JP2021039275A - Laminated optical film and image display device - Google Patents

Abstract

To provide a laminated optical film which offers reduced reflectance from external light and superior visibility, and to provide an image display device, in particular an organic EL display device, having the same.SOLUTION: A laminated optical film is provided, comprising at least a polarizer and a second optical film laminated together via an adhesive layer, the polarizer being disposed on the outer side relative to the second optical film. The adhesive layer exhibits a refractive index RF1 in a polarizer transmission axis on a polarizer-side surface F1 and a refractive index RF2, different from the refractive index RF1, in the polarizer transmission axis direction on a second optical film-side surface F2. A difference between RF1 and a refractive index of the polarizer in the polarizer transmission axis direction is 0.05 or less, and a difference between RF2 and a refractive index of the second optical film in the polarizer transmission axis direction is 0.05 or less.SELECTED DRAWING: Figure 2

Description

The present invention relates to a laminated optical film in which at least a polarizer and a second optical film are laminated via an adhesive layer. The laminated optical film is suitable for an image display device, particularly an organic EL display device.

A display device in which a circular polarizing plate is arranged on the visual side of a display panel is known in order to improve visibility defects due to reflection of external light or reflection of a background on the display screen of the image display device. Patent Documents 1 and 2 propose a polarizing film that reduces reflection of incident light from an oblique direction in black display and realizes an excellent oblique reflected hue, and a display device including the polarizing film.

Japanese Unexamined Patent Publication No. 2015-11136 JP-A-2015-210459

However, the display devices using the polarizing films described in Patent Documents 1 and 2 have a problem that the reflected light becomes uneven and the visibility is insufficient.

In view of the above circumstances, an object of the present invention is to provide a laminated optical film having reduced reflectance from external light and excellent visibility, and an image display device provided with the laminated optical film, particularly an organic EL display device. It is in.

The above problem can be solved by the following configuration. That is, the present invention is a laminated optical film in which at least a polarizing element and a second optical film are laminated via an adhesive layer, and the polarizer is located outside the second optical film. the adhesive layer is for a polarizer refractive index of the polarizer transmission axis direction in the side surface F1 R _F1 and refractive index R _F2 of the polarizer transmission axis of the second optical film surface F2 are different, said R difference between _F1 and the polarizer polarizer transmission axis direction of the refractive index of is within 0.05, the difference between the polarizer transmission axis direction of the refractive index of the second optical film and the R _F2 0.05 The present invention relates to a laminated optical film characterized by being within.

In the laminated optical film, the thickness of the first optical film is preferably 20 μm or less, and the thickness of the second optical film is preferably 30 μm or less.

In the laminated optical film, the thickness of the adhesive layer is preferably 5 μm or less.

The present invention also relates to an image display device provided with the above-mentioned laminated optical film, particularly an organic EL display device.

The image display device includes a laminated optical film in which two or more optical films are laminated, and each optical film constituting the laminated optical film is usually laminated via an adhesive layer. As a result of diligent studies by the present inventors, the adhesive layer provided in the conventionally existing laminated optical film includes one optical film side (this is referred to as "front side") and the other optical film side (this is referred to as "back side"). The refractive index of the adhesive layer is set to the front side in order to suppress reflection at the interface between the front side optical film and the adhesive layer and the interface between the back side optical film and the adhesive. Until now, the concept of making optics different from the other side did not exist.

In the present invention, since the polarizer is located on the outer surface (visual side surface) of the second optical film, when external light, particularly natural light, is transmitted through the polarizer and is incident, the transmitted light is in the direction of the polarizer transmission axis. It becomes the polarized light of. Here, in the present invention, in order to suppress reflection at the interface between each optical film and the adhesive layer, those adhesive layers having different refractive indexes on the front side and the back side are used. Specifically, the use of an adhesive layer and the polarizer transmission axis direction of the refractive index R _F2 is different in the polarizer transmission refractive index of the axis R _F1 and the second optical film side surface F2 of the polarizer surface F1, and within 0.05 the difference between the polarizer transmission axis direction of the refractive index of the polarizer and R _F1, is within 0.05 the difference between the R _F2 polarizer transmission axis direction of the refractive index of the second optical film It is designed to be. Therefore, the reflection at the interface between the polarizer and the adhesive layer and the interface between the second optical film and the adhesive layer can be remarkably suppressed, so that the visibility is improved.

In general, the thinner the laminated optical film, the more uneven the reflected light is likely to occur, which is regarded as a problem. In particular, the laminated optical film according to the present invention has a thin polarizer, a second optical film, and an adhesive layer. However, it is possible to reduce the reflectance of external light, especially natural light, and the visibility is also improved. Therefore, the laminated optical film according to the present invention is particularly useful for an image display device, particularly an organic EL display device.

The figure which shows an example of the reflection from the outside light in the image display device which provided with the laminated optical film which exists conventionally. The figure which shows an example of the image display apparatus provided with the laminated optical film which concerns on this invention.

In the present invention, in a laminated optical film in which at least a polarizer and a second optical film are laminated via an adhesive layer, such an adhesive is used to suppress reflection at the interface between each optical film and the adhesive layer. It is characterized in that a layer having a different refractive index on the front side and the back side is used. Such a feature will be described below in comparison with a conventional image display device provided with a laminated optical film.

Figure 1 is a diagram showing an example of a reflected light L _R from an external light (natural light) L of the image display apparatus having a multilayer optical film that exists conventionally. The image display device M shown in FIG. 1 is an organic EL image display device including an organic light emitting diode 7, and is a laminated optical film 10 in which a polarizer 3 and a second optical film 5 are laminated via a first adhesive layer 4. To be equipped with. In the case of the conventional configuration shown in FIG. 1, the first adhesive layer 4 has the same refractive index on the front side and the back side, the difference between the refractive index of the polarizer 3 and the refractive index of the first adhesive layer 4, and further. Is due to the difference between the refractive indexes of the first adhesive layer 4 and the second optical film 5, the interface between the polarizer 3 and the first adhesive layer 4, and the first adhesive layer 4 and the second optical film 5. Since the external light (natural light) L is reflected at the interface with the light, the reflected light becomes uneven and the visibility becomes insufficient.

FIG. 2 is a diagram showing an example of an image display device provided with a laminated optical film according to the present invention. The image display device M shown in FIG. 2 is an organic EL image display device including the organic light emitting diode 7, and the polarizer 3 is located outside the second optical film 5 via the first adhesive layer 4. A laminated optical film 10 in which a polarizing element 3 and a second optical film 5 are laminated is provided. In the present invention, the laminated optical film may be composed of three or more optical films, and in the embodiment shown in FIG. 2A, the image display device M emits organic light from the outermost surface (visual side surface). Transparent protective film (first optical film) 1 → second adhesive layer 2 → polarizer 3 → first adhesive layer 4 → retardation film (second optical film) 5 → adhesive layer in order toward the diode 7. 6 is provided. As shown in FIG. 2 (b), the first adhesive layer 4 in the multilayer optical film 10 according to the present invention, the refractive index R _F1 and the second optical film side surface of the polarizer transmission axis direction of the polarizer side surface F1 It is different from the polarizer transmission axis direction of the refractive index R _F2 in F2, and the difference between the polarizer transmission axis direction of the refractive index of the polarizer and R _F1 is within 0.05, polarizers and R _F2 second optical film The difference from the refractive index in the transmission axis direction is designed to be within 0.05. As a result, in the laminated optical film 10 according to the present invention, the reflectance of external light (natural light) L at the interface between the polarizer and the adhesive layer and the interface between the adhesive layer and the second optical film is reduced. Excellent visibility.

<First adhesive layer>
The adhesive layer included in the laminated optical film according to the present invention will be described below. In the present invention, the thickness of the adhesive layer is preferably thin, specifically, the thickness of the adhesive layer is preferably 5 μm or less, and more preferably 0.5 to 3 μm.

The adhesive layer included in the laminated optical film according to the present invention is characterized in that the refractive index differs between the front side and the back side. Specifically, different from the polarizer transmission axis direction of the refractive index R _F2 in the polarizer transmission refractive index of the axis R _F1 and the second optical film side surface F2 of the polarizer side surface F1, and the polarizer and R _F1 difference within 0.05 with the polarizer transmission axis direction of the refractive index of the difference between the R _F2 polarizer transmission axis direction of the refractive index of the second optical film is designed within 0.05. The interface between the polarizer and the adhesive layer, and to further suppress the reflection at the interface between the first optical film and the adhesive layer, the difference between the polarizer transmission axis direction of the refractive index of the polarizer and R _F1 0 more preferably to .03 less, and more preferably the difference between the R _F2 polarizer transmission axis direction of the refractive index of the second optical film to more than 0.03.

In the present invention, the "refractive index in the direction of the polarizer transmission axis" on the polarizer side surface F1 (or the second optical film side surface F2) of the adhesive layer is the prism coupler SPA-4000 (manufactured by Cylon Technology Co., Ltd.). The refractive index in the direction of the polarizer transmission axis on each surface side of the adhesive layer was measured. The measurement temperature was 23 ° C. and the measurement wavelength was 532 nm.

In the present invention, the adhesive layer may have any material design as long as it satisfies the above characteristics, and is particularly obtained by irradiating the active energy ray-curable adhesive composition with active energy rays. It is preferably formed by a cured product layer. An example of a method for producing an adhesive layer having different refractive indexes in the direction of the polarizer transmission axis on the front side and the back side will be described later. The active energy ray-curable adhesive composition can be roughly classified into an electron beam-curable type, an ultraviolet-curable type, a visible light-curable type and the like. Further, the ultraviolet curable type adhesive and the visible light curable type adhesive can be classified into a radical polymerization curable type adhesive and a cationic polymerization type adhesive. In the present invention, active energy rays having a wavelength range of 10 nm to less than 380 nm are referred to as ultraviolet rays, and active energy rays having a wavelength range of 380 nm to 800 nm are referred to as visible light.

Examples of the compound constituting the radical polymerization curable adhesive include a radical polymerizable compound. Examples of the radically polymerizable compound include compounds having a radically polymerizable functional group of a carbon-carbon double bond such as a (meth) acryloyl group and a vinyl group. As these curable components, either a monofunctional radical-polymerizable compound or a bifunctional or higher-functional polyfunctional radical-polymerizable compound can be used. In addition, these radically polymerizable compounds may be used alone or in combination of two or more. As these radically polymerizable compounds, for example, compounds having a (meth) acryloyl group are suitable. The active energy ray-curable adhesive composition used in the present invention preferably contains a compound having a (meth) acryloyl group as a main component, and specifically, the total amount of the active energy ray-curable adhesive composition is used. When it is 100% by weight, the compound having a (meth) acryloyl group is preferably contained in an amount of 50% by weight or more, more preferably 80% by weight or more. In addition, in this invention, (meth) acryloyl means acryloyl group and / or methacryloyl group, and "(meth)" has the same meaning below.

Examples of the monofunctional radically polymerizable compound include (meth) acrylamide derivatives having a (meth) acrylamide group. The (meth) acrylamide derivative is preferable in terms of ensuring adhesiveness to a polarizer and various transparent protective films, and also in terms of high polymerization rate and excellent productivity. Specific examples of the (meth) acrylamide derivative include, for example, N-methyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N-isopropyl (meth) acrylamide, and N. N-alkyl group-containing (meth) acrylamide derivatives such as -butyl (meth) acrylamide, N-hexyl (meth) acrylamide; N-methylol (meth) acrylamide, N-hydroxyethyl (meth) acrylamide, N-methylol-N- N-hydroxyalkyl group-containing (meth) acrylamide derivatives such as propane (meth) acrylamide; N-aminoalkyl group-containing (meth) acrylamide derivatives such as aminomethyl (meth) acrylamide and aminoethyl (meth) acrylamide; N-methoxymethyl N-alkoxy group-containing (meth) acrylamide derivatives such as acrylamide and N-ethoxymethylacrylamide; N-mercaptoalkyl group-containing (meth) acrylamide derivatives such as mercaptomethyl (meth) acrylamide and mercaptoethyl (meth) acrylamide; Be done. Examples of the heterocyclic (meth) acrylamide derivative in which the nitrogen atom of the (meth) acrylamide group forms a heterocycle include N-acrylloylmorpholine, N-acrylloylpiperidin, N-methacryloylpiperidin, and N-acrylloylpyridine. And so on.

Among the (meth) acrylamide derivatives, an N-hydroxyalkyl group-containing (meth) acrylamide derivative is preferable from the viewpoint of adhesion to a polarizer and various transparent protective films, and the monofunctional radical polymerizable compound is preferable. For example, various (meth) acrylic acid derivatives having a (meth) acryloyloxy group can be mentioned. Specifically, for example, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, 2-methyl-2-nitropropyl (meth) acrylate, n-butyl ( Meta) acrylate, isobutyl (meth) acrylate, s-butyl (meth) acrylate, t-butyl (meth) acrylate, n-pentyl (meth) acrylate, t-pentyl (meth) acrylate, 3-pentyl (meth) acrylate, 2,2-Dimethylbutyl (meth) acrylate, n-hexyl (meth) acrylate, cetyl (meth) acrylate, n-octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, 4-methyl-2-propylpentyl ( Examples thereof include (meth) acrylic acid (1-20 carbon atoms) alkyl esters such as meta) acrylate and n-octadecyl (meth) acrylate.

Examples of the (meth) acrylic acid derivative include cycloalkyl (meth) acrylates such as cyclohexyl (meth) acrylate and cyclopentyl (meth) acrylate; aralkyl (meth) acrylates such as benzyl (meth) acrylate; 2-isobornyl. (Meta) acrylate, 2-norbornylmethyl (meth) acrylate, 5-norbornen-2-yl-methyl (meth) acrylate, 3-methyl-2-norbornylmethyl (meth) acrylate, dicyclopentenyl (meth) ) Polycyclic (meth) acrylates such as acrylicate, dicyclopentenyloxyethyl (meth) acrylicate, dicyclopentanyl (meth) acrylicate, etc .; 2-methoxyethyl (meth) acrylate, 2-ethoxy Ethyl (meth) acrylate, 2-methoxymethoxyethyl (meth) acrylate, 3-methoxybutyl (meth) acrylate, ethyl carbitol (meth) acrylate, phenoxyethyl (meth) acrylate, alkylphenoxypolyethylene glycol (meth) acrylate, etc. An alkoxy group- or phenoxy group-containing (meth) acrylate; and the like.

Examples of the (meth) acrylic acid derivative include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, and 4-. Hydroxyalkyl (meth) acrylates such as hydroxybutyl (meth) acrylates, 6-hydroxyhexyl (meth) acrylates, 8-hydroxyoctyl (meth) acrylates, 10-hydroxydecyl (meth) acrylates, and 12-hydroxylauryl (meth) acrylates. , [4- (Hydroxymethyl) cyclohexyl] methyl acrylate, cyclohexanedimethanol mono (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate and other hydroxyl group-containing (meth) acrylate; glycidyl (meth) acrylate, 4-Hydroxybutyl (meth) acrylate Epoxy group-containing (meth) acrylate such as glycidyl ether; 2,2,2-trifluoroethyl (meth) acrylate, 2,2,2-trifluoroethyl ethyl (meth) acrylate, tetra Halogen-containing (meth) acrylates such as fluoropropyl (meth) acrylate, hexafluoropropyl (meth) acrylate, octafluoropentyl (meth) acrylate, heptadecafluorodecyl (meth) acrylate, and 3-chloro-2-hydroxypropyl (meth) acrylate. ) Acrylate; Alkylaminoalkyl (meth) acrylate such as dimethylaminoethyl (meth) acrylate; 3-oxytenylmethyl (meth) acrylate, 3-methyl-oxetanylmethyl (meth) acrylate, 3-ethyl-oxetanylmethyl (meth) acrylate , 3-Butyl-oxetanylmethyl (meth) acrylate, 3-hexyluoxetanylmethyl (meth) acrylate and other oxetane group-containing (meth) acrylate; tetrahydrofurfuryl (meth) acrylate, butyrolactone (meth) acrylate, and other heterocycles. (Meta) acrylate having (meth) acrylate, neopentyl glycol (meth) acrylic acid adduct of hydroxypivalate, p-phenylphenol (meth) acrylate and the like can be mentioned.

Examples of the monofunctional radically polymerizable compound include carboxyl group-containing monomers such as (meth) acrylic acid, carboxyethyl acrylate, carboxypentyl acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, and isocrotonic acid.

Examples of the monofunctional radically polymerizable compound include lactam-based vinyl monomers such as N-vinylpyrrolidone, N-vinyl-ε-caprolactam, and methylvinylpyrrolidone; vinylpyridine, vinylpiperidone, vinylpyrimidine, vinylpiperazin, and vinylpyrazine. Examples thereof include vinyl-based monomers having a nitrogen-containing heterocycle such as vinylpyrrole, vinylimidazole, vinyloxazole, and vinylmorpholin.

Further, as the monofunctional radically polymerizable compound, a radically polymerizable compound having an active methylene group can be used. A radically polymerizable compound having an active methylene group is a compound having an active double bond group such as a (meth) acrylic group at the terminal or in the molecule and having an active methylene group. Examples of the active methylene group include an acetoacetyl group, an alkoxymalonyl group, a cyanoacetyl group and the like. The active methylene group is preferably an acetoacetyl group. Specific examples of the radically polymerizable compound having an active methylene group include 2-acetoacetoxyethyl (meth) acrylate, 2-acetoacetoxypropyl (meth) acrylate, 2-acetacetoxy-1-methylethyl (meth) acrylate and the like. Acetacetoxyalkyl (meth) acrylate; 2-ethoxymalonyloxyethyl (meth) acrylate, 2-cyanoacetoxyethyl (meth) acrylate, N- (2-cyanoacetoxyethyl) acrylamide, N- (2-propionylacetoxybutyl) Acrylamide, N- (4-acetoacetoxymethylbenzyl) acrylamide, N- (2-acetoacetylaminoethyl) acrylamide and the like can be mentioned. The radically polymerizable compound having an active methylene group is preferably acetoacetoxyalkyl (meth) acrylate.

Examples of the bifunctional or higher polyfunctional radical polymerizable compound include tripropylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, and 1,9. -Nonandiol di (meth) acrylate, 1,10-decanediol diacrylate, 2-ethyl-2-butylpropanediol di (meth) acrylate, bisphenol A di (meth) acrylate, bisphenol A ethylene oxide adduct di (meth) ) Acrylate, bisphenol A propylene oxide adduct di (meth) acrylate, bisphenol A diglycidyl ether di (meth) acrylate, neopentyl glycol di (meth) acrylate, tricyclodecanedimethanol di (meth) acrylate, cyclic tri Methylolpropanformal (meth) acrylate, dioxane glycol di (meth) acrylate, trimethylpropantri (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate , Dipentaerythritol hexa (meth) acrylate, esterified product of (meth) acrylic acid such as EO-modified diglycerin tetra (meth) acrylate and polyhydric alcohol, 9,9-bis [4- (2- (meth) acryloyl) Oxyethoxy) phenyl] Fluorene can be mentioned. Specific examples include Aronix M-220 (manufactured by Toagosei), Light Acrylate 1,9ND-A (manufactured by Kyoeisha Chemical Co., Ltd.), Light Acrylate DGE-4A (manufactured by Kyoeisha Chemical Co., Ltd.), Light Acrylate DCP-A (manufactured by Kyoeisha Chemical Co., Ltd.). , SR-531 (manufactured by Sartomer), CD-536 (manufactured by Sartomer) and the like. Further, if necessary, various epoxy (meth) acrylates, urethane (meth) acrylates, polyester (meth) acrylates, various (meth) acrylate-based monomers and the like can be mentioned.

When an electron beam or the like is used for the active energy ray, the active energy ray-curable adhesive composition does not need to contain a photopolymerization initiator, but is active. When ultraviolet rays or visible rays are used for the energy rays, it is preferable to contain a photopolymerization initiator.

When a radically polymerizable compound is used, the photopolymerization initiator is appropriately selected by the active energy ray. When curing by ultraviolet rays or visible light, a photopolymerization initiator that cleaves ultraviolet rays or visible light is used. The photopolymerization initiator may be used alone, but when a plurality of photopolymerization initiators are mixed and used, the curing rate and curability can be adjusted, which is preferable. Examples of the photopolymerization initiator include benzophenone compounds such as benzyl, benzophenone, benzoylbenzoic acid, and 3,3'-dimethyl-4-methoxybenzophenone; 4- (2-hydroxyethoxy) phenyl (2-hydroxy-2). -Propyl) ketone, α-hydroxy-α, α'-dimethylacetophenone, 2-methyl-2-hydroxypropiophenone, 1-hydroxycyclohexylphenyl ketone, 1- [4- (2-hydroxyethoxy) -phenyl]- 2-Hydroxy-2-methyl-1-propane-1-one, 2-hirodoxy-1-{4- [4- (2-hydroxy-2-methyl-propionyl) -benzyl] phenyl} -2-methyl-propane Aromatic ketone compounds such as -1-one; methoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxyacetophenone, 2-methyl-1- [4- (methylthio) -phenyl] -2-Acetphenone compounds such as morpholinopropane-1; benzophenone compounds such as venzoin methyl ether, benzoine ethyl ether, benzoin isopropyl ether, benzoine butyl ether, anisoin methyl ether; benzyl dimethyl Aromatic ketal compounds such as ketal; aromatic sulfonyl chloride compounds such as 2-naphthalene sulfonyl chloride; photoactive oxime compounds such as 1-phenone-1,1-propandion-2- (o-ethoxycarbonyl) oxime Thioxanson, 2-chlorothioxanson, 2-methylthioxanson, 2,4-dimethylthioxanson, isopropylthioxanson, 2,4-dichlorothioxanson, 2,4-diethylthioxanson, 2, Examples thereof include thioxanthone compounds such as 4-diisopropylthioxanthone and dodecylthioxanthone; benzophenone; ketone halide; acylphosphinoxide; acylphosphonate and the like.

The blending amount of the photopolymerization initiator is 20% by weight or less when the total amount of the active energy ray-curable adhesive composition is 100% by weight. The blending amount of the photopolymerization initiator is preferably 0.01 to 20% by weight, more preferably 0.05 to 10% by weight, and further preferably 0.1 to 5% by weight.

Further, when the curable adhesive for laminated optical films of the present invention is used in a visible light curable type containing a radically polymerizable compound as a curable component, a photopolymerization initiator having high sensitivity to light of 380 nm or more in particular. Is preferably used. A photopolymerization initiator having high sensitivity to light of 380 nm or more will be described later.

The photopolymerization initiator is a compound represented by the following general formula (1);

（式中、Ｒ^１およびＲ^２は−Ｈ、−ＣＨ_２ＣＨ_３、−ｉＰｒまたはＣｌを示し、Ｒ^１およびＲ^２は同一または異なっても良い）を単独で使用するか、あるいは一般式（１）で表される化合物と後述する３８０ｎｍ以上の光に対して高感度な光重合開始剤とを併用することが好ましい。一般式（１）で表される化合物を使用した場合、３８０ｎｍ以上の光に対して高感度な光重合開始剤を単独で使用した場合に比べて接着性に優れる。一般式（１）で表される化合物の中でも、Ｒ^１およびＲ^２が−ＣＨ_２ＣＨ_３であるジエチルチオキサントンが特に好ましい。接着剤中の一般式（１）で表される化合物の組成比率は、活性エネルギー線硬化型接着剤組成物の全量を１００重量％としたとき、０．１〜５重量％であることが好ましく、０．５〜４重量％であることがより好ましく、０．９〜３重量％であることがさらに好ましい。

(In the formula, R ¹ and R ² indicate -H, -CH ₂ CH ₃ , -iPr or Cl, and R ¹ and R ² may be the same or different), or the general formula (in the formula) may be used alone. It is preferable to use the compound represented by 1) in combination with a photopolymerization initiator having high sensitivity to light of 380 nm or more, which will be described later. When the compound represented by the general formula (1) is used, the adhesiveness is excellent as compared with the case where a photopolymerization initiator having high sensitivity to light of 380 nm or more is used alone. Among the compounds represented by the general formula (1), ^{diethylthioxanthone in which R 1} and R ² are −CH ₂ CH ₃ is particularly preferable. The composition ratio of the compound represented by the general formula (1) in the adhesive is preferably 0.1 to 5% by weight when the total amount of the active energy ray-curable adhesive composition is 100% by weight. , 0.5 to 4% by weight, more preferably 0.9 to 3% by weight.

In addition, it is preferable to add a polymerization initiation aid as needed. Examples of the polymerization initiator include triethylamine, diethylamine, N-methyldiethanolamine, ethanolamine, 4-dimethylaminobenzoic acid, methyl 4-dimethylaminobenzoate, ethyl 4-dimethylaminobenzoate, isoamyl 4-dimethylaminobenzoate, etc. , And ethyl 4-dimethylaminobenzoate is particularly preferable. When a polymerization initiation aid is used, the amount added is usually 0 to 5 parts by weight, preferably 0 to 4 parts by weight, and most preferably 0 to 3 parts by weight, based on 100 parts by weight of the total amount of the curable component. is there.

In addition, a known photopolymerization initiator can be used in combination if necessary. Since the transparent protective film having a UV absorbing ability does not transmit light of 380 nm or less, it is preferable to use a photopolymerization initiator having high sensitivity to light of 380 nm or more as the photopolymerization initiator. Specifically, 2-methyl-1- (4-methylthiophenyl) -2-morpholinopropane-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1 , 2- (Dimethylamino) -2-[(4-Methylphenyl) Methyl] -1- [4- (4-morpholinyl) phenyl] -1-butanone, 2,4,6-trimethylbenzoyl-diphenyl-phosphine Oxide, bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide, bis (η5-2,4-cyclopentadiene-1-yl) -bis (2,6-difluoro-3- (1H-pyrrole-) 1-yl) -phenyl) titanium and the like can be mentioned.

In particular, as the photopolymerization initiator, in addition to the photopolymerization initiator of the general formula (1), a compound represented by the following general formula (2);

（式中、Ｒ^３、Ｒ^４およびＲ^５は−Ｈ、−ＣＨ_３、−ＣＨ_２ＣＨ_３、−ｉＰｒまたはＣｌを示し、Ｒ^３、Ｒ^４およびＲ^５は同一または異なっても良い）を使用することが好ましい。一般式（２）で表される化合物としては、市販品でもある２−メチル−１−（４−メチルチオフェニル）−２−モルフォリノプロパン−１−オン（商品名：Ｏｍｎｉｒａｄ９０７ メーカー：ＩＧＭｒｅｓｉｎｓ）が好適に使用可能である。その他、２−ベンジル−２−ジメチルアミノ−１−（４−モルフォリノフェニル）−ブタノン−１（商品名：Ｏｍｎｉｒａｄ３６９ メーカー：ＩＧＭｒｅｓｉｎｓ）、２−（ジメチルアミノ）−２−［（４−メチルフェニル）メチル］−１−［４−（４−モルホリニル）フェニル］−１−ブタノン（商品名：Ｏｍｎｉｒａｄ３７９ メーカー：ＩＧＭｒｅｓｉｎｓ）が感度が高いため好ましい。

(In the formula, R ³ , R ⁴ and R ⁵ indicate -H, -CH ₃ , -CH ₂ CH ₃ , -iPr or Cl, and R ³ , R ⁴ and R ⁵ may be the same or different). It is preferable to use it. As the compound represented by the general formula (2), 2-methyl-1- (4-methylthiophenyl) -2-morpholinopropane-1-one (trade name: Omnirad907, manufacturer: IGMresins), which is also a commercially available product, is preferable. Can be used for. In addition, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1 (trade name: Omnirad369 manufacturer: IGMresins), 2- (dimethylamino) -2-[(4-methylphenyl) Methyl] -1- [4- (4-morpholinyl) phenyl] -1-butanone (trade name: Omnirad379, manufacturer: IGMresins) is preferable because of its high sensitivity.

In the present invention, among the above photopolymerization initiators, it is preferable to use a hydroxyl group-containing photopolymerization initiator. When the active energy ray-curable adhesive composition contains a hydroxyl group-containing photopolymerization initiator as a polymerization initiator, the solubility in the adhesive layer having a high concentration of the A component on the polarizer side is enhanced, and the adhesive layer is increased. Increases the curability of. Examples of the photopolymerization initiator having a hydroxyl group include 2-methyl-2-hydroxypropiophenone (trade name "DAROCUR1173", manufactured by IGMresins), 1-hydroxycyclohexylphenylketone (trade name "Omnirad184", manufactured by IGMresins). ), 1- [4- (2-Hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propane-1-one (trade name "Omnirad2959", manufactured by IGMresins), 2-hirodoxy-1- {4- [4- (2-Hydroxy-2-methyl-propionyl) -benzyl] phenyl} -2-methyl-propane-1-one (trade name "Omnirad 127", manufactured by IGMresins) and the like can be mentioned. In particular, 1-hydroxycyclohexylphenyl ketone is more preferable because it has particularly excellent solubility in an adhesive layer having a high concentration of component A.

The active energy ray-curable adhesive composition used in the present invention can contain an acrylic oligomer obtained by polymerizing a (meth) acrylic monomer in addition to the curable component of the radically polymerizable compound. By containing an acrylic oligomer component in the active energy ray-curable adhesive composition, the curing shrinkage when the composition is irradiated with the active energy ray and cured is reduced, and the adhesive, the polarizer and the transparent protection are protected. It is possible to reduce the interfacial stress with an adherend such as a film. As a result, it is possible to suppress a decrease in the adhesiveness between the adhesive layer and the adherend. In order to sufficiently suppress the curing shrinkage of the cured product layer (adhesive layer), the content of the acrylic oligomer is 5 to 30 weight by weight when the total amount of the active energy ray-curable adhesive composition is 100% by weight. %, More preferably 10 to 20% by weight.

Since the active energy ray-curable adhesive composition preferably has a low viscosity in consideration of workability and uniformity during coating, the acrylic oligomer obtained by polymerizing a (meth) acrylic monomer also has a low viscosity. Is preferable. As the acrylic oligomer having a low viscosity, those having a weight average molecular weight (Mw) of 15,000 or less are preferable, those having a weight average molecular weight (Mw) of 10000 or less are more preferable, and those having a weight average molecular weight (Mw) of 5000 or less are particularly preferable. On the other hand, in order to further promote the uneven distribution of the components of the adhesive composition between the polarizer and the transparent protective film, the weight average molecular weight (Mw) of the acrylic oligomer (A) is preferably 500 or more. It is more preferably 1000 or more, and particularly preferably 1500 or more. Specific examples of the (meth) acrylic monomer constituting the acrylic oligomer (A) include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, and 2 -Methyl-2-nitropropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, S-butyl (meth) acrylate, t-butyl (meth) acrylate, n-pentyl (meth) acrylate, t-pentyl (meth) acrylate, 3-pentyl (meth) acrylate, 2,2-dimethylbutyl (meth) acrylate, n-hexyl (meth) acrylate, cetyl (meth) acrylate, n-octyl (meth) acrylate, 2 (Meta) acrylic acid (1-20 carbon atoms) alkyl esters such as −ethylhexyl (meth) acrylate, 4-methyl-2-propylpentyl (meth) acrylate, N-octadecyl (meth) acrylate, and further, for example, cyclo. Alkyl (meth) acrylates (eg, cyclohexyl (meth) acrylates, cyclopentyl (meth) acrylates, etc.), aralkyl (meth) acrylates (eg, benzyl (meth) acrylates, etc.), polycyclic (meth) acrylates (eg, 2- Isobornyl (meth) acrylate, 2-norbornylmethyl (meth) acrylate, 5-norbornen-2-yl-methyl (meth) acrylate, 3-methyl-2-norbornylmethyl (meth) acrylate, etc.), hydroxyl group Contains (meth) acrylic acid esters (eg, hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2,3-dihydroxypropylmethyl-butyl (meth) methacrylate, etc.), alkoxy group or phenoxy group (containing) Meta) Acrylate esters (2-methoxyethyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate, 2-methoxymethoxyethyl (meth) acrylate, 3-methoxybutyl (meth) acrylate, ethyl carbitol (meth) Acrylate, phenoxyethyl (meth) acrylate, etc.), epoxy group-containing (meth) acrylic acid esters (eg, glycidyl (meth) acrylate, etc.), halogen-containing (meth) acrylic acid esters (eg, 2,2,2- Trifluoroethyl (meth) acrylate, 2,2 , 2-Trifluoroethyl ethyl (meth) acrylate, tetrafluoropropyl (meth) acrylate, hexafluoropropyl (meth) acrylate, octafluoropentyl (meth) acrylate, heptadecafluorodecyl (meth) acrylate, etc.), Alkylaminoalkyl (Meta) acrylate (for example, dimethylaminoethyl (meth) acrylate and the like) and the like can be mentioned. These (meth) acrylates can be used alone or in combination of two or more. Specific examples of the acrylic oligomer (A) include "ARUFON" manufactured by Toagosei Co., Ltd., "Actflow" manufactured by Soken Chemical Co., Ltd., and "JONCRYL" manufactured by IGMresins.

When the acrylic oligomer is a liquid, it is preferably used because it is not necessary to consider the solubility in the adhesive composition. Acrylic oligomers are usually liquid when the glass transition temperature (Tg) is less than 25 ° C. Further, in order to achieve both compatibility with the adhesive composition and uneven distribution of components in the adhesive layer, the acrylic oligomer preferably contains a polar functional group. Examples of the polar functional group include a hydroxyl group, an epoxy group, a carboxyl group and an alkoxysilyl group. Specific examples thereof include "ARUFON UH series", "ARUFON UC series", "ARUFON UF series", "ARUFON UG series", and "ARUFON US series" (all manufactured by Toagosei Co., Ltd.). Above all, it is preferable to contain an epoxy group because it is expected that the adhesiveness will be improved by the interaction with the polarizer. Specific examples thereof include "ARUFON UG-4000" and "ARUFON UG-4010" (both manufactured by Toagosei Co., Ltd.).

<Polarizer>
The polarizer used in the present invention is not particularly limited, and various types of polarizers can be used. As the polarizer, for example, a hydrophilic polymer film such as a polyvinyl alcohol-based film, a partially formalized polyvinyl alcohol-based film, an ethylene / vinyl acetate copolymerization system partially saponified film, and two colors such as iodine and a bicolor dye are used. Examples thereof include those obtained by adsorbing a sex material and uniaxially stretching, and polyene-based oriented films such as a dehydrated product of polyvinyl alcohol and a dehydrogenated product of polyvinyl chloride. Among these, a polarizer made of a polyvinyl alcohol-based film and a dichroic substance such as iodine is preferable.

In the present invention, the "refractive index in the direction of the polarizing element transmission axis" of the polarizer is the refractive index in the direction of the transmission axis among the refractive indexes in the plane of the polarizer using the prism coupler SPA-4000 (manufactured by Cylon Technology). The rate was measured and used as the refractive index in the direction of the polarizer transmission axis. The measurement temperature was 23 ° C. and the measurement wavelength was 532 nm.

The thickness of the polarizer is generally 1 to 30 μm, but as described above, the thinner the laminated optical film, the more uneven the reflected light is likely to occur. Therefore, particularly in the present invention, it is preferable that the polarizer is a thin polarizer. Specifically, the thickness is preferably 20 μm or less, and more preferably 1 to 12 μm.

Typical examples of the thin polarizing element include JP-A-51-069644, JP-A-2000-338329, WO2010 / 100917 pamphlet, PCT / JP2010 / 00146, or Japanese Patent Application No. 2010-. Examples thereof include the thin polarizing film described in the specification of No. 269002 and the specification of Japanese Patent Application No. 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 base material 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 stretching resin base material.

Among the manufacturing methods including a step of stretching in a laminated state and a step of dyeing, the thin polarizing film can be stretched at a high magnification and the polarization performance can be improved. It is preferably obtained by a production method including a step of stretching in an aqueous boric acid solution as described in JP2010 / 00460, or in Japanese Patent Application No. 2010-269002 and Japanese Patent Application No. 2010-263692, particularly preferably. It is preferably obtained by a production method including a step of auxiliary stretching in the air before stretching in an aqueous boric acid solution described in Japanese Patent Application No. 2010-269002 and Japanese Patent Application No. 2010-263692.

<Second optical film>
The second optical film is not particularly limited, but is used for forming an image display device such as a reflective film, a transflective film, a retardation film (including a wavelength film such as 1/2 or 1/4), or a viewing angle compensation film. An optical layer that may be used can be used. In the present invention, the thickness of the second optical film is preferably thin, specifically 30 μm or less, and more preferably 1 to 20 μm.

In the present invention, the "refractive index in the direction of the polarizer transmission axis" of the retardation film (second optical film) is the in-plane refractive index of the retardation film using a prism coupler SPA-4000 (manufactured by Cylon Technology). Of these, the refractive index of the polarizer located outside the retardation film in the transmission axis direction was measured, and this was taken as the refractive index in the polarizer transmission axis direction. The measurement temperature was 23 ° C. and the measurement wavelength was 532 nm.

The laminated optical film according to the present invention is characterized in that the refractive index in the polarizer transmission axis direction differs between the front side and the back side of the adhesive layer. The laminated optical film provided with such an adhesive layer can be produced, for example, by the following production method.
A method for producing a laminated optical film in which at least a polarizer and a second optical film are laminated via an adhesive layer, wherein the adhesive layer is a first cured product layer and a second adhesive of the first adhesive composition. It contains a second cured product layer of the agent composition, and the first adhesive composition and the second adhesive composition contain at least a part of a different component, and the binder is applied. The first step of applying the first adhesive composition to the mating surface, the second step of applying the second adhesive composition to the laminating surface of the second optical film, and the above-mentioned of the polarizer. The third step of bonding the coated surface of the first adhesive composition and the coated surface of the second adhesive composition of the second optical film, and the active energy rays from the polarizer surface side or the second optical film surface side. A manufacturing method including a fourth step of irradiating and adhering the polarizer and the second optical film.

In the production method, the adhesive layer includes a first cured product layer of the first adhesive composition and a second cured product layer of the second adhesive composition, and the first adhesive composition and the second adhesive composition. since object and are those which contain at least partially different components, different adhesives layer in the in-plane refractive index R _F2 in the polarizer plane refractive index in the side surface F1 R _F1 and the second optical film surface F2 Is formed. Here, the refractive index of the polarizer in the direction of the polarizer transmission axis and the refractive index of the second optical film in the direction of the polarizer transmission axis can be measured in advance, and the first cured product of the first adhesive composition can be measured. polarizer transmission axis direction of the refractive index R _F2 in the polarizer transmission axis direction of the refractive index R _F1 and the second optical film side surface F2 of the polarizer side surface F1 of the layers also, by performing the optimum mix design, respectively, optionally Can be designed to the value of. Therefore, in the manufacturing method, the difference between the transmission axis direction of the refractive index of the polarizer and R _F1 is within 0.05, the difference between the polarizer transmission axis direction of the refractive index of the R _F2 second optical film A laminated optical film having an adhesive layer of 0.05 or less can be produced.

In the first step, the coated first adhesive composition is irradiated with active energy rays from the polarizer surface side or the first adhesive composition coated surface side of the polarizer, and the above. The first adhesive composition may be cured to form the first cured product layer in advance, the coated first adhesive composition may be air-dried, and the coated first adhesive composition may be formed. When the product contains a solvent, the coating layer of the uncured first adhesive composition may be formed in advance by removing the solvent.

In the laminated optical film according to the present invention, the surface modification treatment of the polarizer and the second optical film may be performed before the first step and / or the second coating step (coating process). Specific treatments include corona treatment, plasma treatment, and saponification treatment.

Further, in the first step and / or the second coating step (coating process), the coating method of the active energy ray-curable adhesive composition is appropriately selected depending on the viscosity of the composition and the target thickness. To. Examples of the coating method include a reverse coater, a gravure coater (direct, reverse and offset), a bar reverse coater, a roll coater, a die coater, a bar coater, a rod coater and the like. In addition, a method such as a dipping method can be appropriately used for coating.

In the third step (bonding step), two different types of optical films are bonded together via the coated active energy ray-curable adhesive composition. The optical film can be bonded by, for example, a roll laminator or the like.

In the fourth step (adhesion process), the active energy ray-curable adhesive composition can be used in an electron beam-curable type, an ultraviolet-curable type, or a visible light-curable type. As the active energy ray-curable adhesive composition, a visible light-curable adhesive composition is preferable from the viewpoint of productivity.

In the active energy ray-curable adhesive composition, for example, after bonding a polarizer and a retardation film, an active energy ray (electron beam, ultraviolet rays, visible light, etc.) is irradiated to form an active energy ray-curable adhesive composition. The object is cured to form an adhesive layer. The irradiation direction of the active energy ray (electron beam, ultraviolet ray, visible light, etc.) can be any suitable direction. Preferably, the irradiation is performed from the retardation film side. When irradiated from the polarizer side, the polarizer may be deteriorated by active energy rays (electron beam, ultraviolet rays, visible light, etc.).

In the electron beam curing type, any appropriate conditions can be adopted as the electron beam irradiation conditions as long as the above-mentioned active energy ray-curable adhesive composition can be cured. For example, in electron beam irradiation, the acceleration voltage is preferably 5 kV to 300 kV, and more preferably 10 kV to 250 kV. If the acceleration voltage is less than 5 kV, the electron beam may not reach the adhesive and curing may be insufficient. If the acceleration voltage exceeds 300 kV, the penetrating power through the sample is too strong and damages the retardation film and the polarizer. May be given. The irradiation dose is 5 to 100 kGy, more preferably 10 to 75 kGy. When the irradiation dose is less than 5 kGy, the adhesive is insufficiently cured, and when it exceeds 100 kGy, the retardation film and the polarizer are damaged, the mechanical strength is lowered and yellowing occurs, and the predetermined optical characteristics are obtained. I can't.

The electron beam irradiation is usually performed in an inert gas, but if necessary, it may be performed in the atmosphere or under the condition that a small amount of oxygen is introduced. Depending on the material of the retardation film, by appropriately introducing oxygen, oxygen inhibition can be caused on the surface of the retardation film to which the electron beam first hits, and damage to the retardation film can be prevented, only for the adhesive. The electron beam can be efficiently irradiated.

When producing the laminated optical film according to the present invention, as the active energy ray, one containing visible light having a wavelength range of 380 nm to 450 nm, particularly an active energy ray having the largest irradiation amount of visible light having a wavelength range of 380 nm to 450 nm is used. It is preferable to do so. In the ultraviolet curable type and the visible light curable type, when a retardation film having an ultraviolet absorbing ability (ultraviolet opaque retardation film) is used, it absorbs light having a wavelength shorter than about 380 nm, and therefore has a wavelength shorter than 380 nm. Light does not reach the active energy ray-curable adhesive and does not contribute to its polymerization reaction. Further, the light having a wavelength shorter than 380 nm absorbed by the retardation film is converted into heat, and the retardation film itself generates heat, which causes defects such as curl and wrinkles of the laminated optical film. Therefore, when the ultraviolet curable type or the visible light curable type is adopted in the present invention, it is preferable to use a device that does not emit light having a wavelength shorter than 380 nm as an active energy ray generator, and more specifically, a wavelength range of 380. The ratio of the integrated illuminance of about 440 nm to the integrated illuminance of the wavelength range of 250 to 370 nm is preferably 100: 0 to 100: 50, and more preferably 100: 0 to 100:40. As the active energy ray according to the present invention, a gallium-filled metal halide lamp and an LED light source that emits a wavelength range of 380 to 440 nm are preferable. Alternatively, with ultraviolet rays such as low-pressure mercury lamp, medium-pressure mercury lamp, high-pressure mercury lamp, ultra-high pressure mercury lamp, incandescent lamp, xenon lamp, halogen lamp, carbon arc lamp, metal halide lamp, fluorescent lamp, tungsten lamp, gallium lamp, excima laser or sunlight. A light source containing visible light can be used, and a bandpass filter can be used to block ultraviolet rays having a wavelength shorter than 380 nm. In order to prevent curling of the laminated optical film while improving the adhesive performance of the adhesive layer between the polarizer and the retardation film, a gallium-filled metal halide lamp can be used and light with a wavelength shorter than 380 nm can be blocked. It is preferable to use an active energy ray obtained through a band pass filter or an active energy ray having a wavelength of 405 nm obtained by using an LED light source.

In the ultraviolet curable type or the visible light curable type, it is also preferable to heat the active energy ray-curable adhesive after irradiation with ultraviolet rays or visible light (warming after irradiation), and in that case, it is preferable to heat to 40 ° C. or higher. , It is more preferable to heat to 50 ° C. or higher.

The active energy ray-curable adhesive used in the present invention can be suitably used particularly when forming an adhesive layer for adhering a polarizer and a retardation film having a light transmittance of less than 5% at a wavelength of 365 nm. is there. Here, the active energy ray-curable adhesive according to the present invention irradiates ultraviolet rays through a retardation film having a UV absorbing ability by containing the photopolymerization initiator of the general formula (1) described above. The adhesive layer can be cured and formed. Therefore, the adhesive layer can be cured even in a laminated optical film in which a retardation film having a UV absorbing ability is laminated on both sides of a polarizer. However, as a matter of course, the adhesive layer can be cured even in a laminated optical film in which a retardation film having no UV absorption ability is laminated. The retardation film having a UV absorbing ability means a retardation film having a transmittance of less than 10% with respect to light at 380 nm.

Examples of the method of imparting the UV absorbing ability to the retardation film include a method of incorporating an ultraviolet absorber in the retardation film and a method of laminating a surface treatment layer containing an ultraviolet absorber on the surface of the retardation film.

Specific examples of the ultraviolet absorber include conventionally known oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex salt compounds, triazine compounds and the like. ..

<Second adhesive layer>
In the embodiment shown in FIG. 2, the second adhesive layer 2 can be designed in the same manner as the first adhesive layer. However, it is preferable to use a second adhesive layer 2 having different refractive indexes on the front side and the back side in order to suppress reflection at the interface with each optical film. Specifically, by using the transparent protective film 1 side plane refractive index in-plane refractive index R _F3 in the polarizer 3 side surface F4 at the surface F3 R _F4 is different from the adhesive layer, and a transparent protective and R _F3 film It is preferable to design so that the difference from the in-plane average refractive index of 1 is within 0.05 and the difference between _RF4 and the in-plane average refractive index of the polarizer 3 is within 0.05. In this case, the reflectance is reduced in the entire image display device M, and the visibility is remarkably improved. In the present invention, the "in-plane average refractive index" of the polarizer is the refractive index in the transmission axis direction and the absorption of the in-plane refractive index of the polarizer using the prism coupler SPA-4000 (manufactured by Cylon Technology). The refractive index in the axial direction is measured, and these average values are taken as the in-plane average refractive index of the polarizer. The measurement temperature is 23 ° C. and the measurement wavelength is 532 nm.

<Transparent protective film>
The thickness of the transparent protective film is preferably thin, specifically 30 μm or less, and more preferably 1 to 20 μm. The transparent protective film preferably has excellent transparency, mechanical strength, thermal stability, moisture barrier property, isotropic property, and the like. For example, polyester polymers such as polyethylene terephthalate and polyethylene naphthalate, cellulose polymers such as diacetyl cellulose and triacetyl cellulose, acrylic polymers such as polymethyl methacrylate, and styrene such as polystyrene and acrylonitrile-styrene copolymer (AS resin). Examples thereof include based polymers and polystyrene polymers. In addition, polyethylene, polypropylene, polyolefins having a cyclo- or norbornene structure, polyolefin-based polymers such as ethylene / propylene copolymers, vinyl chloride-based polymers, amide-based polymers such as nylon and aromatic polyamide, imide-based polymers, and sulfone-based polymers. , Polyether sulfone polymer, polyether ether ketone polymer, polyphenylene sulfide polymer, vinyl alcohol polymer, vinylidene chloride polymer, vinyl butyral polymer, allylate polymer, polyoxymethylene polymer, epoxy polymer, or the above. Polymer blends and the like are also examples of polymers that form the transparent protective film. The transparent protective film may contain one or more of any suitable additives. Examples of the additive include an ultraviolet absorber, an antioxidant, a lubricant, a plasticizer, a mold release agent, an antioxidant, a flame retardant, a nucleating agent, an antistatic agent, a pigment, a coloring agent and the like. 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, still more preferably 60 to 98% by weight, and particularly preferably 70 to 97% by weight. .. When the content of the thermoplastic resin in the transparent protective film is 50% by weight or less, the high transparency inherent in the thermoplastic resin may not be sufficiently exhibited.

Further, as the transparent protective film, a polymer film described in JP-A-2001-343529 (WO01 / 37007), for example, (A) a thermoplastic resin having a substituted and / or unsubstituted imide group in the side chain, and a side Examples thereof include resin compositions containing a thermoplastic resin having a substituted and / or unsubstituted phenyl and a nitrile group in the chain. Specific examples include a film of a resin composition containing an alternating copolymer composed of isobutylene and N-methylmaleimide and an acrylonitrile / styrene copolymer. As the film, a film made of a mixed extruded product of a resin composition or the like can be used. Since these films have a small phase difference and a small photoelastic coefficient, problems such as unevenness due to distortion of the polarizing film can be eliminated, and since the moisture permeability is small, they are excellent in humidification durability.

In the present invention, the "in-plane average refractive index" of the transparent protective film is the refraction in the phase-advancing axis direction among the in-plane refractive indexes of the transparent protective film using the prism coupler SPA-4000 (manufactured by Cylon Technology). The index and the refractive index in the slow axis direction were measured, and these average values were taken as the in-plane average refractive index. The measurement temperature was 23 ° C. and the measurement wavelength was 532 nm.

<Adhesive layer>
In the embodiment shown in FIG. 2, the transparent protective film (first optical film) 1, the first adhesive layer 2, the polarizer (second optical film) 3, the second adhesive layer 4, and the retardation film (third) are described above. The laminated optical film including the 3 optical film) 5 is laminated on the organic light emitting diode 7 via the adhesive layer 6. The pressure-sensitive adhesive forming the pressure-sensitive adhesive layer is not particularly limited, and for example, a polymer based on an acrylic polymer, a silicone-based polymer, polyester, polyurethane, polyamide, polyether, fluorine-based or rubber-based polymer is appropriately selected. Can be used. In particular, an acrylic pressure-sensitive adhesive that has excellent optical transparency, exhibits appropriate wettability, cohesiveness, and adhesiveness, and has excellent weather resistance and heat resistance can be preferably used.

The adhesive layer can also be provided on one or both sides of a polarizing film or an optical film as a superimposing layer of different compositions or types. Further, when provided on both sides, adhesive layers having different compositions, types and thicknesses can be formed on the front and back surfaces of the polarizing film or the optical film. The thickness of the adhesive layer can be appropriately determined according to the purpose of use, adhesive strength, etc., and is generally 1 to 500 μm, preferably 1 to 200 μm, and particularly preferably 1 to 100 μm.

The exposed surface of the adhesive layer is temporarily covered with a separator for the purpose of preventing contamination until it is put into practical use. As a result, it is possible to prevent the adhesive layer from coming into contact with the adhesive layer in the usual handling state. As the separator, except for the above-mentioned thickness condition, for example, an appropriate thin leaf body such as a plastic film, a rubber sheet, a paper, a cloth, a non-woven fabric, a net, a foam sheet or a metal leaf, or a laminate thereof may be used as a silicone-based or long separator. Appropriate conventional ones such as those coated with an appropriate release agent such as chain alkyl type, fluorine type and molybdenum sulfide can be used.

<Image display device>
The laminated optical film of the present invention can be preferably used for forming various image display devices such as an organic EL image device and a liquid crystal display device. The image display device can be formed according to the conventional method. That is, the image display device is generally formed by appropriately assembling components such as an organic light emitting diode, a liquid crystal cell, a laminated optical film, and, if necessary, a lighting system, and incorporating a drive circuit. Is not particularly limited except that the laminated optical film according to the present invention is used, and can be the same as the conventional one.

When the laminated optical film of the present invention is used in a liquid crystal display device, an appropriate liquid crystal display such as a liquid crystal display device in which laminated optical films are arranged on one side or both sides of a liquid crystal cell, or a lighting system using a backlight or a reflector. The device can be formed. In that case, the laminated optical film according to the present invention can be installed on one side or both sides of the liquid crystal cell. When laminated optical films are provided on both sides, they may be the same or different. Further, when forming the liquid crystal display device, for example, an appropriate component such as a diffuser plate, an anti-glare layer, an antireflection film, a protective plate, a prism array, a lens array sheet, a light diffuser plate, and a backlight is placed in one layer or at an appropriate position. Two or more layers can be arranged.

In Examples 1 to 3 and Comparative Example 1 shown below, a laminated optical film was model-designed by simulation. A commercially available liquid crystal simulator "LCD Master (manufactured by Shintech)" was used for the simulation. The optical calculation algorithm was the 4 × 4 Jones matrix method. Further, as the incident light (random light) from the first optical film side to the laminated optical film, one having 380 nm to 780 nm was used.

(Polarizer)
As the polarizer, a polarizer (thickness 5 μm) having a refractive index of 1.52 in the polarizer transmission axis direction at 550 nm was used.

(Second optical film (phase difference film))
As the second optical film, a retardation film (thickness 1.5 μm) having a refractive index of 1.65 in the polarizer transmission axis direction at 550 nm was used.

Examples 1-3
Using LCD Master, to design the adhesive layer plane refractive index R _F2 in plane refractive index R _F1 and the second optical film side surface F2 of the polarizer side surface F1 has a value shown in Table 1, according A laminated optical film in which the first optical film and the second optical film were laminated via an adhesive layer was designed, and the reflectance when the laminated optical film was irradiated with random light from the first optical film side was calculated. The results are shown in Table 1.

Comparative Example 1
Using the LCD master, an adhesive layer (single-layer adhesive layer) having a constant in-plane refractive index in the thickness direction is designed, and the first optical film and the second optical film are laminated via the adhesive layer. The laminated optical film was designed and the refractive index was calculated. The results are shown in Table 1.

From the results in Table 1, in the laminated optical films according to Examples 1 to 3, | R _(a) −R _F1 | and | R _(b) −R _F2 | are designed within 0.05, so that they are outside. It can be seen that when light (random light) is incident on the laminated optical film, the reflectance is low and the visibility is excellent. On the other hand, in the laminated optical film according to the comparative example corresponding to the conventional laminated optical film, since | R _(b) −R _F2 | exceeds 0.05, it can be seen that the reflectance is large and the visibility is poor.

Claims (5)

A laminated optical film in which at least a polarizer and a second optical film are laminated via an adhesive layer.
The polarizer is located outside the second optical film and is located outside the second optical film.
The adhesive layer is for a polarizer refractive index of the polarizer transmission axis direction in the side surface F1 R _F1 and refractive index R _F2 of the polarizer transmission axis of the second optical film surface F2 are different,
The difference between the R _F1 and the polarizer polarizer transmission axis direction of the refractive index of is within 0.05, the difference between the polarizer transmission axis direction of the refractive index of the second optical film and the R _F2 is 0 A laminated optical film characterized by being within .05. The laminated optical film according to claim 1, wherein the thickness of the polarizer is 20 μm or less, and the thickness of the second optical film is 30 μm or less. The laminated optical film according to claim 1 or 2, wherein the thickness of the adhesive layer is 5 μm or less. An image display device comprising the laminated optical film according to any one of claims 1 to 3. An organic EL display device comprising the laminated optical film according to any one of claims 1 to 3.

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