JP7401400B2 - Polarizing film, polarizing film, laminated polarizing film, image display panel, image display device, and manufacturing method of polarizing film - Google Patents

Description

The present invention relates to a polarizing film, a polarizing film, a laminated polarizing film, an image display panel, an image display device, and a method for manufacturing a polarizing film.

Conventionally, polarizing films used in various image display devices such as liquid crystal display devices and organic EL display devices have been dyed (using iodine, dichroic dyes, etc.) because they have both high transmittance and high degree of polarization. A polyvinyl alcohol film (containing a dichroic substance) is used. The polarizing film is manufactured by subjecting a polyvinyl alcohol film to various treatments such as swelling, dyeing, crosslinking, and stretching in a bath, followed by washing and 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 or both sides of the polarizing film using an adhesive.

The polarizing film is used as a laminated polarizing film (optical laminate) by laminating other optical layers as necessary, and the polarizing film or the laminated polarizing film (optical laminate) is used as a liquid crystal cell or an organic EL element. etc., and a front transparent member such as a front transparent plate (window layer) or a touch panel on the viewing side through an adhesive layer or an adhesive layer, and can be used as the various image display devices mentioned above. used.

In recent years, the applications of these types of image display devices have been expanding, such as being used not only for mobile devices such as mobile phones and tablet terminals, but also for in-vehicle image display devices such as car navigation devices and rear view monitors. There is. Along with this, the polarizing film and the laminated polarizing film are required to have higher durability under harsher environments (e.g., high temperature environments) than was previously required. A polarizing film for the purpose of ensuring this has been proposed (Patent Document 1).

In addition, dye-based polarizing films that use dichroic dyes such as azo compounds generally require higher temperatures and It is known that the light resistance under high humidity conditions is excellent (Patent Document 2). It has been disclosed that the adhesive used contains a hindered amine compound (Patent Document 3).

Further, in order to improve the heat resistance of a polarizing plate, it is specifically disclosed that a water-insoluble HALS (Hindered Amine Light Stabilizer) is added to an adhesive containing an epoxy compound (Patent Document 4). .

Special Publication No. 2012-516468 Japanese Patent Application Publication No. 2001-240762 Japanese Patent Application Publication No. 2005-338343 Korean Patent Application Publication No. 10-2015-0114149

On the other hand, as mentioned above, polarizing films and laminated polarizing films using iodine-based polarizing films, which are said to have inferior light resistance under high-temperature and high-humidity conditions than dyed-based polarizing films, are Another problem is that the polarizing film becomes colored and its single transmittance decreases.

In view of the above circumstances, an object of the present invention is to provide a polarizing film that is excellent in suppressing a decrease in single transmittance due to coloring of the polarizing film in a high-temperature environment.

The present invention also provides a polarizing film, a laminated polarizing film, an image display panel, an image display device, and a method for producing the polarizing film, each using a polarizing film that is excellent in suppressing a decrease in unit transmittance due to coloring of the polarizing film. The purpose is to provide

That is, the present invention provides a polarizing film formed by adsorbing and aligning iodine on a polyvinyl alcohol film, which contains a hindered amine compound, and the hindered amine compound is added in an amount of 1 weight per 100 parts by weight of water at 25°C. The present invention relates to a polarizing film that is a water-soluble hindered amine compound that can dissolve more than 1% of the water.

The present invention also relates to a polarizing film in which a transparent protective film is bonded to at least one surface of the polarizing film.

The present invention also relates to a laminated polarizing film in which the polarizing film is bonded to an optical layer.

The present invention also relates to an image display panel in which the polarizing film or the laminated polarizing film is bonded to an image display cell.

The present invention also relates to an image display device including a front transparent member on the polarizing film or laminated polarizing film side of the image display panel.

Furthermore, the present invention provides a method for producing the polarizing film, which is obtained by subjecting a polyvinyl alcohol film to an arbitrary swelling step and washing step, and at least a dyeing step, a crosslinking step, and a stretching step; The treatment bath in any one or more of the washing step, the dyeing step, the crosslinking step, and the stretching step contains a hindered amine compound, and the hindered amine compound is mixed with 100% water at 25° C. The present invention relates to a method for producing a polarizing film made of a water-soluble hindered amine compound that can be dissolved in 1 part by weight or more per part.

Furthermore, the present invention provides a method for manufacturing the polarizing film, comprising a step of preparing a laminate by forming a polyvinyl alcohol resin layer containing a polyvinyl alcohol resin on one side of a long thermoplastic resin base material. While conveying the obtained laminate in the longitudinal direction, the laminate is subjected to an optional insolubilization treatment process, a crosslinking treatment process, a washing treatment process, and at least an in-air assisted stretching treatment process, a dyeing treatment process, and an underwater treatment process. The treatment bath obtained by carrying out the stretching treatment step and used in any one or more of the insolubilization treatment step, the crosslinking treatment step, the washing treatment step, the dyeing treatment step, and the underwater stretching treatment step is a hindered amine. The present invention relates to a method for producing a polarizing film in which the hindered amine compound is a water-soluble hindered amine compound that can be dissolved in 1 part by weight or more in 100 parts by weight of water at 25°C.

Although the details of the mechanism of the effect in the polarizing film of the present invention are unclear, it is estimated as follows. However, the present invention does not need to be interpreted as being limited to this mechanism of action.

The polarizing film of the present invention is an iodine-based polarizing film formed by adsorbing and aligning iodine to a polyvinyl alcohol film, and is a water-soluble hindered amine compound that can be dissolved in 1 part by weight or more in 100 parts by weight of water at 25°C. Contains water-soluble hindered amine compounds. As described in Patent Documents 2 and 3 above, it is said that iodine-based polarizing films are generally inferior to dye-based polarizing films in terms of durability such as heat resistance. It is assumed that this is because the iodine contained in the polyvinyl alcohol accelerates the deterioration phenomenon called polyenation, which occurs due to the dehydration reaction of polyvinyl alcohol in a high-temperature environment. On the other hand, since polarizing films generally contain water, the above-mentioned water-soluble hindered amine compounds can efficiently permeate into the polarizing film together with water during the production of the polarizing film. is estimated to be able to efficiently capture radicals generated in the above-mentioned polyenization reaction in a high-temperature environment, and therefore, the polarizing film of the present invention can suppress a decrease in single transmittance due to coloring of the polarizing film.

<Polarizing film>
The polarizing film of the present invention is formed by adsorbing and aligning iodine to a polyvinyl alcohol film, and contains a hindered amine compound, and the hindered amine compound can be dissolved in 1 part by weight or more in 100 parts by weight of water at 25°C. It is a water-soluble hindered amine compound.

The polyvinyl alcohol (PVA) film has transparency in the visible light region and can disperse and adsorb iodine, and can be used without particular limitation. Further, the PVA-based film, which is usually used as the original film, 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 for the polyvinyl alcohol film include polyvinyl alcohol or derivatives thereof. Examples of the polyvinyl alcohol derivatives include polyvinyl formal, polyvinyl acetal; olefins such as ethylene and propylene; unsaturated carboxylic acids such as acrylic acid, methacrylic acid, and crotonic acid, and those modified with their alkyl esters, acrylamide, etc. can be mentioned. The average degree of polymerization of the polyvinyl alcohol is preferably 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 saponification degree of the polyvinyl alcohol is preferably about 80 to 100 mol%, more preferably about 95 mol% to 99.95 mol%. In addition, the said average polymerization degree and the said saponification degree can be calculated|required according to JISK6726.

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

The content of iodine in the polarizing film is preferably 1% by weight or more and 15% by weight or less. In the polarizing film, the iodine content is preferably 1.5% by weight or more, more preferably 2% by weight or more, from the viewpoint of suppressing color fading during a durability test, and From the viewpoint of preventing polyenization, the content is preferably 12% by weight or less, more preferably 10% by weight or less.

The polarizing film includes a hindered amine compound, and the hindered amine compound is a water-soluble hindered amine compound that can be dissolved in 1 part by weight or more in 100 parts by weight of water at 25°C. The hindered amine compounds may be used alone or in combination of two or more.

It is preferable that the hindered amine compound can be dissolved in 2 parts by weight or more in 100 parts by weight of water at 25°C, from the viewpoint of being able to efficiently penetrate into the polarizing film together with water during the production of the polarizing film. It is more preferable that 5 parts by weight or more can be dissolved in 100 parts by weight.

In addition, the molecular weight of the hindered amine compound is preferably 1000 or less, more preferably 500 or less, and even more preferably 300 or less, from the viewpoint of efficiently capturing radicals generated in the polyenation reaction. preferable.

（一般式（１）中、Ｒ^１は、オキシラジカル、水素原子、ヒドロキシ基、または炭素原子数が１～３０のアルキル基、ヒドロキシアルキル基、ヒドロキシアルコキシ基、もしくはアルコキシ基を表し、Ｒ^２からＲ^５は、独立して、水素原子、または炭素原子数が１～１０のアルキル基を表し、ｎは０または１を表す。）なお、一般式（１）中の、点線部の左は任意の有機基を示す。 The hindered amine compound is a secondary amine or tertiary amine in which the carbon adjacent to the amino group is substituted with an alkyl group to sterically protect the amino group, and for example, has an organic group having the following structure. Examples include compounds. Note that the exemplified compounds may include structures that cannot be dissolved in 1 part by weight or more in 100 parts by weight of water at 25°C. It can be immediately confirmed whether 1 part by weight or more can be dissolved in 100 parts by weight of water at 25°C.

(In general formula (1), R ¹ represents an oxy radical, a hydrogen atom, a hydroxy group, or an alkyl group having 1 to 30 carbon atoms, a hydroxyalkyl group, a hydroxyalkoxy group, or an alkoxy group, and from R ² R ⁵ independently represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, and n represents 0 or 1.) In general formula (1), the part to the left of the dotted line is optional. represents an organic group.

The hindered amine compound is a known compound, and is described, for example, in columns 5 to 11 of US Pat. No. 4,619,956 and columns 3 to 5 of US Pat. No. 4,839,405. 2,2,6,6-tetraalkylpiperidine compounds, or acid addition salts thereof or complexes thereof with metal compounds, such as those described above.

（一般式（２）中、Ｒ^１は、オキシラジカル、水素原子、ヒドロキシ基、または炭素原子数が１～３０のアルキル基、ヒドロキシアルキル基、ヒドロキシアルコキシ基、もしくはアルコキシ基を表し、Ｒ^２からＲ^５は、独立して、水素原子、または炭素原子数が１～１０のアルキル基を表し、Ｒ^６は水素原子、または炭素原子数が１～１０のアルキル基、アシル基、もしくはアリール基を表し、ｎは０または１を表す。）

（一般式（３）中、Ｒ^１からＲ^５、およびｎは、上記と同様であり、Ｒ^７およびＲ^８は、独立して、水素原子、または炭素原子数が１～１０のアルキル基、アシル基、もしくはアリール基を表す。）

（一般式（４）中、Ｒ^１からＲ^５、およびｎは、上記と同様であり、Ｒ^９からＲ^１１は、独立して、水素原子、または炭素原子数が１～１０のアルキル基、アシル基、アミノ基、アルコキシ基、ヒドロキシ基、もしくはアリール基を表す。）

（一般式（５）中、Ｒ^１からＲ^５、およびｎは、上記と同様であり、Ｒ^１２は、水素原子、または炭素原子数が１～１０のアルキル基、アミノ基、アルコキシ基、ヒドロキシ基、もしくはアリール基を表す。） Examples of the compound having the above organic group include compounds represented by the following general formulas (2) to (5).

(In general formula (2), R ¹ represents an oxy radical, a hydrogen atom, a hydroxy group, or an alkyl group having 1 to 30 carbon atoms, a hydroxyalkyl group, a hydroxyalkoxy group, or an alkoxy group, and from R ² R ⁵ independently represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, and R ⁶ independently represents a hydrogen atom, or an alkyl group, acyl group, or aryl group having 1 to 10 carbon atoms. (n represents 0 or 1.)

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

(In 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, Represents an acyl group, amino group, alkoxy group, hydroxy group, or aryl group.)

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

In the general formulas (1) to (5), R ¹ is preferably an oxy radical, a hydrogen atom, a hydroxy group, or an alkyl group, from the viewpoint of efficiently suppressing accelerated deterioration of polyvinyl alcohol; It is more preferable that Furthermore, in the general formulas (1) to (5), R ² to R ⁵ are preferably alkyl groups having 1 to 6 carbon atoms from the viewpoint of availability and water solubility; is more preferably 1 to 3 alkyl groups. In addition, in the general formula (2), from the viewpoint of availability and water solubility, R ⁶ is preferably a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, and more preferably a hydrogen atom. preferable. Furthermore, in the general formula (3), from the viewpoint of availability and water solubility, R ⁷ and R ⁸ are preferably independently a hydrogen atom or an alkyl group having 1 to 10 carbon atoms; More preferably, it is an atom. Furthermore, in the general formula (4), from the viewpoint of availability and water solubility, R ⁹ to R ¹¹ are preferably hydrogen atoms or alkyl groups having 1 to 10 carbon atoms. Furthermore, in the general formula (5), from the viewpoint of availability and water solubility, 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.

The content of the hindered amine compound in the polarizing film is preferably 20% by weight or less. The content of the hindered amine compound in the polarizing film is preferably 0.005% by weight or more, and 0.01% by weight from the viewpoint of suppressing a decrease in single transmittance due to coloring of the polarizing film in a high-temperature environment. % or more, further preferably 0.02% by weight or more, and preferably 15% by weight or less, more preferably 12% by weight or less, and 10% by weight or less. It is even more preferable that there be.

<Manufacturing method of polarizing film>
In the method for producing a polarizing film of the present invention, the polyvinyl alcohol film is obtained by subjecting the polyvinyl alcohol film to an arbitrary swelling step and washing step, and at least a dyeing step, a crosslinking step, and a stretching step, and the swelling step and the washing step , the treatment bath in any one or more of the dyeing process, the crosslinking process, and the stretching process contains a hindered amine compound, and the hindered amine compound is 1 part by weight per 100 parts by weight of water at 25°C. It is a water-soluble hindered amine compound that can be dissolved in parts by weight or more. The content of the hindered amine compound and the content of iodine contained in the polarizing film are determined based on the content of the hindered amine compound contained in any of the treatment baths in the swelling process, dyeing process, crosslinking process, stretching process, and washing process. It can be controlled by the concentration of iodine, potassium iodide, etc., and the treatment temperature and treatment time in each of the above treatment baths. In particular, when performing a washing process after dyeing, cross-linking, and stretching, the washing process should be carried out in consideration of the treatment conditions of the dyeing, cross-linking, and stretching processes, and the washing process should be carried out with consideration of the treatment conditions such as hindered amine compounds and From the viewpoint that components such as iodine can be eluted from the polyvinyl alcohol film or adsorbed to the polyvinyl alcohol film, the content of the hindered amine compound and the content of the iodine can be easily adjusted to a desired range.

Further, each treatment bath in the swelling step, the dyeing step, the crosslinking step, the stretching step, and the washing step contains additives such as a zinc salt, a pH adjuster, a pH buffer, and other salts. You can. 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. 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 and their salts such as acetic acid, oxalic acid, and citric acid, and inorganic weak acids and their salts 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 alkali metals and alkaline earth metals. Examples include salt.

The concentration of the hindered amine compound contained in any of the treatment baths cannot be determined unconditionally because it is affected by the number of treatments, treatment time, treatment temperature, etc., but the concentration of the hindered amine compound in the polarizing film From the viewpoint of efficiently controlling the amount, it is usually preferably 0.01% by weight or more, more preferably 0.05% by weight or more, even more preferably 0.1% by weight or more, and , is preferably 30% by weight or less, more preferably 25% by weight or less, and even more preferably 20% by weight or less.

The swelling process is a treatment process in which the polyvinyl alcohol film is immersed in a swelling bath, and dirt and blocking agents on the surface of the polyvinyl alcohol film can be removed, and dyeing can also be achieved by swelling the polyvinyl alcohol film. Unevenness can be suppressed. The swelling bath usually uses a medium mainly composed of water, such as water, distilled water, or pure water. A surfactant, alcohol, etc. 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, and even more preferably about 18 to 30°C. The immersion time in the swelling bath cannot be determined unconditionally because the degree of swelling of the polyvinyl alcohol film is affected by the temperature of the swelling bath, but it is preferably about 5 to 300 seconds, and preferably about 10 to 200 seconds. More preferably, the time is about 20 to 100 seconds. The swelling step may be performed only once, or may be performed multiple times as necessary.

The dyeing step is a treatment step in which the polyvinyl alcohol film is immersed in a dyeing bath (iodine solution), and the polyvinyl alcohol film can adsorb and orient iodine. The iodine solution is usually preferably an aqueous iodine solution, and contains iodine and an iodide as a solubilizing agent. The iodides include 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 preferred from the viewpoint of controlling the potassium content in the polarizing film.

The concentration of iodine in the dyeing bath is preferably about 0.01 to 1% by weight, more preferably about 0.02 to 0.5% by weight. In the dyeing bath, the iodide concentration is preferably about 0.01 to 20% by weight, more preferably about 0.05 to 10% by weight, and about 0.1 to 5% by weight. It is even more preferable that there be.

The temperature of the dyeing bath is preferably about 10 to 50°C, more preferably about 15 to 45°C, even more preferably about 18 to 35°C. The immersion time in the dyeing bath cannot be determined unconditionally because the degree of dyeing of the polyvinyl alcohol film is affected by the temperature of the dyeing bath, but it is preferably about 10 to 300 seconds, and preferably about 20 to 240 seconds. It is more preferable that it be about a certain degree. The dyeing process may be performed only once, or may be performed multiple times as necessary.

The crosslinking step is a treatment step in which the polyvinyl alcohol film is immersed in a treatment bath (crosslinking bath) containing a boron compound, and the polyvinyl alcohol film is crosslinked by the boron compound, and the iodine molecules or dye molecules are Can be adsorbed to structures. Examples of the boron compound include boric acid, borate, and borax. The crosslinking bath is generally an aqueous solution, but may be a mixed solution of water and an organic solvent that is miscible with water, for example. Further, the crosslinking bath may contain potassium iodide from the viewpoint of controlling the potassium content in the polarizing film.

In the crosslinking 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. Further, when potassium iodide is used in the crosslinking bath, the concentration of potassium iodide in the crosslinking bath is preferably about 1 to 15% by weight, and preferably about 1.5 to 10% by weight. More preferably, it is about 2 to 5% by weight.

The temperature of the crosslinking bath is preferably about 20 to 70°C, more preferably about 30 to 60°C. The immersion time in the crosslinking bath cannot be determined unconditionally because the degree of crosslinking of the polyvinyl alcohol film is affected by the temperature of the crosslinking bath, but it is preferably about 5 to 300 seconds, and preferably about 10 to 200 seconds. It is more preferable that it be about a certain degree. The crosslinking step may be performed only once, or may be performed multiple times as necessary.

The stretching process is a process of stretching the polyvinyl alcohol film in at least one direction to a predetermined magnification. Generally, a polyvinyl alcohol 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 performed only once, or may be performed multiple times as necessary. The stretching step may be performed at any stage in the production 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 contain potassium iodide from the viewpoint of controlling the potassium content in the polarizing film. When potassium iodide is used in the stretching bath, the concentration of potassium iodide in the stretching bath is preferably about 1 to 15% by weight, more preferably about 2 to 10% by weight, and 3% by weight. More preferably, it is about 6% by weight. Further, the treatment bath (stretching bath) may contain the boron compound from the viewpoint of suppressing film breakage during stretching, and in this case, the concentration of the boron compound in the stretching bath is 1 to 15. It is preferably about 1.5 to 10% by weight, more preferably about 2 to 5% by weight.

The temperature of the stretching bath is preferably about 25 to 80°C, more preferably about 40 to 75°C, even more preferably about 50 to 70°C. The immersion time in the stretching bath cannot be determined unconditionally because the degree of stretching of the polyvinyl alcohol film is affected by the temperature of the stretching bath, but it is preferably about 10 to 800 seconds, and preferably about 30 to 500 seconds. It is more preferable that it be about a certain degree. Note that the stretching treatment in the wet stretching method may be performed together with any one or more of the swelling step, the dyeing step, the crosslinking step, and the washing step.

Examples of the dry stretching method include an inter-roll stretching method, a heated roll stretching method, a compression stretching method, and the like. Note that the dry stretching method may be performed together with the drying step.

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

The cleaning step is a treatment step in which the polyvinyl alcohol film is immersed in a cleaning bath, and foreign matter remaining on the surface of the polyvinyl alcohol film can be removed. The cleaning bath usually uses a medium mainly composed of water, such as water, distilled water, or pure water. Further, from the viewpoint of controlling the potassium content in the polarizing film, the cleaning bath may contain potassium iodide, and in this case, the concentration of potassium iodide in the cleaning bath is 1 to 10% by weight. %, more preferably about 1.5 to 4% by weight, even more preferably about 1.8 to 3.8% by weight.

The temperature of the cleaning 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 cleaning bath cannot be determined unconditionally because the degree of cleaning of the polyvinyl alcohol film is affected by the temperature of the cleaning bath, but it is preferably about 1 to 100 seconds, and preferably 2 to 50 seconds. More preferably, the time is about 3 to 20 seconds. The swelling step may be performed only once, or may be performed multiple times as necessary.

The method for manufacturing a polarizing film of the present invention may include a drying step. The drying step is a step of drying the polyvinyl alcohol film washed in the washing step to obtain a polarizing film, and by drying, a polarizing film having a desired moisture content is obtained. The drying may be performed by any suitable method, including natural drying, blow drying, and heat drying.

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

The thickness of the polarizing film is preferably about 1 to 50 μm, more preferably about 1 to 25 μm. In particular, in order to obtain a polarizing film having a thickness of 8 μm or less, the following method is used, in which a laminate including a polyvinyl alcohol resin layer formed on a resin base material such as a thermoplastic resin is used as the polyvinyl alcohol film. A method for manufacturing a thin polarizing film can be applied.

<Production method of polarizing film (thin polarizing film)>
The method for manufacturing a polarizing film (thin polarizing film) includes the steps of preparing a laminate by forming a polyvinyl alcohol resin layer containing a polyvinyl alcohol resin on one side of a long thermoplastic resin base material, and While conveying the laminate in the longitudinal direction, the laminate is subjected to an optional insolubilization process, a crosslinking process, and a washing process, and at least an in-air auxiliary stretching process, a dyeing process, and an underwater stretching process. The treatment bath in any one or more of the insolubilization treatment step, the crosslinking treatment step, the washing treatment step, the dyeing treatment step, and the underwater stretching treatment step contains a hindered amine compound. The hindered amine compound is a water-soluble hindered amine compound that can be dissolved in 1 part by weight or more in 100 parts by weight of water at 25°C. The content of the hindered amine compound and the content of iodine contained in the polarizing film are determined in each of the insolubilization treatment step, the crosslinking treatment step, the washing treatment step, the dyeing treatment step, and the underwater stretching treatment step. It can be controlled by the concentration of the hindered amine compound contained in any of the treatment baths, the concentration of iodine, potassium iodide, etc., and the treatment temperature and treatment time in each of the treatment baths. In particular, when performing a cleaning process, the cleaning process takes into consideration the treatment conditions of the dyeing process and the underwater stretching process, and removes components such as hindered amine compounds and iodine from the polyvinyl alcohol film. Alternatively, from the viewpoint of being able to be adsorbed onto a polyvinyl alcohol film, the content of the hindered amine compound and the content of iodine can be easily adjusted to a desired range.

The concentration of the hindered amine compound contained in any of the treatment baths cannot be determined unconditionally because it is affected by the number of treatments, treatment time, treatment temperature, etc., but the concentration of the hindered amine compound in the polarizing film From the viewpoint of efficiently controlling the amount, it is usually preferably 0.01% by weight or more, more preferably 0.05% by weight or more, even more preferably 0.1% by weight or more, and , is preferably 30% by weight or less, more preferably 25% by weight or less, and even more preferably 20% by weight or less.

<Step of preparing the laminate>
Any suitable method may be adopted as a method for producing the laminate. For example, a coating liquid containing the polyvinyl alcohol resin (PVA resin) is applied to the surface of the thermoplastic resin base material, and then dried. There are ways to do this. 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 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 stretching stress, and being able to stretch to a high magnification. % or more is more preferable. On the other hand, the thermoplastic resin base material has a water absorption rate of 3.0% from the viewpoint of preventing problems such as a significant decrease in the dimensional stability of the thermoplastic resin base material and deterioration of the appearance of the resulting polarizing film. % or less, more preferably about 1% or less. Note that 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 determined according to JIS K 7209.

The thermoplastic resin base material has a glass transition temperature (Tg) of about 120° C. or lower, from the viewpoint of being able to sufficiently secure the stretchability of the laminate while suppressing crystallization of the PVA-based resin layer. is preferred. Furthermore, in consideration of plasticizing the thermoplastic resin base material with water and performing underwater stretching well, the glass transition temperature (Tg) is more preferably about 100°C or less, more preferably about 90°C or less. It is even more preferable. On the other hand, the glass transition temperature of the thermoplastic resin base material is a point of view that can prevent defects such as deformation of the thermoplastic resin base material when applying and drying the coating liquid and produce a good laminate. Therefore, it is preferable that the temperature is about 60°C or higher. Note that the glass transition temperature can be adjusted by, for example, introducing a modifying group into the constituent material of the thermoplastic resin base material or heating it using a crystallization material. The glass transition temperature (Tg) is a value determined according to JIS K 7121.

Any suitable thermoplastic resin may be employed 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. etc. Among these, norbornene resins and amorphous polyethylene terephthalate resins are preferred, and thermoplastic resin base materials are preferred because they have extremely excellent stretchability and can suppress crystallization during stretching. , amorphous polyethylene terephthalate resin is preferably used. Examples of the amorphous polyethylene terephthalate resin include copolymers containing isophthalic acid and/or cyclohexanedicarboxylic acid as dicarboxylic acids, and copolymers containing cyclohexanedimethanol and diethylene glycol as glycols.

The thermoplastic resin base material may be subjected to surface treatment (for example, corona treatment, etc.) before forming the PVA resin layer, or an easily adhesive 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 resin layer can be improved. Moreover, the thermoplastic resin base material may be stretched before forming the PVA-based resin layer.

The coating liquid is a solution in which 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 trimethylolpropane, and amines such as ethylenediamine and diethylenetriamine. preferable. These can be used alone or in combination of two or more. The PVA resin concentration of the coating liquid is preferably about 3 to 20 parts by weight based on 100 parts by weight of the solvent, from the viewpoint of being able to form a uniform coating film that adheres to the thermoplastic resin base material. .

The coating liquid preferably contains a halide from the viewpoint of improving the orientation of polyvinyl alcohol molecules during stretching. Any suitable halide can be used as the halide, and examples thereof include iodide and sodium chloride. Examples of the iodide include potassium iodide, sodium iodide, lithium iodide, and the like, with potassium iodide being preferred. 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 resin.

Furthermore, additives may be added to the coating liquid. Examples of the additives include plasticizers such as ethylene glycol and glycerin; surfactants such as nonionic surfactants, and the like.

Any suitable method can be used to apply the coating liquid, such as roll coating, spin coating, wire bar coating, dip coating, die coating, curtain coating, and spray coating. , knife coat method (comma coat method, etc.). Further, the drying temperature of the coating liquid is preferably about 50° C. or higher.

<Aerial auxiliary stretching process>
In the aerial auxiliary stretching process, the thermoplastic resin base material can be stretched while suppressing crystallization, so the laminate can be stretched to a high magnification. The stretching method in the aerial auxiliary stretching process may be fixed end stretching (for example, stretching using a tenter stretching machine) or free end stretching (for example, uniaxial stretching by passing the laminate between rolls with different peripheral speeds). method), but free end stretching is preferred from the viewpoint of obtaining high optical properties.

The stretching ratio in the aerial auxiliary stretching process is preferably about 2 to 3.5 times. The above-mentioned aerial auxiliary stretching process may be performed in one step or in multiple steps. In the case of multi-stage stretching, the stretching ratio is the product of the stretching ratios of each stage.

The stretching temperature in the above-mentioned aerial auxiliary stretching process can be set to any appropriate value depending on the forming material of the thermoplastic resin base material, the stretching method, etc., for example, the glass transition temperature of the thermoplastic resin base material. (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 determined from the viewpoint of suppressing the rapid progress of crystallization of the PVA-based resin and preventing defects due to crystallization (for example, preventing the orientation of the PVA-based resin layer by stretching). , about 170°C.

<Insolubilization process>
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 the PVA 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 a decrease in orientation of PVA when immersed in water. The concentration of the boric acid aqueous solution is preferably about 1 to 5 parts by weight per 100 parts by weight of water. The liquid temperature of the insolubilization treatment bath is preferably about 20 to 50°C.

<Dyeing process>
The dyeing process is performed by dyeing the PVA resin layer with iodine. The adsorption method includes, for example, immersing the PVA resin layer (laminate) in a dye containing iodine, applying the dye to the PVA resin layer, and applying the dye to the PVA resin layer. Examples include a method of spraying, and a method of immersing the PVA resin layer (laminate) in a dyeing solution containing iodine is preferred.

The amount of iodine blended in the dyeing bath is preferably about 0.05 to 0.5 parts by weight per 100 parts by weight of water. In order to increase the solubility of iodine in water, it is preferable to mix the iodide with the iodine aqueous solution. The amount of iodide compounded 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 dissolution of the PVA resin. Further, from the viewpoint of ensuring the transmittance of the PVA resin layer, the immersion time is preferably about 5 seconds to 5 minutes, and more preferably about 30 seconds to 90 seconds. From the viewpoint of obtaining a polarizing film having good optical properties, the ratio of the content of iodine and iodide in the iodine aqueous solution is preferably about 1:5 to 1:20, and preferably about 1:5 to 1:10. It is more preferable that there be.

<Crosslinking process>
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 resin layer in a boric acid aqueous solution. By performing the crosslinking treatment step, water resistance is imparted to the PVA-based resin layer, and in subsequent underwater stretching, it is possible to prevent a decrease in the orientation of PVA when immersed in high-temperature water. 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. Furthermore, when performing the crosslinking treatment step, it is preferable to further include the above-mentioned iodide in the crosslinking bath. By blending the iodide, elution of iodine adsorbed to the PVA resin layer can be suppressed. The amount of the iodide compounded is preferably about 1 to 5 parts by weight per 100 parts by weight of water. The temperature of the crosslinking bath (boric acid aqueous solution) is preferably about 20 to 50°C.

<Underwater stretching process>
The underwater stretching process is performed by immersing the laminate in a stretching bath. According to the underwater stretching process, the thermoplastic resin base material and the PVA resin layer can be stretched at a temperature lower than the glass transition temperature (typically about 80°C), and the PVA resin layer can be stretched at a temperature lower than its crystallization temperature. It is possible to stretch to a high magnification while suppressing the The stretching method in the underwater stretching process may be fixed-end stretching (for example, stretching using a tenter stretching machine) or free-end stretching (for example, uniaxial stretching by passing the laminate between rolls having different circumferential speeds). ), but from the viewpoint of obtaining high optical properties, free end stretching is preferable.

The underwater stretching treatment step is preferably performed by immersing the laminate in an aqueous boric acid solution (stretching in boric acid). By using a boric acid aqueous solution as a stretching bath, it is possible to impart rigidity to the PVA-based resin layer to withstand tension applied during stretching, and water resistance that does not dissolve in water. 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, an iodide may be added to 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 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 process is preferably about 1.5 times or more, more preferably about 3 times or more.

The total stretching ratio of the laminate is preferably about 5 times or more, more preferably about 5.5 times or more, with respect to the original length of the laminate.

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

Furthermore, 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 may contain zinc salts, pH adjusters, pH buffers, and other salts. It may also contain additives. 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. 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 and their salts such as acetic acid, oxalic acid, and citric acid, and inorganic weak acids and their salts 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 alkali metals and alkaline earth metals. Examples include salt.

<Polarizing film>
The polarizing film of the present invention has a transparent protective film bonded to at least one surface of the polarizing film.

The transparent protective film is not particularly limited, and various transparent protective films used for polarizing films can be used. As the material constituting the transparent protective film, for example, a thermoplastic resin having excellent transparency, mechanical strength, thermal stability, moisture barrier properties, isotropy, etc. is used. Examples of the thermoplastic resin include cellulose ester resins such as triacetylcellulose, polyester resins such as polyethylene terephthalate and polyethylene naphthalate, polyether sulfone resins, polysulfone resins, polycarbonate resins, nylon, and aromatic resins. Polyamide resins such as group polyamides, polyimide resins, polyolefin resins such as polyethylene, polypropylene, and ethylene-propylene copolymers, (meth)acrylic resins, cyclic polyolefin resins having a cyclo or norbornene structure (norbornene resins) ), polyarylate resins, polystyrene resins, polyvinyl alcohol resins, and mixtures thereof. Further, the transparent protective film may include a cured layer formed from a thermosetting resin or an ultraviolet curable resin such as (meth)acrylic, urethane, acrylic urethane, epoxy, silicone, or the like. Among these, cellulose ester resins, polycarbonate resins, (meth)acrylic resins, cyclic polyolefin resins, and polyester resins are preferred.

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

When the transparent protective films are 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 frontal 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, the retardation plate also functions as a transparent protective film, so that it is possible to reduce the thickness.

Examples of the retardation plate include a birefringent film formed by uniaxially or biaxially stretching a polymer material, an oriented film of a liquid crystal polymer, and a film in which an oriented 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. Note that the phase plate may be used by bonding it to a transparent protective film that does not have a phase difference.

The transparent protective film may contain any suitable additives such as ultraviolet absorbers, antioxidants, lubricants, plasticizers, mold release agents, color inhibitors, flame retardants, antistatic agents, pigments, colorants, etc. You can stay there. In particular, when the transparent protective film contains an ultraviolet absorber, the light resistance of the polarizing film can be improved.

A functional layer such as a hard coat layer, an anti-reflection layer, an anti-sticking layer, a diffusion layer or an anti-glare layer can be provided on the surface of the transparent protective film on which the polarizing film is not bonded. Note that the functional layers such as the hard coat layer, antireflection layer, antisticking layer, diffusion layer, and antiglare layer can be provided on the protective film itself, or may be provided separately from the protective film. can.

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

As the adhesive forming the adhesive layer, various adhesives used in polarizing films can be used, such as rubber adhesives, acrylic adhesives, silicone adhesives, urethane adhesives, vinyl adhesives, etc. Examples include alkyl ether adhesives, polyvinyl alcohol adhesives, polyvinylporolidone adhesives, polyacrylamide adhesives, cellulose adhesives, and the like. Among these, acrylic adhesives are preferred.

The adhesive layer can be formed by, for example, applying the adhesive to a release-treated separator, drying it to form an adhesive layer, and then transferring it to a polarizing film or the like, or applying the adhesive to a polarizing film, etc. Examples include a method of applying the adhesive onto a film or the like and drying it to form an adhesive layer. The thickness of the adhesive layer is not particularly limited, and is, for example, about 1 to 100 μm, preferably about 2 to 50 μm.

As the adhesive forming the adhesive layer, various adhesives used for polarizing films can be used, such as isocyanate adhesives, polyvinyl alcohol adhesives, gelatin adhesives, vinyl latex adhesives, Examples include water-based polyester. These adhesives are usually used as adhesives made of an aqueous solution (aqueous adhesives), and contain a solid content of 0.5 to 60% by weight. Among these, polyvinyl alcohol adhesives are preferred, and acetoacetyl group-containing polyvinyl alcohol adhesives are more preferred.

The water-based adhesive may contain a crosslinking agent. As the crosslinking agent, a compound having at least two functional groups in one molecule that is reactive with components such as polymers constituting the adhesive is usually used, such as alkylene diamines; isocyanates; epoxies; Aldehydes; examples include amino-formaldehydes such as methylol urea and methylol melamine. The amount of the crosslinking agent in the adhesive is usually about 10 to 60 parts by weight per 100 parts by weight of components such as polymers constituting the adhesive.

In addition to the above adhesives, examples of the adhesive include active energy ray curable adhesives such as ultraviolet ray curable adhesives and electron beam curable adhesives. Examples of the active energy ray-curable adhesive include (meth)acrylate adhesives. Examples of the curable component in the (meth)acrylate adhesive include a compound having a (meth)acryloyl group and a compound having a vinyl group. Examples of compounds having a (meth)acryloyl group include alkyl (meth)acrylates having 1 to 20 carbon atoms, alicyclic alkyl (meth)acrylates, and polycyclic alkyl (meth)acrylates. ) acrylate; hydroxyl group-containing (meth)acrylate; epoxy group-containing (meth)acrylate such as glycidyl (meth)acrylate; and the like. (Meth)acrylate adhesives include hydroxyethyl (meth)acrylamide, N-methylol (meth)acrylamide, N-methoxymethyl (meth)acrylamide, N-ethoxymethyl (meth)acrylamide, (meth)acrylamide, and (meth)acrylate. It may also contain a nitrogen-containing monomer such as acryloylmorpholine. The (meth)acrylate adhesive contains tripropylene glycol diacrylate, 1,9-nonanediol diacrylate, tricyclodecane dimethanol diacrylate, cyclic trimethylolpropane formal acrylate, dioxane glycol diacrylate, EO as a crosslinking component. It may also contain a polyfunctional monomer such as modified diglycerol tetraacrylate. Moreover, a compound having an epoxy group or an oxetanyl group can also be used as a 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 commonly known curable epoxy compounds can be used.

The adhesive may contain appropriate additives as necessary. Examples of the additives include coupling agents such as silane coupling agents and titanium coupling agents, adhesion promoters such as ethylene oxide, ultraviolet absorbers, deterioration inhibitors, dyes, processing aids, ion trapping agents, and antioxidants. agents, tackifiers, fillers, plasticizers, leveling agents, foaming inhibitors, antistatic agents, heat stabilizers, hydrolysis stabilizers, and the like.

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 process is performed to form an adhesive layer consisting of a dry coating 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. When using an electron beam curing adhesive or the like, the thickness is preferably about 0.1 to 100 μm, 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 adhesive layer, a block layer, a refractive index adjustment layer, etc. .

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 forming the easy-adhesive layer include forming materials containing various resins having a polyester skeleton, a polyether skeleton, a polycarbonate skeleton, a polyurethane skeleton, a silicone system, a polyamide skeleton, a polyimide skeleton, a polyvinyl alcohol skeleton, etc. Can be mentioned. The easily bonding layer is usually provided in advance on a protective film, and the easily bonding layer side of the protective film and the polarizing film are laminated using the pressure-sensitive adhesive layer or the adhesive layer.

The blocking layer is a layer having a function of preventing impurities such as oligomers and ions eluted from the transparent protective film from migrating (invading) into the polarizing film. The block layer may be any layer as long as it has transparency and can prevent impurities leached from a transparent protective film, etc. Materials for forming the block layer include, for example, urethane prepolymer-based forming materials, cyanoacrylates, etc. Examples include system forming materials, epoxy forming materials, and the like.

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 the polarizing film. Examples of the refractive index adjusting material forming the refractive index adjusting layer include forming agents containing various resins and additives, such as silica-based, acrylic-based, acrylic-styrene-based, and melamine-based resins.

<Laminated polarizing film>
The laminated polarizing film (optical laminate) of the present invention has the polarizing film bonded to an optical layer. The optical layer is not particularly limited, but may be used, for example, in the formation of a liquid crystal display device such as a reflective plate, a semi-transmissive plate, a retardation plate (including a 1/2 or 1/4 wavelength plate), a viewing angle compensation film, etc. One or more optical layers that are sometimes used can be used. The laminated polarizing film is particularly a reflective polarizing film or a semi-transmissive polarizing film in which a reflective plate or a transflective plate is further laminated on the polarizing film, and a retardation plate is further laminated in the polarizing film. Examples include an elliptical polarizing film or a circularly polarizing film, a wide viewing angle polarizing film in which a viewing angle compensation film is further laminated on the polarizing film, or a polarizing film in which a brightness enhancement film is further laminated on the polarizing film.

On one or both sides of the polarizing film or the laminated polarizing film, an image display cell such as a liquid crystal cell or an organic EL element, and other front transparent members such as a front transparent plate or a touch panel on the viewing side are provided. An adhesive layer for bonding the members together may be provided. A pressure-sensitive adhesive layer is suitable as the adhesive layer. The adhesive forming the adhesive layer is not particularly limited, but examples include those having a base polymer such as an acrylic polymer, a silicone polymer, a polyester, a polyurethane, a polyamide, a polyether, a fluorine-based polymer, or a rubber-based polymer. It can be selected and used as appropriate. In particular, pressure-sensitive adhesives containing acrylic polymers that have excellent optical transparency, exhibit appropriate wettability, cohesiveness, and adhesive properties, and are excellent in weather resistance, heat resistance, etc. are preferably used.

The adhesive layer can be attached to one or both sides of the polarizing film or the laminated polarizing film by any appropriate method. For attaching the adhesive layer, for example, a method of preparing an adhesive solution and applying it directly onto the polarizing film or the laminated polarizing film using an appropriate developing method such as a casting method or a coating method, or a method of applying the adhesive solution directly onto the polarizing film or the laminated polarizing film, or using a separator. Examples include a method of forming an adhesive layer thereon and transferring it onto the polarizing film or the laminated polarizing film. The thickness of the adhesive layer can be determined as appropriate depending on the purpose of use, adhesive strength, etc., and is generally 1 to 500 μm, preferably 5 to 200 μm, and more preferably 10 to 100 μm. In this way, the polarizing film or the laminated polarizing film in which an adhesive layer is provided on at least one surface is referred to as a polarizing film with an adhesive layer or a laminated polarizing film with an adhesive layer.

It is preferable that the exposed surface of the adhesive layer is temporarily covered with a separator for the purpose of preventing contamination until it is put into practical use. This can prevent contamination of the adhesive layer under normal handling conditions. As the separator, for example, appropriate thin materials such as plastic films, rubber sheets, paper, cloth, non-woven fabrics, nets, foam sheets, metal foils, laminates thereof, silicone-based, long-chain alkyl-based, etc. A material coated with an appropriate release agent such as fluorine-based or molybdenum sulfide is used.

<Image display panel and image display device>
In the image display panel of the present invention, the polarizing film or the laminated polarizing film is bonded to an image display cell. Further, the image display device of the present invention includes a front transparent member on the polarizing film or laminated polarizing film side (viewing side) of the image display panel.

Examples of the image display cell include a liquid crystal cell and an organic EL cell. Examples of the liquid crystal cell include a reflective liquid crystal cell that uses external light, a transmissive liquid crystal cell that uses light from a light source such as a backlight, and a transflective liquid crystal cell that uses both external light and light from a light source. Any semi-reflective liquid crystal cell may be used. When the liquid crystal cell uses light from a light source, the image display device (liquid crystal display device) includes a polarizing film on the side opposite to the viewing side of the image display cell (liquid crystal cell), and further includes a light source. Placed. It is preferable that the polarizing film on the light source side and the liquid crystal cell are bonded together via a suitable adhesive layer. As a driving method for the liquid crystal cell, any type of driving method can be used, such as VA mode, IPS mode, TN mode, STN mode, or bend alignment (π type).

As the organic EL cell, for example, a cell in which a transparent electrode, an organic light-emitting layer, and a metal electrode are sequentially laminated on a transparent substrate to form a light-emitting body (organic electroluminescence light-emitting body) is preferably used. The organic light emitting layer is a laminate of various organic thin films, such as a laminate of a hole injection layer made of a triphenylamine derivative or the like and a light emitting layer made of a fluorescent organic solid such as anthracene; Various layer configurations may be adopted, such as a laminate of a light emitting layer and an electron injection layer made of a perylene derivative, or a laminate of a hole injection layer, a light emitting layer, and an electron injection layer.

Examples of the front transparent member disposed on the viewing side of the image display cell include a front transparent plate (window layer), a touch panel, and the like. As the front transparent plate, a transparent plate having appropriate mechanical strength and thickness is used. As such a transparent plate, for example, a transparent resin plate such as acrylic resin or polycarbonate resin, or a glass plate is used. As the touch panel, for example, various touch panels such as a resistive film type, a capacitance type, an optical type, an ultrasonic type, etc., a glass plate, a transparent resin plate, etc. having a touch sensor function are used. When a capacitive touch panel is used as the front transparent member, it is preferable that a front transparent plate made of glass or a transparent resin plate is provided further on the viewing side than the touch panel.

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

<Example 1>
<Preparation of polarizing film>
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 immersed in a 20°C swelling bath (water bath) for 30 seconds between rolls with different circumferential speed ratios to stretch it 2.2 times in the transport direction while swelling (swelling step), and then, The iodine concentration of the final polarizing film obtained in a 30°C dyeing bath (an iodine aqueous solution obtained by mixing iodine and potassium iodide at a weight ratio of 1:7 with respect to 100 parts by weight of water) is 4. While adjusting the concentration so that the concentration is 47% by weight, it is immersed for 30 seconds and dyed while dyeing. (dying process). Next, the dyed polyvinyl alcohol film was immersed for 28 seconds in a 40°C crosslinking bath (an aqueous solution with a boric acid concentration of 3.0% by weight and a potassium iodide concentration of 3.0% by weight) to restore the original polyvinyl alcohol. The film was stretched up to 3.6 times in the transport direction (crosslinking step). Furthermore, the obtained polyvinyl alcohol film was immersed for 60 seconds in a 61°C stretching bath (an aqueous solution with a boric acid concentration of 4.0% by weight and a potassium iodide concentration of 5.0% by weight) to restore the original polyvinyl alcohol film. After stretching the alcohol film up to 6.0 times in the conveying direction (stretching step), a 35°C cleaning bath (with a potassium iodide concentration of 2.0% by weight, a hindered amine type represented by the following general formula (6)) The sample was immersed for 10 seconds in an aqueous solution having a compound concentration of 0.4% by weight (cleaning step). The washed polyvinyl alcohol film was dried at 40° C. for 30 seconds to produce a polarizing film. The content of the hindered amine compound in the polarizing film was 0.28% by weight, as determined by the following measuring method. Further, the thickness of the polarizing film was 18 μm. The hindered amine compound represented by the following general formula (6) is a compound that dissolves in an amount of 1 part by weight or more per 100 parts by weight of water at 25°C.

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

[Method for measuring iodine content (wt%) in polarizing film]
Regarding the polarizing film, the iodine concentration (weight %) was determined using the following formula using a fluorescent X-ray analyzer (manufactured by Rigaku Co., Ltd., trade name "ZSX-PRIMUS IV", measurement diameter: ψ 20 mm).
Iodine concentration (wt%) = 14.474 x (fluorescent X-ray intensity) / (film thickness) (kcps/μm) The coefficient for calculating the concentration differs depending on the measuring device, but the coefficient can be calculated using an appropriate calibration curve. It can be found using

<Preparation of polarizing film>
As an adhesive, a polyvinyl alcohol resin containing an acetoacetyl group (average degree of polymerization: 1,200, degree of saponification: 98.5 mol%, degree of acetoacetylation: 5 mol%) and methylolmelamine were used in a weight ratio of 3: An aqueous solution containing 1 was used. Using this adhesive, a 47 μm thick triacetyl cellulose film (moisture permeability 342 g/(m ² 24 h), Konica Minolta After laminating the film using a roll laminating machine, the transparent protective film was laminated to both sides of the polarizing film by heating and drying in an oven (temperature: 60°C, time: 4 minutes). A polarizing film was produced. The single transmittance of the polarizing film was 37.4%.

<Preparation of acrylic adhesive>
A monomer mixture containing 99 parts of butyl acrylate and 1 part of 4-hydroxybutyl acrylate was charged into a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a condenser. Furthermore, to 100 parts of the monomer mixture (solid content), 0.1 part of 2,2'-azobisisobutyronitrile as a polymerization initiator was charged together with 100 parts of ethyl acetate, and nitrogen gas was added while stirring gently. After introducing the flask and purging it with nitrogen, a polymerization reaction was carried out for 8 hours while maintaining the liquid temperature in the flask at around 55° C. to prepare a solution of an acrylic polymer having a weight average molecular weight (Mw) of 1.8 million. Thereafter, based on 100 parts of the solid content of the obtained acrylic polymer solution, 0.02 part of an isocyanate crosslinking agent (manufactured by Tosoh Corporation, trade name "Takenate D110N", trimethylolpropane/xylylene diisocyanate adduct), silane A solution of an acrylic adhesive composition was prepared by adding 0.2 part of a coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd., trade name "X-41-1056"). Next, the solution of the acrylic adhesive composition obtained above was applied to one side of a polyethylene terephthalate film (manufactured by Mitsubishi Chemical Polyester Film, trade name "MRF38", separator film) treated with a silicone release agent, after drying. was applied so that the thickness of the adhesive layer was 20 μm, and dried at 90° C. for 1 minute to form an adhesive layer on the surface of the separator film. Next, the adhesive layer formed on the separator film was transferred to one side of the polarizing film produced above to produce a polarizing film with an adhesive layer.

[Evaluation of single transmittance in high temperature environment]
The polarizing film with the adhesive layer obtained above was cut into a size of 50 x 25 mm so that the absorption axis of the polarizing film was the long side, and a glass plate (pseudo image display cell) was attached via the adhesive layer. A laminate was produced. The obtained laminate was left standing in a hot air oven at a temperature of 105° C. for 300 hours, and the single transmittance (ΔTs) before and after charging (heating) was measured. Single transmittance was measured using a spectrophotometer (manufactured by Murakami Color Research Institute Co., Ltd., product name "DOT-3") and evaluated based on the following criteria. The single transmittance is a Y value corrected for visual sensitivity using the 2-degree field of view (C light source) of JIS Z 8701-1982. Note that the measurement wavelength is 380 to 700 nm (every 10 nm). The results are shown in Table 1.
ΔTs (%) = Ts ₃₀₀ - Ts ₀
Here, Ts ₀ is the single transmittance of the laminate before heating, and Ts ₃₀₀ is the single transmittance of the laminate after heating for 300 hours.
○: 10≧ΔTs (%)≧0
×: ΔTs (%) > 10, or ΔTs (%) < 0

The ΔTs (%) preferably satisfies 5≧ΔTs (%)≧0, and more preferably 3≧ΔTs (%)≧0.

<Example 2>
<Preparation of polarizing film and polarizing film>
In the production of the polarizing film, the concentration of iodine was adjusted so that the iodine concentration of the polarizing film finally obtained in the dyeing bath step was 4.40% by weight, and the hindered amine represented by the general formula (6) was added to the cleaning bath. A polarizing film and a polarizing film were produced in the same manner as in Example 1, except that the system compound was added at a concentration of 2.0% by weight. The obtained polarizing film had a hindered amine compound content of 0.94% by weight and a thickness of 18 μm. The single transmittance of the polarizing film was 37.7%.

<Example 3>
<Preparation of polarizing film and polarizing film>
In the production of the polarizing film, the iodine concentration in the final polarizing film obtained in the dyeing bath step was adjusted to 4.29% by weight, and the hindered amine represented by the general formula (6) was added to the cleaning bath. A polarizing film and a polarizing film were produced in the same manner as in Example 1, except that the system compound was added at a concentration of 4.0% by weight. The obtained polarizing film had a hindered amine compound content of 2.4% by weight and a thickness of 18 μm. The single transmittance of the polarizing film was 37.9%.

<Example 4>
<Preparation of polarizing film and polarizing film>
In the production of the polarizing film, the concentration of iodine was adjusted so that the iodine concentration of the polarizing film finally obtained in the dyeing bath step was 4.30% by weight, and the hindered amine represented by the general formula (6) was added to the cleaning bath. A polarizing film and a polarizing film were produced in the same manner as in Example 1, except that the system compound was added at a concentration of 10.0% by weight. The obtained polarizing film had a hindered amine compound content of 5.9% by weight and a thickness of 18 μm. The single transmittance of the polarizing film was 37.8%.

<Example 5>
<Preparation of polarizing film and polarizing film>
In the production of the polarizing film, the concentration of iodine was adjusted so that the iodine concentration of the polarizing film finally obtained in the dyeing bath step was 4.12% by weight, and the hindered amine represented by the general formula (6) was added to the cleaning bath. A polarizing film and a polarizing film were produced in the same manner as in Example 1, except that the system compound was added at a concentration of 20.0% by weight. The obtained polarizing film had a hindered amine compound content of 11.1% by weight and a thickness of 18 μm. The single transmittance of the polarizing film was 38.2%.

<Example 6>
<Preparation of polarizing film and polarizing film>
In the production of the polarizing film, the concentration of iodine was adjusted so that the iodine concentration of the polarizing film finally obtained in the dyeing bath step was 4.46% by weight, and the hindered amine represented by the general formula (6) was added to the cleaning bath. A polarizing film and polarized light were prepared in the same manner as in Example 1, except that a hindered amine compound represented by general formula (7) was added in place of the compound at a concentration of 0.4% by weight. A film was produced. The obtained polarizing film had a hindered amine compound content of 0.19% by weight and a thickness of 18 μm. The single transmittance of the polarizing film was 37.6%. Note that the hindered amine compound represented by the following general formula (7) is a compound that dissolves at least 1 part by weight in 100 parts by weight of water at 25°C.

<Example 7>
<Preparation of polarizing film and polarizing film>
In the production of the polarizing film, the concentration was adjusted so that the iodine concentration of the polarizing film finally obtained in the dyeing bath step was 2.38% by weight, and the hindered amine represented by general formula (6) was added in the stretching step. A polarizing film and a polarizing film were produced in the same manner as in Example 1, except that the system compound was added at a concentration of 0.05% by weight. The obtained polarizing film had a hindered amine compound content of 0.03% by weight and a thickness of 18 μm. The single transmittance of the polarizing film was 43.1%.

<Example 8>
<Preparation of polarizing film and polarizing film>
As the thermoplastic resin base material, a long, amorphous isophthalic copolymerized polyethylene terephthalate film (thickness: 100 μm) having a water absorption rate of 0.75% and a Tg of about 75° C. was used. One side of the resin base material was subjected to corona treatment. 100 weight PVA resin prepared by mixing polyvinyl alcohol (degree of polymerization 4200, degree of saponification 99.2 mol%) and acetoacetyl-modified PVA (manufactured by Nippon Gosei Kagaku Kogyo Co., Ltd., trade name "Gosefaimer Z410") at a ratio of 9:1. 13 parts by weight of potassium iodide was added to 13 parts by weight of potassium iodide 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 with a thickness of 13 μm, thereby producing a laminate. The obtained laminate was uniaxially stretched free end to 2.4 times in the longitudinal direction (longitudinal direction) between rolls having different circumferential speeds in an oven at 130° C. (in-air auxiliary stretching treatment). Next, the laminate was immersed in an insolubilization bath (aqueous solution having a boric acid concentration of 4.0% by weight) at a liquid temperature of 40° C. for 30 seconds (insolubilization treatment). Next, the final polarizing film was added to a dyeing bath (an aqueous iodine solution obtained by mixing iodine and potassium iodide in a weight ratio of 1:7 to 100 parts by weight of water) at a liquid temperature of 30°C. The sample was immersed for 60 seconds while adjusting the iodine concentration to 8.11% (staining treatment). Next, it was immersed in a crosslinking bath (an aqueous solution having a potassium iodide concentration of 3.0% by weight and a boric acid concentration of 5.0% by weight) at a liquid temperature of 40° C. for 30 seconds (crosslinking treatment). Thereafter, while immersing the laminate in a boric acid aqueous solution (boric acid concentration 4.0% by weight) at a liquid temperature of 70°C, a total stretching ratio of 5.5 was applied in the longitudinal direction between rolls having different circumferential speeds. Uniaxial stretching was performed to double the size (underwater stretching treatment). Thereafter, the laminate was immersed in a cleaning bath (an aqueous solution having a potassium iodide concentration of 3% by weight and a compound represented by the above general formula (6) concentration of 1.0% by weight) at a liquid temperature of 30°C ( cleaning process). Thereafter, while drying in an oven maintained at 90°C, it was brought into contact with a SUS heating roll whose surface temperature was maintained at 75°C for about 2 seconds (drying shrinkage treatment). In this way, a polarizing film with a thickness of 5 μm was formed on the resin base material. Further, the content of the hindered amine compound in the obtained polarizing film was 0.18% by weight.

Then, as an adhesive, a polyvinyl alcohol resin containing an acetoacetyl group (average degree of polymerization: 1,200, degree of saponification: 98.5 mol%, degree of acetoacetylation: 5 mol%) and methylolmelamine were mixed in a weight ratio. An aqueous solution containing 3:1 was used. Using this adhesive, a 30 μm thick transparent protective film made of (meth)acrylic resin (modified acrylic polymer having a lactone ring structure) is attached to the opposite surface of the polarizing film obtained above from the resin base material. A film (manufactured by Nippon Shokubai, moisture permeability: 125 g/(m ² 24 h)) was laminated using a roll laminating machine. Next, the resin base material was peeled off, and a 47 μm thick triacetyl cellulose film (moisture permeability 342 g/(m ² 24 h), manufactured by Konica Minolta, product name: "KC4UYW") are bonded together using a roll bonding machine using the ultraviolet curable adhesive below, and then UV light is irradiated from the hard coated triacetyl cellulose film surface to harden the adhesive, and the polarizing film is Created. The single transmittance of the polarizing film was 42.8%. In addition, an acrylic adhesive layer was transferred to the transparent protective film made of acrylic resin in the same manner as in Example 1 to produce a polarizing film with an adhesive layer.

Details of the ultraviolet curing adhesive are as follows. An adhesive was prepared by mixing 40 parts by weight of N-hydroxyethyl acrylamide (HEAA), 60 parts by weight of acryloylmorpholine (ACMO), and 3 parts by weight of a photoinitiator "IRGACURE 819" (manufactured by BASF). It was coated on a polarizing film so that the thickness of the adhesive layer after curing was 1.0 μm, and ultraviolet rays were irradiated as active energy rays to cure the adhesive. Ultraviolet irradiation was performed using a gallium-filled metal halide lamp, irradiation device: Light HAMMER10 manufactured by Fusion UV Systems, Inc., bulb: V bulb, peak illuminance: 1600 mW/cm ² , cumulative irradiation amount 1000/mJ/cm ² (wavelength 380 to 440 nm) ), and the illuminance of ultraviolet light was measured using the Sola-Check system manufactured by Solatell.

<Example 9>
<Preparation of polarizing film and polarizing film>
In producing the polarizing film, a polarizing film and a polarizing film were produced in the same manner as in Example 1, except that the ultraviolet curable adhesive described in Example 8 was used as the adhesive.

<Example 10>
<Preparation of polarizing film and polarizing film>
In the production of the polarizing film, the concentration of iodine was adjusted so that the iodine concentration of the polarizing film finally obtained in the dyeing bath step was 4.48% by weight, and the hindered amine represented by the general formula (6) was added to the cleaning bath. A polarizing film and polarized light were prepared in the same manner as in Example 1, except that a hindered amine compound represented by the general formula (8) was added in place of the compound at a concentration of 0.4% by weight. A film was produced. The obtained polarizing film had a hindered amine compound content of 0.22% by weight and a thickness of 18 μm. The single transmittance of the polarizing film was 37.4%. The hindered amine compound represented by the following general formula (8) is a compound that dissolves in an amount of 1 part by weight or more per 100 parts by weight of water at 25°C.

<Example 11>
<Preparation of polarizing film and polarizing film>
In the production of the polarizing film, we adjusted the iodine concentration in the dyeing bath process so that the final polarizing film had an iodine concentration of 4.67% by weight, and also added common iodine to the bath for the stretching process and the bath for the washing process. A polarizing film and a polarizing film were produced in the same manner as in Example 1, except that the hindered amine compound represented by formula (6) was added at a concentration of 0.4% by weight. The obtained polarizing film had a hindered amine compound content of 0.38% by weight and a thickness of 18 μm. The single transmittance of the polarizing film was 37.0%.

<Comparative example 1>
<Preparation of polarizing film and polarizing film>
In the production of the polarizing film, the concentration was adjusted so that the iodine concentration of the polarizing film finally obtained in the dyeing bath step was 4.65% by weight, and the hindered amine compound represented by general formula (6) was added to the cleaning bath. A polarizing film and a polarizing film were produced in the same manner as in Example 1 except that . The obtained polarizing film had a hindered amine compound content of 0% by weight and a thickness of 18 μm. The single transmittance of the polarizing film was 37.1%.

<Comparative example 2>
<Preparation of polarizing film and polarizing film>
In the production of the polarizing film, 1 weight of the compound represented by the general formula (9) (trade name "ADEKA STAB LA-52", manufactured by ADEKA) was added to the cleaning bath instead of the hindered amine compound represented by the general formula (6). %, it did not dissolve in the cleaning bath, making it difficult to produce a polarizing film with a good appearance.

Using the polarizing films of Examples and Comparative Examples obtained above, the above [Evaluation of single transmittance in high temperature environment] was performed. The results are shown in Table 1.

Claims (9)

A polarizing film formed by adsorbing and aligning iodine on a polyvinyl alcohol film,
Contains 0.02% by weight or more of a hindered amine compound,
The polarizing film is characterized in that the hindered amine compound is a water-soluble hindered amine compound that can be dissolved in 1 part by weight or more in 100 parts by weight of water at 25°C. The polarizing film according to claim 1, wherein the content of the hindered amine compound is 20% by weight or less. The polarizing film according to claim 1, wherein the iodine content is 1% by weight or more and 15% by weight or less. A polarizing film characterized in that a transparent protective film is bonded to at least one surface of the polarizing film according to any one of claims 1 to 3 . A laminated polarizing film, characterized in that the polarizing film according to claim 4 is bonded to an optical layer. An image display panel characterized in that the polarizing film according to claim 4 or the laminated polarizing film according to claim 5 is bonded to an image display cell. An image display device comprising a front transparent member on the polarizing film or laminated polarizing film side of the image display panel according to claim 6 . A method for manufacturing a polarizing film according to any one of claims 1 to 3 , comprising:
Obtained by subjecting a polyvinyl alcohol film to an optional swelling process and washing process, and at least a dyeing process, a crosslinking process, and a stretching process,
The treatment bath in any one or more of the swelling step, the washing step, the dyeing step, the crosslinking step, and the stretching step contains a hindered amine compound, and the hindered amine compound is added to water at 25°C. A method for producing a polarizing film, characterized in that it is a water-soluble hindered amine compound that can be dissolved in 1 part by weight or more per 100 parts by weight. A method for manufacturing a polarizing film according to any one of claims 1 to 3 , comprising:
preparing a laminate by forming a polyvinyl alcohol resin layer containing a polyvinyl alcohol resin on one side of a long thermoplastic resin base material;
While conveying the obtained laminate in the longitudinal direction, the laminate is subjected to an optional insolubilization process, a crosslinking process, and a washing process, and at least an in-air auxiliary stretching process, a dyeing process, and an underwater stretching process. Obtained by applying a process,
The treatment bath in any one or more of the insolubilization treatment step, the crosslinking treatment step, the washing treatment step, the dyeing treatment step, and the underwater stretching treatment step contains a hindered amine compound, and the hindered amine compound is a water-soluble hindered amine compound that can be dissolved in 1 part by weight or more in 100 parts by weight of water at 25°C.