JP2010253952A - Method for cutting vinyl alcohol-based polymer film for stretching process - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a vinyl alcohol-based polymer film for a stretching process capable of being easily uniformly stretched and useful for a raw material for forming a broad polarizing film capable of coping with the enlargement of a liquid crystal display screen. <P>SOLUTION: Both ends in the widthwise direction of the vinyl alcohol-based polymer film are cut and removed by a cutter preliminarily before the stretching process where the temperature of the vinyl alcohol-based polymer film supplied for cutting is 10 to 70°C, and the content of a volatile component is 0.1 to 10%. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  INDUSTRIAL APPLICABILITY The present invention is useful as a raw material for producing a polarizing film or a cold chill, has a few breaks from both ends in the width direction of the film during stretching, and is easy to perform uniform stretching, and a method for producing a vinyl alcohol polymer film for stretching. And a polarizing film produced using the film.

  A polarizing plate having a light transmission and shielding function is a basic component of a liquid crystal display (LCD) together with a liquid crystal having a light switching function. This LCD can be applied to small devices such as calculators and wristwatches in the early days of development, and in recent years, laptop computers, word processors, liquid crystal color projectors, in-vehicle navigation systems, liquid crystal televisions, personal phones, and indoor and outdoor measuring devices. There is a need for a polarizing plate that spreads over a wide range and is cheaper than conventional products.

  The polarizing plate is generally dyed by uniaxially stretching a vinyl alcohol polymer film (hereinafter, the vinyl alcohol polymer may be abbreviated as “PVA” and the vinyl alcohol polymer film as “PVA film”). After the dyeing, the film was uniaxially stretched, and then fixed with a boron compound (the dyeing and fixing processes may be performed simultaneously), the cellulose triacetate (TAC) film, and the acetic acid / cellulose butyrate (CAB) film. It is the structure which bonded protective films, such as.

  In addition, with the rationalization and mechanization of agriculture, PVA-made chillers, PVA-made insulation curtains in vinyl houses, and the like are attracting attention.

  By the way, in order to manufacture a polarizing film or a cold water bottle, a stretching process for stretching a PVA film is necessary as described above. However, even if it is a PVA film that looks uniform in appearance, Since the thickness and the degree of drying are different at both ends, when the stretching process is performed, both ends in the width direction of the film may tear and break from there, resulting in a large cost loss. In order to improve the yield, a polarizing plate manufacturer or a cold chiller manufacturer demands a PVA film that does not break during stretching.

  Therefore, an object of the present invention is to obtain a PVA film that is less likely to break from both ends in the width direction of the film during stretching, is easy to stretch uniformly, and is useful as a raw material for cold chills and polarizing films. It is in.

In order to solve the above problems, the present inventors focused on a method of cutting so as to remove both ends in the width direction of the PVA film in advance before stretching, and the temperature and volatile content were kept in a specific range. By subjecting the PVA film to cutting with a blade, uniform stretching can be easily performed, and it has been found that a PVA film useful as a raw material for production of a polarizing film, a cold chill, etc. can be obtained, and the present invention has been completed.
That is, the present invention is a method of cutting so as to remove both ends in the width direction of the PVA film in advance before the drawing process using a blade, and the temperature of the PVA film used for the cutting is 10 ° C. to This is a method of cutting a PVA film for stretching which has a volatile content of 0.1% to 10% at 70 ° C.

  ADVANTAGE OF THE INVENTION According to this invention, the PVA film for extending | stretching process useful as manufacturing raw materials, such as a target polarizing film and a cold chill, is obtained reliably. Therefore, there is little occurrence of breakage at both ends in the width direction of the film during stretching, uniform stretching is easy, wide good products can be obtained with high yield, and it is possible to respond to lower prices of liquid crystal display screens, etc. It becomes.

  As described above, according to the present invention, a PVA film for a polarizing film that can be easily stretched uniformly is obtained. By using this PVA film, an optimum polarizing film for a liquid crystal display screen can be obtained.

Hereinafter, the present invention will be described in detail.
In the present invention, it is important that the temperature of the PVA film is 10 ° C. to 70 ° C., more preferably 20 ° C. to 70 ° C., when cutting so as to remove both ends in the width direction of the PVA film before stretching. 60 ° C. When the temperature of the PVA film exceeds 70 ° C., the PVA film becomes too soft and cannot be slit cleanly, and breakage tends to occur from both ends of the PVA film during stretching. On the other hand, when the temperature of the PVA film is less than 10 ° C., the film becomes hard and the PVA film may be broken at the time of slitting. In addition, if the PVA film is cooled to less than 10 ° C. during film formation, condensation occurs on the surface of the cooling roll, and water droplets may adhere to the PVA film, which may be blocked when rolled up and stored. In addition, breakage may occur from the portion where water droplets adhere during stretching.

  Here, the temperature when slitting the PVA film was measured using a spot type digital radiation thermometer (thermometer 505A, manufactured by Minolta Co., Ltd.).

  In the present invention, when the PVA film is cut so as to remove both ends in the width direction in advance during film formation, after film formation or before stretching, the volatile content of the PVA film is 0.1% to 10%. %, And more preferably 2% to 6%. When the volatile content of the PVA film is less than 0.1%, the film becomes hard and the PVA film may break at the time of slitting. On the other hand, when the volatile content of the PVA film exceeds 10%, the PVA film becomes too flexible and cannot be cleanly slit, and breakage tends to occur from both ends of the PVA film during stretching.

  The volatile content of the PVA film may be dried to a target value by using a heated metal roll or a floating drier alone or in combination of two or more types, or the PVA film dried from the target value may be dried. The volatile content may be given with a humidifier or the like to achieve the target value, and the method is not particularly limited. Here, the volatile content when slitting the PVA film was measured by the weight reduction rate when dried in a vacuum dryer at 83 ° C. for 20 minutes.

  In the present invention, the material of the blade when slitting the PVA film includes metal, ceramic and the like. Specifically, iron, iron alloy, tool steel, stainless steel, particularly martensitic stainless steel are preferable, and a knife whose surface is treated with titanium nitride, titanium carbide, tungsten carbide or the like is preferable. Examples of the type of blade include a single blade (a blade formed on the back of the blade), a double blade (a blade formed on the back of the blade), and a round blade.

  Moreover, it is preferable that the blade when slitting the PVA film has a thickness of 0.05 mm to 1 mm. More preferably, it is 0.1 mm to 0.3 mm. When the wall thickness is less than 0.05 mm, the blade itself is easily damaged, and when it exceeds 1 mm, it cannot be slit cleanly and breaks easily from both ends of the PVA film during stretching.

  Moreover, it is preferable that the blade edge | tip of a cutter is a mountain shape by which both sides | surfaces were grind | polished seeing from the cross section. In the case of a blade whose only one side is polished as seen from the cross section of the blade edge, since it tends to proceed to the left or right with respect to the film width, a stable slit cannot be formed, and both ends of the PVA film are stretched. Breaking easily occurs.

  The angle of the blade edge of the blade is preferably 3 ° to 10 °. If the angle of the blade edge is less than 3 °, the edge of the blade is heavily worn, and a stable slit is often difficult. On the other hand, if the angle of the blade edge exceeds 10 °, the blade edge is dull and a clean slit cannot be formed, and breakage tends to occur from both ends of the PVA film during stretching.

  In the first cutting method in the present invention, the film is substantially in contact with two rolls parallel to each other, and the distance between the contact points is 80 cm or less, more preferably 50 cm or less. When the blade is cut with a blade, the distance between the position where the blade cuts the film and the position where the nearest roll comes into contact with the film is 0.5 cm to 15 cm, more preferably 1 cm to 10 cm. The angle is 25 ° to 75 °, more preferably 30 ° to 60 °. If the distance between the contact points exceeds 80 cm, the running of the PVA film is not stable and a clean slit cannot be made. Also, if the distance between the position where the blade cuts the film and the position where the nearest roll comes into contact with the film is less than 0.5 cm or exceeds 15 cm, a clean slit cannot be formed. As the angle of the blade edge increases, it is preferable to reduce the angle formed by the blade edge and the film.

  In the second cutting method of the present invention, the peripheral speed at the large diameter portion of the metal roll having alternately a plurality of large diameter portions and small diameter portions is substantially the same as the film speed, and the large diameter portion and the film are The diameter of the metal roll at the large diameter portion is 5 cm to 30 cm, and the film is cut by applying the cutting edge of the blade to the position of the small diameter portion, that is, the groove portion. When the peripheral speed and the film speed at the large-diameter portion of the metal roll are different, the PVA film is damaged, and the obtained polarizing film is also damaged and loses commercial value. The diameter of the metal roll at the large diameter portion is more preferably 7.5 cm to 20 cm. If the diameter is less than 5 cm, the degree of curvature of the film along the roll becomes too steep and a clean slit cannot be made. In addition, a roll having a diameter exceeding 30 cm is very expensive and uneconomical.

  Moreover, the width (length in the axial direction) of the large diameter portion of the metal roll is preferably 1 mm or more. Furthermore, the width of the large diameter portion is preferably the same as or wider than the width of the small diameter portion, and the width of the small diameter portion is preferably 2 to 50 times the wall thickness of the blade. The plurality of large diameter portions do not have to have the same width, and have at least three large diameter portions (that is, at least two small diameter portions (grooves)) so that the desired film width can be achieved. Just do it.

  The film width after removing both ends in the width direction of the PVA film of the present invention is 2 m or more, preferably 2.5 m or more, and most preferably 3 m or more. When the film width is less than 2 m, it is easily affected by neck-in (contraction in the width direction) during uniaxial stretching to the vicinity of the center of the film, and it is difficult to obtain a polarizing film having a wide width and uniform optical performance. Further, both end portions in the width direction of the PVA film after film formation need to be removed because the thickness is different from the central portion or the degree of drying is different. Stable stretching cannot be performed without leaving both ends in the width direction of the PVA film after film formation.

  At the time of cutting the film in the first and second cutting methods, the cutter is moved only in one direction parallel to the film flow direction without moving the position at which the cutter cuts the film, and the film speed is 1 / 100,000 or less. Moving at a low speed is economical in that the entire cutting edge of the blade is used. The moving speed of the blade need not be constant and may be intermittent. However, if the blade is moved back and forth in the film flow direction, a clean slit cannot be formed and breakage often occurs during stretching.

  The PVA used in the present invention is produced, for example, by saponifying a polyvinyl ester obtained by polymerizing a vinyl ester. In addition, modified PVA obtained by graft copolymerization of the PVA, modified PVA produced by saponifying a modified polyvinyl ester copolymerized with a monomer copolymerizable with a vinyl ester, and unmodified or modified PVA with hydroxyl groups using aldehydes. A so-called polyvinyl acetal resin partially crosslinked may be used.

  Examples of the vinyl ester include vinyl acetate, vinyl formate, vinyl propionate, vinyl butyrate, vinyl pivalate, vinyl versatate, vinyl laurate, vinyl stearate, vinyl benzoate and the like.

  On the other hand, the monomers copolymerizable with vinyl ester include olefins, acrylic acid and its salts and nitriles, acrylic acid esters, methacrylic acid and its salts and nitriles, methacrylic acid esters, maleic acid and its salts and Nitriles, maleates, itaconic acid and salts thereof and nitriles, itaconic esters, acrylamide and derivatives thereof, methacrylamide and derivatives thereof, N-vinylamides, vinyl ethers, vinyl halides, allyl compounds, vinylsilyl Examples thereof include compounds and isopropenyl acetate.

  When modified PVA is used, the amount of modification is preferably 15 mol% or less, more preferably 5 mol% or less. The comonomer is preferably an α-olefin, and particularly preferably ethylene.

  The saponification degree of PVA is preferably 95 mol% or more, and most preferably 99.5 mol% or more, from the viewpoint of polarization performance and durability.

  The saponification degree indicates the proportion of units that are actually saponified to vinyl alcohol units among units that can be converted to vinyl alcohol units by saponification. The saponification degree of PVA was measured by the method described in JIS.

  The degree of polymerization of PVA is preferably 1000 or more from the viewpoint of polarization performance and durability, and most preferably 2500 or more. The upper limit of the degree of PVA polymerization is preferably 8000 or less, and more preferably 6000 or less.

  The degree of polymerization of the PVA is measured according to JIS K 6726. That is, it is calculated | required from the intrinsic viscosity measured in 30 degreeC water after re-saponifying and refine | purifying PVA.

  Examples of the solvent for dissolving PVA used in producing the PVA film include dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, ethylene glycol, diglycerin, propylene glycol, diethylene glycol, triethylene glycol, tetra Examples thereof include ethylene glycol, trimethylolpropane, ethylenediamine, diethylenetriamine, glycerin, and water, and one or more of these can be used. Among these, dimethyl sulfoxide, water, or a mixed solvent of glycerin and water is preferably used.

  You may make a PVA solution or a water-containing PVA contain a plasticizer, surfactant, dichroic dye, etc. as needed.

  When producing the PVA film, it is preferable to add a polyhydric alcohol as a plasticizer. Examples of the polyhydric alcohol include ethylene glycol, glycerin, propylene glycol, diethylene glycol, diglycerin, triethylene glycol, tetraethylene glycol, trimethylolpropane, etc., and one or more of these are used. can do. Among these, diglycerin, ethylene glycol, and glycerin are preferably used because of the effect of improving stretchability.

  The amount of polyhydric alcohol added is preferably 1 to 30 parts by weight, and most preferably 5 to 20 parts by weight per 100 parts by weight of PVA. If it is less than 1 part by weight, the dyeability and stretchability may be reduced, and if it exceeds 30 parts by weight, the PVA film may be too soft and the handleability may be reduced.

  When producing a PVA film, it is preferable to add a surfactant. The type of the surfactant is not particularly limited, but an anionic or nonionic surfactant is preferable. As the anionic surfactant, a carboxylic acid type, sulfate type or sulfonic acid type anionic surfactant is suitable. As the nonionic surfactant, nonionic surfactants such as alkyl ether type, alkylphenyl ether type, alkyl ester type, alkylamide type, polypropylene glycol ether type, alkanolamide type, and allyl phenyl ether type are suitable. These surfactants can be used alone or in combination of two or more.

  The addition amount of the surfactant is preferably 0.01 to 1 part by weight, most preferably 0.05 to 0.3 part by weight based on 100 parts by weight of PVA. If the amount is less than 0.01 part by weight, the effect of improving stretchability and dyeability is hardly exhibited.

  As a method for producing a PVA film using the above PVA, a melt extrusion method in which water-containing PVA (which may contain an organic solvent. The same applies hereinafter) is extruded in an extruder, or PVA is dissolved in a solvent. Using the prepared PVA solution, the casting film forming method, the wet film forming method (discharging into a poor solvent), the gel film forming method (after the PVA aqueous solution is once cooled and gelated, the solvent is extracted and removed, and the PVA film is removed. And a combination of these methods can be employed. Among these, the casting film forming method and the melt extrusion film forming method using a metal roll for drying are preferable because a good polarizing film can be obtained.

  Each metal roll for drying is heated by steam, a heating medium, hot water, an electric heater or the like. In addition, means such as blowing warm air or cold air on the PVA film or sucking air or steam around the PVA film may be used as an auxiliary. It is also possible to use a drying method other than a heated metal roll, such as a floating dryer such as a tenter method or a free method, after drying with a metal roll until it is ready to dry.

  The thickness of the PVA film is preferably 5 μm to 150 μm, and most preferably 30 μm to 80 μm.

  Moreover, in order to produce a polarizing film from the PVA film of the present invention, for example, the PVA film may be dyed, uniaxially stretched, fixed, dried, and further subjected to heat treatment as necessary. Dyeing, uniaxially stretched, fixed There are no particular restrictions on the order of operations. Each operation may be performed twice or more.

  Dyeing can be performed before uniaxial stretching, during uniaxial stretching, or after uniaxial stretching. As dyes used for dyeing, iodine-potassium iodide, various dichroic dyes, and the like can be used alone or in a mixture of two or more. Usually, the dyeing is generally performed by immersing the PVA film in a solution containing the above-mentioned dye, but the processing conditions such as coating on the PVA film or mixing with the PVA film to form a film. The processing method is not particularly limited.

  The uniaxial stretching can be performed by a wet stretching method or a dry heat stretching method, and can be performed in air using warm water (in a solution containing the dye or in a fixing treatment bath described later) or a PVA film after water absorption. . The stretching temperature is not particularly limited, but 30 ° C. to 90 ° C. is preferable when the PVA film is stretched in warm water (wet stretching), and 50 ° C. to 180 ° C. is preferable when it is dry heat stretched. Further, the stretching ratio of uniaxial stretching (total stretching ratio in the case of multi-stage uniaxial stretching) is preferably 4 times or more, and most preferably 5 times or more from the viewpoint of polarization performance. The upper limit of the stretching ratio is not particularly limited, but it is preferably 8 times or less because uniform stretching is easily obtained. The thickness of the stretched film is preferably 3 μm to 75 μm, more preferably 5 μm to 50 μm.

  Fixing treatment is often performed for the purpose of strengthening the adsorption of the dye to the stretched film. Usually, boric acid and / or boron compounds are added to the treatment bath used for the fixing treatment. Moreover, you may add an iodine compound in a processing bath as needed.

  The drying treatment (heat treatment) of the stretched film is preferably performed at 30 ° C. to 150 ° C., more preferably 50 ° C. to 150 ° C.

  The polarizing film obtained as described above is usually used as a polarizing plate by attaching a protective film optically transparent and having mechanical strength on both sides or one side. As the protective film, a cellulose triacetate (TAC) film, an acetic acid / cellulose 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 a PVA-based adhesive is preferable.

  Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

Example 1
An aqueous solution containing 8 parts by weight of glycerin and having a PVA concentration of 15% by weight with respect to 100 parts by weight of PVA having a saponification degree of 99.9 mol% and a polymerization degree of 2400 was cast using a metal roll.

  The obtained PVA film is made of martensitic stainless steel and has a chevron-like thickness with both sides of the blade edge polished with a single blade (a groove formed on the back of the blade) with a blade edge angle of 5 °. A 0.2 mm cutter, the roll interval is 50 cm, the interval between the cutting part and the roll is 3 cm, and the angle between the film and the blade edge is 45 °, and both ends in the width direction of the PVA film are cut. A PVA film for stretch processing having a width of 6 m and a thickness of 75 μm was obtained. The temperature of the PVA film at that time was 45 ° C., and the volatile content was 3%.

  The PVA film was processed in the order of pre-swelling, dyeing, uniaxial stretching, fixing treatment, drying and heat treatment to prepare a polarizing film. That is, the PVA film was preliminarily swollen in water at 30 ° C. for 5 minutes, and immersed in an aqueous solution at 35 ° C. having an iodine concentration of 0.4 g / liter and a potassium iodide concentration of 40 g / liter for 3 minutes. Subsequently, it was uniaxially stretched 5.5 times in a 40 ° C. aqueous solution with a boric acid concentration of 4%, and a 30 ° C. with a potassium iodide concentration of 40 g / liter, a boric acid concentration of 40 g / liter, and a zinc chloride concentration of 10 g / liter. Fixing was performed by immersing in an aqueous solution for 5 minutes. Thereafter, the stretched film was taken out, dried with hot air at 40 ° C. under a constant length, and further subjected to heat treatment at 100 ° C. for 5 minutes.

  In the stretching process, the film was not cut, and stable stretching was possible. The thickness of the obtained polarizing film was 22 μm, and it was a good product without color spots.

Example 2
For 100 parts by weight of PVA having a saponification degree of 99.9 mol% and a polymerization degree of 3600, 12 parts by weight of glycerin and 120 parts by weight of water are melt-kneaded in an extruder and discharged to a metal roll to perform melt extrusion film formation. It was.

  The obtained PVA film is made of martensite stainless steel at the position of the small diameter portion of the roll having a diameter of 20 cm where the width of the large diameter portion and the width of the small diameter portion are both 2 mm. The width direction of the PVA film is adjusted by combining the peripheral speed of the large-diameter portion of the roll having a plurality of large-diameter portions and the speed of the PVA film, using a chevron-shaped blade with a thickness of 0.15 mm whose both side surfaces are polished. Both ends were cut to obtain a PVA film for stretching having a width of 2.5 m and a thickness of 75 μm. The temperature of the PVA film at that time was 50 ° C., and the volatile content was 4%.

  The PVA film was processed in the order of pre-swelling, dyeing, uniaxial stretching, fixing treatment, drying, and heat treatment to prepare a polarizing film. That is, the PVA film was preliminarily swollen in water at 30 ° C. for 5 minutes, and immersed in an aqueous solution at 35 ° C. having an iodine concentration of 0.4 g / liter and a potassium iodide concentration of 40 g / liter for 3 minutes. Subsequently, it was uniaxially stretched 5.5 times in a 40 ° C. aqueous solution with a boric acid concentration of 4%, and a 30 ° C. with a potassium iodide concentration of 40 g / liter, a boric acid concentration of 40 g / liter, and a zinc chloride concentration of 10 g / liter. Fixing was performed by immersing in an aqueous solution for 5 minutes. Thereafter, the stretched film was taken out, dried with hot air at 40 ° C. under a constant length, and further subjected to heat treatment at 100 ° C. for 5 minutes.

  In the stretching process, the film was not cut and stable stretching was possible. The thickness of the obtained polarizing film was 22 μm, and it was a good product without color spots.

Example 3
In Example 2, both ends in the width direction of the film were cut in the same manner as in Example 2 except that the thickness of the blade was changed to 1.5 mm. During stretching, the film was broken twice per 2000 m, but a good polarizing film was obtained.

Example 4
In Example 2, both ends in the width direction of the film were cut in the same manner as in Example 2 except that the width of the PVA film was changed to 1.5 m. Although there was no trouble during stretching, spots were observed when the obtained polarizing film was observed between two polarizing plates in a crossed Nicol state.

Example 5
In Example 1, both ends in the width direction of the film were cut in the same manner as in Example 1 except that the roll interval was 1 m and the interval between the cutting part and the roll was changed to a position of 30 cm. During stretching, the film was broken three times per 2000 m, but a good polarizing film was obtained.

Example 6
In Example 2, both ends in the width direction of the film were cut in the same manner as in Example 2 except that the roll was changed to a roll having a large diameter part with a diameter of 2 cm. During stretching, the film was broken three times per 2000 m, but a good polarizing film was obtained.

Comparative Example 1
In Example 1, both ends in the width direction of the film were cut in the same manner as in Example 1 except that the temperature of the PVA film was changed to 6 ° C. The work could not be continued due to the breakage of the film at the time of cutting.

Comparative Example 2
In Example 2, both ends in the width direction of the film were cut in the same manner as in Example 2 except that the temperature of the PVA film was changed to 80 ° C. When the film was stretched, the film was continuously broken, and a good polarizing film could not be obtained.

Comparative Example 3
In Example 1, both ends in the width direction of the film were cut in the same manner as in Example 1 except that the volatile content of the PVA film was changed to 0.01%. The work could not be continued due to the breakage of the film at the time of cutting.

Comparative Example 4
In Example 2, both ends in the width direction of the film were cut in the same manner as in Example 2 except that the volatile content of the PVA film was changed to 20%. When the film was stretched, the film was continuously broken, and a good polarizing film could not be obtained.

Claims (6)

  A method of cutting with a knife so as to remove both ends in the width direction of the vinyl alcohol polymer film in advance before stretching, and the temperature of the vinyl alcohol polymer film used for the cutting is 10 A method for cutting a vinyl alcohol polymer film for stretching, having a volatile content of 0.1% to 10% at a temperature of 70 ° C to 70 ° C.   The blade has a chevron shape in which both sides are polished as seen from the cross section of the blade, the thickness is 0.05 mm to 1 mm, and the film width after removing both end portions in the width direction is 2 m or more. Item 2. A method for cutting a vinyl alcohol polymer film for stretching according to Item 1.   The film is in contact with two parallel rolls, the distance between the contact points is 80 cm or less, and when the film is cut with a blade between them, the position where the blade cuts the film and the nearest roll are the film. The method for cutting a vinyl alcohol polymer film for stretching according to claim 2, wherein the distance from the position in contact with the film is 0.5 to 15 cm.   The peripheral speed at the large-diameter portion of the metal roll having alternately a plurality of large-diameter portions and small-diameter portions is substantially the same as the film speed, and the large-diameter portion and the film are in contact with each other. The method for cutting a vinyl alcohol polymer film for drawing according to claim 2, wherein the metal roll has a diameter of 5 to 30 cm, and the film is cut with a blade at the position of the small diameter portion.   The method for cutting a vinyl alcohol polymer film for stretching according to any one of claims 1 to 4, wherein the vinyl alcohol polymer film for stretching is for a polarizing film.   A polarizing film produced from a vinyl alcohol polymer film for stretching obtained by the cutting method according to claim 5.