WO2014024712A1

WO2014024712A1 - Layered object, polarizing film, and process for producing polarizing film

Info

Publication number: WO2014024712A1
Application number: PCT/JP2013/070431
Authority: WO
Inventors: 勝啓高藤; 磯▲ざき▼　孝徳
Original assignee: 株式会社クラレ
Priority date: 2012-08-06
Filing date: 2013-07-29
Publication date: 2014-02-13
Also published as: TWI645221B; TW201411203A; KR102059228B1; TW201719207A; KR20150040925A; TWI710806B; CN104602912B; JP6434309B2; JPWO2014024712A1; CN104602912A

Abstract

Provided is a layered object from which the PVA can be inhibited from dissolving away during a step for bringing the layered object into contact with water, even without an insolubilization treatment, and from which a polarizing film having excellent polarizing performance can be easily produced using common equipment for polarizing-film production. Also provided are a process for producing a polarizing film using the layered object, a polarizing film which has excellent polarizing performance and which under crossed Nicols is reduced in the leakage of red light, and a process for producing the polarizing film. The layered object comprises a thermoplastic resin film layer and a PVA layer having a degree of swelling of 180-260%. The process for polarizing-film production includes the step of stretching the layered object. The polarizing film comprises a matrix having a birefringence of 45×10^-3 or higher and a dichroic dye adsorbed onto the matrix. The process for polarizing-film production includes the step of stretching the layered object, which comprises a thermoplastic resin film layer and a PVA layer, 5.7 times or more, the PVA contained in the PVA layer having an average degree of polymerization of 2,800-9,500.

Description

Laminated body, polarizing film, and manufacturing method of 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 having a dichroic dye adsorbed on a matrix and a method for producing the same.

A polarizing plate having a light transmission and shielding function is a basic component of a liquid crystal display (LCD) together with a liquid crystal that changes a polarization state of light. Many polarizing plates have a structure in which a protective film such as a cellulose triacetate (TAC) film is bonded to the surface of a polarizing film. As a polarizing film constituting the polarizing plate, a polyvinyl alcohol film (hereinafter referred to as “polyvinyl alcohol”). _May be abbreviated as “PVA”) and a uniaxially stretched matrix (stretched film oriented by uniaxial stretching) with iodine pigment (I ₃ ^- or I ₅ ^- etc.) or dichroic organic dye The thing which adsorb | sucks the dichroic dye is becoming mainstream. Such a polarizing film can be obtained by uniaxially stretching a PVA film preliminarily containing a dichroic dye, adsorbing a dichroic dye simultaneously with uniaxial stretching of the PVA film, or dichroic after uniaxially stretching the PVA film. Manufactured by adsorbing dyes.

LCDs are used in a wide range of devices such as small devices such as calculators and wrist watches, notebook computers, liquid crystal monitors, liquid crystal color projectors, liquid crystal televisions, in-vehicle navigation systems, mobile phones, and measuring devices used indoors and outdoors. However, in recent years, it is often used for mobile applications such as small notebook personal computers and mobile phones, and there is an increasing demand for thinner polarizing plates. In particular, there is an increasing demand for the thickness of the polarizing film constituting the polarizing plate to be 10 μm or less.

As a method of thinning a polarizing film constituting a polarizing plate, a thermoplastic resin film is stretched, dyed and dried after being stretched, dyed and dried on a thermoplastic resin film, and then stretched as necessary. A method of peeling and removing a film layer is known (see Patent Documents 1 and 2, etc.).

When producing a polarizing film by the method as described above, it is important that the PVA contained in the PVA layer does not elute in the step of contacting with water at the time of producing the polarizing film, such as dyeing. Therefore, in the conventional method, it has been essential to perform insolubilization treatment of the PVA layer in advance before the step of contacting with water such as dyeing.

Specifically, in Patent Document 1, after a PVA layer is formed on a resin substrate having a thickness of at least 20 μm and a dichroic substance is adsorbed, the total draw ratio is 5 times the original length in an aqueous boric acid solution. A method for producing a polarizing film by stretching as described above is described. Patent Document 1 describes that in order to prevent elution of PVA into an aqueous solution during dyeing, an insolubilization treatment is performed on the PVA layer in advance before immersing the PVA layer produced on the resin base material in the dyeing solution. Specifically, a method of dipping in an aqueous boric acid solution at room temperature is described. In Patent Document 1, the draw ratio is more preferably 5.5 times or more, PVA having a polymerization degree of 1,000 to 10,000 is used, and the maximum draw ratio is 4.0 to It is described that it was 5.5 times.

On the other hand, in Patent Document 2, a laminate formed by forming a PVA layer on an amorphous ester thermoplastic resin base material is stretched in the air at a high temperature of 95 to 150 ° C. and then adsorbed with a dichroic substance. Thereafter, a method for producing a polarizing film by further stretching in an aqueous boric acid solution is described. Patent Document 2 describes a method for producing a polarizing film without insolubilizing treatment with an aqueous boric acid solution as Example 1, but in practice, crystallization in high-temperature stretching in the air at 130 ° C. in Example 1 is described. As a result, the PVA layer is insolubilized. Patent Document 2 describes that PVA having a polymerization degree of 1,000 or more was used.

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

However, the above-mentioned immersion in boric acid aqueous solution and high-temperature stretching in the air in the prior art are complicated in operation, or a general-purpose polarizing film manufacturing facility that has been put to practical use so far cannot be used, and special manufacturing facilities are required. There were problems such as becoming. Therefore, the present invention can suppress the elution of PVA in the step of contacting with water without performing insolubilization treatment such as immersion in boric acid aqueous solution and high temperature stretching in the air in advance, and a polarizing film having excellent polarization performance can be used as a general purpose. It aims at providing the manufacturing method of the laminated body which can be simply manufactured using a polarizing film manufacturing facility, and the polarizing film using the same.

Further, the polarizing film manufactured by the conventional method has a problem that red light leaks in a crossed Nicols state. Therefore, another object of the present invention is to provide a polarizing film having excellent polarization performance and less leakage of red light in a crossed Nicol state, and a method for producing the same.

As a result of intensive studies to achieve the above object, the present inventors have found that an unstretched laminate has a stretched laminate having a thermoplastic resin film layer and a PVA layer to produce a polarizing film. When the degree of swelling of the PVA layer is adjusted to 180% or more and 260% or less, the elution of PVA can be suppressed in the step of contacting with water without performing insolubilization treatment such as immersion in boric acid aqueous solution or high-temperature stretching in the air in advance. Therefore, the insolubilization treatment, which is complicated in operation or requires special production equipment, can be omitted, and a polarizing film having excellent polarization performance can be easily produced using a general-purpose polarizing film production equipment. I found.

Further, the inventors of the present invention, in the polarizing film in which the dichroic dye is adsorbed on the matrix, when the birefringence of the matrix is set to 45 × 10 ⁻³ or higher than the conventional one, the polarizing performance is excellent and the crossed nicols state is achieved. It has been found that the polarizing film has little red light leakage.
Further, when a PVA layer is formed on a thermoplastic resin film to form a laminate, and a polarizing film formed on the thermoplastic resin film by uniaxially stretching the PVA layer is obtained, the average degree of polymerization is 2,800 or more. It has been found that the use of PVA of 9,500 or less improves the limit draw ratio during uniaxial stretching. In general, if the average degree of polymerization of PVA increases, it is considered that the tension at the time of stretching increases and the limit stretching ratio decreases. However, in order to obtain a polarizing film by the above method, when PVA having the above average degree of polymerization is used. For example, it was unexpected that the limit draw ratio did not decrease compared with the case where PVA having an average degree of polymerization of 2,600 was used, but rather improved.
And a PVA layer is formed on a thermoplastic resin film using PVA having an average degree of polymerization of 2,800 or more and 9,500 or less to form a laminate, which is stretched by 5.7 times or more to be a thermoplastic resin film. It has been found that when the polarizing film formed above is produced, a polarizing film having a matrix birefringence of 45 × 10 ⁻³ or higher can be obtained smoothly and easily.

The present inventors have further studied based on these findings and completed the present invention.

That is, the present invention
[1] A laminate having a thermoplastic resin film layer and a PVA layer having a swelling degree of 180% or more and 260% or less (hereinafter, this may be referred to as “laminate (1)”),
[2] The laminate according to [1], wherein the ethylene content of the PVA contained in the PVA layer is 1 mol% or more and 12 mol% or less.
[3] The laminate according to the above [1] or [2], wherein the amount of 1,2-glycol bonds of PVA contained in the PVA layer is 0.4 mol% or more and 1.5 mol% or less,
[4] The laminate according to any one of the above [1] to [3], wherein the average degree of polymerization of PVA contained in the PVA layer is 1,000 or more and 9,500 or less,
[5] The laminate according to any one of the above [1] to [4], wherein the saponification degree of PVA contained in the PVA layer is 98 mol% or more,
[6] The laminate according to any one of the above [1] to [5], wherein the PVA layer contains 1 to 15 parts by mass of a plasticizer with respect to 100 parts by mass of PVA.
[7] The laminate according to [6], wherein the plasticizer is glycerin,
[8] A method for producing a polarizing film comprising a step of stretching any one of the above-mentioned [1] to [7] (hereinafter, this may be referred to as “polarizing film producing method (1)”) ,
[9] The PVA layer of the laminate before stretching; the PVA layer in the course of stretching during stretching of the laminate; and the stretched film layer formed from the PVA layer after stretching the laminate; The production method of the above [8], comprising a step of bringing a dichroic dye into contact with
[10] The method according to the above [9], which does not include a step of contacting with an aqueous solution containing a boron compound before the step of contacting the dichroic dye.
[11] The method according to the above [9] or [10], which does not include a step of stretching at a temperature of 95 ° C. or higher before the step of bringing the dichroic dye into contact.
About.

The present invention also provides
[12] A polarizing film in which a dichroic dye is adsorbed on a matrix having a birefringence of 45 × 10 ⁻³ or more (hereinafter, this may be referred to as “polarizing film (2)”),
[13] The polarizing film according to [12], wherein the matrix contains PVA, and the average degree of polymerization is 2,800 or more and 9,500 or less,
[14] The polarizing film according to [12], wherein the matrix contains PVA, and the average degree of polymerization is 4,100 or more and 9,500 or less,
[15] The polarizing film of any one of the above [12] to [14], having a thickness of 10 μm or less,
[16] A method 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 average degree of polymerization of PVA contained in the PVA layer is 2, 800 to 9,500, a manufacturing method (hereinafter, this may be referred to as “polarizing film manufacturing method (2)”),
[17] The production method of the above [16], wherein the average degree of polymerization of PVA is from 4,100 to 9,500,
[18] The method according to [16] or [17] above, wherein the PVA layer contains a plasticizer in an amount of 1 part by mass to 15 parts by mass with respect to 100 parts by mass of PVA.
[19] The method according to [16] or [17] above, wherein the PVA layer contains a plasticizer in an amount of 4 parts by mass to 12 parts by mass with respect to 100 parts by mass of PVA.
[20] The production method of the above [18] or [19], wherein the plasticizer is glycerin,
About.

According to the laminate (1) of the present invention and the method (1) for producing a polarizing film using the same, in the step of contacting with water without performing insolubilization treatment such as immersion in a boric acid aqueous solution or high temperature stretching in the air in advance. The elution of PVA can be suppressed, and a polarizing film excellent in polarizing performance can be easily manufactured using a general-purpose polarizing film manufacturing facility.

The polarizing film (2) of the present invention is excellent in polarizing performance and has little red light leakage in a crossed Nicol state. Furthermore, according to the manufacturing method (2) of the polarizing film of the present invention, the polarizing film (2) having excellent polarization performance and less red light leakage in the crossed Nicol state can be manufactured smoothly and simply.

Hereinafter, the present invention will be described in detail.

<< 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, polyethylene terephthalate, and their heat. Examples thereof include a copolymer having a plurality of types of monomer units constituting the plastic resin. In the thermoplastic resin film layer, only one kind of thermoplastic resin may be contained, or two or more kinds of thermoplastic resins may be contained. Among 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 within the range of 20 to 250 μm, more preferably within the range of 30 to 230 μm, and even more preferably within the range of 50 to 200 μm. When the thickness of the thermoplastic resin film layer is 20 μm or more, wrinkles can be effectively prevented when forming the PVA layer. On the other hand, it can suppress that the tension at the time of extending | stretching a laminated body (1) becomes too high because the thickness of a thermoplastic resin film layer is 250 micrometers or less.

The degree of swelling of the PVA layer of the laminate (1) of the present invention needs to be 180% or more and 260% or less, preferably 185% or more, more preferably 190% or more, It is preferably 255% or less, and more preferably 250% or less. When the degree of swelling is higher than 260%, PVA contained in the PVA layer is eluted in the step of contacting with water at the time of producing the polarizing film when the insolubilization treatment such as immersion in boric acid aqueous solution and high temperature stretching in the air is not performed in advance. Production of the film becomes difficult. On the other hand, if the degree of swelling is lower than 180%, it is difficult to dye the PVA layer, and spots are likely to be produced, and it is difficult to obtain a polarizing film having excellent polarizing performance. In addition, the swelling degree of the PVA layer in the present invention is the mass of the PVA layer after the PVA layer is immersed in distilled water at 30 ° C. for 30 minutes and then dried at 105 ° C. for 16 hours after immersion. The percentage of the value obtained by dividing. Even if the swelling degree of the PVA layer is measured in the state of the laminated body, it is preferable to measure in the state of the laminated body in consideration of operability because substantially the same value as that obtained when the PVA layer is measured alone is obtained. . Specific methods for measuring the degree of swelling of the PVA layer include the methods described later in the examples.

There is no restriction | limiting in particular in the adjustment method of the swelling degree of a PVA layer, For example, after manufacturing the laminated body which has a thermoplastic resin film layer and a PVA layer using general PVA (saponified product of a homopolymer of vinyl acetate), for example Thus, this can be performed by appropriately heat-treating at a temperature of 100 ° C. or higher. Here, the higher the heat treatment temperature and the longer the heat treatment time, the lower the value of the degree of swelling. However, if a laminate having a thermoplastic resin film layer and a PVA layer is subjected to heat treatment at a temperature of 100 ° C. or higher, wrinkles tend to occur along with the dimensional change of the thermoplastic resin film layer. Therefore, the method of adjusting the swelling degree of a PVA layer by using PVA which tends to reduce the swelling degree mentioned later is preferable. Thereby, even if the laminated body which has a thermoplastic resin film layer and a PVA layer on the conditions which do not become 100 degreeC or more is prepared, the swelling degree of the said PVA layer can be easily adjusted to the said range.

As PVA in the PVA layer, vinyl acetate, vinyl formate, vinyl propionate, vinyl butyrate, vinyl pivalate, vinyl versatate, vinyl laurate, vinyl stearate, vinyl benzoate, isopropenyl acetate, etc. The thing obtained by saponifying the polyvinyl ester obtained by superposing | polymerizing seed | species or 2 or more types can be used. Among the above vinyl esters, vinyl acetate is preferable from the viewpoints of ease of production of PVA, availability, cost, and the like.

The above-mentioned polyvinyl ester may be obtained using only one or two or more kinds of vinyl esters as a monomer. It may be a copolymer of two or more kinds of vinyl esters and other monomers copolymerizable therewith.

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

The proportion of structural units derived from the other monomers described above in the polyvinyl ester is preferably 15 mol% or less based on the number of moles of all structural units constituting the polyvinyl ester, and is preferably 10 mol%. Hereinafter, it may be 5 mol% or less.
In particular, when the other monomer described above is a monomer that may promote the water solubility of the obtained PVA, such as (meth) acrylic acid or unsaturated sulfonic acid, In order to prevent PVA from being dissolved in the production process, the proportion of structural units derived from these monomers in the polyvinyl ester is 5 mol% or less based on the number of moles of all structural units constituting the polyvinyl ester. It is preferable that it is 3 mol% or less.

The above PVA may be modified with one or two or more types of graft copolymerizable monomers as long as the effects of the present invention are not impaired. Examples of the graft copolymerizable monomer include unsaturated carboxylic acids or derivatives thereof; unsaturated sulfonic acids or derivatives thereof; α-olefins having 2 to 30 carbon atoms, and the like. The proportion of structural units derived from the graft copolymerizable monomer in PVA (structural units in the graft modified portion) is preferably 5 mol% or less based on the number of moles of all structural units constituting PVA. .

The above PVA may have a part of its hydroxyl group cross-linked or not cross-linked. Moreover, said PVA may react with aldehyde compounds, such as acetaldehyde and a butyraldehyde, etc. to form an acetal structure, and the said PVA does not react with these compounds and does not form an acetal structure. May be.

When PVA that tends to lower the degree of swelling as described above is used, even if a laminate having a thermoplastic resin film layer and a PVA layer is prepared under conditions that do not exceed 100 ° C., the degree of swelling of the PVA layer falls within the above range. It can be adjusted easily. Examples of such PVA that easily reduces the degree of swelling include PVA having an ethylene content of 1 mol% or more and 12 mol% or less. Here, ethylene content means the ratio (mol%) which the number of moles of the structural unit derived from ethylene accounts with respect to the number of moles of all the structural units which comprise PVA. When the ethylene content is 1 mol% or more, the degree of swelling can be easily reduced to the above upper limit even when drying or heat treatment after application of the stock solution as described later is performed 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 or more. Since the degree of swelling can be easily adjusted to the range specified in the present invention, the ethylene content is preferably 1.5 mol% or more, more preferably 2.0 mol% or more, It is preferably 11.5 mol% or less, and more preferably 11 mol% or less.

Another example of PVA that tends to reduce the degree of swelling is PVA having a 1,2-glycol bond content of 0.4 mol% to 1.5 mol%. Here, the amount of 1,2-glycol bonds accounts for 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. The ratio (mol%) is referred to and can be determined by NMR measurement. When the 1,2-glycol bond amount is 1.5 mol% or less, the degree of swelling can be easily reduced to the above upper limit even when drying or heat treatment after application of the stock solution as described below is performed at a low temperature. it can. 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 be the above lower limit or more. Since the degree of swelling can be easily adjusted within the range specified in the present invention, the amount of 1,2-glycol bonds is preferably 0.5 mol% or more, and preferably 0.6 mol% or more. More preferably, it is preferably 1.4 mol% or less, and more preferably 1.3 mol% or less. PVA having a small 1,2-glycol bond amount can be produced using a polyvinyl ester obtained by polymerizing a vinyl ester at a low temperature as a raw material. Specifically, a PVA having a 1,2-glycol bond content of 0.4 mol% or more and 1.5 mol% or less is obtained by polymerizing a vinyl ester within a range of approximately −50 ° C. or more and + 50 ° C. or less. Esters can be used as raw materials.

The above PVA may satisfy only one of the above-described ethylene content range and 1,2-glycol bond range, or may satisfy both. That is, PVA having an ethylene content within the above range and a 1,2-glycol bond amount exceeding 1.5 mol%; an ethylene content being less than 1 mol% and a 1,2-glycol bond amount within the above range And PVA having both the ethylene content and the 1,2-glycol bond amount within the above ranges can be used as PVA that tends to reduce the degree of swelling. However, PVA in which both the ethylene content and the 1,2-glycol bond content are within the above ranges is particularly suitable when the ethylene content is relatively high and / or the 1,2-glycol bond content is relatively low. The degree of swelling of the layer may be excessively reduced. Therefore, when using PVA in which both the ethylene content and the 1,2-glycol bond content are in the above ranges, the drying treatment and heat treatment after the PVA layer formation are performed at a relatively low temperature, or the ethylene content Is preferably low and / or the amount of 1,2-glycol bonds is high.

The average degree of polymerization of the PVA is preferably in the range of 1,000 to 9,500, and the average degree of polymerization is more preferably 1,500 and more, and 2,000 and more. More preferably, it is more preferably 9,200 or less, and further preferably 6,000 or less. 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 degree of polymerization is 9,500 or less, the productivity of PVA is improved. The average degree of polymerization of PVA used for forming the PVA layer (PVA contained in 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 99 mol% or more from the viewpoint of the polarizing performance of the obtained polarizing film. Is more preferable. When the degree of saponification is less than 98 mol%, PVA tends to be eluted during the production process of the polarizing film, and the eluted PVA may adhere to the film and reduce the polarizing performance of the polarizing film. In this specification, the degree of saponification of PVA refers to the total number of moles of structural units (typically vinyl ester units) that can be converted into vinyl alcohol units by saponification and the vinyl alcohol units of PVA. The proportion (mol%) occupied by the number of moles of vinyl alcohol units. The degree of saponification can be measured according to the description of JIS K6726-1994.

The PVA layer preferably contains a plasticizer from the viewpoint of improving stretchability when the laminate (1) is stretched. Examples of the plasticizer may include polyhydric alcohols such as ethylene glycol, glycerin, propylene glycol, diethylene glycol, diglycerin, triethylene glycol, tetraethylene glycol, and trimethylolpropane. One or more of the agents can be included. Among these, glycerin is preferable from the viewpoint of the effect of improving stretchability.

It is preferable that content of the plasticizer in a PVA layer exists in the range of 1 to 15 mass parts with respect to 100 mass parts of PVA contained in it. When the content is 1 part by mass or more, the stretchability of the laminate (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 flexible and to deteriorate the handleability, or to prevent the PVA layer from peeling off from the thermoplastic resin film layer. can do. The content of the plasticizer in the PVA layer is more preferably 2 parts by mass or more with respect to 100 parts by mass of PVA, further preferably 4 parts by mass or more, and particularly preferably 5 parts by mass or more. It is more preferably 13 parts by mass or less, further preferably 12 parts by mass or less, and particularly preferably 8 parts by mass or less.
In addition, when manufacturing a polarizing film using the laminated body (1) of this invention, although depending on the manufacturing conditions etc., the plasticizer contained in a PVA layer elutes when manufacturing a polarizing film. Therefore, the total amount does not always remain in the polarizing film.

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

The content of PVA in the PVA layer is preferably in the range of 50% by mass or more and 99% by mass or less from the ease of preparation of a desired polarizing film, and the content is 75% by mass or more. More preferably, it is more preferably 80% by mass or more, particularly preferably 85% by mass or more, more preferably 98% by mass or less, and further preferably 96% by mass or less. It is preferably 95% by mass or less.

The thickness of the PVA layer is not particularly limited and can be, for example, 100 μm or less. However, it is preferable to make the PVA layer thin because a thin polarizing film can be easily prepared. Specifically, the PVA layer Is preferably 20 μm or less, more preferably 15 μm or less, and even more preferably 10 μm or less. In the laminate (1) of the present invention, since the PVA layer has the specific configuration as described above, even if the thickness of the PVA layer is reduced as described above, the elution of PVA is suppressed in the step of contacting with water. In addition, a thin polarizing film having excellent polarization performance can be easily produced. Moreover, when the thickness of the PVA layer is thin as described above, it is possible to reduce the tension when the laminate (1) is stretched. In addition, since there exists a tendency for extending | stretching breakage to generate | occur | produce at the time of extending | stretching a laminated body (1) when the thickness of a PVA layer is too thin, the thickness of a PVA layer is 3 micrometers or more, for example.

Although there is no restriction | limiting in particular in the layer structure of the laminated body (1) of this invention, Since the polarizing film excellent in polarizing performance is obtained more simply, etc., it is a two-layer structure of one thermoplastic resin film layer and one PVA layer. It is preferable that

The shape of the laminate (1) is not particularly limited, but a more uniform laminate can be easily produced continuously, and can also be used continuously when producing a polarizing film using the laminate. Since it can do, it is preferable that it is a long laminated body. The length (length in the longitudinal direction) of the long laminate is not particularly limited, and can be appropriately set according to the use of the polarizing film to be produced. For example, the range is 5 m or more and 20,000 m or less. Can be inside.

The width of the laminate (1) is not particularly limited and can be set as appropriate according to the use of the polarizing film to be produced. However, in recent years, liquid crystal televisions and liquid crystal monitors have been increasing in screen size. If the width of the laminate (1) is 0.5 m or more, more preferably 1.0 m or more, it is suitable for these applications. On the other hand, if the width of the laminate (1) is too wide, it tends to be difficult to uniformly stretch the polarizing film when the polarizing film is produced by a practical device. Is preferably 7 m or less.

As a method for producing the laminate (1), for example, a method of forming a PVA layer on a thermoplastic resin film can be mentioned. Specifically, PVA and, if necessary, a plasticizer other than PVA such as the above-described plasticizer can be mentioned. 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; PVA, a liquid medium and, if necessary, a stock solution obtained by melting and kneading other components are thermoplastic resin A method of extruding onto a film and further drying as necessary; a method of producing a PVA film containing PVA and, if necessary, further other components by a known method, and then laminating it with a thermoplastic resin film, etc. . Among these, from the point that a thin PVA layer can be easily prepared and the uniformity of the thickness of the resulting PVA layer, a stock solution in which PVA and, if necessary, further other components are dissolved in a liquid medium is used as a thermoplastic resin film. A method of coating and drying is preferred.

Examples of the liquid medium include water, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, ethylene glycol, glycerin, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, trimethylolpropane, ethylenediamine, and diethylenetriamine. Of these, one or more of these can be used. Among these, water is preferable from the viewpoint of environmental load and recoverability.

Although the volatile content rate of the stock solution (the content ratio in the stock solution of volatile components such as a liquid medium that is removed by volatilization or drying during the formation of the PVA layer) varies depending on the formation method and formation conditions of the PVA layer, It is preferably in the range of 50% by mass to 98% by mass, and more preferably in the range of 55% by mass to 95% by mass. When the volatile content of the stock solution is 50% by mass or more, its viscosity does not become too high, and filtration and defoaming during the preparation of the stock solution are smoothly performed, and formation of a PVA layer with less foreign matter and defects is facilitated. At the same time, the coatability is also improved. On the other hand, when the volatile content of the stock solution is 98% by mass or less, the concentration of the stock solution does not become too low, and industrial production of the laminate is facilitated.

Examples of the coating method for coating the stock solution on the thermoplastic resin film include a die coating method, a comma coating method, and a dip coating method. Among these, the die coating method is preferable from the viewpoint 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 the production of the laminate (1) is subjected to a hydrophilic treatment. By forming the PVA layer so as to be in contact with the hydrophilically treated surface, the adhesion between the thermoplastic resin film layer and the PVA layer is improved. Examples of the hydrophilic treatment include corona treatment, plasma treatment, anchor coat treatment, and the like. Among these, corona treatment is preferable from the viewpoint 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 to adjust the contact angle to 57 ° or more, and to 59 ° or more. More preferably, it is more preferably adjusted to 69 ° or less, and further preferably adjusted to 68 ° or less. When the contact angle is lower than 55 °, the adhesive strength between the thermoplastic resin film layer and the PVA layer tends to be too strong, and when the thermoplastic resin film layer stretched after stretching the laminate (1) is peeled off. Peeling may be difficult. On the other hand, when the contact angle is higher than 70 °, the PVA layer easily peels or tears from the thermoplastic resin film layer during stretching of the laminate (1), making it difficult to stretch at a high stretch ratio. Tend to be. The contact angle of the surface of the thermoplastic resin film is the angle formed by the water surface and the surface of the thermoplastic resin film where the free surface of water is in contact with the thermoplastic resin film (takes an angle inside the water) It can measure by the method mentioned later in an Example.

There is no particular restriction on the corona treatment conditions when the surface contact angle of the thermoplastic resin film is adjusted to the above range by corona treatment, but the surface contact angle of the thermoplastic resin film can be easily adjusted to the above range. Therefore, 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, it is within the range of 200 to 300 W · min / m ² .
Discharge amount (W · min / m ² ) = Output (W / m) / Processing speed (m / min) (1)

There are no particular restrictions on the drying conditions after the stock solution is coated or extruded on the thermoplastic resin film, but in order to prevent wrinkles from entering the thermoplastic resin film, the glass transition temperature is below the glass transition temperature of the thermoplastic resin film. Drying at a temperature is preferred. At this time, it is preferable to use PVA that tends to lower the degree of swelling as PVA and then dry under conditions that do not exceed 100 ° C. Although there is no restriction | limiting in particular in specific drying temperature, when it considers the point which becomes easy to adjust the swelling degree of a PVA layer to the said range, drying efficiency, etc., it may exist in the range of 20 degreeC or more and 95 degrees C or less. The drying temperature is preferably 50 ° C. or higher, more preferably 65 ° C. or higher, more preferably 90 ° C. or lower, and further preferably 85 ° C. or lower. Thereby, the laminated body (1) by which the unstretched PVA layer whose swelling degree is 180% or more and 260% or less was laminated | stacked on the thermoplastic resin film layer can be obtained easily.

<< Production Method of Polarizing Film (1) >>
The manufacturing method (1) of the polarizing film of this invention includes the process of extending | stretching said laminated body (1). Here, if a dichroic dye is previously contained in the PVA layer, a polarizing film on which the dichroic dye is adsorbed can be obtained by stretching the laminate (1). In this case, the method for containing the dichroic dye in the PVA layer is not particularly limited. For example, the method of bringing the dichroic dye into contact with the PVA layer of the laminate (1) or the above-mentioned method for forming the PVA layer A method of adding a dichroic dye to the prepared stock solution in advance can be appropriately employed. When the dichroic dye is not previously contained in the PVA layer, the dichroic dye is brought into contact with the PVA layer that is in the process of stretching during the stretching of the laminate (1), or the laminate ( After stretching 1), the dichroic dye is adsorbed by bringing the dichroic dye into contact with the stretched film layer formed from the PVA layer (before stretching), whereby a polarizing film on which the dichroic dye is adsorbed can be obtained. Among these, the PVA layer of the laminate (1) before stretching; the PVA layer in the course of stretching during stretching of the laminate (1); and the PVA layer after stretching the laminate (1) The effect of the present invention is more remarkably obtained by obtaining a polarizing film in which the dichroic dye is adsorbed by a production method including a step of bringing the dichroic dye into contact with any one of the stretched film layers; Is preferable.

In any of the above-described methods, a swelling treatment, a crosslinking treatment, a fixing treatment, drying, and the like can be further performed as necessary in addition to the treatment (dyeing) in which the drawing and dichroic dye are brought into contact. The order of each process may be changed as needed, each process may be performed twice or more, and different processes may be performed simultaneously. Moreover, according to said manufacturing method, although the polarizing film formed on the stretched thermoplastic resin film layer is obtained, the process of peeling the said stretched thermoplastic resin film as needed is included. Also good.

As mentioned above, in the manufacturing method (1) of the polarizing film of the present invention, the swelling degree of the PVA layer of the laminate (1) is in the range of 180% or more and 260% or less. Even if the insolubilization treatment such as high temperature stretching in the air is not performed in advance, the elution of PVA can be suppressed in the step of contacting with water at the time of producing the polarizing film such as dyeing. Therefore, the effect of the present invention is more remarkably exhibited when a polarizing film is produced without such insolubilization treatment in advance. Specifically, the PVA layer of the laminate (1) before stretching; the PVA layer in the course of stretching during stretching of the laminate (1); and the PVA layer after stretching the laminate (1) When the polarizing film in which the dichroic dye is adsorbed is produced by a production method including a step of bringing the dichroic dye into contact with any of the stretched film layers, the laminate (1 ), And before the step of contacting the dichroic dye, the step of contacting with an aqueous solution containing a boron compound such as boric acid such as boric acid and borax is not included, and / or It is preferable not to include a step of stretching at a temperature of 95 ° C. or higher (more preferably, not including a step of stretching at a temperature of 50 ° C. or higher).

As an example of the production method (1) of the polarizing film of the present invention, first, the laminate (1) having a PVA layer not containing a dichroic dye is subjected to a swelling treatment and then brought into contact with the dichroic dye. In this way, the PVA layer is made to contain a dichroic dye, further subjected to crosslinking treatment as necessary, the obtained laminate is stretched, further subjected to fixing treatment as necessary, and dried, a series of these treatments The method of obtaining the polarizing film formed on the stretched thermoplastic resin film layer and peeling the stretched thermoplastic resin film layer is mentioned.

The swelling treatment can be performed by immersing the laminate (1) in water. The temperature of the water when immersed in water is preferably within a range of 20 ° C. or higher and 40 ° C. or lower, more preferably 22 ° C. or higher, and further preferably 25 ° C. or higher. Moreover, it is more preferable that it is 38 degrees C or less, and it is still more preferable that it is 35 degrees C or less. By making the said temperature into the range of 20 degreeC or more and 40 degrees C or less, a PVA layer can be swollen efficiently. Moreover, as time to immerse in water, it is preferable to exist in the range of 0.1 minute or more and 5 minutes or less, and it is more preferable to exist in the range of 0.5 minute or more and 3 minutes or less. A PVA layer can be efficiently swollen by setting it within the range of 0.1 minute or more and 5 minutes or less. In addition, the water at the time of immersing in water is not limited to pure water, The aqueous solution in which various components melt | dissolved may be sufficient, and the mixture of water and an aqueous medium may be sufficient.

As described above, the PVA layer of the laminate (1) before stretching; the PVA layer in the course of stretching during stretching of the laminate (1); the stretch formed from the PVA layer after stretching the laminate (1) A polarizing film in which the dichroic dye is adsorbed on the matrix can be obtained by bringing the dichroic dye into contact with the film layer and dyeing. The contact of the dichroic dye can be performed by immersing the laminated body before stretching, during stretching, or after stretching in a solution (particularly an aqueous solution) containing the 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 used, for example, 0.001% by mass to 1% by mass. but it is, iodine as a solution containing a dichroic dye - in the case of using a potassium iodide solution (particularly aqueous solution), since that can be efficiently adsorb iodine dye matrix, iodine is used (I ₂ ) Is preferably within a range of 0.01% by mass or more and 1.0% by mass or less, and the concentration of potassium iodide (KI) used is within a range of 0.01% by mass or more and 10% by mass or less. It is preferable that The temperature of the solution containing the dichroic dye is within a range of 20 ° C. or higher and 50 ° C. or lower, particularly 25 ° C. or higher and 40 ° C. or lower because the dichroic dye can be efficiently adsorbed to the matrix. Is preferred.

Examples of the dichroic dye, iodine based dye (I ₃ ^- and I ₅ ^-, etc.), and the like dichroic organic dyes. The iodine dye can be obtained, for example, by bringing iodine (I ₂ ) into contact with potassium iodide. Examples of the dichroic organic dye include direct black 17, 19, 154; direct brown 44, 106, 195, 210, 223; direct red 2, 23, 28, 31, 37, 39, 79, 81, 240, 242, 247; Direct Blue 1, 15, 22, 78, 90, 98, 151, 168, 202, 236, 249, 270; Direct Violet 9, 12, 51, 98; Direct Green 1, 85; Direct Yellow 8, 12, 44, 86, 87; Direct Orange 26, 39, 106, 107 and the like. Among these dichroic dyes, iodine-based dyes are preferable from the viewpoints of handleability, availability, and polarization performance. Incidentally, the dichroic dye may either be two or more even alone, for example, I ₃ ^- may be a balanced mixture as ^- and I _5.

By subjecting the PVA layer to a crosslinking treatment, it is possible to more effectively prevent PVA from eluting into water when wet-stretching at a high temperature. From this viewpoint, the crosslinking treatment is preferably performed after the treatment for bringing the dichroic dye into contact and before the stretching. The crosslinking treatment can be performed by immersing the laminate (1) in an aqueous solution containing a crosslinking agent. As the crosslinking agent, one or more of boron compounds such as boric acid and borate such as borax can be used. The concentration of the crosslinking agent in the aqueous solution containing the crosslinking agent is preferably in the range of 1% by mass or more and 15% by mass or less, more preferably 2% by mass or more, and further preferably 3% by mass or more, Moreover, it is more preferable that it is 7 mass% or less, and it is further more preferable that it is 6 mass% or less. Sufficient stretchability can be maintained when the concentration of the crosslinking agent is in the range of 1% by mass to 15% by mass. The aqueous solution containing a crosslinking agent may contain an auxiliary agent such as potassium iodide. The temperature of the aqueous solution containing the crosslinking agent is preferably in the range of 20 ° C. or higher and 50 ° C. or lower, particularly in the range of 25 ° C. or higher and 40 ° C. or lower. It can bridge | crosslink efficiently by making the said temperature into the range of 20 to 50 degreeC.

There is no restriction | limiting in particular in the extending | stretching method at the time of extending | stretching a laminated body (1), You may carry out by any of a wet extending | stretching method and a dry-type extending | stretching method. In the case of the wet stretching method, it can be carried out in an aqueous solution containing one or more boron compounds such as boric acid and borate such as borax, or in a solution containing the above-mentioned dichroic dye. It can also be performed in a fixed treatment bath described later. In the case of the dry stretching method, stretching may be performed at room temperature, stretching may be performed while applying heat, or stretching may be performed after water absorption. Among these, the wet stretching method is preferable from the viewpoint of the uniformity of the thickness in the width direction of the obtained polarizing film, and it is more preferable to stretch in a boric acid aqueous solution. The concentration of boric acid in the boric acid aqueous solution is preferably in the range of 0.5% by mass or more and 6.0% by mass or less, and the concentration is more preferably 1.0% by mass or more. The content is more preferably 5% by mass or more, more preferably 5.0% by mass or less, and further preferably 4.0% by mass or less. When the concentration of boric acid 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 described above may contain potassium iodide, and the concentration is preferably in the range of 0.01% by mass to 10% by mass. When the concentration of potassium iodide is in the range of 0.01% by mass or more and 10% by mass or less, a polarizing film with better polarizing performance can be obtained.

The temperature at which the laminate (1) is stretched is preferably in the range of 30 ° C. or more and 90 ° C. or less, more preferably 40 ° C. or more, and further preferably 50 ° C. or more. Moreover, it is more preferable that it is 80 degrees C or less, and it is further more preferable that it is 70 degrees C or less. When the temperature is in the range of 30 ° C. or higher and 90 ° C. or lower, a polarizing film having excellent thickness uniformity in the width direction can be obtained.

The draw ratio at the time of drawing the laminate (1) is preferably 5.7 times or more, more preferably 5.8 times or more, and further preferably 5.9 times or more. By making the draw ratio of the laminate (1) within the above range, a polarizing film having better polarizing performance can be obtained. Although the upper limit of the draw ratio of the laminate (1) is not particularly limited, it is preferably 8 times or less. Stretching of the laminate (1) may be performed at one time or divided into a plurality of times, but when performed in a plurality of times, the total stretching ratio obtained by multiplying the stretching ratios of the respective stretching is the above. It only has to be within the range. In addition, the draw ratio in this specification is based on the length of the laminated body (1) before extending | stretching, and the state which is not extending | stretched corresponds to 1 time of draw ratio.

The stretching of the laminate (1) is preferably uniaxial stretching from the viewpoint of the performance of the obtained polarizing film. There is no particular limitation on the direction of uniaxial stretching in the case of stretching the long laminate (1), and uniaxial stretching or lateral uniaxial stretching in the long direction can be adopted, but a polarizing film that is superior in polarization performance is obtained. Therefore, uniaxial stretching in the longitudinal direction is preferable. Uniaxial stretching in the longitudinal direction can be performed by changing the peripheral speed between the rolls using a stretching apparatus including a plurality of rolls parallel to each other. On the other hand, lateral uniaxial stretching can be performed using a tenter type stretching machine.

The fixing treatment is mainly performed in order to strengthen the adsorption of the dichroic dye to the PVA layer or the stretched film (matrix). The fixing treatment can be performed by immersing the laminate before stretching, during stretching, or after stretching in a fixing treatment bath. As the fixing treatment bath, an aqueous solution containing one or more of boron compounds such as boric acid such as boric acid and borax can be used. Moreover, you may add an iodine compound and a metal compound in a fixed treatment bath as needed. The concentration of the boron compound in the aqueous solution containing the boron compound used as the fixing treatment bath is generally in the range of 2% by mass to 15% by mass, and particularly preferably in the range of 3% by mass to 10% by mass. . By making the said density | concentration into the range of 2 mass% or more and 15 mass% or less, adsorption | suction of a dichroic dye can be strengthened more. The temperature of the fixing treatment bath is preferably in the range of 15 ° C. or higher and 60 ° C. or lower, particularly in the range of 25 ° C. or higher and 40 ° C. or lower. By making the said temperature into the range of 15 degreeC or more and 60 degrees C or less, adsorption | suction of a dichroic dye can be strengthened more.

Drying conditions are not particularly limited, but drying is preferably performed at a temperature in the range of 30 ° C. to 150 ° C., particularly in the range of 50 ° C. to 130 ° C. A polarizing film excellent in dimensional stability is easily obtained by drying at a temperature in the range of 30 ° C. or higher and 150 ° C. or lower.

By doing so, a polarizing film formed on the stretched thermoplastic resin film layer can be obtained. The method of using the polarizing film in such a form is not particularly limited. For example, the stretched thermoplastic resin film layer is not peeled off, but is used as it is or optically transparent to the polarizing film side as desired. It is good also as a polarizing plate by laminating | stacking the protective film which has sufficient strength, and after bonding a protective film on the opposite side to the side where the stretched thermoplastic resin film layer is located, the said stretched thermoplastic resin It is good also as a polarizing plate by peeling a film layer and sticking another protective film on the peeling surface as it is, if desired. As the protective film, a cellulose triacetate (TAC) film, an acetic acid / cellulose butyrate (CAB) film, an acrylic film, a polyester film, or the like can be used. In addition, examples of the adhesive for bonding include a PVA adhesive and a urethane adhesive, and a PVA adhesive is preferable.

The thickness of the polarizing film obtained by the manufacturing method (1) of the polarizing film of the present invention is preferably 10 μm or less, and more preferably 8 μm or less. When the polarizing film has such a thickness, the polarizing film can be suitably used in a field where demand for thinning such as a cellular phone is increasing. In addition, since the thickness of a polarizing film too thin is difficult to prepare, the thickness of the polarizing film is, for example, 1 μm or more.

<< Polarizing film (2) >>
In the polarizing film (2) of the present invention, the dichroic dye is adsorbed on a matrix having a birefringence of 45 × 10 ⁻³ or more. Here, the dichroic dye may be adsorbed inside the matrix or on the surface of the matrix, but from the viewpoint of polarization performance, the dichroic dye should be adsorbed inside the matrix. Is preferred. A polarizing film in which a dichroic dye is adsorbed on a matrix can be used to stretch a raw film containing dichroic dye in advance, or to adsorb a dichroic dye simultaneously with the stretching of the original film. It can be produced by, for example, adsorbing a dichroic dye after the film is stretched to form a matrix.

As an explanation of the dichroic dye in the polarizing film (2) and the polarizing film production method (2) described later, the explanation of the dichroic dye described above in the column of the explanation of the polarizing film production method (1) is adopted as it is. Therefore, the overlapping description is omitted here.

The polarizing film (2) of the present invention has an unconventional structure in which the birefringence of the matrix constituting it is 45 × 10 ⁻³ or more. When the birefringence of the matrix is less than 45 × 10 ⁻³ , red light leakage increases when the two polarizing films are arranged in a crossed Nicol state, and the polarization performance is also deteriorated. From the viewpoint of improving the polarization performance and reducing the leakage of red light in the crossed Nicol state, the birefringence of the matrix constituting the polarizing film (2) is preferably 46 × 10 ⁻³ or more, and 47 × 10 ⁻ more preferably ³ or more, still more preferably 48 × ^{10 -3} or more, and particularly preferably at 49 × ^{10 -3} or more, and most preferably 50 × ^{10 -3} or more. In addition, since it is difficult to prepare a matrix having a too high birefringence, the birefringence of the matrix is, for example, 60 × 10 ⁻³ or less.

The birefringence of the matrix constituting the polarizing film (2) corresponds to the birefringence of the polarizing film (2) minus the birefringence 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 light parallel to the thickness direction of the film) by the thickness of the film. Accordingly, the birefringence of the matrix defined in the polarizing film (2) is obtained after 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). This can be determined by dividing by the thickness of the matrix (which is usually the same as the thickness of the polarizing film (2)).

Specifically, in the wavelength region of light generally used for measuring the retardation value of a film, the birefringence of the matrix usually has almost no wavelength dependence, while the doublet based on a dichroic dye is used. Utilizing the fact that the refractive index is highly wavelength-dependent, the birefringence of the matrix can be obtained by the following method.
That is, the retardation value (unit: nm) of the polarizing film (2) measured by light having a wavelength _λ nm is R _λ , the _retardation value (unit: nm) of the matrix is A, and the dichroic dye by the light of wavelength λ When the _retardation value based on (unit: nm) is Bλ, the following formulas (2) and (3);
_Rλ = A + _Bλ (2)
B _λ = B ′ / (λ ² −600 ² ) (3)
The following formulas (2 ′), (3 ′), (2 ″) and (3 ″) obtained by substituting the measurement wavelengths of 800 nm and 1000 nm respectively into λ of these formulas:
R ₈₀₀ = A + B ₈₀₀ (2 ′)
B ₈₀₀ = B ′ / (800 ² −600 ² ) (3 ′)
_R1000 = A + _B1000 (2 ")
B ₁₀₀₀ = B ′ / (1000 ² −600 ² ) (3 ″)
Is obtained using the measured values of R ₈₀₀ and R ₁₀₀₀ to obtain A, which is the retardation value of the matrix, and obtained by dividing this by the thickness (unit: nm) of the polarizing film (2). be able to. Here, B ′ is a value specific to the polarizing film to be measured.

Although there is no restriction | limiting in particular in the component which comprises a matrix, It is preferable that a matrix contains PVA and the average degree of polymerization of PVA contained in the said matrix exists in the range of 2,800-9,500. The polarizing film (2) of the present invention can be easily produced by adopting the method described later using PVA having such an average polymerization degree, and as a result, such a polarizing film has an average polymerization of PVA contained in the matrix. Degrees fall within the above range. In view of ease of preparation of the matrix, the average degree of polymerization of PVA contained in the matrix is more preferably 3,000 or more, further preferably 4,000 or more, and 4,100 or more. Is preferably 4,500 or more, more preferably 5,000 or more, more preferably 9,200 or less, further preferably 8,000 or less, and 6,000 or less. It is particularly preferred. The average degree of polymerization of PVA contained in the matrix is obtained by extracting and removing components other than PVA contained in the matrix by immersing the polarizing film (2) in an aqueous sorbitol solution and washing with water as necessary. Using PVA obtained as a product, it can be determined based on the description of JIS K6726-1994, and specifically, it can be determined by the method described later in Examples.

Although there is no restriction | limiting in particular in the content rate of PVA in a matrix, From the ease of preparation of the polarizing film (2) of this invention, etc., it is preferable to exist in the range of 50 to 100 mass%, The said content rate Is more preferably 80% by mass or more, further preferably 90% by mass or more, more preferably 99% by mass or less, and still more preferably 98% by mass or less. The mass of the matrix is determined by subtracting the mass of the dichroic dye from the mass of the polarizing film (2).

In the polarizing film (2) and the polarizing film production method (2) described later, the description of PVA (including the description of the degree of saponification) other than the description of the average degree of polymerization described above is the column for the description of the laminate (1). The description of PVA described above can be adopted as it is, and therefore redundant description is omitted here. In addition, as PVA in a polarizing film (2) and the manufacturing method (2) of a polarizing film mentioned later, it is necessary to use PVA which is easy to reduce an above-mentioned swelling degree as preferable PVA in the column of description of a laminated body (1). Not particularly.

The thickness of the polarizing film (2) of the present invention is preferably 10 μm or less, and more preferably 8 μm or less. When the polarizing film (2) has such a thickness, the polarizing film (2) can be suitably used in a field where a demand for thinning a mobile phone or the like is increasing. In addition, since the preparation of a polarizing film with too thin thickness is difficult, the thickness of a polarizing film (2) is 1 micrometer or more, for example.

<< Production Method of Polarizing Film (2) >>
Although the method for manufacturing the polarizing film (2) of this invention is not specifically limited, The manufacturing method of a polarizing film including the process of extending | stretching the laminated body which has a thermoplastic resin film layer and a PVA layer more than 5.7 times. And according to the manufacturing method (2) of the polarizing film of this invention whose average degree of polymerization of PVA contained in a PVA layer is 2,800 or more and 9,500 or less, the birefringence of a matrix is in a specific range. In addition, the polarizing film (2) of the present invention having excellent polarization performance and less red light leakage in the crossed Nicol state can be produced smoothly and simply.

As description of the thermoplastic resin film layer which the said laminated body used in the manufacturing method (2) of a polarizing film has, description of the thermoplastic resin film layer mentioned above in the column of description of a laminated body (1) is employ | adopted as it is. Therefore, duplicate descriptions are omitted here.

The average degree of polymerization of PVA contained in the PVA layer of the laminate used in the polarizing film production method (2) is in the range of 2,800 to 9,500, and the average degree of polymerization is 3, 000 or more, more preferably 4,000 or more, further preferably 4,100 or more, particularly preferably 4,500 or more, and most preferably 5,000 or more. It is preferably 9,200 or less, more preferably 8,000 or less, and further preferably 6,000 or less. In general, if the average degree of polymerization of PVA is increased, it is considered that the tension during stretching increases and the limit stretching ratio decreases, but the present inventors have developed a laminate having a thermoplastic resin film layer and a PVA layer. In obtaining a polarizing film by stretching, when using PVA having the above average degree of polymerization, for example, it is rather improved without lowering the limit draw ratio compared to the case of using PVA having an average degree of polymerization of 2,600. And a laminate having a thermoplastic resin film layer and a PVA layer and having an average polymerization degree of PVA contained in the PVA layer within the above range is stretched by 5.7 times or more. It has been found that when a polarizing film formed on a film layer is produced, a polarizing film having a matrix birefringence of 45 × 10 ⁻³ or higher can be obtained smoothly and simply.
The average degree of polymerization of PVA used for forming the PVA layer (PVA contained in the PVA layer) can be determined based on the description of JIS K6726-1994, and specifically, by the method described later in the examples. Can be sought.

It is preferable that the PVA layer which the said laminated body used in the manufacturing method (2) of a polarizing film has a plasticizer from a viewpoint of the extending | stretching improvement at the time of extending | stretching a laminated body. Examples of the plasticizer may include polyhydric alcohols such as ethylene glycol, glycerin, propylene glycol, diethylene glycol, diglycerin, triethylene glycol, tetraethylene glycol, and trimethylolpropane. One or more of the agents can be included. Among these, glycerin is preferable from the viewpoint of the effect of improving stretchability.

Content of the plasticizer in the PVA layer which the said laminated body used in the manufacturing method (2) of a polarizing film has is in the range of 1 mass part or more and 15 mass parts or less with respect to 100 mass parts of PVA contained in it. It is preferable. 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 flexible and to deteriorate the handleability, or to prevent the PVA layer from peeling off from the thermoplastic resin film layer. can do. Moreover, in the manufacturing method (2) of the polarizing film of this invention which has the average degree of polymerization of PVA contained in a PVA layer in the said range, content of the plasticizer in a PVA layer is 2 mass parts or more with respect to 100 mass parts of PVA. Within 13 mass parts or less, further within 4 mass parts or more and 12 mass parts or less, particularly within 5 mass parts or more and 8 mass parts or less, the reason is not clear, but the limit draw ratio is further improved. Therefore, such a content is more preferable.
Although depending on the manufacturing conditions of the polarizing film, the plasticizer contained in the PVA layer is eluted when the polarizing film is manufactured, so that the total amount does not always remain in the polarizing film.

The PVA layer of the laminate used in the method for producing a polarizing film (2) includes an antioxidant, an antifreezing agent, a pH adjusting agent, a concealing agent, an anti-coloring agent, an oil agent, and a surfactant as necessary. And the like.

The PVA content in the PVA layer of the laminate used in the polarizing film production method (2) is in the range of 50% by mass or more and 99% by mass or less from the ease of preparation of the desired polarizing film. The content is preferably 75% by mass or more, more preferably 80% by mass or more, particularly preferably 85% by mass or more, and 98% by mass. More preferably, it is 96 mass% or less, More preferably, it is 95 mass% or less.

The thickness of the PVA layer included in the laminate used in the polarizing film production method (2) is not particularly limited, and can be, for example, 100 μm or less, and a thin polarizing film can be easily prepared. It is preferable to make the PVA layer thinner. Specifically, the thickness of the PVA layer is preferably 20 μm or less, more preferably 15 μm or less, and even more preferably 10 μm or less. In the manufacturing method (2) of the polarizing film of the present invention, since the PVA layer has the specific configuration as described above, even if the thickness of the PVA layer is reduced as described above, the PVA layer can be stretched at a high limit stretch ratio. As a result, it is possible to obtain a thin polarizing film having excellent polarization performance and less red light leakage in the crossed Nicols state. Moreover, when the thickness of the PVA layer is thin as described above, it is possible to reduce the tension when the laminate is stretched. If the thickness of the PVA layer is too thin, the PVA layer has a thickness of, for example, 3 μm or more because there is a tendency for stretching breakage to occur when the laminate is stretched.

Other explanations regarding the laminate used in the polarizing film production method (2) (including explanation of a method for producing a laminate including adjustment of the contact angle of the surface of the thermoplastic resin film) In the column for the description of the body (1), the description regarding the laminated body described above can be adopted as it is, and therefore, the overlapping description is omitted here.

In the production method (2) of the polarizing film of the present invention, the laminate is stretched 5.7 times or more. Here, if a dichroic dye is contained in the PVA layer in advance, the polarizing film (2) in which the dichroic dye is adsorbed on the matrix can be obtained by stretching the laminate. In this case, the method for containing the dichroic dye in the PVA layer is not particularly limited. For example, the method for bringing the dichroic dye into contact with the PVA layer of the laminate or the above-described stock solution for forming the PVA layer may be used. A method of containing a dichroic dye in advance can be appropriately employed. Moreover, when the dichroic dye is not included in the PVA layer in advance, the dichroic dye is brought into contact with the PVA layer that is in the process of stretching during stretching of the laminate, or after the laminate is stretched A polarizing film (2) in which the dichroic dye is adsorbed on the matrix can be obtained by bringing the dichroic dye into contact with the matrix formed from the PVA layer (before stretching).

In any of the above-described methods, in addition to the treatment (dyeing) for stretching and contact with the dichroic dye, insolubilization treatment, swelling treatment, crosslinking treatment, fixing treatment, drying, etc. of the PVA layer are further performed as necessary. Can do. The order of each process may be changed as needed, each process may be performed twice or more, and different processes may be performed simultaneously. Moreover, according to said manufacturing method, although the polarizing film formed on the stretched thermoplastic resin film layer is obtained, the process of peeling the said stretched thermoplastic resin film as needed is included. Also good.

As an example of the production method (2) of the polarizing film of the present invention, first, a laminate having a PVA layer not containing a dichroic dye is subjected to insolubilization treatment, further subjected to swelling treatment as necessary, A dichroic dye is contained in the PVA layer by bringing the chromatic dye into contact with each other, and if necessary, a crosslinking treatment is performed. The obtained laminate is stretched by 5.7 times or more, and further fixed as necessary. The method of giving a process, drying, obtaining the polarizing film formed on the stretched thermoplastic resin film layer by these series of processes, and peeling the said stretched thermoplastic resin film layer is mentioned.

The insolubilization treatment of the PVA layer is mainly performed to prevent elution of PVA contained in the PVA layer into water. As the insolubilization treatment, for example, a method of performing a heat treatment on the laminate, or a method of immersing the laminate in an aqueous solution containing one or more boron compounds such as borate such as boric acid and borax. Is mentioned. Among these, a method of using an aqueous solution containing a boron compound is preferable because if the laminate is subjected to a heat treatment, wrinkles may occur with the dimensional change of the thermoplastic resin film layer. The heat treatment can be performed at a temperature in the range of 80 ° C. or higher and 200 ° C. or lower, for example. From the viewpoint of preventing wrinkles, the heat treatment is preferably performed while applying tension to the laminate. In the method using an aqueous solution containing a boron compound, the temperature of the aqueous solution is preferably within a range of 20 ° C. or higher and 40 ° C. or lower, more preferably 22 ° C. or higher, and further preferably 25 ° C. or higher. Moreover, it is more preferable that it is 38 degrees C or less, and it is still more preferable that it is 35 degrees C or less. By making the said temperature into the range of 20 degreeC or more and 40 degrees C or less, melt | dissolution of PVA can be prevented and it can be made insoluble efficiently. The time for immersing in the aqueous solution containing the boron compound is, for example, in the range of 0.1 minutes to 5 minutes. By making it within the range of 0.1 minutes or more and 5 minutes or less, it can be insolubilized efficiently. 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, and further preferably 1.5% by mass or more, Moreover, it is preferable that it is 6.0 mass% or less, It is more preferable that it is 5.0 mass% or less, It is further more preferable that it is 4.0 mass% or less. By making the said density | concentration into the range of 0.5 mass% or more and 6.0 mass% or less, melt | dissolution of PVA can be prevented and it can insolubilize efficiently.
The insolubilization treatment of the PVA layer is preferably performed before the treatment for bringing the dichroic dye into contact, and further before the swelling treatment.

Each explanation of the swelling treatment, the treatment for contacting the dichroic dye (dyeing), and the crosslinking treatment in the production method (2) of the polarizing film is as described above in the explanation of the production method (1) of the polarizing film. Since the explanations of the swelling treatment, the treatment for contacting the dichroic dye (dyeing), and the crosslinking treatment can be employed as they are, duplicate descriptions are omitted here.

In the polarizing film production method (2), there is no particular limitation on the stretching method when stretching the laminate, and any of wet stretching and dry stretching may be used. In the case of the wet stretching method, it can be carried out in an aqueous solution containing one or more boron compounds such as boric acid and borate such as borax, or in a solution containing the above-mentioned dichroic dye. It can also be performed in a fixed treatment bath described later. In the case of the dry stretching method, stretching may be performed at room temperature, stretching may be performed while applying heat, or stretching may be performed after water absorption. Among these, the wet stretching method is preferable from the viewpoint of the uniformity of the thickness in the width direction of the obtained polarizing film, and it is more preferable to stretch in a boric acid aqueous solution. The concentration of boric acid in the boric acid aqueous solution is preferably in the range of 0.5% by mass or more and 6.0% by mass or less, and the concentration is more preferably 1.0% by mass or more. The content is more preferably 5% by mass or more, more preferably 5.0% by mass or less, and further preferably 4.0% by mass or less. When the concentration of boric acid 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 described above may contain potassium iodide, and the concentration is preferably in the range of 0.01% by mass to 10% by mass. When the concentration of potassium iodide is in the range of 0.01% by mass or more and 10% by mass or less, a polarizing film with better polarizing performance can be obtained.

The temperature at which the laminate is stretched is preferably in the range of 30 ° C. or higher and 90 ° C. or lower, the temperature is more preferably 40 ° C. or higher, further preferably 50 ° C. or higher, 80 ° C. or lower is more preferable, and 70 ° C. or lower is further preferable. When the temperature is in the range of 30 ° C. or higher and 90 ° C. or lower, a polarizing film having excellent thickness uniformity in the width direction can be obtained.

In the manufacturing method (2) of the polarizing film of the present invention, the laminate needs to be stretched to 5.7 times or more, preferably stretched to 5.8 times or more, and stretched to 5.9 times or more. More preferably. By making the stretch ratio of the laminate within the above range, the polarizing film (2) in which the birefringence of the matrix is higher than before, the polarizing performance is excellent, and the red light leaks in the crossed Nicols state is smooth. And it can manufacture simply. Although the upper limit of the draw ratio of the laminate is not particularly limited, it is preferably 8 times or less. The stretching of the laminate may be performed at once or may be performed in multiple times, but when performed in multiple times, the total stretch ratio multiplied by the stretch ratio of each stretch is within the above range. I just need it. In addition, the draw ratio in this specification is based on the length of the laminated body before extending | stretching, and the state which is not extending | stretched corresponds to 1 time of draw ratios.

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

As the explanation of the fixing treatment and the drying in the polarizing film production method (2), the explanation of the fixing treatment and the drying described above in the column of the explanation of the polarizing film production method (1) is adopted as it is. Therefore, duplicate descriptions are omitted here.

By doing so, the polarizing film (2) formed on the stretched thermoplastic resin film layer is obtained. The method of using the polarizing film in such a form is not particularly limited. For example, the stretched thermoplastic resin film layer is not peeled off, but is used as it is or optically transparent to the polarizing film side as desired. It is good also as a polarizing plate by laminating | stacking the protective film which has sufficient strength, and after bonding a protective film on the opposite side to the side where the stretched thermoplastic resin film layer is located, the said stretched thermoplastic resin It is good also as a polarizing plate by peeling a film layer and sticking another protective film on the peeling surface as it is, if desired. As the protective film, a cellulose triacetate (TAC) film, an acetic acid / cellulose butyrate (CAB) film, an acrylic film, a polyester film, or the like can be used. In addition, examples of the adhesive for bonding include a PVA adhesive and a urethane adhesive, and a PVA adhesive is preferable.

The present invention will be specifically described with reference to the following examples, but the present invention is not limited to these examples. In addition, each measurement or evaluation method employ | adopted in the following reference examples, examples, and comparative examples is shown below.

Measurement of the contact angle of the surface of the thermoplastic resin film Using a “DropMaster 500” manufactured by Kyowa Interface Science Co., Ltd., in an environment of 20 ° C. and 65% RH, 2 μL of pure water from a needle having an inner diameter of 0.4 mm is used as the thermoplastic resin. The contact angle was measured by extruding onto the surface of the film.

Measurement of degree of swelling of PVA layer The laminates obtained in the following examples or comparative examples were cut into appropriate sizes (for example, about 300 cm ² ) and immersed in 1,000 g of distilled water at 30 ° C. for 30 minutes. Then, the laminated body was taken out, the surface water was taken with a filter paper, and the mass was measured (the mass is A). Then, this laminated body was dried at 105 degreeC for 16 hours, and mass was measured (the mass is set to B). Furthermore, the laminated body after drying was boiled with hot water at 95 ° C. for 6 hours to dissolve the PVA layer, the remaining thermoplastic resin film layer was dried at 105 ° C. for 16 hours, and the mass was measured (the mass was C). And). The degree of swelling S (%) of the PVA layer was calculated by the following formula (4).
S = 100 × (AC) / (BC) (4)

Measurement of average degree of polymerization of PVA It was measured according to the description of JIS K6726-1994. However, as a test solution, 0.28 g of PVA, 70 g of distilled water, and a stirrer were put into a 100 mL common conical Erlenmeyer flask, stoppered, immersed in a constant temperature bath at 95 ° C. By dissolving, a PVA aqueous solution having a concentration of about 0.4% by mass was filtered through a Buchner funnel glass filter 3G and cooled in a constant temperature water bath at 30 ° C.

Measurement of thickness of polarizing film (1)
Using a digital gauge ("DE12BR" manufactured by Magnescale Co., Ltd.), the thickness of the polarizing film at any position (5 locations) was measured, and the average value was defined as the thickness (1) of the polarizing film.

Measurement of Birefringence of Matrix About polarizing films obtained in the following Reference Examples, Examples or Comparative Examples, using a cell gap inspection device (“RETS-1100” manufactured by Otsuka Electronics Co., Ltd.), a wavelength of 800 nm and 1, The retardation value by light of 000 nm was measured. The measurement positions were any five points on the straight line in the length direction (uniaxially stretched direction) passing through the center of the polarizing film in the width direction (direction in the film plane perpendicular to the uniaxially stretched direction). The average value of the five retardation values measured with light having a wavelength of 800 nm is defined as R ₈₀₀ in the above formula (2 ′), and the average value of the five retardation values measured with light having a wavelength of 1,000 nm is expressed by the above formula ( As R ₁₀₀₀ in 2 ″), solve the simultaneous equations of the above formulas (2 ′), (3 ′), (2 ″) and (3 ″) to obtain A (unit: nm) which is a retardation value of the matrix. The birefringence of the matrix is obtained by dividing this by the thickness of the polarizing film (average value at 5 locations, converted to nm) measured in “Measurement of thickness of polarizing film (2)” described later. Asked.

Measurement of thickness of polarizing film (2)
Using a digital gauge ("DE12BR" manufactured by Magnescale Co., Ltd.), the thickness of the polarizing film at the measurement positions (5 locations) of the retardation value in the measurement of the birefringence of the matrix described above is measured, and the average value is obtained as the polarizing film. Thickness (2).

Evaluation of Polarization Performance (a) Measurement of Transmittance Ts A square sample of 2 cm in the width direction of the polarizing film and 2 cm in the length direction from the center in the width direction of the polarizing film obtained in the following Examples or Comparative Examples 2 samples, using a spectrophotometer with an integrating sphere ("V7100" manufactured by JASCO Corporation), compliant with JIS Z 8722 (object color measurement method), C light source, visible light region of 2 ° field of view Measure the light transmittance when tilted by 45 ° with respect to the length direction and the light transmittance when tilted by -45 ° for one sample. Ts1 (%) was determined. Similarly, with respect to the other sample, the light transmittance when tilted by 45 ° and the light transmittance when tilted by −45 ° were measured, and an average value Ts2 (%) thereof was obtained. Ts1 and Ts2 were averaged by the following formula (5) to obtain the transmittance Ts (%) of the polarizing film.
Ts = (Ts1 + Ts2) / 2 (5)

(B) Measurement of polarization degree V Light transmittance T∥ (%) and length direction when two samples collected in the measurement of transmittance Ts are stacked so that their length directions are parallel to each other. Are measured in the same manner as in the case of “(a) Measurement of transmittance Ts”, and the degree of polarization V ( %).
V = {(T∥−T⊥) / (T∥ + T⊥)} ^1/2 × 100 (6)

(C) Calculation of the dichroic ratio at a transmittance of 44% In each of the following examples and comparative examples, the immersion time in the aqueous solution containing the iodine-based dye was changed from 1 minute to 4 times within a range of 1 to 2 minutes. The same operation was performed by changing, and four polarizing films having different dichroic dye adsorption amounts from the polarizing films manufactured in each of the examples or comparative examples were manufactured. For each of these four polarizing films, the transmittance Ts (%) and the degree of polarization V (%) were determined by the method described above, and for each example and comparative example, the transmittance Ts (%) was plotted on the horizontal axis and the degree of polarization. A total of 5 points including one point based on the transmittance Ts (%) and the degree of polarization V (%) of the polarizing film obtained in each example or comparative example are plotted on the graph with V (%) as the vertical axis. An approximate curve was obtained, and the degree of polarization V ₄₄ (%) when the transmittance Ts (%) was 44% was obtained from the approximate curve.
From the obtained degree of polarization V ₄₄ (%), the dichroic ratio at a transmittance of 44% was determined by the following formula (7) and used as an index of polarization performance.
Dichroic ratio when the transmittance 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 crossed Nicol state For each of the following Examples and Comparative Examples, one polarizing film obtained in each Example or Comparative Example and “(c) Transmittance 44” in the evaluation of the polarizing performance. The orthogonal transmittance T ₇₀₀フィルム (%) of light having a wavelength of 700 nm was measured for a total of five polarizing films obtained in “Calculation of dichroic ratio at%”. That is, for each of the five sets of samples obtained in the evaluation of the polarization performance, two samples were stacked so that the length directions were orthogonal to each other, and a spectrophotometer with an integrating sphere (“V7100” manufactured by JASCO Corporation) was attached. The transmittance of light having a wavelength of 700 nm when tilted by 45 ° with respect to the length direction of one sample and the transmittance of light having a wavelength of 700 nm when tilted by −45 ° are measured, and the average value thereof is measured. Was set to T ₇₀₀ % (%).
Then, the transmittance Ts (%) obtained in the evaluation of the polarization performance is plotted on the graph with a total of five points plotted on the horizontal axis and the orthogonal transmittance T ₇₀₀ ⊥ (%) of light having a wavelength of 700 nm is plotted on the vertical axis. The orthogonal transmittance T ₇₀₀ _{４４ 44} (%) of light having a wavelength of 700 nm when the transmittance Ts (%) is 44% was determined from the approximate curve. When the T ₇₀₀ _{４４ 44} (%) was low, it was evaluated that there was little leakage of red light.

[Example 1]
(1) Hydrophilization treatment of thermoplastic resin film Amorphous polyethylene terephthalate film (A-PET sheet FR thickness 150 μm, manufactured by Teijin Chemicals Ltd.) is used as the thermoplastic resin film, and the amount of discharge on one side of the thermoplastic resin film. Corona treatment was performed at 280 W · min / m ² (output 280 W / m, treatment speed 1.0 m / min). The contact angle of the surface of the thermoplastic resin film after the corona treatment was 60 ° (the contact angle before the corona treatment was 79 °).
(2) Preparation of undiluted solution PVA (vinyl acetate and ethylene with an average polymerization degree of 2,400, saponification degree of 99.8 mol%, ethylene content of 2.5 mol%, 1,2-glycol bond content of 1.6 mol%) A saponified product of 100% by weight, 6 parts by weight of glycerin as a plasticizer, and an aqueous solution having a PVA concentration of 10% by weight prepared as water was prepared as a stock solution for forming a PVA layer.
(3) Production of laminate After coating the stock solution prepared in (2) on the corona-treated surface of the thermoplastic resin film subjected to hydrophilic treatment in (1) using a die coater, it is dried at 80 ° C. for 240 seconds. As a result, a two-layer laminate (a long laminate having a width of 0.5 m) composed of an amorphous polyethylene terephthalate film layer and a PVA layer having a thickness of 6 μm was produced. About the obtained laminated body, the swelling degree of the PVA layer was measured. The results are shown in Table 1.
(4) Production of Polarizing Film A polarizing film was produced by subjecting the laminate produced in (3) to swelling treatment, dyeing, uniaxial stretching, and drying treatment in this order. That is, the laminate was immersed in distilled water for 1 minute as a swelling treatment. Next, PVA is immersed for 1 minute in an aqueous solution containing iodine-based pigment (concentration of iodine used: 0.3 mass%, concentration of potassium iodide used: 2.1 mass%, temperature: 30 ° C.). The layer contained an iodine dye. Subsequently, it was uniaxially stretched to the limit in the longitudinal direction in an aqueous boric acid solution (boric acid concentration: 4 mass%, potassium iodide concentration: 6 mass%, temperature: 65 ° C.). In addition, the magnification which draws and cuts by the same method in advance was confirmed, and a magnification 0.20 times lower than the cut magnification was set as the above limit. Then, it dried at 60 degreeC for 1 minute, and obtained the polarizing film formed on the stretched amorphous polyethylene terephthalate film layer. The stretched amorphous polyethylene terephthalate layer was peeled off, and the thickness (1) and polarization performance were measured or evaluated for the obtained polarizing film. The results are shown in Table 1 together with the adopted draw ratio.

[Examples 2 to 4]
A laminate was obtained in the same manner as in Example 1 except that the ethylene content and 1,2-glycol bond amount of PVA were as shown in Table 1, and the degree of swelling of the PVA layer was measured. A polarizing film (from which the stretched amorphous polyethylene terephthalate layer was peeled) was obtained from the laminate, and each measurement or evaluation of thickness (1) and polarizing performance was performed. The results are shown in Table 1 together with the adopted draw ratio.

[Comparative Example 1]
A laminate was obtained in the same manner as in Example 1 except that the ethylene content of PVA was as shown in Table 1, and the degree of swelling of the PVA layer was measured. Moreover, when it was going to produce a polarizing film from the laminated body like Example 1, since the PVA contained in the PVA layer eluted at the time of a swelling process, the polarizing film was not able to 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 PVA was as shown in Table 1, and the degree of swelling of the PVA layer was measured. Moreover, when the polarizing film was produced from the laminated body like Example 1, since the dyeability was bad and there were spots, only the thickness (1) was measured and the polarizing performance was not evaluated. The results are shown in Table 1 together with the adopted draw ratio.

In Examples 1 to 4, since the degree of swelling of the PVA layer was in the range of 180% or more and 260% or less, the insolubilization treatment such as immersion in a boric acid aqueous solution and high-temperature stretching in the air was not performed in advance. A polarizing film having excellent performance could be produced. On the other hand, in Comparative Example 1, since the degree of swelling of the PVA layer was higher than 260%, PVA contained in the PVA layer was eluted at the time of manufacturing the polarizing film, and a polarizing film could not be produced. Since the swelling degree of the layer was lower than 180%, it became a patchy polarizing film.

[Reference Example 1]
An aqueous solution having an average degree of polymerization of 2,400 and a saponification degree of 99.8 mol% of PVA (saponified vinyl acetate homopolymer) of 100 parts by mass, a volatile fraction of 66% by mass of 12 parts by mass of glycerin as a plasticizer and water. From the T-die onto a first drying roll at 95 ° C. in a film form, dried on the first drying roll until the volatile content is 22% by mass, and peeled off from the first drying roll. After further drying with a plurality of subsequent 80 ° C. drying rolls, heat treatment was performed with a 110 ° C. heat treatment roll to obtain a single layer PVA film having a thickness of 60 μm (long film having a width of 0.5 m).
The 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 30 ° C. water for 1 minute. Next, PVA is immersed for 1 minute in an aqueous solution containing iodine-based pigment (concentration of iodine used: 0.3 mass%, concentration of potassium iodide used: 2.1 mass%, temperature: 30 ° C.). An iodine pigment was contained in the film. Subsequently, the film was uniaxially stretched to the limit in the longitudinal direction in an aqueous boric acid solution (boric acid concentration: 4 mass%, potassium iodide concentration: 6 mass%, temperature: 55 ° C.). In addition, the magnification which draws and cuts by the same method in advance was confirmed, and a magnification 0.20 times lower than the cut magnification was set as the above limit. Then, it dried at 60 degreeC for 4 minute (s), and obtained the polarizing film. Each measurement of the birefringence and thickness (2) of the matrix was performed on this polarizing film. The results are shown in Table 2 together with the draw ratio employed.

[Reference Examples 2 to 4]
A polarizing film was obtained in the same manner as in Reference Example 1 except that PVA (saponification degree: 99.8 mol%, saponified vinyl acetate homopolymer) having the average polymerization degree shown in Table 2 was used. Each of the birefringence and thickness (2) was measured. The results are shown in Table 2 together with the draw ratio employed.

As is clear from Reference Examples 1 to 4, when a polarizing film is produced from a single-layer PVA film, it can be seen that the limit draw ratio decreases as the average degree of polymerization of PVA increases. In addition, 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 Amorphous polyethylene terephthalate film (A-PET sheet FR thickness 150 μm, manufactured by Teijin Chemicals Ltd.) is used as the thermoplastic resin film, and the amount of discharge on one side of the thermoplastic resin film. Corona treatment was performed at 280 W · min / m ² (output 280 W / m, treatment speed 1.0 m / min). The contact angle of the surface of the thermoplastic resin film after the corona treatment was 60 ° (the contact angle before the corona treatment was 79 °).
(2) Preparation of undiluted solution PVA concentration of PVA (saponified product of vinyl acetate homopolymer) having an average polymerization degree of 5,500 and a saponification degree of 99.8 mol%, 12 parts by mass of glycerin as a plasticizer and water Was prepared as a stock solution for forming a PVA layer.
(3) Production of laminate After coating the stock solution prepared in (2) on the corona-treated surface of the thermoplastic resin film subjected to hydrophilic treatment in (1) using a die coater, it is dried at 80 ° C. for 240 seconds. As a result, a two-layer laminate (a long laminate having a width of 0.5 m) composed of an amorphous polyethylene terephthalate film layer and a PVA layer having a thickness of 6 μm was produced.
(4) Production of Polarizing Film A polarizing film was produced by subjecting the laminate produced in (3) to insolubilization treatment, dyeing, uniaxial stretching, and drying treatment in this order. That is, as an insolubilization treatment of the PVA layer, the laminate was immersed in a boric acid aqueous solution (concentration: 3 mass%, temperature: 30 ° C.) for 1 minute. Next, PVA is immersed for 1 minute in an aqueous solution containing iodine-based pigment (concentration of iodine used: 0.3 mass%, concentration of potassium iodide used: 2.1 mass%, temperature: 30 ° C.). The layer contained an iodine dye. Subsequently, it was uniaxially stretched to the limit in the longitudinal direction in an aqueous boric acid solution (boric acid concentration: 4 mass%, potassium iodide concentration: 6 mass%, temperature: 65 ° C.). In addition, the magnification which draws and cuts by the same method in advance was confirmed, and a magnification 0.20 times lower than the cut magnification was set as the above limit. Then, it dried at 60 degreeC for 1 minute, and obtained the polarizing film formed on the stretched amorphous polyethylene terephthalate film layer. 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 crossed Nicol state. It was. The results are shown in Table 3 together with the draw ratio employed.

[Examples 6 to 14 and Comparative Examples 3 to 7]
Polarizing film in the same manner as in Example 5 except that the average polymerization degree of PVA (saponification product of 99.8 mol%, vinyl acetate homopolymer) and the glycerin content are as shown in Table 3. (Stretched amorphous polyethylene terephthalate layer peeled) was obtained, and each measurement or evaluation of the birefringence of the matrix, the thickness (2), the polarization performance, and the leakage of red light in a crossed Nicol state was performed. The results are shown in Table 3 together with the draw ratio employed.

[Comparative Examples 8 and 9]
The average polymerization degree of PVA (saponification degree of 99.8 mol%, vinyl acetate homopolymer) and the glycerin content are as shown in Table 3, and the draw ratio of the laminate is 5.00 times In the same manner as in Example 5, a polarizing film (a film obtained by peeling off the stretched amorphous polyethylene terephthalate layer) was obtained, and the birefringence of the matrix, the thickness (2), the polarizing performance, and the crossed Nicol state Each measurement or evaluation of leakage of red light in was performed. The results are shown in Table 3 together with the draw ratio employed.

In the polarizing films obtained in Examples 5 to 14, the birefringence of the matrix is high, such a polarizing film has a large dichroic ratio value and excellent polarization performance, and has a value of T ₇₀₀ _{４４ 44} . It can be seen that there is little leakage of red light in the small Nicole state. On the other hand, in the polarizing films obtained by Comparative Examples 3 to 9, the birefringence of the matrix is low, the dichroic ratio is small and the polarization performance is inferior, and the value of T ₇₀₀ ⊥ ₄₄ is large and crossed Nicols It can be seen that there is a lot of red light leakage in the state.

According to the laminate (1) of the present invention and the method (1) for producing a polarizing film using the same, a polarizing film such as dyeing can be obtained without performing insolubilization treatment such as immersion in a boric acid aqueous solution or high-temperature stretching in the air in advance. Since the elution of PVA contained in the PVA layer can be suppressed in the process of contact with water during production, the insolubilization treatment, which is complicated and requires special production equipment, can be omitted. Thus, it becomes possible to easily manufacture a polarizing film having excellent polarizing performance using a general-purpose polarizing film manufacturing facility. Moreover, the polarizing film (2) of the present invention is excellent in polarizing performance and has little red light leakage in a crossed Nicol state. Furthermore, according to the manufacturing method (2) of the polarizing film of the present invention, the polarizing film (2) having excellent polarization performance and less red light leakage in the crossed Nicol state can be manufactured smoothly and simply.

Claims

A laminate having a thermoplastic resin film layer and a polyvinyl alcohol layer having a swelling degree of 180% or more and 260% or less.
The laminate according to claim 1, wherein the ethylene content of polyvinyl alcohol contained in the polyvinyl alcohol layer is 1 mol% or more and 12 mol% or less.
The laminate according to claim 1 or 2, wherein the polyvinyl alcohol contained in the polyvinyl alcohol layer has a 1,2-glycol bond content of 0.4 mol% or more and 1.5 mol% or less.
The laminate according to any one of claims 1 to 3, wherein an average degree of polymerization of polyvinyl alcohol contained in the polyvinyl alcohol layer is 1,000 or more and 9,500 or less.
The laminate according to any one of claims 1 to 4, wherein the saponification degree of the polyvinyl alcohol contained in the polyvinyl alcohol layer is 98 mol% or more.
The laminate according to any one of claims 1 to 5, wherein the polyvinyl alcohol layer contains 1 to 15 parts by mass of a plasticizer with respect to 100 parts by mass of polyvinyl alcohol.
The laminate according to claim 6, wherein the plasticizer is glycerin.
A method for producing a polarizing film, comprising a step of stretching the laminate according to any one of claims 1 to 7.
The polyvinyl alcohol layer of the laminate before stretching; the polyvinyl alcohol layer in the course of stretching during stretching of the laminate; and the stretched film layer formed from the polyvinyl alcohol layer after stretching the laminate; The manufacturing method of Claim 8 including the process of making a dichroic dye contact with respect.
The manufacturing method according to claim 9, wherein the step of contacting with an aqueous solution containing a boron compound is not included before the step of contacting the dichroic dye.
The manufacturing method according to claim 9 or 10, which does not include a step of stretching at a temperature of 95 ° C or higher before the step of bringing the dichroic dye into contact.
A polarizing film in which a dichroic dye is adsorbed on a matrix having a birefringence of 45 × 10 −3 or more.
The polarizing film according to claim 12, wherein the matrix contains polyvinyl alcohol, and the average degree of polymerization is from 2,800 to 9,500.
The polarizing film according to claim 12, wherein the matrix contains polyvinyl alcohol, and the average degree of polymerization thereof is 4,100 or more and 9,500 or less.
15. The polarizing film according to claim 12, wherein the thickness is 10 μm or less.
A method for producing a polarizing film comprising a step of stretching a laminate having a thermoplastic resin film layer and a polyvinyl alcohol layer by 5.7 times or more, wherein the average degree of polymerization of polyvinyl alcohol contained in the polyvinyl alcohol layer is 2, The manufacturing method which is 800 or more and 9,500 or less.
The production method according to claim 16, wherein the average degree of polymerization of polyvinyl alcohol is from 4,100 to 9,500.
The manufacturing method of Claim 16 or 17 in which a polyvinyl alcohol layer contains 1 to 15 mass parts of plasticizers with respect to 100 mass parts of polyvinyl alcohol.
The manufacturing method according to claim 16 or 17, wherein the polyvinyl alcohol layer contains a plasticizer in an amount of 4 parts by mass to 12 parts by mass with respect to 100 parts by mass of the polyvinyl alcohol.
The production method according to claim 18 or 19, wherein the plasticizer is glycerin.