JP7685664B2 - Polarizing film with optically functional layer and liquid crystal display device - Google Patents

Description

The present invention relates to a polarizing film with an optical functional layer, which has an optical functional layer having a dye and a polarizing film having a polyvinyl alcohol-based polarizer. The polarizing film with an optical functional layer can be used alone or as an optical film laminated with the optical functional layer to form an image display device such as a liquid crystal display device (LCD) or an organic EL display device.

In image display devices and the like, it is essential to place polarizing elements on both sides of the liquid crystal cell due to the image formation method, and polarizing films are generally attached to them. When attaching the polarizing film to the liquid crystal cell, an adhesive is usually used. Also, in order to reduce light loss, the polarizing film and the liquid crystal cell are usually bonded together by using an adhesive to bond the respective materials. In such cases, an adhesive layer-attached polarizing film is generally used, which has the advantage of not requiring a drying process to fix the polarizing film, and is therefore provided in advance as an adhesive layer on one side of the polarizing film.

It has also been proposed to add a dye or pigment to the adhesive layer to color it, thereby imparting any hue to the polarizing film and obtaining a high-contrast liquid crystal display (Patent Document 1). In recent years, there has been a demand for brightness and vividness (i.e., a wide color gamut) in image display devices, and organic electroluminescent display devices (OLEDs) have been attracting attention, but a wide color gamut is also being sought for liquid crystal display devices. For example, a method for widening the color gamut of liquid crystal display devices has been proposed in which a polarizing film is laminated on one or both sides of the liquid crystal cell via an adhesive layer containing a dye that exhibits a maximum absorption wavelength in a specific wavelength range (560 to 610 nm) (Patent Documents 2 and 3).

Specification No. 3052812 JP 2011-039093 A JP 2014-092611 A

As described above, the dye can be contained in the adhesive layer, and can also be contained in the film layer applied to the optical member. In this way, an optical functional layer containing a dye can be formed by containing the dye in a resin layer such as a film layer or an adhesive layer. However, since the optical functional layer contains a dye, the dye in the optical functional layer deteriorates over time from the viewpoint of the moisture permeability of the resin layer that is the base of the optical functional layer, and the optical functional layer gradually fades. In particular, when the optical functional layer is an adhesive layer containing a dye, the durability of the adhesive layer is insufficient from the viewpoint of moisture permeability, and even an adhesive layer that was initially colored with a dye gradually fades. In this way, when the dye in the optical functional layer (especially the adhesive layer) deteriorates over time, it is difficult to maintain the wide color gamut by the dye.

The present invention aims to provide a polarizing film with an optically functional layer that has an optically functional layer containing a dye that has good stability over time and can maintain the wide color gamut provided by the dye.

As a result of extensive research into solving the above problems, the inventors discovered the following polarizing film with a pressure-sensitive adhesive layer, and completed the present invention.

That is, the present invention relates to a polarizing film with an optical function layer, which has an optical function layer containing a dye on at least one side of a polarizing film having a polyvinyl alcohol-based polarizer, and is characterized in that the distance between the polyvinyl alcohol-based polarizer and the optical function layer containing the dye is 45 μm or less. It is preferable that the distance between the polyvinyl alcohol-based polarizer and the optical function layer is 25 μm or less.

In the polarizing film with the optically functional layer, the pressure-sensitive adhesive layer can be directly laminated to the polyvinyl alcohol-based polarizer.

The polarizing film with optically functional layers may have at least one layer having no dye and a thickness of 45 μm or less between the polyvinyl alcohol-based polarizer and the pressure-sensitive adhesive layer.

In the optically functional layer-attached polarizing film, the polyvinyl alcohol-based polarizer preferably has an oxygen permeability of 1 [cm ³ /(m ² ·24 h·atm)] or less.

In the polarizing film with an optically functional layer, the dye can have a maximum absorption wavelength in at least one of the wavelength ranges of 470 to 510 nm and 570 to 610 nm.

In the polarizing film with the optical functional layer, the dye can be a tetraazaporphyrin dye.

In the polarizing film with an optical functional layer, it is preferable that the dye is contained in an amount of 0.01 to 5 parts by weight per 100 parts by weight of the base polymer that forms the resin layer of the optical functional layer.

In the polarizing film with an optically functional layer, the adhesive layer containing the dye preferably has a thickness of 25 μm or less.

The present invention also relates to an image display device having the polarizing film with the optically functional layer.

The polarizing film with an optical functional layer of the present invention has an optical functional layer containing a dye. The optical functional layer can adjust the overall hue of the liquid crystal display device by absorbing light of a certain wavelength with the dye, and can improve vividness by widening the color gamut. In particular, a dye having a maximum absorption wavelength in at least one of the wavelength ranges of 470 to 510 nm and 570 to 610 nm can absorb and suppress unnecessary emission in color expression in wavelength ranges other than RGB (wavelength range 470 to 510 nm and/or wavelength range 570 to 610 nm), and is effective in widening the color gamut.

It was found that the fading of the dye in the optical functional layer containing the dye is caused by oxygen present in the air or in the resin penetrating the optical functional layer and being activated by heat, attacking the dye. It is believed that oxygen penetrates from the top, bottom, left and right sides of the adhesive layer.

In the polarizing film with an optical function layer of the present invention, the optical function layer containing the dye is applied to a polarizing film using a polyvinyl alcohol-based polarizer. The polyvinyl alcohol-based polarizer has low oxygen permeability and can prevent oxygen from entering the optical function layer from the upper or lower surface of the optical function layer containing the dye. The polarizing film with an optical function layer of the present invention can prevent oxygen from entering the optical function layer by using a separator with low oxygen permeability on the other surface of the optical function layer until specific use, and by applying it to an adherend with low oxygen permeability such as glass when actually used, and can provide an optical function layer that can suppress fading (decomposition) of the dye and maintain a wide color gamut stably over time.

In addition, in the polarizing film with optical functional layer of the present invention, the optical functional layer containing the dye and the polyvinyl alcohol-based polarizer are laminated so that the distance between them is 45 μm or less. By setting the distance to 45 μm or less, it is possible to prevent oxygen from entering from the end of the polarizing film with optical functional layer, and it is possible to suppress fading (decomposition) of the dye even at the end of the polarizing film with optical functional layer, and to maintain a wide color gamut stably over time.

1 is a cross-sectional view that illustrates an outline of an optically functional layer-attached polarizing film of the present invention. 1 is a cross-sectional view illustrating an embodiment of an optically functional layer-attached polarizing film of the present invention. 1 is a cross-sectional view illustrating an embodiment of an optically functional layer-attached polarizing film of the present invention. 1 is a cross-sectional view illustrating an embodiment of an optically functional layer-attached polarizing film of the present invention.

The following describes in detail the embodiment of the polarizing film with an optically functional layer of the present invention with reference to the drawings. However, the present invention is not limited to the embodiment shown in the drawings.

As shown in FIG. 1, the polarizing film with an optical function layer of the present invention has a polyvinyl alcohol-based polarizer P and an optical function layer A containing a dye. The polyvinyl alcohol-based polarizer P and the optical function layer A are laminated so that the distance x between them is 45 μm or less. The shorter the distance x, the more oxygen can be prevented from entering from the ends. The distance x is preferably 25 μm or less, more preferably 10 μm or less, even more preferably 5 μm or less, and even more preferably 1 μm or less.

Figure 2 shows a case where the polyvinyl alcohol polarizer P and the optical functional layer A are directly laminated (x = 0 μm). Note that FIG. 2 illustrates a polarizing film (one-sided protective polarizing film) having a transparent protective film F on one side (the side where the optical functional layer A is not provided) of the polyvinyl alcohol polarizer P. Also, FIG. 2 illustrates a case where a substrate S is provided on the optical functional layer A. Note that examples of the substrate S used until the specific use of the polarizing film with the optical functional layer are a separator, a vapor deposition film, etc. Specific examples of the substrate S used include glass, a transparent substrate with a vapor deposition layer, etc.

In addition, FIG. 3 illustrates the embodiment of FIG. 2 having a layer B with a thickness of 45 μm or less between the polyvinyl alcohol-based polarizer P and the optically functional layer A. Although FIG. 3 illustrates the embodiment of layer B having one layer, layer B can also be a combination of multiple layers. Examples of layer B include a pressure-sensitive adhesive layer and a film layer. The thickness of layer B can be designed according to the characteristics of each layer within the range of 45 μm or less.

In addition, FIG. 4 illustrates the embodiment of FIG. 2 in which the polyvinyl alcohol polarizer P and the optical functional layer A are directly laminated (x=0 μm), and further illustrates the case where the optical functional layer A has a layer C. Although the layer C is illustrated as being a single layer, a plurality of layers can be combined. Examples of the layer C include an adhesive layer and a surface treatment layer (hard coat layer, anti-glare treatment layer, anti-reflection layer, etc.). The thickness of the layer C can be designed according to the characteristics of each layer within a range of 45 μm or less. The layer C can also be applied in combination with the layer B.

The polarizing film with an optically functional layer of the present invention has a polarizing film having a polyvinyl alcohol-based polarizer and an optically functional layer containing a dye. Each component will be described below.

<Optical functional layer>
The optical functional layer of the present invention is not particularly limited as long as it is a resin layer containing a dye. Examples of the resin layer include a film layer, a pressure-sensitive adhesive layer, etc. The optical functional layer can be formed from a composition containing a base polymer and a dye.

<Pigment>
The dye contained in the optical functional layer of the present invention can be various dyes. Examples of the dye include various compounds such as tetraazaporphyrin, porphyrin, cyanine, azo, pyrromethene, squarylium, xanthene, oxonol, and squaraine. From the viewpoint of widening the color gamut, the dye is preferably a tetraazaporphyrin dye, a porphyrin dye, a cyanine dye, a squaraine dye, and a squaraine dye, and more preferably a tetraazaporphyrin dye. The dye is specifically disclosed in JP-A-2011-116818. Only one type of the dye may be used, or two or more types of the dye may be used in combination.

The dye preferably has a maximum absorption wavelength in at least one of the wavelength ranges of 470 to 510 nm and 570 to 610 nm. A dye having a maximum absorption wavelength in the above wavelength range can absorb and suppress unnecessary emission for color expression, and is effective in widening the color gamut. Tetraazaporphyrin dyes can be suitably used as dyes having a maximum absorption wavelength in the above wavelength range. For example, dyes that have a maximum absorption wavelength in the wavelength range of 570 to 610 nm include tetraazaporphyrin compounds (product names: PD-320, PD311) manufactured by Yamamoto Kasei Co., Ltd. and tetraazaporphyrin compounds (product name: FDG-007) manufactured by Yamada Chemical Co., Ltd. The maximum absorption wavelength of the dye was measured using a spectrophotometer (V-570 manufactured by JASCO Corporation).

The content of the dye in the optical functional layer of the present invention is adjusted depending on the absorption wavelength range and absorption coefficient of the dye and the type of base polymer, but is usually preferably 0.01 to 5 parts by weight, more preferably 0.05 to 3 parts by weight, and even more preferably 0.1 to 1 part by weight, per 100 parts by weight of the base polymer. The above range is particularly preferable when a tetraazaporphyrin dye is used.

<Adhesive Layer>
The optical functional layer of the present invention can be a pressure-sensitive adhesive layer containing a dye, and the pressure-sensitive adhesive layer can be formed from a pressure-sensitive adhesive base polymer and a pressure-sensitive adhesive composition containing a dye.The type of the pressure-sensitive adhesive base polymer is not particularly limited, and can be, for example, various polymers such as rubber-based polymers, (meth)acrylic-based polymers, silicone-based polymers, urethane-based polymers, vinyl alkyl ether-based polymers, polyvinyl alcohol-based polymers, polyvinyl pyrrolidone-based polymers, polyacrylamide-based polymers, and cellulose-based polymers.

The adhesive composition of the present invention contains an adhesive base polymer as a main component. The main component refers to the component that is contained in the largest proportion of the total solid content contained in the adhesive composition, for example, a component that occupies more than 50% by weight, or even more than 70% by weight, of the total solid content contained in the adhesive composition.

Among these adhesive base polymers, those that are excellent in optical transparency, exhibit appropriate adhesive properties such as wettability, cohesion, and adhesion, and are excellent in weather resistance and heat resistance are preferably used. (Meth)acrylic polymers are preferably used as they exhibit such characteristics. Below, we will explain the acrylic adhesive that uses a (meth)acrylic polymer containing alkyl (meth)acrylate as a monomer unit as the base polymer, which is a material for forming the adhesive layer.

<(Meth)acrylic polymer>
The (meth)acrylic polymer generally contains an alkyl (meth)acrylate as a monomer unit as a main component. Note that the term "(meth)acrylate" refers to an acrylate and/or a methacrylate, and "(meth)" in the present invention has the same meaning.

As the alkyl (meth)acrylate constituting the main skeleton of the (meth)acrylic polymer, there can be mentioned, for example, a linear or branched alkyl group having 1 to 18 carbon atoms. These can be used alone or in combination. The average carbon number of these alkyl groups is preferably 3 to 9.

In addition, from the standpoint of adhesive properties, durability, adjustment of phase difference, adjustment of refractive index, etc., alkyl (meth)acrylates containing aromatic rings, such as phenoxyethyl (meth)acrylate and benzyl (meth)acrylate, can be used.

In order to improve adhesion and heat resistance, one or more types of copolymerizable monomers having a polymerizable functional group with an unsaturated double bond, such as a (meth)acryloyl group or a vinyl group, can be introduced into the (meth)acrylic polymer by copolymerization. Specific examples of such copolymerizable monomers include hydroxyl group-containing monomers such as 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, and (4-hydroxymethylcyclohexyl)-methyl acrylate; (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, and the like. Examples include carboxyl group-containing monomers such as acrylate, itaconic acid, maleic acid, fumaric acid, and crotonic acid; acid anhydride group-containing monomers such as maleic anhydride and itaconic anhydride; caprolactone adducts of acrylic acid; sulfonic acid group-containing monomers such as styrene sulfonic acid, allyl sulfonic acid, 2-(meth)acrylamido-2-methylpropanesulfonic acid, (meth)acrylamidopropanesulfonic acid, sulfopropyl (meth)acrylate, and (meth)acryloyloxynaphthalenesulfonic acid; and phosphoric acid group-containing monomers such as 2-hydroxyethyl acryloyl phosphate.

In addition, (N-substituted) amide monomers such as (meth)acrylamide, N,N-dimethyl(meth)acrylamide, N-butyl(meth)acrylamide, N-methylol(meth)acrylamide, and N-methylolpropane(meth)acrylamide; alkylaminoalkyl(meth)acrylate monomers such as aminoethyl(meth)acrylate, N,N-dimethylaminoethyl(meth)acrylate, and t-butylaminoethyl(meth)acrylate; alkoxyalkyl(meth)acrylate monomers such as methoxyethyl(meth)acrylate and ethoxyethyl(meth)acrylate; N-(meth)acryloyloxymethylene succinimide and N-(meth) Examples of monomers for modification purposes include succinimide monomers such as acryloyl-6-oxyhexamethylene succinimide, N-(meth)acryloyl-8-oxyoctamethylene succinimide, and N-acryloylmorpholine; maleimide monomers such as N-cyclohexylmaleimide, N-isopropylmaleimide, N-laurylmaleimide, and N-phenylmaleimide; itaconimide monomers such as N-methylitaconimide, N-ethylitaconimide, N-butylitaconimide, N-octylitaconimide, N-2-ethylhexylitaconimide, N-cyclohexylitaconimide, and N-laurylitaconimide.

Further, as the modifying monomer, vinyl monomers such as vinyl acetate, vinyl propionate, N-vinylpyrrolidone, methylvinylpyrrolidone, vinylpyridine, vinylpiperidone, vinylpyrimidine, vinylpiperazine, vinylpyrazine, vinylpyrrole, vinylimidazole, vinyloxazole, vinylmorpholine, N-vinyl carboxylic acid amides, styrene, α-methylstyrene, N-vinylcaprolactam, etc.; cyanoacrylate monomers such as acrylonitrile and methacrylonitrile; epoxy group-containing acrylic monomers such as glycidyl (meth)acrylate; glycol-based acrylic ester monomers such as polyethylene glycol (meth)acrylate, polypropylene glycol (meth)acrylate, methoxyethylene glycol (meth)acrylate, and methoxypolypropylene glycol (meth)acrylate; acrylic ester monomers such as tetrahydrofurfuryl (meth)acrylate, fluorine (meth)acrylate, silicone (meth)acrylate, and 2-methoxyethyl acrylate, etc., can also be used. Further examples include isoprene, butadiene, isobutylene, and vinyl ether.

Furthermore, copolymerizable monomers other than those mentioned above include silane-based monomers containing silicon atoms. Examples of silane-based monomers include 3-acryloxypropyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, 4-vinylbutyltrimethoxysilane, 4-vinylbutyltriethoxysilane, 8-vinyloctyltrimethoxysilane, 8-vinyloctyltriethoxysilane, 10-methacryloyloxydecyltrimethoxysilane, 10-acryloyloxydecyltrimethoxysilane, 10-methacryloyloxydecyltriethoxysilane, 10-acryloyloxydecyltriethoxysilane, and 10-acryloyloxydecyltriethoxysilane.

In addition, examples of copolymerizable monomers include tripropylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, bisphenol A diglycidyl ether di(meth)acrylate, neopentyl glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, and dipentaerythritol. Polyfunctional monomers having two or more unsaturated double bonds such as (meth)acryloyl groups or vinyl groups, such as esters of (meth)acrylic acid and polyhydric alcohols, such as hexa(meth)acrylate and caprolactone-modified dipentaerythritol hexa(meth)acrylate, and polyester (meth)acrylates, epoxy (meth)acrylates, urethane (meth)acrylates, etc., in which two or more unsaturated double bonds such as (meth)acryloyl groups or vinyl groups are added as functional groups similar to those of the monomer components to the backbone of polyester, epoxy, urethane, etc., can also be used.

The (meth)acrylic polymer is mainly composed of alkyl (meth)acrylate in the weight ratio of all constituent monomers, and the ratio of the copolymerization monomer in the (meth)acrylic polymer is not particularly limited, but it is preferable that the ratio of the copolymerization monomer is about 0 to 20%, about 0.1 to 15%, or even about 0.1 to 10% in the weight ratio of all constituent monomers.

Among these copolymerizable monomers, hydroxyl group-containing monomers and carboxyl group-containing monomers are preferably used from the viewpoint of adhesion and durability. Hydroxyl group-containing monomers and carboxyl group-containing monomers can be used in combination. When the pressure-sensitive adhesive composition contains a crosslinking agent, these copolymerizable monomers become reaction sites with the crosslinking agent. Hydroxyl group-containing monomers and carboxyl group-containing monomers are highly reactive with intermolecular crosslinking agents, and are therefore preferably used to improve the cohesiveness and heat resistance of the resulting pressure-sensitive adhesive layer. Hydroxyl group-containing monomers are preferred from the viewpoint of reworkability, and carboxyl group-containing monomers are preferred from the viewpoint of achieving both durability and reworkability.

When the copolymerization monomer contains a hydroxyl group-containing monomer, the proportion is preferably 0.01 to 15% by weight, more preferably 0.03 to 10% by weight, and even more preferably 0.05 to 7% by weight. When the copolymerization monomer contains a carboxyl group-containing monomer, the proportion is preferably 0.05 to 10% by weight, more preferably 0.1 to 8% by weight, and even more preferably 0.2 to 6% by weight.

The (meth)acrylic polymer of the present invention is usually one having a weight average molecular weight in the range of 500,000 to 3,000,000. In consideration of durability, particularly heat resistance, it is preferable to use one having a weight average molecular weight of 700,000 to 2,700,000. It is even more preferable to use one having a weight average molecular weight of 800,000 to 2,500,000. If the weight average molecular weight is less than 500,000, it is not preferable in terms of heat resistance. Also, if the weight average molecular weight is more than 3,000,000, it is not preferable because a large amount of dilution solvent is required to adjust the viscosity to a level suitable for coating, which increases costs. The weight average molecular weight is measured by GPC (gel permeation chromatography) and calculated in terms of polystyrene.

For the production of such (meth)acrylic polymers, a known production method such as solution polymerization, radiation polymerization such as UV polymerization, bulk polymerization, emulsion polymerization, and various radical polymerizations can be appropriately selected. In addition, the obtained (meth)acrylic polymer may be any of a random copolymer, a block copolymer, a graft copolymer, and the like.

In solution polymerization, for example, ethyl acetate, toluene, etc. are used as the polymerization solvent. In a specific example of solution polymerization, the reaction is carried out under a stream of inert gas such as nitrogen, with the addition of a polymerization initiator, usually at about 50 to 70°C, for about 5 to 30 hours.

The polymerization initiator, chain transfer agent, emulsifier, etc. used in the radical polymerization are not particularly limited and can be appropriately selected and used. The weight average molecular weight of the (meth)acrylic polymer can be controlled by the amount of polymerization initiator and chain transfer agent used and the reaction conditions, and the amount used is adjusted appropriately depending on the type of these.

Examples of radical polymerization initiators include azo initiators such as 2,2'-azobisisobutyronitrile, 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 (manufactured by Wako Pure Chemical Industries, Ltd., VA-057), persulfates such as potassium persulfate and ammonium persulfate, di(2-ethylhexyl)peroxydicarbonate, di(4-t-butylcyclohexyl)peroxydicarbonate, di-sec-butyl ... Examples of initiators include, but are not limited to, peroxide initiators such as butyl peroxydicarbonate, t-butyl peroxyneodecanoate, t-hexyl peroxypivalate, t-butyl peroxypivalate, dilauroyl peroxide, di-n-octanoyl peroxide, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, di(4-methylbenzoyl)peroxide, dibenzoyl peroxide, t-butyl peroxyisobutyrate, 1,1-di(t-hexylperoxy)cyclohexane, t-butyl hydroperoxide, and hydrogen peroxide, and redox initiators that combine peroxides and reducing agents, such as combinations of persulfates and sodium hydrogen sulfite, and combinations of peroxides and sodium ascorbate.

The radical polymerization initiators may be used alone or in combination of two or more kinds, but the total content is preferably about 0.005 to 1 part by weight, and more preferably about 0.02 to 0.5 parts by weight, per 100 parts by weight of monomer.

Examples of chain transfer agents include lauryl mercaptan, glycidyl mercaptan, mercaptoacetic acid, 2-mercaptoethanol, thioglycolic acid, 2-ethylhexyl thioglycolate, and 2,3-dimercapto-1-propanol. The chain transfer agents may be used alone or in combination of two or more, but the total content is about 0.1 parts by weight or less per 100 parts by weight of the total amount of the monomer components.

Examples of emulsifiers used in emulsion polymerization include anionic emulsifiers such as sodium lauryl sulfate, ammonium lauryl sulfate, sodium dodecylbenzenesulfonate, polyoxyethylene alkyl ether ammonium sulfate, and sodium polyoxyethylene alkyl phenyl ether sulfate, and nonionic emulsifiers such as polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene fatty acid ester, and polyoxyethylene-polyoxypropylene block polymer. These emulsifiers may be used alone or in combination of two or more.

Furthermore, examples of reactive emulsifiers that have been introduced with radically polymerizable functional groups such as propenyl groups and allyl ether groups include Aqualon HS-10, HS-20, KH-10, BC-05, BC-10, and BC-20 (all manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) and Adeka Reasoap SE10N (manufactured by Asahi Denka Kogyo Co., Ltd.). Reactive emulsifiers are preferred because they are incorporated into the polymer chain after polymerization, improving water resistance. The amount of emulsifier used is 0.3 to 5 parts by weight per 100 parts by weight of the total amount of monomer components, and 0.5 to 1 part by weight is more preferred in terms of polymerization stability and mechanical stability.

<Crosslinking Agent>
Furthermore, in the present invention, a crosslinking agent can be contained in the adhesive composition forming the adhesive layer having the dye. As the crosslinking agent, an organic crosslinking agent or a polyfunctional metal chelate can be used. As the organic crosslinking agent, an isocyanate crosslinking agent, a peroxide crosslinking agent, an epoxy crosslinking agent, an imine crosslinking agent, etc. can be mentioned. In the polyfunctional metal chelate, a polyvalent metal is covalently bonded or coordinately bonded to an organic compound. As the polyvalent metal atom, Al, Cr, Zr, Co, Cu, Fe, Ni, V, Zn, In, Ca, Mg, Mn, Y, Ce, Sr, Ba, Mo, La, Sn, Ti, etc. can be mentioned. As the atom in the organic compound that is covalently bonded or coordinately bonded, an oxygen atom can be mentioned, and as the organic compound, an alkyl ester, an alcohol compound, a carboxylic acid compound, an ether compound, a ketone compound, etc. can be mentioned.

Examples of compounds related to isocyanate-based crosslinking agents include isocyanate monomers such as tolylene diisocyanate, chlorophenylene diisocyanate, tetramethylene diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate, and hydrogenated diphenylmethane diisocyanate, as well as isocyanate compounds and isocyanurates obtained by adding these isocyanate monomers to trimethylolpropane, biuret-type compounds, and urethane prepolymer-type isocyanates obtained by addition reaction of polyether polyols, polyester polyols, acrylic polyols, polybutadiene polyols, polyisoprene polyols, etc. Particularly preferred are polyisocyanate compounds, and are one or more polyisocyanate compounds derived from the group consisting of hexamethylene diisocyanate, hydrogenated xylylene diisocyanate, and isophorone diisocyanate. Here, the polyisocyanate compound selected from the group consisting of hexamethylene diisocyanate, hydrogenated xylylene diisocyanate, and isophorone diisocyanate or derived therefrom includes hexamethylene diisocyanate, hydrogenated xylylene diisocyanate, isophorone diisocyanate, polyol-modified hexamethylene diisocyanate, polyol-modified hydrogenated xylylene diisocyanate, trimer-type hydrogenated xylylene diisocyanate, and polyol-modified isophorone diisocyanate. The polyisocyanate compounds exemplified above are preferred because the reaction with hydroxyl groups proceeds quickly, especially with the acid and base contained in the polymer acting as a catalyst, which contributes to the rapidity of crosslinking.

Any peroxide can be used as long as it generates radical active species when heated or irradiated with light and promotes crosslinking of the base polymer of the adhesive composition. Taking into consideration workability and stability, it is preferable to use a peroxide with a one-minute half-life temperature of 80°C to 160°C, and it is even more preferable to use a peroxide with a one-minute half-life temperature of 90°C to 140°C.

Examples of the peroxides include di(4-t-butylcyclohexyl) peroxydicarbonate (1-minute half-life temperature: 92.1°C), di-sec-butyl peroxydicarbonate (1-minute half-life temperature: 92.4°C), t-butyl peroxyneodecanoate (1-minute half-life temperature: 103.5°C), t-hexyl peroxypivalate (1-minute half-life temperature: 109.1°C), t-butyl peroxypivalate (1-minute half-life temperature: 110.3°C), dilauroyl peroxide (1-minute half-life temperature: 116.4°C), di-n -octanoyl peroxide (1-minute half-life temperature: 117.4°C), 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate (1-minute half-life temperature: 124.3°C), di(4-methylbenzoyl)peroxide (1-minute half-life temperature: 128.2°C), dibenzoyl peroxide (1-minute half-life temperature: 130.0°C), t-butylperoxyisobutyrate (1-minute half-life temperature: 136.1°C), 1,1-di(t-hexylperoxy)cyclohexane (1-minute half-life temperature: 149.2°C), and the like. Among these, di(4-t-butylcyclohexyl) peroxydicarbonate (1-minute half-life temperature: 92.1°C), dilauroyl peroxide (1-minute half-life temperature: 116.4°C), dibenzoyl peroxide (1-minute half-life temperature: 130.0°C), etc. are preferably used because they have particularly excellent crosslinking reaction efficiency.

The half-life of a peroxide is an index showing the decomposition rate of the peroxide, and refers to the time it takes for the remaining amount of peroxide to be reduced to half. The decomposition temperature for obtaining the half-life at any time and the half-life time at any temperature are listed in manufacturer catalogs, for example, NOF Corporation's "Organic Peroxide Catalog 9th Edition (May 2003)."

The amount of the crosslinking agent used is preferably 20 parts by weight or less, more preferably 0.01 to 20 parts by weight, and even more preferably 0.03 to 10 parts by weight, per 100 parts by weight of the base polymer, such as a (meth)acrylic polymer, in the adhesive composition. If the amount of the crosslinking agent is more than 20 parts by weight, the moisture resistance is insufficient, and peeling is likely to occur during reliability tests, etc.

Furthermore, the adhesive composition that forms the adhesive layer having the dye of the present invention can contain a silane coupling agent. By using a silane coupling agent, durability can be improved. Specific examples of silane coupling agents 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-dimethylbutylidene)propylamine, and N-phenyl-γ-aminopropyltrimethoxysilane; (meth)acrylic group-containing silane coupling agents such as 3-acryloxypropyltrimethoxysilane and 3-methacryloxypropyltriethoxysilane; and isocyanate group-containing silane coupling agents such as 3-isocyanatepropyltriethoxysilane.

The silane coupling agent may be used alone or in a mixture of two or more kinds. The total content is preferably 0.001 to 5 parts by weight, more preferably 0.01 to 1 part by weight, even more preferably 0.02 to 1 part by weight, and even more preferably 0.05 to 0.6 parts by weight, per 100 parts by weight of the base polymer such as the (meth)acrylic polymer. This is an amount that improves durability and maintains a suitable adhesive strength to optical members such as liquid crystal cells.

In addition, in the present invention, polyether-modified silicone can be blended in the adhesive composition that forms the adhesive layer having the dye. For example, the polyether-modified silicone disclosed in JP-A-2010-275522 can be used.

In addition, in the present invention, the adhesive composition forming the adhesive layer having a dye may contain other known additives, such as colorants, powders such as pigments, dyes, surfactants, plasticizers, tackifiers, surface lubricants, leveling agents, softeners, antioxidants, antioxidants, light stabilizers, UV absorbers, polymerization inhibitors, inorganic or organic fillers, metal powders, particles, and foil-like materials, which can be added as appropriate depending on the application. Also, a redox system may be used by adding a reducing agent within a controllable range.

The adhesive composition is used to form an adhesive layer containing a dye. When forming the adhesive layer, it is preferable to adjust the amount of crosslinking agent added and to fully consider the effects of the crosslinking temperature and time.

The crosslinking temperature and time can be adjusted depending on the crosslinking agent used. The crosslinking temperature is preferably 170°C or less.

This crosslinking treatment may be carried out at the temperature during the drying process of the adhesive layer, or may be carried out in a separate crosslinking treatment process after the drying process.

The crosslinking time can be set taking into consideration productivity and workability, but is usually about 0.2 to 20 minutes, and preferably about 0.5 to 10 minutes.

The adhesive layer having the dye can be formed, for example, by applying the adhesive composition to a peel-treated separator, drying and removing the polymerization solvent, etc. to form an adhesive layer, which is then transferred to a polarizing film having a polyvinyl alcohol-based polarizer, or by applying the adhesive composition to a polarizing film having a polyvinyl alcohol-based polarizer, drying and removing the polymerization solvent, etc. to form an adhesive layer on a polarizing film having a polyvinyl alcohol-based polarizer. When applying the adhesive, one or more solvents other than the polymerization solvent may be added as appropriate.

As the release-treated separator, a silicone release liner is preferably used. In the process of applying the adhesive composition of the present invention onto such a liner and drying it to form a pressure-sensitive adhesive layer, a suitable method may be adopted as a method for drying the pressure-sensitive adhesive, depending on the purpose. A method of overheating and drying the coating film is preferably used. The heat-drying temperature is preferably 40°C to 200°C, more preferably 50°C to 180°C, and particularly preferably 70°C to 170°C. By setting the heating temperature within the above range, a pressure-sensitive adhesive with excellent adhesive properties can be obtained.

Any suitable drying time can be used. The drying time is preferably 5 seconds to 20 minutes, more preferably 5 seconds to 10 minutes, and particularly preferably 10 seconds to 5 minutes.

In addition, an anchor layer (e.g., about 0.5 to 2 μm thick) can be formed on the surface of a polarizing film having a polyvinyl alcohol-based polarizer, or various adhesion-enhancing treatments such as corona treatment and plasma treatment can be performed, after which a pressure-sensitive adhesive layer can be formed. In addition, the surface of the pressure-sensitive adhesive layer can be subjected to an adhesion-enhancing treatment.

Various methods can be used to form the adhesive layer. Specific examples include roll coating, kiss roll coating, gravure coating, reverse coating, roll brushing, spray coating, dip roll coating, bar coating, knife coating, air knife coating, curtain coating, lip coating, and extrusion coating using a die coater.

The thickness of the adhesive layer is not particularly limited and is, for example, about 1 to 100 μm. It is preferably 2 to 50 μm, more preferably 2 to 40 μm, and even more preferably 5 to 35 μm. The adhesive layer containing the dye is preferably 25 μm or less in thickness in order to prevent oxygen from entering from the ends of the adhesive layer.

If the adhesive layer is exposed, it may be protected with a release-treated sheet (separator) until it is put to practical use.

<Film Layer>
In addition, the optical functional layer of the present invention may be a film layer containing a dye, and the film layer may be formed from a composition containing a base polymer for film formation and a dye. Examples of the material of the base polymer forming the film layer include the same materials as those constituting the transparent protective film described below. In particular, cellulose resins such as triacetyl cellulose, polyester resins, (meth)acrylic resins, cyclic polyolefin resins (norbornene-based resins), etc. are preferably used as the material. The film layer may be applied to a polyvinyl alcohol-based polarizer by using an adhesive, a pressure sensitive adhesive, etc. as appropriate.

Various methods can be used to form a film layer containing a dye. For example, when pellets of the resin material are dissolved in a solvent, a dye is mixed to prepare a composition, and the composition is cast or extruded to produce a film layer. At that time, the film layer can be formed to an appropriate thickness. When preparing the composition, additives can be added as appropriate.

The thickness of the film layer is not particularly limited and is the same as that of the adhesive layer, for example, about 1 to 100 μm. Preferably, it is 2 to 50 μm, more preferably 2 to 40 μm, and even more preferably 5 to 35 μm. The separator can also be applied to a film layer containing a dye.

Examples of materials that can be used to form the separator include plastic films such as polyethylene, polypropylene, polyethylene terephthalate, and polyester films; porous materials such as paper, cloth, and nonwoven fabrics; nets, foam sheets, metal foils, and laminates of these materials; and other suitable thin materials. Plastic films are preferred because of their excellent surface smoothness.

The plastic film is not particularly limited as long as it is a film capable of protecting the optical functional layer (particularly the adhesive layer), and examples include polyvinyl alcohol film, polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, vinyl chloride copolymer film, polyethylene terephthalate film, polybutylene terephthalate film, polyurethane film, ethylene-vinyl acetate copolymer film, etc.

The thickness of the separator is usually 5 to 200 μm, and preferably about 5 to 100 μm. If necessary, the separator can be subjected to a release and antifouling treatment using a silicone-based, fluorine-based, long-chain alkyl-based or fatty acid amide-based release agent, silica powder, or the like, or an antistatic treatment such as a coating type, kneading type, or deposition type. In particular, by appropriately performing a release treatment such as silicone treatment, long-chain alkyl treatment, or fluorine treatment on the surface of the separator, the releasability from the optical functional layer (particularly the adhesive layer) can be further improved.

The peel-treated sheet used in producing the above-mentioned polarizing film with an adhesive layer can be used as a separator for the polarizing film with an optically functional layer, which simplifies the process.

The separator preferably has an oxygen permeability of 1 [cm ³ /(m ² ·24h ·atm)] or less. The oxygen permeability is preferably 0.8 [cm ³ /(m ² ·24h ·atm)] or less, more preferably 0.6 [cm ³ /(m ² ·24h ·atm)] or less, and even more preferably 0.5 [cm ³ /(m ² ·24h ·atm)] or less. The oxygen permeability is determined by the material, thickness, etc. The oxygen permeability of the optical member is specifically measured as described in the examples.

Preferable examples of separators that can satisfy the low oxygen permeability requirement include polyvinyl alcohol film, polyethylene terephthalate film, aluminum-deposited film, polyacrylonitrile, ethylene vinyl alcohol, etc. The thickness of the film is preferably 10 to 100 μm, and more preferably 25 to 75 μm.

<Polarizing film>
The polarizing film of the present invention has the polyvinyl alcohol-based polarizer. The polyvinyl alcohol-based polarizer has low oxygen permeability and can satisfy the oxygen permeability of 1 [cm ³ /(m ² ·24 h ·atm)] or less.

The polarizing film generally used is a polyvinyl alcohol-based polarizer having a transparent protective film on one or both sides.

The polyvinyl alcohol polarizer is not particularly limited, and various types can be used. Examples of polarizers include hydrophilic polymer films such as polyvinyl alcohol films, partially formalized polyvinyl alcohol films, and partially saponified ethylene-vinyl acetate copolymer films, which are uniaxially stretched after adsorbing a dichroic substance such as iodine or a dichroic dye, and polyene-based oriented films such as dehydrated polyvinyl alcohol and dehydrochlorinated polyvinyl chloride. Among these, polarizers made of a polyvinyl alcohol film and a dichroic substance such as iodine are preferable. The thickness of these polarizers is not particularly limited, but is generally about 80 μm or less.

A polarizer obtained by dyeing a polyvinyl alcohol-based film with iodine and stretching it uniaxially can be produced, for example, by immersing the polyvinyl alcohol-based film in an aqueous solution of iodine to dye it and stretching it to 3 to 7 times its original length. If necessary, it can also be immersed in an aqueous solution of potassium iodide or the like which may contain boric acid, zinc sulfate, zinc chloride, or the like. Furthermore, if necessary, the polyvinyl alcohol-based film can be immersed in water and washed before dyeing. Washing the polyvinyl alcohol-based film with water can wash off dirt and blocking inhibitors on the surface of the polyvinyl alcohol-based film, and also has the effect of preventing unevenness such as uneven dyeing by swelling the polyvinyl alcohol-based film. Stretching can be performed after dyeing with iodine, or it can be stretched while dyeing, or it can be dyed with iodine after stretching. Stretching can be performed in an aqueous solution of boric acid, potassium iodide, or the like, or in a water bath.

As the polarizer, a thin polarizer having a thickness of 10 μm or less can be used. From the viewpoint of thinning, the thickness is preferably 1 to 7 μm. Such thin polarizers have little thickness unevenness, excellent visibility, and excellent durability due to little dimensional change, and are also preferable in that the thickness as a polarizing film can be made thin.

Representative examples of thin polarizers include the thin polarizing films described in JP-A-51-069644 and JP-A-2000-338329, WO2010/100917, PCT/JP2010/001460, and Japanese Patent Application Nos. 2010-269002 and 2010-263692. These thin polarizing films can be obtained by a manufacturing method including a step of stretching a polyvinyl alcohol-based resin (hereinafter also referred to as PVA-based resin) layer and a resin substrate for stretching in a laminated state, and a step of dyeing. With this manufacturing method, even if the PVA-based resin layer is thin, it can be stretched without problems such as breakage due to stretching because it is supported by the resin substrate for stretching.

As the thin polarizing film, among the manufacturing methods including the steps of stretching and dyeing the laminate, those obtained by a manufacturing method including a step of stretching in an aqueous boric acid solution as described in WO2010/100917, PCT/JP2010/001460, or Japanese Patent Application Nos. 2010-269002 and 2010-263692 are preferred, because they can be stretched at a high ratio and have improved polarization performance. In particular, those obtained by a manufacturing method including a step of supplementary air-stretching before stretching in an aqueous boric acid solution as described in Japanese Patent Application Nos. 2010-269002 and 2010-263692 are preferred.

As a material for forming the transparent protective film, for example, a thermoplastic resin excellent in transparency, mechanical strength, thermal stability, moisture blocking property, isotropy, etc. is used. Specific examples of such thermoplastic resins include cellulose resins such as triacetyl cellulose, polyester resins, polyethersulfone resins, polysulfone resins, polycarbonate resins, polyamide resins, polyimide resins, polyolefin resins, (meth)acrylic resins, cyclic polyolefin resins (norbornene resins), polyarylate resins, polystyrene resins, polyvinyl alcohol resins, and mixtures thereof. A transparent protective film is attached to one side of the polarizer with an adhesive layer, and a thermosetting resin or an ultraviolet-curing resin such as a (meth)acrylic, urethane, acrylic urethane, epoxy, or silicone resin can be used as the transparent protective film on the other side. The transparent protective film may contain one or more suitable additives. Examples of additives include ultraviolet absorbers, antioxidants, lubricants, plasticizers, release agents, coloring inhibitors, flame retardants, nucleating agents, antistatic agents, pigments, colorants, etc. The content of the thermoplastic resin in the transparent protective film is preferably 50 to 100% by weight, more preferably 50 to 99% by weight, even more preferably 60 to 98% by weight, and particularly preferably 70 to 97% by weight. If the content of the thermoplastic resin in the transparent protective film is 50% by weight or less, the inherent high transparency of the thermoplastic resin may not be fully exhibited.

The thickness of the transparent protective film is not particularly limited and is, for example, about 10 to 90 μm. It is preferably 15 to 60 μm, and more preferably 20 to 50 μm. When a transparent protective film is disposed between the polyvinyl alcohol polarizer and the adhesive layer containing the dye, a transparent protective film with a thickness adjusted so that the total thickness with the adhesive layer, etc. is 45 μm or less is used.

A functional layer (surface layer) such as a hard coat layer, an anti-reflection layer, an anti-sticking layer, a diffusion layer, or an anti-glare layer can be provided on the surface of the transparent protective film to which the polarizer is not attached.

The adhesive used to bond the polarizer and the transparent protective film is not particularly limited as long as it is optically transparent, and various types of adhesives such as water-based, solvent-based, hot melt, radical curing, and cationic curing types can be used, but water-based adhesives or radical curing adhesives are preferred. The thickness of the adhesive layer is usually about 0.01 to 3 μm, preferably 0.3 to 2 μm, and more preferably 0.5 to 1.5 μm.

Examples of the layer having no pigment (for example, layer B in the embodiment of FIG. 3) that can be provided between the polyvinyl alcohol polarizer and the adhesive layer having the pigment include the anchor layer, a transparent protective film applied to the polarizer, an adhesive layer (for bonding the transparent protective film to the polarizer), an adhesive layer (having no pigment), a retardation layer (or retardation film), a light scattering layer, a light emitting layer, an undercoat layer, a liquid crystal layer, and a polarizing layer. The layer B can be used as a single layer, or multiple layers can be combined. When multiple layers of the layer B (for example, layers B1 and B2) are used, a layer in which multiple layers B are laminated via an adhesive layer having no pigment, such as polarizer P/layer B1/adhesive layer (having no pigment)/layer B2/adhesive layer A (having pigment), can be used. The thickness of the layer B can be designed according to the characteristics of each layer within a range of 45 μm or less. It is also preferable that the layer B has low oxygen permeability.

<Liquid crystal panel>
The optically functional layer-attached polarizing film of the present invention can be suitably used when forming a liquid crystal panel. For example, in the case of a pressure-sensitive adhesive layer-attached polarizing film in which the optically functional layer of the optically functional layer-attached polarizing film of the present invention is an adhesive layer, the adhesive layer-attached polarizing film is attached to at least one surface of a liquid crystal cell via the adhesive layer of the adhesive layer-attached polarizing film to form a liquid crystal panel. The adhesive layer-attached polarizing film of the present invention is suitably used on the viewing side of the liquid crystal cell.

Any type of liquid crystal cell can be used, such as TN type, STN type, π type, VA type, or IPS type, but an IPS mode liquid crystal cell is preferably used for the liquid crystal panel of the present invention.

In addition to the polarizing film, other optical layers can be used to form the liquid crystal panel. There are no particular limitations on the optical layers, but for example, one or more optical layers that are sometimes used to form liquid crystal panels, such as a reflector, semi-transmitting plate, retardation plate (including 1/2 or 1/4 wavelength plates), viewing angle compensation film, and brightness enhancement film, can be used on the viewing side and/or back side of the liquid crystal cell.

<Liquid crystal display device>
The liquid crystal display device uses the above-mentioned liquid crystal panel, and is formed by appropriately assembling components such as an illumination system as necessary and incorporating a driving circuit. Furthermore, when forming the liquid crystal display device, suitable components such as a diffusion plate, an anti-glare layer, an anti-reflection film, a protective plate, a prism array, a lens array sheet, a light diffusion plate, a backlight, etc. can be arranged in one or more layers at suitable positions. Also, suitable liquid crystal display devices such as those using a backlight or a reflector as the illumination system can be formed.

The present invention will be specifically explained below with reference to examples, but the present invention is not limited to these examples. Note that all parts and percentages in each example are by weight. Unless otherwise specified below, all room temperature storage conditions are 23°C and 65% RH.

<Measurement of weight average molecular weight of (meth)acrylic polymer>
The weight average molecular weight (Mw) of the (meth)acrylic polymer was measured by gel permeation chromatography (GPC). The Mw/Mn was also measured in the same manner.
Analytical equipment: Tosoh Corporation, HLC-8120GPC
Column: Tosoh Corporation, G7000H _XL + GMH _XL + GMH _XL
Column size: 7.8 mm diameter x 30 cm, total 90 cm
Column temperature: 40°C
・Flow rate: 0.8mL/min
・Injection volume: 100μL
Eluent: Tetrahydrofuran Detector: Differential refractometer (RI)
・Standard sample: polystyrene

<Measurement of oxygen permeability>
The oxygen transmission rate was measured using an oxygen transmission rate measuring device OX-TRAN manufactured by Mocon Co., Ltd. under conditions of 23° C. and 0% RH in accordance with JIS K 7126-2.

Example 1
<Preparation of Polarizing Film>
To produce a thin polarizing layer, a laminate having a 9 μm-thick PVA layer formed on an amorphous PET substrate was first subjected to auxiliary air stretching at a stretching temperature of 130° C. to produce a stretched laminate, the stretched laminate was then dyed to produce a colored laminate, and the colored laminate was further stretched in boric acid water at a stretching temperature of 65° C. to produce an optical film laminate including a 4 μm-thick PVA layer, in which the PVA molecules of the PVA layer formed on the amorphous PET substrate were highly oriented, and an optical film laminate including a 4 μm-thick PVA layer was produced, which constitutes a highly functional polarizing layer in which iodine adsorbed by dyeing was highly oriented in one direction as a polyiodine ion complex, by such two-stage stretching. Furthermore, a polyvinyl alcohol-based adhesive was applied to the surface of the polarizing layer of the optical film laminate (thickness of the formed adhesive layer: 1 μm), and a saponified 40 μm-thick first acrylic resin film (oxygen permeability: 5 [cm ³ /(m ² ·24 h ·atm)]) was laminated thereon, and then the amorphous PET substrate was peeled off to produce a single-protected polarizing film using a thin polarizer (oxygen permeability: less than 0.02 [cm ³ /(m ² ·24 h ·atm)]). This is referred to as a thin single-protected polarizing film.

<Preparation of (meth)acrylic polymer>
A monomer mixture containing 100 parts of butyl acrylate, 0.01 parts of 2-hydroxyethyl acrylate, and 5 parts of acrylic acid was charged into a reaction vessel equipped with a cooling tube, a nitrogen introduction tube, a thermometer, and a stirrer. Furthermore, 0.1 parts of 2,2'-azobisisobutyronitrile as a polymerization initiator was charged together with 100 parts of ethyl acetate with respect to 100 parts of the monomer mixture, and nitrogen gas was introduced to replace the atmosphere with nitrogen while gently stirring. The liquid temperature in the flask was kept at about 55°C, and a polymerization reaction was carried out for 8 hours to prepare a solution of an acrylic polymer having a weight average molecular weight (Mw) of 1.8 million and Mw/Mn=4.1 (solid concentration 30% by weight).

(Preparation of Pressure-Sensitive Adhesive Composition)
For 100 parts of the solid content of the acrylic polymer solution produced above,
0.3 parts of benzoyl peroxide (trade name: Niper BMT, manufactured by Nippon Oil & Fats Co., Ltd.),
1 part of an isocyanate crosslinking agent (manufactured by Tosoh Corporation under the trade name of Coronate L),
0.25 parts of a tetraazaporphyrin dye (product name PD-320, manufactured by Yamamoto Chemical Industries, Ltd., having a maximum absorption wavelength at a wavelength of 595 nm) and were mixed to obtain a pressure-sensitive adhesive composition.

(Preparation of Polarizing Film with Pressure-Sensitive Adhesive Layer)
The adhesive composition was applied uniformly directly onto the polarizer (PVA layer) surface of the thin piece-protected polarizing film using an applicator, and then dried for 2 minutes in an air-circulating thermostatic oven at 155°C to form an adhesive layer having a thickness of 20 μm on the surface of the polarizer, thereby producing an adhesive layer-attached piece-protected polarizing film.

Example 2
An adhesive layer-attached piece-protected polarizing film was prepared in the same manner as in Example 1, except that in Example 1, a 20 μm-thick adhesive layer not containing a dye was laminated on the surface of the polarizer, and then a 20 μm-thick adhesive layer containing a dye was formed.
In addition, the formation of the 20 μm thick dye-free adhesive layer was performed by using the same adhesive composition as that used for forming the above-mentioned dye-containing adhesive layer, except that the dye was not blended in. The adhesive layer was formed by uniformly applying the adhesive composition to the surface of a release substrate (Mitsubishi Plastics, Inc. MRF38CK) of a polyethylene terephthalate film treated with a silicone-based release agent with an applicator, drying for 2 minutes in an air-circulating thermostatic oven at 155° C., and transferring the adhesive layer to the polarizer and laminating it.

Example 3
An adhesive layer-attached piece-protected polarizing film was produced in the same manner as in Example 1, except that in Example 1, a 20 μm-thick adhesive layer containing no dye was formed after two layers (total thickness 40 μm) of the adhesive layer containing no dye used in Example 2 were laminated on the surface of the polarizer. The formation of the adhesive layer containing no dye was similar to that described in Example 2.

Example 4
<Preparation of Polarizing Film>
A double-protected polarizing film was produced by bonding a saponified 40 μm-thick second acrylic resin film (oxygen permeability 5 [cm ³ /(m ² 24 h atm)]) via an adhesive (adhesive layer thickness 1 μm) to the polarizer (PVA layer) surface of the thin one-sided protected polarizing film obtained in Example 1. This is called a thin double-protected polarizing film.

(Preparation of Polarizing Film with Pressure-Sensitive Adhesive Layer)
The adhesive composition used in Example 1 was directly and uniformly applied with an applicator to the back surface (the side opposite the adhesive layer) of the second acrylic resin film of each of the above-mentioned two protective polarizing films, and then dried for 2 minutes in an air-circulating constant temperature oven at 155°C to form a 20 µm-thick adhesive layer having a dye on the back surface of the second acrylic resin film, thereby producing an adhesive layer-attached piece-protected polarizing film.

Comparative Example 1
An adhesive layer-attached piece-protected polarizing film was produced in the same manner as in Example 1, except that in Example 1, three 20 μm-thick adhesive layers not containing a dye as used in Example 2 were laminated on the surface of the polarizer (total thickness 60 μm), and then an adhesive layer containing a dye of 20 μm was formed. The formation of the adhesive layer not containing a dye was the same as described in Example 2.

Comparative Example 2
An acrylic resin film with an adhesive layer was prepared in the same manner as in Example 1, except that the adhesive composition was formed on a saponified 40 μm thick acrylic resin film (oxygen permeability 5 [cm ³ /(m ² ·24 h ·atm)]) instead of on the surface of the polarizer (PVA layer) of the thin piece-protected polarizing film.

The following evaluations were carried out using the adhesive layer-attached piece-protected or double-protected polarizing films, or adhesive layer-attached acrylic resin films obtained in the above examples and comparative examples. The evaluation results are shown in Table 1.

(Evaluation of fading)
After cutting the sample into a test piece of 50 mm length x 25 mm width, the front and end states (initial state) were photographed using a scanner (specifically, Canon's PIXUS MX923). Next, the sample was subjected to a durability test in which it was left in a thermostatic chamber at 85°C for 24 hours, and then removed and returned to room temperature (23°C), and the front and end states (after 24 hours) of the sample were photographed again using the same scanner. The photographs taken before (initial state) and after (24 hours) the test were binarized, and the presence or absence of color loss at the front and the amount of color loss at the end were measured by the following method.

<Color loss on the front>
Based on the images of the binarized photographs before and after the test pieces were put into the durability test, the presence or absence of color was visually evaluated. The transmittances before and after the test pieces were put into the durability test are also shown in Table 1. The transmittances were measured using a spectral transmittance meter with an integrating sphere (Dot-3c, manufactured by Murakami Color Research Laboratory) with the test pieces at 23°C.
○ There is no difference in color compared to before application.
× The color is clearly lighter than before it was added.

<Color loss at the edge>
The longest distance from the peripheral edge of the test piece toward the center where the color had clearly faded was measured with a ruler, and this was evaluated as the color loss (fading progression distance: mm).

In the examples, there was no color loss at the front, and the amount of color loss at the edges was small. The color loss at the edges (fading progression distance: mm) is preferably 3 mm or less, more preferably 2 mm or less, and even more preferably 1 mm or less, and is preferably 0 mm. On the other hand, in Comparative Example 1, since the polyvinyl alcohol polarizer was used, color loss at the front was not observed, but the distance between the polyvinyl alcohol polarizer and the optical functional layer (adhesive layer) exceeded 45 μm, and color loss at the edges (fading progression distance: mm) was observed. In Comparative Example 2, since the polyvinyl alcohol polarizer was not used, color loss at both the front and edges was observed.

P: Polyvinyl alcohol-based polarizer A: Optical functional layer F: Transparent protective film S: Separator B, C: Other layers x: Distance between the pressure-sensitive adhesive layer and the polyvinyl alcohol-based polarizer

Claims (5)

A polarizing film with an optical functional layer, comprising a polarizing film having a polyvinyl alcohol-based polarizer and a pressure-sensitive adhesive layer containing a dye and a base polymer on at least one side of the polarizing film, the distance between the polyvinyl alcohol-based polarizer and the pressure-sensitive adhesive layer containing the dye being 25 μm or less,
a base polymer of the dye-containing pressure -sensitive adhesive layer is a (meth)acrylic polymer,
an adhesive layer and a transparent protective film are provided between the polyvinyl alcohol- based polarizer and the dye-containing pressure-sensitive adhesive layer,
The total thickness of the transparent protective film and the adhesive layer is 25 μm or less,
The adhesive layer bonds the polyvinyl alcohol- based polarizer and the transparent protective film, and the adhesive layer has a thickness of 0.01 to 3 μm. 2. The polarizing film with an optical function layer according to claim 1, wherein the polyvinyl alcohol-based polarizer has an oxygen permeability of 1 [cm ³ /(m ² ·24 h ·atm)] or less. The polarizing film with an optically functional layer according to claim 1 or 2, characterized in that the adhesive layer containing the dye has a thickness of 25 μm or less. The polarizing film with an optically functional layer according to any one of claims 1 to 3, characterized in that the weight average molecular weight of the (meth)acrylic polymer is 500,000 to 3,000,000. An image display device having a polarizing film with an optically functional layer according to any one of claims 1 to 4.