KR20180006899A - Polyvinyl alcohol film - Google Patents

Abstract

The present invention relates to a long polyvinyl alcohol film (1) having a thickness of at most 55 m and a length of at least 500 m, characterized in that at least one of the two ends along the longitudinal direction of the film is a cut end (A, A , And the maximum height height Rz of the cut end faces B and B 'of the cut end portions is not more than 2.5 m over a section of the film having a length of 500 m or more, and the polyvinyl alcohol film (1) The present invention relates to a roll in which an alcohol film is rolled up.

Description

[0001] POLYVINYL ALCOHOL FILM [0002]

The present invention relates to a thin polyvinyl alcohol film (hereinafter sometimes referred to as " PVA ") having a specific cut section, a roll obtained by winding it in a roll form, To a method for producing a PVA film.

A polarizing plate having light transmission and shielding functions is a fundamental component of a liquid crystal display (LCD) together with a liquid crystal having a light switching function. The application field of this LCD is also being developed from small electronic devices such as an electronic desk calculator and a wrist watch at the early stage of development to a laptop PC, a word processor, a liquid crystal color projector, a vehicle navigation system, a liquid crystal television, a personal phone, And the like. In view of this, a polarizer having higher quality and moreover lower cost is required.

The polarizing plate is generally prepared by a method in which a PVA film is uniaxially stretched after dyeing or uniaxially or uniaxially stretched while dyeing to form a dyed uniaxially stretched film and fixed with a boron compound, After the polarizing film is produced by a method such as dyeing and fixing treatment with a boron compound in the uniaxial stretching and dyeing treatment, a cellulose acetic acid (TAC) film, cellulose acetate butyrate ( CAB) film or the like.

In the production of a polarizing plate, a method of continuously performing processes such as uniaxial stretching, dyeing, fixing, and adhesion of a protective film by using a raw film in which a long PVA film is wound in a roll form is widely used Has been adopted.

In the PVA film, both end portions in the width direction of the film tend to differ in thickness and degree of drying with respect to the central portion after film formation, and when uniaxially elongating with both end portions in the width direction remaining, Direction is cut off and then wound in a roll form and supplied to a customer such as a polarizing plate maker.

In addition, in order to provide a film width equivalent to a demand of a demanding customer such as a polarizing plate maker, the formed PVA film may be cut at the center portion in the width direction of the film, The film is cut in the longitudinal direction at the outer position to make the film have a predetermined width as desired, and the film is rolled up and delivered to the customer.

In the production of a polarizing film from a PVA film, in order to obtain a high polarization performance, a PVA film is generally uniaxially stretched in the longitudinal direction at a high stretching magnification. However, when the cutting edge of the film is roughened, The roughened portion at the time of uniaxial stretching becomes a starting point of crack generation and cracks are generated at the end portion and in the severe case, the film may be broken from the crack portion in some cases. When the film is broken, it is necessary to temporarily stop the uniaxial stretching process to remove the ruptured portion, and then to perform the stretching process again, resulting in a drastic decrease in the 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 section along the longitudinal direction of the film, which does not cause cracking or breakage during stretching.

Several methods for cutting PVA films have been known so far (see Patent Documents 1 to 3, etc.). Patent Document 1 discloses a method of setting the temperature and volatile content of the PVA film provided for cutting to respective specific ranges. As a cutting method, there is a method of cutting a film between two rolls, a method of cutting on a groove forming roll . Patent Document 2 discloses an optical PVA film having a specific surface average roughness (Ra). As a cutting method, a method of using a shear blade composed of an upper blade and a lower blade or a method of using a laser blade is described have. Patent Document 3 discloses an elongated PVA film in which the maximum height Ry of the cut section is in a specific range over the entire length of the film. In order to form one cut end as a cutting method, each one rounded round blade , A groove forming roll is used, and an edge angle of a round blade is preferably 3 to 20 DEG.

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

In recent years, a PVA film having a thickness of about 75 占 퐉 has been generally used as a raw material film for polarizing film production in recent years, but recently, a PVA film having a thickness of less than 70 占 퐉 has been used Is required. However, a thin PVA film has a problem that it is liable to be broken more than a conventional thickness at the time of processing such as uniaxial stretching.

An object of the present invention is to provide a thin PVA film which is hard to break at the time of processing such as uniaxial stretching and a roll in which it is wound in a roll form. It is also an object of the present invention to provide a method for producing a PVA film for smoothly producing such a PVA film.

The inventors of the present invention have made intensive investigations in order to achieve the above object. As a result, it has been found that, in a PVA film having a thickness of 55 m or less, the maximum height By setting the roughness Rz to a specific range, it has been found that even though it is a thin PVA film, it is difficult to break at the time of processing such as uniaxial stretching. Further, the inventors of the present invention have found that when a PVA film is cut along a longitudinal direction by a rotating round blade while conveying the PVA film before cutting with a groove forming roll, the circular blade has a specific blade angle, Has a hardness in a specific range, it is possible to smoothly produce the above-mentioned thin PVA film which is difficult to be broken. The inventors of the present invention have conducted further studies based on these findings and completed the present invention.

That is,

[1] A long PVA film having a thickness of 55 탆 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 cut end formed by a cutting edge, A PVA film having a height roughness Rz of not more than 2.5 mu m over a section of the film having a length of 500 m or more;

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

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

[4] A PVA film according to any one of [1] to [3], which is a raw film for producing an optical film.

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

[6] A roll obtained by winding a PVA film of any one of the above [1] to [5] in a roll form;

[7] A method for producing an elongated PVA film having a thickness of 55 m 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 cut end formed by a cutting blade, A groove forming roll having a small diameter portion in which the diameter portion and the film are not in contact with each other in the roll axis direction is used and a long PVA film is brought into contact with the surface of the large diameter portion of the groove forming roll, Wherein the rounded edge has a blade angle of 25 to 50 ° and a Vickers hardness of the blade edge of 1,500 HV or more;

[8] The production method of the above-mentioned [7], wherein the PVA film is brought into contact with the circumference of the groove forming roll at an angle of 10 to 100 °.

[9] A production method for producing a PVA film according to any one of [1] to [5], wherein the production method of the above [7] or [8]

.

According to the present invention, there is provided a thin PVA film which is difficult to break at the time of processing such as uniaxial stretching, and a roll in which it is wound in a roll form. According to the present invention, there is also provided a process for producing a PVA film capable of smoothly producing such a PVA film.

Fig. 1 is a view 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 diagram schematically showing an example of a groove forming roll and an example of a cutting method of a PVA film using a groove forming roll.

Hereinafter, the present invention will be described in detail.

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 edge. In the PVA film, only one end portion along the longitudinal direction of the film may be provided with a cut end, and both end portions along the longitudinal direction of the film may be provided with cut ends. Both end portions along the longitudinal direction of the film It is preferable to be a cut end. There is no particular limitation on the cutting edge forming the cut end, and for example, a shear blade, a laser blade, a round blade, or the like can be mentioned, and a round blade described later is preferable.

In the PVA film of the present invention, the maximum height of the cut surface (Rz) of the cut end of the cut end is 2.5 占 퐉 or less over the section of the film having a length of 500 m or more. That is, for example, when the length of the PVA film of the present invention is 3,000 m, the maximum height illuminance Rz is within the above range in at least a continuous section of 500 m of the length of the cut section.

1, cut end portions A and A 'along the longitudinal direction of the PVA film 1 (Fig. 1, both end portions along the longitudinal direction of the PVA film 1 are cut off) (Cut surfaces) (B and B ') corresponding to the thickness portion of the PVA film 1 in the case where the PVA film 1 is the end portion.

The maximum height height Rz can be obtained by measuring the surface roughness of the cut surface in a range of a predetermined length L along the longitudinal direction of the cut surface by using, for example, an ultrafine shape measuring microscope or the like, (Rz = Rp + Rv) of the maximum peak height Rp of the upper part of the average line of the roughness curve (the average line in the longitudinal direction of the film) and the maximum valley depth Rv of the lower part, The following is described in JIS B 0601: 2001. The roughness curve can be obtained from the surface state on the line in the longitudinal direction of the film at the center in the thickness direction on the cut surface to be measured. Generally, when cutting the PVA film, since the cut surface gradually becomes rough as time elapses from the start of cutting, the maximum height roughness (Rz) and the arithmetic mean roughness (Ra) Becomes larger as the time elapses from the start of cutting. Therefore, the maximum height roughness (Rz) to the arithmetic mean roughness (Ra) of the cut section at a portion (measurement point) after cutting a specific length (for example, 500 m) (Rz) to the arithmetic mean roughness (Ra) in the cross section of the cut may be equal to or less than their measured values over the entire range from the cutting start point to the measurement point when their measured values are below a specific value have.

The PVA film of the present invention is required to have a maximum height Rz of the cut section of 2.5 m or less over a section of 500 m or longer in length from the viewpoint of preventing breakage during processing such as uniaxial stretching, Mu m or less, more preferably 1.5 mu m or less, further preferably 1 mu m or less, particularly preferably 0.9 mu m or less. There is no particular limitation on the lower limit of the maximum height Rz of the film. From the viewpoint of ease of production of the PVA film of the present invention, the maximum height Rz of the cut section is preferably 0.01 占 퐉 The PVA film is preferably a PVA film having no section in which the maximum height roughness Rz of the cut section is 0.1 mu m or less over a section of 500 m in length of the film, The maximum height Rz of the PVA film is 0.3 mu m or less over the length of 500 m of the film.

In the PVA film of the present invention, if the arithmetic average roughness Ra of the cut section is 0.4 mu m or less over the section regarding the maximum height roughness Rz, fracture at the time of processing such as uniaxial stretching can be prevented more effectively . From such a viewpoint, in the PVA film of the present invention, the arithmetic mean roughness Ra of the cut section is more preferably 0.3 mu m or less, more preferably 0.2 mu m or less, and particularly preferably 0.14 mu m or less . There is no particular limitation on the lower limit of the arithmetic average roughness Ra, but from the viewpoint of easiness of production of the PVA film of the present invention and the like, the arithmetic mean roughness Ra of the cut section is 0.001 탆 or less over the above- And the arithmetic average roughness Ra of the cut section is more preferably 0.01 m or less over the section is more preferable and the arithmetic average roughness Ra of the cut section is larger than the range Is preferably 0.03 mu m or less.

Here, the arithmetic average roughness Ra can be obtained according to the description of JIS B 0601: 2001 for 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 average roughness Rz over the above section with respect to the maximum height roughness Rz from the viewpoint of further effectively preventing breakage during processing such as uniaxial stretching, 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 an index of the degree of abrasion of the blade used for cutting the PVA film. When the abrasion of the blade is severe, the ratio (Rz / Ra) The degree of roughening is likely to increase.

The thickness of the PVA film of the present invention is preferably 55 탆 or less, preferably 50 탆 or less, more preferably 45 탆 or less, and even more preferably 40 탆 or less for reasons such as meeting the requirement for a thinner PVA film , And particularly preferably 30 m or less. The thickness is preferably not less than 3 占 퐉, more preferably not less than 5 占 퐉, and more preferably not less than 15 占 퐉 in view of practicality, ease of production of the film, ease of stretching treatment, Or more.

The width of the PVA film of the present invention can be selected according to the use of the PVA film and the demand of the demand of the PVA film, and the like. In general, the width is preferably 2 m or more, more preferably 2.5 m or more, And is preferably 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 in terms of being able to be used continuously for a long time in use. The upper limit of the length is not particularly limited, and the length may be, for example, 30,000 m or less. The PVA film of the present invention is preferably in the form of a roll rolled up in terms of ease of transportation, storage and use.

Examples of the PVA constituting the PVA film of the present invention include unmodified PVA obtained by saponifying a polyvinyl ester obtained by polymerizing a vinyl ester, modified PVA obtained by graft copolymerizing a comonomer with a main chain of the PVA, Modified PVA produced by saponifying a modified polyvinyl ester copolymerized with a monomer, so-called polyvinyl acetal resin obtained by crosslinking a part of the hydroxyl groups of unmodified PVA or modified PVA 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 ester used in the production of PVA include vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl valerate, vinyl pivalate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl valerate And the like. These vinyl esters can be used singly or in combination. Among these vinyl esters, vinyl acetate is preferable from the viewpoint of productivity.

Examples of the comonomer include olefins having 2 to 30 carbon atoms such as ethylene, propylene, 1-butene and isobutene (e.g.,? -Olefins); acrylic acid or its salts; methyl acrylate, ethyl acrylate, Acrylic acid esters such as propyl acrylate, i-propyl acrylate, n-butyl acrylate, i-butyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate and octadecyl acrylate Propyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, and the like), methacrylic acid or its salt, methyl methacrylate, ethyl methacrylate, n- Methacrylic acid esters such as t-butyl methacrylate, 2-ethylhexyl methacrylate, undecyl methacrylate and octadecyl methacrylate (for example, alkyl esters having 1 to 18 carbon atoms in the methacrylic acid); Acrylamide, N-methylacrylamide , Acrylamide such as N-ethyl acrylamide, N, N-dimethyl acrylamide, diacetone acrylamide, acrylamide propane sulfonic acid or its salt, acrylamide propyl dimethyl amine or its salt, N-methylol acrylamide or its derivative Derivatives thereof, methacrylamide, N-methylmethacrylamide, N-ethylmethacrylamide, methacrylamide propanesulfonic acid or salts thereof, methacrylamidopropyldimethylamine or salts thereof, N-methylolmethacrylamide or derivatives thereof N-vinylamides such as N-vinylformamide, N-vinylacetamide and N-vinylpyrrolidone, methylvinylether, ethylvinylether, n-propylvinylether, i-propylvinylether Vinyl ethers such as vinyl ether, n-butyl vinyl ether, i-butyl vinyl ether, t-butyl vinyl ether, dodecyl vinyl ether and stearyl vinyl ether; acrylonitrile, Nitriles such as acetonitrile, nitrile and the like, 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, And derivatives thereof; vinylsilyl compounds such as vinyltrimethoxysilane; isopropenyl acetate; and unsaturated sulfonic acid or derivatives thereof. These comonomers may be used singly or in combination of two or more. Among these comonomers,? -Olefins are preferable, and ethylene is particularly preferable.

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 view of obtaining a polarizing film excellent in polarization performance and durability when a polarizing film is produced by uniaxially stretching the PVA film of the present invention . From the viewpoints of ease of production and elongation property for producing a homogeneous PVA film, the degree of polymerization of PVA is preferably 8,000 or less, more preferably 6,000 or less. The degree of polymerization of PVA in the present specification means an average degree of polymerization measured according to the description of JIS K6726-1994. The degree of polymerization of PVA is obtained from intrinsic viscosity measured in water at 30 캜 after re-saponification and purification of PVA.

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

The PVA film of the present invention preferably contains a plasticizer in that it can improve handleability, dyeability, stretchability and the like. As the plasticizer, a polyhydric alcohol-based plasticizer is preferable in view of affinity with PVA. Examples of polyhydric alcohol plasticizers include ethylene glycol, glycerin, propylene glycol, diethylene glycol, diglycerin, triethylene glycol, tetraethylene glycol, trimethylol propane, etc., and one or more of these Can be used. Among them, one or two or more of glycerin, diglycerin and ethylene glycol are preferably used from the viewpoints of improving the stretchability and handling properties.

The content of the plasticizer is preferably 1 part by mass or more, more preferably 5 parts by mass or more, further preferably 30 parts by mass or less, and more preferably 20 parts by mass or less, based on 100 parts by mass of PVA. When the content of the plasticizer is lower than the lower limit described above, the dyeability and stretchability are improved. On the other hand, when the content of the plasticizer is not more than the upper limit, it is possible to prevent the PVA film from becoming too soft, and handling property, uniformity of cutting and the like are improved.

The PVA film of the present invention preferably contains a surfactant from the viewpoints of handling properties and improvement of peelability from the film forming apparatus when the PVA film is produced. The kind of the surfactant is not particularly limited, and examples thereof include anionic surfactants and nonionic surfactants. Examples of the anionic surfactant include a carboxylic acid type, a sulfuric acid ester type, and a sulfonic acid type. Examples of the nonionic surfactant include alkyl ether type, alkyl phenyl ether type, alkyl ester type, alkyl amide type, polypropylene glycol ether type, alkanolamide type and allyl phenyl ether type. The PVA film of the present invention may contain one or more of these surfactants.

The content of the surfactant is preferably 0.01 parts by mass or more, more preferably 0.05 parts by mass or more, further preferably 1 part by mass or less, and further preferably 0.3 parts by mass or less, based on 100 parts by mass of PVA. When the content of the surfactant is less than or equal to the upper limit, deterioration of the handling property can be prevented because the surfactant dissolves on the surface of the PVA film to cause blocking.

The PVA film of the present invention may further contain other components such as a dichroic dye, an antioxidant, an ultraviolet absorber, a lubricant, a colorant, an antiseptic, a viscous agent, a polymer compound other than the above-mentioned components, do. The PVA film of the present invention may contain one or more of these other components. The content of PVA in the PVA film of the present invention is preferably 70 mass% or more, more preferably 80 mass% or more, and further preferably 90 mass% or more.

The method for producing the PVA film of the present invention is not particularly limited, but the following production method of the present invention is preferable because the PVA film of the present invention can be smoothly produced. That is, the production method of the present invention is a method for producing an elongated PVA film having a thickness of 55 m 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 cut end formed by a cutting edge , A groove forming roll having a large diameter portion in contact with the film and a small diameter portion in which the film is not in contact in the roll axis direction is used and a long PVA film is brought into contact with the surface of the large diameter portion of the groove forming roll, Wherein the rounded blade has a blade angle of 25 to 50 ° and a Vickers hardness of the blade tip of 1,500 HV or more, Lt; / RTI > In general, a thin PVA film tends to have a rough cross section when cut, compared with a thick PVA film. According to the production method of the present invention, although it is a thin PVA film, PVA film satisfying the requirements can be smoothly produced.

The groove forming roll used in the production method of the present invention has 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. As the groove forming roll, it is preferable to use, for example, a metal, and in particular, when chromium plating is applied, the surface hardness of the groove forming roll is increased, and the occurrence of scratches can be prevented . The grooved roll has at least three large diameter portions (convex portions) in the roll axis direction and a small diameter portion (grooves, concave portions) between the large diameter portion and the large diameter portion Can be used.

The diameter of the large diameter portion of the groove forming roll is preferably 5 cm in terms of satisfactory conveyance of the PVA film, good cutting of the PVA film in the groove forming roll, manufacturing cost of the groove forming roll, More preferably at least 7.5 cm, further preferably at least 10 cm, further preferably at most 30 cm, more preferably at most 25 cm, even more preferably at most 20 cm. The diameter of the large diameter portion of the groove forming roll is equal to or more than the above-mentioned lower limit, so that the PVA film can be more uniformly cut. On the other hand, when the diameter of the large diameter portion of the groove forming roll is equal to or smaller than the upper limit, the manufacturing cost of the groove forming roll can be reduced. When there are a plurality of large-diameter portions in the grooved roll, the PVA film is transported in contact with the surfaces of the plurality of large-diameter portions while maintaining the flattened state, and therefore these large diameter portions are preferably all the same diameter.

The width of the large diameter portion of the groove forming roll (the length in the roll axis direction; the width of each large diameter portion when a plurality of large diameter portions exist) is 1 mm or more, particularly 3 to 10 mm, And the size of the slit width (width after cutting) of the film can be freely changed. In the case where a plurality of large-diameter portions exist in the grooved roll, the width of the large-diameter portion may be the same in all the large-diameter portions, or some or all of them may be different from each other.

The diameter of the small diameter portion of the groove forming roll is preferably in the range of from 1 mm to 20 mm from the viewpoints of preventing breakage of the rounded edge, Is preferably 0.5 cm or smaller, more preferably 1 cm or smaller, more preferably 2 cm or smaller, and more preferably 1.5 cm or smaller.

It is preferable that the width of the small diameter portion of the groove forming roll (length in the roll axis direction; width of each small diameter portion when a plurality of small diameter portions exist) is equal to or less than the width of the adjacent large diameter portion. In addition, the width of the small diameter portion can be set to a wide range in which the cutting edge of the PVA film can be satisfactorily cut in a stable state without the blade edge of the round blade contacting the groove forming roll, Preferably 2 times or more, more preferably 5 times or more, and more preferably 50 times or less, with respect to the thick portion (the dimension of d in Fig. 2) of the non- , 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 the film around the entire periphery 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. 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 resistant to abrasion and has excellent durability and smoothness of a cutting section.

The Vickers hardness of at least the tip of the rounded edge of the round blade is preferably 1,500 HV or more and preferably 1,800 HV or more in view of smooth production of the PVA film of the present invention. The upper limit of the Vickers hardness is not particularly limited. For example, the Vickers hardness may be 2,400 HV or less. Also, in the present specification, the unit of Vickers hardness is kgf / mm < 2 >.

The length of Ea in the cross-sectional view in the thickness direction of the round blade 2 illustrated in Figs. 2 (a) and 2 (b)) is preferably 15 mm or more, more preferably 20 mm or more More preferably 40 mm or more. When the diameter of the round blade is in the above range, progress of the abrasion is suppressed, and it becomes easy to form a smooth cut section over the entire length of the elongated PVA film. The upper limit of the diameter of the rounded edge is not particularly limited. However, if the diameter of the rounded edge becomes too large, the mass of the rounded edge itself becomes too large to freely rotate when cutting the PVA film. Further, The diameter of the round blade is preferably 200 mm or less, and more preferably 120 mm or less.

As shown in Fig. 2A, the shape of the blade edge of the round blade is a mountain-like shape in which the polished surfaces 4 and 4 'on both sides are converged in a tapered shape on the blade tip 3 at the center 2), or as shown in Fig. 2 (b), another one of the abraded tapered faces 6 toward the blade edge 3 at the tip of one of the vertical faces 5 converges Or may be in the form of a knitted fabric. Among them, the blade edge of the round blade is preferably in the shape of an angle as shown in Fig. 2 (a) because the PVA film is stably cut, and an excellent cut section is formed by the smoothness.

In the manufacturing method of the present invention, it is necessary that the blade edge angle [the angle [alpha] shown in FIGS. 2 (a) and 2 (b)] is within a range of 25 to 50 degrees. If the edge angle of the round blade is less than 25 DEG, the reason for this is not always clear, but when the thin PVA film having a thickness of 55 mu m or less is cut, the blade tip is easily worn, It is difficult to continuously obtain the cut section. In order to maintain a good sharpness for a long time while suppressing the abrasion of the nib, and thus to obtain a smooth cutting cross section with a small degree of roughening over the entire length of the film even if the length of the PVA film is long, Is preferably 30 DEG or more, more preferably 35 DEG or more. On the other hand, when the blade edge angle of the round blade exceeds 50 deg., The sharpness becomes dull and it becomes difficult to form a smooth cut section having a low degree of roughening. From this viewpoint, the edge angle of the rounded edge is preferably 45 DEG or less, more preferably 43 DEG or less.

The thick portion of the blade tip portion in the round blade (the thick portion just before the thickness gradually decreases toward the tip of the blade tip, the dimension d shown in Figs. 2A and 2B) is preferably 0.05 mm or more, More preferably 0.1 mm or more, further preferably 1 mm or less, and more preferably 0.5 mm or less. By making the thick portion of the nose base portion equal to or more than the lower limit, breakage of the round blade itself can be suppressed. On the other hand, since the thick portion of the nose base portion is equal to or smaller than the upper limit, the degree of roughening is small over the entire length of the film, and a smooth cut section can be formed.

The length of the blade in the round blade (the distance from the blade tip to the tip of the blade tip: the dimension of e shown in Figs. 2A and 2B) is preferably one or more times the thickness of the PVA film to be cut More preferably not less than 5 times, more preferably not more than 50 times, and more preferably not more than 45 times. The cutting edge of the PVA film can be prevented from being damaged at the blade tip due to the blade length being equal to or larger than the lower limit. On the other hand, when the length of the blade is equal to or smaller than the upper limit, wear and breakage of the blade can be suppressed.

In cutting the PVA film along the longitudinal direction by a circular blade rotating at the position of the minor diameter portion of the groove groove forming roll while feeding the long PVA film in contact with the surface of the large diameter portion of the groove forming roll, The PVA film is transported in a taut state without being loosened on the groove forming rolls at the same speed as that of the PVA film at the peripheral speed of the large diameter portion of the forming roll, It is important. In this regard, in cutting the PVA film along the longitudinal direction, the PVA film is brought into contact with the circumference of the groove-forming roll at an angle of 10 to 100 degrees (a contact angle [beta] shown in Fig. 3 (b) , It is preferable to cut the PVA film by a rotating round blade disposed at a position of a small diameter portion of the groove forming roll while keeping the PVA film along the groove forming roll (holding state). At this time, it is preferable that the rounded edge is disposed at the center or substantially the center of the above-mentioned angle of attack. By doing so, at the time of cutting, the peripheral speed of the large diameter portion of the groove forming roll and the feeding speed of the PVA film become substantially equal to each other. Further, while the PVA film is fed by the groove forming roll in a tense state, It is possible to form a smooth cutting section with a low degree of roughening. In view of the above, the angle of attack is more preferably 30 degrees or more, more preferably 45 degrees or more, further preferably 98 degrees or less, and further preferably 95 degrees or less.

When the PVA film is cut along the longitudinal direction by the rotating round blade, the PVA film may be cut while positively driving and rotating the round blade. However, since the difference between the rotation speed of the round blade and the feed speed of the PVA film is reduced, It is preferable to carry out the cutting while freely rotating the round blade in accordance with the feeding of the PVA film, rather than positively driving and rotating the round blade. It is possible to prevent a great difference between the rotation speed of the round blade and the feed speed of the PVA film by cutting the PVA film while freely rotating the round blade so that the PVA film can be smoothly cut smoothly, It is possible to form a smooth cut section having a smaller size. The method for freely rotating the round blade is not particularly limited. For example, as shown in the schematic view of Fig. 2 (sectional view in the thickness direction of the round blade 2), the round blade 2 may be round And the rotary shaft 8 is integrally or fixedly formed at the center (center position) of the circular blade mounting member 7 on the disk and is formed to extend around the rotary shaft 8 A method of disposing a bearing 9 such as a ball bearing to freely rotate the rotary shaft 8, the round blade mounting member 7 and the round blade 2 integrally can be adopted.

In cutting the PVA film along the longitudinal 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, more preferably 25 m / min or less desirable. When the conveying speed is equal to or less than the upper limit, the degree of roughening of the cut surface can be further reduced. On the other hand, if the feed speed is too slow, it takes too much time to cut and the productivity may be lowered. Therefore, the feed speed is preferably 5 m / min or more.

The volatile fraction of the PVA film at the time of cutting the PVA film along the longitudinal direction by the rotating round blade is preferably 0.1 mass% or more, more preferably 2 mass% or more, and more preferably 10 mass% or less By mass, and more preferably 6% by mass or less. Since the volatile fraction is lower than the lower limit described above, the PVA film is not too hard, and cutting is facilitated. On the other hand, when the volatile fraction is less than the upper limit, the PVA film can be prevented from becoming too soft, and the degree of roughening of the cut surface can be further reduced. The term "volatile matter content of the PVA film" as used herein means the content of volatile matter contained in the PVA film. Examples of such volatile components include, for example, solvents such as an organic solvent and water used for producing a PVA film, water absorbed into the film by moisture absorption after the production of the PVA film, and the like. The volatile fraction of the PVA film can be controlled by using a heated metal roll or a floating dryer alone or in combination of two or more types and drying to a desired value. A PVA film having a volatile content lower than the above range is treated with a humidifier or the like Can be adjusted by the following method. The volatile content 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 reduction in mass.

The film temperature at the time of cutting the PVA film along the longitudinal direction by the rotating circular blade is preferably 10 ° C or more, more preferably 20 ° C or more, and preferably 70 ° C or less, Is more preferable. When the film temperature is lower than the lower limit described above, the PVA film is not too hard to be easily cut. Furthermore, water droplets based on condensation are adhered to the PVA film. When the PVA film after the cutting treatment is rolled up and stored for preservation, blocking may occur, or the PVA film may be prevented from being broken from the part with water droplets have. On the other hand, when the film temperature is lower than the upper limit, the PVA film can be prevented from becoming too soft, and the degree of roughening of the cut section can be further reduced. The film temperature of the PVA film can be measured using a spot-type digital radiation thermometer (e.g., "Thermometer 505A" manufactured by Minolta Co., Ltd.).

The cutting along the longitudinal direction of the PVA film by the rotating round blade may be carried out continuously or continuously after the production process of the PVA film or after the PVA film is wound and rolled up, .

The production method of the PVA film to be provided for cutting is not particularly limited and can be produced by a conventionally known method. For example, the PVA film constituting the PVA film and, if necessary, the plasticizer, surfactant And other components are dissolved in a liquid medium, PVA and, if necessary, further one or more of a plasticizer, a surfactant and other components, and PVA It can be produced by using a molten film forming stock solution. When the stock solution for film formation contains at least one of a plasticizer, a surfactant and other components, it is preferable that the components are uniformly mixed.

Examples of the liquid medium used for the preparation of the film-forming stock solution include water, dimethylsulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, ethylene glycol, glycerin, propylene glycol, diethylene glycol, Ethylene glycol, tetraethylene glycol, trimethylol propane, ethylenediamine, diethylenetriamine, and the like, and one or more of these may be used. Among them, water is preferred from the viewpoint of environmental load and recoverability.

Examples of the film forming method for forming the PVA film using the above-mentioned film forming stock 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 in that a PVA film for imparting a good polarizing film can be smoothly produced. The film thus formed can be dried or heat-treated as required.

As a specific example of the production method of the PVA film to be provided for cutting, there can be mentioned a method of producing a PVA film by using a T-shaped slit die, hopper plate, I-die, lip coater die, (Or belt), and the volatile component is evaporated from one side of the discharged or softened film on the circumferential surface of the first roll (or belt) and dried, A method of re-drying on the circumferential surface of one or a plurality of heated rolls disposed on the downstream side thereof, or drying the same by passing through a hot-air drying apparatus and then winding it up by a winding device is referred to as industrial Can be preferably employed. The drying by the heated roll and the drying by the hot air drying apparatus may be carried out in appropriate combination.

The use of the PVA film of the present invention is not particularly limited, and examples thereof include films for packaging drugs, fluid pressure transfer base films, embroidery base films, release films for molding artificial marbles, seed packaging films, The PVA film of the present invention in which at least one, preferably both of the two end portions along the longitudinal direction of the film, constitutes a cut end portion, can be used for various water-soluble films. In the PVA film of the present invention, (Rz) " is not more than a specific value, the cut surface has a very low degree of roughening and is excellent in smoothness. Therefore, when stretching in the longitudinal direction, cracks are generated in the cut ends And as a result, breakage of the film is difficult to occur. In view of this, the PVA film of the present invention is preferably used as a raw film for producing an optical film (raw film for producing an optical film). Examples of such an optical film include a polarizing film and a retardation film, and a polarizing film is preferable. Such an optical film can be produced, for example, by subjecting the film of the present invention to a treatment such as uniaxial stretching.

The method for producing the polarizing film using the PVA film of the present invention is not particularly limited, and any conventionally known method may be employed. Such methods include, for example, dyeing and uniaxial stretching using the PVA film of the present invention, or uniaxial stretching of the PVA film of the present invention containing a dye . As a more specific method for producing the polarizing film, there can be mentioned a method in which the PVA film of the present invention is subjected to swelling, dyeing, uniaxial stretching and, if necessary, further crosslinking treatment, fixing treatment, drying and heat treatment have. In this case, the order of each treatment such as swelling, dyeing, crosslinking treatment, uniaxial stretching, and fixing treatment is not particularly limited, and one or two or more treatments may be simultaneously carried out. In addition, one or two or more of the treatments may be performed twice or more.

The swelling can be carried out by immersing the PVA film in water. The temperature of the water at the time of immersion in water is preferably in the range of 20 to 40 占 폚, more preferably in the range of 22 to 38 占 폚, and still more preferably in the range of 25 to 35 占 폚. The time for immersing in water is preferably within a range of, for example, 0.1 to 5 minutes, and more preferably within a range of 0.5 to 3 minutes. Further, the water at the time of immersion 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.

The dyeing can be carried out by bringing the dichroic dye into contact with the PVA film. As the dichroic dye, an iodine dye is generally used. The dyeing may be performed at any stage before uniaxial stretching, uniaxial stretching, or uniaxial stretching. The dyeing is generally carried out by immersing the PVA film as a dyeing bath in a solution (particularly an aqueous solution) containing potassium iodide-iodide, and such a dyeing method is preferably employed also in the present invention. The concentration of iodine in the dyeing bath is preferably in the range of 0.01 to 0.5 mass%, and the concentration of potassium iodide is preferably in the range of 0.01 to 10 mass%. The temperature of the dyeing bath is preferably 20 to 50 캜, particularly 25 to 40 캜.

By performing the crosslinking treatment on the PVA film, it is possible to more effectively prevent the PVA from eluting into water when the film is subjected to wet stretching at a high temperature. From this point of view, the crosslinking treatment is preferably carried out after uniaxially stretching as a treatment after bringing the dichroic dye into contact. The crosslinking treatment can be carried out by immersing the PVA film in an aqueous solution containing a crosslinking agent. As the cross-linking agent, boron compounds such as boric acid, borax, and other boron compounds may be used. The concentration of the crosslinking agent in the aqueous solution containing the crosslinking agent is preferably within a range of 1 to 15 mass%, more preferably within a range of 2 to 7 mass%, and further preferably within a range of 3 to 6 mass%. The concentration of the cross-linking agent is in the range of 1 to 15 mass%, so that sufficient stretchability can be maintained. The aqueous solution containing the 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 캜, particularly in the range of 25 to 40 캜. The crosslinking can be effected 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 a fixed treatment bath as described above or in a dyeing bath described below. In the case of the dry stretching method, stretching may be performed at room temperature, followed by stretching while heating, or may be carried out in the air using a PVA film after the absorption. Among them, the wet drawing method is preferable, and the uniaxial drawing is more preferable in an aqueous solution containing boric acid. The concentration of boric acid in the aqueous solution of boric acid is preferably within a range of 0.5 to 6.0 mass%, more preferably within a range of 1.0 to 5.0 mass%, and particularly preferably within a range of 1.5 to 4.0 mass%. The boric acid aqueous solution may contain potassium iodide, and the concentration thereof is preferably within a range of 0.01 to 10 mass%.

The stretching temperature in the uniaxial stretching is not particularly limited, but in the case of the wet stretching method, it is preferably within the range of 30 to 90 占 폚, more preferably within the range of 40 to 80 占 폚, Is particularly preferable. In the case of the dry heat stretching method, the temperature is preferably in the range of 50 to 180 ° C.

The stretching magnification in the uniaxial stretching (in the case of uniaxial stretching in multiple stages, the stretching magnification of the total of the stretching magnifications multiplied by the respective stretching magnifications) is preferably four times or more in view of the polarizing performance of the resulting polarizing film, Times or more. The upper limit of the draw ratio is not particularly limited, but is preferably 8 times or less for uniform drawing.

There is no particular limitation in the direction of uniaxial stretching, and uniaxial stretching or transverse uniaxial stretching in the longitudinal direction of a long PVA film can be adopted. However, since a polarizing film excellent in polarization performance can be obtained, Stretching is preferred. The uniaxial stretching in the longitudinal direction can be carried out by using a stretching device having a plurality of rolls parallel to each other and changing the peripheral velocity between the rolls. On the other hand, transverse uniaxial stretching can be carried out using a tenter-type stretching machine.

In the production of the polarizing film, it is preferable to carry out the fixing treatment to strengthen the adsorption of the dichroic dye (iodine dye or the like) to the PVA film. The fixing treatment can be carried out by immersing the PVA film in a fixed treatment bath. As the fixed treatment bath, an aqueous solution containing one kind or two or more kinds of boron compounds such as boric acid and borax can be used. If necessary, an iodine compound or a metal compound may be added to the fixed treatment bath. The concentration of the boron compound in the fixed treatment bath is generally preferably about 2 to 15 mass%, particularly about 3 to 10 mass%. By making the concentration within the range of 2 to 15 mass%, the adsorption of the dichroic dye can be made stronger. The temperature of the fixed treatment bath is preferably 15 to 60 ° C, particularly 25 to 40 ° C.

The drying conditions are not particularly limited, but it is preferable to carry out the drying at a temperature within the range of 30 to 150 ° C, particularly 50 to 140 ° C. It is easy to obtain a polarizing film having excellent dimensional stability and suppressing a decrease in polarization performance based on decomposition of a dichroic dye by drying at a temperature within a range of 30 to 150 ° C.

The thickness of the polarizing film thus obtained varies depending on the thickness of the PVA film to be used and the like, but is preferably 30 m or less, more preferably 25 m or less, and more preferably 20 m More preferably at most 15 mu m, further preferably at least 1 mu m, more preferably at least 2 mu m, even more preferably at least 4 mu m, particularly preferably at least 6 mu m.

The polarizing film thus obtained is usually used in the form of a polarizing plate by adhering a protective film having optically transparent and mechanical strength on both sides or one side thereof. As the protective film, a cellulose triacetate (TAC) film, a cycloolefin polymer (COP) film, an acetic acid-butyric acid cellulose (CAB) film, an acrylic film, a polyester film and the like are used. Examples of the adhesive for bonding include a PVA adhesive and a urethane adhesive, and among them, a PVA adhesive is preferable.

The polarizing plate obtained as described above can be used as a component of an LCD after being coated with a pressure-sensitive adhesive such as an acryl-based adhesive and then adhered to a glass substrate. At the same time, it may be laminated with a retardation film, a viewing angle improving film, a luminance improving film or the like.

Example

Hereinafter, the present invention will be described in detail by way of 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 carried out in the following manner.

(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 (the PVA film having the cut end along the longitudinal direction) after cutting along the longitudinal direction of the film (particularly 500 m cut in the longitudinal direction of the film from the start point of cutting) (Sampling point 3 of the sample) was taken from the portion of the sample taken along the longitudinal direction of the film at a predetermined position along the longitudinal direction of the film The cut section was measured using an ultra-precision shape measuring microscope " VK-8500 " manufactured by Keans Co. over a length of 100 mu m, and the surface state on the line in the longitudinal direction of the film in the thickness- (Rz) and the arithmetic average roughness (Ra), which are defined in JIS B 0601: 2001, Calculation of the "maximum height roughness (Rz)" or the "arithmetic mean roughness (Ra)", respectively, followed by calculating the average of the three points.

In addition, at the start and intermediate stages of cutting, there is no abrasion of the cutting edge of the cutting edge or a small cutting edge is formed with a low degree of roughening, so that at the start of winding of the roll and at the midpoint of winding, The measurement of the degree of roughening is omitted, and the maximum height of the cut surface is measured with respect to the point of time immediately before the end of the cutting (the film portion of the outermost surface layer of the roll of the PVA film wound in the roll form after cutting) (Rz) " and the arithmetic mean roughness (Ra) were obtained, and the degree of roughening of the cut section was evaluated.

(2) Confirmation of occurrence of breakage of the PVA film at the time of stretching (stretching magnification at break of the film):

(i) Whether or not the PVA film having a cut end along the longitudinal direction is broken at the time of stretching is naturally required to be carried out in the continuous stretching operation at the time of producing the polarizing film. However, Is a frequency of whether or not breakage is normally occurred once every several hours. Since it is difficult to carry out a test based on actual use, the evaluation was carried out by the following model test (ii).

(ii) the film portion of the outermost layer of the roll of the PVA film (the PVA film having the cut end along the longitudinal direction) rolled up in the roll after cutting along the longitudinal direction of the film (in particular, 500 (long side) in the longitudinal direction of the sample is a cut end so as to be parallel to the longitudinal direction of the film, as shown in Fig. 1, and a length of 15 cm x 10 cm (Sample S shown in Fig. 1) was sampled (sample sampling score 3). At this time, the cuts of the three sides other than the sides corresponding to the cut ends were cutter knives (" A ", manufactured by Nutty Co., Ltd.) that were cut at every cut of one side so as to form a smooth cut surface without roughening Quot; day ").

(iii) The sample was held at a distance of 4 cm between chucks by a pair of chucks at both ends in the longitudinal direction of the sample taken in the above (ii) (two lateral sides), and the sample was mounted on a batch stretching machine. And then swollen with water. The sample was immediately taken out from the water and immediately immersed in a boric acid 4% aqueous solution at 50 캜 for one minute. After 1 minute, the sample was immersed in an aqueous boric acid solution at a draw speed of 0.15 m / Then, the distance between the chucks when the sample was broken was measured, and the stretching magnification at break was obtained from the following equation, and the average value of the three samples was adopted.

Drawing magnification at break (times) = distance between chucks at sample breakage (cm) / 4 (cm)

(iv) As a control, the film portion of the outermost layer of the roll of the PVA film (the PVA film having the cut end along the longitudinal direction) rolled up in the same roll as the sample taken in the above (ii) A rectangular sample having a size of length x width = 15 cm x 10 cm was obtained in parallel with the longitudinal direction of the film from a substantially central portion in the width direction of the film (the portion immediately after cutting 500 m in the longitudinal direction of the film) Lt; / RTI > sample) (sampling score 3 of the sample). In the sampling of the sample (iv), a cutter knife (a cutter knife) that has been renewed so as to be cut well at each cut of one side is prepared so that four sides of the sample (four cut edges) ("A blade" manufactured by Enuchi Co., Ltd.).

(v) Using the sample for comparison obtained in the above (iv), the stretching magnification at break was obtained in the same manner as in the above (iii), and the average value of the three samples was adopted.

[Example 1]

(1) 12 parts by mass of glycerin and 220 parts by mass of water were impregnated with 100 parts by mass of a PVA chip (having a degree of polymerization of 2,400 of PVA and a degree of saponification of 99.9 mol%), and then the PVA chip after impregnation was supplied to an extruder, (The surface temperature of the metal roll was 95 DEG C and the diameter of the metal roll was 3.8 m), and then the surface of the film was alternately turned on ten metal rolls To prepare a long PVA film continuously (film width 3 m, thickness 20 m).

(2) A cutting apparatus for cutting a PVA film, comprising: a groove forming roll 10 (metal; see Fig. 3) as shown in Fig. 3 (a) on the upstream side of a winder for winding a formed PVA film into a roll; The diameter Eb of the large diameter portion 20 cm, 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) A double-edged round blade 2 (a Vickers hardness of the blade edge portion 1,850 HV; a diameter of a round blade Ea 45 mm; Fig. 3 (b)) as shown in Fig. 3 (a), which rotates freely at the position of the small- (The thick part just before the thickness gradually decreases toward the tip of the blade edge) d 0.3 mm; The blade length (distance from the base of the blade to the edge of the blade edge) e 0.85 mm) Placed dogs.

(3) The PVA film (volatile matter content in the film: 3 mass%) prepared in the above (1) was supplied to the cutting apparatus prepared in the above (2) The PVA film is brought into contact with the surface of the large diameter portion of the groove forming roll 10 in a state in which the PVA film is along the part of the circumference of the groove forming roll 10 (holding state) with the contact angle? Both ends of the PVA film were cut along the longitudinal direction by a new rounded edge 2 of the new product which was fed at a speed of 17 m / min and freely rotated by ball-bearing to form a film having a width of 2.6 m (Diameter: about 15.2 cm) with a winder to obtain a PVA film having a total length of about 500 m (winding length: about 500 m) having a cut surface at both ends along the longitudinal direction. The temperature of the PVA film at the time of cutting by the rotating round blade was 30 ° C.

(4) The " maximum height illuminance Rz " and the " arithmetic mean illuminance Ra " of the cut section of the PVA film obtained in the above (3) (Rz) of 0.85 mu m, an arithmetic mean roughness (Ra) of 0.13 mu m and Rz / Ra of 6.8, and the cut section along the longitudinal direction (overall length) The degree of cotton was very low and smoothness was excellent.

(5) The stretching magnification at the breaking of the film was 6.1 times as measured by the above-mentioned method using the PVA film obtained in the above (3) and wound in a roll shape with a length of 500 m or more. On the other hand, the stretching ratio at the time of breaking the film in the sample (sample taken from almost the central portion in the width direction of the PVA film) of the control sample was also 6.1 times.

[Example 2]

(1) In the same manner as in (1) to (3) of Example 1 except that a new round blade having a blade angle? Of 45 占 was used in (2) To obtain a PVA film having a cut section having a total length of about 500 m (winding length: about 500 m).

(2) The "maximum height roughness (Rz)" and the "arithmetic mean roughness (Ra)" of the cut section of the PVA film obtained in the above (1) (Rz) of 0.98 mu m, an arithmetic mean roughness (Ra) of 0.15 mu m and Rz / Ra of 6.7, and a cut section along the longitudinal direction (overall length) The degree of cotton was very low and smoothness was excellent.

(3) Using a PVA film obtained in the above (1) and wound in a roll shape with a length of about 500 m or more, the stretching magnification at break of the film was measured by the aforementioned method and found to be 6.0 times.

[Example 3]

(1) In the same manner as in (1) to (3) of Example 1 except that a new round blade having a blade angle? Of 30 ° was used in (2) of Example 1, To obtain a PVA film having a cut section having a total length of about 500 m (winding length: about 500 m).

(2) The "maximum height roughness (Rz)" and the "arithmetic mean roughness (Ra)" of the cut section of the PVA film obtained in the above (1) (Rz) of 1.19 mu m, an arithmetic mean roughness (Ra) of 0.15 mu m and Rz / Ra of 7.8, and the cut section along the longitudinal direction (overall length) The degree of cotton was very low and smoothness was excellent.

(3) The stretching magnification at the breaking of the film was measured by the above-mentioned method using the PVA film obtained in (1) and wound in a roll shape with a length of about 500 m or more.

[Comparative Example 1]

(1) Same as (1) to (3) of Example 1 except that a new round blade of 300 HV or less (SKS-7) was used as the Vickers hardness of the blade edge portion in (3) To obtain a PVA film having a total length of 500 m or more (winding length: about 500 m) having cut sections at both ends along the longitudinal direction.

(2) The "maximum height roughness (Rz)" and the "arithmetic mean roughness (Ra)" of the cut section of the PVA film obtained in the above (1) (Rz) of 2.68 mu m, arithmetic mean roughness (Ra) of 0.50 mu m, and Rz / Ra of 5.4. As compared with Examples 1 to 3, the degree of roughening of the cut section was high.

(3) The stretching magnification at the time of breaking the film was 5.6 times as measured by the above-mentioned method using the PVA film obtained in (1) and wound in a roll shape with a length of 500 m or more. 3, it was easy to break at the time of stretching.

[Comparative Example 2]

(1) In the same manner as in (1) to (3) of Example 1, except that a new round blade having a blade angle? Of 23 ° was used in (3) of Example 1, To obtain a PVA film having a cut section having a total length of about 500 m (winding length: about 500 m).

(2) The "maximum height roughness (Rz)" and the "arithmetic mean roughness (Ra)" of the cut section of the PVA film obtained in the above (1) (Rz) of 3.22 mu m, an arithmetic average roughness (Ra) of 0.67 mu m, and Rz / Ra of 4.8. As compared with Examples 1 to 3, the degree of roughening of the cut section was high.

(3) The stretching magnification at the time of breaking the film was 5.6 times as measured by the above-mentioned method using the PVA film obtained in (1) and wound in a roll shape with a length of 500 m or more. 3, it was easy to break at the time of stretching.

The above results are shown in the table below.

1: PVA film
2: round day
3: round edge of the blade
4, 4 ': The polished surface
5: vertical face
6: Polished face
7: round blade mounting member
8:
9: Bearings
10: groove forming roll
10a: Groove portion of groove forming roll
10b: small diameter portion of the groove forming roll

Claims (9)

A long polyvinyl alcohol film having a thickness of at most 55 탆 and a length of at least 500 m, characterized in that at least one of the two ends along the longitudinal direction of the film is a cut end formed by a cutting edge, Wherein the roughness Rz is 2.5 占 퐉 or less over a section of the film having a length of 500 m or more. The method according to claim 1,
Wherein the arithmetic mean roughness (Ra) of the cut section is 0.4 占 퐉 or less over the section. 3. The method according to claim 1 or 2,
A polyvinyl alcohol film having a length of at least 1,000 m. 4. The method according to any one of claims 1 to 3,
A polyvinyl alcohol film which is a fabric film for optical film production. 5. The method according to any one of claims 1 to 4,
A polyvinyl alcohol film wherein the optical film is a polarizing film. A roll formed by winding the polyvinyl alcohol film according to any one of claims 1 to 5 in a roll form. A process for producing an elongated polyvinyl alcohol film having a thickness of 55 m 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 cut end formed by a cutting edge, And a long-diameter polyvinyl alcohol film is brought into contact with the surface of the large-diameter portion of the groove-forming roll in the roll-axis direction so that the small-diameter portion of the small-diameter portion of the groove- Wherein the rounded edge has a blade angle of 25 to 50 DEG and a Vickers hardness at the blade edge of 1,500 HV or more. 8. The method of claim 7,
Wherein the polyvinyl alcohol film is brought into contact with the circumference of the groove-forming roll at an angle of 10 to 100 °. 9. The method according to claim 7 or 8,
A production method for producing the polyvinyl alcohol film according to any one of claims 1 to 5.

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