CN116107004A - Laminate and display device - Google Patents

Laminate and display device Download PDF

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Publication number
CN116107004A
CN116107004A CN202211388761.XA CN202211388761A CN116107004A CN 116107004 A CN116107004 A CN 116107004A CN 202211388761 A CN202211388761 A CN 202211388761A CN 116107004 A CN116107004 A CN 116107004A
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China
Prior art keywords
layer
meth
adhesive layer
adhesive
less
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Chinese (zh)
Inventor
李昇祐
佐濑光敬
西上由纪
坂口哲生
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Sumitomo Chemical Co Ltd
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Sumitomo Chemical Co Ltd
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
    • B32B7/04—Interconnection of layers
    • B32B7/12—Interconnection of layers using interposed adhesives or interposed materials with bonding properties
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/30—Polarising elements
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B17/00—Layered products essentially comprising sheet glass, or glass, slag, or like fibres
    • B32B17/06—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material
    • B32B17/10—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material of synthetic resin
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/28—Layered products comprising a layer of synthetic resin comprising synthetic resins not wholly covered by any one of the sub-groups B32B27/30 - B32B27/42
    • B32B27/281—Layered products comprising a layer of synthetic resin comprising synthetic resins not wholly covered by any one of the sub-groups B32B27/30 - B32B27/42 comprising polyimides
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/34—Layered products comprising a layer of synthetic resin comprising polyamides
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B37/00—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding
    • B32B37/02—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding characterised by a sequence of laminating steps, e.g. by adding new layers at consecutive laminating stations
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
    • B32B7/02—Physical, chemical or physicochemical properties
    • B32B7/023—Optical properties
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J133/00—Adhesives 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
    • C09J133/04—Homopolymers or copolymers of esters
    • C09J133/06—Homopolymers or copolymers of esters of esters containing only carbon, hydrogen and oxygen, the oxygen atom being present only as part of the carboxyl radical
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J7/00—Adhesives in the form of films or foils
    • C09J7/30—Adhesives in the form of films or foils characterised by the adhesive composition
    • C09J7/38—Pressure-sensitive adhesives [PSA]
    • C09J7/381—Pressure-sensitive adhesives [PSA] based on macromolecular compounds obtained by reactions involving only carbon-to-carbon unsaturated bonds
    • C09J7/385—Acrylic polymers
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/30—Polarising elements
    • G02B5/3083—Birefringent or phase retarding elements
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F1/00—Details not covered by groups G06F3/00 - G06F13/00 and G06F21/00
    • G06F1/16—Constructional details or arrangements
    • G06F1/1613—Constructional details or arrangements for portable computers
    • G06F1/1633—Constructional details or arrangements of portable computers not specific to the type of enclosures covered by groups G06F1/1615 - G06F1/1626
    • G06F1/1637—Details related to the display arrangement, including those related to the mounting of the display in the housing
    • G06F1/1652—Details related to the display arrangement, including those related to the mounting of the display in the housing the display being flexible, e.g. mimicking a sheet of paper, or rollable
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09F—DISPLAYING; ADVERTISING; SIGNS; LABELS OR NAME-PLATES; SEALS
    • G09F9/00—Indicating arrangements for variable information in which the information is built-up on a support by selection or combination of individual elements
    • G09F9/30—Indicating arrangements for variable information in which the information is built-up on a support by selection or combination of individual elements in which the desired character or characters are formed by combining individual elements
    • G09F9/301—Indicating arrangements for variable information in which the information is built-up on a support by selection or combination of individual elements in which the desired character or characters are formed by combining individual elements flexible foldable or roll-able electronic displays, e.g. thin LCD, OLED
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B37/00—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding
    • B32B37/14—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding characterised by the properties of the layers
    • B32B37/24—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding characterised by the properties of the layers with at least one layer not being coherent before laminating, e.g. made up from granular material sprinkled onto a substrate
    • B32B2037/243—Coating
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B37/00—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding
    • B32B37/14—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding characterised by the properties of the layers
    • B32B37/26—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding characterised by the properties of the layers with at least one layer which influences the bonding during the lamination process, e.g. release layers or pressure equalising layers
    • B32B2037/268—Release layers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2255/00—Coating on the layer surface
    • B32B2255/10—Coating on the layer surface on synthetic resin layer or on natural or synthetic rubber layer
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2255/00—Coating on the layer surface
    • B32B2255/26—Polymeric coating
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2307/00—Properties of the layers or laminate
    • B32B2307/40—Properties of the layers or laminate having particular optical properties
    • B32B2307/42—Polarizing, birefringent, filtering
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2307/00—Properties of the layers or laminate
    • B32B2307/50—Properties of the layers or laminate having particular mechanical properties
    • B32B2307/546—Flexural strength; Flexion stiffness
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2309/00—Parameters for the laminating or treatment process; Apparatus details
    • B32B2309/08—Dimensions, e.g. volume
    • B32B2309/10—Dimensions, e.g. volume linear, e.g. length, distance, width
    • B32B2309/105—Thickness
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2457/00—Electrical equipment
    • B32B2457/20—Displays, e.g. liquid crystal displays, plasma displays

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Theoretical Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Computer Hardware Design (AREA)
  • Optics & Photonics (AREA)
  • Human Computer Interaction (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Engineering & Computer Science (AREA)
  • Adhesives Or Adhesive Processes (AREA)
  • Laminated Bodies (AREA)
  • Polarising Elements (AREA)
  • Liquid Crystal (AREA)
  • Surface Treatment Of Optical Elements (AREA)
  • Electroluminescent Light Sources (AREA)
  • Paints Or Removers (AREA)

Abstract

The present invention relates to a laminate and a display device. Provided is a laminate having excellent flexibility and optical characteristics even when irradiated with ultraviolet rays having a large cumulative light amount. A laminated body, which has, in order: front layer, use of the 1 st adhesive compositionThe adhesive layer 1, the polarizing plate including at least a linear polarizing layer, the adhesive layer 2 and the back layer formed using the adhesive composition 2. The 1 st reference adhesive layer formed at a thickness of 0.6mm using the 1 st adhesive composition was irradiated with a cumulative amount of 100J/cm 2 The line shrinkage of the 1 st reference adhesive layer after ultraviolet ray at a temperature of 25 ℃ under a load of 1N and a strain of 350% was set to D1[%]The 2 nd reference adhesive layer formed at a thickness of 0.6mm using the 2 nd adhesive composition was irradiated to a cumulative amount of 100J/cm 2 The line shrinkage of the 2 nd reference adhesive layer after ultraviolet ray at a temperature of 25 ℃ under a load of 1N and a strain of 350% was set to D2[%]When D1 is less than D2 and D2 is more than or equal to 2.5 and less than or equal to 6.5.

Description

Laminate and display device
Technical Field
The present invention relates to a laminate and a display device.
Background
In order to achieve good flexibility in a flexible display including a bendable display panel, a method of adjusting stress relaxation characteristics and the like of an adhesive layer included in a laminate for a display panel is known (for example, patent documents 1, 2, 4, and 5).
Prior art literature
Patent literature
Patent document 1: korean laid-open patent No. 10-2014-0085299
Patent document 2: japanese patent laid-open No. 2018-27995
Patent document 3: japanese patent laid-open publication No. 2017-125195
Patent document 4: japanese patent laid-open No. 2018-28573
Patent document 5: japanese patent application laid-open No. 2019-528330
Disclosure of Invention
Problems to be solved by the invention
It was found that if a laminate for a display panel is irradiated with ultraviolet rays having a large accumulated light amount, the flexibility decreases or the optical characteristics of the laminate decrease.
The purpose of the present invention is to provide a laminate having excellent flexibility and optical characteristics even when irradiated with ultraviolet rays having a large cumulative light amount, and a display device comprising the laminate.
Means for solving the problems
The present invention provides the following laminate and display device.
[ 1 ] A laminate comprising, in order: a front layer, a 1 st adhesive layer formed using the 1 st adhesive composition, a polarizing plate including at least a linearly polarizing layer, a 2 nd adhesive layer formed using the 2 nd adhesive composition, and a back layer,
the 1 st reference adhesive layer formed at a thickness of 0.6mm using the 1 st adhesive composition was irradiated with a cumulative amount of 100J/cm 2 The line shrinkage of the 1 st reference pressure-sensitive adhesive layer after ultraviolet ray at a temperature of 25 ℃ under a load of 1N and a strain of 350% was set to D1[%]，
And irradiating the 2 nd reference adhesive layer formed at a thickness of 0.6mm using the above 2 nd adhesive composition with an accumulated amount of 100J/cm 2 The line shrinkage of the 2 nd reference pressure-sensitive adhesive layer after ultraviolet ray at 25 ℃ under a load of 1N and a strain of 350% was set to D2[%]In the time-course of which the first and second contact surfaces,
satisfies the following relationships of the formulas (1) and (2),
D1＜D2 (1)
2.5≤D2≤6.5 (2)。
the laminate according to [ 2 ], wherein,
the gel fraction of the 2 nd reference pressure-sensitive adhesive layer after irradiation with the ultraviolet light is 50% to 90%.
The laminate according to [ 1 ] or [ 2 ], wherein,
the thickness of the 2 nd adhesive layer is 15 μm or more and 100 μm or less.
The laminate according to any one of [ 1 ] to [ 3 ], wherein,
the glass transition temperature of the 2 nd adhesive layer is-55 ℃ or lower.
The laminate according to any one of [ 1 ] to [ 4 ], wherein,
the 2 nd adhesive composition comprises a (meth) acrylic polymer,
the (meth) acrylic polymer contains a structural unit derived from an alkyl (meth) acrylate having an alkyl group having 1 to 24 carbon atoms.
The laminate according to [ 5 ], wherein,
the (meth) acrylic polymer contains a structural unit derived from an alkyl (meth) acrylate having an alkyl group having 20 to 24 carbon atoms.
The laminate according to [ 5 ] or [ 6 ], wherein,
the content of the structural unit derived from the monomer having a reactive functional group is 2 mass% or less with respect to the total structural units constituting the (meth) acrylic polymer.
The laminate according to any one of [ 1 ] to [ 7 ], wherein,
the front layer includes a 1 st base material layer and a coating layer formed on at least one surface of the 1 st base material layer,
the coating layer is formed using a composition containing a (meth) acrylic compound having a dendrimer structure.
The laminate according to any one of [ 1 ] to [ 8 ], wherein,
the polarizing plate is a circular polarizing plate having the linear polarizing layer and the retardation layer in this order from the front surface layer side.
The laminate according to any one of [ 1 ] to [ 9 ], wherein,
the back surface layer is a separator having a release treatment layer and a 2 nd base material layer in this order from the 2 nd adhesive layer side.
A display device comprising the laminate of any one of [ 1 ] to [ 10 ].
The display device according to [ 11 ], which is bendable so that the back surface layer is positioned inward.
Effects of the invention
The laminate of the present invention can have excellent flexibility and optical characteristics even when irradiated with ultraviolet rays having a large cumulative light amount.
Drawings
Fig. 1 is a schematic cross-sectional view schematically showing a laminate according to an embodiment of the present invention.
Fig. 2 is a schematic cross-sectional view schematically showing a laminate according to another embodiment of the present invention.
Detailed Description
Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to the following embodiments.
(laminate)
Fig. 1 and 2 are schematic cross-sectional views schematically showing an example of a laminate according to the present embodiment. The laminated bodies 1, 2 have, in order: a front layer 11, a 1 st adhesive layer 21 formed using the 1 st adhesive composition, a polarizing plate 30 including at least a linearly polarizing layer, a 2 nd adhesive layer 22 formed using the 2 nd adhesive composition, and a back layer 15.
The front layer 11 is a layer provided on the visible side of the polarizing plate 30, and the back layer 15 is a layer provided on the opposite side of the polarizing plate 30 from the visible side. In the laminated bodies 1 and 2, the 1 st adhesive layer 21 is preferably in direct contact with the front layer 11 and the polarizing plate 30. The 2 nd adhesive layer 22 is preferably in direct contact with the polarizing plate 30 and the back layer 15. The polarizing plate 30 includes at least a linear polarizing layer 31, and may be a linear polarizing plate or a circular polarizing plate as described later.
As described later, the laminated bodies 1 and 2 can be applied to a display device (flexible display) that can be bent, wound, or the like. The laminated bodies 1 and 2 are excellent in bending property particularly when bent so that the back surface layer 15 side is inward.
The 1 st reference adhesive layer formed at a thickness of 0.6mm using the 1 st adhesive composition was irradiated with a cumulative amount of 100J/cm 2 The linear shrinkage of the 1 st reference adhesive layer (hereinafter, sometimes referred to as "1 st reference adhesive layer after UV irradiation") after ultraviolet rays at a temperature of 25 ℃ under a load of 1N and a strain of 350% was set to D1[%]，
And irradiating the 2 nd reference adhesive layer formed at a thickness of 0.6mm using the 2 nd adhesive composition with an accumulated amount of 100J/cm 2 The line shrinkage of the 2 nd reference pressure-sensitive adhesive layer after ultraviolet rays (hereinafter, sometimes referred to as "2 nd reference pressure-sensitive adhesive layer after UV irradiation") under conditions of a temperature of 25 ℃, a load of 1N, and a strain of 350% was set to D2[%]In the time-course of which the first and second contact surfaces,
the laminated bodies 1 and 2 satisfy the relationship of the following formulas (1) and (2).
D1＜D2 (1)
2.5≤D2≤6.5 (2)
The linear shrinkage ratios D1 and D2 are calculated by the following formulas (3) and (4).
D1[％]＝{1-(T 10 1/T 0 1)}×100(3)
D2[％]＝{1-(T 10 2/T 0 2)}×100(4)
In the formula (3) of the present invention,
T 0 1 is the thickness [ mu ] m of the 1 st reference adhesive layer measured immediately after the 1 st reference adhesive layer after UV irradiation is subjected to a load of 1N and a strain of 350% at a temperature of 25 DEG C ]，
T 10 1 is the thickness [ mu ] m of the 1 st reference adhesive layer measured after the 1 st reference adhesive layer after UV irradiation is kept for 10 hours in a state where a load of 1N and a strain of 350% are applied to the 1 st reference adhesive layer at a temperature of 25 DEG C]。
T 0 2 is the thickness [ mu ] m of the 2 nd reference adhesive layer measured immediately after the 2 nd reference adhesive layer after UV irradiation is subjected to a load of 1N and a strain of 350% at a temperature of 25 DEG C]，
T 10 2 is the thickness [ mu ] m of the 1 st reference adhesive layer measured after the 2 nd reference adhesive layer after UV irradiation is kept for 10 hours in a state where a load of 1N and a strain of 350% are applied to the 2 nd reference adhesive layer at a temperature of 25 DEG C]。]
Line shrinkage D1 and D2, thickness T of 1 st reference adhesive layer 0 1 and T 10 1. Thickness T of the 2 nd reference adhesive layer 0 2 and T 10 2 can be measured by the method described in examples described later, and each of the above thicknesses is measured by a viscoelasticity measuring device.
The linear shrinkage D1 may be 2.0 or more, or 2.5 or more, or 3.0 or more, or 3.5 or more, or 4.0 or more, or 6.4 or less, or 6.0 or less, or 5.5 or less, or 5.0 or less.
The linear shrinkage D1 can be adjusted by the kind and amount of the polymer contained in the 1 st adhesive composition, the weight average molecular weight of the polymer, the kind and amount of the monomer for forming the polymer, the kind and amount of the polymerization initiator and additive contained in the 1 st adhesive composition, and the like.
By satisfying the relationship of the above-described formulas (1) and (2) in the laminated body 1, 2, excellent flexibility and optical characteristics can be obtained even when the laminated body is irradiated with ultraviolet rays having a large cumulative light amount.
The linear shrinkage D2 may be 2.5 or more, 3.0 or more, 3.3 or more, or 4.0 or more, and may be 6.5 or less, 6.0 or less, 5.5 or less, 5.0 or less, or 4.5 or less.
The linear shrinkage D2 can be adjusted by the kind and amount of the polymer contained in the 2 nd adhesive composition, the weight average molecular weight of the polymer, the kind and amount of the monomer for forming the polymer, the kind and amount of the polymerization initiator and additive contained in the 2 nd adhesive composition, and the like.
If the laminated bodies 1 and 2 are bent so that the back surface layer 15 side is inward, the bending radius of the 2 nd adhesive layer 22 is smaller than the bending radius of the 1 st adhesive layer 21, and therefore, it is considered that the 2 nd adhesive layer 22 is expected to shrink more easily than the 1 st adhesive layer 21. Therefore, by satisfying the relationship of the above-described formulas (1) and (2) in the laminated body 1, 2, even when the laminated body 1, 2 subjected to the ultraviolet irradiation having a large accumulated light amount is bent so that the back surface layer 15 side is inside, the generation of bubbles in the 1 st adhesive layer 21 and/or the 2 nd adhesive layer 22 or the generation of peeling between the back surface layer 15 and the 2 nd adhesive layer 22 can be suppressed.
In particular, by satisfying the relationship of the above formula (2), even when the laminated bodies 1 and 2 are irradiated with ultraviolet rays having a large cumulative light amount, deterioration of the 2 nd adhesive layer 22 can be suppressed, and degradation of optical characteristics can be suppressed.
The gel fraction of the 1 st reference pressure-sensitive adhesive layer after UV irradiation and the gel fraction of the 2 nd reference pressure-sensitive adhesive layer after UV irradiation may be 50% or more, or 60% or more, or 70% or more, and may be 90% or less, preferably 85% or less, or 80% or less, or 75% or less, respectively, independently. The gel fraction of the 1 st reference adhesive layer after UV irradiation may be the same as or different from the gel fraction of the 2 nd reference adhesive layer after UV irradiation. The gel fraction of the 1 st reference pressure-sensitive adhesive layer and the 2 nd reference pressure-sensitive adhesive layer can be adjusted by, for example, the amount of structural units derived from a monomer having a reactive functional group in the (meth) acrylic polymer to be described later contained in the 1 st pressure-sensitive adhesive composition and the 2 nd pressure-sensitive adhesive composition, the amount of the crosslinking agent contained in the 1 st pressure-sensitive adhesive composition and the 2 nd pressure-sensitive adhesive composition, and the like. Gel fraction can be measured by the method described in examples described below.
By using the 1 st adhesive layer 21 and/or the 2 nd adhesive layer 22, it is easy to obtain a laminate 1, 2 having excellent bending properties and optical characteristics even when irradiated with ultraviolet light having a large cumulative light amount, the 1 st adhesive layer 21 is formed using a 1 st adhesive composition capable of forming a 1 st reference adhesive layer having the above gel fraction, and the 2 nd adhesive layer 22 is formed using a 2 nd adhesive composition capable of forming a 2 nd reference adhesive layer having the above gel fraction.
The thickness of the laminated bodies 1, 2 is preferably 100 μm or more, but may be 150 μm or more, and may be 2000 μm or less, but may be 1000 μm or less, but may be 500 μm or less, preferably 250 μm or less, and may be 200 μm or less.
(1 st adhesive layer, 2 nd adhesive layer)
The 1 st pressure-sensitive adhesive layer 21 may have a thickness of 10 μm or more, 15 μm or more, 20 μm or more, 25 μm or more, 30 μm or more, 40 μm or more, 100 μm or less, 90 μm or less, 80 μm or less, or 70 μm or less.
The thickness of the 2 nd pressure-sensitive adhesive layer 22 may be 10 μm or more, 15 μm or more, 20 μm or more, 25 μm or more, 30 μm or more, 100 μm or less, 80 μm or less, 60 μm or less, or 50 μm or less. The thickness of the 2 nd adhesive layer 22 is preferably 15 μm or more and 100 μm or less, more preferably 20 μm or more and 80 μm or less.
By making the thickness of the 1 st adhesive layer 21 and/or the 2 nd adhesive layer 22 satisfy the above-described range, it is easy to obtain the laminated body 1, 2 having excellent bendability and optical characteristics even when irradiated with ultraviolet rays having a large cumulative light amount.
The glass transition temperature of the 1 st pressure-sensitive adhesive layer 21 and the glass transition temperature of the 2 nd pressure-sensitive adhesive layer 22 may be, independently, not higher than-55 ℃, not higher than-56 ℃, not higher than-57 ℃, and usually not lower than-80 ℃. By providing the 1 st adhesive layer 21 and/or the 2 nd adhesive layer 22 with the glass transition temperature in the above-described range, the laminated body 1, 2 having excellent bendability and optical characteristics even when irradiated with ultraviolet rays having a large cumulative light amount can be easily obtained. The glass transition temperature of the 1 st adhesive layer 21 may be the same as or different from the glass transition temperature of the 2 nd adhesive layer 22. The glass transition temperatures of the 1 st adhesive layer 21 and the 2 nd adhesive layer 22 can be adjusted by, for example, the kind and amount of the polymer contained in the adhesive composition, the kind and amount of the monomer used for forming the polymer, and the like. The glass transition temperature can be measured by the method described in examples described below.
(adhesive composition 1, adhesive composition 2)
The 1 st adhesive composition and the 2 nd adhesive composition (hereinafter, both may be collectively referred to as "adhesive composition") each independently preferably contain a (meth) acrylic polymer. The composition of the 1 st adhesive composition may be the same as or different from the composition of the 2 nd adhesive composition. In the present specification, "(meth) acrylic polymer" means at least one selected from the group consisting of acrylic polymers and methacrylic polymers. The same applies to other expressions with "(methyl)".
The (meth) acrylic polymer preferably contains a structural unit derived from an alkyl (meth) acrylate (monomer) having an alkyl group having 1 to 24 carbon atoms. The (meth) acrylic polymer preferably contains a structural unit derived from an alkyl (meth) acrylate having an alkyl group having 20 to 24 carbon atoms. The alkyl group may be linear or branched. By forming the 1 st adhesive layer 21 and/or the 2 nd adhesive layer 22 using the adhesive composition containing the above-described structural units, it is easy to obtain the laminated body 1, 2 having excellent bendability and optical characteristics even when irradiated with ultraviolet rays having a large accumulated light amount.
Examples of the alkyl (meth) acrylate having an alkyl group include butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, methyl (meth) acrylate, ethyl (meth) acrylate, hexyl (meth) acrylate, octyl (meth) acrylate, isooctyl (meth) acrylate, lauryl (meth) acrylate, isononyl (meth) acrylate, isodecyl (meth) acrylate, tridecyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, stearyl (meth) acrylate, and behenyl (meth) acrylate. The alkyl (meth) acrylate may be used alone or in combination of two or more.
The content of the structural unit derived from the alkyl (meth) acrylate having an alkyl group is preferably 50% by mass or more, or 60% by mass or more, or 70% by mass or more, or 99% by mass or less, or 97% by mass or less, or 90% by mass or less, relative to the total structural units of the (meth) acrylic polymer.
The (meth) acrylic polymer preferably contains, in the structural unit derived from the above alkyl (meth) acrylate: structural units derived from alkyl (meth) acrylates (hereinafter, sometimes referred to as "low Tg monomers") having a glass transition temperature of-40 ℃ or less of the homopolymer, and structural units derived from alkyl (meth) acrylates (hereinafter, sometimes referred to as "high Tg monomers") having a glass transition temperature of more than 0 ℃ of the homopolymer. By forming the 1 st adhesive layer 21 and/or the 2 nd adhesive layer 22 using an adhesive composition containing such a (meth) acrylic polymer, it is easy to obtain a laminate 1, 2 having excellent bendability and optical characteristics even when irradiated with ultraviolet rays having a large cumulative light amount. One or two or more kinds of low Tg monomers and high Tg monomers may be used, respectively. The glass transition temperature of the homopolymer of the alkyl (meth) acrylate may be, for example, a value reported in the literature such as POLYMER HANDBOOK (Wiley-Interscience).
The (meth) acrylic polymer may further contain a structural unit derived from an alkyl (meth) acrylate (hereinafter, sometimes referred to as "medium Tg monomer") having a glass transition temperature of more than-40 ℃ and 0 ℃ or less of a homopolymer. One or two or more of the medium Tg monomers may be used.
The glass transition temperature of the low Tg monomer may be-45℃or lower, or-50℃or lower. The content of the structural unit derived from the low Tg monomer may be, for example, 10 mass% or more, or 30 mass% or more, or 40 mass% or more, and 95 mass% or less, or 80 mass% or less, or 60 mass% or less, with respect to the total structural units of the (meth) acrylic polymer.
The glass transition temperature of the high Tg monomer may be 5℃or more, or 10℃or more, and may be 100℃or less, or 50℃or less, or 30℃or less. The content of the structural unit derived from the high Tg monomer may be, for example, 1 mass% or more, or 3 mass% or more, or 5 mass% or more, and may be 20 mass% or less, or 15 mass% or less, or 10 mass% or less, with respect to the total structural units of the (meth) acrylic polymer.
The (meth) acrylic polymer may contain structural units derived from monomers having reactive functional groups. Examples of the reactive functional group include: functional groups capable of forming covalent bonds by reacting with other functional groups through irradiation treatment with active energy rays, heat treatment, or heat moisture treatment. The heated moisture treatment is a treatment of contacting water or steam in a high temperature environment (for example, a temperature of 80 ℃) and may be a humidification treatment in a high temperature environment. Examples of the reactive functional group include a hydroxyl group, a carboxyl group, an amino group, an epoxy group, and an amide group.
Examples of the monomer having a reactive functional group include:
(meth) acrylic esters having a hydroxyl group such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 3-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 2- (2-hydroxyethoxy) ethyl (meth) acrylate, 2-chloro-2-hydroxypropyl (meth) acrylate, 3-chloro-2-hydroxypropyl (meth) acrylate, diethylene glycol mono (meth) acrylate;
ethylenically unsaturated carboxylic acids such as (meth) acrylic acid, crotonic acid, maleic acid, itaconic acid, citraconic acid, and β -carboxyethyl (meth) acrylate;
Amino group-containing (meth) acrylates such as aminoethyl (meth) acrylate, N-butylaminoethyl (meth) acrylate, dimethylaminopropyl (meth) acrylate, and N, N-dimethylaminoethyl (meth) acrylate;
(meth) acrylic esters having an epoxy group such as (3, 4-epoxycyclohexyl) methyl (meth) acrylate and glycidyl (meth) acrylate;
(meth) acrylic acid esters having an amide group such as (meth) acrylamide, N-dimethyl (meth) acrylamide and N-hydroxymethyl (meth) acrylamide;
monomers having a heterocyclic group such as (meth) acryloylmorpholine, vinylcaprolactam, N-vinyl-2-pyrrolidone, vinylpyridine, tetrahydrofurfuryl (meth) acrylate, and the like;
etc. The monomer having a reactive functional group may be used alone or in combination of two or more.
The content of the structural unit derived from the monomer having a reactive functional group is preferably 2 mass% or less, or may be less than 2 mass%, or may be 1 mass% or less, with respect to the total structural units of the (meth) acrylic polymer. The (meth) acrylic polymer may contain structural units derived from monomers having reactive functional groups. By forming the 1 st adhesive layer 21 and/or the 2 nd adhesive layer 22 using a (meth) acrylic polymer having a reduced content of structural units derived from a monomer having a reactive functional group, it is easy to obtain a laminate 1, 2 having excellent bendability and optical characteristics even when irradiated with ultraviolet rays having a large cumulative light amount.
The (meth) acrylic polymer may contain a monofunctional (meth) acrylic monomer having an alkoxy group, or the like.
Examples of the alkoxy group contained in the monofunctional (meth) acrylic monomer include: methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, sec-butoxy, tert-butoxy and the like. Examples of monofunctional (meth) acrylic monomers having an alkoxy group include ethoxyethoxyethoxyethyl acrylate (EOEOEA), nonylphenol EO modified acrylate [ NP (EO) 8A ], and the like. The monofunctional (meth) acrylic monomer may be used alone or in combination of two or more.
The content of the structural unit derived from the monofunctional (meth) acrylic monomer is preferably 1 mass% or more, or may be 2 mass% or more, or may be 10 mass% or more, or may be 20 mass% or more, or may be 30 mass% or more, or may be 50 mass% or less, or may be 40 mass% or less, relative to the total structural units of the (meth) acrylic polymer.
The (meth) acrylic polymer is obtained by mixing the above monomers, adding a polymerization initiator, and the like, and polymerizing the monomers. The polymerization method is not particularly limited, and known polymerization methods such as solution polymerization, bulk polymerization, emulsion polymerization, and photopolymerization may be mentioned. The (meth) acrylic polymer may be a random copolymer, a block copolymer, or a graft copolymer.
The polymerization initiator may be selected according to the polymerization method, and examples thereof include: cationic polymerization initiators or radical polymerization initiators. In the case where the polymerization method is photopolymerization, a photopolymerization initiator may be used. One or two or more photopolymerization initiators may be used.
When two or more photopolymerization initiators are used, it is preferable to use a 1 st photopolymerization initiator having a maximum absorption wavelength of 250nm or less and a 2 nd photopolymerization initiator having a maximum absorption wavelength of more than 250nm and 300nm or less. Since the polymerization reaction of the (meth) acrylic polymer can be sufficiently performed by including the 1 st photopolymerization initiator and the 2 nd photopolymerization initiator in the polymerization initiator, the physical properties of the 1 st adhesive layer 21 and/or the 2 nd adhesive layer 22 formed using the (meth) acrylic polymer can be suppressed from being lowered. The maximum absorption wavelength of the photopolymerization initiator can be measured by the method described in examples described later.
As the 1 st photopolymerization initiator, there may be mentioned ketone photopolymerization initiators such as 1-hydroxycyclohexyl benzophenone, 2-hydroxy-2-methylpropenyl acetone, (2, 4-cyclopentadien-1-yl) [ (1-methylethyl) benzene ] -Fe (II) hexafluorophosphate and the like.
Examples of the 2 nd photopolymerization initiator include a benzoic acid ester type photopolymerization initiator such as a mixture of 2-hydroxy-4' - (2-hydroxyethoxy) -2-methylpropaneketone and 2- [ 2-oxo-2-phenyl-acetoxy-ethoxy ] -ethyl oxy-phenyl-acetate and 2- [ 2-hydroxy-ethoxy ] -ethyl-oxy-phenyl-acetate.
The weight average molecular weight (Mw) of the (meth) acrylic polymer is preferably 60 ten thousand or more, and may be 70 ten thousand or more, or 90 ten thousand or more, or 200 ten thousand or less, or 180 ten thousand or less, and preferably 150 ten thousand or less. The weight average molecular weight may be determined by Gel Permeation Chromatography (GPC).
The adhesive composition may contain one or more of the above (meth) acrylic polymers, and may further contain a (meth) acrylic compound and a polymerization initiator.
The adhesive composition preferably contains two or more (meth) acrylic polymers. The content of the (meth) acrylic polymer may be, for example, 70 mass% or more, 80 mass% or more, 90 mass% or more, 95 mass% or more, 99 mass% or less, 98 mass% or less, or 97 mass% or less, based on the solid content of the adhesive composition. In the case where the adhesive composition contains two or more (meth) acrylic polymers, the content of the (meth) acrylic polymers is the total amount thereof.
Examples of the (meth) acrylic compound include the above-mentioned alkyl (meth) acrylate having an alkyl group having 1 to 24 carbon atoms. The (meth) acrylic compound contained in the adhesive composition may be one kind or two or more kinds. The content of the (meth) acrylic compound with respect to the solid content of the adhesive composition is, for example, 0.1 mass% or more, or 0.5 mass% or more, or 1.0 mass% or more, or 1.5 mass% or more, or 10.0 mass% or less, or 5.0 mass% or less, or 3.0 mass% or less.
The alkyl group of the alkyl (meth) acrylate having an alkyl group preferably has 1 to 15 carbon atoms, may be 2 to 10 carbon atoms, and is preferably at least one of butyl (meth) acrylate and 2-ethylhexyl (meth) acrylate. The content of the alkyl (meth) acrylate is, for example, 0.1 mass% or more, or 0.5 mass% or more, or 1.0 mass% or more, or 1.5 mass% or more, or 10.0 mass% or less, or 5.0 mass% or less, or 3.0 mass% or less, based on the solid content of the adhesive composition.
Examples of the polymerization initiator contained in the adhesive composition include a photopolymerization initiator, a thermal polymerization initiator, and the like. One or two or more kinds of polymerization initiators may be used. The content of the polymerization initiator may be, for example, 0.1 mass% or more, or 1 mass% or more, and may be 10 mass% or less, or 5 mass% or less, relative to the solid content of the adhesive composition.
Examples of the photopolymerization initiator include: 1-hydroxycyclohexyl benzophenone, 2-hydroxy-2-methylpropenyl acetone, (2, 4-cyclopentadien-1-yl) [ (1-methylethyl) benzene ] -Fe (II) hexafluorophosphate, 2-hydroxy-4' - (2-hydroxyethoxy) -2-methylpropenyl acetone, a mixture of oxy-phenyl-acetic acid 2- [ 2-oxo-2-phenyl-acetoxy-ethoxy ] -ethyl ester and oxy-phenyl-acetic acid 2- [ 2-hydroxy-ethoxy ] -ethyl ester, benzildimethyl ketal, 1-hydroxycyclohexyl benzophenone, and the like.
Examples of the thermal polymerization initiator include azo compounds, organic peroxides, and inorganic peroxides. 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-methoxypentanenitrile), dimethyl 2,2' -azobis (2-methylpropionate), 4' -azobis (4-cyanovaleric acid), 2' -azobis (2-hydroxymethylpropionitrile), 2' -azobis [2- (2-imidazolin-2-yl) propane ], and the like.
Examples of the organic peroxide include: benzoyl peroxide, t-butyl peroxybenzoate, cumene hydroperoxide, diisopropyl peroxydicarbonate, di-n-propyl peroxydicarbonate, di (2-ethoxyethyl) peroxydicarbonate, t-butyl peroxyneodecanoate, t-butyl peroxypivalate, (3, 5-trimethylhexanoyl) peroxide, dipropyl peroxide, diacetyl peroxide, and the like.
Examples of the inorganic peroxide include: potassium persulfate, ammonium persulfate, hydrogen peroxide, and the like.
The adhesive composition may contain additives such as a crosslinking agent, a silane coupling agent, a crosslinking catalyst, a weather-resistant stabilizer, a tackifier, a plasticizer, a softener, a dye, a pigment, an inorganic filler, light scattering particles, an antistatic agent such as an ionic compound, and the like.
Examples of the crosslinking agent include: isocyanate-based crosslinking agents, epoxy-based crosslinking agents, amine-based crosslinking agents, melamine-based crosslinking agents, aziridine-based crosslinking agents, hydrazine-based crosslinking agents, aldehyde-based crosslinking agents, oxazoline-based crosslinking agents, metal alkoxide-based crosslinking agents, metal chelate-based crosslinking agents, metal salt-based crosslinking agents, ammonium salt-based crosslinking agents, and the like.
As the silane coupling agent, a silicone compound having at least one alkoxysilyl group in a molecule is exemplified. Examples of the silane coupling agent include:
Silicon compounds containing polymerizable unsaturated groups such as vinyltrimethoxysilane, vinyltriethoxysilane, and methacryloxypropyl trimethoxysilane;
silicon compounds having an epoxy structure such as 3-glycidoxypropyl trimethoxysilane and 2- (3, 4-epoxycyclohexyl) ethyl trimethoxysilane;
mercapto-containing silicon compounds such as 3-mercaptopropyl trimethoxysilane, 3-mercaptopropyl triethoxysilane, and 3-mercaptopropyl dimethoxymethylsilane;
amino-containing silicon compounds such as 3-aminopropyl trimethoxysilane, N- (2-aminoethyl) -3-aminopropyl trimethoxysilane and N- (2-aminoethyl) -3-aminopropyl methyldimethoxysilane;
and condensates of 3-chloropropyltrimethoxysilane, 3-isocyanatopropyltriethoxysilane, or at least one of them with an alkyl-containing silicon compound such as methyltriethoxysilane, ethyltriethoxysilane, methyltrimethoxysilane, ethyltrimethoxysilane, etc.
The adhesive composition can be prepared by mixing a (meth) acrylic polymer, a (meth) acrylic compound, a polymerization initiator, an additive, and the like. The adhesive composition may form the 1 st adhesive layer 21 or the 2 nd adhesive layer 22 by coating itself or an organic solvent dilution of the adhesive composition on the substrate and drying it. Examples of the method for applying the adhesive composition or the organic solvent diluent thereof include: bar coating, knife coating, roll coating, knife coating, die coating, gravure coating, and the like.
The 1 st adhesive layer 21 or the 2 nd adhesive layer 22 may be formed by subjecting the adhesive composition applied to the substrate to irradiation treatment with active energy rays, heating treatment, or the like. The active energy ray includes ultraviolet rays, electron beams, and the like, and ultraviolet rays are preferable.
(front layer)
When the laminate 1 or 2 is applied to a display device, the front layer 11 may be a front panel constituting the outermost surface on the viewing side of the display device, or may be a 3 rd base layer of a protective film including the 3 rd base layer and the 1 st adhesive layer 21. The protective film is generally provided in a peelable manner to the polarizing plate 30.
The front layer 11 may have a single-layer structure or a multi-layer structure. The thickness of the front layer 11 may be, for example, 10 μm or more, or 20 μm or more, or 30 μm or more, or 500 μm or less, or 200 μm or less, or 100 μm or less.
When the front layer 11 is a front panel, the front layer 11 may be a resin plate-like body (e.g., a resin plate, a resin film, etc.), or a glass plate-like body (e.g., a glass plate, a glass film, etc.). The resin plate-like body is not limited as long as it can transmit light. Examples of the resin constituting the resin plate-like body such as a resin film include: films formed from polymers such as cellulose triacetate, cellulose acetate butyrate, ethylene-vinyl acetate copolymers, cellulose propionate, cellulose butyrate, cellulose acetate propionate, polyesters, polystyrene, polyamides, polyetherimides, poly (meth) acrylic acid, polyimides, polyethersulfones, polysulfones, polyethylenes, polypropylenes, polymethylpentene, polyvinylchlorides, polyvinylidene chlorides, polyvinyl alcohols, polyvinyl acetals, polyetherketones, polyetheretherketones, polyethersulfones, polymethyl methacrylates, polyethylene terephthalates, polybutylene terephthalates, polyethylene naphthalates, polycarbonates, polyamideimides, and the like. These polymers may be used alone or in combination of two or more. From the viewpoint of improving strength and transparency, a resin film formed of a polymer such as polyimide, polyamide, or polyamideimide is preferable.
From the viewpoint of hardness, the resin plate-like body may be a 1 st base material layer having a coating layer such as a hard coat layer. The coating layer may be formed on one side or both sides of the 1 st base material layer. The 1 st base layer is the resin film described above.
The coating layer is preferably formed using a composition containing a monofunctional (meth) acrylic resin, a polyfunctional (meth) acrylic resin, a (meth) acrylic compound having a dendrimer structure, or the like, more preferably a composition containing a (meth) acrylic compound having a dendrimer structure. The coating may be a cured layer of an ultraviolet curable resin. Examples of the ultraviolet curable resin include: the (meth) acrylic resin described above; a silicone resin; a polyester resin; a urethane resin; an amide resin; epoxy resins, and the like.
To increase strength, the coating may contain additives. The additive is not particularly limited, and examples thereof include inorganic fine particles, organic fine particles, or a mixture thereof. In the case where the 1 st base material layer has the coating layers on both sides, the composition and thickness of each coating layer may be the same or different from each other.
The glass plate is preferably reinforced glass for display. By using a glass plate, a front panel having excellent mechanical strength and surface hardness can be formed.
In the case where the front layer 11 is the 3 rd base material layer of the protective film, the 3 rd base material layer may be a resin film. The resin film may be formed of, for example, a thermoplastic resin for forming a protective film as a protective layer described later.
From the viewpoint of flexibility, the front layer 11 preferably has a tensile elastic modulus of 2GPa to 10GPa, more preferably 3GPa to 9GPa, still more preferably 4GPa to 8GPa at a temperature of 60 ℃. The tensile elastic modulus can be measured at a temperature of 60℃using a tensile tester (AG-1S, manufactured by Shimadzu corporation).
(polarizing plate)
The polarizing plate 30 may include at least a linear polarizing layer. The polarizing plate 30 may be a linear polarizing plate (fig. 1) or a circular polarizing plate (fig. 2). The linear polarization plate has a protective layer 32 on one or both sides of the linear polarization layer 31. The protective layer 32 may be provided directly on one or both sides of the linear polarization layer 31, or may be provided via a bonding layer (adhesive layer or pressure-sensitive adhesive layer). As shown in fig. 1 and 2, the linear polarization plate preferably has a protective layer 32 at least on the front surface layer 11 side of the linear polarization layer 31.
As shown in fig. 2, the circularly polarizing plate includes a linearly polarizing layer 31 and a 1 st retardation layer 33 (retardation layer) in this order from the front layer 11 side. The circularly polarizing plate may have a linearly polarizing plate having a protective layer 32 on one or both sides of a linearly polarizing layer 31, and a 1 st phase difference layer 33. The 1 st retardation layer 33 may be a λ/4 retardation layer or a λ/4 retardation layer having inverse wavelength dispersibility.
The circularly polarizing plate may have a 2 nd retardation layer 34 in addition to the 1 st retardation layer 33. The 2 nd retardation layer 34 may be provided between the linear polarization layer 31 and the 1 st retardation layer 33, or may be provided between the 1 st retardation layer 33 and the back surface layer 15 as shown in fig. 2. The 2 nd retardation layer 34 is preferably a lambda/2 retardation layer or a positive C layer. The 1 st phase difference layer 33 and the 2 nd phase difference layer 34 may be laminated via the adhesive layer 38 (adhesive layer or pressure-sensitive adhesive layer).
As shown in fig. 2, in the case where the circular polarizing plate includes a linear polarizing plate, the linear polarizing plate may have a protective layer 32 on one side of the linear polarizing layer 31. In this case, the 1 st retardation layer 33 or the 2 nd retardation layer 34 may be provided on the side of the linearly polarizing layer 31 opposite to the protective layer 32 side via a bonding layer (adhesive layer or pressure-sensitive adhesive layer) 37.
(Linear polarization layer)
The linear polarization layer transmits linearly polarized light having a vibration plane orthogonal to an absorption axis when unpolarized light is incident thereon. The linear polarization layer may be a polyvinyl alcohol resin film (hereinafter, sometimes referred to as "PVA-based film") having iodine adsorbed and oriented, or may be a film including a liquid crystal linear polarization layer formed by applying a composition including a compound having absorption anisotropy and liquid crystal property to a base film. The compound having absorption anisotropy and liquid crystallinity may be a mixture of a dye having absorption anisotropy and a compound having liquid crystallinity, or may be a dye having absorption anisotropy and liquid crystallinity.
Examples of the linearly polarizing layer of the PVA film include those obtained by dyeing a PVA film such as a polyvinyl alcohol film, a partially formalized polyvinyl alcohol film, or an ethylene-vinyl acetate copolymer partially saponified film with iodine and stretching the same. If necessary, the PVA-based film obtained by adsorbing and orienting iodine by dyeing treatment may be treated with an aqueous boric acid solution, and then a washing step of washing away the aqueous boric acid solution may be performed. The steps may be performed by a known method.
Polyvinyl alcohol resins (hereinafter, sometimes referred to as "PVA-based resins") can be produced by saponifying polyvinyl acetate resins. The polyvinyl acetate resin may be a copolymer of vinyl acetate and another monomer copolymerizable with vinyl acetate, in addition to polyvinyl acetate which is a homopolymer of vinyl acetate. Examples of the other monomer copolymerizable with vinyl acetate include: unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, acrylamides having an ammonium group, and the like.
The saponification degree of the PVA-based resin is usually about 85 to 100 mol%, preferably 98 mol% or more. The PVA-based resin may be modified, and for example, polyvinyl formal, polyvinyl acetal, or the like modified with aldehydes may be used. The average polymerization degree of the PVA-based resin is usually about 1,000 to 10,000, preferably about 1,500 to 5,000. The saponification degree and the average polymerization degree of the PVA based resin can be determined based on JIS K6726 (1994). When the average polymerization degree is less than 1000, it is difficult to obtain preferable polarization properties, and when it exceeds 10000, film processability may be poor.
The method for producing the linear polarization layer as the PVA-based film may include: preparing a base film, applying a solution of a resin such as a PVA-based resin to the base film, and drying the solution to remove the solvent, thereby forming a resin layer on the base film. The primer layer may be formed in advance on the side of the base film on which the resin layer is to be formed. As the base film, use can be made of: a film of a resin material described as a thermoplastic resin used for forming a protective film as a protective layer described later is used. Examples of the material of the primer layer include a resin obtained by crosslinking a hydrophilic resin used for the linear polarizing layer.
Next, the amount of solvent such as moisture in the resin layer is adjusted as needed, then the base film and the resin layer are uniaxially stretched, and then the resin layer is dyed with iodine, so that the iodine is adsorbed to the resin layer and oriented. Next, the resin layer having iodine adsorbed and oriented is treated with an aqueous boric acid solution as needed, and then a washing step of washing away the aqueous boric acid solution is performed. Thus, a resin layer having iodine adsorbed and oriented, that is, a PVA-based film serving as a linearly polarizing layer was produced. The steps may be performed by a known method.
The amount of boric acid in the aqueous solution containing boric acid to which iodine is adsorbed and which is subjected to the treatment of the oriented PVA-based film or resin layer is usually about 2 to 15 parts by mass, preferably 5 to 12 parts by mass, per 100 parts by mass of water. The aqueous boric acid-containing solution preferably contains potassium iodide. The amount of potassium iodide in the aqueous boric acid-containing solution is usually about 0.1 to 15 parts by mass, preferably about 5 to 12 parts by mass, per 100 parts by mass of water. The immersion time in the aqueous solution containing boric acid is usually about 60 to 1, 200 seconds, preferably about 150 to 600 seconds, and more preferably about 200 to 400 seconds. The temperature of the aqueous solution containing boric acid is usually 50℃or higher, preferably 50 to 85℃and more preferably 60 to 80 ℃.
The uniaxial stretching of the PVA-based film, the base film, and the resin layer may be performed before dyeing, during boric acid treatment after dyeing, or in a plurality of stages. The PVA-based film, the base film, and the resin layer may be uniaxially stretched in the MD direction (film conveyance direction), and in this case, stretching may be performed uniaxially between rolls having different peripheral speeds, or stretching may be performed uniaxially using a hot roll. In addition, the PVA-based film, the base film, and the resin layer may be uniaxially stretched in the TD direction (the direction perpendicular to the film conveying direction), and in this case, a so-called tenter method may be used. The stretching may be a dry stretching performed in the atmosphere, or a wet stretching performed in a state where the PVA-based film or the resin layer is swollen by a solvent. In order to exhibit the performance of the linearly polarizing layer, the stretching ratio is 4 times or more, preferably 5 times or more, and particularly preferably 5.5 times or more. The upper limit of the stretching ratio is not particularly limited, but is preferably 8 times or less from the viewpoint of suppressing breakage or the like.
The linear polarization layer produced by the production method using the base material film can be obtained by peeling the base material film after laminating the protective layer. According to this method, further thinning of the linear polarization layer can be achieved.
The thickness of the linear polarization layer as the PVA-based film is preferably 1 μm or more, may be 2 μm or more, may be 5 μm or more, and is preferably 30 μm or less, more preferably 15 μm or less, may be 10 μm or less, and may be 8 μm or less.
Examples of the film including the liquid crystal linear polarizing layer include: a linearly polarizing layer obtained by applying a composition containing a dye having liquid crystallinity and absorption anisotropy, or a composition containing a dye having absorption anisotropy and a polymerizable liquid crystal to a substrate film. The liquid crystal linear polarization layer may be a cured product of a polymerizable liquid crystal compound, or may include an alignment layer. The alignment layer includes an alignment layer included in a retardation layer described later. The film including the liquid crystal linear polarization layer may be a liquid crystal linear polarization layer, or may have a laminated structure of a liquid crystal linear polarization layer and a base film. Examples of the base film include: a film of a resin material described as a thermoplastic resin used for forming a protective film as a protective layer described later is used. Examples of the film including the liquid crystal linear polarization layer include: a polarizing layer described in japanese patent application laid-open publication No. 2013-33249 and the like.
The total thickness of the base film and the linearly polarizing layer formed as described above is preferably small, but if too small, strength tends to be low and workability tends to be poor, and therefore, it is usually 20 μm or less, preferably 5 μm or less, and more preferably 0.5 to 3 μm.
(protective layer)
Examples of the protective layer include: a protective film which is a film formed of a thermoplastic resin excellent in transparency, mechanical strength, thermal stability, moisture barrier property, isotropy, stretchability, and the like; an overcoat layer formed from a composition excellent in solvent resistance, transparency, mechanical strength, thermal stability, masking properties, isotropy, and the like. The protective film is preferably laminated on the linear polarization layer 31 via a lamination layer, and the overcoat layer is preferably laminated so as to directly contact the linear polarization layer 31.
Specific examples of the thermoplastic resin for forming the protective film include: cellulose resins such as cellulose triacetate; polyester resins such as polyethylene terephthalate and polyethylene naphthalate; polyether sulfone resin; polysulfone resin; a polycarbonate resin; polyamide resins such as nylon and aromatic polyamide; polyimide resin; polyolefin resins such as polyethylene, polypropylene and ethylene-propylene copolymers; a cyclic polyolefin resin having a ring system and a norbornene structure (also referred to as a norbornene-based resin); (meth) acrylic resins; a polyarylate resin; a polystyrene resin; polyvinyl alcohol resins, and mixtures thereof. The thickness of the protective film is preferably 3 μm or more, more preferably 5 μm or more, and preferably 50 μm or less, more preferably 30 μm or less.
The overcoating layer may be formed, for example, by coating a material (composition) for forming the overcoating layer on the linearly polarizing layer. Examples of the material constituting the overcoat layer include: as the photocurable resin, the water-soluble polymer, etc., a (meth) acrylic resin, a polyvinyl alcohol resin, a polyamide epoxy resin, etc. can be used. The thickness of the overcoat layer may be, for example, 0.1 μm or more and 10 μm or less.
The protective layer may have an antireflection property, an antiglare property, a hard coat property, or the like (hereinafter, a protective layer having such a property may be referred to as a "functional protective layer"). In the case where the protective layer is not a functional protective layer, a surface functional layer such as an antireflection layer, an antiglare layer, or a hard coat layer may be provided on one surface of the linear polarizing plate. The surface functional layer is preferably provided in direct contact with the protective layer. The surface functional layer is preferably provided on the side of the protective layer opposite to the side of the linearly polarized layer.
(No. 1 phase difference layer, no. 2 phase difference layer)
The 1 st retardation layer and the 2 nd retardation layer (hereinafter, both may be collectively referred to as "retardation layers") may be stretched films, or may be retardation layers including cured layers of polymerizable liquid crystal compounds, and are preferably cured layers.
When the retardation layer is a stretched film, a stretched film known in the art can be used as the stretched film, and a stretched film to which a retardation is imparted by uniaxially stretching or biaxially stretching a resin film can be used. As the resin film, a cellulose film such as cellulose triacetate and cellulose diacetate, a polyester film such as polyethylene terephthalate, polyethylene isophthalate and polybutylene terephthalate, an acrylic resin film such as polymethyl (meth) acrylate and polyethyl (meth) acrylate, a polycarbonate film, a polyethersulfone film, a polysulfone film, a polyimide film, a polyolefin film, a polynorbornene film, and the like can be used, but are not limited thereto.
When the retardation layer is a stretched film, the thickness of the retardation layer is usually 5 μm or more and 200 μm or less, preferably 10 μm or more and 80 μm or less, and more preferably 40 μm or less.
When the retardation layer includes the cured layer, a known polymerizable liquid crystal compound can be used as the polymerizable liquid crystal compound. The polymerizable liquid crystal compound has at least one polymerizable group and has liquid crystallinity.
The type of the polymerizable liquid crystal compound is not particularly limited, and a rod-like liquid crystal compound, a discotic liquid crystal compound, and a mixture thereof may be used. The cured layer formed by polymerizing the polymerizable liquid crystal compound can exhibit a phase difference by curing the polymerizable liquid crystal compound in a state of being oriented in an appropriate direction. When the rod-shaped polymerizable liquid crystal compound is oriented horizontally or vertically with respect to the planar direction of the laminate, the optical axis of the polymerizable liquid crystal compound coincides with the long axis direction of the polymerizable liquid crystal compound. When the disk-shaped polymerizable liquid crystal compound is aligned, the optical axis of the polymerizable liquid crystal compound is present in a direction perpendicular to the disk surface of the polymerizable liquid crystal compound. As the rod-shaped polymerizable liquid crystal compound, for example, a rod-shaped polymerizable liquid crystal compound described in JP-A-11-513019 (claim 1, etc.) can be suitably used. As the discotic polymerizable liquid crystal compound, discotic polymerizable liquid crystal compounds described in japanese patent application laid-open nos. 2007-108732 (paragraphs [0020] to [0067] and the like) and 2010-244038 (paragraphs [0013] to [0108] and the like) can be suitably used.
The polymerizable group of the polymerizable liquid crystal compound is a group involved in polymerization reaction, and is preferably a photopolymerizable group. Photopolymerizable groups refer to: the group that participates in the polymerization reaction may be a reactive radical, an acid, or the like generated by the photopolymerization initiator. Examples of the polymerizable group include vinyl, vinyloxy, 1-chlorovinyl, isopropenyl, 4-vinylphenyl, (meth) acryloyloxy, oxiranyl, oxetanyl, styryl, and allyl. Among them, (meth) acryloyloxy, ethyleneoxy and oxetanyl groups are preferred, and acryloyloxy is more preferred. The liquid crystallinity of the polymerizable liquid crystal compound may be either thermotropic liquid crystal or lyotropic liquid crystal, and if the thermotropic liquid crystal is classified according to order, it may be nematic liquid crystal or smectic liquid crystal. When two or more polymerizable liquid crystal compounds are used in combination to form a cured layer of the polymerizable liquid crystal compound, at least one of them preferably has two or more polymerizable groups in the molecule.
In the case where the retardation layer includes the cured layer, the retardation layer may include an alignment layer. The alignment layer has an alignment regulating force for aligning the polymerizable liquid crystal compound in a desired direction. The alignment layer may be a vertical alignment layer that aligns the molecular axis of the polymerizable liquid crystal compound vertically with respect to the planar direction of the laminate, a horizontal alignment layer that aligns the molecular axis of the polymerizable liquid crystal compound horizontally with respect to the planar direction of the laminate, or an oblique alignment layer that aligns the molecular axis of the polymerizable liquid crystal compound obliquely with respect to the planar direction of the laminate. When the retardation layer includes two or more alignment layers, the alignment layers may be the same or different from each other.
As the alignment layer, preferable are: the alignment layer has a solvent resistance which is not dissolved by coating or the like of a composition for forming a liquid crystal layer containing a polymerizable liquid crystal compound, and has a heat resistance to a heat treatment for removing a solvent and aligning the polymerizable liquid crystal compound. As the alignment layer, there may be mentioned: an alignment polymer layer formed of an alignment polymer, a photo-alignment polymer layer formed of a photo-alignment polymer, and a trench alignment layer having a concave-convex pattern and a plurality of trenches (trenches) on the layer surface.
The cured product layer may be formed by applying a composition for forming a retardation layer containing a polymerizable liquid crystal compound, a solvent, and various additives as needed to an alignment layer, forming a coating film, and solidifying (curing) the coating film. Alternatively, the cured product layer may be formed by coating the composition on a base film, forming a coating film, and stretching the coating film together with the base film. The composition may contain a polymerization initiator, a reactive additive, a leveling agent, a polymerization inhibitor, and the like in addition to the polymerizable liquid crystal compound and the solvent. The polymerizable liquid crystal compound, solvent, polymerization initiator, reactive additive, leveling agent, polymerization inhibitor, etc. may be any known ones.
As the base film, a film formed of a resin material can be used, and examples thereof include: a film of a resin material described as a thermoplastic resin for forming a protective film as the protective layer is used. The thickness of the base film is not particularly limited, but is preferably 1 to 300 μm or less, more preferably 20 to 200 μm, and even more preferably 30 to 120 μm in view of handling properties such as strength and handling properties. The base film may be introduced into the laminate together with the cured layer of the polymerizable liquid crystal compound, or the base film may be peeled off, and only the cured layer of the polymerizable liquid crystal compound, or the cured layer and the alignment layer may be introduced into the laminate.
(Back layer)
The back layer may be a diaphragm or a back plate which is a member disposed on the side of the display device opposite to the viewing side. The back panel is, for example, a touch sensor panel, a display element, a combination thereof, or the like.
The thickness of the back surface layer may be, for example, 5 μm or more, or 10 μm or more, or 30 μm or more, or 50 μm or more, or 2000 μm or less, or 1000 μm or less, or 500 μm or less.
In the case where the back surface layer is a separator, the separator is provided in a releasable manner to the 2 nd adhesive layer, and the surface of the 2 nd adhesive layer is covered with a protection. The separator has a 2 nd base material layer and a release treatment layer. The 2 nd base material layer may be a resin film. The resin film may be formed of, for example, a thermoplastic resin for forming a protective film as the protective layer described above. The release treatment layer may be a known release treatment layer, and examples thereof include a layer formed by applying a release agent such as a fluorine compound or a silicone compound to a base layer.
The touch sensor panel may detect a position touched by a user with a finger or the like. The touch sensor panel included in the back layer may be formed as a touch sensor panel of, for example, a resistive film type, a capacitive coupling type, a photosensor type, an ultrasonic type, an electromagnetic induction coupling type, a surface elastic wave type, or the like.
In the case where the back surface layer includes a display element, the display element is not particularly limited, and an organic EL display element is preferable. The organic EL display element may have, for example, a light-emitting layer, an electrode, and the like.
From the viewpoint of flexibility, the tensile elastic modulus of the back surface layer at a temperature of 60 ℃ is preferably 2GPa or more and 10GPa or less, more preferably 3GPa or more and 9GPa or less, and still more preferably 4GPa or more and 8GPa or less. The tensile elastic modulus can be measured at a temperature of 60℃using a tensile tester (AG-1S, manufactured by Shimadzu corporation).
(bonding layer)
The bonding layer is an adhesive layer or an adhesive layer. When the bonding layer is an adhesive layer, the bonding layer is an adhesive layer formed using an adhesive. The adhesive exhibits adhesiveness by adhering itself to an adherend, and is called a so-called pressure-sensitive adhesive. The adhesive may be the adhesive composition described above, or a known adhesive excellent in optical transparency may be used. As the known adhesive, for example, an adhesive containing a base polymer such as an acrylic polymer, a urethane polymer, a silicone polymer, or a polyvinyl ether can be used. The adhesive may be an active energy ray-curable adhesive, a thermosetting adhesive, or the like. Among these, an acrylic resin excellent in transparency, adhesion, removability (reworkability), weather resistance, heat resistance, and the like is preferable as the binder of the base polymer. The pressure-sensitive adhesive layer is preferably composed of a pressure-sensitive adhesive containing a (meth) acrylic resin, a crosslinking agent, and a silane coupling agent, and may contain other components.
The thickness of the pressure-sensitive adhesive layer is not particularly limited, and may be preferably 5 μm or more, or may be 10 μm or more, or may be 15 μm or more, or may be 20 μm or more, or may be 25 μm or more, or may be 300 μm or less, or may be 250 μm or less, or may be 100 μm or less, or may be 50 μm or less.
Examples of the aqueous adhesive include: an adhesive obtained by dissolving or dispersing a polyvinyl alcohol resin in water. The drying method in the case of using the aqueous adhesive is not particularly limited, and for example, a method of drying using a hot air dryer or an infrared dryer may be employed.
Examples of the active energy ray-curable adhesive include: solvent-free active energy ray-curable adhesives containing curable compounds that cure by irradiation with active energy rays such as ultraviolet rays, visible rays, electron beams, and X-rays. The use of the solvent-free active energy ray-curable adhesive can improve interlayer adhesion.
The active energy ray-curable adhesive preferably contains either or both of a cationically polymerizable curable compound and a radically polymerizable curable compound from the viewpoint of exhibiting good adhesion. The active energy ray-curable adhesive may further include a cationic polymerization initiator such as a photo-cationic polymerization initiator or a radical polymerization initiator for initiating the curing reaction of the curable compound.
The thickness of the adhesive layer is preferably 0.1 μm or more, but may be 0.5 μm or more, and preferably 10 μm or less, but may be 5 μm or less.
(display device)
The display device includes laminated bodies 1, 2. The display device is preferably a flexible display that can be bent so that the front layer 11 is inward. The bendable means that the number of bending times based on a high temperature bending test described later is less than 10 ten thousand times, and the bendable is capable of bending without generating bubbles or dropping of the adhesive in the laminated bodies 1, 2.
In the laminated body 1, 2 included in the display device, the front layer 11 is preferably a front panel, and the back layer 15 includes at least one of a touch sensor panel and a display element. The display device is not particularly limited, and is preferably an organic EL display device.
The display device may be a mobile terminal such as a smart phone or a tablet, or may be a television, a digital photo frame, an electronic sign, a measuring instrument, an office machine, a medical instrument, an electronic computer, or the like.
Examples
Hereinafter, the present invention will be described more specifically by way of examples, but the present invention is not limited to these examples.
[ measurement of thickness ]
The thickness was measured using a contact film thickness measuring apparatus (ZC-101, nikon, inc.).
[ measurement of the line shrinkage (D1 or D2) of the reference adhesive layer after UV irradiation ]
(production of reference pressure-sensitive adhesive sheet)
A reference pressure-sensitive adhesive sheet having a layer structure of separator a/reference pressure-sensitive adhesive layer/separator B was obtained by the same procedure as in the production of the pressure-sensitive adhesive sheet described later except that the thickness of the reference pressure-sensitive adhesive layer was set to 0.6mm using the pressure-sensitive adhesive composition described later. So that the cumulative light quantity becomes 100J/cm 2 The illuminance was 100mW/cm 2 (UVreference) the reference pressure-sensitive adhesive sheet was irradiated with Ultraviolet (UV) light.
Cutting the UV-irradiated reference adhesive sheet into pieces having a width of 20mm×a length of 20mm, separating the separator, and separating the obtained reference adhesive layer from the viscoelasticity measuring device(MCR-301, anton Paar Co.) and confirming the thickness T of the reference adhesive layer immediately after the application of 1N load and 350% strain 0 [μm]. Then, the thickness T of the reference adhesive layer after the state of the applied load and strain was maintained for 10 hours was confirmed 10 [μm]. Using the resulting thickness T 0 T and T 10 And the linear shrinkage (D1 or D2) is determined according to the following formula.
Linear shrinkage (D1 or D2) [%]＝{1-(T1 0 /T 0 )}×100
[ measurement of gel fraction of reference adhesive layer after UV irradiation ]
So that the cumulative light quantity becomes 100J/cm 2 The illuminance was 100mW/cm 2 (UVreference) Ultraviolet (UV) irradiation was performed on the reference pressure-sensitive adhesive sheet including the above-mentioned reference pressure-sensitive adhesive layer. After cutting the UV-irradiated reference pressure-sensitive adhesive sheet to a width of 80mm×a length of 80mm, the reference pressure-sensitive adhesive layer contained in the cut reference pressure-sensitive adhesive sheet was used as a sample. The test specimen was wrapped with a polyester mesh (mesh size 200), and its mass was measured with a precision balance. The mass M1 of the sample alone was calculated by subtracting the mass of the net alone from the weighed mass.
Next, the base adhesive layer wrapped with the polyester net was immersed in ethyl acetate at room temperature (23 ℃) for 72 hours, and the sample was taken out (hereinafter, the sample after the taking out was referred to as "sample after immersion"). The immersed sample was air-dried at 23℃and 50% relative humidity for 24 hours, and further dried in an oven at 120℃for 4 hours, and then the mass thereof was measured using a precision balance. The mass M2 of the sample after only dipping was calculated by subtracting the individual mass of the net from the weighed mass. Gel fraction was determined from mass M1 and mass M2 according to the following formula.
Gel fraction [% ] × (M2/M1) ×100
[ measurement of glass transition temperature ]
The separator was peeled off from an adhesive sheet described later to obtain an adhesive layer. The glass transition temperature of the obtained adhesive layer was measured using a Differential Scanning Calorimeter (DSC) "EXSTAR DSC6000" manufactured by SII Nanotechnology, inc., under a nitrogen atmosphere at a temperature ranging from-80 to 50℃and a heating rate of 10℃per minute.
[ measurement of maximum absorption wavelength ]
The maximum absorption wavelength of the polymerization initiator is determined as follows: the solution obtained by dissolving the polymerization initiator in methyl ethyl ketone was placed in a quartz cell, and the visible ultraviolet spectrum having a wavelength of 200nm to 600nm was measured and determined by using an ultraviolet-visible spectrophotometer "UV-2450" manufactured by Shimadzu corporation.
[ test for light-bending resistance ]
The laminate obtained in examples and comparative examples was cut out to have a width of 10mm×a length of 100mm using a super cutter as a test piece. The test piece was wound around a cylindrical mandrel (spindle) using a bending resistance tester (cylindrical spindle method) manufactured by TP technology and company such that the back surface layer side of the test piece was inside. In this state, the cumulative light amount was set to 100J/cm by an ultraviolet ray tester (CT UVT 15W UVB lamp manufactured by Migo electric Co., ltd.) 2 After ultraviolet light was irradiated to the system of (a), the presence or absence of occurrence of air bubbles in the 1 st adhesive layer or the 2 nd adhesive layer and the presence or absence of peeling between the 2 nd adhesive layer and the back surface layer of the test piece were confirmed.
The above-described operations were performed by changing the diameter of the mandrel, and the minimum diameter of the mandrel when no air bubbles were generated in the 1 st adhesive layer or the 2 nd adhesive layer and no peeling was generated between the 1 st adhesive layer and the front layer was determined, and the evaluation was performed according to the following criteria. The smaller the minimum diameter of the mandrel determined, the more excellent the light bending resistance of the laminate.
A: the minimum diameter of the mandrel is determined to be 10mm or less.
B: the minimum diameter of the mandrel was determined to be in excess of 10mm.
[ light resistance test ]
The test piece was produced and irradiated with ultraviolet rays according to the procedure described in the weather-resistant bending test. The transmission b was measured using a colorimeter measuring device "V7100" manufactured by japan spectroscopic corporation for the test pieces before and after irradiation with ultraviolet light, and the absolute value of the change in the transmission b was calculated and evaluated according to the following criteria.
a: the absolute value of the change in transmission b is 0.9 or less.
b: the absolute value of the change in transmission b is more than 0.9.
[ (meth) acrylic polymers A1 to A6 ]
The mixture in which the monomer components shown in Table 1 were mixed in the blending amounts shown in Table 1 was charged into a 1L reactor equipped with a cooling device so that the temperature adjustment was facilitated by refluxing the nitrogen gas. To remove oxygen, after refluxing nitrogen in the reactor for 1 hour, the mixture was maintained at a temperature of 60 ℃. After the mixture was uniformly mixed, the polymerization initiator shown in table 1 was charged in the amount shown in table 1, and the UV lamp (10 mW) was irradiated while stirring, to obtain (meth) acrylic polymers A1 to A6. The blending amount shown in table 1 represents the mass ratio with respect to the total mass of the monomer components and the polymerization initiator. The results are shown in Table 1.
TABLE 1
Figure BDA0003930224050000271
The abbreviations in table 1 are as follows.
HA: hexyl acrylate (glass transition temperature: -57 ℃ C.)
IDA: isodecyl acrylate (glass transition temperature: -60 ℃ C.)
Eoeoeoea: ethoxyethoxyethoxyethyl acrylate (glass transition temperature: -56 ℃ C.)
EA: ethyl acrylate (glass transition temperature: -24 ℃ C.)
2-EHA: 2-ethylhexyl acrylate (glass transition temperature: -70 ℃ C.)
BA: butyl acrylate (glass transition temperature: -55 ℃ C.)
2-HEA: 2-hydroxyethyl acrylate (glass transition temperature: -15 ℃ C.)
LA: lauryl acrylate (glass transition temperature: 15 ℃ C.)
DCA: behenyl acrylate
I-184:1-hydroxycyclohexyl benzophenone (absorption maximum: 246 nm)
D-1173 (Darocure 1173): 2-hydroxy-2-methylpropionyl ketone (maximum absorption wavelength: 245 nm)
I-754: mixtures of oxy-phenyl-acetic acid 2- [ 2-oxo-2-phenyl-acetoxy-ethoxy ] -ethyl ester with oxy-phenyl-acetic acid 2- [ 2-hydroxy-ethoxy ] -ethyl ester (absorption wavelength max: 255 nm)
I-2959: 2-hydroxy-4' - (2-hydroxyethoxy) -2-methylpropionyl benzene (maximum absorption wavelength: 276 nm)
[ preparation of adhesive compositions B1 to B7 ]
The acrylic polymer, the compound and the polymerization initiator shown in Table 2 were mixed in the compounding amounts shown in Table 2 to obtain adhesive compositions B1 to B7. The blending amount shown in table 2 represents the mass ratio to the total mass of the polymer, the compound and the polymerization initiator.
TABLE 2
Figure BDA0003930224050000281
The abbreviations in table 2 are as illustrated in table 1.
[ production of pressure-sensitive adhesive sheets (1) to (7) ]
The pressure-sensitive adhesive composition shown in table 3 was applied to the release treated surface of the separator a (polyethylene terephthalate film coated with a release agent containing a silicone compound) so that the pressure-sensitive adhesive layer had a thickness shown in table 3. After a separator B (polyethylene terephthalate film coated with a release agent containing a silicone compound) was laminated on the coating layer so that the release treated surface side became the coating layer side, UV irradiation was performed to obtain adhesive sheets (1) to (7) having a layer structure of separator a/adhesive layer/separator B. UV irradiation to make the cumulative light quantity 400mJ/cm 2 Illuminance was 1.8mW/cm 2 (UVV reference). The glass transition temperatures Tg of the adhesive layers of the obtained adhesive sheets (1) to (7) were measured. In addition, use is made of a device forThe adhesive compositions of the adhesive sheets (1) to (7) were prepared, a reference adhesive sheet was prepared by the above-described procedure, and the line shrinkage and gel fraction were measured by the above-described procedure using the reference adhesive sheet. The results are shown in Table 3.
TABLE 3
Figure BDA0003930224050000291
[ examples 1 and 4, comparative example 3]
(preparation of front Panel)
As the front surface layer, a front panel having a hard coat layer (thickness 10 μm) formed on one surface of a resin film (polyimide resin film, thickness 40 μm) as the 1 st base material layer was prepared. The hard coat layer is a layer formed from a composition containing a (meth) acrylic compound having a dendrimer structure having a polyfunctional acrylic group at the terminal.
(preparation of circular polarizing plate (1))
According to the procedure of [ polarizer layer ] of the example of Japanese patent application laid-open No. 2020-138376, a linear polarizing plate (1) having an overcoat layer as a protective layer and a linear polarizing layer as a cured product layer of a polymerizable liquid crystal compound was produced. The layer structure of the linear polarization plate (1) is a protective layer/linear polarization layer/orientation layer/TAC film.
A retardation laminate (1) in which a 1 st retardation layer (thickness: 3 μm), an adhesive layer (thickness: 1 μm) and a 2 nd retardation layer (thickness: 2 μm) were laminated in this order was obtained. The 1 st retardation layer is a lambda/4 retardation layer and is a cured layer of a polymerizable liquid crystal compound. The adhesive layer is a cured layer of an epoxy adhesive as a photocurable adhesive composition. The 2 nd retardation layer is a positive C layer and is a cured layer of a polymerizable liquid crystal compound.
The protective layer side of the linear polarizing plate (1) obtained above was bonded to the 1 st retardation layer side of the retardation laminate (1) using a bonding layer (an adhesive layer using an acrylic adhesive, thickness 5 μm), to obtain a circular polarizing plate (1) as a polarizing plate. The layer structure of the circularly polarizing plate (1) is a linearly polarizing plate (1) (TAC film/alignment layer/linearly polarizing layer/protective layer)/adhesive layer/retardation laminate (1) (1 st retardation layer/adhesive layer/2 nd retardation layer).
(production of laminate)
The surface of the TAC film on the linear polarization plate (2) side of the circular polarization plate (1) was subjected to corona treatment (output 0.3kW, speed 3 m/min). The corona-treated surface was bonded to the 1 st base layer (resin film) side of the front panel obtained as described above using the 1 st adhesive layers shown in tables 4 and 5, and the 2 nd adhesive layers shown in tables 4 and 5 and the separator (polyimide resin film, thickness 50 μm) as the back layer were laminated on the retardation laminate (1) side of the circularly polarizing plate (1), to prepare laminates (1), (4) and (7). The laminate had a layer structure of a front layer (hard coat layer/1 st base layer)/1 st adhesive layer/linear polarizing plate (1) (TAC film/alignment layer/linear polarizing layer/protective layer)/lamination layer/retardation laminate (1) (1 st retardation layer/adhesive layer/2 nd retardation layer)/2 nd adhesive layer/back layer. The obtained laminate was subjected to a light bending resistance test and a light resistance test. The results are shown in tables 4 and 5.
[ example 2, comparative examples 1, 2 and 4 ]
(preparation of circular polarizing plate (2))
A protective film (cycloolefin resin film, 18 μm in thickness) as a protective layer and a linear polarizing layer (8 μm in thickness) as a polyvinyl alcohol film having iodine adsorbed and oriented were bonded together with an aqueous adhesive to obtain a linear polarizing plate (2) having a layer structure of protective layer/adhesive layer/linear polarizing layer.
The linearly polarizing layer side of the linearly polarizing plate (2) obtained above and the 1 st retardation layer side of the retardation laminate (1) obtained by the procedure described in example 1 were bonded using a bonding layer (an adhesive layer using an acrylic adhesive, thickness 5 μm), to obtain a circularly polarizing plate (2) as a polarizing plate. The layer structure of the circularly polarizing plate (2) is a linearly polarizing plate (2) (protective layer/adhesive layer/linearly polarizing layer)/adhesive layer/retardation laminate (1) (1 st retardation layer/adhesive layer/2 nd retardation layer).
(production of laminate)
The 1 st base layer (resin film) side of the front layer obtained by the procedure described in example 1 and the linear polarizing plate (2) side of the circular polarizing plate (2) were bonded to each other using the 1 st adhesive layers shown in tables 4 and 5, and the 2 nd adhesive layers shown in tables 4 and 5 and the separator (polyimide resin film, thickness 50 μm) as the back layer were laminated on the phase difference laminate (1) side of the circular polarizing plate (2), to prepare laminates (2), (5), (6) and (8). The laminate has a layer structure of a front layer (hard coat layer/1 st base layer)/1 st adhesive layer/linear polarizing plate (2) (protective layer/adhesive layer/linear polarizing layer)/adhesive layer/retardation laminate (1) (1 st retardation layer/adhesive layer/2 nd retardation layer)/2 nd adhesive layer/back layer. The obtained laminate was subjected to a light bending resistance test and a light resistance test. The results are shown in tables 4 and 5.
[ example 3 ]
(preparation of circular polarizing plate (3))
A retardation laminate (2) in which a 2 nd retardation layer (thickness: 2 μm), an adhesive layer (thickness: 2 μm) and a 1 st retardation layer (thickness: 1 μm) were laminated in this order was obtained. The 2 nd retardation layer is a lambda/2 retardation layer and is a cured layer of a polymerizable liquid crystal compound. The adhesive layer is a cured layer of an epoxy adhesive as a photocurable adhesive composition. The 1 st retardation layer is a lambda/4 retardation layer and is a cured layer of a polymerizable liquid crystal compound.
The linear polarization layer side of the linear polarization plate (2) obtained by the procedure described in example 2 and the 2 nd retardation layer side of the retardation laminate (2) obtained above were bonded using a bonding layer (an adhesive layer using an acrylic adhesive, thickness 5 μm), to obtain a circular polarization plate (3) as a polarization plate. The layer structure of the circularly polarizing plate (3) is a linearly polarizing plate (2) (protective layer/adhesive layer/linearly polarizing layer)/adhesive layer/retardation laminate (2) (2 nd retardation layer/adhesive layer/1 st retardation layer).
(production of laminate)
The 1 st base material layer (resin film) side of the front layer obtained by the procedure described in example 1 and the linear polarizing plate (2) side of the circular polarizing plate (3) were bonded to each other using the 1 st adhesive layers shown in tables 4 and 5, and the 2 nd adhesive layers shown in tables 4 and 5 and the separator (polyimide resin film, thickness 50 μm) as the back layer were laminated on the retardation laminate (2) side of the circular polarizing plate (3) to produce a laminate (3). The laminate has a layer structure of a front layer (hard coat layer/1 st base material layer)/1 st adhesive layer/linear polarizing plate (2) (protective layer/adhesive layer/linear polarizing layer)/adhesive layer/retardation laminate (2) (2 nd retardation layer/adhesive layer/1 st retardation layer)/2 nd adhesive layer/back layer. The obtained laminate was subjected to a light bending resistance test and a light resistance test. The results are shown in tables 4 and 5.
TABLE 4
Figure BDA0003930224050000331
TABLE 5
Figure BDA0003930224050000341
Description of the reference numerals
1. The laminated layers 2, 11 front layer, 15 back layer, 21 st adhesive layer, 22 nd adhesive layer, 30 polarizing plate, 31 linear polarizing layer, 32 protective layer, 33 st retardation layer (retardation layer), 34 nd retardation layer, 37, 38.

Claims (12)

1. A laminated body, which has, in order: a front layer, a 1 st adhesive layer formed using the 1 st adhesive composition, a polarizing plate including at least a linearly polarizing layer, a 2 nd adhesive layer formed using the 2 nd adhesive composition, and a back layer,
the 1 st reference adhesive layer formed with a thickness of 0.6mm using the 1 st adhesive composition was irradiated with an accumulated amount of 100J/cm 2 The line shrinkage of the 1 st reference pressure-sensitive adhesive layer after ultraviolet rays at a temperature of 25 ℃ under a load of 1N and a strain of 350% was set to D1[%]，
And irradiating the 2 nd reference adhesive layer formed at a thickness of 0.6mm using the 2 nd adhesive composition with an accumulated amount of 100J/cm 2 Is after ultraviolet rayThe line shrinkage of the 2 nd reference adhesive layer at a temperature of 25 ℃ and a load of 1N and a strain of 350% was set to D2[%]In the time-course of which the first and second contact surfaces,
satisfies the following relationships of the formulas (1) and (2),
D1＜D2 (1)
2.5≤D2≤6.5 (2)。
2. the laminate according to claim 1, wherein,
The gel fraction of the 2 nd reference pressure-sensitive adhesive layer after irradiation with the ultraviolet light is 50% or more and 90% or less.
3. The laminate according to claim 1 or 2, wherein,
the thickness of the 2 nd adhesive layer is 15 μm or more and 100 μm or less.
4. The laminate according to any one of claim 1 to 3, wherein,
the glass transition temperature of the 2 nd adhesive layer is below-55 ℃.
5. The laminate according to any one of claims 1 to 4, wherein,
the 2 nd adhesive composition comprises a (meth) acrylic polymer,
the (meth) acrylic polymer contains a structural unit derived from an alkyl (meth) acrylate having an alkyl group having 1 to 24 carbon atoms.
6. The laminate according to claim 5, wherein,
the (meth) acrylic polymer contains a structural unit derived from an alkyl (meth) acrylate having an alkyl group having 20 to 24 carbon atoms.
7. The laminate according to claim 5 or 6, wherein,
the content of structural units derived from the monomer having a reactive functional group is 2 mass% or less with respect to the total structural units constituting the (meth) acrylic polymer.
8. The laminate according to any one of claims 1 to 7, wherein,
the front layer comprises a 1 st substrate layer and a coating layer formed on at least one surface of the 1 st substrate layer,
the coating layer is formed using a composition containing a (meth) acrylic compound having a dendrimer structure.
9. The laminate according to any one of claims 1 to 8, wherein,
the polarizing plate is a circular polarizing plate having the linear polarizing layer and the retardation layer in this order from the front surface layer side.
10. The laminate according to any one of claims 1 to 9, wherein,
the back surface layer is a separator having a release treatment layer and a 2 nd base material layer in this order from the 2 nd adhesive layer side.
11. A display device comprising the laminate according to any one of claims 1 to 10.
12. The display device according to claim 11, which is bendable so that the back surface layer is inward.
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