KR20220063119A - The manufacturing method of a polarizing film, and the manufacturing method of a polarizing film - Google Patents

Abstract

A step (I-1) of producing a polarizing film containing water by subjecting the polyvinyl alcohol-based film to at least a dyeing process, a crosslinking process, and a stretching process while conveying the polyvinyl alcohol-based film in the longitudinal direction; A step (I-2) of manufacturing a polarizing film impregnated with a component in the liquid by performing a step of applying a liquid to the polarizing film containing the polarizing film in a state where the moisture content of the polarizing film is 20 wt% or more, and a polarizing film impregnated with a component in the obtained liquid The manufacturing method of a polarizing film including the process (I-3) of giving a drying process to and manufacturing the polarizing film after drying. The manufacturing method of the polarizing film of this invention can make a polarizing film contain arbitrary components simply and fully.

Description

The manufacturing method of a polarizing film, and the manufacturing method of a polarizing film

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

Conventionally, as a polarizing film (polarizer) used for various image display devices such as a liquid crystal display device and an organic EL display device, since it has high transmittance and high polarization degree, it is dyed (dichroism such as iodine or dichroic dye) A polyvinyl alcohol-based film containing material) is used. The said polarizing film is manufactured by performing each process, such as dyeing, crosslinking, and extending|stretching, in a bath (treatment bath) on a polyvinyl alcohol-type film, and then drying. Moreover, the said polarizing film is normally used as a polarizing film (polarizing plate) in which the protective film, such as a triacetyl cellulose, was bonded on one or both surfaces using an adhesive agent.

As a manufacturing method of a polarizing film, for example, in patent documents 1 and 2, by adding components, such as a metal salt containing zinc, copper, aluminum, etc. to a process bath, these components are contained in a polarizing film, and improving the durability characteristic of a polarizing film is disclosed. has been In addition, 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. 2016/117659 Japanese Patent Laid-Open No. 2006-047978 Japanese Patent Laid-Open No. 2008-46257 Japanese Patent Laid-Open No. 6-172554

However, in the manufacturing method of a polarizing film, when adding the above components to a treatment bath, there existed a problem, such as that the usage-amount would become large, and waste liquid treatment of a treatment liquid would be required.

In view of the above circumstances, an object of this invention is to provide the manufacturing method of a polarizing film which can make a polarizing film simply and fully contain arbitrary components.

Moreover, an object of this invention is to provide the manufacturing method of the polarizing film using the polarizing film obtained by the manufacturing method of the said polarizing film.

That is, the present invention is a method for manufacturing a polarizing film, wherein the polyvinyl alcohol-based film is subjected to at least a dyeing process, a crosslinking process, and a stretching process while conveying the polyvinyl alcohol-based film in the longitudinal direction to produce a water-containing polarizing film Step (I-1) and the step (I-2) of manufacturing a polarizing film impregnated with a component in the liquid by carrying out the step of applying a liquid to the obtained polarizing film containing water in a state where the moisture content of the polarizing film is 20 wt% or more (I-2) And it relates to the manufacturing method of a polarizing film including the process (I-3) of giving a drying process to the polarizing film impregnated with the component in the obtained liquid, and manufacturing the polarizing film after drying.

In addition, the present invention provides a method for manufacturing a polarizing film, comprising 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 substrate to prepare a laminate; A step (II-1) of manufacturing a laminate having a polarizing film containing water by subjecting the laminate to at least an aerial auxiliary stretching treatment step, a dyeing treatment step, and an underwater stretching treatment step while conveying the laminate in the longitudinal direction; , a step of applying a liquid to the obtained laminate having a polarizing film containing water in a state where the moisture content of the polarizing film is 20 wt% or more to produce a laminate having a polarizing film impregnated with a component in the liquid (II-2) And it relates to the manufacturing method of a polarizing film including the process (II-3) of giving a drying treatment process to the laminated body which has a polarizing film impregnated with the component in the obtained liquid, and manufacturing the polarizing film after drying.

Further, the present invention relates to a method for manufacturing a polarizing film, comprising the step of bonding a transparent protective film to at least one side of the polarizing film obtained by the method for manufacturing the polarizing film through an adhesive layer.

Although the detail of the action mechanism of the effect in the manufacturing method of the polarizing film of this invention has an unclear part, it is estimated as follows. However, the present invention does not need to be interpreted as being limited to this mechanism of action.

The manufacturing method of the polarizing film of the present invention is a process of manufacturing a polarizing film containing water by subjecting the polyvinyl alcohol-based film to at least a dyeing process, a crosslinking process, and a stretching process while conveying the polyvinyl alcohol-based film in the longitudinal direction (I -1) and a step of applying a liquid to the obtained polarizing film containing water in a state where the moisture content of the polarizing film is 20% by weight or more to produce a polarizing film impregnated with a component in the liquid (I-2); A drying step is performed on the polarizing film impregnated with the component in the liquid, and a step (I-3) of manufacturing the polarizing film after drying is included. Alternatively, in the method for producing a polarizing film of the present invention, a step (II-0) of preparing a laminate by forming a polyvinyl alcohol-based resin layer containing a polyvinyl alcohol-based resin on one side of a long thermoplastic resin substrate (II-0); A step (II-1) of producing a laminate having a polarizing film containing water by subjecting the laminate to at least an air-assisted stretching treatment step, a dyeing treatment step, and an underwater stretching treatment step while conveying in the longitudinal direction; A step of applying a liquid to a laminate having a polarizing film containing water in a state where the moisture content of the polarizing film is 20% by weight or more to produce a laminate having a polarizing film impregnated with a component in the liquid (II-2); The process (II-3) of giving a drying treatment process to the laminated body which has the polarizing film impregnated with the component in the obtained liquid, and manufacturing the polarizing film after drying is included. In the conventional manufacturing method of a polarizing film, after giving a dyeing process, a crosslinking process, and an extending|stretching process to a polyvinyl alcohol-type film at least, a drying process is performed continuously. Alternatively, in the conventional method for producing a polarizing film, a step of preparing a laminate by forming a polyvinyl alcohol-based resin layer containing a polyvinyl alcohol-based resin on one side of a long thermoplastic resin substrate, and at least aerial auxiliary stretching treatment on the obtained laminate After implementing a process, a dyeing|staining treatment process, and an underwater extending|stretching process process, a drying treatment process is performed continuously. On the other hand, in the manufacturing method of the polarizing film of this invention, the laminated body which has a polarizing film containing water or a polarizing film containing water as mentioned above is manufactured. The water-containing polarizing film or the polarizing film in a laminate having a water-containing polarizing film is subjected to a process of applying a liquid in a state where the moisture content of the polarizing film is 20 wt% or more, so that the water-containing polarizing film is Any component included in the liquid can be easily and sufficiently impregnated.

<Method for producing a polarizing film>

The manufacturing method of the polarizing film of the present invention is a process of manufacturing a polarizing film containing water by subjecting the polyvinyl alcohol-based film to at least a dyeing process, a crosslinking process, and a stretching process while conveying the polyvinyl alcohol-based film in the longitudinal direction (I -1) and a step of applying a liquid to the obtained polarizing film containing water in a state where the moisture content of the polarizing film is 20% by weight or more to produce a polarizing film impregnated with a component in the liquid (I-2); A drying step is performed on the polarizing film impregnated with the component in the liquid, and a step (I-3) of manufacturing the polarizing film after drying is included.

<Step (I-1) for producing a polarizing film containing water>

The manufacturing method of the polarizing film of the present invention is a process of manufacturing a polarizing film containing water by subjecting the polyvinyl alcohol-based film to at least a dyeing process, a crosslinking process, and a stretching process while conveying the polyvinyl alcohol-based film in the longitudinal direction (I -1) is included.

The polyvinyl alcohol (PVA)-based film has light-transmitting properties in the visible region, and dispersion and adsorption of dichroic substances such as iodine and dichroic dye can be used without particular limitation. Moreover, normally, it is preferable that thickness is about 1-100 micrometers, as for the PVA-type film used as a raw material, it is more preferable that it is about 1-50 micrometers, It is preferable that it is about 100-5000 mm in width.

Examples of the material of the polyvinyl alcohol-based film include polyvinyl alcohol or a derivative thereof. As a derivative of the said polyvinyl alcohol, For example, polyvinyl formal, polyvinyl acetal; olefins such as ethylene and propylene; What modified with unsaturated carboxylic acids, such as acrylic acid, methacrylic acid, and a crotonic acid, its alkylester, acrylamide, etc. are 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 still more preferably about 1,500 to 4,500. In addition, the polyvinyl alcohol preferably has a degree of saponification of about 80 to 100 mol%, and more preferably about 95 mol% to about 99.95 mol. In addition, the said average degree of polymerization and the said saponification degree can be calculated|required according to JISK6726.

The polyvinyl alcohol-based film may contain additives such as plasticizers and surfactants. As said plasticizer, polyols, such as glycerol, diglycerol, triglycerol, ethylene glycol, propylene glycol, polyethyleneglycol, its condensate, etc. are mentioned, for example. The amount of the additive used is not particularly limited, but for example, about 20% by weight or less of the polyvinyl alcohol-based film is suitable.

<Dyeing process>

The dyeing process is a treatment process in which the polyvinyl alcohol-based film is immersed in a dyeing bath, and a dichroic substance such as iodine or a dichroic dye may be adsorbed and oriented to the polyvinyl alcohol-based film. It is preferable that the said dyeing solution is usually an iodine aqueous solution, and it contains iodine and iodide as a dissolution aid. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, titanium iodide, and the like. Among these, potassium iodide is suitable.

The concentration of iodine in the dyeing bath is preferably about 0.01 to 1% by weight, and more preferably about 0.02 to 0.5% by weight. It is preferable that the density|concentration of the said iodide in the said dyeing bath is about 0.01 to 10 weight%, and it is more preferable that it is about 0.05 to 5 weight%.

It is preferable that it is about 10-50 degreeC, and, as for the temperature of the said dyeing bath, it is more preferable that it is about 15-45 degreeC. In addition, the immersion time in the dyeing bath cannot be determined uniformly because the degree of dyeing of the polyvinyl alcohol-based film is affected by the temperature of the dyeing bath, but it is preferably about 10 to 300 seconds, and about 20 to 240 seconds. more preferably. The said dyeing process may be performed only once, and may be performed multiple times as needed.

<Crosslinking process>

The crosslinking step is a treatment step in which the polyvinyl alcohol-based film dyed in the dyeing step is immersed in a treatment bath (crosslinking bath) containing a boron compound. Molecules can adsorb to the crosslinked structure. As said boron compound, boric acid, a borate, a boron etc. are mentioned, for example. The crosslinking bath is generally an aqueous solution, but may be, for example, a mixed solution of water and an organic solvent miscible with water. In addition, the crosslinking bath may contain iodide such as potassium iodide.

The concentration of the boron compound in the crosslinking bath 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. Further, when an iodide such as potassium iodide is used in the crosslinking bath, the concentration of an iodide such as potassium iodide in the crosslinking bath is preferably about 1 to 15% by weight, and more preferably about 1.5 to 10% by weight.

It is preferable that it is about 20-70 degreeC, and, as for the temperature of the said crosslinking bath, it is more preferable that it is about 30-60 degreeC. In addition, the immersion time in the crosslinking bath cannot be uniformly determined because the degree of crosslinking of the polyvinyl alcohol-based film is affected by the temperature of the crosslinking bath, but it is preferably about 5 to 300 seconds, and about 10 to 200 seconds. more preferably. The said crosslinking process may be performed only once, and may be performed multiple times as needed.

<Stretching process>

The stretching step is a treatment step of stretching the polyvinyl alcohol-based film in at least one direction at a predetermined magnification. In general, the polyvinyl alcohol-based film is uniaxially stretched in the conveying direction (longitudinal direction). The stretching method is not particularly limited, and either a wet stretching method or a dry stretching method may be employed. The said extending process may be performed only once, and may be performed multiple times as needed. The said extending process may be performed at any stage in manufacture of a polarizing film.

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

It is preferable that it is about 25-80 degreeC, and, as for the temperature of the said stretching bath, it is more preferable that it is about 40-75 degreeC. In addition, the immersion time in the stretching bath cannot be determined uniformly because the degree of stretching of the polyvinyl alcohol-based film is affected by the temperature of the stretching bath, but it is preferably about 10 to 800 seconds, and about 30 to 500 seconds. more preferably. Moreover, you may implement the extending|stretching process in the said wet extending|stretching method together with any 1 or more treatment process of the said dyeing process, the said bridge|crosslinking process, the swelling process mentioned later, and the washing|cleaning process mentioned later.

Examples of the dry stretching method include an inter-roll stretching method, a heated roll stretching method, and a compression stretching method. Moreover, you may implement the said dry extending|stretching method together with the drying process mentioned later.

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

In the step of manufacturing the water-containing polarizing film, the polyvinyl alcohol-based film may be subjected to a swelling step or a washing step in addition to performing the dyeing step, the crosslinking step, and the stretching step.

<Swelling process>

The swelling process is a treatment process in which the polyvinyl alcohol-based film is immersed in a swelling bath, and it is possible to remove contamination or blocking agents on the surface of the polyvinyl alcohol-based film, and also to remove dyeing stains by swelling the polyvinyl alcohol-based film. can be suppressed As the swelling bath, a medium containing water as a main component, such as water, distilled water, or pure water, is usually used. In the swelling bath, a surfactant, alcohol, etc. may be suitably added according to a conventional method.

It is preferable that it is about 10-60 degreeC, and, as for the temperature of the said swelling bath, it is more preferable that it is about 15-45 degreeC. In addition, the immersion time in the swelling bath cannot be determined uniformly because the degree of swelling of the polyvinyl alcohol-based film is affected by the temperature of the swelling bath, but it is preferably about 5 to 300 seconds, and about 10 to 200 seconds. more preferably. The said swelling process may be implemented only once, and may be implemented multiple times as needed.

<Washing process>

The cleaning step is a treatment step of immersing the polyvinyl alcohol-based film in a washing bath, and foreign substances remaining on the surface of the polyvinyl alcohol-based film can be removed. As the washing bath, a medium containing water as a main component, such as water, distilled water, or pure water, is usually used. In addition, an iodide such as potassium iodide can be used in the washing bath. In this case, the concentration of iodide such as potassium iodide in the washing bath is preferably about 1 to 10% by weight, and about 2 to 4% by weight. It is more preferable, and it is still more preferable that it is about 1.6 to 3.8 weight%.

It is preferable that the temperature of the said washing|cleaning bath is about 5-50 degreeC, It is more preferable that it is about 10-40 degreeC, It is still more preferable that it is about 15-30 degreeC. In addition, the immersion time in the cleaning bath cannot be determined uniformly because the degree of cleaning of the polyvinyl alcohol-based film is affected by the temperature of the cleaning bath, but it is preferably about 1 to 100 seconds, and about 2 to 50 seconds. It is more preferable, and it is still more preferable that it is about 3 to 20 second. The said swelling process may be implemented only once, and may be implemented multiple times as needed.

Further, each treatment bath in the swelling step, the dyeing step, the crosslinking step, the stretching step and the washing step may contain additives such as zinc salt, a pH adjuster, a pH buffer, and other salts. Examples of the zinc salt include zinc halides such as zinc chloride and zinc iodide; Inorganic zinc salts, such as zinc sulfate and zinc acetate, etc. are mentioned. As said pH adjuster, strong acids, such as hydrochloric acid, sulfuric acid, and nitric acid, and strong bases, such as sodium hydroxide and potassium hydroxide, are mentioned, for example. Examples of the pH buffering agent include carboxylic acids and salts thereof such as acetic acid, oxalic acid, and citric acid, and weak inorganic acids and salts thereof such as phosphoric acid and carbonic acid. 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 salts of alkali metals and alkaline earth metals.

<Step (I-2) of manufacturing a polarizing film impregnated with a component in a liquid>

The manufacturing method of the polarizing film of the present invention is a process of manufacturing a polarizing film impregnated with a component in the liquid by applying a liquid to the polarizing film containing water obtained above in a state where the moisture content of the polarizing film is 20% by weight or more (I- 2) is included. Here, the component in the liquid is usually a solute contained in the solution. The solute may be any substance that can be dissolved or dispersed in a solvent, and any of gaseous substances, liquid substances, and solid substances may be used as the single compound. Moreover, when the solute is a liquid substance (for example, under the conditions of 25°C and 1 atm), the liquid substance itself (liquid substance itself) may be a liquid or a component in the liquid.

In the above step (I-2), it is preferable that the moisture content of the polarizing film is 22 wt% or more from the viewpoint of being easy to impregnate the components contained in the liquid and making it easier to penetrate in the thickness direction of the polarizing film, It is more preferable that the moisture content of the film is 25% by weight or more, and from the viewpoint of preventing wrinkles during transport, it is preferable that the moisture content of the polarizing film is 70% by weight or less, and the moisture content of the polarizing film is 60% by weight or less. more preferably.

As a coating (coating) method in the step of applying the liquid, a 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, and a die coating method. Coating methods, such as a method, the curtain coat method, the spray coat method, and the knife coat method (comma coat method), etc. are mentioned. In addition, the single side|surface may be sufficient as the application surface of a polarizing film, and both surfaces may be sufficient as it.

A water-soluble compound may be sufficient as the component in the said liquid from a viewpoint of making it easy to impregnate the component in the said polarizing film containing said water. In addition, it is said that the solubility to 100 g of water at 25 degreeC is 1 g or more with the said water-soluble compound.

Examples of the component 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); Organic titanium compounds (titanium alkoxide, titanium chelate, titanium chelate ammonium salt, titanium chelate acylate, etc.), organic zirconium (zirconia alkoxide, zirconyl chelate, zirconyl chelate ammonium salt, zirconyl acylate), alkali metal salt, alkaline earth metal salt , and metal halides.

Moreover, as a component in the said liquid, the compound (it is also mentioned a radical scavenger) which has a radical trapping function is mentioned. The compound having the radical trapping function can suppress polyenization by trapping radicals generated by heating of polyvinyl alcohol of the polarizing film, and thus can improve the durability of the polarizing film against heat. As a compound which has the said radical trapping function, it is preferable that it is a compound which has a nitroxy radical or a nitroxide group from a viewpoint which can suppress polyenization easily, for example.

As a compound which has the said nitroxy radical or a nitroxide group, the compound etc. which have an organic group of the following structures are mentioned, for example.

(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 represents 0 or 1.) The left side of the dotted line portion in the general formula (1) represents an arbitrary organic group.

As a compound which has the said organic group, the compound etc. which are represented, for example by the following general formula (2) - (5) are mentioned.

(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, acyl group, or aryl group having 1 to 10 carbon atoms.)

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

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

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

In the general formulas (1) to (5), R ² to R ⁵ are preferably an alkyl group having 1 to 6 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms, from the viewpoint of availability. Moreover, in the said General formula (2), from a viewpoint of availability, it is preferable that R< ⁶ > is a hydrogen atom or a C1-C10 alkyl group, and it is more preferable that it is a hydrogen atom. Further, in the general formula (3), from the viewpoint of availability, R ⁷ and R ⁸ independently represent a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, more preferably a hydrogen atom. Further, in the general formula (4), from the viewpoint of availability, R ⁹ to R ¹¹ are preferably a hydrogen atom or an alkyl group having 1 to 10 carbon atoms. Moreover, in the said General formula (5), it is preferable from a viewpoint of availability that R< ¹² > is a hydroxyl group, an amino group, or an alkoxy group. In the general formulas (1) to (5), n is preferably 1 from the viewpoint of availability.

Moreover, as a compound which has the said nitroxy radical or a nitroxide group, the following compounds etc. are mentioned, for example.

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

Moreover, as a component in the said liquid, the compound which has a crosslinking function (it is also called a crosslinking agent) is mentioned. The compound having the crosslinking function may react with the hydroxyl group of polyvinyl alcohol of the polarizing film to form a crosslinked structure, and may improve durability of the polarizing film against humidification. As the compound having the crosslinking function, in addition to organic compounds having an isocyanate group, an isocyanate-derived functional group, an epoxy group, a carbonyl group, an aziridine ring, a vinyl ether group, a vinyl sulfone group, and an oxazoline group, an organic titanium compound ( a titanium alkoxide, a titanium chelate, a titanium chelate ammonium salt, a titanium chelate acylate, etc.) etc. are mentioned.

Moreover, as a component in the said liquid, the compound (it is also called a plasticizer) which has a function of providing plasticity is mentioned. The compound having the function of imparting plasticity can reduce quality problems such as dents caused by pushing force by imparting plasticity to the polarizing film. Examples of the compound having the function of imparting plasticity include ethylene glycol, polyethylene glycol, other ethylene glycol derivatives, and glycerin.

Moreover, as a component in the said liquid, a dye type compound (it is also called dye) is mentioned. The dye-based compound may impart characteristics such as color adjustment or pattern printing of the polarizing film. As said dye type compound, an azo compound, an anthraquinone type, a quinophthalone type compound, etc. are mentioned, for example.

Although the liquid cannot be determined uniformly because it is affected by the application (coating) type, the concentration of the components in the liquid is preferably 0.1% by weight or more, and 1.0% by weight or more from the viewpoint of efficiently penetrating the components in the liquid. More preferably, it is preferably 30% by weight or less, and more preferably 20% by weight or less from the viewpoint of preventing quality problems due to precipitation of components in the liquid.

Examples of the solvent include water; Water-soluble solvents, such as methanol, ethanol, ethylene glycol, polyethyleneglycol, other ethylene glycol derivatives, glycerol, and dimethyl sulfoxide, etc. are mentioned.

The time from the step (I-1) to the start of the step (I-2) (transfer time of the polarizing film in actual machine production) is from the viewpoint of maintaining the moisture 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, still more preferably 60 seconds or less, and 10 seconds or less more preferably.

Moreover, in the said process (I-2), you may implement the process of apply|coating a liquid to the said polarizing film containing water as needed, and then impregnate a part of a liquid, and you may implement the process of removing the remaining liquid. Examples of the liquid removal method include a wiping removal method using a waste or sponge roll, a suction removal method, a blowing removal method, a scratch removal method using a bar or gravure roll, and the like.

<Step of manufacturing a polarizing film after drying (I-3)>

The manufacturing method of the polarizing film of this invention includes the process (I-3) of giving a drying process to the polarizing film impregnated with the component in the liquid obtained above, and manufacturing the polarizing film after drying.

The said drying process is a process of drying the polarizing film impregnated with the component in the liquid obtained above, and obtaining a polarizing film, and the polarizing film which has a desired moisture content is obtained by drying. Said drying is performed by any suitable method, for example, natural drying, air drying, and heat drying are mentioned.

It is preferable that it is about 20-150 degreeC, and, as for the said drying temperature, it is more preferable that it is about 25-100 degreeC. The drying time cannot be uniformly determined because the degree of drying of the polarizing film is affected by the drying temperature, but is preferably about 10 to 600 seconds, and more preferably about 30 to 300 seconds. The said drying process may be performed only once, and may be performed multiple times as needed.

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

It is preferable that the thickness of the said polarizing film after drying is about 1-30 micrometers, It is more preferable that it is about 5-25 micrometers, It is still more preferable that it is 5-20 micrometers. In particular, in order to obtain a polarizing film after drying having a thickness of about 8 μm or less, as the polyvinyl alcohol-based film, a laminate including a polyvinyl alcohol-based resin layer formed on a thermoplastic resin substrate is used. method can be applied.

<Method for producing a polarizing film (thin polarizing film)>

A method for producing a polarizing film (thin polarizing film) includes a step (II-0) of preparing a laminate by forming a polyvinyl alcohol-based resin layer containing a polyvinyl alcohol-based resin on one side of a long thermoplastic resin substrate; Step (II-1) of manufacturing a laminate having a polarizing film containing water by subjecting the laminate to at least an aerial assisted stretching treatment step, a dyeing treatment step, and an underwater stretching treatment step while conveying the obtained layered product in the longitudinal direction (II-1) and a step of applying a liquid to the obtained laminate having a polarizing film containing water in a state where the moisture content of the polarizing film is 20 wt% or more to produce a laminate having a polarizing film impregnated with a component in the liquid (II-2 ), and a step (II-3) of manufacturing a polarizing film after drying by subjecting the laminate having a polarizing film impregnated with a component in the obtained liquid to a drying treatment process.

<Step of preparing a laminate (II-0)>

In the method for producing a polarizing film (thin polarizing film) of the present invention, a polyvinyl alcohol-based resin layer (PVA-based resin layer) containing a polyvinyl alcohol-based resin (PVA-based resin) is formed on one side of a long thermoplastic resin substrate. Thus, the step (II-0) of preparing the laminate is included.

Any suitable method is employ|adopted as a method of producing the said laminated body, For example, the method of apply|coating the coating liquid containing the said PVA-type resin to the surface of the said thermoplastic resin base material, and drying is mentioned. It is preferable that it is about 20-300 micrometers, and, as for the thickness of the said thermoplastic resin base material, it is more preferable that it is about 50-200 micrometers. It is preferable that it is about 3-40 micrometers, and, as for the thickness of the said PVA-type resin layer, it is more preferable that it is about 3-20 micrometers.

The thermoplastic resin substrate absorbs water to significantly reduce the stretching stress, and from the viewpoint of being able to stretch at a high magnification, the water absorption is preferably about 0.2% or more, and more preferably about 0.3% or more. On the other hand, the thermoplastic resin substrate has a water absorption of about 3% or less, preferably about 3% or less, from the viewpoint of preventing problems such as significantly lowering the dimensional stability of the thermoplastic resin substrate and deterioration of the appearance of the resulting polarizing film. more preferably. Moreover, the said water absorption rate can be adjusted by introduce|transducing a modifier into the constituent material of the said thermoplastic resin base material, for example. The said water absorption is a value calculated|required according to JISK7209.

The thermoplastic resin substrate preferably has a glass transition temperature (Tg) of about 120° C. or less from the viewpoint of sufficiently securing the stretchability of the laminate while suppressing crystallization of the PVA-based resin layer. In addition, in consideration of plasticization of the thermoplastic resin substrate with water and good stretching in water, the glass transition temperature (Tg) is more preferably about 100° C. or less, and still more preferably about 90° C. or less. On the other hand, the glass transition temperature of the thermoplastic resin substrate is preferably about 60° C. or higher from the viewpoint of preventing problems such as deformation of the thermoplastic resin substrate during application and drying of the coating solution, thereby producing a good laminate. In addition, the said glass transition temperature can be adjusted by heating using the crystallization material which introduce|transduces a modifying group into the constituent material of the said thermoplastic resin base material, for example. The glass transition temperature (Tg) is a value obtained according to JIS K 7121.

Any suitable thermoplastic resin may be employed as the constituent material of the thermoplastic resin substrate. Examples of the thermoplastic resin include ester-based resins such as polyethylene terephthalate-based resins, cycloolefin-based resins such as norbornene-based resins, olefinic resins such as polypropylene, polyamide-based resins, polycarbonate-based resins, and public A synthetic resin etc. are mentioned. Among these, norbornene-based resins and amorphous (non-crystalline) polyethylene terephthalate-based resins are preferable, and the thermoplastic resin substrate has very excellent stretchability and is amorphous (non-crystalline) from the viewpoint that crystallization can be suppressed during stretching. Amorphous) A polyethylene terephthalate-based resin is preferably used. As the amorphous (non-crystalline) polyethylene terephthalate-based resin, a copolymer containing isophthalic acid and/or cyclohexanedicarboxylic acid as dicarboxylic acid, or a copolymer containing cyclohexanedimethanol or diethylene glycol as glycol can be heard

The thermoplastic resin substrate may be subjected to surface treatment (eg, corona treatment, etc.) before forming the PVA-based resin layer, or an easily adhesive layer may be formed on the thermoplastic resin substrate. By performing such a process, the adhesiveness of a thermoplastic resin base material and a PVA-type resin layer can be improved. In addition, the said thermoplastic resin base material may be extended|stretched before forming a PVA-type resin layer.

The coating solution is a solution in which a PVA-based resin is dissolved in a solvent. Examples of the solvent include water, dimethylsulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, various glycols, polyhydric alcohols such as trimethylolpropane, and amines such as ethylenediamine and diethylenetriamine. and water is preferred. These can be used individually or in combination of 2 or more types. The concentration of the PVA-based resin in the coating solution is preferably about 3 to 20 parts by weight based on 100 parts by weight of the solvent from the viewpoint of forming a uniform coating film in close contact with the thermoplastic resin substrate.

It is preferable that a halide is mix|blended with the said coating liquid from a viewpoint of improving the orientation of polyvinyl alcohol molecules by extending|stretching. Any suitable halide can be employed as the halide, and examples thereof include iodide and sodium chloride. As said iodide, potassium iodide, sodium iodide, lithium iodide etc. are mentioned, for example, Potassium iodide is preferable. It is preferable that it is about 5-20 weight part with respect to 100 weight part of PVA-type resin, and, as for the density|concentration of the said halide in the said coating liquid, it is more preferable that it is about 10-15 weight part.

Moreover, you may mix|blend an additive with the said coating liquid. As said additive, For example, plasticizers, such as ethylene glycol and glycerol; Surfactants, such as a nonionic surfactant, etc. are mentioned.

Any suitable method can be adopted as a method for applying the coating liquid, for example, a roll coat method, a spin coat method, a wire bar coat method, a dip coat method, a die coat method, a curtain coat method, a spray coat method, and a knife A coat method (comma coat method, etc.) etc. are mentioned. Moreover, it is preferable that the drying temperature of the said coating liquid is about 50 degreeC or more.

<Step (II-1) of manufacturing a laminate having a polarizing film containing water>

In the method for manufacturing a polarizing film (thin polarizing film) of the present invention, while conveying the laminate obtained above 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, A step (II-1) of manufacturing a laminate having a polarizing film containing

In the air-assisted stretching treatment step, since the thermoplastic resin substrate can be stretched while suppressing crystallization, the laminate can be stretched at a high magnification. The stretching method of 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 (eg, uniaxial stretching by passing a laminate between rolls having different peripheral speeds) method), but free-end stretching is preferable from the viewpoint of obtaining high optical properties.

It is preferable that the draw ratio in the said aerial auxiliary extending|stretching process process is about 2-3.5 times. The said aerial auxiliary extending|stretching process may be performed in one step, and may be performed in multiple steps. When carrying out in multiple steps, the draw ratio is the product of the draw ratios of each step.

The stretching temperature in the aerial auxiliary stretching treatment step can be set to any suitable value depending on the forming material of the thermoplastic resin substrate, the stretching method, etc., for example, it is preferably not less than the glass transition temperature (Tg) of the thermoplastic resin substrate, , It is more preferable that the glass transition temperature (Tg) + 10 ℃ or more, and more preferably the glass transition temperature (Tg) + 15 ℃ or more. On the other hand, the upper limit of the stretching temperature is 170° C. from the viewpoint of suppressing the rapid progress of crystallization of the PVA-based resin and suppressing problems due to crystallization (for example, hindering the orientation of the PVA-based resin layer due to stretching). It is preferable that the degree

If necessary, you may implement an insolubilization treatment process after the said aerial auxiliary extending|stretching process process, before a dyeing|staining process process or an underwater extending|stretching process process. The insolubilization treatment step is typically performed by immersing the PVA-based resin layer in an aqueous boric acid solution. By performing an insolubilization treatment process, water resistance can be provided to a PVA-type resin layer, and the orientation fall of PVA at the time of being immersed in water can be prevented. The concentration of the boric acid aqueous solution is preferably about 1 to 5 parts by weight based on 100 parts by weight of water. It is preferable that the liquid temperature of an insolubilization treatment bath is about 20-50 degreeC.

The dyeing treatment step is performed by dyeing the PVA-based resin layer with iodine. As the adsorption method, for example, a method of immersing the 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 spraying the dyeing solution onto the PVA-based resin layer Method etc. are mentioned, The method of immersing the PVA-type resin layer (laminated body) in the dyeing solution containing iodine is preferable.

It is preferable that the compounding quantity of the iodine in the said dyeing bath is about 0.05-0.5 weight part with respect to 100 weight part of water. In order to improve the solubility of iodine in water, it is preferable to mix|blend the said iodide with iodine aqueous solution. It is preferable that it is about 0.1-10 weight part with respect to 100 weight part of water, and, as for the compounding quantity of the said iodide, it is more preferable that it is about 0.3-5 weight part. It is preferable that the liquid temperature of a dyeing bath is about 20-50 degreeC in order to suppress dissolution of PVA-type resin. Moreover, it is preferable that it is about 5 second - about 5 minutes from a viewpoint of ensuring the transmittance|permeability of a PVA-type resin layer, and, as for immersion time, it is more preferable that it is about 30 second - about 90 seconds. From the viewpoint of obtaining a polarizing film having good optical properties, the ratio of the content of iodine to iodide in the aqueous iodine solution is preferably about 1:5 to 1:20, more preferably about 1:5 to 1:10.

If necessary, a crosslinking treatment step may be performed after the dyeing treatment step and before the underwater stretching treatment step. The crosslinking treatment step is typically performed by immersing the PVA-based resin layer in an aqueous boric acid solution. By implementing a crosslinking treatment process, water resistance can be provided to a PVA-type resin layer, and the orientation fall of PVA at the time of immersing in high temperature water by subsequent underwater extending|stretching can be prevented. The boric acid concentration of the boric acid aqueous solution is preferably about 1 to 5 parts by weight based on 100 parts by weight of water. Moreover, when performing a crosslinking treatment process, it is further preferable to mix|blend the said iodide with a crosslinking bath. By mix|blending the said iodide, the elution of the iodine made to adsorb|suck to the PVA-type resin layer can be suppressed. It is preferable that the compounding quantity of the said iodide is about 1-5 weight part with respect to 100 weight part of water. It is preferable that the liquid temperature of a crosslinking bath (boric acid aqueous solution) is about 20-50 degreeC.

The above-mentioned underwater stretching treatment step is performed by immersing the laminate in a stretching bath. According to the underwater stretching treatment process, it can be stretched at a temperature lower than the glass transition temperature (typically about 80° C.) of the thermoplastic resin substrate or the PVA-based resin layer, and the PVA-based resin layer is stretched at a high magnification while suppressing its crystallization. can do. 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 (eg, uniaxial stretching by passing 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 properties.

It is preferable to carry out the said underwater extending|stretching process process by immersing a laminated body in boric-acid aqueous solution (boric-acid water extending|stretching). By using the aqueous boric acid solution as the stretching bath, it is possible to impart rigidity to the PVA-based resin layer to withstand tension applied during stretching and water resistance insoluble in water. It is preferable that it is 1-10 weight part with respect to 100 weight part of water, and, as for the boric acid concentration of boric-acid aqueous solution, it is more preferable that it is 2.5-6 weight part. In addition, you may mix|blend an iodide with the said stretching bath (boric acid aqueous solution). It is preferable that it is about 40-85 degreeC, and, as for the liquid temperature of a stretching bath, it is more preferable that it is about 60 degreeC - 75 degreeC. The immersion time of the laminate in the stretching bath is preferably about 15 seconds to 5 minutes.

It is preferable that it is about 1.5 times or more, and, as for the draw ratio in the said underwater extending|stretching process process, it is more preferable that it is about 3 times or more.

Moreover, it is preferable that it is about 5 times or more with respect to the original length of a laminated body, and, as for the total draw ratio of a laminated body, it is more preferable that it is about 5.5 times or more.

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

In addition, in each treatment bath in the dyeing treatment step, the underwater stretching treatment step, the insolubilization treatment step, the crosslinking treatment step, and the washing treatment step, zinc salt, a pH adjuster, a pH buffer, other salts such as You may contain an additive. Examples of the zinc salt include zinc halides such as zinc chloride and zinc iodide; Inorganic zinc salts, such as zinc sulfate and zinc acetate, etc. are mentioned. As said pH adjuster, strong acids, such as hydrochloric acid, sulfuric acid, and nitric acid, and strong bases, such as sodium hydroxide and potassium hydroxide, are mentioned, for example. Examples of the pH buffering agent include carboxylic acids and salts thereof such as acetic acid, oxalic acid, and citric acid, and weak inorganic acids and salts thereof such as phosphoric acid and carbonic acid. 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 salts of alkali metals and alkaline earth metals.

<Step (II-2) of manufacturing a laminate having a polarizing film impregnated with a component in a liquid>

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

In the above step (II-2), it is preferable that the moisture content of the polarizing film is 22 wt% or more from the viewpoint of being easy to impregnate the components contained in the liquid and making it easier to penetrate in the thickness direction of the polarizing film, It is more preferable that the moisture content of the film is 25% by weight or more, and from the viewpoint of preventing wrinkles during transport, it is preferable that the moisture content of the polarizing film is 70% by weight or less, and the moisture content of the polarizing film is 60% by weight or less. more preferably.

The time from the step (II-1) to the start of the step (II-2) (transfer time of the laminate having a polarizing film in actual machine production) is a viewpoint of maintaining the moisture 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, still more preferably 60 seconds or less, , more preferably 10 seconds or less.

<Step (II-3) of manufacturing a polarizing film after drying>

The manufacturing method of the polarizing film (thin polarizing film) of the present invention includes a step (II-3) of manufacturing the polarizing film after drying by subjecting the laminate having the polarizing film impregnated with the component in the liquid obtained above to a drying treatment step do.

The said drying treatment process is performed by arbitrary suitable methods, for example, natural drying, air drying, and heat drying are mentioned. In addition, the said drying treatment process may be performed by zone heating performed by heating the whole zone, and may be performed by heating a conveyance roll (a so-called heating roll is used). By drying using a heating roll, it is possible to efficiently suppress heating curl of the laminate to manufacture a polarizing film excellent in appearance, and also to keep the laminate in a flat state while drying it, thereby suppressing the occurrence of wrinkles as well as curls. can do. In addition, by shrinking in the width direction during the drying treatment step, from the viewpoint of improving the optical properties of the polarizing film obtained, the shrinkage ratio in the width direction of the laminate by the drying treatment step is preferably about 1 to 10%, and 2 to 8 % is more preferable.

Drying conditions can be controlled by adjusting the heating temperature of the conveying rolls (temperature of the heating rolls), the number of heating rolls, the contact time with the heating rolls, and the like. It is preferable that the temperature of a heating roll is about 60-120 degreeC, It is more preferable that it is about 65-100 degreeC, It is still more preferable that it is 70-80 degreeC. From the viewpoint of increasing the crystallinity of the thermoplastic resin favorably and suppressing curl satisfactorily, the number of conveying rolls is usually about 2 to 40, preferably about 4 to 30. It is preferable that it is about 1 to 300 second, as for the contact time (total contact time) of a laminated body and a heating roll, it is more preferable that it is 1 to 20 second, It is still more preferable that it is 1 to 10 second.

The heating roll may be installed in a heating furnace or may be installed in a normal production line (under a room temperature environment). Preferably, it is installed in the heating furnace provided with the blowing means. By using the drying by heating rolls and hot air drying together, the rapid temperature change between heating rolls can be suppressed, and the shrinkage|contraction in the width direction can be easily controlled. It is preferable that the temperature of hot air drying is about 30-100 degreeC. Moreover, it is preferable that hot air drying time is about 1-300 second.

<Method for producing polarizing film>

The manufacturing method of the polarizing film of this invention includes the process of bonding a transparent protective film through an adhesive bond layer to at least one side of the polarizing film obtained by the manufacturing method of the said polarizing film.

The transparent protective film is not particularly limited, and various kinds of transparent protective films used for polarizing films can be used. As a material constituting the transparent protective film, for example, a thermoplastic resin excellent in transparency, mechanical strength, thermal stability, moisture barrier property, isotropy, and the like is used. Examples of the thermoplastic resin include cellulose ester-based resins such as triacetyl cellulose, polyester-based resins such as polyethylene terephthalate and polyethylene naphthalate, polyethersulfone-based resins, polysulfone-based resins, polycarbonate-based resins, Polyamide-based resins such as nylon and aromatic polyamide, polyimide-based resins, polyolefin-based resins such as polyethylene, polypropylene, and ethylene/propylene copolymers, (meth)acrylic-based resins, and cyclo- or cyclic polyolefins having a norbornene structure resins (norbornene-based resins), polyarylate-based resins, polystyrene-based resins, polyvinyl alcohol-based resins, and mixtures thereof. In addition, as the transparent protective film, a cured layer formed of a thermosetting resin such as (meth)acrylic, urethane, acrylic urethane, epoxy, or silicone resin or UV curable resin may be used. Among these, cellulose ester-type resin, polycarbonate-type resin, (meth)acrylic-type resin, cyclic polyolefin-type resin, and polyester-type resin are suitable.

Although the thickness of the transparent protective film can be appropriately determined, in general, from the viewpoint of workability such as strength and handleability, thin layer properties, etc., it is preferably about 1 to 500 µm, and more preferably about 1 to 300 µm. And, it is more preferable that it is about 5-100 micrometers.

When bonding the said transparent protective film to both surfaces of the said polarizing film, the same or different transparent protective films on the both surfaces may be sufficient as it.

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

Examples of the retardation plate include a birefringent film formed by subjecting a polymer material to uniaxial or biaxial stretching treatment, 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. Although the thickness in particular of a retardation plate is not restrict|limited, About 20-150 micrometers is common. Moreover, you may use by bonding the said phase plate to the transparent protective film which does not have a phase difference.

The transparent protective film may contain any appropriate additives such as an ultraviolet absorber, antioxidant, lubricant, plasticizer, mold release agent, color inhibitor, flame retardant, antistatic agent, pigment, and colorant.

Functional layers, such as a hard coat layer, an antireflection layer, a sticking prevention layer, a diffusion layer, and an anti-glare layer, can be formed on the surface to which the polarizing film of the said transparent protective film is not bonded. In addition, the functional layers such as the hard coat layer, the antireflection layer, the anti-sticking layer, the diffusion layer and the antiglare layer can be formed on the protective film itself, and can also be formed separately from the protective film.

The polarizing film and the transparent protective film, or the polarizing film and the functional layer are usually bonded through a pressure-sensitive adhesive layer or an adhesive layer.

As the pressure-sensitive adhesive for 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 pressure-sensitive adhesives, silicone pressure-sensitive adhesives, urethane pressure-sensitive adhesives, vinyl alkyl ether pressure-sensitive adhesives, polyvinyl alcohol-based pressure-sensitive adhesives, poly Acrylamide-type adhesive, polyacrylamide-type adhesive, a cellulose-type adhesive, etc. are mentioned. Among these, an acrylic adhesive is suitable.

As a method of forming the pressure-sensitive adhesive layer, for example, a method in which the pressure-sensitive adhesive is applied to a peeling-treated separator or the like and dried to form a pressure-sensitive adhesive layer, then transferred to a polarizing film or the like, or the pressure-sensitive adhesive is applied to a polarizing film or the like and dried to form an pressure-sensitive adhesive layer A method of forming the , etc. can be illustrated. The thickness in particular of the said adhesive layer is not restrict|limited, For example, it is about 1-100 micrometers, and it is preferable that it is about 2-50 micrometers.

As the adhesive for forming the adhesive layer, various adhesives used in polarizing films can be applied, for example, isocyanate-based adhesives, polyvinyl alcohol-based adhesives, gelatin-based adhesives, vinyl-based latex-based adhesives, water-based polyesters, etc. there is. These adhesives are usually used as adhesives composed of aqueous solutions, and contain 0.5 to 60% by weight of solid content.

As said adhesive agent, other than the above, active energy ray hardening adhesives, such as an ultraviolet curing adhesive and an electron beam curing adhesive, are mentioned. As said active energy ray hardening-type adhesive agent, a (meth)acrylate-type adhesive agent is mentioned, for example. As a curable component in the said (meth)acrylate-type adhesive agent, the compound which has a (meth)acryloyl group, and the compound which has a vinyl group are mentioned, for example. Moreover, the compound which has an epoxy group or an oxetanyl group can also be used as a cationic polymerization hardening-type adhesive agent. 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.

Application of the adhesive may be performed either on the transparent protective film side (or on the functional layer side) or on the polarizing film side, or both. After bonding, a drying step is performed to form an adhesive layer comprising a coating and drying layer. After the drying step, if necessary, ultraviolet rays or electron beams can be irradiated. 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 when using an ultraviolet curing adhesive, an electron beam curing adhesive, etc. It is preferable that it is about 0.1-100 micrometers, and it is more preferable that it is about 0.5-10 micrometers.

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 easily adhesive layer, a block layer, and 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.

The easily adhesive agent for forming the easily adhesive layer includes, for example, various resins having a polyester skeleton, polyether skeleton, polycarbonate skeleton, polyurethane skeleton, silicone system, polyamide skeleton, polyimide skeleton, polyvinyl alcohol skeleton, etc. A forming material is mentioned. The said easily adhesive layer is normally formed in advance in a protective film, and the easily adhesive layer side of the said protective film and a polarizing film are laminated|stacked with the said adhesive layer or the said adhesive bond layer.

The blocking layer is a layer having a function to prevent impurities such as oligomers and ions eluted from the transparent protective film or the like from migrating (infiltrating) into the polarizing film. The block layer may be a layer that has transparency and can prevent impurities eluted from the transparent protective film or the like. Epoxy-type forming materials etc. are mentioned.

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

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

Example

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

<Example 1>

<Production of polarizing film>

<Preparation of polarizing film containing water (I-1)>

A polyvinyl alcohol film having an average degree of polymerization of 2,400, a degree of saponification of 99.9 mol%, and a thickness of 45 μm was prepared. The polyvinyl alcohol film was stretched 2.2 times in the conveying direction while swelling by immersing it in a 20°C swelling bath (water bath) for 30 seconds between rolls with different circumferential speed ratios (swelling step), followed by a 30°C dyeing bath (iodine concentration of 0.03) The original polyvinyl alcohol film (polyvinyl alcohol film not stretched at all in the conveying direction) was stretched 3.3 times in the conveying direction while immersed in an aqueous solution having a concentration of 0.3% by weight and potassium iodide in an aqueous solution of 0.3% by weight) for 30 seconds. (dyeing process). Next, the dyed polyvinyl alcohol film was immersed in a crosslinking bath (a solution having a boric acid concentration of 3.0% by weight and potassium iodide concentration of 3.0% by weight) at 40° C. for 28 seconds in the transport direction based on the original polyvinyl alcohol film. It was extended to 3.6 times (crosslinking process). Further, the obtained polyvinyl alcohol film was immersed in a stretching bath at 61° C. (aqueous solution having a boric acid concentration of 4.0 wt% and potassium iodide concentration of 5.0 wt%) for 60 seconds, and 6.0 in the conveying direction based on the original polyvinyl alcohol film. After extending|stretching to twice (stretching process), it immersed for 5 second (washing process) in a 20 degreeC washing|cleaning bath (aqueous solution with a potassium iodide concentration of 2.0 weight%), and the polarizing film containing water was manufactured.

<Preparation of a polarizing film impregnated with a component in a liquid (I-2)>

Liquid A (10 wt% aqueous solution of a compound represented by the following formula (9)) was applied to the water-containing polarizing film obtained above using a wire bar (manufactured by Daiichi Chemical Co., Ltd., No. 3), After leaving still for 3 seconds at 25 degreeC, the liquid A remaining on the surface was wiped off, and the polarizing film impregnated with the component in the liquid was manufactured. Here, the moisture content of the polarizing film containing water calculated|required by the following measuring method was 33.0 weight%.

[Measuring method of moisture content (wt%) in polarizing film]

About 0.2 g of a polarizing film was weighed, dried at 120 degreeC for 2 hours, the weight after drying was measured, and the moisture content (W) in a polarizing film was computed based on the following formula.

Moisture content W (wt%) of the polarizing film = {(M ₀ -M ₁ )/M ₀ }×100

M ₀ : Weighed polarizing film weight (g)

M ₁ : Weight of polarizing film after drying at 120°C for 2 hours (g)

<Preparation of polarizing film after drying (I-3)>

The polarizing film impregnated with the component in the liquid obtained above was dried at 60° C. for 4 minutes to prepare a dried polarizing film (hereinafter, simply referred to as a polarizing film). The moisture content of the polarizing film after drying determined by the above measurement method was 11.3% by weight. The content (M _H ) of the compound represented by the formula (9) in the polarizing film obtained by the following measurement method is 0.27 wt%, and the content (M _H ) of the compound represented by the formula (9) per unit area is 5.8 μg/cm 2 it was Moreover, the thickness (T) of the polarizing film was 18 micrometers.

[Method for measuring content (% by weight) of the compound represented by the formula (9) in the polarizing film]

About 20 mg of the polarizing film was collected, quantified, and dissolved by heating in 1 mL of water, diluted with 4.5 mL of methanol, and the resulting extract was filtered through a membrane filter, and the filtrate was used by HPLC (ACQUITY UPLC H-class Bio manufactured by Waters). Thus, the concentration of the compound represented by the formula (9) was measured.

[Method for measuring the content (μg/cm 2 ) of the compound represented by the formula (9) per unit area in the polarizing film]

The content (M _H ) of the compound represented by the formula (9) per unit area was calculated based on the following formula.

m _H =1.2×T×M _H (μg/㎠)

T: thickness of the polarizing film (㎛)

M _H : Content (weight%) of the compound represented by Formula (9) in a polarizing film

<Production of polarizing film>

As an adhesive, an aqueous solution containing polyvinyl alcohol resin containing an acetacetyl group (average degree of polymerization 1,200, saponification degree 98.5 mol%, acetacetylation degree 5 mol%) and methylolmelamine in a weight ratio of 3:1 was used. Using this adhesive, a 40 μm thick triacetyl cellulose film having a hard coat layer on both sides of the polarizing film obtained above (water vapor transmission rate of 342 g/(m 2 ·24 h), manufactured by Konica Minolta, trade name “KC4UYW”) was rolled with a roll bonding machine. After bonding, it was made to heat-dry continuously in oven (temperature is 60 degreeC, time is 4 minutes), and the polarizing film by which the transparent protective film was bonded on both surfaces of a polarizing film was manufactured.

[Measurement method of polarization degree]

The degree of polarization of a polarizing film can be measured using a spectrophotometer (made by Nippon Bunko, product name "V7100"). As a specific method for measuring the degree of polarization, parallel transmittance (H0) and orthogonal transmittance (H90) of the polarizing film are measured, and from the formula: polarization degree (%) = {(H0-H90)/(H0+H90)} 1/2×100 can be saved The parallel transmittance (H0) is a value of transmittance of a parallel laminated polarizing film prepared by stacking two identical polarizing films so that their absorption axes are parallel to each other. In addition, the orthogonal transmittance (H90) is a value of transmittance of an orthogonal laminated polarizing film prepared by stacking two same polarizing films so that their absorption axes are orthogonal to each other. In addition, these transmittance|permeability is the Y value which performed visibility correction|amendment with the 2 degree field of view (C light source) of JISZ8701-1982.

[Heat durability evaluation (A)]

The polarizing film obtained above is cut into a size of 5.0 x 4.5 cm so that the absorption axis of the polarizing film is parallel to the long side, and a glass plate (pseudo image display cell) was bonded, and the autoclave process was carried out at 50 degreeC and 0.5 MPa for 15 minutes, and the laminated body was produced. The obtained laminate was left still in a hot-air oven with a temperature of 110 degreeC, and the time until coloring was visually judged by the following references|standards.

○: It was not colored for 500 hours or more.

(triangle|delta): Colored in 300 hours or more and less than 500 hours.

x: It was colored in less than 300 hours.

<Example 2>

<Preparation of a polarizing film and a polarizing film>

After the polarizing film after the washing step was left still at 25° C. for 30 seconds to obtain a polarizing film containing water, a polarizing film and a polarizing film were prepared in the same manner as in Example 1 except that Liquid A was applied, and the measurement was performed. A result is shown in Table 1.

<Example 3>

<Preparation of a polarizing film and a polarizing film>

After the polarizing film after the washing step was left still at 25° C. for 1 minute to obtain a polarizing film containing water, a polarizing film and a polarizing film were prepared in the same manner as in Example 1 except that Liquid A was applied, and the measurement was performed. A result is shown in Table 1.

<Comparative Example 1>

<Preparation of a polarizing film and a polarizing film>

After the polarizing film after the washing step was left still at 25° C. for 3 minutes to obtain a polarizing film containing water, a polarizing film and a polarizing film were prepared in the same manner as in Example 1 except that Liquid A was applied, and the measurement was performed. A result is shown in Table 1.

<Comparative Example 2>

<Preparation of a polarizing film and a polarizing film>

After drying the polarizing film after a washing|cleaning process at 60 degreeC for 1 minute, except having apply|coated liquid A, a polarizing film and a polarizing film were manufactured by operation similar to Example 1, and the said measurement was performed. A result is shown in Table 1.

<Example 4>

<Preparation of a polarizing film and a polarizing film>

A polarizing film and a polarizing film were manufactured in the same manner as in Example 1 except that a polyvinyl alcohol film having a thickness of 30 µm was used and the iodine concentration of the dyeing bath was adjusted so that the single transmittance of the finally obtained polarizing film was about the same. and the above and the following measurements were performed. A result is shown in Table 2. Moreover, the thickness (T) of the polarizing film was 12 micrometers.

[Heat durability evaluation (B)]

The polarizing film obtained above is cut into a size of 5.0 x 4.5 cm so that the absorption axis of the polarizing film is parallel to the long side, and a glass plate (pseudo image display cell) was bonded, and the autoclave process was carried out at 50 degreeC and 0.5 MPa for 15 minutes, and the laminated body was produced. The obtained laminate was left still in a hot-air oven with a temperature of 105 degreeC, and the time until coloring was visually judged by the following reference|standard.

○: It was not colored for more than 750 hours.

(triangle|delta): It was colored in 750 hours or more and less than 500 hours.

x: It was colored in less than 500 hours.

<Comparative Example 3>

<Preparation of a polarizing film and a polarizing film>

After drying the polarizing film after a washing|cleaning process at 60 degreeC for 1 minute, except having apply|coated liquid A, a polarizing film and a polarizing film were manufactured by operation similar to Example 4, and the said measurement was performed. A result is shown in Table 2.

<Example 5>

<Production of polarizing film>

<Production (Preparation) of Laminate (II-0)>

As the thermoplastic resin base material, an amorphous isophthalic copolymerized polyethylene terephthalate film (thickness: 100 µm) having a long water absorption rate of 0.75% and a Tg of about 75°C was used. Corona treatment was performed on one side of the resin substrate. Potassium iodide in 100 parts by weight of a PVA-based resin in which polyvinyl alcohol (polymerization degree 4200, saponification degree 99.2 mol%) and acetacetyl-modified PVA (Nippon Kosei Chemical Co., Ltd., trade name "Gosepimer Z410") were mixed at 9:1 13 weight part was added, and the PVA aqueous solution (coating liquid) was prepared. The PVA-type resin layer with a thickness of 13 micrometers was formed by apply|coating the said PVA aqueous solution to the corona-treated surface of a resin base material, and drying at 60 degreeC, and the laminated body was manufactured (prepared).

<Step (II-1) of manufacturing a laminate having a polarizing film containing water>

The free-end uniaxial stretching of the obtained laminated body was carried out in the longitudinal direction (longitudinal direction) by 2.4 times between rolls with different circumferential speeds in 130 degreeC oven (air-assisted extending|stretching process process). Next, the laminate was immersed in an insolubilization bath (a boric acid aqueous solution obtained by blending 4 parts by weight of boric acid with respect to 100 parts by weight of water) at a liquid temperature of 40°C for 30 seconds (insolubilization treatment step). Next, the concentration is adjusted so that the single transmittance (Ts) of the finally obtained polarizing film is about the same in a dyeing bath (aqueous solution of iodine obtained by mixing iodine and potassium iodide in a weight ratio of 1:7 with respect to 100 parts by weight of water) at a liquid temperature of 30°C. It was immersed for 60 second while adjusting (dyeing treatment process). Next, it was made to immerse for 30 second in the crosslinking bath (boric acid aqueous solution obtained by mix|blending 3 weight part of potassium iodide with respect to 100 weight part of water, and mix|blending 5 weight part of boric acid) with a liquid temperature of 40 degreeC (crosslinking treatment process). After that, while immersing the laminate in a boric acid aqueous solution (boric acid concentration of 4.0 wt%) at a liquid temperature of 70 ° C., uniaxial stretching was performed between rolls having different peripheral speeds so that the total draw ratio in the longitudinal direction (longitudinal direction) was 5.5 times (underwater stretching treatment) fair). Thereafter, the laminate was immersed in a washing bath (aqueous solution obtained by blending 4 parts by weight of potassium iodide with respect to 100 parts by weight of water) at a liquid temperature of 20° C. to prepare a laminate having a polarizing film containing water (washing treatment step) .

<Production of a laminate having a polarizing film impregnated with a component in a liquid (II-2)>

Using a wire bar (manufactured by Daiichi Chemical Co., Ltd., No. 3), liquid A (10 wt% aqueous solution of a compound represented by formula (9) ) was applied and left still at 25°C for 3 seconds, then the liquid A remaining on the surface was wiped off to prepare a laminate having a polarizing film impregnated with a component in the liquid. Here, the moisture content of the water-containing polarizing film obtained by the above measurement method was 35.5 wt%.

<Preparation of polarizing film after drying (II-3)>

It dried in the oven maintained at 95 degreeC for 10 minutes (drying treatment process). In this way, a polarizing film with a thickness of 5 µm was formed on the resin substrate. The moisture content of the polarizing film after drying determined by the above measurement method was 9.9% by weight. The content (M _H ) of the compound represented by the formula (9) in the polarizing film was 0.41 wt%, and the content (M _H ) of the compound represented by the formula (9) per unit area was 2.5 μg/cm 2 .

<Production of polarizing film>

As the adhesive, an aqueous solution containing a polyvinyl alcohol resin containing an acetacetyl group (average degree of polymerization 1,200, saponification degree 98.5 mol%, acetacetylation degree 5 mol%) and methylolmelamine in a weight ratio of 3:1 was used. Using this adhesive, a triacetyl cellulose film with a thickness of 40 µm having a hard coat layer on the opposite side to the resin substrate of the polarizing film obtained above (water vapor transmission rate 342 g/(m 2 ·24 h), manufactured by Konica Minolta, trade name "KC4UYW") After bonding by a roll bonding machine, it was made to heat-dry (temperature 60 degreeC, time 4 minutes) in oven then, and the polarizing film by which the transparent protective film was bonded by the single side|surface of the polarizing film was manufactured. Next, the resin substrate is peeled off, and the triacetyl cellulose film is bonded to the peeled side using the adhesive with a roll bonding machine, followed by heating and drying in an oven (temperature: 60°C, time: 4 minutes) , A polarizing film in which a transparent protective film was bonded to both surfaces of the polarizing film was prepared.

[Heat durability evaluation (C)]

The polarizing film obtained above is cut into a size of 5.0 x 4.5 cm so that the absorption axis of the polarizing film is parallel to the long side, and a glass plate (pseudo image display cell) was bonded, and the autoclave process was carried out at 50 degreeC and 0.5 MPa for 15 minutes, and the laminated body was produced. The obtained laminate was left still in a hot-air oven with a temperature of 95 degreeC, and the time until coloring was visually judged by the following reference|standard.

○: It was not colored for more than 750 hours.

(triangle|delta): It was colored in 750 hours or more and less than 500 hours.

x: It was colored in less than 500 hours.

<Comparative Example 4>

<Preparation of a polarizing film and a polarizing film>

After drying the polarizing film after a washing|cleaning process process at 95 degreeC for 10 minutes, except having apply|coated liquid A, a polarizing film and a polarizing film were manufactured by operation similar to Example 5, and the said measurement was performed. A result is shown in Table 3.

<Example 6>

<Preparation of a polarizing film and a 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 liquid B (zinc sulfate heptahydrate 10% by weight and Olfin EXP. 4200 (manufactured by Nisshin Chemical Industry Co., Ltd.) instead of liquid A.) A polarizing film and a polarizing film were manufactured by operation similar to Example 1 except having used the aqueous solution containing 0.2 weight%), and the above and following measurements were performed. The results are shown in Table 4.

[Measurement of the content (wt%) of zinc in the polarizing film]

About 25 mg of the polarizing film was weighed in a Teflon (registered trademark) container, and an acid was added and sealed, followed by irradiation with microwaves and acid decomposition under pressure at a maximum of 200°C. After complete decomposition, ultrapure water was added to adjust the volume to 50 mL, and the zinc concentration was measured using ICP-MS (Agilent 8800 manufactured by Agilent Technologies). MARS5 manufactured by CEM was used for the decomposition apparatus.

[Heat durability evaluation (D)]

The polarizing film obtained above is cut into a size of 5.0 x 4.5 cm so that the absorption axis of the polarizing film is parallel to the long side, and a glass plate (pseudo image display cell) was bonded, and the autoclave process was carried out at 50 degreeC and 0.5 MPa for 15 minutes, and the laminated body was produced. The obtained laminate was left still in a hot air oven at a temperature of 105° C. for 500 hours, the sample after the test was placed in a cross nicol, and the orthogonal transmittance (%) at a wavelength of 700 nm was measured with the spectrophotometer (V7100), respectively, and judged according to the following criteria. did.

(circle): No heating redness (the difference of the orthogonal transmittance|permeability in wavelength 700nm before and behind the heat test of 105 degreeC 500 hours is less than 1 %).

x: There is heat redness (the difference of the orthogonal transmittance|permeability in wavelength 700nm before and behind the heat test of 105 degreeC 500 hours is 1 % or more).

<Comparative Example 5>

<Preparation of a polarizing film and a polarizing film>

After drying the polarizing film after a washing|cleaning process at 60 degreeC for 1 minute, except having apply|coated liquid B, a polarizing film and a polarizing film were manufactured by operation similar to Example 6, and the said measurement was performed. A result is shown in Table 4.

Since the heat 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 contains sufficient components in the liquid than the polarizing film of the comparative example. Therefore, it can be seen that the heating durability is excellent.

Claims (8)

A method for manufacturing a polarizing film, comprising:
A step (I-1) of producing a water-containing polarizing film by subjecting the polyvinyl alcohol-based film to at least a dyeing process, a crosslinking process, and an extending process while conveying the polyvinyl alcohol-based film in the longitudinal direction;
A step (I-2) of producing a polarizing film impregnated with a component in the liquid by applying a liquid to the obtained polarizing film containing water in a state where the moisture content of the polarizing film is 20 wt% or more;
A method for producing a polarizing film, comprising a step (I-3) of manufacturing the polarizing film after drying by subjecting the polarizing film impregnated with the component in the obtained liquid to a drying step. A method for manufacturing a polarizing film, comprising:
A step of preparing a laminate by forming a polyvinyl alcohol-based resin layer containing a polyvinyl alcohol-based resin on one side of a long thermoplastic resin substrate (II-0);
Step (II-1) of manufacturing a laminate having a polarizing film containing water by subjecting the laminate to at least an aerial auxiliary stretching treatment step, a dyeing treatment step, and an underwater stretching treatment step while conveying the obtained laminate in the longitudinal direction (II-1) class,
A step (II-2) of producing a laminate having a polarizing film impregnated with a component in the liquid by applying a liquid to the obtained laminate having a polarizing film containing water in a state where the moisture content of the polarizing film is 20 wt% or more (II-2); ,
A method for producing a polarizing film, comprising a step (II-3) of manufacturing a polarizing film after drying by subjecting the laminate having a polarizing film impregnated with a component in the obtained liquid to a drying treatment step. 3. The method of claim 1 or 2,
The method for manufacturing a polarizing film, wherein the liquid is a solution, and a component in the liquid is a solute. 4. The method according to any one of claims 1 to 3,
The method of manufacturing a polarizing film, characterized in that the moisture content of the polarizing film after drying is 20% by weight or less. 5. The method according to any one of claims 1 to 4,
A method for producing a polarizing film, wherein the component in the liquid is a water-soluble compound. 6. The method according to any one of claims 1 to 5,
The component in the liquid is at least one selected from the group consisting of a radical scavenger, a crosslinking agent, a plasticizer, and a dye. 7. The method according to any one of claims 1 to 6,
The component in the said liquid is a radical scavenger, The manufacturing method of the polarizing film characterized by the above-mentioned. The manufacturing method of the polarizing film characterized by including the process of bonding a transparent protective film to at least one side of the polarizing film obtained by the manufacturing method of the polarizing film in any one of Claims 1-7 through an adhesive bond layer.