Optical adhesive sheet

Abstract

The adhesive sheet (10) (optical adhesive sheet) contains a base polymer and an oligomer having a glass transition temperature of 40 DEG C or higher, and has a shear storage modulus at-10 DEG C of 100 kPa or less. In the adhesive sheet (10), the hydrogen bond component [delta] H1 of the Hansen solubility parameter of the base polymer and the hydrogen bond component [delta] H2 of the Hansen solubility parameter of the oligomer satisfy 0.1 < = [delta] H2-[delta] H1 < = 1.3.

Description

Technical Field

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

[0002] Display panels, for example, have a laminated structure that includes components such as pixel panels, polarizing films, touch panels, and protective films. In the manufacturing process of such display panels, transparent adhesive sheets (optical adhesive sheets) are used, for example, to bond the components contained in the laminated structure together.

[0003] On the other hand, the development of repeatedly bendable (foldable) display panels, such as those for smartphones and tablet terminals, is underway. Specifically, foldable display panels can repeatedly deform between a curved shape and a flat, non-curved shape. In such foldable display panels, the elements in the stacked structure are manufactured in a manner that allows for repeated bending, and thin optical adhesive sheets are used to join such elements. Optical adhesive sheets for flexible devices such as foldable display panels are described, for example, in Patent Document 1 below.

[0004] Prior art literature

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2018-111754 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] Optical adhesive sheets for flexible devices require high flexibility to ensure adequate conformability to the adhered object during device deformation and excellent stress relaxation properties. However, conventional optical adhesive sheets tend to have lower adhesive strength the softer they are.

[0009] In conventional foldable display panels, optical adhesive sheets tend to peel off from the adhered components at the bending points. This is because when the display panel bends, a relatively large shear force is applied to the bent portion of the optical adhesive sheet along the direction of the adhered components. This peeling leads to display malfunctions and is therefore undesirable. Optical adhesive sheets for foldable display panels must possess a high level of resistance to peeling off from the components (adhesives) when the display is bent.

[0010] The development of rollable display panels, as flexible devices, is underway. Rollable display panels, for example, can repeatedly deform between a rolled-up shape (whole or partially rolled) and a flat shape (unrolled). In such rollable display panels, the elements in the stacked structure are manufactured in a manner capable of repeated deformation, and thin optical adhesive sheets are used to join these elements. When the rollable display panel is rolled into its current shape, the optical adhesive sheets that bond with the elements in the rolled-up shape are continuously subjected to shear forces along the direction of the adhered material. Such optical adhesive sheets are required to have an extremely high level of resistance to peeling from the elements (adheded material) when the display is rolled into its current shape.

[0011] This invention provides an optical adhesive sheet suitable for use in flexible devices.

[0012] means for solving problems

[0013] The present invention [1] is an optical adhesive sheet, wherein the optical adhesive sheet comprises a base polymer and an oligomer with a glass transition temperature of 40°C or higher, the optical adhesive sheet has a shear storage modulus of 100 kPa or lower at -10°C, and the hydrogen bond component δH1 of the Hansen solubility parameter of the base polymer and the hydrogen bond component δH2 of the Hansen solubility parameter of the oligomer satisfy: 0.1 ≤ δH2 - δH1 ≤ 1.3.

[0014] The present invention [2] includes the optical adhesive sheet described in [1] above, wherein the optical adhesive sheet has a haze of less than 1%.

[0015] The present invention [3] includes the optical adhesive sheet described in [1] or [2] above, wherein the adhesive force of the optical adhesive sheet in the peel test under the conditions of 25°C, peel angle of 180° and pulling speed of 300 mm / min is 7.6 N / 20 mm or more.

[0016] The present invention [4] includes the optical adhesive sheet described in any one of [1] to [3] above, wherein the optical adhesive sheet has an adhesive force F1 in a peel test under the conditions of 25°C, peel angle 180° and pulling speed 300 mm / min, and the optical adhesive sheet has an adhesive force F2 in a peel test under the conditions of 25°C, peel angle 180° and pulling speed 60 mm / min, and the ratio of adhesive force F2 to adhesive force F1 is 0.5 or more and 1.1 or less.

[0017] The present invention [5] includes the optical adhesive sheet described in any one of [1] to [4] above, wherein the ratio of the shear storage modulus of the optical adhesive sheet at 60°C to the shear storage modulus at -10°C is 0.2 or more and 1.0 or less.

[0018] The present invention [6] comprises the optical adhesive sheet described in any one of [1] to [5] above, wherein the optical adhesive sheet has a gel fraction of 60% or more and 87% or less by mass.

[0019] Effects of the Invention

[0020] As described above, the optical adhesive sheet of the present invention has a shear storage modulus of less than 100 kPa at -10°C. Such a soft optical adhesive sheet is suitable for relaxing the stress generated on the optical adhesive sheet and the adhered object when the adhered object deforms (stress relaxation function). The stress relaxation of the optical adhesive sheet is suitable for ensuring the conformability of the optical adhesive sheet to the adhered object. The stress relaxation of the adhered object is suitable for suppressing breakage such as cracking of the adhered object. Furthermore, as described above, the optical adhesive sheet of the present invention comprises a base polymer and an oligomer with a glass transition temperature (Tg) of 40°C or higher, wherein the hydrogen bonding component δH1 of the Hansen solubility parameter (HSP) of the base polymer and the hydrogen bonding component δH2 of the HSP of the oligomer satisfy: 0.1 ≤ δH2 - δH1 ≤ 1.3. This configuration is suitable for ensuring the overall softness of the optical adhesive sheet while concentrating the oligomer with a Tg of 40°C or higher on and near the surface (adhesive surface) of the optical adhesive sheet, thereby achieving good adhesive force of the adhesive sheet. The high adhesive strength of optical adhesive sheets makes them suitable for preventing peeling from repeatedly deformed substrates. As described above, optical adhesive sheets are suitable for flexible device applications. Attached Figure Description

[0021] Figure 1 This is a schematic cross-sectional view of one embodiment of the optical adhesive sheet of the present invention.

[0022] Figure 2 shows an example of the method of using the optical adhesive sheet of the present invention. Figure 2A This indicates the process of attaching an optical adhesive sheet to a first substrate. Figure 2B This refers to the process of joining a first substrate to a second substrate using an optical adhesive film. Figure 2C This indicates the ripening process. Detailed Implementation

[0023] like Figure 1 As shown, the adhesive sheet 10, as one embodiment of the optical adhesive sheet of the present invention, has a sheet shape with a predetermined thickness and extends in a direction orthogonal to the thickness direction (plane direction). The adhesive sheet 10 has an adhesive surface 11 and an adhesive surface 12 on the side opposite to the adhesive surface 11. Figure 1This illustration exemplifies the state in which release liner L1 and release liner L2 are attached to the adhesive surfaces 11 and 12 of the adhesive sheet 10. Release liner L1 is disposed on the adhesive surface 11. Release liner L2 is disposed on the adhesive surface 12. Furthermore, the adhesive sheet 10 is an optically transparent adhesive sheet (optical adhesive sheet) to be disposed in the light-passing portion of a flexible device. Examples of flexible devices include, for example, flexible display panels. Examples of flexible display panels include, for example, foldable display panels and rollable display panels. Flexible display panels, for example, have a laminated structure including elements such as a pixel panel, a polarizing film, a touch panel, and a protective film. The adhesive sheet 10 is used, for example, during the manufacturing process of the flexible display panel to bond the elements included in the laminated structure to each other. Release liner L1 and L2 are removed at predetermined times when using the adhesive sheet 10.

[0024] The adhesive sheet 10 is formed from an adhesive composition. The adhesive composition comprises a base polymer and an oligomer with a glass transition temperature (Tg) of 40°C or higher. That is, the adhesive sheet 10 comprises a base polymer and an oligomer with a Tg of 40°C or higher. The adhesive sheet 10 has a shear storage modulus of 100 kPa or lower at -10°C. In addition, the hydrogen bonding component δH1 of the Hansen solubility parameter (HSP) of the base polymer and the hydrogen bonding component δH2 of the HSP of the oligomer satisfy the following equation (1).

[0025] 0.1≤δH2-δH1≤1.3 (1)

[0026] As described above, the adhesive sheet 10 has a shear storage modulus of less than 100 kPa at -10°C. This soft adhesive sheet 10 is suitable for relaxing the stress generated on the adhesive sheet 10 and the adhered object during deformation (stress relaxation function). The stress relaxation of the adhesive sheet 10 is suitable for ensuring the conformability of the adhesive sheet 10 to the adhered object. The stress relaxation of the adhered object is suitable for suppressing breakage such as cracking of the adhered object. Therefore, the adhesive sheet 10 is suitable for achieving good repeated deformation of flexible devices using the adhesive sheet 10.

[0027] Furthermore, as described above, the adhesive sheet 10 comprises a base polymer and an oligomer with a Tg of 40°C or higher. The hydrogen bonding component δH1 of the HSP of the base polymer and the hydrogen bonding component δH2 of the HSP of the oligomer satisfy 0.1 ≤ δH2 - δH1 ≤ 1.3. The difference (δH2 - δH1) between the hydrogen bonding component δH1 of the HSP of the base polymer and the hydrogen bonding component δH2 of the HSP of the oligomer is an indicator of the compatibility between the base polymer and the oligomer in the adhesive sheet 10. Such a difference ΔH (δH2 - δH1) is 0.1 or higher and 1.3 or lower, which is suitable for achieving a moderately low compatibility between the base polymer and the oligomer, so that the oligomer is concentrated on and near the surface (adhesive surface 11, adhesive surface 12) of the adhesive sheet 10. Therefore, the difference ΔH(δH2-δH1) being 0.1 or more and 1.3 or less is suitable for ensuring the overall flexibility of the adhesive sheet 10 while allowing oligomers with a Tg of 40°C or more to concentrate on and near the surface (adhesive surface 11, adhesive surface 12) of the adhesive sheet 10, thereby achieving high adhesive strength of the adhesive sheet 10. The high adhesive strength of the adhesive sheet 10 is also suitable for suppressing the peeling of the adhesive sheet 10 from repeatedly deformed adherends.

[0028] As described above, the adhesive sheet 10 is suitable for flexible device applications. In other words, the adhesive sheet 10 facilitates good repeated deformation of the flexible device using the adhesive sheet 10.

[0029] From the viewpoint of stress relaxation at the deformed portion when the adhesive sheet 10 is deformed (bending, buckling, etc.), the shear storage modulus G1 of the adhesive sheet 10 at -10°C is preferably 90 kPa or less, more preferably 85 kPa or less, and even more preferably 80 kPa or less. From the viewpoint of ensuring the cohesiveness of the adhesive sheet 10 in the low-temperature region, the shear storage modulus G1 (-10°C) is preferably 30 kPa or more, more preferably 40 kPa or more, even more preferably 50 kPa or more, and even more preferably 60 kPa or more. The shear storage modulus G1 is determined by the dynamic viscoelasticity measurement described in the following examples (the same applies to the shear storage moduli G2 and G3 described later). As methods for adjusting the shear storage modulus of the adhesive sheet 10, examples include the selection of the type of base polymer in the adhesive sheet 10, the adjustment of the molecular weight, the adjustment of the amount of compounding, and the selection of the type of crosslinking agent and the adjustment of the amount of compounding (the same applies to the shear storage modulus G2 and G3 described later).

[0030] From the viewpoint of stress relaxation of the adhesive sheet 10, the shear storage modulus G2 of the adhesive sheet 10 at 60°C is preferably 35 kPa or less, more preferably 32 kPa or less, and even more preferably 27 kPa or less. From the viewpoint of ensuring the cohesiveness of the adhesive sheet 10 in the high-temperature region, the shear storage modulus G2 (60°C) is preferably 10 kPa or more, more preferably 15 kPa or more, even more preferably 20 kPa or more, and even more preferably 22 kPa or more.

[0031] From the viewpoint of ensuring the stable stress relaxation function of the adhesive sheet 10 over a wide temperature range, the ratio of shear storage modulus G2 to shear storage modulus G1 (G2 / G1) is preferably 0.2 or more, more preferably 0.25 or more, and even more preferably 0.3 or more. In addition, (G2 / G1) is preferably 1.0 or less, more preferably 0.5 or less, and even more preferably less than 0.4.

[0032] From the viewpoint of stress relaxation of the adhesive sheet 10, the shear storage modulus G3 of the adhesive sheet 10 at -20°C is preferably 150 kPa or less, more preferably 130 kPa or less, and even more preferably 120 kPa or less. From the viewpoint of ensuring the cohesiveness of the adhesive sheet 10 in the low-temperature region, the shear storage modulus G3 (-20°C) is preferably 40 kPa or more, more preferably 50 kPa or more, more preferably 70 kPa or more, and even more preferably 90 kPa or more.

[0033] From the viewpoint of moderately reducing the compatibility between the base polymer and the oligomer, and ensuring that the oligomer is sufficiently concentrated in and around the adhesive surfaces 11 and 12, the difference (δH2-δH1) between the hydrogen bonding component δH1 of the HSP of the base polymer and the hydrogen bonding component δH2 of the HSP of the oligomer is preferably 0.2 or more, more preferably 0.3 or more. From the viewpoint of preventing the compatibility between the base polymer and the oligomer from becoming too low, the difference (δH2-δH1) is preferably 1.26 or less. Ensuring the compatibility between the base polymer and the oligomer helps to achieve low haze in the adhesive sheet 10. Methods for adjusting the δH1 of the base polymer include, for example, adjusting the monomer composition of the base polymer. Methods for adjusting the δH2 of the oligomer include, for example, adjusting the monomer composition of the oligomer.

[0034] From the viewpoint of moderately reducing the compatibility between the base polymer and the oligomer, and ensuring that the oligomer is sufficiently concentrated in and around the adhesive surfaces 11 and 12, the ratio (δH2 / δH1) of the hydrogen bonding component δH2 of the oligomer's HSP to the hydrogen bonding component δH1 of the base polymer's HSP is preferably 1.04 or more, more preferably 1.06 or more, further preferably 1.08 or more, and even more preferably 1.10 or more. From the viewpoint of preventing the compatibility between the base polymer and the oligomer from becoming too low, the ratio (δH2 / δH1) is preferably 1.28 or less, more preferably 1.25 or less, and even more preferably 1.22 or less. The ratio (δH2 / δH1) is also an indicator of the compatibility between the base polymer and the oligomer in the adhesive sheet 10.

[0035] The Hansen solubility parameter (HSP) is represented by the following equation (2), where δH is the hydrogen bonding component representing the energy of the hydrogen bonding forces between molecules. Additionally, δD is the dispersion component representing the energy of the dispersion forces between molecules. δP is the polar component representing the energy of the polar forces between molecules.

[0036] HSP=(δD 2 +δP 2 +δH 2 ) 1 / 2 (2)

[0037] The δH of a polymer is determined by the monomer m that forms the polymer. i mole fraction x i and the monomer m i hydrogen bond component δh i The value is obtained using equation (3) below. The δH of the oligomer is also obtained in the same way. The hydrogen bonding component δh of the monomer can be calculated, for example, using the computer software HSPiP (Hansen Solubility Parameters in Practice). The method for determining δH is specifically described in the examples below.

[0038] δH=Σx i ×δh i (3)

[0039] From the viewpoint of achieving high adhesion to the surface of the soft adhesive sheet 10 as described above, the Tg of the oligomer is preferably 50°C or higher, more preferably 60°C or higher, and even more preferably 70°C or higher. Furthermore, the Tg of the oligomer is preferably 145°C or lower, more preferably 135°C or lower, and even more preferably 130°C or lower. The Tg of the oligomer is preferably higher than that of the base polymer. Methods for adjusting the Tg of the oligomer include adjusting the monomer composition and the molecular weight of the oligomer. The method for determining the Tg of the oligomer is specifically described in the following examples.

[0040] The glass transition temperature (Tg) of oligomers can be calculated using the theoretical value based on the Fox formula. The Fox formula is the ratio of the glass transition temperature (Tg) of the polymer to the glass transition temperature (Tg) of the homopolymer of the monomers constituting the polymer. i The relationship is as follows. In the Fox formula below, Tg represents the glass transition temperature (°C) of the oligomer, and W... i The monomer m that constitutes the polymer i weight fraction, Tg i Indicates that it is composed of monomer m i The glass transition temperature (°C) of the resulting homopolymer. The glass transition temperature of the homopolymer can be obtained from literature values. For example, the glass transition temperatures of various homopolymers can be listed in *Polymer Handbook* (4th edition, John Wiley & Sons, Inc., 1999). Alternatively, the glass transition temperature of the monomer homopolymer can be determined using the method specifically described in Japanese Patent Application Publication No. 2007-51271.

[0041] Fox's formula 1 / (273+Tg)=Σ[W i / (273+Tg i )]

[0042] The haze of the adhesive sheet 10 is preferably 1% or less, more preferably 0.8% or less, even more preferably 0.7% or less, and even more preferably 0.5% or less. For example, the haze is 0.01% or more. The haze of the adhesive sheet 10 can be measured using a haze meter according to JIS K7136 (2000). Examples of haze meters include the "NDH2000" manufactured by Nippon Denshoku Kogyo Co., Ltd., and the "HM-150" manufactured by Murakami Color Technology Research Institute Co., Ltd. The method for measuring haze is described in detail in the following examples.

[0043] The total light transmittance of the adhesive sheet 10 is preferably 60% or more, more preferably 80% or more, and even more preferably 85% or more. The total light transmittance of the adhesive sheet 10 is, for example, 100% or less. The total light transmittance of the adhesive sheet 10 can be measured according to JIS K7375 (2008).

[0044] From the viewpoint of ensuring the cohesiveness of the adhesive sheet 10 in the high-temperature region, the gel fraction of the adhesive sheet 10 is preferably 60% by mass or more, more preferably 70% by mass or more, and even more preferably 73% by mass or more. From the viewpoint of ensuring the flexibility of the adhesive sheet 10, the gel fraction of the adhesive sheet 10 is preferably 87% by mass or less, more preferably 85% by mass or less, and even more preferably 83% by mass or less. Methods for adjusting the gel fraction of the adhesive sheet 10 include, for example, the selection of the type of base polymer in the adhesive sheet 10, the adjustment of the molecular weight, and the adjustment of the amount of the compound. Methods for adjusting the gel fraction also include the selection of the type of crosslinking agent and the adjustment of the amount of the compound. Furthermore, the method for determining the gel fraction is as described in the following examples.

[0045] From the viewpoint of suppressing the peeling of the adhesive sheet 10 from the adhered object, the adhesive force F1 of the adhesive sheet 10 in the peel test (first peel test) under the conditions of 25°C, peel angle of 180° and pulling speed of 300 mm / min is preferably 7.6 N / 20 mm or more, more preferably 7.8 N / 20 mm or more, further preferably 8.0 N / 20 mm or more, even more preferably 8.2 N / 20 mm or more, even more preferably 8.4 N / 20 mm or more, even more preferably 8.6 N / 20 mm or more, and particularly preferably 8.8 N / 20 mm or more. The adhesive force F1 is, for example, 15 N / 20 mm or less. The method for measuring the adhesive force F1 is as described in the following examples. As a method for adjusting the adhesive force F1, examples include the selection of the type of base polymer in the adhesive sheet 10, the adjustment of the molecular weight, and the adjustment of the compounding amount. The selection of the type of base polymer includes the adjustment of the composition of the monomers forming the base polymer. As a method for adjusting adhesive force F1, the selection of the types of components other than the base polymer in the adhesive sheet 10 and the adjustment of the amount of these components can also be listed. Examples of these components include crosslinking agents, silane coupling agents, and oligomers. The same method for adjusting adhesive force as described above applies to adhesive force F2, which will be discussed later.

[0046] From the viewpoint of suppressing the peeling of the adhesive sheet 10 from the adhered object, the adhesive force F2 of the adhesive sheet 10 in the peel test (second peel test) under the conditions of 25°C, peel angle of 180° and pulling speed of 60 mm / min is preferably 4.1 N / 20 mm or more, more preferably 6.0 N / 20 mm or more, even more preferably 6.4 N / 20 mm or more, even more preferably 6.8 N / 20 mm or more, even more preferably 7.2 N / 20 mm or more, even more preferably 7.6 N / 20 mm or more, and particularly preferably 8.0 N / 20 mm or more. The adhesive force F2 is, for example, 12 N / 20 mm or less.

[0047] From the viewpoint of ensuring stable adhesive force in the adhesive sheet 10, the ratio of adhesive force F2 to adhesive force F1 (F2 / F1) is preferably 0.5 or more, more preferably 0.6 or more, more preferably 0.7 or more, more preferably 0.75 or more, even more preferably 0.8 or more, and preferably 1.1 or less, more preferably 1.0 or less.

[0048] The base polymer is the adhesive component that exhibits adhesive properties in the adhesive sheet 10. Examples of base polymers include: acrylic polymers, silicone polymers, polyester polymers, polyurethane polymers, polyamide polymers, polyvinyl ether polymers, vinyl acetate / vinyl chloride copolymers, modified polyolefin polymers, epoxy polymers, fluorinated polymers, and rubber polymers. The base polymer can be used alone or in combination of two or more. From the viewpoint of ensuring good transparency and adhesion of the adhesive sheet 10, acrylic polymers are preferred as the base polymer.

[0049] Acrylic polymers are polymers containing alkyl (meth)acrylate monomers (the first monomer component) in a proportion of 50% by mass or more. "(Meth)acrylic acid" refers to acrylic acid and / or methacrylic acid.

[0050] As an alkyl methacrylate, it is preferable to use an alkyl methacrylate having 1 to 20 carbon atoms in the alkyl group. Examples of alkyl methacrylates include (meth)acrylates having chain alkyl groups (chain alkyl methacrylates) and (meth)acrylates having alicyclic alkyl groups (alicyclic alkyl methacrylates).

[0051] Examples of alkyl esters of (meth)acrylate include: methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, sec-butyl methacrylate, tert-butyl methacrylate, pentyl methacrylate, isoamyl methacrylate, neopentyl methacrylate, n-hexyl methacrylate, heptyl methacrylate, 2-ethylhexyl methacrylate, n-octyl methacrylate, isooctyl methacrylate, nonyl methacrylate, isononyl methacrylate, decyl methacrylate, isodecyl methacrylate, undecyl methacrylate, lauryl methacrylate, isotridecyl methacrylate, tetradecyl methacrylate, isotetradecyl methacrylate, pentadecyl methacrylate, cetyl methacrylate, heptadecanyl methacrylate, octadecyl methacrylate, isooctadecyl methacrylate, and nonadecanyl methacrylate.

[0052] Examples of cycloalkyl methacrylates include: cycloalkyl methacrylates, methacrylates having a bicyclic aliphatic hydrocarbon ring, and methacrylates having three or more aliphatic hydrocarbon rings. Examples of cycloalkyl methacrylates include: cyclopentyl methacrylate, cyclohexyl methacrylate, methylcyclohexyl methacrylate, tert-butylcyclohexyl methacrylate, cycloheptyl methacrylate, cyclooctyl methacrylate, and cyclododecyl methacrylate. Examples of methacrylates having a bicyclic aliphatic hydrocarbon ring include: isobornyl methacrylate. Examples of (meth)acrylates having three or more aliphatic hydrocarbon rings include: tetrahydrodicyclopentadienyl (meth)acrylate, dihydrodicyclopentadienyl (meth)acrylate, tetrahydrodicyclopentadienyloxyethyl (meth)acrylate, tetrahydrotricyclopentadienyl (meth)acrylate, 1-adamantyl (meth)acrylate, 2-methyl-2-adamantyl (meth)acrylate, and 2-ethyl-2-adamantyl (meth)acrylate.

[0053] From the viewpoint of achieving a balance between softness and adhesive strength required for adhesive sheets used in flexible devices, it is preferable to use at least one alkyl methacrylate selected from a first alkyl group having 8 to 12 carbon atoms, or at least one alkyl methacrylate selected from a first alkyl group having 8 to 12 carbon atoms and a second alkyl methacrylate having 1 to 4 carbon atoms. The first alkyl methacrylate is preferably at least one selected from the group consisting of 2-ethylhexyl acrylate (2EHA), n-octyl acrylate (NOAA), isononyl acrylate (INAA), and lauryl acrylate (LA). The second alkyl methacrylate is preferably n-butyl acrylate (BA).

[0054] From the viewpoint of appropriately exhibiting softness and adhesive strength in the adhesive sheet 10, the proportion of (meth)acrylate alkyl ester in the first monomer component is preferably 80% by mass or more, more preferably 85% by mass or more, further preferably 88% by mass or more, and particularly preferably 90% by mass or more. This proportion is, for example, 99.9% by mass or less, 99.5% by mass or less, or 99% by mass or less. When using a first alkyl methacrylate selected from alkyl methacrylates having 8 to 12 carbon atoms and a second alkyl methacrylate selected from alkyl methacrylates having 1 to 4 carbon atoms, the proportion of the first alkyl methacrylate in the monomer component is preferably 60% by mass or more, more preferably 65% ​​by mass or more, even more preferably 70% by mass or more, and preferably 85% by mass or less, more preferably 80% by mass or less, even more preferably 75% by mass or less. The proportion of the second alkyl methacrylate in the monomer component is preferably 10% by mass or more, more preferably 15% by mass or more, even more preferably 20% by mass or more, and preferably 35% by mass or less, more preferably 30% by mass or less, even more preferably 25% by mass or less.

[0055] The first monomer component may contain a copolymerizable monomer capable of copolymerizing with alkyl (meth)acrylates. Examples of copolymerizable monomers include, for example, monomers with polar groups. Examples of monomers containing polar groups include, for example, hydroxyl-containing monomers, monomers with nitrogen-containing rings, and carboxyl-containing monomers. Monomers containing polar groups facilitate the modification of acrylic polymers, such as introducing crosslinking points and ensuring the cohesiveness of acrylic polymers. Copolymerizable monomers may be used alone or in combination of two or more.

[0056] Examples of hydroxyl-containing monomers include: 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylaurate (meth)acrylate, and methyl (4-hydroxymethylcyclohexyl)methacrylate. Preferably, the hydroxyl-containing monomer is at least one selected from the group consisting of 2-hydroxyethyl acrylate (2HEA) and 4-hydroxybutyl acrylate (4HBA).

[0057] From the viewpoint of introducing a cross-linking structure into the acrylic polymer and ensuring cohesion in the adhesive sheet 10, the proportion of the hydroxyl-containing monomer in the first monomer component is preferably 1% by mass or more, more preferably 3% by mass or more, and even more preferably 5% by mass or more. From the viewpoint of adjusting the polarity of the acrylic polymer (which relates to the compatibility between the various additive components in the adhesive sheet 10 and the acrylic polymer), this proportion is preferably 12% by mass or less, more preferably 10% by mass or less, and even more preferably 9% by mass or less.

[0058] Examples of monomers having a nitrogen-containing ring include: N-vinyl-2-pyrrolidone, N-methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, N-vinylpiperazine, N-vinylpyrazine, N-vinylpyrrole, N-vinylimidazolium, and N-vinylpyrrolidone. azole, 4-acryloylmorpholine, N-vinyl-2-caprolactam, N-vinyl-1,3- Azine-2-one, N-vinyl-3,5-morpholinedione, N-vinylpyrazole, N-vinylisothione Zyrazoles, N-vinylthiazoles, and N-vinylisothiazoles. Monomers having a nitrogen-containing ring are preferably N-vinyl-2-pyrrolidone (NVP).

[0059] When using monomers with nitrogen-containing atomic rings, from the viewpoint of ensuring cohesion in the adhesive sheet 10 and adhesion of the adhesive sheet 10 to the adhered object, the proportion of the monomer with nitrogen-containing atomic rings in the first monomer component is preferably 0.5% by mass or more, more preferably 1% by mass or more, and even more preferably 1.5% by mass or more. From the viewpoint of adjusting the glass transition temperature of the acrylic polymer and adjusting the polarity of the acrylic polymer (which relates to the compatibility between the various additive components in the adhesive sheet 10 and the acrylic polymer), this proportion is preferably 10% by mass or less, more preferably 6% by mass or less, and even more preferably 4% by mass or less.

[0060] Examples of carboxyl-containing monomers include: acrylic acid, methacrylic acid, carboxyethyl acrylate, carboxypentyl acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, and isocrotonic acid.

[0061] When using carboxyl-containing monomers, from the viewpoint of introducing a cross-linking structure into the acrylic polymer, ensuring the cohesiveness of the adhesive sheet 10, and ensuring the adhesion of the adhesive sheet 10 to the adhered object, the proportion of carboxyl-containing monomers in the monomer component is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and even more preferably 0.8% by mass or more. From the viewpoint of adjusting the glass transition temperature of the acrylic polymer and avoiding the risk of corrosion of the adhered object due to acid, this proportion is preferably 3% by mass or less, more preferably 1% by mass or less.

[0062] The first monomer component may contain other copolymerizable monomers. Examples of other copolymerizable monomers include: acid anhydride monomers, sulfonic acid monomers, phosphate monomers, epoxy monomers, cyano monomers, alkoxy monomers, and aromatic vinyl compounds. These other copolymerizable monomers may be used alone or in combination of two or more.

[0063] The first monomer component preferably comprises: a first (meth)acrylate alkyl ester having an alkyl group having 8 to 12 carbon atoms, a second (meth)acrylate alkyl ester having an alkyl group having 1 to 4 carbon atoms, a hydroxyl-containing monomer, and a monomer having a nitrogen-containing ring. More preferably, the first monomer component comprises NOAA, BA, NVP, and 4HBA.

[0064] The base polymer preferably has a crosslinked structure. Examples of methods for introducing a crosslinked structure into the base polymer include the following first and second methods. In the first method, a base polymer having functional groups capable of reacting with a crosslinking agent and a crosslinking agent are incorporated into an adhesive composition, and the base polymer and the crosslinking agent are reacted in an adhesive sheet. In the second method, a multifunctional compound serving as a crosslinking agent is included in a first monomer component forming the base polymer, and a base polymer with a branched structure (crosslinked structure) introduced into the polymer chain is formed by polymerization of this first monomer component. These methods can be used in combination.

[0065] Examples of crosslinking agents used in the first method described above include compounds that react with functional groups (hydroxyl and carboxyl groups, etc.) contained in the base polymer. Examples of such crosslinking agents include: isocyanate crosslinking agents, peroxide crosslinking agents, epoxy crosslinking agents, etc. Azoline crosslinking agents, aziridine crosslinking agents, and carbodiimide crosslinking agents. The crosslinking agent in the first method can be used alone or in combination of two or more. As the crosslinking agent in the first method, isocyanate crosslinking agents are preferred from the perspective of high reactivity with the hydroxyl and carboxyl groups in the base polymer and ease of incorporating crosslinking structures.

[0066] Examples of isocyanate crosslinking agents include: toluene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, phenylenediamine diisocyanate, hydrogenated phenylenediamine diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, tetramethylphenylenediamine diisocyanate, naphthalene diisocyanate, triphenylmethane triisocyanate, and polymethylene polyphenyl isocyanate. Furthermore, derivatives of these isocyanates can also be listed as isocyanate crosslinking agents. Examples of isocyanurate-modified derivatives and polyol-modified derivatives can be listed. Commercially available isocyanate crosslinking agents include, for example, CORONATE L (trimethylolpropane adduct of toluene diisocyanate, manufactured by Tosoh), CORONATE HL (trimethylolpropane adduct of hexamethylene diisocyanate, manufactured by Tosoh), CORONATE HX (isocyanurate form of hexamethylene diisocyanate, manufactured by Tosoh), TAKENATED 110N (trimethylolpropane adduct of phenyl diisocyanate, manufactured by Mitsui Chemicals), and TAKENATE 600 (1,3-bis(isocyanate methyl)cyclohexane, manufactured by Mitsui Chemicals).

[0067] Examples of peroxide crosslinking agents include: benzoyl peroxide, di(2-ethylhexyl) peroxide dicarbonate, di(4-tert-butylcyclohexyl) peroxide dicarbonate, disec-butyl peroxide dicarbonate, tert-butyl peroxide neodecanoate, tert-hexyl peroxide neopentanoate, and tert-butyl peroxide neopentanoate.

[0068] Examples of epoxy crosslinking agents include: bisphenol A, epichlorohydrin-type epoxy resin, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerol diglycidyl ether, glycerol triglycidyl ether, 1,6-hexanediol glycidyl ether, trimethylolpropane triglycidyl ether, diglycidyl aniline, diamine glycidyl amine, N,N,N',N'-tetraglycidyl m-phenylenediamine, and 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane.

[0069] From the viewpoint of ensuring the cohesiveness of the adhesive sheet 10, the amount of crosslinking agent in the first method, relative to 100 parts by mass of the base polymer, is, for example, 0.01 parts by mass or more, preferably 0.05 parts by mass or more, and more preferably 0.1 parts by mass or more. From the viewpoint of ensuring good adhesion of the adhesive sheet 10, the amount of crosslinking agent, relative to 100 parts by mass of the base polymer, is, for example, 5 parts by mass or less, preferably 1 part by mass or less, and more preferably 0.2 parts by mass or less.

[0070] In the second method described above, the first monomer component (containing a multifunctional compound and a monofunctional monomer for introducing the crosslinking structure) can be polymerized in one step or in multiple steps. In the multi-step polymerization method, firstly, the monofunctional monomer used to form the base polymer is polymerized (prepolymerization), thereby preparing a prepolymer composition containing a portion of the polymer (a mixture of a low-degree polymer and unreacted monofunctional monomers). Next, the multifunctional compound, as a crosslinking agent, is added to the prepolymer composition, and then a polymerization reaction (main polymerization) is carried out in a reaction system containing the portion of the polymer and the multifunctional compound.

[0071] Examples of multifunctional compounds include multifunctional monomers and multifunctional oligomers containing two or more olefinic unsaturated double bonds in one molecule. Examples of multifunctional monomers include multifunctional (meth)acrylates.

[0072] Examples of polyfunctional (meth)acrylates include difunctional (meth)acrylates, trifunctional (meth)acrylates, and polyfunctional (meth)acrylates with four or more functions.

[0073] Examples of difunctional (meth)acrylates include ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, 1,6-hexanediol dimethacrylate, 1,9-nonanediol dimethacrylate, glycerol dimethacrylate, ethoxylated bisphenol A dimethacrylate (BPAEODE), and neopentyl glycol dimethacrylate.

[0074] Examples of trifunctional (meth)acrylates include: trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, and tri(acryloyloxyethyl)isocyanurate.

[0075] Examples of polyfunctional (meth)acrylates with more than four functions include: di(trimethylolpropane)tetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol monohydroxypenta(meth)acrylate, alkyl-modified dipentaerythritol penta(meth)acrylate, and dipentaerythritol hexa(meth)acrylate.

[0076] Examples of multifunctional oligomers include: urethane (meth)acrylate oligomers, polyester (meth)acrylate oligomers, polyether (meth)acrylate oligomers, polyol (meth)acrylate oligomers, epoxy (meth)acrylate oligomers, polyethylene glycol di(meth)acrylate, and polypropylene glycol di(meth)acrylate.

[0077] The multifunctional compound used as the crosslinking agent in the second method can be used alone or in combination with two or more. As the multifunctional compound, a multifunctional monomer is preferred, and at least one selected from the group consisting of 1,9-nonanediol diacrylate, dipentaerythritol hexaacrylate, 1,6-hexanediol diacrylate and trimethylolpropane triacrylate is more preferred.

[0078] From the viewpoint of ensuring the cohesiveness of the adhesive sheet 10, the amount of the polyfunctional compound acting as a crosslinking agent in the first monomer component is preferably 0.02 parts by mass or more, more preferably 0.05 parts by mass or more, and even more preferably 0.07 parts by mass or more, relative to 100 parts by mass of the monofunctional monomer. From the viewpoint of ensuring good adhesion of the adhesive sheet 10, the amount of the polyfunctional compound is preferably 3 parts by mass or less, more preferably 2 parts by mass or less, and even more preferably 1 part by mass or less, relative to 100 parts by mass of the monofunctional monomer.

[0079] Acrylic polymers (basic polymers) can be formed by polymerizing the first monomer component described above. Examples of polymerization methods include solution polymerization, emulsion polymerization, and solvent-free photopolymerization (e.g., ultraviolet polymerization). Examples of solvents for solution polymerization include ethyl acetate and toluene. Chain transfer agents can be used in the polymerization. Additionally, examples of polymerization initiators include thermal polymerization initiators and photopolymerization initiators. The polymerization initiator can be used alone or in combination of two or more. The amount of polymerization initiator used relative to 100 parts by mass of the first monomer component is preferably 0.03 parts by mass or more, more preferably 0.05 parts by mass or more, even more preferably 0.07 parts by mass or more, and preferably 1 part by mass or less, more preferably 0.5 parts by mass or less, and even more preferably 0.3 parts by mass or less.

[0080] Examples of thermal polymerization initiators include azo polymerization initiators and peroxide polymerization initiators. Examples of azo polymerization initiators include 2,2'-azobisisobutyronitrile, 2,2'-azobis-2-methylbutyronitrile, dimethyl 2,2'-azobis(2-methylpropionic acid) ester, 4,4'-azobis-4-cyanopentanoic acid, azobisisovalerate, and 2,2'-azobis(2-amidinylpropane) dihydrochloride. Examples of peroxide polymerization initiators include benzoyl peroxide, tert-butyl maleate peroxide, and lauroyl peroxide.

[0081] Examples of photopolymerization initiators include: free radical photopolymerization initiators, cationic photopolymerization initiators, and anionic photopolymerization initiators.

[0082] Examples of free radical photopolymerization initiators include: acylphosphine oxide photopolymerization initiators, benzoin ether photopolymerization initiators, and acetophenone photopolymerization initiators.

[0083] Examples of acylphosphine oxide photopolymerization initiators include: bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-2,4-di-n-butoxyphenylphosphine oxide, 2,4,6-trimethylbenzoyl diphenylphosphine oxide, and bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide. Examples of benzoin ether photopolymerization initiators include: benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isopropyl ether, benzoin isobutyl ether, and 2,2-dimethoxy-1,2-diphenylethane-1-one. Examples of acetophenone photopolymerization initiators include: 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexylphenyl ketone, 4-phenoxydichloroacetophenone, and 4-(tert-butyl)dichloroacetophenone.

[0084] From the viewpoint of ensuring cohesion in the adhesive sheet 10, the weight-average molecular weight of the base polymer is preferably 100,000 or more, more preferably 300,000 or more, and even more preferably 500,000 or more. The weight-average molecular weight of the base polymer is determined by gel permeation chromatography (GPC) and calculated by polystyrene conversion.

[0085] The glass transition temperature (Tg) of the base polymer is preferably below 0°C, more preferably below -10°C, and even more preferably below -20°C. This glass transition temperature is, for example, above -80°C. The theoretical glass transition temperature (Tg) of the base polymer can be used, calculated based on the Fox formula described above.

[0086] When using acrylic polymers as the base polymer, acrylic oligomers are preferred as oligomers. Acrylic oligomers are copolymers containing a monomeric component (second monomeric component) of alkyl (meth)acrylate in a proportion of 50% by mass or more, and have a weight-average molecular weight, for example, of 1000 or more and 30000 or less. Oligomers can be used alone or in combination of two or more.

[0087] When using two or more oligomers, at least one oligomer must satisfy a specified parameter (e.g., glass transition temperature, the difference ΔH (=δH2-δH1) between the hydrogen bonding component δH1 of the base polymer's HSP and the hydrogen bonding component δH2 of the oligomer's HSP). That is, when using two or more oligomers, oligomers that do not satisfy the specified parameters (e.g., glass transition temperature, the difference ΔH (=δH2-δH1) between the hydrogen bonding component δH1 of the base polymer's HSP and the hydrogen bonding component δH2 of the oligomer's HSP) may be included, without impairing the effects of the invention. Preferably, all oligomers used satisfy the specified parameters.

[0088] Alkyl esters of (meth)acrylate as the second monomer component include, for example, cycloalkyl esters of (meth)acrylate and chain alkyl esters of (meth)acrylate.

[0089] Examples of (meth)acrylate cyclic alkyl esters as the second monomer component include, for instance, the (meth)acrylate cyclic alkyl esters described with respect to the first monomer component. The (meth)acrylate cyclic alkyl ester in the second monomer component is preferably at least one selected from the group consisting of cyclohexyl methacrylate (CHMA), methylcyclohexyl methacrylate, tert-butylcyclohexyl methacrylate, cyclododecyl methacrylate, isobornyl methacrylate (IBXMA), tetrahydrodicyclopentadienyl methacrylate (DCPMA), dihydrodicyclopentadienyl methacrylate, and 1-adamantyl methacrylate (ADMA), more preferably at least one selected from the group consisting of DCPMA, CHMA, IBXMA, and ADMA.

[0090] From the viewpoint of increasing the Tg of the oligomer, the proportion of (meth)acrylate cyclic alkyl esters in the second monomer component is preferably 30% by mass or more, more preferably 35% by mass or more, and even more preferably 40% by mass or more. From the viewpoint of the polymerizability of the second monomer component, the proportion of (meth)acrylate cyclic alkyl esters in the second monomer component is preferably 80% by mass or less, more preferably 75% by mass or less, and even more preferably 65% ​​by mass or less.

[0091] Examples of (meth)acrylate alkyl esters as the second monomer component include, for instance, the (meth)acrylate alkyl esters described with respect to the first monomer component. The (meth)acrylate alkyl ester in the second monomer component is preferably an alkyl ester having 1 to 6 carbon atoms, more preferably methyl methacrylate (MMA). MMA homopolymers have high glass transition temperatures and high compatibility with the base polymer, therefore they are preferred.

[0092] From the viewpoint of ensuring high Tg of the oligomer and adjusting the compatibility between the oligomer and the base polymer, the proportion of (meth)acrylate alkyl ester in the second monomer component is preferably 15% by mass or more, more preferably 20% by mass or more, even more preferably 25% by mass or more, and even more preferably 30% by mass or more. In addition, it is preferably 60% by mass or less, more preferably 55% by mass or less, and even more preferably 50% by mass or less.

[0093] From the viewpoint of increasing the Tg of the oligomer and adjusting the compatibility between the oligomer and the base polymer, the mass ratio of (meth)acrylate cyclic alkyl ester to (meth)acrylate chain alkyl ester in the second monomer component is preferably 0.6 or more, more preferably 0.8 or more, and preferably 9.0 or less, more preferably 5.0 or less, and even more preferably 2.0 or less.

[0094] The second monomer component may include a copolymerizable monomer capable of copolymerizing with alkyl (meth)acrylates. Examples of copolymerizable monomers include hydrophilic monomers. Examples of hydrophilic monomers include hydroxyl-containing monomers, monomers having a nitrogen-containing ring, carboxyl-containing monomers, and ether-containing monomers, preferably at least one selected from the group consisting of hydroxyl-containing monomers, nitrogen-containing ring monomers, carboxyl-containing monomers, and ether-containing monomers. The hydrophilic monomer may be used alone or in combination with two or more monomers.

[0095] The hydroxyl-containing monomer in the second monomer component can be, for example, the hydroxyl-containing monomers described with respect to the first monomer component. The hydroxyl-containing monomer in the second monomer component is preferably at least one selected from the group consisting of 2-hydroxyethyl methacrylate (HEMA), 2-hydroxypropyl methacrylate (HPMA), and 4-hydroxybutyl acrylate (4HBA).

[0096] From the viewpoint of adjusting the compatibility between the oligomer and the base polymer, the proportion of hydroxyl-containing monomers in the second monomer component is preferably 1% by mass or more, more preferably 3% by mass or more, even more preferably 5% by mass or more, and preferably 18% by mass or less, more preferably 15% by mass or less, and even more preferably 12% by mass or less.

[0097] The monomer having a nitrogen-containing ring as the second monomer component can be, for example, the monomer having the aforementioned nitrogen-containing ring described with respect to the first monomer component. The monomer having a nitrogen-containing ring in the second monomer component is preferably 4-acryloylmorpholine (ACMO).

[0098] From the viewpoint of adjusting the compatibility between the oligomer and the base polymer, the proportion of monomers having nitrogen-containing rings in the second monomer component is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 15% by mass or more. From the viewpoint of controlling the molecular weight of the oligomer, the proportion of monomers having nitrogen-containing rings in the second monomer component is preferably 30% by mass or less, more preferably 25% by mass or less, and even more preferably 22% by mass or less.

[0099] The carboxyl-containing monomer in the second monomer component can be, for example, the carboxyl-containing monomers described with respect to the first monomer component. The carboxyl-containing monomer in the second monomer component is preferably acrylic acid (AA).

[0100] From the viewpoint of adjusting the compatibility between the oligomer and the base polymer, the proportion of carboxyl-containing monomers in the second monomer component is preferably 1% by mass or more, more preferably 3% by mass or more, even more preferably 5% by mass or more, and preferably 18% by mass or less, more preferably 15% by mass or less, and even more preferably 12% by mass or less.

[0101] Examples of ether-containing monomers include: ethyl carbitol acrylate (CBA), 2-methoxyethyl acrylate (CBA), ethoxyethyl acrylate (CBA), tetrahydrofurfuryl acrylate (CBA), 2-phenoxyethyl acrylate (CBA), phenoxyethyl acrylate (CBA), and ethyleneoxyethoxyethyl acrylate (CBA). Ethyl carbitol acrylate (CBA) is preferred as the ether-containing monomer.

[0102] From the viewpoint of adjusting the compatibility between the oligomer and the base polymer, the proportion of the ether-containing monomer in the second monomer component is preferably 3% by mass or more, more preferably 5% by mass or more, even more preferably 7% by mass or more, and preferably 40% by mass or less, more preferably 35% by mass or less, and even more preferably 32% by mass or less.

[0103] The second monomer component preferably comprises a (meth)acrylate cyclic alkyl ester, a (meth)acrylate chain alkyl ester, and a hydrophilic monomer. That is, the acrylic oligomer is preferably a copolymer of the second monomer component comprising a (meth)acrylate cyclic alkyl ester, a (meth)acrylate chain alkyl ester, and a hydrophilic monomer.

[0104] From the viewpoint of increasing the Tg of the oligomer and adjusting the compatibility between the oligomer and the base polymer, the proportion of hydrophilic monomer in the second monomer component is preferably 1% by mass or more, more preferably 3% by mass or more, even more preferably 5% by mass or more, and preferably 40% by mass or less, more preferably 35% by mass or less, and even more preferably 32% by mass or less.

[0105] Acrylic oligomers can be used alone or in combination of two or more, as described above. When using two or more acrylic oligomers in combination, it is preferable that at least one oligomer is a copolymer containing a second monomer component of a (meth)acrylate cycloalkyl ester, a (meth)acrylate chain alkyl ester, and a hydrophilic monomer. Specifically, examples include copolymers containing a second monomer component of a (meth)acrylate cycloalkyl ester and a (meth)acrylate chain alkyl ester, and copolymers containing a second monomer component of a (meth)acrylate cycloalkyl ester, a (meth)acrylate chain alkyl ester, and a hydrophilic monomer in combination.

[0106] When two or more acrylic oligomers are used together, the content ratio of each copolymer (each acrylic oligomer) in the total amount of acrylic oligomers is not particularly limited and can be appropriately adjusted within the range where the two or more acrylic oligomers used together meet the specified parameters. Specifically, the content ratio of the copolymer (one acrylic oligomer) containing a second monomer component comprising a (meth)acrylate cycloalkyl ester, a (meth)acrylate chain alkyl ester, and a hydrophilic monomer in the total amount of acrylic oligomers is preferably 50% by mass or more, more preferably 55% by mass or more, and even more preferably 58% by mass or more.

[0107] Acrylic oligomers are obtained by polymerizing a second monomer component of the acrylic oligomer. Examples of polymerization methods include solution polymerization, emulsion polymerization, and solvent-free photopolymerization (e.g., UV polymerization). Examples of solvents used in solution polymerization are ethyl acetate and toluene. Chain transfer agents can be used to adjust the molecular weight during polymerization. Additionally, examples of polymerization initiators include thermal polymerization initiators and photopolymerization initiators. The polymerization initiator can be used alone or in combination of two or more. The amount of polymerization initiator used relative to 100 parts by mass of the second monomer component is preferably 0.03 parts by mass or more, more preferably 0.05 parts by mass or more, even more preferably 0.07 parts by mass or more, and preferably 1 part by mass or less, more preferably 0.5 parts by mass or less, and even more preferably 0.3 parts by mass or less.

[0108] From the viewpoint of achieving high adhesion on the surfaces (adhesive surfaces 11 and 12) of the adhesive sheet 10, the weight-average molecular weight (Mw) of the oligomer is preferably 4300 or more, more preferably 4500 or more, and even more preferably 4700 or more. From the viewpoint of the concentrated presence (migration to the surface) of the adhesive sheet 10 and its vicinity of the oligomer, the weight-average molecular weight (Mw) of the oligomer is preferably 10000 or less, more preferably 8000 or less, and even more preferably 6000 or less. The method for determining the weight-average molecular weight (Mw) of the oligomer is described in detail in the following examples.

[0109] To sufficiently improve the adhesive strength of the adhesive sheet 10, the content of acrylic oligomers in the adhesive sheet 10 is preferably 0.2 parts by mass or more, more preferably 0.3 parts by mass or more, and even more preferably 0.5 parts by mass or more, relative to 100 parts by mass of the base polymer. From the viewpoint of ensuring the transparency of the adhesive sheet 10, the content of acrylic oligomers in the adhesive sheet 10 is preferably 5 parts by mass or less, more preferably 4 parts by mass or less, and even more preferably 3 parts by mass or less, relative to 100 parts by mass of the base polymer. If the content of acrylic oligomers in the adhesive sheet 10 is too high, the reduced compatibility of the acrylic oligomers tends to lead to increased haze and decreased transparency.

[0110] The adhesive composition may contain a silane coupling agent. The content of the silane coupling agent in the adhesive composition is preferably 0.1 parts by weight or more, more preferably 0.2 parts by weight or more, relative to 100 parts by weight of the base polymer. This content is preferably 5 parts by weight or less, more preferably 3 parts by weight or less.

[0111] The adhesive composition may contain other components as needed. Examples of such other components include, for example, solvents, tackifiers, plasticizers, softeners, antioxidants, fillers, colorants, UV absorbers, antioxidants, surfactants, and antistatic agents. Examples of solvents include, for example, the polymerization solvent used as needed during the polymerization of acrylic polymers, and the solvent added to the polymerization reaction solution after polymerization. Ethyl acetate and toluene can be used as examples of such solvents.

[0112] The adhesive sheet 10 can be manufactured, for example, by applying the adhesive composition described above onto the release liner L1 (first release liner) to form a coating film, and then irradiating the coating film with ultraviolet light or drying the coating film. The adhesive sheet 10 can also be manufactured by applying the adhesive composition described above onto the release liner L1 (first release liner) to form a coating film, stacking the release liner L2 (second release liner) on the coating film, and then irradiating the coating film between the release liners with ultraviolet light or drying the coating film.

[0113] Examples of release liner L1 include, for example, a flexible plastic film. Examples of such plastic films include, for example, polyester films such as polyethylene terephthalate films, polyethylene films, and polypropylene films. The thickness of release liner L1 is, for example, 3 μm or more, and also, for example, 200 μm or less. The surface of release liner L1 is preferably treated with a release coating.

[0114] Examples of coating methods for adhesive compositions include: roller coating, licking coating, gravure coating, reverse coating, brush coating, spraying, dip roller coating, doctor blade coating, knife coating, air knife coating, curtain coating, die lip coating, and die-cutting. The drying temperature of the coating film is, for example, 50°C to 200°C. The drying time is, for example, 5 seconds to 20 minutes.

[0115] The release liner L2 is preferably a flexible plastic film with a surface that has undergone a release treatment. The plastic film described with respect to the release liner L1 can be used as the release liner L2.

[0116] As described above, an adhesive sheet 10 can be manufactured in which the adhesive surfaces 11 and 12 are covered and protected by release pads L1 and L2.

[0117] Figures 2A to 2C This is an example of how to use the adhesive sheet 10.

[0118] In this method, firstly, as Figure 2A As shown, the adhesive sheet 10 is attached to one surface of the first component 21 (the object to be adhered) in the thickness direction H. The first component 21 is, for example, a component in the laminated structure of a flexible display panel. Examples of such components include pixel panels, polarizing films, touch panels, and protective films (the same applies to the second component 22 described later). Through this process, an adhesive sheet 10 for bonding with other components is provided on the first component 21.

[0119] Next, as Figure 2B As shown, one side of the first component 21 in the thickness direction H is joined to the other side of the second component 22 in the thickness direction H via an adhesive tab 10 on the first component 21. The second component 22 is, for example, another element in the laminated structure of the flexible display panel.

[0120] Next, as Figure 2C As shown, the adhesive sheet 10 between the first component 21 and the second component 22 is cured. Curing increases the bonding strength between the adhesive sheet 10 and components 21 and 22. The curing temperature is, for example, 20°C to 160°C. The curing time is, for example, 1 minute to 21 days. When curing is performed using an autoclave (heated and pressurized treatment), the temperature is, for example, 30°C to 80°C, the pressure is, for example, 0.1 MPa to 0.8 MPa, and the treatment time is, for example, 15 minutes or more.

[0121] Example

[0122] The following examples illustrate the present invention in detail. However, the present invention is not limited to these examples. Furthermore, the specific values ​​of the amount (content), physical property values, parameters, etc., described below can be replaced with the upper limit (defined as "less than" or "less than") or lower limit (defined as "more than" or "greater than") of the corresponding amount (content), physical property values, parameters, etc., described in the above "Specific Embodiments".

[0123] <Preparation of the first prepolymer composition>

[0124] In a reaction vessel equipped with a stirrer, thermometer, reflux condenser, and nitrogen inlet pipe, 0.05 parts by weight of a first photopolymerization initiator (trade name "Omnirad 184", 1-hydroxycyclohexylphenyl ketone, manufactured by IGM Resins) and 0.05 parts by weight of a second photopolymerization initiator (trade name "Omnirad 651", 2,2-dimethoxy-1,2-diphenylethane-1-one, manufactured by IGM Resins) and 0.05 parts by weight of a second photopolymerization initiator (trade name "Omnirad 651", 2,2-dimethoxy-1,2-diphenylethane-1-one, manufactured by IGM Resins) were added to a monomer mixture of 70 parts by weight of n-octyl acrylate (NOAA), 20 parts by weight of n-butyl acrylate (BA), 8 parts by weight of 4-hydroxybutyl acrylate (4HBA), and 2 parts by weight of N-vinyl-2-pyrrolidone (NVP). The mixture was then irradiated with ultraviolet light under a nitrogen atmosphere, thereby polymerizing a portion of the monomer components in the mixture to obtain a first prepolymer composition. A black light lamp was used for ultraviolet irradiation. Ultraviolet irradiation continued until the viscosity of the composition reached 10 Pa·s to 20 Pa·s. The viscosity was measured using a Type B viscometer (trade name "TVB-10M", manufactured by Toki Sangyo Co., Ltd.) under the conditions of rotor No. 22, rotor speed 6 rpm, and temperature 30°C (the same applies to the viscosity described later). The resulting first prepolymer composition is a partial polymer containing acrylic polymer P1 and unpolymerized monomer components (residual monomers). The weight-average molecular weight of acrylic polymer P1 in the first prepolymer composition is approximately 4.3 million.

[0125] <Preparation of the Second Prepolymer Composition>

[0126] In a reaction vessel equipped with a stirrer, thermometer, reflux condenser, and nitrogen inlet pipe, 0.05 parts by mass of a first photopolymerization initiator (Omnirad 184) and 0.05 parts by mass of a second photopolymerization initiator (Omnirad 651) were added to a monomer mixture consisting of 48 parts by mass of lauryl acrylate (LA), 51 parts by mass of 2-ethylhexyl acrylate (2EHA), and 1 part by mass of 4-hydroxybutyl acrylate (4HBA). The mixture was then irradiated with ultraviolet light under a nitrogen atmosphere, thereby polymerizing a portion of the monomer components to obtain a second prepolymer composition. A black light lamp was used for ultraviolet irradiation. Irradiation continued until the viscosity of the composition reached 10 Pa·s to 20 Pa·s. The resulting second prepolymer composition is a partial polymer containing acrylic polymer P2 and unpolymerized monomer components (residual monomers). The weight-average molecular weight of acrylic polymer P2 in the second prepolymer composition is approximately 4.8 million.

[0127] <Preparation of the Third Prepolymer Composition>

[0128] In a reaction vessel equipped with a stirrer, thermometer, reflux condenser, and nitrogen inlet pipe, 0.05 parts by weight of a first photopolymerization initiator (Omnirad 184) and 0.05 parts by weight of a second photopolymerization initiator (Omnirad 651) were added to a monomer mixture comprising 70 parts by weight of n-octyl acrylate (NOAA), 20 parts by weight of n-butyl acrylate (BA), 30 parts by weight of lauryl acrylate (LA), 8 parts by weight of 4-hydroxybutyl acrylate (4HBA), and 2 parts by weight of N-vinyl-2-pyrrolidone (NVP). The mixture was then irradiated with ultraviolet light under a nitrogen atmosphere, thereby polymerizing a portion of the monomer components to obtain a third prepolymer composition. A black light lamp was used for ultraviolet irradiation. Irradiation continued until the viscosity of the composition reached 10 Pa·s to 20 Pa·s. The resulting third prepolymer composition is a partial polymer containing acrylic polymer P3 and unpolymerized monomer components (residual monomers). The acrylic polymer P3 in the third prepolymer composition has a weight-average molecular weight of approximately 5 million.

[0129] <Preparation of acrylic oligomer M1>

[0130] First, in a reaction vessel equipped with a stirrer, thermometer, reflux condenser, and nitrogen inlet, a mixture (solid content concentration 26 by mass) containing 45 parts by mass of isobornyl methacrylate (IBXMA), 45 parts by mass of methyl methacrylate (MMA), 10 parts by mass of ethyl carbitol acrylate (CBA), 3 parts by mass of α-thioglycerol as a chain transfer agent, 0.3 parts by mass of 2,2'-azobisisobutyronitrile (AIBN) as a thermal polymerization initiator, and ethyl acetate as a solvent was reacted at 72°C–74°C for 6 hours under a nitrogen atmosphere (polymerization reaction). Next, the reaction solution was heated at 90°C for 12 hours, thereby causing the ethyl acetate, chain transfer agent, and unreacted monomers to evaporate and be removed. This yielded a solid acrylic oligomer M1. The weight-average molecular weight (Mw) of acrylic oligomer M1 is 4880. The glass transition temperature (Tg) of acrylic oligomer M1 is 98.5°C.

[0131] <Preparation of acrylic oligomer M2>

[0132] Except that the amount of IBXMA was set to 35 parts by mass, the amount of MMA was set to 35 parts by mass, and the amount of CBA was set to 30 parts by mass, the same procedure as for acrylic oligomer M1 was followed to obtain solid acrylic oligomer M2. The Mw of acrylic oligomer M2 is 5400. The Tg of acrylic oligomer M2 is 50.9℃.

[0133] <Preparation of acrylic oligomer M3>

[0134] First, in a reaction vessel equipped with a stirrer, thermometer, reflux condenser, and nitrogen inlet, a mixture (solid concentration 26 by mass) containing 45 parts by mass of tetrahydrodicyclopentadienyl methacrylate (DCPMA), 45 parts by mass of MMA, 10 parts by mass of CBA, 3 parts by mass of α-thioglycerol as a chain transfer agent, 0.3 parts by mass of AIBN as a thermal polymerization initiator, and ethyl acetate as a solvent was reacted at 72°C–74°C for 6 hours under a nitrogen atmosphere (polymerization reaction). Next, the reaction solution was heated at 90°C for 12 hours, thereby causing the ethyl acetate, chain transfer agent, and unreacted monomers to evaporate and be removed. This yielded a solid acrylic oligomer M3. The Mw of acrylic oligomer M3 is 5230. The Tg of acrylic oligomer M3 is 97.7°C.

[0135] <Preparation of acrylic oligomer M4>

[0136] Except that the amount of IBXMA and MMA was set to 40 parts by mass, and 20 parts by mass of 4-acryloylmorpholine (ACMO) was used instead of 10 parts by mass of CBA, the same procedure was followed as for acrylic oligomer M1 to obtain solid acrylic oligomer M4. The Mw of acrylic oligomer M4 is 4940. The Tg of acrylic oligomer M4 is 129.2℃.

[0137] <Preparation of acrylic oligomer M5>

[0138] Except that the amount of DCPMA and MMA was set to 40 parts by mass, and 20 parts by mass of ACMO was used instead of 10 parts by mass of CBA, the same procedure as for acrylic oligomer M3 was followed to obtain solid acrylic oligomer M5. The Mw of acrylic oligomer M5 is 5110. The Tg of acrylic oligomer M5 is 128.3℃.

[0139] <Preparation of acrylic oligomer M6>

[0140] Except that 10 parts by mass of acrylic acid (AA) were used instead of 10 parts by mass of CBA, the same procedure as for acrylic oligomer M1 was followed to obtain solid acrylic oligomer M6. The Mw of acrylic oligomer M6 is 5670. The Tg of acrylic oligomer M6 is 121.9℃.

[0141] <Preparation of acrylic oligomer M7>

[0142] Except that 10 parts by mass of 2-hydroxyethyl methacrylate (HEMA) were used instead of 10 parts by mass of CBA, the same procedure was followed as for acrylic oligomer M3 to obtain solid acrylic oligomer M7. The Mw of acrylic oligomer M7 is 5600. The Tg of acrylic oligomer M7 is 115.8℃.

[0143] <Preparation of acrylic oligomer M8>

[0144] Except that the amount of DCPMA was set to 60 parts by mass, the amount of MMA was set to 30 parts by mass, and 10 parts by mass of HEMA was used instead of 10 parts by mass of CBA, the same procedure as for acrylic oligomer M3 was followed to obtain solid acrylic oligomer M8. The Mw of acrylic oligomer M8 is 5570. The Tg of acrylic oligomer M8 is 123.9℃.

[0145] <Preparation of acrylic oligomer M9>

[0146] First, in a reaction vessel equipped with a stirrer, thermometer, reflux condenser, and nitrogen inlet, a mixture (solid concentration 26 by mass) containing 45 parts by mass of cyclohexyl methacrylate (CHMA), 45 parts by mass of MMA, 10 parts by mass of HEMA, 3 parts by mass of α-thioglycerol as a chain transfer agent, 0.3 parts by mass of AIBN as a thermal polymerization initiator, and ethyl acetate as a solvent was reacted at 72°C–74°C for 6 hours under a nitrogen atmosphere (polymerization reaction). Next, the reaction solution was heated at 90°C for 12 hours, thereby causing the ethyl acetate, chain transfer agent, and unreacted monomers to evaporate and be removed. This yielded a solid acrylic oligomer M9. The Mw of acrylic oligomer M9 is 5920. The Tg of acrylic oligomer M9 is 85.4°C.

[0147] <Preparation of acrylic oligomer M10>

[0148] Except that 10 parts by mass of 4HBA were used instead of 10 parts by mass of HEMA, the same procedure as for acrylic oligomer M9 was followed to obtain solid acrylic oligomer M10. The Mw of acrylic oligomer M10 is 5740. The Tg of acrylic oligomer M10 is 72.2℃.

[0149] <Preparation of acrylic oligomer M11>

[0150] Except that 10 parts by mass of 2-hydroxypropyl methacrylate (HPMA) were used instead of 10 parts by mass of HEMA, the same procedure was followed as for acrylic oligomer M9 to obtain solid acrylic oligomer M11. The Mw of acrylic oligomer M11 is 5840. The Tg of acrylic oligomer M11 is 82.4℃.

[0151] <Preparation of acrylic oligomer M12>

[0152] Except that 10 parts by mass of 4HBA were used instead of 10 parts by mass of CBA, the same procedure was followed as for acrylic oligomer M1 to obtain acrylic oligomer M12. The Mw of acrylic oligomer M12 is 5320. The Tg of acrylic oligomer M12 is 99.2℃.

[0153] <Preparation of acrylic oligomer M13>

[0154] First, in a reaction vessel equipped with a stirrer, thermometer, reflux condenser, and nitrogen inlet, a mixture (solid concentration 26% by mass) containing 50 parts by mass of IBXMA, 50 parts by mass of NVP, 3 parts by mass of α-thioglycerol as a chain transfer agent, 0.3 parts by mass of AIBN as a thermal polymerization initiator, and ethyl acetate as a solvent was reacted at 72°C–74°C for 6 hours under a nitrogen atmosphere (polymerization reaction). Next, the reaction solution was heated at 90°C for 12 hours, thereby causing the ethyl acetate, chain transfer agent, and unreacted monomers to evaporate and be removed. This yielded a solid acrylic oligomer M13. The Mw of acrylic oligomer M13 is 10200. The Tg of acrylic oligomer M13 is 193°C.

[0155] <Preparation of acrylic oligomer M14>

[0156] First, in a reaction vessel equipped with a stirrer, thermometer, reflux condenser, and nitrogen inlet, a mixture (solid concentration 26 by mass) containing 50 parts by mass of n-amyl acrylate (NPA) (trade name "LIMA", manufactured by Osaka Organic Chemical Industry Co., Ltd.), 50 parts by mass of MMA, 3 parts by mass of α-thioglycerol as a chain transfer agent, 0.3 parts by mass of AIBN as a thermal polymerization initiator, and ethyl acetate as a solvent was reacted at 72°C–74°C for 6 hours under a nitrogen atmosphere (polymerization reaction). Next, the reaction solution was heated at 90°C for 12 hours, thereby causing the ethyl acetate, chain transfer agent, and unreacted monomers to evaporate and be removed. This yielded a solid acrylic oligomer M14. The Mw of acrylic oligomer M14 is 5220. The Tg of acrylic oligomer M14 is 20.6°C.

[0157] <Preparation of acrylic oligomer M15>

[0158] Except that the amount of IBXMA was set to 90 parts by mass and no MMA was added, the process was the same as with acrylic oligomer M1 to obtain solid acrylic oligomer M15. The Mw of acrylic oligomer M15 is 4230. The Tg of acrylic oligomer M15 is 123.4℃.

[0159] <Preparation of acrylic oligomer M16>

[0160] Except for setting the amount of DCPMA and MMA to 40 parts by mass and replacing 10 parts by mass of CBA with 20 parts by mass of 4HBA, the same procedure as for acrylic oligomer M3 was followed to obtain solid acrylic oligomer M16. The Mw of acrylic oligomer M16 is 5350. The Tg of acrylic oligomer M16 is 76.8℃.

[0161] <Preparation of acrylic oligomer M17>

[0162] Except that 10 parts by mass of lauryl methacrylate (LMA) were used instead of 10 parts by mass of CBA, the same procedure was followed as for acrylic oligomer M1 to obtain acrylic oligomer M17. The Mw of acrylic oligomer M17 is 5780. The Tg of acrylic oligomer M17 is 125.5℃.

[0163] <Preparation of acrylic oligomer M18>

[0164] Except for setting the amount of IBXMA to 75 parts by mass, the amount of MMA to 20 parts by mass, and replacing 10 parts by mass of CBA with 5 parts by mass of HEMA, the same procedure was followed as for acrylic oligomer M1 to obtain solid acrylic oligomer M18. The Mw of acrylic oligomer M18 is 4610. The Tg of acrylic oligomer M18 is 141.0℃.

[0165] <Preparation of acrylic oligomer M19>

[0166] Except that 10 parts by mass of 4HBA were used instead of 10 parts by mass of HEMA, the same procedure as for acrylic oligomer M7 was followed to obtain solid acrylic oligomer M19. The Mw of acrylic oligomer M19 is 5430. The Tg of acrylic oligomer M19 is 99.2℃.

[0167] <Preparation of acrylic oligomer M20>

[0168] Except that the amount of IBXMA was set to 80 parts by mass, the amount of CMA was set to 20 parts by mass, and no MMA was added, the process was the same as that for acrylic oligomer M1, thus obtaining solid acrylic oligomer M20. The Mw of acrylic oligomer M20 is 3820. The Tg of acrylic oligomer M20 is 80.8℃.

[0169] <Preparation of acrylic oligomer M21>

[0170] Except that the amount of IBXMA was set to 70 parts by mass, the amount of MMA to 20 parts by mass, and the amount of CBA to 10 parts by mass, the same procedure as for acrylic oligomer M1 was followed to obtain solid acrylic oligomer M21. The Mw of acrylic oligomer M21 is 4060. The Tg of acrylic oligomer M21 is 109.3℃.

[0171] <Preparation of acrylic oligomer M22>

[0172] Except that the amount of DCPMA was set to 47.5 parts by mass, the amount of MMA was set to 47.5 parts by mass, and the amount of HEMA was set to 5 parts by mass, the same procedure as for acrylic oligomer M8 was followed to obtain solid acrylic oligomer M22. The Mw of acrylic oligomer M22 is 5150. The Tg of acrylic oligomer M22 is 120.0℃.

[0173] <Preparation of acrylic oligomer M23>

[0174] Except that the amount of DCPMA was set to 70 parts by mass, the amount of MMA to 20 parts by mass, and the amount of HEMA to 10 parts by mass, the same procedure as for acrylic oligomer M8 was followed to obtain solid acrylic oligomer M23. The Mw of acrylic oligomer M23 is 5840. The Tg of acrylic oligomer M23 is 130.8℃.

[0175] <Preparation of acrylic oligomer M24>

[0176] Except that 70 parts by mass of 1-adamantyl methacrylate (ADMA) were used instead of 70 parts by mass of DCPMA, the same procedure as for acrylic oligomer M23 was followed to obtain solid acrylic oligomer M24. The Mw of acrylic oligomer M24 is 5150. The Tg of acrylic oligomer M24 is 160.7℃.

[0177] <Preparation of acrylic oligomer M25>

[0178] Except that the amount of DCPMA was set to 60 parts by mass, the amount of MMA was set to 40 parts by mass, and HEMA was not used, the process was the same as for acrylic oligomer M8, thus obtaining solid acrylic oligomer M25. The Mw of acrylic oligomer M25 is 4940. The Tg of acrylic oligomer M25 is 130.6℃.

[0179] [Example 1]

[0180] <Preparation of Adhesive Compositions>

[0181] In the first prepolymer composition, 3.0 parts by mass of acrylic oligomer M1 and 0.07 parts by mass of crosslinking agent (trade name "Viscoat #260", 1,9-nonanediol diacrylate, manufactured by Osaka Organic Chemical Industry Co., Ltd.) were added and mixed relative to 100 parts by mass of the monomer component (the monomer component forming the base polymer in the adhesive layer described later in this embodiment) to prepare the first adhesive composition. The relative parts of acrylic oligomer in the adhesive layer described later in this embodiment relative to 100 parts by mass of the base polymer are shown as "parts" in Tables 1 and 2.

[0182] <Formation of Adhesive Layer>

[0183] Next, a first adhesive composition was applied to the release-treated surface of a first release liner, which had undergone silicone release treatment on one side, to form a coating film. The first release liner was a single-sided silicone-treated polyethylene terephthalate (PET) film (brand name "Diafoil MRE#75", thickness 75 μm, manufactured by Mitsubishi Chemical Corporation). Next, the release-treated surface of a second release liner, also single-sided silicone-treated, was adhered to the coating film on the first release liner. The second release liner was a single-sided silicone-treated PET film (brand name "Diafoil MRF#75", thickness 75 μm, manufactured by Mitsubishi Chemical Corporation). Next, the coating film between the release liners was irradiated with ultraviolet light to photocur and form an adhesive layer (thickness 50 μm). A black light lamp was used as the irradiation source, and the irradiation intensity was set to approximately 2.5 mW / cm². 2 The irradiation time was set to 16 minutes. An adhesive sheet (50 μm thick) with a release liner of Example 1 was produced by the above operation.

[0184] [Examples 2 to 12]

[0185] In the preparation of the adhesive composition, the type and amount of the acrylic oligomers were changed as shown in Tables 1 and 2. Otherwise, the same procedure was followed as for the adhesive sheet with release liner in Example 1, thereby producing adhesive sheets with release liner for Examples 2 to 12.

[0186] [Comparative Example 1]

[0187] In the preparation of the adhesive composition, no acrylic oligomers were incorporated. Otherwise, the same procedure was followed as for the adhesive sheet with release liner in Example 1, thereby producing the adhesive sheet with release liner of Comparative Example 1.

[0188] [Comparative Examples 2 to 6]

[0189] In the preparation of the adhesive composition, the type and amount of the acrylic oligomers were changed as shown in Table 2. Otherwise, the same procedure was followed as for the adhesive sheet with release liner in Example 1, thereby producing adhesive sheets with release liner for Comparative Examples 2 to 6.

[0190] [Example 13]

[0191] <Preparation of Adhesive Compositions>

[0192] In the second prepolymer composition, 1.0 part by weight of acrylic oligomer M18 and 0.07 parts by weight of crosslinking agent (trade name "Viscoat #260", 1,9-nonanediol diacrylate, manufactured by Osaka Organic Chemical Industry Co., Ltd.) were added and mixed relative to 100 parts by weight of the monomer components (the monomer components forming the base polymer in the adhesive layer described later in this embodiment) to prepare the second adhesive composition. The relative parts of acrylic oligomers in the adhesive layer described later in this embodiment relative to 100 parts by weight of the base polymer are shown as "parts" in Table 3.

[0193] <Formation of Adhesive Layer>

[0194] The second adhesive composition was used instead of the first adhesive composition, except that the same procedure was followed as described above for the formation of the adhesive layer in Example 1, thereby forming an adhesive layer with a thickness of 50 μm between the release liner. An adhesive sheet (50 μm thick) with a release liner of Example 13 was thus produced by the above procedure.

[0195] [Comparative Example 7]

[0196] In the preparation of the adhesive composition, no acrylic oligomers were incorporated. Otherwise, the same procedure was followed as for the adhesive sheet with release liner in Example 13, thereby producing the adhesive sheet with release liner of Comparative Example 7.

[0197] [Comparative Example 8, Comparative Example 9]

[0198] In the preparation of the adhesive composition, the type of acrylic oligomer was changed as shown in Table 3. Otherwise, the same procedure was followed as for the adhesive sheet with release liner in Example 13, thereby producing adhesive sheets with release liner for Comparative Examples 8 and 9.

[0199] [Example 14]

[0200] <Preparation of Adhesive Compositions>

[0201] In the third prepolymer composition, 1.0 part by weight of acrylic oligomer M8 and 0.07 parts by weight of crosslinking agent (trade name "Viscoat #260", 1,9-nonanediol diacrylate, manufactured by Osaka Organic Chemical Industry Co., Ltd.) were added and mixed relative to 100 parts by weight of the monomer component (the monomer component that forms the base polymer in the adhesive layer described later in this embodiment) to prepare the third adhesive composition. The relative parts of acrylic oligomer in the adhesive layer described later in this embodiment relative to 100 parts by weight of the base polymer are shown as "parts" in Table 4.

[0202] <Formation of Adhesive Layer>

[0203] The third adhesive composition was used instead of the first adhesive composition, except that the same procedure was followed as described above for the formation of the adhesive layer in Example 1, thereby forming an adhesive layer with a thickness of 50 μm between the release liner. An adhesive sheet (50 μm thick) with a release liner of Example 14 was thus produced by the above procedure.

[0204] [Example 15]

[0205] In the preparation of the adhesive composition, the type of acrylic oligomer was changed as shown in Table 4. Otherwise, the same procedure was followed as for the adhesive sheet with release liner of Example 15, thereby producing the adhesive sheet with release liner of Example 15.

[0206] [Comparative Example 10]

[0207] In the preparation of the adhesive composition, no acrylic oligomers were incorporated. Otherwise, the same procedure was followed as for the adhesive sheet with release liner in Example 14, thereby producing the adhesive sheet with release liner of Comparative Example 10.

[0208] [Comparative Example 11, Comparative Example 12]

[0209] In the preparation of the adhesive composition, the type of acrylic oligomer was changed as shown in Table 4. Otherwise, the same procedure was followed as for the adhesive sheet with release liner in Example 14, thereby producing adhesive sheets with release liner for Comparative Examples 11 and 12.

[0210] [Example 16]

[0211] <Preparation of Adhesive Compositions>

[0212] In the first prepolymer composition, 1.5 parts by mass of acrylic oligomer M22, 0.11 parts by mass of dipentaerythritol hexaacrylate (DPHA), 0.02 parts by mass of additional photopolymer initiator (trade name "Omnirad 819", bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, manufactured by IGM Resins) and 0.5 parts by mass of silane coupling agent (trade name "KBM-403", 3-epoxypropoxypropyltrimethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd.) were added and mixed relative to 100 parts by mass of the monomer component (the monomer component forming the base polymer in the adhesive layer described later in this embodiment) to prepare a fourth adhesive composition. The relative parts of acrylic oligomer in the adhesive layer described later in this embodiment relative to 100 parts by mass of the base polymer are shown as "parts" in Table 5.

[0213] <Formation of Adhesive Layer>

[0214] The fourth adhesive composition was used instead of the first adhesive composition, except that the same procedure was followed as described above for the formation of the adhesive layer in Example 1, thereby forming an adhesive layer with a thickness of 50 μm between the release liner. An adhesive sheet (50 μm thick) with a release liner of Example 16 was thus produced by the above procedure.

[0215] [Examples 17 to 19]

[0216] In the preparation of the adhesive compositions, the types of acrylic oligomers used were varied as shown in Table 5. Otherwise, the same procedure was followed as with the adhesive sheet with release liner in Example 16, thereby producing adhesive sheets with release liners for Examples 17 to 19. It should be noted that in Example 19, two acrylic oligomers were used (0.5 parts by mass of acrylic oligomer M25 and 1.0 parts by mass of acrylic oligomer M22 were added to the first prepolymer composition, relative to 100 parts by mass of the monomer components in the composition).

[0217] <First Method for Determining Weight-Average Molecular Weight>

[0218] Under the first determination conditions described below, the weight-average molecular weight (Mw) of the above-mentioned acrylic polymers and acrylic oligomers without nitrogen-containing monomers was determined by gel permeation chromatography (GPC), and converted to polystyrene values. A GPC apparatus (product name "HLC-8120 GPC", manufactured by Tosoh) was used for the determination. The sample solution was prepared as follows: First, using the above-mentioned acrylic polymers or acrylic oligomers without nitrogen-containing monomers as samples, a 0.20% by mass tetrahydrofuran (THF) solution (containing 10 mM phosphoric acid) was prepared, and then the THF solution was left to stand for 20 hours. Next, the THF solution was filtered using a membrane filter with an average pore size of 0.45 μm, and the filtrate was used as the sample solution for molecular weight determination.

[0219] [GPC First Measurement Conditions]

[0220] Column: G7000H XL +GMH XL +GMH XL Each TSKgel (manufactured by Tosoh)

[0221] Column temperature: 40℃

[0222] Elution buffer: THF solution (10mM phosphate concentration)

[0223] Flow rate: 0.8 mL / min

[0224] Sample injection volume: 100 μL

[0225] Standard sample: Polystyrene (manufactured by Agilent)

[0226] Detector: Differential refractometer (RI)

[0227] <Second Method for Determining Weight-Average Molecular Weight>

[0228] Under the second determination conditions described below, the weight-average molecular weight (Mw) of the aforementioned acrylic polymers and acrylic oligomers containing nitrogen-containing monomers was determined by gel permeation chromatography (GPC), and converted to polystyrene values. A GPC apparatus (product name "HLC-8120 GPC", manufactured by Tosoh) was used for the determination. The sample solution was prepared as follows: First, a 0.20% by mass dimethylformamide (DMF) solution (with added salt) was prepared using the aforementioned acrylic polymers or acrylic oligomers containing nitrogen-containing monomers as the sample, and then the DMF solution was left to stand for 20 hours. Next, the DMF solution was filtered through a membrane filter with an average pore size of 0.45 μm, and the filtrate was used as the sample solution for molecular weight determination.

[0229] [Second determination conditions for GPC]

[0230] Column: SuperAWM-H + SuperAW 4000 + SuperAW 2500, each TSKgel (manufactured by Tosoh)

[0231] Column temperature: 40 °C

[0232] Eluent: DMF solution (with salt added)

[0233] Flow rate: 0.4 mL / min

[0234] Sample injection volume: 40 μL

[0235] Standard sample: Polystyrene (manufactured by Agilent)

[0236] Detector: Differential refractive index detector (RI)

[0237] [Tg of oligomer]

[0238] The glass transition temperatures (Tg) of acrylic oligomers M1 - M25 were calculated based on the above Fox formula. The values are shown in Tables 1 - 5.

[0239] [Hydrogen bond component of HSP]

[0240] For acrylic oligomers M1 - M25, the hydrogen bond components of the Hansen solubility parameter (HSP) were calculated respectively. Specifically, as follows.

[0241] First, using the computer software HSPiP (Hansen Solubility Parameters in Practice), for each monomer m forming the acrylic oligomer i the hydrogen bond component of HSP (δh i ) was calculated. Then, from the mole fraction x i of monomer m i in the acrylic oligomer and the hydrogen bond component δh i of this monomer m i , the hydrogen bond component (δH) of the acrylic oligomer was calculated by the following formula. For example, based on the mole fraction 0.289 of IBXMA (molecular weight 220.0) and the hydrogen bond component 2.4 MPa 1 / 2 , the mole fraction 0.636 of MMA (molecular weight 100.1) and the hydrogen bond component 6.6 MPa 1 / 2 , the mole fraction 0.075 of CBA (molecular weight 188.2) and the hydrogen bond component 6.5 MPa 1 / 2 , the hydrogen bond component of acrylic oligomer M1 was calculated to be 5.39 MPa by the following formula 1 / 2The hydrogen bonding components of acrylic oligomers M1 to M25 are shown as δH2 in Tables 1 to 5.

[0242] δH=Σx i ×δh i

[0243] Similarly, the hydrogen bonding component (δH1) of the HSP of the above-mentioned acrylic polymers was determined. For example, in the acrylic polymer containing the first prepolymer composition, its value is 5.07 MPa. 1 / 2 The ratio of δH2 of the acrylic oligomer to δH1 of the acrylic polymer in the adhesive sheet (δH2 / δH1), and the difference between δH2 and δH1 ΔH (=δH2-δH1) are also shown in Tables 1 to 5.

[0244] <Gel fraction>

[0245] For each adhesive sheet of Examples 1 to 19 and Comparative Examples 1 to 12, the gel fraction was measured as follows.

[0246] First, approximately 500 mg of adhesive sample was collected from the adhesive sheet between the peeling liner. Next, the mass of the adhesive sample (W1) was determined. Then, the adhesive sample was immersed in approximately 40 g of ethyl acetate in a container for 7 days. Next, all components insoluble in ethyl acetate (undissolved portion) were recovered. Next, the undissolved portion was dried at 130°C for 2 hours (removal of ethyl acetate). Next, the mass of the undissolved portion (W2) was determined. Then, the gel fraction (mass %) of the photocured adhesive sheet was calculated based on the following formula. The values ​​are shown in Tables 1 to 5.

[0247] Gel fraction (mass%) = (W2 / W1) × 100

[0248] <Haze>

[0249] For each adhesive sheet of Examples 1 to 19 and Comparative Examples 1 to 12, the haze was measured as follows.

[0250] First, a sample for measurement was prepared. Specifically, a first release liner was peeled off from the adhesive sheet, and then the adhesive sheet was attached to alkali glass (1.0 mm thick, 92% total transmittance, 0.4% haze, manufactured by Matsunami Glass Co., Ltd.). Next, the first release liner was peeled off from the adhesive sheet on the glass. This prepared the sample for measurement. Then, the haze of the adhesive sheet in the sample was measured using a haze meter (product name "HM-150", manufactured by Murakami Color Technology Research Institute). The measurement was performed according to JIS K7136 (2000). In this measurement, the sample was placed in the apparatus such that light shone onto the sample from the alkali glass side. The measured haze of the adhesive sheet is shown in Tables 1 to 5.

[0251] <Shear storage modulus>

[0252] For each adhesive sheet of Examples 1 to 19 and Comparative Examples 1 to 12, dynamic viscoelasticity (first measurement) was measured.

[0253] The necessary number of test samples were prepared for each adhesive sheet. Specifically, firstly, multiple adhesive sheets cut from the adhesive sheets were glued together to create a sample sheet with a thickness of approximately 1.0 mm. Next, the sheet was punched to obtain cylindrical particles (7.9 mm in diameter) that served as the test samples.

[0254] Then, for the test samples, dynamic viscoelasticity measurements were performed using a dynamic viscoelasticity measuring device (product name "Advanced Rheometric Expansion System (ARES)", manufactured by Rheometric Scientific). The test samples were fixed in a clamp with a parallel plate of 7.9 mm diameter. In this measurement, the measurement mode was set to shear mode, the measurement temperature range was set to -65℃ to 200℃, the heating rate was set to 5℃ / min, and the frequency was set to 1Hz. The shear storage modulus at specified temperatures (-20℃, -10℃, 60℃) was read from the measurement results. The shear storage modulus G1 (kPa) at -10℃, the shear storage modulus G2 (kPa) at 60℃, the shear storage modulus G3 (kPa) at -20℃, and the ratio of shear storage modulus G2 to shear storage modulus G1 (G2 / G1) are shown in Tables 1 to 5.

[0255] <Peeling Test>

[0256] For each adhesive sheet of Examples 1 to 19 and Comparative Examples 1 to 12, the adhesive force to the adhered object was investigated by peel test.

[0257] Specifically, firstly, a necessary number of test specimens were prepared for each adhesive sheet. In preparing the test specimens, firstly, the first release liner was peeled off from the adhesive sheet, and the exposed surface was then bonded to a plasma-treated polyethylene terephthalate (PET) film (trade name "Lumirror S10", thickness 25 μm, manufactured by Toray Industries), thus obtaining a laminate. In the plasma treatment, a plasma irradiation device (product name "AP-TO5", manufactured by Sekisui Industries) was used, with the voltage set to 160V, the frequency set to 10kHz, and the processing speed set to 5000mm / min (the same applies to the plasma treatment described later). Next, test pieces (20mm wide × 100mm long) were cut from the laminate (PET film / adhesive sheet / second release liner). Then, the second release liner was peeled off from the adhesive sheet of this test piece, and the exposed surface was bonded to a glass plate (acrylic glass manufactured by Matsunami Glass Co., Ltd.). Next, the glass plate with the adhesive sheet (test piece) was subjected to heat and pressure treatment at 50°C and 0.5 MPa for 15 minutes. This pressed the test piece onto the glass plate. The test sample was prepared through the above operation.

[0258] Next, the test specimen was allowed to stand at room temperature for 30 minutes, and then a 180° peel test was performed to peel the test piece from the glass plate of the test specimen, and the force required for peeling (peel strength) was measured (first peel test). A tensile testing machine (product name "Autograph AG-50NXplus", manufactured by Shimadzu Corporation) was used in this test. In this test, the test temperature was set to 25°C, the relative humidity was set to 55%, the peel angle from the glass plate was set to 180°, the pulling speed of the test piece was set to 300 mm / min, and the peel length was set to 50 mm. The average value of the measured peel strengths is shown as the adhesive force F1 (N / 20 mm) in Tables 1 to 5.

[0259] On the other hand, except that the pulling speed was changed to 60 mm / min, a peel test (second peel test) was conducted under the same conditions as the first peel test. The results of this test are shown in Tables 1 to 5 as adhesive force F2 (N / 20 mm). In addition, the ratio of adhesive force F2 to the adhesive force F1 (F2 / F1) is also shown in Tables 1 to 5.

[0260] [evaluate]

[0261] The adhesive sheet of Comparative Example 1 is a soft adhesive sheet with a shear storage modulus G1 of less than 100 kPa at -10°C, but does not contain oligomers with a Tg of more than 40°C, and has small adhesive forces F1 and F2.

[0262] The adhesive sheet of Comparative Example 2 contains an oligomer (acrylic oligomer M13) with a Tg of 40°C or higher, but the difference ΔH (=δH2-δH1) is less than 0.1, and the adhesive forces F1 and F2 are small. In the adhesive sheet of Comparative Example 2, the acrylic oligomer M13 is not concentrated on or near the adhesive surface.

[0263] The adhesive sheet of Comparative Example 3 does not contain oligomers with a Tg of 40°C or higher, and has low adhesive forces F1 and F2.

[0264] The adhesive sheet of Comparative Example 4 contains an oligomer (acrylic oligomer M15) with a Tg of 40°C or higher, but the difference ΔH (=δH2-δH1) is less than 0.1, and the adhesive forces F1 and F2 are small. In the adhesive sheet of Comparative Example 4, the acrylic oligomer M15 is not concentrated on or near the adhesive surface.

[0265] The adhesive sheet of Comparative Example 5 contains an oligomer (acrylic oligomer M16) with a Tg of 40°C or higher, but the difference ΔH (=δH2-δH1) is greater than 1.3, resulting in excessive haze. In the adhesive sheet of Comparative Example 5, the acrylic oligomer M16 has low compatibility with the base polymer, forming phase domains and causing light scattering.

[0266] The adhesive sheet of Comparative Example 6 contains an oligomer (acrylic oligomer M17) with a Tg of 40°C or higher, but the difference ΔH (=δH2-δH1) is less than 0.1, and the adhesive forces F1 and F2 are small. In the adhesive sheet of Comparative Example 6, the acrylic oligomer M17 is not sufficiently concentrated on and around the adhesive surface.

[0267] In contrast, the adhesive sheets of Examples 1 to 12 have a shear storage modulus G1 of less than 100 kPa at -10°C, making them relatively soft. They contain oligomers with a Tg of 40°C or higher, and the HSP δH1 of the base polymer and the HSP δH2 of the oligomer satisfy 0.1 ≤ δH2 - δH1 ≤ 1.3. The adhesive sheets of Examples 1 to 12 have a relatively high adhesive force F1 of 8.0 N / 20 mm or higher. In each adhesive sheet of Examples 1 to 12, the oligomers with a Tg of 40°C or higher are sufficiently concentrated on and near the adhesive surface.

[0268] Comparative Example 7's adhesive sheet is a soft adhesive sheet with a shear storage modulus G1 of less than 100 kPa at -10°C, but it does not contain oligomers with a Tg of 40°C or higher, and its adhesive forces F1 and F2 are small. Comparative Example 8's adhesive sheet contains oligomers (acrylic oligomer M19) with a Tg of 40°C or higher, but its difference ΔH (=δH2-δH1) is greater than 1.3, resulting in excessive haze. Furthermore, its adhesive forces F1 and F2 are also small. Comparative Example 9's adhesive sheet contains oligomers (acrylic oligomer M20) with a Tg of 40°C or higher, but its difference ΔH (=δH2-δH1) is less than 0.1, and its adhesive forces F1 and F2 are small. In the adhesive sheet of Comparative Example 9, the acrylic oligomer M20 is not concentrated on or near the adhesive surface. Compared to the adhesive sheets of Comparative Examples 7 to 9, the adhesive sheet of Example 13 has a shear storage modulus G1 of less than 100 kPa at -10°C, making it relatively soft. It contains oligomers with a Tg of 40°C or higher, and the δH1 of the HSP of the base polymer and the δH2 of the HSP of the oligomer satisfy 0.1 ≤ δH2 - δH1 ≤ 1.3. The adhesive force F1 of this Example 13 adhesive sheet is 7.7 N / 20 mm, which is greater than the adhesive force F1 of the adhesive sheets of Comparative Examples 7 to 9 (with the same base polymer as Example 13). In each adhesive sheet of Example 13, oligomers with a Tg of 40°C or higher are sufficiently concentrated on and near the adhesive surface. The adhesive sheet of Example 13 has a shear storage modulus G1 of less than 40 kPa at -10°C, making it very soft and possessing both softness and adhesive strength.

[0269] Comparative Example 10's adhesive sheet is a soft adhesive sheet with a shear storage modulus G1 of less than 100 kPa at -10°C, but it does not contain oligomers with a Tg of 40°C or higher, and its adhesive forces F1 and F2 are small. Comparative Example 11's adhesive sheet contains oligomers (acrylic oligomer M19) with a Tg of 40°C or higher, but the difference ΔH (=δH2-δH1) is greater than 1.3, and its adhesive forces F1 and F2 are small. Comparative Example 12's adhesive sheet contains oligomers (acrylic oligomer M21) with a Tg of 40°C or higher, but the difference ΔH (=δH2-δH1) is less than 0.1, and its adhesive forces F1 and F2 are small. In the adhesive sheet of Comparative Example 12, acrylic oligomer M21 is not concentrated on or near the adhesive surface. Compared to the adhesive sheets of Comparative Examples 10 to 12, the adhesive sheets of Examples 14 and 15 are relatively soft because their shear storage modulus G1 at -10°C is less than 100 kPa. They contain oligomers with a Tg of 40°C or higher, and the δH1 of the HSP of the base polymer and the δH2 of the HSP of the oligomer satisfy 0.1 ≤ δH2 - δH1 ≤ 1.3. The adhesive force F1 of these adhesive sheets of Examples 14 and 15 is 7.6 N / 20 mm or higher, which is greater than the adhesive force F1 of the adhesive sheets of Comparative Examples 10 to 12 (whose base polymers are the same as those of Examples 14 and 15). In each adhesive sheet of Examples 14 and 15, oligomers with a Tg of 40°C or higher are sufficiently concentrated on and near the adhesive surface.

[0270] Furthermore, the adhesive sheets of Examples 16 to 19 have a shear storage modulus G1 of less than 100 kPa at -10°C, making them relatively soft. They contain oligomers with a Tg of 40°C or higher, and the δH1 of the HSP of the base polymer and the δH2 of the HSP of the oligomer satisfy 0.1 ≤ δH2 - δH1 ≤ 1.3. The adhesive sheets of Examples 16 to 19 have an adhesive force F1 of 7.9 N / 20 mm or higher, which is relatively large. In each adhesive sheet of Examples 16 to 19, the oligomers with a Tg of 40°C or higher are sufficiently concentrated on and near the adhesive surface. It should be noted that the adhesive sheet of Example 19 contains two types of oligomers, each with a Tg of 40°C or higher, and the δH1 of the HSP of the base polymer and the δH2 of the HSP of each oligomer satisfy 0.1 ≤ δH2 - δH1 ≤ 1.3.

[0271]

[0272]

[0273]

[0274]

[0275]

[0276] It should be noted that the above-described invention is provided as an illustrative embodiment of the present invention, but this is merely illustrative and not intended to be limiting. All modifications of the invention that will be apparent to those skilled in the art are included within the scope of the claims.

[0277] Industrial practicality

[0278] The optical adhesive sheet of the present invention is suitable for use in light-passing portions of flexible devices (e.g., flexible display panels such as foldable display panels and rollable display panels).

[0279] Label Explanation

[0280] 10. Adhesive sheet (optical adhesive sheet)

[0281] 11 First page

[0282] 12 Second page

[0283] L1, L2 peeling pads

[0284] 21 First Component

[0285] 22 Second component

[0286] H Thickness direction

Claims

1. An optical adhesive sheet, wherein, The optical adhesive sheet comprises a base polymer and oligomers with a glass transition temperature above 40°C. The optical adhesive sheet has a shear storage modulus below 100 kPa at -10°C. The hydrogen bonding component δH1 of the Hansen solubility parameter of the base polymer and the hydrogen bonding component δH2 of the Hansen solubility parameter of the oligomer satisfy the following: 0.1≤δH2-δH1≤1.

3.

2. The optical adhesive sheet according to claim 1, wherein, The optical adhesive sheet has a haze of less than 1%.

3. The optical adhesive sheet according to claim 1, wherein, The adhesive strength of the optical adhesive sheet in the peel test under the conditions of 25°C, peel angle of 180° and pulling speed of 300 mm / min is above 7.6 N / 20 mm.

4. The optical adhesive sheet according to claim 1, wherein, The optical adhesive sheet exhibits adhesive force F1 in a peel test conducted under conditions of 25°C, a peel angle of 180°, and a pulling speed of 300 mm / min. The optical adhesive sheet exhibits an adhesive force F2 in a peel test conducted under conditions of 25°C, a peel angle of 180°, and a pulling speed of 60 mm / min. The ratio of adhesive force F2 to adhesive force F1 is greater than 0.5 and less than 1.

1.

5. The optical adhesive sheet according to claim 1, wherein, The ratio of the shear storage modulus of the optical adhesive sheet at 60°C to its shear storage modulus at -10°C is greater than 0.2 and less than 1.

0.

6. The optical adhesive sheet according to any one of claims 1 to 5, wherein, The optical adhesive sheet has a gel fraction of 60% to 87% by mass.

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