CN112444903A - Laminated optical film and image display device - Google Patents

Laminated optical film and image display device Download PDF

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Publication number
CN112444903A
CN112444903A CN202010919876.1A CN202010919876A CN112444903A CN 112444903 A CN112444903 A CN 112444903A CN 202010919876 A CN202010919876 A CN 202010919876A CN 112444903 A CN112444903 A CN 112444903A
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meth
optical film
acrylate
adhesive layer
refractive index
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菅野亮
座间优人
高田胜则
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Nitto Denko Corp
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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/30—Polarising elements
    • G02B5/3025—Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state
    • G02B5/3033—Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state in the form of a thin sheet or foil, e.g. Polaroid
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/30—Polarising elements
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
    • B32B7/02—Physical, chemical or physicochemical properties
    • B32B7/023—Optical properties
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
    • B32B7/04—Interconnection of layers
    • B32B7/12—Interconnection of layers using interposed adhesives or interposed materials with bonding properties
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
    • G02B1/10—Optical coatings produced by application to, or surface treatment of, optical elements
    • G02B1/14—Protective coatings, e.g. hard coatings
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/30—Polarising elements
    • G02B5/3025—Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state
    • G02B5/3033—Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state in the form of a thin sheet or foil, e.g. Polaroid
    • G02B5/3041—Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state in the form of a thin sheet or foil, e.g. Polaroid comprising multiple thin layers, e.g. multilayer stacks
    • G02B5/305—Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state in the form of a thin sheet or foil, e.g. Polaroid comprising multiple thin layers, e.g. multilayer stacks including organic materials, e.g. polymeric layers
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/1333—Constructional arrangements; Manufacturing methods
    • G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
    • G02F1/133528—Polarisers
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K50/00—Organic light-emitting devices
    • H10K50/80—Constructional details
    • H10K50/86—Arrangements for improving contrast, e.g. preventing reflection of ambient light
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K59/00—Integrated devices, or assemblies of multiple devices, comprising at least one organic light-emitting element covered by group H10K50/00
    • H10K59/50—OLEDs integrated with light modulating elements, e.g. with electrochromic elements, photochromic elements or liquid crystal elements
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2457/00—Electrical equipment
    • B32B2457/20—Displays, e.g. liquid crystal displays, plasma displays

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  • Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • General Physics & Mathematics (AREA)
  • Nonlinear Science (AREA)
  • Mathematical Physics (AREA)
  • Chemical & Material Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Polarising Elements (AREA)
  • Devices For Indicating Variable Information By Combining Individual Elements (AREA)
  • Electroluminescent Light Sources (AREA)
  • Laminated Bodies (AREA)

Abstract

The invention provides a laminated optical film, which at least comprises a first optical film and a second optical film laminated via an adhesive layer, wherein the in-plane refractive index R of the first optical film side surface F1 of the adhesive layerF1In-plane refractive index R with second optical film side surface F2F2Different, and the in-plane refractive index has a gradient in the thickness direction.

Description

Laminated optical film and image display device
Technical Field
The present invention relates to a laminated optical film in which at least a first optical film and a second optical film are laminated with an adhesive layer interposed therebetween. The laminated optical film is suitable for use in an image display device, particularly an organic EL display device.
Background
In order to improve poor visibility caused by reflection of external light or reflection of a background on a display screen of an image display device, a display device in which a circularly polarizing plate is disposed on a visible side of a display panel is known. 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.
Documents of the prior art
Patent document
Patent document 1: japanese patent laid-open publication No. 2015-111236
Patent document 2: japanese patent laid-open publication No. 2015-210459
Disclosure of Invention
Problems to be solved by the invention
However, the display devices using the polarizing films described in patent documents 1 and 2 have problems in that unevenness occurs in reflected light and visibility is insufficient.
In view of the above circumstances, an object of the present invention is to provide a laminated optical film having a reduced reflectance from external light and excellent visibility, and an image display device, particularly an organic EL display device, including the laminated optical film.
Means for solving the problems
The above problem can be solved by the following constitution. That is, the present invention relates to a laminated optical film in which at least a first optical film and a second optical film are laminated via an adhesive layer, and the in-plane refractive index R of the first optical film side surface F1 of the adhesive layerF1In-plane refractive index R with second optical film side surface F2F2Different, and the in-plane refractive index has a gradient in the thickness direction.
Preferably, in the laminated optical film, R isF1The difference between the in-plane average refractive index of the first optical film and the in-plane average refractive index of the first optical film is 0.05 or less, and the R isF2The difference between the in-plane average refractive index of the second optical film and the in-plane average refractive index of the second optical film is 0.05 or less.
In the laminated optical film, the first optical film preferably has a thickness of 30 μm or less, and the second optical film preferably has a thickness of 20 μm or less.
In the laminated optical film, the adhesive layer preferably has a thickness of 5 μm or less.
The present invention also relates to an image display device, particularly an organic EL display device, including the laminated optical film described above.
ADVANTAGEOUS EFFECTS OF INVENTION
An image display device includes a laminated optical film in which 2 or more optical films are laminated, and the optical films constituting the laminated optical film are usually laminated together with an adhesive layer interposed therebetween. As a result of intensive studies, the present inventors have found that the refractive index of an adhesive layer included in a currently available laminated optical film is the same on one optical film side (referred to as "front side") and the other optical film side (referred to as "back side"), and there has been no concept that the refractive index of the adhesive layer is different on the front side and the back side in order to suppress reflection at the interface between the front side optical film and the adhesive layer and at the interface between the back side optical film and the adhesive.
In the present invention, however, in a laminated optical film in which at least a first optical film and a second optical film are laminated via an adhesive layer, the adhesive layer is used as the adhesive layer, the adhesive layer having a refractive index different between the front surface side and the back surface side, in order to suppress reflection at the interface between each optical film and the adhesive layer. Specifically, the design is made as follows: in-plane refractive index R using first optical film side surface F1F1In-plane refractive index R with second optical film side surface F2F2Different adhesive layers, and the in-plane refractive index of the adhesive layers has a gradient in the thickness direction. This can significantly suppress reflection at the interface between the first optical film and the adhesive layer and at the interface between the second optical film and the adhesive layer, and can similarly suppress reflection because the in-plane refractive index also has a gradient in the thickness direction in the adhesive layer. When incorporated into an image display device, the transmittance of internal light such as panel light can be increased.
In general, as the thickness of the laminated optical film is thinner, unevenness of reflected light is likely to occur, and as a result of focusing attention on the above-described problems, particularly, in the laminated optical film of the present invention, even if the thicknesses of the first optical film, the second optical film, and the adhesive layer are thinner, the reflectance of external light, particularly natural light, can be reduced, and visibility is improved. Therefore, the laminated optical film of the present invention is particularly useful for an image display device, particularly an organic EL display device.
Drawings
Fig. 1 is a diagram illustrating an example of reflection of external light in an image display device including a conventional laminated optical film.
Fig. 2(a) to (b) are diagrams showing an example of an image display device including the laminated optical film of the present invention.
Detailed Description
In the present invention, the laminated optical film is formed by laminating at least a first optical film and a second optical film with an adhesive layer interposed therebetween, and the adhesive layer is formed using an adhesive layer having a different refractive index on the front surface side and the back surface side in order to suppress reflection at the interface between each optical film and the adhesive layer. The above features are described below in contrast to an image display device including a conventional laminated optical film.
FIG. 1 is a diagram showing reflected light L from external light (natural light) L in an image display device including a currently existing laminated optical filmRAn example of the method (3). An image display device M shown in fig. 1 is an organic EL image display device including an organic light emitting diode 7, and includes a laminated optical film 10 in which a first optical film (transparent protective film) 1 and a second optical film (polarizer) 3 are laminated with a first adhesive layer 2 interposed therebetween. In the case of the conventional configuration shown in fig. 1, since the refractive indices of the first adhesive layer 2 on the front surface side and the back surface side are the same, the refractive index of the transparent protective film 1 is different from the refractive index of the first adhesive layer 2, and the refractive index of the first adhesive layer 2 is different from the refractive index of the polarizer 3, external light (natural light) L is reflected at the interface between the transparent protective film 1 and the first adhesive layer 2 and at the interface between the first adhesive layer 2 and the polarizer 3, and therefore, unevenness occurs in reflected light, and visibility becomes insufficient.
Fig. 2 is a diagram showing an example of an image display device including the laminated optical film of the present invention. An image display device M shown in fig. 2 is an organic EL image display device including an organic light emitting diode 7, and includes a laminated optical film 10 in which a first optical film (transparent protective film) 1 and a second optical film (polarizer) 3 are laminated with an adhesive layer 2 interposed therebetween. In the present invention, the optical film may be laminated at leastThe image display device M may be configured of 3 or more optical films, including a transparent protective film (first optical film) 1 → a first adhesive layer 2 → a polarizer (second optical film) 3 → a second adhesive layer 4 → a phase difference film (third optical film) 5 → an adhesive layer 6 in this order from the outermost surface to the organic light emitting diode 7 in the embodiment shown in fig. 2 (a). As shown in fig. 2(b), the first adhesive layer 2 included in the laminated optical film 10 of the present invention is designed as follows: in-plane refractive index R of surface F1 on surface 1 of transparent protective film (first optical film)F1In-plane refractive index R with respect to the polarizer (second optical film) 3 side F2F2Different, and the in-plane refractive index of the adhesive layer has a gradient in the thickness direction. Thus, the laminated optical film 10 of the present invention has a reduced reflectance of the external light (natural light) L at the interface between the transparent protective film and the adhesive layer, at the interface between the adhesive layer and the polarizer, and in the adhesive layer, and is excellent in visibility.
< first adhesive layer >
The adhesive layer provided in the laminated optical film of the present invention will be described below. In the present invention, the thickness of the adhesive layer is preferably small, and specifically, the thickness of the adhesive layer is preferably 5 μm or less, more preferably 0.5 to 3 μm.
The adhesive layer provided in the laminated optical film of the present invention is characterized in that the refractive index is different between the front surface side and the back surface side. Specifically, the in-plane refractive index R of the first optical film side surface F1F1In-plane refractive index R with second optical film side surface F2F2Different, and the in-plane refractive index of the adhesive layer has a gradient in the thickness direction.
In the present invention, the "in-plane refractive index" of the first optical film side surface F1 (or the second optical film side surface F2) of the adhesive layer was measured for the in-plane refractive index on each surface side of the adhesive layer using a prism coupler SPA-4000 (manufactured by Cylon technology corporation). The measurement temperature was 23 ℃ and the measurement wavelength was 532 nm.
In the present invention, the adhesive layer may be designed to be any material as long as the above characteristics are satisfied, and is particularly preferably formed from a cured product layer obtained by irradiating an active energy ray-curable adhesive composition with an active energy ray. An example of a method for producing an adhesive layer having an in-plane refractive index different between the front surface side and the back surface 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, ultraviolet-curable adhesives and visible-light-curable adhesives can be broadly classified into radical polymerization-curable adhesives and cationic polymerization-curable adhesives. In the present invention, the active energy ray having a wavelength of 10nm to 380nm is referred to as ultraviolet ray, and the active energy ray having a wavelength of 380nm to 800nm is referred to as visible ray.
Examples of the compound constituting the radical polymerization curing adhesive include radical polymerizable compounds. Examples of the radical polymerizable compound include compounds having a radical polymerizable functional group having a carbon-carbon double bond such as a (meth) acryloyl group or a vinyl group. Any of monofunctional radical polymerizable compounds and difunctional or higher polyfunctional radical polymerizable compounds can be used as the curable component. These radical polymerizable compounds may be used alone in 1 kind, or in combination with 2 or more kinds. As these radical polymerizable compounds, for example, compounds having a (meth) acryloyl group are preferable. 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 compound having a (meth) acryloyl group is preferably contained in an amount of 50 wt% or more, more preferably 80 wt% or more, based on 100 wt% of the total amount of the active energy ray-curable adhesive composition. In the present invention, (meth) acryloyl means acryloyl and/or methacryloyl, and "(meth)" means the same as defined below.
Examples of the monofunctional radical polymerizable compound include a (meth) acrylamide derivative having a (meth) acrylamide group. The (meth) acrylamide derivative is preferable in terms of securing adhesiveness to a polarizer and various transparent protective films, and in terms of high polymerization rate and excellent productivity. Specific examples of the (meth) acrylamide derivative include: n-alkyl group-containing (meth) acrylamide derivatives such as N-methyl (meth) acrylamide, N-dimethyl (meth) acrylamide, N-diethyl (meth) acrylamide, N-isopropyl (meth) acrylamide, N-butyl (meth) acrylamide, and N-hexyl (meth) acrylamide; n-hydroxyalkyl (meth) acrylamide-containing derivatives such as N-methylol (meth) acrylamide, N-hydroxyethyl (meth) acrylamide, and N-methylol-N-propyl (meth) acrylamide; n-aminoalkyl-containing (meth) acrylamide derivatives such as aminomethyl (meth) acrylamide and aminoethyl (meth) acrylamide; n-alkoxy group-containing (meth) acrylamide derivatives such as N-methoxymethylacrylamide and N-ethoxymethylacrylamide; n-mercaptoalkyl group-containing (meth) acrylamide derivatives such as mercaptomethyl (meth) acrylamide and mercaptoethyl (meth) acrylamide; and so on. Examples of the heterocyclic ring-containing (meth) acrylamide derivative in which the nitrogen atom of the (meth) acrylamide group forms a heterocyclic ring include: n-acryloylmorpholine, N-acryloylpiperidine, N-methacryloylpiperidine, N-acryloylpyrrolidine and the like.
Among the above (meth) acrylamide derivatives, N-hydroxyalkyl (meth) acrylamide derivatives are preferable from the viewpoint of adhesion to polarizers and various transparent protective films, and examples of the monofunctional radical polymerizable compound include various (meth) acrylic acid derivatives having a (meth) acryloyloxy group. Specific examples thereof include: methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, 2-methyl-2-nitropropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, sec-butyl (meth) acrylate, tert-butyl (meth) acrylate, n-pentyl (meth) acrylate, (C1-20) alkyl (meth) acrylates such as t-amyl (meth) acrylate, 3-pentyl (meth) acrylate, 2-dimethylbutyl (meth) acrylate, n-hexyl (meth) acrylate, hexadecyl (meth) acrylate, n-octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, 4-methyl-2-propylpentyl (meth) 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; polycyclic (meth) acrylates such as 2-isobornyl (meth) acrylate, 2-norbornyl methyl (meth) acrylate, 5-norbornen-2-yl methyl (meth) acrylate, 3-methyl-2-norbornyl methyl (meth) acrylate, dicyclopentenyl (meth) acrylate, dicyclopentenyloxyethyl (meth) acrylate, and dicyclopentanyl (meth) acrylate; (meth) acrylic esters having an alkoxy group or a phenoxy group such as 2-methoxyethyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate, 2-methoxymethoxyethyl (meth) acrylate, 3-methoxybutyl (meth) acrylate, ethyl carbitol (meth) acrylate, phenoxyethyl (meth) acrylate, and alkylphenoxypolyethylene glycol (meth) acrylate; and so on.
Further, examples of the (meth) acrylic acid derivative include: hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 8-hydroxyoctyl (meth) acrylate, 10-hydroxydecyl (meth) acrylate, and 12-hydroxylauryl (meth) acrylate, hydroxy-containing (meth) acrylates such as [4- (hydroxymethyl) cyclohexyl ] methyl acrylate, cyclohexanedimethanol mono (meth) acrylate, and 2-hydroxy-3-phenoxypropyl (meth) acrylate; epoxy group-containing (meth) acrylates such as glycidyl (meth) acrylate and 4-hydroxybutyl (meth) acrylate glycidyl ether; halogen-containing (meth) acrylates such as 2,2, 2-trifluoroethyl (meth) acrylate, tetrafluoropropyl (meth) acrylate, hexafluoropropyl (meth) acrylate, octafluoropentyl (meth) acrylate, heptadecafluorodecyl (meth) acrylate, and 3-chloro-2-hydroxypropyl (meth) acrylate; alkylaminoalkyl (meth) acrylates such as dimethylaminoethyl (meth) acrylate; oxetanyl (meth) acrylates such as 3-oxetanyl methyl (meth) acrylate, 3-methyloxetanyl methyl (meth) acrylate, 3-ethyloxetanyl methyl (meth) acrylate, 3-butyloxetanyl methyl (meth) acrylate, and 3-hexyloxetanyl methyl (meth) acrylate; and (meth) acrylates having a heterocyclic ring such as tetrahydrofurfuryl (meth) acrylate and butyrolactone (meth) acrylate, hydroxypivalic acid neopentyl glycol (meth) acrylic acid adducts, and p-phenylphenol (meth) acrylate.
Examples of the monofunctional radical 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 radical polymerizable compound include: lactam-type vinyl monomers such as N-vinylpyrrolidone, N-vinyl-epsilon-caprolactam and methyl vinyl pyrrolidone; vinylpyridine, vinylpiperidone, vinylpyrimidine, vinylpiperazine, vinylpyrazine, vinylpyrrole, vinylimidazole, vinylpyridine
Figure BDA0002666342680000071
Vinyl monomers having a nitrogen-containing heterocycle such as oxazole and vinyl morpholine.
As the monofunctional radical polymerizable compound, a radical polymerizable compound having an active methylene group can be used. The radical polymerizable compound having an active methylene group is a compound having an active methylene group and an active double bond group such as a (meth) acrylic group at a terminal or in a molecule. Examples of the active methylene group include: acetoacetyl, alkoxymalonyl, cyanoacetyl, or the like. The active methylene group is preferably an acetoacetyl group. Specific examples of the radical polymerizable compound having an active methylene group include: acetoacetoxyethyl alkyl (meth) acrylates such as 2-acetoacetoxyethyl (meth) acrylate, 2-acetoacetoxyethyl propyl (meth) acrylate, and 2-acetoacetoxyethyl-1-methylethyl (meth) acrylate; 2-ethoxymalonyloxyethyl (meth) acrylate, 2-cyanoacetoxyethyl (meth) acrylate, N- (2-cyanoacetoxyethyl) acrylamide, N- (2-propionylacetyloxybutyl) acrylamide, N- (4-acetoacetoxyethylmethylbenzyl) acrylamide, N- (2-acetoacetylaminoethyl) acrylamide and the like. The radical polymerizable compound having an active methylene group is preferably acetoacetoxyethyl (meth) acrylate.
Further, 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, 1, 9-nonanediol di (meth) Acrylate, 1, 10-decanediol diacrylate, 2-ethyl-2-butylpropanediol 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, tricyclodecane dimethanol di (meth) Acrylate, Cyclic Trimethylolpropane formal (meth) Acrylate, diethylene glycol dimethacrylate, and the like
Figure BDA0002666342680000072
Esters of (meth) acrylic acid and polyhydric alcohol such as alkanediol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, and EO-modified diglycerol tetra (meth) acrylate, and 9, 9-bis [4- (2- (meth) acryloyloxyethoxy) phenyl]Fluorene. Specific examples thereof include ARONIX M-220 (manufactured by Toyo Kabushiki Kaisha), LIGHT ACRYLATE 1,9ND-A (manufactured by Kyowa Kaisha), LIGHT ACRYLATE DGE-4A (manufactured by Kyowa Kaisha), and LIGHT ACRYLATE DCP-A (manufactured by Kyoeisha chemical Co., Ltd.), SR-531 (manufactured by Sartomer Co., Ltd.), CD-536 (manufactured by Sartomer Co., Ltd.), and the like. Further, as necessary, there may be mentioned: various epoxy (meth) acrylates, urethane (meth) acrylates, polyester (meth) acrylates, various (meth) acrylate monomers, and the like.
The active energy ray-curable adhesive composition does not need to contain a photopolymerization initiator when an electron beam or the like is used as an active energy ray, but preferably contains a photopolymerization initiator when ultraviolet rays or visible light is used as an active energy ray.
The photopolymerization initiator in the case of using a radical polymerizable compound can be appropriately selected depending on the active energy ray. In the case of curing by ultraviolet rays or visible light, a photopolymerization initiator that is cleaved by ultraviolet rays or visible light is used. The photopolymerization initiator may be used alone, but when a plurality of photopolymerization initiators are used in combination, the curing rate and curability can be adjusted, which is preferable. Examples of the photopolymerization initiator include: benzophenone compounds such as benzil, benzophenone, benzoylbenzoic acid, and 3, 3' -dimethyl-4-methoxybenzophenone; aromatic ketone compounds such as 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-propan-1-one, and 2-hydroxy-1- {4- [4- (2-hydroxy-2-methylpropanoyl) benzyl ] phenyl } -2-methylpropan-1-one; acetophenone compounds such as methoxyacetophenone, 2-dimethoxy-2-phenylacetophenone, 2-diethoxyacetophenone, 2-methyl-1- [4- (methylthio) phenyl ] -2-morpholinopropan-1-one, etc.; benzoin ether compounds such as benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin butyl ether, and anisoin methyl ether; aromatic ketal compounds such as benzil dimethyl ketal; aromatic sulfonyl chloride compounds such as 2-naphthalenesulfonyl chloride; optically active oximes such as 1-phenyl-1, 1-propanedione-2- (o-ethoxycarbonyl) oxime; thioxanthone compounds such as thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2, 4-dimethylthioxanthone, isopropylthioxanthone, 2, 4-dichlorothioxanthone, 2, 4-diethylthioxanthone, 2, 4-diisopropylthioxanthone and dodecylthioxanthone; camphorquinone; a halogenated ketone; acyl phosphine oxides; acyl phosphonates and the like.
The amount of the photopolymerization initiator is 20% by weight or less, based on 100% by weight of the total amount of the active energy ray-curable adhesive composition. The amount of the photopolymerization initiator is preferably 0.01 to 20% by weight, more preferably 0.05 to 10% by weight, and still more preferably 0.1 to 5% by weight.
When the curable adhesive for a laminated optical film of the present invention is used in a visible light curable type containing a radical polymerizable compound as a curable component, it is particularly preferable to use a photopolymerization initiator having high sensitivity to light of 380nm or more. The photopolymerization initiator having high sensitivity to light of 380nm or more will be described later.
As the photopolymerization initiator, a compound represented by the following general formula (1) is preferably used alone; or a combination of a compound represented by the general formula (1) and a photopolymerization initiator having high sensitivity to light of 380nm or more as described later.
[ chemical formula 1]
Figure BDA0002666342680000091
(in the formula, R1And R2represents-H, -CH2CH3-iPr or Cl, R1And R2May be the same or different). When the compound represented by the general formula (1) is used, the adhesiveness is superior to that when a photopolymerization initiator having high sensitivity to light of 380nm or more is used alone. Among the compounds represented by the general formula (1), R is particularly preferable1And R2is-CH2CH3Diethyl thioxanthone (ll). The composition ratio of the compound represented by the general formula (1) in the adhesive is preferably 0.1 to 5% by weight, more preferably 0.1 to 5% by weight, based on 100% by weight of the total amount of the active energy ray-curable adhesive composition0.5 to 4 wt%, and more preferably 0.9 to 3 wt%.
Further, it is preferable to add a polymerization initiation aid as needed. Examples of the polymerization initiation aid include: triethylamine, diethylamine, N-methyldiethanolamine, ethanolamine, 4-dimethylaminobenzoic acid, methyl 4-dimethylaminobenzoate, ethyl 4-dimethylaminobenzoate, isoamyl 4-dimethylaminobenzoate, etc., with ethyl 4-dimethylaminobenzoate being particularly preferred. When the polymerization initiator is used, the amount thereof to be 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 components.
Further, a known photopolymerization initiator may be used in combination as necessary. Since the transparent protective film having UV absorption ability does not transmit light of 380nm or less, it is preferable to use a photopolymerization initiator having high sensitivity to light of 380nm or more as the photopolymerization initiator. Specifically, there may be mentioned: 2-methyl-1- (4-methylthiophenyl) -2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -1-butanone, 2- (dimethylamino) -2- [ (4-methylphenyl) methyl ] -1- [4- (4-morpholino) phenyl ] -1-butanone, 2,4, 6-trimethylbenzoyldiphenylphosphine oxide, bis (2,4, 6-trimethylbenzoyl) phenylphosphine oxide, bis (. eta.5-2, 4-cyclopentadien-1-yl) bis (2, 6-difluoro-3- (1H-pyrrol-1-yl) phenyl) titanium and the like.
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) is preferably further used,
[ chemical formula 2]
Figure BDA0002666342680000101
(in the formula, R3、R4And R5represents-H, -CH3、-CH2CH3-iPr or Cl, R3、R4And R5May be the same or different). As the compound represented by the general formula (2), commercially available 2-methyl-1- (4-methylthio) can be suitably usedPhenyl) -2-morpholinopropan-1-one (trade name: omnirad907 manufacturer: IGMresins). Furthermore, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -1-butanone (trade name: IGMresins, manufactured by Omnirad 369), 2- (dimethylamino) -2- [ (4-methylphenyl) methyl]-1- [4- (4-morpholinyl) phenyl]1-butanone (trade name: Omnirad379 manufacturer: IGMresins) is preferred because of its high sensitivity.
In the present invention, among the above photopolymerization initiators, a hydroxyl group-containing photopolymerization initiator is preferably used. When the active energy ray-curable adhesive composition contains a hydroxyl group-containing photopolymerization initiator as a polymerization initiator, the solubility of the adhesive layer having a high concentration of the component a on the polarizer side is improved, and the curability of the adhesive layer is improved. Examples of the photopolymerization initiator having a hydroxyl group include: 2-methyl-2-hydroxypropiophenone (trade name "DAROCUR 1173", manufactured by IGMresins), 1-hydroxycyclohexyl phenyl ketone (trade name "Omnirad 184", manufactured by IGMresins), 1- [4- (2-hydroxyethoxy) -phenyl ] -2-hydroxy-2-methyl-1-propan-1-one (trade name "Omnirad 2959", manufactured by IGMresins), 2-hydroxy-1- {4- [4- (2-hydroxy-2-methyl-propionyl) -benzyl ] phenyl } -2-methyl-propan-1-one (trade name "Omnirad 127", manufactured by IGMresins), and the like. In particular, 1-hydroxycyclohexylphenyl ketone is more preferable because it is particularly excellent in solubility in an adhesive layer having a high concentration of component A.
The active energy ray-curable adhesive composition used in the present invention may contain an acrylic oligomer obtained by polymerizing a (meth) acrylic monomer, in addition to the curable component of the radical polymerizable compound. By including an acrylic oligomer component in the active energy ray-curable adhesive composition, the curing shrinkage when the composition is cured by irradiation with active energy rays can be reduced, and the interface stress between the adhesive and an adherend such as a polarizer and a transparent protective film can be reduced. As a result, the adhesive layer can be prevented from being deteriorated in adhesiveness to the adherend. In order to sufficiently suppress the curing shrinkage of the cured product layer (adhesive layer), the content of the acrylic oligomer is preferably 5 to 30% by weight, more preferably 10 to 20% by weight, based on 100% by weight of the total amount of the active energy ray-curable adhesive composition.
In view of workability and uniformity in application, the active energy ray-curable adhesive composition preferably has a low viscosity, and therefore an acrylic oligomer obtained by polymerizing a (meth) acrylic monomer is also preferably low in viscosity. The weight average molecular weight (Mw) of the low-viscosity acrylic oligomer is preferably 15000 or less, more preferably 10000 or less, and particularly preferably 5000 or less. On the other hand, in order to further concentrate the components of the adhesive composition interposed between the polarizer and the transparent protective film, the weight average molecular weight (Mw) of the acrylic oligomer (a) is preferably 500 or more, more preferably 1000 or more, and particularly preferably 1500 or more. Specific examples of the (meth) acrylic monomer constituting the acrylic oligomer (a) include: (meth) acrylic acid (C1-20) alkyl esters such as methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, 2-methyl-2-nitropropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, sec-butyl (meth) acrylate, tert-butyl (meth) acrylate, n-pentyl (meth) acrylate, tert-pentyl (meth) acrylate, 3-pentyl (meth) acrylate, 2-dimethylbutyl (meth) acrylate, n-hexyl (meth) acrylate, cetyl (meth) acrylate, n-octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, 4-methyl-2-propylpentyl (meth) acrylate, and n-octadecyl (meth) acrylate, And for example: cycloalkyl (meth) acrylates (e.g., cyclohexyl (meth) acrylate, cyclopentyl (meth) acrylate, etc.), (aralkyl (meth) acrylates (e.g., benzyl (meth) acrylate, etc.), polycyclic (meth) acrylates (e.g., 2-isobornyl (meth) acrylate, 2-norbornyl methyl (meth) acrylate, 5-norborn-2-ylmethyl (meth) acrylate, 3-methyl-2-norbornyl methyl (meth) acrylate, etc.), hydroxyl-containing (meth) acrylates (e.g., hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2, 3-dihydroxypropylmethylbutyl (meth) acrylate, etc.), alkoxy-or phenoxy-containing (meth) acrylates ((2-methoxyethyl (meth) acrylate, 2-methoxypropyl (meth) acrylate, etc.), 2-ethoxyethyl (meth) acrylate, 2-methoxymethoxyethyl (meth) acrylate, 3-methoxybutyl (meth) acrylate, ethylcarbitol (meth) acrylate, phenoxyethyl (meth) acrylate, and the like, epoxy group-containing (meth) acrylates (e.g., glycidyl (meth) acrylate, and the like), halogen-containing (meth) acrylates (e.g., 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 (meth) acrylates (e.g., dimethylaminoethyl (meth) acrylate, etc.), and the like. These (meth) acrylates may be used singly or in combination of 2 or more. Specific examples of the acrylic oligomer (A) include "ARUFON" manufactured by Toyo Synthesis Co., Ltd, "ACTFLOW" manufactured by Sokka Seisakusho, and "JONCRYL" manufactured by IGMresins Ltd.
When the acrylic oligomer is a liquid, it is not necessary to consider the solubility in the adhesive composition, and therefore it can be suitably used. Acrylic oligomers are typically liquid with a glass transition temperature (Tg) of less than 25 ℃. In addition, in order to achieve compatibility with the adhesive composition and concentration 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: "ARUFONUH series", "ARUFON UC series", "ARUFON UF series", "ARUFON UG series", "ARUFON US series" (all manufactured by Toyo chemical Co., Ltd.), etc. Among them, epoxy groups are preferably contained because the adhesion property due to the interaction with the polarizer can be improved. Specific examples thereof include: "ARUFON UG-4000" and "ARUFON UG-4010" (both manufactured by Toyo Seisaku-Sho Co., Ltd.).
< first optical film >
In the present invention, a transparent protective film can be suitably used as the first optical film. The thickness of the transparent protective film is preferably small, and more specifically, it is preferably 30 μm or less, and more preferably 1 to 20 μm. The transparent protective film is preferably excellent in transparency, mechanical strength, thermal stability, moisture barrier property, isotropy, and the like. Examples thereof include: polyester polymers such AS polyethylene terephthalate and polyethylene naphthalate, cellulose polymers such AS cellulose diacetate and cellulose triacetate, acrylic polymers such AS polymethyl methacrylate, styrene polymers such AS polystyrene and acrylonitrile-styrene copolymer (AS resin), and polycarbonate polymers. Further, polyethylene, polypropylene, polyolefin having a cyclic or norbornene structure, polyolefin polymer such as ethylene-propylene copolymer, vinyl chloride polymer, polyamide polymer such as nylon and aromatic polyamide, imide polymer, sulfone polymer, polyether ether ketone polymer, polyphenylene sulfide polymer, vinyl alcohol polymer, vinylidene chloride polymer, vinyl butyral polymer, polyaryl ester polymer, polyacetal polymer, epoxy polymer, or a mixture of the above polymers may be cited as examples of the polymer forming the transparent protective film. The transparent protective film may contain 1 or more kinds of any appropriate additives. Examples of additives include: ultraviolet absorbers, antioxidants, lubricants, plasticizers, mold release agents, anti-coloring agents, flame retardants, nucleating agents, antistatic agents, pigments, colorants, 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, even 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 wt% or less, there is a fear that high transparency and the like originally possessed by the thermoplastic resin cannot be sufficiently expressed.
Further, as the transparent protective film, there can be mentioned a polymer film described in Japanese patent laid-open No. 2001-343529 (WO01/37007), for example, a resin composition containing (A) a thermoplastic resin having a substituted and/or unsubstituted imide group in a side chain and a thermoplastic resin having a substituted and/or unsubstituted phenyl group and a nitrile group in a side chain. Specifically, a film of a resin composition containing an alternating copolymer of isobutylene and N-methylmaleimide and an acrylonitrile-styrene copolymer is exemplified. As the film, a film formed from a mixed extrusion of a resin composition or the like can be used. These films have a small phase difference and a small photoelastic coefficient, and therefore can eliminate problems such as unevenness due to strain of the polarizing film, and have a small moisture permeability, and therefore have excellent humidification durability.
In the laminated optical film, the in-plane refractive index of the first optical film side surface F1 of the adhesive layer is represented by R in order to reduce reflection at the interface between the first optical film and the adhesive layerF1In the case of (2), R is preferably the above-mentionedF1The difference from the in-plane average refractive index of the first optical film is 0.05 or less, more preferably 0.03 or less.
In the present invention, the "in-plane average refractive index" of the transparent protective film (first optical film) was measured by using a prism coupler SPA-4000 (manufactured by Cylon technology), and the refractive index in the fast axis direction and the refractive index in the slow axis direction among the in-plane refractive indices of the transparent protective film were determined, and the average value of these was defined as the in-plane average refractive index. The measurement temperature was 23 ℃ and the measurement wavelength was 532 nm.
< second optical film >
In the present invention, a polarizer can be suitably used as the second optical film. The polarizer is not particularly limited, and various polarizers can be used. Examples of polarizers include: a polyolefin-based alignment film obtained by uniaxially stretching a hydrophilic polymer film such as a polyvinyl alcohol-based film, a partially acetalized polyvinyl alcohol-based film, or an ethylene-vinyl acetate copolymer-based partially saponified film, while adsorbing a dichroic material such as iodine or a dichroic dye, a dehydrated polyvinyl alcohol-based film, or a desalted polyvinyl chloride-based film. Among these, a polarizer made of a dichroic material such as a polyvinyl alcohol film and iodine is preferable.
In the laminated optical film, in order to reduce reflection at the interface between the second optical film and the adhesive layer, the in-plane refractive index of the second optical film side surface F2 of the adhesive layer is represented by RF2In the case of (2), R is preferably the above-mentionedF2And the in-plane average refractive index of the second optical filmThe difference is 0/05 or less, more preferably 0.03 or less.
In the present invention, the prism coupler SPA-4000 (manufactured by Cylon technology) was used to measure the refractive index in the transmission axis direction and the refractive index in the absorption axis direction among the in-plane refractive indices of the polarizer, and the average value of these was defined as the in-plane average refractive index of the polarizer. The measurement temperature was 23 ℃ 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 is, the more likely the unevenness of the reflected light is to occur, and in the present invention, the polarizer is particularly preferably a thin polarizer, and specifically, the thickness is preferably 20 μm or less, more preferably 1 to 12 μm.
Representative examples of the thin polarizer include: a thin polarizing film described in Japanese patent laid-open Nos. 51-069644, 2000-338329, WO2010/100917, PCT/JP2010/001460, 2010-269002 and 2010-263692. These thin polarizing films can be obtained by a production method including a step of stretching a polyvinyl alcohol resin (hereinafter, also referred to as PVA-based resin) layer and a stretching resin substrate in a laminated state and a step of dyeing. With this production method, even if the PVA-based resin layer is thin, it can be stretched while being supported by the resin base material for stretching without causing troubles such as breakage due to stretching.
As the thin polarizing film, among the production methods including the step of stretching in a laminated state and the step of dyeing, it is preferable to obtain the film by a production method including the step of stretching in an aqueous boric acid solution as described in WO2010/100917 pamphlet, PCT/JP2010/001460, japanese patent application 2010-269002 and japanese patent application 2010-263692, and particularly preferable to obtain the film by a production method including the step of stretching in an air atmosphere in an auxiliary manner before stretching in an aqueous boric acid solution as described in japanese patent application 2010-269002 and japanese patent application 2010-263692, in view of being capable of stretching at a high magnification and improving polarization performance.
The laminated optical film of the present invention is characterized in that the in-plane refractive index is different between the front surface side and the back surface side of the adhesive layer, and the in-plane refractive index has a gradient in the thickness direction. The laminated optical film including the 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 first optical film and a second optical film are laminated via an adhesive layer, the adhesive layer including a first cured product layer of a first adhesive composition and a second cured product layer of a second adhesive composition, the first adhesive composition and the second adhesive composition containing at least partially different components, the method comprising: a first step of applying the first adhesive composition to a bonding surface of the first optical film; a second step of applying the second adhesive composition to the bonding surface of the second optical film; a third step of bonding the first adhesive composition-coated surface of the first optical film and the second adhesive composition-coated surface of the second optical film; and a fourth step of irradiating the first optical film surface side or the second optical film surface side with an active energy ray to bond the first optical film and the second optical film.
In the above production method, since the adhesive layer includes the first cured product layer of the first adhesive composition and the second cured product layer of the second adhesive composition, and the first adhesive composition and the second adhesive composition contain at least partially different components, the in-plane refractive index R1 of the first optical film side surface F1 is formedF1In-plane refractive index R with second optical film side surface F2F2Different adhesive layers. Here, the in-plane average refractive index of the first optical film and the in-plane average refractive index of the second optical film may be measured in advance, and the in-plane refractive index R of the first optical film side surface F1 of the first cured product layer of the first adhesive compositionF1And in-plane refractive index R of second optical film side surface F2F2The values can be designed to be arbitrary by performing optimum fitting design. Thus, in the above-mentioned manufactureIn the method, the adhesive layer having different in-plane refractive indices on the front side and the back side, and the adhesive layer having the same refractive index as the adhesive layer can be producedF1The difference between the in-plane average refractive index of the first optical film and the in-plane average refractive index of the first optical film is 0.05 or less, RF2And an adhesive layer having an in-plane average refractive index difference of 0.05 or less from the second optical film.
In the third step, the first adhesive composition and the second adhesive composition are stacked in an uncured state, and therefore, even when components different from each other are present, the components can be appropriately mixed with each other. As a result, an in-plane refractive index difference is less likely to occur at the interface between the first cured material layer and the second cured material layer, and the in-plane refractive index has a gradient in the thickness direction.
In the first step, the first adhesive composition after coating may be air-dried, and the solvent may be removed when the first adhesive composition after coating contains the solvent, thereby forming a coating layer of the uncured first adhesive composition in advance.
In the laminated optical film of the present invention, when the first optical film is a transparent protective film and the second optical film is a polarizer, the surface modification treatment may be performed before the first step and/or the second coating step (coating step). Specific examples of the treatment include corona treatment, plasma treatment, and saponification treatment.
In the first step and/or the second application step (application step), the application method of the active energy ray-curable adhesive composition may be appropriately selected depending on the viscosity of the composition and the target thickness. Examples of the coating method include: reverse coaters, gravure coaters (direct, reverse, or offset), bar reverse coaters, roll coaters, die coaters, wire wound bar coaters, and the like. In addition, a dipping method or the like can be suitably used for coating.
In the third step (bonding step), 2 different optical films were bonded to each other with the active energy ray-curable adhesive composition applied. The optical film can be laminated by, for example, a roll laminator.
In the fourth step (bonding step), the active energy ray-curable adhesive composition may be used in an electron beam-curable, ultraviolet-curable, or visible light-curable form. As the active energy ray-curable adhesive composition, a visible light-curable adhesive composition is preferable from the viewpoint of productivity.
The active energy ray-curable adhesive composition is formed by, for example, bonding a polarizer and a transparent protective film, and then irradiating the resulting film with active energy rays (e.g., electron beams, ultraviolet rays, visible light, etc.) to cure the active energy ray-curable adhesive composition. In the fourth step (bonding step), the irradiation direction of the active energy ray (e.g., electron beam, ultraviolet ray, visible light, etc.) may be any appropriate irradiation direction. Irradiation is preferably from the transparent protective film side. If the irradiation is performed from the polarizer side, the polarizer may be deteriorated by active energy rays (electron beams, ultraviolet rays, visible light, and the like).
In the electron beam curing type, any appropriate conditions may be employed as long as the irradiation conditions of the electron beam are conditions capable of curing the active energy ray-curable adhesive composition. For example, the acceleration voltage for electron beam irradiation is preferably 5kV to 300kV, and more preferably 10kV to 250 kV. If the acceleration voltage is less than 5kV, the electron beam may not reach the adhesive and may be insufficiently cured, and if the acceleration voltage is more than 300kV, the penetration force through the sample may be too strong and damage may be caused to the transparent protective film and the polarizer. The dose of the radiation is 5 to 100kGy, and more preferably 10 to 75 kGy. When the irradiation dose is less than 5kGy, the adhesive is insufficiently cured, and when it exceeds 100kGy, the transparent protective film and the polarizer are damaged, and the mechanical strength is reduced and the polarizer is yellowed, so that the optical characteristics cannot be obtained.
The electron beam irradiation is usually carried out in an inert gas, and may be carried out in an atmosphere with a small amount of oxygen introduced as required. Oxygen is introduced as appropriate depending on the material of the transparent protective film, and the surface of the transparent protective film which is in contact with the first electron beam is in contact with the oxygen, whereby oxygen inhibition occurs, damage to the transparent protective film can be prevented, and only the adhesive can be efficiently irradiated with an electron beam.
In the production of the laminated optical film of the present invention, it is preferable to use, as the active energy ray, an active energy ray containing visible light having a wavelength range of 380nm to 450nm, particularly an active energy ray having the largest dose of visible light having a wavelength range of 380nm to 450 nm. In the case of using a transparent protective film (ultraviolet-opaque transparent protective film) having ultraviolet absorptivity, the ultraviolet-curable or visible-light-curable adhesive absorbs light having a wavelength shorter than about 380nm, and therefore, light having a wavelength shorter than 380nm does not reach the active energy ray-curable adhesive and does not contribute to the polymerization reaction. Further, light having a wavelength shorter than 380nm absorbed by the transparent protective film is converted into heat, and the transparent protective film itself generates heat, which causes defects such as curling and wrinkling of the laminated optical film. Therefore, in the present invention, when the ultraviolet curing type or the visible light curing type is used, it is preferable to use a device that does not emit light having a wavelength shorter than 380nm as the active energy ray generating device, and more specifically, the ratio of the cumulative illuminance in the wavelength range of 380 to 440nm to the cumulative illuminance in the wavelength range of 250 to 370nm is preferably 100:0 to 100:50, and more preferably 100:0 to 100: 40. As the active energy ray of the present invention, a metal halide lamp in which gallium is sealed, and an LED light source which emits light in a wavelength range of 380 to 440nm are preferable. Alternatively, a light source containing ultraviolet rays and visible light such as a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, an ultrahigh-pressure mercury lamp, an incandescent lamp, a xenon lamp, a halogen lamp, a carbon arc lamp, a metal halide lamp, a fluorescent lamp, a tungsten lamp, a gallium lamp, an excimer laser, or sunlight may be used, or ultraviolet rays having a wavelength shorter than 380nm may be blocked by a band-pass filter and used. In order to improve the adhesion performance of the adhesive layer between the polarizer and the transparent protective film and to prevent curling of the laminated optical film, it is preferable to use a gallium-sealed metal halide lamp and to use an active energy ray having a wavelength of 405nm obtained by using a band-pass filter capable of blocking light having a wavelength shorter than 380nm or an LED light source.
In the ultraviolet-curable or visible-light-curable type, it is also preferable to heat the active energy ray-curable adhesive after irradiation with ultraviolet rays or visible light (heating after irradiation), and in this case, it is preferable to heat the adhesive to 40 ℃ or higher, and more preferably to 50 ℃ or higher.
The active energy ray-curable adhesive used in the present invention can be suitably used particularly when forming an adhesive layer for bonding a polarizer and a transparent protective film having a light transmittance of less than 5% at a wavelength of 365 nm. Here, the active energy ray-curable adhesive of the present invention contains the photopolymerization initiator of the general formula (1) and can be cured to form an adhesive layer by irradiating ultraviolet rays through a transparent protective film having UV absorbability. Therefore, even in a laminated optical film in which transparent protective films having UV absorbing ability are laminated on both surfaces of a polarizer, the adhesive layer can be cured. However, it is needless to say that the adhesive layer can be cured also for a laminated optical film in which a transparent protective film having no UV absorbing ability is laminated. The transparent protective film having UV absorption ability means a transparent protective film having a transmittance of light of 380nm of less than 10%.
Examples of the method for imparting UV absorption capability to the transparent protective film include: a method of incorporating an ultraviolet absorber into a transparent protective film, and a method of laminating a surface treatment layer containing an ultraviolet absorber on the surface of a transparent protective film.
Specific examples of the ultraviolet absorber include: conventionally known oxybenzophenone compounds, benzotriazole compounds, salicylate 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 4 can be designed in the same way as the first adhesive layer described above. However, in the embodiment shown in fig. 2, the light L incident on the second adhesive layer 4 passes through the polarizer (second optical film) 3 and enters, and therefore, becomes polarized light in the transmission axis direction of the polarizer 3. Therefore, in order to suppress the scattering of the light at the interface between the polarizer 3 and the second adhesive layer 4 and at the retardation film 5Reflection at the interface with the second adhesive layer 4 is preferably a refractive index R in the transmission axis direction of the polarizer 3 on the polarizer 3 side surface F3 of the second adhesive layer 4F3A refractive index R in the transmission axis direction of the polarizer 3 facing the surface F4 of the retardation film 5F4In a different sense, RF3The difference of refractive index in the transmission axis direction of the polarizer 3 is not more than 0.05, RF4The difference in refractive index from the retardation film 5 in the transmission axis direction of the polarizer 3 is 0.05 or less. In this case, the reflectance of the entire image display device M is reduced, and visibility is significantly improved.
< third optical film >
The third optical film is not particularly limited, and an optical layer used in forming an image display device or the like, such as a reflective film, a semi-transmissive film, a retardation film (including a wave plate such as 1/2 or 1/4), or a visual compensation film, can be used. In the present invention, the thickness of the third optical film is preferably small, and specifically, is preferably 20 μm or less, and more preferably 1 to 10 μm.
< adhesive layer >
In the embodiment shown in fig. 2, the laminated optical film including 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 optical film) 5 is laminated on the organic light emitting diode 7 via the pressure-sensitive adhesive layer 6. The pressure-sensitive adhesive forming the pressure-sensitive adhesive layer is not particularly limited, and for example, a pressure-sensitive adhesive using a polymer such as an acrylic polymer, a silicone polymer, a polyester, a polyurethane, a polyamide, a polyether, a fluorine polymer, or a rubber as a base polymer can be suitably selected and used. In particular, an acrylic pressure-sensitive adhesive, which is excellent in optical transparency, exhibits adhesive properties such as appropriate wettability, aggregability and adhesiveness, and is excellent in weather resistance, heat resistance and the like, can be preferably used.
The adhesive layer may be provided on one side or both sides of the polarizing film, the optical film in the form of stacked layers of different compositions, kinds, or the like. In addition, when the polarizing film and the optical film are provided on both surfaces, adhesive layers having different compositions, kinds, thicknesses, and the like may be formed on the front and back surfaces of the polarizing film and the optical film. The thickness of the adhesive layer may be suitably determined depending on the purpose of use, adhesion, etc., and is usually 1 to 500. mu.m, preferably 1 to 200. mu.m, and particularly preferably 1 to 100. mu.m.
The exposed surface of the adhesive layer is temporarily covered with a separator by adhesion for the purpose of preventing contamination and the like until the adhesive layer is actually used. This prevents contact with the adhesive layer in a normal processing state. As the separator, a conventionally specified suitable separator such as a separator obtained by coating a suitable thin layer body such as a plastic film, a rubber sheet, paper, cloth, nonwoven fabric, a net, a foamed sheet, a metal foil, or a laminate thereof with a suitable release agent such as silicone, long-chain alkyl, fluorine, or molybdenum sulfide, if necessary, can be used in addition to the above thickness conditions.
< image display device >
The laminated optical film of the present invention can be preferably used for formation of 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 a conventional method. That is, the image display device is generally formed by appropriately assembling the organic light emitting diode, the liquid crystal cell, the laminated optical film, and components such as the illumination system used as needed, and incorporating the driving circuit, etc., and in the present invention, the laminated optical film of the present invention is used, but the present invention is not particularly limited thereto, and can be performed according to a conventional method.
When the laminated optical film of the present invention is used for a liquid crystal display device, a liquid crystal display device in which the laminated optical film is disposed on one side or both sides of a liquid crystal cell, a liquid crystal display device using a backlight or a reflector in an illumination system, or the like can be formed. In this case, the laminated optical film of the present invention may be disposed on one side or both sides of the liquid crystal cell. In the case where the laminated optical films are provided on both sides, they may be the same or different. Further, in the formation of the liquid crystal display device, appropriate members such as a diffusion plate, an antiglare layer, an antireflection film, a protective plate, a prism array, a lens array sheet, a light diffusion plate, and a backlight may be disposed in appropriate positions in 1 layer or 2 layers or more.
Examples
In examples 1 to 3 and comparative example 1 shown below, the laminated optical film was subjected to model design by simulation. For the simulation, "LCD mate (manufactured by Shintech corporation)" as a commercially available liquid crystal simulator was used. The optical calculation algorithm was set to a 4 × 4 jones matrix method. As the incident light (random light) from the first optical film side to the laminated optical film, 380nm to 780nm light was used.
(first optical film (transparent protective film))
As the first optical film, a QL film (thickness 1.2 μm, manufactured by Fuji film Co., Ltd.) having an in-plane average refractive index of 1.6 at 550nm was used.
(second optical film (polarizer))
As the second optical film, a polarizer (thickness 12 μm) having an in-plane average refractive index of 1.5 at 550nm was used.
Examples 1 to 3
The in-plane refractive index R of the first optical film side surface F1 was designed using an LCD MaterF1And in-plane refractive index R of second optical film side surface F2F2The adhesive layers having the values shown in table 1 were designed, and a laminated optical film in which a first optical film and a second optical film were laminated with the adhesive layers interposed therebetween was designed, and the reflectance when random light was irradiated from the first optical film side to the laminated optical film was calculated, and the results are shown in table 1.
Comparative example 1
The results of calculating the reflectance of a laminated optical film in which an adhesive layer (single-layer adhesive layer) having a constant refractive index in the thickness direction on the upper surface was designed using an LCD Mater and the first optical film and the second optical film were laminated with the adhesive layer interposed therebetween are shown in table 1.
Figure BDA0002666342680000201
From the results in Table 1, it is clear that | R is used for the laminated optical films of examples 1 to 3(a)-RF1I and | R(b)-RF2Designed to be within 0.05, andsince the in-plane refractive index of the adhesive layer has a gradient in the thickness direction, the reflectance when external light (random light) is incident on the laminated optical film is low, and the visibility is excellent. On the other hand, it is known that | R is a laminated optical film corresponding to a comparative example of a conventional laminated optical film(a)-RF1I and | R(b)-RF2If | exceeds 0.05, and the in-plane refractive index of the adhesive layer does not have a gradient in the thickness direction, the reflectance is high, and the visibility is poor.

Claims (6)

1. A laminated optical film in which at least a first optical film and a second optical film are laminated with an adhesive layer interposed therebetween,
an in-plane refractive index R of the first optical film side surface F1 of the adhesive layerF1In-plane refractive index R with second optical film side surface F2F2Different, and the in-plane refractive index has a gradient in the thickness direction.
2. The laminated optical film of claim 1,
the R isF1The difference between the in-plane average refractive index of the first optical film and the in-plane average refractive index of the first optical film is 0.05 or less, and R isF2And the in-plane average refractive index of the second optical film is within 0.05.
3. The laminated optical film according to claim 1 or 2,
the first optical film has a thickness of 30 [ mu ] m or less, and the second optical film has a thickness of 20 [ mu ] m or less.
4. The laminated optical film according to claim 1 or 2,
the adhesive layer has a thickness of 5 μm or less.
5. An image display device comprising the laminated optical film according to any one of claims 1 to 4.
6. An organic EL display device comprising the laminated optical film according to any one of claims 1 to 4.
CN202010919876.1A 2019-09-04 2020-09-04 Laminated optical film and image display device Pending CN112444903A (en)

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