JP6668338B2 - Polyvinyl alcohol film - Google Patents

Description

  The present invention relates to a thin polyvinyl alcohol film having a specific cut end face (hereinafter, "polyvinyl alcohol" may be abbreviated as "PVA"), a roll obtained by winding the roll into a roll, and a roll obtained by winding the roll. The present invention relates to a method for producing a PVA film for obtaining a PVA film.

  A polarizing plate having a function of transmitting and blocking light is a fundamental component of a liquid crystal display (LCD) together with a liquid crystal having a function of switching light. The application fields of this LCD range from small devices such as calculators and wristwatches in the early stages of development, to recent years, such as laptop computers, word processors, liquid crystal color projectors, navigation systems for vehicles, liquid crystal televisions, personal phones, and indoor and outdoor measuring instruments. In view of this, a polarizing plate with higher quality and lower cost has been demanded.

  A polarizing plate is generally a method in which a PVA film is stretched uniaxially after dyeing, or stretched uniaxially while dyeing, or dyed after stretching uniaxially, to form a dyed uniaxially stretched film and fixing it with a boron compound. Also, after a polarizing film is manufactured by a method of fixing with a boron compound at the same time as dyeing in the uniaxial stretching / dyeing treatment, a cellulose triacetate (TAC) film, cellulose acetate / butyrate is formed on the surface of the polarizing film. It is manufactured by bonding a protective film such as a (CAB) film.

In the production of polarizing plates, in order to reduce production costs, etc., use a raw film rolled up of a long PVA film in a roll shape, and use it for uniaxial stretching, dyeing, fixing, laminating a protective film, etc. A method in which the steps are performed continuously has been widely adopted.
In the PVA film, both ends in the width direction of the film after film formation tend to differ in thickness and the degree of drying with respect to the center, and stable stretching is difficult when uniaxially stretched while leaving both ends in the width direction. It is common practice to cut and remove both ends in the width direction of a film, wind it up in a roll, and supply it to a demand destination such as a polarizing plate maker.
In addition, in order to provide a film having a film width that meets the demands of the demand destinations of polarizing plate manufacturers, etc., the formed PVA film is subjected to film cutting at the same time or without cutting and removing the ears. It is also possible to cut the film to the required width by cutting it in the length direction at the center or other positions in the width direction of the film, wind it up in a roll, and deliver it to the customer as required. Have been done.

  In manufacturing a polarizing film from a PVA film, it is common practice to uniaxially stretch the PVA film in the length direction at a high stretching ratio in order to obtain high polarizing performance, but the cut end face of the film is rough. When the surface is planarized, the rough surface portion becomes a starting point of crack generation at the time of uniaxial stretching, and a crack is generated at an end portion. In extreme cases, a problem that the film is broken from the crack portion may occur. When the film breaks, it is necessary to temporarily stop the uniaxial stretching process, remove the broken portion, and then perform the stretching process again, which causes a great decrease in productivity and a decrease in the yield of the polarizing film. From such a point, there is a need for a PVA film having a smooth cut end surface along the length direction of the film, which does not cause cracking or breakage during stretching.

  Heretofore, several methods for cutting a PVA film have been known (see Patent Documents 1 to 3). Patent Literature 1 describes a method in which the temperature and volatile content of a PVA film to be cut are respectively set to specific ranges. As a cutting method, a method of cutting a film between two rolls, a method of forming a groove, and the like. A method for cutting on a roll is described. Patent Literature 2 describes an optical PVA film having a specific surface average roughness (Ra). As a cutting method, a method using a shear blade including an upper blade and a lower blade and a method using a razor blade are described. Have been. Patent Literature 3 describes a long PVA film in which a maximum height (Ry) of a cut end surface is in a specific range over the entire length of the film. As a cutting method, one PVA film is used to form one cut end. The method describes that a grooved roll is used, and that the cutting edge angle of the round blade is preferably 3 to 20 °.

JP-A-2002-144418 JP-A-2003-12827 JP 2005306981 A

  In recent years, a thinner polarizing film has been demanded, and from this point, as a raw film for manufacturing a polarizing film, a PVA film having a thickness of about 75 μm has conventionally been generally used, but in recent years, a thickness of less than 70 μm has been reduced. There is a need for a PVA film. However, there is a problem that a thin PVA film is more likely to break during processing such as uniaxial stretching than a conventional thickness.

  An object of the present invention is to provide a thin PVA film that is not easily broken 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 producing such a PVA film smoothly.

  The present inventors have conducted intensive studies 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 of the cut end face of the cut end portion over a specific section in the length direction of the film. It has been found that by setting the height roughness (Rz) to a specific range, it is difficult to break during processing such as uniaxial stretching even though it is a thin PVA film. Further, the present inventors, when cutting the PVA film along the length direction by a rotating round blade while contacting and transferring the PVA film before cutting in contact with the grooved roll, as the round blade, a specific It has been found that the use of a material having a cutting edge angle and having a cutting edge portion having a specific range of hardness can smoothly produce the above-mentioned thin PVA film that is difficult to break. The present inventors have further studied based on these findings and completed 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 two ends along the length direction of the film is a cut end formed by a cutting blade. A PVA film having a maximum height roughness (Rz) of a cut end face of the cut end portion of not more than 2.5 μm over a section having a length of 500 m or more;
[2] The PVA film of the above-mentioned [1], wherein the arithmetic average roughness (Ra) of the cut end face is 0.4 μm or less over the section;
[3] The PVA film of the above-mentioned [1] or [2], wherein the length of the film is 1,000 m or more;
[4] The PVA film according to any one of the above [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 formed by winding the PVA film according to any one of the above [1] to [5] into a roll;
[7] A method for producing a long PVA film having a thickness of 55 m or less and a length of 500 m or more, in which at least one of two ends along the length direction of the film is a cut end formed by a cutting blade. And, using a grooved 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, contacting a long PVA film to the surface of the large diameter portion of the grooved roll A step of cutting the PVA film along the length direction by a round blade rotating at the position of the small-diameter portion of the grooved roll while transferring the grooved roll. The round blade has a blade edge angle of 25 to 50 °. A manufacturing method in which the Vickers hardness of the cutting edge portion is 1,500 HV or more;
[8] The method of the above-mentioned [7], wherein the PVA film is contacted at an angle of 10 to 100 ° along the circumference of the grooved roll;
[9] The method according to [7] or [8], which is a method for producing the PVA film according to any one of [1] to [5];
About.

  ADVANTAGE OF THE INVENTION According to this invention, the thin PVA film which is hard to break at the time of processes, such as a uniaxial stretching, and the roll by which it is wound up in roll shape are provided. Further, according to the present invention, there is provided a method for producing a PVA film capable of producing such a PVA film smoothly.

It is the figure which showed some PVA films of this invention typically. It is the figure which showed typically an example of the cross section in the thickness direction of a round blade. It is the figure which showed typically an example of the grooved roll, and an example of the cutting method of the PVA film using a grooved 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 two ends along the length direction of the film is a cut end formed by a cutting blade. The PVA film may be a cut end only at one end along the length direction of the film, or may be a cut end at both ends along the length direction of the film. Preferably, both ends along the length of the film are cut ends. There is no particular limitation on the cutting blade that forms the cutting end, and examples thereof include a shear blade, a razor blade, and a round blade, and a round blade described below is preferable.

  In the PVA film of the present invention, the maximum height roughness (Rz) of the cut end face of the cut end portion is 2.5 μm or less over a 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 roughness (Rz) is at least in a continuous section of 500 m of the length of the cut end face. Is in the above range.

  Here, the cut end faces are, as shown in FIG. 1, cut ends A and A ′ along the length direction of the PVA film 1 (FIG. 1 shows both end portions along the length direction of the PVA film 1). Is a cut end), the planes (cut planes) B and B ′ corresponding to the thickness portions of the PVA film 1.

  The maximum height roughness (Rz) is determined by measuring the surface roughness of the cut end surface within a range of a predetermined length (L) along the length direction of the cut end surface using, for example, an ultra-depth shape measuring microscope. A roughness curve is determined, and the sum (Rz) of the maximum peak height (Rp) of the upper part of the average line of the roughness curve (average line in the length direction of the film) and the maximum valley depth (Rv) of the lower part thereof is obtained. = Rp + Rv), the details of which are described in JIS B 0601: 2001. The roughness curve can be obtained from the surface condition on the line in the length direction of the film at the center in the thickness direction on the cut end surface to be measured. Normally, when cutting a PVA film, the cut surface gradually becomes rougher as time elapses from the start of cutting, so that the above-described maximum height roughness (Rz) at the cut end surface and the arithmetic mean roughness (described later) The value of Ra) increases as time elapses from the start of cutting. Accordingly, the maximum height roughness (Rz) or arithmetic average roughness (Ra) at the cut end surface of a portion (measurement point) after cutting a specific length (for example, 500 m) in the length direction of the film from the cutting start point is calculated. When the measured values are equal to or less than a specific numerical value, the maximum height roughness (Rz) or the arithmetic average roughness (Ra) at the cut end face is at least over the entire area from the cutting start point to the measurement point. It can be said that it is below the measured value.

  From the viewpoint of preventing breakage during processing such as uniaxial stretching, the PVA film of the present invention has a maximum height roughness (Rz) of the cut end surface of 2.5 μm or less over a section of the film having a length of 500 m or more. Is necessary, it is preferably 2 μm or less, more preferably 1.5 μm or less, further preferably 1 μm or less, and particularly preferably 0.9 μm or less. Although the lower limit of the maximum height roughness (Rz) is not particularly limited, the maximum height roughness (Rz) of the cut end face is determined by the length of the film from the viewpoint of ease of production of the PVA film of the present invention. A PVA film without such a section having a width of 0.01 μm or less over a section of 500 m is preferable, and a PVA film having a maximum height roughness (Rz) of a cut end face of 0.1 μm or less over a section of 500 m of the film is preferable. A PVA film without a section is more preferable, and a PVA film without a section such that the maximum height roughness (Rz) of the cut end surface is 0.3 μm or less over a section of 500 m in length of the film is more preferable.

  In the PVA film of the present invention, when the arithmetic mean roughness (Ra) of the cut end surface is 0.4 μm or less over the above-described section related to the maximum height roughness (Rz), the breakage during processing such as uniaxial stretching is more effective. It is preferable because it can be prevented from occurring. From such a viewpoint, in the PVA film of the present invention, the arithmetic average roughness (Ra) of the cut end face is more preferably 0.3 μm or less, more preferably 0.2 μm or less, over the section. It is particularly preferred that the thickness be 0.14 μm or less. Although the lower limit of the arithmetic average roughness (Ra) is not particularly limited, from the viewpoint of the ease of manufacturing the PVA film of the present invention, the arithmetic average roughness (Ra) of the cut end face is 0.001 μm over the above section. A PVA film having no such section as described below is preferable, and a PVA film having no such section such that the arithmetic average roughness (Ra) of the cut end face is 0.01 μm or less over the above section is more preferable. A PVA film having no section where the average roughness (Ra) is 0.03 μm or less over the section is more preferable.

  Here, the arithmetic average roughness (Ra) can be determined according to the description of JIS B 0601: 2001 for a roughness curve (reference length: L) obtained in the measurement of the maximum height roughness (Rz). it can.

  The PVA film of the present invention has a maximum height roughness (Rz) and an arithmetic value over the above section related to the maximum height roughness (Rz) from the viewpoint of more effectively preventing breakage during processing such as uniaxial stretching. The ratio (Rz / Ra) to the average roughness (Ra) is preferably 5 or more, more preferably 6 or more, and 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 for cutting the PVA film, and when the blade is severely worn, the ratio (Rz / Ra) often decreases, and accordingly, the cut end face is cut. Tends to increase the degree of surface roughening.

  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 more preferably 40 μm or less, for example, in order to meet the demand for a thinner PVA film. More preferably, it is particularly preferably 30 μm or less. Although the lower limit of the thickness of the PVA film is not particularly limited, the thickness is preferably 3 μm or more, and more preferably 5 μm or more, from the viewpoints of practicality, ease of film production, ease of stretching treatment, and the like. It is more preferable that the thickness be 15 μm or more.

  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 demander, and the like. In general, the width is preferably 2 m or more, and more preferably 2.5 m or more. More preferably, it is more preferably 3 m or more, and more 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 more preferably 8,000 m or more, since the PVA film can be used continuously for a long time when used. It is even more preferred. There is no particular limitation on the upper limit of the length, and the length can be, for example, 30,000 m or less. The PVA film of the present invention is preferably in the form of a roll wound into a roll from the viewpoint of ease of transportation, storage and use.

Examples of the PVA constituting the PVA film of the present invention include, for example, unmodified PVA obtained by saponifying a polyvinyl ester obtained by polymerizing a vinyl ester, modified PVA obtained by graft-copolymerizing a comonomer to the main chain of PVA, vinyl So-called polyvinyl acetal resin in which a part of the hydroxyl groups of modified PVA, unmodified PVA or modified PVA produced by saponifying a modified polyvinyl ester obtained by copolymerizing an ester and a comonomer with aldehydes such as formalin, butyl aldehyde, and benzaldehyde. And the like.
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, and versatic acid. Vinyl etc. can be mentioned. These vinyl esters can be used alone or in combination. Among these vinyl esters, vinyl acetate is preferred 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 (α-olefins and the like); acrylic acid or a salt thereof; methyl acrylate, ethyl acrylate, acrylic Acrylates such as n-propyl acrylate, i-propyl acrylate, n-butyl acrylate, i-butyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, octadecyl acrylate (for example, Methacrylic acid or a salt thereof; methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, i-propyl methacrylate, n-butyl methacrylate, i-butyl methacrylate , T-butyl methacrylate, methacrylic acid 2 Methacrylic esters such as ethylhexyl, dodecyl methacrylate and octadecyl methacrylate (for example, alkyl esters of methacrylic acid having 1 to 18 carbon atoms); acrylamide; N-methylacrylamide, N-ethylacrylamide, N, N-dimethylacrylamide, Acrylamide derivatives such as acetone acrylamide, acrylamidopropanesulfonic acid or a salt thereof, acrylamidopropyldimethylamine or a salt thereof, N-methylolacrylamide or a derivative thereof; methacrylamide; N-methylmethacrylamide, N-ethylmethacrylamide, methacrylamidepropanesulfone Acid or a salt thereof, methacrylamidopropyldimethylamine or a salt thereof, N-methylol methacrylamide or a derivative thereof, and the like. Methacrylamide derivatives; N-vinylamides such as N-vinylformamide, N-vinylacetamide, N-vinylpyrrolidone; methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, n-butyl vinyl ether, i-butyl vinyl ether , Vinyl ethers such as t-butyl vinyl ether, dodecyl vinyl ether and stearyl vinyl ether; nitriles such as acrylonitrile and methacrylonitrile; vinyl halides such as vinyl chloride, vinylidene chloride, vinyl fluoride and vinylidene fluoride; allyl acetate, chloride Derivatives such as allyl compounds such as allyl; unsaturated dicarboxylic acids such as maleic acid and itaconic acid, salts and esters thereof; and derivatives such as vinyltrimethoxysilane Rushiriru compounds; isopropenyl acetate; an unsaturated sulfonic acid or its derivatives. 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 from the viewpoint that when the polarizing film is produced by uniaxially stretching the PVA film of the present invention, a polarizing film having excellent polarizing performance and durability is obtained. It is more preferably 2,000 or more, and may be 2,500 or more. Further, the degree of polymerization of PVA is preferably 8,000 or less, more preferably 6,000 or less, from the viewpoints of easiness of production for obtaining a uniform PVA film, stretchability, and the like. The degree of polymerization of PVA in this specification refers to the average degree of polymerization measured according to the description of JIS K6726-1994, and is obtained from the intrinsic viscosity measured in water at 30 ° C. after re-saponifiing and purifying PVA. .

  The degree of saponification of PVA is preferably 95 mol% or more from the viewpoint that when a polarizing film is produced by uniaxially stretching the PVA film of the present invention, a polarizing film having excellent polarizing performance and durability can be obtained. It is more preferably at least 99 mol%, further preferably at least 99 mol%, particularly preferably at least 99.3 mol%. The degree of saponification of PVA in the present specification means the number of moles of the vinyl alcohol unit with respect to the total number of moles of the structural unit (typically, a vinyl ester unit) and the vinyl alcohol unit which can be converted into a vinyl alcohol unit by saponification. Means the ratio (mol%) occupied by. The degree of saponification of PVA can be measured according to the description of JIS K6726-1994.

  The PVA film of the present invention preferably contains a plasticizer because it can improve handleability, dyeability, stretchability, and the like. As the plasticizer, a polyhydric alcohol plasticizer is preferable from the viewpoint of affinity with PVA. Examples of the polyhydric alcohol plasticizer include, for example, ethylene glycol, glycerin, propylene glycol, diethylene glycol, diglycerin, triethylene glycol, tetraethylene glycol, trimethylolpropane, and the like. Two or more can be used. Among these, one or more of glycerin, diglycerin, and ethylene glycol are preferably used from the viewpoint of the effect of improving the stretchability and the handleability.

  The content of the plasticizer is preferably 1 part by mass or more, more preferably 5 parts by mass or more, and preferably 30 parts by mass or less, and more preferably 20 parts by mass with respect to 100 parts by mass of PVA. It is more preferred that: When the content of the plasticizer is equal to or 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 soft, and to improve the handleability and the uniformity of cutting.

  It is preferable that the PVA film of the present invention contains a surfactant from the viewpoints of handleability and improvement of the releasability from a film forming apparatus when producing the PVA film. The type of the surfactant is not particularly limited, and examples thereof include an anionic surfactant and a nonionic surfactant. Examples of the anionic surfactant include a carboxylic acid type, a sulfate type, and a sulfonic acid type. Examples of the nonionic surfactant include an alkyl ether type, an alkyl phenyl ether type, an alkyl ester type, an alkyl amide type, a polypropylene glycol ether type, an alkanol amide type and an allyl phenyl ether type. The PVA film of the present invention can include one or more of these surfactants.

  The content of the surfactant is preferably at least 0.01 part by mass, more preferably at least 0.05 part by mass, and preferably at most 1 part by mass with respect to 100 parts by mass of PVA. , 0.3 parts by mass or less. When the content of the surfactant is equal to or less than the above upper limit, it is possible to prevent the surfactant from being eluted on the surface of the PVA film, causing blocking, and deterioration in handleability.

  The PVA film of the present invention may contain, if necessary, a dichroic dye, an antioxidant, an ultraviolet absorber, a lubricant, a coloring agent, a preservative, a fungicide, a polymer compound other than the above-described components, moisture, and the like. May be further included. The PVA film of the present invention can include one or more of these other components. The content of PVA in the PVA film of the present invention is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by 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 produced smoothly. That is, in the production method of the present invention, at least one of the two ends along the length direction of the film is a cut end formed by a cutting blade, and has a thickness of 55 μm or less and a length of 500 m or more. Using a grooved roll having a large-diameter portion where the film contacts and a small-diameter portion where the film does not contact in the roll axis direction, and a long surface on the large-diameter portion of the grooved roll. A step of cutting the PVA film along the length direction with a round blade rotating at the position of the small-diameter portion of the grooved roll while transferring and contacting the PVA film of the present invention. 25 to 50 °, and the Vickers hardness of the cutting edge portion is 1,500 HV or more. In general, a thin PVA film tends to have a rough cut end surface when cut as compared with a thick PVA film, but according to the production method of the present invention, even a thin PVA film Regardless, a PVA film satisfying the requirements of the present invention can be produced smoothly.

  The grooved roll used in the production method of the present invention has a large-diameter portion where the film contacts and a small-diameter portion where the film does not contact in the roll axis direction. As the grooved roll, for example, a metal roll can be preferably used.In particular, if a chrome-plated roll is used, the surface hardness of the grooved roll is increased, and the occurrence of scratches can be prevented. It is preferable because it can be performed. The grooved roll has at least three large-diameter portions (projections) in the roll axis direction, and has a small-diameter portion (groove, concave portion) between the large-diameter portions (the small-diameter portion). Having at least two parts).

  The diameter of the large-diameter portion of the grooved roll is 5 cm from the viewpoint of good transfer of the PVA film, good cutting of the PVA film with the grooved roll, and the manufacturing cost of the grooved roll. It is preferably at least 7.5 cm, more preferably at least 7.5 cm, even more preferably at least 10 cm, preferably at most 30 cm, more preferably at most 25 cm, and at most 20 cm. Is more preferable. When the diameter of the large diameter portion of the grooved roll is equal to or larger than the lower limit, the PVA film can be cut more uniformly. On the other hand, when the diameter of the large-diameter portion of the grooved roll is equal to or less than the upper limit, the manufacturing cost of the grooved roll can be reduced. When a plurality of large-diameter portions are present on the grooved roll, all of the large-diameter portions have the same diameter in order to transfer the PVA film in contact with the surface of the plurality of large-diameter portions while keeping the film flat. It is preferred that

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

  The diameter of the small-diameter portion of the grooved roll is determined from the viewpoint of preventing damage to the round blade, smoothness of cutting the PVA film at the position of the small-diameter portion, and ease of processing the groove in the grooved roll. It is preferably smaller than the diameter of the part by 0.5 cm or more, more preferably 1 cm or more, more preferably 2 cm or less, and more preferably 1.5 cm or less.

  The width of the small diameter portion of the grooved roll (the length in the roll axis direction; the width of each small diameter portion when there are a plurality of small diameter portions) is equal to or less than the width of the adjacent large diameter portion. Preferably, there is. Also, 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 edge of the round blade contacting the grooved roll, and that the cutting point of the film is prevented from shifting. Therefore, it is preferably at least twice, more preferably at least 5 times, the thickness (dimension d in FIG. 2) of the non-tapered base portion at the blade portion of the round blade. It is more preferably at most 30 times, more preferably at most 30 times.

  The round blade used in the production method of the present invention is a blade having a blade for cutting a film around the entire circumference of a disk-shaped main body rotating around an axis. The round blade is preferably made of metal or ceramic, and specific examples include iron, iron alloy, high-speed tool steel, alloy tool steel, stainless steel, martensite stainless steel, and tungsten steel. Further, the blade portion 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. In particular, a round blade made of tungsten steel is preferable because it is hard to be worn and has excellent durability, and the cut end surface has good smoothness.

The Vickers hardness of at least the cutting edge portion of the round blade needs to be 1,500 HV or more, and preferably 1,800 HV or more, since the PVA film of the present invention can be manufactured smoothly. There is no particular upper limit on the Vickers hardness. For example, the Vickers hardness can be 2,400 HV or less. 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) of FIG. 2] is preferably 15 mm or more, and more preferably 20 mm or more. More preferably, it is more preferably 40 mm or more. When the diameter of the round blade is in the above range, the progress of abrasion is suppressed, and a smooth cut end face is easily formed 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 increases, and it becomes difficult to rotate freely when cutting the PVA film, and to prevent breakage. The diameter of the round blade is preferably 200 mm or less, and more preferably 120 mm or less, because it is necessary to increase the thickness of the blade base.

  The shape of the cutting edge of the round blade is, as exemplified in FIG. 2 (a), a chevron shape (both blades) in which the polished surfaces 4, 4 'on both sides converge in a tapered shape at the center cutting edge 3. Alternatively, or as illustrated in FIG. 2B, the other polished tapered surface 6 converges toward the cutting edge 3 at the end of one vertical surface 5. May be a single-edged shape. Among them, it is preferable that the cutting edge of the round blade has a chevron shape as shown in FIG. 2A, since the cutting of the PVA film is performed stably, and a cut end surface having more excellent smoothness is formed.

  In the manufacturing method of the present invention, the cutting edge angle of the round blade [the angle α shown in FIGS. 2A and 2B] needs to be in the range of 25 to 50 °. If the cutting edge angle of the round blade is less than 25 °, the reason is not necessarily clear, but in cutting a thin PVA film having a thickness of 55 μm or less, the cutting edge is easily worn, and a long PVA film roll is manufactured. In this case, it is difficult to continuously obtain the required cut end face. It is possible to maintain good sharpness over a long period of time while suppressing the wear of the cutting edge, so that even if the length of the PVA film is long, the degree of roughening is small over the entire length of the film and a smooth cut end surface is formed. Preferably, the cutting edge angle of the round blade is at least 30 °, more preferably at least 35 °. On the other hand, if the cutting edge angle of the round blade exceeds 50 °, the sharpness becomes dull and it becomes difficult to form a smooth cut end surface with a low degree of roughening. From this viewpoint, the cutting edge angle of the round blade is preferably 45 ° or less, and more preferably 43 ° or less.

  The thickness of the base of the cutting edge of the round blade [the thickness immediately before the thickness gradually decreases toward the tip of the cutting edge; the dimension of d shown in FIGS. 2A and 2B] is 0.05 mm or more. Is preferably 0.1 mm or more, more preferably 1 mm or less, and even more preferably 0.5 mm or less. When the thickness of the blade base is equal to or greater than the lower limit, breakage of the round blade itself can be suppressed. On the other hand, when the thickness of the blade base is equal to or less than the upper limit, a smooth cut end surface having a small degree of roughening over the entire length of the film can be formed.

  The length of the blade in the round blade [distance from the base of the blade edge to the tip of the blade edge: the dimension of e shown in FIGS. 2 (a) and 2 (b)] is at least 1 times the thickness of the PVA film to be cut. Preferably, it is 5 times or more, more preferably 50 times or less, and even more preferably 45 times or less. When the length of the blade is equal to or more than the lower limit, it is possible to prevent the cut end surface of the PVA film from being damaged at the base of the blade. On the other hand, when the length of the blade is equal to or less than the upper limit, wear and breakage of the blade can be suppressed.

  While the long PVA film is brought into contact with the surface of the large-diameter portion of the grooved roll and transferred, the PVA film is moved along the length direction by a round blade rotating at the position of the small-diameter portion of the grooved roll. When cutting, the peripheral speed of the large-diameter portion of the grooved roll and the transfer speed of the PVA film are made the same, and the PVA film is transferred on the grooved roll in a tensioned state without loosening. This is important for forming a smooth cut end surface with a low degree of surface roughening. From this point, when cutting the PVA film along the length direction, the PVA film is angled (embraced angle) of 10 to 100 ° along the circumference of the grooved roll [shown in FIG. [Contact angle β], the PVA film is placed along the grooved roll (in a hugged state), and the PVA film is cut by a rotating round blade arranged at the position of the small diameter portion of the grooved roll. Is preferred. In this case, it is preferable that the round blade is disposed at the center or substantially the center of the holding angle. By doing so, the peripheral speed of the large diameter portion of the grooved roll and the transfer speed of the PVA film at the time of cutting become substantially the same, and the groove is formed while the PVA film is transferred by the grooved roll in a tensioned state. Since the cutting roll is cut by the rotating round blade disposed at the position of the small diameter portion, a smooth cut end surface with a low degree of surface roughening can be formed. From the above viewpoint, the holding angle is more preferably 30 ° or more, further preferably 45 ° or more, and further preferably 98 ° or less, and more preferably 95 ° or less. preferable.

  When cutting the PVA film along the length direction by the rotating round blade, the PVA film may be cut while positively driving and rotating the round blade. However, the rotation speed of the round blade and the transfer speed of the PVA film may be reduced. From the viewpoint that the degree of surface roughening of the cut end surface can be made smaller by reducing the difference from the above, the round blade can be freed with the transfer of the PVA film rather than actively driving and rotating the round blade. It is preferable to perform cutting while rotating. When the cutting is performed while the round blade is freely rotating, it is possible to prevent a large difference between the rotation speed of the round blade and the transport speed of the PVA film from occurring, thereby cutting the PVA film smoothly and smoothly. It is possible to form a smooth cut end face with a smaller degree of surface flattening. The method for freely rotating the round blade is not particularly limited. For example, as illustrated in a schematic diagram of FIG. 2 (a cross-sectional view in the thickness direction of the round blade 2), the round blade 2 is a disk-shaped round blade. The rotary shaft 8 is fixedly attached to the mounting member 7, and the rotating shaft 8 is integrally or fixedly extended at the center (center position) of the disk-shaped round blade mounting member 7, and a ball bearing or the like is provided around the rotating shaft 8. A system in which the bearing 9 is arranged and the rotating shaft 8, the round blade mounting member 7, and the round blade 2 are freely rotated integrally can be adopted.

  When the PVA film is cut along the length direction by the rotating round blade, the transport speed of the PVA film is preferably 40 m / min or less, more preferably 30 m / min or less, and more preferably 25 m / min or less. Is more preferable. When the transfer speed is equal to or less than the upper limit, the degree of surface roughening of the cut end surface can be further reduced. On the other hand, if the transfer speed is too slow, the cutting may take too much time and productivity may be reduced. Therefore, the transfer speed is preferably 5 m / min or more.

  The volatile content of the PVA film when the PVA film is cut along the length direction by the rotating round blade is preferably 0.1% by mass or more, more preferably 2% by mass or more, and , Preferably 10% by mass or less, more preferably 6% by mass or less. When the volatile content is equal to or higher than the lower limit, the PVA film is not too hard and can be easily cut. On the other hand, when the volatile content is equal to or less than the upper limit, the PVA film can be prevented from being too soft, and the degree of roughening of the cut end surface can be further reduced. In addition, the "volatile content of the PVA film" as used in the present specification means the content of volatile components contained in the PVA film. Examples of such volatile components include a solvent such as an organic solvent and water used in producing a PVA film, and moisture taken into the film by absorbing moisture after the production of the PVA film. The volatile content of the PVA film is dried to a target value by using a heated metal roll, a floating dryer or the like alone or in combination of two or more types; the PVA film having a volatile content lower than the above range is humidified. It can be adjusted by such a method. The volatile content of the PVA film can be determined from the weight loss 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 the weight is reduced.

  Further, the film temperature when the PVA film is cut along the length direction by the rotating round blade is preferably 10 ° C. or more, more preferably 20 ° C. or more, and 70 ° C. or less. The temperature is preferably 60 ° C. or lower. When the film temperature is equal to or higher than the lower limit, the PVA film does not become too hard and can be easily cut. In addition, water droplets due to dew condensation adhere to the PVA film, and blocking occurs when the cut PVA film is rolled up and stored, or when the PVA film is stretched, it breaks from the portion where the water droplets adhere. Can also be suppressed. On the other hand, when the film temperature is equal to or lower than the upper limit, the PVA film can be prevented from being too soft, and the degree of roughening of the cut end surface can be further reduced. In addition, the film temperature of a PVA film can be measured using a spot-type digital radiation thermometer (for example, “Thermometer 505A” manufactured by Minolta Co., Ltd.).

  The cutting along the length direction of the PVA film by the rotating round blade may be performed continuously following the PVA film manufacturing process, or after the PVA film is manufactured and wound into a roll, the PVA film may be cut. This may be performed while unwinding the film from the roll.

  The method for producing the PVA film to be cut is not particularly limited, and can be produced by a conventionally known method. For example, the above-mentioned PVA constituting the PVA film, and if necessary, the above-mentioned plasticizer and interface One or two or more of the activator and other components are dissolved in a liquid medium, PVA, and if necessary, a plasticizer, a surfactant, and other components. And one or two or more of these, and can be produced using a film forming stock solution in which PVA is melted. When the film-forming stock solution contains at least one of a plasticizer, a surfactant and other components, it is preferable that those components are uniformly mixed.

  Examples of the liquid medium used for preparing the membrane-forming stock solution include water, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, ethylene glycol, glycerin, propylene glycol, diethylene glycol, triethylene glycol, and tetraethylene glycol. , Trimethylolpropane, ethylenediamine, diethylenetriamine, and the like, and one or more of these can be used. Among them, water is preferable from the viewpoint of load on the environment and recoverability.

  Examples of a film forming method for forming a PVA film using the above 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 employ only one kind or a combination of two or more kinds. Among these film-forming methods, the cast film-forming method and the extrusion film-forming method are preferable because a PVA film giving a good polarizing film can be smoothly manufactured. The formed film can be dried or heat-treated as necessary.

  As an example of a specific production method of the PVA film to be subjected to cutting, for example, using a T-shaped slit die, a hopper plate, an I-die, a lip coater die, and the like, the above film forming stock solution is placed on the most upstream side. One surface of a film which is uniformly discharged or cast on the peripheral surface of the rotating heated first roll (or belt) positioned thereon and discharged or cast on the peripheral surface of the first roll (or belt) From the volatile components, followed by further drying on the circumference of one or more rotating heated rolls located downstream thereof, or by passing through a hot-air dryer. After drying, a method of winding with a winding device can be industrially preferably employed. Drying with a heated roll and drying with a hot air drying device may be performed in an appropriate combination.

  There are no particular restrictions on the use of the PVA film of the present invention, and examples thereof include a film for drug packaging, a base film for hydraulic transfer, a base film for embroidery, a release film for forming artificial marble, a film for seed packaging, and a bag for storing filth. The PVA film of the present invention, which can be used for various water-soluble films such as films, has at least one of two ends along the length direction of the film, and preferably both ends are cut ends. The "maximum height roughness (Rz)" of the cut end face of the end is not more than a specific value, and the cut end face has a very low degree of roughening and is excellent in smoothness, so that it is stretched in the length direction. When this is done, cracks are less likely to occur at the cut end (the end in the width direction of the film), and as a result, the film is less likely to break. From this point, the PVA film of the present invention is preferably used as a raw film for producing an optical film (a 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 a polarizing film using the PVA film of the present invention is not particularly limited, and any conventionally known method may be employed. Examples of such a method include a method of performing dyeing and uniaxial stretching using the PVA film of the present invention, and a method of performing uniaxial stretching on the PVA film of the present invention containing a dye. As a more specific method for producing a polarizing film, the PVA film of the present invention is subjected to swelling, dyeing, uniaxial stretching, and, if necessary, further crosslinking treatment, fixing treatment, drying, heat treatment, and the like. Method. 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 more treatments can be performed simultaneously. Further, one or two or more of the processes can be performed twice or more.

  Swelling can be performed by immersing the PVA film in water. The temperature of 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 preferably in the range of 25 to 35 ° C. More preferred. The time for immersion in water is, for example, preferably in the range of 0.1 to 5 minutes, and more preferably in the range of 0.5 to 3 minutes. The water used for immersion in water is not limited to pure water, and may be an aqueous solution in which various components are dissolved, or may be a mixture of water and an aqueous medium.

  Dyeing can be performed by bringing a dichroic dye into contact with the PVA film. Generally, an iodine-based dye is used as the dichroic dye. The stage of dyeing may be any stage before uniaxial stretching, during uniaxial stretching, or after uniaxial stretching. Dyeing is generally performed by immersing the PVA film in a solution containing iodine-potassium iodide (especially an aqueous solution) as a dyeing bath, and such a dyeing method is suitably employed in the present invention. . 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. The temperature of the dyeing bath is preferably from 20 to 50C, particularly preferably from 25 to 40C.

  By subjecting the PVA film to a crosslinking treatment, it is possible to more effectively prevent the PVA from being eluted into water during wet stretching at a high temperature. From this viewpoint, the crosslinking treatment is preferably performed after the treatment for contacting the dichroic dye and before the uniaxial stretching. The crosslinking treatment can be performed by immersing the PVA film in an aqueous solution containing a crosslinking agent. As the cross-linking agent, one or more boron compounds such as borate 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. Is more preferable. 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 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 50C, particularly preferably in the range of 25 to 40C. By setting the temperature in the range of 20 to 50 ° C, crosslinking can be performed efficiently.

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

  The stretching temperature in the 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 50 to 70 ° C. It is particularly preferred that it is within the range. In the case of the dry heat drawing method, the temperature is preferably in the range of 50 to 180 ° C.

  Further, the stretching ratio in uniaxial stretching (in the case of performing uniaxial stretching in multiple stages, the total stretching ratio obtained by multiplying each stretching ratio) is preferably 4 times or more from the viewpoint of the polarizing performance of the obtained polarizing film. 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.

  There is no particular limitation on the direction of the uniaxial stretching, and uniaxial stretching or transverse uniaxial stretching in the longitudinal direction of the long PVA film can be employed. However, in the longitudinal direction, a polarizing film having excellent polarization performance is obtained. Is preferred. Uniaxial stretching in the longitudinal direction can be performed by using a stretching device having a plurality of rolls parallel to each other and changing the peripheral speed between the rolls. On the other hand, horizontal uniaxial stretching can be performed using a tenter type stretching machine.

  In the production of the polarizing film, it is preferable to perform a fixing treatment in order to strengthen the adsorption of the dichroic dye (such as an iodine dye) to the PVA film. The fixing treatment can be performed by immersing the PVA film in a fixing treatment bath. As the fixing bath, an aqueous solution containing one or more 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 fixing bath. The concentration of the boron compound in the fixing treatment bath is generally preferably 2 to 15% by mass, particularly preferably about 3 to 10% by mass. By setting the concentration within the range of 2 to 15% by mass, the adsorption of the dichroic dye can be further enhanced. The temperature of the fixing bath is preferably 15 to 60C, particularly preferably 25 to 40C.

  The drying conditions are not particularly limited, but it is preferable to perform the drying at a temperature within the range of 30 to 150 ° C, particularly 50 to 140 ° C. By drying at a temperature in the range of 30 to 150 ° C., a polarizing film having excellent dimensional stability and capable of suppressing a decrease in polarizing performance due to decomposition of a dichroic dye is easily obtained.

  The thickness of the polarizing film obtained as described above depends on the thickness of the PVA film to be used, but is preferably 30 μm or less, and more preferably 25 μm or less, from the viewpoints of polarization performance, handleability, and durability. Is more preferably 20 μm or less, still more preferably 15 μm or less, further preferably 1 μm or more, more preferably 2 μm or more, and still more preferably 4 μm or more. , 6 μm or more.

  The polarizing film obtained as described above is usually used in the form of a polarizing plate by bonding an optically transparent protective film having mechanical strength to both surfaces or one surface thereof. As the protective film, a cellulose triacetate (TAC) film, a cycloolefin polymer (COP) film, a cellulose acetate / butyrate (CAB) film, an acrylic film, a polyester film, or the like is used. Examples of the adhesive for bonding include a PVA-based adhesive and a urethane-based adhesive, and among them, a PVA-based adhesive is preferable.

  The polarizing plate obtained as described above can be used as an LCD component by being coated with an adhesive such as an acrylic resin and then bonded to a glass substrate. At the same time, it may be bonded to a retardation film, a viewing angle improving film, a brightness improving film, or the like.

Hereinafter, the present invention will be described specifically with reference to Examples and the like, but the present invention is not limited to the following Examples.
In the following examples, each physical property was evaluated by the following methods.

(1) Measurement of “maximum height roughness (Rz)” and “arithmetic mean roughness (Ra)” of the cut end face of the PVA film:
A film portion of the outermost layer of a roll of a PVA film (a PVA film having a cut end along the length direction) which is cut into a roll shape after being cut along the length direction of the film (particularly from the starting point of cutting). A sample including a cut end having a length of 30 mm along the length direction of the film is collected from the portion immediately after being cut by 500 m in the length direction (sample number 3), and an arbitrary cut end surface of the collected sample is obtained. At a position along the length of the film over a length of 100 μm using a Keyence's ultra-depth shape measuring microscope “VK-8500” to measure the cut end face, and at the center in the thickness direction on the cut end face A roughness curve based on the surface condition on a line in the length direction of the film is determined, and “maximum height roughness (Rz)” and JIS B 0601: 2001 are defined. The “maximum height roughness (Rz)” and the “arithmetic mean roughness (Ra)” of the cut end face were calculated according to the calculation method of “arithmetic mean roughness (Ra)”, respectively, and the average value at three locations was calculated. .
In addition, at the start of cutting and at an intermediate stage, there is no or small wear of the cutting edge of the cutting blade, and a smooth cut end surface with a low degree of surface roughening is formed. The measurement of the degree of surface roughening of the cut end surface at the intermediate point in time of the cutting is omitted, and the point immediately before the end of the cut where the wear of the cutting blade is greatest (the roll of the PVA film wound into a roll after cutting) (The film portion of the outermost layer), the “maximum height roughness (Rz)” and the arithmetic average roughness (Ra) of the cut end face were obtained, and the degree of surface roughening of the cut end face was evaluated.

(2) Confirmation of occurrence of breakage during stretching of PVA film (stretching ratio at breakage of film):
(I) Confirmation of whether or not a PVA film having a cut end along the length direction breaks during stretching originally needs to be performed in a continuous stretching operation at the time of producing a polarizing film. Since the breakage of the PVA film usually occurs once every several hours or not, and it is difficult to carry out a test suitable for actual use, it was evaluated by the following model test (ii).
(Ii) A film portion of the outermost layer of the roll of the PVA film (a PVA film having a cut end along the length direction) which is cut into a roll shape after being cut along the length direction of the film (particularly, a cutting start point) As shown in FIG. 1, one side (long side) of the sample in the longitudinal direction is a cut end from the portion immediately after being cut by 500 m in the length direction of the film, as shown in FIG. 1. Then, a rectangular sample (sample S shown in FIG. 1) having a size of length × width = 15 cm × 10 cm was collected (sample collection points: 3). At this time, the cuts on the three sides other than the side corresponding to the cut end should be cut well each time one side is cut so that a smooth cut surface that is not roughened is formed. The cutting operation was performed using a cutter knife ("A blade" manufactured by NTT Corporation) with an updated blade edge.
(Iii) At both ends (two horizontal sides) of the sample collected in the above (ii), the sample is gripped by a pair of chucks at a distance of 4 cm between the chucks and attached to a batch stretching machine. Immersed in water for 1 minute to swell with water, immediately taken out of the water, immediately immersed in a 4% aqueous solution of boric acid at 50 ° C., and stretched as it was in an aqueous solution of boric acid 1 minute after immersion The sample was stretched under the condition of a speed of 0.15 m / min, the distance between the chucks when the sample was broken was measured, and the stretching ratio at the time of breaking was determined from the following equation, and the average value of the three samples was obtained.
Stretch ratio at break (times) = distance between chucks at sample break (cm) / 4 (cm)

(Iv) As a control, a film portion of the outermost layer of the roll of the PVA film (a PVA film having a cut end along the length direction) wound up in the same roll shape as the sample taken in (ii) above ( In particular, a rectangular sample with a size of 15 cm x 10 cm (length x width = 15 cm x 10 cm) is placed in parallel with the length direction of the film from almost the center in the width direction (the portion immediately after cutting 500 m in the length direction of the film from the cutting start point). The sample was collected (a sample having no cut end face along the length direction) (sample collection points: 3). In this (iv) sampling, the four sides (four cut end faces) of the sample should be cut well every time one side is cut so that the sample is finished smoothly without roughening. The cutting operation was performed using a cutter knife ("A blade" manufactured by NTT Corporation) with an updated blade edge.
(V) Using the control sample obtained in (iv) above, the stretch ratio at break was determined in the same manner as in (iii) above, and the average value of the three samples was taken.

[Example 1]
(1) After impregnating 12 parts by mass of glycerin and 220 parts by mass of water with respect to 100 parts by mass of PVA chips (degree of polymerization of PVA: 2,400, degree of saponification: 99.9 mol%), extrude the impregnated PVA chips. It is supplied to a machine and melted under heat and pressure to prepare a film forming solution in which PVA is melted, and the film forming stock solution is used as a first metal roll (metal roll surface temperature 95 ° C., metal roll diameter 3.8 m). After being extruded upward, the front and back surfaces were alternately dried on another 10 metal rolls to continuously produce a long PVA film (film width 3 m, thickness 20 μm).

(2) As a cutting device for cutting the PVA film, a grooved roll 10 (as illustrated in FIG. 3A) is provided upstream of a winder for winding the formed PVA film into a roll. Metal; large-diameter portion diameter Eb 20 cm, large-diameter portion Eb width Wa 8 mm; small-diameter portion diameter Ec 19 cm, small-diameter portion width Wb 2 mm), and the position of the small-diameter portion near both ends in the width direction of grooved roll 10. (A) Vickers hardness of the cutting edge portion: 1,850 HV; round blade diameter Ea: 45 mm; cutting edge angle: α40 °; flesh of the cutting edge base One piece of thickness (thickness immediately before the thickness gradually decreases toward the tip of the blade edge) d 0.3 mm; and one piece of the blade length (distance from the base of the blade edge to the tip of the blade edge) e 0.85 mm) were arranged.

(3) The PVA film produced in the above (1) (the volatile content in the film is 3% by mass) is supplied to the cutting device prepared in the above (2). The large-diameter portion of the grooved roll 10 with the PVA film being held along the part of the circumference of the grooved roll 10 with the contact angle β (embrace angle) of the PVA being 90 ° The PVA film is transported at a speed of 17 m / min while being in contact with the surface of the PVA film, and both ends of the PVA film are cut along the length direction by a new renewed round blade 2 which is freely rotated by a ball bearing to have a width of 2.6 m And wound continuously in a roll on an aluminum tube (approximately 15.2 cm in diameter) with a winder, and a total length of 500 m or more with cut end faces at both ends along the length direction (winding length More than 500m ) Was obtained of the PVA film. The temperature of the PVA film at the time of cutting by the rotating round blade was 30 ° C.

(4) Using the PVA film wound in a roll with a length of about 500 m obtained in (3) above, the “maximum height roughness (Rz)” and the “arithmetic mean roughness ( Ra) "was measured by the method described above, and the maximum height roughness (Rz) was 0.85 μm, the arithmetic average roughness (Ra) was 0.13 μm, Rz / Ra was 6.8, and the length was The cut end face along the direction (total length) had a very low degree of roughening over a section of 500 m or more, and was excellent in smoothness.

(5) Further, when the stretch ratio at the time of film breakage was measured by the above-mentioned method using the PVA film wound up in a roll shape with a length of about 500 m obtained in (3) above, it was 6.1 times. Met. On the other hand, the stretch ratio at the time of film breakage in the control sample (a sample collected from a substantially central portion in the width direction of the PVA film) was also 6.1 times.

[Example 2]
(1) In (2) of Example 1, except that a new round blade having a blade edge angle α of 45 ° was used, the lengthwise direction was the same as (1) to (3) of Example 1. A PVA film with a total length of 500 m or more (winding length of 500 m or more) having cut end faces at both ends was obtained.
(2) Using the PVA film wound in a roll with a length of about 500 m obtained in the above (1), the “maximum height roughness (Rz)” and the “arithmetic average roughness (Rz)” of the cut end face are used. Ra) "was measured by the method described above, and the maximum height roughness (Rz) was 0.98 μm, the arithmetic average roughness (Ra) was 0.15 μm, Rz / Ra was 6.7, and the length was The cut end face along the direction (total length) had a very low degree of roughening over a section of 500 m or more, and was excellent in smoothness.
(3) When the stretch ratio at the time of film breakage was measured by the above-mentioned method using the PVA film wound into a roll with a length of about 500 m obtained in (1) above, it was 6.0 times. Met.

[Example 3]
(1) In (2) of Example 1, except that a new round blade with a blade angle α of 30 ° was used, the lengthwise direction was the same as in (1) to (3) of Example 1. A PVA film with a total length of 500 m or more (winding length of 500 m or more) having cut end faces at both ends was obtained.
(2) Using the PVA film wound in a roll with a length of about 500 m obtained in the above (1), the “maximum height roughness (Rz)” and the “arithmetic mean roughness (Rz)” Ra) "was measured by the method described above, and the maximum height roughness (Rz) was 1.19 μm, the arithmetic average roughness (Ra) was 0.15 μm, Rz / Ra was 7.8, and the length was The cut end face along the direction (total length) had a very low degree of roughening over a section of 500 m or more, and was excellent in smoothness.
(3) Using the PVA film wound in a roll shape with a length of about 500 m or more obtained in the above (1), the stretch ratio at the time of film breakage was measured by the above-mentioned method, and was 5.9 times. Met.

[Comparative Example 1]
(1) Same as (1) to (3) of Example 1 except that a new round blade having a Vickers hardness of 300 HV or less (SKS-7) in the cutting edge portion in (3) of Example 1 was used. Thus, a PVA film having a total length of 500 m or more (winding length of 500 m or more) having cut end faces at both ends along the length direction was obtained.
(2) Using the PVA film wound in a roll with a length of about 500 m obtained in the above (1), the “maximum height roughness (Rz)” and the “arithmetic average roughness (Rz)” of the cut end face are used. Ra) "was measured by the above-described method. As a result, the maximum height roughness (Rz) was 2.68 μm, the arithmetic average roughness (Ra) was 0.50 μm, and Rz / Ra was 5.4. The degree of roughening of the cut end surface was higher than that of Nos. 1 to 3.
(3) Further, when the stretch ratio at the time of film breakage was measured by the above-mentioned method using the PVA film wound into a roll with a length of about 500 m obtained in (1) above, it was 5.6 times. And it was easy to break at the time of stretching as compared with Examples 1-3.

[Comparative Example 2]
(1) In (3) of Example 1, the lengthwise direction was changed in the same manner as (1) to (3) of Example 1 except that a new round blade having a blade angle α of 23 ° was used. A PVA film with a total length of 500 m or more (winding length of 500 m or more) having cut end faces at both ends was obtained.
(2) Using the PVA film wound in a roll with a length of about 500 m obtained in the above (1), the “maximum height roughness (Rz)” and the “arithmetic average roughness (Rz)” of the cut end face are used. Ra) "was measured by the method described above, and the maximum height roughness (Rz) was 3.22 μm, the arithmetic average roughness (Ra) was 0.67 μm, and Rz / Ra was 4.8. The degree of roughening of the cut end surface was higher than that of Nos. 1 to 3.
(3) Further, when the stretch ratio at the time of film breakage was measured by the above-mentioned method using the PVA film wound into a roll with a length of about 500 m obtained in (1) above, it was 5.6 times. And it was easy to break at the time of stretching as compared with Examples 1-3.

  The above results are shown in the table below.

Reference Signs List 1 PVA film 2 Round blade 3 Tip of round blade 4, 4 'Polished surface 5 Vertical surface 6 Polished surface 7 Round blade mounting member 8 Rotating shaft 9 Bearing 10 Grooved roll 10a Large diameter of grooved roll Part 10b Small diameter part of grooved roll

Claims (7)

A long polyvinyl alcohol film having a thickness of 55 μm or less and a length of 500 m or more ,
At least one of the two ends along the length direction of the film is a cut end formed by a cutting blade, and the maximum height roughness (Rz) of the cut end face of the cut end and the arithmetic average roughness ( A polyvinyl alcohol film, wherein Ra) and their ratio (Rz / Ra) are 2.5 μm or less , 0.4 μm or less, and 5 to 11 , respectively, over a section of the film having a length of 500 m or more. The polyvinyl alcohol film according to claim 1, wherein the length of the film is 1,000 m or more. The polyvinyl alcohol film according to claim 1 or 2 , which is a raw film for producing an optical film. The polyvinyl alcohol film according to any one of claims 1 to 3 , wherein the optical film is a polarizing film. A roll obtained by winding the polyvinyl alcohol film according to any one of claims 1 to 4 in a roll shape. It is a manufacturing method of the polyvinyl alcohol film according to any one of claims 1 to 4 ,
Using a grooved roll having a large-diameter portion where the film comes into contact and a small-diameter portion where the film does not contact in the roll axis direction, contacting and transferring a long polyvinyl alcohol film to the surface of the large-diameter portion of the grooved roll. A step of cutting the polyvinyl alcohol film along the length direction by a round blade rotating at the position of the small-diameter portion of the grooved roll, wherein the round blade has a blade angle of 25 to 50 ° and a blade edge of The production method, wherein the Vickers hardness of the portion is 1,500 HV or more. The method according to claim 6 , wherein the polyvinyl alcohol film is brought into contact with the grooved roll at an angle of 10 to 100 along the circumference of the grooved roll.

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