Adhesive sheet

Abstract

The present application relates to an adhesive sheet. The adhesive sheet includes an adhesive layer having a creep recovery rate of 75% or more at-20 DEG C, a creep recovery rate of 80% or more at 25 DEG C, and a creep recovery rate of 85% or more at 70 DEG C after applying a stress of 10000 Pa for 10 minutes, removing the applied stress, and recovering for 10 minutes under a stress of 1 Pa. The adhesive sheet according to the present invention can be stably used over a wide temperature range, is free of creases, cracks, fractures and degumming when used at low and normal temperatures, can be normally used even at high temperatures, and has excellent folding characteristics and bending resistance over a wide temperature range.

Description

Technical Field

[0001] This invention relates to adhesive sheets, and more particularly to adhesive sheets that can be used stably over a wide temperature range. Background Technology

[0002] In existing technologies, adhesive sheets are widely used in various industrial and everyday scenarios, such as in electronic products. Because electronic products need to operate in different temperature environments, including the low temperatures of winter and the high temperatures of summer, and the potential for overheating due to prolonged user use, adhesive sheets may become brittle and lose their adhesiveness at low temperatures, while aging may occur too quickly at high temperatures. When used in flexible screens for foldable phones, reliable resilience after folding is also required over a wide temperature range. Therefore, adhesive sheets that can operate stably over a wide temperature range are essential.

[0003] Existing adhesive sheets struggle to maintain stable performance across a wide temperature range. In particular, they are prone to delamination and cracking after folding, and may leave creases and adhesive residue. These problems severely impact the effectiveness and reliability of the adhesive sheets, limiting their use over a broad temperature range. Summary of the Invention

[0004] The problem the invention aims to solve

[0005] The present invention is made to solve the above-mentioned existing problems. Its purpose is to provide an adhesive sheet that can be used stably in a wide temperature range. It does not crease, crack, break, or delaminate when used at low and normal temperatures, and can also be used normally at high temperatures. Furthermore, it has excellent folding and bending resistance properties in a wide temperature range.

[0006] Solution for solving the problem

[0007] In order to solve the above-mentioned problems, the inventors conducted in-depth research and found that by applying a stress of 10,000 Pa for 10 minutes to the adhesive layer contained in the adhesive sheet, removing the applied stress, and then allowing it to recover for 10 minutes under a stress of 1 Pa, the creep recovery rates at -20°C, 25°C, and 70°C are all within specific ranges, thus solving the above-mentioned problems and completing the present invention. That is, the present invention is as follows.

[0008] [1] An adhesive sheet comprising an adhesive layer, wherein, after applying a stress of 10000 Pa for 10 minutes, the applied stress is removed, and after recovering under a stress of 1 Pa for 10 minutes, the creep recovery rate at -20°C is more than 75%, the creep recovery rate at 25°C is more than 80%, and the creep recovery rate at 70°C is more than 85%.

[0009] [2] According to the adhesive sheet described in [1], wherein the glass transition temperature Tg of the adhesive layer is less than -30°C.

[0010] [3] According to the adhesive sheet described in [1] or [2], after the adhesive layer with a thickness of 20 μm is bonded to the PET sheet and placed at 23°C for 24 hours, the peel adhesion force when peeled at 23°C in the 180° direction at a tensile speed of 300 mm / min is 5.0 to 8.0 N / inch.

[0011] After the adhesive layer with a thickness of 20 μm was bonded to the SUS304BA board and placed at 23°C for 24 hours, the peel adhesion force when peeled off at 23°C in the 180° direction at a tensile speed of 300 mm / min was 5.0 to 11.0 N / inch.

[0012] [4] According to the adhesive sheet described in [1] or [2], the peel adhesion force when the 20 μm thick adhesive layer is bonded to the PET sheet and placed at 23°C for 24 hours, is 2.0 to 3.5 N / inch when peeled at 80°C in a 180° direction at a tensile speed of 300 mm / min.

[0013] After the adhesive layer with a thickness of 20 μm was bonded to the SUS304BA board and placed at 23°C for 24 hours, the peel adhesion force when peeled off at 80°C in the 180° direction at a tensile speed of 300 mm / min was 3.0 to 5.6 N / inch.

[0014] [5] According to the adhesive sheet described in [1] or [2], wherein the storage modulus G' of the adhesive layer at -20°C is 1.5 × 10⁻⁶. 5 ~3.4×10 5 Pa,

[0015] The storage modulus G' of the adhesive layer at 23°C is 3.0 × 10⁻⁶. 4 ~4.5×10 4 Pa,

[0016] The storage modulus G' of the adhesive layer at 85°C is 1.0 × 10⁻⁶. 4 ~2.5×10 4 Pa,

[0017] The difference between the storage modulus G' of the adhesive layer at 23°C and the storage modulus G' of the adhesive layer at 85°C is 1.1 × 10⁻⁶. 4 ~2.0×10 4 Pa.

[0018] [6] According to the adhesive sheet described in [5], the average value of the storage modulus G' of the adhesive layer at -20°C and the storage modulus G' of the adhesive layer at 23°C is 1.0 × 10⁻⁶. 5 ~1.9×10 5 Pa.

[0019] [7] According to the adhesive sheet described in [5], the average value of the storage modulus G' of the adhesive layer at -20°C, the storage modulus G' of the adhesive layer at 23°C, and the storage modulus G' of the adhesive layer at 85°C is 7.0 × 10⁻⁶. 4 ~1.3×10 5 Pa.

[0020] [8] According to the adhesive sheet of [1] or [2], wherein the adhesive layer is formed of an adhesive composition comprising a base polymer comprising structural units derived from alkyl (meth)acrylate monomers, wherein the homopolymer of the alkyl (meth)acrylate monomers has a glass transition temperature (Tg) of -75 to 110 °C.

[0021] The (meth)acrylate alkyl ester monomer comprises soft monomers and hard monomers.

[0022] The glass transition temperature (Tg) of the homopolymer of the soft monomer is ≤0℃, and the content of the soft monomer is 83-97 parts by weight relative to 100 parts by weight of the total monomer components of the base polymer.

[0023] The glass transition temperature (Tg) of the homopolymer of the hard monomer is greater than 0°C, and the content of the hard monomer is 0 to 7 parts by weight relative to 100 parts by weight of all monomer components of the base polymer.

[0024] [9] According to the adhesive sheet of [8], wherein the alkyl methacrylate monomer comprises one or more selected from the group consisting of methyl methacrylate, n-butyl methacrylate, n-octyl methacrylate, 2-ethylhexyl methacrylate, cyclohexyl methacrylate, isononyl methacrylate, decyl methacrylate, isodecyl methacrylate, dodecyl methacrylate, and heptadecanyl methacrylate.

[0025]

[10] According to the adhesive sheet of [8], wherein the base polymer further comprises a functional monomer, and the content of the functional monomer is 1 to 10 parts by weight relative to 100 parts by weight of all monomer components of the base polymer.

[0026] The functional monomers include (meth)acrylate monomers containing carboxyl groups and (meth)acrylate monomers containing hydroxyl groups.

[0027]

[11] According to the adhesive sheet of

[10] , wherein when the carboxyl-containing (meth)acrylate monomer contains a monomer with a glass transition temperature Tg > 50°C of homopolymer, the ratio of the content of the carboxyl-containing (meth)acrylate monomer to the content of the hydroxyl-containing (meth)acrylate monomer is 0.5 to 29.

[0028] When the carboxyl-containing (meth)acrylate monomer is composed of a homopolymer with a glass transition temperature Tg ≤ 50°C, the ratio of the content of the carboxyl-containing (meth)acrylate monomer to the content of the hydroxyl-containing (meth)acrylate monomer is 10 to 45.

[0029]

[12] According to the adhesive sheet of

[10] , wherein the carboxyl-containing (meth)acrylate monomer comprises one or more selected from the group consisting of fumaric acid, maleic acid, (meth)acrylate, β-carboxyethyl (meth)acrylate, itaconic acid, crotonic acid, isocrotonic acid, and citraconic acid.

[0030]

[13] According to the adhesive sheet of

[10] , wherein the hydroxyl-containing (meth)acrylate monomer comprises one or more selected from the group consisting of 4-hydroxybutyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 2-hydroxybutyl methacrylate, 3-hydroxypropyl methacrylate, 6-hydroxyhexyl methacrylate, 8-hydroxyoctyl methacrylate, 10-hydroxydecyl methacrylate, 12-hydroxylauryl methacrylate, and methyl methacrylate (4-hydroxymethylcyclohexyl)

[0031]

[14] The adhesive sheet according to [1] or [2] further includes a substrate layer, wherein the adhesive layer is disposed on one or both sides of the substrate layer.

[0032] The effects of the invention

[0033] The adhesive sheet of the present invention can be used stably over a wide temperature range. It does not crease, crack, break, or delaminate when used at low and normal temperatures, and can also be used normally at high temperatures. It also exhibits folding and bending resistance over a wide temperature range. Attached Figure Description

[0034] Figure 1 This is a cross-sectional view schematically illustrating the structure of an adhesive sheet according to one embodiment of the present invention.

[0035] Figure 2 This is a cross-sectional view schematically illustrating the structure of an adhesive sheet according to another embodiment of the present invention.

[0036] Figure 3 This is a cross-sectional view schematically illustrating the structure of an adhesive sheet according to another embodiment of the present invention.

[0037] Explanation of reference numerals in the attached figures

[0038] 1, 2, 3 adhesive sheets

[0039] 10 Adhesive Layer

[0040] 20 Substrate layer

[0041] 30 adhesive layers Detailed Implementation

[0042] The following describes suitable embodiments of the present invention. Matters necessary for carrying out the present invention, other than those specifically mentioned in this specification, are understood by those skilled in the art based on the teachings on the implementation of the invention as set forth in this specification and common technical knowledge at the time of application. The present invention can be implemented based on the disclosures in this specification and common technical knowledge in the field.

[0043] Furthermore, in the following figures, components or parts that perform the same function are sometimes labeled with the same symbols and described, and repeated descriptions are sometimes omitted or simplified. In addition, the embodiments described in the figures are schematic for the purpose of clearly illustrating the invention and do not necessarily accurately represent the dimensions or scale of the actual product provided.

[0044] <Adhesive Sheet>

[0045] The adhesive sheet of the present invention includes an adhesive layer, wherein, after applying a stress of 10000 Pa for 10 minutes, the applied stress is removed, and after recovering under a stress of 1 Pa for 10 minutes, the creep recovery rate of the adhesive layer is 75% or more at -20°C, 80% or more at 25°C, and 85% or more at 70°C.

[0046] Figure 1 This is a cross-sectional view schematically illustrating the structure of an adhesive sheet according to one embodiment of the present invention. For example... Figure 1 As shown, the adhesive sheet 1 includes an adhesive layer 10.

[0047] Figure 2 This is a cross-sectional view schematically illustrating the structure of an adhesive sheet according to another embodiment of the present invention. Figure 2 As shown, the adhesive sheet 1 includes an adhesive layer 10 and a substrate layer 20. The adhesive layer 10 is disposed on one side of the substrate layer 20, and the adhesive layer 20 is preferably disposed on the entire surface of one side of the substrate layer 10.

[0048] Figure 3 This is a cross-sectional view schematically illustrating the structure of an adhesive sheet according to another embodiment of the present invention. Figure 3As shown, the adhesive sheet 1 includes an adhesive layer 10, a substrate layer 20, and an adhesive layer 30. The adhesive layer 10 and adhesive layer 30 are respectively disposed on both sides of the substrate layer 20, and preferably respectively disposed on the entire surface of both sides of the substrate layer 20. Without impairing the technical effect of the present invention, the adhesive layer 10 and adhesive layer 30 may be the same or different.

[0049] The concept of adhesive sheet as used in this specification can include objects referred to as adhesive tape, adhesive label, adhesive film, etc. It should be noted that the adhesive sheet disclosed herein can be a single sheet or an adhesive sheet that has been further processed into various shapes. In some preferred embodiments, the adhesive sheet of the present invention can be provided in a strip shape.

[0050] Additionally, although not illustrated, the adhesive sheet of the present invention may have a release liner provided on the outside of the adhesive layer for the purpose of protecting the adhesive surface before it is supplied for use.

[0051] The adhesive sheet of the present invention has the following characteristics:

[0052] The adhesive sheet of the present invention includes an adhesive layer, wherein, after applying a stress of 10000 Pa for 10 minutes and removing the applied stress, the adhesive layer recovers for 10 minutes under a stress of 1 Pa, and exhibits a creep recovery rate of 75% or more at -20°C, preferably 78% or more, more preferably 80% or more, and on the other hand, it can be less than 88% or less, and less than 85%; a creep recovery rate of 80% or more at 25°C, preferably 82% or more, more preferably 85% or more, and on the other hand, it can be less than 93% or less, and less than 90%; and a creep recovery rate of 85% or more at 70°C, preferably 90% or more, more preferably 95% or more, and on the other hand, it can be less than 100%.

[0053] When the creep recovery rates of the adhesive layer at -20°C, 25°C, and 70°C fall within the aforementioned ranges, the adhesive sheet can be used without creases, cracks, breaks, or delamination at low and normal temperatures, and can also be used normally at high temperatures, exhibiting excellent folding and bending resistance over a wide temperature range. However, if the creep recovery rates of the adhesive sheet at -20°C, 25°C, and 70°C are outside the aforementioned ranges, the aforementioned properties of the adhesive sheet may be compromised, making it impossible to use stably over a wide temperature range.

[0054] The creep recovery rate of the adhesive layer at -20°C, the creep recovery rate at 25°C, and the creep recovery rate at 70°C can be determined, for example, by the method described in the examples described later.

[0055] More preferably, the glass transition temperature Tg of the adhesive layer is < -30°C, more preferably -70°C < Tg < -30°C, and even more preferably -40°C ≤ Tg < -30°C. The glass transition temperature Tg of the adhesive layer can be determined, for example, by the method described in the embodiments described later.

[0056] When the glass transition temperature (Tg) of the adhesive layer contained in the adhesive sheet falls within the above range, it can be used normally over a wide temperature range.

[0057] More preferably, after the 20μm thick adhesive layer is bonded to the PET board and placed at 23°C for 24 hours, the peel adhesion force when peeled off at 23°C in the 180° direction at a tensile speed of 300mm / min is preferably 5.0 to 8.0 N / inch, more preferably 5.5 to 7.8 N / inch, and even more preferably 6.0 to 7.5 N / inch.

[0058] More preferably, after the adhesive layer with a thickness of 20 μm is bonded to the SUS304BA board and placed at 23°C for 24 hours, the peel adhesion force when peeled off at 23°C in the 180° direction at a tensile speed of 300 mm / min is preferably 5.0 to 11.0 N / inch, more preferably 5.5 to 10.5 N / inch, and even more preferably 6.0 to 10.0 N / inch.

[0059] When the adhesive layer contained in the adhesive sheet has a peel adhesion force of 23°C to a PET sheet and a peel adhesion force of 23°C to a SUS304BA sheet within the above range, the adhesive sheet has appropriate tackiness, which allows the adhesive sheet to fully bond with the adhered object while not easily generating adhesive residue.

[0060] The peel adhesion of the adhesive layer to PET sheets at 23°C and to SUS304BA sheets at 23°C can be measured, for example, by the method described in the examples described later.

[0061] More preferably, after the 20μm thick adhesive layer is bonded to the PET board and placed at 23°C for 24 hours, the peel adhesion force when peeled off at 80°C in the 180° direction at a tensile speed of 300mm / min is preferably 2.0 to 3.5 N / inch, more preferably 2.5 to 3.4 N / inch, and even more preferably 2.8 to 3.3 N / inch.

[0062] After the adhesive layer with a thickness of 20 μm is bonded to the SUS304BA board and placed at 23°C for 24 hours, the peel adhesion force when peeled off at 80°C in the 180° direction at a tensile speed of 300 mm / min is preferably 3.0 to 5.6 N / inch, more preferably 3.5 to 5.4 N / inch, and even more preferably 4.0 to 5.2 N / inch.

[0063] When the peel adhesion force of the adhesive layer contained in the adhesive sheet to the PET sheet at 80°C and to the SUS304BA sheet at 80°C fall within the above-mentioned range, the adhesive sheet can have appropriate tack at high temperature, so that the adhesive sheet and the adhered object are fully bonded and not easily leave residue, thereby further improving the stability of the adhesive sheet in use over a wide temperature range.

[0064] The peel adhesion of the adhesive layer to PET sheets at 80°C and to SUS304BA sheets at 80°C can be measured, for example, by the method described in the examples below.

[0065] More preferably, the storage modulus G' of the adhesive layer at -20°C is preferably 1.5 × 10⁻⁶. 5 ~3.4×10 5 Pa, more preferably 1.7 × 10 Pa. 5 ~3.3×10 5 Pa, more preferably 2.2 × 10 Pa. 5 ~3.1×10 5 Pa, more preferably 2.5 × 10 Pa. 5 ~3.0×10 5 Pa. When the storage modulus G' of the adhesive layer contained in the adhesive sheet falls within the above range at -20°C, the adhesive sheet exhibits excellent folding and bending properties over a wide temperature range.

[0066] More preferably, the storage modulus G' of the adhesive layer at 23°C is preferably 3.0 × 10⁻⁶. 4 ~4.5×10 4 Pa, more preferably 3.3 × 10 Pa. 4 ~4.3×10 4 Pa, more preferably 3.5 × 10 Pa. 4 ~4.0×10 4 Pa. When the storage modulus G' of the adhesive layer at 23°C falls within the aforementioned range, the adhesive sheet can exhibit better folding and bending properties over a wide temperature range.

[0067] More preferably, the storage modulus G' of the adhesive layer at 85°C is preferably 1.0 × 10⁻⁶. 4~2.5×10 4 Pa, more preferably 1.4 × 10 Pa. 4 ~2.1×10 4 Pa, more preferably 1.7 × 10 Pa. 4 ~2.0×10 4 Pa. When the storage modulus G' of the adhesive layer at 85°C falls within the aforementioned range, the adhesive sheet can exhibit better folding and bending properties over a wide temperature range.

[0068] More preferably, the difference between the storage modulus G' of the adhesive layer at 23°C and the storage modulus G' of the adhesive layer at 85°C is preferably 1.1 × 10⁻⁶. 4 ~2.0×10 4 Pa, more preferably 1.3 × 10 Pa. 4 ~1.8×10 4 Pa, more preferably 1.4 × 10 Pa. 4 ~1.7×10 4 Pa. When the difference between the storage modulus G' of the adhesive layer at 23°C and the storage modulus G' of the adhesive layer at 85°C falls within the aforementioned range, the adhesive sheet can possess better folding and bending resistance properties over a wide range of temperatures.

[0069] The storage modulus G' of the adhesive layer at -20°C, the storage modulus G' at 23°C, and the storage modulus G' at 85°C can be determined, for example, by the method described in the embodiments described later. The difference between the storage modulus G' of the adhesive layer at 23°C and the storage modulus G' of the adhesive layer at 85°C is the value obtained by subtracting the storage modulus G' of the adhesive layer at 85°C from the storage modulus G' of the adhesive layer at 23°C.

[0070] More preferably, the average value of the storage modulus G' of the adhesive layer at -20°C and the storage modulus G' of the adhesive layer at 23°C is preferably 1.0 × 10⁻⁶. 5 ~1.9×10 5 Pa, more preferably 1.1 × 10 Pa 5 ~1.6×10 5 Pa, more preferably 1.3 × 10 Pa. 5 ~1.4×10 5 Pa.

[0071] More preferably, the average value of the storage modulus G' of the adhesive layer at -20°C, the storage modulus G' of the adhesive layer at 23°C, and the storage modulus G' of the adhesive layer at 85°C is preferably 7.0 × 10⁻⁶. 4 ~1.3×10 5 Pa, more preferably 8.0 × 10 Pa4 ~1.2×10 5 Pa, more preferably 9.0 × 10 Pa. 4 ~1.0×10 5 Pa.

[0072] For the adhesive layer contained in the adhesive sheet, when the average value of the storage modulus G' of the adhesive layer at -20°C and the storage modulus G' of the adhesive layer at 23°C falls within the aforementioned range, and / or when the average value of the storage modulus G' of the adhesive layer at -20°C, the storage modulus G' of the adhesive layer at 23°C, and the storage modulus G' of the adhesive layer at 85°C falls within the aforementioned range, the adhesive sheet can maintain stable operation over a wide temperature range. The aforementioned average value refers to the arithmetic mean.

[0073] [Adhesive layer]

[0074] The adhesive layer is formed from an adhesive composition, which preferably contains a base polymer. The form of the adhesive composition is not particularly limited; for example, it can be a water-dispersible, solvent-based, hot-melt, or photocurable (e.g., light-curable) adhesive composition.

[0075] The components of the adhesive composition of the present invention will be described in detail below.

[0076] (Basic Polymer)

[0077] The adhesive composition of the present invention preferably comprises a base polymer, which may include, for example, acrylic polymers, rubber polymers, polyester polymers, urethane polymers, polyether polymers, silicone polymers, polyamide polymers, fluoropolymers, etc. Preferably, the adhesive composition comprises an acrylic polymer.

[0078] In this invention, there is no particular limitation on the content of the base polymer. From the viewpoint of obtaining sufficient adhesive reliability, it is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more, relative to the total amount of the adhesive composition (total mass, 100% by mass). By adjusting the content of the base polymer in the adhesive composition to the above range, an adhesive composition with superior stress relief and durability and excellent adhesion to the adhered objects can be provided.

[0079] In a preferred embodiment, the adhesive composition comprises structural units derived from (meth)acrylate monomers. In this specification, "(meth)acrylate" refers to "alkyl acrylate" and / or "alkyl methacrylate," and so on.

[0080] Examples of alkyl methacrylate monomers include: methyl methacrylate, n-butyl methacrylate, n-octyl methacrylate, 2-ethylhexyl methacrylate, cyclohexyl methacrylate, isononyl methacrylate, decyl methacrylate, isodecanyl methacrylate, dodecyl methacrylate, and heptadecanyl methacrylate. One or more of these monomers may be used.

[0081] In a preferred embodiment, the glass transition temperature (Tg) of the homopolymer of the (meth)acrylate alkyl ester monomer is preferably -75 to 110°C, more preferably -72 to 90°C, and even more preferably -70 to 50°C.

[0082] In a preferred embodiment, the content of the (meth)acrylate alkyl monomer is preferably 83 parts by weight or more, more preferably 90 parts by weight or more, and even more preferably 95 parts by weight or more, relative to 100 parts by weight of all monomer components of the base polymer.

[0083] In a preferred embodiment, from the viewpoint of enabling the adhesive sheet to possess excellent folding and bending resistance over a wide temperature range, the (meth)acrylate alkyl monomer preferably comprises soft monomers and hard monomers. The glass transition temperature (Tg) of the homopolymer of the soft monomer is ≤0°C, preferably -10°C ≤ Tg ≤ -70°C, more preferably -20°C ≤ Tg ≤ -60°C. The glass transition temperature (Tg) of the homopolymer of the hard monomer is >0°C, preferably 2°C ≤ Tg ≤ 50°C, more preferably 5°C ≤ Tg ≤ 20°C. The content of the soft monomer is preferably 83-97 parts by weight, more preferably 86-94 parts by weight, and even more preferably 88-92 parts by weight, relative to 100 parts by weight of all monomer components of the base polymer; the content of the hard monomer is preferably 0-7 parts by weight, more preferably 1-5 parts by weight, and even more preferably 2-4 parts by weight, relative to 100 parts by weight of all monomer components of the base polymer.

[0084] Examples of soft monomers include: 2-ethylhexyl (meth)acrylate, dodecyl (meth)acrylate, heptadecanyl (meth)acrylate, isononyl (meth)acrylate, and isodecanyl (meth)acrylate.

[0085] Examples of hard monomers include methyl methacrylate and cyclohexyl methacrylate.

[0086] On the other hand, in a preferred embodiment, the (meth)acrylate alkyl monomer preferably comprises a long-chain monomer and a short-chain monomer. The long-chain monomer is a (meth)acrylate alkyl monomer with 10 to 12 carbon atoms, and the short-chain monomer is a (meth)acrylate alkyl monomer with 1 to 9 carbon atoms. Relative to 100 parts by weight of all monomer components of the base polymer, the content of the long-chain monomer is preferably 5 to 15 parts by weight, more preferably 6 to 12 parts by weight, and even more preferably 8 to 10 parts by weight. Relative to 100 parts by weight of all monomer components of the base polymer, the content of the short-chain monomer is preferably 83 to 97 parts by weight, more preferably 86 to 94 parts by weight, and even more preferably 88 to 92 parts by weight.

[0087] Examples of long-chain monomers include: dodecyl (meth)acrylate, heptadecanyl (meth)acrylate, isodecyl (meth)acrylate, and decyl (meth)acrylate.

[0088] Examples of short-chain monomers include: 2-ethylhexyl (meth)acrylate, isononyl (meth)acrylate, methyl (meth)acrylate, and cyclohexyl (meth)acrylate.

[0089] In a preferred embodiment, the base polymer further comprises a functional monomer.

[0090] As functional monomers (comonomers), monomers with polar groups can be suitably used. Monomers with polar groups are useful for introducing crosslinking points into the base polymer or for improving the cohesive strength of the base polymer. Functional monomers can be used alone or in combination of two or more.

[0091] More preferably, the content of the functional monomer is 1 to 10 parts by weight relative to 100 parts by weight of all monomer components of the base polymer, more preferably 1.5 to 8.5 parts by weight, and even more preferably 2 to 8 parts by weight.

[0092] Examples of functional monomers include (meth)acrylate monomers containing carboxyl groups, (meth)acrylate monomers containing hydroxyl groups, and monomers containing amide groups. One type or a combination of two or more types can be used. More preferably, the functional monomer is a linear or branched monomer (i.e., acyclic monomer), thereby ensuring the adhesiveness of the sheet while possessing excellent folding and bending resistance.

[0093] Carboxyl-containing (meth)acrylate monomers (sometimes referred to simply as "carboxyl-containing monomers" in this invention) refer to (meth)acrylate monomers having at least one carboxyl group within their molecule. By including carboxyl-containing (meth)acrylate monomers in the raw material monomers of the base polymer, the cohesive force of the base polymer (suitably an acrylic polymer) is increased due to the formation of secondary bonds such as hydrogen bonds with the adherends. This more effectively suppresses changes in adhesive strength over time, results in less residue on the adherends after peeling, and exhibits higher aggregation properties. Furthermore, by including carboxyl-containing (meth)acrylate monomers in the raw material monomers of the base polymer, a crosslinking reaction with a crosslinking agent can occur effectively when using the crosslinking agent, fully demonstrating its effect as an adhesive, and effectively preventing delamination and breakage of the adherends during peeling operations over a wide temperature range.

[0094] Examples of (meth)acrylate monomers containing carboxyl groups include: fumaric acid, maleic acid, (meth)acrylic acid, β-carboxyethyl (meth)acrylate, itaconic acid, crotonic acid, isocrotonic acid, and citraconic acid. One or more of these can be used, or a combination of two or more can be used.

[0095] Hydroxyl-containing (meth)acrylate monomers (sometimes referred to simply as "hydroxyl-containing monomers" in this invention) refer to (meth)acrylate monomers having at least one hydroxyl group within their molecule. When the monomer components used to constitute the base polymer include hydroxyl-containing (meth)acrylate monomers, i.e., when the base polymer contains monomer units derived from hydroxyl-containing (meth)acrylate monomers, the cohesive strength of the base polymer (suitably an acrylic polymer) is increased due to the formation of secondary bonds such as hydrogen bonds with the adherends. This more effectively suppresses changes in adhesive strength over time, results in less residue on the adherends after peeling, and exhibits higher aggregation properties. Furthermore, by including hydroxyl-containing (meth)acrylate monomers in the raw monomers of the base polymer, a crosslinking reaction with a crosslinking agent can occur effectively when using the crosslinking agent, fully demonstrating its effect as an adhesive. In addition, delamination and breakage of the adherends during peeling operations over a wide temperature range can be effectively prevented.

[0096] Examples of (meth)acrylate monomers containing hydroxyl groups include: 4-hydroxybutyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylaurate (meth)acrylate, and (4-hydroxymethylcyclohexyl)methyl (meth)acrylate. One or more of these monomers may be used.

[0097] Examples of monomers containing an amide group (sometimes referred to as "amide-containing monomers" in this invention) include N-vinylpyrrolidone, N,N-dimethyl (meth)acrylamide, and N,N-diethyl (meth)acrylamide. One of these monomers may be used, or two or more may be used in combination.

[0098] In a preferred embodiment, when the carboxyl-containing (meth)acrylate monomer comprises a monomer with a glass transition temperature (Tg) > 50°C for the homopolymer, the ratio of the content of the carboxyl-containing (meth)acrylate monomer to the content of the hydroxyl-containing (meth)acrylate monomer is preferably 0.5–29, more preferably 1–25, further preferably 2–21, and even more preferably 3–20.

[0099] When the carboxyl-containing (meth)acrylate monomer is composed of a homopolymer with a glass transition temperature Tg ≤ 50°C, the ratio of the content of the carboxyl-containing (meth)acrylate monomer to the content of the hydroxyl-containing (meth)acrylate monomer is preferably 10–45, preferably 12–43, more preferably 14–41, and even more preferably 15–40.

[0100] More preferably, when the carboxyl-containing (meth)acrylate monomer comprises a monomer with a glass transition temperature (Tg) > 50°C of the homopolymer, the content of the carboxyl-containing (meth)acrylate monomer is preferably 0.5 to 5.5 parts by weight, more preferably 1 to 5 parts by weight, and even more preferably 1.5 to 3 parts by weight, relative to 100 parts by weight of all monomer components of the base polymer; and the content of the hydroxyl-containing (meth)acrylate monomer is preferably 0.05 to 2 parts by weight, more preferably 0.1 to 1.5 parts by weight, and even more preferably 0.2 to 1 part by weight, relative to 100 parts by weight of all monomer components of the base polymer.

[0101] When the carboxyl-containing (meth)acrylate monomer is composed of monomers with a glass transition temperature (Tg) ≤ 50°C of the homopolymer, the content of the carboxyl-containing (meth)acrylate monomer is preferably 1 to 9 parts by weight, more preferably 3 to 8.5 parts by weight, and even more preferably 5 to 8 parts by weight, relative to 100 parts by weight of all monomer components of the base polymer. The content of the hydroxyl-containing (meth)acrylate monomer is preferably 0.1 to 2 parts by weight, more preferably 0.15 to 1 part by weight, and even more preferably 0.2 to 0.5 parts by weight, relative to 100 parts by weight of all monomer components of the base polymer.

[0102] There are no particular limitations on the method for obtaining the basic polymer; various known polymerization methods such as solution polymerization, emulsion polymerization, bulk polymerization, suspension polymerization, and photopolymerization can be appropriately employed. For example, solution polymerization is preferred. As for the monomer supply method during solution polymerization, appropriate methods can be adopted such as batch feeding (supplying all monomer raw materials at once), continuous feeding (dropleting), or partial feeding (dropleting). The polymerization temperature during solution polymerization can be appropriately selected based on the type of monomer and solvent used, as well as the type of polymerization initiator; for example, it can be set to approximately 20–170°C (typically approximately 40–140°C).

[0103] The solvent used in solution polymerization (polymerization solvent) can be appropriately selected from existing known organic solvents. For example, any one or a mixture of two or more solvents selected from aromatic compounds such as toluene (typically aromatic hydrocarbons); acetates such as ethyl acetate; aliphatic or alicyclic hydrocarbons such as hexane and cyclohexane; haloalkanes such as 1,2-dichloroethane; lower alcohols such as isopropanol (e.g., monohydric alcohols with 1 to 4 carbon atoms); ethers such as tert-butyl methyl ether; ketones such as methyl ethyl ketone, etc.

[0104] The initiator used in the polymerization can be appropriately selected from existing known polymerization initiators depending on the type of polymerization method. Examples of polymerization initiators include: azo polymerization initiators such as 2,2'-azobisisobutyronitrile (AIBN); persulfates such as potassium persulfate; peroxide initiators such as benzoyl peroxide, dibenzoyl peroxide, and hydrogen peroxide; substituted ethane initiators such as phenyl-substituted ethane; and aromatic carbonyl compounds. Other examples of polymerization initiators include redox initiators obtained by combining peroxides with reducing agents. Such polymerization initiators can be used alone or in combination of two or more. The amount of polymerization initiator used is the usual amount, for example, selected from about 0.005 parts by weight to about 1 part by weight (typically about 0.01 parts by weight to about 1 part by weight) relative to 100 parts by weight of the total monomer composition.

[0105] The weight-average molecular weight of the base polymer used in this disclosed technology is not particularly limited, and can be, for example, 4,000,000 or less, preferably 2,000,000 or less.

[0106] Weight-average molecular weight refers to the value converted from standard polystyrene obtained by gel permeation chromatography (GPC). A GPC apparatus, for example, can be model "HLC-8320GPC" (column: TSKgelGMH-H(S), manufactured by Tosoh Corporation).

[0107] The adhesive composition of the present invention preferably also contains a crosslinking agent.

[0108] (Cross-linking agent)

[0109] In this invention, the adhesive composition preferably includes a crosslinking agent to regulate cohesion, etc. Commonly used crosslinking agents can be used, such as epoxy-based crosslinking agents, isocyanate-based crosslinking agents, melamine-based crosslinking agents, aziridine-based crosslinking agents, metal chelate-based crosslinking agents, etc., with isocyanate-based crosslinking agents being preferred. By using these crosslinking agents, a suitable crosslinking reaction can be generated, significantly improving cohesion, ensuring good adhesion, and effectively preventing the adhesion from breaking during peeling operations. These crosslinking agents can be used alone or in combination of two or more.

[0110] As an epoxy crosslinking agent, compounds having two or more epoxy groups per molecule can be used without particular limitation. Preferably, epoxy crosslinking agents have 3 to 5 epoxy groups per molecule. One epoxy crosslinking agent can be used alone, or two or more can be used in combination.

[0111] Specific examples of epoxy crosslinking agents are not particularly limited, and can include: bisphenol A, epichlorohydrin-type epoxy resins, ethylene glycidyl ether, N,N,N',N'-tetraglycidyl-m-phenylenediamine, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, 1,6-hexanediol diglycidyl ether, polyethylene glycol diglycidyl ether, polyglycerol polyglycidyl ether, etc. Commercially available epoxy crosslinking agents include those manufactured by Mitsubishi Gas Chemical Co., Ltd. under the trade names "TETRAD-C" and "TETRAD-X", those manufactured by DIC under the trade name "EPICLON CR-5L", those manufactured by Nagase Chemical Co., Ltd. under the trade name "DENACOL EX-512", and those manufactured by Nissan Chemical Industries Co., Ltd. under the trade name "TEPIC-G", etc.

[0112] There is no particular limitation on the amount of epoxy crosslinking agent used. For example, it is preferably 0.05 to 8 parts by weight, more preferably 0.1 to 5 parts by weight, based on 100 parts by weight of the base polymer.

[0113] In embodiments containing an epoxy crosslinking agent, the epoxy equivalent of the epoxy crosslinking agent is preferably 80 to 120 g / eq.

[0114] As isocyanate-based crosslinking agents, polyfunctional isocyanates (compounds having an average of two or more isocyanate groups per molecule, including compounds with isocyanurate structures) are preferred. Isocyanate-based crosslinking agents can be used alone or in combination of two or more.

[0115] Examples of polyfunctional isocyanates include aliphatic polyisocyanates, alicyclic polyisocyanates, and aromatic polyisocyanates.

[0116] Specific examples of aliphatic polyisocyanates include: 1,2-ethylene diisocyanate; succinic diisocyanates such as 1,2-butanediisocyanate, 1,3-butanediisocyanate, and 1,4-butanediisocyanate; hexanediisocyanates such as 1,2-hexanediisocyanate, 1,3-hexanediisocyanate, 1,4-hexanediisocyanate, 1,5-hexanediisocyanate, 1,6-hexanediisocyanate, and 2,5-hexanediisocyanate; 2-methyl-1,5-pentanediisocyanate, 3-methyl-1,5-pentanediisocyanate, and lysine diisocyanate.

[0117] Specific examples of alicyclic polyisocyanates include: isophorone diisocyanate; cyclohexyl diisocyanates such as 1,2-cyclohexyl diisocyanate, 1,3-cyclohexyl diisocyanate, and 1,4-cyclohexyl diisocyanate; cyclopentyl diisocyanates such as 1,2-cyclopentyl diisocyanate and 1,3-cyclopentyl diisocyanate; hydrogenated diphenylmethylene diisocyanate, hydrogenated toluene diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated tetramethylxylene diisocyanate, and 4,4'-dicyclohexylmethane diisocyanate.

[0118] Specific examples of aromatic polyisocyanates include: 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 2,2'-diphenylmethane diisocyanate, 4,4'-diphenyl ether diisocyanate, 2-nitrobiphenyl-4,4'-diisocyanate, and 2,2'-diphenylpropane-4,4'-diphenylmethane diisocyanate. Isocyanates, 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, 4,4'-diphenylpropane diisocyanate, m-phenylene diisocyanate, terephthalene diisocyanate, naphthalene-1,4-diisocyanate, naphthalene-1,5-diisocyanate, 3,3'-dimethoxybiphenyl-4,4'-diisocyanate, phenylenediamine-1,4-diisocyanate, phenylenediamine-1,3-diisocyanate, etc.

[0119] Preferred polyfunctional isocyanates include those having an average of three or more isocyanate groups per molecule. Trifunctional or higher isocyanates can be polymers (typically dimers or trimers) of difunctional or trifunctional isocyanates, derivatives (e.g., addition reaction products of polyols with two or more molecules of polyfunctional isocyanates), polymers, etc. Examples include: dimers or trimers of diphenylmethane diisocyanate, isocyanurate forms of hexamethylene diisocyanate (trimeric adducts of the isocyanurate structure), reaction products of trimethylolpropane and toluene diisocyanate, reaction products of trimethylolpropane and hexamethylene diisocyanate, polymethylene polyphenyl isocyanates, polyether polyisocyanates, polyester polyisocyanates, and other polyfunctional isocyanates. Commercially available examples of the aforementioned polyfunctional isocyanates include "DURANATE TPA-100" manufactured by Asahi Kasei Chemicals, "CORONATE L" manufactured by Nippon Polyurethane Industries, Ltd., "CORONATE HL" manufactured by Nippon Polyurethane Industries, Ltd., "CORONATE HK" manufactured by Nippon Polyurethane Industries, Ltd., "CORONATE HX" manufactured by Nippon Polyurethane Industries, Ltd., and "CORONATE 2096" manufactured by Nippon Polyurethane Industries, Ltd.

[0120] In embodiments containing isocyanate-based crosslinking agents, the isocyanate group content (NCO content) in the isocyanate-based crosslinking agent is preferably 7-15%.

[0121] There is no particular limitation on the amount of isocyanate-based crosslinking agent used; for example, it is preferably 0.1 to 6 parts by weight, more preferably 0.5 to 5 parts by weight, based on 100 parts by weight of the base polymer.

[0122] Examples of melamine-based crosslinking agents include: hexamethylol melamine, butylated melamine resin (for example, the trade name "SUPER BECKAMINE J-820-60N" available from DIC Corporation), etc.

[0123] There is no particular limitation on the amount of melamine-based crosslinking agent used. For example, based on 100 parts by weight of the base polymer, it is preferably 0.5 to 12 parts by weight, and more preferably 1 to 8 parts by weight.

[0124] Examples of aziridine-based crosslinking agents include, for instance, trimethylolpropane tris[3-(1-aziridine)propionate] and trimethylolpropane tris[3-(1-(2-methyl)aziridine propionate)]. Commercially available aziridine-based crosslinking agents can be used. Examples include Chemitite PZ-33, Chemitite DZ-22E, and other Chemitite series products (manufactured by Nippon Shokubai Co., Ltd.).

[0125] Examples of metal chelate crosslinking agents include aluminum chelate compounds, titanium chelate compounds, zinc chelate compounds, zirconium chelate compounds, iron chelate compounds, cobalt chelate compounds, nickel chelate compounds, tin chelate compounds, manganese chelate compounds, and chromium chelate compounds.

[0126] The amount of crosslinking agent used is preferably 0.1 to 5 parts by weight relative to 100 parts by weight of the base polymer. By setting the amount of crosslinking agent within the above range, the cohesive force of the adhesive can be improved, residue on the adhered surfaces can be prevented, and it also has moderate fluidity, good wetting properties on the adhered surfaces, and thus tends to achieve a tight bond. In some embodiments, from the viewpoint of avoiding a decrease in tackiness due to excessive increase in cohesive force, the amount of crosslinking agent used is more preferably 0.3 to 2 parts by weight relative to 100 parts by weight of the base polymer, and even more preferably 0.5 to 1.5 parts by weight.

[0127] To facilitate the crosslinking reaction more effectively, a crosslinking catalyst may be used. Tin-based catalysts (e.g., dioctyltin dilaurate) are preferred as crosslinking catalysts. There is no particular limitation on the amount of crosslinking catalyst used; for example, 0.0001 to 1 part by weight relative to 100 parts by weight of the base polymer is preferred.

[0128] (Tackifying resin)

[0129] The adhesive composition of the present invention preferably contains a tackifying resin. By using the tackifying resin, adhesive strength can be improved.

[0130] Examples of tackifying resins include (meth)acrylic oligomers, phenolic tackifying resins, terpene tackifying resins, modified terpene tackifying resins, rosin tackifying resins, and hydrocarbon tackifying resins. These tackifying resins can be used alone or in combination of two or more.

[0131] As monomeric components of (meth)acrylate oligomers, alkyl (meth)acrylate monomers, functional monomers, and other copolymerizable monomers (e.g., (meth)acrylates containing alicyclic hydrocarbon groups) exemplified as monomers that can be used in the aforementioned basic polymers can be used. Examples of monomeric components constituting (meth)acrylate oligomers include: isobornyl acrylate, isobornyl methacrylate, tricyclodecanediethanol dimethacrylate, cyclohexyl methacrylate, cyclohexyl acrylate, and other (meth)acrylate monomers with a Tg > 20°C and containing a cyclic structure; polar monomers such as N-vinylpyrrolidone, acrylic acid, β-carboxyethyl acrylate, 2-hydroxyethyl acrylate, hydroxypropyl acrylate, and 4-hydroxybutyl acrylate. Preferred examples include: isobornyl acrylate, cyclohexyl methacrylate, N-vinylpyrrolidone, acrylic acid, and β-carboxyethyl acrylate. For each monomer exemplified above, one can be used alone, or two or more can be used in combination.

[0132] The acrylate monomer containing a cyclic structure with a Tg > 20°C is preferably 60 to 95% by weight relative to the total monomer content of the (meth)acrylic acid oligomer, more preferably 65 to 85% by weight.

[0133] The polar monomer is preferably 5% to 30% by weight, more preferably 10% to 25% by weight, relative to the total monomer content of the (meth)acrylic acid oligomer.

[0134] In a preferred embodiment, the (meth)acrylic acid oligomer is polymerized using a chain transfer agent, which allows control of the polymer molecular weight. Examples of chain transfer agents include: thiols (such as n-dodecyl mercaptan, mercaptoacetic acid, thioethylene glycol), carbon disulfide, haloalkanes (such as CCl4), and 2,4-diphenyl-4-methyl-1-pentene. Preferred examples include: n-dodecyl mercaptan and 2,4-diphenyl-4-methyl-1-pentene. The amount of chain transfer agent added relative to the total monomer content of the (meth)acrylic acid oligomer can be 5% to 10% by weight, preferably 6% to 8% by weight.

[0135] The proportion of (meth)acrylic acid monomers in the total monomer composition of the (meth)acrylic acid oligomer typically exceeds 50% by weight, preferably 60% by weight or more, more preferably 70% by weight or more (e.g., 80% by weight or more, and even more preferably 90% by weight or more). In a preferred embodiment, the (meth)acrylic acid oligomer has a monomer composition that substantially consists only of (meth)acrylic acid monomers.

[0136] The weight-average molecular weight of (meth)acrylic acid oligomers is not particularly limited, but is typically 3,000 to 8,000. From the viewpoint of improving adhesive properties (e.g., adhesion strength, resilience), the weight-average molecular weight of (meth)acrylic acid oligomers is preferably 4,000 to 6,000.

[0137] (Meth)acrylic acid oligomers can be formed by polymerizing their constituent monomer components. There are no particular restrictions on the polymerization method or mode; various conventionally known polymerization methods (such as solution polymerization, emulsion polymerization, bulk polymerization, photopolymerization, radiation polymerization, etc.) can be used in an appropriate manner.

[0138] Examples of phenolic tackifying resins include terpene phenol resins, hydrogenated terpene phenol resins, alkylphenol aldehyde resins, and rosin phenol resins. Terpene phenol resins refer to polymers containing terpene and phenol residues, encompassing both copolymers of terpenes and phenolic compounds (terpene-phenol copolymer resins) and resins obtained by modifying homopolymers or copolymers of terpenes with phenol (phenol-modified terpene resins). Suitable examples of terpenes constituting such terpene phenol resins include monoterpenes such as α-pinene, β-pinene, and limonene (including d-formaldehyde, l-formaldehyde, and d / l-formaldehyde (dipentene)). Hydrogenated terpene phenol resins refer to hydrogenated terpene phenol resins with a structure obtained by hydrogenating this type of terpene phenol resin. They are sometimes also called hydrogenated terpene phenol resins. Alkylphenol aldehyde resins are resins obtained from alkylphenols and formaldehyde (oil-based phenolic resins). Examples of alkylphenol aldehyde resins include phenolic varnish type and methyl phenolic type.

[0139] Examples of terpene-based tackifying resins include polymers of terpenes (typically monoterpenes) such as α-pinene, β-pinene, d-limonene, l-limonene, and dipentene. They can be homopolymers of a single terpene or copolymers of two or more terpenes. Examples of homopolymers of a single terpene include α-pinene polymers, β-pinene polymers, and dipentene polymers.

[0140] Examples of modified terpene-based tackifying resins include those modified from the aforementioned terpene-based tackifying resins. Specifically, examples include styrene-modified terpene resins and hydrogenated terpene resins.

[0141] The concept of rosin-based tackifying resins includes both rosin-based resins and rosin derivative resins. Examples of rosin-based resins include: unmodified rosin (raw rosin), such as resin rosin, wood rosin, and tall oil rosin; and modified rosin (hydrogenated rosin, disproportionated rosin, polymerized rosin, and other chemically modified rosin) produced through hydrogenation, disproportionation, polymerization, etc. Rosin derivative resins are typically derivatives of the aforementioned rosin-based resins. Therefore, the concept of rosin-based tackifying resins here includes derivatives of unmodified rosin and derivatives of modified rosin (including hydrogenated rosin, disproportionated rosin, and polymerized rosin). Examples of rosin derivative resins include: rosin esters such as unmodified rosin esters (esters of unmodified rosin and alcohols) and modified rosin esters (esters of modified rosin and alcohols); unsaturated fatty acid-modified rosin obtained by modifying rosin with unsaturated fatty acids; unsaturated fatty acid-modified rosin esters obtained by modifying rosin esters with unsaturated fatty acids; rosin alcohols obtained by reducing the carboxyl group of rosin or the various rosin derivatives mentioned above (including rosin esters, unsaturated fatty acid-modified rosin, and unsaturated fatty acid-modified rosin esters); metal salts of rosin or the various rosin derivatives mentioned above; etc. Specific examples of rosin esters include methyl esters, triethylene glycol esters, glyceryl esters, and pentaerythritol esters of unmodified rosin or modified rosin (hydrogenated rosin, disproportionated rosin, polymerized rosin, etc.).

[0142] Examples of hydrocarbon-based tackifying resins include: aliphatic hydrocarbon resins, aromatic hydrocarbon resins, aliphatic cyclic hydrocarbon resins, aliphatic petroleum resins (e.g., C8-C10 petroleum resins), aliphatic-aromatic petroleum resins (styrene-olefin copolymers, etc.), aliphatic-alicyclic petroleum resins, hydrogenated hydrocarbon resins, coumarone resins, coumarone-indene resins, and other hydrocarbon-based resins. Examples of aliphatic hydrocarbon resins include polymers of one or more aliphatic hydrocarbons selected from olefins and dienes with approximately 4 to 5 carbon atoms. Examples of olefins include 1-butene, isobutene, and 1-pentene. Examples of dienes include butadiene, 1,3-pentadiene, and isoprene. Examples of aromatic hydrocarbon resins include polymers containing vinyl aromatic hydrocarbons (styrene, vinyltoluene, α-methylstyrene, indene, methylindene, etc.) with approximately 8 to 10 carbon atoms. Examples of aliphatic cyclic hydrocarbon resins include alicyclic hydrocarbon resins obtained by polymerizing so-called "C4 petroleum fractions" and "C5 petroleum fractions" after cyclization and dimerization; polymers or hydrides of cyclic diene compounds (cyclopentadiene, dicyclopentadiene, ethylidene norbornene, dipentene, etc.); and alicyclic hydrocarbon resins obtained by hydrogenating the aromatic rings of aromatic hydrocarbon resins or aliphatic / aromatic petroleum resins.

[0143] In a preferred embodiment, the content of the tackifying resin is 1 to 20 parts by weight relative to 100 parts by weight of the base polymer, preferably 2 to 10 parts by weight, and more preferably 3 to 7 parts by weight.

[0144] In addition to the components described above, the adhesive composition of the present invention may, as needed, contain various additives commonly used in the adhesive field, such as photoinitiators, plasticizers, softeners, antioxidants, and anti-aging agents, without impairing the effects of the present invention. Such additives can be obtained using conventional methods with existing, known additives.

[0145] In a preferred embodiment, the gelation rate of the adhesive layer is preferably 50% or more, more preferably 60% or more, and even more preferably 65% ​​or more. As an upper limit for the gelation rate, it is preferably 95% or less, more preferably 90% or less, and even more preferably 85% or less. When the gelation rate is within the above range, excellent adhesive properties can be obtained. The gelation rate can be adjusted, for example, according to the composition and molecular weight of the base polymer, the presence and type of crosslinking agent used, and the selection of its amount. The gelation rate can be measured, for example, by the method described in the examples described later.

[0146] In a preferred embodiment, the soluble molecular weight (Mw) of the adhesive layer can be from 500,000 to 2,000,000, preferably from 700,000 to 1,500,000. When the soluble molecular weight of the adhesive layer is within the above range, excellent adhesive properties can be obtained. The soluble molecular weight (Mw) of the adhesive layer refers to the weight-average molecular weight of the soluble portion of the adhesive layer. The soluble molecular weight (Mw) can be determined by the method described, for example, in the embodiments described later.

[0147] (Formation of the adhesive layer)

[0148] The adhesive layer disclosed herein can be formed using methods known in the art. For example, it can be formed by directly applying (typically coating) the adhesive composition to the substrate layer and allowing it to dry (direct method). Alternatively, it can be formed by applying the adhesive composition to a peelable surface (peel surface), allowing it to dry, and then transferring the adhesive layer onto the substrate layer (transfer method). From a productivity point of view, the transfer method is preferred. The peel surface can be the surface of a release liner, the back side of the substrate layer after peeling treatment, etc. It should be noted that the adhesive layer disclosed herein is typically formed continuously, but is not limited to this form; it can also be formed as a regular or irregular pattern, such as dots or stripes.

[0149] The adhesive composition can be coated using existing, known coating machines such as gravure roller coaters, die coaters, and bar coaters. Alternatively, the adhesive composition can be coated using methods such as dip coating or curtain coating.

[0150] From the perspective of promoting cross-linking reactions and improving manufacturing efficiency, the drying of the adhesive composition is preferably carried out under heating. The drying temperature can be set to around 40–150°C, and is usually preferably set to around 60–130°C. After the adhesive composition is dried, it can be further aged for purposes such as regulating component migration within the adhesive layer, proceeding with the cross-linking reaction, and relaxing any strain that may exist within the substrate film or the adhesive layer.

[0151] There is no particular limitation on the thickness of the adhesive layer. Considering the balance between adhesion and cohesion of the adhered objects, the thickness of the adhesive layer is preferably 1 to 40 μm, more preferably 3 to 35 μm. By setting the thickness of the adhesive layer within the above range, good adhesion can be achieved.

[0152] [Substrate Layer]

[0153] The material of the substrate layer constituting the adhesive sheet of the present invention is not particularly limited, and can be appropriately selected according to the purpose or method of use of the adhesive sheet. Non-limiting examples of usable substrate layers include: polyester films with polyethylene terephthalate (PET) as the main component; polyolefin films with polyolefins such as polyethylene, polypropylene, polybutene, and ethylene-propylene copolymer as the main component; polyvinyl chloride films with polyvinyl chloride as the main component; films with cast polypropylene as the main component; thermoplastic polyurethane films; foamed sheets formed from foams such as polyurethane foam, polyethylene foam, and polychloroprene foam; woven and nonwoven fabrics obtained by various fibrous materials (such as natural fibers such as hemp and cotton, synthetic fibers such as polyester and vinylon, and semi-synthetic fibers such as acetate) alone or through blending; paper such as Japanese paper, high-quality paper, kraft paper, and crepe paper; and metal foils such as aluminum foil and copper foil. Among these, the substrate layer preferably includes a polyester film selected from polyethylene terephthalate (PET) as the main component. Examples of such composite substrates include substrates with structures formed by laminating metal foil and the aforementioned plastic film, and plastic substrates reinforced with inorganic fibers such as glass cloth.

[0154] For the surface of the substrate layer of the present invention, any surface treatment can be performed to improve the adhesion and retention with adjacent layers. Examples of such surface treatments include chemical or physical treatments and coating treatments such as chromic acid treatment, ozone exposure, flame exposure, high-voltage electric shock exposure, and ionization radiation treatment.

[0155] The thickness of the substrate layer of the present invention can be set to any appropriate thickness depending on the desired strength or flexibility, and the intended use. The thickness of the substrate layer is preferably 5 to 300 μm, more preferably 8 to 200 μm, and even more preferably 10 to 100 μm.

[0156] (Manufacturing method of adhesive sheet)

[0157] The adhesive sheet of the present invention can be manufactured by any suitable method. For example, the following methods can be listed: a method of coating an adhesive composition onto a substrate layer, a method of transferring a coating layer formed by coating an adhesive composition onto an adhesive substrate onto a substrate layer, or a method of forming an adhesive layer by coating an adhesive composition onto an adhesive substrate, etc.

[0158] As a coating method for the above-mentioned adhesive composition, any suitable coating method can be used. For example, each layer can be formed by drying after coating. Examples of coating methods include multi-coating machines, die-casting machines, gravure coating machines, applicators, bar coating machines, air knife coating, reverse roller coating, lip coating, dip coating, offset printing, flexographic printing, and screen printing. Examples of drying methods include natural drying and heat drying. In the case of heat drying, the heating temperature can be set to any suitable temperature depending on the characteristics of the substance being dried.

[0159] (use)

[0160] The adhesive sheet disclosed in this invention can be attached to various components or devices, and is preferably used in electronic devices, especially foldable screen mobile phones.

[0161] Example

[0162] The present invention will now be described in detail through embodiments, but the present invention is not limited to these embodiments. The evaluation methods in the embodiments are as follows. Furthermore, in the embodiments, unless otherwise specified, "parts" and "%" are based on weight. Where specific conditions are not specified in the embodiments, they are performed under conventional conditions or conditions recommended by the manufacturer. Unless otherwise specified, all materials or instruments used are commercially available conventional products.

[0163] Example 1

[0164] <Preparation of Basic Polymer Solutions>

[0165] In a reaction vessel equipped with a stirrer, thermometer, nitrogen inlet pipe, and reflux condenser, 64 parts of 2-ethylhexyl acrylate (2EHA), 30 parts of dodecyl acrylate (LA), 5 parts of N-vinylpyrrolidone (NVP), 1 part of acrylic acid (AA), 0.2 parts of 4-hydroxybutyl acrylate (4-HBA), and 200-300 parts of toluene as a polymerization solvent were added. After stirring at 65°C under a nitrogen atmosphere for 1.5 hours, 0.05-0.5 parts by weight of benzoyl peroxide (BPO) (reaction initiator) were added, and the reaction was carried out at 65°C for 3-4 hours to obtain a solution of the basic polymer.

[0166] <Making Adhesive Sheets>

[0167] To a solution of the aforementioned base polymer, 1 part of an isocyanate crosslinking agent (L-75(C), trade name "Desmodur L-75(C)", manufactured by Sumitomo Chemical Bayer Polyurethanes Co., Ltd.) and 5 parts of (meth)acrylate oligomer (OAC) (formed by polymerization of 90 parts by weight of isobornyl acrylate, 5 parts by weight of acrylic acid, and 5 parts by weight of 2,4-diphenyl-4-methyl-1-pentene relative to 100 parts by weight of all monomer components of the oligomer) are added as crosslinking agents, and the mixture is uniformly mixed to prepare an adhesive layer composition.

[0168] An adhesive layer composition was coated on one side of a PET film with a thickness of 23 μm, which served as the substrate layer. After coating, the adhesive layer was dried to a thickness of 20 μm by heating at 130°C for 2 minutes.

[0169] Thus, the adhesive sheet was obtained. The evaluation results are shown in Table 4.

[0170] Examples 2-9

[0171] Except for changing the monomer composition and content of the base polymer as shown in Tables 1-2, adhesive sheets were obtained in the same manner as in Example 1. The evaluation results are shown in Tables 4-5.

[0172] Comparative Examples 1-5

[0173] Except for altering the monomer composition and content of the base polymer as shown in Table 3, adhesive sheets were obtained in the same manner as in Example 1. The evaluation results are shown in Table 6.

[0174] In the table below:

[0175] 2EHA: 2-Ethylhexyl acrylate (the glass transition temperature of the homopolymer of this monomer is Tg = -70℃)

[0176] LA: Dodecyl acrylate (the glass transition temperature of the homopolymer of this monomer is Tg = -30℃)

[0177] C17A: Heptadecanyl acrylate (the glass transition temperature of the homopolymer of this monomer is Tg = -72℃)

[0178] INAA: Isononyl acrylate (the glass transition temperature of the homopolymer of this monomer is Tg = -58℃)

[0179] IDAA: Isodecyl acrylate containing more than one branched isomer (the glass transition temperature of the homopolymer of this monomer is Tg = -62℃).

[0180] IDA: Isodecyl acrylate containing a methyl branch (the glass transition temperature of the homopolymer of this monomer is Tg = -60℃).

[0181] MA: Methyl acrylate (the glass transition temperature Tg of the homopolymer of this monomer is 9℃)

[0182] CHA: Cyclohexyl acrylate (the glass transition temperature Tg of the homopolymer of this monomer is 22℃)

[0183] NVP: N-vinylpyrrolidone

[0184] AA: Acrylic acid (the glass transition temperature of the homopolymer of this monomer is Tg = 106℃)

[0185] β-CEA: β-Carboxyethyl acrylate (the glass transition temperature Tg of the homopolymer of this monomer is 37℃)

[0186] 4-HBA: 4-Hydroxybutyl acrylate (the glass transition temperature of the homopolymer of this monomer is Tg = -65℃)

[0187] L-75(C): Isocyanate crosslinking agent, trade name "Desmodur L-75(C)"

[0188] OAC: (meth)acrylic acid oligomer, the preparation of which is as described above.

[0189] Table 1

[0190]

[0191] Table 2

[0192]

[0193] Table 3

[0194]

[0195] Table 4

[0196]

[0197] Table 5

[0198]

[0199] Table 6

[0200]

[0201] <Evaluation Experiment>

[0202] (1) Creep recovery rate

[0203] According to the various embodiments and comparative examples, adhesive layers are prepared, laminated to a thickness of approximately 1 mm, and then punched out. Cylindrical particles were prepared as samples for testing. The obtained samples were fixed in a dynamic viscoelasticity measuring apparatus (TA Instruments, DHR2). The clamp for the parallel plate. At 25°C, the deformation strain (%) after applying a deformation stress of 10 kPa and holding it for 10 minutes is set as value A. Then, the deformation strain (%) after applying a deformation stress of 1 Pa and holding it for 10 minutes is set as value B. The value calculated by [(value A - value B) / value A} × 100] is used as the creep recovery rate.

[0204] (2) Glass transition temperature Tg of the adhesive layer

[0205] Approximately 5 mg of the polymer constituting the adhesive layer in each example and comparative example was taken as the test subject, and the glass transition temperature Tg was determined by DSC under the following conditions.

[0206] Measuring apparatus: Manufactured by TA Instruments, Product name: Q-2000

[0207] <Measurement Conditions>

[0208] Temperature program: 0℃→150℃→0℃→200℃

[0209] Atmospheric gas: N2 (50 mL / min)

[0210] Measurement speed: 10℃ / minute

[0211] (3) Peel adhesion

[0212] (3-a) Peel adhesion to PET sheets at 23°C

[0213] Adhesive sheets were prepared according to the various embodiments and comparative examples, and test sheets were cut with a width of 20 mm and a length of 150 mm. PET sheets cleaned with toluene were used as the substrates. Under a standard environment of 23°C and 50% RH, a 2 kg roller was passed back and forth once to press the exposed adhesive surface against the substrate. After the test sheets pressed against the substrate in this manner were placed under the above standard environment for 24 hours, peeling was performed using a universal testing machine (manufactured by Shimadzu Corporation, product name "AG-Xplus Electronic Universal Testing Machine") under the following test conditions according to JIS Z0237, and the force (N / inch) required for peeling was measured as the peel adhesion force:

[0214] <Measurement Conditions>

[0215] Peeling temperature: 23℃

[0216] Stretching speed: 300mm / min

[0217] Peeling angle: 180°

[0218] (3-b) Peel adhesion to PET sheets at 80°C

[0219] Except for setting the peel temperature to 80°C in the test conditions, repeat the steps of the above evaluation test (1) and measure the force (N / inch) required for peeling as the peel adhesion force.

[0220] (3-c) Peel adhesion to SUS430BA board at 23°C

[0221] In addition to using the SUS430BA board as the substrate, the steps of the above evaluation test (1) were repeated, and the force (N / inch) required for the peel was measured as the peel adhesion force.

[0222] (3-d) Peel adhesion to SUS430BA board at 80°C

[0223] Except for using the SUS430BA board as the substrate and setting the peel temperature in the test conditions to 80°C, the steps of the above evaluation test (1) were repeated, and the force (N / inch) required for peeling was measured as the peel adhesion force.

[0224] (4) Soluble molecular weight

[0225] The soluble molecular weight of the adhesive layer refers to the weight-average molecular weight of the soluble portion, which is determined by using the weight-average molecular weight of the soluble portion (sol portion) obtained by toluene extraction.

[0226] Collect approximately 0.1 g of the adhesive layer to be tested from the adhesive sheet, wrap it in a porous polytetrafluoroethylene sheet (manufactured by Nitto Denko Corporation) with a thickness of 85 μm, an average pore size of 0.2 μm, and a porosity of 75%, and then tie it with kite string.

[0227] Then, the adhesive layer wrapped with polytetrafluoroethylene sheet and tied with kite string was placed in a 50 mL container filled with toluene and left to stand at 23°C for 7 days. After that, the toluene solution (containing the extracted sol portion) in the container was removed and dried under reduced pressure to evaporate the solvent (toluene) to obtain the sol portion.

[0228] The above-mentioned sol fraction was dissolved in tetrahydrofuran (THF), and the weight-average molecular weight of the sol fraction was determined using a GPC apparatus (manufactured by TOSOHCORPORATION, HLC-8220GPC). The determination conditions are as follows, and the molecular weight was calculated using standard polystyrene.

[0229] Sample concentration: 0.2 wt% (tetrahydrofuran (THF) solution)

[0230] Sample injection volume: 10 μL

[0231] Elution buffer: THF

[0232] Flow rate: 0.6 ml / min

[0233] Measurement temperature: 40℃

[0234] Columns: Sample column, TSKguardcolumnSuperHZ-H (1 column) + TSKgelSuperHZM-H (2 columns); Reference column, TSKgelSuperH-RC (1 column)

[0235] Detector: Differential refractometer (RI)

[0236] (5) Energy storage modulus G'

[0237] According to the various embodiments and comparative examples, an adhesive layer (thickness: 20 μm) was prepared for testing. The adhesive layer was then punched to a diameter of 7.9 mm and fixed using a parallel plate clamp. The resulting sample was used as the test specimen. For the above test specimen, dynamic viscoelasticity was measured using a dynamic viscoelasticity measuring apparatus (manufactured by Rheometrics, product name "ARES") under the following conditions, determining the storage modulus at -20°C, 23°C, and 85°C.

[0238] <Measurement Conditions>

[0239] Measurement mode: Shear mode

[0240] Temperature range: -70℃~150℃

[0241] Heating rate: 5℃ / minute

[0242] Measurement frequency: 1Hz

[0243] (6) Gel content

[0244] Approximately 0.1 g of a sample (weight Wg1) formed from the adhesive layer composition was packaged into a drawstring bag using a porous polytetrafluoroethylene membrane (weight Wg2) with an average pore size of 0.2 μm, and the opening was secured with kite string (weight Wg3). The bag was then immersed in 50 mL of ethyl acetate and kept at room temperature (typically 23°C) for 7 days. Afterward, the bag was removed, the ethyl acetate adhering to its outer surface was wiped off, and the bag was dried at 130°C for 2 hours. The weight of the bag (Wg4) was then measured. The gelation rate was calculated by substituting the values ​​into the following formula.

[0245] Gelation rate (%) = [(Wg4 - Wg2 - Wg3) / Wg1] × 100

[0246] (7) Residual glue

[0247] The adhesive sheets prepared in each embodiment and comparative example were cut into test pieces with a width of 400 mm and a length of 150 mm. The adhesive sheet samples were pressed against a 125 μm PET film with a surface dyn value greater than 38 dyn (mN / m) by applying a 2 kg roller back and forth once. The test pieces, pressed onto the substrate in this manner, were placed in a standard environment of 23°C and 50% RH for 3 days. After peeling at a high temperature (80°C) at 1000 mm / min, the surface of the 125 μm PET film was visually inspected for any adhesive residue. "No adhesive residue" was defined as visually no adhesive residue, and "with adhesive residue" was defined as visually present.

[0248] (8) Folding restoration

[0249] (8-1) Folding recovery at 23℃

[0250] A U-shaped laminate with a radius of curvature of approximately 3 mm was fabricated by applying an adhesive layer composition prepared according to the various embodiments and comparative examples onto a 23 μm PET substrate, and then laminating a 75 μm release film. The sample was then bent into a U-shaped laminate comprising two parallel surfaces and a bent portion with a radius of curvature of approximately 3 mm.

[0251] At 23°C, the aforementioned U-shaped laminate was placed horizontally on a plane, with the two parallel faces of the U-shaped laminate parallel to the plane, and held in this position for 24 hours. After 24 hours, if the adhesive layer did not exhibit buckling or delamination, the sample was considered to have passed the static holding test. Furthermore, after 24 hours, the sample was released and allowed to recover. At the end of 3 minutes, the time required to achieve angles of 90 degrees and 45 degrees relative to the plane (i.e., the included angles of the two faces of the U-shaped laminate were 90 degrees and 135 degrees), and the final angles, were recorded. In some cases, the sample could not recover to an angle of 45 degrees or 90 degrees relative to the plane within the 3-minute test time; for these samples, the final angle recovered during that time period was recorded.

[0252] ○: After static folding for 24 hours, the adhesive did not show buckling or delamination; after 24 hours, the recovery angle relative to the plane was 45 degrees or 90 degrees within 3 minutes. The shorter the time, the better the recovery characteristics of the sample after folding.

[0253] △: After static folding for 24 hours, the adhesive did not show buckling or delamination; after 24 hours, the recovery angles relative to the plane of 45 degrees and 90 degrees were not within 3 minutes, and the longer the time, the more general the recovery characteristics of the sample after folding.

[0254] ×: After static folding for 24 hours, the adhesive shows buckling or delamination, indicating that there are appearance problems after the sample is folded.

[0255] (8-2) Folding recovery at -20℃

[0256] Except for setting the measurement temperature to -20℃, the measurement method is the same as in (8-1).

[0257] (8-3) Folding recovery at 85℃

[0258] Except for setting the measurement temperature to 85℃, the measurement method is the same as in (8-1).

[0259] (9) Comprehensive judgment

[0260] All of the above evaluation results are considered as “○”; all of the above measured values ​​are excellent and there is at least one “△” in the evaluation results are considered as “△”; and the above measured values ​​are poor and there is at least one “×” in the evaluation results are considered as “×”.

[0261] As shown in the table above, Examples 1-9 exhibited no creases, cracks, breaks, or delamination when used at low and normal temperatures, and could also be used normally at high temperatures. Furthermore, they demonstrated excellent folding and bending resistance over a wide temperature range, enabling stable use across a broad temperature spectrum. In contrast, Comparative Examples 1-5 failed to achieve excellent folding and bending resistance over a wide temperature range, particularly exhibiting poor folding and bending resistance at low temperatures.

Claims

1. An adhesive sheet comprising an adhesive layer, characterized in that the adhesive layer has a creep recovery rate of 75% or more at -20°C, 80% or more at 25°C, and 85% or more at 70°C after the application of a stress of 10,000 Pa for 10 minutes, the removal of the applied stress, and the recovery for 10 minutes at a stress of 1 Pa.

2. The adhesive sheet according to claim 1, wherein The adhesive layer has a glass transition temperature Tg of less than -30°C.

3. The adhesive sheet according to claim 1 or 2, characterized in that, The adhesive sheet has a peel adhesion of 5.0 to 8.0 N / inch when peeled at a stretching speed of 300 mm / min in the 180° direction at 23°C after the adhesive layer having a thickness of 20 μm was attached to a PET plate and left to stand for 24 hours at 23°C. The adhesive sheet has a peel adhesion of 5.0 to 11.0 N / inch when peeled at a stretching speed of 300 mm / min in the 180° direction at 23°C after the adhesive layer having a thickness of 20 μm was attached to a SUS304BA plate and left to stand for 24 hours at 23°C.

4. The adhesive sheet according to claim 1 or 2, characterized by The adhesive sheet has a peel adhesion of 2.0 to 3.5 N / inch when peeled at a stretching speed of 300 mm / min in the 180° direction at 80°C after the adhesive layer having a thickness of 20 μm was attached to a PET plate and left to stand for 24 hours at 23°C. The adhesive sheet has a peel adhesion of 3.0 to 5.6 N / inch when peeled at a stretching speed of 300 mm / min in the 180° direction at 80°C after the adhesive layer having a thickness of 20 μm was attached to a SUS304BA plate and left to stand for 24 hours at 23°C.

5. The adhesive sheet according to claim 1 or 2, characterized in that, The storage modulus G' of the adhesive layer at -20°C is 1.5 x 10 5 ~ 3.4 x 10 5 Pa, The adhesive layer has a storage modulus G' of 3.0 x 10 4 ~ 4.5 x 10 4 Pa at 23°C. The storage modulus G' of the adhesive layer at 85°C is 1.0 x 10 4 ~ 2.5 x 10 4 Pa, The difference between the storage modulus G' of the adhesive layer at 23 °C and the storage modulus G' of the adhesive layer at 85 °C is 1.1 x 10 4 ~ 2.0 x 10 4 Pa.

6. The adhesive sheet according to claim 5, wherein The average of the storage modulus G' of the adhesive layer at -20°C and the storage modulus G' of the adhesive layer at 23°C is 1.0 x 10 5 ~ 1.9 x 10 5 Pa.

7. The adhesive sheet according to claim 5, wherein The average of the storage modulus G' of the adhesive layer at -20°C, the storage modulus G' of the adhesive layer at 23°C, and the storage modulus G' of the adhesive layer at 85°C is 7.0 x 10 4 ~ 1.3 x 10 5 Pa.

8. The adhesive sheet according to claim 1 or 2, characterized by The adhesive layer is formed from an adhesive composition comprising a base polymer containing a structural unit derived from an alkyl (meth)acrylate monomer, a homopolymer of which has a glass transition temperature Tg of -75 to 110°C, The alkyl (meth)acrylate monomer contains a soft monomer and a hard monomer, The homopolymer of the soft monomer has a glass transition temperature Tg of 0°C or less, and the content of the soft monomer is 83 to 97 parts by weight relative to 100 parts by weight of the total monomer component of the base polymer, The homopolymer of the hard monomer has a glass transition temperature Tg of more than 0°C, and the content of the hard monomer is 0 to 7 parts by weight relative to 100 parts by weight of the total monomer component of the base polymer.

9. The adhesive sheet according to claim 8, wherein The alkyl (meth)acrylate monomer contains one or more selected from the group consisting of methyl (meth)acrylate, n-butyl (meth)acrylate, n-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, cyclohexyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, dodecyl (meth)acrylate, and heptadecyl (meth)acrylate.

10. The adhesive sheet according to claim 8, wherein The base polymer further contains a functional monomer, and the content of the functional monomer is 1 to 10 parts by weight relative to 100 parts by weight of the total monomer component of the base polymer, The functional monomer contains a (meth)acrylate monomer containing a carboxyl group and a (meth)acrylate monomer containing a hydroxyl group.

11. The adhesive sheet according to claim 10, wherein when the carboxyl group-containing (meth)acrylate monomer contains a monomer having a glass transition temperature Tg of a homopolymer of > 50°C, the ratio of the content of the carboxyl group-containing (meth)acrylate monomer to the content of the hydroxyl group-containing (meth)acrylate monomer is 0.5 to 29; when the carboxyl group-containing (meth)acrylate monomer is composed of a monomer having a glass transition temperature Tg of a homopolymer of ≤ 50°C, the ratio of the content of the carboxyl group-containing (meth)acrylate monomer to the content of the hydroxyl group-containing (meth)acrylate monomer is 10 to 45.

12. The adhesive sheet according to claim 10, wherein The carboxyl group-containing (meth)acrylate monomer contains one or more selected from the group consisting of fumaric acid, maleic acid, (meth)acrylic acid, β-carboxyethyl (meth)acrylate, itaconic acid, crotonic acid, isocrotonic acid, and citraconic acid.

13. The adhesive sheet according to claim 10, wherein The hydroxyl group-containing (meth)acrylate monomer contains one or more selected from the group consisting of 4-hydroxybutyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, and (4-hydroxymethylcyclohexyl)methyl (meth)acrylate.

14. The adhesive sheet according to claim 1 or 2, wherein The adhesive sheet further includes a substrate layer, and the adhesive layer is provided on one side or both sides of the substrate layer.

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