CN113391391A - Optical laminate and display device - Google Patents

Optical laminate and display device Download PDF

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Publication number
CN113391391A
CN113391391A CN202110251032.9A CN202110251032A CN113391391A CN 113391391 A CN113391391 A CN 113391391A CN 202110251032 A CN202110251032 A CN 202110251032A CN 113391391 A CN113391391 A CN 113391391A
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Prior art keywords
layer
adhesive layer
optical laminate
film
display device
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CN202110251032.9A
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Chinese (zh)
Inventor
李昇祐
金正熙
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Sumitomo Chemical Co Ltd
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Sumitomo Chemical Co Ltd
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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
    • 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
    • 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
    • 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
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F3/00—Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
    • G06F3/01—Input arrangements or combined input and output arrangements for interaction between user and computer
    • G06F3/03—Arrangements for converting the position or the displacement of a member into a coded form
    • G06F3/041—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09F—DISPLAYING; ADVERTISING; SIGNS; LABELS OR NAME-PLATES; SEALS
    • G09F9/00—Indicating arrangements for variable information in which the information is built-up on a support by selection or combination of individual elements
    • G09F9/30—Indicating arrangements for variable information in which the information is built-up on a support by selection or combination of individual elements in which the desired character or characters are formed by combining individual elements
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09F—DISPLAYING; ADVERTISING; SIGNS; LABELS OR NAME-PLATES; SEALS
    • G09F9/00—Indicating arrangements for variable information in which the information is built-up on a support by selection or combination of individual elements
    • G09F9/30—Indicating arrangements for variable information in which the information is built-up on a support by selection or combination of individual elements in which the desired character or characters are formed by combining individual elements
    • G09F9/301—Indicating arrangements for variable information in which the information is built-up on a support by selection or combination of individual elements in which the desired character or characters are formed by combining individual elements flexible foldable or roll-able electronic displays, e.g. thin LCD, OLED
    • 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)
  • Engineering & Computer Science (AREA)
  • General Physics & Mathematics (AREA)
  • Theoretical Computer Science (AREA)
  • Optics & Photonics (AREA)
  • Nonlinear Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Mathematical Physics (AREA)
  • Human Computer Interaction (AREA)
  • Polarising Elements (AREA)
  • Devices For Indicating Variable Information By Combining Individual Elements (AREA)
  • Electroluminescent Light Sources (AREA)
  • Liquid Crystal (AREA)
  • Adhesives Or Adhesive Processes (AREA)

Abstract

The invention provides an optical laminate in which generation of bubbles in an adhesive layer is suppressed when the optical laminate is bent, and a display device including the optical laminate. The invention provides an optical laminate comprising a front plate, a1 st adhesive layer, a polarizing plate, a 2 nd adhesive layer and a back plate in this order, wherein the slopes of stress [ Pa ] -strain [ (% ]values from the origin to the maximum stress value in the curves of the 1 st adhesive layer and the 2 nd adhesive layer at 60 ℃ and 90% RH are respectively GL1' and GL2In the case of (1), the following formulae (1) and (2) are satisfied. G is not less than 70L1’≤250(1)70≤GL2’≤250(2)。

Description

Optical laminate and display device
Technical Field
The present invention relates to an optical laminate and a display device.
Background
Japanese patent application laid-open No. 2018-027995 (patent document 1) describes a flexible image display device having an adhesive layer excellent in stress relaxation characteristics.
Patent document 1: japanese patent laid-open publication No. 2018-027995
Disclosure of Invention
An optical laminate having a plurality of layers laminated via an adhesive layer has the following problems: bubbles are likely to be generated in the adhesive layer during bending, and particularly, bubbles are likely to be generated in a high-temperature and high-humidity environment.
The purpose of the present invention is to provide an optical laminate in which the generation of bubbles in an adhesive layer is suppressed when the optical laminate is bent, and a display device including the optical laminate.
The present invention provides an optical laminate and a display device exemplified below.
[1] An optical laminate comprising a front plate, a1 st adhesive layer, a polarizing plate, a 2 nd adhesive layer and a back plate in this order,
the slopes from the origin to the maximum stress value in the stress [ Pa ] -strain [ (% ] curves at 60 ℃ and 90% RH of the 1 st and 2 nd adhesive layers are respectively GL1' and GL2In the case of (1), the following formulae (1) and (2) are satisfied.
70≤GL1’≤250 (1)
70≤GL2’≤250 (2)
[2] The optical laminate according to [1], wherein the following formulae (1 ') and (2') are satisfied.
90≤GL1’≤150 (1’)
90≤GL2’≤150 (2’)
[3] The optical laminate according to [1] or [2], wherein the back surface plate is a touch sensor panel.
[4] A display device comprising the optical laminate according to any one of [1] to [3 ].
[5] The display device according to item [4], wherein the front panel side can be bent with the inside being the front panel side.
According to the present invention, an optical laminate in which generation of bubbles in an adhesive layer is suppressed when the optical laminate is bent, and a display device including the optical laminate are provided.
Drawings
Fig. 1 is a schematic cross-sectional view showing an example of an optical laminate of the present invention.
Fig. 2 is a schematic diagram illustrating a method for measuring a stress-strain value by a tensile test.
Fig. 3 is a schematic diagram illustrating a bending test.
Description of the symbols
100 optical laminate, 101 front panel, 102 1 st adhesive layer, 103 polarizer, 104 nd adhesive layer 2, 105 back panel, 501 polycarbonate rod, 502 adhesive layer, 601, 602 mounting table.
Detailed Description
Embodiments of the optical laminate according to the present invention will be described below with reference to the drawings, but the present invention is not limited to the embodiments below. In all the drawings below, the scale of each component shown in the drawings is appropriately adjusted to facilitate understanding of the component, and the scale of the component does not necessarily coincide with the scale of the actual component.
< optical laminate >
Figure 1 is a schematic cross-sectional view of an optical stack according to one embodiment of the present invention. The optical laminate 100 shown in fig. 1 includes a front plate 101, a1 st adhesive layer 102, a polarizing plate 103, a 2 nd adhesive layer 104, and a back plate 105 in this order. Hereinafter, the 1 st adhesive layer 102 and the 2 nd adhesive layer 104 may be collectively referred to as an adhesive layer.
The thickness of the optical laminate 100 is not particularly limited, and is, for example, 30 to 1500 μm, preferably 40 to 1000 μm, and more preferably 50 to 500 μm, since it varies depending on the functions required for the optical laminate, the application of the optical laminate, and the like.
The shape of the optical laminate 100 in a plan view may be, for example, a square shape, preferably a square shape having long sides and short sides, and more preferably a rectangle. When the shape of the optical laminate 100 in the plane direction is rectangular, the length of the long side may be, for example, 10mm to 1400mm, and preferably 50mm to 600 mm. The length of the short side is, for example, 5mm to 800mm, preferably 30mm to 500mm, and more preferably 50mm to 300 mm. Each layer constituting the optical laminate 100 may be subjected to a corner rounding process (R process), or may be subjected to a notch process or a hole opening process on an end portion.
The optical laminate 100 can be used for a display device or the like, for example. The display device is not particularly limited, and examples thereof include an organic electroluminescence (organic EL) display device, an inorganic electroluminescence (inorganic EL) display device, a liquid crystal display device, and an electroluminescence display device. The optical stack 100 is suitable for a bendable display device.
[ slope G from origin to maximum stress value in stress-strain curveL’]
The slopes from the origin to the maximum stress value in the stress [ Pa ] -strain curves [% ] at 60 ℃ and 90% RH of the 1 st and 2 nd adhesive layers 102 and 104 were respectively GL1' and GL2In the case of (1), the optical layered body 100 satisfies the following formulae (1) and (2).
70≤GL1’≤250 (1)
70≤GL2’≤250 (2)
When the adhesive layer is subjected to a tensile test, a stress-strain curve in which the vertical axis represents stress and the horizontal axis represents strain can be plotted. In general, as the strain becomes larger, the stress generated in the adhesive layer becomes larger, and the stress reaches a maximum immediately before cohesive failure of the adhesive layer occurs. Slope G from origin to maximum stress value in stress-strain curve of adhesive layerL' is represented by (maximum stress value)/(amount of strain at which stress reaches maximum). GL"reflects not only the change in stress when the adhesive layer is elastically deformed but also the change in stress when the adhesive layer is plastically deformed, and is an index of durability until cohesive failure occurs in the adhesive layer. Consider GLWhen the amount is larger, the stress generated by the strain of the adhesive layer is large, and the cohesive force of the adhesive layer is excellent. GLWhen the thickness is small, stress generated by strain of the adhesive layer is small, and the adhesive layer is easily deformed and hardly broken. GL' can be obtained by the method described in the section of examples, which will be described later.
The optical laminate 100 satisfying the formulae (1) and (2) is less likely to generate bubbles in the pressure-sensitive adhesive layer even when it is bent. In particular, even when the pressure-sensitive adhesive layer is bent under a high-temperature and high-humidity environment, the generation of air bubbles in the pressure-sensitive adhesive layer can be suppressed. The optical laminate 100 satisfying the formulae (1) and (2) can improve the durability of the pressure-sensitive adhesive layer to such an extent that bubbles are not generated even when the optical laminate is repeatedly bent 2 ten thousand or more times so that the bending radius is 2.5mm at 60 ℃ and 90% RH as described in the section of examples below. The generation of bubbles in the adhesive layer can be judged by observation under an optical microscope.
In the present specification, the bending includes a bent form in which a curved surface is formed at a bent portion, and a curvature radius of an inner surface of the bent form is not particularly limited. In addition, bending also includes meanders where the inner surface has a meander angle greater than 0 degrees and less than 180 degrees and folds where the radius of curvature of the inner surface is near zero or where the meander angle of the inner surface is 0 degrees.
The optical laminate 100 preferably satisfies the following formulae (1 ') and (2').
90≤GL1’≤150 (1’)
90≤GL2’≤150 (2’)
The optical laminate 100 satisfying the formulae (1 ') and (2') can further suppress the generation of bubbles in the adhesive layer even when bent under a high-temperature and high-humidity environment.
When the front panel is bent inward, the optical laminate 100 preferably satisfies the following formula (3) or (3').
GL1’≤GL2’ (3)
GL1’＜GL2’ (3’)
When the front plate is bent outward, the optical laminate 100 preferably satisfies the following formula (4) or (4').
GL1’≥GL2’ (4)
GL1’＞GL2’ (4’)
When the optical laminate 100 is bent, a larger stress is generated in the pressure-sensitive adhesive layer on the inner diameter side. Thus, by mixing GLThe adhesive layer which is smaller and has excellent stress relaxation properties is disposed inside when bent, and the generation of air bubbles in the adhesive layer of the optical laminate 100 can be further suppressed.
GL' the pressure-sensitive adhesive layer can be formed into a desired numerical range by adjusting the kind and the amount of the monomer constituting the base polymer contained in the pressure-sensitive adhesive composition used in the pressure-sensitive adhesive layer, the kind and the amount of the polymerizable compound, the kind and the amount of the active energy ray, the irradiation amount, and the like. For example, when the base polymer contained in the adhesive composition contains a large amount of structural units derived from a long-chain alkyl (meth) acrylic monomer having 10 or more carbon atoms, GL' in a tendency to become smaller. When the binder composition contains a large amount of a long-chain alkyl (meth) acrylic monomer having 10 or more carbon atoms, a diluent monomer, or the like as a polymerizable compound, GL' in a tendency to become smaller. For example, tetrahydrofurfuryl acrylate may be used as the diluent monomer. For example, when the pressure-sensitive adhesive composition contains a large amount of a compound having a cyclic structure such as cyclohexyl as the polymerizable compound, GL' is in a tendency to become larger.
[ front panel ]
The material and thickness of the front panel 101 are not limited as long as the front panel is a plate-like body capable of transmitting light. The front panel 101 may be composed of only 1 layer, or may be composed of 2 or more layers. Examples of the front panel 101 include a resin plate-like body (e.g., a resin plate, a resin sheet, a resin film, etc.), a glass plate-like body (e.g., a glass plate, a glass film, etc.), and a laminate of a resin plate-like body and a glass plate-like body. The front panel 101 may constitute the outermost surface of the display device.
The thickness of the front plate 101 may be, for example, 10 to 300. mu.m, preferably 20 to 200. mu.m, and more preferably 30 to 100. mu.m. In the present invention, the thickness of each layer constituting the optical laminate 100 can be measured by the thickness measurement method described in the examples described below.
Examples of the resin constituting the plate-like body made of a resin include polymers such as triacetyl cellulose, acetyl cellulose butyrate, ethylene-vinyl acetate copolymer, propionyl cellulose, butyryl cellulose, levulinyl cellulose, polyester, polystyrene, polyamide, polyetherimide, poly (meth) acrylic acid, polyimide, polyethersulfone, polysulfone, polyethylene, polypropylene, polymethylpentene, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, polyvinyl acetal, polyether ketone, polyether ether ketone, polyethersulfone, polymethyl methacrylate, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate, and polyamideimide. These polymers may be used alone or in combination of 2 or more. From the viewpoint of improving strength and transparency, the resin plate-like body is preferably a resin film made of a polymer such as polyimide, polyamide, polyamideimide, or the like.
From the viewpoint of hardness, the front panel 101 may be a resin film provided with a hard coat layer. The hard coat layer may be formed on one surface of the resin film or on both surfaces thereof. By providing the hard coat layer, hardness and scratch resistance can be improved. The hard coat layer is a cured layer of, for example, an ultraviolet curable resin. Examples of the ultraviolet curable resin include acrylic resins, silicone resins, polyester resins, polyurethane resins, amide resins, and epoxy resins. The hard coating may also contain additives in order to increase the hardness. The additive is not particularly limited, and examples thereof include inorganic fine particles, organic fine particles, and a mixture thereof. When the resin film has hard coat layers on both surfaces thereof, the composition and thickness of each hard coat layer may be the same or different from each other.
When the front plate 101 is a glass plate, a strengthened glass for display is preferably used as the glass plate. The thickness of the glass plate may be, for example, 10 to 1000 μm, or 10 to 100 μm. By using the glass plate, the front panel 101 having excellent mechanical strength and surface hardness can be configured.
When the optical laminate 100 is used in a display device, the front panel 101 has a function of protecting the front surface (screen) of the display device (a function as a window film), a function as a touch sensor, a blue light cut-off function, a viewing angle adjustment function, and the like.
[1 st adhesive layer ]
The 1 st adhesive layer 102 is interposed between the front panel 101 and the polarizing plate 103, and bonded thereto. The 1 st pressure-sensitive adhesive layer 102 may be composed of 1 layer or 2 or more layers, but is preferably composed of 1 layer.
The 1 st pressure-sensitive adhesive layer 102 may be composed of a pressure-sensitive adhesive composition containing a (meth) acrylic resin, a rubber-based resin, a urethane-based resin, an ester-based resin, a silicone-based resin, or a polyvinyl ether-based resin as a main component (base polymer). The pressure-sensitive adhesive composition constituting the 1 st pressure-sensitive adhesive layer 102 is preferably a pressure-sensitive adhesive composition containing a (meth) acrylic resin as a base polymer, which is excellent in transparency, weather resistance, heat resistance, and the like.
As the (meth) acrylic resin used in the adhesive composition, a polymer or copolymer in which 1 or 2 or more kinds of (meth) acrylic esters such as butyl (meth) acrylate, ethyl (meth) acrylate, isooctyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate are used as monomers is preferably used. It is preferred to copolymerize the polar monomer with the base polymer. Examples of the polar monomer include monomers having a carboxyl group, a hydroxyl group, an amide group, an amino group, an epoxy group, and the like, such as a (meth) acrylic acid compound, a 2-hydroxypropyl (meth) acrylate compound, a hydroxyethyl (meth) acrylate compound, a (meth) acrylamide compound, an N, N-dimethylaminoethyl (meth) acrylate compound, and a glycidyl (meth) acrylate compound.
The active energy ray-curable pressure-sensitive adhesive composition has a property of being cured by irradiation with an active energy ray such as an ultraviolet ray or an electron beam, has an adhesive property even before irradiation with an active energy ray, and has a property of being capable of being bonded to an adherend such as a film and being cured by irradiation with an active energy ray, whereby the bonding force can be adjusted. The active energy ray-curable adhesive composition is preferably an ultraviolet-curable adhesive composition. The active energy ray-curable adhesive composition further contains an active energy ray-polymerizable compound in addition to the base polymer and the crosslinking agent. The photopolymerization initiator, the photosensitizer and the like may be contained as necessary.
Examples of the active energy ray-polymerizable compound include (meth) acrylate monomers having at least 1 (meth) acryloyloxy group in the molecule; (meth) acrylic compounds such as (meth) acryloyloxy group-containing compounds such as (meth) acrylate oligomers having at least 2 (meth) acryloyloxy groups in the molecule, which are obtained by reacting 2 or more kinds of functional group-containing compounds. The binder composition may contain the active energy ray-polymerizable compound in an amount of 0.1 part by mass or more or 1 part by mass or more, and may contain the active energy ray-polymerizable compound in an amount of 10 parts by mass or less or 5 parts by mass or less, based on 100 parts by mass of the base polymer.
Examples of the photopolymerization initiator include benzophenone, benzildimethylketal, and 1-hydroxycyclohexylphenylketone. The photopolymerization initiator may contain 1 or 2 or more species. When the pressure-sensitive adhesive composition contains a photopolymerization initiator, the total content thereof may be, for example, 0.01 to 3.0 parts by mass per 100 parts by mass of the solid content of the pressure-sensitive adhesive composition.
The binder composition may contain additives such as fine particles, beads (resin beads, glass beads, and the like), glass fibers, resins other than the base polymer, adhesion-imparting agents, fillers (metal powders, other inorganic powders, and the like), antioxidants, ultraviolet absorbers, dyes, pigments, colorants, antifoaming agents, anticorrosive agents, and crosslinking agents for imparting light scattering properties.
The 1 st pressure-sensitive adhesive layer 102 can be formed by applying a diluted solution of the above-mentioned pressure-sensitive adhesive composition in an organic solvent to a substrate and drying the applied solution. The 1 st adhesive layer 102 may be formed using an adhesive sheet formed using an adhesive composition. When an active energy ray-curable adhesive composition is used, an adhesive layer having a desired degree of curing can be formed by irradiating the formed adhesive layer with an active energy ray.
The thickness of the 1 st pressure-sensitive adhesive layer 102 is not particularly limited, and is, for example, preferably 1 μm to 100 μm, more preferably 3 μm to 50 μm, and may be 20 μm or more.
[ polarizing plate ]
The polarizing plate 103 may be, for example, a linear polarizing plate, a circular polarizing plate, an elliptical polarizing plate, or the like. Hereinafter, the circularly polarizing plate and the elliptically polarizing plate may be collectively referred to simply as a circularly polarizing plate. The circularly polarizing plate comprises a linear polarizing plate and a retardation layer. Since the circularly polarizing plate can absorb external light reflected by the image display device, the optical laminate 100 can be provided with a function as an antireflection film.
The thickness of the polarizing plate 103 is usually 5 μm or more, and may be 20 μm or more, 25 μm or more, or 30 μm or more. The thickness of the polarizing plate 103 is preferably 80 μm or less, and more preferably 60 μm or less.
(Linear polarizing plate)
The linearly polarizing plate has a function of selectively transmitting linearly polarized light in one direction from light beams of unpolarized light such as natural light. The linear polarizing plate may include a stretched film or a stretched layer having a dichroic dye adsorbed thereon, a cured product containing a polymerizable liquid crystal compound, a liquid crystal layer in which a dichroic dye is dispersed in a cured product of a polymerizable liquid crystal compound and oriented, and the like as a polarizer layer. When the pigment is dispersed in a medium having anisotropy and oriented, the following conditions are applied: it looks colored from a certain direction, but it looks substantially colorless from a direction perpendicular thereto. A dye exhibiting such a phenomenon is referred to as a dichroic dye. A linear polarizing plate using a liquid crystal layer as a polarizer layer is preferable because the bending direction is not limited as compared with a stretched film or a stretched layer having a dichroic dye adsorbed thereon.
(1) Polarizer layer as stretched film or stretched layer having dichroic dye adsorbed thereon
The polarizer layer as a stretched film having a dichroic dye adsorbed thereon can be generally produced through the following steps: the method for producing a polyvinyl alcohol film comprises a step of uniaxially stretching a polyvinyl alcohol resin film, a step of dyeing the polyvinyl alcohol resin film with a dichroic dye such as iodine to adsorb the dichroic dye, a step of treating the polyvinyl alcohol resin film adsorbed with the dichroic dye with an aqueous boric acid solution, and a step of washing the polyvinyl alcohol resin film with water after the treatment with the aqueous boric acid solution.
The thickness of the polarizer layer is usually 30 μm or less, preferably 18 μm or less, and more preferably 15 μm or less. Making the thickness of the polarizer layer thin is advantageous for making the polarizing plate 103 thin. The thickness of the polarizer layer is usually 1 μm or more, and for example, may be 5 μm or more.
The polyvinyl alcohol resin can be obtained by saponifying a polyvinyl acetate resin. As the polyvinyl acetate-based resin, in addition to polyvinyl acetate which is a homopolymer of vinyl acetate, a copolymer of vinyl acetate and another monomer copolymerizable therewith may be used. Examples of the other monomer copolymerizable with vinyl acetate include unsaturated carboxylic acid compounds, olefin compounds, vinyl ether compounds, unsaturated sulfone compounds, and (meth) acrylamide compounds having an ammonium group.
The saponification degree of the polyvinyl alcohol resin is usually about 85 mol% to 100 mol%, and preferably 98 mol% or more. The polyvinyl alcohol resin may be modified, and polyvinyl formal, polyvinyl acetal, or the like modified with aldehydes may be used. The polymerization degree of the polyvinyl alcohol resin is usually 1000 to 10000, preferably 1500 to 5000.
The polarizer layer as the stretched layer having the dichroic dye adsorbed thereon can be generally produced through the following steps: the method for producing a polarizer comprises a step of applying a coating liquid containing the polyvinyl alcohol resin to a base film, a step of uniaxially stretching the obtained laminated film, a step of dyeing the polyvinyl alcohol resin layer of the uniaxially stretched laminated film with a dichroic dye to adsorb the dichroic dye to form a polarizer layer, a step of treating the film adsorbed with the dichroic dye with an aqueous boric acid solution, and a step of washing the film with water after the treatment with the aqueous boric acid solution. The substrate film for forming the polarizer layer may be used as a protective layer for the polarizer layer. The substrate film may be peeled off from the polarizer layer as necessary. The material and thickness of the base film may be the same as those of the thermoplastic resin film described later.
The polarizer layer as a stretched film or a stretched layer having a dichroic dye adsorbed thereon may be used as it is as a linear polarizing plate, or may be used as a linear polarizing plate by forming a protective layer on one or both surfaces thereof. As the protective layer, a thermoplastic resin film described later can be used. The polarizer layer and the protective layer may be laminated via a lamination layer described later. The thickness of the linear polarizing plate obtained is preferably 2 to 40 μm.
Examples of the thermoplastic resin film include a cyclic polyolefin resin film; cellulose acetate resin films made of resins such as triacetyl cellulose and diacetyl cellulose; polyester resin films made of resins such as polyethylene terephthalate, polyethylene naphthalate, and polybutylene terephthalate; a polycarbonate-based resin film; a (meth) acrylic resin film; a polypropylene resin film and the like known in the art.
From the viewpoint of improving the bendability, the thickness of the thermoplastic resin film is usually 100 μm or less, preferably 80 μm or less, more preferably 60 μm or less, further preferably 40 μm or less, further preferably 30 μm or less, and further usually 5 μm or more, preferably 10 μm or more.
A hard coat layer may be formed on the thermoplastic resin film. The hard coat layer may be formed on one surface or both surfaces of the thermoplastic resin film. By providing the hard coat layer, a thermoplastic resin film having improved hardness and scratch resistance can be produced. The hard coat layer can be formed by the same method as that for the hard coat layer formed on the resin film.
(2) Polarizer layer as a liquid crystal layer
The polymerizable liquid crystal compound used for forming the liquid crystal layer is a compound having a polymerizable reactive group and exhibiting liquid crystallinity. The polymerizable reactive group is a group participating in a polymerization reaction, and is preferably a photopolymerizable reactive group. The photopolymerizable reactive group means a group that can participate in a polymerization reaction by an active radical, an acid, or the like generated from a photopolymerization initiator. Examples of the photopolymerizable functional group include a vinyl group, a vinyloxy group, a 1-chloroethenyl group, an isopropenyl group, a 4-vinylphenyl group, an acryloyloxy group, a methacryloyloxy group, an oxirane group, and an oxetanyl group. Among them, acryloxy, methacryloxy, vinyloxy, oxirane and oxetanyl groups are preferable, and acryloxy group is more preferable. The type of the polymerizable liquid crystal compound is not particularly limited, and a rod-like liquid crystal compound, a discotic liquid crystal compound, and a mixture thereof can be used. The liquid crystallinity of the polymerizable liquid crystal compound may be thermotropic liquid crystal or lyotropic liquid crystal, and the phase sequence structure may be nematic liquid crystal or smectic liquid crystal.
The dichroic dye used in the polarizer layer as a liquid crystal layer preferably has an absorption maximum wavelength (λ MAX) in the range of 300 to 700 nm. Examples of such dichroic dyes include acridine dyes,
Figure BDA0002966067100000091
Oxazine pigments, cyanine pigments, naphthalene pigments, azo pigments, anthraquinone pigments, and the like, and among them, azo pigments are preferable. Examples of the azo dye include monoazo dye, disazo dye, trisazo dye, tetraazo dye, and stilbene azo dye, and disazo dye and trisazo dye are preferable. The dichroic dye may be used alone in 1 kind, or may be used in combination in 2 or more kinds, preferably in combination in 3 or more kinds. Particularly, 3 or more azo compounds are more preferably combined. A part of the dichroic dye may have a reactive group and may also have liquid crystallinity.
The polarizer layer as the liquid crystal layer can be formed, for example, by applying a composition for forming a polarizer layer containing a polymerizable liquid crystal compound and a dichroic dye onto an alignment film formed on a base film, and polymerizing and curing the polymerizable liquid crystal compound. The composition for forming a polarizer layer may be applied to a base film to form a coating film, and the coating film may be stretched together with the base film to form a polarizer layer. The substrate film for forming the polarizer layer may be used as a protective layer for the polarizer layer. The material and thickness of the base film may be the same as those of the thermoplastic resin film described above.
Examples of the composition for forming a polarizer layer containing a polymerizable liquid crystal compound and a dichroic dye and the method for producing a polarizer layer using the composition include the production methods described in jp 2013-37353 a, jp 2013-33249 a, and jp 2017-83843 a. The composition for forming a polarizer layer may further contain additives such as a solvent, a polymerization initiator, a crosslinking agent, a leveling agent, an antioxidant, a plasticizer, and a sensitizer in addition to the polymerizable liquid crystal compound and the dichroic dye. These components may be used alone in 1 kind, or 2 or more kinds may be used in combination.
The polymerization initiator that can be contained in the composition for forming a polarizer layer is a compound that can initiate the polymerization reaction of the polymerizable liquid crystal compound, and a photopolymerization initiator is preferable in that the polymerization reaction can be initiated at a lower temperature. Specifically, there may be mentioned photopolymerization initiators capable of generating active radicals or acids by the action of light, and among them, photopolymerization initiators capable of generating radicals by the action of light are preferred. The content of the polymerization initiator is preferably 1 to 10 parts by mass, and more preferably 3 to 8 parts by mass, based on 100 parts by mass of the total amount of the polymerizable liquid crystal compound. When the amount is within this range, the reaction of the polymerizable group proceeds sufficiently, and the alignment state of the liquid crystal compound is easily stabilized.
The thickness of the polarizer layer as the liquid crystal layer is usually 10 μm or less, preferably 0.5 to 8 μm, and more preferably 1 to 5 μm.
The polarizer layer as the liquid crystal layer may be used as a linear polarizing plate without peeling and removing the substrate film, or may be used as a linear polarizing plate by peeling and removing the substrate film from the polarizer layer. The polarizer layer as the liquid crystal layer may or may not have an alignment film. The polarizer layer as the liquid crystal layer may be used as a linear polarizing plate by forming a protective layer on one or both surfaces thereof. As the protective layer, the above thermoplastic resin film can be used.
The polarizer layer as the liquid crystal layer may have an overcoat layer on one side or both sides of the polarizer layer for the purpose of protecting the polarizer layer or the like. The overcoat layer can be formed, for example, by coating a material (composition) for forming the overcoat layer on the polarizer layer. Examples of the material constituting the overcoat layer include a photocurable resin and a water-soluble polymer. As a material constituting the overcoat layer, a (meth) acrylic resin, a polyvinyl alcohol resin, or the like can be used.
(retardation layer)
The retardation layer may be 1 layer or 2 or more layers. The retardation layer may have an overcoat layer for protecting the surface thereof, a substrate film for supporting the retardation layer, and the like. The phase difference layer includes a lambda/4 layer, and may further include at least one of a lambda/2 layer and a positive C layer. When the retardation layer includes a lambda/2 layer, the lambda/2 layer and the lambda/4 layer are stacked in this order from the linear polarizer side. When the phase difference layer includes a positive C layer, the λ/4 layer and the positive C layer may be stacked in this order from the linear polarizer side, or the positive C layer and the λ/4 layer may be stacked in this order from the linear polarizer side. The thickness of the retardation layer is, for example, 0.1 to 10 μm, preferably 0.5 to 8 μm, and more preferably 1 to 6 μm.
The retardation layer may be formed of a resin film exemplified as a material of the protective layer, or may be formed of a layer in which a polymerizable liquid crystal compound is cured. The retardation layer may further include an alignment film. The phase difference layer may have a lamination layer for laminating the λ/4 layer with the λ/2 layer and the positive C layer.
When the polymerizable liquid crystal compound is cured to form the retardation layer, the retardation layer can be formed by applying a composition containing the polymerizable liquid crystal compound to a substrate film and curing the composition. An alignment film may be formed between the substrate film and the coating layer. The material and thickness of the base film may be the same as those of the thermoplastic resin film described above. When the retardation layer is formed from a layer obtained by curing a polymerizable liquid crystal compound, the retardation layer may be incorporated into an optical laminate in a form having an alignment film and a base film. The retardation layer may be bonded to the surface of the linear polarizing plate on the side opposite to the viewing side through a bonding layer described later.
[2 nd adhesive layer ]
The 2 nd adhesive layer 104 is interposed between the polarizing plate 103 and the back surface plate 105, and bonded thereto. The 2 nd pressure-sensitive adhesive layer 104 may be 1 layer or may be composed of 2 or more layers, but is preferably 1 layer.
The composition and blending components of the pressure-sensitive adhesive composition constituting the 2 nd pressure-sensitive adhesive layer 104, the type of the pressure-sensitive adhesive composition (whether it is an active energy ray-curable type, a thermosetting type, or the like), additives that can be blended into the pressure-sensitive adhesive composition, the method for producing the 2 nd pressure-sensitive adhesive layer, the thickness of the 2 nd pressure-sensitive adhesive layer, and the like are the same as those described in the above description of the 1 st pressure-sensitive adhesive layer 102.
The 2 nd adhesive layer 104 may be the same as or different from the 1 st adhesive layer 102 in composition, blending components, thickness, and the like of the adhesive composition.
[ adhesive layer ]
The optical stack 100 may include a lamination layer for bonding 2 layers. The adhesive layer is a layer made of an adhesive or a bonding agent. As the adhesive agent for the material of the laminating layer, the same adhesive agent composition as that constituting the adhesive agent layer 102 of the 1 st embodiment described above can be used. Other adhesives may be used for the adhesive layer, for example, (meth) acrylic adhesives, styrene adhesives, silicone adhesives, rubber adhesives, polyurethane adhesives, polyester adhesives, epoxy copolymer adhesives, and the like, which are different from the adhesive constituting the 1 st adhesive layer 102.
The adhesive used as the material of the adhesive layer may be formed by combining 1 or 2 or more kinds of water-based adhesives, active energy ray-curable adhesives, and the like, for example. Examples of the aqueous adhesive include a polyvinyl alcohol resin aqueous solution and an aqueous two-pack polyurethane emulsion adhesive. The active energy ray-curable adhesive is an adhesive that is cured by irradiation with an active energy ray such as ultraviolet ray, and examples thereof include an adhesive containing a polymerizable compound and a photopolymerization initiator, an adhesive containing a photoreactive resin, and an adhesive containing a binder resin and a photoreactive crosslinking agent. Examples of the polymerizable compound include photopolymerizable monomers such as a photocurable epoxy monomer, a photocurable acrylic monomer, and a photocurable polyurethane monomer, and oligomers derived from these monomers. Examples of the photopolymerization initiator include compounds containing an active species that generates a neutral radical, an anionic radical, a cationic radical, and the like by irradiation with active energy rays such as ultraviolet rays.
The thickness of the adhesive layer may be, for example, 1 μm or more, preferably 1 to 25 μm, more preferably 2 to 15 μm, and still more preferably 2.5 to 5 μm.
The 2 opposing surfaces bonded via the bonding layer may be subjected to corona treatment, plasma treatment, flame treatment, or the like in advance, or may have a primer layer or the like.
[ Back Panel ]
As the back plate 105, a plate-like body capable of transmitting light, a component used in a general display device, or the like can be used.
The thickness of back plate 105 may be, for example, 5 μm to 2000 μm, preferably 10 μm to 1000 μm, and more preferably 15 μm to 500 μm.
The plate-like body used for the back plate 105 may be composed of only 1 layer, or may be composed of 2 or more layers. Rear plate 105 may be a plate as exemplified in front plate 101.
Examples of the components used in a typical display device include a touch sensor panel and an organic EL display element. The back panel 105 is preferably a touch sensor panel. Examples of the order of stacking the components in the display device include a front panel, a circularly polarizing plate, a touch sensor panel, an organic EL display element, a front panel, a touch sensor panel, a circularly polarizing plate, and an organic EL display element.
(touch sensor panel)
The touch sensor panel is not limited as long as it is a panel having a sensor capable of detecting a touched position (i.e., a touch sensor). The detection method of the touch sensor is not limited, and examples thereof include a touch sensor panel of a resistive film method, a capacitive coupling method, an optical sensor method, an ultrasonic method, an electromagnetic induction coupling method, a surface acoustic wave method, and the like. From the viewpoint of low cost, a touch sensor panel of a resistive film type or a capacitive coupling type is preferably used.
An example of a resistive film type touch sensor includes a pair of substrates arranged to face each other, an insulating spacer sandwiched between the pair of substrates, a transparent conductive film as a resistive film provided on an inner front surface of each substrate, and a touch position detection circuit. In an image display device provided with a resistive touch sensor, if a surface of a front panel is touched, an opposing resistive film is short-circuited, and a current flows through the resistive film. The touch position detection circuit detects a change in voltage at that time, and detects a touched position.
An example of a capacitive coupling type touch sensor includes a substrate, a position detection transparent electrode provided on the entire surface of the substrate, and a touch position detection circuit. In an image display device provided with a capacitive coupling type touch sensor, if the surface of a front panel is touched, a transparent electrode is grounded at the touched point via the capacitance of a human body. The touch position detection circuit detects the grounding of the transparent electrode and detects the touched position.
The thickness of the touch sensor panel may be, for example, 5 to 2000 μm, preferably 5 to 100 μm, more preferably 5 to 50 μm, or 5 to 20 μm.
The touch sensor panel may be a member in which a pattern of touch sensors is formed on a base film. Examples of the base film may be the same as those in the description of the thermoplastic resin film. In addition, the touch sensor panel can be transferred from the base material film to an adherend via an adhesive layer. That is, the touch sensor panel may not have a base material film. The thickness of the touch sensor pattern may be, for example, 1 μm to 20 μm.
[ method for producing optical laminate ]
The optical laminate 100 can be manufactured by a method including a step of bonding the layers constituting the optical laminate 100 to each other via an adhesive layer. When the layers are bonded to each other via the adhesive layer and the bonding layer, it is preferable to perform surface activation treatment such as corona treatment on one side or both sides of the bonding surface for the purpose of adjusting the adhesion force. The conditions of the corona treatment may be set as appropriate, and the conditions may be different between one surface and the other surface of the faying surface.
[ display device ]
The display device of the present invention includes the optical laminate 100 described above. The display device is not particularly limited, and examples thereof include image display devices such as an organic EL display device, an inorganic EL display device, a liquid crystal display device, and an electroluminescence display device. The optical laminate may further be laminated with a touch sensor, and the display device may have a touch panel function. The display device including the optical laminate 100 of the present invention has excellent bending durability, and can be used as a flexible display that can be bent or rolled.
In the display device, the optical laminate 100 is disposed on the viewing side of the display element included in the display device with the front panel 101 facing outward (the side opposite to the display element side, i.e., the viewing side). The display device can be curved with the front panel 101 side being inside or outside.
Examples of the image display element included in the image display device include an organic EL display element, an inorganic EL display element, a liquid crystal display element, a plasma display element, and a field emission type display element.
The display device of the present invention can be used as mobile devices such as smart phones and tablet computers, televisions, digital photo frames, electronic signboards, measuring instruments, office equipment, medical equipment, computer equipment, and the like.
Examples
The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.
[ measurement method ]
The measurement method and calculation method of each physical property value (layer thickness, adhesive layer property) used in the present example are as follows.
Thickness of layer
The film thickness was measured using a contact type film thickness measuring apparatus ("MS-5C" manufactured by Nikon K.K.). The polarizer layer and the alignment film were measured using a laser microscope ("OLS 3000" manufactured by olympus corporation).
< slope G from origin to maximum stress value in stress-strain curveL’＞
The slope from the origin to the maximum stress value was measured by a tensile test using a dynamic mechanical analyzer (DMA, Q-800, TA Instruments). First, as shown in fig. 2, a test piece in which the end portions of 2 Polycarbonate (PC) rods 501 were joined to each other via an adhesive layer 502 was prepared. FIG. 2 is a cross-sectional view of a test piece. The adhesive layer 502 has a shape of 6mm × 10mm × 25 μm in width × length × thickness, and the PC rod 501 has a shape of 6mm × 20mm × 1mm in width × length × thickness. The area of the bond between the adhesive layer 502 and the PC rod 501 is 6mm × 10mm in width × length. The test piece was left at 60 ℃ and 90% RH for 1 day. A jig is attached to a 5 mm-long area of both ends of the PC rod 501 of the test piece, and one jig (5 mm-long area of the upper end in the test piece of FIG. 2) is attached. The other jig (in the test piece of FIG. 2, the region having a length of 5mm at the lower end) was pulled at a speed of 100 μm/min at a temperature of 25 ℃ to prepare a stress [ Pa ] -strain [ (% ]curve. In the obtained stress-strain curve, the slope GL' from the origin to the point where the stress reaches the maximum is calculated.
[ production of adhesive sheet comprising adhesive layer ]
A1L reaction vessel equipped with a cooling tube, a nitrogen introduction tube, a thermometer, and a stirrer was charged with a monomer mixture solution of 2-ethylhexyl acrylate (2-EHA), Butyl Acrylate (BA), 2-propylheptyl acrylate (2-PHA), Acrylic Acid (AA), behenyl acrylate (C22A), and octadecyl acrylate (ODA) at the compounding amounts shown in Table 1. The nitrogen gas was circulated for 1 hour to remove oxygen in the vessel, and the internal temperature was maintained at 60 ℃. The monomer mixed solution was uniformly mixed, and then the photopolymerization initiators benzildimethylketal (I-651) and 1-hydroxycyclohexylphenylketone (I-184) were added in the amounts shown in Table 1. (meth) acrylic polymers A1 to A4 were produced by irradiating the mixture with a UV lamp (10mW) while stirring.
[ Table 1]
Figure BDA0002966067100000151
The obtained (meth) acrylic polymers a1 to a4 were mixed with tetrahydrofurfuryl acrylate (THFA), isodecyl acrylate (IDA), or isobornyl acrylate (IBOA) and 1-hydroxycyclohexyl phenyl ketone (I-184) in the blending amounts shown in table 2 to produce adhesive compositions B1 to B8.
[ Table 2]
Figure BDA0002966067100000161
The pressure-sensitive adhesive compositions B1 to B8 were applied to a release film A (polyethylene terephthalate film, thickness 38 μm) coated with a silicon release agent so that the thickness became 25 μm. A release film B (polyethylene terephthalate film, 38 μm thick) was bonded thereto, and UV irradiation was performed to prepare a pressure-sensitive adhesive sheet composed of a release film A/a pressure-sensitive adhesive layer/a release film B. The condition of UV irradiation was a cumulative light amount of 400mJ/cm2Illuminance of 1.8mW/cm2(UVV reference). Slope G from origin to maximum stress value in stress-strain curve obtained by subjecting adhesive layer to tensile testL' are shown in Table 2.
The suppliers of the compounds used are as follows.
2-EHA: tokyo chemical industry Co., Ltd, Japan
BA: tokyo chemical industry Co., Ltd, Japan
2-PHA: BASF, Germany
AA: tokyo chemical industry Co., Ltd, Japan
C22A: tokyo chemical industry Co., Ltd, Japan
ODA: miwon specialty chemical, Korea
I-651: BASF, Germany
I-184: BASF, Germany
THFA: tokyo chemical industry Co., Ltd, Japan
IDA: tokyo chemical industry Co., Ltd, Japan
IOBA: tokyo chemical industry Co., Ltd, Japan
[ front panel ]
As the front panel 101, a film having a hard coat layer formed on one surface of a resin film is prepared. The resin film was a polyimide resin film having a thickness of 40 μm. The hard coat layer is a layer having a thickness of 10 μm and formed of a composition containing a dendritic polymer having a multifunctional acrylic group at the terminal.
[ polarizing plate ]
As the polarizing plate 103, a circularly polarizing plate was prepared. A linear polarizing plate having a triacetyl cellulose (TAC) film (KC2UA, manufactured by Konika Mentoda, thickness 25 μm), an alignment film, a polarizer layer and an overcoat layer in this order was prepared. The polarizer layer was formed using a composition containing a polymerizable liquid crystal compound and a dichroic dye, and had a thickness of 2 μm. The outer coating is a polyvinyl alcohol resin layer with the thickness of 1.0 μm.
The retardation laminate was laminated on the outer coating side of the linear polarizer via an adhesive layer to obtain a circular polarizer. The retardation laminate comprises a lambda/4 retardation layer, an adhesive layer, and a positive C layer in this order from the linear polarizer side. The λ/4 retardation layer was a cured layer of a polymerizable liquid crystal compound and had a thickness of 3 μm. The thickness of the adhesive layer was 5 μm. The positive C layer was a cured layer of a polymerizable liquid crystal compound and had a thickness of 3 μm.
[ Back Panel ]
As the back panel 105, a touch sensor panel in which a touch sensor pattern layer, an adhesive layer, and a base material layer are laminated in this order is prepared. The touch sensor pattern layer included an ITO layer as a transparent conductive layer and a cured layer of an acrylic resin composition as a separation layer, and had a thickness of 7 μm. The adhesive layer was provided on the separation layer side of the touch sensor pattern layer and had a thickness of 3 μm. As the substrate layer, a cycloolefin resin (COP) film (ZF-14, manufactured by Nippon Ralskikai Co., Ltd., thickness: 23 μm) was used.
[ production of optical layered body ]
As shown in table 3, an adhesive sheet composed of the adhesive composition shown in table 2 was used as the 1 st adhesive layer 102, and the side of the front panel 101 not having a hard coat layer was bonded to the TAC film side of the polarizing plate 103. Further, an adhesive sheet composed of the adhesive composition shown in table 2 was used as the 2 nd adhesive layer 104 shown in table 3, and the retardation layer side of the circularly polarizing plate was bonded to the touch sensor pattern layer side of the touch sensor panel. Optical laminates 100 (examples 1 to 6 and comparative examples 1 to 2) having the layer structure shown in fig. 1 were obtained. The adhesive layer is adhered to the front panel, the circular polarizer, the touch sensor panel, and the adhesive layer by corona treatment. For the corona treatment, TEC-4 AX (available from Ushio Motor Co., Ltd.) was used.
The optical laminate 100 thus produced was subjected to the following bending test. The results are shown in Table 3.
< bending test >
An evaluation test for confirming the bendability of the optical laminate was performed using a bending evaluation apparatus (STS-VRT-500, manufactured by Science Town). Fig. 3 is a diagram schematically showing the method of the evaluation test. As shown in fig. 3, 2 tables 601 and 602 which are individually movable are arranged so that the gap C is 5mm (bending radius 2.5mm) or the gap C is 3mm (bending radius 1.5mm), and the optical layered body is fixed and arranged with the center in the width direction positioned at the center of the gap C and the front panel positioned on the upper side (fig. 3 (a)). Then, the 2 mounting tables 601 and 602 are rotated upward by 90 degrees with the position P1 and the position P2 as the center of the rotation axis, and a bending force is applied to the region of the laminate corresponding to the gap C of the mounting tables (fig. 3 (b)). Then, the 2 tables 601 and 602 are returned to the original positions ((a) in fig. 3). The series of operations was completed, and the number of times of applying the bending force was counted as 1. After repeating the above operations at a temperature of 60 ℃ and a humidity of 90% RH, it was confirmed whether or not air bubbles were generated in the pressure-sensitive adhesive layer in the region corresponding to the gap C of the mounting tables 601 and 602 in the optical laminate 100. The moving speed of the mounting tables 601 and 602 and the speed of applying the bending force are the same in both the evaluation tests of the optical layered body.
A: no bubble was generated even if the number of times of the force addition for bending reached 5 ten thousand.
B: bubbles are generated when the number of times of applying the bending force is 2 ten thousand or more and less than 5 ten thousand.
C: bubbles are generated when the number of times of applying the bending force is 1 ten thousand or more and less than 2 ten thousand.
D: bubbles are generated when the number of times of force addition of bending is less than 1 ten thousand.
[ Table 3]
Figure BDA0002966067100000181

Claims (5)

1. An optical laminate comprising a front plate, a1 st pressure-sensitive adhesive layer, a polarizing plate, a 2 nd pressure-sensitive adhesive layer and a back plate in this order, wherein the slopes of stress [ Pa ] -strain [ (% ]curves at a temperature of 60 ℃ and a humidity of 90% RH of the 1 st pressure-sensitive adhesive layer and the 2 nd pressure-sensitive adhesive layer from the origin to the maximum stress value are respectively represented by GL1' and GL2When the formula (1) and the formula (2) are satisfied,
70≤GL1’≤250 (1)
70≤GL2’≤250 (2)。
2. the optical laminate according to claim 1, wherein the following formulae (1 ') and (2') are satisfied,
90≤GL1’≤150 (1’)
90≤GL2’≤150 (2’)。
3. the optical stack of claim 1 or 2, wherein the back panel is a touch sensor panel.
4. A display device comprising the optical stack of any of claims 1-3.
5. The display device according to claim 4, wherein the front panel side can be bent to be an inner side.
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