CN113474165A - Laminate, adhesive composition, and adhesive sheet - Google Patents

Laminate, adhesive composition, and adhesive sheet Download PDF

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Publication number
CN113474165A
CN113474165A CN202080016162.8A CN202080016162A CN113474165A CN 113474165 A CN113474165 A CN 113474165A CN 202080016162 A CN202080016162 A CN 202080016162A CN 113474165 A CN113474165 A CN 113474165A
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meth
adhesive
layer
laminate
adhesive layer
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CN202080016162.8A
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Chinese (zh)
Inventor
李昇祐
金正熙
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Sumitomo Chemical Co Ltd
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Sumitomo Chemical Co Ltd
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Publication of CN113474165A publication Critical patent/CN113474165A/en
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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
    • 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
    • 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
    • B32B27/30—Layered products comprising a layer of synthetic resin comprising vinyl (co)polymers; comprising acrylic (co)polymers
    • 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
    • B32B7/022—Mechanical properties
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
    • B32B7/02—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
    • 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]
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
    • G02B1/10—Optical coatings produced by application to, or surface treatment of, optical elements
    • G02B1/14—Protective coatings, e.g. hard coatings
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/30—Polarising elements
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F3/00—Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
    • G06F3/01—Input arrangements or combined input and output arrangements for interaction between user and computer
    • G06F3/03—Arrangements for converting the position or the displacement of a member into a coded form
    • G06F3/041—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Organic Chemistry (AREA)
  • Chemical & Material Sciences (AREA)
  • Theoretical Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Human Computer Interaction (AREA)
  • Adhesive Tapes (AREA)
  • Adhesives Or Adhesive Processes (AREA)
  • Laminated Bodies (AREA)
  • Polarising Elements (AREA)
  • Surface Treatment Of Optical Elements (AREA)

Abstract

The purpose of the present invention is to provide a laminate having excellent bendability and heat resistance at low temperatures. The present invention provides a laminate comprising a front sheet, a1 st adhesive layer, a polarizer layer, a2 nd adhesive layer and a back sheet in this order, wherein the 1 st adhesive layer and the 2 nd adhesive layer each have a tan delta of 1.5 to 2.0 at a temperature of-40 ℃, and the 1 st adhesive layer and the 2 nd adhesive layer are each formed from an adhesive composition comprising a (meth) acrylic polymer in which a constituent unit derived from a monomer having a reactive functional group is less than 5% by mass based on the total mass of the polymer.

Description

Laminate, adhesive composition, and adhesive sheet
Technical Field
The invention relates to a laminate, an adhesive composition and an adhesive sheet.
Background
An adhesive film having an adhesive layer made of an adhesive composition is used for a display device (patent documents 1 to 3).
Documents of the prior art
Patent document
Patent document 1: korean patent No. 10-2014-0085299
Patent document 2: korean patent No. 10-2016-0053736
Patent document 3: japanese patent laid-open No. 2018-27995
Disclosure of Invention
When a laminate used in a display device is bent at a low temperature, cracks may occur in the adhesive layer. Further, at low temperatures, the adhesive force of the adhesive layer is reduced, and floating or peeling may occur between the adhesive layer and the member to be adhered.
The purpose of the present invention is to provide a laminate having excellent bendability at low temperatures and excellent adhesive strength at low temperatures, and an adhesive composition and an adhesive sheet used for the laminate.
The invention provides the following laminated body, adhesive composition and adhesive sheet.
[1] A laminate comprising, in order, a front sheet, a1 st adhesive layer, a polarizer layer, a2 nd adhesive layer and a back sheet,
wherein the 1 st adhesive layer and the 2 nd adhesive layer each have a tan delta of 1.5 to 2.0 at a temperature of-40 ℃ and are each formed from an adhesive composition containing a (meth) acrylic polymer,
in the (meth) acrylic polymer, the constituent unit derived from the monomer having a reactive functional group is less than 5% by mass based on the total mass of the polymer.
[2] The laminate according to [1], wherein the front sheet is a film having a hard coat layer provided on at least one surface of a base film.
[3] The laminate according to [1] or [2], wherein the weight average molecular weight (Mw) of the (meth) acrylic polymer is 20 to 150 ten thousand.
[4] The laminate according to any one of [1] to [3], wherein the adhesive composition further contains a monofunctional (meth) acrylic monomer having an alkoxy group.
[5] The laminate according to any one of [1] to [4], wherein the back surface plate is a touch sensor panel.
[6] A display device comprising the laminate according to any one of [1] to [5 ].
[7] An adhesive composition comprising a (meth) acrylic polymer and a monofunctional (meth) acrylic monomer having an alkoxy group,
in the (meth) acrylic polymer, the constituent unit derived from the monomer having a reactive functional group is less than 5% by mass based on the total mass of the polymer.
[8] An adhesive sheet comprising an adhesive layer formed from the adhesive composition according to [7 ].
According to the present invention, a laminate excellent in bendability at low temperatures and adhesive strength at low temperatures, and an adhesive composition and an adhesive sheet used for the laminate can be provided.
Drawings
Fig. 1 is a schematic cross-sectional view showing an example of the laminate of the present invention.
Fig. 2 is a schematic cross-sectional view showing an example of the laminate of the present invention.
Fig. 3 is a schematic diagram illustrating a method of the bending test.
Fig. 4 is a sectional view schematically showing a method for producing a laminate according to the present invention.
Detailed Description
A laminate according to an embodiment of the present invention (hereinafter simply referred to as "laminate") will be described below with reference to the drawings.
< layered product >
Fig. 1 is a schematic cross-sectional view of a laminate according to an embodiment of the present invention. The laminate 100 includes a front panel 101, a1 st adhesive layer 102, a polarizer layer 103, a2 nd adhesive layer 104, and a back panel 105 in this order. Hereinafter, the 1 st adhesive layer 102 and the 2 nd adhesive layer 104 may be collectively referred to as an adhesive layer.
The thickness of the laminate 100 is not particularly limited, and is, for example, 50 to 4000 μm, preferably 100 to 2000 μm, and more preferably 150 to 1000 μm, depending on the functions required for the laminate, the application of the laminate, and the like.
The shape of the laminate 100 in plan view may be, for example, a square shape, preferably a square shape having long sides and short sides, and more preferably a rectangle. When the shape of the laminate 100 in the plane direction is a rectangle, the length of the long side may be, for example, 10mm to 1400mm, and preferably 50mm to 600 mm. The length of the short side is, for example, 5mm to 800mm, preferably 30mm to 500mm, and more preferably 50mm to 300 mm. Each layer constituting the laminate may be subjected to a corner rounding process, or an end cutting process or a hole forming process.
The laminate 100 can be used for a display device or the like, for example. The display device is not particularly limited, and examples thereof include an organic electroluminescence (organic EL) display device, an inorganic electroluminescence (inorganic EL) display device, a liquid crystal display device, and an electroluminescence display device. The display device may have a touch panel function.
[ tan. delta. of adhesive layer ]
In the laminate 100, tan δ of the 1 st adhesive layer 102 and tan δ of the 2 nd adhesive layer 104 are both 1.5 to 2.0 at a temperature of-40 ℃. This tends to make the laminate 100 excellent in bendability at low temperatures. In the laminate 100, the 1 st adhesive layer 102 and the 2 nd adhesive layer 104 preferably have tan δ of 1.6 to 1.9 at a temperature of-40 ℃ from the viewpoint of suppressing cracking. The tan. delta. at a temperature of-40 ℃ can be measured according to the measurement method described in the section of examples, which will be described later.
In a laminate used for a display device, one of the characteristics required for an adhesive layer is a stress relaxation characteristic. However, even in the pressure-sensitive adhesive layer having excellent stress relaxation properties, cracks may occur in the pressure-sensitive adhesive layer due to bending at low temperatures. As a result of studies by the present inventors, it was found that when tan δ at a temperature of-40 ℃ is within the above range, stress relaxation properties tend to be easily maintained even at low temperatures, and as a result, adhesion between the pressure-sensitive adhesive layer and the constituent member of the laminate is maintained even when the laminate is repeatedly bent at low temperatures, and cracking of the pressure-sensitive adhesive layer can be suppressed.
The excellent bendability at low temperatures means that bending can be performed without generating cracks when bending is performed at a temperature of-20 ℃ in at least one direction in the plane of the laminate 100 so that the bending radius of the inner surface of the laminate 100 becomes 3.0 mm. When the laminate 100 is repeatedly bent at a temperature of-20 ℃ in at least one direction in the plane so that the bending radius of the inner surface of the laminate 100 becomes 3.0mm, it is preferable that the number of bending times is 1 ten thousand and no cracks are generated. In the present invention, the cracks in the pressure-sensitive adhesive layer include cracks generated in the pressure-sensitive adhesive layer, peeling between the pressure-sensitive adhesive layer and the constituent member of the laminate, and the like. In the present specification, the bending includes a bent form in which a curved surface is formed at a bent portion. In the bent form, the bending radius of the inner surface of the bend is not particularly limited. The bending includes a form in which the inner surface is bent at a bending angle of more than 0 degrees and less than 180 degrees, and a form in which the inner surface is folded such that the bending radius of the inner surface is approximately zero or the bending angle of the inner surface is 0 degrees.
In the laminate 100, since tan δ of the 1 st adhesive layer and tan δ of the 2 nd adhesive layer at-40 ℃ are both 1.5 to 2.0, the front panel side may be bent inward (folded inward) or the front panel side may be bent outward (folded outward).
The laminate 100 has a tan δ of 1.5 to 2.0 at-40 ℃ in both the 1 st adhesive layer 102 and the 2 nd adhesive layer 104, and when repeatedly bent at-20 ℃ in at least one direction in the plane so that the bending radius of the inner surface of the laminate 100 becomes 3.0mm, it is preferable that cracks are not generated even if the number of bending times is 1 ten thousand. When the laminate 100 is repeatedly bent at a temperature of-20 ℃ in at least one direction in the plane so that the bending radius of the inner surface of the laminate 100 becomes 3.0mm, the laminate is more preferably not cracked even when bent 2 ten thousand times, even more preferably not cracked even when bent 5 ten thousand times, and even more preferably not cracked even when bent 10 ten thousand times. The laminate 100 is preferably bent at a temperature of-40 ℃ without causing cracks in at least one direction in the plane and in the direction perpendicular thereto. The display device to which the laminate 100 is applied can be used as a flexible display which can be bent, rolled, or the like.
Examples of the method of setting the tan δ at-40 ℃ in the 1 st adhesive layer 102 and the 2 nd adhesive layer 104 to 1.5 to 2.0 include a method of forming an adhesive layer from the adhesive composition a described later, changing the kind of monomers forming the (meth) acrylic polymer a described later, adjusting the molecular weight of the (meth) acrylic polymer a, adding a monofunctional (meth) acrylic monomer having an alkoxy group to the adhesive composition a, adjusting the kind of a crosslinking agent and the content of each component in the adhesive composition a, and a method of combining these methods.
[ adhesive composition ]
From the viewpoint of suppressing cracking, the 1 st adhesive layer 102 and the 2 nd adhesive layer 104 are each formed of an adhesive composition containing a (meth) acrylic polymer (hereinafter, also referred to as an adhesive composition a). The adhesive composition a may be an active energy ray-curable type or a heat-curable type. In the present specification, "(meth) acrylic polymer" means at least 1 selected from acrylic polymers and methacrylic polymers. The same applies to other terms labeled "methyl". Hereinafter, the (meth) acrylic polymer contained in the adhesive composition a is also referred to as a (meth) acrylic polymer a.
(1) Active energy ray-curable adhesive composition
When the adhesive composition a is an active energy ray-curable adhesive composition, the constituent unit derived from the monomer having a reactive functional group in the (meth) acrylic polymer a is less than 5% by mass based on the total mass of the polymer. Examples of the reactive functional group include a hydroxyl group, a carboxyl group, an amino group, an amide group, and an epoxy group. This improves the flexibility of the pressure-sensitive adhesive layer, and tends to easily suppress cracking of the pressure-sensitive adhesive layer at low temperatures. From the viewpoint of suppressing cracking, the (meth) acrylic polymer a preferably has 1 mass% or less, more preferably 0.01 mass% or less, even more preferably has no constituent unit derived from a monomer having a reactive functional group, and even more preferably has no hydroxyl group, carboxyl group, alkyl group, amide group, and epoxy group, based on the total mass of the polymer.
The (meth) acrylic polymer A may contain a constituent unit derived from a (meth) acrylic monomer having a linear or branched alkyl group having 1 to 24 carbon atoms. Examples of the (meth) acrylic monomer having a linear or branched alkyl group having 1 to 24 carbon atoms include alkyl (meth) acrylates, such as butyl (meth) acrylate, methyl (meth) acrylate, ethyl (meth) acrylate, hexyl (meth) acrylate, octyl (meth) acrylate, lauryl (meth) acrylate, isooctyl (meth) acrylate, isodecyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and isobornyl (meth) acrylate. The (meth) acrylic polymer a may be a polymer or copolymer having 1 or 2 or more of the above-mentioned alkyl (meth) acrylates as a monomer. The content of the (meth) acrylic polymer a in the pressure-sensitive adhesive composition a may be, for example, 50 to 100 mass%, preferably 80 to 99.5 mass%, and more preferably 90 to 99 mass%, based on the total mass% of the solid content of the pressure-sensitive adhesive composition a.
The weight average molecular weight (Mw) of the (meth) acrylic polymer a may be, for example, 20 to 150 ten thousand, or 30 to 70 ten thousand, and preferably 30 to 60 ten thousand from the viewpoint of improving the bendability. The weight average molecular weight (Mw) can be measured according to the method described in the section of examples, which will be described later.
The adhesive composition a may contain 1 or 2 or more (meth) acrylic polymers a. The pressure-sensitive adhesive composition a may contain only the (meth) acrylic polymer a as a constituent component thereof, or may further contain a crosslinking agent. Examples of the crosslinking agent include metal ions having a valence of 2 or more and a metal carboxylate salt formed between the crosslinking agent and a carboxyl group; a polyamine compound and a substance forming an amide bond with a carboxyl group; a polyepoxy compound or a polyhydric alcohol and forming an ester bond with a carboxyl group; polyisocyanate compounds and those which form amide bonds with carboxyl groups. Among them, as the crosslinking agent, a polyisocyanate compound is preferable. When the pressure-sensitive adhesive composition a contains a crosslinking agent, the content of the crosslinking agent may be, for example, 5 parts by mass or less, preferably 1 part by mass or less, more preferably 0.5 part by mass or less, and still more preferably 0.1 part by mass or less, per 100 parts by mass of the (meth) acrylic polymer a. Most preferably, the adhesive composition a does not contain a crosslinking agent.
The active energy ray-curable pressure-sensitive adhesive composition is a pressure-sensitive adhesive composition having a property of being cured by irradiation with an active energy ray such as an ultraviolet ray or an electron beam, and having a property of having an adhesive property even before irradiation with an active energy ray, and being capable of being bonded to an adherend such as a film and being cured by irradiation with an active energy ray, thereby being capable of adjusting the property such as the bonding force.
The active energy ray-curable adhesive composition is preferably an ultraviolet-curable adhesive composition.
From the viewpoint of improving the flexibility, the pressure-sensitive adhesive composition a preferably contains a monofunctional (meth) acrylic monomer having an alkoxy group in addition to the (meth) acrylic polymer a. Examples of the alkoxy group include a methoxy group, an ethoxy group, an n-propoxy group, an isopropoxy group, an n-butoxy group, a sec-butoxy group, and a tert-butoxy group. Examples of the monofunctional (meth) acrylic monomer having an alkoxy group include ethoxyethoxyethyl acrylate (EOEOEA), nonylphenol EO-modified acrylate [ np (EO)8A ], and the like. The content of the monofunctional (meth) acrylic monomer having an alkoxy group in the adhesive composition a may be, for example, 3 to 10% by mass based on the total mass of the solid components of the adhesive composition a. The inclusion of the monofunctional (meth) acrylic monomer having an alkoxy group tends to make the polymer chain form a soft linear structure.
When the pressure-sensitive adhesive composition a is an active energy ray-curable pressure-sensitive adhesive composition, the pressure-sensitive adhesive composition a may further contain an active energy ray-polymerizable compound, a photopolymerization initiator, a photosensitizer, and the like.
Examples of the active energy ray-polymerizable compound include (meth) acrylate monomers having at least 1 (meth) acryloyloxy group in the molecule; a (meth) acrylic compound such as a (meth) acryloyloxy group-containing compound obtained by reacting 2 or more kinds of functional group-containing compounds and having at least 2 (meth) acryloyloxy groups in the molecule, e.g., a (meth) acrylate oligomer. The binder composition a may contain the active energy ray-polymerizable compound in an amount of 3 to 10 mass% based on the total mass of the solid components of the binder composition a.
Examples of the photopolymerization initiator include benzildimethylketal and 1-hydroxycyclohexylphenylketone. When the adhesive composition a contains a photopolymerization initiator, 1 or 2 or more species may be contained. When the adhesive composition a contains a photopolymerization initiator, the total content thereof may be, for example, 0.01 to 1.0% by mass based on the total mass of the solid components of the adhesive composition a.
The adhesive composition a may contain additives such as fine particles, beads (resin beads, glass beads, and the like), glass fibers, resins other than the base polymer, adhesion-imparting agents, fillers (metal powders, other inorganic powders, and the like), antioxidants, ultraviolet absorbers, dyes, pigments, colorants, antifoaming agents, anticorrosion agents, and photopolymerization initiators for imparting light scattering properties. From the viewpoint of preventing the problem of the reduction in durability caused by the residual solvent, the adhesive composition a preferably does not contain an organic solvent.
In the case where the adhesive layer is formed of the adhesive composition a, the adhesive layer may be formed by coating the adhesive composition a on a substrate. When an active energy ray-curable pressure-sensitive adhesive composition is used, a cured product having a desired degree of curing can be obtained by irradiating the pressure-sensitive adhesive layer formed with an active energy ray.
(2) Heat-curable adhesive composition
When the adhesive composition a is a heat-curable adhesive composition, the (meth) acrylic polymer a preferably contains, as monomer units constituting the polymer, an alkyl (meth) acrylate having an alkyl group and 2 to 20 carbon atoms and a monomer having a reactive functional group in a molecule (reactive functional group-containing monomer).
The (meth) acrylic polymer A can exhibit preferable adhesiveness by containing an alkyl (meth) acrylate having an alkyl group and 2 to 20 carbon atoms as a monomer unit constituting the polymer. The alkyl (meth) acrylate having an alkyl group with 2 to 20 carbon atoms is preferably an alkyl (meth) acrylate having a glass transition temperature (Tg) of-40 ℃ or lower (hereinafter, may be referred to as "low Tg alkyl acrylate") as a homopolymer. By containing the low Tg alkyl acrylate as a constituent monomer unit, flexibility of the pressure-sensitive adhesive layer is improved, and the occurrence of cracks in the pressure-sensitive adhesive layer at low temperature, the occurrence of floating and peeling of the pressure-sensitive adhesive layer at low temperature, and the occurrence of bubbles at low temperature tend to be easily prevented.
Examples of the low Tg alkyl acrylate include n-butyl acrylate (Tg-55 ℃ C.), n-octyl acrylate (Tg-65 ℃ C.), isooctyl acrylate (Tg-58 ℃ C.), 2-ethylhexyl acrylate (Tg-70 ℃ C.), isononyl acrylate (Tg-58 ℃ C.), isodecyl acrylate (Tg-60 ℃ C.), isodecyl methacrylate (Tg-41 ℃ C.), n-lauryl methacrylate (Tg-65 ℃ C.), tridecyl acrylate (Tg-55 ℃ C.), and tridecyl methacrylate (-40 ℃ C.). Among them, from the viewpoint that the tan. delta. at-40 ℃ of the obtained adhesive is likely to fall within the above range, the low Tg alkyl acrylate is more preferably an alkyl acrylate having a homopolymer Tg of-45 ℃ or less, and particularly preferably an alkyl acrylate having a homopolymer Tg of-50 ℃ or less. Specifically, n-butyl acrylate and 2-ethylhexyl acrylate are particularly preferable. These may be used alone, or 2 or more of them may be used in combination.
The (meth) acrylic polymer a preferably contains the low Tg alkyl acrylate in an amount of 85 mass% or more, more preferably 90 mass% or more, and still more preferably 95 mass% or more, as a monomer unit constituting the polymer, at the lower limit. Within such a range, the tan. delta. at a temperature of-40 ℃ is likely to fall within the above-mentioned range.
The (meth) acrylic polymer a preferably contains the low Tg alkyl acrylate in an amount of 99.9 mass% or less as a monomer unit constituting the polymer, more preferably 99.5 mass% or less, and still more preferably 99 mass% or less. By containing 99.9 mass% or less of the low Tg alkyl acrylate, an appropriate amount of other monomer components (particularly, reactive functional group-containing monomers) can be introduced into the (meth) acrylic polymer a.
In order to easily set the glass transition temperature (Tg) of the main polymer of the adhesive of the present embodiment to the above range, the content of a monomer having a glass transition temperature (Tg) exceeding 0 ℃ as a homopolymer (hereinafter, may be referred to as "hard monomer") is preferably reduced as much as possible in the (meth) acrylic polymer a. Specifically, the content of the hard monomer in the (meth) acrylic polymer a is preferably 15% by mass or less, more preferably 10% by mass or less, and still more preferably 5% by mass or less, as the monomer unit constituting the polymer. The hard monomer also includes a reactive functional group-containing monomer described later.
Examples of the hard monomer include methyl acrylate (Tg10 ℃ C.), methyl methacrylate (Tg105 ℃ C.), ethyl methacrylate (Tg65 ℃ C.), n-butyl methacrylate (Tg20 ℃ C.), isobutyl methacrylate (Tg48 ℃ C.), tert-butyl methacrylate (Tg107 ℃ C.), n-stearyl acrylate (Tg30 ℃ C.), n-stearyl methacrylate (Tg38 ℃ C.), cyclohexyl acrylate (Tg15 ℃ C.), cyclohexyl methacrylate (Tg66 ℃ C.), phenoxyethyl acrylate (Tg5 ℃ C.), phenoxyethyl methacrylate (Tg54 ℃ C.), benzyl methacrylate (Tg54 ℃ C.), isobornyl acrylate (Tg94 ℃ C.), isobornyl methacrylate (Tg180 ℃ C.), acryloylmorpholine (Tg145 ℃ C.), adamantyl acrylate (Tg115 ℃ C.), adamantyl methacrylate (Tg141 ℃ C.), acrylic acid (Tg103 ℃ C.), dimethylacrylamide (Tg89 ℃ C.), and so forth, Acrylic monomers such as acrylamide (Tg165 ℃ C.), vinyl acetate (Tg32 ℃ C.), styrene (Tg80 ℃ C.), and the like.
The (meth) acrylic polymer a contains a reactive functional group-containing monomer as a monomer unit constituting the polymer, and forms a crosslinked structure (three-dimensional network structure) by reacting the reactive functional group of the reactive functional group-containing monomer with a heat crosslinking agent described later through the reaction, thereby obtaining an adhesive having a desired cohesive force.
Examples of the reactive functional group-containing monomer contained as a monomer unit constituting the (meth) acrylic polymer a include a monomer having a hydroxyl group in the molecule (hydroxyl group-containing monomer), a monomer having a carboxyl group in the molecule (carboxyl group-containing monomer), and a monomer having an amino group in the molecule (amino group-containing monomer). Among these, monomers having a glass transition temperature (Tg) of 0 ℃ or lower are more preferable, and hydroxyl group-containing monomers are particularly preferable.
Examples of the hydroxyl group-containing monomer include hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 3-hydroxybutyl (meth) acrylate, and 4-hydroxybutyl (meth) acrylate. Among them, from the viewpoint of the glass transition temperature (Tg), the reactivity of the hydroxyl group in the obtained (meth) acrylic polymer a with a thermal crosslinking agent, and the copolymerizability with other monomers, at least one of 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 3-hydroxypropyl acrylate, and 4-hydroxybutyl acrylate is preferable. These may be used alone, or 2 or more of them may be used in combination.
Examples of the carboxyl group-containing monomer include ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, and citraconic acid. These may be used alone, or 2 or more of them may be used in combination.
Examples of the amino group-containing monomer include aminoethyl (meth) acrylate, n-butylaminoethyl (meth) acrylate, and the like. These may be used alone, or 2 or more of them may be used in combination.
In the (meth) acrylic polymer a, the constituent unit derived from the monomer having a reactive functional group is less than 5% by mass based on the total mass of the polymer. In the (meth) acrylic polymer a, the lower limit of the constituent unit derived from the monomer having a reactive functional group is preferably 0.1% by mass or more, particularly preferably 0.5% by mass or more, and more preferably 1% by mass or more. The upper limit is preferably 4% by mass or less, particularly preferably 3.5% by mass or less, and further preferably 3% by mass or less. When the (meth) acrylic polymer A contains a reactive functional group-containing monomer, particularly a hydroxyl group-containing monomer, as a monomer unit in the above-mentioned amount, the tan. delta. at-40 ℃ of the obtained adhesive is likely to fall within the above-mentioned range.
The (meth) acrylic polymer a may contain no carboxyl group-containing monomer, particularly acrylic acid, which is also a hard monomer, as a monomer unit constituting the polymer. Since the carboxyl group is an acid component, the carboxyl group-containing monomer is not contained, and therefore even when there are components that cause troubles due to acid, for example, a transparent conductive film such as tin-doped indium oxide (ITO), a metal film, a metal mesh, or the like in the object to which the adhesive is attached, it is possible to suppress the troubles (corrosion, change in resistance value, or the like) caused by acid.
The (meth) acrylic polymer a may contain other monomers as the monomer unit constituting the polymer, if necessary. As the other monomer, a monomer containing no reactive functional group is also preferable in order not to hinder the action of the reactive functional group-containing monomer. Examples of the other monomer include, in addition to alkoxyalkyl (meth) acrylates such as methoxyethyl (meth) acrylate and ethoxyethyl (meth) acrylate, monomers having a glass transition temperature (Tg) of more than-40 ℃ and not more than 0 ℃ as homopolymers (hereinafter, sometimes referred to as "medium Tg alkyl acrylate"), and the like, and examples of the medium Tg alkyl acrylate include ethyl acrylate (Tg of-20 ℃), isobutyl acrylate (Tg of-26 ℃), 2-ethylhexyl methacrylate (Tg of-10 ℃), n-lauryl acrylate (Tg of-23 ℃), isostearyl acrylate (Tg of-18 ℃) and the like, and these may be used alone or in combination of 2 or more.
The (meth) acrylic polymer a may be a random copolymer or a block copolymer in a polymerized state.
The lower limit of the weight average molecular weight of the (meth) acrylic polymer a is preferably 20 ten thousand or more, particularly preferably 30 ten thousand or more, and more preferably 40 ten thousand or more. When the lower limit of the weight average molecular weight of the (meth) acrylic polymer a is not less than the above range, troubles such as bleeding out of the adhesive can be suppressed. The weight average molecular weight in the present specification is a value in terms of standard polystyrene measured by a Gel Permeation Chromatography (GPC) method.
The upper limit of the weight average molecular weight of the (meth) acrylic polymer a is preferably 150 ten thousand or less, particularly preferably 135 ten thousand or less, and more preferably 120 ten thousand or less. When the upper limit of the weight average molecular weight of the (meth) acrylate polymer (A) is not more than the above range, the tan. delta. at a temperature of-40 ℃ of the obtained adhesive is likely to fall within the above range.
In the adhesive composition a, 1 kind of the (meth) acrylic polymer a may be used alone, or 2 or more kinds may be used in combination.
When the adhesive composition A containing a thermal crosslinking agent is heated, the thermal crosslinking agent crosslinks the (meth) acrylic polymer A to form a three-dimensional network structure. This improves the cohesive strength of the resulting adhesive, and the adhesive is likely to have tan δ within the above range at a temperature of-40 ℃.
The thermal crosslinking agent may be any thermal crosslinking agent that reacts with the reactive group of the (meth) acrylic polymer a, and examples thereof 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, amine-based crosslinking agents, and the like,
Figure BDA0003224658660000101
An oxazoline-based crosslinking agent, a metal alkoxide-based crosslinking agent, a metal chelate-based crosslinking agent, a metal salt-based crosslinking agent, an ammonium salt-based crosslinking agent, and the like. Among the above, when the reactive group of the (meth) acrylic polymer a is a hydroxyl group, an isocyanate-based crosslinking agent having excellent reactivity with the hydroxyl group is preferably used. The thermal crosslinking agent may be used alone in 1 kind, or in combination of 2 or more kinds.
The isocyanate-based crosslinking agent contains at least a polyisocyanate compound.
Examples of the polyisocyanate compound include aromatic polyisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, and xylylene diisocyanate; aliphatic polyisocyanates such as hexamethylene diisocyanate; alicyclic polyisocyanates such as isophorone diisocyanate and hydrogenated diphenylmethane diisocyanate; and biuret or isocyanurate adducts thereof, and adducts thereof which are reaction products with low molecular active hydrogen-containing compounds such as ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane and castor oil. Among them, trimethylolpropane-modified aromatic polyisocyanates are preferable from the viewpoint of reactivity with hydroxyl groups, and trimethylolpropane-modified tolylene diisocyanate and trimethylolpropane-modified xylylene diisocyanate are particularly preferable.
Examples of the epoxy-based crosslinking agent include 1, 3-bis (N, N-diglycidylaminomethyl) cyclohexane, N, N, N ', N' -tetraglycidylmethylenem-xylylenediamine, ethylene glycol diglycidyl ether, 1, 6-hexanediol diglycidyl ether, trimethylolpropane diglycidyl ether, diglycidylaniline, and diglycidylamine.
The content of the thermal crosslinking agent in the adhesive composition a is preferably 0.01 mass% or more, more preferably 0.05 mass% or more, and still more preferably 0.1 mass% or more, with respect to 100 mass% of the (meth) acrylic polymer a. The content is preferably 1% by mass or less, more preferably 0.8% by mass or less, and still more preferably 0.5% by mass or less. When the content of the thermal crosslinking agent is within the above range, the tan δ at-40 ℃ of the obtained adhesive is easily within the above range.
The adhesive composition a preferably contains the silane coupling agent. This improves the adhesion between the pressure-sensitive adhesive layer and each member in the flexible laminate as an adherend, and improves the durability against bending.
The silane coupling agent is preferably an organosilicon compound having at least 1 alkoxysilyl group in the molecule, and the (meth) acrylic polymer a is an organosilicon compound having good compatibility and light transmittance.
Examples of the silane coupling agent include silicon compounds containing a polymerizable unsaturated group such as vinyltrimethoxysilane, vinyltriethoxysilane, methacryloxypropyltrimethoxysilane and the like; silicon compounds having an epoxy structure such as 3-glycidoxypropyltrimethoxysilane and 2- (3, 4-epoxycyclohexyl) ethyltrimethoxysilane; mercapto group-containing silicon compounds such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropyldimethoxymethylsilane, etc.; amino group-containing silicon compounds such as 3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropyltrimethoxysilane and N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane; 3-chloropropyltrimethoxysilane, 3-isocyanatopropyltriethoxysilane, or a condensate of at least one of these with an alkyl-containing silicon compound such as methyltriethoxysilane, ethyltriethoxysilane, methyltrimethoxysilane, or ethyltrimethoxysilane. These can be used alone in 1 kind, also can be combined with 2 or more kinds.
The content of the silane coupling agent in the adhesive composition a is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and still more preferably 0.1% by mass or more, based on 100% by mass of the (meth) acrylic polymer a. The content is preferably 1% by mass or less, more preferably 0.5% by mass or less, and still more preferably 0.3% by mass or less. When the content of the silane coupling agent is in the above range, the obtained pressure-sensitive adhesive layer becomes a layer having more preferable adhesion to each member in the flexible laminate as an adherend.
The adhesive composition a may contain the above-mentioned various additives as required. The additive constituting the adhesive composition a does not contain a polymerization solvent or a dilution solvent.
The (meth) acrylic polymer a can be produced by polymerizing a mixture of monomers constituting the polymer by a general radical polymerization method. The polymerization of the (meth) acrylic polymer a is preferably carried out by a solution polymerization method using a polymerization initiator as needed. Examples of the polymerization solvent include ethyl acetate, n-butyl acetate, isobutyl acetate, toluene, acetone, hexane, and methyl ethyl ketone, and 2 or more kinds thereof may be used in combination.
The polymerization initiator may be an azo compound, an organic peroxide, or the like, and 2 or more kinds may be used in combination. Examples of the azo compound include 2,2 ' -azobisisobutyronitrile, 2 ' -azobis (2-methylbutyronitrile), 1 ' -azobis (cyclohexane 1-carbonitrile), 2 ' -azobis (2, 4-dimethylvaleronitrile), 2 ' -azobis (2, 4-dimethyl-4-methoxyvaleronitrile), dimethyl 2,2 ' -azobis (2-methylpropionate), 4 ' -azobis (4-cyanovaleric acid), 2 ' -azobis (2-hydroxymethylpropionitrile), and 2,2 ' -azobis [2- (2-imidazolin-2-yl) propane ].
Examples of the organic peroxide include benzoyl peroxide, t-butyl perbenzoate, cumene hydroperoxide, diisopropyl peroxydicarbonate, di-n-propyl peroxydicarbonate, di (2-ethoxyethyl) peroxydicarbonate, t-butyl peroxyneodecanoate, t-butyl peroxyvalerate, (3,5, 5-trimethylhexanoyl) peroxide, dipropionylperoxide, and diacetyl peroxide.
In the polymerization step, a chain transfer agent such as 2-mercaptoethanol is added to adjust the weight average molecular weight of the obtained polymer.
After obtaining the (meth) acrylic polymer a, a thermal crosslinking agent, a silane coupling agent, and if necessary, an additive and a diluting solvent are added to a solution of the (meth) acrylic polymer a and sufficiently mixed to obtain a binder composition a (coating solution) diluted with a solvent.
In the case where a solid component is used or in the case where a precipitate is generated when the solid component is mixed with another component in an undiluted state, any of the above components may be dissolved or diluted in a diluting solvent alone and then mixed with another component.
Examples of the diluting solvent include aliphatic hydrocarbons such as hexane, heptane and cyclohexane; aromatic hydrocarbons such as toluene and xylene; halogenated hydrocarbons such as dichloromethane and dichloroethane; alcohols such as methanol, ethanol, propanol, butanol, and 1-methoxy-2-propanol; ketones such as acetone, methyl ethyl ketone, 2-pentanone, isophorone, and cyclohexanone; esters such as ethyl acetate and butyl acetate; and cellosolve-based solvents such as ethyl cellosolve.
The concentration and viscosity of the coating solution prepared in this manner are not particularly limited as long as the coating solution can be applied, and may be appropriately selected according to the situation. For example, the binder composition A is diluted so that the concentration thereof is 10 to 60 mass%. The addition of a diluting solvent or the like is not an essential condition when obtaining a coating solution, and the diluting solvent may not be added if the adhesive composition a has a viscosity capable of being coated or the like. In this case, the pressure-sensitive adhesive composition a is a coating solution in which the polymerization solvent of the (meth) acrylic polymer a is directly used as a dilution solvent.
A preferable pressure-sensitive adhesive as the pressure-sensitive adhesive of the present embodiment is a pressure-sensitive adhesive composition a obtained by crosslinking. Crosslinking of the adhesive composition a may be performed by heat treatment. The heat treatment may be used in combination with a drying treatment for volatilizing a diluent solvent or the like from a coating film of the pressure-sensitive adhesive composition a applied to a desired object.
The heating temperature of the heating treatment is preferably 50 to 150 ℃, and more preferably 70 to 120 ℃. The heating time is preferably 10 seconds to 10 minutes, and more preferably 50 seconds to 2 minutes.
After the heat treatment, if necessary, a curing period of about 1 to 2 weeks may be set at normal temperature (e.g., 23 ℃ C., 50% RH). In the case where the curing period is required, the adhesive is formed after the curing period, and in the case where the curing period is not required, the adhesive is formed after the heat treatment is completed.
By the heat treatment (and curing), the (meth) acrylic polymer a is sufficiently crosslinked via the crosslinking agent to form a crosslinked structure, thereby obtaining an adhesive. The adhesive has a tan delta at-40 ℃ easily falling within the above range.
The adhesive sheet of the present invention comprises an adhesive layer formed from the adhesive composition a of the present invention described above. The adhesive layer may be formed by applying the adhesive composition a to a substrate. When a thermosetting adhesive composition is used as the adhesive composition a, the adhesive layer formed is subjected to heat treatment (and curing) to produce a cured product having a desired degree of curing. The conditions of the heat treatment and the aging are as described above.
The substrate may be a release film subjected to a release treatment. The pressure-sensitive adhesive sheet can be produced by forming a layer made of a pressure-sensitive adhesive on a release film in a sheet form in advance, and further bonding another release film on the pressure-sensitive adhesive layer.
As a method for applying the coating liquid of the adhesive composition a, for example, a bar coating method, a knife coating method, a roll coating method, a blade coating method, a die coating method, a gravure coating method, or the like can be used.
[ front panel ]
The front panel 101 is not limited in material and thickness as long as it is a plate-like body that can transmit light, and may be composed of only 1 layer, or 2 or more layers. Examples thereof include a plate-like body made of resin (for example, a resin plate, a resin sheet, a resin film, etc.), a plate-like body made of glass (for example, a glass plate, a glass film, etc.), and a touch sensor panel described later. The front panel may constitute the outermost surface of the display device.
The thickness of the front plate 101 may be, for example, 10 to 500. mu.m, preferably 20 to 200. mu.m, and more preferably 30 to 100. mu.m. In the present invention, the thickness of each layer can be measured by the thickness measurement method described in the examples described below.
When the front panel 101 is a resin plate-like body, the resin plate-like body is not limited as long as light can be transmitted therethrough. Examples of the resin constituting the plate-like body made of a resin such as a resin film include films made of polymers such as triacetyl cellulose, acetyl cellulose butyrate, ethylene-vinyl acetate copolymer, propionyl cellulose, butyryl cellulose, acetyl propionyl cellulose, polyester, polystyrene, polyamide, polyetherimide, poly (meth) acrylic acid, polyimide, polyethersulfone, polysulfone, polyethylene, polypropylene, polymethylpentene, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, polyvinylacetal, polyetherketone, polyetheretherketone, polyethersulfone, polymethylmethacrylate, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate, and polyamideimide. These polymers may be used alone or in combination of 2 or more. From the viewpoint of improving strength and transparency, a resin film made of a polymer such as polyimide, polyamide, polyamideimide, or the like is preferable. The thickness of the resin plate-like body may be, for example, 10 to 500. mu.m, preferably 20 to 200. mu.m, more preferably 30 to 150 μm, or 100 μm or less.
From the viewpoint of enhancing the hardness, the front panel 101 is preferably a film in which a hard coat layer is provided on at least one surface of a base film. As the base film, a film formed of the above resin can be used. The hard coat layer may be formed on one surface of the substrate film or on both surfaces. By providing the hard coat layer, a resin film having improved hardness and scratch resistance can be produced. The hard coat layer is a cured layer of, for example, an ultraviolet curable resin. Examples of the ultraviolet curable resin include acrylic resins, silicone resins, polyester resins, urethane resins, amide resins, and epoxy resins. The hard coating may also contain additives in order to increase hardness. The additive is not limited, and examples thereof include inorganic fine particles, organic fine particles, and a mixture thereof.
When the front panel 101 is a glass plate, a strengthened glass for display is preferably used as the glass plate. The thickness of the glass plate may be, for example, 10 to 500. mu.m. By using the glass plate, the front panel 101 having excellent mechanical strength and surface hardness can be configured.
When the laminate 100 is used in a display device, the front panel 101 may have a function of protecting the front surface (screen) of the display device (a function as a window film), a function as a touch sensor, a blue light cut-off function, a viewing angle adjustment function, and the like.
[1 st adhesive layer ]
The 1 st adhesive layer 102 is a layer interposed between and bonded to the front panel 101 and the polarizer layer 103, and may be a layer made of, for example, an adhesive or a bonding agent, or a layer obtained by subjecting the layer to some kind of treatment. The 1 st adhesive layer may be an adhesive layer disposed closest to the front panel among the adhesive layers constituting the laminate. Adhesives are also known as pressure sensitive adhesives. In the present specification, the "adhesive" refers to an adhesive other than an adhesive (pressure-sensitive adhesive), and is clearly distinguished from an adhesive. The 1 st adhesive layer 102 may be composed of 1 layer, or may be composed of 2 or more layers, preferably 1 layer.
The 1 st adhesive layer 102 may be formed of the adhesive composition a as described above.
From the viewpoint of suppressing cracking, the 1 st adhesive layer 102 preferably has a tan δ of 1.6 to 1.9 at a temperature of-40 ℃.
The thickness of the 1 st pressure-sensitive adhesive layer 102 is, for example, preferably 3 μm to 100 μm, more preferably 5 μm to 50 μm, and may be 20 μm or more.
[ polarizer layer ]
Examples of the polarizer layer 103 include a stretched film or a stretched layer having a dichroic dye adsorbed thereon, and a layer obtained by applying and curing a composition containing a dichroic dye and a polymerizable compound. As the dichroic dye, specifically, iodine or a dichroic organic dye can be used. The dichroic organic dye includes a dichroic direct dye composed of a bisazo compound such as c.i. direct RED (c.i. direct RED)39, and a dichroic direct dye composed of a compound such as trisazo or tetraazo.
Examples of the polarizer layer obtained by applying and curing a composition containing a dichroic dye and a polymerizable compound include a polarizer layer containing a cured product of a polymerizable liquid crystal compound, such as a layer obtained by applying and curing a composition containing a dichroic dye having liquid crystallinity or a composition containing a dichroic dye and a polymerizable liquid crystal.
The polarizing layer obtained by applying and curing a composition containing a dichroic dye and a polymerizable compound is preferable to the stretched film or the stretched layer having the dichroic dye adsorbed thereon because the polarizing layer has no limitation in the bending direction.
[ polarizer layer as stretched film or stretched layer ]
The polarizer layer as a stretched film having a dichroic dye adsorbed thereon can be generally produced through the following steps: a step of uniaxially stretching a polyvinyl alcohol resin film; a step of adsorbing a dichroic dye by dyeing a polyvinyl alcohol resin film with the dichroic dye; treating the polyvinyl alcohol resin film having the dichroic dye adsorbed thereon with an aqueous boric acid solution; and a step of washing with water after the treatment with the aqueous boric acid solution.
The thickness of the polarizer layer 103 is, for example, 2 μm to 40 μm. The thickness of the polarizer layer 103 may be 5 μm or more, 20 μm or less, further 15 μm or less, and further 10 μm or less.
The polyvinyl alcohol resin is obtained by saponifying a polyvinyl acetate resin. As the polyvinyl acetate-based resin, in addition to polyvinyl acetate which is a homopolymer of vinyl acetate, a copolymer of vinyl acetate and another monomer copolymerizable therewith may be used. Examples of the other monomer copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and (meth) acrylamides having an ammonium group.
The saponification degree of the polyvinyl alcohol resin is usually about 85 mol% to 100 mol%, and preferably 98 mol% or more. The polyvinyl alcohol resin may be modified, and for example, polyvinyl formal or polyvinyl acetal modified with aldehydes may be used. The polymerization degree of the polyvinyl alcohol resin is usually 1000 to 10000, preferably 1500 to 5000.
The polarizer layer as the stretched layer having the dichroic dye adsorbed thereon can be generally produced through the following steps: a step of applying a coating liquid containing the polyvinyl alcohol resin onto a base film; a step of uniaxially stretching the obtained laminated film; a step of dyeing the polyvinyl alcohol resin layer of the uniaxially stretched laminated film with a dichroic dye to adsorb the dichroic dye to produce a polarizer; treating the film having the dichroic dye adsorbed thereon with an aqueous boric acid solution; and a step of washing with water after the treatment with the aqueous boric acid solution.
The substrate film may be peeled off from the polarizer layer as necessary. The material and thickness of the base film may be the same as those of the thermoplastic resin film described later.
The polarizer layer as the stretched film or the stretched layer may be assembled in a laminate in a form in which a thermoplastic resin film is bonded to one surface or both surfaces thereof. The thermoplastic resin film can function as a protective film or a retardation film for the polarizer layer 103. The thermoplastic resin film may be formed of a polyolefin resin such as a chain polyolefin resin (e.g., a polypropylene resin) or a cyclic polyolefin resin (e.g., a norbornene resin); cellulose resins such as triacetyl cellulose; polyester resins such as polyethylene terephthalate, polyethylene naphthalate and polybutylene terephthalate; a polycarbonate-based resin; (meth) acrylic resins; or a mixture thereof.
From the viewpoint of thinning, the thickness of the thermoplastic resin film is usually 300 μm or less, preferably 200 μm or less, more preferably 100 μm or less, further preferably 80 μm or less, further preferably 60 μm or less, and usually 5 μm or more, preferably 20 μm or more.
The thermoplastic resin film may or may not have a phase difference.
The thermoplastic resin film may be bonded to the polarizer layer 103 using an adhesive layer, for example.
[ polarizer layer obtained by applying and curing a composition containing a dichroic dye and a polymerizable compound ]
Examples of the polarizer layer obtained by applying and curing a composition containing a dichroic dye and a polymerizable compound include a polarizer layer containing a cured product of a polymerizable liquid crystal compound, such as a layer obtained by applying and curing a composition containing a liquid crystal-polymerizable dichroic dye or a composition containing a dichroic dye and a polymerizable liquid crystal to a base film.
The substrate film may be peeled off from the polarizer layer as necessary. The material and thickness of the base film may be the same as those of the thermoplastic resin film described above. The polarizer layer may be provided with an orientation film. The alignment film may be peeled off.
The polarizer layer obtained by applying and curing a composition containing a dichroic dye and a polymerizable compound may be incorporated in the optical laminate in a form in which a thermoplastic resin film is bonded to one or both surfaces thereof. As the thermoplastic resin film, the same thermoplastic resin film as that usable for the stretched film or the polarizer layer of the stretched layer can be used. The thermoplastic resin film may be bonded to the polarizer layer using an adhesive layer, for example.
The polarizer layer obtained by applying and curing a composition containing a dichroic dye and a polymerizable compound may have an Overcoat (OC) layer formed on one or both surfaces thereof as a protective layer. Examples thereof include photocurable resins and water-soluble polymers. Examples of the photocurable resin include a (meth) acrylic resin, a urethane resin, a (meth) acrylic urethane resin, an epoxy resin, and a silicone resin. Examples of the water-soluble polymer include poly (meth) acrylamide polymers; vinyl alcohol polymers such as polyvinyl alcohol and ethylene-vinyl alcohol copolymers, ethylene-vinyl acetate copolymers, (meth) acrylic acid or anhydride thereof-vinyl alcohol copolymers; a carboxyvinyl polymer; polyvinylpyrrolidone; starches; sodium alginate; polyethylene oxide polymers, and the like. The thickness of the OC layer is preferably 20 μm or less, more preferably 15 μm or less, still more preferably 10 μm or less, and may be 5 μm or less, and further may be 0.05 μm or more, and may be 0.5 μm or more.
The thickness of the polarizer layer obtained by applying and curing a composition containing a dichroic dye and a polymerizable compound is usually 10 μm or less, preferably 0.5 to 8 μm, and more preferably 1 to 5 μm.
[2 nd adhesive layer ]
The 2 nd adhesive layer 104 is an adhesive layer disposed between the polarizer layer 103 and the back surface plate 105. The 2 nd adhesive layer may be an adhesive layer disposed closest to the back surface plate among the adhesive layers constituting the laminate. The 2 nd adhesive layer 104 may be 1 layer, or may be composed of 2 or more layers, and preferably 1 layer.
The 2 nd adhesive layer 104 may be formed of the adhesive composition a as described above. The thickness of the 2 nd adhesive layer, the tan δ at the temperature of the 2 nd adhesive layer-40 ℃ and the range thereof are the same as those shown in the above description of the 1 st adhesive layer 102, the tan δ at the temperature of-40 ℃ and the range thereof.
The 2 nd pressure-sensitive adhesive layer 104 may be the same as or different from the 1 st pressure-sensitive adhesive layer 102 in composition, blending component, thickness, tan δ at a temperature of-40 ℃.
[ Back Panel ]
As the back plate 105, a plate-like body that can transmit light, a component used in a general display device, or the like can be used.
The thickness of back plate 105 may be, for example, 5 μm to 2000 μm, preferably 10 μm to 1000 μm, and more preferably 15 μm to 500 μm.
The plate-like body used for rear plate 105 may be formed of only 1 layer or 2 or more layers, and the plate-like body exemplified for the plate-like body described in front plate 101 may be used.
Examples of the constituent elements used in a typical display device used for the back panel 105 include a spacer, a touch sensor panel, and an organic EL display element. Examples of the order of stacking the components in the display device include a front panel, a circularly polarizing plate, a spacer, a front panel, a circularly polarizing plate, an organic EL display element, a front panel, a circularly polarizing plate, a touch sensor panel, an organic EL display element, a front panel, a touch sensor panel, a circularly polarizing plate, and an organic EL display element.
(touch sensor panel)
The touch sensor panel is not limited to a detection method as long as it is a sensor capable of detecting a touched position, and examples thereof include touch sensor panels of a resistive film method, a capacitive coupling method, an optical sensor method, an ultrasonic wave method, an electromagnetic induction coupling method, a surface acoustic wave method, and the like. From the viewpoint of low cost, a touch sensor panel of a resistive film type or a capacitive coupling type can be preferably used.
An example of a resistive touch sensor panel includes a pair of substrates arranged to face each other, an insulating spacer sandwiched between the pair of substrates, a transparent conductive film provided as a resistive film on an inner front surface of each of the substrates, and a touch position detection circuit. In an image display device provided with a resistive touch sensor panel, if a surface of a front panel is touched, an opposing resistive film is short-circuited, and a current flows through the resistive film. The touch position detecting circuit detects the voltage change at this time, thereby detecting the touched position.
An example of a capacitive coupling type touch sensor panel includes a substrate, a position detection transparent electrode provided on the entire surface of the substrate, and a touch position detection circuit. In an image display device provided with a capacitive coupling type touch sensor panel, if the front surface of the front panel is touched, the transparent electrode is grounded via the capacitance of a human body at the touched point. The touch position detection circuit detects the grounding of the transparent electrode, thereby detecting the touched position.
The thickness of the touch sensor panel may be, for example, 5 to 2000 μm, or 5 to 100 μm.
[ phase difference layer ]
The laminate 100 may further include 1 or 2 or more retardation layers. The phase difference layer is typically disposed between the polarizer layer 103 and the back panel 105. The retardation layer may be laminated on the 1 st pressure-sensitive adhesive layer 102 or the 2 nd pressure-sensitive adhesive layer 104, or may be laminated on another layer (including another retardation layer) via a layer (hereinafter, also referred to as a laminating layer) made of a pressure-sensitive adhesive or an adhesive other than these layers.
[ adhesive layer ]
The laminating layer is a layer disposed between the 1 st adhesive layer 102 and the 2 nd adhesive layer 104, and is a layer made of an adhesive or an adhesive. The adhesive constituting the laminating layer may be the same adhesive as exemplified for the adhesive composition constituting the 1 st adhesive layer 102 or the 2 nd adhesive layer, or may be another adhesive such as a (meth) acrylic adhesive, a styrene-based adhesive, a silicone-based adhesive, a rubber-based adhesive, a urethane-based adhesive, a polyester-based adhesive, an epoxy-based copolymer adhesive, or the like.
The adhesive constituting the adhesive layer may be formed by combining 1 or 2 or more kinds of water-based adhesives, active energy ray-curable adhesives, pressure-sensitive adhesives, and the like. Examples of the aqueous adhesive include a polyvinyl alcohol resin aqueous solution and an aqueous two-pack type urethane emulsion adhesive. The active energy ray-curable adhesive is an adhesive that is cured by irradiation with an active energy ray such as ultraviolet ray, and examples thereof include an adhesive containing a polymerizable compound and a photopolymerization initiator, an adhesive containing a photoreactive resin, and an adhesive containing a binder resin and a photoreactive crosslinking agent. Examples of the polymerizable compound include photopolymerizable monomers such as a photocurable epoxy monomer, a photocurable acrylic monomer, and a photocurable urethane monomer, and oligomers derived from these monomers. Examples of the photopolymerization initiator include photopolymerization initiators containing active species that generate neutral radicals, anionic radicals, cationic radicals, and the like by irradiation with active energy rays such as ultraviolet rays.
The thickness of the adhesive layer may be, for example, 1 μm or more, preferably 1 to 25 μm, more preferably 2 to 15 μm, and still more preferably 2.5 to 5 μm.
The laminate 200 shown in fig. 2 includes a front plate 101, a1 st adhesive layer 102, a polarizer layer 103, a bonding layer 108, and a back plate 105, and further includes a1 st retardation layer 106, a bonding layer 109, a2 nd retardation layer 107, and a2 nd adhesive layer 104.
Examples of the retardation layer include a positive A plate and a positive C plate such as a λ/4 plate and a λ/2 plate.
The retardation layer may be, for example, a retardation film that can be formed of the thermoplastic resin film, or a layer obtained by curing a polymerizable liquid crystal compound, that is, a layer containing a cured product of a polymerizable liquid crystal compound, and the latter is preferable.
The thickness of the retardation film may be the same as that of the thermoplastic resin film described above. The thickness of the retardation layer obtained by curing the polymerizable liquid crystal compound is, for example, 0.1 to 10 μm, preferably 0.5 to 8 μm, and more preferably 1 to 6 μm.
The retardation layer obtained by curing the polymerizable liquid crystal compound can be formed by applying a composition containing the polymerizable liquid crystal compound to a substrate film and curing the composition. An alignment layer may also be formed between the substrate film and the coating layer. The material and thickness of the base film may be the same as those of the thermoplastic resin film described above.
The retardation layer obtained by curing the polymerizable liquid crystal compound may be incorporated in the laminate 100 in a form having an alignment layer and/or a substrate film. The back panel 105 may also be a substrate film coated with the above composition.
As described above, the adhesive or the adhesive may be used for the adhesion layer 108. The binder may be the binder composition a described above.
As the adhesive, an aqueous adhesive or an active energy ray-curable adhesive can be used. Examples of the aqueous adhesive include an adhesive composed of a polyvinyl alcohol resin aqueous solution, and an aqueous two-pack type urethane emulsion adhesive.
The active energy ray-curable adhesive is an adhesive that is cured by irradiation with an active energy ray such as ultraviolet ray, and examples thereof include an adhesive containing a polymerizable compound and a photopolymerization initiator, an adhesive containing a photoreactive resin, and an adhesive containing a binder resin and a photoreactive crosslinking agent.
Examples of the polymerizable compound include photopolymerizable monomers such as a photocurable epoxy monomer, a photocurable (meth) acrylic monomer, and a photocurable urethane monomer, and oligomers derived from a photopolymerizable monomer.
Examples of the photopolymerization initiator include photopolymerization initiators containing active species that generate neutral radicals, anionic radicals, and cationic radicals by irradiation with active energy rays such as ultraviolet rays. As the active energy ray-curable adhesive containing a polymerizable compound and a photopolymerization initiator, an active energy ray-curable adhesive containing a photocurable epoxy monomer and a photocationic polymerization initiator can be preferably used.
[ method for producing laminate ]
The laminate 100 can be manufactured by a method including the following steps: the layers constituting the laminate 100 are bonded to each other via an adhesive layer or further via an adhesive layer. When the layers are bonded to each other via an adhesive layer or an adhesive layer, one or both of the bonding surfaces are preferably subjected to a surface activation treatment such as corona treatment in order to improve the adhesion.
The polarizer layer 103 may be formed directly on a thermoplastic resin film or a base film, which may be incorporated in the laminate 100, or may be separated from the polarizer layer 103 without being a constituent of the laminate.
< display device >
The display device of the present invention includes the laminate 100 of the present invention described above. The display device is not particularly limited, and examples thereof include image display devices such as an organic EL display device, an inorganic EL display device, a liquid crystal display device, and an electroluminescence display device. The display device may have a touch panel function. The optical laminate is suitable for a flexible display device which can be bent or bent.
In the display device, the optical laminate is disposed on the viewing side of the display element included in the display device such that the front panel faces outward (the side opposite to the display element side, i.e., the viewing side).
The display device of the present invention can be used as a mobile device such as a smart phone or a tablet computer, a television, a digital photo frame, an electronic sign, a measuring instrument, an office machine, a medical machine, a computer machine, or the like.
< adhesive composition >
The adhesive composition of the present invention is an adhesive composition containing a (meth) acrylic polymer in which constituent units derived from a monomer having a reactive functional group are less than 5% by mass based on the total mass of the polymer and a monofunctional (meth) acrylic monomer having an alkoxy group. The adhesive composition of the present invention is excellent in adhesion durability in a low-temperature environment, and therefore is suitable as a material for forming an adhesive layer of a laminate.
Examples of the kind and molecular weight of the monomer constituting the (meth) acrylic polymer, the kind of the monofunctional (meth) acrylic monomer having an alkoxy group, the kind of the reactive functional group, the content thereof, the composition of the adhesive composition, the type of the adhesive composition, the additive which can be blended in the adhesive composition, and the like are the same as those exemplified in the description of the adhesive composition a described above.
The adhesive composition of the present invention can be produced by mixing the respective components together by a known method, for example, using a mixer or the like.
< pressure-sensitive adhesive sheet >
The adhesive sheet of the present invention comprises an adhesive layer formed from the adhesive composition of the present invention described above. The adhesive layer may be formed by coating an adhesive composition on a substrate. When an active energy ray-curable pressure-sensitive adhesive composition is used as the pressure-sensitive adhesive composition, a cured product having a desired degree of curing can be obtained by irradiating the pressure-sensitive adhesive layer thus formed with active energy rays.
The substrate may be a release film subjected to a release treatment. The pressure-sensitive adhesive sheet can be produced by forming a layer made of a pressure-sensitive adhesive on a release film in a sheet form in advance, and further bonding another release film on the pressure-sensitive adhesive layer.
The adhesive sheet of the present invention has excellent adhesion durability in a low-temperature environment. The adhesive sheet of the present invention has a tan delta of 1.5 to 2.0 at a temperature of-40 ℃. Therefore, when the adhesive sheet of the present invention is used in a laminate, the laminate tends to have excellent bendability at low temperatures. From the viewpoint of suppressing cracking of the pressure-sensitive adhesive layer, the tan δ of the pressure-sensitive adhesive sheet at a temperature of-40 ℃ is preferably 1.6 to 1.9. The tan. delta. at a temperature of-40 ℃ can be measured according to the measurement method described in the section of examples, which will be described later.
The present invention will be described in further detail with reference to examples, but the present invention is not limited to these examples.
Examples
[ thickness of layer ]
The film thickness was measured using a contact type film thickness measuring apparatus ("MS-5C" manufactured by Nikon K.K.).
The polarizer layer and the alignment film were measured using a laser microscope (OLS 3000, Olympus).
[ tan. delta. at a temperature of-40 ]
The tan. delta. at-40 ℃ was measured using a viscoelasticity measuring apparatus (MCR-301, Anton Paar Co.). The same adhesive sheets as used in examples and comparative examples were cut to a width of 30mm x a length of 30 mm. The release film was peeled from the pressure-sensitive adhesive sheet, and a plurality of layers were laminated so that the thickness of the pressure-sensitive adhesive layer became 150 μm, and the pressure-sensitive adhesive layer was joined to a glass plate. In a state where the pressure-sensitive adhesive layer was bonded to the measurement chip, the measurement was performed at a frequency of 1.0Hz, a strain amount of 1% and a temperature rise rate of 5 ℃/min in a temperature range of-40 ℃ to 100 ℃ to confirm the measured value of tan δ at-40 ℃. The tan δ has the following relationship with the storage elastic modulus G' and the loss elastic modulus G ″.
Figure BDA0003224658660000231
[ Low temperature bendability (-20 ℃ C.) ]
The laminates obtained in the examples and comparative examples were subjected to a low-temperature bending property test as follows. Fig. 3 is a diagram schematically showing the method of the evaluation test. First, the heavy separator of the laminate was peeled off, and a PET film (thickness 100 μm) was laminated. A bending apparatus (STS-VRT-500, manufactured by Science Town) having 2 stages 501 and 502 was prepared, and the laminate 100 was placed on the stages 501 and 502 (FIG. 3 a). The distance (gap) C between the 2 tables 501 and 502 is set to 6mm (3R). The tables 501 and 502 are swingable about the gap C between 2 tables, and the initial 2 tables 501 and 502 form the same plane. The 2 tables 501 and 502 are rotated upward by 90 degrees about the positions P1 and P2 as the centers of the rotation axes, the 2 tables 501 and 502 are closed (fig. 3b), the tables 501 and 502 are opened again, and this operation is defined as 1-time bending. This operation was repeated to count the number of bends until the laminate 100 first cracked. The evaluation criteria are as follows.
Very good: the preparation process is carried out for more than 2 ten thousand times,
good (good): more than 1 ten thousand times and less than 2 ten thousand times,
Δ (available): more than 0.5 ten thousand times and less than 1 ten thousand times,
x (slightly worse): more than 0.1 ten thousand times and less than 0.5 ten thousand times,
xxx (poor): less than 0.1 ten thousand times
[ Low temperature adhesion durability (-40 ℃ C.) ]
The laminates obtained in each of examples and comparative examples were cut into a width of 100mm × a length of 100 mm. And stripping the heavy separator and attaching the heavy separator to the alkali-free glass. The pressure-bonding treatment was carried out in an autoclave (50 ℃ C., 5 atm) for about 20 minutes and maintained under constant temperature and humidity conditions (23 ℃ C., 50% RH) for 4 hours. The sample was put in an oven at-40 ℃ and judged for the presence of floating, peeling, and bubbling after 250 hours.
O: the appearance change such as floating, peeling, foaming and the like was hardly observed.
And (delta): the appearance changes such as floating, peeling, foaming and the like are slightly obvious.
X: the appearance changes such as floating, peeling, foaming and the like are obviously seen.
[ weight average molecular weight (Mw) ]
The weight average molecular weight (Mw) of the (meth) acrylic polymer was determined as a number average molecular weight (Mn) in terms of polystyrene, and the mobile phase was obtained by the Size Exclusion Chromatography (SEC) described below using tetrahydrofuran. The measured (meth) acrylic polymer was dissolved in tetrahydrofuran at a concentration of about 0.05 mass%, and 10. mu.L of the solution was injected into SEC. The mobile phase flowed at a rate of 1.0 mL/min. As the column, PLGel MIXED-B (manufactured by Polymer Laboratories) was used. The detector used was a UV-VIS detector (trade name: Agilent GPC).
< example 1>
[ (preparation of meth) acrylic Polymer A1 ]
A (meth) acrylic polymer A1 was prepared by copolymerizing 54 parts by mass of n-butyl acrylate, 45 parts by mass of 2-ethylhexyl acrylate, and 1 part by mass of 4-hydroxybutyl acrylate. The molecular weight of the (meth) acrylic polymer a1 was measured by the method described later, and the weight average molecular weight (Mw) was 80 ten thousand.
[ preparation of adhesive composition ]
1100 parts by mass (solid content equivalent; the same applies hereinafter) of the (meth) acrylic polymer A obtained in the above step, 0.25 parts by mass of trimethylolpropane-modified xylylene diisocyanate (product name "TD-75" manufactured by Soken chemical Co., Ltd.) as a thermal crosslinking agent B, and 0.2 parts by mass of 3-glycidoxypropyltrimethoxysilane (product name "KBM 403" manufactured by shin-Etsu chemical Co., Ltd.) as a silane coupling agent C were mixed, sufficiently stirred, and diluted with methyl ethyl ketone to obtain a coating solution of the adhesive composition.
[ production of adhesive sheet ]
The obtained coating solution of the adhesive composition was applied to a release-treated surface of a light separator (product name "SP-PET 752150" manufactured by LINTEC corporation) by a knife coater. Then, the coating layer was heat-treated at 90 ℃ for 1 minute to form a coating layer. Subsequently, the coating layer on the light separator obtained above was bonded to a heavy separator (product name "SP-PET 382120" manufactured by LINTEC) so that the release-treated surface of the separator was in contact with the coating layer, and the resultant was cured at 23 ℃ and 50% RH for 7 days to prepare an adhesive sheet having an adhesive layer with a thickness of 25 μm, that is, an adhesive sheet having a structure of light separator/adhesive layer (thickness: 25 μm)/heavy separator. The thickness of the pressure-sensitive adhesive layer is a value measured by the above-described method. Table 1 shows the respective formulations (solid content equivalent) of the adhesive compositions when the (meth) acrylic polymer a1 was set to 100 parts by mass (solid content equivalent). The abbreviations and the like shown in table 1 are as follows.
BA: acrylic acid n-butyl ester
2 EHA: 2-ethylhexyl acrylate
4 HBA: acrylic acid 4-hydroxybutyl ester
< examples 2 and 3>
(meth) acrylic polymers a2 and A3 and adhesive sheets thereof were produced in the same manner as in example 1, except that the proportions of the monomers constituting (meth) acrylic polymer a1, the weight average molecular weight (Mw) of (meth) acrylic polymer a1 and the blending amount of the crosslinking agent were changed as shown in table 1.
< comparative examples 1 and 2>
(meth) acrylic polymers B1 and B2 and adhesive sheets thereof were produced in the same manner as in example 1, except that the proportions of the monomers constituting (meth) acrylic polymer a1, the weight average molecular weight (Mw) of (meth) acrylic polymer a1 and the blending amount of the crosslinking agent were changed as shown in table 1.
[ Table 1]
Figure BDA0003224658660000251
< comparative example 3>
[ production of Silicone urethane acrylate resin ]
Polyisocyanate, polysilicon having hydroxyl groups at both ends, and dibutyltin dilaurate as a catalyst were put into a 2L flask equipped with an electronic stirrer, a heating mantle, a cooling tube, and a temperature controller in the following parts by mass, and the reaction temperature was raised to 70 ℃ while stirring, and the reaction was maintained for 4 hours. Thereafter, the (meth) acrylate having a hydroxyl group and methoxyhydroquinone as a polymerization inhibitor were reacted, and the reaction mixture was maintained for 2 hours after the completion of the charge.
Polyisocyanate (4, 4' -methylenedicyclohexyldiisocyanate, molecular weight 262): 524 parts by mass
Polysilicon having hydroxyl groups at both ends (X-22-160AS, molecular weight 933, Signal-to-Cross chemistry): 933 parts by mass
Dibutyltin dilaurate: 0.4 part by mass
Methoxy hydroquinone: 0.3 part by mass
(meth) acrylate having hydroxyl group (2-hydroxyethyl acrylate, molecular weight 116): 232 parts by mass
[ production of adhesive sheet ]
The adhesive composition was applied to a release film coated with a silicon release agent to a thickness of 25 μm, and after the release film was bonded thereto, the adhesive composition was applied to a high-pressure UV lamp at a thickness of 500mJ/cm2The adhesive sheet is produced.
< example 4>
[ (preparation of meth) acrylic Polymer (A4) ]
A1L reactor equipped with a cooling device to reflux nitrogen gas and easily controlled in temperature was charged with a monomer mixture comprising 89.9 mass% of 2-ethylhexyl acrylate (2-EHA) monomer and 10 mass% of Butyl Acrylate (BA) monomer, and then the mixture was refluxed with nitrogen gas for 1 hour to remove oxygen and maintained at 80 ℃. After the monomer mixture was uniformly mixed, 0.05 mass% of benzildimethylketal (I-651) and 0.05 mass% of 1-hydroxycyclohexylphenylketone (I-184) as photopolymerization initiators were added. Subsequently, a UV lamp (10mW) was irradiated with the resulting mixture while stirring to produce a (meth) acrylate polymer (A4) having a weight-average molecular weight (Mw) of 33 ten thousand. The ratios of the components are shown in table 2.
[ production of adhesive sheet ]
The adhesive composition prepared in the composition shown in table 3 was coated on a light separator (polyethylene terephthalate film, thickness 38 μm) coated with a silicon release agent so that the thickness became 25 μm. A heavy separator (polyethylene terephthalate film, 38 μm thick) was bonded thereto, and UV irradiation was performed to produce an adhesive sheet composed of a light separator/an adhesive layer/a heavy separator. The abbreviations and the like shown in table 3 are as follows.
EOEOEOEA: acrylic acid ethoxy ethyl ester
NP (EO) 8A: nonyl phenol EO modified acrylate
< example 5>
[ (preparation of meth) acrylic Polymer (A5) ]
After a monomer mixture comprising 89.9 mass% of 2-ethylhexyl acrylate (2-EHA) monomer, 4 mass% of Butyl Acrylate (BA) monomer and 6 mass% of Lauryl Acrylate (LA) monomer was charged into a 1L reactor equipped with a cooling device to allow nitrogen gas to flow back and facilitate temperature adjustment, nitrogen gas was refluxed for 1 hour to remove oxygen and then maintained at 80 ℃. After the monomer mixture was uniformly mixed, 0.05 mass% of benzildimethylketal (I-651) and 0.05 mass% of 1-hydroxycyclohexylphenylketone (I-184) as photopolymerization initiators were added. Subsequently, a UV lamp (10mW) was irradiated with the resulting mixture while stirring to obtain a (meth) acrylate polymer (A5) having a weight-average molecular weight (Mw) of 40 ten thousand.
[ production of adhesive sheet ]
A pressure-sensitive adhesive sheet was produced in the same manner as in example 4 using the pressure-sensitive adhesive composition produced with the composition shown in table 3.
< example 6>
[ (preparation of meth) acrylic Polymer (A6) ]
After a monomer mixture comprising 89.9 mass% of 2-ethylhexyl acrylate (2-EHA) monomer, 6 mass% of Lauryl Acrylate (LA) monomer and 4 mass% of isodecyl acrylate (IDA) monomer was charged into a 1L reactor equipped with a cooling device to allow nitrogen gas to flow back and facilitate temperature adjustment, nitrogen gas was refluxed for 1 hour to remove oxygen and then maintained at 80 ℃. After the monomer mixture was uniformly mixed, 0.05 mass% of benzildimethylketal (I-651) and 0.05 mass% of 1-hydroxycyclohexylphenylketone (I-184) as photopolymerization initiators were added. Subsequently, a UV lamp (10mW) was irradiated with the mixture while stirring to produce a (meth) acrylate polymer (a6) having a weight average molecular weight (mW) of 40 ten thousand.
[ production of adhesive sheet ]
A pressure-sensitive adhesive sheet was produced in the same manner as in example 4 using the pressure-sensitive adhesive composition produced with the composition shown in table 3.
[ Table 2]
Figure BDA0003224658660000281
[ Table 3]
Figure BDA0003224658660000282
The adhesive sheets produced in examples 1 to 6 and comparative examples 1 to 3 were measured for tan δ at a temperature of-40 ℃. The results are shown in Table 4.
[ front Panel (Window film) ]
A polyimide film (thickness: 50 μm) having a hard coat layer (thickness: 10 μm) on one surface was prepared as a front panel.
[ polarizer layer ]
1. The following materials were prepared.
1) TAC film with thickness of 25 μm.
2) An alignment film-forming composition.
[ Polymer 1]
A polymer 1 having a photoreactive group composed of the following structural units was prepared.
Figure BDA0003224658660000283
A solution obtained by dissolving polymer 1 in cyclopentanone at a concentration of 5 mass% was used as the composition for forming an alignment film [ hereinafter, also referred to as composition (D-1) ].
3) Composition for forming polarizer layer
[ polymerizable liquid Crystal Compound ]
As the polymerizable liquid crystal compound, a polymerizable liquid crystal compound represented by the formula (1-1) [ hereinafter, also referred to as compound (1-1) ] and a polymerizable liquid crystal compound represented by the formula (1-2) [ hereinafter, also referred to as compound (1-2) ] were used.
Figure BDA0003224658660000291
The compound (1-1) and the compound (1-2) were synthesized by the method described in Lub et al, Recl, Trav, Chim, Pays-Bas, 115, 321-328 (1996).
[ dichroic dye ]
As the dichroic dye, azo dyes described in examples of Japanese patent application laid-open No. 2013-101328 represented by the following formulae (2-1a), (2-1b), and (2-3a) are used.
Figure BDA0003224658660000292
The composition for forming a polarizer layer [ hereinafter also referred to as composition (a-1) ] was prepared by: 75 parts by mass of the compound (1-1), 25 parts by mass of the compound (1-2), 2.5 parts by mass of each of the azo dyes represented by the above formulae (2-1a), (2-1b) and (2-3a) as dichroic dyes, 6 parts by mass of 2-dimethylamino-2-benzyl-1- (4-morpholinophenyl) butan-1-one (Irgacure369, manufactured by BASF Japan) as a polymerization initiator and 1.2 parts by mass of a polyacrylate compound (BYK-361N, manufactured by BYK-Chemie) as a leveling agent were mixed with 400 parts by mass of toluene as a solvent, and the resulting mixture was stirred at 80 ℃ for 1 hour.
4) Composition for forming protective layer (OC layer)
The composition for forming a protective layer (OC layer) [ hereinafter also referred to as composition (E-1) ] is prepared by mixing water: 100 parts by mass of a polyvinyl alcohol resin powder (manufactured by Kuraray Co., Ltd., average polymerization degree 18000, trade name: KL-318): 3 parts by mass of a polyamide epoxy resin (crosslinking agent, product name: SR650(30) available from Suzuki Chemtex): 1.5 parts by mass.
2. Manufacturing method
1) The alignment film-forming composition was applied to the TAC film side in the following manner.
First, a corona treatment is applied to the TAC film side. The conditions of the corona treatment were an output of 0.3kW and a treatment speed of 3 m/min. Thereafter, the composition (D-1) obtained as described above was coated on the TAC by a bar coating method, and heat-dried in a drying oven at 80 ℃ for 1 minute. The obtained dried film was subjected to polarized UV irradiation treatment to form a1 st alignment film (AL 1). The polarized UV treatment was carried out by passing light irradiated from a UV irradiation device (SPOT CURE SP-7; manufactured by Usio Motor Co., Ltd.) through a wire grid (UIS-27132#, manufactured by Usio Motor Co., Ltd.) and measuring the cumulative light quantity at a wavelength of 365nm to be 100mJ/cm2Under the conditions of (1). The thickness of the 1 st alignment film (AL1) was 100 nm.
2) The composition for forming a polarizer layer was applied to the side of the alignment film in the following manner.
First, the composition (a-1) was coated on the formed 1 st alignment film (AL1) by a bar coating method, dried by heating in a drying oven at 120 ℃ for 1 minute, and then cooled to room temperature. Using the UV irradiation apparatus described above, the cumulative light amount was 1200mJ/cm2The dried film was irradiated with ultraviolet light (365nm basis) to form a polarizer layer (pol). The thickness of the obtained polarizer layer (pol) was measured by a laser microscope (OLS 3000, manufactured by Olympus corporation), and it was 1.8. mu.m. A laminate composed of "TAC/AL 1/pol" was obtained in this manner.
3) The composition for forming a protective layer (OC layer) was applied to the polarizer layer side in the following manner.
The composition (E-1) was coated on the formed polarizer layer (pol) by a bar coating method so that the thickness after drying became 1.0 μm, and dried at a temperature of 80 ℃ for 3 minutes. In this manner, a laminate composed of "TAC film/cPL (AL1+ pol + protective layer)" was obtained.
[ phase difference layer ]
1. Material preparation
The following materials were prepared.
1) PET film with a thickness of 100 μm.
2) An alignment film-forming composition.
[ Polymer 1]
A polymer 1 having a photoreactive group composed of the following structural units was prepared.
Figure BDA0003224658660000311
A solution obtained by dissolving polymer 1 in cyclopentanone at a concentration of 5% by weight was used as the composition for forming an alignment film [ hereinafter, also referred to as composition (D-1) ].
3) Composition for forming phase difference layer
The ingredients shown below were mixed, and the resulting mixture was stirred at 80 ℃ for 1 hour, thereby obtaining composition (B-1).
A compound b-1 represented by the following formula: 80 parts by mass
Figure BDA0003224658660000312
A compound b-2 represented by the following formula: 20 parts by mass
Figure BDA0003224658660000313
Polymerization initiator (Irgacure369, 2-dimethylamino-2-benzyl-1- (4-morpholinophenyl) butan-1-one manufactured by BASF Japan): 6 parts by mass
Leveling agent (BYK-361N, polyacrylate compound, BYK-Chemie Co., Ltd.): 0.1 part by mass
Solvent (cyclopentanone): 400 parts by mass
2. Manufacturing method
1) The composition for forming an alignment film was applied to a PET film in the following manner.
A polyethylene terephthalate film (PET) having a thickness of 100 μm was prepared as a substrate, and the composition (D-1) was applied to the film by a bar coating method and heat-dried in a drying oven at 80 ℃ for 1 minute. The obtained dried film was subjected to polarized UV irradiation treatment to form a2 nd alignment film (AL 2). Polarized UV treatment Using the UV irradiation device, the cumulative quantity of light measured at a wavelength of 365nm was 100mJ/cm2Under the conditions of (1). The polarization direction of polarized UV was set to 45 ° with respect to the absorption axis of the polarizer layer. In this manner, a laminate composed of "substrate (PET)/2 nd alignment film (AL 2)" was obtained.
2) The retardation layer-forming composition was applied to the orientation film side of the PET film in the following manner.
The composition (B-1) was applied to the 3 rd alignment film (AL2) of the 1 st substrate thus obtained by a bar coating method, dried by heating in a drying oven at 120 ℃ for 1 minute, and then cooled to room temperature. The obtained dried film was irradiated with a cumulative light amount of 1000mJ/cm using the UV irradiation device2Ultraviolet rays (365nm basis), thereby forming a retardation layer. The thickness of the obtained retardation layer was measured by a laser microscope (OLS 3000, manufactured by Olympus Co., Ltd.) to be 2.0. mu.m. The phase difference layer is a lambda/4 plate (QWP) exhibiting a phase difference value of lambda/4 in the in-plane direction. A laminate composed of "substrate (PET)/AL 2/QWP" was obtained in this manner.
[ common adhesive sheet ]
1) Polymerization of acrylic resins
The following components were reacted at 55 ℃ under nitrogen atmosphere with stirring, thereby obtaining an acrylic resin.
Butyl acrylate: 70 parts by mass
Methyl acrylate: 20 parts by mass
Acrylic acid: 2.0 parts by mass
Radical polymerization initiator (2, 2' -azobisisobutyronitrile): 0.2 part by mass
2) Liquid preparation of adhesive composition
The following ingredients were mixed to obtain an adhesive composition.
Acrylic resin: 100 parts by mass
Crosslinking agent ("Coronate L" manufactured by tokyo corporation): 1.0 part by mass
Silane coupling agent (trade name silicon corporation "X-12-981"): 0.5 part by mass
Ethyl acetate was added so that the total solid content concentration became 10 mass%, to obtain a pressure-sensitive adhesive composition.
3) Production of adhesive sheet
The obtained pressure-sensitive adhesive composition was applied by an applicator to a release-treated surface of a polyethylene terephthalate film (heavy separator, thickness 38 μm) which had been subjected to release treatment so that the thickness after drying became 5 μm. The coating layer was dried at 100 ℃ for 1 minute to obtain a film having an adhesive layer. Thereafter, another polyethylene terephthalate film (light separator, 38 μm thick) subjected to mold release treatment was attached to the exposed surface of the adhesive layer. Thereafter, the mixture was aged at 23 ℃ and 50% RH relative humidity for 7 days to obtain a light separator/a common adhesive layer/a heavy separator.
< example 7>
The laminate was produced by the following procedure. First, a laminate 410[ TAC film 301/cPL ((AL1+ pol)302/OC layer 303) ] including the above-described polarizer layer and the above-described common adhesive sheet 420 (light spacer 304/common adhesive layer 305/heavy spacer 306) were prepared (fig. 4 a). Laminate a430 was obtained by applying corona treatment (output 0.3KW, speed 3 m/min) to the OC layer 303 side of laminate 410 including the polarizer layer and the side of common adhesive sheet 420 from which light separator 304 was peeled, and then laminating them. The above phase difference layer 440[ substrate (PET)308/AL2/QWP307] was prepared. (FIG. 4 b).
Next, the QWP307 side of the retardation layer 440 and the surface of the laminate a from which the heavy separator 306 was peeled were subjected to corona treatment (output 0.3KW, speed 3 m/min), and then laminated to obtain a laminate b 450. Thereafter, an adhesive sheet 460 (light spacer 309/adhesive layer 310/heavy spacer 311) produced in example 1 was prepared (fig. 4 c).
Laminate c470 was obtained by laminating the surface of laminate b450 from which substrate (PET)308 was peeled and the surface of adhesive sheet 460 from which light separator 309 was peeled after corona treatment (output 0.3KW, speed 3 m/min). Further, the pressure-sensitive adhesive sheet 490 (light separator 314/pressure-sensitive adhesive layer 315/heavy separator 316) produced in example 1 was prepared, and the surface from which the light separator 314 was peeled and the polyimide film 313 side of the front panel 480 (polyimide film 313/hard coat layer 312) were subjected to corona treatment (output 0.3KW, speed 3 m/min) and then bonded to obtain a laminate d500 (fig. 4 d).
The surface of the laminate d500 from which the heavy separator 316 was peeled and the TAC301 side of the laminate c470 were subjected to corona treatment (output 0.3KW, speed 3 m/min) and then laminated to obtain a laminate 300 of example 7 (fig. 4 e). The results are shown in Table 4.
< examples 8 to 12 and comparative examples 4 to 6>
A laminate was produced in the same manner as in example 7, except that in example 7, the pressure-sensitive adhesive sheets shown in table 4 were used instead of the pressure-sensitive adhesive sheet produced in example 1. The results are shown in Table 4.
[ Table 4]
Figure BDA0003224658660000341
Description of the symbols
100. 200, 300 laminated body, 101 front panel, 102 1 st adhesive layer, 103 polarizer layer, 104 nd 2 nd adhesive layer, 105 back panel, 106 st 1 st phase difference layer, 107 nd 2 nd phase difference layer, 108, 109 laminating layer, 301 TAC film, 302 pol, 303 OC layer, 305 common adhesive layer, 306, 311, 316 heavy separator, 307 QWP, 308 substrate, 304, 309, 314 light separator, 310, 315 adhesive layer, 312 hard coat layer, 313 polyimide film, 410 laminated body containing polarizer layer, 420 common adhesive sheet, 430 laminated body a, 440 phase difference layer, 450 laminated body b, 460, 490 adhesive sheet, 470 laminated body c, 500 laminated body d, 501, 502 carrying platform.

Claims (8)

1. A laminate comprising, in order, a front sheet, a1 st adhesive layer, a polarizer layer, a2 nd adhesive layer and a back sheet,
wherein the 1 st adhesive layer and the 2 nd adhesive layer each have a tan delta of 1.5 to 2.0 at a temperature of-40 ℃ and are each formed from an adhesive composition containing a (meth) acrylic polymer,
in the (meth) acrylic polymer, the constituent unit derived from the monomer having a reactive functional group is less than 5% by mass based on the total mass of the polymer.
2. The laminate according to claim 1, wherein the front sheet is a film provided with a hard coat layer on at least one side of a substrate film.
3. The laminate according to claim 1 or 2, wherein the weight average molecular weight (Mw) of the (meth) acrylic polymer is 20 to 150 ten thousand.
4. The laminate according to any one of claims 1 to 3, wherein the adhesive composition further comprises a monofunctional (meth) acrylic monomer having an alkoxy group.
5. The laminate according to any one of claims 1 to 4, wherein the back sheet is a touch sensor panel.
6. A display device comprising the laminate according to any one of claims 1 to 5.
7. An adhesive composition comprising a (meth) acrylic polymer and a monofunctional (meth) acrylic monomer having an alkoxy group,
in the (meth) acrylic polymer, the constituent unit derived from the monomer having a reactive functional group is less than 5% by mass based on the total mass of the polymer.
8. An adhesive sheet comprising an adhesive layer formed from the adhesive composition of claim 7.
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