CN112433287B - Polarizing film with adhesive layer and image display device - Google Patents

Abstract

The present invention relates to a polarizing film with an adhesive layer and an image display device. The polarizing film with an adhesive layer of the present invention is used in an image display device at a position closer to the viewing side than an image display portion, and has a polarizing film and adhesive layers on both sides of the polarizing film, wherein the polarizing film has a polarizer and transparent protective films on both sides of the polarizer, the transparent protective film on the viewing side of the polarizer has a transmittance of less than 6% at 380nm, and the adhesive layer on the viewing side of the polarizing film has an ultraviolet absorbing function. According to the present invention, it is possible to provide a polarizing film with an adhesive layer which can solve the problem of reduction in yield, can provide a sufficient ultraviolet blocking function even when the polarizing film is thin, and can suppress the occurrence of curling.

Description

Polarizing film with adhesive layer and image display device

This application is a divisional application of the Chinese patent application with application date of November 18, 2016 and application number 201680072755.X.

Technical Field

The present invention relates to a polarizing film with an adhesive layer used in an image display device. In addition, the present invention relates to an image display device using the polarizing film with an adhesive layer. Examples of the image display device include a liquid crystal display device, an organic EL (electroluminescent) display device, a PDP (plasma display panel), and electronic paper.

Background Art

For liquid crystal display devices and organic EL display devices, due to their image formation methods, for example, in liquid crystal display devices, it is essential to configure polarizing elements on both sides of the liquid crystal unit, and polarizing films are usually attached. In addition, in addition to polarizing films, various optical elements have been used on display panels such as liquid crystal panels and organic EL panels to improve the display quality of the display.

The polarizing film used in these image display devices generally has a structure in which a polarizer is sandwiched between two protective films, and triacetyl cellulose (TAC) is widely used as the protective film.

In recent years, with the trend of image display devices being lightweight and thinner, thinner films are required for various components used in image display devices, and thinner films are also required for protective films of polarizing films. When the thickness of the protective film is reduced, it is not possible to fully block ultraviolet rays incident on the image display device, resulting in the following problem: not only the polarizer, but also various optical components including liquid crystal panels and organic EL elements used in image display devices are accelerated to deteriorate due to ultraviolet rays.

In order to eliminate such problems, for example, the following adhesive sheets are known: a transparent double-sided adhesive sheet for an image display device, which is a double-sided adhesive sheet arranged between a surface protection panel in an image display device and a visual recognition side of a liquid crystal module to integrate the two components, wherein the adhesive sheet has at least one ultraviolet absorption layer, and the light transmittance at a wavelength of 380nm is 30% or less, and the visible light transmittance at a wavelength longer than 430nm is 80% or more (see, for example, Patent Document 1); an adhesive sheet having an adhesive layer containing an acrylic polymer and a triazine ultraviolet absorber (see, for example, Patent Document 2). In addition, it is known that in an adhesive optical film having an adhesive layer on one or both sides of an optical film, the above-mentioned adhesive layer can be given an ultraviolet absorption function (see, for example, Patent Document 3).

Prior art literature

Patent Literature

Patent Document 1: Japanese Patent Application Publication No. 2012-211305

Patent Document 2: Japanese Patent Application Publication No. 2013-75978

Patent Document 3: Japanese Patent No. 4208187

Summary of the invention

Problems to be solved by the invention

In recent years, as described in Patent Documents 1 to 3, it is well known to use a transparent adhesive having an ultraviolet absorption function to bond various components used in image display devices. However, in this case, uneven thickness occurs or the yield rate deteriorates, which is problematic from the perspective of workability.

In addition, depending on the use of the polarizing film, the polarizing film is sometimes required to have a higher ultraviolet absorption function. Specifically, it is required that the optical properties do not change even when exposed to ultraviolet rays for a long time (specifically about 300 hours) or when exposed to ultraviolet rays with a wide wavelength range, and such a polarizing film that satisfies a higher ultraviolet absorption function is desired.

In addition, there is a problem that the obtained polarizing film may curl due to the thinning of the polarizer and the protective film of the polarizing film.

Therefore, the object of the present invention is to provide a polarizing film with an adhesive layer that can solve the problem of reduced yield and can provide a higher ultraviolet blocking function and suppress curling even when the polarizing film is thin. In addition, the object of the present invention is to provide an image display device using the polarizing film with an adhesive layer.

Methods for solving problems

The present inventors have conducted intensive studies to solve the above-mentioned problems and, as a result, have discovered the following pressure-sensitive adhesive layer-attached polarizing film, thereby completing the present invention.

That is, the present invention relates to a polarizing film with an adhesive layer, which is used in an image display device at a portion closer to the visual recognition side than the image display portion, and is characterized in that:

The above-mentioned polarizing film with an adhesive layer comprises a polarizing film and adhesive layers on both sides of the polarizing film.

The polarizing film comprises a polarizer and transparent protective films on both sides of the polarizer.

The transparent protective film on the visual recognition side of the polarizer has a transmittance of less than 6% at a wavelength of 380 nm, and

The pressure-sensitive adhesive layer on the viewing side of the polarizing film has an ultraviolet absorbing function.

Preferably, the transparent protective film on the visual recognition side of the polarizer is at least one film selected from the group consisting of triacetylcellulose film, acrylic film, polyethylene terephthalate film and polyolefin film having a cyclic or norbornene structure, and the thickness of the transparent protective film on the visual recognition side of the polarizer is 40 μm or less.

It is preferable that the thickness of the pressure-sensitive adhesive layer on the visual inspection side of the polarizing film is at least twice the thickness of the pressure-sensitive adhesive layer on the image display unit side of the polarizing film.

It is preferred that the pressure-sensitive adhesive layer on the viewing side of the polarizing film has a transmittance of 9% or less at a wavelength of 380 nm and a transmittance of 60% or more at a wavelength of 400 nm.

It is preferred that the b* value of the pressure-sensitive adhesive layer on the viewing side of the polarizing film is 3.0 or less.

It is preferred that the pressure-sensitive adhesive layer on the viewing side of the polarizing film has a transmittance of 9% or less at a wavelength of 380 nm and a transmittance of 75% or less at a wavelength of 420 nm.

It is preferred that the pressure-sensitive adhesive layer on the viewing side of the polarizing film contain an acrylic polymer as a base polymer.

The pressure-sensitive adhesive layer-attached polarizing film of the present invention is preferably used in a liquid crystal display device or an organic EL display device.

The present invention also relates to an image display device, characterized in that the pressure-sensitive adhesive layer-attached polarizing film of the present invention is used in a portion closer to the visual recognition side than the image display portion.

Effects of the Invention

The polarizing film with an adhesive layer of the present invention is a structure in which an adhesive layer having an ultraviolet absorption function is pre-laminated on the visual recognition side of the polarizing film, so that the problems of process elimination and reduced yield can be solved, and even when the polarizing film is thin, a higher ultraviolet blocking function can be imparted, and curling can be suppressed. In addition, the image display device of the present invention uses the polarizing film with an adhesive layer, so that the degradation of various optical components including liquid crystal panels, organic EL elements, etc. used in the image display device caused by ultraviolet rays can be suppressed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view schematically showing one embodiment of the pressure-sensitive adhesive layer-attached polarizing film of the present invention.

FIG. 2 is a cross-sectional view schematically showing one embodiment of the image display device of the present invention.

FIG. 3 is a cross-sectional view schematically showing an embodiment of the image display device of the present invention.

FIG. 4 is a cross-sectional view schematically showing an embodiment of the image display device of the present invention.

DETAILED DESCRIPTION

1. Polarizing film with adhesive layer

The pressure-sensitive adhesive layer-attached polarizing film of the present invention is characterized in that:

In an image display device, it is used at a position closer to the visual recognition side than the image display portion.

The above-mentioned polarizing film with an adhesive layer comprises a polarizing film and adhesive layers on both sides of the polarizing film.

The polarizing film comprises a polarizer and transparent protective films on both sides of the polarizer.

The transparent protective film on the visual recognition side of the polarizer has a transmittance of less than 6% at a wavelength of 380 nm, and

The pressure-sensitive adhesive layer on the viewing side of the polarizing film has an ultraviolet absorbing function.

As shown in Figure 1, the polarizing film 1 with an adhesive layer of the present invention can be composed of a visual recognition side adhesive layer 2a/visual recognition side transparent protective film 3a/polarizer 4/image display side transparent protective film 3b/image display side adhesive layer 2b, or a composition further comprising a phase difference film, etc. Specifically, it can be composed of a visual recognition side adhesive layer 2a/visual recognition side transparent protective film 3a/polarizer 4/image display side transparent protective film 3b/image display side adhesive layer 2b/phase difference film (not shown)/image display side adhesive layer (not shown), etc. The polarizing film 5 is composed of a visual recognition side transparent protective film 3a/polarizer 4/image display side transparent protective film 3b. Each layer is described in detail below.

(1) Visual recognition side adhesive layer

In the present invention, the pressure-sensitive adhesive layer on the viewing side of the polarizing film (pressure-sensitive adhesive layer on the viewing side) is characterized by having an ultraviolet absorbing function. The pressure-sensitive adhesive layer on the viewing side is not particularly limited in composition as long as it has an ultraviolet absorbing function.

The formation of the above-mentioned visual recognition side adhesive layer can use suitable adhesive, and its kind is not particularly limited.As adhesive, can enumerate rubber adhesive, acrylic adhesive, polysiloxane adhesive, polyurethane adhesive, vinyl alkyl ether adhesive, polyvinyl alcohol adhesive, polyvinyl pyrrolidone adhesive, polyacrylamide adhesive, cellulose adhesive etc.In these adhesives, from optical transparency excellence, demonstrate the excellent aspects such as the bonding characteristics, weather resistance and heat resistance such as suitable adhesion, cohesion and tackiness, preferably use acrylic adhesive.Above-mentioned acrylic adhesive (composition) contains acrylic polymer as base polymer.

The acrylic pressure-sensitive adhesive composition preferably contains, for example, a partially polymerized product of a monomer component containing an alkyl (meth)acrylate and/or a (meth)acrylic polymer obtained from the monomer component, and a UV absorber.

(1-1) Partially polymerized monomer components and (meth)acrylic acid polymer

The acrylic pressure-sensitive adhesive composition includes a partially polymerized product of a monomer component containing an alkyl (meth)acrylate and/or a (meth)acrylic polymer obtained from the monomer component.

As the above-mentioned alkyl (meth)acrylate, there can be exemplified an alkyl (meth)acrylate having a linear or branched alkyl group with 1 to 24 carbon atoms at the ester end. The alkyl (meth)acrylate can be used alone or in combination of two or more. It should be noted that the alkyl (meth)acrylate refers to an alkyl acrylate and/or an alkyl methacrylate, and the (meth) in the present invention has the same meaning.

As the above-mentioned alkyl (meth)acrylate, for example, the above-mentioned alkyl (meth)acrylate having a branched chain with 1 to 9 carbon atoms can be preferably exemplified. The alkyl (meth)acrylate is preferred from the perspective of easily obtaining a balance in adhesive properties. Specifically, n-butyl (meth)acrylate, sec-butyl (meth)acrylate, tert-butyl (meth)acrylate, isobutyl (meth)acrylate, n-pentyl (meth)acrylate, isopentyl (meth)acrylate, isohexyl (meth)acrylate, isoheptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, isononyl (meth)acrylate, etc. can be cited, and one of them can be used alone or two or more of them can be used in combination.

In the present invention, the amount of the alkyl (meth)acrylate having an alkyl group having 1 to 24 carbon atoms at the ester terminal is preferably 40% by weight or more, more preferably 50% by weight or more, and even more preferably 60% by weight or more, based on the total amount of the monofunctional monomer components forming the (meth)acrylic polymer.

The monomer components may contain a comonomer other than the alkyl (meth)acrylate as a monofunctional monomer component. The comonomer may be used as the remainder of the alkyl (meth)acrylate in the monomer components.

唑、乙烯基吗啉等具有含氮杂环的乙烯基类单体等。另外，可以列举含有吗啉环、哌啶环、吡咯烷环、哌嗪环等杂环的(甲基)丙烯酸类单体。具体而言，可以列举N-丙烯酰基吗啉、N-丙烯酰基哌啶、N-甲基丙烯酰基哌啶、N-丙烯酰基吡咯烷等。上述环状含氮单体中，优选内酰胺类乙烯基单体。As the comonomer, for example, a cyclic nitrogen-containing monomer may be included. As the above-mentioned cyclic nitrogen-containing monomer, a monomer having a polymerizable functional group having an unsaturated double bond such as a (meth)acryloyl group or a vinyl group and having a cyclic nitrogen structure may be used without particular limitation. The cyclic nitrogen structure preferably has a nitrogen atom in the cyclic structure. As the cyclic nitrogen-containing monomer, for example, lactam vinyl monomers such as N-vinylpyrrolidone, N-vinyl-ε-caprolactam, and methylvinylpyrrolidone; vinylpyridine, vinylpiperidone, vinylpyrimidine, vinylpiperazine, vinylpyrazine, vinylpyrrole, vinylimidazole, vinyl

Examples of the present invention include vinyl monomers having nitrogen-containing heterocycles such as oxazole and vinyl morpholine. In addition, (meth) acrylic monomers containing heterocycles such as morpholine rings, piperidine rings, pyrrolidine rings, and piperazine rings can be cited. Specifically, N-acryloylmorpholine, N-acryloylpiperidine, N-methacryloylpiperidine, and N-acryloylpyrrolidine can be cited. Among the above-mentioned cyclic nitrogen-containing monomers, lactam vinyl monomers are preferred.

In the present invention, the cyclic nitrogen-containing monomer is preferably 0.5 to 50 wt %, more preferably 0.5 to 40 wt %, and even more preferably 0.5 to 30 wt % based on the total amount of monofunctional monomer components forming the (meth)acrylic polymer.

The monomer components used in the present invention may include hydroxyl-containing monomers as monofunctional monomer components. As hydroxyl-containing monomers, monomers containing polymerizable functional groups having unsaturated double bonds such as (meth) acryloyl or vinyl groups and having hydroxyl groups may be used without particular limitation. As hydroxyl-containing monomers, for example, (meth) 2-hydroxyethyl acrylate, (meth) 2-hydroxypropyl acrylate, (meth) 2-hydroxybutyl acrylate, (meth) 3-hydroxypropyl acrylate, (meth) 4-hydroxybutyl acrylate, (meth) 6-hydroxyhexyl acrylate, (meth) 8-hydroxyoctyl acrylate, (meth) 10-hydroxydecyl acrylate, (meth) 12-hydroxylauryl acrylate and other (meth) hydroxyalkyl acrylates; (meth) hydroxyalkyl cycloalkyl acrylates such as (meth) (4-hydroxymethylcyclohexyl) methyl acrylate. In addition, hydroxyethyl (meth) acrylamide, allyl alcohol, 2-hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl ether, diethylene glycol monovinyl ether and the like may be cited. These hydroxyl-containing monomers may be used alone or in combination. Among them, hydroxyalkyl (meth)acrylates are preferred.

In the present invention, from the perspective of improving adhesive strength and cohesive strength, the hydroxyl-containing monomer is preferably 1% by weight or more, more preferably 2% by weight or more, and even more preferably 3% by weight or more, relative to the total amount of the monofunctional monomer components forming the (meth) acrylic polymer. On the other hand, when the hydroxyl-containing monomer is too much, the adhesive layer may become hard and the adhesive strength may decrease, and the viscosity of the adhesive may be too high or gelation may occur. Therefore, the hydroxyl-containing monomer is preferably 30% by weight or less, more preferably 27% by weight or less, and even more preferably 25% by weight or less, relative to the total amount of the monofunctional monomer components forming the (meth) acrylic polymer.

The monomer components forming the (meth)acrylic polymer may contain other functional group-containing monomers as monofunctional monomers, for example, carboxyl group-containing monomers and monomers having a cyclic ether group.

As carboxyl-containing monomers, monomers containing polymerizable functional groups having unsaturated double bonds such as (meth) acryloyl or vinyl and having carboxyl groups can be used without particular limitation. As carboxyl-containing monomers, for example, (meth) acrylic acid, (meth) carboxyethyl acrylate, (meth) carboxypentyl acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, isocrotonic acid, etc. can be cited, and these carboxyl-containing monomers can be used alone or in combination. For itaconic acid and maleic acid, their anhydrides can be used. Among them, acrylic acid and methacrylic acid are preferred, and acrylic acid is particularly preferred. It should be noted that carboxyl-containing monomers can be optionally used in the monomer components used in the manufacture of the (meth) acrylic polymer of the present invention, and on the other hand, carboxyl-containing monomers can also be omitted.

As a monomer with a cyclic ether group, a monomer containing a polymerizable functional group with an unsaturated double bond such as a (meth) acryloyl group or a vinyl group and having a cyclic ether group such as an epoxy group or an oxetane group can be used without particular limitation. As an epoxy-containing monomer, for example, (meth) glycidyl acrylate, (meth) 3,4-epoxycyclohexyl methyl ester, (meth) 4-hydroxybutyl glycidyl ether, etc. can be cited. As an oxetane-containing monomer, for example, (meth) 3-oxetane methyl ester, (meth) 3-methyloxetane methyl ester, (meth) 3-ethyloxetane methyl ester, (meth) 3-butyloxetane methyl ester, (meth) 3-hexyloxetane methyl ester, etc. can be cited. These monomers with a cyclic ether group can be used alone or in combination.

In the present invention, the carboxyl group-containing monomer and the monomer having a cyclic ether group are preferably contained in an amount of 30 wt % or less, more preferably 27 wt % or less, and even more preferably 25 wt % or less, based on the total amount of the monofunctional monomer components forming the (meth)acrylic polymer.

Among the monomer components forming the (meth)acrylic polymer of the present invention, examples of the comonomer include (meth)acrylic acid alkyl esters represented by CH ₂ ═C(R ¹ )COOR ² (wherein R ¹ represents hydrogen or methyl, and R ² represents a substituted alkyl group having 1 to 3 carbon atoms or a cyclic cycloalkyl group).

Here, the substituent of the substituted alkyl group having 1 to 3 carbon atoms as R ² is preferably an aryl group having 3 to 8 carbon atoms or an aryloxy group having 3 to 8 carbon atoms. The aryl group is not limited, but is preferably a phenyl group.

Examples of such monomers represented by CH ₂ =C(R ¹ )COOR ² include phenoxyethyl (meth)acrylate, benzyl (meth)acrylate, cyclohexyl (meth)acrylate, 3,3,5-trimethylcyclohexyl (meth)acrylate, isobornyl (meth)acrylate, etc. These monomers can be used alone or in combination.

In the present invention, the (meth)acrylate represented by CH ₂ =C(R ¹ )COOR ² may be used in an amount of 50 wt % or less, preferably 45 wt % or less, more preferably 40 wt % or less, and further preferably 35 wt % or less, based on the total amount of the monofunctional monomer components forming the (meth)acrylic polymer.

As other comonomers, vinyl acetate, vinyl propionate, styrene, α-methylstyrene, glycol acrylate monomers such as polyethylene glycol (meth)acrylate, polypropylene glycol (meth)acrylate, methoxyethylene glycol (meth)acrylate, methoxypolypropylene glycol (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, fluoro (meth)acrylate, polysiloxane (meth)acrylate, 2-methoxyethyl acrylate, acrylate monomers, amide-containing monomers, amino-containing monomers, imide-containing monomers, N-acryloylmorpholine, vinyl ether monomers, etc. In addition, as comonomers, monomers having a cyclic structure such as terpene (meth)acrylate and tetrahydrodicyclopentadienyl (meth)acrylate can be used.

In addition, silane monomers containing silicon atoms can be cited. Examples of silane monomers include 3-acryloxypropyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, 4-vinylbutyltrimethoxysilane, 4-vinylbutyltriethoxysilane, 8-vinyloctyltrimethoxysilane, 8-vinyloctyltriethoxysilane, 10-methacryloxydecyltrimethoxysilane, 10-acryloxydecyltrimethoxysilane, 10-methacryloxydecyltriethoxysilane, and 10-acryloxydecyltriethoxysilane.

The monomer components forming the (meth)acrylic polymer of the present invention may contain, in addition to the monofunctional monomers exemplified above, a polyfunctional monomer as necessary in order to adjust the cohesive force of the pressure-sensitive adhesive.

The multifunctional monomer is a monomer having at least two polymerizable functional groups having unsaturated double bonds such as (meth)acryloyl groups or vinyl groups, and examples thereof include: ester compounds of polyols and (meth)acrylic acid such as (poly)ethylene glycol di(meth)acrylate, (poly)propylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, 1,2-ethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,12-dodecanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, and tetramethylolmethane tri(meth)acrylate; allyl (meth)acrylate, vinyl (meth)acrylate, divinylbenzene, epoxy acrylate, polyester acrylate, urethane acrylate, butanediol di(meth)acrylate, and hexanediol di(meth)acrylate; Among them, trimethylolpropane tri(meth)acrylate, hexanediol di(meth)acrylate, and dipentaerythritol hexa(meth)acrylate can be preferably used. The polyfunctional monomer can be used alone or in combination of two or more.

The usage amount of the multifunctional monomer varies according to its molecular weight, number of functional groups, etc., and is preferably used in an amount of 3 parts by weight or less, more preferably 2 parts by weight or less, and further preferably 1 part by weight or less relative to a total of 100 parts by weight of the monofunctional monomer. In addition, there is no particular restriction as a lower limit, but it is preferably 0 parts by weight or more, and more preferably 0.001 parts by weight or more. By the usage amount of the multifunctional monomer being within the above range, the adhesive force can be improved.

The (meth)acrylic polymer can be produced by a known production method such as solution polymerization, radiation polymerization such as ultraviolet (UV) polymerization, bulk polymerization, various free radical polymerizations such as emulsion polymerization, etc. The obtained (meth)acrylic polymer can be any of a random copolymer, a block copolymer, a graft copolymer, etc.

In the present invention, partial polymers of the above-mentioned monomer components may also be used appropriately.

When the (meth) acrylic polymer is produced by free radical polymerization, a polymerization initiator, chain transfer agent, emulsifier, etc. used in the free radical polymerization may be appropriately added to the monomer components to perform polymerization. The polymerization initiator, chain transfer agent, emulsifier, etc. used in the free radical polymerization are not particularly limited and may be appropriately selected for use. It should be noted that the weight average molecular weight of the (meth) acrylic polymer may be controlled by the amount of the polymerization initiator and chain transfer agent used and the reaction conditions, and the amount used may be appropriately adjusted according to their types.

For example, in solution polymerization, ethyl acetate, toluene, etc. are used as polymerization solvents. As a specific example of solution polymerization, a polymerization initiator is added under an inert gas flow such as nitrogen, and the reaction is usually carried out under reaction conditions of about 50° C. to about 70° C. and about 5 hours to about 30 hours.

Examples of the thermal polymerization initiator used in solution polymerization include azo initiators such as 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), 2,2'-azobis(2-methylpropionic acid) dimethyl ester, 4,4'-azobis(4-cyanovaleric acid), azobisisovaleronitrile, 2,2'-azobis(2-amidinopropane) dihydrochloride, 2,2'-azobis[2-(5-methyl-2-imidazolin-2-yl)propane] dihydrochloride, 2,2'-azobis(2-methylpropionamidine) disulfate, 2,2'-azobis(N,N'-dimethyleneisobutylamidine), and 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamidine] hydrate (VA-057, manufactured by Wako Pure Chemical Industries, Ltd.); Peroxide initiators include persulfates such as potassium sulfate and ammonium persulfate, di(2-ethylhexyl) peroxydicarbonate, di(4-tert-butylcyclohexyl) peroxydicarbonate, di-sec-butyl peroxydicarbonate, tert-butyl peroxyneodecanoate, tert-hexyl peroxypivalate, tert-butyl peroxypivalate, dilauroyl peroxide, di-n-octanoyl peroxide, 1,1,3,3-tetramethylbutyl peroxy-2-ethylhexanoate, di(4-methylbenzoyl) peroxide, dibenzoyl peroxide, tert-butyl peroxyisobutyrate, 1,1-di(tert-hexylperoxy)cyclohexane, tert-butyl hydroperoxide, hydrogen peroxide, and the like; and redox initiators obtained by combining peroxides with reducing agents, such as combinations of persulfates and sodium bisulfite, and combinations of peroxides and sodium ascorbate. However, the invention is not limited thereto.

The above-mentioned polymerization initiator can be used alone or in combination of two or more. The amount of the above-mentioned polymerization initiator used is preferably about 1 part by weight or less, more preferably about 0.005 part by weight to about 1 part by weight, and further preferably about 0.02 part by weight to about 0.5 part by weight, relative to 100 parts by weight of the total amount of the monomer components.

When 2,2'-azobisisobutyronitrile is used as the polymerization initiator, the amount of the polymerization initiator used is preferably about 0.2 parts by weight or less, more preferably about 0.06 to 0.2 parts by weight, based on 100 parts by weight of the total amount of the monomer components.

Examples of the chain transfer agent include lauryl mercaptan, glycidyl mercaptan, thioglycolic acid, 2-mercaptoethanol, thioglycolic acid, 2-ethylhexyl thioglycolate, 2,3-dimercapto-1-propanol, etc. The chain transfer agent may be used alone or in combination of two or more, and the total content is about 0.3 parts by weight or less relative to 100 parts by weight of the total amount of the monomer components.

In addition, as the emulsifier used in the case of emulsion polymerization, for example, there can be mentioned: anionic emulsifiers such as sodium lauryl sulfate, ammonium lauryl sulfate, sodium dodecylbenzene sulfonate, ammonium polyoxyethylene alkyl ether sulfate, sodium polyoxyethylene alkylphenyl ether sulfate; nonionic emulsifiers such as polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, polyoxyethylene fatty acid ester, polyoxyethylene-polyoxypropylene block polymer, etc. These emulsifiers may be used alone or in combination of two or more.

In addition, as a reactive emulsifier, as an emulsifier introduced with a radical polymerizable functional group such as an acrylic group or an allyl ether group, specifically, there are Aqualon HS-10, HS-20, KH-10, BC-05, BC-10, BC-20 (all of which are manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), ADEKA REASOAP SE10N (manufactured by ADEKA Corporation), etc. The amount of the emulsifier used is preferably 5 parts by weight or less relative to 100 parts by weight of the total amount of the monomer components.

In addition, when the (meth)acrylic polymer is produced by radiation polymerization, it can be produced by irradiating the monomer components with radiation such as electron beams, ultraviolet rays (UV) and polymerizing them. Among them, ultraviolet polymerization is preferred. The following describes ultraviolet polymerization as a preferred embodiment of radiation polymerization.

When ultraviolet polymerization is performed, it is preferred that a photopolymerization initiator is contained in the monomer component because of the advantage of being able to shorten the polymerization time. Therefore, when ultraviolet polymerization is performed, it is preferred to form the adhesive layer by ultraviolet polymerization of, for example, an ultraviolet curable acrylic adhesive composition containing the above-mentioned monomer component containing the (meth) alkyl acrylate and/or a partial polymer of the above-mentioned monomer component, an ultraviolet absorber, and a photopolymerization initiator. The adhesive layer formed by ultraviolet polymerization of the above-mentioned ultraviolet curable acrylic adhesive composition can also form a thicker adhesive layer of 150 μm or more, and is preferred because it can form an adhesive layer with a wide thickness range.

As the above-mentioned photopolymerization initiator, it is preferred to include a photopolymerization initiator (A) having an absorption band at a wavelength of 400 nm or more. When a UV absorber is included in the adhesive composition, when UV polymerization is performed, the UV rays are absorbed by the UV absorber and sufficient polymerization cannot be performed. However, if the photopolymerization initiator (A) has an absorption band at a wavelength of 400 nm or more, sufficient polymerization can be performed despite the inclusion of the UV absorber, and therefore, it is preferred.

Examples of the photopolymerization initiator (A) having an absorption band at a wavelength of 400 nm or longer include bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (Irgacure 819, manufactured by BASF) and 2,4,6-trimethylbenzoyldiphenylphosphine oxide (LUCIRIN TPO, manufactured by BASF).

The photopolymerization initiator (A) having an absorption band at a wavelength of 400 nm or longer may be used alone or in combination of two or more.

In addition, the amount of the photopolymerization initiator (A) having an absorption band at a wavelength of 400 nm or more is not particularly limited, but is preferably less than the amount of the ultraviolet absorber described later, and is preferably about 0.005 to 1 part by weight, more preferably about 0.02 to 0.5 parts by weight, relative to 100 parts by weight of the monofunctional monomer component forming the (meth)acrylic polymer. When the amount of the photopolymerization initiator (A) is within the above range, ultraviolet polymerization can be fully carried out, which is preferred.

In addition, the above-mentioned photopolymerization initiator may contain a photopolymerization initiator (B) having an absorption band at a wavelength of less than 400nm. In addition, the photopolymerization initiator (B) preferably does not have an absorption band at a wavelength of more than 400nm. As for the photopolymerization initiator (B), as long as it is a photopolymerization initiator that generates free radicals under the action of ultraviolet rays to initiate photopolymerization and has an absorption band at a wavelength of less than 400nm, there is no particular limitation, and any one of the commonly used photopolymerization initiators can be appropriately used. For example, benzoin ether photopolymerization initiators, acetophenone photopolymerization initiators, α-ketol photopolymerization initiators, photoactive oxime photopolymerization initiators, benzoin photopolymerization initiators, benzyl photopolymerization initiators, benzophenone photopolymerization initiators, ketal photopolymerization initiators, thioxanthone photopolymerization initiators, acylphosphine oxide photopolymerization initiators, etc. can be used.

Specific examples of the benzoin ether-based photopolymerization initiator include benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isopropyl ether, benzoin isobutyl ether, 2,2-dimethoxy-1,2-diphenylethane-1-one, and anisoin methyl ether.

Examples of the acetophenone-based photopolymerization initiator include 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexylphenyl ketone, 4-phenoxydichloroacetophenone, and 4-tert-butyldichloroacetophenone.

Examples of the α-ketol-based photopolymerization initiator include 2-methyl-2-hydroxypropiophenone and 1-[4-(2-hydroxyethyl)phenyl]-2-hydroxy-2-methylpropane-1-one.

Examples of the photoactive oxime-based photopolymerization initiator include 1-phenyl-1,2-propanedione-2-(O-ethoxycarbonyl)oxime.

As a benzoin type photopolymerization initiator, benzoin etc. are mentioned, for example.

Examples of the benzyl-based photopolymerization initiator include benzil and the like.

Examples of the benzophenone-based photopolymerization initiator include benzophenone, benzoylbenzoic acid, 3,3'-dimethyl-4-methoxybenzophenone, polyvinyl benzophenone, and α-hydroxycyclohexyl phenyl ketone.

The ketal-based photopolymerization initiator includes benzyl dimethyl ketal and the like.

Examples of the thioxanthone-based photopolymerization initiator include thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-dichlorothioxanthone, 2,4-diethylthioxanthone, 2,4-diisopropylthioxanthone, and dodecylthioxanthone.

Examples of the acylphosphine oxide-based photopolymerization initiator include 2,4,6-trimethylbenzoyldiphenylphosphine oxide and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide.

The photopolymerization initiator (B) having an absorption band at a wavelength of less than 400 nm may be used alone or in combination of two or more. The photopolymerization initiator (B) having an absorption band at a wavelength of less than 400 nm may be added within a range that does not impair the effects of the present invention, and the amount added is preferably about 0.005 to 0.5 parts by weight, more preferably about 0.02 to 0.1 parts by weight, relative to 100 parts by weight of the monofunctional monomer component forming the (meth)acrylic polymer.

In the present invention, when the above-mentioned monomer component is subjected to ultraviolet polymerization, it is preferred that: a photopolymerization initiator (B) having an absorption band at a wavelength less than 400 nm is first added to the above-mentioned monomer component, a part of the monomer component is polymerized by irradiation with ultraviolet rays to obtain a partial polymer (prepolymer composition) of the monomer component, and the above-mentioned photopolymerization initiator (A) having an absorption band at a wavelength of 400 nm or more and an ultraviolet absorber are added to the prepolymer composition to perform ultraviolet polymerization. When adding the above-mentioned photopolymerization initiator (A) having an absorption band at a wavelength of 400 nm or more to the partial polymer (prepolymer composition) of the monomer component obtained by irradiation with ultraviolet rays for partial polymerization, it is preferred that the above-mentioned photopolymerization initiator is dissolved in the monomer before adding.

(1-2) Ultraviolet absorber

As for the ultraviolet absorber contained in the above-mentioned acrylic adhesive composition, there is no particular limitation, for example, triazine ultraviolet absorbers, benzotriazole ultraviolet absorbers, benzophenone ultraviolet absorbers, hydroxybenzophenone ultraviolet absorbers, salicylate ultraviolet absorbers, cyanoacrylate ultraviolet absorbers, etc. can be listed, and these ultraviolet absorbers can be used alone or in combination of two or more. Among them, triazine ultraviolet absorbers and benzotriazole ultraviolet absorbers are preferred, and at least one ultraviolet absorber selected from the group consisting of triazine ultraviolet absorbers having two or less hydroxyl groups in one molecule and benzotriazole ultraviolet absorbers having one benzotriazole skeleton in one molecule is preferred, because it has good solubility in the monomer used in the formation of the acrylic adhesive composition and has high ultraviolet absorption ability near the wavelength of 380nm.

Specific examples of triazine ultraviolet absorbers having two or less hydroxyl groups in one molecule include: 2,4-bis[{4-(4-ethylhexyloxy)-4-hydroxy}phenyl]-6-(4-methoxyphenyl)-1,3,5-triazine (Tinosorb S, manufactured by BASF); 2,4-bis[2-hydroxy-4-butoxyphenyl]-6-(2,4-dibutoxyphenyl)-1,3,5-triazine (TINUVIN 460, manufactured by BASF); 2-(4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine-2-yl)-5-hydroxyphenyl and [(C ₁₀ -C ₁₆ (mainly C ₁₂ -C ₁₃ )alkyloxy)methyl] ethylene oxide reaction product (TINUVIN400, manufactured by BASF); 2-[4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine-2-yl]-5-[3-(dodecyloxy)-2-hydroxypropoxy]phenol), 2-(2,4-dihydroxyphenyl)-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine reaction product with 2-ethylhexyl glycidate (TINUVIN405, manufactured by BASF); 2-(4,6-diphenyl-1,3,5-triazine-2-yl)-5-[(hexyl)oxy]phenol (TINUVIN1577, manufactured by BASF); 2-(4,6-diphenyl-1,3,5-triazine-2-yl)-5-[2-(2-ethylhexanoyloxy)ethoxy]phenol (ADK STAB LA46, manufactured by ADEKA); 2-(2-hydroxy-4-[1-octyloxycarbonylethoxy]phenyl)-4,6-bis(4-phenylphenyl)-1,3,5-triazine (TINUVIN479, manufactured by BASF);

In addition, as benzotriazole ultraviolet absorbers having one benzotriazole skeleton in one molecule, there can be mentioned: 2-(2H-benzotriazole-2-yl)-6-(1-methyl-1-phenylethyl)-4-(1,1,3,3-tetramethylbutyl)phenol (TINUVIN 928, manufactured by BASF), 2-(2-hydroxy-5-tert-butylphenyl)-2H-benzotriazole (TINUVIN PS, manufactured by BASF), ester compound of phenylpropionic acid and 3-(2H-benzotriazole-2-yl)-5-(1,1-dimethylethyl)-4-hydroxy (C7-9 side chain and linear alkyl) (TINUVIN 384-2, manufactured by BASF); 2-(2H-benzotriazole-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol (TINUVIN 900, manufactured by BASF); 2-(2H-benzotriazole- 2-(2H-benzotriazol-2-yl)-6-(1-methyl-1-phenylethyl)-4-(1,1,3,3-tetramethylbutyl)phenol (TINUVIN928, manufactured by BASF); 3-(3-(2H-benzotriazol-2-yl)-5-tert-butyl-4-hydroxyphenyl)propionic acid methyl ester/polyethylene glycol 300 reaction product (TINUVIN1130, manufactured by BASF); 2-(2H-benzotriazol-2-yl)-p-cresol (TINUVIN P, manufactured by BASF); 2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol (TINUVIN234, manufactured by BASF); 2-[5-chloro(2H)-benzotriazol-2-yl]-4-methyl-6-tert-butylphenol (TINUVIN326, manufactured by BASF); 2-(2H-benzotriazol-2-yl)-4,6-di-tert-amylphenol (TINUVIN328, manufactured by BASF); 2-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol (TINUVIN UVIN329, manufactured by BASF); reaction product of methyl 3-(3-(2H-benzotriazol-2-yl)-5-tert-butyl-4-hydroxyphenyl) propionate and polyethylene glycol 300 (TINUVIN213, manufactured by BASF); 2-(2H-benzotriazol-2-yl)-6-dodecyl-4-methylphenol (TINUVIN571, manufactured by BASF); 2-[2-hydroxy-3-(3,4,5,6-tetrahydrophthalimidomethyl)-5-methylphenyl]benzotriazole (Sumisorb250, manufactured by Sumitomo Chemical Co., Ltd.), etc.

In addition, examples of the benzophenone-based ultraviolet absorbers (benzophenone-based compounds) and hydroxybenzophenone-based ultraviolet absorbers (hydroxybenzophenone-based compounds) include 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxybenzophenone-5-sulfonic acid (anhydrous salt and trihydrate salt), 2-hydroxy-4-octyloxybenzophenone, 4-dodecyloxy-2-hydroxybenzophenone, 4-benzyloxy-2-hydroxybenzophenone, 2,2',4,4'-tetrahydroxybenzophenone, and 2,2'-dihydroxy-4,4-dimethoxybenzophenone.

In addition, examples of the salicylate ultraviolet absorber (salicylate compound) include 2-acryloyloxyphenyl benzoate, 2-acryloyloxy-3-methylphenyl benzoate, 2-acryloyloxy-4-methylphenyl benzoate, 2-acryloyloxy-5-methylphenyl benzoate, 2-acryloyloxy-3-methoxyphenyl benzoate, 2-hydroxyphenyl benzoate, 2-hydroxy-3-methylphenyl benzoate, 2-hydroxy-4-methylphenyl benzoate, 2-hydroxy-5-methylphenyl benzoate, 2-hydroxy-3-methoxyphenyl benzoate, and 3,5-di-tert-butyl-4-hydroxybenzoic acid 2,4-di-tert-butylphenyl ester (TINUVIN120, manufactured by BASF).

Examples of the cyanoacrylate ultraviolet absorber (cyanoacrylate compound) include 2-cyanoacrylate alkyl esters, 2-cyanoacrylate cycloalkyl esters, 2-cyanoacrylate alkoxyalkyl esters, 2-cyanoacrylate alkenyl esters, and 2-cyanoacrylate alkynyl esters.

In addition, as ultraviolet absorbers, for example, dyes such as trade name "FDB-001" (manufactured by Yamada Chemical Industry Co., Ltd.), trade name "SMP-122" (manufactured by Hayashibara Co., Ltd.), azomethine compounds (trade name: BONASORBU A-3911, manufactured by Orient Chemical Industry Co., Ltd.), indole compounds (trade name: BONASORB UA-3701, manufactured by Orient Chemical Industry Co., Ltd.), Disperse Yellow 54 (trade name: KAYASET YELLOW AG, manufactured by Nippon Kayaku Co., Ltd.), quinophthalone compounds (trade name: MS YELLOW HD-137, manufactured by Yamada Chemical Industry Co., Ltd.), Solvent Yellow 93 (PLASTYELLOW 8000, manufactured by Arimoto Chemical Industry Co., Ltd.), and Solvent Yellow 163 (KP Plast Yellow MK, manufactured by Kiwa Chemical Industry Co., Ltd.) can also be used.

The above-mentioned ultraviolet absorber can be used alone or in combination of two or more, and the content as a whole is preferably about 0.1 to about 5 parts by weight, more preferably about 0.5 to about 3 parts by weight, relative to 100 parts by weight of the monofunctional monomer component forming the (meth) acrylic polymer. By setting the addition amount of the ultraviolet absorber within the above range, the ultraviolet absorption function of the adhesive layer can be fully exerted, and when ultraviolet polymerization is performed, the polymerization is not hindered, so it is preferred.

(1-3) Silane coupling agent

In addition, the acrylic adhesive composition used in the present invention may contain a silane coupling agent. The amount of the silane coupling agent is preferably 1 part by weight or less, more preferably 0.01 to 1 part by weight, and further preferably 0.02 to 0.6 parts by weight, relative to 100 parts by weight of the monofunctional monomer component forming the (meth)acrylic polymer.

Examples of the silane coupling agent include epoxy group-containing silane coupling agents such as 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; amino group-containing silane coupling agents such as 3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, 3-triethoxysilyl-N-(1,3-dimethylbutylene)propylamine, and N-phenyl-γ-aminopropyltrimethoxysilane; (meth)acryloyl group-containing silane coupling agents such as 3-acryloxypropyltrimethoxysilane and 3-methacryloxypropyltriethoxysilane; and isocyanate group-containing silane coupling agents such as 3-isocyanatepropyltriethoxysilane.

(1-4) Cross-linking agent

唑啉类交联剂、氮丙啶类交联剂、硅烷类交联剂、烷基醚化三聚氰胺类交联剂、金属螯合物类交联剂、过氧化物等交联剂。交联剂可以单独使用一种或组合使用两种以上。其中，优选使用异氰酸酯类交联剂。The acrylic adhesive composition used in the present invention may contain a crosslinking agent. Examples of the crosslinking agent include isocyanate crosslinking agents, epoxy crosslinking agents, polysiloxane crosslinking agents,

Azoline crosslinking agent, aziridine crosslinking agent, silane crosslinking agent, alkyl etherified melamine crosslinking agent, metal chelate crosslinking agent, peroxide and the like crosslinking agent. The crosslinking agent can be used alone or in combination of two or more. Among them, isocyanate crosslinking agents are preferably used.

The cross-linking agent may be used alone or in combination of two or more. The total content is preferably 5 parts by weight or less, more preferably 0.01 to 5 parts by weight, further preferably 0.01 to 4 parts by weight, and particularly preferably 0.02 to 3 parts by weight, based on 100 parts by weight of the monofunctional monomer component forming the (meth)acrylic polymer.

An isocyanate crosslinking agent refers to a compound having two or more isocyanate groups (including isocyanate regeneration functional groups in which the isocyanate groups are temporarily protected by a blocking agent or polymerization) in one molecule. Examples of the isocyanate crosslinking agent include aromatic isocyanates such as toluene diisocyanate and xylylene diisocyanate, alicyclic isocyanates such as isophorone diisocyanate, and aliphatic isocyanates such as hexamethylene diisocyanate.

More specifically, for example, lower aliphatic polyisocyanates such as butylene diisocyanate and hexamethylene diisocyanate; alicyclic isocyanates such as cyclopentylene diisocyanate, cyclohexylene diisocyanate, and isophorone diisocyanate; aromatic diisocyanates such as 2,4-toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, xylylene diisocyanate, and polymethylene polyphenyl isocyanate; trimethylolpropane/toluene diisocyanate trimer adduct (trade name: CORONATE L, manufactured by Nippon Polyurethane Industry Co., Ltd.), trimethylolpropane/hexamethylene diisocyanate trimer adduct (trade name: CORONATE HL, manufactured by Nippon Polyurethane Industry Co., Ltd.), isocyanurate form of hexamethylene diisocyanate (trade name: CORONATE HL, manufactured by Nippon Polyurethane Industry Co., Ltd.), HX, manufactured by Nippon Polyurethane Industry Co., Ltd.), isocyanate adducts such as trimethylolpropane adduct of xylylene diisocyanate (trade name: D110N, manufactured by Mitsui Chemicals, Inc.), trimethylolpropane adduct of hexamethylene diisocyanate (trade name: D160N, manufactured by Mitsui Chemicals, Inc.); polyether polyisocyanates, polyester polyisocyanates, and adducts thereof with various polyols, polyisocyanates obtained by multifunctionalization using isocyanurate bonds, biuret bonds, allophanate bonds, etc.

(1-5) Other additives

The acrylic adhesive composition used in the present invention may contain appropriate additives in addition to the above-mentioned components according to the application. Examples thereof include tackifiers (solid, semi-solid or liquid substances at room temperature, such as rosin derivative resins, polyterpene resins, petroleum resins, oil-soluble phenol resins, etc.); fillers such as hollow glass microspheres; plasticizers; anti-aging agents; antioxidants, etc.

(1-6) Method for forming visual recognition side adhesive layer

In the present invention, it is preferred to adjust the above-mentioned acrylic adhesive composition to a viscosity suitable for coating on a substrate. The viscosity of the acrylic adhesive composition is adjusted, for example, by adding various polymers or multifunctional monomers such as thickening additives, or partially polymerizing the monomer components in the acrylic adhesive composition. It should be noted that the partial polymerization can be performed before or after the addition of various polymers or multifunctional monomers such as thickening additives. The viscosity of the above-mentioned acrylic adhesive composition varies depending on the amount of additives, etc., so the polymerization rate when partially polymerizing the monomer components in the acrylic adhesive composition cannot be uniquely determined. As a rough benchmark, it is preferably about 20% or less, more preferably about 3% to about 20%, and further preferably about 5% to about 15%. When it exceeds 20%, the viscosity becomes too high, so it is difficult to apply to the substrate.

The visual recognition side PSA layer can be formed by applying the acrylic PSA composition on at least one surface of a substrate and drying the coating film formed of the acrylic PSA composition; or by irradiating active energy rays such as ultraviolet rays.

As the substrate, there is no particular limitation, and for example, various substrates such as a release film, a transparent resin film substrate, or a polarizing film described later can be appropriately used as the substrate. When the visual recognition side adhesive layer is formed on a substrate other than the polarizing film, the visual recognition side adhesive layer can be bonded and transferred to the polarizing film.

As the constituent material of the above-mentioned release film, for example, resin films such as polyethylene, polypropylene, polyethylene terephthalate, and polyester films, porous materials such as paper, cloth, and non-woven fabrics, meshes, foam sheets, metal foils, and appropriate thin paper-like materials (thin sheets) such as laminates thereof can be listed. From the perspective of excellent surface smoothness, it is preferred to use a resin film.

Examples of the resin film include polyethylene films, polypropylene films, polybutylene films, polybutadiene films, polymethylpentene films, polyvinyl chloride films, vinyl chloride copolymer films, polyethylene terephthalate films, polybutylene terephthalate films, polyurethane films, and ethylene-vinyl acetate copolymer films.

The thickness of the release film is usually 5 μm to 200 μm, preferably about 5 μm to about 100 μm. The release film may be subjected to release and antifouling treatment using silicone, fluorine-containing, long-chain alkyl or fatty acid amide release agents, silica powder, etc., or antistatic treatment such as coating, kneading, and vapor deposition, as required. In particular, by appropriately subjecting the surface of the release film to a release treatment such as silicone treatment, long-chain alkyl treatment, and fluorine treatment, the releasability from the adhesive layer can be further improved.

As the above-mentioned transparent resin film substrate, there is no particular restriction, and various resin films with transparency are used. The resin film is formed by a layer of film. As its material, for example, polyester resins such as polyethylene terephthalate and polyethylene naphthalate, acetate resins, polyether sulfone resins, polycarbonate resins, polyamide resins, polyimide resins, polyolefin resins, (methyl) acrylic resins, polyvinyl chloride resins, polyvinylidene chloride resins, polystyrene resins, polyvinyl alcohol resins, polyarylate resins, polyphenylene sulfide resins, etc. can be cited. Among these, polyester resins, polyimide resins and polyether sulfone resins are particularly preferred.

The thickness of the film substrate is preferably 15 μm to 200 μm, more preferably 25 μm to 188 μm.

The method for coating the above-mentioned acrylic adhesive composition on the above-mentioned substrate can use a known appropriate method such as roll coating, lick roll coating, gravure coating, reverse coating, roll brush, spray coating, dip roll coating, doctor bar coating, doctor blade coating, air knife coating, curtain coating, lip die coating, and die coater, without particular limitation.

When the visual recognition side adhesive layer is formed by drying a coating film formed from the above-mentioned acrylic adhesive composition, the drying conditions (temperature, time) are not particularly limited and can be appropriately set according to the composition and concentration of the adhesive composition, for example, at about 60°C to about 170°C, preferably 60°C to 150°C, for 1 minute to 60 minutes, preferably 2 minutes to 30 minutes.

In the case where the acrylic adhesive composition is an ultraviolet curing acrylic adhesive composition and is formed by irradiating a coating film formed of the ultraviolet curing acrylic adhesive composition with ultraviolet rays, the irradiated ultraviolet rays preferably have an illuminance of 5 mW/ ^cm2 or more. When the illuminance of the ultraviolet rays is less than 5 mW/ ^cm2 , the polymerization reaction time becomes long, and sometimes the productivity is poor. It should be noted that the illuminance of the ultraviolet rays is preferably 200 mW/ ^cm2 or less. When the illuminance of the ultraviolet rays exceeds 200 mW/ ^cm2 , the photopolymerization initiator is rapidly consumed, so that sometimes the polymer is reduced in molecular weight, and the retention force at high temperature is reduced. In addition, the cumulative light amount of ultraviolet rays is preferably 100 mJ/ ^cm2 to 5000 mJ/ ^cm2 .

The ultraviolet lamp used in the present invention is not particularly limited, and LED lamp is preferred. Compared with other ultraviolet lamps, LED lamps are lamps that release less heat, so the temperature in the polymerization of the adhesive layer can be suppressed. Therefore, it is possible to prevent the low molecular weight of the polymer, prevent the reduction of the cohesive force of the adhesive layer, and improve the holding power at high temperatures when the adhesive sheet is made. In addition, a plurality of ultraviolet lamps can also be combined. In addition, ultraviolet rays can also be irradiated intermittently, and a bright period for irradiating ultraviolet rays and a dark period for not irradiating ultraviolet rays can be set.

In the present invention, the final polymerization rate of the monomer components in the ultraviolet curable acrylic pressure-sensitive adhesive composition is preferably 90% or more, more preferably 95% or more, and even more preferably 98% or more.

In the present invention, the peak wavelength of ultraviolet rays irradiated to the ultraviolet curable acrylic adhesive composition is preferably in the range of 200nm to 500nm, more preferably in the range of 300nm to 450nm. When the peak wavelength of ultraviolet rays exceeds 500nm, the photopolymerization initiator may not decompose and the polymerization reaction may not be initiated. In addition, when the peak wavelength of ultraviolet rays is less than 200nm, the polymer chain may be cut and the adhesive properties may be reduced.

The reaction is inhibited by oxygen in the air. Therefore, in order to block oxygen, it is preferred to form a release film on the coating film formed by the ultraviolet curable acrylic adhesive composition, or to perform the photopolymerization reaction under a nitrogen atmosphere. As the release film, the above-mentioned release film can be cited. It should be noted that when a release film is used, the release film can be directly used as a spacer for the polarizing film with an adhesive layer.

In addition, when the ultraviolet curable acrylic adhesive composition used in the present invention contains a photopolymerization initiator (B), it is preferred that: a composition containing a monomer component containing an alkyl (meth)acrylate and the above-mentioned photopolymerization initiator (B) (sometimes also referred to as "pre-added polymerization initiator") is irradiated with ultraviolet rays to form a partial polymer of the above-mentioned monomer component, and an ultraviolet absorber and a photopolymerization initiator (A) having an absorption band at a wavelength of more than 400 nm (sometimes also referred to as "post-added polymerization initiator") are added to the partial polymer of the above-mentioned monomer component, thereby preparing the ultraviolet curable acrylic adhesive composition. The polymerization rate of the partial polymer is preferably about 20% or less, more preferably about 3% to about 20%, and further preferably about 5% to about 15%. The ultraviolet irradiation conditions are as described above.

As described above, when forming a pressure-sensitive adhesive layer from a UV-curable acrylic pressure-sensitive adhesive composition containing a photopolymerization initiator (B), the polymerization rate of the monomer components can be increased by performing the polymerization in two steps as described above, and the UV absorption function of the pressure-sensitive adhesive layer finally produced can be improved.

From the viewpoint of ensuring the ultraviolet absorption function, the thickness of the above-mentioned visual recognition side adhesive layer is preferably more than twice the thickness of the adhesive layer on the image display side of the polarizing film (image display side adhesive layer) described later, more preferably more than 5 times, and further preferably more than 10 times. Specifically, the thickness of the above-mentioned visual recognition side adhesive layer is preferably more than 50 μm, more preferably more than 100 μm, and further preferably more than 150 μm. The upper limit of the thickness of the visual recognition side adhesive layer is not particularly limited, and is preferably less than 10 mm. When the thickness of the adhesive layer exceeds 10 mm, ultraviolet rays are difficult to transmit, the polymerization of the monomer components takes time, and sometimes the productivity is poor, so it is not preferred.

The gel fraction of the visual recognition side adhesive layer of the present invention is not particularly limited, but is preferably 35% or more, more preferably 50% or more, further preferably 75% or more, and particularly preferably 85% or more. When the gel fraction of the visual recognition side adhesive layer is small, the cohesive force is poor, and when it is too large, the adhesive force is sometimes poor.

The transmission b* value of the visual recognition side adhesive layer is not particularly limited, but is preferably 3.0 or less, more preferably 1.5 or less, and further preferably 0.5 or less. The b* value refers to the b* value (chromaticity) in the L*a*b* colorimetric system according to JIS Z8729, and can be measured, for example, using a spectrophotometer (product name: U4100, manufactured by Hitachi High-Technologies Corporation).

The transmittance of the above-mentioned visual recognition side adhesive layer at a wavelength of 380nm is preferably 9% or less, more preferably 7% or less, further preferably 5% or less, and particularly preferably 3% or less. When the transmittance at a wavelength of 380nm is within the above range, incident ultraviolet rays can be more highly blocked, thereby significantly suppressing the degradation of optical components including liquid crystal panels, organic EL elements, polarizers, etc.

The transmittance of the visual recognition side adhesive layer at a wavelength of 400 nm is preferably 60% or more, preferably 70% or more, and more preferably 75% or more. When the transmittance at a wavelength of 400 nm is within the above range, the incident visible light can be fully transmitted, and sufficient visual recognition can be ensured in the image display device, so it is preferred.

In addition, when the polarizing film with an adhesive layer of the present invention is used in an organic EL display device (OLED), the transmittance of the above-mentioned visual recognition side adhesive layer at a wavelength of 420nm is preferably 75% or less, more preferably 50% or less, and further preferably 40% or less. It is preferred from the viewpoint of protecting the light-emitting element of the OLED that the transmittance at a wavelength of 420nm is within the above range.

When the visual recognition side pressure-sensitive adhesive layer is exposed, the pressure-sensitive adhesive layer may be protected by a release film until it is actually used. The release film may be used directly as a separator of the pressure-sensitive adhesive layer-attached polarizing film, which can simplify the process.

(2) Image display side adhesive layer

There are no particular restrictions on the adhesive layer on the image display side surface of the polarizing film (image display side adhesive layer). An adhesive layer of the same acrylic adhesive composition as described in detail in the visual recognition side adhesive layer can be used, and various commonly used adhesive layers can be used.

In the formation of the adhesive layer on the side surface of the image display part, suitable adhesive can be used, and there is no particular restriction on its kind. As adhesive, rubber adhesive, acrylic adhesive, polysiloxane adhesive, polyurethane adhesive, vinyl alkyl ether adhesive, polyvinyl alcohol adhesive, polyvinyl pyrrolidone adhesive, polyacrylamide adhesive, cellulose adhesive etc. can be listed. In these adhesives, from the excellent aspects such as excellent optical transparency, demonstrating suitable adhesion, cohesion and tackiness, weather resistance and heat resistance, it is preferred to use acrylic adhesive.

The acrylic adhesive uses an acrylic polymer as a base polymer, and the acrylic polymer uses a monomer unit of an alkyl (meth)acrylate as a main skeleton. As the alkyl (meth)acrylate constituting the main skeleton of the acrylic polymer, the same alkyl (meth)acrylate used in the acrylic adhesive composition forming the visual recognition side adhesive layer can be cited. In addition, as comonomers and their ratios, the same comonomers and their ratios as those used in the above-mentioned acrylic adhesive composition can also be cited.

The above-mentioned acrylic polymer can be manufactured by various known methods, for example, free radical polymerization methods such as bulk polymerization, solution polymerization, and suspension polymerization can be appropriately selected. As free radical polymerization initiators, various known free radical polymerization initiators of azo and peroxide can be used. The reaction temperature is usually set to about 50°C to about 80°C, and the reaction time is set to 1 hour to 8 hours. In addition, solution polymerization is preferred in the above-mentioned manufacturing method, and ethyl acetate, toluene, etc. are usually used as solvents for acrylic polymers. The solution concentration is usually set to about 20% by weight to about 80% by weight.

In addition, the above-mentioned adhesive can be made into an adhesive composition containing a crosslinking agent. As the crosslinking agent, the above-mentioned crosslinking agents can also be listed, and isocyanate crosslinking agents are particularly preferred. There is no particular restriction on the mixing ratio of the acrylic polymer and the crosslinking agent. Generally, relative to 100 parts by weight of the acrylic polymer (solid content), the crosslinking agent (solid content) is preferably about 0.001 parts by weight to about 20 parts by weight, and more preferably about 0.01 parts by weight to about 15 parts by weight.

In addition, various additives such as tackifiers, plasticizers, fillers including glass fibers, glass beads, metal powders, other inorganic powders, pigments, colorants, fillers, antioxidants, ultraviolet absorbers, and silane coupling agents may be appropriately used in the above-mentioned adhesives as needed and within the scope of not deviating from the purpose of the present invention. In addition, an adhesive layer containing microparticles and showing light diffusion properties may also be made. As for the silane coupling agent, the above-mentioned silane coupling agent may be cited.

The image display side adhesive layer is formed by applying the above-mentioned adhesive composition to various substrates such as a polarizing film or a release film and drying. When the adhesive layer is formed on various substrates such as a release film, the adhesive layer can be transferred by laminating to the polarizing film. The coating method of the above-mentioned adhesive and the above-mentioned various substrates can be the same as the coating method of the above-mentioned acrylic adhesive composition and various substrates.

In addition, in the above-mentioned coating process, the coating amount is controlled in such a way that the formed adhesive layer reaches a predetermined thickness (thickness after drying). The thickness of the adhesive layer on the image display side is not particularly limited, and is preferably less than 1/2 of the thickness of the adhesive layer on the visual recognition side, preferably less than 1/5, and preferably less than 1/10. Specifically, the thickness of the adhesive layer on the image display side is preferably about 1 μm to about 100 μm, more preferably about 3 μm to about 50 μm, and further preferably about 5 μm to about 30 μm.

When forming the pressure-sensitive adhesive layer on the image display part side, the applied pressure-sensitive adhesive is dried. The drying temperature and drying time are not particularly limited and can be appropriately set, and are preferably set at about 80° C. to about 200° C. for 0.5 to 10 minutes, for example.

When the pressure-sensitive adhesive layer on the image display side is exposed, the pressure-sensitive adhesive layer may be protected by a release film until it is actually used. The release film may be directly used as a separator for the pressure-sensitive adhesive layer-attached polarizing film, thereby simplifying the process.

(3) Polarizing film

The polarizing film used in the present invention is characterized by comprising a polarizer and transparent protective films on both surfaces of the polarizer, wherein the transparent protective film on the viewing side of the polarizer (viewing side transparent protective film) has a transmittance of less than 6% at a wavelength of 380 nm.

(3-1) Transparent protective film on the visual recognition side

The visual recognition side transparent protective film used in the present invention has a transmittance of less than 6% at a wavelength of 380nm, preferably less than 3%, more preferably less than 2%, and further preferably less than 1%. In the present invention, a visual recognition side transparent protective film having a transmittance of less than 6% at a wavelength of 380nm is combined with the above-mentioned visual recognition side adhesive layer (containing an ultraviolet absorber) to achieve a higher ultraviolet absorption capacity. In addition, there is no particular restriction on the lower limit of the transmittance of the visual recognition side transparent protective film at a wavelength of 380nm. From the perspective of ultraviolet absorption function, the smaller the transmittance, the more preferred.

As the material for forming the transparent protective film on the visual recognition side, it is preferred to have excellent transparency, mechanical strength, thermal stability, moisture barrier, isotropy, etc. For example, polyester polymers such as polyethylene terephthalate or polyethylene naphthalate, cellulose polymers such as diacetyl cellulose or triacetyl cellulose, acrylic polymers such as polymethyl methacrylate, styrene polymers such as polystyrene or acrylonitrile-styrene copolymer (AS resin), polycarbonate polymers, etc. In addition, polyethylene, polypropylene, polyolefins with cyclic or norbornene structures, polyolefin polymers such as ethylene-propylene copolymers, vinyl chloride polymers, amide polymers such as nylon or aromatic polyamide, imide polymers, sulfone polymers, polyethersulfone polymers, polyetheretherketone polymers, polyphenylene sulfide polymers, vinyl alcohol polymers, vinylidene chloride polymers, vinyl butyral polymers, arylate polymers, polyoxymethylene polymers, epoxy polymers or blends of the above polymers can also be cited as examples of polymers forming the above transparent protective film. The transparent protective film may also be formed in the form of a cured layer of a thermosetting or ultraviolet curing resin such as acrylic, polyurethane, acrylic polyurethane, epoxy, polysiloxane, etc. Among them, as the visual recognition side transparent protective film, at least one film selected from the group consisting of triacetyl cellulose film, acrylic film (film using acrylic polymer), polyethylene terephthalate film and polyolefin film having a cyclic or norbornene structure is preferred, and triacetyl cellulose film is more preferred.

The thickness of the visual recognition side transparent protective film is not particularly limited, and is preferably 40 μm or less, more preferably 35 μm or less, and further preferably 30 μm or less. In addition, the lower limit of the thickness of the visual recognition side transparent protective film is not particularly limited, and is preferably 1 μm or more. When the thickness of the visual recognition side transparent protective film is within the above range, the polarizing film can be fully thinned without damaging the protective function of the polarizer, so it is preferred.

The polarizer and the visual recognition side protective film described later are preferably adhered via an aqueous adhesive or the like. As aqueous adhesives, isocyanate adhesives, polyvinyl alcohol adhesives, gelatin adhesives, vinyl latexes, aqueous polyurethanes, aqueous polyesters, etc. can be exemplified. In addition to the above, as adhesives for the polarizer and the visual recognition side transparent protective film, ultraviolet curing adhesives, electron beam curing adhesives, etc. can be cited. Electron beam curing polarizing film adhesives show suitable adhesion to the above-mentioned various visual recognition side transparent protective films. In addition, the adhesive used in the present invention can contain a metal compound filler.

The surface of the viewing-side transparent protective film to which the polarizer is not adhered may be subjected to a hard coating or anti-reflection treatment, or treatment for the purpose of anti-sticking, diffusion, or anti-glare.

(3-2) Polarizer

There is no particular limitation on the polarizer, and various polarizers can be used. As polarizers, for example, a polarizer obtained by uniaxially stretching a hydrophilic polymer film such as a polyvinyl alcohol film, a partially formylated polyvinyl alcohol film, and a partially saponified film of an ethylene-vinyl acetate copolymer after adsorbing a dichroic substance such as iodine or a dichroic dye, a polyolefin oriented film such as a dehydrated product of polyvinyl alcohol or a dehydrochlorinated product of polyvinyl chloride, etc., can be cited. Among them, a polarizer containing a polyvinyl alcohol film and a dichroic substance such as iodine is preferred. The thickness of these polarizers is not particularly limited, and is usually about 5 μm to about 80 μm.

The polarizer obtained by dyeing the polyvinyl alcohol film with iodine and uniaxially stretching can be made, for example, by immersing polyvinyl alcohol in an aqueous solution of iodine for dyeing and stretching to 3 to 7 times the original length. It can also be immersed in an aqueous solution of potassium iodide, etc., which can contain boric acid or zinc sulfate, zinc chloride, etc. as needed. Further, the polyvinyl alcohol film can be immersed in water and washed with water before dyeing as needed. The stains and anti-blocking agents on the surface of the polyvinyl alcohol film can be washed away by washing the polyvinyl alcohol film with water. In addition, it also has the effect of preventing uneven dyeing by swelling the polyvinyl alcohol film. Stretching can be carried out after dyeing with iodine, or it can be stretched while dyeing, and it can also be dyed with iodine after stretching. It can be stretched in an aqueous solution or a water bath of boric acid, potassium iodide, etc.

In addition, in the present invention, a thin polarizer with a thickness of 10 μm or less can also be used. From the perspective of thinning, the thickness is preferably 1 μm to 7 μm. Such a thin polarizer has less uneven thickness, excellent visual recognition, and less dimensional change, so it is excellent in durability. In addition, it is preferred from the perspective of achieving thinning as a polarizing film.

As thin polarizers, representative examples include thin polarizing films described in Japanese Patent Application Publication No. 51-069644, Japanese Patent Application Publication No. 2000-338329, International Publication No. 2010/100917, International Publication No. 2010/100917, Japanese Patent No. 4751481, and Japanese Patent Application Publication No. 2012-073563. These thin polarizing films can be obtained by a manufacturing method including a step of stretching a polyvinyl alcohol resin (hereinafter also referred to as a PVA resin) layer and a stretching resin substrate in a laminated state and a step of dyeing. With this manufacturing method, even if the PVA resin layer is thin, it can be stretched without problems such as breakage caused by stretching by being supported by the stretching resin substrate.

As for the above-mentioned thin polarizing film, in the manufacturing method including the steps of stretching and dyeing in the state of a laminate, in terms of being able to stretch at a high ratio to improve the polarization performance, a polarizing film obtained by a manufacturing method including a step of stretching in an aqueous boric acid solution as described in International Publication No. 2010/100917, International Publication No. 2010/100917, or Japanese Patent No. 4751481 and Japanese Patent Gazette No. 2012-073563 is preferred, and a polarizing film obtained by a manufacturing method including a step of auxiliary stretching in air before stretching in an aqueous boric acid solution as described in Japanese Patent No. 4751481 and Japanese Patent Gazette No. 2012-073563 is particularly preferred.

(3-3) Image display side transparent protective film

As for the image display side transparent protective film, conventionally used transparent protective films can be appropriately used. Specifically, a transparent protective film formed of a material having excellent transparency, mechanical strength, thermal stability, moisture barrier properties, isotropy, etc. is preferred, for example, polyester polymers such as polyethylene terephthalate or polyethylene naphthalate, cellulose polymers such as diacetyl cellulose or triacetyl cellulose, acrylic polymers such as polymethyl methacrylate, styrene polymers such as polystyrene or acrylonitrile-styrene copolymer (AS resin), polycarbonate polymers, etc. can be cited. In addition, examples of polymers forming the transparent protective film include polyethylene, polypropylene, polyolefins having a cyclic or norbornene structure, polyolefin polymers such as ethylene-propylene copolymers, vinyl chloride polymers, amide polymers such as nylon or aromatic polyamide, imide polymers, sulfone polymers, polyethersulfone polymers, polyetheretherketone polymers, polyphenylene sulfide polymers, vinyl alcohol polymers, vinylidene chloride polymers, vinyl butyral polymers, arylate polymers, polyoxymethylene polymers, epoxy polymers, or blends of the above polymers. The transparent protective film can also be formed in the form of a cured layer of a thermosetting or ultraviolet curing resin such as acrylic, polyurethane, acrylic polyurethane, epoxy, or polysiloxane.

The thickness of the image display portion side protective film can be appropriately determined, and is generally about 1 μm to 500 μm in view of strength, workability such as handling properties, and thin film properties.

The polarizer and the image display unit side transparent protective film are usually adhered to each other via a water-based adhesive or the like. Examples of the water-based adhesive include the above-mentioned water-based adhesives.

The surface of the image display portion side transparent protective film which is not bonded to the polarizer may be subjected to a hard coating or anti-reflection treatment, or treatment for the purpose of anti-sticking, diffusion or anti-glare.

2. Image display device

The image display device of the present invention is characterized by using the pressure-sensitive adhesive layer-attached polarizing film of the present invention.

As an example of a specific structure of an image display device, for example, an image display device can be obtained by stacking the layers in the following order as shown in FIGS. 2 to 4: protective glass or protective plastic 6/visual recognition side adhesive layer 2a/visual recognition side transparent protective film 3a/polarizer 4/image display side transparent protective film 3b/image display side adhesive layer 2b/liquid crystal display device (LCD) or organic EL display device (OLED) 7 (FIG. 2); protective glass or protective plastic 6/adhesive layer 8a/sensor layer 9/visual recognition side adhesive layer 2a/visual recognition side transparent Protective film 3a/polarizer 4/transparent protective film 3b on image display side/adhesive layer 2b on image display side/liquid crystal display device (LCD) or organic EL display device (OLED) 7 (Figure 3); protective glass or protective plastic 6/adhesive layer 8a/sensor layer 9/adhesive layer 8b/sensor layer 9/visual recognition side adhesive layer 2a/visual recognition side transparent protective film 3a/polarizer 4/image display side transparent protective film 3b/image display side adhesive layer 2b/liquid crystal display device (LCD) or organic EL display device (OLED) 7 (Figure 4). The polarizing film 1 with adhesive layer of the present invention refers to the part of "visual recognition side adhesive layer 2a/visual recognition side transparent protective film 3a/polarizer 4/image display side transparent protective film 3b/image display side adhesive layer 2b" in the above-mentioned structure, and it can also include phase difference film, etc. in addition to them. In addition, when a phase difference film is included, specifically, the phase difference film can be laminated between the image display unit side adhesive layer 2b and the liquid crystal display device (LCD) or organic EL display device (OLED) 7 via an adhesive layer. In addition, an adhesive layer and/or an adhesive layer can be appropriately used in the lamination of each layer.

As image display devices, liquid crystal display devices, organic EL (electroluminescence) display devices, PDP (plasma display panel), electronic paper, etc. can be listed. Among them, liquid crystal display devices, organic EL (electroluminescence) display devices, etc. having the above-mentioned structures are preferred.

Example

The present invention will be described in detail below by way of examples, but the present invention is not limited to these examples. It should be noted that the parts and % in each example are based on weight.

Production Example 1 (Production of Acrylic Pressure-Sensitive Adhesive Composition (a-1))

A monomer mixture consisting of 78 parts by weight of 2-ethylhexyl acrylate (2EHA), 18 parts by weight of N-vinyl-2-pyrrolidone (NVP) and 4 parts by weight of 2-hydroxyethyl acrylate (HEA) was mixed with 0.035 parts by weight of 1-hydroxycyclohexyl phenyl ketone (trade name: IRGACURE 184, having an absorption band at a wavelength of 200 nm to 370 nm, manufactured by BASF) as a photopolymerization initiator and 0.035 parts by weight of 2,2-dimethoxy-1,2-diphenylethane-1-one (trade name: IRGACURE 651, having an absorption band at a wavelength of 200 nm to 380 nm, manufactured by BASF), and then irradiated with ultraviolet rays until the viscosity (measurement conditions: BH viscometer No. 5 rotor, 10 rpm, measurement temperature 30°C) reached about 20 Pa·s, thereby obtaining a prepolymer composition (polymerization rate: 8%) in which part of the above monomer components were polymerized. Next, 0.15 parts by weight of hexanediol diacrylate (HDDA) and 0.3 parts by weight of a silane coupling agent (trade name: KBM-403, manufactured by Shin-Etsu Chemical Co., Ltd.) were added to the prepolymer composition and mixed to obtain an acrylic pressure-sensitive adhesive composition (a-1).

Production Example 2 (Production of Acrylic Pressure-Sensitive Adhesive Composition (a-2))

0.2 parts by weight of azobisisobutyronitrile (AIBN) and 233 parts by weight of ethyl acetate were added as polymerization initiators to a monomer mixture consisting of 72 parts by weight of 2-ethylhexyl acrylate (2EHA), 1 part by weight of methyl methacrylate (MMA), 12 parts by weight of N-vinyl pyrrolidone (NVP), and 15 parts by weight of hydroxyethyl acrylate (HEA), and then reacted at 60° C. for 7 hours under a nitrogen atmosphere to obtain a partial polymer obtained by polymerizing a part of the above monomer components. Subsequently, 0.3 parts by weight of a silane coupling agent (trade name: KBM-403, manufactured by Shin-Etsu Chemical Co., Ltd.) and 0.21 parts by weight of an isocyanate crosslinking agent (trade name: TAKENATE D110N, manufactured by Mitsui Chemicals, Inc.) were added to the partial polymer to obtain an acrylic adhesive composition (a-2).

Production Example 3 (Production of Image Display Section Side Pressure-Sensitive Adhesive Layer (B-1))

In a separable flask equipped with a thermometer, a stirrer, a reflux condenser and a nitrogen inlet tube, 95 parts by weight of butyl acrylate, 5 parts by weight of acrylic acid, 0.2 parts by weight of azobisisobutyronitrile as a polymerization initiator and 233 parts by weight of ethyl acetate were added, and then nitrogen was introduced and nitrogen replacement was performed for about 1 hour while stirring. Then, the flask was heated to 60°C and reacted for 7 hours to obtain an acrylic polymer with a weight average molecular weight (Mw) of 1.1 million.

0.8 parts by weight of trimethylolpropane toluene diisocyanate (trade name: CORONATE L, manufactured by Nippon Polyurethane Industries, Ltd.) and 0.1 parts by weight of a silane coupling agent (trade name: KBM-403, manufactured by Shin-Etsu Chemical Co., Ltd.) were added to the acrylic polymer solution (solid content was 100 parts by weight) as an isocyanate crosslinking agent to prepare an adhesive composition (solution).

The obtained adhesive composition solution was applied to a separator (polyethylene terephthalate film with a release treatment on the surface) with a thickness of 38 μm so that the thickness after drying was 12 μm, and the solvent was removed by drying at 100° C. for 3 minutes to obtain an adhesive layer. Then, the adhesive layer was heated at 50° C. for 48 hours for cross-linking treatment. Hereinafter, the adhesive layer is referred to as the “image display side adhesive layer (B-1)”.

Production Example 4 (Production of Image Display Section Side Pressure-Sensitive Adhesive Layer (B-2))

The adhesive composition solution obtained in Manufacturing Example 3 was applied to a 38 μm thick spacer (polyethylene terephthalate film with a release treatment on the surface) in such a manner that the thickness after drying was 15 μm, and the solvent was removed at 100° C. for 3 minutes to obtain an adhesive layer. Then, the adhesive layer was heated at 50° C. for 48 hours for cross-linking treatment. Hereinafter, the adhesive layer is referred to as the “image display side adhesive layer (B-2)”.

Example 1

(Manufacturing of Adhesive Composition with Ultraviolet Absorption Function)

To the obtained acrylic adhesive composition (a-1), 1.4 parts by weight of 2,4-bis[{4-(4-ethylhexyloxy)-4-hydroxy}phenyl]-6-(4-methoxyphenyl)-1,3,5-triazine (trade name: Tinosorb S, "ultraviolet absorber 1" in Tables 1 and 2, manufactured by BASF Japan Co., Ltd.) dissolved in butyl acrylate so as to have a solid content of 15% and 0.2 parts by weight of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (trade name: IRGACURE 819, having an absorption band at a wavelength of 200 nm to 450 nm, manufactured by BASF Japan Co., Ltd.) were added and stirred to obtain an adhesive composition having ultraviolet absorbing function.

The adhesive composition with ultraviolet absorption function was applied to the release film of the release film so that the thickness of the adhesive layer after formation was 150 μm, and then the release film was attached to the surface of the adhesive composition layer. Then, ultraviolet irradiation was performed under the conditions of illumination: 6.5 mW/cm ² , light quantity: 1500 mJ/cm ² , and peak wavelength: 350 nm to photocure the adhesive composition layer, thereby forming a visual recognition side adhesive layer (A-1).

(Manufacture of polarizing film (P-1))

A polarizing film (P-1) was prepared by laminating a 25 μm thick cycloolefin polymer (COP) film on the visual recognition side of a polarizer including a 5 μm thick stretched polyvinyl alcohol film impregnated with iodine using a polyvinyl alcohol adhesive, and laminating a 20 μm thick acrylic film on the image display side of the polarizer using a polyvinyl alcohol adhesive. The polarization degree of the polarizing film was 99.995.

(Manufacture of Polarizing Film with Adhesive Layer)

A visual recognition side adhesive layer (A-1) is laminated on the visual recognition side of the above-mentioned polarizing film (P-1) (i.e., the surface of a cycloolefin polymer (COP) film with a thickness of 25 μm). An image display side adhesive layer (B-1) is laminated on the image display side surface of the above-mentioned polarizing film (P-1) (i.e., the surface of an acrylic film with a thickness of 20 μm), and a phase difference film (thickness: 56 μm, material: polycarbonate) and an image display side adhesive layer (B-2) are further laminated to form a polarizing film with an adhesive layer. The obtained polarizing film with an adhesive layer has a structure of visual recognition side adhesive layer (A-1)/polarizing film (P-1)/image display side adhesive layer (B-1)/phase difference film/image display side adhesive layer (B-2).

Embodiment 2-3

A pressure-sensitive adhesive layer-attached polarizing film was formed in the same manner as in Example 1 except that the type of the acrylic pressure-sensitive adhesive composition, the amount of the ultraviolet absorber 1 added, and the thickness of the pressure-sensitive adhesive layer on the viewing side after formation were as shown in Table 1.

Example 4

A pressure-sensitive adhesive-attached polarizing film was formed in the same manner as in Example 1, except that the pressure-sensitive adhesive layer on the visual recognition side was changed from the pressure-sensitive adhesive layer (A-1) on the visual recognition side to the pressure-sensitive adhesive layer (A-2) obtained below.

(Manufacturing of Visual Recognition Side Pressure-Sensitive Adhesive Layer (A-2))

To the acrylic adhesive composition (a-2) obtained in Production Example 2, 1.4 parts by weight of 2,4-bis[{4-(4-ethylhexyloxy)-4-hydroxy}phenyl]-6-(4-methoxyphenyl)-1,3,5-triazine (trade name: Tinosorb S, manufactured by BASF Japan Ltd.) dissolved in ethyl acetate was added so as to have a solid content of 15%, and the mixture was stirred to obtain an adhesive composition with ultraviolet absorbing function.

The above-mentioned adhesive composition with ultraviolet absorption function is applied to the release film of the release film in a manner so that the thickness of the adhesive layer after formation is 150 μm, dried at 60° C. for 2 minutes and at 120° C. for 2 minutes, and then the release film is attached to form a visual recognition side adhesive layer (A-2).

Embodiment 5-6

A pressure-sensitive adhesive layer-attached polarizing film was formed in the same manner as in Example 4 except that the thickness of the pressure-sensitive adhesive layer on the viewing side and the pressure-sensitive adhesive layer on the image display side were as shown in Table 1.

Example 7

(Manufacturing of Visual Recognition Side Pressure-Sensitive Adhesive Layer (A-3))

To the acrylic adhesive composition (a-1) obtained in Production Example 1, 0.7 parts by weight of 2,4-bis[{4-(4-ethylhexyloxy)-4-hydroxy}phenyl]-6-(4-methoxyphenyl)-1,3,5-triazine (trade name: Tinosorb S, manufactured by BASF Japan) dissolved in butyl acrylate so as to have a solid content of 15%, 0.2 parts by weight of Solvent Yellow 163 (KPPlast Yellow MK, "ultraviolet absorber 2" in Table 2, manufactured by Kiwa Chemical Industry Co., Ltd.), and 0.2 parts by weight of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (trade name: IRGACURE 819, having an absorption band at a wavelength of 200 nm to 450 nm, manufactured by BASF Japan) were added and stirred to obtain an adhesive composition having an ultraviolet absorbing function.

The adhesive composition with ultraviolet absorption function was applied to the release film of the release film so that the thickness of the adhesive layer after formation was 150 μm, and then the release film was attached to the surface of the adhesive composition layer. Then, ultraviolet irradiation was performed under the conditions of illumination: 6.5 mW/cm ² , light quantity: 3000 mJ/cm ² , and peak wavelength: 350 nm to photocure the adhesive composition layer, thereby forming a visual recognition side adhesive layer (A-3).

A pressure-sensitive adhesive-attached polarizing film was formed in the same manner as in Example 1, except that the pressure-sensitive adhesive layer on the viewing side was changed from the pressure-sensitive adhesive layer (A-1) on the viewing side to the pressure-sensitive adhesive layer (A-3) obtained above.

Comparative Example 1

A pressure-sensitive adhesive layer-attached polarizing film was formed in the same manner as in Example 1, except that the pressure-sensitive adhesive layer (A-1) on the viewing side, the phase difference film, and the pressure-sensitive adhesive layer (B-2) on the image display unit side were not formed.

Comparative Example 2

A pressure-sensitive adhesive layer-attached polarizing film was formed in the same manner as in Example 1, except that the pressure-sensitive adhesive layer (A-1) on the viewing side was not formed.

Comparative Examples 3 and 4

A pressure-sensitive adhesive-attached polarizing film was formed by the same method as in Examples 1 and 4, except that no ultraviolet absorber was added to the pressure-sensitive adhesive layers (A-1) and (A-2) on the viewing side.

Comparative Example 5

(Manufacture of polarizing film (P-2))

A 25 μm thick triacetyl cellulose film was bonded to the visual recognition side of a polarizer including a 12 μm thick stretched polyvinyl alcohol film impregnated with iodine using a polyvinyl alcohol adhesive, and a 20 μm thick acrylic film was laminated to the image display side of the polarizer using a polyvinyl alcohol adhesive to prepare a polarizing film (P-2). The polarization degree of the polarizing film was 99.995.

A polarizing film with an adhesive was formed in the same manner as in Example 2, except that the polarizing film (P-1) in Example 2 was changed to the above-mentioned polarizing film (P-2).

The following evaluations were performed on the obtained pressure-sensitive adhesive layer and pressure-sensitive adhesive layer-attached polarizing film.

<Polymerization rate>

The release film of the visual recognition side adhesive layer obtained in the embodiment and the comparative example is peeled off, and only the visual recognition side adhesive layer is placed on the aluminum dish whose weight is measured. The weight of (aluminum dish + visual recognition side adhesive layer) is measured to obtain the weight of the adhesive layer before drying. Dry at 130°C for 2 hours, then cool at room temperature for about 20 minutes, and then measure the weight of (aluminum dish + adhesive) again to obtain the weight of the visual recognition side adhesive layer after drying. The polymerization rate is calculated using the following calculation formula.

<Gel Fraction>

About 0.1 g of the adhesive layer on the visual recognition side obtained in the examples and comparative examples was separated and taken, and wrapped in a porous tetrafluoroethylene sheet (trade name: NTF1122, manufactured by Nitto Denko Corporation) with an average pore size of 0.2 μm, and then tied with a kite string, and the weight at this time (Zg) was measured, and this weight was taken as the weight before immersion. It should be noted that the weight before immersion is the total weight of the adhesive layer on the visual recognition side (the adhesive layer collected and selected above), the tetrafluoroethylene sheet and the kite string. In addition, the total weight (Yg) of the tetrafluoroethylene sheet and the kite string was also measured. Next, the material (referred to as "sample") wrapped with the adhesive layer on the visual recognition side with a tetrafluoroethylene sheet and tied with a kite string was placed in a 50 mL container filled with ethyl acetate and left to stand at 23°C for 7 days. Then, the sample (after ethyl acetate treatment) was taken out of the container, moved to an aluminum cup, dried in a dryer at 130°C for 2 hours to remove the ethyl acetate, and then the weight (Xg) was measured, and this weight was taken as the weight after immersion. The gel fraction was calculated by the following formula.

Gel fraction (weight %) = (X-Y)/(Z-Y) × 100

<Measurement of transmittance and b* value of adhesive layer on the visual recognition side>

The release film of the visual recognition side adhesive layer obtained in the examples and comparative examples was peeled off, and the visual recognition side adhesive layer was mounted on a measuring fixture and measured using a spectrophotometer (product name: U4100, manufactured by Hitachi High-Technologies Co., Ltd.). Regarding the transmittance, the transmittance at wavelengths of 380nm, 400nm, and 420nm was measured (however, for a wavelength of 420nm, it was measured only in Examples 2 and 7).

<Residual Stress>

Cut out 30mm width and 50mm length from the visual recognition side adhesive layer obtained from the embodiment and the comparative example, and make it into a cylindrical shape to make a test piece. It is set with a chuck spacing of 20mm, and the test piece is stretched 60mm (300%) at a tensile speed of 200mm/minute (the chuck spacing after stretching is 80mm). Fixed (maintained) 300 seconds at the position of stretching 60mm, the stress value (N) after 300 seconds is measured. Utilize the following formula to obtain residual stress.

Residual stress after 300 seconds = Stress value after 300 seconds (N) / (4 × thickness of test piece / 10)

<Optical reliability>

The COP film of the polarizing film (P-1) used in Example 1 was bonded with the visual recognition side adhesive layer obtained in Examples 1 to 7 and Comparative Examples 3 to 5. Furthermore, a 56 μm phase difference film (manufactured by Nitto Denko Corporation) with a 15 μm adhesive was bonded to the opposite side (acrylic film side) of the polarizing film to which the visual recognition side adhesive layer was bonded. Both sides of the sample were bonded to glass (trade name: S200200, thickness: 1.3 mm, size: 45 mm × 50 mm, manufactured by Matsunami Glass Industries, Ltd.) and subjected to a 15-minute autoclave treatment (air pressure: 0.5 MPa, temperature: 50°C). Then, the sample was subjected to the following various reliability conditions, and the transmittance was measured using a spectroscopic transmittance meter (product name: DOT-3, manufactured by Murakami Color Technology Research Institute Co., Ltd.). The transmittance change compared to the initial value was calculated. The evaluation was performed according to the following evaluation criteria.

(Various reliability conditions)

(Condition 1) 85°C x 500 hours

(Condition 2) 60°C, 95% x 500 hours

(Condition 3) Heat shock (HS) (-40℃～85℃) × 300 cycles

(Condition 4) UV irradiation × 100 hours, illumination: 500 W/cm ² (300 nm to 700 nm), ambient temperature: 60°C to 65°C, ambient humidity: 50%

(Condition 5) Xenon lamp irradiation × 300 hours, illumination: 2.40 W/cm ² (420 nm), ambient temperature: 50°C, ambient humidity: 30%

(Evaluation Criteria)

○: The amount of change in transmittance is 2.0% or less.

Δ: The transmittance change amount exceeds 2.0% and is 3.0% or less.

×: The transmittance change amount exceeds 3.0%.

<Glue stains, dimensional accuracy, and end appearance>

The polarizing film with adhesive layer obtained in the examples and comparative examples was cut into a size of 25 mm × 30 mm using a super cutter. Then, the four sides of the cut piece were cut by 0.05 mm using an end processing machine (manufactured by MEGARO TECHNICA Co., Ltd.) to prepare a sample. The side of the sample was visually checked for adhesive stains to confirm the presence or absence of adhesive stains. The dimensional accuracy and end appearance were observed using an optical microscope and evaluated according to the following evaluation criteria.

(Dimensional accuracy)

○: within ±0.3mm

×: more than ±0.3mm

(End appearance)

○: No stickiness at the edge when touched

×: The edge is sticky when touched by hand

<Curl Measurement>

A sample cut into 50 mm×40 mm was placed on a flat table, and the curl was measured using a feeler gauge.

(curly)

○: within ±1.0mm

△: greater than ±1.0mm and within ±2.0mm

×: greater than ±2.0mm

In Table 1, P-1 represents a polarizing film (P-1), P-2 represents a polarizing film (P-2), a-1 represents the acrylic adhesive composition (a-1) obtained in Manufacturing Example 1, a-2 represents the acrylic adhesive composition (a-2) obtained in Manufacturing Example 2, UV absorber 1 represents 2,4-bis[{4-(4-ethylhexyloxy)-4-hydroxy}phenyl]-6-(4-methoxyphenyl)-1,3,5-triazine (trade name: Tinosorb S, manufactured by BASF Japan Co., Ltd.), UV absorber 2 represents Solvent Yellow 163 (KP PlastYellow MK, manufactured by Kiwa Chemical Industry Co., Ltd.), B-1 represents the image display side adhesive layer (B-1) obtained in Manufacturing Example 3, and B-2 represents the image display side adhesive layer (B-2) obtained in Manufacturing Example 4.

Reference numerals

1 Polarizing film with adhesive layer

2a Visual recognition side adhesive layer

2b Image display side adhesive layer

3a Transparent protective film on the visual identification side

3b Transparent protective film on the image display side

4 Polarizer

5. Polarizing film

6 Protective glass or protective plastic

7 Liquid crystal display device (LCD) or organic EL display device (OLED)

8a, 8b Adhesive layer

9 Sensor Layer

Claims (9)

1. A polarizing film with an adhesive layer for use in an image display device at a position closer to the viewing side than an image display portion, characterized in that,

the adhesive layer-equipped polarizing film has a polarizing film and adhesive layers on both sides of the polarizing film,

the polarizing film has a polarizer and transparent protective films on both sides of the polarizer,

the transmittance of the transparent protective film on the visual recognition side of the polarizer at 380nm is less than 6%,

the adhesive layer on the viewing side of the polarizing film has an ultraviolet absorbing function,

the adhesive layer on the visual recognition side of the polarizing film contains one or more of triazine ultraviolet absorbent, benzotriazole ultraviolet absorbent, benzophenone ultraviolet absorbent, hydroxybenzophenone ultraviolet absorbent, salicylate ultraviolet absorbent and cyanoacrylate ultraviolet absorbent and dye as ultraviolet absorbent, and

The transparent protective film on the viewing side of the polarizer is at least one film selected from the group consisting of a triacetyl cellulose film and a polyolefin film having a cyclic or norbornene structure.

2. The adhesive layer-carrying polarizing film according to claim 1, wherein the transparent protective film on the viewing side of the polarizer has a thickness of 40 μm or less.

3. The polarizing film with an adhesive layer according to claim 1, wherein the thickness of the adhesive layer on the viewing side of the polarizing film is 2 times or more the thickness of the adhesive layer on the image display portion side of the polarizing film.

4. The polarizing film with an adhesive layer according to claim 1, wherein the adhesive layer on the viewing side of the polarizing film has a transmittance of 9% or less at a wavelength of 380nm and a transmittance of 60% or more at a wavelength of 400 nm.

5. The polarizing film with an adhesive layer according to claim 1, wherein the adhesive layer on the viewing side of the polarizing film has a transmittance of 9% or less at a wavelength of 380nm and a transmittance of 75% or less at a wavelength of 420 nm.

6. The adhesive layer-carrying polarizing film according to claim 1, wherein the b-x value of the adhesive layer on the viewing side of the polarizing film is 3.0 or less.

7. The polarizing film with an adhesive layer according to claim 1, wherein the adhesive layer on the viewing side of the polarizing film contains an acrylic polymer as a base polymer.

8. The adhesive layer-attached polarizing film according to any one of claims 1 to 7, wherein the adhesive layer-attached polarizing film is used for a liquid crystal display device or an organic EL display device.

9. An image display device using the polarizing film with an adhesive layer according to any one of claims 1 to 8 at a position closer to the viewing side than the image display portion.

Images