WO2021054346A1

WO2021054346A1 - Method for manufacturing polarizing membrane, and method for manufacturing polarizing film

Info

Publication number: WO2021054346A1
Application number: PCT/JP2020/035001
Authority: WO
Inventors: 拓馬黒田; 山下　智弘; 汐海八木; 勝則高田; 真宮崎
Original assignee: 日東電工株式会社
Priority date: 2019-09-20
Filing date: 2020-09-16
Publication date: 2021-03-25
Also published as: CN114126820A; KR20220063119A

Abstract

Provided is a method for manufacturing a polarizing membrane, the method comprising: a step (I-1) for at least dyeing, cross-linking, and stretching a polyvinyl alcohol-based film while conveying the polyvinyl alcohol-based film in the longitudinal direction, to produce a water-containing polarizing membrane; a step (I-2) for applying a liquid to the obtained water-containing polarizing membrane in a state in which the water content in the polarizing membrane is at least 20 wt%, to produce a polarizing membrane which is impregnated with components in the liquid; and a step (I-3) for drying the obtained polarizing membrane which is impregnated with components in the liquid to produce a dried polarizing membrane. The method for manufacturing a polarizing membrane according to the present invention permits an arbitrary component to be easily and sufficiently contained in the polarizing membrane.

Description

Method for manufacturing polarizing film and method for manufacturing polarizing film

The present invention relates to a method for producing a polarizing film and a method for producing a polarizing film.

Conventionally, the polarizing film (polarizer) used in various image display devices such as liquid crystal display devices and organic EL display devices has high transmittance and high degree of polarization, and therefore has been dyed (iodine or dichroism). A polyvinyl alcohol-based film (containing a dichroic substance such as a sex dye) is used. The polarizing film is produced by subjecting a polyvinyl alcohol-based film to various treatments such as dyeing, cross-linking, and stretching in a bath (treatment bath) and then drying. Further, the polarizing film is usually used as a polarizing film (polarizing plate) in which a protective film such as triacetyl cellulose is bonded to one side or both sides thereof using an adhesive.

As a method for producing a polarizing film, for example, in Patent Documents 1 and 2, by adding a component such as a metal salt containing zinc, copper, aluminum, etc. to a treatment bath, the polarizing film is made to contain these components, and the polarizing film is contained. It is disclosed to improve the durability characteristics of. Further, Patent Documents 3 to 4 disclose a method for producing a polarizing film in which a component such as an organic titanium compound is added to a treatment bath.

International Publication No. 2016/1176559 Japanese Unexamined Patent Publication No. 2006-047978 Japanese Unexamined Patent Publication No. 2008-46257 Japanese Unexamined Patent Publication No. 6-172554

However, in the method for producing a polarizing film, when the above-mentioned components are added to the treatment bath, there are problems such as an enormous amount of the components used and the need for waste treatment of the treatment liquid.

In view of the above circumstances, an object of the present invention is to provide a method for producing a polarizing film, which can easily and sufficiently contain an arbitrary component in the polarizing film.

Another object of the present invention is to provide a method for producing a polarizing film using the polarizing film obtained by the above method for producing a polarizing film.

That is, the present invention is a method for producing a polarizing film, in which the polyvinyl alcohol-based film is subjected to at least a dyeing step, a cross-linking step, and a stretching step while transporting the polyvinyl alcohol-based film in the longitudinal direction to obtain water. (I-1), and a step of applying a liquid to the obtained polarizing film containing water while the water content of the polarizing film is 20% by weight or more. , A step (I-2) of producing a polarizing film impregnated with components in the liquid and a drying step are performed on the obtained polarizing film impregnated with the components in the liquid to produce a dried polarizing film. The present invention relates to a method for producing a polarizing film, which comprises the step (I-3).

Further, the present invention is a method for producing a polarizing film, in which a polyvinyl alcohol-based resin layer containing a polyvinyl alcohol-based resin is formed on one side of a long thermoplastic resin base material to prepare a laminate (a step of preparing a laminate). While transporting II-0) and the obtained laminate in the longitudinal direction, the laminate is subjected to at least an aerial auxiliary stretching treatment step, a dyeing treatment step, and an underwater stretching treatment step to carry out polarization containing water. A liquid is applied to the step (II-1) of manufacturing a laminate having a film and the obtained laminate having a polarizing film containing water in a state where the water content of the polarizing film is 20% by weight or more. A step (II-2) of performing a step to produce a laminate having a polarizing film impregnated with components in the liquid and drying the laminate having a polarizing film impregnated with the components in the obtained liquid. The present invention relates to a method for producing a polarizing film, which comprises a step (II-3) of performing a treatment step to produce a polarizing film after drying.

The present invention also relates to a method for producing a polarizing film, which comprises a step of attaching a transparent protective film to at least one surface of the polarizing film obtained by the method for producing a polarizing film via an adhesive layer.

The details of the working mechanism of the effect in the method for producing the polarizing film of the present invention are unknown, but it is presumed as follows. However, the present invention does not have to be construed as being limited to this mechanism of action.

In the method for producing a polarizing film of the present invention, while transporting a polyvinyl alcohol-based film in the longitudinal direction, the polyvinyl alcohol-based film is subjected to at least a dyeing step, a cross-linking step, and a stretching step to contain a water-containing polarizing film. (I-1) and a step of applying a liquid to the obtained polarizing film containing water in a state where the water content of the polarizing film is 20% by weight or more, and the components in the liquid are applied. (I-2) and a step of subjecting the obtained polarizing film impregnated with the components in the liquid to a drying step to produce a dried polarizing film (I-). 3) is included. Alternatively, the method for producing a polarizing film of the present invention is a step of forming a polyvinyl alcohol-based resin layer containing a polyvinyl alcohol-based resin on one side of a long thermoplastic resin base material to prepare a laminate (II-0). ), While transporting the obtained laminate in the longitudinal direction, the laminate is subjected to at least an aerial auxiliary stretching treatment step, a dyeing treatment step, and an underwater stretching treatment step to have a water-containing polarizing film. A step of manufacturing a laminate (II-1) and a step of applying a liquid to the obtained laminate having a polarizing film containing water in a state where the water content of the polarizing film is 20% by weight or more are performed. Then, a step (II-2) of producing a laminate having a polarizing film impregnated with components in the liquid and a drying treatment step are performed on the obtained laminate having a polarizing film impregnated with the components in the liquid. This includes a step (II-3) of producing a polarizing film after application and drying. In the conventional method for producing a polarizing film, a polyvinyl alcohol-based film is subjected to at least a dyeing step, a cross-linking step, and a stretching step, followed by a drying step. Alternatively, in the conventional method for producing a polarizing film, a step of forming a polyvinyl alcohol-based resin layer containing a polyvinyl alcohol-based resin on one side of a long thermoplastic resin base material to prepare a laminate was obtained. The laminate is subjected to at least an aerial auxiliary stretching treatment step, a dyeing treatment step, and an underwater stretching treatment step, followed by a drying treatment step. On the other hand, in the method for producing a polarizing film of the present invention, as described above, a polarizing film containing water or a laminate having a polarizing film containing water is produced. The polarizing film in the water-containing polarizing film or the laminated body having the water-containing polarizing film is subjected to a step of applying a liquid in a state where the water content of the polarizing film is 20% by weight or more. The water-containing polarizing film can be easily and sufficiently impregnated with any component contained in the liquid.

<Manufacturing method of polarizing film>
In the method for producing a polarizing film of the present invention, while transporting a polyvinyl alcohol-based film in the longitudinal direction, the polyvinyl alcohol-based film is subjected to at least a dyeing step, a cross-linking step, and a stretching step to contain a water-containing polarizing film. (I-1) and a step of applying a liquid to the obtained polarizing film containing water in a state where the water content of the polarizing film is 20% by weight or more, and the components in the liquid are applied. (I-2) and a step of subjecting the obtained polarizing film impregnated with the components in the liquid to a drying step to produce a dried polarizing film (I-). 3) is included.

<Step of manufacturing a polarizing film containing water (I-1)>
In the method for producing a polarizing film of the present invention, while transporting a polyvinyl alcohol-based film in the longitudinal direction, the polyvinyl alcohol-based film is subjected to at least a dyeing step, a cross-linking step, and a stretching step to contain a water-containing polarizing film. (I-1) is included.

The polyvinyl alcohol (PVA) -based film has translucency in the visible light region, and can be used without particular limitation if it disperses and adsorbs a dichroic substance such as iodine or a dichroic dye. Further, the PVA-based film usually used as a raw material preferably has a thickness of about 1 to 100 μm, more preferably about 1 to 50 μm, and preferably a width of about 100 to 5000 mm.

Examples of the material of the polyvinyl alcohol-based film include polyvinyl alcohol or a derivative thereof. Examples of the polyvinyl alcohol derivative include polyvinyl formal, polyvinyl acetal; olefins such as ethylene and propylene; unsaturated carboxylic acids such as acrylic acid, methacrylic acid and crotonic acid, and alkyl esters and acrylamides thereof. Can be mentioned. The polyvinyl alcohol preferably has an average degree of polymerization of about 100 to 10,000, more preferably about 1,000 to 10,000, and even more preferably about 1,500 to 4,500. .. Further, the polyvinyl alcohol preferably has a saponification degree of about 80 to 100 mol%, and more preferably about 95 mol% to 99.95 mol. The average degree of polymerization and the degree of saponification can be determined according to JIS K 6726.

The polyvinyl alcohol-based film may contain additives such as a plasticizer and a surfactant. Examples of the plasticizer include polyols such as glycerin, diglycerin, triglycerin, ethylene glycol, propylene glycol, and polyethylene glycol, and condensates thereof. The amount of the additive used is not particularly limited, but is preferably about 20% by weight or less in the polyvinyl alcohol-based film, for example.

<Dyeing process>
The dyeing step is a treatment step of immersing the polyvinyl alcohol-based film in a dyeing bath, and a dichroic substance such as iodine or a dichroic dye can be adsorbed and oriented on the polyvinyl alcohol-based film. The staining solution is usually preferably an aqueous iodine solution and contains iodine and iodide as a solubilizing agent. The iodide includes potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and iodide. Examples include titanium. Among these, potassium iodide is preferable.

In the dyeing bath, the iodine concentration is preferably about 0.01 to 1% by weight, more preferably about 0.02 to 0.5% by weight. In the dyeing bath, the concentration of the iodide is preferably about 0.01 to 10% by weight, more preferably about 0.05 to 5% by weight.

The temperature of the dyeing bath is preferably about 10 to 50 ° C, more preferably about 15 to 45 ° C. The immersion time in the dyeing bath cannot be unconditionally determined because the degree of dyeing of the polyvinyl alcohol-based film is affected by the temperature of the dyeing bath, but is preferably about 10 to 300 seconds, preferably 20 to 240 seconds. More preferably. The dyeing step may be carried out only once, or may be carried out a plurality of times as needed.

<Crosslinking process>
The cross-linking step is a treatment step of immersing the polyvinyl alcohol-based film dyed in the dyeing step in a treatment bath (cross-linking bath) containing a boron compound, and the polyvinyl alcohol-based film is cross-linked by the boron compound. Iodine molecules or dye molecules can be adsorbed on the crosslinked structure. Examples of the boron compound include boric acid, borate, borax and the like. The crosslinked bath is generally an aqueous solution, but may be, for example, a mixed solution of an organic solvent and water that is miscible with water. In addition, the cross-linked bath can contain iodide such as potassium iodide.

In the crosslinked bath, the concentration of the boron compound is preferably about 1 to 15% by weight, more preferably about 1.5 to 10% by weight, and more preferably about 2 to 5% by weight. preferable. When an iodide such as potassium iodide is used in the cross-linking bath, the concentration of the iodide such as potassium iodide in the cross-linking bath is preferably about 1 to 15% by weight, preferably 1.5 to 15% by weight. It is more preferably about 10% by weight.

The temperature of the crosslinked bath is preferably about 20 to 70 ° C, more preferably about 30 to 60 ° C. The immersion time in the cross-linking bath cannot be unconditionally determined because the degree of cross-linking of the polyvinyl alcohol-based film is affected by the temperature of the cross-linking bath, but is preferably about 5 to 300 seconds, preferably 10 to 200 seconds. More preferably. The cross-linking step may be carried out only once, or may be carried out a plurality of times as needed.

<Stretching process>
The stretching step is a treatment step of stretching a polyvinyl alcohol-based film to a predetermined magnification in at least one direction. Generally, the polyvinyl alcohol-based film is uniaxially stretched in the transport direction (longitudinal direction). The stretching method is not particularly limited, and either a wet stretching method or a dry stretching method can be adopted. The stretching step may be carried out only once, or may be carried out a plurality of times as needed. The stretching step may be performed at any stage in the production of the polarizing film.

As the treatment bath (stretching bath) in the wet stretching method, a solvent such as water or an organic solvent miscible with water and a mixed solution of water can be usually used. The stretching bath can contain iodide such as potassium iodide. When iodide such as potassium iodide is used in the stretching bath, the concentration of iodide such as potassium iodide in the stretching bath is preferably about 1 to 15% by weight, preferably about 2 to 10% by weight. Is more preferable. Further, the treatment bath (stretching bath) can contain the boron compound in order to improve the degree of cross-linking. In this case, the concentration of the boron compound in the stretching bath is about 1 to 15% by weight. It is preferably present, and more preferably about 1.5 to 10% by weight.

The temperature of the stretching bath is preferably about 25 to 80 ° C, more preferably about 40 to 75 ° C. The immersion time in the stretching bath cannot be unconditionally determined because the degree of stretching of the polyvinyl alcohol-based film is affected by the temperature of the stretching bath, but is preferably about 10 to 800 seconds, preferably 30 to 500 seconds. More preferably. The stretching treatment in the wet stretching method may be performed together with any one or more of the dyeing step, the cross-linking step, the swelling step described later, and the washing step described later.

Examples of the dry stretching method include an inter-roll stretching method, a heating roll stretching method, and a compression stretching method. The dry stretching method may be performed together with the drying step described later.

The total draw ratio (cumulative draw ratio) applied to the polyvinyl alcohol-based film can be appropriately set depending on the intended purpose, but is preferably about 2 to 7 times, and preferably about 3 to 6.8 times. More preferably, it is more preferably about 3.5 to 6.5 times.

In the step of producing the water-containing polarizing film, the polyvinyl alcohol-based film may be subjected to the dyeing step, the cross-linking step, the stretching step, a swelling step, or a washing step. Good.

<Swelling process>
The swelling step is a treatment step of immersing the polyvinyl alcohol-based film in a swelling bath, and can remove stains and blocking agents on the surface of the polyvinyl alcohol-based film, and dyes the polyvinyl alcohol-based film by swelling it. Unevenness can be suppressed. As the swelling bath, a medium containing water as a main component, such as water, distilled water, and pure water, is usually used. A surfactant, alcohol, or the like may be appropriately added to the swelling bath according to a conventional method.

The temperature of the swelling bath is preferably about 10 to 60 ° C, more preferably about 15 to 45 ° C. The immersion time in the swelling bath cannot be unconditionally determined because the degree of swelling of the polyvinyl alcohol-based film is affected by the temperature of the swelling bath, but is preferably about 5 to 300 seconds, preferably 10 to 200 seconds. More preferably. The swelling step may be carried out only once, or may be carried out a plurality of times as needed.

<Washing process>
The cleaning step is a treatment step of immersing the polyvinyl alcohol-based film in a washing bath, and can remove foreign substances remaining on the surface of the polyvinyl alcohol-based film or the like. As the washing bath, a medium containing water as a main component, such as water, distilled water, and pure water, is usually used. Further, iodide such as potassium iodide can be used in the washing bath, and in this case, the concentration of iodide such as potassium iodide in the washing bath is preferably about 1 to 10% by weight. It is more preferably about 2 to 4% by weight, and further preferably about 1.6 to 3.8% by weight.

The temperature of the washing bath is preferably about 5 to 50 ° C, more preferably about 10 to 40 ° C, and even more preferably about 15 to 30 ° C. The immersion time in the washing bath cannot be unconditionally determined because the degree of washing of the polyvinyl alcohol-based film is affected by the temperature of the washing bath, but is preferably about 1 to 100 seconds, preferably 2 to 50 seconds. It is more preferably about 3 to 20 seconds. The swelling step may be carried out only once, or may be carried out a plurality of times as needed.

Further, each treatment bath in the swelling step, the dyeing step, the cross-linking step, the stretching step and the washing step contains an additive such as a zinc salt, a pH adjuster, a pH buffer, and other salts. You may. Examples of the zinc salt include zinc halides such as zinc chloride and zinc iodide; and inorganic zinc salts such as zinc sulfate and zinc acetate. Examples of the pH adjuster include strong acids such as hydrochloric acid, sulfuric acid and nitric acid, and strong bases such as sodium hydroxide and potassium hydroxide. Examples of the pH buffer include carboxylic acids such as acetic acid, oxalic acid and citric acid and salts thereof, and inorganic weak acids such as phosphoric acid and carbonic acid and salts thereof. Examples of the other salts include chlorides such as sodium chloride, potassium chloride and barium chloride, nitrates such as sodium nitrate and potassium nitrate, sulfates such as sodium sulfate and potassium sulfate, and alkali metals and alkaline earth metals. Examples include salt.

<Step of manufacturing a polarizing film impregnated with components in a liquid (I-2)>
In the method for producing a polarizing film of the present invention, a step of applying a liquid to the water-containing polarizing film obtained above in a state where the water content of the polarizing film is 20% by weight or more is performed in the liquid. The step (I-2) of producing a polarizing film impregnated with components is included. Here, the component in the liquid is usually a solute contained in the solution. The solute may be a substance that can be dissolved or dispersed in a solvent, and the simple substance may be a gaseous substance, a liquid substance, or a solid substance. When the solute is a liquid substance (for example, under the conditions of 25 ° C. and 1 atm), the liquid substance itself (the liquid substance itself) may be a liquid or a component in the liquid.

In the step (I-2), the water content of the polarizing film is 22% by weight or more from the viewpoint of easily impregnating the components contained in the liquid and making it easier to penetrate the polarizing film in the thickness direction. It is more preferable that the water content of the polarizing film is 25% by weight or more, and from the viewpoint of preventing wrinkles during transportation, the water content of the polarizing film is 70% by weight or less. It is preferably in a state, and more preferably in a state where the water content of the polarizing film is 60% by weight or less.

As the coating (coating) method in the step of applying the liquid, the conventional coating (coating) method can be applied, for example, a roll coating method, a spin coating method, a wire bar coating method, a dip coating method, a die coating method, and the like. Examples thereof include a coating method such as a curtain coating method, a spray coating method, and a knife coating method (comma coating method, etc.). The coating surface of the polarizing film may be one side or both sides.

The component in the liquid may be a water-soluble compound from the viewpoint of easily impregnating the component into the water-containing polarizing film. The above-mentioned water-soluble compound is said to have a solubility in 100 g of water at 25 ° C. of 1 g or more.

Examples of the components in the liquid include zinc salts (zinc halides such as zinc chloride and zinc iodide; inorganic zinc salts such as zinc sulfate and zinc acetate); and organic titanium compounds (titanium alkoxide, titanium chelate, titanium chelate). Ammonium salt, titanium chelate acylate, etc.), organic zirconium (zirconyl alkoxide, zirconyl chelate, zirconyl chelate ammonium salt, zirconyl acylate), alkali metal salt, alkaline earth metal salt, metal halide and the like.

Further, as the component in the liquid, a compound having a radical scavenging function (also referred to as a radical scavenger) can be mentioned. Since the compound having a radical scavenging function can capture radicals generated by heating by polyvinyl alcohol in the polarizing film and suppress polyene formation, the durability of the polarizing film against heat can be improved. The compound having a radical scavenging function is preferably, for example, a nitroxy radical or a compound having a nitroxide group from the viewpoint of easily suppressing polyene formation.

Examples of the compound having a nitroxyl radical or a nitroxide group include a compound having an organic group having the following structure.

(In the general formula (1), R ¹ represents an oxy radical, R ² to R ⁵ independently represent a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, and n is 0 or 1. In addition, in the general formula (1), the left side of the dotted line part shows an arbitrary organic group.

Examples of the compound having an organic group include compounds represented by the following general formulas (2) to (5).

(In the general formula (2), R ¹ to R ⁵ and n are the same as above, and R ⁶ represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, an acyl group, or an aryl group. .)

(In the general formula (3), R ¹ to R ⁵ and n are the same as above, and R ⁷ and R ⁸ are independently hydrogen atoms or alkyl groups having 1 to 10 carbon atoms. Represents an acyl group or an aryl group.)

(In the general formula (4), R ¹ to R ⁵ and n are the same as described above, and R ⁹ to R ¹¹ are independently hydrogen atoms or alkyl groups having 1 to 10 carbon atoms. Represents an acyl group, an amino group, an alkoxy group, a hydroxy group, or an aryl group.)

(In the general formula (5), R ¹ to R ⁵ and n are the same as above, and R ¹² is a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, an amino group, an alkoxy group and a hydroxy group. Represents a group or an aryl group.)

In the general formulas (1) to (5), R ² to R ⁵ are preferably alkyl groups having 1 to 6 carbon atoms and having 1 to 3 carbon atoms from the viewpoint of availability. It is more preferably an alkyl group. Further, in the general formula (2), from the viewpoint of availability, R ⁶ is preferably a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, and more preferably a hydrogen atom. Further, in the general formula (3), from the viewpoint of availability, R ⁷ and R ⁸ are preferably hydrogen atoms independently or alkyl groups having 1 to 10 carbon atoms, and are hydrogen atoms. Is more preferable. Further, in the general formula (4), from the viewpoint of availability, R ⁹ to R ¹¹ are preferably hydrogen atoms or alkyl groups having 1 to 10 carbon atoms. Further, in the general formula (5), from the viewpoint of availability, R ¹² is preferably a hydroxy group, an amino group, or an alkoxy group. In the general formulas (1) to (5), n is preferably 1 from the viewpoint of availability.

Examples of the compound having a nitroxyl radical or a nitroxide group include the following compounds.

(In the general formula (6), R represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, an acyl group, or an aryl group.)

Further, as the component in the liquid, a compound having a cross-linking function (also referred to as a cross-linking agent) can be mentioned. The compound having a cross-linking function can react with the hydroxyl group of polyvinyl alcohol of the polarizing film to form a cross-linked structure and improve the durability of the polarizing film against humidification. Examples of the compound having a cross-linking function include organic compounds having an isocyanate group, an isocyanate-induced functional group, an epoxy group, a carbonyl group, an aziridine ring, a vinyl ether group, a vinyl sulfone group, and an oxazoline group from the viewpoint of improving humidification durability. Other examples include organic titanium compounds (titanium alkoxide, titanium chelate, titanium chelate ammonium salt, titanium chelate acylate, etc.).

Further, as the component in the liquid, a compound having a function of imparting plasticity (also referred to as a plasticizer) can be mentioned. By imparting plasticity to the polarizing film, the compound having the function of imparting plasticity can reduce quality defects such as dents caused by the pushing force. Examples of the compound having the function of imparting plasticity include ethylene glycol, polyethylene glycol, other ethylene glycol derivatives, and glycerin.

Further, as the component in the liquid, a dye-based compound (also referred to as a dye) can be mentioned. The dye-based compound can impart characteristics such as hue adjustment of a polarizing film and pattern printing. Examples of the dye-based compound include azo compounds, anthraquinone-based compounds, and quinophthalone-based compounds.

The liquid cannot be unconditionally determined because it is affected by the above coating type, but from the viewpoint of efficiently permeating the components in the liquid, the concentration of the components in the liquid is 0.1% by weight or more. It is preferably 1.0% by weight or more, and from the viewpoint of preventing quality defects due to precipitation of components in the liquid, it is preferably 30% by weight or less, and 20% by weight or less. Is more preferable.

Examples of the solvent include water; water-soluble solvents such as methanol, ethanol, ethylene glycol, polyethylene glycol, other ethylene glycol derivatives, glycerin, and dimethyl sulfoxide.

The time from the step (I-1) to the start of the step (I-2) (transportation time of the polarizing film in the actual manufacturing) is from the viewpoint of retaining the water contained in the polarizing film containing water, or From the viewpoint of productivity, the temperature is about 15 ° C. to 35 ° C., preferably the temperature is about 20 ° C. to 30 ° C., preferably 300 seconds or less, more preferably 180 seconds or less, and 60 seconds or less. It is more preferably present, and even more preferably 10 seconds or less.

Further, in the step (I-2), if necessary, the polarizing film containing water is subjected to a step of applying a liquid, and then a part of the liquid is impregnated to remove the remaining liquid. The process may be performed. Examples of the liquid removing method include a wiping removal method using a waste cloth or a sponge roll, a suction removal method, a removal method by blowing air, a scraping removal method using a bar or a gravure roll, and the like.

<Step of manufacturing a polarizing film after drying (I-3)>
The method for producing a polarizing film of the present invention includes a step (I-3) of subjecting a polarizing film impregnated with components in the liquid obtained above to a drying step to produce a dried polarizing film.

The drying step is a step of drying the polarizing film impregnated with the components in the liquid obtained above to obtain a polarizing film, and drying obtains a polarizing film having a desired moisture content. The drying is carried out by any suitable method, and examples thereof include natural drying, blast drying, and heat drying.

The drying temperature is preferably about 20 to 150 ° C, more preferably about 25 to 100 ° C. Further, the drying time cannot be unconditionally determined because the degree of drying of the polarizing film is affected by the drying temperature, but is preferably about 10 to 600 seconds, more preferably about 30 to 300 seconds. preferable. The drying step may be carried out only once, or may be carried out a plurality of times as needed.

The moisture content of the dried polarizing film is preferably 10% by weight or more, more preferably 12% by weight or more, from the viewpoint of preventing quality defects such as dents due to loss of plasticity. It is preferable, and from the viewpoint of improving optical characteristics such as the degree of polarization, the water content is preferably 20% by weight or less, and more preferably 16% by weight or less. In the case of the dried polarizing film having a thickness of about 8 μm or less, which will be described later, the dried polarizing film has a moisture content of 2 from the viewpoint of preventing quality defects such as dents due to loss of plasticity. It is preferably 20% by weight or more, more preferably 3% by weight or more, and from the viewpoint of improving optical characteristics such as the degree of polarization, the water content is preferably 20% by weight or less, preferably 10% by weight. More preferably, it is less than%.

The thickness of the dried polarizing film is preferably about 1 to 30 μm, more preferably about 5 to 25 μm, and even more preferably 5 to 20 μm. In particular, in order to obtain a dried polarizing film having a thickness of about 8 μm or less, a laminate containing a polyvinyl alcohol-based resin layer formed on a thermoplastic resin base material is used as the polyvinyl alcohol-based film. The method for producing a thin polarizing film is applicable.

<Manufacturing method of polarizing film (thin polarizing film)>
The method for manufacturing a polarizing film (thin polarizing film) is a step of forming a polyvinyl alcohol-based resin layer containing a polyvinyl alcohol-based resin on one side of a long thermoplastic resin base material to prepare a laminate (II-. 0), while transporting the obtained laminate in the longitudinal direction, the laminate is subjected to at least an aerial auxiliary stretching treatment step, a dyeing treatment step, and an underwater stretching treatment step to obtain a water-containing polarizing film. A step of manufacturing the laminated body having the same (II-1) and a step of applying a liquid to the obtained laminated body having the polarizing film containing water in a state where the water content of the polarizing film is 20% by weight or more. A step (II-2) of producing a laminate having a polarizing film impregnated with a component in the liquid, and a drying treatment step on the obtained laminate having a polarizing film impregnated with a component in the liquid. (II-3) is included in the process of producing a polarizing film after drying.

<Step of preparing the laminate (II-0)>
The method for producing a polarizing film (thin polarizing film) of the present invention is a polyvinyl alcohol-based resin layer (PVA-based resin layer) containing a polyvinyl alcohol-based resin (PVA-based resin) on one side of a long thermoplastic resin base material. ) Is formed to prepare a laminate (II-0).

Any suitable method is adopted as the method for producing the laminate. For example, a method of applying a coating liquid containing the PVA-based resin to the surface of the thermoplastic resin base material and drying the laminate can be mentioned. Be done. The thickness of the thermoplastic resin base material is preferably about 20 to 300 μm, more preferably about 50 to 200 μm. The thickness of the PVA-based resin layer is preferably about 3 to 40 μm, more preferably about 3 to 20 μm.

The thermoplastic resin base material preferably has a water absorption rate of about 0.2% or more, preferably 0.3, from the viewpoint of absorbing water, significantly reducing the stretching stress, and being able to stretch at a high magnification. More preferably, it is about% or more. On the other hand, the thermoplastic resin base material has a water absorption rate of 3 from the viewpoint that the dimensional stability of the thermoplastic resin base material is remarkably lowered and problems such as deterioration of the appearance of the obtained polarizing film can be prevented. It is preferably about% or less, and more preferably about 1% or less. The water absorption rate can be adjusted, for example, by introducing a modifying group into the constituent material of the thermoplastic resin base material. The water absorption rate is a value obtained according to JIS K 7209.

The thermoplastic resin base material has a glass transition temperature (Tg) of about 120 ° C. or less from the viewpoint of being able to sufficiently secure the stretchability of the laminate while suppressing the crystallization of the PVA-based resin layer. Is preferable. Further, in consideration of plasticizing the thermoplastic resin base material with water and satisfactorily stretching in water, the glass transition temperature (Tg) is more preferably about 100 ° C. or lower, and more preferably about 90 ° C. or lower. Is even more preferable. On the other hand, the glass transition temperature of the thermoplastic resin base material is a viewpoint that a good laminate can be produced by preventing problems such as deformation of the thermoplastic resin base material when the coating liquid is applied and dried. Therefore, it is preferably about 60 ° C. or higher. The glass transition temperature can be adjusted, for example, by introducing a modifying group into the constituent material of the thermoplastic resin base material or heating with a crystallization material. The glass transition temperature (Tg) is a value obtained according to JIS K7121.

Any suitable thermoplastic resin can be adopted as the constituent material of the thermoplastic resin base material. Examples of the thermoplastic resin include ester resins such as polyethylene terephthalate resins, cycloolefin resins such as norbornene resins, olefin resins such as polypropylene, polyamide resins, polycarbonate resins, and copolymer resins thereof. And so on. Among these, norbornene-based resin and amorphous (amorphous) polyethylene terephthalate-based resin are preferable, and further, the thermoplastic resin base material is extremely excellent in stretchability and crystallization during stretching can be suppressed. , Amorphous (amorphous) polyethylene terephthalate resin is preferably used. Examples of the amorphous (amorphous) polyethylene terephthalate resin include a copolymer containing isophthalic acid and / or cyclohexanedicarboxylic acid as a dicarboxylic acid, and a copolymer containing cyclohexanedimethanol or diethylene glycol as a glycol.

The thermoplastic resin base material may be surface-treated (for example, corona treatment or the like) before forming the PVA-based resin layer, or the easy-adhesion layer may be formed on the thermoplastic resin base material. .. By performing such a treatment, the adhesion between the thermoplastic resin base material and the PVA-based resin layer can be improved. Further, the thermoplastic resin base material may be stretched before forming the PVA-based resin layer.

The coating liquid is a solution in which a PVA-based resin is dissolved in a solvent. Examples of the solvent include water, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, various glycols, polyhydric alcohols such as trimethylpropane, and amines such as ethylenediamine and diethylenetriamine. preferable. These can be used alone or in combination of two or more. The PVA-based resin concentration of the coating liquid is preferably about 3 to 20 parts by weight with respect to 100 parts by weight of the solvent from the viewpoint of being able to form a uniform coating film in close contact with the thermoplastic resin base material. ..

The coating liquid preferably contains a halide from the viewpoint of improving the orientation of polyvinyl alcohol molecules by stretching. As the halide, any suitable halide can be adopted, and examples thereof include iodide and sodium chloride. Examples of the iodide include potassium iodide, sodium iodide, lithium iodide and the like, and potassium iodide is preferable. The concentration of the halide in the coating liquid is preferably about 5 to 20 parts by weight, more preferably about 10 to 15 parts by weight, based on 100 parts by weight of the PVA-based resin.

Further, an additive may be added to the coating liquid. Examples of the additive include plasticizers such as ethylene glycol and glycerin; and surfactants such as nonionic surfactants.

Any suitable method can be adopted as the coating method of the coating liquid, and for example, a roll coating method, a spin coating method, a wire bar coating method, a dip coating method, a die coating method, a curtain coating method, and a spray coating method can be adopted. , Knife coat method (comma coat method, etc.) and the like. The drying temperature of the coating liquid is preferably about 50 ° C. or higher.

<Step of manufacturing a laminate having a polarizing film containing water (II-1)>
In the method for producing a polarizing film (thin polarizing film) of the present invention, at least an aerial auxiliary stretching treatment step, a dyeing treatment step, and water are applied to the laminate while transporting the laminate obtained above in the longitudinal direction. It includes a step (II-1) of producing a laminate having a polarizing film containing water by performing a stretching treatment step.

Since the aerial auxiliary stretching treatment step can be stretched while suppressing the crystallization of the thermoplastic resin base material, the laminated body can be stretched at a high magnification. The stretching method in the aerial auxiliary stretching treatment step may be fixed-end stretching (for example, a method of stretching using a tenter stretching machine) or free-end stretching (for example, uniaxial stretching through a laminate between rolls having different peripheral speeds). Method) may be used, but free-end stretching is preferable from the viewpoint of obtaining high optical characteristics.

The stretching ratio in the aerial auxiliary stretching treatment step is preferably about 2 to 3.5 times. The aerial auxiliary stretching treatment may be performed in one step or in multiple steps. When performed in multiple stages, the draw ratio is the product of the draw ratios of each stage.

The stretching temperature in the aerial auxiliary stretching treatment step can be set to an arbitrary appropriate value depending on the material for forming the thermoplastic resin base material, the stretching method, and the like. For example, the glass transition temperature of the thermoplastic resin base material. It is preferably (Tg) or higher, more preferably the glass transition temperature (Tg) + 10 ° C. or higher, and even more preferably the glass transition temperature (Tg) + 15 ° C. or higher. On the other hand, the upper limit of the stretching temperature is from the viewpoint of suppressing the rapid progress of crystallization of the PVA-based resin and suppressing defects due to crystallization (for example, hindering the orientation of the PVA-based resin layer due to stretching). , It is preferably about 170 ° C.

If necessary, an insolubilization treatment step may be performed after the aerial auxiliary stretching treatment step and before the dyeing treatment step or the underwater stretching treatment step. The insolubilization treatment step is typically performed by immersing a PVA-based resin layer in an aqueous boric acid solution. By performing the insolubilization treatment step, it is possible to impart water resistance to the PVA-based resin layer and prevent the orientation of PVA from being lowered when immersed in water. The concentration of the boric acid aqueous solution is preferably about 1 to 5 parts by weight with respect to 100 parts by weight of water. The liquid temperature of the insolubilization treatment bath is preferably about 20 to 50 ° C.

The dyeing treatment step is performed by dyeing the PVA-based resin layer with iodine. Examples of the adsorption method include a method of immersing a PVA-based resin layer (laminate) in a dyeing solution containing iodine, a method of applying the dyeing solution to the PVA-based resin layer, and a method of applying the dyeing solution to the PVA-based resin layer. Examples thereof include a method of spraying, and a method of immersing a PVA-based resin layer (laminate) in a dyeing solution containing iodine is preferable.

The amount of iodine compounded in the dyeing bath is preferably about 0.05 to 0.5 parts by weight with respect to 100 parts by weight of water. In order to increase the solubility of iodine in water, it is preferable to add the iodide to an aqueous iodine solution. The blending amount of the iodide is preferably about 0.1 to 10 parts by weight, more preferably about 0.3 to 5 parts by weight, based on 100 parts by weight of water. The liquid temperature of the dyeing bath is preferably about 20 to 50 ° C. in order to suppress the dissolution of the PVA-based resin. The immersion time is preferably about 5 seconds to 5 minutes, more preferably about 30 seconds to 90 seconds, from the viewpoint of ensuring the transmittance of the PVA-based resin layer. From the viewpoint of obtaining a polarizing film having good optical characteristics, the ratio of the iodine and iodide contents in the iodine aqueous solution is preferably about 1: 5 to 1:20, preferably about 1: 5 to 1:10. More preferably.

If necessary, a cross-linking treatment step may be performed after the dyeing treatment step and before the underwater stretching treatment step. The cross-linking treatment step is typically performed by immersing a PVA-based resin layer in an aqueous boric acid solution. By performing the cross-linking treatment step, water resistance can be imparted to the PVA-based resin layer, and the orientation of PVA can be prevented from being lowered when immersed in high-temperature water by subsequent stretching in water. The boric acid concentration of the boric acid aqueous solution is preferably about 1 to 5 parts by weight with respect to 100 parts by weight of water. Further, when the cross-linking treatment step is performed, it is preferable to further add the iodide to the cross-linking bath. By blending the iodide, the elution of iodine adsorbed on the PVA-based resin layer can be suppressed. The blending amount of the iodide is preferably about 1 to 5 parts by weight with respect to 100 parts by weight of water. The liquid temperature of the cross-linked bath (boric acid aqueous solution) is preferably about 20 to 50 ° C.

The underwater stretching treatment step is performed by immersing the laminate in a stretching bath. According to the underwater stretching treatment step, the thermoplastic resin base material or the PVA-based resin layer can be stretched at a temperature lower than the glass transition temperature (typically about 80 ° C.), and the PVA-based resin layer can be crystallized. It is possible to stretch at a high magnification while suppressing the above. The stretching method in the underwater stretching treatment step may be fixed-end stretching (for example, a method of stretching using a tenter stretching machine) or free-end stretching (for example, a method of uniaxial stretching through a laminate between rolls having different peripheral speeds). ), But free-end stretching is preferable from the viewpoint of obtaining high optical characteristics.

The underwater stretching treatment step is preferably performed by immersing the laminate in a boric acid aqueous solution (boric acid water stretching). By using an aqueous boric acid solution as the stretching bath, it is possible to impart rigidity to withstand the tension applied during stretching and water resistance that does not dissolve in water to the PVA-based resin layer. The boric acid concentration of the boric acid aqueous solution is preferably 1 to 10 parts by weight, more preferably 2.5 to 6 parts by weight, based on 100 parts by weight of water. Further, iodide may be blended in the stretching bath (boric acid aqueous solution). The liquid temperature of the stretching bath is preferably about 40 to 85 ° C, more preferably about 60 ° C to 75 ° C. The immersion time of the laminate in the stretching bath is preferably about 15 seconds to 5 minutes.

The stretching ratio in the underwater stretching treatment step is preferably about 1.5 times or more, and more preferably about 3 times or more.

The total draw ratio of the laminated body is preferably about 5 times or more, and more preferably about 5.5 times or more with respect to the original length of the laminated body.

It is preferable to perform a cleaning treatment step after the underwater stretching treatment step. The cleaning treatment step is typically performed by immersing a PVA-based resin layer in an aqueous potassium iodide solution.

Further, each treatment bath in the dyeing treatment step, the underwater stretching treatment step, the insolubilization treatment step, the cross-linking treatment step, and the cleaning treatment step includes zinc salts, pH adjusters, pH buffers, and other salts. Additives may be contained. Examples of the zinc salt include zinc halides such as zinc chloride and zinc iodide; and inorganic zinc salts such as zinc sulfate and zinc acetate. Examples of the pH adjuster include strong acids such as hydrochloric acid, sulfuric acid and nitric acid, and strong bases such as sodium hydroxide and potassium hydroxide. Examples of the pH buffer include carboxylic acids such as acetic acid, oxalic acid and citric acid and salts thereof, and inorganic weak acids such as phosphoric acid and carbonic acid and salts thereof. Examples of the other salts include chlorides such as sodium chloride, potassium chloride and barium chloride, nitrates such as sodium nitrate and potassium nitrate, sulfates such as sodium sulfate and potassium sulfate, and alkali metals and alkaline earth metals. Examples include salt.

<Step of manufacturing a laminate having a polarizing film impregnated with components in a liquid (II-2)>
In the method for producing a polarizing film (thin polarizing film) of the present invention, a liquid is applied to a laminate having a polarizing film containing water obtained above in a state where the water content of the polarizing film is 20% by weight or more. The step of applying is included to produce a laminate having a polarizing film impregnated with components in the liquid (II-2). In the step (II-2), all the steps (I-2) for producing a polarizing film impregnated with the components in the liquid described above can be applied. However, the liquid is applied (coated) on the surface of the polarizing film.

In the step (II-2), the water content of the polarizing film is 22% by weight or more from the viewpoint of easily impregnating the components contained in the liquid and making it easier to penetrate the polarizing film in the thickness direction. It is more preferable that the water content of the polarizing film is 25% by weight or more, and from the viewpoint of preventing wrinkles during transportation, the water content of the polarizing film is 70% by weight or less. It is preferably in a state, and more preferably in a state where the water content of the polarizing film is 60% by weight or less.

The time from after the step (II-1) to the start of the step (II-2) (transportation time of the laminate having the polarizing film in the actual manufacturing)) retains the water contained in the polarizing film containing water. From the viewpoint of productivity or productivity, the temperature is about 15 ° C. to 35 ° C., preferably the temperature is about 20 ° C. to 30 ° C., preferably 300 seconds or less, and more preferably 180 seconds or less. , 60 seconds or less, more preferably 10 seconds or less.

<Step of manufacturing a polarizing film after drying (II-3)>
In the method for producing a polarizing film (thin polarizing film) of the present invention, a layer having a polarizing film impregnated with components in the liquid obtained above is subjected to a drying treatment step to obtain a dried polarizing film. The step of manufacturing (II-3) is included.

The drying treatment step is performed by any suitable method, and examples thereof include natural drying, blast drying, and heat drying. Further, the drying treatment step may be performed by heating the entire zone, or by heating the transport roll (using a so-called heating roll). By drying using a heating roll, it is possible to efficiently suppress the heating curl of the laminate to produce a polarizing film having an excellent appearance, and it is possible to dry the laminate while maintaining it in a flat state. Therefore, not only curl but also wrinkles can be suppressed. Further, from the viewpoint that the optical characteristics of the obtained polarizing film can be improved by shrinking in the width direction during the drying treatment step, the shrinkage rate in the width direction of the laminate in the drying treatment step is 1 to 10%. It is preferably about 2 to 8%, and more preferably about 2 to 8%.

The drying conditions can be controlled by adjusting the heating temperature of the transport roll (temperature of the heating roll), the number of heating rolls, the contact time with the heating roll, and the like. The temperature of the heating roll is preferably about 60 to 120 ° C, more preferably about 65 to 100 ° C, and even more preferably 70 to 80 ° C. From the viewpoint of being able to satisfactorily increase the crystallinity of the thermoplastic resin and satisfactorily suppress curling, the number of transport rolls is usually about 2 to 40, preferably about 4 to 30. The contact time (total contact time) between the laminate and the heating roll is preferably about 1 to 300 seconds, more preferably 1 to 20 seconds, and even more preferably 1 to 10 seconds.

The heating roll may be provided in a heating furnace or in a normal production line (in a room temperature environment). Preferably, it is provided in a heating furnace provided with a blowing means. By using both drying with a heating roll and hot air drying together, a steep temperature change between the heating rolls can be suppressed, and shrinkage in the width direction can be easily controlled. The temperature of hot air drying is preferably about 30 to 100 ° C. The hot air drying time is preferably about 1 to 300 seconds.

<Manufacturing method of polarizing film>
The method for producing a polarizing film of the present invention includes a step of attaching a transparent protective film to at least one surface of the polarizing film obtained by the method for producing a polarizing film with an adhesive layer.

The transparent protective film is not particularly limited, and various transparent protective films used for the polarizing film can be used. As the material constituting the transparent protective film, for example, a thermoplastic resin having excellent transparency, mechanical strength, thermal stability, moisture blocking property, isotropic property and the like is used. Examples of the thermoplastic resin include cell roll ester resins such as triacetyl cell rolls, polyester resins such as polyethylene terephthalate and polyethylene naphthalate, polyether sulfone resins, polysulfone resins, polycarbonate resins, nylon and fragrances. Polyamide-based resin such as group polyamide, polyimide-based resin, polyethylene, polypropylene, polyolefin-based resin such as ethylene / propylene copolymer, (meth) acrylic-based resin, cyclic polyolefin-based resin having a cyclo-based or norbornene structure (norbornene-based resin) ), Polyallylate-based resin, polystyrene-based resin, polyvinyl alcohol-based resin, and mixtures thereof. Further, as the transparent protective film, a cured layer formed of a thermosetting resin such as (meth) acrylic, urethane, acrylic urethane, epoxy, silicone or the like or an ultraviolet curable resin can be used. Among these, cell roll ester-based resins, polycarbonate-based resins, (meth) acrylic-based resins, cyclic polyolefin-based resins, and polyester-based resins are preferable.

The thickness of the transparent protective film can be appropriately determined, but in general, it is preferably about 1 to 500 μm, preferably about 1 to 300 μm, from the viewpoint of workability such as strength and handleability, and thin layer property. More preferably, it is more preferably about 5 to 100 μm.

When the transparent protective film is attached to both sides of the polarizing film, the transparent protective films on both sides may be the same or different.

As the transparent protective film, a retardation plate having a front retardation of 40 nm or more and / or a thickness direction retardation of 80 nm or more can be used. The front phase difference is usually controlled in the range of 40 to 200 nm, and the thickness direction phase difference is usually controlled in the range of 80 to 300 nm. When a retardation plate is used as the transparent protective film, the retardation plate also functions as a transparent protective film, so that the thickness can be reduced.

Examples of the retardation plate include a birefringent film formed by uniaxially or biaxially stretching a polymer material, an alignment film of a liquid crystal polymer, and a film in which an alignment layer of a liquid crystal polymer is supported by a film. The thickness of the retardation plate is not particularly limited, but is generally about 20 to 150 μm. The phase plate may be attached to a transparent protective film having no phase difference.

The transparent protective film contains any suitable additives such as UV absorbers, antioxidants, lubricants, plasticizers, mold release agents, color inhibitors, flame retardants, antistatic agents, pigments, colorants and the like. You may.

Functional layers such as a hard coat layer, an antireflection layer, a sticking prevention layer, a diffusion layer and an antiglare layer can be provided on the surface of the transparent protective film to which the polarizing film is not bonded. The functional layers such as the hard coat layer, the antireflection layer, the sticking prevention layer, the diffusion layer and the antiglare layer can be provided on the protective film itself, or may be provided separately from the protective film. it can.

The polarizing film and the transparent protective film, or the polarizing film and the functional layer are usually bonded via an adhesive layer or an adhesive layer.

As the pressure-sensitive adhesive forming the pressure-sensitive adhesive layer, various pressure-sensitive adhesives used in polarizing films can be applied. For example, rubber-based pressure-sensitive adhesives, acrylic-based pressure-sensitive adhesives, silicone-based pressure-sensitive adhesives, urethane-based pressure-sensitive adhesives, and vinyls. Examples thereof include alkyl ether-based pressure-sensitive adhesives, polyvinyl alcohol-based pressure-sensitive adhesives, polyvinyl porolidone-based pressure-sensitive adhesives, polyacrylamide-based pressure-sensitive adhesives, and cellulose-based pressure-sensitive adhesives. Among these, an acrylic pressure-sensitive adhesive is preferable.

As a method for forming the pressure-sensitive adhesive layer, for example, a method in which the pressure-sensitive adhesive is applied to a separator or the like that has been peeled off and dried to form a pressure-sensitive adhesive layer and then transferred to a polarizing film or the like, or the pressure-sensitive adhesive is polarized. Examples thereof include a method of applying to a film or the like and drying to form an adhesive layer. The thickness of the pressure-sensitive adhesive layer is not particularly limited, and is, for example, about 1 to 100 μm, preferably about 2 to 50 μm.

As the adhesive for forming the adhesive layer, various adhesives used for polarizing films can be applied. For example, isocyanate-based adhesives, polyvinyl alcohol-based adhesives, gelatin-based adhesives, vinyl-based latex-based adhesives, and the like. Water-based polyester and the like can be mentioned. These adhesives are usually used as adhesives consisting of aqueous solutions and contain 0.5 to 60% by weight of solids.

In addition to the above, examples of the adhesive include active energy ray-curable adhesives such as ultraviolet curable adhesives and electron beam curable adhesives. Examples of the active energy ray-curable adhesive include (meth) acrylate-based adhesives. Examples of the curable component in the (meth) acrylate-based adhesive include a compound having a (meth) acryloyl group and a compound having a vinyl group. Further, a compound having an epoxy group or an oxetanyl group can also be used as the cationic polymerization curable adhesive. The compound having an epoxy group is not particularly limited as long as it has at least two epoxy groups in the molecule, and various generally known curable epoxy compounds can be used.

The adhesive may be applied to either the transparent protective film side (or the functional layer side) or the polarizing film side, or both. After bonding, a drying step is performed to form an adhesive layer composed of a coating and drying layer. After the drying step, ultraviolet rays or electron beams can be irradiated if necessary. The thickness of the adhesive layer is not particularly limited, and when a water-based adhesive or the like is used, it is preferably about 30 to 5000 nm, more preferably about 100 to 1000 nm, and an ultraviolet curable adhesive. When an electron beam curable adhesive or the like is used, it is preferably about 0.1 to 100 μm, and more preferably about 0.5 to 10 μm.

The transparent protective film and the polarizing film, or the polarizing film and the functional layer may be laminated via an intervening layer such as a surface modification treatment layer, an easy-adhesive layer, a block layer, or a refractive index adjusting layer. ..

Examples of the surface modification treatment for forming the surface modification layer include corona treatment, plasma treatment, primer treatment, and saponification treatment.

Examples of the easy-adhesive agent for forming the easy-adhesive layer include a forming material containing various resins having a polyester skeleton, a polyether skeleton, a polycarbonate skeleton, a polyurethane skeleton, a silicone-based, a polyamide skeleton, a polyimide skeleton, a polyvinyl alcohol skeleton, and the like. Can be mentioned. The easy-adhesive layer is usually provided in advance on a protective film, and the easy-adhesive layer side of the protective film and the polarizing film are laminated by the adhesive layer or the adhesive layer.

The block layer is a layer having a function to prevent impurities such as oligomers and ions eluted from the transparent protective film and the like from migrating (invading) into the polarizing film. The block layer may be a layer having transparency and capable of preventing impurities eluted from the transparent protective film or the like, and examples of the material forming the block layer include urethane prepolymer-based forming materials and cyanoacrylates. Examples include system-forming materials and epoxy-based forming materials.

The refractive index adjusting layer is a layer provided to suppress a decrease in transmittance due to reflection between layers having different refractive indexes such as the transparent protective film and a polarizing film. Examples of the refractive index adjusting material for forming the refractive index adjusting layer include forming agents containing various resins having silica-based, acrylic-based, acrylic-styrene-based, melamine-based, and the like, and additives.

The polarizing film preferably has a degree of polarization of 99.98% or more, and more preferably a degree of polarization of 99.99% or more.

The present invention will be described in more detail with reference to Examples below, but the present invention is not limited to these Examples.

<Example 1>
<Manufacturing of polarizing film>
<Manufacture of polarizing film containing water (I-1)>
A polyvinyl alcohol film having an average degree of polymerization of 2,400, a saponification degree of 99.9 mol%, and a thickness of 45 μm was prepared. The polyvinyl alcohol film was immersed in a swelling bath (water bath) at 20 ° C. for 30 seconds between rolls having different peripheral speed ratios and stretched 2.2 times in the transport direction while swelling (swelling step), followed by The original polyvinyl alcohol film (extremely stretched in the transport direction) while being dyed by immersing it in a dyeing bath at 30 ° C. (an aqueous solution having an iodine concentration of 0.03% by weight and a potassium iodide concentration of 0.3% by weight) for 30 seconds. It was stretched 3.3 times in the transport direction with reference to the uncoated polyvinyl alcohol film (dyeing step). Next, the dyed polyvinyl alcohol film is immersed in a cross-linked bath at 40 ° C. (an aqueous solution having a boric acid concentration of 3.0% by weight and a potassium iodide concentration of 3.0% by weight) for 28 seconds to obtain the original polyvinyl alcohol. The film was stretched up to 3.6 times in the transport direction with reference to the film (crosslinking step). Further, the obtained polyvinyl alcohol film is immersed in a stretching bath at 61 ° C. (an aqueous solution having a boric acid concentration of 4.0% by weight and a potassium iodide concentration of 5.0% by weight) for 60 seconds to obtain the original polyvinyl alcohol film. After stretching up to 6.0 times in the transport direction with reference to the alcohol film (stretching step), it is immersed in a washing bath at 20 ° C. (an aqueous solution having a potassium iodide concentration of 2.0% by weight) for 5 seconds (washing step). ) To produce a polarizing film containing water.

<Manufacture of polarizing film impregnated with components in liquid (I-2)>
Using a wire bar (manufactured by Daiichi Rikagaku Co., Ltd., No. 3), liquid A (10 wt% aqueous solution of the compound represented by the following chemical formula (9)) is applied to the water-containing polarizing film obtained above. Then, after allowing to stand at 25 ° C. for 3 seconds, the liquid A remaining on the surface was wiped off to produce a polarizing film impregnated with the components in the liquid. Here, the water content of the polarizing film containing water, which was determined by the following measuring method, was 33.0% by weight.

[Measurement method of moisture content (% by weight) in polarizing film]
Approximately 0.2 g of the polarizing film was measured, dried at 120 ° C. for 2 hours, the weight after drying was measured, and the water content (W) in the polarizing film was calculated based on the following formula.
Moisture content of polarizing film W (% by weight) = {(M _0- M ₁ ) / M ₀ } x 100
M ₀ : Measured weight of polarizing film (g)
M ₁ : Weight of polarizing film after drying at 120 ° C. for 2 hours (g)

<Manufacturing of polarizing film after drying (I-3)>
The polarizing film impregnated with the components in the liquid obtained above was dried at 60 ° C. for 4 minutes to produce a dried polarizing film (hereinafter, also simply referred to as a polarizing film). The moisture content of the polarizing film after drying determined by the above measuring method was 11.3% by weight. _{The content (MH} ) of the compound represented by the chemical formula (9) in the polarizing film determined by the following measuring method is 0.27% by weight, and the content of the compound represented by the chemical formula (9) per unit area is 0.27% by weight. The content (m _H ) was 5.8 μg / cm ² . The thickness (T) of the polarizing film was 18 μm.

[Method for measuring the content (% by weight) of the compound represented by the chemical formula (9) in the polarizing film]
Approximately 20 mg of the polarizing film is collected, quantified, heated and dissolved in 1 mL of water, diluted with 4.5 mL of methanol, the obtained extract is filtered through a membrane filter, and the filtrate is HPLC (ACQUITY UPLC manufactured by Waters). The concentration of the compound represented by the chemical formula (9) was measured using H-class Bio).

[Method for measuring ^{the content (μg / cm 2} ) of the compound represented by the chemical formula (9) per unit area in the polarizing film]
_{The content (MH} ) of the compound represented by the chemical formula (9) per unit area was calculated based on the following formula.
m _H = 1.2 × T × _MH (μg / cm ² )
T: Thickness of polarizing film (μm)
_MH : Content (% by weight) of the compound represented by the chemical formula (9) in the polarizing film.

<Manufacturing of polarizing film>
As an adhesive, a polyvinyl alcohol resin containing an acetoacetyl group (average degree of polymerization of 1,200, saponification degree of 98.5 mol%, acetoacetylation degree of 5 mol%) and methylol melamine in a weight ratio of 3: The aqueous solution contained in 1 was used. Using this adhesive, triacetyl cellulose film having a thickness of 40μm with a hard coat layer on both surfaces of the polarizing film obtained in the above (moisture permeability ^{342g / (m 2 · 24h)} , manufactured by Konica Minolta, trade name "KC4UYW ”) Is bonded with a roll bonding machine, and then continuously heated and dried in an oven (temperature is 60 ° C., time is 4 minutes) to manufacture a polarizing film in which transparent protective films are bonded to both sides of the polarizing film. did.

[Measurement method of degree of polarization]
The degree of polarization of the polarizing film can be measured using a spectrophotometer (manufactured by JASCO Corporation, product name "V7100"). As a specific method for measuring the degree of polarization, the parallel transmittance (H0) and the orthogonal transmittance (H90) of the polarizing film are measured, and the formula: degree of polarization (%) = {(H0-H90) / (H0 + H90)}. It can be obtained from 1/2 × 100. The parallel transmittance (H0) is a value of the transmittance of a parallel type laminated polarizing film produced by superimposing two same polarizing films so that their absorption axes are parallel to each other. The orthogonal transmittance (H90) is a value of the transmittance of an orthogonal laminated polarizing film produced by superimposing two identical polarizing films so that their absorption axes are orthogonal to each other. These transmittances are Y values obtained by correcting the luminosity factor with the 2 degree field of view (C light source) of JlS Z 8701-1982.

[Heating durability evaluation (A)]
The polarizing film obtained above is cut into a size of 5.0 × 4.5 cm so that the absorption axis of the polarizing film is parallel to the long side, and the thickness is formed on the protective film surface on the image display cell side of the polarizing film. A glass plate (pseudo-image display cell) was laminated via a 20 μm acrylic pressure-sensitive adhesive layer, and autoclaved at 50 ° C. and 0.5 MPa for 15 minutes to prepare a laminate. The obtained laminate was allowed to stand in a hot air oven at a temperature of 110 ° C., and the time until coloring was visually determined according to the following criteria.
〇: No coloring was performed for 500 hours or more.
Δ: Coloring was performed for 300 hours or more and less than 500 hours.
X: Colored in less than 300 hours.

<Example 2>
<Manufacturing of polarizing film and polarizing film>
The polarizing film after the washing step was allowed to stand at 25 ° C. for 30 seconds to obtain a polarizing film containing water, and then the polarizing film and the polarizing film were operated in the same manner as in Example 1 except that the liquid A was applied. A polarizing film was manufactured and the above measurement was performed. The results are shown in Table 1.

<Example 3>
<Manufacturing of polarizing film and polarizing film>
The polarizing film after the washing step was allowed to stand at 25 ° C. for 1 minute to obtain a polarizing film containing water, and then the polarizing film and the polarizing film were operated in the same manner as in Example 1 except that the liquid A was applied. A polarizing film was manufactured and the above measurement was performed. The results are shown in Table 1.

<Comparative example 1>
<Manufacturing of polarizing film and polarizing film>
The polarizing film after the washing step was allowed to stand at 25 ° C. for 3 minutes to obtain a polarizing film containing water, and then the polarizing film and the polarizing film were operated in the same manner as in Example 1 except that the liquid A was applied. A polarizing film was manufactured and the above measurement was performed. The results are shown in Table 1.

<Comparative example 2>
<Manufacturing of polarizing film and polarizing film>
The polarizing film after the washing step was dried at 60 ° C. for 1 minute, and then the liquid A was applied. However, the polarizing film and the polarizing film were produced by the same operation as in Example 1, and the above measurement was performed. It was. The results are shown in Table 1.

<Example 4>
<Manufacturing of polarizing film and polarizing film>
Using a polyvinyl alcohol film having a thickness of 30 μm, the same operation as in Example 1 was performed except that the iodine concentration in the dyeing bath was adjusted so that the single transmittance of the finally obtained polarizing film was about the same. , A polarizing film and a polarizing film were manufactured, and the above and the following measurements were carried out. The results are shown in Table 2. The thickness (T) of the polarizing film was 12 μm.

[Heating durability evaluation (B)]
The polarizing film obtained above is cut into a size of 5.0 × 4.5 cm so that the absorption axis of the polarizing film is parallel to the long side, and the thickness is formed on the protective film surface on the image display cell side of the polarizing film. A glass plate (pseudo-image display cell) was laminated via a 20 μm acrylic pressure-sensitive adhesive layer, and autoclaved at 50 ° C. and 0.5 MPa for 15 minutes to prepare a laminate. The obtained laminate was allowed to stand in a hot air oven at a temperature of 105 ° C., and the time until coloring was visually determined according to the following criteria.
〇: No coloring was performed for 750 hours or more.
Δ: Coloring was performed for 750 hours or more and less than 500 hours.
X: Colored in less than 500 hours.

<Comparative example 3>
<Manufacturing of polarizing film and polarizing film>
The polarizing film after the washing step was dried at 60 ° C. for 1 minute, and then the liquid A was applied. However, the polarizing film and the polarizing film were manufactured by the same operation as in Example 4, and the above measurement was performed. It was. The results are shown in Table 2.

<Example 5>
<Manufacturing of polarizing film>
<Manufacturing (preparation) of laminated body (II-0)>
As the thermoplastic resin base material, an amorphous isophthalic copolymerized polyethylene terephthalate film (thickness: 100 μm) having a long shape, a water absorption rate of 0.75%, and a Tg of about 75 ° C. was used. One side of the resin base material was corona-treated. 100 weight of PVA-based resin in which polyvinyl alcohol (polymerization degree 4200, saponification degree 99.2 mol%) and acetoacetyl-modified PVA (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "Gosefima Z410") are mixed at a ratio of 9: 13 parts by weight of potassium iodide was added to the part to prepare a PVA aqueous solution (coating liquid). The PVA aqueous solution was applied to the corona-treated surface of the resin base material and dried at 60 ° C. to form a PVA-based resin layer having a thickness of 13 μm, and a laminate was produced (prepared).

<Step of manufacturing a laminate having a polarizing film containing water (II-1)>
The obtained laminate was uniaxially stretched at the free end 2.4 times in the longitudinal direction (longitudinal direction) between rolls having different peripheral speeds in an oven at 130 ° C. (aerial auxiliary stretching treatment step). Next, the laminate was immersed in an insolubilizing bath at a liquid temperature of 40 ° C. (an aqueous boric acid solution obtained by blending 4 parts by weight of boric acid with 100 parts by weight of water) for 30 seconds (insolubilization treatment step). Next, the finally obtained polarizing film was placed in a dyeing bath having a liquid temperature of 30 ° C. (an aqueous iodine solution obtained by mixing iodine and potassium iodide in a weight ratio of 1: 7 with respect to 100 parts by weight of water). Immersion was carried out for 60 seconds while adjusting the concentration so that the simple substance transmittance (Ts) was about the same (dyeing treatment step). Then, it was immersed in a cross-linked bath at a liquid temperature of 40 ° C. (an aqueous boric acid solution obtained by blending 3 parts by weight of potassium iodide and 5 parts by weight of boric acid with respect to 100 parts by weight of water) for 30 seconds. (Crossing process). Then, while immersing the laminate in a boric acid aqueous solution (boric acid concentration 4.0% by weight) at a liquid temperature of 70 ° C., the total draw ratio is 5.5 in the longitudinal direction (longitudinal direction) between rolls having different peripheral speeds. The uniaxial stretching was carried out so as to be doubled (underwater stretching treatment step). Then, the laminate is immersed in a washing bath at a liquid temperature of 20 ° C. (an aqueous solution obtained by blending 4 parts by weight of potassium iodide with respect to 100 parts by weight of water), and the laminate has a polarizing film containing water. Manufactured the body (cleaning process).

<Manufacture of a laminate having a polarizing film impregnated with components in a liquid (II-2)>
Using a wire bar (manufactured by Daiichi Rikagaku Co., Ltd., No. 3), liquid A (compound represented by the chemical formula (9)) was applied to the polarizing film surface of the laminate having the water-containing polarizing film obtained above. A 10 wt% aqueous solution) was applied and allowed to stand at 25 ° C. for 3 seconds, and then the liquid A remaining on the surface was wiped off to produce a laminate having a polarizing film impregnated with components in the liquid. Here, the water content of the water-containing polarizing film determined by the above measurement method was 35.5% by weight.

<Manufacturing of polarizing film after drying (II-3)>
It was dried in an oven maintained at 95 ° C. for 10 minutes (drying step). In this way, a polarizing film having a thickness of 5 μm was formed on the resin base material. The moisture content of the polarizing film after drying, which was determined by the above measurement method, was 9.9% by weight. _{The content (MH} ) of the compound represented by the chemical formula (9) in the polarizing film _{is 0.41% by weight, and the content (MH} ) of the compound represented by the chemical formula (9) per unit area is 2. It was 5 μg / cm ^2.

<Manufacturing of polarizing film>
As an adhesive, a polyvinyl alcohol resin containing an acetoacetyl group (average degree of polymerization of 1,200, saponification degree of 98.5 mol%, acetoacetylation degree of 5 mol%) and methylol melamine in a weight ratio of 3: The aqueous solution contained in 1 was used. Using this adhesive, triacetyl cellulose film having a thickness of 40μm with a hard coat layer on the opposite surface and the resin substrate of the polarizing film obtained in the above (moisture permeability ^{342g / (m 2 · 24h)} , manufactured by Konica Minolta , Product name "KC4UYW") is bonded with a roll bonding machine, and then heat-dried in an oven (temperature is 60 ° C., time is 4 minutes), and a transparent protective film is bonded to one side of the polarizing film. A polarizing film was manufactured. Next, the resin base material was peeled off, the triacetyl cellulose film was bonded to the peeled surface with the roll bonding machine using the above adhesive, and then heat-dried in the oven (temperature: 60 ° C., time). (4 minutes) to produce a polarizing film in which transparent protective films were bonded to both sides of the polarizing film.

[Heating durability evaluation (C)]
The polarizing film obtained above is cut into a size of 5.0 × 4.5 cm so that the absorption axis of the polarizing film is parallel to the long side, and the thickness is formed on the protective film surface on the image display cell side of the polarizing film. A glass plate (pseudo-image display cell) was laminated via a 20 μm acrylic pressure-sensitive adhesive layer, and autoclaved at 50 ° C. and 0.5 MPa for 15 minutes to prepare a laminate. The obtained laminate was allowed to stand in a hot air oven at a temperature of 95 ° C., and the time until coloring was visually determined according to the following criteria.
〇: No coloring was performed for 750 hours or more.
Δ: Coloring was performed for 750 hours or more and less than 500 hours.
X: Colored in less than 500 hours.

<Comparative example 4>
<Manufacturing of polarizing film and polarizing film>
The polarizing film after the cleaning treatment step was dried at 95 ° C. for 10 minutes, and then the liquid A was applied. However, the polarizing film and the polarizing film were produced by the same operation as in Example 5, and the above measurement was performed. went. The results are shown in Table 3.

<Example 6>
<Manufacturing of polarizing film and polarizing film>
In the production of the polarizing film, the potassium iodide concentration in the washing bath was set to 4.0% by weight, and instead of liquid A, liquid B (zinc sulfate heptahydrate 10% by weight and Orphine EXP.4200 (day). A polarizing film and a polarizing film were manufactured by the same operation as in Example 1 except that an aqueous solution containing 0.2% by weight (manufactured by Shinkagaku Kogyo Co., Ltd.) was used, and the above and the following measurements were performed. .. The results are shown in Table 4.

[Measurement of zinc content (% by weight) in polarizing film]
Approximately 25 mg of the polarizing film was weighed in a Teflon (registered trademark) container, acid was added, the film was sealed, and then microwaves were irradiated to perform pressure acid decomposition at a maximum of 200 ° C. After complete decomposition, ultrapure water was added and the volume was adjusted to 50 mL, and the zinc concentration was measured using ICP-MS (Agilent 8800 manufactured by Agilent Technologies). MARS 5 manufactured by CEM was used as the disassembling device.

[Heating durability evaluation (D)]
The polarizing film obtained above is cut into a size of 5.0 × 4.5 cm so that the absorption axis of the polarizing film is parallel to the long side, and the thickness is formed on the protective film surface on the image display cell side of the polarizing film. A glass plate (pseudo-image display cell) was laminated via a 20 μm acrylic pressure-sensitive adhesive layer, and autoclaved at 50 ° C. and 0.5 MPa for 15 minutes to prepare a laminate. The obtained laminate was allowed to stand in a hot air oven at a temperature of 105 ° C. for 500 hours, the sample after the test was placed on a cross Nicol, and the orthogonal transmittance (%) at a wavelength of 700 nm was measured by the spectrophotometer (V7100). Each was measured and judged according to the following criteria.
〇: No reddening due to heating (the difference in orthogonal transmittance at a wavelength of 700 nm before and after the heating test at 105 ° C. for 500 hours is less than 1%).
X: There is reddening of heating (the difference in orthogonal transmittance at a wavelength of 700 nm before and after the heating test at 105 ° C. for 500 hours is 1% or more).

<Comparative example 5>
<Manufacturing of polarizing film and polarizing film>
The polarizing film after the washing step was dried at 60 ° C. for 1 minute, and then the liquid B was applied. The polarizing film and the polarizing film were produced by the same operation as in Example 6, and the above measurement was performed. It was. The results are shown in Table 4.

Since the above heating durability test is affected by the film thickness of the polarizing film, it is sufficient to compare the polarizing films having the same film thickness, and the polarizing film of the example is more than the polarizing film of the comparative example. It can be seen that the heating durability is excellent because the components in the liquid are sufficiently contained.

Claims

It is a method of manufacturing a polarizing film.
While transporting the polyvinyl alcohol-based film in the longitudinal direction, the polyvinyl alcohol-based film is subjected to at least a dyeing step, a cross-linking step, and a stretching step to produce a polarizing film containing water (I-1). ,
A step of applying a liquid to the obtained polarizing film containing water in a state where the water content of the polarizing film is 20% by weight or more to produce a polarizing film impregnated with components in the liquid (a step of producing a polarizing film impregnated with components in the liquid. I-2) and
A method for producing a polarizing film, which comprises a step (I-3) of subjecting a polarizing film impregnated with components in the obtained liquid to a drying step to produce a dried polarizing film.
It is a method of manufacturing a polarizing film.
A step (II-0) of forming a polyvinyl alcohol-based resin layer containing a polyvinyl alcohol-based resin on one side of a long thermoplastic resin base material to prepare a laminate, and
While transporting the obtained laminate in the longitudinal direction, the laminate is subjected to at least an aerial auxiliary stretching treatment step, a dyeing treatment step, and an underwater stretching treatment step to obtain a laminate having a polarizing film containing water. Manufacturing process (II-1) and
A step of applying a liquid to the obtained laminate having a polarizing film containing water in a state where the water content of the polarizing film is 20% by weight or more is performed to obtain a polarizing film impregnated with components in the liquid. Step (II-2) of manufacturing a laminate having
A polarizing film comprising a step (II-3) of subjecting a laminate having a polarizing film impregnated with components in the obtained liquid to a drying treatment step to produce a dried polarizing film. Production method.
The method for producing a polarizing film according to claim 1 or 2, wherein the liquid is a solution and the components in the liquid are solutes.
The method for producing a polarizing film according to any one of claims 1 to 3, wherein the dried polarizing film has a moisture content of 20% by weight or less.
The method for producing a polarizing film according to any one of claims 1 to 4, wherein the component in the liquid is a water-soluble compound.
The production of the polarizing film according to any one of claims 1 to 5, wherein the component in the liquid is at least one selected from the group consisting of a radical scavenger, a cross-linking agent, a plasticizer, and a dye. Method.
The method for producing a polarizing film according to any one of claims 1 to 6, wherein the component in the liquid is a radical scavenger.
A polarizing film comprising a step of attaching a transparent protective film to at least one surface of the polarizing film obtained by the method for producing a polarizing film according to any one of claims 1 to 7 via an adhesive layer. Production method.