Alcohol-peelable optical adhesive sheet

Abstract

A pressure-sensitive adhesive sheet (10), which is an alcohol-peelable optical pressure-sensitive adhesive sheet according to the present invention, contains a photopolymerizable polymer as a base polymer. The adhesive sheet (10) has an adhesive force (Fn1) of 9.0 N / 25 mm or more in a prescribed initial normal-temperature peeling test, an adhesive force (Fa1) of 3.0 N / 25 mm or less in a prescribed first ethanol peeling test, and an adhesive force (Fh) of 2.0 N / 25 mm or more in a prescribed high-temperature and high-humidity peeling test.

Description

Technical Field

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

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

[0003] On the other hand, water-removable optical adhesive sheets are known. Water-removable optical adhesive sheets are those that reduce adhesive strength by allowing water droplets to seep into the interface between the adhesive sheet and the substrate after it has been bonded to the substrate. Such optical adhesive sheets can be easily peeled off from the substrate using water as needed after being bonded to it. For example, in the manufacturing process of a display panel, if poor bonding (positional misalignment, etc.) occurs when the optical adhesive sheet is bonded to the substrate, water can be used to peel the adhesive sheet off the substrate (water-removable), and a bonding operation using an alternative optical adhesive sheet can be performed. Such water-removable optical adhesive sheets are described, for example, in Patent Document 1 below.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2020-23679 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] The optical adhesive sheet described in Patent Document 1 contains an acrylic-based polymer and a surfactant. In this adhesive sheet, the acrylic-based polymer ensures adhesion to the adhered objects. Furthermore, the presence of a surfactant on the adhesive surface in this adhesive sheet exhibits water-repellent properties. However, the optical adhesive sheet of Patent Document 1 has low moisture resistance due to the presence of the surfactant on the adhesive surface. For example, the optical adhesive sheet of Patent Document 1 exhibits low adhesion in high humidity environments. In such an optical adhesive sheet, good adhesive reliability to the adhered objects cannot be obtained.

[0009] This invention provides an alcohol-peelable optical adhesive sheet suitable for balancing adhesive reliability and reworkability of the adhered materials.

[0010] means for solving problems

[0011] The present invention [1] includes an alcohol-peelable optical adhesive sheet containing a photopolymer as a base polymer, wherein the adhesive force Fn1 of the alcohol-peelable optical adhesive sheet in the following initial room temperature peel test is 9.0 N / 25 mm or more, the adhesive force Fa1 of the alcohol-peelable optical adhesive sheet in the following first ethanol peel test is 3.0 N / 25 mm or less, and the adhesive force Fh of the alcohol-peelable optical adhesive sheet in the following high temperature and high humidity peel test is 2.0 N / 25 mm or more.

[0012] Initial room temperature peel test: First, a small piece of the alcohol-release optical adhesive sheet, 25 mm wide and 100 mm long, is bonded to an alkali glass plate made using the float glass method to obtain a laminate (preparation step). Next, the laminate is subjected to heat and pressure treatment at 50°C, 0.5 MPa, and 15 minutes (heating and pressure treatment step). Then, the laminate is allowed to stand at room temperature for 72 hours (standing step). Next, under the first conditions of 25°C, 50% relative humidity, a peel angle of 180°, and a pulling speed of 300 mm / min, one end of the adhesive sheet in the longitudinal direction is pulled to peel the adhesive sheet from the alkali glass plate, and the adhesive strength is measured (measurement step).

[0013] First ethanol stripping test: Except for the following, the procedure is the same as the initial room temperature peel test. In the settling step, the laminate is set at 50°C for 168 hours. An ethanol supply step is performed after the settling step and before the measurement step. In the ethanol supply step, 10 μL of ethanol is supplied to the alkali glass plate of the laminate in such a manner that the ethanol contacts one end of the adhesive sheet at the interface between the alkali glass plate and the adhesive sheet.

[0014] High temperature and high humidity peel test: Except for the following, the process is the same as the initial room temperature peel test. In the settling step, the laminate is set at room temperature for 24 hours. After the settling step and before the measurement step, a high-temperature and high-humidity treatment step is performed. In the high-temperature and high-humidity treatment step, the laminate after the settling step is subjected to high-temperature and high-humidity treatment at 60°C, 93% relative humidity, and for 15 minutes. In the measurement step, instead of the first conditions, a 180° peel test is performed under the second conditions of 60°C, 93% relative humidity, a peel angle of 180°, and a pulling speed of 300 mm / min.

[0015] The present invention [2] includes the alcohol-peelable optical adhesive sheet described in [1] above, wherein the alcohol-peelable optical adhesive sheet has an adhesive force Fa2 in the second ethanol peel test described below, and the adhesive force Fa1 varies with the adhesive force Fa2 at a rate of -50% to 100%.

[0016] Second ethanol stripping test: Except for the settling step, in which the laminate is set at room temperature for 72 hours, the process is the same as the first ethanol peel test.

[0017] The present invention [3] includes the alcohol-peelable optical adhesive sheet described in [2] above, wherein the duration of ethanol peeling in the second ethanol peeling test is more than 20 mm.

[0018] The present invention [4] includes any one of the above [1] to [3] alcohol-release optical adhesive sheets, wherein the alcohol-release optical adhesive sheets do not contain surfactants.

[0019] Invention Effects

[0020] As described above, the base polymer of the alcohol-peelable optical adhesive sheet of the present invention is a photopolymerizable polymer. The adhesive force Fn1 of the alcohol-peelable optical adhesive sheet is 9.0 N / 25 mm or more in the initial room temperature peel test, the adhesive force Fa1 is 3.0 N / 25 mm or less in the first ethanol peel test, and the adhesive force Fh is 2.0 N / 25 mm or more in the high temperature and high humidity peel test. The high adhesive force Fn1 (adhesive force without ethanol supply) of 9.0 N / 25 mm or more is suitable for ensuring the adhesive reliability of the adhesive sheet to the substrate after it has been bonded to the substrate. The low adhesive force Fa1 (adhesive force after storage, under ethanol supply) of 3.0 N / 25 mm or less is suitable for ensuring good alcohol peelability of the adhesive sheet over a long period after it has been bonded to the substrate, thereby ensuring reworkability. A high adhesive strength Fh (adhesive strength under conditions of no ethanol supply and high temperature and humidity) of 2.0 N / 25 mm or higher is suitable for ensuring the adhesive reliability of the optical adhesive sheet to the adherend even in high humidity environments. Therefore, the alcohol-peelable optical adhesive sheet of the present invention is suitable for balancing adhesive reliability and reworkability. Attached Figure Description

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

[0022] Figure 2 This schematically illustrates the ethanol stripping test.

[0023] Figure 3This represents an example of a peel force-peel length curve obtained in an ethanol peel test.

[0024] Figure 4 express Figure 1 An example of the use of alcohol-peelable optical adhesive sheet is shown. Figure 4 A represents the process of attaching an alcohol-release optical adhesive sheet to a first substrate. Figure 4 B indicates the process of bonding the first substrate to the second substrate using an alcohol-release optical adhesive sheet. Figure 4 C represents the ripening process. Detailed Implementation

[0025] like Figure 1 As shown, the adhesive sheet 10, as one embodiment of the alcohol-release 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 H (plane direction). The adhesive sheet 10 has an adhesive surface 11 and an adhesive surface 12 opposite to the adhesive surface 11. Figure 1 This 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.

[0026] The adhesive sheet 10 is an optically transparent adhesive sheet (optical adhesive sheet). The adhesive sheet 10 is an optical adhesive sheet with alcohol-removable properties. That is, the adhesive sheet 10 is an optical adhesive sheet (alcohol-removable) that can reduce the adhesive force by allowing alcohol (e.g., alcohol droplets) to penetrate into the interface between the adhesive sheet 10 and the substrate after being adhered to it.

[0027] The adhesive sheet 10 is a sheet-like pressure-sensitive adhesive. The adhesive sheet 10 contains a photopolymer as its base polymer. Specifically, the base polymer is a polymer obtained by photopolymerization of polymerizable components such as monomers. Photopolymerization refers to a polymerization method in which polymerizable components undergo a polymerization reaction under irradiation by active energy rays such as ultraviolet light. Furthermore, the adhesive sheet 10 exhibits an adhesive strength Fn1 of 9.0 N / 25 mm or more in the initial room temperature peel test described below, an adhesive strength Fa1 of 3.0 N / 25 mm or less in the first ethanol peel test described below, and an adhesive strength Fh of 2.0 N / 25 mm or more in the high temperature and high humidity peel test described below.

[0028] Initial room temperature peel test: First, a small adhesive sheet 10, 25 mm wide and 100 mm long, is bonded to an alkali glass plate made using the float glass method to obtain a laminate (preparation step). In this step, the small adhesive sheet is bonded to the tin side of the alkali glass plate (the same applies to other peel tests described later). Next, the laminate is subjected to heat and pressure treatment at 50°C, 0.5 MPa, and 15 minutes (heat and pressure treatment step). Next, the laminate is allowed to stand at room temperature for 72 hours (standing step). Next, under the first conditions of 25°C, 50% relative humidity, a peel angle of 180°, and a pulling speed of 300 mm / min, one end of the adhesive sheet in the longitudinal direction is pulled to peel the small adhesive sheet from the alkali glass plate, and the adhesive strength is measured (testing step). The method for the initial room temperature peel test is more specifically as described in the examples described later.

[0029] First ethanol stripping test: Except for the following, the procedure is the same as the initial room temperature peel test. In the settling step, the laminate is set at 50°C for 168 hours. An ethanol supply step is performed after the settling step and before the measurement step. In the ethanol supply step, 10 μL of ethanol (100% ethanol) is supplied to the alkali glass plate of the laminate in such a way that the ethanol contacts one end of the adhesive sheet at the interface between the ethanol and the adhesive sheet. Specifically, as follows... Figure 2 As shown, 10 μL of ethanol 22 is supplied to the alkali glass plate 21 of the laminate W in such a way that one end 10a of the adhesive piece 10A along the length direction D at the interface B between ethanol 22 and the alkali glass plate 21 and the adhesive piece 10A. In the measurement step after the ethanol supply step, the adhesive piece 10A is pulled along one end along the length direction (D). Figure 2 The adhesive strength is measured by peeling the adhesive piece 10A from the alkali glass plate at one end (10e). The method for the first ethanol peel test is more specifically as described in the examples below.

[0030] Figure 3 This represents an example of a peel force-peel length curve obtained in ethanol peel tests (first ethanol peel test, second ethanol peel test described later). Figure 3In the graph, the horizontal axis represents the peel length (mm) of the adhesive sheet piece from the start of peeling (peel length 0 mm) in the measurement step, and the vertical axis represents the peel force (N / 25 mm) required for peeling during the peeling process of the adhesive sheet piece. In the measurement step of the ethanol peel test, during the peeling process of the adhesive sheet piece, the peel length d1 when the peel force begins to stabilize and the peel length d2 when the peel force increases by 10% relative to the peel length d1 are determined (if the peel force does not increase by 10%, the peel length d2 is the length of the adhesive sheet piece 100 mm - d1). Then, the average value of the peel force measured from peel length d1 to peel length d2 is taken as the adhesive force (adhesive forces Fa1 and Fa2 in the ethanol peel test).

[0031] High temperature and high humidity peel test: Except for the following, the process is the same as the initial room temperature peel test. In the settling step, the laminate is set at room temperature for 24 hours. After the settling step and before the measurement step, a high-temperature and high-humidity treatment step is performed. In the high-temperature and high-humidity treatment step, the laminate after the settling step is subjected to high-temperature and high-humidity treatment at 60°C, 93% relative humidity, and for 15 minutes. In the measurement step, instead of the first condition, a 180° peel test is performed under the second condition of 60°C, 93% relative humidity, a peel angle of 180°, and a pulling speed of 300 mm / min. The method for the high-temperature and high-humidity peel test is more specifically as described in the examples described later.

[0032] As described above, the base polymer of the adhesive sheet 10 is a photopolymer. The adhesive sheet 10 exhibits an adhesive force Fn1 of 9.0 N / 25 mm or higher in the initial room temperature peel test, an adhesive force Fa1 of 3.0 N / 25 mm or lower in the first ethanol peel test, and an adhesive force Fh of 2.0 N / 25 mm or higher in the high temperature and high humidity peel test. The high adhesive force Fn1 (adhesive force without ethanol supply) of 9.0 N / 25 mm or higher is suitable for ensuring the adhesive reliability of the adhesive sheet 10 to the substrate after it has been bonded to the substrate. The low adhesive force Fa1 (adhesive force after storage, under ethanol supply) of 3.0 N / 25 mm or lower is suitable for ensuring good alcohol peelability of the adhesive sheet 10 over a long period after it has been bonded to the substrate, thus ensuring reworkability (long-term reworkability). A high adhesive strength Fh (adhesive strength under conditions of no ethanol supply and high temperature and humidity) of 2.0 N / 25 mm or higher is suitable for ensuring the adhesive reliability of the adhesive sheet 10 to the adherend even in high humidity environments. Therefore, the adhesive sheet 10 is suitable for balancing adhesive reliability to the adherend and reworkability (alcohol reworkability).

[0033] Furthermore, the inventors have realized that, unlike the optical adhesive sheet in Patent Document 1 where water-removable properties depend on surfactants, the optical adhesive sheet exhibits alcohol-removable properties over a relatively long period without the need for surfactants. This invention is based on this realization. The surfactant-independent nature of the optical adhesive sheet ensures reliable adhesion to the adhered objects even in high-humidity environments.

[0034] From the viewpoint of ensuring the aforementioned adhesive reliability, the adhesive strength Fn1 is preferably 9.5 N / 25 mm or more, more preferably 10 N / 25 mm or more. From the viewpoint of ensuring the aforementioned reworkability, the adhesive strength Fn1 is preferably 19 N / 25 mm or less, more preferably 18 N / 25 mm or less, and even more preferably 17 N / 25 mm or less. From the viewpoint of balancing adhesive reliability and reworkability, the adhesive strength Fn1 is preferably 9.0 N / 25 mm to 19 N / 25 mm, more preferably 9.5 N / 25 mm to 18 N / 25 mm, and even more preferably 10 N / 25 mm to 17 N / 25 mm. Methods for adjusting the adhesive strength Fn1 include, for example, the selection of the type of base polymer in the adhesive sheet 10, the adjustment of the molecular weight, the adjustment of the degree of crosslinking, and the adjustment of the amount of compounding. Methods for these adjustments include, for example, the selection of the type of monofunctional monomer, polyfunctional polymerizable compound (crosslinking agent), and polymerization initiator used in the formation of the base polymer, and the adjustment of the amount of compounding. Methods for adjusting the adhesive force Fn1 include 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. Examples of these components include oligomers (hydrophilic oligomers, hydrophobic oligomers), surfactants, and silane coupling agents. The same methods apply to the adhesive forces Fa1, Fh, and the adhesive forces Fn2, Fa2, which will be described later.

[0035] From the viewpoint of ensuring the alcohol reworkability of the adhesive sheet 10, the adhesive force Fa1 is preferably 2.7 N / 25 mm or less, more preferably 2.4 N / 25 mm or less, and even more preferably 2.0 N / 25 mm or less. From the viewpoint of suppressing accidental peeling of the adhesive sheet 10 when an alcohol-containing liquid (such as disinfectant) adheres to the adhesive sheet 10, the adhesive force Fa1 is preferably 0.5 N / 25 mm or more, more preferably 0.8 N / 25 mm or more, even more preferably 1.0 N / 25 mm or more, and even more preferably 1.2 N / 25 mm or more. From the viewpoint of balancing the alcohol reworkability of the adhesive sheet 10 and suppressing the above-mentioned accidental peeling, the adhesive force Fa1 is preferably 0.5 N / 25 mm to 3.0 N / 25 mm, more preferably 0.8 N / 25 mm to 2.7 N / 25 mm, even more preferably 1.0 N / 25 mm to 2.4 N / 25 mm, and even more preferably 1.2 N / 25 mm to 2.0 N / 25 mm.

[0036] From the viewpoint of ensuring the adhesive reliability of the adhesive sheet 10 in high humidity environments, the adhesive force Fh is preferably 2.1 N / 25 mm or more, more preferably 2.2 N / 25 mm or more. From the viewpoint of ensuring reworkability, the adhesive force Fh is preferably 10 N / 25 mm or less, more preferably 7.0 N / 25 mm or less, and even more preferably 5.0 N / 25 mm or less. From the viewpoint of balancing the adhesive reliability and reworkability of the adhesive sheet 10 in high humidity environments, the adhesive force Fn1 is preferably 2.0 N / 25 mm to 10 N / 25 mm, more preferably 2.1 N / 25 mm to 7.0 N / 25 mm, and even more preferably 2.2 N / 25 mm to 5.0 N / 25 mm.

[0037] The adhesive sheet 10 exhibits adhesive strength Fn2 in the following post-storage room temperature peel test.

[0038] Post-storage room temperature peel test: Except for the initial room temperature peel test, in which the laminate is left to stand at 50°C for 168 hours during the settling step, the procedure is the same as the initial room temperature peel test. The method for the post-storage room temperature peel test is specifically as described in the examples below.

[0039] From the viewpoint of ensuring the long-term adhesive reliability of the adhesive sheet 10, the adhesive force Fn2 is preferably 9.0 N / 25 mm or more, more preferably 9.5 N / 25 mm or more, and even more preferably 10 N / 25 mm or more. From the viewpoint of ensuring the reworkability mentioned above, the adhesive force Fn2 is preferably 19 N / 25 mm or less, more preferably 18 N / 25 mm or less, and even more preferably 17 N / 25 mm or less. From the viewpoint of balancing long-term adhesive reliability and reworkability, the adhesive force Fn2 is preferably 9.0 N / 25 mm to 19 N / 25 mm, more preferably 9.5 N / 25 mm to 18 N / 25 mm, and even more preferably 10 N / 25 mm to 17 N / 25 mm.

[0040] The adhesive sheet 10 has an adhesive force Fa2 in the second ethanol peel test described below.

[0041] Second ethanol stripping test: Except for the step of allowing the laminate to stand at room temperature for 72 hours, the second ethanol peel test is the same as the first ethanol peel test. The method for the second ethanol peel test is specifically as described in the examples below.

[0042] From the viewpoint of ensuring the reworkability of the adhesive sheet 10, the variation rate of the adhesive force Fa1 relative to the adhesive force Fa2, expressed by the following formula, is preferably -50% to 100%, more preferably -20% to 70%, and even more preferably 0% to 60%.

[0043] Change rate (%) = [(Fa1-Fa2) / Fa2] × 100

[0044] From the viewpoint of ensuring the alcohol reworkability of the adhesive sheet 10, the adhesive force Fa2 is preferably 2.5 N / 25 mm or less, more preferably 2.0 N / 25 mm or less, and even more preferably 1.8 N / 25 mm or less. From the viewpoint of suppressing accidental peeling of the adhesive sheet 10 when the alcohol-containing liquid adheres to it, the adhesive force Fa2 is preferably 0.5 N / 25 mm or more, more preferably 0.8 N / 25 mm or more, and even more preferably 1.0 N / 25 mm or more. From the viewpoint of balancing alcohol reworkability in the adhesive sheet 10 and suppressing accidental peeling as described above, the adhesive force Fa2 is preferably 0.5 N / 25 mm to 2.5 N / 25 mm, more preferably 0.8 N / 25 mm to 2.0 N / 25 mm, and even more preferably 1.0 N / 25 mm to 1.8 N / 25 mm.

[0045] From the viewpoint of ensuring the reworkability of the adhesive sheet 10, the ethanol peel length d in the second ethanol peel test is preferably 20 mm or more, more preferably 26 mm or more, and even more preferably 28 mm or more. The ethanol peel length d is, for example, 100 mm or less. The ethanol peel length d refers to the difference (d2-d1) between the peel length d2 and the peel length d1 described above. The method for determining the ethanol peel length d is specifically as described in the examples below.

[0046] Adhesive sheet 10 is a sheet-like pressure-sensitive adhesive formed from an adhesive composition. Adhesive sheet 10 (adhesive composition) contains at least the aforementioned photopolymer as a base polymer.

[0047] Examples of base polymers include acrylic polymers, polyurethane polymers, polyamide polymers, and polyvinyl ether polymers. Base polymers can be used alone or in combination of two or more. From the viewpoint of ensuring good adhesion and transparency in the adhesive sheet 10, acrylic polymers are preferred as base polymers. Acrylic polymers are copolymers containing monomer components of (meth)acrylates in a proportion of 50% by mass or more. "(Meth)acrylate" refers to acrylic acid and / or methacrylic acid.

[0048] In this embodiment, the acrylic polymer is a polymer (photopolymerized polymer) that comprises a monofunctional monomer and a polyfunctional polymerizable compound as a crosslinking agent, obtained by photopolymerization. For example, the acrylic polymer is a polymer obtained by photopolymerization of a portion of a monofunctional monomer (a mixture of a monofunctional monomer polymer and unreacted monofunctional monomers) and a polyfunctional polymerizable compound.

[0049] Such acrylic polymers include photopolymers with photocrosslinked structures (first photopolymers). A photocrosslinked structure is a structure in which linear structures of units derived from monofunctional monomers are crosslinked through units derived from a crosslinking agent. The base polymer may include photopolymers without such photocrosslinked structures (second photopolymers). The second photopolymer is a polymer of monofunctional monomers.

[0050] The monofunctional monomer preferably comprises a monofunctional alkyl (meth)acrylate, more preferably a alkyl (meth)acrylate comprising an alkyl group having 1 to 20 carbon atoms. The alkyl (meth)acrylate may have a straight-chain or branched alkyl group, or it may have a cyclic alkyl group (alicyclic alkyl group).

[0051] Examples of alkyl (meth)acrylates having straight or branched alkyl groups include: methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, tert-butyl (meth)acrylate, pentyl (meth)acrylate, isoamyl (meth)acrylate, neopentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, and nonyl (meth)acrylate. Isononyl methacrylate, decyl methacrylate, isodecyl methacrylate, undecyl methacrylate, dodecyl methacrylate (i.e., lauryl methacrylate), isotridecyl methacrylate, tetradecyl methacrylate, isotetradecyl methacrylate, pentadecyl methacrylate, hexadecyl methacrylate, heptadecanyl methacrylate, octadecyl methacrylate, isooctadecyl methacrylate, and nonadecanyl methacrylate.

[0052] Examples of alkyl (meth)acrylates having an alicyclic alkyl group include: cycloalkyl (meth)acrylates, alkyl (meth)acrylates having a bicyclic aliphatic hydrocarbon ring, and alkyl (meth)acrylates having three or more aliphatic hydrocarbon rings. Examples of cycloalkyl (meth)acrylates include: cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, cycloheptyl (meth)acrylate, and cyclooctyl (meth)acrylate. Examples of alkyl (meth)acrylates having a bicyclic aliphatic hydrocarbon ring include: isobornyl (meth)acrylate. Examples of alkyl (meth)acrylates having three or more aliphatic hydrocarbon rings include: tetrahydrodicyclopentadienyl (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] Monofunctional alkyl (meth)acrylates can be used alone or in combination with two or more. Preferably, the monofunctional alkyl (meth)acrylate is an alkyl acrylate having an alkyl group having 6 to 12 carbon atoms, more preferably at least one selected from the group consisting of 2-ethylhexyl acrylate (2EHA) and lauryl acrylate (LA).

[0054] The proportion of alkyl (meth)acrylate in the monofunctional monomer is preferably 70% to 99.9% by mass, more preferably 80% to 99.5% by mass, and even more preferably 90% to 99% by mass. The proportion of alkyl (meth)acrylate in the monofunctional monomer is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more. When this proportion of alkyl (meth)acrylate is at or above the aforementioned lower limit, the adhesive sheet 10 can appropriately exhibit basic properties such as adhesion. Furthermore, the proportion of monofunctional alkyl (meth)acrylate in the monofunctional monomer is, for example, 99.9% by mass or less, 99.5% by mass or less, or 99% by mass or less.

[0055] Monofunctional monomers may include copolymerizable monomers capable of copolymerizing with alkyl (meth)acrylates. Examples of copolymerizable monomers include those containing polar groups. Examples of monomers containing polar groups include hydroxyl-containing monomers, monomers having nitrogen-containing rings, and carboxyl-containing monomers. Copolymerizable monomers may be used alone or in combination of two or more. Monomers containing polar groups help ensure the cohesiveness and other properties of acrylic polymers during modification. Preferably, the monomer containing polar groups is at least one selected from the group consisting of hydroxyl-containing monomers and monomers having nitrogen-containing rings.

[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, and 12-hydroxylaurate (meth)acrylate. The hydroxyl-containing monomer is preferably at least one selected from the group consisting of 2-hydroxyethyl acrylate (2HEA), 4-hydroxyethyl acrylate (4HEA), and 4-hydroxybutyl acrylate (4HBA).

[0057] The proportion of hydroxyl-containing monomers in the monofunctional monomer is preferably 0.1% to 20% by mass, more preferably 0.5% to 15% by mass, and even more preferably 1% to 12% by mass. The proportion of hydroxyl-containing monomers in the monofunctional monomer is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and even more preferably 1% by mass or more. When this proportion of hydroxyl-containing monomers is at or above the aforementioned lower limit, the cohesive force of the adhesive sheet 10 can be ensured, and the adhesion force of the adhesive sheet 10 to the adhered object can also be ensured. Furthermore, the proportion of hydroxyl-containing monomers in the monomer component is preferably 20% by mass or less, more preferably 15% by mass or less, and even more preferably 12% by mass or less. When this proportion of hydroxyl-containing monomers is at or below the aforementioned upper limit, the polarity of the acrylic polymer (which relates to the compatibility of various additive components in the adhesive sheet 10 with the acrylic polymer) can be appropriately adjusted.

[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-vinylpyrrazine, N-vinylpyrrole, N-vinylimidazolium, N-vinylpyrazole, N-(meth)acryloyl-2-pyrrolidone, N-(meth)acryloylpiperidine, N-(meth)acryloylpyrrolidine, N-vinylmorpholine, N-vinyl-3-morpholinone, N-vinyl-2-caprolactam, N-vinyl-1,3-pyrazin-2-one, N-vinyl-3,5-morpholinedione, N-vinylpyrazole, N-vinylisopyrazole, N-vinylthiazole, N-vinylisothiazole, and acryloylmorpholine. N-vinyl-2-pyrrolidone (NVP) is preferred as the monomer having a nitrogen-containing ring.

[0059] The proportion of the monomer containing a nitrogen-containing ring in the monofunctional monomer is preferably 0.1% to 20% by mass, more preferably 0.5% to 12% by mass, and even more preferably 1% to 8% by mass. The proportion of the monomer containing a nitrogen-containing ring in the monofunctional monomer is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and even more preferably 1% by mass or more. When this proportion of the monomer containing a nitrogen-containing ring is at or above the lower limit mentioned above, the cohesive force of the adhesive sheet 10 can be ensured, and the adhesion force of the adhesive sheet 10 to the adhered object can also be ensured. Furthermore, the proportion of the monomer containing a nitrogen-containing ring in the monofunctional monomer is preferably 20% by mass or less, more preferably 12% by mass or less, and even more preferably 8% by mass or less. When this proportion of the monomer containing a nitrogen-containing ring is at or below the upper limit mentioned above, the glass transition temperature of the acrylic polymer can be appropriately adjusted, and the polarity of the acrylic polymer (which relates to the compatibility between various additive components in the adhesive sheet and the acrylic polymer) can be appropriately adjusted.

[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] The proportion of carboxyl-containing monomers in the monofunctional monomer is preferably 0.0% to 3% by mass, more preferably 0.0% to 1% by mass, even more preferably 0.0% to 0.5% by mass, and even more preferably 0.0% to 0.1% by mass. The proportion of carboxyl-containing monomers in the monofunctional monomer is preferably 3% by mass or less, more preferably 1% by mass or less, even more preferably 0.5% by mass or less, even more preferably 0.1% by mass or less, and particularly preferably 0.0% by mass. When the proportion of carboxyl-containing monomers in the monofunctional monomer is below the above-mentioned upper limit, corrosion caused by acid in the adhered material of the adhesive sheet 10 can be suppressed.

[0062] Monofunctional monomers may include 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.

[0063] Examples of polyfunctional polymerizable compounds include polyfunctional monomers containing two or more olefinic unsaturated double bonds in one molecule. Examples of polyfunctional monomers include polyfunctional (meth)acrylates. Examples of polyfunctional (meth)acrylates include difunctional (meth)acrylates, trifunctional (meth)acrylates, and polyfunctional (meth)acrylates with four or more functions.

[0064] Examples of bifunctional (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, neopentyl glycol dimethacrylate, stearic acid modified pentaerythritol dimethacrylate, dihydrodicyclopentadienyl diacrylate, di(meth)acryloyl isocyanurate, and ethoxylated bisphenol A diacrylate (BPAEODE).

[0065] Examples of trifunctional (meth)acrylates include: trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, and tri(acryloyloxyethyl) isocyanurate.

[0066] 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 pentaacrylate, and dipentaerythritol hexa(meth)acrylate.

[0067] The multifunctional polymerizable compound can be used alone or in combination of two or more. The multifunctional polymerizable compound is preferably at least one selected from the group consisting of dipentaerythritol hexaacrylate (DPHA) and 1,9-nonanediol diacrylate (NDDA).

[0068] Relative to 100 parts by mass of the monofunctional monomer, the amount of the polyfunctional polymeric compound in the polymerizable component is preferably 0.01 to 2 parts by mass, more preferably 0.03 to 1.5 parts by mass, and even more preferably 0.05 to 1.2 parts by mass. When the amount of the polyfunctional polymeric compound is at or above the lower limit mentioned above, the cohesive force of the adhesive sheet 10 can be improved, and the adhesive reliability after being bonded to the substrate can be improved. When the amount of the polyfunctional polymeric compound is below the upper limit mentioned above, the wettability of the adhesive sheet 10 to the substrate can be ensured, and the initial adhesive force of the adhesive sheet 10 to the substrate can be ensured.

[0069] In this embodiment, the acrylic polymer is formed by photopolymerization of a polymerizable component. The polymerizable component (containing a monofunctional monomer and a polyfunctional polymerizable compound as a crosslinking agent) can be polymerized in one step or in multiple steps. In the multi-step polymerization method, firstly, a prepolymer composition (prepolymerization) containing a portion of the polymer (a mixture of the polymer of the monofunctional monomer and unreacted monofunctional monomers) is prepared by polymerizing the monofunctional monomer. Next, the polyfunctional polymerizable 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 polyfunctional polymerizable compound. In photopolymerization, a photopolymerization initiator can be used.

[0070] Examples of photopolymerization initiators include: free radical photopolymerization initiators, cationic photopolymerization initiators, and anionic photopolymerization initiators.

[0071] Examples of free radical photopolymerization initiators include: acylphosphine oxide photopolymerization initiators, benzoin ether photopolymerization initiators, acetophenone photopolymerization initiators, α-keto alcohol photopolymerization initiators, and aromatic sulfonyl chloride photopolymerization initiators.

[0072] 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. Examples of α-keto alcohol polymerization initiators include 2-methyl-2-hydroxyphenylacetone and 1-[4-(2-hydroxyethyl)phenyl]-2-methylpropane-1-one. Examples of aromatic sulfonyl chloride photopolymerization initiators include 2-naphthalenesulfonyl chloride. Photopolymerization initiators can be used alone or in combination of two or more. Preferably, the photopolymerization initiator is at least one selected from the group consisting of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, 2,2-dimethoxy-2-phenylacetophenone, and 1-hydroxycyclohexylphenyl methyl ketone.

[0073] The amount of photopolymerization initiator relative to 100 parts by weight of the polymerizable component is preferably 0.03 to 0.5 parts by weight, more preferably 0.06 to 0.3 parts by weight, and even more preferably 0.08 to 0.2 parts by weight. The amount of photopolymerization initiator relative to 100 parts by weight of the polymerizable component is preferably 0.03 parts by weight or more, more preferably 0.06 parts by weight or more, and even more preferably 0.08 parts by weight or more. When the amount of photopolymerization initiator is at or above the aforementioned lower limit, a cross-linked network with sufficient cross-linking density can be formed in the acrylic polymer, thereby ensuring the adhesive strength of the adhesive sheet 10. The amount of photopolymerization initiator relative to 100 parts by weight of the polymerizable component is preferably 0.5 parts by weight or less, more preferably 0.3 parts by weight or less, and even more preferably 0.2 parts by weight or less. When the amount of photopolymerization initiator is at or below the aforementioned upper limit, the coagulation and destruction of the adhesive surface of the adhesive sheet 10 can be suppressed when peeling the adhesive sheet 10 from the adhered object. This helps to ensure, for example, alcohol reworkability. In the case of obtaining acrylic polymers by photopolymerization through prepolymerization and main polymerization, a photopolymerization initiator can be added after prepolymerization and during main polymerization.

[0074] From the viewpoint of ensuring the cohesiveness of the adhesive sheet 10, the weight-average molecular weight of the base polymer is preferably 100,000 to 5,000,000, more preferably 300,000 to 3,000,000, and even more preferably 500,000 to 2,000,000. 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. When the weight-average molecular weight of the base polymer is at or above the aforementioned lower limit, the cohesiveness of the adhesive sheet 10 can be ensured. The weight-average molecular weight of the base polymer is preferably 5,000,000 or less, more preferably 3,000,000 or less, and even more preferably 2,000,000 or less. When the weight-average molecular weight of the base polymer is below the aforementioned upper limit, the flexibility of the adhesive sheet 10 can be ensured. The weight-average molecular weight of the acrylic polymer is determined by gel permeation chromatography (GPC) and calculated by conversion to polystyrene.

[0075] 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. That is, the glass transition temperature of the base polymer is preferably between -80°C and 0°C, more preferably between -80°C and -10°C, and even more preferably between -80°C and -20°C.

[0076] The glass transition temperature (Tg) of a basic polymer can be calculated using the theoretical value based on the Fox formula. The Fox formula expresses the relationship between the Tg of the polymer and the Tgi of the homopolymer of the monomers constituting the polymer. In the Fox formula, Tg represents the glass transition temperature (°C) of the polymer, Wi represents the weight fraction of monomer i constituting the polymer, and Tgi represents the glass transition temperature (°C) of the homopolymer formed from monomer i. The glass transition temperature of the homopolymer can be obtained from literature. For example, the glass transition temperatures of various homopolymers listed in *Polymer Handbook* (4th edition, John Wiley & Sons, Inc., 1999) can be used. Alternatively, the glass transition temperature of the homopolymer of the monomers can be calculated using the method specifically described in Japanese Patent Application Publication No. 2007-51271.

[0077] Fox formula 1 / (273+Tg)=Σ[Wi / (273+Tgi)]

[0078] From the viewpoint of ensuring the alcohol affinity of the adhesive sheet 10, the hydrogen bond component δH of the Hansen solubility parameter (HSP) of the base polymer is preferably 3.5 or more, preferably 3.8 or more, and preferably 4.0 or more. From the viewpoint of suppressing the hydrophilicity of the adhesive sheet 10, the hydrogen bond component δH of the HSP of the base polymer is preferably 4.9 or less, preferably 4.7 or less, and preferably 4.6 or less. From the viewpoint of balancing ensuring the alcohol affinity of the adhesive sheet 10 and suppressing hydrophilicity, the hydrogen bond component δH of the HSP of the base polymer is preferably 3.5 to 4.9, preferably 3.8 to 4.7, and preferably 4.0 to 4.6. As a method for adjusting the δH of the base polymer, for example, adjusting the monomer composition of the base polymer can be cited.

[0079] The Hansen solubility parameter (HSP) is represented by the following equation (1), 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.

[0080] HSP=(δD 2 +δP 2 +δH 2 ) 1 / 2 (1)

[0081] The δH of a polymer depends on the monomer m that forms the polymer. i mole fraction x i and the monomer m i hydrogen bond component δh iThe hydrogen bonding component δh of the monomer is obtained by equation (2) below. For example, it can be calculated using the computer software HSPiP (HansenSolubility Parameters in Practice). The method for determining δH is specifically described in the examples described later.

[0082] δH=Σx i ×δh i (2)

[0083] From the viewpoint of ensuring the alcohol affinity of the adhesive sheet 10, the polar component δP of the HSP of the base polymer is preferably 2.5 or more, preferably 2.8 or more, and preferably 3.0 or more. From the viewpoint of suppressing the hydrophilicity of the adhesive sheet 10, the polar component δP of the HSP of the base polymer is preferably 3.7 or less, preferably 3.5 or less, and preferably 3.3 or less. From the viewpoint of balancing ensuring the alcohol affinity of the adhesive sheet 10 and suppressing hydrophilicity, the polar component δP of the HSP of the base polymer is preferably 2.5 to 3.7, preferably 2.8 to 3.5, and preferably 3.0 to 3.3. As a method for adjusting the δP of the base polymer, for example, adjusting the monomer composition of the base polymer can be cited. The δP of the polymer depends on the monomer m forming the polymer. i mole fraction x i and the monomer m i polar component δp i The polar component δp of the monomer is obtained by equation (3) below. For example, it can be calculated using the computer software HSPiP (Hansen Solubility Parameters in Practice). The method for determining δp is specifically described in the embodiments described later.

[0084] δP=Σx i ×δp i (3)

[0085] The content of the base polymer in the adhesive sheet 10 is preferably 80% to 99.9% by mass, more preferably 85% to 99.5% by mass, and even more preferably 90% to 99.0% by mass. The content of the base polymer in the adhesive sheet 10 is preferably 80% by mass or more, more preferably 85% by mass or more, and even more preferably 90% by mass or more. When the content of the base polymer is at or above the aforementioned lower limit, the adhesive sheet 10 can appropriately exhibit basic properties such as adhesion. The content of the base polymer in the adhesive sheet 10 is preferably 99.9% by mass or less, more preferably 99.5% by mass or less, and even more preferably 99.0% by mass or less. When the content of the base polymer is at or below the aforementioned upper limit, the content of the oligomers described later can be ensured.

[0086] The adhesive sheet 10 may contain oligomers. Examples of oligomers include hydrophilic oligomers and hydrophobic oligomers. A hydrophilic oligomer is a polymer in which the monomeric component comprises a hydrophilic monomer at a proportion of 3% by mass or more. A hydrophobic oligomer is a polymer in which the monomeric component comprises a hydrophilic monomer at a proportion of less than 3% by mass. The weight-average molecular weight of the oligomer is, for example, 1000 or more and 30000 or less. The weight-average molecular weight of the oligomer is determined by gel permeation chromatography (GPC) and calculated using polystyrene conversion.

[0087] When the base polymer is an acrylic polymer, the oligomer is preferably an acrylic oligomer. That is, a hydrophilic oligomer is preferably a hydrophilic acrylic oligomer. A hydrophobic oligomer is preferably a hydrophobic acrylic oligomer. The acrylic oligomer is an oligomer that is a polymer containing a monomer component of alkyl (meth)acrylate in a proportion of 50% by mass or more.

[0088] The hydrophilic acrylic oligomer is preferably a polymer comprising a monomer component of an alkyl (meth)acrylate having a chain alkyl group ((meth)acrylate chain alkyl ester), an alkyl (meth)acrylate having an alicyclic alkyl group ((meth)acrylate alicyclic alkyl ester), and a hydrophilic monomer. Specific examples of alkyl (meth)acrylates include, for example, the alkyl (meth)acrylates described above as monomer components of acrylic polymers. Specific examples of hydrophilic monomers include, for example, hydroxyl-containing monomers and carboxyl-containing monomers. Specific examples of hydroxyl-containing monomers and carboxyl-containing monomers include, for example, the hydroxyl-containing monomers and carboxyl-containing monomers described above as monomer components of acrylic polymers.

[0089] Considering the high glass transition temperature and high compatibility with the base polymer, the (meth)acrylate alkyl chain ester is preferably methyl methacrylate (MMA). The (meth)acrylate cycloalkyl aliphatic ester is preferably at least one selected from the group consisting of tetrahydrodicyclopentadienyl acrylate (DCPA), tetrahydrodicyclopentadienyl methacrylate (DCPMA), cyclohexyl acrylate (CHA), and cyclohexyl methacrylate (CHMA). The hydrophilic monomer is preferably at least one selected from the group consisting of 2-hydroxyethyl methacrylate (HEMA), 2-hydroxypropyl methacrylate (HPMA), and 4-hydroxybutyl methacrylate (HBMA). That is, the acrylic oligomer is preferably a polymer containing a monomer component comprising at least one selected from the group consisting of DCPA, DCPMA, CHA, and CHMA, at least one selected from the group consisting of HEMA, HPMA, and HBMA, and MMA.

[0090] The proportion of (meth)acrylate cyclic alkyl esters in the monomer component of the hydrophilic acrylic oligomer is preferably 10% by mass or more, more preferably 30% by mass or more, further preferably 40% by mass or more, and preferably 80% by mass or less, more preferably 60% by mass or less, and further preferably 50% by mass or less. A proportion of (meth)acrylate cyclic alkyl esters at or above the aforementioned lower limit helps ensure the adhesive strength and cohesiveness of the adhesive sheet 10. A proportion of (meth)acrylate cyclic alkyl esters at or below the aforementioned upper limit helps ensure the compatibility between the acrylic polymer and the hydrophilic oligomer in the adhesive sheet 10. The proportion of (meth)acrylate chain alkyl esters in the monomer component of the hydrophilic acrylic oligomer is preferably 10% by mass or more, more preferably 30% by mass or more, further preferably 40% by mass or more, and preferably 80% by mass or less, more preferably 60% by mass or less, and further preferably 50% by mass or less. A proportion of (meth)acrylate chain alkyl esters at or above the aforementioned lower limit helps ensure the compatibility between the acrylic polymer and the hydrophilic oligomer in the adhesive sheet 10. The proportion of (meth)acrylate alkyl esters below the aforementioned upper limit helps ensure the adhesive strength and cohesiveness of the adhesive sheet 10. The proportion of hydrophilic monomers in the monomer component of the hydrophilic acrylic oligomer is preferably 6% by mass or more, more preferably 8% by mass or more, further preferably 10% by mass or more, and preferably 20% by mass or less, more preferably 15% by mass or less, and further preferably 12% by mass or less. When the proportion of hydrophilic monomers is above the aforementioned lower limit, the adhesive strength and cohesiveness of the adhesive sheet 10 can be ensured. When the proportion of hydrophilic monomers is below the aforementioned upper limit, the compatibility between the acrylic polymer and the hydrophilic oligomer in the adhesive sheet 10 can be ensured.

[0091] Hydrophilic acrylic oligomers are obtained by polymerizing the monomeric components of the acrylic oligomer (the same applies to hydrophobic acrylic oligomers, which will be described later). Examples of polymerization methods include solution polymerization, active energy radiation polymerization (e.g., UV polymerization), bulk polymerization, and emulsion polymerization. In the polymerization of acrylic oligomers, polymerization initiators can be used, and chain transfer agents can be used to adjust the molecular weight.

[0092] The content of hydrophilic oligomers in the adhesive sheet 10 is preferably 0.1 to 3 parts by mass relative to 100 parts by mass of the base polymer, more preferably 0.3 to 2 parts by mass, and even more preferably 0.4 to 1.2 parts by mass. The content of hydrophilic oligomers in the adhesive sheet 10 is preferably 0.1 parts by mass or more, more preferably 0.3 parts by mass or more, and even more preferably 0.4 parts by mass or more. When the content of hydrophilic oligomers is at or above the aforementioned lower limit, the adhesive strength of the adhesive sheet 10 can be improved (especially the adhesive strength under high humidity conditions). The content of hydrophilic oligomers in the adhesive sheet 10 is preferably 3 parts by mass or less relative to 100 parts by mass of the base polymer, more preferably 2 parts by mass or less, and even more preferably 1.2 parts by mass or less. When the content of hydrophilic oligomers is at or below the aforementioned upper limit, the transparency of the adhesive sheet 10 can be ensured. If there is too much oligomer in the adhesive sheet 10, there is a tendency for haze to increase and transparency to decrease due to the reduced compatibility of the oligomer.

[0093] The hydrophobic acrylic oligomer is preferably a polymer comprising monomer components of (meth)acrylate chain alkyl esters and (meth)acrylate cycloalkyl esters. Considering its high glass transition temperature and high compatibility with the base polymer, the (meth)acrylate chain alkyl ester is preferably MMA. The (meth)acrylate cycloalkyl ester is preferably at least one selected from the group consisting of tetrahydrodicyclopentadienyl acrylate, tetrahydrodicyclopentadienyl methacrylate, cyclohexyl acrylate, and cyclohexyl methacrylate. That is, the acrylic oligomer is preferably a polymer comprising monomer components of one or more selected from the group consisting of tetrahydrodicyclopentadienyl acrylate, tetrahydrodicyclopentadienyl methacrylate, cyclohexyl acrylate, and cyclohexyl methacrylate, and MMA.

[0094] The proportion of (meth)acrylate cyclic alkyl esters in the monomer component of the hydrophobic acrylic oligomer is preferably 10% by mass or more, more preferably 30% by mass or more, further preferably 40% by mass or more, and preferably 90% by mass or less, more preferably 70% by mass or less, and further preferably 60% by mass or less. A proportion of (meth)acrylate cyclic alkyl esters at or above the aforementioned lower limit helps ensure the adhesive strength and cohesiveness of the adhesive sheet 10. A proportion of (meth)acrylate cyclic alkyl esters at or below the aforementioned upper limit helps ensure the compatibility of the acrylic polymer in the adhesive sheet 10 with the hydrophobic oligomer. The proportion of (meth)acrylate chain alkyl esters in the monomer component of the hydrophobic acrylic oligomer is preferably 10% by mass or more, more preferably 30% by mass or more, further preferably 40% by mass or more, and preferably 90% by mass or less, more preferably 70% by mass or less, and further preferably 60% by mass or less. A proportion of (meth)acrylate chain alkyl esters at or above the aforementioned lower limit helps ensure the compatibility of the acrylic polymer in the adhesive sheet 10 with the hydrophobic oligomer. The proportion of (meth)acrylic acid chain alkyl esters below the above upper limit helps to ensure the adhesion and cohesion of adhesive sheet 10.

[0095] The content of hydrophobic oligomers in the adhesive sheet 10 is preferably 0.1 to 3 parts by mass relative to 100 parts by mass of the base polymer, more preferably 0.3 to 2 parts by mass, and even more preferably 0.4 to 1.2 parts by mass. The content of hydrophobic oligomers in the adhesive sheet 10 is preferably 0.1 parts by mass or more, more preferably 0.3 parts by mass or more, and even more preferably 0.4 parts by mass or more. When the content of hydrophobic oligomers is at or above the aforementioned lower limit, the adhesive strength of the adhesive sheet 10 can be improved. The content of hydrophobic oligomers in the adhesive sheet 10 is preferably 3 parts by mass or less relative to 100 parts by mass of the base polymer, more preferably 2 parts by mass or less, and even more preferably 1.2 parts by mass or less. When the content of hydrophobic oligomers is at or below the aforementioned upper limit, the transparency of the adhesive sheet 10 can be ensured.

[0096] Relative to 100 parts by weight of the base polymer, the total content of hydrophilic and hydrophobic oligomers in the adhesive sheet 10 is preferably 0.2 parts by weight or more, more preferably 0.6 parts by weight or more, even more preferably 0.8 parts by weight or more, and preferably 5 parts by weight or less, more preferably 4 parts by weight or less, and even more preferably 3 parts by weight or less. When the total content of oligomers is at or above the aforementioned lower limit, the adhesive strength of the adhesive sheet 10 can be improved. When the total content of oligomers is at or below the aforementioned upper limit, the transparency of the adhesive sheet 10 can be ensured.

[0097] The adhesive sheet 10 may contain other components. Examples of such other components include: silane coupling agents, ultraviolet absorbers, antioxidants, surfactants, and rust inhibitors.

[0098] Examples of silane coupling agents include, for example, silane coupling agents containing epoxy groups. Examples of silane coupling agents containing epoxy groups include, for example, 3-epoxypropoxydialkyldialkoxysilane and 3-epoxypropoxyalkyltrialkoxysilane. Examples of 3-epoxypropoxydialkyldialkoxysilanes include, for example, 3-epoxypropoxypropylmethyldimethoxysilane and 3-epoxypropoxypropylmethyldiethoxysilane. Examples of 3-epoxypropoxyalkyltrialkoxysilanes include, for example, 3-epoxypropoxypropyltrimethoxysilane and 3-epoxypropoxypropyltriethoxysilane. 3-epoxypropoxyalkyltrialkoxysilane is preferred as a silane coupling agent, and more preferably, 3-epoxypropoxypropyltrimethoxysilane. Silane coupling agents can be used alone or in combination of two or more. From the viewpoint of exhibiting good alcohol peelability by suppressing the adhesion of the adhesive sheet 10 to the glass, the proportion of silane coupling agent in the adhesive sheet 10 is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, even more preferably 0.3% by mass or more, and preferably 3% by mass or less, more preferably 2% by mass or less, and even more preferably 1% by mass or less.

[0099] The adhesive sheet 10 preferably does not contain surfactants. From the viewpoint of ensuring the adhesive strength of the adhesive sheet 10 in a high humidity environment, the content of surfactant in the adhesive sheet 10 is preferably 0.3% by mass or less, more preferably 0.2% by mass or less, even more preferably 0.1% by mass or less, and particularly preferably 0.0% by mass.

[0100] Examples of release liner L1 include, for example, release liners having a release treatment layer on the surface of the liner substrate and release liners formed of low-adhesion materials. Examples of liner substrates include, for example, resin films and paper. Examples of resins used in resin films include, for example, polyester resins and polycarbonate resins. Examples of polyester resins include, for example, polyethylene terephthalate (PET) and polybutylene terephthalate. The release treatment layer can be formed by surface treatment of the liner substrate using a release treatment agent. Examples of release treatment agents include, for example, polysiloxane release treatment agents, long-chain alkyl release treatment agents, and fluorinated release treatment agents. Examples of low-adhesion materials include, for example, polyolefin resins and fluorinated polymers. Examples of polyolefin resins include, for example, polyethylene, polypropylene, and cyclic olefin polymers (COP). Examples of fluorinated polymers include, for example, polytetrafluoroethylene (PTFE).

[0101] Examples of release liner L2 include, for instance, release liners having a release treatment layer on the surface of the liner substrate and release liners formed of low-adhesion materials. Release liner L2 is specifically the same as described above regarding release liner L1.

[0102] The adhesive sheet 10 can be manufactured, for example, by the following operation.

[0103] First, a prepolymer composition is prepared. Specifically, a mixture (liquid) comprising the aforementioned monofunctional monomer for forming the basic polymer and a photopolymerization initiator is first prepared. Next, a portion of the monofunctional monomer in the mixture is photopolymerized by irradiating the mixture with ultraviolet light, thereby obtaining the prepolymer composition. Examples of light sources for ultraviolet irradiation include: ultraviolet LED lamps, black light lamps, high-pressure mercury lamps, and metal halide lamps. The illuminance during ultraviolet irradiation is, for example, 5 mJ / cm². 2 ~200mW / cm 2 The cumulative irradiation intensity is, for example, 100 mJ / cm². 2 ~5000mJ / cm 2 Ultraviolet irradiation is preferably continued until the viscosity of the composition reaches about 15 Pa·s to about 25 Pa·s. This viscosity is measured using a Type B viscometer under the conditions of rotor No. 5, rotor speed 10 rpm, and temperature 30°C. The prepolymer composition contains photopolymers of monofunctional monomers and unreacted monofunctional monomers (residual monomers). Furthermore, the prepolymer composition does not contain solvents.

[0104] Next, a multifunctional polymerizable compound (crosslinking agent) and other desired components are added to the prepolymer composition to prepare an adhesive composition. Examples of other components include oligomers, additional photopolymerization initiators, silane coupling agents, antioxidants, and rust inhibitors. This adhesive composition is solvent-free. That is, the adhesive composition prepared in this step is a solvent-free adhesive composition.

[0105] Next, an adhesive composition is applied to the release liner L1 to form a coating film, and then the release liner L2 is bonded onto the coating film on the release liner L1. Examples of methods for applying the adhesive composition include: roller coating, licker coating, gravure coating, reverse coating, roller brush coating, spray coating, dip roller coating, doctor blade coating, doctor knife coating, air knife coating, curtain coating, die lip coating, and die-cutting.

[0106] Next, the coating between the release liner L1 and L2 is photocured by irradiating it with ultraviolet light to form an adhesive layer. Under ultraviolet irradiation, a polymerization reaction occurs in the coating within a reaction system containing the aforementioned residual monomers and multifunctional polymerizable compounds, thereby forming a first photopolymer with a photocrosslinked structure. The adhesive layer can then be dried by heating. The drying temperature is, for example, 80°C to 150°C. The drying time is, for example, 30 seconds to 10 minutes. This drying process allows unreacted monomers within the adhesive layer to evaporate and be removed.

[0107] Through the above operations, an adhesive sheet 10 can be manufactured, in which the adhesive surfaces 11 and 12 are covered and protected by release liner L1 and L2. The release liner L1 and L2 are peeled off from the adhesive sheet 10 as needed when using the adhesive sheet 10.

[0108] The adhesive sheet 10 can be formed from a solvent-free adhesive composition. Such an adhesive sheet 10 is suitable for reducing environmental impact. That is, the adhesive sheet 10 formed from a solvent-free adhesive composition is environmentally friendly and preferred from a sustainable development perspective.

[0109] From the viewpoint of ensuring sufficient adhesion to the adhered object, the thickness of the adhesive sheet 10 is preferably 10 μm or more, more preferably 20 μm or more, and even more preferably 30 μm or more. From the viewpoint of operability and thinness of the adhesive sheet 10, the thickness of the adhesive sheet 10 is preferably 300 μm or less, more preferably 200 μm or less, and even more preferably 100 μm or less. From the viewpoint of balancing the above-mentioned adhesion, operability, and thinness, the thickness of the adhesive sheet 10 is preferably 10 μm to 300 μm, more preferably 20 μm to 200 μm, and even more preferably 30 μm to 100 μm.

[0110] From the viewpoint of ensuring the transparency of the adhesive sheet 10, the total light transmittance of the adhesive sheet 10 is preferably 90% or more, more preferably 95% or more, and, for example, 100% or less. The total light transmittance can be measured according to JIS K7375 (2008).

[0111] Figure 4 A to Figure 4 C represents an example of how the adhesive sheet 10 is used.

[0112] In this method, firstly, as Figure 4 As shown in Figure A, the adhesive sheet 10 is bonded to one surface of the component 31 (the first adherend) in the thickness direction H (bonding process). Examples of components 31 include, for instance, the pixel panel in a display panel and a polarizing film. This process provides the adhesive sheet 10 for bonding with other components onto the component 31.

[0113] Next, as Figure 4 As shown in B, the component 31 is joined to the component 32 (the second adherend) by the adhesive tab 10 on the component 31 (joining process). For example, a cover film in a display panel can be cited as an example of component 32.

[0114] Next, as Figure 4 As shown in Figure C, the adhesive sheet 10 between components 31 and 32 is cured (curing process). This process improves the bonding strength between the adhesive sheet 10 and components 31 and 32. The curing temperature is, for example, 20°C to 160°C. The curing time is, for example, 1 minute to 21 days. When autoclaving (heating and pressurizing) is performed as curing, 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.

[0115] According to the adhesive sheet 10, after the bonding process or the curing process, the bonding state between components 31 and 32 can be easily eliminated (alcohol rework) using alcohol as needed. Specifically, as described below.

[0116] By allowing alcohol to penetrate the interface between component 31 and adhesive sheet 10, the adhesive force of adhesive sheet 10 on component 31 can be reduced, and then component 32 with adhesive sheet 10 can be easily peeled off from component 31. Afterwards, for example, a replacement component 32 with adhesive sheet 10 can be bonded to component 31 using adhesive sheet 10. Alternatively, by allowing alcohol to penetrate the interface between component 32 and adhesive sheet 10, the adhesive force of adhesive sheet 10 on component 32 can be reduced, and then component 31 with adhesive sheet 10 can be easily peeled off from component 32. Afterwards, for example, a replacement component 31 with adhesive sheet 10 can be bonded to component 32 using adhesive sheet 10. Examples of alcohols include methanol, ethanol, propanol, and butanol.

[0117] According to the adhesive sheet 10, the adhesive force Fa1 in the first ethanol peel test is less than 3.0 / 25mm, so ethanol rework as described above is possible, for example.

[0118] The adhesive sheet 10 is, for example, an optical adhesive sheet to be disposed in the light-passing portion of a display panel. Examples of display panels include liquid crystal panels and organic EL panels. The display panel may have, for example, a laminated structure comprising elements such as a pixel panel, a polarizing film, a touch panel, and a cover film. The adhesive sheet 10 is used, for example, during the manufacturing process of the display panel to bond the elements included in the laminated structure to each other.

[0119] Example

[0120] 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".

[0121] <Preparation of oligomer M1>

[0122] First, in a reaction vessel equipped with a stirrer, thermometer, reflux condenser, and nitrogen inlet, a mixture containing 60 parts by mass of tetrahydrodicyclopentadienyl methacrylate (DCPMA), 40 parts by mass of methyl methacrylate (MMA), 3.5 parts by mass of α-thioglycerol as a chain transfer agent, and 100 parts by mass of toluene as a polymerization solvent was stirred at 70°C for 1 hour under a nitrogen atmosphere. Next, 0.2 parts by mass of 2,2'-azobisisobutyronitrile (AIBN) as a thermal polymerization initiator was added to the mixture to prepare a reaction solution. The reaction was carried out at 70°C for 2 hours under a nitrogen atmosphere, followed by a reaction at 80°C for 2 hours (polymerization reaction). Then, the reaction solution was heated at 130°C to volatilize and remove the toluene, chain transfer agent, and unreacted monomers. This yielded a solid acrylic oligomer (oligomer M1). Oligomer M1 has a weight-average molecular weight of 5100 and a glass transition temperature of 130°C. Oligomer M1 is a hydrophobic oligomer.

[0123] <Preparation of oligomer M2>

[0124] First, in a reaction vessel equipped with a stirrer, thermometer, reflux condenser, and nitrogen inlet, a mixture containing 45 parts by mass of DCPMA, 45 parts by mass of MMA, 10 parts by mass of 2-hydroxyethyl methacrylate (HEMA), 3.5 parts by mass of α-thioglycerol as a chain transfer agent, and 100 parts by mass of toluene as a polymerization solvent was stirred at 70°C for 1 hour under a nitrogen atmosphere. Next, 0.2 parts by mass of AIBN as a thermal polymerization initiator was added to the mixture to prepare a reaction solution, which was reacted at 70°C for 2 hours under a nitrogen atmosphere, and then at 80°C for 2 hours (polymerization reaction). Then, the reaction solution was heated at 130°C to volatilize and remove the toluene, chain transfer agent, and unreacted monomers. This yielded a solid acrylic oligomer (oligomer M2). Oligomer M2 has a weight-average molecular weight of 5300 and a glass transition temperature of 115°C. Oligomer M2 is a hydrophilic oligomer.

[0125] [Example 1]

[0126] <Preparation of Prepolymer Compositions>

[0127] First, 58 parts by weight of 2-ethylhexyl acrylate (2EHA), 39 parts by weight of lauryl acrylate (LA), 3 parts by weight of 4-hydroxybutyl acrylate (4HBA), 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-2-phenylacetophenone, manufactured by IGM Resins) were mixed in a flask. The mixture was then irradiated with ultraviolet light under a nitrogen atmosphere, thereby causing a portion of the monomer components in the mixture to polymerize, resulting in a prepolymer composition with a polymerization rate of approximately 10%. This prepolymer composition is a partial polymer containing a photopolymer (photopolymer P1a) and unreacted monomer components (residual monomers).

[0128] <Preparation of Adhesive Compositions>

[0129] Next, 100 parts by weight of the prepolymer composition, 1.0 parts by weight of the oligomer M1, 0.06 parts by weight of dipentaerythritol hexaacrylate (DPHA) (trade name "KAYARAD DPHA", manufactured by Nippon Kayaku Co., Ltd.), which is a multifunctional polymerizable compound, and 0.3 parts by weight of the silane coupling agent (trade name "KBM-403", manufactured by Shin-Etsu Chemical Co., Ltd.) were mixed to obtain the adhesive composition C1.

[0130] <Making Adhesive Sheets>

[0131] Next, adhesive composition C1 is applied to the release-treated surface of a first release liner (trade name "Diafoil MRF", thickness 38 μm, manufactured by Mitsubishi Chemical Corporation) with a release-treated surface on one side, thereby forming a coating film. Then, the release-treated surface of a second release liner (trade name "Diafoil MRN", thickness 38 μm, manufactured by Mitsubishi Chemical Corporation) with a release-treated surface on one side is bonded to the coating film on the first release liner. Next, ultraviolet light is irradiated onto the coating film between the release liners from the second release liner side to photocur the coating film, thereby forming an adhesive layer with a thickness of 50 μm (UV irradiation process). During UV irradiation, a black light lamp (manufactured by Toshiba) is used as the light source, and the illuminance is set to 5.0 mW / cm². 2 The cumulative irradiation intensity was set to 1500 mJ / cm. 2In the ultraviolet irradiation process, a photopolymerization reaction is carried out in the coating film in a reaction system containing the aforementioned residual monomer and a multifunctional polymerizable compound, thereby forming a photopolymer P1b with a photocrosslinked structure. Furthermore, this photopolymerization reaction occurs around the aforementioned photopolymer P1a, thus photopolymer P1b is formed around photopolymer P1a. The adhesive layer formed in this process contains photopolymer P1a and photopolymer P1b as base polymers.

[0132] Next, after peeling the first release liner from the adhesive layer, the adhesive layer on the second release liner is dried in a hot air oven at 130°C for 3 minutes. This causes unreacted monomers in the adhesive layer to evaporate and be removed. Then, after naturally cooling at room temperature, the release-treated side of a third release liner (trade name "Diafoil MRF", thickness 38 μm, manufactured by Mitsubishi Chemical Corporation) with a release-treated surface on one side is bonded onto the adhesive layer on the second release liner.

[0133] Through the above operations, the adhesive sheet with release liner of Example 1 (second release liner / adhesive sheet (thickness 50μm) / third release liner) was produced.

[0134] [Example 2]

[0135] Except for the following, the adhesive sheet with a release liner of Example 1 was produced by operating in the same manner as the adhesive sheet with a release liner of Example 2. In the preparation of the adhesive composition, the amount of oligomer M1 was set to 0.5 parts by weight, and 0.5 parts by weight of oligomer M2 was also incorporated.

[0136] [Example 3]

[0137] Except for the following, the adhesive sheet with a release liner of Example 1 was produced by operating in the same manner as the adhesive sheet with a release liner of Example 3. In the preparation of the prepolymer composition, the amount of 2EHA was set to 56 parts by weight, and 2 parts by weight of N-vinyl-2-pyrrolidone (NVP) was also incorporated.

[0138] [Example 4]

[0139] Except for the following, the adhesive sheet with a release liner of Example 4 was produced by operating in the same manner as the adhesive sheet with a release liner of Example 1. In the preparation of the prepolymer composition, the amount of 2EHA was set to 52 parts by mass and the amount of 4HBA was set to 9 parts by mass.

[0140] [Example 5]

[0141] Except for the following, the adhesive sheet with a release liner of Example 1 was produced by operating in the same manner as the adhesive sheet with a release liner of Example 5. The composition of the prepolymer composition was changed to the composition shown in Table 1. In the preparation of the adhesive composition, 1.0 parts by weight of oligomer M2 was used instead of oligomer M1, 0.08 parts by weight of 1,9-nonanediol diacrylate (NDDA) (brand name "Viscoat#260", manufactured by Osaka Organic Chemical Industry Co., Ltd.) was used instead of DPHA, and 0.1 parts by weight of a first additional photopolymerization initiator (Omnirad 651) was used.

[0142] [Comparative Example 1]

[0143] Except that oligomer M1 was not incorporated in the preparation of the prepolymer composition, the adhesive sheet with release liner of Comparative Example 1 was produced by operating in the same manner as the adhesive sheet with release liner of Example 1.

[0144] [Comparative Example 2]

[0145] <Preparation of Prepolymer Compositions>

[0146] In a flask, 0.05 parts by weight of a first photopolymerization initiator (Omnirad 184) and 0.05 parts by weight of a third photopolymerization initiator (brand name "Omnirad 819", bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, manufactured by IGM Resins) were mixed with 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 4HBA, and 2 parts by weight of 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 prepolymer composition with a polymerization rate of approximately 10%.

[0147] <Preparation of Adhesive Compositions>

[0148] Next, 100 parts by weight of the prepolymer composition, 0.5 parts by weight of oligomer M1, 0.5 parts by weight of oligomer M2, 0.01 parts by weight of DPHA (KAYARAD DPHA) as a multifunctional polymerizable compound, 0.3 parts by weight of the first reactive surfactant (brand name "ACRIT 8WX-046-NS", manufactured by Taisei Fine Chemicals Co., Ltd.), 0.1 parts by weight of the non-reactive surfactant (brand name "RHEODOL TW-L120", manufactured by Kao Corporation), and 0.04 parts by weight of the second additional photopolymerization initiator (Omnirad 819) were mixed to prepare the adhesive composition C2.

[0149] <Making Adhesive Sheets>

[0150] In addition to adhesive composition C1, adhesive composition C2 was used instead of adhesive composition C1. Otherwise, an adhesive layer with a thickness of 50 μm was formed in the same manner as described above with respect to Example 1, thereby producing the adhesive sheet with release liner of Comparative Example 2 (second release liner / adhesive sheet (thickness 50 μm) / third release liner).

[0151] [Comparative Example 3]

[0152] Except for the following, the adhesive sheet with a release liner of Comparative Example 3 was produced by operating in the same manner as the adhesive sheet with a release liner of Comparative Example 2. In the preparation of the adhesive composition, the amount of DPHA was set to 0.02 parts by weight, no first reactive surfactant and non-reactive surfactant were added, and 0.3 parts by weight of second reactive surfactant (brand name "Aqualon KH-10", manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd.) and 0.1 parts by weight of third reactive surfactant (brand name "Aminoion RE3000MA", manufactured by Nippon Emulsifier Co., Ltd.) were added.

[0153] [Comparative Example 4]

[0154] Except for the following, the adhesive sheet with a release liner of Comparative Example 4 was produced by operating in the same manner as the adhesive sheet with a release liner of Comparative Example 2. In the preparation of the adhesive composition, the amount of oligomer M1 was set to 1.5 parts by mass, oligomer M2 was not added, the amount of DPHA was set to 0.045 parts by mass, and neither the first reactive surfactant nor the non-reactive surfactant was added.

[0155] [Comparative Example 5]

[0156] Except for the following, the adhesive sheet with a release liner of Comparative Example 5 was produced by operating in the same manner as the adhesive sheet with a release liner of Comparative Example 2. In the preparation of the adhesive composition, the amount of oligomer M1 was set to 1.5 parts by mass, oligomer M2 was not added, the amount of DPHA was set to 0.11 parts by mass, 0.5 parts by mass of silane coupling agent (KBM-403) was added, and the amount of the second additional photopolymerization initiator (Omnirad 819) was set to 0.02 parts by mass.

[0157] <Weight-average molecular weight of oligomers>

[0158] The weight-average molecular weights (Mw) of oligomers M1 and M2 were determined by gel permeation chromatography (GPC) under the following conditions, and the values ​​were converted to polystyrene. A GPC apparatus (HLC-8120GPC, manufactured by Tosoh) was used for the determination. The sample solution was prepared as follows: First, using the acrylic oligomer as the sample, a 0.20% by mass dimethylformamide (DMF) solution (with added salt) was prepared and then 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.

[0159] [GPC Measurement Conditions]

[0160] Pillars: SuperAWM-H + SuperAW4000 + SuperAW2500, each with TSKgel (manufactured by Tosoh).

[0161] Column temperature: 40℃

[0162] Eluent: DMF solution (with salt)

[0163] Flow rate: 0.4 mL / min

[0164] Sample injection volume: 40 μL

[0165] Standard sample: Polystyrene (manufactured by Agilent)

[0166] Detector: Differential refractometer (RI)

[0167] <hsp>

[0168] For each acrylic polymer used in the examples and comparative examples, the hydrogen bonding component δH, dispersion component δD, and polar component δP of the Hansen solubility parameter (HSP) were determined. Specifically, as described below.

[0169] Regarding the hydrogen bond component δH, firstly, using the computer software HSPiP (Hansen Solubility Parameters in Practice), the individual monomers m that form the acrylic polymers are analyzed. i Calculate the hydrogen bond component (δh) of HSP i Next, based on monomer m in the acrylic monomers... i mole fraction x i and the monomer m i hydrogen bond component δh i The hydrogen bonding component (δH) of acrylic polymers can be determined by the following equation (2).

[0170] δH=Σx i ×δh i (2)

[0171] Similarly, regarding the dispersion component δD, the individual monomers m forming the acrylic polymer were analyzed using the computer software HSPiP. i Calculate the dispersive component (δd) of the HSP i Then, based on monomer m in the acrylic monomers... i mole fraction x i and the monomer m i The dispersive component δd i The dispersion component (δD) of the acrylic polymer was determined. Similarly, the polar component δP was determined using the computer software HSPiP for each monomer m that forms the acrylic polymer. i Calculate the polar component (δp) of HSP i Then, based on monomer m in the acrylic monomers... i mole fraction x i and the monomer m i polar component δp i The polar component (δP) of acrylic polymers was determined. The hydrogen bonding component δH, dispersion term δD, and polar component δP of acrylic polymers are shown in Tables 1 and 2.

[0172] <Initial room temperature peel test>

[0173] An initial room temperature peel test was performed on each adhesive sheet of the examples and comparative examples to determine the adhesive force Fn1. Specifically, it is described below.

[0174] Preparation steps: First, the third release liner is peeled off from the adhesive sheet (second release liner / adhesive sheet / third release liner). Next, the exposed adhesive sheet is bonded to a plasma-treated polyethylene terephthalate (PET) film (brand name "Lumirror S10", thickness 50 μm, manufactured by Toray Industries). This yields a laminated film. In the plasma treatment, a plasma irradiation device (brand name "AP-TO5", manufactured by Sekisui Industries) is used, with the voltage set to 160V, the frequency set to 10kHz, and the processing speed set to 5000mm / min. During bonding, the adhesive sheet is pressed onto the PET film by pressing a 2kg hand roller back and forth once at 25°C. Next, a 25mm wide × 100mm long laminated film piece is cut from the laminated film. This laminated film sequentially comprises a PET film, an adhesive sheet piece, and a second release liner in the thickness direction. Then, the second release liner is peeled off from the adhesive sheet piece on the PET film. Next, the exposed adhesive sheet (25mm wide × 100mm long) is attached to the tin side of an alkali glass plate made by float glass, thus obtaining a laminate.

[0175] Heating and pressurizing steps: Next, the laminate was subjected to heat and pressure treatment at 50°C, 0.5 MPa, and 15 minutes. This caused the adhesive sheet pieces to be pressed onto the alkali glass plate.

[0176] Let it stand: Next, the laminate was left to stand at room temperature for 72 hours.

[0177] Measurement steps: Next, a 180° peel test was performed to peel the adhesive sheet from the alkali glass plate in the laminate, and the force required for peeling (peel force) was measured. A tensile testing machine (Autograph AG-50NXplus, manufactured by Shimadzu Corporation) was used in this test. Specifically, under the conditions of 25°C, 50% relative humidity, a peel angle of 180°, and a pulling speed of 300 mm / min (first condition), the adhesive sheet was peeled from the alkali glass plate by pulling one end along its length, and the peel force was measured. The peel length (total length) was set to 50 mm, and the average peel force measured between 10 mm and 40 mm was taken as the adhesive force.

[0178] The adhesive force measured in the initial room temperature peel test is taken as adhesive force Fn1 (N / 25mm) and is shown in Tables 1 and 2.

[0179] <Post-storage peel test at room temperature>

[0180] The adhesive strength Fn2 was determined by performing a post-storage room temperature peel test on each adhesive sheet of the examples and comparative examples. The post-storage room temperature peel test was the same as the initial room temperature peel test, except that the laminate was left to stand at 50°C for 168 hours in the standing step.

[0181] In the post-storage room temperature peel test, the peel length (total length) was set to 50 mm, and the average peel force measured between 10 mm and 40 mm was taken as the adhesive force. The adhesive force measured in the post-storage room temperature peel test was taken as the adhesive force Fn2 (N / 25 mm) and is shown in Tables 1 and 2.

[0182] <First Ethanol Stripping Test>

[0183] The adhesive strength Fa1 was measured by performing a first ethanol peel test on each adhesive sheet of the Examples and Comparative Examples. The first ethanol peel test was the same as the initial room temperature peel test except for the following: In the settling step, the laminate was set at 50°C for 168 hours. An ethanol supply step was performed after the settling step and before the measurement step. In the ethanol supply step, 10 μL of ethanol was supplied to the alkali glass plate of the laminate in such a way that the ethanol contacted one end of the adhesive sheet along its length at the interface between the ethanol and the alkali glass plate and the adhesive sheet.

[0184] In the first ethanol peel test procedure, the peel length d1 at which the peel force begins to stabilize during the peeling process of the adhesive sheet piece and the peel length d2 at which the peel force increases by 10% relative to the peel length d1 are determined. Then, the average value of the peel force measured from peel length d1 to peel length d2 is taken as the adhesive force. The adhesive force measured in the first ethanol peel test procedure is taken as the adhesive force Fa1 (N / 25mm) and is shown in Tables 1 and 2.

[0185] <Second Ethanol Stripping Test>

[0186] The adhesive strength Fa2 was measured by performing a second ethanol peel test on each adhesive sheet of the examples and comparative examples. The second ethanol peel test was the same as the first ethanol peel test except for the following: In the standing step, the laminate was left to stand at room temperature for 72 hours.

[0187] In the second ethanol peel test procedure, the peel length d1 when the peel force begins to stabilize during the peeling process and the peel length d2 when the peel force increases by 10% relative to the peel length d1 are determined. The average value of the peel force measured from peel length d1 to peel length d2 is taken as the adhesive force. The adhesive force measured in the second ethanol peel test procedure is taken as the adhesive force Fa2 (N / 25mm) and shown in Tables 1 and 2. The difference between peel length d2 and peel length d1 (d2-d1) is taken as the ethanol peel duration length d (mm) and shown in Tables 1 and 2. In addition, the rate of change (%) of adhesive force Fa1 relative to adhesive force Fa2 is also shown in Tables 1 and 2. This rate of change is calculated by the following formula.

[0188] Rate of change (%) = [(Fa1 - Fa2) / Fa2] × 100

[0189] High Temperature and High Humidity Peeling Test

[0190] The adhesive strength Fh was determined by performing a high-temperature and high-humidity peel test on each adhesive sheet of the Examples and Comparative Examples. The high-temperature and high-humidity peel test was the same as the initial room-temperature peel test except for the following: In the settling step, the laminate was set at room temperature for 24 hours. A high-temperature and high-humidity treatment step was performed after the settling step and before the measurement step. In the high-temperature and high-humidity treatment step, the laminate after the settling step was subjected to high-temperature and high-humidity treatment at 60°C, 93% relative humidity, and for 15 minutes. In the measurement step, instead of the first condition, a 180° peel test was performed under the second condition of 60°C, 93% relative humidity, a peel angle of 180°, and a pulling speed of 300 mm / min.

[0191] In the high temperature and high humidity peel test procedure, the peel length (total length) was set to 50 mm, and the average peel force measured between 10 mm and 40 mm of peel length was taken as the adhesive force. The adhesive force measured in the high temperature and high humidity peel test procedure was taken as the adhesive force Fh (N / 25 mm) and is shown in Tables 1 and 2.

[0192] <First Water Stripping Test>

[0193] The adhesive force Fw1 was measured by performing a first water peel test on each adhesive sheet of the comparative examples. The first water peel test was the same as the second ethanol peel test, except that the water supply step was performed instead of the ethanol supply step as described below.

[0194] Water supply steps: In the laminate after the settling step, 25 μL of water is supplied to the alkali glass plate of the laminate in such a way that the water contacts one end of the adhesive sheet at the interface between the water and the alkali glass plate and the adhesive sheet.

[0195] In the first water peel test, the peel length d1 at which the peel force begins to stabilize during the peeling process and the peel length d2 at which the peel force increases by 10% relative to the peel length d1 are determined. The average peel force measured from peel length d1 to peel length d2 is taken as the adhesive force. The adhesive force measured in the first water peel test is taken as the adhesive force Fw1 (N / 25mm) and shown in Tables 1 and 2.

[0196] <Second Water Stripping Test>

[0197] The adhesive force Fw2 was measured by performing a second water peel test on each adhesive sheet of the comparative examples. The second water peel test was the same as the first ethanol peel test, except that the water supply step was performed instead of the ethanol supply step described above.

[0198] In the second water peel test, the peel length d1 at which the peel force begins to stabilize during the peeling process and the peel length d2 at which the peel force increases by 10% relative to the peel length d1 are determined. The average peel force measured from peel length d1 to peel length d2 is taken as the adhesive force. The adhesive force measured in the second water peel test is taken as the adhesive force Fw2 (N / 25mm) and shown in Tables 1 and 2.

[0199] In the adhesive sheets of Comparative Examples 2 and 3, surfactants were used. As a result, the adhesive sheets of Comparative Examples 2 and 3 exhibited low adhesive strength Fw1 in the first water peel test, demonstrating water peelability. However, the adhesive sheets of Comparative Examples 2 and 3 also exhibited low adhesive strength Fh in the high temperature and high humidity peel test. Such adhesive sheets cannot ensure good adhesive reliability under high humidity conditions. Furthermore, the adhesive strength Fw2 of the adhesive sheets of Comparative Examples 2 and 3 increased significantly compared to the adhesive strength Fw1 in the second water peel test. That is, the adhesive sheets of Comparative Examples 2 and 3 could not maintain water peelability (and therefore lacked long-term reworkability).

[0200] Table 1

[0201] Table 2

[0202] 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 a limiting interpretation. All modifications of the present invention that will be apparent to those skilled in the art are included within the scope of the claims.

[0203] Industrial practicality

[0204] The alcohol-peelable optical adhesive sheet of the present invention is suitable for use in display panels such as liquid crystal panels and organic EL panels.

[0205] Label Explanation

[0206] 10. Adhesive sheet (alcohol-release optical adhesive sheet)

[0207] H Thickness direction

[0208] 11, 12 Adhesive surfaces

[0209] 21. Alkali glass plate

[0210] 22 Ethanol

[0211] L1, L2 peeling pads< / hsp>

Claims

1. An alcohol-release optical adhesive sheet, wherein, The alcohol-peelable optical adhesive sheet contains a photopolymer as the base polymer. The adhesive force Fn1 of the alcohol-peelable optical adhesive sheet is 9.0 N / 25 mm or more in the initial room temperature peel test described below. The adhesive force Fa1 of the alcohol-peelable optical adhesive sheet in the first ethanol peel test described below is less than 3.0 N / 25 mm. The adhesive force Fh of the alcohol-peelable optical adhesive sheet is greater than 2.0 N / 25 mm in the following high temperature and high humidity peel test. Initial room temperature peel test: First, a small piece of the alcohol-peelable optical adhesive sheet, 25 mm wide and 100 mm long, is bonded to an alkali glass plate made by the float glass process to obtain a laminate (preparation step); next, the laminate is subjected to heating and pressurization treatment at 50°C, 0.5 MPa, and 15 minutes (heating and pressurization step); next, the laminate is allowed to stand at room temperature for 72 hours (standing step); next, under the first conditions of 25°C, 50% relative humidity, 180° peel angle, and 300 mm / min, one end of the adhesive sheet in the longitudinal direction is pulled to peel the adhesive sheet from the alkali glass plate and the adhesive strength is measured (measurement step). First ethanol stripping test: Except for the following, it is the same as the initial room temperature peel test; In the settling step, the laminate is settling at 50°C for 168 hours; after the settling step and before the measurement step, an ethanol supply step is performed; in the ethanol supply step, 10 μL of ethanol is supplied to the alkali glass plate of the laminate in such a way that the ethanol contacts one end of the adhesive sheet at the interface between the alkali glass plate and the adhesive sheet. High temperature and high humidity peel test: Except for the following, it is the same as the initial room temperature peel test; In the settling step, the laminate is settling at room temperature for 24 hours; after the settling step and before the measurement step, a high temperature and high humidity treatment step is performed; in the high temperature and high humidity treatment step, the laminate after the settling step is subjected to high temperature and high humidity treatment at 60°C, 93% relative humidity and for 15 minutes; in the measurement step, instead of the first conditions, a 180° peel test is performed under the second conditions of 60°C, 93% relative humidity, peel angle of 180° and pulling speed of 300 mm / min.

2. The alcohol releasable optical adhesive sheet according to claim 1, wherein, The alcohol-peelable optical adhesive sheet exhibits an adhesive force Fa2 in the second ethanol peel test described below, wherein the adhesive force Fa1 varies with the adhesive force Fa2 by a rate of -50% to 100%. Second ethanol stripping test: Except that the laminate is left to stand at room temperature for 72 hours during the settling step, the process is the same as the first ethanol peel test.

3. The alcohol-peelable optical adhesive sheet according to claim 2, wherein, The duration of ethanol peeling in the second ethanol peeling test is more than 20 mm.

4. The alcohol-peelable optical adhesive sheet according to any one of claims 1 to 3, wherein, The alcohol-peelable optical adhesive sheet does not contain surfactants.

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