CN113474696A - Laminated body - Google Patents

Laminated body Download PDF

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Publication number
CN113474696A
CN113474696A CN202080016161.3A CN202080016161A CN113474696A CN 113474696 A CN113474696 A CN 113474696A CN 202080016161 A CN202080016161 A CN 202080016161A CN 113474696 A CN113474696 A CN 113474696A
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adhesive layer
layer
adhesive
meth
mass
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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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    • GPHYSICS
    • G02OPTICS
    • G02BOPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00Optical elements other than lenses
    • G02B5/30Polarising elements
    • G02B5/3025Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state
    • G02B5/3033Polarisers, 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
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B32LAYERED PRODUCTS
    • B32BLAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00Layered products comprising a layer of synthetic resin
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B32LAYERED PRODUCTS
    • B32BLAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00Layered products comprising a layer of synthetic resin
    • B32B27/30Layered products comprising a layer of synthetic resin comprising vinyl (co)polymers; comprising acrylic (co)polymers
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B32LAYERED PRODUCTS
    • B32BLAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B7/00Layered 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
    • B32B7/02Physical, chemical or physicochemical properties
    • B32B7/023Optical properties
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B32LAYERED PRODUCTS
    • B32BLAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B7/00Layered 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
    • B32B7/04Interconnection of layers
    • B32B7/12Interconnection of layers using interposed adhesives or interposed materials with bonding properties
    • CCHEMISTRY; METALLURGY
    • C09DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09JADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J133/00Adhesives based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Adhesives based on derivatives of such polymers
    • CCHEMISTRY; METALLURGY
    • C09DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09JADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J7/00Adhesives in the form of films or foils
    • C09J7/30Adhesives in the form of films or foils characterised by the adhesive composition
    • C09J7/38Pressure-sensitive adhesives [PSA]
    • GPHYSICS
    • G02OPTICS
    • G02BOPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00Optical elements other than lenses
    • GPHYSICS
    • G02OPTICS
    • G02BOPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00Optical elements other than lenses
    • G02B5/30Polarising elements
    • GPHYSICS
    • G02OPTICS
    • G02FOPTICAL 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
    • G02F1/00Devices 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
    • G02F1/01Devices 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 
    • G02F1/13Devices 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
    • G02F1/133Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/1333Constructional arrangements; Manufacturing methods
    • G02F1/1335Structural association of cells with optical devices, e.g. polarisers or reflectors
    • G02F1/133528Polarisers
    • GPHYSICS
    • G06COMPUTING; CALCULATING OR COUNTING
    • G06FELECTRIC DIGITAL DATA PROCESSING
    • G06F3/00Input 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
    • G06F3/01Input arrangements or combined input and output arrangements for interaction between user and computer
    • G06F3/03Arrangements for converting the position or the displacement of a member into a coded form
    • G06F3/041Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
    • GPHYSICS
    • G09EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09FDISPLAYING; ADVERTISING; SIGNS; LABELS OR NAME-PLATES; SEALS
    • G09F9/00Indicating arrangements for variable information in which the information is built-up on a support by selection or combination of individual elements
    • GPHYSICS
    • G09EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09FDISPLAYING; ADVERTISING; SIGNS; LABELS OR NAME-PLATES; SEALS
    • G09F9/00Indicating arrangements for variable information in which the information is built-up on a support by selection or combination of individual elements
    • G09F9/30Indicating 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
    • HELECTRICITY
    • H10SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10KORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K59/00Integrated devices, or assemblies of multiple devices, comprising at least one organic light-emitting element covered by group H10K50/00
    • H10K59/50OLEDs integrated with light modulating elements, e.g. with electrochromic elements, photochromic elements or liquid crystal elements

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • General Physics & Mathematics (AREA)
  • Theoretical Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • General Engineering & Computer Science (AREA)
  • Optics & Photonics (AREA)
  • Organic Chemistry (AREA)
  • Nonlinear Science (AREA)
  • Human Computer Interaction (AREA)
  • Mathematical Physics (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Adhesives Or Adhesive Processes (AREA)
  • Adhesive Tapes (AREA)
  • Laminated Bodies (AREA)
  • Devices For Indicating Variable Information By Combining Individual Elements (AREA)
  • Optical Elements Other Than Lenses (AREA)
  • Polarising Elements (AREA)

Abstract

The purpose of the present invention is to provide a laminate having excellent adhesive strength, which suppresses the occurrence of air bubbles even when the front panel is repeatedly bent with the front panel side on the inside. The present invention provides a laminate comprising a front sheet, a1 st adhesive layer formed using a1 st adhesive composition, a polarizer layer, a2 nd adhesive layer formed using a2 nd adhesive composition, and a back sheet in this order, wherein the following relational expression (1) is satisfied when the shear elastic modulus at 25 ℃ of the 1 st adhesive layer is G1[ Pa and the shear elastic modulus at 25 ℃ of the 2 nd adhesive layer is G2[ Pa): g1 < G2(1), and the gel fraction of the 1 st adhesive layer and the 2 nd adhesive layer is 45 to 85%.

Description

Laminated body
Technical Field
The present invention relates to a laminate.
Background
Jp 2018 a-28573 (patent document 1) describes a laminate for a flexible image display device having a plurality of adhesive layers.
Documents of the prior art
Patent document
Patent document 1: japanese patent laid-open publication No. 2018-28573
Disclosure of Invention
In a display device including a laminate having a front panel and a plurality of adhesive layers, when the front panel side is repeatedly bent inward, air bubbles may be generated in the adhesive layers in the laminate. Further, the adhesive force of the adhesive layer is weak, and the adhesive layer and the member to be adhered may be lifted or peeled off.
The purpose of the present invention is to provide a laminate excellent in adhesive strength, which suppresses the occurrence of air bubbles even when the front panel side is repeatedly bent inward, and an adhesive composition and an adhesive sheet used for the laminate.
The present invention provides the following laminate.
[1] A laminate comprising, in order, a front sheet, a1 st adhesive layer formed using a1 st adhesive composition, a polarizer layer, a2 nd adhesive layer formed using a2 nd adhesive composition, and a back sheet,
when the shear elastic modulus at 25 ℃ of the first pressure-sensitive adhesive layer 1 is G1[ Pa ] and the shear elastic modulus at 25 ℃ of the second pressure-sensitive adhesive layer 2 is G2[ Pa ], the following relational expression (1) is satisfied:
G1<G2 (1),
the gel fraction of the 1 st pressure-sensitive adhesive layer and the 2 nd pressure-sensitive adhesive layer is 45% to 85%.
[2] the laminate according to [1], wherein the 1 st adhesive composition and the 2 nd adhesive composition each contain a (meth) acrylic polymer,
the structural unit derived from the monomer having a reactive functional group in the (meth) acrylic polymer is less than 5% by mass based on the total mass.
[ 3] the laminate according to [1] or [2], wherein the 1 st adhesive layer and the 2 nd adhesive layer each contain a (meth) acrylic polymer,
the weight average molecular weight (Mw) of the (meth) acrylic polymer is 20 to 150 ten thousand.
The laminate according to any one of [1] to [ 3], wherein the back panel is a touch sensor panel.
A display device comprising the laminate according to any one of [1] to [ 4 ].
The display device according to [ 6 ] above [ 5 ], wherein the front panel side can be bent inward.
According to the present invention, a laminate excellent in adhesive force can be provided in which the generation of air bubbles is suppressed even when the front panel side is repeatedly bent inward.
Drawings
Fig. 1 is a schematic cross-sectional view showing an example of a laminate of the present invention.
Fig. 2 is a schematic cross-sectional view showing an example of the laminate of the present invention.
Fig. 3 is a schematic diagram illustrating a method of the bending test.
Fig. 4 is a cross-sectional view schematically showing a method for producing a laminate according to the present invention.
Detailed Description
A laminate according to an embodiment of the present invention (hereinafter, also simply referred to as "laminate") will be described below with reference to the drawings.
< layered product >
Fig. 1 is a schematic cross-sectional view of a laminate according to an embodiment of the present invention. The laminate 100 includes a front panel 101, a1 st adhesive layer 102, a polarizer layer 103, a2 nd adhesive layer 104, and a back panel 105 in this order. The 1 st adhesive layer 102 is formed of a1 st adhesive composition, and the 2 nd adhesive layer 104 is formed of a2 nd adhesive composition. 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 laminate 100 is not particularly limited, and is, for example, 50 to 4000 μm, preferably 100 to 2000 μm, and more preferably 150 to 1000 μm, since it varies depending on the functions required for the laminate, the use of the laminate, and the like.
The shape of the laminate 100 in 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 laminate 100 in the plane direction is rectangular, the length of the long side may be, for example, 10mm to 1400mm, 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 laminate may be subjected to a corner rounding process (corner R), or a notch process or a hole forming process for the end.
The 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 display device may have a touch panel function.
[ Properties of adhesive layer ]
In the laminate 100, when the shear elastic modulus at 25 ℃ of the 1 st pressure-sensitive adhesive layer 102 is G1[ Pa and the shear elastic modulus at 25 ℃ of the 2 nd pressure-sensitive adhesive layer 104 is G2[ Pa ], the following relational expression (1) is satisfied:
G1<G2 (1)
as to whether or not the relation (1) is satisfied, there is a determination method as follows:
i) a method of making a judgment based on each of the values of G1 and G2, and
ii) a method of judging according to another combination having the same magnitude relationship as that of the combination of G1 and G2.
In other combinations of ii) above, for example, when the 1 st adhesive layer 102 and the 2 nd adhesive layer 104 have the same thickness, the determination can be made by comparing the 1 st reference adhesive layer formed from the 1 st adhesive composition with the 2 nd reference adhesive layer formed from the 2 nd adhesive composition. Shear elastic modulus G at 25 ℃ of the 1 st reference adhesive layer provided that the 1 st reference adhesive layer and the 2 nd reference adhesive layer are the same thickness01[Pa]Shear modulus of elasticity G at 25 ℃ with reference adhesive layer No. 202[Pa]Satisfies the following relational expression (1 a):
G01<G02(1 a) can be regarded as satisfying the relational expression (1). Shear modulus of elasticity G at 25 ℃ of No. 1 reference adhesive layer and No. 2 reference adhesive layer having a thickness of 150 μm01、G02 measured according to the measurement method described in the section of examples described later.
The gel fraction of the 1 st adhesive layer 102 and the 2 nd adhesive layer 104 is 45% to 85%, preferably 50% to 80%. The gel fraction of the 1 st pressure-sensitive adhesive layer 102 and the 2 nd pressure-sensitive adhesive layer 104 was measured according to the measurement method described in the column of the examples described later.
The laminate 100 can be bent with the front panel 101 side facing inward. In a display device including a laminate, when the front panel side is repeatedly bent inward, air bubbles may be generated in the pressure-sensitive adhesive layer. The generation of the above-described air bubbles is particularly noticeable in the adhesive layer on the side close to the front panel, i.e., the 1 st adhesive layer 102 in the laminate 100. As a result of studies, the inventors found that when the shear elastic modulus of the 1 st pressure-sensitive adhesive layer 102 and the 2 nd pressure-sensitive adhesive layer 104 satisfy the relational expression (1) and the gel fraction of each is 45% to 85%, bubbles generated in the pressure-sensitive adhesive layer in the laminate 100 can be suppressed even when the front panel 101 side is repeatedly bent inward. More specifically, it was found that bubbles generated in the pressure-sensitive adhesive layer in the laminate 100 can be suppressed (hereinafter, also referred to as having excellent "room-temperature flexibility") even when the laminate 100 is repeatedly bent 10 ten thousand times so that the inner surface of the laminate 100 has a bending radius of 3 mm. The room temperature flexibility can be evaluated by the evaluation method described in the section of examples described later. The laminate 100 can be bent with the front panel side facing outward. The display device to which the laminate 100 is applied can be used as a flexible display which can be bent, rolled, or the like. In the present specification, the bending includes a form of bending in which a curved surface is formed at a bent portion, and a bending radius of an inner surface of the bending is not particularly limited. The bending also includes bending in which the bending angle of the inner surface is greater than 0 degrees and less than 180 degrees, and folding in which the bending radius of the inner surface is approximately zero or the bending angle of the inner surface is 0 degrees.
The shear modulus at 25 ℃ of the 1 st reference adhesive layer having a thickness of 150 μm was designated as G01[Pa]And the shear modulus at 25 ℃ of the 2 nd reference adhesive layer having a thickness of 150 μm is set to G02[Pa]In this case, the following relational expressions (2) and (3) are preferably satisfied:
1.0×104≤G01≤5.0×105 (2)
1.0×104≤G02≤5.0×105 (3),
more preferably, the following relational expressions (2a) and (3a) are satisfied:
2.0×104≤G01≤2.0×105 (2a)
2.0×104≤G02≤2.0×105 (3a),
preferably, the following relational expressions (2b) and (3b) are satisfied:
2.0×104≤G01≤7.0×104 (2b)
3.0×104≤G02≤1.0×105 (3b)。
examples of the method for producing the 1 st pressure-sensitive adhesive composition and the 2 nd pressure-sensitive adhesive composition so that the shear elastic modulus of the 1 st pressure-sensitive adhesive layer 102 and the 2 nd pressure-sensitive adhesive layer 104 satisfy the relational expression (1) and the gel fraction of each is 45% to 85% include a method for forming a pressure-sensitive adhesive layer from the pressure-sensitive adhesive composition a described later, a method for changing the kind of monomers forming the (meth) acrylic polymer a described later, a method for adjusting the molecular weight of the (meth) acrylic polymer a, and a method for containing a compound having an acetoacetoxyethyl group.
[ adhesive composition ]
In one embodiment, the 1 st adhesive layer 102 and the 2 nd adhesive layer 104 are formed from an adhesive composition containing a (meth) acrylic polymer (hereinafter, also referred to as an adhesive composition a). The adhesive composition a may be an active energy ray-curable type or a thermosetting type. In the present specification, "(meth) acrylic polymer" means at least 1 selected from acrylic polymers and methacrylic polymers. The same applies to other terms with "(methyl)". When both the 1 st adhesive composition and the 2 nd adhesive composition contain a (meth) acrylic polymer, the (meth) acrylic polymers may be the same or different. Hereinafter, the (meth) acrylic polymer contained in the adhesive composition a is also referred to as a (meth) acrylic polymer a.
From the viewpoint that the obtained pressure-sensitive adhesive layer easily satisfies the relational expression (2) or the relational expression (3), the weight average molecular weight (Mw) of the (meth) acrylic polymer a is preferably 20 to 150 ten thousand, more preferably 30 to 120 ten thousand.
In the (meth) acrylic polymer a, the structural unit derived from the monomer having a reactive functional group is preferably less than 5% by mass based on the total mass of the polymer. Examples of the reactive functional group include a hydroxyl group, a carboxyl group, an amino group, an amide group, and an epoxy group. This improves the flexibility of the pressure-sensitive adhesive layer, and tends to easily suppress the generation of bubbles in the pressure-sensitive adhesive layer. In the (meth) acrylic polymer a, from the viewpoint of suppressing bubbles at the time of bending, the structural unit derived from the monomer having a reactive functional group is more preferably 0.01% by mass or less based on the total mass of the polymer, and the structural unit derived from the monomer having a reactive functional group is more preferably not present, and further preferably not have a hydroxyl group, a carboxyl group, an amino group, an amide group, and an epoxy group.
(1) Active energy ray-curable adhesive composition
When the pressure-sensitive adhesive composition a is an active energy ray-curable pressure-sensitive adhesive composition, the (meth) acrylic polymer a contained in the pressure-sensitive adhesive composition a may contain a structural unit derived from a (meth) acrylic monomer having a linear or branched alkyl group having 1 to 24 carbon atoms. Examples of the (meth) acrylic monomer having a linear or branched alkyl group having 1 to 24 carbon atoms include alkyl (meth) acrylates, such as butyl (meth) acrylate, methyl (meth) acrylate, ethyl (meth) acrylate, hexyl (meth) acrylate, octyl (meth) acrylate, lauryl (meth) acrylate, isooctyl (meth) acrylate, isodecyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and isobornyl (meth) acrylate. The (meth) acrylic polymer a may be a polymer or copolymer containing 1 or 2 or more of the above-mentioned alkyl (meth) acrylates as monomers. The content of the (meth) acrylic polymer a in the pressure-sensitive adhesive composition a may be, for example, 50 to 100 mass%, preferably 80 to 99.5 mass%, and more preferably 90 to 99 mass% with respect to 100 parts by mass of the solid content of the pressure-sensitive adhesive composition a.
The weight average molecular weight (Mw) of the (meth) acrylic polymer a may be, for example, 20 to 80 ten thousand, and preferably 30 to 70 ten thousand from the viewpoint of suppressing bubbles at the time of bending. The weight average molecular weight (Mw) can be measured by the measurement method described in the column of examples described later.
The adhesive composition a may contain 1 or 2 or more (meth) acrylic polymers a. The pressure-sensitive adhesive composition a may contain only the (meth) acrylic polymer a as a constituent component thereof, or may further contain a crosslinking agent. A metal salt of a carboxylic acid which is a metal ion having a valence of 2 or more and forms a carboxyl group with the crosslinking agent; is a polyamine compound and forms an amide bond with a carboxyl group; is a polyepoxy compound or a polyol and forms an ester bond with a carboxyl group; examples of the polyisocyanate compound include a polyisocyanate compound and an amide bond formed with a group. Among them, polyisocyanate compounds are preferable. When the pressure-sensitive adhesive composition a contains a crosslinking agent, the content of the crosslinking agent may be, for example, 5 parts by mass or less, preferably 1 part by mass or less, more preferably 0.5 parts by mass or less, further preferably 0.1 parts by mass or less, per 100 parts by mass of the (meth) acrylic polymer a, and the pressure-sensitive adhesive composition a most preferably does not contain a crosslinking agent.
The active energy ray-curable pressure-sensitive adhesive composition is a pressure-sensitive adhesive composition having a property of being cured by irradiation with an active energy ray such as an ultraviolet ray or an electron beam, and having a property of having an adhesive property even before irradiation with an active energy ray, being capable of being adhered to an adherend such as a film, being cured by irradiation with an active energy ray, and being capable of adjusting the adhesion force.
The active energy ray-curable adhesive composition is preferably an ultraviolet-curable adhesive composition.
When the pressure-sensitive adhesive composition a is an active energy ray-curable pressure-sensitive adhesive composition, the pressure-sensitive adhesive composition a may further contain an active energy ray-polymerizable compound, a photopolymerization initiator, a photosensitizer, and the like.
Examples of the active energy ray-polymerizable compound include (meth) acrylate monomers having at least one (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 obtained by reacting 2 or more functional group-containing compounds. The binder composition a may contain 0.1 to 10 parts by mass of the active energy ray-polymerizable compound per 100 parts by mass of the solid content of the binder composition a.
Examples of the photopolymerization initiator include diphenyl (2, 4, 6-trimethylbenzoyl) phosphine oxide, benzyldimethylketal, and 1-hydroxycyclohexylphenylketone. When the pressure-sensitive adhesive composition a contains a photopolymerization initiator, 1 or 2 or more species may be contained. When the pressure-sensitive adhesive composition a contains a photopolymerization initiator, the total content thereof may be, for example, 0.01 to 1.0 part by mass per 100 parts by mass of the solid content of the pressure-sensitive adhesive composition a.
The adhesive composition a preferably contains a compound having an acetoacetoxyethyl group. Preferably, at least one of the adhesive composition 1 and the adhesive composition 2 is an adhesive composition a containing a compound having an acetoacetoxyethyl group. With the adhesive composition a containing a compound having an acetoacetoxyethyl group, the 1 st reference adhesive layer and the 2 nd reference adhesive layer satisfying the above relational expressions (2) and (3) can be easily formed. In addition, the adhesive composition a containing the compound having an acetoacetoxyethyl group can easily form an adhesive layer having a gel fraction of 45% to 85%. The adhesive composition a may contain, for example, 0.01 to 20 parts by mass, preferably 0.1 to 10 parts by mass, and more preferably 0.1 to 8 parts by mass of a compound having an acetoacetoxyethyl group per 100 parts by mass of the solid content of the adhesive composition a.
The compound having an acetoacetoxyethyl group is not particularly limited, and compounds represented by the following formula are exemplified.
Figure BDA0003224658170000071
In the above formula, R1Is hydrogen or methyl.
The binder composition a may contain additives for imparting light scattering properties, 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, defoaming agents, and anticorrosive agents. From the viewpoint of preventing the reduction in durability due to the residual solvent, the adhesive composition a preferably contains no organic solvent.
When the adhesive layer is formed from the adhesive composition a, the adhesive layer can be formed by coating the adhesive composition a on a substrate. When an active energy ray-curable pressure-sensitive adhesive composition is used, a cured product having a desired degree of curing can be obtained by irradiating the pressure-sensitive adhesive layer formed with an active energy ray.
(2) Heat-curable adhesive composition
When the adhesive composition a is a heat-curable adhesive composition, the (meth) acrylic polymer a preferably contains, as monomer units constituting the polymer, an alkyl (meth) acrylate having an alkyl group and 2 to 20 carbon atoms and a monomer having a reactive functional group in a molecule (reactive functional group-containing monomer).
The (meth) acrylic polymer A can exhibit a desired adhesive property by containing an alkyl (meth) acrylate having an alkyl group and 2 to 20 carbon atoms as a monomer unit constituting the polymer. The alkyl (meth) acrylate having an alkyl group with 2 to 20 carbon atoms preferably has a homopolymer glass transition temperature (Tg) of-40 ℃ or lower (hereinafter, the "low Tg alkyl acrylate" may be referred to as "low Tg alkyl acrylate"). By containing the low Tg alkyl acrylate monomer unit, the flexibility of the pressure-sensitive adhesive layer is improved, and the generation of bubbles during bending tends to be easily suppressed.
Examples of the low Tg alkyl acrylate include n-butyl acrylate (Tg-55 ℃ C.), n-octyl acrylate (Tg-65 ℃ C.), isooctyl acrylate (Tg-58 ℃ C.), 2-ethylhexyl acrylate (Tg-70 ℃ C.), isononyl acrylate (Tg-58 ℃ C.), isodecyl acrylate (Tg-60 ℃ C.), isodecyl methacrylate (Tg-41 ℃ C.), n-lauryl methacrylate (Tg-65 ℃ C.), tridecyl acrylate (Tg-55 ℃ C.), and tridecyl methacrylate (-40 ℃ C.). Among them, the low Tg alkyl acrylate is more preferably an alkyl acrylate having a homopolymer Tg of-45 ℃ or less, particularly preferably an alkyl acrylate having a homopolymer Tg of-50 ℃ or less, from the viewpoint of easily satisfying the relation (2) or the relation (3) in obtaining the pressure-sensitive adhesive layer. In particular, n-butyl acrylate and 2-ethylhexyl acrylate are particularly preferred. These may be used alone, or 2 or more kinds may be used in combination.
The (meth) acrylic polymer a preferably contains 85 mass% or more, more preferably 90 mass% or more, and still more preferably 95 mass% or more of the low Tg alkyl acrylate in terms of the lower limit of the monomer units constituting the polymer. If the content is within such a range, the obtained pressure-sensitive adhesive layer easily satisfies the relational expression (2) or the relational expression (3).
The (meth) acrylic polymer a preferably contains 99.9% by mass or less, more preferably 99.5% by mass or less, and still more preferably 99% by mass or less of the low Tg alkyl acrylate, as the upper limit of the monomer units constituting the polymer. By containing 99.9 mass% or less of the low Tg alkyl acrylate, an appropriate amount of other monomer components (particularly, reactive functional group-containing monomers) can be introduced into the (meth) acrylic polymer a.
In order to easily set the glass transition temperature (Tg) of the main polymer of the adhesive of the present embodiment within the above range, the (meth) acrylic polymer a preferably has a content of a monomer having a glass transition temperature (Tg) exceeding 0 ℃ as a homopolymer (hereinafter, sometimes referred to as "hard monomer") as small as possible. Specifically, the content of the hard monomer in the (meth) acrylic polymer a is preferably 15% by mass or less, more preferably 10% by mass or less, and further preferably 5% by mass or less as an upper limit value as a monomer unit constituting the polymer. The hard monomer also includes a reactive functional group-containing monomer described later.
Examples of the hard monomer include methyl acrylate (Tg10 ℃ C.), methyl methacrylate (Tg105 ℃ C.), ethyl methacrylate (Tg65 ℃ C.), n-butyl methacrylate (Tg20 ℃ C.), isobutyl methacrylate (Tg48 ℃ C.), tert-butyl methacrylate (Tg107 ℃ C.), n-stearyl acrylate (Tg30 ℃ C.), n-stearyl methacrylate (Tg38 ℃ C.), cyclohexyl acrylate (Tg15 ℃ C.), cyclohexyl methacrylate (Tg66 ℃ C.), phenoxyethyl acrylate (Tg5 ℃ C.), phenoxyethyl methacrylate (Tg54 ℃ C.), benzyl methacrylate (Tg54 ℃ C.), isobornyl acrylate (Tg94 ℃ C.), isobornyl methacrylate (Tg180 ℃ C.), acryloylmorpholine (Tg145 ℃ C.), adamantyl acrylate (Tg115 ℃ C.), adamantyl methacrylate (Tg141 ℃ C.), acrylic acid (Tg103 ℃ C.), dimethylacrylamide (Tg89 ℃ C.), and so forth, Acrylic monomers such as acrylamide (Tg165 ℃), vinyl acetate (Tg32 ℃), styrene (Tg80 ℃), and the like.
In the (meth) acrylic polymer a, a monomer having a reactive functional group is contained as a monomer unit constituting the polymer, and a heat crosslinking agent described later is reacted with the reactive functional group derived from the monomer having a reactive functional group, whereby a pressure-sensitive adhesive having a desired cohesive force and a crosslinked structure (three-dimensional network structure) is obtained.
The reactive functional group-containing monomer contained as a monomer unit constituting the (meth) acrylic polymer a preferably includes a monomer having a hydroxyl group in the molecule (hydroxyl group-containing monomer), a monomer having a carboxyl group in the molecule (carboxyl group-containing monomer), a monomer having an amino group in the molecule (amino group-containing monomer), and the like. Among them, the hydroxyl group-containing monomer is particularly preferable because the glass transition temperature (Tg) is usually 0 ℃ or lower.
Examples of the hydroxyl group-containing monomer include hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 3-hydroxybutyl (meth) acrylate, and 4-hydroxybutyl (meth) acrylate. Among them, at least one of 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 3-hydroxypropyl acrylate and 4-hydroxybutyl acrylate is preferable from the viewpoint of the glass transition temperature (Tg), the reactivity of the hydroxyl group in the obtained (meth) acrylic polymer a with a thermal crosslinking agent and the copolymerizability with other monomers. These may be used alone, or 2 or more kinds may be used in combination.
Examples of the carboxyl group-containing monomer include ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, and citraconic acid. These may be used alone, or 2 or more kinds may be used in combination.
Examples of the amino group-containing monomer include aminoethyl (meth) acrylate, n-butylaminoethyl (meth) acrylate, and the like. These may be used alone, or 2 or more kinds may be used in combination.
In the (meth) acrylic polymer a, the reactive functional group-containing monomer is contained in an amount of preferably 0.1% by mass or more, particularly preferably 0.5% by mass or more, and further preferably 1% by mass or more, in terms of the lower limit of the monomer unit constituting the polymer. The content of the organic solvent is preferably 10% by mass or less, particularly preferably 8% by mass or less, and further preferably less than 5% by mass, based on the upper limit. If the (meth) acrylic polymer a contains a reactive functional group-containing monomer, particularly a hydroxyl group-containing monomer, as a monomer unit in the above-mentioned amount, the resulting pressure-sensitive adhesive layer easily satisfies the relational expression (2) or the relational expression (3).
The (meth) acrylic polymer a may not contain a carboxyl group-containing monomer, and particularly may not contain acrylic acid which is also a hard monomer, as a monomer unit constituting the polymer. Since the carboxyl group is an acid component, the carboxyl group-containing monomer is not contained, and therefore, even when there are components that cause troubles due to an acid, for example, a transparent conductive film such as tin-doped indium oxide (ITO), a metal film, a metal mesh, or the like in the target to which the adhesive is attached, these troubles (corrosion, change in resistance value, or the like) due to an acid can be suppressed.
The (meth) acrylic polymer a may contain other monomers as a monomer unit constituting the polymer, as desired. As the other monomer, a monomer having no reactive functional group is also preferable in order not to hinder the action of the reactive functional group-containing monomer. Examples of the other monomer include alkoxyalkyl (meth) acrylates such as methoxyethyl (meth) acrylate and ethoxyethyl (meth) acrylate, and monomers having a homopolymer glass transition temperature (Tg) of more than-40 ℃ and 0 ℃ or less (hereinafter, sometimes referred to as "medium Tg alkyl acrylate"). Examples of the medium Tg alkyl acrylate include ethyl acrylate (Tg-20 ℃ C.), isobutyl acrylate (Tg-26 ℃ C.), 2-ethylhexyl methacrylate (Tg-10 ℃ C.), n-lauryl acrylate (Tg-23 ℃ C.), and isostearyl acrylate (Tg-18 ℃ C.). These may be used alone, or 2 or more kinds may be used in combination.
The polymerization system of the (meth) acrylic polymer a may be a random copolymer or a block copolymer.
The lower limit of the weight average molecular weight of the (meth) acrylic polymer a is preferably 20 ten thousand or more, particularly preferably 30 ten thousand or more, and more preferably 40 ten thousand or more. When the lower limit of the weight average molecular weight of the (meth) acrylic polymer a is not less than the above range, troubles such as bleeding out of the adhesive can be suppressed. The weight average molecular weight in the present specification is a value in terms of standard polystyrene measured by a Gel Permeation Chromatography (GPC) method.
The upper limit of the weight average molecular weight of the (meth) acrylic polymer a is preferably 150 ten thousand or less, particularly preferably 135 ten thousand or less, and more preferably 120 ten thousand or less. If the upper limit value of the weight average molecular weight of the (meth) acrylate polymer (a) is the above-mentioned or less, the obtained pressure-sensitive adhesive layer easily satisfies the relational expression (2) or the relational expression (3).
In the adhesive composition a, 1 kind of the (meth) acrylic polymer a may be used alone, or 2 or more kinds may be used in combination.
When the adhesive composition A containing a thermal crosslinking agent is heated, the thermal crosslinking agent crosslinks the (meth) acrylic polymer A to form a three-dimensional network structure. This improves the cohesive force of the resulting pressure-sensitive adhesive, and the resulting pressure-sensitive adhesive layer easily satisfies the relational expression (2) or the relational expression (3).
The thermal crosslinking agent may be reacted with a reactive group of the (meth) acrylic polymer a, and examples thereof include an isocyanate crosslinking agent, an epoxy crosslinking agent, an amine crosslinking agent, a melamine crosslinking agent, an aziridine crosslinking agent, a hydrazine crosslinking agent, an aldehyde crosslinking agent, an oxazoline crosslinking agent, a metal alkoxide crosslinking agent, a metal chelate crosslinking agent, a metal salt crosslinking agent, and an ammonium salt crosslinking agent. Among the above, when the reactive group of the (meth) acrylic polymer a is a hydroxyl group, an isocyanate-based crosslinking agent having excellent reactivity with the hydroxyl group is preferably used. The thermal crosslinking agent may be used alone in 1 kind or in combination with 2 or more kinds.
The isocyanate-based crosslinking agent contains at least a polyisocyanate compound. Examples of the polyisocyanate compound include aromatic polyisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate and xylylene diisocyanate, aliphatic polyisocyanates such as hexamethylene diisocyanate, alicyclic polyisocyanates such as isophorone diisocyanate and hydrogenated diphenylmethane diisocyanate, biuret and isocyanurate compounds thereof, and adducts with reactants of low-molecular active hydrogen-containing compounds such as ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane and castor oil. Among them, trimethylolpropane-modified aromatic polyisocyanates are preferable from the viewpoint of reactivity with hydroxyl groups, and trimethylolpropane-modified tolylene diisocyanate and trimethylolpropane-modified xylylene diisocyanate are particularly preferable.
Examples of the epoxy-based crosslinking agent include 1, 3-bis (N, N-diglycidylaminomethyl) cyclohexane, N' -tetraglycidyl-m-xylylenediamine, ethylene glycol diglycidyl ether, 1, 6-hexanediol diglycidyl ether, trimethylolpropane diglycidyl ether, diglycidylaniline, and diglycidylamine.
The content of the thermal crosslinking agent in the adhesive composition a is preferably 0.01 mass% or more, more preferably 0.05 mass% or more, and still more preferably 0.1 mass% or more, based on 100 mass% of the (meth) acrylic polymer a. The content is preferably 1% by mass or less, more preferably 0.8% by mass or less, and still more preferably 0.5% by mass or less. When the content of the thermal crosslinking agent is in the above range, the obtained pressure-sensitive adhesive layer easily satisfies the relational expression (2) or the relational expression (3).
The adhesive composition a preferably contains the above-mentioned silane coupling agent. This improves the adhesion between the pressure-sensitive adhesive layer and each member in the flexible laminate to be an adherend, and further improves the durability against bending.
The silane coupling agent is preferably an organosilicon compound having at least one alkoxysilyl group in the molecule, and has good compatibility with the (meth) acrylic polymer a and light transmittance.
Examples of the silane coupling agent include silicon compounds containing a polymerizable unsaturated group such as vinyltrimethoxysilane, vinyltriethoxysilane and methacryloxypropyltrimethoxysilane, silicon compounds having an epoxy structure such as 3-glycidoxypropyltrimethoxysilane and 2- (3, 4-epoxycyclohexyl) ethyltrimethoxysilane, silicon compounds containing a mercapto group such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane and 3-mercaptopropyldimethoxymethylsilane, silicon compounds containing an amino group such as 3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropyltrimethoxysilane and N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane, 3-chloropropyltrimethoxysilane, 3-isocyanatopropyltriethoxysilane, methacryloxypropyltrimethoxysilane, and the like, Or a condensate of at least one of these with an alkyl group-containing silicon compound such as methyltriethoxysilane, ethyltriethoxysilane, methyltrimethoxysilane, ethyltrimethoxysilane, or the like. These can be used alone in 1, can be combined with more than 2.
The content of the silane coupling agent in the adhesive composition a is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and still more preferably 0.1% by mass or more, based on 100% by mass of the (meth) acrylic polymer a. The content is preferably 1% by mass or less, more preferably 0.5% by mass or less, and still more preferably 0.3% by mass or less. When the content of the silane coupling agent is within the above range, the adhesion between the pressure-sensitive adhesive layer obtained and each member in the flexible laminate to be an adherend is more preferable.
The adhesive composition a may contain the above-mentioned various additives as desired. The polymerization solvent and the diluting solvent are not included in the additives constituting the adhesive composition a.
The (meth) acrylic polymer a can be produced by polymerizing a mixture of monomers constituting the polymer by a general radical polymerization method. The polymerization of the (meth) acrylic polymer a is preferably carried out by a solution polymerization method using a polymerization initiator as desired. Examples of the polymerization solvent include ethyl acetate, n-butyl acetate, isobutyl acetate, toluene, acetone, hexane, methyl ethyl ketone, and two or more kinds thereof may be used in combination.
Examples of the polymerization initiator include azo compounds and organic peroxides, and two or more kinds thereof may be used in combination. Examples of the azo compound include 2, 2 ' -azobisisobutyronitrile, 2 ' -azobis (2-methylbutyronitrile), 1 ' -azobis (cyclohexane 1-carbonitrile), 2 ' -azobis (2, 4-dimethylvaleronitrile), 2 ' -azobis (2, 4-dimethyl-4-methoxyvaleronitrile), dimethyl 2, 2 ' -azobis (2-methylpropionate), 4 ' -azobis (4-cyanovaleric acid), 2 ' -azobis (2-hydroxymethylpropionitrile), and 2, 2 ' -azobis [ 2- (2-imidazolin-2-yl) propane ].
Examples of the organic peroxide include benzoyl peroxide, tert-butyl perbenzoate, cumene hydroperoxide, diisopropyl peroxydicarbonate, di-n-propyl peroxydicarbonate, di (2-ethoxyethyl) peroxydicarbonate, tert-butyl peroxyneodecanoate, tert-butyl peroxyvalerate, (3, 5, 5-trimethylhexanoyl) peroxide, dipropyl peroxide, and diacetyl peroxide.
In the polymerization step, a chain transfer agent such as 2-mercaptoethanol is added to adjust the weight average molecular weight of the obtained polymer.
After the (meth) acrylic polymer a is obtained, a thermal crosslinking agent, a silane coupling agent, and, if necessary, additives and a diluting solvent are added to a solution of the (meth) acrylic polymer a, and the mixture is thoroughly mixed to obtain a solvent-diluted adhesive composition a (coating solution).
In the case where a solid substance is used as any one of the above-mentioned components, or in the case where a precipitate is generated when the solid substance is mixed with another component in a diluted state, the component may be dissolved or diluted in a diluting solvent alone in advance and then mixed with another component.
Examples of the diluent solvent include aliphatic hydrocarbons such as hexane, heptane and cyclohexane, aromatic hydrocarbons such as toluene and xylene, halogenated hydrocarbons such as methylene chloride and vinyl chloride, alcohols such as methanol, ethanol, propanol, butanol and 1-methoxy-2-propanol, ketones such as acetone, methyl ethyl ketone, 2-pentanone, isophorone and cyclohexanone, esters such as ethyl acetate and butyl acetate, and cellosolve-based solvents such as ethyl cellosolve.
The concentration and viscosity of the coating solution prepared in this way are not particularly limited as long as the coating solution can be applied, and may be appropriately selected according to the situation. For example, the binder composition A is diluted so that the concentration thereof is 10 to 60 mass%. In addition, when obtaining a coating solution, the addition of a diluting solvent or the like is not essential, and the diluting solvent may not be added as long as the adhesive composition a has a coatable viscosity or the like. In this case, the pressure-sensitive adhesive composition a is a coating solution in which the polymerization solvent of the (meth) acrylic polymer a is directly used as a dilution solvent.
A preferable pressure-sensitive adhesive as the pressure-sensitive adhesive of the present embodiment is a pressure-sensitive adhesive composition a obtained by crosslinking. The heat treatment may be used in combination with a drying treatment when a diluent solvent or the like is volatilized from a coating film of the binder composition a applied to a desired object.
The heating temperature of the heating treatment is preferably 50 to 150 ℃, and more preferably 70 to 120 ℃. The heating time is preferably 10 seconds to 10 minutes, and more preferably 50 seconds to 2 minutes.
After the heat treatment, if necessary, a curing period of about 1 to 2 weeks at room temperature (e.g., 23 ℃ C., 50% RH) may be set. When the curing period is required, the adhesive is formed after the curing period, and when the curing period is not required, the adhesive is formed after the heat treatment is completed.
By the heat treatment (and curing), the (meth) acrylic polymer a is sufficiently crosslinked with the crosslinking agent to form a crosslinked structure, thereby obtaining an adhesive. The pressure-sensitive adhesive easily satisfies the relational expression (2) or the relational expression (3) with respect to the pressure-sensitive adhesive layer obtained.
The adhesive sheet of the present invention comprises an adhesive layer formed from the adhesive composition a of the present invention described above. The adhesive layer may be formed by coating the adhesive composition a on a substrate. When a thermosetting adhesive composition is used as the adhesive composition a, the formed adhesive layer is subjected to heat treatment (and curing) to obtain a cured product having a desired degree of curing. The conditions of the heat treatment and the aging are as described above.
The substrate may be a release film subjected to a release treatment. The pressure-sensitive adhesive sheet can be produced by forming a layer made of a pressure-sensitive adhesive in a sheet form on a release film in advance, and further bonding another release film to the pressure-sensitive adhesive layer.
As a method for applying the coating liquid of the adhesive composition a, for example, a bar coating method, a knife coating method, a roll coating method, a blade coating method, a die coating method, a gravure coating method, or the like can be used.
The adhesive composition a can be produced by mixing the respective components together by a known method, for example, using a mixer or the like.
[ front panel ]
The front panel 101 is not limited in material and thickness as long as it is a plate-like body that can transmit light, and may be configured with only 1 layer, or 2 or more layers. Examples thereof include a plate-like body made of resin (for example, a resin plate, a resin sheet, a resin film, etc.), a plate-like body made of glass (for example, a glass plate, a glass film, etc.), and a touch sensor panel described later. The front panel may constitute the outermost surface of the display device.
The thickness of the front plate 101 may be, for example, 10 to 500. mu.m, preferably 30 to 200. mu.m, and more preferably 50 to 100. mu.m. In the present invention, the thickness of each layer can be measured by the thickness measurement method described in the examples described below.
When the front panel 101 is a resin plate-like body, the resin plate-like body is not limited as long as light can be transmitted therethrough. Examples of the resin constituting the plate-like body made of a resin such as a resin film include films made of polymers such as triacetyl cellulose, acetyl cellulose butyrate, ethylene-vinyl acetate copolymer, propionyl cellulose, butyryl cellulose, acetyl propionyl cellulose, polyester, polystyrene, polyamide, polyetherimide, poly (meth) acrylic acid, polyimide, polyarylether sulfone, polysulfone, polyethylene, polypropylene, polymethylpentene, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, polyvinyl acetal, polyether ketone, polyetheretherketone, polyarylether sulfone, polymethylmethacrylate, 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, a resin film made of a polymer such as polyimide, polyamide, polyamideimide, or the like is preferable.
From the viewpoint of enhancing the hardness, the front panel 101 is preferably a film in which a hard coat layer is provided on at least one surface of a base film. As the base film, a film formed of the above resin can be used. The hard coat layer may be formed on one surface of the base film or on both surfaces. By providing the hard coat layer, a resin film having improved hardness and scratch resistance can be produced. 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 coat layer may contain an additive in order to increase hardness. The additive is not limited, and examples thereof include inorganic fine particles, organic fine particles, or a mixture thereof.
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. mu.m. By using the glass plate, the front panel 101 having excellent mechanical strength and surface hardness can be configured.
When the laminate 100 is used in a display device, the front panel 101 may have a function of protecting the front surface (screen) of the display device (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 a layer interposed between the front panel 101 and the polarizer layer 103 and bonded to each other, and may be a layer made of, for example, an adhesive or a bonding agent, or a layer obtained by subjecting the layer to any treatment. The 1 st adhesive layer may be an adhesive layer disposed at a position close to the frontmost plate among the adhesive layers constituting the laminate. Adhesives are also known as pressure sensitive adhesives. The term "adhesive" as used herein refers to an adhesive other than an adhesive (pressure-sensitive adhesive), and is clearly distinguished from an adhesive. The 1 st adhesive layer 102 may be composed of 1 layer, or may be composed of two or more layers, preferably 1 layer.
The 1 st adhesive layer 20 may be formed directly from the adhesive composition or using an adhesive sheet having an adhesive layer formed using the adhesive composition. The adhesive composition may be formed from adhesive composition a as described above.
The thickness of the 1 st pressure-sensitive adhesive layer 102 is, for example, preferably 3 μm to 100 μm, more preferably 5 μm to 50 μm, and may be 20 μm or more.
[ polarizer layer ]
Examples of the polarizer layer 103 include a stretched film or a stretched layer having a dichroic dye adsorbed thereon, and a layer obtained by applying and curing a composition containing a dichroic dye and a polymerizable compound. As the dichroic dye, specifically, iodine or a dichroic organic dye can be used. The dichroic organic dye includes a dichroic direct dye composed of a bisazo compound such as c.i. direct RED 39, and a dichroic direct dye composed of a compound such as trisazo or tetraazo.
Examples of the polarizer layer obtained by applying and curing a composition containing a dichroic dye and a polymerizable compound include a polarizer layer containing a cured product of a polymerizable liquid crystal compound, such as a layer obtained by applying and curing a composition containing a dichroic dye having liquid crystal properties or a composition containing a dichroic dye and a polymerizable liquid crystal.
The polarizer layer obtained by applying and curing a composition containing a dichroic dye and a polymerizable compound is preferable because the bending direction is not limited as compared with the stretched film or the stretched layer having the dichroic dye adsorbed thereon.
[ polarizer layer as stretched film or stretched layer ]
The polarizer layer of the stretched film having a dichroic dye adsorbed thereon can be generally produced through the following steps: the method for producing a resin film comprises a step of uniaxially stretching a polyvinyl alcohol resin film, a step of adsorbing a dichroic dye by dyeing the polyvinyl alcohol resin film with 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 with water after the treatment with the aqueous boric acid solution.
The thickness of the polarizer layer 103 is, for example, 2 μm to 40 μm. The thickness of the polarizer layer 103 may be 5 μm or more, 20 μm or less, further 15 μm or less, and further 10 μm or less.
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 acids, olefins, vinyl ethers, unsaturated sulfonic acids, and (meth) acrylamides 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 for example, polyvinyl alcohol or polyvinyl acetal 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 and adsorbing 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 with water after the treatment with the aqueous boric acid solution.
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 the stretched film or the stretched layer may be assembled in a laminate in a form in which a thermoplastic resin film is bonded to one surface or both surfaces thereof. The thermoplastic resin film can function as a protective film or a retardation film for the polarizer layer 103. The thermoplastic resin film may be formed of a polyolefin resin such as a chain polyolefin resin (e.g., a polypropylene resin) or a cyclic polyolefin resin (e.g., a norbornene resin); cellulose resins such as triacetyl cellulose; polyester resins such as polyethylene terephthalate, polyethylene naphthalate and polybutylene terephthalate; a polycarbonate-based resin; (meth) acrylic resins; or a mixture thereof.
From the viewpoint of light thinning, the thickness of the thermoplastic resin film is usually 300 μm or less, preferably 200 μm or less, more preferably 100 μm or less, further preferably 80 μm or less, further preferably 60 μm or less, and usually 5 μm or more, preferably 20 μm or more.
The thermoplastic resin film may or may not have a phase difference.
The thermoplastic resin film may be bonded to the polarizer layer 103 using an adhesive layer, for example.
[ polarizer layer obtained by applying and curing composition containing dichroic dye and polymerizable compound ]
Examples of the polarizer layer obtained by applying and curing a composition containing a dichroic dye and a polymerizable compound include a polarizer layer containing a cured product of a polymerizable liquid crystal compound, such as a composition containing a polymerizable dichroic dye having liquid crystal properties or a layer obtained by applying and curing a composition containing a dichroic dye and a polymerizable liquid crystal to a base film.
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 above. The polarizer layer may be provided with an orientation film. The alignment film may be peeled off.
The polarizer layer obtained by applying and curing a composition containing a dichroic dye and a polymerizable compound may be incorporated in the optical laminate in such a manner that a thermoplastic resin film is bonded to one surface or both surfaces of the polarizer layer. As the thermoplastic resin film, the same one as that usable for the stretched film or the polarizer layer of the stretched layer can be used. The thermoplastic resin film may be bonded to the polarizer layer using an adhesive layer, for example.
The polarizer layer obtained by applying and curing a composition containing a dichroic dye and a polymerizable compound may have an Overcoat (OC) layer formed on one or both surfaces thereof as a protective layer. Examples thereof include photocurable resins and water-soluble polymers. Examples of the photocurable resin include (meth) acrylic resins, urethane resins, (meth) acrylic urethane resins, epoxy resins, and silicone resins. Examples of the water-soluble polymer include poly (meth) acrylamide polymers; polyvinyl alcohol, and vinyl alcohol polymers such as ethylene-vinyl alcohol copolymers, ethylene-vinyl acetate copolymers, (meth) acrylic acid or acid anhydride thereof-vinyl alcohol copolymers; a carboxyvinyl polymer; polyvinylpyrrolidone; starches; sodium alginate; polyethylene oxide polymers, and the like. The thickness of the OC layer is preferably 20 μm or less, more preferably 15 μm or less, still more preferably 10 μm or less, and may be 5 μm or less, and may be 0.05 μm or more, or may be 0.5 μm or more.
The thickness of the polarizer layer obtained by applying and curing a composition containing a dichroic dye and a polymerizable compound is usually 10 μm or less, preferably 0.5 to 8 μm, and more preferably 1 to 5 μm.
[2 nd adhesive layer ]
The 2 nd adhesive layer 104 is an adhesive layer disposed between the polarizer layer 103 and the back surface plate 105. The 2 nd adhesive layer may be an adhesive layer disposed at a position close to the rearmost panel among the adhesive layers constituting the laminate. The 2 nd adhesive layer 104 may be 1 layer, or may be composed of 2 or more layers, 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 in the pressure-sensitive adhesive composition, the method for producing the 2 nd pressure-sensitive adhesive layer, and the thickness of the 2 nd pressure-sensitive adhesive layer 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 different from the 1 st adhesive layer 102 in composition, blending component, thickness, and the like of the adhesive composition.
[ Back Panel ]
As the back plate 105, a plate-like body that transmits 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 rear plate 105 may be formed of only 1 layer or 2 or more layers, and the plate-like body exemplified by the plate-like body described in front plate 101 may be used.
Examples of the components used in a general display device used in the back panel 105 include a spacer, a touch sensor panel, and an organic EL display element. Examples of the order of lamination of the components in the display device include a front panel, a circularly polarizing plate, and a spacer, a front panel, a circularly polarizing plate, and an organic EL display element, a front panel, a circularly polarizing plate, a touch sensor panel, and an organic EL display element, and 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 to a detection method as long as it is a sensor capable of detecting a touched position, and examples thereof include touch sensor panels of a resistive film method, a capacitive coupling method, an optical sensor method, an ultrasonic wave method, an electromagnetic induction coupling method, a surface acoustic wave method, and the like. From the viewpoint of low cost, a resistive-film type or capacitive-coupling type touch sensor panel is preferably used.
An example of a resistive touch sensor panel includes a pair of substrates arranged to face each other, an insulating spacer sandwiched between the pair of substrates, a transparent conductive film provided as a resistive film on the front surface of each of the substrates, and a touch position detection circuit. In an image display device provided with a resistive touch sensor panel, 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 this time, thereby detecting that a touched position current flows through the resistive film.
An example of a capacitive coupling type touch sensor panel 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 panel, if the front surface of the front panel is touched, the transparent electrode is grounded via the electrostatic capacitance of the human body at the point of touch. The touch position detection circuit detects the grounding of the transparent electrode, thereby detecting the position of the touch.
The thickness of the touch sensor panel may be, for example, 5 to 2000 μm, or 5 to 100 μm.
[ phase difference layer ]
The laminate 100 may further include 1 or 2 or more retardation layers. The retardation layer is generally disposed between the polarizer layer 103 and the back plate 105. The retardation layer may be laminated on the 1 st pressure-sensitive adhesive layer 102, the 2 nd pressure-sensitive adhesive layer 104, or on another layer (including another retardation layer) via a layer made of a pressure-sensitive adhesive or an adhesive other than these layers (hereinafter, also referred to as a laminating layer).
[ adhesive layer ]
The adhesive layer is a layer disposed between the 1 st adhesive layer 102 and the 2 nd adhesive layer 104, and is a layer made of an adhesive or an adhesive. The adhesive constituting the bonding layer may be the same adhesive as exemplified for the adhesive composition constituting the 1 st adhesive layer 102 or the 2 nd adhesive layer, or may be another adhesive such as a (meth) acrylic adhesive, a styrene-based adhesive, a silicone-based adhesive, a rubber-based adhesive, a polyurethane-based adhesive, a polyester-based adhesive, an epoxy-based copolymer adhesive, or the like.
As the adhesive constituting the adhesive layer, for example, 1 or a combination of 2 or more of an aqueous adhesive, an active energy ray-curable adhesive, an adhesive, and the like can be formed. Examples of the aqueous adhesive include a polyvinyl alcohol resin aqueous solution and an aqueous two-pack polyurethane emulsion adhesive. Examples of the active energy ray-curable adhesive include adhesives containing a polymerizable compound and a photopolymerization initiator, adhesives containing a photoreactive resin, and adhesives 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 those which generate active species such as neutral radicals, anionic radicals and cationic radicals 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 laminate 200 shown in fig. 2 includes a front plate 101, a1 st adhesive layer 102, a polarizer layer 103, a bonding layer 108, and a back plate 105, and further includes a1 st retardation layer 106, a bonding layer 109, a2 nd retardation layer 107, and a2 nd adhesive layer 104.
Examples of the retardation layer include a photo-alignment material parallel alignment film (positive-Aplate) and a photo-alignment material perpendicular alignment film (positive-C plate) such as a λ/4 plate and a λ/2 plate.
The retardation layer may be, for example, a retardation film formed of the above-described thermoplastic resin film, or a layer obtained by curing a polymerizable liquid crystal compound, that is, a layer containing a cured product of a polymerizable liquid crystal compound, but the latter is preferable.
The thickness of the retardation film may be the same as that of the thermoplastic resin film described above. The thickness of the retardation layer obtained by curing the polymerizable liquid crystal compound is, for example, 0.1 to 10 μm, preferably 0.5 to 8 μm, and more preferably 1 to 6 μm.
The retardation layer obtained by curing the polymerizable liquid crystal compound can be formed by applying a composition containing the polymerizable liquid crystal compound to a substrate film and curing the composition. An alignment layer 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.
The retardation layer obtained by curing the polymerizable liquid crystal compound may be incorporated in the laminate 100 in a form having an alignment layer and/or a base film. The back surface plate 105 may be a substrate film coated with the above composition.
As described above, the adhesive or the adhesive may be used for the adhesive layer 108. The binder may be the binder composition a described above.
As the adhesive, an aqueous adhesive or an active energy ray-curable adhesive can be used. Examples of the aqueous adhesive include an adhesive composed of 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 of a photoreactive resin, an adhesive of a binder resin and a photoreactive crosslinking agent, and the like.
Examples of the polymerizable compound include photopolymerizable monomers such as a photocurable epoxy monomer, a photocurable (meth) acrylic monomer, and a photocurable urethane monomer, and oligomers derived from a photopolymerizable monomer.
Examples of the photopolymerization initiator include photopolymerization initiators containing active species that generate neutral radicals, anionic radicals, and cationic radicals by irradiation with active energy rays such as ultraviolet rays. As the active energy ray-curable adhesive containing a polymerizable compound and a photopolymerization initiator, an active energy ray-curable adhesive containing a photocurable epoxy monomer and a photocationic polymerization initiator can be preferably used.
[ method for producing laminate ]
The laminate 100 can be produced by a method including a step of bonding the layers constituting the laminate 100 to each other via an adhesive layer or via an adhesive layer. When the layers are bonded to each other via the pressure-sensitive adhesive layer or the adhesive layer, one or both of the bonding surfaces are preferably subjected to a surface activation treatment such as corona treatment in order to improve the adhesion.
The polarizer layer 103 may be formed directly on a thermoplastic resin film or a base film, which may be incorporated in the laminate 100, or may be separated from the polarizer layer 103 without being a constituent of the laminate.
< display device >
The display device of the present invention includes the laminate 100 of the present invention 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 display device may have a touch panel function. The optical laminate is suitable for a display device having flexibility such as being bendable or bendable.
In the display device, the optical laminate is disposed on the viewing side of the display element included in the display device such that the front panel faces outward (the side opposite to the display element side, i.e., the viewing side).
The display device can be used as mobile equipment such as a smart phone and a tablet personal computer, a television, a digital photo frame, an electronic billboard, a measuring instrument, instruments, office equipment, medical equipment, computer equipment and the like.
< adhesive composition >
The adhesive composition of the present invention is preferably the adhesive composition a described above. The adhesive composition of the present invention can be produced by a known method, for example, by mixing the respective components together using a mixer or the like.
< pressure-sensitive adhesive sheet >
The adhesive sheet of the present invention preferably includes an adhesive layer formed from the adhesive composition a. The adhesive layer may be formed by coating an adhesive composition on a substrate. When an active energy ray-curable pressure-sensitive adhesive composition is used as the pressure-sensitive adhesive composition, a cured product having a desired degree of curing can be obtained by irradiating the pressure-sensitive adhesive layer formed with an active energy ray. When a thermosetting adhesive composition is used as the adhesive composition, the adhesive layer formed can be subjected to heat treatment (and curing) to obtain a cured product having a desired degree of curing.
The substrate may be a release film subjected to a release treatment. The pressure-sensitive adhesive sheet can be produced by forming a layer made of a pressure-sensitive adhesive in a sheet form on a release film in advance, and further bonding another release film to the pressure-sensitive adhesive layer.
The adhesive layer of the adhesive sheet of the present invention has excellent adhesion durability in a room temperature environment. G represents a shear elastic modulus at 25 ℃ of a reference pressure-sensitive adhesive layer having a thickness of 150 μm and formed from a pressure-sensitive adhesive composition used for forming the pressure-sensitive adhesive layer0[Pa]In this case, the following relational expression (4) is preferably satisfied:
1.0×104≤G0≤5.0×105 (4),
more preferably, the following relational expression (4a) is satisfied:
2.0×104≤G0≤2.0×105 (4a)。
the adhesive layer of the adhesive sheet of the present invention preferably has a gel fraction of 45% to 85%, more preferably 50% to 80%. The gel fraction of the pressure-sensitive adhesive layer was measured by the measurement method described in the column of the examples described later.
The present invention will be described in further detail with reference to examples, but the present invention is not limited to these examples.
Examples
[ adhesive sheet Using Heat-curable adhesive composition ]
[1] Production of adhesive sheet A11
(1) Preparation of (meth) acrylic polymer
A (meth) acrylic polymer was prepared by copolymerizing 54 parts by mass of n-butyl acrylate, 45 parts by mass of 2-ethylhexyl acrylate, and 1 part by mass of 4-hydroxybutyl acrylate. The molecular weight of the (meth) acrylic polymer was measured by the method described later, and the weight average molecular weight (Mw) was 80 ten thousand.
(2) Preparation of adhesive composition
100 parts by mass (solid content equivalent; the same applies hereinafter) of the (meth) acrylic polymer obtained in the above-mentioned step, 0.25 part by mass of trimethylolpropane-modified xylylene diisocyanate (product name "TD-75" manufactured by Soken chemical Co., Ltd.) as a thermal crosslinking agent, and 0.2 part by mass of 3-glycidoxypropyltrimethoxysilane (product name "KBM 403" manufactured by shin-Etsu chemical Co., Ltd.) as a silane coupling agent were mixed, sufficiently stirred, and diluted with methyl ethyl ketone to obtain a coating solution of the pressure-sensitive adhesive composition. The respective compounding ratios (solid content equivalent) of the adhesive composition when the (meth) acrylic polymer is taken as 100 parts by mass (solid content equivalent) are shown in table 1. The abbreviations and the like described in table 1 are as follows.
BA: acrylic acid n-butyl ester
2 EHA: 2-ethylhexyl acrylate
4 HBA: acrylic acid 4-hydroxybutyl ester
(3) Production of adhesive sheet A11
The obtained coating solution of the adhesive composition was applied to a release-treated surface of a light separator (manufactured by Lintec Corporation, product name "SP-PET 752150") by a blade coater. The coating layer was subjected to a heat treatment at 90 ℃ for 1 minute to form a coating layer. Then, the coating layer on the light separator and the heavy separator (manufactured by Lintec Corporation, product name "SP-PET 382120") obtained above were bonded so that the release-treated surface of the separator was in contact with the coating layer, and the resultant was cured at 23 ℃ and 50% RH for 7 days to obtain an adhesive sheet A11 having an adhesive layer with a thickness of 25 μm, that is, an adhesive sheet A11 having a composition of light separator/adhesive layer (thickness: 25 μm)/heavy separator. The adhesive layer of the adhesive sheet a11 was referred to as adhesive layer a 11. The shear modulus and gel fraction of the psa sheet a11 were measured and are shown in table 1. The thickness, shear modulus and gel fraction of the pressure-sensitive adhesive layer a11 were measured by the methods described below.
[2] Production of adhesive sheets A12 to A16
(1) Preparation of (meth) acrylic polymer
The proportions of the respective monomers constituting the (meth) acrylic polymer were prepared as shown in table 1, and the (meth) acrylic polymer having the weight average molecular weight (Mw) shown in table 1 was prepared in the same manner as in the production process of the adhesive sheet a 11.
(2) Preparation of adhesive composition
100 parts by mass of the (meth) acrylic polymer obtained in the above-mentioned step, trimethylolpropane-modified xylylene diisocyanate (product name "TD-75" available from Soken chemical Co., Ltd.) as a thermal crosslinking agent, and 3-glycidoxypropyltrimethoxysilane (product name "KBM 403" available from shin-Etsu chemical Co., Ltd.) as a silane coupling agent were mixed in the blending ratio shown in Table 1, sufficiently stirred, and diluted with methyl ethyl ketone to obtain a coating solution of the adhesive composition.
(3) Production of adhesive sheets A12 to A16
Using the obtained coating solution of the adhesive composition, adhesive sheets a12 to a16 were produced in the same manner as in the production process of the adhesive sheet a 11. The pressure-sensitive adhesive layers of the pressure-sensitive adhesive sheets a12 to a16 were referred to as pressure-sensitive adhesive layers a12 to a 16. The thicknesses, shear elastic modulus and gel fractions of the pressure-sensitive adhesive layers a12 to a16 of the pressure-sensitive adhesive sheets a12 to a16, which were measured by the methods described later, are shown in table 1.
[ Table 1]
Figure BDA0003224658170000251
[ adhesive sheet Using active energy ray-curable adhesive composition ]
[1] Production of adhesive sheet A21
(1) Preparation of (meth) acrylic Polymer A21
A 1L reactor equipped with a cooling device to reflux nitrogen gas and easily adjusted in temperature was charged with a monomer mixture comprising 92.9 mass% of 2-ethylhexyl acrylate (2-EHA) monomer and 7 mass% of Butyl Acrylate (BA) monomer, and then the nitrogen gas was refluxed for 1 hour to remove oxygen and maintained at 80 ℃. After the monomer mixture was uniformly mixed, 0.05 mass% of benzyl dimethyl ketal (I-651) and 0.05 mass% of 1-hydroxycyclohexyl phenyl ketone (I-184) as photopolymerization initiators were added. Subsequently, a UV lamp (10mW) was irradiated with the resulting mixture while stirring to produce a (meth) acrylic polymer A21 having a weight-average molecular weight (Mw) of 49 ten thousand.
The proportions of the monomers and components of the acrylic polymer a21 are shown in table 2. The abbreviations and the like described in table 2 are as follows.
2-EHA: 2-ethylhexyl acrylate (Tokyo chemical Co., Ltd., Japan),
BA: butyl acrylate (Tokyo chemical industry Co., Ltd., Japan),
2-HEA: 2-hydroxyethyl acrylate (Tokyo chemical industry Co., Ltd., Japan),
LA: lauryl acrylate (Tokyo chemical industry Co., Ltd., Japan),
i-651: benzyl dimethyl ketal (photopolymerization initiator, BASF, germany),
i-184: 1-Hydroxycyclohexyl phenyl ketone (photopolymerization initiator, BASF, Germany).
(2) Preparation of adhesive composition
95.5 mass% (solid content equivalent; the same applies hereinafter) of the (meth) acrylic polymer obtained in the above-mentioned step, 1 mass% of isodecyl acrylate (IDA, Miwon specialty chemical, korea) and 2.5 mass% of 2-acetoacetoxyethyl methacrylate (AAEM, Sigma-Aldrich, usa) as additives, 0.5 mass% of diphenyl (2, 4, 6-trimethylbenzoyl) phosphine oxide (TPO, tokyo chemical industry co., ltd., japan) as a photopolymerization initiator, and 0.5 mass% of 1-hydroxycyclohexyl phenyl ketone (I-184, BASF, germany) were mixed, sufficiently stirred, and diluted with methyl ethyl ketone to obtain a coating solution of the adhesive composition. The respective compounding ratios (solid content conversion values) of the pressure-sensitive adhesive compositions are shown in table 3. The abbreviations and the like described in table 3 are as follows.
IDA: isodecyl acrylate (Miwon specialty chemical, Korea)
AAEM: 2-Acetoacetoxyethyl methacrylate (Sigma-Aldrich, USA) TPO: diphenyl (2, 4, 6-trimethylbenzoyl) phosphine oxide (Tokyo Kasei Kogyo, Japan)
I-184: 1-Hydroxycyclohexylphenylketone (BASF, Germany)
(3) Production of adhesive sheet A21
The obtained coating solution of the adhesive composition was applied to a release-treated surface of a light separator (polyethylene terephthalate film, thickness 38 μm) with a blade coater. Subsequently, the coating layer on the separator obtained above and a heavy separator (polyethylene terephthalate film, thickness 38 μm) were bonded so that the release-treated surface of the separator was in contact with the coating layer, and UV irradiation was performed to obtain a pressure-sensitive adhesive sheet a21 having a pressure-sensitive adhesive layer with a thickness of 25 μm, i.e., a pressure-sensitive adhesive sheet a21 having a structure of light separator/pressure-sensitive adhesive layer (thickness: 25 μm)/heavy separator. The adhesive layer of the adhesive sheet a21 was referred to as adhesive layer a 21. The measured shear modulus and gel fraction of the psa sheet a21 are shown in table 3. The thickness, shear modulus and gel fraction of the pressure-sensitive adhesive layer a21 were measured by the methods described below.
[2] Production of adhesive sheets A22 and A23
(1) Preparation of (meth) acrylic polymers A22, A23
The proportions of the respective monomers constituting the (meth) acrylic polymer shown in table 2 were prepared, and (meth) acrylic polymers a22 and a23 having weight average molecular weights (Mw) shown in table 2 were prepared in the same manner as in the production process of the adhesive sheet a 21.
(2) Preparation of adhesive composition
The (meth) acrylic polymer obtained in the above-mentioned step and the additive were mixed at the blending ratio shown in table 3, sufficiently stirred, and diluted with methyl ethyl ketone to obtain a coating solution of the adhesive composition.
(3) Production of adhesive sheets A22 and A23
Using the obtained coating solution of the pressure-sensitive adhesive composition, pressure-sensitive adhesive sheets a22 and a23 were produced in the same manner as in the production process of the pressure-sensitive adhesive sheet a 21. The pressure-sensitive adhesive layers of the pressure-sensitive adhesive sheets a22 and a23 were referred to as pressure-sensitive adhesive layers a22 and a 23. The thicknesses, shear moduli, and gel fractions of the pressure-sensitive adhesive sheets a22 and a23 of the pressure-sensitive adhesive layers a22 and a23 measured by the methods described later are shown in table 3.
[ Table 21
Figure BDA0003224658170000271
[ Table 3]
Figure BDA0003224658170000272
< measurement of weight average molecular weight (Mw) >
The weight average molecular weight (Mw) of the (meth) acrylic polymer is a number average molecular weight (Mn) in terms of polystyrene, and the mobile phase is determined by the Size Exclusion Chromatography (SEC) described below using tetrahydrofuran.
The measured (meth) acrylic polymer was dissolved in tetrahydrofuran at a concentration of about 0.05 mass%, and 10. mu.L of SEC was injected. The mobile phase was passed at a flow rate of 1.0 mL/min. The column used was PLgel MIXED-B (manufactured by Polymer Laboratories). The detector used was a UV-VIS detector (trade name: Agilent GPC).
< 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).
< modulus of elasticity in shear >
The shear modulus was measured using a viscoelasticity measuring apparatus (MCR-301, Anton Paar Co.). The same adhesive sheets as those used in examples and comparative examples were cut into pieces having a width of 20mm × a length of 20 mm. The release film was peeled off from the pressure-sensitive adhesive sheet, and a plurality of pressure-sensitive adhesive layers were stacked to a thickness of 150 μm and joined to a glass plate. The measurement was carried out in a temperature range from-20 ℃ to 100 ℃ with the pressure-sensitive adhesive layer bonded to the measurement chip under the conditions of a frequency of 1.0Hz, a deformation amount of 1% and a temperature rise rate of 5 ℃/min, and the shear modulus value at 25 ℃ was confirmed.
< gel fraction >
The obtained adhesive sheet was cut into a size of 80mm × 80mm, the adhesive layer was wrapped in a polyester net (mesh size 200), the mass thereof was weighed with a precision balance, and the mass of the net alone was subtracted to calculate the mass of the adhesive alone. The mass at this time was taken as M1.
Next, the adhesive coated on the polyester net was immersed in ethyl acetate at room temperature (23 ℃ C.) for 24 hours. Thereafter, the adhesive was taken out, air-dried at a temperature of 23 ℃ and a relative humidity of 50% for 24 hours, and further dried in an oven at 80 ℃ for 12 hours. After drying, the mass was weighed with a precision balance, and the mass of the web alone was subtracted, thereby calculating the mass of the adhesive alone. The mass at this time was taken as M2. The gel fraction (%) is represented by (M2/M1). times.100.
[ front Panel (Window film) ]
A polyimide film (thickness: 50 μm) having a hard coat layer (thickness: 10 μm) on one surface was prepared as a front panel.
[ polarizer layer ]
1. The following materials were prepared.
1) TAC film with thickness of 25 μm.
2) An alignment film-forming composition.
< Polymer 1>
A polymer 1 having a photoreactive group composed of the following structural units was prepared.
Figure BDA0003224658170000281
A solution in which polymer 1 was dissolved in cyclopentanone at a concentration of 5 mass% was used as the composition for forming an alignment film [ hereinafter, also referred to as composition (D-1) ].
3) Composition for forming polarizer layer
< polymerizable liquid Crystal Compound >
As the polymerizable liquid crystal compound, a polymerizable liquid crystal compound represented by the formula (1-1) [ hereinafter, also referred to as compound (1-1) ] and a polymerizable liquid crystal compound represented by the formula (1-2) [ hereinafter, also referred to as compound (1-2) ] were used.
Figure BDA0003224658170000291
The compound (1-1) and the compound (1-2) were synthesized by the method described in Lub et al, Recl, Trav, Chim, Pays-Bas, 115, 321-328 (1996).
< dichroic dye >
As the dichroic dye, azo dyes described in examples of Japanese patent application laid-open No. 2013-101328 represented by the following formulae (2-1 a), (2-1 b), and (2-3 a) are used.
Figure BDA0003224658170000292
The composition for forming a polarizer layer [ hereinafter, also referred to as composition (a-1) ] was prepared by: 75 parts by mass of the compound (1-1), 25 parts by mass of the compound (1-2), 2.5 parts by mass of each of the azo dyes represented by the above formulae (2-1 a), (2-1 b) and (2-3 a) as dichroic dyes, 6 parts by mass of 2-dimethylamino-2-benzyl-1- (4-morpholinophenyl) butan-1-one (Irgacure369, manufactured by BASF Japan) as a polymerization initiator, and 1.2 parts by mass of a polyacrylate compound (BYK-361N, manufactured by BYK-Chemie) as a leveling agent were mixed with 400 parts by mass of toluene as a solvent, and the resulting mixture was stirred at 80 ℃ for 1 hour.
4) Composition for forming protective layer (OC layer)
The composition for forming a protective layer (OC layer) [ hereinafter, also referred to as composition (E-1) ] is prepared by mixing water: 100 parts by mass of a polyvinyl alcohol resin powder (manufactured by Kuraray Co., Ltd., average polymerization degree 18000, trade name: KL-318): 3 parts by mass of a polyamide epoxy resin (crosslinking agent, product name: SR650(30) manufactured by Sumika Chemtex): 1.5 parts by mass.
2. Manufacturing method
1) The TAC film side was coated with the alignment film-forming composition as follows.
The TAC film side was first subjected to corona treatment 1 time. The conditions of the corona treatment were an output of 0.3kW and a treatment speed of 3 m/min. Thereafter, the composition (D-1) obtained above was coated on the TAC by a bar coating method, and heat-dried in a drying oven at 80 ℃ for 1 minute. The obtained dried film was subjected to polarized UV irradiation treatment to form a1 st alignment film (AL 1). The polarized light UV treatment was carried out by passing light irradiated from a UV irradiation apparatus (SPOT CURE SP-7; manufactured by Ushio Electric Co., Ltd.) through a wire grid (UIS-27132 # #, manufactured by Ushio Electric Co., Ltd.) and measuring a cumulative light amount at a wavelength of 365nm of 100mJ/cm2Under the conditions of (1). The thickness of the 1 st alignment film (AL1) was 100 nm.
2) The composition for forming a polarizer layer was applied to the alignment film side as follows.
The composition (a-1) was first applied to the formed 1 st alignment film (AL1) by a bar coating method, dried by heating in a drying oven at 120 ℃ for 1 minute, and then cooled to room temperature. Using the above UV irradiation apparatus, the cumulative light amount was 1200mJ/cm2The dried film was irradiated with ultraviolet light (365nm basis) to form a polarizer layer (pol). The thickness of the obtained polarizer layer (pol) was measured by a laser microscope (OLS 3000, Olympus corporation), and found to be 1.8. mu.m. This gave a laminate composed of "TAC/AL 1/pol".
3) The composition for forming a protective layer (OC layer) was applied to the polarizer layer side as follows.
The composition (E-1) was applied to the formed polarizer layer (pol) by a bar coating method, and the resultant coating was dried to a thickness of 1.0 μm and dried at 80 ℃ for 3 minutes. This gave a laminate composed of "TAC film/cPL (AL1+ pol + protective layer)".
[ phase difference layer ]
1. Material preparation
The following materials were prepared.
1) PET film with a thickness of 100 μm.
2) An alignment film-forming composition.
< Polymer 1>
A polymer 1 having a photoreactive group composed of the following structural units was prepared.
Figure BDA0003224658170000311
A solution in which polymer 1 was dissolved in cyclopentanone at a concentration of 5 mass% was used as the composition for forming an alignment film [ hereinafter, also referred to as composition (D-1) ].
3) Composition for forming phase difference layer
The following components were mixed, and the resulting mixture was stirred at 80 ℃ for 1 hour to obtain composition (B-1).
A compound b-1 represented by the following formula: 80 parts by mass
Figure BDA0003224658170000312
A compound b-2 represented by the following formula: 20 parts by mass
Figure BDA0003224658170000313
Polymerization initiator (Irgacure369, 2-dimethylamino-2-benzyl-1- (4-morpholinophenyl) butan-1-one manufactured by BASF Japan): 6 parts by mass
Leveling agent (BYK-361N, polyacrylate compound, BYK-Chemie Co., Ltd.): 0.1 part by mass
Solvent (cyclopentanone): 400 parts by mass
2. Manufacturing method
1) The composition for forming an oriented film was applied to a PET film as follows.
A polyethylene terephthalate film (PET) having a thickness of 100 μm was prepared as a substrate, and the composition (D-1) was applied to the film by a bar coating method and dried by heating in a drying oven at 80 ℃ for 1 minute.The obtained dried film was subjected to polarized UV irradiation treatment to form a2 nd alignment film (AL 2). Polarized light UV treatment Using the UV irradiation device described above, the cumulative light amount measured at a wavelength of 365nm was 100mJ/cm2Under the conditions of (1). The polarization direction of the polarized light UV is set to 45 ° with respect to the absorption axis of the polarizer layer. This gave a laminate composed of "base material (PET)/2 nd alignment film (AL 2)".
2) The retardation layer-forming composition was applied to the orientation film side of the PET film as follows.
The composition (B-1) was applied to the 2 nd alignment film (AL2) of the 1 st substrate thus obtained by a bar coating method, dried by heating in a drying oven at 120 ℃ for 1 minute, and then cooled to room temperature. The obtained dried film was irradiated with a cumulative light amount of 1000mJ/cm using the UV irradiation apparatus described above2Ultraviolet rays (365nm basis), thereby forming a retardation layer. The thickness of the obtained retardation layer was measured by a laser microscope (OLS 3000, Olympus corporation), and found to be 2.0. mu.m. The phase difference layer is a lambda/4 plate (QWP) exhibiting a phase difference value of lambda/4 in the in-plane direction. This gave a laminate composed of "substrate (PET)/AL 2/QWP".
[ common adhesive sheet ]
1) Polymerization of acrylic resins
The following components were reacted at 55 ℃ while stirring in a nitrogen atmosphere to obtain an acrylic resin.
Butyl acrylate: 70 parts by mass
Methyl acrylate: 20 parts by mass
Acrylic acid: 2.0 parts by mass
Radical polymerization initiator (2, 2' -azobisisobutyronitrile): 0.2 part by mass
2) Liquid preparation of adhesive composition
The following ingredients were mixed to obtain an adhesive composition.
Acrylic resin: 100 parts by mass
Crosslinking agent ("Coronate L" manufactured by tokyo corporation): 1.0 part by mass
Silane coupling agent (trade name silicon corporation "X-12-981"): 0.5 part by mass
Ethyl acetate was added so that the total solid content concentration was 10 mass%, to obtain a pressure-sensitive adhesive composition.
3) Production of adhesive sheet
The obtained adhesive composition was applied by an applicator to a release-treated surface of a polyethylene terephthalate film (heavy separator, thickness 38 μm) which had been subjected to release treatment so that the dried thickness was 5 μm. The coating layer was dried at 100 ℃ for 1 minute to obtain a film having an adhesive layer. Thereafter, another polyethylene terephthalate film (light separator, 38 μm thick) subjected to mold release treatment was attached to the exposed surface of the adhesive layer. Thereafter, the mixture was aged at 23 ℃ and 50% RH relative humidity for 7 days to obtain a light separator/a common adhesive layer/a heavy separator.
[ example 1]
The laminate was produced in the order shown in FIGS. 4(a) to (e). First, a laminate 410[ TAC film 301/cPL ((AL1+ pol)302/OC layer 303) ] including the above-described polarizer layer and the above-described common adhesive sheet 420 (light spacer 304/common adhesive layer 305/heavy spacer 306) were prepared (fig. 4 (a)). Laminate a430 was obtained by applying corona treatment (output 0.3KW, speed 3 m/min) to the OC layer 303 side of laminate 410 including the polarizer layer and the side of common adhesive sheet 420 from which light separator 304 was peeled, and then laminating them. The above phase difference layer 440[ substrate (PET)308/AL2/QWP307] was prepared. (FIG. 4 (b)).
Next, the QWP307 side from which the retardation layer 440 was peeled and the surface of the heavy separator 306 of the laminate a430 were subjected to corona treatment (output 0.3KW, speed 3 m/min), and then laminated to obtain a laminate b 450. Thereafter, the adhesive sheet a12 prepared as described above was prepared as an adhesive sheet 460 (light separator 309/adhesive layer 310/heavy separator 311) (fig. 4 (c)). The adhesive layer 310 of the adhesive sheet 460 corresponds to the 2 nd adhesive layer.
Laminate c470 was obtained by applying corona treatment (output 0.3KW, speed 3 m/min) to the surface of laminate b450 from which substrate (PET)308 was peeled and the surface of adhesive sheet 460 from which light separator 309 was peeled, and then laminating them. Then, the pressure-sensitive adhesive sheet a11 thus prepared was prepared as a pressure-sensitive adhesive sheet 490 (light separator 314/pressure-sensitive adhesive layer 315/heavy separator 316), and the surface from which the light separator 314 was peeled and the polyimide film 313 side of the front panel 480 (polyimide film 313/hard coat layer 312) were subjected to corona treatment (output 0.3KW, speed 3 m/min), followed by lamination to obtain a laminate d500 (fig. 4 (d)). The adhesive layer 315 of the adhesive sheet 490 corresponds to the 1 st adhesive layer.
The surface of the laminate d500 from which the heavy separator 316 was peeled and the TAC301 side of the laminate c470 were subjected to corona treatment (output 0.3KW, speed 3 m/min), and then laminated to obtain a laminate 300 of example 1 (fig. 4 (e)). The laminate of example 1 was evaluated for room temperature bendability and room temperature adhesion durability by the method described below. The results are shown in Table 4.
Examples 2 to 5 and comparative examples 1 and 2
Laminates of examples 2 to 5 and comparative examples 1 and 2 were prepared in the same manner as in example 1, except that in example 1, adhesive sheets having adhesive layers shown in table 4 were used instead of the adhesive sheets a11 and a 12. The laminates of examples 2 to 5 and comparative examples 1 and 2 were evaluated for room-temperature bendability and room-temperature adhesion durability by the methods described below. The results are shown in Table 4.
< Normal temperature bendability >
The laminates obtained in the examples and comparative examples were subjected to an evaluation test for confirming room temperature bendability using a bending apparatus (STS-VRT-500, manufactured by Science Town). The heavy separator 311 was peeled off and bonded to a PET film having a thickness of 100 μm to obtain a laminate. The PET film corresponds to the back panel. Fig. 3 is a diagram schematically showing the method of the evaluation test. As shown in fig. 3, 2 tables 501 and 502, which can be moved independently, are arranged so that the gap C is 6.0mm (3R), and the laminate is fixedly arranged so that the center in the width direction is located at the center of the gap C and the hard coat layer 312 is located on the upper side (fig. 3 (a)). Then, the 2 tables 501 and 502 are rotated upward by 90 degrees around the positions P1 and P2 as the centers of the rotation axes, and a bending force (a force to bend the front panel 480 inward) is applied to a region of the laminated body corresponding to the gap C of the tables (fig. 3 (b)). Thereafter, the 2 tables 501 and 502 are returned to their original positions (fig. 3 a). The above series of operations was completed, and the number of times of application of the bending force was counted as 1 time. After repeating this at a temperature of 25 ℃, it was confirmed that air bubbles were generated in the adhesive layer in the region corresponding to the gap C between the mounting tables 501 and 502 of the laminate. The moving speed of the mounting tables 501 and 502 and the step of applying the bending force are the same in the evaluation test of any laminate. "adhesive release" means that the adhesive layer bleeds out from the end of the laminate.
A: the number of bending forces applied reaches 20 thousands and no bubbles are generated.
B: the number of times of applying the bending force is 15 ten thousand or more and less than 20 ten thousand, and bubbles are generated.
C: bubbles are generated when the number of times of applying the bending force is 10 ten thousand or more and less than 15 ten thousand.
D: the number of times of applying the bending force is 5 ten thousand or more and less than 10 ten thousand, and bubbles are generated.
E: the number of bending forces applied is less than 5 ten thousand resulting in bubble/adhesive detachment.
< Normal temperature adhesion durability >
The laminates obtained in each example and each comparative example were cut to a width of 100mm × a length of 100 mm. The heavy separator 311 is peeled off and attached to the alkali-free glass. The pressure bonding treatment was carried out in an autoclave (50 ℃ C., 5 atm) for about 20 minutes, and the pressure bonding treatment was maintained under constant temperature and humidity conditions (23 ℃ C., 50% RH) for 4 hours. The sample was put in an oven at 25 ℃ and judged for the presence of floating, peeling, and bubbling after 250 hours. The alkali-free glass in the laminated laminate corresponds to the back plate.
O: almost no appearance change such as floating, peeling, foaming, etc.
And (delta): the appearance change such as floating, peeling, foaming and the like is slightly conspicuous.
X: the appearance changes such as floating, peeling, foaming and the like are obviously seen.
[ Table 4]
Figure BDA0003224658170000351
Example 1E5 satisfies "G01<G0The relationship of 2 "is that the thicknesses of the 1 st adhesive layer and the 2 nd adhesive layer are the same, and thus it can be judged that the relationship" G1 < G2 "is satisfied. On the other hand, comparative examples 1 and 2 are "G01≥G0The relationship of "G1 ≧ G2" was judged because the thicknesses of the 1 st pressure-sensitive adhesive layer and the 2 nd pressure-sensitive adhesive layer were the same.
Description of the symbols
100. 200 laminated body, 101 front panel, 102 1 st adhesive layer, 103 polarizer layer, 104 nd 2 nd adhesive layer, 105 back panel, 106 st phase difference layer, 107 nd 2 nd phase difference layer, 108, 109 adhesive layer, 301TAC film, 302pol, 303OC layer, 305 common adhesive layer, 306, 311, 316 heavy separator, 307QWP, 308 base material, 304, 309, 314 light separator, 310, 315 adhesive layer, 312 hard coat layer, 313 polyimide film, 410 laminated body containing polarizer layer, 420 common adhesive sheet, 430 laminated body a, 440 phase difference layer, 450 laminated body b, 460, 490 adhesive sheet, 470 laminated body c, 500 laminated body d, 501, 502 carrying platform.

Claims (6)

1. A laminate comprising, in order, a front sheet, a1 st adhesive layer formed using a1 st adhesive composition, a polarizer layer, a2 nd adhesive layer formed using a2 nd adhesive composition, and a back sheet,
when the shear elastic modulus at 25 ℃ of the 1 st adhesive layer is G1[ Pa ] and the shear elastic modulus at 25 ℃ of the 2 nd adhesive layer is G2[ Pa ], the following relational expression (1) is satisfied:
G1<G2(1),
the 1 st adhesive layer and the 2 nd adhesive layer have a gel fraction of 45% to 85%.
2. The laminate according to claim 1, wherein each of the 1 st adhesive composition and the 2 nd adhesive composition contains a (meth) acrylic polymer,
the structural unit derived from the monomer having a reactive functional group in the (meth) acrylic polymer is less than 5% by mass based on the total mass.
3. The laminate according to claim 1 or 2, wherein each of the 1 st adhesive layer and the 2 nd adhesive layer contains a (meth) acrylic polymer,
the weight average molecular weight (Mw) of the (meth) acrylic polymer is 20 to 150 ten thousand.
4. The laminate according to any one of claims 1 to 3, wherein the back surface plate is a touch sensor panel.
5. A display device comprising the laminate according to any one of claims 1 to 4.
6. The display device according to claim 5, wherein the front panel side can be bent to be an inner side.
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