Adhesive sheet

Abstract

The purpose of the present invention is to provide an adhesive sheet which has excellent bending resistance and which is not susceptible to peeling and floating even when repeated bending operations are performed. The present invention relates to an adhesive sheet having an adhesive layer, the adhesive sheet being subjected to a cohesive force test of a series of steps in which SUS plates are adhered to the upper and lower surfaces of the adhesive sheet, and the SUS plates are adhered to the upper and lower surfaces of the adhesive sheet. A cohesion test is performed until a time point (time point t2) at which a stress of 10 kPa is applied to the SUS plate on the upper surface for 3 minutes in the shear direction and the stress of 10 kPa is unloaded immediately after the time point (time point t1) and the SUS plate is left to stand for 3 minutes, the shear strain at the time point t1 being 250% or more, and the shear deformation recovery rate at the time point t2 being 80% or more.

Description

Technical Field

[0001] This invention relates to adhesive sheets. Background Technology

[0002] In portable electronic devices such as mobile phones and personal digital assistants (PDAs), 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).

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2009-242541

[0006] Patent Document 2: Japanese Patent Application Publication No. 2009-258274

[0007] Patent Document 3: Japanese Patent Application Publication No. 2012-214544 Summary of the Invention

[0008] The problem that the invention aims to solve

[0009] For adhesive sheets used in flexible displays that are capable of bending image display devices, such as optical films and optical film laminates with adhesive layers, in addition to the optical properties and durability required for conventional flat-panel display panels, it is also required that the optical film will not peel off or lift even when bending operations that deform the optical film are performed.

[0010] Therefore, in the past, for adhesive sheets used in the optical films of flexible displays, bending resistance was improved by adjusting the shear storage modulus of the adhesive layer to an appropriate range, making it less prone to peeling or lifting even during bending operations. This is because, when the shear storage modulus is within an appropriate range, the adhesive layer can easily undergo shear deformation even during bending operations, thus mitigating the small deformation stresses applied to the adhesive sheet.

[0011] However, in the future, with the research and application of bendable image display devices to achieve larger screen sizes, thinner designs, and rollable devices, the deformation of the adhesive layer increases during bending operations on such bendable image display devices, resulting in greater deformation stress on the adhesive sheet. As a result, even adjusting the shear storage modulus of the adhesive layer to an appropriate range cannot alleviate the deformation stress on the adhesive sheet, and sometimes peeling and lifting occur even during bending operations.

[0012] The purpose of this invention is to provide an adhesive sheet with excellent bending resistance that is not easily peeled or lifted even when repeatedly bent.

[0013] Methods for solving problems

[0014] This disclosure 1 relates to an adhesive sheet having an adhesive layer. When conducting a series of cohesive force tests on the adhesive sheet, the series of processes is as follows: starting from the state where SUS plates are attached to the upper and lower surfaces of the adhesive sheet, until the time point t1 (time point 1) when a stress of 10 kPa is applied to the SUS plate on the upper surface in the shear direction for 3 minutes, the stress of 10 kPa is immediately unloaded and the sheet is left to stand for 3 minutes (time point t2), the shear strain at the time point t1 is 250% or more, and the shear deformation recovery rate at the time point t2 is 80% or more.

[0015] This disclosure 2 relates to the adhesive sheet of this disclosure 1, wherein the shear deformation recovery rate at the aforementioned time point t2 is 90% or more.

[0016] This disclosure 3 relates to the adhesive sheet of disclosure 1 or 2, wherein the shear strain at the aforementioned time point t1 is 300% or more.

[0017] This disclosure 4 relates to adhesive sheets of disclosure 1, 2 or 3, having a 180° peel strength to polyimide of 10.0 N / 25 mm or more.

[0018] This disclosure 5 relates to the adhesive sheet of this disclosure 4, which has a 180° peel strength of 14.0 N / 25 mm or more against polyimide.

[0019] This disclosure 6 relates to an adhesive sheet of disclosure 1, 2, 3, 4 or 5, wherein the adhesive layer comprises a block copolymer comprising a block (A) and a block (B), the block (A) having a structural unit derived from a monomer component (a) being at least one selected from styrene and (meth)acrylates having a cyclic structure, and the block (B) having a structural unit derived from a monomer component (b) being a (meth)acrylate represented by the following formula (1).

[0020] This disclosure 7 relates to the adhesive sheet of this disclosure 6, wherein the block (A) further has a structural unit derived from a monomer containing a polar functional group.

[0021] This disclosure 8 relates to the adhesive sheet of this disclosure 7, wherein the block (A) further has a structural unit derived from (meth)acrylic acid.

[0022] This disclosure 9 relates to an adhesive sheet of disclosure 6, 7 or 8, wherein the structural unit derived from monomer component (a) in the block (A) contains 80% by mass or more.

[0023] This disclosure 10 relates to adhesive sheets of disclosures 6, 7, 8 or 9, wherein the structural unit derived from monomer component (b) in the block (B) is present in a proportion of 20% by mass or more and 45% by mass or less.

[0024] This disclosure 11 relates to adhesive sheets of disclosures 6, 7, 8, 9 or 10, wherein the block (B) further comprises a structural unit derived from an olefin polymer having a polymerizable unsaturated double bond at the end, wherein the structural unit derived from the olefin polymer having a polymerizable unsaturated double bond at the end comprises 5% by mass or more and 30% by mass or less in the block (B).

[0025] This disclosure 12 relates to adhesive sheets of disclosures 6, 7, 8, 9, 10 or 11, wherein the block copolymers have structural units derived from monomers containing polar functional groups.

[0026] This disclosure 13 relates to an adhesive sheet of this disclosure 12, wherein the block copolymer has structural units derived from (meth)acrylic acid.

[0027] This disclosure 14 relates to adhesive sheets of disclosures 6, 7, 8, 9, 10, 11, 12 or 13, wherein the block copolymer is an ABA-type triblock structure in which the block (B) is sandwiched between the block (A).

[0028] This disclosure 15 relates to adhesive sheets of disclosures 6, 7, 8, 9, 10, 11, 12, 13 or 14, wherein the block copolymer contains a content of block (A) of 7.25% by mass or more and 15% by mass or less.

[0029] This disclosure 16 relates to adhesive sheets of disclosures 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 less than 1,000,000.

[0030] This disclosure 17 relates to adhesive sheets of disclosures 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 or 16, wherein the solubility parameter (SP value) of the block copolymer is 9.30 (J / cm³). 3 ) 1 / 2 above.

[0031] This disclosure 18 relates to an adhesive sheet having an adhesive layer comprising a block copolymer including blocks (A) and blocks (B), wherein the blocks (A) have structural units derived from monomer component (a), said monomer component (a) being at least one selected from styrene and (meth)acrylate having a cyclic structure, and the blocks (B) have structural units derived from monomer component (b), said monomer component (b) being a (meth)acrylate represented by the following formula (1), wherein the content of the structural units derived from monomer component (a) in the blocks (A) is 80% by mass or more, the content of the structural units derived from monomer component (b) in the blocks (B) is 20% by mass or more and 45% by mass or less, and the content of the blocks (A) in the block copolymer is 7.25% by mass or more and 15% by mass or less.

[0032] This disclosure 19 relates to the adhesive sheet of this disclosure 18, wherein the block (B) further comprises a structural unit derived from an olefin polymer having a polymerizable unsaturated double bond at the end, wherein the structural unit derived from the olefin polymer having a polymerizable unsaturated double bond at the end comprises 5% by mass or more and 30% by mass or less in the block (B).

[0033] This disclosure 20 relates to an adhesive sheet of this disclosure 18 or 19, wherein the block copolymer is an ABA-type triblock structure in which the block (B) is sandwiched between the block (A).

[0034] This disclosure 21 relates to adhesive sheets of disclosures 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.

[0035] This disclosure 22 relates to adhesive sheets of disclosures 18, 19, 20, or 21, wherein the solubility parameter (SP value) of the block copolymer is 9.30 (J / cm³). 3 ) 1 / 2 above.

[0036] This disclosure 23 relates to adhesive sheets of disclosures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21 or 22 that do not have a substrate.

[0037] [Chemical Formula 1]

[0038]

[0039] In equation (1), R 1 R represents a hydrogen atom or a methyl group. 2 It indicates an alkyl group with 9 or more carbon atoms.

[0040] The present invention will now be described in detail.

[0041] The inventors investigated adhesive sheets by adjusting the shear strain under a specific stress for a certain period of time and the shear deformation recovery rate after unloading the stress for a certain period of time to specific values. The results showed that an adhesive sheet with excellent bending resistance, which is not easily peeled or lifted even after repeated bending operations, was obtained, thus completing this invention.

[0042] The adhesive sheet of the present invention is not prone to peeling or lifting during bending operations with small deformation, and it is also not prone to peeling or lifting even during bending operations with large deformation.

[0043] The adhesive sheet of the present invention has an adhesive layer. When the adhesive sheet is subjected to a series of cohesive force tests, the series of processes are as follows: from the state where SUS plates are attached to the upper and lower surfaces of the adhesive sheet, until the time point t1 when a stress of 10 kPa is applied to the SUS plate on the upper surface in the shear direction for 3 minutes, the stress of 10 kPa is immediately unloaded and left to stand for 3 minutes (time point t2). The shear strain at the time point t1 is 250% or more, and the shear deformation recovery rate at the time point t2 is 80% or more.

[0044] exist Figure 1 The diagram shows a method for conducting a cohesive force test.

[0045] That is, such as Figure 1 As shown, SUS plates 21 and 22 (SUS304 plates cleaned with ethanol and then dry-rubbed) at 80°C were bonded to the upper and lower surfaces respectively using an adhesive sheet 1 with a width of 10mm and a length of 20mm. One end of the SUS plate 22 bonded to the lower surface was fixed with a clamp 3. While maintaining the SUS plates 21 and 22 at 80°C, a 200g weight 4 was suspended at one end of the SUS plate 21 bonded to the upper surface at a temperature of 23°C, and a stress of 10kPa was applied along the shear direction. After the stress of 10kPa was applied for 3 minutes (time point t1), the displacement δ1 of the adhesive sheet 1 in the shear direction was precisely measured using a micro-shear creep measuring device (manufactured by Asahi Seiko Corporation, "micro-shear creep measuring device"). Furthermore, after removing the weight 4 at time t1 and unloading the stress of 10 kPa, the displacement δ2 in the shear direction of the adhesive sheet 1 was precisely measured 3 minutes later (time t2) from time t1, just as the displacement δ1 was precisely measured. The shear strain of the adhesive sheet of the present invention at time t1 and the shear deformation recovery rate of the adhesive sheet of the present invention at time t2 were calculated according to the following formulas (I) and (II).

[0046] Shear strain (%) = 100 × δ¹ / h (I)

[0047] Shear deformation recovery rate (%) = 100 × { (δ1 / h) - (δ2 / h)} / (δ1 / h) (II)

[0048] (δ1: Displacement in the shear direction at time point t1 of adhesive sheet 1, δ2: Displacement in the shear direction at time point t2 of adhesive sheet 1, h: Thickness of adhesive sheet 1)

[0049] It should be noted that, in the case where the adhesive sheet of the present invention has adhesive layers on both sides and the adhesive layers on both sides are different, there are no particular limitations on the upper surface and the lower surface of the adhesive layer for the cohesion test. In addition, in the case where the adhesive sheet of the present invention is a single-sided adhesive sheet having a base material and an adhesive layer on one surface of the base material, the adhesive layer is used as the lower surface and adhered to the SUS plate ( Figure 1 the SUS plate 22 in Figure 1 ), and a 200 g weight is mounted on the base material at the upper surface (corresponding to the position of the SUS plate 21 in Figure 1 ) as described above to conduct the cohesion test.

[0050] The lower limit of the shear strain of the adhesive sheet of the present invention at the above-mentioned time point t1 is 250%. By making the shear strain of the adhesive sheet of the present invention at the above-mentioned time point t1 250% or more, the adhesive sheet of the present invention has excellent deformability, and thus the adhesive sheet of the present invention has excellent bending resistance, and peeling and lifting can be prevented even during bending operations. The preferred lower limit of the shear strain of the adhesive sheet of the present invention at the above-mentioned time point t1 is 300%, and the more preferred lower limit is 350%.

[0051] The preferred upper limit of the shear strain of the adhesive sheet of the present invention at the above-mentioned time point t1 is 500%. By making the shear strain of the adhesive sheet of the present invention at the above-mentioned time point t1 500% or less, the adhesive sheet of the present invention has more excellent recovery from deformation, and thus the adhesive sheet of the present invention can further prevent peeling and lifting even when bending operations are repeated. The more preferred upper limit of the shear strain of the adhesive sheet of the present invention at the above-mentioned time point t1 is 450%, and the further preferred upper limit is 400%.

[0052] As a method for adjusting the shear strain of the adhesive sheet of the present invention at the above-mentioned time point t1 to the above range, for example, there can be mentioned: a method of changing the composition of the block copolymer contained in the adhesive layer described later; a method of reducing the crosslinking degree between block copolymers by changing the type of curing agent or reducing the content of the curing agent; a method of increasing the weight-average molecular weight; a method of increasing the molecular weight between entanglement points (Japanese: 絡み合い点) of the block copolymer described later; a method of reducing the molecular weight distribution (Mw / Mn) etc. (Mw: Weight-average molecular weight, Mn: Number-average molecular weight)

[0053] It should be noted that the number-average molecular weight (Mn) and weight-average molecular weight (Mw) refer to the molecular weight converted from standard polystyrene based on GPC (Gel Permeation Chromatography). In the GPC method, for example, the 2690 Separations Module (manufactured by Waters Corporation) can be used. Specifically, the block copolymer is diluted 50-fold with tetrahydrofuran (THF), and the resulting dilution is filtered through a filter (material: polytetrafluoroethylene, pore size: 0.2 μm) to prepare the test sample. Next, the test sample is fed into a gel permeation chromatograph (e.g., the Waters Corporation "2690 Separations Module"), and GPC analysis is performed at a sample flow rate of 1 mL / min and a column temperature of 40 °C. The polystyrene-converted molecular weight of the block copolymer is determined, and this value is used as the weight-average molecular weight and number-average molecular weight of the block copolymer.

[0054] The lower limit of the shear deformation recovery rate of the adhesive sheet of the present invention at the aforementioned time point t2 is 80%. By achieving a shear deformation recovery rate of 80% or more at the aforementioned time point t2, the adhesive sheet of the present invention exhibits excellent deformation recovery properties, and can prevent peeling or lifting even after repeated bending operations. The preferred lower limit of the shear deformation recovery rate of the adhesive sheet of the present invention at the aforementioned time point t2 is 90%, and a more preferred lower limit is 95%.

[0055] Furthermore, the preferred upper limit of the shear deformation recovery rate of the adhesive sheet at the aforementioned time point t2 is 100%.

[0056] As a method for adjusting the shear deformation recovery rate of the adhesive sheet of the present invention at the aforementioned time point t2 to the aforementioned range, examples include: changing the composition of the block copolymer contained in the adhesive layer described later; reducing the molecular weight distribution (Mw / Mn); and using a curing agent to crosslink the block copolymers with each other.

[0057] The preferred lower limit of the 180° peel force of the adhesive sheet of the present invention on polyimide is 10.0 N / 25 mm. By making the 180° peel force of the adhesive sheet of the present invention on polyimide 10.0 N / 25 mm or more, the flexural resistance of the adhesive sheet of the present invention becomes more excellent, and peeling from the adhered object can be further suppressed even when it is placed in a bent state. From the viewpoint that peeling from the adhered object can be further suppressed even when the bending radius is increased, and that the thinness of the flexible device can be realized, the more preferred lower limit of the 180° peel force of the adhesive sheet of the present invention on polyimide is 14.0 N / 25 mm, and the more preferred lower limit is 20.0 N / 25 mm.

[0058] Furthermore, from the viewpoint of the deformability of the adhesive sheet of the present invention, there is no preferred upper limit to the 180° peel force of the adhesive sheet of the present invention on polyimide; the higher the better.

[0059] It should be noted that the 180° peel force of the adhesive sheet of the present invention against polyimide can be measured by performing a tensile test according to JIS Z0237 using a tensile testing machine (such as the "Autograph AGS-X" manufactured by Shimadzu Corporation).

[0060] As a method for adjusting the 180° peel force of the adhesive sheet of the present invention to polyimide to the above-mentioned range, examples include: changing the composition of the block copolymer contained in the adhesive layer described later; making the adhesive layer described later contain a tackifying resin; adding a silane coupling agent to the adhesive layer described later; adjusting the weight-average molecular weight of the block copolymer; adjusting the degree of crosslinking between the block copolymers by changing the type of curing agent and adjusting the content of the curing agent; adding particulate fillers to the adhesive layer described later; and foaming and structuring the adhesive layer.

[0061] The adhesive sheet of the present invention has an adhesive layer.

[0062] The adhesive layer described above preferably contains a block copolymer comprising blocks (A) and blocks (B), wherein the blocks (A) have structural units derived from monomer component (a), wherein the monomer component (a) is at least one selected from styrene and (meth)acrylate having a cyclic structure, and the blocks (B) have structural units derived from monomer component (b), wherein the monomer component (b) is (meth)acrylate represented by formula (1) above.

[0063] It should be noted that in this specification, "(meth)acrylic acid" refers to acrylic acid or methacrylic acid.

[0064] By incorporating block copolymers with blocks (A), the cohesive strength of the adhesive sheet of the present invention is increased, resulting in superior deformation recovery. The adhesive sheet of the present invention can further prevent peeling and lifting even under repeated bending operations. By incorporating block copolymers with blocks (B), the molecular weight between entanglement points of the molecules in the adhesive layer is increased, resulting in a larger free volume of the molecules. Therefore, the deformability of the resulting adhesive layer is improved. As a result, the flexural strength of the adhesive sheet of the present invention is improved, and peeling and lifting can be further prevented even under bending operations. Therefore, by incorporating blocks (A) and (B) into the block copolymer, the adhesive layer achieves both superior deformation recovery and superior deformability, resulting in superior flexural strength of the adhesive sheet of the present invention.

[0065] It should be noted that the molecular weight between entanglement points refers to the molecular weight between points of a physical bond known as entanglement, arising from the inability of long polymer chains to move laterally across each other. This molecular weight between entanglement points is represented by the product of the molecular weight Mv of the monomer units constituting the polymer backbone and the number of backbone bonds Nv between entanglement points.

[0066] From the viewpoint of the resilience of the adhesive sheet of the present invention to bending, the monomer component (a) mentioned above preferably contains styrene.

[0067] Furthermore, examples of cyclic (meth)acrylates include: benzyl (meth)acrylate, 2-phenoxyethyl (meth)acrylate, and other (meth)acrylates with aromatic ring structures such as cyclohexyl (meth)acrylate, dicyclopentyl (meth)acrylate, and isobornyl (meth)acrylate, and other (meth)acrylates with alicyclic structures such as benzoyl (meth)acrylate. From the viewpoint of further improving the resilience of the adhesive sheet of the present invention to bending, benzyl (meth)acrylate is preferred.

[0068] In the aforementioned block (A), the preferred lower limit for the content of the structural unit derived from monomer component (a) is 80% by mass. By making the content of the structural unit derived from monomer component (a) 80% by mass or more, the cohesive force of the resulting adhesive layer becomes greater, thus improving the recovery of deformation. The adhesive sheet of the present invention can further prevent peeling and lifting even under repeated bending operations. A more preferred lower limit for the content of the structural unit derived from monomer component (a) is 85% by mass, and a more preferably lower limit is 90% by mass.

[0069] In addition, there is no particular limit to the upper limit of the proportion of the structural units derived from the monomeric component (a) mentioned above, which can be 100 by mass.

[0070] It should be noted that, in the case of multiple structural units derived from monomeric component (a) mentioned above, the proportion of structural units derived from monomeric component (a) mentioned above refers to the total proportion of the structural units derived from monomeric component (a) contained therein.

[0071] The aforementioned block (A) preferably further comprises structural units derived from monomers containing polar functional groups. By making the aforementioned block (A) comprise structural units derived from monomers containing polar functional groups, the cohesive and adhesive forces of the resulting adhesive layer are increased, thus improving the resilience to deformation. The adhesive sheet of the present invention can further prevent peeling and lifting even under repeated bending operations. Furthermore, due to the increased interaction with the adhered object, the adhesive force of the adhesive sheet of the present invention is further improved.

[0072] Examples of monomers containing polar functional groups include, for instance, monomers containing carboxyl groups, monomers containing hydroxyl groups, monomers containing glycidyl groups, monomers containing amino groups, monomers containing amide groups, monomers containing nitrile groups, and monomers containing acid anhydride groups. From the viewpoint of further improving the bending resilience and adhesive strength of the adhesive sheet of the present invention, monomers containing carboxyl groups and monomers containing hydroxyl groups are preferred, and monomers containing carboxyl groups are more preferred.

[0073] Examples of the aforementioned carboxyl-containing monomers include unsaturated carboxylic acids such as (meth)acrylic acid, itaconic acid, crotonic acid, maleic acid, and fumaric acid. Among these, from the viewpoint of the deformability of the resulting adhesive layer, monomers with small molecular weight and few carbon atoms are preferred, and (meth)acrylic acid (i.e., the aforementioned block (A) also has structural units derived from (meth)acrylic acid) is particularly preferred).

[0074] In the above-described block (A), the preferred lower limit for the content of the structural unit derived from the carboxyl-containing monomer is 5% by mass, and the preferred upper limit is 20% by mass. By making the content of the structural unit derived from the carboxyl-containing monomer in the above-described block (A) 5% by mass or more, the cohesive force and adhesive force of the resulting adhesive layer are greater, and therefore the recovery of deformation is more excellent. The adhesive sheet of the present invention can further prevent peeling and lifting even when repeatedly bent. By making the content of the structural unit derived from the carboxyl-containing monomer in the above-described block (A) 20% by mass or less, the deformability of the resulting adhesive layer and the adhesive sheet of the present invention is more excellent. As a result, the bending resistance of the adhesive sheet of the present invention is more excellent, and peeling and lifting can be further prevented even when bent. The more preferred lower limit for the content of the structural unit derived from the carboxyl-containing monomer in the above-described block (A) is 6.5% by mass, the more preferred upper limit is 15% by mass, the more preferably lower limit is 8% by mass, and the more preferably upper limit is 12% by mass.

[0075] Examples of hydroxyl-containing monomers include 4-hydroxybutyl methacrylate, 2-hydroxyethyl methacrylate, and N-hydroxyethyl acrylamide (HEAA), among other hydroxyl-containing methacrylates.

[0076] In the above-described block (A), the preferred lower limit for the content of the structural unit derived from the hydroxyl-containing monomer is 5% by mass, and the preferred upper limit is 20% by mass. By making the content of the structural unit derived from the hydroxyl-containing monomer in the above-described block (A) 5% by mass or more, the cohesive force of the resulting adhesive layer becomes greater, and therefore the recovery of deformation becomes more excellent. The adhesive sheet of the present invention can further prevent peeling and lifting even when repeatedly bent. By making the content of the structural unit derived from the hydroxyl-containing monomer in the above-described block (A) 20% by mass or less, the deformability of the resulting adhesive layer and the adhesive sheet of the present invention becomes more excellent. As a result, the bending resistance of the adhesive sheet of the present invention becomes more excellent, and peeling and lifting can be further prevented even when bent. The more preferred lower limit for the content of the structural unit derived from the hydroxyl-containing monomer in the above-described block (A) is 6.5% by mass, the more preferred upper limit is 15% by mass, the more preferably lower limit is 8% by mass, and the more preferably upper limit is 12% by mass.

[0077] Examples of monomers containing anhydride groups include maleic anhydride.

[0078] Examples of monomers containing glycidyl groups include glycidyl (meth)acrylate.

[0079] Examples of monomers containing amide groups include isopropyl (meth)acrylamide.

[0080] Examples of nitrile-containing monomers include acrylonitrile and methacrylonitrile.

[0081] In the aforementioned block (A), the preferred lower limit for the total content of the structural units derived from monomers containing polar functional groups is 5% by mass, and the preferred upper limit is 20% by mass. By ensuring that the total content of the structural units derived from monomers containing polar functional groups in the aforementioned block (A) is 5% by mass or more, the cohesive force of the resulting adhesive layer becomes greater, thus improving the recovery from deformation. The adhesive sheet of the present invention can further prevent peeling and lifting even under repeated bending operations. By ensuring that the total content of the structural units derived from monomers containing polar functional groups in the aforementioned block (A) is 20% by mass or less, the deformability of the resulting adhesive layer and the adhesive sheet of the present invention becomes more excellent. As a result, the adhesive sheet of the present invention exhibits better bending resistance, and peeling and lifting can be further prevented even under bending operations. The preferred lower limit of the total proportion of the structural units derived from the monomer containing polar functional groups in the above block (A) is 6.5% by mass, the preferred upper limit is 15% by mass, the further preferred lower limit is 8% by mass, and the further preferred upper limit is 12% by mass.

[0082] Examples of (meth)acrylates represented by formula (1) in block (B) above include: nonyl methacrylate, decyl methacrylate, lauryl methacrylate, tridecyl methacrylate, pentadecyl methacrylate, isostearyl methacrylate, etc. From the viewpoint of further improving the deformability of the adhesive sheet of the present invention, R in formula (1) above is more preferred. 2 The alkyl groups shown are lauryl acrylate (meth)acrylate, isostearyl acrylate (meth)acrylate, etc., with 12 or more carbon atoms.

[0083] Furthermore, from the viewpoint of the adhesive layer's resilience to deformation and its adhesive strength, R in the above equation (1) 2 The preferred upper limit for the number of carbon atoms in the alkyl group is 22, and the more preferred upper limit is 18.

[0084] In the aforementioned block (B), the preferred lower limit of the content ratio of the structural unit derived from monomer component (b) is 20% by mass, and the preferred upper limit is 45% by mass or less. By making the content ratio of the structural unit derived from monomer component (b) 20% by mass or more, the molecular weight of the molecules entangled with each other in the adhesive layer becomes larger, and therefore the free volume of the molecules becomes larger, resulting in better deformability of the adhesive layer. As a result, the flexural strength of the adhesive sheet of the present invention becomes better, and peeling and lifting can be further prevented even when bending operations are performed. By making the content ratio of the structural unit derived from monomer component (b) 45% by mass or less, the cohesive force of the adhesive layer becomes larger, and therefore the recovery of deformation becomes better, and the adhesive sheet of the present invention can be further prevented from peeling and lifting even when repeatedly bending operations are performed. The preferred lower limit for the content of the structural unit derived from the monomer component (b) is 25% by mass, the preferred upper limit is 40% by mass, the further preferred lower limit is 30% by mass, and the further preferred upper limit is 38% by mass.

[0085] It should be noted that, in the case of multiple structural units derived from monomeric component (b) mentioned above, the content ratio of the structural units derived from monomeric component (b) mentioned above refers to the total content ratio of the structural units derived from monomeric component (b) contained therein.

[0086] The aforementioned block (B) preferably further comprises structural units derived from olefin polymers with terminal polymerizable unsaturated double bonds. By having the aforementioned block (B) comprise olefin polymers with terminal polymerizable unsaturated double bonds, the aforementioned block (B) comprises structural units derived from alkyl methacrylates of the aforementioned formula (1) and structural units derived from olefin polymers with terminal polymerizable unsaturated double bonds. The structural units derived from olefin polymers with terminal polymerizable unsaturated double bonds in the side chains aggregate through interaction, and the aforementioned block (B) has a pseudo-crosslinked structure. By having the aforementioned block (B) have such a structure, when peel stress is applied and the strain increases, the pseudo-crosslinks break, and the molecules of the block copolymer having the aforementioned block (B) elongate. Therefore, the aforementioned adhesive layer exhibits highly flexible properties, thereby having higher adhesive strength and better deformability. That is, by further including the above-mentioned block (B) with an olefin polymer having polymerizable unsaturated double bonds at the end, the adhesive strength and deformability of the adhesive sheet of the present invention are further improved. As a result, the bending resistance becomes more excellent, especially when left to stand in a bent state, it is able to further suppress peeling from the adhered object.

[0087] The aforementioned olefin polymers with polymerizable unsaturated double bonds at their ends can have polymerizable unsaturated double bonds at one end or at both ends. From the viewpoint of reducing the likelihood of intramolecular chemical crosslinking and further improving the retention of the adhesive composition of the present invention, olefin polymers with polymerizable unsaturated double bonds at one end are preferred.

[0088] Examples of olefin polymers with polymerizable unsaturated double bonds at the ends include ethylene-butene copolymers, ethylene-propylene copolymers, ethylene polymers, propylene polymers, and butene polymers, which have groups containing polymerizable unsaturated carbon-carbon double bonds at one or both ends. Examples of groups containing polymerizable unsaturated carbon-carbon double bonds include (meth)acryloyl, vinyl ether, and styrene groups. Among these, (meth)acryloyl is preferred from the perspective of excellent copolymerization properties with the aforementioned alkyl (meth)acrylates.

[0089] Specifically, examples of olefin polymers with polymerizable unsaturated double bonds at the ends include: ethylene macromonomers with (meth)acryloyl groups at one end, propylene macromonomers with (meth)acryloyl groups at one end, ethylene-butene macromonomers with (meth)acryloyl groups at one end, and ethylene-propylene macromonomers with (meth)acryloyl groups at one end. From the viewpoint that the glass transition temperature of the acrylic copolymers described later easily falls within a suitable range and that the adhesive strength of the adhesive composition of the present invention is further improved, ethylene-butene macromonomers with (meth)acryloyl groups at one end and ethylene-propylene macromonomers with (meth)acryloyl groups at one end are preferred.

[0090] It should be noted that these olefin polymers with polymerizable unsaturated double bonds at the ends can be used alone or in combination of two or more.

[0091] In addition, in this specification, "macromonomer" refers to a monomer with a weight-average molecular weight of about 1,000 to 100,000 and containing functional groups capable of polymerization.

[0092] In the aforementioned block (B), the preferred lower limit for the content of the structural unit derived from the olefin polymer with terminal polymeric unsaturated double bonds is 5% by mass, and the preferred upper limit is 30% by mass. By making the content of the structural unit derived from the olefin polymer with terminal polymeric unsaturated double bonds 5% by mass or more, the adhesive strength of the adhesive layer is further improved. By making the content of the structural unit derived from the olefin polymer with terminal polymeric unsaturated double bonds 30% by mass or less, the adhesive layer does not become too stiff, and the deformability becomes more excellent. The more preferred lower limit for the content of the structural unit derived from the olefin polymer with terminal polymeric unsaturated double bonds is 8% by mass, the more preferred upper limit is 25% by mass, the further preferred lower limit is 10% by mass, and the further preferred upper limit is 20% by mass.

[0093] The block (B) described above may have structural units derived from (meth)acrylates as shown in formula (1) above, structural units derived from other monomers other than structural units derived from olefin polymers with polymerizable unsaturated double bonds at the ends.

[0094] As structural units derived from other monomers contained in the above block (B), for example, R derived from the above equation (1) can be cited. 2 The alkyl group shown is a structural unit of (meth)acrylate alkyl ester with 8 or fewer carbon atoms. As R in the above formula (1) 2 Alkyl esters of (meth)acrylate with 8 or fewer carbon atoms are shown, such as butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, hexyl (meth)acrylate, octyl (meth)acrylate, and cyclohexyl (meth)acrylate. Additionally, structural units derived from acrylic acid, maleic anhydride, N,N-dimethylacrylamide, etc., can be used as structural units derived from other monomers as described above.

[0095] The block copolymers described above preferably have structural units derived from monomers containing polar functional groups. By giving the block copolymers structural units derived from monomers containing polar functional groups, the cohesive and adhesive forces of the resulting adhesive layer are increased, resulting in better deformation recovery. The adhesive sheet of the present invention can further prevent peeling and lifting even under repeated bending operations. Furthermore, due to the increased interaction with the adhered object, the adhesive force of the adhesive sheet of the present invention is further improved.

[0096] As structural units derived from monomers containing polar functional groups in the above-mentioned block copolymers, examples can be made of structural units identical to those derived from monomers containing polar functional groups in block (A). From the viewpoint of the deformability of the resulting adhesive layer, the above-mentioned block copolymers preferably have structural units derived from (meth)acrylic acid.

[0097] The preferred lower limit for the content of structural units derived from the carboxyl-containing monomers in the block copolymer is 1% by mass, and the preferred upper limit is 10% by mass. By making the content of structural units derived from the carboxyl-containing monomers in the block copolymer 1% by mass or more, the cohesive and adhesive forces of the resulting adhesive layer are greater, and therefore the recovery from deformation is more excellent. The adhesive sheet of the present invention can further prevent peeling and lifting even when repeatedly bent. By making the content of structural units derived from the carboxyl-containing monomers in the block copolymer 10% by mass or less, the deformability of the resulting adhesive layer and the adhesive sheet of the present invention is more excellent. As a result, the bending resistance of the adhesive sheet of the present invention is more excellent, and peeling and lifting can be further prevented even when bent. The more preferred lower limit for the content of structural units derived from the carboxyl-containing monomers in the block copolymer is 2% by mass, the more preferred upper limit is 8% by mass, the more preferably lower limit is 3% by mass, and the more preferably upper limit is 5% by mass.

[0098] The preferred lower limit for the content of structural units derived from the hydroxyl-containing monomers in the block copolymer is 1% by mass, and the preferred upper limit is 10% by mass. By making the content of structural units derived from the hydroxyl-containing monomers 1% by mass or more, the cohesive force of the resulting adhesive layer becomes greater, and therefore the recovery of deformation becomes more excellent. The adhesive sheet of the present invention can further prevent peeling and lifting even when repeatedly bent. By making the content of structural units derived from the hydroxyl-containing monomers in the block copolymer 10% by mass or less, the deformability of the resulting adhesive layer and the adhesive sheet of the present invention becomes more excellent. As a result, the bending resistance of the adhesive sheet of the present invention becomes more excellent, and peeling and lifting can be further prevented even when bent. The more preferred lower limit for the content of structural units derived from the hydroxyl-containing monomers in the block copolymer is 2% by mass, the more preferred upper limit is 8% by mass, the more preferably lower limit is 3% by mass, and the more preferably upper limit is 5% by mass.

[0099] The preferred lower limit for the total content of the structural units derived from monomers containing polar functional groups in the above-mentioned block copolymer is 1% by mass, and the preferred upper limit is 10% by mass. By making the total content of the structural units derived from monomers containing polar functional groups in the above-mentioned block copolymer 1% by mass or more, the cohesive force of the resulting adhesive layer becomes greater, and therefore the recovery of deformation becomes more excellent. The adhesive sheet of the present invention can further prevent peeling and lifting even when repeatedly bent. By making the total content of the structural units derived from monomers containing polar functional groups in the above-mentioned block copolymer 10% by mass or less, the deformability of the resulting adhesive layer and the adhesive sheet of the present invention becomes more excellent. As a result, the bending resistance of the adhesive sheet of the present invention becomes more excellent, and peeling and lifting can be further prevented even when bent. The more preferred lower limit for the total content of the structural units derived from monomers containing polar functional groups in the above-mentioned block copolymer is 2% by mass, the more preferred upper limit is 8% by mass, the more preferably lower limit is 3% by mass, and the more preferably upper limit is 5% by mass.

[0100] The block copolymers described above preferably comprise ABA-type triblock copolymers in which the block (B) is sandwiched between the block (A) (hereinafter, sometimes simply referred to as "ABA-type triblock copolymers").

[0101] In the case where the block copolymer comprises an ABA-type triblock copolymer, the blocks (A) present at both ends of the block copolymer form a pseudo-crosslinked structure derived from styrene and a cyclic (meth)acrylate at both ends of the ABA-type triblock copolymer. As a result, the resulting adhesive layer exhibits superior deformation recovery, and the adhesive sheet of the present invention can further prevent peeling and lifting even under repeated bending operations. Furthermore, the deformability of the resulting adhesive layer is improved, and the bending resistance of the adhesive sheet of the present invention is improved, further preventing peeling and lifting even under bending operations.

[0102] Furthermore, by incorporating alkyl groups with 9 or more carbon atoms derived from the (meth)acrylate shown in formula (1) within the aforementioned ABA-type triblock copolymer, the molecular weight between entanglement points of the aforementioned block copolymer increases. As a result, the free volume of the molecules becomes larger, the deformability of the resulting adhesive layer is more excellent, and the bending resistance of the adhesive sheet of the present invention becomes more excellent, further preventing peeling and lifting even during bending operations.

[0103] When the block copolymer is an ABA-type triblock copolymer, the preferred lower limit of the molecular weight between the entanglement points of the monomer component (b) in the ABA-type triblock copolymer is 5,000, and the preferred upper limit is 500,000. By keeping the molecular weight between the entanglement points within the above range, the adhesive sheet of the present invention exhibits superior deformability, preventing peeling and lifting even during bending operations. A more preferred lower limit of the molecular weight between the entanglement points is 10,000, a more preferred upper limit is 400,000, a further preferred lower limit is 50,000, and a further preferred upper limit is 300,000.

[0104] When the block copolymer is an ABA-type triblock copolymer, the preferred lower limit of the total content of the structural units derived from styrene and having a cyclic (meth)acrylate structure in the block copolymer is 5% by mass, and the preferred upper limit is 20% by mass. By keeping the total content of the structural units derived from styrene and having a cyclic (meth)acrylate structure within the above range, the microphase separation structure of the ABA-type triblock copolymer easily exhibits a spherical structure. As a result, the deformability and deformation recovery of the obtained adhesive layer are more excellent, the flexural strength of the adhesive sheet of the present invention is more excellent, and peeling and lifting can be further prevented even when bending operations are performed. In addition, by keeping the total content of the structural units derived from styrene and having a cyclic (meth)acrylate structure at 20% by mass or less, the transparency of the adhesive sheet of the present invention is more excellent. The more preferred lower limit of the total content of the structural units derived from styrene and having a cyclic (meth)acrylate structure is 6.5% by mass, the more preferred upper limit is 15% by mass, the further preferred lower limit is 9.0% by mass, and the further preferred upper limit is 13% by mass.

[0105] It should be noted that the microphase separation structure can be observed, for example, through the following methods.

[0106] That is, the adhesive layer processed into sheets can be stained with ruthenium and then cut with a cryostat (such as the "EM FC cryostat" manufactured by Leica) on a surface perpendicular to the stacking direction of the coating and spacers. The cross-section of the coating can then be observed at a magnification of 20,000 times using a transmission electron microscope (such as the "JEM-F200" manufactured by JEOL).

[0107] When the block copolymer is an ABA-type triblock copolymer, the preferred lower limit for the content of the structural units derived from monomer component (b) in block (B) of the ABA-type triblock copolymer is 25% by mass, and the preferred upper limit is 45% by mass. By making the content of the structural units derived from monomer component (b) 25% by mass or more, the molecular weight between the entanglement points of the block copolymer becomes larger. As a result, the free volume of the molecules becomes larger, the deformability of the resulting adhesive layer is more excellent, and the bending resistance of the adhesive sheet of the present invention becomes more excellent, further preventing peeling and lifting even when bending operations are performed. By making the content of the structural units derived from monomer component (b) 45% by mass or less, the cohesive force of the resulting adhesive layer becomes larger, and therefore the recovery of deformation becomes excellent, further preventing peeling and lifting even when the adhesive sheet of the present invention is repeatedly bent. The preferred lower limit for the content of the structural unit derived from the monomer component (b) in the above-mentioned block (B) is 28% by mass, the preferred upper limit is 40% by mass, the further preferred lower limit is 30% by mass, and the further preferred upper limit is 38% by mass.

[0108] In the aforementioned block copolymer, the preferred lower limit of the content of block (A) is 7.25% by mass, and the preferred upper limit is 15% by mass. By keeping the content of block (A) within the above range, the pseudo-crosslinked structures formed at the ends of the aforementioned ABA-type triblock copolymer exist in positions that are sufficiently separated from each other, thus increasing the free volume of the molecules. As a result, the deformability of the resulting adhesive layer is more excellent, and the flexural resistance of the adhesive sheet of the present invention is more excellent, further preventing peeling and lifting even during bending operations. The more preferred lower limit of the content of block (A) is 8% by mass, the more preferred upper limit is 12% by mass, the further preferred lower limit is 9% by mass, and the further preferred upper limit is 11% by mass.

[0109] The preferred lower limit for the weight-average molecular weight (Mw) of the aforementioned block copolymer is 250,000, and the preferred upper limit is 1,000,000. By making the weight-average molecular weight (Mw) of the aforementioned block copolymer 250,000 or more, the shear deformation of the aforementioned block copolymer becomes larger, and therefore the deformability of the resulting adhesive layer becomes more excellent. As a result, the flexural strength of the adhesive sheet of the present invention becomes more excellent, and peeling and lifting can be further prevented even when bending operations are performed. By making the weight-average molecular weight (Mw) of the aforementioned block copolymer 1,000,000 or less, the viscosity of the adhesive solution containing the aforementioned block copolymer does not become too high during the manufacture of the adhesive sheet of the present invention, as described later, and a good appearance can be manufactured. The more preferred lower limit for the weight-average molecular weight (Mw) of the aforementioned block copolymer is 300,000, the more preferred upper limit is 900,000, the further preferred lower limit is 400,000, and the further preferred upper limit is 800,000.

[0110] Methods for adjusting the weight-average molecular weight (Mw) of the block copolymers mentioned above include, for example, adjusting the amount of monomer components, using isothermal polymerization, or living radical polymerization in the manufacture of the block copolymers described later.

[0111] The preferred lower limit for the solubility parameter (SP value) of the above-mentioned block copolymer is 9.30 (J / cm³). 3 ) 1 / 2 The solubility parameter (SP value) of the above block copolymer was set to 9.30 (J / cm³). 3 ) 1 / 2 As a result, the adhesive strength of the resulting adhesive layer is further improved, and the flexural resistance of the adhesive sheet of the present invention becomes more excellent, further suppressing peeling from the adhered object even when left to stand in a bent state. A more preferred lower limit for the solubility parameter (SP value) of the above-mentioned block copolymer is 9.40 (J / cm³). 3 ) 1 / 2 The further preferred lower limit is 9.50 (J / cm). 3 ) 1 / 2 .

[0112] Furthermore, from the viewpoint of the deformability of the adhesive sheet of the present invention, the preferred upper limit of the solubility parameter (SP value) of the above-mentioned block copolymer is 12 (J / cm). 3 ) 1 / 2 The preferred upper limit is 11 (J / cm). 3 ) 1 / 2 The upper limit for further optimization is 10 (J / cm). 3 ) 1 / 2 .

[0113] It should be noted that the solubility parameter (SP value) is a parameter used as an indicator of polarity. In this specification, the solubility parameter (SP value) mentioned above refers to the Hansen solubility parameter, which can be derived by calculation based on the structural formula using HSP software. The HSP software mentioned above can be Hansen Solubility Parameter in Practice (HSPiP).

[0114] Examples of methods for manufacturing the block copolymers described above include: subjecting a mixture of structural unit monomers comprising block (A) containing monomer component (a) and a mixture of structural unit monomers comprising block (B) containing monomer component (b) to free radical reactions in the presence of a polymerization initiator to obtain block (A) and block (B) respectively, and then reacting or copolymerizing the two. Alternatively, after obtaining block (A), a mixture of structural unit monomers comprising block (B) containing monomer component (b) may be added to copolymerize the copolymer.

[0115] As a method for carrying out the above-mentioned free radical reaction, i.e., a polymerization method, conventionally known methods can be used, such as solution polymerization (boiling point polymerization or isothermal polymerization), emulsion polymerization, suspension polymerization, bulk polymerization, etc.

[0116] Furthermore, when the block copolymer is the ABA-type triblock copolymer, it can be obtained by, for example, living polymerization. Examples of living polymerization include living anionic polymerization and RAFT polymerization, with RAFT polymerization being particularly preferred. In the case of producing the ABA-type triblock copolymer by RAFT polymerization, after polymerizing or copolymerizing the structural unit monomers of block (A) containing the monomer component (a) using a RAFT agent to obtain block (A), the structural unit monomers of block (B) containing the monomer component (b) are polymerized or copolymerized in the presence of the obtained block (A) to produce the block copolymer.

[0117] Examples of polymerization initiators used in the above polymerization methods include azo compounds and organic peroxides.

[0118] Examples of the aforementioned azo compounds include: 2,2'-azobis(isobutyronitrile), 2,2'-azobis(2-methylbutyronitrile), 2,2'-azobis(2,4-dimethylpentanitrile), 2,2'-azobis(4-methoxy-2,4-dimethylpentanitrile), 1,1-azobis(cyclohexane-1-carboxylonitrile), 1-((1-cyano-1-methylethyl)azo)formamide, 4,4'-azobis(4-cyanopentanoic 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)propionamide), 2,2'-azobis(2-methyl-N-(2-hydroxyethyl)propionamide), 2,2'-azobis(2-azobis(2-methyl ... Bis(N-(2-propenyl)-2-methylpropionamide), 2,2'-azobis(N-butyl-2-methylpropionamide), 2,2'-azobis(N-cyclohexyl-2-methylpropionamide), 2,2'-azobis(2-(2-imidazolin-2-yl)propane) dihydrochloride, 2,2'-azobis(2-(1-(2-hydroxyethyl)-2-imidazolin-2-yl)propane) dihydrochloride Salts, 2,2'-azobis(2-(2-imidazolin-2-yl)propane), 2,2'-azobis(2-amidinylpropane) dihydrochloride, 2,2'-azobis(N-(2-carboxyethyl)-2-methylpropanediamine) tetrahydrate, 2,2'-azobis(1-imino-1-pyrrolyl-2-methylpropane) dihydrochloride, 2,2'-azobis(2,4,4-trimethylpentane), etc. These azo compounds can be used alone or in combination of two or more.

[0119] Examples of the aforementioned organic peroxides include: 1,1-bis(tert-hexylperoxide)-3,3,5-trimethylcyclohexane, tert-hexyl peroxypentanoate, tert-butyl peroxypentanoate, 2,5-dimethyl-2,5-bis(2-ethylhexanoylperoxide)hexane, tert-hexyl peroxy-2-ethylhexanoate, tert-butyl peroxy-2-ethylhexanoate, tert-butyl peroxyisobutyrate, tert-butyl peroxy-3,5,5-trimethylhexanoate, and tert-butyl peroxylaurate. These organic peroxides can be used alone or in combination of two or more.

[0120] Examples of RAFT agents used in the above-mentioned RAFT polymerization include, for example, dithioesters, dithiocarbonates, trithiocarbonates, xanthates, and other sulfur compounds. Specifically, examples include compounds represented by the formula (2) below.

[0121] [Chemical Formula 2]

[0122]

[0123] The preferred lower limit for the content of the block copolymer in the adhesive layer is 75% by mass. By making the content of the block copolymer 75% by mass or more, the resulting adhesive layer achieves both superior deformability and superior recovery from deformation, thus improving the flexural strength of the adhesive sheet of the present invention. A more preferred lower limit for the content of the block copolymer is 80% by mass, and a further preferred lower limit is 85% by mass.

[0124] Furthermore, there is no particular upper limit to the content of the block copolymer mentioned above, which can be 100% by mass. However, from the viewpoint that the obtained adhesive layer has further improved deformability recovery, it is preferable to contain the curing agent described later. Therefore, the preferred upper limit is 99.9% by mass.

[0125] The adhesive layer described above preferably further contains a curing agent.

[0126] By including a curing agent in the adhesive layer, when the block (A) contains structural units derived from monomers containing polar functional groups, the functional groups of the monomers containing polar functional groups react with the curing agent to form a chemically cross-linked structure. As a result, the cohesive strength of the resulting adhesive layer becomes greater, thus improving its resilience to deformation. The adhesive sheet of the present invention can further prevent peeling and lifting even when repeatedly bent.

[0127] As the curing agent, depending on the type of functional group contained in the block (A), isocyanate-based curing agents, aziridine-based curing agents, epoxy-based curing agents, metal chelate-type curing agents, etc., can be used. Among these, from the viewpoint of maintaining good storage stability, having superior deformability and recovery from deformation of the adhesive sheet of the present invention, and further preventing peeling and lifting even during bending operations, isocyanate-based curing agents are preferred.

[0128] Examples of isocyanate-based curing agents include isocyanate compounds having two or more isocyanate groups within a single molecule. Specifically, examples include 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-toluene diisocyanate, 2,6-toluene diisocyanate, phenylenediamine diisocyanate, 1,5-naphthalene diisocyanate, and 4,4-diphenyl diisocyanate; and alicyclic isocyanates such as dicycloheptane triisocyanate.

[0129] The preferred lower limit for the content of the curing agent relative to 100 parts by weight of the block copolymer is 0.005 parts by weight, and the preferred upper limit is 5 parts by weight. By making the content of the curing agent 0.005 parts by weight or more, the cohesive force of the resulting adhesive layer becomes greater, thus improving the recovery of deformation. The adhesive sheet of the present invention can further prevent peeling and lifting even when repeatedly bent. By making the content of the curing agent 5 parts by weight or less, the deformability of the resulting adhesive layer is excellent, and the bending resistance of the adhesive sheet of the present invention becomes more excellent. Even when bent, peeling and lifting can be further prevented. The more preferred lower limit for the curing agent is 0.01 parts by weight, the more preferred upper limit is 3 parts by weight, the more preferred lower limit is 0.1 parts by weight, and the more preferred upper limit is 1.5 parts by weight.

[0130] The adhesive layer described above may contain tackifying resin.

[0131] By including the above-mentioned adhesive layer with tackifying resin, the adhesive strength of the resulting adhesive layer is further improved, and the bending resistance of the adhesive sheet of the present invention becomes more excellent, which can further suppress peeling from the adhered object when it is left to stand in a bent state.

[0132] The preferred upper limit for the content of the tackifying resin is 20 parts by mass relative to 100 parts by mass of the block copolymer. By keeping the content of the tackifying resin at 20 parts by mass or less, the transparency of the adhesive sheet of the present invention becomes more excellent. The more preferred upper limit for the content of the tackifying resin is 10 parts by mass, and from the viewpoint of the transparency of the adhesive sheet of the present invention, it is most preferable that the adhesive layer does not contain the tackifying resin.

[0133] The adhesive layer described above may contain a silane coupling agent.

[0134] By including a silane coupling agent in the adhesive layer, the adhesive strength of the resulting adhesive layer is further improved, and the bending resistance of the adhesive sheet of the present invention becomes more excellent, further suppressing peeling from the adhered object when left in a bent state.

[0135] The preferred upper limit for the content of the silane coupling agent is 3 parts by mass relative to 100 parts by mass of the block copolymer. By keeping the content of the silane coupling agent at 3 parts by mass or less, the transparency of the adhesive sheet of the present invention becomes more excellent. The more preferred upper limit for the content of the silane coupling agent is 1 part by mass, and even more preferred is 0.5 parts by mass. From the viewpoint of the transparency of the adhesive sheet of the present invention, it is most preferable that the adhesive layer does not contain the silane coupling agent.

[0136] The adhesive layer described above may contain additives such as solvents, plasticizers, emulsifiers, softeners, fillers, pigments, dyes, and antioxidants, without impairing the effects of the present invention.

[0137] The preferred lower limit for the shear storage modulus G' of the above-mentioned adhesive layer at -20°C is 1.0 × 10⁻⁶. 4 Pa, preferably with an upper limit of 5.0 × 10 5 Pa. By ensuring that the shear storage modulus G' of the adhesive layer at -20°C is within the aforementioned range, the shear deformation properties of the adhesive layer are improved in low-temperature environments, and the flexural resistance of the adhesive sheet of the present invention to minor bending operations in low-temperature environments is further improved. A more preferred lower limit for the shear storage modulus G' of the adhesive layer at -20°C is 3.0 × 10⁻⁶. 4 Pa, more preferably an upper limit of 3.0 × 10 Pa. 5 Pa, the further preferred lower limit is 5.0 × 10 4 Pa, with a further preferred upper limit of 2.0 × 10⁻⁶. 5 Pa.

[0138] The preferred lower limit for the shear storage modulus G' of the aforementioned adhesive layer at 25°C is 1.0 × 10⁻⁶. 4 Pa, preferably with an upper limit of 2.0 × 10 5 Pa. By ensuring that the shear storage modulus G' of the adhesive layer at 25°C is within the aforementioned range, the shear deformability of the adhesive layer is improved, and the bending resistance of the adhesive sheet of the present invention to minute bending operations is further improved. A more preferred lower limit for the shear storage modulus G' of the adhesive layer at 25°C is 2.0 × 10⁻⁶. 4 Pa, more preferably an upper limit of 1.0 × 10 Pa. 5 Pa, the further preferred lower limit is 3.0 × 10 4 Pa, with a further optimized upper limit of 9.0 × 10 4 Pa.

[0139] The preferred lower limit for the shear storage modulus G' of the aforementioned adhesive layer at 85°C is 1.0 × 10⁻⁶. 3 Pa, preferably with an upper limit of 1.0 × 10 5 Pa. By ensuring that the shear storage modulus G' of the adhesive layer at 85°C is within the aforementioned range, the shear deformation properties of the adhesive layer under high-temperature conditions are improved, and the flexural resistance of the adhesive sheet of the present invention to minor bending operations under high-temperature conditions is further improved. A more preferred lower limit for the shear storage modulus G' of the adhesive layer at 85°C is 5.0 × 10⁻⁶. 3 Pa, with a more preferred upper limit of 7.5 × 10 Pa. 4 Pa, the further preferred lower limit is 2.0 × 104 Pa, with a further preferred upper limit of 5.0 × 10 4 Pa.

[0140] The shear storage modulus of the above-mentioned adhesive layer at -20℃, 25℃, and 85℃ can be determined by dynamic viscoelasticity measurement. Specifically, it can be determined by, for example, the following methods.

[0141] That is, the obtained adhesive layer is stacked to a thickness of about 1 mm, and cut into a flat rectangle with a width of 6 mm and a length of 10 mm to make a test piece. For the test piece, a dynamic viscoelasticity test device (such as "DVA-200" manufactured by IT Measurement and Control Co., Ltd.) is used to perform dynamic viscoelasticity tests in shear mode, under a nitrogen atmosphere, at a test temperature of -50℃ to 200℃, a heating rate of 5℃ / min, and a frequency of 1Hz.

[0142] As a method for adjusting the shear storage modulus of the above-mentioned adhesive layer at -20°C, 25°C, and 85°C, for example, the total content ratio of the structural units derived from styrene and (meth)acrylates having a cyclic structure (i.e., monomer component (a)) in the above-mentioned block (A) and the content ratio of the structural units derived from (alkyl meth)acrylates (i.e., monomer component (b)) shown in formula (1) in the above-mentioned block (B) can be adjusted to an appropriate amount.

[0143] The adhesive sheet of the present invention can be a non-supported type without a substrate or a supported type with a substrate, wherein the non-supported type without a substrate is preferred.

[0144] By eliminating the substrate from the adhesive sheet of the present invention, the adhesive sheet of the present invention is thin and has excellent transparency, thus making it more suitable for use as an optical film for thin flexible displays.

[0145] When the adhesive sheet of the present invention has a substrate, a resin film is preferably used as the material of the substrate. Among the resin films mentioned above, polyester resin film, polypropylene resin film, and transparent polyimide resin film are preferred. Of these, transparent polyimide resin film is preferred from the perspectives of flatness, minimal thickness variation, and high flexural strength.

[0146] The aforementioned substrate may contain additives such as fillers, ultraviolet absorbers, light stabilizers, and antistatic agents within a range that does not impair its physical properties.

[0147] The thickness of the aforementioned substrate is appropriately selected according to the application, with a preferred upper limit of 50 μm. By keeping the thickness of the aforementioned substrate below 50 μm, the transparency of the adhesive sheet of the present invention becomes more excellent. A more preferred upper limit for the thickness of the aforementioned substrate is 25 μm, and a further preferred upper limit is 10 μm.

[0148] Furthermore, there is no particular limitation on the lower limit of the thickness of the aforementioned substrate, but from the viewpoint of bending resistance, it is preferable to have no substrate.

[0149] The adhesive sheet of the present invention may have the adhesive layer on only one side of the substrate, or it may have the adhesive layer on both sides of the substrate. Preferably, the adhesive layer is present on both sides of the substrate.

[0150] The method for manufacturing the adhesive sheet of the present invention is not particularly limited, but the following methods can be cited as examples.

[0151] First, an adhesive comprising block copolymers, a curing agent as needed, and other additives is prepared. Next, the obtained adhesive is applied to the release-treated surface of a release film that has undergone release treatment and allowed to dry to form an adhesive layer. The exposed surface of the adhesive layer is then bonded to the release-treated surface of another prepared release film to create a laminate. The resulting laminate is used as an adhesive sheet.

[0152] Furthermore, by bonding the adhesive layer of the obtained laminate to a substrate, an adhesive sheet containing the substrate can be manufactured. Specifically, for example, by bonding the adhesive layer of the laminate to one side of the substrate, and then bonding the adhesive layer of another laminate made in the same manner to the other side of the substrate, thereby performing transfer printing and lamination integration, and then curing at 40°C and 50%RH for 2 days, an adhesive sheet with adhesive layers on both sides of the substrate can be obtained.

[0153] The preferred lower limit of the thickness of the adhesive sheet of the present invention is 1 μm, and the preferred upper limit is 100 μm.

[0154] By making the thickness of the adhesive sheet of the present invention 1 μm or more, the adhesive force of the resulting adhesive layer is further improved, and the bending resistance and adhesive force of the adhesive sheet of the present invention become more excellent. When left at rest in a bent state, peeling from the adhered object can be further suppressed. By making the thickness of the adhesive sheet of the present invention 100 μm or less, it is a preferred method that does not hinder bending in terms of compressive deformation generated at the bending portion. The more preferred lower limit of the thickness of the adhesive sheet of the present invention is 5 μm, the more preferred upper limit is 75 μm, the further preferred lower limit is 10 μm, and the further preferred upper limit is 50 μm.

[0155] The adhesive sheet of the present invention exhibits excellent bending resistance and is not prone to peeling or lifting even under repeated bending operations. Therefore, it is suitable for use in optical films of flexible displays in flexible devices such as bendable image display devices. Furthermore, the adhesive sheet of the present invention does not peel or lift even under bending operations that result in significant deformation of the adhesive layer, even under repeated bending operations. Therefore, it is more suitable for optical films such as those used in large-screen, thin flexible displays where the adhesive layer deforms significantly during bending operations.

[0156] Invention Effects

[0157] According to the present invention, an adhesive sheet with excellent bending resistance can be provided, which is not prone to peeling or lifting even when repeatedly bent. Attached Figure Description

[0158] Figure 1 This is a schematic diagram illustrating the method of cohesive force testing. Detailed Implementation

[0159] The present invention will be described in more detail below with examples, but the present invention is not limited to these examples.

[0160] (Manufacturing of RAFT agent (R1))

[0161] 0.902 g (6.00 mmol) of 1,6-hexanedithiol, 1.83 g (24.0 mmol) of carbon disulfide, and 11 mL of dimethylformamide were added to a two-necked flask and stirred at 25 °C using a magnetic stirrer. 2.49 g (24.6 mmol) of triethylamine was added dropwise over 15 minutes, and the mixture was stirred further at 25 °C for 3 hours. After the addition was complete, the color of the reaction solution in the flask changed from colorless and transparent to yellow. Next, 2.75 g (1.0 mmol) of methyl-bromophenylacetic acid was added dropwise over 15 minutes, and the mixture was stirred further at 25 °C for 4 hours. A precipitate was observed in the flask during the addition. Then, 100 mL of extraction solvent (n-hexane / ethyl acetate = 50 / 50) and 50 mL of water were added to the reaction solution for separation extraction. 50 mL of the same extraction solvent was added to the resulting aqueous phase, and separation extraction was performed again. The organic phases obtained from the first and second fractional extractions were mixed and washed sequentially with 50 mL of 1M hydrochloric acid, 50 mL of water, and 50 mL of saturated saline solution. After drying the washed organic phase with sodium sulfate, the sodium sulfate was filtered off, and the filtrate was concentrated using an evaporator. The organic solvent was removed by vacuum distillation. The concentrate was purified by silica gel column chromatography (eluent: n-hexane / ethyl acetate = 80 / 20) to obtain 0.86 g of RAFT agent (R1) (yield 80%) as a yellow oil. The 1H-NMR spectrum of the obtained RAFT agent (R1) confirmed the alkyl structure derived from methyl-phenylacetic acid and dithiol, and the compound represented by the above formula (2) as RAFT agent (R1) was determined. The 1H-NMR determination was performed using a nuclear magnetic resonance analyzer (Hitachi, Ltd., "R-1200").

[0162] (Example 1)

[0163] (Preparation of solutions containing copolymers)

[0164] A mixture of block (A) structural unit monomers consisting of 7.28 g of styrene (St) and 0.72 g of acrylic acid (AAc), 0.19 g of RAFT agent (R1), and 0.035 g of 2,2'-azobis(2-methylbutyronitrile) (ABN-E) as a polymerization initiator were added to a two-necked flask. The flask was purged with nitrogen while the temperature was raised to 85°C. The mixture was then stirred at 85°C for 6 hours to carry out the polymerization reaction (stage 1 reaction).

[0165] After the first stage of reaction was completed, 400g of n-hexane was added to the flask and stirred to precipitate the reactants. The unreacted monomers and RAFT agent (R1) were separated by filtration. The reactants were dried under reduced pressure at 70°C to obtain the copolymer (block (A)).

[0166] Next, a mixture of the structural unit monomers of block (B), consisting of 69.0 g of butyl acrylate (BA) and 23.0 g of lauryl acrylate (LA), 0.0027 g of 2,2'-azobis(2-methylbutyronitrile) (ABN-E) as a polymerization initiator, 5 g of ethyl acetate as a solvent, and the previously obtained copolymer (block (A)) were added to a two-necked flask. The flask was purged with nitrogen while the temperature was raised to 85°C. Then, the polymerization reaction was carried out at 85°C for 6 hours (second stage reaction), resulting in a copolymer-containing solution (1) containing both block (A) and block (B). It should be noted that the amount of the mixture of structural unit monomers of block (B) and block (A) was set such that the content of block (A) in the obtained copolymer (1) was 8.00% by mass. In addition, copolymer (1) is a triblock copolymer.

[0167] (Determination of weight-average molecular weight of copolymers)

[0168] The copolymer-containing solution was dissolved in tetrahydrofuran (THF), and the concentration was adjusted to 0.1% by mass. The diluted solution was then filtered using a filter (polytetrafluoroethylene, pore size: 0.2 μm) to prepare the assay sample. Next, the assay sample was fed into a gel permeation chromatography (Waters, “2690 Separations Module”) and GPC was performed at a sample flow rate of 1 mL / min and a column temperature of 40 °C to determine the polystyrene-converted molecular weight of the copolymer, thus obtaining the weight-average molecular weight of the copolymer. The results are shown in Table 1.

[0169] (Determination of SP value of copolymer)

[0170] For the obtained copolymers, the SP values ​​were calculated based on the structural formula using Hansen Solubility Parameter in Practice (HSPiP) as the HSP software. The results are shown in Table 1.

[0171] (Making of adhesive sheets)

[0172] A copolymer-containing solution is applied to the release-treated side of a polyethylene terephthalate (PET) film with one release treatment layer, and dried at 110°C for 5 minutes to produce a laminated film with an adhesive layer of 50 μm thickness. Further, the release-treated side of the PET film with one release treatment layer is laminated onto the laminated film with the adhesive layer facing each other, thereby obtaining an adhesive sheet.

[0173] (Determination of the shear storage modulus G' of the adhesive layer at -20℃, 25℃ and 85℃)

[0174] The obtained adhesive layers were overlapped to create a 1.0 mm thick laminate, which was then cut into 6 mm wide x 10 mm long samples to obtain the test samples. For the obtained test samples, dynamic viscoelasticity was measured using a dynamic viscoelasticity measuring device (IT Measurement & Control Co., Ltd., "DVA-200") in shear mode under a nitrogen atmosphere, at a measurement temperature of -50℃ to 200℃, a heating rate of 5℃ / min, and a frequency of 1 Hz. The shear storage modulus G' of the adhesive layer at -20℃, 25℃, and 85℃ was obtained. The results are shown in Table 4.

[0175] (Determination of shear strain and shear deformation recovery rate of adhesive sheet)

[0176] Cut the obtained adhesive sheet into a flat rectangle with a width of 10mm and a length of 20mm, and then... Figure 1 The cohesive test shown. (As illustrated) Figure 1 As shown, SUS plates 21 and 22 (both SUS304 plates cleaned with ethanol and then dry-rubbed) at 80°C were bonded together with a cut adhesive sheet 1. One end of the SUS plate 22 bonded to the lower surface was fixed with a clamp 3. While maintaining SUS plates 21 and 22 at 80°C, a 200g weight 4 was installed on one end of the SUS plate 21 bonded to the upper surface at a temperature of 23°C. After applying a stress of 10kPa in the shear direction for 3 minutes (time point t1), the displacement δ1 of the adhesive sheet 1 in the shear direction was precisely measured using a micro-shear creep measuring device (manufactured by Asahi Seiko Corporation, "micro-shear creep measuring device"). Furthermore, after removing the weight 4 from the SUS plate 21 at the above time point t1 and unloading the 10kPa stress, the displacement δ2 of the adhesive sheet 1 in the shear direction was precisely measured 3 minutes later (time point t2) from the above time point t1, just like the displacement δ1. Using the obtained displacements δ1 and δ2, the shear strain of the adhesive sheet after 3 minutes of being subjected to a 10 kPa stress and the shear deformation recovery rate after 3 minutes of being subjected to a 10 kPa stress are calculated according to the following equations (I) and (II). The results are shown in Table 4.

[0177] Shear strain (%) = 100 × δ¹ / h (I)

[0178] Shear deformation recovery rate (%) = 100 × {(δ1 / h) - (δ2 / h)} / (δ1 / h) (II)

[0179] (δ1: displacement in the shear direction at time point t1 of adhesive sheet 1, δ2: displacement in the shear direction of adhesive sheet 1 at time point t2, h: thickness of adhesive sheet 1)

[0180] (Determination of the 180° peel strength of the adhesive sheet to polyimide)

[0181] The obtained adhesive sheet was cut into a flat rectangle 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 strip was then rolled back and forth once using a rubber roller at a speed of 10 mm / min, thereby bonding it to a 75 μm thick polyimide film (manufactured by DU PONT-TORAY, "Kapton", 50 mm × 150 mm) fixed to a 2 mm thick SUS plate. Further curing at 23°C and 50% RH for 20 minutes yielded the test sample.

[0182] For the obtained test samples, a tensile testing machine (Shimadzu Corporation, "Autograph AGS-X") was used to conduct a peel test at 23°C, 50%RH, tensile speed of 300 mm / min, and peel angle of 180°, according to JIS Z0237. The adhesive sheet was peeled from the polyimide film, and the 180° peel force of the adhesive sheet on the polyimide was measured. The results are shown in Table 4.

[0183] (Example 2)

[0184] In the above-mentioned “(Preparation of the copolymer-containing solution)”, a mixture consisting of 59.8 g of butyl acrylate (BA) and 32.2 g of lauryl acrylate (LA) was added as a mixture of the structural unit monomers of block (B). Otherwise, the same procedure as in Example 1 was followed to prepare a copolymer-containing solution containing copolymer (2), and adhesive sheets were made and measured. It should be noted that the amount of the mixture of structural unit monomers of block (B) and block (A) was set such that the content of block (A) in the obtained copolymer (2) was 8.00% by mass. In addition, copolymer (2) is a triblock copolymer. The results are shown in Tables 1 and 4.

[0185] (Example 3)

[0186] In the above-mentioned "(Preparation of the copolymer-containing solution)", during the second stage reaction, the flask was purged with nitrogen while the temperature was raised to 80°C, and then the polymerization reaction was carried out by stirring at 80°C for 7 hours. Otherwise, the same procedure as in Example 1 was followed to prepare a copolymer-containing solution containing copolymer (3), and adhesive sheets were made and measured. It should be noted that the mixture of the structural unit monomers of block (B) and the amount of block (A) were set such that the content of block (A) in the obtained copolymer (3) was 8.00% by mass. In addition, copolymer (3) is a triblock copolymer. The results are shown in Tables 1 and 4.

[0187] (Example 4)

[0188] In the above-mentioned “(Preparation of the copolymer-containing solution)”, a mixture consisting of 9.1 g of styrene (St) and 0.9 g of acrylic acid (AAc) was added as the mixture of structural 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 the mixture of structural unit monomers of block (B). Otherwise, a copolymer-containing solution containing copolymer (4) was prepared by the same method as in Example 1, adhesive sheets were made, and measurements were performed. It should be noted that the amount of the mixture of structural unit monomers of block (B) and block (A) was set such that the content of block (A) in the obtained copolymer (4) was 9.80% by mass. In addition, copolymer (4) is a triblock copolymer. The results are shown in Tables 1 and 4.

[0189] (Example 5)

[0190] In the above-mentioned “(Preparation of the copolymer-containing solution)”, a mixture consisting of 9.1 g of styrene (St) and 0.9 g of acrylic acid (AAc) was added as the mixture of structural unit monomers of block (A), and a mixture consisting of 50.6 g of butyl acrylate (BA) and 41.4 g of lauryl acrylate (LA) was added as the mixture of structural unit monomers of block (B). Otherwise, a copolymer-containing solution containing copolymer (5) was prepared in the same manner as in Example 1, adhesive sheets were made, and measurements were performed. It should be noted that the amount of the mixture of structural unit monomers of block (B) and block (A) was set such that the content of block (A) in the obtained copolymer (5) was 9.80% by mass. Furthermore, copolymer (5) was a triblock copolymer. The results are shown in Tables 1 and 4.

[0191] (Example 6)

[0192] In the above-mentioned “(Preparation of the 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). Otherwise, a copolymer-containing solution containing copolymer (6) was prepared in the same manner as in Example 1, adhesive sheets were made, and measurements were performed. It should be noted that the amount of the mixture of structural unit monomers of block (B) and block (A) was set such that the content of block (A) in the obtained copolymer (6) was 9.80% by mass. Furthermore, copolymer (6) is a triblock copolymer. The results are shown in Tables 1 and 4.

[0193] (Example 7)

[0194] In the above-mentioned “(Preparation of the copolymer-containing solution)”, a mixture consisting of 9.1 g of styrene (St) and 0.9 g of acrylic acid (AAc) was added as the 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 lauryl acrylate (LA) was added as the mixture of structural unit monomers of block (B). Otherwise, a copolymer-containing solution containing copolymer (7) was prepared in the same manner as in Example 1, adhesive sheets were made, and measurements were performed. It should be noted that the amount of the mixture of structural unit monomers of block (B) and block (A) was set such that the content of block (A) in the obtained copolymer (7) was 9.80% by mass. In addition, copolymer (7) is a triblock copolymer. The results are shown in Tables 1 and 4.

[0195] (Example 8)

[0196] In the above-mentioned “(Preparation of the copolymer-containing solution)”, a mixture consisting of 9.1 g of styrene (St) and 0.9 g of acrylic acid (AAc) was added as the mixture of structural unit monomers of block (A), and a mixture consisting 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 the mixture of structural unit monomers of block (B). Otherwise, a copolymer-containing solution containing copolymer (8) was prepared in the same manner as in Example 1, adhesive sheets were made, and measurements were performed. It should be noted that the amount of the mixture of structural unit monomers of block (B) and block (A) was set such that the content of block (A) in the obtained copolymer (8) was 9.80% by mass. In addition, copolymer (8) is a triblock copolymer. The results are shown in Tables 1 and 4.

[0197] (Example 9)

[0198] In the above-mentioned “(Preparation of the solution containing the copolymer)”, 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), 31.28 g of lauryl acrylate (LA) and 0.92 g of dimethacrylamide (DMAA) was added as a mixture of structural unit monomers of block (B). Otherwise, copolymer (9) was synthesized in the same manner as in Example 1, adhesive sheets were made, and measurements were performed. It should be noted that the amount of mixture of structural unit monomers of block (B) and block (A) was set such that the content of block (A) in the obtained copolymer (9) was 9.80% by mass. In addition, copolymer (9) is a triblock copolymer. The results are shown in Tables 1 and 4.

[0199] (Example 10)

[0200] In the above-mentioned “(Preparation of the copolymer-containing solution)”, a mixture consisting of 9.1 g of styrene (St) and 0.9 g of acrylic acid (AAc) was added as the mixture of structural unit monomers of block (A), and a mixture consisting 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 the mixture of structural unit monomers of block (B). Otherwise, a copolymer-containing solution containing copolymer (10) was prepared in the same manner as in Example 1, adhesive sheets were made, and measurements were performed. It should be noted that the amount of the mixture of structural unit monomers of block (B) and block (A) was set such that the content of block (A) in the obtained copolymer (10) was 9.80% by mass. In addition, copolymer (10) is a triblock copolymer. The results are shown in Tables 2 and 5.

[0201] (Example 11)

[0202] In the above-mentioned “(Preparation of the copolymer-containing solution)”, a mixture consisting of 11.3 g of styrene (St) and 1.1 g of acrylic acid (AAc) was added as the mixture of structural unit monomers of block (A), and a mixture consisting 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 the 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, adhesive sheets were made, and measurements were performed. It should be noted that the amount of the mixture of structural unit monomers of block (B) and block (A) was set such that the content of block (A) in the obtained copolymer (11) was 9.80% by mass. In addition, copolymer (11) is a triblock copolymer. The results are shown in Tables 2 and 5.

[0203] (Example 12)

[0204] In the above-mentioned “(Preparation of the copolymer-containing solution)”, a mixture consisting of 5.95 g of styrene (St) and 0.59 g of acrylic acid (AAc) was added as the mixture of structural unit monomers of block (A), and a mixture consisting 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 the mixture of structural unit monomers of block (B). Otherwise, a copolymer-containing solution containing copolymer (12) was prepared in the same manner as in Example 1, adhesive sheets were made, and measurements were performed. It should be noted that the amount of the mixture of structural unit monomers of block (B) and block (A) was set such that the content of block (A) in the obtained copolymer (12) was 9.80% by mass. In addition, copolymer (12) is a triblock copolymer. The results are shown in Tables 2 and 5.

[0205] (Example 13)

[0206] In the above-mentioned “(Preparation of the copolymer-containing solution)”, a mixture consisting of 13.65 g of styrene (St) and 1.35 g of acrylic acid (AAc) was added as the mixture of structural unit monomers of block (A), and a mixture consisting 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 the mixture of structural unit monomers of block (B). Otherwise, a copolymer-containing solution containing copolymer (13) was prepared in the same manner as in Example 1, adhesive sheets were made, and measurements were performed. It should be noted that the amount of the mixture of structural unit monomers of block (B) and block (A) was set such that the content of block (A) in the obtained copolymer (13) was 14.0% by mass. Furthermore, copolymer (13) was a triblock copolymer. The results are shown in Tables 2 and 5.

[0207] (Example 14)

[0208] In the above-mentioned “(Preparation of the copolymer-containing solution)”, a mixture consisting of 9.60 g of styrene (St) and 0.95 g of acrylic acid (AAc) was added as the mixture of structural unit monomers of block (A), and a mixture consisting 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 the mixture of structural unit monomers of block (B). Otherwise, a copolymer-containing solution containing copolymer (14) was prepared in the same manner as in Example 1, adhesive sheets were made, and measurements were performed. It should be noted that the amount of the mixture of structural unit monomers of block (B) and block (A) was set such that the content of block (A) in the obtained copolymer (14) was 9.80% by mass. In addition, copolymer (14) is a triblock copolymer. The results are shown in Tables 2 and 5.

[0209] (Example 15)

[0210] In the above-mentioned “(Preparation of the copolymer-containing solution)”, a mixture consisting of 9.1 g of styrene (St) and 0.9 g of 2-hydroxyethyl acrylate (HEA) was added as the mixture of structural unit monomers of block (A), and a mixture consisting 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 the mixture of structural unit monomers of block (B). Otherwise, a copolymer-containing solution containing copolymer (15) was prepared in the same manner as in Example 1, adhesive sheets were made, and measurements were performed. It should be noted that the amount of the mixture of structural unit monomers of block (B) and block (A) was set such that the content of block (A) in the obtained copolymer (15) was 9.80% by mass. In addition, copolymer (15) is a triblock copolymer. The results are shown in Tables 2 and 5.

[0211] (Example 16)

[0212] In the above-described "(Preparation of the copolymer-containing solution)", a mixture consisting 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 the mixture of structural unit monomers for block (A). A mixture consisting 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 the mixture of structural unit monomers for block (B). Otherwise, a copolymer-containing solution containing copolymer (16) was prepared under the same conditions as in Example 1. It should be noted that the amount of the mixture of structural unit monomers for block (B) and the amount of block (A) was set such that the proportion of block (A) in the obtained copolymer (16) was 9.89% by mass. Furthermore, copolymer (16) is a triblock copolymer.

[0213] In addition, in the above-mentioned "(Preparation of adhesive sheet)", 0.92g of Coronate L-45E (manufactured by Tosoh Corporation), which is an isocyanate-based curing agent, was added to the copolymer-containing solution containing copolymer (16) relative to 100g of copolymer (16), stirred thoroughly, and the prepared adhesive solution was coated onto a PET film. After drying at 110°C for 5 minutes, it was cured at 40°C and 50%RH for 48 hours, thereby obtaining an adhesive sheet with an adhesive layer of 50μm thickness.

[0214] Otherwise, the same procedure as in Example 1 was followed for the determination. The results are shown in Tables 2 and 5.

[0215] (Example 17)

[0216] In the above-described "(Preparation of the copolymer-containing solution)", a mixture consisting 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 the mixture of structural unit monomers for block (A). A mixture consisting 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 the mixture of structural unit monomers for block (B). Otherwise, a copolymer-containing solution containing copolymer (17) was prepared under the same conditions as in Example 1. It should be noted that the amount of the mixture of structural unit monomers for block (B) and the amount of block (A) were set such that the proportion of block (A) in the obtained copolymer (17) was 9.89% by mass. Furthermore, copolymer (17) is a triblock copolymer.

[0217] In addition, in the above-mentioned "(Preparation of adhesive sheet)", 0.92g of Coronate L-45E (manufactured by Tosoh Corporation), which is an isocyanate-based curing agent, was added to a copolymer-containing solution containing copolymer (17) relative to 100g of copolymer (17), stirred thoroughly, and the prepared adhesive solution was coated onto a PET film. After drying at 110°C for 5 minutes, it was cured at 40°C and 50%RH for 48 hours, thereby producing an adhesive sheet with an adhesive layer of 50μm thickness.

[0218] Otherwise, the same procedure as in Example 1 was followed for the determination. The results are shown in Tables 2 and 5.

[0219] (Example 18)

[0220] 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) relative to 100 g of copolymer (8). The mixture was stirred thoroughly, and the prepared adhesive solution was coated onto a PET film. After drying at 110°C for 5 minutes, the film was cured at 40°C and 50%RH for 48 hours, thereby obtaining an adhesive sheet with an adhesive layer of 50 μm thickness.

[0221] Otherwise, the same procedure as in Example 1 was followed for the determination. The results are shown in Tables 1 and 5.

[0222] (Example 19)

[0223] In the above-mentioned “(Preparation of the copolymer-containing solution)”, as a mixture of structural unit monomers of block (A), a mixture consisting of 8.2 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 (B), a mixture consisting of 55.8 g of butyl acrylate (BA), 28.6 g of lauryl acrylate (LA), 0.50 g of maleic anhydride, 0.10 g of 4-hydroxybutyl acrylate (4HBA), and 15 g of ethylene-butene macromonomer: an olefin polymer with a single methacryloyl group at the end (manufactured by Kraton Polymers Japan, HPVM-L1253). Otherwise, a copolymer-containing solution containing copolymer (18) was prepared under the same conditions as in Example 1. It should be noted that the mixture of the structural unit monomers of block (B) and the amount of block (A) are set such that the content of block (A) in the obtained copolymer (18) is 9.89% by mass. In addition, the copolymer (18) is a triblock copolymer.

[0224] In addition, in the above-mentioned "(Preparation of adhesive sheet)", 0.92g of Coronate L-45E (manufactured by Tosoh Corporation), which is an isocyanate-based curing agent, was added to a copolymer-containing solution containing copolymer (18) relative to 100g of copolymer (18), stirred thoroughly, and the prepared adhesive solution was coated onto a PET film. After drying at 110°C for 5 minutes, it was cured at 40°C and 50%RH for 48 hours, thereby producing an adhesive sheet with an adhesive layer of 50μm thickness.

[0225] Otherwise, the same procedure as in Example 1 was followed for the determination. The results are shown in Tables 2 and 5.

[0226] (Example 20)

[0227] In the above-mentioned “(Preparation of the copolymer-containing solution)”, a mixture consisting of 9.1 g of benzyl acrylate, 0.9 g of 2-hydroxyethyl acrylate (HEA), and 0.9 g of acrylic acid (AAc) was added as the mixture of structural unit monomers for block (A), and a mixture consisting 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 the mixture of structural unit monomers for block (B). Otherwise, a copolymer-containing solution containing copolymer (27) was prepared in the same manner as in Example 1, adhesive sheets were made, and measurements were performed. It should be noted that the amount of the mixture of structural unit monomers for block (B) and the amount of block (A) were set such that the content of block (A) in the obtained copolymer (27) was 9.89% by mass. Furthermore, copolymer (27) was a triblock copolymer. The results are shown in Tables 3 and 5.

[0228] (Example 21)

[0229] In the above-mentioned “(Preparation of the copolymer-containing solution)”, a mixture consisting of 9.1 g of cyclohexyl acrylate, 0.9 g of 2-hydroxyethyl acrylate (HEA), and 0.9 g of acrylic acid (AAc) was added as the mixture of structural unit monomers for block (A), and a mixture consisting 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 the mixture of structural unit monomers for block (B). Otherwise, a copolymer-containing solution containing copolymer (28) was prepared in the same manner as in Example 1, adhesive sheets were made, and measurements were performed. It should be noted that the amount of the mixture of structural unit monomers for block (B) and the amount of block (A) were set such that the content of block (A) in the obtained copolymer (28) was 9.89% by mass. Furthermore, copolymer (28) was a triblock copolymer. The results are shown in Tables 3 and 5.

[0230] (Comparative Example 1)

[0231] In the above-mentioned “(Preparation of the copolymer-containing solution)”, 82.8 g of butyl acrylate (BA) and 9.2 g of lauryl acrylate (LA) were added as a mixture of the structural unit monomers of block (B). Otherwise, a copolymer-containing solution containing copolymer (19) was prepared in the same manner as in Example 1, adhesive sheets were made, and measurements were performed. It should be noted that the amount of the mixture of structural unit monomers of block (B) and the amount of block (A) were set such that the content of block (A) in the obtained copolymer (19) was 8.00% by mass. In addition, copolymer (19) is a triblock copolymer. The results are shown in Tables 3 and 6.

[0232] (Comparative Example 2)

[0233] In the above-mentioned “(Preparation of the copolymer-containing solution)”, a mixture consisting of 4.5 g of styrene (St) and 0.5 g of acrylic acid (AAc) was added as a mixture of the structural unit monomers of block (A). Otherwise, a copolymer-containing solution containing copolymer (20) was prepared in the same manner as in Example 1, adhesive sheets were made, and measurements were performed. It should be noted that the amount of the mixture of structural unit monomers of block (B) and block (A) was set such that the content of block (A) in the obtained copolymer (20) was 5.16% by mass. In addition, copolymer (20) is a triblock copolymer. The results are shown in Tables 3 and 6.

[0234] (Comparative Example 3)

[0235] In the above-mentioned “(Preparation of the copolymer-containing solution)”, a mixture consisting of 7.5 g of styrene (St) and 2.5 g of acrylic acid (AAc) was added as the 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 lauryl acrylate (LA) was added as the mixture of structural unit monomers of block (B). Otherwise, a copolymer-containing solution containing copolymer (21) was prepared in the same manner as in Example 1, adhesive sheets were made, and measurements were performed. It should be noted that the amount of the mixture of structural unit monomers of block (B) and block (A) was set such that the content of block (A) in the obtained copolymer (21) was 9.80% by mass. Furthermore, copolymer (21) was a triblock copolymer. The results are shown in Tables 3 and 6.

[0236] (Comparative Example 4)

[0237] In the above-mentioned “(Preparation of the copolymer-containing solution)”, a mixture consisting of 9.0 g of styrene (St) and 1.0 g of acrylic acid (AAc) was added as the mixture of structural unit monomers of block (A), and a mixture consisting of 41.4 g of butyl acrylate (BA) and 50.6 g of lauryl acrylate (LA) was added as the mixture of structural unit monomers of block (B). Otherwise, a copolymer-containing solution containing copolymer (22) was prepared in the same manner as in Example 1, adhesive sheets were made, and measurements were performed. It should be noted that the amount of the mixture of structural unit monomers of block (B) and block (A) was set such that the content of block (A) in the obtained copolymer (22) was 9.80% by mass. Furthermore, copolymer (22) was a triblock copolymer. The results are shown in Tables 3 and 6.

[0238] (Comparative Example 5)

[0239] In the above-mentioned “(Preparation of the copolymer-containing solution)”, a mixture consisting of 18.0 g of styrene (St) and 2.0 g of acrylic acid (AAc) was added as the mixture of structural unit monomers of block (A), and a mixture consisting of 59.8 g of butyl acrylate (BA), 31.28 g of isostearyl acrylate (ISTA), and 0.98 g of maleic anhydride was added as the mixture of structural unit monomers of block (B). Otherwise, a copolymer-containing solution containing copolymer (23) was prepared in the same manner as in Example 1, adhesive sheets were made, and measurements were performed. It should be noted that the amount of the mixture of structural unit monomers of block (B) and block (A) was set such that the content of block (A) in the obtained copolymer (23) was 17.9% by mass. In addition, copolymer (23) is a triblock copolymer. The results are shown in Tables 3 and 6.

[0240] (Comparative Example 6)

[0241] (Preparation of solutions containing copolymers)

[0242] In a reaction vessel equipped with a nitrogen inlet tube, a thermometer, and a stirrer, a mixture consisting of 59.8 g of butyl acrylate (BA), 31.28 g of lauryl acrylate (LA), 0.92 g of maleic anhydride, 0.0027 g of 2,2'-azobis(2-methylbutyronitrile) (ABN-E) as a polymerization initiator, and 5 g of ethyl acetate as a solvent was added to a flask. The flask was purged with nitrogen while the temperature was raised to 85°C. The polymerization reaction was then carried out by stirring at 85°C for 6 hours, yielding a copolymer-containing solution (24).

[0243] (Making of adhesive sheets)

[0244] 0.15 parts by weight of 1,6-hexanediol diacrylate (manufactured by Nakamura Chemical Co., Ltd., "A-HD-N") as a curing agent were added to the obtained copolymer-containing solution containing copolymer (24), and the mixture was stirred thoroughly to prepare an adhesive solution. The prepared adhesive solution was coated onto a PET film, dried at 110°C for 5 minutes, and then cured at 40°C and 50%RH for 48 hours, thereby producing an adhesive sheet with an adhesive layer of 50 μm thickness.

[0245] The determinations of the weight-average molecular weight of the copolymer, the SP value of the copolymer, the shear storage modulus G' of the adhesive layer at -20°C, 25°C, and 85°C, the shear strain and shear recovery rate of the adhesive sheet, and the 180° peel force of the adhesive sheet to polyimide were performed in the same manner as in Example 1. The results are shown in Tables 3 and 6.

[0246] (Comparative Example 7)

[0247] (Preparation of solutions containing copolymers)

[0248] In a reaction vessel equipped with a nitrogen inlet tube, thermometer, and stirrer, a monomer mixture containing 59g lauryl acrylate (LA), 40g 2-ethylhexyl acrylate (2EHA), 0.9g 4-hydroxybutyl acrylate (4HBA), and 5.0g N-vinylpyrrolidone, along with 0.1 parts by mass of 2,2-dimethoxy-1,2-diphenylethane-1-one as a photopolymerization initiator relative to 100 parts by mass of the monomer mixture, was added to a four-necked flask. To initiate polymerization, a black light (Sankyo Electric Co., Ltd., "FL20SBL") was used, irradiating the mixture at room temperature (23°C) with an emission wavelength of 360nm and an illuminance of 4mW / cm². 2Ultraviolet light is used to initiate photopolymerization. After the reaction begins, the temperature of the reaction system is raised. When the temperature rises to 7°C, air is introduced into the flask using an air pump to forcibly stop the reaction, thereby obtaining a copolymer-containing solution containing copolymer (25).

[0249] (Determination of weight-average molecular weight of copolymers)

[0250] The weight-average molecular weight of copolymer (25) was determined using the obtained copolymer-containing solution (25) in the same manner as in Example 1. The results are shown in Table 3.

[0251] (Determination of SP value of copolymer)

[0252] For copolymer (25), the SP value was calculated based on the structural formula using Hansen Solubility Parameter in Practice (HSPiP) as the HSP software. The results are shown in Table 3.

[0253] (Making of adhesive sheets)

[0254] To the copolymer-containing solution containing copolymer (25), 0.15 g of 1,6-hexanediol diacrylate (manufactured by Nakamura Chemical Co., Ltd., "A-HD-N") as a curing agent, 0.3 g of silane coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd., "KBM-403"), and 0.1 g of 2,2-dimethoxy-1,2-diphenylethane-1-one as a photopolymerization initiator were added, and the mixture was homogeneously mixed to obtain an adhesive solution.

[0255] An adhesive solution was applied to the mold-treated surface of a polyethylene terephthalate (PET) film that had undergone a mold release treatment. The solution was then applied using a gallium-encapsulated metal halide lamp (Fusion UV Systems, "LightHAMMER10") with a peak illuminance of 1600 mW / cm². 2 Cumulative exposure dose 1000 mJ / cm 2 Irradiation with ultraviolet light (wavelength 254nm) produces a laminated film with an adhesive layer of 50μm thickness. Further, a PET film with a release treatment side is laminated onto the laminated film with the adhesive layer facing each other, thus obtaining an adhesive sheet.

[0256] The determination of the shear storage modulus G' of the adhesive layer at -20°C, 25°C, and 85°C, the determination of the shear strain and shear recovery rate of the adhesive sheet, and the determination of the 180° peel force of the adhesive sheet to polyimide were performed in the same manner as in Example 1. The results are shown in Table 6.

[0257] (Comparative Example 8)

[0258] (Preparation of solutions containing copolymers)

[0259] In a reaction vessel equipped with a nitrogen inlet tube, a thermometer, and a stirrer, a mixture of 43 g of 2-ethylhexyl acrylate, 40 g of 2-ethylhexyl diethylene glycol acrylate, 15 g of 4-hydroxybutyl acrylate (4HBA), 1.0 g of N-hydroxyethylacrylamide (HEAA), and 1.0 g of methyl methacrylate macromonomer (manufactured by Toa Synthetic Co., Ltd., "AA-6") was added, replacing the air in the flask with nitrogen. Next, relative to 100 parts by weight of the mixture, 0.005 parts by weight of 2,2-dimethoxy-1,2-diphenylethane-1-one, as a photopolymerization initiator, was added while the mixture was stirred and mixed uniformly. To initiate polymerization, a black light (Sankyo Electric Co., Ltd., "FL20SBL") was used to irradiate the area at room temperature (23°C) with an emission wavelength of 360 nm and an illuminance of 4 mW / cm². 2 Ultraviolet light. After the reaction started, the temperature of the reaction system was raised. When the temperature of the reaction system reached 7°C, air was introduced into the flask using an air pump, thereby forcibly stopping the reaction and preparing a copolymer-containing solution (26).

[0260] (Determination of weight-average molecular weight of copolymers)

[0261] The weight-average molecular weight of copolymer (26) was determined using the obtained copolymer-containing solution (26) in the same manner as in Example 1. The results are shown in Table 3.

[0262] (Making of adhesive sheets)

[0263] A solution (S1) was prepared by dissolving 10 g of polyvinylpyrrolidone (PVP) in 90 g of 4-hydroxybutyl acrylate. To the obtained copolymer-containing solution (26), 0.1 g of the resulting solution (S1) (0.01 g of polyvinylpyrrolidone, 0.09 g of 4-hydroxybutyl acrylate) and 0.3 g of 1-hydroxycyclohexylphenyl ketone as a photopolymerization initiator were added, relative to 100 g of copolymer (26), to obtain an adhesive solution.

[0264] An adhesive solution was applied to the mold-treated surface of a polyethylene terephthalate (PET) film that had undergone a mold release treatment. The solution was then applied using a gallium-encapsulated metal halide lamp (Fusion UV Systems, "LightHAMMER10") with a peak illuminance of 1600 mW / cm². 2 Cumulative exposure dose 1000 mJ / cm 2 Irradiation with ultraviolet light (wavelength 254nm) synthesizes copolymer (C2), producing a laminated film with an adhesive layer containing copolymer (C2) and a thickness of 50μm. Further, a demolded PET film with one side having undergone demolding treatment is laminated onto the laminated film with the adhesive layer facing it, thereby obtaining an adhesive sheet.

[0265] (Determination of SP value of copolymer)

[0266] For copolymer (C2), the SP value was calculated based on the structural formula using Hansen Solubility Parameter in Practice (HSPiP) as the HSP software. The results are shown in Table 3.

[0267] The determination of the shear storage modulus G' of the adhesive layer at -20°C, 25°C, and 85°C, the determination of the shear strain and shear recovery rate of the adhesive sheet, and the determination of the 180° peel force of the adhesive sheet to polyimide were performed in the same manner as in Example 1. The results are shown in Table 6.

[0268] The materials in Tables 1 to 3 are as follows.

[0269] St: Styrene

[0270] AAc: Acrylic acid

[0271] HEA: 2-Hydroxyethyl acrylate

[0272] LA: Lauryl acrylate

[0273] ISTA: Isostearyl acrylate

[0274] BA: n-Butyl acrylate

[0275] 2EHA: 2-Ethylhexyl acrylate

[0276] DMAA: N,N-dimethylacrylamide

[0277] 4HBA: 4-Hydroxybutyl acrylate

[0278] HEAA: N-(2-hydroxyethyl)acrylamide

[0279] NVP: N-vinyl-2-pyrrolidone

[0280] PVP: Polyvinylpyrrolidone

[0281] [Table 1]

[0282]

[0283] [Table 2]

[0284]

[0285] [Table 3]

[0286]

[0287] <Evaluation>

[0288] The adhesive sheets obtained in the examples and comparative examples were evaluated as follows. The results are shown in Tables 4 to 6.

[0289] (Dynamic bending test)

[0290] Peel off the PET film from one side of the obtained adhesive sheet and laminate it to a 75 μm thick polyimide film (manufactured by DUPONT-TORAY, "Kapton200H"). Peel off the PET film from the other side of the laminated adhesive sheet and laminate it to the same 75 μm thick polyimide film. Repeat this operation to create a laminate with a total thickness of 375 μm. Shape the resulting laminate into a 20 × 80 mm size and prepare a test sample. Place the obtained test sample in a U-shaped stretch tester (manufactured by YuasaSystem Machinery Co., Ltd., "ETS with chamber") set to 25°C with the long side approximately at the center of the bend. Perform a dynamic bending test at 25°C, 50% RH, a bending radius of 2.0 mm, and a bending speed of 60 times / min. It should be noted that the U-shaped expansion tester used in this evaluation is a mechanism that repeatedly bends the surface into a U-shape by 180° under no load. The bending radius can be adjusted by adjusting the distance between the surfaces that are bent into the U-shape.

[0291] Test samples were collected after 100,000 and 200,000 repeated bending cycles. Peeling and cracking at the bending points were observed using a digital microscope (KEYENCE, "VHX-6000"). Samples that did not peel or crack after 200,000 bending cycles were marked with "◎", samples that peeled or cracked after 200,000 bending cycles but not after 100,000 bending cycles were marked with "○", and samples that peeled or cracked after 100,000 bending cycles were marked with "×". The bending resistance of the adhesive sheet was evaluated.

[0292] (Static bending test)

[0293] Test specimens were prepared using the same method as described above for the "(Dynamic Bending Test)". The resulting test specimens were placed in a U-shaped expansion and contraction testing machine (manufactured by YuasaSystem Machinery Co., Ltd., "ETS with chamber") equipped with a thermostat, with the bending portion approximately at the center of the long side of the specimen. The specimens were then bent 180° into a U-shape at 25°C, 50% RH, and a bending radius of 2.0 mm, and held in this bent state for 240 hours. The same test was also conducted with a bending radius of 0.5 mm.

[0294] After the recovery test, the samples were examined for peeling and cracking at the bends using a digital microscope (KEYENCE, "VHX-6000"). Cases where no peeling or cracking occurred at a bending radius of 0.5 mm were marked with "◎", cases where peeling or cracking occurred at a bending radius of 0.5 mm but not at a bending radius of 2.0 mm were marked with "○", and cases where peeling or cracking occurred at a bending radius of 2.0 mm were marked with "×". This process was used to evaluate the bending resistance of the adhesive sheet.

[0295] It should be noted that even if the evaluation is "×", the adhesive sheet of the present invention can still be used without problems depending on the application.

[0296] [Table 4]

[0297]

[0298] [Table 5]

[0299]

[0300] [Table 6]

[0301]

[0302] Industrial availability

[0303] According to the present invention, an adhesive sheet with excellent bending resistance can be provided, which is not prone to peeling or lifting even when repeatedly bent.

[0304] Explanation of reference numerals in the attached figures

[0305] 1: Adhesive sheet

[0306] 21, 22: SUS board

[0307] 3: Fixture

[0308] 4: A 200g weight

Claims

1. An adhesive sheet, characterized in that, It has an adhesive layer. When conducting a series of cohesive force tests on the adhesive sheet, the series of processes begins from the state where SUS plates are attached to both the top and bottom surfaces of the adhesive sheet, and continues until time point t1, when a stress of 10 kPa is applied to the SUS plate on the top surface along the shear direction for 3 minutes, and then the 10 kPa stress is immediately unloaded and the sheet is left to stand for 3 minutes, which is time point t2. The shear strain at time point t1 is greater than 250%. The shear deformation recovery rate at time point t2 is above 80%.

2. The adhesive sheet according to claim 1, wherein, The shear deformation recovery rate at time point t2 is over 90%.

3. The adhesive sheet according to claim 1 or 2, wherein, The shear strain at time point t1 is above 300%.

4. The adhesive sheet according to claim 1, 2 or 3, wherein its 180° peel force on polyimide is 10.0 N / 25 mm or more.

5. The adhesive sheet according to claim 4, wherein its 180° peel force on polyimide is 14.0 N / 25 mm or more.

6. The adhesive sheet according to claim 1, 2, 3, 4 or 5, wherein, The adhesive layer contains a block copolymer comprising block A and block B. Block A has a structural unit derived from monomer component a, which is at least one selected from styrene and (meth)acrylates having a cyclic structure. Block B has structural units derived from monomer component b, which is a (meth)acrylate represented by formula (1). In equation (1), R 1 R represents a hydrogen atom or a methyl group. 2 It indicates an alkyl group with 9 or more carbon atoms.

7. The adhesive sheet according to claim 6, wherein, Block A also has structural units derived from monomers containing polar functional groups.

8. The adhesive sheet according to claim 7, wherein, Block A also has structural units derived from (meth)acrylic acid.

9. The adhesive sheet according to claim 6, 7 or 8, wherein, In block A, the structural unit derived from monomer component a contains 80% or more by mass.

10. The adhesive sheet according to claim 6, 7, 8 or 9, wherein, In the block B, the structural unit derived from monomer component b is present in a proportion of 20% by mass or more and 45% by mass or less.

11. The adhesive sheet according to claim 6, 7, 8, 9 or 10, wherein, Block B further comprises a structural unit derived from an olefin polymer with a polymerizable unsaturated double bond at the end, wherein the structural unit derived from the olefin polymer with a polymerizable unsaturated double bond at the end comprises 5% by mass or more and 30% by mass or less in Block B.

12. The adhesive sheet according to claim 6, 7, 8, 9, 10 or 11, wherein, The block copolymer has structural units derived from monomers containing polar functional groups.

13. The adhesive sheet according to claim 12, wherein, The block copolymer has structural units derived from (meth)acrylic acid.

14. The adhesive sheet according to claim 6, 7, 8, 9, 10, 11, 12 or 13, wherein, The block copolymer is an ABA-type triblock structure in which block B is sandwiched between block A.

15. The adhesive sheet according to claim 6, 7, 8, 9, 10, 11, 12, 13 or 14, wherein, In the block copolymer, the content of block A is 7.25% by mass or more and 15% by mass or less.

16. The adhesive sheet according to claim 6, 7, 8, 9, 10, 11, 12, 13, 14 or 15, wherein, The block copolymer has a weight-average molecular weight (Mw) of 250,000 or more and 1 million or less.

17. The adhesive sheet according to claim 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 or 16, wherein, The solubility parameter (SP value) of the block copolymer is 9.30 (J / cm³). 3 ) 1 / 2 above.

18. An adhesive sheet, characterized in that, It has an adhesive layer. The adhesive layer contains a block copolymer comprising block A and block B. Block A has a structural unit derived from monomer component a, which is at least one selected from styrene and (meth)acrylates having a cyclic structure. Block B has structural units derived from monomer component b, which is a (meth)acrylate represented by formula (1). In block A, the structural unit derived from monomer component a accounts for more than 80% by mass. In block B, the structural unit derived from monomer component b is present in a proportion of 20% by mass or more and 45% by mass or less. In the block copolymer, the content of block A is 7.25% by mass or more and 15% by mass or less. In equation (1), R 1 R represents a hydrogen atom or a methyl group. 2 It indicates an alkyl group with 9 or more carbon atoms.

19. The adhesive sheet according to claim 18, wherein, Block B further comprises a structural unit derived from an olefin polymer with a polymerizable unsaturated double bond at the end, wherein the structural unit derived from the olefin polymer with a polymerizable unsaturated double bond at the end comprises 5% by mass or more and 30% by mass or less in Block B.

20. The adhesive sheet according to claim 18 or 19, wherein, The block copolymer is an ABA-type triblock structure in which block B is sandwiched between block A.

21. The adhesive sheet according to claim 18, 19 or 20, wherein, The block copolymer has a weight-average molecular weight (Mw) of 250,000 or more and 1 million or less.

22. The adhesive sheet according to claim 18, 19, 20 or 21, wherein, The solubility parameter (SP value) of the block copolymer is 9.30 (J / cm³). 3 ) 1 / 2 above.

23. The adhesive sheet according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21 or 22, wherein it does not have a substrate.

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