WO2016182010A1

WO2016182010A1 - Polyvinyl alcohol film

Info

Publication number: WO2016182010A1
Application number: PCT/JP2016/064090
Authority: WO
Inventors: 保二郎森; 佐藤　直人; 晃村上
Original assignee: 株式会社クラレ
Priority date: 2015-05-13
Filing date: 2016-05-12
Publication date: 2016-11-17
Also published as: TW201708267A; KR102330883B1; JP6668338B2; KR20180006899A; JPWO2016182010A1; CN107530892A; CN107530892B; KR20200090959A; TWI714581B

Abstract

The present invention relates to: an elongated polyvinyl alcohol film 1 having a thickness of no more than 55 μm 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 μm 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” may be abbreviated as “PVA”), a roll obtained by winding the roll into a roll, and such The present invention relates to a method for producing a PVA film for obtaining a PVA 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. In view of this, there is a demand for a polarizing plate with higher quality and lower cost.

A polarizing plate is generally a method in which a PVA film is uniaxially stretched after dyeing, uniaxially stretched while being dyed, or dyed after being uniaxially stretched to produce a dyed uniaxially stretched film, which is fixed with a boron compound. Or after producing a polarizing film by a method of fixing with a boron compound at the same time as dyeing in the uniaxial stretching / dyeing process, a cellulose triacetate (TAC) film, acetic acid / butyric acid cellulose on the surface of the polarizing film (CAB) Manufactured by bonding a protective film such as a film.

In the production of polarizing plates, in order to reduce production costs, etc., using a raw film in which a long PVA film is wound in a roll shape, uniaxial stretching, dyeing, fixing, laminating a protective film, etc. A method of continuously performing the process is widely adopted.
In the PVA film, both ends in the width direction of the film after film formation tend to differ in thickness and degree of drying with respect to the central portion, and stable stretching is difficult when uniaxially stretching while leaving both ends in the width direction. In general, it is common practice to cut and remove both end portions in the width direction of the film, and then to take up the film in a roll and supply it to a customer such as a polarizing plate manufacturer.
In addition, in order to provide a film width that meets the demands of customers such as polarizing plate manufacturers, the formed PVA film can be removed simultaneously with or without cutting off the ears. The film is cut in the length direction at the center in the width direction or at other positions to obtain the desired width of the film, which is then rolled up and delivered to customers. It has been broken.

In producing a polarizing film from a PVA film, in order to obtain high polarizing performance, the PVA film is generally uniaxially stretched in the length direction at a high stretch ratio, but the cut end face of the film is rough. If the surface is flattened, the rough surface portion may become a starting point of crack generation during uniaxial stretching, and a crack may occur at the end portion. In severe cases, the film may break from the crack portion. When the film breaks, it is necessary to temporarily stop the uniaxial stretching process, remove the broken part, and then perform the stretching process again, which causes a significant reduction in productivity and a decrease in the yield of the polarizing film. From such a point, there is a demand for a PVA film having a smooth cut end surface along the length direction of the film that does not generate cracks or breaks during stretching.

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 volatile content of a PVA film subjected to cutting are in a specific range, respectively. As a cutting method, a method of cutting a film between two rolls, or a groove A method of cutting on a roll is described. Patent Document 2 describes an optical PVA film having a specific surface average roughness (Ra), and describes a method using a shear blade composed of an upper blade and a lower blade, and a method using a leather blade as a cutting method. Has been. Patent Document 3 describes a long PVA film in which the maximum height (Ry) of the cut end face is in a specific range over the entire length of the film, and one piece each for forming one cut end as a cutting method. A method using a rotating round blade is described, that a grooved roll is used, and that a cutting edge angle of the round blade is preferably 3 to 20 °.

JP 2002-144418 A Japanese Patent Laid-Open No. 2003-12827 JP 2005-306981 A

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

An object of the present invention is to provide a thin PVA film that is not easily broken during processing such as uniaxial stretching, and a roll obtained by winding the PVA film into a roll. Moreover, the objective of this invention is providing the manufacturing method of the PVA film for manufacturing such a PVA film smoothly.

As a result of intensive studies to achieve the above object, the inventors of the present invention have found that in a long PVA film having a thickness of 55 μm or less, the maximum in the cut end surface of the cut end portion over a specific section in the length direction of the film. It has been found that by making the height roughness (Rz) in a specific range, it is difficult to break during processing such as uniaxial stretching, despite being a thin PVA film. Moreover, when cutting the said PVA film along the length direction with the round blade which rotates while making the PVA film before cutting contact the grooved roll and transferring the PVA film, It has been found that when a film having a cutting edge angle and a hardness of the cutting edge portion in a specific range is used, the thin PVA film which is difficult to break can be smoothly manufactured. The present inventors have further studied based on these findings to complete the present invention.

That is, the present invention
[1] A long PVA film having a thickness of 55 μm or less and a length of 500 m or more, wherein at least one of two ends along the length direction of the film is a cutting end formed by a cutting blade. A PVA film having a maximum height roughness (Rz) of the cut end surface of the cut end portion of 2.5 μm or less over a section having a length of 500 m or more;
[2] The PVA film of the above [1], wherein the arithmetic average roughness (Ra) of the cut end surface is 0.4 μm or less over the section;
[3] The PVA film of the above [1] or [2], wherein the length of the film is 1,000 m or more;
[4] The PVA film according to any one of the above [1] to [3], which is a raw film for producing an optical film;
[5] The PVA film according to any one of [1] to [4], wherein the optical film is a polarizing film;
[6] A roll obtained by winding the PVA film of any one of the above [1] to [5] into a roll;
[7] Method for producing a long PVA film having a thickness of 55 μm or less and a length of 500 m or more, wherein at least one of the two end portions along the length direction of the film is a cut end formed by a cutting blade And using a grooved roll having a large-diameter portion in contact with the film and a small-diameter portion not in contact with the film in the roll axis direction, and bringing the long PVA film into contact with the surface of the large-diameter portion of the grooved roll The PVA film is cut along the length direction by a round blade that rotates at the position of the small diameter portion of the grooved roll, and the blade edge angle is 25 to 50 °. The manufacturing method in which the Vickers hardness of the blade edge part is 1,500 HV or higher;
[8] The production method of the above [7], wherein the PVA film is contacted at an angle of 10 to 100 ° along the circumference of the grooved roll;
[9] The production method of the above [7] or [8], which is a production method for producing any one PVA film of the above [1] to [5];
About.

According to the present invention, there are provided a thin PVA film that is difficult to break during processing such as uniaxial stretching, and a roll obtained by winding the PVA film into a roll. Moreover, according to this invention, the manufacturing method of the PVA film which can manufacture such a PVA film smoothly is provided.

It is the figure which showed a part of PVA film of this invention typically. It is the figure which showed typically an example of the cross section in the thickness direction of a round blade. It is the figure which showed typically an example of the cutting method of a PVA film using an example of a grooved roll, and a grooved roll.

The present invention is described in detail below.
The PVA film of the present invention is a long film, and at least one of two ends along the length direction of the film is a cut end formed by a cutting blade. The PVA film may be either a cut end or only one end along the length of the film, or both ends along the length of the film may be cut ends. It is preferable that both ends along the length direction of the film are cut ends. There is no restriction | limiting in particular in the cutting blade which forms a cutting | disconnection edge part, For example, a shear blade, a leather blade, a round blade etc. are mentioned, The round blade mentioned 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 over a section having a length of 500 m or more. That is, for example, when the length of the PVA film of the present invention is 3,000 m, the maximum height roughness (Rz) at least in any 500 m continuous section of the length of the cut end face. Is in the above range.

Here, as shown in FIG. 1, the cut end surfaces are cut end portions A and A ′ along the length direction of the PVA film 1 (FIG. 1 shows both end portions along the length direction of the PVA film 1. Means the surfaces (cut surfaces) B and B ′ corresponding to the thickness portion of the PVA film 1 in FIG.

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

In the PVA film of the present invention, from the viewpoint of preventing breakage during processing such as uniaxial stretching, the maximum height roughness (Rz) of the cut end surface is 2.5 μm or less over a section having a length of 500 m or more. 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. Although there is no restriction | limiting in particular in the minimum of the said maximum height roughness (Rz), From viewpoints, such as the ease of manufacture of the PVA film of this invention, the maximum height roughness (Rz) of a cut end surface is the length of a film. A PVA film without such a section that is 0.01 μm or less over a section of 500 m is preferable, and the maximum height roughness (Rz) of the cut end surface is 0.1 μm or less over a section of the length of 500 m of the film. A PVA film having no section is more preferable, and a PVA film having no section in which the maximum height roughness (Rz) of the cut end surface is 0.3 μm or less over the section having a length of 500 m is further preferable.

When the arithmetic average roughness (Ra) of the cut end face is 0.4 μm or less over the above-mentioned section relating to the maximum height roughness (Rz), the PVA film of the present invention is more effective in breaking during processing such as uniaxial stretching. Therefore, it can be prevented. From such a viewpoint, the PVA film of the present invention preferably has an arithmetic average roughness (Ra) of the cut end face of 0.3 μm or less over the above section, and more preferably 0.2 μm or less. Particularly preferably, it is 0.14 μm or less. Although there is no restriction | limiting in particular in the minimum of the said arithmetic mean roughness (Ra), From viewpoints, such as the ease of manufacture of the PVA film of this invention, arithmetic mean roughness (Ra) of a cut end surface is 0.001 micrometer over the said area. PVA film having no such section as follows is preferable, PVA film having no section in which the arithmetic average roughness (Ra) of the cut end face is 0.01 μm or less over the above section is more preferable, and arithmetic of the cut end face More preferable is a PVA film having no section in which the average roughness (Ra) is 0.03 μm or less over the section.

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

The PVA film of the present invention has the maximum height roughness (Rz) and arithmetic over the above-mentioned section concerning the maximum height roughness (Rz) from the viewpoint of more effectively preventing breakage during processing such as uniaxial stretching. The ratio (Rz / Ra) to the average roughness (Ra) is preferably 5 or more, more preferably 6 or more, and preferably 25 or less, more preferably 11 or less. The ratio (Rz / Ra) can be used as an index of the degree of wear of the blade used for cutting the PVA film, and when the blade is heavily worn, the ratio (Rz / Ra) is often small, and the cut end face is accordingly accompanied. The degree of roughening tends to increase.

The thickness of the PVA film of the present invention is 55 μm or less, preferably 50 μm or less, more preferably 45 μm or less, and more preferably 40 μm or less, for reasons such as meeting the demand for thinner PVA films. More preferably, it is particularly preferably 30 μm or less. Although there is no restriction | limiting in particular in the minimum of the thickness of the said PVA film, From viewpoints, such as practicality, the ease of manufacture of a film, the ease of extending | stretching process, it is preferable that the said thickness is 3 micrometers or more, and is 5 micrometers or more. More preferably, it is more preferably 15 μm or more.

Although the width | variety of the PVA film of this invention can be selected according to the use of the PVA film, the demand of the customer of a PVA film, etc., generally it is preferable that it is 2 m or more, and is 2.5 m or more. More preferably, it is 3 m or more, more preferably 8 m or less.

The length of the PVA film of the present invention is 500 m or more. The length of the PVA film is preferably 1,000 m or more, more preferably 5,000 m or more, and more preferably 8,000 m or more because it can be used continuously for a long time when used. More preferably it is. There is no restriction | limiting in particular in the upper limit of the said length, The said length can be 30,000 m or less, for example. The PVA film of the present invention is preferably in the form of a roll that is wound into a roll shape from the viewpoint of ease of transportation, storage, and use.

Examples of the PVA constituting the PVA film of the present invention include unmodified PVA obtained by saponifying a polyvinyl ester obtained by polymerizing vinyl ester, modified PVA obtained by graft copolymerizing a comonomer with the main chain of PVA, vinyl A so-called polyvinyl acetal resin in which a part of hydroxyl groups of modified PVA, unmodified PVA or modified PVA produced by saponification of a modified polyvinyl ester obtained by copolymerizing an ester and a comonomer is crosslinked with aldehydes such as formalin, butyraldehyde, and benzaldehyde And so on.
When the PVA forming the PVA film of the present invention is a modified PVA, the amount of modification in the PVA is preferably 15 mol% or less, and 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 valelate, vinyl pivalate, vinyl laurate, vinyl stearate, vinyl benzoate, versatic acid. Vinyl etc. can be mentioned. These vinyl esters can be used alone or in combination. Of these vinyl esters, vinyl acetate is preferred from the viewpoint of productivity.

Examples of the comonomer include olefins having 2 to 30 carbon atoms (such as α-olefin) such as ethylene, propylene, 1-butene and isobutene; acrylic acid or a salt thereof; methyl acrylate, ethyl acrylate, acrylic Acrylic acid esters such as n-propyl acid, i-propyl acrylate, n-butyl acrylate, i-butyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, octadecyl acrylate, etc. Methacrylic acid or a salt thereof; methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, i-propyl methacrylate, n-butyl methacrylate, i-butyl methacrylate , T-butyl methacrylate, methacrylic acid -Methacrylic acid esters such as ethylhexyl, dodecyl methacrylate, octadecyl methacrylate (eg, alkyl esters of 1 to 18 carbon atoms of methacrylic acid); acrylamide; N-methylacrylamide, N-ethylacrylamide, N, N-dimethylacrylamide, Acrylamide derivatives such as diacetone acrylamide, acrylamide propane sulfonic acid or salts thereof, acrylamide propyl dimethylamine or salts thereof, N-methylol acrylamide or derivatives thereof; methacrylamide; N-methyl methacrylamide, N-ethyl methacrylamide, methacrylamide propane Sulfonic acid or its salt, methacrylamidopropyldimethylamine or its salt, N-methylolmethacrylamide or its derivative, etc. N-vinylamides such as N-vinylformamide, N-vinylacetamide, N-vinylpyrrolidone; methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, n-butyl vinyl ether, i-butyl Vinyl ethers such as vinyl ether, t-butyl vinyl ether, dodecyl vinyl ether and stearyl vinyl ether; nitriles such as acrylonitrile and methacrylonitrile; vinyl halides such as vinyl chloride, vinylidene chloride, vinyl fluoride and vinylidene fluoride; allyl acetate; Allyl compounds such as allyl chloride; unsaturated dicarboxylic acids such as maleic acid and itaconic acid; derivatives thereof such as salts or esters thereof; and vinyltrimethoxysilane Nirushiriru compounds; isopropenyl acetate; an unsaturated sulfonic acid or its derivatives. These comonomers may be used individually by 1 type, or may use 2 or more types together. Of these comonomers, α-olefins are preferable, and ethylene is particularly preferable.

The degree of polymerization of PVA is preferably 1,000 or more from the viewpoint of obtaining a polarizing film excellent in polarizing performance and durability when a polarizing film is produced by uniaxially stretching the PVA film of the present invention. Is more preferably 2,000 or more, and may be 2,500 or more. Moreover, from the viewpoint of ease of production for obtaining a homogeneous PVA film, stretchability, etc., the degree of polymerization of PVA is preferably 8,000 or less, and more preferably 6,000 or less. The polymerization degree of PVA in this specification means an average polymerization degree measured according to the description of JIS K6726-1994, and is obtained from the intrinsic viscosity measured in water at 30 ° C. after re-saponifying and purifying PVA. .

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

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

The content of the plasticizer is preferably 1 part by mass or more, more preferably 5 parts by mass or more, and preferably 30 parts by mass or less, based on 100 parts by mass of PVA, and 20 parts by mass. The following is more preferable. When the content of the plasticizer is not less than the above lower limit, 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 handling properties, cutting uniformity, and the like are improved.

The PVA film of the present invention preferably contains a surfactant from the viewpoint of its handleability and the improvement of peelability from the film forming apparatus when the PVA film is produced. There is no restriction | limiting in particular in the kind of surfactant, For example, anionic surfactant, a nonionic surfactant, etc. are mentioned. Examples of the anionic surfactant include carboxylic acid type, sulfuric acid ester type, and sulfonic acid type. Examples of the nonionic surfactant include an alkyl ether type, an alkyl phenyl ether type, an alkyl ester type, an alkyl amide type, a polypropylene glycol ether type, an alkanol amide type, and an allyl phenyl ether type. The PVA film of the present invention can contain one or more of these surfactants.

The surfactant content is preferably 0.01 parts by mass or more, more preferably 0.05 parts by mass or more, and preferably 1 part by mass or less with respect to 100 parts by mass of PVA. More preferably, it is 0.3 parts by mass or less. When the content of the surfactant is not more than the above upper limit, it is possible to prevent the surfactant from being eluted on the surface of the PVA film and causing a blocking to deteriorate the handleability.

The PVA film of the present invention is a dichroic dye, an antioxidant, an ultraviolet absorber, a lubricant, a colorant, an antiseptic, an antifungal agent, other polymer compounds other than the above components, moisture, etc., if necessary. Other components may be further included. The PVA film of the present invention can contain one 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, and still more preferably 90% by mass or more.

The production method of the PVA film of the present invention is not particularly limited, but the following production method of the present invention is preferable because the PVA film of the present invention can be produced smoothly. That is, the manufacturing method of the present invention is a long end having a thickness of 55 μm or less and a length of 500 m or more, in which at least one of two end portions along the length direction of the film is a cut end formed by a cutting blade. A method for producing a PVA film, wherein a grooved roll 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 is used, and the surface of the large diameter portion of the grooved roll is long. The PVA film has a step of cutting the PVA film along the length direction by a round blade rotating at the position of the small diameter portion of the grooved roll while contacting and transferring the PVA film, and the round blade has a cutting edge angle. This is a manufacturing method in which the Vickers hardness of the blade edge portion is 1,500 HV or more at 25 to 50 °. In general, a thin PVA film tends to have a rougher cut end surface when it is cut than a thick PVA film. However, according to the production method of the present invention, a thin PVA film is also a thin PVA film. Regardless, it is possible to smoothly produce a PVA film that satisfies the provisions of the present invention.

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

The diameter of the large-diameter portion of the grooved roll is 5 cm from the viewpoint of good transfer of the PVA film, good cutting of the PVA film with the grooved roll, and the manufacturing cost of the grooved roll. Preferably, it is 7.5 cm or more, more preferably 10 cm or more, further preferably 30 cm or less, more preferably 25 cm or less, and 20 cm or less. More preferably. A PVA film can be cut | disconnected more uniformly because the diameter of the large diameter part of a grooved roll is more than the said minimum. On the other hand, the manufacturing cost of a grooved roll can be reduced because the diameter of the large diameter part of a grooved roll is below the said upper limit. When there are a plurality of large-diameter portions in the grooved roll, the large-diameter portions have the same diameter in order to bring the PVA film into contact with the surface of the plurality of large-diameter portions while keeping it flat. It is preferable that

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

The diameter of the small-diameter portion of the grooved roll is the large diameter adjacent from the standpoints of preventing breakage of the round blade, smoothness of cutting of the PVA film at the position of the small-diameter portion, and ease of processing of the groove in the grooved roll. The diameter of the part is preferably 0.5 cm or more, more preferably 1 cm or more, more preferably 2 cm or less, and even more preferably 1.5 cm or less.

The width of the small diameter portion of the grooved roll (the length in the roll axis direction; if there are a plurality of small diameter portions, the width of each small diameter portion) is equal to or less than the width of the adjacent large diameter portion Preferably there is. Moreover, the width | variety of a small diameter part is a point which can perform the cutting | disconnection of a PVA film satisfactorily without the blade edge of a round blade contacting a grooved roll, the point which suppresses that the cutting | disconnection point of a film shifts | deviates, etc. Therefore, it is preferably 2 times or more, more preferably 5 times or more with respect to the thickness of the non-tapered base portion (the dimension of d in FIG. 2) in the blade portion of the round blade, and 50 It is more preferable that it is not more than twice, and it is more preferable that it is not more than 30 times.

The round blade used in the production method of the present invention is a blade having a blade for cutting a film on the entire circumference of a disk-shaped main body that rotates around an axis. The round blade is preferably made of metal or ceramic, and specifically, iron, iron alloy, high speed tool steel, alloy tool steel, stainless steel, martensitic stainless steel, tungsten steel and the like can be mentioned. Further, the blade portion of the round blade may be made of the above-described material and the surface thereof may be treated with titanium nitride, titanium carbide, tungsten carbide or the like. In particular, a round blade made of tungsten steel is preferable because it is difficult to wear and has excellent durability and the smoothness of the cut end face.

The Vickers hardness of at least the cutting edge portion of the round blade is required to be 1,500 HV or higher, preferably 1,800 HV or higher, because the PVA film of the present invention can be produced smoothly. There is no restriction | limiting in particular in the upper limit of the said Vickers hardness, For example, the said Vickers hardness can be made into 2,400HV or less. In this specification, the unit of Vickers hardness is kgf / mm ² .

The diameter of the round blade [the length of Ea in the cross-sectional view in the thickness direction of the round blade 2 illustrated in FIGS. 2A and 2B] is preferably 15 mm or more, and preferably 20 mm or more. More preferably, it is 40 mm or more. When the diameter of the round blade is in the above range, the progress of wear is suppressed, and it becomes easy to form a smooth cut end face over the entire length of the long PVA film. The upper limit of the diameter of the round blade is not particularly limited, but if the diameter of the round blade becomes too large, the mass of the round blade itself will increase, making it difficult to rotate freely when cutting the PVA film, and to prevent breakage The diameter of the round blade is preferably 200 mm or less, more preferably 120 mm or less, because it is necessary to increase the thickness of the blade base.

The shape of the cutting edge of the round blade is, as illustrated in FIG. 2 (a), a chevron shape (double-edged) in which the polished surfaces 4, 4 ′ on both sides converge to a taper shape at the center cutting edge tip 3. As shown in FIG. 2B, the other polished tapered surface 6 converges toward the blade tip 3 at the tip of one vertical surface 5 as illustrated in FIG. It may be a single-edged shape. Among these, it is preferable that the cutting edge of the round blade has a chevron shape as shown in FIG. 2A because the cutting of the PVA film is stably performed and a cut end surface that is superior in smoothness is formed.

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

The thickness of the base of the cutting edge in the round blade [thickness immediately before the thickness gradually decreases toward the tip of the cutting edge; the dimension d shown in FIGS. 2A and 2B] is 0.05 mm or more. Is preferably 0.1 mm or more, more preferably 1 mm or less, and even more preferably 0.5 mm or less. When the thickness of the blade base is equal to or more than the above lower limit, it is possible to prevent the round blade itself from being damaged. On the other hand, when the thickness of the blade base is not more than the above upper limit, a smooth cut end face can be formed with a small degree of roughening over the entire length of the film.

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

While the long PVA film is brought into contact with the surface of the large-diameter portion of the grooved roll and transferred, the PVA film is moved along the length direction by a round blade rotating at the position of the small-diameter portion of the grooved roll. When cutting, the peripheral speed of the large-diameter portion of the grooved roll and the transfer speed of the PVA film are the same, and the PVA film is transported in a tensioned state without being slackened on the grooved roll. It is important for forming a smooth cut end face with a low degree of roughening. From this point, when the PVA film is cut along the length direction, the PVA film is cut at an angle (holding angle) of 10 to 100 ° along the circumference of the grooved roll [shown in FIG. The contact angle β] is used to bring the PVA film along the grooved roll (held), and the PVA film is cut by a rotating round blade disposed at the small diameter portion of the grooved roll. Is preferred. In that case, it is preferable to arrange | position a round blade in the center or the substantially center of the said holding angle. By doing so, the peripheral speed of the large-diameter portion of the grooved roll and the transfer speed of the PVA film become substantially the same at the time of cutting, and the groove is being transferred by the grooved roll while the PVA film is in tension. Since it cut | disconnects by the rotating round blade arrange | positioned in the position of the small diameter part of an attaching roll, the smooth cutting | disconnection end surface with a low degree of roughening can be formed. In view of the above, the holding angle is more preferably 30 ° or more, further preferably 45 ° or more, more preferably 98 ° or less, and further preferably 95 ° or less. preferable.

When the PVA film is cut along the length direction by the rotating round blade, the PVA film may be cut while actively driving and rotating the round blade, but the rotation speed of the round blade and the transfer speed of the PVA film From the standpoint of reducing the difference between the cutting edge and the degree of roughening of the cut end face, the round blade can be freely moved along with the transfer of the PVA film, rather than actively driving and rotating the round blade. Cutting is preferably performed while rotating. If the cutting is performed while freely rotating the round blade, it is possible to prevent a large difference between the rotational speed of the round blade and the transfer speed of the PVA film, thereby smoothly and smoothly cutting the PVA film. A smooth cut end face with a smaller degree of surfaceization can be formed. The method for freely rotating the round blade is not particularly limited. For example, as illustrated in the schematic diagram of FIG. 2 (cross-sectional view in the thickness direction of the round blade 2), the round blade 2 is a disc-shaped round blade. The rotary shaft 8 is fixedly attached to the mounting member 7 and attached to the center (center position) of the disc-shaped round blade mounting member 7 so as to be integrated or fixed and extended. A ball bearing or the like is provided around the rotary shaft 8. A system in which the bearing 9 is disposed and the rotary shaft 8, the round blade mounting member 7, and the round blade 2 are freely rotated integrally can be employed.

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

The volatile content of the PVA film when the PVA film is cut along the length direction by a rotating round blade is preferably 0.1% by mass or more, more preferably 2% by mass or more. The content is preferably 10% by mass or less, and more preferably 6% by mass or less. When the volatile content is equal to or more than the above lower limit, the PVA film is not too hard and can be easily cut. On the other hand, when the volatile content is less than or equal to the above upper limit, the PVA film can be prevented from becoming too soft, and the degree of roughening of the cut end surface can be further reduced. In addition, "the volatile matter rate of a PVA film" as used in this specification means the content rate of the volatile matter contained in a PVA film. Examples of such a volatile component include organic solvents and water solvents used when producing the PVA film, moisture taken into the film by moisture absorption after the production of the PVA film, and the like. The volatile content of the PVA film is dried to a target value by using a heated metal roll or a floating dryer alone or in combination of two or more; a PVA film having a volatile content lower than the above range is humidified It can be adjusted by a method such as; The volatile fraction of the PVA film can be determined from the mass reduction rate when the PVA film is placed in a vacuum dryer at a temperature of 50 ° C. and a pressure of 0.1 kPa or less and dried until there is no loss of mass.

The film temperature when the PVA film is cut along the length direction by a rotating round blade is preferably 10 ° C or higher, more preferably 20 ° C or higher, and 70 ° C or lower. The temperature is preferably 60 ° C. or lower. When the film temperature is equal to or higher than the lower limit, the PVA film does not become too hard and can be easily cut. Moreover, water droplets based on condensation adhere to the PVA film, and when the PVA film after the cutting treatment is rolled up and stored, blocking occurs, or when the PVA film is stretched, it breaks from the portion where the water droplets are adhered. Can also be suppressed. On the other hand, when the said film temperature is below the said upper limit, it can suppress that a PVA film becomes too soft, and can make the degree of roughening of a cut end surface smaller. The film temperature of the PVA film can be measured using a spot type digital radiation thermometer (for example, “Thermometer 505A” manufactured by Minolta Co., Ltd.).

The cutting along the length direction of the PVA film by the rotating round blade may be performed continuously following the production process of the PVA film, or after the PVA film is produced and wound into a roll, You may carry out, unwinding a film from a roll.

The production method of the PVA film to be subjected to cutting is not particularly limited, and can be produced by a conventionally known method. For example, the above-described PVA constituting the PVA film, and the above-described plasticizer and interface as necessary. A film-forming stock solution in which one or more of the active agent and other components are dissolved in a liquid medium, PVA, and optionally, a plasticizer, a surfactant, and other components It can manufacture using the film-forming stock solution which contains 1 type (s) or 2 or more types, and PVA is fuse | melting. When the film-forming stock solution contains at least one of a plasticizer, a surfactant, and other components, it is preferable that these components are uniformly mixed.

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

Examples of the film forming method for forming a PVA film using the above-described film forming stock solution include a cast film forming method, an extrusion film forming method, a wet film forming method, and a gel film forming method. These film forming methods may be used alone or in combination of two or more. Among these film forming methods, the cast film forming method and the extrusion film forming method are preferable because a PVA film that gives a good polarizing film can be produced smoothly. The formed film can be dried or heat-treated as necessary.

Examples of a specific method for producing a PVA film to be used for cutting include, for example, a T-type slit die, a hopper plate, an I-die, a lip coater die, etc. One surface of the film discharged or cast uniformly on the peripheral surface of the first heated roll (or belt) that is positioned and rotated, and discharged or cast on the peripheral surface of the first roll (or belt) The volatile components are then evaporated and dried, followed by further drying on the circumference of one or more rotating heated rolls located downstream thereof, or passing through a hot air dryer. Furthermore, after drying, the method of winding with a winding device can be preferably employed industrially. Drying with a heated roll and drying with a hot air dryer may be performed in an appropriate combination.

The use of the PVA film of the present invention is not particularly limited. For example, a film for drug packaging, a base film for hydraulic transfer, a base film for embroidery, a release film for molding artificial marble, a film for seed packaging, and a bag for waste container The PVA film of the present invention, which can be used for various water-soluble film applications such as a film, has at least one of two ends along the length direction of the film, preferably both of which are cut ends. “Maximum height roughness (Rz)” of the cut end face at the end is less than a specific value, and the cut end face has a very low degree of roughening and excellent smoothness. When it does, a crack is hard to generate | occur | produce in a cutting | disconnection edge part (edge part of the width direction of a film), and, as a result, a fracture | rupture of a film does not occur easily. From this point, it is preferable to use the PVA film of the present invention as an original film for producing an optical film (an original film for producing an optical film). Examples of such an optical film include a polarizing film and a retardation film, and a polarizing film is preferable. Such an optical film can be produced, for example, by subjecting the film of the present invention to a treatment such as uniaxial stretching.

The method for producing a polarizing film using the PVA film of the present invention is not particularly limited, and any conventionally known method may be adopted. Examples of such a method include a method of performing dyeing and uniaxial stretching using the PVA film of the present invention, and uniaxial stretching of the PVA film of the present invention containing a dye. As a more specific method for producing the polarizing film, the PVA film of the present invention is subjected to swelling, dyeing, uniaxial stretching, and, if necessary, crosslinking treatment, fixing treatment, drying, heat treatment, etc. A method is mentioned. In this case, the order of each treatment such as swelling, dyeing, crosslinking treatment, uniaxial stretching, and fixing treatment is not particularly limited, and one or two or more treatments can be performed simultaneously. Also, one or more of each process can be performed twice or more.

Swelling can be performed by immersing the PVA film in water. The temperature of the water when immersed in water is preferably in the range of 20 to 40 ° C., more preferably in the range of 22 to 38 ° C., and preferably in the range of 25 to 35 ° C. Further preferred. The time for immersion in water is preferably in the range of 0.1 to 5 minutes, for example, and more preferably in the range of 0.5 to 3 minutes. In addition, the water at the time of immersing in water is not limited to pure water, The aqueous solution in which various components melt | dissolved may be sufficient, and the mixture of water and an aqueous medium may be sufficient.

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

By subjecting the PVA film to a crosslinking treatment, it is possible to more effectively prevent PVA from eluting into water when wet-stretching at a high temperature. From this viewpoint, the crosslinking treatment is preferably performed after the treatment for bringing the dichroic dye into contact and before the uniaxial stretching. The crosslinking treatment can be performed by immersing the PVA film in an aqueous solution containing a crosslinking agent. As the crosslinking agent, one or more of boron compounds such as boric acid and borate such as borax can be used. The concentration of the crosslinking agent in the aqueous solution containing the crosslinking agent is preferably in the range of 1 to 15% by mass, more preferably in the range of 2 to 7% by mass, and in the range of 3 to 6% by mass. More preferably. Sufficient stretchability can be maintained when the concentration of the crosslinking agent is in the range of 1 to 15% by mass. The aqueous solution containing a crosslinking agent may contain an auxiliary agent such as potassium iodide. The temperature of the aqueous solution containing the crosslinking agent is preferably in the range of 20 to 50 ° C., particularly in the range of 25 to 40 ° C. By setting the temperature within the range of 20 to 50 ° C., crosslinking can be performed efficiently.

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

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

The stretching ratio in uniaxial stretching (the total stretching ratio obtained by multiplying the stretching ratios when performing uniaxial stretching in multiple stages) is preferably 4 times or more from the viewpoint of the polarizing performance of the obtained polarizing film. It is more preferable that the number is twice or more. The upper limit of the draw ratio is not particularly limited, but is preferably 8 times or less in order to perform uniform drawing.

There is no particular limitation on the direction of uniaxial stretching, and uniaxial stretching or lateral uniaxial stretching in the longitudinal direction of a long PVA film can be adopted, but since a polarizing film having excellent polarization performance is obtained, the longitudinal direction is increased. Uniaxial stretching is preferred. Uniaxial stretching in the longitudinal direction can be performed by changing the peripheral speed between the rolls using a stretching apparatus including a plurality of rolls parallel to each other. On the other hand, lateral uniaxial stretching can be performed using a tenter type stretching machine.

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

Drying conditions are not particularly limited, but it is preferable to perform the drying at a temperature in the range of 30 to 150 ° C, particularly in the range of 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 that is excellent in dimensional stability and that suppresses a decrease in polarization performance due to decomposition of the dichroic dye.

Although the thickness of the polarizing film obtained as described above depends on the thickness of the PVA film used, etc., it is preferably 30 μm or less, preferably 25 μm or less from the viewpoint of polarization performance, handleability, durability and the like. Is more preferably 20 μm or less, particularly preferably 15 μm or less, more preferably 1 μm or more, more preferably 2 μm or more, and still more preferably 4 μm or more. It is particularly preferable that the thickness is 6 μm or more.

The polarizing film obtained as described above is usually used in the form of a polarizing plate by laminating a protective film having optical transparency and mechanical strength on both sides or one side. As the protective film, a cellulose triacetate (TAC) film, a cycloolefin polymer (COP) 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 PVA adhesives and urethane adhesives, among which PVA adhesives are suitable.

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

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

(1) Measurement of “maximum height roughness (Rz)” and “arithmetic average roughness (Ra)” of the cut end face of the PVA film:
The film portion of the outermost layer of the roll of the PVA film (PVA film having a cut end portion along the length direction) wound in a roll shape after being cut along the length direction of the film (particularly from the cutting start point of the film) A sample including a cutting end portion having a length of 30 mm along the length direction of the film is taken from a portion immediately after being cut by 500 m in the length direction (the number of sampling points of the sample is 3). The cut end face was measured using the ultra-deep shape measurement microscope “VK-8500” manufactured by Keyence Corporation over the length of 100 μm along the length direction of the film at the position of A roughness curve based on the surface condition on the longitudinal line of the film is obtained, and the “maximum height roughness (Rz)” defined in JIS B 0601: 2001 and According to the calculation method of “arithmetic average roughness (Ra)”, “maximum height roughness (Rz)” and “arithmetic average roughness (Ra)” of the cut end face were calculated respectively, and the average value of three locations was calculated. .
It should be noted that, at the start of cutting and in the middle stage, there is no or little wear on the cutting edge of the cutting blade, and a smooth cutting end surface with a low degree of roughening is formed. The measurement of the degree of roughening of the cut end face at the intermediate point of cutting is omitted, and the point of time immediately before the end of cutting when the wear of the cutting blade is the largest (the roll of the PVA film wound up into a roll after cutting) The “maximum height roughness (Rz)” and the arithmetic average roughness (Ra) of the cut end face were determined for the outermost film portion of the film, and the degree of roughening of the cut end face was evaluated.

(2) Confirmation of presence / absence of breakage during stretching of PVA film (stretching ratio during film breakage):
(I) Confirmation of whether or not the PVA film having a cut end along the length direction is broken at the time of stretching must be performed in a continuous stretching operation when manufacturing a polarizing film. Since the breakage of the PVA film usually occurs once every few hours and it is difficult to conduct a test in accordance with actual use, the evaluation was performed by the following model test (ii).
(Ii) The film portion of the outermost layer of the roll of the PVA film (PVA film having a cut end portion along the length direction) wound in a roll shape after being cut along the length direction of the film (particularly the cutting start point) As shown in FIG. 1, one side (long side) in the vertical direction of the sample is a cut end portion in parallel with the length direction of the film from a portion immediately after cutting 500 m in the length direction of the film. Then, a rectangular sample (sample S shown in FIG. 1) having a size of length × width = 15 cm × 10 cm was collected (the number of samples collected was 3). At that time, the cuts of three sides other than the side corresponding to the cut end portion are cut well every time one side is cut so that a smooth cut surface that is not roughened is formed. A cutting operation was performed using a cutter knife ("A blade" manufactured by NT Co., Ltd.) with an updated blade edge.
(Iii) The sample collected in the above (ii) is held at both ends (two horizontal sides) in the longitudinal direction by a pair of chucks at a distance of 4 cm between the chucks and attached to a batch stretching machine, and the entire sample is placed at 30 ° C. After being immersed in water for 1 minute and swollen with water, the sample was immediately removed from the water and immersed in a 4% aqueous solution of boric acid at 50 ° C., and then immersed in the aqueous boric acid solution one minute after immersion. The sample was stretched at a speed of 0.15 m / min, the distance between the chucks when the sample broke was measured, the stretch ratio at the time of breaking was determined from the following formula, and the average value of three samples was taken.
Stretch ratio at break (times) = distance between chucks at break of sample (cm) / 4 (cm)

(Iv) As a control, the film portion of the outermost layer of a roll of a PVA film (PVA film having a cut end along the length direction) wound in the same roll shape as that obtained in (ii) above ( In particular, a rectangular sample with a size of length × width = 15 cm × 10 cm in parallel to the length direction of the film from a substantially central portion in the width direction of a portion immediately after cutting 500 m in the length direction of the film from the cutting start point. Collected (sample without a cut end surface along the length direction) (number of sampling points 3). When collecting the sample of (iv), the sample can be cut well every time one side is cut so that the four sides (four cut end faces) of the sample are finished smoothly without roughening. The cutting operation was performed using a cutter knife ("A blade" manufactured by NT Co., Ltd.) with the blade edge updated.
(V) Using the control sample obtained in (iv) above, the stretch ratio at break was determined in the same manner as in (iii) above, and the average value of the three samples was taken.

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

(2) As a cutting device for cutting the PVA film, on the upstream side of the winder for winding the formed PVA film into a roll, a grooved roll 10 (as illustrated in FIG. 3A) ( The diameter of the large diameter portion Eb 20 cm, the width Wa 8 mm of the large diameter portion Eb; the diameter Ec 19 cm of the small diameter portion, the width Wb 2 mm of the small diameter portion), and the position of the small diameter portion near both ends in the width direction of the grooved roll 10. 3 is a new double-edged round blade 2 illustrated in FIG. 3A that freely rotates by a ball bearing (Vickers hardness 1,850 HV of the cutting edge portion; round blade diameter Ea 45 mm; cutting edge angle α 40 °; Thicknesses (thickness immediately before the thickness gradually decreases toward the blade tip) d0.3 mm; blade lengths (distance from the blade base to the blade tip) e0.85 mm) were arranged one by one.

(3) The PVA film manufactured in (1) above (the volatile content ratio in the film is 3% by mass) is supplied to the cutting device prepared in (2) above. The large diameter portion of the grooved roll 10 with the PVA film in a state where the PVA contact angle β (holding angle) is 90 ° and the PVA film is placed along a part of the circumference of the grooved roll 10. The PVA film is transferred at a speed of 17 m / min while being in contact with the surface of the sheet, and the both ends of the PVA film are cut along the length direction by a new renewed round blade 2 that freely rotates by a ball bearing. In addition, it is continuously wound in a roll on an aluminum tube (diameter: about 15.2 cm) with a winder, and has a total length of about 500 m having a cut end face at both ends along the length direction (winding length) Over 500m ) Was obtained of the PVA film. The temperature of the PVA film at the time of cutting with a rotating round blade was 30 ° C.

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

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

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

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

[Comparative Example 1]
(1) Same as (1) to (3) of Example 1 except that a new round blade having a Vickers hardness of 300 HV or less (SKS-7) was used in (3) of Example 1. Thus, a PVA film having a total length of about 500 m (winding length of about 500 m) having a cut end face at both ends along the length direction was obtained.
(2) Using the PVA film wound up in a roll with a length of about 500 m obtained in the above (1), the “maximum height roughness (Rz)” and “arithmetic average roughness ( Ra) ”was measured by the method described above, the maximum height roughness (Rz) was 2.68 μm, the arithmetic average roughness (Ra) was 0.50 μm, and Rz / Ra was 5.4. Compared with 1-3, the degree of roughening of the cut end face was high.
(3) When the stretch ratio at the time of film breakage was measured by the above-described method using the PVA film wound up in a roll shape with a length of about 500 m obtained in the above (1), it was 5.6 times. In comparison with Examples 1 to 3, the film was easily broken during stretching.

[Comparative Example 2]
(1) In the same manner as in (1) to (3) of Example 1, except that a new round blade with a blade edge angle α of 23 ° was used in (3) of Example 1, the length direction was followed. A PVA film having a total length of about 500 m (winding length of about 500 m) having cut end faces at both ends was obtained.
(2) Using the PVA film wound up in a roll with a length of about 500 m obtained in the above (1), the “maximum height roughness (Rz)” and “arithmetic average roughness ( Ra) ”was measured by the method described above, the maximum height roughness (Rz) was 3.22 μm, the arithmetic average roughness (Ra) was 0.67 μm, and Rz / Ra was 4.8. Compared with 1-3, the degree of roughening of the cut end face was high.
(3) When the stretch ratio at the time of film breakage was measured by the above-described method using the PVA film wound up in a roll shape with a length of about 500 m obtained in the above (1), it was 5.6 times. In comparison with Examples 1 to 3, the film was easily broken during stretching.

The above results are shown in the table below.

DESCRIPTION OF SYMBOLS 1 PVA film 2 Round blade 3 Round-tip edge tip 4, 4 'Polished surface 5 Vertical surface 6 Polished surface 7 Round blade mounting member 8 Rotating shaft 9 Bearing 10 Grooved roll 10a Grooved roll large diameter Part 10b Small diameter part of grooved roll

Claims

A long polyvinyl alcohol film having a thickness of 55 μm or less and a length of 500 m or more, wherein at least one of two ends along the length direction of the film is a cutting end formed by a cutting blade, The polyvinyl alcohol film whose maximum height roughness (Rz) of the cut end face of the cut end portion is 2.5 μm or less over a section having a length of 500 m or more.
The polyvinyl alcohol film according to claim 1, wherein the arithmetic average roughness (Ra) of the cut end face is 0.4 μm or less over the section.
The polyvinyl alcohol film according to claim 1 or 2, wherein the length of the film is 1,000 m or more.
The polyvinyl alcohol film according to any one of claims 1 to 3, which is a raw 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 formed by winding the polyvinyl alcohol film according to any one of claims 1 to 5 into a roll shape.
A method for producing a long polyvinyl alcohol film having a thickness of 55 μm or less and a length of 500 m or more, wherein at least one of two ends along the length direction of the film is a cut end formed by a cutting blade. Using a grooved roll having a large diameter part in contact with the film and a small diameter part in which the film does not contact in the roll axis direction, and contacting the surface of the large diameter part of the grooved roll with a long polyvinyl alcohol film. A step of cutting the polyvinyl alcohol film along the length direction by a round blade rotating at the position of the small diameter portion of the grooved roll while being transferred, and the round blade has a cutting edge angle of 25 to 50 °. The manufacturing method whose Vickers hardness of a blade edge | tip part is 1,500 HV or more.
The method according to claim 7, wherein the polyvinyl alcohol film is contacted at an angle of 10 to 100 ° along the circumference of the grooved roll.
The production method according to claim 7 or 8, which is a production method for producing the polyvinyl alcohol film according to any one of claims 1 to 5.