "arithmetic mean roughness (Ra)" of the cut section As a result, the maximum height roughness (Rz) was 3.22 µm, the arithmetic mean roughness (Ra) was 0.67 µm, and Rz/Ra was 4.8, and the degree of roughening of the cut section was higher than in Examples 1 to 3.

(3) In addition, using the PVA film wound in a roll shape with a length of 500 m or more obtained in the above (1), the stretching magnification at the time of film breakage was measured by the method described above, which was 5.6 times, Examples 1 to It was easy to break when stretched compared to 3.

The above results are shown in the table below.

1: PVA film
2: round blade
3: Round blade tip
4, 4': Polished surface
5: vertical plane
6: Polished cotton
7: Round blade mounting member
8: Rotation axis
9: bearing
10: groove forming roll
10a: large diameter portion of the groove forming roll
10b: Small diameter portion of the groove forming roll

Claims (9)

A long polyvinyl alcohol film having a thickness of 55 μm or less and a length of 500 m or more, wherein at least one of the two ends along the length direction of the film is a cutting end formed by a cutting blade, and the maximum height of the cutting section of the cutting end The polyvinyl alcohol film whose roughness (Rz) is 2.5 µm or less over a section of 500 m or more in length of the film. According to claim 1,
The polyvinyl alcohol film whose arithmetic mean roughness (Ra) of a cut section is 0.4 micrometer or less over the said section. The method of claim 1 or 2,
A polyvinyl alcohol film having a length of 1,000 m or more. The method according to any one of claims 1 to 3,
A polyvinyl alcohol film, which is a raw film for optical film production. The method according to any one of claims 1 to 4,
The polyvinyl alcohol film whose optical film is a polarizing film. A roll comprising the polyvinyl alcohol film according to any one of claims 1 to 5 wound in a roll shape. A method for producing a long polyvinyl alcohol film having a thickness of 55 µm or less and a length of 500 m or more, wherein at least one of the two ends along the length direction of the film is a cutting end formed by a cutting blade, the large-diameter portion of which the film contacts Using a groove-forming roll having a small-diameter portion where the film does not contact the roll-axis direction, and conveying a long polyvinyl alcohol film to the surface of the large-diameter portion of the groove-forming roll while transferring the small-diameter portion of the groove-forming roll It has a process of cutting the polyvinyl alcohol film along the longitudinal direction by a round blade rotating in position, wherein the round blade has a blade tip angle of 25-50°, and a Vickers hardness of the blade tip portion is 1,500 HV or higher. The method of claim 7,
A manufacturing method in which a polyvinyl alcohol film is contacted at an angle of 10 to 100° along the circumference of the groove forming roll. The method of claim 7 or 8,
The manufacturing method which is a manufacturing method for manufacturing the polyvinyl alcohol film in any one of Claims 1-5.

Images