TW201719207A - Layered object, polarizing film, and process for producing polarizing film - Google Patents

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 Nichol state 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<SP>-3</SP> 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

Polarized film and method of manufacturing same

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 same. Further, the present invention relates to a polarizing film in which a dichroic dye is adsorbed on a substrate and a method for producing the same.

A polarizing plate having a light transmission and shielding function and a liquid crystal that changes a polarization state of light are fundamental components of a liquid crystal display (LCD). In many polarizing plates, a protective film such as a cellulose triacetate (TAC) film is bonded to the surface of the polarizing film, and a polyvinyl alcohol film is used as a polarizing film constituting the polarizing plate (hereinafter, "polyethylene" An alcohol (abbreviated as "PVA") is a substrate composed of uniaxial stretching (a uniaxially stretched and oriented stretched film) adsorbed with an iodine dye (I ₃ ^- or I ₅ ^- ) or a dichroic organic dye. The dichroic pigment system has become the mainstream. In the polarizing film described above, the PVA film containing the dichroic dye in advance is uniaxially stretched, and the dichroic dye is adsorbed simultaneously with the uniaxial stretching of the PVA film, and the PVA film is uniaxially stretched to adsorb the two colors. It is produced by sex pigments and the like.

LCD is used in a wide range of small machines such as computers and wristwatches, notebook computers, LCD monitors, liquid crystal color projectors, LCD TVs, car navigation systems, mobile phones, and measurement machines used inside and outside. But in recent years, it has been used especially for small pens. It is used for mobile computers such as notebook computers and mobile phones, and the requirements for thinning of polarizing plates are becoming stronger. In particular, the thickness of the polarizing film constituting the polarizing plate is required to be 10 μm or less.

As a method of reducing the thickness of a polarizing film constituting a polarizing plate, a laminated body obtained by forming a PVA layer on one surface of a thermoplastic resin film is stretched, dyed, dried, and then stretched as needed. A method of peeling off the layer of the film (see Patent Documents 1 and 2, etc.).

When the polarizing film is produced by the above-described method, in the step of contacting the water during the production of the polarizing film such as dyeing, it is important that the PVA contained in the PVA layer is not eluted. Therefore, in the conventional method, it is necessary to perform the insolubilization treatment of the PVA layer in advance before the step of contacting with water such as dyeing.

Specifically, in Patent Document 1, it is described that a PVA layer is formed on a resin substrate having a thickness of at least 20 μm, and after the dichroic substance is adsorbed, the total stretching ratio is made 5 times or more of the original length in the boric acid aqueous solution. And a method of stretching to make a polarizing film. Patent Document 1 describes that in order to prevent elution of PVA in an aqueous solution during dyeing, an insolubilization treatment is applied to a PVA layer before immersing a PVA layer formed on a resin substrate in a dyeing liquid, and specifically, immersion is described. A method of aqueous boric acid at room temperature. Further, Patent Document 1 describes a stretching ratio, more preferably 5.5 times or more, a PVA having a polymerization degree of 1,000 to 10,000, and a maximum stretching ratio of 4.0 to 5.5 times.

On the other hand, Patent Document 2 discloses that a laminate obtained by forming a PVA layer on an amorphous ester-based thermoplastic resin substrate is subjected to high-temperature stretching in an air bath at 95 to 150 ° C, and adsorbs two colors. Sex After that, it is further stretched in an aqueous boric acid solution to prepare a polarizing film. Patent Document 2 describes a method of producing a polarizing film which is not subjected to insolubilization treatment with a boric acid aqueous solution as in Example 1, but actually, PVA is carried out by airborne high-temperature stretching at 130 ° C in Example 1. The layer system becomes insoluble. Further, Patent Document 2 describes the use of PVA having a polymerization degree of 1,000 or more.

Prior technical literature Patent literature

Patent Document 1 International Publication No. 2010/100917

Patent Document 2 Japanese Patent No. 4691205

However, there is a problem in that the conventional technique for impregnation of an aqueous boric acid solution or high-temperature stretching in the air is complicated or does not use a general-purpose polarizing film manufacturing apparatus which has been put to practical use until now, and requires special manufacture. Equipment, etc. Therefore, an object of the present invention is to provide a method for suppressing the elution of PVA in a step of contacting with water without performing an insolubilization treatment for impregnation with an aqueous boric acid solution or high-temperature stretching in the air, and a general polarizing film manufacturing apparatus can be used. A laminate for producing a polarizing film having excellent polarizing properties and a method for producing a polarizing film using the same.

Moreover, the polarizing film manufactured by the conventional method has a problem that the red light of the crossed nicol state leaks a lot. Therefore, another object of the present invention is to provide a polarizing film which is excellent in polarizing performance and which has little leakage of red light in a state of orthogonal polarization, and a method for producing the same.

In order to achieve the above object, the inventors of the present invention have repeatedly studied and found that when a laminate having a thermoplastic resin film layer and a PVA layer is stretched to produce a polarizing film, the PVA layer of the unstretched laminate is When the degree of moisture is adjusted to 180% or more and 260% or less, the dissolution of the PVA can be suppressed in the step of contacting with water without performing the insolubilization treatment of the boric acid aqueous solution or the high-temperature stretching in the air. Therefore, the operation can be omitted. The above-described insolubilization treatment which is complicated and requires special manufacturing equipment can easily produce a polarizing film having excellent polarizing performance by using a general polarizing film manufacturing apparatus.

Moreover, the inventors of the present invention have found that in the polarizing film in which the dichroic dye is adsorbed on the substrate, when the birefringence of the substrate is 45 × 10 ^-3 or more higher than the conventional one, the polarizing property can be improved and the orthogonal polarized light can be obtained. A polarizing film with less leakage of red light in the state.

In addition, when a PVA layer is formed on a thermoplastic resin film as a laminate and uniaxially stretched or the like to obtain a polarizing film formed on a thermoplastic resin film, an average polymerization degree of 2,800 or more and 9,500 or less is used. In the case of PVA, the ultimate draw ratio at the time of uniaxial stretching can be improved. It is considered that the higher the average degree of polymerization of PVA, the higher the tension at the time of stretching, and the ultimate stretching ratio is lowered, but when the polarizing film is obtained by the aforementioned method, it is unexpectedly to use the above average degree of polymerization. In the case of PVA, for example, compared with the case of using a PVA having an average degree of polymerization of 2,600, the ultimate draw ratio does not decrease but increases.

Then, it was found that a PVA layer was formed as a laminate on the thermoplastic resin film by using a PVA having an average degree of polymerization of 2,800 or more and 9,500 or less, and it was stretched to 5.7 times or more to produce a polarizing film formed on the thermoplastic resin film. The polarizing film having a birefringence of the substrate higher than the conventionally high 45 × 10 ^-3 or more can be obtained smoothly and simply.

The inventors of the present invention have further repeated the discussion based on the knowledge to complete the present invention.

That is, the present invention relates to the following:

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

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

[3] The laminate according to the above [1] or [2], wherein the amount of the 1,2-glycol bond of the 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 PVA contained in the PVA layer has an average degree of polymerization of 1,000 or more and 9,500 or less.

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

[6] The layered product according to any one of the above [1] to [5], wherein the PVA layer contains 1 part by mass or more and 15 parts by mass or less of the plasticizer with respect to 100 parts by mass of the PVA.

[7] The laminate according to the above [6], wherein the plasticizer is glycerin.

[8] A method for producing a polarizing film (hereinafter referred to as "the method for producing a polarizing film (1)"), which comprises laminating a laminate according to any one of the above [1] to [7] Steps to stretch.

[9] The production method according to the above [8], which comprises a PVA layer for a laminate before stretching; a PVA layer in the middle of stretching in stretching of the laminate; and, after stretching the laminate A step of contacting the dichroic dye with either of the stretched film layers formed of the PVA layer;

[10] The production method according to the above [9], wherein the step of contacting the aqueous solution containing the boron compound is not included before the step of bringing the dichroic dye into contact.

[11] The production method according to [9] or [10] above, wherein the step of stretching at a temperature of 95 ° C or higher is not included before the step of bringing the dichroic dye into contact.

Further, the present invention relates to the following:

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

[13] The polarizing film according to the above [12], wherein the substrate contains PVA and has an average degree of polymerization of 2,800 or more and 9,500 or less.

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

[15] The polarizing film according to any one of [12] to [14], which has a thickness of 10 μm or less.

[16] A production method (hereinafter referred to as "the method for producing a polarizing film (2)"), which comprises the step of stretching a laminate having a thermoplastic resin film layer and a PVA layer to 5.7 times or more. In the method for producing a polarizing film, the average degree of polymerization of the PVA contained in the PVA layer is 2,800 or more and 9,500 or less.

[17] The production method according to the above [16], wherein the average degree of polymerization of the PVA is 4,100 or more and 9,500 or less.

[18] The production method according to the above [16] or [17], wherein the PVA layer contains 1 part by mass or more and 15 parts by mass or less of the plasticizer with respect to 100 parts by mass of the PVA.

[19] The production method according to the above [16] or [17], wherein the PVA layer contains 4 parts by mass or more and 12 parts by mass or less of the plasticizer with respect to 100 parts by mass of the PVA.

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

According to the layered product (1) of the present invention and the method (1) for producing a polarizing film using the same, it is possible to suppress the step of contacting with water without performing the insolubilization treatment for the boric acid aqueous solution or the high-temperature stretching in the air. The PVA is eluted, and a polarizing film having excellent polarizing properties can be easily produced by using a general polarizing film manufacturing apparatus.

Further, the polarizing film (2) of the present invention has excellent polarizing performance and at the same time has less leakage of red light in the orthogonally polarized state. Further, according to the method (2) for producing a polarizing film of the present invention, it is possible to smoothly and easily produce the polarizing film (2) which is excellent in polarizing performance and which has little leakage of red light in a state of orthogonal polarization.

The invention is explained in detail below.

"Laminar (1)"

The layered product (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 polyethylene, polypropylene, polymethylpentene, polystyrene, polycarbonate, polyvinyl chloride, methacrylic resin, nylon, and poly. Various thermoplastic resins such as ethylene terephthalate, and copolymers having a plurality of monomer units constituting the thermoplastic resins. In the thermoplastic resin film layer, only one type of thermoplastic resin may be contained, or two or more types may be contained, either of them. Among these, polyethylene terephthalate is preferred from the viewpoint of high heat resistance and stretchability, and amorphous polyethylene terephthalate is more preferable.

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

The PVA layer of the laminate (1) of the present invention needs to have a swelling degree of 180% or more and 260% or less, more preferably 185% or more, more preferably 190% or more, more preferably 25% or less, and still more preferably 250% or less. When the degree of swelling is higher than 260%, the PVA contained in the PVA layer is eluted in the step of contacting the water during the production of the polarizing film, and the polarizing film is not formed in the step of insolubilizing the aqueous boric acid solution or the high-temperature stretching in the air. The manufacturing becomes difficult. On the other hand, when the degree of swelling is less than 180%, the dyeing of the PVA layer becomes difficult, and spots are likely to occur, and it is difficult to obtain polarized light having good polarizing performance. membrane. Further, the degree of swelling of the PVA layer of the present invention means the mass of the PVA layer after immersing the PVA layer in distilled water at 30 ° C for 30 minutes, and dividing the mass of the PVA layer after drying at 105 ° C for 16 hours after immersion. And the percentage of the value obtained. The degree of swelling of the PVA layer is substantially the same as that measured when the PVA layer is measured by the state of the laminate. Therefore, in view of the operability, it is preferable to measure the state of the laminate. As a specific measurement method of the degree of swelling of the PVA layer, a method to be described later can be given in the examples.

The method for adjusting the degree of swelling of the PVA layer is not particularly limited. For example, a general PVA (saponified product of a single polymer of vinyl acetate) can be used to produce a laminate having a thermoplastic resin film layer and a PVA layer. This is carried out by appropriately heat-treating at a temperature of 100 ° C or higher. Here, as the heat treatment temperature is increased, the heat treatment time is further increased, and the value of the degree of swelling can be lowered. However, when the laminate having the thermoplastic resin film layer and the PVA layer is heat-treated at a temperature of 100 ° C or higher, wrinkles tend to occur as the size of the thermoplastic resin film layer changes. Therefore, a method of adjusting the degree of swelling of the PVA layer by using PVA which is easy to reduce the degree of swelling described later is preferable. According to the above, even if a laminate having a thermoplastic resin film layer and a PVA layer is prepared under conditions of not more than 100 ° C, the swelling degree of the PVA layer can be easily adjusted to the above range.

As the PVA of the PVA layer, by polymerizing vinyl acetate, vinyl formate, vinyl propionate, vinyl butyrate, trimethyl vinyl acetate, vinyl versatic acid, vinyl laurate , vinyl stearate, vinyl benzoate, isopropenyl acetate, etc. The polyvinyl ester obtained by one or two or more kinds of vinyl esters is saponified. Among the above vinyl esters, vinyl acetate is preferred from the viewpoints of easiness of production of PVA, ease of availability, cost, and the like.

The polyvinyl ester may be one or two or more kinds of vinyl esters as the monomer. However, one or two or more kinds may be used as long as the effects of the present invention are not impaired. A copolymer of a vinyl ester with other monomers copolymerizable therewith.

Examples of the other monomer copolymerizable with the vinyl ester include, for example, an α-olefin having 2 to 30 carbon atoms such as ethylene, propylene, 1-butene or isobutylene; or (meth)acrylic acid or a salt thereof; Methyl)methyl acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate (meth) acrylate such as (meth)acrylic acid tertiary butyl ester, (ethyl)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) acrylamide, (meth) acrylamide sulfonic acid or a salt thereof, (meth) acrylamide propyl dimethylamine or a salt thereof, N-methylol (meth) acrylamide (meth)acrylamide derivatives such as N-vinylformamide, N-vinylacetamide, N-vinylpyrrolidone, etc.; methyl vinyl ether, B Vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, n-butyl vinyl ether a vinyl ether such as isobutyl vinyl ether, tertiary butyl vinyl ether, lauryl vinyl ether or octadecyl vinyl ether; vinyl cyanide such as (meth)acrylonitrile; vinyl chloride or vinylidene chloride; Ethylene fluoride of vinyl fluoride, vinylidene fluoride, etc.; allyl compound of allyl acetate, allyl chloride, etc. Maleic acid or a salt, ester or anhydride thereof; itaconic acid or a salt, ester or anhydride thereof; an ethylene mercapto compound such as ethylene trimethoxyoxane; an unsaturated sulfonic acid or the like. The above-mentioned polyvinyl ester may have one or two or more types of structural units derived from the other monomers described above.

The ratio of the structural unit derived from the other monomer described above to the above-mentioned polyvinyl ester is preferably 15 mol% or less based on the number of moles of the entire structural unit constituting the polyvinyl ester, and may be 10 or less. Mole% or less, even 5 mol% or less.

In particular, when the other monomer, such as (meth)acrylic acid or unsaturated sulfonic acid, is a monomer which promotes the possibility of water solubility of the obtained PVA, in order to prevent PVA from being produced in the polarizing film. The ratio of the structural unit derived from the monomer to the polyvinyl ester is preferably 5 mol% or less, and preferably 3 mol% or less, based on the number of moles of the entire structural unit constituting the polyvinyl ester.

The above-mentioned PVA may be modified by one or two or more kinds of monomers which are graft-copolymerizable, as long as the effects of the present invention are not impaired. Examples of the graft-copolymerizable monomer include an unsaturated carboxylic acid or a derivative thereof; an unsaturated sulfonic acid or a derivative thereof; and an α-olefin having 2 to 30 carbon atoms. The proportion of the structural unit derived from the graft-polymerizable monomer (the structural unit of the graft-modified portion) derived from PVA is preferably 5 mol% or less based on the number of moles of the entire structural unit constituting the PVA.

In the above PVA, one of the hydroxyl groups may be crosslinked or may not be crosslinked. Further, in the above PVA, a part of the hydroxyl group may react with an aldehyde compound such as acetaldehyde or butyraldehyde to form an acetal structure, or may not react with the compounds to form an acetal structure.

When PVA which is easy to reduce the degree of swelling is used as described above, the swelling degree of the PVA layer can be easily adjusted to the above even if a laminate having a thermoplastic resin film layer and a PVA layer is prepared under conditions of not more than 100 ° C. range. As the PVA which is easy to lower the degree of swelling, for example, PVA having an ethylene content of 1 mol% or more and 12 mol% or less is exemplified. The ethylene content herein means the ratio of the number of moles of the structural unit derived from ethylene (% by mole) with respect to the number of moles of the entire structural unit constituting the PVA. When the ethylene content is 1 mol% or more, the degree of swelling can be easily made equal to or lower than the above upper limit even if the raw liquid to be described later is dried or heat-treated at a low temperature. On the other hand, by setting the ethylene content to 12 mol% or less, the degree of swelling can be easily made the above lower limit or more. From the viewpoint that 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, and further preferably 11.5 mol% or less, 11 mol. Ear% or less is preferred.

Moreover, as another example of the PVA which is easy to reduce the degree of swelling, a PVA having a 1,2-glycol bond amount of 0.4 mol% or more and 1.5 mol% or less is exemplified. The 1,2-glycol bond amount herein may refer to the total number of moles bonded to the adjacent vinyl alcohol units, and the adjacent vinyl alcohol units bonded by the 1,2-diol bond. The proportion of the molar number of the bond (% by mole) can also 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 made equal to or lower than the above upper limit even if drying or heat treatment after application of the stock solution described later is carried out at a low temperature. On the other hand, the amount of the 1,2-diol bond is 0.4 mol% or more, and the degree of swelling can be easily made the above lower limit or more. Easy to adjust the degree of swelling From the viewpoint of the range defined in the present invention, the amount of the 1,2-diol bond is preferably 0.5 mol% or more, more preferably 0.6 mol% or more, and further preferably 1.4 mol% or less, 1.3 mol. % is better. PVA having a small value of 1,2-glycol bond amount can be produced by using a polyvinyl ester obtained by polymerizing a vinyl ester at a low temperature as a raw material. Specifically, the PVA having a 1,2-glycol bond amount of 0.4 mol% or more and 1.5 mol% or less can be obtained by polymerizing a vinyl ester in a range of about -50 ° C or more and +50 ° C or less. Polyvinyl ester is produced as a raw material.

The PVA described above may satisfy only one of the range of the ethylene content and the range of the 1,2-diol bond amount, and may satisfy both of them. That is, any ethylene content is within the foregoing range, while the 1,2-diol bond amount exceeds 1.5 mol% of PVA; the ethylene content is less than 1 mol%, and the 1,2-glycol bond amount is as described above. The range of PVA; and the PVA having the ethylene content and the 1,2-glycol bond amount in the above range at the same time can be used as PVA which is easy to lower the degree of swelling. However, the ethylene content and the 1,2-glycol bond amount are simultaneously in the range of PVA, especially in the case where the ethylene content is relatively high and/or the 1,2-diol bond amount is relatively low. There is a case where the degree of swelling of the PVA layer is excessively lowered. Therefore, when the PVA having the ethylene content and the 1,2-glycol bond amount in the above range is used, the drying treatment or heat treatment after the formation of the PVA layer is performed at a relatively low temperature, or the ethylene content is lowered and/or It is preferred that the amount of 1,2-diol bond becomes high.

The average degree of polymerization of the above PVA is preferably in the range of 1,000 or more and 9,500 or less, and the average degree of polymerization is preferably 1,500 or more, more preferably 2,000 or more, further preferably 9,200 or less, and 6,000 or less. Better. By the average degree of polymerization of 1,000 or more, the polarizing performance of the obtained polarizing film can be improved. On the other hand, the productivity of PVA can be improved by an average degree of polymerization of 9,500 or less. In addition, the average degree of polymerization of PVA (PVA contained in the PVA layer) used for formation of the PVA layer can be measured in accordance with the description of JIS K6726-1994.

The saponification degree of the PVA is preferably 98 mol% or more, more preferably 98.5 mol% or more, and more preferably 99 mol% or more from the viewpoint of the polarizing performance of the obtained polarizing film. When the degree of saponification is less than 98% by mole, PVA is easily eluted in the production process of the polarizing film, and the eluted PVA adheres to the film to lower the polarizing performance of the polarizing film. In addition, the degree of saponification of the PVA of the present specification means the total number of moles of the structural unit (typically a vinyl ester unit) and the vinyl alcohol unit which PVA has with respect to the conversion into a vinyl alcohol unit by saponification, The proportion of the number of moles of the vinyl alcohol unit (% by mole). The degree of saponification can be measured in accordance with the description of JIS K6726-1994.

The PVA layer is preferably a plasticizer from the viewpoint of improving the stretchability at the time of stretching the laminated body (1). Examples of the plasticizer include polyhydric alcohols such as ethylene glycol, glycerin, propylene glycol, diethylene glycol, diglycerin, triethylene glycol, tetraethylene glycol, and trimethylolpropane. The PVA layer can be used. One or two or more kinds of these plasticizers are contained. Among these, glycerin is preferable from the viewpoint of the effect of improving the stretchability.

The content of the plasticizer of PVA is preferably in the range of 1 part by mass or more and 15 parts by mass or less based on 100 parts by mass of the PVA contained therein. When the content is 1 part by mass or more, the stretchability of the layered product (1) can be further improved. On the other hand, the content is 15 parts by mass. In the following, it is possible to prevent the PVA layer from becoming too soft and to deteriorate the handleability, and to prevent the PVA layer from peeling off from the thermoplastic resin film layer. The content of the plasticizer in the PVA layer is preferably 2 parts by mass or more based on 100 parts by mass of the PVA, more preferably 4 parts by mass or more, more preferably 5 parts by mass or more, more preferably 13 parts by mass or less, and particularly preferably 12 parts by mass or less. It is best to use 8 parts by mass or less.

In the case where the polarizing film is produced by using the layered product (1) of the present invention, the total amount of the plasticizer contained in the PVA layer is eluted during the production of the polarizing film, etc., depending on the production conditions and the like. It is not limited to remain in the polarizing film.

The PVA layer may further contain components such as an antioxidant, an antifreezing agent, a pH adjuster, a masking agent, an anti-coloring agent, an oil agent, a surfactant, and the like, as needed.

The content of the PVA of the PVA layer is preferably in the range of 50% by mass or more and 99% by mass or less, from the viewpoint of easiness of preparation of the desired polarizing film, etc., and the content ratio is preferably 75% by mass or more. 80% by mass or more is more preferable, and 85% by mass or more is particularly preferable, and 98% by mass or less is more preferable, and 96% by mass or less is more preferable, and 95% by mass or less is particularly preferable.

The thickness of the PVA layer is not particularly limited, and may be, for example, 100 μm or less. However, from the viewpoint of easily producing a thin polarizing film or the like, it is preferable to make the PVA layer thin. Specifically, the thickness of the PVA layer is 20 μm or less. Preferably, it is preferably 15 μm or less, more preferably 10 μm or less. In the layered product (1) of the present invention, since the PVA layer has a specific configuration as described above, even if the thickness of the PVA layer is made thinner as described above, the elution of PVA can be suppressed in the step of contacting with water, and it is simple. A thin polarizing film with good polarizing properties is produced. Also, the thickness of the PVA layer is as described above. In the case of a thin sample, it is also possible to reduce the tension at the time of stretching the laminated body (1). In addition, when the thickness of the PVA layer is too small, tensile fracture tends to occur during stretching of the laminate (1). Therefore, the thickness of the PVA layer is, for example, 3 μm or more.

The layer structure of the layered product (1) of the present invention is not particularly limited. However, from the viewpoint of more easily obtaining a polarizing film having excellent polarizing performance, a two-layer structure of the thermoplastic resin film layer 1 and the PVA layer 1 layer is preferable.

The shape of the laminated body (1) is not particularly limited, but a long laminated body is preferable from the viewpoint that a more uniform laminated body can be continuously and easily produced, and it can be continuously used even when a polarizing film is produced. The length of the long laminated body (the length in the longitudinal direction) is not particularly limited, and may be appropriately set depending on the use of the polarizing film to be produced, and the like, and may be, for example, in the range of 5 m or more and 20,000 m or less.

The width of the laminated body (1) is not particularly limited, and can be appropriately set in accordance with the use of the polarizing film to be produced, etc., but in recent years, the width of the laminated body (1) is widened from the viewpoint of making a large screen of the liquid crystal television or the liquid crystal monitor. When it is 0.5 m or more, and it is preferable to be 1.0 m or more, it is suitable for such use. On the other hand, when the width of the laminated body (1) is too large, it is difficult to uniformly stretch the polarizing film when it is used in a practical device. Therefore, the width of the laminated body (1) is preferably 7 m or less.

For the method of producing the layered product (1), for example, a method of forming a PVA layer on a thermoplastic resin film, and specifically, a PVA in which PVA is dissolved and, if necessary, the plasticizer or the like is further dissolved, may be mentioned. a method in which a raw material in a liquid medium is applied onto a thermoplastic resin film and dried; the melt-kneading PVA, liquid medium And a method in which a raw material obtained by further melting and kneading other components is extruded on a thermoplastic resin film and further dried as necessary; and a PVA film containing PVA and optionally further containing other components is produced by a known method, and A method of bonding a thermoplastic resin film or the like. Among these, from the viewpoint that a thin PVA layer can be easily prepared and the uniformity of the thickness of the obtained PVA layer, a stock solution in which PVA is dissolved and, if necessary, other components are further dissolved in a liquid medium is applied. A method of drying on a thermoplastic resin film is preferred.

Examples of the liquid medium include water, dimethyl hydrazine, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, ethylene glycol, glycerin, propylene glycol, and diethyl ether. Diol, triethylene glycol, tetraethylene glycol, trimethylolpropane, ethylenediamine, diethylenetriamine, etc., and one or two or more of these may be used. Among them, water is preferred from the viewpoint of giving environmental load or recycling property.

The volatile matter ratio of the stock solution (the content ratio in the stock solution of the volatile component such as the liquid medium which is removed by volatilization or drying at the time of formation of the PVA layer) varies depending on the formation method or formation conditions of the PVA layer, but is 50. It is preferably in the range of from 5% by mass to 98% by mass, and more preferably from 55% by mass to 95% by mass. When the volatile matter content of the stock solution is 50% by mass or more, the viscosity does not become too high, and the filtration or defoaming at the time of preparation of the stock solution proceeds smoothly, and it is easy to form a PVA layer having a foreign matter or a small defect, and the coating is also improved. Sex. On the other hand, when the volatile matter fraction 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 easy.

As a coating method at the time of apply|coating a raw material on the thermoplastic resin film, a die-coating method, a point coating method, a dip coating method, etc. are mentioned, for example. Among these, the die coating method is preferable from the viewpoint of the uniformity of the thickness of the obtained PVA layer.

The thermoplastic resin film used for the production of the laminate (1) is preferably subjected to hydrophilization treatment on at least one surface in advance. The adhesion of the thermoplastic resin film layer to the PVA layer can be improved by forming the PVA layer in contact with the surface subjected to the hydrophilization treatment as described above. Examples of the hydrophilization treatment include corona treatment, plasma treatment, and tie layer treatment. Among these, corona treatment is preferred from the viewpoint of easy adjustment of hydrophilicity.

The contact angle of the surface of the thermoplastic resin film is preferably 55° or more and 70° or less by the hydrophilization treatment, and the contact angle is preferably adjusted to 57° or more, more preferably adjusted to 59° or more, and further, It is preferable to adjust to 69° or less, and it is more preferable to adjust to 68° or less. When the contact angle is less than 55°, the adhesive strength between the thermoplastic resin film layer and the PVA layer tends to be too strong, and the stretched thermoplastic resin film layer is peeled off after the laminate (1) is stretched. Stripping can become difficult. On the other hand, when the contact angle is higher than 70°, the PVA layer is easily peeled off from the thermoplastic resin film layer during the stretching of the laminated body (1), and it is difficult to stretch at a high draw ratio. The tendency. Further, the contact angle of the surface of the thermoplastic resin film may mean an angle formed by the surface of the surface where the free surface of the water is in contact with the thermoplastic resin film and the surface of the thermoplastic resin film (taken at the inside of the water), It can be measured by the method mentioned later in an Example.

The condition of the corona treatment when the contact angle of the surface of the thermoplastic resin film is adjusted to the above range by the corona treatment is not particularly limited, but the contact angle of the surface of the thermoplastic resin film can be easily adjusted to the aforementioned range. The viewpoint is that the discharge amount shown by the following formula (1) is 180 to 350 W. The range of minutes/m ² is better, 190~320W. It is better in the range of minutes/m ² , 200~300W. More preferably in the range of minutes/m ² .

Discharge amount (W.min/m ² )=output (W/m)/processing speed (m/min) (1)

The conditions for drying the coating solution after being applied to the thermoplastic resin film are not particularly limited. However, in order to prevent wrinkles on the thermoplastic resin film, it is preferred to dry at a temperature lower than the glass transition temperature of the thermoplastic resin film. In this case, it is preferable to use PVA or the like which is easy to lower the degree of swelling as the PVA, and it is preferable to dry it under conditions of not more than 100 °C. The specific drying temperature is not particularly limited. However, in view of the fact that the degree of swelling of the PVA layer is easily adjusted to the above range, the drying efficiency, and the like, it is preferably in the range of from 20 ° C to 95 ° C. The drying temperature is 50 ° C. The above is preferable, more preferably 65 ° C or more, further preferably 90 ° C or less, and more preferably 85 ° C or less. Thereby, the laminate (1) of the unstretched PVA layer having a degree of swelling of the thermoplastic resin film layer of 180% or more and 260% or less can be easily obtained.

"Method for manufacturing polarizing film (1)"

The method (1) for producing a polarizing film of the present invention includes a step of stretching the layered product (1).

Here, when the PVA layer contains a dichroic dye in advance, a polarizing film having a dichroic dye adsorbed thereon can be obtained by stretching the layered product (1). In this case, the method of making the PVA layer contain a dichroic dye is not particularly limited. For example, a method in which the PVA layer of the layered product (1) is brought into contact with the dichroic dye, or a method in which the PVA layer is used to form the dichroic dye in advance is used. Further, when the PVA layer is not provided with the dichroic dye in advance, the PVA layer in the middle of stretching is brought into contact with the dichroic dye during stretching of the laminated body (1), or the laminated body is 1) After stretching, the stretched film layer formed of the (pre-stretched) PVA layer is brought into contact with the dichroic dye to obtain a polarizing film having a dichroic dye adsorbed thereon. Among these, from the viewpoint of more prominently exerting the effects of the present invention, the PVA layer for the layered body (1) before stretching is included, and the stretching is carried out during stretching of the layered body (1). a PVA layer; and a stretched film layer formed of a PVA layer after stretching the layered product (1); or a method for producing a dichroic dye by a method of contacting the dichroic dye; A polarizing film is preferred.

In any of the above methods, in addition to the treatment and the treatment (dyeing) of bringing the dichroic dye into contact, a swelling treatment, a crosslinking treatment, a fixing treatment, drying, or the like may be further performed as needed. The order of the respective processes may be appropriately changed as needed, and each process may be performed twice or more, and even different processes may be simultaneously performed. Moreover, according to the above-described production method, a polarizing film formed on the thermoplastic resin film layer after stretching can be obtained, but a step of peeling off the stretched thermoplastic resin film layer may be included as needed.

As described above, in the method (1) for producing a polarizing film of the present invention, the PVA layer of the layered product (1) has a swelling degree of 180% or more and 260% or less. Therefore, even if the impregnation with the aqueous boric acid solution is not performed in advance or The insolubilization treatment in the high-temperature stretching in the air can also suppress the elution of PVA in the step of contacting with water during the production of a polarizing film such as dyeing. therefore, In the case where the polarizing film is not previously prepared by insolubilization as described above, the effects of the present invention can be exhibited more remarkably. Specifically, the PVA layer including the PVA layer for the laminate (1) before stretching; the PVA layer during stretching in the stretching of the laminate (1); and the tensile laminate (1) In the method for producing a step of contacting a dichroic dye, a method of producing a dichroic dye-adsorbing film is used to prepare a laminate of the present invention. 1) The step before the step of bringing the dichroic dye into contact does not include a step of contacting an aqueous solution containing a boron compound such as a borate such as boric acid or borax, and/or a temperature stretching not exceeding 95 ° C. The step (preferably, the step of stretching at a temperature not exceeding 50 ° C) is preferred.

An example of the method (1) for producing a polarizing film of the present invention is that first, a layered body (1) having a PVA layer not containing a dichroic dye is subjected to a swelling treatment, and then contacted with a dichroic dye. The PVA layer contains a dichroic dye, and if necessary, further subjected to a crosslinking treatment, and the obtained laminate is stretched, further subjected to a fixing treatment as needed, and dried, and the series of treatments are obtained. A method of peeling the stretched thermoplastic resin film layer by a polarizing film formed on the stretched thermoplastic resin film layer.

The swelling treatment can be carried out by immersing the layered body (1) in water. The temperature of the water immersed in water is preferably in the range of 20 ° C to 40 ° C. The temperature is preferably 22 ° C or higher, more preferably 25 ° C or higher, and more preferably 38 ° C or lower and 35 ° C or lower. Better. By setting the temperature to a range of from 20 ° C to 40 ° C, the PVA layer can be effectively swollen. Moreover, as the time of immersion in water, it is 0.1 minute or more and 5 minutes. The range below is preferably within a range of from 0.5 minutes to 3 minutes. The PVA layer can be effectively swollen by being in the range of 0.1 minute or more and 5 minutes or less. Further, the water immersed in water is not limited to pure water, and may be an aqueous solution in which various components are dissolved, or may be a mixture of water and an aqueous medium.

As described above, the PVA layer in the middle of stretching in the stretching of the laminated body (1) by the PVA layer of the laminated body (1) before stretching; and the PVA after stretching the laminated body (1) The stretched film layer formed by the layer is dyed by contact with the dichroic dye to obtain a polarizing film in which a dichroic dye is adsorbed on the substrate. The contact of the dichroic dye can be carried out by immersing the layered body before stretching, stretching, or stretching in a solution (particularly an aqueous solution) containing a dichroic dye. The concentration of the dichroic dye in the solution containing the dichroic dye can be appropriately set depending on the type of the dichroic dye to be used, and the like, and can be, for example, 0.001% by mass or more and 1% by mass or less. When a potassium iodide solution (particularly an aqueous solution) is used as a solution containing a dichroic dye, the concentration of iodine (I ₂ ) used is 0.01% by mass or more and 1.0% by mass or less from the viewpoint of efficiently adsorbing the iodine-based dye to the substrate. The concentration is preferably in the range of 0.01% by mass or more and 10% by mass or less based on the concentration of potassium iodide (KI) to be used. The temperature of the solution containing the dichroic dye is preferably in the range of 20 ° C to 50 ° C from the viewpoint of efficiently adsorbing the iodine dye in the substrate, and particularly preferably in the range of 25 ° C to 40 ° C.

Examples of the dichroic dye include an iodine dye (I ₃ ^- or I ₅ ^- ), a dichroic organic dye, and the like. The iodine dye can be obtained, for example, by bringing iodine (I ₂ ) into contact with potassium iodide. Further, examples of the dichroic organic dye include direct blacks 17, 19, and 154; direct browns 44, 106, 195, 210, and 223; and direct red 2, 23, 28, 31, 37, 39, 79, and 81. 240, 242, 247; direct blue 1, 15, 22, 78, 90, 98, 151, 168, 202, 236, 249, 270; direct purple 9, 12, 51, 98; direct green 1, 85; direct yellow 8, 12, 44, 86, 87; direct orange 26, 39, 106, 107 and so on. Among these dichroic dyes, an iodine-based dye is preferred from the viewpoints of handleability, availability, and polarizing performance. Further, the dichroic dye may be used alone or in combination of two or more kinds, and may be, for example, an equilibrium mixture such as I ₃ ^- and I ₅ ^- .

By subjecting the PVA layer to a crosslinking treatment, it is possible to more effectively prevent the PVA from eluting with water at the time of wet stretching at a high temperature. From this point of view, the crosslinking treatment is preferably carried out after the treatment of bringing the dichroic dye into contact, and before the stretching. The crosslinking treatment can be carried out by immersing the layered product (1) in an aqueous solution containing a crosslinking agent. As the crosslinking agent, one type or two or more types of boron compounds such as a borate such as boric acid or 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, more preferably 3% by mass or more, and still more preferably 7% by mass or less. More preferably, 6 mass% or less. By setting the concentration of the crosslinking agent in the range of 1% by mass or more and 15% by mass or less, sufficient stretchability can be maintained. The aqueous solution containing a crosslinking agent may also contain an adjuvant such as potassium iodide. The temperature of the aqueous solution containing the crosslinking agent is preferably in the range of 20 ° C to 50 ° C, particularly preferably in the range of 25 ° C to 40 ° C. By setting the temperature to a range of from 20 ° C to 50 ° C, crosslinking can be effectively carried out.

The stretching method at the time of stretching the laminated body (1) is not particularly limited, and may be carried out by any of a wet stretching method and a dry stretching method. In the case of the wet stretching method, it may be carried out in one or two or more aqueous solutions containing a boron compound such as a borate such as boric acid or borax, or in the above-mentioned solution containing a dichroic dye or It is carried out in a fixed treatment bath to be described later. Further, in the case of the dry stretching method, the film may be directly stretched at room temperature, or may be stretched while being heated, or may be stretched after water absorption. Among these, from the viewpoint of the uniformity of the thickness in the width direction of the obtained polarizing film, a wet stretching method is preferred, and stretching in a boric acid aqueous solution is preferred. The concentration of boric acid in the aqueous boric acid solution is preferably in the range of 0.5% by mass or more and 6.0% by mass or less, and the concentration is preferably 1.0% by mass or more, more preferably 1.5% by mass or more, further preferably 5.0% by mass or less, and 4.0% by mass. % is better. When the concentration of the boric acid is in the range of 0.5% by mass or more and 6.0% by mass or less, a polarizing film having a uniform thickness in the width direction can be obtained. The aqueous solution containing the boron compound described above may further contain potassium iodide, and the concentration thereof is preferably in the range of 0.01% by mass or more and 10% by mass or less. 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 having more excellent polarizing performance can be obtained.

The temperature at which the laminate (1) is stretched is preferably in the range of 30 ° C to 90 ° C. The temperature is preferably 40 ° C or higher, more preferably 50 ° C or higher, and more preferably 80 ° C or lower and 70 ° C or lower. Better. By setting the temperature in the range of 30 ° C to 90 ° C, a polarizing film having a uniform thickness in the width direction can be obtained.

The stretching ratio at the time of stretching of the laminated body (1) is preferably 5.7 times or more, more preferably 5.8 times or more, and still more preferably 5.9 times or more. By layering The stretching ratio of (1) is within the above range, and a polarizing film having better polarizing performance can be obtained. The upper limit of the stretching ratio of the laminated body (1) is not particularly limited, but preferably 8 times or less. The stretching of the laminated body (1) may be carried out once or may be carried out in multiple steps, both of which may be used, but when divided into a plurality of times, the total stretching ratio multiplied by the stretching ratio of each stretching is in the aforementioned range Just inside. In addition, the draw ratio in this specification is based on the length of the laminated body (1) before stretching, and the state which is not stretched is equivalent to the draw ratio one time.

The stretching of the laminate (1) is preferably uniaxial stretching from the viewpoint of the performance of the obtained polarizing film. The direction of uniaxial stretching when stretching the long laminated body (1) is not particularly limited, and uniaxial stretching or transverse uniaxial stretching for the longitudinal direction may be employed, but from which polarizing performance can be obtained. From the viewpoint of a good polarizing film, uniaxial stretching for the longitudinal direction is preferred. The uniaxial stretching in the longitudinal direction can be carried out by using a stretching device having a plurality of rolls parallel to each other and changing the peripheral speed between the rolls. On the other hand, the transverse uniaxial stretching can be carried out using a tenter type stretching machine.

The fixing treatment is mainly performed to enhance the adsorption of the dichroic dye to the PVA layer or the stretched film (base). The fixing treatment can be carried out by immersing the layered body before stretching, during stretching or after stretching in a fixed treatment bath. As a fixed treatment bath. As the fixed treatment bath, one type or two or more types of aqueous solutions containing a boron compound such as a borate such as boric acid or borax can be used. Further, an iodine compound or a metal compound may be added to the fixed treatment bath as needed. The concentration of the boron compound in the aqueous solution containing the boron compound used as the fixed treatment bath is generally in the range of 2% by mass to 15% by mass, particularly preferably in the range of 3% by mass to 10% by mass. By making the concentration above 2% by mass In the range of 15% by mass or less, the adsorption of the dichroic dye can be further enhanced. The temperature of the fixed treatment bath is preferably in the range of 15 ° C to 60 ° C, particularly preferably in the range of 25 ° C to 40 ° C. By setting the temperature in the range of 15 ° C or more and 60 ° C or less, the adsorption of the dichroic dye can be further enhanced.

The drying conditions are not particularly limited, but it is preferably in the range of 30 ° C or more and 150 ° C or less, particularly in the range of 50 ° C or more and 130 ° C or less. By drying at a temperature in the range of 30 ° C or more and 150 ° C or less, it is easy to obtain a polarizing film having excellent dimensional stability.

By performing the above, a polarizing film formed on the stretched thermoplastic resin film layer can be obtained. The method of using the polarizing film as described above is not particularly limited. For example, the stretched thermoplastic resin film layer may not be peeled off, and it may be optically transparent and mechanically bonded directly or as desired on the polarizing film side. The protective film having a strength may be used as a polarizing plate, and the protective film may be bonded to the side opposite to the side of the stretched thermoplastic resin film layer, and then the stretched thermoplastic resin film layer may be peeled off, or directly or according to It is necessary to bond another protective film on the peeling surface as a polarizing plate. As a protective film, a cellulose triacetate (TAC) film, acetic acid can be used. A cellulose butyrate (CAB) film, an acrylic film, a polyester film, or the like. Further, examples of the adhesive to be bonded include a PVA-based adhesive or a urethane-based adhesive, and a PVA-based adhesive is preferred.

The thickness of the polarizing film obtained by the method (1) for producing a polarizing film of the present invention is preferably 10 μm or less, and preferably 8 μm or less. Since the polarizing film has the thickness as described above, it can be suitably used in a field where the demand for thinning of a mobile phone or the like is high. Further, since the polarizing film having an excessively small thickness is difficult to prepare, the thickness of the polarizing film is, for example, 1 μm or more.

Polarized Film (2)

In the polarizing film (2) of the present invention, a dichroic dye is adsorbed to a substrate having a birefringence of 45 × 10 ^-3 or more. Here, the dichroic dye may be adsorbed to the inside of the substrate or may be adsorbed on the surface of the substrate, and both of them may be adsorbed to the inside of the substrate by dichroic dye from the viewpoint of polarizing performance. The polarizing film in which the dichroic dye is adsorbed on the substrate can stretch the initial film containing the dichroic dye in advance, adsorb the dichroic dye together with the stretching of the initial film, and stretch the initial film to form a matrix. Thereafter, it is produced by adsorbing a dichroic dye or the like.

As a description of the dichroic dye of the polarizing film (2) and the method for producing a polarizing film (2) to be described later, since the description of the dichroic dye in the description column of the method for producing a polarizing film (1) can be directly used, The duplicated description is omitted here.

The polarizing film (2) of the present invention has a configuration in which the birefringence of the substrate constituting the substrate is not more than 45 × 10 ^-3 or more. When the birefringence of the substrate is less than 45 × 10 ^-3 , the red light leakage is increased and the polarizing performance is also lowered when the two polarizing films are arranged in the orthogonal polarization state. From the viewpoint of improving the polarization performance and reducing the leakage of the red light in the orthogonal polarization state, the birefringence of the substrate constituting the polarizing film (2) is preferably 46 × 10 ^-3 or more, and more preferably 47 × 10 ^-3 or more. , 48 × 10 ^-3 or more more preferably, 49 × 10 ^-3 or more and particularly preferably, 50 × 10 ^-3 or more optimal. Further, from the viewpoint that the substrate having an excessively high birefringence is difficult to prepare, the birefringence of the substrate 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. Rate. Further, the birefringence of a general film can be determined by dividing the retardation value of the film (the in-plane retardation value measured by light parallel to the thickness direction of the film) by the thickness of the film. Therefore, the birefringence of the substrate specified in the polarizing film (2) can be determined by subtracting the retardation value of the polarizing film (2) from the retardation value of the dichroic dye. After the value, it is obtained by dividing it by the thickness of the substrate (this is usually the same as the thickness of the polarizing film (2)).

Specifically, in the wavelength range of light generally used for measuring the retardation value of a film, generally, the birefringence of the matrix has almost no wavelength dependency, and on the other hand, the birefringence based on the dichroic dye is utilized. The wavelength dependence is high, and the birefringence of the matrix can be obtained by the following method.

In other words, the retardation value (unit: nm) of the polarizing film (2) measured by light having a wavelength of _λ nm is taken as R _λ , and the retardation value (unit: nm) of the substrate is taken as A, and the light of the wavelength λ is used. When the retardation value (unit: nm) of the dichroic dye is taken as B _λ , the relationship of the following formulas (2) and (3) is regarded as true, and R _λ = A + B _λ (2)

B _λ =B'/(λ ² -600 ² ) (3)

And the simultaneous equations of the following formulas (2'), (3'), (2"), and (3") obtained by substituting λ of the equation into 800 nm and 1000 nm of the measurement wavelength, R ₈₀₀ = A + B ₈₀₀ (2')

B ₈₀₀ =B'/(800 ² -600 ² ) (3')

R ₁₀₀₀ =A+B ₁₀₀₀ (2")

B ₁₀₀₀ =B'/(1000 ² -600 ² ) (3")

The measured values of R ₈₀₀ and R _{1000 were used} and the A obtained as the retardation value of the substrate was obtained and determined by dividing the thickness (unit: nm) of the polarizing film (2). Here, B' is a value inherent in the measured polarizing film.

The component constituting the matrix is not particularly limited, but the matrix contains PVA, and the average degree of polymerization of the PVA contained in the matrix is preferably in the range of 2,800 or more and 9,500 or less. The polarizing film (2) of the present invention can be easily produced by using the PVA having the average degree of polymerization as described above, and the polarizing film of the present invention can be easily produced by the method described later. As a result, the average degree of polymerization of the PVA contained in the substrate is Enter the above range. From the viewpoint of easiness of preparation of the substrate, the average degree of polymerization of the PVA contained in the substrate is preferably 3,000 or more, more preferably 4,000 or more, more preferably 4,100 or more, and may be 4,500 or more, even 5,000 or more, and 9,200 or less. Preferably, it is more preferably 8,000 or less, and particularly preferably 6,000 or less. Further, the average degree of polymerization of the PVA contained in the substrate may be such that the polarizing film (2) may be immersed in a sorbitol aqueous solution or the like, and further washed with water or the like as necessary to extract components other than the PVA contained in the matrix. The PVA obtained by removing and using the residue is obtained according to the description of JIS K6726-1994, and specifically, it can be obtained by the method described later in the examples.

The content of the PVA of the substrate is not particularly limited. However, from the viewpoint of easiness of preparation of the polarizing film (2) of the present invention, etc., it is preferably in the range of 50% by mass or more and 100% by mass or less, and the content ratio is 80% by mass. More preferably, it is more preferably 90% by mass or more, more preferably 99% by mass or less, and still more preferably 98% by mass or less. Further, the mass of the substrate is obtained by subtracting the mass of the dichroic dye from the mass of the polarizing film (2).

In the polarizing film (2) and the method (2) for producing a polarizing film to be described later, the description of the PVA other than the description of the average degree of polymerization (including the description of the degree of saponification) can be directly adopted in the description of the laminated body (1). In the column, the description of the PVA is omitted, so the duplicated description is omitted here. Furthermore, As the PVA of the polarizing film (2) and the method (2) for producing a polarizing film to be described later, it is not necessary to particularly use the PVA which is preferable in the column of the description of the laminated body (1), which is preferable in that the degree of moisture is lowered. .

The thickness of the polarizing film (2) of the present invention is preferably 10 μm or less, and more preferably 8 μm or less. The polarizing film (2) has a thickness as described above, and can be suitably used in a field where the demand for thinning of a mobile phone or the like is high. Further, since the polarizing film having an excessively small thickness is difficult to prepare, the thickness of the polarizing film (2) is, for example, 1 μm or more.

"Method for manufacturing polarizing film (2)"

The method for producing the polarizing film (2) of the present invention is not particularly limited, but a method for producing a polarizing film comprising a step of stretching a layered body having a thermoplastic resin film layer and a PVA layer to 5.7 times or more Moreover, the method (2) for producing a polarizing film of the present invention having an average polymerization degree of PVA contained in the PVA layer of 2,800 or more and 9,500 or less can smoothly and easily produce a birefringence of the substrate in a specific range and excellent in polarizing performance. At the same time, the polarizing film (2) of the present invention which has less leakage of red light in the orthogonally polarized state.

As a description of the thermoplastic resin film layer of the laminate used in the method for producing a polarizing film (2), since the description of the thermoplastic resin film layer in the description column of the laminate (1) can be directly used, The duplicated description is omitted.

The average degree of polymerization of the PVA contained in the PVA layer of the layered product used in the method for producing a polarizing film (2) is in the range of 2,800 or more and 9,500 or less, and the average degree of polymerization is preferably 3,000 or more, more preferably 4,000 or more. More preferably, 4,100 or more, 4,500 or more, 5,000 or more, and 9,200 or less, 8,000 or less, and 6,000 or less. It is considered that the higher the average degree of polymerization of PVA, the higher the tension at the time of stretching and the lower limit draw ratio, but the inventors of the present invention found that the laminate having the thermoplastic resin film layer and the PVA layer is stretched to obtain polarized light. In the case of using a PVA having the above average degree of polymerization, for example, compared with the case of using a PVA having an average degree of polymerization of 2,600, the ultimate draw ratio does not decrease but rises, and the thermoplastic resin film layer and the PVA layer are provided, and The average degree of polymerization of the PVA contained in the PVA layer is 5.7 times or more in the laminate in the above range, and when the polarizing film formed on the thermoplastic resin film is produced, the birefringence of the substrate can be smoothly and easily obtained. It is a polarizing film of 45 × 10 ^-3 or more.

In addition, the average degree of polymerization of PVA (PVA contained in the PVA layer) used for formation of the PVA layer can be obtained according to the description of JIS K6726-1994, and specifically, in the examples, the method described later can be used. Got it.

From the viewpoint of the stretchability at the time of raising the stretched laminate, the PVA layer of the laminate used in the method for producing a polarizing film (2) preferably contains a plasticizer. Examples of the plasticizer include polyhydric alcohols such as ethylene glycol, glycerin, propylene glycol, diethylene glycol, diglycerin, triethylene glycol, tetraethylene glycol, and trimethylolpropane. The PVA layer can be used. One or two or more kinds of these plasticizers are contained. Among these, glycerin is preferred from the viewpoint of the effect of improving the stretchability.

The content of the plasticizer of the PVA layer which the laminated body used in the method of producing the polarizing film (2) is preferably in the range of 1 part by mass or more and 15 parts by mass or less based on 100 parts by mass of the PVA contained therein. Further, the product can be further increased by the content of 1 part by mass or more. The stretchability of the layer. On the other hand, when the content is 15 parts by mass or less, the PVA layer can be prevented from being too soft and the handleability is lowered, and the PVA layer can be prevented from being peeled off from the thermoplastic resin film layer. Further, in the method (2) for producing a polarizing film of the present invention in which the average degree of polymerization of the PVA contained in the PVA layer is in the above range, the content of the plasticizer in the PVA layer is 2 parts by mass or more and 13 parts by mass based on 100 parts by mass of the PVA. In the following range, even in the range of 4 parts by mass or more and 12 parts by mass or less, particularly in the range of 5 parts by mass or more and 8 parts by mass or less, the reason is not clear, but is further improved according to the ultimate draw ratio, as described above. The content is better.

In addition, although the plasticizer contained in the PVA layer is eluted at the time of manufacturing the polarizing film, it is not limited to the total amount remaining in the polarizing film.

The PVA layer of the laminate which is used in the method for producing a polarizing film (2) may further contain an antioxidant, an antifreezing agent, a pH adjuster, a masking agent, an anti-coloring agent, an oil agent, and a surfactant, if necessary. Ingredients.

The content ratio of the PVA of the PVA layer which is used in the above-mentioned laminated body to be used in the method for producing a polarizing film is 50% by mass or more and 99% by mass or less from the viewpoint of easiness of preparation of a desired polarizing film. The content is preferably in the range of 75 mass% or more, more preferably 80 mass% or more, more preferably 85 mass% or more, further preferably 98 mass% or less, more preferably 96 mass% or less, and 95 mass%. The following is especially good.

The thickness of the PVA layer which the laminate has used in the method for producing a polarizing film (2) is not particularly limited. For example, it can be set to 100 μm or less, but a thin polarizing film can be easily prepared. In particular, the thickness of the PVA layer is preferably 20 μm or less, more preferably 15 μm or less, and still more preferably 10 μm or less. In the method (2) for producing a polarizing film of the present invention, since the PVA layer has a 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 ultimate draw ratio, and as a result, A thin polarizing film which is excellent in polarizing performance and has little leakage of red light in a crossed polarized state can be obtained. Further, in the case where the thickness of the PVA layer is as thin as described above, the tension at the time of stretching the laminated body can be reduced. In addition, when the thickness of the PVA layer is too small, tensile fracture tends to occur during stretching of the laminate, and the thickness of the PVA layer is, for example, 3 μm or more.

The other description of the laminated body used in the method for producing a polarizing film (2) (including the description of a method of manufacturing a laminated body including the adjustment of the contact angle of the surface of the thermoplastic resin film), since it can be directly used The description of the laminated body in the description column of the laminated body (1) is omitted here.

In the method (2) for producing a polarizing film of the present invention, the laminated body is stretched to 5.7 times or more. Here, when the PVA layer contains a dichroic dye in advance, a polarizing film (2) having a dichroic dye adsorbed on the substrate can be obtained by stretching the laminate. In this case, the method of containing the dichroic dye in the PVA layer is not particularly limited. For example, a method of contacting the PVA layer of the laminate with the dichroic dye or a solution for forming the PVA layer may be appropriately used in advance. A method of coloring pigments, and the like. Further, when the PVA layer is not contained in the dichroic dye in advance, the PVA layer in the middle of stretching is brought into contact with the dichroic dye during stretching of the laminate, or the laminate is stretched. Stretch film formed of (pre-stretched) PVA layer When the layer is in contact with the dichroic dye, a polarizing film (2) having a dichroic dye adsorbed on the substrate can be obtained.

In any of the above methods, in addition to the treatment (dyeing) of bringing the dichroic dye into contact, the PVA layer may be further subjected to insolubilization treatment, swelling treatment, crosslinking treatment, fixation treatment, drying, or the like. The order of each process may be appropriately changed as needed, or each process may be performed twice or more, and different processes may be simultaneously performed. Moreover, according to the above-described production method, a polarizing film formed on the thermoplastic resin film layer after stretching can be obtained, but a step of peeling off the stretched thermoplastic resin film layer as needed may be included.

An example of the method (2) for producing a polarizing film of the present invention is to first perform an insolubilization treatment on a laminate having a PVA layer containing no dichroic dye, and further perform a swelling treatment as needed, followed by When the coloring pigment is in contact, the PVA layer contains a dichroic dye, and if necessary, further subjected to a crosslinking treatment, and the obtained laminated body is stretched to 5.7 times or more, and further subjected to a fixing treatment as needed, and dried. By the series of processes, a polarizing film formed on the stretched thermoplastic resin film layer is obtained, and the stretched thermoplastic resin film layer is peeled off.

The insolubilization treatment of the PVA layer is mainly performed to prevent the PVA contained in the PVA layer from eluting with water. For the insolubilization treatment, for example, a method of heat-treating the laminate or a method of immersing the laminate in one or more aqueous solutions containing a boron compound such as a borate such as boric acid or borax. Among these, since the heat treatment is applied to the laminated body, the rule of the thermoplastic resin film layer is accompanied. The change in inch has a wrinkle, so it is preferred to use an aqueous solution containing a boron compound. The above heat treatment can be carried out, for example, at a temperature in the range of 80 ° C or more and 200 ° C or less. From the viewpoint of preventing wrinkles, it is preferred that the heat treatment be performed while applying tension to the laminate. Further, in the method of using an aqueous solution containing a boron compound, the temperature of the aqueous solution is preferably in the range of from 20 ° C to 40 ° C, more preferably 22 ° C or more, more preferably 25 ° C or more, and further preferably 38 ° C or less. More preferably below 35 °C. By setting the temperature to a range of from 20 ° C to 40 ° C, the PVA can be prevented from being dissolved and effectively insolubilized. The time of immersion in the aqueous solution containing a boron compound is, for example, in the range of 0.1 minute or more and 5 minutes or less. It can be effectively insolubilized by being in the range of 0.1 minute or more and 5 minutes or less. The concentration of the boron compound in the aqueous solution containing the boron compound is preferably 0.5% by mass or more, preferably 1.0% by mass or more, more preferably 1.5% by mass or more, more preferably 6.0% by mass or less, and most preferably 5.0% by mass or less, and 4.0. The mass % or less is better. By setting the concentration in the range of 0.5% by mass or more and 6.0% by mass or less, the dissolution of PVA can be prevented and the insolubilization can be effectively insolubilized.

The insolubilization treatment of the PVA layer is preferably carried out before the swelling treatment before the treatment of contacting the dichroic dye.

The description of the swelling treatment of the method (2) for producing the polarizing film, the treatment (dyeing) for contacting the dichroic dye, and the crosslinking treatment can be directly employed in the description column of the method (1) for producing the polarizing film. The description of the swelling treatment, the treatment (dyeing) for bringing the dichroic dye into contact, and the crosslinking treatment will be omitted.

In the method (2) for producing a polarizing film, the stretching method at the time of stretching the laminated body is not particularly limited, and the wet stretching method and the dry method may be used. Performing in any of the stretching methods. In the case of the wet stretching method, it may be carried out in one or two or more aqueous solutions containing a boron compound such as a borate such as boric acid or borax, or in the above-mentioned solution containing a dichroic dye or It is carried out in a fixed treatment bath to be described later. Further, in the case of the dry stretching method, the film may be directly stretched at room temperature, or may be stretched while being heated, or may be stretched after water absorption. Among these, from the viewpoint of the uniformity of the thickness in the width direction of the obtained polarizing film, a wet stretching method is preferred, and stretching in a boric acid aqueous solution is preferred. The concentration of boric acid in the aqueous boric acid solution is preferably in the range of 0.5% by mass or more and 6.0% by mass or less, and the concentration is preferably 1.0% by mass or more, more preferably 1.5% by mass or more, further preferably 5.0% by mass or less, and 4.0% by mass. % is better. When the concentration of the boric acid is in the range of 0.5% by mass or more and 6.0% by mass or less, a polarizing film having a uniform thickness in the width direction can be obtained. The aqueous solution containing the boron compound described above may contain potassium iodide, and the concentration thereof is preferably in the range of 0.01% by mass or more and 10% by mass or less. 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 having more excellent polarizing performance can be obtained.

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

In the method (2) for producing a polarizing film of the present invention, it is necessary to stretch the layered product to 5.7 times or more, preferably 5.8 times or more, and preferably 5.9 times or more. By making the stretch ratio of the laminate in the aforementioned range In the inside, the polarizing film (2) in which the birefringence of the substrate is higher than that of the conventional one and the polarizing performance is good, and the leakage of the red light in the orthogonally polarized state is small can be produced smoothly and simply. The upper limit of the stretching ratio of the laminate is not particularly limited, but preferably 8 times or less. The stretching of the laminate may be carried out once or may be carried out in multiple steps, both of which may be used. However, when the separation is carried out a plurality of times, the total stretching ratio multiplied by the stretching ratio of each stretching may be within the above range. . In addition, the draw ratio in this specification is based on the length of the laminated body before a stretch, and the state which is not extended is equivalent to the draw ratio one time.

The stretching of the laminate is preferably uniaxial stretching from the viewpoint of the performance of the obtained polarizing film. The direction of uniaxial stretching when stretching the long laminated body is not particularly limited, and uniaxial stretching or transverse uniaxial stretching for the longitudinal direction may be employed, but polarized light having better polarizing performance can be obtained. From the viewpoint of the film, it is preferable for uniaxial stretching in the longitudinal direction. The uniaxial stretching in the longitudinal direction can be carried out by using a stretching device having a plurality of rolls parallel to each other and changing the peripheral speed between the rolls. On the other hand, the transverse uniaxial stretching can be carried out using a tenter type stretching machine.

In the description of the fixing treatment and the drying of the method (2) for producing the polarizing film, the respective descriptions of the fixing treatment and the drying in the description column of the method (1) for producing the polarizing film can be used as it is. Repeated records.

By performing the above, a polarizing film (2) formed on the stretched thermoplastic resin film layer can be obtained. The method of using the polarizing film as described above is not particularly limited. For example, the stretched thermoplastic resin film layer may not be peeled off, and it may be optically transparent and mechanically bonded directly or as desired on the polarizing film side. Intensity of protective film as polarized light The plate may be bonded to the side opposite to the side on which the stretched thermoplastic resin film layer is located, and then the stretched thermoplastic resin film layer may be peeled off, and bonded directly or as needed on the peeling surface. Another protective film serves as a polarizing plate. As a protective film, a cellulose triacetate (TAC) film, acetic acid can be used. A cellulose butyrate (CAB) film, an acrylic film, a polyester film, or the like. Further, examples of the adhesive to be bonded include a PVA-based adhesive or a urethane-based adhesive, and a PVA-based adhesive is preferred.

[Examples]

The present invention will be specifically described based on the following examples, but the present invention is not limited to the examples. In addition, each measurement or evaluation method used in the following Reference Examples, Examples, and Comparative Examples is shown below.

[Measurement of Contact Angle of Surface of Thermoplastic Resin Film]

Using a "DropMaster 500" manufactured by Kyowa Interface Science Co., Ltd., 2 μL of pure water was extruded from a needle having an inner diameter of 0.4 mm onto the surface of a thermoplastic resin film at 20 ° C and 65% RH, and the contact angle was measured.

[Measurement of swelling degree of PVA layer]

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

S=100×(A-C)/(B-C) (4)

[Measurement of average polymerization degree of PVA]

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 placed in an interchangeable milled joint conical flask of 100 mL, and the mixture was immersed in a thermostatic chamber at 95 ° C, and dissolved while stirring with a stirrer. PVA was a PVA aqueous solution having a concentration of about 0.4% by mass, which was filtered through a Buchner funnel-shaped glass filter 3G, and cooled in a constant temperature water bath at 30 °C.

[Measurement of Thickness of Polarizing Film (1)]

The thickness of the polarizing film at any position (5 places) was measured using a Digital Gauge ("DE12BR" manufactured by Magn. Co., Ltd.), and the average value thereof was defined as the thickness (1) of the polarizing film.

[Measurement of Birefringence of Substrate]

With respect to the polarizing film obtained in the following Reference Examples, Examples, and Comparative Examples, a retardation value was measured using a cell gap inspection device ("RETS-1100" manufactured by Otsuka Electronics Co., Ltd.) using light having a wavelength of 800 nm and 1,000 nm. The measurement position is set to any five points on a straight line passing through the longitudinal direction of the polarizing film (the direction perpendicular to the direction of the uniaxial stretching, the direction perpendicular to the film surface) in the longitudinal direction (the direction of the uniaxial stretching). . Then, the average value of the five retardation values measured by light having a wavelength of 800 nm is taken as R _{800 of the} above formula (2'), and the average value of the five retardation values measured by light having a wavelength of 1,000 nm is taken as the above formula ( R _{1000 of} 2"), and the simultaneous equations of the above formulas (2'), (3'), (2"), and (3") are solved, and the retardation value of the matrix is determined as A (unit: nm). The birefringence of the substrate is determined by dividing the thickness of the polarizing film (the average value at 5 points and converting the unit into nm) measured by "measurement of the thickness of the polarizing film (2)" described later.

[Measurement of Thickness of Polarizing Film (2)]

The thickness of the polarizing film at the measurement position (5 places) of the measurement of the birefringence of the substrate was measured using a Digital Gauge ("DE12BR" manufactured by Magnescale Co., Ltd.), and the average value thereof was defined as the thickness of the polarizing film ( 2).

[Evaluation of polarized light performance]

(a) Determination of transmittance Ts

In the central portion in the width direction of the polarizing film obtained in the following examples or comparative examples, two samples of a square of 2 cm in the width direction and 2 cm in the longitudinal direction of the polarizing film were used, and a spectrophotometer with an integrating sphere was used (Japan Shikotsu Co., Ltd.) Co., Ltd. "V7100"), according to JIS Z 8722 (measurement method of object color), the C-light source and the visible light field in the visible field of 2° field of view are corrected, and when one piece is sampled, the measurement is inclined at 45° with respect to the longitudinal direction. The transmittance of light and the transmittance of light at a tilt of -45°, and the average value Ts1 (%) of these is obtained. The same was carried out for the other sample, and the transmittance of light at a tilt of 45° and the transmittance of light at an inclination of -45° were measured, and the average value Ts2 (%) of the light was obtained. The average Ts1 and Ts2 are expressed by the following formula (5) as the transmittance Ts (%) of the polarizing film.

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

(b) Determination of the degree of polarization V

The transmittance of light when the longitudinal direction is parallel and overlaps, and the transmittance of light when the length direction is orthogonal and overlaps, is obtained by measuring the transmittance Ts. T⊥ (%) is measured in the same manner as in the case of "(a) measurement of transmittance Ts", and the degree of polarization V (%) is obtained from the following formula (6).

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 of the aqueous solution containing the iodine-based dye was changed from 1 minute to 4 minutes in the range of 1 to 2 minutes, and the same operation was carried out to produce and each of the examples. Or four polarizing films in which the amount of adsorption of the dichroic dye of the polarizing film produced in the comparative example is different. The transmissivity Ts (%) and the degree of polarization V (%) were determined by the above-described methods for each of the four polarizing films, and the transmittance Ts (%) was plotted as the horizontal axis for each of the examples and the comparative examples. The degree of polarization V (%) is taken as the vertical axis, and the transmittance Ts (%) and the degree of polarization V (%) of the polarizing film obtained in each of the examples or the comparative examples are 1 point, and are included in the total of 5 The dot plot is an approximation curve for the graph, and the degree of polarization V ₄₄ (%) when the transmittance Ts (%) is 44% is obtained from the approximation curve.

From the obtained degree of polarization V ₄₄ (%), the dichroic ratio at a transmittance of 44% was obtained from the following formula (7), and was used as an index of the polarizing performance.

The dichroic ratio at 44% transmittance = log(44/100-44/100×V ₄₄ /100)/log (44/100+44/100×V ₄₄ /100) (7)

[Evaluation of Leakage of Red Light in Orthogonal Polarized State]

In each of the following examples and comparative examples, one piece of the polarizing film obtained in each of the examples or the comparative examples and the evaluation of the polarization performance "(c) calculation of the dichroic ratio at a transmittance of 44%" A total of five polarizing films of the obtained polarizing film were measured, and the orthogonal transmittance T ₇₀₀ ⊥ (%) of light having a wavelength of 700 nm was measured. In the samples of the five groups obtained by the evaluation of the polarizing performance, the two samples were vertically overlapped in the longitudinal direction, and a spectrophotometer with an integrating sphere ("V7100" manufactured by JASCO Corporation) was used. The transmittance of light having a wavelength of 700 nm when tilted by 45° with respect to the longitudinal direction of one sample and the transmittance of light having a wavelength of 700 nm at an inclination of -45° were measured, and the average value of these was taken as T ₇₀₀ ⊥ ( %).

Then, the transmittance Ts (%) obtained by the evaluation of the polarizing performance is taken as the vertical axis and the orthogonal transmittance T ₇₀₀ ⊥ (%) of the light having a wavelength of 700 nm as the vertical axis, and the total of 5 points is plotted as a graph. An approximate curve was obtained, and the orthogonal transmittance T ₇₀₀ ⊥ ₄₄ (%) of light having a wavelength of 700 nm when the transmittance Ts (%) was 44% was obtained from the approximate curve. When the T ₇₀₀ ⊥ ₄₄ (%) is low, it is evaluated that there is little leakage of red light.

[Example 1]

(1) Hydrophilization treatment of thermoplastic resin film

An amorphous polyethylene terephthalate film (A-PET sheet FR thickness 150 μm made by Teijin Chemicals Co., Ltd.) was used as the thermoplastic resin film, and the discharge amount was 280 W on one side of the thermoplastic resin film. The corona treatment was performed in minutes/m ² (output 280 W/m, processing speed 1.0 m/min). The contact angle of the surface of the thermoplastic resin film after corona treatment was 60 (the contact angle before corona treatment was 79).

(2) Preparation of stock solution

Preparation of PVA (saponified product of copolymer of vinyl acetate and ethylene) containing an average degree of polymerization of 2,400, a degree of saponification of 99.8 mol%, an ethylene content of 2.5 mol%, and a 1,2-glycol bond amount of 1.6 mol%. The mass fraction, 6 parts by mass of glycerin as a plasticizer, and an aqueous solution having a PVA concentration of 10% by mass of water were used as a stock solution for forming a PVA layer.

(3) Production of laminated body

The raw material prepared in (2) was applied to the corona-treated surface of the thermoplastic resin film subjected to the hydrophilization treatment in (1), and then dried at 80 ° C for 240 seconds to prepare an amorphous poly-containing polymer. A laminate of a two-layer structure of a polyethylene terephthalate film layer and a PVA layer having a thickness of 6 μm (a laminate having a width of 0.5 m). The obtained laminate was subjected to measurement of the degree of swelling of the PVA layer. The results are shown in Table 1.

(4) Manufacture of polarizing film

The layered body produced in (3) was subjected to swelling treatment, dyeing, uniaxial stretching, and drying treatment in this order to produce a polarizing film. That is, the laminate was immersed in distilled water for 1 minute as a swelling treatment. Subsequently, it was immersed in an aqueous solution containing an iodine-based dye (concentration of iodine used: 0.3% by mass, concentration of potassium iodide used: 2.1% by mass, temperature: 30° C.) for 1 minute, and the PVA layer contained an iodine-based dye. Next, in a boric acid aqueous solution (boric acid concentration: 4% by mass, potassium iodide concentration: 6% by mass, temperature: 65 ° C), it was uniaxially stretched in the longitudinal direction to the limit. Further, the film was stretched in the same manner in advance, and the magnification of the fracture was determined, and a magnification of 0.20 times the magnification of the fracture was set as the aforementioned limit. Thereafter, it was dried at 60 ° C for 1 minute to obtain a film formed on the stretched amorphous polyethylene terephthalate film layer. Polarized film. Thus, the stretched amorphous polyethylene terephthalate layer was peeled off, and each of the thickness (1) and the polarizing performance was measured or evaluated for the obtained polarizing film. The results are shown in Table 1 together with the draw ratio employed.

[Examples 2 to 4]

The ethylene content and the 1,2-glycol bond amount of PVA were as shown in Table 1, and a laminate was obtained in the same manner as in Example 1, and the degree of swelling of the PVA layer was measured, and the laminate was produced. A polarizing film (a person who peeled the stretched amorphous polyethylene terephthalate layer) was obtained, and each thickness (1) and polarizing performance was measured or evaluated. The results are shown in Table 1 together with the draw ratio employed.

[Comparative Example 1]

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

[Comparative Example 2]

The ethylene content of the PVA was as shown in Table 1, and the laminate was obtained in the same manner as in Example 1 to obtain a laminate, and the degree of swelling of the PVA layer was measured. Further, in the same manner as in Example 1, when the polarizing film was produced from the laminated body, the dyeing property was poor and the spots were formed. Therefore, only the thickness (1) was measured, and the evaluation of the polarizing performance was not performed. The results are shown in Table 1 together with the draw ratio employed.

In the examples 1 to 4, since the degree of swelling of the PVA layer is in the range of 180% or more and 260% or less, the polarizing property of the polarizing property can be produced regardless of whether or not the impregnation of the boric acid aqueous solution or the insolubilization in the air at high temperature is performed in advance. membrane. On the other hand, in Comparative Example 1, since the degree of swelling of the PVA layer was higher than 260%, the PVA contained in the PVA layer was eluted during the production of the polarizing film, and the polarizing film could not be produced. Further, in Comparative Example 2, the swelling degree of the PVA layer was obtained. Below 180%, it becomes a speckle polarizing film.

[Reference Example 1]

100 parts by mass of PVA (saponified product of vinyl acetate individual polymer) having an average degree of polymerization of 2,400 and a degree of saponification of 99.8 mol%, 12 parts by mass of glycerin as a plasticizer, and an aqueous solution having a water content of 66% by mass. The stock solution was discharged into a film shape from a first drying roll at 95 ° C by a T-die, and dried on the first drying roll until the volatile matter ratio was 22% by mass, and was peeled off from the first drying roll, followed by After drying at a plurality of drying rolls of 80 ° C, heat treatment was performed by a heat treatment roll at 110 ° C to obtain a single-layer PVA film having a thickness of 60 μm (a film having a width of 0.5 m)

The polarizing film was produced by performing the swelling treatment, the dyeing, the uniaxial stretching, and the drying treatment in this order with respect to the PVA film. That is, the PVA film was immersed in water at 30 ° C for 1 minute. Subsequently, the solution was immersed in an aqueous solution containing an iodine-based dye (concentration of iodine used: 0.3% by mass, concentration of potassium iodide used: 2.1% by mass, temperature: 30° C.) for 1 minute, and the PVA layer contained an iodine-based dye. Next, in a boric acid aqueous solution (boric acid concentration: 4% by mass, potassium iodide concentration: 6% by mass, temperature: 55 ° C), it was uniaxially stretched in the longitudinal direction up to the limit. Further, the film was stretched in the same manner in advance, and the magnification of the fracture was determined, and a magnification of 0.20 times the magnification of the fracture was set as the aforementioned limit. Thereafter, it was dried at 60 ° C for 4 minutes to obtain a polarizing film. For the polarizing film, each of the birefringence and the thickness (2) of the substrate was measured. The results are shown in Table 2 together with the draw ratio employed.

[Reference Example 2~4]

A polarizing film was obtained in the same manner as in Reference Example 1 except that PVA having an average degree of polymerization shown in Table 2 (saponification degree: 99.8 mol%, saponified product of a vinyl acetate individual polymer) was used. Measurement of the birefringence and thickness (2) of the substrate. The results are shown in Table 2 together with the draw ratio employed.

As is apparent from Reference Examples 1 to 4, when a polarizing film was produced from a single-layer PVA film, the average degree of polymerization of PVA was increased, and it was found that the ultimate stretching ratio was lowered. Further, in the polarizing film obtained in Reference Examples 1 to 4, the birefringence of the substrate was low.

[Example 5]

(1) Hydrophilization treatment of thermoplastic resin film

An amorphous polyethylene terephthalate film (A-PET sheet FR thickness 150 μm made by Teijin Chemicals Co., Ltd.) was used as the thermoplastic resin film, and the discharge amount was 280 W on one side of the thermoplastic resin film. The corona treatment was performed in minutes/m ² (output 280 W/m, processing speed 1.0 m/min). The contact angle of the surface of the thermoplastic resin film after corona treatment was 60 (the contact angle before corona treatment was 79).

(2) Preparation of stock solution

100 parts by mass of PVA (saponified product of vinyl acetate individual polymer) having an average degree of polymerization of 5,500 and a degree of saponification of 99.8 mol%, 12 parts by mass of glycerin as a plasticizer, and an aqueous solution having a PVA concentration of 5 mass% in water were prepared. And as a stock solution for forming a PVA layer.

(3) Production of laminated body

The raw material prepared in (2) was applied to the corona-treated surface of the thermoplastic resin film subjected to the hydrophilization treatment in (1), and then dried at 80 ° C for 240 seconds to prepare an amorphous poly-containing polymer. A laminate of a two-layer structure of a polyethylene terephthalate film layer and a PVA layer having a thickness of 6 μm (a laminate having a width of 0.5 m).

(4) Manufacture of polarizing film

In the layered body produced in (3), the polarizing film was produced by insolubilizing, dyeing, uniaxially stretching, and drying the PVA layer in this order. In other words, the laminate was immersed in a boric acid aqueous solution (concentration: 3% by mass, temperature: 30 ° C) for 1 minute as an insolubilization treatment of the PVA layer. Subsequently, the solution was immersed in an aqueous solution containing an iodine-based dye (concentration of iodine used: 0.3% by mass, concentration of potassium iodide used: 2.1% by mass, temperature: 30° C.) for 1 minute, and the PVA layer contained an iodine-based dye. Next, in a boric acid aqueous solution (boric acid concentration: 4% by mass, potassium iodide concentration: 6% by mass, temperature: 65 ° C), it was uniaxially stretched in the longitudinal direction to the limit. Further, the film was stretched in the same manner in advance, and the magnification of the fracture was determined, and a magnification of 0.20 times the magnification of the fracture was set as the aforementioned limit. Thereafter, it was dried at 60 ° C for 1 minute to obtain a polarizing film formed on the stretched amorphous polyethylene terephthalate film layer. Thereby, the stretched amorphous polyethylene terephthalate layer is peeled off, and the obtained polarizing film is subjected to a birefringence of the substrate, a thickness (2), a polarizing property, and a red light leakage in a state of orthogonal polarization. Each measurement or evaluation. The results are shown in Table 3 together with the draw ratio employed.

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

The average degree of polymerization and the glycerin content of PVA (saponification degree: 99.8 mol%, saponified product of a vinyl acetate individual polymer) were the same as in Example 5 except that the average degree of polymerization and the glycerin content were as shown in Table 3, and polarized light was obtained. Film (desorbed from the stretched amorphous polyethylene terephthalate layer), and the measurement of the birefringence, thickness (2), polarization performance, and red light leakage in the orthogonal polarization state of the substrate Or evaluation. The results are shown in Table 3 together with the draw ratio employed.

[Comparative Examples 8 and 9]

The average degree of polymerization and the content of glycerin of PVA (saponification degree: 99.8 mol%, saponified product of vinyl acetate alone) were as shown in Table 3, and the draw ratio of the laminate was set to 5.00 times. In the same manner as in Example 5, a polarizing film (a peeled amorphous amorphous polyethylene terephthalate layer) was obtained, and the birefringence, thickness (2), and polarizing properties of the substrate were obtained. And measurement or evaluation of leakage of red light in a state of orthogonal polarization. The results are shown in Table 3 together with the draw ratio employed.

In the polarizing film obtained in Examples 5 to 14, the birefringence of the substrate was high, and as described above, it was found that the dichroic ratio was large and the polarizing property was good, and the value of T ₇₀₀ ⊥ ₄₄ was small and The red light in the orthogonal polarization state has less leakage. On the other hand, in the polarizing film obtained in Comparative Examples 3 to 9, it was found that the birefringence of the substrate was low, the value of the dichroic ratio was small, and the polarizing performance was poor, and the value of T ₇₀₀ ⊥ ₄₄ was large and the orthogonal polarization was observed. The red light of the state leaks more.

[Industrial use]

According to the layered product (1) of the present invention and the method (1) for producing a polarizing film using the same, even if the insolubilization treatment of the boric acid aqueous solution or the high-temperature stretching in the air is not performed in advance, the polarizing film such as dyeing is produced. In the step of contacting the water, the elution of the PVA contained in the PVA layer can be suppressed. Therefore, the insolubilization treatment which is complicated in operation and requires special manufacturing equipment can be omitted, whereby the polarizing film manufacturing apparatus can be used to easily produce polarized light. A polarizing film with good performance. Further, the polarizing film (2) of the present invention has excellent polarizing performance and at the same time has less leakage of red light in the orthogonally polarized state. Further, according to the method (2) for producing a polarizing film of the present invention, it is possible to smoothly and easily produce the polarizing film (2) which is excellent in polarizing performance and which has little leakage of red light in a state of orthogonal polarization.

Claims (9)

A polarizing film which adsorbs a dichroic dye to a substrate having a birefringence of 45 × 10 ^-3 or more. The polarizing film of claim 1, wherein the substrate comprises polyvinyl alcohol and has an average degree of polymerization of 2,800 or more and 9,500 or less. The polarizing film of claim 1, wherein the substrate comprises polyvinyl alcohol and has an average degree of polymerization of from 4,100 to 9,500. The polarizing film according to any one of claims 1 to 3, which has a thickness of 10 μm or less. A method for producing a polarizing film according to any one of claims 1 to 4, which comprises a method for producing a polarizing film comprising the step of stretching a laminate having a thermoplastic resin film layer and a polyvinyl alcohol layer to 5.7 times or more The polyvinyl alcohol contained in the polyvinyl alcohol layer has an average degree of polymerization of 2,800 or more and 9,500 or less. The production method of claim 5, wherein the polyvinyl alcohol has an average degree of polymerization of 4,100 or more and 9,500 or less. The production method of claim 5, wherein the polyvinyl alcohol layer contains 1 part by mass or more and 15 parts by mass or less of the plasticizer based on 100 parts by mass of the polyvinyl alcohol. The production method of claim 5, wherein the polyvinyl alcohol layer contains 4 parts by mass or more and 12 parts by mass or less of the plasticizer based on 100 parts by mass of the polyvinyl alcohol. The method of manufacturing of claim 7 or 8, wherein the plasticizer is glycerin.