CN114080416A

CN114080416A - Method for producing polarizing film, and method for producing polarizing film

Info

Publication number: CN114080416A
Application number: CN202080049855.7A
Authority: CN
Inventors: 山下智弘; 黑田拓马; 八木汐海; 高田胜则; 宫崎真
Original assignee: Nitto Denko Corp
Current assignee: Nitto Denko Corp
Priority date: 2019-09-20
Filing date: 2020-09-16
Publication date: 2022-02-22
Also published as: WO2021054357A1; KR20220063120A

Abstract

The present invention provides a method for manufacturing a polarizing film, the method comprising: a step (I-1) of producing a water-containing polarizing film by carrying a polyvinyl alcohol film in the longitudinal direction and subjecting the polyvinyl alcohol film to at least a dyeing step, a crosslinking step and a stretching step; a step (I-2) of applying a liquid to the obtained polarizing film containing water in a state where the water content of the polarizing film is X wt% or more, thereby producing a polarizing film impregnated with a component in the liquid; and a step (I-3) of producing a dried polarizing film by subjecting the obtained polarizing film impregnated with the component in the liquid to a drying step, wherein the method for producing a polarizing film satisfies formula (1): the above X (% by weight)/thickness (μm) > 1 of the polarizing film after drying (in the formula (1), X is 10 or more and 70 or less). The method for producing a polarizing film of the present invention can easily and sufficiently contain an arbitrary component in the polarizing film.

Description

Method for producing polarizing film, and method for producing polarizing film

Technical Field

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

Background

Conventionally, as a polarizing film (polarizer) used for various image display devices such as a liquid crystal display device and an organic EL display device, a polyvinyl alcohol-based film (containing a dichroic material such as iodine or a dichroic dye) subjected to dyeing treatment has been used in view of having both high transmittance and high polarization degree. The polarizing film was produced as follows: the polyvinyl alcohol-based film is subjected to various treatments such as dyeing, crosslinking, and stretching in a bath (treatment bath), and then dried. The polarizing film is generally used in the form of a polarizing film (polarizing plate) in which a protective film such as triacetylcellulose is bonded to one surface or both surfaces thereof with an adhesive.

As a method for producing a polarizing film, for example, patent documents 1 to 2 disclose that a component containing a metal salt of zinc, copper, aluminum, or the like is added to a treatment bath to make the polarizing film contain the component, thereby improving the durability of the polarizing film. Patent documents 3 to 4 disclose a method for producing a polarizing film in which a component such as an organic titanium compound is added to a treatment bath.

Documents of the prior art

Patent document

Patent document 1: international publication No. 2016/117659

Patent document 2: japanese patent laid-open publication No. 2006-047978

Patent document 3: japanese laid-open patent publication No. 2008-46257

Patent document 4: japanese laid-open patent publication No. 6-172554

Disclosure of Invention

Problems to be solved by the invention

However, in the method for producing a polarizing film, when the above-mentioned components are added to the treatment bath, there are problems that the amount of the components used becomes large and waste liquid treatment of the treatment liquid is required.

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

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

Means for solving the problems

That is, the present invention relates to a method for producing a polarizing film, the method comprising: a step (I-1) of producing a water-containing polarizing film by carrying a polyvinyl alcohol film in the longitudinal direction and subjecting the polyvinyl alcohol film to at least a dyeing step, a crosslinking step and a stretching step; a step (I-2) of applying a liquid to the obtained polarizing film containing water in a state where the water content of the polarizing film is X wt% or more, thereby producing a polarizing film impregnated with a component in the liquid; and a step (I-3) of producing a dried polarizing film by subjecting the obtained polarizing film impregnated with the component in the liquid to a drying step, the method satisfying formula (1): the above X (% by weight)/thickness (μm) > 1 of the polarizing film after drying (in the formula (1), X is 10 or more and 70 or less).

In addition, the present invention relates to a method for manufacturing a polarizing film, the method comprising: a step (II-0) 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; a step (II-1) of carrying the laminate obtained in the longitudinal direction and subjecting the laminate to at least an auxiliary stretching treatment step in a gas atmosphere, a dyeing treatment step, and a stretching treatment step in an aqueous solution, thereby producing a laminate having a polarizing film containing water; a step (II-2) of applying a liquid to the obtained laminate having a polarizing film containing water in a state where the moisture percentage of the polarizing film is Y wt% or more, thereby producing a laminate having a polarizing film impregnated with a component in the liquid; and a step (II-3) of producing a dried polarizing film by subjecting the obtained laminate having the polarizing film impregnated with the component in the liquid to a drying treatment step, the method satisfying formula (3): the condition of Y (weight%)/thickness (. mu.m) > 1 of the polarizing film after drying (in formula (3), Y is 10 or more and 70 or less).

In addition, the present invention relates to a method for manufacturing a polarizing film, the method comprising: and a step of bonding a transparent protective film to at least one surface of the polarizing film obtained by the above method for producing a polarizing film via an adhesive layer.

ADVANTAGEOUS EFFECTS OF INVENTION

The details of the mechanism of action of the effect in the method for producing a polarizing film of the present invention are not clear, but are presumed as follows. However, the present invention may be explained without being limited to this mechanism of action.

The method for producing a polarizing film of the present invention comprises: a step (I-1) of producing a water-containing polarizing film by carrying a polyvinyl alcohol film in the longitudinal direction and subjecting the polyvinyl alcohol film to at least a dyeing step, a crosslinking step and a stretching step; a step (I-2) of applying a liquid to the obtained polarizing film containing water in a state where the water content of the polarizing film is X wt% or more, thereby producing a polarizing film impregnated with a component in the liquid; and a step (I-3) of producing a dried polarizing film by subjecting the obtained polarizing film impregnated with the component in the liquid to a drying step, the method satisfying formula (1): the above X (% by weight)/thickness (μm) > 1 of the polarizing film after drying (in the formula (1), X is 10 or more and 70 or less). Alternatively, the method for producing a polarizing film of the present invention comprises: a step (II-0) 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; a step (II-1) of carrying the laminate obtained in the longitudinal direction and subjecting the laminate to at least an auxiliary stretching treatment step in a gas atmosphere, a dyeing treatment step, and a stretching treatment step in an aqueous solution, thereby producing a laminate having a polarizing film containing water; a step (II-2) of applying a liquid to the obtained laminate having a polarizing film containing water in a state where the moisture percentage of the polarizing film is Y wt% or more, thereby producing a laminate having a polarizing film impregnated with a component in the liquid; and a step (II-3) of producing a dried polarizing film by subjecting the obtained laminate having the polarizing film impregnated with the component in the liquid to a drying treatment step, the method satisfying formula (3): the condition of Y (weight%)/thickness (. mu.m) > 1 of the polarizing film after drying (in formula (3), Y is 10 or more and 70 or less). In a conventional method for producing a polarizing film, a polyvinyl alcohol-based film is subjected to at least a dyeing step, a crosslinking step, and a stretching step, and then is subjected to a drying step. Alternatively, in a conventional method for producing a polarizing film, 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 substrate, and a step of subjecting the laminate obtained to at least an auxiliary stretching step in a gas atmosphere, a dyeing step, and a stretching step in an aqueous solution are followed by a drying step. On the other hand, in the method for producing a polarizing film of the present invention, a polarizing film containing water or a laminate having a polarizing film containing water is produced as described above. Further, the method for producing a polarizing film of the present invention satisfies the conditions of the above formula (1) or (3), and therefore, in the above liquid application step, the polarizing film containing water can be easily and sufficiently impregnated with an arbitrary component contained in the liquid, and a polarizing film having a good degree of polarization can be produced.

Detailed Description

< method for producing polarizing film >

The method for producing a polarizing film of the present invention comprises: a step (I-1) of producing a water-containing polarizing film by carrying a polyvinyl alcohol film in the longitudinal direction and subjecting the polyvinyl alcohol film to at least a dyeing step, a crosslinking step and a stretching step; a step (I-2) of applying a liquid to the obtained polarizing film containing water in a state where the water content of the polarizing film is X wt% or more, thereby producing a polarizing film impregnated with a component in the liquid; and a step (I-3) of producing a dried polarizing film by subjecting the obtained polarizing film impregnated with the component in the liquid to a drying step, the method satisfying formula (1): the above X (% by weight)/thickness (μm) > 1 of the polarizing film after drying (in the formula (1), X is 10 or more and 70 or less).

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

The method for producing a polarizing film of the present invention comprises: and (I-1) a step of producing a water-containing polarizing film by carrying a polyvinyl alcohol film in the longitudinal direction and subjecting the polyvinyl alcohol film to at least a dyeing step, a crosslinking step and a stretching step.

The polyvinyl alcohol (PVA) film may be one having light transmittance in the visible light region and obtained by dispersing and adsorbing a dichroic material such as iodine or a dichroic dye, without any particular limitation. The PVA film used in the roll film generally has a thickness of about 1 to 100 μm, more preferably about 1 to 50 μm, and a width of about 100 to 5000 mm.

Examples of the material of the polyvinyl alcohol film include polyvinyl alcohol and derivatives thereof. Examples of the derivative of the polyvinyl alcohol include: polyvinyl formal, polyvinyl acetal; olefins such as ethylene and propylene; and derivatives obtained by modification with unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, and alkyl esters thereof, acrylamide, and the like. The polyvinyl alcohol preferably has an average polymerization degree of about 100 to 10000, more preferably about 1000 to 10000, and further preferably about 1500 to 4500. The saponification degree of the polyvinyl alcohol is preferably about 80 to 100 mol%, more preferably about 95 to 99.95 mol%. The average polymerization degree and the saponification degree can be determined according to JIS K6726.

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

< dyeing Process >

The dyeing step is a treatment step of immersing the polyvinyl alcohol-based film in a dyeing bath, and a dichroic substance such as iodine or a dichroic dye may be adsorbed on the polyvinyl alcohol-based film and oriented. The dyeing liquid is preferably an aqueous iodine solution, and more preferably contains iodine and an iodide as a dissolution aid. The iodide includes potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, titanium iodide, and the like. Of these, potassium iodide is preferred.

The concentration of iodine in the dyeing bath is preferably about 0.01 to 1 wt%, more preferably about 0.02 to 0.5 wt%. The concentration of the iodide in the dyeing bath is preferably about 0.01 to 10 wt%, more preferably about 0.05 to 5 wt%.

The temperature of the dyeing bath is preferably about 10 to 50 ℃, and more preferably about 15 to 45 ℃. The immersion time in the dyeing bath is not generally determined because the degree of dyeing of the polyvinyl alcohol-based film is affected by the temperature of the dyeing bath, and is preferably about 10 to 300 seconds, and more preferably about 20 to 240 seconds. The dyeing step may be performed only 1 time, or may be performed a plurality of times as needed.

< crosslinking step >

The crosslinking step is a treatment step of immersing the polyvinyl alcohol film dyed in the dyeing step in a treatment bath (crosslinking bath) containing a boron compound, and the polyvinyl alcohol film can be crosslinked with the boron compound to adsorb iodine molecules or dye molecules to the crosslinked structure. Examples of the boron compound include: boric acid, borates, borax, and the like. The crosslinking bath is generally an aqueous solution, and may be, for example, a mixed solution of an organic solvent miscible with water and water. The crosslinking bath may contain an iodide such as potassium iodide.

The concentration of the boron compound in the crosslinking bath is preferably about 1 to 15 wt%, more preferably about 1.5 to 10 wt%, and still more preferably about 2 to 5 wt%. When an iodide such as potassium iodide is used in the crosslinking bath, the concentration of the iodide such as potassium iodide in the crosslinking bath is preferably about 1 to 15 wt%, more preferably about 1.5 to 10 wt%.

The temperature of the crosslinking bath is preferably about 20 to 70 ℃, and more preferably about 30 to 60 ℃. The immersion time in the crosslinking bath is not generally determined because the degree of crosslinking of the polyvinyl alcohol-based film is affected by the temperature of the crosslinking bath, and is preferably about 5 to 300 seconds, and more preferably about 10 to 200 seconds. The crosslinking step may be performed only 1 time, or may be performed a plurality of times as needed.

< stretching Process >

The stretching step is a treatment step of stretching the polyvinyl alcohol-based film in at least one direction at a predetermined magnification. In general, a polyvinyl alcohol-based film is uniaxially stretched in the transport direction (longitudinal direction). The method of stretching is not particularly limited, and any of wet stretching and dry stretching may be employed. The stretching step may be performed only 1 time, or may be performed a plurality of times as needed. The stretching step may be performed at any stage in the production of the polarizing film.

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

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

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

The total stretching ratio (cumulative stretching ratio) of the polyvinyl alcohol-based film may be set as appropriate according to the purpose, and is preferably about 2 to 7 times, more preferably about 3 to 6.8 times, and still more preferably about 3.5 to 6.5 times.

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

< swelling step >

The swelling step is a treatment step of immersing the polyvinyl alcohol-based film in a swelling bath, and can remove dirt, an anti-blocking agent, and the like on the surface of the polyvinyl alcohol-based film, and can suppress uneven dyeing by swelling the polyvinyl alcohol-based film. The swelling bath generally uses a medium containing water as a main component, such as water, distilled water, or pure water. The swelling bath may be added with a surfactant, an alcohol, or the like as appropriate according to a conventional method.

The temperature of the swelling bath is preferably about 10 to 60 ℃, and more preferably about 15 to 45 ℃. The immersion time in the swelling bath is not generally determined because the swelling degree of the polyvinyl alcohol-based film is affected by the temperature of the swelling bath, and is preferably about 5 to 300 seconds, and more preferably about 10 to 200 seconds. The swelling step may be performed only 1 time, or may be performed a plurality of times as needed.

< cleaning Process >

The cleaning step is a treatment step of immersing the polyvinyl alcohol-based film in a cleaning bath, and can remove foreign matter remaining on the surface of the polyvinyl alcohol-based film. The cleaning bath usually uses a medium containing water as a main component, such as water, distilled water, or pure water. In this case, the concentration of the iodide such as potassium iodide in the cleaning bath is preferably about 1 to 10% by weight, more preferably about 2 to 4% by weight, and still more preferably about 1.6 to 3.8% by weight.

The temperature of the cleaning bath is preferably about 5 to 50 ℃, more preferably about 10 to 40 ℃, and further preferably about 15 to 30 ℃. The immersion time in the cleaning bath is not generally determined because the degree of cleaning of the polyvinyl alcohol-based film is affected by the temperature of the cleaning bath, and is preferably about 1 to 100 seconds, more preferably about 2 to 50 seconds, and still more preferably about 3 to 20 seconds. The swelling step may be performed only 1 time, or may be performed a plurality of times as needed.

In addition, additives such as zinc salt, pH adjuster, pH buffer, and other salts may be contained in each treatment bath in the swelling step, the dyeing step, the crosslinking step, the stretching step, and the washing step. 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 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 salts of alkali metals and alkaline earth metals.

< Process (I-2) > < producing polarizing film impregnated with component in liquid

The method for producing a polarizing film of the present invention comprises: and (I-2) applying a liquid to the water-containing polarizing film obtained above in a state in which the polarizing film has a water content of X wt% or more, thereby producing a polarizing film impregnated with a component in the liquid. Here, the component in the liquid is usually a solute contained in the solution. The solute may be any substance that can be dissolved, dispersed, or the like in a solvent, and may be any of a gaseous substance, a liquid substance, and a solid substance as a single compound. In the case where the solute is a liquid substance (for example, under the conditions of 25 ℃ and 1 atmosphere), the liquid substance itself (liquid substance itself) may be a liquid or a component in the liquid.

In the step (I-2), from the viewpoint of ease of impregnation of the components contained in the liquid and easier penetration in the thickness direction of the polarizing film, the moisture content (X wt%) of the polarizing film is preferably 20 wt% or more, more preferably 22 wt% or more, still more preferably 25 wt% or more, and from the viewpoint of prevention of wrinkles during transportation, the moisture content of the polarizing film is preferably 65 wt% or less, and more preferably 60 wt% or less.

As a coating (application) method in the step of applying the liquid, a conventional coating (application) method can be applied, and examples thereof include: coating methods such as roll coating, spin coating, wire bar coating, dip coating, die coating, curtain coating, spray coating, and blade coating (comma coating, etc.). The polarizing film may have one or both of its coated surfaces.

The component in the liquid may be a water-soluble compound from the viewpoint of easily impregnating the component in the polarizing film containing water. The water-soluble compound is a compound having a solubility in 100g of water of 1g or more at 25 ℃.

Examples of the components in the liquid include: zinc salts (zinc halides such as zinc chloride and zinc iodide; inorganic zinc salts such as zinc sulfate and zinc acetate); organic titanium compounds (titanium alkoxides, titanium chelates, titanium chelate ammonium salts, titanium chelate acylates, etc.), organic zirconium (zirconium alkoxides, zirconium chelates, zirconium chelate ammonium salts, zirconium acylates), alkali metal salts, alkaline earth metal salts, metal halides, etc.

Further, as the component in the liquid, a compound having a radical trapping function (also referred to as a radical trapping agent) can be cited. The compound having a radical trapping function can trap radicals generated by heating polyvinyl alcohol of the polarizing film and suppress the polyalkylene oxide, and therefore, the durability of the polarizing film against heat can be improved. As the compound having a radical-capturing function, for example, a compound having a nitroxyl radical or a nitroxyl group is preferable from the viewpoint of easily suppressing the polyalkyleneition.

Examples of the compound having a nitroxyl radical or nitroxyl group include: and organic group compounds having the following structures.

[ chemical formula 1]

(in the general formula (1), R¹Represents an oxygen radical, R²～R⁵Independently represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, and n represents 0 or 1), and the left side of the dotted line portion in the general formula (1) represents an arbitrary organic group.

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

[ chemical formula 2]

(in the general formula (2), R¹～R⁵And n is as defined above, R⁶Represents a hydrogen atom, or an alkyl group, an acyl group or an aryl group having 1 to 10 carbon atoms. )

[ chemical formula 3]

(in the general formula (3), R¹～R⁵And n is as defined above, R⁷And R⁸Independently represents a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an acyl group, or an aryl group. )

[ chemical formula 4]

(in the general formula (4), R¹～R⁵And n is as defined above, R⁹～R¹¹Independently represents a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an acyl group, an amino group, an alkoxy group, a hydroxyl group, or an aryl group. )

[ chemical formula 5]

(in the general formula (5), R¹～R⁵And n is as defined above, R¹²Represents a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an amino group, an alkoxy group, a hydroxyl group, or an aryl group. )

In the above general formulae (1) to (5), R is R from the viewpoint of easy acquisition²～R⁵Preferably an alkyl group having 1 to 6 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms. In the general formula (2), R is R from the viewpoint of easy acquisition⁶Preferably a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, and more preferably a hydrogen atom. In the general formula (3), R is preferably R from the viewpoint of easy acquisition⁷And R⁸Independently a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, more preferably a hydrogen atom. In the general formula (4), R is R from the viewpoint of easy acquisition⁹～R¹¹Preferably a hydrogen atom or an alkyl group having 1 to 10 carbon atoms. In the general formula (5), R is R from the viewpoint of easy acquisition¹²Preferably hydroxyl, amino or alkoxy. In the general formulae (1) to (5), n is preferably 1 from the viewpoint of easy acquisition.

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

[ chemical formula 6]

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

[ chemical formula 7]

[ chemical formula 8]

Further, as the component in the liquid, a compound having a crosslinking function (also referred to as a crosslinking agent) can be cited. The compound having the crosslinking function reacts with the hydroxyl group of the polyvinyl alcohol of the polarizing film to form a crosslinked structure, so that the durability of the polarizing film against humidification can be improved. The compound having a crosslinking function may contain, in addition to an isocyanate group, an isocyanate-derived functional group, an epoxy group, a carbonyl group, an aziridine ring, a vinyl ether group, a vinyl sulfone group, a vinyl ether group, and a vinyl ester group, from the viewpoint of improving the moisture durability,

Examples of the oxazoline-based organic compound include organic titanium compounds (e.g., alkoxy titanium, titanium chelate ammonium salt, and titanium chelate acylate).

Further, as the component in the liquid, a compound having a function of imparting plasticity (also referred to as a plasticizer) can be cited. The compound having a function of imparting plasticity can reduce quality defects such as scratches due to a pressing force by imparting plasticity to the polarizing film. Examples of the compound having a function of imparting plasticity include: ethylene glycol, polyethylene glycol, ethylene glycol derivatives, glycerol, and the like.

Further, as the component in the liquid, a dye-based compound (also referred to as a dye) is exemplified. The dye compound can provide characteristics such as hue adjustment and pattern printing to the polarizing film. Examples of the dye-based compound include: azo compounds, anthraquinones, quinophthalones, and the like.

The liquid is affected by the above-described application (coating) form, and therefore cannot be determined in a general manner, and the concentration of the component in the liquid is preferably 0.1 wt% or more, more preferably 1.0 wt% or more from the viewpoint of being able to permeate the component in the liquid with good efficiency, and the concentration of the component in the liquid is preferably 30 wt% or less, more preferably 20 wt% or less from the viewpoint of preventing quality defects caused by precipitation of the component in the liquid.

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

The time from the start of the step (I-2) after the step (I-1) (the transport time of the polarizing film in actual equipment production) is preferably 300 seconds or less, more preferably 180 seconds or less, further preferably 60 seconds or less, and more preferably 10 seconds or less when the temperature is about 15 to 35 ℃, preferably about 20 to 30 ℃, from the viewpoint of holding the water contained in the polarizing film containing water, or from the viewpoint of productivity.

In addition, in the step (I-2), after the step of applying a liquid to the polarizing film containing water, a step of impregnating a part of the liquid and removing the remaining liquid may be performed, if necessary. Examples of the method for removing the liquid include a wiping method using a cotton yarn end or a sponge roll, a suction method, a removal method using air blowing, and a scraping method using a bar or a gravure roll.

In the step (I-2), the polarizing film containing water preferably satisfies the condition of the following formula (a). By setting the content of boron in the water-containing polarizing film in accordance with the thickness of the polarizing film after drying as in this condition, the component in the liquid can be permeated with good efficiency.

Formula (a): a (wt%) < 0.08 XB (mum) +3.3

(in the formula (a), A represents the boron content (wt%) in the polarizing film containing water, and B represents the thickness (. mu.m) of the polarizing film after drying.)

< Process (I-3) > < producing a polarizing film after drying

The method for producing a polarizing film of the present invention comprises: and (I-3) a step of drying the polarizing film impregnated with the component in the liquid obtained above to produce a dried polarizing film.

The drying step is a step of drying the polarizing film impregnated with the component in the liquid obtained in the above step to obtain a polarizing film, and the polarizing film having a desired moisture content can be obtained by drying. The drying is carried out by any suitable method, and examples thereof include: natural drying, air-blowing drying, heating drying.

The drying temperature is preferably about 20 to 150 ℃, and more preferably about 25 to 100 ℃. The drying time is not generally determined because the degree of drying of the polarizing film is affected by the drying temperature, and is preferably about 10 to 600 seconds, and more preferably about 30 to 300 seconds. The drying step may be performed only 1 time, or may be performed a plurality of times as needed.

The moisture content of the polarizing film after drying is preferably 10% by weight or more, more preferably 12% by weight or more from the viewpoint of preventing quality defects such as scratches accompanied by disappearance of plasticity, and is preferably 20% by weight or less, more preferably 16% by weight or less from the viewpoint of improving optical characteristics such as a degree of polarization. In the case of a dried polarizing film having a thickness of about 8 μm or less, which will be described later, the moisture content of the dried polarizing film is preferably 2 wt% or more, more preferably 3 wt% or more, from the viewpoint of preventing quality defects such as scratches caused by the disappearance of plasticity, and the moisture content is preferably 20 wt% or less, more preferably 10 wt% or less, from the viewpoint of improving optical characteristics such as the degree of polarization.

The thickness of the polarizing film after drying is preferably about 1 to 30 μm, more preferably about 5 to 25 μm, and further preferably 5 to 20 μm. In particular, in order to obtain a dried polarizing film having a thickness of about 8 μm or less, a method for producing a thin polarizing film using a laminate comprising a thermoplastic resin substrate and a polyvinyl alcohol resin layer formed thereon as the polyvinyl alcohol film can be applied.

The method for producing a polarizing film of the present invention satisfies formula (1): the condition of X (% by weight)/thickness (μm) > 1 of the polarizing film after drying is preferably formula (1) > 1.2, more preferably formula (1) > 1.5.

In addition, from the viewpoint of improving the degree of polarization when the polarizing film is formed into a polarizing film, the method for producing a polarizing film of the present invention preferably satisfies formula (2): the above X (% by weight) and the above moisture percentage (% by weight) of the polarizing film after drying are more than 0 (% by weight), more preferably, the above formula (2) > 2 (% by weight), and still more preferably, the above formula (2) > 5 (% by weight).

< method for producing polarizing film (thin polarizing film) >

The method for producing a polarizing film (thin polarizing film) includes: a step (II-0) 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; a step (II-1) of transporting the obtained laminate in the longitudinal direction, and subjecting the laminate to at least an auxiliary stretching treatment step in a gas atmosphere, a dyeing treatment step, and a stretching treatment step in an aqueous solution, thereby producing a laminate having a polarizing film containing water; a step (II-2) of applying a liquid to the obtained laminate having a polarizing film containing water in a state where the moisture percentage of the polarizing film is Y wt% or more, thereby producing a laminate having a polarizing film impregnated with a component in the liquid; and a step (II-3) of producing a dried polarizing film by subjecting the obtained laminate having the polarizing film impregnated with the component in the liquid to a drying treatment step, the method satisfying formula (3): the condition of Y (weight%)/thickness (. mu.m) > 1 of the polarizing film after drying (in formula (3), Y is 10 or more and 70 or less).

< Process for preparing a laminate (II-0) >)

The method for producing a polarizing film (thin polarizing film) of the present invention includes: and (II-0) forming a polyvinyl alcohol resin layer (PVA type resin layer) containing a polyvinyl alcohol resin (PVA type resin) on one side of the long thermoplastic resin base material to prepare a laminate.

As a method for producing the laminate, any suitable method can be adopted, and examples thereof include: a method of applying a coating solution containing the PVA-based resin on the surface of the thermoplastic resin substrate and drying the coating solution. The thickness of the thermoplastic resin substrate is preferably about 20 to 300 μm, and more preferably about 50 to 200 μm. The thickness of the PVA based resin layer is preferably about 3 to 40 μm, and more preferably about 3 to 20 μm.

The thermoplastic resin base absorbs water to significantly reduce the tensile stress, and the water absorption rate is preferably about 0.2% or more, more preferably about 0.3% or more, from the viewpoint of enabling stretching at a high rate. On the other hand, the water absorption rate of the thermoplastic resin substrate is preferably about 3% or less, more preferably about 1% or less, from the viewpoint of preventing a defect such as deterioration in appearance of the polarizing film obtained due to a significant decrease in dimensional stability of the thermoplastic resin substrate. The water absorption can be adjusted by, for example, introducing a modifying group into the constituent material of the thermoplastic resin substrate. The water absorption is a value determined in accordance with JIS K7209.

The glass transition temperature (Tg) of the thermoplastic resin substrate is preferably about 120 ℃ or lower from the viewpoint of suppressing crystallization of the PVA-based resin layer and sufficiently ensuring stretchability of the laminate. In view of plasticization of the thermoplastic resin substrate with water and favorable stretching in an aqueous solution, the glass transition temperature (Tg) is preferably about 100 ℃ or lower, and more preferably about 90 ℃ or lower. On the other hand, the glass transition temperature of the thermoplastic resin substrate is preferably about 60 ℃ or higher from the viewpoint of preventing a defect such as deformation of the thermoplastic resin substrate when the coating liquid is applied and dried and producing a good laminate. The glass transition temperature can be adjusted by, for example, introducing a modifying group into the constituent material of the thermoplastic resin substrate and heating the resultant with a crystallizing material. The glass transition temperature (Tg) is a value determined in accordance with JIS K7121.

As the constituent material of the thermoplastic resin substrate, any suitable thermoplastic resin can be used. Examples of the thermoplastic resin include: ester resins such as polyethylene terephthalate resins, cycloolefin resins such as norbornene resins, olefin resins such as polypropylene resins, polyamide resins, polycarbonate resins, and copolymer resins thereof. Among these, norbornene-based resins and amorphous (noncrystalline) polyethylene terephthalate-based resins are preferable, and amorphous (noncrystalline) polyethylene terephthalate-based resins are preferably used from the viewpoint that the thermoplastic resin substrate is very excellent in stretchability and can be inhibited from crystallizing during stretching. Examples of the amorphous (noncrystalline) polyethylene terephthalate resin include copolymers containing isophthalic acid and/or cyclohexanedicarboxylic acid as dicarboxylic acid, and copolymers containing cyclohexanedimethanol and diethylene glycol as diol.

The thermoplastic resin substrate may be subjected to a surface treatment (e.g., corona treatment) before the PVA-based resin layer is formed, or an easy-adhesion layer may be formed on the thermoplastic resin substrate. By performing such treatment, the adhesion between the thermoplastic resin substrate and the PVA-based resin layer can be improved. The thermoplastic resin substrate may be stretched before the PVA-based resin layer is formed.

The coating liquid is a solution obtained by dissolving a PVA-based resin 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, and water is preferred. These solvents may be used alone, or two or more kinds may be used in combination. The concentration of the PVA-based resin in the coating solution is preferably about 3 to 20 parts by weight per 100 parts by weight of the solvent, from the viewpoint of forming a uniform coating film which adheres to the thermoplastic resin substrate.

From the viewpoint of improving the orientation of the polyvinyl alcohol molecules by stretching, it is preferable to add a halide to the coating liquid. As the halide, any suitable halide can be used, and examples thereof include iodide, sodium chloride, and the like. Examples of the iodide include: potassium iodide, sodium iodide, lithium iodide, etc., 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-based resin.

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

As a method for applying the coating liquid, any suitable method can be adopted, and examples thereof include: roll coating, spin coating, wire bar coating, dip coating, die coating, curtain coating, spray coating, and blade coating (comma coating, etc.). The drying temperature of the coating liquid is preferably about 50 ℃.

< Process (II-1) > < producing a laminate having a polarizing film containing water

The method for producing a polarizing film (thin polarizing film) of the present invention includes: and (II-1) a step of transporting the laminate obtained in the above manner in the longitudinal direction, and subjecting the laminate to at least an auxiliary stretching treatment step in an air atmosphere, a dyeing treatment step, and a stretching treatment step in an aqueous solution, thereby producing a laminate having a polarizing film containing water.

In the auxiliary stretching step in the gas atmosphere, the laminate may be stretched at a high stretch ratio so that the thermoplastic resin substrate can be stretched while crystallization thereof is suppressed. The stretching method for assisting the stretching step in the gas atmosphere may be fixed-end stretching (for example, a method of stretching using a tenter) or free-end stretching (for example, a method of uniaxially stretching a laminate by passing the laminate between rolls having different peripheral speeds), and the free-end stretching is preferable from the viewpoint of obtaining high optical characteristics.

The stretching ratio in the auxiliary stretching step in the gas atmosphere is preferably about 2 to 3.5 times. The auxiliary stretching step in the gas atmosphere may be performed in one stage or in multiple stages. In the case of performing in multiple stages, the stretching magnification is the product of the stretching magnifications in each stage.

The stretching temperature in the auxiliary stretching step in the gas atmosphere may be set to any suitable value depending on the material for forming the thermoplastic resin substrate, the stretching method, and the like, and is preferably not lower than the glass transition temperature (Tg) of the thermoplastic resin substrate, more preferably not lower than the glass transition temperature (Tg) +10 ℃, and still more preferably not lower than the glass transition temperature (Tg) +15 ℃. On the other hand, the upper limit of the stretching temperature is preferably about 170 ℃ from the viewpoint of suppressing rapid progress of crystallization of the PVA type resin and suppressing defects caused by crystallization (for example, inhibition of orientation of the PVA type resin layer by stretching).

If necessary, the insolubilization treatment step may be performed after the auxiliary stretching treatment step in the gas atmosphere and before the dyeing treatment step and the stretching treatment step in an aqueous solution. The insolubilization step is typically performed by immersing the PVA-based resin layer in an aqueous boric acid solution. By performing the insolubilization step, water resistance can be imparted to the PVA-based resin layer, and the PVA can be prevented from being degraded in orientation when immersed in water. The concentration of the boric acid aqueous solution is preferably about 1 to 5 parts by weight relative to 100 parts by weight of water. The liquid temperature of the insolubilization treatment bath is preferably about 20 to 50 ℃.

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

The amount of iodine in the dyeing bath is preferably about 0.05 to 0.5 parts by weight based on 100 parts by weight of water. In order to increase the solubility of iodine in water, it is preferable to add the iodide to an aqueous iodine solution. The amount of the iodide is preferably about 0.1 to 10 parts by weight, more preferably about 0.3 to 5 parts by weight, based on 100 parts by weight of water. In order to suppress the dissolution of the PVA based resin, the liquid temperature of the dyeing bath is preferably about 20 to 50 ℃. From the viewpoint of ensuring the transmittance of the PVA-based 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 characteristics, the ratio of the contents of iodine and iodide in the iodine aqueous solution is preferably about 1:5 to 1:20, and more preferably about 1:5 to 1: 10.

If necessary, the crosslinking treatment step may be performed after the dyeing treatment step and before the stretching treatment step in an aqueous solution. The crosslinking treatment step is typically performed by immersing the PVA-based resin layer in an aqueous boric acid solution. By performing the crosslinking treatment step, water resistance can be imparted to the PVA-based resin layer, and the orientation of the PVA can be prevented from being lowered when the PVA is immersed in high-temperature water during subsequent stretching in an aqueous solution. The boric acid concentration of the aqueous boric acid solution is preferably about 1 to 5 parts by weight relative to 100 parts by weight of water. In addition, when the crosslinking treatment step is performed, it is preferable to further mix the iodide in the crosslinking bath. The iodine compound can suppress elution of iodine adsorbed on the PVA-based resin layer. The amount of the iodide is preferably about 1 to 5 parts by weight based on 100 parts by weight of water. The liquid temperature of the crosslinking bath (aqueous boric acid solution) is preferably about 20 to 50 ℃.

The step of stretching in an aqueous solution is performed by immersing the laminate in a stretching bath. In the step of stretching in an aqueous solution, the stretching can be performed at a temperature lower than the glass transition temperature (typically, about 80 ℃) of the thermoplastic resin substrate or the PVA type resin layer, and the stretching can be performed at a high magnification while suppressing crystallization of the PVA type resin layer. The stretching method in the aqueous solution stretching step may be fixed-end stretching (for example, a method of stretching using a tenter) or free-end stretching (for example, a method of uniaxially stretching a laminate by passing the laminate between rolls having different peripheral speeds), and the free-end stretching is preferable from the viewpoint of obtaining high optical characteristics.

The step of stretching in an aqueous solution is preferably performed by immersing the laminate in an aqueous solution of boric acid (stretching in an aqueous solution of boric acid). By using an aqueous boric acid solution as a stretching bath, the PVA-based resin layer can be provided with rigidity capable of withstanding the tension applied during stretching and water resistance insoluble in water. The boric acid concentration of the aqueous boric acid 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. In addition, an iodide may be added to the stretching bath (aqueous boric acid solution). The liquid temperature of the stretching bath is preferably about 40 to 85 ℃, and more preferably about 60 to 75 ℃. The immersion time of the laminate in the stretching bath is preferably about 15 seconds to 5 minutes.

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

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

Preferably, the step of stretching in an aqueous solution is followed by a step of cleaning. The cleaning treatment step is typically performed by immersing the PVA-based resin layer in an aqueous potassium iodide solution.

In addition, additives such as zinc salt, pH adjuster, pH buffer, and other salts may be contained in each treatment bath in the dyeing treatment step, the stretching treatment step in aqueous solution, the insolubilizing treatment step, the crosslinking treatment step, and the washing treatment step. 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 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 salts of alkali metals and alkaline earth metals.

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

The method for producing a polarizing film (thin polarizing film) of the present invention includes: and (II-2) applying a liquid to the obtained laminate having a polarizing film containing water in a state where the polarizing film has a moisture content of Y wt% or more, thereby producing a laminate having a polarizing film impregnated with a component in the liquid. In this step (II-2), the step (I-2) of producing a polarizing film impregnated with a component in a liquid applied (coated) to one surface of the polarizing film can be applied to all of the above-described steps.

In the step (II-2), from the viewpoint of ease of impregnation of the components contained in the liquid and easier penetration in the thickness direction of the polarizing film, a state in which the moisture content (Y wt%) of the polarizing film is 20 wt% or more is preferable, a state in which the moisture content (Y wt%) of the polarizing film is 22 wt% or more is more preferable, a state in which the moisture content of the polarizing film is 25 wt% or more is further preferable, and a state in which the moisture content of the polarizing film is 65 wt% or less is preferable, and a state in which the moisture content of the polarizing film is 60 wt% or less is more preferable, from the viewpoint of prevention of wrinkles during transportation.

The time (the transport time of the laminate having a polarizing film in actual equipment production) after the step (II-1) until the step (II-2) is started is preferably 300 seconds or less, more preferably 180 seconds or less, further preferably 60 seconds or less, and further preferably 10 seconds or less, when the temperature is about 15 to 35 ℃, preferably about 20 to 30 ℃, from the viewpoint of holding the water contained in the polarizing film containing water, or from the viewpoint of productivity.

In the step (II-2), the laminate having the polarizing film containing water preferably satisfies the following condition of formula (b). By setting the content of boron in the polarizing film in the laminate having the above-described polarizing film containing water according to the thickness of the polarizing film after drying as in this condition, the component in the liquid can be permeated with good efficiency.

Formula (b): a (wt%) < 0.08 XB (mum) +3.3

(in the formula (B), A represents the boron content (wt%) in the polarizing film in the laminate having a polarizing film containing water, and B represents the thickness (. mu.m) of the polarizing film after drying.)

< Process (II-3) > < producing a polarizing film after drying

The method for producing a polarizing film (thin polarizing film) of the present invention includes: and (II-3) a step of subjecting the laminate having the polarizing film impregnated with the component in the liquid obtained above to a drying treatment step to produce a dried polarizing film.

The drying step is carried out by any suitable method, and examples thereof include: natural drying, air-blowing drying, heating drying. The drying step may be performed by zone heating in which the entire zone is heated, or may be performed by heating a transport roller (so-called heating roller). By drying with a hot roller, the laminate can be efficiently inhibited from curling by heating, and a polarizing film having excellent appearance can be produced. In addition, the shrinkage rate in the width direction of the laminate in the drying step is preferably about 1 to 10%, more preferably about 2 to 8%, from the viewpoint of improving the optical properties of the obtained polarizing film by shrinking the laminate in the width direction in the drying step.

The drying conditions can be controlled by adjusting the heating temperature of the transport roller (temperature of the heating roller), the number of heating rollers, the contact time with the heating roller, and the like. The temperature of the heating roller is preferably about 60 to 120 ℃, more preferably about 65 to 100 ℃, and further preferably 70 to 80 ℃. The number of the conveying rollers is usually about 2 to 40, preferably about 4 to 30, from the viewpoint of increasing the crystallinity of the thermoplastic resin and suppressing the curling satisfactorily. The contact time (total contact time) between the laminate and the heating roller is preferably about 1 to 300 seconds, more preferably 1 to 20 seconds, and still more preferably 1 to 10 seconds.

The heating roller may be installed in a heating furnace, or may be installed in a general manufacturing line (room temperature environment), and is preferably installed in a heating furnace provided with an air blowing mechanism. By using drying with a heating roller and hot air drying in combination, a rapid temperature change between the heating rollers can be suppressed, and shrinkage in the width direction can be easily controlled. The temperature of hot air drying is preferably about 30-100 ℃. The hot air drying time is preferably about 1 to 300 seconds.

The method for producing a polarizing film of the present invention satisfies formula (3): the condition of Y (% by weight)/thickness (μm) > 1 of the polarizing film after drying is preferably formula (3) > 1.5, more preferably formula (3) > 2.0, and still more preferably formula (3) > 3.0.

In addition, from the viewpoint of improving the degree of polarization when the polarizing film is formed into a polarizing film, the method for producing a polarizing film of the present invention preferably satisfies formula (4): the above-mentioned condition of Y (% by weight) — the moisture percentage (% by weight) of the polarizing film after drying is > 0 (% by weight), more preferably formula (4) > 2 (% by weight), and still more preferably formula (4) > 5 (% by weight).

< method for producing polarizing film >

The method for manufacturing a polarizing film of the present invention comprises: and a step of bonding a transparent protective film to at least one surface of the polarizing film obtained by the above method for producing a polarizing film via an adhesive layer.

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

The thickness of the transparent protective film may be suitably determined, and is generally preferably about 1 to 500 μm, more preferably about 1 to 300 μm, and still more preferably about 5 to 100 μm from the viewpoints of strength, handling properties such as handling properties, and thin layer properties.

When the transparent protective films are bonded to both surfaces of the polarizing film, the transparent protective films may be the same or different.

The transparent protective film may be a retardation plate having a front retardation of 40nm or more and/or a thickness direction retardation of 80nm or more. The front retardation is usually controlled to be in the range of 40 to 200nm, and the thickness direction retardation is usually controlled to be 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, and therefore, the thickness can be reduced.

Examples of the phase difference plate include: birefringent films obtained by subjecting a polymer material to uniaxial or biaxial stretching treatment, alignment films of liquid crystal polymers, retardation plates obtained by supporting alignment layers of liquid crystal polymers with films, and the like. The thickness of the retardation plate is not particularly limited, and is usually about 20 to 150 μm. The retardation plate can be used by laminating the retardation plate on a transparent protective film having no retardation.

The transparent protective film may contain any suitable additive such as an ultraviolet absorber, an antioxidant, a lubricant, a plasticizer, a mold release agent, a coloring inhibitor, a flame retardant, an antistatic agent, a pigment, and a colorant.

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

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

As the adhesive for forming the adhesive layer, various adhesives used for a polarizing film can be applied, and examples thereof include: rubber-based adhesives, acrylic-based adhesives, silicone-based adhesives, urethane-based adhesives, vinyl alkyl ether-based adhesives, polyvinyl alcohol-based adhesives, polyvinyl pyrrolidone-based adhesives, polyacrylamide-based adhesives, cellulose-based adhesives, and the like. Among these, acrylic adhesives are preferred.

As a method of forming the adhesive layer, for example: a method in which the adhesive is applied to a separator or the like subjected to a peeling treatment, dried to form an adhesive layer, and then transferred to a polarizing film or the like; or a method in which the adhesive is applied to a polarizing film or the like and dried 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 a polarizing film can be applied, and examples thereof include: isocyanate adhesives, polyvinyl alcohol adhesives, gelatin adhesives, vinyl latexes, water-based polyesters, and the like. These adhesives are generally used in the form of an adhesive comprising an aqueous solution and containing 0.5 to 60% by weight of a solid content.

The adhesive may be an active energy ray-curable adhesive such as an ultraviolet-curable adhesive or an electron beam-curable adhesive, in addition to the above. 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, a compound having a vinyl group. Further, as the cationic polymerization curing adhesive, a compound having an epoxy group or an oxetane group may be used. The compound having an epoxy group is not particularly limited as long as it has at least 2 epoxy groups in the molecule, and various curable epoxy compounds generally known can be used.

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

The transparent protective film and the polarizing film, or the polarizing film and the functional layer may be laminated with a surface modification treatment layer, an easy adhesion layer, a barrier layer, a refractive index adjustment layer, or the like interposed therebetween.

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

Examples of the easy adhesive agent for forming the easy adhesive layer include: the material for forming the resin composition includes various resins having a polyester skeleton, a polyether skeleton, a polycarbonate skeleton, a polyurethane skeleton, silicones, a polyamide skeleton, a polyimide skeleton, a polyvinyl alcohol skeleton, and the like. The easy-adhesion layer may be provided in advance on a protective film, and the easy-adhesion layer side of the protective film may be laminated on the polarizing film with the adhesive layer or the adhesive layer interposed therebetween.

The barrier layer is a layer having a function of preventing impurities such as oligomers and ions eluted from the transparent protective film from migrating (entering) into the polarizing film. The barrier layer may be any layer that has transparency and can prevent impurities from eluting from a transparent protective film or the like, and examples of materials for forming the barrier layer include: urethane prepolymer-based forming materials, cyanoacrylate-based forming materials, epoxy-based forming materials, and the like.

The refractive index adjustment layer is provided to suppress a decrease in transmittance due to reflection between the transparent protective film and the polarizing film or other layers having different refractive indices. Examples of the refractive index adjusting material for forming the refractive index adjusting layer include: the material for forming the resin composition contains various resins including silica-based resins, acrylic-styrene resins, melamine resins, and the like, and additives.

The polarization degree of the polarizing film is preferably 99.98% or more, and more preferably 99.99% or more.

Examples

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

< example 1 >

< production of polarizing film >

< production of polarizing film containing Water (I-1) >

A polyvinyl alcohol film having an average polymerization degree of 2400, a saponification degree of 99.9 mol% and a thickness of 45 μm was prepared. The polyvinyl alcohol film was immersed between rolls having different peripheral speed ratios for 30 seconds in a swelling bath (water bath) at 20 ℃ to swell the polyvinyl alcohol film and stretched 2.2 times in the transport direction (swelling step), and then immersed in a dyeing bath (aqueous solution having an iodine concentration of 0.03 wt% and a potassium iodide concentration of 0.3 wt%) at 30 ℃ for 30 seconds to stretch the original polyvinyl alcohol film (polyvinyl alcohol film completely unstretched in the transport direction) by 3.3 times in the transport direction while dyeing the film (dyeing step). Next, the dyed polyvinyl alcohol film was immersed in a crosslinking bath (aqueous solution having a boric acid concentration of 3.0 wt% and a potassium iodide concentration of 3.0 wt%) at 40 ℃ for 28 seconds, and the original polyvinyl alcohol film was stretched 3.6 times in the transport direction (crosslinking step). Further, the obtained polyvinyl alcohol film was immersed in a stretching bath (aqueous solution having a boric acid concentration of 4.0 wt% and a potassium iodide concentration of 5.0 wt%) at 61 ℃ for 60 seconds, stretched 6.0 times in the transport direction based on the original polyvinyl alcohol film (stretching step), and then immersed in a cleaning bath (aqueous solution having a potassium iodide concentration of 2.0 wt%) at 20 ℃ for 5 seconds (cleaning step), thereby producing a polarizing film containing water.

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

A liquid a (a 10 wt% aqueous solution of a compound represented by the following chemical formula (9)) was applied to the water-containing polarizing film obtained above using a wire bar (No. 3, manufactured by first physico-chemical co., ltd.), and left to stand at 25 ℃ for 3 seconds, and then the liquid a remaining on the surface was wiped off to produce a polarizing film impregnated with components in the liquid. Here, the water content of the polarizing film containing water was determined to be 33.0 wt% by the following measurement method.

[ chemical formula 9]

[ method for measuring moisture percentage (wt%) in polarizing film ]

The polarizing film was measured about 0.2g, dried at 120 ℃ for 2 hours, and the weight after drying was measured to calculate the moisture percentage (W) in the polarizing film based on the following formula.

Water content W (wt%) of the polarizing film { (M)₀－M₁)/M₀}×100

M₀: measured weight (g) of polarizing film

M₁: weight (g) of polarizing film after drying at 120 ℃ for 2 hours

[ method for measuring boron content (wt%) in polarizing film containing water ]

The above polarizing film containing water (0.2 to 0.3g) was dried at 120 ℃ for 2 hours, dissolved in water, and then neutralized and titrated in an aqueous solution obtained by adding a small amount of mannitol and a BTB solution dropwise thereto, using a burette and a 0.1mol/L NaOH aqueous solution, and the boron content of the polarizing film was calculated based on the following formula.

The boron content (wt%) of the polarizing film containing water is C × V × Mw/M × 100

C: concentration of NaOH aqueous solution (mol/L)

V: dropping amount (L) of NaOH aqueous solution

Mw: atomic weight of boron (g/mol)

M: weight (g) of polarizing film after drying at 120 ℃ for 2 hours

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

The polarizing film impregnated with the component in the liquid obtained above was dried at 60 ℃ for 4 minutes to produce a dried polarizing film (hereinafter also simply referred to as a polarizing film). The moisture percentage of the polarizing film after drying, which was determined by the above measurement method, was 11.3 wt%. The content (M) of the compound represented by chemical formula (9) in the polarizing film was determined by the following measurement method_H) 0.27 wt%, content (m) of the compound represented by the formula (9) per unit area_H) Is 5.4 mu g/cm². The polarizing film had a thickness (T) of 18 μm.

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

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

[ content of the compound represented by the formula (9) per unit area of the polarizing film (. mu.g/cm)²) Method of measurement of]

The content (m) of the compound represented by the formula (9) per unit area was calculated based on the following formula_H)。

m_H＝1.2×T×M_H(μg/cm²)

T: thickness of polarizing film (μm)

M_H: the content (wt%) of the compound represented by the formula (9) in the polarizing film

< production of polarizing film >

As the adhesive, an aqueous solution containing a polyvinyl alcohol resin having an acetoacetyl group (average polymerization degree of 1200, saponification degree of 98.5 mol%, acetoacetylation degree of 5 mol%) and methylolmelamine at a weight ratio of 3:1 was used. Using this adhesive, a cellulose triacetate film having a hard coat layer and a thickness of 40 μm (moisture permeability: 342 g/(m) was bonded to both sides of the polarizing film obtained above by a roll laminator²·24h) And konicamida, trade name "KC 4 UYW"), followed by drying by heating in an oven (temperature 60 ℃ c. for 4 minutes), a polarizing film was produced in which transparent protective films were laminated on both sides of the polarizing film.

[ method for measuring degree of polarization ]

The degree of polarization of the polarizing film can be measured using a spectrophotometer (product name "V7100" by japanese spectral system). As a specific method for measuring the degree of polarization, the parallel transmittance (H0) and the orthogonal transmittance (H90) of a polarizing film can be measured according to the formula: the polarization degree (%) { (H0-H90)/(H0 + H90) }1/2 × 100 was determined. The parallel transmittance (H0) is a transmittance value of a parallel laminated polarizing film produced by laminating 2 identical polarizing films so that their absorption axes are parallel to each other. The orthogonal transmittance (H90) is a transmittance value of an orthogonal laminated polarizing film produced by laminating 2 identical polarizing films so that their absorption axes are orthogonal to each other. These transmittances are Y values obtained by correcting visibility with a 2-degree field of view (C light source) of JlS Z8701-1982.

[ evaluation of heating durability (A) ]

The polarizing film obtained above was cut into a size of 5.0 × 4.5cm so that the absorption axis of the polarizing film was parallel to the long side, a glass plate (analog image display unit) was bonded to the protective film surface of the polarizing film on the image display unit side via an acrylic pressure-sensitive adhesive layer having a thickness of 20 μm, and autoclave treatment was performed at 50 ℃ and 0.5MPa for 15 minutes to prepare a laminate. The obtained laminate was left standing in a hot air oven at a temperature of 110 ℃ and the time until coloring was visually observed, and was judged according to the following criteria.

O: no coloration occurred for more than 500 hours.

And (delta): the coloring occurred in 300 hours or more and less than 500 hours.

X: coloration occurs in less than 300 hours.

[ evaluation of heating durability (B) ]

The polarizing film obtained above was cut into a size of 5.0 × 4.5cm so that the absorption axis of the polarizing film was parallel to the long side, a glass plate (analog image display unit) was bonded to the protective film surface of the polarizing film on the image display unit side via an acrylic pressure-sensitive adhesive layer having a thickness of 20 μm, and autoclave treatment was performed at 50 ℃ and 0.5MPa for 15 minutes to prepare a laminate. The obtained laminate was left to stand in a hot air oven at a temperature of 105 ℃, and the time until coloring was visually observed, and was determined based on the following criteria.

O: coloring did not occur for more than 750 hours.

And (delta): the coloring occurred in 500 hours or more and less than 750 hours.

X: coloration occurs in less than 500 hours.

< example 2 >

< polarizing film and production of polarizing film >

A polarizing film and a polarizing film were produced in the same manner as in example 1 except that the polarizing film after the washing step was allowed to stand at 25 ℃ for 30 seconds to obtain a water-containing polarizing film, and then liquid a was applied thereto, and the above-described measurement was performed. The results are shown in Table 1.

< example 3 >

< polarizing film and production of polarizing film >

A polarizing film and a polarizing film were produced in the same manner as in example 1 except that the polarizing film after the washing step was allowed to stand at 25 ℃ for 1 minute to obtain a polarizing film containing water, and then liquid a was applied thereto, and the above-described measurement was performed. The results are shown in Table 1.

< comparative example 1 >

< polarizing film and production of polarizing film >

A polarizing film and a polarizing film were produced in the same manner as in example 1 except that the polarizing film after the washing step was allowed to stand at 25 ℃ for 3 minutes to obtain a water-containing polarizing film, and then liquid a was applied thereto, and the above-described measurement was performed. The results are shown in Table 1.

< comparative example 2 >

< polarizing film and production of polarizing film >

A polarizing film and a polarizing film were produced in the same manner as in example 1, except that the polarizing film after the washing step was allowed to stand at 60 ℃ for 1 minute, and then liquid a was applied, and the above-described measurement was performed. The results are shown in Table 1.

< comparative example 3 >

< polarizing film and production of polarizing film >

A polarizing film and a polarizing film were produced in the same manner as in example 1 except that the dried polarizing film was not dried by heating at 60 ℃ for 4 minutes in the step (I-3) for producing a dried polarizing film, and the above-described measurement was performed. The results are shown in Table 1.

< example 4 >

< polarizing film and production of polarizing film >

A polarizing film and a polarizing film were produced in the same manner as in example 1, except that a polyvinyl alcohol film having a thickness of 30 μm was used, and the iodine concentration in the dyeing bath was adjusted so that the monomer transmittance of the finally obtained polarizing film became the same, and the above-described measurement was performed. The results are shown in Table 1. The thickness (T) of the polarizing film was 12 μm.

< comparative example 4 >

< polarizing film and production of polarizing film >

A polarizing film and a polarizing film were produced in the same manner as in example 4, except that the polarizing film after the washing step was dried at 60 ℃ for 1 minute, and then liquid a was applied, and the above-described measurement was performed. The results are shown in Table 1.

< example 5 >

< production of polarizing film >

< production (preparation) of laminate (II-0) >)

As the thermoplastic resin substrate, a long-sized amorphous isophthalic acid copolymerized polyethylene terephthalate film (thickness: 100 μm) having a water absorption of 0.75% and a Tg of about 75 ℃ was used. One side of the resin substrate was subjected to corona treatment. To 100 parts by weight of a PVA resin obtained by mixing polyvinyl alcohol (polymerization degree 4200, saponification degree 99.2 mol%) and acetoacetyl-modified PVA (trade name "GOHSEFIMER Z410" manufactured by Nippon synthetic chemical Co., Ltd.) at a ratio of 9:1, 13 parts by weight of potassium iodide was added to prepare an aqueous PVA solution (coating solution). The above aqueous PVA solution was applied to the corona-treated surface of the resin substrate, and dried at 60 ℃ to form a PVA-based resin layer having a thickness of 13 μm, thereby producing (preparing) a laminate.

The obtained laminate was subjected to free-end uniaxial stretching (auxiliary stretching step in a gas atmosphere) in a longitudinal direction (longitudinal direction) by 2.4 times between rolls having different peripheral speeds in an oven at 130 ℃. Next, the laminate was immersed in an insolubilization bath (an aqueous boric acid solution prepared by adding 4 parts by weight of boric acid to 100 parts by weight of water) at a liquid temperature of 40 ℃ for 30 seconds (insolubilization treatment step). Next, the polarizing film finally obtained was immersed in a dyeing bath (aqueous iodine solution prepared by mixing iodine and potassium iodide in a weight ratio of 1:7 with respect to 100 parts by weight of water) at a liquid temperature of 30 ℃ for 60 seconds while adjusting the concentration so that the monomer transmittance (Ts) of the polarizing film becomes 42% (dyeing step). Subsequently, the substrate was immersed in a crosslinking bath (an aqueous solution of boric acid containing 3 parts by weight of potassium iodide and 5 parts by weight of boric acid per 100 parts by weight of water) at a liquid temperature of 40 ℃ for 30 seconds (crosslinking step). Then, the laminate was uniaxially stretched in the longitudinal direction (longitudinal direction) between rolls having different peripheral speeds so that the total stretching ratio became 5.5 times while being immersed in an aqueous boric acid solution (boric acid concentration: 4.0 wt%) having a liquid temperature of 70 ℃. Then, the laminate was immersed in a cleaning bath (aqueous solution containing 4 parts by weight of potassium iodide per 100 parts by weight of water) at a liquid temperature of 20 ℃.

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

A laminate having a polarizing film impregnated with a component in a liquid was produced by applying a liquid a (a 10 wt% aqueous solution of a compound represented by formula (9)) to the polarizing film surface of the laminate having a polarizing film containing water obtained above using a wire bar (No. 3, manufactured by first physico-chemical co., ltd.), standing the laminate at 25 ℃ for 3 seconds, and then wiping off the liquid a remaining on the surface. Here, the water content of the polarizing film containing water determined by the above measurement method was 35.5 wt%.

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

Dried in an oven maintained at 95 ℃ for 10 minutes (drying treatment process). Thus, a polarizing film having a thickness of 5 μm was formed on the resin substrate. The moisture percentage of the polarizing film after drying, which was determined by the above measurement method, was 9.9 wt%. The content (M) of the compound represented by the formula (9) in the polarizing film_H) 0.41% by weight, a content (m) of the compound represented by the formula (9) per unit area_H) Is 2.5 mu g/cm²。

< production of polarizing film >

As the adhesive, an aqueous solution containing an acetoacetyl group-containing polyvinyl alcohol resin (average polymerization degree of 1200, saponification degree of 98.5 mol%, acetoacetylation degree of 5 mol%) and methylolmelamine at a weight ratio of 3:1 was used. Using this adhesive, a 40 μm thick cellulose triacetate film (having a moisture permeability of 342 g/(m) with a hard coat layer was bonded to the surface of the polarizing film obtained above opposite to the resin substrate by a roll laminator²24 hours), manufactured by konica minolta, trade name "KC 4 UYW"), and then dried by heating in an oven (temperature 60 ℃ for 4 minutes), to manufacture a polarizing film having a transparent protective film attached to one surface of the polarizing film. Next, the resin base material was peeled off, and the cellulose triacetate films were bonded to the peeled surfaces by a roll laminator using the adhesive, followed by drying by heating in an oven (temperature 60 ℃ c., time 4 minutes), thereby producing a polarizing film in which transparent protective films were bonded to both surfaces of the polarizing film.

[ evaluation of heating durability (C) ]

The polarizing film obtained above was cut into a size of 5.0 × 4.5cm so that the absorption axis of the polarizing film was parallel to the long side, a glass plate (analog image display unit) was bonded to the protective film surface of the polarizing film on the image display unit side via an acrylic pressure-sensitive adhesive layer having a thickness of 20 μm, and autoclave treatment was performed at 50 ℃ and 0.5MPa for 15 minutes to prepare a laminate. The obtained laminate was left standing in a hot air oven at a temperature of 95 ℃ and the time until coloring was visually observed, and was judged according to the following criteria.

O: coloring did not occur for more than 750 hours.

X: coloration occurs in less than 500 hours.

< comparative example 5 >

< polarizing film and production of polarizing film >

A polarizing film and a polarizing film were produced in the same manner as in example 5, except that the polarizing film after the washing treatment step was dried at 95 ℃ for 10 minutes, and then liquid a was applied, and the above measurements were performed. The results are shown in Table 2.

< example 6 >

< polarizing film and production of polarizing film >

A polarizing film and a polarizing film were produced in the same manner as in example 1 except that the potassium iodide concentration in the cleaning bath was set to 4.0 wt%, and liquid B (an aqueous solution containing 10 wt% of zinc sulfate 7 hydrate and 0.2 wt% of Olfine exp.4200 (manufactured by mitsui chemical industries) was used instead of liquid a in the production of the polarizing film, and the above and the following measurements were performed. The results are shown in Table 3.

[ measurement of Zinc content (% by weight) in polarizing film ]

About 25mg of the polarizing film was weighed into a Teflon (registered trademark) container, added with an acid and tightly closed, and then irradiated with a microwave to be subjected to acid decomposition under pressure at 200 ℃ or lower. After complete decomposition, ultrapure water was added thereto to make a volume of 50mL, and the zinc concentration was measured by ICP-MS (Agilent 8800, Agilent technologies). The decomposition apparatus used MARS5 manufactured by CEM.

[ evaluation of heating durability (D) ]

The polarizing film obtained above was cut into a size of 5.0 × 4.5cm so that the absorption axis of the polarizing film was parallel to the long side, a glass plate (analog image display unit) was bonded to the protective film surface of the polarizing film on the image display unit side via an acrylic pressure-sensitive adhesive layer having a thickness of 20 μm, and autoclave treatment was performed at 50 ℃ and 0.5MPa for 15 minutes to prepare a laminate. The obtained laminate was left standing in a hot air oven at a temperature of 105 ℃ for 500 hours, and the samples after the test were arranged in a cross nicol manner, and the cross transmittance (%) at a wavelength of 700nm was measured by the above spectrophotometer (V7100) and determined based on the following criteria.

O: no heating red change (105 ℃, 500 hours of heating test before and after the orthogonal transmittance at 700nm wavelength difference less than 1%).

X: there was a reddish change upon heating (difference in orthogonal transmittance at a wavelength of 700nm between before and after a heating test at 105 ℃ for 500 hours: 1% or more).

< comparative example 6 >

< polarizing film and production of polarizing film >

A polarizing film and a polarizing film were produced in the same manner as in example 6, except that the polarizing film after the washing step was dried at 60 ℃ for 1 minute, and then liquid B was applied, and the above-described measurement was performed. The results are shown in Table 3.

The heating durability test described above is affected by the film thickness of the polarizing film, and therefore, it is sufficient to compare polarizing films having the same film thickness, and it is found that the polarizing film of the example contains components in the liquid more sufficiently than the polarizing film of the comparative example, and therefore, the heating durability is more excellent.

Claims

1. A method for producing a polarizing film, comprising:

step (I-1): carrying a polyvinyl alcohol film along a longitudinal direction, and carrying out at least a dyeing step, a crosslinking step and a stretching step on the polyvinyl alcohol film to manufacture a polarizing film containing water;

step (I-2): applying a liquid to the obtained polarizing film containing water in a state where the water content of the polarizing film is X wt% or more, thereby producing a polarizing film impregnated with a component in the liquid; and

step (I-3): the obtained polarizing film impregnated with the component in the liquid is subjected to a drying step to produce a dried polarizing film,

the method satisfies the condition of the following formula (1),

formula (1): the X (% by weight)/the thickness (μm) > 1 of the polarizing film after drying

In the formula (1), X is 10 to 70 inclusive.

2. The method for producing a polarizing film according to claim 1, which satisfies the condition of the following formula (2),

formula (2): said X (wt%) -the moisture percentage (wt%) > 0 (wt%) of said dried polarizing film,

in the formula (2), X is 10 to 70 inclusive.

3. A method for producing a polarizing film, comprising:

step (II-0): forming a polyvinyl alcohol resin layer containing a polyvinyl alcohol resin on one side of a long thermoplastic resin base material to prepare a laminate;

step (II-1): a step of producing a laminate having a polarizing film containing water by carrying the laminate obtained in the longitudinal direction and subjecting the laminate to at least an auxiliary stretching treatment step in a gas atmosphere, a dyeing treatment step, and a stretching treatment step in an aqueous solution;

step (II-2): applying a liquid to the obtained laminate having a polarizing film containing water in a state where the moisture percentage of the polarizing film is Y wt% or more, thereby producing a laminate having a polarizing film impregnated with a component in the liquid; and

step (II-3): the obtained laminate having the polarizing film impregnated with the component in the liquid is subjected to a drying treatment step to produce a dried polarizing film,

the method satisfies the condition of the following formula (3),

formula (3): the Y (% by weight)/the thickness (μm) > 1 of the polarizing film after drying,

in the formula (3), Y is 10 to 70 inclusive.

4. The method for producing a polarizing film according to claim 3, which satisfies the condition of the following formula (4),

formula (4): the Y (wt%) -the moisture percentage (wt%) > 0 (wt%) of the dried polarizing film,

in the formula (4), Y is 10 to 70 inclusive.

5. The method for producing a polarizing film according to any one of claims 1 to 4,

the liquid is a solution, and the components in the liquid are solutes.

6. The method for producing a polarizing film according to any one of claims 1 to 5,

the moisture percentage of the dried polarizing film is 20 wt% or less.

7. The method for producing a polarizing film according to any one of claims 1 to 6,

the components in the liquid are water-soluble compounds.

8. The method for producing a polarizing film according to any one of claims 1 to 7,

the component in the liquid is at least one selected from a radical scavenger, a crosslinking agent, a plasticizer, and a dye.

9. The method for producing a polarizing film according to any one of claims 1 to 8,

the component in the liquid is a radical scavenger.

10. A method for manufacturing a polarizing film, comprising:

a step of laminating a transparent protective film to at least one surface of the polarizing film obtained by the method for producing a polarizing film according to any one of claims 1 to 9 via an adhesive layer.