CN116438271A - Laminate and laminate structure - Google Patents

Laminate and laminate structure Download PDF

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Publication number
CN116438271A
CN116438271A CN202180075859.7A CN202180075859A CN116438271A CN 116438271 A CN116438271 A CN 116438271A CN 202180075859 A CN202180075859 A CN 202180075859A CN 116438271 A CN116438271 A CN 116438271A
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Prior art keywords
meth
adhesive sheet
photocurable adhesive
acrylate
photopolymerization initiator
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CN202180075859.7A
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Chinese (zh)
Inventor
野泽大希
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Mitsubishi Chemical Corp
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Mitsubishi Chemical Corp
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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
    • B32B7/02—Physical, chemical or physicochemical properties
    • B32B7/023—Optical properties
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K5/00—Use of organic ingredients
    • C08K5/0008—Organic ingredients according to more than one of the "one dot" groups of C08K5/01 - C08K5/59
    • C08K5/0025—Crosslinking or vulcanising agents; including accelerators
    • 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
    • C09J11/00—Features of adhesives not provided for in group C09J9/00, e.g. additives
    • C09J11/02—Non-macromolecular additives
    • C09J11/06—Non-macromolecular additives organic
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J133/00—Adhesives based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Adhesives based on derivatives of such polymers
    • C09J133/04—Homopolymers or copolymers of esters
    • 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
    • C09J151/00—Adhesives based on graft polymers in which the grafted component is obtained by reactions only involving carbon-to-carbon unsaturated bonds; Adhesives based on derivatives of such polymers
    • C09J151/06—Adhesives based on graft polymers in which the grafted component is obtained by reactions only involving carbon-to-carbon unsaturated bonds; Adhesives based on derivatives of such polymers grafted on to homopolymers or copolymers of aliphatic hydrocarbons containing only one carbon-to-carbon double bond
    • 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
    • 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
    • G02B5/00—Optical elements other than lenses
    • G02B5/30—Polarising elements
    • 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
    • C09J2203/00—Applications of adhesives in processes or use of adhesives in the form of films or foils
    • C09J2203/318—Applications of adhesives in processes or use of adhesives in the form of films or foils for the production of liquid crystal displays
    • 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
    • C09J2301/00—Additional features of adhesives in the form of films or foils
    • C09J2301/30—Additional features of adhesives in the form of films or foils characterized by the chemical, physicochemical or physical properties of the adhesive or the carrier
    • C09J2301/312—Additional features of adhesives in the form of films or foils characterized by the chemical, physicochemical or physical properties of the adhesive or the carrier parameters being the characterizing feature
    • 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
    • C09J2301/00—Additional features of adhesives in the form of films or foils
    • C09J2301/40—Additional features of adhesives in the form of films or foils characterized by the presence of essential components
    • C09J2301/416—Additional features of adhesives in the form of films or foils characterized by the presence of essential components use of irradiation

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Health & Medical Sciences (AREA)
  • Medicinal Chemistry (AREA)
  • Polymers & Plastics (AREA)
  • Adhesives Or Adhesive Processes (AREA)
  • Polarising Elements (AREA)

Abstract

As a laminate which can be cured by visible light and which is free from appearance defects such as discoloration, foaming, peeling of the polarizing plate even in a severe high-temperature and high-humidity environment, the following laminate was produced: [I] the polarizing plate (II) has a layer structure in which both surfaces of a polarizing plate are laminated with a protective film, the distance (alpha) between the photocurable adhesive sheet (III) and the polarizing plate is 80 [ mu ] m or less, the photocurable adhesive sheet (IV-1) is formed from a photocurable adhesive composition comprising a (meth) acrylic acid ester (co) polymer and a photopolymerization initiator (A), the laminate has a light transmittance of less than 90% at 390nm and a light transmittance of 80% or more at 410nm, and the total concentration of an acylphosphine oxide-based photopolymerization initiator and a phenylglyoxylate-based photopolymerization initiator contained in the photocurable adhesive composition is 0.5% by mass or less.

Description

Laminate and laminate structure
Technical Field
The present invention relates to a laminate having an adhesive sheet for attaching a resin member having ultraviolet ray blocking properties that does not transmit ultraviolet rays, the laminate having a photocurable adhesive sheet that is cured by irradiation with light (hereinafter referred to as "photocurable").
Background
In recent years, in order to improve the observability of an image display device, an adhesive is used to fill a gap between an image display panel such as a Liquid Crystal Display (LCD), a Plasma Display (PDP), or an electroluminescence display (ELD) and a protective panel or a touch panel member disposed on a front surface side (observation side) thereof, thereby suppressing reflection of incident light or outgoing light from a display image at an air layer interface. As a method of filling the gaps between such image display device constituent members with an adhesive, a method of filling the gaps between the image display device constituent members with an adhesive sheet is known.
In addition, in an image display device for a vehicle, since the image display device is easily exposed to ultraviolet rays, in order to prevent yellowing and deterioration of a conductive member, a polarizing plate, and other resin members inside the image display device due to ultraviolet ray exposure, a glass cover member, a resin cover member, and other structural members having ultraviolet ray shielding properties may be used as a window member and a windshield panel member.
In this case, a photocurable pressure-sensitive adhesive sheet capable of being cured by light in a wavelength region that can transmit the ultraviolet-shielding constituent member when ultraviolet rays are irradiated from the outside of the ultraviolet-shielding constituent member may be used.
For example, patent document 1 discloses a method for producing a display, in which an adhesive sheet is produced from a solvent-free adhesive composition containing an active energy ray-curable component and a photopolymerization initiator having a wavelength of 390nm and an optical path length of 10mm and having an absorbance of 0.3 or more in an acetonitrile solution having a concentration of 0.1 mass%, the adhesive sheet is adhered to an ultraviolet shielding member to produce a laminate, and then the adhesive sheet is cured by irradiation with active energy rays through the ultraviolet shielding member.
Patent document 2 discloses a method for producing a display, in which a display constituent member containing an ultraviolet absorber is adhered to an ultraviolet curable adhesive sheet containing a photopolymerization initiator having an absorbance of 0.3 or more at 380nm in an acetonitrile solution having a concentration of 0.1 mass%, to produce a laminate, and ultraviolet rays are irradiated through the ultraviolet absorber-containing display constituent member to cure the adhesive sheet.
Patent document 3 discloses an adhesive sheet for attaching an ultraviolet shielding member having ultraviolet shielding properties, the adhesive sheet being formed of an active energy ray-curable adhesive containing an active energy ray-curable component and a cured product of the active energy ray-curable component, and the adhesive sheet being formed of an active energy ray-curable adhesive containing a cured product of the active energy ray-curable component and the cured product being 1000mJ/cm through the ultraviolet shielding member 2 The adhesive sheet has a gel fraction of 70% or more and less than 100% when the adhesive sheet is cured by irradiation with active energy rays having a substantial intensity of luminescence in a wavelength region of 380 to 450 nm.
Patent document 4 discloses a method for producing a display including a display constituent member containing an ultraviolet absorber and a cured adhesive layer for adhering the display constituent member containing the ultraviolet absorber, wherein the adhesive layer is cured by irradiation of ultraviolet rays through the display constituent member to produce a cured adhesive layer, and the gel fraction of the cured adhesive layer is 40% or more.
Prior art literature
Patent literature
Patent document 1: japanese patent No. 6360605
Patent document 2: japanese patent No. 6420519
Patent document 3: japanese patent No. 6438165
Patent document 4: japanese patent No. 6676720
Disclosure of Invention
Problems to be solved by the invention
Known are: a polarizing plate used as a member of an image display device is subject to discoloration such as discoloration due to polyene of a polyvinyl alcohol resin constituting the polarizing plate under a hot and humid environment. In addition, in a laminate in which a polarizing plate and other constituent members are laminated via a photocurable adhesive sheet, discoloration of the polarizing plate in a hot and humid environment may be promoted by interaction between the polarizing plate and the photocurable adhesive sheet. Therefore, the image display device for vehicle use and the like are also required to have excellent durability in a high-temperature and high-humidity environment.
Patent documents 1 to 4 disclose adhesive sheets which are capable of being cured by light in a wavelength region that is transmitted through an ultraviolet-shielding component member when ultraviolet light is irradiated from the outside of the ultraviolet-shielding component member, and which are free from appearance defects such as foaming and peeling even in a severe high-temperature and high-humidity environment, and only an acylphosphine oxide photopolymerization initiator is exemplified as the photopolymerization initiator used. However, the pressure-sensitive adhesive sheets disclosed in patent documents 1 to 4 do not address the problem of discoloration of the polarizing plate in severe high-temperature and high-humidity environments.
Therefore, the photocurable pressure-sensitive adhesive sheet, which can be cured by visible light and further can suppress discoloration of the polarizing plate in a hot and humid environment, is unsatisfactory and has room for improvement.
The present invention provides a laminate comprising a photocurable adhesive sheet and a polarizing plate, which can be cured by light in a wavelength region that is transmissive to an ultraviolet-shielding component member when ultraviolet light is irradiated from the outside of the ultraviolet-shielding component member, and which is free from appearance defects such as discoloration, foaming, peeling, etc. of the polarizing plate even in a severe high-temperature and high-humidity environment.
Solution for solving the problem
The inventors have found as a result of intensive studies that: the above problems can be solved by using a photopolymerization initiator capable of generating radicals by visible light as the photocurable adhesive sheet and using an adhesive layer in which the content of the acylphosphine oxide-based photopolymerization initiator and the phenylglyoxylate-based photopolymerization initiator in the adhesive layer is reduced as much as possible.
Specifically, the present invention is based on the following [ 1] to [ 14 ].
[ 1] A laminate comprising a laminate of a polarizing plate and a photocurable adhesive sheet,
[ II ] A polarizing plate having a layer structure in which both surfaces of a polarizing plate are laminated with protective films,
[ III ] the distance (alpha) between the photocurable adhesive sheet and the polarizing plate is 80 μm or less,
[ IV-1] A photocurable adhesive sheet is formed from a photocurable adhesive composition comprising a (meth) acrylate (co) polymer and a photopolymerization initiator (A), and
[ IV-2] the photocurable adhesive sheet has a light transmittance at 390nm of less than 90% and a light transmittance at 410nm of 80% or more,
[ IV-3] As the photopolymerization initiator (A), the total concentration of the acylphosphine oxide-based photopolymerization initiator and the phenylglyoxylate-based photopolymerization initiator contained in the photocurable adhesive composition is 0.5% by mass or less.
The laminate according to [ 1 ], wherein the photocurable adhesive sheet of [ IV-4] is one which can be cured even under irradiation of light having a wavelength of 390 to 410 nm.
The laminate according to [ 1 ] or [ 2 ], wherein another constituent member (X) is laminated via the photocurable adhesive sheet, and the light transmittance of the other constituent member (X) at 365nm is 10% or less and the light transmittance at 405nm is 60% or more.
The laminate according to [ 3 ], wherein the other constituent member (X) is an ultraviolet-shielding covering material.
The laminate according to any one of [ 1 ] to [ 4], wherein the protective film in the polarizing plate is a triacetyl cellulose resin film.
The laminate according to any one of [ 1 ] to [ 5 ], wherein a ratio (α/β) of a distance (α) between the photocurable adhesive sheet and the polarizing plate to a thickness (β) of the photocurable adhesive sheet is 0.1 to 0.5.
The laminate according to any one of [ 1 ] to [ 6 ], wherein the photocurable pressure-sensitive adhesive sheet has a thickness (. Beta.) of 50 to 500. Mu.m.
The laminate according to any one of [ 1 ] to [ 7 ], wherein the photopolymerization initiator (A) contains at least 1 photopolymerization initiator selected from the group consisting of an α -aminoacetophenone photopolymerization initiator and a ketocoumarin photopolymerization initiator.
The laminate according to any one of [ 1 ] to [ 8 ], wherein the photocurable adhesive sheet has a yellow index value (YI value) of 2.0 or less.
The laminate according to any one of [ 1 ] to [ 9 ], wherein the photocurable adhesive composition contains a trifunctional or higher polyfunctional (meth) acrylate and/or a silane coupling agent.
The laminate according to any one of [ 1 ] to [ 10 ], wherein the (meth) acrylate (co) polymer is a graft copolymer having a macromonomer as a branch component.
The laminate according to any one of [ 1 ] to [ 11 ], wherein the cumulative light amount of the photocurable adhesive sheet at 405nm (mJ/cm) is 3000 (mJ/cm) when the adhesive sheet is irradiated with an ultraviolet shielding member having an ultraviolet shielding property through the ultraviolet shielding member 2 ) The difference (G2-G1) between the gel fraction G1 before light irradiation and the gel fraction G2 after light irradiation is 10% or more.
The laminate according to any one of [ 1 ] to [ 12 ], wherein the photocurable adhesive sheet has a multilayer structure of 2 or more layers.
The laminated structure of any one of [ 1 ] to [ 13 ], which is obtained by curing the laminated structure with visible light.
ADVANTAGEOUS EFFECTS OF INVENTION
The laminate of the present invention can be cured by visible light, and even in a severe high-temperature and high-humidity environment, the polarizing plate does not change color, and further, appearance defects such as foaming and peeling can be suppressed.
Detailed Description
The following describes embodiments for carrying out the present invention, but the present invention is not limited to these embodiments.
In the present invention, "(meth) acrylic" means acrylic acid or methacrylic acid, "(meth) acryl" means acryl or methacryl, and "(meth) acrylate" means acrylate or methacrylate.
The "(meth) acrylate (co) polymer" means a resin obtained by polymerizing a polymerization component containing at least 1 (meth) acrylate monomer, and the "(co) polymer" means a polymer or a copolymer.
In the present invention, "sheet" means: the terms "film" and "tape" are not particularly limited, but are intended to be included within the meaning of these terms.
In the present invention, when "X to Y" (X, Y is any number), unless otherwise specified, the meaning of "X or more and Y or less" and the meaning of "preferably greater than X" or "preferably less than Y" are included.
In addition, the meaning of "preferably greater than X" or "preferably less than Y" is also included in the case of "X" (X is an arbitrary number) or "Y" or less (Y is an arbitrary number).
Further, "X and/or Y (X, Y is an arbitrary structure)" means at least one of X and Y, and means three of X alone, Y, X alone and Y alone.
The laminate of the present invention (hereinafter, sometimes referred to as "the present laminate") is a laminate composed of layers laminated into a photocurable adhesive sheet/a polarizing plate. The laminate may further include another constituent member (X) laminated via the photocurable adhesive sheet. The laminate is mainly used for an image display device for a vehicle.
Generally, a photocurable pressure-sensitive adhesive sheet is adhered to an adherend, and then cured by ultraviolet irradiation to adhere to the adherend. However, as described above, in the image display device for vehicle use, since the polarizing plate and the like are easily degraded by ultraviolet rays, a glass cover member or a resin cover member that shields ultraviolet rays may be used. Therefore, the photocurable pressure-sensitive adhesive sheet constituting the present laminate, which is mainly used in an image display device for vehicle use, has a visible light curability that enables curing by visible light rather than ultraviolet light.
The photocurable adhesive sheet is characterized by comprising a photocurable adhesive composition containing a (meth) acrylic acid ester (co) polymer and a photopolymerization initiator (A) that generates radicals by visible light, wherein the photopolymerization initiator (A) is a small amount of an acylphosphine oxide photopolymerization initiator and a phenylglyoxylate photopolymerization initiator contained in the photocurable adhesive composition. Hereinafter, each component contained in the photocurable adhesive composition will be described.
[ (meth) acrylate (Co) Polymer ]
The (meth) acrylic acid ester (co) polymer used in the photocurable adhesive composition includes, for example, a homopolymer of an alkyl (meth) acrylate, and a copolymer obtained by copolymerizing a monomer component copolymerizable therewith. Among them, a (meth) acrylate copolymer is preferable.
Examples of the (meth) acrylate copolymer include copolymers of an alkyl (meth) acrylate having 1 to 18 carbon atoms in the alkyl group and a monomer component copolymerizable therewith, for example, a monomer component containing any one or more monomers selected from the group consisting of (a) carboxyl group-containing monomers, (b) hydroxyl group-containing monomers, (c) amino group-containing monomers, (d) epoxy group-containing monomers, (e) amide group-containing monomers, (f) vinyl monomers and (g) macromonomers. Among them, preferred is a (meth) acrylate copolymer obtained from a copolymerization component of an alkyl (meth) acrylate having 1 to 18 carbon atoms in the alkyl group and a (g) macromonomer containing (e) an amide group-containing monomer.
[ alkyl (meth) acrylate having 1 to 18 carbon atoms in the alkyl group ]
Examples of the alkyl (meth) acrylate having 1 to 18 carbon atoms in the alkyl group include linear alkyl (meth) acrylates such as methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, n-butyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, n-octyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, undecyl (meth) acrylate, lauryl (meth) acrylate, tridecyl (meth) acrylate, tetradecyl (meth) acrylate, cetyl (meth) acrylate, stearyl (meth) acrylate and the like; branched alkyl (meth) acrylates such as isopropyl (meth) acrylate, isobutyl (meth) acrylate, sec-butyl (meth) acrylate, tert-butyl (meth) acrylate, isopentyl (meth) acrylate, neopentyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, isononyl (meth) acrylate, tert-butylcyclohexyl (meth) acrylate, isodecyl (meth) acrylate, and isostearyl (meth) acrylate; alicyclic alkyl (meth) acrylates such as cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, 3, 5-trimethylcyclohexane (meth) acrylate, dicyclopentanyl (meth) acrylate, dicyclopentenyl (meth) acrylate, and dicyclopentenyloxyethyl (meth) acrylate. They may be used singly or in combination of 2 or more. Among them, the linear and branched alkyl (meth) acrylate having 6 to 14 carbon atoms as the alkyl group is preferable, and the lauryl (meth) acrylate and the 2-ethylhexyl (meth) acrylate are more preferable.
The content of the alkyl (meth) acrylate having 1 to 18 carbon atoms in the alkyl group is usually 30 to 90% by mass, preferably 35 to 88% by mass, more preferably 40 to 85% by mass, and particularly preferably 55 to 85% by mass, based on the total monomer components of the copolymer. If the content is too small, the hydrophobicity tends to be low, and water absorption tends to be difficult to be suppressed, and if it is too large, the polarity tends to be low, and the adhesion tends to be low.
[ (a) carboxyl group-containing monomer ]
Examples of the carboxyl group-containing monomer (a) include (meth) acrylic acid, 2- (meth) acryloyloxyethyl hexahydrophthalic acid, 2- (meth) acryloyloxypropyl hexahydrophthalic acid, 2- (meth) acryloyloxyethyl phthalic acid, 2- (meth) acryloyloxypropyl phthalic acid, 2- (meth) acryloyloxyethyl maleic acid, 2- (meth) acryloyloxypropyl maleic acid, 2- (meth) acryloyloxyethyl succinic acid, 2- (meth) acryloyloxypropyl succinic acid, crotonic acid, fumaric acid, maleic acid, itaconic acid, and the like. They may be used singly or in combination of 2 or more.
The content of the carboxyl group-containing monomer (a) is usually 10% by mass or less, preferably 8% by mass or less, and particularly preferably 5% by mass or less, based on the total monomer components of the copolymer.
[ (b) hydroxyl group-containing monomer ]
Examples of the hydroxyl group-containing monomer (b) include hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, and 2-hydroxybutyl (meth) acrylate. They may be used singly or in combination of 2 or more.
The content of the hydroxyl group-containing monomer (b) is usually 30% by mass or less, preferably 25% by mass or less, and particularly preferably 20% by mass or less, based on the total monomer components of the copolymer.
[ (c) amino group-containing monomer ]
Examples of the amino group-containing monomer (c) include aminoalkyl (meth) acrylates such as aminomethyl (meth) acrylate, aminoethyl (meth) acrylate, aminopropyl (meth) acrylate, and aminopropyl (meth) acrylate; n, N-dialkylaminoalkyl (meth) acrylates such as N-alkylaminoalkyl (meth) acrylate, N-dimethylaminoethyl (meth) acrylate, and N, N-dimethylaminopropyl (meth) acrylate. They may be used singly or in combination of 2 or more.
The content of the amino group-containing monomer (c) is usually 20 mass% or less, preferably 10 mass% or less, of the total monomer components of the copolymer.
[ (d) epoxy group-containing monomer ]
Examples of the epoxy group-containing monomer (d) include glycidyl (meth) acrylate, methyl glycidyl (meth) acrylate, 3, 4-epoxycyclohexylmethyl (meth) acrylate, and 4-hydroxybutyl glycidyl (meth) acrylate. They may be used singly or in combination of 2 or more.
The content of the epoxy group-containing monomer (d) is usually 20 mass% or less, preferably 10 mass% or less, of the total monomer components of the copolymer.
[ (e) amide group-containing monomer ]
Examples of the amide group-containing monomer (e) include (meth) acrylamide, N-dimethyl (meth) acrylamide, N-butyl (meth) acrylamide, N-hydroxymethyl propane (meth) acrylamide, N-methoxymethyl (meth) acrylamide, N-butoxymethyl (meth) acrylamide, diacetone (meth) acrylamide, maleimide, and the like. They may be used singly or in combination of 2 or more. Among them, (meth) acrylamide is preferable.
The content of the amide group-containing monomer (e) is usually 1 to 20% by mass based on the total monomer components of the copolymer, and among them, 1.5 to 15% by mass, particularly 2 to 10% by mass is preferable from the viewpoint of obtaining excellent adhesive properties.
[ (f) vinyl monomer ]
The vinyl monomer (f) may be a compound having a vinyl group in the molecule. Examples of such a compound include vinyl ester monomers such as vinyl acetate, vinyl propionate, and vinyl laurate; aromatic vinyl monomers such as styrene, chlorostyrene, chloromethylstyrene, α -methylstyrene, and other substituted styrenes; polyalkylene glycol di (meth) acrylates, and the like. They may be 1 or 2 or more in combination.
The content of the vinyl monomer (f) is usually 40% by mass or less, preferably 35% by mass or less, and particularly preferably 30% by mass or less based on the total monomer components of the copolymer.
[ (g) macromer ]
The above-mentioned (g) macromonomer means a macromonomer having a terminal functional group and a high molecular weight skeleton component. Among them, the (g) macromonomer is preferably a monomer having 20 or more carbon atoms in the side chain when a (meth) acrylate copolymer is formed by copolymerization.
By using the above-mentioned (g) macromonomer, the (meth) acrylic acid ester copolymer can be made into a graft copolymer by introducing the macromonomer as a branch component of the (meth) acrylic acid ester copolymer. The characteristics of the main chain and side chains of the graft copolymer can be changed by selecting and mixing the (g) macromonomer and the other monomers.
Examples of the terminal functional group of the macromonomer include radical polymerizable groups such as a (meth) acryloyl group and a vinyl group; hydroxyl, isocyanate, epoxy, carboxyl, amino, amido, thiol, and other functional groups. Among them, a radical polymerizable group copolymerizable with other monomers is preferable, and a (meth) acryl group is particularly preferable. The terminal functional group may contain one or two or more, and among them, one is particularly preferable.
In addition, (g) the macromer may have the functional groups listed above in addition to the terminal functional groups.
The backbone component of the (g) macromonomer is preferably composed of a (meth) acrylic acid ester (co) polymer or a vinyl-based polymer, and examples of the structural unit include structural units exemplified by alkyl (meth) acrylates having 1 to 18 carbon atoms in the alkyl group, the carboxyl group-containing monomer (a), the hydroxyl group-containing monomer (b), the epoxy group-containing monomer (d), and the amide group-containing monomer (e). They may be used singly or in combination of 2 or more. Among them, the backbone component of the (g) macromonomer preferably contains a hydrophobic monomer and a hydrophilic monomer as structural units.
Examples of the hydrophobic monomer include alkyl esters having no polar group (excluding methyl (meth) acrylate), such as n-butyl (meth) acrylate, isobutyl (meth) acrylate, sec-butyl (meth) acrylate, tert-butyl (meth) acrylate, pentyl (meth) acrylate, isopentyl (meth) acrylate, neopentyl (meth) acrylate, hexyl (meth) acrylate, cyclohexyl (meth) acrylate, heptyl (meth) acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, isooctyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, tert-butylcyclohexyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, undecyl (meth) acrylate, lauryl (meth) acrylate, cetyl (meth) acrylate, stearyl (meth) acrylate, isostearyl (meth) acrylate, behenyl (meth) acrylate, isobornyl (meth) acrylate, cyclohexyl (meth) acrylate, cyclopentenyl (meth) acrylate, and methyl (meth) acrylate. They may be used singly or in combination of 2 or more.
Examples of the hydrophobic monomer other than the alkyl ester include vinyl monomers such as vinyl acetate, styrene, t-butylstyrene, α -methylstyrene, vinyltoluene, and alkyl vinyl monomers. They may be used singly or in combination of 2 or more.
The hydrophilic monomer is preferably methyl (meth) acrylate or an ester having a polar group, and examples thereof include hydroxyl group-containing (meth) acrylates such as methyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, and glycerin (meth) acrylate; carboxyl group-containing monomers such as (meth) acrylic acid, 2- (meth) acryloyloxyethyl hexahydrophthalic acid, 2- (meth) acryloyloxypropyl hexahydrophthalic acid, 2- (meth) acryloyloxyethyl phthalic acid, 2- (meth) acryloyloxypropyl phthalic acid, 2- (meth) acryloyloxyethyl maleic acid, 2- (meth) acryloyloxypropyl maleic acid, 2- (meth) acryloyloxyethyl succinic acid, 2- (meth) acryloyloxypropyl succinic acid, crotonic acid, fumaric acid, maleic acid, itaconic acid, monomethyl maleate, monomethyl itaconate; anhydride group-containing monomers such as maleic anhydride and itaconic anhydride; epoxy group-containing monomers such as glycidyl (meth) acrylate, glycidyl alpha-ethacrylate, and 3, 4-epoxybutyl (meth) acrylate; alkoxy polyalkylene glycol (meth) acrylates such as methoxy polyethylene glycol (meth) acrylate; n, N-dimethylacrylamide, hydroxyethylacrylamide, and the like. They may be used singly or in combination of 2 or more.
Among the above-mentioned (g) macromers, from the viewpoint that the macromers of the main chain and the side chain of the graft copolymer exhibit a moderate phase separation structure, a macromer obtained by reacting isobornyl (meth) acrylate as a hydrophobic monomer and methyl (meth) acrylate as a hydrophilic monomer at a ratio of 1:1 is preferable.
The glass transition temperature (Tg) of the (g) macromonomer is preferably higher than the glass transition temperature of the copolymerization component constituting the (meth) acrylic (co) polymer.
Specifically, the glass transition temperature (Tg) of the (g) macromonomer affects the heat melting temperature (hot melt temperature) of the photocurable adhesive composition, and is therefore preferably 30 to 120 ℃, more preferably 40 to 110 ℃, and particularly preferably 50 to 100 ℃. If the glass transition temperature (Tg) of (g) the macromonomer is within the aforementioned range, there is a tendency that: the molecular weight is adjusted to maintain excellent processability and storage stability, and the hot melt property can be provided at a temperature of about 50 to 80 ℃.
The glass transition temperature of the macromonomer (g) is the glass transition temperature of the macromonomer itself, and can be measured by a Differential Scanning Calorimeter (DSC).
When (g) a macromonomer is used as a copolymerization component of the (meth) acrylic acid ester (co) polymer, the resulting (meth) acrylic acid ester (co) polymer can maintain a state in which branch components are attracted to each other and physically crosslinked at room temperature (25 ℃). Further, the physical cross-linking is decomposed by heating to a proper temperature, and fluidity can be obtained. Therefore, when the adhesive sheet to be described later is formed, the sheet shape can be maintained in an uncured state. In order to obtain such physical properties, the molecular weight and content of the macromer are also preferably adjusted.
The number average molecular weight of the macromonomer (g) is preferably 500 to 20000, more preferably 600 to 10000, further preferably 800 to 8000, particularly preferably 1000 to 7000, particularly preferably 1500 to 6000.
The content of the macromonomer (g) is preferably 5 to 30% by mass, more preferably 6 to 25% by mass, and particularly preferably 8 to 20% by mass, based on the total monomer components of the copolymer. If the content is too small, physical crosslinking of the branch components tends to be too weak, and storage stability in a room temperature (25 ℃) state tends to be poor, and if too large, physical crosslinking of the branch components tends to be too strong, and fluidity tends to be poor when heated.
The (meth) acrylic acid ester-based (co) polymer can be obtained by polymerizing an alkyl (meth) acrylate or an alkyl (meth) acrylate having 1 to 18 carbon atoms in an alkyl group with a monomer component copolymerizable therewith according to a conventionally known method such as solution radical polymerization, suspension polymerization, bulk polymerization, emulsion polymerization, or the like.
The weight average molecular weight of the (meth) acrylic acid ester-based (co) polymer thus obtained is usually 5 to 150 tens of thousands, preferably 7 to 130 tens of thousands, particularly preferably 10 to 120 tens of thousands, further preferably 15 to 100 tens of thousands.
The weight average molecular weight was measured by the following method.
The weight average molecular weight (Mw) was determined by measuring a molecular weight distribution curve using a gel permeation chromatography (Gel Permeation Chromatography: GPC) analyzer (device name: HLC-8320GPC manufactured by Tosoh corporation) using a substance obtained by dissolving a (meth) acrylic acid ester (co) polymer in Tetrahydrofuran (THF) as a measurement sample under the following conditions.
Protection column: TSKguardcolumnHXL
Separation column: TSKgelGMHXL (4 root)
Temperature: 40 DEG C
Injection amount: 100 mu L
Polystyrene conversion
Solvent: THF (tetrahydrofuran)
Flow rate: 1.0 mL/min
The (meth) acrylate (co) polymer preferably has an active energy ray-crosslinkable structural part.
The active energy ray-crosslinkable structure means: for example, in the presence of a photopolymerization initiator (a) described later, a structural site of a crosslinked structure can be formed by reacting with a part of the (meth) acrylate (co) polymer or a curing component other than the (meth) acrylate (co) polymer.
Examples of the active energy ray-crosslinkable structural moiety include a structure having a radical polymerizable functional group having a carbon-carbon double bond, such as a functional group having an unsaturated double bond, e.g., a (meth) acryloyl group or a vinyl group.
By providing the polymer chains of the aforementioned (meth) acrylate (co) polymer with a radically polymerizable functional group, the polymer chains can be directly polymerized with each other even in the absence of a crosslinking agent.
In order to introduce a structure having a radically polymerizable functional group into a (meth) acrylic acid ester (co) polymer, for example, a (meth) acrylic acid ester copolymer is produced by using a monomer having a functional group such as a hydroxyl group or a carboxyl group as a copolymerization component, and then a compound having a functional group capable of reacting with the functional group and an unsaturated double bond (for example, 2-isocyanatoethyl (meth) acrylate) may be reacted while maintaining the polymerizability of the unsaturated double bond.
[ photopolymerization initiator (A) ]
The photopolymerization initiator (a) contained in the photocurable adhesive composition is a visible light initiator that generates radicals by irradiation with visible light, light having wavelengths of at least 390nm, 405nm and 410nm, for example, light in a wavelength region of 380 to 700nm, and becomes a reaction start point of the (meth) acrylate (co) polymer. By including the photopolymerization initiator (a) in the photocurable adhesive composition, the photocurable adhesive composition can be cured by visible light. The photopolymerization initiator (a) may generate radicals only by irradiation with visible light, or may generate radicals by irradiation with light in a wavelength region other than the visible light region.
The light absorption coefficient of the photopolymerization initiator (A) at a wavelength of 405nm is preferably 10 mL/(g.cm) or more, more preferably 15 mL/(g.cm) or more, and particularly preferably 25 mL/(g.cm) or more. By setting the absorbance at 405nm to the above-described value or more, curing (crosslinking) can be sufficiently performed by irradiation with visible rays.
On the other hand, the upper limit of the absorbance at 405nm is preferably 1X 10 4 mL/(g.cm) or less, more preferably 1X 10 3 mL/(g.cm) or less. In the present invention, a photopolymerization initiator having an absorbance at 405nm of less than 10 mL/(g.cm) may be used in combination.
The photopolymerization initiator (a) is classified into two types according to a radical initiation mechanism, and is classified into: a cleavage type photopolymerization initiator capable of cleaving a single bond of the photopolymerization initiator itself to generate a radical; and a hydrogen abstraction type photopolymerization initiator capable of transferring hydrogen of a hydrogen donor, wherein the initiator is excited by light to form an excitation complex with the hydrogen donor in the system.
The cleavage type photopolymerization initiator is decomposed to form other compounds when irradiated with light to generate radicals, and does not function as a reaction initiator when excited once. Therefore, the adhesive after the completion of the crosslinking reaction is preferably not left as an active species, since there is no possibility that unexpected photodegradation or the like is caused to the adhesive.
Examples of the cleavage type photopolymerization initiator include α -aminoacetophenone type photopolymerization initiators such as 2-methyl-1- [4- (methylthio) phenyl ] -2-morpholinopropane-1-one, 2-benzyl-2- (dimethylamino) -4' -morpholinopropylbenzophenone, 2-dimethylamino-2- (4-methylbenzyl) -1- (4-morpholin-4-yl-phenyl) -butan-1-one, and the like; acyl phosphine oxide photopolymerization initiators such as bis (2, 4, 6-trimethylbenzoyl) phenylphosphine oxide, 2,4, 6-trimethylbenzoyl-diphenyl-phosphine oxide, (2, 4, 6-trimethylbenzoyl) ethoxyphenylphosphine oxide, and bis (2, 6-dimethoxybenzoyl) -2, 4-trimethylpentylphosphine oxide; 2, 2-dimethoxy-1, 2-diphenylethan-1-one and the like; α -hydroxyacetophenone photopolymerization initiators such as 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 1- (4- (2-hydroxyethoxy) phenyl) -2-hydroxy-2-methyl-1-propan-1-one, 2-hydroxy-1- [4- {4- (2-hydroxy-2-methyl-propionyl) benzyl } phenyl ] -2-methyl-propan-1-one, and oligo (2-hydroxy-2-methyl-1- (4- (1-methylethenyl) phenyl) propanone; a phenylglyoxylate photopolymerization initiator such as methyl phenylglyoxylate; derivatives of these cleavage type visible light polymerization initiators, and the like.
The cleavage type photopolymerization initiator is preferably an α -aminoacetophenone type photopolymerization initiator. The α -aminoacetophenone photopolymerization initiator does not generate an acid when decomposed by light irradiation, and therefore, the polarizing plate tends to be inhibited from being discolored.
In the present invention, since the center wavelength of the light absorption peak of the α -aminoacetophenone photopolymerization initiator is deviated from the visible light range, it is possible to estimate the defect of curing failure, and therefore, it is intended to avoid the use of the composition, but even when the composition is used to be hard, the defect is not caused, and the discoloration of the polarizing plate can be effectively suppressed.
On the other hand, even if the same cleavage type photopolymerization initiator is used, the center wavelength of the light absorption peak of the acylphosphine oxide type photopolymerization initiator and the phenylglyoxylate type photopolymerization initiator is usually the visible light absorption peak, and when the same cleavage type photopolymerization initiator is used as the photopolymerization initiator from the standpoint of small possibility of curing failure, the reduction of the acylphosphine oxide type photopolymerization initiator and the phenylglyoxylate type photopolymerization initiator contained in the adhesive sheet can suppress the discoloration of the polarizing plate. That is, among the aforementioned cleavage type photopolymerization initiators, an acylphosphine oxide type photopolymerization initiator, a phenylglyoxylate type photopolymerization initiator, or the like is decomposed to generate an acid when a radical is generated by light irradiation. If the acid remains in the adhesive sheet bonded to the polarizing plate, the acid acts as a catalyst, and discoloration may be caused by the polyeneization of the polyvinyl alcohol resin constituting the polarizing plate. Therefore, in the present invention, it is preferable that the acylphosphine oxide-based photopolymerization initiator and the phenylglyoxylate-based photopolymerization initiator are not used, and the acylphosphine oxide-based photopolymerization initiator and the phenylglyoxylate-based photopolymerization initiator can be used within a range (not more than 0.5% by mass of the photocurable adhesive composition) that does not affect the effects of the present invention.
Examples of the hydrogen abstraction photopolymerization initiator include ketocoumarin photopolymerization initiators such as bis (2-phenyl-2-glyoxylate) oxydivinyl ester, methyl phenylglyoxylate, a mixture of 2- [ 2-oxo-2-phenyl-acetoxy-ethoxy ] ethyl hydroxyphenylacetate and 2- [ 2-hydroxy-ethoxy ] ethyl hydroxyphenylacetate, thioxanthone, 2-chlorothioxanthone, 3-methylthioxanthone, 2, 4-dimethylthioxanthone, anthraquinone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-t-butylanthraquinone, 2-aminoanthraquinone, camphorquinone or its derivatives, ketocoumarin or its derivatives, and the like.
The hydrogen abstraction type photopolymerization initiator is preferably a ketocoumarin type photopolymerization initiator. The ketocoumarin photopolymerization initiator has sufficient visible light reactivity, and the yellowing can be adjusted to a practically unproblematic level by adjusting the addition amount, and the polarizing plate tends to be inhibited from discoloring.
In the present invention, it is assumed that the use of a ketocoumarin photopolymerization initiator is avoided because of the yellowing defect, but the discoloration of the polarizing plate can be effectively suppressed even when the composition is hard to use.
Among them, the photopolymerization initiator (a) preferably contains at least 1 photopolymerization initiator selected from the group consisting of α -aminoacetophenone photopolymerization initiators and ketocoumarin photopolymerization initiators.
The photopolymerization initiator (a) is not limited to the above-listed materials. Any 1 kind or a derivative thereof among the above-listed photopolymerization initiators (a) may be used, or 2 or more kinds may be used in combination.
In addition to the photopolymerization initiator (a), a substance that generates radicals only by irradiation with other light rays such as ultraviolet rays may be mixed.
The content of the photopolymerization initiator (a) in the photocurable adhesive composition is usually 0.1 to 10 parts by mass, preferably 0.2 to 5 parts by mass, and more preferably 0.3 to 3 parts by mass, relative to 100 parts by mass of the (meth) acrylate (co) polymer.
By setting the content of the photopolymerization initiator (a) to the above range, a proper reaction sensitivity with respect to visible light can be obtained.
The photocurable adhesive composition used in the present invention preferably contains a crosslinking agent and/or a silane coupling agent in addition to the (meth) acrylate (co) polymer and the photopolymerization initiator (a).
[ Cross-linking agent ]
Examples of the crosslinking agent include compounds having at least 1 crosslinkable functional group selected from the group consisting of (meth) acryl, epoxy, isocyanate, carboxyl, hydroxyl, carbodiimide, oxazoline, aziridine, vinyl, amino, imino, and amide groups. They may be used singly or in combination of 2 or more. The crosslinkable functional group may be protected with a protecting group capable of deprotection, or may be chemically bonded to the (meth) acrylate (co) polymer.
Among them, photopolymerizable compounds having a carbon-carbon double bond such as a (meth) acryloyl group and a vinyl group are preferable, and polyfunctional (meth) acrylates are particularly preferable. The term "polyfunctional" as used herein means having 2 or more (meth) acryloyl groups.
Examples of the polyfunctional (meth) acrylate include difunctional (meth) acrylates such as 1, 4-butanediol di (meth) acrylate, glycerol di (meth) acrylate, neopentyl glycol di (meth) acrylate, glycerol glycidyl ether di (meth) acrylate, 1, 6-hexanediol di (meth) acrylate, 1, 9-nonanediol di (meth) acrylate, hydroxypivalic acid neopentyl glycol di (meth) acrylate, di (meth) acrylate of epsilon-caprolactone adduct of hydroxypivalic acid neopentyl glycol, tricyclodecane dimethacrylate, tricyclodecane dimethanol di (meth) acrylate, bisphenol a polyethoxy di (meth) acrylate, bisphenol a polypropoxy di (meth) acrylate, bisphenol F polyethoxy di (meth) acrylate, and ethylene glycol di (meth) acrylate; trifunctional (meth) acrylates such as trimethylolpropane trioxyethyl (meth) acrylate, epsilon-caprolactone modified tris (2-hydroxyethyl) isocyanurate tri (meth) acrylate, pentaerythritol tri (meth) acrylate, propoxylated pentaerythritol tri (meth) acrylate, ethoxylated pentaerythritol tri (meth) acrylate, and the like; and (meth) acrylates having four or more functions such as pentaerythritol tetra (meth) acrylate, propoxylated pentaerythritol tetra (meth) acrylate, ethoxylated pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, polyethylene glycol di (meth) acrylate, tris (acryloxyethyl) isocyanurate, dipentaerythritol hexa (meth) acrylate, dipentaerythritol penta (meth) acrylate, tripentaerythritol hexa (meth) acrylate, tripentaerythritol penta (meth) acrylate, trimethylolpropane tri (meth) acrylate, trimethylolpropane polyethoxy tri (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate, and the like.
In addition to the above, examples of the polyfunctional (meth) acrylate include polyfunctional (meth) acrylic oligomers such as polyester (meth) acrylate, epoxy (meth) acrylate, urethane (meth) acrylate, and polyether (meth) acrylate. They may be used singly or in combination of 2 or more.
Among them, a multifunctional (meth) acrylate having three or more functions is preferable, a trifunctional (meth) acrylate is more preferable, and a propoxylated pentaerythritol tri (meth) acrylate is particularly preferable.
The content of the crosslinking agent is preferably 0.5 to 50 parts by mass, more preferably 1 to 40 parts by mass, and even more preferably 5 to 30 parts by mass, based on 100 parts by mass of the (meth) acrylate (co) polymer. When the content is within the above range, the adhesive force and the aggregation force can be improved, which is preferable.
[ silane coupling agent ]
The silane coupling agent is preferable because it can improve adhesion, and can improve adhesion to glass materials.
Examples of the silane coupling agent include compounds having an unsaturated group such as a vinyl group, an acryloxy group, or a methacryloxy group, an amino group, an epoxy group, or the like, and having a hydrolyzable functional group such as an alkoxy group.
Examples of the silane coupling agent include N- (. Beta. -aminoethyl) - γ -aminopropyl trimethoxysilane, N- (. Beta. -aminoethyl) - γ -aminopropyl methyl dimethoxy silane, γ -aminopropyl triethoxy silane, γ -glycidoxypropyl trimethoxysilane, and γ -methacryloxypropyl trimethoxysilane. They may be used singly or in combination of 2 or more. Among them, gamma-glycidoxypropyl trimethoxysilane is preferable from the viewpoints of good adhesion, less discoloration such as yellowing, and the like.
The content of the silane coupling agent is usually 0.05 to 5 parts by mass, preferably 0.1 to 3 parts by mass, relative to 100 parts by mass of the (meth) acrylate (co) polymer. When the content is within the above range, the occurrence of whitening can be avoided, and the adhesion can be improved, which is preferable.
In addition to the silane coupling agent, a coupling agent such as an organotitanate compound may be effectively used in the photocurable adhesive composition.
[ other materials ]
The photocurable adhesive composition may contain, as other components, various additives such as a light stabilizer, an ultraviolet absorber, a metal deactivator, a metal corrosion inhibitor, an anti-aging agent, an antistatic agent, a moisture absorbent, a foaming agent, a defoaming agent, inorganic particles, a viscosity regulator, a tackifying resin, a photosensitizer, and a fluorescent agent; a reaction catalyst (tertiary amine compound, quaternary ammonium compound, tin laurate compound, etc.), and the like. In addition, other known components which are generally blended into the adhesive composition may be appropriately contained. These other components may be used singly or in combination of 2 or more.
(preparation of photocurable adhesive composition)
The photocurable adhesive composition is obtained by mixing, for example, a (meth) acrylate (co) polymer, a photopolymerization initiator (a), preferably a crosslinking agent, a silane coupling agent, and other materials as needed, in predetermined amounts.
In addition, a heat treatment step may be added at the time of producing the photocurable adhesive composition, and in this case, it is desirable to mix the components of the photocurable adhesive composition in advance and then heat treat the mixture.
Further, for the mixing, a substance obtained by concentrating various mixed components to prepare a master batch may be used.
The mixing method is not particularly limited, and for example, a universal mixer, a planetary mixer, a Banbury mixer, a kneader, a frame mixer, a pressure kneader, a three-roll mill, a two-roll mill, or the like can be used. When the components of the photocurable adhesive composition are mixed, a solvent may be used as needed, or the components may be mixed in the form of a solvent-free system containing no solvent. The photocurable adhesive composition can be used in a solvent-free system, and thus has the advantages of no solvent residue, and improved heat resistance and light resistance.
< photocurable pressure-sensitive adhesive sheet >
The photocurable pressure-sensitive adhesive sheet is formed of the photocurable pressure-sensitive adhesive composition, and may be formed of, for example, a single layer of only 1 layer, or may be formed of a plurality of layers of 2 or more layers, and preferably, a plurality of layers of 2 or more layers. In the case of a multilayer structure, at least the outermost layer may be formed of the photocurable adhesive composition, and all the layers may be formed of the photocurable adhesive composition.
In order to form the photocurable adhesive sheet from the photocurable adhesive composition, the photocurable adhesive composition may be applied. The method of applying the photocurable adhesive composition is not particularly limited as long as it is a general application method, and examples thereof include roll coating, die coating, gravure coating, comma coating, screen printing, and the like.
The thickness (. Beta.) of the photocurable pressure-sensitive adhesive sheet is preferably 50 to 500. Mu.m, more preferably 70 to 400. Mu.m, particularly preferably 100 to 300. Mu.m, from the viewpoint of practical applicability.
The photocurable pressure-sensitive adhesive sheet thus formed has photocurability to be cured by irradiation with light. In this case, the photocurable pressure-sensitive adhesive sheet may be cured in a state where an excess of the photocuring remains (also referred to as "pre-curing"), or may be uncured (referred to as "uncured") that is uncured and has photocurability.
If the photocurable adhesive sheet to be formed is a pre-cured product or an uncured product, the photocurable adhesive sheet can be subjected to photocuring (also referred to as "primary curing") after the photocurable adhesive sheet is adhered to an adherend, and as a result, the cohesive force can be improved and the adhesion can be improved.
In the case of performing the pre-curing, the adhesive sheet may be irradiated with light so that the gel fraction thereof is 60% or less. The photocurable pressure-sensitive adhesive sheet may be precured without being irradiated with light, or may be precured by heat or curing, for example.
The photocurable pressure-sensitive adhesive sheet may be laminated with a release sheet in advance in an unused state before being attached to an adherend to form a pressure-sensitive adhesive sheet with a release sheet, and the release sheet may be peeled off and used when in use. The release sheet is usually laminated on both sides of the photocurable pressure-sensitive adhesive sheet. The pressure-sensitive adhesive sheet with a release sheet can be produced, for example, by applying the photocurable pressure-sensitive adhesive composition to a release sheet to form a pressure-sensitive adhesive layer, and then laminating other release sheets.
As the release sheet, a known release sheet can be suitably used, and for example, a release sheet obtained by applying a silicone resin to a sheet made of a polyester resin, a polyolefin resin, a polycarbonate resin, a polystyrene resin, an acrylic resin, a triacetyl cellulose resin, a fluorine resin, etc., and subjecting the resultant sheet to a release treatment, a release paper, etc., can be suitably selected and used. They may be present alone or in a stack of 2 or more.
The light transmittance of the release sheet at a wavelength of 410nm or less is preferably 40% or less, more preferably 30% or less, and particularly preferably 20%. When the light transmittance of the release sheet is not more than the above-mentioned value at a wavelength of 410nm, photopolymerization of the adhesive sheet due to visible light during storage or the like can be effectively prevented.
Here, examples of the release sheet having a light transmittance of 40% or less at a wavelength of 410nm or less, that is, a sheet having a function of partially blocking transmission of visible light and ultraviolet light, include the following (1) to (7).
(1) A laminate sheet having an ultraviolet absorbing layer, which is obtained by coating a releasable micro-adhesive resin on one surface of a cast film or a stretched film made of a resin such as a polyester resin, a polypropylene resin, or a polyethylene resin, and coating a coating material containing an ultraviolet absorber on the other surface.
(2) A laminate sheet obtained by coating a film formed from a resin such as a polyester resin, a polypropylene resin, or a polyethylene resin, or a film formed by stretching one surface of the film with a micro-adhesive resin having a re-peelability and containing an ultraviolet absorber.
(3) A laminate obtained by coating a releasable micro-adhesive resin on a cast film or a stretched film made of a polyester resin, a polypropylene resin, a polyethylene resin or the like blended with an ultraviolet absorber.
(4) A laminate sheet is obtained by molding a layer made of a resin containing no ultraviolet absorber on one or both sides of a layer made of a resin such as a polyester resin, a polypropylene resin, or a polyethylene resin, in which an ultraviolet absorber is blended, and coating a releasable micro-adhesive resin on one side of a multilayer cast film or a stretched film obtained by this molding.
(5) A laminate sheet is obtained by coating a coating material containing an ultraviolet absorber on one surface of a cast film or a stretched film made of a resin such as a polyester resin, a polypropylene resin, or a polyethylene resin, to provide an ultraviolet absorbing layer, and further coating a releasable micro-adhesive resin on the ultraviolet absorbing layer.
(6) A laminate sheet obtained by applying a coating material containing an ultraviolet absorber to one surface of a cast film or a stretched film made of a resin such as a polyester resin, a polypropylene resin, or a polyethylene resin, to provide an ultraviolet absorbing layer, and applying a releasable micro-adhesive resin to the other surface.
(7) And a laminate sheet obtained by laminating the other surface of a resin film having one surface coated with a releasable micro-adhesive resin and formed of a resin such as a polyester resin, a polypropylene resin, or a polyethylene resin, and a resin film prepared separately via an adhesive layer and/or an adhesive layer containing an ultraviolet absorber.
The thickness of the release sheet is not particularly limited, but is preferably 25 to 500. Mu.m, more preferably 38 to 250. Mu.m, particularly preferably 50 to 200. Mu.m, from the viewpoints of processability and handleability.
In the case where release sheets are laminated on both sides of the pressure-sensitive adhesive layer of the photocurable pressure-sensitive adhesive sheet, these release sheets may have the same laminated structure, material, and thickness, or may have different laminated structures, materials, and thicknesses. As the release sheet, release sheets having different release forces can be used.
The release sheet may have other layers such as an antistatic layer, a hard coat layer, and an anchor layer, as required.
By laminating another release sheet on the formed adhesive layer, an adhesive sheet with a release sheet can be obtained.
In addition, in the case where the photocurable pressure-sensitive adhesive sheet is a multilayer structure, the production can be performed by the following method: a method of coating the photocurable adhesive composition onto a substrate sheet or a release sheet to form a first adhesive sheet, further coating the photocurable adhesive composition onto the formed first adhesive sheet to form a second adhesive sheet, and repeating the above-described operations; a method of forming a first adhesive sheet and a second adhesive sheet, respectively, and then adhering the respective coated surfaces to each other; a method of simultaneously forming a first adhesive sheet and a second adhesive sheet from the photocurable adhesive composition by multilayer coating and coextrusion molding.
The photocurable pressure-sensitive adhesive sheet may be formed by directly applying the photocurable pressure-sensitive adhesive composition to a polarizing plate or an adherend (other constituent member (X)) and forming the composition into a sheet form without using a release sheet as described above, or may be formed by directly extruding the photocurable pressure-sensitive adhesive composition to form a photocurable pressure-sensitive adhesive sheet. Further, the photocurable adhesive composition may be molded by injecting the photocurable adhesive composition into a mold, or the photocurable adhesive sheet may be produced by directly filling the photocurable adhesive composition between a polarizing plate and another constituent member (X) as an adherend.
When the photocurable pressure-sensitive adhesive sheet thus obtained contains the acylphosphine oxide-based photopolymerization initiator and the phenylglyoxylate-based photopolymerization initiator as the photopolymerization initiator (a), the total concentration thereof is 0.5 mass% or less, preferably 0.2 mass% or less, more preferably 0.1 mass% or less, and particularly preferably 0.05 mass% or less. The lower limit is, of course, 0 mass%. That is, the photocurable pressure-sensitive adhesive sheet can suppress discoloration of the polarizing plate due to acid by reducing the contents of the acid-generating acylphosphine oxide photopolymerization initiator and the phenylglyoxylate photopolymerization initiator, which decompose by light irradiation.
In the case where the photocurable pressure-sensitive adhesive sheet has a multilayer structure of 2 or more layers, the concentration of the acylphosphine oxide-based photopolymerization initiator and the phenylglyoxylate-based photopolymerization initiator contained in the photocurable pressure-sensitive adhesive composition forming the layer to be in contact with the polarizing plate may be within the above-mentioned range.
(light transmittance)
The light transmittance of the photocurable adhesive sheet at 390nm is less than 90% and the light transmittance at 410nm is 80% or more.
In the photocurable adhesive composition obtained by blending a photopolymerization initiator having an absorption in the ultraviolet to visible light range of about 400nm, the photopolymerization initiator has a large light absorption, and the lower the light transmittance at 390nm, the better the photosensitivity, and the easier the curing.
On the other hand, if the light transmittance at the wavelength of 410nm is not higher than a certain value, the sheet is colored yellow when it is made into a photocurable pressure-sensitive adhesive sheet, and it is difficult to use the sheet in an image display apparatus.
Since sufficient visible light curability can be ensured if the light transmittance at 390nm is less than 90%, it is preferable that a yellow index value (YI value) that is sufficiently low for bonding an optical member requiring transparency can be achieved if the light transmittance at 410nm is 80% or more.
The light transmittance of the photocurable adhesive sheet at a wavelength of 390nm is less than 90%, preferably 88% or less.
The light transmittance of the photocurable pressure-sensitive adhesive sheet at a wavelength of 410nm is 80% or more, preferably 85% or more, and particularly preferably 90% or more.
In order to set the light transmittance of the photocurable pressure-sensitive adhesive sheet as described above, it is sufficient to use a substance having such light absorption peak characteristics that the peak edge of the absorption peak is sufficiently reached to 390nm and the absorption peak at relatively 410nm becomes smaller, among the photopolymerization initiator (a) having absorption to visible light, and in particular, at least 1 selected from the group consisting of α -aminoacetophenone photopolymerization initiators and ketocoumarin photopolymerization initiators may be used. But is not limited to this method.
The photocurable pressure-sensitive adhesive sheet is curable even when irradiated with light having a wavelength of 390 to 410 nm.
(yellow index value)
The photocurable pressure-sensitive adhesive sheet was cured at a cumulative light amount of 3000 (mJ/cm from the viewpoint of transparency 2 ) After the high-pressure mercury lamp UV light is irradiated, the yellow index value measured according to JIS K7103 is preferably 2.0 or less, more preferably 1.9 or less.
(gel fraction)
The gel fraction G1 of the photocurable adhesive sheet before light irradiation is usually 50% or less, preferably 40% or less, and particularly preferably 20% or less. The lower limit is 0%. If the gel fraction is below the aforementioned value, there is a tendency that: the extra uncrosslinked component which is cured by irradiation with light is present in a sufficiently large amount (in a pre-cured state or an uncured state), and the flexibility is increased.
The gel fraction was obtained by the following method.
The mass of the photocurable adhesive sheet (mass before impregnation) was measured, and it was packed in a bag shape with an SUS mesh (# 200), immersed in ethyl acetate, and stored in the dark at 23 ℃ for 24 hours. Thereafter, the package was taken out and heated at 70 ℃ for 4.5 hours, and the attached ethyl acetate was evaporated, and the mass of the remaining photocurable adhesive sheet (mass after impregnation) was measured, and the gel fraction was determined according to the following formula.
Gel fraction (%) = [ (mass after impregnation)/(mass before impregnation) ]×100
In order to adjust the gel fraction G1 before the light irradiation to the above range, it is sufficient to remove the residual catalyst during the polymerization of the (meth) acrylic acid ester (co) polymer and during the processing of the photocurable pressure-sensitive adhesive sheet, or to use a polymerization inhibitor, an antioxidant, or the like, so that an unexpected curing (crosslinking) reaction is not performed by heat, light, or the like before the primary curing. In the case of performing the pre-curing by light irradiation, the cumulative light amount of the light irradiated for pre-curing may be sufficiently reduced so that the non-crosslinked component is sufficiently increased. But is not limited to this method.
In addition, the cumulative light quantity at 405nm of the irradiation wavelength of the photocurable adhesive sheet through the ultraviolet shielding member having ultraviolet shielding property was 3000 (mJ/cm) 2 ) In the case of the light of (2), the gel fraction G2 after light irradiation is usually 40 to 100%, preferably 50 to 100%, particularly preferably 60 to 100%. If the gel fraction G2 of the photocurable adhesive sheet after light irradiation falls within the above range, no appearance defects such as foaming and peeling tend to be observed even in a severe high-temperature and high-humidity environment.
The difference (G2-G1) between the gel fraction G1 before light irradiation and the gel fraction G2 after light irradiation is preferably 10% or more, more preferably 30% or more, and particularly preferably 60% or more. If the gel fraction difference between the photocurable pressure-sensitive adhesive sheet before and after photocuring is equal to or greater than the above-mentioned value, the pressure-sensitive adhesive sheet tends to exhibit high cohesive strength and high foaming resistance reliability even in a severe high-temperature and high-humidity environment or the like. The upper limit is usually 100%.
In order to set the difference in gel fraction of the photocurable adhesive sheet before and after the light irradiation to the above-mentioned value or more, a photopolymerization initiator (a) having an absorption at a wavelength of 405nm, for example, may be used. But is not limited to this method.
The term "having ultraviolet shielding property" means that: the light transmittance at 365nm is 10% or less and the light transmittance at 405nm is 60% or more. As such an ultraviolet shielding member, for example, "Iupilon sheet MR58, thickness 1.0mm" manufactured by mitsubishi gas chemical company may be used.
In addition, "cumulative light amount at wavelength 405 nm" means: the total amount of irradiation energy received per unit area means: the total amount of light irradiation energy measured using an ultraviolet cumulative light meter "UIT-250" (manufactured by USIO motor company) and a light receiver "UVD-C405" (manufactured by USIO motor company) among light irradiated by a high-pressure mercury lamp or the like is an cumulative light amount in a wavelength region corresponding to the photosensitive characteristic of the light receiver (having a light sensitivity in a wavelength range of 320 to 470nm with a 405nm photosensitive peak, and a peak edge extending). More specifically, the cumulative light amount obtained by the method described in the examples is referred to.
As described above, the photocurable adhesive sheet is laminated into a laminate of layers of a polarizing plate and a photocurable adhesive sheet, and an object having the laminated structure is the laminate.
(polarizing plate)
The polarizing plate is not particularly limited, and examples thereof include polarizing plates obtained by laminating protective films such as triacetyl cellulose resin films, acrylic resin films, polyester resin films, and cycloolefin polymer resin films on both surfaces of a polyvinyl alcohol resin layer (polarizing plate) obtained by adsorbing and orienting iodine compound molecules to the polyvinyl alcohol resin films. Among them, from the viewpoint of excellent optical isotropy due to non-stretching, a polarizing plate obtained by laminating triacetyl cellulose resin films on both surfaces of a polarizing plate is preferable.
In addition, the protective film preferably has a moisture permeability of 1 to 1000 (g/m from the viewpoint of preventing discoloration of the polarizing plate due to moisture penetration 2 Per day), particularly preferably from 5 to 800 (g/m) 2 Preferably 10 to 600 (g/m) 2 Day/day)。
In the present laminate, it is important that the distance (α) between the photocurable pressure-sensitive adhesive sheet and the polarizing plate is 80 μm or less, preferably 10 to 80 μm, and more preferably 10 to 50 μm.
The distance (α) between the photocurable adhesive sheet and the polarizing plate is: the distance from the surface of the polarizing plate (polyvinyl alcohol resin film layer) on the surface to be bonded to the photocurable adhesive sheet to the surface of the photocurable adhesive sheet in contact with the polarizing plate.
Further, from the viewpoint of suppressing discoloration of the polarizing plate, the ratio (α/β) of the distance (α) between the pressure-sensitive adhesive sheet and the polarizing plate to the thickness (β) of the photocurable pressure-sensitive adhesive sheet is preferably 0.1 to 0.5, more preferably 0.1 to 0.4, and particularly preferably 0.1 to 0.3.
In recent years, the thickness of the display tends to be reduced for weight reduction, and the thickness of the polarizing plate tends to be reduced, but when the thickness of the polarizing plate is reduced, the above-described range is preferable in view of suppressing discoloration of the polarizing plate even in the case of the present laminate having a structure in which the distance (α) between the photocurable adhesive sheet and the polarizing plate is close.
The laminate is preferably further laminated with another constituent member (X) via the photocurable adhesive sheet.
(other constituent Member (X))
As the other constituent member (X), a constituent member having a light transmittance at 365nm of 10% or less and a light transmittance at 405nm of 60% or more, that is, a member having ultraviolet light-shielding properties (ultraviolet light-shielding covering material), is preferable.
If the transmittance of the other constituent member (X) at the wavelength of 365nm is 10% or less and the transmittance at the wavelength of 405nm is 60% or more, the transmittance of ultraviolet rays can be sufficiently blocked (isolated), the photodegradation of the other constituent member (X) itself and the polarizing plate existing via the photocurable adhesive sheet can be suppressed, and the yellow index value (YI value) can be reduced to a level required for the laminate.
Examples of such other constituent members (X) include those having a resin material as a main component and having the light transmittance adjusted by using an ultraviolet absorber.
Examples of the resin material include a material containing a polycarbonate resin or an acrylic resin as a main component resin. Here, "main component resin" means: the resin constituting the other constituent member (X) contains the most mass of resin.
The method of laminating the other constituent member (X) via the photocurable adhesive sheet is not particularly limited, and either one of the polarizing plate and the other constituent member (X) may be laminated with the photocurable adhesive sheet after the other is laminated with the photocurable adhesive sheet, or the polarizing plate and the other constituent member (X) may be laminated with the photocurable adhesive sheet at the same time.
The laminate thus obtained is then irradiated with visible light to cure the photocurable adhesive sheet, thereby forming a laminate structure. The laminated structure is mainly used as a component of an image display device for a vehicle.
Examples
Hereinafter, examples of the present invention will be described in further detail together with comparative examples. However, the present invention is not limited to the examples described below.
Example 1
(production of photocurable pressure-sensitive adhesive sheet)
To 1kg of an acrylic graft copolymer (mass average molecular weight: 16 ten thousand) obtained by randomly copolymerizing 13.5 parts by mass of a macromonomer (number average molecular weight: 3000) having a methacryloyl group as a terminal functional group and 40 parts by mass of 2-ethylhexyl acrylate and 2.8 parts by mass of acrylamide, 1.5g of α -aminoacetophenone 2-benzyl-2- (dimethylamino) -4' -morpholinopropylbenzophenone (manufactured by IGM corporation: omnirad 369) as a photopolymerization initiator, 50g of propoxylated pentaerythritol triacrylate (manufactured by Xinzhongcun chemical corporation, NK ESTER ATM-4 PL) as a crosslinking agent, and 1.5g of 3-glycidoxypropyl trimethoxysilane (manufactured by Xinyue chemical corporation: KBM 403) as a silane coupling agent were added and uniformly mixed to obtain a photocurable adhesive composition.
Then, the photocurable adhesive composition was formed into a sheet on a polyethylene terephthalate film (DIAFOIL MRV, thickness 100 μm, manufactured by Mitsubishi chemical corporation) having its surface subjected to a release treatment so that the thickness became 150 μm, and then a photocurable adhesive sheet with a release sheet was produced by covering the polyethylene terephthalate film (DIAFOIL MRQ, thickness 75 μm, manufactured by Mitsubishi chemical corporation) having its surface subjected to a release treatment.
(polarizing plate)
As the polarizing plate, the following polarizing plate was used: an adhesive layer, a triacetyl cellulose resin film and a coating layer were laminated in this order on both sides of a polyvinyl alcohol resin film (12 μm) having iodine adsorbed and oriented, and the surface of the polyvinyl alcohol resin film layer was located at a depth of 35 μm from the outermost surface of a polarizing plate to which an adhesive sheet was to be attached.
(other constituent Member (X))
As the other constituent member (X), a polycarbonate resin plate having ultraviolet shielding properties (thickness of 1.0mm, light transmittance at 365nm of 0%, light transmittance at 405nm of 83%, and Iupilon sheet MR58 manufactured by mitsubishi gas chemical company) was used.
(production of laminate)
After peeling off the release sheet on one side of the photocurable adhesive sheet with the release sheet, roll bonding is performed on one side of the polarizing plate, and then peeling off the release sheet on the other side of the photocurable adhesive sheet, and a polycarbonate resin sheet having ultraviolet shielding properties is roll bonded as the other constituent member (X), thereby obtaining a laminate of a polycarbonate resin sheet having polarizing plate/photocurable adhesive sheet/ultraviolet shielding properties.
The distance between the photocurable adhesive sheet and the polarizing plate (the distance from the surface of the polyvinyl alcohol resin film layer on the surface to be bonded with the photocurable adhesive sheet to the surface in contact with the polarizing plate) of the laminate obtained was 35 μm. The ratio of the distance between the photocurable adhesive sheet and the polarizer to the thickness of the photocurable adhesive sheet was 0.2.
Example 2
A photocurable adhesive sheet with a release sheet and a laminate of a polarizing plate/a photocurable adhesive sheet/a polycarbonate resin plate having ultraviolet shielding properties were obtained in the same manner as in example 1 except that 15g of α -aminoacetophenone-based 2-dimethylamino-2- (4-methylbenzyl) -1- (4-morpholinophenyl) -butan-1-one (manufactured by IGM Co., ltd.: omnirad 379) was used as a photopolymerization initiator.
Example 3
A photocurable adhesive sheet with a release sheet and a laminate of a polarizing plate/a photocurable adhesive sheet/a polycarbonate resin plate having ultraviolet shielding properties were obtained in the same manner as in example 1 except that 15g of α -aminoacetophenone-based 2-methyl-1- [4- (methylthio) phenyl ] -2-morpholinopropane-1-one (manufactured by IGM Co., ltd.: omnirad 907) was used as a photopolymerization initiator.
Example 4
A photo-curable adhesive sheet with a release sheet, and a laminate of a polarizing plate, a photo-curable adhesive sheet and a polycarbonate resin plate having ultraviolet shielding properties were obtained in the same manner as in example 1, except that 5g of a ketocoumarin derivative (Esacure 3644, manufactured by IGM Co.) was used as a photopolymerization initiator.
Example 5
A photocurable adhesive composition thus obtained was used as an adhesive sheet (1) (thickness: 200 μm) for an interlayer in the same manner as in example 1, except that 3g of phenyl (2, 4, 6-trimethylbenzoyl) phosphinic acid ethyl ester (manufactured by IGM Co., ltd.: omnirad TPO-L) was used as a photopolymerization initiator, and 50g of pentaerythritol triacrylate (manufactured by Sanyo chemical Co., ltd., NK ESTER ATMM-3L) was used as a crosslinking agent.
A photocurable adhesive composition was obtained in the same manner as in example 1 except that 3g of acyl phosphine oxide-based ethyl phenyl (2, 4, 6-trimethylbenzoyl) phosphinate (manufactured by IGM Co., ltd.: omnirad TPO-L) was used as the photopolymerization initiator, and 80g of propoxylated pentaerythritol triacrylate (manufactured by Sanyo chemical Co., ltd., NK ESTER ATM-4 PL) was used as the crosslinking agent. In addition, a photocurable pressure-sensitive adhesive sheet with a release sheet was produced from the obtained photocurable pressure-sensitive adhesive composition in the same manner as in example 1, and a pressure-sensitive adhesive sheet (2) for front and back layers (thickness: 25 μm) ('2') (thickness: 25 μm) was produced.
The PET films on both sides of the adhesive sheet for the intermediate layer were peeled off in this order, and the adhesive surfaces of the adhesive sheet for the front and back layers (2) and ('2') were bonded in this order to each other on both surfaces, to thereby produce a photocurable adhesive sheet with a release sheet having a thickness of 250. Mu.m, which was composed of (2)/(1)/('2').
Thereafter, a photocurable adhesive sheet with a release sheet and a laminate of a polarizing plate, a photocurable adhesive sheet, and a polycarbonate resin plate having ultraviolet shielding properties were obtained in the same manner as in example 1.
Comparative example 1
A photocurable adhesive sheet with a release sheet and a laminate of a polarizing plate/a photocurable adhesive sheet/a polycarbonate resin sheet having ultraviolet shielding properties were obtained in the same manner as in example 1 except that 15g of an acylphosphine oxide-based diphenyl (2, 4, 6-trimethylbenzoyl) phosphine oxide (Omnirad TPO, manufactured by IGM Co.) was used as a photopolymerization initiator.
Comparative example 2
A photocurable adhesive sheet with a release sheet and a laminate of a polarizing plate/a photocurable adhesive sheet/a polycarbonate resin plate having ultraviolet shielding properties were obtained in the same manner as in example 1 except that 15g of ethyl (2, 4, 6-trimethylbenzoyl) phosphinate (manufactured by IGM Co., ltd.: omnirad TPO-L) was used as the photopolymerization initiator.
Comparative example 3
A photocurable adhesive sheet with a release sheet and a laminate of a polarizing plate/a photocurable adhesive sheet/a polycarbonate resin sheet having ultraviolet shielding properties were obtained in the same manner as in example 1 except that 15g of a mixture of acylphosphine oxides [ 2,4, 6-trimethylbenzoyl-diphenyl-phosphine oxide (concentration ratio: about 46%), oligo (2-hydroxy-2-methyl-1- (4- (1-methylvinyl) phenyl) propanone) (concentration ratio: about 50%), 2,4, 6-trimethylbenzophenone (concentration ratio: about 3.2%), and 4-methylbenzophenone (concentration ratio: about 0.8%) ] (manufactured by IGM Co., ltd.) was used as the photopolymerization initiator.
Comparative example 4
A photocurable adhesive sheet with a release sheet and a laminate of a polarizing plate/a photocurable adhesive sheet/a polycarbonate resin plate having ultraviolet shielding properties were obtained in the same manner as in example 1 except that 15g of phenylglyoxylate methyl benzoate (manufactured by IGM Co., ltd.: omnirad MBF) was used as a photopolymerization initiator.
Reference example
A laminate of a polarizing plate, a photocurable adhesive sheet, and a polycarbonate resin plate having ultraviolet shielding properties was obtained in the same manner as in comparative example 1, except that a polarizing plate having a surface of a polyvinyl alcohol resin film layer at a depth of 90 μm from the outermost surface of the polarizing plate to which the adhesive sheet was to be attached was used as the polarizing plate.
The photocurable adhesive sheets with release sheets and laminates of examples 1 to 5, comparative examples 1 to 4 and reference examples were used for the following evaluation. The results are shown in Table 1 below.
(1) Transmittance of light
The release sheet was peeled off from the photocurable adhesive sheet with the release sheet, and the spectral transmittance (% T) of the photocurable adhesive sheet at a wavelength of 300 to 800nm was measured using a spectrophotometer (UV 2000 manufactured by Shimadzu corporation).
(2) Yellow index value (YI value)
Stripping the release sheet from the photocurable adhesive sheet with release sheet to a cumulative light quantity of 3000 (mJ/cm) 2 ) After UV light was irradiated from a high-pressure mercury lamp, a yellow index value (YI value) was measured according to JIS K7103 using a spectrocolorimeter (manufactured by Suga Test Instruments company) 'SC-T'.
(3) Gel fraction
Peeling off the release sheet from the photocurable adhesive sheet with release sheet, wrapping the sheet with SUS mesh (# 200) of predetermined mass (M) to form a bag, folding and sealing the mouth of the bag, and measuring the wrapped mass (M) 1 ) Then, the mixture was immersed in 100mL of ethyl acetate, stored in the dark at 23℃for 24 hours, and then the package was taken out and added at 70 ℃After heating for 4.5 hours, the attached ethyl acetate was evaporated, and the mass (M 2 ) The mass obtained was substituted into the following equation to obtain the gel fraction G1 before light irradiation.
Gel fraction g1 (%) = [ (M) 2 -M)/(M 1 -M)]×100
Further, the laminate of the polarizing plate, the photocurable adhesive sheet, and the polycarbonate resin plate having ultraviolet shielding property was subjected to a high-pressure mercury lamp so that the cumulative light amount at 405nm became 3000 (mJ/cm) 2 ) After light was irradiated from the polycarbonate resin plate side having ultraviolet shielding properties, the cured photocurable adhesive sheet was scraped off with a doctor blade, and the gel fraction G2 after light irradiation was determined by the same method.
(4) High temperature and high humidity resistance
For the laminate of polarizing plate/photocurable adhesive sheet/polycarbonate resin plate having ultraviolet shielding property, the cumulative light amount at 405nm was 3000 (mJ/cm) using a high-pressure mercury lamp 2 ) In the method (2), light is irradiated from the polycarbonate resin plate side having ultraviolet shielding property, and a high-temperature and high-humidity resistant reliability evaluation sample is prepared.
The following evaluation was performed after exposing the above-mentioned evaluation sample to 85℃and 85% RH for 1000 hours.
[ appearance evaluation ]
The case where no appearance defect such as foaming or peeling was observed was determined as "good", and the case where foaming or peeling was observed was determined as "× (pool)".
[ evaluation of discoloration of polarizing plate ]
Based on visual observation, the case where discoloration of the polarizing plate was not observed was judged as "good", and the case where lightening was clearly observed was judged as "× (pool)".
TABLE 1
Figure BDA0004220606100000321
In the laminate of examples 1 to 5, the photocurable adhesive composition for forming the layer in contact with the polarizing plate was irradiated with light from the laminate side of the polycarbonate resin plate having ultraviolet shielding property without using an acylphosphine oxide-based photopolymerization initiator and a phenylglyoxylate-based photopolymerization initiator as photopolymerization initiators, thereby sufficiently curing the photocurable adhesive sheet. Further, the laminate after the light irradiation is exposed to 85 ℃ and 85% RH for 1000 hours, and the laminate does not discolor the polarizing plate, and can have excellent heat and humidity resistance without appearance defects such as foaming and peeling.
In the laminate of the polarizing plate/photocurable adhesive sheet/polycarbonate resin plate having ultraviolet shielding property of comparative examples 1 to 4, the adhesive layer contained the specific amount or more of the acylphosphine oxide-based photopolymerization initiator or the phenylglyoxylate-based photopolymerization initiator, and therefore, the laminate after light irradiation was exposed to 85 ℃ for 1000 hours at 85% rh, and no appearance defects such as foaming and peeling were observed, but the polarizing plate was significantly discolored.
In the reference example in which the surface of the polyvinyl alcohol resin film layer was located at a depth of 90 μm from the outermost surface of the polarizing plate to which the adhesive sheet was attached, even when the photocurable adhesive sheet of comparative example 1 in which the photocurable adhesive composition contained a specific amount or more of the acylphosphine oxide-based photopolymerization initiator was used, the polarizing plate was not discolored, and good results were exhibited.
This shows that: the present invention is particularly suitable for use in a structure in which the distance between the photocurable pressure-sensitive adhesive sheet and the polarizing plate is short.
In the above embodiments, the specific embodiments of the present invention have been described by way of example only, and the above embodiments are not to be construed as limiting. Various modifications apparent to those skilled in the art should be considered to fall within the scope of the invention.
Industrial applicability
The laminate of the present invention can be cured by visible light, and can suppress appearance defects such as discoloration, foaming, peeling, etc. of the polarizing plate even under high temperature and high humidity, and therefore can be suitably used for a structural member of an image display device for a vehicle.

Claims (14)

1. A laminate comprising a laminate of a polarizing plate and a photocurable adhesive sheet,
[ II ] A polarizing plate having a layer structure in which both surfaces of a polarizing plate are laminated with protective films,
[ III ] the distance (alpha) between the photocurable adhesive sheet and the polarizing plate is 80 μm or less,
[ IV-1] A photocurable adhesive sheet is formed from a photocurable adhesive composition comprising a (meth) acrylate (co) polymer and a photopolymerization initiator (A), and
[ IV-2] the laminate has a light transmittance of less than 90% at 390nm and a light transmittance of 80% or more at 410nm,
[ IV-3] As the photopolymerization initiator (A), the total concentration of the acylphosphine oxide-based photopolymerization initiator and the phenylglyoxylate-based photopolymerization initiator contained in the photocurable adhesive composition is 0.5% by mass or less.
2. The laminate according to claim 1, wherein the photocurable adhesive sheet [ IV-4] is one which can be cured even under irradiation of light having a wavelength of 390 to 410 nm.
3. The laminate according to claim 1 or 2, wherein another constituent member (X) having a light transmittance of 10% or less at a wavelength of 365nm and a light transmittance of 60% or more at a wavelength of 405nm is laminated via the photocurable adhesive sheet.
4. A laminate according to claim 3, wherein the other constituent member (X) is an ultraviolet light-shielding cover material.
5. The laminate according to any one of claims 1 to 4, wherein the protective film in the polarizing plate is a triacetyl cellulose resin film.
6. The laminate according to any one of claims 1 to 5, wherein a ratio (α/β) of a distance (α) between the photocurable adhesive sheet and the polarizing plate to a thickness (β) of the photocurable adhesive sheet is 0.1 to 0.5.
7. The laminate according to any one of claims 1 to 6, wherein the photocurable adhesive sheet has a thickness (β) of 50 to 500 μm.
8. The laminate according to any one of claims 1 to 7, wherein the photopolymerization initiator (a) contains at least 1 photopolymerization initiator selected from the group consisting of an α -aminoacetophenone-based photopolymerization initiator and a ketocoumarin-based photopolymerization initiator.
9. The laminate according to any one of claims 1 to 8, wherein the photocurable adhesive sheet has a yellow index value (YI value) of 2.0 or less.
10. The laminate according to any one of claims 1 to 9, wherein the photocurable adhesive composition contains a trifunctional or higher polyfunctional (meth) acrylate and/or a silane coupling agent.
11. The laminate according to any one of claims 1 to 10, wherein the (meth) acrylate (co) polymer is a graft copolymer having a macromer as a branch component.
12. The laminate according to any one of claims 1 to 11, wherein the photocurable adhesive sheet is irradiated with an accumulated light amount of 3000 (mJ/cm) at a wavelength of 405nm through an ultraviolet shielding member having ultraviolet shielding property 2 ) The difference between the gel fraction G1 before light irradiation and the gel fraction G2 after light irradiation, that is, the gel fraction G2 after light irradiation-the gel fraction G1 before light irradiation is 10% or more.
13. The laminate according to any one of claims 1 to 12, wherein the photocurable adhesive sheet has a multilayer structure of 2 or more layers.
14. A laminated structure obtained by curing the laminated structure according to any one of claims 1 to 13 with visible light.
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