Optical adhesive sheet

Abstract

The objective of this invention is to provide an optical adhesive sheet suitable for reducing environmental impact and for use in display panels. The adhesive sheet 10 of this invention is an optical adhesive sheet containing a base polymer as a photopolymer and possessing photocurability. The adhesive sheet 10, after being photocured under conditions of irradiation with a cumulative light intensity of 3000 mJ / cm², has a gel content of 75% by mass or more. The adhesive sheet 10 is light-cured under a cumulative light intensity of 3000 mJ / cm². Then, the adhesive sheet 10 is bonded to an alkali glass plate made by the float glass method. After being heated and pressurized on the alkali glass plate at 50°C, 0.5 MPa and 15 minutes, the adhesive sheet 10 exhibits an adhesion force of more than 2.5 N / 10 mm in a peel test at 85°C, a peel angle of 180° and a tensile speed of 300 mm / min.

Description

Optical adhesive sheet This invention relates to an optical adhesive sheet. Display panels, for example, have a multilayer structure comprising elements such as pixel panels, polarizing films, and cover glass. During the manufacturing process of a display panel, transparent adhesive sheets (optical adhesive sheets) are used, for example, to bond the elements of the multilayer structure together. Adhesive sheets used in display panels are described, for example, in Patent Document 1 below. [Prior Art Documents] [Patent Documents] [Patent Document 1] Japanese Patent Application Publication No. 2012-62345 [The problem the invention aims to solve] The optical adhesive sheet of Patent Document 1 is manufactured as follows: First, after preparing a reaction solution containing monomer components for forming an acrylic-based base polymer, a thermal polymerization initiator, and a solvent, an acrylic-based base polymer is formed by solution polymerization in the reaction solution. Next, a solvent is added to the reaction solution to prepare a polymer solution with adjusted polymer concentration. Next, a thermal crosslinking agent is added to the polymer solution to prepare an adhesive composition (solvent-based adhesive composition). Next, the adhesive composition is coated onto a substrate to form a coating film. Next, the coating film on the substrate is dried by heating to form an adhesive layer (drying step). Next, an aging treatment is performed to allow crosslinking of the base polymer caused by the thermal crosslinking agent to occur within the adhesive layer. An optical adhesive sheet is formed on a substrate in the above manner. Thus, Patent Document 1 describes an optical adhesive sheet formed from a solvent-based adhesive composition. However, during the aforementioned drying step, a relatively large amount of solvent in the coating evaporates outside the coating. From an environmental perspective, manufacturing optical adhesive sheets that includes this step is undesirable. On the other hand, the laminated structure of a display panel includes elements with surface gradients. For example, a decorative or light-shielding printed layer is provided at the edge of the pixel panel side surface of the cover glass, resulting in a gradient between the surface of the cover glass and the surface of the printed layer (printing gradient). Similarly, on the polarizing film side surface of a pixel panel with a polarizing film, a specific resin layer is provided along a portion of the peripheral edge of the polarizing film on the pixel panel, resulting in a gradient between the surface of the polarizing film edge and the surface of the resin layer (resin gradient). This type of pixel panel with a polarizing film and the aforementioned cover glass are bonded to the display panel during the manufacturing process via an optical adhesive sheet. Therefore, the optical adhesive sheet used in display panels requires flexibility to follow the degree of printing gradient (gradient following). When an optical adhesive sheet is bonded to the surface of an adherend with surface gradients (such as a cover glass with printed gradients and a pixel panel with a polarizing film and resin gradients), insufficient gradient following of the optical adhesive sheet can lead to the formation of bubbles along the gradients, which is undesirable. Furthermore, the laminated structure of display panels includes elements with high surface smoothness, such as cover glass and polarizing film. Therefore, optical adhesive sheets used in display panels also require high adhesion. This invention provides an optical adhesive sheet suitable for reducing environmental impact and for use in display panels. [Technical Means for Solving the Problem] The present invention [1] is an optical adhesive sheet comprising a base polymer as a photopolymer and having photocurability, and is capable of being cured by irradiation with a cumulative light intensity of 3000 mJ / cm. 2 The optical adhesive sheet was subjected to photocuring treatment under the above conditions, and after curing, it had a gel content of 75% or more by mass. The optical adhesive sheet was then photocured under the above conditions and then bonded to an alkali glass plate made by the float glass method. After that, the optical adhesive sheet on the alkali glass plate was subjected to heat and pressure treatment at 50°C, 0.5 MPa and 15 minutes. In the peel test of peeling the optical adhesive sheet from the alkali glass plate at 85°C, peel angle of 180° and tensile speed of 300 mm / min, it had an adhesion of 2.5 N / 10 mm or more. The present invention [2] comprises an optical adhesive sheet as described in [1] above, which further comprises a photopolymerizable multifunctional compound and a photopolymerization initiator. The present invention [3] includes an optical adhesive sheet as described in [1] or [2] above, wherein the weight average molecular weight of the base polymer is 800,000 or more. The present invention [4] comprises an optical adhesive sheet as described in any one of [1] to [3] above, wherein the material is subjected to an irradiation of a cumulative light intensity of 3000 mJ / cm. 2 The optical adhesive sheet, after being cured by photocuring under the conditions of 23°C and a tensile speed of 200 mm / min, was stretched to 6 times its original length and then, after 5 minutes, the residual stress of the optical adhesive sheet was 55 N / m. 2 the following. The present invention [5] comprises an optical adhesive sheet as described in any one of [1] to [4] above, wherein the cumulative light intensity under illumination is 3000 mJ / cm 2Under certain conditions, the optical adhesive sheet was photocured, and then bonded to an alkali glass plate manufactured by the float glass method. The optical adhesive sheet on the alkali glass plate was then subjected to heat and pressure treatment at 50°C, 0.5 MPa, and 15 minutes. In a constant load peel test at 23°C, a peel angle of 90°, and a tensile load of 2.5 N / 10 mm, the peel speed was less than 35 μm / s. [Effects of the Invention] The optical adhesive sheet of the present invention, as described above, uses a photopolymer as its base polymer. This type of adhesive sheet is suitable for manufacture using a solvent-free adhesive composition. Furthermore, in the process of manufacturing the adhesive sheet from this solvent-free adhesive composition, a drying step requiring the solvent to evaporate and be removed from the coating of the composition is unnecessary, thus reducing environmental impact. Furthermore, the optical adhesive sheet of the present invention, as described above, possesses photocurability. This optical adhesive sheet can be adhered to the surface of the substrate with surface gradients in a soft state before photocuring. Moreover, the optical adhesive sheet can be photocured and become highly elastic after being adhered to the substrate. This optical adhesive sheet is suitable for achieving good gradient tracking when adhered to a substrate with a surface gradient. Therefore, the optical adhesive sheet of the present invention is suitable for bonding elements including elements with surface gradients (such as cover glass) together during the manufacturing process of a display panel. Furthermore, the optical adhesive sheet of the present invention, after photocuring under specific conditions as described above, exhibits an adhesion of 2.5 N / 10 mm or more to alkali glass plates manufactured by the float glass method at high temperatures (85°C). Alkali glass plates manufactured by the float glass method are difficult to adhere to adhesives due to their high surface smoothness, but the optical adhesive sheet of the present invention exhibits excellent adhesion to such glass plates. This optical adhesive sheet is suitable for bonding substrates with high surface smoothness, such as cover glass and polarizing films, in display panels. Therefore, the optical adhesive sheet of the present invention is suitable for display panel applications. Furthermore, the optical adhesive sheet of the present invention, after photocuring under specific conditions as described above, has a gel fraction of 75% by mass or higher. Such a high gel fraction optical adhesive sheet is not easily peeled off from the adhered object before curing (high elasticity) of the adhesive sheet, nor is it easily peeled off from the adhered object after curing (high elasticity) of the adhesive sheet. This type of optical adhesive sheet capable of achieving a high gel fraction is suitable for bonding the first adhered object and the second adhered object together by adhering the adhesive sheet to a first adhered object with a surface gradient (adhered in a soft state before photocuring of the adhesive sheet), allowing the adhesive sheet to photocure, and then bonding the first adhered object and the second adhered object together via the adhesive sheet, thereby ensuring good bonding reliability between the first and second adhered objects. Therefore, the optical adhesive sheet of the present invention is suitable for display panel applications. As shown in FIG1, the adhesive sheet 10, as one embodiment of the present invention, has a sheet shape of a specific thickness and extends in a direction orthogonal to the thickness direction H (plane direction). The adhesive sheet 10 has an adhesive surface 11 and an adhesive surface 12 opposite to the adhesive surface 11. FIG1 illustratively shows the state in which release liner 21 and 22 are attached to the adhesive surfaces 11 and 12 of the adhesive sheet 10. The release liner 21 is disposed on the adhesive surface 11. The release liner 22 is disposed on the adhesive surface 12. Furthermore, the adhesive sheet 10 is an optical adhesive sheet disposed on the light-passing portion of a display panel. Examples of display panels include liquid crystal panels and organic EL panels. The display panel, for example, has a multilayer structure including elements such as a pixel panel, a polarizing film, a touch panel, and a cover glass. The adhesive sheet 10 is used, for example, in the manufacturing process of the display panel to bond the elements included in the multilayer structure to each other. The adhesive sheet 10 is a sheet-like pressure-sensitive adhesive. The adhesive sheet 10 contains a base polymer as a photopolymer, and in this embodiment further contains a photopolymerizable multifunctional compound and a photopolymerization initiator, exhibiting photocurability. Photocurability refers to the property of becoming highly elastic upon exposure to active energy rays such as ultraviolet light. The adhesive sheet 10, upon exposure to a cumulative light intensity of 3000 mJ / cm², achieves photocurability. 2 Under certain conditions, the material is light-cured and, after curing, exhibits a gel content of 75% or more by mass, and an adhesion force F of 2.5 N / 10 mm or more in the peel test described below. The method for determining the gel content is as described in the examples below. The adhesion force F is the adhesion force of the adhesive sheet 10 to the alkali glass plate after light curing. The strength of the adhesion force of the adhesive sheet to the alkali glass plate is, for example, an indicator of the strength of the adhesion force of the adhesive sheet to the polarizing film. In the peeling test, the cumulative light intensity was 3000 mJ / cm. 2 Under certain conditions, the adhesive sheet 10 was light-cured, and then bonded to an alkali glass plate produced by the float glass method. The adhesive sheet 10 was then subjected to heat and pressure treatment on the alkali glass plate at 50°C, 0.5 MPa, and 15 minutes. Finally, the adhesive sheet 10 was peeled from the alkali glass plate at 85°C, a peel angle of 180°, and a tensile speed of 300 mm / min, and the adhesion force F was measured. The peel test is more specifically described below with reference to the examples. As described above, the base polymer of the adhesive sheet 10 is a photopolymer. This type of adhesive sheet 10 is suitable for manufacture from a solvent-free adhesive composition. Moreover, in the process of manufacturing the adhesive sheet from the solvent-free adhesive composition, there is no need for a drying step that allows the solvent to evaporate and be removed from the coating of the composition, thus reducing environmental impact. Furthermore, the adhesive sheet 10, as described above, possesses photocurability. This adhesive sheet 10 can adhere to the surface of the substrate with surface gradients in a soft state before photocuring. Moreover, the adhesive sheet 10 can become highly elastic after photocuring upon adhesion to the substrate. This adhesive sheet 10 is suitable for achieving good gradient following when adhered to a substrate with a surface gradient. Therefore, the adhesive sheet 10 is suitable for bonding elements containing elements with surface gradients (such as cover glass) together during the manufacturing process of a display panel. Furthermore, as described above, after photocuring under specific conditions, the adhesive sheet 10 exhibits an adhesion force F of 2.5 N / 10 mm or more to alkali glass sheets produced by the float glass method at high temperatures (85°C). Alkali glass sheets produced by the float glass method are difficult to adhere to with adhesives due to their high surface smoothness, but the adhesive sheet 10 exhibits excellent adhesion to these glass sheets. This adhesive sheet 10 is suitable for bonding substrates with high surface smoothness, such as glass substrates and polarizing films, in display panels. Therefore, the adhesive sheet 10 is suitable for display panel applications. Furthermore, as described above, the adhesive sheet 10, after photocuring under specific conditions, has a gel fraction of 75% by mass or higher. This high gel fraction of the adhesive sheet 10 makes it difficult for the adhered object to peel off from itself before curing (before becoming highly elastic), and also makes it difficult for the adhered object to peel off from itself after curing (before becoming highly elastic). This type of adhesive sheet 10, capable of achieving a high gel fraction, is suitable for photocuring by adhering it to a first adhered object with a surface gradient (adhered in its soft state before photocuring), thereby bonding the first and second adhered objects together and ensuring good bonding reliability between the first and second adhered objects. Therefore, the adhesive sheet 10 is suitable for display panel applications. As described above, the adhesive sheet 10 is suitable for reducing environmental impact and for display panel applications. From the viewpoint of good adhesion to adherents with high surface smoothness, the adhesion force F is preferably 2.7 N / 10 mm or more, more preferably 2.9 N / 10 mm or more, and even more preferably 3.1 N / 10 mm or more. For example, the adhesion force F is 4 N / 10 mm or less, 7 N / 10 mm or less, or 10 N / 10 mm or less. Methods for adjusting the adhesion force F include, for example, selecting the type of base polymer in the adhesive sheet 10, adjusting the molecular weight, and adjusting the formulation amount. The selection of the type of base polymer includes adjusting the composition of the monomers forming the base polymer. Methods for adjusting the adhesion force F also include selecting the type of components other than the base polymer in the adhesive sheet 10 and adjusting the formulation amount of those components. Examples of such components include photopolymerizable multifunctional compounds, photopolymerization initiators, silane coupling agents, and oligomers. In the adhesive sheet 10, from the viewpoint of ensuring the bonding reliability between the adhered bodies using the adhesive sheet 10, the weight-average molecular weight (Mw) of the base polymer is preferably 800,000 or more, more preferably 850,000 or more, and even more preferably 900,000 or more. From the viewpoint of ensuring the bonding reliability between the adhered bodies using the adhesive sheet 10, the weight-average molecular weight of the base polymer is preferably 1,500,000 or less, more preferably 1,200,000 or less, and even more preferably 1,000,000 or less. The weight-average molecular weight is determined by gel permeation chromatography (GPC) and calculated using polystyrene. Regarding the gel content of the adhesive sheet 10 after photocuring, from the viewpoint of ensuring the flexibility of the cured adhesive sheet 10, it is preferably 76% or more, more preferably 77% or more, and even more preferably 78% or more. Regarding the gel content of the adhesive sheet 10 after photocuring, from the viewpoint of ensuring the flexibility of the cured adhesive sheet 10, it is preferably 90% or less, more preferably 85% or less, and even more preferably 80% or less. Examples of methods for adjusting the gel content of the adhesive sheet 10 after photocuring include: selecting the type of base polymer in the adhesive sheet 10, adjusting the molecular weight, and adjusting the formulation amount. Examples of methods for adjusting the gel content after photocuring include: selecting the type of photopolymerizable multifunctional compound in the adhesive sheet 10, adjusting the molecular weight, and adjusting the formulation amount. Furthermore, the method for determining the gel content is described below in the examples. Regarding the gel fraction of the adhesive sheet 10 (before light curing), from the viewpoint of ensuring the workability of the adhesive sheet 10, it is preferably 20% or more, more preferably 25% or more, and even more preferably 30% or more, and preferably 65% ​​or less, even more preferably 60% or less, and even more preferably 55% or less. Methods for adjusting the gel fraction of the adhesive sheet 10 before light curing include, for example, selecting the type of base polymer in the adhesive sheet 10, adjusting the molecular weight, and adjusting the formulation amount. The adhesive sheet 10 is subjected to a cumulative light intensity of 3000 mJ / cm. 2 After curing under light-curing conditions, the residual stress S after elongation to 6 times its original length at 23°C and a tensile speed of 200 mm / min for 5 minutes is preferably 55 N / m. 2 Below, 50 N / m is preferred. 2 The following is preferred: 40 N / m 2 The residual stress S is preferably 10 N / m. 2The above is preferred to be 20 N / m. 2 The above, and preferably 30 N / m 2 The above describes the composition of the residual stress S, which is beneficial for ensuring the step followability of the adhesive sheet 10 after photocuring. Examples of methods for adjusting the residual stress S include adjusting the monomer composition, molecular weight, formulation amount, and degree of crosslinking of the base polymer in the adhesive sheet 10. The method for measuring the residual stress S is specifically described below with reference to the examples. The peel speed of the adhesive sheet 10 in the following constant load peel test is preferably 35 μm / s or less, more preferably 30 μm / s or less, and even more preferably 25 μm / s or less. This peel speed is, for example, 0.1 μm / s or more, 0.5 μm / s or more, or 1 μm / s or more. This configuration of peel speed is better for ensuring the bonding reliability of the adhesive sheet 10 to the adherend when the photocured adhesive sheet 10 is bonded to the surface step portion of the adherend with surface step. In the constant load peel test, the cumulative light intensity was 3000 mJ / cm. 2 Under certain conditions, the adhesive sheet 10 was photocured, and then bonded to an alkali glass plate made by a float glass method. The adhesive sheet 10 was then subjected to heat and pressure treatment on the alkali glass plate at 50°C, 0.5 MPa, and 15 minutes. The peeling speed was then measured by peeling the optical adhesive sheet from the alkali glass plate at 23°C, a peel angle of 90°, and a tensile load of 2.5 N / 10 mm. The constant load peel test is more specifically described below with reference to the examples. Examples of methods for adjusting the peeling speed include: selecting the type of the first photopolymerizable multifunctional compound in the adhesive sheet 10, adjusting its molecular weight, and adjusting its formulation amount. Examples of methods for adjusting the peeling speed also include: adjusting the monomer composition of the base polymer in the adhesive sheet 10, adjusting its molecular weight, adjusting its formulation amount, and adjusting its degree of crosslinking. The adhesive sheet 10 has a transmittance R1 of 85% or more at a wavelength of 420 nm, and a transmittance R2 of 15% or less at a wavelength of 380 nm. This configuration is preferable for ensuring the transparency required for the adhesive sheet 10 in display panel applications and for ensuring the UV protection function of the display panel. From the viewpoint of transparency, the transmittance R1 is preferably 87% or more, more preferably 89% or more, and even more preferably 90% or more. For example, the transmittance R1 is 99% or less. From the viewpoint of protection, the transmittance R2 is preferably 14% or less, more preferably 13% or less, more preferably 12% or less, more preferably 11% or less, more preferably 10% or less, more preferably 9% or less, more preferably 8% or less, more preferably 7% or less, more preferably 6% or less, and more preferably 5% or less. For example, the transmittance R2 is 0.1% or more. The methods for measuring transmittance at a wavelength of 380 nm and at a wavelength of 420 nm are specifically described in the following examples. The adhesive sheet 10 contains a base polymer (photopolymer), a photopolymerizable polyfunctional compound (first photopolymerizable polyfunctional compound), and a photopolymerization initiator, and exhibits photocurability. In addition to the photopolymerizable polyfunctional compound, the adhesive sheet 10 may also contain monofunctional monomers as polymerizable components. A photopolymer refers to a polymer produced through photopolymerization. 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. The basic polymer is a polymer obtained by photopolymerization of a polymeric component comprising a monofunctional monomer and a photopolymerizable polyfunctional compound (a second photopolymerizable polyfunctional compound). For example, the basic polymer is obtained by photopolymerization of a partial polymer (a mixture of the monofunctional monomer polymer and unreacted monofunctional monomers) produced by the photopolymerization of a monofunctional monomer and a second photopolymerizable polyfunctional compound. Monofunctional monomers can be used alone or in combination of two or more. Second photopolymerizable polyfunctional compounds can be used alone or in combination of two or more. This base polymer includes photopolymers with a photocrosslinking structure (first photopolymer). The photocrosslinking structure is a structure obtained by crosslinking linear structures formed by units of monofunctional monomers through units derived from second photopolymerizable polyfunctional compounds. The base polymer may also include photopolymers without this photocrosslinking structure (second photopolymer). The second photopolymer is a polymer of monofunctional monomers. Furthermore, the base polymer is preferably an acrylic polymer. An acrylic polymer is a copolymer containing a polymerizable component of (meth)acrylate at a ratio of 50% by mass or more. "(meth)acrylate" means acrylic acid and / or methacrylic acid. As a monofunctional monomer, a monofunctional (meth)acrylate is preferred. As a monofunctional (meth)acrylate, an alkyl (meth)acrylate is preferred, and more preferably an alkyl (meth)acrylate with an alkyl group having 1 to 20 carbon atoms. The alkyl (meth)acrylate may have a straight-chain or branched alkyl group, or may have a cyclic alkyl group such as an alicyclic alkyl group. Examples of linear or branched alkyl methacrylates include: methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, dibutyl methacrylate, terbutyl methacrylate, pentyl methacrylate, isoamyl methacrylate, neopentyl methacrylate, hexyl methacrylate, heptyl methacrylate, 2-ethylhexyl methacrylate, octyl methacrylate, isooctyl methacrylate, and so on. Nonyl acrylate, isononyl acrylate, decyl acrylate, isodecyl acrylate, undecyl acrylate, dodecyl acrylate, isotridecyl acrylate, tetradecyl acrylate, isotetradecyl acrylate, pentadecyl acrylate, cetyl acrylate, heptadecanyl acrylate, octadecyl acrylate, isooctadecyl acrylate, and nonadecanyl acrylate. Examples of alkyl (meth)acrylates having an alicyclic alkyl group include: cycloalkyl (meth)acrylates, meth)acrylates having a bicyclic aliphatic hydrocarbon ring, and meth)acrylates having three or more aliphatic hydrocarbon rings. Examples of cycloalkyl (meth)acrylates include: cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, cycloheptyl (meth)acrylate, and cyclooctyl (meth)acrylate. Examples of meth)acrylates having a bicyclic aliphatic hydrocarbon ring include: isocyanate (meth)acrylate. Examples of meth)acrylates having three or more aliphatic hydrocarbon rings include: dicyclopentyl (meth)acrylate, dicyclopentoxyethyl (meth)acrylate, tricyclopentyl (meth)acrylate, 1-adamantyl (meth)acrylate, 2-methyl-2-adamantyl (meth)acrylate, and 2-ethyl-2-adamantyl (meth)acrylate. As an alkyl methacrylate, it is preferred to use an alkyl acrylate having an alkyl group having 3 to 15 carbon atoms, and more preferably to use at least one selected from the group consisting of n-butyl acrylate, 2-ethylhexyl acrylate and dodecyl acrylate. Regarding the ratio of monofunctional monomers in the polymerizable components that form the basic polymer, from the viewpoint that the adhesive sheet 10 should appropriately exhibit basic properties such as adhesion, it is preferably 50% by mass or more, more preferably 60% by mass or more, and even more preferably 70% by mass or more. This ratio is, for example, 99% by mass or less. The polymerizable component may also include a comonomer capable of copolymerizing with monofunctional (meth)acrylates as a monofunctional monomer. Examples of comonomers containing polar groups include, for example, monomers containing hydroxyl groups, monomers containing carboxyl groups, and monomers with a nitrogen-containing ring. Monomers containing polar groups contribute to the modification of acrylic polymers, such as ensuring the cohesiveness of the acrylic polymer. Examples of hydroxyl-containing monomers include, for example, 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. Preferably, at least one monomer selected from the group consisting of 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate is used. Regarding the ratio of hydroxyl-containing monomers in the polymerizable components, from the viewpoint of ensuring the cohesive force in the adhesive sheet 10, it is preferably 1% by mass or more, more preferably 3% by mass or more, and even more preferably 5% by mass or more. From the viewpoint of adjusting the polarity of the acrylic polymer (regarding the compatibility of various additive components in the adhesive sheet 10 with the acrylic polymer), this ratio is preferably 30% by mass or less, more preferably 20% by mass or less, and even more preferably 15% by mass or less. Examples of carboxyl-containing monomers include: acrylic acid, methacrylic acid, carboxyethyl acrylate, carboxypentyl acrylate, itaconic acid, maleic acid, trans-butenedioic acid, butenoic acid, and isobutenoic acid. From the viewpoint of ensuring the cohesive force of the adhesive sheet 10 and the adhesion force of the adhesive sheet 10 to the adherend, the proportion of carboxyl-containing monomers in the polymeric component is preferably 1% by mass or more, more preferably 3% by mass or more, and even more preferably 5% by mass or more. From the viewpoint of adjusting the glass transition temperature of the acrylic polymer and avoiding the risk of corrosion of the adherend caused by acid, this proportion is preferably 20% by mass or less, and more preferably 10% by mass or less. Examples of monomers having a ring containing a nitrogen atom include: N-vinyl-2-pyrrolidone, N-methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, N-vinylpiperidone, N-vinylpyrrole, N-vinylimidazolium, N-vinylpyrazole, N-(meth)acryl-2-pyrrolidone, N-(meth)acrylpiperidine, N-(meth)acrylpyrrolidone, N-vinylmorpholine, N-vinyl-3-morpholinone, N-vinyl-2-caprolactone, N-vinyl-1,3-vinyl-2-one, N-vinyl-3,5-morpholinedione, N-vinylpyrazole, N-vinylisothiazole, N-vinylisothiazole, and acrylmorpholine. The monomer having a ring containing a nitrogen atom is preferably selected from at least one of the group consisting of N-vinyl-2-pyrrolidone and acrylamide morpholine. Regarding the proportion of monomers containing nitrogen-containing rings in the polymeric component, from the viewpoint of ensuring cohesiveness in the adhesive sheet and adhesion between the adhesive sheet and the adherend, it is preferably 1% by mass or more, more preferably 3% by mass or more, and even more preferably 5% by mass or more. From the viewpoint of adjusting the glass transition temperature of the acrylic polymer and adjusting the polarity of the acrylic polymer (regarding the compatibility of various additive components in the adhesive sheet with the acrylic polymer), this proportion is preferably 30% by mass or less, more preferably 20% by mass or less. As a second photopolymerizable multifunctional compound, examples include multifunctional monomers and multifunctional oligomers, with multifunctional oligomers being preferred. Examples of multifunctional monomers include multifunctional (meth)acrylates containing two or more vinyl unsaturated double bonds in one molecule. From the viewpoint that multifunctional monomers are more easily cross-linked by photopolymerization (active energy line polymerization), multifunctional (meth)acrylates are preferred. Examples of polyfunctional (meth)acrylates include difunctional (meth)acrylates, trifunctional (meth)acrylates, and polyfunctional (meth)acrylates with four or more functions. 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, dicyclopentenyl diacrylate, dimethacrylamide isocyanurate, and ethoxylated bisphenol A diacrylate (BPAEODE). Examples of trifunctional (meth)acrylates include: trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, and tri(acryloxyethyl)isocyanurate. Examples of polyfunctional (meth)acrylates with four or more functions include: di-trimethylolpropane tetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol monohydroxy penta(meth)acrylate, alkyl-modified dipentaerythritol pentaacrylate, and dipentaerythritol hexa(meth)acrylate. The molecular weight of the multifunctional monomer is preferably below 5000, more preferably below 3000, further preferably below 2000, especially below 1000, and preferably above 200. This configuration is preferable from the viewpoint of appropriately adjusting the viscoelasticity (e.g., shear storage modulus and loss tangent) of the base polymer. Examples of multifunctional oligomers include: urethane acrylate oligomers (oligomers having an urethane backbone and two or more acrylonitrile groups), epoxy acrylate oligomers (oligomers having an epoxy backbone and two or more acrylonitrile groups), and polysiloxane acrylate oligomers (oligomers having a silicate backbone and two or more acrylonitrile groups). Uramate acrylate oligomers are preferred as multifunctional oligomers. Commercially available urethane acrylate oligomers include, for example, Artresin UN-333, UN-350, UN-353, UN-5500, and UN-5590 manufactured by Genjo Industries. The weight-average molecular weight (Mw) of the multifunctional oligomer is preferably below 20,000, more preferably below 15,000, and even more preferably above 5,000. This configuration is preferable from the viewpoint of appropriately adjusting the viscoelasticity (e.g., shear storage modulus and loss tangent) of the base polymer. The weight-average molecular weight was determined by gel permeation chromatography (GPC) and calculated using polystyrene. The proportion of the second photopolymerizable multifunctional compound in the polymerizable component is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, and even more preferably 0.5% by mass or more. This configuration is better for maintaining the sheet shape of the adhesive sheet 10 before photocuring, and therefore better for ensuring the operability of the adhesive sheet 10. The proportion of the second photopolymerizable multifunctional compound in the polymerizable component is preferably 5% by mass or less, more preferably 3% by mass or less, and even more preferably 2% by mass or less. This configuration is better for ensuring a high degree of flexibility of the adhesive sheet 10 before photocuring, thereby achieving good step followability. The polymerizable component may also include other comonomers. Examples of other comonomers include acid anhydride monomers, sulfonic acid monomers, phosphate monomers, epoxy monomers, cyano monomers, alkoxy monomers, and aromatic vinyl compounds. These other comonomers may be used alone or in combination of two or more. Examples of the first photopolymerizable multifunctional compound include multifunctional monomers and multifunctional oligomers, with multifunctional monomers being preferred. Examples of multifunctional monomers include those described above regarding the second photopolymerizable multifunctional compound. Examples of multifunctional oligomers include those described above regarding the second photopolymerizable multifunctional compound. The first photopolymerizable multifunctional compound can be used alone or in combination of two or more. Preferably, the first photopolymerizable multifunctional compound is selected from at least one of the group consisting of ethoxylated bisphenol A diacrylate (BPAEODE), trimethylolpropane triacrylate (TMPTA), and dipentaerythritol hexaacrylate (DPHA). The content of the first photopolymerizable polyfunctional compound in the adhesive sheet 10 is preferably 2.5 parts by mass or more, more preferably 3 parts by mass or more, and even more preferably 3.5 parts by mass or more, and preferably 8 parts by mass or less, more preferably 7 parts by mass or less, and even more preferably 6 parts by mass or less, relative to 100 parts by mass of the base polymer. This configuration is suitable for ensuring good bonding reliability of the adhesive sheet 10 after photocuring. Examples of photopolymerization initiators include free radical photopolymerization initiators, cationic photopolymerization initiators, and anionic photopolymerization initiators. Examples of free radical photopolymerization initiators include: phosphonium oxychloride-based photopolymerization initiators, benzoin ether-based photopolymerization initiators, acetophenone-based photopolymerization initiators, α-keto alcohol-based photopolymerization initiators, aromatic sulfonylurea-chloro-based photopolymerization initiators, photoactive oxime-based photopolymerization initiators, benzoin-based photopolymerization initiators, benzophenone-based photopolymerization initiators, ketal-based photopolymerization initiators, and 9-oxosulfuron-methyl. It is a photopolymerization initiator. Examples of phosphine oxide-based photopolymerization initiators include: bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-2,4-di-n-butoxyphenylphosphine oxide, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, and bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide. Examples of benzoin ether-based photopolymerization initiators include: benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isopropyl ether, benzoin isobutyl ether, and 2,2-dimethoxy-1,2-diphenylethane-1-one. Examples of acetophenone-based photopolymerization initiators include: 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexylphenyl ketone, 4-phenoxydichloroacetophenone, and 4-(tert-butyl)dichloroacetophenone. Examples of α-keto-alcohol-based photopolymerization initiators include: 2-methyl-2-hydroxyphenylacetone and 1-[4-(2-hydroxyethyl)phenyl]-2-methylpropane-1-one. Examples of aromatic sulfonyl chloride-based photopolymerization initiators include: 2-naphthalenesulfonyl chloride. Examples of photoactive oxime-based photopolymerization initiators include: 1-phenyl-1,1-propanedione-2-(O-ethoxycarbonyl)-oxime. Examples of benzoin-based photopolymerization initiators include: benzoin. Examples of benzoin-based photopolymerization initiators include: benzoin. Examples of benzophenone-based photopolymerization initiators include benzophenone, benzoylbenzoic acid, 3,3'-dimethyl-4-methoxybenzophenone, and polyvinylbenzophenone. Examples of ketal-based photopolymerization initiators include benzodiazepine dimethyl ketal. As a 9-oxosulfuron... Photopolymerization initiators, such as 9-oxosulfuron-methyl. 2-Chloro-9-oxysulfur 2-Methyl-9-oxosulfur 2,4-Dimethyl-9-oxosulfur Isopropyl 9-Oxysulfur 2,4-Diisopropyl-9-oxosulfur and dodecyl 9-oxosulfur . Examples of cationic photopolymerization initiators (photoacid generators) include onium compounds that generate acids upon ultraviolet irradiation. These onium compounds are provided, for example, as onium salts of onium cations and anions. Examples of onium cations include strontium and monium. Examples of anions include Cl. - ,Br - I - ZnCl 3 - HSO 3 - BF 4 - PF 6 - AsF 6 - 、SbF 6 - CH 3SO 3 - CF 3SO 3 - C 4F 9HSO 3 - (C) 6F 5) 4B - and (C) 4H 9) 4B - Commercially available cationic photopolymerization initiators include, for example, CPI-100, CPI-100P, CPI-101A, CPI-200K, CPI-210S, IK-1, IK-2, CPI-310B, and CPI-410S manufactured by SAN-APRO. Commercially available cationic photopolymerization initiators also include, for example, SP-056, SP-066, SP-130, SP-140, SP-150, SP-170, SP-171, and SP-172 manufactured by ADEKA. Examples of anionic photopolymerization initiators (photoalkalizing agents) include: α-aminoacetophenone compounds, oxime ester compounds, and compounds having biguanide cations. Examples of biguanide cations include: alkyl biguanide, cycloalkyl biguanide, and cycloalkyl-alkyl biguanide. Examples of anions paired with biguanide cations include: borate anions. Examples of commercially available anionic photopolymerization initiators include: WPBG-018 (9-anthramethyl N,N'-diethylaminocarbamate), WPBG-027 ((E)-1-[3-(2-hydroxyphenyl)-2-propenyl]piperidine), WPBG-082 (2-(3-benzoylphenyl)propionate guanidine), and WPBG-140 (1-(anthraquinone-2-yl)ethyl... (Imidazole carboxylate), WPBG-266 (1,2-diisopropyl-3-[bis(dimethylamino)methylene]guanidinium), WPBG-300 (1,2-dicyclohexyl-4,4,5,5-tetramethylbiguanidinium butyltriphenylboronic acid), and WPBG-345 (1,2-dicyclohexyl-4,4,5,5-tetramethylbiguanidinium tetra(3-fluorophenyl)boronic acid). The content of the photopolymerization initiator in the adhesive sheet 10 is preferably 0.01 parts by mass or more, more preferably 0.02 parts by mass or more, further preferably 0.03 parts by mass or more, even more preferably 0.05 parts by mass or more, even more preferably 0.07 parts by mass or more, even more preferably 0.1 parts by mass or more, and particularly preferably 0.2 parts by mass or more, relative to 100 parts by mass of the base polymer. This configuration is preferable for forming a cross-linked network structure with sufficient cross-linking density within the adhesive sheet 10 through photopolymerization reaction when the adhesive sheet 10 is irradiated with light, thereby significantly changing the viscoelasticity of the adhesive sheet 10. The content of the photopolymerization initiator in the adhesive sheet 10 is preferably 3 parts by mass or less, more preferably 2 parts by mass or less, and even more preferably 1 part by mass or less, relative to 100 parts by mass of the base polymer. This configuration is better for suppressing the generation of more polymerization initiators when the adhesive sheet 10 is irradiated with light, thereby forming a long-distance and continuous cross-linked network structure through photopolymerization. The adhesive sheet 10 may also contain other components. Examples of other components include: oligomers, ultraviolet absorbers, antioxidants, silane coupling agents, rust inhibitors, secondary processing enhancers, isocyanate crosslinking agents, and metal deactivators. When the base polymer is an acrylic polymer, it is preferable to use an acrylic oligomer as the oligomer. An acrylic oligomer is a copolymer containing (meth)acrylate monomer components at a ratio of 50% by mass or more, and has a weight average molecular weight of, for example, 1,000 to 30,000. The acrylic oligomer is preferably a polymer comprising monomer 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 such alkyl (meth)acrylates include, for instance, the alkyl (meth)acrylates described above as polymerizable components of acrylic polymers. As a (meth)acrylate chain alkyl ester, methyl methacrylate is preferred in terms of its high glass transition temperature and excellent compatibility with the base polymer. As a (meth)acrylate cyclocyclic alkyl ester, dicyclopentyl acrylate, dicyclopentyl methacrylate, cyclohexyl acrylate, and cyclohexyl methacrylate are preferred. That is, the acrylic oligomer is preferably a polymer comprising one or more monomers selected from the group consisting of dicyclopentyl acrylate, dicyclopentyl methacrylate, cyclohexyl acrylate, and cyclohexyl methacrylate, and methyl methacrylate. The proportion of (meth)acrylate cyclic alkyl esters in the monomer component of the acrylic oligomer is preferably 10% by mass or more, more preferably 20% by mass or more, and even more preferably 30% by mass or more. This proportion is preferably 90% by mass or less, more preferably 80% by mass or less, and even more preferably 70% by mass or less. The proportion of (meth)acrylate chain alkyl esters in the monomer component of the acrylic oligomer is preferably 90% by mass or less, more preferably 80% by mass or less, and even more preferably 70% by mass or less. This proportion is preferably 10% by mass or more, more preferably 20% by mass or more, and even more preferably 30% by mass or more. Acrylic oligomers are obtained by polymerizing the monomeric 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 solvent are evaporated and removed from the reaction system, such as the reaction solution, by heating. Examples of low-molecular-weight components include unreacted monomers, chain transfer agents, thermal polymerization initiators, and their decomposition products (residues). 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, 2,2'-azobis(2-methylpropionic acid) dimethyl ester, 4,4'-azobis-4-cyanopentanoic acid, azobisisovalerate, 2,2'-azobis(2-amidinylpropane) dihydrochloride, 2,2'-azobis[2-(5-methyl-2-imidazolin-2-yl)propane] dihydrochloride, 2,2'-azobis(2-methylpropanediamine) disulfide, and 2,2'-azobis(N,N'-dimethyleneisobutylamidine) dihydrochloride. Examples of peroxide polymerization initiators include benzoyl peroxide, tributyl maleate peroxide, and lauryl peroxide. 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. The weight-average molecular weight of the oligomer is preferably 1000 or more, more preferably 1500 or more, and even more preferably 2000 or more. This molecular weight is preferably 30000 or less, more preferably 10000 or less, and even more preferably 8000 or less. This range of molecular weights is preferable for ensuring the adhesion of the adhesive sheet 10. To sufficiently improve the adhesion of the adhesive sheet 10, the content of oligomers in the adhesive sheet 10 is preferably 0.5 parts by mass or more, more preferably 0.8 parts by mass or more, and even more preferably 1 part 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 10 parts by mass or less, more preferably 7 parts by mass or less, even more preferably 5 parts by mass or less, further preferably 4 parts by mass or less, and particularly preferably 3 parts by mass or less, relative to 100 parts by mass of the base polymer. Examples of UV absorbers include triazine-based, benzotriazole-based, benzophenone-based, salicylate-based, and cyanoacrylate-based UV absorbers. Triazine-based and benzotriazole-based UV absorbers are preferred in terms of high UV absorption in the 320–370 nm wavelength range and excellent compatibility with acrylic polymers. UV absorbers can be used alone or in combination of two or more. Commercially available triterpenoid UV absorbers include, for example: bis(ethylhexyloxyphenol)methoxyphenyltriterpenoid (trade name "Tinosorb S", manufactured by BASF), the reaction product of 2-(4,6-bis(2,4-dimethylphenyl)-1,3,5-triterpenoid-2-yl)-5-hydroxyphenyl with [(alkoxy)methyl]ethylene oxide (trade name "TINUVIN 400", manufactured by BASF), the reaction product of 2-(2,4-dihydroxyphenyl)-4,6-bis(2,4-dimethylphenyl)-1,3,5-triterpenoid with (2-ethylhexyl) glycidyl ester (trade name "TINUVIN 405", manufactured by BASF), and (2,4-bis[2-hydroxy-4-butoxyphenyl]-6-(2,4-dibutoxyphenyl)-1,3,5-triterpenoid (trade name "TINUVIN")... 460”, manufactured by BASF), 2-(4,6-diphenyl-1,3,5-tris(2-ethylhexyloxy)ethoxy]phenol (trade name “TINUVIN 577”, manufactured by BASF), 2-(2-hydroxy-4-[1-octyloxycarbonylethoxy]phenyl)-4,6-bis(4-phenylphenyl)-1,3,5-tris(2-ethylhexyloxy)ethoxy]phenol (trade name “TINUVIN 479”, manufactured by BASF), and 2-(4,6-diphenyl-1,3,5-tris(2-ethylhexyloxy)ethoxy]phenol (“ADK STAB LA-46”, manufactured by ADEKA). Commercially available benzotriazole-based ultraviolet absorbers include, for example: 2-(2H-benzotriazole-2-yl)-6-(1-methyl-1-phenylethyl)-4-(1,1,3,3-tetramethylbutyl)phenol (trade name "TINUVIN 928", manufactured by BASF), 2-(2-hydroxy-5-tert-butylphenyl)-2H-benzotriazole (trade name "TINUVIN PS", manufactured by BASF), 2-(2H-benzotriazole-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol (trade name "TINUVIN 900", manufactured by BASF), 2-(2H-benzotriazole-2-yl)-6-dodecyl-4-methylphenol (trade name "TINUVIN 571", manufactured by BASF), and 2-(2H-benzotriazole-2-yl)-p-cresol (trade name "TINUVIN"). P”, manufactured by BASF), 2-(2H-benzotriazol-2-yl)-4-6-bis(1-methyl-1-phenylethyl)phenol (trade name "TINUVIN 234", manufactured by BASF), 2-[5-chloro(2H)-benzotriazol-2-yl]-4-methyl-6-(tert-butyl)phenol (trade name "TINUVIN 326", manufactured by BASF), 2-(2H-benzotriazol-2-yl)-4,6-ditert-pentylphenol (trade name "TINUVIN 328", manufactured by BASF), 2-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol (trade name "TINUVIN 234"). 329 (manufactured by BASF), and 2-[2-hydroxy-3-(3,4,5,6-tetrahydrophthalimide-methyl)-5-methylphenyl]benzotriazole (trade name "Sumisorb250", manufactured by Sumitomo Chemical). In the adhesive sheet 10, the photopolymerization initiator preferably has a specific absorbance (first specific absorbance) of 10 or more, more preferably 15 or more, at a wavelength of 405 nm, and the ultraviolet absorber preferably has a specific absorbance (second specific absorbance) of 5 or less, more preferably 3 or less, at a wavelength of 405 nm. This configuration is preferable from the viewpoint of balancing the ultraviolet blocking function of the adhesive sheet 10 for device protection and its photocurability. Among the aforementioned photopolymerization initiators, for example, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide and 2,4,6-trimethylbenzoyldiphenylphosphine oxide have a first specific absorbance of 15 or more. Among the aforementioned ultraviolet absorbers, for example, bis(ethylhexyloxyphenol) methoxyphenyltriazine and 2-(2H-benzotriazol-2-yl)-6-(1-methyl-1-phenylethyl)-4-(1,1,3,3-tetramethylbutyl)phenol have a second absorbance of 3 or less. The content of the ultraviolet absorber in the adhesive sheet 10 is preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more, and 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 preferable from the viewpoint of balancing the ultraviolet blocking function of the adhesive sheet 10 for device protection with its photocurability. Examples of antioxidants include phenolic antioxidants, phosphorus antioxidants, sulfur antioxidants, and amine antioxidants. Antioxidants can be used alone or in combination of two or more. As antioxidants, phenolic antioxidants are preferred, and hindered phenolic antioxidants are even more preferred. Examples of hindered phenolic antioxidants include pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (trade name "Irganox 1010", manufactured by BASF) and octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (trade name "Irganox 1076", manufactured by BASF). 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 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 preferable from the viewpoint of balancing the inhibition of oxidative degradation of the adhesive sheet 10 and its photocurability. Examples of silane coupling agents include, for example, silane coupling agents containing epoxy groups. Examples of silane coupling agents containing epoxy groups include 3-glycidoxydialkyldialkoxysilane and 3-glycidoxyalkyltrialkoxysilane. Examples of 3-glycidoxydialkyldialkoxysilanes include 3-glycidoxypropylmethyldimethoxysilane and 3-glycidoxypropylmethyldiethoxysilane. Examples of 3-glycidoxyalkyltrialkoxysilanes include 3-glycidoxypropyltrimethoxysilane and 3-glycidoxypropyltriethoxysilane. 3-glycidoxyalkyltrialkoxysilane is preferred as a silane coupling agent, and more preferably 3-glycidoxypropyltrimethoxysilane. The silane coupling agent can be used alone or in combination with two or more. The content of the 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 more preferably 5 parts by mass or less, and more preferably 3 parts by mass or less, relative to 100 parts by mass of the base polymer. The adhesive sheet 10 is substantially free of residues of the thermal polymerization initiator. Residues of the thermal polymerization initiator include decomposition products of the thermal polymerization initiator. The proportion of thermal polymerization initiator residues in the adhesive sheet 10 is preferably less than 0.005% by mass, more preferably less than 0.001% by mass, and even more preferably 0%. From the viewpoint of ensuring sufficient adhesion to the adhered object, the thickness of the adhesive sheet 10 is preferably 10 μm or more, and more preferably 15 μm or more. From the viewpoint of the operability and laser processingability of the adhesive sheet 10, the thickness of the adhesive sheet 10 is preferably 500 μm or less, more preferably 400 μm or less, more preferably 300 μm or less, more preferably 250 μm or less, more preferably 200 μm or less, more preferably 150 μm or less, more preferably 135 μm or less, more preferably 100 μm or less, more preferably 75 μm or less, and more preferably 50 μm or less. The total light transmittance of the adhesive sheet 10 is preferably 90% or higher, and more preferably 92% or higher. This configuration is better for ensuring the transparency required for the adhesive sheet 10 in display panel applications. The total light transmittance of the adhesive sheet 10 is, for example, 100% or lower. The total light transmittance can be measured according to JIS K 7375 (2008). The adhesive sheet 10 can be manufactured, for example, in the following manner. First, a prepolymer composition is prepared (prepolymer composition preparation step). Specifically, first, a mixture (liquid) comprising the aforementioned monofunctional monomers used for forming the basic polymer and a photopolymerization initiator is prepared. This mixture is solvent-free. Second, by irradiating the mixture with ultraviolet light, a portion of the monofunctional monomers in the mixture undergoes photopolymerization to obtain a prepolymer composition (solvent-free prepolymer composition). Examples of ultraviolet 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 may be used as needed to block a portion of the wavelength range of light emitted from the light source. During ultraviolet irradiation, the illuminance is, for example, 5–200 mW / cm². 2 m, the cumulative light intensity of the irradiation is, for example, 100–5000 mJ / cm. 2 The ultraviolet irradiation is preferably continued until the viscosity of the composition reaches approximately 15–25 Pa·s. This viscosity is set as the value 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 (the aforementioned second photopolymer) and unpolymerized monofunctional monomers (residual monomers). Furthermore, the prepolymer composition does not contain solvents. Next, a second photopolymerizable multifunctional compound, a photopolymerization initiator, and other components as needed are added to the prepolymer composition to prepare an adhesive composition (adhesive composition preparation step). Other components may include, for example, antioxidants and silane coupling agents. Since the adhesive composition does not contain solvents, it is a solvent-free adhesive composition. Next, as shown in Figure 2A, a coating 10A is formed between the release liner 21 and 22' (coating formation step). Specifically, an adhesive composition is applied to the release liner 21 to form a coating 10A, and then the release liner 22' is bonded onto the coating 10A on the release liner 21. The release liner 21 and 22' are, for example, flexible plastic films. Examples of such plastic films include polyester films such as polyethylene terephthalate films, polyethylene films, and polypropylene films. The thickness of the release liner is, for example, 3 μm or more, and, for example, 200 μm or less. Preferably, the surface of the release liner has undergone a release treatment. Examples of coating methods for adhesive compositions include: roller coating, contact roller coating, gravure coating, reverse coating, roller brush coating, spray coating, dip roller coating, bar coating, squeegee coating, air knife coating, curtain coating, die lip coating, and nozzle coating. Next, as shown in Figure 2B, the coating 10A between the release liner 21 and 22' is irradiated with ultraviolet light to photocur it, forming a base adhesive sheet 10B (base adhesive sheet formation step). During ultraviolet irradiation, a photopolymerization reaction containing the aforementioned residual monomer and a second photopolymerizable polyfunctional compound is carried out in the coating to form a first photopolymerizable polymer with a photocrosslinked structure. Next, as shown in Figure 2C, the release liner 22' is peeled off from the base adhesive sheet 10B (peeling step). Next, as shown in Figure 2D, an additive component is supplied to the base adhesive sheet 10B (additive component supply step). For example, a additive component solution (not shown) containing the additive component and solvent is applied to the exposed surface of the base adhesive sheet 10B. The additive component includes a first photopolymerizable multifunctional compound and a photopolymerization initiator, and may also include additives such as ultraviolet absorbers or antioxidants. Next, while allowing the additive component to penetrate from the surface of the base adhesive sheet 10B to the base adhesive sheet 10B, heating is performed as needed to vaporize the solvent. Before this step, the base polymer already has a cross-linked structure to form the base adhesive sheet 10B. Therefore, it is not easy for an orange peel surface to form on the base adhesive sheet 10B due to the vaporization of the solvent in this step (it is not actually formed). Furthermore, a photocurable adhesive sheet 10 is formed by the base adhesive sheet 10B and the additive component. The amount of the first photopolymerizable polyfunctional compound added in this step is preferably 2.5 parts by mass or more, more preferably 3 parts by mass or more, and even more preferably 3.5 parts by mass or more, and preferably 8 parts by mass or less, more preferably 7 parts by mass or less, and even more preferably 6 parts by mass or less, relative to the total 100 parts by mass of the prepolymer composition and the second photopolymerizable polyfunctional compound. This configuration is suitable for ensuring good bonding reliability of the adhesive sheet 10 after photocuring. Next, as shown in Figure 2E, the release liner 22 is bonded to the adhesive sheet 10 (bonding step). As the release liner 22, for example, the plastic film described above regarding release liners 21 and 22' can be cited. In the manner described above, an adhesive sheet 10 with its adhesive surfaces covered and protected by release liner 21, 22 can be manufactured. The adhesive sheet 10, formed from a solvent-free adhesive composition, is suitable for reducing environmental impact. Furthermore, the release liner 21, 22 are self-peeling from the adhesive sheet 10 as needed when using it. Figures 3A to 3C illustrate one example of the use of the adhesive sheet 10. The method of using the adhesive sheet 10 refers to a method of bonding the adhered bodies together using the adhesive sheet 10. The method includes a bonding step (Figure 3A), a light curing step (Figure 3B), and a joining step (Figure 3C). First, in the bonding step, as shown in FIG3A, an adhesive sheet 10 is bonded to the cover glass 31 (the first adherend). The cover 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 on the edge of the first surface 31a. The printed layer 32 is provided, for example, throughout the entire circumference of the edge of the cover glass 31. There is a step difference (printing step difference) between the surface of the first surface 31a and the surface of the printed layer 32 on the cover glass 31. That is, the cover glass 31 is an adherend with a step difference on its surface. In this step, specifically, the adhesive sheet 10 before light curing is bonded to the area of ​​the surface 31a of the cover glass 31 containing the printed layer 32. FIG3A illustrates the case where the adhesive sheet 10 before light curing is bonded to the entire surface 31a of the cover glass 31. Secondly, in the photocuring step, as shown in Figure 3B, the adhesive sheet 10 on the cover glass 31 is photocured by ultraviolet irradiation. Under ultraviolet irradiation, a photopolymerization reaction of a first photopolymerizable multifunctional compound occurs in the adhesive sheet 10, forming a photopolymer of the first photopolymerizable multifunctional compound. Since this photopolymerization reaction occurs around the base polymer (the first photopolymerizable polymer and the second photopolymerizable polymer having a photocrosslinking structure), the photopolymer of the first photopolymerizable multifunctional compound forms an interpenetrating polymer network (IPN) with the base polymer on one side. This makes the adhesive sheet 10 highly elastic. Examples of ultraviolet light sources for ultraviolet irradiation include ultraviolet LED lamps, black light lamps, high-pressure mercury lamps, and metal halide lamps. Furthermore, a wavelength cutoff filter can also be used to cut off a portion of the wavelength range of light emitted from the light source during ultraviolet irradiation. During ultraviolet irradiation, the cumulative irradiation intensity is, for example, 50–10000 mJ / cm². 2 . Next, in the bonding step, as shown in FIG3C, the cover glass 31 and the component 33 are bonded via the photocured adhesive sheet 10 on the cover glass 31. The component 33 is, for example, a pixel panel for a display panel, a polarizing film, or a touch panel. The component 33 has the aforementioned resin step difference on the surface (one side in the thickness direction H) on the side of the adhesive sheet 10. In this way, a bond W (cover glass 31 / adhesive sheet 10 / component 33) can be obtained. As described above, the adhesive sheet 10 has photocurability. During the bonding step (FIG. 3A), this adhesive sheet 10 can be bonded to the stepped surface of the substrate (surface 31a of the cover glass 31) in a soft state before photocuring. Therefore, the adhesive sheet 10 is suitable for achieving good step tracking. As described above, after photocuring under specific conditions, the adhesive sheet 10 exhibits an adhesion force F of 2.5 N / 10 mm or more to an alkali glass plate manufactured by the float glass method at high temperature (85°C). This adhesive sheet 10 is suitable for bonding substrates with high surface smoothness, such as glass substrates and polarizing films, in display panels. Therefore, the adhesive sheet 10 is suitable for display panel applications. As described above, the adhesive sheet 10, after photocuring under specific conditions, has a gel fraction of 75% by mass or higher. This high gel fraction of the adhesive sheet 10 makes it difficult for the adhered object to peel off before or after curing. This adhesive sheet 10, capable of achieving a high gel fraction, is suitable for bonding the cover glass 31 (first adhered object) with a surface gradient (Fig. 3A) to a component 33 (second adhered object) via photocuring (Fig. 3B), thus ensuring good bonding reliability between the first and second adhered objects. Therefore, the adhesive sheet 10 is suitable for display panel applications. [Example] The present invention will be specifically described below with reference to the embodiments shown. However, the present invention is not limited to the embodiments. Furthermore, the specific values ​​of the dosage (content), physical property value, parameters, etc. described below can be replaced with the upper limit (defined as "below" or "not reached") or lower limit (defined as "above" or "exceeded") of the dosage (content), physical property value, parameters, etc., corresponding to those described in the above "Embodiment". <Preparation of Acrylic Oligomers> First, in a reaction vessel equipped with a stirrer, thermometer, reflux condenser, and nitrogen inlet, a mixture comprising 60 parts by mass of dicyclopentyl 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). Next, the reaction solution was heated at 130°C to volatilize and remove the toluene, chain transfer agent, and unreacted monomers. This yielded an acrylic oligomer (solid). The weight average molecular weight of this acrylic oligomer was 5100. <Preparation of the Prepolymer Composition> In a flask, to a monomer mixture comprising 71 parts by weight of n-butyl acrylate (BA), 13 parts by weight of N-vinyl-2-pyrrolidone (NVP), 13 parts by weight of 4-hydroxybutyl acrylate (4HBA), and 3 parts by weight of acrylamide (ACMO), 0.031 parts by weight of a first photopolymerization initiator (trade name "Omnirad 184", 1-hydroxycyclohexylphenyl ketone, manufactured by BASF) and 0.031 parts by weight of a second photopolymerization initiator (trade name "Omnirad 651", 2,2-dimethoxy-1,2-diphenylethane-1-one, manufactured by BASF) were added. The mixture was then irradiated with ultraviolet light under a nitrogen atmosphere, thereby partially polymerizing one of the monomer components in the mixture to obtain the prepolymer composition. Ultraviolet irradiation continued until the viscosity of the composition reached approximately 20 Pa·s. The viscosity was measured using a type B viscometer at rotor No. 5, rotor speed of 10 rpm, and temperature of 30°C. The obtained prepolymer composition contains a photopolymer (photopolymer P1a) and unpolymerized monomer components (residual monomers). <Preparation of Adhesive Composition> 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 (trade name "UN-350", manufactured by Nejou Kogyo Co., Ltd.) as the second photopolymerizable multifunctional compound, 0.4 parts by weight of the third photopolymerization initiator (trade name "Omnirad819", bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, manufactured by BASF), 0.5 parts by weight of the antioxidant (trade name "Irganox1010", manufactured by BASF), 0.2 parts by weight of the rust inhibitor (trade name "BT-120", manufactured by Jōhoku Chemical Co., Ltd.), and 0.3 parts by weight of the silane coupling agent (trade name "KBM-403", manufactured by Shin-Etsu Chemical Co., Ltd.) were mixed to obtain the adhesive composition. <Preparation of the Base Adhesive Sheet> Next, an adhesive composition is coated onto 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. Next, 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 onto the coating film on the first release liner. Next, ultraviolet light is irradiated onto the coating film between the release liners from the second release liner side to photocur the coating film and form an adhesive layer with a thickness of 100 μm (ultraviolet irradiation step). During ultraviolet irradiation, a black light lamp (wavelength 320 nm to 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 ultraviolet irradiation step, a photopolymerization reaction is carried out on the coating film, comprising the aforementioned residual monomer and a second photopolymerizable multifunctional compound (urethane acrylate oligomer), to form a photopolymerizable polymer P1b with a photocrosslinked structure. Furthermore, since the photopolymerization reaction occurs around the photopolymerizable polymer P1a, the photopolymerizable polymer P1b is formed around the photopolymerizable polymer P1a. The adhesive layer formed in this step comprises both photopolymerizable polymer P1a and photopolymerizable polymer P1b as the base polymer P1. A base adhesive sheet with release liner attached to both sides (first release liner / base adhesive sheet (100 μm thick) / second release liner) is prepared in the above manner. [Example 1] <Preparation of Post-Addition Component Solution> First, 4.0 parts by mass of a polyfunctional acrylate monomer (trade name "Viscoat #295", trimethylolpropane triacrylate (TMPTA), manufactured by Osaka Organic Chemicals Co., Ltd.) as the first photopolymerizable polyfunctional compound, 0.3 parts by mass of a third photopolymerization initiator (trade name "Omnirad 819", manufactured by BASF), 7.0 parts by mass of a UV absorber (trade name "Tinosorb S", manufactured by BASF), and 88.7 parts by mass of ethyl acetate as a solvent were mixed to prepare a post-addition component solution (the components other than the solvent in the solution are post-addition components). The mixing amounts of the post-addition component solution are shown in Table 1. The units of the mixing amounts shown in Table 1 are relative "parts by mass". <Fabrication of Photocurable Optical Adhesive Sheet> Next, after peeling off the second release liner from the base adhesive sheet with release liner on both sides, a coating of the additive solution (coating treatment) is applied to the exposed surface of the base adhesive sheet to a thickness of 20 μm. During coating, an RDS No.10 rod coater manufactured by RD SPECIALTIES is used. Next, a drying treatment is performed in a desiccator at 110°C for 60 seconds. Through the coating treatment and drying treatment, the additive components (polyfunctional acrylate monomer, third photopolymerization initiator, and UV absorber) penetrate into the base adhesive sheet, and the solvent is vaporized. The base adhesive sheet is transformed into a photocurable adhesive sheet due to the penetration of the additive components. In this embodiment, 4 parts by mass of the first photopolymerizable polyfunctional compound (TMPTA in Example 1) relative to 100 parts by mass of the prepolymer composition and the second photopolymerizable polyfunctional compound (i.e., 100 parts by mass of the base polymer) were added to the base adhesive sheet (the mass parts of the first photopolymerizable polyfunctional compound relative to 100 parts by mass of the base polymer are shown in Table 2). Next, 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 was bonded onto the adhesive sheet on the first release liner. The optical adhesive sheet with release liner attached to both sides of Example 1 was fabricated in the manner described above (first release liner / photocurable optical adhesive sheet (100 μm thick) / third release liner). [Examples 2-5] Except for changing the composition of the post-added component solution to the composition shown in Table 1, the adhesive sheets with release liner on both sides of Examples 2-5 were prepared in the same manner as the adhesive sheet with release liner on both sides of Example 1. In Examples 3-5, in the preparation of the post-added component solution, in addition to TMPTA, ethoxylated bisphenol A diacrylate (BPAEODE) (trade name "ABE-300", manufactured by Shin-Nakamura Chemical Industry Co., Ltd.) was used as the first photopolymerizable multifunctional compound. [Comparative Examples 1-3] Except as described below, adhesive sheets with release liner on both sides of Comparative Examples 1-3 were prepared in the same manner as the adhesive sheet with release liner on both sides of Example 1. The composition of the added component solution was changed to the composition shown in Table 1. In the ultraviolet irradiation step for the preparation of the base adhesive sheet, after ultraviolet irradiation using a black light lamp (first irradiation), ultraviolet irradiation was performed using an ultraviolet LED lamp (wavelength 365 nm, manufactured by Quark Technology) (second irradiation). In the second irradiation, the illuminance was set to 90 mW / cm². 2 The cumulative irradiation intensity was set to 1800 mJ / cm. 2 Through this ultraviolet irradiation step, a base polymer P2 with a weight average molecular weight (Mw) lower than that of the base polymer P1 is formed. <Weight-Average Molecular Weight> The weight-average molecular weight (Mw) of the base polymers P1 and P2 was determined. Specifically, the Mw of the base polymers was determined by gel permeation chromatography (GPC) under the following conditions and converted to polystyrene. A GPC apparatus (trade name "Alliance", manufactured by Waters) was used for the determination. The sample solution was prepared as follows: First, a 0.15% by mass tetrahydrofuran (THF) solution (containing 10 mM phosphoric acid) was prepared using the base polymers as the sample, and the THF solution was left to stand for 20 hours. Second, 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. [GPC Measurement Conditions] Column: G7000H XL (Upstream side), GMH XL and GMH XL(Downstream side) Tosoh manufacturing column temperature: 40°C; Solution: Tetrahydrofuran solution containing phosphoric acid (10 mM); Flow rate: 0.8 mL / min; Sample injection volume: 100 μL; Standard sample: Polystyrene (PS); Detector: Differential refractometer (RI). <Gel Fraction> The gel fraction after photocuring was measured for each optical adhesive sheet of Examples 1-5 and Comparative Examples 1-3. Specifically, as described below. First, the optically bonded sheets between the release liner and the release liner are irradiated with ultraviolet light. 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. 2 Next, approximately 1 g of adhesive sample was collected from the optical adhesive sheet. Then, the mass (W) of the adhesive sample was determined. 1) Next, the adhesive sample was immersed in 40 g of ethyl acetate in a container for 7 days. Next, all components insoluble in ethyl acetate (undissolved portion) were recovered. Next, the undissolved portion was dried at 130°C for 2 hours (to remove ethyl acetate). Next, the mass (W) of the undissolved portion was determined. 2). Then, based on the following formula, the gel fraction of the photocured optical adhesive sheet is calculated. Its value is shown in Table 2. Gel fraction (mass%) = (W 2 / W 1)×100 <Transmittance> The transmittance of each optical adhesive sheet in Examples 1-5 and Comparative Examples 1-3 was measured as follows. First, a sample for transmittance measurement was prepared. Specifically, after peeling a release liner from the optical adhesive sheet, the exposed surface of the optical adhesive sheet was adhered to alkali-free glass (manufactured by Matsunami Glass Co., Ltd.), and the release liner was peeled off from the optical adhesive sheet on the glass. This yielded the sample for measurement. Next, the transmittance of the optical adhesive sheet in the sample was measured using a spectrophotometer (trade name "U4100", manufactured by Hitachi High Technology). Furthermore, in this measurement, the measurement results obtained only under the same conditions for alkali-free glass were used as a baseline. The transmittance at a wavelength of 380 nm and the transmittance at a wavelength of 420 nm measured for the optical adhesive sheet are shown in Table 1. <Adhesion> The adhesion of each optical adhesive sheet in Examples 1-5 and Comparative Examples 1-3 was determined by the following peel test. First, test pieces were prepared for each optical adhesive sheet. In preparing the test pieces, firstly, the third release liner was peeled off from the optical adhesive sheet, and a PET film (50 μm thick) was laminated onto the exposed surface of the optical adhesive sheet to obtain a laminated film (first release liner / optical adhesive sheet / PET film). Next, test pieces (10 mm wide × 100 mm long) were cut from the laminated film. Then, the optical adhesive sheet in the test piece was irradiated with ultraviolet light (photocuring treatment) from the first release liner side. During ultraviolet irradiation, a metal halide lamp was used as the light source, and the illuminance was set to 300 mW / cm². 2 The cumulative irradiation intensity was set to 3000 mJ / cm. 2 Next, under conditions of 23°C and 50% relative humidity, the first release liner is peeled off from the optical adhesive sheet of the test piece. The exposed surface of the optical adhesive sheet is then bonded to the air surface of an alkali glass plate (blue glass, manufactured by Matsunami Glass Industry Co., Ltd.) produced by the float glass method, thus obtaining the first laminate (alkali glass plate / optical adhesive sheet / PET film). The air surface refers to the exposed surface of the alkali glass plate (the opposite side of the surface in contact with the molten metal) when the alkali glass plate flows on the molten metal during the manufacturing process. During bonding, the test piece is pressed onto the alkali glass plate by moving a 2 kg roller back and forth once (the same process is repeated in the following bonding process). Next, the first laminate is subjected to autoclave treatment (heat and pressure treatment). During autoclave treatment, the temperature is set to 50°C, the pressure is set to 0.5 MPa, and the treatment time is set to 15 minutes. Next, the first laminate was left to stand for 30 minutes at 23°C and 50% relative humidity. Subsequently, tensile tests were performed on the specimens peeled from the alkali glass plate under the conditions of 85°C, 50% relative humidity, a peel angle of 180°, and a tensile speed of 300 mm / min to determine the peel strength. In this test, a tensile testing machine (trade name "Tension and Compression Testing Machine TCM-1kNB", manufactured by Minebea) was used. The measured peel strength is shown in Table 2 as the adhesion force F (N / 10 mm) to the light-cured alkali glass plate prepared by the float glass method. <Residual Stress> The residual stress during elongation (strain) was investigated for each optical adhesive sheet of Examples 1-5 and Comparative Examples 1-3. Specifically, it is described below. First, a sheet with a width of 10 mm and a length of 60 mm was cut from the optical adhesive sheet with release liner on both sides (first release liner / optical adhesive sheet / third release liner). Next, the first and third release liners were peeled from the optical adhesive sheet to obtain a specimen (optical adhesive sheet). Then, the specimen was stretched along its length using a tensile testing machine (trade name "Autograph AGS-J", manufactured by Shimadzu Corporation), and the residual stress generated in the specimen was measured at a strain value of 600% (6 times the length). In this test, the initial clamping distance was 100 mm, and the temperature condition was 23°C. In this test, while measuring the stress generated in the specimen, the specimen was stretched to 6 times its length (clamping distance 600 mm) at a tensile speed of 200 mm / min and then held at that length. The residual stress S after the specimen was stretched to 6 times its length and for 5 minutes is shown in Table 2. <Constant Load Peel Test> The peel speed in the constant load peel test was measured for each optical adhesive sheet in Examples 1-5 and Comparative Examples 1-3. First, test pieces were prepared for each optical adhesive sheet. In preparing the test pieces, firstly, the third release liner was peeled off from the optical adhesive sheet, and a PET film (50 μm thick) was laminated onto the exposed surface of the optical adhesive sheet to obtain a laminated film (first release liner / optical adhesive sheet / PET film). Next, test pieces (10 mm wide × 100 mm long) were cut from the laminated film. Then, the optical adhesive sheet in the test piece was irradiated with ultraviolet light (photocuring treatment) from the first release liner side. During ultraviolet irradiation, a metal halide lamp was used as the light source, and the illuminance was set to 300 mW / cm². 2 The cumulative irradiation intensity was set to 3000 mJ / cm. 2 Next, at 23°C and 50% relative humidity, the first release liner was peeled off from the optical adhesive sheet of the test piece. The exposed surface of the optical adhesive sheet was then bonded to the air surface of an alkali glass plate (blue glass, manufactured by Matsunami Glass Industry Co., Ltd.) produced by the float glass method, thus obtaining a second laminate (alkali glass plate / optical adhesive sheet / PET film). Next, the second laminate was subjected to autoclave treatment (heat and pressure treatment). In the autoclave treatment, the temperature was set to 50°C, the pressure to 0.5 MPa, and the treatment time to 15 minutes. Next, the second laminate was allowed to stand for 30 minutes at 23°C and 50% relative humidity. Subsequently, tensile tests were performed on the specimens peeled from the alkali glass plate under the conditions of 23°C, 50% relative humidity, a peel angle of 90°, and a tensile load of 2.5 N / 10 mm (fixed), and the peel speed was measured. A tensile testing machine (trade name "Tensile Compression Testing Machine TCM-1kNB", manufactured by Minebea) was used in this measurement. The measured peel speeds (μm / s) are shown in Table 2. <Step Follow-up Before Photocuring> The step follow-up of each optical adhesive sheet of Examples 1-5 and Comparative Examples 1-3 before photocuring was investigated in the following manner. First, a sample sheet (75 mm long × 45 mm wide) is cut from the optical adhesive sheet with release liner on both sides. Second, a third release liner is peeled from the optical adhesive sheet of the sample sheet, and the exposed surface of the optical adhesive sheet is then bonded to the center of a PET film (100 mm long × 50 mm wide, 125 μm thick). During bonding, a roller laminator is used, with the roller pressure set to 0.2 MPa and the feed speed set to 100 mm / min (the same applies to the bonding described below). Next, a first release liner is peeled from the optical adhesive sheet on the PET film, and the exposed surface of the optical adhesive sheet is bonded to a glass plate with a printed layer (100 mm long × 50 mm wide, 500 μm thick) by vacuum bonding (surface pressure 0.3 MPa, pressure 100 Pa), thus obtaining the first bond. Figure 4 shows the positional relationship between the glass plate 41 and the optical adhesive sheet 42 in the first bonding assembly. A printed layer 43 (45 μm thick, black ink layer) is formed around the entire circumference of the end edge of the glass plate 41 on the thickness direction side. The printed layer 43 is formed in the length direction L1 within a range of 15 mm inward from each end of the glass plate 41, and in the width direction L2 within a range of 5 mm inward from each end of the glass plate 41 (in Figure 4, the printed layer is indicated by shading). The optical adhesive sheet 42 is attached to the center of the thickness direction side of the glass plate 41, and is in contact with the printed layer 43 around the entire circumference of its end edge. That is, the printed layer 43 on the glass plate 41 is sandwiched between the glass plate 41 and the optical adhesive sheet 42 within a range of 2.5 mm outward from the inner end of the layer. Next, the first bond was autoclaved at 50°C and 0.5 MPa for 30 minutes. Afterward, the area near the inner edge of the printed layer in the first bond was observed. Specifically, using a digital microscope at 20x magnification, the inner side of the inner edge of the printed layer (the area where the optical adhesive sheet should be in close contact with the glass plate) was observed from the PET film side of the first bond. Then, regarding the step tracking performance of the optical adhesive sheet, cases where no bubbles were detected within the observation range were rated as "excellent," and cases where bubbles were detected were rated as "poor." The results are shown in Table 2. <Step Follow-up After Photocuring> The step follow-up of each optical adhesive sheet of Examples 1-5 and Comparative Examples 1-3 after photocuring was investigated in the following manner. First, a sample sheet of a specific size is cut from the optical adhesive sheet with release liner on both sides. Second, a third release liner is peeled from the optical adhesive sheet of the sample sheet, and the exposed surface of the optical adhesive sheet is then bonded to a glass plate. Ultraviolet light is irradiated onto the optical adhesive sheet on the glass plate from the side with the first release liner to photocur the optical 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. 2 . On the other hand, after a specific polarizing film is laminated to one side of a PET film (75 μm thick), a polyimide (PI) tape (50 μm thick) with an adhesive layer on one side is laminated to a portion of the polarizing film on the PET film. This results in a PET film with a polarizing film having surface aberrations (simulating resin aberrations) formed by the PI tape. Next, after peeling the first release liner from the optical adhesive sheet on the glass plate, the optical adhesive sheet is bonded to the polarizing film side of the PET film with a polarizing film to obtain the second bond. Specifically, the optical adhesive sheet and the PET film with a polarizing film are bonded with the end of the PI tape overlapping the end of the optical adhesive sheet by 180 μm. A vacuum bonding device is used for this bonding. The bonding pressure is set to 0.1 MPa. After bonding, the second bond is subjected to autoclaving at 40°C and 0.4 MPa for 5 minutes. Next, the edge of the PI tape in the second bond was observed using an optical microscope to confirm that no bubbles were generated. Then, the second bond was subjected to a 100-hour high-temperature and humidification test. In this test, the heating temperature was set to 85°C and the relative humidity to 85%. After the high-temperature and humidification test, the edge of the PI tape in the second bond was observed using an optical microscope. Then, regarding the step followability of the optically bonded sheet after photocuring, cases where no bubbles were detected within the observation range were evaluated as "excellent," and cases where bubbles were detected were evaluated as "poor." The results are shown in Table 2. [Table 1] [Table 2] 10: Optical Adhesive Sheet (Optical Adhesive Sheet) 10A: Coating 10B: Base Adhesive Sheet 11: Adhesive Surface 12: Adhesive Surface 21: Release Pad 22: Release Pad 22': Release Pad 31: Cover Glass 31a: First Surface 31b: Second Surface 32: Printed Layer 33: Component 41: Glass Plate 42: Optical Adhesive Sheet 43: Printed Layer H: Thickness Direction W: Bond Figure 1 is a cross-sectional schematic diagram of one embodiment of the optical adhesive sheet of the present invention. Figures 2A to 2E show an example of a method for manufacturing the optical adhesive sheet shown in Figure 1. Figure 2A shows the coating film formation step of the adhesive composition, Figure 2B shows the base adhesive sheet formation step, Figure 2C shows the peeling step of the light release liner, Figure 2D shows the step of adding components after supplying the base adhesive sheet, and Figure 2E shows the step of attaching the light release liner to the sheet. Figures 3A to 3C show an example of a method for using the optical adhesive sheet shown in Figure 1. Figure 3A shows the step of attaching the optical adhesive sheet to a first adherend (attaching step), Figure 3B shows the step of photocuring the optical adhesive sheet on the first adherend (photocuring step), and Figure 3C shows the step of joining the first adherend and a second adherend via the optical adhesive sheet on the first adherend (joining step). Figure 4 shows the positional relationship between the glass plate and the adhesive sheet in the laminate used to evaluate the step follow-through (before light curing) of the embodiments and comparative examples. 10: Optical adhesive sheet (optical adhesive sheet) 11: Sticky dough 12: Sticky dough 21: Peeling the gasket 22: Peeling the gasket H: Thickness direction

Claims

1. An optical adhesive sheet comprising a base polymer as a photopolymer, a photopolymerizable multifunctional compound, and a photopolymerization initiator, and having photocurability, and having a gel fraction of 75% by mass or more after photocuring by photocuring under a cumulative light intensity of 3000 mJ / cm², wherein the optical adhesive sheet is photocured under the above conditions, and then the optical adhesive sheet is bonded to an alkali glass plate produced by a float glass method, and then the optical adhesive sheet on the alkali glass plate is subjected to heat and pressure treatment at 50°C, 0.5 MPa, and 15 minutes, and in a peel test at 85°C, a peel angle of 180°, and a tensile speed of 300 mm / min, the optical adhesive sheet exhibits an adhesion of 2.5 N / 10 mm or more when peeled from the alkali glass plate.

2. The optical adhesive sheet as claimed in claim 1, wherein the weight average molecular weight of the base polymer is 800,000 or more.

3. The optical adhesive sheet of claim 1, wherein the optical adhesive sheet that has been cured by photocuring under a cumulative light intensity of 3000 mJ / cm2, after being stretched to 6 times its length at 23°C and a stretching speed of 200 mm / min for 5 minutes, has a residual stress of 55 N / m2 or less.

4. The optical adhesive sheet of any one of claims 1 to 3, wherein the optical adhesive sheet is photocured under a cumulative light intensity of 3000 mJ / cm2, and then the optical adhesive sheet is bonded to an alkali glass plate made by the float glass method. After the optical adhesive sheet on the alkali glass plate is subjected to heat and pressure treatment at 50°C, 0.5 MPa and 15 minutes, in a constant load peel test at 23°C, peel angle of 90° and tensile load of 2.5 N / 10 mm, the peel speed is less than 35 μm / s.

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