TW201708267A - Polyvinyl alcohol film - Google Patents

Abstract

The present invention relates to: an elongated polyvinyl alcohol film 1 having a thickness of no more than 55 [mu]m and a length of at least 500 m, wherein at least one of the two end sections in the lengthwise direction of the film is a cut end section A, A' formed by a cutting blade, and the maximum height roughness (Rz) of cut end surfaces B, B' of the cut end sections is no more than 2.5 [mu]m over a segment of the film having a length of at least 500 m; and a roll formed by winding the polyvinyl alcohol film into a roll shape.

Description

Polyvinyl alcohol film

The present invention relates to a thin polyvinyl alcohol film having a specific cut end face (hereinafter, "polyvinyl alcohol" is abbreviated as "PVA"), a roll obtained by winding it into a roll shape, and a method for A method for producing a PVA film of such a PVA film is obtained.

Polarizing plates with light penetration and shielding functions and liquid crystals with optical switching functions are the basic components of liquid crystal displays (LCDs). The application fields of LCDs are also from small machines such as calculators and watches at the beginning of development. In recent years, it has expanded to a wide range of fields such as laptop computers, word processors, liquid crystal color projectors, car navigation systems, LCD TVs, mobile phones, and indoor and outdoor measuring instruments. Quality and low price polarizer.

The polarizing plate is generally produced by uniaxially stretching a PVA film after dyeing, or uniaxially stretching while dyeing, or dyeing after uniaxial stretching to produce a dyed uniaxially stretched film. a method of fixing the same; or, after the uniaxial stretching and dyeing treatment, a polarizing film is produced by a method of fixing with a boron compound at the same time as dyeing, and a triacetate fiber is attached to the surface of the polarizing film. It is produced by a protective film such as a TAC film or a cellulose acetate butyrate (CAB) film.

In the production of a polarizing plate, in order to reduce the production cost and the like, a raw material film in which a long PVA film is wound into a roll is used, and uniaxial stretching, dyeing, fixing, and bonding of a protective film are continuously performed. method.

In the PVA film, the thickness of the both ends of the film in the width direction or the degree of drying tends to be different from the center portion after the film is formed, and it is difficult to perform uniaxial stretching while retaining both end portions in the width direction. Since the film is stably stretched, it is generally wound at both ends in the width direction of the film, and then wound into a roll to be supplied to a polarizing plate manufacturer or the like.

Further, in order to provide a film width film which meets the requirements of a polarizing plate manufacturer and the like, it is also possible to carry out the filming of the PVA film while cutting the edge without edge cutting, but in the width direction of the film. The central portion or other position is cut along the length direction to make the film a desired width, and then rolled into a roll to be transported to a desired object.

When a polarizing film is produced from a PVA film, in order to obtain high polarizing performance, the PVA film is generally uniaxially stretched in the longitudinal direction at a high stretching ratio, but if the cut end face of the film is roughened, the uniaxial stretching is thick. The chemical portion becomes a starting point of cracking and cracks occur at the ends, and even the problem that the film breaks from the crack portion occurs. In the case where the film is broken, the uniaxial stretching treatment must be temporarily stopped, and the rupture portion is removed, and then the stretching treatment is performed, so that the productivity is drastically lowered and the yield of the polarizing film is lowered. From this point of view, a PVA film which does not cause cracking or cracking during stretching and has a smooth cut end face along the longitudinal direction of the film is required.

So far, several methods for cutting PVA films have been known (see Patent Documents 1 to 3, etc.). Patent Document 1 describes a method in which the temperature and the volatile component of the cut PVA film are each set within a specific range, and a method of cutting a film between two rolls or a method of cutting on a corrugating roll has been described as a cut. Break method. Patent Document 2 describes an optical PVA film having a specific surface average roughness (Ra), and a method of using a shearing blade composed of an upper blade and a lower blade or a method using a razor blade as a cutting method has been described. Patent Document 3 describes an elongated PVA film having a maximum height (Ry) of the cut end face in a specific range over the entire length of the film, and has been described as forming one cut end portion and using one rotating circle. The method of the blade is used as a cutting method, and it has been described that the blade angle of the corrugating roller and the circular blade is preferably 3 to 20°.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2002-144418

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2003-12827

[Patent Document 3] Japanese Patent Laid-Open Publication No. 2005-306981

In recent years, a thin film having a thickness of about 75 μm has been conventionally used for a raw material film for producing a polarizing film. However, in recent years, a PVA film having a thickness of 70 μm or less has been required. However, a thin PVA film has a problem that it is more likely to be broken than a film of a conventional thickness when processed by uniaxial stretching or the like.

SUMMARY OF THE INVENTION An object of the present invention is to provide a thin PVA film which is not easily broken during processing such as uniaxial stretching and a roll which is wound into a roll shape, and an object of the present invention is to provide a smooth manufacturing method. A method for producing a PVA film of a PVA film.

In order to achieve the above object, the inventors of the present invention have found that in the elongated PVA film having a thickness of 55 μm or less, the cut end face of the cut end portion is maximized in a specific section in the longitudinal direction of the film. The height roughness (Rz) is in a specific range, and although it is a thin PVA film, it is not easily broken during processing such as uniaxial stretching. Moreover, the present inventors have found that when the PVA film before cutting is brought into contact with the corrugating roller and the PVA film is cut in the longitudinal direction by using a rotating circular blade, a specific blade angle is used and When the hardness of the tip portion is within a specific range as the circular blade, the above-mentioned thin PVA film which is not easily broken can be smoothly manufactured. The present inventors further studied the present invention based on these findings, and completed the present invention.

That is, the present invention relates to: [1] a PVA film having a thickness of 55 μm or less and a length of 500 m or more, wherein at least one of the two end portions along the longitudinal direction of the film is By cutting the cut end portion formed by the blade, the maximum height roughness (Rz) of the cut end surface of the cut end portion is 2.5 μm or less in the interval of the film length of 500 m or more; [2] as described above [ 1) The PVA film, wherein the arithmetic mean roughness (Ra) of the cut end face is 0.4 μm or less in the above-mentioned section; [3] The PVA film according to [1] or [2] above, wherein the length of the film is The PVA film according to any one of the above [1] to [3], which is a raw material film for producing an optical film; [5] as described in any one of the above [1] to [4] a PVA film in which the optical film is a polarizing film; [6] a roll obtained by winding a PVA film according to any one of the above [1] to [5] into a roll; [7] a polyvinyl alcohol film The manufacturing method is a method for producing an elongated PVA film having a thickness of 55 μm or less and a length of 500 m or more, wherein at least one of the two end portions along the longitudinal direction of the film is formed by cutting the blade The cutting method has a step of using an elongated PVA film and the corrugating roller on one side of a corrugating roller having a large diameter portion in contact with the film and a small diameter portion not in contact with the film in the roll axis direction. The large-diameter portion is transported in contact with the surface, and the PVA film is cut along the longitudinal direction at a position of the small-diameter portion of the corrugating roller, wherein the blade angle of the circular blade is 25~ 50°, the Vickers hardness of the tip portion is 1,500 HV or more; [8] The manufacturing method of the above [7], which is to make the PVA film along the corrugating roller [9] The manufacturing method of the above [7] or [8], which is used for manufacturing the PVA film according to any one of the above [1] to [5]. method.

According to the present invention, it is possible to provide a thin PVA film which is less likely to be broken during processing such as uniaxial stretching, and a roll which is wound into a roll. Moreover, according to the present invention, it is possible to provide a A method for producing a PVA film of such a PVA film is advantageously produced.

1‧‧‧PVA film

2‧‧‧ Round blade

3‧‧‧The tip of the round blade

4, 4'‧‧‧ Grinded noodles

5‧‧‧Vertical

6‧‧‧ Grinded surface

7‧‧‧Circular blade mounting member

8‧‧‧Rotary axis

9‧‧‧ bearing

10‧‧‧cord roller

10a‧‧‧ Large diameter section of the corrugating roller

10b‧‧‧ Small diameter section of the corrugating roller

Fig. 1 is a schematic view showing a part of a PVA film of the present invention.

[Fig. 2] A schematic view showing an example of a cross section in the thickness direction of the circular blade.

[Fig. 3] A schematic view showing an example of a corrugating roller and a cutting method of a PVA film using a corrugating roller.

[Formation of the Invention]

The invention is described in detail below.

The PVA film of the present invention is an elongated film, and at least one of the two end portions along the longitudinal direction of the film is a cut end portion formed by cutting the blade. The PVA film may have only one end portion along the longitudinal direction of the film as a cut end portion, or both end portions along the longitudinal direction of the film may be cut ends, preferably along the edge. The end portions on both sides in the longitudinal direction of the film are cut ends. The cutting blade that forms the cut end portion is not particularly limited, and examples thereof include a shearing blade, a razor blade, a circular blade, and the like, and a circular blade to be described later is preferable.

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

Here, the cut end face is as shown in Fig. 1, which means along the PVA. The cut end portions A and A' in the longitudinal direction of the film 1 (the first drawing shows the end portions on both sides in the longitudinal direction of the PVA film 1 as the cut end portions) correspond to the thickness portion of the PVA film 1 Face (cut face) B, B'.

The maximum height roughness (Rz) is obtained by measuring the surface roughness of the cut end surface in a range of a predetermined length (L) along the longitudinal direction of the cut end surface, for example, using an ultra-depth shape measuring microscope. The value obtained by the sum of the maximum peak height (Rp) of the upper portion of the roughness curve (the average line in the longitudinal direction of the film) and the maximum valley depth (Rv) of the lower portion (Rz = Rp + Rv) The details are described in JIS B 0601:2001. The roughness curve can be obtained from the surface state of the line in the longitudinal direction of the film in the central portion in the thickness direction on the cut end surface to be measured. Usually, when the PVA film is cut, the cut surface gradually becomes rough as time passes from the start of the cutting, so the above-described maximum height roughness (Rz) of the cut end face and the arithmetic mean roughness (Ra) described later are usually obtained. The value will increase as time passes from the beginning of the cut. Therefore, the maximum height roughness (Rz) or the arithmetic mean roughness (Ra) of the cut end face is measured from a portion (measurement point) at which a predetermined length (for example, 500 m) is cut in the longitudinal direction of the film from the cutting start point. When the measured values are equal to or less than a specific value, the maximum height roughness (Rz) or arithmetic mean roughness (Ra) of the cut end face can be at least in all regions from the cutting start point to the measurement point. The measured value is equal to or lower.

From the viewpoint of preventing cracking during processing such as uniaxial stretching, the maximum height roughness (Rz) of the cut end surface of the PVA film of the present invention must be 2.5 μm or less in the interval of the film length of 500 m or more. It is preferably 2 μm or less, more preferably 1.5 μm or less, still more preferably 1 μm or less, and particularly preferably 0.9 μm or less. The lower limit of the maximum height roughness (Rz) is not particularly limited, but from the viewpoint of easiness of production of the PVA film of the present invention, etc., the maximum height roughness (Rz) of the cut end face is not included in the length of the film. In the interval of 500 m, the PVA film in the range of 0.01 μm or less is preferable, and the PVA film having a maximum height roughness (Rz) of the cut end face of 0.1 μm or less in the section of the film length of 500 m is more. Preferably, the PVA film having a maximum height roughness (Rz) of the cut end face of 0.3 μm or less in the section of the film length of 500 m is more preferable.

When the arithmetic mean roughness (Ra) of the cut end surface of the PVA film of the present invention is 0.4 μm or less in the above-described section of the maximum height roughness (Rz), it is possible to more effectively prevent the processing such as uniaxial stretching. Broken, and better. From such a viewpoint, the arithmetic mean roughness (Ra) of the cut end surface of the PVA film of the present invention is preferably 0.3 μm or less, more preferably 0.2 μm or less, and particularly preferably 0.14 μm or less in the above-described section. . The lower limit of the arithmetic mean roughness (Ra) is not particularly limited. However, from the viewpoint of easiness of production of the PVA film of the present invention, etc., the arithmetic mean roughness (Ra) without the cut end face is within the above range. It is preferable that the PVA film of the range of 0.001 μm or less is preferable, and the PVA film having the arithmetic mean roughness (Ra) of the cut end face of 0.01 μm or less in the above-described section is more preferable, and the end face is not cut. The PVA film having an arithmetic mean roughness (Ra) of 0.03 μm or less in the above-described section is more preferable.

Here, for the measurement of the maximum height roughness (Rz) The obtained roughness curve (reference length: L) and the arithmetic mean roughness (Ra) described above can be obtained in accordance with JIS B 0601:2001.

From the viewpoint of more effectively preventing cracking during processing such as uniaxial stretching, etc., the PVA film of the present invention has a maximum height roughness (Rz) and an arithmetic mean roughness in the above-described interval relating to the maximum height roughness (Rz). The ratio (Rz/Ra) of the degree (Ra) is preferably 5 or more, more preferably 6 or more, and is preferably 25 or less, more preferably 11 or less. The ratio (Rz/Ra) can be used as an index of the degree of wear of the blade for cutting the PVA film. When the wear of the blade is intense, the ratio (Rz/Ra) is often small, and the surface of the end face is roughened. The degree is easy to become bigger.

The PVA film of the present invention has a thickness of 55 μm or less, preferably 50 μm or less, more preferably 45 μm or less, still more preferably 40 μm or less, and particularly preferably 30 μm or less, for the reason of requiring a thinner PVA film or the like. . The lower limit of the thickness of the PVA film is not particularly limited, but the thickness is preferably 3 μm or more, and more preferably 5 μm or more, from the viewpoints of practicality, easiness of film production, easiness of stretching treatment, and the like. More preferably, it is 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 requirements of the PVA film, and the like, but is generally preferably 2 m or more, more preferably 2.5 m or more, and still more preferably 3 m or more. And it is preferably 8m or less.

The PVA film of the present invention has a length of 500 m or more, and the PVA film preferably has a length of 1,000 m or more, more preferably 5,000 m or more, and still more preferably 8,000, from the viewpoint of being able to be used continuously for a long period of time. Above m, the upper limit of the length is not particularly limited, the length It can be, for example, 30,000 m or less. The PVA film of the present invention is preferably in the form of a roll formed into a roll shape from the viewpoints of ease of handling, storage, and use.

The PVA constituting the PVA film of the present invention may, for example, be an unmodified PVA obtained by saponifying a polyvinyl ester obtained by polymerizing a vinyl ester, and graft-copolymerizing a comonomer to a main chain of PVA. A modified PVA obtained by saponifying a modified polyvinyl ester obtained by copolymerizing a vinyl ester with a comonomer, and a part of a hydroxyl group of an unmodified PVA or a modified PVA as formaldehyde, A so-called polyvinyl acetal resin obtained by crosslinking an aldehyde such as butanal or benzaldehyde.

In the case where the PVA forming the PVA film of the present invention is a modified PVA, the modified mass of 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, trimethyl vinyl acetate, and vinyl laurate. , vinyl stearate, vinyl benzoate, vinyl visacic acid, and the like. These vinyl esters can be used singly or in combination, and among these vinyl esters, vinyl acetate is preferable from the viewpoint of productivity.

In addition, examples of the comonomer include olefins (α-olefins) having 2 to 30 carbon atoms such as ethylene, propylene, 1-butene, and isobutylene; acrylic acid or a salt thereof; methyl acrylate and acrylic acid. Ethyl ester, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, octadecyl acrylate, etc. Class (for example: carbon number of acrylic acid 1~ 18 alkyl ester); methacrylic acid or a salt thereof; methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate Ethyl esters such as esters, butyl methacrylate, 2-ethylhexyl methacrylate, dodecyl methacrylate, octadecyl methacrylate (eg, carbon number of methacrylic acid 1) ~18 alkyl ester); acrylamide; N-methyl acrylamide, N-ethyl acrylamide, N, N-dimethyl acrylamide, diacetone acrylamide, acrylamide propylene sulfonate or a acrylamide derivative such as a salt, acrylamidopropyldimethylamine or a salt thereof, N-methylol acrylamide or a derivative thereof; methacrylamide; N-methyl methacrylamide , N-ethyl methacrylamide, methacrylamide sulfonic acid or a salt thereof, methacrylamide propyl dimethylamine or a salt thereof, N-methylol methacrylamide or the like a methacrylamide derivative such as a derivative; N-vinylguanamine such as N-vinylformamide, N-vinylacetamide or N-vinylpyrrolidone; methyl vinyl ether, ethyl B Ether, n-propyl vinyl ether, isopropyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, tert-butyl vinyl ether, dodecyl vinyl ether, octadecyl ethylene Vinyl ethers such as alkyl ethers; nitriles such as acrylonitrile and methacrylonitrile; halogenated vinyls such as vinyl chloride, vinylidene chloride, vinyl fluoride and vinylidene fluoride; allyl acetates such as allyl acetate and chloropropene a compound; a derivative of an unsaturated dicarboxylic acid such as maleic acid or itaconic acid, a salt thereof or an ester thereof; a vinyl decyl compound such as vinyltrimethoxydecane; an isopropenyl acetate; an unsaturated sulfonic acid or Its derivatives and so on. These copolymerization systems may be used singly or in combination of two or more. Among these comonomers, an α-olefin is preferred, and ethylene is particularly preferred.

Polarizing the PVA film of the present invention to produce polarized light In the case of a film, the degree of polymerization of PVA is preferably 1,000 or more, more preferably 2,000 or more, and may be 2,500 or more from the viewpoint of obtaining a polarizing film excellent in polarizing performance and durability. Moreover, the degree of polymerization of PVA is preferably 8,000 or less, and more preferably 6,000 or less, from the viewpoints of ease of production, stretchability, and the like for producing a homogeneous PVA film. The degree of polymerization of PVA in the present specification means the average degree of polymerization measured according to the description of JIS K6726-1994, and can be obtained from the ultimate viscosity measured by re-saponification and purification of PVA in water at 30 °C.

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

The PVA film of the present invention preferably contains a plasticizer from the viewpoint of improving workability, dyeability, stretchability and the like. As the plasticizer, a polyol-based plasticizer is preferred from the viewpoint of affinity with PVA. Examples of the polyol-based plasticizer include ethylene glycol, glycerin, propylene glycol, diethylene glycol, diglycerin, triethylene glycol, tetraethylene glycol, trimethylolpropane, etc., and can be used. One or two or more of the above. Among these, one or two of glycerin, diglycerin, and ethylene glycol are preferably used from the viewpoint of the effect of improving stretchability, workability, and the like. More than one species.

The content of the plasticizer is preferably 1 part by mass or more, more preferably 5 parts by mass or more, more preferably 30 parts by mass or less, still more preferably 20 parts by mass or less, per 100 parts by mass of the PVA. When the content of the plasticizer is at least the above lower limit, the dyeability and stretchability are improved. On the other hand, when the content of the plasticizer is not more than the above upper limit, the PVA film can be prevented from becoming too soft, and the workability and the uniformity of cutting can be improved.

The PVA film of the present invention preferably contains a surfactant from the viewpoints of workability of the PVA film and improvement in peelability of the film forming apparatus when the PVA film is produced. 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 alkylphenyl ether type, an alkyl ester type, a alkylguanamine type, a polypropylene glycol ether type, an alkanolamine type, and an allyl group. Phenyl ether type and the like. The PVA film of the present invention can contain one or two or more kinds of these surfactants.

The content of the surfactant is preferably 0.01 parts by mass or more, more preferably 0.05 parts by mass or more, still more preferably 1 part by mass or less, still more preferably 0.3 parts by mass or less, per 100 parts by mass of the PVA. When the content of the surfactant is less than or equal to the above upper limit, it is possible to prevent "the surfactant is eluted to the surface of the PVA film to cause agglomeration and the workability is lowered".

The PVA film of the present invention may further optionally contain a dichroic dye, an antioxidant, an ultraviolet absorber, a lubricant, a colorant, a preservative, an antifungal agent, and other polymer compounds other than the above components. The PVA film of the present invention can contain one or two or more of these other components. The PVA content in the PVA film of the present invention is preferably 70% by mass or more, more preferably 80% by mass or more, still more preferably 90% by mass or more.

The method for producing the PVA film of the present invention is not particularly limited. However, according to the production method of the present invention below, the PVA film of the present invention can be smoothly produced, which is preferable. That is, the manufacturing method of the present invention is a method for producing an elongated PVA film having a thickness of 55 μm or less and a length of 500 m or more, wherein at least one of the two end portions along the longitudinal direction of the film is by cutting the blade. In the formed cutting end portion, the manufacturing method has a step of using an elongated PVA film and a corrugating roller having a large diameter portion in contact with the film in the roll axis direction and a small diameter portion not in contact with the film. The surface of the large diameter portion of the corrugating roller is transported in contact with each other, and the PVA film is cut along the longitudinal direction at a position of the small diameter portion of the corrugating roller at a position of a small diameter portion of the corrugating roller. For 25 to 50°, the Vickers hardness of the tip portion is 1,500 HV or more. In general, a thin PVA film tends to have a cut end face thicker when it is cut, compared to a thick PVA film. However, according to the manufacturing method of the present invention, although it is a thin PVA film, it is capable of A PVA film conforming to the specifications of the present invention was successfully produced.

The corrugating roller used in the production method of the present invention has a large-diameter portion in which the film is in contact with the small-diameter portion which is not in contact with the film in the roll axis direction. For the corrugating roller, for example, a groove made of metal can be preferably used. In the embossing roller, if the chrome plating is used in particular, the surface hardness of the fluted roller is increased, and scratching or the like can be prevented, which is preferable. In the case of a corrugating roller, It has at least three large diameter portions (protrusions) in the direction of the roll axis and has small diameter portions (grooves and recesses) between the large diameter portion and the large diameter portion (that is, those having at least two small diameter portions) .

The diameter of the large diameter portion of the corrugating roller is preferably from the point of satisfactory conveyance of the PVA film, good cutting of the PVA film of the corrugating roller, manufacturing cost of the corrugating roller, and the like. It is 5 cm or more, more preferably 7.5 cm or more, still more preferably 10 cm or more, further preferably 30 cm or less, more preferably 25 cm or less, still more preferably 20 cm or less. When the diameter of the large diameter portion of the corrugating roller is equal to or higher than the above lower limit, the PVA film can be cut more uniformly. On the other hand, the diameter of the large diameter portion of the corrugating roller is equal to or less than the above upper limit, so that the production cost of the corrugating roller can be reduced. When a plurality of large-diameter portions are present on the corrugating roller, the PVA film is transported while being in a flat state while being in contact with the surface of the plurality of large-diameter portions. These large-diameter portions are preferably the same diameter. .

The width of the large diameter portion of the corrugating roller (the length in the roll axis direction; the plurality of large diameters) from the viewpoint of the transportability of the PVA film and the size of the slit width (width after cutting) of the film can be freely changed. The width of each large diameter portion in the case where the portion is present is preferably 1 mm or more, and particularly preferably 3 to 10 mm. In the case where a plurality of large diameter portions are present in the corrugating rolls, the width of the large diameter portions may be the same for all the large diameter portions, or may be partially or entirely different from each other.

The diameter of the small diameter portion of the corrugating roller is determined from the viewpoints of preventing breakage of the circular blade, smoothness of cutting of the PVA film at the position of the small diameter portion, and ease of processing of the groove on the corrugating roller. It is preferably smaller than the diameter of the adjacent large diameter portion by 0.5 cm or more, more preferably smaller than 1 cm, and smaller It is preferably 2 cm or less, and more preferably 1.5 cm or less.

The width of the small diameter portion of the corrugating roller (the length in the roll axis direction; the width of each small diameter portion when the plurality of small diameter portions exist) is the same as or smaller than the width of the adjacent large diameter portion. The width of the large diameter portion is preferably good. In addition, the width of the small-diameter portion can be improved from the point where the cutting edge of the PVA film is satisfactorily in a stable state and the point at which the cutting point of the film is prevented from being shifted from the blade tip of the circular blade. The thickness of the non-tapered base portion of the blade portion of the circular blade (the size of d in FIG. 2) is preferably 2 times or more, more preferably 5 times or more, still more preferably 50 times or less, and still more Good is 30 times or less.

The circular blade used in the manufacturing method of the present invention is a cutter having a blade for cutting a film over the entire circumference of the disk-shaped body around the rotating shaft. The circular blade is preferably made of metal or ceramic, and specific examples thereof include iron, iron alloy, high speed tool steel, alloy tool steel, stainless steel, martensitic stainless steel, and tungsten steel. Further, the blade portion of the circular blade may be composed of the aforementioned material and the surface thereof may be treated with titanium nitride, titanium carbide, tungsten carbide or the like. From the viewpoint of being hard to wear, excellent in durability, and good smoothness of the cut end face, a circular blade made of tungsten steel is particularly preferable.

From the viewpoint of being able to smoothly produce the PVA film of the present invention, at least the tip end portion of the circular blade must have a Vickers hardness of 1,500 HV or more, preferably 1,800 HV or more. The upper limit of the Vickers hardness is not particularly limited, and for example, the Vickers hardness can be 2,400 HV or less. Further, in the present specification, the unit of the Vickers hardness is kgf/mm ² .

The diameter of the circular blade [illustrated in (a) and (b) of Fig. 2 The length of Ea in the cross-sectional view in the thickness direction of the circular blade 2 is preferably 15 mm or more, more preferably 20 mm or more, still more preferably 40 mm or more. When the diameter of the circular blade is within the above range, the progress of abrasion can be suppressed, and a smooth cut end face can be easily formed over the entire length of the elongated PVA film. The upper limit of the diameter of the circular blade is not particularly limited, but if the diameter of the circular blade becomes too large, the quality of the circular blade itself becomes large, it is difficult to freely rotate when the PVA film is cut, and it is required to prevent breakage. The thickness of the base of the tip is increased, and therefore the diameter of the circular blade is preferably 200 mm or less, more preferably 120 mm or less.

The shape of the blade tip of the circular blade can be exemplified in (a) of Fig. 2, and is a mountain shape in which the sides of the polished surface 4, 4' are gathered in a tapered shape at the center. Or, as exemplified in FIG. 2(b), it is a single-blade shape in which the other polished tapered surface 6 is gathered toward the tip end 3 of the tip end of the vertical surface 5. In particular, the blade tip of the circular blade preferably has a mountain shape as shown in FIG. 2( a ) from the viewpoint of stably cutting the PVA film and forming a cut end surface having a more excellent smoothness.

In the manufacturing method of the present invention, the blade edge angle of the circular blade [the angle α shown in (a) and (b) of Fig. 2] must be in the range of 25 to 50°. If the blade tip angle of the circular blade is less than 25°, the reason is not too clear. However, when the thin PVA film having a thickness of 55 μm or less is cut, the blade tip is easily worn, and it is difficult to continuously obtain a long PVA film roll. The cut end face is required. It is possible to maintain a good sharpness for a long time while suppressing the wear of the blade tip, whereby even if the length of the PVA film is long, in order to be able to form a surface roughening degree throughout the entire length of the film, The smooth cut end face, the blade tip angle of the circular blade is preferably 30 or more, more preferably 35 or more. On the other hand, if the blade tip angle of the circular blade exceeds 50°, the sharpness becomes dull, and it is difficult to form a cut end face which is low in surface roughening and smooth. From this point of view, the blade tip angle of the circular blade is preferably 45 or less, more preferably 43 or less.

The thickness of the base of the blade in the circular blade [the thickness before the tip of the blade is gradually reduced; the dimension of d shown in (a) and (b) of Fig. 2] is preferably 0.05 mm or more, more preferably It is 0.1 mm or more, and preferably 1 mm or less, more preferably 0.5 mm or less. When the thickness of the base of the blade tip is equal to or higher than the above lower limit, damage of the circular blade itself can be suppressed. On the other hand, by the thickness of the base of the blade tip being equal to or less than the above upper limit, it is possible to form a cut end face having a small degree of surface roughening and smoothness over the entire length of the film.

The length of the blade in the circular blade [the distance from the base of the blade tip to the tip end of the blade: the size of e shown in (a) and (b) of Fig. 2] is relative to the thickness of the cut PVA film. It is preferably 1 time or more, more preferably 5 times or more, further preferably 50 times or less, more preferably 45 times or less. When the length of the blade is equal to or higher than the above lower limit, it is possible to suppress damage of the cut end surface of the PVA film at the base of the blade tip. On the other hand, if the blade length is equal to or lower than the above upper limit, abrasion or breakage of the blade portion can be suppressed.

When the long PVA film is brought into contact with the surface of the large-diameter portion of the above-described corrugating roller, the PVA film is cut along the longitudinal direction by using a rotating circular blade at the position of the small-diameter portion of the corrugating roller. When the time is off, the peripheral speed of the large diameter portion of the corrugating roller is made the same as the conveying speed of the PVA film, and the PVA film is conveyed on the corrugating roller in a state of being not slack and tensioned, which forms the degree of surface roughening. Low and smooth cut The end face is important. Therefore, when the PVA film is cut along the longitudinal direction, the PVA film is placed at an angle of 10 to 100 degrees along the circumference of the corrugating roller (holding angle) [Fig. 3 (b) The contact angle β] shown is brought into contact so that the PVA film is in a state of being along the corrugating roller (holding state), and the PVA is rotated by a circular blade disposed at a position of the small diameter portion of the corrugating roller. Film cutting is preferred. At this time, the circular blade is preferably disposed at the center or substantially the center of the aforementioned holding angle. Thereby, the peripheral speed of the large-diameter portion of the corrugating roller is substantially the same as the transport speed of the PVA film at the time of cutting, and the PVA film is transported by the corrugating roller while being stretched. The circular blade that rotates at the position of the small diameter portion of the corrugating roller is cut, so that a smooth cut end surface having a low degree of surface roughening can be formed. From the viewpoint of the above, the holding angle is more preferably 30 or more, still more preferably 45 or more, still more preferably 98 or less, still more preferably 95 or less.

When the PVA film is cut along the longitudinal direction by using a rotating circular blade, the PVA film can be cut while actively driving the rotating circular blade, but the rotation speed of the circular blade and the conveying speed of the PVA film can be reduced. The difference is that the surface of the cut end surface is roughened to a smaller extent, and the centrifugal blade is preferably rotated while the PVA film is being conveyed, as compared with the case where the rotating circular blade is actively driven. Cut off. When the cutting is performed while the circular blade is freely rotated, it is possible to prevent a large difference between the rotational speed of the circular blade and the conveying speed of the PVA film, whereby the PVA film can be cut without being forced and smoothly. A smooth cut end face having a smaller surface roughening is formed. There is no special restriction on the way the circular blade can rotate freely. For example, a schematic diagram as shown in FIG. 2 (a cross-sectional view in the thickness direction of the circular blade 2) may be employed, and the like: the circular blade 2 is fixedly mounted on a disk-shaped circular blade. In the mounting member 7, the rotating shaft 8 is integrally or fixedly provided at the center (center position) of the disk-shaped circular blade mounting member 7, and a bearing 9 such as a ball bearing is disposed around the rotating shaft 8, so that the rotating shaft 8 is provided. The circular blade mounting member 7 and the circular blade 2 are integrally freely rotatable.

When the PVA film is cut along the longitudinal direction by using a rotating circular blade, the conveying speed of the PVA film is preferably 40 m/min or less, more preferably 30 m/min or less, still more preferably 25 m/min or less. When the conveying speed is equal to or lower than the above upper limit, the degree of roughening of the surface of the cut end surface can be made smaller. On the other hand, if the conveying speed becomes too slow, the cutting may become time-consuming and the productivity may be lowered. Therefore, the conveying speed is preferably 5 m/min or more.

When the PVA film is cut along the longitudinal direction by using a rotating circular blade, the volatile component ratio of the PVA film is preferably 0.1% by mass or more, more preferably 2% by mass or more, and still more preferably 10% by mass or less. Good is 6 mass% or less. When the volatile component ratio is at least the above lower limit, the PVA film does not become too hard and is easily cut. On the other hand, when the volatile component ratio is equal to or less than the above upper limit, it is possible to suppress the PVA film from becoming too soft and to reduce the surface roughening degree of the cut end surface. In addition, the "volatile component ratio of the PVA film" as used in the present specification means the content of the volatile component contained in the PVA film, and examples of such a volatile component include an organic solvent used in the production of a PVA film. Or a solvent such as water, or a moisture which enters the film by moisture absorption after the PVA film is produced. PVA The volatile component ratio of the film can be dried to a target value by using two or more kinds of heated metal rolls or a floating dryer alone or in combination; and a PVA film having a volatile component ratio lower than the above range is used as a humidifier. Wait for the process; wait for the method to adjust. The volatile component ratio of the PVA film can be determined by disposing the PVA film in a vacuum dryer having a temperature of 50 ° C and a pressure of 0.1 kPa or less, and performing a drying to a mass reduction rate when the mass is not reduced.

Further, when the PVA film is cut along the longitudinal direction by using a rotating circular blade, the film temperature is preferably 10 ° C or higher, more preferably 20 ° C or higher, further preferably 70 ° C or lower, more preferably 60 ° C or lower. . When the film temperature is at least the above lower limit, the PVA film does not become too hard and is easily cut. Further, water droplets due to condensation are adhered to the PVA film, and it is also possible to suppress occurrence of agglomeration when the PVA film after the cutting process is wound into a roll shape or when a PVA film is stretched and which is broken from the water droplet. On the other hand, when the film temperature is not more than the above upper limit, the PVA film can be prevented from being too soft, and the surface roughened portion of the cut end surface can be made smaller. In addition, the film temperature of the PVA film can be measured using a dot type digital radiation thermometer (for example, "thermometer 505A" manufactured by MINOLTA Co., Ltd.).

The cutting of the PVA film using the rotating circular blade in the longitudinal direction can be continued continuously following the manufacturing steps of the PVA film, or the PVA film can be removed from the roll after the PVA film is produced and rolled into a roll shape. The roll is going on.

The method for producing the PVA film subjected to the cutting is not particularly limited, and can be produced by a conventionally known method, for example, can include One or two or more of the above-mentioned PVA and the above-mentioned plasticizer, surfactant, and other components, which are further added to the PVA film, are dissolved in a liquid medium, or PVA and One or two or more kinds of a plasticizer, a surfactant, and other components which are further added, which are required to be further added, are produced by using a film-forming stock solution obtained by melting PVA. When the film forming stock solution contains at least one of a plasticizer, a surfactant, and other components, it is preferred to uniformly mix the components.

The liquid medium used for preparing the film forming stock solution may, for example, be water, dimethyl hydrazine, dimethylformamide, dimethylacetamide, N-methylpyrrolidone or ethylene glycol. In the case of glycerin, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, trimethylolpropane, ethylenediamine or diethylenetriamine, one or more of these may be used. Among them, water is preferred from the viewpoint of imparting load or recovery to the environment.

The film forming method for producing a PVA film using the film forming raw material may, for example, be a casting film forming method, an extrusion film forming method, a wet film forming method, or a gel film forming method. These film forming methods may be used alone or in combination of two or more. Among these film forming methods, from the viewpoint of being able to smoothly produce a PVA film to which a good polarizing film is applied, a cast film forming method or an extrusion film forming method is preferable. The film-formed film can be dried or heat treated as needed.

As an example of a specific manufacturing method of the PVA film subjected to the cutting, for example, the following method can be preferably used industrially: a T-slot die, a hopper plate, an I-shaped die, a lip a lip coater die or the like, which uniformly discharges or casts the film forming stock solution to a first roll (or a conveyor belt) that is rotated on the most upstream side. On the circumferential surface, the volatile component is evaporated and dried from the other side of the film discharged or cast onto the circumferential surface of the first roll (or the conveyor belt), and then one or more rotations disposed on the downstream side thereof The method of further drying the circumferential surface of the heated roll or further drying it by a hot air drying device and then using a take-up device. Drying using a heated roll and drying using a hot air drying device may be carried out by appropriately combining them.

The use of the PVA film of the present invention is not particularly limited. For example, it can be used for a film for pharmaceutical packaging, a base film for hydraulic transfer, a substrate film for embroidery, a release film for artificial marble molding, a film for seed packaging, and a dirt storage. For the use of various water-soluble films such as a film for a bag, at least one of the two end portions along the longitudinal direction of the film, preferably both of which are cut ends, the PVA film of the present invention, the cut end portion The "maximum height roughness (Rz)" of the cut end surface is equal to or less than a specific value, and the surface of the cut end surface is extremely rough and excellent in smoothness, so that the end portion is stretched in the longitudinal direction at the cut end portion (film The end portion in the width direction is less likely to be cracked, and as a result, cracking of the film is less likely to occur. From this point of view, the PVA film of the present invention is preferably used as a raw material film (a raw material film for producing an optical film) for producing an optical film. The optical film may, for example, be a polarizing film or a retardation film, and is preferably a polarizing film. Such an optical film can be produced, for example, by using a film of the present invention and applying 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 of the conventional methods can be employed. As such a method, for example, the PVA film of the present invention is used and dyeing and uniaxial stretching are applied, or the dye-containing book is used. A method of applying uniaxial stretching to the inventive PVA film. More specific methods for producing a polarizing film include swelling, dyeing, uniaxial stretching, and further application of crosslinking treatment, fixing treatment, drying, heat treatment, etc. to the PVA film of the present invention. The method. In this case, the order of each treatment such as swelling, dyeing, cross-linking treatment, uniaxial stretching, and fixation treatment is not particularly limited, and one or two or more treatments can be simultaneously performed. Further, one or two or more times of each treatment or two or more times can be performed.

The swelling can be carried out by immersing the PVA film in water, and the temperature of the water when immersed in water is preferably in the range of 20 to 40 ° C, more preferably in the range of 22 to 38 ° C, and further Good is in the range of 25~35 °C. Further, the time of immersion in water is, for example, preferably in the range of 0.1 to 5 minutes, more preferably in the range of 0.5 to 3 minutes. Further, the water when immersed in water is not limited to pure water, and may be an aqueous solution in which various components are dissolved, or a mixture of water and an aqueous medium.

The dyeing system can be carried out by bringing the dichroic dye into contact with the PVA film, and in the case of the dichroic dye, an iodine dye is generally used. The dyeing period may be any one of uniaxial stretching, uniaxial stretching, and uniaxial stretching. The dyeing is generally carried out by immersing the PVA film in a solution (especially an aqueous solution) containing iodine-potassium iodide as a dyeing bath, and such a dyeing method is also preferably 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. Further, the temperature of the dyeing bath is preferably from 20 to 50 ° C, particularly preferably from 25 to 40 ° C.

By applying a cross-linking treatment to the PVA film, it is possible to have more The effect is to prevent PVA from eluting into water during wet stretching at high temperatures. From this point of view, the crosslinking treatment is preferably carried out after the treatment of contacting the dichroic dye and before the uniaxial stretching. The crosslinking treatment can be carried out by immersing the PVA film in an aqueous solution containing a crosslinking agent. In the above-mentioned crosslinking agent, one type or two or more types of boron compounds such as a borate such as boric acid or borax can be used. The concentration of the crosslinking agent in the aqueous solution containing a crosslinking agent is preferably in the range of 1 to 15% by mass, more preferably in the range of 2 to 7% by mass, still more preferably in the range of 3 to 6% by mass. The concentration of the crosslinking agent is in the range of 1 to 15% by mass, and sufficient stretchability can be maintained. The aqueous solution containing a crosslinking agent may also contain an auxiliary agent such as potassium iodide, and the temperature of the aqueous solution containing the crosslinking agent is preferably set in the range of 20 to 50 ° C, and is preferably set in the range of 25 to 40 ° C. By setting the temperature within the range of 20 to 50 ° C, crosslinking can be performed efficiently.

The uniaxial stretching can be carried out by either a wet stretching method or a dry heat stretching method. In the case of the wet stretching method, it can be carried out in an aqueous solution containing boric acid or in a dye bath or in a fixed treatment bath to be described later. Further, in the case of the dry stretching method, the stretching may be carried out directly at room temperature, or may be carried out while heating, and may be carried out in the air using a water-absorbed PVA film. Among these, a wet stretching method is preferred, and uniaxial stretching is more preferably carried out in an aqueous solution containing boric acid. The concentration of boric acid in the aqueous boric acid 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, particularly preferably in the range of 1.5 to 4.0% by mass. Further, the aqueous boric acid solution may contain potassium iodide, and the concentration thereof is preferably in the range of 0.01 to 10% by mass.

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

Moreover, from the viewpoint of the polarizing performance of the obtained polarizing film, the stretching ratio of uniaxial stretching (the total stretching ratio multiplied by the stretching ratio in the case of uniaxial stretching in a plurality of stages) is preferably 4 times. More preferably, it is 5 times 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.

The direction of the uniaxial stretching is not particularly limited, and uniaxial stretching or transverse uniaxial stretching in the longitudinal direction of the elongated PVA film can be employed, but from the viewpoint of obtaining a polarizing film excellent in polarizing performance, it is preferred. Uniaxial stretching for the long direction. The uniaxial stretching in the elongate direction can be performed by changing the peripheral speed between the rolls by using a stretching device having a plurality of rolls parallel to each other. On the other hand, the horizontal uniaxial stretching system can be carried out using a tenter type stretching machine.

When the polarizing film is produced, in order to make the adsorption of the dichroic dye (such as an iodine dye) to the PVA film firm, it is preferable to carry out the fixing treatment. The fixing treatment can be carried out by immersing the PVA film in a fixed treatment bath. In the fixed treatment bath, one type or two or more types of aqueous solutions containing a boron compound such as boric acid or borax can be used. Further, an iodine compound or a metal compound may be added to the fixed treatment bath as needed. The concentration of the boron compound in the fixed treatment bath is generally preferably from 2 to 15% by mass, particularly preferably from about 3 to 10% by mass. By making the concentration in the range of 2 to 15% by mass, the adsorption of the dichroic dye can be made stronger. The temperature of the fixed treatment bath is preferably from 15 to 60 ° C, particularly preferably from 25 to 40 ° C.

The drying conditions are not particularly limited, but it is preferably dried at a temperature in 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, it is easy to obtain a polarizing film which is excellent in dimensional stability and can suppress a decrease in polarizing performance due to decomposition of a dichroic dye.

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

The polarizing film obtained as described above is usually used in the form of a polarizing plate in which a protective film which is optically transparent and has mechanical strength is bonded to both surfaces or a single 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 can be used. In addition, examples of the adhesive to be bonded include a PVA-based adhesive or a urethane-based adhesive, and among them, a PVA-based adhesive is preferable.

The polarizing plate obtained as described above can be applied to a glass substrate by applying an adhesive such as an acrylic resin, and can be used as a component of an LCD, and can be bonded to a retardation film, a viewing angle enhancing film, a brightness enhancement film, or the like.

[Examples]

The present invention will be specifically described below based on examples and the like, but the present invention is not limited by the following examples.

In the following examples, the evaluation of each physical property was carried out in the following manner.

(1) Measurement of "maximum height roughness (Rz)" and "arithmetic mean roughness (Ra)" of the cut end surface of the PVA film: The film portion of the outermost layer of the roll which is wound into a roll-shaped PVA film (PVA film having a cut end portion along the longitudinal direction) after being cut along the longitudinal direction of the film (particularly from the cutting start point to the film) A sample having a cut end portion of 30 mm in length (3 sample points of the sample) was sampled along the longitudinal direction of the film in the longitudinal direction of the film, and an ultra-depth shape measuring microscope "VK- manufactured by KEYENCE Corporation" was used. 8500", at any position of the cut end surface of the sample to be sampled, the cut end surface is measured along the longitudinal direction of the film in a length range of 100 μm, based on the longitudinal direction of the film in the central portion in the thickness direction of the cut end surface. The roughness state is obtained from the surface state, and the "maximum height roughness of the cut end face" is calculated according to the calculation method of "maximum height roughness (Rz)" and "arithmetic mean roughness (Ra)" prescribed in JIS B 0601:2001. Degree (Rz) and "Arithmetic Average Roughness (Ra)", and the average value at three points is calculated.

Further, since the cutting edge of the cutting blade is not worn or the wear is small at the beginning and the middle of the cutting, a smooth cut end surface having a low degree of surface roughening is formed, so that the winding start of the roll is omitted. And the measurement of the degree of surface roughening of the cut end surface at the intermediate point of the winding, the time at which the cutting of the cutting blade is maximized at the end of the cutting (the most roller of the PVA film wound into a roll after cutting) In the film portion of the surface layer, the "maximum height roughness (Rz)" and the arithmetic mean roughness (Ra) of the cut end surface were determined, and the degree of surface roughening of the cut end surface was evaluated.

(2) Confirmation of cracking during stretching of the PVA film (stretching ratio at break of the film):

(i) Confirmation of whether or not the PVA film having the cut end portion along the longitudinal direction is broken during stretching, which is originally required to be carried out under a continuous stretching operation at the time of producing a polarizing film, but the PVA film at the time of stretching The rupture has a frequency which usually occurs once in a few hours, and since it is difficult to carry out a test which is practically used, it is evaluated by the following model test (ii).

(ii) the outermost film portion of the roll which is wound into a roll-shaped PVA film (PVA film having a cut end portion along the longitudinal direction) after being cut along the longitudinal direction of the film (particularly from the cutting) The portion which is cut after 500 m in the longitudinal direction of the film, as shown in Fig. 1, one side (long side) of the longitudinal direction of the sample sample parallel to the longitudinal direction of the film is the cut end portion and the length × width = 15 cm × A rectangular sample of 10 cm size (sample S shown in Fig. 1) (sample number of samples 3). In addition, in this case, in order to form a smooth cut surface which does not cause surface roughening, the cutting of the three sides other than the side of the cut end portion is performed in order to cut off one side. The cutting operation was performed using a cutting blade that renewed the tip ("A-blade" manufactured by NT Co., Ltd.).

(iii) In the longitudinal both ends (2 lateral sides) of the sample sampled in the above (ii), the sample was clamped at a distance of 4 cm between the chucks using a pair of chucks and mounted on a batch stretching machine. After immersing the whole sample in water at 30 ° C for 1 minute and swelling with water, immediately after taking out from the water, the whole sample was immersed in a 4% aqueous solution of boric acid at 50 ° C, and after immersion for 1 minute, directly in a boric acid aqueous solution at a stretching speed. Stretching under conditions of 0.15 m/min, measurement The distance between the nips at the time of rupture of the product was determined by the following formula, and the stretching ratio at the time of rupture was determined, and the average value of the three samples was taken.

Stretching magnification at break (times) = distance between chucks when the sample is broken (cm) / 4 (cm)

(iv) as a control, the film portion of the outermost layer of the roll which was wound into the same roll-shaped PVA film (PVA film having the cut end portion along the longitudinal direction) which was sampled in the above (ii) It is a substantially central portion in the width direction of a portion cut from the cutting start point to the longitudinal direction of the film by 500 m, and a rectangular sample of a size of vertical × horizontal = 15 cm × 10 cm is sampled in parallel with the longitudinal direction of the film (without length) Sample of the cut end face in the direction) (sample number of samples 3). In addition, in the sampling of the sample (iv), in order to smooth the surface of the four sides (four cut end faces) of the sample without surface roughening, it is necessary to cut one edge each time in order to cut it well. The cutting tool ("A-blade" manufactured by NT Co., Ltd.) that is updated with a cutting edge is used for the cutting operation.

(v) Using the comparative sample obtained in the above (iv), the stretching ratio at the time of the rupture was determined in the same manner as in the above (iii), and the average value of the three samples was taken.

[Example 1]

(1) 100 parts by mass of a PVA sheet (degree of polymerization of PVA of 2,400, degree of saponification of 99.9 mol%) is impregnated with 12 parts by mass of glycerin and 220 parts by mass of water, and then the impregnated PVA sheet is supplied to an extruder and heated. The film forming stock solution obtained by melting the PVA was prepared by being melted under pressure, and the film forming stock solution was extruded on the first metal roll (the surface temperature of the metal roll was 95 ° C, the diameter of the metal roll was 3.8 m), and further, 10 pieces. The back surface of the watch was alternately dried on a metal roll, and an elongated PVA film (having a width of 3 m and a thickness of 20 μm) was continuously produced.

(2) As a cutting device for cutting the PVA film, a groove as illustrated in (a) of Fig. 3 is disposed on the upstream side of the winder for winding the formed PVA film into a roll shape. The roller 10 (made of metal; the diameter Eb of the large diameter portion is 20 cm, the width Wa8 of the large diameter portion Eb; the diameter Ec 19 cm of the small diameter portion and the width Wb 2 mm of the small diameter portion), and both ends in the width direction of the corrugating roller 10 In the position of the small-diameter portion in the vicinity, a new two-blade circular blade 2 exemplified in (a) of Fig. 3, which is freely rotatable by a ball bearing, is disposed (the Vickers hardness of the blade tip portion is 1,850 HV) The diameter of the circular blade is Ea45mm; the angle of the tip is α40°; the thickness of the base of the tip (thickness before the thickness of the tip is gradually reduced) d0.3mm; the length of the blade (the distance from the base of the tip to the tip of the tip) )e0.85mm).

(3) The PVA film (the volatile component ratio in the film (3 mass%) in the film (1)) is supplied to the cutting device prepared in the above (2), and at this time, the PVA is applied to the circumferential surface of the corrugating roller 10. The contact angle β (holding angle) reaches 90°, and the PVA film is brought into contact with the surface of the large diameter portion of the corrugating roller 10 while the PVA film is along a part of the circumference of the corrugating roller 10 (holding state). a new circular blade 2 which is conveyed at a speed of 17 m/min and which is freely rotatable by using a ball bearing, cuts both end portions of the PVA film along the longitudinal direction to form a film having a width of 2.6 m, and The aluminum tube (diameter: about 15.2 cm) was continuously wound into a roll shape by a winder, and a PVA film having a total length of 500 m (winding length of 500 m) having a cut end surface at both end portions along the longitudinal direction was obtained. . The temperature of the PVA film when cut with a rotating circular blade was 30 °C.

(4) The PVA film which was wound into a roll shape with a length of 500 m or more obtained in the above (3) was used, and the cut end face thereof was measured by the above method. "Maximum height roughness (Rz)" and "arithmetic mean roughness (Ra)", the maximum height roughness (Rz) is 0.85 μm, the arithmetic mean roughness (Ra) is 0.13 μm, and Rz/Ra is 6.8. The cut end surface in the longitudinal direction (full length) has an extremely low surface roughness in a range of 500 m or more, and is excellent in smoothness.

(5) Further, the PVA film wound into a roll shape having a length of 500 m or more obtained in the above (3) was used, and the draw ratio at the time of film breakage was measured by the above method, and it was 6.1 times. On the other hand, the draw ratio at the time of film breakage of the control sample (the sample sampled from the substantially central portion in the width direction of the PVA film) was also 6.1 times.

[Embodiment 2]

(1) In the same manner as (1) to (3) of the first embodiment, except that a new circular blade having a blade edge angle α of 45° was used in (2) of the first embodiment, it was obtained along the longitudinal direction. Both ends of the PVA film having a total length of 500 m (winding length of 500 m) of the cut end face are provided.

(2) Using the PVA film wound in a roll shape having a length of 500 m or more obtained in the above (1), the "maximum height roughness (Rz)" and "arithmetic mean roughness" of the cut end face were measured by the above method. (Ra)", the maximum height roughness (Rz) was 0.98 μm, the arithmetic mean roughness (Ra) was 0.15 μm, Rz/Ra was 6.7, and the cut end face along the longitudinal direction (full length) was in the range of 500 m or more. The degree of surface roughening is extremely low in the range, and the smoothness is excellent.

(3) Further, the PVA film wound into a roll shape having a length of 500 m or more obtained in the above (1) was used, and the draw ratio at the time of film breakage was measured by the above method, and it was 6.0 times.

[Example 3]

(1) In the same manner as (1) to (3) of the first embodiment, except that a new circular blade having a blade edge angle α of 30° was used in (2) of the first embodiment, it was obtained along the longitudinal direction. Both ends of the PVA film having a total length of 500 m (winding length of 500 m) of the cut end face are provided.

(2) Using the PVA film wound in a roll shape having a length of 500 m or more obtained in the above (1), the "maximum height roughness (Rz)" and "arithmetic mean roughness" of the cut end face were measured by the above method. (Ra)", the maximum height roughness (Rz) was 1.19 μm, the arithmetic mean roughness (Ra) was 0.15 μm, Rz/Ra was 7.8, and the cut end face along the longitudinal direction (full length) was in the range of 500 m or more. The degree of surface roughening is extremely low in the range, and the smoothness is excellent.

(3) Further, the PVA film wound into a roll shape having a length of 500 m or more obtained in the above (1) was used, and the draw ratio at the time of film breakage was measured by the above method, and it was 5.9 times.

[Comparative Example 1]

(1) The same as (1) to (3) of the first embodiment except that a new circular blade having a Vickers hardness of 300 HV or less (SKS-7) in the blade edge portion is used in (3) of the first embodiment. In the same manner, a PVA film having a total length of 500 m (a winding length of 500 m) having a cut end surface was obtained at both end portions along the longitudinal direction.

(2) Using the PVA film wound in a roll shape having a length of 500 m or more obtained in the above (1), the "maximum height roughness (Rz)" and "arithmetic mean roughness" of the cut end face were measured by the above method. (Ra)", the maximum height roughness (Rz) is 2.68 μm, and the arithmetic mean roughness (Ra) is 0.50 μm and Rz/Ra were 5.4. Compared with Examples 1 to 3, the surface roughness of the cut end surface was high.

(3) Further, the PVA film wound in a roll shape having a length of 500 m or more obtained in the above (1) was used, and the stretching ratio at the time of film breakage was measured by the above method, and it was 5.6 times, and Example 1 was used. Compared with 3, it is easier to break when stretched.

[Comparative Example 2]

(1) In the same manner as (1) to (3) of the first embodiment, except that a new circular blade having a blade edge angle α of 23° was used in (3) of the first embodiment, it was obtained along the longitudinal direction. Both ends of the PVA film having a total length of 500 m (winding length of 500 m) of the cut end face are provided.

(2) Using the PVA film wound in a roll shape having a length of 500 m or more obtained in the above (1), the "maximum height roughness (Rz)" and "arithmetic mean roughness" of the cut end face were measured by the above method. (Ra)", the maximum height roughness (Rz) was 3.22 μm, the arithmetic mean roughness (Ra) was 0.67 μm, and the Rz/Ra was 4.8. The surface roughening of the cut end surface was compared with Examples 1 to 3. A higher degree.

(3) Further, the PVA film wound in a roll shape having a length of 500 m or more obtained in the above (1) was used, and the stretching ratio at the time of film breakage was measured by the above method, and it was 5.6 times, and Example 1 was used. Compared with 3, it is easier to break when stretched.

The above results are shown in the table below.

1‧‧‧PVA film

Claims (9)

A polyvinyl alcohol film having an elongated polyvinyl alcohol film having a thickness of 55 μm or less and a length of 500 m or more, wherein at least one of two end portions along a longitudinal direction of the film is formed by cutting a blade In the cut end portion, the maximum height roughness (Rz) of the cut end surface of the cut end portion is 2.5 μm or less in the interval of the film length of 500 m or more. The polyvinyl alcohol film of claim 1, wherein the arithmetic mean roughness (Ra) of the cut end face is 0.4 μm or less in the interval. A polyvinyl alcohol film according to claim 1 or 2, wherein the film has a length of 1,000 m or more. The polyvinyl alcohol film according to any one of claims 1 to 3, which is a raw material film for producing an optical film. The polyvinyl alcohol film according to any one of claims 1 to 4, wherein the optical film is a polarizing film. A roll obtained by winding a polyvinyl alcohol film according to any one of claims 1 to 5 into a roll. A manufacturing method for producing an elongated polyvinyl alcohol film having a thickness of 55 μm or less and a length of 500 m or more, wherein at least one of the two end portions along the longitudinal direction of the film is cut by a blade The formed cut end portion has a step of using an elongated polyvinyl alcohol film on one side with a corrugating roller having a large diameter portion in contact with the film in the roll axis direction and a small diameter portion not in contact with the film. The surface of the large diameter portion of the corrugating roller is transported in contact with each other, and the polyvinyl alcohol film is cut along the longitudinal direction at a position of the small diameter portion of the corrugating roller, wherein the circular blade is cut. Tip angle is 25~50° The Vickers hardness of the tip portion is 1,500 HV or more. The manufacturing method of claim 7, wherein the polyvinyl alcohol film is brought into contact at an angle of 10 to 100° along the circumference of the corrugating roller. The manufacturing method of claim 7 or 8, which is a method for producing a polyvinyl alcohol film according to any one of claims 1 to 5.