KR20150040925A - Layered object, polarizing film, and process for producing polarizing film - Google Patents

Abstract

A laminate capable of suppressing elution of PVA in a process of contacting with water even if it is not preceded by the insolubilization treatment and capable of easily producing a polarizing film having excellent polarization performance by using a general polarizing film production facility, A polarizing film having excellent polarizing performance and little leakage of red light in a crossed Nicol state, and a method for producing the polarizing film. The thermoplastic resin film layer and the degree of swelling is laminated with a PVA layer less than 180% 260% material, and the method of manufacturing a polarizing film, which comprises the steps of stretching the laminate, and the birefringence is 45 × 10 ^-3 or more different-color in the matrix And a step of stretching a laminated body having a thermoplastic resin film layer and a PVA layer to a polarizing film on which a coloring matter is adsorbed and a layered product having a PVA layer at a ratio of 5.7 times or more, wherein the average degree of polymerization of PVA contained in the PVA layer is 2,800 Or more and 9,500 or less.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a polarizing film, a polarizing film,

The present invention relates to a laminate having a thermoplastic resin film layer and a polyvinyl alcohol layer, and a method for producing a polarizing film using the laminate. The present invention also relates to a polarizing film in which a dichroic dye is adsorbed to a matrix and a method for producing the polarizing film.

A polarizing plate having light transmission and shielding functions is a fundamental component of a liquid crystal display (LCD) together with a liquid crystal that changes the polarization state of light. Most polarizing plates have a structure in which a protective film such as a cellulose acylate (TAC) film is stuck to the surface of the polarizing film. As the polarizing film constituting the polarizing plate, a polyvinyl alcohol film (hereinafter referred to as " polyvinyl alcohol (I ₃ ^- , I ₅ ^-, etc.) and dichroic organic dyes are added to a matrix (uniaxially stretched oriented film) obtained by uniaxially stretching a polylactic acid The mainstream is that the dichroic dye is adsorbed. Such a polarizing film can be obtained by uniaxially stretching a PVA film containing a dichroic dye in advance or by adsorbing a dichroic dye simultaneously with uniaxial stretching of the PVA film or by uniaxially stretching a PVA film and then adsorbing the dichroic dye And the like.

The LCD is intended to be used in a wide range of small devices such as an electronic calculator and a wrist watch, a notebook PC, a liquid crystal monitor, a liquid crystal color projector, a liquid crystal television, a car navigation system, a mobile phone, , Particularly in mobile applications such as small notebook PCs and mobile phones, and the demand for thinner polarizers has become stronger. In particular, there is a growing demand for a polarizing film constituting a polarizing plate to have a thickness of 10 m or less.

As a method of thinning the polarizing film constituting the polarizing plate, there is a method of stretching, dyeing and drying a laminate formed by forming a PVA layer on one side of a thermoplastic resin film and then peeling off the layer of the stretched thermoplastic resin film (See Patent Documents 1 and 2, etc.).

When the polarizing film is produced by the above-described method, it is important that the PVA contained in the PVA layer does not dissolve in the step of contacting with water at the time of producing the polarizing film, such as dyeing. For this reason, in the conventional method, it is necessary to perform the insolubilization treatment of the PVA layer before the step of contacting with water, such as dyeing.

Specifically, in Patent Document 1, a PVA layer is formed on a resin base material having a thickness of at least 20 탆, and a dichroic substance is adsorbed thereon, and then stretched so as to have a total stretching magnification of 5 times or more the original length in an aqueous boric acid solution A method of producing a polarizing film is described. Patent Document 1 discloses that the PVA layer is subjected to insolubilization treatment in advance before the PVA layer formed on the resin substrate is immersed in the dyeing solution in order to prevent elution of the PVA in the aqueous solution during dyeing, Is immersed in an aqueous solution of boric acid at room temperature. Further, Patent Document 1 describes that the stretching magnification is more preferably 5.5 times or more, that PVA having a polymerization degree of 1,000 to 10,000 is used, and that the maximum draw ratio is 4.0 to 5.5 times.

On the other hand, in Patent Document 2, a laminate obtained by forming a PVA layer on an amorphous ester-based thermoplastic resin base material is stretched at an air temperature of 95 to 150 ° C in an oven to adsorb a dichroic substance, And further stretched to produce a polarizing film. Patent Document 2 discloses a method for producing a polarizing film without the insolubilization treatment by an aqueous solution of boric acid as Example 1. However, actually, in the case of crystallization at a public high temperature stretching at 130 ° C in Example 1 , The PVA layer is insoluble. Patent Document 2 discloses that PVA having a degree of polymerization of 1,000 or more is used.

International Publication No. 2010/100917 Japanese Patent No. 4691205 Specification

However, the above-mentioned boron-containing aqueous solution and the public high-temperature stretching in the prior art in the prior art can not be used because of complicated operations or the use of a general-purpose polarizing film production facility which has been put to practical use so far and special manufacturing facilities are required There was a problem. Thus, the present invention can suppress the elution of PVA in the step of contacting water with a boric acid aqueous solution, even if the insolubilization treatment such as dipping or air high temperature stretching is not performed in advance, and a polarizing film having excellent polarization performance can be used as a general polarizing film The present invention provides a laminate which can be easily manufactured by using a manufacturing facility, and a method for producing a polarizing film using the same.

Further, the polarizing film produced by the conventional method has a problem that the leakage of red light in the cross-Nicol state is large. Therefore, another object of the present invention is to provide a polarizing film having excellent polarizing performance and little leakage of red light in a crossed Nicol state, and a manufacturing method thereof.

DISCLOSURE OF THE INVENTION The inventors of the present invention have made intensive investigations in order to achieve the above object. As a result, in producing a polarizing film by stretching a laminate having a thermoplastic resin film layer and a PVA layer, the swelling degree of the PVA layer of the non- By adjusting the ratio to not less than 180% and not more than 260%, it is possible to inhibit the elution of the PVA in the step of contacting the water with the boric acid aqueous solution even if the insolubilization treatment such as dipping or air high temperature stretching is not performed in advance, Or the above-mentioned insolubilization treatment which requires special manufacturing facilities can be omitted, and a polarizing film excellent in polarization performance can be easily manufactured using a general-purpose polarizing film production facility.

Further, the inventors of the present invention found that, in a polarizing film in which a dichroic dye is adsorbed to a matrix, when the birefringence of the matrix is 45 x 10 < ^-3 > or more higher than the conventional one, It was found that the polarizing film was less leaky.

In order to obtain a polarizing film formed on a thermoplastic resin film by forming a PVA layer on a thermoplastic resin film to form a laminate and performing uniaxial stretching thereon, PVA having an average degree of polymerization of 2,800 to 9,500 It was found that the limiting draw ratio at the time of uniaxial stretching was improved. Generally, when the average degree of polymerization of PVA is high, it is considered that the tension at the time of stretching becomes high and the critical stretching magnification decreases. However, when PVA having the above average polymerization degree is used in obtaining the polarizing film by the above method, As a result, it was unexpected that the limiting draw ratio was not decreased but rather improved as compared with the case of using PVA having an average degree of polymerization of 2,600.

When a polarizing film formed on a thermoplastic resin film is produced by forming a PVA layer on a thermoplastic resin film by using PVA having an average degree of polymerization of 2,800 to 9,500 to form a laminate and stretching it to 5.7 times or more, It has been found that a polarizing film of 45 x 10 < ^-3 > or higher, which is higher than the conventional polarizing film, can be smoothly and easily obtained.

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

That is,

[1] A laminate having a thermoplastic resin film layer and a PVA layer having a degree of swelling of 180% or more and 260% or less (hereinafter sometimes referred to as "laminate (1)")

[2] The laminate of the above-mentioned [1], wherein the PVA contained in the PVA layer has an ethylene content of 1 mol% or more and 12 mol%

[3] The laminate of the above [1] or [2], wherein the 1,2-glycol bond amount of PVA contained in the PVA layer is 0.4 mol% or more and 1.5 mol%

[4] The laminate according to any one of [1] to [3], wherein the average degree of polymerization of the PVA contained in the PVA layer is 1,000 or more and 9,500 or less,

[5] The laminate of any one of the above [1] to [4], wherein the PVA contained in the PVA layer has a saponification degree of 98 mol%

[6] The laminate according to any one of [1] to [5] above, wherein the PVA layer contains a plasticizer in an amount of 1 part by mass or more and 15 parts by mass or less based on 100 parts by mass of PVA.

[7] The laminate of the above [6], wherein the plasticizer is glycerin,

[8] A method of producing a polarizing film comprising a step of stretching a laminate of any one of the above-mentioned [1] to [7] (hereinafter this may be referred to as "polarizing film producing method (1)

[9] a PVA layer of a laminate before stretching; A PVA layer in the middle of stretching during drawing of the laminate; And a step of bringing the dichroic dye into contact with any of the stretched film layers formed from the PVA layer after stretching the laminate,

[10] The production method of the above-mentioned [9], which does not include a step of bringing a dichroic dye into contact with an aqueous solution containing a boron compound before the step of contacting the dichroic dye,

[11] The production method of the above [9] or [10], which does not include a step of stretching at a temperature of 95 ° C or more before the step of contacting the dichroic dye.

Further, according to the present invention,

[12] A polarizing film (hereinafter sometimes referred to as "polarizing film (2)") in which a dichroic dye is adsorbed to a matrix having a birefringence of 45 × 10 ^-3 or more,

[13] The polarizing film according to the above [12], wherein the matrix contains PVA and has an average degree of polymerization of from 2,800 to 9,500,

[14] The polarizing film according to the above [12], wherein the matrix contains PVA and has an average polymerization degree of 4,100 or more and 9,500 or less,

[15] The polarizing film according to any one of the above-mentioned [12] to [14], wherein the thickness is 10 [

[16] A process for producing a polarizing film comprising a step of stretching a laminate having a thermoplastic resin film layer and a PVA layer to 5.7 times or more, wherein the PVA layer has an average degree of polymerization of 2,800 to 9,500 Hereinafter, this may be referred to as " polarizing film production method (2) "))

[17] The production method of the above-mentioned [16], wherein the PVA has an average degree of polymerization of 4,100 or more and 9,500 or less,

[18] The production method of the above [16] or [17], wherein the PVA layer contains not less than 1 part by mass and not more than 15 parts by mass of a plasticizer relative to 100 parts by mass of PVA,

[19] The production method of the above [16] or [17], wherein the PVA layer contains not less than 4 parts by mass and not more than 12 parts by mass of a plasticizer relative to 100 parts by mass of PVA,

[20] The production method of the above [18] or [19], wherein the plasticizer is glycerin.

According to the laminate (1) of the present invention and the production method (1) of the polarizing film using the laminate (1) of the present invention, in the step of contacting the aqueous solution of boric acid with water without any insolubilization treatment such as dipping or air- Can be suppressed, and a polarizing film excellent in polarization performance can be easily manufactured using a general-purpose polarizing film production facility.

Further, the polarizing film (2) of the present invention has excellent polarizing performance and less leakage of red light in cross-Nicol state. Further, according to the production method (2) of the polarizing film of the present invention, it is possible to smoothly and simply produce the polarizing film (2) having excellent polarizing performance and less leakage of red light in the crossed Nicols state.

Hereinafter, the present invention will be described in detail.

&Quot; Laminate (1) "

The laminate (1) of the present invention has a thermoplastic resin film layer and a PVA layer. Examples of the thermoplastic resin constituting the thermoplastic resin film layer include various thermoplastic resins such as polyethylene, polypropylene, polymethylpentene, polystyrene, polycarbonate, polyvinyl chloride, methacrylic resin, nylon and polyethylene terephthalate; And copolymers having a plurality of monomer units constituting these thermoplastic resins. In the thermoplastic resin film layer, the thermoplastic resin may be contained in one kind alone, or two or more kinds thereof may be contained in the layer. Of these, polyethylene terephthalate is preferable, and amorphous polyethylene terephthalate is more preferable because it has high heat resistance and stretchability.

The thickness of the thermoplastic resin film layer is preferably in the range of 20 to 250 占 퐉, more preferably in the range of 30 to 230 占 퐉, and still more preferably in the range of 50 to 200 占 퐉. When the thickness of the thermoplastic resin film layer is 20 占 퐉 or more, wrinkles can be effectively prevented from occurring when the PVA layer is formed. On the other hand, when the thickness of the thermoplastic resin film layer is 250 占 퐉 or less, it is possible to prevent the tension at the time of stretching the layered product (1) from becoming excessively high.

The degree of swelling of the PVA layer of the layered product (1) of the present invention needs to be not less than 180% and not more than 260%, preferably not less than 185%, more preferably not less than 190%, more preferably not more than 255% % Or less. If the degree of swelling is higher than 260%, the PVA contained in the PVA layer is eluted in the step of making contact with water at the time of producing the polarizing film, if the insolubilization treatment such as dipping or air high-temperature stretching is not performed beforehand in the aqueous solution of boric acid, Making it difficult to produce a polarizing film. On the other hand, if the degree of swelling is lower than 180%, dyeing of the PVA layer becomes difficult and unevenness tends to occur, and a polarizing film having excellent polarization performance can not be obtained well. The degree of swelling of the PVA layer in the present invention means a value obtained by dividing the mass of the PVA layer after immersing the PVA layer in distilled water at 30 캜 for 30 minutes divided by the mass of the PVA layer after drying at 105 캜 for 16 hours after immersion ≪ / RTI > The degree of swelling of the PVA layer is preferably measured in the state of the laminated body in consideration of operability in that the value of the degree of swelling of the PVA layer is substantially the same as that of the PVA layer alone when measured in a laminated state. As a specific method for measuring the degree of swelling of the PVA layer, there may be mentioned the method described later in the Examples.

The method for adjusting the degree of swelling of the PVA layer is not particularly limited. For example, a laminate having a thermoplastic resin film layer and a PVA layer is produced by using general PVA (saponified vinyl acetate homopolymer) Or more. Here, the higher the heat treatment temperature and the longer the heat treatment time, the lower the degree of swelling. However, when a laminate having a thermoplastic resin film layer and a PVA layer is heat-treated at a temperature of 100 占 폚 or more, wrinkles tend to occur along with the dimensional change of the thermoplastic resin film layer. Therefore, a method of adjusting the degree of swelling of the PVA layer by using PVA which is easy to lower the swelling degree described later is preferable. Thus, even if a laminate having a thermoplastic resin film layer and a PVA layer is prepared under the condition that the temperature is not higher than 100 ° C, the degree of swelling of the PVA layer can be easily adjusted within the above range.

Examples of the PVA in the PVA layer include vinyl esters such as vinyl acetate, vinyl formate, vinyl propionate, vinyl butyrate, vinyl pivalate, vinyl versatate, vinyl laurate, vinyl stearate, vinyl benzoate and isopropenyl acetate Or a polyvinyl ester obtained by polymerizing two or more kinds of polyvinyl esters can be used. Of the above vinyl esters, vinyl acetate is preferable from the viewpoints of ease of production, availability, cost, and the like of PVA.

The polyvinyl ester may be one obtained by using only one kind of vinyl ester or two or more kinds of vinyl esters as long as it does not impair the effect of the present invention. However, the polyvinyl ester may contain one or more kinds of vinyl esters, Or may be a copolymer with another monomer as far as possible.

Examples of other monomers copolymerizable with the above vinyl ester include? -Olefins having 2 to 30 carbon atoms such as ethylene, propylene, 1-butene and isobutene; (Meth) acrylic acid or a salt thereof; (Meth) acrylate, n-butyl (meth) acrylate, i-butyl (meth) acrylate, t- (Meth) acrylic acid esters such as butyl, 2-ethylhexyl (meth) acrylate, dodecyl (meth) acrylate and octadecyl (meth) acrylate; (Meth) acrylamide, N, N-dimethyl (meth) acrylamide, diacetone (meth) acrylamide, (meth) acrylamide propanesulfonic acid Or a salt thereof, (meth) acrylamidopropyldimethylamine or a salt thereof, a (meth) acrylamide derivative such as N-methylol (meth) acrylamide or a derivative thereof; 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 (meth) acrylonitrile; 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; Unsaturated sulfonic acid, and the like. The above-mentioned polyvinyl esters may have a structural unit derived from one or more of the above-mentioned other monomers.

The proportion of the structural units derived from the other monomers in the polyvinyl ester is preferably 15 mol% or less, more preferably 10 mol% or less, further preferably 5 mol% or less based on the moles of the total structural units constituting the polyvinyl ester Mol% or less.

Particularly, when the above-mentioned other monomer is a monomer capable of promoting the water-solubility of the obtained PVA, such as (meth) acrylic acid, unsaturated sulfonic acid, etc., The proportion of the structural units derived from these monomers in the ester is preferably 5 mol% or less, more preferably 3 mol% or less, based on the number of moles of the total structural units constituting the polyvinyl ester.

The above-mentioned PVA may be modified by one or more graft copolymerizable monomers as far as the effect of the present invention is not impaired. Examples of the graft copolymerizable monomer include unsaturated carboxylic acids or derivatives thereof; Unsaturated sulfonic acid or a derivative thereof; And? -Olefins having 2 to 30 carbon atoms. The ratio of the structural unit derived from the graft copolymerizable monomer in PVA (the structural unit in the graft-modified part) is preferably 5 mol% or less based on the number of moles of all structural units constituting the PVA.

In the above-mentioned PVA, a part of the hydroxyl groups may or may not be crosslinked. In the above-mentioned PVA, a part of the hydroxyl groups may react with an aldehyde compound such as acetaldehyde, butylaldehyde or the like to form an acetal structure, or may not react with these compounds and form an acetal structure.

Using the PVA which easily lowers the degree of swelling as described above, even if a laminate having a thermoplastic resin film layer and a PVA layer is prepared under the condition that the temperature is not higher than 100 DEG C, the swelling degree of the PVA layer can be easily adjusted within the above range . Examples of the PVA that tends to lower the degree of swelling include PVA having an ethylene content of 1 mol% or more and 12 mol% or less. Here, the ethylene content refers to the ratio (mol%) of the number of moles of the structural units derived from ethylene to the total number of moles of the structural units constituting PVA. Since the ethylene content is 1 mol% or more, the degree of swelling can be easily made lower than or equal to the upper limit even if drying or heat treatment after the application of the undiluted liquid as described later is carried out at a low temperature. On the other hand, when the ethylene content is 12 mol% or less, the degree of swelling can be easily set to the above lower limit. The ethylene content is preferably 1.5 mol% or more, more preferably 2.0 mol% or more, further preferably 11.5 mol% or less, and more preferably 11 mol% or less, in view of the fact that the swelling degree can be easily adjusted to the range specified in the present invention. % Or less.

Another example of the PVA that tends to lower the degree of swelling includes PVA having a 1,2-glycol bond content of 0.4 mol% or more and 1.5 mol% or less. Here, the 1,2-glycol bond amount means the ratio (mol%) of the number of moles of bonds between adjacent vinyl alcohol units bonded by 1,2-glycol bonds to the total number of moles of bonds between adjacent vinyl alcohol units And can be obtained by NMR measurement. When the 1,2-glycol bond amount is 1.5 mol% or less, the degree of swelling can be easily made lower than the upper limit even if drying or heat treatment is performed at a low temperature after the application of the undiluted liquid as described later. On the other hand, when the 1,2-glycol bond amount is 0.4 mol% or more, the degree of swelling can be easily made to the lower limit or more. The amount of 1,2-glycol bond is preferably 0.5 mol% or more, more preferably 0.6 mol% or more, and further preferably 1.4 mol% or less, because the swelling degree can be easily adjusted to the range specified in the present invention , And more preferably 1.3 mol% or less. PVA having a small 1,2-glycol bond amount value can be produced from a polyvinyl ester obtained by polymerizing a vinyl ester at a low temperature as a raw material. Specifically, PVA having a 1,2-glycol bond content of 0.4 mol% or more and 1.5 mol% or less can be produced from a polyvinyl ester obtained by polymerizing a vinyl ester in a range of generally -50 ° C to +50 ° C.

The PVA may satisfy either one of the above-mentioned range of the ethylene content and the range of the 1,2-glycol bond amount, or both of them may be satisfied. That is, PVA having an ethylene content falling within the above range and having a 1,2-glycol bond content exceeding 1.5 mol%; PVA having an ethylene content of less than 1 mol% and a 1,2-glycol bond amount in the above range; And PVA in which both the ethylene content and the 1,2-glycol bond amount fall within the above ranges can be used as a PVA which tends to lower the degree of swelling. However, the PVA in which the ethylene content and the 1,2-glycol bond amount are both in the above range is excessively swollen in the PVA layer, particularly when the ethylene content is relatively high and / or the 1,2-glycol bond amount is relatively low There may be a case where it is lowered. Therefore, in the case of using PVA in which the ethylene content and the 1,2-glycol bond amount are both in the above-mentioned range, the drying treatment or the heat treatment after the formation of the PVA layer is carried out at a relatively low temperature or the ethylene content is lowered / Or 1,2-glycol bond is increased.

The average degree of polymerization of the PVA is preferably in the range of 1,000 to 9,500, more preferably 1,500 or more, further preferably 2,000 or more, further preferably 9,200 or less, and 6,000 or less desirable. When the average degree of polymerization is 1,000 or more, the polarizing performance of the obtained polarizing film is improved. On the other hand, when the average polymerization degree is 9,500 or less, the productivity of PVA is improved. The average degree of polymerization of PVA (PVA contained in the PVA layer) used for forming the PVA layer can be measured according to the description of JIS K6726-1994.

The degree of saponification of the PVA is preferably 98 mol% or more, more preferably 98.5 mol% or more, and further preferably 99 mol% or more from the viewpoint of the polarizing performance and the like of the resulting polarizing film. When the degree of saponification is less than 98 mol%, PVA tends to elute during the production of the polarizing film, and the eluted PVA adheres to the film to lower the polarizing performance of the polarizing film in some cases. The saponification degree of PVA in the present specification means a degree of saponification of the PVA in which the total amount of the structural unit (typically a vinyl ester unit) that can be converted into a vinyl alcohol unit by saponification and the total number of moles of the vinyl alcohol unit (Mole%) occupied by the number of moles. The degree of saponification can be measured in accordance with the description of JIS K6726-1994.

The PVA layer preferably includes a plasticizer from the viewpoint of improvement in stretchability upon stretching the layered product (1). Examples of the plasticizer include polyhydric alcohols such as ethylene glycol, glycerin, propylene glycol, diethylene glycol, diglycerin, triethylene glycol, tetraethylene glycol, and trimethylolpropane, and the PVA layer may contain these plasticizers , And the like. Among these, glycerin is preferable from the viewpoint of the effect of improving the stretchability.

The content of the plasticizer in the PVA layer is preferably in the range of 1 part by mass or more and 15 parts by mass or less with respect to 100 parts by mass of the PVA contained therein. When the content is 1 part by mass or more, the stretchability of the layered product (1) can be further improved. On the other hand, when the content is 15 parts by mass or less, it is possible to prevent the PVA layer from being excessively softened and deteriorate the handling property, or to prevent the PVA layer from being peeled off from the thermoplastic resin film layer. The content of the plasticizer in the PVA layer is more preferably 2 parts by mass or more, more preferably 4 parts by mass or more, particularly preferably 5 parts by mass or more, and further preferably 13 parts by mass or less, based on 100 parts by mass of PVA More preferably 12 mass parts or less, and particularly preferably 8 mass parts or less.

In the case of producing the polarizing film using the layered product (1) of the present invention, the plasticizer contained in the PVA layer may be eluted or the like when the polarizing film is produced, But the total amount thereof is not limited to remain in the polarizing film.

The PVA layer may further contain components such as an antioxidant, a cryoprotectant, a pH adjuster, a masking agent, a coloring inhibitor, an oil agent and a surfactant, if necessary.

The content of PVA in the PVA layer is preferably within a range of 50 mass% or more and 99 mass% or less, more preferably 75 mass% or more, and more preferably 80 mass% or less, More preferably 85% by mass or more, particularly preferably 98% by mass or less, further preferably 96% by mass or less, and particularly preferably 95% by mass or less.

The thickness of the PVA layer is not particularly limited and may be, for example, 100 占 퐉 or less. However, it is preferable to make the PVA layer thinner in the point that a thin polarizing film can be easily prepared. Specifically, The thickness is preferably 20 占 퐉 or less, more preferably 15 占 퐉 or less, and even more preferably 10 占 퐉 or less. In the layered product (1) of the present invention, since the PVA layer has a specific constitution as described above, even when the thickness of the PVA layer is as thin as described above, the elution of PVA can be suppressed in the step of contacting with water, An excellent thin polarizing film can be easily produced. In addition, when the thickness of the PVA layer is as thin as described above, it is possible to reduce the tensile force at the time of stretching the layered product (1). Further, when the thickness of the PVA layer is too thin, the thickness of the PVA layer is, for example, 3 占 퐉 or more because the layered product 1 tends to cause stretching breakage at the time of stretching.

The layer structure of the layered product (1) of the present invention is not particularly limited, but a two-layer structure of one thermoplastic resin film layer and one PVA layer is preferable in that a polarizing film excellent in polarization performance can be obtained more easily.

The shape of the layered product 1 is not particularly limited, but a more uniform laminate can be easily produced continuously, and a continuous film can be continuously used even when a polarizing film is produced using the layered product. . The length (length in the longitudinal direction) of the elongated laminate is not particularly limited and may be suitably set according to the intended use of the polarizing film to be produced, for example, within a range of 5 m or more and 20,000 m or less.

The width of the layered product 1 is not particularly limited and can be appropriately set according to the use of the polarizing film to be produced and the like. In recent years, the width of the layered product 1 0.5 m or more, more preferably 1.0 m or more, is preferable for these applications. On the other hand, when the width of the laminate 1 is excessively wide, it is difficult to uniformly stretch the polarizing film when a polarizing film is produced by a device that has been put to practical use. Thus, the width of the laminate 1 is 7 m or less desirable.

As a method for producing the layered product (1), for example, there can be mentioned a method of forming a PVA layer on a thermoplastic resin film. Specifically, PVA and, if necessary, A method in which a stock solution in which other components are dissolved in a liquid medium is coated on a thermoplastic resin film and dried; A method in which a raw liquid obtained by melt kneading PVA, a liquid medium and, if necessary, another component is extruded onto a thermoplastic resin film and further dried if necessary; A PVA film containing PVA and, if necessary, other components, is prepared by a known method, and then the resultant is kneaded with a thermoplastic resin film. Among them, in view of the ease of preparing a thin PVA layer and the uniformity of the thickness of the resulting PVA layer, a raw liquid in which PVA and, if necessary, further other components are dissolved in a liquid medium is coated on a thermoplastic resin film Drying method is preferable.

Examples of the liquid medium include water, dimethylsulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, ethylene glycol, glycerin, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene Glycol, trimethylol propane, ethylenediamine, diethylenetriamine, and the like, and one or more of these may be used. Among them, water is preferred from the viewpoints of imparting to the environment and recoverability.

The volatile matter content of the undiluted solution (the content ratio of the volatile component such as a liquid medium removed by volatilization or drying at the time of forming the PVA layer in the undiluted solution) varies depending on the method of forming the PVA layer and the forming conditions, And more preferably in the range of not less than 98% by mass and not more than 55% by mass and not more than 95% by mass. When the volatile matter content of the undiluted solution is 50 mass% or more, the viscosity is not excessively increased, filtration and de-foaming are smoothly performed at the time of preparation of the undiluted solution, so that formation of the PVA layer with few foreign matters or defects is facilitated, . On the other hand, when the volatile fraction of the undiluted solution is 98 mass% or less, the concentration of the undiluted solution does not become too low, and industrial production of the laminated body becomes easy.

Examples of the coating method for coating the undiluted solution on the thermoplastic resin film include a die coating method, a comma coating method and a dip coating method. Among them, the die coating method is preferable in view of the uniformity of the thickness of the obtained PVA layer.

It is preferable that at least one surface of the thermoplastic resin film used for producing the layered product (1) is subjected to hydrophilization treatment. By forming the PVA layer so as to contact with the hydrophilized surface, adhesion between the thermoplastic resin film layer and the PVA layer is improved. Examples of the hydrophilic treatment include a corona treatment, a plasma treatment, and an anchor coat treatment. Of these, corona treatment is preferable in view of easy adjustment of hydrophilicity.

It is preferable to adjust the contact angle of the surface of the thermoplastic resin film to 55 ° or more and 70 ° or less by the hydrophilization treatment, more preferably 57 ° or more, and more preferably 59 ° or more More preferably 69 ° or less, and more preferably 68 ° or less. If the contact angle is lower than 55 °, the adhesive strength between the thermoplastic resin film layer and the PVA layer tends to become excessively strong. If the stretched thermoplastic resin film layer after the stretching of the laminate 1 is peeled off, . On the other hand, when the contact angle is higher than 70 DEG, the PVA layer tends to peel off or tear from the thermoplastic resin film layer during stretching of the layered product 1, and it tends to be difficult to stretch at a high stretching magnification. The contact angle of the surface of the thermoplastic resin film refers to an angle formed between the water surface in the place where the free surface of the water contacts the thermoplastic resin film and the surface of the thermoplastic resin film (taking an angle in the interior of the water) Can be measured by a method described later.

The condition of the corona treatment in the case where the contact angle of the surface of the thermoplastic resin film is adjusted to the above range by the corona treatment is not particularly limited but from the viewpoint that the contact angle of the surface of the thermoplastic resin film can be easily adjusted within the above range, The discharge amount represented by the following formula (1) is preferably in the range of 180 to 350 W min / m 2, more preferably in the range of 190 to 320 W min / m 2, more preferably in the range of 200 to 300 W min / It is more preferable that it is inner.

(W / min) = output (W / m) / processing speed (m / min) (1)

There is no particular limitation on the drying conditions after coating or extruding the raw liquid onto the thermoplastic resin film. However, in order to prevent wrinkles from forming on the thermoplastic resin film, it is preferable to dry the thermoplastic resin film at a temperature not higher than the glass transition temperature of the thermoplastic resin film . At this time, it is preferable that PVA which is easy to lower the degree of swelling is used as the PVA, and then the PVA is dried under a condition that the temperature is not higher than 100 캜. Although the specific drying temperature is not particularly limited, it is preferable that the degree of swelling of the PVA layer is easily adjusted to the above range, and in consideration of the drying efficiency and the like, it is preferably within a range of 20 ° C or more and 95 ° C or less, More preferably 65 deg. C or higher, further preferably 90 deg. C or lower, still more preferably 85 deg. C or lower. Thereby, the laminate 1 in which the non-stretched PVA layer having a swelling degree of 180% or more and 260% or less is laminated on the thermoplastic resin film layer can be easily obtained.

&Quot; Method of producing polarizing film (1) "

The method (1) for producing a polarizing film of the present invention includes a step of stretching the above-mentioned laminate (1). If the dichroic dye is previously contained in the PVA layer, the polarizing film in which the dichroic dye is adsorbed can be obtained by stretching the layered product (1). In this case, the method of containing the dichroic dye in the PVA layer is not particularly limited. For example, the dichroic dye may be brought into contact with the PVA layer of the layered product (1) A method of previously incorporating a dichroic dye into a stock solution, and the like can be suitably employed. When the dichroic dye is not previously contained in the PVA layer, the dichroic dye may be brought into contact with the PVA layer in the middle of the stretching during the stretching of the layered product (1), or after the layered product (1) A polarizing film in which the dichroic dye is adsorbed can be obtained by bringing the dichroic dye into contact with the stretched film layer formed from the (stretched) PVA layer. Among them, the PVA layer of the layered product (1) before stretching; A PVA layer in the middle of stretching of the laminate (1) during stretching; And a step of bringing the dichroic dye into contact with any of the stretched film layers formed from the PVA layer after stretching the layered product (1), to obtain a polarizing film in which the dichroic dye is adsorbed And the effect of the invention is more conspicuous.

In any of the above methods, swelling treatment, crosslinking treatment, fixing treatment, drying and the like can be additionally carried out as needed in addition to the treatment of bringing the dye into contact with the drawing and the dichroic dye (dyeing). The order of each process may be changed as required, or each process may be performed two or more times, or different processes may be performed at the same time. According to the above production method, a polarizing film formed on the stretched thermoplastic resin film layer is obtained, but may include a step of peeling off the stretched thermoplastic resin film if necessary.

As described above, in the production method (1) of the polarizing film of the present invention, since the swelling degree of the PVA layer of the layered product (1) is in the range of 180% or more and 260% or less, It is possible to inhibit the elution of PVA in the step of contacting with water at the time of producing a polarizing film, such as dyeing, even if the insolubilization treatment such as stretching is not performed in advance. For this reason, the effect of the present invention becomes more remarkable when the polarizing film is produced without performing such insolubilization treatment in advance. Specifically, the PVA layer of the layered product (1) before stretching; A PVA layer in the middle of stretching of the laminate (1) during stretching; And a step of bringing the dichroic dye into contact with any of the stretched film layers formed from the PVA layer after stretching the laminate (1) to produce a polarizing film on which the dichroic dye is adsorbed, Does not include a step of bringing the layered product (1) of the present invention into contact with an aqueous solution containing a boron compound such as a boric acid salt such as boric acid, borax and the like, before the step of contacting the dichroic dye, and / , And preferably does not include a step of drawing at a temperature of 95 占 폚 or more (more preferably, does not include a step of stretching at a temperature of 50 占 폚 or more).

As an example of the production method (1) of the polarizing film of the present invention, first, the layered product (1) having the PVA layer not containing the dichroic dye is swelled and then the dichroic dye is contacted, The layer containing the dichroic dye is further subjected to a crosslinking treatment if necessary and the resultant laminate is stretched and further subjected to a fixing treatment as required and dried and by these series of treatments, A polarizing film formed on the thermoplastic resin film layer is obtained and the stretched thermoplastic resin film layer is peeled off.

The swelling treatment can be carried out by immersing the layered product (1) in water. The temperature of the water when immersed in water is preferably in the range of 20 ° C to 40 ° C, more preferably 22 ° C or more, still more preferably 25 ° C or more, and more preferably 38 ° C or less And more preferably 35 DEG C or less. By making the temperature within the range of 20 占 폚 to 40 占 폚, the PVA layer can be efficiently swollen. The time for immersing in water is preferably within a range from 0.1 minute to 5 minutes, more preferably from 0.5 minutes to 3 minutes. The PVA layer can be efficiently swelled by keeping the temperature within the range of 0.1 minute to 5 minutes. Further, the water to be immersed in water is not limited to pure water, and may be an aqueous solution in which various components are dissolved, or a mixture of water and an aqueous medium.

As described above, the PVA layer of the layered product (1) before stretching; A PVA layer in the middle of stretching of the laminate (1) during stretching; A polarizing film in which the dichroic dye is adsorbed to the matrix can be obtained by staining the dichroic dye in contact with the stretched film layer or the like formed from the PVA layer after stretching the layered product (1). The dichroic dye may be contacted by immersing the laminate before, during, or after stretching in a solution (particularly an aqueous solution) containing a dichroic dye. The concentration of the dichroic dye in the solution containing the dichroic dye can be appropriately set according to the type of the dichroic dye to be used and can be set to, for example, 0.001 mass% or more and 1 mass% or less. (I ₂ ) as a concentration of 0.01 mass% or more and 1.0 mass or less as the concentration of iodine (I ₂ ) to be used in order to efficiently adsorb the iodine dye to the matrix when a solution of potassium iodide-iodide %, And it is preferable that the concentration of potassium iodide (KI) used is in the range of 0.01 mass% or more and 10 mass% or less. The temperature of the solution containing the dichroic dye is preferably in the range of 20 占 폚 to 50 占 폚, particularly 25 占 폚 to 40 占 폚 in that the dichroic dye can be efficiently adsorbed to the matrix .

Examples of the dichroic dye include iodine dyes (I ₃ ^- and I ₅ ^- ) and dichroic organic dyes. The iodine dye can be obtained, for example, by contacting iodine (I ₂ ) with potassium iodide. The dichroic organic dyes 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. Of these dichroic dyes, iodine dyes are preferred from the viewpoints of handleability, availability, and polarization performance. The dichroic dye may be used alone or in combination of two or more species. For example, it may be an equilibrium mixture such as I ₃ ^- and I ₅ ^- .

By performing the crosslinking treatment on the PVA layer, it is possible to more effectively prevent the PVA from being eluted into water when wet-stretched at a high temperature. From this point of view, the crosslinking treatment is preferably carried out after the treatment of bringing the dichroic dye into contact and before the stretching. The crosslinking treatment can be carried out by immersing the layered product (1) in an aqueous solution containing a crosslinking agent. As the crosslinking agent, boron compounds such as boric acid salts such as boric acid and 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% by mass to 15% by mass, more preferably 2% by mass or more, further preferably 3% by mass or more, further preferably 7% By mass or less, and more preferably 6% by mass or less. When the concentration of the crosslinking agent is in the range of 1 mass% to 15 mass%, sufficient stretchability can be maintained. The aqueous solution containing the 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 占 폚 to 50 占 폚, particularly preferably in the range of 25 占 폚 to 40 占 폚. By effectively setting the temperature within the range of 20 占 폚 to 50 占 폚, crosslinking can be efficiently carried out.

The stretching method for stretching the layered product (1) is not particularly limited, and either wet stretching or dry stretching may be employed. In the case of the wet stretching method, it may be carried out in an aqueous solution containing one or two or more kinds of boron compounds such as boric acid salts such as boric acid and borax. In the solution containing the dichroic dye or in a fixed treatment bath . In the case of the dry stretching method, the stretching may be performed at room temperature, or the stretching may be performed while heat is applied, or the stretching may be performed after absorption. Among them, the wet stretching method is preferable from the viewpoint of the uniformity of the thickness in the width direction in the obtained polarizing film, and it is more preferable to stretch in the aqueous solution of boric acid. The concentration of boric acid in the aqueous solution of boric acid is preferably in the range of 0.5% by mass to 6.0% by mass, more preferably 1.0% by mass or more, still more preferably 1.5% by mass or more, Or less, more preferably 4.0 mass% or less. When the boric acid concentration is in the range of 0.5% by mass or more and 6.0% by mass or less, a polarizing film having excellent thickness uniformity in the width direction can be obtained. The aqueous solution containing the boron compound may contain potassium iodide, and the concentration thereof is preferably in the range of 0.01% by mass or more and 10% by mass or less. Since the concentration of potassium iodide is in the range of 0.01 mass% or more and 10 mass% or less, a polarizing film having better polarizing performance can be obtained.

The temperature for stretching the layered product (1) is preferably in the range of 30 占 폚 to 90 占 폚, more preferably 40 占 폚 or higher, still more preferably 50 占 폚 or higher, and 80 占 폚 Or less, more preferably 70 deg. C or less. When the temperature is in the range of 30 占 폚 to 90 占 폚, a polarizing film excellent in thickness uniformity in the width direction can be obtained.

The draw ratio at the time of drawing the layered product (1) is preferably 5.7 times or more, more preferably 5.8 times or more, and further preferably 5.9 times or more. By setting the draw ratio of the layered product 1 within the above range, a polarizing film having better polarizing performance can be obtained. The upper limit of the draw ratio of the layered product (1) is not particularly limited, but is preferably 8 times or less. The layered product (1) may be stretched at one time, or may be divided into a plurality of circuits or any of them. In the case of dividing into a plurality of circuits, the total stretch ratio multiplied by the stretch ratio of each stretch may be within the above range. The drawing magnification in the present specification is based on the length of the layered product 1 before drawing, and the state without drawing is equivalent to a drawing magnification of 1 time.

Stretching of the layered product (1) is preferably uniaxial stretching in view of the performance of the resulting polarizing film. There is no particular limitation on the direction of uniaxial stretching in the case of elongating the elongate laminate 1, and uniaxial stretching in the longitudinal direction or transverse uniaxial stretching can be employed. However, the polarizing film The uniaxial stretching in the longitudinal direction is preferable. The uniaxial stretching in the longitudinal direction can be carried out by using a stretching apparatus having a plurality of rolls parallel to each other and changing the peripheral speed between the rolls. On the other hand, transverse uniaxial stretching can be carried out using a tenter-type stretching machine.

The fixing treatment is performed mainly to strengthen the adsorption of the dichroic dye to the PVA layer or the stretched film (matrix). The fixing treatment can be carried out by immersing the laminate before stretching, during stretching or after stretching in a fixed treatment bath. As the fixed treatment bath, an aqueous solution containing one kind or two or more kinds of boron compounds such as boric acid salts such as boric acid and borax can be used. If necessary, an iodine compound or a metal compound may be added to the fixed treatment bath. The concentration of the boron compound in the aqueous solution containing the boron compound used as the fixed treatment bath is generally in the range of 2 mass% to 15 mass%, particularly preferably in the range of 3 mass% to 10 mass% . By making the concentration within the range of 2 mass% to 15 mass%, the adsorption of the dichroic dye can be strengthened. The temperature of the fixed treatment bath is preferably in the range of 15 占 폚 to 60 占 폚, particularly 25 占 폚 to 40 占 폚. By setting the temperature within the range of 15 占 폚 to 60 占 폚, the adsorption of the dichroic dye can be made stronger.

The drying conditions are not particularly limited, but it is preferable to carry out the drying at a temperature within the range of 30 ° C to 150 ° C, more preferably 50 ° C to 130 ° C. It is easy to obtain a polarizing film having excellent dimensional stability by drying at a temperature within the range of 30 ° C to 150 ° C.

By doing so, a polarizing film formed on the stretched thermoplastic resin film layer is obtained. The method of using the polarizing film of this type is not particularly limited, and for example, it is possible to use a polarizing film having optical transparency and mechanical strength on the polarizing film side as it is or without being peeled off the stretched thermoplastic resin film layer The protective film may be laminated to form a polarizing plate. Alternatively, after the protective film is bonded to the side opposite to the side where the stretched thermoplastic resin film layer is located, the stretched thermoplastic resin film layer is peeled off, Another protective film may be laminated to form a polarizing plate. As the protective film, a cellulose triacetate (TAC) film, an acetic acid-butyric acid cellulose (CAB) film, an acrylic film, a polyester film, or the like can be used. Examples of the adhesive for bonding include a PVA adhesive and a urethane adhesive, but a PVA adhesive is preferred.

The thickness of the polarizing film obtained by the production method (1) of the polarizing film of the present invention is preferably 10 m or less, more preferably 8 m or less. The polarizing film having such a thickness can be preferably used in a field where the demand for thinning of a cellular phone or the like is increasing. In addition, the thickness of the polarizing film is, for example, 1 占 퐉 or more, since it is difficult to prepare a polarizing film that is too thin.

&Quot; Polarizing film (2) "

In the polarizing film (2) of the present invention, a dichroic dye is adsorbed to a matrix having a birefringence of 45 x 10 < ^-3 > Here, the dichroic dye may be adsorbed in the inside of the matrix or may be adsorbed to the surface of the matrix. In view of the polarization performance, it is preferable that the dichroic dye is adsorbed in the inside of the matrix. The polarizing film in which the dichroic dye is adsorbed to the matrix can be obtained by stretching a raw film previously containing a dichroic dye or by adsorbing a dichroic dye simultaneously with drawing the original film or by stretching the original film, And then adsorbing the dichroic dye.

The description of the dichroic dye in the polarizing film (2) and the production method (2) of the polarizing film to be described later includes the description of the dichroic dye in the description of the polarizing film production method (1) Therefore, redundant description will be omitted here.

In the polarizing film (2) of the present invention, the matrix constituting the polarizing film (2) has a non-conventional configuration in which the birefringence is 45 x 10 < ^-3 > When the birefringence of the matrix is less than 45 x 10 ^-3 , when two polarizing films are arranged in the cross-Nicol state, the leakage of red light increases and the polarization performance also decreases. The birefringent index of the matrix constituting the polarizing film 2 is preferably 46 x 10 < ^-3 > or more, more preferably 47 x 10 < ^-3 > more preferably, more preferably not less than 48 × 10 ^-3 and 49 × 10 ^-3 or more and most preferably it is particularly preferably, 50 × 10 ^-3 or more. In addition, the birefringence of the matrix is, for example, 60 x 10 < ^-3 > or less in that the preparation of a matrix having an excessively high birefringence is difficult.

The birefringence of the matrix constituting the polarizing film 2 corresponds to the birefringence of the polarizing film 2 minus the birefringence index based on the dichroic dye. In general, the birefringence of the film can be obtained by dividing the retardation value of the film (in-plane retardation value measured by the light parallel to the thickness direction of the film) by the thickness of the film. Therefore, the birefringence of the matrix specified in the polarizing film 2 is obtained by obtaining the retardation value of the matrix corresponding to the value obtained by subtracting the retardation value based on the dichroic dye from the retardation value of the polarizing film 2, (Which is usually the same as the thickness of the polarizing film 2).

Concretely, in the wavelength range of light generally used when measuring the retardation value of the film, the birefringence index of the matrix generally has little wavelength dependency, while the birefringence index based on the dichroic dye has a high wavelength dependency The birefringence index of the matrix can be obtained by the following method.

That is, the retardation value (unit: nm) of the polarizing film 2 measured by the light of wavelength? Nm is denoted by R _{?, The} retardation value (unit: nm) of the matrix is denoted by A, the retardation value which is based on a dichroic dye according to (unit: ㎚) when the called B _λ, the following equation (2) and (3);

R _? = A + B _? (2)

B _? = B '/ (? ² - 600 ² ) (3)

(2 '), (3'), (2 '') and (3 '') obtained by substituting the measured wavelengths of 800 nm and 1000 nm into? Of these equations, respectively.

R ₈₀₀ = A + B ₈₀₀ (2 ')

B ₈₀₀ = B '/ (800 ² - 600 ² ) (3')

R ₁₀₀₀ = A + B ₁₀₀₀ (2 ")

B ₁₀₀₀ = B '/ (1000 ² - 600 ² ) (3'')

Can be obtained by dividing: (㎚ unit) of the system of equations, released by using a value of the measured R ₈₀₀ and R ₁₀₀₀ to obtain a matrix of A hit retardation, this thickness of the polarizing film (2). Here, B 'is a value unique to the polarizing film to be measured.

There is no particular limitation on the component constituting the matrix, but it is preferable that the matrix contains PVA and the average degree of polymerization of the PVA contained in the matrix is in the range of 2,800 to 9,500. The polarizing film (2) of the present invention can be easily produced by employing PVA having such an average degree of polymerization as described later, and as a result, the polarizing film of the present invention can be obtained as a result that the average degree of polymerization of the PVA contained in the matrix falls within the above range I will enter. The average degree of polymerization of PVA contained in the matrix is more preferably 3,000 or more, more preferably 4,000 or more, particularly preferably 4,100 or more, 4,500 or more, and even 5,000 or more, from the ease of preparation of the matrix and the like, More preferably 9,200 or less, even more preferably 8,000 or less, and particularly preferably 6,000 or less. The average degree of polymerization of the PVA contained in the matrix is determined by extracting and removing components other than PVA contained in the matrix by immersing the polarizing film 2 in a sorbitol aqueous solution or the like and further washing with water as necessary, Can be obtained on the basis of the description of JIS K6726-1994 by using the obtained PVA. Specifically, the PVA can be obtained by the method described later in Examples.

The content of PVA in the matrix is not particularly limited, but is preferably within a range from 50 mass% to 100 mass%, and the content is preferably 80 mass% or less, for ease of preparation of the polarizing film (2) More preferably 90% by mass or more, further preferably 99% by mass or less, further preferably 98% by mass or less. Further, the mass of the matrix is obtained by subtracting the mass of the dichroic dye from the mass of the polarizing film (2).

Examples of the PVA (including the description of the degree of saponification) other than the above description of the average degree of polymerization in the polarizing film (2) and the polarizing film production method (2) to be described later include descriptions of the laminated product (1) , The description of the PVA described above can be adopted as it is, so the overlapping description is omitted here. The PVA in the polarizing film (2) and the polarizing film production method (2) to be described later need not use the PVA which is easy to lower the degree of swelling as a preferable PVA in the description of the layered product (1) There is no particular.

The thickness of the polarizing film (2) of the present invention is preferably 10 占 퐉 or less, more preferably 8 占 퐉 or less. By having the polarizing film 2 having such a thickness, the polarizing film 2 can be preferably used in a field where the demand for thinning of a cellular phone or the like is increasing. Further, the thickness of the polarizing film 2 is, for example, 1 占 퐉 or more, since it is difficult to prepare a polarizing film having an excessively thin thickness.

&Quot; Method for producing polarizing film (2) "

The method for producing the polarizing film (2) of the present invention is not particularly limited, but includes a step of stretching the laminate having the thermoplastic resin film layer and the PVA layer to 5.7 times or more, (2) of the polarizing film of the present invention having an average degree of polymerization of PVA in the range of 2,800 to 9,500, the birefringence of the matrix is within a specific range, and the polarization performance is excellent, The polarizing film 2 of the present invention with little leakage can be produced smoothly and easily.

As the description of the thermoplastic resin film layer of the laminate used in the production method (2) of the polarizing film, the description of the thermoplastic resin film layer described above can be employed as it is in the description of the laminate (1) Therefore, redundant descriptions are omitted here.

The average degree of polymerization of the PVA contained in the PVA layer of the laminate used in the production method (2) of the polarizing film is preferably in the range of from 2,800 to 9,500, and the average degree of polymerization is preferably 3,000 or more, more preferably 4,000 or more More preferably 4,100 or more, particularly preferably 4,500 or more, most preferably 5,000 or more, further preferably 9,200 or less, more preferably 8,000 or less, still more preferably 6,000 or less. Generally, when the average degree of polymerization of PVA is increased, it is considered that the tension at stretching becomes higher and the critical stretching magnification decreases. However, the present inventors have found that, in order to obtain a polarizing film by stretching a laminate having a thermoplastic resin film layer and a PVA layer The use of PVA having an average degree of polymerization as described above is considered to be improved rather than lowering the critical stretch ratio as compared with, for example, PVA having an average degree of polymerization of 2,600, And the average degree of polymerization of PVA contained in the PVA layer is within the above range is stretched by 5.7 times or more to produce a polarizing film formed on the thermoplastic resin film layer, the birefringence of the matrix is 45 x It has been found that a polarizing film of 10 < ^-3 > or more can be obtained smoothly and easily.

In addition, the average degree of polymerization of PVA (PVA contained in the PVA layer) used for forming the PVA layer can be obtained based on the description of JIS K6726-1994, and specifically, it can be obtained by the method described later in Examples have.

The PVA layer included in the laminate used in the method (2) for producing a polarizing film preferably includes a plasticizer from the viewpoint of improvement in stretchability when the laminate is stretched. Examples of the plasticizer include polyhydric alcohols such as ethylene glycol, glycerin, propylene glycol, diethylene glycol, diglycerin, triethylene glycol, tetraethylene glycol, and trimethylolpropane, and the PVA layer may contain these plasticizers , And the like. Among these, glycerin is preferable from the viewpoint of the effect of improving the stretchability.

The content of the plasticizer in the PVA layer of the laminate used in the production method (2) of the polarizing film is preferably in the range of 1 part by mass or more and 15 parts by mass or less with respect to 100 parts by mass of the PVA contained therein Do. When the content is 1 part by mass or more, the stretchability of the laminate can be further improved. On the other hand, when the content is 15 parts by mass or less, it is possible to prevent the PVA layer from being excessively softened and deteriorate the handling property, or to prevent the PVA layer from being peeled off from the thermoplastic resin film layer. In the production method (2) of the polarizing film of the present invention wherein the average degree of polymerization of the PVA contained in the PVA layer is in the above range, the content of the plasticizer in the PVA layer is preferably not less than 2 parts by mass The reason is not clear, but the limit drawing magnification ratio is further improved in the range of not less than 13 parts by mass, further more than 4 parts by mass and not more than 12 parts by mass, particularly not less than 5 parts by mass and not more than 8 parts by mass, Such content is more preferable.

The plasticizer contained in the PVA layer may be eluted when the polarizing film is produced, etc., though it may vary depending on the production conditions of the polarizing film. Therefore, the total amount thereof is not limited to the polarizing film.

The PVA layer of the laminate used in the production method (2) of the polarizing film may further contain components such as an antioxidant, a cryoprotectant, a pH adjuster, a masking agent, a coloring inhibitor, an oil agent and a surfactant .

The content of PVA in the PVA layer of the laminate used in the production method (2) of the polarizing film is preferably within a range of 50 mass% or more and 99 mass% or less from the viewpoint of ease of preparation of a desired polarizing film , More preferably at least 75 mass%, even more preferably at least 80 mass%, even more preferably at least 85 mass%, even more preferably at most 98 mass%, even more preferably at most 96 mass% By mass, and particularly preferably not more than 95% by mass.

The thickness of the PVA layer of the laminate used in the production method (2) of the polarizing film is not particularly limited and may be, for example, 100 탆 or less. However, in the point that a thin polarizing film can be easily prepared It is preferable to make the PVA layer thin. Specifically, the thickness of the PVA layer is preferably 20 占 퐉 or less, more preferably 15 占 퐉 or less, and further preferably 10 占 퐉 or less. In the production method (2) of the polarizing film of the present invention, since the PVA layer has such a specific constitution as described above, even if the thickness of the PVA layer is made as thin as described above, it can be stretched at a high critical stretching ratio, It is possible to obtain a thin polarizing film which is excellent in sensitivity and low in leakage of red light in cross-Nicol state. When the thickness of the PVA layer is as thin as described above, it is also possible to reduce the tensile force at the time of stretching the laminate. In addition, when the thickness of the PVA layer is too small, the thickness of the PVA layer is, for example, 3 占 퐉 or more in that the stretching of the laminate tends to occur during stretching.

As another description of the laminate used in the method (2) for producing a polarizing film (including a description of a method of producing a laminate including adjustment of the contact angle of the surface of the thermoplastic resin film), the laminate 1), the description related to the above-described laminate can be adopted as it is, so the overlapping description will be omitted here.

In the production method (2) of the polarizing film of the present invention, the above laminate is stretched to 5.7 times or more. Here, if the dichroic dye is previously contained in the PVA layer, the polarizing film (2) in which the dichroic dye is adsorbed to the matrix can be obtained by stretching the laminate. In this case, the method of containing the dichroic dye in the PVA layer is not particularly limited. For example, a method of bringing the dichroic dye into contact with the PVA layer of the laminate, or a method of adding the dichroic dye to the PVA layer A method of previously incorporating a dichroic dye, and the like can be suitably employed. When the dichroic dye is not previously contained in the PVA layer, the dichroic dye may be brought into contact with the PVA layer in the middle of the stretching during the stretching of the laminate, or after the stretching of the laminate (before stretching) The polarizing film 2 in which the dichroic dye is adsorbed to the matrix can be obtained by bringing the dichroic dye into contact with the matrix formed from the dye.

In any of the methods described above, in addition to the treatment of bringing the dye into contact with the stretching and dichroic dye (dyeing), the PVA layer may be further subjected to insolubilization treatment, swelling treatment, crosslinking treatment, fixing treatment and drying. The order of each process may be changed as required, or each process may be performed two or more times, or different processes may be performed at the same time. Further, according to the above production method, a polarizing film formed on the stretched thermoplastic resin film layer is obtained, and it may include a step of peeling the stretched thermoplastic resin film if necessary.

In an example of the production method (2) of the polarizing film of the present invention, the laminate having the PVA layer not containing the dichroic dye is first subjected to the insolubilization treatment and, if necessary, further subjected to the swelling treatment, Then, the dichroic dye is brought into contact with the dichroic dye to bring the dichroic dye into the PVA layer. If necessary, the dichroic dye is further subjected to a crosslinking treatment. The resulting laminate is stretched to 5.7 times or more, Followed by drying and a series of treatments to obtain a polarizing film formed on the stretched thermoplastic resin film layer and peeling off the stretched thermoplastic resin film layer.

The insolubilization treatment of the PVA layer is mainly carried out in order to prevent elution of PVA contained in the PVA layer into water. Examples of the insolubilization treatment include a method of performing heat treatment on the laminate, a method of immersing the laminate in an aqueous solution containing one or more kinds of boron compounds such as boric acid salts such as boric acid and borax . Among these methods, a method using an aqueous solution containing a boron compound is preferable in that heat treatment is applied to the laminate, which may cause wrinkling along with the dimensional change of the thermoplastic resin film layer. The heat treatment can be performed at a temperature within a range of, for example, 80 ° C or higher and 200 ° C or lower. From the viewpoint of preventing wrinkles, the heat treatment is preferably carried out while applying a tensile force to the laminate. Further, in the method using an aqueous solution containing a boron compound, the temperature of the aqueous solution is preferably in the range of 20 ° C to 40 ° C, more preferably 22 ° C or more, further preferably 25 ° C or more, More preferably 38 DEG C or lower, and still more preferably 35 DEG C or lower. By keeping the temperature within the range of 20 ° C or higher and 40 ° C or lower, dissolution of PVA can be prevented and the PVA can be insolubilized efficiently. The time for immersing in an aqueous solution containing a boron compound is, for example, within a range from 0.1 minute to 5 minutes. It can be effectively insolubilized by keeping the temperature within 0.1 minute to 5 minutes. The concentration of the boron compound in the aqueous solution containing the boron compound is preferably 0.5% by mass or more, more preferably 1.0% by mass or more, further preferably 1.5% by mass or more, further preferably 6.0% More preferably 5.0% by mass or less, and still more preferably 4.0% by mass or less. By keeping the concentration within the range of 0.5% by mass or more and 6.0% by mass or less, dissolution of PVA can be prevented, and insolubility can be efficiently ensured.

The insolubilization treatment of the PVA layer is preferably carried out before the dichroic dye is contacted, and furthermore before the swelling treatment.

In the explanation of each of the swelling treatment, the treatment (dying) for bringing the dichroic dye into contact with each other, and the crosslinking treatment in the production method (2) of the polarizing film, The description of the swelling treatment, the treatment of bringing the dichroic dye into contact (dyeing), and the cross-linking treatment can be adopted as they are, so the overlapping description is omitted here.

In the method (2) for producing a polarizing film, the stretching method for stretching the laminate is not particularly limited, and may be carried out by any of a wet stretching method and a dry stretching method. In the case of the wet stretching method, it may be carried out in an aqueous solution containing one or two or more kinds of boron compounds such as boric acid salts such as boric acid and borax. In the solution containing the dichroic dye or in a fixed treatment bath . In the case of the dry stretching method, the stretching may be performed at room temperature, or the stretching may be performed while heat is applied, or the stretching may be performed after absorption. Among them, the wet stretching method is preferable from the viewpoint of the uniformity of the thickness in the width direction in the obtained polarizing film, and it is more preferable to stretch in the aqueous solution of boric acid. The concentration of boric acid in the aqueous solution of boric acid is preferably in the range of 0.5% by mass to 6.0% by mass, more preferably 1.0% by mass or more, still more preferably 1.5% by mass or more, Or less, more preferably 4.0 mass% or less. When the boric acid concentration is in the range of 0.5% by mass or more and 6.0% by mass or less, a polarizing film having excellent thickness uniformity in the width direction can be obtained. The aqueous solution containing the boron compound may contain potassium iodide, and the concentration thereof is preferably in the range of 0.01% by mass or more and 10% by mass or less. Since the concentration of potassium iodide is in the range of 0.01 mass% or more and 10 mass% or less, a polarizing film having better polarizing performance can be obtained.

The temperature at which the laminate is drawn is preferably in the range of 30 DEG C to 90 DEG C, more preferably 40 DEG C or more, still more preferably 50 DEG C or more, and more preferably 80 DEG C or less More preferably 70 DEG C or less. When the temperature is in the range of 30 占 폚 to 90 占 폚, a polarizing film excellent in thickness uniformity in the width direction can be obtained.

In the production method (2) of the polarizing film of the present invention, it is necessary to stretch the laminate to 5.7 times or more, preferably 5.8 times or more, and more preferably 5.9 times or more. By setting the stretching magnification of the laminate within the above-mentioned range, the polarizing film (2) having a higher birefringence index of the matrix than the conventional one and having less polarizing performance and less leakage of red light in the cross-Nicol state can be produced smoothly and easily . The upper limit of the draw ratio of the laminate is not particularly limited, but is preferably 8 times or less. The stretching of the laminate may be carried out at one time or may be carried out in a plurality of circuits or any of them. In the case of dividing the laminate into a plurality of circuits, the total stretch ratio multiplied by the stretch ratio of each stretch may be within the above range. The drawing magnification in this specification is based on the length of the laminate before drawing, and the state without drawing is equivalent to a drawing magnification of 1 time.

The stretching of the laminate is preferably uniaxial stretching in view of the performance of the resulting polarizing film. There is no particular limitation on the direction of uniaxial stretching in the case of elongating the elongated laminate. Uniaxial stretching in the longitudinal direction or transverse uniaxial stretching can be adopted, but a polarizing film having better polarizing performance can be obtained The uniaxial stretching in the longitudinal direction is preferable. The uniaxial stretching in the longitudinal direction can be carried out by changing the peripheral velocity between the rolls by using a stretching apparatus having a plurality of rolls parallel to each other. On the other hand, transverse uniaxial stretching can be carried out using a tenter-type stretching machine.

In the description of the fixing process and drying in the polarizing film producing method (2), the description of the fixing process and the drying in the description of the polarizing film producing method (1) The overlapping description will be omitted here.

In this way, the polarizing film 2 formed on the stretched thermoplastic resin film layer is obtained. The method of using the polarizing film of this type is not particularly limited, and for example, it is possible to use a polarizing film having optical transparency and mechanical strength on the polarizing film side as it is or without being peeled off the stretched thermoplastic resin film layer The protective film may be laminated to form a polarizing plate. Alternatively, after the protective film is bonded to the side opposite to the side where the stretched thermoplastic resin film layer is located, the stretched thermoplastic resin film layer is peeled off, Another protective film may be laminated to form a polarizing plate. As the protective film, a cellulose triacetate (TAC) film, an acetic acid-butyric acid cellulose (CAB) film, an acrylic film, a polyester film, or the like can be used. Examples of the adhesive for bonding include a PVA adhesive and a urethane adhesive, but a PVA adhesive is preferred.

Example

The present invention will be described concretely with reference to the following examples, but the present invention is not limited at all by these examples. The measurement or evaluation methods employed in the following Reference Examples, Examples and Comparative Examples are shown below.

Measurement of the contact angle of the surface of the thermoplastic resin film

2 쨉 l of pure water was extruded from the needle having an inner diameter of 0.4 mm onto the surface of the thermoplastic resin film under the environment of 20 캜 and 65% RH by using "DropMaster 500" manufactured by Kyowa Interface Science Co., Ltd. and the contact angle was measured.

Measurement of swelling degree of PVA layer

The laminate obtained in the following examples or comparative examples was cut into a suitable size (for example, about 300 cm 2), and immersed in 1,000 g of distilled water at 30 ° C for 30 minutes. Thereafter, the laminate was taken out, water on the surface was removed with a filter paper, and its mass was measured (its mass was referred to as A). Subsequently, this laminate was dried at 105 DEG C for 16 hours, and the mass thereof was measured (its mass is referred to as B). Further, the dried laminate was blended with hot water at 95 DEG C for 6 hours to dissolve the PVA layer, and the remaining thermoplastic resin film layer was dried at 105 DEG C for 16 hours, and its mass was measured (its mass is referred to as C). The swelling degree S (%) of the PVA layer was calculated by the following equation (4).

S = 100 x (A - C) / (B - C) (4)

Measurement of average degree of polymerization of PVA

And measured according to the description of JIS K6726-1994. As the test solution, 0.28 g of PVA, 70 g of distilled water, and a stirrer were placed in a 100 ml replaceable ground joint Erlenmeyer flask, the stopper was closed, the resultant was immersed in a thermostatic chamber at 95 ° C, and the PVA was dissolved with stirring A PVA aqueous solution having a concentration of about 0.4% by mass was used, which was filtered with a Buchner funnel-type glass filter 3G and cooled in a constant temperature water bath at 30 캜.

Measurement of thickness of polarizing film (1)

The thickness at an arbitrary position (five points) of the polarizing film was measured using a digital gauge (" DE12BR " manufactured by Magnescape), and the average value was defined as the polarizing film thickness (1).

Measurement of birefringence of matrix

Retardation due to light having wavelengths of 800 nm and 1,000 nm was measured using a cell gap inspecting apparatus (" RETS-1100 " manufactured by Otsuka Electronics Co., Ltd.) for the polarizing films obtained in the following Reference Examples, Respectively. The measurement positions were arbitrary five points on a straight line extending in the longitudinal direction (monoaxially stretched direction) passing through the center of the polarizing film in the width direction (direction in the film plane perpendicular to the uniaxial stretching direction). The average value of the five retardations measured by the light having the wavelength of 800 nm is represented by R ₈₀₀ in the formula (2 '), and the average value of the five retardations measured by the light having the wavelength of 1,000 nm is represented by the formula a: (㎚ unit) (2 ") to the R _1000, the above formula (2 ', 3'), (2 in.") and (3 ") releasing the simultaneous equations hit by the matrix retardation a of , And the birefringence index of the matrix was obtained by dividing this by the thickness of the polarizing film (average value at five points, unit converted to nm) measured by "Measurement of thickness of polarizing film (2)" .

Measurement of thickness of polarizing film (2)

The thickness of the polarizing film at the measurement position (five points) of the retardation in the measurement of the birefringence index of the above-mentioned matrix was measured using a digital gauge (" DE12BR " And the thickness of the film (2).

Evaluation of polarization performance

(a) Measurement of transmittance Ts

Two samples each having a square of 2 cm in the width direction of the polarizing film and 2 cm in the longitudinal direction were collected from the central portion in the width direction of the polarizing film obtained in the following Examples and Comparative Examples and a spectrophotometer The visual sensitivity of the C light source and the visible light region in the visible range of 2 degrees were corrected in accordance with JIS Z 8722 (measurement method of object color) by using Nikon Spectrometer Co., Ltd., "V7100" The transmittance of light when tilted at 45 ° and the transmittance of light when tilted at -45 ° were measured to obtain an average value Ts1 (%) thereof. In the same manner for the other one sample, the transmittance of light at an angle of 45 DEG and the transmittance of light at an angle of -45 DEG were measured, and their average value Ts2 (%) was determined. Ts1 and Ts2 were averaged by the following equation (5) to obtain the transmittance Ts (%) of the polarizing film.

Ts = (Ts1 + Ts2) / 2 (5)

(b) Measurement of polarization degree V

The transmittance T // (%) of the light in the case where the two samples taken in the measurement of the transmittance Ts are overlapped so that their lengthwise directions become parallel to each other and the transmittance T⊥ (% Measurement was made in the same manner as in "(a) Measurement of transmittance Ts", and the degree of polarization V (%) was obtained by the following formula (6).

V = {(T // - T?) / (T // + T?)} ^1/2 100 (6)

(c) Calculation of dichroism ratio at 44% transmittance

In each of the following examples and comparative examples, the immersion time for an aqueous solution containing an iodine dye was changed from 1 minute to 4 times within a range of 1 to 2 minutes, and the same operation was carried out. To prepare four polarizing films having different adsorption amounts of the dichroic dye. The transmittance Ts (%) and the polarization degree V (%) were determined for each of these four polarizing films by the above-described method, and the transmittance Ts (% And a point based on the transmittance Ts (%) and the polarization degree V (%) of the polarizing film obtained in each of the examples and comparative examples on the ordinate axis were plotted on a graph to obtain an approximate curve. From the approximate curve , And the degree of polarization V ₄₄ (%) when the transmittance Ts (%) was 44%.

The dichroism ratio at the transmittance of 44% was determined from the obtained degree of polarization V ₄₄ (%) by the following formula (7), and the index was used as an index of the polarization performance.

Transmission dichroic ratio at the time of 44% = log (44/100 - 44/100 × V 44/100) / log (44/100 + 44/100 × V 44/100) (7)

Evaluation of Leakage of Red Light in Cross-Nicol State

One polarizing film obtained in each of the examples and comparative examples and the polarizing film obtained by the calculation of the dichroism ratio at the time of (c) transmissivity of 44% in the evaluation of the polarizing performance The orthogonal transmittance T ₇₀₀ ⊥ (%) of light having a wavelength of 700 nm was measured for five polarizing films in total, four films. That is, for each of five samples obtained by the evaluation of the polarization performance, two samples were superimposed in such a manner that the longitudinal directions thereof were orthogonal to each other, and a spectrophotometer ("V7100" manufactured by Nihon Spectroscopy Co., Ltd.) the measurement of the transmittance of light having a wavelength of 700 cases ㎚ length with respect to a direction inclined ㎚ wavelength 700 of light transmittance and -45 ° in the case of the 45 ° tilt, and as their average value T ₇₀₀ ⊥ (%).

Then, an approximate curve is obtained by plotting a total of five points on the graph, assuming that the transmittance Ts (%) obtained by the evaluation of the polarization performance is plotted on the abscissa axis and the orthogonal transmittance T ₇₀₀ ⊥ (%) of the light with a wavelength of 700 nm is plotted on the ordinate axis, , The orthogonal transmittance T ₇₀₀ ⊥ ₄₄ (%) of light having a wavelength of 700 nm when the transmittance Ts (%) was 44% was determined. It was evaluated that the leakage of red light was small when the T ₇₀₀ ⊥ ₄₄ (%) was low.

[Example 1]

(1) Hydrophilization treatment of thermoplastic resin film

As a thermoplastic resin film, an amorphous polyethylene terephthalate film (A-PET sheet FR thickness 150 占 퐉, manufactured by Teijin Co., Ltd.) was used and a discharge amount 280 W / min / m 2 (output 280 W / m , Processing speed: 1.0 m / min). The contact angle of the surface of the thermoplastic resin film after the corona treatment was 60 占 (the contact angle before the corona treatment was 79 占).

(2) Preparation of stock solution

100 parts by mass of PVA (saponified copolymer of vinyl acetate and ethylene) having an average degree of polymerization of 2,400, a saponification degree of 99.8 mol%, an ethylene content of 2.5 mol% and a 1,2-glycol bond content of 1.6 mol%, 6 parts by mass of glycerin And water was prepared as an aqueous solution having a PVA concentration of 10 mass% to prepare a PVA layer.

(3) Fabrication of laminate

(2) was coated on the corona-treated surface of the thermoplastic resin film subjected to the hydrophilization treatment in (1) using a die coater and then dried at 80 DEG C for 240 seconds to form an amorphous polyethylene terephthalate film layer (Having a width of 0.5 m) of a PVA layer having a thickness of 6 mu m was prepared. The degree of swelling of the PVA layer was measured for the resulting laminate. The results are shown in Table 1.

(4) Production of polarizing film

The laminate produced in (3) was subjected to swelling treatment, dyeing, uniaxial stretching, and drying treatment in this order to prepare a polarizing film. Namely, as a swelling treatment, the laminate was immersed in distilled water for 1 minute. Subsequently, the substrate was immersed in an aqueous solution containing iodine dye (concentration of iodine to be used: 0.3 mass%, concentration of potassium iodide used: 2.1 mass%, temperature: 30 ° C) for 1 minute to contain an iodine dye in the PVA layer . Subsequently, the film was uniaxially stretched to the limit in the longitudinal direction in an aqueous solution of boric acid (boric acid concentration: 4 mass%, potassium iodide concentration: 6 mass%, temperature: 65 占 폚). Further, the magnification to be cut by stretching by the same method in advance was confirmed, and the magnification which was 0.20 times lower than the cut magnification was defined as the above limit. Thereafter, the film was dried at 60 DEG C for 1 minute to obtain a polarizing film formed on the stretched amorphous polyethylene terephthalate film layer. The stretched amorphous polyethylene terephthalate layer was peeled from the film, and the thickness (1) and the polarization performance were measured or evaluated for the obtained polarizing film. The results are shown in Table 1 together with the adopted stretching magnification.

[Examples 2 to 4]

Except that the ethylene content and the 1,2-glycol bond amount of PVA were changed as shown in Table 1, the degree of swelling of the PVA layer was measured in the same manner as in Example 1, and the degree of swelling of the PVA layer was measured, A polarizing film (obtained by delaminating a stretched amorphous polyethylene terephthalate layer) was obtained, and thickness (1) and polarization performance were measured or evaluated. The results are shown in Table 1 together with the adopted stretching magnification.

[Comparative Example 1]

A laminate was obtained in the same manner as in Example 1 except that the ethylene content of the PVA was changed as shown in Table 1, and the degree of swelling of the PVA layer was measured. Further, in the same manner as in Example 1, when a polarizing film was produced from the laminate, PVA contained in the PVA layer was eluted at the time of swelling treatment, so that a polarizing film could not be produced. The results are shown in Table 1.

[Comparative Example 2]

A laminate was obtained in the same manner as in Example 1 except that the ethylene content of the PVA was changed as shown in Table 1, and the degree of swelling of the PVA layer was measured. Further, in the same manner as in Example 1, a polarizing film was produced from the laminate, and as a result, only the thickness (1) was measured, and evaluation of the polarization performance was not performed because the dyeability was bad and uneven. The results are shown in Table 1 together with the adopted stretching magnification.

In Examples 1 to 4, the degree of swelling of the PVA layer was in the range of 180% or more and 260% or less. Therefore, even though the insolubilization treatment such as dipping or air high temperature stretching was not previously performed for the aqueous boric acid solution, A polarizing film could be produced. On the other hand, in Comparative Example 1, since the degree of swelling of the PVA layer was higher than 260%, the PVA contained in the PVA layer was eluted at the time of producing the polarizing film and the polarizing film could not be produced. In Comparative Example 2, Since the degree of swelling was lower than 180%, the polarizing film became nonuniform.

[Referential Example 1]

100 parts by mass of PVA (saponified vinyl acetate homopolymer) having an average degree of polymerization of 2,400 and a degree of saponification of 99.8 mol%, 12 parts by mass of glycerin as a plasticizer and an aqueous solution having a volatile fraction of 66% by mass composed of water were used as an undiluted solution, Dried on a first drying roll at 95 ° C until it had a volatile fraction of 22% by mass on the first drying roll, peeled off from the first drying roll, and dried on a plurality of subsequent drying rolls at 80 ° C Followed by heat treatment by a heat treatment roll at 110 캜 to obtain a single-layer PVA film (long film having a width of 0.5 m) having a thickness of 60 탆.

This PVA film was subjected to swelling treatment, dyeing, uniaxial stretching, and drying treatment in this order to produce a polarizing film. That is, the PVA film was immersed in water at 30 DEG C for 1 minute. Subsequently, the substrate was immersed in an aqueous solution containing iodine dye (concentration of iodine to be used: 0.3 mass%, concentration of potassium iodide used: 2.1 mass%, temperature: 30 ° C) for 1 minute to contain the iodine dye in the PVA film . Subsequently, the film was uniaxially stretched to the limit in an elongated direction in an aqueous boric acid solution (boric acid concentration: 4 mass%, potassium iodide concentration: 6 mass%, temperature: 55 ° C). Further, the magnification to be cut by stretching by the same method in advance was confirmed, and the magnification which was 0.20 times lower than the cut magnification was defined as the above limit. Thereafter, the film was dried at 60 DEG C for 4 minutes to obtain a polarizing film. The birefringence index and the thickness (2) of the matrix were measured for each polarizing film. The results are shown in Table 2 together with the adopted stretching magnification.

[Reference Examples 2 to 4]

A polarizing film was obtained in the same manner as in Reference Example 1 except that PVA (saponification degree of saponification degree: 99.8 mol%, homopolymer of saponification product of vinyl acetate) having an average degree of polymerization shown in Table 2 was used to obtain a birefringent index and thickness (2) Respectively. The results are shown in Table 2 together with the adopted stretching magnification.

As is clear from Reference Examples 1 to 4, when the polarizing film was produced from the single-layer PVA film, it was found that the limiting stretch ratio decreased as the average degree of polymerization of PVA increased. In the polarizing films obtained in Reference Examples 1 to 4, the birefringence of the matrix was low.

[Example 5]

(1) Hydrophilization treatment of thermoplastic resin film

As a thermoplastic resin film, an amorphous polyethylene terephthalate film (A-PET sheet FR thickness 150 占 퐉, manufactured by Teijin Co., Ltd.) was used and a discharge amount 280 W / min / m 2 (output 280 W / m , Processing speed: 1.0 m / min). The contact angle of the surface of the thermoplastic resin film after the corona treatment was 60 占 (the contact angle before the corona treatment was 79 占).

(2) Preparation of stock solution

100 parts by mass of PVA (saponified vinyl acetate homopolymer) having an average degree of polymerization of 5,500 and a degree of saponification of 99.8 mol%, 12 parts by mass of glycerin as a plasticizer and an aqueous solution containing 5% by mass of PVA concentration in water were prepared to form a PVA layer .

(3) Fabrication of laminate

(2) was coated on the corona-treated surface of the thermoplastic resin film subjected to the hydrophilization treatment in (1) using a die coater and then dried at 80 DEG C for 240 seconds to form an amorphous polyethylene terephthalate film layer (Having a width of 0.5 m) of a PVA layer having a thickness of 6 mu m was prepared.

(4) Production of polarizing film

(3), the PVA layer was subjected to insolubilization treatment, dyeing, uniaxial stretching and drying treatment in this order to prepare a polarizing film. Namely, as a treatment for insolubilizing the PVA layer, the laminate was immersed in an aqueous boric acid solution (concentration: 3 mass%, temperature: 30 ° C) for 1 minute. Subsequently, the substrate was immersed in an aqueous solution containing iodine dye (concentration of iodine to be used: 0.3 mass%, concentration of potassium iodide used: 2.1 mass%, temperature: 30 ° C) for 1 minute to contain an iodine dye in the PVA layer . Subsequently, the film was uniaxially stretched to the limit in the longitudinal direction in an aqueous solution of boric acid (boric acid concentration: 4 mass%, potassium iodide concentration: 6 mass%, temperature: 65 占 폚). Further, the magnification to be cut by stretching by the same method in advance was confirmed, and the magnification which was 0.20 times lower than the cut magnification was defined as the above limit. Thereafter, the film was dried at 60 DEG C for 1 minute to obtain a polarizing film formed on the stretched amorphous polyethylene terephthalate film layer. From this, the stretched amorphous polyethylene terephthalate layer was peeled off, and the obtained polarizing film was measured or evaluated for the birefringence of the matrix, the thickness (2), the polarization performance, and the leakage of red light in the cross-Nicol state . The results are shown in Table 3 together with the adopted stretching magnification.

[Examples 6 to 14 and Comparative Examples 3 to 7]

Except that the average degree of polymerization of PVA (saponification degree: 99.8 mol%, saponified homopolymer of vinyl acetate) and glycerin content were changed as shown in Table 3, and a polarizing film (stretched amorphous polyethylene terephthalate (2), the polarization performance of the matrix, and the leakage of red light in the Cross-Nicol state were measured or evaluated. The results are shown in Table 3 together with the adopted stretching magnification.

[Comparative Examples 8 and 9]

The average polymerization degree of PVA (saponification degree: 99.8 mol%, saponified homopolymer of vinyl acetate) and glycerin content were as shown in Table 3, and the stretching magnification of the laminate was changed to 5.00 times. In the same manner, a polarizing film (obtained by delaminating an elongated amorphous polyethylene terephthalate layer) was obtained to measure or evaluate the birefringence of the matrix, the thickness (2), the polarization performance, and the leakage of red light in the cross- Respectively. The results are shown in Table 3 together with the adopted stretching magnification.

In the polarizing films obtained in Examples 5 to 14, the birefringence of the matrix was high, the polarizing films had a large dichroic ratio value, and thus the polarization performance was excellent. Further, the value of T ₇₀₀ ⊥ ₄₄ was small, The leakage of the red light is small. On the other hand, in the polarizing films obtained in Comparative Examples 3 to 9, the birefringence of the matrix was low, the value of the dichroic ratio was small and the polarization performance was poor, and the value of T ₇₀₀ ⊥ ₄₄ was large, It can be seen that there is a large amount of leakage of the liquid.

Industrial availability

According to the laminate (1) of the present invention and the production method (1) for producing a polarizing film using the laminate (1) of the present invention, water insolubility such as dyeing, etc., It is possible to omit dissolution of PVA contained in the PVA layer in the process of contacting the polarizing film with the polarizing film, Can be easily manufactured by using a polarizing film production equipment of the present invention. Further, the polarizing film (2) of the present invention has excellent polarizing performance and less leakage of red light in cross-Nicol state. Further, according to the production method (2) of the polarizing film of the present invention, it is possible to smoothly and simply produce the polarizing film (2) having excellent polarizing performance and less leakage of red light in the crossed Nicols state.

Claims (20)

A thermoplastic resin film layer and a polyvinyl alcohol layer having a swelling degree of 180% or more and 260% or less. The method according to claim 1,
Wherein the polyvinyl alcohol contained in the polyvinyl alcohol layer has an ethylene content of 1 mol% or more and 12 mol% or less. 3. The method according to claim 1 or 2,
Wherein the 1,2-glycol bond amount of the polyvinyl alcohol contained in the polyvinyl alcohol layer is from 0.4 mol% to 1.5 mol%. 4. The method according to any one of claims 1 to 3,
Wherein the polyvinyl alcohol contained in the polyvinyl alcohol layer has an average degree of polymerization of 1,000 or more and 9,500 or less. 5. The method according to any one of claims 1 to 4,
Wherein the polyvinyl alcohol contained in the polyvinyl alcohol layer has a saponification degree of 98 mol% or more. 6. The method according to any one of claims 1 to 5,
Wherein the polyvinyl alcohol layer contains the plasticizer in an amount of 1 part by mass or more and 15 parts by mass or less based on 100 parts by mass of the polyvinyl alcohol. The method according to claim 6,
Wherein the plasticizer is glycerin. A method for producing a polarizing film, comprising the step of stretching the laminate according to any one of claims 1 to 7. 9. The method of claim 8,
A polyvinyl alcohol layer of a laminate before stretching; A polyvinyl alcohol layer in the course of stretching during drawing of the laminate; And a step of bringing the dichroic dye into contact with any of the stretched film layers formed from the polyvinyl alcohol layer after stretching the laminate. 10. The method of claim 9,
Wherein the step of bringing the dichroic dye into contact with an aqueous solution containing a boron compound before the step of contacting the dichroic dye is not included. 11. The method according to claim 9 or 10,
Does not include a step of drawing at a temperature of 95 占 폚 or more before the step of contacting the dichroic dye. Wherein a dichroic dye is adsorbed to a matrix having a birefringence of 45 x 10 < ^-3 > or more. 13. The method of claim 12,
Wherein the matrix contains polyvinyl alcohol and has an average degree of polymerization of from 2,800 to 9,500. 13. The method of claim 12,
Wherein the matrix contains polyvinyl alcohol and has an average degree of polymerization of 4,100 or more and 9,500 or less. 15. The method according to any one of claims 12 to 14,
And a thickness of 10 m or less. A process for producing a polarizing film comprising a step of stretching a laminate having a thermoplastic resin film layer and a polyvinyl alcohol layer to a stretching ratio of 5.7 times or more, wherein the polyvinyl alcohol contained in the polyvinyl alcohol layer has an average degree of polymerization of 2,800 to 9,500, A method for producing a polarizing film. 17. The method of claim 16,
Wherein the average degree of polymerization of polyvinyl alcohol is 4,100 or more and 9,500 or less. 18. The method according to claim 16 or 17,
Wherein the polyvinyl alcohol layer contains the plasticizer in an amount of 1 part by mass or more and 15 parts by mass or less based on 100 parts by mass of the polyvinyl alcohol. 18. The method according to claim 16 or 17,
Wherein the polyvinyl alcohol layer contains the plasticizer in an amount of 4 parts by mass or more and 12 parts by mass or less based on 100 parts by mass of the polyvinyl alcohol. 20. The method according to claim 18 or 19,
Wherein the plasticizer is glycerin.