WO2021225114A1

WO2021225114A1 - Image display device

Info

Publication number: WO2021225114A1
Application number: PCT/JP2021/017181
Authority: WO
Inventors: 智弘山下; 汐海八木; かおる ▲黒▼原; 卓哉湯峯; 勝則高田
Original assignee: 日東電工株式会社
Priority date: 2020-05-08
Filing date: 2021-04-30
Publication date: 2021-11-11
Also published as: TW202144819A; CN115516346A; KR20230007310A; JP2021179604A

Abstract

This image display device comprising a front transparent member, a polarizing film, and an image display cell provided, in this order, with a pressure-sensitive adhesive layer or an adhesive layer between each, wherein a laminate formed by bonding glass sheets via the pressure-sensitive adhesive layer or the adhesive layer to both surfaces of the polarizing film has a change amount in single transmittance of 0 to 3% and a change amount in single hue b value of 0 to 4 in NBS ratings before and after a heat resistance test under conditions of 105°C and 500 hours. The image display device is superior in suppressing a reduction in single transmittance and suppressing an increase in the single hue b value of a polarizing membrane in a high temperature environment.

Description

Image display device

The present invention relates to an image display device.

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

The polarizing film is used as a laminated polarizing film (optical laminate) by laminating other optical layers as needed, and the polarizing film or the laminated polarizing film (optical laminate) can be a liquid crystal cell or an organic. It is used as an image display panel attached to an image display cell such as an EL element, and further, the image display panel is a front transparent plate (window layer), a touch panel, or the like on the visual side via an adhesive layer or an adhesive layer. It is attached to the front transparent member of the above and used as the above-mentioned various image display devices (Patent Document 1).

In recent years, such various image display devices have been widely used, such as being used as in-vehicle image display devices such as car navigation devices and back monitors in addition to mobile devices such as mobile phones and tablet terminals. There is. Along with this, the polarizing film and the laminated polarizing film are required to have higher durability in a harsher environment (for example, in a high temperature environment) than conventionally required, and such durability is required. A polarizing film and an image display device for the purpose of securing have been proposed (Patent Document 2-3).

Japanese Unexamined Patent Publication No. 2014-102353 Special Table 2012-516468 Gazette Japanese Unexamined Patent Publication No. 2018-10117

In the above-mentioned in-vehicle image display device, the display design is becoming more deformed and larger due to the recent development of automatic driving technology. With such changes in display design, there is a demand for a means for further improving the durability of the polarizing film in a high temperature environment.

In view of the above circumstances, an object of the present invention is to provide an image display device excellent in suppressing a decrease in the single transmittance of a polarizing film and suppressing an increase in a single hue b value in a high temperature environment.

That is, the present invention is an image display device in which a front transparent member, a polarizing film, and an image display cell are provided in this order via an adhesive layer or an adhesive layer, and the adhesive is provided on both sides of the polarizing film. In the laminate in which the glass plates are bonded via the agent layer or the adhesive layer, the amount of change in the single transmittance is 0 to 3% before and after the heat resistance test under the conditions of 105 ° C. and 500 hours. The present invention relates to an image display device in which the amount of change in the single hue b value is 0 to 4 NBS.

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

In the image display device of the present invention, the front transparent member, the polarizing film, and the image display cell are provided in this order via the pressure-sensitive adhesive layer or the adhesive layer, and the pressure-sensitive adhesive layer or the pressure-sensitive adhesive layer or the image display cell is provided on both sides of the polarizing film. In the laminate in which the glass plates are bonded via the adhesive layer, the amount of change in the single transmittance is 0 to 3% before and after the heat resistance test under the conditions of 105 ° C. and 500 hours, and the single body hue. The amount of change in the b value is 0 to 4 NBS. Since the glass plate corresponds to the front transparent member and the image display cell, the laminated body corresponds to the pseudo image display device. So far, under the above heat resistance test conditions, a laminated body (pseudo-image display device) in which the amount of change in the single-unit transmittance is 0 to 3% and the amount of change in the single-unit hue b value is 0 to 4 NBS has been obtained. unknown. On the other hand, in order to suppress a decrease in the single transmittance of the polarizing film, for example, in Patent Document 1 described above, an image display panel is formed by bonding a polarizing film having an adhesive layer on one side and an image display cell. It is described that it is effective to reduce the water content of the polarizing film by performing a heating (aging) treatment later (hereinafter, also referred to as a conventional aging treatment). In the present invention, the moisture contained in the adhesive layer or the adhesive layer provided on both sides of the polarizing film for bonding to the front transparent member or the image display cell is polarized after the heat resistance test of the image display device. Since it was found that it affects the decrease in the single-unit transmittance of the film and the increase in the single-unit hue b value (high temperature durability), the adhesive on both sides of the polarizing film for bonding to the above-mentioned front transparent member and image display cell. By heating (aging) the layer or the adhesive layer, the high temperature durability of the polarizing film can be further improved. Further, in the present invention, in addition to the above-mentioned conventional aging treatment, by incorporating a water-soluble radical scavenger into the polarizing film, the generated radicals are captured even in a high temperature environment where polyene is likely to occur in the polarizing film. As a result, polyene formation can be suppressed, so that the high temperature durability of the polarizing film can be further improved. Further, in addition to the above method, the present invention can further improve the high temperature durability of the polarizing film by increasing the potassium concentration of the polarizing film.

It is a schematic cross-sectional view which shows one form of an image display device. It is a schematic cross-sectional view which shows one form of a polarizing film.

FIG. 1 is a schematic cross-sectional view showing a form of the image display device of the present invention. In the image display device 100 of FIG. 1, the front transparent member 80 and the polarizing film 10 are bonded to each other via the pressure-sensitive adhesive layer or the adhesive layer 20, and the image display cell 90 and the polarizing film 10 are bonded to the pressure-sensitive adhesive layer or the bonding film 10. It is bonded via the agent layer 30.

FIG. 2 is a schematic cross-sectional view showing a form of the polarizing film of the present invention. In the polarizing film 10 of FIG. 3, the polarizing film 11 and the transparent protective film 13 are bonded and exposed via the adhesive layer or the adhesive layer 50, and the polarizing film 11 and the transparent protective film 12 are the pressure-sensitive adhesive layer or the transparent protective film 12. It is bonded via the adhesive layer 40.

In the image display device of the present invention, the front transparent member, the polarizing film, and the image display cell are provided in this order via the pressure-sensitive adhesive layer or the adhesive layer, and the pressure-sensitive adhesive layer or the pressure-sensitive adhesive layer or the image display cell is provided on both sides of the polarizing film. In the laminate in which the glass plates are bonded via the adhesive layer, the amount of change in the single transmittance is 0 to 3% before and after the heat resistance test under the conditions of 105 ° C. and 500 hours, and the single body hue. The amount of change in the b value is 0 to 4 NBS.

<Polarizing film>
The polarizing film of the present invention has a polarizing film formed by adsorbing and orienting a dichroic substance such as iodine or a dichroic dye on a polyvinyl alcohol-based film. From the viewpoint of the initial polarization performance of the polarizing film, an iodine-based polarizing film containing iodine as the dichroic substance is preferable.

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

The polarizing film may contain a water-soluble radical scavenger from the viewpoint of suppressing a decrease in the simple substance transmittance of the polarizing film and an increase in the simple substance hue b value in a high temperature environment. The water-soluble radical trapping agent is preferably a compound that can dissolve 1 part by weight or more with respect to 100 parts by weight of water at 25 ° C. from the viewpoint of easily transferring to water in the polarizing film, and 100 parts by weight of water at 25 ° C. A compound that can dissolve 2 parts by weight or more with respect to parts is more preferable, and a compound that can dissolve 5 parts by weight or more with respect to 100 parts by weight of water at 25 ° C. is further preferable. 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 radical scavengers such as hindered phenol-based, hindered amine-based, phosphorus-based, sulfur-based, benzotriazole-based, benzophenone-based, hydroxylamine-based, salicylate ester-based, and triazine-based compounds. Examples include compounds having a function. The water-soluble radical scavenger is preferably, for example, a nitroxy radical or a compound having a nitroxide group from the viewpoint of the radical species generated in the polarizing film.

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

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

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

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

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

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

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

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

Examples of the N-oxyl compound include N- described in JP-A-2003-64022, JP-A-11-222462, JP-A-2002-284737, and International Publication No. 2016/047655. Oxyl compounds can be mentioned.

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

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

Further, the water-soluble radical scavenger preferably has a molecular weight of 1000 or less, more preferably 500 or less, and more preferably 300 or less, from the viewpoint of efficiently capturing radicals generated in the polarizing film. Is even more preferable.

When the polarizing film contains the water-soluble radical scavenger, the content of the water-soluble radical scavenger causes a decrease in the single transmittance of the polarizing film and an increase in the single hue b value in a high temperature environment. From the viewpoint of suppressing, it is preferably 0.005% by weight or more, more preferably 0.01% by weight or more, further preferably 0.1% by weight or more, and 15% by weight or less. It is preferably 12% by weight or less, more preferably 10% by weight or less, and even more preferably 5% by weight or less.

Further, the polarizing film may have an increased potassium concentration in a high temperature environment from the viewpoint of suppressing a decrease in the single transmittance of the polarizing film and an increase in the single hue b value. When increasing the potassium concentration, the polarizing film preferably has a potassium concentration of 0.3% by weight or more, more preferably 0.35% by weight or more, and preferably 0.4% by weight or more. Further, from the viewpoint of suppressing the reflected hue change in a high temperature environment, it is preferably 0.8% by weight or less, more preferably 0.6% by weight or less in the polarizing film.

The polarizing film is obtained by a conventional method for producing a polarizing film, and is obtained, for example, by subjecting the polyvinyl alcohol-based film to an arbitrary swelling step and a washing step, and at least a dyeing step, a crosslinking step, and a stretching step. .. When the polarizing film contains the water-soluble radical scavenger, the treatment bath in any one or more of the swelling step, the washing step, the dyeing step, the cross-linking step, and the stretching step , A water-soluble radical scavenger may be contained. Further, when increasing the potassium concentration of the polarizing film, a halogen such as potassium iodide contained in any one or more of the swelling step, the washing step, the dyeing step, the cross-linking step, and the stretching step. It can be controlled by the concentration of the potassium component donor such as potassium iodide, the treatment temperature and the treatment time in each of the above treatment baths.

The thickness of the polarizing film is preferably 1 μm or more, more preferably 2 μm or more, and 20 μm or less from the viewpoint of preventing warpage of the panel, from the viewpoint of improving the initial degree of polarization of the polarizing film. It is preferably 15 μm or less, more preferably 10 μm or less, and even more preferably 8 μm or less. In particular, in order to obtain a polarizing film having a thickness of about 8 μm or less, a laminate containing a polyvinyl alcohol-based resin layer formed on a thermoplastic resin base material is used as the polyvinyl alcohol-based film, and the following thin type is used. A method for producing a polarizing film can be applied.

The polarizing film (thin polarizing film) is obtained by a conventional method for producing a polarizing film. For example, a polyvinyl alcohol-based resin containing a polyvinyl alcohol-based resin (PVA-based resin) on one side of a long thermoplastic resin base material. A step of forming a resin layer (PVA-based resin layer) to prepare a laminate, and an arbitrary insolubilization treatment step, a cross-linking treatment step, and cleaning of the laminate while transporting the obtained laminate in the longitudinal direction. It is obtained by performing a treatment step and at least an aerial auxiliary stretching treatment step, a dyeing treatment step, and an underwater stretching treatment step. When the polarizing film contains the water-soluble radical scavenger, any one or more of the insolubilization treatment step, the cross-linking treatment step, the cleaning treatment step, the dyeing treatment step, and the underwater stretching treatment step. The treatment bath in the treatment step may contain the water-soluble radical scavenger. Further, when increasing the potassium concentration of the polarizing film, the treatment bath in any one or more of the insolubilization treatment step, the cross-linking treatment step, the cleaning treatment step, the dyeing treatment step, and the underwater stretching treatment step. It can be controlled by the concentration of the potassium component donor such as potassium halide such as potassium iodide contained in the above, the treatment temperature and the treatment time in each of the above treatment baths.

The polarizing film is usually a transparent protective film bonded to at least one surface of the polarizing film via an adhesive layer or an adhesive layer.

<Adhesive layer>
As the pressure-sensitive adhesive forming the pressure-sensitive adhesive layer, various pressure-sensitive adhesives used in polarizing films can be applied. Examples thereof include alkyl ether adhesives, polyvinyl alcohol adhesives, polyvinyl porolidone adhesives, polyacrylamide adhesives, cellulose adhesives and the like. Among these, an acrylic pressure-sensitive adhesive is preferable. The acrylic pressure-sensitive adhesive contains an acrylic polymer as a base polymer, and examples thereof include the acrylic pressure-sensitive adhesives described in JP-A-2017-75998.

The acrylic polymer in the acrylic pressure-sensitive adhesive has a monomer unit of (meth) acrylic acid alkyl ester as a main skeleton. As the (meth) acrylic acid alkyl ester, a (meth) acrylic acid alkyl ester having an alkyl group having 1 to 20 carbon atoms is preferably used, and the content of the (meth) acrylic acid alkyl ester is the base polymer. It is preferably 40% by weight or more, more preferably 60% by weight or more, based on the total amount of the constituent monomer components. Further, from the viewpoint of adjusting the adhesiveness of the pressure-sensitive adhesive, a monomer unit such as a nitrogen-containing monomer unit or a hydroxy group-containing monomer may be contained. Further, a cross-linking agent may be used to form a cross-linked structure in the pressure-sensitive adhesive layer. Examples of the cross-linking agent include an isocyanate-based cross-linking agent, an epoxy-based cross-linking agent, an oxazoline-based cross-linking agent, an aziridine-based cross-linking agent, and a carbodiimide-based cross-linking agent. Commonly used cross-linking agents, metal chelate-based cross-linking agents, and the like can be used. The amount of the cross-linking agent used is usually 10 parts by weight or less, preferably 5 parts by weight or less, based on 100 parts by weight of the base polymer.

From the viewpoint of adjusting the adhesive strength, the pressure-sensitive adhesives include silane coupling agents; terpen-based pressure-sensitive adhesives, styrene-based pressure-sensitive adhesives, phenol-based pressure-sensitive adhesives, rosin-based pressure-sensitive adhesives, epoxy-based pressure-sensitive adhesives, and the like. A tackifier may be added. Further, from the viewpoint of improving the light resistance, an ultraviolet absorber may be added. In addition to the above-exemplified components, the pressure-sensitive adhesives include additives such as plasticizers, softeners, deterioration inhibitors, fillers, colorants, antioxidants, surfactants, and antistatic agents, and the characteristics of the pressure-sensitive adhesives. Can be used as long as it does not impair.

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

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

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

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

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

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

<Transparent protective film>
The transparent protective film is not particularly limited, and various transparent protective films used for the polarizing film can be used. As the material constituting the transparent protective film, for example, a thermoplastic resin having excellent transparency, mechanical strength, thermal stability, moisture blocking property, isotropic property and the like is used. Examples of the thermoplastic resin include cell roll ester resins such as triacetyl cellulol, polyester resins such as polyethylene terephthalate and polyethylene naphthalate, polyether sulfone resins, polysulfone resins, polycarbonate resins, nylon and fragrances. Polyamide-based resin such as group polyamide, polyimide-based resin, polyethylene, polypropylene, polyolefin-based resin such as ethylene / propylene copolymer, (meth) acrylic-based resin, cyclic polyolefin-based resin having a cyclo-based or norbornene structure (norbornene-based resin) ), Polyallylate-based resin, polystyrene-based resin, polyvinyl alcohol-based resin, and mixtures thereof. Further, as the transparent protective film, a cured layer formed of a thermosetting resin such as (meth) acrylic, urethane, acrylic urethane, epoxy, silicone or the like or an ultraviolet curable resin can be used. Among these, cell roll ester-based resins, polycarbonate-based resins, (meth) acrylic-based resins, cyclic polyolefin-based resins, and polyester-based resins are preferable.

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

When the transparent protective film is attached to both sides of the polarizing film, the transparent protective films on both sides may be the same or different.

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

Examples of the retardation plate include a birefringent film formed by uniaxially or biaxially stretching a polymer material, an alignment film of a liquid crystal polymer, and a film in which an alignment layer of a liquid crystal polymer is supported by a film. The thickness of the retardation plate is not particularly limited, but is generally about 20 to 150 μm. The phase plate may be attached to a transparent protective film having no phase difference.

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

The transparent protective film, if bonded to the polarizing film on the viewing side is preferably from the viewpoint of durability of the polarizing film of high temperature and high humidity, moisture permeability is 600g / (m 2 · ^24h) or less, 400 g / more preferably ^(m 2 · 24h) or less. The transparent protective film is preferably case of bonding the image display cell side of the polarizing film, is from the viewpoint of the production efficiency of the drying process after bonding, moisture permeability 50g / (m 2 · ^24h) or more, more preferably 100g ^/ (m 2 · 24h) or more, and permeability is preferably humidity is 1000g ^/ (m 2 · 24h) or less, more not less 600g ^/ (m 2 · 24h) or less preferable. The humidity permeability is determined according to the JIS Z0208 moisture permeability test (cup method), and a sample cut to a diameter of 60 mm is set in a moisture permeability cup containing about 15 g of calcium chloride, and the temperature is 40 ° C. and the humidity is 90%. R. H. It can be calculated by measuring the weight increase of calcium chloride before and after being placed in a constant temperature machine and left for 24 hours.

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

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

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

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

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

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

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

Further, in the polarizing film, an optical layer may be attached to at least one surface of the polarizing film via the adhesive layer or the adhesive layer.

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

In order to bond an image display cell such as a liquid crystal cell or an organic EL element to one surface or both surfaces of the polarizing film, and another member such as a front transparent plate or a front transparent member such as a touch panel on the viewing side. , The adhesive layer or the adhesive layer may be attached in advance.

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

<Front transparent member>
The front transparent member of the present invention is a front transparent member arranged on the visual side of the image display cell. Examples of the front transparent member include a front transparent plate (window layer) and a touch panel. As the front transparent plate, a front transparent plate having appropriate mechanical strength and thickness is 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 is used. As the touch panel, for example, various touch panels such as a resistive film method, a capacitance method, an optical method, and an ultrasonic method, a glass plate having a touch sensor function, a transparent resin plate, and the like are used. When a capacitance type touch panel is used as the front transparent member, it is preferable to provide a front transparent plate made of glass or a transparent resin plate on the visual side of the touch panel.

<Image display cell>
Examples of the image display cell of the present invention include a liquid crystal cell and an organic EL cell. Examples of the liquid crystal cell include a reflective liquid crystal cell that uses external light, a transmissive liquid crystal cell that uses light from a light source such as a backlight, and a semi-transmissive liquid crystal cell that uses both external light and light from a light source. Any of the semi-reflective liquid crystal cells may be used. When the liquid crystal cell uses light from a light source, in the image display device (liquid crystal display device), a polarizing film is also arranged on the side opposite to the viewing side of the image display cell (liquid crystal cell), and the light source is further arranged. Be placed. It is preferable that the polarizing film on the light source side and the liquid crystal cell are bonded to each other via an appropriate adhesive layer. As the driving method of the liquid crystal cell, for example, any type such as VA mode, IPS mode, TN mode, STN mode and bend orientation (π type) can be used.

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

When forming the image display device, after the image display cell and the polarizing film are bonded to form an image display panel, and before bonding to the front transparent member, the polarizing film is transmitted alone in a high temperature environment. The image display panel may be heated (aged) from the viewpoint of suppressing a decrease in the rate and an increase in the single hue b value. In this case, by heating (aging) the pressure-sensitive adhesive layers or the adhesive layers on both sides of the polarizing film for bonding to the front transparent member and the image display cell, the single transmittance can be reduced in a high temperature environment. The increase in the single hue b value can be further suppressed. The heating conditions in the heating (aging) treatment are not particularly limited as long as the moisture contained in the pressure-sensitive adhesive layer or the adhesive layer provided on both sides of the polarizing film and the polarizing film can be sufficiently reduced. For example, the heating temperature is 70. The temperature is preferably about 90 ° C, more preferably about 75 to 85 ° C. The heating time is preferably about 30 minutes to 5 hours, more preferably about 1 hour to 3 hours. Further, when the heat (aging) treatment is performed with the pressure-sensitive adhesive layer or the adhesive layer on both sides of the polarizing film, it is effective that the pressure-sensitive adhesive layer or the adhesive layer has high moisture permeability, while it is effective on one side. When heat (aging) treatment is performed with the pressure-sensitive adhesive layer or adhesive layer attached to the surface, the water content of the pressure-sensitive adhesive layer or adhesive layer (the pressure-sensitive adhesive layer or adhesive layer on the other surface) to be laminated later is The lower one is more effective. When forming the image display device, the front transparent member and the polarizing film may be bonded together, and then the heating (aging) treatment may be performed to attach the image display cell.

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

<Example 1>
<Preparation of polarizing film>
A polyvinyl alcohol film having an average degree of polymerization of 2,400, a saponification degree of 99.9 mol%, and a thickness of 45 μm was prepared. The polyvinyl alcohol film is immersed in a swelling bath (water bath) at 30 ° C. for 30 seconds between rolls having different peripheral speed ratios and stretched 2.2 times in the transport direction while swelling (swelling step), followed by In a dyeing bath at 30 ° C. (an iodine aqueous solution obtained by mixing iodine and potassium iodide in a weight ratio of 1: 7 with respect to 100 parts by weight of water), the polarizing film has a predetermined transmittance. While adjusting the iodine concentration, it was immersed for 30 seconds and dyed while being stretched 3.3 times in the transport direction based on the original polyvinyl alcohol film (polyvinyl alcohol film that was not stretched at all in the transport direction) (dyeing step). .. Next, the dyed polyvinyl alcohol film is placed in a cross-linked bath at 40 ° C. (an aqueous solution having a boric acid concentration of 3.5% by weight, a potassium iodide concentration of 3.0% by weight, and a zinc sulfate concentration of 3.6% by weight). It was immersed for 28 seconds and stretched up to 3.6 times in the transport direction with reference to the original polyvinyl alcohol film (crosslinking step). Further, the obtained polyvinyl alcohol film is placed in a stretching bath at 64 ° C. (an aqueous solution having a boric acid concentration of 4.5% by weight, a potassium iodide concentration of 5.0% by weight, and a zinc sulfate concentration of 5.0% by weight). After immersing in for 60 seconds and stretching up to 6.0 times in the transport direction with reference to the original polyvinyl alcohol film (stretching step), a washing bath at 27 ° C. (potassium iodide concentration 2.3% by weight, water-soluble) As the radical trapping agent, the compound was immersed in an aqueous solution having a compound concentration of 1.0% by weight represented by the following general formula (9) for 10 seconds (washing step). The washed polyvinyl alcohol film was dried at 40 ° C. for 30 seconds to prepare a polarizing film. The potassium content in the polarizing film was 0.31% by weight, the content of the compound represented by the following general formula (9) was 0.3% by weight, and the thickness of the polarizing film was 18 μm.

<Measuring method of potassium content (% by weight) in polarizing film>
For the polarizing film, the fluorescent X-ray intensity (kcps) of the potassium element was measured using a fluorescent X-ray analyzer (manufactured by Rigaku Corporation, trade name "ZSX100E", measurement diameter: ψ10 mm). On the other hand, the thickness (μm) of the polarizing film was measured using a spectroscopic film thickness meter (manufactured by PEACOCK, trade name “DG-205”). From the obtained fluorescent X-ray intensity and thickness, the potassium content (% by weight) was determined using the following formula. In addition, the following "2.99" is the fluorescence X-ray intensity (kcps) of a sample having a known thickness (μm) and potassium concentration (% by weight) (for example, a PVA-based resin film to which a certain amount of KI is added). It is the coefficient of the calibration curve measured and derived.
Potassium content in polarizing film (% by weight) = 2.99 × (fluorescent X-ray intensity of potassium element) / (thickness of polarizing film)

<Method for measuring the content (% by weight) of the water-soluble radical scavenger in the polarizing film>
Approximately 20 mg of the polarizing film was collected, quantified, and dissolved by heating in 1 mL of water, diluted with 4.5 mL of methanol, the obtained extract was filtered through a membrane filter, and the filtrate was HPLC (ACQUITY UPLC manufactured by Waters). The concentration of the water-soluble radical trapping agent was measured using H-class Bio).

<Manufacturing of polarizing film>
As an adhesive, a polyvinyl alcohol resin containing an acetoacetyl group (average degree of polymerization of 1,200, saponification degree of 98.5 mol%, acetoacetylation degree of 5 mol%) and methylol melamine in a weight ratio of 3: The aqueous solution contained in 1 was used. Using this adhesive, a transparent protection with a thickness of 30 μm made of a (meth) acrylic resin (modified acrylic polymer having a lactone ring structure) on one surface (image display cell side) of the polarizing film obtained above. film (manufactured by Nippon Shokubai Co., moisture permeability ^{125g / (m 2 · 24h)} ), also formed on the other surface (viewing side), triacetyl cellulose film HC in (Fuji film Co., Ltd., trade name "TJ40UL") the transparent protective film having a thickness of 48 [mu] m (moisture permeability ^{300g / (m 2 · 24h)} ) after bonding with a roll lamination coupling machine, subsequently heated and dried (temperature of 90 ° C., the time is 10 minutes) in an oven by , A polarizing film was prepared in which a transparent protective film was bonded to both sides of the polarizing film.

<Preparation of acrylic adhesive>
A monomer mixture containing 99 parts of butyl acrylate and 1 part of 4-hydroxybutyl acrylate was charged into a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas introduction tube, and a cooler. Further, 0.1 part of 2,2'-azobisisobutyronitrile was charged together with 100 parts of ethyl acetate as a polymerization initiator with respect to 100 parts of the monomer mixture (solid content), and nitrogen gas was added while gently stirring. After the introduction and substitution with nitrogen, the liquid temperature in the flask was maintained at around 55 ° C. and a polymerization reaction was carried out for 8 hours to prepare a solution of an acrylic polymer having a weight average molecular weight (Mw) of 1.8 million. Then, with respect to 100 parts of the solid content of the obtained acrylic polymer solution, 0.02 part of an isocyanate cross-linking agent (manufactured by Tosoh Corporation, trade name "Takenate D110N", trimethylolpropane / xylylene diisocyanate adduct), silane A solution of the acrylic pressure-sensitive adhesive composition was prepared by blending 0.2 parts of a coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd., trade name "X-41-1056").

<Preparation of polarizing film with adhesive layer>
Adhesion of the solution of the acrylic pressure-sensitive adhesive composition obtained above to one side of a polyethylene terephthalate film (manufactured by Mitsubishi Chemical Polyester Film, trade name "MRF38", separator film) treated with a silicone-based release agent after drying. The coating was applied so that the thickness of the agent layer was 20 μm, and the film was dried at 90 ° C. for 1 minute to form an adhesive layer on the surface of the separator film. Next, the pressure-sensitive adhesive layer formed on the separator film was transferred to the protective film surface on the image display cell side of the polarizing film produced above to prepare a polarizing film with a pressure-sensitive adhesive layer.

<Manufacturing of pseudo image display device (laminated body)>
The polarizing film with an adhesive layer obtained above is cut into a size of 150 x 45 mm so that the absorption axis of the polarizing film is parallel to the long side, and a glass plate (Hiraoka Special Glass) is manufactured via the adhesive layer. EG-XG manufactured by the company, 165 x 50 mm, thickness 0.7 mm) is laminated and autoclaved at 50 ° C. and 0.5 MPa for 15 minutes to perform a pseudo image display panel (laminate having a polarizing film with a single-sided adhesive layer). ) Was prepared. Then, the pseudo image display panel was allowed to stand in a hot air oven at 80 ° C. for 2 hours for aging treatment, then taken out from the oven and allowed to stand in an environment of 23 ° C. and 55% for 1 hour. After that, another glass panel was attached to the protective film surface on the visual side via an acrylic acid monomer-free adhesive (manufactured by Nitto Denko Corporation, trade name LUCIACS CS98210) with a thickness of 200 μm, and the temperature was 50 ° C. and 0.5 MPa. A pseudo image display device (laminated body) was produced by autoclaving for 15 minutes.

<Evaluation of durability in high temperature environment>
The pseudo image display device (laminate) obtained above is allowed to stand in a hot air oven at a temperature of 105 ° C. for 500 hours, and the single transmittance (ΔTs) and the single hue b value (Δb) before and after charging (heating) are measured. It was measured. The simple substance transmittance and the simple substance hue b value were measured using a spectrophotometer (LPF-200, manufactured by Otsuka Electronics Co., Ltd.). The simple substance transmittance is a Y value obtained by correcting the luminosity factor with a 2 degree field of view (C light source) of JlS Z 8701-1982. The measurement wavelength is 380 to 780 nm (every 5 nm).
ΔTs (%) = Ts ₅₀₀ _{-Ts 0}
Δb (NBS) = b ₅₀₀ −b ₀
Here, Ts ₀ and b ₀ are the initial (before heating) single transmittance and single hue b value, and Ts ₅₀₀ and b ₅₀₀ are the single transmittance and single hue b value after heating for 500 hours. ΔTs (%) is preferably 0% or more and 3% or less, and more preferably 0% or more and 2% or less. Δb (NBS) is preferably 0 NBS or more and 4 NBS or less, and more preferably 0 NBS or more and 3 NBS or less. The results are shown in Table 1.

<Example 2>
In the production of the polarizing film, the potassium iodide concentration was adjusted to 3.6% by weight without adding the compound represented by the general formula (9) to the washing bath, and in the production of the pseudo image display device, 80 A pseudo image display panel (a laminate having a polarizing film with a double-sided pressure-sensitive adhesive layer) was prepared by laminating a 200 μm-thick acrylic acid monomer-free pressure-sensitive adhesive on the protective film surface on the visual side before putting it in a hot air oven at ° C. Except for the above, a polarizing film, a polarizing film, and a pseudo image display device (laminated body) were produced by the same operation as in Example 1.

<Comparative example 1>
In the production of the polarizing film, the potassium iodide concentration was adjusted to 3.6% by weight without adding the compound represented by the general formula (9) to the washing bath, and in the production of the pseudo image display device, pseudo. The polarizing film, the polarizing film, and the pseudo image display device (laminate) were operated in the same manner as in Example 1 except that the image display panel was allowed to stand in a hot air oven at 80 ° C. for 2 hours without aging treatment. ) Was prepared.

<Comparative example 2>
In the preparation of the polarizing film, the polarizing film, the polarizing film, and the pseudo image display device (pseudo-image display device) were operated in the same manner as in Example 1 except that the compound represented by the general formula (9) was not added to the washing bath. Laminated body) was produced.

<Comparative example 3>
In the production of the pseudo image display device, the polarizing film and the polarizing film were operated in the same manner as in Example 1 except that the pseudo image display panel was allowed to stand in a hot air oven at 80 ° C. for 2 hours without aging treatment. , And a pseudo image display device (laminated body) was produced.

<Comparative example 4>
In the preparation of the polarizing film, a polyvinyl alcohol film having a thickness of 75 μm was used, and the potassium iodide concentration was adjusted to 4.0% by weight without adding the compound represented by the general formula (9) to the washing bath. In the production of the pseudo-image display device, the polarizing film, the polarizing film, and the pseudo-image display device (laminate) were operated in the same manner as in Example 1 except that they were allowed to stand in a hot air oven at 90 ° C. for 5 hours. Was produced. The thickness of the polarizing film was 28 μm.

Using the pseudo image display devices (laminates) of the examples and comparative examples obtained above, the above <evaluation of durability in a high temperature environment> was performed. The results are shown in Table 1.

10: Polarizing film 11: Polarizing film 12, and 13: Transparent

protective film

20, 30, 40, and 50: Adhesive layer or adhesive layer 80: Front transparent member 90: Image display cell 100: Image display device

Claims

An image display device in which a front transparent member, a polarizing film, and an image display cell are provided in this order via an adhesive layer or an adhesive layer.
The laminated body in which the adhesive layer or the glass plate is bonded to both sides of the polarizing film via the adhesive layer has a change amount of the single transmittance before and after the heat resistance test under the conditions of 105 ° C. and 500 hours. Is 0 to 3%, and the amount of change in the single hue b value is 0 to 4 NBS.
The image display device according to claim 1, wherein the polarizing film is a transparent protective film bonded to at least one surface of the polarizing film via the adhesive layer or the adhesive layer.
The image display device according to claim 1 or 2, wherein the polarizing film has an optical layer bonded to at least one surface of the polarizing film via the adhesive layer or the adhesive layer. ..