CN115427850A

CN115427850A - Polarizing film, laminated polarizing film, image display panel, and image display device

Info

Publication number: CN115427850A
Application number: CN202180029484.0A
Authority: CN
Inventors: 黑原薰; 山下智弘; 黑田拓马; 八木汐海; 高田胜则; 汤峰卓哉
Original assignee: Nitto Denko Corp
Current assignee: Nitto Denko Corp
Priority date: 2020-04-20
Filing date: 2021-04-19
Publication date: 2022-12-02
Also published as: WO2021215385A1; KR20230002270A; JP2021174002A; TW202146243A

Abstract

The invention provides a polarizing film which constitutes an image display device having an image display unit, wherein the polarizing film has a polarizing film, a functional layer, an adhesive layer, and a 1 st transparent protective film, the functional layer is adjacent to the image display unit side of the polarizing film and contains a water-soluble radical scavenger, and the 1 st transparent protective film is provided on the functional layer with the adhesive layer interposed therebetween. The polarizing film is excellent in the effect of suppressing a decrease in the transmittance of monomers in a high-temperature environment.

Description

Polarizing film, laminated polarizing film, image display panel, and image display device

Technical Field

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

Background

Conventionally, as a polarizing film 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 can be produced by subjecting a polyvinyl alcohol-based film to various treatments such as swelling, dyeing, crosslinking, and stretching in a bath, then washing the film, and then drying the film. 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.

The various image display devices described above generally include: an image display unit such as a liquid crystal cell or an organic EL element, a viewing-side polarizing film disposed on a viewing side of the image display unit, and a back-side polarizing film disposed on a side (backlight side) opposite to the viewing side of the image display unit (patent documents 1 to 2). The polarizing film may be used in the form of a laminated polarizing film (optical laminate) by laminating another optical layer as necessary, and further, the polarizing film or the laminated polarizing film (optical laminate) may be used as an image display panel to be bonded to the image display unit (patent document 3).

In recent years, such various image display devices have been used as in-vehicle image display devices such as car navigation devices and rear view monitors in addition to mobile devices such as mobile phones and tablet terminals, and their applications have been widened. Accordingly, the polarizing film and the laminated polarizing film are required to have high durability in a severer environment (for example, a high-temperature environment) than the conventional ones, and therefore, a polarizing film and an image display device have been proposed for the purpose of securing such durability (patent documents 4 to 5).

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2017-227731

Patent document 2: japanese patent laid-open publication No. 2019-128430

Patent document 3: japanese patent laid-open publication No. 2014-102353

Patent document 4: japanese Kokai publication Hei 2012-516468

Patent document 5: japanese patent laid-open publication No. 2018-101117

Disclosure of Invention

Problems to be solved by the invention

In recent years, with the development of the automatic driving technology, the above-described in-vehicle image display device has been developed to have a display with a different shape and a larger size. With such a change in display design, a method for further improving durability in a high-temperature environment is required for a polarizing film.

In view of the above circumstances, an object of the present invention is to provide a polarizing film having an excellent effect of suppressing a decrease in the transmittance of monomers in a high-temperature environment.

Another object of the present invention is to provide a laminated polarizing film, an image display panel, and an image display device using the polarizing film.

Means for solving the problems

That is, the present invention relates to a polarizing film constituting an image display device having an image display unit, wherein the polarizing film has a polarizing film, a functional layer, an adhesive layer, and a 1 st transparent protective film, the functional layer is adjacent to the image display unit side of the polarizing film and contains a water-soluble radical scavenger, and the 1 st transparent protective film is provided on the functional layer with the adhesive layer interposed therebetween.

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

The present invention also relates to an image display panel including the polarizing film or the laminated polarizing film, and an image display unit.

The present invention also relates to an image display device including the image display panel and a front surface transparent member.

ADVANTAGEOUS EFFECTS OF INVENTION

The detailed action mechanism of the effect of the polarizing film of the present invention is not clear, but it is presumed as follows. The explanation of the present invention is not limited to this mechanism of action.

The polarizing film of the present invention is an image display device having an image display unit, wherein the polarizing film includes a polarizing film, a functional layer, an adhesive layer, and a 1 st transparent protective film, the functional layer is adjacent to the image display unit side of the polarizing film and contains a water-soluble radical scavenger, and the 1 st transparent protective film is provided on the functional layer with the adhesive layer interposed therebetween. In general, it is presumed that, when the image display unit side of the above-described polarizing film constituting the image display device is heated, moisture in the polarizing film is not easily discharged out of the system, and deterioration of the polarizing film is promoted by the remaining moisture, thereby causing a decrease in the monomer transmittance (polyene). Therefore, in the polarizing film of the present invention, the water-soluble radical scavenger contained in the functional layer adjacent to the cell side of the polarizing film is easily moved into the moisture in the polarizing film, and can scavenge radicals that may be generated by the progress of the polyalkylenization, and therefore, a decrease in the monomer transmittance (polyene) from the cell side of the polarizing film can be effectively suppressed, and therefore, the effect of suppressing a decrease in the monomer transmittance in a high-temperature environment is excellent.

Drawings

Fig. 1 is a schematic cross-sectional view showing one embodiment of an image display device.

Fig. 2 is a schematic cross-sectional view showing one mode of a polarizing film (visible-side polarizing film).

Fig. 3 is a schematic cross-sectional view showing one mode of a polarizing film (visible-side polarizing film).

Fig. 4 is a schematic cross-sectional view showing one embodiment of a polarizing film (back-side polarizing film).

Fig. 5 is a schematic cross-sectional view showing one embodiment of a polarizing film (back-side polarizing film).

Description of the symbols

10 (a): polarizing film (visual side polarizing film)

10 (b): polarizing film (backside polarizing film)

11: polarizing film

12: functional layer

13: no. 1 transparent protective film

14: no. 2 transparent protective film

20: adhesive layer

40 and 50: adhesive or adhesive layer

80: front surface transparent member

90: image display unit

100: image display device

Detailed Description

Fig. 1 is a schematic cross-sectional view showing one embodiment of an image display device of the present invention. Fig. 1 shows an embodiment of an image display panel on the image display unit side, in which a polarizing film of a polarizing film (visible-side polarizing film) 10 (a) is bonded to an image display unit 90 via an adhesive layer or an adhesive layer 40. Fig. 1 shows an embodiment of an image display panel on the image display unit side in which a polarizing film of a polarizing film (back-side polarizing film) 10 (b) is bonded to an image display unit 90 via an adhesive layer or an adhesive layer 50. Fig. 1 shows an embodiment of an image display device 100 including a front transparent member 80 on the polarizing film (visible-side polarizing film) 10 (a) side of an image display panel. The polarizing film (polarizing film on the back side) 10 (b) is provided with a backlight unit (not shown) on the opposite side of the polarizing film from the image display unit side.

Fig. 2 is a schematic cross-sectional view showing one mode of a polarizing film (visible-side polarizing film) of the present invention. Fig. 1 shows an embodiment of a polarizing film 10 (a) in which a functional layer 12 is adjacent to the image display unit side of a polarizing film 11, and a 1 st transparent protective film 13 is provided on the functional layer 12 with an adhesive layer 20 interposed therebetween.

Fig. 3 is a schematic cross-sectional view showing one mode of a polarizing film (visible-side polarizing film) of the present invention. Fig. 3 shows an embodiment of the polarizing film 10 (a) in which the functional layer 12 is adjacent to the image display unit side of the polarizing film 11, the 1 st transparent protective film 13 is provided on the functional layer 12 via the adhesive layer 20, and the 2 nd transparent protective film 14 is provided on the side (visible side) of the polarizing film 11 opposite to the image display unit side via the adhesive layer or adhesive layer 30.

Fig. 4 is a schematic cross-sectional view showing one embodiment of the polarizing film (back-side polarizing film) of the present invention. Fig. 4 shows an embodiment of a polarizing film 10 (b) in which a functional layer 12 is adjacent to the image display unit side of a polarizing film 11, and a 1 st transparent protective film 13 is provided on the functional layer 12 with an adhesive layer 20 interposed therebetween.

Fig. 5 is a schematic cross-sectional view showing one embodiment of the polarizing film (back-side polarizing film) of the present invention. Fig. 5 shows an embodiment of the polarizing film 10 (b) in which the functional layer 12 is adjacent to the image display unit side of the polarizing film 11, the 1 st transparent protective film 13 is provided on the functional layer 12 via the adhesive layer 20, and the 2 nd transparent protective film 14 is provided on the side (backlight side) opposite to the image display unit side of the polarizing film 11 via the adhesive layer or adhesive layer 30.

< polarizing film >

The polarizing film of the present invention is an image display device having an image display unit, wherein the polarizing film includes a polarizing film, a functional layer, an adhesive layer, and a 1 st transparent protective film, the functional layer is adjacent to the image display unit side of the polarizing film and contains a water-soluble radical scavenger, and the 1 st transparent protective film is provided on the functional layer with the adhesive layer interposed therebetween. The polarizing film may be any of a viewing-side polarizing film disposed on the viewing side of the image display unit and a back-side polarizing film disposed on the side opposite to the viewing side (backlight side) of the image display unit. The visible-side polarizing film and the back-side polarizing film may be the same or different.

< polarizing film >

The polarizing film of the present invention is formed by adsorbing and orienting a dichroic material such as iodine or a dichroic dye to a polyvinyl alcohol film. From the viewpoint of initial polarization performance of the polarizing film, iodine is preferable as the dichroic substance.

The polyvinyl alcohol (PVA) film may be one having light transmittance in the visible light range and having a dichroic material such as iodine or a dichroic dye dispersed and adsorbed therein, without any particular limitation. The thickness of the PVA film to be used in a roll of film is preferably about 1 to 100. Mu.m, more preferably about 1 to 50 μm, and the width thereof is preferably 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 additive is not particularly limited, and is preferably about 20 wt% or less in the polyvinyl alcohol film, for example.

The polarizing film can be produced by, for example, immersing the polyvinyl alcohol film in an aqueous solution of a dichroic substance such as iodine or a dichroic dye, dyeing the film, and stretching the film to 3 to 7 times the original length. If necessary, the substrate may be immersed in an aqueous solution of boric acid, potassium iodide, or the like. Further, the polyvinyl alcohol film may be washed with water by immersing it in water before dyeing, if necessary. By washing the polyvinyl alcohol film with water, not only dirt and an anti-blocking agent on the surface of the polyvinyl alcohol film can be washed away, but also the polyvinyl alcohol film is swollen to prevent unevenness such as uneven dyeing. The stretching may be performed after the dyeing with iodine, or may be performed while dyeing, or may be performed after the stretching with iodine. Stretching may be carried out in an aqueous solution of boric acid, potassium iodide, or the like, or in a water bath.

The thickness of the polarizing film is preferably 1 μm or more, more preferably 2 μm or more from the viewpoint of improving the initial degree of polarization of the polarizing film, and is preferably 15 μm or less, more preferably 10 μm or less, and even more preferably 8 μm or less from the viewpoint of preventing warpage of the panel. In particular, in order to obtain a polarizing film having a thickness of about 8 μm or less, a thin polarizing film production method using a laminate comprising a thermoplastic resin substrate and a polyvinyl alcohol resin layer formed on the thermoplastic resin substrate as the polyvinyl alcohol film can be used.

< method for producing thin polarizing film >

The method for manufacturing a thin polarizing film comprises the following steps: forming a polyvinyl alcohol resin layer (PVA type resin layer) containing a polyvinyl alcohol resin (PVA type resin) on one side of a long thermoplastic resin base material to prepare a laminate; and sequentially subjecting the laminate to an auxiliary stretching treatment in a gas atmosphere, a dyeing treatment, a stretching treatment in an aqueous solution, and a drying shrinkage treatment. In particular, in order to obtain a polarizing film having high optical characteristics, a two-stage stretching method in which an auxiliary stretching treatment (dry stretching) in a gas atmosphere and a stretching treatment in an aqueous solution in an aqueous boric acid solution are combined may be selected.

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

The thermoplastic resin base 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 allowing 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 ℃. 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 a copolymer containing isophthalic acid and/or cyclohexanedicarboxylic acid as a dicarboxylic acid, and a copolymer containing cyclohexanedimethanol and diethylene glycol as a diol.

The thermoplastic resin substrate may be subjected to a surface treatment (for example, 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 PVA-based resin concentration of the coating liquid 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 adhering to the thermoplastic resin substrate.

From the viewpoint of improving the orientation of the polyvinyl alcohol molecules by stretching, it is preferable to mix a halide in 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, blade coating (comma coating, etc.), and the like. The drying temperature of the coating liquid is preferably about 50 ℃.

In the auxiliary stretching treatment 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 treatment 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), but free-end stretching is preferable from the viewpoint of obtaining high optical characteristics.

The stretching ratio in the auxiliary stretching in the gas atmosphere is preferably about 2 to 3.5 times. The auxiliary stretching in the gas atmosphere may be performed in one stage or may be performed 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 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, for example, 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, after the auxiliary stretching treatment in the gas atmosphere and before the dyeing treatment or the stretching treatment in an aqueous solution, an insolubilization treatment may be performed. The insolubilization is typically performed by immersing the PVA-based resin layer in an aqueous boric acid solution. By performing insolubilization treatment, water resistance can be imparted to the PVA-based resin layer, and the orientation of PVA can be prevented from being lowered when immersed in water. The concentration of the aqueous boric acid solution is preferably about 1 to 5 parts by weight relative to 100 parts by weight of water. The liquid temperature of the bath for the insolubilization treatment is preferably about 20 to 50 ℃.

The dyeing treatment 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. The liquid temperature of the dyeing bath is preferably about 20 to 50 ℃ in order to suppress dissolution of the PVA based resin. 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 aqueous iodine solution is preferably about 1.

If necessary, the crosslinking treatment may be performed after the dyeing treatment and before the stretching treatment in an aqueous solution. The crosslinking treatment is typically performed by immersing the PVA-based resin layer in an aqueous boric acid solution. By performing the crosslinking treatment, 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 is performed, it is preferable to further add the iodide to a crosslinking bath in the crosslinking treatment. 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 relative to 100 parts by weight of water. The liquid temperature of the crosslinking bath (boric acid aqueous solution) is preferably about 20 to 50 ℃.

The stretching treatment in the aqueous solution is performed by immersing the laminate in a stretching bath. The stretching treatment in an aqueous solution 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 thus 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 treatment 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), but free-end stretching is preferable from the viewpoint of obtaining high optical characteristics.

The stretching treatment in an aqueous solution is preferably performed by immersing the laminate in an aqueous boric acid solution (stretching in an aqueous boric acid solution). 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, relative to 100 parts by weight of water. In addition, an iodide may be added to the stretching bath (boric acid aqueous solution). The liquid temperature of the stretching bath is preferably about 40 to 85 ℃, 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 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.

The drying shrinkage treatment may be performed by heating the entire area to perform area heating, or may be performed by heating a transport roller (using a so-called heating roller), but both of them are preferably used. By drying with a hot roller, the laminate can be effectively prevented from curling by heating, and a polarizing film having excellent appearance can be produced. In addition, the shrinkage ratio in the width direction of the laminate body by the drying and shrinking treatment is preferably about 1 to 10%, more preferably about 2 to 8%, from the viewpoint of improving the optical characteristics of the obtained polarizing film by shrinking in the width direction during the drying and shrinking treatment.

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 still more 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 the hot air drying is preferably about 30 to 100 ℃. The hot air drying time is preferably about 1 to 300 seconds.

It is preferable to perform the washing treatment after the stretching treatment in the aqueous solution and before the drying shrinkage treatment. The cleaning treatment 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 an 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.

< functional layer >

The functional layer of the present invention is adjacent to the image display unit side of the polarizing film described above, and contains a water-soluble radical scavenger.

From the viewpoint of easy migration to the moisture in the polarizing film, the water-soluble radical scavenger is preferably a compound that can dissolve 1 part by weight or more in 100 parts by weight of 25 ℃ water, more preferably a compound that can dissolve 2 parts by weight or more in 100 parts by weight of 25 ℃ water, and even more preferably a compound that can dissolve 5 parts by weight or more in 100 parts by weight of 25 ℃ water. The water-soluble radical scavenger may be used alone or in combination of two or more.

It is presumed that the water-soluble radical scavenger can suppress polyene formation of the polarizing film in a high-temperature environment. Examples of the water-soluble radical scavenger include: hindered phenol, hindered amine, phosphorus, sulfur, benzotriazole, benzophenone, hydroxylamine, salicylate, triazine compounds and other compounds with free radical trapping function. The water-soluble radical scavenger is preferably a compound having a nitroxyl radical or a nitroxyl group, for example, from the viewpoint of the radical species generated in the polarizing film.

Examples of the compound having a nitroxyl radical or nitroxyl group include N-oxyl compounds (having C-N (-C) -O) in view of having a relatively stable radical in air at room temperature ^· Compound (O) as a functional group ^· Oxygen radical)), a known compound can be used. Examples of the N-oxyl compound include compounds having an organic group having the following structure.

[ chemical formula 1]

(in the general formula (1), R ¹ Represents an oxygen radical, R ² ～R ⁵ Independently represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, and n represents 0 or 1). In the general formula (1), the left side of the dotted line 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), R ¹ ～R ⁵ And n is as defined above, R ⁶ Represents a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an acyl group or an aryl group, and n represents 0 or 1. )

[ chemical formula 3]

(in the general formula (3), R ¹ ～R ⁵ And n is as defined above, R ⁷ And R ⁸ Independently 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), R ¹ ～R ⁵ And n is as defined above, R ⁹ ～R ¹¹ Independently 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), R ¹ ～R ⁵ And n is as defined above, R ¹² Represents 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 availability ² ～R ⁵ Preferably an alkyl group having 1 to 6 carbon atoms, and more preferably an alkyl group having 1 to 3 carbon atoms. In the general formula (2), R is R from the viewpoint of easy acquisition ⁶ Preferably 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 acquisition ⁷ And R ⁸ Independently 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 acquisition ⁹ ～R ¹¹ Preferably 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 acquisition ¹² Preferably hydroxy, amino or alkoxyAnd (4) a base. In the general formulae (1) to (5), n is preferably 1 from the viewpoint of easy acquisition.

Examples of the N-oxyl compound include: n-oxyl compounds described in, for example, japanese patent application laid-open Nos. 2003-64022, 11-222462, 2002-284737 and 2016/047655.

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]

The molecular weight of the water-soluble radical scavenger is preferably 1000 or less, more preferably 500 or less, and even more preferably 300 or less, from the viewpoint of suppressing the polyalkyleneition of the polarizing film in a high-temperature environment.

The content of the water-soluble radical scavenger in the functional layer is preferably 0.1 wt% or more, more preferably 5 wt% or more, and even more preferably 10 wt% or more from the viewpoint of suppressing the polyalkyleneition of the polarizing film, and is preferably 50 wt% or less, more preferably 40 wt% or less, and even more preferably 30 wt% or less in the functional layer from the viewpoint of appearance after the drying process of the functional layer.

The functional layer may be used without limitation as long as the material forming the layer is a binder resin capable of forming a layer such as a coating film, and examples thereof include: water-soluble plastic resins such as polyvinyl alcohol resins and polyacrylamides. Among these, polyvinyl alcohol resins are preferable from the viewpoint of adhesion to the polarizing film and durability. The binder resins may be used alone or in combination of two or more.

Examples of the polyvinyl alcohol resin include polyvinyl alcohol. Polyvinyl alcohol can be obtained by saponifying polyvinyl acetate. Examples of the polyvinyl alcohol resin include: saponified copolymers of vinyl acetate and copolymerizable monomers. When the copolymerizable monomer is ethylene, an ethylene-vinyl alcohol copolymer can be obtained. Examples of the copolymerizable monomer include: unsaturated carboxylic acids such as maleic acid (anhydride), fumaric acid, crotonic acid, itaconic acid, and (meth) acrylic acid, and esters thereof; α -olefins such as ethylene and propylene, (meth) allylsulfonic acid (sodium), sodium sulfonate (monoalkyl maleate), disulfonic acid sodium alkyl maleate, N-methylolacrylamide, alkali salts of acrylamide alkyl sulfonic acid, N-vinylpyrrolidone, and N-vinylpyrrolidone derivatives. Examples of the polyvinyl alcohol resin include: a modified polyvinyl alcohol resin having a hydrophilic functional group in a side chain of the polyvinyl alcohol or the copolymer thereof. Examples of the hydrophilic functional group include: acetoacetyl, carbonyl, and the like. The modified polyvinyl alcohol resin may be obtained by acetalization, urethanization, etherification, grafting, phosphorylation or the like of a polyvinyl alcohol resin.

The saponification degree of the polyvinyl alcohol resin may be, for example, 88% or more, and is preferably 90% or more, and more preferably 95% or more, from the viewpoint of optical durability under high temperature and high humidity. The degree of saponification can be determined in accordance with JIS K6726.

The functional layer is formed of a resin composition containing the binder resin as a main component, and the proportion of the binder resin is preferably 70 wt% or more, more preferably 80 wt% or more, and further preferably 90 wt% or more in the functional layer, for example.

The resin composition may be adjusted to a form of a solution obtained by dissolving and dispersing the binder resin in a solvent. Examples of the solvent include: and amines such as water, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, glycols, alcohols, ethylenediamine, and diethylenetriamine. The above solvents may be used alone, or two or more thereof may be used in combination.

The functional layer may contain additives such as a crosslinking agent, a plasticizer, a surfactant, a coupling agent, an adhesion-imparting agent, a heat stabilizer, and a hydrolysis-resistant stabilizer.

The functional layer may be formed by, for example, applying the resin composition to the polarizing film and drying the resin composition. The coating method is not particularly limited, and examples thereof include roll coating, spin coating, bar coating, dip coating, die coating, curtain coating, spray coating, and blade coating.

The functional layer is preferably 0.1 μm or more, more preferably 0.2 μm or more, and even more preferably 0.5 μm or more from the viewpoint of suppressing the polyalkyleneition of the polarizing film, and is preferably 10 μm or less, more preferably 5 μm or less, even more preferably 2 μm or less, and even more preferably 1 μm or less from the viewpoint of optical durability under high temperature and high humidity.

The polarizing film is provided with a 1 st transparent protective film on the functional layer with an adhesive layer interposed therebetween. The polarizing film may be provided with a 2 nd transparent protective film on a surface thereof opposite to the image display unit.

< 1 st and 2 nd transparent protective films >

The 1 st and 2 nd transparent protective films are 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 1 st and 2 nd transparent protective films may be appropriately 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 1 st and 2 nd transparent protective films are bonded to both surfaces of the polarizing film, the transparent protective films on both surfaces 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 retardation 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 may be bonded to a transparent protective film having no retardation.

The 1 st and 2 nd transparent protective films may contain any suitable additives 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. In particular, when the transparent protective film contains an ultraviolet absorber, the light resistance of the polarizing film can be improved.

From the viewpoint of production efficiency in the drying step after bonding, the moisture permeability of the 1 st transparent protective film is preferably 300 g/(m) ² 24 h) or less, more preferably 200 g/(m) ² 24 h) or less. The moisture permeability of the 2 nd transparent protective film is preferably 100 g/(m) from the viewpoint of durability of the polarizing plate under high temperature and high humidity ² 24 h) or more, more preferably 200 g/(m) ² 24 h) or more, and the moisture permeability is preferably 1000 g/(m) ² 24 h) or less, more preferably 600 g/(m) ² 24 h) or less. The moisture permeability can be calculated as follows: according to the moisture permeability test (cup method) of JIS Z0208, a sample cut into 60mm in diameter was placed in a moisture permeable cup containing about 15g of calcium chloride, and the sample was placed in a thermostatic apparatus at a temperature of 40 ℃ and a humidity of 90% by weight R.H., to measure the weight increase of calcium chloride before and after 24 hours of standing.

Other layers 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 surfaces of the 1 st and 2 nd transparent protective films to which the polarizing film is not bonded. The other 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 a layer different from the protective film, in addition to the protective film itself.

The functional layer and the 1 st transparent protective film are bonded together with an adhesive layer interposed therebetween. The polarizing film and the 2 nd transparent protective film, the 1 st and 2 nd transparent protective films and the other layers, or the polarizing film and the other layers are usually bonded together via an adhesive layer or an adhesive layer.

As the adhesive for forming the adhesive layer, various adhesives used for polarizing films can be used, 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 which has been 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 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 a polarizing film can be used, 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 (aqueous adhesive) made of an aqueous solution, and contain 0.5 to 60% by weight of a solid content. Among these, a polyvinyl alcohol-based adhesive is preferable, and a polyvinyl alcohol-based adhesive containing an acetoacetyl group is more preferable. In particular, as the adhesive for bonding the functional layer and the 1 st transparent protective film, an aqueous adhesive is preferable from the viewpoint of adhesiveness to the functional layer and the polarizing film.

The aqueous adhesive may contain a crosslinking agent. As the crosslinking agent, a compound having at least 2 functional groups reactive with components such as a polymer constituting the adhesive in 1 molecule can be usually used, and examples thereof include: alkylene diamines; isocyanates; epoxy resin; aldehydes; amino-formaldehydes such as methylolurea and methylolmelamine. The amount of the crosslinking agent in the adhesive is usually about 10 to 60 parts by weight based on 100 parts by weight of the components such as the polymer constituting the adhesive.

Examples of the adhesive include active energy ray-curable adhesives such as ultraviolet-curable adhesives and electron beam-curable adhesives other than the above adhesives. Examples of the active energy ray-curable adhesive include (meth) acrylate adhesives. Examples of the curable component in the (meth) acrylate adhesive include: a compound having a (meth) acryloyl group, a compound having a vinyl group. Examples of the compound having a (meth) acryloyl group include: alkyl (meth) acrylates such as chain alkyl (meth) acrylates having an alkyl group of 1 to 20 carbon atoms, alicyclic alkyl (meth) acrylates, and polycyclic alkyl (meth) acrylates; a hydroxyl group-containing (meth) acrylate; epoxy group-containing (meth) acrylates such as glycidyl (meth) acrylate, and the like. The (meth) acrylate adhesive may contain a nitrogen-containing monomer such as hydroxyethyl (meth) acrylamide, N-methylol (meth) acrylamide, N-methoxymethyl (meth) acrylamide, N-ethoxymethyl (meth) acrylamide, or (meth) acryloylmorpholine. The (meth) acrylic adhesive may contain tripropylene glycol diacrylate, 1, 9-nonanediol diacrylate, tricyclodecane dimethanol diacrylate, cyclic trimethylolpropane formal acrylate, and ditrimethylolpropane formal acrylate

A polyfunctional monomer such as alkylene glycol diacrylate or EO-modified diglycerol tetraacrylate as a crosslinking component. 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 contain an appropriate additive as needed. Examples of the additives include: silane coupling agents, coupling agents such as titanium coupling agents, bonding accelerators such as ethylene oxide, ultraviolet absorbers, deterioration prevention agents, dyes, processing aids, ion trapping agents, antioxidants, tackifiers, fillers, plasticizers, leveling agents, foaming inhibitors, antistatic agents, heat-resistant stabilizers, hydrolysis-resistant stabilizers and the like.

The adhesive may be applied to any one of the functional layer side, the 1 st and 2 nd transparent protective films (or the other layer side), and the polarizing film side, or may be applied 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 or electron beams may be irradiated as necessary. The thickness of the adhesive layer is not particularly limited, but 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.

In the embodiment in which the functional layer and the 1 st transparent protective film are bonded to each other through the adhesive layer, the total thickness of the functional layer and the adhesive layer is preferably 0.2 μm or more, more preferably 0.3 μm or more, and still more preferably 0.6 μm or more from the viewpoint of suppressing the polyalkyleneition of the polarizing film, and is preferably 11 μm or less, more preferably 6 μm or less, still more preferably 4 μm or less, and still more preferably 2 μm or less from the viewpoint of durability of the polarizing plate under high temperature and high humidity.

The polarizing film, the functional layer, the 1 st and 2 nd transparent protective films, and the other layers may be subjected to surface modification treatment or easy adhesion treatment.

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

Examples of the easy adhesion treatment include: treatment with a forming material containing 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, or the like.

The functional layer and the 1 st transparent protective film, the 2 nd transparent protective film and the polarizing film, the 1 st and 2 nd transparent protective films and the other layers, or the polarizing film and the other layers may be laminated with a barrier layer, a refractive index adjusting layer, or the like interposed therebetween.

The barrier layer is a layer having a function of preventing impurities such as oligomers and ions dissolved from the transparent protective film from moving (entering) into the polarizing film. The barrier layer may be any layer that has transparency and can prevent impurities from dissolving out of 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 a layer having a different refractive index such as a polarizing film. Examples of the refractive index adjusting material for forming the refractive index adjusting layer include: the resin composition contains various resins containing silica, acrylic-styrene, melamine, etc., and additives.

< laminated polarizing film >

In the laminated polarizing film (optical laminate) of the present invention, the polarizing film is bonded to an optical layer. The optical layer is not particularly limited, and for example, optical layers used in the formation of a liquid crystal display device and the like may be used, such as 1-layer or 2-layer or more reflective plates, semi-transmissive plates, retardation plates (including 1/2, 1/4, and the like wave plates), and viewing angle compensation films. Examples of the laminated polarizing film include a reflective polarizing film or a semi-transmissive polarizing film in which a reflective plate or a semi-transmissive reflective plate is further laminated on the polarizing film, an elliptical polarizing film or a circular polarizing film in which a phase difference plate is further laminated on the polarizing film, a wide-viewing-angle polarizing film in which a viewing angle compensation film is further laminated on the polarizing film, and a polarizing film in which a brightness enhancement film is further laminated on the polarizing film.

An adhesive layer for bonding an image display unit such as a liquid crystal cell or an organic EL element to another member such as a front transparent plate on the viewing side or a front transparent member such as a touch panel may be provided on one surface or both surfaces of the polarizing film or the laminated polarizing film. The adhesive layer is preferably an adhesive layer. The pressure-sensitive adhesive forming the pressure-sensitive adhesive layer is not particularly limited, and for example, a pressure-sensitive adhesive using a polymer such as an acrylic polymer, a silicone polymer, a polyester, a polyurethane, a polyamide, a polyether, a fluorine polymer, or a rubber as a base polymer can be appropriately selected and used. In particular, a pressure-sensitive adhesive excellent in optical transparency, exhibiting appropriate wettability, cohesiveness and adhesiveness, and excellent in weather resistance, heat resistance and the like, such as a pressure-sensitive adhesive containing an acrylic polymer, can be preferably used.

The pressure-sensitive adhesive layer may be provided on one or both surfaces of the polarizing film or the laminated polarizing film in an appropriate manner. Examples of the pressure-sensitive adhesive layer include: a method of preparing an adhesive solution and directly applying the adhesive solution to the polarizing film or the laminated polarizing film by an appropriate spreading method such as a casting method or a coating method; or a method of forming an adhesive layer on a separator and transferring it to the polarizing film or the laminated polarizing film. The thickness of the pressure-sensitive adhesive layer may be suitably determined depending on the purpose of use, the adhesive strength, and the like, and is generally 1 to 500. Mu.m, preferably 5 to 200. Mu.m, and more preferably 10 to 100. Mu.m. The polarizing film having a pressure-sensitive adhesive layer provided on at least one surface thereof is referred to as a pressure-sensitive adhesive layer-attached polarizing film or a pressure-sensitive adhesive layer-attached laminated polarizing film.

The exposed surface of the pressure-sensitive adhesive layer is preferably covered by a temporary adhesive film for the purpose of preventing contamination or the like until the pressure-sensitive adhesive layer is actually used. This can prevent contamination of the pressure-sensitive adhesive layer in a normal handling state. As the separator, for example, a separator obtained by coating an appropriate thin layer body such as a plastic film, a rubber sheet, paper, cloth, nonwoven fabric, net, foamed sheet, metal foil, or a laminate thereof with an appropriate release agent such as silicone, long-chain alkyl, fluorine, or molybdenum sulfide, if necessary, can be used.

< image display panel and image display device >

The image display panel of the present invention includes an image display unit, and the polarizing film or the laminated polarizing film. The image display device of the present invention includes the image display panel and a front surface transparent member.

Examples of the image display means include: liquid crystal cells, organic EL cells, and the like. As the liquid crystal cell, any of a reflective liquid crystal cell using external light, a transmissive liquid crystal cell using light from a light source such as a backlight, and a transflective liquid crystal cell using both light from the outside and light from the light source can be used, for example. In the case where the liquid crystal cell uses light from the light source, the image display device (liquid crystal display device) is also provided with a polarizing film on the side opposite to the viewing side of the image display cell (liquid crystal cell) and a light source. The polarizing film on the light source side and the liquid crystal cell are preferably bonded together with an appropriate adhesive layer interposed therebetween. As a driving method of the liquid crystal cell, for example: VA mode, IPS mode, TN mode, STN mode, bend (bend) orientation (pi-type), and the like.

As the organic EL unit, for example, an organic EL unit in which a transparent electrode, an organic light emitting layer, and a metal electrode are sequentially stacked on a transparent substrate to form a light emitting body (organic electroluminescence light emitting body) can be suitably used. The organic light-emitting layer is a laminate of various organic thin films, and various layer structures including, for example: a laminate of a hole injection layer formed of a triphenylamine derivative or the like and a light-emitting layer formed of a fluorescent organic solid such as anthracene, a laminate of these light-emitting layers and an electron injection layer formed of a perylene derivative or the like, a laminate of a hole injection layer, a light-emitting layer, and an electron injection layer, and the like.

Examples of the front transparent member disposed on the visible side of the image display unit include: a front surface transparent plate (window layer), a touch panel, and the like. As the front surface transparent plate, a transparent plate having appropriate mechanical strength and thickness can be used. As such a transparent plate, for example, a transparent resin plate such as an acrylic resin or a polycarbonate resin, a glass plate, or the like can be used. As the touch panel, various touch panels of a resistive type, a capacitive type, an optical type, an ultrasonic type, or the like, a glass plate having a touch sensor function, a transparent resin plate, or the like can be used, for example. In the case of using a capacitive touch panel as the front surface transparent member, a front surface transparent plate made of glass or a transparent resin plate is preferably provided on the side closer to the visible side than the touch panel.

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 >

< preparation of polarizing film >

A laminate was produced by subjecting one surface of a substrate of an amorphous polyethylene terephthalate isophthalate copolymer (IPA-copolymerized PET) film (thickness: 100 μm) having a water absorption rate of 0.75% and a Tg of 75 ℃ to corona treatment, applying an aqueous solution containing polyvinyl alcohol (polymerization degree 4200, saponification degree 99.2 mol%) and acetoacetyl-modified PVA (polymerization degree 1200, acetoacetyl-modification rate 4.6%, saponification degree 99.0 mol% or more, manufactured by Nippon synthetic chemical industries, ltd., trade name "Gohsefimer Z200") at a ratio of 9. The obtained laminate was subjected to free-end uniaxial stretching (auxiliary stretching treatment in a gas atmosphere) of 2.0 times in the longitudinal direction (longitudinal direction) between rolls having different peripheral speeds in an oven at 120 ℃. Next, the laminate was immersed in an insolubilization bath (an aqueous boric acid solution prepared by mixing 4 parts by weight of boric acid with 100 parts by weight of water) at a liquid temperature of 30 ℃ for 30 seconds (insolubilization treatment). Next, in a dyeing bath at a liquid temperature of 30 ℃, immersion (dyeing treatment) was performed while adjusting the iodine concentration and immersion time so that the polarizing plate could have a predetermined transmittance. Subsequently, the substrate was immersed for 30 seconds in a crosslinking bath (aqueous boric acid solution containing 3 parts by weight of potassium iodide and 3 parts by weight of boric acid based on 100 parts by weight of water) at a liquid temperature of 30 ℃ (crosslinking treatment). Then, the laminate was immersed in an aqueous boric acid solution (an aqueous solution prepared by mixing 4 parts by weight of boric acid and 5 parts by weight of potassium iodide with respect to 100 parts by weight of water) at a liquid temperature of 70 ℃, and uniaxially stretched in the longitudinal direction (longitudinal direction) between rolls having different peripheral speeds so that the total stretching ratio became 5.5 times (stretching treatment in an aqueous solution). 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 30 ℃ (cleaning treatment). Then, while drying in an oven maintained at 90 ℃, the sheet was contacted with a heated roll made of SUS maintained at a surface temperature of 75 ℃ for about 2 seconds (drying shrinkage treatment). By the above operation, an optical film laminate including a polarizing film having a thickness of 5 μm was obtained.

< preparation of resin composition for Forming functional layer >

A polyvinyl alcohol resin (product name: JC-25H, manufactured by JAPAN VAM & POVAL Co., ltd.) having a polymerization degree of 2500 and a saponification degree of 99.8 mol% was dissolved in pure water to obtain a solution, and an aqueous solution (solid content: 25 wt%) containing the solution and a water-soluble radical scavenger represented by the following general formula (9) was prepared in a weight ratio of 3 after drying and film formation.

[ chemical formula 9]

< production of polarizing film >

The polyethylene terephthalate film of the optical film laminate cut out in pieces along the direction of the stretching axis was peeled off, the polarizing film on the peeled surface was subjected to corona treatment, the resin composition thus adjusted was applied by a wire bar coater so that the thickness after drying became 0.8 μm, and then dried at 60 ℃ for 5 minutes to form a functional layer on the polarizing film. As a pretreatment for the thickness of the functional layer, a cross-sectional cut was performed by a microtome (manufactured by Leica, "EM UC 7"), and a metal ion sputtering was performed on the cut surface, and then a film thickness was measured by SEM (manufactured by japan electronics corporation, "JSM-7100F"). The results are shown in Table 1. Then, makeAn acrylic resin film (moisture permeability 100 g/(m) was formed as a 1 st transparent protective film by roll laminator with an aqueous adhesive ² 24 h), toyo Steel plate K.K. "RZ 30") was bonded so that the easy-adhesion treated surface was in contact with the functional layer, and then the polarizing film was continuously heated and dried in an oven (temperature 60 ℃ C., time 4 minutes) to prepare a polarizing film. The aqueous adhesive used was an aqueous solution containing an acetoacetyl group-containing polyvinyl alcohol resin (average degree of polymerization 1200, degree of saponification 98.5 mol%, degree of acetoacetylation 5 mol%) and methylolmelamine at a weight ratio of 3. In addition, when the aqueous adhesive and the functional layer are laminated, the functional layer is deformed by swelling, and the interface is mixed, so that separation is difficult. Therefore, the total thickness of the functional layer and the aqueous adhesive layer was measured by SEM in the same manner as the functional layer. The results are shown in Table 1.

< making of analog image display Panel >

Using the polarizing film obtained above, a 48 μm thick cellulose triacetate film (moisture permeability of 300 g/(m) having a hard coat layer as a 2 nd transparent protective film was bonded to the exposed surface of the polarizing film via the above-mentioned aqueous adhesive ² 24 h), fuji film, "TJ40 UL"), and then, the cellulose triacetate film was dried by heating in an oven (temperature 60 ℃ C., time 4 minutes). Then, a small piece of glass (analog image display unit) having a size of 45 × 50mm was bonded to the acrylic film surface with an adhesive, and an analog image display panel was produced.

< evaluation of monomer transmittance Change in high temperature Environment (1) >)

The analog image display panel obtained above was left in a hot air oven at a temperature of 105 ℃ for 500 hours, and the monomer transmittance (Δ Ts) before and after the input (heating) was measured. Before the input is set to Ts ₀ Ts is set after the casting ₅₀₀ Then, the monomer transmittance change amount (Δ Ts) was obtained using the following formula.

ΔTs(％)＝Ts ₅₀₀ －Ts ₀

For monomer transmittance, an ultraviolet-visible spectrophotometer was used(Otsuka electronic System, "LPF-200") optical characteristics were measured to obtain an initial monomer transmittance Ts ₀ . The monomer transmittance is a Y value obtained by correcting visibility with a 2-degree field of view (C light source) according to JIS Z8701-1982. The measurement wavelength was 380 to 780nm (5 nm interval). The results are shown in Table 1 for the Δ Ts.

< evaluation of monomer transmittance Change in high temperature Environment (2) >

The analog image display panel obtained above was left standing in a hot air oven at a temperature of 95 ℃ for 500 hours, and Δ Ts was determined in the same manner as in the above evaluation (1). The results are shown in Table 1 for the Δ Ts.

The evaluation was made based on the heat resistance evaluation results described above and according to the following criteria. The results of the determination are shown in table 1.

◎：3％≥ΔTs≥0

○：5％≥ΔTs＞3％

×：ΔTs＜0

< example 2 >

Polarizing films and simulated image panels were produced in the same manner as in example 1, except that the functional layer single-layer films were laminated so that the thickness thereof became 0.4 μm, and the polarizing films and the simulated image panels were subjected to evaluation. The results are shown in Table 1.

< example 3 >

Polarizing films and simulated image panels were produced in the same manner as in example 1, except that the functional layer single-layer films were laminated so that the thickness thereof became 1.5 μm, and were subjected to evaluation. The results are shown in Table 1.

< example 4 >

A polarizing film and a pseudo image panel were produced in the same manner as in example 1 except that the polarizing film and the pseudo image panel were prepared so that the solid content ratio of the water-soluble radical scavenger contained in the functional layer was 15 wt%, and the polarizing film and the pseudo image panel were evaluated. The results are shown in Table 1.

< comparative example 1 >

A polarizing film and a pseudo image panel were produced in the same manner as in example 1, except that the functional layer was not formed, and were subjected to evaluation. The results are shown in Table 1.

Claims

1. A polarizing film constituting an image display device having an image display unit,

the polarizing film has:

a polarizing film,

A functional layer,

Adhesive layer, and

a 1 st transparent protective film, which is transparent,

the functional layer is adjacent to the image display unit side of the polarizing film and contains a water-soluble radical scavenger,

the 1 st transparent protective film is provided on the functional layer with an adhesive layer interposed therebetween.

2. The polarizing film of claim 1,

the functional layer contains a polyvinyl alcohol-based resin.

3. The polarizing film according to claim 1 or 2,

the water-soluble radical scavenger is a compound having a nitroxyl radical or nitroxyl group.

4. The polarizing film according to any one of claims 1 to 3,

the functional layer has a thickness of 10 μm or less.

5. The polarizing film according to any one of claims 1 to 4,

the polarizing film has a thickness of 15 [ mu ] m or less.

6. The polarizing film according to any one of claims 1 to 5,

the adhesive forming the adhesive layer is an aqueous adhesive.

7. The polarizing film according to any one of claims 1 to 6,

the total thickness of the functional layer and the adhesive layer is 0.2 to 11 [ mu ] m.

8. The polarizing film according to any one of claims 1 to 7,

a2 nd transparent protective film is provided on the opposite surface of the polarizing film from the image display unit side.

9. A laminated polarizing film comprising the polarizing film according to any one of claims 1 to 8 bonded to an optical layer.

10. An image display panel having:

an image display unit; and

the polarizing film according to any one of claims 1 to 7, or the laminated polarizing film according to claim 8.

11. An image display device, comprising:

an image display panel as claimed in claim 10, and

a front surface transparent member.