Optical adhesive sheet

Abstract

The adhesive sheet (10) of the present application is an optical adhesive sheet containing a base polymer and having photocurability. The base polymer is a photopolymer containing a polymerizable component of a monofunctional monomer and a photopolymerizable multifunctional compound. The adhesive sheet 10 has a shear storage modulus G1 of 0.3 MPa or less at 25°C. After ultraviolet irradiation curing is performed under the condition that the cumulative irradiation light amount is 3000 mJ / cm 2 The adhesive sheet 10 satisfies Bs ≥ -0.17G2 + 3.74 in the breaking strain Bs in a pulling test at 23°C and a pulling speed of 300 mm / min and the shear storage modulus G2 of the adhesive sheet 10 at 25°C after ultraviolet irradiation curing is performed under the condition that the cumulative irradiation light amount is 3000 mJ / cm

Description

Technical Field

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

[0002] Display panels, for example, have a laminated structure including elements such as pixel panels, polarizing films, and protective glass. During the manufacturing process of the display panel, optically transparent adhesive sheets (optical adhesive sheets) are used, for example, to bond the elements included in the laminated structure to each other. Optical adhesive sheets for display panel applications are described, for example, in Patent Document 1 below.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2010-97070 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] The laminated structure of a display panel includes elements with surface height differences. For example, a decorative or light-shielding printed layer is provided at the edge of the pixel panel side surface of the protective glass. The printed layer, for example, is provided across the entire edge of the protective glass. This printed layer has a specified thickness. Therefore, there is a height difference (printing height difference) between the surface of the protective glass and the surface of the printed layer on the pixel panel side of the protective glass. Therefore, optical adhesive sheets for display panel applications require flexibility (height difference following ability) to follow the degree of the printing height difference. Insufficient height difference following ability of the optical adhesive sheet is unsatisfactory, as it can cause air bubbles to form along the printed layer between the optical adhesive sheet adhered to the printed surface of the protective glass.

[0008] From the perspective of height difference tracking, a flexible optical adhesive sheet is preferred. However, the more flexible the conventional optical adhesive sheet, the lower its cohesiveness, which makes it easy for air bubbles to form at the interface between the substrate and the optical adhesive sheet (e.g., air bubbles formed with foreign objects as nuclei).

[0009] Therefore, from the viewpoint of suppressing air bubbles, high elasticity of the optical adhesive sheet (i.e., the adhesive forming the optical adhesive sheet) is required. However, the higher the elasticity of a conventional optical adhesive sheet, the more easily stress concentrates at the interface between the optical adhesive sheet and the substrate to which it is bonded. Under such stress concentration, the optical adhesive sheet is prone to peeling off from the substrate, which is undesirable (reduced bonding reliability). For example, in the manufacturing process of display panels, after two components are bonded using an optical adhesive sheet, the aforementioned stress concentration on the adhesive sheet can sometimes trigger peeling between the components due to physical stimulation of the adhesive sheet's ends, which is also undesirable.

[0010] For optical adhesive sheets, the adhesive design is required to not only have good height difference tracking when bonding between the adhered objects, but also to have high elasticity to suppress air bubbles at the interface with the adhered objects and stress relaxation to suppress peeling at the interface. The inventors have considered these considerations in the optical adhesive sheet and have completed the present invention.

[0011] The present invention provides an optical adhesive sheet that is suitable for achieving good height difference tracking when bonding between adhered objects, while also taking into account bubble suppression and bonding reliability after bonding between the adhered objects.

[0012] means for solving problems

[0013] The present invention [1] includes an optical adhesive sheet, the optical adhesive sheet comprising a base polymer and having photocurability, wherein the base polymer is a photopolymer comprising a polymerizable component of a monofunctional monomer and a photopolymerizable polyfunctional compound, the optical adhesive sheet having a shear storage modulus G1 of less than 0.3 MPa at 25°C, and a cumulative irradiation intensity of 3000 mJ / cm 2 After being cured by ultraviolet irradiation under certain conditions, the fracture strain Bs of the optical adhesive sheet in the tensile test at 23°C and a tensile speed of 300 mm / min satisfies the shear storage modulus G2 of the optical adhesive sheet at 25°C as Bs≥-0.17G2+3.74.

[0014] The present invention [2] includes the optical adhesive sheet described in [1] above, wherein the ratio of the shear storage modulus G2 to the shear storage modulus G1 is 300 or less.

[0015] The present invention [3] includes the optical adhesive sheet described in [1] or [2] above, wherein the fracture strain Bs is 2.0 or more.

[0016] The present invention [4] includes the optical adhesive sheet described in any one of [1] to [3] above, wherein the adhesive force F in the peel test described below is 2.0 N / 10 mm or more.

[0017] Peel test: First, a small piece of the optical adhesive sheet, 100 mm in length and 10 mm in width, is bonded to an alkali glass plate made using the float glass method to obtain a laminate. Next, the laminate is subjected to heat and pressure treatment at 50°C, 0.5 MPa, and 15 minutes. Then, it is subjected to a cumulative irradiation dose of 3000 mJ / cm². 2Under certain conditions, the adhesive sheet in the laminate is irradiated with ultraviolet light from the side of the alkali glass plate to cure it. Then, one end of the adhesive sheet in the longitudinal direction is pulled at 23°C, a peel angle of 180°, and a pulling speed of 300 mm / min to peel the adhesive sheet from the alkali glass plate, and the adhesive force F is measured.

[0018] Invention Effects

[0019] As described above, the optical adhesive sheet of the present invention has a shear storage modulus G1 of less than 0.3 MPa at 25°C and is photocurable. Such an optical adhesive sheet can be bonded to the surface of an object with a height difference in a soft state before curing by light irradiation (photocuring) (and can be photocured after bonding). Therefore, this optical adhesive sheet is suitable for achieving good height difference tracking in bonding objects with surfaces having height differences.

[0020] Furthermore, in the optical adhesive sheet of the present invention, as described above, the base polymer is a photopolymer comprising a polymeric component of a monofunctional monomer and a photopolymerizable polyfunctional compound. Such a base polymer has a network structure in which linear units derived from the monofunctional monomer are linked by the photopolymerizable polyfunctional compound. When the optical adhesive sheet is irradiated with light, the optical adhesive sheet comprising the base polymer with such a network structure is photocured. This is suitable for ensuring high elasticity in the photocured optical adhesive sheet.

[0021] Furthermore, as described above, after photocuring under specified conditions, the optical adhesive sheet of the present invention exhibits a fracture strain Bs in a tensile test at 23°C and a tensile speed of 300 mm / min, and a shear storage modulus G2 at 25°C satisfying Bs ≥ -0.17G2 + 3.74. This is suitable for achieving both high elasticity and stress relaxation in the photocured optical adhesive sheet. Moreover, the balance between high elasticity and stress relaxation in the photocured optical adhesive sheet used to bond the adhered materials contributes to achieving both bubble suppression and bonding reliability as described above.

[0022] Therefore, the optical adhesive sheet of the present invention is suitable for achieving good height difference tracking when bonding between adhered objects, and also takes into account bubble suppression and bonding reliability after bonding between adhered objects. Attached Figure Description

[0023] Figure 1 This is a schematic cross-sectional view of one embodiment of the optical adhesive sheet of the present invention.

[0024] Figure 2 shows Figure 1 An example of a method for manufacturing an optical adhesive sheet. Figure 2AThis indicates the process of forming a coating film of the adhesive composition. Figure 2B This indicates the process of forming the base adhesive sheet. Figure 2C This indicates a peeling process for a peeling liner. Figure 2D This indicates the process of adding components after the base adhesive sheet is supplied. Figure 2E This indicates the process of attaching the peeling backing to the adhesive sheet.

[0025] Figure 3 shows Figure 1 An example of how to use the optical adhesive sheet is shown. Figure 3A This refers to the process of attaching an optical adhesive sheet to a component (the object to be bonded). Figure 3B This refers to the process of joining components together using optical adhesive sheets. Figure 3C This refers to the process of photocuring optical adhesive sheets between components.

[0026] Figure 4 The graph is a plot of the measured results of the shear storage modulus G2 and fracture strain Bs of each adhesive sheet of the examples and comparative examples.

[0027] Figure 5 The positional relationship between the glass plate and the adhesive sheet in the laminate used in the evaluation of the height difference tracking of the embodiments and comparative examples is shown. Detailed Implementation

[0028] like Figure 1 As shown, the adhesive sheet 10, as an embodiment 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 (first adhesive surface) and an adhesive surface 12 (second adhesive surface) opposite to the adhesive surface 11. Figure 1 The images illustrate the state in which release liner 21 and 22 are attached to the adhesive surfaces 11 and 12 of the adhesive sheet 10. Release liner 21 is removably in contact with adhesive surface 11. Release liner 22 is removably in contact with adhesive surface 12.

[0029] The adhesive sheet 10 is an optically transparent adhesive sheet (optical adhesive sheet). The adhesive sheet 10 contains a base polymer and is photocurable. In this embodiment, the adhesive sheet 10 also contains a multifunctional monomer and a photopolymerization initiator, and is photocurable. Such an adhesive sheet 10 is, for example, an optical adhesive sheet to be disposed in a light-transmitting portion of a display panel. Examples of display panels include, for example, liquid crystal display panels and organic EL display panels. The display panel, for example, has a laminated structure including elements such as a pixel panel, a polarizing film, a touch panel, and a protective glass. 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.

[0030] A basic polymer is a photopolymer containing polymerizable components of monofunctional monomers and photopolymerizable polyfunctional compounds. Photopolymerization refers to a polymerization method in which polymerizable components undergo a polymerization reaction under the irradiation of active energy rays such as ultraviolet light. A photopolymer is a product formed through such a polymerization method. Such a basic polymer has a network structure in which linear units derived from monofunctional monomers are linked together by photopolymerizable polyfunctional compounds acting as crosslinking agents.

[0031] The adhesive sheet 10 has a shear storage modulus G1 (elastic modulus before curing) of less than 0.3 MPa at 25°C. The method for measuring the shear storage modulus G1 is as described in the examples below. Additionally, the adhesive sheet 10 is subjected to cumulative irradiation of 3000 mJ / cm². 2 After curing under ultraviolet irradiation under certain conditions, the fracture strain Bs in the tensile test at 23°C and a tensile speed of 300 mm / min satisfies the shear storage modulus G2 (elastic modulus after curing) at 25°C as Bs ≥ -0.17G2 + 3.74. Fracture strain Bs refers to the ratio (ΔL / L0) of the elongation length ΔL of the test piece at the moment of fracture of the adhesive sheet 10 in the tensile test to the initial length L0 of the test piece. The elongation length ΔL refers to the amount of elongation measured from the initial length L0 of the test piece. The method for measuring fracture strain Bs is as described in the examples below. Furthermore, the thickness of the adhesive sheet 10 in the measurement of fracture strain Bs is 420 μm ± 80 μm. If the thickness of the adhesive sheet 10 is within the above range, equivalent evaluation can be obtained. Alternatively, multiple adhesive sheets 10 can be manufactured separately and stacked to ensure that the thickness of the adhesive sheet 10 is within the above range. In addition, the method for determining the shear storage modulus G2 is as described in the examples below.

[0032] As described above, the adhesive sheet 10 has a shear storage modulus G1 of less than 0.3 MPa at 25°C and is photocurable. Such an adhesive sheet 10 can be bonded to the surface of an object with a height difference in a soft state before curing by light irradiation (photocuring) (and can be photocured after bonding). Therefore, the adhesive sheet 10 is suitable for achieving good height difference tracking in bonding objects with surfaces of varying heights.

[0033] Furthermore, in the adhesive sheet 10, as described above, the base polymer is a photopolymer containing a polymerizable component of a monofunctional monomer and a photopolymerizable polyfunctional compound. Such a base polymer, as described above, has a network structure. When the adhesive sheet 10 is irradiated with light, the adhesive sheet 10 containing such a network structure of base polymer is photocured. This is suitable for ensuring high elasticity properties in the photocured adhesive sheet 10.

[0034] Furthermore, as described above, after photocuring under specified conditions, the adhesive sheet 10 exhibits a fracture strain Bs at 23°C and a pulling speed of 300 mm / min, and a shear storage modulus G2 at 25°C, satisfying Bs ≥ -0.17G2 + 3.74. This is suitable for achieving both high elasticity and stress relaxation properties in the photocured adhesive sheet 10. Moreover, the balance between high elastic modulus and stress relaxation properties in the photocured adhesive sheet 10 for bonding the adhered materials contributes to achieving both bubble suppression and bonding reliability as mentioned above.

[0035] Therefore, the adhesive sheet 10 is suitable for achieving good height difference tracking when bonding between adhered objects, and also takes into account bubble suppression and bonding reliability after bonding between adhered objects.

[0036] From the viewpoint of the height difference tracking of the adhesive sheet 10 before photocuring, the shear storage modulus G1 is preferably 0.25 MPa or less, more preferably 0.2 MPa or less, more preferably 0.18 MPa or less, more preferably 0.16 MPa or less, more preferably 0.15 MPa or less, more preferably 0.14 MPa or less, more preferably 0.12 MPa or less, more preferably 0.10 MPa or less, and more preferably 0.09 MPa or less. From the viewpoint of ensuring the ease of handling of the adhesive sheet 10 before photocuring, the shear storage modulus G1 is preferably 0.03 MPa or more, more preferably 0.04 MPa or more. As a method for adjusting the shear storage modulus G1, examples include the selection of the type of base polymer in the adhesive sheet 10, the adjustment of the molecular weight, and the adjustment of the compounding amount (the adjustment methods for shear storage modulus G2 and shear storage modulus G3 described later are also the same). The selection of the type of base polymer includes the adjustment of the composition of the monomers forming the base polymer.

[0037] From the viewpoint of suppressing the formation of air bubbles between the adhered objects and the adhesive sheet 10 when the adhered objects are bonded together using the photocured adhesive sheet 10 (air bubble suppression viewpoint), the shear storage modulus G2 is preferably 0.5 MPa or more, more preferably 0.55 MPa or more, more preferably 0.6 MPa or more, more preferably 0.65 MPa or more, more preferably 0.7 MPa or more, more preferably 0.8 MPa or more, more preferably 0.9 MPa or more, more preferably 1 MPa or more, more preferably 1.1 MPa or more, and more preferably 1.2 MPa or more. From the viewpoint of suppressing the adhesive sheet 10 from peeling off from the adhered objects due to the stress concentration mentioned above, the shear storage modulus G2 is preferably 12 MPa or less, more preferably 8 MPa or less, further preferably 5 MPa or less, and even more preferably 3.5 MPa or less.

[0038] From the perspective of balancing the height difference tracking and bubble suppression, the ratio of shear storage modulus G2 to shear storage modulus G1 (G2 / G1) is preferably 3 or more, more preferably 5 or more, and preferably 300 or less, more preferably 200 or less, even more preferably 100 or less, even more preferably 60 or less, and even more preferably 40 or less.

[0039] From the viewpoint of suppressing the formation of air bubbles between the adhered objects and the adhesive sheet 10 under high temperature conditions when the adhesive sheet 10 is in a state of bonding between the adhered objects after photocuring, the cumulative irradiation intensity of the adhesive sheet 10 is 3000 mJ / cm. 2 The shear storage modulus G3 at 70°C after curing by light irradiation is preferably 0.1 MPa or more, more preferably 0.2 MPa or more. From the viewpoint of suppressing the peeling of the adhesive sheet 10 from the adherend caused by the stress concentration described above under high-temperature conditions, the shear storage modulus G3 is preferably 3 MPa or less, more preferably 2.7 MPa or less, more preferably 2.4 MPa or less, more preferably 2.1 MPa or less, more preferably 1.8 MPa or less, and more preferably 1.6 MPa or less. The method for measuring the shear storage modulus G3 is as described in the examples described later.

[0040] From the viewpoint of ensuring stress relaxation in the adhesive sheet 10, the fracture strain Bs of the adhesive sheet 10 is preferably 2.0 or more, more preferably 2.5 or more, further preferably 3.0 or more, and even more preferably 3.5 or more. From the viewpoint of suppressing excessive deformation of the adhesive sheet 10, the fracture strain Bs is preferably 30 or less, more preferably 28 or less, more preferably 26 or less, more preferably 24 or less, more preferably 22 or less, more preferably 20 or less, more preferably 18 or less, more preferably 16 or less, more preferably 14 or less, more preferably 12 or less, and more preferably 10 or less. In addition, from the viewpoint of suppressing excessive deformation of the adhesive sheet 10, the fracture strain Bs preferably satisfies Bs ≤ -0.17G2 + 6.0.

[0041] From the perspective of balancing stress relaxation and bubble suppression, the ratio of fracture strain Bs to shear storage modulus G2 (Bs / G2) is preferably 0.2 or more, more preferably 0.5 or more, more preferably 0.7 or more, more preferably 0.8 or more, more preferably 0.9 or more, more preferably 1.0 or more, more preferably 1.2 or more, more preferably 1.4 or more, more preferably 1.5 or more, more preferably 1.7 or more, more preferably 1.8 or more, more preferably 1.9 or more, and preferably 12 or less, more preferably 10 or less, more preferably 9.0 or less, and more preferably 8.0 or less.

[0042] From the viewpoint of the aforementioned bonding reliability, the adhesive force F of the adhesive sheet 10 in the peel test described below is preferably 2.0 N / 10 mm or more, more preferably 2.5 N / 10 mm or more, more preferably 3.0 N / 10 mm or more, more preferably 3.5 N / 10 mm or more, more preferably 4.0 N / 10 mm or more, more preferably 4.5 N / 10 mm or more, more preferably 5.0 N / 10 mm or more, more preferably 5.5 N / 10 mm or more, and more preferably 6.0 N / 10 mm or more. The adhesive force F refers to the adhesive force to alkali glass (adhesive force to alkali glass).

[0043] Peel test: First, a small adhesive sheet 10, 100 mm in length and 10 mm in width, is bonded to an alkali glass plate manufactured using the float glass process to obtain a laminate. The small adhesive sheet is bonded to the air side (non-tin side) of the alkali glass plate. The air side refers to the exposed surface of the alkali glass plate (the side opposite to the surface in contact with the molten metal) during the manufacturing process. Next, the laminate is subjected to heat and pressure treatment at 50°C, 0.5 MPa, and 15 minutes. Then, it is subjected to a cumulative irradiation dose of 3000 mJ / cm². 2 Under certain conditions, the adhesive sheet pieces in the laminate are irradiated with ultraviolet light from the alkali glass plate side to cure them. Then, at 23°C, a peel angle of 180°, and a pulling speed of 300 mm / min, one end of the adhesive sheet piece is pulled along its length to peel it off from the alkali glass plate, and the adhesive force F is measured. More specifically, the method for measuring the adhesive force F is as described in the examples below.

[0044] Methods for adjusting the adhesive force F include, for example, the selection of the type of base polymer in the adhesive sheet 10, the adjustment of its molecular weight, the adjustment of its degree of crosslinking, and the adjustment of its compounding amount. The selection of the type of base polymer includes adjusting the composition of the monomers forming the base polymer. Methods for adjusting the adhesive force F include the selection of the types of components other than the base polymer in the adhesive sheet 10, and the adjustment of the compounding amount of these components. Examples of these components include photopolymerizable multifunctional compounds, photopolymerization initiators, silane coupling agents, and oligomers.

[0045] The base polymer is preferably an acrylic polymer. An acrylic polymer is a copolymer containing a polymerizable component of alkyl (meth)acrylate in a proportion of 50% by mass or more. That is, the monofunctional monomer preferably contains an alkyl (meth)acrylate.

[0046] “(Meth)acrylic acid” refers to acrylic acid and / or methacrylic acid.

[0047] Alkyl methacrylates are preferably alkyl methacrylates having an alkyl group having 1 to 20 carbon atoms. Examples of such alkyl methacrylates include: methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, sec-butyl methacrylate, tert-butyl methacrylate, amyl methacrylate, isoamyl methacrylate, neopentyl methacrylate, hexyl methacrylate, heptyl methacrylate, 2-ethylhexyl methacrylate, n-octyl methacrylate, isooctyl methacrylate, nonyl methacrylate, and so on. Isononyl acrylate, n-decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, n-tridecyl (meth)acrylate, isotridecyl (meth)acrylate, tetradecyl (meth)acrylate, isotetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecanyl (meth)acrylate, n-octadecyl (meth)acrylate, isooctadecyl (meth)acrylate, and nonadecanyl (meth)acrylate. Alkyl (meth)acrylates can be used alone or in combination with two or more. Preferably, an alkyl (meth)acrylate is at least one selected from the group consisting of n-butyl acrylate (BA) and 2-ethylhexyl acrylate (2EHA).

[0048] From the viewpoint of appropriately exhibiting basic properties such as adhesion in the adhesive sheet 10, the proportion of (meth)acrylate alkyl ester in the monofunctional monomer is preferably 60% by mass or more, more preferably 62% by mass or more, more preferably 64% by mass or more, more preferably 65% ​​by mass or more, more preferably 67% by mass or more, more preferably 68% by mass or more, and more preferably 70% by mass or more. This proportion is, for example, 99.9% by mass or less, 99.5% by mass or less, or 99% by mass or less.

[0049] Monofunctional monomers may include copolymerizable monomers capable of copolymerizing with alkyl (meth)acrylates. Examples of copolymerizable monomers include monomers containing polar groups. Examples of monomers containing polar groups include hydroxyl-containing monomers, carboxyl-containing monomers, and monomers having a nitrogen-containing ring. 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 a nitrogen-containing ring.

[0050] 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) and 4-hydroxybutyl acrylate (4HBA).

[0051] From the viewpoint of ensuring the cohesiveness of the adhesive sheet 10, the proportion of hydroxyl-containing monomers in the monofunctional monomers is preferably 1% by mass or more, more preferably 2% by mass or more, more preferably 3% by mass or more, more preferably 5% by mass or more, more preferably 6% by mass or more, more preferably 7% by mass or more, and more preferably 8% by mass or more. From the viewpoint of adjusting the polarity of the acrylic polymer (which relates to the compatibility between the various additive components in the adhesive sheet 10 and the acrylic polymer), this proportion is preferably 30% by mass or less, more preferably 28% by mass or less, more preferably 26% by mass or less, more preferably 24% by mass or less, more preferably 22% by mass or less, more preferably 20% by mass or less, more preferably 18% by mass or less, more preferably 16% by mass or less, and more preferably 15% by mass or less.

[0052] 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.

[0053] From the viewpoint of avoiding the risk of acid corrosion to the adhered material, the proportion of carboxyl-containing monomers in the monofunctional monomer is preferably 3% by mass or less, more preferably 1% by mass or less, further preferably 0.5% by mass or less, and even more preferably 0.1% by mass or less.

[0054] 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. The monomer having a nitrogen-containing ring is preferably at least one selected from the group consisting of N-vinylpyrrolidone (NVP) and acryloylmorpholine (ACMO).

[0055] From the viewpoint of ensuring the cohesiveness of the adhesive sheet 10 and its adhesion to the adhered object, the proportion of the monomer having a nitrogen-containing ring in the monofunctional monomer is preferably 1% by mass or more, more preferably 2% by mass or more, more preferably 3% by mass or more, more preferably 5% by mass or more, more preferably 6% by mass or more, more preferably 7% by mass or more, and more preferably 8% by mass or more. From the viewpoint of adjusting the glass transition temperature of the acrylic polymer and adjusting the polarity of the acrylic polymer (which relates to the compatibility between the various additive components in the adhesive sheet and the acrylic polymer), this proportion is preferably 30% by mass or less, more preferably 28% by mass or less, more preferably 26% by mass or less, more preferably 24% by mass or less, more preferably 22% by mass or less, and more preferably 20% by mass or less.

[0056] Examples of photopolymerizable multifunctional compounds include, for example, multifunctional oligomers and multifunctional monomers.

[0057] Examples of multifunctional oligomers include: urethane acrylate oligomers (oligomers having a urethane backbone and two or more acryloyl groups), epoxy acrylate oligomers (oligomers having an epoxy backbone and two or more acryloyl groups), and polysiloxane acrylate oligomers (oligomers having a siloxane backbone and two or more acryloyl groups). Commercially available urethane acrylate oligomers include, for example, ArtResin UN-333, UN-350, UN-353, UN-5500, and UN-5590 manufactured by Nekami Industries, Ltd.

[0058] From the viewpoint of compatibility between monofunctional monomers and polyfunctional oligomers, the weight-average molecular weight (Mw) of the polyfunctional oligomers is preferably 5000 or more, and more preferably 20000 or less, and even more preferably 15000 or less. The weight-average molecular weight is determined by gel permeation chromatography (GPC) and calculated by conversion to polystyrene.

[0059] Examples of multifunctional monomers include polyfunctional (meth)acrylates containing two or more olefinic unsaturated double bonds in one molecule. From the viewpoint of easily introducing cross-linking structures through photopolymerization, polyfunctional (meth)acrylates are preferred as multifunctional monomers. Examples of polyfunctional (meth)acrylates include difunctional (meth)acrylates, trifunctional (meth)acrylates, and polyfunctional (meth)acrylates with four or more functions.

[0060] Examples of difunctional (meth)acrylates include ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, 1,6-hexanediol dimethacrylate, 1,9-nonanediol dimethacrylate, glycerol dimethacrylate, neopentyl glycol dimethacrylate, stearic acid modified pentaerythritol dimethacrylate, dihydrodicyclopentadienyl acrylate, and di(meth)acryloyl isocyanurate.

[0061] Examples of trifunctional (meth)acrylates include: trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, and tri(acryloyloxyethyl) isocyanurate.

[0062] 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.

[0063] Photopolymerizable multifunctional compounds can be used alone or in combination of two or more. Preferably, the photopolymerizable multifunctional compound is a multifunctional oligomer, more preferably a urethane acrylate oligomer.

[0064] From the viewpoint of achieving good bonding reliability in the photocured adhesive sheet 10 that bonds the materials to be bonded, the amount of photopolymerizable polyfunctional compound is preferably 0.1 parts by mass or more, more preferably 0.3 parts by mass or more, and even more preferably 0.5 parts by mass or more, relative to 100 parts by mass of the monofunctional monomer. From the viewpoint of ensuring flexibility and achieving good height difference tracking, the amount of photopolymerizable polyfunctional compound is preferably 2.0 parts by mass or less, more preferably 1.8 parts by mass or less, more preferably 1.6 parts by mass or less, more preferably 1.4 parts by mass or less, more preferably 1.2 parts by mass or less, more preferably 1.0 parts by mass or less, and even more preferably 0.8 parts by mass or less, relative to 100 parts by mass of the monofunctional monomer.

[0065] A basic polymer can be formed by photopolymerizing a polymerizable component containing a monofunctional monomer and a photopolymerizable polyfunctional compound. Examples of photopolymerization include photopolymerization by ultraviolet irradiation. The polymerizable component (monofunctional monomer, photopolymerizable polyfunctional compound) can be polymerized in one step or in multiple steps. In a multi-step polymerization method, firstly, a prepolymer composition containing a portion of the polymer (a mixture of low-degree polymers and unreacted monofunctional monomers) is prepared by polymerizing the monofunctional monomer (prepolymerization). Next, a photopolymerizable polyfunctional compound is added to the prepolymer composition, and a polymerization reaction (main polymerization) is carried out in a reaction system containing the portion of the polymer and the photopolymerizable polyfunctional compound. A photopolymerization initiator is used as the polymerization initiator.

[0066] Examples of photopolymerization initiators include: free radical photopolymerization initiators, cationic photopolymerization initiators, and anionic photopolymerization initiators.

[0067] Examples of free radical photopolymerization initiators include: acylphosphine oxide photopolymerization initiators, benzoin ether photopolymerization initiators, acetophenone photopolymerization initiators, α-keto alcohol photopolymerization initiators, aromatic sulfonyl chloride photopolymerization initiators, photoactive oxime photopolymerization initiators, benzoin photopolymerization initiators, benzoyl photopolymerization initiators, ketal photopolymerization initiators, and thioxanone photopolymerization initiators.

[0068] 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-2-phenylacetophenone. Examples of acetophenone photopolymerization initiators include: 2,2-diethoxyacetophenone, 1-hydroxycyclohexylphenyl ketone, 4-phenoxydichloroacetophenone, and 4-(tert-butyl)dichloroacetophenone. Examples of α-keto alcohol photopolymerization 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. Examples of photoactive oxime photopolymerization initiators include 1-phenyl-1,1-propanedione-2-(O-ethoxycarbonyl)-oxime. Examples of benzoin photopolymerization initiators include benzoin. Examples of benzoyl photopolymerization initiators include benzoyl. Examples of benzophenone photopolymerization initiators include benzoyl. Examples of benzophenone photopolymerization initiators include benzophenone, benzoylbenzoic acid, 3,3'-dimethyl-4-methoxybenzophenone, and poly(vinylbenzophenone). Examples of ketal photopolymerization initiators include benzoyl dimethyl ketal. Examples of photopolymerization initiators for thioxanthone include: thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-diisopropylthioxanthone, and dodecylthioxanthone. The photopolymerization initiator 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.

[0069] The amount of photopolymerization initiator (first photopolymerization initiator) used in the prepolymerization process relative to 100 parts by mass of the monofunctional monomer (the total amount of multiple photopolymerization initiators if multiple photopolymerization initiators are used) is, for example, 0.02 parts by mass or more, preferably 0.04 parts by mass or more, more preferably 0.06 parts by mass or more, and, for example, 1.0 parts by mass or less, preferably 0.8 parts by mass or less, more preferably 0.6 parts by mass or less, more preferably 0.5 parts by mass or less, more preferably 0.4 parts by mass or less, more preferably 0.3 parts by mass or less, more preferably 0.2 parts by mass or less, and more preferably 0.1 parts by mass or less. Relative to 100 parts by mass of the polymerizable component (monofunctional monomer, photopolymerizable polyfunctional compound), the amount of photopolymerization initiator (second photopolymerization initiator) used in the main polymerization (the total amount of multiple photopolymerization initiators if multiple photopolymerization initiators are used) is, for example, 0.1 parts by mass or more, preferably 0.2 parts by mass or more, more preferably 0.3 parts by mass or more, and, for example, 2.0 parts by mass or less, preferably 1.8 parts by mass or less, more preferably 1.6 parts by mass or less, more preferably 1.4 parts by mass or less, more preferably 1.2 parts by mass or less, more preferably 1.0 parts by mass or less, and more preferably 0.8 parts by mass or less.

[0070] From the viewpoint of ensuring the cohesiveness of the adhesive sheet 10, the weight-average molecular weight (Mw) of the base polymer is preferably 500,000 or more, more preferably 600,000 or more, and even more preferably 800,000 or more. From the viewpoint of ensuring the height difference tracking of the adhesive sheet 10, the weight-average molecular weight of the base polymer is preferably 1,200,000 or less, more preferably 1,100,000 or less, and even more preferably 1,000,000 or less. The weight-average molecular weight of the base polymer is determined by gel permeation chromatography (GPC) and calculated by conversion to polystyrene.

[0071] From the viewpoint of ensuring sufficient flexibility in the adhesive sheet 10 before photocuring, the glass transition temperature (Tg) of the base polymer is preferably below 10°C, more preferably below 8°C, more preferably below 6°C, more preferably below 4°C, more preferably below 2°C, more preferably below 0°C, more preferably below -2°C, more preferably below -4°C, more preferably below -6°C, more preferably below -8°C, more preferably below -10°C, more preferably below -12°C, more preferably below -14°C, more preferably below -16°C, more preferably below -18°C, more preferably below -20°C, more preferably below -22°C, more preferably below -24°C, more preferably below -26°C, more preferably below -28°C, more preferably below -30°C, more preferably below -32°C, more preferably below -34°C, more preferably below -36°C, more preferably below -38°C, and more preferably below -40°C. This glass transition temperature is, for example, above -80°C.

[0072] 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.

[0073] Fox formula: 1 / (273+Tg)=Σ[Wi / (273+Tgi)]

[0074] The multifunctional monomers in the adhesive sheet 10 include multifunctional monomers containing cyclic structures. Examples of multifunctional monomers containing cyclic structures include alicyclic multifunctional monomers and aromatic multifunctional monomers. The cyclic structure of an alicyclic multifunctional monomer can be a monocyclic ring, a fused ring of multiple rings, or a bridging ring structure. That is, an alicyclic multifunctional monomer can be a monocyclic alicyclic multifunctional monomer with or without a bridging structure, or a fused ring alicyclic multifunctional monomer with or without a bridging structure. Examples of cyclic structures for alicyclic multifunctional monomers include norbornene, tricyclodecane, tetracyclododecane, pentacyclopentadecane, adamantane, and disadamantane. The cyclic structure of an aromatic multifunctional monomer can be a monocyclic ring, a fused ring of multiple rings, or a bridging ring structure. That is, the polyfunctional monomer containing an aromatic ring can be a monocyclic polyfunctional monomer containing an aromatic ring with or without a bridging structure, or a fused-ring polyfunctional monomer containing an aromatic ring with or without a bridging structure. In addition, the polyfunctional monomer containing a cyclic structure can be a difunctional monomer or a polyfunctional monomer with three or more functions.

[0075] Examples of alicyclic multifunctional monomers include: tricyclodecanediethanol diacrylate, tricyclodecanediethanol dimethacrylate, tris(2-acryloyloxyethyl) isocyanurate, and bis(vinyl sulfone)tricyclo[5.2.1.0] 2 ,6Decane. Examples of polyfunctional monomers containing aromatic rings include ethoxylated bisphenol A diacrylate (BPAEODE). Polyfunctional monomers containing cyclic structures are preferably alicyclic polyfunctional monomers, more preferably fused-ring alicyclic polyfunctional monomers, even more preferably fused-ring alicyclic polyfunctional monomers with bridging structures, and even more preferably at least one selected from the group consisting of tricyclodecanediethanol diacrylate and tricyclodecanediethanol dimethacrylate.

[0076] From the perspective of balancing the high elasticity and stress relaxation properties of the photocured optical adhesive sheet, the molecular weight Me between the entanglement points of the homopolymer containing the cyclic polyfunctional monomer is preferably 10 or more, more preferably 20 or more, more preferably 40 or more, more preferably 60 or more, more preferably 80 or more, more preferably 100 or more, and preferably 400,000 or less, more preferably 380,000 or less, more preferably 360,000 or less, more preferably 340,000 or less, more preferably 320,000 or less, more preferably 300,000 or less, more preferably 270,000 or less, more preferably 250,000 or less, more preferably 230,000 or less, more preferably 200,000 or less, more preferably 1,700,000 or less, more preferably 150,000 or less, more preferably 130,000 or less, more preferably 100,000 or less, more preferably 80,000 or less, more preferably 60,000 or less, more preferably 50,000 or less.

[0077] From the viewpoint of high elasticity of the photocured adhesive sheet 10, the content of polyfunctional monomers containing cyclic structures in the adhesive sheet 10, relative to 100 parts by mass of the base polymer, is preferably 5 parts by mass or more, more preferably 5.5 parts by mass or more, more preferably 6 parts by mass or more, more preferably 6.5 parts by mass or more, more preferably 7 parts by mass or more, more preferably 8 parts by mass or more, more preferably 9 parts by mass or more, and more preferably 10 parts by mass or more. From the viewpoint of stress relaxation of the photocured adhesive sheet 10, the content of polyfunctional monomers containing cyclic structures in the adhesive sheet 10, relative to 100 parts by mass of the base polymer, is preferably 50 parts by mass or less, more preferably 48 parts by mass or less, more preferably 46 parts by mass or less, more preferably 45 parts by mass or less, more preferably 43 parts by mass or less, more preferably 41 parts by mass or less, and more preferably 40 parts by mass or less.

[0078] Multifunctional monomers may include multifunctional monomers that do not contain cyclic structures (non-cyclic multifunctional monomers). Examples of such multifunctional monomers include the multifunctional monomers mentioned above, i.e., multifunctional monomers that are photopolymerizable multifunctional compounds. From the viewpoint of stress relaxation properties of the photocured adhesive sheet 10, the adhesive sheet 10 preferably does not contain multifunctional monomers that do not contain cyclic structures.

[0079] As a photopolymerization initiator (third photopolymerization initiator) in the adhesive sheet 10, examples include free radical photopolymerization initiators, cationic photopolymerization initiators, and anionic photopolymerization initiators. Specifically, the photopolymerization initiators described above regarding the photopolymerization of the base polymer can be listed.

[0080] From the viewpoint of ensuring good photocurability in the adhesive sheet 10, the content of the photopolymerization initiator (third photopolymerization initiator) in the adhesive sheet 10 is preferably 0.1 parts by mass or more, more preferably 0.15 parts by mass or more, more preferably 0.18 parts by mass or more, more preferably 0.2 parts by mass or more, more preferably 0.22 parts by mass or more, more preferably 0.24 parts by mass or more, more preferably 0.25 parts by mass or more, and preferably 3.0 parts by mass or less, more preferably 2.8 parts by mass or less, more preferably 2.6 parts by mass or less, more preferably 2.4 parts by mass or less, more preferably 2.2 parts by mass or less, more preferably 2.0 parts by mass or less, more preferably 1.9 parts by mass or less, more preferably 1.8 parts by mass or less, more preferably 1.7 parts by mass or less, more preferably 1.6 parts by mass or less, more preferably 1.5 parts by mass or less, more preferably 1.3 parts by mass or less, and more preferably 1.0 parts by mass or less, relative to 100 parts by mass.

[0081] The adhesive sheet 10 may contain other components. Examples of such other components include oligomers, UV absorbers, antioxidants, silane coupling agents, and rust inhibitors.

[0082] When the base polymer is an acrylic polymer, the oligomer is preferably an acrylic oligomer. An acrylic oligomer is a copolymer containing a polymerizable component of (meth)acrylate in a proportion of 50% by mass or more, and has a weight-average molecular weight of, for example, 1,000 or more and 30,000 or less.

[0083] The acrylic oligomers are preferably polymers containing polymerizable components of alkyl (meth)acrylates having chain alkyl groups ((meth)acrylate chain alkyl esters) and alkyl (meth)acrylates having alicyclic alkyl groups ((meth)acrylate alicyclic alkyl esters). Specific examples of these alkyl (meth)acrylates include, for instance, the alkyl (meth)acrylates described above as polymerizable components of acrylic polymers.

[0084] Methyl methacrylate is preferred as a (meth)acrylate chain alkyl ester from the perspective of high glass transition temperature and excellent compatibility with the base polymer. Tetrahydrodicyclopentadienyl acrylate, tetrahydrodicyclopentadienyl methacrylate, cyclohexyl acrylate, and cyclohexyl methacrylate are preferred as (meth)acrylate alicyclic alkyl esters. That is, the acrylic oligomer is preferably a polymer comprising one or more polymerizable components selected from the group consisting of tetrahydrodicyclopentadienyl acrylate, tetrahydrodicyclopentadienyl methacrylate, cyclohexyl acrylate, and cyclohexyl methacrylate, and methyl methacrylate.

[0085] The proportion of (meth)acrylate cyclic alkyl esters in the polymerizable component of acrylic oligomers is preferably 10% by mass or more, more preferably 12% by mass or more, more preferably 14% by mass or more, more preferably 16% by mass or more, more preferably 18% by mass or more, more preferably 20% by mass or more, more preferably 22% by mass or more, more preferably 24% by mass or more, more preferably 26% by mass or more, more preferably 28% by mass or more, and more preferably 30% by mass or more. This proportion is preferably 90% by mass or less, more preferably 88% by mass or less, more preferably 86% by mass or less, more preferably 84% by mass or less, more preferably 82% by mass or less, more preferably 80% by mass or less, more preferably 78% by mass or less, more preferably 76% by mass or less, more preferably 74% by mass or less, more preferably 72% by mass or less, and more preferably 70% by mass or less. The proportion of (meth)acrylate chain alkyl esters in the polymerizable component of acrylic oligomers is preferably 90% by mass or less, more preferably 88% by mass or less, more preferably 86% by mass or less, more preferably 84% by mass or less, more preferably 82% by mass or less, more preferably 80% by mass or less, more preferably 78% by mass or less, more preferably 76% by mass or less, more preferably 74% by mass or less, more preferably 72% by mass or less, and more preferably 70% by mass or less. This proportion is preferably 10% by mass or more, more preferably 12% by mass or more, more preferably 14% by mass or more, more preferably 16% by mass or more, more preferably 18% by mass or more, more preferably 20% by mass or more, more preferably 22% by mass or more, more preferably 24% by mass or more, more preferably 26% by mass or more, more preferably 28% by mass or more, and more preferably 30% by mass or more.

[0086] Acrylic oligomers are obtained by polymerizing the polymerizable components of the acrylic oligomer. Examples of polymerization methods include solution polymerization, bulk polymerization, and emulsion polymerization. Acrylic oligomers are preferably formed by solution polymerization. Examples of solvents used in solution polymerization include toluene and ethyl acetate. In the polymerization of acrylic oligomers, thermal polymerization initiators can be used, and chain transfer agents can be used to adjust the molecular weight. Furthermore, in this embodiment, after the acrylic oligomer is formed, the low-molecular-weight components and solvents are removed by heating to evaporate them from the reaction system, such as the reaction solution. Examples of low-molecular-weight components include unreacted monomers, chain transfer agents, thermal polymerization initiators, and their decomposition products (residues).

[0087] Examples of thermal polymerization initiators include azo polymerization initiators and peroxide polymerization initiators. Examples of azo polymerization initiators include 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), and dimethyl 2,2'-azobis(2-methylpropionic acid). Examples of peroxide polymerization initiators include benzoyl peroxide, tert-butyl maleate peroxide, and lauroyl peroxide.

[0088] Examples of chain transfer agents include α-thioglycerol, lauryl thiol, glycidyl thiol, mercaptoacetic acid, 2-mercaptoethanol, thioglycolic acid, 2-ethylhexyl thioglycolic acid, 2,3-dimercapto-1-propanol, and α-methylstyrene dimer.

[0089] From the viewpoint of ensuring the adhesive strength of the adhesive sheet 10, the weight-average molecular weight (Mw) of the oligomer is preferably 1000 or more, more preferably 1200 or more, more preferably 1400 or more, more preferably 1500 or more, more preferably 1700 or more, more preferably 1800 or more, more preferably 2000 or more, and preferably 30000 or less, more preferably 27000 or less, more preferably 25000 or less, more preferably 23000 or less, more preferably 20000 or less, more preferably 17000 or less, more preferably 15000 or less, more preferably 13000 or less, more preferably 10000 or less, and more preferably 8000 or less. The weight-average molecular weight of the oligomer is determined by gel permeation chromatography (GPC) and calculated by conversion to polystyrene. The method for determining the Mw of the oligomer is specifically described in the examples described later.

[0090] From the viewpoint of ensuring the adhesive strength of the adhesive sheet 10, the content of oligomers in the adhesive sheet 10 is preferably 0.05 parts by mass or more, more preferably 0.07 parts by mass or more, more preferably 0.09 parts by mass or more, more preferably 0.1 parts by mass or more, more preferably 0.12 parts by mass or more, more preferably 0.14 parts by mass or more, more preferably 0.16 parts by mass or more, more preferably 0.18 parts by mass or more, and more preferably 0.2 parts by mass or more, relative to 100 parts by mass of the base polymer. From the viewpoint of ensuring the transparency of the adhesive sheet 10, the content of oligomers in the adhesive sheet 10 is preferably 5 parts by mass or less, more preferably 4.7 parts by mass or less, more preferably 4.5 parts by mass or less, more preferably 4.3 parts by mass or less, more preferably 4 parts by mass or less, more preferably 3.7 parts by mass or less, more preferably 3.6 parts by mass or less, and more preferably 3.5 parts by mass or less, relative to 100 parts by mass of the base polymer.

[0091] Examples of UV absorbers include triazine UV absorbers, benzotriazole UV absorbers, benzophenone UV absorbers, salicylate UV absorbers, and cyanoacrylate UV absorbers. Considering their high absorption of UV light in the 320nm–370nm wavelength range and excellent compatibility with acrylic polymers, triazine UV absorbers are preferred. UV absorbers can be used alone or in combination of two or more.

[0092] Commercially available triazine-based ultraviolet absorbers include, for example: bis(ethylhexyloxyphenol)methoxyphenyltriazine (brand name "Tinosorb S", manufactured by BASF), the reaction product of 2-(4,6-bis(2,4-dimethylphenyl)-1,3,5-triazin-2-yl)-5-hydroxyphenyl with [(alkoxy)methyl]ethylene oxide (brand name "TINUVIN 400", manufactured by BASF), the reaction product of 2-(2,4-dihydroxyphenyl)-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine with (2-ethylhexyl)glycidyl ester (brand name "TINUVIN 405", manufactured by BASF), and (2,4-bis[2-hydroxy-4-butoxyphenyl]-6-(2,4-dibutoxyphenyl)-1,3,5-triazine) (brand name "TINUVIN"). 460, manufactured by BASF), 2-(4,6-diphenyl-1,3,5-triazin-2-yl)-5-[(hexyl)oxy]-phenol (brand name "TINUVIN 577", manufactured by BASF), 2-(2-hydroxy-4-[1-octoxycarbonylethoxy]phenyl)-4,6-bis(4-phenylphenyl)-1,3,5-triazine (brand name "TINUVIN 479", manufactured by BASF) and 2-(4,6-diphenyl-1,3,5-triazin-2-yl)-5-[2-(2-ethylhexanoyloxy)ethoxy]-phenol ("ADK STAB LA-46", manufactured by ADEKA).

[0093] The content of the ultraviolet absorber in the adhesive sheet 10 relative to 100 parts by weight is preferably 0.5 parts by weight or more, more preferably 0.6 parts by weight or more, more preferably 0.7 parts by weight or more, more preferably 0.8 parts by weight or more, more preferably 0.85 parts by weight or more, more preferably 0.9 parts by weight or more, and even more preferably 1 part by weight or more. It is also preferably 15 parts by weight or less, more preferably 13 parts by weight or less, more preferably 11 parts by weight or less, more preferably 10 parts by weight or less, more preferably 8 parts by weight or less, more preferably 6 parts by weight or less, more preferably 5 parts by weight or less, more preferably 4 parts by weight or less, more preferably 3 parts by weight or less, more preferably 2 parts by weight or less, more preferably 1.8 parts by weight or less, more preferably 1.6 parts by weight or less, and more preferably 1.5 parts by weight or less. This configuration is preferred from the viewpoint of balancing the ultraviolet blocking function of the adhesive sheet 10 for device protection with its photocurability.

[0094] Examples of antioxidants include phenolic antioxidants, phosphorus-containing antioxidants, sulfur-containing antioxidants, and amine antioxidants. Antioxidants can be used alone or in combination of two or more.

[0095] Phenolic antioxidants are preferred as antioxidants, and hindered phenolic antioxidants are more preferred. Examples of hindered phenolic antioxidants include pentaerythritol tetra[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (brand name "Irganox 1010", manufactured by BASF) and octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (brand name "Irganox 1076", manufactured by BASF).

[0096] The antioxidant content in the adhesive sheet 10 is preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more, and more preferably 3 parts by mass or less, more preferably 2 parts by mass or less, relative to 100 parts by mass of the base polymer. This configuration is preferred from the viewpoint of balancing the inhibition of oxidative degradation of the adhesive sheet 10 and its photocurability.

[0097] 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. The content of silane coupling agent in the adhesive sheet 10 is preferably 0.1 parts by mass or more, more preferably 0.2 parts by mass or more, and preferably 5 parts by mass or less, more preferably 3 parts by mass or less, relative to 100 parts by mass of the base polymer.

[0098] Examples of rust inhibitors include benzotriazole compounds. Examples of benzotriazole compounds include 1,2,3-benzotriazole, 5-methylbenzotriazole, 4-methylbenzotriazole, and carboxybenzotriazole.

[0099] The content of the rust inhibitor in the adhesive sheet 10 is preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more, and even more preferably 0.15 parts by mass or more, relative to 100 parts by mass of the base polymer. In addition, it is preferably 2 parts by mass or less, more preferably 1.7 parts by mass or less, more preferably 1.5 parts by mass or less, more preferably 1.2 parts by mass or less, more preferably 1 part by mass or less, more preferably 0.8 parts by mass or less, more preferably 0.7 parts by mass or less, more preferably 0.6 parts by mass or less, and more preferably 0.5 parts by mass or less.

[0100] From the viewpoint of ensuring sufficient adhesion to the adhered objects, 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 the operability and ease of cutting of the adhesive sheet 10, the thickness of the adhesive sheet 10 is preferably 300 μm or less, more preferably 280 μm or less, more preferably 260 μm or less, more preferably 240 μm or less, more preferably 220 μm or less, more preferably 200 μm or less, more preferably 180 μm or less, more preferably 160 μm or less, more preferably 150 μm or less, more preferably 140 μm or less, more preferably 130 μm or less, more preferably 120 μm or less, and more preferably 115 μm or less. When the thickness of the adhesive sheet 10 is 45μm, 50μm, 55μm, 60μm, 65μm, 70μm, 75μm, 80μm, 85μm, 90μm, 95μm, 100μm, 105μm, 110μm or 115μm, it is preferred that the adhesive composition for forming the adhesive sheet 10 has good coatability and the diffusion of the later-added components in the adhesive sheet 10 can be produced stably.

[0101] The light transmittance of the adhesive sheet 10 at a wavelength of 380 nm is preferably 10% or less, more preferably 9% or less, more preferably 8% or less, more preferably 7% or less, more preferably 6.5% or less, more preferably 6% or less, more preferably 5.5% or less, and more preferably 5% or less; additionally, for example, it is 0.05% or more. When the adhesive sheet 10 is used in a display panel, the light transmittance of the adhesive sheet 10 at a wavelength of 380 nm is below the above-mentioned upper limit value, ensuring the protective function of the display panel obtained by ultraviolet blocking in the adhesive sheet 10. As a method for adjusting the light transmittance of the adhesive sheet 10 at a wavelength of 380 nm, examples include the selection of the type of ultraviolet absorber in the adhesive sheet 10 and the adjustment of its amount.

[0102] The release liner 21 is, for example, a flexible, transparent resin film. Examples of materials that can be used for the release liner 21 include: polyester resin, polyolefin resin, polycarbonate resin, polyethersulfone resin, polyarylate resin, melamine resin, polyamide resin, cellulose resin, and polystyrene resin. Examples of polyester resins include: polyethylene terephthalate (PET), polybutylene terephthalate, and polyethylene naphthalate. Examples of polyolefin resins include: polyethylene, polypropylene, and cyclic olefin polymers (COP). From the viewpoint of transparency and strength, the material of the release liner 21 is preferably polyester resin, and more preferably PET.

[0103] The surface of the adhesive sheet 10 side of the release liner 21 can be treated with a release agent. Examples of release agents include polysiloxane release treatment, long-chain alkyl acrylate release treatment, and fluorinated release treatment. From the viewpoint of ease of adjusting the peel force of the self-adhesive sheet 10, polysiloxane release treatment is preferred.

[0104] From the viewpoint of ensuring the protective function of the adhesive sheet 10, the thickness of the release liner 21 is preferably 5 μm or more, more preferably 10 μm or more, and even more preferably 20 μm or more. From the viewpoint of operability, the thickness of the release liner 21 is preferably 200 μm or less, more preferably 150 μm or less, and even more preferably 100 μm or less.

[0105] The release liner 22 is a flexible, transparent resin film. Examples of materials that can be used as the release liner 22 include, for example, the materials described above for the release liner 21. From the viewpoint of transparency and strength, the material for the release liner 22 is preferably polyester resin, and more preferably PET.

[0106] In this embodiment, the surface of the adhesive sheet 10 side of the release liner 22 is treated with a release agent. Examples of release treatments include polysiloxane release treatment, long-chain alkyl acrylate release treatment, and fluorinated release treatment. From the viewpoint of ease of adjusting the peel force of the self-adhesive sheet 10, polysiloxane release treatment is preferred.

[0107] From the viewpoint of ensuring the protective function of the adhesive sheet 10, the thickness of the release liner 22 is preferably 5 μm or more, more preferably 10 μm or more, and even more preferably 20 μm or more. From the viewpoint of operability, the thickness of the release liner 22 is preferably 200 μm or less, more preferably 150 μm or less, and even more preferably 100 μm or less.

[0108] The adhesive sheet 10 can be manufactured, for example, by the following operation.

[0109] First, a prepolymer composition is prepared. Specifically, first, a mixture (liquid state) comprising the aforementioned monofunctional monomer for forming the basic polymer and a photopolymerization initiator (first photopolymerization initiator) is prepared (prepolymer composition preparation step). Next, by irradiating the mixture with ultraviolet light, a portion of the monofunctional monomer in the mixture undergoes photopolymerization, 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. Furthermore, during ultraviolet irradiation, a wavelength cutoff filter can be used as needed to cut off a portion of the wavelength range of light emitted from the light source. During ultraviolet irradiation, the illuminance is, for example, 5 mW / cm². 2 ~200mW / cm2 The cumulative irradiation intensity is, for example, 100 mW / 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 a photopolymer of a monofunctional monomer and a monofunctional monomer that has not undergone polymerization (residual monomer). In addition, the prepolymer composition does not contain solvent.

[0110] Next, a photopolymerizable multifunctional compound (crosslinking agent), a photopolymerization initiator (second photopolymerization initiator), and other components as needed are added to the prepolymer composition, thereby preparing an adhesive composition (adhesive composition preparation step). Other components may include, for example, oligomers, antioxidants, silane coupling agents, and rust inhibitors. This adhesive composition does not contain solvents. That is, the adhesive composition prepared in this step is a solvent-free adhesive composition.

[0111] Next, as Figure 2A As shown, a coating 10A is formed between release pads 21 and 22' (coating formation process). Specifically, firstly, an adhesive composition is applied to the release surface of the release pad 21 to form the coating 10A. Examples of methods for applying the adhesive composition include roller coating, licking coating, gravure coating, reverse coating, brush coating, spraying, dip roller coating, doctor blade coating, knife coating, air knife coating, curtain coating, die lip coating, and die-cutting. Next, the release surface of the release pad 22' is adhered to the coating 10A on the release pad 21. For example, the same release pad as the release pad 22 can be used as the release pad 22.

[0112] Next, as Figure 2B As shown, ultraviolet light is irradiated onto the coating 10A between the release liner 21 and 22' to form a base adhesive sheet 10B (base adhesive sheet formation step). During ultraviolet irradiation, a photopolymerization reaction occurs in the reaction system containing a monofunctional monomer (residual monomer) and a photopolymerizable polyfunctional compound (crosslinking agent) in the coating to form a base polymer. This base polymer has a network structure in which linear units derived from the monofunctional monomer are linked by the photopolymerizable polyfunctional compound.

[0113] Next, as Figure 2C As shown, the peeling pad 22' is removed from the base adhesive sheet 10B. Figure 2B Peeling (peeling process).

[0114] Next, as Figure 2DAs shown, a post-addition component is supplied to the base adhesive sheet 10B (post-addition component supply step). Specifically, a post-addition component solution containing the post-addition component and a solvent is coated onto the exposed surface of the base adhesive sheet 10B (illustration omitted). The post-addition component contains the aforementioned polyfunctional monomer with a cyclic structure and a photopolymerization initiator (third photopolymerization initiator), and may also contain other additives. Examples of other additives include, for example, ultraviolet absorbers and antioxidants. In this step, for example, the post-addition component is allowed to penetrate from the surface of the base adhesive sheet 10B into the base adhesive sheet 10B, and heating is performed as needed, thereby vaporizing the solvent. Prior to this step, the base polymer has already formed the base adhesive sheet 10B by having a cross-linked structure.

[0115] Therefore, due to the vaporization of the solvent in this process, an orange peel-like surface is not easily formed on the base adhesive sheet 10B (it is practically not formed). Furthermore, the base adhesive sheet 10B and the subsequently added components form a photocurable adhesive sheet 10. The amount of the polyfunctional monomer containing a cyclic structure added in this process, as described above, is preferably 5 parts by mass or more, more preferably 5.5 parts by mass or more, more preferably 6 parts by mass or more, more preferably 6.5 parts by mass or more, more preferably 7 parts by mass or more, more preferably 8 parts by mass or more, more preferably 9 parts by mass or more, more preferably 10 parts by mass or more, and preferably 50 parts by mass or less, more preferably 48 parts by mass or less, more preferably 46 parts by mass or less, more preferably 45 parts by mass or less, more preferably 43 parts by mass or less, more preferably 41 parts by mass or less, and more preferably 40 parts by mass or less, relative to 100 parts by mass of the base polymer.

[0116] Next, as Figure 2E As shown, an additional release liner 22 is bonded to the adhesive sheet 10 (bonding process).

[0117] The above operations allow for the manufacture of an adhesive sheet 10 whose adhesive surface is covered and protected by release liner 21, 22. In the above manufacturing method, the adhesive sheet 10 can be manufactured using a solvent-free adhesive composition. With such an adhesive sheet 10, during sheet formation, it is not necessary to allow the solvent to evaporate from the coating, thereby suppressing the formation of orange peel-like unevenness on the surface of the adhesive sheet 10. Furthermore, by controlling the generation of unevenness, good visual recognizability can be achieved. Additionally, for example, when the adhesive sheet 10 is adhered to a printed height difference provided on a display cover plate, the thicker the adhesive sheet 10, the easier it is to fill the printed height difference, thereby maintaining a smooth surface of the adhesive sheet 10 (excellent height difference absorption). For adhesive sheets 10 based on solvent-free adhesive compositions, the thickness does not decrease with solvent evaporation during sheet formation, thus making it easy to manufacture uniform and thick adhesive sheets 10. Moreover, such adhesive sheets 10 exhibit excellent height difference absorption. Furthermore, adhesive sheets 10 based on solvent-free adhesive compositions are suitable for reducing environmental impact. That is, the adhesive sheet 10 formed from the solvent-free adhesive composition is environmentally friendly and preferred from the perspective of sustainable development.

[0118] Furthermore, in this method, during the base adhesive sheet formation step, a network-structured base polymer is formed from a solvent-free adhesive composition. During the subsequent ingredient supply step, a photopolymerization reaction of multifunctional monomers (including multifunctional monomers containing cyclic structures) occurs around the network-structured base polymer. Therefore, the photopolymer of the multifunctional monomers is formed simultaneously with the network-structured base polymer to form an interpenetrating polymer network (IPN). This results in highly elastic optical adhesive sheets.

[0119] On the other hand, for example, after a base polymer is formed from a solvent-based adhesive composition, if a multifunctional monomer is incorporated into a solution containing the base polymer and photopolymerized, a portion of the monofunctional monomer remains in the solution containing the base polymer. Therefore, the aforementioned interpenetrating polymer network (IPN) cannot be fully formed from the outset, and the high elasticity of the optical adhesive sheet cannot be achieved. Furthermore, the residual monofunctional monomer polymerizes over time, thus the elasticity also changes over time.

[0120] When using adhesive sheet 10, release pads 21 and 22 are peeled off from adhesive sheet 10 at specified times.

[0121] Figures 3A to 3C This is an example of how to use the adhesive sheet 10.

[0122] In this method, firstly, as Figure 3AAs shown, the adhesive sheet 10 is attached to the protective glass 31 (the first adherend). The protective glass 31 has a first surface 31a and a second surface 31b opposite to the first surface 31a. A decorative or light-shielding printed layer 32 is formed at the edge of the first surface 31a. The printed layer 32 is provided, for example, along the entire edge of the protective glass 31. There is a height difference (printed height difference) between the surface of the first surface 31a and the surface of the printed layer 32 on the protective glass 31. That is, the protective glass 31 is an adherend with a height difference on its surface. In this process, specifically, the adhesive sheet 10 before light curing is attached to the area containing the printed layer 32 on the surface 31a of the protective glass 31. Figure 3A An exemplary case is shown in which an adhesive sheet 10, before light curing, is bonded to the entire surface 31a of the protective glass 31.

[0123] Next, as Figure 3B As shown, the protective glass 31 is bonded to the component 33 by the adhesive sheet 10 on the protective glass 31 before light curing. The component 33 is, for example, a pixel panel, a polarizing film, or a touch panel for a display panel.

[0124] Next, as Figure 3C As shown, the adhesive sheet 10 between component 33 and protective glass 31 is photocured by ultraviolet (UV) irradiation. Under UV irradiation, a photopolymerization reaction of multifunctional monomers containing cyclic structures occurs in the adhesive sheet 10, thereby forming a photopolymer of multifunctional monomers. This photopolymerization reaction occurs around the base polymer, thus the photopolymer of multifunctional monomers is formed simultaneously with the base polymer to form an interpenetrating polymer network (IPN). As a result, the adhesive sheet 10 becomes highly elastic (photocuring of the adhesive sheet 10). Examples of UV light sources for UV irradiation include UV LED lamps, black light lamps, high-pressure mercury lamps, and metal halide lamps. Additionally, a wavelength cutoff filter can be used to cut off a portion of the wavelength range of light emitted from the light source during UV irradiation. The illuminance during UV irradiation is, for example, 5 mW / cm². 2 ~600mW / cm 2 The cumulative irradiation intensity is, for example, 50 mW / cm². 2 ~15000mJ / cm 2 .

[0125] The adhesive sheet 10 is used, for example, as described above. In the above method of use, the adhesive sheet 10 is light-cured after it is used to join two components (protective glass 31 and component 33 in the above example). Alternatively, an adhesive sheet 10 with a release liner on one side (uncured) can be attached to a component, the adhesive sheet 10 can be light-cured, and after the release liner is peeled off from the cured adhesive sheet 10, one component can be joined to another component using the cured adhesive sheet 10.

[0126] As described above, the adhesive sheet 10 comprises a base polymer, a multifunctional monomer, and a photopolymerization initiator (a third photopolymerization initiator). Figure 3A As shown, such an adhesive sheet 10 can adhere to the surface of the substrate with a height difference in a soft state before light curing. Therefore, the adhesive sheet 10 is suitable for achieving good height difference tracking in the bonding of substrates with surfaces with height differences.

[0127] Furthermore, in the adhesive sheet 10, as described above, the base polymer is a photopolymer containing a polymerizable component of a monofunctional monomer and a photopolymerizable polyfunctional compound. This base polymer has a network structure in which linear units derived from the monofunctional monomer are linked by the photopolymerizable polyfunctional compound. When the adhesive sheet 10 is irradiated with light, a photopolymerization reaction of polyfunctional monomers (including polyfunctional monomers containing cyclic structures) occurs around the base polymer of this network structure. Therefore, the photopolymer of the polyfunctional monomers is formed simultaneously with the base polymer of the network structure to form an interpenetrating polymer network (IPN). As a result, the adhesive sheet 10 achieves high elasticity. Moreover, the polyfunctional monomers containing cyclic structures have a larger volume than those without cyclic structures. Therefore, the mesh size of the network structure formed by the polymerization reaction of polyfunctional monomers containing cyclic structures is larger than that of the network structure formed by the polymerization reaction of polyfunctional monomers without cyclic structures. This is suitable for achieving both high elasticity and stress relaxation properties in the photocured adhesive sheet 10. Furthermore, the combination of high elasticity and stress relaxation properties of the light-cured adhesive sheet 10, which joins the adhered materials, helps to balance the aforementioned bubble suppression and joint reliability.

[0128] Therefore, the adhesive sheet 10 is suitable for achieving good height difference tracking when bonding between adhered objects, and is also suitable for balancing bubble suppression and bonding reliability after bonding between adhered objects.

[0129] Example

[0130] The following examples illustrate the present invention in detail. However, the present invention is not limited to these examples. Furthermore, the specific numerical values ​​of the formulation amount (content), physical property value, parameters, etc., described below can be replaced with the upper limit (defined as a value "below" or "less than") or lower limit (defined as a value "above" or "greater than") of the formulation amount (content), physical property value, parameters, etc., corresponding to them described in the above "Specific Embodiments".

[0131] <Preparation of acrylic oligomers>

[0132] 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 with a weight-average molecular weight of 5100.

[0133] [Example 1]

[0134] <Preparation of Prepolymer Compositions>

[0135] In a flask, 0.062 parts by weight of two first photopolymerization initiators were added to a monomer mixture comprising 71 parts by weight of n-butyl acrylate (BA), 13 parts by weight of 4-hydroxybutyl acrylate (4HBA), 13 parts by weight of N-vinyl-2-pyrrolidone (NVP), and 3 parts by weight of acryloylmorpholine (ACMO). The mixture was then irradiated with ultraviolet light under a nitrogen atmosphere, thereby polymerizing a portion of the polymerizable components in the mixture to obtain a prepolymer composition. As the first photopolymerization initiators, 0.031 parts by weight of BASF's "Omnirad 184" (1-hydroxycyclohexylphenyl ketone) and 0.031 parts by weight of BASF's "Omnirad 651" (2,2-dimethoxy-2-phenylacetophenone) were used. Ultraviolet irradiation continued until the viscosity of the composition reached approximately 20 Pa·s. This viscosity was measured using a Type B viscometer under the conditions of rotor No. 5, rotor speed of 10 rpm, and temperature of 30°C. The resulting prepolymer composition is a partial polymer containing a photopolymer (photopolymer P1a) and unpolymerized polymeric components (residual monomers).

[0136] <Preparation of Adhesive Compositions>

[0137] Next, 100 parts by weight of the prepolymer composition, 3 parts by weight of the above-mentioned acrylic oligomer, 0.6 parts by weight of the urethane acrylate oligomer (UAO) (brand name "UN-350", manufactured by Negami Kogyo Co., Ltd.) as a photopolymerizable multifunctional compound, 0.4 parts by weight of the second photopolymerization initiator (brand name "Omnirad 819", bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, manufactured by BASF), 0.5 parts by weight of the antioxidant (brand name "Irganox 1010", manufactured by BASF), 0.2 parts by weight of the rust inhibitor (brand name "BT-120", 1,2,3-benzotriazole, manufactured by Jōhoku Chemical Co., Ltd.), and 0.3 parts by weight of the silane coupling agent (brand name "KBM-403", manufactured by Shin-Etsu Chemical Co., Ltd.) were mixed to obtain the adhesive composition.

[0138] <Making Basic Adhesive Sheets>

[0139] Next, an adhesive composition is applied to the release-treated surface of a first release liner (trade name "Diafoil MRF", thickness 75 μm, manufactured by Mitsubishi Chemical Corporation) with a release-treated surface on one side to form a coating film. Then, the release-treated surface of a second release liner (trade name "Diafoil MRE", thickness 75 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 light-cur the coating film, thereby forming an adhesive layer with a thickness of 90 μm (UV irradiation process). The UV irradiation process includes a first step and a subsequent second step. In the first step of UV irradiation, a black light lamp (wavelength 320 nm–400 nm, manufactured by Toshiba) is used as the light source, and the illuminance is set to 6.5 mW / cm². 2 The cumulative irradiation intensity was set to 1500 mJ / cm. 2 In the second step of ultraviolet irradiation, an ultraviolet LED lamp (wavelength 365nm, manufactured by Quark Technology) was used, with the illuminance set to 90mW / cm². 2 The cumulative irradiation intensity was set to 1800 mJ / cm. 2In the ultraviolet irradiation process, a photopolymerization reaction is carried out in a reaction system containing the aforementioned residual monomer and photopolymerizable multifunctional compound in the coating film, thereby forming a photopolymerizable polymer P1b with a crosslinked structure. Furthermore, this photopolymerization reaction occurs around the photopolymerizable polymer P1a, thus the photopolymerizable polymer P1b is formed around the photopolymerizable polymer P1a. The adhesive layer formed in this process contains such photopolymerizable polymers P1a and P1b as a base polymer P1. A base adhesive sheet with a release liner (first release liner / base adhesive sheet (90 μm thickness) / second release liner) is produced through the above operation.

[0140] <Preparation of the solution with added components>

[0141] A post-addition component solution was prepared by mixing 27.8 parts by mass of a difunctional acrylate monomer (brand name "Light acrylate DCP-A", tricyclodecanediethanol diacrylate (CAS No. 42594-17-2), manufactured by Kyoeisha Chemical) as a multifunctional monomer, 1.2 parts by mass of a third photopolymerization initiator (brand name "Omnirad 819", manufactured by BASF), 3.6 parts by mass of a UV absorber (brand name "Tinosorb S", manufactured by BASF), and 67.4 parts by mass of ethyl acetate as a solvent. The composition of the post-addition component solution is shown in Table 1. In Table 1, the proportions of each component are expressed in parts by mass.

[0142] <Post-addition ingredient supply process>

[0143] First, after peeling the second release liner from the aforementioned base adhesive sheet with the release liner, a post-addition component solution is applied to the exposed surface of the base adhesive sheet to a thickness of 30 μm. The coating is performed using a rod coater RDS No. 14 manufactured by RDSPECIALTIES. Next, a drying process is carried out in a desiccator at 110°C for 3 minutes. Through the coating and drying processes, the post-addition components (multifunctional monomers, a third photopolymerization initiator, and a UV absorber) are penetrated into the base adhesive sheet, and the solvent is vaporized. By allowing the post-addition components to penetrate the base adhesive sheet, a photocurable optical adhesive sheet is formed. By adding the post-addition components to the base adhesive sheet, the thickness of the formed optical adhesive sheet becomes thicker than that of the base adhesive sheet (this is also true in the examples and comparative examples described later). The thicknesses of the formed adhesive sheets are shown in Table 2. Relative to 100 parts by weight of the base polymer (100 parts by weight of the prepolymer composition and the photopolymerizable multifunctional compound), the amount of multifunctional monomer (DCP-A) added is 8.5 parts by weight, the amount of third photopolymerization initiator (Omnirad 819) added is 0.4 parts by weight, and the amount of ultraviolet absorber (Tinosorb S) added is 1.1 parts by weight. Next, on the adhesive sheet on the first release liner, the release-treated surface of the third release liner (trade name "Diafoil MRE", thickness 75 μm, manufactured by Mitsubishi Chemical Corporation) with a release-treated surface on one side is bonded.

[0144] The adhesive sheet with release liner of Example 1 (first release liner / adhesive sheet (thickness 103 μm) / third release liner) was prepared by the above operation. The adhesive sheet is a photocurable optical adhesive sheet containing a base polymer, a multifunctional monomer (DCP-A) and a third photopolymerization initiator.

[0145] [Example 2]

[0146] Except for the following, the adhesive sheet with a release liner of Example 2 was produced by operating in the same manner as the adhesive sheet with a release liner of Example 1. In the preparation of the post-added component solution, the composition of the post-added component solution was changed as shown in Table 1. The thickness of the adhesive sheet formed by adding the post-added component was 104 μm.

[0147] [Example 3]

[0148] Except for the following, the adhesive sheet with a release liner of Example 3 was produced by operating in the same manner as the adhesive sheet with a release liner of Example 1. In the preparation of the post-added component solution, the composition of the post-added component solution was changed as shown in Table 1. The thickness of the adhesive sheet formed by adding the post-added component was 106 μm.

[0149] [Example 4]

[0150] 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 post-added component solution, the composition of the post-added component solution was changed as shown in Table 1. In the post-added component supply process, a bar coater RDS No. 20 manufactured by RDSPECIALTIES was used, and the coating thickness of the post-added component solution was set to 44 μm. The thickness of the adhesive sheet formed by adding the post-added component was 112 μm.

[0151] [Example 5]

[0152] Except for the following, the adhesive sheet with a release liner of Example 5 was produced by operating in the same manner as the adhesive sheet with a release liner of Example 1. In the preparation of the post-added component solution, the composition of the post-added component solution was changed as shown in Table 1. In the post-added component supply process, a bar coater RDS No. 24 manufactured by RDSPECIALTIES was used, and the coating thickness of the post-added component solution was set to 50 μm. The thickness of the adhesive sheet formed by adding the post-added component was 121 μm.

[0153] [Example 6]

[0154] Except for the following, the adhesive sheet with a release liner of Example 6 was produced by operating in the same manner as the adhesive sheet with a release liner of Example 1. In the UV irradiation process used to produce the base adhesive sheet, the second step (irradiation using a UV LED lamp) was not performed. Through this UV irradiation process, a base polymer P2 with a weight-average molecular weight (Mw) greater than that of the base polymer P1 was formed. In the preparation of the post-added component solution, the composition of the post-added component solution was changed as shown in Table 1. In the post-added component supply process, a bar coater RDS No. 10 manufactured by RDSPECIALTIES was used, and the coating thickness of the post-added component solution was set to 23 μm. The thickness of the adhesive sheet formed by adding the post-added component was 106 μm.

[0155] [Example 7]

[0156] Except for the following, the adhesive sheet with a release liner of Example 7 was produced by operating in the same manner as the adhesive sheet with a release liner of Example 6. In the preparation of the post-added component solution, 23.8 parts by mass of tricyclodecanedimethylethanol dimethacrylate (CAS No. 43048-08-4), manufactured by Osaka Organic Chemical Industry Co., Ltd. (hereinafter sometimes referred to as DCP-DMA), a difunctional acrylate monomer, was used instead of DCP-A as a multifunctional monomer, and the composition of other components was changed as shown in Table 1. Furthermore, in the post-added component supply process, a rod coater RDSNo. 16 manufactured by RDSPECIALTIES Co., Ltd. was used, and the coating thickness of the post-added component solution was set to 37 μm. The thickness of the adhesive sheet formed by adding the post-added component was 103 μm.

[0157] [Example 8]

[0158] Except for the following, the adhesive sheet with a release liner of Example 8 was produced by operating in the same manner as the adhesive sheet with a release liner of Example 7. In the preparation of the post-added component solution, the composition of each component was changed as shown in Table 1. The thickness of the adhesive sheet formed by adding the post-added component was 104 μm.

[0159] [Comparative Example 1]

[0160] Except for the following, an adhesive sheet with a release liner of Comparative Example 1 was prepared by operating in the same manner as the adhesive sheet with a release liner of Example 1. In the preparation of the post-added component solution, 44.1 parts by weight of trimethylolpropane triacrylate (TMPTA) (CAS No. 15625-89-5) (brand name "Viscoat#295", manufactured by Osaka Organic Chemicals Co., Ltd.) was used instead of DCP-A as a multifunctional monomer, and the composition of other components was changed as shown in Table 1. The thickness of the adhesive sheet formed by adding the post-added component was 106 μm.

[0161] [Comparative Example 2]

[0162] Except for the following, an adhesive sheet with a release liner of Comparative Example 2 was prepared by operating in the same manner as the adhesive sheet with a release liner of Example 1. In the preparation of the post-added component solution, 43.6 parts by mass of TMPTA (Viscoat #295) was used instead of DCP-A as a multifunctional monomer, and the composition of other components was changed as shown in Table 1. In the post-added component supply process, a bar coater RDS No. 20 manufactured by RDSPECIALTIES was used, and the coating thickness of the post-added component solution was set to 44 μm. The thickness of the adhesive sheet formed by adding the post-added component was 111 μm.

[0163] [Comparative Example 3]

[0164] Except for the following, an adhesive sheet with a release liner of Comparative Example 3 was prepared by operating in the same manner as the adhesive sheet with a release liner in Example 1. In the preparation of the post-addition component solution, 56.5 parts by weight of TMPTA (Viscoat #295) was used instead of DCP-A as a multifunctional monomer, and the composition of other components was changed as shown in Table 1. In the post-addition component supply process, a bar coater RDS No. 24 manufactured by RDSPECIALTIES was used, and the coating thickness of the post-addition component solution was set to 50 μm. The thickness of the adhesive sheet formed by adding the post-addition component was 122 μm.

[0165] [Comparative Example 4]

[0166] Except for the following, the adhesive sheet with a release liner of Comparative Example 4 (first release liner / adhesive sheet / second release liner) was produced by operating in the same manner as the adhesive sheet with a release liner of Example 1. No post-addition component solution was prepared, and no post-addition component supply process was performed.

[0167] <Determination of weight-average molecular weight>

[0168] Under the following determination conditions, the weight-average molecular weight (Mw) of the aforementioned acrylic oligomers was determined using gel permeation chromatography (GPC) and expressed as a polystyrene equivalent. A GPC apparatus (HLC-8120 GPC, manufactured by Tosoh) was used for the determination. The sample solution was prepared as follows: First, using the acrylic oligomers as the sample, a 0.15% by mass tetrahydrofuran (THF) solution (with added salt) was prepared and left to stand for 20 hours. Next, the THF solution was filtered using a membrane filter with an average pore size of 0.45 μm, and the filtrate was used as the sample solution for molecular weight determination.

[0169] [GPC Measurement Conditions]

[0170] Column: G 7000H XL +GMH XL +GMH XL All are TSK gel (manufactured by Tosoh).

[0171] Column temperature: 40℃

[0172] Elution buffer: THF solution

[0173] Flow rate: 0.8 mL / min

[0174] Sample injection volume: 100 μL

[0175] Standard sample: Polystyrene (manufactured by Agilent)

[0176] Detector: Differential refractometer (RI)

[0177] <Light transmittance>

[0178] For each adhesive sheet of Examples 1 to 8 and Comparative Examples 1 to 4, the light transmittance was measured using a spectrophotometer (brand name "U 4100", manufactured by Hitachi High-Tech). In this measurement, a sample sheet (first release liner / adhesive sheet / third release liner (second release liner only in Comparative Example 4)) was cut from the adhesive sheet, and ultraviolet light was irradiated onto the sample sheet through the first release liner. A metal halide lamp was used as the light source for the ultraviolet irradiation, and the illuminance was set to 300 mW / cm². 2 The cumulative irradiation intensity was set to 3000 mJ / cm. 2 Next, the release liner was peeled off from both sides of the adhesive sheet, and the adhesive sheet was fixed to the measuring fixture of the spectrophotometer in a manner that prevented deformation. In Comparative Example 4, no ultraviolet irradiation was performed. In this measurement, the temperature was set to 23°C, and the measurement range wavelength was set to 300 nm to 800 nm. The light transmittance (%) at a measured wavelength of 380 nm is shown in Table 2.

[0179] <Adhesion>

[0180] For each adhesive sheet of Examples 1 to 8 and Comparative Examples 1 to 4, the adhesive strength was determined by the following peel test.

[0181] First, test pieces were made for each adhesive sheet. In the preparation of the test pieces, firstly, the third release liner (the second release liner in Comparative Example 4 only) was peeled off from the adhesive sheet, and a PET film (50 μm thick) was laminated onto the exposed surface of the adhesive sheet, thus obtaining a laminated film (first release liner / adhesive sheet / PET film). Next, test pieces (100 mm long × 10 mm wide) were cut from the laminated film. Then, at 23°C and 50% relative humidity, the first release liner was peeled off from the adhesive sheet of the test piece, and the exposed surface of the adhesive sheet was laminated to the air surface (non-tin side) of an alkali glass plate (blue plate glass, manufactured by Matsunaga Glass Industry Co., Ltd.) produced by the float glass process, thus obtaining a laminate (alkali glass plate / adhesive sheet / PET film). During lamination, the test piece was pressed onto the alkali glass plate by pressing a 2 kg roller back and forth once. Next, the laminate was subjected to autoclaving. In the autoclaving process, the temperature was set to 50°C, the pressure to 0.5 MPa, and the processing time to 15 minutes. Next, ultraviolet light (UV curing) was applied to the adhesive sheets in the laminate from the alkali glass plate side. A metal halide lamp was used as the light source for the UV irradiation, and the illuminance was set to 300 mW / cm². 2 The cumulative irradiation intensity was set to 3000 mJ / cm. 2 Next, the laminate was left to stand for 15 hours at 23°C and 50% relative humidity. Then, a peel test was conducted on the test piece from the alkali glass plate at 23°C and 50% relative humidity to determine the peel strength.

[0182] A tensile testing machine (Autograph AG-Xplus 200N, manufactured by Shimadzu Corporation) was used in this test. In this test, the peel angle of the test piece relative to the substrate was set to 180°, the pulling speed of the test piece was set to 300 mm / min, and the peel length was set to 50 mm (test conditions for the peel test). The arithmetic mean of the peel strength from three tests (n=3) for each adhesive piece is shown in Table 2 as the adhesion force F (N / 10mm) to the float glass plate after light curing.

[0183] <Dynamic Viscoelasticity Measurement>

[0184] For each adhesive sheet of Examples 1 to 8 and Comparative Examples 1 to 4, dynamic viscoelasticity (first measurement) was measured.

[0185] First, a necessary number of test samples are prepared for each adhesive sheet. Specifically, multiple small pieces of adhesive sheet cut from the adhesive sheet are first glued together to create a sample sheet with a thickness of 0.8 mm to 1.2 mm. Next, the sheet is punched to obtain cylindrical particles (8 mm in diameter) that serve as the test samples.

[0186] Next, dynamic viscoelasticity measurements were performed on the test samples using an Advanced Rheometric Expansion System (ARES) G2 (manufactured by TA Instruments). Specifically, the test samples were fixed to the clamps of the 8mm diameter parallel plates of the device before measurement. In this measurement, the measurement mode was set to shear mode, the measurement temperature was set to the range of -50℃ to 150℃ with an interval of 5℃, the heating rate was set to 5℃ / min, the frequency was set to 1Hz, the set load was set to 30g, and the set strain was set to 0.1%. Then, based on the measurement results, the shear storage modulus G1 (MPa) at 25℃ was read. Its value is shown in Table 2.

[0187] On the other hand, the dynamic viscoelasticity (second measurement) of each adhesive sheet of Examples 1 to 8 and Comparative Examples 1 to 3 after photocuring was measured. When preparing the test samples, adhesive sheets that had been photocured by ultraviolet irradiation from the first release liner side were used. During ultraviolet irradiation, a metal halide lamp was used, and the illuminance was set to 300 mW / cm². 2 The cumulative irradiation intensity was set to 3000 mJ / cm. 2 In addition, the load set during the measurement was set to 100g. Apart from this, the measuring apparatus and conditions in the second measurement were the same as those in the first measurement. Based on the measurement results, the shear storage modulus G2 (MPa) at 25°C and the shear storage modulus G3 (MPa) at 70°C were read. Their values ​​are shown in Table 2.

[0188] Fracture strain

[0189] For each adhesive sheet of Examples 1 to 8 and Comparative Examples 1 to 4, the strain at fracture in the tensile fracture test was examined. Specifically, as described below.

[0190] First, the adhesive sheet with the release liner is irradiated with ultraviolet light through the first release liner to photocur the adhesive sheet. A metal halide lamp is used as the light source for the ultraviolet irradiation, and the illuminance is set to 300 mW / cm². 2 The cumulative irradiation intensity was set to 3000 mJ / cm. 2Next, four small adhesive sheet pieces, each 30 mm long and 5 mm wide, were cut from the adhesive sheet with a release liner. These four adhesive sheet pieces were then stacked to create a test piece (30 mm long × 5 mm wide). The test piece was then subjected to autoclaving. The autoclaving temperature was set to 50°C, the pressure to 0.5 MPa, and the treatment time to 15 minutes. Next, using a tensile testing machine (Autograph AGS-50NX, manufactured by Shimadzu Corporation), the test piece was stretched along its length until fracture (tensile test) at 25°C, an initial chuck distance of 10 mm, and a pulling speed of 300 mm / min. In this tensile test, the elongation ΔL of the test piece at the moment of fracture was measured. The elongation ΔL refers to the amount of elongation measured from the initial length of the test piece (L0) between the chucks (10 mm). Then, the ratio (ΔL / L0) of the elongation length ΔL to the initial length 10 mm was calculated. The arithmetic mean of the ratios for each adhesive sheet in three tests (n=3) is shown as the fracture strain Bs in Table 2. Additionally, no ultraviolet irradiation was performed in Comparative Example 4.

[0191] Figure 4 The graph is a plot of the measured shear storage modulus G2 and fracture strain Bs of each adhesive sheet in the examples and comparative examples. Figure 4 In the graph, the horizontal axis represents the shear storage modulus G2 (MPa), and the vertical axis represents the fracture strain Bs. Figure 4 In the diagram, points E1 to E8 represent the measurement results of Examples 1 to 8, and points C1 to C3 represent the measurement results of Comparative Examples 1 to 3. Line L1 is a regression line derived from points C1 to C3 using the least squares method, represented by Bs = -0.109G² + 2.43. In contrast, line L2 is represented by Bs = -0.17G² + 3.74. Points E1 to E8 (Examples 1 to 8) are located above line L2. That is, each adhesive sheet of Examples 1 to 8 satisfies the following equation (1). Furthermore, each adhesive sheet of Examples 1 to 8 shows good results in the evaluation of height difference followability described later, good results in the evaluation of bonding reliability described later, and good results in the evaluation of bonding reliability of foaming resistance described later. That is, Examples 1 to 8, which satisfy Equation (1) below, achieve good height difference tracking when bonding the adhered materials, and also take into account bubble suppression and bonding reliability after bonding the adhered materials. In contrast, although the adhesive sheets of Comparative Examples 1 to 3 showed good results in the evaluation of height difference tracking and foaming resistance reliability, they did not show good results in the evaluation of bonding reliability.

[0192] Bs≥-0.17G2+3.74(1)

[0193] <Elevation Difference Following>

[0194] The height difference tracking performance of each adhesive sheet in Examples 1 to 8 and Comparative Examples 1 to 4 was examined through the following operations.

[0195] First, a sample sheet (75 mm long × 45 mm wide) was cut from the adhesive sheet with a release liner. Next, a third release liner (the second release liner in Comparative Example 4 only) was peeled from the adhesive sheet in the sample sheet, and the exposed surface of the adhesive sheet was bonded to the center of a PET film (100 mm long × 50 mm wide, 125 μm thick). During bonding, a roller press was used, with the roller pressure set to 0.2 MPa and the feed speed set to 100 mm / min. Next, a first release liner was peeled from the adhesive sheet on the PET film, and the exposed surface of the adhesive sheet was bonded to a glass plate with a printed layer (100 mm long × 50 mm wide, 500 μm thick), thus obtaining a bond (first bond). During bonding, a roller press was used, with the roller pressure set to 0.2 MPa and the feed speed set to 100 mm / min. Figure 5 This indicates the positional relationship between the glass plate 41 and the adhesive sheet 42 (optical adhesive sheet) in the first joint.

[0196] On one surface of the glass plate 41 along its thickness direction, a printing layer 43 (black ink layer) with a thickness of 45 μm is formed over the entire edge of the glass plate 41. The printing layer 43 is formed along the length direction L1 within a range 15 mm inward from each end of the glass plate 41, and along the width direction L2 within a range 5 mm inward from each end of the glass plate 41. Figure 5 (The printed layer 43 is indicated by a shading line in the diagram). The adhesive sheet 42 is attached to the center of one side of the glass plate 41 in the thickness direction, and contacts the printed layer 43 at its entire edge. That is, the printed layer 43 on the glass plate 41 is sandwiched between the glass plate 41 and the adhesive sheet 42 within a range of 2.5 mm outward from the inner end of the layer.

[0197] Next, the first bond was subjected to autoclaving at 50°C, 0.5 MPa, and for 30 minutes. Afterward, the area near the inner edge of the printed layer 43 in the first bond was observed. Specifically, the inner side of the inner edge of the printed layer 43 (the area where the adhesive sheet 42 should adhere to the glass plate 41) was observed from the PET film side of the first bond using a digital microscope at a magnification of 20. Then, regarding the height difference tracking of each adhesive sheet, cases where no bubbles were detected within the observation range were rated as "good," and cases where bubbles were detected were rated as "poor."

[0198] These results are shown in Table 2.

[0199] <Joint Reliability>

[0200] The bonding reliability of each adhesive sheet of Examples 1 to 8 and Comparative Examples 1 to 4 was evaluated by the following operations.

[0201] First, the evaluation sample is prepared. In preparing the evaluation sample, a small piece of polarizing film with a phase retardation layer (28mm in length × 10mm in width) is cut from the polarizing film with the phase retardation layer.

[0202] The polarizing film with a phase retardation layer is fabricated as described later, having a first side (the side on the side of the phase retardation layer) and a second side opposite to the first side (the hard coating surface of the TAC film described later).

[0203] Next, a sample piece (25 mm in length × 10 mm in width) was cut from the adhesive sheet with release liner (first release liner / adhesive sheet (uncured) / third release liner (second release liner only in Comparative Example 4)).

[0204] Next, the third release liner (the second release liner in Comparative Example 4 only) is peeled off from the adhesive sheet in the sample sheet, and the exposed surface of the adhesive sheet is then attached to the second surface of the polarizing film with the phase difference layer.

[0205] Specifically, one short side of the polarizing film with the phase retardation layer is aligned with one short side of the adhesive sheet along its length, and then bonded using a manual roller. Next, the first release liner is peeled off from the adhesive sheet on the polarizing film with the phase retardation layer, and the exposed surface of the adhesive sheet is bonded to an alkali-free glass plate (brand name "Eagle XG," manufactured by Corning Incorporated) using a manual roller. This yields a laminate (alkali-free glass plate / adhesive sheet / polarizing film). The laminate is then subjected to autoclaving at 50°C and 0.5 MPa for 15 minutes. Next, the adhesive sheet in the laminate is photocured by irradiating it with ultraviolet light from the alkali-free glass plate side. During ultraviolet irradiation, a 405nm wavelength LED lamp is used as the light source, and the illuminance is set to 400mW / cm². 2 The cumulative light intensity was set to 3000 mJ / cm. 2 Evaluation samples (alkali-free glass plate / photocured adhesive sheet / small polarizing film with phase retardation layer) were prepared using the above procedures.

[0206] Next, the evaluation sample was heated at 105°C for 1 hour. Then, the evaluation sample was visually observed from the alkali-free glass plate side. Regarding the bonding reliability of the adhesive sheet, a sample where no substantial bulging or peeling was observed between the adhesive sheet and the alkali-free glass plate, and / or between the adhesive sheet and the polarizing film, was rated as "good," while a sample with obvious bulging or peeling was rated as "poor." The results are shown in Table 2.

[0207] As another evaluation criterion, the evaluation samples were heated at 105°C for 3 hours and then visually observed from the alkali-free glass plate side. Regarding the bonding reliability of the adhesive sheet, a sample where no substantial bulging or peeling was observed between the adhesive sheet and the alkali-free glass plate, and / or between the adhesive sheet and the polarizing film, was rated as "good," while a sample with obvious bulging or peeling was rated as "poor." Furthermore, after heating at 115°C for 1 hour, the evaluation samples were again visually observed from the alkali-free glass plate side. Again, regarding the bonding reliability of the adhesive sheet, a sample where no substantial bulging or peeling was observed between the adhesive sheet and the alkali-free glass plate, and / or between the adhesive sheet and the polarizing film, was rated as "excellent." The results are shown in Table 2. It should be noted that in Examples 7, 8, and Comparative Example 4, the bonding reliability after heating at 105°C for 1 hour was not evaluated; instead, the bonding reliability after heating at 105°C for 3 hours and then at 115°C for 1 hour was evaluated.

[0208] Fabrication of Polarizing Films with Phase Difference Layers

[0209] A polarizing film with a phase retardation layer is produced by fabricating a polarizing film and a phase retardation film with an adhesive layer and bonding them together (the bonding process described later).

[0210] <Fabrication of Polarizing Film with Adhesive Layer>

[0211] A polarizer with a thickness of 12 μm was fabricated by sequentially performing swelling, dyeing, crosslinking, cleaning, and drying processes on an elongated polyvinyl alcohol (PVA) film (brand name "PE 3000", thickness 30 μm, manufactured by Kuraray). Specifically, the process is described below.

[0212] In the swelling treatment, the PVA film is immersed in a pure water bath at 20°C, and then uniaxially stretched along its length. Uniaxial stretching is performed using a roller stretching machine (as described later in the section on uniaxial stretching). The stretching ratio in the swelling treatment is set to 2.2 times.

[0213] In the dyeing process, the PVA film was immersed in a dyeing bath at 30°C and then uniaxially stretched along its length. The dyeing bath was an aqueous solution containing iodine and potassium iodide in a mass ratio of 1:7. The iodine concentration in the dyeing bath was adjusted to achieve a transmittance of 45.0% for the polarizer used as the target material. The stretching ratio during the dyeing process was set to 1.4 times.

[0214] The crosslinking process comprises a first crosslinking treatment (first crosslinking treatment) and a second crosslinking treatment (second crosslinking treatment). In the first crosslinking treatment, the PVA film is immersed in a first crosslinking bath at 40°C, and under this condition, it is uniaxially stretched along its length. The first crosslinking bath is an aqueous solution containing boric acid and potassium iodide (boric acid concentration 5.0 wt%, potassium iodide concentration 3.0 wt%). The stretching ratio in the first crosslinking treatment is set to 1.2 times. In the subsequent second crosslinking treatment, the PVA film is immersed in a second crosslinking bath at 65°C, and under this condition, it is uniaxially stretched along its length. The second crosslinking bath is an aqueous solution containing boric acid and potassium iodide (boric acid concentration 4.3 wt%, potassium iodide concentration 5.0 wt%). The stretching ratio in the second crosslinking treatment is set to 1.6 times.

[0215] In the cleaning process, the PVA film was immersed in a potassium iodide aqueous solution (concentration 2.6% by mass) at 20°C. In the drying process, the PVA film was dried at 70°C for 5 minutes.

[0216] A polarizer (12 μm thick) with a total stretching ratio of 5.9 was fabricated using the above operations.

[0217] Next, a first triacetyl cellulose (TAC) film (brand name "KC2UA", thickness 25 μm, manufactured by Konica Minolta) was bonded to one side of the polarizer using a polyvinyl alcohol adhesive. A second TAC film (brand name "KC2UA", thickness 25 μm, manufactured by Konica Minolta) with a hard coating (7 μm thickness) was then bonded to the other side of the polarizer using the same polyvinyl alcohol adhesive. The side of the second TAC film opposite to the hard coating was then bonded to the polarizer. This resulted in a polarizing film with a laminated structure of protective layer (with hard coating) / polarizer / protective layer (without hard coating).

[0218] On the other hand, in a reaction vessel equipped with a reflux condenser, a nitrogen inlet pipe, a thermometer, and a stirrer, a mixture (reaction solution) containing 79.9 parts by mass of n-butyl acrylate, 15 parts by mass of benzyl acrylate, 5 parts by mass of acrylic acid, 0.1 parts by mass of 4-hydroxybutyl acrylate (4HBA), 0.1 parts by mass of 2,2'-azoisobutyronitrile (2,2'-azoisobutyronitrile) as a polymerization initiator, and ethyl acetate as a solvent was stirred at 55°C for 7 hours under a nitrogen atmosphere (polymerization reaction). Next, ethyl acetate was added to the reaction solution to adjust the solids concentration to 30% by mass. This yielded a polymer solution containing acrylic polymers. The weight-average molecular weight of the acrylic polymers in the polymer solution was 2.2 million.

[0219] Next, in the polymer solution, relative to 100 parts by weight of the acrylic polymer, 0.5 parts by weight of the first crosslinking agent (brand name "CORONATE L", trimethylolpropane / toluene diisocyanate trimer adduct, manufactured by Tosoh), 0.1 parts by weight of the second crosslinking agent (benzoyl peroxide), 0.2 parts by weight of the silane coupling agent (brand name "KBM-403", manufactured by Shin-Etsu Chemical Industry), and 0.5 parts by weight of the polyether compound with reactive silyl groups (brand name "Silyl SAT 10", manufactured by Kaneka) are added and mixed to obtain the adhesive composition.

[0220] Next, an adhesive composition is applied to the peeled surface of a 38 μm thick release film (brand name "MRF#38", PET film, manufactured by Mitsubishi Chemical Corporation) that has undergone single-sided peeling treatment to form a coating. The coating is then dried by heating at 155°C for 1 minute. This forms a 12 μm thick adhesive layer on the release film. The adhesive layer on the release film is then attached to the protective layer (without hard coating) side of the aforementioned polarizing film.

[0221] This resulted in a polarizing film with an adhesive layer.

[0222] <Fabrication of Phase Retardation Coating>

[0223] First, in a reaction vessel, 26.2 parts by mass of isosorbide (ISB), 100.5 parts by mass of 9,9-[4-(2-hydroxyethoxy)phenyl]fluorene (BHEPF), 10.7 parts by mass of 1,4-cyclohexanediethanol (1,4-CHDM), 105.1 parts by mass of diphenyl carbonate (DPC), and 0.591 parts by mass of cesium carbonate (0.2% aqueous solution) as a catalyst were mixed and dissolved under a nitrogen atmosphere. At this point, the temperature of the heat medium in the reaction vessel was adjusted to 150°C. Next, the pressure inside the reaction vessel was reduced to 13.3 kPa, and the temperature of the heat medium was raised to 190°C over 1 hour. Phenol produced as the temperature of the heat medium increased was extracted from the reaction vessel (the same process was repeated for each subsequent temperature increase described later). Next, the temperature inside the reaction vessel was maintained at 190°C for 15 minutes, then the pressure inside the reaction vessel was changed to 6.67 kPa, and the temperature of the heating medium was raised to 230°C over 15 minutes. Then, at the moment when the stirring torque of the stirrer in the reaction vessel was increased, the temperature of the heating medium was raised to 250°C over 8 minutes, and the pressure inside the reaction vessel was adjusted to below 0.200 kPa. Then, after reaching the specified stirring torque, the reaction was stopped, and the resulting reactants were extruded into water for granulation. Polycarbonate (PC) resin was obtained through the above operation. The composition of the PC resin is BHEPF / ISB / 1,4-CHDM = 47.4 mol% / 37.1 mol% / 15.5 mol%. In addition, the glass transition temperature of the PC resin is 136.6°C, and the specific viscosity is 0.395 dL / g.

[0224] Next, after vacuum drying the PC resin granules at 80°C for 5 hours, a long resin film with a thickness of 120 μm was extruded using these granules as raw material through a film forming apparatus. The film forming apparatus consisted of a single-screw extruder (screw diameter 25 mm, barrel set temperature 220°C) manufactured by Isuzu Chemical Equipment, a T-die (width 200 mm, set temperature 220°C), a cooling roller (set temperature 120°C–130°C), and a winding machine. Then, the resin film was stretched along its width using a tenter frame at a stretching temperature of 137°C–139°C. The stretching ratio was set to 2.5 times. This yielded a first retardation film serving as the first retardation layer.

[0225] On the other hand, a liquid crystal composition was prepared by mixing 20 parts by mass of a side-chain type liquid crystal polymer (weight average molecular weight 5000) represented by the following chemical formula (1) (where "65" and "35" are molar percentages of each structural unit), 80 parts by mass of a polymerizable liquid crystal having a nematic liquid crystal phase (brand name "Paliocolor LC242"), 5 parts by mass of a photopolymerization initiator (brand name "Irgacure 907", manufactured by Ciba Specialty Chemicals), and 200 parts by mass of cyclopentanone as a solvent. Next, the liquid crystal composition was coated onto one side of a norbornene film (trade name "ZEONEX", manufactured by ZEON Japan) as a substrate film using a bar coater, thereby forming a coating film. Then, the coating film on the substrate film was dried by heating it at 80°C for 4 minutes, thereby forming a liquid crystal layer (orienting the liquid crystal in the coating film). Next, the liquid crystal layer on the substrate film was photocured by ultraviolet irradiation, thereby forming a liquid crystal cured layer (second retardation layer) with a thickness of 0.58 μm as a second retardation film. Regarding this liquid crystal curing layer, the in-plane phase difference Re under 550nm light is 0nm, and the thickness-direction phase difference Rth under 550nm light is -71nm. In addition, the liquid crystal curing layer exhibits refractive index characteristics of nz > nx = ny (nx = 1.5326, ny = 1.5326, nz = 1.6550).

[0226]

[0227] By bonding one side of the first phase retardation film (first phase retardation layer) to the second phase retardation film (second phase retardation layer) on the substrate film with an adhesive, a phase retardation film (first phase retardation layer / adhesive layer / second phase retardation layer) with a substrate film is thus produced.

[0228] <Jointing Process>

[0229] The first phase retardation layer side of the phase retardation film is bonded to the adhesive layer side of the aforementioned polarizing film with an adhesive layer. At this time, the polarizing film with the adhesive layer and the phase retardation film are aligned and bonded with an angle of 45 degrees counterclockwise when viewed from the first phase retardation layer side, with the angle between the slow axis of the first phase retardation layer and the absorption axis of the polarizing film being the same. A polarizing film with a phase retardation layer is fabricated through the above operation.

[0230] <Foaming Resistance and Reliability>

[0231] The foaming resistance reliability of each adhesive sheet from Examples 1 to 8 and Comparative Examples 1 to 4 was evaluated.

[0232] First, a sample sheet (30 mm long × 30 mm wide) was cut from the adhesive sheet (uncured) with a release liner. Next, a third release liner (the second release liner in Comparative Example 4 only) was peeled from the adhesive sheet in the sample sheet, and an alkali-free glass plate (Eagle XG, Corning Incorporated) was bonded to the exposed surface of the adhesive sheet using a hand roller, thus creating a laminate. Next, a polycarbonate sheet with a hard coating (Iupilon MR 58, Mitsubishi Gas Chemical Co., Ltd., 1 mm thick) was cut into 40 mm × 40 mm pieces.

[0233] Next, the first release liner is peeled off from the laminate, and the polycarbonate surface of the hard-coated polycarbonate sheet is adhered to the exposed surface of the adhesive sheet using a hand roller. The laminate is then subjected to autoclaving at 50°C and 0.5 MPa for 15 minutes.

[0234] Next, ultraviolet light was irradiated onto the adhesive sheet in the laminate from the alkali-free glass plate side, thereby photocuring the adhesive sheet. During ultraviolet irradiation, an LED lamp (wavelength 405nm) was used as the light source, and the illuminance was set to 400mW / cm². 2 The cumulative irradiation intensity was set to 3000 mJ / cm. 2 This led to the creation of evaluation samples.

[0235] Next, the evaluation samples were heated at 95°C for 3 hours. Then, the samples were visually observed from the alkali-free glass plate side, and the number of bubbles generated at the adhesive sheet or the interface between the adhesive sheet and the polycarbonate sheet was measured. This operation was performed twice, and the result with the higher number of bubbles was used. Regarding foaming resistance reliability, a result with fewer than 20 bubbles was rated "Excellent," a result with 20 or more but less than 35 bubbles was rated "Good," and a result with more than 35 bubbles was rated "Poor." The results are shown in Table 2.

[0236] Table 1

[0237] Table 2

[0238] 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.

[0239] Industrial practicality

[0240] The optical adhesive sheet of the present invention can be used, for example, in the manufacture of display panels.

[0241] Label Explanation

[0242] 10. Adhesive sheet (optical adhesive sheet)

[0243] H Thickness direction

[0244] 21, 22 Peeling off the gasket

[0245] 41 Protective Glass

[0246] 43 Printed Layer

Claims

1. An optical adhesive sheet, said optical adhesive sheet comprising a base polymer and having photocurability, wherein, The base polymer is a photopolymer containing polymerizable components of monofunctional monomers and photopolymerizable polyfunctional compounds. The optical adhesive sheet has a shear storage modulus G1 of less than 0.3 MPa at 25°C. The cumulative irradiation intensity was 3000 mJ / cm². 2 After being cured by ultraviolet irradiation under certain conditions, the fracture strain Bs of the optical adhesive sheet in the tensile test at 23°C and a tensile speed of 300 mm / min satisfies the shear storage modulus G2 of the optical adhesive sheet at 25°C as Bs≥-0.17G2+3.

74.

2. The optical adhesive sheet according to claim 1, wherein, The ratio of the shear storage modulus G2 to the shear storage modulus G1 is less than 300.

3. The optical adhesive sheet according to claim 1, wherein, The fracture strain Bs is greater than 2.

0.

4. The optical adhesive sheet according to any one of claims 1 to 3, wherein, The adhesive force F in the following peel test is ≥ 2.0 N / 10 mm. Peel test: First, a small piece of the optical adhesive sheet, 100 mm in length and 10 mm in width, is bonded to an alkali glass plate made using the float glass method to obtain a laminate. Next, the laminate is subjected to heat and pressure treatment at 50°C, 0.5 MPa, and 15 minutes. Then, it is subjected to a cumulative irradiation of 3000 mJ / cm². 2 Under certain conditions, the adhesive sheet in the laminate is irradiated with ultraviolet light from the side of the alkali glass plate to cure the adhesive sheet; then, one end of the adhesive sheet in the length direction is pulled at 23°C, a peel angle of 180° and a pulling speed of 300 mm / min to peel the adhesive sheet from the alkali glass plate and measure the adhesive force F.

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