Classifications

• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
  • C09J133/00—Adhesives based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Adhesives based on derivatives of such polymers
  • C09J133/04—Homopolymers or copolymers of esters
  • C09J133/06—Homopolymers or copolymers of esters of esters containing only carbon, hydrogen and oxygen, the oxygen atom being present only as part of the carboxyl radical
  • C09J133/08—Homopolymers or copolymers of acrylic acid esters
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F220/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride ester, amide, imide or nitrile thereof
  • C08F220/02—Monocarboxylic acids having less than ten carbon atoms; Derivatives thereof
  • C08F220/10—Esters
  • C08F220/12—Esters of monohydric alcohols or phenols
  • C08F220/16—Esters of monohydric alcohols or phenols of phenols or of alcohols containing two or more carbon atoms
  • C08F220/18—Esters of monohydric alcohols or phenols of phenols or of alcohols containing two or more carbon atoms with acrylic or methacrylic acids
  • C08F220/1808—C8-(meth)acrylate, e.g. isooctyl (meth)acrylate or 2-ethylhexyl (meth)acrylate
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F222/00—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 a carboxyl radical and containing at least one other carboxyl radical in the molecule; Salts, anhydrides, esters, amides, imides, or nitriles thereof
  • C08F222/10—Esters
  • C08F222/1006—Esters of polyhydric alcohols or polyhydric phenols
  • C08F222/102—Esters of polyhydric alcohols or polyhydric phenols of dialcohols, e.g. ethylene glycol di(meth)acrylate or 1,4-butanediol dimethacrylate
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F265/00—Macromolecular compounds obtained by polymerising monomers on to polymers of unsaturated monocarboxylic acids or derivatives thereof as defined in group C08F20/00
  • C08F265/04—Macromolecular compounds obtained by polymerising monomers on to polymers of unsaturated monocarboxylic acids or derivatives thereof as defined in group C08F20/00 on to polymers of esters
  • C08F265/06—Polymerisation of acrylate or methacrylate esters on to polymers thereof
• • 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
  • C09J151/003—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 macromolecular compounds obtained by reactions only involving unsaturated carbon-to-carbon bonds
• • 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
  • C09J4/00—Adhesives based on organic non-macromolecular compounds having at least one polymerisable carbon-to-carbon unsaturated bond ; adhesives, based on monomers of macromolecular compounds of groups C09J183/00 - C09J183/16
  • C09J4/06—Organic non-macromolecular compounds having at least one polymerisable carbon-to-carbon unsaturated bond in combination with a macromolecular compound other than an unsaturated polymer of groups C09J159/00 - C09J187/00
• • 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
  • C09J7/10—Adhesives in the form of films or foils without carriers
• • 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
  • 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
  • C09J2433/00—Presence of (meth)acrylic polymer
• • G—PHYSICS
  • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
  • G09F—DISPLAYING; ADVERTISING; SIGNS; LABELS OR NAME-PLATES; SEALS
  • G09F9/00—Indicating arrangements for variable information in which the information is built-up on a support by selection or combination of individual elements
  • G09F9/30—Indicating arrangements for variable information in which the information is built-up on a support by selection or combination of individual elements in which the desired character or characters are formed by combining individual elements
  • G09F9/301—Indicating arrangements for variable information in which the information is built-up on a support by selection or combination of individual elements in which the desired character or characters are formed by combining individual elements flexible foldable or roll-able electronic displays, e.g. thin LCD, OLED
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K2102/00—Constructional details relating to the organic devices covered by this subclass
  • H10K2102/301—Details of OLEDs
  • H10K2102/311—Flexible OLED
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K59/00—Integrated devices, or assemblies of multiple devices, comprising at least one organic light-emitting element covered by group H10K50/00
  • H10K59/80—Constructional details
  • H10K59/87—Passivation; Containers; Encapsulations
  • H10K59/873—Encapsulations
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K77/00—Constructional details of devices covered by this subclass and not covered by groups H10K10/80, H10K30/80, H10K50/80 or H10K59/80
  • H10K77/10—Substrates, e.g. flexible substrates
  • H10K77/111—Flexible substrates

Definitions

• the present invention relates to an adhesive sheet, particularly an adhesive sheet that can be suitably used for bonding constituent members of an image display device having a curved surface or a bendable flexible image display device, and a flexible image display device using the adhesive sheet.
• Such image display devices have a laminated structure in which multiple component sheets such as a cover lens, a circularly polarizing plate, a touch film sensor, and a light emitting element are bonded together using transparent adhesive sheets. , it can be regarded as a laminated sheet formed by laminating a member sheet and an adhesive sheet.
• thermosetting resin for example, in Patent Document 1, it includes a thermosetting resin and a crosslinking agent, and the thermosetting resin has at least one N or O in the molecule and at least one An adhesive composition for a foldable display, which contains a unit derived from a compound containing an unshared electron pair, and wherein the thermosetting resin has a glass transition temperature of -70°C or less, an adhesive film using the same, and A foldable display including the same is disclosed.
• the adhesive composition for foldable displays is a composition in which a thermosetting resin made by copolymerizing carbitol acrylate, ethylhexyl acrylate, and acrylic acid is blended with an epoxy crosslinking agent or an isocyanate crosslinking agent.
• An adhesive film using the same, and a foldable display including the same are disclosed.
• Patent Documents 2 and 3 disclose adhesives that aim to improve durability and step followability by focusing on distortion and distortion recovery power when shearing force is applied.
• the adhesive film containing a large amount of carbitol acrylate disclosed in Patent Document 1 has a low storage modulus at low temperatures, so although it can reduce the stress caused by folding, it has low adhesive strength, especially at low temperatures.
• the adhesive film containing a large amount of carbitol acrylate disclosed in Patent Document 1 has a low storage modulus at low temperatures, so although it can reduce the stress caused by folding, it has low adhesive strength, especially at low temperatures.
• delamination easily occurred between the sheet and the component sheet.
• carbitol acrylate tends to relieve internal stress through internal rotation around ether bonds, it also has the problem that creases are difficult to disappear when folding operations are performed.
• Patent Documents 2 and 3 are aimed at improving durability and step followability, they do not relate to adhesive sheets used for laminating constituent members of flexible image display devices, and they do not relate to adhesive sheets that are used for bonding components of flexible image display devices, and are particularly suitable for folding in low-temperature environments. No consideration is given to the unique problems such as delamination and creases remaining due to the high elastic modulus when the operation is performed, and these problems are not solved in Patent Documents 2 and 3. It's something that doesn't exist.
• the present invention relates to a pressure-sensitive adhesive sheet having a low storage shear modulus at low temperatures, which is formed from a pressure-sensitive adhesive composition containing an acrylic polymer, and which is in a flat state when folded.
• Adhesive sheet with improved adhesive strength to prevent delamination when folded while having restorability also referred to as "strain recovery", especially adhesive used for laminating components of flexible image display devices.
• the present invention provides a sheet and a flexible image display device using the sheet.
• an adhesive sheet whose storage shear modulus [G' (-20°C)] at -20°C is below a predetermined value, and which is an acrylic adhesive sheet. It is an adhesive sheet formed from an adhesive composition containing an acrylic polymer and a radically polymerizable compound, and an acrylic polymer containing a relatively long chain alkyl group and a hydroxyl group is used as the acrylic polymer, and further comparison is made. It has been found that by using in combination a di(meth)acrylate having an alkylene group with a short target chain length, it is possible to further improve the adhesive strength while maintaining good flexibility and restorability.
• the present invention has the following aspects.
• the pressure-sensitive adhesive sheet is a pressure-sensitive adhesive sheet formed from a pressure-sensitive adhesive composition [I] containing an acrylic polymer (A) and a radically polymerizable compound (B),
• the acrylic polymer (A) contains a structural part derived from an alkyl (meth)acrylate (a1) whose alkyl group has 5 to 20 carbon atoms and a structural part derived from a hydroxyl group-containing (meth)acrylate (a2),
• the glass transition temperature (Tg) defined by the maximum point of loss tangent (tan ⁇ ) obtained by dynamic viscoelasticity measurement in a shear mode at a frequency of 1 Hz of the acrylic polymer (A) is ⁇ 50° C. or higher.
• the glass transition temperature (Tg) defined by the maximum point of loss tangent (tan ⁇ ) obtained by dynamic viscoelasticity measurement in a shear mode at a frequency of 1 Hz of the acrylic polymer (A) is ⁇ 50° C. or higher.
• the adhesive sheet of the present invention has a low storage shear modulus at low temperatures, and is formed from an adhesive composition containing a specific alkyl group- and hydroxyl group-containing acrylic polymer and a specific di(meth)acrylate. Since it is a pressure-sensitive adhesive sheet, it has good flexibility and restorability, and has further improved adhesive strength, and can be particularly suitably used as a pressure-sensitive adhesive sheet for use in flexible image display devices.
• the term "main component” refers to a component that has a large effect on the properties of an object, and the content of this component is usually 30% by mass or more, preferably 35% by mass in the object.
• the content is more preferably 50% by mass or more.
• the content is 80% by mass or more, particularly 90% by mass or more (including 100% by mass).
• (meth)acrylic refers to “acrylic” and “methacrylic”
• (meth)acrylate refers to “acrylate” and “methacrylate”
• (meth)acryloyl refers to " The meaning includes ⁇ acryloyl'' and ⁇ methacryloyl,'' respectively.
• acrylic polymer refers to a polymer containing a monomer unit derived from (meth)acrylate, and includes a (meth)acrylic copolymer.
• a pressure-sensitive adhesive sheet (also referred to as "this pressure-sensitive adhesive sheet") according to an example of an embodiment of the present invention is formed from a pressure-sensitive adhesive composition [I] containing an acrylic polymer (A) and a radically polymerizable compound (B). It is a pressure-sensitive adhesive sheet, and is particularly useful as a pressure-sensitive adhesive sheet used for laminating components of a flexible image display device.
• the adhesive composition [I] contains an acrylic polymer (A) and a radically polymerizable compound (B), and preferably contains the acrylic polymer (A) as a main component.
• the acrylic polymer (A) used in this pressure-sensitive adhesive sheet has a structural part derived from an alkyl (meth)acrylate (a1) in which the alkyl group has 5 to 20 carbon atoms and a structural part derived from a hydroxyl group-containing (meth)acrylate (a2). It is an acrylic polymer containing
• the copolymerization components constituting the acrylic polymer (A) include an alkyl (meth)acrylate (a1) in which the alkyl group has 5 to 20 carbon atoms and a hydroxyl group-containing (meth)acrylate (a2); It is obtained by polymerization.
• copolymerization component it is copolymerized with other monomer components (a3) other than the alkyl (meth)acrylate (a1) whose alkyl group has 5 to 20 carbon atoms and the hydroxyl group-containing (meth)acrylate (a2). It can be whatever you can get.
• Alkyl (meth)acrylate (a1) in which the alkyl group has 5 to 20 carbon atoms examples include n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, n-heptyl (meth)acrylate, and n-octyl.
• Linear alkyl (meth)acrylates such as (meth)acrylate, n-nonyl (meth)acrylate, and n-decyl (meth)acrylate; isopentyl (meth)acrylate, neopentyl (meth)acrylate, 2-ethylhexyl (meth)acrylate , branched alkyl (meth)acrylates such as isooctyl (meth)acrylate, isononyl (meth)acrylate, isodecyl (meth)acrylate; alicyclic (meth)acrylates such as cyclohexyl (meth)acrylate, t-butylcyclohexyl (meth)acrylate, etc. Examples include acrylate. These may be used alone or in combination of two or more.
• straight-chain alkyl (meth)acrylates or branched alkyl (meth)acrylates are preferred from the viewpoint of adhesiveness, and among them, those in which the alkyl group has 6 to 18 carbon atoms, more preferably 6 to 16 carbon atoms, and especially 8 to 12 carbon atoms Linear or branched alkyl (meth)acrylates are preferred.
• linear alkyl (meth)acrylates are preferred from the viewpoint of adhesiveness and restorability, and in particular, alkyl (meth)acrylates are preferred from the viewpoint of suppressing the increase in storage shear modulus (G') at low temperatures and improving flexibility.
• Linear alkyl (meth)acrylates having a group having 6 to 18 carbon atoms, more preferably 6 to 16 carbon atoms, especially 8 to 12 carbon atoms are preferred, such as n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, n -octyl (meth)acrylate, n-nonyl (meth)acrylate, decyl (meth)acrylate and the like.
• n-octyl (meth)acrylate, n-nonyl (meth)acrylate, and n-decyl (meth)acrylate are preferred, and n-octyl (meth)acrylate is particularly preferred.
• acrylate is particularly preferred.
• the alkyl (meth)acrylate (a1) in which the alkyl group has 5 to 20 carbon atoms is contained in an amount of 50 to 95% by mass based on the total copolymer components constituting the acrylic polymer (A). It is preferable that the amount is from 60 to 90% by mass, particularly preferably from 70 to 85% by mass from the viewpoint of suppressing an increase in the storage shear modulus (G') at low temperatures.
• the proportion of alkyl (meth)acrylate (a1) is above the lower limit value, the increase in storage shear modulus (G') at low temperatures can be suppressed, and when it is below the upper limit value, it can be compatible with other physical properties such as adhesiveness. preferred.
• hydroxyl group-containing (meth)acrylate (a2) examples include 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 5-hydroxypentyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, Hydroxy (meth)acrylates such as 8-hydroxyoctyl (meth)acrylate, caprolactone-modified hydroxy (meth)acrylates such as caprolactone-modified 2-hydroxyethyl (meth)acrylate, diethylene glycol (meth)acrylate, polyethylene glycol (meth)acrylate, etc.
• Oxyalkylene-modified (meth)acrylate primary hydroxyl group-containing (meth)acrylate such as 2-acryloyloxyethyl-2-hydroxyethylphthalic acid; 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, Secondary hydroxyl group-containing (meth)acrylates such as 3-chloro-2-hydroxypropyl (meth)acrylate; tertiary hydroxyl group-containing (meth)acrylates such as 2,2-dimethyl 2-hydroxyethyl (meth)acrylate, etc. I can do it. These can be used alone or in combination of two or more.
• hydroxyl group-containing (meth)acrylates (a2) primary hydroxyl group-containing (meth)acrylates, such as 2-hydroxyethyl (meth)acrylate, 4 -Hydroxybutyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, etc. are preferred, and in particular hydroxyl group-containing (meth) having a hydroxyalkyl group having 1 to 10 carbon atoms, particularly 1 to 6 carbon atoms, especially 2 to 4 carbon atoms.
• acrylates such as 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, especially 2-hydroxyethyl (meth)acrylate.
• the content of the hydroxyl group-containing (meth)acrylate (a2) is preferably from 5 to 50% by mass, more preferably from the viewpoint of adhesive strength, based on the entire copolymerization component of the acrylic polymer (A). is 10 to 40% by weight, particularly preferably 15 to 30% by weight.
• the hydroxyl group-containing (meth)acrylate (a2) is at least the lower limit, high tackiness can be obtained, and when it is at most the upper limit, the increase in storage shear modulus (G') at low temperatures can be suppressed, which is preferable.
• the monomer component (a3) copolymerizable with the alkyl (meth)acrylate (a1) in which the alkyl group has 5 to 20 carbon atoms and/or the hydroxyl group-containing (meth)acrylate (a2) (the (a1) ) and (excluding component (a2)) can also be used together.
• Examples of such monomer component (a3) include ethylenically unsaturated group monomers having a functional group other than hydroxyl groups, alkyl (meth)acrylates containing an alkyl group having 1 to 4 or more than 20 carbon atoms, other copolymerizable monomers, etc. can be mentioned. These can be used alone or in combination of two or more.
• Examples of the ethylenically unsaturated group monomer having a functional group other than the hydroxyl group include a functional group-containing monomer having a nitrogen atom, a carboxyl group-containing monomer, Examples include acetoacetyl group-containing monomers and glycidyl group-containing monomers.
• functional group-containing monomers having a nitrogen atom are preferable from the viewpoint of imparting cohesive force and crosslinking promoting effect, more preferably amino group-containing monomers, amide group-containing monomers, and isocyanate group-containing monomers, and even more preferably It is an amino group-containing monomer.
• amino group-containing monomer examples include primary amino group-containing (meth)acrylates such as aminomethyl (meth)acrylate and aminoethyl (meth)acrylate; t-butylamino Secondary amino group-containing (meth)acrylates such as ethyl (meth)acrylate and t-butylaminopropyl (meth)acrylate; ethylaminoethyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate , tertiary amino group-containing (meth)acrylates such as dimethylaminopropyl (meth)acrylate, diethylaminopropyl (meth)acrylate, and dimethylaminopropylacrylamide.
• primary amino group-containing (meth)acrylates such as aminomethyl (meth)acrylate and aminoethyl (meth)acrylate
• amide group-containing monomer examples include (meth)acrylamide; N-methyl (meth)acrylamide, N-ethyl (meth)acrylamide, N-propyl (meth)acrylamide, Nn-butyl (meth)acrylamide, and diacetone.
• (meth)acrylamide N-alkyl (meth)acrylamide such as N,N'-methylenebis(meth)acrylamide; N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N,N-dipropyl (meth)acrylamide, N,N-dialkyl(meth)acrylamide such as N,N-ethylmethylacrylamide, N,N-diallyl(meth)acrylamide; N-hydroxymethyl(meth)acrylamide, N-hydroxyethyl(meth)acrylamide Examples include hydroxyalkyl (meth)acrylamides such as acrylamide; alkoxyalkyl (meth)acrylamides such as N-methoxymethyl (meth)acrylamide and N-(n-butoxymethyl)(meth)acrylamide;
• Examples of the isocyanate group-containing monomer include 2-(meth)acryloyloxyethyl isocyanate and alkylene oxide adducts thereof.
• the isocyanate group may be protected with a blocking agent such as methyl ethyl ketone oxime, 3,5-dimethylpyrazole, 1,2,4-triazole, and diethyl malonate.
• carboxy group-containing monomer examples include (meth)acrylic acid, carboxyethyl (meth)acrylate, 2-(meth)acryloyloxyethylhexahydrophthalic acid, 2-(meth)acryloyloxypropylhexahydrophthalic acid, and 2-(meth)acryloyloxypropylhexahydrophthalic acid.
• (meth)acryloyloxyethyl phthalic acid 2-(meth)acryloyloxypropylphthalic acid, 2-(meth)acryloyloxyethylmaleic acid, 2-(meth)acryloyloxypropylmaleic acid, 2-(meth)acryloyloxyethyl
• succinic acid 2-(meth)acryloyloxypropylsuccinic acid, crotonic acid, fumaric acid, maleic acid, itaconic acid, monomethyl maleate, monomethyl itaconate, and the like.
• acetoacetyl group-containing monomer examples include 2-(acetoacetoxy)ethyl (meth)acrylate, allyl acetoacetate, and the like.
• glycidyl group-containing monomer examples include glycidyl (meth)acrylate, allylglycidyl (meth)acrylate, and the like.
• the upper limit of the content of the functional group-containing ethylenically unsaturated monomer is 30% by mass or less based on the entire copolymerization component of the acrylic polymer (A), from the viewpoint of reducing the decrease in tackiness due to bleed-out. It is preferably at most 20% by mass, even more preferably at most 10% by mass, particularly preferably at most 5% by mass.
• the lower limit is usually 0% by mass.
• alkyl (meth)acrylate containing an alkyl group having 1 to 4 or more than 20 carbon atoms examples include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, and n-butyl (meth)acrylate.
• Straight chain alkyl (meth)acrylates such as acrylate, icosyl (meth)acrylate; isopropyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, t-butyl (meth)acrylate, isoicosyl (meth)acrylate
• the upper limit of the content is determined from the viewpoint of maintaining restorability of the acrylic polymer (A). It is preferably 20% by mass or less, more preferably 10% by mass or less, even more preferably 5% by mass or less, based on the total copolymerization components.
• the lower limit is usually 0% by mass.
• Examples of the other copolymerizable monomers include phenyl (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenyldiethylene glycol (meth)acrylate, phenoxypolyethylene glycol (meth)acrylate, and phenoxypolyethylene glycol-polypropylene.
• Aromatic (meth)acrylates such as glycol (meth)acrylate, nonylphenol ethylene oxide adduct (meth)acrylate, 4-acryloyloxybenzophenone, 4-acryloyloxyethoxybenzophenone, 4-acryloyloxy-4'-methoxybenzophenone , 4-acryloyloxyethoxy-4'-methoxybenzophenone, 4-acryloyloxy-4'-bromobenzophenone, 4-acryloyloxyethoxy-4'-bromobenzophenone, 4-methacryloyloxybenzophenone, 4-methacryloyloxyethoxybenzophenone, 4 -methacryloyloxy-4'-methoxybenzophenone, 4-methacryloyloxyethoxy-4'-methoxybenzophenone, 4-methacryloyloxy-4'-bromobenzophenone, 4-methacryloyloxyethoxy-4'-bromobenzophenone, and mixtures thereof
• (Meth)acrylate with benzophenone structure acrylonitrile, methacrylonitrile, styrene, ⁇ -methylstyrene, vinyl stearate, vinyl propionate, vinyl acetate, vinyl chloride, vinylidene chloride, alkyl vinyl ether, vinyltoluene, vinylpyridine, vinylpyrrolidone , itaconic acid dialkyl ester, fumaric acid dialkyl ester, allyl alcohol, acrylic chloride, methyl vinyl ketone, N-acrylamidomethyltrimethylammonium chloride, allyltrimethylammonium chloride, dimethylallyl vinyl ketone, and other vinyl monomers. These can be used alone or in combination of two or more.
• the upper limit of the content of the other copolymerizable monomers is 20% by mass or less based on the total copolymerization components of the acrylic polymer (A) from the viewpoint of improving flexibility and stress relaxation properties.
• the content is preferably 15% by mass or less, further preferably 10% by mass or less, particularly preferably 5% by mass or less.
• the lower limit is usually 0% by mass.
• the acrylic polymer (A) can be obtained by copolymerizing the various monomer components according to conventionally known polymerization methods, such as solution radical polymerization, suspension polymerization, bulk polymerization, emulsion polymerization, etc.
• the acrylic polymer (A) may have a photoactive site, such as a polymerizable carbon double bond group, introduced into the side chain.
• a photoactive site such as a polymerizable carbon double bond group
• a copolymer containing the above-mentioned hydroxyl group-containing (meth)acrylate (a2) or a functional group-containing ethylenically unsaturated monomer can be used as a method for introducing a polymerizable carbon double bond group into the side chain of the acrylic polymer (A).
• a copolymer containing the above-mentioned hydroxyl group-containing (meth)acrylate (a2) or a functional group-containing ethylenically unsaturated monomer can be used.
• a method in which a compound is produced, and then a compound having a functional group that can react with these functional groups and a polymerizable carbon double bond group undergoes a condensation or addition reaction while maintaining the activity of the polymerizable carbon double bond group. can be mentioned.
• Combinations of these functional groups include epoxy groups (glycidyl groups) and carboxy groups, amino groups and carboxy groups, amino groups and isocyanate groups, epoxy groups (glycidyl groups) and amino groups, hydroxyl groups and epoxy groups, and hydroxyl groups and isocyanate groups. etc. can be mentioned.
• a combination of a hydroxyl group and an isocyanate group is preferred from the viewpoint of ease of reaction control.
• a combination in which the copolymer has a hydroxyl group and the compound has an isocyanate group is preferred.
• Examples of the isocyanate compound having a polymerizable carbon double bond group include the aforementioned 2-(meth)acryloyloxyethyl isocyanate and alkylene oxide adducts thereof.
• the content of the compound having a functional group that can react with the functional group and a polymerizable carbon double bond group is determined based on 100 parts by mass of the acrylic polymer (A) from the viewpoint of improving adhesiveness and stress relaxation properties.
• the amount is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, further preferably 1 part by mass or less, particularly preferably 0.1 part by mass or less. Note that the lower limit is usually 0 parts by mass.
• the glass transition temperature (Tg) defined by the maximum point of the loss tangent (tan ⁇ ) obtained by measuring the dynamic viscoelasticity of the acrylic polymer (A) in a shear mode at a frequency of 1 Hz is the storage shear elasticity at low temperatures.
• the temperature is preferably -10°C or lower, more preferably -20°C or lower, even more preferably lower than -25°C, particularly preferably -27°C or lower, and most preferably -30°C or lower.
• the lower limit of the glass transition temperature (Tg) is usually -50°C, preferably -45°C, due to concerns about glue oozing out.
• Tg glass transition temperature
• an acrylic polymer (A) is molded into a cylinder with a diameter of 8 mm (height: 1.0 mm), and this is measured using a viscoelasticity measuring device (manufactured by TA Instruments, product name "DHR 2").
• the loss tangent (tan ⁇ ) can be measured using the following measurement conditions.
• the theoretical Tg of the acrylic polymer (A) is preferably -52°C or lower, more preferably -54°C or lower, and more preferably -54°C or lower, from the viewpoint of suppressing an increase in storage shear modulus (G') at low temperatures. Preferably it is -56°C or lower. Note that, due to concerns such as glue oozing out, the lower limit of the theoretical Tg of the acrylic polymer (A) is usually -70°C, preferably -65°C.
• the theoretical Tg of the acrylic polymer (A) means a value calculated by the Fox formula from the glass transition temperature and composition ratio of the polymer obtained from the homopolymer of each component of the copolymer.
• the Fox calculation formula is a calculated value determined by the following formula, and is described in the Polymer Handbook, J. It can be determined using the values described in [Brandrup, Interscience, 1989].
• (Formula) 1/(273+Tg) ⁇ (Wi/(273+Tgi)) [Wherein, Wi represents the weight fraction of monomer i, and Tgi represents the Tg (°C) of the homopolymer of monomer i. ]
• the weight average molecular weight (Mw) of the acrylic polymer (A) is preferably 600,000 or more, more preferably 700,000 or more, and more preferably 700,000 or more, from the viewpoint of obtaining the adhesive composition [I] with high cohesive force. Preferably it is 800,000 or more.
• the upper limit of the weight average molecular weight (Mw) of the acrylic polymer (A) is preferably 1.5 million or less, more preferably 1.2 million or less, even more preferably 1.1 million or less.
• the weight average molecular weight (Mw) can be determined, for example, as follows. (Method for measuring weight average molecular weight) The measurement sample was prepared by dissolving 4 mg of acrylic polymer (A) in 12 mL of tetrahydrofuran (THF), and a gel permeation chromatography (GPC) analyzer (manufactured by Tosoh Corporation, HLC- The weight average molecular weight (Mw) can be determined by measuring the molecular weight distribution curve using a 8320 GPC) under the following conditions.
• GPC gel permeation chromatography
• the pressure-sensitive adhesive composition [I] contains a radically polymerizable compound (B) in addition to the acrylic polymer (A). Thereby, the adhesive composition [I] forms a crosslinked structure, and can provide the adhesive layer (adhesive sheet) with cohesive force and high restorability when bent.
• the adhesive layer has an appropriate cohesive force, it is possible to prevent the glue from oozing out when rolled into a roll, and to maintain good adhesiveness.
• by having high restorability when bent it is possible to improve creases and prevent delamination at bent portions.
• the radically polymerizable compound (B) is a di(meth)acrylate (B1) having an alkylene group having 2 to 4 carbon atoms (hereinafter sometimes abbreviated as "di(meth)acrylate (B1)"). It is important to include this material, and as a result, it is possible to further improve the adhesion while having good flexibility and restorability.
• di(meth)acrylate (B1) both di(meth)acrylates having a linear alkylene group and di(meth)acrylates having a branched alkylene group can be used, but from the viewpoint of restorability, linear Di(meth)acrylates having an alkylene group are preferred.
• di(meth)acrylates having a linear alkylene group include ethanediol di(meth)acrylate, propanediol di(meth)acrylate, butanediol di(meth)acrylate, and the like.
• butanediol di(meth)acrylate is preferred from the viewpoint of adhesiveness, versatility, restorability, and low storage shear modulus (G') at low temperatures. Furthermore, from the viewpoint of suppressing an increase in storage shear modulus (G') at low temperatures and improving flexibility, acrylate is particularly preferred. These can be used alone or in combination of two or more.
• a radically polymerizable compound (B2) other than the di(meth)acrylate (B1) can also be used in combination.
• the radically polymerizable compound (B2) is a di(meth)acrylate other than the di(meth)acrylate (B1), such as a di(meth)acrylate having an alkylene group having 1 or 5 or more carbon atoms, or having 2 or more functional groups. Examples include (meth)acrylic monomers and (meth)acrylic oligomers. These can be used alone or in combination of two or more.
• Examples of the di(meth)acrylate having an alkylene group having 1 or more than 5 carbon atoms include methanediol di(meth)acrylate, pentanediol di(meth)acrylate, hexadiol di(meth)acrylate, and heptanediol di(meth)acrylate. Examples include (meth)acrylate, octanediol di(meth)acrylate, nonanediol di(meth)acrylate, decanediol di(meth)acrylate, undecanediol di(meth)acrylate, dodecanediol di(meth)acrylate, and the like.
• Examples of the (meth)acrylic monomer having two or more functional groups include glycerin di(meth)acrylate, neopentyl glycol di(meth)acrylate, glycerin glycidyl ether di(meth)acrylate, tricyclodecane dimethacrylate, and tricyclodecane dimethacrylate.
• Examples of the (meth)acrylic oligomers having two or more functional groups include polyester (meth)acrylate oligomers, epoxy (meth)acrylate oligomers, urethane (meth)acrylate oligomers, and polyether (meth)acrylate oligomers.
• Examples include polyfunctional (meth)acrylic oligomers such as. Among these, urethane (meth)acrylate oligomers are preferred from the viewpoint of imparting appropriate toughness to the cured product.
• the content of the radical polymerizable compound (B) is determined based on 100 parts by mass of the acrylic polymer (A) from the viewpoint of imparting shape stability to the pressure-sensitive adhesive sheet and durability when made into a laminated sheet. , is preferably 0.1 part by mass or more, more preferably 0.5 part by mass or more, and even more preferably 1 part by mass or more. Further, the upper limit is preferably 10 parts by mass or less from the viewpoint of reducing the storage shear modulus (G') at low temperatures, more preferably 7 parts by mass or less, particularly preferably 5 parts by mass or less, and still more preferably 3 parts by mass or less. It is.
• the di(meth)acrylate (B1) is used as the radically polymerizable compound (B), and the content of the di(meth)acrylate (B1) is 100% of the acrylic polymer (A). It is preferably 0.1 part by mass or more, more preferably 0.5 part by mass or more, still more preferably 0.7 part by mass or more, particularly preferably 1 part by mass or more.
• the upper limit is preferably 10 parts by mass or less, more preferably 7 parts by mass or less, particularly preferably 5 parts by mass or less, still more preferably 3 parts by mass or less, from the viewpoint of maintaining high adhesiveness.
• di(meth)acrylate (B1) as the main component of the radically polymerizable compound (B), and especially, it is preferable to use only the di(meth)acrylate (B1) as the radically polymerizable compound (B). preferable.
• thermal crosslinking agent in addition to the radically polymerizable compound (B), a thermal crosslinking agent can be used in combination to further increase the crosslinking density and improve long-term reliability.
• thermal crosslinking agents include isocyanate crosslinking agents, epoxy crosslinking agents, aziridine crosslinking agents, melamine crosslinking agents, aldehyde crosslinking agents, amine crosslinking agents, and metal chelate crosslinking agents.
• the pressure-sensitive adhesive sheet preferably further contains a photopolymerization initiator (C).
• the photopolymerization initiator (C) may be any compound that generates radicals when exposed to active energy rays.
• Photopolymerization initiators (C) are broadly classified into two types depending on the radical generation mechanism: cleavable photopolymerization initiators that can generate radicals by cleaving and decomposing the single bonds of the initiator itself, and excited initiators. and a hydrogen donor in the system to form an exciplex, and a hydrogen abstraction type photopolymerization initiator that can transfer the hydrogen of the hydrogen donor.
• the photopolymerization initiator (C) may be either a cleavage type photopolymerization initiator or a hydrogen abstraction type photopolymerization initiator, and each may be used alone or in combination. Furthermore, each may be used alone or in combination of two or more.
• a hydrogen abstraction type photopolymerization initiator is used because it can be efficiently crosslinked without requiring a functional group such as a polymerizable carbon double bond group in the acrylic polymer (A) itself. is preferred.
• cleavable photopolymerization initiator examples include 2,2-dimethoxy-1,2-diphenylethan-1-one, 1-hydroxycyclohexylphenylketone, and 2-hydroxy-2-methyl-1-phenyl-propane-1.
• Examples of the hydrogen abstraction type photopolymerization initiator include benzophenone, 4-methylbenzophenone, 2,4,6-trimethylbenzophenone, 4-phenylbenzophenone, 3,3'-dimethyl-4-methoxybenzophenone, 4-(meth) Acryloyloxybenzophenone, methyl 2-benzoylbenzoate, methyl benzoyl formate, bis(2-phenyl-2-oxoacetic acid)oxybisethylene, 4-(1,3-acryloyl-1,4,7,10,13-penta oxotridecyl)benzophenone, thioxanthone, 2-chlorothioxanthone, 3-methylthioxanthone, 2,4-dimethylthioxanthone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-t-butylanthraquinone, 2-aminoanthraquinone and derivatives thereof, etc. can be mentioned. Among
• the content of the photopolymerization initiator (C) is usually 0.1 to 10 parts by weight, especially 0.5 to 5 parts by weight, and especially 1 to 3 parts by weight, per 100 parts by weight of the acrylic polymer (A).
• the content is at least the lower limit, curing failure tends to be prevented, and when it is at most the upper limit, it is easy to prevent deterioration in solution stability such as precipitation from the adhesive composition [I], and it tends to prevent embrittlement and embrittlement. There is a tendency to easily suppress coloring problems.
• Adhesive composition [I] may contain as "other components” such as a plasticizer, a silane coupling agent, an ultraviolet absorber, a rust preventive, and a tackifier, as necessary to the extent that the effects of the present invention are not impaired.
• Various additives such as a resin, an antioxidant, a light stabilizer, a metal deactivator, an anti-aging agent, a moisture absorbent, a rust preventive, and inorganic particles can be included as appropriate.
• a reaction catalyst such as a tertiary amine compound, a quaternary ammonium compound, or a tin laurate compound may be appropriately contained. These can be used alone or in combination of two or more.
• plasticizer is a material that improves processability and flexibility by softening a resin with a high elastic modulus.
• the plasticizer include monofunctional (meth)acrylic oligomers such as polyester (meth)acrylate, urethane (meth)acrylate, and polyether (meth)acrylate. Among these, urethane (meth)acrylate oligomers are preferred from the viewpoint of imparting appropriate toughness to the cured product.
• the silane coupling agent is an organosilicon compound containing one or more reactive functional groups and one or more silicon-bonded alkoxy groups in its structure.
• the reactive functional groups include epoxy groups, (meth)acryloyl groups, mercapto groups, hydroxyl groups, carboxy groups, amino groups, amide groups, and isocyanate groups. Among these, epoxy and mercapto groups are preferred.
• the alkoxy group bonded to the silicon atom preferably contains an alkoxy group having 1 to 8 carbon atoms from the viewpoint of durability and storage stability, and particularly preferably a methoxy group or an ethoxy group.
• the silane coupling agent may have a reactive functional group and an organic substituent other than the alkoxy group bonded to a silicon atom, such as an alkyl group or a phenyl group.
• silane coupling agent used in this adhesive sheet examples include 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 3-glycidoxypropyltrimethoxysilane.
• an oligomer-type epoxy group-containing silane coupling agent which is a silane compound obtained by co-condensing the silane compound with an alkyl group-containing silane compound such as methyltriethoxysilane, ethyltriethoxysilane, methyltrimethoxysilane, or ethyltrimethoxysilane; 3; - Monomer-type mercapto group-containing silane coupling agents that are silane compounds such as mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, ⁇ -mercaptopropyldimethoxymethylsilane, and 3-mercaptopropylmethyldimethoxysilane, and the aforementioned silanes.
• Oligomeric mercapto group-containing silane coupling agent 3-acryloxypropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane (Meth)acryloyl group-containing silane coupling agents such as roxypropyltrimethoxysilane; N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxy Silane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine, N-phenyl-3-aminopropyltrimeth
• Examples include amino group-containing silane coupling agents; isocyanate group-containing silane coupling agents such as 3-isocyanatepropyltriethoxysilane; vinyl group-containing silane coupling agents such as vinyltrimethoxysilane and vinyltriethoxysilane; These may be used alone or in combination of two or more.
• epoxy group-containing silane coupling agents and mercapto group-containing silane coupling agents are preferably used because of their excellent durability, and among them, epoxy group-containing silane coupling agents are preferred.
• the content of the silane coupling agent is preferably 0.005 to 10 parts by mass, particularly preferably 0.01 to 5 parts by mass, and even more preferably is 0.05 to 1 part by mass. When this content is within the above range, durability tends to improve.
• UV absorber examples include benzophenone UV absorbers, benzotriazole UV absorbers, triazine UV absorbers, salicylic acid UV absorbers, cyanoacrylate UV absorbers, and benzoxazine UV absorbers. These ultraviolet absorbers can be used alone or in combination of two or more.
• the content of the ultraviolet absorber is preferably 0.01 to 20 parts by mass, particularly preferably 0.1 to 15 parts by mass, and even more preferably The amount is 0.5 to 10 parts by mass.
• the content is at least the lower limit, light resistance reliability tends to improve, and when the content is at most the upper limit, yellowing resistance tends to improve.
• rust preventive agent for example, triazoles, benzotriazoles, etc. are preferable, and can prevent corrosion of the optical member.
• the content of the rust preventive agent is preferably 0.01 to 5 parts by mass, particularly preferably 0.1 parts by mass or more and 3 parts by mass or less, based on 100 parts by mass of the acrylic polymer (A). .
• the content of the other components is preferably 5 parts by mass or less, particularly preferably 1 part by mass or less, and even more preferably 0.5 parts by mass or less based on 100 parts by mass of the acrylic polymer (A). be. If this content is too large, the compatibility with the acrylic polymer (A) tends to decrease and the durability tends to decrease.
• Adhesive composition [I] comprises an acrylic polymer (A) and a radically polymerizable compound (B), preferably a photopolymerization initiator (C), and optionally a silane coupling agent, an ultraviolet absorber, It is prepared by mixing predetermined amounts of other components such as rust preventives.
• the pressure-sensitive adhesive composition [I] thus obtained is used as a pressure-sensitive adhesive sheet, particularly a pressure-sensitive adhesive sheet used for laminating components of a flexible image display device.
• the present adhesive sheet may be a single-layer sheet consisting only of an adhesive layer formed from the adhesive composition [I] (also referred to as "main adhesive layer"), or a multilayer sheet in which a plurality of main adhesive layers are laminated. It may be a sheet. Alternatively, it may be a multilayer sheet in which the main adhesive layer and an adhesive layer other than the main adhesive layer are laminated.
• This pressure-sensitive adhesive sheet can have the following physical properties.
• the adhesive sheet preferably has a storage shear modulus [G' (-40°C)] of 50,000 kPa or less at -40°C, which is obtained by dynamic viscoelasticity measurement in a shear mode at a frequency of 1 Hz. Since the storage shear modulus [G' (-40°C)] of the present adhesive sheet is within the above range, for example, when the present adhesive sheet is attached to a member sheet to form a laminated sheet or a flexible image display device member. Especially in a low-temperature environment, it is possible to reduce interlayer stress when folding a laminated sheet or a flexible image display device member, and it is possible to suppress delamination and cracking of the member sheet or flexible member.
• the present adhesive sheet has a storage shear modulus [G' (-40 °C)] of 40,000 kPa or less at -40 °C, which is obtained by dynamic viscoelasticity measurement in a shear mode at a frequency of 1 Hz. It is more preferably 30,000 kPa, even more preferably 10,000 kPa or less, particularly preferably 9,000 kPa or less, and most preferably 8,000 kPa or less.
• the lower limit of the storage shear modulus [G' (-40° C.)] of the adhesive sheet is preferably 100 kPa or more in view of the balance with the storage shear modulus at high temperatures.
• the adhesive sheet has a storage shear modulus [G' (-20°C)] of 700 kPa or less at -20°C, which is obtained by dynamic viscoelasticity measurement in a shear mode at a frequency of 1 Hz.
• a storage shear modulus [G' (-20°C)] of 700 kPa or less at -20°C which is obtained by dynamic viscoelasticity measurement in a shear mode at a frequency of 1 Hz.
• it is preferably 600 kPa or less, more preferably 500 kPa or less, even more preferably 400 kPa or less, even more preferably 300 kPa or less, particularly preferably 200 kPa or less.
• the lower limit of the storage shear modulus [G' (-20° C.)] of the adhesive sheet is preferably 50 kPa or more from the viewpoint of preventing glue extrusion and maintaining the shape of the adhesive sheet.
• the storage shear modulus [G' (-20°C)] of the present adhesive sheet is within the above range, for example, when the present adhesive sheet is attached to a member sheet to form a laminated sheet or a flexible image display device member.
• the present adhesive sheet is attached to a member sheet to form a laminated sheet or a flexible image display device member.
• interlayer stress during bending of a laminated sheet or flexible image display device member can be reduced, and delamination and cracking of the member sheet or flexible member can be suppressed.
• This adhesive sheet has a storage shear modulus [G' (25°C)] of 100 kPa or less at 25°C, which is obtained by dynamic viscoelasticity measurement in a shear mode at a frequency of 1 Hz, from the viewpoint of obtaining high adhesiveness.
• the pressure is preferably 50 kPa or less, more preferably 40 kPa or less, and particularly preferably 30 kPa or less.
• the lower limit of the storage shear modulus [G' (25° C.)] of the adhesive sheet is preferably 5 kPa or more from the viewpoint of preventing glue from seeping out and maintaining the shape of the adhesive sheet.
• This adhesive sheet has a storage shear modulus [G' (80 °C)] of 100 kPa or less at 80 °C, which is obtained by dynamic viscoelasticity measurement in a shear mode with a frequency of 1 Hz, from the viewpoint of obtaining high adhesiveness.
• the pressure is preferably 50 kPa or less, more preferably 30 kPa or less, and particularly preferably 20 kPa or less.
• the lower limit of the storage shear modulus [G' (80° C.)] of the adhesive sheet is preferably 1 kPa or more from the viewpoint of preventing glue from seeping out and maintaining the shape of the adhesive sheet.
• the loss shear modulus [G" (23°C)] of the adhesive sheet at 23°C obtained by dynamic viscoelasticity measurement in a shear mode at a frequency of 1 Hz is preferably 8 kPa or more, more preferably 10 kPa or more.
• the upper limit of the loss shear modulus [G'' (23°C)] is preferably 400 kPa or less, particularly preferably 12 kPa or more, from the viewpoint of stress reduction during bending. preferable.
• the adhesive force of the present pressure-sensitive adhesive sheet can be further enhanced.
• the maximum point of loss tangent (tan ⁇ ) and glass transition temperature (Tg) In the present adhesive sheet, the maximum point of loss tangent (tan ⁇ ) obtained by dynamic viscoelasticity measurement in a shear mode with a frequency of 1 Hz is preferably at -25°C or lower, and more preferably at -30°C or lower. . The lower limit is usually -50°C.
• the maximum point of the loss tangent (tan ⁇ ) can be interpreted as the glass transition temperature (Tg), and when the glass transition temperature (Tg) is within the above range, the storage shear modulus [G'( -20°C)] to 700 kPa or less, especially 500 kPa or less.
• the glass transition temperature (Tg ) can be considered to be single.
• the "maximum point" of the loss tangent (tan ⁇ ) is the peak value in the tan ⁇ curve, that is, the inflection point where it changes from positive (+) to negative (-) when differentiated, in a predetermined range or the entire range. This is the meaning of a point with a value of .
• the storage shear modulus (G'), the loss shear modulus (G''), and the loss tangent (tan ⁇ ) are calculated based on the components of the adhesive composition [I] constituting the present adhesive sheet (for example, the acrylic polymer described above). It can be adjusted within the above range by adjusting the type and weight average molecular weight of (A) and the radically polymerizable compound (B)), and further adjusting the gel fraction of the pressure-sensitive adhesive sheet. However, the method is not limited to this method.
• this adhesive sheet has such resilience, even if this adhesive sheet is attached to a component sheet and folded at low or high temperatures, it will not bend when placed in a bent state. It is possible to obtain an adhesive sheet with excellent restorability without leaving crease marks. From this point of view, after applying a shear strain equivalent to 7 times the thickness at 25°C and maintaining it for 10 minutes, the restorability calculated from the residual strain value after 10 minutes after removing the stress is 20% or more, 40% It is preferably 50% or more, particularly 70% or more. Since higher restorability is preferable, the upper limit is 100%.
• the gel fraction of the pressure-sensitive adhesive sheet is preferably 30 to 95% by mass, more preferably 50 to 90% by mass, even more preferably 55 to 85% by mass, particularly preferably 60 to 85% by mass.
• the gel fraction of the present pressure-sensitive adhesive sheet is at least the lower limit value, the shape can be sufficiently maintained, and when it is at most the upper limit value, the adhesive force can be increased.
• the gel fraction of the adhesive sheet is preferably 30 to 65% by mass, more preferably 35 to 60% by mass.
• the gel fraction is a measure of the degree of crosslinking (degree of curing), and can be measured under the measurement conditions described in Examples below.
• the total light transmittance of the adhesive sheet is preferably 85% or more, more preferably 88% or more, and even more preferably 90% or more.
• the haze of the pressure-sensitive adhesive sheet is preferably 1.0% or less, more preferably 0.8% or less, particularly preferably 0.5% or less. Since the haze of the adhesive sheet is 1.0% or less, it can be used for image display devices. In order to keep the haze of the adhesive sheet within the above range, it is preferable that the adhesive sheet does not contain particles such as organic particles.
• the thickness of this adhesive sheet is not particularly limited, and if the thickness is 10 ⁇ m or more, handling properties are good, and if the thickness is 1000 ⁇ m or less, it will contribute to making the adhesive sheet thinner. be able to. Therefore, the thickness of the pressure-sensitive adhesive sheet is preferably 10 ⁇ m or more, particularly 15 ⁇ m or more, particularly 20 ⁇ m or more, and even more preferably 25 ⁇ m or more. On the other hand, the upper limit is preferably 1000 ⁇ m or less, particularly 500 ⁇ m or less, particularly 250 ⁇ m or less, further preferably 100 ⁇ m or less, particularly 50 ⁇ m or less.
• This adhesive sheet is used for laminating members that make up display members (also referred to as “display members”), especially flexible members for displays used for manufacturing displays, and is used for laminating display members that constitute display members (also referred to as “display members”). Used as adhesive parts for flexible displays. Note that the same flexible members as those described later can be used.
• this adhesive sheet In the production of this adhesive sheet, the adhesive sheet for forming this adhesive sheet containing an acrylic polymer (A), a radically polymerizable compound (B), a photopolymerization initiator (C), and other components as necessary is used.
• This pressure-sensitive adhesive sheet is prepared by preparing the pressure-sensitive adhesive composition [I], molding the pressure-sensitive adhesive composition [I] into a sheet, curing it by crosslinking or polymerization reaction, and performing appropriate processing as necessary. Just make it.
• the pressure-sensitive adhesive composition [I] for forming the present pressure-sensitive adhesive sheet is prepared in the same manner as described above, and this is coated on a member sheet or flexible member, and the pressure-sensitive adhesive composition [I] is coated on a member sheet or a flexible member.
• the present pressure-sensitive adhesive sheet may be formed by curing [I]. However, it is not limited to this method.
• the raw materials are mixed in a temperature-adjustable kneader (e.g., single-screw extruder, twin-screw extruder, planetary mixer, twin-screw mixer, pressure kneader). etc.) for kneading.
• a temperature-adjustable kneader e.g., single-screw extruder, twin-screw extruder, planetary mixer, twin-screw mixer, pressure kneader). etc.
• various additives such as silane coupling agents and antioxidants may be blended with the resin in advance and then fed to the kneader, or all materials may be melt-mixed in advance.
• a masterbatch in which only the additives are concentrated in the resin may be prepared and supplied.
• Methods for forming the adhesive composition [I] into a sheet include known methods, such as wet lamination, dry lamination, extrusion casting using a T-die, extrusion lamination, calendaring, inflation, and injection molding. , liquid injection curing method, etc. can be adopted. Among these, wet lamination, extrusion casting, and extrusion lamination are suitable for manufacturing sheets.
• a cured product of the adhesive composition [I] can be produced by irradiating and curing active energy rays.
• further curing can also be achieved by heating.
• the present pressure-sensitive adhesive sheet can be produced by irradiating active energy rays to a molded object, such as a sheet, of the pressure-sensitive adhesive composition [I].
• further curing can also be achieved by heating.
• the irradiation energy, irradiation time, irradiation method, etc. of the active energy rays are not particularly limited, as long as they can activate the photopolymerization initiator (C) and polymerize the monomer components.
• a hydrogen abstraction type photopolymerization initiator is used as the photopolymerization initiator (C)
• a hydrogen abstraction reaction also occurs from the acrylic polymer (A)
• the acrylic polymer (A) is incorporated into the crosslinked structure.
• a crosslinked structure with many crosslinking points can be formed. Therefore, it is preferable that the pressure-sensitive adhesive sheet is cured using a hydrogen abstraction type photopolymerization initiator.
• the pressure-sensitive adhesive composition [I] can be dissolved in an appropriate solvent and various coating methods can be used.
• the present pressure-sensitive adhesive sheet can also be obtained by thermal curing in addition to curing by irradiation with active energy rays as described above.
• the thickness of the adhesive sheet can be adjusted by the coating thickness and the solid content concentration of the coating liquid.
• the adhesive composition [I] can be dissolved in a solvent, coated on a release film, dried, and cured by active energy ray irradiation to form the present adhesive sheet.
• a release film may be laminated if necessary.
• the release film may be coated and dried, cured by active energy ray irradiation, and the release film may be laminated thereon, or the release film may be coated and dried, and the release film After laminating, the adhesive sheet may be formed by curing by irradiation with active energy rays.
• Such a solvent is not particularly limited as long as it dissolves the adhesive composition [I], and examples thereof include ester solvents such as methyl acetate, ethyl acetate, methyl acetoacetate, and ethyl acetoacetate, acetone, methyl ethyl ketone, Examples include ketone solvents such as methyl isobutyl ketone, aromatic solvents such as toluene and xylene, and alcohol solvents such as methanol, ethanol and propyl alcohol. These can be used alone or in combination of two or more.
• ethyl acetate acetone, methyl ethyl ketone, and toluene are preferred from the viewpoint of solubility, drying properties, cost, etc., and ethyl acetate is particularly preferably used.
• the content of the solvent is preferably 600 parts by mass or less, more preferably 500 parts by mass or less, even more preferably 400 parts by mass or less, and 300 parts by mass based on drying properties. Parts below are particularly preferred. On the other hand, it is preferably 1 part by mass or more, more preferably 50 parts by mass or more, even more preferably 100 parts by mass or more, and particularly preferably 150 parts by mass or more.
• a coating method conventional methods such as roll coating, die coating, gravure coating, comma coating, screen printing, and bar coating can be used.
• the solvent content in the adhesive composition [I] after drying is preferably 1% by mass or less, more preferably 0.5% by mass or less, particularly preferably 0.1% by mass or less, Most preferably it is 0% by mass.
• the drying temperature is usually 40 to 150°C, more preferably 45 to 140°C, even more preferably 50 to 130°C, particularly preferably 55 to 120°C. Within the above temperature range, the solvent can be removed efficiently and relatively safely while suppressing thermal deformation of the release film.
• the drying time is usually 1 to 30 minutes, more preferably 3 to 25 minutes, and still more preferably 5 to 20 minutes. Within the above time range, the solvent can be removed efficiently and sufficiently.
• drying method examples include drying using a dryer, heating rolls, and drying by blowing hot air onto the film.
• a dryer it is preferable to use a dryer because drying can be done uniformly and easily. These can be used alone or in combination of two or more.
• Examples of active energy rays in the active energy ray irradiation include far ultraviolet rays, ultraviolet rays, near ultraviolet rays, infrared rays, visible rays, etc., X-rays, ⁇ -rays, ⁇ -rays, ⁇ -rays, electron beams, proton beams, neutron beams, etc. ionizing radiation.
• ultraviolet rays are preferable from the viewpoint of suppressing damage to the constituent members of the optical device and controlling reactions.
• curing by ultraviolet irradiation is advantageous in terms of curing speed, availability of irradiation equipment, price, etc.
• Examples of light sources for ultraviolet irradiation include high-pressure mercury lamps, ultra-high-pressure mercury lamps, carbon arc lamps, metal halide lamps, xenon lamps, chemical lamps, electrodeless discharge lamps, LEDs, etc. that emit light in the wavelength range of 150 to 450 nm. It will be done. Among these, it is preferable to use a high-pressure mercury lamp.
• the active energy ray irradiation amount (cumulative light amount) is preferably 30 to 3000 mJ/cm 2 , more preferably 100 to 2000 mJ/cm 2 , and even more preferably 300 to 1500 mJ/cm 2 . . After irradiation with active energy rays, heating can be performed as necessary to increase the degree of curing.
• a release film can also be provided on at least one side of the pressure-sensitive adhesive sheet obtained above from the viewpoint of preventing blocking and foreign matter adhesion.
• release film a known release film can be used as appropriate.
• the material of the release film include polyester film, polyolefin film, polycarbonate film, polystyrene film, acrylic film, triacetyl cellulose film, fluororesin film, etc., which are coated with silicone resin and subjected to release treatment.
• a release paper or the like can be appropriately selected and used.
• the thickness of the release film is not particularly limited. Among these, from the viewpoint of processability and handling, it is preferably 10 to 250 ⁇ m, more preferably 25 to 200 ⁇ m, and even more preferably 35 to 190 ⁇ m.
• embossing or various unevenness processing may be performed as necessary.
• the surface may be subjected to various surface treatments such as corona treatment, plasma treatment, and primer treatment.
• the present pressure-sensitive adhesive sheet can also be provided as a pressure-sensitive adhesive sheet with a release film by laminating a release film on one or both sides of the pressure-sensitive adhesive layer (present pressure-sensitive adhesive sheet) made of the pressure-sensitive adhesive composition [I].
• the laminated sheet (hereinafter sometimes referred to as "this laminated sheet") according to an example of an embodiment of the present invention is a sheet that includes the present adhesive sheet and other layers.
• the thickness of the adhesive sheet preferably accounts for 10 to 90% of the total thickness of the laminated sheet, particularly 20% to 80%, particularly 30% to 70%. It is more preferable that the Moreover, it is preferable that the present laminated sheet is one in which a member sheet is provided on at least one side of the present adhesive sheet, or one in which the present adhesive sheet is provided on at least one side of the member sheet.
• the present laminated sheet includes, for example, a component sheet (hereinafter sometimes referred to as a "first component sheet”), an actual adhesive sheet, and a component sheet different from the above (hereinafter sometimes referred to as a "second component sheet”). It is preferable that the laminated sheet has a structure in which the two (1) and (1) are laminated in this order.
• the present laminated sheet can be produced by attaching the present adhesive sheet to the first member sheet and/or the second member sheet.
• the manufacturing method is not limited to this. Note that the first member sheet and the second member sheet may be the same or different.
• the member sheet constituting the present laminated sheet that is, the member sheet (including the "first member sheet” and/or the "second member sheet") to be adhered to the present adhesive sheet, includes, for example, polyester resin, A resin sheet or thin film glass containing as a main component at least one resin selected from the group consisting of cycloolefin resin, triacetyl cellulose resin, polymethyl methacrylate resin, epoxy resin, polyimide resin, aramid resin, and polyurethane resin. Glasses such as Here, the thin film glass refers to glass having the thickness of the member sheet mentioned above.
• the 25°C tensile strength (ASTM D882) of a resin sheet whose main component is cycloolefin resin is as low as 40 to 60 MPa at a thickness of 100 ⁇ m. Occasionally, cracks tend to occur, and it has been difficult to eliminate cracks within the scope of conventional technology.
• the member sheet conventionally known materials can be used, and examples thereof include, but are not limited to, the following materials.
• PI film “manufactured by KOLON, C_50, thickness 53um” tensile strength: 204MPa
• main component refers to a component that occupies the largest mass ratio among the resin components constituting the member sheet, and specifically refers to the component sheet or the resin composition forming the member sheet. It occupies 50% by mass or more, and more preferably 55% by mass or more, more preferably 60% by mass or more.
• the first member sheet and the second member sheet include a cover lens, a polarizing plate, a retardation film, a barrier film, a touch sensor film, and a light emitting film. Elements, etc. can be mentioned.
• the first member sheet has a touch input function.
• the second member sheet may also have a touch input function.
• the tensile strength at 25°C measured in accordance with ASTM D882 (also referred to as “25°C tensile strength (ASTM D882)) is 10 to 900 MPa, particularly 15 MPa. It is more preferably 20 MPa or more and 700 MPa or less, more preferably 20 MPa or more and 700 MPa or less. It is preferable that the 25° C. tensile strength (ASTM D882) of the first member sheet is within the above range because it is difficult to break even when bent.
• the second member sheet preferably has a tensile strength of 10 to 900 MPa at 25°C measured in accordance with ASTM D882, particularly 15 MPa or more and 800 MPa.
• ASTM D882 the pressure is 20 MPa or more and 700 MPa or less.
• ASTM D882 the 25° C. tensile strength
• both the first member sheet and the second member sheet have a tensile strength of 10 to 900 MPa at 25° C. as measured in accordance with ASTM D882.
• the first member sheet and the second member sheet may be made of the same material or may be made of different materials.
• Examples of the member sheet with high tensile strength include polyimide films, polyethylene naphthalate (PEN) films, etc. is generally 900 MPa or less. The lower limit is usually 50 MPa.
• examples of the member sheet having a slightly low tensile strength include polyethylene terephthalate (PET) film, triacetyl cellulose (TAC) film, cycloolefin polymer (COP) film, etc., and the tensile strength of these films is usually It is 10 MPa or more.
• the upper limit is usually 200 MPa. Even if the present laminated sheet includes a member sheet made of such a material with a rather low tensile strength, defects such as cracking can be suppressed by the action of the present adhesive sheet.
• This laminated sheet can have the following physical properties.
• the adhesive force of the present adhesive sheet to the component sheet is preferably 1 to 30 N/cm, more preferably 2 to 20 N/cm. , more preferably 3 to 10 N/cm.
• the adhesive force of the present adhesive sheet to the component sheet is preferably 0.5 to 30 N/cm, more preferably 1 ⁇ 20N/cm, more preferably 1.5 ⁇ 10N/cm.
• the adhesive has sufficient adhesiveness and tends to be suitably used as an adhesive sheet for flexible image display devices.
• the adhesive strength can be measured under the measurement conditions described in Examples below.
• a bifunctional (meth)acrylate monomer having an alkylene group having a length of a certain length or less is used as the radically polymerizable compound (B).
• a di(meth)acrylate (B1) containing an alkylene group having 2 to 4 carbon atoms It is important to contain a structural moiety derived from the alkyl (meth)acrylate (a1) having an alkyl group.
• a bifunctional (meth)acrylate having an alkylene group having a length of a certain length or less forms a crosslinked structure with the acrylic polymer (A) using a photopolymerization initiator.
• acrylates By selecting acrylates, a small network of crosslinked structures is formed. This makes it difficult for the polymers to slip through each other when conducting adhesion tests and restorability tests, increasing the loss shear modulus G" and loss tangent tan ⁇ , while maintaining flexibility and restorability. performance can be further improved.
• the peeling mode when peeling off the adhesive sheet from the member sheet is preferably interfacial peeling.
• Image display device components used in image display devices, especially bendable flexible image display devices, are often expensive, and if a failure occurs during the component bonding process, reworkability is required so that they can be peeled off without leaving any adhesive residue.
• a surface protection film may be further laminated on the surface of the cover window. In such a case, when the adhesive layer of the surface protection film is peeled off, it is necessary to prevent the adhesive layer from remaining on the surface of the cover window, so-called "separation".
• the peeling mode is interfacial peeling
• a pressure-sensitive adhesive sheet with excellent reworkability that does not contaminate the product can be obtained.
• the pressure-sensitive adhesive sheet is made to have excellent flexibility, the cohesive force decreases, and the peeling mode when peeling force is applied tends to be cohesive failure.
• the radically polymerizable compound (B) a difunctional (meth)acrylate monomer having an alkylene group having a length below a certain level, specifically a di(meth)acrylate monomer having an alkylene group having 2 to 4 carbon atoms, is used.
• acrylate (B1) By using acrylate (B1), a pressure-sensitive adhesive sheet that is flexible and has excellent cohesive force can be obtained.
• the peeling mode of the acrylic adhesive can be determined, for example, by visually observing the adherend after the adhesive force measurement test and checking for the presence or absence of adhesive residue. More specifically, cohesive failure can be determined when there is a level of adhesive residue that can be visually confirmed.
• the thickness of the present laminated sheet is not particularly limited.
• the present laminated sheet when used in an image display device, the present laminated sheet is in the form of a sheet, and if the thickness is 0.01 mm or more, it has good handling properties, and if the thickness is 1 mm or less, it has good handling properties. For example, it can contribute to making the laminated sheet thinner. Therefore, the thickness of the present laminated sheet is preferably 0.01 mm or more, more preferably 0.03 mm or more, and particularly preferably 0.05 mm or more.
• the upper limit is preferably 1 mm or less, more preferably 0.7 mm or less, and particularly preferably 0.5 mm or less.
• the present laminated sheet is prepared by preparing the adhesive composition [I] in the same manner as in the manufacturing method of the present adhesive sheet, and applying the adhesive composition [I] on the first member sheet and/or the second member sheet, for example.
• the present laminated sheet may be manufactured by applying and curing the adhesive to form an adhesive sheet.
• the method for preparing the adhesive composition [I], the method for coating it, the method for curing the adhesive composition [I], etc. are the same as the method for producing the present adhesive sheet.
• the present laminated sheet may be manufactured by laminating the present pressure-sensitive adhesive sheet manufactured in advance to the first member sheet and/or the second member sheet.
• various surface treatments such as corona treatment, plasma treatment, and primer treatment may be performed on the respective surfaces of the present adhesive sheet, the first member sheet, and the second member sheet.
• the laminated sheet has a structure in which a component sheet is laminated only on one side of the adhesive sheet, a protective film with a release layer laminated on one side of the adhesive sheet on which the component sheet is not laminated. You can also do it.
• a flexible image display device member (hereinafter sometimes referred to as “this flexible image display device member”) according to an example of an embodiment of the present invention has a structure in which two flexible members are bonded together via the present adhesive sheet.
• a flexible image display device member having:
• the present adhesive sheet is as described above, and the elements other than the adhesive sheet will be explained below.
• the flexible members constituting the present flexible image display device member include, for example, a flexible display such as an organic electroluminescence (EL) display, a cover lens (cover film), a polarizing plate, a polarizer, a retardation film, a barrier film, and a viewing angle compensation film.
• a flexible display such as an organic electroluminescence (EL) display, a cover lens (cover film), a polarizing plate, a polarizer, a retardation film, a barrier film, and a viewing angle compensation film.
• Examples include flexible members for displays such as films, brightness enhancement films, contrast enhancement films, diffusion films, transflective films, electrode films, transparent conductive films, metal mesh films, and touch sensor films. Any one of these or a combination of two of these may be used. Examples include combinations of a flexible display and other flexible members, and combinations of a cover lens and other flexible members.
• a flexible member means a member that can be bent, particularly a member that can be bent repeatedly. Particularly preferred is a member that can be fixed in a curved shape with a radius of curvature of 25 mm or more, particularly a member that can withstand repeated bending actions with a radius of curvature of less than 25 mm, more preferably less than 3 mm.
• the main component of the flexible member may be a resin sheet, glass, or the like.
• the material for such a resin sheet include polyester resin, cycloolefin resin, triacetyl cellulose resin, polymethyl methacrylate resin, polyurethane resin, epoxy resin, polyimide resin, and aramid resin, which are one type of resin. or two or more types of resins.
• a resin sheet containing as a main component at least one resin selected from the group consisting of polyester resin, cycloolefin resin, triacetyl cellulose resin, polymethyl methacrylate resin, epoxy resin, polyimide resin, aramid resin, and polyurethane resin.
• the term "main component” refers to a component that accounts for the largest mass ratio among the components constituting the flexible member, and specifically refers to the component that accounts for the largest proportion by mass of the resin composition (resin sheet) that forms the flexible member. % or more, more preferably 55% by mass or more, particularly preferably 60% by mass or more. Further, the flexible member may be made of thin film glass.
• one of the two flexible members preferably has a tensile strength of 10 to 900 MPa at 25° C., especially 15 MPa or more, as measured in accordance with ASTM D882. It is more preferably 800 MPa or less, particularly 20 MPa or more and 700 MPa or less. If the 25° C. tensile strength (ASTM D882) of one flexible member is within the above range, it is preferable because it will not break easily when bent.
• the tensile strength at 25°C measured according to ASTM D882 is 10 to 900 MPa, especially 15 MPa or more and 800 MPa or less, and especially 20 MPa or more. More preferably, it is 700 MPa or less. It is preferable that the 25° C. tensile strength (ASTM D882) of the other flexible member is within the above range because it will not break easily when bent.
• Examples of the flexible member having high tensile strength include polyimide films, polyester films, aramid films, etc., and the tensile strength of these films is generally 900 MPa or less.
• examples of the flexible member sheet having a rather low tensile strength include triacetyl cellulose (TAC) film, cycloolefin polymer (COP) film, etc., and the tensile strength of these films is usually 10 MPa or more. Even if the present flexible image display device member includes a flexible member made of such a material with a rather low tensile strength, defects such as cracking can be suppressed by the action of the present adhesive sheet.
• the method for manufacturing the present flexible image display device member is not particularly limited, and as described above, the adhesive composition [I] may be applied onto the flexible member to form an adhesive sheet, A pressure-sensitive adhesive sheet may be formed in advance using the pressure-sensitive adhesive composition [I] and then bonded to a flexible member.
• a flexible image display device is an image display device incorporating the present laminated sheet or the present flexible image display device member.
• the present flexible image display device including the present laminated sheet can be formed by laminating the present laminated sheet on other image display device constituent members.
• a "flexible image display device” is an image display device that does not leave any bending marks even after repeated bending, can quickly restore itself to the state before the bending when released from the bend, and can display images without distortion even after bending.
• this laminated sheet has excellent adhesiveness, can prevent delamination and cracking of the laminated sheet, and has good restorability, so that a flexible image display device with excellent flexibility can be manufactured.
• Acrylic polymers (1) to (3) were prepared with the copolymer component compositions shown in Table 1.
• ⁇ Radical polymerizable compound> The following radically polymerizable compounds were prepared.
• BDDA 1,4-butanediol diacrylate
• DDDA 1,10-decanediol diacrylate
• Example 1 An acrylic polymer, a radically polymerizable compound, a photopolymerization initiator, and ethyl acetate as a solvent were uniformly mixed with the composition shown in Table 2 to obtain an adhesive composition solution (solid content concentration 33%). Ta.
• the adhesive composition solution was coated onto a release film (manufactured by Mitsubishi Chemical Corporation, silicone release treated polyester film, thickness 100 ⁇ m) so that the thickness after drying was as shown in Table 2. After coating, it was placed in a dryer heated to 90° C. and held for 7 minutes to volatilize the solvent contained in the adhesive composition and dry it.
• a release film manufactured by Mitsubishi Chemical Corporation, silicone release treated polyester film, thickness 100 ⁇ m
• a laminate was formed by laminating a release film (manufactured by Mitsubishi Chemical Corporation, silicone release treated polyester film, thickness 75 ⁇ m) on the surface of the adhesive composition after drying the solvent, and using a high pressure mercury lamp, The pressure-sensitive adhesive composition was irradiated with ultraviolet light through the release film (see Table 2 for each irradiation amount) to obtain a pressure-sensitive adhesive sheet laminate (adhesive sheet with release film).
• the obtained adhesive sheet laminate was evaluated as follows.
• ⁇ Adhesive strength> A polyethylene terephthalate film (manufactured by Mitsubishi Chemical Corporation, Diafoil "S100'', thickness 50 ⁇ m) were roll bonded using a hand roller. This was cut into strips of 10 mm width x 150 mm length, the remaining release film was peeled off, and the exposed adhesive surface was bonded to a stainless steel plate in advance using a transparent polyimide film (main component: transparent polyimide, manufactured by KOLON).
• C_50 (hereinafter referred to as "CPI film”) using a hand roller to produce a laminate sheet consisting of CPI film/adhesive sheet/backing film, and this laminate sheet was placed in a room temperature (23°C) environment. The sample was left for 24 hours to cure under the same conditions, and a sample for measuring adhesive strength was prepared.
• the backing film was peeled off while being pulled at an angle of 180° with the CPI film at a peeling speed of 300 mm/min, and the tensile strength was measured using a load cell.
• the 180° peel strength (N/10 mm) was measured and defined as the adhesive strength (23°C or 60°C).
• the peeling mode when peeling off the adhesive sheet produced in the example from the CPI film was interfacial peeling. In addition, those whose peeling mode was cohesive failure are indicated with "*" in the table.
• ⁇ Viscoelasticity measurement> The dynamic viscoelasticity of the adhesive sheet was measured, and the maximum temperature of loss tangent (tan ⁇ ) (glass transition temperature: Tg) and storage shear modulus at -40°C, -20°C, 25°C and 80°C were determined from the results. G') was read.
• Table 3 shows the results obtained from the above measurements and evaluations.
• the adhesive sheet has a low storage shear modulus at low temperatures, and the adhesive composition has an alkylene group with a relatively short chain length in the acrylic polymer (A).
• the adhesive composition has an alkylene group with a relatively short chain length in the acrylic polymer (A).
• a bifunctional (meth)acrylate monomer By containing a bifunctional (meth)acrylate monomer, it has even better adhesive strength. This is because the difunctional (meth)acrylate monomer bonds the side chains of the acrylic polymer (A), making it difficult for the polymers to slip through each other, and the loss shear modulus G'' increases.
• the network structure accompanying crosslinking becomes smaller, making it even more difficult for the polymers to slip through each other, resulting in high adhesive strength. Therefore, it can be seen that the flexible image display device using the present pressure-sensitive adhesive sheet has restorability and flexibility, and also has excellent adhesive strength, so that delamination is suppressed.
• Comparative Example 1 does not contain a bifunctional (meth)acrylate monomer having an alkylene group with a relatively short chain length, whereas Example 1 does not contain such a bifunctional (meth)acrylate monomer.
• the adhesion of Example 1 is better than that of Comparative Example 1, and similarly, the adhesion of Example 2 is better than that of Comparative Example 2.
• the adhesive sheet according to the example has restorability and further excellent adhesive strength, and the flexible image display device using the adhesive sheet according to the example has restorability and flexibility, and also has excellent adhesive strength. It turns out that it is very powerful.
• Example 3 contains a bifunctional (meth)acrylate monomer having an alkylene group with a relatively short chain length
• Comparative Example 3 does not contain such a (meth)acrylate monomer. Therefore, the adhesive sheet has a high storage shear modulus, especially at low temperatures. Therefore, it can be seen that when used for bonding constituent members of a flexible image display device, problems such as delamination and creases remaining during folding operations cannot be solved.
• Comparative Example 3 when measuring the adhesive force, the adhesive sheet and the CPI film could not be peeled off at the interface, and cohesive failure of the adhesive sheet occurred, so it was not possible to accurately measure the adhesive force at the CPI interface. This shows that reworkability is improved in the examples in which the peeling mode is interfacial peeling.
• the adhesive composition contains a bifunctional (meth)acrylate monomer having an alkylene group with a relatively long chain length in the acrylic polymer (A). It can be seen that although the sample has restorability, the adhesive force is lower than that of the example.
• the pressure-sensitive adhesive sheet of the present invention has excellent flexibility and restorability, as well as superior adhesive strength. Therefore, it is useful as an adhesive sheet for obtaining various flexible image display devices such as bendable, foldable, rollable, and stretchable, and is particularly suitable for adhesive sheets for foldable image display devices that are repeatedly bent.

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• 2023
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