CN116194543A - Adhesive composition for image display device, optical film with adhesive layer, and image display device - Google Patents
Adhesive composition for image display device, optical film with adhesive layer, and image display device Download PDFInfo
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- CN116194543A CN116194543A CN202180064024.1A CN202180064024A CN116194543A CN 116194543 A CN116194543 A CN 116194543A CN 202180064024 A CN202180064024 A CN 202180064024A CN 116194543 A CN116194543 A CN 116194543A
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- 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
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- 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
- C09J133/14—Homopolymers or copolymers of esters of esters containing halogen, nitrogen, sulfur or oxygen atoms in addition to the carboxy oxygen
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- 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]
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- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
- C09J7/00—Adhesives in the form of films or foils
- C09J7/30—Adhesives in the form of films or foils characterised by the adhesive composition
- C09J7/38—Pressure-sensitive adhesives [PSA]
- C09J7/381—Pressure-sensitive adhesives [PSA] based on macromolecular compounds obtained by reactions involving only carbon-to-carbon unsaturated bonds
- C09J7/385—Acrylic polymers
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- 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
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- 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
Abstract
The adhesive composition comprises a (meth) acrylic copolymer having a structural unit derived from at least one monomer selected from the group consisting of a cyclized polymerizable monomer and a (meth) acrylate monomer having a urethane structure. The adhesive composition is an adhesive composition for an image display device capable of exhibiting good characteristics even at low temperatures. The adhesive composition provided by the invention can have a storage modulus G' of 2.0X10 at-20 DEG C 6 A composition having an adhesive force of 8.0N/25mm or more to a polyimide film at-20 ℃ and Pa or less.
Description
Technical Field
The invention relates to an adhesive composition for an image display device, an optical film with an adhesive layer, and an image display device.
Background
Various thin image display devices such as liquid crystal displays and organic EL displays generally have a laminated structure including an image forming layer such as a liquid crystal layer and an organic EL light emitting layer, and 1 or 2 or more optical films. In joining the layers constituting the image display device, an adhesive composition is generally used. In addition, in an optical film composed of a plurality of layers, for example, a polarizing plate composed of a polarizer and a polarizer protective film, or an optical film composed of a polarizing plate and a retardation film, the plurality of layers may be bonded by an adhesive composition.
Prior art literature
Patent literature
Patent document 1: korean patent laid-open publication No. 10-2019-0094119
Disclosure of Invention
Problems to be solved by the invention
The image display device is sometimes used at a low temperature of about-20 ℃. Therefore, for an adhesive composition for an image display device, it is required to exhibit good characteristics even at low temperatures. In patent document 1, the problem concerning the characteristics of the adhesive composition at low temperature is not considered at all.
The purpose of the present invention is to provide an adhesive composition for an image display device, which can exhibit good characteristics even at low temperatures.
Means for solving the problems
The inventors have studied to find out: by preventing the adhesive composition from hardening while suppressing an increase in the storage modulus G' at low temperature, and at the same time ensuring adhesion to an adherend contacted with the adhesive composition at low temperature, such as a Polyimide (PI) film, in an image display device, good characteristics at low temperature, such as good impact resistance, bendability can be obtained; and, by making the adhesive composition contain a (meth) acrylic copolymer having a structural unit derived from a specific monomer, it is possible to secure adhesion to an adherend while suppressing an increase in storage modulus G' at low temperatures.
Based on the above-described findings, the present invention provides an adhesive composition for an image display device, the adhesive composition comprising a (meth) acrylic copolymer having a structural unit derived from at least one monomer selected from a cyclized polymerizable monomer and a (meth) acrylate monomer having a urethane structure.
In other aspects, the present invention provides an adhesive composition for an image display device,
the adhesive composition has a storage modulus G' at-20 ℃ of 2.0X10 6 The adhesive force to the PI film at-20 ℃ is 8.0N/25mm or more under Pa.
In another aspect, the present invention provides an optical film with an adhesive layer, comprising:
optical film
An adhesive layer bonded to the optical film,
the adhesive layer contains the adhesive composition of the present invention.
In another aspect, the present invention provides an image display device including:
an adhesive layer comprising the adhesive composition of the present invention described above, or
The adhesive layer-attached optical film of the present invention is described above.
ADVANTAGEOUS EFFECTS OF INVENTION
According to the present invention, an adhesive composition for an image display device that can exhibit good characteristics even at low temperatures can be realized.
Drawings
Fig. 1 is a cross-sectional view schematically showing an example of an optical film with an adhesive layer according to the present invention.
Fig. 2 is a cross-sectional view schematically showing another example of the adhesive layer-attached optical film of the present invention.
Fig. 3 is a cross-sectional view schematically showing an example of the image display device of the present invention.
Detailed Description
Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to the embodiments shown below.
[ adhesive composition ]
The adhesive composition (a) of the present embodiment is used for an image display device, and comprises a (meth) acrylic copolymer (B) having a structural unit (C) derived from at least one monomer selected from the group consisting of a cyclized polymerizable monomer and a (meth) acrylate monomer having a urethane structure (hereinafter referred to as a "urethane-containing (meth) acrylic monomer"). The adhesive composition (a) is typically an acrylic adhesive composition. In the present specification, "(meth) acrylic" means acrylic acid and methacrylic acid. "(meth) acrylate" means acrylate and methacrylate.
The cyclized polymerizable monomer is a monomer having no ring structure in the state of the monomer, but having a ring structure in the state of a structural unit derived from the monomer (in other words, the monomer is formed by polymerization). In the (meth) acrylic copolymer (B), the structural unit (C) derived from the cyclized polymerizable monomer has a ring structure.
In the case where the at least one monomer contains a cyclized polymerizable monomer, the (meth) acrylic copolymer (B) contains a structural unit (C) having a ring structure. When the ring structure is bulky, the density of the (meth) acrylic copolymer (B) in the adhesive composition (a) can be reduced, and the regular arrangement of the copolymer (B) in the composition can be hindered. From this, it is estimated that the increase in the storage modulus G' of the adhesive composition (A) at a low temperature (for example, 0 ℃ or lower and-25 ℃ or higher) can be suppressed. It is also presumed that, unlike the case where the monomer has a ring structure, it is less susceptible to steric hindrance caused by the ring structure at the time of polymerization, and the configuration of the structural unit (C) in the (meth) acrylic copolymer (B) can be made more random, which also contributes to suppressing the rise of the storage modulus G' at low temperature.
The structural unit (C) may have a ring structure formed by polymerizing a cyclized polymerizable monomer in the main chain. In this case, by locating the ring structure in the main chain, the molecular weight between the winding points in the (meth) acrylic copolymer (B) can be increased, and the effect of suppressing the increase in the storage modulus G' at low temperature can be made more reliable. The number of the ring structures of the structural unit (C) may be 1 or 2 or more, and typically 1.
The structural unit (C) may have a ring structure formed by polymerizing a cyclized polymerizable monomer, and the ring structure may have a polar group. Examples of polar groups are ether groups, amino groups, amide groups and thioether groups. The polar group is preferably an ether group, an amino group, or an amide group. The polar groups may form part of the backbone of the ring structure. The ring structure having a polar group is particularly suitable for improving adhesion to an adherend such as a PI film at low temperature. The number of polar groups in the ring structure may be, for example, 1 to 4 or 1 to 2.
The ring structure may be, for example, a 4-membered ring, a 5-membered ring, a 6-membered ring, a 7-membered ring or an 8-membered ring, preferably a 5-membered ring or a 6-membered ring.
The cyclized polymerizable monomer may have two or more kinds of polymerizable groups. At least one polymerizable group selected from two or more polymerizable groups may be a group that forms a main chain of the (meth) acrylic copolymer (B) by polymerization, or may be a group that forms a ring structure of the structural unit (C) by polymerization. At least one polymerizable group selected from two or more polymerizable groups may be a group which forms both a main chain of the (meth) acrylic copolymer (B) and a ring structure of the structural unit (C) by polymerization with one or more other polymerizable groups. The cyclized polymerizable monomer may have a polymerizable group constituting the main chain of the (meth) acrylic copolymer (B) by polymerization and a polymerizable group constituting the ring structure of the structural unit (C) by polymerization.
Examples of polymerizable groups are vinyl and allyl. However, the polymerizable group is not limited to the above examples.
The cyclized polymerizable monomer may be a (meth) acrylate monomer. The (meth) acrylate monomer may have a polymerizable group only in the main chain thereof or may have a polymerizable group in a side chain thereof (the polymerizable group in the main chain is usually a vinyl group). In the present specification, the main chain and the side chain of a monomer denote a portion located in the main chain and a portion located in the side chain, respectively, in a polymer formed by polymerization of the monomer.
The cyclized polymerizable monomer may be 2- (allyloxymethyl) acrylate represented by the following formula (1) (hereinafter, referred to as "AOMA"). AOMA is one of the (meth) acrylate monomers. AOMA has 2 polymerizable groups. The 2 polymerizable groups may form a main chain constituting the (meth) acrylic copolymer (B) by polymerizing AOMA with other monomers including other AOMA, and a ring structure is formed in the main chain by polymerization between the 2 polymerizable groups.
[ chemical formula 1]
The structural unit (C) derived from AOMA has a ring structure as a 5-membered ring in the main chain. The ring structure has 1 polar group, which is an ether group constituting a skeleton of the ring structure. In other words, the (meth) acrylic copolymer (B) having the structural unit (C) derived from AOMA has an ether group in the main chain. By having an ether group in the main chain, for example, a further increase in the molecular weight between the winding points in the (meth) acrylic copolymer (B) can be achieved. The ether group in the main chain can function as a hydrogen bond acceptor in a state less affected by steric hindrance caused by other side chains. Therefore, the adhesive force of the adhesive composition at low temperature can be ensured more reliably.
Typically, the urethane-containing (meth) acrylic monomer has a urethane structure in its side chain. In the case where the at least one monomer contains a urethane-containing (meth) acrylic monomer, the (meth) acrylic copolymer (B) has a high-density polar structure such as a urethane structure (-COO-NH-) in the side chain. In addition, the distribution in the adhesive composition is more uniform than, for example, when the adhesive composition comprises a polyurethane polymer. The high-density polar structure in the side chain can reduce the density of the (meth) acrylic copolymer (B) in the adhesive composition (a) by the repulsive force of the polar structures to each other, and can hinder the regular arrangement of the copolymer (B) in the composition. From this, it is presumed that the increase in the storage modulus G' of the adhesive composition (a) at low temperature can be suppressed. The polar structure is suitable for improving the adhesion to an adherend at low temperatures.
Typically, the urethane structure in the urethane-containing (meth) acrylic monomer is located in the side chain of the monomer. In this case, the COO group of the acrylate structure in the urethane-containing (meth) acrylic monomer and the urethane structure nearest to the COO group may be linked together through an alkylene group having 1 to 5 carbon atoms. The number of carbon atoms of the alkylene group may be 4 or less and 3 or less, and may be 2 or less. The present inventors have studied and found that in the above-described case, the distance between the COO group of the acrylate structure and the urethane structure does not become excessively large, and therefore the action by the urethane structure becomes more reliable. The alkylene group may be linear or branched.
The urethane-containing (meth) acrylic monomer may be 2-butylcarbamoyloxyethyl acrylate represented by the following formula (2).
[ chemical formula 2]
For the cyclized polymerizable monomer and urethane-containing (meth) acrylic monomer, the glass transition temperature (Tg) at the time of preparing each monomer into a homopolymer may be, for example, -80 to 100℃or-70 to 90 ℃. In the present specification, tg of a polymer (polymer) is defined as a temperature at which tan δ (loss tangent) obtained by evaluating dynamic viscoelasticity of the polymer shows a peak.
The proportion of the structural unit (C) in the total structural units of the (meth) acrylic copolymer (B) is, for example, 0.5 to 80% by weight, may be 1 to 40% by weight, and may be further 2 to 20% by weight.
Hereinafter, other structural units that the (meth) acrylic copolymer (B) may have will be described.
The (meth) acrylic copolymer (B) may have a structural unit derived from the (meth) acrylic monomer (a) having an alkyl group having 4 to 30 carbon atoms in a side chain, or may have the structural unit as a main unit. The alkyl group may be linear or branched. The (meth) acrylic copolymer (B) may have one or two or more structural units derived from the (meth) acrylic monomer (a). Examples of the (meth) acrylic monomer (a) include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, sec-butyl (meth) acrylate, tert-butyl (meth) acrylate, isobutyl (meth) acrylate, n-pentyl (meth) acrylate, isopentyl (meth) acrylate, n-hexyl (meth) acrylate, isohexyl (meth) acrylate, isoheptyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, n-nonyl (meth) acrylate, isononyl (meth) acrylate, n-decyl (meth) acrylate, isodecyl (meth) acrylate, n-dodecyl (meth) acrylate, n-tridecyl (meth) acrylate, and n-tetradecyl (meth) acrylate. In the present specification, "main unit" means a unit that occupies, for example, 50 mass% or more, preferably 80 mass% or more, more preferably 90 mass% or more, and still more preferably 94 mass% or more of all the structural units of the polymer. The upper limit of the proportion of the main unit is, for example, 99 mass% or less.
The (meth) acrylic copolymer (B) may have a structural unit derived from a (meth) acrylic monomer (a) having a long-chain alkyl group in its side chain. The structural unit can, for example, help to reduce the storage modulus G' of the adhesive composition (A) at low temperatures and over high temperatures. The structural unit is, for example, n-dodecyl (meth) acrylate (lauryl (meth) acrylate). In the present specification, "long-chain alkyl group" means an alkyl group having 6 to 30 carbon atoms.
The (meth) acrylic copolymer (B) may also have structural units derived from a (meth) acrylic monomer (a) having a Tg in the range of-70℃to-20℃at the time of producing a homopolymer. In this case, the increase in the storage modulus G' at low temperature can be more reliably suppressed. The structural unit is, for example, 2-ethylhexyl acrylate.
The (meth) acrylic copolymer (B) may have a structural unit other than the structural unit derived from the (meth) acrylic monomer (a). The structural unit is derived from a cyclized polymerizable monomer and/or a urethane-containing (meth) acrylic monomer, and a monomer (b) copolymerizable with the (meth) acrylic monomer (a). The (meth) acrylic copolymer (B) may have one or two or more of the structural units.
The monomer (b) is, for example, a (meth) acrylic monomer (c) having a hydroxyl group. Examples of the (meth) acrylic monomer (c) include hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 8-hydroxyoctyl (meth) acrylate, 10-hydroxydecyl (meth) acrylate, 12-hydroxylauryl (meth) acrylate, and 4-hydroxymethylcyclohexyl (meth) methyl acrylate. Since the durability of the adhesive composition (a) can be improved, the (meth) acrylic monomer (c) is preferably 2-hydroxyethyl (meth) acrylate or 4-hydroxybutyl (meth) acrylate.
The monomer (b) may be a carboxyl group-containing monomer, an amino group-containing monomer, or an amide group-containing monomer. Examples of the carboxyl group-containing monomers include (meth) acrylic acid, carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, itaconic acid, maleic acid, fumaric acid, and crotonic acid. The amino group-containing monomer is, for example, N-dimethylaminoethyl (meth) acrylate, N-dimethylaminopropyl (meth) acrylate. Examples of the amide group-containing monomer include acrylamide monomers such as (meth) acrylamide, N-dimethyl (meth) acrylamide, N-diethyl (meth) acrylamide, N-isopropyl acrylamide, N-methyl (meth) acrylamide, N-butyl (meth) acrylamide, N-hexyl (meth) acrylamide, N-hydroxymethyl-N-propyl (meth) acrylamide, aminomethyl (meth) acrylamide, aminoethyl (meth) acrylamide, mercaptomethyl (meth) acrylamide, and mercaptoethyl (meth) acrylamide; n-acryl heterocyclic monomers such as N- (meth) acryl morpholine, N- (meth) acryl piperidine, and N- (meth) acryl pyrrolidine; n-vinyl group-containing lactam monomers such as N-vinylpyrrolidone and N-vinyl-. Epsilon. -caprolactam.
The monomer (b) may be a polyfunctional monomer. By using the polyfunctional monomer, the gel fraction of the adhesive composition (a) can be adjusted and the cohesive force can be controlled. Examples of the polyfunctional monomer include polyfunctional acrylates such as hexanediol di (meth) acrylate (1, 6-hexanediol di (meth) acrylate), butanediol di (meth) acrylate, (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, trimethylolpropane tri (meth) acrylate, tetramethylolmethane tri (meth) acrylate, allyl (meth) acrylate, vinyl (meth) acrylate, epoxy acrylate, polyester acrylate, urethane acrylate and divinylbenzene. The multifunctional acrylate is preferably 1, 6-hexanediol diacrylate, dipentaerythritol hexa (meth) acrylate.
Examples of the other monomer (b) than the above monomer include (meth) acrylic acid alkoxyalkyl esters such as 2-methoxyethyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate, methoxytriethylene glycol (meth) acrylate, 3-methoxypropyl (meth) acrylate, 3-ethoxypropyl (meth) acrylate, 4-methoxybutyl (meth) acrylate, and 4-ethoxybutyl (meth) acrylate; epoxy group-containing monomers such as glycidyl (meth) acrylate and methyl glycidyl (meth) acrylate; sulfonic acid group-containing monomers such as sodium vinylsulfonate; a phosphate group-containing monomer; (meth) acrylic esters having an alicyclic hydrocarbon group such as cyclopentyl (meth) acrylate, cyclohexyl (meth) acrylate, and isobornyl (meth) acrylate; (meth) acrylic esters having an aromatic hydrocarbon group such as phenyl (meth) acrylate, phenoxyethyl (meth) acrylate, benzyl (meth) acrylate, and the like; vinyl esters such as vinyl acetate and vinyl propionate; aromatic vinyl compounds such as styrene and vinyl toluene; olefins or dienes such as ethylene, propylene, butadiene, isoprene, and isobutylene; vinyl ethers such as vinyl alkyl ether; vinyl chloride.
The total content of the structural units derived from the (meth) acrylic monomer (c) having a hydroxyl group, the carboxyl group-containing monomer, the amino group-containing monomer, the amide group-containing monomer, and the polyfunctional monomer in the (meth) acrylic copolymer (B) is, for example, 20 mass% or less, 10 mass% or less, 8 mass% or less, and further 5 mass% or less. When the (meth) acrylic copolymer (B) has the structural unit, the total content of the structural units may be, for example, 0.01 mass% or more, or 0.05 mass% or more.
The total content of the structural units derived from the other monomer (B) in the (meth) acrylic copolymer (B) may be, for example, 30 mass% or less, 10 mass% or less, or 0 mass% (excluding the structural units).
The (meth) acrylic copolymer (B) can be formed by polymerizing a monomer group containing the above monomers by a known method. The monomers may also be polymerized with a partial polymer of the monomers. The polymerization may be carried out by, for example, solution polymerization, emulsion polymerization, bulk polymerization, thermal polymerization, active energy ray polymerization. Since the adhesive composition (a) excellent in optical transparency can be formed, the polymerization is preferably solution polymerization or active energy ray polymerization. The polymerization is preferably carried out while avoiding contact between the monomer and/or a part of the polymer and oxygen, and thus, for example, polymerization in an inert gas atmosphere such as nitrogen or polymerization in a state of blocking oxygen by a resin film or the like may be employed. The (meth) acrylic copolymer (B) to be formed may be any of random copolymer, block copolymer, graft copolymer, etc., but may be random copolymer from the viewpoint of improving the degree of dispersion of the structural units (C) in the (meth) acrylic copolymer (B).
The polymerization system forming the (meth) acrylic copolymer (B) may contain one or two or more polymerization initiators. The type of the polymerization initiator may be selected according to the polymerization reaction, and may be, for example, a photopolymerization initiator or a thermal polymerization initiator.
The solvent used in the solution polymerization is, for example, esters such as ethyl acetate and n-butyl acetate; aromatic hydrocarbons such as toluene and benzene; aliphatic hydrocarbons such as n-hexane and n-heptane; alicyclic hydrocarbons such as cyclohexane and methylcyclohexane; ketones such as methyl ethyl ketone and methyl isobutyl ketone, but the solvent is not limited to the above examples. The solvent may be a mixed solvent of two or more solvents.
The polymerization initiator used in the solution polymerization is, for example, azo-based polymerization initiator, peroxide-based polymerization initiator, and redox-based polymerization initiator. The peroxide-based polymerization initiator is, for example, dibenzoyl peroxide or t-butyl peroxymaleate. Among them, the azo-based polymerization initiator disclosed in Japanese patent application laid-open No. 2002-69411 is preferable. The azo-based polymerization initiator is, for example, 2 '-Azobisisobutyronitrile (AIBN), 2' -azobis (2-methylbutyronitrile), dimethyl 2,2 '-azobis (2-methylpropionate), 4' -azobis (4-cyanovaleric acid), but the polymerization initiator is not limited to the above examples. The azo-based polymerization initiator may be used in an amount of, for example, 0.05 to 0.5 part by weight or 0.1 to 0.3 part by weight based on 100 parts by weight of the total amount of the monomers.
The active energy rays used for active energy ray polymerization include, for example, ionizing rays such as α rays, β rays, γ rays, neutron rays, and electron rays, and ultraviolet rays. The active energy ray is preferably ultraviolet ray. Polymerization by irradiation with ultraviolet rays is also called photopolymerization. The polymerization system of active energy ray polymerization typically contains a photopolymerization initiator. The polymerization conditions for the active energy polymerization are not limited as long as the (meth) acrylic polymer can be formed.
The photopolymerization initiator is, for example, benzoin ether type photopolymerization initiator, acetophenone type photopolymerization initiator, α -ketonic type photopolymerization initiator, aromatic sulfonyl chloride type photopolymerization initiator, photoactive oxime type photopolymerization initiator, benzoin type photopolymerization initiator, benzil type photopolymerization initiator, benzophenone type photopolymerization initiator, ketal type photopolymerization initiator, thioxanthone type photopolymerization initiator, but the photopolymerization initiator is not limited to the above examples.
The benzoin ether photopolymerization initiator is, for example, benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isopropyl ether, benzoin isobutyl ether, 2-dimethoxy-1, 2-diphenylethane-1-one, anisole methyl ether. Examples of the acetophenone photopolymerization initiator include 2, 2-diethoxyacetophenone, 2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexylphenyl ketone, 4-phenoxydichloroacetophenone, and 4- (t-butyl) dichloroacetophenone. The α -ketonic photopolymerization initiator is, for example, 2-methyl-2-hydroxyphenylacetone, 1- [4- (2-hydroxyethyl) phenyl ] -2-methylpropan-1-one. The aromatic sulfonyl chloride-based photopolymerization initiator is, for example, 2-naphthalenesulfonyl chloride. The photo-active oxime photopolymerization initiator is, for example, 1-phenyl-1, 1-propanedione-2- (O-ethoxycarbonyl oxime). The benzoin photopolymerization initiator is, for example, benzoin. The benzil photopolymerization initiator is, for example, benzil. Examples of the benzophenone photopolymerization initiator include benzophenone, benzoylbenzoic acid, 3' -dimethyl-4-methoxybenzophenone, polyvinylbenzophenone, and α -hydroxycyclohexyl phenyl ketone. The ketal photopolymerization initiator is, for example, benzil dimethyl ketal. Examples of the thioxanthone photopolymerization initiator include thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2, 4-dimethylthioxanthone, isopropylthioxanthone, 2, 4-diisopropylthioxanthone and dodecylthioxanthone.
The photopolymerization initiator may be used in an amount of, for example, 0.01 to 1 part by weight or 0.05 to 0.5 part by weight based on 100 parts by weight of the total amount of the monomers.
The polyfunctional monomer (polyfunctional acrylate or the like) as the monomer (b) may be used for any type of solvent-based or active energy ray-curable adhesive composition, but in the case where both the polyfunctional monomer and the photopolymerization initiator are used for the solvent-based adhesive composition, for example, the solvent may be removed by heat drying and then the adhesive composition irradiated with active energy rays may be cured.
The weight average molecular weight (Mw) of the (meth) acrylic copolymer (B) is, for example, 100 to 300 tens of thousands, and may be 110 to 200 tens of thousands, and further may be 110 to 180 tens of thousands, from the viewpoints of the durability and heat resistance of the adhesive composition (A).
The molecular weight distribution (Mw/number average molecular weight (Mn)) of the (meth) acrylic copolymer (B) may be, for example, 2 to 20 or 4 to 15. The Mw and Mn of the polymer and oligomer in the present specification are values (in terms of polystyrene) obtained by measurement based on GPC (gel permeation chromatography).
The content of the (meth) acrylic copolymer (B) in the adhesive composition (a) may be, for example, 50 mass% or more, 60 mass% or more, and further 70 mass% or more, based on the solid content.
[ (meth) acrylic oligomer ]
The adhesive composition (a) may further comprise a (meth) acrylic oligomer. By containing the (meth) acrylic oligomer, the entanglement of the molecular chains of the (meth) acrylic copolymer (B) is reduced, and thus, the rise in the storage modulus G' at low temperature can be more reliably suppressed with respect to the adhesive composition (a).
The (meth) acrylic oligomer may have the same composition as the above-described (meth) acrylic copolymer (B), except that the Mw is different. However, the (meth) acrylic oligomer may not have the structural unit (C) derived from the cyclized polymerizable monomer and the urethane-containing (meth) acrylic monomer. The Mw of the (meth) acrylic oligomer may be 1000 or more, 2000 or more, 3000 or more, or 4000 or more, for example. The upper limit of the Mw of the (meth) acrylic oligomer may be 30000 or less, 15000 or less, 10000 or less, or 7000 or less, for example.
The (meth) acrylic oligomer has, for example, one or two or more structural units derived from each of the following monomers: alkyl (meth) acrylates such as methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, sec-butyl (meth) acrylate, tert-butyl (meth) acrylate, pentyl (meth) acrylate, isopentyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, isooctyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, undecyl (meth) acrylate, dodecyl (meth) acrylate, and the like; esters of (meth) acrylic acid and alicyclic alcohols such as cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, and dicyclopentanyl (meth) acrylate; aryl (meth) acrylates such as phenyl (meth) acrylate and benzyl (meth) acrylate; (meth) acrylic esters derived from terpene compound derivative alcohols.
The (meth) acrylic oligomer may also have a structural unit derived from an acrylic monomer having a bulky structure. Examples of the acrylic monomer include alkyl (meth) acrylates having an alkyl group having a branched structure, such as isobutyl (meth) acrylate and tert-butyl (meth) acrylate; esters of (meth) acrylic acid and alicyclic alcohols such as cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, and dicyclopentanyl (meth) acrylate; phenyl (meth) acrylate, benzyl (meth) acrylate, and other aryl (meth) acrylates. Preferably, the acrylic monomer has a cyclic structure, and more preferably has 2 or more cyclic structures. Further, since the polymerization and/or formation of the (meth) acrylic monomer is not easily inhibited when the ultraviolet irradiation is performed during the polymerization of the (meth) acrylic oligomer and/or the formation of the adhesive composition, it is preferable that the acrylic monomer does not have an unsaturated bond, and for example, an alkyl (meth) acrylate having an alkyl group with a branched structure, an ester of (meth) acrylic acid and an alicyclic alcohol may be used.
Specific examples of the (meth) acrylic oligomer are a copolymer of butyl acrylate and methyl acrylate and acrylic acid, a copolymer of cyclohexyl methacrylate and isobutyl methacrylate, a copolymer of cyclohexyl methacrylate and isobornyl methacrylate, a copolymer of cyclohexyl methacrylate and acryloylmorpholine, a copolymer of cyclohexyl methacrylate and diethylacrylamide, a copolymer of 1-adamantyl acrylate and methyl methacrylate, a copolymer of dicyclopentanyl methacrylate and isobornyl methacrylate, a copolymer of at least one selected from dicyclopentanyl methacrylate, cyclohexyl methacrylate, isobornyl acrylate and cyclopentyl methacrylate and methyl methacrylate, a homopolymer of dicyclopentanyl acrylate, a homopolymer of 1-adamantyl methacrylate, and a homopolymer of 1-adamantyl acrylate.
The polymerization method of the (meth) acrylic oligomer may be the polymerization method of the (meth) acrylic copolymer (B) described above.
When the adhesive composition (a) contains a (meth) acrylic oligomer, the amount of the (meth) acrylic oligomer to be blended is, for example, 70 parts by weight or less, 50 parts by weight or less, and further 40 parts by weight or less, based on 100 parts by weight of the (meth) acrylic copolymer (B). The lower limit of the amount to be blended is, for example, 1 part by weight or more, or 2 parts by weight or more, or more preferably 3 parts by weight or more, based on 100 parts by weight of the (meth) acrylic copolymer (B).
The (meth) acrylic oligomer can also be used in any type of adhesive composition in solvent-based and active energy ray-curable adhesive compositions. However, in the case of using the adhesive composition of the active energy ray-curable type, that is, in the case where the (meth) acrylic oligomer is dissolved in a solvent, the curing by irradiation with active energy rays may be performed after the solvent is removed by, for example, thermal drying with respect to the mixture in which the (meth) acrylic oligomer is mixed.
[ Cross-linking agent ]
The adhesive composition (a) may further comprise a crosslinking agent. By using a crosslinking agent, the cohesive force of the adhesive composition (a) is improved.
The crosslinking agent is, for example, an organic crosslinking agent, a polyfunctional metal chelate. The organic crosslinking agent is, for example, an isocyanate crosslinking agent, a peroxide crosslinking agent, an epoxy crosslinking agent, or an imine crosslinking agent. The polyfunctional metal chelate has a structure obtained by covalent bonding or coordinate bonding of a polyvalent metal and an organic compound. The polyvalent metal is Al, cr, zr, co, cu, fe, ni, V, zn, in, ca, mg, mn, Y, ce, sr, ba, mo, la, sn, ti, for example. The atoms in the organic compound resulting from covalent bonding or coordinate bonding of the polyvalent metal are typically oxygen atoms. Examples of the organic compound include alkyl esters, alcohol compounds, carboxylic acid compounds, ether compounds, and ketone compounds. The organic crosslinking agent and the polyfunctional metal chelate compound may be used for any of solvent-type and active energy ray-curable adhesive compositions.
When the adhesive composition is a solvent type, the crosslinking agent is preferably a peroxide crosslinking agent or an isocyanate crosslinking agent, and more preferably a peroxide crosslinking agent. Since the peroxide-based crosslinking agent causes crosslinking between the side chains of the (meth) acrylic polymer, the degree of freedom of the molecular chain after crosslinking by the peroxide-based crosslinking agent is higher than that by the isocyanate-based crosslinking agent. Therefore, the cohesive force of the adhesive composition (a) can be improved, and the increase in the storage modulus G' at low temperature can be more reliably suppressed than in the case where an isocyanate-based crosslinking agent is used. On the other hand, crosslinking with an isocyanate-based crosslinking agent can improve the durability of the adhesive composition (a) as compared with crosslinking with a peroxide-based crosslinking agent. The isocyanate-based crosslinking agent is preferably a difunctional crosslinking agent. In crosslinking with a difunctional crosslinking agent, a two-dimensional crosslinked structure can be formed. Therefore, the degree of freedom of the crosslinked molecular chain can be improved as compared with a trifunctional crosslinking agent that forms a three-dimensional crosslinked structure. When an isocyanate-based crosslinking agent is used, the use of a difunctional crosslinking agent in combination with a trifunctional crosslinking agent can improve the balance between durability and storage modulus G' at low temperature. In order to further improve the balance, a peroxide-based crosslinking agent may be used in combination with an isocyanate-based crosslinking agent. The polyfunctional monomer (b) may be used in combination with a crosslinking agent.
When the pressure-sensitive adhesive composition contains a crosslinking agent, the amount of the crosslinking agent to be blended is, for example, 0.01 to 10 parts by weight, or 0.1 to 5 parts by weight, or even more preferably 0.1 to 3 parts by weight, based on 100 parts by weight of the (meth) acrylic copolymer (B).
When the peroxide-based crosslinking agent is used alone, the amount of the peroxide-based crosslinking agent may be, for example, 0.2 to 5 parts by weight or 0.5 to 3 parts by weight based on 100 parts by weight of the (meth) acrylic copolymer (B).
When the peroxide-based crosslinking agent and the isocyanate-based crosslinking agent are used in combination, the weight ratio of the peroxide-based crosslinking agent to the isocyanate-based crosslinking agent may be, for example, 1.2 or more, or may be 1.5 or more, or may be 2 or more. The upper limit of the weight ratio is, for example, 500 or less, 300 or less, and further 200 or less.
[ additive ]
The adhesive composition (A) may also contain other additives. Examples of the additives include silane coupling agents, polyether compounds (such as polyalkylene glycols represented by polypropylene glycols), colorants such as pigments and dyes, surfactants, plasticizers, tackifiers, surface lubricants, leveling agents, softeners, antioxidants, anti-aging agents, light stabilizers, ultraviolet absorbers, polymerization inhibitors, antistatic agents (such as alkali metal salts of ionic compounds, ionic liquids, and ionic solids), inorganic fillers, organic fillers, and powders such as metal powders, particles, and foils.
The adhesive composition (a) may have the following characteristics.
Storage modulus G' at-20℃is, for example, 2.0X10 6 Pa or less, or 1.0X10 g 6 Pa or less, 5.0X10 s 5 Pa or less, 3.0X10 s 5 Pa or lower, 2.5X10 5 Pa or less, 2.0X10 s 5 Pa or less, further may be 1.6X10 5 Pa or below. The lower limit of the storage modulus G' at-20℃is, for example, 1.0X10 4 Pa or more.
Storage modulus G' at 25℃is, for example, less than 1.0X10 5 Pa, may be 8.0X10 4 Pa or less, 5.0X10 s 4 Pa or less, 4.0X10 s 4 Pa or less, further may be 3.0X10 4 Pa or below. The lower limit of the storage modulus G' at 25℃is, for example, 1.0X10 4 Pa or more.
The adhesive force to the PI film at-20℃may be, for example, 8.0N/25mm or more, 10.0N/25mm or more, 12.0N/25mm or more, and further 13.0N/25mm or more. The upper limit of the adhesive force is, for example, 30N/25mm or less. The adhesion to the PI film was evaluated in a state where the adhesive composition (a) was layered, in other words, in an adhesive layer. From this point of view, the adhesive force with respect to the PI film is the adhesive force when formed into an adhesive layer.
The adhesive force to the PI film at 25℃may be, for example, 2.0N/25mm or more, 3.0N/25mm or more, 4.0N/25mm or more, 6.0N/25mm or more, and further 8.0N/25mm or more. The upper limit of the adhesive force is, for example, 30N/25mm or less.
The adhesion to PI film at-20 ℃ may be greater than the adhesion to PI film at 25 ℃.
The above range can be satisfied simultaneously with respect to the storage modulus G' at-20℃and the adhesion to the PI film at-20℃of the adhesive composition (A). In addition, the above range can be satisfied simultaneously with respect to the storage modulus G' of the adhesive composition (a) at 25 ℃ and the adhesion to the PI film at 25 ℃.
The Tg of the adhesive composition (A) is, for example, from-55℃to-30 ℃. The lower limit of Tg may be-50℃or higher, or-45℃or higher, or more preferably-40℃or higher. The upper limit of Tg may be-35℃or lower.
The gel fraction of the pressure-sensitive adhesive layer composition (a) is, for example, 55% or more, 60% or more, 65% or more, 70% or more, and further 75% or more. The upper limit of the gel fraction of the adhesive composition (a) is, for example, 95% or less, or 90% or less, or further 85% or less. When the gel fraction of the adhesive composition (a) is within the above range, the above effects can be more reliably obtained.
The present inventors have studied and found that excellent properties of an adhesive composition at low temperature, such as impact resistance and bendability, can be achieved by suppressing the rise of storage modulus G' at-20 ℃ and securing adhesion to PI films at-20 ℃ when assembled in an image display device. In this respect, the invention discloses a storage modulus G' of 2.0X10 at 20 DEG C 6 An adhesive composition (D) for an image display device, which has an adhesive force of 8.0N/25mm or more against a PI film at-20 ℃ and Pa or less. The storage modulus G' at-20℃and/or the adhesion to the PI film at-20℃may be within the respective ranges described in the above description of the adhesive composition (A).
The storage modulus G' at 25 ℃ and/or the adhesion to PI film at 25 ℃ of the adhesive composition (D) may be within the respective ranges described in the above description of the adhesive composition (a).
The adhesive composition (D) is typically an acrylic adhesive composition. The adhesive composition (D) may contain the (meth) acrylic copolymer (B). The adhesive composition (D) may contain not the (meth) acrylic copolymer (B) but the (meth) acrylic polymer (E) other than the (meth) acrylic copolymer (B). The (meth) acrylic polymer (E) may have structural units derived from the respective monomers described in the above description of the (meth) acrylic copolymer (B), in addition to the structural units (C) derived from the cyclized polymerizable monomer and the urethane-containing (meth) acrylic monomer. The adhesive composition (D) may contain the oligomer, the crosslinking agent, the additive, and the like described in the above description of the adhesive composition (a).
The adhesive composition (D) may have the same characteristics as the adhesive composition (a).
The types of the adhesive compositions (a) and (D) are, for example, emulsion type, solvent type (solution type), active energy ray-curable type, and hot melt type (hot melt type). Among them, a solvent-based or active energy ray-curable adhesive composition is preferable, and from the viewpoints of productivity and easiness of forming an adhesive layer having a thickness, the active energy ray-curable adhesive composition may be used. The type of the adhesive composition is not limited to the above examples.
The adhesive compositions (a) and (D) are compositions for use in image display devices. The image display device is typically an organic EL display or a liquid crystal display. The image display device may be a flexible image display device, and the flexible image display device may be a foldable image display device that can be folded or a rollable image display device that can be rolled. The image display device is not limited to the above example.
[ optical film with adhesive layer ]
Fig. 1 shows an example of an optical film with an adhesive layer. The adhesive layer-attached optical film 1 (1A) of fig. 1 is a film for an image display device, and includes an adhesive layer 2 and an optical film 3. The adhesive layer-attached optical film 1A of fig. 1 has a double-layer structure of an adhesive layer 2 and an optical film 3, and the adhesive layer 2 is bonded to one side of the optical film 3. The adhesive layer 2 contains the adhesive composition (a) or (D). The adhesive layer 2 may be composed of the adhesive composition (a) or (D).
The thickness of the pressure-sensitive adhesive layer 2 may be, for example, 1 to 200. Mu.m, 5 to 150. Mu.m, 10 to 100. Mu.m, or further 10 to 50. Mu.m.
The adhesive layer 2 may be formed as follows. When the adhesive composition is a solvent type, for example, a mixture of a (meth) acrylic copolymer and a solvent, and optionally a (meth) acrylic oligomer, a crosslinking agent, an additive, and the like is applied to a base film, and dried to form the adhesive layer 2. When the adhesive composition is an active energy ray-curable adhesive composition, for example, a mixture of a monomer (group) that is a (meth) acrylic copolymer by polymerization, and a partial polymer of a monomer (group) that is used if necessary, a polymerization initiator, a (meth) acrylic oligomer, a crosslinking agent, an additive, a solvent, and the like may be applied to a base film, and if necessary, the solvent is removed by drying, and then an active energy ray is irradiated to form the adhesive layer 2. The substrate film may be a film having a surface subjected to a peeling treatment. The adhesive layer 2 formed on the base film may be transferred to an arbitrary layer. In addition, the base film may be an optical film, and in this case, an optical film with an adhesive layer having the adhesive layer 2 can be obtained. The substrate film may be a separator. The pressure-sensitive adhesive layer 2 formed on the base film can be bonded (adhered) to the optical film, and an optical film with a pressure-sensitive adhesive layer having the pressure-sensitive adhesive layer 2 can be obtained.
The application of the above mixture to the substrate film may be carried out by a known method. The coating may be performed by roll coating, roll-lick coating, gravure coating, reverse coating, roll brushing, spray coating, dip roll coating, bar coating, doctor blade coating, air knife coating, shower coating, die lip coating, extrusion coating using a die coater, or the like.
Preferably, the mixture applied to the substrate film has a viscosity suitable for handling and application. Therefore, in the case where the adhesive composition is an active energy ray-curable type, it is preferable that the mixture contains a partial polymer of the monomer(s).
The release film that can be used for the base film is, for example, a resin film whose surface is subjected to a release treatment by an organosilicon compound.
The drying temperature of the mixture may be, for example, 40 to 200 ℃, 50 to 180 ℃, or 70 to 170 ℃. The drying time of the mixture is, for example, 5 seconds to 20 minutes, may be 5 seconds to 10 minutes, and may be further 10 seconds to 5 minutes.
The optical film 3 is, for example, a polarizing film, a retardation film, a laminated film including a polarizing film and/or a retardation film, or an optical laminate. However, the optical film 3 is not limited to the above examples as long as it can be used in an image display device. The optical film 3 may include a glass film.
The thickness of the optical film 3 is, for example, 1 μm or more, may be 5 μm or more, and further may be 25 μm or more. The upper limit of the thickness of the optical film 3 is, for example, 200 μm or less.
The polarizing film includes a polarizer. A polarizer protective film may be bonded to at least one surface of the polarizer. Any adhesive or bonding agent may be used for bonding the polarizer to the polarizer protective film. The polarizer is typically a polyvinyl alcohol (PVA) film obtained by orienting iodine by various methods such as stretching in a gas atmosphere (dry stretching), stretching in an aqueous boric acid solution, and coating.
The retardation film is a film having birefringence in the in-plane direction and/or the thickness direction. The retardation film is, for example, a stretched resin film or a film obtained by aligning and fixing a liquid crystal material.
The retardation film is, for example, a λ/4 plate, a λ/2 plate, an antireflection retardation film (see, for example, paragraphs 0221, 0222, and 0228 of japanese unexamined patent application publication No. 2012-133303), a viewing angle compensation retardation film (see, for example, paragraphs 0225 and 0226 of japanese unexamined patent application publication No. 2012-133303), and a viewing angle compensation tilt orientation retardation film (see, for example, paragraph 0227 of japanese unexamined patent application publication No. 2012-13303). However, the retardation film is not limited to the above examples as long as it has birefringence in the in-plane direction and/or the thickness direction. The retardation value, the arrangement angle, the three-dimensional birefringence, the single layer or the multiple layers of the retardation film are not limited. The retardation film may be a known film.
The thickness of the retardation film may be, for example, 50 μm or less, 20 μm or less, 10 μm or less, or 1 to 9 μm.
Another example of an optical film with an adhesive layer is shown in fig. 2. The adhesive layer-attached optical film 1 (1B) of fig. 2 is a film for an image display device, and includes: the pressure-sensitive adhesive layer 2, the optical film 3, and the separator 4, wherein the separator 4 is disposed on a surface of the pressure-sensitive adhesive layer 2 opposite to the surface of the pressure-sensitive adhesive layer 2 bonded to the optical film 3. The adhesive layer-attached optical film 1B of fig. 2 has a three-layer structure of an optical film 3, an adhesive layer 2, and a separator 4. The separator 4 has a function of protecting the adhesive layer 2 during the circulation and storage of the adhesive layer-attached optical film 1B, and is peeled off when the adhesive layer-attached optical film 1B is used.
The separator 4 is typically a resin film. The resin constituting the separator 4 is, for example, polyester such as PET, polyolefin such as polyethylene and polypropylene, polycarbonate, acrylic, polystyrene, polyamide, and polyimide. The separator 4 may be subjected to a peeling treatment on the surface thereof contacting the adhesive layer 2. The peeling treatment can be performed, for example, using an organosilicon compound. The separator 4 is not limited to the above example.
The thickness of the separator 4 is, for example, 20 μm to 100 μm.
The adhesive optical film 1 may have a layer other than the above layer. The other layer is, for example, a protective film disposed on a surface of the optical film 3 opposite to the surface of the adhesive layer 2. The protective film may be bonded to the optical film 3 by an arbitrary adhesive layer including the adhesive layer 2. The protective film is typically a resin film. Examples of the resin constituting the protective film include polyesters such as PET, polyolefins such as polyethylene and polypropylene, acrylic acid and cycloolefin. The protective film is not limited to the above examples. The protective film may be a film made of glass or a laminated film including a film made of glass.
The thickness of the protective film may be, for example, 5 to 60. Mu.m, 10 to 40. Mu.m, and further 10 to 30. Mu.m. The protective film may be subjected to surface treatments such as antiglare, antireflection, antistatic, etc.
The other layer may be, for example, an antistatic layer. Examples of antistatic layers are layers containing ionic compounds, layers containing conductive particles, and layers containing conductive polymers.
The optical film 1 with an adhesive layer may be circulated and stored, for example, in the form of a roll obtained by winding the film 1 in a band shape, or in the form of a laminate of the films 1 in a sheet shape.
The adhesive layer-attached optical film 1 is an optical film for an image display device.
[ image display device ]
Fig. 3 shows an example of an image display device. The image display device 8 shown in fig. 3 has an optical laminate in which a substrate 6, an image forming layer (organic EL layer) 5, an adhesive layer 2, an optical film 3, and a protective film 7 are laminated in this order. The image display device 8 includes an adhesive layer 2. The image display device 8 includes the pressure-sensitive adhesive layer-attached optical film 1 having the pressure-sensitive adhesive layer 2 and the optical film 3. The substrate 6 and the image forming layer 5 may have the same constitution as those of a substrate and an image forming layer provided in a known organic EL display, respectively. In the image display device 8, good characteristics such as impact resistance and bending resistance can be obtained even at low temperatures.
The image display device 8 of fig. 3 is an organic EL display. The image display device 8 is not limited to the above example.
The image display device 8 may have any configuration as long as it includes the pressure-sensitive adhesive layer 2 or the pressure-sensitive adhesive layer-attached optical film 1.
The image display device 8 may be a flexible image display device.
Examples
Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the examples shown below.
The method for producing each adhesive composition of examples and comparative examples will be described.
The abbreviations or names shown in the following description correspond to the compounds as follows.
2EHA: 2-ethylhexyl acrylate
4HBA: acrylic acid 4-hydroxybutyl ester
BA: butyl acrylate
LA: lauryl acrylate
AOMA:2- (allyloxymethyl) acrylate (manufactured by Japanese catalyst Co., ltd.)
V#216: 2-butylcarbamoyloxyethyl acrylate (Osaka mechanism)
V#190: ethyl carbitol acrylate (osaka organic mechanism)
AIBN:2,2' -azobisisobutyronitrile
Irgacure651:2, 2-dimethoxy-1, 2-diphenyl-1-one (manufactured by BASF Japan)
Irgacure184: 1-hydroxy-cyclohexyl-phenyl-one (manufactured by BASF Japan)
C/HX: isocyanurate of hexamethylene diisocyanate (Coronate HX manufactured by Japanese polyurethane Industrial Co., ltd.)
BPO: benzoyl peroxide (Nyper BMT manufactured by Japanese fat and oil)
C/L: trimethylolpropane/toluene diisocyanate (Coronate L manufactured by Japanese polyurethane Industrial Co., ltd.)
HDDA:1, 6-hexanediol diacrylate
Irganox1010: pentaerythritol tetrakis (3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate) (manufactured by BASF)
A100: silane coupling agent containing acetoacetyl group (fully-mechanized chemical system)
[ (meth) acrylic acid copolymer production ]
Synthesis example 1
Into a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen inlet tube, and a condenser, 100 parts by weight of 2EHA, 10 parts by weight of 4hba, and 2.7 parts by weight of AOMA were charged. Subsequently, 0.2 parts by weight of AIBN as a polymerization initiator was added to 100 parts by weight of a mixture of 2EHA, 4HBA and AOMA, nitrogen was introduced into the flask while stirring slowly, the inside of the flask was replaced with nitrogen, and then the liquid temperature in the flask was kept at about 55℃for 7 hours to perform polymerization. Next, ethyl acetate was added to the obtained reaction solution, and the solid content concentration was adjusted to 30% by weight, thereby obtaining a solution of the (meth) acrylic copolymer A1. The Mw of the (meth) acrylic copolymer A1 was 133 million and the molecular weight distribution Mw/Mn was 11.8. The Mw and Mn of the (meth) acrylic copolymer and the (meth) acrylic oligomer produced in each synthesis example were measured by GPC under the following measurement conditions.
Analysis device: waters, acquisition APC
Chromatographic column: east Cao System, G7000HXL+GMHXL+GMHXL
Column temperature: 40 DEG C
Eluent: tetrahydrofuran (acid addition)
Flow rate: 0.8 mL/min
Injection amount: 100 mu L
Detector: differential Refractometer (RI)
Standard sample: agilent made Polystyrene (PS)
Synthesis examples 2 to 9
(meth) acrylic copolymers A2 to A9 were obtained in the same manner as in synthesis example 1 except that the monomers and polymerization initiators of the types and amounts shown in table 1 below were added to the flask.
Synthesis example 10
The monomers and photopolymerization initiators of the types and amounts shown in Table 1 below were charged into a four-necked flask, and the photopolymerization was carried out by irradiating ultraviolet rays in a nitrogen atmosphere until the viscosity of the liquid in the flask (measured by a BH viscometer; using a No.5 spindle, the rotation speed of the spindle at 10rpm, and the measurement temperature at 30 ℃) reached about 15 Pa.s. Thus, a partially polymerized monomer syrup (partial polymer of monomer component) a10 was obtained.
[ (meth) acrylic oligomer production ]
Synthesis example 11
Into a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen inlet pipe and a condenser, 95 parts by weight of BA, 2 parts by weight of Acrylic Acid (AA), 3 parts by weight of Methyl Acrylate (MA), 0.1 part by weight of 2,2' -Azobisisobutyronitrile (AIBN) as a polymerization initiator and 140 parts by weight of toluene were charged, and nitrogen was introduced while being slowly stirred, whereby nitrogen substitution was sufficiently performed. Next, polymerization was performed for 8 hours while maintaining the liquid temperature in the flask at around 70 ℃, and an acrylic oligomer (oligomer B1) solution was prepared. The Mw of the oligomer B1 was 4500.
The compositions (monomer feed ratios), mw and molecular weight distribution (Mw/Mn) of the (meth) acrylic copolymer and the (meth) acrylic oligomer produced in each synthesis example are shown in Table 1 below. With respect to Mw and Mw/Mn, "-" means not measured.
TABLE 1
* A1 to A10 are (meth) acrylic acid copolymers
[ production of adhesive composition ]
Examples 1 to 9 and comparative example 1
The (meth) acrylic copolymer, the (meth) acrylic oligomer, the crosslinking agent and the additive were mixed so as to have the compositions shown in table 2 below, to obtain solvent-based or UV-curable adhesive compositions.
TABLE 2
The unit of the composition is weight part
Hereinafter, the method for evaluating the adhesive compositions produced in examples and comparative examples is shown.
[ storage modulus G' and Tg ]
Each of the adhesive compositions of examples 1 to 9 prepared above was applied to the release treated surface of a release film (mitsubishi resin, mrf#38) by a spray coater (fountain coater), and then dried in an air circulation type constant temperature oven set at 155 ℃ for 2 minutes, thereby forming a layer (thickness 20 μm) of the adhesive composition. Alternatively, the adhesive composition of comparative example 1 was applied to the release treated surface of the release film by a jet coater, and another release film was bonded to the applied adhesive composition. The lamination is performed such that the release treated surface of the other release film is brought into contact with the adhesive composition. Next, at an illuminance of 4mW/cm 2 Light quantity 1200mJ/cm 2 The adhesive composition was photo-cured by irradiation of ultraviolet rays on the whole under the conditions of (a) to form a layer (thickness: 20 μm) of the adhesive composition.
Next, the adhesive compositions of examples and comparative examples were laminated (thickness: 2 mm) by laminating a plurality of layers of each adhesive composition. Next, the laminated film was punched into a circular shape having a diameter of 7.9mm, and test pieces were obtained. Next, the dynamic viscoelasticity of the obtained test piece was measured, and the peak temperatures of the storage modulus G 'at-20℃and the storage modulus G' and tan delta (loss tangent) at 25℃were evaluated. tan δ is determined as the ratio G "/G 'of the loss modulus G" to the storage modulus G'. The peak temperature of tan delta evaluated was taken as Tg of the adhesive composition. Dynamic viscoelasticity was measured using Advanced Rheometric Expansion System (ARES) manufactured by Rheometric Scientific. The measurement conditions are as follows.
(measurement conditions)
Deformation mode: torsion
Measuring temperature: 70 ℃ to 150 DEG C
Heating rate: 5 ℃/min
[ gel fraction ]
The gel fraction was evaluated as follows. First, about 0.2g of the adhesive composition was scraped from the laminated film produced as described above, and a small piece was obtained. Next, the obtained small pieces were wrapped with a stretched porous film of polytetrafluoroethylene (NTF 1122, average pore size 0.2 μm, manufactured by Nitto electric Co., ltd.) and bound with kite strings to obtain test pieces. Next, the weight W of the obtained test piece was measured 1 . Weight W 1 Is the sum of the weights of the small pieces of the adhesive layer, the stretched porous film and the kite string. Wherein the total weight W of the stretched porous film and kite string used 0 The assay was performed in advance. Next, the test piece was immersed in a 50mL container filled with ethyl acetate, and allowed to stand at 23℃for 1 week. After standing, the test piece was taken out from the container, dried in a dryer set at 130℃for 2 hours, and then the weight W of the test piece was measured 2 . Then, based on the measured weight W 0 Weight W 1 Weight W 2 And by the formula: gel fraction (wt%) = (W 2 －W 0 )/(W 1 －W 0 ) The gel fraction of the adhesive layer was calculated by x 100 (%).
[ adhesion to PI film ]
The adhesion to PI films was evaluated as follows. First, a PET film (50 μm) having a corona-treated surface was laminated on a layer (thickness: 20 μm) of the adhesive composition prepared as described above, and the resultant was cut into strips having a width of 25mm and a length of 100mm, to obtain test pieces. The lamination is performed so that the corona treated surface is in contact with the layer. Next, a test piece was bonded to a PI film (KAPTON, manufactured by Toray-DuPont, thickness 50 μm) fixed to the surface of a stainless steel plate, to obtain a test sample. The fixing of the PI film is performed using a double-sided adhesive tape having sufficient adhesive strength so that the PI film is not peeled from the stainless steel plate in a peeling test described later. The test piece was bonded such that the end portion on one side in the longitudinal direction of the test piece was free end in a range of 20mm in length without being in contact with the PI film, and such that the entire exposed surface of the layer of the adhesive composition in the test piece except for the free end was in contact with the PI film. In addition, in order to make the bonding between the laminated film and the PI film more reliable during bonding, a lamination roller of 2kg mass prescribed in japanese industrial standard (japanese industrial standard is used; JIS) Z0237:2009 was reciprocated once at a temperature of 25 ℃. Next, in order to stabilize the bonding of the laminated film and the PI film, a test sample that was left standing for 30 minutes after the reciprocation of the pressing roller was set in a tensile tester with a constant temperature bath. The test piece is provided so that the longitudinal direction of the test piece matches the direction between chucks of the test machine, and so that the chucks on one side of the test machine hold the guide belt attached to the free end and the chucks on the other side hold the PI film and the stainless steel plate. Next, the ambient temperature of the tester and the test sample was controlled to each evaluation temperature (-20 ℃ C. Or 25 ℃ C.; and the relative humidity was 50.+ -. 5%). After the ambient temperature reached the evaluation temperature, the test piece was allowed to stand for 5 minutes, and then a 180 ° peel test was performed to peel the test piece from the PI film under conditions of a peel angle of 180 ° and a test speed of 300 mm/min. After the start of the test, the measurement value of 10mm in length from which peeling was originally generated was ignored, and then the average value of the measurement values of 70mm in length from which peeling was generated was taken as the adhesive force to the PI film.
The evaluation results are shown in table 3 below.
TABLE 3
As shown in table 3, in each adhesive composition of examples, the adhesive force with respect to the PI film at low temperature was ensured, and the increase in the storage modulus G' at low temperature was suppressed.
Industrial applicability
The adhesive composition of the present invention can be used for an image display device.
Claims (20)
1. An adhesive composition for an image display device,
the adhesive composition comprises a (meth) acrylic copolymer having a structural unit derived from at least one monomer selected from the group consisting of a cyclized polymerizable monomer and a (meth) acrylate monomer having a urethane structure.
2. The adhesive composition of claim 1, wherein,
the structural unit has a ring structure formed by polymerizing the cyclized polymerizable monomer in a main chain.
3. The adhesive composition of claim 1, wherein,
the structural unit has a ring structure formed by polymerizing the cyclized polymerizable monomer,
the ring structure has a polar group.
4. The adhesive composition according to any one of claim 1 to 3, wherein,
the cyclized polymerizable monomer has two or more kinds of polymerizable groups.
5. The adhesive composition according to any one of claims 1 to 4, wherein,
the cyclized polymerizable monomer is a (meth) acrylate monomer.
6. The adhesive composition of claim 1, wherein,
the cyclized polymerizable monomer is 2- (allyloxymethyl) acrylate.
7. The adhesive composition according to any one of claims 1 to 6, wherein,
the urethane structure in the urethane structure-containing (meth) acrylate monomer is located in a side chain of the monomer.
8. The adhesive composition of claim 7, wherein,
the COO group of the acrylate structure in the urethane structure-containing (meth) acrylate monomer and the urethane structure nearest to the COO group are linked together through an alkylene group having 1 to 5 carbon atoms.
9. The adhesive composition according to any one of claims 1 to 8, wherein,
the (meth) acrylic copolymer has, as a main unit, a structural unit derived from a (meth) acrylic monomer having an alkyl group having 4 to 30 carbon atoms in a side chain.
10. The adhesive composition according to any one of claims 1 to 9, wherein,
The (meth) acrylic copolymer has a structural unit derived from a (meth) acrylic monomer having a hydroxyl group.
11. The adhesive composition according to any one of claims 1 to 10, having a storage modulus G' at-20 ℃ of 2.0 x 10 6 Pa or lower, and the adhesive force at-20 ℃ to the polyimide film is 8.0N/25mm or higher.
12. The adhesive composition according to any one of claims 1 to 11 having a storage modulus G' at 25 ℃ of less than 1.0 x 10 5 Pa。
13. The adhesive composition according to any one of claims 1 to 12, which has an adhesive force at 25 ℃ to a polyimide film of 2.0N/25mm or more.
14. An adhesive composition for an image display device,
the adhesive composition has a storage modulus G' at-20 ℃ of 2.0X10 6 Pa or lower, and the adhesive force at-20 ℃ to the polyimide film is 8.0N/25mm or higher.
15. The adhesive composition of claim 14 having a storage modulus G' at 25 ℃ of less than 1.0 x 10 5 Pa。
16. The adhesive composition according to claim 14 or 15, which has an adhesive force at 25 ℃ with respect to a polyimide film of 2.0N/25mm or more.
17. The adhesive composition according to any one of claims 1 to 16, wherein,
The image display device is a flexible image display device.
18. An optical film with an adhesive layer, comprising:
optical film
An adhesive layer bonded to the optical film,
the adhesive layer comprising the adhesive composition of any one of claims 1 to 17.
19. An image display device is provided with:
an adhesive layer comprising the adhesive composition of any one of claims 1 to 17, or
The adhesive layer-carrying optical film of claim 18.
20. The image display device of claim 19, being a flexible image display device.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2020-156440 | 2020-09-17 | ||
| JP2020156440A JP2022050067A (en) | 2020-09-17 | 2020-09-17 | Adhesive composition to be used for image display device, optical film with adhesive layer, and image display device |
| PCT/JP2021/030264 WO2022059408A1 (en) | 2020-09-17 | 2021-08-18 | Adhesive composition used in image display device, optical film with adhesive layer, and image display device |
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| Publication Number | Publication Date |
|---|---|
| CN116194543A true CN116194543A (en) | 2023-05-30 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202180064024.1A Pending CN116194543A (en) | 2020-09-17 | 2021-08-18 | Adhesive composition for image display device, optical film with adhesive layer, and image display device |
Country Status (5)
| Country | Link |
|---|---|
| JP (1) | JP2022050067A (en) |
| KR (1) | KR20230066606A (en) |
| CN (1) | CN116194543A (en) |
| TW (1) | TW202212522A (en) |
| WO (1) | WO2022059408A1 (en) |
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| JP2023154283A (en) * | 2022-04-06 | 2023-10-19 | 株式会社レゾナック | Adhesive composition, adhesive film for circuit connection, circuit connection structure and method for manufacturing the same |
| JP2024016815A (en) * | 2022-07-26 | 2024-02-07 | ａｒｔｉｅｎｃｅ株式会社 | Flexible display laminates and flexible displays |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP2733186A1 (en) * | 2012-11-19 | 2014-05-21 | 3M Innovative Properties Company | Highly tackified acrylate pressure sensitive adhesives |
| JP2015003959A (en) * | 2013-06-19 | 2015-01-08 | 株式会社日本触媒 | Optical adhesive composition and optical adhesive product |
| JP2015003960A (en) * | 2013-06-19 | 2015-01-08 | 株式会社日本触媒 | Resin composition for optical adhesive tape, and optical adhesive tape |
| JP2017066243A (en) * | 2015-09-29 | 2017-04-06 | アイカ工業株式会社 | Adhesive composition |
| CN111278946B (en) | 2018-02-02 | 2021-06-15 | 株式会社Lg化学 | Adhesive composition for foldable display, adhesive film using the same, and foldable display including the same |
| JP7268967B2 (en) * | 2018-06-22 | 2023-05-08 | 日東電工株式会社 | Adhesive layer for flexible image display device, laminate for flexible image display device, and flexible image display device |
| JP2020164619A (en) * | 2019-03-29 | 2020-10-08 | 三菱ケミカル株式会社 | Adhesive sheet, laminated sheet using the same, and image display device |
-
2020
- 2020-09-17 JP JP2020156440A patent/JP2022050067A/en active Pending
-
2021
- 2021-08-18 WO PCT/JP2021/030264 patent/WO2022059408A1/en active Application Filing
- 2021-08-18 CN CN202180064024.1A patent/CN116194543A/en active Pending
- 2021-08-18 KR KR1020237012408A patent/KR20230066606A/en active Search and Examination
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| Publication number | Publication date |
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| WO2022059408A1 (en) | 2022-03-24 |
| KR20230066606A (en) | 2023-05-16 |
| TW202212522A (en) | 2022-04-01 |
| JP2022050067A (en) | 2022-03-30 |
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