JP2021170044A - Polarization membrane and polarization film - Google Patents

Abstract

To provide a polarization membrane containing much iodine, in which an initial single body transmission is 41% or less and the transmission is prevented from becoming smaller due to coloring of the polarization membrane under a high-temperature environment.SOLUTION: There is provided a polarization film formed in such a manner that iodine is adsorbed and oriented to a polyvinyl alcohol film. The content of iodine is larger than 10% by weight, the single body transmission is 41% or smaller, and the peak temperature when detected water has the largest intensity is at least 175°C under the condition in which there is an inactive gas, the rate of rise of the temperature is 10°C/minute, the range of rise of the temperature is 40°C-350°C in a gas generation analysis.SELECTED DRAWING: Figure 1

Description

The present invention relates to polarizing films and polarizing films.

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

On the other hand, as the polarizing film becomes thinner, a polarizing film having a high iodine content is required (Patent Document 1). Further, it is known that even such a thin polarizing film can suppress the amount of change in the simple substance transmittance in a high temperature environment (105 ° C. × 30 hours) (Patent Document 2).

International Publication No. 2018/186244 International Publication No. 2019/103002

However, the thin polarizing films specifically disclosed in Patent Documents 1 and 2 do not sufficiently suppress the decrease in the single transmittance in a high temperature environment, and there is room for improvement in the performance.

On the other hand, the present inventors have found that iodine contained in an iodine-based polarizing film promotes polyene formation in a high temperature environment. Therefore, it is effective to reduce the iodine content in the polarizing film in order to suppress the decrease in the simple substance transmittance due to the coloring of the polarizing film in a high temperature environment. On the other hand, it has been difficult to obtain a polarizing film having a good degree of polarization and a high content of iodine.

Further, as described in Patent Document 2, in a polarizing film having a high iodine content, a polarizing film having a simple substance transmittance of 41% or less can be used from the viewpoint that the contrast can be increased by setting the simple substance transmittance low. It has been demanded.

In view of the above circumstances, the present invention has an initial single transmittance of 41% or less in a polarizing film having a high iodine content, and a decrease in the simple substance transmittance due to coloring of the polarizing film in a high temperature environment. An object of the present invention is to provide a polarizing film having an excellent suppressing effect.

Another object of the present invention is to provide a polarizing film using the above-mentioned polarizing film.

That is, the present invention is a polarizing film formed by adsorbing and orienting iodine on a polyvinyl alcohol-based film, in which the iodine content is more than 10% by weight, the simple substance transmittance is 41% or less, and In the generated gas analysis, the peak temperature of the maximum intensity of detected water is 175 ° C. under the conditions that the temperature rise rate is 10 ° C./min and the temperature rise range is 40 ° C. to 350 ° C. in the presence of an inert gas. The above is related to the polarizing film.

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

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

The polarizing film of the present invention is a polarizing film formed by adsorbing and orienting iodine on a polyvinyl alcohol-based film, and has an iodine content of more than 10% by weight, a simple substance transmittance of 41% or less, and a single transmittance of 41% or less. In the generated gas analysis, the peak temperature of the maximum intensity of detected water is 175 under the conditions that the temperature rise rate is 10 ° C./min and the temperature rise range is 40 ° C. to 350 ° C. in the presence of an inert gas. It is above ℃. As described above, the iodine-based polarizing film undergoes polyene formation due to the dehydration reaction of polyvinyl alcohol in a high temperature environment, but the polarizing film of the present invention sets the temperature at which this dehydration reaction occurs to the high temperature side, that is, the generated gas analysis method. By setting the peak temperature of the maximum intensity of the water detected (observed) to 175 ° C. or higher, it is possible to suppress a decrease in the single transmittance due to the coloring of the polarizing film in a high temperature environment. Further, in the polarizing film of the present invention, by setting the iodine content in the polarizing film to a certain level or higher, the peak temperature of the maximum intensity of water detected (observed) by the generated gas analysis method is set to 175 ° C. or higher. However, the single transmittance is 41% or less, and the initial degree of polarization is good.

On the other hand, the present inventors observed the generation of radicals from the polarizing film when the polarizing film formed by adsorbing and orienting iodine on an iodine-containing polyvinyl alcohol-based film was exposed to a high temperature environment for a certain period of time. The timing at which the polarizing film was colored by polyene formation and the timing at which this radical was generated were very similar, suggesting a phenomenon in which radicals are generated due to the progress of polyene formation of the polarizing film. Therefore, in order to set the temperature at which the above-mentioned dehydration reaction occurs in the polarizing film to the high temperature side, that is, to set the peak temperature of the maximum intensity of water detected (observed) by the generated gas analysis method to 175 ° C. or higher, polarized light is used. It is preferable that the membrane contains a radical scavenger.

This is an example of a chart showing the peak of water detected in the generated gas analysis method using an iodine-based polarizing film as a sample.

<Polarizing film>
The polarizing film of the present invention is an iodine-based polarizing film formed by adsorbing and orienting iodine on a polyvinyl alcohol-based film, and has an iodine content of more than 10% by weight and a simple substance transmittance of 41% or less. In addition, in the generated gas analysis method, the peak temperature of the maximum intensity of water detected under the conditions of a temperature rising rate of 10 ° C./min and a temperature rising range of 40 ° C. to 350 ° C. in the presence of an inert gas. Is above 175 ° C.

The polarizing film has an iodine content of more than 10% by weight from the viewpoint of improving the initial degree of polarization of the polarizing film. From the viewpoint of controlling the initial degree of polarization of the polarizing film to 99.98 or more, the iodine content is preferably 12% by weight or more, more preferably 15% by weight or more, and From the viewpoint of controlling the peak temperature of the maximum intensity of water detected by the generated gas analysis method to 175 ° C. or higher, the iodine content is preferably 30% by weight or less, preferably 25% by weight or less. Is more preferable.

From the viewpoint of controlling the initial degree of polarization to 99.98 or more, the polarizing film preferably has a thickness of 0.2 μm or more, more preferably 0.5 μm or more, and makes the polarizing film thinner. From the above viewpoint, the thickness is preferably 10 μm or less, more preferably 8 μm or less, and further preferably 5 μm or less.

The polarizing film has a simple substance transmittance of 41% or less. From the viewpoint of display panel brightness, the polarizing film preferably has a single transmittance of 30% or more, more preferably 35% or more, and controls the initial degree of polarization to 99.98 or more. From the viewpoint, the single transmittance is preferably 41% or less, and more preferably 40% or less. The single transmittance was measured using a spectrophotometer with an integrating sphere (for example, manufactured by Nippon Spectroscopy Co., Ltd., product name: V7100) with a 2-degree field of view (C light source) of JIS Z8701 to correct the luminosity factor. It is a Y value.

The polarizing film has the maximum intensity of water detected in the generated gas analysis method under the conditions that the temperature rise rate is 10 ° C./min and the temperature rise range is 40 ° C. to 350 ° C. in the presence of an inert gas. The peak temperature of is 175 ° C. or higher. By setting the temperature at which the dehydration reaction of polyvinyl alcohol occurs on the high temperature side, that is, the peak temperature of the maximum intensity of water detected by the generated gas analysis method at 175 ° C. or higher, the polarizing film is used in a high temperature environment. , It is possible to suppress a decrease in the single transmittance due to coloring of the polarizing film. On the other hand, when the peak temperature of the maximum intensity of water is lower than 175 ° C. or higher, the change in the single transmittance of the polarizing film before and after the heating durability test (105 ° C. × 96 hours), which is an index of the heat resistance of the display. It becomes difficult to control the amount to 0% or more and 5% or less.

FIG. 1 is an example of a chart showing the peak of water detected by the above-mentioned generated gas analysis method, and the peak temperature of the maximum intensity of detected water is 175 ° C. or higher.

Further, the above-mentioned generated gas analysis method is an analysis method in which a gas chromatography device and a mass spectrometer are directly connected by an inert metal capillary or the like, and the gas generated when the sample is heated and heated is monitored in real time. In addition, it is called an EGA / MS method, an EGA / TOFMS method, or the like.

The polarizing film preferably contains a radical scavenger. It is presumed that the radical scavenger can set the temperature at which the dehydration reaction of polyene formation occurs on the high temperature side by capturing the radicals generated by heating the polyvinyl alcohol of the polarizing film. Examples of the radical scavenger include radical scavengers such as hindered phenol-based, hindered amine-based, phosphorus-based, sulfur-based, benzotriazole-based, benzophenone-based, hydroxylamine-based, salicylate ester-based, and triazine-based compounds. Be done. The radical scavenger is preferably, for example, a nitroxy radical or a compound having a nitroxide group from the viewpoint that the temperature at which the dehydration reaction of polyene formation occurs can be easily set on the high temperature side.

（一般式（１）中、Ｒ^１は、オキシラジカルを表し、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。 Examples of the compound having a nitroxyl radical or a nitroxide group, at room temperature, from the viewpoint of having a relatively stable radical in air, as N- oxyl compound (functional group, the C-N (-C) -O ^· compounds having (O ^· is an oxy radical)) can be mentioned, known materials can be used. Examples of the N-oxyl compound include compounds having an organic group having the following structure.

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

（一般式（２）中、Ｒ^１〜Ｒ^５、およびｎは、上記と同様であり、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 an organic group include compounds represented by the following general formulas (2) to (5).

(In the general formula (2), R ^{1 to} R ⁵ and n are the same as above, and R ⁶ represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, an acyl group, or an aryl group. , N represents 0 or 1.)

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

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

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

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

Further, as the N-oxyl compound, for example, N- described in JP-A-2003-64022, JP-A-11-222462, JP-A-2002-284737, International Publication No. 2016/047655 and the like. Oxyl compounds can be mentioned.

Further, the radical scavenger preferably has a molecular weight of 1000 or less, more preferably 500 or less, and further preferably 300 or less, from the viewpoint of efficiently capturing radicals generated in the polyene reaction. preferable.

The radical trapping agent is short from the viewpoint of being able to efficiently soak into the polarizing film together with water during the production of the polarizing film, from the viewpoint of being able to impregnate the polarizing film at a high concentration, and even when a thick polyvinyl alcohol-based film is used. Since it can be impregnated with time, it is preferable that 1 part by weight or more can be dissolved in 100 parts by weight of water at 25 ° C., and 2 parts by weight with respect to 100 parts by weight of water at 25 ° C. from the viewpoint of increasing the productivity of the polarizing film. It is more preferable that it can be dissolved as described above, and it is further preferable that it can be dissolved in 5 parts by weight or more with respect to 100 parts by weight of water at 25 ° C.

（一般式（６）中、Ｒ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す。）

In addition, examples of the compound having a nitroxyl radical or a nitroxide group include the following compounds.

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

When the polarizing film contains the radical scavenger, the content of the radical scavenger is 0.1% by weight in the polarizing film from the viewpoint of suppressing a decrease in single transmittance due to coloring of the polarizing film in a high temperature environment. % Or more, more preferably 0.2% by weight or more, further preferably 0.5% by weight or more, and preferably 30% by weight or less from the viewpoint of appearance. , 20% by weight or less, more preferably 10% by weight or less.

When the polarizing film contains the radical scavenger, the polarizing film has a weight ratio of the content of the radical scavenger to the content of the iodine (the content of the radical scavenger / the weight of the iodine content). The ratio) is preferably 0.01 or more, more preferably 0.05 or more, and from the viewpoint of appearance, from the viewpoint of suppressing a decrease in the radical transmittance due to coloring of the polarizing film in a high temperature environment. Therefore, it is preferably 1.0 or less, and more preferably 0.5 or less.

<Manufacturing method of polarizing film>
The method for producing a polarizing film is obtained by subjecting a polyvinyl alcohol-based film (PVA-based film) to an arbitrary swelling step, a washing step and a drying step, and at least a dyeing step, a cross-linking step and a stretching step. The content of the iodine contained in the polarizing film is the content of the iodine and iodide such as potassium iodide contained in any of the treatment baths in the swelling step, the dyeing step, the cross-linking step, the stretching step and the washing step. It can be controlled by the concentration, the treatment temperature and the treatment time of each of the above treatment baths. Further, each step may be performed in an arbitrary appropriate order, and one step may be performed a plurality of times as needed.

As the polyvinyl alcohol-based film, a film having translucency in the visible light region and dispersing and adsorbing a dichroic substance such as iodine or a dichroic dye can be used without particular limitation. Examples of the material of the polyvinyl alcohol-based film include polyvinyl alcohol or a derivative thereof. Examples of the polyvinyl alcohol derivative include polyvinyl formal, polyvinyl acetal; olefins such as ethylene and propylene; unsaturated carboxylic acids such as acrylic acid, methacrylic acid and crotonic acid, and alkyl esters and acrylamides thereof. Can be mentioned. The polyvinyl alcohol preferably has an average degree of polymerization of about 100 to 10,000, more preferably about 1,000 to 10,000, and even more preferably about 1,500 to 4,500. .. The polyvinyl alcohol preferably has a degree of saponification of about 80 to 100 mol%, more preferably about 95 mol% to 99.95 mol. The average degree of polymerization and the degree of saponification can be determined according to JIS K 6726.

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

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

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

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

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

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

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

Any suitable method can be adopted as the coating method of the coating liquid, and for example, a roll coating method, a spin coating method, a wire bar coating method, a dip coating method, a die coating method, a curtain coating method, and a spray coating method can be adopted. , Knife coat method (comma coat method, etc.) and the like.

In the stretching step, the PVA-based film is typically uniaxially stretched about 3 to 7 times. The stretching direction may be the longitudinal direction of the film (MD direction) or the width direction of the film (TD direction). The stretching direction is preferably the TD direction from the viewpoint of laminating the transparent protective film or the optical functional film with the roll-to-roll. The stretching method may be dry stretching, wet stretching, or a combination of these. Further, the PVA-based film may be stretched when performing a crosslinking step, a swelling step, a dyeing step, or the like. The stretching step may be performed in one step or in multiple steps. When performed in multiple stages, the draw ratio is the product of the draw ratios of each stage. The stretching direction can correspond to the absorption axis direction of the obtained polarizing film.

The swelling step is performed before the dyeing step, if necessary. The swelling step is performed, for example, by immersing a PVA-based film in a swelling bath. As the swelling bath, water such as distilled water or pure water is usually used. The swollen bath may contain any suitable other component other than water. Examples of the other components include solvents such as alcohol, additives such as surfactants, and iodides. 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, and iodide. Examples thereof include titanium, and potassium iodide is preferable. The temperature of the swelling bath is, for example, about 20 to 45 ° C. The immersion time is, for example, about 10 to 300 seconds.

The dyeing step is a step of dyeing a PVA-based film with a dichroic substance. Examples of the adsorption method include a method of immersing a PVA-based film in a dyeing solution containing a dichroic substance, a method of applying the dyeing solution to the PVA-based film, a method of spraying the dyeing solution onto the PVA-based film, and the like. From the viewpoint that the dichroic substance can be adsorbed well, the method of immersing the PVA-based film in the dyeing solution is preferable.

Examples of the dichroic substance include iodine and a dichroic dye, and iodine is preferable. When iodine is used as the dichroic substance, an aqueous iodine solution is preferably used as the staining solution. The iodine content of the iodine aqueous solution is preferably about 0.04 to 5.0 parts by weight with respect to 100 parts by weight of water. Further, in order to increase the solubility of iodine in water, it is preferable to add iodide to the aqueous iodine solution. Potassium iodide is preferably used as the iodide. The content of the iodide is preferably about 0.3 to 15 parts by weight with respect to 100 parts by weight of water. From the viewpoint of obtaining a polarizing film having good optical characteristics, the ratio of the iodine and iodide contents in the iodine aqueous solution is preferably about 1: 5 to 1:20, preferably about 1: 5 to 1:10. More preferably. The temperature of the dyeing solution is, for example, 20 to 50 ° C. The immersion time is, for example, 5 seconds to 5 minutes.

In the cross-linking step, a boron compound is usually used as a cross-linking agent. Examples of the boron compound include boric acid and borax, and boric acid is preferable. The boron compound is usually used in the form of an aqueous solution. In the aqueous solution containing the boron compound, the concentration of the boron compound is, for example, about 0.5 to 15% by weight, preferably about 1 to 10% by weight. Further, the aqueous solution containing the boron compound may contain iodide such as potassium iodide.

The cross-linking step includes, for example, a method of immersing a PVA-based film in an aqueous solution containing a boron compound, a method of applying an aqueous solution containing a boron compound to a PVA-based film, a method of spraying an aqueous solution containing a boron compound onto a PVA-based film, and the like. The method of immersing in an aqueous solution containing a boron compound is preferable.

In the cross-linking step, the temperature of the aqueous solution containing the boron compound is, for example, 25 ° C. or higher, preferably about 30 to 85 ° C., and even more preferably about 40 to 70 ° C. The immersion time is, for example, about 5 to 800 seconds, preferably about 8 to 500 seconds.

The cleaning step is performed after the cross-linking step, if necessary. The cleaning step is typically performed by immersing a PVA-based film in a cleaning solution. Pure water is a typical example of the cleaning liquid. The cleaning solution may contain iodide such as potassium iodide. The temperature of the cleaning liquid is, for example, about 5 to 50 ° C. The immersion time is, for example, about 1 to 300 seconds.

Further, when a polarizing film containing the radical scavenger is produced, the radical scavenging is performed in one or more of the swelling step, the washing step, the dyeing step, the cross-linking step, and the stretching step. It may contain an agent. The concentration of the radical scavenger contained in any of the treatment baths cannot be unconditionally determined because it is affected by the number of treatments, the treatment time, the treatment temperature, etc. of each treatment, but the concentration of the radical scavenger in the polarizing film is contained. 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, further preferably 0.1% by weight or more, and , 30% by weight or less, more preferably 25% by weight or less, still more preferably 20% by weight or less.

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

Examples of the drying step include natural drying, blast drying, vacuum drying, heat drying and the like, and heat drying is preferable. When heat drying is performed, the heating temperature is, for example, 30 to 100 ° C. The drying time is, for example, 20 seconds to 10 minutes.

<Polarizing film>
The polarizing film of the present invention is one in which a film such as a transparent protective film or an optical functional film is 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 the polarizing film can be used. As the material constituting the transparent protective film, for example, a thermoplastic resin having excellent transparency, mechanical strength, thermal stability, moisture blocking property, isotropic property and the like is used. Examples of the thermoplastic resin include cell roll ester resins such as triacetyl cellulol, polyester resins such as polyethylene terephthalate and polyethylene naphthalate, polyether sulfone resins, polysulfone resins, polycarbonate resins, nylon and fragrances. Polyamide-based resin such as group polyamide, polyimide-based resin, polyethylene, polypropylene, polyolefin-based resin such as ethylene / propylene copolymer, (meth) acrylic-based resin, cyclic polyolefin-based resin having a cyclo-based or norbornene structure (norbornene-based resin) ), Polyallylate-based resin, polystyrene-based resin, polyvinyl alcohol-based resin, and mixtures thereof. Further, as the transparent protective film, a cured layer formed of a thermosetting resin such as (meth) acrylic, urethane, acrylic urethane, epoxy, silicone or the like or an ultraviolet curable resin can be used. Among these, cell roll ester-based resins, polycarbonate-based resins, (meth) acrylic-based resins, cyclic polyolefin-based resins, and polyester-based resins are preferable.

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

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

The optical functional film is not particularly limited, and for example, a reflector, a semitransparent plate, a retardation plate (including a wave plate such as 1/2 or 1/4), a viewing angle compensation film, a linearly polarizing separation film, or the like. One layer or two or more layers of an optical functional film that may be used for forming a liquid crystal display device such as a brightness improving film can be used. Examples of the polarizing film having the optical functional film include a reflective polarizing film or a semi-transmissive polarizing film in which a reflecting plate or a semi-transmissive reflecting plate is further laminated on the polarizing film, and a retardation plate further formed on the polarizing film. Examples thereof include an elliptically polarized light film or a circularly polarizing film laminated, a wide viewing angle polarizing film obtained by further laminating a viewing angle compensating film on the polarizing film, and a polarizing film obtained by further laminating a brightness improving film on the polarizing film. ..

When a film such as the transparent protective film or an optical functional film is attached to both sides of the polarizing film, the films on both sides may be the same or different.

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

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

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

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

As the adhesive for forming the adhesive layer, various adhesives used for the polarizing film can be applied. For example, isocyanate-based adhesives, polyvinyl alcohol-based adhesives, gelatin-based adhesives, vinyl-based latex-based adhesives, and the like. Water-based polyester and the like can be mentioned. These adhesives are usually used as an adhesive (water-based adhesive) composed of an aqueous solution, and contain 0.5 to 60% by weight of a solid content.

The water-based adhesive may contain a cross-linking agent. As the cross-linking agent, a compound having at least two functional groups in one molecule having reactivity with a component such as a polymer constituting the adhesive is usually used, and for example, alkylenediamines; isocyanates; epoxies; Aldehydes: Amino-formaldehyde and the like such as methylol urea and methylol melamine can be mentioned. The blending amount of the cross-linking agent in the adhesive is usually about 10 to 60 parts by weight with respect to 100 parts by weight of the components such as the polymer constituting the adhesive.

In addition to the above, examples of the adhesive include active energy ray-curable adhesives such as an ultraviolet curable adhesive and an electron beam curable adhesive. Examples of the active energy ray-curable adhesive include (meth) acrylate-based adhesives. Examples of the curable component in the (meth) acrylate-based adhesive include a compound having a (meth) acryloyl group and a compound having a vinyl group. Examples of the compound having a (meth) acryloyl group include alkyl (meth) acrylates having 1 to 20 carbon atoms, such as chain alkyl (meth) acrylates, 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 can be mentioned. The (meth) acrylate-based adhesives are hydroxyethyl (meth) acrylamide, N-methylol (meth) acrylamide, N-methoxymethyl (meth) acrylamide, N-ethoxymethyl (meth) acrylamide, (meth) acrylamide, and (meth). It may contain a nitrogen-containing monomer such as acrylamide. The (meth) acrylate-based adhesive contains tripropylene glycol diacrylate, 1,9-nonanediol diacrylate, tricyclodecanedimethanol diacrylate, cyclic trimethylolpropane formal acrylate, dioxane glycol diacrylate, and EO as cross-linking components. It may contain a polyfunctional monomer such as modified diglycerin tetraacrylate. Further, a compound having an epoxy group or an oxetanyl group can also be used as the cationic polymerization curable adhesive. The compound having an epoxy group is not particularly limited as long as it has at least two epoxy groups in the molecule, and various generally known curable epoxy compounds can be used.

The adhesive may contain an appropriate additive, if necessary. Examples of the additive include a silane coupling agent, a coupling agent such as a titanium coupling agent, an adhesion promoter such as ethylene oxide, an ultraviolet absorber, a deterioration inhibitor, a dye, a processing aid, an ion trap agent, and an antioxidant. Examples thereof include agents, tackifiers, fillers, plasticizers, leveling agents, foaming inhibitors, antistatic agents, heat-resistant stabilizers, and hydrolysis-resistant stabilizers.

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

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

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

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

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

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

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

An adhesive layer for bonding the other members may be attached to one surface or both surfaces of the polarizing film. As the adhesive layer, an adhesive layer is suitable. The pressure-sensitive adhesive forming the pressure-sensitive adhesive layer is not particularly limited, and for example, those using a polymer such as an acrylic polymer, a silicone-based polymer, a polyester, a polyurethane, a polyamide, a polyether, a fluorine-based polymer, or a rubber-based polymer as a base polymer are used. It can be appropriately selected and used. In particular, a pressure-sensitive adhesive containing an acrylic polymer, which has excellent optical transparency, exhibits appropriate wettability, cohesiveness, and adhesiveness, and has excellent weather resistance, heat resistance, and the like is preferably used.

The pressure-sensitive adhesive layer may be attached to one or both sides of the polarizing film by an appropriate method. The pressure-sensitive adhesive layer may be attached, for example, by preparing a pressure-sensitive adhesive solution and directly attaching the pressure-sensitive adhesive solution onto the polarizing film by an appropriate development method such as a casting method or a coating method, or a pressure-sensitive adhesive layer on a separator. A method of forming the above-mentioned material and transferring it onto the polarizing film can be mentioned. The thickness of the pressure-sensitive adhesive layer can be appropriately determined according to 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. Such a polarizing film provided with an adhesive layer on at least one surface is also referred to as a polarizing film with an adhesive layer.

It is preferable that the exposed surface of the pressure-sensitive adhesive layer is temporarily covered with a separator for the purpose of preventing contamination or the like until it is put into practical use. As a result, contamination of the adhesive layer can be prevented under normal handling conditions. As the separator, for example, an appropriate thin leaf such as a plastic film, a rubber sheet, a paper, a cloth, a non-woven fabric, a net, a foam sheet or a metal foil, or a laminate thereof can be used, if necessary, a silicone-based or long-chain alkyl-based separator. Those coated with an appropriate release agent such as fluorine-based or molybdenum sulfide are used.

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>
<Manufacturing of polarizing film and polarizing film>
As the thermoplastic resin base material, an isophthalic acid copolymerized polyethylene terephthalate (IPA copolymerized PET) film (thickness: 100 μm) was used. One side of the base material is corona-treated, and polyvinyl alcohol (polymerization degree 4200, saponification degree 99.2 mol%) and acetoacetyl-modified PVA (polymerization degree 1200, acetoacetyl modification degree 4.6) are applied to the corona-treated surface. %, Degree of polymerization of 99.0 mol% or more, manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "Gosefimer Z200") is applied at a ratio of 9: 1 and dried at 25 ° C. to apply a PVA-based resin. A layer was formed to prepare a laminate. The obtained laminate was stretched 4.5 times in the air at 140 ° C. in a direction orthogonal to the longitudinal direction of the laminate using a tenter stretching machine (stretching treatment). Next, the laminate was immersed in a dyeing bath at a liquid temperature of 25 ° C. (an aqueous solution having an iodine concentration of 1.0% by weight and a potassium iodide concentration of 7.0% by weight) for 12 seconds for dyeing (dyeing treatment). Next, an aqueous solution having a liquid temperature of 60 ° C., a crosslinked bath (boron concentration 1.0% by weight, potassium iodide concentration 1.0% by weight, and a compound represented by the following general formula (9) of 5.0% by weight). ) For 21 seconds (crosslinking treatment). Next, the laminate was immersed in a washing bath (an aqueous solution having a potassium iodide concentration of 4.5% by weight) at a liquid temperature of 25 ° C. for 10 seconds (washing treatment). Next, the laminate was dried in an oven at 60 ° C. for 21 seconds (drying treatment) to obtain a laminate having a PVA-based resin layer (polarizing film) having a thickness of 1.2 μm. Next, a linear polarizing separation film (manufactured by 3M, trade name "DBEF") is applied to the polarizing film side of the laminate having the obtained PVA-based resin layer (polarizing film) via an acrylic pressure-sensitive adhesive layer having a thickness of 20 μm. After bonding, the thermoplastic resin base material was peeled off, and an acrylic pressure-sensitive adhesive layer having a thickness of 20 μm was applied to the peeled surface to prepare a polarizing film. The simple substance transmittance was 39.7%.

[Method for measuring iodine content (% by weight) in polarizing film]
The iodine concentration (% by weight) of the polarizing film was determined using the following formula using a fluorescent X-ray analyzer (manufactured by Rigaku Corporation, trade name "ZSX-PRIMUS IV", measurement diameter: ψ20 mm).
Iodine concentration (wt%) = 14.474 × (fluorescent X-ray intensity) / (film thickness) (kcps / μm) The coefficient for calculating the concentration differs depending on the measuring device, but the coefficient is an appropriate calibration curve. Can be obtained using. The results are shown in Table 1.

[Generated gas analysis method]
The polarizing film is introduced into a heating furnace type pyrolyzer (PY-2020iD manufactured by Frontier Lab), and the generated gas is directly introduced into TOFMS (JEOL, JMS-T100GCV) to perform a generated gas analysis (EGA / TOFMS) method. rice field. The results are shown in Table 1.
[Measurement condition]
Heating conditions: 40 ° C → + 10 ° C / min → 350 ° C
Interface: Inactive Fused Silica Tube, 2.5m x 0.15mm id
Carrier gas: He (1.0 mL / min)
Injection port temperature: 300 ° C
Injection: split ratio 20: 1
Interface temperature: 300 ° C
Mass spectrometer: TOFMS
Ionization method: EI method Mass range: m / z = 18

[Method for measuring the content (% by weight) of radical scavenger in the 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, the obtained extract was filtered through a membrane filter, and the filtrate was HPLC (ACQUITY UPLC manufactured by Waters). The concentration of the radical trapping agent was measured using H-class Bio). The results are shown in Table 1.

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

[Evaluation of single transmittance in high temperature environment]
The polarizing film obtained above was cut into a size of 5.0 × 4.5 cm so that the absorption axis of the polarizing film was parallel to the long side, and 1.3 mm alkali-free glass was formed on the pressure-sensitive adhesive layer surface of the polarizing film. The plates were laminated to prepare a laminate. The obtained laminate was allowed to stand in a hot air oven at a temperature of 105 ° C. for 96 hours, and the single transmittance (ΔTs) before and after charging (heating) was measured. The single transmittance was measured using a spectrophotometer (manufactured by JASCO Corporation, product name "V7100") and evaluated according to the following criteria. The measurement wavelength is 380 to 700 nm (every 5 nm). The results are shown in Table 1.
ΔTs (%) = Ts _{96 -Ts 0}
Here, Ts ₀ is the single transmittance of the laminate before heating, and Ts ₉₆ is the single transmittance of the laminate after heating for 96 hours. The ΔTs (%) is preferably 5 ≧ ΔTs (%) ≧ 0, and more preferably 3 ≧ ΔTs (%) ≧ 0.

<Example 2>
In the above <Preparation of polarizing film and polarizing film>, the cross-linking bath is a cross-linking bath (boron concentration 1.0% by weight, potassium iodide concentration 1.0% by weight, and the compound represented by the above general formula (9). A polarizing film and a polarizing film were produced by the same operation as in Example 1 except that the concentration was changed to 10.0% by weight aqueous solution). Table 1 shows the results of the above measurements and evaluations of the polarizing film and the polarizing film.

<Example 3>
In the above <Preparation of polarizing film and polarizing film>, the cross-linking bath is a cross-linking bath (boron concentration 1.0% by weight, potassium iodide concentration 1.0% by weight, and the compound represented by the above general formula (8). A polarizing film and a polarizing film were produced by the same operation as in Example 1 except that the concentration was changed to 10.0% by weight aqueous solution). Table 1 shows the results of the above measurements and evaluations of the polarizing film and the polarizing film.

<Example 4>
In the above <Preparation of polarizing film and polarizing film>, the cross-linking bath is a cross-linking bath (boron concentration 1.0% by weight, potassium iodide concentration 1.0% by weight, and the compound represented by the above general formula (7). A polarizing film and a polarizing film were produced by the same operation as in Example 1 except that the concentration was changed to 10.0% by weight aqueous solution). Table 1 shows the results of the above measurements and evaluations of the polarizing film and the polarizing film.

<Example 5>
In the above <Preparation of polarizing film and polarizing film>, a PVA-based resin layer is formed so that the thickness of the finally obtained polarizing film is 4.8 μm to prepare a laminated body, and the cross-linked bath is used as a cross-linked bath. Examples except that the boron concentration was changed to 1.0% by weight, the potassium iodide concentration was 1.0% by weight, and the concentration of the compound represented by the general formula (9) was changed to 10.0% by weight. A polarizing film and a polarizing film were produced by the same operation as in 1. Table 1 shows the results of the above measurements and evaluations of the polarizing film and the polarizing film.

<Example 6>
In the above <Preparation of polarizing film and polarizing film>, the dyeing bath was changed to a dyeing bath (an aqueous solution having an iodine concentration of 0.7% by weight and a potassium iodide concentration of 4.9% by weight), and the cross-linking bath was changed to a cross-linking bath (boron). Example 1 except that the concentration was changed to 1.0% by weight, the potassium iodide concentration was 1.0% by weight, and the concentration of the compound represented by the general formula (9) was changed to 10.0% by weight. A polarizing film and a polarizing film were produced by the same operation as in the above. Table 1 shows the results of the above measurements and evaluations of the polarizing film and the polarizing film.

<Example 7>
In the above <Preparation of polarizing film and polarizing film>, a PVA-based resin layer is formed so that the thickness of the finally obtained polarizing film is 2.5 μm to prepare a laminate, and the dyeing bath is a dyeing bath (dyeing bath). Change to an aqueous solution with an iodine concentration of 0.5% by weight and a potassium iodide concentration of 3.5% by weight), and change the cross-linking bath to a cross-linking bath (boron concentration 1.0% by weight, potassium iodide concentration 1.0% by weight, and the above. A polarizing film and a polarizing film were produced by the same operation as in Example 1 except that the concentration of the compound represented by the general formula (9) was changed to 10.0% by weight aqueous solution). Table 1 shows the results of the above measurements and evaluations of the polarizing film and the polarizing film.

<Example 8>
In the above <Preparation of polarizing film and polarizing film>, a PVA-based resin layer is formed so that the thickness of the finally obtained polarizing film is 4.8 μm to prepare a laminate, and the dyeing bath is used as a dyeing bath (dyeing bath). Change to an aqueous solution with an iodine concentration of 0.5% by weight and a potassium iodide concentration of 3.5% by weight), and change the cross-linking bath to a cross-linking bath (boron concentration 1.0% by weight, potassium iodide concentration 1.0% by weight, and the above. A polarizing film and a polarizing film were produced by the same operation as in Example 1 except that the concentration of the compound represented by the general formula (9) was changed to 10.0% by weight aqueous solution). Table 1 shows the results of the above measurements and evaluations of the polarizing film and the polarizing film.

<Comparative example 1>
Example 1 except that the cross-linking bath was changed to a cross-linking bath (an aqueous solution having a boron concentration of 1.0% by weight and a potassium iodide concentration of 1.0% by weight) in the above <Preparation of polarizing film and polarizing film>. A polarizing film and a polarizing film were produced by the same operation as in the above. Table 1 shows the results of the above measurements and evaluations of the polarizing film and the polarizing film.

<Comparative example 2>
In the above <Preparation of polarizing film and polarizing film>, the dyeing bath was changed to a dyeing bath (an aqueous solution having an iodine concentration of 0.5% by weight and a potassium iodide concentration of 3.5% by weight), and the cross-linking bath was changed to a cross-linking bath (boron). Example 1 except that the concentration was changed to 1.0% by weight, the potassium iodide concentration was 1.0% by weight, and the concentration of the compound represented by the general formula (9) was changed to 10.0% by weight. A polarizing film and a polarizing film were produced by the same operation as in the above. Table 1 shows the results of the above measurements and evaluations of the polarizing film and the polarizing film.

<Comparative example 3>
In the above <Production of polarizing film and polarizing film>, a linear polarizing separation film (manufactured by 3M) is provided on the polarizing film side of the laminate having a PVA-based resin layer (polarizing film) via an acrylic pressure-sensitive adhesive layer having a thickness of 20 μm. , Trade name "DBEF"), the thermoplastic resin base material is peeled off, and a treatment liquid (0.5% by weight of sodium hydrogen carbonate and 50% by weight of isopropyl alcohol) is used on the peeled surface using a bar coater. : PH 6.0), dried at 50 ° C. × 60 seconds, and then coated with an acrylic pressure-sensitive adhesive layer having a thickness of 20 μm to prepare a polarizing film, which is the same as in Example 1. By operation, a polarizing film and a polarizing film were produced. Table 1 shows the results of the above measurements and evaluations of the polarizing film and the polarizing film.

<Comparative example 4>
In the above <Preparation of polarizing film and polarizing film>, the dyeing bath was changed to a dyeing bath (an aqueous solution of potassium iodide concentration 15.0% by weight and ferric sulfate n hydrate 2.0% by weight). A polarizing film and a polarizing film were produced by the same operation as in Example 1 except for the above. Table 1 shows the results of the above measurements and evaluations of the polarizing film and the polarizing film.

In the examples, the polarizing film having an iodine content of more than 10% by weight, a simple substance transmittance of 41% or less, and a peak temperature of the maximum intensity of water in the generated gas analysis of 175 ° C. or higher is high temperature. In the environment, it is excellent in the effect of suppressing a decrease in the single transmittance due to the coloring of the polarizing film.

On the other hand, in the polarizing film of Comparative Example 1, since the peak temperature of the maximum intensity of water in the generated gas analysis was 173 ° C., the effect of suppressing the decrease in the single transmittance due to the coloring of the polarizing film was poor in a high temperature environment. rice field. Further, since the polarizing film of Comparative Example 2 had a simple substance transmittance of 41.5%, it did not satisfy the standard of the simple substance transmittance of the present invention. Further, Comparative Examples 3 and 4 correspond to the polarizing films disclosed in Patent Documents 1 and 2 of the prior art documents, and the peak temperature of the maximum intensity of water in the generated gas analysis was less than 175 ° C., so that the environment was high. In the above, the effect of suppressing the decrease in the single transmittance due to the coloring of the polarizing film was poor.

Claims (7)

A polarizing film formed by adsorption orientation of iodine on a polyvinyl alcohol-based film.
The iodine content is more than 10% by weight, the simple substance transmittance is 41% or less, and
In the generated gas analysis, the peak temperature of the maximum intensity of water detected is 175 ° C. under the conditions that the temperature rise rate is 10 ° C./min and the temperature rise range is 40 ° C. to 350 ° C. in the presence of an inert gas. A polarizing film characterized by the above. The polarizing film according to claim 1, wherein the thickness is 10 μm or less. The polarizing film according to claim 1 or 2, wherein the polarizing film contains a radical scavenger. The polarizing film according to claim 3, wherein the weight ratio (content of radical scavenger / content of iodine) between the content of the radical scavenger and the content of iodine is 0.01 or more. .. The polarizing film according to claim 3 or 4, wherein the radical scavenger is a nitroxy radical or a compound having a nitroxide group. A polarizing film, characterized in that a transparent protective film or an optical functional film is bonded to at least one surface of the polarizing film according to any one of claims 1 to 5. The polarizing film according to claim 6, wherein the degree of polarization is 99.98% or more.

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