KR20140143206A - Polyvinyl alcohol-based polymer film - Google Patents

Abstract

[PROBLEMS] To provide a PVA polymer film capable of producing a polarizing film having a less defects and a polarizing plate at a good yield, and to provide a PVA polymer film having a small difference in surface characteristics from a winding start portion to a winding end portion of the PVA polymer film, Provided is a film roll capable of producing a film and further a polarizing plate.
[MEANS FOR SOLVING PROBLEMS] A PVA polymer film having an area of 400 μm ² or more and a number of defects having a depth of 0.3 μm or more of 0.25 number / m 2 or less as a recess defect from the film surface, and a PVA polymer film having a long PVA polymer film As the film roll, the number of defects of the PVA polymer film relative to the number of defects at the winding start portion of the PVA polymer film with respect to the defects having an area of not less than 400 탆 ² and a depth of not less than 0.3 탆, Wherein the number of defects in the end portion is 1.4 times or less.

Description

POLYVINYL ALCOHOL-BASED POLYMER FILM [0002]

The present invention relates to a polyvinyl alcohol polymer film (hereinafter sometimes referred to as " PVA ") useful as an original film for producing a polarizing film, a polarizing film production method using the polarizing film, And a method for producing a PVA polymer film. The present invention also relates to a method for producing a PVA polymer film.

PVA polymer films have been used for various applications by using unique properties regarding transparency, optical properties, mechanical strength, water solubility and the like. In particular, recently, by using their excellent optical properties, a polarizing plate (Raw film) of a polarizing film constituting the polarizing film. In the field of liquid crystal monitors and liquid crystal televisions, a large-sized screen is rapidly proceeding. However, if there is a defect in the polarizing plate, the product can not be inserted into the product and the yield (product yield) is lowered. .

However, various techniques have been known up to now with respect to an optical film including not only a polarizing film but also a protective film and a retardation film. For example, when a thermoplastic resin such as polyester, polyamide, or polyolefin is heated to a melting point or higher to form a molten polymer, and the film is extruded and cooled from a spinneret to produce a film for use in optical applications, (Low polymer) is deposited on the surface of the film to adhere to the surface of the casting drum or the roll to become a surface defect of the film. The outer surface has a surface roughness of 1 S or less and a chromium atom A chromium-plated film containing 0.5 to 5% of carbon atoms in terms of the number of atoms of carbon atoms relative to the total mass of the chromium-plated film (see Patent Document 1). In Patent Document 1, polyethylene terephthalate is melted at 275 占 폚, extruded from a T-die, quenched into a casting drum cooled to 25 占 폚 to obtain a non-flat sheet, and then heated by a plurality of metal rolls disposed downstream of the casting drum Or a roll having a specific chromium-plated film as a part of the plurality of metal rolls when cooling is used.

In addition, a polymer resin film excellent in transparency and surface flatness, which is useful for optical applications, is obtained by eliminating surface defects (defects that are projected on the surface of a film) when a solution of the polymer resin solution is softened on a support, In order to achieve this, it is known that the number of defects of a specific size existing on the surface of a support to be used is set to a specific value or less (see Patent Document 2). In Patent Document 2, a solution prepared by dissolving an aromatic polycarbonate resin in a mixed solvent of ethanol and methylene chloride and a support having a specific surface property (a mirror-polished plate made of SUS-316) , And the solution is hand-coated on a support and dried to give an aromatic polycarbonate film.

Further, when an optical film is produced by a process for producing a flexible flexible film in which a thermoplastic resin (an alicyclic structure-containing polymer, a cellulose ester, or the like) on a film melt-extruded from an extruder is cooled by a cooling drum, As a means for eliminating the problem that external defects called "crushed scratches" are generated, by attaching an organic solvent to the surface of a cooling drum, and then wiping the surface of the cooling drum by means of cleaning, It is known to remove the contamination of the surface of the drum and then to attach the thermoplastic resin melt-extruded from the extruder to the surface portion of the cooling drum after the wiping to cool the optical film. (See Patent Document 3). In Patent Document 3, a mixture containing a hydrogenated product of a norbornene-based ring-opening polymer and cellulose acetate propionate is melt-extruded, and the resin melt of the film is extruded from a cooling drum (Vickers hardness chromium plating film having a hardness of 800 Having a surface or an amorphous chromium plated film surface having a Vickers hardness of 1200) and cooled and solidified while being conveyed to obtain a resin sheet.

Japanese Patent Application Laid-Open No. 9-207210 Japanese Patent Application Laid-Open No. 2000-84960 Japanese Laid-Open Patent Publication No. 2006-82261 Japanese Patent Publication No. 1-19477 Japanese Patent Application Laid-Open No. 2005-238833 Japanese Patent Application Laid-Open No. 9-1568 Japanese Patent Application Laid-Open No. 2001-315138

However, it has been difficult to manufacture a polarizing film or a polarizing plate having a few defects at a recently required level by merely adopting the above-described conventional technique. That is, in the method of Patent Document 1, it is necessary to heat the thermoplastic resin to the melting point or higher to obtain a molten polymer. However, the PVA polymer is not a thermoplastic resin except for a specific modified PVA polymer, It is difficult to adopt it in the production of a PVA polymer film, and even if it can be employed, a film having excellent surface characteristics can not be obtained. Further, as a method for producing a film of a PVA polymer film, there is a method for producing a film, in which a PVA polymer is dissolved in a liquid medium, a raw material for making a film containing a PVA polymer and a liquid medium, There is known a method of producing a film by pliability on a support to dry the film. However, this method is not a method of producing a film by cooling a molten polymer substantially not containing a liquid medium as described in Patent Document 1 on a casting drum Even if the PVA polymer film is produced by simply using the drum for producing a film described in Patent Document 1 and using the undiluted solution for forming a film to soften it on the drum for producing a film and drying it, A fine crack existing on the surface of the chromium-plated film of the drum for producing a film Can not sufficiently control defects caused by the PVA polymer film, and the polarizing plate or polarizing film produced using the obtained PVA polymer film can not sufficiently attain the recently required quality level.

On the other hand, Patent Document 2 relates to a film production method for casting a solution containing a polymer resin and a solvent as a main component on a support, followed by drying to remove the solvent. Although the method of Patent Document 2 is simply adopted, It is not possible to sufficiently control defects that are indentations from the surface of the film even if the defects caused by the projections can be solved and the polarizing plate or polarizing film produced using the obtained PVA polymer film can sufficiently attain the recently required quality level I can not.

Further, since the method of Patent Document 3 is to cool the melt of the thermoplastic resin with the cooling drum in the same manner as in the method of Patent Document 1, it is difficult to employ the method of Patent Document 3 in the production of the PVA polymer film, A film having excellent surface properties can not be obtained even if it can be employed. In addition, if the polishing means described in Patent Document 3 is simply adopted, a film-forming stock solution obtained by dissolving a PVA polymer in a liquid medium, a film-forming stock solution containing a PVA polymer and a liquid medium, , It is impossible to sufficiently control defects in the concave state even when the PVA polymer film is formed by pliability on a metal support and drying the film. Rather, the surface of the metal support is brought into contact with the surface of the metal support, And the surface properties of the obtained PVA polymer film may be rather deteriorated.

Under such circumstances, it is an object of the present invention to provide a PVA polymer film capable of producing a polarizing film having less defects and a polarizing plate at a good yield. The present invention also relates to a film roll in which a long PVA polymer film is continuously wound, in which the difference in surface characteristics from the winding start portion to the winding end portion of the PVA polymer film is small and thus a polarizing film having a stable quality can be produced. It is an object of the present invention to provide a film roll.

In many cases, the PVA polymer film is in the form of a film roll in which a long PVA polymer film is continuously wound because of ease of storage and transportation or that it can be used continuously. In such a film roll Wrinkles tend to occur in the film due to poor slip property between the films, and such wrinkles are liable to deteriorate the quality of the polarizing film to be produced. On the other hand, in the polarizing film, it is sometimes required to reduce uneven staining that is different from the above-mentioned defects. Another aspect of the present invention is to provide a PVA polymer film capable of easily producing a polarizing film in which wrinkles are less likely to occur in the film roll and further the staining unevenness is reduced and a film roll in which the PVA polymer film is continuously wound .

When a polarizing film is produced by using a PVA polymer film as an original film, the PVA polymer film is usually dyed, uniaxially oriented, fixed, and the like. In the case of uniaxially oriented film In the case of uniaxial stretching in the dyeing step or the fixing treatment step and in the case of uniaxial stretching in the wet state, in addition to these steps, in the swelling step before uniaxial stretching or in the uniaxial stretching step, a part of the PVA- And the eluted PVA polymer is precipitated in the treatment bath and adhered to the film or precipitated on the film to remain as a foreign substance in the resulting polarizing film to lower the quality and yield thereof. Therefore, it is an object of the present invention to provide a polarizing film producing method for producing such a polarizing film having a small amount of foreign substances, and a polarizing film produced by the method.

It is another object of the present invention to provide a method for producing a PVA polymer film which can easily produce a PVA polymer film or a film roll as described above.

As a result of intensive investigations to achieve the above object, the present inventors have found that when a PVA polymer film in a solution state or a molten state is plied and dried on the surface of a metal support such as a drum or a belt to dry the PVA polymer film , A foreign substance, which is considered to be a resin deposit, adheres to a very large part of a countless number of cracks existing on the surface of the metal support, and the convex shape is transferred to the film. Thus, a PVA polymer film And such a PVA polymer film has an increased number of defects in a polarizing film or a polarizing plate produced therefrom and can not sufficiently attain a recently required quality level or is associated with a decrease in the yield of a polarizing film or a polarizing plate And so on.

When a metal support having a chromium plated layer on its surface and having a surface hardness in a specific range is used, it is possible to obtain a metal support which is present on the surface of the metal support by a general treatment performed on the surface of the metal support, The number of cracks can be easily reduced and the number of defects that are indented from the surface of the obtained PVA polymer film can be reduced compared with the conventional case. When such a PVA polymer film is used as the original film for producing a polarizing film, It has been found that a polarizing film or a polarizing plate having few defects and satisfying a recently required quality level can be produced at a good yield.

Further, in addition to the above findings, when a metal support having a chromium plating layer on its surface and having a surface hardness in a specific range is used, even if a PVA polymer film is continuously formed over a long period of time, fluctuations in the number of defects Can be maintained at a level lower than that of the prior art. For example, when producing a film roll in which a long PVA polymer film is continuously wound, the surface property of the PVA polymer film from the winding start portion to the winding end portion It is possible to easily obtain a polarizing film having a stable quality and a film roll capable of producing a polarizing plate.

When a metal support having a chromium plating layer on its surface and having a surface hardness in a specific range is used, a PVA polymer film having surface characteristics of both sides of the film in a specific range is easily obtained, and the PVA polymer film A wrinkle is not easily generated in the film roll which is wound up continuously, the deterioration of the quality of the polarizing film can be suppressed, the polarizing film in which staining unevenness is reduced can be easily obtained by the PVA polymer film, It has been found that when a polarizing film is produced by a specific method using a polymer film, a polarizing film having a small amount of foreign substances can be easily obtained.

The inventors of the present invention have conducted further studies based on such findings and completed the present invention.

That is,

[1] A PVA polymer film having an area of not less than 400 탆 ² and a depth of not less than 0.3 탆 and a number of defects not larger than 0.25 number / m ² as the indentation defects (hereinafter referred to as " PVA polymer film ) &Quot;);

[2] The PVA polymer film of [1], wherein the number of defects is 0.15 / m 2 or less;

[3] The PVA polymer film of [1] or [2], wherein the PVA polymer contained in the PVA polymer film has a degree of polymerization of 3,000 or more and 10,000 or less;

[4] A PVA polymer film according to any one of [1] to [3], which is a long PVA polymer film;

[5] The PVA polymer film of [4], wherein the PVA polymer film has a length of 6,000 m or more;

[6] The PVA polymer film according to the above [4] or [5], wherein the defects include defects in which the defects are substantially uniformly spaced in the longitudinal direction of the film and exist at substantially the same position in the width direction of the film.

[7] A film roll comprising an elongated PVA polymer film wound continuously, characterized in that the film has a surface area of 400 μm ² or more and a depth of 0.3 μm or more as a depressed defect from the film surface, (Hereinafter, this film roll may be referred to as " film roll (1) " in some cases) having a number of such defects at the winding end portion of the PVA polymer film relative to the number of defects in the film roll at 1.4 times or less;

[8] The film roll according to the above [7], wherein the number of defects is 0.25 / m 2 or less;

[9] The film roll according to the above [7], wherein the number of defects is 0.15 / m 2 or less;

[10] The film roll according to any one of [7] to [9], wherein the PVA polymer contained in the PVA polymer film has a degree of polymerization of 3,000 or more and 10,000 or less;

[11] The film roll according to any one of the above [7] to [10], wherein the length of the PVA polymer film is 6,000 m or more;

[12] The film roll according to any one of [7] to [11], wherein the defects include defects in which the defects are substantially uniformly spaced in the longitudinal direction of the film and exist at substantially the same position in the width direction of the film.

[13] A PVA polymer film (hereinafter referred to as a "PVA film") having a square-root mean square roughness of 0.3 nm or more and 10 nm or less and a square-root mean square roughness of 10 nm or less , This PVA polymer film is sometimes referred to as " PVA polymer film (2) ");

[14] The PVA polymer film according to the above [13], wherein the larger square mean roughness is 1 nm or more and 20 nm or less;

[15] A PVA polymer film according to the above [13] or [14], which is a long PVA polymer film;

[16] A film roll in which the PVA polymer film of the above-mentioned [15] is continuously wound (hereinafter, this film roll may be referred to as "film roll 2");

[17] A method for producing a polarizing film using a PVA polymer film as described in any one of [13] to [15] above as a disc film, comprising a dyeing step, a uniaxial stretching step, a fixing treatment step and a drying step, Wherein an angle formed between the liquid surface of the treatment bath and the film surface is not less than 30 degrees and not more than 85 degrees and a surface on the upper side of the film is a polyvinyl alcohol polymer film having a smaller A method of producing a surface having a root mean square roughness;

[18] A polarizing film produced by the method of [17] above;

A PVA polymer having a chromium plating layer on its surface and having a surface hardness of not less than 550 HV and not more than 900 HV at Vickers hardness and a surface temperature of not lower than 50 ° C but not higher than 115 ° C, A method for producing a PVA polymer film having a process of producing a PVA polymer film by softening and drying, characterized in that, immediately before starting to soften the PVA polymer in a solution state or a molten state, The number of cracks having a diameter of 200 mu m < ² > or more is 0.7 pieces / mm < ² > or less;

[20] The production method of the above-mentioned [19], wherein the PVA polymer in a solution state or a molten state is in the form of a film-forming stock solution containing a PVA polymer and water;

[21] The production method of the above [19] or [20], wherein the PVA polymer has a degree of polymerization of 3,000 or more and 10,000 or less;

[22] The production method of any one of [19] to [21], wherein the surface hardness of the metal support is 600 HV or more and less than 800 HV by Vickers hardness;

[23] A process for producing a metal support having a chromium plating layer on its surface and a surface hardness of not less than 550 HV and not more than 900 HV in terms of Vickers hardness at a temperature of not less than 50 ° C and not more than 115 ° C at a rate of 0.5 ° C / ] To [22];

[24] A method for producing a PVA polymer film according to any one of [19] to [23], wherein the PVA polymer film of any one of [1] to [6] and [13]

.

According to the present invention, it is possible to provide a PVA polymer film capable of producing a polarizing film having less defects and a polarizing plate at a good yield. Further, according to the present invention, as a film roll in which a long PVA polymer film is continuously wound, the difference in surface characteristics from the winding start portion to the winding end portion of the PVA polymer film is small, so that a polarizing film having a stable quality can be obtained. A film roll which is capable of providing a film can be provided.

Further, according to the present invention, it is possible to provide a PVA polymer film which can easily produce a polarizing film in which wrinkles are not easily generated in the film roll and the staining unevenness is reduced, a film roll in which the polarizing film is wound by continuous winding, It is possible to provide a polarizing film producing method for producing a polarizing film and a polarizing film having a small amount of foreign substances produced thereby.

Further, according to the present invention, it is possible to provide a method for producing a PVA polymer film which can easily produce the above-mentioned PVA polymer film or film roll.

Hereinafter, the present invention will be described in more detail.

[PVA polymer film (1)]

The PVA polymer film (PVA polymer film (1)) of the present invention has a defect which is a recessed defect from the surface of the film and has an area of not less than 400 μm ² and a depth of not less than 0.3 μm (hereinafter referred to as "defect A" ) Is 0.25 pieces / m 2 or less. Defects present in the plastic film include voids (bubbles) in the film; So-called fish eyes due to the incorporation and attachment of foreign substances; Scratches (mostly spherical depressions) that occur during handling of the film; And the defect caused by the transfer of the convex shape on the film production apparatus. The inventors of the present invention have found that when the number of the defects A is specifically controlled, excellent effects such as a polarizing film or a polarizing plate with few defects can be produced at a good yield I found what appeared. This defect A is considered to be one of the causes of the transfer of the convex shape on the above-mentioned film production apparatus. In particular, when a PVA polymer film is produced by using a metal support such as a drum or a belt as described later, It is considered that one of the causes is that the convex shape due to the foreign substance considered as the resin deposit adhered on the metal support is transferred to the film. When a defect A is generated in a long PVA polymer film due to such a cause, it is preferable that at least a part of the defect A is formed at a substantially constant interval in the longitudinal direction of the film and at a substantially same position in the width direction of the film For example, three or more). Here, the above-mentioned substantially constant interval typically corresponds to the length of one week (total circumference length) of a metal support such as a drum or a belt, but in some cases corresponds to an integral multiple of the length of one week There is also. Further, since a plurality of convex shapes by foreign substances can be formed on the metal support, there can be a plurality of groups of defects A arranged as described above.

As described above, in the PVA polymer film (1) of the present invention, the number of defects A needs to be 0.25 / m 2 or less. If the number of defects A exceeds 0.25 number / m 2, the number of defects in a polarizing film or a polarizing plate produced therefrom increases, so that a quality level required recently can not be sufficiently attained, or a polarizing film having many defects or a polarizing plate Which leads to a reduction in yield of these products. From this point of view, the number of defects A is preferably 0.20 pieces / m 2 or less, more preferably 0.15 pieces / m 2 or less, more preferably 0.10 pieces / m 2 or less, and particularly preferably 0.075 pieces / m 2 or less.

On the other hand, the lower limit of the number of defects A is not necessarily limited. However, in order to extremely reduce the number of defects A, there is a possibility that the cost for installing the film manufacturing facility becomes extremely high. Is preferably 0.001 number / m 2 or more, more preferably 0.003 number / m 2 or more, and still more preferably 0.005 number / m 2 or more.

Defect A is a defective defect which is indented from the film surface and has an area of 400 탆 ² or more and a depth of 0.3 탆 or more. In this case, the defect A may be indented from either one of the two sides of the film toward the inside of the film. Usually, most of the defect A is a depression from the side in contact with the metal support, It is flawed. The area of the defect A means the area of the opening of the defect A. The depth of the defect A means the depth at the deepest position as the depth in the direction perpendicular to the film surface from the opening of the defect A.

The number of defects A (units / m 2) is determined by looking at defect A from one end of the PVA polymer film to be examined, and determining the area (unit (M < 2 >) by dividing 10 (pieces), and specifically, it can be obtained by the method described later in Examples. Here, whether or not each defect is defect A can be determined using a non-contact surface shape measuring device.

The shape of the PVA polymer film (1) is not particularly limited, but it is preferable that the polarizing film can be continuously produced with good productivity, for example, when the PVA polymer film (1) is used as a original film for producing a polarizing film , It is preferable that the film is a long PVA polymer film.

The length of the elongated PVA polymer film is not particularly limited and may be suitably set according to the use of the PVA polymer film (1). Specifically, the length is preferably 1,000 m or more, more preferably 4,000 m or more More preferably 6,000 m or more, particularly preferably 7,000 m or more, and most preferably 8,000 m or more. Particularly, according to the method for producing a PVA polymer film described later, the number of defects A in the PVA polymer film can be reduced, and even when the PVA polymer film is continuously formed over a long period of time, It is possible to easily obtain a PVA polymer film in which the number of defects A is reduced even when the length is longer (for example, 6,000 m or more). With such a longer PVA polymer film, it is possible to stably produce a product satisfying the recently required quality level for a long period of time at a satisfactory yield due to few defects when the polarizing film is continuously produced, It is possible to reduce the complexity and the time loss accompanying the replacement of the film roll. The upper limit of the length of the elongated PVA polymer film is not particularly limited. However, when the length is too long, the handling and handling of the PVA polymer film may deteriorate due to excessive weight or roll diameter, Is preferably 30,000 m or less, more preferably 25,000 m or less, and even more preferably 20,000 m or less.

The width of the elongated PVA polymer film is not particularly limited and may be 0.5 m or more, for example. In view of the recent demand for a polarizing film for a violet light, it is preferably 1 m or more, more preferably 2 m or more And more preferably 4 m or more. There is no particular limitation on the upper limit of the width of the elongated PVA polymer film. However, if the width is excessively wide, there is a tendency that uniform elongation becomes difficult in the case of producing a polarizing film by a practical apparatus , And the width of the PVA polymer film is preferably 7 m or less.

The thickness of the PVA polymer film (1) is not particularly limited and may be suitably set according to the use of the PVA polymer film. Specifically, the thickness is preferably 300 탆 or less, more preferably 150 탆 or less, Mu m or less. Further, in recent years, a thinner polarizing film is sometimes required. In view of this, the thickness of the PVA polymer film 1 is preferably 45 탆 or less, more preferably 35 탆 or less, and more preferably 25 탆 or less More preferable. There is no particular limitation on the lower limit of the thickness of the PVA polymer film 1, but the thickness is preferably 3 占 퐉 or more, and more preferably 5 占 퐉 or more, because the polarizing film can be produced more smoothly.

As the PVA polymer constituting the PVA polymer film (1), those produced by saponifying a vinyl ester polymer obtained by polymerizing a vinyl ester monomer can be used. Examples of the vinyl ester-based monomer include vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl pivalate and vinyl versatate. Among them, vinyl acetate is preferable.

The above-mentioned vinyl ester polymer is preferably obtained by using only one kind or two or more kinds of vinyl ester-based monomers as monomers, more preferably one obtained by using only one kind of vinyl ester-based monomer as monomers, Or a copolymer of the above-mentioned vinyl ester-based monomer and other monomers copolymerizable therewith.

Other monomers copolymerizable with such vinyl ester-based monomers include, for example, ethylene; Olefins having 3 to 30 carbon atoms such as propylene, 1-butene and isobutene; Acrylic acid or a salt thereof; Acrylic acid esters such as methyl acrylate, ethyl acrylate, n-propyl acrylate, i-propyl acrylate, n-butyl acrylate, i-butyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate and octadecyl acrylate; 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, 2- Methacrylic acid esters such as ethylhexyl, undecyl methacrylate and octadecyl methacrylate; Acrylamide, N-methylacrylamide, N-ethyl acrylamide, N, N-dimethylacrylamide, diacetone acrylamide, acrylamidepropanesulfonic acid or salts thereof, acrylamidopropyldimethylamine or salts thereof, An acrylamide derivative such as an amide or a derivative thereof; Methacrylamide, N-methyl methacrylamide, N-ethyl methacrylamide, methacrylamide propanesulfonic acid or a salt thereof, methacrylamide propyldimethylamine or a salt thereof, N-methylol methacrylamide or a derivative thereof Acrylamide derivatives; N-vinyl amides such as N-vinyl formamide, N-vinylacetamide and N-vinyl pyrrolidone; Vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, n-butyl vinyl ether, i-butyl vinyl ether, t-butyl vinyl ether, dodecyl vinyl ether and stearyl vinyl ether Ether; Vinyl cyanide such as acrylonitrile and methacrylonitrile; Vinyl halides such as vinyl chloride, vinylidene chloride, vinyl fluoride and vinylidene fluoride; Allyl compounds such as allyl acetate and allyl chloride; Maleic acid or its salt, ester or acid anhydride; Itaconic acid or its salt, ester or acid anhydride; Vinylsilyl compounds such as vinyltrimethoxysilane; Isopropenyl acetate, and isopropenyl acetate. The above-mentioned vinyl ester-based polymer may have a structural unit derived from one kind or two or more kinds of these other monomers.

The proportion of the structural unit derived from the other monomer in the vinyl ester polymer is not particularly limited, but is preferably 15 mol% or less based on the number of moles of all the structural units constituting the vinyl ester polymer, % Or less.

The polymerization degree of the PVA polymer is not limited, but is preferably 200 or more, more preferably 300 or more, further preferably 400 or more, particularly preferably 400 or more, from the standpoint of lowering the film strength as the polymerization degree is lowered 500 or more. When the degree of polymerization is too high, the viscosity of the aqueous solution or the molten PVA polymer tends to be high, and the film tends to be difficult to be produced. Therefore, it is preferably 10,000 or less, more preferably 9,000 or less, still more preferably 8,000 or less Preferably 7,000 or less. Here, the degree of polymerization of the PVA polymer means an average degree of polymerization measured according to the description of JIS K6726-1994. The degree of polymerization of the PVA polymer is measured by measuring the intrinsic viscosity [?] (Unit : Deciliter / g) by the following equation.

Polymerization degree = ([?] X 10 ³ /8.29) ^{(1 / 0.62)}

When a PVA polymer film is produced using a PVA polymer having a degree of polymerization of 3,000 or more and 10,000 or less by a method to be described later, a PVA polymer film having a very small number of defects A is obtained, and a PVA polymer The variation of the number of defects A can be maintained at a lower level even if the film is continuously formed over a long period of time. From such a viewpoint, the degree of polymerization of the PVA polymer is more preferably 4,000 or more, and still more preferably 5,000 or more. The reason why the above effect is exhibited by using the PVA polymer having a polymerization degree in the range of 3,000 or more and 10,000 or less is not necessarily clear, but the number of defects A in the PVA polymer film is not limited to the number of cracks Is considered to increase as the PVA polymer in a solution state or a molten state is more likely to be introduced into the PVA polymer. When the PVA polymer having the above polymerization degree is used, it is presumed that this is suppressed.

There is no particular limitation on the degree of saponification of the PVA polymer, and for example, a PVA polymer of 60 mol% or more can be used. However, when the PVA polymer film is used as an original film for producing optical films, The saponification degree of the PVA polymer is preferably 95 mol% or more, more preferably 98 mol% or more, and further preferably 99 mol% or more. Here, the saponification degree of the PVA polymer refers to the total mole number of the structural unit (typically vinyl ester monomer unit) and the vinyl alcohol unit which can be converted into the vinyl alcohol unit by saponification of the PVA polymer and the total mole number of the vinyl alcohol unit (Mole%) occupied by the number of moles. The degree of saponification of the PVA polymer can be measured according to the description of JIS K6726-1994.

In producing the PVA polymer film (1), one type of PVA polymer may be used alone, or two or more kinds of PVA polymers differing from each other in one or more of polymerization degree, saponification degree, Or may be used in combination. The content of the PVA polymer in the PVA polymer film (1) is preferably 50 mass% or more, more preferably 70 mass% or more, and further preferably 85 mass% or more.

The PVA polymer film (1) preferably contains a plasticizer. By including the plasticizer in the PVA polymer film (1), it is possible to prevent the occurrence of wrinkles in the film roll or improve the processability in the secondary processing. As the plasticizer, a polyhydric alcohol is preferable, and specific examples thereof include ethylene glycol, glycerin, diglycerin, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, trimethylolpropane and the like. These plasticizers may be used alone or in combination of two or more. Of these plasticizers, ethylene glycol or glycerin is preferred from the viewpoint of compatibility with the PVA polymer and availability.

The content of the plasticizer in the PVA polymer film (1) is preferably within a range of 1 to 30 parts by mass, more preferably within a range of 3 to 25 parts by mass, and still more preferably 5 to 20 parts by mass, relative to 100 parts by mass of the PVA polymer More preferably within the range of.

The PVA polymer film (1) preferably contains a surfactant from the viewpoints of improving the peelability from the metal support used for its production and improving the handling property of the PVA polymer film. The kind of the surfactant is not particularly limited, but anionic or nonionic surfactant can be preferably used.

Examples of the anionic surfactant include a carboxylic acid type such as potassium laurate, a sulfuric acid ester type such as octyl sulfate, and a sulfonic acid type such as dodecylbenzenesulfonate.

Examples of the nonionic surfactant include alkyl ether types such as polyoxyethylene oleyl ether and the like, alkylphenyl ether types such as polyoxyethylene octylphenyl ether and the like, alkyl ester types such as polyoxyethylene laurate, Alkylamines such as ethylene lauryl amino ether, alkyl amides such as polyoxyethylene lauryl amide, polypropylene glycol ether types such as polyoxyethylene polyoxypropylene ether, lauric acid diethanol amide, oleic acid diethanol amide, etc. , And allylphenyl ether types such as polyoxyalkylene allylphenyl ether.

These surfactants may be used singly or in combination of two or more.

The content of the surfactant in the PVA polymer film (1) is preferably in the range of 0.01 to 1 part by mass with respect to 100 parts by mass of the PVA polymer, from the viewpoints of the releasability from the metal support and the handleability of the PVA polymer film More preferably in the range of 0.02 to 0.5 part by mass, and still more preferably in the range of 0.05 to 0.3 part by mass.

The PVA polymer film (1) may further contain other components than the above-mentioned PVA polymer, plasticizer, and surfactant, if necessary. Such other components include, for example, water, an antioxidant, an ultraviolet absorber, a lubricant, a colorant, a filler (inorganic particles, starch and the like), a preservative, .

[Film roll (1)]

The film roll (film roll (1)) of the present invention is a film roll in which an elongated PVA polymer film is continuously wound, in which the PVA polymer film starts to be wound (The film portion when the winding of the PVA polymer film is finished by winding the PVA polymer film) with respect to the number of the defects A in the film portion of the PVA polymer film The number is 1.4 times or less. In such a film roll, since the difference in surface characteristics from the winding start portion to the winding end portion of the PVA polymer film is small, according to the film roll, it is possible to produce a polarizing film having a stable quality and hence a polarizing plate. From this viewpoint, the number of the defects A in the winding end portion of the PVA polymer film relative to the number of the defects A in the winding start portion of the PVA polymer film is preferably 1.3 times or less, more preferably 1.2 times or less More preferably 1.1 times or less. In addition, since the number of defect A tends to increase over time in the production of a long PVA polymer film, the number of defects A in the PVA polymer film relative to the number of the defect A in the beginning of winding of the PVA polymer film The number of the defects A in the winding end portion of the polymer film is usually not less than 0.6 times and in view of producing a polarizing film having a stable quality and a polarizing plate, The number of the defects A in the winding end portion of the PVA polymer film relative to the number of the defects A in the film is preferably 0.7 or more, more preferably 0.75 or more, still more preferably 0.8 or more, 0.9 times or more.

In the PVA polymer film in the film roll (1) of the present invention, the number of defects A per unit area is not particularly limited, but the number of defects A in the PVA polymer film (1) M 2 or less (preferably about 0.20 / m 2 or less, more preferably about 0.15 / m 2 or less, and even more preferably about 0.10 / m 2 or less for the upper limit) M 2 or more, and more preferably 0.005 number / m 2 or more) with respect to the lower limit, the polarizing film is preferably used in an amount of 0.001 / m 2 or more, more preferably 0.005 / In the case of continuous production, it is preferable because there are few defects and it is possible to stably produce a product satisfying the recently required quality level over a long period of time at a good yield. When the number of defects A per unit area satisfies the above-mentioned number in both the winding start portion and the winding end portion of the PVA polymer film, the total number of defects A in the entire PVA polymer film is satisfied I can think.

The length (winding length) of the PVA polymer film used in the film roll 1 of the present invention is not particularly limited and may be suitably set according to the use of the PVA polymer film, and specifically, the length is preferably 1,000 m or more . In recent years, however, PVA polymer films longer than the conventional length of about 4,000 m have been required in order to reduce complications and time loss involved in the replacement of film rolls in the production of polarizing films, The length of the PVA polymer film is preferably 6,000 m or more, more preferably 7,000 m or more, and more preferably 7,000 m or more in view of stabilizing the quality of the product even if a polarizing film is continuously produced over a long period of time by using the PVA polymer film. More preferably 8,000 m or more. The upper limit of the length of the elongated PVA polymer film is not particularly limited. However, when the length is too long, the handling property may be lowered, such as excessively increasing the weight or the roll diameter, It is preferable that the length is 30,000 m or less, more preferably 25,000 m or less, and even more preferably 20,000 m or less. In addition, if the length is 14,000 m or less, and more preferably 10,000 m or less, the production of the film roll satisfying the requirements of the present invention becomes easier.

The other constitution of the PVA polymer film used in the film roll (1) of the present invention is the same as the above description as the description of the PVA polymer film (1) of the present invention. Description will be omitted.

The film roll (1) of the present invention is formed by continuously winding a long PVA polymer film, and for example, a long PVA polymer film is continuously wound on a cylindrical core. In the case where a cylindrical core is used, it is preferable that both ends of the core form protrusions protruding from the end face of the film roll.

There is no particular limitation on the type of the above-mentioned cylindrical core, and examples thereof include metal, plastic, paper, and wood. In addition, composite type cores such as those using both metal and plastic, those using both metal and paper, and those using both plastic and paper can also be used. Of these, cores made of metals and / or plastics are preferable in view of strength, durability and low emissivity, and metal cores are more preferable because they are not easily affected by wear or the like even if they are repeatedly used. Examples of the metal include iron, stainless steel, and aluminum. One of these metals may be used alone, or two or more metals may be used in combination. Examples of the plastic include polyvinyl chloride, polyvinylidene chloride, polyester, polycarbonate, polyamide, epoxy resin, polyurethane, polyurea, silicone resin and the like. Of these, May be used alone, or two or more of them may be used in combination. Further, the plastic may be fiber reinforced plastic (FRP) such as carbon fiber reinforced plastic from the viewpoint of strength and the like.

[PVA polymer film (2)]

The PVA polymer film (PVA polymer film (2)) of the present invention is characterized in that when the root mean square roughness of each film is measured on both sides of the film, the difference in the resultant two root mean square roughness is 0.3 nm or more and 10 nm or less, Side has a root mean square roughness of 10 nm or less. In the conventional film roll in which the PVA polymer film is continuously wound, wrinkles easily occur in the film due to defective slip between the films. According to the PVA polymer film (2) of the present invention, . The wrinkles of the film roll are affected by the stress that is generated when the PVA polymer film is wound, and when the film is once stored in the film roll and stored in a warehouse or the like, the film remains in the PVA polymer film, , And the PVA polymer film (2) of the present invention can effectively reduce the occurrence of wrinkles of the former, but can also reduce the occurrence of the latter wrinkles. In addition, according to the PVA polymer film (2) of the present invention, a polarizing film with reduced staining unevenness different from the above-mentioned defects can be easily produced.

The root mean square roughness in the present invention means the root mean square roughness (Rq) described in JIS B0601: 2001, and is obtained by averaging the square of the deviation from the average roughness curve to the roughness curve in the roughness curve obtained from the surface of the film . The square mean roughness of each of both surfaces of the PVA polymer film can be measured by the method described later in Examples.

In the PVA polymer film (2) of the present invention, when the square mean roughness is measured on each of both surfaces of the film, the difference in the obtained two mean square roughnesses must be 0.3 nm or more and 10 nm or less. The difference between the two is 0.3 nm or more, so that occurrence of wrinkles in the film roll can be effectively reduced. On the other hand, since the difference therebetween is 10 nm or less, it is possible to effectively reduce staining unevenness in the polarizing film. From such a viewpoint, the difference between the two is preferably 0.5 nm or more, more preferably 0.8 nm or more, still more preferably 1.2 nm or more, particularly preferably 1.5 nm or more, most preferably 2 nm or more, Or less, and more preferably 5 nm or less.

In the PVA polymer film (2) of the present invention, the smaller square mean roughness of the film should be 10 nm or less. And the smaller square-average roughness is smaller than 10 nm, it is possible to effectively reduce staining unevenness in the polarizing film. From such a viewpoint, the smaller the root mean square roughness is preferably 8 nm or less, more preferably 6 nm or less, and further preferably 4 nm or less. In addition, in order to extremely lower the root mean square roughness, it is necessary to perform special processing, and the production cost of the PVA polymer film tends to increase. Therefore, the smaller root mean square roughness is preferably 0.3 nm or more, More preferably 0.9 nm or more, and particularly preferably 1.2 nm or more.

In the PVA polymer film (2), it is preferable that the larger square mean roughness is 1 nm or more and 20 nm or less. The square-root mean roughness of the larger side is 1 nm or more, so that occurrence of wrinkles in the film roll can be more effectively reduced. On the other hand, since the square-averaged roughness on the larger side is 20 nm or less, unevenness in dyeing in the polarizing film can be more effectively reduced. From this viewpoint, the square-root mean roughness of the larger one is more preferably 2 nm or more, still more preferably 4 nm or more, further preferably 15 nm or less, still more preferably 11 nm or less, And most preferably 6 nm or less.

The shape of the PVA polymer film (2) is not particularly limited, but it is preferable that the polarizing film can be continuously produced with good productivity, for example, when the PVA polymer film (2) is used as a original film for producing polarizing films , It is preferable that the film is a long PVA polymer film.

The length of the elongated PVA polymer film is not particularly limited and may be suitably set according to the use of the PVA polymer film (2). Specifically, the length is preferably 1,000 m or more, more preferably 4,000 m or more More preferably 6,000 m or more, particularly preferably 7,000 m or more, and most preferably 8,000 m or more. With such a longer PVA polymer film, it is possible to reduce troubles and time loss accompanying replacement of the film roll. The upper limit of the length of the elongated PVA polymer film is not particularly limited. However, when the length is too long, the handling and handling of the PVA polymer film may deteriorate due to excessive weight or roll diameter, Is preferably 30,000 m or less, more preferably 25,000 m or less, and even more preferably 20,000 m or less. One of the causes of the wrinkles to be generated when the film roll is stored is the winding by the residual stress in the PVA polymer film. This winding is stronger in the longer and wider PVA polymer film The effect of the present invention is more conspicuous in a longer PVA polymer film.

The width of the elongated PVA polymer film is not particularly limited and may be 0.5 m or more, for example. In view of the recent demand for a polarizing film for a violet light, it is preferably 1 m or more, more preferably 2 m or more And more preferably 4 m or more. There is no particular limitation on the upper limit of the width of the elongated PVA polymer film. However, if the width is excessively wide, there is a tendency that uniform elongation becomes difficult in the case of producing a polarizing film by a practical apparatus , And the width of the PVA polymer film is preferably 7 m or less. In addition, as described for the length of the PVA polymer film, since the winding is likely to appear strongly in a longer and wider PVA polymer film, the effect of the present invention can be obtained in a wider PVA polymer film It is remarkable.

The thickness of the PVA polymer film (2) is not particularly limited and may be suitably set according to the use of the PVA polymer film. Specifically, the thickness is preferably 300 탆 or less, more preferably 150 탆 or less, Mu m or less. Further, in recent years, a thinner polarizing film is sometimes required. In view of this, the thickness of the PVA polymer film 2 is preferably 45 탆 or less, more preferably 35 탆 or less, and more preferably 25 탆 or less More preferable. There is no particular limitation on the lower limit of the thickness of the PVA polymer film 2, but the thickness is preferably 3 占 퐉 or more, more preferably 5 占 퐉 or more, because the polarizing film can be produced more smoothly. Further, since the wrinkles in the film roll are more likely to occur as the thickness of the PVA polymer film is thinner, the effect of the present invention is more remarkably exhibited in a thinner PVA polymer film.

Other constitutions relating to the PVA polymer film (2) of the present invention are the same as those described above as the description of the PVA polymer film (1) of the present invention, and therefore duplicate explanations are omitted here.

The method for producing the PVA polymer film (2) is not particularly limited, but the method for producing the PVA polymer film of the present invention described later is preferable because the intended PVA polymer film (2) can be easily produced . In this case, the side facing the surface of the metal support tends to be a surface having a larger square-averaged roughness. In addition to the above-mentioned production method, there is also a method of passing the PVA polymer film produced between the metal rolls having different surface roughness, or a method of passing the foreign material (deteriorated resin, Nation, etc.) are removed by using a filter or the like, and ultrafine particles of an inorganic material are added to the stock solution for film production to prepare a film on a smooth surface to adjust the square-root mean roughness of both surfaces.

[Film roll (2)]

The film roll (film roll (2)) of the present invention is obtained by continuously winding a long PVA polymer film as the above PVA polymer film (2). For example, a PVA polymer film 2), a long PVA polymer film is continuously wound. In the case where a cylindrical core is used, it is preferable that both ends of the core form protrusions protruding from the end face of the film roll. As the core, the above-described film roll 1 can be used, and a repetitive description thereof will be omitted.

Other constitutions of the film roll 2 of the present invention can be made the same as those described above as the description of the film roll 1 of the present invention.

In the film roll (2) of the present invention, it is possible to reduce occurrence of wrinkles which are likely to occur when the conventional film roll is stored. The temperature at which the film roll is stored is preferably not higher than 40 ° C, more preferably not higher than 35 ° C, and even more preferably not higher than 30 ° C from the viewpoint of excessively high PVA polymer film being deformed to easily cause wrinkles . On the other hand, there is no particular limitation on the lower limit of the temperature at the time of storing the film roll, but the temperature is preferably -10 ° C or higher, more preferably -5 ° C or higher, and still more preferably 0 ° C or higher.

[Production method of PVA polymer film]

The production method of the present invention for producing a PVA polymer film is characterized in that the surface of a metal support having a chromium plating layer on its surface and having a surface hardness of 550 HV to 900 HV at Vickers hardness and a surface temperature of 50 캜 to 115 캜 , And a step of softening and drying the PVA polymer in a solution state or a molten state to produce a film. The number of cracks having a surface area (a product of a maximum width and a maximum end distance) of 200 mu m ² or more on the surface of the metal support immediately before starting to soften the PVA polymer in a solution state or a molten state is 0.7 / to be. According to this production method, the PVA polymer film (PVA polymer film (1) and (2)) of the present invention or the film roll (film rolls (1) and (2) It is possible to easily produce a long PVA polymer film to be wound.

Examples of the metal support used in the present invention include a drum and a belt, and a chromium plated layer is provided on the surface. Here, the surface of the metal support means a surface (film production surface) on which a PVA polymer in a solution state or a molten state is flexible, and in the case where the metal support is a drum, a chromium plating layer may be provided on the outer peripheral surface of the drum. It is sufficient if the outer surface of the continuous surface of the belt has a chromium plating layer.

Thickness of the chromium plating layer is not particularly limited, but is preferably within a range of 10 占 퐉 to 500 占 퐉, because corrosion of the surface of the metal support can be more effectively prevented and the number of cracks to be described later can be easily reduced. The chromium plating layer may be formed at one time or may be divided into a plurality of circuits. For example, when the chromium plating layer is divided into a plurality of circuits, the chromium plating layer is once formed, Or the like, and a chromium plating layer may be further formed thereon. In this manner, the pinhole of the chromium plating layer can be reduced. Further, as described in Patent Document 4 and the like, if a nickel plating layer is formed under the chromium plating layer, the crack in the chromium plating layer can be further reduced.

In the metal support having a chromium plating layer on its surface, its surface hardness needs to be 550 HV or more and less than 900 HV in Vickers hardness. Although a metal support having a general chromium plating layer is known (see, for example, Patent Documents 4 to 7 and the like), when a metal support having a specific surface hardness such as the present invention is used, the reason is unknown. It is possible to easily reduce the number of cracks existing on the surface of the metal support by the general treatment carried out on the surface of the metal support before the start of the production and to reduce the number of said defects A in the resulting PVA polymer film Moreover, even if the PVA polymer film is continuously formed over a long period of time, the variation of the number of defects A can be maintained at a level lower than that of the prior art. Further, the square mean roughness of both sides of the film can be adjusted to a desired range. When the surface hardness is 900 HV or more in terms of Vickers hardness, it is difficult to reduce the number of cracks present on the surface of the metal support, and when the PVA polymer film is continuously formed for a long time, The variation of the number becomes large. In addition, the square mean roughness of both sides of the film tends to deviate from the desired range. In view of the above, the surface hardness is preferably Vickers hardness of less than 800 HV, more preferably less than 780 HV. On the other hand, if the surface hardness is less than 550 HV in terms of Vickers hardness, problems such as scratches are liable to be caused at the time of production of a continuous film or at the time of cleaning of the surface of a metal support, and when a PVA polymer film is continuously formed The variation of the number of defects A is also large. In addition, the square mean roughness of both sides of the film tends to deviate from the desired range. From this point of view, the surface hardness is preferably 600 HV or higher, more preferably 650 HV or higher, and even more preferably 700 HV or higher, in Vickers hardness.

The surface hardness of the metal support can be determined by measuring the Vickers hardness of the surface of the chromium plating layer at a plurality of points using a hardness tester or the like and averaging them. The measurement of the surface hardness (Vickers hardness) may be carried out on the surface (film production surface) on which the PVA polymer in a solution state or a molten state is flexible, and the quality of the PVA polymer film (Film production surface) where the PVA polymer in a solution state or a molten state is soft, such as a portion where a chromium plating layer is formed at the end portion of the drum or the belt, or in a solution state or a molten state Even when the PVA polymer of the PVA polymer is flexible (film production surface), the surface hardness is measured at the surface corresponding to the film portion removed by the cut-off after the production of the film, . Specifically, the surface hardness of the metal support can be obtained by the method described later in Examples.

The adjustment of the surface hardness of the metal support having the chromium plating layer on its surface can be easily carried out by a known method. Specifically, a method of adjusting the temperature of the chromium plating bath used for chromium plating treatment to a specific range ; A method of adjusting the current density at the chromium plating treatment within a specific range; A method of adjusting the composition of a chromium plating bath; And a method of adjusting the concentration of hydrogen occluded in the chromium plating layer by heat treatment (annealing) or exposure to hydrogen gas after the chromium plating treatment. Of these, a method of adjusting the temperature of the chromium plating bath within a specific range in terms of simplicity of operation and the like; A method of adjusting the current density at the chromium plating treatment within a specific range; A method of adjusting the concentration of hydrogen occluded in the chromium plating layer after the chromium plating treatment is preferable and a method of adjusting the temperature of the chromium plating bath to a specific range is more preferable. With respect to the above-mentioned method, a chromium-sulfuric acid aqueous solution, which is a general chromium plating bath, is used, and the temperature of the chromium plating bath is set within a range of 40 캜 to 70 캜 and a current density of 60 A / Taking the chromium plating treatment as an example, the higher the temperature of the chromium plating bath and the lower the current density, the lower the surface hardness is generally lowered. With respect to the hydrogen concentration stored in the chromium plating layer, the surface hardness tends to be generally lower as the temperature of the heat treatment is increased or the treatment time is increased and the concentration thereof is lowered.

The method of forming the chromium plating layer is not particularly limited as long as the method can form a metal support having a surface hardness satisfying the above range. Known methods can be employed. Typically, the surface of the metal support Is subjected to abrasion treatment such as buffing or glaine polishing to remove roughness of the surface as much as possible and then to undergo treatment such as immersion degreasing, electrolytic degreasing, immersion in an aqueous hydrochloric acid solution, and then chromium plating And further heat treatment is exemplified. As the chromium plating bath, a sergeant bath is typical and can be preferably used. Examples of the composition of the chlorine-containing bath and chromium plating treatment are shown below.

<Composition of Sergeant Bath>

Chromic anhydride: 100 to 300 g / ℓ (concentration based on the chemicals used)

Sulfuric acid: 1/50 to 1/150 (mass ratio) of anhydrous chromic acid used

<Condition of chromium plating treatment>

Current density 10 to 60 A / dm 2

The temperature of the chromium plating bath greatly affects the surface hardness of the metal support obtained as described above. The specific temperature of the chromium plating bath may vary depending on other conditions employed in the chromium plating treatment and the conditions of the heat treatment after the chromium plating treatment, but is preferably 50 ° C or higher, more preferably 53 ° C or higher, Or more. If the temperature of the chromium plating bath is too low, the surface hardness of the obtained metal support tends to become excessively high. On the other hand, the temperature of the chromium plating bath is preferably 66 ° C or lower, more preferably 63 ° C or lower, still more preferably 61 ° C or lower, and particularly preferably 58 ° C or lower. If the temperature of the chromium plating bath is excessively high, the surface hardness of the obtained metal support tends to excessively lower.

It is preferable to perform heat treatment (annealing) after the chromium plating treatment. When the heat treatment is carried out at a high temperature, the time required for the heat treatment can be shortened. However, when the temperature is too high, cracks tend to occur in the chromium plating layer. Therefore, the heat treatment temperature is preferably 130 ° C or lower, desirable. On the other hand, when the heat treatment is performed at a low temperature, the risk of cracking is lowered, but the time required for the heat treatment becomes longer. Therefore, the heat treatment temperature is preferably 70 ° C or higher, more preferably 90 ° C or higher. The heat treatment time may be set within the range of 24 to 120 hours although it may vary depending on the conditions of the chromium plating treatment and the temperature of the heat treatment.

Examples of the PVA polymer in a solution state or a molten state include a film-forming stock solution obtained by dissolving a PVA polymer in a liquid medium, a PVA system such as a PVA polymer and a liquid medium, And in the form of a film-forming stock solution containing a polymer and a liquid medium. The film-forming stock solution may further contain a plasticizer, a surfactant, and other components as described above, if necessary.

Examples of the liquid medium in the stock solution for membrane production include water, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, ethylene glycol, glycerin, propylene glycol, diethylene glycol, tri Ethylene glycol, tetraethylene glycol, trimethylol propane, ethylenediamine, diethylenetriamine, and the like, and one or more of these may be used. Among them, water is preferable in terms of small load on the environment and recoverability. That is, preferred examples of the PVA polymer in a solution state or a molten state include those in the form of a film-forming stock solution containing a PVA polymer and water.

The volatile fraction of the stock solution of the film production (the content ratio of the volatile component such as a liquid medium which is removed by volatilization or evaporation in the film production in the film-forming stock solution) varies depending on the film production method, By mass to 90% by mass, and more preferably within the range of 55 to 80% by mass. Since the volatile fraction of the membrane-forming raw liquid is 50 mass% or more, the viscosity of the membrane-forming undiluted solution does not become excessively high, filtration and defoaming at the time of preparation of the membrane-forming stock solution are smoothly carried out and production of a PVA polymer film . On the other hand, when the volatile fraction of the film-forming raw liquid is 90 mass% or less, the concentration of the film-making stock solution is not excessively low, and the production of an industrial PVA polymer film becomes easy.

There is no particular limitation on the method for preparing the above-mentioned membrane-fabrication stock solution, and for example, a PVA polymer is dissolved in a liquid medium such as water, and at this time, a plasticizer, a surfactant, A method in which a PVA polymer containing a liquid medium such as water is melted and kneaded using an extruder and at the same time at least one of plasticizer, surfactant and other components is melted and kneaded .

In the production method of the present invention for producing a PVA polymer film, the PVA polymer in a solution state or a molten state is softened and dried on the surface of the above metal support having a surface temperature of not less than 50 ° C and not more than 115 ° C, . If the surface temperature of the metal support exceeds 115 캜, the number of defects A in the resulting PVA polymer film becomes large. In addition, the square mean roughness of both sides of the film tends to deviate from the desired range. From this viewpoint, the surface temperature of the metal support is preferably 105 占 폚 or lower, more preferably 102 占 폚 or lower, even more preferably 99 占 폚 or lower, particularly preferably 96 占 폚 or lower, and most preferably 95 占 폚 or lower. On the other hand, if the surface temperature of the metal support is less than 50 캜, problems such as difficulty in peeling of the film from the metal support or deterioration of transparency of the film tend to occur. From this viewpoint, the surface temperature of the metal support is preferably 60 DEG C or higher, more preferably 70 DEG C or higher, and even more preferably 80 DEG C or higher. Further, as the surface temperature of the metal support, an average value (average temperature) of surface temperatures of arbitrary plural points (for example, 10 points or more) on the surface of the metal support may be employed.

There is no particular limitation on the method of bringing the surface temperature of the metal support into the above range before the start of the film production. For example, in the case of using the drum as the metal support, the water such as water, oil, Heating by a dielectric heater provided on the inner side of the drum, or heating by means of an infrared heater or a hot-air heating apparatus provided so as to face the surface of the drum.

As described in, for example, Patent Document 5, the rate of temperature change when the surface temperature of the metal support is set within the above range before the start of the film production can be set at 3 占 폚 / hour or less. In the production method of the present invention using the metal support having the above-described surface hardness, the reason is unknown. However, even when the above-mentioned rate of change in temperature is relatively high, an increase in the number of cracks present on the surface of the metal support can be suppressed, The number of defects A in the obtained PVA polymer film can be controlled to a low level even when the productivity is improved by reducing the temperature adjustment time. From this point of view, the rate of temperature change when the surface temperature of the metal support is set within the above range before the start of film production is preferably 0.5 deg. C / hour or more, more preferably 1 deg. C / 4 ° C / hour or more, 4.5 ° C / hour or more, and further 5 ° C / hour or more. Further, the above-mentioned temperature-change rate is preferably 10 ° C / hour or less, more preferably 7 ° C / hour or less, from the viewpoint of reducing the number of cracks.

When the surface temperature of the metal support is set within the above range before starting the film production, it is preferable to reduce the temperature difference in the width direction of the metal support from the viewpoint of reducing the cracks. Specifically, And the maximum value of the absolute value of the slope is preferably not more than 10 占 폚 / m, more preferably not more than 5 占 폚 / m or less, more preferably 4 deg. C / m or less, and particularly preferably 3 deg. C / m or less.

In the production method of the present invention for producing the PVA based polymer film, in solution or in just before starting to flexible the PVA based polymer in the molten state, the crack area 200 ㎛ ² or more on the surface of the metal support The number is 0.7 pieces / mm 2 or less. Here, the area of the crack means the product of the maximum width of the crack and the maximum end distance. Generally, cracks such as cracks in the chromium plating layer are present on the surface of the metal support before the start of film production. It is believed that a foreign substance, which is considered to be a resin deposit, gradually adheres to such a crack during the production of the film to form a convex shape, which is transferred to the film to form a defect A on the film. Particularly, since the PVA polymer has high hydrophilicity and good affinity with metals as compared with other polymers, it is considered that the PVA polymer easily enters cracks existing on the surface of the metal support and adheres as a resin deposit, It is considered that a convex shape is easily formed and grown. For this reason, in order to reduce the number of defects A, it is preferable to reduce the number of cracks present on the surface of the metal support as much as possible. As described above, it is preferable to use a metal having a surface chromium- When the support is used, the reason for this is unclear. However, the number of cracks existing on the surface of the metal support can be easily reduced by a general treatment carried out on the surface of the metal support before the start of film production such as buff polishing or the like. The number of the defects A in the polymer film can be reduced compared with the conventional case and even if the PVA polymer film is continuously formed over a long period of time, . If the number of cracks on the surface of the metal support exceeds 0.7 pcs / mm 2, the number of defects A in the resulting PVA polymer film becomes large. The number of cracks on the surface of the metal support is 0.3 or less before the start of softening of the PVA polymer in a solution state or a molten state in view of reducing the number of defect A in the obtained PVA polymer film, / Mm &lt; 2 &gt; and more preferably 0.15 / mm &lt; 2 &gt; or less. On the other hand, in order to extremely reduce the number of cracks on the surface of the metal support, it is cumbersome and the effect tends to reach a limit. The water is preferably 0.005 / mm 2 or more, more preferably 0.01 / Do.

The number of cracks on the surface of the metal support of 200 mu m &lt; ^{2 &gt;} or more was determined by arbitrarily setting 25 points on the surface of the metal support and measuring the cracks in a range of 2 mm x 2 mm (4 mm &"Size of cracks 200 ㎛ ² or more" specifies a in, and by obtaining the number of "area 200 ㎛ ² or more cracks" in the range of × 25 points of that 4 ㎟, calculate the number per 1 ㎟ from this Can be obtained. Here, the area of the crack means the product of the maximum width and the maximum end distance in each crack, and the maximum end distance means the distance between the ends (straight distance) when only two ends of the crack are present, Quot; means the maximum distance among the plurality of end portions. Specifically, the number of cracks having an area of 200 mu m &lt; ^{2 &gt;} or more on the surface of the metal support can be obtained by the method described later in Examples.

The width of the metal support may be suitably set according to the width of the intended PVA polymer film. The specific width of the metal support may vary depending on the width of the desired PVA polymer film, but it is preferable that the PVA polymer film having a light absorption of 0.5 m or more and capable of producing a polarizing film of a light- From the viewpoint of production, it is preferably at least 4.5 m, more preferably at least 5.0 m, and even more preferably at least 5.5 m. In consideration of cost and ease of maintenance of the metal support, the width of the metal support is preferably 7.5 m or less, more preferably 7.0 m or less, and more preferably 6.5 m or less.

There is no particular limitation on the method of pouring the PVA polymer in the solution state or the molten state on the surface of the metal support, and the PVA polymer may be obtained by a known method using a T-shaped slit die, hopper plate, I-die, lip coater die, . The temperature of the PVA polymer in a molten state or in a solution state is preferably within a range of 50 ° C or more and 105 ° C or less.

The drying after the softening can be carried out by a known method and can be carried out by drying with heat applied from a metal support or by catching hot air. The desired PVA polymer film may be produced only by drying on the surface of the metal support. However, the PVA polymer film may be partially dried on the surface of the metal support by a known method or the like, The desired PVA polymer film may be produced by further drying the film by one or more drying rolls or a hot-air dryer in which the metal support and the rotating shaft are parallel to each other.

The PVA polymer film thus obtained can be subjected to heat treatment as required or both ends (ear portions) in the width direction can be cut. Further, the film may be continuously wound as described above to form a film roll.

[Usage]

The PVA polymer film wound from the PVA polymer films (PVA polymer films (1) and (2)) of the present invention and the film rolls (film rolls (1) and (2) Less; Quality is stable; It is preferable to use it as a original film for producing an optical film such as a polarizing film and a retardation film. In view of the fact that the effect of the present invention is more conspicuous, It is more preferable to use it as a original film for producing a polarizing film.

There is no particular limitation on the method for producing the polarizing film using the above PVA polymer film as the original film, and a known method can be adopted. For example, by using the above PVA polymer film, Stretching, fixing treatment, drying and, if necessary, washing or heat treatment. Here, the order of each treatment such as dyeing, uniaxial stretching, fixed treatment, etc. is not particularly limited, and one or two or more treatments may be simultaneously performed. In addition, one or two or more of the respective treatments may be carried out twice or more, for example, uniaxial stretching may be performed twice or more times. The swelling treatment may be carried out as necessary before each step such as dyeing, uniaxial stretching, and fixing treatment is carried out.

The dyeing may be performed at any stage before uniaxial stretching, uniaxial stretching, or uniaxial stretching. Dyes used for dyeing include iodine-potassium iodide; Direct Black 17, 19, 154; Direct Brown 44, 106, 195, 210, 223; Direct Red 2, 23, 28, 31, 37, 39, 79, 81, 240, 242, 247; Direct Blue 1, 15, 22, 78, 90, 98, 151, 168, 202, 236, 249, 270; Direct Violet 9, 12, 51, 98; Direct Green 1, 85; Direct Yellow 8, 12, 44, 86, 87; Dichromatic dyes such as Direct Orange 26, 39, 106 and 107, and the like can be used. The dyeing can be carried out by immersing the PVA polymer film in a solution (dye bath) containing the dye. The above-mentioned dyes may be contained in advance when the PVA polymer film is formed into a film.

The uniaxial stretching may be carried out by wet stretching or dry heat stretching, or may be carried out in hot water (including the dyeing bath described above or a fixed treatment bath described later), or by using a PVA polymer film after absorption Or in air.

The temperature at the time of uniaxial stretching is not particularly limited. However, when the PVA polymer film is subjected to uniaxial stretching (wet stretching) in hot water, it is preferably within a range of 30 DEG C or more and 90 DEG C or less, Lt; 0 &gt; C to 180 &lt; 0 &gt; C.

The stretching magnification of uniaxial stretching (in the case of uniaxially stretching in multiple stages, the total stretching ratio) is preferably four times or more, more preferably five times or more, from the viewpoint of the polarization performance. There is no particular limitation on the upper limit of the draw ratio, but if it is 8 or more, it is preferable because uniaxial stretching can be stably performed. The thickness of the film after uniaxial stretching may vary depending on the thickness of the PVA polymer film to be used, but is preferably within the range of 3 占 퐉 to 75 占 퐉, and more preferably within the range of 5 占 퐉 to 50 占 퐉.

Fixing treatment is often carried out in order to strengthen the adsorption of the dye on the PVA polymer film. As the fixed treatment bath used for the fixing treatment, an aqueous solution containing one kind or two or more kinds of boron compounds such as boric acid and borax can be used. An iodine compound may be added to the fixed treatment bath as needed.

It is preferable to carry out cleaning such as dyeing, uniaxial stretching, fixing treatment, and the like, and then, before drying, in order to remove the processing bath liquid or foreign matter of each treatment adhered to the film surface. Pure water may be used for the cleaning liquid used for cleaning, or water in which a small amount of these agents are added may be used in order to suppress the outflow of the dye or the boron compound by cleaning. The cleaning liquid may be sprayed on the surface of the film subjected to each treatment with a shower or the like, or may be carried out by immersing the film after each treatment in a cleaning bath.

The drying or heat treatment is preferably carried out in a range of 30 ° C to 150 ° C, more preferably in a range of 50 ° C to 150 ° C.

Each step of the dyeing step, the uniaxial stretching step, the fixing treatment step and the drying step is carried out by using the PVA polymer film 2 or the PVA polymer film wound from the film roll 2 as an original film for producing a polarizing film (For example, a fixed treatment bath, a cleansing bath, or the like) before entering the drying process, the angle formed by the liquid surface of the treatment bath and the film surface (the angle of the acute angle side ) Is set to 30 ° or more and 85 ° or less and the surface on the upper side of the film is the surface having the smaller root mean square roughness in the PVA polymer film used as the original film, It is preferable because it can be easily obtained.

The reason why the above effects are exhibited is not necessarily clear, but it is considered that the polarizing film is produced as described above, and the adhesion of the PVA polymer precipitated in each treatment bath and the treatment liquid used in each treatment is reduced. The angle formed between the liquid surface of the treatment bath and the film surface at the time of leaving the last treatment bath before entering the drying process is too large or too small to easily adhere and remain in the deposited PVA polymer or the treatment liquid, More preferably 40 degrees or more, further preferably 50 degrees or more, further preferably 80 degrees or less, more preferably 75 degrees or less, and even more preferably 70 degrees or less.

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

Example

Hereinafter, the present invention will be described concretely with examples and the like, but the present invention is not limited thereto at all. In the following, each measurement or evaluation method employed in the following Preparation Examples, Examples, Reference Examples and Comparative Examples will be described.

[Measurement of surface hardness of drum for membrane production]

On the surface (peripheral surface) of the drum for producing a film, eight points in total were determined by dividing the total circumferential length of the drum for film production into four equal parts on a line extending 5 mm inward from both ends. At each point, the Vickers hardness of the surface of the chromium plating layer was measured with a UCI hardness meter MIC10 (manufactured by GE Sensing & Inspection Technologies, Inc., using a probe MIC-2101-A) Respectively.

[Measurement of the number of cracks having an area of 200 mu m ² or more on the surface of the drum for membrane production]

Arbitrary 25 points were determined on the surface (peripheral surface) of the drum for producing a film, and each of them was measured with a digital video microscope VHX-900 (manufactured by Keens) at a magnification of 1000 times, (Cracks on the chromium plating layer) within the range of the thickness of the film. The maximum width and the maximum end distance of the cracks shown in the photograph (if there are only two end portions, it means the distance between the end portions, and when there are a plurality of end portions, it means the maximum distance among the plurality of end portions) calculated by obtaining the product thereof, and the multiplication of a crack that is more than 200 ㎛ ² was referred to as "area 200 ㎛ ² or more cracks." In this manner, the number of "cracks having an area of 200 μm ² or more" was obtained in the range of 4 mm 2 × 25 points, and the number of cracks per 1 mm 2 was calculated from the number.

[Measurement of surface temperature of drum for membrane production]

One straight line passing through any one point on the surface (peripheral surface) of the drum for producing a film and three straight lines parallel to the one straight line and dividing the peripheral surface into four halves together with the one straight line And the temperature distribution on these four straight lines was measured using a thermotracer TH9100MR (manufactured by NEC Avio Infrared Technology Co., Ltd.). Next, from the obtained temperature distribution data, the temperature of each of the three points (total of 12 points) at the central portion in the width direction and at the position of 20 cm from the both ends toward the central portion with respect to each straight line was obtained, The surface temperature of the drum for preparing a film was measured. Further, the obtained temperature distribution data for each straight line is divided into four graphs in which the horizontal axis represents the position in the width direction and the vertical axis represents the temperature, and the maximum value of the absolute value of the slope is obtained. Respectively.

[Measurement of number of defects of PVA film]

The PVA film was unwound from the film roll, passed through the film, and the defects of the film were found from the distortion of the image of the fluorescent lamp when the fluorescent lamp was placed behind the film. The periphery of the film was rounded with a magic marker. Next, the defects found were observed using a non-contact surface shape measuring instrument "NewView" 6300 (manufactured by Zygosha), and defects (defects) having an area (opening area) of 400 μm ² or more and a depth of 0.3 μm or more Defect A). This operation was repeated until the number of defects A became 10, starting from the winding end portion of the produced film roll (and further, the portion up to 10 m from the end portion in the longitudinal direction of the film was excluded for the purpose of reducing the error) (The length to the 10th shortest defect A after the start of operation, the width of the film, the unit is m 2), and dividing 10 (the number thereof) by the area of the PVA film of the defect A The number (unit: 개 / ㎡) was calculated. Also, of the ten defects A, two or more defects (which are substantially in the same position in the width direction of the film and in which the longitudinal gap of the film is substantially coincident with an integral multiple of the total circumference length of the used film- Such a drawback is that even if a portion other than the portion provided for the measurement is used, the film is substantially constant (an integer multiple of the entire peripheral length of the film-forming drum) in the longitudinal direction of the film, (Units / m 2) at the winding end portion by dividing the number of the rotation period defects by the area (unit: m 2) Respectively.

Subsequently, a polarizing film (a polarizing film produced from the PVA film on the winding end portion side) was produced using the remaining film rolls as described later, and the PVA film was removed from the remaining film rolls in which most PVA films were in an unused state And wound up again on the film roll so that the starting portion of the original film roll was located outside the new film roll. The new film roll was used to carry out the same operations as above to determine the defect A and the number of rotation cycle defects (all in units / m 2) at the beginning of winding of the original film roll, To prepare a polarizing film (polarizing film produced from the PVA film on the winding start portion side) as described later.

[Evaluation of wrinkles of film rolls]

The film roll was visually observed and wrinkles were evaluated according to the following criteria.

A Rank: No wrinkles found

Rank B: Wrinkles are slightly present, but practically no problem level

Rank C: Wrinkles at levels that are problematic in practice

[Measurement of root mean square roughness of PVA film]

The square mean roughness of arbitrary 10 points on one side of the PVA film was measured using a white interference microscope NV6300 (manufactured by Zigong Co.), and the average value thereof was defined as the root mean square roughness of the surface. Subsequently, a square-averaged roughness was obtained in the same manner for the other side of the PVA film.

[Evaluation of polarizing film (20 sheets test)]

The PVA film extruded from the above-mentioned film roll was continuously treated in the order of preliminary swelling, dyeing, uniaxial stretching, fixing treatment, drying, and heat treatment to prepare a polarizing film.

That is, the PVA film was preliminarily swollen by immersing in water at 30 DEG C for 30 seconds and then dipped in an aqueous solution (dyeing bath) at 35 DEG C of an iodine concentration of 0.4 g / L and a potassium iodide concentration of 40 g / L for 3 minutes to stain. Subsequently, uniaxial stretching was carried out in an aqueous solution (drawing bath) having a boric acid concentration of 4% at a temperature of 50 DEG C in a longitudinal direction at a draw ratio of 5, and further a potassium iodide concentration of 40 g / l, a boric acid concentration of 40 g / And immersed in an aqueous solution (fixed treatment bath) at 30 캜 at a concentration of 10 g / l for 5 minutes to perform fixing treatment. Thereafter, the film was subjected to hot-air drying at 40 占 폚 and further heat-treated at 100 占 폚 for 5 minutes.

From the obtained polarizing film at arbitrary positions, 20 pieces of test specimens having a length of 50 cm and a width of 25 cm were collected. On the other hand, a polarizing plate of 50 cm x 50 cm having few defects was prepared, and the above test pieces were superimposed on the polarizing plate so that the alignment axes thereof were perpendicular to each other. The polarizing plates were placed on a shaukasten for observation of a rented image, The defect was confirmed. When there is no defect in the test piece, the overlapped polarizing plate / test piece appears to be black, but when there is a defect in the test piece, light leaks from the portion and can be recognized as a bright defect on the spot. A test piece having two or more bright defects was rejected, and the acceptance rate in 20 test pieces was calculated.

[Evaluation of polarizing film (100 sheets test)]

The passing rate in 100 test pieces was calculated in the same manner as in the above-mentioned 20 test except that the number of test pieces was changed from 20 to 100 pieces and the test pieces having at least one bright defect were rejected.

[Uneven dyeing of polarizing film and evaluation of foreign matter]

From the obtained polarizing film, test pieces having a length of 50 cm and a width of 25 cm were collected. On the other hand, a polarizing plate of 50 cm x 50 cm having little uneven dyeing or foreign matter was prepared, and the above test pieces were superimposed on the polarizing plate so that the alignment axes thereof were perpendicular to each other. Were evaluated according to the following criteria. &Lt; tb &gt; &lt; TABLE &gt;

· Uneven dyeing

A Rank: Uneven dyeing is not confirmed

Rank B: Dyeing stains slightly present, but practically no problem level

Rank C: There is staining unevenness at the level of practical problems

· Foreign matter

A Rank: No foreign matter

Rank B: There are a few foreign substances, but there is no problem in practice

Rank C: There is a level of foreign matter in practical use.

[Preparation Example 1]

"Preparation of Drum 1"

The surface (peripheral surface) of the drum of the carbon-made film for producing carbon steel having a width of 1.0 m was buffed and subjected to a pretreatment such as degreasing treatment and chrome plating treatment was carried out on the surface of the drum using a chromium plating bath under the following conditions Respectively. A chromium plating bath was prepared by dissolving these chemicals in distilled water so as to have a concentration of 200 g / l of anhydrous chromic acid and 2 g / l of sulfuric acid at a concentration based on the chemical used.

· Chrome plating bath temperature: 55 ° C

Current density: 20 A / dm 2

Chromium plated layer thickness (after polishing): 50 탆

After completion of the chromium plating treatment, the drum for film production was heat-treated at 102 DEG C for 50 hours and then cooled.

The surface hardness of the film-forming drum having the chromium plating layer formed on the surface (peripheral surface) by the above chromium plating treatment and heat treatment was measured according to the above-mentioned method and was 760 HV. Hereinafter, this drum for making a film is referred to as &quot; drum 1 &quot;.

[Preparation Example 2]

"Preparation of Drum 2"

A chromium plating treatment and a heat treatment were carried out in the same manner as in Preparation Example 1 except that the chromium plating bath temperature was changed to 52 캜 to prepare a drum for producing a film having a chromium plating layer on its surface (peripheral surface). The surface hardness of this film-forming drum was measured according to the above-mentioned method, and it was 840 HV. Hereinafter, this drum for producing a film is referred to as &quot; drum 2 &quot;.

[Preparation Example 3]

"Preparation of Drum 3"

A chromium plating treatment and a heat treatment were carried out in the same manner as in Preparation Example 1 except that the chromium plating bath temperature was changed to 48 캜 to prepare a drum for producing a film having a chromium plating layer on its surface (peripheral surface). The surface hardness of this film-forming drum was measured according to the above-mentioned method, and it was 950 HV. Hereinafter, this drum for producing a film is referred to as &quot; drum 3 &quot;.

[Preparation Example 4]

"Preparation of Drum 4"

A chromium plating treatment and a heat treatment were carried out in the same manner as in Preparation Example 1 except that the chromium plating bath temperature was changed to 67 캜 to prepare a drum for producing a film having a chromium plating layer on its surface (peripheral surface). The surface hardness of this film-forming drum was measured according to the above-mentioned method and found to be 525 HV. Hereinafter, this drum for making a film is referred to as &quot; drum 4 &quot;.

[Example 1]

The drum 1 was mounted on a cast film manufacturing facility and connected to a hot water circulating device. Subsequently, the peripheral surface of the drum 1 was buffed. The number of cracks having an area of 200 mu m &lt; ^{2 &gt;} or more on the surface (peripheral surface) of the drum 1 after buffing was measured by the above method and found to be 0.10 pieces / mm & Thereafter, the surface temperature of the drum 1 was raised by a hot water circulating device at a rate of 1 占 폚 / hour and maintained at a surface temperature of 90 占 폚. The maximum temperature gradient at this time was 3.8 ° C / m at the maximum.

On the other hand, 100 parts by mass of a chip of PVA (saponified vinyl acetate homopolymer) having a degree of saponification of 99.9 mol% and a degree of polymerization of 2,400 was immersed in 2,500 parts by mass of distilled water at 35 DEG C for 24 hours, followed by centrifugal dehydration to obtain PVA function chips &Lt; / RTI &gt; The volatile fraction in the PVA function chip was 70 mass%. 12 parts by mass of glycerin and 0.3 part by mass of a surfactant (containing 95% by mass of lauric acid diethanolamide) were added to 333 parts by mass (100 parts by mass in terms of PVA in terms of dry state) of the PVA function chip, And this was heated and melted by a twin-screw extruder equipped with a vent at a maximum temperature of 130 ° C. The molten PVA thus obtained was cooled to 100 캜 by a heat exchanger and then extruded from the coat hanger die having a width of 900 mm to a drum 1 having a surface temperature of 90 캜 and further passed through a hot air drying furnace , And both ends in the width direction (ear portions) were cut to continuously produce a PVA film having a width of 0.7 m. The film forming speed was set at 8 m / min. The PVA film (thickness of 60 mu m, length of 8,000 m) after the film production was stabilized was continuously wound up into a cylindrical core made of aluminum having a diameter of 6 inches to make a film roll.

As a result of measuring the number of defects of the PVA film and evaluating the polarizing film (20 sheets test) by using the obtained film roll, the number of defects A in the winding start portion was 0.102 pieces / m 2 ( The number of defects A in the winding end portion was 0.098, and the number of defects A in the end portion of the winding was 0.098 pieces / mm 2). In the twenty test pieces of the polarizing film produced from the PVA film on the winding start portion side, / M &lt; 2 &gt; (among them, 0.029 pcs / m 2 rotation period defects), and the acceptance rate in the 20 sheets test of the polarizing film produced from the PVA film on the winding start side was 100%. The number of defects A at the winding end portion with respect to the number of defects A in the winding start portion was calculated to be 0.96 times.

[Example 2]

A PVA film was continuously produced in the same manner as in Example 1 except that the length of the PVA film was changed from 8,000 m to 3,000 m to make a film roll. The number of cracks having an area of 200 mu m &lt; ^{2 &gt;} or more on the surface (peripheral surface) of the drum 1 after buffing was measured by the above method and found to be 0.11 pieces / mm &

As a result of measuring the number of defects of the PVA film and evaluating the polarizing film (20 sheets test) by using the obtained film roll, the number of defects A in the winding start portion was 0.110 pieces / m 2 ( The rate of acceptance in the test of 20 sheets of the polarizing film produced from the PVA film at the winding start side was 100%, the number of defects A at the end of winding was 0.121 / M &lt; 2 &gt; (among them, rotation cycle defects of 0.036 number / m 2), and the passing rate in the test of 20 sheets of the polarizing film produced from the PVA film on the winding start side was 100%. The number of defects A at the winding end portion with respect to the number of defects A in the winding start portion was calculated to be 1.10 times.

[Referential Example 1]

A PVA film was continuously produced in the same manner as in Example 1 except that the length of the PVA film was changed from 8,000 m to 15,000 m to make a film roll. The number of cracks having an area of 200 mu m &lt; ^{2 &gt;} or more on the surface (peripheral surface) of the drum 1 after buffing was measured by the above method and found to be 0.10 pieces / mm2.

As a result of measuring the number of defects of the PVA film by the above-mentioned method using the obtained film roll, the number of defects A in the winding start portion was 0.108 pieces / m 2 (among them, rotation cycle defects were 0.032 pieces / M &lt; 2 &gt;) and the number of defects A at the end of winding was 0.160 pieces / m &lt; 2 &gt; The number of defects A at the winding end portion with respect to the number of defects A in the winding start portion was calculated to be 1.48 times.

[Example 3]

The PVA film was continuously produced in the same manner as in Example 1 except that the polymerization degree of PVA was changed from 2,400 to 3,300 and the length of the PVA film was changed from 8,000 m to 15,000 m. The number of cracks having an area of 200 mu m &lt; ^{2 &gt;} or more on the surface (peripheral surface) of the drum 1 after buffing was measured by the above method and found to be 0.10 pieces / mm2.

As a result of measuring the number of defects of the PVA film and evaluating the polarizing film (100 sheets test) using the obtained film roll, the number of defects A in the winding start portion was 0.088 pieces / m 2 ( The number of defects A at the end of winding was 0.118, and the number of defects A at the end of the winding was 0.118 / M &lt; 2 &gt; (0.024 number / period of rotation period defects), and the acceptance rate in a 100-sheet test of the polarizing film produced from the PVA film on the winding start side was 95%. The number of defects A in the winding end portion with respect to the number of defects A in the winding start portion was calculated to be 1.34 times.

[Example 4]

A PVA film was continuously produced and film rolls were produced in the same manner as in Example 1 except that the polymerization degree of PVA was changed from 2,400 to 6,000 and the length of the PVA film was changed from 8,000 m to 15,000 m. The number of cracks having an area of 200 mu m &lt; ^{2 &gt;} or more on the surface (peripheral surface) of the drum 1 after buffing was 0.13 pieces / mm2 as measured by the above method.

As a result of measuring the number of defects of the PVA film and evaluating the polarizing film (100 sheets test) using the obtained film roll, the number of defects A in the winding start portion was 0.067 pieces / m 2 ( The number of defects A at the end of winding was 0.074, and the number of defects A at the end of the winding was 0.074 pieces / / M &lt; 2 &gt; (among them, rotation cycle defects were 0.007 pieces / m &lt; 2 &gt;), and the acceptance rate in the 100 sheet test of the polarizing film produced from the PVA film on the winding start side was 99%. The number of defects A at the winding end portion with respect to the number of defects A in the winding start portion was calculated to be 1.10 times.

[Example 5]

A PVA film was continuously produced in the same manner as in Example 1 except that the drum 2 was used in place of the drum 1 and the length of the PVA film was changed from 8,000 m to 3,000 m. The number of cracks having an area of 200 mu m &lt; ^{2 &gt;} or more on the surface (peripheral surface) of the drum 2 after buffing was measured by the above method and found to be 0.39 pieces / mm2.

As a result of measuring the number of defects of the PVA film and evaluating the polarizing film (20 sheets test) by using the obtained film roll, the number of defects A in the winding start portion was 0.172 pieces / m 2 ( The number of defects A at the end of the winding was 0.224 pieces, and the number of defects A at the end of the winding was 0.224 pieces / / M &lt; 2 &gt; (among them, rotation cycle defects was 0.134 pieces / m 2), and the acceptance rate in the 20 sheets test of the polarizing film produced from the PVA film on the winding start side was 85%. The number of defects A at the winding end portion with respect to the number of defects A in the winding start portion was calculated to be 1.30 times.

[Example 6]

A PVA film was continuously produced in the same manner as in Example 1 except that the surface temperature of the drum 1 was changed from 90 占 폚 to 110 占 폚 and the length of the PVA film was changed from 8,000 m to 3,000 m, . The number of cracks having an area of 200 mu m &lt; ^{2 &gt;} or more on the surface (peripheral surface) of the drum 1 after buffing was 0.13 pieces / mm2 as measured by the above method.

As a result of measuring the number of defects of the PVA film and evaluating the polarizing film (20 sheets test) using the obtained film roll, the number of defects A in the winding start portion was 0.132 pieces / m 2 ( The number of defects A at the end of the winding was 0.180 pieces / mm 2), the acceptance rate in the 20-sheet test of the polarizing film produced from the PVA film at the winding start portion side was 95% / M &lt; 2 &gt; (among them, rotation period defects: 0.090 pcs / m 2), and the passing rate in the test of 20 sheets of the polarizing film produced from the PVA film on the winding start side was 90%. The number of defects A at the winding end portion with respect to the number of defects A in the winding start portion was calculated to be 1.36 times.

[Example 7]

A PVA film was continuously produced in the same manner as in Example 1 except that the rate of temperature change was changed from 1 占 폚 / hour to 5 占 폚 / hour to make a film roll. The number of cracks having an area of 200 mu m &lt; ^{2 &gt;} or more on the surface (peripheral surface) of the drum 1 after buffing was measured by the above method and found to be 0.10 pieces / mm2.

As a result of measuring the number of defects of the PVA film by the above-mentioned method using the obtained film roll, the number of defects A in the winding start portion was 0.110 pieces / m 2 (among them, rotation cycle defects were 0.044 pieces / M &lt; 2 &gt;), and the number of defects A in the winding end portion was 0.122 pieces / m &lt; 2 &gt; The number of defects A at the winding end portion with respect to the number of defects A in the winding start portion was calculated to be 1.11 times.

[Comparative Example 1]

A PVA film was continuously produced in the same manner as in Example 1 except that the drum 3 was used in place of the drum 1 to form a film roll. The number of cracks having an area of 200 mu m &lt; ^{2 &gt;} or more on the surface (peripheral surface) of the drum 3 after buffing was measured by the above-mentioned method and was found to be 0.73 pieces / mm2.

As a result of measuring the number of defects of the PVA film and evaluating the polarizing film (20 sheets test) by using the obtained film roll, the number of defects A in the winding start portion was 0.291 pieces / m 2 ( M 2), the acceptance rate in the 20-sheet test of the polarizing film produced from the PVA film at the winding start side was 80%, the number of defects A at the end of winding was 0.938 / M &lt; 2 &gt; (among them, rotation period defects were 0.750 pieces / m &lt; 2 &gt;) and the acceptance rate in the 20 sheets test of the polarizing film produced from the PVA film on the winding start side was 50%. The number of defects A at the winding end portion with respect to the number of defects A in the winding start portion was calculated to be 3.22 times.

[Comparative Example 2]

A PVA film was continuously produced in the same manner as in Example 1 except that the surface temperature of the drum 1 was changed from 90 占 폚 to 120 占 폚 and the length of the PVA film was changed from 8,000 m to 3,000 m, . The number of cracks having an area of 200 mu m &lt; ^{2 &gt;} or more on the surface (peripheral surface) of the drum 1 after buffing was measured by the above method and found to be 0.11 pieces / mm &

As a result of measuring the number of defects of the PVA film and evaluating the polarizing film (20 sheets test) using the obtained film roll, the number of defects A in the winding start portion was 0.252 pieces / m 2 ( M 2), the acceptance rate in the 20-sheet test of the polarizing film produced from the PVA film on the winding start side was 80%, the number of defects A in the winding end portion was 0.358 / M &lt; 2 &gt; (among them, rotation period defects were 0.251 pieces / m &lt; 2 &gt;) and the acceptance rate in the test of 20 sheets of the polarizing film produced from the PVA film on the winding start side was 65%. The number of defects A at the winding end portion with respect to the number of defects A in the winding start portion was calculated to be 1.42 times.

[Comparative Example 3]

In Example 1, the PVA film was produced by changing the surface temperature of the drum 1 from 90 캜 to 40 캜. However, since drying on the drum was insufficient, it was difficult to separate the film from the drum. Did not do it.

[Comparative Example 4]

A PVA film was continuously produced in the same manner as in Comparative Example 1 except that the rate of temperature change was changed from 1 占 폚 / hour to 5 占 폚 / hour to make a film roll. The number of cracks having an area of 200 mu m &lt; ^{2 &gt;} or more on the surface (peripheral surface) of the drum 3 after buffing was measured by the above-mentioned method and was found to be 0.73 pieces / mm2.

As a result of measuring the number of defects of the PVA film by the above-mentioned method using the obtained film roll, the number of defects A at the winding start portion was 0.332 pieces / m 2 (among them, rotation cycle defects were 0.166 pieces / M &lt; 2 &gt;), and the number of defects A at the winding end portion was 1.349 pieces / m &lt; 2 &gt; The number of defects A at the winding end portion with respect to the number of defects A in the winding start portion was calculated to be 4.06 times.

[Example 8]

The drum 1 was mounted on a cast film manufacturing facility and connected to a hot water circulating device. Subsequently, the peripheral surface of the drum 1 was buffed. The number of cracks having an area of 200 mu m &lt; ^{2 &gt;} or more on the surface (peripheral surface) of the drum 1 after buffing was measured by the above method and found to be 0.10 pieces / mm & Thereafter, the surface temperature of the drum 1 was raised by a warm water circulating apparatus and maintained at a surface temperature of 90 占 폚.

On the other hand, 100 parts by mass of a chip of PVA (saponified vinyl acetate homopolymer) having a degree of saponification of 99.9 mol% and a degree of polymerization of 2,400 was immersed in 2,500 parts by mass of distilled water at 35 DEG C for 24 hours, followed by centrifugal dehydration to obtain PVA function chips &Lt; / RTI &gt; The volatile fraction in the PVA function chip was 70 mass%. 12 parts by mass of glycerin and 0.3 part by mass of a surfactant (containing 95% by mass of lauric acid diethanolamide) were added to 333 parts by mass (100 parts by mass in terms of PVA in terms of dry state) of the PVA function chip, And this was heated and melted by a twin-screw extruder equipped with a vent at a maximum temperature of 130 ° C. The molten PVA thus obtained was cooled to 100 캜 by a heat exchanger and then extruded from the coat hanger die having a width of 900 mm to a drum 1 having a surface temperature of 90 캜 and further passed through a hot air drying furnace , And both ends in the width direction (ear portions) were cut to continuously produce a PVA film having a width of 0.7 m. The film forming speed was set at 8 m / min. The PVA film (having a thickness of 60 占 퐉 and a length of 12,000 m) after the film production was stabilized was continuously wound into a cylindrical core made of aluminum having a diameter of 6 inches to form a film roll.

The wrinkles of the obtained film rolls (wrinkles generated when the PVA film was wound) were evaluated by the above-mentioned method, and as a result, they were A rank. The square average roughness of the PVA film was measured by the above-mentioned method using the PVA film obtained from the obtained film roll. As a result, the square mean roughness on the side of the drum 1 on the side facing the surface was 4.1 nm, And the root mean square roughness on the other side was 1.9 nm. The difference between them was calculated to be 2.2 nm.

The PVA film wound from the film roll was continuously treated in the order of preliminary swelling, dyeing, fixing, uniaxial stretching, washing, and drying to prepare a polarizing film. That is, the PVA film was preliminarily swollen by immersing in water at 30 DEG C for 60 seconds and then dipped in an aqueous solution (dyeing bath) at 35 DEG C having an iodine concentration of 0.4 g / L and a potassium iodide concentration of 40 g / L for 110 seconds to stain. Subsequently, the substrate was immersed in an aqueous solution (fixed treatment bath) having a boric acid concentration of 30 g / l for 90 seconds so as to be subjected to fixation treatment, and further stretched in an aqueous solution (drawing bath) at 50 캜 with a boric acid concentration of 4% The uniaxial stretching was carried out at a magnification of 5 times. Thereafter, the substrate was immersed in an aqueous solution (cleansing bath) at a boric acid concentration of 15 g / l at 30 캜 for 10 seconds to perform cleaning, followed by hot air drying at 55 캜 to obtain a polarizing film. Further, the angle formed between the liquid surface of the cleansing bath and the film surface when the cleansing bath, which is the last treatment bath before entering the drying process, is set to 60 degrees by changing the position of the guide roll, and at the same time, Surface of the PVA film used had a smaller square-root mean roughness.

The unevenness of staining of the obtained polarizing film was evaluated by the above-mentioned method, and it was the A rank. Further, the foreign substance of the obtained polarizing film was evaluated by the above-mentioned method, and it was ranked as A.

[Example 9]

A PVA film was continuously produced in the same manner as in Example 8 except that the drum 2 was used in place of the drum 1 to prepare a film roll. The number of cracks having an area of 200 mu m &lt; ^{2 &gt;} or more on the surface (peripheral surface) of the drum 2 after buffing was measured by the above-mentioned method and was found to be 0.37 pieces / mm2.

The wrinkles of the obtained film rolls (wrinkles generated when the PVA film was wound) were ranked rank B as a result of the evaluation. Using the PVA film obtained from the obtained film roll, the square average roughness of the PVA film was measured by the above method. As a result, the square mean roughness on the side of the drum 2 on the side facing the surface was 6.7 nm, And the square mean roughness on the other surface was 2.0 nm. The difference between them was calculated to be 4.7 nm.

A polarizing film was produced in the same manner as in Example 8 with respect to the PVA film wound from the film roll. The unevenness of staining of the obtained polarizing film was evaluated as B rank by the above-mentioned method. Further, the foreign substance of the obtained polarizing film was evaluated as B rank by the above-mentioned method.

[Comparative Example 5]

A PVA film was continuously produced in the same manner as in Example 8 except that the drum 3 was used in place of the drum 1 to form a film roll. The number of cracks having an area of 200 mu m &lt; ^{2 &gt;} or more on the surface (peripheral surface) of the drum 3 after buffing was measured by the above-mentioned method and was found to be 0.73 pieces / mm2.

The wrinkles of the obtained film rolls (wrinkles generated when the PVA film was wound) were evaluated by the above-mentioned method, and as a result, they were A rank. Using the PVA film obtained from the obtained film roll, the square average roughness of the PVA film was measured by the above method. As a result, the square mean roughness on the side of the drum 3 on the side facing the surface was 28.3 nm, And the root mean square roughness on the other surface was 2.6 nm. The difference between them was calculated to be 25.7 nm.

A polarizing film was produced in the same manner as in Example 8 with respect to the PVA film wound from the film roll. The staining unevenness of the obtained polarizing film was evaluated by the above-mentioned method, and it was ranked as C rank. The foreign substance of the obtained polarizing film was evaluated by the above-mentioned method, and it was ranked as C rank.

[Comparative Example 6]

A PVA film was continuously produced in the same manner as in Example 8 except that the drum 4 was used in place of the drum 1 to form a film roll. The number of cracks having an area of 200 mu m &lt; ^{2 &gt;} or more on the surface (peripheral surface) of the drum 4 after buffing was measured by the above-mentioned method and found to be 0.15 pieces / mm2.

The corrugation of the obtained film roll (corrugation that occurs when the PVA film was wound) was evaluated by the above-mentioned method, and the result was C rank. Using the PVA film obtained from the obtained film roll, the square average roughness of the PVA film was measured by the above-mentioned method. As a result, the square average roughness of the surface on the side of the drum 4 facing the surface was 2.8 nm, And the root mean square roughness on the other surface was 2.6 nm. The difference between them was calculated to be 0.2 nm.

A polarizing film was produced in the same manner as in Example 8 with respect to the PVA film wound from the film roll. The unevenness of staining of the obtained polarizing film was evaluated by the above-mentioned method, and it was the A rank. Further, the foreign substance of the obtained polarizing film was evaluated by the above-mentioned method, and it was found to be the A rank.

[Example 10]

Using the film roll obtained in Example 8, a polarizing film was produced in the same manner as in Example 8 except that the angle formed by the liquid surface of the cleansing bath and the film surface when the cleansing bath was removed was changed from 60 ° to 45 ° . The unevenness of staining of the obtained polarizing film was evaluated by the above-mentioned method, and it was the A rank. Further, the foreign substance of the obtained polarizing film was evaluated as B rank by the above-mentioned method.

[Comparative Example 7]

The same procedure as in Example 8 was carried out using the film roll obtained in Example 8 except that the upper surface of the film when the cleansing bath was exposed was changed to be the surface having the larger root mean square roughness in the PVA film used To prepare a polarizing film. The unevenness of staining of the obtained polarizing film was evaluated by the above-mentioned method, and it was the A rank. The foreign substance of the obtained polarizing film was evaluated by the above-mentioned method, and it was ranked as C rank.

[Comparative Example 8]

Using the film roll obtained in Example 8, a polarizing film was produced in the same manner as in Example 8 except that the angle formed by the liquid surface of the cleansing bath and the film surface when the cleansing bath was removed was changed from 60 ° to 25 ° . The unevenness of staining of the obtained polarizing film was evaluated by the above-mentioned method, and it was the A rank. The foreign substance of the obtained polarizing film was evaluated by the above-mentioned method, and it was ranked as C rank.

[Comparative Example 9]

Using the film roll obtained in Example 8, a polarizing film was produced in the same manner as in Example 8, except that the angle formed by the liquid surface of the cleansing bath and the film surface when the cleansing bath was exposed was changed from 60 ° to 88 ° . The unevenness of staining of the obtained polarizing film was evaluated by the above-mentioned method, and it was the A rank. The foreign substance of the obtained polarizing film was evaluated by the above-mentioned method, and it was ranked as C rank.

Claims (24)

A polyvinyl alcohol polymer film having an area of not less than 400 占 퐉 ² and a number of defects having a depth of not less than 0.3 占 퐉 not more than 0.25 parts / The method according to claim 1,
Wherein the number of said defects is 0.15 / m &lt; 2 &gt; or less. 3. The method according to claim 1 or 2,
Wherein the polyvinyl alcohol polymer contained in the polyvinyl alcohol polymer film has a degree of polymerization of 3,000 or more and 10,000 or less. 4. The method according to any one of claims 1 to 3,
A polyvinyl alcohol-based polymer film which is a long-film polyvinyl alcohol-based polymer film. 5. The method of claim 4,
A polyvinyl alcohol polymer film having a length of 6,000 m or more. The method according to claim 4 or 5,
Wherein the defects are substantially uniformly spaced in the longitudinal direction of the film and exist at substantially the same position in the width direction of the film. A film roll in which a long polyvinyl alcohol polymer film is continuously wound, wherein the film roll has a surface area of 400 mu m &lt; ² &gt; or more and a depth of 0.3 mu m or more as a depressed defect from the film surface, Wherein the number of defects in the winding end portion of the polyvinyl alcohol polymer film relative to the number of defects in the portion is 1.4 times or less. 8. The method of claim 7,
Wherein the number of said defects is 0.25 pieces / m 2 or less. 8. The method of claim 7,
Wherein the number of defects is 0.15 / m 2 or less. 10. The method according to any one of claims 7 to 9,
Wherein the polyvinyl alcohol polymer contained in the polyvinyl alcohol polymer film has a degree of polymerization of 3,000 or more and 10,000 or less. 11. The method according to any one of claims 7 to 10,
Wherein the polyvinyl alcohol polymer film has a length of 6,000 m or more. 12. The method according to any one of claims 7 to 11,
Wherein the defects are substantially uniformly spaced in the longitudinal direction of the film and are present at substantially the same position in the width direction of the film. Wherein the difference in the two mean square roughnesses obtained when the square mean roughness is measured on each of both sides of the film is 0.3 nm or more and 10 nm or less and the square mean roughness on the minor axis is 10 nm or less. 14. The method of claim 13,
And a larger square-averaged roughness of 1 nm or more and 20 nm or less. The method according to claim 13 or 14,
A polyvinyl alcohol-based polymer film which is a long-film polyvinyl alcohol-based polymer film. A film roll comprising the polyvinyl alcohol-based polymer film according to claim 15 continuously wound. A process for producing a polarizing film using the polyvinyl alcohol polymer film according to any one of claims 13 to 15 as an original film, which comprises a dyeing step, a uniaxial stretching step, a fixing treatment step and a drying step, Wherein an angle formed between the liquid surface of the treatment bath and the film surface is not less than 30 degrees and not more than 85 degrees and a surface on the upper side of the film is a polyvinyl alcohol polymer film, And having a root mean square roughness. A polarizing film produced by the manufacturing method according to claim 17. A polyvinyl alcohol polymer having a chromium plating layer on its surface and having a surface hardness of not less than 550 HV and not more than 900 HV at Vickers hardness and a surface temperature of not less than 50 ° C but not more than 115 ° C, Wherein the polyvinyl alcohol polymer in a solution state or in a molten state has an area (maximum width and a maximum width) on the surface of the metal support immediately before starting to soften the polyvinyl alcohol polymer, Mm &lt; ² &gt;) is not more than 0.7 pieces / mm &lt; ² &gt;. 20. The method of claim 19,
Wherein the polyvinyl alcohol-based polymer in a solution state or a molten state is in the form of a film-forming stock solution containing a polyvinyl alcohol-based polymer and water. 21. The method according to claim 19 or 20,
Wherein the polymerization degree of the polyvinyl alcohol polymer is from 3,000 to 10,000. 22. The method according to any one of claims 19 to 21,
Wherein the surface hardness of the metal support is 600 HV or more and less than 800 HV by Vickers hardness. 23. The method according to any one of claims 19 to 22,
And a step of setting a surface temperature of a metal support having a chromium plating layer on its surface and having a surface hardness of 550 HV or more and 900 HV or less in terms of Vickers hardness at 50 占 폚 or more and 115 占 폚 or less at a rate of 0.5 占 폚 / hour or longer. 24. The method according to any one of claims 19 to 23,
A process for producing the polyvinyl alcohol-based polymer film according to any one of claims 1 to 6 and 13 to 15.