JP7779018B2 - Adhesive sheet, laminate using said adhesive sheet, and method for producing same - Google Patents

Description

The present invention relates to an adhesive sheet that can be suitably used to join metal surfaces and components with uneven surfaces.

Display devices such as televisions, smartphones, personal assistant devices (PADs), tablet computers, and car navigation systems typically consist of a combination of components such as display panels, wiring boards, lighting devices, and other electronic components.

Many of the components that make up display devices have uneven surfaces due to the various components arranged on a single component. Therefore, when joining such components with uneven surfaces to other components in the manufacture of display devices, methods such as applying an adhesive are used. Specifically, a commonly used method involves applying adhesive to the uneven surface to fill in the surface unevenness, then smoothing the adhesive-coated surface by squeegeeing the applied adhesive to remove thickness variations, and then laminating the other component (see, for example, Patent Document 1). However, this method requires management of the amount of adhesive applied, and a time-consuming cleaning process after application. Therefore, there is a need for an alternative joining method to adhesives in order to improve work efficiency.

In light of this background, the use of adhesive sheets with excellent conformability to uneven surfaces has been proposed in recent years in place of adhesives (see, for example, Patent Document 2). The adhesive sheet disclosed in Patent Document 2 is a photocurable adhesive sheet that is flexible before light irradiation, allowing it to conform to uneven surfaces on the components while making contact. By irradiating the sheet with light while it is attached to the components, the components can be firmly bonded together via the cured adhesive sheet. Unlike when using adhesives, this method of joining components using the adhesive sheet does not require application amount management or cleaning processes, simplifying the lamination process.

Japanese Patent Application Laid-Open No. 2003-136677 Japanese Patent Application Laid-Open No. 2015-120773

The adhesive sheet disclosed in Patent Document 2 rapidly hardens immediately after light irradiation, causing it to lose flexibility in a short period of time and resulting in poor adhesion and conformance to uneven surfaces. For this reason, when joining components using the above-mentioned adhesive sheet, it is necessary to first bring the components into contact with the adhesive sheet to create a laminate before irradiating it with light, and then irradiate the laminate through the components with light to promote the curing reaction of the adhesive sheet. However, in order to irradiate the adhesive sheet with sufficient light to cause the curing reaction, the components must be light-transmitting. However, components with metal surfaces, such as metal components or components with metal parts mounted on them, have low light transmittance or do not transmit light at all, making them difficult to join using the above-mentioned method.

Furthermore, when joining components using a thermosetting adhesive sheet, high temperatures and pressure must be applied to sufficiently promote the curing reaction. However, this method is not suitable for joining components with low heat resistance, and the application of heat and pressure can cause thermal degradation, damage, and reduced functionality of the components and parts. Other problems include distortion and deformation between components due to differences in thermal expansion between the components, and cracks that can occur between the adhesive sheet and the component, leading to separation.

Furthermore, many of the components used in display devices are made of metal (metal components) or components with metal parts mounted thereon, and when an adhesive or adhesive sheet comes into contact with the surface of a metal component or a component with a metal part mounted thereon, the components contained in the adhesive can corrode the metal, resulting in a deterioration in the functionality of the metal component or metal part. In particular, the greater the adhesive sheet or adhesive used to join components is able to conform to unevenness in the adherend surface, the more corrosion of the metal surface contained in the adherend surface is accelerated, resulting in a more pronounced deterioration in the functionality of the metal component or metal part.

The present disclosure has been made in consideration of the above problems, and aims to provide an adhesive sheet that can be used without being restricted by the optical transparency or heat resistance of the adherend, that has excellent conformal adhesion to unevenness in the adherend surface, and that is effective in preventing corrosion of metal surfaces contained in the adherend surface, as well as a laminate using this adhesive sheet and a method for producing the same.

The present invention provides an adhesive sheet having an adhesive layer containing a photocurable resin (A) having a polymerizable functional group other than a polymerizable unsaturated double bond, a thermoplastic resin (B) having a polymerizable functional group other than a polymerizable unsaturated double bond, a photopolymerization initiator (C), and one or more additives (D) that have the function of capturing or neutralizing halogen ions and/or acids containing the halogen ions.

The present invention also provides a laminate comprising the above-mentioned adhesive sheet, a first member bonded to a first main surface of the adhesive sheet, and a second member bonded to a second main surface of the adhesive sheet.

The present invention also provides a method for manufacturing a laminate using the above-mentioned adhesive sheet, comprising step [1] of bonding a first member to the first main surface of the adhesive sheet, step [2] of bonding a second member to the second main surface of the adhesive sheet, and step [3] of curing the adhesive layer of the adhesive sheet, and further comprising a step of irradiating the first main surface or the second main surface of the adhesive sheet with active energy rays before step [1] or between steps [1] and [2], and wherein at least one of the first member and the second member includes a metal surface on the surface that contacts the adhesive sheet.

The present invention provides an adhesive sheet that can be used without being restricted by the optical transparency or heat resistance of the adherend, that has excellent conformal adhesion to unevenness in the adherend surface, and that is effective in preventing corrosion of metal surfaces contained in the adherend surface, as well as a laminate using the adhesive sheet and a method for producing the same.

The adhesive sheet of the present invention, as well as a laminate using the adhesive sheet and a method for producing the same, are described below.

1. Adhesive Sheet The adhesive sheet of the present invention has an adhesive layer containing a photocurable resin (A) having a polymerizable functional group other than a polymerizable unsaturated double bond, a thermoplastic resin (B) having a polymerizable functional group other than a polymerizable unsaturated double bond, a photopolymerization initiator (C), and one or more additives (D) having the function of capturing or neutralizing halogen ions and/or acids containing the halogen ions.

The adhesive sheet of the present invention can be used without being restricted by the optical transparency or heat resistance of the adherend, has high conformal adhesion to uneven surfaces, allowing for strong bonding, and can also inhibit corrosion of metal surfaces included in the adherend surface.

More specifically, the adhesive sheet of the present invention contains the desired components described above in the adhesive layer, so that the curing reaction does not proceed rapidly but gradually after light irradiation, allowing the adhesive sheet to retain flexibility even after light irradiation. This allows the adhesive sheet of the present invention to conform to and adhere to unevenness on the adherend surface as the adhesive layer cures, and furthermore, because it retains appropriate flexibility even after curing, it can exhibit high adhesive strength to components.

In addition, the adhesive sheet of the present invention has a slow curing reaction rate after light irradiation, and the reaction progresses gradually. Therefore, when joining components, the adhesive sheet can be irradiated with light in advance to initiate a curing reaction in the adhesive layer. This allows the curing reaction to continue even after the components to be joined are placed through the adhesive sheet, making it possible to firmly join the components together. As a result, the adhesive sheet of the present invention does not require light irradiation or heating and pressure at high temperatures to initiate a curing reaction, as is the case with conventional photocurable adhesive sheets and thermosetting adhesive sheets, where the components to be joined are stacked through the adhesive sheet. This makes it possible to easily join components together without being limited by the light transmittance or heat resistance of the components.

Furthermore, when an adhesive sheet comes into contact with the surface of a metal member such as a metal plate or a surface on which metal components such as metal wiring are placed, the metal surface included in the adherend surface is susceptible to corrosion by the acid generated from the adhesive layer. In particular, the greater the adhesive layer's ability to conform to unevenness on the adherend surface, the more susceptible the metal surface to corrosion. Examples of acids that cause metal corrosion include hydrogen halides generated by the reaction of hydrogen ions with halogen ions derived from halogen compounds such as chlorine and fluorine contained in the adhesive layer. Furthermore, when a cationic photopolymerization initiator is used as the photopolymerization initiator (C), examples of acids that can cause metal corrosion include those generated by the reaction of halogen compounds generated by the photopolymerization initiator (C) absorbing light and decomposing with hydrogen extracted from the solvent or the photopolymerization initiator (C) itself. In the presence of these acids, the metal surface included in the adherend surface is easily corroded by the acid. Corrosion is particularly likely to progress when the sheet is left in a humid and hot environment. Furthermore, contact with acid ionizes the metal included in the metal surface, making migration more likely.

In contrast, the adhesive sheet of the present invention uses additive (D) contained in the adhesive layer to capture or neutralize halogen ions and/or acids containing said halogen ions in the adhesive layer, thereby suppressing the generation and increase of acids and making metal corrosion less likely to occur even when the adhesive sheet adheres closely to metal surfaces, thereby preventing deterioration in the function and performance of metal members and parts due to corrosion.

When the adhesive containing additive (D) of the present invention is applied directly to the adherend surface, additive (D) may not be uniformly dispersed on the adherend surface due to aggregation, etc., which may result in processing problems such as coating defects during application, making it impossible to achieve the desired adhesive strength, or the corrosion inhibition effect on the metal surface may be localized. In contrast, according to the present invention, by using a sheet with a pre-formed adhesive layer in which additive (D) is uniformly dispersed, the occurrence of problems such as coating defects can be prevented, and when applied to the adherend surface, corrosion of the metal surface can be inhibited across the entire application surface, making it unnecessary to adjust the dispersion level of the additive.

The components to be joined using the adhesive sheet of the present invention may or may not include a metal surface on the adherend surface, but it is suitable for use in joining components that include a metal surface on the adherend surface. This is because the adhesive layer contains the desired components, allowing it to exhibit high conformal adhesion to the adherend surface, and even when conformal adhesion to the metal surface occurs, metal corrosion is unlikely to occur. Furthermore, the components to be joined using the adhesive sheet of the present invention may or may not have steps on the adherend surface, but due to the high conformal adhesion of the adhesive sheet of the present invention, it is suitable for use in joining components that have steps on the adherend surface.

Here, "the adherend surface includes a metal surface" and "the surface in contact with the adhesive sheet includes a metal surface" refer to an embodiment in which a portion of the adherend surface of the member to be attached to the adhesive sheet has an area containing a metal material, or an embodiment in which the entire adherend surface is an area containing a metal material. An embodiment in which a portion of the adherend surface (surface of the member) of the member has an area containing a metal material includes, for example, an embodiment in which metal components are disposed on a portion of the adherend surface (surface of the member), specifically, an embodiment in which metal wiring is disposed in a pattern on the surface of a support, and the patterned metal wiring forms the metal surface. Furthermore, an embodiment in which the entire adherend surface is an area containing a metal material includes, for example, an embodiment in which metal components are disposed on the entire adherend surface (surface of the member), or an embodiment in which the member itself is made of a metal material, specifically, an embodiment in which the adherend surface (surface of the member) of the member is covered with a metal layer, or an embodiment in which the member is a metal substrate, etc.

The components bonded using the adhesive sheet of the present invention may or may not be optically transparent. In particular, the adhesive sheet of the present invention is suitable for bonding components with low optical transparency or optically opaque components. As described above, the adhesive sheet of the present invention has a slow curing reaction rate after light irradiation and maintains flexibility even after light irradiation. Therefore, by irradiating the adhesive sheet with light before bonding the components, the curing reaction proceeds without irradiating the adhesive sheet with light through the components, thereby firmly bonding the components. The optical transmittance of the component (adherend) is not particularly limited, but is preferably 90% or less in the wavelength range of 200 nm to 780 nm, with 80% or less, 70% or less, 60% or less, or 50% or less being particularly preferred. An optically opaque component refers to a component with a light transmittance of 0% in the above wavelength range. The optical transmittance of the adherend (component) is measured using an ultraviolet-visible spectrophotometer such as the V-570 manufactured by JASCO Corporation.

Furthermore, the members to be bonded using the adhesive sheet of the present invention may or may not be heat resistant. As mentioned above, the adhesive sheet of the present invention undergoes a curing reaction upon light irradiation, and remains flexible even after light irradiation, so the curing reaction proceeds without the need for high-temperature heating and pressure. Furthermore, to accelerate the curing reaction, light irradiation and heat treatment may be used in combination as a curing method. In this case, it is preferable that the members have heat resistance sufficient to withstand the heating temperature of the heat treatment performed to accelerate the curing reaction after light irradiation.

The following describes each component of the adhesive sheet of the present invention.

(1) Adhesive Layer The adhesive layer in the present invention contains a photocurable resin (A) having a polymerizable functional group other than a polymerizable unsaturated double bond, a thermoplastic resin (B) having a polymerizable functional group other than a polymerizable unsaturated double bond, a photopolymerization initiator (C), and an additive (D) having a function of capturing or neutralizing halogen ions and/or acids containing the halogen ions.

The adhesive layer of the present invention contains a photocurable resin (A) and a thermoplastic resin (B), each of which has a polymerizable functional group other than a polymerizable unsaturated double bond. When the adhesive layer is irradiated with light, the polymerizable functional groups of the photocurable resin (A) and the thermoplastic resin (B) are activated, and curing proceeds in a state of enhanced reactivity. Therefore, the adhesive layer is prevented from undergoing a rapid curing reaction after light irradiation, allowing the curing reaction to proceed gradually. Furthermore, because the curing reaction after light irradiation proceeds gradually, the adhesive layer retains flexibility even after light irradiation, enabling the bonding of components. In other words, the adhesive layer of the present invention is a delayed-curing adhesive layer. Furthermore, the adhesive layer of the present invention retains appropriate flexibility even after curing.

The adhesive layer in the present invention is a layer composed of an adhesive composition containing: a photocurable resin (A) having a polymerizable functional group other than a polymerizable unsaturated double bond; a thermoplastic resin (B) having a polymerizable functional group other than a polymerizable unsaturated double bond; a photopolymerization initiator (C); and an additive (D) that has the function of capturing or neutralizing halogen ions and/or acids containing the halogen ions. In other words, the total amount of the adhesive layer refers to the entire amount of adhesive composition that constitutes the adhesive layer, and the content in the adhesive layer refers to the content in the entire amount of adhesive composition that constitutes the adhesive layer. Note that the total amount of adhesive composition does not include the solvent.

<Photocurable resin (A)>
The photocurable resin (A) has a polymerizable functional group other than a polymerizable unsaturated double bond. By including the photocurable resin (A), the adhesive layer in the present invention undergoes polymerization by light irradiation due to the polymerizable functional group of the photocurable resin (A), and the polymerization proceeds even in the dark or at low temperatures, so that bonding can be performed without being limited by the light transmittance or heat resistance of the members.

Examples of the photocurable resin (A) include photopolymerizable compounds such as photoradical polymerizable compounds, photocationic polymerizable compounds, and photoanionic polymerizable compounds. Among these, photocationic polymerizable compounds and/or photoanionic polymerizable compounds are preferred. In other words, the photocurable resin (A) preferably has a photocationic polymerizable functional group and/or a photoanionic polymerizable functional group as a polymerizable functional group other than a polymerizable unsaturated double bond. By including a polymerizable compound having such a functional group in the adhesive layer, the adhesive layer is less susceptible to oxygen inhibition during curing and facilitates continued reaction even after light irradiation. This allows bonding of components via the adhesive layer after light irradiation, regardless of the light transmittance or heat resistance of the components. Photocationic polymerizable compounds are particularly preferred because they exhibit excellent reactivity after light irradiation and are likely to achieve high bondability after curing. The above photopolymerizable compounds may be used alone or in combination.

The photocationically polymerizable compound is not particularly limited as long as it has one or more photocationically polymerizable functional groups per molecule. Preferably, the photocationically polymerizable compound has one or more photocationically polymerizable functional groups per molecule, such as an epoxy group, oxetanyl group, hydroxyl group, vinyl ether group, episulfide group, ethyleneimine group, or oxazoline group. In particular, to achieve high curability and bondability after curing, the photocationically polymerizable compound is more preferably one having an epoxy group or an oxetanyl group, and particularly preferably one having an epoxy group.

The photocationically polymerizable compound having an epoxy group may be a compound having one or more epoxy groups per molecule. Specific examples include bisphenol A epoxy resin, bisphenol F epoxy resin, biphenyl epoxy resin, tetramethylbiphenyl epoxy resin, polyhydroxynaphthalene epoxy resin, isocyanate-modified epoxy resin, 10-(2,5-dihydroxyphenyl)-9,10-dihydro Examples of epoxy resins that can be used include 9-oxa-10-phosphaphenanthrene-10-oxide-modified epoxy resins, phenol novolac epoxy resins, cresol novolac epoxy resins, hexanediol epoxy resins, triphenylmethane epoxy resins, tetraphenylethane epoxy resins, dicyclopentadiene-phenol addition reaction epoxy resins, phenol aralkyl epoxy resins, naphthol novolac epoxy resins, naphthol aralkyl epoxy resins, naphthol-phenol co-condensed novolac epoxy resins, naphthol-cresol co-condensed novolac epoxy resins, aromatic hydrocarbon formaldehyde resin-modified phenolic resin-type epoxy resins, biphenyl-modified novolac epoxy resins, trimethylolpropane epoxy resins, alicyclic epoxy resins, acrylic resins containing epoxy groups, polyurethane resins containing epoxy groups, polyester resins containing epoxy groups, and flexible epoxy resins.

Among these, it is preferable to use at least one of an alicyclic epoxy resin and a polyfunctional aliphatic epoxy resin, and it is even more preferable to use an alicyclic epoxy resin. These have excellent photocationic polymerization properties, making it possible to obtain an adhesive sheet with excellent curing properties, and also to impart an appropriate elastic modulus to suppress deformation over time of the adhesive layer after bonding.

The epoxy resin may be modified. By blending or adding other resin components to the epoxy resin, the flexibility of the adhesive layer can be increased and its adhesive strength and flexural strength can be improved. Examples of such modified resins include CTBN (carboxyl-terminated butadiene-acrylonitrile rubber) modified epoxy resins; epoxy resins in which various rubbers such as acrylic rubber, NBR, SBR, butyl rubber, or isoprene rubber are dispersed in the resin; epoxy resins modified with the above liquid rubbers; epoxy resins to which various resins such as acrylic, urethane, urea, polyester, and styrene have been added; chelate-modified epoxy resins; and polyol-modified epoxy resins.

On the other hand, examples of photocationically polymerizable compounds having the oxetanyl group include oxetane compounds such as 1,4-bis[(3-ethyl-3-oxetanylmethoxy)methyl]benzene, 1,4-bis[(3-methyl-3-oxetanylmethoxy)methyl]benzene, 3-methyl-3-glycidyloxetane, 3-ethyl-3-glycidyloxetane, 3-methyl-3-hydroxymethyloxetane, 3-ethyl-3-hydroxymethyloxetane, and di{1-ethyl(3-oxetanyl)}methyl ether.

Furthermore, it is preferable to use a photocurable resin (a1) as the photocurable resin (A) whose temperature (Tg-Tan δ) at which the loss tangent after curing reaches its maximum value is 100°C or higher. This is because it can impart high heat resistance to the adhesive sheet after curing. In particular, the temperature at which the loss tangent after curing of the photocurable resin (a1) reaches its maximum value is preferably 105°C or higher, 110°C or higher, or 115°C or higher, and is preferably 250°C or lower, more preferably 230°C or lower, or 200°C or lower. The temperature at which the loss tangent after curing of the photocurable resin (a1) reaches its maximum value (Tg-Tan δ) is measured at a frequency of 1.0 Hz using a dynamic viscoelasticity measuring device (manufactured by Rheometrics, product name: RSA-II) for a cured product obtained by curing the photocurable resin (a1) alone.

Examples of photocurable resins (a1) whose temperature (Tg-Tanδ) at which the loss tangent after curing reaches a maximum value are 100°C or higher include epoxy resins that are solid at room temperature (hereinafter referred to as "room-temperature solid epoxy resins"). Room temperature refers to 25°C.

Specific examples of room-temperature solid epoxy resins include bisphenol A epoxy resins, bisphenol F epoxy resins, biphenyl epoxy resins, tetramethylbiphenyl epoxy resins, polyhydroxynaphthalene epoxy resins, isocyanate-modified epoxy resins, 10-(2,5-dihydroxyphenyl)-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide-modified epoxy resins, phenol novolac epoxy resins, cresol novolac epoxy resins, hexanediol epoxy resins, triphenylmethane epoxy resins, tetraphenylethane epoxy resins, dicyclopentadiene-phenol addition reaction epoxy resins, phenol aralkyl epoxy resins, naphthol novolac epoxy resins, naphthol aralkyl epoxy resins, naphthol-phenol co-condensed novolac epoxy resins, naphthol-cresol co-condensed novolac epoxy resins, aromatic hydrocarbon formaldehyde resin-modified phenolic resin-modified epoxy resins, and biphenyl-modified novolac epoxy resins.

Furthermore, when the photocurable resin (A) is an epoxy resin, it is preferable to use both an epoxy resin that is solid at room temperature and an epoxy resin that is liquid at room temperature (hereinafter referred to as a room-temperature liquid epoxy resin). That is, the photocurable resin (A) contained in the adhesive layer of the present invention is preferably one or more epoxy resins that are solid at room temperature and one or more epoxy resins that are liquid at room temperature. The combined use of a room-temperature solid epoxy resin and a room-temperature liquid epoxy resin facilitates processing into a sheet shape and imparts appropriate adhesiveness to the sheet before curing, making it easy to bond to an adherend. Furthermore, the combined use of a room-temperature solid epoxy resin and a room-temperature liquid epoxy resin enables excellent adhesive reliability after curing. Furthermore, the combined use of a multifunctional epoxy resin, such as a novolac epoxy resin, as a room-temperature solid epoxy resin, with a room-temperature liquid epoxy resin enables even better adhesiveness at high temperatures.
The epoxy resin that is liquid at room temperature is not particularly limited as long as it is liquid at room temperature, but specific examples include trimethylolpropane epoxy resins, alicyclic epoxy resins, acrylic resins having epoxy groups, polyurethane resins having epoxy groups, polyester resins having epoxy groups, etc. Among these, alicyclic epoxy resins are preferred.

The proportion of the photocurable resin (a1) in the photocurable resin (A) having a temperature (Tg-Tanδ) at which the loss tangent after curing reaches a maximum value of 100°C or higher is preferably within the range of 20% to 80% by mass, more preferably within the range of 30% to 70% by mass, even more preferably within the range of 35% to 65% by mass, and even more preferably within the range of 40% to 65% by mass. Furthermore, when the photocurable resin (A) is an epoxy resin, the proportion of the epoxy resin solid at room temperature relative to the total amount of epoxy resin is preferably within the range of 20% to 80% by mass, even more preferably within the range of 30% to 70% by mass, even more preferably within the range of 35% to 65% by mass, and even more preferably within the range of 40% to 65% by mass. This is because it can impart heat resistance to the cured sheet while also allowing curing to be completed in a relatively short time. The proportion of the epoxy resin solid at room temperature relative to the total amount of epoxy resin can be calculated using the following formula:
<Formula>
Proportion of epoxy resin solid at room temperature in the total amount of epoxy resin = (content of epoxy resin solid at room temperature [parts by mass] / total amount of epoxy resin [parts by mass]) × 100 [mass%]

The photocurable resin (A) preferably has a weight-average molecular weight in the range of 100 to 5,000, more preferably in the range of 150 to 3,000, and even more preferably in the range of 200 to 2,500. By ensuring that the weight-average molecular weight of the photocurable resin (A) is within the above range, the sheet shape before curing becomes more stable, improving handleability and increasing conformal adhesion to the adherend surface. If the weight-average molecular weight of the photocurable resin (A) is too small, the cohesive strength of the adhesive layer before curing may be insufficient, which may lead to poor handleability, such as bleeding of the adhesive layer over time. On the other hand, if the weight-average molecular weight of the photocurable resin (A) is too large, compatibility with the thermoplastic resin (B) may decrease, making it difficult for the reaction to proceed.

The weight average molecular weight of each component described in this specification is a value measured by gel permeation chromatography (GPC) in terms of polystyrene under the following conditions.
(conditions)
Resin sample solution: 0.4% by mass tetrahydrofuran (THF) solution Measurement device model number: HLC-8220GPC (manufactured by Tosoh Corporation)
Column: TSKgel (manufactured by Tosoh Corporation)
Eluent: tetrahydrofuran (THF)

The content of the photocurable resin (A) in the adhesive layer of the present invention is preferably 10% by mass or more, 15% by mass or more, 20% by mass or more, or 25% by mass or more of the total amount of the adhesive layer, in other words, the total amount of the adhesive composition, and is preferably 90% by mass or less, 85% by mass or less, 80% by mass or less, or 75% by mass or less. Specifically, the content of the photocurable resin (A) is preferably within the range of 10% to 90% by mass of the total amount of the adhesive layer, preferably within the range of 15% to 85% by mass, preferably within the range of 20% to 80% by mass, or preferably within the range of 25% to 75% by mass. By keeping the content of the photocurable resin (A) in the adhesive layer within the above range, the adhesive layer can better conform to and adhere to uneven surfaces, allowing two members to be firmly bonded via the cured adhesive layer. If the content of photocurable resin (A) exceeds the above range, it may not be possible to process the composition into a sheet; on the other hand, if it is less than the above range, the heat resistance of the adhesive layer after curing may deteriorate.

<Thermoplastic resin (B)>
The thermoplastic resin (B) has a polymerizable functional group other than a polymerizable unsaturated double bond. By containing the thermoplastic resin (B), the adhesive layer in the present invention can react with the photocurable resin (A), suppressing a rapid curing reaction after light irradiation and allowing the curing reaction to proceed gradually. As a result, the adhesive layer in the present invention can retain flexibility even after light irradiation, and can follow and adhere to steps on the adherend surfaces of the members after light irradiation, making it possible to firmly bond two members via the adhesive layer.

The polymerizable functional group other than the polymerizable unsaturated double bond possessed by the thermoplastic resin (B) is preferably a group selected from the group consisting of an isocyanate group, a hydroxyl group, an oxetanyl group, and an epoxy group. Using a thermoplastic resin (B) containing at least one polymerizable functional group selected from the group consisting of an isocyanate group, a hydroxyl group, an oxetanyl group, and an epoxy group enables the thermoplastic resin (B) to react with the photocurable resin (A), suppresses a rapid curing reaction after light irradiation, and allows the curing reaction to proceed gradually. This allows the adhesive layer of the present invention to retain flexibility even after light irradiation, improves its ability to conform to uneven surfaces, and firmly bond two members together via the adhesive layer.

Examples of the thermoplastic resin (B) include polyester resins, polyurethane resins, acrylic resins, polyvinyl acetal resins, and epoxy resins (thermoplastic epoxy resins), each of which has a polymerizable functional group other than a polymerizable unsaturated double bond. These thermoplastic resins may be homopolymers or copolymers. Furthermore, these thermoplastic resins may be used alone or in combination of two or more.

The polyurethane resin having a polymerizable functional group other than a polymerizable unsaturated double bond is preferably a polyurethane resin (B') having at least one group selected from the group consisting of an isocyanate group, a hydroxyl group, an oxetanyl group, and an epoxy group.

The polyurethane resin (B') can be obtained, for example, by reacting polyol (b'1) with polyisocyanate (b'2).

Polyol (b'1) preferably has a number average molecular weight in the range of 500 to 5,000, and more preferably in the range of 1,000 to 3,000 in order to obtain an adhesive layer with excellent shape retention, coating workability, initial cohesive strength, etc. The above number average molecular weight is a value measured under the following conditions.

The number average molecular weight described in this specification is a value measured by gel permeation chromatography (GPC) in polystyrene equivalent under the following conditions.
(conditions)
Resin sample solution: 0.4% by mass tetrahydrofuran (THF) solution Measurement device model number: HLC-8220GPC (manufactured by Tosoh Corporation)
Column: TSKgel (manufactured by Tosoh Corporation)
Eluent: tetrahydrofuran (THF)

As such polyol (b'1), for example, one or more selected from the group consisting of polyester polyols, polycarbonate polyols, and polyether polyols can be suitably used.

In particular, in the present invention, it is preferable to use one or more types of at least one of polyester polyols and polycarbonate polyols as the polyol (b'1), and it is preferable to use at least one or two types of polyester polyols. A more preferred example is to use two or more types of polyester polyols as the polyol (b'1). Another preferred example is to use one or two or more types of polyester polyols and one or two or more types of polycarbonate polyols as the polyol (b'1). Another preferred example is to use one or two or more types of polyester polyols and one or two or more types of polyether polyols as the polyol (b'1). By using different types of polyester polyols in combination, or by using a polyester polyol in combination with a polyol other than the polyester polyol, the adhesive sheet of the present invention has a more stable sheet shape before curing, improving handleability and improving conformability and adhesion to uneven surfaces on the adherend.

The total amount of polyols selected from polyester polyols, polycarbonate polyols, and polyether polyols in the polyol (b'1) preferably accounts for 20% by mass or more, more preferably 50% by mass or more, and particularly preferably 100% by mass, of the total amount of the polyol (b'1). This is because the adhesive layer containing polyurethane resin (B') can maintain a level of adhesion that allows application at room temperature and can further improve its ability to conform to unevenness in the adherend surface.

When the above polycarbonate polyol and the above polyester polyol are used in combination, the mass ratio of the polycarbonate polyol to the polyester polyol (polycarbonate polyol/polyester polyol) is preferably in the range of 0.4 to 7.0, and more preferably in the range of 1.0 to 2.0. This is because a polyurethane resin having a loss tangent (tan δ40 and tan δ60) value within the desired range can be obtained, and an adhesive layer can be formed that has excellent handleability before curing and excellent conformability and adhesion to uneven surfaces. Furthermore, when the above polyether polyol and the above polyester polyol are used in combination, the mass ratio of the polyether polyol to the polyester polyol (polyether polyol/polyester polyol) can also be in the same range as above.

The polyester polyols that can be used include, for example, those obtained by the esterification reaction of a low-molecular-weight polyol with a polycarboxylic acid, polyesters obtained by the ring-opening polymerization reaction of a cyclic ester compound such as ε-caprolactone, and copolymerized polyesters of these.

Examples of the low molecular weight polyols that can be used include aliphatic alkylene glycols such as ethylene glycol, propylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, diethylene glycol, neopentyl glycol, and 1,3-butanediol, which have a molecular weight of approximately 50 to 300, as well as cyclohexanedimethanol.

Furthermore, examples of the polycarboxylic acids that can be used in the production of the polyester polyols include aliphatic dicarboxylic acids such as succinic acid, adipic acid, sebacic acid, and dodecanedicarboxylic acid, aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, phthalic acid, and naphthalenedicarboxylic acid, and anhydrides or esters thereof.

As the polyester polyol, it is preferable to use an aliphatic polyester polyol, and it is more preferable to use a linear aliphatic polyester polyol. This is because a polyurethane resin (B') having a loss tangent (tanδ40 and tanδ60) value within the desired range can be obtained, and an adhesive layer can be formed that is easy to handle before curing and has excellent conformability and adhesion to uneven surfaces. The linear aliphatic polyester polyol refers to a polyester polyol that does not have an alkyl group in the side chain.

The above-mentioned aliphatic polyester polyols include those obtained by reacting the above-mentioned aliphatic alkylene glycols with aliphatic dicarboxylic acids, and it is preferable to use an aliphatic polyester polyol obtained by the esterification reaction of 1,6-hexanediol with adipic acid.

It is also preferable to use an aromatic polyester polyol as the polyester polyol. This is because it can increase the elastic modulus of the polyurethane resin (B') and improve rigidity, making it possible to suppress misalignment, warping, and deformation over time before and after curing of the adhesive layer. Examples of the aromatic polyester polyol include those obtained by reacting an aromatic polyol with an aliphatic or aromatic dicarboxylic acid. For example, an aromatic polyester polyol obtained by reacting an ethylene oxide adduct of bisphenol A with phthalic acid and adipic acid is preferably used.

The polyester polyol may be an aliphatic polyester polyol alone, an aromatic polyester polyol alone, or a combination of an aliphatic polyester polyol and an aromatic polyester polyol. Among these, it is preferable to use an aliphatic polyester polyol and an aromatic polyester polyol together, that is, it is preferable to use one or more aromatic polyester polyols and one or more aliphatic polyester polyols as the polyester polyol. The adhesive layer containing the polyurethane resin (B') prepared by using an aromatic polyester polyol and an aliphatic polyester polyol in combination can achieve a good balance between the hardness and softness of the layer before and after curing, exhibit high conformal adhesion to unevenness on the adherend surface, and suppress the adhesive layer from slipping, warping, or deformation over time.
In order to achieve a good balance between the above-mentioned conflicting physical properties, the content ratio of the aromatic polyester polyol and the aliphatic polyester polyol (aromatic polyester polyol/aliphatic polyester polyol) is preferably within a range of 20/80 to 90/10 in mass ratio, and more preferably within a range of 50/50 to 80/20.

The polyester polyol preferably has a number-average molecular weight in the range of 1,000 to 5,000. This is because it is possible to obtain a polyurethane resin (B') with loss tangents (tanδ40 and tanδ60) within the desired range, and to produce an adhesive layer that is easy to handle before curing and has excellent conformability and adhesion to uneven surfaces.

In particular, when using a polyester polyol obtained by reacting an aliphatic diol such as 1,2-ethanediol or 1,4-butanediol with adipic acid as the polyester polyol, it is preferable to use one having a number average molecular weight in the range of 1100 to 2900. When using a polyester polyol obtained by reacting 1,6-hexanediol with adipic acid, it is preferable to use one having a number average molecular weight in the range of 1100 to 5000. When using a polyester polyol obtained by reacting 1,6-hexanediol with sebacic acid, it is preferable to use one having a number average molecular weight in the range of 1000 to 5000.

When the polyol (b'1) contains a polyester polyol and a polyol other than the polyester polyol, the polyester polyol can be used in a range of 10% to 80% by mass, preferably 20% to 80% by mass, more preferably 30% to 70% by mass, and even more preferably 40% to 50% by mass, based on the total amount of the polyol (b'1). This is because the adhesive layer containing the polyurethane resin (B') can maintain a level of adhesion that allows application at room temperature and can further improve its ability to conform to unevenness in the adherend surface.

The polycarbonate polyol may be, for example, one obtained by reacting a carbonate ester and/or phosgene with a low-molecular-weight polyol. Examples of the carbonate ester that can be used include methyl carbonate, dimethyl carbonate, ethyl carbonate, diethyl carbonate, cyclocarbonate, and diphenyl carbonate.

Examples of low molecular weight polyols that can react with the above carbonate esters and phosgene include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propanediol, 1,3-propanediol, dipropylene glycol, tripropylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,5-pentanediol, 1,5-hexanediol, 1,6-hexanediol, 2,5-hexanediol, 1,7-heptanediol, 1,8- Octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol, 2-methyl-1,3-propanediol, neopentyl glycol, 2-butyl-2-ethyl-1,3-propanediol, 3-methyl-1,5-pentanediol, 2-ethyl-1,3-hexanediol, 2-methyl-1,8-octanediol, 1,4-cyclohexanedimethanol, hydroquinone, resorcinol, bisphenol A, bisphenol F, 4,4'-biphenol, etc. can be used.

It is also preferable to use an aliphatic polycarbonate polyol or an alicyclic polycarbonate polyol as the polycarbonate polyol.

As the aliphatic polycarbonate polyol, it is preferable to use one obtained by reacting a dialkyl carbonate with one or more polyols selected from the group consisting of 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, and 1,6-hexanediol. This is because the adhesive layer containing polyurethane resin (B') can have a level of adhesion that allows application at room temperature.

As the alicyclic polycarbonate polyol, it is preferable to use one obtained by reacting, for example, a dialkyl carbonate with a polyol containing one or more members selected from the group consisting of cyclohexanedimethanol and its derivatives. This is because the adhesive layer containing polyurethane resin (B') can have a level of adhesion that allows application at room temperature and excellent initial cohesion.

The polycarbonate polyol preferably has a number average molecular weight in the range of 500 to 5,000, and more preferably in the range of 800 to 3,000. This is because a polyurethane resin (B') having a loss tangent (tanδ40 and tanδ60) value within the desired range can be obtained, and an adhesive layer can be formed that is easy to handle before curing and has excellent conformability and adhesion to uneven surfaces.

When the polyol (b'1) contains the polycarbonate polyol and a polyol other than the polycarbonate polyol, the polycarbonate polyol is preferably used in an amount of 20% to 80% by mass, more preferably 30% to 70% by mass, and even more preferably 40% to 50% by mass, based on the total amount of the polyol (b'1). This is because the adhesive layer containing the polyurethane resin (B') can maintain a level of adhesion that allows application under light at room temperature, and can further improve conformability and adhesion to unevenness on the adherend surface.

Examples of the polyether polyol include those obtained by addition polymerization of alkylene oxide using one or more compounds having two or more active hydrogen atoms as an initiator.

Examples of initiators that can be used include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, trimethylene glycol, 1,3-butanediol, 1,4-butanediol, 1,6-hexanediol, bisphenol A, glycerin, trimethylolethane, and trimethylolpropane.

Examples of alkylene oxides that can be used include ethylene oxide, propylene oxide, butylene oxide, styrene oxide, epichlorohydrin, and tetrahydrofuran.

As the polyether polyol, it is preferable to use an aliphatic polyether polyol or a polyether polyol having an alicyclic structure.

The polyether polyol may, in particular, be polytetramethylene glycol obtained by ring-opening polymerization of tetrahydrofuran, a polytetramethylene glycol derivative obtained by reacting tetrahydrofuran with alkyl-substituted tetrahydrofuran, or a polytetramethylene glycol derivative obtained by copolymerizing neopentyl glycol and tetrahydrofuran. Among these, it is preferable to use polytetramethylene glycol (PTMG) or a polytetramethylene glycol derivative (PTXG) as the polyether polyol, as this ensures that the adhesive sheet containing the adhesive layer maintains a level of adhesion possible at room temperature and also improves flexibility, durability (particularly hydrolysis resistance), etc.

In addition to the above, other polyols can be used as the polyol (b'1). Examples of such other polyols include acrylic polyols.

As the polyisocyanate (b'2), alicyclic polyisocyanates, aliphatic polyisocyanates, aromatic polyisocyanates, etc. can be used, and it is preferable to use alicyclic polyisocyanates.

The above-mentioned alicyclic polyisocyanates include, for example, isophorone diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, 4,4'-dicyclohexylmethane diisocyanate, 2,4- and/or 2,6-methylcyclohexane diisocyanate, cyclohexylene diisocyanate, methylcyclohexylene diisocyanate, bis(2-isocyanatoethyl)-4-cyclohexylene-1,2-dicarboxylate, 2,5- and/or 2,6-norbornane diisocyanate, dimer acid diisocyanate, bicycloheptane triisocyanate, etc., which can be used alone or in combination of two or more.

Of the above-mentioned alicyclic polyisocyanates, 4,4'-dicyclohexylmethane diisocyanate (HMDI), isophorone diisocyanate (IPDI), and 1,3-bis(isocyanatomethyl)cyclohexane (BICH) are preferred for use in obtaining adhesive sheets that have good reactivity with the polyol (b'1) and excellent heat resistance, light transmittance, etc.

As a method for producing polyurethane resin (B') having isocyanate groups by reacting the polyol (b'1) with the polyisocyanate (b'2), for example, the polyol (b'1) charged in a reaction vessel is heated under normal or reduced pressure to remove moisture, and then the polyisocyanate (b'2) is supplied all at once or in portions and reacted.

The reaction between the polyol (b'1) and the polyisocyanate (b'2) is preferably carried out in such a manner that the equivalent ratio of the isocyanate groups in the polyisocyanate (b'2) to the hydroxyl groups in the polyol (b'1) (hereinafter referred to as the "NCO/OH equivalent ratio") is in the range of 1.1 to 20.0, more preferably 1.1 to 13.0, even more preferably 1.1 to 5.0, and particularly preferably 1.5 to 3.0.

The reaction conditions (temperature, time, etc.) for the polyol (b'1) and the polyisocyanate (b'2) can be set appropriately taking into consideration various factors such as safety, quality, and cost, and are not particularly limited. For example, the reaction temperature is preferably in the range of 70 to 120°C, and the reaction time is preferably in the range of 30 minutes to 5 hours.

When reacting the polyol (b'1) with the polyisocyanate (b'2), a catalyst such as a tertiary amine catalyst or an organometallic catalyst can be used as needed.

The reaction between the polyol (b'1) and the polyisocyanate (b'2) may be carried out in a solvent-free environment or in the presence of an organic solvent. Examples of the organic solvent include ester solvents such as methyl acetate, ethyl acetate, propyl acetate, and butyl acetate; ketone solvents such as acetone, methyl ethyl ketone, methyl butyl ketone, and cyclohexanone; ether ester solvents such as methyl cellosolve acetate and butyl cellosolve acetate; aromatic hydrocarbon solvents such as toluene and xylene; and amide solvents such as dimethylformamide and dimethylacetamide. These solvents may be used alone or in combination. The organic solvent may be removed during or after the production of the polyurethane resin (B') by an appropriate method such as heating under reduced pressure or drying at normal pressure.

As the polyurethane resin (B') having isocyanate groups, for example, a polyurethane resin (B'1) having isocyanate groups obtained by reacting a polyol (b'1) with a polyisocyanate (b'2) can be used. Details (such as type and composition) of the polyol (b'1) and polyisocyanate (b'2) used to prepare the polyurethane resin (B') having isocyanate groups can be the same as those for the polyol (b'1) and polyisocyanate (b'2) described above.

The hydroxyl group-containing polyurethane resin (B') can be, for example, a hydroxyl group-containing polyurethane resin (B'2) obtained by reacting a polyol (b'1) with a polyisocyanate (b'2). Details (such as type and composition) of the polyol (b'1) and polyisocyanate (b'2) used to prepare the hydroxyl group-containing polyurethane resin (B') can be the same as those for the polyol (b'1) and polyisocyanate (b'2) described above.

The polyurethane resin (B') having an oxetanyl group or an epoxy group may be, for example, a polyurethane (B'1) having an isocyanate group,
2) a monomer (B") having a functional group (b"1) capable of reacting with an isocyanate group, an oxetanyl group or an epoxy group, and a polymerizable functional group (b"2) other than one or more polymerizable unsaturated double bonds;
It is possible to use a polyurethane resin (B'3) obtained by reacting the above.

The functional group (b"1) that can react with the isocyanate group can be, for example, a hydroxyl group, an amino group, a carboxyl group, a mercapto group, etc., with the use of a hydroxyl group or an amino group being preferred.

The polymerizable functional group (b"2) other than the above-mentioned polymerizable unsaturated double bond refers to a functional group other than so-called radically polymerizable functional groups, such as functional groups with cationic polymerizability and functional groups with anionic polymerizability, including, for example, epoxy groups, oxetanyl groups, and ethylene sulfide groups.

The above-mentioned monomer (B") is not particularly limited as long as it has a functional group (b"1) and a polymerizable functional group (b"2), and examples include 3-ethyl-3-(4-hydroxybutyl)oxymethyl-oxetane, 3-hydroxymethyl-3-ethyloxetane, 2-hydroxymethyloxetane, and 3-hydroxyoxetane.

The above-mentioned monomer (B") is preferably used in the range of 5 to 20 parts by mass, and more preferably 5 to 15 parts by mass, per 100 parts by mass of polyurethane resin (B').

More specifically, the monomer (B") can be used in an amount sufficient to provide functional groups reactive with the isocyanate groups, preferably greater than 50 mol% and less than 100 mol%, more preferably 60 mol% to 100 mol%, and even more preferably 80 mol% to 100 mol%, relative to the number of moles of isocyanate groups in the polyurethane resin (B'). This allows for the production of a polyurethane resin with appropriate flexibility, fast curing properties, shape retention after application to a substrate, mechanical strength, durability (particularly hydrolysis resistance), and excellent conformability and adhesion to the adherend surface.

When reacting the urethane resin (B') with the monomer (B"), a urethane-forming catalyst can be used, if necessary. The urethane-forming catalyst can be added as needed at any stage of the urethane-forming reaction. The urethane-forming reaction is preferably carried out until the isocyanate group content (%) becomes substantially constant. Examples of the urethane-forming catalyst that can be used include nitrogen-containing compounds such as triethylamine, triethylenediamine, and N-methylmorpholine; organometallic salts such as potassium acetate, zinc stearate, and stannous octoate; and organometallic compounds such as dibutyltin dilaurate.

Epoxy resins having polymerizable functional groups other than polymerizable unsaturated double bonds include polymers or copolymers of epoxy compounds having a linear structure, and copolymers of epoxy compounds and monomers polymerizable with the epoxy compounds having a linear structure. Specific examples include bisphenol A epoxy resins, bisphenol fluorene epoxy resins, cresol novolac epoxy resins, phenol novolac epoxy resins, cyclic aliphatic epoxy resins, long-chain aliphatic epoxy resins, glycidyl ester epoxy resins, and glycidyl amine epoxy resins, with bisphenol A epoxy resins and bisphenol fluorene epoxy resins being preferred.

In particular, the adhesive layer of the present invention preferably contains, as the thermoplastic resin (B), one or more resins selected from the group consisting of polyurethane resins, acrylic resins, and epoxy resins, each having a polymerizable functional group other than a polymerizable unsaturated double bond, and preferably contains at least one or more polyurethane resins having a polymerizable functional group other than a polymerizable unsaturated double bond. Using a polyurethane resin having a polymerizable functional group other than a polymerizable unsaturated double bond as the thermoplastic resin (B) suppresses a rapid curing reaction after light irradiation and allows the curing reaction to proceed gradually, thereby maintaining the flexibility required for bonding even after light irradiation. This allows the adhesive layer of the present invention to conform to and adhere to uneven surfaces of the components to be bonded after light irradiation, enabling the components to be firmly bonded together via the adhesive layer.

The melting point of the thermoplastic resin (B) is preferably in the range of 30°C to 120°C, more preferably in the range of 35°C to 100°C, and even more preferably in the range of 40°C to 80°C. By using a thermoplastic resin (B) with a melting point within the above range, the adhesive sheet of the present invention has a more stable sheet shape before curing, improving handleability, and also improving its ability to conform to uneven surfaces and adhere to the adhesion.

The melting point of thermoplastic resin (B) is the temperature at which the maximum exothermic peak (exothermic peak top) is observed when the sample is heated from 20°C to 150°C at a rate of 10°C/min using differential scanning calorimetry (DSC), held for 1 minute, cooled to -10°C at a rate of 10°C/min, held for 10 minutes, and then measured again at a rate of 10°C/min.

The thermoplastic resin (B) preferably has a weight-average molecular weight in the range of 5,500 to 2,000,000, preferably in the range of 5,500 to 1,000,000, and more preferably in the range of 5,500 to 800,000. By ensuring that the weight-average molecular weight of the thermoplastic resin (B) is within the above range, the sheet shape before curing becomes more stable, improving handleability and enhancing adhesion to uneven surfaces. If the weight-average molecular weight of the thermoplastic resin (B) is too small, the cohesive strength of the adhesive layer before curing may be insufficient, which may lead to poor handleability, such as bleeding of the adhesive layer over time. On the other hand, if the weight-average molecular weight of the thermoplastic resin (B) is too large, compatibility with the photocurable resin (A) may decrease, making it difficult for the reaction to proceed.

The content of thermoplastic resin (B) in the adhesive layer of the present invention is preferably 5% by mass or more, 10% by mass or more, 15% by mass or more, 20% by mass or more, or 30% by mass or more of the total amount of the adhesive layer, in other words, the total amount of the adhesive composition, and is also preferably 80% by mass or less, 70% by mass or less, 60% by mass or less, or 50% by mass or less. Specifically, it is preferably within the range of 5% to 80% by mass, more preferably within the range of 10% to 60% by mass, and more preferably within the range of 20% to 50% by mass. By keeping the content of thermoplastic resin (B) in the adhesive layer of the present invention within the above range, flexibility can be imparted that ensures conformability to the adherend even after light irradiation. Note that if the content of thermoplastic resin (B) is higher than the above range, the heat resistance of the cured product may be impaired. On the other hand, if it is lower than the above range, the proportion of high-molecular-weight components in the entire adhesive layer is reduced, and it may not be possible to process it into a sheet.

The content ratio of the thermoplastic resin (B) to the photocurable resin (A) ([content of thermoplastic resin (B)/photocurable resin (A)]) is preferably within the range of 0.1 to 10 by mass, preferably within the range of 0.15 to 2, preferably within the range of 0.2 to 1.7, preferably within the range of 0.3 to 1.5, and preferably within the range of 0.4 to 0.8. By maintaining the content ratio of thermoplastic resin (B) to the photocurable resin (A) within the above range, flexibility is imparted that ensures conformability to the adherend even after light irradiation, and heat resistance can be imparted to the adhesive layer after curing. In particular, by using a lower ratio of thermoplastic resin (B) than photocurable resin (A), excellent adhesive reliability can be achieved after curing, and excellent adhesion at high temperatures can also be obtained.

<Photopolymerization initiator (C)>
The adhesive layer of the present invention contains one or more photopolymerization initiators (C), which promotes reactivity after irradiation with active energy rays and improves bonding strength after curing. Furthermore, the adhesive layer contains a photopolymerization initiator that is activated by light and whose reaction proceeds. Therefore, the reaction continues even after irradiation with active energy rays is stopped, allowing the reaction to proceed even in dark places or at low temperatures, resulting in a good curing reaction. This allows for high bonding strength to be achieved without damaging the components to be bonded, without causing distortion between the components that could deform the components, or without causing cracks between the adhesive sheet and the components.

The photopolymerization initiator (C) is not particularly limited as long as it is activated by light. Examples of the photopolymerization initiator (C) include photoradical polymerization initiators, photocationic polymerization initiators, and photoanionic polymerization initiators. Among these, at least one of photocationic polymerization initiators and photoanionic polymerization initiators is preferred, with photocationic polymerization initiators being more preferred as they allow for favorable adjustment of polymerization by dark reaction.

The above-mentioned cationic photopolymerization initiator is not particularly limited, as long as it can induce a ring-opening reaction of a cationic polymerizable functional group when exposed to light of the wavelength used. Among these, compounds that induce a ring-opening reaction of a cationic polymerizable functional group when exposed to light of a wavelength between 300 nm and 370 nm and are inactive in the wavelength range above 370 nm are preferred. Examples of such cationic photopolymerization initiators include onium salts such as aromatic diazonium salts, aromatic iodonium salts, and aromatic sulfonium salts.

Specific examples of onium salts include Optomer SP-150, Optomer SP-170, and Optomer SP-171 (all manufactured by ADEKA Corporation), UVE-1014 (manufactured by General Electronics Corporation), OMNICAT 250 and OMNICAT 270 (both manufactured by IGM Resin), IRGACURE 290 (manufactured by BASF), San-Aid SI-60L, San-Aid SI-80L, and San-Aid SI-100L (all manufactured by Sanshin Chemical Industry Co., Ltd.), CPI-100P, CPI-101A, and CPI-200K (all manufactured by San-Apro Ltd.), etc.

A single cationic photopolymerization initiator may be used, or two or more may be used in combination. Furthermore, two-stage curing may be performed using multiple cationic photopolymerization initiators with different effective active wavelengths.

The above cationic photopolymerization initiators may be used in combination with sensitizers such as anthracene-based and thioxanthone-based sensitizers, if necessary.

The cationic photopolymerization initiator is preferably contained in the range of 0.001% to 30% by mass, more preferably 0.01% to 20% by mass, and even more preferably 0.1% to 10% by mass of the total adhesive layer, in other words, the total adhesive composition that forms the adhesive layer. If the proportion of the cationic photopolymerization initiator is too low, the curing required to achieve high bondability will be insufficient; if the proportion is too high, curing will improve, but the curing reaction after light irradiation will proceed too quickly, making it difficult to adequately follow and adhere to uneven surfaces, making it difficult to firmly bond the components together.

<Additive (D)>
The adhesive layer in the present invention contains an additive (D) having the function of capturing or neutralizing halogen ions and/or acids containing halogen ions. In the present invention, the additive (D) having the function of capturing halogen ions can be referred to as a halogen ion scavenger, and the additive (D) having the function of neutralizing acids containing halogen ions can be referred to as a halogen acid neutralizer. The additive (D) can be used alone or in combination of two or more.

Additive (D) has the function of capturing halogen ions and/or neutralizing acids containing the above-mentioned halogen ions, and in particular, it preferably has the function of capturing or neutralizing chloride ions and/or hydrogen chloride.

Additives (D) that have the function of capturing or neutralizing halogen ions and/or acids containing the halogen ions include ion scavengers, basic solids, and amphoteric metal oxides.

The ion trapping agent may be used alone or in combination of two or more types. It is sufficient for the ion trapping agent to have the function of trapping at least halogen ions, and it is preferably a compound selected from the group consisting of anion trapping agents that trap anions, and amphoteric ion trapping agents that trap both cations and anions. Amphoteric ion trapping agents are particularly preferred, as they can further enhance the corrosion inhibition effect on metal surfaces by simultaneously trapping halogen ions (anions) and metal ions (cations).

The ion trapping agent may be an inorganic ion trapping agent made from an inorganic compound, an organic ion trapping agent made from an organic compound, or a combination of inorganic and organic ion trapping agents. Among these, inorganic ion trapping agents are preferred. Inorganic ion trapping agents have higher heat resistance than organic ion trapping agents, and their excellent dispersibility allows them to be uniformly dispersed in the adhesive layer, making it possible to suppress metal corrosion across the entire contact area with the metal surface included in the adherend surface.

The ion trapping agent preferably contains one or more compounds selected from the group consisting of inorganic anion trapping agents, which are inorganic ion trapping agents that trap anions, and inorganic amphoteric ion trapping agents, which are inorganic ion trapping agents that trap both cations and anions, because these can be uniformly dispersed in the adhesive layer and efficiently trap halogen ions throughout the layer. Among these, it is preferable to contain one or more inorganic amphoteric ion trapping agents, because these agents can trap metal ions in addition to achieving the effects described above.

Specific examples of inorganic anion scavengers and inorganic amphoteric ion scavengers include inorganic compounds containing one or more metal atoms selected from the group consisting of antimony, bismuth, zirconium, titanium, tin, magnesium, and aluminum. Among these, inorganic compounds containing the three metal atoms of zirconium, aluminum, and magnesium are preferred. Commercially available inorganic anion scavengers include "IXE-700F" manufactured by Toagosei Co., Ltd., and commercially available inorganic amphoteric ion scavengers include "IXEPLAS-A1," "IXEPLAS-A2," "IXEPLAS-A3," and "IXEPLAS-B1" manufactured by Toagosei Co., Ltd.

In addition, a cation scavenger capable of capturing metal ions may be used in combination with the anion scavenger and both ion scavenger. This is because it can prevent the metal contained on the metal surface from ionizing and migrating. Examples of cation scavenger include triazine thiol compounds and bisphenol-based reducing agents. Examples of bisphenol-based reducing agents include 2,2'-methylene-bis-(4-methyl-6-tert-butylphenol) and 4,4'-thio-bis-(3-methyl-6-tert-butylphenol).

The basic solid may be used alone or in combination of two or more types. The basic solid may be any compound capable of neutralizing an acid containing a halogen ion, and may be either an inorganic basic solid or an organic basic solid.

Specific examples of inorganic basic solids include inorganic solids selected from the group consisting of inorganic salts, metal oxides, metal hydroxides, metal sulfides, metal nitrides, and clay minerals, as well as those whose surfaces have been treated with a basic agent.

Here, basic treatment refers to a treatment in which an inorganic solid selected from the group consisting of metal oxides, metal hydroxides, metal sulfides, metal nitrides, and clay minerals is used as a core compound, and the surface of the core compound is made basic by reacting or adsorbing a silane coupling agent having a basic group or a nitrogen compound such as hexamethyldisilazane to the core compound. Examples of basic groups include organic amino groups and hydroxyl groups. The treatment is not limited to these, as long as it can make the surface of the core compound basic. An example of an inorganic solid whose surface has been basic-treated is an inorganic basic solid whose surface has been silanized.

Inorganic salts used as basic solids include, for example, calcium carbonate, barium carbonate, magnesium carbonate, lithium carbonate, strontium carbonate, sodium carbonate, potassium carbonate, cesium carbonate, sodium bicarbonate, potassium bicarbonate, calcium bicarbonate, magnesium bicarbonate, zinc carbonate, calcium phosphate, magnesium phosphate, sodium phosphate, potassium phosphate, barium phosphate, sodium citrate, potassium citrate, calcium citrate, magnesium citrate, magnesium oxalate, sodium oxalate, potassium oxalate, sodium tartrate, potassium tartrate, etc.

Examples of metal oxides (basic metal oxides) used as basic solids include basic glass beads, basic alumina (activated alumina), basic zeolite, basic titanium oxide, basic zinc oxide, basic lead oxide, basic silica, basic tin oxide, basic zirconium oxide, basic magnesium oxide, and basic calcium oxide.

An example of a metal sulfide (basic metal sulfide) used as a basic solid is basic zinc sulfide.

An example of a metal nitride (basic metal nitride) used as a basic solid is basic titanium nitride.

Examples of clay minerals (basic clay minerals) used as basic solids include basic talc and basic mica.

An example of a metal hydroxide (basic metal hydroxide) used as a basic solid is basic magnesium hydroxide.

Basic glass beads, basic alumina, basic titanium oxide, basic zinc oxide, basic silica, basic tin oxide, basic zirconium oxide, basic titanium nitride, basic zinc sulfide, etc. can be prepared by, for example, basic treatment to introduce basic functional groups onto the surface of a core compound such as a precursor metal oxide, metal nitride, or metal sulfide.

Examples of organic basic solids include polymers with basic functional groups, organic polymer beads whose surfaces have been subjected to coupling treatment with a compound containing basic functional groups, and organic polymer beads coated with polymers with basic functional groups. Examples of basic functional groups include organic amino groups, nitrogen-containing heterocyclic groups, and weak acid/strong base salt functional groups. Polymers with basic functional groups are synthesized by polymerizing monomers with basic functional groups. Organic basic solids can be synthesized by known methods, or commercially available products can be used.

Amphoteric metal oxides are compounds that can react with both acids and bases, and may be used alone or in combination of two or more. Any amphoteric metal oxide can be used as long as it is capable of neutralizing acids containing halogen ions, and examples include alumina, zinc oxide, tin oxide, and lead oxide. Note that alumina, zinc oxide, tin oxide, and lead oxide, which are amphoteric metal oxides, are distinguished from the basic alumina (activated alumina), basic zinc oxide, basic tin oxide, and basic lead oxide, which are basic metal oxides, in that they do not contain basic functional groups.

In particular, the adhesive layer of the present invention preferably contains, as additive (D), one or more compounds selected from the group consisting of inorganic ion scavengers and basic solids. This is because these compounds can exhibit high halogen ion trapping or acid neutralizing capabilities even in small amounts. It is particularly preferable to contain one or more inorganic ion scavengers. This is because, compared to basic solids, inorganic ion scavengers are more likely to provide acid corrosion resistance with smaller addition amounts.

When an inorganic ion scavenger is included as additive (D), for the reasons described above, the inorganic ion scavenger is preferably a compound selected from the group consisting of inorganic anion scavengers and inorganic amphoteric ion scavengers, and more preferably an inorganic amphoteric ion scavengers.

Furthermore, when a basic solid is included as additive (D), it is preferable that the basic solid be an inorganic salt. This is because it can exhibit high halogen ion capture ability or acid neutralization ability without introducing basic functional groups onto the surface. Among inorganic salts, calcium carbonate is preferably used.

Additive (D) can have various shapes, such as particles, needles, or flakes. Particulates are preferred from the viewpoint of uniform dispersibility. When additive (D) is particulate, the smaller the average particle size of additive (D), the better. Specifically, it is preferably 0.01 μm to 500 μm, more preferably 0.02 μm to 400 μm, more preferably 0.05 μm to 300 μm, and more preferably 0.5 μm to 200 μm. When the additive is in the form of primary particles without agglomeration, the average particle size of the primary particles is preferably within the above range. On the other hand, when the additive is in the form of secondary particles due to agglomeration, the size of the secondary particles is preferably within the above range. The average particle size of the additive is measured using a scanning electron microscope (SEM). Specifically, the average particle size was measured using a surface observation device (VE-9800, manufactured by Keyence Corporation).

It is preferable that additive (D) be dispersed throughout the adhesive layer. If additive (D) is unevenly distributed, the corrosion-inhibiting effect on the metal surface will be localized, making it difficult to achieve a sufficient effect. Here, "additive (D) is dispersed throughout the adhesive layer" means that when a 5 cm x 5 cm piece is cut from any location after sheet processing and observed under a microscope, there are fewer than three agglomerates of additive (D) exceeding 1000 μm.

Additive (D) may be embedded in the adhesive layer, or a portion of it may be exposed from the adhesive layer.

In the present invention, the content of the additive (D) in the adhesive layer is preferably 0.01% by mass or more and 30% by mass or less, preferably 0.01% by mass or more and 25% by mass or less, preferably 0.01% by mass or more and 10% by mass or less, and preferably 0.015% by mass or more and 5% by mass or less, of the total amount of the adhesive layer, in other words, the total amount of the adhesive composition forming the adhesive layer. By setting the content of additive (D) in the adhesive layer within the above range, additive (D) can be sufficiently dispersed in the adhesive layer, and corrosion of the metal surface contained in the adherend can be sufficiently inhibited. Note that if the content of additive (D) exceeds the above range, the proportion of the additive in the adhesive will be high, which may result in insufficient adhesion to the adherend, or in other cases, insufficient adhesion. On the other hand, if the content is less than the above range, halogen ions and/or acids containing them may not be sufficiently captured and neutralized, making it difficult to achieve corrosion inhibition effect on the metal surface.

<Other Components (E)>
The adhesive layer may contain, in addition to the above-mentioned photocurable resin (A), thermoplastic resin (B), photopolymerization initiator (C), and additive (D), other components (E) as necessary.

The adhesive layer in the present invention may contain a pressure-sensitive adhesive resin. This is because the adhesive sheet of the present invention can exhibit good room-temperature lamination properties and can further improve its ability to conform to uneven surfaces on the adherend.

The weight-average molecular weight of the above-mentioned adhesive resin is preferably in the range of 2,000 to 2,000,000, more preferably in the range of 5,000 to 1,000,000, and even more preferably in the range of 5,000 to 800,000.

Examples of the adhesive resin include polyester resin, polyurethane resin, poly(meth)acrylate resin, and polyvinyl acetal resin. These adhesive resins may be homopolymers or copolymers. Furthermore, these adhesive resins may be used alone or in combination of two or more types.

The adhesive resin preferably has a glass transition temperature in the range of -30°C to 20°C, and more preferably in the range of -25°C to 10°C. When the adhesive layer contains an adhesive resin with a glass transition temperature within the above range, the adhesive sheet of the present invention can exhibit good adhesion and a high elastic modulus at room temperature, and can exhibit good adhesion to the adherend and high bonding strength.

The glass transition temperature can be calculated, for example, by using a dynamic viscoelasticity tester (manufactured by Rheometrics, product name: Ares 2KSTD) to measure a test piece of adhesive resin between the parallel disks that make up the tester's measurement section, measuring the storage modulus (G') and loss modulus (G") at a frequency of 1 Hz, and determining the temperature at which the loss tangent (tanδ), calculated by dividing the loss modulus (G") by the storage modulus (G') (G"/G'), reaches its maximum value.

The adhesive resin may contain functional groups that can react with the crosslinking agent or the functional groups contained in the photocurable resin (A) and thermoplastic resin (B). This allows the adhesive resin to be crosslinked. Examples of such functional groups include hydroxyl groups, carboxyl groups, epoxy groups, and amino groups. It is preferable to select the functional groups appropriately within a range that does not inhibit the polymerization reaction of the photocurable resin (A) and thermoplastic resin (B).

The adhesive resin is preferably contained in the adhesive layer, in other words, in the range of 0.1 to 100 parts by mass relative to the total amount of the adhesive composition forming the adhesive layer, more preferably in the range of 1 to 50 parts by mass, and even more preferably in the range of 5 to 30 parts by mass. By incorporating the adhesive resin in a proportion within the above range, it is possible to obtain an adhesive sheet that exhibits excellent lamination at room temperature without reducing the bonding strength of the adhesive layer after curing.

The adhesive layer of the present invention may contain fillers other than additive (D), silane coupling agents, phosphate-based additives, acrylate-based additives, etc. When the material of the adherend surface contains glass, the adhesive layer may contain a silane coupling agent that is highly reactive with glass to further enhance adhesion to the adherend. The adhesive layer may also contain a photocurable silane coupling agent that can react with photocurable resin (A), thermoplastic resin (B), etc.

The adhesive layer of the present invention may also contain optional components such as softeners, stabilizers, adhesion promoters, leveling agents, defoamers, plasticizers, tackifying resins, fibers, antioxidants, hydrolysis inhibitors, thickeners, colorants such as pigments, fillers, and tackifying resins.

<Others>
The adhesive layer in the present invention preferably comprises one or more resins (AA) having an epoxy group or an oxetanyl group and a weight average molecular weight in the range of 100 to 5000, one or more resins (BB) having a polymerizable functional group other than a polymerizable unsaturated double bond and a weight average molecular weight in the range of 5500 to 2000000 selected from the group consisting of polyester resins, polyurethane resins, acrylic resins, polyvinyl acetal resins, and epoxy resins (thermoplastic epoxy resins), a photopolymerization initiator (C), and one or more additives (D) having the function of capturing or neutralizing halogen ions and/or acids containing the halogen ions. Here, the resins (AA) and (BB) correspond to the photocurable resin (A) and thermoplastic resin (B), respectively.

<Physical properties of adhesive layer>
The adhesive layer in the present invention preferably has a thickness of 10 μm or more and 3000 μm or less, preferably 20 μm or more and 2500 μm or less, preferably 30 μm or more and 2000 μm or less, and preferably 50 μm or more and 650 μm or less. By setting the thickness of the adhesive layer within the above range, it is possible to achieve excellent handleability before curing, high conformal adhesion to the adherend surface, and metal corrosion inhibition effect. If the thickness of the adhesive layer is smaller than the above range, it is not possible to contain the desired amount of additive (D), and the corrosion inhibition effect on the metal surface may not be sufficiently achieved, or sufficient adhesive strength may not be achieved due to the thin thickness. On the other hand, if the thickness of the adhesive layer is larger than the above range, it is difficult to process into a sheet shape. As described below, when the adhesive layer in the present invention is a multilayer body, the thickness of the adhesive layer refers to the total thickness of the multilayer body.

The adhesive layer in the present invention preferably has a loss tangent (tanδ) at 23°C measured at a frequency of 1 Hz of less than 1.5, more preferably 0.01 to 1.0, and even more preferably 0.1 to 0.8. This is because it allows the adhesive sheet to maintain a constant thickness, provides excellent handling before curing, and improves conformability and adhesion to the adherend surface before and after curing.

The loss tangent (tanδ) of the adhesive layer was measured by cutting the adhesive layer into a circular specimen with a thickness of 1 mm and a diameter of 8 mm. Using a dynamic viscoelasticity tester (manufactured by Rheometrics, product name: Ares 2KSTD), the specimen was sandwiched between the parallel disks in the measuring section of the tester, and the storage modulus (G') and loss modulus (G") were measured at a temperature of 23°C and a frequency of 1 Hz. The loss tangent (tanδ) was calculated by dividing the loss modulus (G") by the storage modulus (G') (G"/G').

The loss tangent (tan δ) of the adhesive layer can be adjusted by appropriately selecting the composition and average molecular weight of the photocurable resin (A), thermoplastic resin (B), and other components as needed.

The adhesive layer in the present invention preferably has a melting point of 25°C or higher, preferably 30°C or higher, preferably 35°C or higher, and preferably 40°C or higher. The melting point is preferably 120°C or lower, preferably 90°C or lower, and preferably 60°C or lower. More specifically, the melting point of the adhesive layer is preferably in the range of 30°C to 120°C, preferably 30°C to 90°C, and preferably 40°C to 85°C. By setting the melting point of the adhesive layer within the above range, the adhesive sheet of the present invention has excellent handleability before curing and improved conformability and adhesion to the adherend surface. The melting point of the adhesive layer is synonymous with the melting point of the adhesive composition that constitutes the adhesive layer.

The melting point of the adhesive layer is the temperature at which the maximum exothermic peak (exothermic peak top) is observed when the temperature is increased from 20°C to 150°C at a rate of 10°C/min using differential scanning calorimetry (DSC), held for 1 minute, then cooled to -10°C at a rate of 10°C/min, held for 10 minutes, and then measured again at a rate of 10°C/min.

The adhesive layer in the present invention preferably has a storage modulus (E' ₂₅ ) at 25°C at a frequency of 1 Hz of 1.0×10 ⁵ Pa or more, more preferably 1.0×10 ⁶ Pa or more, and even more preferably 1.0×10 ⁷ Pa or more, after curing. This is because, when the adhesive layer after curing exhibits a desired storage modulus under predetermined conditions, it is possible to suppress misalignment and deformation of the adhesive layer over time after bonding.

Furthermore, the adhesive layer in the present invention preferably has a storage modulus (E'40) at 40°C at a frequency of 1 Hz of 1.0 x 10 ⁴ Pa or more after curing, and a storage modulus (E'60) at 60°C at a frequency of 1 Hz of 1.0 x 10 ⁴ Pa or more after curing. This is because the adhesive layer after curing exhibits a desired storage modulus under predetermined conditions, making it possible to firmly bond members together.

The storage modulus of the cured adhesive layer at each temperature was measured using a dynamic viscoelasticity measuring device (manufactured by Rheometrics, product name: RSA-II) using test specimens prepared by punching out a 100 μm thick cured adhesive layer into the shape of a Type 5 test specimen specified in JIS K 7127 using a dumbbell cutter.

In the adhesive sheet of the present invention, the gel fraction of the adhesive layer after curing is preferably 40% by mass or more and 100% by mass or less, more preferably 60% by mass or more and 100% by mass or less, and even more preferably 70% by mass or more and 100% by mass or less. By keeping the gel fraction within the above range, it becomes possible to firmly bond components together.

The gel fraction is calculated using the following formula from the mass of the adhesive layer remaining in the cured adhesive sheet after immersion in toluene adjusted to 23°C for 24 hours, and the mass of the adhesive layer before immersion in toluene.

Gel fraction (mass%) = {(mass of adhesive layer remaining in toluene) / (mass of adhesive layer before immersion in toluene)} x 100

(2) Embodiments of the Adhesive Sheet The adhesive sheet of the present invention may have any embodiment as long as it has an adhesive layer containing the above-described composition, and may have any configuration as required.

One embodiment (embodiment (I)) of the adhesive sheet of the present invention is an embodiment consisting only of an adhesive layer, i.e., a substrate-less embodiment. The adhesive sheet of embodiment (I) can be an embodiment having only a single adhesive layer composed of an adhesive composition containing at least the above-mentioned photocurable resin (A), thermoplastic resin (B), photopolymerization initiator (C), and additive (D). Alternatively, the adhesive sheet of embodiment (I) can have only an adhesive layer of a multilayer structure consisting of two or more laminated layers, and at least the outermost layers on both sides of the adhesive layer of the multilayer structure may be composed of an adhesive composition containing the above-mentioned photocurable resin (A), thermoplastic resin (B), photopolymerization initiator (C), and additive (D). It is particularly preferred that all of the multiple layers constituting the adhesive layer of the multilayer structure be composed of the same or different adhesive compositions containing the above-mentioned photocurable resin (A), thermoplastic resin (B), photopolymerization initiator (C), and additive (D).

The adhesive sheet of embodiment (I) may have a release liner disposed on one or both of the pair of opposing main surfaces of the adhesive layer. The adhesive sheet of embodiment (I) is used by peeling off and removing the release liner when laminating it to a component. Therefore, in a laminate in which a pair of components are bonded via the adhesive sheet of embodiment (I), the release liner is not considered to be included in the configuration of the adhesive sheet.

Another embodiment of the adhesive sheet of the present invention (Aspect (II)) includes a substrate, a first adhesive layer formed on a first main surface of the substrate, and a second adhesive layer formed on a second main surface of the substrate opposite the first main surface, wherein the first adhesive layer and the second adhesive layer are each composed of the same or different adhesive compositions containing at least the above-mentioned photocurable resin (A), thermoplastic resin (B), photopolymerization initiator (C), and additive (D). The adhesive sheet of Aspect (II) can have increased sheet strength by having a substrate between the two adhesive layers. In Aspect (II), only one of the first adhesive layer and the second adhesive layer may be composed of an adhesive composition containing at least the above-mentioned photocurable resin (A), thermoplastic resin (B), photopolymerization initiator (C), and additive (D).

In the adhesive sheet of embodiment (II), the substrate is not particularly limited, and examples thereof include plastic films made of polyester resins or polyolefin resins, and plastic foams made of polyolefin resins, polyurethane resins, polychloroprene resins, acrylic resins, and the like. The substrate is preferably optically transparent. By irradiating one adhesive layer with light, the other adhesive layer can be activated through the substrate, causing a polymerization reaction.

The adhesive sheet of embodiment (II) may have a release liner on at least one of the surface of the first adhesive layer opposite the surface that contacts the substrate and the surface of the second adhesive layer opposite the surface that contacts the substrate, or may have a release liner on both surfaces. The adhesive sheet of embodiment (II) is used by peeling off and removing the release liner when bonding to a component. Therefore, in a laminate in which a pair of components are bonded via the adhesive sheet of embodiment (II), the release liner is not considered to be included in the configuration of the adhesive sheet.

The release liner for each embodiment of the adhesive sheet can be, for example, paper such as kraft paper, glassine paper, or fine paper; resin films such as polyethylene, polypropylene (OPP, CPP), or polyethylene terephthalate; laminated paper made by laminating the above-mentioned paper with a resin film; or the above-mentioned paper sealed with clay, polyvinyl alcohol, or the like, with one or both sides treated with a release agent such as a silicone resin.

The thickness of the adhesive sheet of the present invention is preferably 10 μm to 3000 μm, more preferably 20 μm to 2500 μm, more preferably 30 μm to 2000 μm, and more preferably 50 μm to 650 μm.

When the adhesive sheet of the present invention is irradiated with light, polymerization begins within the adhesive layer, and curing progresses. Because the adhesive layer of the present invention is activated by light, curing does not progress regardless of the storage temperature before light irradiation, resulting in good storage stability before curing. Furthermore, the adhesive layer of the present invention has reactive sites activated by light irradiation, and the activity is sustained, allowing the curing reaction to proceed even at low temperatures.

The adhesive sheet of the present invention can accelerate its curing reaction by applying external stimuli such as heat and moisture (humidity) in addition to light. In particular, it is preferable to use a combination of light and heat as a means for curing the adhesive sheet of the present invention. The adhesive sheet is first irradiated with light to activate the adhesive layer and initiate polymerization, and the curing reaction can be accelerated by heating the adhesive sheet after laminating it to a member (adherend). This eliminates the need for curing by high-temperature heating, and allows the curing reaction to proceed even at low temperatures. When heat is used in combination, the reaction has already begun with light irradiation, so heat is used solely for the purpose of accelerating the curing reaction. High-temperature heating is not necessary, and a good curing reaction can be achieved even at low temperatures and in a short period of time.

(3) Method for Producing Adhesive Sheet The adhesive sheet of the present invention can be produced using an adhesive solution prepared by mixing an adhesive composition containing at least the above-described photocurable resin (A), thermoplastic resin (B), photopolymerization initiator (C), and additive (D) in a solvent. Specifically, the adhesive sheet of the present invention can be produced, for example, by applying the above-described adhesive solution to the surface of a release sheet, drying the solution to form an adhesive layer, and then removing the release sheet. By forming an adhesive layer using an adhesive solution prepared by mixing the adhesive composition in a solvent, the dispersibility of the additive (D) in the adhesive layer is improved compared to when the adhesive is directly applied.

The adhesive sheet of the present invention can also be produced, for example, by applying the above-mentioned adhesive solution to both sides of a substrate and drying it to form an adhesive layer.

The adhesive sheet of the present invention can also be produced, for example, by applying the above-mentioned adhesive solution to the surface of a release sheet, drying it to form an adhesive layer, and then attaching a substrate to the surface of the adhesive layer.

When manufacturing an adhesive sheet in which two or more adhesive layers made of the same or different compositions are laminated, it can be manufactured, for example, by applying an adhesive solution containing adhesive composition 1 to both sides of a substrate and drying to form first adhesive layer 1, and then applying an adhesive solution containing adhesive composition 2 to the surface of first adhesive layer 1 and drying to form second adhesive layer 2. In this case, adhesive composition 2 contains at least the above-mentioned photocurable resin (A), thermoplastic resin (B), photopolymerization initiator (C), and additive (D). In particular, it is preferable that both adhesive compositions 1 and 2 contain the above-mentioned photocurable resin (A), thermoplastic resin (B), photopolymerization initiator (C), and additive (D).

The adhesive sheet of the present invention can also be produced, for example, by applying an adhesive solution containing adhesive composition 1 to the surface of a release sheet and drying to form adhesive layer 1, and then applying an adhesive solution containing adhesive composition 2 to the surface of adhesive layer 1 and drying to form adhesive layer 2. In this case, at least one of adhesive compositions 1 and 2 contains at least the above-mentioned photocurable resin (A), thermoplastic resin (B), photopolymerization initiator (C), and additive (D). It is particularly preferred that both adhesive compositions 1 and 2 contain at least the above-mentioned photocurable resin (A), thermoplastic resin (B), photopolymerization initiator (C), and additive (D).

The adhesive solution used in the adhesive sheet manufacturing method of the present invention can be prepared by mixing a solvent with an adhesive composition containing at least the above-mentioned photocurable resin (A), thermoplastic resin (B), photopolymerization initiator (C), and additive (D). Examples of solvents used in the adhesive solution include ester-based solvents such as methyl acetate, ethyl acetate, propyl acetate, and butyl acetate; ketone-based solvents such as acetone, methyl ketyl ketone, methyl isobutyl ketone, diisobutyl ketone, and cyclohexanone; and aromatic hydrocarbon solvents such as toluene and xylene. A dissolver, butterfly mixer, BDM twin-shaft mixer, planetary mixer, or the like can be used to mix the adhesive composition and solvent.

The adhesive sheet manufacturing method of the present invention includes a drying step to remove the solvent after applying the adhesive solution. The drying step is preferably carried out at a temperature of 40°C to 120°C, more preferably about 50°C to 90°C. This is because it can suppress the progress of the curing reaction of the adhesive sheet before light irradiation and also suppress foaming on the sheet surface due to rapid evaporation of the solvent, etc.

(4) Uses The adhesive sheet of the present invention can be used to bond components without being limited by the light transmittance or heat resistance of the components, but is particularly suitable for bonding components with low light transmittance, non-light transmittance, or low heat resistance. As described above, the adhesive sheet of the present invention has a slow curing reaction rate after light irradiation and can retain flexibility even after light irradiation. Therefore, by irradiating the adhesive sheet with light before bonding components, the curing reaction proceeds without irradiating the adhesive sheet with light through the components or heating and pressurizing at high temperatures, and the components can be firmly bonded.

The adhesive sheet of the present invention can be suitably used in the manufacture of image display devices. In other words, the adhesive sheet of the present invention can be suitably used as a bonding material for joining various components used in image display devices.

Examples of the image display device include components of flat-panel image display devices that use image display panels equipped with LCDs, PDPs, ELs, organic ELs, micro LEDs, quantum dots (QDs), etc., such as personal computers, mobile phones, smartphones, tablet PCs, and other mobile terminals (PDAs), game consoles, televisions (TVs), car navigation systems, touch panels, and pen tablets. Constituent components include, for example, image display panels, circuit boards, rear covers, bezels, frames, and chassis.

The adhesive sheet of the present invention can also be suitably used to bond components that make up large image display devices used in industrial and advertising applications.

2. Laminate The laminate of the present invention comprises the adhesive sheet described above in the section "1. Adhesive Sheet," a first member bonded to a first main surface of the adhesive sheet, and a second member bonded to a second main surface of the adhesive sheet.

In the laminate of the present invention, the adhesive layer of the adhesive sheet is cured. That is, in the laminate of the present invention, the first member and the second member are bonded together by the adhesive layer of the adhesive sheet after curing. In other words, the first member and the second member are bonded together by a cured layer of the adhesive composition described in the above section "1. Adhesive Sheet."

With the laminate of the present invention, the first and second components are bonded via the adhesive sheet described above in "1. Adhesive Sheet," making the components less likely to peel and demonstrating high interlayer peel strength. Furthermore, because the adhesive layer of the adhesive sheet contains the desired components, the adherend surface of the metal component or the adherend surface on which the metal part is placed is less likely to corrode due to contact with the adhesive sheet, thereby maintaining the performance of the metal component or the metal part placed on the adherend surface.

In the laminate of the present invention, as long as a first member is bonded to the first main surface of the adhesive sheet described above in Section "1. Adhesive Sheet," and a second member is bonded to the second main surface of the adhesive sheet opposite the first main surface, there are no limitations on the number of first and second members. That is, the laminate of the present invention may have one first member bonded to the first main surface of the adhesive sheet and one second member bonded to the second main surface of the adhesive sheet; one first member bonded to the first main surface of the adhesive sheet and multiple second members bonded to the second main surface of the adhesive sheet; or multiple first members bonded to the first main surface of the adhesive sheet and multiple second members bonded to the second main surface of the adhesive sheet.

The members in the laminate of the present invention may or may not be light-transmitting. The preferred light transmittance of the members is as explained above in the section "1. Adhesive Sheet." Furthermore, the members may or may not be heat-resistant, but it is preferable that they have heat resistance sufficient to withstand the heating temperature of the heat treatment performed after light irradiation to promote the curing reaction.

An example of a laminate of the present invention is one in which a first member, the adhesive sheet described above in "1. Adhesive Sheet," and a second member are laminated in this order, and at least one of the first member and the second member includes a metal surface on the surface to be adhered. Both the first member and the second member may include a metal surface on the surface to be adhered. Note that "including a metal surface on the surface to be adhered" has the same definition as described above in "1. Adhesive Sheet."

In the laminate of the present invention, the types of the first and second members are not particularly limited. However, since metal corrosion caused by bonding with an adhesive sheet is suppressed, it is preferable to use a member that includes a metal surface on the adherend surface for at least one of the first and second members. Both the first and second members may also be members that include a metal surface on the adherend surface.

The member having a metal surface on its adherend surface is not particularly limited, but is preferably a substrate or a wiring board having metal wiring on one side of the substrate. In particular, in the case of a wiring board having patterned metal wiring, the surface has unevenness and steps due to the wiring pattern and other components. The adhesive sheet of the present invention is able to conform to and adhere to such surface steps, thereby enabling a strong bond between the wiring board and other components. Furthermore, because the adhesive layer in the adhesive sheet contains additive (D), corrosion of the metal wiring due to contact over time is unlikely to occur even when the adhesive sheet conforms to and adheres to the wiring pattern for an extended period of time, and therefore deterioration of the functionality of the wiring board can be suppressed for an extended period of time.

When the component is a wiring board having a substrate and metal wiring on one side of the substrate, the substrate may or may not be optically transparent. The substrate may also be transparent or opaque. Known materials can be used for the substrate, such as glass and insulating resin.

When the component is a substrate and a wiring board having metal wiring on one side of the substrate, known materials can be used for the metal wiring, such as metal materials such as silver, copper, nickel, tin, bismuth, zinc, indium, palladium, aluminum, chromium, or alloys thereof, and conductive resin materials containing metal fine particles composed of binder resin and the above-mentioned metal materials. Examples of conductive resin materials include metal pastes or metal nanoinks containing metal fine particles and binder resin, and metal-carbon inks containing metal fine particles, carbon material, and binder resin.

The laminate of the present invention is preferably a substrate component or semiconductor chip for an image display. The laminate of the present invention is also preferably used in an image display device. Examples of the image display device include components of flat-panel image display devices that use image display panels equipped with LCDs, PDPs, ELs, organic ELs, micro LEDs, quantum dots (QDs), etc., such as mobile terminals (PDAs) such as personal computers, mobile phones, smartphones, and tablet PCs, game consoles, televisions (TVs), car navigation systems, touch panels, and pen tablets. Constituent components include, for example, image display panels, substrate components for image displays, rear covers, bezels, frames, and chassis.

3. Manufacturing Method of Laminate The manufacturing method of a laminate of the present invention is a manufacturing method of a laminate using the adhesive sheet described above in the section "1. Adhesive Sheet," and includes the steps of: step [1] bonding a first member to a first main surface of the adhesive sheet; step [2] bonding a second member to a second main surface of the adhesive sheet; and step [3] curing the adhesive layer of the adhesive sheet. The manufacturing method of a laminate of the present invention further includes a step of irradiating the first main surface or the second main surface of the adhesive sheet with active energy rays (hereinafter, sometimes referred to as step [0]) before step [1] or between steps [1] and [2]. Furthermore, in the manufacturing method of a laminate of the present invention, at least one of the first member and the second member includes a metal surface on the adhesion surface that contacts the adhesive layer.

If the adhesive sheet of the present invention is the adhesive sheet of embodiment (I) described above, the first and second main surfaces of the adhesive sheet refer to the two opposing outermost surfaces of the adhesive layer of the single layer or multilayer body. Furthermore, if the adhesive sheet of the present invention is the adhesive sheet of embodiment (II) described above, the first and second main surfaces of the adhesive sheet refer to the surface facing the first adhesive layer and the surface facing the second adhesive layer, respectively, of the adhesive sheet of embodiment (II).

In the laminate manufacturing method of the present invention, at least one of the first member and the second member may include a metal surface on the adherend surface that contacts the adhesive layer, and both the first member and the second member may include a metal surface on the adherend surface that contacts the adhesive layer.

In the above step [1], it is preferable to press and bond the first member to the first main surface of the adhesive sheet. Furthermore, in the above step [2], it is preferable to press and bond the second member to the second main surface of the adhesive sheet. By pressing and bonding the member to the adhesive sheet, the adhesive sheet can more easily conform to unevenness in the adherend surface of the member, thereby improving adhesion between the adhesive sheet and the member, thereby further increasing the bonding strength between the first member and the second member via the adhesive layer after curing.

In steps [1] and [2] above, the pressure used to press the component onto the adhesive sheet can be within the range of 0.1 to 3000 kPa, preferably within the range of 0.5 to 1000 kPa, and more preferably within the range of 1.0 to 500 kPa. Pressing within the above range allows the component to be attached to the adhesive sheet without being damaged, and achieves the adhesion required to obtain high bonding strength.

In steps [1] and [2] above, the components may be pressure-bonded to the adhesive sheet while heating. Pressure-bonding while heating allows for stronger adhesion and higher bonding strength when bonding the components together via the adhesive sheet. The heating temperature can be set within a range that does not damage the components, cause distortion between the components that could deform the components, or cause cracks between the bonding material and the components. It is preferably set to 150°C or less, 120°C or less, 100°C or less, 80°C or less, or 70°C or less. Setting an upper limit for the heating temperature can prevent damage to the components, and can also prevent distortion between the components that could cause distortion, or cracks between the adhesive sheet and the components. The heating temperature can also be set to preferably 5°C or more, 10°C or more, 20°C or more, 30°C or more, or 40°C or more. Setting a lower limit for the heating temperature improves the adhesive sheet's ability to conform to surface irregularities. The pressure-bonding time is not particularly limited, as long as it is long enough to allow sufficient conformal adhesion and adhesion to the surfaces of the components to be bonded.

The above step [3] may involve a heat treatment. In the manufacturing method of the present invention, the curing reaction of the adhesive sheet is initiated by irradiation with active energy rays, and curing proceeds even at room temperature. However, by performing the above step [3] with heat, the curing reaction is accelerated when bonding components together via the adhesive sheet, allowing for high bonding strength to be achieved in a shorter time.

When heat treatment is performed in step [3] above, the heating conditions can be set within a range that does not damage the laminated components, cause distortion between the components that could deform the components, or cause cracks between the adhesive sheet and the components. The heating temperature is preferably 150°C or less, more preferably 120°C or less, and even more preferably 100°C or less, and most preferably 80°C or less to prevent damage to the laminated components and deformation and flow of the bonding material.

In step [3] above, it is preferable to allow the curing reaction to proceed so that the cured adhesive layer exhibits the gel fraction described above in section "1. Adhesive Sheet."

The step of irradiating the first or second main surface of the adhesive sheet with active energy rays (step [0]) can be carried out before step [1]. In this case, steps [1] and [2] are preferably carried out within 24 hours, more preferably within 12 hours, and even more preferably within 3 hours after carrying out step [0], and most preferably within 1 hour, as this ensures stronger adhesion and higher bonding strength when the adhesive sheet is attached to a member.

In addition, step [0] may be performed between step [1] and step [2]. In this case, step [2] is preferably performed within 24 hours, more preferably within 12 hours, and even more preferably within 3 hours after step [0] is performed, and most preferably within 1 hour, as this ensures stronger adhesion and higher bonding strength when the adhesive sheet is applied to the member.

Ultraviolet light, visible light, etc. are preferably used as the active energy ray, with ultraviolet light being particularly preferred. To efficiently carry out the ultraviolet curing reaction, the ultraviolet light may be irradiated in an inert gas atmosphere such as nitrogen gas, or in an air atmosphere. If necessary, heat may also be used as an energy source, and heating may be performed after light irradiation.

Furthermore, it is preferable that the light used for irradiation has a wavelength range capable of activating the photopolymerization initiator, and in particular, it is preferable to use active energy rays with a wavelength of 300 nm or more and 420 nm or less.

Light sources for irradiating actinic energy rays include, for example, low-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, metal halide lamps, electrodeless lamps (fusion lamps), chemical lamps, black light lamps, xenon lamps, mercury-xenon lamps, short arc lamps, helium-cadmium lasers, argon lasers, sunlight, LEDs, germicidal lamps, carbon arcs, scanning and curtain-type electron beam accelerators, etc. Xenon flash lamps, which can irradiate light in a flashing manner, are preferred because they can minimize the effects of heat.

The irradiation intensity of the active energy rays is preferably 0.1 to 1000 mW/ ^cm² , more preferably 0.5 to 800 mW, and even more preferably 0.1 to 400 mW/ ^cm² . The irradiation time of the active energy rays is preferably 1 to 60 seconds, more preferably 5 to 50 seconds, and even more preferably 10 to 40 seconds. By setting the irradiation intensity and time within the above ranges, the heat generated upon irradiation with active energy rays can be reduced, and therefore the cure rate after irradiation with active energy rays can be suitably adjusted.

The above-mentioned active energy rays may be irradiated in one go or in multiple divided doses.

Specific examples of laminates that can be produced using the present invention include those described above in section "2. Laminates."

This disclosure is not limited to the above-described embodiments. The above-described embodiments are merely examples, and any configuration that is substantially identical to the technical concept described in the claims of this disclosure and that provides similar effects is within the technical scope of this disclosure.

The present invention will be explained in more detail below through examples and comparative examples.

1. Synthesis Example of Thermoplastic Resin (B) <Preparation of Polyurethane (B-1)>
Into a reaction vessel,
50.3 parts by mass of an aromatic polyester polyol having a number average molecular weight of 1,300 obtained by reacting an ethylene oxide 2-mol adduct of bisphenol A with phthalic acid and adipic acid, 32 parts by mass of an aliphatic polyester polyol having a number average molecular weight of 3,500 obtained by reacting 1,6-hexanediol with dodecanedioic acid, 32.2 parts by mass of polypropylene glycol having a number average molecular weight of 1,000, and 1.8 parts by mass of an ethylene oxide 2-mol adduct of bisphenol A were mixed and heated to 100°C under reduced pressure conditions to dehydrate until the moisture content was 0.05% by mass, thereby obtaining mixture (1).

Next, this mixture (1) was cooled to 70°C and mixed with 7.9 parts by mass of 4,4'-diphenylmethane diisocyanate, and the mixture was heated to 100°C and reacted for 3 hours until the hydroxyl group content reached a constant level, yielding polyurethane (B-1). The polyurethane (B-1) has hydroxyl groups as polymerizable functional groups.

<Preparation of Polyurethane (B-2)>
A reaction vessel was charged with 50.3 parts by mass of an aromatic polyester polyol having a number average molecular weight of 1,300 obtained by reacting an ethylene oxide 2-mol adduct of bisphenol A with phthalic acid and adipic acid, 32 parts by mass of an aliphatic polyester polyol having a number average molecular weight of 3,500 obtained by reacting 1,6-hexanediol and dodecanedioic acid, 32.2 parts by mass of polypropylene glycol having a number average molecular weight of 1,000, and 1.8 parts by mass of the ethylene oxide 2-mol adduct of bisphenol A, and the resulting mixture was heated to 100°C under reduced pressure conditions to dehydrate until the moisture content reached 0.05% by mass, thereby obtaining mixture (2).

Next, this mixture (2) was cooled to 70°C and mixed with 4.3 parts by mass of 4,4'-diphenylmethane diisocyanate and 4.3 parts by mass of 2,4'-diphenylmethane diisocyanate. The mixture was then heated to 100°C and reacted for 5 hours until the hydroxyl group content reached a constant level, yielding polyurethane (B-2). The polyurethane (B-2) has hydroxyl groups as polymerizable functional groups.

<Preparation of Polyurethane (B-3)>
60 parts by mass of an aliphatic polycarbonate polyol having a number average molecular weight of 2000 obtained by reacting 1,5-pentanediol, 1,6-hexanediol, and a dialkyl carbonate, and 20 parts by mass of a polyester polyol having a number average molecular weight of 1000 obtained by reacting 1,4-butanediol and adipic acid were mixed in a reaction vessel, and the mixture was heated to 100°C under reduced pressure conditions to dehydrate until the moisture content reached 0.05% by mass, thereby obtaining mixture (3).

Next, mixture (3) was cooled to 70°C and mixed with 20 parts by mass of dicyclohexylmethane-4,4'-diisocyanate. The mixture was then heated to 100°C and reacted for 3 hours to obtain a urethane prepolymer having isocyanate groups. 100 parts by mass of the above urethane prepolymer was heated and melted at 100°C, and this was mixed with 11.4 parts by mass of 2-hydroxyethyl acrylate and 0.01 parts by mass of stannous octoate. The mixture was reacted at 100°C until the NCO% reached a constant value, yielding polyurethane (B-3). Polyurethane (B-3) had a polymerizable unsaturated double bond as the polymerizable functional group, and the isocyanate group content (NCO%) was 0% by mass.

2. Preparation of adhesive sheet (Example 1)
An adhesive solution containing adhesive composition (a-1) was obtained by mixing and stirring 33 parts by mass of the polyurethane (B-1), 22 parts by mass of an alicyclic epoxy resin (manufactured by Daicel Corporation, "CEL-2021P"), 45 parts by mass of a cresol novolac epoxy resin (manufactured by DIC Corporation, "N-685-EXP-S"), 1.6 parts by mass of a sulfonium salt-based cationic photopolymerization initiator (manufactured by San-Apro Co., Ltd., "CPI-100P", solids concentration 50%), and 40 parts by mass of calcium bicarbonate particles (manufactured by Shiraishi Calcium Co., Ltd., "BF-200", average particle size 5 μm), and adding methyl ethyl ketone to adjust the nonvolatile content to 75% by mass. Note that the calcium bicarbonate particles were a basic solid.

Next, an adhesive solution containing the adhesive composition (a-1) was applied to the surface of release liner A (a 50 μm-thick polyethylene terephthalate film with one side subjected to a release treatment with a silicone compound) using a rod-shaped metal applicator so that the thickness after drying would be 150 μm. The film was then placed in a dryer at 85°C for 5 minutes and dried to obtain a coating layer of adhesive composition (a-1).

Furthermore, three of the above coating layers were laminated together to form a 450 μm thick multi-layer adhesive layer with release liner A on one side, and release liner B (a 38 μm thick polyethylene terephthalate film with one side release-treated with a silicone compound) was laminated to the other side of the above adhesive layer, resulting in an adhesive sheet with a total thickness of 450 μm (excluding the thickness of the release liner).

Example 2
An adhesive solution containing adhesive composition (a-2) was obtained by mixing and stirring 33 parts by mass of the polyurethane (B-1), 22 parts by mass of an alicyclic epoxy resin (manufactured by Daicel Corporation, "CEL-2021P"), 45 parts by mass of a cresol novolac epoxy resin (manufactured by DIC Corporation, "N-685-EXP-S"), 1.6 parts by mass of a sulfonium salt-based cationic photopolymerization initiator (manufactured by San-Apro Co., Ltd., "CPI-100P", solids concentration 50%), 20 parts by mass of calcium bicarbonate particles (manufactured by Shiraishi Calcium Co., Ltd., "BF-200", average particle size 5 μm), and 16.2 parts by mass of hydrophobic silica particles (manufactured by Fuji Silysia Chemical Industries, Ltd., "Sylohorbic 603", average particle size 6.7 μm), and adding methyl ethyl ketone to adjust the nonvolatile content to 75% by mass. Note that the calcium bicarbonate particles were a basic solid, and the hydrophobic silica particles were a non-basic solid with no basic functional groups on their surfaces.

Next, the adhesive solution containing the adhesive composition (a-2) was applied to the surface of release liner A (a 50 μm-thick polyethylene terephthalate film with one side subjected to a release treatment with a silicone compound) using a rod-shaped metal applicator so that the thickness after drying would be 150 μm, and then dried to obtain a coating layer of adhesive composition (a-2).

Furthermore, three of the above coating layers were laminated together to form a 450 μm thick multi-layer adhesive layer with release liner A on one side, and release liner B (a 38 μm thick polyethylene terephthalate film with one side release-treated with a silicone compound) was laminated to the other side of the above adhesive layer, resulting in an adhesive sheet with a total thickness of 450 μm (excluding the thickness of the release liner).

Example 3
An adhesive solution containing adhesive composition (a-3) was obtained by mixing and stirring 43 parts by mass of the polyurethane (B-2), 22 parts by mass of an alicyclic epoxy resin (manufactured by Daicel Corporation, "CEL-2021P"), 35 parts by mass of a cresol novolac epoxy resin (manufactured by DIC Corporation, "N-685-EXP-S"), 2.0 parts by mass of a sulfonium salt-based cationic photopolymerization initiator (manufactured by San-Apro Co., Ltd., "CPI-100P", solids concentration 50%), and 13.3 parts by mass of calcium bicarbonate particles (manufactured by Shiraishi Calcium Co., Ltd., "BF-200", average particle size 5 μm), and adding methyl ethyl ketone to adjust the nonvolatile content to 75% by mass. Note that the calcium bicarbonate particles were a basic solid.

Next, an adhesive solution containing the adhesive composition (a-3) was applied to the surface of release liner A (a 50 μm-thick polyethylene terephthalate film with one side subjected to a release treatment with a silicone compound) using a rod-shaped metal applicator so that the thickness after drying would be 150 μm, and the film was then placed in a dryer at 85°C for 5 minutes to dry, yielding a coating layer of adhesive composition (a-3).

Furthermore, three of the above coating layers were laminated together to form a 450 μm thick multi-layer adhesive layer with release liner A on one side, and release liner B (a 38 μm thick polyethylene terephthalate film with one side release-treated with a silicone compound) was laminated to the other side of the above adhesive layer, resulting in an adhesive sheet with a total thickness of 450 μm (excluding the thickness of the release liner).

Example 4
An adhesive solution containing adhesive composition (a-4) was obtained by mixing and stirring 43 parts by mass of the polyurethane (B-2), 22 parts by mass of an alicyclic epoxy resin (manufactured by Daicel Corporation, "CEL-2021P"), 35 parts by mass of a cresol novolac epoxy resin (manufactured by DIC Corporation, "N-685-EXP-S"), 2.0 parts by mass of a sulfonium salt-based photocationic polymerization initiator (manufactured by San-Apro Co., Ltd., "CPI-100P", solids concentration 50%), 1.7 parts by mass of an ion scavenger (manufactured by Toagosei Co., Ltd., "IXE-700F", average particle size 1.5 μm), and 20 parts by mass of hydrophobic silica particles (manufactured by Fuji Silysia Chemical Ltd., "Sylohorbic 603", average particle size 6.7 μm), and adding methyl ethyl ketone to adjust the nonvolatile content to 75% by mass. The ion scavenger was an inorganic amphoteric ion scavenger containing two metal atoms, aluminum and magnesium. Furthermore, the hydrophobic silica particles did not have basic functional groups on the surface and were non-basic solids.

Next, an adhesive solution containing the adhesive composition (a-4) was applied to the surface of release liner A (a 50 μm-thick polyethylene terephthalate film with one side subjected to a release treatment with a silicone compound) using a rod-shaped metal applicator so that the thickness after drying would be 150 μm, and the film was then placed in a dryer at 85°C for 5 minutes to dry, yielding a coating layer of adhesive composition (a-4).

Furthermore, three of the above coating layers were laminated together to form a 450 μm thick multi-layer adhesive layer with release liner A on one side, and release liner B (a 38 μm thick polyethylene terephthalate film with one side release-treated with a silicone compound) was laminated to the other side of the above adhesive layer, resulting in an adhesive sheet with a total thickness of 450 μm (excluding the thickness of the release liner).

Example 5
An adhesive solution containing adhesive composition (a-5) was obtained by mixing and stirring 43 parts by mass of the polyurethane (B-2), 22 parts by mass of an alicyclic epoxy resin (manufactured by Daicel Corporation, "CEL-2021P"), 35 parts by mass of a cresol novolac epoxy resin (manufactured by DIC Corporation, "N-685-EXP-S"), 2.0 parts by mass of a sulfonium salt-based photocationic polymerization initiator (manufactured by San-Apro Co., Ltd., "CPI-100P", solids concentration 50%), 1.7 parts by mass of an ion scavenger (manufactured by Toagosei Co., Ltd., "IXEPLAS-A3", average particle size 0.5 μm), and 20 parts by mass of hydrophobic silica particles (manufactured by Fuji Silysia Chemical Ltd., "Sylohorbic 603", average particle size 6.7 μm). Methyl ethyl ketone was added to adjust the nonvolatile content to 75% by mass. The ion scavenger was an inorganic amphoteric ion scavenger containing three metal atoms: zirconium, aluminum, and magnesium. Furthermore, the hydrophobic silica particles did not have basic functional groups on the surface and were non-basic solids.

Next, an adhesive solution containing the adhesive composition (a-5) was applied to the surface of release liner A (a 50 μm-thick polyethylene terephthalate film with one side subjected to a release treatment with a silicone compound) using a rod-shaped metal applicator so that the thickness after drying would be 150 μm, and the film was then placed in a dryer at 85°C for 5 minutes to dry, yielding a coating layer of adhesive composition (a-5).

Furthermore, three of the above coating layers were laminated together to form a 450 μm thick multi-layer adhesive layer with release liner A on one side, and release liner B (a 38 μm thick polyethylene terephthalate film with one side release-treated with a silicone compound) was laminated to the other side of the above adhesive layer, resulting in an adhesive sheet with a total thickness of 450 μm (excluding the thickness of the release liner).

Example 6
An adhesive solution containing adhesive composition (a-6) was obtained by mixing and stirring 43 parts by mass of the polyurethane (B-2), 22 parts by mass of an alicyclic epoxy resin (manufactured by Daicel Corporation, "CEL-2021P"), 35 parts by mass of a cresol novolac epoxy resin (manufactured by DIC Corporation, "N-685-EXP-S"), 4.0 parts by mass of a sulfonium salt-based photocationic polymerization initiator (manufactured by San-Apro Co., Ltd., "CPI-100P", solids concentration 50%), 1.7 parts by mass of an ion scavenger (manufactured by Toagosei Co., Ltd., "IXEPLAS-A3", average particle size 0.5 μm), and 20 parts by mass of hydrophobic silica particles (manufactured by Fuji Silysia Chemical Ltd., "Sylohorbic 603", average particle size 6.7 μm), and adding methyl ethyl ketone to adjust the nonvolatile content to 75% by mass. The ion scavenger was an inorganic amphoteric ion scavenger containing three metal atoms: zirconium, aluminum, and magnesium. Furthermore, the hydrophobic silica particles did not have basic functional groups on the surface and were non-basic solids.

Next, an adhesive solution containing the adhesive composition (a-6) was applied to the surface of release liner A (a 50 μm-thick polyethylene terephthalate film with one side subjected to a release treatment with a silicone compound) using a rod-shaped metal applicator so that the thickness after drying would be 150 μm, and the film was then placed in a dryer at 85°C for 5 minutes to dry, yielding a coating layer of adhesive composition (a-6).

Furthermore, three of the above coating layers were laminated together to form a 450 μm thick multi-layer adhesive layer with release liner A on one side, and release liner B (a 38 μm thick polyethylene terephthalate film with one side release-treated with a silicone compound) was laminated to the other side of the above adhesive layer, resulting in an adhesive sheet with a total thickness of 450 μm (excluding the thickness of the release liner).

Example 7
An adhesive solution containing adhesive composition (a-7) was obtained by mixing and stirring 43 parts by mass of the polyurethane (B-2), 22 parts by mass of an alicyclic epoxy resin (manufactured by Daicel Corporation, "CEL-2021P"), 35 parts by mass of a cresol novolac epoxy resin (manufactured by DIC Corporation, "N-685-EXP-S"), 2.0 parts by mass of a sulfonium salt-based photocationic polymerization initiator (manufactured by San-Apro Co., Ltd., "CPI-100P", solids concentration 50%), 0.85 parts by mass of an ion scavenger (manufactured by Toagosei Co., Ltd., "IXEPLAS-A3", average particle size 0.5 μm), and 20 parts by mass of hydrophobic silica particles (manufactured by Fuji Silysia Chemical Ltd., "Sylophorbic 603", average particle size 6.7 μm). Methyl ethyl ketone was added to adjust the nonvolatile content to 75% by mass. The ion scavenger was an inorganic amphoteric ion scavenger containing three metal atoms: zirconium, aluminum, and magnesium. Furthermore, the hydrophobic silica particles did not have basic functional groups on the surface and were non-basic solids.

Next, an adhesive solution containing the adhesive composition (a-7) was applied to the surface of release liner A (a 50 μm-thick polyethylene terephthalate film with one side subjected to a release treatment with a silicone compound) using a rod-shaped metal applicator so that the thickness after drying would be 150 μm, and the film was then placed in a dryer at 85°C for 5 minutes to dry, yielding a coating layer of adhesive composition (a-7).

Furthermore, three of the above coating layers were laminated together to form a 450 μm thick multi-layer adhesive layer with release liner A on one side, and release liner B (a 38 μm thick polyethylene terephthalate film with one side release-treated with a silicone compound) was laminated to the other side of the above adhesive layer, resulting in an adhesive sheet with a total thickness of 450 μm (excluding the thickness of the release liner).

(Example 8)
An adhesive solution containing adhesive composition (a-8) was obtained by mixing and stirring 43 parts by mass of the polyurethane (B-2), 22 parts by mass of an alicyclic epoxy resin (manufactured by Daicel Corporation, "CEL-2021P"), 35 parts by mass of a cresol novolac epoxy resin (manufactured by DIC Corporation, "N-685-EXP-S"), 2.0 parts by mass of a sulfonium salt-based photocationic polymerization initiator (manufactured by San-Apro Co., Ltd., "CPI-100P", solids concentration 50%), 0.034 parts by mass of an ion scavenger (manufactured by Toagosei Co., Ltd., "IXEPLAS-A3", average particle size 0.5 μm), and 20 parts by mass of hydrophobic silica particles (manufactured by Fuji Silysia Chemical Ltd., "Sylohorbic 603", average particle size 6.7 μm). Methyl ethyl ketone was added to adjust the nonvolatile content to 75% by mass. The ion scavenger was an inorganic amphoteric ion scavenger containing three metal atoms: zirconium, aluminum, and magnesium. Furthermore, the hydrophobic silica particles did not have basic functional groups on the surface and were non-basic solids.

Next, an adhesive solution containing the adhesive composition (a-8) was applied to the surface of release liner A (a 50 μm-thick polyethylene terephthalate film with one side subjected to a release treatment with a silicone compound) using a rod-shaped metal applicator so that the thickness after drying would be 150 μm, and the film was then placed in a dryer at 85°C for 5 minutes to dry, yielding a coating layer of adhesive composition (a-8).

Furthermore, three of the above coating layers were laminated together to form a 450 μm thick multi-layer adhesive layer with release liner A on one side, and release liner B (a 38 μm thick polyethylene terephthalate film with one side release-treated with a silicone compound) was laminated to the other side of the above adhesive layer, resulting in an adhesive sheet with a total thickness of 450 μm (excluding the thickness of the release liner).

Example 9
An adhesive solution containing adhesive composition (a-9) was obtained by mixing and stirring 43 parts by mass of the polyurethane (B-2), 22 parts by mass of an alicyclic epoxy resin (manufactured by Daicel Corporation, "CEL-2021P"), 35 parts by mass of a cresol novolac epoxy resin (manufactured by DIC Corporation, "N-685-EXP-S"), 2.0 parts by mass of a sulfonium salt-based photocationic polymerization initiator (manufactured by San-Apro Co., Ltd., "CPI-100P", solids concentration 50%), 0.017 parts by mass of an ion scavenger (manufactured by Toagosei Co., Ltd., "IXEPLAS-A3", average particle size 0.5 μm), and 20 parts by mass of hydrophobic silica particles (manufactured by Fuji Silysia Chemical Ltd., "Sylophorbic 603", average particle size 6.7 μm). Methyl ethyl ketone was added to adjust the nonvolatile content to 75% by mass. The ion scavenger was an inorganic amphoteric ion scavenger containing three metal atoms: zirconium, aluminum, and magnesium. Furthermore, the hydrophobic silica particles did not have basic functional groups on the surface and were non-basic solids.

Next, an adhesive solution containing the adhesive composition (a-9) was applied to the surface of release liner A (a 50 μm-thick polyethylene terephthalate film with one side subjected to a release treatment with a silicone compound) using a rod-shaped metal applicator so that the thickness after drying would be 150 μm, and the film was then placed in a dryer at 85°C for 5 minutes to dry, yielding a coating layer of adhesive composition (a-9).

Furthermore, three of the above coating layers were laminated together to form a 450 μm thick multi-layer adhesive layer with release liner A on one side, and release liner B (a 38 μm thick polyethylene terephthalate film with one side release-treated with a silicone compound) was laminated to the other side of the above adhesive layer, resulting in an adhesive sheet with a total thickness of 450 μm (excluding the thickness of the release liner).

Example 10
An adhesive solution containing adhesive composition (a-10) was obtained by mixing and stirring 43 parts by mass of the polyurethane (B-2), 22 parts by mass of an alicyclic epoxy resin (manufactured by Daicel Corporation, "CEL-2021P"), 35 parts by mass of a cresol novolac epoxy resin (manufactured by DIC Corporation, "N-685-EXP-S"), 2.0 parts by mass of a sulfonium salt-based photocationic polymerization initiator (manufactured by San-Apro Co., Ltd., "CPI-100P", solids concentration 50%), 0.0085 parts by mass of an ion scavenger (manufactured by Toagosei Co., Ltd., "IXEPLAS-A3", average particle size 0.5 μm), and 20 parts by mass of hydrophobic silica particles (manufactured by Fuji Silysia Chemical Ltd., "Sylohorbic 603", average particle size 6.7 μm). Methyl ethyl ketone was added to adjust the nonvolatile content to 75% by mass. The ion scavenger was an inorganic amphoteric ion scavenger containing three metal atoms: zirconium, aluminum, and magnesium. Furthermore, the hydrophobic silica particles did not have basic functional groups on the surface and were non-basic solids.

Next, an adhesive solution containing the adhesive composition (a-10) was applied to the surface of release liner A (a 50 μm-thick polyethylene terephthalate film with one side subjected to a release treatment with a silicone compound) using a rod-shaped metal applicator so that the thickness after drying would be 150 μm, and the film was then placed in a dryer at 85°C for 5 minutes to dry, yielding a coating layer of adhesive composition (a-10).

Furthermore, three of the above coating layers were laminated together to form a 450 μm thick multi-layer adhesive layer with release liner A on one side, and release liner B (a 38 μm thick polyethylene terephthalate film with one side release-treated with a silicone compound) was laminated to the other side of the above adhesive layer, resulting in an adhesive sheet with a total thickness of 450 μm (excluding the thickness of the release liner).

Example 11
An adhesive solution containing adhesive composition (a-11) was obtained by mixing and stirring 33 parts by mass of the polyurethane (B-1), 22 parts by mass of an alicyclic epoxy resin (manufactured by Daicel Corporation, "CEL-2021P"), 45 parts by mass of a cresol novolac epoxy resin (manufactured by DIC Corporation, "N-685-EXP-S"), 1.6 parts by mass of a sulfonium salt-based cationic photopolymerization initiator (manufactured by San-Apro Co., Ltd., "CPI-100P", solids concentration 50%), and 84 parts by mass of zinc oxide particles (manufactured by Sakai Chemical Industry Co., Ltd., "LPZINC-11", average particle size 11 μm), and adding methyl ethyl ketone to adjust the nonvolatile content to 75% by mass. Note that the zinc oxide was an amphoteric metal oxide.

Next, an adhesive solution containing the adhesive composition (a-11) was applied to the surface of release liner A (a 50 μm-thick polyethylene terephthalate film with one side subjected to a release treatment with a silicone compound) using a rod-shaped metal applicator so that the thickness after drying would be 150 μm, and the film was then placed in a dryer at 85°C for 5 minutes to dry, yielding a coating layer of adhesive composition (a-11).

Furthermore, three of the above coating layers were laminated together to form a 450 μm thick multi-layer adhesive layer with release liner A on one side, and release liner B (a 38 μm thick polyethylene terephthalate film with one side release-treated with a silicone compound) was laminated to the other side of the above adhesive layer, resulting in an adhesive sheet with a total thickness of 450 μm (excluding the thickness of the release liner).

(Comparative Example 1)
An adhesive solution containing adhesive composition (b-1) was obtained by mixing and stirring 33 parts by mass of the polyurethane (B-1), 22 parts by mass of an alicyclic epoxy resin (manufactured by Daicel Corporation, "CEL-2021P"), 45 parts by mass of a cresol novolac epoxy resin (manufactured by DIC Corporation, "N-685-EXP-S"), and 1.6 parts by mass of a sulfonium salt-based cationic photopolymerization initiator (manufactured by San-Apro Co., Ltd., "CPI-100P", solids concentration 50%), and adding methyl ethyl ketone to adjust the nonvolatile content to 75% by mass.

Next, an adhesive solution containing the adhesive composition (b-1) was applied to the surface of release liner A (a 50 μm-thick polyethylene terephthalate film with one side subjected to a release treatment with a silicone compound) using a rod-shaped metal applicator so that the thickness after drying would be 150 μm, and the film was then placed in a dryer at 85°C for 5 minutes to dry, yielding a coating layer of adhesive composition (b-1).

Furthermore, three of the above coating layers were laminated together to form a 450 μm thick multi-layer adhesive layer with release liner A on one side, and release liner B (a 38 μm thick polyethylene terephthalate film with one side release-treated with a silicone compound) was laminated to the other side of the above adhesive layer, resulting in an adhesive sheet with a total thickness of 450 μm (excluding the thickness of the release liner).

(Comparative Example 2)
An adhesive solution containing adhesive composition (b-2) was obtained by mixing and stirring 33 parts by mass of the polyurethane (B-1), 22 parts by mass of an alicyclic epoxy resin (manufactured by Daicel Corporation, "CEL-2021P"), 45 parts by mass of a cresol novolac epoxy resin (manufactured by DIC Corporation, "N-685-EXP-S"), 1.6 parts by mass of a sulfonium salt-based cationic photopolymerization initiator (manufactured by San-Apro Co., Ltd., "CPI-100P", solids concentration 50%), and 20 parts by mass of hydrophobic silica particles (manufactured by Fuji Silysia Chemical Ltd., "Sylohorbic 603", average particle size 6.7 μm), and adding methyl ethyl ketone to adjust the nonvolatile content to 75% by mass. Note that the hydrophobic silica particles were non-basic solids having no basic functional groups on their surfaces.

Next, an adhesive solution containing the adhesive composition (b-2) was applied to the surface of release liner A (a 50 μm-thick polyethylene terephthalate film with one side subjected to a release treatment with a silicone compound) using a rod-shaped metal applicator so that the thickness after drying would be 150 μm. The resulting film was then placed in a dryer at 85°C for 5 minutes to dry, forming a coating layer of adhesive composition (b-2).

Furthermore, three of the above coating layers were laminated together to form a 450 μm thick multi-layer adhesive layer with release liner A on one side, and release liner B (a 38 μm thick polyethylene terephthalate film with one side release-treated with a silicone compound) was laminated to the other side of the above adhesive layer, resulting in an adhesive sheet with a total thickness of 450 μm (excluding the thickness of the release liner).

(Comparative Example 3)
An adhesive solution containing adhesive composition (b-3) was obtained by mixing and stirring 100 parts by mass of the urethane resin (B-3), 43 parts by mass of an alicyclic epoxy resin (CEL-2021P manufactured by Daicel Corporation), and 11.4 parts by mass of a sulfonium salt-based cationic photopolymerization initiator (CPI-100P manufactured by San-Apro Co., Ltd., solids concentration 50%), and adding methyl ethyl ketone to adjust the nonvolatile content to 75% by mass.

Next, an adhesive solution containing the adhesive composition (b-3) was applied to the surface of release liner A (a 50 μm-thick polyethylene terephthalate film with one side subjected to a release treatment with a silicone compound) using a rod-shaped metal applicator so that the thickness after drying would be 150 μm, and the film was placed in a dryer at 85°C for 5 minutes to dry, forming a coating layer of adhesive composition (b-3).

Furthermore, three of the above coating layers were laminated together to form a 450 μm thick multi-layer adhesive layer with release liner A on one side, and release liner B (a 38 μm thick polyethylene terephthalate film with one side release-treated with a silicone compound) was laminated to the other side of the above adhesive layer, resulting in an adhesive sheet with a total thickness of 450 μm (excluding the thickness of the release liner).

(Reference example 1)
Liquid adhesive (c-1) was obtained by mixing and stirring 43 parts by mass of the polyurethane (B-2), 22 parts by mass of an alicyclic epoxy resin (manufactured by Daicel Corporation "CEL-2021P"), 35 parts by mass of a cresol novolac epoxy resin (manufactured by DIC Corporation "N-685-EXP-S"), 2.0 parts by mass of a sulfonium salt-based photocationic polymerization initiator (manufactured by San-Apro Co., Ltd. "CPI-100P", solids concentration 50%), 1.7 parts by mass of an ion scavenger (manufactured by Toagosei Co., Ltd. "IXEPLAS-A3", average particle size 0.5 μm), and 20 parts by mass of hydrophobic silica particles (manufactured by Fuji Silysia Chemical Ltd. "Sylohorbic 603", average particle size 6.7 μm) at 110°C. The ion scavenger was an inorganic amphoteric ion scavenger containing three metal atoms, zirconium, aluminum, and magnesium, and the hydrophobic silica particles were a non-basic solid.

3. Evaluation The adhesive sheets obtained in the Examples and Comparative Examples were evaluated as follows. Note that, for Reference Example 1, liquid adhesive (c-1) was heated to 100°C, then dropped directly onto release liner B (a 38 μm thick polyethylene terephthalate film with one side release-treated with a silicone compound), covered with a release liner, and pressed down to a thickness of 450 μm to produce an adhesive sheet, which was then evaluated as follows.

[Method for evaluating the amount of halogen contained in the cured sheet]
The adhesive sheets obtained in the Examples and Comparative Examples (except Comparative Example 3), as well as the adhesive sheet prepared using the Reference Example adhesive, were each cut to a size of 35 mm wide x 18 mm long to prepare test samples. Next, the test samples were irradiated with ultraviolet light at an intensity of 300 mW/ ^cm² for 15 seconds using an air-cooled mercury lamp (manufactured by iGraphics). The release liner was not removed during the ultraviolet irradiation. After the ultraviolet irradiation, the test samples were heated at 80°C for 3 hours, then left at 23°C for 30 minutes or more before cooling, to prepare evaluation samples. The evaluation samples were placed in an XRF sample holder, and the elemental amounts were measured under vacuum conditions using a scanning X-ray fluorescence analyzer (ZSX Primus, manufactured by Rigaku Corporation). The quantitative results (ppm) of F, Cl, Br, and I were summed to obtain the total halogen content.

[Method for evaluating copper foil corrosion]
The adhesive sheets obtained in the Examples and Comparative Examples, and the adhesive sheet produced using the adhesive of the Reference Example were each cut to a size of 30 mm wide x 30 mm long to prepare test samples. One of the release liners was removed from each of the test samples, and the sheet was pressed against a 0.35 mm thick electrolytic copper foil with a smooth surface at a pressure of 0.05 MPa for 10 seconds in a temperature environment of 23°C to obtain a patch.

The patch was irradiated with ultraviolet light at an intensity of 300 mW/cm ² for 15 seconds using an air-cooled mercury lamp (manufactured by Eye Graphics Co., Ltd.) without removing the release liner.

After UV irradiation, the patch was heated at 80°C for 3 hours, then left in a 23°C environment for at least 30 minutes before cooling, and this was used as an evaluation sample.

The evaluation sample was left in an environment of 60° C. and 90% RH, and the appearance change (Cu corrosion resistance) of the bonded surface of the adhesive sheet and electrolytic copper foil was evaluated according to the following criteria.
(standard)
Good: No change in appearance was observed after the evaluation sample was left in an environment of 60°C and 90% RH for 100 hours.
Δ: No change in appearance was observed after the evaluation sample was left in an environment of 60° C. and 90% RH for 50 hours, but a change in appearance (blackening) was observed after being left for 100 hours.
×: A change in appearance (blackening) of the electrolytic copper foil was observed within 50 hours after the evaluation sample was left in an environment of 60° C. and 90% RH.

[Method for Evaluating Dispersibility of Additive (D) in Adhesive Sheet]
The adhesive sheets obtained in the Examples and Comparative Examples, and the adhesive sheet produced using the adhesive of the Reference Example were each cut into a size of 50 mm wide x 50 mm long to serve as test samples, and the dispersibility of the additive (D) in the sheets was evaluated according to the following criteria when observed with an optical microscope.
(standard)
◎: Less than one additive-derived agglomerate exceeding 1000 μm and less than one additive-derived agglomerate exceeding 150 μm ○: Less than one additive-derived agglomerate exceeding 1000 μm △: Two or more but less than three additive-derived agglomerates exceeding 1000 μm ×: Three or more additive-derived agglomerates exceeding 1000 μm

[Method for evaluating conformability after irradiation with active energy rays (method for evaluating conformability to unevenness when force is applied to the adhesive sheet after UV irradiation against the deflection or unevenness of the adherend surface)]
The adhesive sheets obtained in the Examples and Comparative Examples were each cut to 5 cm x 5 cm to prepare test specimens. Next, one release sheet was peeled off from each test specimen, and the test specimen was pressed and bonded to the center of a 50 μm-thick release liner C cut to 7 cm x 7 cm at a pressure of 0.05 MPa for 10 seconds at a temperature of 23°C. The adhesive sheet was then left in a 23°C environment for 60 minutes, and then irradiated with ultraviolet light at an intensity of 100 mW/ ^cm2 for 10 seconds using an electrodeless lamp (Fusion Lamp H bulb). After the ultraviolet irradiation, the adhesive sheet was left in a 23°C environment for 10 minutes, and then press-molded for 10 seconds at a pressure of 0.5 MPa using a heat press machine heated to 80°C. The ratio of the thickness change of the adhesive sheet after heat pressing to the thickness of the test specimen before heat pressing (0.45 mm) (thickness of the adhesive sheet after heat pressing/thickness of the adhesive sheet before heat pressing) was evaluated according to the following criteria.
(standard)
Good: The ratio of the thickness of the adhesive sheet after heat pressing to the thickness of the adhesive sheet before heat pressing was less than 90%.
x: The ratio of the thickness of the adhesive sheet after standing to the thickness of the adhesive sheet before standing was 90% or more and less than 100% (no change).

[Method for evaluating bondability to members that do not transmit active energy rays]
The adhesive sheets obtained in the Examples and Comparative Examples were each cut to a size of 10 mm wide x 10 mm long, one of the release liners was removed, and the sheets were then pressed and bonded to a smooth-surfaced aluminum plate measuring 15 mm wide x 150 mm long x 0.05 mm thick at a temperature of 23°C under a pressure of 0.05 MPa for 10 seconds.

The patch was left in a 23°C temperature environment for 60 minutes, and then irradiated with ultraviolet light at an intensity of 100 mW/ ^cm2 for 10 seconds using an electrodeless lamp (Fusion Lamp H bulb). At this time, the ultraviolet light irradiation was carried out without removing the release liner.

Next, the above-mentioned UV-irradiated patch was left in a 23°C environment for 10 minutes, after which the release liner was removed and the patch was press-bonded to a smooth-surfaced aluminum plate measuring 15 mm wide x 150 mm long x 0.05 mm thick for 10 minutes using a heat press heated to 70°C at 0.5 MPa. The press-bonded laminate was then heated to 80°C for 1 hour, left in a 23°C environment for at least 30 minutes, and cooled to prepare a test sample. The aluminum plate used in this evaluation is an opaque material with a light transmittance of 0%.

The shear adhesive strength [MPa] of the test sample was determined by chucking both ends of the adherend and conducting a tensile test in the 180-degree direction at a tensile speed of 10 mm/min using a tensile tester.

The evaluation results are shown in the table below.

The adhesive sheets of the Examples exhibited good conformability after exposure to active energy rays, demonstrating that corrosion was suppressed even when laminated to a metal surface (copper foil). On the other hand, the adhesive sheet of Comparative Example 1, in which the adhesive layer did not contain additive (D), and the adhesive sheet of Comparative Example 2, in which the adhesive layer contained a non-basic solid, exhibited good conformability after exposure to active energy rays, but corrosion of the metal surface (electrodeposited copper foil) was confirmed. Although the adhesive sheets of the Examples and Comparative Examples had similar amounts of halogen ions in the adhesive layer after curing, the adhesive sheets of the Examples exhibited better corrosion resistance to the electrolytic copper foil than the adhesive sheet of the Comparative Examples. This suggests that the inclusion of additive (D) in the adhesive layer resulted in the capture or neutralization of halogen ions and/or acids containing the halogen ions by additive (D), thereby suppressing acid-induced corrosion of the electrolytic copper foil.

Among the adhesive sheets of the examples, the adhesive sheets of Examples 1 to 10, which contained calcium bicarbonate or an inorganic ion scavenger, exhibited better metal corrosion resistance with a smaller content of additive (D) than the adhesive sheet of Example 11, which contained zinc oxide. Furthermore, the adhesive sheets of Examples 4 to 10, which contained an inorganic ion scavenger, exhibited better metal corrosion resistance with an even smaller content of additive (D) than the adhesive sheets of Examples 1 to 3, which contained calcium bicarbonate.

The adhesive sheet of Comparative Example 3, which did not simultaneously contain a photocurable resin (A) having a polymerizable functional group other than a polymerizable unsaturated double bond, a thermoplastic resin (B) having a polymerizable functional group other than a polymerizable unsaturated double bond, and a photopolymerization initiator (C), exhibited poor conformability after exposure to active energy rays and also had poor adhesion to components that are not transparent to active energy rays. This suggests that the adhesive sheet of Comparative Example 3 does not function as a delayed-cure adhesive sheet. Furthermore, the adhesive sheet of Reference Example 1 was evaluated as good in corrosion resistance as the Examples, but the dispersibility of the additive (D) in the adhesive was poor, and processing problems such as coating defects were observed when applying the adhesive.

Claims (16)

an epoxy resin (A);
a polyurethane resin (B) having a hydroxyl group;
a photopolymerization initiator (C);
one or more additives (D) having a function of capturing or neutralizing halogen ions and/or acids containing the halogen ions;
an adhesive sheet having an adhesive layer comprising:
the content of the epoxy resin (A) in the adhesive layer is 25% by mass to 75% by mass,
the content of the polyurethane resin (B) having a hydroxyl group is 20% by mass to 50% by mass,
The content of the photopolymerization initiator (C) is 0.1% by mass to 10% by mass,
An adhesive sheet in which the content of the additive (D) is 0.01% by mass or more and 30% by mass or less. The adhesive sheet according to claim 1, wherein the additive (D) comprises one or more compounds selected from the group consisting of inorganic ion scavengers and basic solids. The adhesive sheet according to claim 2, wherein the basic solid is an inorganic salt. The adhesive sheet according to claim 2, wherein the inorganic ion scavenger is a compound selected from the group consisting of inorganic anion scavenger and inorganic amphoteric ion scavenger. The adhesive sheet according to any one of claims 1 to 4, wherein the thickness of the adhesive layer is 10 μm or more and 3000 μm or less. The adhesive sheet according to any one of claims 1 to 5, wherein the additive (D) is dispersed in the adhesive layer. The adhesive sheet according to any one of claims 1 to 6 , wherein the photopolymerization initiator (C) is a photocationic polymerization initiator. The adhesive sheet according to any one of claims 1 to 7 , which is used for bonding an adherend having a metal surface on the adherend surface. The adhesive sheet according to any one of claims 1 to 8 , which is used to bond a substrate to a wiring board having metal wiring on one surface of the substrate. A laminate comprising: the adhesive sheet according to any one of claims 1 to 9 ; a first member bonded to a first main surface of the adhesive sheet; and a second member bonded to a second main surface of the adhesive sheet. The laminate according to claim 10 , wherein at least one of the first member and the second member includes a metal surface on the surface to be adhered to the adhesive sheet. 12. The laminate according to claim 10 , wherein at least one of the first member and the second member is a substrate and a wiring substrate having metal wiring on one surface of the substrate. The laminate according to any one of claims 10 to 12 , which is used in an image display device. A method for producing a laminate using the adhesive sheet according to any one of claims 1 to 9 , comprising:
A step [1] of bonding a first member to a first main surface of the adhesive sheet;
a step [2] of bonding a second member to a second main surface of the adhesive sheet;
and step [3] of curing the adhesive layer of the adhesive sheet,
The method further comprises a step of irradiating the first main surface or the second main surface of the adhesive sheet with active energy rays before the step [1] or between the step [1] and the step [2],
A method for manufacturing a laminate, wherein at least one of the first member and the second member includes a metal surface on the surface that comes into contact with the adhesive sheet. 15. The method for manufacturing a laminate according to claim 14 , wherein at least one of the first member and the second member is a wiring board having a substrate and metal wiring arranged on one surface of the substrate. The method for producing a laminate according to claim 14 or 15 , wherein the laminate is a substrate part of an image display or a semiconductor chip.