WO2025018369A1 - 粘着シート - Google Patents

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Publication number
WO2025018369A1
WO2025018369A1 PCT/JP2024/025701 JP2024025701W WO2025018369A1 WO 2025018369 A1 WO2025018369 A1 WO 2025018369A1 JP 2024025701 W JP2024025701 W JP 2024025701W WO 2025018369 A1 WO2025018369 A1 WO 2025018369A1
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WO
WIPO (PCT)
Prior art keywords
adhesive sheet
block
pressure
sensitive adhesive
copolymer
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
PCT/JP2024/025701
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English (en)
French (fr)
Japanese (ja)
Inventor
大翔 市川
稔朗 平田
徳之 内田
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Sekisui Chemical Co Ltd
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Sekisui Chemical Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Sekisui Chemical Co Ltd filed Critical Sekisui Chemical Co Ltd
Priority to KR1020257032945A priority Critical patent/KR20260041005A/ko
Priority to CN202480018198.8A priority patent/CN120958094A/zh
Priority to JP2024547309A priority patent/JPWO2025018369A1/ja
Publication of WO2025018369A1 publication Critical patent/WO2025018369A1/ja
Anticipated expiration legal-status Critical
Pending legal-status Critical Current

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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
    • C09J125/00—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 an aromatic carbocyclic ring; Adhesives based on derivatives of such polymers
    • C09J125/02—Homopolymers or copolymers of hydrocarbons
    • C09J125/04—Homopolymers or copolymers of styrene
    • C09J125/08—Copolymers of styrene
    • 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
    • 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
    • C09J133/10—Homopolymers or copolymers of methacrylic acid 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
    • 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
    • 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]

Definitions

  • the present invention relates to an adhesive sheet.
  • adhesive sheets are used for assembly (e.g., Patent Documents 1 and 2).
  • Adhesive sheets are also used for bonding optical components (e.g., Patent Document 3).
  • Adhesive sheets used in optical films for flexible displays applied to bendable image display devices and optical film laminates with adhesive layers are required to have the optical properties and durability required for conventional flat display panels, as well as to not peel off or float even when bending operations that deform the optical film are performed.
  • the shear storage modulus of the adhesive layer was adjusted to an appropriate range to improve bending resistance, making peeling or lifting less likely to occur even when bending was performed. This is because, when the shear storage modulus is within an appropriate range, the adhesive layer easily undergoes shear deformation even when bending is performed, and the minute deformation stress applied to the adhesive sheet can be alleviated.
  • the present invention aims to provide an adhesive sheet that has excellent bending resistance and is unlikely to peel off or float even when repeatedly bent.
  • Disclosure 1 relates to an adhesive sheet having an adhesive layer, in which, when a cohesive strength test is performed in which SUS plates are attached to both the top and bottom surfaces of the adhesive sheet, a stress of 10 kPa is applied in the shear direction to the upper SUS plate for 3 minutes (time t1 ), and immediately thereafter the stress of 10 kPa is removed and the sheet is allowed to stand for 3 minutes (time t2 ), the adhesive sheet has a shear strain of 250% or more at time t1 and a shear deformation recovery rate of 80% or more at time t2 .
  • Disclosure 2 is the pressure-sensitive adhesive sheet of Disclosure 1, in which the shear deformation recovery rate at time t2 is 90% or more.
  • Disclosure 3 is the pressure-sensitive adhesive sheet of Disclosure 1 or 2, in which the shear strain at time t1 is 300% or more.
  • Disclosure 4 is the pressure-sensitive adhesive sheet of Disclosure 1, 2, or 3, in which the 180° peel strength against polyimide is 10.0 N/25 mm or more.
  • Disclosure 5 is the pressure-sensitive adhesive sheet of Disclosure 4, in which the 180° peel strength against polyimide is 14.0 N/25 mm or more.
  • the present disclosure 6 is a pressure-sensitive adhesive sheet according to the present disclosure 1, 2, 3, 4, or 5, wherein the pressure-sensitive adhesive layer contains a block copolymer constituted of a block (A) having a structural unit derived from a monomer component (a) which is at least one selected from the group consisting of styrene and a (meth)acrylic acid ester having a cyclic structure, and a block (B) having a structural unit derived from a monomer component (b) which is a (meth)acrylic acid ester represented by the following formula (1):
  • the present disclosure 7 is the pressure-sensitive adhesive sheet of the present disclosure 6, wherein the block (A) further has a structural unit derived from a polar functional group-containing monomer.
  • the present disclosure 8 is the pressure-sensitive adhesive sheet of the present disclosure 7, wherein the block (A) further has a structural unit derived from (meth)acrylic acid.
  • the present disclosure 9 is the pressure-sensitive adhesive sheet of the present disclosure 6, 7, or 8, wherein the content of structural units derived from the monomer component (a) in the block (A) is 80 mass % or more.
  • the present disclosure 10 is the pressure-sensitive adhesive sheet of the present disclosure 6, 7, 8, or 9, wherein the content of the structural unit derived from the monomer component (b) in the block (B) is 20% by mass or more and 45% by mass or less.
  • the present disclosure 11 is the pressure-sensitive adhesive sheet of the present disclosure 6, 7, 8, 9, or 10, wherein the block (B) further has a structural unit derived from an olefin polymer having a terminal polymerizable unsaturated double bond, and the content of the structural unit derived from an olefin polymer having a terminal polymerizable unsaturated double bond in the block (B) is 5 mass% or more and 30 mass% or less.
  • the present disclosure 12 is the pressure-sensitive adhesive sheet of the present disclosure 6, 7, 8, 9, 10, or 11, wherein the block copolymer has a constituent unit derived from a polar functional group-containing monomer.
  • the present disclosure 13 is the pressure-sensitive adhesive sheet of the present disclosure 12, wherein the block copolymer has a structural unit derived from (meth)acrylic acid.
  • the present disclosure 14 is the pressure-sensitive adhesive sheet of the present disclosure 6, 7, 8, 9, 10, 11, 12, or 13, wherein the block copolymer has an A-B-A type triblock structure in which the block (B) is sandwiched between the block (A).
  • the present disclosure 15 is the pressure-sensitive adhesive sheet of the present disclosure 6, 7, 8, 9, 10, 11, 12, 13, or 14, wherein the content of the block (A) in the block copolymer is 7.25 mass % or more and 15 mass % or less.
  • the present disclosure 16 is the PSA sheet of the present disclosure 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15, wherein the weight average molecular weight (Mw) of the block copolymer is 250,000 or more and 1,000,000 or less.
  • the present disclosure 17 is the PSA sheet of the present disclosure 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, or 16, wherein the block copolymer has a solubility parameter (SP value) of 9.30 (J/cm 3 ) 1/2 or more.
  • SP value solubility parameter
  • Disclosure 18 is a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer, the pressure-sensitive adhesive layer containing a block copolymer constituted of a block (A) having a constituent unit derived from a monomer component (a) which is at least one selected from the group consisting of styrene and a (meth)acrylic acid ester having a cyclic structure, and a block (B) having a constituent unit derived from a monomer component (b) which is a (meth)acrylic acid ester represented by the following formula (1), wherein the content of the constituent units derived from the monomer component (a) in the block (A) is 80% by mass or more, the content of the constituent units derived from the monomer component (b) in the block (B) is 20% by mass or more and 45% by mass or less, and the content of the block (A) in the block copolymer is 7.25% by mass or more and 15% by mass or less.
  • a block copolymer constituted of a block
  • the present disclosure 19 is the pressure-sensitive adhesive sheet of the present disclosure 18, wherein the block (B) further has a structural unit derived from an olefin polymer having a terminal polymerizable unsaturated double bond, and the content of the structural unit derived from an olefin polymer having a terminal polymerizable unsaturated double bond in the block (B) is 5 mass% or more and 30 mass% or less.
  • Present Disclosure 20 is the pressure-sensitive adhesive sheet of Present Disclosure 18 or 19, wherein the block copolymer has an A-B-A type triblock structure in which the block (B) is sandwiched between the block (A).
  • the present disclosure 21 is the pressure-sensitive adhesive sheet of the present disclosure 18, 19, or 20, wherein the weight average molecular weight (Mw) of the block copolymer is 250,000 or more and 1,000,000 or less.
  • Present Disclosure 22 is the pressure-sensitive adhesive sheet of Present Disclosure 18, 19, 20, or 21, wherein the block copolymer has a solubility parameter (SP value) of 9.30 (J/cm 3 ) 1/2 or more.
  • the present disclosure 23 is a pressure-sensitive adhesive sheet of the present disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, or 22 having no substrate.
  • R 1 represents a hydrogen atom or a methyl group
  • R 2 represents an alkyl group having 9 or more carbon atoms.
  • the present inventors have investigated how to adjust the shear strain of a pressure-sensitive adhesive sheet when a specific stress is applied for a certain period of time, and the shear deformation recovery rate after the stress is removed for a certain period of time, to specific values. As a result, they have found that a pressure-sensitive adhesive sheet that is excellent in bending resistance and does not easily peel or float even when repeatedly bent can be obtained, and have completed the present invention.
  • the pressure-sensitive adhesive sheet of the present invention is unlikely to peel off or float not only when subjected to bending operations that cause a small amount of deformation, but also when subjected to bending operations that cause a large amount of deformation.
  • the pressure-sensitive adhesive sheet of the present invention is a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer, and when a cohesive strength test is performed in which SUS plates are attached to both the top and bottom surfaces of the pressure-sensitive adhesive sheet, a stress of 10 kPa is applied in the shear direction to the upper SUS plate for 3 minutes (time t1 ), and immediately thereafter the stress of 10 kPa is removed and the sheet is allowed to stand for 3 minutes (time t2 ), the pressure-sensitive adhesive sheet has a shear strain of 250% or more at time t1 and a shear deformation recovery rate of 80% or more at time t2 .
  • FIG. 1 shows a schematic diagram illustrating the cohesive strength test method. That is, as shown in Fig. 1, SUS plates 21 and 22 (SUS304 plates washed with ethanol and then wiped dry) at 80°C were laminated on top and bottom with an adhesive sheet 1 having a width of 10 mm and a length of 20 mm, and one end of the SUS plate 22 laminated on the bottom surface was fixed with a clamp 3. While the SUS plates 21 and 22 were maintained at 80°C, a weight 4 of 200 g was hung from one end of the SUS plate 21 laminated on the top surface in a temperature environment of 23°C, and a stress of 10 kPa was applied in the shear direction.
  • SUS plates 21 and 22 SUS304 plates washed with ethanol and then wiped dry
  • the displacement ⁇ 1 in the shear direction of the adhesive sheet 1 was precisely measured using a microshear creep measurement device (manufactured by Asahi Seiko Co., Ltd., "Microshear Creep Measurement Device") or the like. Furthermore, at the time t1, the weight 4 is removed, the stress of 10 kPa is released, and then the displacement ⁇ 2 in the shear direction of the PSA sheet 1 3 minutes after the time t1 (time t2 ) is precisely measured in the same manner as the displacement ⁇ 1 .
  • Shear strain of the PSA sheet of the present invention at the time t1 and the shear deformation recovery rate of the PSA sheet of the present invention at the time t2 are calculated from the following formulas (I) and (II).
  • Shear strain (%) 100 x ⁇ 1 /h (I)
  • Shear deformation recovery rate (%) 100 x ⁇ ( ⁇ 1 /h) - ( ⁇ 2 /h) ⁇ /( ⁇ 1 /h) (II) ( ⁇ 1 : displacement of the adhesive sheet 1 in the shear direction at time t 1
  • ⁇ 2 displacement of the adhesive sheet 1 in the shear direction at time t 2
  • h thickness of the adhesive sheet 1 )
  • the pressure-sensitive adhesive sheet of the present invention has pressure-sensitive adhesive layers on both sides and the pressure-sensitive adhesive layers on both sides are different, there is no particular limitation on the upper and lower surfaces of the pressure-sensitive adhesive layer in the cohesive strength test.
  • the pressure-sensitive adhesive sheet of the present invention has a substrate and is a single-sided pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer on one side of the substrate, the pressure-sensitive adhesive layer is attached to a SUS plate (SUS plate 22 in Figure 1) as the lower surface, and a 200 g weight is attached to the substrate located on the upper surface (corresponding to the position of SUS plate 21 in Figure 1) as shown in Figure 1, and the cohesive strength test is performed.
  • SUS plate SUS plate 22 in Figure 1
  • a 200 g weight is attached to the substrate located on the upper surface (corresponding to the position of SUS plate 21 in Figure 1) as shown in Figure 1, and the cohesive strength test is performed.
  • the pressure-sensitive adhesive sheet of the present invention has a lower limit of shear strain at time t1 of 250%. Since the pressure-sensitive adhesive sheet of the present invention has excellent deformability due to the shear strain of 250% or more at time t1 , the pressure-sensitive adhesive sheet of the present invention has excellent bending resistance, and can prevent peeling or lifting even when bending.
  • the pressure-sensitive adhesive sheet of the present invention has a preferred lower limit of shear strain at time t1 of 300%, and a more preferred lower limit of 350%.
  • the preferred upper limit of the shear strain of the pressure-sensitive adhesive sheet of the present invention at time t1 is 500%.
  • the pressure-sensitive adhesive sheet of the present invention at time t1 be 500% or less, the pressure-sensitive adhesive sheet of the present invention has better recovery from deformation, so that the pressure-sensitive adhesive sheet of the present invention can be more prevented from peeling or lifting even when repeatedly subjected to bending operations.
  • the more preferred upper limit of the shear strain of the pressure-sensitive adhesive sheet of the present invention at time t1 is 450%, and even more preferred upper limit is 400%.
  • Methods for adjusting the shear strain at the time t1 of the pressure-sensitive adhesive sheet of the present invention within the above-mentioned range include, for example, a method for changing the composition of the block copolymer contained in the pressure-sensitive adhesive layer described below, a method for decreasing the degree of crosslinking between block copolymers by changing the type of curing agent or decreasing the content of the curing agent, a method for increasing the weight average molecular weight, a method for increasing the molecular weight between entanglement points of the block copolymer described below, a method for decreasing the molecular weight distribution (Mw/Mn) and the like (Mw: weight average molecular weight, Mn: number average molecular weight).
  • the number average molecular weight (Mn) and weight average molecular weight (Mw) are molecular weights calculated based on standard polystyrene by GPC (Gel Permeation Chromatography). In the GPC method, for example, 2690 Separations Module (Waters) can be used. Specifically, the block copolymer is diluted 50 times with tetrahydrofuran (THF), and the resulting diluted solution is filtered through a filter (material: polytetrafluoroethylene, pore diameter: 0.2 ⁇ m) to prepare a measurement sample.
  • GPC Gel Permeation Chromatography
  • the measurement sample is supplied to a gel permeation chromatograph (for example, "2690 Separations Module” manufactured by Waters), and GPC measurement is performed under the conditions of a sample flow rate of 1 mL/min and a column temperature of 40 ° C.
  • GPC measurement is performed under the conditions of a sample flow rate of 1 mL/min and a column temperature of 40 ° C.
  • the polystyrene-equivalent molecular weight of the block copolymer is measured, and these values are regarded as the weight-average molecular weight and number-average molecular weight of the block copolymer.
  • the pressure-sensitive adhesive sheet of the present invention has a lower limit of the shear deformation recovery rate at the time t2 of 80%.
  • the pressure-sensitive adhesive sheet of the present invention has a shear deformation recovery rate of 80% or more at the time t2 , the pressure-sensitive adhesive sheet of the present invention has excellent recovery properties against deformation, and the pressure-sensitive adhesive sheet of the present invention can prevent peeling or lifting even when repeatedly bending.
  • the pressure-sensitive adhesive sheet of the present invention has a preferred lower limit of the shear deformation recovery rate at the time t2 of 90%, and a more preferred lower limit of 95%.
  • the preferred upper limit of the shear deformation recovery rate of the pressure-sensitive adhesive sheet of the present invention at the time point t2 is 100%.
  • Methods for adjusting the shear deformation recovery rate of the pressure-sensitive adhesive sheet of the present invention at the above-mentioned time t2 within the above-mentioned range include, for example, a method of changing the composition of the block copolymer contained in the pressure-sensitive adhesive layer described below, a method of reducing the molecular weight distribution (Mw/Mn), a method of crosslinking the block copolymers with a curing agent, and the like.
  • the preferred lower limit of the 180° peel strength of the pressure-sensitive adhesive sheet of the present invention against polyimide is 10.0 N/25 mm.
  • the pressure-sensitive adhesive sheet of the present invention has a 180° peel strength of 10.0 N/25 mm or more against polyimide, so that the pressure-sensitive adhesive sheet of the present invention has better bending resistance, and even when the sheet is left bent, peeling from the adherend can be more suppressed. Even when the bending radius is increased, peeling from the adherend can be more suppressed, and from the viewpoint of enabling a thin flexible device, the more preferred lower limit of the 180° peel strength of the pressure-sensitive adhesive sheet of the present invention against polyimide is 14.0 N/25 mm, and the even more preferred lower limit is 20.0 N/25 mm.
  • the 180° peel strength of the pressure-sensitive adhesive sheet of the present invention against polyimide can be measured by conducting a tensile test in accordance with JIS Z0237 using a tensile tester (Shimadzu Corporation's "Autograph AGS-X” or the like).
  • Methods for adjusting the 180° peel strength of the pressure-sensitive adhesive sheet of the present invention against polyimide within the above-mentioned range include, for example, a method for changing the composition of the block copolymer contained in the pressure-sensitive adhesive layer described below, a method for adding a tackifier resin to the pressure-sensitive adhesive layer described below, a method for adding a silane coupling agent to the pressure-sensitive adhesive layer described below, a method for adjusting the weight-average molecular weight of the block copolymer, a method for adjusting the degree of cross-linking between block copolymers by changing the type of curing agent or adjusting the amount of curing agent contained therein, a method for adding particles/fillers to the pressure-sensitive adhesive layer described below, and a method for forming a foam structure in the pressure-sensitive adhesive layer.
  • the pressure-sensitive adhesive sheet of the present invention has a pressure-sensitive adhesive layer.
  • the pressure-sensitive adhesive layer preferably contains a block copolymer composed of a block (A) having a structural unit derived from a monomer component (a) which is at least one selected from the group consisting of styrene and a (meth)acrylic acid ester having a cyclic structure, and a block (B) having a structural unit derived from a monomer component (b) which is a (meth)acrylic acid ester represented by the above formula (1).
  • (meth)acrylic means acrylic or methacrylic.
  • the cohesive force of the pressure-sensitive adhesive sheet of the present invention becomes greater, and the pressure-sensitive adhesive sheet of the present invention can be more prevented from peeling or floating even when repeatedly bent.
  • the block (B) in the block copolymer By containing the block (B) in the block copolymer, the molecular weight between the entanglement points of the molecules contained in the pressure-sensitive adhesive layer becomes greater, and the free volume of the molecules becomes larger, so that the pressure-sensitive adhesive layer obtained has better deformability.
  • the pressure-sensitive adhesive sheet of the present invention has better bending resistance, and the pressure-sensitive adhesive sheet of the present invention can be more prevented from peeling or floating even when bent.
  • the pressure-sensitive adhesive layer has both better deformation recovery and better deformability, and the pressure-sensitive adhesive sheet of the present invention has better bending resistance.
  • the entanglement molecular weight means the molecular weight between the bond points of the physical bond called entanglement, which is derived from the fact that long polymer chains are not allowed to move across each other.
  • the entanglement molecular weight is expressed as the product of the molecular weight Mv of the monomer unit constituting the main chain of the polymer and the number Nv of the main chain bonds between the entanglement points.
  • the monomer component (a) preferably contains styrene.
  • the (meth)acrylic acid ester having a cyclic structure include (meth)acrylic acid esters having an aromatic ring structure such as benzyl (meth)acrylate and 2-phenoxyethyl (meth)acrylate, and (meth)acrylic acid esters having an alicyclic structure such as cyclohexyl (meth)acrylate, dicyclopentanyl (meth)acrylate, isobornyl (meth)acrylate, etc.
  • benzyl (meth)acrylate is preferred from the viewpoint of further improving the recovery from bending of the pressure-sensitive adhesive sheet of the present invention.
  • the preferred lower limit of the content of the constituent unit derived from the monomer component (a) in the block (A) is 80% by mass.
  • the content of the constituent unit derived from the monomer component (a) is 80% by mass or more, so that the cohesive strength of the obtained pressure-sensitive adhesive layer is greater, and the pressure-sensitive adhesive sheet of the present invention can be more prevented from peeling or lifting even when repeatedly bending.
  • the more preferred lower limit of the content of the constituent unit derived from the monomer component (a) is 85% by mass, and the even more preferred lower limit is 90% by mass.
  • the upper limit of the content of the structural units derived from the monomer component (a) is not particularly limited, and may be 100% by mass.
  • the content ratio of the constituent units derived from the above monomer component (a) means the total content ratio of the constituent units derived from the monomer component (a) contained.
  • the block (A) preferably further comprises a constituent unit derived from a polar functional group-containing monomer.
  • the block (A) comprises a constituent unit derived from a polar functional group-containing monomer
  • the cohesive strength and adhesive strength of the resulting pressure-sensitive adhesive layer are increased, resulting in superior recovery from deformation, and the pressure-sensitive adhesive sheet of the present invention can be more effectively prevented from peeling or lifting even when repeatedly bent.
  • the interaction with the adherend is increased, resulting in improved adhesive strength of the pressure-sensitive adhesive sheet of the present invention.
  • Examples of the polar functional group-containing monomer include carboxy group-containing monomers, hydroxy group-containing monomers, glycidyl group-containing monomers, amino group-containing monomers, amide group-containing monomers, nitrile group-containing monomers, and acid anhydride group-containing monomers.
  • carboxy group-containing monomers and hydroxy group-containing monomers are preferred, and carboxy group-containing monomers are more preferred.
  • carboxyl group-containing monomer examples include unsaturated carboxylic acids such as (meth)acrylic acid, itaconic acid, crotonic acid, maleic acid, and fumaric acid.
  • unsaturated carboxylic acids such as (meth)acrylic acid, itaconic acid, crotonic acid, maleic acid, and fumaric acid.
  • monomers having a small molecular weight and a small number of carbon atoms are preferred, and (meth)acrylic acid (i.e., the block (A) further has a structural unit derived from (meth)acrylic acid) is particularly preferred.
  • the preferred lower limit of the content of the structural unit derived from the carboxyl group-containing monomer in the block (A) is 5% by mass, and the preferred upper limit is 20% by mass.
  • the content of the structural unit derived from the carboxyl group-containing monomer in the block (A) is 5% by mass or more, the cohesive strength and adhesive strength of the resulting adhesive layer are greater, and the adhesive sheet of the present invention has better recovery from deformation, and the adhesive sheet of the present invention can be more prevented from peeling or floating even when repeatedly bending.
  • the content of the structural unit derived from the carboxyl group-containing monomer in the block (A) is 20% by mass or less, the resulting adhesive layer of the adhesive sheet of the present invention has better deformability.
  • hydroxyl group-containing monomer examples include (meth)acrylic acid esters having a hydroxyl group, such as 4-hydroxybutyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, and N-hydroxyethylacrylamide (HEAA).
  • (meth)acrylic acid esters having a hydroxyl group such as 4-hydroxybutyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, and N-hydroxyethylacrylamide (HEAA).
  • the preferred lower limit of the content of the structural unit derived from the hydroxyl group-containing monomer in the block (A) is 5% by mass, and the preferred upper limit is 20% by mass.
  • the content of the structural unit derived from the hydroxyl group-containing monomer in the block (A) is 5% by mass or more, the cohesive force of the resulting adhesive layer is greater, and the adhesive sheet of the present invention has better recovery from deformation, and the adhesive sheet of the present invention can be more prevented from peeling or floating even when repeatedly bending.
  • the content of the structural unit derived from the hydroxyl group-containing monomer in the block (A) is 20% by mass or less, the adhesive layer of the resulting adhesive sheet of the present invention has better deformability.
  • the adhesive sheet of the present invention has better bending resistance, and the adhesive sheet of the present invention can be more prevented from peeling or floating even when bending.
  • the more preferred lower limit of the content of the structural unit derived from the hydroxyl group-containing monomer in the block (A) is 6.5% by mass, the more preferred upper limit is 15% by mass, the even more preferred lower limit is 8% by mass, and the even more preferred upper limit is 12% by mass.
  • An example of the acid anhydride group-containing monomer is maleic anhydride.
  • An example of the glycidyl group-containing monomer is glycidyl (meth)acrylate.
  • the amide group-containing monomer may, for example, be isopropyl(meth)acrylamide.
  • Examples of the nitrile group-containing monomer include acrylonitrile and methacrylonitrile.
  • the preferred lower limit of the total content ratio of the constituent units derived from the polar functional group-containing monomer in the block (A) is 5% by mass, and the preferred upper limit is 20% by mass.
  • the total content ratio of the constituent units derived from the polar functional group-containing monomer in the block (A) is 5% by mass or more, the cohesive force of the obtained adhesive layer becomes larger, and the adhesive sheet of the present invention has better recovery against deformation, and the adhesive sheet of the present invention can be more prevented from peeling or floating even when repeatedly bending.
  • the total content ratio of the constituent units derived from the polar functional group-containing monomer in the block (A) is 20% by mass or less, the adhesive layer of the obtained adhesive sheet of the present invention has better deformability.
  • the adhesive sheet of the present invention has better bending resistance, and the adhesive sheet of the present invention can be more prevented from peeling or floating even when bending.
  • the more preferred lower limit of the total content ratio of the constituent units derived from the polar functional group-containing monomer in the block (A) is 6.5% by mass, the more preferred upper limit is 15% by mass, the even more preferred lower limit is 8% by mass, and the even more preferred upper limit is 12% by mass.
  • Examples of the (meth)acrylic acid ester represented by the above formula (1) in the block (B) include nonyl (meth)acrylate, decyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, pentadecyl (meth)acrylate, isostearyl (meth)acrylate, etc.
  • lauryl (meth)acrylate, isostearyl (meth)acrylate, etc., in which the alkyl group represented by R2 in the above formula (1) has 12 or more carbon atoms are more preferred.
  • the upper limit of the number of carbon atoms in the alkyl group represented by R2 in formula (1) is preferably 22, and more preferably 18.
  • the preferred lower limit of the content of the constituent unit derived from the monomer component (b) in the block (B) is 20% by mass, and the preferred upper limit is 45% by mass or less.
  • the content of the constituent unit derived from the monomer component (b) is 20% by mass or more, the molecular weight of the molecules contained in the pressure-sensitive adhesive layer becomes larger, and the free volume of the molecules becomes larger, so that the resulting pressure-sensitive adhesive layer has better deformability.
  • the pressure-sensitive adhesive sheet of the present invention has better bending resistance, and can better prevent peeling or lifting even when bending is performed.
  • the content of the constituent unit derived from the monomer component (b) is 45% by mass or less, the cohesive force of the resulting pressure-sensitive adhesive layer becomes larger, and the recovery against deformation becomes better, and the pressure-sensitive adhesive sheet of the present invention can better prevent peeling or lifting even when bending is performed repeatedly.
  • the content of the structural units derived from the monomer component (b) is more preferably 25% by mass at the lower limit and 40% by mass at the upper limit, and even more preferably 30% by mass at the lower limit and 38% by mass at the upper limit.
  • the content ratio of the constituent units derived from the above monomer component (b) means the total content ratio of the constituent units derived from the monomer component (b) contained.
  • the block (B) further has a structural unit derived from an olefin-based polymer having a polymerizable unsaturated double bond at the end.
  • the block (B) has a structural unit derived from the (meth)acrylic acid alkyl ester represented by the above formula (1) and a structural unit derived from an olefin-based polymer having a polymerizable unsaturated double bond at the end, and the structural unit derived from the olefin-based polymer having a polymerizable unsaturated double bond at the end of the side chain aggregates by interaction to form a pseudo-crosslinked structure.
  • the block (B) By having the block (B) have such a structure, when a peel stress is applied and the strain becomes large, the pseudo-crosslink is broken and the molecules of the block copolymer having the block (B) are stretched, so that the pressure-sensitive adhesive layer exhibits high flexibility and has higher adhesion and better deformability.
  • the adhesive strength and deformability of the pressure-sensitive adhesive sheet of the present invention are further improved, resulting in superior bending resistance, and in particular, peeling from the adherend can be more effectively prevented when the sheet is left bent.
  • the olefin polymer having a polymerizable unsaturated double bond at the terminal may have a polymerizable unsaturated double bond at one terminal, or may have a polymerizable unsaturated double bond at both terminals.
  • an olefin polymer having a polymerizable unsaturated double bond at one terminal is preferred from the viewpoint of preventing chemical crosslinking within the molecule and further improving the retention of the pressure-sensitive adhesive composition of the present invention.
  • Examples of the olefin polymer having a polymerizable unsaturated double bond at its terminal include ethylene-butylene copolymers, ethylene-propylene copolymers, ethylene polymers, propylene polymers, butylene polymers, etc., each of which has a group containing a polymerizable unsaturated carbon-carbon double bond at one or both terminals.
  • Examples of the group containing a polymerizable unsaturated carbon-carbon double bond include a (meth)acryloyl group, a vinyl ether group, a styryl group, etc. Among these, a (meth)acryloyl group is preferred because of its excellent copolymerizability with the (meth)acrylic acid alkyl ester.
  • the olefin polymer having a polymerizable unsaturated double bond at the terminal include an ethylene macromonomer having a (meth)acryloyl group at one terminal, a propylene macromonomer having a (meth)acryloyl group at one terminal, an ethylene-butylene macromonomer having a (meth)acryloyl group at one terminal, an ethylene-propylene macromonomer having a (meth)acryloyl group at one terminal, etc.
  • an ethylene-butylene macromonomer having a (meth)acryloyl group at one terminal and an ethylene-propylene macromonomer having a (meth)acryloyl group at one terminal are preferred.
  • These olefin polymers having a polymerizable unsaturated double bond at the terminal may be used alone or in combination of two or more kinds.
  • the term "macromonomer” refers to a monomer having a weight average molecular weight of about 1,000 to 100,000 and having a polymerizable functional group.
  • the content ratio of the structural unit derived from the olefin-based polymer having a polymerizable unsaturated double bond at the terminal in the block (B) is preferably 5% by mass at the lower limit and 30% by mass at the upper limit.
  • the content ratio of the structural unit derived from the olefin-based polymer having a polymerizable unsaturated double bond at the terminal is 5% by mass or more, the adhesive strength of the pressure-sensitive adhesive layer is further improved.
  • the content ratio of the structural unit derived from the olefin-based polymer having a polymerizable unsaturated double bond at the terminal is 30% by mass or less, the pressure-sensitive adhesive layer does not become too hard and has better deformability.
  • the more preferred lower limit of the content ratio of the structural unit derived from the olefin-based polymer having a polymerizable unsaturated double bond at the terminal is 8% by mass, the more preferred upper limit is 25% by mass, the even more preferred lower limit is 10% by mass, and the even more preferred upper limit is 20% by mass.
  • the block (B) may have a constituent unit derived from a monomer other than the constituent unit derived from the (meth)acrylic acid ester represented by the formula (1) and the constituent unit derived from the olefin polymer having a terminal polymerizable unsaturated double bond.
  • Examples of the structural units derived from other monomers contained in the block (B) include structural units derived from (meth)acrylic acid alkyl esters in which the alkyl group represented by R 2 in the formula (1) has 8 or less carbon atoms.
  • Examples of the (meth)acrylic acid alkyl esters in which the alkyl group represented by R 2 in the formula (1) has 8 or less carbon atoms include butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, hexyl (meth)acrylate, octyl (meth)acrylate, and cyclohexyl (meth)acrylate.
  • Other examples of structural units derived from other monomers include structural units derived from acrylic acid, maleic anhydride, N,N-dimethylacrylamide, and the like.
  • the block copolymer preferably has a constituent unit derived from a polar functional group-containing monomer.
  • the cohesive strength and adhesive strength of the resulting pressure-sensitive adhesive layer are increased, resulting in superior recovery from deformation, and the pressure-sensitive adhesive sheet of the present invention can be more effectively prevented from peeling or lifting even when repeatedly bent.
  • the interaction with the adherend is increased, resulting in improved adhesive strength of the pressure-sensitive adhesive sheet of the present invention.
  • the constituent units derived from the polar functional group-containing monomer in the block copolymer include the same as the constituent units derived from the polar functional group-containing monomer in the block (A) described above.
  • the block copolymer has a constituent unit derived from (meth)acrylic acid.
  • the preferred lower limit of the content of the constituent unit derived from the carboxyl group-containing monomer in the block copolymer is 1% by mass, and the preferred upper limit is 10% by mass.
  • the content of the constituent unit derived from the carboxyl group-containing monomer in the block copolymer is 1% by mass or more, the cohesive strength and adhesive strength of the resulting adhesive layer are greater, and the adhesive sheet of the present invention has better recovery from deformation, and the adhesive sheet of the present invention can be more prevented from peeling or floating even when repeatedly bending.
  • the content of the constituent unit derived from the carboxyl group-containing monomer in the block copolymer is 10% by mass or less, the resulting adhesive layer of the adhesive sheet of the present invention has better deformability.
  • the adhesive sheet of the present invention has better bending resistance, and the adhesive sheet of the present invention can be more prevented from peeling or floating even when bending.
  • the more preferred lower limit of the content of the constituent unit derived from the carboxyl group-containing monomer in the block copolymer is 2% by mass, and the more preferred upper limit is 8% by mass, and the even more preferred lower limit is 3% by mass, and the even more preferred upper limit is 5% by mass.
  • the preferred lower limit of the content of the structural unit derived from the hydroxyl group-containing monomer in the block copolymer is 1% by mass, and the preferred upper limit is 10% by mass.
  • the content of the structural unit derived from the hydroxyl group-containing monomer is 1% by mass or more, the cohesive strength of the resulting adhesive layer is greater, and the adhesive sheet of the present invention has better recovery from deformation, and the adhesive sheet of the present invention can be more prevented from peeling or floating even when repeatedly bending.
  • the content of the structural unit derived from the hydroxyl group-containing monomer in the block copolymer is 10% by mass or less, the resulting adhesive layer of the adhesive sheet of the present invention has better deformability.
  • the adhesive sheet of the present invention has better bending resistance, and the adhesive sheet of the present invention can be more prevented from peeling or floating even when bending.
  • the more preferred lower limit of the content of the structural unit derived from the hydroxyl group-containing monomer in the block copolymer is 2% by mass, and the more preferred upper limit is 8% by mass, and the even more preferred lower limit is 3% by mass, and the even more preferred upper limit is 5% by mass.
  • the preferred lower limit of the total content ratio of the constituent units derived from the polar functional group-containing monomer in the block copolymer is 1% by mass, and the preferred upper limit is 10% by mass.
  • the total content ratio of the constituent units derived from the polar functional group-containing monomer in the block copolymer is 1% by mass or more, the cohesive force of the obtained adhesive layer becomes larger, and the adhesive sheet of the present invention has better recovery against deformation, and the adhesive sheet of the present invention can be more prevented from peeling or floating even when repeatedly bending.
  • the total content ratio of the constituent units derived from the polar functional group-containing monomer in the block copolymer is 10% by mass or less, the adhesive layer of the obtained adhesive sheet of the present invention has better deformability.
  • the adhesive sheet of the present invention has better bending resistance, and the adhesive sheet of the present invention can be more prevented from peeling or floating even when bending.
  • the more preferred lower limit of the total content ratio of the constituent units derived from the polar functional group-containing monomer in the block copolymer is 2% by mass, and the more preferred upper limit is 8% by mass, and the even more preferred lower limit is 3% by mass, and the even more preferred upper limit is 5% by mass.
  • the block copolymer preferably contains a block copolymer having an A-B-A triblock structure in which the block (B) is sandwiched between the block (A) (hereinafter, sometimes simply referred to as an "A-B-A triblock copolymer").
  • the block copolymer contains an A-B-A type triblock copolymer
  • the block (A) present at both ends of the block copolymer forms a pseudo-crosslinked structure derived from styrene and a (meth)acrylic acid ester having a cyclic structure at both ends of the A-B-A type triblock copolymer.
  • the obtained pressure-sensitive adhesive layer has better recovery against deformation, and the pressure-sensitive adhesive sheet of the present invention can be more effectively prevented from peeling or lifting even when repeatedly subjected to bending operations. Furthermore, the obtained pressure-sensitive adhesive layer has better deformability, and the pressure-sensitive adhesive sheet of the present invention has better bending resistance, and can be more effectively prevented from peeling or lifting even when subjected to bending operations.
  • the alkyl group having 9 or more carbon atoms derived from the (meth)acrylic acid ester represented by formula (1) in block (B) present inside the A-B-A type triblock copolymer increases the molecular weight between entanglement points of the block copolymer.
  • the free volume of the molecule becomes larger, the resulting pressure-sensitive adhesive layer has better deformability, and the pressure-sensitive adhesive sheet of the present invention has better bending resistance, so that peeling or lifting can be more effectively prevented even when bending is performed.
  • the preferred lower limit of the molecular weight between the entanglement points of the monomer component (b) in the A-B-A type triblock copolymer is 5,000, and the preferred upper limit is 500,000.
  • the pressure-sensitive adhesive sheet of the present invention has excellent deformability and can prevent peeling or lifting even when bending is performed.
  • a more preferred lower limit of the molecular weight between the entanglement points is 10,000, a more preferred upper limit is 400,000, an even more preferred lower limit is 50,000, and an even more preferred upper limit is 300,000.
  • the block copolymer is the A-B-A type triblock copolymer
  • the preferred lower limit of the total content ratio of the structural units derived from the styrene and (meth)acrylic acid ester having a cyclic structure in the block copolymer is 5% by mass, and the preferred upper limit is 20% by mass.
  • the microphase separation structure of the A-B-A type triblock copolymer is likely to exhibit a spherical structure.
  • the obtained pressure-sensitive adhesive layer is more excellent in deformability and recovery from deformation, and the pressure-sensitive adhesive sheet of the present invention is more excellent in bending resistance, and peeling or lifting can be more prevented even when bending is performed.
  • the pressure-sensitive adhesive sheet of the present invention is more excellent in transparency when the total content ratio of the structural units derived from the styrene and (meth)acrylic acid ester having a cyclic structure is 20% by mass or less, the pressure-sensitive adhesive sheet of the present invention is more excellent in transparency.
  • a more preferable lower limit of the total content of the structural units derived from the styrene and the (meth)acrylic acid ester having a cyclic structure is 6.5% by mass, a more preferable upper limit is 15% by mass, an even more preferable lower limit is 9.0% by mass, and a still more preferable upper limit is 13% by mass.
  • the microphase-separated structure can be observed, for example, by the following method.
  • the pressure-sensitive adhesive layer processed into a sheet shape is stained with ruthenium, and then cut into a plane perpendicular to the lamination direction of the coating film and the separator using a cryomicrotome (such as "EM FC cryomicrotome” manufactured by Leica), and the cross section of the coating film can be observed at a magnification of 20,000 times using a transmission electron microscope ("JEM-F200" manufactured by JEOL).
  • a cryomicrotome such as "EM FC cryomicrotome” manufactured by Leica
  • the block copolymer is the A-B-A type triblock copolymer
  • the preferred lower limit of the content ratio of the constituent unit derived from the monomer component (b) in block (B) in the A-B-A type triblock copolymer is 25% by mass
  • the preferred upper limit is 45% by mass.
  • the content ratio of the constituent unit derived from the monomer component (b) is 25% by mass or more
  • the molecular weight between the entanglement points of the block copolymer becomes larger.
  • the free volume of the molecule becomes larger, the resulting adhesive layer has better deformability, and the adhesive sheet of the present invention has better bending resistance, and peeling and lifting can be more effectively prevented even when bending is performed.
  • the content ratio of the constituent unit derived from the monomer component (b) of the above formula is 45% by mass or less, the cohesive force of the resulting adhesive layer becomes larger, resulting in excellent recovery against deformation, and the adhesive sheet of the present invention can be more effectively prevented from peeling and lifting even when bending is performed repeatedly.
  • the more preferred lower limit of the content of the structural unit derived from the monomer component (b) in the block (B) is 28% by mass, the more preferred upper limit is 40% by mass, the even more preferred lower limit is 30% by mass, and the even more preferred upper limit is 38% by mass.
  • the preferred lower limit of the content of the block (A) in the block copolymer is 7.25% by mass, and the preferred upper limit is 15% by mass.
  • the content of the block (A) is within the above range, the pseudo-crosslinked structures formed at the ends of the A-B-A triblock copolymer are located at positions sufficiently apart from each other, so that the free volume of the molecule is larger.
  • the obtained pressure-sensitive adhesive layer has better deformability, and the pressure-sensitive adhesive sheet of the present invention has better bending resistance, and peeling or lifting can be more effectively prevented even when bending is performed.
  • the more preferred lower limit of the content of the block (A) is 8% by mass, the more preferred upper limit is 12% by mass, the even more preferred lower limit is 9% by mass, and the even more preferred upper limit is 11% by mass.
  • the preferred lower limit of the weight average molecular weight (Mw) of the block copolymer is 250,000, and the preferred upper limit is 1,000,000.
  • Mw weight average molecular weight
  • the preferred upper limit of the weight average molecular weight (Mw) of the block copolymer is 250,000 or more, the amount of shear deformation of the block copolymer is greater, and the resulting pressure-sensitive adhesive layer has better deformability.
  • the pressure-sensitive adhesive sheet of the present invention has better bending resistance, and peeling or lifting can be more effectively prevented even when bending is performed.
  • the weight average molecular weight (Mw) of the block copolymer is 1,000,000 or less, the viscosity of the pressure-sensitive adhesive solution containing the block copolymer does not become too high in the production of the pressure-sensitive adhesive sheet of the present invention described below, and the pressure-sensitive adhesive sheet can be produced with a good appearance.
  • the more preferred lower limit of the weight average molecular weight (Mw) of the block copolymer is 300,000, the more preferred upper limit is 900,000, the even more preferred lower limit is 400,000, and the even more preferred upper limit is 800,000.
  • Methods for adjusting the weight average molecular weight (Mw) of the block copolymer include, for example, adjusting the amount of monomer components mixed, or employing constant temperature polymerization or living radical polymerization in the production of the block copolymer described below.
  • the preferred lower limit of the solubility parameter (SP value) of the block copolymer is 9.30 (J/cm 3 ) 1/2 .
  • the solubility parameter (SP value) of the block copolymer is 9.30 (J/cm 3 ) 1/2 or more, the adhesive strength of the obtained pressure-sensitive adhesive layer is further improved, and the pressure-sensitive adhesive sheet of the present invention has better bending resistance, and even when left stationary in a bent state, peeling from the adherend can be further suppressed.
  • the more preferred lower limit of the solubility parameter (SP value) of the block copolymer is 9.40 (J/cm 3 ) 1/2 , and the even more preferred lower limit is 9.50 (J/cm 3 ) 1/2 .
  • the upper limit of the solubility parameter (SP value) of the block copolymer is preferably 12 (J/cm 3 ) 1/2 , more preferably 11 (J/cm 3 ) 1/2 , and even more preferably 10 (J/cm 3 ) 1/2 .
  • the solubility parameter (SP value) is a parameter used as an index of polarity, and in this specification, the solubility parameter (SP value) is the Hansen solubility parameter, which can be derived by calculation from the structural formula using HSP software.
  • HSP software Hansen Solubility Parameter in Practice (HSPiP) can be used.
  • the block copolymer may be produced, for example, by subjecting a mixture of constituent unit monomers of block (A) containing the monomer component (a) and a mixture of constituent unit monomers of block (B) containing the monomer component (b) to a radical reaction in the presence of a polymerization initiator to obtain block (A) and block (B), respectively, and then reacting or copolymerizing both of them.
  • a mixture of constituent unit monomers of block (B) containing the monomer component (b) may be added and copolymerized.
  • the method for carrying out the radical reaction that is, the polymerization method
  • a conventionally known method can be used, and examples thereof include solution polymerization (boiling point polymerization or constant temperature polymerization), emulsion polymerization, suspension polymerization, bulk polymerization, and the like.
  • the block copolymer when the block copolymer is the A-B-A type triblock copolymer, the block copolymer can be obtained by, for example, living polymerization. Examples of living polymerization include living anionic polymerization and RAFT polymerization, and RAFT polymerization is particularly preferred.
  • a RAFT agent is used to polymerize or copolymerize the constituent unit monomers of block (A) containing the monomer component (a) to obtain block (A), and then, in the presence of the obtained block (A), a constituent unit monomer of block (B) containing the monomer component (b) is polymerized or copolymerized to produce a block copolymer.
  • Examples of the polymerization initiator used in the above polymerization method include azo compounds and organic peroxides.
  • the azo compound include 2,2'-azobis(isobutyronitrile), 2,2'-azobis(2-methylbutyronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 1,1-azobis(cyclohexane-1-carbonitrile), 1-((1-cyano-1-methylethyl)azo)formamide, 4,4'-azobis(4-cyanovaleric acid), dimethyl-2,2'-azobis(2-methylpropionate), dimethyl-1,1'-azobis(1-cyclohexanecarboxylate), 2,2'-azobis(2-methyl-N-(1,1'-bis(hydroxymethyl)-2-hydroxyethyl)propionamide), 2,2'-azobis(2-methyl-N-(2-hydroxyethyl)
  • azo compounds may be used alone or in combination of two or more.
  • organic peroxides include 1,1-bis(t-hexylperoxy)-3,3,5-trimethylcyclohexane, t-hexylperoxypivalate, t-butylperoxypivalate, 2,5-dimethyl-2,5-bis(2-ethylhexanoylperoxy)hexane, t-hexylperoxy-2-ethylhexanoate, t-butylperoxy-2-ethylhexanoate, t-butylperoxyisobutyrate, t-butylperoxy-3,5,5-trimethylhexanoate, t-butylperoxylaurate, etc.
  • organic peroxides may be used alone or in combination of two or more.
  • examples of the RAFT agent used in the RAFT polymerization include sulfur-based compounds such as dithioesters, dithiocarbonates, trithiocarbonates, and xanthates. Specific examples include compounds represented by the following formula (2).
  • the preferred lower limit of the content of the block copolymer in the pressure-sensitive adhesive layer is 75% by mass. By making the content of the block copolymer 75% by mass or more, the pressure-sensitive adhesive layer obtained has both better deformability and better recovery from deformation, and the pressure-sensitive adhesive sheet of the present invention has better bending resistance.
  • the more preferred lower limit of the content of the block copolymer is 80% by mass, and the even more preferred lower limit is 85% by mass.
  • the upper limit of the content of the block copolymer is not particularly limited and may be 100% by mass; however, from the viewpoint of further improving the recovery of the resulting pressure-sensitive adhesive layer against deformability, it is preferable to contain a curing agent described later, and therefore the preferred upper limit is 99.9% by mass.
  • the pressure-sensitive adhesive layer preferably further contains a curing agent.
  • the curing agent reacts with the functional group derived from the polar functional group-containing monomer to form a chemical crosslinked structure.
  • the cohesive strength of the resulting adhesive layer is increased, resulting in a more excellent recovery from deformation, and the adhesive sheet of the present invention can be more effectively prevented from peeling or lifting even when repeatedly bent.
  • an isocyanate-based curing agent for example, an isocyanate-based curing agent, an aziridine-based curing agent, an epoxy-based curing agent, a metal chelate-type curing agent, etc. can be used depending on the type of functional group contained in the block (A).
  • an isocyanate-based curing agent is preferred from the viewpoints of maintaining good storage stability, providing the pressure-sensitive adhesive sheet of the present invention with excellent deformability and recovery from deformation, and better preventing peeling or lifting even when bending is performed.
  • isocyanate curing agent examples include isocyanate compounds having two or more isocyanate groups in one molecule, specifically, aliphatic isocyanates such as tetramethylene diisocyanate, hexamethylene diisocyanate, 1,3,6-hexamethylene triisocyanate, isophorone diisocyanate, and 4,4'-dicyclohexylmethane diisocyanate, aromatic isocyanates such as 4,4'-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, xylylene diisocyanate, 1,5-naphthalene diisocyanate, and 4,4-diphenyl diisocyanate, and alicyclic isocyanates such as dicycloheptane triisocyanate.
  • aliphatic isocyanates such as tetramethylene diisocyanate, hexamethylene diisocyanate, 1,
  • the preferred lower limit of the content of the curing agent relative to 100 parts by mass of the block copolymer is 0.005 parts by mass, and the preferred upper limit is 5 parts by mass.
  • the content of the curing agent is 0.005 parts by mass or more, the cohesive force of the obtained adhesive layer becomes greater, resulting in excellent recovery from deformation, and the adhesive sheet of the present invention can be more effectively prevented from peeling or floating even when repeatedly bending.
  • the content of the curing agent is 5 parts by mass or less, the obtained adhesive layer has excellent deformability, and the adhesive sheet of the present invention has excellent bending resistance, resulting in better prevention of peeling or floating even when bending.
  • a more preferred lower limit of the curing agent is 0.01 parts by mass, a more preferred upper limit is 3 parts by mass, an even more preferred lower limit is 0.1 parts by mass, and an even more preferred upper limit is 1.5 parts by mass.
  • the pressure-sensitive adhesive layer may contain a tackifier resin.
  • a tackifier resin By including a tackifier resin in the above-mentioned adhesive layer, the adhesive strength of the obtained adhesive layer is further improved, and the adhesive sheet of the present invention has better bending resistance, and peeling from the adherend when left undisturbed in a bent state can be further suppressed.
  • the preferred upper limit of the content of the tackifier resin relative to 100 parts by mass of the block copolymer is 20 parts by mass.
  • the pressure-sensitive adhesive sheet of the present invention has better transparency.
  • a more preferred upper limit of the content of the tackifier resin is 10 parts by mass, and from the viewpoint of the transparency of the pressure-sensitive adhesive sheet of the present invention, it is most preferred that the pressure-sensitive adhesive layer does not contain the tackifier resin.
  • the pressure-sensitive adhesive layer may contain a silane coupling agent.
  • a silane coupling agent included in the pressure-sensitive adhesive layer, the adhesive strength of the obtained pressure-sensitive adhesive layer is further improved, and the pressure-sensitive adhesive sheet of the present invention has superior bending resistance, and peeling from the adherend when left stationary in a bent state can be further suppressed.
  • the preferred upper limit of the content of the silane coupling agent relative to 100 parts by mass of the block copolymer is 3 parts by mass.
  • the pressure-sensitive adhesive sheet of the present invention has better transparency.
  • a more preferred upper limit of the content of the silane coupling agent is 1 part by mass, and an even more preferred upper limit is 0.5 parts by mass. From the viewpoint of the transparency of the pressure-sensitive adhesive sheet of the present invention, it is most preferred that the pressure-sensitive adhesive layer does not contain the silane coupling agent.
  • the adhesive layer may contain additives such as solvents, plasticizers, emulsifiers, softeners, fillers, pigments, dyes, and antioxidants, within the range that does not impair the effects of the present invention.
  • the pressure-sensitive adhesive layer has a preferred lower limit of shear storage modulus G' at -20°C of 1.0 x 10 4 Pa, and a preferred upper limit of 5.0 x 10 5 Pa.
  • the pressure-sensitive adhesive layer has superior shear deformability in a low-temperature environment, and the pressure-sensitive adhesive sheet of the present invention has superior bending resistance to minute bending operations in a low-temperature environment.
  • the pressure-sensitive adhesive layer has a more preferred lower limit of 3.0 x 10 4 Pa, a more preferred upper limit of 3.0 x 10 5 Pa, an even more preferred lower limit of 5.0 x 10 4 Pa, and an even more preferred upper limit of 2.0 x 10 5 Pa.
  • the pressure-sensitive adhesive layer has a preferred lower limit of shear storage modulus G' at 25°C of 1.0 x 104 Pa, and a preferred upper limit of 2.0 x 105 Pa.
  • the pressure-sensitive adhesive layer has better shear deformability, and the pressure-sensitive adhesive sheet of the present invention has better bending resistance to minute bending operations.
  • the pressure-sensitive adhesive layer has a more preferred lower limit of 2.0 x 104 Pa, a more preferred upper limit of 1.0 x 105 Pa , an even more preferred lower limit of 3.0 x 104 Pa, and an even more preferred upper limit of 9.0 x 104 Pa.
  • the preferred lower limit of the shear storage modulus G' of the pressure-sensitive adhesive layer at 85°C is 1.0 x 103 Pa, and the preferred upper limit is 1.0 x 105 Pa.
  • the shear storage modulus G' of the pressure-sensitive adhesive layer at 85°C is within the above range, the pressure-sensitive adhesive layer has better shear deformability in a high-temperature environment, and the pressure-sensitive adhesive sheet of the present invention has better bending resistance to small bending operations in a high-temperature environment.
  • the more preferred lower limit of the shear storage modulus G' of the pressure-sensitive adhesive layer at 85°C is 5.0 x 103 Pa
  • the more preferred upper limit is 7.5 x 104 Pa
  • the even more preferred lower limit is 2.0 x 104 Pa
  • the even more preferred upper limit is 5.0 x 104 Pa.
  • the shear storage modulus of the pressure-sensitive adhesive layer at ⁇ 20° C., 25° C. and 85° C. can be measured by dynamic viscoelasticity measurement, specifically, for example, by the following method. That is, the obtained pressure-sensitive adhesive layer is laminated to a thickness of about 1 mm, and cut into a flat rectangular shape of 6 mm width ⁇ 10 mm length to prepare a test piece.
  • the prepared test piece can be subjected to dynamic viscoelasticity measurement in shear mode in a nitrogen atmosphere, at a measurement temperature of -50°C to 200°C, a heating rate of 5°C/min, and a frequency of 1 Hz using a dynamic viscoelasticity measuring device (manufactured by IT Measurement & Control Co., Ltd., "DVA-200" or the like).
  • a dynamic viscoelasticity measuring device manufactured by IT Measurement & Control Co., Ltd., "DVA-200" or the like.
  • Examples of methods for adjusting the shear storage modulus of the pressure-sensitive adhesive layer at -20°C, 25°C, and 85°C include adjusting the total content of structural units derived from the styrene and (meth)acrylic acid ester having a cyclic structure (i.e., monomer component (a)) in block (A) and the content of structural units derived from the (meth)acrylic acid alkyl ester represented by formula (1) (i.e., monomer component (b)) in block (B) to appropriate amounts.
  • the pressure-sensitive adhesive sheet of the present invention may be a non-support type having no substrate, or a supported type having a substrate, with the non-support type having no substrate being preferred. Since the pressure-sensitive adhesive sheet of the present invention does not have a substrate, the pressure-sensitive adhesive sheet of the present invention is thin and has excellent transparency, and therefore can be suitably used as an optical film for a thin flexible display.
  • the substrate is preferably made of a resin film.
  • resin film polyester resin film, polypropylene resin film, and transparent polyimide resin film are preferable.
  • transparent polyimide resin film is preferable because it is flat, has little thickness variation, and has high bending strength.
  • the above-mentioned base material may contain additives such as fillers, UV absorbers, light stabilizers, and antistatic agents, as long as the additives do not impair the physical properties of the base material.
  • the thickness of the substrate is appropriately selected according to the application, but the preferred upper limit is 50 ⁇ m. By making the thickness of the substrate 50 ⁇ m or less, the pressure-sensitive adhesive sheet of the present invention has better transparency.
  • the more preferred upper limit of the thickness of the substrate is 25 ⁇ m, and the even more preferred upper limit is 10 ⁇ m.
  • the pressure-sensitive adhesive sheet of the present invention may have the pressure-sensitive adhesive layer on only one side of the substrate, or may have the pressure-sensitive adhesive layer on both sides of the substrate. In particular, it is preferable that the pressure-sensitive adhesive layer be on both sides of the substrate.
  • the method for producing the pressure-sensitive adhesive sheet of the present invention is not particularly limited, and examples thereof include the following methods. First, a pressure-sensitive adhesive containing a block copolymer and, if necessary, a curing agent and other additives is prepared. Next, the obtained pressure-sensitive adhesive is applied to a release-treated surface of a release film, one side of which has been subjected to a release treatment, and dried to form a pressure-sensitive adhesive layer. The exposed surface of the pressure-sensitive adhesive layer is bonded to the release-treated surface of a separately prepared release film, to produce a laminated sheet. The obtained laminated sheet is used as a pressure-sensitive adhesive sheet. In addition, the adhesive layer of the obtained laminated sheet is laminated to a substrate to produce an adhesive sheet including the substrate.
  • the adhesive layer of the laminated sheet is laminated to one side of the substrate, and the adhesive layer of another laminated sheet prepared in the same manner is laminated to the other side of the substrate to transfer and laminate together, and then the laminate is cured for two days under conditions of 40° C. and 50% RH to produce an adhesive sheet having adhesive layers on both sides of the substrate.
  • the preferred lower limit of the thickness of the pressure-sensitive adhesive sheet of the present invention is 1 ⁇ m, and the preferred upper limit is 100 ⁇ m.
  • the thickness of the pressure-sensitive adhesive sheet of the present invention being 1 ⁇ m or more, the adhesive strength of the obtained pressure-sensitive adhesive layer is further improved, and the pressure-sensitive adhesive sheet of the present invention has better bending resistance and adhesive strength, and when left to stand while bending, peeling from the adherend can be further suppressed.
  • the thickness of the pressure-sensitive adhesive sheet of the present invention being 100 ⁇ m or less, it is a preferred embodiment in which bending is not hindered by compression deformation occurring at the bending part.
  • the more preferred lower limit of the thickness of the pressure-sensitive adhesive sheet of the present invention is 5 ⁇ m, the more preferred upper limit is 75 ⁇ m, the even more preferred lower limit is 10 ⁇ m, and the even more preferred upper limit is 50 ⁇ m.
  • the adhesive sheet of the present invention has excellent bending resistance and is unlikely to peel off or float even when repeatedly bent, so it can be suitably used for optical films of flexible displays applied to flexible devices such as bendable image display devices.
  • the adhesive sheet of the present invention does not peel off or float even when repeatedly bent, even when the bending operation increases the deformation amount of the adhesive layer, so it can be more suitably used for optical films in which the deformation amount of the adhesive layer increases when bending operations are performed, such as optical films for large-screen or thin flexible displays.
  • the present invention provides an adhesive sheet that has excellent bending resistance and is unlikely to peel off or float even when repeatedly bent.
  • FIG. 2 is a schematic diagram showing a method for testing cohesive strength.
  • the organic phases obtained by the first and second liquid-liquid separation extractions were mixed, and the mixture was washed in turn with 50 mL of 1M hydrochloric acid, 50 mL of water, and 50 mL of saturated saline.
  • Sodium sulfate was added to the washed organic phase and dried, after which the sodium sulfate was filtered, and the filtrate was concentrated with an evaporator to remove the organic solvent under reduced pressure.
  • Example 1 (Preparation of Copolymer-Containing Solution) A mixture of structural unit monomers of block (A) consisting of 7.28 g of styrene (St) and 0.72 g of acrylic acid (AAc), 0.19 g of a RAFT agent (R1), and 0.035 g of 2,2'-azobis(2-methylbutyronitrile) (ABN-E) as a polymerization initiator were placed in a two-neck flask, and the flask was heated to 85°C while replacing the atmosphere with nitrogen gas. Thereafter, the mixture was stirred at 85°C for 6 hours to carry out a polymerization reaction (first-stage reaction).
  • the mixture was stirred at 85°C for 6 hours to carry out a polymerization reaction (second stage reaction), and a copolymer-containing solution containing a copolymer (1) consisting of block (A) and block (B) was obtained.
  • the blending amounts of the mixture of the constituent unit monomers of block (B) and block (A) were such that the content ratio of block (A) in the obtained copolymer (1) was 8.00% by mass.
  • the copolymer (1) was a triblock copolymer.
  • this measurement sample was supplied to a gel permeation chromatograph (manufactured by Waters, "2690 Separations Module") and GPC measurement was performed under conditions of a sample flow rate of 1 mL/min and a column temperature of 40 ° C., and the polystyrene-equivalent molecular weight of the copolymer was measured to obtain the weight average molecular weight of the copolymer.
  • the results are shown in Table 1.
  • the obtained copolymer-containing solution was applied to the release-treated surface of a polyethylene terephthalate (PET) film, one side of which had been release-treated, and dried for 5 minutes at 110° C. to produce a laminated film having a 50 ⁇ m-thick adhesive layer. Furthermore, a pressure-sensitive adhesive sheet was obtained by laminating the release-treated surface of the PET film, one side of which had been release-treated, on the laminated film so that the release-treated surface faced the adhesive layer.
  • PET polyethylene terephthalate
  • the obtained measurement sample was subjected to dynamic viscoelasticity measurement in a shear mode under a nitrogen atmosphere at a measurement temperature of -50°C to 200°C, a heating rate of 5°C/min, and a frequency of 1 Hz using a dynamic viscoelasticity measuring device (manufactured by IT Measurement & Control Co., Ltd., "DVA-200") to obtain the shear storage modulus G' of the pressure-sensitive adhesive layer at -20°C, 25°C, and 85°C.
  • DVA-200 dynamic viscoelasticity measuring device
  • the obtained pressure-sensitive adhesive sheet was cut into a planar rectangular shape of 10 mm width x 20 mm length, and subjected to the cohesive strength test shown in Fig. 1.
  • SUS plates 21 and 22 both SUS304 plates washed with ethanol and then wiped dry) at 80°C were bonded with the cut pressure-sensitive adhesive sheet 1, and one end of the SUS plate 22 bonded to the lower surface was fixed with a clamp 3.
  • the weight 4 was removed from the SUS plate 21, and the stress of 10 kPa was released, and then the displacement ⁇ 2 in the shear direction of the pressure-sensitive adhesive sheet 1 3 minutes after the time t1 (time t2 ) was precisely measured in the same manner as the displacement ⁇ 1 .
  • the shear strain after 3 minutes of loading the pressure-sensitive adhesive sheet with a stress of 10 kPa, and the shear deformation recovery rate after 3 minutes of releasing the stress of 10 kPa were calculated from the following formulas (I) and (II). The results are shown in Table 4.
  • Shear strain (%) 100 x ⁇ 1 /h (I)
  • Shear deformation recovery rate (%) 100 x ⁇ ( ⁇ 1 /h) - ( ⁇ 2 /h) ⁇ /( ⁇ 1 /h) (II) ( ⁇ 1 : displacement of the adhesive sheet 1 in the shear direction at time t 1 , ⁇ 2 : displacement of the adhesive sheet 1 in the shear direction at time t 2 , h: thickness of the adhesive sheet 1 )
  • the obtained adhesive sheet was cut into a flat rectangular shape with a width of 25 mm and a length of 100 mm.
  • One PET film of the cut adhesive sheet was peeled off, and the sheet was rolled back and forth at a speed of 10 mm/min using a rubber roller to attach it to a 75 ⁇ m thick polyimide film (manufactured by Toray DuPont Co., Ltd., "Kapton", 50 mm x 150 mm) fixed on a 2 mm thick SUS plate.
  • the sheet was then aged for 20 minutes in an environment of 23°C and 50% RH to obtain a test sample.
  • Example 2 In the above-mentioned "(Preparation of copolymer-containing solution)", a mixture of 59.8 g of butyl acrylate (BA) and 32.2 g of lauryl acrylate (LA) was added as the mixture of structural unit monomers of block (B), and the same procedure as in Example 1 was used to prepare a copolymer-containing solution containing copolymer (2), produce a pressure-sensitive adhesive sheet, and perform measurements. The blending amounts of the mixture of structural unit monomers of block (B) and block (A) were such that the content ratio of block (A) in the obtained copolymer (2) was 8.00% by mass. The copolymer (2) was a triblock copolymer. The results are shown in Tables 1 and 4.
  • Example 3 In the above-mentioned "(Preparation of copolymer-containing solution)", the flask was heated to 80°C while replacing with nitrogen gas in the second-stage reaction, and then the polymerization reaction was carried out by stirring at 80°C for 7 hours.
  • a copolymer-containing solution containing copolymer (3) was prepared, a pressure-sensitive adhesive sheet was produced, and measurements were performed.
  • the blending amounts of the mixture of structural unit monomers of block (B) and block (A) were set so that the content ratio of block (A) in the obtained copolymer (3) was 8.00 mass%.
  • the copolymer (3) was a triblock copolymer. The results are shown in Tables 1 and 4.
  • Example 4 In the above-mentioned "(Preparation of copolymer-containing solution)", a mixture consisting of 9.1 g of styrene (St) and 0.9 g of acrylic acid (AAc) was added as a mixture of constituent unit monomers of block (A), and a mixture consisting of 69.0 g of 2-ethylhexyl acrylate (2EHA) and 23.0 g of lauryl acrylate (LA) was added as a mixture of constituent unit monomers of block (B). Otherwise, a copolymer-containing solution containing copolymer (4) was prepared in the same manner as in Example 1, a pressure-sensitive adhesive sheet was produced, and measurements were performed.
  • St styrene
  • AAc acrylic acid
  • EHA 2-ethylhexyl acrylate
  • LA lauryl acrylate
  • copolymer (4) was a triblock copolymer. The results are shown in Tables 1 and 4.
  • Example 5 In the above-mentioned "(Preparation of copolymer-containing solution)", a mixture of 9.1 g of styrene (St) and 0.9 g of acrylic acid (AAc) was added as a mixture of the constituent unit monomers of block (A), and a mixture of 50.6 g of butyl acrylate (BA) and 41.4 g of lauryl acrylate (LA) was added as a mixture of the constituent unit monomers of block (B). Otherwise, a copolymer-containing solution containing copolymer (5) was prepared in the same manner as in Example 1, a pressure-sensitive adhesive sheet was produced, and measurements were performed.
  • St styrene
  • AAc acrylic acid
  • BA butyl acrylate
  • LA lauryl acrylate
  • copolymer (5) was a triblock copolymer. The results are shown in Tables 1 and 4.
  • Example 6 In the above-mentioned "(Preparation of copolymer-containing solution)", 9.1 g of styrene (St) and 0.9 g of acrylic acid (AAc) were added as a mixture of structural unit monomers of block (A), and a mixture consisting of 59.8 g of butyl acrylate (BA) and 32.2 g of isostearyl acrylate (ISTA) was added as a mixture of structural unit monomers of block (B). Other than that, a copolymer-containing solution containing copolymer (6) was prepared in the same manner as in Example 1, a pressure-sensitive adhesive sheet was produced, and measurements were performed.
  • copolymer (6) was a triblock copolymer. The results are shown in Tables 1 and 4.
  • Example 7 In the above-mentioned “(Preparation of copolymer-containing solution)", a mixture of 9.1 g of styrene (St) and 0.9 g of acrylic acid (AAc) was added as a mixture of the constituent unit monomers of block (A), and a mixture of 59.8 g of butyl acrylate (BA) and 32.2 g of lauryl acrylate (LA) was added as a mixture of the constituent unit monomers of block (B). Otherwise, a copolymer-containing solution containing copolymer (7) was prepared in the same manner as in Example 1, a pressure-sensitive adhesive sheet was produced, and measurements were performed.
  • St styrene
  • AAc acrylic acid
  • BA butyl acrylate
  • LA lauryl acrylate
  • copolymer (7) was a triblock copolymer. The results are shown in Tables 1 and 4.
  • Example 8 In the above-mentioned "(Preparation of copolymer-containing solution)", a mixture of 9.1 g of styrene (St) and 0.9 g of acrylic acid (AAc) was added as a mixture of the constituent unit monomers of block (A), and a mixture of 59.8 g of butyl acrylate (BA), 31.28 g of lauryl acrylate (LA), and 0.92 g of maleic anhydride was added as a mixture of the constituent unit monomers of block (B). Otherwise, a copolymer-containing solution containing copolymer (8) was prepared in the same manner as in Example 1, a pressure-sensitive adhesive sheet was produced, and measurements were performed.
  • St styrene
  • AAc acrylic acid
  • copolymer (8) was a triblock copolymer. The results are shown in Tables 1 and 4.
  • copolymer (9) was a triblock copolymer. The results are shown in Tables 1 and 4.
  • Example 10 In the above-mentioned "(Preparation of copolymer-containing solution)", a mixture of 9.1 g of styrene (St) and 0.9 g of acrylic acid (AAc) was added as a mixture of the constituent unit monomers of block (A), and a mixture of 59.8 g of butyl acrylate (BA), 31.28 g of lauryl acrylate (LA), and 0.92 g of acrylic acid (AAc) was added as a mixture of the constituent unit monomers of block (B). Otherwise, a copolymer-containing solution containing copolymer (10) was prepared in the same manner as in Example 1, a pressure-sensitive adhesive sheet was produced, and measurements were performed.
  • St styrene
  • AAc acrylic acid
  • Example 11 In the above-mentioned "(Preparation of copolymer-containing solution)", a mixture of 11.3 g of styrene (St) and 1.1 g of acrylic acid (AAc) was added as a mixture of structural unit monomers of block (A), and a mixture of 74.1 g of butyl acrylate (BA), 38.8 g of lauryl acrylate (LA), and 1.14 g of maleic anhydride was added as a mixture of structural unit monomers of block (B). Otherwise, a copolymer-containing solution containing copolymer (11) was prepared in the same manner as in Example 1, a pressure-sensitive adhesive sheet was produced, and measurements were performed.
  • St styrene
  • AAc acrylic acid
  • copolymer (11) was a triblock copolymer. The results are shown in Tables 2 and 5.
  • Example 12 In the above-mentioned "(Preparation of copolymer-containing solution)", a mixture of 5.95 g of styrene (St) and 0.59 g of acrylic acid (AAc) was added as a mixture of the constituent unit monomers of block (A), and a mixture of 39.13 g of butyl acrylate (BA), 20.5 g of lauryl acrylate (LA), and 0.50 g of maleic anhydride was added as a mixture of the constituent unit monomers of block (B). Otherwise, a copolymer-containing solution containing copolymer (12) was prepared in the same manner as in Example 1, a pressure-sensitive adhesive sheet was produced, and measurements were performed.
  • St styrene
  • AAc acrylic acid
  • the blending amounts of the mixture of the constituent unit monomers of block (B) and block (A) were such that the content ratio of block (A) in the obtained copolymer (12) was 9.80% by mass.
  • the copolymer (12) was a triblock copolymer. The results are shown in Tables 2 and 5.
  • Example 13 In the above-mentioned "(Preparation of copolymer-containing solution)", a mixture of 13.65 g of styrene (St) and 1.35 g of acrylic acid (AAc) was added as a mixture of the constituent unit monomers of block (A), and a mixture of 59.8 g of butyl acrylate (BA), 31.28 g of lauryl acrylate (LA), and 0.92 g of maleic anhydride was added as a mixture of the constituent unit monomers of block (B). Otherwise, a copolymer-containing solution containing copolymer (13) was prepared in the same manner as in Example 1, a pressure-sensitive adhesive sheet was produced, and measurements were performed.
  • St styrene
  • AAc acrylic acid
  • the blending amounts of the mixture of the constituent unit monomers of block (B) and block (A) were set so that the content ratio of block (A) in the obtained copolymer (13) was 14.0% by mass.
  • the copolymer (13) was a triblock copolymer. The results are shown in Tables 2 and 5.
  • Example 14 In the above-mentioned "(Preparation of copolymer-containing solution)", a mixture of 9.60 g of styrene (St) and 0.95 g of acrylic acid (AAc) was added as a mixture of the constituent unit monomers of block (A), and a mixture of 42.1 g of butyl acrylate (BA), 22.0 g of lauryl acrylate (LA), and 0.65 g of maleic anhydride was added as a mixture of the constituent unit monomers of block (B). Otherwise, a copolymer-containing solution containing copolymer (14) was prepared in the same manner as in Example 1, a pressure-sensitive adhesive sheet was produced, and measurements were performed.
  • St styrene
  • AAc acrylic acid
  • the blending amounts of the mixture of the constituent unit monomers of block (B) and block (A) were such that the content ratio of block (A) in the obtained copolymer (14) was 9.80% by mass.
  • the copolymer (14) was a triblock copolymer. The results are shown in Tables 2 and 5.
  • Example 15 In the above-mentioned "(Preparation of copolymer-containing solution)", a mixture of 9.1 g of styrene (St) and 0.9 g of 2-hydroxyethyl acrylate (HEA) was added as a mixture of structural unit monomers of block (A), and a mixture of 59.8 g of butyl acrylate (BA), 31.28 g of lauryl acrylate (LA), and 0.92 g of maleic anhydride was added as a mixture of structural unit monomers of block (B).
  • a copolymer-containing solution containing copolymer (15) was prepared in the same manner as in Example 1, a pressure-sensitive adhesive sheet was produced, and measurements were performed.
  • copolymer (15) was a triblock copolymer. The results are shown in Tables 2 and 5.
  • Example 16 In the above-mentioned "(Preparation of copolymer-containing solution)", a mixture of 9.1 g of styrene (St), 0.9 g of 2-hydroxyethyl acrylate (HEA), and 0.9 g of acrylic acid (AAc) was added as a mixture of structural unit monomers of block (A), and a mixture of 59.8 g of butyl acrylate (BA), 31.28 g of lauryl acrylate (LA), and 0.92 g of maleic anhydride was added as a mixture of structural unit monomers of block (B).
  • a copolymer-containing solution containing copolymer (16) was prepared under the same conditions as in Example 1.
  • the blending amounts of the mixture of structural unit monomers of block (B) and block (A) were such that the content ratio of block (A) in the obtained copolymer (16) was 9.89% by mass.
  • the copolymer (16) was a triblock copolymer.
  • Example 17 In the above-mentioned "(Preparation of copolymer-containing solution)", a mixture of 16.4 g of styrene (St), 1.8 g of 2-hydroxyethyl acrylate (HEA), and 1.8 g of acrylic acid (AAc) was added as a mixture of structural unit monomers of block (A), and a mixture of 119.6 g of butyl acrylate (BA), 62.56 g of lauryl acrylate (LA), and 1.84 g of maleic anhydride was added as a mixture of structural unit monomers of block (B).
  • a copolymer-containing solution containing copolymer (17) was prepared under the same conditions as in Example 1.
  • the blending amounts of the mixture of structural unit monomers of block (B) and block (A) were such that the content ratio of block (A) in the obtained copolymer (17) was 9.89% by mass.
  • the copolymer (17) was a triblock copolymer.
  • Example 18 In the same manner as in Example 8, a copolymer-containing solution containing copolymer (8) was prepared. Further, in “(Preparation of adhesive sheet)", 0.92 g of Coronate L-45E (manufactured by Tosoh Corporation) as an isocyanate curing agent and 0.5 g of KBM-403 (manufactured by Shin-Etsu Chemical Co., Ltd.) as a silane coupling agent were added to the copolymer-containing solution containing copolymer (8) per 100 g of copolymer (8), and the resulting adhesive solution was thoroughly stirred and applied to a PET film.
  • Coronate L-45E manufactured by Tosoh Corporation
  • KBM-403 manufactured by Shin-Etsu Chemical Co., Ltd.
  • the adhesive solution was then dried at 110°C for 5 minutes, and then aged at 40°C and 50% RH for 48 hours to obtain an adhesive sheet having an adhesive layer with a thickness of 50 ⁇ m. Other than that, the measurements were carried out in the same manner as in Example 1. The results are shown in Tables 1 and 5.
  • a copolymer-containing solution containing copolymer (18) was prepared under the same conditions as in Example 1. The amounts of the mixture of structural unit monomers of block (B) and block (A) were set so that the content of block (A) in the resulting copolymer (18) was 9.89% by mass.
  • the copolymer (18) was a triblock copolymer.
  • a copolymer-containing solution containing copolymer (27) was prepared in the same manner as in Example 1, a pressure-sensitive adhesive sheet was produced, and measurements were performed.
  • the blending amounts of the mixture of structural unit monomers of block (B) and block (A) were such that the content ratio of block (A) in the obtained copolymer (27) was 9.89% by mass.
  • copolymer (27) was a triblock copolymer. The results are shown in Tables 3 and 5.
  • a copolymer-containing solution containing copolymer (28) was prepared in the same manner as in Example 1, a pressure-sensitive adhesive sheet was produced, and measurements were performed.
  • the blending amounts of the mixture of structural unit monomers of block (B) and block (A) were such that the content ratio of block (A) in the obtained copolymer (28) was 9.89% by mass.
  • copolymer (28) was a triblock copolymer. The results are shown in Tables 3 and 5.
  • the blending amounts of the mixture of structural unit monomers of block (B) and block (A) were set so that the content ratio of block (A) in the obtained copolymer (21) was 9.80% by mass.
  • the copolymer (21) was a triblock copolymer. The results are shown in Tables 3 and 6.
  • the blending amounts of the mixture of the constituent unit monomers of block (B) and block (A) were such that the content ratio of block (A) in the obtained copolymer (22) was 9.80% by mass.
  • the copolymer (22) was a triblock copolymer. The results are shown in Tables 3 and 6.
  • copolymer (23) was a triblock copolymer. The results are shown in Tables 3 and 6.
  • the obtained adhesive solution was applied to the release-treated surface of a polyethylene terephthalate (PET) film, one side of which had been release-treated, and ultraviolet light was irradiated from a gallium-filled metal halide lamp ("Light HAMMER10" manufactured by Fusion UV Systems) at a peak illuminance of 1600 mW/ cm2 and an accumulated dose of 1000 mJ/ cm2 (wavelength 254 nm) to produce a laminated film having an adhesive layer of 50 ⁇ m in thickness. Furthermore, a pressure-sensitive adhesive sheet was obtained by laminating the release-treated surface of the PET film, one side of which had been release-treated, on the laminated film so that it faced the adhesive layer.
  • a gallium-filled metal halide lamp (“Light HAMMER10" manufactured by Fusion UV Systems)
  • a solution (S1) was prepared by dissolving 10 g of polyvinylpyrrolidone (PVP) in 90 g of 4-hydroxybutyl acrylate. 0.1 g of the obtained solution (S1) (polyvinylpyrrolidone: 0.01 g, 4-hydroxybutyl acrylate 0.09 g) and 0.3 g of 1-hydroxycyclohexyl phenyl ketone as a photopolymerization initiator were added to the copolymer-containing solution containing the obtained copolymer (26) per 100 g of the copolymer (26) to obtain a pressure-sensitive adhesive solution.
  • PVP polyvinylpyrrolidone
  • the obtained adhesive solution was applied to the release-treated surface of a polyethylene terephthalate (PET) film, one side of which had been release-treated, and ultraviolet light was irradiated at a peak illuminance of 1600 mW/cm 2 and an accumulated dose of 1000 mJ/cm 2 (wavelength 254 nm) using a gallium-filled metal halide lamp (Fusion UV Systems, "Light HAMMER10" to synthesize copolymer (C2), and a laminated film was produced in which an adhesive layer having a thickness of 50 ⁇ m was formed containing copolymer (C2). Furthermore, a pressure-sensitive adhesive sheet was obtained by laminating the release-treated surface of the PET film, one side of which had been release-treated, on the laminated film so as to face the adhesive layer.
  • PTT polyethylene terephthalate
  • the PET film on one side of the obtained adhesive sheet was peeled off and bonded to a 75 ⁇ m thick polyimide film (manufactured by Toray DuPont Co., Ltd., "Kapton 200H”), and the PET film on the other side of the bonded adhesive sheet was peeled off and bonded to a similar polyimide film having a thickness of 75 ⁇ m. This was repeated to produce a laminate with a total thickness of 375 ⁇ m, and the obtained laminate was made into a size of 20 ⁇ 80 mm to produce a test sample.
  • a 75 ⁇ m thick polyimide film manufactured by Toray DuPont Co., Ltd., "Kapton 200H
  • the obtained test sample was set in a thermostatic U-shaped stretch tester (manufactured by Yuasa System Co., Ltd., "ETS with chamber”) with a thermostatic chamber set at 25 ° C. so that the approximate center of the long side of the test sample was the bending part, and a dynamic bending test was performed under the conditions of 25 ° C., 50% RH, bending radius 2.0 mm, and bending speed 60 times / min.
  • the U-shaped stretch tester used in this evaluation has a mechanism for repeatedly bending the material into a U-shape by 180° without any load on the surface, and the bending radius can be adjusted by adjusting the distance between the surfaces bent into the U-shape.
  • test samples were collected after repeatedly bending 100,000 times and 200,000 times, and peeling or cracking at the bent portion was observed using a digital microscope (Keyence Corporation, "VHX-6000").
  • the bending resistance of the pressure-sensitive adhesive sheet was evaluated as follows: “ ⁇ ” indicates that no peeling or cracking occurred in the sample after bending 200,000 times; “ ⁇ ” indicates that peeling or cracking occurred in the sample after bending 200,000 times but no peeling or cracking occurred in the sample after bending 100,000 times; and " ⁇ ” indicates that peeling or cracking occurred in the sample after bending 100,000 times.
  • the samples after the test were collected, and peeling or cracking at the bent portion was observed with a digital microscope (Keyence Corporation, "VHX-6000").
  • the bending resistance of the pressure-sensitive adhesive sheet was evaluated as follows: “ ⁇ " indicates that there was no peeling or cracking at a bending radius of 0.5 mm; “ ⁇ ” indicates that peeling or cracking occurred at a bending radius of 0.5 mm but no peeling or cracking occurred at a bending radius of 2.0 mm; and “ ⁇ ” indicates that peeling or cracking occurred at a bending radius of 2.0 mm. Even if the evaluation is "x”, the pressure-sensitive adhesive sheet of the present invention can be used without problems depending on the application.
  • the present invention provides an adhesive sheet that has excellent bending resistance and is unlikely to peel off or float even when repeatedly bent.

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JP2018524425A (ja) * 2015-06-03 2018-08-30 スリーエム イノベイティブ プロパティズ カンパニー フレキシブルディスプレイ用のアクリルブロックコポリマー系アセンブリ層
JP2021059644A (ja) * 2019-10-03 2021-04-15 東亞合成株式会社 粘着剤組成物及び粘着シート
WO2021117723A1 (ja) * 2019-12-13 2021-06-17 東洋インキＳｃホールディングス株式会社 ブロック共重合体、樹脂組成物、伸縮性導体、電子デバイスおよび粘着フィルム
JP2022189944A (ja) * 2022-10-28 2022-12-22 株式会社クラレ ホットメルト型粘着剤組成物
JP7491456B1 (ja) * 2023-10-30 2024-05-28 ａｒｔｉｅｎｃｅ株式会社 フレキシブルディスプレイ用粘着シート、フレキシブルディスプレイ用積層体、およびフレキシブルディスプレイ

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