WO2015079920A1

WO2015079920A1 - Polarizing-film manufacturing method

Info

Publication number: WO2015079920A1
Application number: PCT/JP2014/080019
Authority: WO
Inventors: 真由美内野; 絵美藤井; 豊和杉原; 修風藤
Original assignee: 株式会社クラレ
Priority date: 2013-11-26
Filing date: 2014-11-13
Publication date: 2015-06-04
Also published as: TW201530180A; KR20160091313A; JPWO2015079920A1; CN105745563A; JP6444858B2; CN105745563B; TWI689745B; KR102234601B1

Abstract

[Problem] To provide a polarizing-film manufacturing method that: minimizes film breakage during stretching and drying, for example, even when using a thin polyvinyl-alcohol film; and makes it easy to manufacture a polarizing film that exhibits excellent polarizing performance. [Solution] A polarizing-film manufacturing method that has a stretching step in which a polyvinyl-alcohol film is stretched. Said polarizing-film manufacturing method also has a step in which a gas is blown onto both widthwise edges of a polyvinyl-alcohol film that has water adhering to the surface thereof and/or a step in which a thin body is made to contact same. Preferably, this polarizing-film manufacturing method also has a water immersion step in which a polyvinyl-alcohol film is immersed in water, and the aforementioned polyvinyl-alcohol film that has water adhering to the surface thereof is the polyvinyl-alcohol film that was immersed in water in said water immersion step and has been taken out of said water.

Description

Manufacturing method of polarizing film

Even when a thin polyvinyl alcohol film is used, the present invention can suppress the folding of the end portion of the polyvinyl alcohol film, hardly cause the film to break during stretching or drying, and has a polarizing performance. The present invention relates to a method for producing a polarizing film capable of easily producing an excellent polarizing film.

A polarizing plate having a light transmission and shielding function is a basic component of a liquid crystal display (LCD) together with a liquid crystal that changes a polarization state of light. Many polarizing plates have a structure in which a protective film such as a cellulose triacetate (TAC) film is bonded to the surface of a polarizing film. As a polarizing film constituting the polarizing plate, a polyvinyl alcohol film (hereinafter referred to as “polyvinyl”). alcohol "and" PVA "and is sometimes abbreviated) iodine dye stretched film was oriented uniaxially stretched (I ₃ ^- and I ₅ ^-, etc.), such as a dichroic organic dye dichroic dye is adsorbed What you are doing is the mainstream. Such a polarizing film is usually obtained by uniaxially stretching a PVA film preliminarily containing a dichroic dye, adsorbing a dichroic dye simultaneously with uniaxial stretching of the PVA film, or uniaxially stretching the PVA film. It is continuously produced by adsorbing chromatic dyes.

LCDs are used in a wide range of devices such as small devices such as calculators and wrist watches, notebook computers, liquid crystal monitors, liquid crystal color projectors, liquid crystal televisions, in-vehicle navigation systems, mobile phones, and measuring devices used indoors and outdoors. However, in recent years, it is often used for mobile applications such as small notebook personal computers and mobile phones, and there is an increasing demand for thinner polarizing plates.

One way to reduce the thickness of the polarizing plate is to reduce the thickness of the polarizing film. To this end, it is conceivable to reduce the thickness of the PVA film that is the raw material of the polarizing film. However, a thin PVA film is liable to break when stretched or dried, and the productivity and yield of the polarizing film are reduced, leading to high costs.

As a technique for producing a thin polarizing film without causing breakage of the film, there is known a method of forming a thin PVA layer on a plastic film by a coating method and stretching the laminate (for example, Patent Document 1 and 2).

Japanese Patent No. 4804588 Japanese Patent No. 4815544

However, the method using a laminate formed by forming a PVA layer on a plastic film by a coating method has the following problems.
(I) The coating operation and the subsequent drying operation are complicated.
(Ii) Since the heat treatment for insolubilizing the PVA layer needs to be performed in the state of a laminate, the plastic film used is limited to a film that can be stretched even after the heat treatment, and the cost increases.
(Iii) In a laminate formed by forming a PVA layer on a plastic film by a coating method, the adhesive strength between the plastic film and the PVA layer is relatively high, and when a laminate having such a high adhesive strength is stretched, A moderate neck-in of the PVA layer is hindered, and it is difficult to obtain a polarizing film excellent in polarizing performance.

The present invention is a method for producing a polarizing film, which is capable of easily producing a polarizing film that is less likely to break during stretching or drying even when a thin PVA film is used, and that has excellent polarizing performance. The purpose is to provide.

As a result of intensive studies to achieve the above object, the inventors of the present invention, when producing a polarizing film using a thin PVA film, remove the PVA film such as a swelling process and a dyeing process performed before stretching. PVA film with water adhering to the surface after passing through the water contact step to be contacted with the surface tends to bend at the end in the width direction, and this causes breakage in the subsequent stretching step. PVA film with water adhering to the surface even after stretching is still likely to be folded at the end in the width direction, which causes the film to break due to shrinkage in the subsequent drying process. It tends to occur, and a gas such as air is blown on both ends of the PVA film with water attached to the surface. The occurrence of folding at the end in the width direction of the PVA film is suppressed by bringing a thin body such as a film into contact, and the film breaks during stretching or drying (stretch breakage, etc.) The present invention was completed through further studies based on these findings.

That is, the present invention
[1] A method for producing a polarizing film having a stretching step of stretching a PVA film, which includes a step of blowing gas and / or contacting a thin body on both ends in the width direction of the PVA film having water attached to the surface. ,Production method;
[2] The PVA film having a water immersion step of immersing the PVA film in water, wherein the PVA film having water attached to the surface is after the PVA film immersed in water by the water immersion step is taken out of the water, [1] production method;
[3] The production method of the above [2], wherein the water immersion step is at least one selected from the group consisting of a swelling step, a dyeing step, a crosslinking step, a stretching step, and a fixing treatment step;
[4] A manufacturing method including a step of bringing a thin body into contact with both ends in the width direction of a PVA film having water attached to the surface, and after removing the PVA film immersed in water by the water immersion step, The thin body is brought into contact with both ends in the width direction of the PVA film in a period from the time when the PVA film is separated from the water surface to the first contact with the roll. ] Or [3] production method;
[5] The PVA film in the portion where the thin body is in contact with both ends in the width direction with respect to the length in the length direction of the PVA film between the PVA film and the first contact roll after leaving the water surface The production method according to the above [4], wherein the ratio of the length in the length direction is 10% or more;
[6] A manufacturing method including a step of bringing a thin body into contact with both ends in the width direction of a PVA film having water attached to the surface, wherein both ends in the width direction of the PVA film are thin at a portion where the PVA film is separated from the water surface. Any one of the above-mentioned [2] to [5], which is in contact with the body;
[7] A manufacturing method including a step of bringing a thin body into contact with both end portions in the width direction of a PVA film having water attached to the surface, wherein two or more rolls sequentially contacting the PVA film having water attached to the surface The method according to any one of [1] to [6] above, wherein the thin body is brought into contact with both ends in the width direction of the PVA film between at least one set of two continuous rolls. ;
[8] The ratio of the length in the length direction of the PVA film at the portion where the thin body is in contact with both ends in the width direction to the length in the length direction of the PVA film between the two continuous rolls Is 10% or more, the production method of the above [7];
[9] A production method comprising a step of bringing a thin body into contact with both ends in the width direction of a PVA film having water attached to the surface, wherein the width of the thin body is 1 cm or more. Any one of the production methods;
[10] A manufacturing method including a step of bringing a thin body into contact with both ends in the width direction of a PVA film having water attached to the surface, wherein the water contact angle of the thin body at a portion in contact with the PVA film is 90 ° or less Any one of the production methods of [1] to [9] above;
[11] The production method according to any one of [1] to [10] above, wherein a gas having a wind speed of 0.1 m / second or more is blown to both ends in the width direction of the PVA film having water attached thereto;
[12] The method according to any one of [1] to [11] above, further comprising a step of bringing a plastic film into contact with both ends in the width direction of the PVA film having water attached thereto;
[13] Any of the above [1] to [12], which includes a step of blowing a gas and / or contacting a thin body on both ends in the width direction of the PVA film having water attached to the surface before the stretching step One manufacturing method;
[14] The production method of any one of [1] to [13] above, wherein the PVA film has a thickness of 50 μm or less;
About.

According to the present invention, even when a thin PVA film is used, the polarizing film is less likely to break during stretching or drying, and a polarizing film excellent in polarizing performance can be easily produced. A manufacturing method is provided.

It is the schematic which shows an example (method A) of making the plastic film which is a thin body contact the width direction both ends of the PVA film with which water adhered to the surface. It is the schematic which shows an example (method B) of making the plastic film which is a thin body contact the width direction both ends of the PVA film with which water adhered to the surface. FIG. 4 is a schematic diagram showing the positions of L1 and L2 in a particular embodiment. FIG. 6 is a schematic diagram showing the positions of L3 and L4 in a particular embodiment. It is the schematic which shows the manufacturing method of the polarizing film in Example 7.

Hereinafter, the present invention will be described in detail.
The production method of the present invention for producing a polarizing film has a stretching step of stretching a PVA film. And in the manufacturing method of the present invention, water adheres to the surface, which is generated by passing a PVA film such as a swelling step, a dyeing step, a cross-linking step, a stretching step, a fixing treatment step, etc. through a water contact step that makes contact with water. It has the process of spraying gas and / or the process of making a thin body contact with respect to the width direction both ends of a PVA film. Usually, when manufacturing a polarizing film using a PVA film, it is easy to generate | occur | produce in the edge part of the width direction of a PVA film after passing a water contact process, and it causes stretching in an extending process. Breaking or film breakage due to shrinkage in the drying process is likely to occur, but as described above, gas is blown to both ends of the PVA film in a state where water is attached to the surface, or a thin body is contacted The occurrence of folding at the end in the width direction of the PVA film is suppressed, the occurrence of film breakage during stretching or drying is reduced, and the film can be stretched at a higher stretch ratio. It is considered that a polarizing film having excellent polarization performance can be easily produced.

In the production method of the present invention, the step of blowing the gas and the step of bringing the thin body into contact with each other may be employed together, or only one of them may be employed. When both processes are employed, both processes may be performed on the same part of the PVA film with water adhering to the surface (for example, one side and the other side of the corresponding part of the PVA film). Both steps may be carried out in different parts of the PVA film.

[PVA film]
As PVA constituting the PVA film, vinyl esters such as vinyl acetate, vinyl formate, vinyl propionate, vinyl butyrate, vinyl pivalate, vinyl versatate, vinyl laurate, vinyl stearate, vinyl benzoate, isopropenyl acetate, etc. Those obtained by saponifying a polyvinyl ester obtained by polymerizing one or more of the above can be used. Among the above-mentioned vinyl esters, a compound having a vinyloxycarbonyl group (H ₂ C═CH—O—CO—) in the molecule is preferable from the viewpoint of ease of production, availability, and cost of PVA, More preferred is vinyl acetate.

The polyvinyl ester is preferably obtained using only one or two or more vinyl esters as monomers, and more preferably obtained using only one vinyl ester as a monomer. However, as long as the effect of the present invention is not significantly impaired, a copolymer of one or more vinyl esters and other monomers copolymerizable therewith may be used.

Examples of the other monomer copolymerizable with the vinyl ester include α-olefins having 2 to 30 carbon atoms such as ethylene, propylene, 1-butene, and isobutene; (meth) acrylic acid or a salt thereof; (Meth) methyl acrylate, (meth) ethyl acrylate, (meth) acrylate n-propyl, (meth) acrylate i-propyl, (meth) acrylate n-butyl, (meth) acrylate i-butyl, ( (Meth) acrylic acid esters such as t-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, dodecyl (meth) acrylate and octadecyl (meth) acrylate; (meth) acrylamide; N-methyl ( (Meth) acrylamide, N-ethyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, diacetone (meth) acryl (Meth) acrylamide derivatives such as amides, (meth) acrylamide propanesulfonic acid or salts thereof, (meth) acrylamide propyldimethylamine or salts thereof, N-methylol (meth) acrylamide or derivatives thereof; N-vinylformamide, N-vinyl N-vinylamides such as acetamide and N-vinylpyrrolidone; 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, stearyl vinyl ether, etc. Vinyl ether; vinyl cyanide such as (meth) acrylonitrile; vinyl halide such as vinyl chloride, vinylidene chloride, vinyl fluoride, vinylidene fluoride; Allyl compounds such as allyl acetate and allyl chloride; maleic acid or salts thereof, esters or acid anhydrides; itaconic acid or salts thereof, esters or acid anhydrides; vinylsilyl compounds such as vinyltrimethoxysilane; unsaturated sulfonic acids or salts thereof And so on. Said polyvinyl ester can have a structural unit derived from 1 type, or 2 or more types of an above described other monomer.

The proportion of structural units derived from the other monomers in the polyvinyl ester is preferably 15 mol% or less based on the number of moles of all structural units constituting the polyvinyl ester, and is preferably 10 mol% or less. More preferably, it is more preferably 5 mol% or less.

As the above-mentioned PVA, those not graft-copolymerized can be preferably used, but PVA can be used for one or more kinds of graft copolymer as long as the effects of the present invention are not significantly impaired. It may be modified with a monomer. The said graft copolymerization can be performed with respect to at least one of polyvinyl ester and PVA obtained by saponifying it. Examples of the graft copolymerizable monomer include unsaturated carboxylic acids or derivatives thereof; unsaturated sulfonic acids or derivatives thereof; α-olefins having 2 to 30 carbon atoms, and the like. The proportion of structural units derived from the graft copolymerizable monomer in the polyvinyl ester or PVA is preferably 5 mol% or less based on the number of moles of all structural units constituting the polyvinyl ester or PVA.

In the above PVA, a part of the hydroxyl group may be cross-linked or may not be cross-linked. In addition, the PVA may have a hydroxyl group partially reacted with an aldehyde compound such as acetaldehyde or butyraldehyde to form an acetal structure, or may not react with these compounds to form an acetal structure. Also good.

The polymerization degree of the above PVA is not particularly limited, but is preferably 1,000 or more. When the degree of polymerization of PVA is 1,000 or more, the polarizing performance of the obtained polarizing film can be further improved. If the degree of polymerization of PVA is too high, it tends to lead to an increase in the production cost of PVA and poor processability during film formation, so the degree of polymerization of PVA should be in the range of 1,000 to 10,000. Is more preferably 1,500 to 8,000, even more preferably 2,000 to 5,000. The degree of polymerization of PVA as used herein means the average degree of polymerization measured according to the description of JIS K6726-1994.

The saponification degree of PVA is preferably 99.0 mol% or more, more preferably 99.8 mol% or more, and 99.9 mol% or more because the heat and heat resistance of the obtained polarizing film is improved. More preferably. In this specification, the saponification degree of PVA refers to the vinyl alcohol unit relative to the total number of moles of structural units (typically vinyl ester units) and vinyl alcohol units that can be converted into vinyl alcohol units by saponification of PVA. Refers to the proportion (mol%) occupied by the number of moles. The degree of saponification can be measured according to the description of JIS K6726-1994.

The PVA film may contain a plasticizer together with the above PVA. When the PVA film contains a plasticizer, it is possible to improve the handleability and stretchability of the PVA film. As the plasticizer, polyhydric alcohol is preferably used, and specific examples include ethylene glycol, glycerin, propylene glycol, diethylene glycol, diglycerin, triethylene glycol, tetraethylene glycol, trimethylolpropane, and the like. PVA film Can contain one or more of these plasticizers. Among these, glycerin is preferable because the stretchability of the PVA film becomes better.

The content of the plasticizer in the PVA film is preferably 3 to 20 parts by mass, more preferably 5 to 17 parts by mass, and still more preferably 7 to 14 parts by mass with respect to 100 parts by mass of PVA. . When the content of the plasticizer in the PVA film is 3 parts by mass or more with respect to 100 parts by mass of PVA, the stretchability of the PVA film is improved. On the other hand, when the content of the plasticizer in the PVA film is 20 parts by mass or less with respect to 100 parts by mass of PVA, the plasticizer bleeds out on the surface of the PVA film and the handling property of the PVA film is reduced. be able to.

In addition, when a PVA film is produced using a film-forming stock solution for producing a PVA film, which will be described later, the film-forming property is improved and the occurrence of film thickness unevenness is suppressed, and a metal roll is used for film-forming. Since a PVA film can be easily peeled off from these metal rolls and belts when a belt or a belt is used, it is preferable to add a surfactant to the film-forming stock solution. When a PVA film is produced from a film-forming stock solution containing a surfactant, the PVA film may contain a surfactant. There are no particular limitations on the type of surfactant that is blended in the film-forming stock solution for producing the PVA film, and thus the surfactant contained in the PVA film, but from the viewpoint of releasability from a metal roll or belt, an anion is used. Surfactants or nonionic surfactants are preferred, and nonionic surfactants are particularly preferred.

As the anionic surfactant, for example, a carboxylic acid type such as potassium laurate; a sulfate ester type such as octyl sulfate; a sulfonic acid type such as dodecylbenzene sulfonate is suitable.

Nonionic surfactants include, for example, alkyl ether types such as polyoxyethylene oleyl ether; alkylphenyl ether types such as polyoxyethylene octylphenyl ether; alkyl ester types such as polyoxyethylene laurate; polyoxyethylene laurylamino Alkylamine type such as ether; alkylamide type such as polyoxyethylene lauric acid amide; polypropylene glycol ether type such as polyoxyethylene polyoxypropylene ether; alkanolamide type such as lauric acid diethanolamide and oleic acid diethanolamide; polyoxy An allyl phenyl ether type such as alkylene allyl phenyl ether is preferred.
These surfactants can be used alone or in combination of two or more.

When a surfactant is blended in a film-forming stock solution for producing a PVA film, the content of the surfactant in the film-forming stock solution, and thus the content of the surfactant in the PVA film is determined as the film-forming stock solution or the PVA film. The amount is preferably in the range of 0.01 to 0.5 parts by mass, more preferably in the range of 0.02 to 0.3 parts by mass with respect to 100 parts by mass of PVA contained in. When the content of the surfactant is 0.01 parts by mass or more with respect to 100 parts by mass of PVA, the film forming property and the peelability can be improved. On the other hand, when the content of the surfactant is 0.5 parts by mass or less with respect to 100 parts by mass of PVA, the surfactant bleeds out on the surface of the PVA film, resulting in blocking, and handling properties are reduced. Can be suppressed.

The PVA film may be composed only of PVA, or may be composed only of PVA and the above-described plasticizer and / or surfactant. If necessary, an antioxidant, an antifreeze agent, a pH adjuster, You may contain other components other than above-mentioned PVA, a plasticizer, and surfactant, such as a masking agent, a coloring inhibitor, and an oil agent.

The PVA content in the PVA film is preferably in the range of 50 to 100% by mass, more preferably in the range of 80 to 100% by mass, and in the range of 85 to 100% by mass. Further preferred.

The thickness of the PVA film is not particularly limited. However, when a thin PVA film is used, the above-described folding tends to occur at the end in the width direction, and the effect of the present invention is more effective when a thin PVA film is used. The thickness is preferably 50 μm or less, more preferably 45 μm or less, still more preferably 35 μm or less, particularly preferably 25 μm or less, and particularly preferably 20 μm or less because it is remarkably played. Most preferred. Although there is no restriction | limiting in particular in the minimum of the thickness of a PVA film, Since the polarizing film can be manufactured more smoothly, it is preferable that the said thickness is 3 micrometers or more. Further, the PVA film may be a single layer or a laminate in which a PVA layer and other layers are laminated, but it is a single layer because the effects of the present invention are more remarkably exhibited. It is preferable. In the case of a laminate, the thickness of the PVA layer is preferably in the above range.

The shape of the PVA film is not particularly limited, but is preferably a long film because the polarizing film can be continuously produced with high productivity. The length of the long film is not particularly limited, and can be set as appropriate according to the application of the polarizing film to be produced. For example, the length can be in the range of 5 to 20,000 m. There is no restriction | limiting in particular in the width | variety of the said elongate film, For example, although it can be 50 cm or more, since the wide polarizing film is calculated | required in recent years, it is preferable that it is 1 m or more, and it is 2 m or more more. Preferably, it is 4 m or more. There is no particular limitation on the upper limit of the width of the long film, but if the width is too wide, it tends to be difficult to stretch uniformly when a polarizing film is produced with an apparatus in practical use. Therefore, the width of the PVA film is preferably 7 m or less.

The manufacturing method of a PVA film is not specifically limited, The manufacturing method from which the thickness and width | variety of the film after film forming become more uniform can be employ | adopted preferably, For example, above-mentioned PVA which comprises a PVA film, and as needed In addition, a film forming stock solution in which a plasticizer, a surfactant, and other components are dissolved in a liquid medium, and PVA, and if necessary, further include a plasticizer, a surfactant, other components, and a liquid medium, It can manufacture using the melt | dissolution film forming stock solution. When the film-forming stock solution contains at least one of a plasticizer, a surfactant, and other components, it is preferable that these components are uniformly mixed.

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

The volatile fraction of the film-forming stock solution (the content ratio of volatile components such as a liquid medium removed by volatilization or evaporation during film-forming in the film-forming stock solution) varies depending on the film-forming method, film-forming conditions, etc., but 50 to 95 It is preferably in the range of mass%, more preferably in the range of 55 to 90 mass%, and still more preferably in the range of 60 to 85 mass%. When the volatile fraction of the film-forming stock solution is 50% by mass or more, the viscosity of the film-forming stock solution does not become too high, and filtration and defoaming are smoothly performed during preparation of the film-forming stock solution, and there are few foreign matters and defects. Film production is facilitated. On the other hand, when the volatile fraction of the film-forming stock solution is 95% by mass or less, the concentration of the film-forming stock solution does not become too low, and the production of an industrial PVA film becomes easy.

Examples of the film forming method for forming a PVA film using the above-described film forming stock solution include a cast film forming method, an extrusion film forming method, a wet film forming method, a gel film forming method, and the like. A membrane method and an extrusion film forming method are preferred. These film forming methods may be used alone or in combination of two or more. Among these film forming methods, the extrusion film forming method is more preferable because a PVA film having a uniform thickness and width and good physical properties can be obtained. The PVA film can be dried or heat-treated as necessary.

[PVA film with water on the surface]
In the production method of the present invention, a gas is blown to the both ends in the width direction of the PVA film having water attached to the surface and / or a thin body produced by passing through a water contact step of bringing the PVA film into contact with water. A step of contacting. The polarizing film can be usually produced through each process such as a swelling process, a dyeing process, a crosslinking process, a stretching process, and a fixing treatment process, and the production method of the present invention is one or two of these processes. More than one can be included as the water contact step.

The water contact step may be either a water spraying step of spraying water on the PVA film or a water immersion step of immersing the PVA film in water, but the ease and productivity of manufacturing the polarizing film From the viewpoint of the above, it is preferable to be a water immersion step. In particular, since the polarizing film excellent in polarization performance can be easily produced, the production method of the present invention is at least one selected from the group consisting of a swelling process, a dyeing process, a crosslinking process, a stretching process, and a fixing process process. It is preferable to have one process as a water immersion process, and it is more preferable to have at least one process selected from the group consisting of a swelling process, a dyeing process and a crosslinking process as the water immersion process. The PVA film after taking out the PVA film immersed in water by the water immersion step is usually the above-described PVA film having water attached to the surface.
The water used in the water contact step is not limited to pure water, and an aqueous solution or an aqueous dispersion as described later can be used according to the purpose of each step.
Below, each process which can be employ | adopted in the manufacturing method of this invention including the process which can be employ | adopted as a water contact process is demonstrated in detail.

-Swelling process The swelling process in a swelling process can be performed by immersing a PVA film in water. The temperature of the water when immersed in water is preferably in the range of 20 to 40 ° C., more preferably in the range of 22 to 38 ° C., and preferably in the range of 25 to 35 ° C. Further preferred. The time for immersion in water is, for example, preferably in the range of 0.5 to 5 minutes, and more preferably in the range of 1 to 3 minutes. In addition, the water at the time of immersing in water is not limited to pure water, The aqueous solution in which various components melt | dissolved may be sufficient, and the mixture of water and an aqueous medium may be sufficient.

-Dyeing | staining process The dyeing | staining process in a dyeing | staining process can be performed by immersing a PVA film in the aqueous solution containing a dichroic dye. The concentration of the dichroic dye in the aqueous solution containing the dichroic dye can be appropriately set according to the type of the dichroic dye to be used, for example, within the range of 0.001 to 1% by mass. However, when an iodine-potassium iodide aqueous solution is used as an aqueous solution containing a dichroic dye, iodine-based dye can be efficiently adsorbed on the PVA film, so that the concentration of iodine (I ₂ ) used is Is preferably in the range of 0.01 to 1.0 mass%, and the concentration of potassium iodide (KI) used is preferably in the range of 0.01 to 10 mass%. The temperature of the aqueous solution containing the dichroic dye is preferably in the range of 20 to 50 ° C., and preferably in the range of 25 to 40 ° C., because the dichroic dye can be efficiently adsorbed to the PVA film. It is more preferable. In addition, a dyeing | staining process can be abbreviate | omitted when using the PVA film which previously contained the dichroic dye.

Examples of the dichroic dye, iodine based dye (I ₃ ^- and I ₅ ^-, etc.), and the like dichroic organic dyes. The iodine dye can be obtained, for example, by bringing iodine (I ₂ ) into contact with potassium iodide. Examples of the dichroic organic dye include 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; Direct Orange 26, 39, 106, 107 and the like. Among these dichroic dyes, iodine-based dyes are preferable from the viewpoints of handleability, availability, and polarization performance. Incidentally, the dichroic dye may either be two or more even alone, for example, I ₃ ^- may be a balanced mixture as ^- and I _5.

-Crosslinking step When the crosslinking step is performed, crosslinking is introduced into the PVA film, and when the stretching step is performed at a relatively high temperature and wet, it is possible to effectively prevent the PVA from eluting into water. From such a viewpoint, the crosslinking step is preferably performed after the dyeing step. The crosslinking treatment can be performed by immersing the PVA film in an aqueous solution containing a crosslinking agent. As the crosslinking agent, one or more of boron compounds such as boric acid and borate such as borax can be used. The concentration of the crosslinking agent in the aqueous solution containing the crosslinking agent is preferably in the range of 1 to 15% by mass, and more preferably in the range of 2 to 7% by mass. The aqueous solution containing a crosslinking agent may contain an auxiliary agent such as potassium iodide. The temperature of the aqueous solution containing the crosslinking agent is preferably in the range of 20 to 50 ° C., and more preferably in the range of 25 to 40 ° C.

Separately from the stretching step described below, the PVA film can be stretched during the water contact step and / or during each water contact step when the water contact step spans multiple steps. By performing such stretching (pre-stretching), wrinkles can be prevented from entering the PVA film. The draw ratio of the pre-stretching is preferably 4 times or less based on the original length of the PVA film before stretching from the viewpoint of the polarizing performance of the polarizing film to be obtained, and is in the range of 1.5 to 3.5 times More preferably, it is within. Regarding the stretching ratio in each water contact step, for example, the stretching ratio in the swelling step is preferably in the range of 1.1 to 3 times, and in the range of 1.2 to 2.5 times. More preferably, it is more preferably within the range of 1.4 to 2.3 times; the draw ratio in the dyeing step is preferably 2 times or less, more preferably 1.8 times or less. Preferably, it is more preferably in the range of 1.1 to 1.5 times; the draw ratio in the crosslinking step is preferably 2 times or less, more preferably 1.5 times or less. More preferably, it is in the range of 0.05 to 1.3 times.

-Stretching process In the stretching process of stretching the PVA film, the stretching method is not particularly limited, and may be performed by either a wet stretching method or a dry stretching method. In the case of the wet stretching method, it can be carried out in an aqueous solution containing one or two or more of boron compounds such as boric acid such as boric acid and borax, or in an aqueous solution containing the dichroic dye described above. It can also be performed in a fixed treatment bath described later. In the case of the dry stretching method, stretching may be performed at room temperature, stretching may be performed while applying heat, or stretching may be performed after water absorption. Among these, the wet stretching method is preferable from the viewpoint of the uniformity of the thickness in the width direction of the obtained polarizing film, and it is more preferable to stretch in a boric acid aqueous solution. The concentration of boric acid in the boric acid aqueous solution is preferably within the range of 0.5 to 6.0% by mass, more preferably within the range of 1.0 to 5.0% by mass, More preferably, it is in the range of -4.0 mass%. The aqueous solution containing the boron compound may contain potassium iodide, and its concentration is preferably in the range of 0.01 to 10% by mass.

The temperature at which the PVA film is stretched in the stretching step is preferably within a range of 30 to 90 ° C, more preferably within a range of 40 to 80 ° C, and within a range of 50 to 70 ° C. Is more preferable.

The stretching ratio in the stretching step is preferably 1.2 times or more, more preferably 1.5 times or more, and more preferably 2 times or more, because a polarizing film superior in polarization performance can be obtained. Is more preferable. Further, the total draw ratio including the above-described draw ratio of the pre-stretch (the ratio obtained by multiplying the draw ratios of the respective stretches) is 5.5 times or more based on the original length of the PVA film used. Is preferably 5.7 times or more, more preferably 5.8 times or more, and particularly preferably 5.9 times or more. By setting each stretching ratio within the above range, a polarizing film having better polarizing performance can be obtained. The upper limit of the total draw ratio is not particularly limited, but is preferably 8 times or less.

The stretching of the PVA film in the stretching step is preferably uniaxial stretching from the viewpoint of the performance of the obtained polarizing film. There is no particular limitation on the direction of uniaxial stretching, and uniaxial stretching or lateral uniaxial stretching in the length direction of a long film can be adopted, but since it is easy to obtain a polarizing film superior in polarization performance, in the length direction Uniaxial stretching is preferred. Uniaxial stretching in the length direction can be performed by changing the peripheral speed between the rolls using a stretching apparatus including a plurality of rolls parallel to each other. On the other hand, lateral uniaxial stretching can be performed using a tenter type stretching machine.

-Fixing process The fixing process in a fixing process is mainly performed in order to strengthen adsorption | suction of the dichroic dye to the stretched PVA film. The fixing treatment can be performed by immersing the stretched PVA film in a fixing treatment bath. As the fixing treatment bath, an aqueous solution containing one or more of boron compounds such as boric acid such as boric acid and borax can be used. Moreover, you may add an iodine compound and a metal compound in a fixed treatment bath as needed. The concentration of the boron compound in the aqueous solution containing the boron compound used as the fixing treatment bath is generally preferably in the range of 2 to 15% by mass, and more preferably in the range of 3 to 10% by mass. The temperature of the fixing treatment bath is preferably in the range of 15 to 60 ° C, more preferably in the range of 25 to 40 ° C.

[Process of blowing gas]
The blowing of gas in the step of blowing the gas to both ends in the width direction of the PVA film having water attached to the surface caused by passing the water contact step is caused by shrinkage in the drying step even after the stretching step. Although it becomes possible to reduce the occurrence of film breakage, the film breakage during the production of a polarizing film is particularly likely to occur during stretching, and therefore it may have a step of blowing the gas before the stretching step. preferable. In this case, at least one process selected from the group consisting of a swelling process, a dyeing process, and a crosslinking process is used as a water contact process, and both ends in the width direction of the PVA film in which water adheres to the surface after passing through the water contact process A gas may be sprayed on the surface. In addition, when it has multiple processes which spray the said gas, it is preferable that at least 1 process of them exists before an extending process.

When the production method of the present invention has a plurality of water contact steps, gas is blown to both ends in the width direction of the PVA film in which water adheres to the surface after passing through the water contact step for all of the water contact steps. Alternatively, for some of these water contact processes, gas may be blown to both ends in the width direction of the PVA film with water adhering to the surface after passing through the water contact process. As a preferred embodiment of the present invention, each of the swelling process, the dyeing process, the crosslinking process, the stretching process, and the fixing process process has a water contact process in this order, and at least the swelling process, the dyeing process, and the crosslinking process are passed. The aspect which sprays gas to the width direction both ends of the PVA film which water adhered to the back surface is mentioned, and as a more preferred mode of the present invention, a swelling process, a dyeing process, a crosslinking process, an extending process, and a fixing process process, All have this order as a water contact process, and the aspect which sprays gas on the width direction both ends of the PVA film in which water adhered to the surface after passing through at least a swelling process, a dyeing process, a crosslinking process, and a fixing treatment process among these. Can be mentioned.

There are no particular limitations on the type of gas to be blown, and examples thereof include nitrogen gas, argon gas, air, and the like, but air is preferable because it is inexpensive.

Although there is no restriction | limiting in particular in the wind speed of the gas to blow, Since generation | occurrence | production of the folding in the edge part of the width direction of a PVA film can be suppressed more effectively, it is preferable that it is 0.1 m / second or more, and is 0.0. It is more preferably 5 m / second or more, further preferably 1.0 m / second or more, and particularly preferably 1.5 m / second or more. The upper limit of the wind speed is not particularly limited. However, if the wind speed is too high, the PVA film tends to be wrinkled. Therefore, the wind speed is preferably 20 m / second or less.

Although there is no restriction | limiting in particular in the direction of the gas to blow, Since generation | occurrence | production of the folding in the edge part of the width direction of a PVA film can be suppressed more effectively, it goes to the width direction outer side from the width direction center part side of a PVA film. And it is preferable to spray so that it may follow a substantially PVA film surface.

[Step of contacting the thin body]
The contact of the thin body in the step of bringing the thin body into contact with both ends in the width direction of the PVA film having water attached to the surface, which is caused by passing the water contact step, may be performed after the stretching step. Although it becomes possible to reduce the occurrence of film breakage due to shrinkage in the drying process, the film breakage during the production of the polarizing film is particularly likely to occur during stretching. It is preferable to have a step of contacting. In this case, at least one process selected from the group consisting of a swelling process, a dyeing process, and a crosslinking process is used as a water contact process, and both ends in the width direction of the PVA film in which water adheres to the surface after passing through the water contact process What is necessary is just to make a thin body contact. In addition, when it has two or more processes which make the said thin body contact, it is preferable that at least 1 process of them exists before an extending process.

When the production method of the present invention has a plurality of water contact steps, the thin body is formed at both ends in the width direction of the PVA film in which water adheres to the surface after passing through the water contact step. Or, for some of these water contact processes, the thin body is contacted to both ends in the width direction of the PVA film with water adhering to the surface after passing through the water contact process. Can be either. As a preferred embodiment of the present invention, each of the swelling step, the dyeing step, the crosslinking step and the stretching step has a water contact step in this order, and at least the surface after passing through the swelling step, the dyeing step and the crosslinking step. The aspect which makes a thin body contact the width direction both ends of the PVA film to which water adhered is mentioned.

The material constituting the thin body is not particularly limited, and examples thereof include plastics; fabrics such as woven fabrics, knitted fabrics and nonwoven fabrics; composites obtained by impregnating these fabrics with plastics and the like; metals; glass and the like. Although mentioned, since the effect of this invention is show | played more notably, it is preferable that the said thin body is a plastic film.

Examples of the plastic constituting the plastic film include various thermoplastic resins such as polyolefin (polyethylene, polypropylene, polymethylpentene, etc.), polystyrene, polycarbonate, polyvinyl chloride, methacrylic resin, nylon, polyester (polyethylene terephthalate, etc.), And copolymers having a plurality of types of monomer units constituting these thermoplastic resins. In the plastic film, only one type of plastic or two or more types of plastic may be included. Among these, since generation | occurrence | production of the folding in the edge part of the width direction of a PVA film can be suppressed more effectively, polyester and polyolefin are preferable and polyester is more preferable. In addition, there is no restriction | limiting in particular in the method of manufacturing a plastic film, It can manufacture by well-known methods, such as melt molding and calendar molding.

It is preferable that the water contact angle of the thin body in the portion in contact with the PVA film is 90 ° or less. When the water contact angle is 90 ° or less, the occurrence of folding at the end in the width direction of the PVA film can be more effectively suppressed. In this respect, the water contact angle is more preferably 80 ° or less, and further preferably 60 ° or less. The water contact angle can be measured by a contact angle test as described in JIS R3257: 1999, and can be specifically measured by the method described later in the examples. The water contact angle can be adjusted, for example, by corona treatment of the surface of the thin body using a corona surface treatment apparatus (Kasuga Denki Co., Ltd.).

Although there is no restriction | limiting in particular in the thickness of a thin-shaped body, Since generation | occurrence | production of the folding in the edge part of the width direction of a PVA film can be suppressed more effectively, the said thickness is preferably 10 micrometers or more, 15 micrometers or more It is more preferable that it is 20 μm or more. Moreover, there is no restriction | limiting in particular in the upper limit of the thickness of a thin body, The said thickness can be made into 1 cm or less, but since the polarizing film can be manufactured more smoothly, the said thickness may be 5 mm or less. Preferably, it is 1 mm or less, more preferably 500 μm or less, and particularly preferably 100 μm or less.

Although there is no restriction | limiting in particular in the shape of a thin body, Since generation | occurrence | production of the folding in the edge part of the width direction of a PVA film can be suppressed more effectively, the width | variety (when making it contact with a PVA film) The length in the same direction as the width direction of the PVA film is preferably 1 cm or more, more preferably 2 cm or more, still more preferably 3 cm or more, and particularly preferably 5 cm or more. Moreover, it is preferable that the said width | variety is 20 cm or less from a viewpoint of reducing disturbances, such as a damage | wound in a PVA film and a polarizing film. By contacting the thin body having such a width, at each end in the width direction of the PVA film, the width of the portion where the PVA film and the thin body are in contact, preferably 0.5 cm or more, More preferably 1 cm or more, still more preferably 1.5 cm or more, particularly preferably 2 cm or more, and preferably 20 cm or less, more preferably 10 cm or less.

When the production method of the present invention includes a water immersion step as a water contact step, both ends of the PVA film in the width direction with water attached to the surface after the PVA film immersed in water by the water immersion step is taken out of the water. It is sufficient that the thin body is brought into contact with the PVA film, for example, the position before the thin body is brought into contact with both ends of the PVA film in the width direction before the PVA film immersed in water by the water immersion step is taken out of the water. Or you may set to the time of taking out from water, or you may set the said position to the time after taking out the PVA film immersed in water by the water immersion process from water. Moreover, although the thin body may contact the both ends of the width direction of the PVA film only once, it may be performed twice or more. In the case where the production method of the present invention has a water immersion step as the water contact step, it is possible to more effectively suppress the occurrence of folding at the end in the width direction of the PVA film. It is preferable to set the position at which the thin body starts to come into contact with both ends in the width direction of the film at a time point before or after taking out the PVA film immersed in water by the water dipping process. In this case, both ends of the PVA film in the width direction are in contact with the thin body in the portion where the PVA film is separated from the water surface.

As a method of bringing the thin body into contact with both ends in the width direction of the PVA film having water attached to the surface, for example,
Method A: For the moving direction of the PVA film, by installing a pair of thin bodies with the upstream end as a fixed end and the downstream end as a free end in the vicinity of both ends of the PVA film , A method of contacting the PVA film over the downstream end from any position between the upstream end and the downstream end by the tension or water pressure by the water,
Method B: A pair of endless belt-like thin bodies are installed in the vicinity of both ends of the PVA film, and the portions that are brought into contact with both ends in the width direction of the PVA film are along the moving direction of the PVA film as necessary. A method of contacting with the PVA film while moving,
The method A is preferable because the operation is simple. In addition, there is no restriction | limiting in particular in the direction at the time of making a thin body contact the width direction both ends of a PVA film, either from the vertical direction upper side of a PVA film, or from the vertical direction lower side of a PVA film, But you can.

FIG. 1 is a schematic view showing a contact method according to Method A, (a) is a view seen from the upper side in the vertical direction, and (b) is a view seen from the side. FIG. 1 shows that when a PVA film 1 is moving in the length direction, a pair of thin plastic films 2 installed in the vicinity of both ends of the PVA film are seen from the lower side in the vertical direction of the PVA film 1. A mode of contacting the PVA film 1 is shown. The plastic film 2 has an upstream end 3 in the moving direction of the PVA film as a fixed end, and a downstream end 4 in the free end. Then, from the position 5 between the fixed end 3 and the free end 4 on the plastic film 2 to the free end 4, the end 6 in the width direction of the PVA film and the plastic film are in contact.

FIG. 2 is a schematic view showing a contact method according to Method B, (a) is a view seen from the upper side in the vertical direction, and (b) is a view seen from the side. FIG. 2 shows that when the PVA film 1 is moving in the length direction, a pair of endless belt-like plastic films 2 installed in the vicinity of both ends of the PVA film are perpendicular to the PVA film 1. The mode which contacts the PVA film 1 from the direction lower side is shown. The endless belt-shaped plastic film 2 is moving at a speed substantially equal to the moving speed of the PVA film so that the portions brought into contact with both ends in the width direction of the PVA film are along the moving direction of the PVA film.

Usually, when producing a polarizing film from a PVA film, after passing through the water contact step, preferably after taking out the PVA film immersed in water by the water immersion step (in one example, the next water contact step). In many cases, the PVA film is held or conveyed using one or two or more rolls (guide roll, nip roll, etc.). In the production method of the present invention, it is preferable to use such a roll. For example, when the PVA film that has been immersed in water by the water immersion process has one or more rolls that come into contact with the PVA film, Since the occurrence of folding at the end in the width direction of the PVA film can be more effectively suppressed, both ends of the PVA film in the width direction are between the PVA film and the first contact roll after leaving the water surface. It is preferable to bring a thin body into contact with the part.

Moreover, as mentioned above, when making a thin body contact the both ends of the width direction of a PVA film between the rolls which contact a PVA film first after it leaves | separates from a water surface, a PVA film (both surfaces) is from a water surface. The length in the length direction of the PVA film at the portion where the thin body is in contact with both ends in the width direction with respect to the length L1 in the length direction of the PVA film between the roll and the first contact after the separation The ratio of L2 (100 × L2 / L1 (%)) is preferably 10% or more because it can more effectively suppress the occurrence of folding at the end in the width direction of the PVA film. % Or more is more preferable, and 80% or more is still more preferable. There is no restriction | limiting in particular in the upper limit of the said ratio, For example, the said ratio can be 95% or less.

FIG. 3 shows a case in which a thin plastic film 2 is brought into contact with both ends in the width direction of the PVA film 1 between the PVA film 1 and the first roll 10 after the PVA film 1 leaves the water surface. The position of L1 and L2 in the case of making the plastic film 2 contact is shown schematically. In FIG. 3, the position 5 at which the plastic film 2 starts to come into contact with both ends in the width direction of the PVA film 1 is set to a time point before the PVA film 1 immersed in water by the water immersion process is taken out from the water. That is, both ends of the PVA film 1 in the width direction are already in contact with the plastic film 2 in the portion where the PVA film 1 is separated from the water surface 8. Therefore, in FIG. 3, the starting point of L1 and the starting point of L2 are the same.

Moreover, the PVA film which water adhered to the surface produced by letting a water contact process pass etc., Preferably the PVA film which water adhered to the surface after taking out the PVA film immersed in water by the water immersion process from water Between two successive rolls of at least one set of these rolls (until the PVA film leaves the upstream roll and contacts the downstream roll) In the meantime, it is also preferable to bring the thin body into contact with both ends of the PVA film in the width direction because the occurrence of folding at the ends of the PVA film in the width direction can be more effectively suppressed. As a preferable aspect in the production method of the present invention, the thin body is contacted at both ends in the width direction of the PVA film with water attached to the surface after the PVA film is separated from the water surface until the first contact with the roll. Then, after releasing the contact with the thin body, between the two continuous rolls of at least one of the two or more rolls sequentially contacted by the PVA film having water attached to the surface, again The method of making a thin body contact the both ends of the width direction of a PVA film is mentioned.

Moreover, as mentioned above, it has two or more rolls which the PVA film which the water adhered to the surface contacts sequentially, and between two rolls of at least 1 set of these rolls, a PVA film of When the thin body is brought into contact with both ends in the width direction, the portion where the thin body is in contact with both ends in the width direction with respect to the length L3 in the length direction of the PVA film between the two continuous rolls. Since the ratio (100 × L4 / L3 (%)) of the length L4 in the length direction of the PVA film can more effectively suppress the occurrence of folding at the end in the width direction of the PVA film, 10 % Or more, preferably 30% or more, and more preferably 80% or more. There is no restriction | limiting in particular in the upper limit of the said ratio, For example, the said ratio can be 95% or less.

FIG. 4 shows a case where the plastic film 2 as a thin body is brought into contact with both ends in the width direction of the PVA film 1 between a pair of two continuous rolls 11, and the plastic film 2 is brought into contact with the method A. The positions of L3 and L4 in FIG.

[Drying process]
A polarizing film can be produced by stretching, further performing a fixing treatment as required, and then drying. The drying conditions are not particularly limited, but the drying temperature is preferably within the range of 30 to 150 ° C, and more preferably within the range of 50 to 130 ° C. A polarizing film excellent in dimensional stability is easily obtained by drying at a temperature within the above range.

[Polarizer]
The polarizing film obtained as described above is usually used as a polarizing plate by attaching a protective film that is optically transparent and has mechanical strength to both sides or one side. As the protective film, a cellulose triacetate (TAC) film, an acetic acid / cellulose butyrate (CAB) film, an acrylic film, a polyester film, or the like can be used. Examples of the adhesive for bonding include PVA adhesives and urethane adhesives, among which PVA adhesives are suitable.

Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited to these examples. In addition, each measurement or evaluation method of the wind speed of the gas employ | adopted in the following Examples and the comparative examples, the water contact angle of a plastic film, the draw ratio which can be continuously operated, and the polarizing performance of a polarizing film is shown below.

[Gas wind speed]
It calculated | required based on description of JIS A1431: 1994 (the air volume measurement method of an air conditioning and ventilation equipment) using the anemometer. Specifically, the wind speed of the gas blown from the gas (air) blowing nozzle used in the following examples or comparative examples was determined. The measurement was performed under conditions of temperature: 25 ° C. and humidity: 50% RH.

[Water contact angle of plastic film]
A 200 mm × 15 mm strip-shaped film piece is cut out from the same plastic film as the plastic film used in the following Examples or Comparative Examples, and the water contact angle on the surface of the film piece in contact with the PVA film is determined according to JIS R3257: 1999. It measured based on the description of (the wettability test method of the substrate glass surface). That is, a water droplet of 4 μl or less is allowed to stand on a horizontally placed film piece, from the shape of the water drop to the radius r (mm) of the surface of the water drop in contact with the film piece, and from the film piece surface to the top of the water drop. Height h (mm) was measured and water contact angle (theta) (degree) was calculated | required by following formula (1).
θ = 2 tan ⁻¹ (h / r) (1)
In addition, the measurement was implemented 5 times and the average value was made into the water contact angle of the plastic film. The measurement was performed under conditions of temperature: 25 ° C. and humidity: 50% RH.

[Stretch ratio for continuous operation]
In the following examples or comparative examples, the total draw ratio is increased stepwise by 0.1 by adjusting the draw ratio in the drawing step, and set immediately before the total draw ratio when the film breaks. The total draw ratio was set as the draw ratio at which continuous operation was possible.

[Polarization performance of polarizing film]
(A) Measurement of transmittance Ts Two square samples of 2 cm in the length direction of the polarizing film and 2 cm in the width direction were collected from the central portion in the width direction of the polarizing film obtained in the following examples or comparative examples. Then, using a spectrophotometer with an integrating sphere ("V7100" manufactured by JASCO Corporation), in accordance with JIS Z8722: 2009 (method for measuring object color), C light source, visibility in visible light region of 2 ° field of view Correction is performed, and for one sample, the light transmittance when tilted by 45 ° with respect to the length direction and the light transmittance when tilted by −45 ° are measured, and an average value Ts1 (% ) Similarly, with respect to the other sample, the light transmittance when tilted by 45 ° and the light transmittance when tilted by −45 ° were measured, and an average value Ts2 (%) thereof was obtained. Ts1 and Ts2 were averaged by the following formula (2) to obtain the transmittance Ts (%) of the polarizing film.
Ts = (Ts1 + Ts2) / 2 (2)

(B) Measurement of polarization degree V Light transmittance T∥ (%) and length when two samples collected by measuring the transmittance Ts are stacked so that their length directions are parallel to each other. The light transmittance T ⊥ (%) when stacked so that the vertical directions are orthogonal to each other is measured in the same manner as in the case of “(a) Measurement of transmittance Ts”, and the degree of polarization is calculated by the following equation (3). V (%) was determined.
V = {(T∥−T⊥) / (T∥ + T⊥)} ^1/2 × 100 (3)

(C) Measurement of fluctuation range (Ts) and fluctuation range (V) On the line passing through the central portion in the width direction of the polarizing film obtained in the following examples or comparative examples, 5 places were spaced at intervals in the length direction. For each location, two square samples of 2 cm in the length direction of the polarizing film and 2 cm in the width direction were collected, and the transmittance Ts (%) and the degree of polarization V (%) were obtained in the same manner as described above. ) For each example or comparative example, the difference between the maximum value and the minimum value of the obtained five transmittances Ts is defined as the fluctuation range (Ts), and the maximum value and the minimum value of the five polarization degrees V obtained are obtained. The difference was defined as the fluctuation range (V).

[Example 1]
A long PVA film having a thickness of 20 μm and a width of 1 m (including PVA, glycerin and a surfactant, the glycerin content is 12 parts by mass with respect to 100 parts by mass of PVA, and the surfactant content is 100 parts by mass of PVA) The PVA film is 0.03 parts by mass with respect to the saponification product of PVA, which is a homopolymer of vinyl acetate, the polymerization degree of PVA is 2,400, and the saponification degree of PVA is 99.9 mol%. The film roll was continuously unwound and subjected to the swelling process, the dyeing process and the crosslinking process in this order.

Here, as a swelling process, the PVA film was immersed in distilled water (temperature: 30 ° C.) for 1 minute, and uniaxially stretched in the length direction at a stretching ratio of 2.0 times. Further, as a dyeing process, the PVA film is in an aqueous solution containing iodine pigments (concentration of iodine used: 0.05 mass%, concentration of potassium iodide used: 1.2 mass%, temperature: 30 ° C.). And uniaxially stretched in the length direction at a stretch ratio of 1.2. Further, as a crosslinking step, the PVA film was immersed in an aqueous boric acid solution (boric acid concentration: 2.6% by mass, temperature: 30 ° C.) for 2 minutes, and uniaxially stretched at a draw ratio of 1.1 times in the length direction. .

Moreover, about any of a swelling process, a dyeing process, and a bridge | crosslinking process, the width direction both ends of the PVA film in the state where water adhered to the surface after taking out the PVA film immersed in water by these each process from water Then, air was blown at a wind speed of 2.0 m / sec so as to be substantially along the PVA film surface from the width direction center side of the PVA film toward the width direction outer side. The air was blown using an air blowing nozzle.

The stretching step was continuously performed following the above-described crosslinking step, and a polarizing film was produced through a fixing treatment step and a drying step in this order. In the stretching step, the PVA film is uniaxially stretched in a length direction in a boric acid aqueous solution (boric acid concentration: 2.8 mass%, potassium iodide concentration: 5 mass%, temperature: 57 ° C.) at a stretching ratio of 1.9 times. (The total draw ratio including the draw ratio of the pre-stretch is 5.0 times). The fixing treatment step was performed by immersing the stretched PVA film in an aqueous boric acid solution (boric acid concentration: 2.6 mass%, potassium iodide concentration: 5 mass%, temperature: 22 ° C.) for 2 minutes. . Furthermore, the drying process was performed by drying the stretched PVA film at 60 ° C. for 1 minute. In addition, the width direction outer side from the width direction center part side of the PVA film in the width direction both ends of the PVA film in a state where water has adhered to the surface after taking out the PVA film immersed in water by the fixing treatment step Then, air was blown at a wind speed of 2.0 m / sec so as to substantially follow the PVA film surface. The air was blown using an air blowing nozzle.

And the draw ratio which can be continuously operated was calculated | required by the above-mentioned method, The polarizing performance of the polarizing film was evaluated by the above-mentioned method using the polarizing film obtained when the said draw ratio which can be continuously operated was employ | adopted. These results are shown in Table 1. In the production of the polarizing film, no fold was observed at the end in the width direction of the PVA film even after passing through any water contact step.

[Examples 2 and 3]
A polarizing film was continuously produced in the same manner as in Example 1 except that the thickness of the PVA film was changed to 15 μm (Example 2) or 60 μm (Example 3).

And the draw ratio which can be continuously operated was calculated | required by the above-mentioned method, The polarizing performance of the polarizing film was evaluated by the above-mentioned method using the polarizing film obtained when the said draw ratio which can be continuously operated was employ | adopted. These results are shown in Table 1. In any of Examples 2 and 3, in the production of the polarizing film, no folding occurred at the end in the width direction of the PVA film even after passing through any water contact step.

[Example 4]
In any of the swelling process, the dyeing process, the crosslinking process, and the fixing treatment process, it was continuously performed in the same manner as in Example 1 except that the air speed of air blown to both ends in the width direction of the PVA film was 1.0 m / second. A polarizing film was manufactured.

And the draw ratio which can be continuously operated was calculated | required by the above-mentioned method, The polarizing performance of the polarizing film was evaluated by the above-mentioned method using the polarizing film obtained when the said draw ratio which can be continuously operated was employ | adopted. These results are shown in Table 1. In addition, in manufacture of said polarizing film, after passing each water contact process, slight folding of width 0.5mm generate | occur | produced in the both ends of the width direction of a PVA film.

[Example 5]
About the fixing process, the polarizing film was continuously manufactured like Example 1 except not having sprayed air.

And the draw ratio which can be continuously operated was calculated | required by the above-mentioned method, The polarizing performance of the polarizing film was evaluated by the above-mentioned method using the polarizing film obtained when the said draw ratio which can be continuously operated was employ | adopted. These results are shown in Table 1. In the production of the above polarizing film, only after passing through the fixing treatment step, slight folding with a width of 0.2 mm occurred at both ends in the width direction of the PVA film.

[Example 6]
About the swelling process, the bridge | crosslinking process, and the fixing process process, the polarizing film was continuously manufactured like Example 1 except not having sprayed air.

And the draw ratio which can be continuously operated was calculated | required by the above-mentioned method, The polarizing performance of the polarizing film was evaluated by the above-mentioned method using the polarizing film obtained when the said draw ratio which can be continuously operated was employ | adopted. These results are shown in Table 1. In the production of the polarizing film, after passing through the cross-linking step and the fixing treatment step, slight folding with a width of 0.7 mm occurred at both ends in the width direction of the PVA film.

[Comparative Example 1]
A polarizing film was continuously produced in the same manner as in Example 1 except that air was not blown in any of the swelling process, the dyeing process, the crosslinking process, and the fixing process.

And the draw ratio which can be continuously operated was calculated | required by the above-mentioned method, The polarizing performance of the polarizing film was evaluated by the above-mentioned method using the polarizing film obtained when the said draw ratio which can be continuously operated was employ | adopted. These results are shown in Table 1. In addition, in manufacture of said polarizing film, after passing each water contact process, the remarkable folding generate | occur | produced in the both ends of the width direction of a PVA film.

[Example 7]
A long PVA film having a thickness of 30 μm and a width of 1 m (including PVA, glycerin and a surfactant, the glycerin content being 12 parts by mass with respect to 100 parts by mass of PVA, and the surfactant content being 100 parts by mass of PVA) The PVA film is 0.03 parts by mass with respect to the saponification product of PVA, which is a homopolymer of vinyl acetate, the polymerization degree of PVA is 2,400, and the saponification degree of PVA is 99.9 mol%. The film roll was continuously unwound and subjected to the swelling process, the dyeing process and the crosslinking process in this order.

In addition, as shown in FIG. 5, in any of the swelling process, the dyeing process, and the crosslinking process, PVA in a state where water adheres to the surface after the PVA film immersed in water by these processes is taken out from the water. The film was brought into contact with the guide roll, and then further brought into contact with a pair of nip rolls. And, after the PVA film is separated from the water surface of water in each process until it comes into contact with the guide roll, the plastic film is brought into contact with both ends in the width direction of the PVA film, and also between the guide roll and the nip roll. The plastic film was brought into contact with both ends in the width direction of the PVA film with water attached to the surface. Each of the plastic films used is a biaxially stretched polyethylene terephthalate (PET) film ("Lumirror" S10 manufactured by Toray Industries, Inc.) having a thickness of 75 μm and a width of 3 cm, and the surface on the side in contact with the PVA film by corona treatment The water contact angle of the PVA film is adjusted to 57 °. With respect to the direction of movement of the PVA film, the upstream end of the plastic film is the fixed end and the downstream end is the free end. The plastic film was brought into contact with both end portions in the width direction of the PVA film by installing on the lower side (the width of the contact portion at each end portion was 2 cm).
In any of the swelling process, the dyeing process, and the crosslinking process, the position at which the plastic film is brought into contact with both ends in the width direction of the PVA film is set to the time point before the PVA film immersed in water is taken out of the water in each process. By doing this, the width direction both ends of the PVA film were made to contact the plastic film in the part which the PVA film leaves | separates from the water surface in each process. In any of the swelling process, the dyeing process, and the crosslinking process, 100 × L2 / L1 was set to 80%, and 100 × L4 / L3 was set to 80%.

The stretching step was continuously performed following the above-described crosslinking step, and a polarizing film was produced through a fixing treatment step and a drying step in this order. In the stretching step, the PVA film is uniaxially stretched in a length direction in a boric acid aqueous solution (boric acid concentration: 2.8 mass%, potassium iodide concentration: 5 mass%, temperature: 57 ° C.) at a stretching ratio of 1.9 times. (The total draw ratio including the draw ratio of the pre-stretch is 5.0 times). The fixing treatment step was performed by immersing the stretched PVA film in an aqueous boric acid solution (boric acid concentration: 2.6 mass%, potassium iodide concentration: 5 mass%, temperature: 22 ° C.) for 2 minutes. . Furthermore, the drying process was performed by drying the stretched PVA film at 60 ° C. for 1 minute.

And the draw ratio which can be continuously operated was calculated | required by the above-mentioned method, The polarizing performance of the polarizing film was evaluated by the above-mentioned method using the polarizing film obtained when the said draw ratio which can be continuously operated was employ | adopted. These results are shown in Table 2. In the production of the polarizing film, no fold was observed at the end in the width direction of the PVA film even after passing through any water contact step.

[Examples 8 and 9]
A polarizing film was continuously produced in the same manner as in Example 7 except that the thickness of the PVA film was changed to 15 μm (Example 8) or 60 μm (Example 9).

And the draw ratio which can be continuously operated was calculated | required by the above-mentioned method, The polarizing performance of the polarizing film was evaluated by the above-mentioned method using the polarizing film obtained when the said draw ratio which can be continuously operated was employ | adopted. These results are shown in Table 2. In any of Examples 8 and 9, in the production of the polarizing film, no fold was observed at the end in the width direction of the PVA film after passing through any water contact step.

[Example 10]
In any of the swelling process, the dyeing process and the crosslinking process, the polarizing film was continuously formed in the same manner as in Example 7 except that 100 × L2 / L1 was set to 5% and 100 × L4 / L3 was set to 5%. Manufactured.

And the draw ratio which can be continuously operated was calculated | required by the above-mentioned method, The polarizing performance of the polarizing film was evaluated by the above-mentioned method using the polarizing film obtained when the said draw ratio which can be continuously operated was employ | adopted. These results are shown in Table 2. In the production of the polarizing film, after passing through the water contact step, a slight fold of 0.5 mm in width occurred at one end in the width direction of the PVA film.

[Example 11]
A polarizing film was continuously produced in the same manner as in Example 7 except that the plastic film was not brought into contact with the crosslinking step.

And the draw ratio which can be continuously operated was calculated | required by the above-mentioned method, The polarizing performance of the polarizing film was evaluated by the above-mentioned method using the polarizing film obtained when the said draw ratio which can be continuously operated was employ | adopted. These results are shown in Table 2. In the production of the polarizing film, after passing through the cross-linking step, slight folding with a width of 0.5 mm occurred at both ends in the width direction of the PVA film.

[Example 12]
Regarding the contact of the plastic film, a polarizing film was continuously produced in the same manner as in Example 7 except that the width of the contact portion at each end was 1 cm.

And the draw ratio which can be continuously operated was calculated | required by the above-mentioned method, The polarizing performance of the polarizing film was evaluated by the above-mentioned method using the polarizing film obtained when the said draw ratio which can be continuously operated was employ | adopted. These results are shown in Table 2. In the production of the polarizing film, after passing through the water contact step, slight folding with a width of 0.7 mm occurred at both ends in the width direction of the PVA film.

[Example 13]
All of the plastic films used are polyethylene terephthalate (PET) films with a thickness of 75 μm and a width of 3 cm, and the water contact angle on the surface in contact with the PVA film is adjusted to 100 ° by corona treatment. A polarizing film was continuously produced in the same manner as in Example 7 except that was used.

[Example 14]
Each of the plastic films used is a linear low density polyethylene (LLDPE) film (SE620N Tamapoly Co., Ltd.) having a thickness of 50 μm and a width of 3 cm, and water on the surface in contact with the PVA film by corona treatment. A polarizing film was continuously produced in the same manner as in Example 7 except that a contact angle adjusted to 85 ° was used.

[Comparative Example 2]
A polarizing film was continuously produced in the same manner as in Example 7 except that the plastic film was not contacted in any of the swelling process, the dyeing process, and the crosslinking process.

And the draw ratio which can be continuously operated was calculated | required by the above-mentioned method, The polarizing performance of the polarizing film was evaluated by the above-mentioned method using the polarizing film obtained when the said draw ratio which can be continuously operated was employ | adopted. These results are shown in Table 2. In the production of the polarizing film, after passing through the water contact step, significant folding occurred at both ends in the width direction of the PVA film.

[Comparative Example 3]
A polarizing film was continuously produced in the same manner as in Example 8 except that the plastic film was not contacted in any of the swelling process, the dyeing process, and the crosslinking process.

And the draw ratio which can be continuously operated was calculated | required by the above-mentioned method, The polarizing performance of the polarizing film was evaluated by the above-mentioned method using the polarizing film obtained when the said draw ratio which can be continuously operated was employ | adopted. These results are shown in Table 2. In addition, in manufacture of said polarizing film, after passing each water contact process, the remarkable folding generate | occur | produced in the both ends of the width direction of a PVA film.

1 PVA film, 2 plastic film, 3 upstream end (fixed end) of plastic film, 4 downstream end of plastic film (free end), 5 plastic film is brought into contact with both widthwise ends of PVA film Start position, 6: Edge of PVA film in width direction, 7: Part where PVA film and plastic film are in contact, 8: Water surface, 9: Position where PVA film is separated from water surface, 10: First after PVA film is separated from water surface 1 roll out of 11 rolls, 13 guide rolls, 14 nip rolls, 15 PVA film rolls.

Claims

A method for producing a polarizing film having a stretching step of stretching a polyvinyl alcohol film, the method comprising a step of blowing a gas and / or contacting a thin body on both ends in the width direction of the polyvinyl alcohol film with water attached to the surface, Production method.
A polyvinyl alcohol film having a water immersion step of immersing the polyvinyl alcohol film in water and having water attached to the surface is after the polyvinyl alcohol film immersed in water by the water immersion step is taken out of the water, Item 2. The manufacturing method according to Item 1.
The production method according to claim 2, wherein the water immersion step is at least one selected from the group consisting of a swelling step, a dyeing step, a crosslinking step, a stretching step, and a fixing treatment step.
A production method comprising a step of bringing a thin body into contact with both ends in the width direction of a polyvinyl alcohol film having water attached to the surface, wherein the polyvinyl alcohol film immersed in water in the water immersion step is taken out of water A thin body is brought into contact with both ends in the width direction of the polyvinyl alcohol film from the time when the polyvinyl alcohol film is separated from the water surface to the first contact with the roll. Item 4. The production method according to Item 2 or 3.
The polyvinyl alcohol film of the portion where the thin body is in contact with both ends in the width direction with respect to the length in the length direction of the polyvinyl alcohol film between the roll after the polyvinyl alcohol film is separated from the water surface and the first contact with the roll The manufacturing method according to claim 4, wherein the ratio of the length in the length direction is 10% or more.
A manufacturing method comprising a step of bringing a thin body into contact with both ends in the width direction of a polyvinyl alcohol film having water attached to the surface, wherein both ends in the width direction of the polyvinyl alcohol film are thin at a portion where the polyvinyl alcohol film is separated from the water surface. The production method according to any one of claims 2 to 5, which is in contact with the shaped body.
A manufacturing method including a step of bringing a thin body into contact with both ends in the width direction of a polyvinyl alcohol film having water attached to the surface, and having two or more rolls that sequentially contact the polyvinyl alcohol film having water attached to the surface. The method according to any one of claims 1 to 6, wherein the thin body is brought into contact with both ends in the width direction of the polyvinyl alcohol film between at least one set of two continuous rolls. .
The ratio of the length in the length direction of the polyvinyl alcohol film in the portion where the thin body is in contact with both ends in the width direction with respect to the length in the length direction of the polyvinyl alcohol film between the two continuous rolls. The manufacturing method of Claim 7 which is 10% or more.
9. The production method comprising a step of bringing a thin body into contact with both ends in the width direction of a polyvinyl alcohol film having water attached thereto, wherein the width of the thin body is 1 cm or more. The production method according to item.
It is a manufacturing method which has the process of making a thin body contact the width direction both ends of the polyvinyl alcohol film with which water adhered to the surface, Comprising: The water contact angle of the thin body in the part which contacts a polyvinyl alcohol film is 90 degrees or less The production method according to any one of claims 1 to 9, wherein:
The production method according to any one of claims 1 to 10, further comprising a step of blowing a gas having a wind speed of 0.1 m / second or more to both ends in the width direction of the polyvinyl alcohol film having water attached to the surface.
The production method according to any one of claims 1 to 11, further comprising a step of bringing a plastic film into contact with both ends in the width direction of the polyvinyl alcohol film having water attached to the surface.
The method according to any one of claims 1 to 12, further comprising a step of blowing a gas and / or bringing a thin body into contact with both ends in the width direction of the polyvinyl alcohol film having water attached to the surface before the stretching step. Production method.
The production method according to any one of claims 1 to 13, wherein the polyvinyl alcohol film has a thickness of 50 袖 m or less.