TW202428816A - Adhesive Sheet - Google Patents

Abstract

The present invention provides an adhesive sheet having a photocurable adhesive layer based on a polymer having a carbon-carbon double bond and not utilizing solution polymerization. The present invention provides an adhesive sheet having an adhesive layer that is cured by light irradiation. The adhesive layer contains a polymer having a carbon-carbon double bond and a photoinitiator. The content of the photoinitiator in the adhesive layer is 1.0×10 ^-4 mol/100 g or more. The total content of the azo-based polymerization initiator and the peroxide-based polymerization initiator in the adhesive layer is 1.0 μg/g or less.

Description

Adhesive Sheet

The present invention relates to an adhesive sheet. This application claims priority based on Japanese Patent Application No. 2022-185186 filed on November 18, 2022, the entire contents of which are incorporated into this specification by reference.

Generally, adhesives (also called pressure-sensitive adhesives. The same applies hereinafter) are in a soft solid (viscoelastic) state in a temperature range near room temperature, and are easily bonded to the adherend due to pressure. Taking full advantage of this property, adhesives are widely used in various fields, for example, in the form of adhesive sheets having an adhesive layer. Some adhesive sheets have an adhesive layer that is cured by light irradiation (photocurable adhesive layer). As a prior art document related to this technology, Patent Document 1 can be cited. Prior Art Document Patent Document

Patent document 1: Japanese Patent Application Publication No. 2015-059179

[The problem the invention is trying to solve]

As an example of a photocurable adhesive layer, there can be cited one formed in the following manner: containing a polymer having a carbon-carbon double bond, the carbon-carbon double bond is hardened by forming a cross-linked structure by light irradiation. Previously, such a photocurable adhesive layer is formed by applying a solvent-type adhesive composition containing the polymer having a carbon-carbon double bond in an organic solvent to a suitable surface and drying it. Generally speaking, the polymer having a carbon-carbon double bond is manufactured by modification, and the modification is to introduce carbon-carbon double bonds into a polymer obtained by solution polymerization using an azo-based or peroxide-based polymerization initiator by a reaction in a solution. Therefore, in the photocurable adhesive layer formed of the solvent-based adhesive composition containing the polymer having a carbon-carbon double bond, the azo-based or peroxide-based polymerization initiator generally used in the solution polymerization is present in the form of a decomposition product or residue of the polymerization initiator.

On the other hand, in recent years, due to environmental hygiene considerations, the demand for reducing the amount of organic solvents used has gradually increased. Therefore, the purpose of the present invention is to provide an adhesive sheet having a photocurable adhesive layer based on a polymer containing carbon-carbon double bonds and not utilizing solution polymerization. [Technical means for solving the problem]

According to the specification, an adhesive sheet having an adhesive layer that is cured by light irradiation (photocurable adhesive layer) can be provided. The total content of azo-based polymerization initiators and peroxide-based polymerization initiators in the adhesive layer is 1.0 μg/g or less. In this way, by limiting the total content of azo-based polymerization initiators and peroxide-based polymerization initiators, it is possible to prevent or inhibit the disadvantages caused by the polymerization initiators (for example, due to the decomposition of the polymerization initiators due to heat, the physical properties of the adhesive change over time, the deterioration or contamination of the surface of the adherend to which the adhesive sheet is attached, the generation of outgassing, etc.). For example, the adhesive layer can be an adhesive layer that does not contain either azo-based or peroxide-based polymerization initiators. The adhesive layer contains a polymer having a carbon-carbon double bond and a photoinitiator. The content of the photoinitiator in the adhesive layer is 1.0×10 ^-4 mol/100 g or more. Since the adhesive layer does not utilize solution polymerization using an azo or peroxide polymerization initiator, the amount of organic solvent used can be reduced according to the adhesive sheet having the adhesive layer. In addition, by making the adhesive layer contain a polymer having a carbon-carbon double bond and a photoinitiator of a specific amount or more, it can be properly cured by light irradiation.

In some aspects, the amount of carbon-carbon double bonds contained in the adhesive layer is preferably 1.0×10 ^-4 mol/g or more. If the amount of carbon-carbon double bonds contained in the adhesive layer increases, it tends to be easier to obtain changes in characteristics and physical properties due to light irradiation.

In some embodiments, the polymer having a carbon-carbon double bond is preferably crosslinked by a multifunctional monomer having two or more ethylenically unsaturated groups in one molecule. From the perspective of imparting appropriate cohesiveness to the photocurable adhesive layer containing the polymer, it is advantageous for the polymer to have a crosslinked structure generated by the multifunctional monomer.

The adhesive layer preferably has an organic solvent content of 1.0 μg/g or less. An adhesive layer with a lower organic solvent content has a lower odor and is more ideal from the perspective of environmental hygiene. A lower organic solvent content in the adhesive layer is also advantageous from the perspective of suppressing foaming caused by the volatility of the organic solvent or low pollution.

In some embodiments, the polymer having a carbon-carbon double bond is an acrylic polymer. The technology disclosed herein can be preferably implemented in the form of an adhesive sheet having a photocurable adhesive layer containing an acrylic polymer having a carbon-carbon double bond.

The peel strength reduction rate of some better adhesive sheets obtained by the following formula is more than 50%. Peel strength reduction rate [%] = (1-B/A) × 100 Wherein, A in the above formula is the initial peel strength measured at a tensile speed of 300 mm/min and a peel angle of 180 degrees after being attached to a silicon wafer (unit: [N/20 mm]). B in the above formula is the peel strength after hardening treatment measured at a tensile speed of 300 mm/min and a peel angle of 180 degrees after being attached to a silicon wafer and irradiated with ultraviolet light (UV) with a cumulative light dose of 300 mJ/ ^cm2 (unit: [N/20 mm]). In this way, the adhesive sheet whose peeling force (peeling strength) is greatly reduced by UV irradiation can be used as an adhesive sheet that can be easily peeled by irradiating light at a desired time after being attached to an adherend.

Furthermore, an appropriate combination of the elements described in this specification may also be included in the scope of the invention claimed for patent protection by the patent application of this case.

The following is a description of the appropriate implementation of the present invention. Furthermore, matters other than those specifically mentioned in this specification and necessary for the implementation of the present invention can be understood as design matters based on the prior art in the field by practitioners. The present invention can be implemented based on the contents disclosed in this specification and the technical common sense in the field. Furthermore, in the following figures, components and parts with the same function are sometimes described with the same component symbols, and repeated descriptions are sometimes omitted or simplified. In addition, the implementation methods recorded in the figures are modeled for the purpose of clearly explaining the present invention, and do not necessarily accurately represent the size or reduction ratio of the adhesive sheet actually provided as a product.

In the specification, "acrylic polymer" refers to a polymer derived from a monomer component containing more than 50% by weight (preferably more than 70% by weight, for example more than 90% by weight) of an acrylic monomer. The above-mentioned acrylic monomer refers to a monomer derived from a monomer having at least one (meth)acryl group in one molecule. Furthermore, in the specification, "(meth)acryl" refers to an inclusive meaning of acryl and methacryl. Similarly, "(meth)acrylate" refers to an inclusive meaning of acrylate and methacrylate, and "(meth)acrylic acid" refers to an inclusive meaning of acrylic acid and methacrylic acid.

In the specification, "ethylenically unsaturated compound" refers to a compound having at least one ethylenically unsaturated group in the molecule. Examples of ethylenically unsaturated groups include (meth)acryloyl, vinyl, and allyl groups. Hereinafter, a compound having one ethylenically unsaturated group may be referred to as a "monofunctional monomer", and a compound having two or more ethylenically unsaturated groups may be referred to as a "polyfunctional monomer". In addition, a compound having X ethylenically unsaturated groups among polyfunctional monomers may be referred to as an "X-functional monomer".

<Configuration example of adhesive sheet> The adhesive sheet disclosed in this article has an adhesive layer. Typically, the adhesive layer constitutes at least one surface of the adhesive sheet. The adhesive sheet may be an adhesive sheet with a substrate in the form of having an adhesive layer on one or both sides of a substrate (support), or an adhesive sheet without a substrate in the form of the adhesive layer being retained on a peeling pad (which can also be understood as a substrate with a peeling surface). In this case, the adhesive sheet may be one that only includes an adhesive layer. The concept of the adhesive sheet here may include adhesive tapes, adhesive labels, adhesive films, etc. Furthermore, typically, the adhesive layer is formed continuously, but is not limited to this form. For example, it can also be an adhesive layer formed into a regular or irregular pattern such as dots or stripes. Furthermore, the adhesive sheet provided in this specification can be in a roll or a single sheet. Alternatively, it can also be an adhesive sheet processed into various shapes.

FIG1 shows an example of a structure of an adhesive sheet with an adhesive layer disclosed herein. The adhesive sheet 1 is a double-sided adhesive sheet without a substrate and includes an adhesive layer 10. The adhesive sheet 1 before use (before being attached to an adherend) can be, for example, as shown in FIG1 , a form of an adhesive sheet 50 with a peel-off liner, in which each surface 10A, 10B of the adhesive layer 10 is protected by a peel-off liner 31, 32 whose side of the adhesive layer is a peel-off surface (peel-off surface). Alternatively, the back side of the peeling pad 31 (the surface opposite to the adhesive side) may be the peeling surface, and the adhesive surface 10B may be rolled or laminated in a contacting manner on the back side of the peeling pad 31 to protect the adhesive surfaces 10A and 10B. The adhesive layer 10 may be a single layer or a laminated structure of two or more layers.

The adhesive layer 10 is formed by containing a polymer having a carbon-carbon double bond and a photoinitiator, and is cured by light irradiation. In some embodiments, the amount of the photoinitiator contained in the adhesive layer 10 is preferably 1.0×10 ^-4 mol/100 g or more. With this content, good light irradiation curability is easily obtained. For the same reason, in some embodiments, the amount of the carbon-carbon double bond contained in the adhesive layer 10 is preferably 1.0×10 ^-4 mol/100 g or more.

The content of the organic solvent in the adhesive layer 10 is preferably 1.0 μg/g or less. An adhesive layer containing a polymer having carbon-carbon double bonds and a photoinitiator, and in which the content of the above-mentioned organic solvent is limited, can be preferably formed, for example, by irradiating an active energy ray (e.g., ultraviolet ray)-curable adhesive composition with active energy rays to cure it, thereby forming a primary adhesive layer containing a primary polymer (typically a polymer without carbon-carbon double bonds obtained by active energy ray polymerization), and then, by not using or using only a small amount (within the limit that the above-mentioned organic solvent content can be achieved) of an organic solvent, adding a photoinitiator to the above-mentioned primary adhesive layer and introducing carbon-carbon double bonds into the above-mentioned primary polymer. In this formation method, since the pre-formed primary adhesive layer newly contains a photoinitiator and a carbon-carbon double bond, an active energy ray-curable adhesive composition can be preferably used as the adhesive composition for forming the primary adhesive layer. As the active energy ray-curable adhesive composition, one containing no organic solvent or only a small amount (within the limit of the content of the organic solvent) is used.

The adhesive layer 10 preferably has a total content of azo-based polymerization initiators and peroxide-based polymerization initiators of 1.0 μg/g or less. Such an adhesive layer 10 can be preferably realized in the following configuration: for example, it contains a polymer obtained by solution polymerization without using an azo-based or peroxide-based polymerization initiator (for example, a polymer obtained by introducing a carbon-carbon double bond into a primary polymer obtained by active energy ray polymerization without carbon-carbon double bonds) as a polymer having a carbon-carbon double bond.

FIG. 2 shows another example of the adhesive sheet with an adhesive layer disclosed herein. The adhesive sheet 2 is configured as a single-sided adhesive sheet (single-sided adhesive sheet with substrate) including a photocurable adhesive layer 10 having a surface 10A serving as an attachment surface (adhesive surface) on an adherend, and a substrate (support) 20 laminated on the other surface 10B of the adhesive layer 10. The adhesive layer 10 is bonded to one surface 20A of the substrate 20. As the substrate 20, for example, a resin film such as a polyester film can be used. Regarding the adhesive sheet 1 before use, for example, as shown in FIG. 2 , it may be in the form of an adhesive sheet 50 with a peeling liner, in which the adhesive surface 10A is protected by a peeling liner 30 whose adhesive layer side is a peeling surface (peeling surface). Alternatively, it may be in the form of a second surface 20B (the surface opposite to the first surface 20A, also referred to as the back surface) of the substrate 20 as the peeling surface, and the adhesive surface 10A is rolled or laminated in abutting manner on the second surface 20B of the substrate 20, thereby protecting the adhesive surface 10A.

Furthermore, the adhesive sheet disclosed herein may also be in the form of a double-sided adhesive sheet with a substrate, in which a first adhesive layer is formed on one surface of a sheet-shaped substrate, and a second adhesive layer is formed on the other surface of the substrate. In the adhesive sheet in this form, either or both of the first adhesive layer and the second adhesive layer may be formed by the photocurable adhesive layer disclosed herein.

<Adhesive layer> In the technology disclosed in this article, the type of adhesive constituting the photocurable adhesive layer is not particularly limited. The above-mentioned adhesive may be, for example, one or more of various rubbery polymers such as acrylic polymers, rubber polymers, polyester polymers, urethane polymers, polyether polymers, silicone polymers, polyamide polymers, and fluorine polymers as a base polymer. From the perspective of adhesive performance or cost, it is preferable to use an adhesive containing an acrylic polymer or a rubber polymer as a base polymer. In some preferred embodiments, the adhesive constituting the photocurable adhesive layer may be an acrylic adhesive containing a polymer having a carbon-carbon double bond. Among them, it is preferred that the base polymer of the acrylic adhesive is a polymer having a carbon-carbon double bond, that is, an acrylic adhesive containing an acrylic polymer having a carbon-carbon double bond as a base polymer. Hereinafter, the acrylic adhesive will be mainly described, but it is not intended to limit the adhesive disclosed in this article to the acrylic adhesive.

Furthermore, in the specification, the "base polymer" of the adhesive layer refers to the main component of the polymer contained in the adhesive layer. The above polymer is preferably a rubber-like polymer that exhibits rubber elasticity in a temperature range near room temperature. In addition, in the specification, unless otherwise specified, the "main component" refers to a component contained in an amount exceeding 50% by weight.

(Polymer with carbon-carbon double bonds) The adhesive sheet disclosed herein has an adhesive layer containing a polymer with carbon-carbon double bonds. The adhesive layer containing a polymer with carbon-carbon double bonds can be hardened by a mechanism including causing the carbon-carbon double bonds in the polymer to react by light irradiation, and the elastic modulus of the adhesive layer is increased by the hardening. In some embodiments, by irradiating the adhesive layer attached to the adherend with light, the carbon-carbon double bonds in the polymer react, thereby causing the adhesive layer to harden and shrink, and the adhesive sheet having the adhesive layer can be effectively made easy to peel off. Among them, the adhesive containing a polymer having a carbon-carbon double bond as the base polymer is preferred.

The existence form of the carbon-carbon double bonds in the above-mentioned polymer is not particularly limited. The above-mentioned polymer may be a polymer having carbon-carbon double bonds in the side chain, or a polymer having carbon-carbon double bonds in the main chain. Here, the so-called carbon-carbon double bonds in the main chain include the presence of carbon-carbon double bonds in the main chain skeleton of the polymer and the presence of carbon-carbon double bonds at the end of the main chain. From the viewpoints of the reactivity of the carbon-carbon double bonds or the increase in elastic modulus produced by the reaction of the carbon-carbon double bonds, the polymer having carbon-carbon double bonds in the side chain can be preferably used. Here, the main chain of the polymer refers to the chain structure forming the skeleton of the polymer. In addition, the side chain of a polymer refers to a group bonded to the main chain (side chain group, pendant group) or a molecular chain that can be regarded as a side chain.

In some preferred embodiments, the polymer having a carbon-carbon double bond has a carbon-carbon double bond in the form of an ethylenically unsaturated group. The polymer having a carbon-carbon double bond may be, for example, a polymer having a carbon-carbon double bond in the form of a reactive group ((meth)acryloyl) represented by the following formula (1). [Chemical 1] (In the formula, R is a hydrogen atom or a methyl group)

The polymer having carbon-carbon double bonds is not particularly limited, and an appropriate polymer can be selected for use in consideration of the properties of the adhesive layer, etc. The polymer having carbon-carbon double bonds can be, for example, a primary polymer having no carbon-carbon double bonds introduced with carbon-carbon double bonds by chemical modification or the like (secondary polymer).

As a specific example of a method for introducing a carbon-carbon double bond into a primary polymer, the following method can be cited: a primary polymer is prepared by copolymerizing a monomer having a functional group (hereinafter also referred to as "functional group A"), and a compound having a functional group (hereinafter also referred to as "functional group B") and a carbon-carbon double bond (for example, an ethylenically unsaturated compound having functional group B) that can react with the functional group A is reacted in the primary polymer in such a manner that the carbon-carbon double bond does not disappear, thereby obtaining a polymer (secondary polymer) having a carbon-carbon double bond introduced. The reaction between the functional group A and the functional group B is preferably a reaction that is not accompanied by the generation of free radicals, such as a condensation reaction or an addition reaction. Examples of the combination of functional groups A and functional groups B include: a combination of a carboxyl group and an epoxy group, a combination of a carboxyl group and an aziridine group, a combination of a hydroxyl group and an isocyanate group, etc. Among them, from the perspective of tracking reactivity, a combination of a hydroxyl group and an isocyanate group is preferred. In addition, regarding the combination of the functional groups A and B, as long as it is a combination that can obtain a polymer having a carbon-carbon double bond, one of the functional groups in the above combination can be set as the functional group A and the other functional group can be set as the functional group B, or one of the functional groups can be set as the functional group B and the other functional group can be set as the functional group A. For example, if the combination of a hydroxyl group and an isocyanate group is used for explanation, the functional group A of the primary polymer may be a hydroxyl group (in which case, the functional group B is an isocyanate group) or an isocyanate group (in which case, the functional group B is a hydroxyl group). Among them, a combination in which the primary polymer has a hydroxyl group and the compound having a carbon-carbon double bond and containing a functional group B (preferably an ethylenically unsaturated compound having a functional group B) has an isocyanate group is preferred. This combination is particularly preferred when the primary polymer is an acrylic polymer.

When the functional group A of the primary polymer reacts with the functional group B of the compound having a carbon-carbon double bond, from the viewpoint of the reactivity of both, the molar ratio (MA/ _MB ) of the mole of the functional group A ( _{MA ) to the mole of the functional group B (MB )} is usually preferably set to 0.2 or more, preferably 0.5 or more (e.g. 0.7 or more, typically 1.0 or more), may be set to more than 1.0 (e.g. 1.1 or more), and may also be set to 1.2 or more. The molar ratio ( _MA / _MB ) is usually preferably set to 2000 or less (e.g. 1500 or less or 1000 or less), preferably 500 or less, may be 200 or less, may be 100 or less, and may be 50 or less. In some aspects, the molar ratio ( _MA / _MB ) is preferably 30 or less, 20 or less, 10 or less, 5.0 or less, 3.0 or less, 2.5 or less, 2.0 or less, or 1.5 or less. In addition, from the viewpoint of increasing the contact opportunity between the functional group A and the functional group B, more compounds containing the functional group B having a carbon-carbon double bond may be used. In this case, the molar ratio ( _MA / _MB ) is preferably set to less than 1 (e.g., less than 0.99, less than 0.95). In addition, for example, when the remaining functional group A is also used for other purposes (e.g., improving the adhesion of the photocurable adhesive layer before curing treatment), the molar ratio ( _MA / _MB ) is preferably greater than 1.

Regarding the usage amount of the compound containing the functional group B having a carbon-carbon double bond (preferably an ethylenically unsaturated compound having the functional group B), relative to 100 parts by weight of the polymer having the functional group A (typically, the polymer before the introduction of the carbon-carbon double bond), it can be set to, for example, about 0.001 parts by weight or more, about 0.01 parts by weight or more, or about 0.1 parts by weight or more, more appropriately about 0.5 parts by weight or more (for example, about 1.0 parts by weight or more), preferably about 3.0 parts by weight or more, more preferably about 5.0 parts by weight or more, can be about 7.0 parts by weight or more, can also be about 9.0 parts by weight or more, can also be about 10 parts by weight or more, and can also be about 12 parts by weight or more. In addition, the amount of the compound containing the functional group B having a carbon-carbon double bond is preferably set to about 40 parts by weight or less, preferably about 35 parts by weight or less, more preferably about 30 parts by weight or less, about 25 parts by weight or less, about 20 parts by weight or less, or about 17 parts by weight or less, relative to 100 parts by weight of the polymer having the functional group A (typically, the polymer before the carbon-carbon double bond is introduced). The above amount is preferably set to meet the above molar ratio ( _MA / _MB ). For example, for the use of the acrylic polymer described later as the composition of the polymer, the above molar ratio (MA _{/ MB} ) or the amount of the compound containing the functional group B having a carbon-carbon double bond can be preferably applied.

(Acrylic polymer with carbon-carbon double bond) From the viewpoint of ease of curing by light irradiation, the photocurable adhesive layer disclosed in this article can be preferably implemented in the form of containing an acrylic polymer (i.e., an acrylic polymer with carbon-carbon double bond) as the above-mentioned polymer with carbon-carbon double bond. Acrylic polymers are also advantageous in terms of higher freedom in selecting monomer raw materials and easier control of physical properties. From the viewpoint of being suitable for production by a method that does not utilize an organic solvent as described later, acrylic polymers with carbon-carbon double bonds and adhesive layers containing the acrylic polymers are also preferred.

The acrylic polymer having a carbon-carbon double bond may be one in which a carbon-carbon double bond is introduced by chemically modifying an acrylic polymer as a primary polymer (typically, an acrylic polymer not containing a carbon-carbon double bond). The method for introducing a carbon-carbon double bond into an acrylic polymer is not particularly limited. For example, the following method may be preferably adopted: a functional group (functional group A) introduced into an acrylic polymer by copolymerization is reacted with a compound having a functional group (functional group B) that can react with the functional group A and a carbon-carbon double bond in such a manner that the carbon-carbon double bond does not disappear (typically, condensation, addition reaction). Examples of the combination of functional group A and functional group B include a combination of a carboxyl group and an epoxy group, a combination of a carboxyl group and an aziridine group, and a combination of a hydroxyl group and an isocyanate group. Among them, from the perspective of tracking reactivity, a combination of a hydroxyl group and an isocyanate group is preferred. From the perspective of polymer design, a combination in which an acrylic polymer has a hydroxyl group and the above compound has an isocyanate group is particularly preferred. Furthermore, from the perspective of the photocurability of the photocurable adhesive layer, the above compound having a functional group B and a carbon-carbon double bond is preferably an ethylenically unsaturated compound having a functional group B.

As a suitable example of an ethylenically unsaturated compound having a functional group B, an isocyanate-containing monomer (isocyanate-containing compound) can be cited. As a specific example of an isocyanate-containing monomer, those described later as secondary monomers that can be used in the polymerization of an acrylic polymer can be cited. Among them, 2-(methyl)acryloyloxyethyl isocyanate is more preferred. By reacting and bonding the isocyanate group (functional group B) of the isocyanate-containing monomer with the hydroxyl group (functional group A) of the acrylic polymer (typically, a urethane bond), an acrylic polymer having a carbon-carbon double bond can be suitably realized.

From the viewpoint of reactivity with the hydroxyl group as the functional group A, the amount of the isocyanate group-containing monomer used can be appropriately set within the range satisfying the above molar ratio ( _MA / _MB ). For example, the amount of the isocyanate group-containing monomer used is preferably set to about 1 part by weight or more (e.g., 3 parts by weight or more) relative to 100 parts by weight of the acrylic polymer (primary polymer) having a hydroxyl group. From the viewpoint of being able to better exert the effect produced by the curing treatment (e.g., reducing the peel strength, improving the storage elastic modulus, etc.), it is preferably set to 5 parts by weight or more (e.g., 7 parts by weight or more), and can be set to 8.5 parts by weight or more, and can also be set to 10 parts by weight or more, and can also be set to 12 parts by weight or more. The upper limit of the amount of the isocyanate group-containing monomer used is not particularly limited. It is preferably set to about 40 parts by weight or less, preferably about 35 parts by weight or less, more preferably about 30 parts by weight or less, for example, about 25 parts by weight or less, relative to 100 parts by weight of the above-mentioned acrylic polymer having a hydroxyl group.

As another preferred example of an ethylenically unsaturated compound having a functional group B, a hydroxyl-containing monomer can be cited. As a specific example of a hydroxyl-containing monomer, those described later as secondary monomers that can be used in the polymerization of an acrylic polymer can be cited. For example, preferred are (meth) alkyl acrylates such as 2-hydroxyethyl acrylate (HEA) and 4-hydroxybutyl acrylate (4HBA), among which 4HBA is preferred. By reacting and bonding the hydroxyl group (functional group B) of the hydroxyl-containing monomer with the isocyanate group (functional group A) of the acrylic polymer (typically, a urethane bond), an acrylic polymer having a carbon-carbon double bond can be suitably achieved. From the viewpoint of reactivity with the isocyanate group as the functional group A, the amount of the hydroxyl group-containing monomer used as the ethylenically unsaturated compound having the functional group B can be appropriately set within the range satisfying the above molar ratio ( _MA / _MB ).

As other examples of ethylenically unsaturated compounds having the functional group B, an epoxy group-containing monomer can be cited. As specific examples of epoxy group-containing monomers, those described later as secondary monomers that can be used in the polymerization of acrylic polymers can be cited. For example, glycidyl acrylate or glycidyl methacrylate (GMA) is preferred. By reacting and bonding the epoxy group (functional group B) of the epoxy group-containing monomer with the carboxyl group (functional group A) of the acrylic polymer, an acrylic polymer having a carbon-carbon double bond can be suitably realized. From the viewpoint of reactivity with the carboxyl group as the functional group A, the amount of the epoxy group-containing monomer as the ethylenically unsaturated compound having the functional group B can be appropriately set within the range satisfying the above molar ratio ( _MA / _MB ). In some aspects, by setting the molar ratio ( _MA / _MB ) to be greater than 1, the effects of the remaining carboxyl groups (for example, improving the peeling strength before curing the photocurable adhesive layer, improving the cohesion or heat resistance before and/or after curing, etc.) can be utilized. In this aspect, the molar ratio ( _MA / _MB ) can be set to, for example, 1.1 or more, or 1.5 or more, or 2.0 or more.

The acrylic polymer as the primary polymer may be, for example, a polymer of the following monomer raw materials, that is, containing an alkyl (meth)acrylate as a main monomer, and may further contain a secondary monomer copolymerizable with the main monomer. Here, the main monomer refers to a component in the above-mentioned monomer raw materials that accounts for more than 50% by weight of the monomer composition.

As the (meth)acrylic acid alkyl ester, for example, a compound represented by the following formula (2) can be suitably used. CH ₂ =C(R ¹ )COOR ² (2) wherein R ¹ in the above formula (2) is a hydrogen atom or a methyl group. Also, R ² is a chain alkyl group having 1 to 20 carbon atoms (hereinafter, such a range of carbon atoms may be represented as "C _1-20 "). From the viewpoint of the storage elastic modulus of the adhesive layer, a (meth)acrylic acid alkyl ester in which R ² is a chain alkyl group having _{1 to 14} carbon atoms (e.g., C _1-12 carbon atoms) is preferred, and an alkyl acrylate in which R ¹ is a hydrogen atom and R ² is a chain alkyl group having 1 _{to 20} carbon atoms (e.g., C _{1-14 carbon} atoms, typically C _1-12 carbon atoms) is more preferred.

Examples of the alkyl (meth)acrylate in which ^R2 is a _C1-20 chain alkyl group include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, The alkyl (meth)acrylates may be octyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate, nonadecyl (meth)acrylate, eicosyl (meth)acrylate, etc. These alkyl (meth)acrylates may be used alone or in combination of two or more. Preferred alkyl (meth)acrylates include ethyl acrylate (EA), n-butyl acrylate (BA), 2-ethylhexyl acrylate (2EHA), and lauryl acrylate (LA).

In some preferred aspects, the alkyl (meth)acrylate contains an alkyl (meth)acrylate A1 in which the carbon number of the alkyl group is 9 or less (i.e., an alkyl (meth)acrylate in which ^R2 is a _C1-9 alkyl group). In this way, by limiting the length of the side chain alkyl group, a photocurable adhesive layer suitable for improving the elastic modulus by light irradiation can be easily obtained. For example, in a photocurable adhesive layer containing an acrylic polymer having a carbon-carbon double bond in the side chain (typically, at the end of the side chain) as a polymer having a carbon-carbon double bond, since the length of the side chain alkyl group is limited, the carbon-carbon double bond reaction can be smoothly carried out during the curing treatment by light irradiation.

The proportion of the (meth)acrylic acid alkyl ester A1 in all monomer components constituting the acrylic polymer is preferably about 10% by weight or more. From the viewpoint of better exerting the effect of the (meth)acrylic acid alkyl ester A1, it is preferably 20% by weight or more, more preferably 40% by weight or more, and further preferably 55% by weight or more, and can be 65% by weight or more, 75% by weight or more, 80% by weight or more, 85% by weight or more, 90% by weight or more, and 95% by weight or more. The upper limit of the proportion of the (meth)acrylic acid alkyl ester A1 in all monomer components is not particularly limited. In some embodiments, considering the balance with the usage amount of the side monomer (for example, the monomer having the functional group A), the blending ratio of the (meth)acrylate A1 in all monomer components is preferably set to about 99.5 wt % or less (for example, 99 wt % or less), preferably 95 wt % or less, 92 wt % or less, 90 wt % or less, 85 wt % or less, 80 wt % or less, 75 wt % or less, or 70 wt % or less.

The content ratio of the alkyl (meth)acrylate A1 in the entire alkyl (meth)acrylate as the main monomer is preferably about 50 wt % or more (e.g., more than 50 wt %). From the viewpoint of better exertion of the effect of the alkyl (meth)acrylate A1, it is preferably 70 wt % or more, more preferably 80 wt % or more, further preferably 90 wt % or more, and can be 95 wt % or more, and can also be 99-100 wt %.

In some preferred embodiments, the alkyl (meth)acrylate A1 contains an alkyl (meth)acrylate A3 in which the carbon number of the alkyl group is less than 8. The alkyl (meth)acrylate A3 can help improve the adhesion to polar adherends such as metals. The carbon number of the alkyl group in the alkyl (meth)acrylate A3 is typically 7 or less, preferably 6 or less, more preferably 4 or less, and can be 2 or less. In some embodiments, from the viewpoint of the softness of the photocurable adhesive layer before the curing treatment, the carbon number of the alkyl group in the alkyl (meth)acrylate A3 is preferably 2 or more.

The proportion of the (meth)acrylic acid alkyl ester A3 in the total monomer components is preferably about 10% by weight or more. From the perspective of better exertion of the effect of the (meth)acrylic acid alkyl ester A3, it is preferably 20% by weight or more, more preferably 30% by weight or more, further preferably 40% by weight or more, particularly preferably 50% by weight or more, and can be 60% by weight or more, 70% by weight or more, 80% by weight or more, or 90% by weight or more. The upper limit of the proportion of the (meth)acrylic acid alkyl ester A3 in the total monomer components is not particularly limited. In some embodiments, considering the balance with the usage amount of the side monomer, the blending ratio of the (meth)acrylate A3 in all monomer components is preferably set to about 99.5 wt % or less (for example, 99 wt % or less), preferably set to 95 wt % or less, can be set to 90 wt % or less or 80 wt % or less, can also be set to 70 wt % or less, can also be set to 60 wt % or less, can also be set to 50 wt % or less, can also be set to 30 wt % or less, can also be set to 15 wt % or less, can also be set to 10 wt % or less, or can also be set to 5 wt % or less.

The content ratio of the alkyl (meth)acrylate A3 in the total alkyl (meth)acrylate as the main monomer is preferably about 5% by weight or more. From the perspective of better exertion of the effect of the alkyl (meth)acrylate A3, it is preferably 20% by weight or more, more preferably 35% by weight or more, further preferably 45% by weight or more, and particularly preferably 55% by weight or more, and can be 65% by weight or more, 75% by weight or more, and can be 85% by weight or more (for example, 90% by weight or more). The upper limit of the content ratio of the alkyl (meth)acrylate A3 in the total alkyl (meth)acrylate is 100% by weight. In some aspects, for example, from the viewpoint of better exerting its effect when containing the (meth)acrylate alkyl ester A2 described later, the content ratio of the (meth)acrylate alkyl ester A3 in the entire (meth)acrylate alkyl ester may be, for example, 90% by weight or less, 75% by weight or less, 60% by weight or less, 45% by weight or less, 30% by weight or less, or 15% by weight or less.

In some embodiments, the above-mentioned alkyl (meth)acrylate contains an alkyl (meth)acrylate A2 having an alkyl group with 5 or more carbon atoms as the above-mentioned alkyl (meth)acrylate A1 or A3, or as a monomer different from the alkyl (meth)acrylate A1 or A3. By using the alkyl (meth)acrylate A2, for example, it is easy to reduce the adhesion after the curing treatment, and it is easy to obtain better peelability or low contamination. The number of carbon atoms of the alkyl group in the alkyl (meth)acrylate A2 is preferably 7 or more (for example, 8 or more), and can be 9 or more. From the viewpoint of adhesion properties such as adhesion, the number of carbon atoms of the alkyl group in the alkyl (meth)acrylate A2 is preferably 14 or less, more preferably 12 or less, and can be 10 or less or 9 or less.

The proportion of the (meth)acrylic acid alkyl ester A2 in all monomer components constituting the acrylic polymer is preferably about 10% by weight or more. From the viewpoint of better exerting the effect of the (meth)acrylic acid alkyl ester A2, it is preferably about 20% by weight or more, more preferably about 40% by weight or more, further preferably about 55% by weight or more, and particularly preferably about 65% by weight or more. For example, it may be about 75% by weight or more, or about 80% by weight or more, or about 85% by weight or more, or about 90% by weight or more, or about 95% by weight or more. The proportion of the (meth)acrylic acid alkyl ester A2 in all monomer components is not particularly limited. In some embodiments, considering the balance with the usage amount of the side monomer, the blending ratio of the (meth)acrylate A2 in all monomer components is preferably set to about 99.5 wt % or less (for example, 99 wt % or less), preferably set to 95 wt % or less, can be set to 90 wt % or less or 80 wt % or less, can also be set to 70 wt % or less, can also be set to 60 wt % or less, can also be set to 50 wt % or less, can also be set to 30 wt % or less, can also be set to 15 wt % or less, can also be set to 10 wt % or less, or can also be set to 5 wt % or less.

The content ratio of the alkyl (meth)acrylate A2 in the total alkyl (meth)acrylate as the main monomer may be, for example, about 1% by weight or more. From the viewpoint of better expressing the effect of the alkyl (meth)acrylate A2, it is preferably 5% by weight or more, more preferably 15% by weight or more, further preferably 25% by weight or more, particularly preferably 35% by weight or more, and may be 45% by weight or more, 60% by weight or more, or 80% by weight or more (e.g., 90% by weight or more). The upper limit of the content ratio of the alkyl (meth)acrylate A2 in the total alkyl (meth)acrylate is 100% by weight. In some aspects, for example, from the viewpoint of better exerting its effect when containing the (meth)acrylate alkyl ester A3, the content ratio of the (meth)acrylate alkyl ester A2 in the entire (meth)acrylate alkyl ester may be, for example, 90 wt % or less, or 75 wt % or less, or 60 wt % or less, or 45 wt % or less, or 30 wt % or less, or 15 wt % or less.

The blending ratio of the main monomer in all monomer components constituting the acrylic polymer is preferably 55% by weight or more, more preferably 60% by weight or more (e.g., 65% by weight or more). The upper limit of the blending ratio of the main monomer is not particularly limited. In some embodiments, in consideration of the balance with the amount of the secondary monomer used, the blending ratio of the main monomer is, for example, preferably set to 99.5% by weight or less (e.g., 99% by weight or less), can be set to 95% by weight or less, can also be set to 90% by weight or less, 85% by weight or less, or about 75% by weight or less.

The secondary monomer copolymerizable with the (meth) alkyl acrylate as the main monomer can, for example, help to improve the cohesive force of the acrylic polymer as the primary polymer or the secondary polymer, or introduce crosslinking points into the polymer. It is preferred to use a monomer having a functional group (functional group A) that can react with a functional group (functional group B) of a compound having a carbon-carbon double bond as described later as at least a part of the secondary monomer. As secondary monomers, for example, the following monomer components containing functional groups can be used alone or in combination of two or more. A monomer having a functional group A and a monomer having other functional groups can also be used in combination.

Monomers containing hydroxyl groups: for example, hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate; unsaturated alcohols such as vinyl alcohol and allyl alcohol; ether compounds such as 2-hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl ether, and diethylene glycol monovinyl ether. Monomers containing isocyanate groups: (meth)acryloyl isocyanate, 2-(meth)acryloyloxyethyl isocyanate, and m-isopropenyl-α,α-dimethylbenzyl isocyanate. Carboxyl-containing monomers: for example, ethylenically unsaturated monocarboxylic acids such as acrylic acid (AA), methacrylic acid (MAA), and crotonic acid; ethylenically unsaturated dicarboxylic acids such as maleic acid, itaconic acid, and liconic acid, and their anhydrides (maleic anhydride, itaconic anhydride, etc.). Amide-containing monomers: for example, (meth)acrylamide, N,N-dimethyl(meth)acrylamide, N-butyl(meth)acrylamide, N-hydroxymethyl(meth)acrylamide, N-hydroxymethylpropane(meth)acrylamide, N-methoxymethyl(meth)acrylamide, and N-butoxymethyl(meth)acrylamide. Amide-containing monomers: for example, aminoethyl(meth)acrylate, N,N-dimethylaminoethyl(meth)acrylate, and tert-butylaminoethyl(meth)acrylate. Epoxy-containing monomers: for example, glycidyl (meth)acrylate, methyl glycidyl (meth)acrylate, allyl glycidyl ether. Cyanide-containing monomers: for example, acrylonitrile, methacrylonitrile. Ketone-containing monomers: for example, diacetone (meth)acrylamide, diacetone (meth)acrylate, vinyl methyl ketone, vinyl ethyl ketone, allyl acetylacetate, vinyl acetylacetate. Monomers having a ring containing a nitrogen atom: for example, N-vinyl-2-pyrrolidone, N-methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, N-vinylpiperidone, N-vinylpyrrolidone, N-vinylpyrrole, N-vinylimidazole, N-vinyloxazole, N-vinylpyrrolidine, N-vinylcaprolactam, N-(methyl)acryloylpyrrolidine. Monomers containing an alkoxysilyl group: for example, 3-(methyl)acryloyloxypropyltrimethoxysilane, 3-(methyl)acryloyloxypropyltriethoxysilane, 3-(methyl)acryloyloxypropylmethyldimethoxysilane, 3-(methyl)acryloyloxypropylmethyldiethoxysilane.

When a side monomer having a functional group (functional group A) that can react with a functional group (functional group B) of a compound having a carbon-carbon double bond is used, the type of the side monomer can be selected according to the type of functional group B. As the side monomer having the functional group A, for example, a hydroxyl group-containing monomer, an isocyanate group-containing monomer, a carboxyl group-containing monomer, and an epoxy group-containing monomer are preferred.

In some embodiments, as the side monomer having the functional group A, a hydroxyl group-containing monomer may be preferably used from the viewpoint of reactivity with the compound having the functional group B. Since the hydroxyl group-containing monomer is used as the side monomer, the obtained acrylic polymer (primary polymer) has a hydroxyl group. In contrast, by using a compound having an isocyanate group as the compound having a carbon-carbon double bond, the hydroxyl group of the acrylic polymer reacts with the isocyanate group of the compound, and the carbon-carbon double bond from the compound is introduced into the acrylic polymer, thereby obtaining an acrylic polymer having a carbon-carbon double bond (secondary polymer). Preferred examples of the hydroxyl group-containing monomer include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl acrylate (HEA) and 4-hydroxybutyl acrylate (4HBA). Among them, 4HBA is preferred.

The amount of the above-mentioned side monomer is not particularly limited, as long as it is appropriately selected in a manner that can achieve the desired purpose of use (introducing a reaction point with the functional group B, adjusting the cohesiveness or adhesive properties of the photocurable adhesive layer, etc.). Generally, from the perspective of easily and appropriately exerting the effect produced by light irradiation (hardening treatment) of the photocurable adhesive layer (for example, reducing the peeling force, improving the storage elastic modulus, etc.), the amount of the above-mentioned side monomer is preferably set to 0.1% by weight or more, preferably 0.3% by weight or more (for example, 1% by weight or more) of the total monomer components of the acrylic polymer. In addition, regarding the amount of the sub-monomer, it is more appropriate to set it to less than 70 weight % (for example, less than 60 weight %) of the total monomer components. In some embodiments, from the perspective of the flexibility of the photocurable adhesive layer, it is preferably set to less than 50 weight %, and more preferably set to less than 45 weight %. It can be set to less than 40 weight %, or less than 30 weight %, or less than 20 weight %, less than 10 weight % or less than 5 weight %.

In the case where a side monomer having a functional group A is used in order to achieve a reaction with a compound having a carbon-carbon double bond (preferably an ethylenically unsaturated compound having a functional group B), from the viewpoint of easily obtaining the effect produced by a curing treatment (typically, a light irradiation treatment) (for example, reducing the peel force, increasing the storage elastic modulus, etc.), the amount of the side monomer having the functional group A (depending on the type of the functional group B, for example, a hydroxyl group-containing monomer, a carboxyl group-containing monomer, an isocyanate group-containing monomer, an epoxy group-containing monomer, etc.) is preferably set to be 1% by weight or more of the total monomer components of the acrylic polymer, preferably 5% by weight or more, more preferably 10% by weight or more, and further preferably 12% by weight or more (for example, 14% by weight or more). Furthermore, from the perspective of maintaining good adhesion properties such as adhesion in the adhesive layer (photocurable adhesive layer) before curing treatment, the amount of the above-mentioned side monomer having a functional group A is preferably set to be less than 50 weight % (for example, less than 40 weight %) in all monomer components, preferably less than 30 weight %, more preferably less than 25 weight %, can be less than 20 weight %, and can also be less than 15 weight %.

In some embodiments, it is preferable to use a monomer having a ring containing a nitrogen atom as the above-mentioned secondary monomer. The monomer having a ring containing a nitrogen atom can help to improve the peel strength of the photocurable adhesive layer in the initial state (before curing treatment). In addition, it can also be advantageous from the perspective of increasing the decrease in peel strength (peel strength difference) caused by light irradiation (curing treatment) of the photocurable adhesive layer. Specific examples of monomers having a ring containing a nitrogen atom are as described above, and suitable examples include N-vinyl-2-pyrrolidone (NVP) and N-acryloyl pyrrolidone (ACMO). The amount of the monomer having a ring containing a nitrogen atom used may be, for example, 0.5% by weight or more or 1% by weight of the total monomer components used as the raw material of the acrylic polymer (primary polymer). From the viewpoint of obtaining a higher effect of use, it is preferably 3% by weight or more, more preferably 5% by weight or more, and may be 10% by weight or more, or 12% by weight or more, or 17% by weight or more or 20% by weight or more. Furthermore, the amount of the monomer having a ring containing a nitrogen atom used may be, for example, 40% by weight or less of the total monomer components used as the raw material of the acrylic polymer (primary polymer). From the viewpoint of the flexibility of the photocurable adhesive layer, in some embodiments, it is preferably 35% by weight or less, and preferably 30% by weight or less (e.g., 28% by weight or less).

In order to improve the cohesive force of the acrylic polymer, other copolymer components other than the above-mentioned secondary monomers may be used as needed. Examples of such copolymer components include: vinyl ester monomers such as vinyl acetate and vinyl propionate; aromatic vinyl compounds such as styrene, substituted styrenes (such as α-methylstyrene), and vinyltoluene; cycloalkyl (meth)acrylates such as cyclohexyl (meth)acrylate, cyclopentyl di(meth)acrylate, and isobutyl (meth)acrylate; aryl (meth)acrylates (such as phenyl (meth)acrylate), and aryloxyalkyl (meth)acrylates. (Meth)acrylates containing aromatic rings such as phenoxyethyl (meth)acrylate, arylalkyl (meth)acrylate (such as benzyl (meth)acrylate); olefin monomers such as ethylene, propylene, isoprene, butadiene, isobutylene; chlorine-containing monomers such as vinyl chloride and vinylidene chloride; alkoxy-containing monomers such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate; vinyl ether monomers such as methyl vinyl ether and ethyl vinyl ether; etc. The other copolymer components other than the side monomers can be used alone or in combination of two or more. The amount of the above-mentioned other copolymer components is not particularly limited, as long as it is appropriately selected according to the purpose and use. For example, it is preferably set to 20% by weight or less (for example, 2 to 20% by weight, typically 3 to 10% by weight) of all monomer components constituting the acrylic polymer.

A multifunctional monomer may also be used as the above-mentioned other copolymerization component. Examples of the multifunctional monomer include: various multifunctional (meth)acrylates having two or more (meth)acrylic groups in one molecule, multifunctional vinyl monomers such as divinylbenzene, and multifunctional monomers having a combination of a (meth)acrylic group and other ethylenically unsaturated groups such as allyl (meth)acrylate and vinyl (meth)acrylate. The multifunctional monomer may be used alone or in combination of two or more. Among them, multifunctional (meth)acrylates are preferably used. Examples of the multifunctional (meth)acrylate include 1,6-hexanediol di(meth)acrylate, butanediol di(meth)acrylate, (poly)ethylene glycol di(meth)acrylate, (poly)propylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, trihydroxymethylpropane tri(meth)acrylate, tetrahydroxymethylmethane tri(meth)acrylate, allyl (meth)acrylate, and vinyl (meth)acrylate. As the multifunctional (meth)acrylate used for the acrylic polymer, one type of multifunctional (meth)acrylate may be used alone, or two or more types of multifunctional (meth)acrylates may be used in combination. In some aspects, as the multifunctional (meth)acrylate for the acrylic polymer, it is preferred to use at least one selected from the group consisting of 1,6-hexanediol diacrylate, dipentaerythritol hexaacrylate, and trihydroxymethylpropane triacrylate.

By polymerizing the monomer components containing a multifunctional monomer, typically, an acrylic polymer (primary polymer) having a structure crosslinked by the multifunctional monomer can be obtained. That is, the multifunctional monomer can function as a copolymerizable crosslinking agent. By introducing a carbon-carbon double bond into the acrylic polymer having the structure, an acrylic polymer (secondary polymer) having a carbon-carbon double bond and crosslinked by the multifunctional monomer can be obtained. From the viewpoint of imparting appropriate cohesiveness to the photocurable adhesive layer containing the polymer, it is advantageous for the acrylic polymer having a carbon-carbon double bond to have a crosslinked structure. In the photocurable adhesive layer containing an acrylic polymer having a carbon-carbon double bond as a base polymer, it is particularly significant that the acrylic polymer is crosslinked.

The amount of the multifunctional monomer (copolymerizable crosslinking agent) used as the above-mentioned other copolymer components is not particularly limited, and can be appropriately selected according to the purpose and use. For example, it can be set to 0.001 wt % or more in all monomer components constituting the acrylic polymer (primary polymer). From the viewpoint of easily obtaining a higher use effect, it is preferably set to 0.005 wt % or more, and more preferably set to 0.007 wt % or more. It can be set to 0.01 wt % or more, and can also be set to 0.03 wt % or more. Furthermore, from the viewpoint of easily and appropriately exerting the effect produced by the curing treatment of the photocurable adhesive layer (for example, the effect of reducing the peeling strength) or the softness of the photocurable adhesive layer, the amount of the multifunctional monomer used in all the monomer components constituting the acrylic polymer can be set to, for example, 10 wt % or less, more preferably 5 wt % or less, more preferably less than 5 wt %, can be 3 wt % or less, and can also be 1 wt % or less. In some aspects, the amount of the multifunctional monomer used in the total monomer components constituting the acrylic polymer (typically, the acrylic polymer as the primary polymer) is preferably less than 1% by weight (e.g., 0.9% by weight or less), more preferably less than 0.5% by weight, less than 0.3% by weight, less than 0.2% by weight, less than 0.1% by weight (e.g., less than 0.1% by weight), less than 0.09% by weight, less than 0.08% by weight, or less than 0.07% by weight. From the viewpoint of easily and appropriately exerting the effect (e.g., easy peeling effect) produced by the curing treatment (e.g., ultraviolet irradiation treatment) of the photocurable adhesive layer, it is advantageous to avoid using too much of the multifunctional monomer used as the copolymerization component of the primary polymer.

The method for obtaining an acrylic polymer (primary polymer) from the monomer components as described above can be selected from various polymerization methods known as methods for synthesizing acrylic polymers. From the viewpoint of avoiding the use of an organic solvent, it is preferred to adopt a polymerization method other than solution polymerization (e.g., solution polymerization using an azo-based polymerization initiator or a peroxide-based polymerization initiator). In some embodiments, the acrylic polymer (primary polymer) can be obtained by hardening an active energy ray-curable adhesive composition in which a portion of the monomer components constituting the polymer are included in the form of a polymer and the remaining portion is included in the form of an unpolymerized (unreacted monomer) component. For example, by applying the above-mentioned active energy ray-curing adhesive composition to an appropriate surface and irradiating it with active energy rays (such as ultraviolet rays) to cure it, an adhesive layer (primary adhesive layer) containing an acrylic polymer formed by the above-mentioned monomer components can be obtained. The above-mentioned acrylic polymer is an active energy ray polymer of the above-mentioned monomer components. Generally speaking, the carbon-carbon double bonds (such as ethylenic unsaturated bonds) contained in the active energy ray-curing adhesive composition will react due to the irradiation of active energy rays when the adhesive composition is cured to form an adhesive layer, thereby disappearing. Therefore, by the above-mentioned method, typically, an adhesive layer (primary adhesive layer) that does not contain carbon-carbon double bonds is formed.

In some embodiments, for the primary adhesive layer, carbon-carbon double bonds are introduced into the acrylic polymer (acrylic polymer without carbon-carbon double bonds) in the adhesive layer, and an appropriate amount of photoinitiator is added as needed. In this way, the primary adhesive layer can be given photocurability, and a photocurable adhesive layer (secondary adhesive layer) containing an acrylic polymer with carbon-carbon double bonds and a specific amount of photoinitiator or more is obtained. The acrylic polymer with carbon-carbon double bonds is an acrylic polymer obtained by chemically modifying the active energy ray polymer of the monomer component to introduce carbon-carbon double bonds, and is a modified product of the active energy ray polymer. Some suitable examples of methods for obtaining a secondary adhesive layer from a primary adhesive layer are described below.

In some preferred embodiments, the active energy ray-curable adhesive composition used to form the primary adhesive layer contains a partial polymer of a monomer mixture, and the monomer mixture contains at least a portion of monomer components (raw monomers) constituting an acrylic polymer. This partial polymer is a mixture of a polymer from the above-mentioned monomer mixture and unreacted monomers, and is typically in a syrupy state (viscous liquid state). Hereinafter, the partial polymer of this nature is sometimes referred to as "monomer syrup" or simply "syrup".

The polymerization method for obtaining the above-mentioned polymerized reactant is not particularly limited, and various known polymerization methods can be appropriately selected for use. From the perspective of avoiding the use of organic solvents, it is preferred to use a method other than solution polymerization (for example, solution polymerization using an azo-based polymerization initiator or a peroxide-based polymerization initiator). Among them, from the perspective of efficiency and simplicity, photopolymerization can be preferably used. If photopolymerization is used, the polymerization conversion rate of the above-mentioned monomer mixture can be easily controlled according to polymerization conditions such as the amount of light irradiation (light intensity).

The polymerization conversion rate (monomer conversion rate) of the monomer mixture in the above-mentioned partial polymer is not particularly limited. The above-mentioned polymerization conversion rate can be set to, for example, about 70 weight % or less, preferably about 60 weight % or less. From the viewpoint of the ease of preparation and coating of the adhesive composition containing the above-mentioned partial polymer, the above-mentioned polymerization conversion rate is usually more appropriately about 50 weight % or less, preferably about 40 weight % or less (for example, about 35 weight % or less). The lower limit of the polymerization conversion rate is not particularly limited, and is typically about 1 weight % or more, and is usually more appropriately about 5 weight % or more.

The adhesive composition containing the partial polymer of the above-mentioned monomer mixture can be obtained, for example, by the following method: using an appropriate polymerization method (e.g., photopolymerization) to partially polymerize a monomer mixture containing a part or all of the monofunctional monomers in the raw monomers. Other components (e.g., photoinitiators, multifunctional monomers as copolymerizable crosslinking agents, etc.) that are used as needed can be mixed into the adhesive composition containing the above-mentioned partial polymer. The method of mixing such other components is not particularly limited, for example, the above-mentioned monomer mixture can be pre-containing, or it can be added to the above-mentioned partial polymer.

The adhesive composition disclosed herein may be in the form of a partially polymerized or fully polymerized monomer mixture containing a portion of the monomers of the monomer components (raw monomers) dissolved in the remaining monomers or their partially polymerized monomers. Such adhesive compositions are also included in the examples of polymerized and unpolymerized adhesive compositions containing monomer components. Furthermore, in this specification, "fully polymerized" refers to a polymerization conversion rate exceeding 95% by weight.

(First photoinitiator) For the purpose of accelerating curing, the active energy ray-curing adhesive composition used to form the primary adhesive layer may contain a photoinitiator. When ultraviolet light or other light is used as the active energy ray, it is particularly preferred to mix the photoinitiator into the adhesive composition. As the photoinitiator to be included in the adhesive composition, one or more of the materials selected from the examples of the photoinitiator contained in the adhesive layer (photocurable adhesive layer) of the adhesive sheet disclosed in this article can be used. Furthermore, the above-mentioned photoinitiator mixed in the adhesive composition functions as a catalyst for the polymerization and crosslinking reaction of the above-mentioned monomer components or crosslinking agents to form an acrylic polymer. Therefore, the photoinitiator is inactivated and decomposed by irradiation with active energy rays (typically, ultraviolet irradiation) when the adhesive layer (primary adhesive layer) is formed from the adhesive composition, and thus does not remain in the adhesive layer of the adhesive sheet disclosed herein, or even if it remains, it is considered to be an amount that leaves traces. On the other hand, the photoinitiator contained in the adhesive layer (photocurable adhesive layer) of the adhesive sheet disclosed herein is contained in the adhesive together with the polymer having a carbon-carbon double bond, and promotes the crosslinking reaction through the carbon-carbon double bond. Hereinafter, the photoinitiator contained in the adhesive composition and used to form the adhesive layer from the adhesive composition is sometimes referred to as the "first photoinitiator". In addition, the photoinitiator contained in the adhesive layer (photocurable adhesive layer) of the adhesive sheet disclosed herein and used in the photocuring of the adhesive layer is sometimes referred to as the "second photoinitiator". The first photoinitiator and the second photoinitiator may be the same material or different materials.

(Catalyst) In some embodiments, the primary adhesive layer may contain a catalyst that promotes the reaction between the functional group A and the functional group B. For example, as a catalyst that can be used to promote the addition reaction between an isocyanate group and a hydroxyl group, examples include metal catalysts such as tetra-n-butyl titanium, tetra-isopropyl titanium, triacetylacetonate iron, butyltin oxide, and dioctyltin dilaurate. In addition, as a catalyst that can be used to promote the addition reaction between a carboxyl group and an epoxy group, examples include: quaternary ammonium compounds such as tetrabutylammonium bromide (TBAB) and tetrabenzylammonium bromide and their derivatives; phosphorus compounds such as triphenylphosphine (TPP) and their derivatives; amine compounds such as dimethylbenzylamine and their derivatives; imidazole compounds such as 2-ethyl-4-methyl-imidazole and their derivatives; etc. The amount of the catalyst used is not particularly limited and can be set in a manner that can appropriately promote the reaction between functional group A and functional group B. In some embodiments, the amount of the catalyst used in every 100 g of the primary adhesive layer can be set to about 0.05 to 15 g, or about 0.1 to 10 g, or about 0.5 to 5 g.

By using an adhesive composition (e.g., an active energy ray-curable adhesive composition) for forming a primary adhesive layer that contains the above-mentioned catalyst in advance, a primary adhesive layer containing the catalyst can be easily obtained. For example, by allowing an ethylenically unsaturated compound having a functional group B to permeate into a primary polymer (preferably an acrylic polymer) having a functional group A and the above-mentioned catalyst, and then allowing the above-mentioned functional group A to react with the above-mentioned functional group B in the presence of the above-mentioned catalyst, a polymer having a carbon-carbon double bond (a modified product of the above-mentioned primary polymer after chemical modification) can be efficiently obtained. As another method for reacting the functional group A with the functional group B in the presence of the catalyst, for example, a method in which the subsequent coating liquid described below contains the catalyst can be cited. From the viewpoint of controllability of the reaction between the functional group A and the functional group B, a method in which the adhesive composition used to form the primary adhesive layer contains the catalyst in advance is preferred.

(Second photoinitiator) The adhesive layer (photocurable adhesive layer) constituting the adhesive sheet disclosed in this article contains a photoinitiator in addition to a polymer having a carbon-carbon double bond. By containing the photoinitiator, free radicals are generated by the photoinitiator during the curing process, which react with the carbon-carbon double bonds in the adhesive layer, so that the photocuring of the adhesive layer proceeds rapidly. Examples of the photoinitiator include ketal photoinitiators, acetophenone photoinitiators, benzoin ether photoinitiators, acylphosphine oxide photoinitiators, α-keto alcohol photoinitiators, aromatic sulfonyl chloride photoinitiators, photoactive oxime photoinitiators, benzoin photoinitiators, benzyl photoinitiators, benzophenone photoinitiators, 9-oxosulfuron photoinitiators, The photoinitiator is a photoinitiator, etc. The photoinitiator can be used alone or in combination of two or more.

Specific examples of ketal photoinitiators include 2,2-dimethoxy-1,2-diphenylethane-1-one (e.g., trade name "Omnirad 651", manufactured by IGM Resins BV), etc. Specific examples of acetophenone photoinitiators include 1-hydroxycyclohexyl-phenyl-ketone (e.g., trade name "Omnirad 184", manufactured by IGM Resins BV), 4-phenoxydichloroacetophenone, 4-tert-butyl-dichloroacetophenone, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propane-1-one, 2-hydroxy-2-methyl-1-phenyl-propane-1-one, methoxyacetophenone, etc. Specific examples of benzoin ether-based photoinitiators include benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isopropyl ether, benzoin isobutyl ether and other benzoin ethers, and substituted benzoin ethers such as anisole methyl ether. Specific examples of acylphosphine oxide-based photoinitiators include bis(2,4,6-trimethylbenzyl)phenylphosphine oxide, bis(2,4,6-trimethylbenzyl)-2,4-di-n-butoxyphenylphosphine oxide, 2,4,6-trimethylbenzyldiphenylphosphine oxide, bis(2,6-dimethoxybenzyl)-2,4,4-trimethylpentylphosphine oxide, and the like. Specific examples of α-ketoalcohol photoinitiators include 2-methyl-2-hydroxypropiophenone, 1-[4-(2-hydroxyethyl)phenyl]-2-methylpropane-1-one, and the like. Specific examples of aromatic sulfonyl chloride photoinitiators include 2-naphthalenesulfonyl chloride, and the like. Specific examples of photoactive oxime photoinitiators include 1-phenyl-1,1-propanedione-2-(o-ethoxycarbonyl)-oxime, and the like. Specific examples of benzoin photoinitiators include benzoin, and the like. Specific examples of benzyl photoinitiators include benzyl, and the like. Specific examples of benzophenone photoinitiators include benzophenone, benzoylbenzoic acid, 3,3'-dimethyl-4-methoxybenzophenone, polyvinylbenzophenone, α-hydroxycyclohexylphenylketone, and the like. 9-Oxysulfuron Specific examples of the photoinitiator include 9-oxosulfuron , 2-chloro-9-oxysulfuron , 2-methyl 9-oxosulfuron , 2,4-dimethyl 9-oxosulfuron 、Isopropyl 9-oxysulfide , 2,4-dichloro-9-oxysulfuron , 2,4-diethyl 9-oxysulfide 、Isopropyl 9-oxysulfide 、2,4-Diisopropyl 9-oxysulfide , dodecyl 9-oxysulfide wait.

The content of the photoinitiator in the photocurable adhesive layer disclosed herein is preferably 1.0×10 ^-4 mol/100 g or more (i.e., 1.0×10 ^{-4 mol or more per 100 g of the adhesive layer). From the perspective of performing the curing reaction with high precision, it is preferably 3.0×10 -4 mol} /100 g or more, preferably 5.0×10 ^-4 mol/100 g or more, and may be 7.0×10 ^-4 mol/100 g or more, 1.0×10 ^-3 mol/100 g or more, 2.0×10 ^-3 mol/100 g or more, or 3.0×10 ^-3 mol/100 g or more. The upper limit of the content of the photoinitiator is not particularly limited. In some aspects, from the perspective of storage stability of the adhesive sheet, for example, it may be 1.0×10 ^-1 mol/100 g or less, 5.0×10 ^-2 mol/100 g or less, 1.0×10 ^-2 mol/100 g or less, or 5.0×10 ^-3 mol/100 g or less.

The content of the photoinitiator in the photocurable adhesive layer can be calculated based on the total weight fraction of the materials used as raw materials for manufacturing the adhesive layer, or the weight fraction of the photoinitiator used in a manner remaining in the obtained adhesive layer and the molecular weight of the photoinitiator. For example, in the case where an additional photoinitiator is post-coated on a primary adhesive layer formed using an adhesive composition containing a photoinitiator and allowed to penetrate to obtain a photocurable adhesive layer, if no treatment (ultraviolet irradiation treatment, etc.) is subsequently performed to actively decompose the photoinitiator, it can be said that at least the photoinitiator supplied by post-coating is a photoinitiator used in a manner that remains in the obtained photocurable adhesive layer. Therefore, the content of the photoinitiator in the photocurable adhesive layer can be regarded as being equal to or greater than the content calculated based on the photoinitiator supplied by post-coating. If a photocurable adhesive layer is obtained by post-coating a photoinitiator on a primary adhesive layer obtained by curing an adhesive composition containing a photoinitiator by light irradiation (primary curing) and allowing the photoinitiator to penetrate, the content of the photoinitiator in the photocurable adhesive layer can be considered to be approximately the same as the content calculated based on the photoinitiator supplied by post-coating.

When such information is unclear, the value obtained by analysis based on HPLC (high performance liquid chromatography) can be used as the content of the photoinitiator in the photocurable adhesive layer. The photoinitiator is identified by analyzing the components of the eluted product corresponding to the peak of the photoinitiator among the peaks appearing in the chromatogram, and the identification substance or a compound having a molecular structure similar to the identification substance is used as a standard to prepare a calibration curve, thereby determining the content of the photoinitiator in the measurement sample. Based on the content and the molecular weight of the photoinitiator, the content of the photoinitiator in the adhesive layer [mole/100 g] can be calculated.

The test sample for HPLC can be prepared as follows. That is, take an appropriate amount (for example, about 0.1 g) of adhesive from the adhesive layer, put it in a spiral tube and weigh it. Add 3 mL of chloroform to the above spiral tube, shake it in a cool place overnight (about 16 hours), so that the photoinitiator in the above sample is dissolved into the chloroform. Then, add 10 mL of acetonitrile to reprecipitate the adhesive component, and filter the supernatant containing the photoinitiator with a membrane filter (pore size 0.20 μm). Use it as a test sample for HPLC. As an analytical device, "UltiMate 3000" or its equivalent from Thermo Fisher Scientific can be used. As measurement conditions, the following conditions can be used. [Measurement conditions] Column: ZORBAX Eclipse Plus C18 (3.0 mm ×100 mm, average particle size of the carrier 1.8 μm) Column temperature: 40℃ Column flow rate: 0.5 mL/min Solvent composition: pure water/acetonitrile gradient conditions Injection volume: 10 μL Detector: DAD (Diode Array Detector) (190 nm~800 nm, 210 nm and 245 nm extraction)

(Other polymers) In the case where the photocurable adhesive layer disclosed in this article contains an acrylic polymer having a carbon-carbon double bond, the photocurable adhesive layer may contain other polymers in addition to the above-mentioned acrylic polymer having a carbon-carbon double bond. The above-mentioned other polymers may be acrylic polymers without carbon-carbon double bonds, or polymers other than acrylic polymers. As the above-mentioned polymers other than acrylic polymers, various polymers exemplified as polymers that can be contained in the adhesive layer, other than acrylic polymers, can be cited as appropriate examples. Such a polymer may be a polymer having a carbon-carbon double bond. As the acrylic polymer without carbon-carbon double bonds, the acrylic polymer as the primary polymer (i.e., the acrylic polymer without chemical modification for introducing carbon-carbon double bonds) can be cited as a suitable example. When the adhesive layer disclosed herein contains other polymers in addition to the acrylic polymer with carbon-carbon double bonds, the content of the other polymer is preferably set to 100 parts by weight or less, preferably 50 parts by weight or less, more preferably 30 parts by weight or less, and further preferably 10 parts by weight or less relative to 100 parts by weight of the acrylic polymer with carbon-carbon double bonds. The content of the other polymer can be 5 parts by weight or less, or 1 part by weight or less relative to 100 parts by weight of the acrylic polymer with carbon-carbon double bonds. The technology disclosed herein can be preferably implemented, for example, in a state where 99.5 to 100 weight % of the polymer contained in the adhesive layer is an acrylic polymer having a carbon-carbon double bond.

(Compounds containing carbon-carbon double bonds other than polymers) The photocurable adhesive layer disclosed herein may also contain compounds containing carbon-carbon double bonds other than polymers containing carbon-carbon double bonds. Examples of such compounds containing carbon-carbon double bonds include: multifunctional monomers, monofunctional monomers, multifunctional or multifunctional oligomers having carbon-carbon double bonds, etc. The photocurable adhesive layer contains the above-mentioned compounds containing carbon-carbon double bonds, which means that the carbon-carbon double bonds of the compounds containing carbon-carbon double bonds are contained in an unreacted form.

In some embodiments, the photocurable adhesive layer may also contain a multifunctional monomer as the above-mentioned compound containing a carbon-carbon double bond. As the multifunctional monomer contained in the photocurable adhesive layer, one or more types can be selected from the same multifunctional monomers (copolymerizable crosslinking agents) that can be used as copolymer components of the primary polymer. In the case where the photocurable adhesive layer contains a multifunctional monomer, the photocurable adhesive layer is preferably a combination of a polymer having a carbon-carbon bond (preferably an acrylic polymer having a carbon-carbon bond) and the above-mentioned multifunctional monomer. The multifunctional monomer contained in the photocurable adhesive layer can help improve the flexibility of the photocurable adhesive layer or increase the elastic modulus after curing. For example, as a method for making the photocurable adhesive layer contain a multifunctional monomer, a method can be adopted in which the multifunctional monomer is applied to a primary adhesive layer (which may be a primary adhesive layer formed by irradiating an active energy ray-curable adhesive composition with active energy rays) and allowed to permeate.

In the photocurable adhesive layer disclosed herein, the content of the compound containing a carbon-carbon double bond (e.g., a multifunctional monomer) other than the polymer containing a carbon-carbon double bond can be set in a manner that can appropriately exert the desired effect of use. For example, it can be set to 0.01 parts by weight or more, or 0.1 parts by weight or more, or 0.5 parts by weight or more, relative to 100 parts by weight of the base polymer (e.g., an acrylic polymer having a carbon-carbon bond) of the above-mentioned photocurable adhesive layer. Furthermore, from the viewpoint of the cohesiveness of the photocurable adhesive layer or the releasability of the self-peeling pad, in some aspects, the content of the compound containing a carbon-carbon double bond is preferably set to 10 parts by weight or less, preferably 5 parts by weight or less, and can be set to 1 part by weight or less, or can be set to less than 1 part by weight, relative to 100 parts by weight of the base polymer of the photocurable adhesive layer. The technology disclosed herein can be preferably implemented in an aspect in which the photocurable adhesive layer does not contain a compound containing a carbon-carbon double bond other than the polymer containing a carbon-carbon double bond.

(Other optional components) The adhesive layer disclosed in this article may contain various additives commonly used in the field of adhesives, such as leveling agents, crosslinking aids, plasticizers, softeners, fillers, colorants (pigments, dyes, etc.), antistatic agents, ultraviolet absorbers, and light stabilizers, as other optional components as needed. Regarding these various additives, since previously known ones can be used by conventional methods and are not specifically used to characterize the present invention, detailed descriptions are omitted.

In some preferred aspects, the adhesive layer disclosed herein may be composed of a polymer (typically, a base polymer) that accounts for about 90% by weight or more of the total weight of the adhesive (solid component of the adhesive composition) (i.e., the weight of the adhesive layer containing the adhesive). In this way, the effects produced by the hardening treatment (easy peeling of the adhesive layer, increased elastic modulus, etc.) can be better achieved. From this point of view, the content of the above-mentioned polymer is preferably about 95% by weight or more of the total weight of the adhesive layer, more preferably about 97% by weight or more, and further preferably about 98% by weight or more, and can be about 99% by weight or more (e.g., 99-100% by weight). In other words, the content of components other than polymers (additives, etc.) in the solid components (adhesive layer) of the above-mentioned adhesive composition is preferably less than about 10 weight %, preferably less than about 5 weight %, more preferably less than about 3 weight %, further preferably less than about 2 weight %, and can be less than about 1 weight %.

The amount of carbon-carbon double bonds contained in the adhesive layer disclosed herein may be, for example, 1.0×10 ^-6 mol/100 g or more, or 1.0×10 ^-5 mol/100 g or more. In some aspects, from the viewpoint of easily obtaining changes in characteristics or physical properties caused by light irradiation, the amount of the above-mentioned carbon-carbon double bonds is preferably 5.0× ^10-5 mol/100 g or more, more preferably 1.0× ^10-4 mol/100 g or more, more preferably 5.0× ^10-4 mol/100 g or more or 1.0× ^10-3 mol/100 g or more, and can be 5.0× ^10-3 mol/100 g or more, or 1.0× ^10-2 mol/100 g or more, or 3.0× ^10-2 mol/100 g or more, or 4.0× ^10-2 mol/100 g or more, or 5.0× ^10-2 mol/100 g or more. Furthermore, the amount of carbon-carbon double bonds contained in the adhesive layer may be, for example, 1.0 mol/100 g or less, 5.0×10 ^-1 mol/100 g or less, 1.0×10 ^-1 mol/100 g or less, 8.0×10 ^-2 mol/100 g or less, or 7.0×10 ^-2 mol/100 g or less. From the perspective of storage stability of the adhesive layer or an adhesive sheet having the adhesive layer, or from the perspective of easily achieving a balance with other properties, it is advantageous to avoid excessive carbon-carbon double bond content. Furthermore, in this specification, the unit "mole/100 g" of the amount of carbon-carbon double bonds contained in the adhesive layer means the molar amount of carbon-carbon double bonds per 100 g of the adhesive layer.

The carbon-carbon double bonds contained in the adhesive layer disclosed herein may be contained in the form of a polymer having carbon-carbon double bonds, or in a form other than a polymer having carbon-carbon double bonds (e.g., a multifunctional monomer, a monofunctional monomer, an oligomer, etc. having carbon-carbon double bonds). At least a portion of the carbon-carbon double bonds contained in the adhesive layer is preferably contained in the form of a polymer having carbon-carbon double bonds. In some embodiments, the amount of carbon-carbon double bonds contained in the adhesive layer in the form of a polymer having carbon-carbon double bonds may be, for example, 1.0×10 ^-6 mol/100 g or 1.0×10 ^-5 mol/100 g or more. From the viewpoint of easily obtaining the characteristics or physical property changes caused by light irradiation, it is preferably 5.0×10 ^-5 mol/100 g or more, more preferably 1.0×10 ^-4 mol/100 g or more, more preferably 5.0×10 ^-4 mol/100 g or more or 1.0×10 ^-3 mol/100 g or more, and may be 5.0×10 ^-3 mol/100 g or more, may be 1.0×10 ^-2 mol/100 g or more, and may be 3.0×10 ^-2 mol/100 g or more. The molecular ^weight may be greater than or equal to 1.0 mol/100 g, may be greater than or equal to 5.0× ^10-2 mol/100 g, and may be, for example, less than or equal to 1.0 mol/100 g, may be less than or equal to 5.0× ^10-1 mol/100 g, may be less than or equal to 1.0× ^10-1 mol/100 g, may be less than or equal to 8.0× ^10-2 mol/100 g, or may be less than or equal to 7.0× ^10-2 mol/100 g.

The amount of carbon-carbon double bonds (typically, ethylenically unsaturated groups) contained in the adhesive layer can be calculated based on the total weight fraction of the materials used as raw materials for manufacturing the adhesive layer, or the weight fraction and molecular weight of the materials used in such a way that carbon-carbon double bonds remain in the adhesive layer. When such information is unclear, the content of carbon-carbon double bonds in the adhesive layer can be determined by using a value determined based on the NMR (nuclear magnetic resonance) method. Specifically, an appropriate amount of sample is taken from the adhesive layer, and the sample is dissolved in a measuring solvent to which a specific amount of an internal standard substance is added, and the amount of carbon-carbon double bonds present is determined. As an analytical device, a Fourier transform NMR device (manufactured by Bruker Biospin, "AVANCE III-600") or its equivalent can be used. As measurement conditions, the following conditions can be used. [Measurement conditions] Observation frequency: ¹ H 600 MHz Measurement solvent: CDCl ₃ Measurement temperature: 300 K Chemical shift standard: Measurement solvent ¹ H; 7.25 ppm

In some aspects of the adhesive layer disclosed herein, the content of the organic solvent in the adhesive layer is preferably less than 1.0 μg/g (i.e., the content of the organic solvent in every 1 g of the adhesive layer is less than 1.0 μg), for example, preferably less than 1.0 μg/g, more preferably less than 0.5 μg/g, less than 0.2 μg/g, and 0 μg/g. Specific examples of the above-mentioned organic solvents include ethyl acetate and toluene. An adhesive layer with a lower content of organic solvent has a lower odor, which is more ideal from the perspective of environmental hygiene. The organic solvent content of the adhesive layer can be measured by the method described in the embodiments described below.

The adhesive layer disclosed herein preferably has a total content of azo polymerization initiators and peroxide polymerization initiators (which may be polymerization initiators contained in the form of decomposition products or residues) limited to 1.0 μg/g or less. That is, the total content of azo polymerization initiators and peroxide polymerization initiators in each 1 g of the above-mentioned adhesive layer is 1.0 μg or less. In this way, the disadvantages caused by the above-mentioned polymerization initiators can be prevented or suppressed. As examples of the above-mentioned disadvantages, there can be cited: due to the decomposition of azo-based polymerization initiators or peroxide-based polymerization initiators as thermal polymerization initiators due to heat or time and the generation of free radicals, the physical properties of the adhesive may undergo unintentional changes (such as hardening); or the surface of the adherend to which the adhesive sheet is attached may be deteriorated (for example, oxidation accompanied by the decomposition of peroxide-based polymerization initiators) or contaminated (for example, contamination caused by low molecular weight decomposition products or reactants); or outgassing may be generated (for example, _N2 gas generated by the decomposition of azo-based polymerization initiators), etc. From the perspective of better suppressing the drawback, in some aspects, the total content of the azo-based polymerization initiator and the peroxide-based polymerization initiator in the adhesive layer is preferably less than 1.0 μg/g, more preferably less than 0.5 μg/g, less than 0.2 μg/g, or 0 μg/g (i.e., no azo-based polymerization initiator). The total content of the azo-based and peroxide-based polymerization initiators in the adhesive layer can be measured by the method of the embodiment described below.

(Thickness of adhesive layer) The thickness of the adhesive layer (photocurable adhesive layer) of the adhesive sheet disclosed herein is not particularly limited and can be appropriately selected according to the purpose. The thickness of the adhesive layer can be selected, for example, from a range of 2 μm to about 2000 μm. In some embodiments, from the perspective of thinning the adhesive sheet, the thickness of the adhesive layer can be, for example, less than 1000 μm, less than 500 μm, less than 200 μm, less than 150 μm, or less than 100 μm. From the perspective of reducing the peeling strength after light irradiation, in some embodiments, the thickness of the adhesive layer may be, for example, less than 100 μm, less than 80 μm, less than 60 μm, less than 40 μm, or less than 30 μm. By preventing the thickness of the photocurable adhesive layer from being too large, there is a tendency to easily obtain the easy peeling effect caused by light irradiation of the adhesive layer. For example, in the case of forming a photocurable adhesive layer by a method including forming a primary adhesive layer having a functional group A, applying a subsequent coating liquid containing an ethylenically unsaturated compound having a functional group B on the primary adhesive layer and allowing it to penetrate, and then reacting the functional group A in the primary adhesive layer with the ethylenically unsaturated compound having a functional group B, it is also advantageous to avoid making the photocurable adhesive layer too thick from the viewpoint of allowing the reaction between the functional group A and the functional group B to proceed uniformly over the entire thickness of the adhesive layer. In addition, from the perspective of adhesion to the adherend before curing treatment, the thickness of the adhesive layer is preferably 10 μm or more, more preferably 15 μm or more, and can be 20 μm or more. When the adhesive sheet disclosed in this article is a double-sided adhesive sheet with adhesive layers on both sides of the substrate, the thickness of each adhesive layer can be the same or different.

<Preparation of Adhesive Layer> The adhesive layer disclosed herein can be suitably prepared, for example, by a method including the following. (a) forming a primary adhesive layer containing a primary polymer having a functional group A (primary adhesive layer forming step); (b) preparing a subsequent coating liquid containing a compound containing a functional group B having a carbon-carbon double bond (for example, an ethylenically unsaturated compound having a functional group B) and a photoinitiator, and applying the subsequent coating liquid to at least one surface of the primary adhesive layer (subsequent coating liquid applying step); (c) allowing the compound containing the functional group B having a carbon-carbon double bond and the photoinitiator contained in the above-mentioned subsequent coating liquid to penetrate into the above-mentioned primary adhesive layer (subsequent coating liquid penetration step); (d) heating the primary adhesive layer permeated with the above-mentioned subsequent coating liquid to allow the above-mentioned functional group A to react with the above-mentioned functional group B (reaction step).

The primary adhesive layer forming step may include: applying an adhesive composition for forming the primary adhesive layer on a support; and curing the applied adhesive composition to form a primary adhesive layer containing a primary polymer having a functional group A. As the support, a plastic film that can be used as a base layer described later, or a peeling pad described later can be used. The adhesive composition can be applied by a known coating method, for example, a gravure roll coater, reverse roll coater, contact roll coater, dip roll coater, rod coater, scraper coater, spray coater, notch wheel coater, direct coater, or the like.

In the above-mentioned primary adhesive layer forming step, the method for hardening the applied adhesive composition is not particularly limited, and for example, the applied adhesive composition can be heated or the adhesive composition can be irradiated with active energy rays to harden it. If necessary, heating and drying can be further performed. In some embodiments, the following method can be preferably adopted: using an active energy ray-hardening adhesive composition (preferably an active energy ray-hardening adhesive composition without organic solvent) as the above-mentioned adhesive composition, and irradiating the composition with active energy rays to harden it. As active energy rays, for example, ionizing radiation such as α rays, β rays, γ rays, neutron rays, electron beams, or ultraviolet rays can be cited, and ultraviolet rays are particularly preferred.

Although ultraviolet rays can be directly irradiated onto the applied adhesive composition, in order to block oxygen that would hinder the curing based on ultraviolet irradiation, it is better to irradiate through a support (which may be a peeling film). For example, the surface of the adhesive composition applied on the support is covered with another support, and ultraviolet rays are irradiated through the other support. The illumination and time of ultraviolet irradiation can be appropriately set according to the composition of the primary adhesive layer or the thickness of the adhesive layer. Ultraviolet irradiation can be performed using a high-pressure mercury lamp, a low-pressure mercury lamp, a metal halide lamp, etc.

Next, the support is peeled off from one surface of the primary adhesive layer, and a subsequent coating liquid containing a compound having a carbon-carbon double bond and a photoinitiator (second photopolymerization initiator) is prepared, and the subsequent coating liquid is applied to one surface of the primary adhesive layer (subsequent coating liquid application step). The subsequent coating liquid is not particularly limited as long as it is liquid and can be applied and permeated into the adhesive layer. For example, when the compound containing a functional group B having a carbon-carbon double bond and/or the photoinitiator are in liquid form, they can be applied separately in any order, or a mixed liquid of the compound containing a functional group B having a carbon-carbon double bond and the photoinitiator can be applied. In addition, a subsequent coating liquid in which the photoinitiator is dissolved in the compound containing a functional group B having a carbon-carbon double bond can be applied, or vice versa.

If the subsequent coating liquid is applied to the surface of the primary adhesive layer, the components contained in the subsequent coating liquid will penetrate into the above-mentioned adhesive layer. After the subsequent coating liquid is applied to the primary adhesive layer, before entering the next reaction step, a static time can be set as needed to allow the above-mentioned penetration to proceed fully. The static time is not particularly limited, for example, it can be appropriately selected from within 15 minutes. In some embodiments, it can be selected from the range of 1 second to 10 minutes (for example, 10 seconds to 10 minutes), preferably 5 seconds to 5 minutes (for example, 10 seconds to 5 minutes). The static temperature can be set to about room temperature (for example, about 10 to 30°C). By statically standing under the above conditions, the subsequent coating liquid can fully penetrate into the primary adhesive layer.

Thereafter, the primary adhesive layer infiltrated with the subsequent coating liquid is heated to react the functional group A with the functional group B (reaction step). The heating temperature in the reaction step is preferably 40 to 200°C, more preferably 50 to 180°C, and further preferably 60 to 170°C (e.g. 100 to 150°C). The heating time can be an appropriate and suitable time, for example, 5 seconds to 20 minutes, preferably 5 seconds to 10 minutes, and more preferably 10 seconds to 5 minutes.

<Base layer> In single-sided adhesive or double-sided adhesive sheets with base materials, various sheet-like base materials can be used as the base material (layer) supporting the adhesive layer. As the above-mentioned base material, resin film, paper, cloth, rubber sheet, foam sheet, metal foil, and composites thereof can be used. Examples of resin films include: polyolefin films such as polyethylene (PE), polypropylene (PP), and ethylene-propylene copolymer; polyester films such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN); vinyl chloride resin films; vinyl acetate resin films; polyamide resin films; fluororesin films; and celuphine. As other examples of resin films, there can be cited resin films formed from one or more engineering plastics (which may be super engineering plastics) selected from polyphenylene sulfide resins, polysulfide resins, polyethersulfide resins, polyetheretherketone resins, polyarylate resins, polyamide imide resins, and polyimide resins. From the viewpoint of heat resistance, it is preferred to use engineering plastics. As examples of paper, there can be cited Japanese paper, kraft paper, glassine paper, high-grade paper, synthetic paper, and coated paper. As examples of cloth, there can be cited woven or non-woven fabrics made from various fiber-like materials used alone or in a blend. Examples of the above-mentioned fibrous material include cotton, staple fiber, Manila hemp, pulp, rayon, acetate fiber, polyester fiber, polyvinyl alcohol fiber, polyamide fiber, polyolefin fiber, etc. Examples of rubber sheets include natural rubber sheets, butyl rubber sheets, etc. Examples of foam sheets include foamed polyurethane sheets, foamed polychloroprene rubber sheets, etc. Examples of metal foils include aluminum foil, copper foil, etc.

In a preferred embodiment, a resin film having a specific rigidity (strength) and excellent processability and operability is used as a substrate (layer). By using a resin film substrate with high rigidity, when the adherend is thin-walled, it is possible to properly prevent the adherend from being bent or damaged during transportation. From the same point of view, it is preferred to use a polyester film as the resin film substrate. Furthermore, in this specification, "resin film" is typically a non-porous film, which is different from the concept of so-called non-woven fabric or woven fabric. The density of the resin film that can be used as the substrate can be about 0.85 to 1.50 g/cm ³ (eg, 0.90 to ^1.20 g/cm ³ , typically ^0.92 to 1.05 g/cm ³ ).

Furthermore, various additives such as fillers (inorganic fillers, organic fillers, etc.), anti-aging agents, antioxidants, ultraviolet absorbers, antistatic agents, lubricants, plasticizers, colorants (pigments, dyes, etc.) can also be added to the above-mentioned substrate (such as a resin film substrate) as needed.

The surface of the substrate layer (such as a resin film substrate, a rubber sheet substrate, a foam sheet substrate, etc.) on which the adhesive layer is disposed (the adhesive layer side surface) may be subjected to a known or commonly used surface treatment such as a corona discharge treatment, a plasma treatment, an ultraviolet irradiation treatment, an acid treatment, an alkali treatment, or application of a primer. Such a surface treatment may be used to improve the adhesion between the substrate and the adhesive layer, in other words, to improve the grip of the adhesive layer on the substrate.

In some preferred embodiments, a primer layer is provided on the adhesive layer side surface of the substrate layer. In other words, the primer layer can be arranged between the substrate layer and the adhesive layer. The primer layer forming material is not particularly limited, and one or more of polyurethane (polyisocyanate) resins, polyester resins, acrylic resins, polyamide resins, melamine resins, olefin resins, polystyrene resins, epoxy resins, phenolic resins, isocyanurate resins, polyvinyl acetate resins, etc. can be used. When an acrylic adhesive layer is provided on a resin film substrate, a polyester, urethane or acrylic primer layer is preferred. When an acrylic adhesive layer is provided on a polyester substrate layer such as a PET film, a polyester primer layer is particularly preferred. The thickness of the primer layer is not particularly limited, and generally, it can be in the range of about 0.1 μm to 10 μm (e.g., 0.1 μm to 3 μm, typically 0.1 μm to 1 μm). The primer layer can be formed using a known or commonly used coating machine such as a gravure roll coater or a reverse roll coater.

In addition, when the adhesive sheet disclosed in this article is a single-sided adhesive sheet having an adhesive layer disposed on one side of a substrate layer, a stripping treatment agent (back surface treatment agent) can be used to perform a stripping treatment on the non-adhesive layer-forming side (back surface) of the substrate layer. The back surface treatment agent that can be used in forming the back surface treatment layer is not particularly limited, and silicone-based back surface treatment agents, fluorine-based back surface treatment agents, long-chain alkyl-based back surface treatment agents, and other known or commonly used treatment agents can be used depending on the purpose or use.

The thickness of the substrate layer is not particularly limited and can be appropriately selected according to the purpose. Generally, it can be 1 to 800 μm. From the perspective of processability, operability, and workability, the thickness of the substrate layer is preferably 2 μm or more (e.g., 3 μm or more, typically, 5 μm or more), preferably about 10 μm or more, more preferably about 25 μm or more (e.g., 30 μm or more), and more preferably about 700 μm or less (e.g., 500 μm or less, typically, 200 μm or less), preferably about 100 μm or less, and more preferably about 80 μm or less (e.g., about 70 μm or less).

<Peel-off pad> There is no particular limitation on the peel-off pad, and conventional peel-off paper etc. can be used. For example, a peel-off pad having a peel-off treatment layer on the surface of a pad substrate such as a resin film or paper, or a peel-off pad made of a low-adhesion material including a fluorine-based polymer (polytetrafluoroethylene, etc.) or a polyolefin-based resin (polyethylene, polypropylene, etc.) can be used. The peel-off treatment layer can be formed by surface treating the pad substrate using a peel-off treatment agent such as a silicone-based, long-chain alkyl-based, fluorine-based, or molybdenum sulfide-based.

The total thickness of the adhesive sheet disclosed herein (which may contain an adhesive layer and a substrate layer but does not contain a release pad) is not particularly limited, and is preferably set to a range of about 5 to 1000 μm. Considering the adhesive properties, etc., the total thickness of the adhesive sheet is preferably set to about 10 to 500 μm (e.g., 15 to 300 μm, typically 20 to 200 μm). In addition, from the perspective of operability, the total thickness of the adhesive sheet is more preferably 30 μm or more (e.g., 50 μm or more, typically 70 μm or more).

<Characteristics of Adhesive Sheet> Regarding the adhesive layer of the adhesive sheet disclosed in this article (i.e., the adhesive layer before curing treatment by light irradiation), the storage elastic modulus G' (hereinafter also referred to as "initial elastic modulus G'") at 25°C measured by the method described in the embodiments described later is not particularly limited, and may be, for example, less than 5.0×10 ⁶ Pa, more preferably less than 3.0×10 ⁶ Pa, more advantageously less than 1.0×10 ⁶ Pa, less than 5.0×10 ⁵ Pa, less than 1.0×10 ⁵ Pa, less than 8.0×10 ⁴ Pa, less than 6.0×10 ⁴ Pa, or less than 5.0×10 ⁴ Pa. The lower initial elastic modulus G' of the adhesive layer is advantageous in that a larger elastic modulus change can be easily obtained by light irradiation and is also preferred in terms of improving the ability to follow the surface shape of the adherend. The lower limit of the initial elastic modulus G' is not particularly limited and may be, for example, 1.0×10 ³ Pa or more. In some embodiments, from the viewpoint of the appropriate cohesion in the adhesive layer before the curing treatment, or the processability and operability of the adhesive sheet having the adhesive layer, the initial elastic modulus G' of the adhesive layer is preferably 5.0×10 ³ Pa or more, more advantageously 8.0×10 ³ Pa or more, more preferably 1.0×10 ⁴ Pa or more, and can be 3.0×10 ⁴ Pa or more, and can also be 5.0×10 ⁴ Pa or more.

Regarding the adhesive layer of the adhesive sheet disclosed in this article, the storage elastic modulus G' at 25°C (hereinafter also referred to as "elastic modulus G' after curing treatment") measured after curing treatment using the method described in the embodiment described later is not particularly limited, and is preferably higher than the initial elastic modulus G' of the adhesive layer. The elastic modulus G' after hardening treatment is higher than the initial elastic modulus G' and may be, for example, 1.0×10 ⁴ Pa or more, 3.0× ^{10 4} Pa or more, 5.0× ^{10 4 Pa or more, or 1.0×10 5 Pa or} more. In some embodiments, the elastic modulus G' after the hardening treatment is higher than the initial elastic modulus G', and is preferably 2.0×10 ⁵ Pa or more, preferably 4.0×10 ⁵ Pa or more, and more preferably 6.0×10 ⁵ Pa or more (e.g., 8.0×10 ⁵ Pa or more, 1.0×10 ⁶ Pa or more, 1.3×10 ⁶ Pa or more, or 1.5×10 ⁶ Pa or more). From the perspective of being easy to peel off by light irradiation, it is more advantageous that the elastic modulus G' after the hardening treatment is higher. The upper limit of the elastic modulus G' after the hardening treatment is not particularly limited, and may be, for example, 1.0×10 ⁸ Pa or less, 1.0×10 ⁷ Pa or less, 5.0×10 ⁶ Pa or less, or 3.0×10 ⁶ Pa or less.

Based on the initial elastic modulus G' and the elastic modulus G' after the curing treatment, the storage elastic modulus increase rate of the adhesive layer is calculated by the following formula. Storage elastic modulus increase rate [%] = (R/Q-1) × 100 Wherein, Q in the above formula is the initial elastic modulus G' [Pa], and R in the above formula is the elastic modulus G' [Pa] after the curing treatment. The storage elastic modulus increase rate is typically more than 0% (e.g., more than 2.5×10 ² %), preferably more than 3.0×10 ² %, more preferably more than 5.0×10 ² % (e.g., more than 7.0×10 ² %), and may be more than 1.0×10 ³ %, more than 1.5×10 ³ %, more than 2.0×10 ³ %, more than 2.5×10 ³ %, or more than 3.0×10 ³ %. There is no particular upper limit to the storage elastic modulus increase rate. From the viewpoint of being able to easily exert appropriate cohesion before hardening treatment, in some aspects, the storage elastic modulus increase rate may be, for example, 1.0×10 ⁵ % or less, 1.0×10 ⁴ % or less, or 5.0×10 ³ % or less.

Regarding the adhesive layer of the adhesive sheet disclosed herein, the loss elastic modulus G'' measured at 25°C by the method described in the embodiments described later is not particularly limited. In some aspects, for example, from the perspective of easily exerting appropriate adhesiveness in the adhesive layer before curing treatment, the loss elastic modulus G'' is preferably about 1.0×10 ⁶ Pa or less, more preferably less than 5.0×10 ⁵ Pa (for example, less than 3.0×10 ⁵ Pa), more preferably less than 1.5×10 ⁵ Pa (for example, less than 1.0×10 ⁵ Pa), less than 5.0×10 ⁴ Pa, less than 1.0×10 ⁴ Pa, or less than 7.0×10 ³ Pa. Furthermore, the loss modulus G'' of the adhesive layer may be, for example, 1.0×10 ² Pa or more. From the viewpoint of being able to dissipate external forces that may be applied to the adhesive layer to maintain close contact with the adherend, it is preferably 5.0×10 ² Pa or more, and preferably 1.0×10 ³ Pa or more. The adhesive layer having the loss modulus G'' tends not to be easily peeled off from the adherend even when subjected to external forces (for example, external forces in the shear direction). In some embodiments, the above-mentioned loss modulus G'' may be 3.0×10 ³ Pa or more, 5.0×10 ³ Pa or more, 7.0×10 ³ Pa or more, or 1.0×10 ⁴ Pa or more.

Regarding the adhesive layer of the adhesive sheet disclosed herein, the Young's modulus (Young's modulus after curing treatment) after curing treatment by light irradiation measured by the method described in the embodiments described later is not particularly limited, and can be, for example, more than 0.05 MPa. In some aspects, for example, from the perspective of low contamination in the use aspect of applying a curing treatment to the adhesive sheet attached to the adherend and then peeling the adhesive sheet from the adherend, the Young's modulus after curing treatment is preferably more than 0.1 MPa, more preferably more than 0.5 MPa, and more preferably more than 1.0 MPa. If the Young's modulus of the adhesive layer increases after the curing treatment, it tends to be easy to obtain good peeling properties from the adherend after light irradiation. For example, when peeling from the adherend, it is easy to prevent or suppress the phenomenon that a part of the adhesive layer is broken and remains on the adherend (paste residue). From the perspective of more easily exerting this effect, in some embodiments, the Young's modulus after the curing treatment can be, for example, 1.2 MPa or more, 1.5 MPa or more, 2.0 MPa or more, 2.5 MPa or more, 3.5 MPa or more, 4.0 MPa or more, or 4.5 MPa or more. The Young's modulus after the hardening treatment may be, for example, 10 MPa or less, but is preferably 7.0 MPa or less, and more preferably 5.0 MPa or less, from the viewpoint of making it easier to maintain the good flexibility before the hardening treatment.

Regarding the adhesive layer of the adhesive sheet disclosed herein, the gel fraction after curing by light irradiation measured by the method described in the embodiments described later is not particularly limited, and can be, for example, 50% or more, 60% or more, or 70% or more. From the perspective of easily and appropriately exerting the easy-peeling effect caused by light irradiation, in some aspects, the gel fraction is preferably 80% or more, more preferably 82% or more, and further preferably 84% or more, and can be 86% or more, and can also be 88% or more, and can also be 90% or more. Furthermore, from the perspective of making it easier to achieve both good softness and adhesion before hardening, in some aspects, the gel fraction may be, for example, 99.5% or less, 99% or less, 97% or less, or 95% or less.

Regarding the adhesive sheet disclosed in this article, based on JIS Z 0237:2000, the initial peel strength (initial adhesion) measured at a peeling angle of 180 degrees and a tensile speed of 300 mm/min with a silicon wafer as the adherend in an environment of 23°C and 50%RH is not particularly limited and can be adjusted to an appropriate range depending on the purpose or use. The above initial adhesion can be, for example, 0.5 N/20 mm or more, or 0.8 N/20 mm or more. An adhesive sheet showing an initial adhesion above a specific value can be well adhered to the adherend. From this point of view, in some embodiments, the initial adhesion is preferably 1.0 N/20 mm or more (e.g., more than 1.0 N/20 mm), more preferably 1.5 N/20 mm or more, and further preferably 2.0 N/20 mm or more, and may be 2.5 N/20 mm or more, or 3.0 N/20 mm or more, or 3.5 N/20 mm or more, or 4.0 N/20 mm or more, or 4.5 N/20 mm or more. The upper limit of the initial adhesion is not particularly limited, for example, it may be less than 30 N/20 mm, and from the perspective of easy balance with other characteristics, it may be less than 25 N/20 mm, or less than 20 N/20 mm, or less than 15 N/20 mm. Furthermore, the initial adhesion is the peel strength measured before the curing treatment. Specifically, the initial adhesion can be measured using the method described in the embodiments described below.

Regarding the adhesive sheet disclosed herein, after the adhesive layer is attached to a silicon wafer and subjected to a curing treatment by light irradiation, the peeling strength after curing treatment (adhesion after curing treatment) measured is preferably 2.0 N/20 mm or less, and more preferably 1.0 N/20 mm or less. In this way, the adhesive sheet with limited peeling force after curing treatment can exhibit good peeling ease (easy peeling property) in the usage mode of peeling from the adherend after curing treatment. From this point of view, in some aspects, the above-mentioned adhesion after hardening treatment is preferably less than 1.0 N/20 mm, more preferably less than 0.7 N/20 mm, and further preferably less than 0.5 N/20 mm, and can be less than 0.3 N/20 mm, or less than 0.2 N/20 mm, or less than 0.1 N/20 mm, or less than 0.1 N/20 mm (for example, less than 0.08 N/20 mm or less than 0.05 N/20 mm). There is no particular limitation on the lower limit of the adhesion after hardening treatment, for example, it can be 0 N/20 mm, or it can be more than 0 N/20 mm (for example, more than 0.005 N/20 mm). Specifically, the adhesion after hardening treatment can be measured by the method described in the embodiments described below.

In the adhesive sheet disclosed in this article, the peel strength reduction rate obtained according to the following formula can be, for example, 10% or more, 20% or more, or 30% or more. Peel strength reduction rate [%] = (1-B/A) × 100 Wherein, A in the formula is the above-mentioned initial peel strength [N/20 mm], and B in the formula is the above-mentioned peel strength after hardening treatment [N/20 mm]. In some embodiments, the above-mentioned peel strength reduction rate is preferably 50% or more, more preferably 65% or more, further preferably 75% or more, particularly preferably 85% or more, and can be 90% or more, 94% or more, 96% or more, 97% or more, or 98% or more. Thus, the adhesive sheet whose peeling force is greatly reduced by UV irradiation can be used as an adhesive sheet that can be easily peeled off by irradiating light at a desired time after being attached to the adherend. The above-mentioned peeling strength reduction rate is typically less than 100%, and may be less than 100%, for example, less than 99.8% or less than 99.5%. For example, from the perspective of preventing the adhesive sheet after the hardening treatment from being unintentionally separated from the adherend, it is more advantageous if the peeling strength reduction rate is less than 100%.

In the adhesive sheet disclosed herein, the difference between the initial peel strength [N/20 mm] and the peel strength [N/20 mm] after the curing treatment (peel strength difference) may be, for example, 0 N/20 mm or more, typically more than 0 N/20 mm, preferably 0.5 N/20 mm or more, more preferably 1.0 N/20 mm or more, further preferably 1.5 N/20 mm or more or 2.0 N/20 mm or more, and may be 3.0 N/20 mm or more, and may be 4.0 N/20 mm or more. In this way, the adhesive sheet whose peeling force is greatly reduced by UV irradiation can be used as an adhesive sheet that can be easily peeled by light irradiation at a desired time after being attached to the adherend. The above-mentioned peel strength difference may be, for example, less than 30 N/20 mm. From the perspective of easy balance with other characteristics, it may be less than 25 N/20 mm, less than 20 N/20 mm, less than 15 N/20 mm, or less than 10 N/20 mm.

<Application> The application of the adhesive sheet disclosed in this article is not particularly limited. It can be used to highly prevent the paste residue when separating from the adherend after hardening treatment, and is preferably used in applications that need to be peeled off after being attached to the adherend. Examples of such applications include temporary fixing sheets and protective sheets. In addition, for example, it can be preferably used as a process material that is fixed to the adherend and peeled off in the manufacturing process of electronic equipment and electronic parts.

As a suitable use of the adhesive sheet disclosed in this article, the use in semiconductor device manufacturing can be cited. For example, it can be preferably used as a wafer fixing sheet (typically, a sheet for laser cutting) for fixing the wafer on a fixing plate (such as a hard substrate such as a glass plate or an acrylic plate) during semiconductor wafer processing (typically, silicon wafer processing). In addition, the adhesive sheet disclosed in this article can also be preferably used as a protective sheet for protecting the wafer (such as the circuit forming surface) during the above-mentioned wafer processing. The above-mentioned sheet can be required to have a suitable degree of adhesion to the extent that it will not peel off from the adherend (typically, a semiconductor device or a hard substrate) during the above-mentioned manufacturing process or during transportation, and the property of being well peeled off from the adherend after achieving the purpose. The adhesive sheet disclosed herein can be preferably used as one that satisfies the properties required for the above-mentioned purposes.

In addition, for example, a plurality of miniaturized semiconductor chips (LED chips, etc.) are fixed on the adhesive surface of an adhesive sheet, and the semiconductor chips are processed by resin sealing on the adhesive sheet, and the semiconductor chips are separated from the adhesive sheet after the processing is completed. The adhesive sheet disclosed in this article can well fix the semiconductor chip during the above-mentioned processing, and can be easily peeled off from the attached body (semiconductor chip) by light irradiation. With this adhesive sheet, it is possible to prevent the surface of the attached body from being damaged during peeling. The adhesive sheet is suitable as an adhesive sheet used in FOWLP (Fan Out Wafer Level Package) and CSP (Chip Scale Package). By being used for the above purposes, it can contribute to the high capacity and high performance of various semiconductor products.

As described above, the adhesive sheet disclosed herein can be preferably used in the manufacture of semiconductor components. Therefore, according to the specification, a method for manufacturing a semiconductor component using the adhesive sheet disclosed herein can be provided. In a preferred embodiment, the manufacturing method includes: a step of fixing a semiconductor on the adhesive sheet (fixing step); and a step of processing the semiconductor (processing step). The above-mentioned processing step can be, for example, a back grinding step, a crystal cutting step, a resin sealing step of a semiconductor chip, etc.

Furthermore, the manufacturing method may include a step of separating the adhesive sheet from the semiconductor (typically, the semiconductor chip) after the processing step (a removal step. Typically, a peeling step). The separation may be performed by attaching a transfer tape to the surface of the semiconductor (the surface opposite to the surface contacting the adhesive sheet). In the manufacturing method, the adhesive sheet is typically hardened after the processing step and before the separation step. The hardening treatment may preferably be an active energy ray (e.g., UV) irradiation step. Furthermore, other technical matters required in the manufacture of semiconductor elements are not specifically described here because the industry can implement them based on the technical common sense in this field.

Furthermore, the adhesive sheet disclosed herein is suitable as a temporary fixing sheet used in the manufacture of thin-walled substrates such as circuit substrates (e.g., printed wiring boards (PCBs), flexible circuit substrates (FPCs)), organic EL (Electroluminescence) panels, color filters, electronic paper, and flexible displays. For example, in the fixation of chips on PCBs, the adhesive sheet disclosed herein can be used to fix the attached body well, and harden it at the required time, thereby highly preventing the residue of the paste and separating the adhesive sheet well from the attached body. Furthermore, the adhesive sheet disclosed herein can be preferably used as a supporting tape for thin wafers. In this application, for example, when printing solder paste on a thin wafer, the adhesive sheet disclosed in this article is attached to the thin wafer as the adherend and used as a supporting tape, and then hardening treatment is performed at an appropriate time. This can highly prevent paste residue from remaining when separating from the adherend, and at the same time, the adhesive sheet can be well separated from the adherend.

As described above, the adhesive sheet disclosed herein can be preferably used in the manufacture of thin-walled substrates such as circuit substrates (typically PCBs). Therefore, according to the specification, a method for manufacturing a thin-walled substrate (such as a circuit substrate, an organic EL panel, a color filter, an electronic paper, a flexible display) using the adhesive sheet can be provided. In a preferred embodiment, the manufacturing method includes: a step of fixing the thin-walled substrate on the adhesive sheet (typically, the back side of the substrate) (fixing step); and a step of processing the thin-walled substrate.

Some aspects of the processing steps include a die bonding step and a wire bonding step, and may further include a molding step and a packaging and cutting step. The above-mentioned die bonding is typically a step of configuring a plurality of chips on a thin-walled substrate such as a PCB, the above-mentioned wire bonding step is a step of bonding wires to the above-mentioned chips, and the above-mentioned molding step may be, for example, a step of sealing the chips on the PCB with resins such as epoxy resins. In addition, the above-mentioned manufacturing method may include a step of separating the adhesive sheet from the thin-walled substrate after the above-mentioned processing step (removal step. Typically a peeling step). In the above-mentioned manufacturing method, typically, the adhesive sheet is hardened after the above-mentioned processing step and before the above-mentioned separation step. The curing treatment is preferably an active energy ray (eg UV) irradiation step. In addition, other technical matters required in the manufacture of thin-walled substrates such as PCBs are not specifically described here because the industry can implement them based on the technical common sense in this field.

The manufacturing method of some other aspects of circuit substrates (typically, FPC: Flexible Print Circuit) includes: a step of laminating the adhesive sheet disclosed in this article as a supporting tape on the back side of the fixing tape on which the thin wafer is fixed; and a step of processing the thin wafer. The above-mentioned manufacturing method may include a step of separating the adhesive sheet from the fixing tape after the above-mentioned processing step (a removal step, typically a peeling step). In the above-mentioned manufacturing method, typically, the adhesive sheet is hardened after the above-mentioned processing step and before the above-mentioned separation step. The hardening treatment is preferably a step of irradiating the thin wafer with active energy rays (such as UV). Furthermore, regarding other technical matters required in the manufacture of thin-walled substrates such as FPC, since the industry can implement them based on the technical common sense in this field, they are not specifically explained here.

The matters disclosed in the specification include the following. [1] An adhesive sheet having an adhesive layer that is cured by light irradiation, wherein the total content of an azo-based polymerization initiator and a peroxide-based polymerization initiator in the adhesive layer is 1.0 μg/g or less, the adhesive layer contains a polymer having a carbon-carbon double bond and a photoinitiator, and the content of the photoinitiator in the adhesive layer is 1.0×10 ^-4 mol/100 g or more. [2] An adhesive sheet as described in [1] above, wherein the adhesive layer contains 1.0×10 ^-4 mol/100 g or more of carbon-carbon double bonds. [3] An adhesive sheet as described in [1] or [2] above, wherein the polymer having a carbon-carbon double bond is cross-linked by a multifunctional monomer having two or more ethylenically unsaturated groups in one molecule. [4] An adhesive sheet as described in any one of [1] to [3] above, wherein the content of the organic solvent in the adhesive layer is 1.0 μg/g or less. [5] An adhesive sheet as described in any one of [1] to [4] above, wherein the polymer having a carbon-carbon double bond is an acrylic polymer. [6] An adhesive sheet as described in any one of [1] to [5] above, wherein the peel strength reduction rate calculated from the following formula is 50% or more. Peel strength reduction rate [%] = (1-B/A) × 100 (where A is the initial peel strength measured at a pull rate of 300 mm/min and a peel angle of 180 degrees after being attached to a silicon wafer (unit: [N/20 mm]), and B is the peel strength after hardening treatment measured at a pull rate of 300 mm/min and a peel angle of 180 degrees after being attached to a silicon wafer and irradiated with UV light with a cumulative light dose of 300 mJ/ ^cm2 (unit: [N/20 mm])).

Furthermore, the adhesive sheet disclosed in the specification includes an aspect that the adhesive layer of the adhesive sheet does not limit the total content of the azo polymerization initiator and the peroxide polymerization initiator, and in this aspect, the total content is not limited. For example, the following items are also included in the items disclosed in the specification. [7] An adhesive sheet having an adhesive layer that is cured by light irradiation, wherein the adhesive layer satisfies at least one of the following conditions: (A) the total content of azo-based polymerization initiators and peroxide-based polymerization initiators is 1.0 μg/g or less; (B) the content of organic solvent is 1.0 μg/g or less; (C) it is a photocurable product of a photocurable adhesive composition or a modified product thereof; and (D) it contains a polymer that is a photopolymer or a modified product thereof as a base polymer; the adhesive layer contains a polymer having a carbon-carbon double bond and a photoinitiator, and the content of the photoinitiator in the adhesive layer is 1.0×10 ^-4 mol/100 g or more. [8] The adhesive sheet as described in [7] above, wherein the adhesive layer contains 1.0×10 ^-4 mol/100 g or more of carbon-carbon double bonds. [9] The adhesive sheet as described in [7] or [8] above, wherein the polymer having carbon-carbon double bonds is crosslinked by a multifunctional monomer having two or more ethylenically unsaturated groups in one molecule. [10] The adhesive sheet as described in any one of [7] to [9] above, wherein the adhesive layer satisfies at least the condition (B). [11] The adhesive sheet as described in any one of [7] to [10] above, wherein the polymer having carbon-carbon double bonds is an acrylic polymer. [12] The adhesive sheet as described in any one of the above [7] to [11] has a peel strength reduction rate calculated by the following formula of 50% or more. Peel strength reduction rate [%] = (1-B/A) × 100 (where A is the initial peel strength measured at a tensile speed of 300 mm/ ^min and a peel angle of 180 degrees after being attached to a silicon wafer (unit: [N/20 mm]), and B is the peel strength after hardening treatment measured at a tensile speed of 300 mm/min and a peel angle of 180 degrees after being attached to a silicon wafer and irradiated with ultraviolet light with a cumulative light intensity of 300 mJ/cm2 (unit: [N/20 mm])). [13] The adhesive sheet as described in any one of [1] to [12] above, wherein the polymer having a carbon-carbon double bond is a photopolymer or a modified product thereof. [14] The adhesive sheet as described in any one of [1] to [13] above, wherein the polymer having a carbon-carbon double bond is an acrylic polymer, and 50% by weight or more of all monomer components constituting the acrylic polymer are (meth) acrylic acid chain alkyl esters having an alkyl group with 5 or more carbon atoms. [15] The adhesive sheet as described in any one of [1] to [14] above, wherein the adhesive layer contains the polymer having a carbon-carbon double bond as a base polymer. [16] The adhesive sheet as described in any one of [1] to [15] above, wherein the thickness of the adhesive layer is 10 μm or more and less than 100 μm.

[17] The adhesive sheet as described in any one of the above [1] to [16], after being attached to a silicon wafer, has an initial peel strength of 1.0 N/20 mm or more (e.g., 2.0 N/20 mm or more) measured at a tensile speed of 300 mm/min and a peel angle of 180 degrees. [18] The adhesive sheet as described in any one of the above [1] to [17], after being attached to a silicon wafer and subjected to a curing treatment by irradiating ultraviolet light with a cumulative light dose of 300 mJ/ ^cm2 , has a post-curing peel strength of less than 1.0 N/20 mm measured at a tensile speed of 300 mm/min and a peel angle of 180 degrees. [19] The adhesive sheet as described in any one of the above [1] to [18], wherein after the adhesive layer is subjected to ultraviolet irradiation treatment with a cumulative light dose of 300 mJ/ ^cm2 , the Young's modulus measured by a tensile test is 1.0 MPa or more. [20] The adhesive sheet as described in any one of the above [1] to [19], wherein the storage elastic modulus increase rate calculated by the following formula is 300% or more. Storage modulus increase rate [%] = (R/Q-1) × 100 (where Q and R are the storage modulus G' (unit: [Pa]) at 25°C based on dynamic viscoelasticity measurement, Q is the storage modulus G' (initial modulus G') measured using the test sample containing the above adhesive layer, and R is the storage modulus G' (post-hardening modulus G') measured after the test sample is hardened by ultraviolet irradiation)) [21] The adhesive sheet as described in any one of [1] to [20] above, wherein the storage elastic modulus G' (initial elastic modulus G') of the adhesive layer measured using a test sample containing the adhesive layer is less than 1.0×10 ⁶ Pa, and the storage elastic modulus G' (elastic modulus after curing treatment G') measured after the test sample is subjected to a curing treatment by irradiating ultraviolet rays is greater than or equal to 1.0×10 ⁶ Pa. [22] The adhesive sheet as described in any one of [1] to [21] above, wherein the loss elastic modulus of the adhesive layer at 25°C is greater than or equal to 1.0×10 ³ Pa and less than or equal to 1.0×10 ⁶ Pa. [23] An adhesive sheet as described in any one of [1] to [22] above, wherein the adhesive layer has a gel fraction of 70% or more after being cured by irradiating ultraviolet light with a cumulative light dose of 300 mJ/ ^cm2 .

[24] A method for producing an adhesive layer, which is a method for producing an adhesive layer that is cured by light irradiation (photocurable adhesive layer), wherein the adhesive layer is produced by a method comprising the following steps: forming a primary adhesive layer containing a primary polymer having a functional group A; preparing a subsequent coating liquid containing a compound containing a functional group B having a carbon-carbon double bond and a photoinitiator, and applying the subsequent coating liquid to at least one surface of the primary adhesive layer; allowing the compound containing a functional group B having a carbon-carbon double bond and the photoinitiator contained in the subsequent coating liquid to penetrate into the primary adhesive layer; and The primary adhesive layer permeated with the subsequent coating liquid is heated to allow the functional group A to react with the functional group B. [25] The adhesive layer manufacturing method described in [24] can be applied to the manufacturing of an adhesive layer possessed by an adhesive sheet described in any one of [1] to [23]. [26] An adhesive sheet having an adhesive layer obtained by the adhesive layer manufacturing method described in [24] or [25]. [Example]

Hereinafter, some embodiments related to the present invention are described, but it is not intended to limit the present invention to those shown in the embodiments. Furthermore, in the following description, unless otherwise specified, "parts" and "%" are weight basis.

<Example 1> (Preparation of prepolymer composition) After adding 0.05 parts of a photoinitiator (trade name "Omnirad 184", manufactured by IGM Resins B.V.; hereinafter referred to as "Omni.184") to a mixture of 100 parts of 2-ethylhexyl acrylate (2EHA) and 13 parts of 4-hydroxybutyl acrylate (4HBA) as monomer components, the mixture was irradiated with ultraviolet light in a nitrogen atmosphere until the viscosity (BH viscometer, No. 5 rotor, 10 rpm, measuring temperature 30°C) reached about 20 Pa･s, thereby obtaining a prepolymer composition in which a part of the above monomer components was polymerized.

(Preparation of UV-curable adhesive composition) 0.05 parts of multifunctional acrylate (hexanediol diacrylate (HDDA)) as a crosslinking agent, 0.05 parts of photoinitiator (Omni.184) and 1 part of dioctyltin dilaurate (trade name "Enbilizer OL-1", manufactured by Tokyo Fine Chemical Co., Ltd.; hereinafter referred to as "OL-1") were added to the above prepolymer composition and mixed to obtain a UV-curable adhesive composition C1.

(Formation of primary adhesive layer) The adhesive composition C1 was applied on the peeling-treated surface of a release film (trade name "MRF#38", manufactured by Mitsubishi Chemical Co., Ltd.) to form an adhesive composition layer. The surface of the adhesive composition layer was covered with a release film (trade name "MRE#38", manufactured by Mitsubishi Chemical Co., Ltd.) to block air, and ultraviolet light was irradiated under the conditions of illumination: 5 mW/cm ² and cumulative light amount: 2400 mJ/cm ² to photoharden the adhesive composition layer to form a primary adhesive layer (unmodified adhesive layer) D1. The primary adhesive layer D1 contains the polymer of the above-mentioned monomer components, namely, an acrylic polymer cross-linked by the above-mentioned multifunctional acrylate as a base polymer (primary polymer).

(Preparation and application of subsequent coating liquid) 11 parts of methacryloyl ethyl isocyanate (MOI) and 1 part of a photoinitiator (trade name "Omnirad 651", manufactured by IGM Resins B.V.; hereinafter referred to as "Omni.651") were mixed to prepare the subsequent coating liquid E1. The above-mentioned peeling film was peeled off from one surface of the above-mentioned primary adhesive layer D1, and the above-mentioned subsequent coating liquid E1 was applied to the exposed surface using a wire wound rod type rod coating machine manufactured by RD Specialties. After coating, let it stand for about 10 seconds to 10 minutes to allow the subsequent coating liquid E1 to penetrate into the primary adhesive layer D1.

(Introduction of carbon-carbon double bonds) Then, the primary adhesive layer D1 infiltrated with the subsequent coating liquid E1 is heated in an oven at 130°C for 3 minutes to cause an addition reaction of MOI, thereby introducing carbon-carbon double bonds into the side chains of the above-mentioned base polymer. In this way, a photocurable adhesive layer (substrate-free adhesive sheet) S1 containing a base polymer with carbon-carbon double bonds and a photoinitiator is obtained. The release-treated surface of the release film is attached to the above-mentioned surface of the obtained adhesive layer S1 for protection. Furthermore, the coating amount of the above-mentioned adhesive composition C1 and the coating amount of the above-mentioned subsequent coating liquid E1 are adjusted so that the content of each component in the above-mentioned adhesive layer S1 reaches as shown in the following table, and the thickness of the adhesive layer S1 reaches 25 μm.

<Example 2> 0.05 parts of photoinitiator (Omni.184) were mixed into 100 parts of 2EHA as a monomer component, and ultraviolet rays were irradiated in the same manner as in Example 1 to obtain a prepolymer composition in which part of the above monomer component was polymerized. 13 parts of 4HBA as a monomer component, 0.05 parts of HDDA as a crosslinking agent, 0.05 parts of photoinitiator (Omni.184), and 1 part of OL-1 were added to the above prepolymer composition and mixed to obtain a UV-curable adhesive composition C2. The adhesive layer (substrate-free adhesive sheet) S2 of this example was prepared in the same manner as in Example 1 except that adhesive composition C2 was used instead of adhesive composition C1.

<Example 3> 0.05 parts of photoinitiator (Omni.184) were mixed into 100 parts of 2EHA as a monomer component, and ultraviolet rays were irradiated in the same manner as in Example 1 to obtain a prepolymer composition in which a part of the above monomer component was polymerized. 12 parts of MOI as a monomer component, 0.05 parts of HDDA as a crosslinking agent, 0.05 parts of photoinitiator (Omni.184), and 1 part of OL-1 were added to the above prepolymer composition and mixed to obtain a UV-curable adhesive composition C3. 11 parts of 4HBA were mixed with 1 part of photoinitiator (Omni.651) to prepare a subsequent coating liquid E3. The adhesive layer (substrate-free adhesive sheet) S3 of this example was prepared in the same manner as in Example 1 except that the adhesive composition C3 was used instead of the adhesive composition C1, and the subsequent coating liquid E3 was used instead of the subsequent coating liquid E1.

<Example 4> 0.05 part of photoinitiator (Omni.184) was added to a mixture of 100 parts of 2EHA and 13 parts of acrylic acid (AA) as monomer components, and ultraviolet rays were irradiated in the same manner as in Example 1 to obtain a prepolymer composition in which a part of the above monomer components was polymerized. 0.05 part of HDDA as a crosslinking agent, 0.05 part of photoinitiator (Omni.184), and 4 parts of tetrabutylammonium bromide (TBAB) were added to the above prepolymer composition and mixed to obtain a UV-curable adhesive composition C4. 11 parts of glycidyl methacrylate (GMA) and 1 part of photoinitiator (Omni.651) were mixed to prepare a coating liquid E4. The adhesive layer (adhesive sheet without substrate) S4 of this example was prepared in the same manner as in Example 1 except that adhesive composition C4 was used instead of adhesive composition C1 and subsequent coating liquid E4 was used instead of subsequent coating liquid E1.

<Examples 5 to 7> Except for changing the composition of the subsequent coating liquid as shown in Table 1, the same operation as Example 2 was performed to prepare the adhesive layer (substrate-free adhesive sheet) S5 to S7 of each example.

<Example 8> In a reaction container equipped with a thermometer, a stirrer, a nitrogen inlet tube, etc., a monomer mixture is prepared according to a mixing ratio of 85 parts of 2EHA and 15 parts of hydroxyethyl acrylate (HEA), 0.2 parts of N,N'-azobisisobutyronitrile (AIBN) as an azo polymerization initiator and ethyl acetate as a polymerization solvent are added to 100 parts of the monomer mixture, and solution polymerization is carried out at about 60°C under a nitrogen flow to obtain an ethyl acetate solution of an acrylic polymer. 0.02 parts of OL-1 and 12 parts of MOI are added to the solution for addition reaction to prepare an acrylic polymer having a carbon-carbon double bond. To the ethyl acetate solution of the acrylic polymer having carbon-carbon double bonds, 1 part of an isocyanate crosslinking agent (trade name "Takenate D-101E" manufactured by Mitsui Chemicals Co., Ltd.) was added as a solid component relative to 100 parts of the solid content of the acrylic polymer, and 1 part of a photoinitiator (Omni.651) was added. In this way, a solvent-type adhesive composition C8 (solid content 50%) was prepared. The adhesive composition C8 was applied to the peeling surface of the polyester film that had been peeled, and dried at 120°C for 3 minutes, and then aged at 50°C for 24 hours to prepare the adhesive layer (substrate-free adhesive sheet) S8 of this example.

<Example 9> In the above solution polymerization, 0.2 parts of benzoyl peroxide (trade name "Nyper BMT-40SV" manufactured by NOF Corporation) was used as a peroxide polymerization initiator instead of 0.2 parts of AIBN. With regard to other aspects, the same operation as in Example 8 was carried out to prepare the adhesive layer (substrate-free adhesive sheet) S9 of this example.

<Examples 10 and 11> Except that the monomers of the types and amounts shown in Table 2 were further added to the prepolymer composition, the same operation as in Example 1 was performed to prepare adhesive layers (substrate-free adhesive sheets) S10 and S11 of each example. In Table 2, "ACMO" represents N-acryloylpyrrolidone, and "NVP" represents N-vinyl-2-pyrrolidone.

<Example 12> 0.05 parts of photoinitiator (Omni.184) was added to a mixture of 100 parts of n-butyl acrylate (BA) and 22 parts of 4HBA as monomer components, and ultraviolet rays were irradiated in the same manner as in Example 1 to obtain a prepolymer composition in which part of the above monomer components were polymerized. 0.05 parts of HDDA as a crosslinking agent, 0.05 parts of photoinitiator (Omni.184), and 1 part of OL-1 were added to the above prepolymer composition and mixed to obtain a UV-curable adhesive composition C12. 18 parts of MOI were mixed with 1 part of photoinitiator (Omni.651) to prepare a subsequent coating liquid E12. The adhesive layer (substrate-free adhesive sheet) S12 of this example was prepared in the same manner as in Example 1 except that adhesive composition C12 was used instead of adhesive composition C1, and subsequent coating liquid E12 was used instead of subsequent coating liquid E1.

<Example 13> Except that the monomers of the types and amounts shown in Table 2 are further added to the prepolymer composition, the same operation as in Example 12 is performed to prepare the adhesive layer (substrate-free adhesive sheet) S13 of this example.

<Measurement and evaluation> [Carbon-carbon double bond content] The amount of carbon-carbon double bonds (unreacted double bond content) contained in the adhesive layer (adhesive layers S1 to S13) obtained in each example was calculated by the following formula. Carbon-carbon double bond content [mole/100 g] = ((the number of carbon-carbon double bond-containing compounds contained in the subsequent coating liquid [parts] × the number of carbon-carbon double bonds contained in one molecule of the carbon-carbon double bond-containing compound) / the total number of adhesive formulations [parts]) × 100 [g] / molecular weight of the carbon-carbon double bond-containing compound [g/mole]

[Photoinitiator amount] The amount of photoinitiator contained in the adhesive layer obtained in each example (unreacted photoinitiator amount) is calculated by the following formula. Photoinitiator amount [mole/100 g] = (number of photoinitiators contained in the subsequent coating liquid [parts] / total number of adhesive preparation parts [parts]) × 100 [g] / molecular weight of the photoinitiator [g/mole]

[Azo and peroxide polymerization initiators] About 3 mg of the sample was taken from the adhesive layer obtained in each example, and the outgassing analysis was performed by gas chromatography-mass spectrometry (GC/MS) at 180°C for 1 hour. The specific measurement conditions are as follows. Based on the measurement results, the total content of the azo polymerization initiator and the peroxide polymerization initiator in the above adhesive layer (including the amount contained in the form of decomposition products or residues) was calculated. (Analysis equipment) Heating device: GERSTEL, TDU2 GC/MS: Agilent Technologies, 8890/5977B (Measurement conditions) TDU conditions (sample): 30℃ (1 min) → 720℃/min → 180℃ (60 min) TDU conditions (standard): 30℃ (1 min) → 720℃/min → 300℃ (5 min) CIS conditions: -150℃ (2.5 min) → 12℃/sec → 300℃ (10 min) GC/MS conditions Column: HP-Ultra1 (0.20 mm ×25 m, df＝0.33 μm) Column temperature: 40℃(5 min)→10℃/min→100℃→20℃/min→300℃(9 min) Column pressure: Constant flow mode (113 kPa, Vac) Column flow rate: 1 mL/min(He) Injection method: CIS, Split(20:1) Detector: MS Ion source temperature: 230℃ Ionization method: EI(70 eV) Scanning range: m/z10～800

[Organic solvent content] About 3 mg of sample was taken from the adhesive layer obtained in each example, and the outgassing analysis was performed by gas chromatography-mass spectrometry (GC/MS) at 180°C for 1 hour to determine the organic solvent content in the adhesive layer. The specific measurement conditions are as above.

[Dynamic viscoelasticity measurement] The adhesive layer (adhesive sheet without substrate) obtained in each example is laminated to a thickness of about 2 mm, and a disc with a diameter of 7.9 mm is punched out as a measurement sample. Dynamic viscoelasticity measurement is performed under the following conditions using the "Advanced Rheometric Expansion System (ARES)" manufactured by Rheometric Scientific, and the initial elastic modulus G' and loss elastic modulus G'' at 25°C are obtained. (Measurement conditions) Deformation mode: Torsion Measurement frequency: 1 Hz Heating rate: 5°C/min Shape: Parallel plate 7.9 mm

Then, the above-mentioned measurement sample was subjected to a curing treatment by irradiating ultraviolet light with an illuminance of 300 mW/cm2 and a cumulative light quantity of 3000 mJ/ ^cm2 . The treated sample was used to perform a dynamic viscoelasticity measurement using the above-mentioned method to determine the elastic modulus G' after curing treatment at 25°C.

Based on the obtained initial elastic modulus G'[Pa] and the elastic modulus G'[Pa] after hardening treatment, the increase rate of storage elastic modulus G' is calculated by the following formula. Increase rate of storage elastic modulus G'[%]＝(R/Q－1)×100 (where Q is the initial elastic modulus G' and R is the elastic modulus G' after hardening treatment)

[Young's modulus (Young's modulus after curing treatment)] The adhesive layer (substrate-free adhesive sheet) obtained by each example was subjected to curing treatment by irradiation with ultraviolet light under the following conditions in a state where the adhesive layer was sandwiched between two peeling films. Then, the adhesive layer and the peeling film were cut into a size of 80 mm in width and 30 mm in length. The width of 80 mm was set according to the thickness of the adhesive layer in such a way that the cross-sectional area of the adhesive layer in the cross section along the width direction was about 2 ^mm2 . Next, a peeling film was removed from the adhesive layer, and the adhesive layer was rolled up on another peeling film with its length as the axis to avoid air bubbles from entering, thereby making a rod-shaped specimen with a length of 30 mm. The rod-shaped specimen was placed on a tensile testing machine (manufactured by ORIENTEC, trade name "RTC-1150A"), and the SS (stress-strain) curve was measured under the conditions of a measuring temperature of 23°C, a chuck distance of 10 mm, and a tensile speed of 300 mm/min. The initial elastic modulus was obtained based on the rise of the SS curve, and it was set as the tensile elastic modulus of the adhesive layer after hardening treatment (Young's modulus after hardening treatment). (UV irradiation conditions) UV irradiator: manufactured by Nitto Seiki Co., Ltd., trade name "NEL SYSTEM UM810", high-pressure mercury lamp light source (characteristic wavelength 365 nm) Irradiation: Illuminance 60 mW/ ^cm2 , cumulative light intensity 300 mJ/ ^cm2

[Gel fraction] The adhesive layer (adhesive sheet without substrate) obtained in each example is subjected to a curing treatment by irradiating ultraviolet rays under the following conditions in a state where the adhesive layer is sandwiched between two peeling films. Then, a measurement sample of about 0.5 g is taken from the above-mentioned adhesive layer and accurately weighed (weight W1). The measurement sample is wrapped in a porous PTFE (polytetrafluoroethylene) sheet, immersed in ethyl acetate at room temperature for 1 week and then dried, and the weight of the insoluble component in ethyl acetate is measured (weight W2). The above-mentioned weights W1 and W2 are substituted into the following formula: Gel fraction [%] = W2/W1×100; The gel fraction of the adhesive layer after the curing treatment is calculated. As the porous PTFE sheet, the product name "NITOFLON NTF1122" manufactured by Nitto Denko Co., Ltd. was used. (UV irradiation conditions) UV irradiator: manufactured by Nitto Seiki Co., Ltd., product name "NEL SYSTEM UM810", high-pressure mercury lamp light source (characteristic wavelength 365 nm) Irradiation amount: illuminance 60 mW/ ^cm2 , cumulative light amount 300 mJ/ ^cm2

[180 degree peel strength] A peeling pad was peeled off from the adhesive layer (substrate-free adhesive sheet) obtained in each example, and a transparent PET film with a thickness of 50 μm was attached as a backing, and then cut into short strips with a width of 20 mm and a length of 80 mm to prepare a test piece. In an environment of 23°C and 50% RH, another peeling pad was peeled off from the above test piece and attached to the mirror surface of a silicon wafer (manufactured by Shin-Etsu Chemical Co., Ltd., 6 inches, N<100>-100) as the adherend using a hand roller. After autoclaving (50°C, 5 atm, 15 minutes), the test piece was peeled off from the silicon wafer using a tensile tester (manufactured by Minebea, universal tensile compression tester, device name "tensile compression tester, TCM-1kNB") at a tensile speed of 300 mm/min and a peeling angle of 180 degrees in an environment of 23°C and 50% RH, and the peeling strength at this time was measured. The measurement was performed 3 times, and the arithmetic average of the values was taken as the value of the initial peeling strength.

After the autoclave treatment, the PET film side was subjected to UV curing treatment under the following conditions, and then the test piece was peeled off from the silicon wafer. The peeling strength after curing treatment was measured in the same manner as the initial peeling strength measurement. (UV irradiation conditions) UV irradiator: manufactured by Nitto Seiki Co., Ltd., trade name "NEL SYSTEM UM810", high-pressure mercury lamp light source (characteristic wavelength 365 nm) Irradiation: illuminance 60 mW/ ^cm2 , cumulative light quantity 300 mJ/ ^cm2

Based on the obtained initial peel strength [N/20 mm] and the peel strength [N/20 mm] after hardening treatment, the peel strength reduction rate is calculated by the following formula. Peel strength reduction rate [%] = (1-B/A) × 100 (A is the initial peel strength, B is the peel strength after hardening treatment)

The obtained results are shown in Tables 1 and 2 together with the summary of the adhesive layer of each example. Example 1 in Table 2 is a re-disclosure of Example 1 in Table 1.

[Table 1] Table 1 Project Unit Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Example 9 polymerization Single 2EHA [share] 100 100 100 100 100 100 100 85 85 4HBA [share] 13 HEA [share] 15 15 AA [share] 13 Initiator Omni.184 [share] 0.05 0.05 0.05 0.05 0.05 0.05 0.05 AIBN [share] 0.2 BPO [share] 0.2 addition Single MOI [share] 12 12 Catalyst OL-1 [share] 0.02 0.02 Coating liquid Single 4HBA [share] 13 13 13 13 MOI [share] 12 Crosslinking agent D-101E [share] 1 1 HDDA [share] 0.05 0.05 0.05 0.05 0.05 0.05 0.05 Initiator Omni.184 [share] 0.05 0.05 0.05 0.05 0.05 0.05 0.05 Omni.651 [share] 1 1 Catalyst OL-1 [share] 1 1 1 1 1 1 TBAB [share] 4 Follow-up coating liquid Single MOI [share] 11 11 11 0.5 4HBA [share] 11 GMA [share] 11 Photoinitiator Omni.651 [share] 1 1 1 1 0.2 1 1 Unreacted double bond amount [mol/100 g] 5.6E-02 5.6E-02 6.1E-02 6.0E-02 5.7E-02 2.8E-03 0 0 0 Unreacted photoinitiator dose [mol/100 g] 3.1E-03 3.1E-03 3.1E-03 3.0E-03 6.2E-04 3.4E-03 3.4E-03 0 0 Adhesive layer thickness [μm] 25 25 25 25 25 25 25 25 25 Azo and peroxide polymerization initiators [μg/g] 0 0 0 0 0 0 0 13 96 Organic solvent content [μg/g] 0 0 0 0 0 0 0 15 13 Viscoelasticity G'(25℃) initial [Pa] 4.3E+04 4.1E+04 4.1E+04 5.2E+04 4.0E＋04 4.1E+04 3.9E+04 8.0E＋04 8.0E＋04 After hardening [Pa] 1.7E+06 1.7E+06 1.3E+06 1.8E+06 1.1E+06 1.2E+06 1.4E+05 1.8E+06 1.9E+06 Increase rate [%] 3.7E+03 4.0E+03 3.2E+03 3.3E+03 2.7E+03 2.8E+03 2.5E+02 2.2E+03 2.3E+03 G''(25℃) initial [Pa] 6.9E+03 6.8E+03 6.6E+03 7.5E+03 6.5E+03 6.6E+03 6.8E+03 9.0E＋03 8.8E+03 Young's modulus after hardening treatment [MPa] 4.8 4.9 3.9 5.2 1.9 2.0 0.040 5.3 5.5 Gel fraction after hardening [%] 92 92 88 86 81 80 78 92 91 180° peel strength initial [N/20 mm] 3.2 3.0 2.5 10.0 3.4 3.3 3.3 3.4 3.2 After hardening [N/20 mm] 0.02 0.03 0.08 0.2 1.0 0.9 3.3 0.02 0.08 Peel strength reduction rate [%] 99.4 99.0 96.8 98.0 70.6 72.7 0 99.4 97.5 Poor peeling force [N/20 mm] 3.2 3.0 2.4 9.8 2.4 2.4 0.0 3.4 3.1

[Table 2] Table 2 Project Unit Example 1 Example 10 Example 11 Example 12 Example 13 polymerization Single 2EHA [share] 100 100 100 BA [share] 100 100 4HBA [share] 13 13 13 twenty two twenty two HEA [share] AA [share] Initiator Omni.184 [share] 0.05 0.05 0.05 0.05 0.05 Coating liquid Single 4HBA [share] ACMO [share] 40 40 NVP [share] 20 MOI [share] Crosslinking agent D-101E [share] HDDA [share] 0-05 0.05 0.05 0.05 0.05 Initiator Omni.184 [share] 0.05 0.05 0.05 0.05 0.05 Omni.651 [share] Catalyst OL-1 [share] 1 1 1 1 1 TBAB [share] Follow-up coating liquid Single MOI [share] 11 11 11 18 18 4HBA [share] GMA [share] Photoinitiator Omni.651 [share] 1 1 1 1 1 Unreacted double bond amount [mol/100 g] 5.6E-02 4.3E-02 4.9E-02 8.2E-02 6.4E-02 Unreacted photoinitiator dose [mol/100 g] 3.1E-03 2.3E-03 2.7E-03 2.7E-03 2.1E-03 Adhesive layer thickness [μm] 25 25 25 25 25 Azo and peroxide polymerization initiators [μg/g] 0 0 0 0 0 Organic solvent content [μg/g] 0 0 0 0 0 Viscoelasticity G'(25℃) initial [Pa] 4.3E+04 2.0E＋05 1.0E＋05 4.7E+04 2.1E+05 After hardening [Pa] 1.7E+06 1.7E+06 1.7E+06 1.6E+06 1.6E+06 Increase rate [%] 3.7E+03 8.6E+02 1.7E+03 3.4E+03 7.7E+02 G"(25℃) initial [Pa] 6.9E+03 4.6E+04 1.0E＋04 1.0E＋04 1.3E+05 Young's modulus After hardening [MPa] 4.8 5.0 5.0 4.6 4.7 Gel fraction After hardening [%] 92 91 93 89 88 180° peel strength initial [N/20 mm] 3.2 9.8 5.2 2.8 11.2 After hardening [N/20 mm] 0.02 0.1 0.1 0.1 0.1 Peel strength reduction rate [%] 99.4 99.0 98.1 96.4 99.1 Poor peeling force [N/20 mm] 3.2 9.7 5.1 2.7 11.1

As shown in Tables 1 and 2, the adhesive layers of Examples 1 to 6 and 10 to 13 contain a polymer having a carbon-carbon double bond and a photoinitiator of 1.0×10 ^-4 mol/100 g or more. The storage elastic modulus G' of the adhesive layers increases significantly due to ultraviolet irradiation, thereby showing good photocurability. In addition, the peel strength of the adhesive layers of Examples 1 to 6 and 10 to 13 decreases significantly due to ultraviolet irradiation, thereby showing excellent easy peelability. The adhesive layers of Examples 1 to 6 and 10 to 13 exhibit such excellent performance, and can be manufactured using a solvent-free adhesive composition obtained by solution polymerization without using an azo-based or peroxide-based polymerization initiator, and a method that does not use an organic solvent in the process of obtaining the adhesive layers of each example from the adhesive composition, so it is more ideal from the perspective of environmental hygiene.

On the other hand, the adhesive layer of Example 7 does not contain a polymer having a carbon-carbon double bond, and does not show the same curability (characteristic change) as Examples 1 to 6 and Examples 10 to 13 when exposed to light. Furthermore, the adhesive layers of Examples 8 and 9 shown in Table 1 are obtained by coating and drying a solvent-based adhesive composition containing an acrylic polymer (acrylic polymer having a carbon-carbon double bond) obtained by introducing a carbon-carbon double bond into an acrylic polymer obtained by solution polymerization using an azo-based polymerization initiator in Example 8 and a peroxide-based polymerization initiator in Example 9 as a base polymer. The adhesive layers of Examples 8 and 9 reflect this manufacturing process. The values of the azo and peroxide polymerization initiators are as high as 13 to 96 μg/100 g. It can be seen that the residual solvent amount (organic solvent content) is also significantly higher.

The specific examples of the present invention have been described in detail above, but these are only examples and do not limit the scope of the patent application. The technology described in the scope of the patent application includes various changes and modifications of the specific examples described above.

1: Adhesive sheet 2: Adhesive sheet 10: Adhesive layer 10A: One surface (adhesive surface) 10B: The other surface 20: Substrate 20A: First surface 20B: Second surface (back surface) 30: Peel-off pad 31,32: Peel-off pad 50: Adhesive sheet with peel-off pad

FIG1 is a cross-sectional view schematically showing the structure of an adhesive sheet in one embodiment. FIG2 is a cross-sectional view schematically showing the structure of an adhesive sheet in another embodiment.

1: Adhesive sheet

10: Adhesive layer

10A: One surface (adhesive surface)

10B: Another surface

31,32: Peel off the liner

50: Adhesive sheet with peel-off liner

Claims (6)

An adhesive sheet having an adhesive layer that is cured by light irradiation, wherein the total content of an azo polymerization initiator and a peroxide polymerization initiator in the adhesive layer is 1.0 μg/g or less, the adhesive layer contains a polymer having a carbon-carbon double bond and a photoinitiator, and the content of the photoinitiator in the adhesive layer is 1.0×10 ^-4 mol/100 g or more. The adhesive sheet of claim 1, wherein the adhesive layer contains more than 1.0×10 ^-4 mol/100 g of carbon-carbon double bonds. The adhesive sheet of claim 1, wherein the polymer having carbon-carbon double bonds is cross-linked by a multifunctional monomer having two or more ethylenically unsaturated groups in one molecule. The adhesive sheet according to any one of claims 1 to 3, wherein the content of the organic solvent in the adhesive layer is 1.0 μg/g or less. The adhesive sheet according to any one of claims 1 to 3, wherein the polymer having carbon-carbon double bonds is an acrylic polymer. For the adhesive sheet of any one of claim 1 to 3, the peel strength reduction rate calculated by the following formula is 50% or more: Peel strength reduction rate [%] = (1-B/A) × 100 (where A is the initial peel strength measured at a tensile speed of 300 mm/min and a peel angle of 180 degrees after being attached to a silicon wafer (unit: [N/20 mm]), and B is the peel strength after hardening treatment measured at a tensile speed of 300 mm/min and a peel angle of 180 degrees after being attached to a silicon wafer and hardening treated with ultraviolet light having a cumulative light dose of 300 mJ/ ^cm2 (unit: [N/20 mm])).